Contents 3 5 17 21 33 · also our education system, as one of the awardees, Venkatraman...

Contents

Editorial

Nobel Prize in Sciences–2009Archana Sharma

Holography–The Fascinating World of 3-DView ingP. K. Mukherjee and U.P. Tyagi

Episodic Conceptualisation – A Possible Sourceof Alternative Conception about 'Kinetic Energy'and 'Work'O.P. Arora and J.K. Mohapatra and B.K. P arida

Nanoscience Curriculum in School EducationIntegrating Nanoscience into the ClassroomR. Ravichandran and P. Sasi kala

Energy and Electronic Charge ConservationDuring Alpha and Beta EmissionPras anta Kumar P atra

The Role of Metacognition in Learning andTeaching of PhysicsS. Raj kumar

Students' Science Related Experiences, Interestin Science Topics and their Interrelation–SomeImplicationsK. Abdul Gafoor and S mitha Narayan

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Computer Aided LearningPreety Chwala

Formal Charge – A Novel Method for TeachingTheoretical Inorganic ChemistryBibhuti Narayan Biswal

Alternative Fuels – A Boon for FutureGenerationsGurkirat Kaur

Science News

Web Watch

You've Asked

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In the first fortnight of October every year, thescientific community eagerly awaits theannouncement of Nobel Awards, the symbol ofhighest recognition, a scientist aspires to receivefor her/his work in basic sciences. Instituted in1901 as per the will of Alfred Nobel, the NobelAwards are conferred on those who have donetheir best to serve mankind in the field ofPhysics, Chemistry, Medicine, Literature andPeace. “Sveriges Riksbank Prize in EconomicSciences in Memory of Alfred Nobel” has beenadded since 1969 though technically it is not aNobel award but its announcements andpresentations are made along with it. The Nobelawards for Physics and Chemistry areannounced by the Swedish Academy of Science.The Nobel Prize in Physics for the year 2009 hasbeen shared by three scientists– Charles K. Kao,Willard S. Boyle, and George E. Smith. Charles K.Kao receives the award for his “groundbreakingachievements concerning the transmission oflight in fibres for optical communication” whileMakoto Kobayashi and Toshihide Maskawa werenominated for the “invention of an imagingsemiconductor circuit – the CCD sensor”. NobelPrize in Chemistry has been awarded by theSwedish Academy of Science to VenkatramanRamakrishnan, Thomas A. Steitz, and Ada E.Yonath for enlightening the science communityon the ‘structure and function of the ribosome’.Nobel Prize for Physiology and Medicine is to beshared by three scientists– Elizabeth H.Blackburn, Carol W. Greider, and Jack W.Szostak for their discovery “how chromosomes

are protected by telomeres and the telomeraseenzyme”. The lead article of this issue attemptsto highlight the work of these Nobel laureatesand its significance for future developments.This year’s announcement for the Nobel Prize inchemistry had special significance for Indians asalso our education system, as one of theawardees, Venkatraman Ramakrishnan, happensto be an Indian American. VenkatramanRamakrishnan is the third Indian American, afterHargobind Khorana and S. Chandrasekhar, whohas been bestowed with this honour.Venkatraman Ramakrishnan has been a brilliantstudent right from his school days. In fact, as astudent of the then higher secondary stage(Class XI) in 1968, he was selected for award ofscholarship under National Science TalentSearch Scheme (NSTS) instituted by the NCERTin 1963 for nurturance of talent in science.

It has been our endeavour to keep our patronsabreast with recent developments in basicsciences and upcoming technologies througharticles, features and science news. In the last fewyears, an attempt has been made through thearticles and science news through the pages ofthis journal to highlight important developmentsin the field of nanotechnology. An articlepresenting a design of a curriculum to introducenanotechnology as a subject of study at the highersecondary stage has been included in this issue. Itis envisaged that educationists, especiallycurriculum developers, would ponder over the

Editorial

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School Science Quarterly Journal March-June 2010

implications in the event such a futuristictechnology is accepted at school stage.Holography is another technology, which in recentpast have become quite common, particularly as apotent tool to protect copy right infringements.To have a three dimensional view of a picture witha holograph is always a fascinating experience.Students often wonder how holographs areproduced and what the scientific principle behindit is. It is envisaged that the article on this subjectwould facilitate understanding the basic principlesof holography.

Studies on various aspects of science educationbesides providing us ideas for improving qualityof teaching science in schools, also give us anin-depth understanding about issues andproblems that need be addressed. In recent times‘episodic conceptualisation’ has been identified asone of the origins of pupils’ alternativeconceptions. It is hypothesised that the episodicformat of the form, content, and mode ofpresentation of two interrelated concepts, say

kinetic energy and work, is likely to generate twoisolated, mutually independent cognitivestructures amongst learners often emanatingfrom the manner these are presented in thetextbook and by the teachers in the classroom.The research design, methodology and outcomeof a study on episodic conceptualisation and itsimplications form the basis of another article inthis issue. Children’s concepts on some aspectsof environment, application of computers inteaching learning of science, theory ofmetacognition and its role in learning andteaching are some other issues on which articlesfind a place in this number, in addition to regularfeatures like the ‘Science News’, ‘Web Watch’ and‘You’ve Asked’.

We sincerely hope that our readers would find thearticles, features and news items interesting andeducative. Your valuable suggestions,observations and comments are always a sourceof inspiration and guide us to bring furtherimprovement in the quality of the journal.

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NOBEL PRIZE IN SCIENCES–2009Archana SharmaJunior Project FellowDepartment of Education in Science and MathematicsNational Council of Educational Research and Training, New Delhi

The prestigious Nobel award, instituted at thebehest of the great scientist and the inventor ofdynamite ‘Alfred Nobel,’ is tribute to persons whorender most valuable service to humanity by theirresolute and concerted work in different fields ofphysics, chemistry, physiology and medicine,economics and peace. The award is more than amere symbol of recognition. The prize money of1,66,000 US dollars is also of substantial help toindividual scientists to carry forward research intheir field of interest to satisfy their insatiabledesire, in knowing the unknown for the benefit ofmankind for which they have devoted their livesand effort. The Nobel Prize is an internationalaward administered by the Nobel Foundation inStockholm, Sweden.

Like every year, the Nobel Prize for physics andchemistry for the year 2009 were announced bythe Swedish Academy of Science while TheStockholm Faculty of Medicine recommended theawards for physiology and medicine.

Nobel Prize in Chemistry

This year’s Nobel Prize in Chemistry has beenawarded to three scientists: VenkatramanRamakrishnan, Thomas A. Steitz, and Ada E.

Yonath for enlightening the science community onthe ‘structure and function of the ribosome’. Outof the three big molecules for life (DNA, RNA, andProteins), proteins arguably take lion’s share ofthe work. Proteins provide structural stability tothe cells, give mechanical motion to muscles,transport oxygen and play many other key role innearly every chemical reaction that occurs in thecells. The three Nobel awardees, Ramakrishnan,Steitz, and Yonath, used- X-ray crystallography toidentify and map the positions of the atoms in theribosome to provide its 3-D models to scientiststo facilitate further studies and dissect them forcrucial information at the atomic level. This was aunique achievement as there are hundreds ofthousands of atoms involved. Their work hasbenefited many other areas of research, includingthe study of antibiotics. As synthesis of proteins isessential for the survival of bacteria, the ribosomeis a practical target for drugs. The researchescarried out by Nobel laurates have provided vitalinformation for the design of new antibiotics.The three-dimensional model (3-D), developed bythe three scientists showed how differentantibiotics bind to ribosomes. These models arenow used by scientists in order to develop newantibiotics, directly assisting the saving of livesand decreasing humanity’s suffering.

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Venkatraman Ramakrishnan, born in 1952 inTamil Nadu, India, did his Ph.D from University ofOhio in 1976. He is a senior scientist and nowleads a strong research group at the MedicalResearch Council (MRC) Laboratory of MolecularBiology in Cambridge, UK. He has determined thestructure of the Thermus thermophilus’s (heat-stable bacterium) 30S ribosomal subunit incomplex with several antibiotics. DrRamakrishnan’s research into the ribosome andits complexes with antibiotics, initiation factor 1(IF1), as well as cognate and near-cognate tRNAhas resulted in an extensive body of publications.

Thomas A. Steitz, born in 1940 in Milwaukee, WI,did his Ph.D from Harvard University in 1966. Heis now Sterling Professor of Molecular Biophysicsand Biochemistry, and an investigator of theHoward Hughes Medical Institute. His scientificcareer has been focused on studying thestructural basis of the molecular and chemicalmechanisms by which proteins and nucleic acidsexecute their biological functions. Dr Steitz’simaged the first high-resolution crystal structureof the large ribosomal subunit known as 50sfrom Haloarcula marismortui with a resolutionof 9 Å.

Ada E. Yonath, born in 1939 in Jerusalem, Israel,did her Ph.D in X-ray Crystallography fromWeizmann Institute, Israel in 1968. She is presentlythe Director of the Kimmelman Centre forBiomolecular Assemblies at the WeizmannInstitute of Science in Rehovot, Israel. Theribosome was central to her research from theinitial crystallisation studies in the late 1970s toher first electron density map of the smallribosomal subunit from Thermus thermophilus,constructed at 4.5 Å.

VenkatramanRamakr ishnan

Thomas A. Steitz

Ada E. Yonath

Fig. 1 : Nobel Prize awardees in Chemistry

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Yonath and Ramakrishnan obtained the structureof the small subunit (30S) from Thermusthermophilus. Thus, it was possible to mapribosome functionality at the most basic, atomiclevel.

Their research showed how the ribosome lookslike and how it functions at the atomic l evel.They have used a method cal led X-raycrystallography to map the pos ition of every oneof the hundreds of thousands of atom s thatmake up the ribos ome. This method determinesthe three dimensional structure of moleculeswhich are organised in different pattern in thecrystals. These molecules within the crystaldiffr act the X-rays in s pecific directions whenthese are exposed to a beam of X-rays. Bystudying the diffraction pattern, the intens itiesand position of the diffracted beam,crystallographers can identif y the position andatomic details of the molecules.

By building a (3-D) structure of the ribosomeusing X-ray crystallography method, they solved

an important part of the problem posed byFrancis Crick and James Watson, when theyproposed the twisted double helical structure ofDNA, i.e. how does genetic code become a livingthing? DNA is made available to the ribosome by“transcription” of genes into chunks ofmessenger RNA (mRNA). In the ribosome, thesemRNA are translated into various amino acidsequences by the method of translation and makeup an organism’s proteins. The work is based ona technique called X-ray crystallography, whereprotein molecules are removed from cells,purified and made into crystals that can beexamined by X-rays.Every cell of the organism have DNA molecules intheir nucleus. They contain the blueprints for howan organism, say a human being, a plant or abacterium, looks and functions. These blueprintsget transformed into living matter through thefunction of ribosomes. Based upon theinformation coded in DNA, proteins are formed in

ribosomes. There are tens ofthousands of proteins in the body of anorganism and they have differentstructures and functions. They buildand control life at the chemical level.

Ribosomes were first discovered in themid 1950s by a cell biologist GeorgePalade using electron microscope andthe term ‘ribosome’ for them wasproposed by Biologist Richard B.

Fig. 2: Translation Process(the synthesis of protein)

(S ourc e : http://w ww.ortodoxi atinerilor.ro/20 08/0 9/genele-s int eza-protei nelor-codul-genet ic-5)

NOBEL PRIZE IN SCIENCES–2009

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antibiotics cure the disease by interfering in thefunction of bacterial (infecting) ribosomes bypreventing them to make the proteins they needto survive. As making proteins is essential for thesurvival of bacteria, ribosome in them is the maintarget of antibiotics, which stops the proteinsynthesis. Without functional ribosomes, bacteriacannot survive because of its inability tosynthesise protein. This is why ribosome is suchan important target for new antibiotics. Thisresearch could help scientists to designantibiotics to treat people who are infected with abacterium that has developed resistance againsttraditional antibiotics. Better targeting of thebacterial ribosome should also help to avoidnegative effects on human cells thereby reducingthe side effects of taking antibiotics. Biologists inpharmaceutical and biotechnology companies willalso use this valuable information to develop newantibiotics to fight the growing problem ofbacterial drug resistance.

Nobel Prize in Physics

The Nobel Prize in Physics–2009 has beenawarded jointly to three Scientists– Charles K.Kao, Willard S. Boyle, and George E. Smith. Thisyear’s Nobel Prize in Physics is awarded for twoscientific achievements that have helped to shapethe foundations of today’s networked societies.Charles K. Kao received the award for his“groundbreaking achievements concerning thetransmission of light in fibres for opticalcommunication” while Makoto Kobayashi andToshihide Maskawa were nominated for the“invention of an imaging semiconductorcircuit – the CCD sensor “.

Roberts. An understanding of structure andfunction of the ribosome is important for ascientific understanding of life. Ribosome is thepart of cellular components that make the protein.It is20 nm in diametre and is made up of a complexcomprising 65 per cent RNAs and 35 per centProtein. Ribosomes are divided into two sub-units:larger and smaller. The unit of measurement ofsub-unit is Svedberg unit (s), a measure of the rateof sedimentation in centrifugation. The ribosomeis the site of protein synthesis (protein factory) in aliving cell. The ribosome translates genetic codeinto proteins, which are the building blocks of allliving organisms. The sub-unit of ribosome inprokaryotes and eukaryotes are different, theprokaryotes have 70S ribosome made up of largersub-unit of 50S and smaller sub-unit of 30S.Eukaryotes have 80S ribosome, it has largersub-unit of 60S and smaller sub-unit of 40S.These sub-units play an important role intranslation, a process for the synthesis of protein.The three nucleotide genetic codon bind to thesesub-unit with the help of tRNA and make theprotein in this process.

Human and bacterial ribosomes are slightlydifferent, making the ribosome a good target forantibiotic therapy that works by blocking thebacterium’s ability to make the proteins it needsto function. Nowadays, various antibiotics are inuse that cure diseases by blocking the function ofbacterial metabolic activity in the translationprocess (protein synthesis). Dr Ramakrishnandiscovered the function of these ribosomalsub-units complex with various antibiotics. Healso determined that how antibiotics bind tospecific pockets in the ribosome structure. The

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Charles K Kao, born in 1933 in Shanghai, China, isalso known as Father of ModernCommunications. He did his Ph.D from Universityof London in 1965. He is retired Director ofEngineering at Standard TelecommunicationLaboratories, Harlow, UK and Vice-Chancellor atChinese University of Hong Kong. He was citedfor his 1966 discovery that showed how totransmit light over long distances via fibre-opticcables, which became the backbone of moderncommunication networks that carry phone callsand high-speed Internet data around the world.

Willard S. Boyle, born in 1924 in Nova Scotia,Canada, did his Ph.D from McGill University in1950. He was Executive Director ofCommunication Sciences Division, BellLaboratories, Murray Hill, New Jersey, USA. In1962, he worked with Dr Nelson and invented thefirst continuously operating ruby laser; he wasappointed as director of Bellcomm’s (a Bell Labssubsidiary) Space Science and Exploratory Studiesprogramme. He returned to Bell Labs in 1964. In1969, he worked with George E. Smith to developCharge-Coupled Devices (CCDs).

George Elwood Smith, born in 1930 in WhitePlains, New York, did his Ph.D from University ofChicago in 1959. He is retired Head of VLSI DeviceDepartment, Bell Laboratories, Murray Hill, USA.He was involved in a variety of investigations onjunction lasers, semiconducting ferroelectrics,electroluminescence, transition-metal oxides,the silicon-diode-array camera tube, andCharge Coupled Devices (CCDs).

Boyle and Smith jointly invented the firstsuccessful imaging technology using a digitalsensor, a Charge Coupled Device (CCD).

Willard S. Boyle

George E. Smith


Charles K. Kao

Fig. 3: Nobel Prize awardees in Physics

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The CCD uses semiconductors, the same kind ofmaterials as computer chips, to capture light andturn it into an electric signal. The CCD is theelectronic eye of digital camera. The invention hasrevolutionised photography, as light could now becaptured electronically instead of on films. Thedigital form facilitates the processing anddistribution of these images. The CCD allowedwhole two-dimensional fields of optical data to beread out more quickly and efficiently. The CCD hasbeen the backbone of the commercial digitalcamera industry.

The CCD technology makes use of thephotoelectric effect, as theorised by AlbertEinstein and for which he was awarded the NobelPrize in the year 1921. By this effect, light istransformed into electric signals. The challengewhen designing an image sensor was to gatherand read out the signals in a large number ofimage points, pixels, in a short time. Digitalphotography has become an irreplaceable tool inmany fields of research. The CCD has providednew possibilities to visualise the previously

unseen. It has given us crystal clear images ofdistant places in our universe as well as thedepths of the oceans. The CCD contains a siliconchip that is divided into cells or “pixels”. Whenlight hits a pixel, it excites an electric charge in thesilicon, which then induces a charge in a tinyelectrode on the surface of the chip. The chargethen quickly passes from electrode to electrodedown a whole row of pixels known as “chargecoupling” and is read out at the edge of the chip.The CCD technology is also used in many medicalapplications, e.g. for imaging the inside of thehuman body, both for diagnostics and formicrosurgery.

Today optical fibres make up the circulatorysystem that nourishes our communicationsociety. These low-loss glass fibres facilitateglobal broadband communication such as theInternet. Light flows in thin threads of glass, and itcarries almost all of the telephony and data trafficin each and every direction. Music, video, Text andimages can be transferred around the globe in asplit second. Dr Kao carefully calculated how totransmit light over long distances via optical glassfibres. With a fibre of purest glass it would bepossible to transmit light signals over 100kilometres, compared to only 20 metres for thefibres available previously. His passion inspiredother researchers to share his vision of the futurepotential of fibre optics. The first ultrapure fibrewas successfully fabricated in 1970. This is one ofthe main technologies in modern photography. Itmakes the capture and reading of light fast andefficient and it essentially made photographic filmobsolete, the cost of capturing an image wentdown to literally zero. It is also one of the standardtechnologies for investigation in astrophysics and

Fig. 4: Optical Fibres

(Source : oc w.mi t.edu/... /det ail/f ibre_opt ics_hom.htm)

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most importantly, it is not restricted to the visiblespectrum. This mode of communication isessential for high speed internet and forms theoptical backbone of 21st century commerce.

Nobel Prize in Physiology andMedicine

This year's Nobel Prize for physiology and medicineis shared by three scientists: Elizabeth H. Blackburn,Carol W. Greider, and Jack W. Szostak for theirdiscovery “how chromosomes are protected bytelomeres and the telomerase enzyme”.

Elizabeth H. Blackburn was born on 26 November1948 in Hobart, Tasmania. She is an Australianborn U.S. biologist and done her Ph.D. atUniversity of California, San Francisco (UCSF), shestudied telomere, a structure at the end ofchromosomes which protects the chromosome.

Born in 1961 at San Diego, California, Carol W.Greider completed her Ph.D. in molecular biologyin 1987 at the University of California, Berkeley,under Elizabeth Blackburn. Presently, she is aProfessor and Director of Molecular Biology andGenetics at the John Hopkins Institute of BasicBiomedical Sciences. She discovered the enzymetelomerase in 1984 while working with ElizabethBlackburn. She pioneered research on thestructure of telomeres, the ends ofchromosomes.

Jack W. Szostak was born on 9 November 1952 inLondon. He completed his Ph.D. from CornellUniversity (US). Presently, he is a biologist andProfessor of Genetics at Harvard Medical Schooland Alexander Rich Distinguished Investigator atMassachusetts General Hospital, Boston. He is

Elizabeth H.Bla ckburn

Carol W. Greider

Jack W. Szostak

Fig. 5: Nobel Prize awardees inPhysiology a nd Medicine


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credited with the construction of the world’s firstyeast artificial chromosome. This constructionhelped him to map the location of gene inmammals which played a pivotal role in HumanGenome Project. Dr Szostak’s discoveries havepaved the way to clarify the events that lead tochromosomal recombination, the reshuffling ofgenes that occurs during meiosis and also tounravel the function of telomere gene.

(1952-11-09) The DNA of all organisms (whetherprokaryotic or eukaryotic) multiply (get divided) by aprocess called DNA Replication, such that the newlyformed strand of DNA is the exact copy of itsparent DNA. The replication process is different inprokaryotes and eukaryotes. In prokaryotes thecircular DNA replication is terminated by Ter(terminus)-Tus (terminus utilisation sequences)complex sequences. But termination of lineareukaryotic chromosome involves the synthesis ofspecial structure, called telomeres chromosome,present at the end of all eukaryotic chromosome.Telomeres consist of tandem repetitive arrays ofthe hexameric sequence TTAGGG and play animportant protective role in the cells. Theirpresence on the tips of chromosomes preventsimportant genetic material from being lost duringcell division. The overall size of telomere is rangingfrom ~15 Kilobase (kb) at birth sometimes 55 kb inchronic disease states. The telomeric repeats helpmaintain chromosomal integrity and provide abuffer of potentially expendable DNA. The ends oftelomeres are protected and regulated bytelomere-binding proteins and form a speciallariat-like structure called the t-loop. Thispackaging or protective cap at the end of linearchromosomes is thought to mask telomeres frombeing recognised as broken or DNA damage, thus

protecting chromosome termini from degradation,recombination and end-joining reactions.

Fig 6 depicts the chromosome in blue colour andthe white point like structure present at the tip ofchromosome is the telomeric DNA.

The inability of DNA polymerase to replicate theend of the chromosome during lagging strandsynthesis (‘end replication problem’) coupled withpossible processing events in both leading andlagging daughters, results in the loss of telomericrepeats each time a cell divides and ultimatelyleads to replicative senescence. This problem issolved by the ‘Telomerase enzyme’. Thetelomerase is a ribonucleoprotein enzymeessential for the replication of chromosometermini in eukaryotes. It is an essential enzymethat maintains telomeres on eukaryoticchromosomes. The importance of telomeres wasfirst elucidated in plants 60 years ago. Little isknown about the role of telomeres andtelomerase in plant growth and development.enzyme adding telomeric repeats onto the 32 This

Fig. 6: Chromosome and Telomeric DNA

(Source : physics .berkeley .edu/.../ yildiz/Researc h.ht ml)

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Fig. 7: Telemere Function and SynthesisSource : www .highlight health.com/... /200 9/10/ telom ere.gif


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ends (3 prime ends) of the DNA limits. Telomeraseact like a cellular reverse transcriptase enzyme,which is RNA dependent DNA synthesis.The enzyme telomerase, which builds telomeres, enables the entire length of thechromosome to be copied without missing theend portion.

Telomerase uses its integral RNA component as atemplate in order to synthesise telomeric DNA(TTAGGG)n, directly onto the ends ofchromosomes. After adding six bases, theenzyme pauses while it repositions (translocates)the template RNA for the synthesis of the next6 bp repeat. This extension of the 32 DNAtemplate eventually permits additional replicationof the C-rich strand, thus compensating for theend-replication problem. Average telomerelength, gives some indication of how manydivisions the cell has already undergone and howmany remain before it can no longer replicate.

All telomeres have the same short sequence ofDNA bases repeated thousands of times. Ratherthan containing any genetic information, theserepetitive snippets help keep chromosomesintact. Short telomeres are more common inolder cells; telomere capping problems may berelated to the development of age-relateddiseases. Telomerase expression is also detectedin a majority of cancers, but is absent in mostsomatic tissues and correlates to clinical outcomein a number of cancer types. Cancer and agingresearch merge in the study of telomeres. Thetails at the ends of chromosomes that becomeshorter as a cell divides, is defected in cancercells. It divides continuously as cancer cell hasuncontrolled growth regulatory system.

Role of Telomere and Telomerase inCancer

In cancer cells, telomeres act abnormally; they nolonger shorten with each cell division. Healthyhuman cells are mortal because they can divideonly a finite number of times, growing older eachtime they divide. It has been proposed thattelomere shortening may be a molecularclock mechanism that counts the number oftimes a cell has divided and when telomeresare short, cellular senescence (growth arrest)occurs.

The cancer cell has uncontrolled growthregulatory system as it divides beyond the normallimits. Telomerase is an enzyme that “rewinds”the mitotic or cellular clocks. Telomerasestrengthens and lengthens the shortenedtelomeres in the cells, replacing the bits of DNAlost in normal cell division. If telomerase stopstelomere shortening, those cells with telomerasecan live forever. Since most cancer cells containtelomerase, researchers believe it is a criticalfactor in conferring immortality upon these cells.

Dr Blackburn and Dr Greider discovered theenzyme telomerase, which is not active in mostadult cells but becomes active in advancedcancers, enabling cells to replace lost telomericsequences and divide indefinitely. Their discoverytherefore, might aid in cancer treatment. Lots ofwork is going on cancer which is related totelomerase enzyme. If the telomerase activity inthe cancer cell stops or reduces then it is easy tocure to some extent the cancer in persons.Telomerase expression is associated with thestage of differentiation but not necessarily with

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the rate of cell proliferation. The inhibition orabsence of telomerase may result in cell crisis incancer cells and tumor regression in cancerpatients. These results suggest that cancertherapy based on telomerase inhibition could be amore effective and safer treatment for cancer; itcould as well provide a more accurate means fordiagnosing and predicting clinical outcome incancer. In addition, some inherited diseases arenow known to be caused by telomerase defects,including certain forms of congenital aplasticanemia, and some inherited skin and lungdiseases.

Role of Telomere and Telomerase inAging

Natural aging involves the telomeres, which overtime lose their ability to replicate as frequently aswhen they were younger. Aging is a progressivedecline in vitality over time leading to death. It is aside product of metabolism. The process of celldivision is called mitosis. Each time mitosisoccurs, the telomeres of the dividing cells get justa bit shorter. Once a cell’s telomeres have reacheda critically short length, that cell can no longerdivide. Its structure and function begins to fail,and some cells even die. The telomere hypothesisof aging postulates that as the telomeres naturallyshorten during the lifetime of an individual, asignal or set of signals is given to the cells tocause the cells to cease growing (senesce).According to, Dr Langmore, at birth, humantelomeres are about 10,000 base pairs long, butby 100 years of age this has been reduced to about5,000 base pairs. Many scientists speculated thattelomere shortening could be the reason for

aging, not only in the individual cells but also inthe organism as a whole. But the aging processhas turned out to be complex and it is nowthought to depend on several different factors, thetelomere being one of them. In the absence oftelomerase, the telomere will become shorterafter each cell division. When it reaches a certainlength, the cell may cease to divide and they die.Therefore, telomerase plays an essential role inthe aging process. There is little evidence thatcommonly observed changes in older individuals,such as anemia and impaired wound healing,result from impaired cellular proliferation, whichwould be the anticipated consequence ofshortened telomeres. Despite the lack of clearevidence for impaired proliferation in aging thereis, in fact, good evidence for progressive telomereshortening in many human cell types, includingperipheral white blood cells, smooth muscle cells,endothelial cells, lens epithelial cells, musclesatellite cells, and adrenocortical cells, etc. Theproliferative capacity is closely related to telomerelength in endothelial cells. Telomere lengths inendothelial cells decreases as a function of donorage, with a greater decline being observed in cellsisolated from the iliac artery. The greater declinein telomere length was observed in the cells thathave likely undergone more proliferation in vivo,because they resided in a part of the vascularsystem where blood flow might cause mostchronic damage to the endothelium.

The discoveries of the Nobel laureates hasadded a new dimension to the scientificcommunity’s understanding of the cell, shed lighton disease mechanisms, and introduced newdirections for the development of potentialnew therapies.


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BLASCO, M. A., S. M. GASSER and J. LINGNER. 1999. Gene and Development, 13, pp. 2353-2359.CHO, A., 2009. Physics Nobel Winners See the Big Picture, Science NOW Dai ly News.GUARENTE L. 2000. Sir 2 Links Chromatin Silencing, Metabolism and Aging. Genes and

Development, Vol.-1; 14(9), pp.1021-1026.HORNSBY, P. J. 2001. Cell Proliferation in Mammalian Aging. Handbook of the Biology of Aging.

Fifth Edition, pp. 207–266. Academic Press, San Diego.Indian-origin scientist, two others win Nobel Prize in Chemistry. The Times of India, October 7,

2009.SHAY, J. W. WRIGHT. 2002. Telomerase: A Target for Cancer Therapeutics. Cancer Cell, Vol.

2(4), pp. 257-265.KIM, N.W. 1997. Clinical Implications of Telo merase in Cancer. Science Direct, Euro pean

Journal of Cancer, Vol. 33(5), pp. 781-786.MASON, I. Nobel Prize in Physics Goes to “Masters of Light”. National Geographic News, Online

article at news.nationalgeograph ic.com.NELSON, D.L. and M.M. COX. 2004. Principle of Biochemistry. Third Edition, pp.1012-1055. London

Universit y Press.REINHARDT, D. 2009. Ribosome Structure, Chemistry Nobel Prize, Ribosomal Crystalline

Structure Analysis Explains Protein Acti vities. Online article at suite101.com.XIE, YUN. Chemistry Nobel Goes to Ribosomes, the Protein Manufacturer. ars Technica, Online

article.

Websiteshttp://nobelprize.org/index.htmlhttp://news.nationalgeographic.com/news/2009/10/091006-nobel-prize-2009-physics-communications-light-fibre-optics.htmlhttp://www.aip.org/news/nobelprize2009.htmlhttp://www.dpreview.com/news/0910/09100601nobelprize.asphttp://medgadget.com/archives/2009/10,the nobel prize in chemistry 2009.htmlhttp://www.nih.gov/news/health/oct2009/od-06.htm

References

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P.K. Mukherjee and U.P. TyagiAssociate Professors of PhysicsDeshbandhu College, University of DelhiKalkaji, New Delhi

Memories of people, events etc. are better storedin the form of photographs. In fact, thetechnology of photography has been with us for along time. Regular photograph “freezes” a two-dimensional image of the three-dimensionalworld, thereby enabling only a two-dimensionalview of reality. Standard photographic filmregisters the total light intensity (which is squareof amplitude of light wave) falling on each point ofthe film during exposure i.e. when the shutter isopen. The resulting image is a two-dimensionalmapping which contains only the intensityattributes of the wave. The phase attributes of thewave related to the depth of the fieldare thereforelost. An ordinary photography, therefore, losesthe phase completely. It records only theintensities. However, if both the intensity and thephase attributes of the wave are recorded, one canget a three-dimensional image of the object. Thisis achieved by using the principles of what isknown as holography.

History

The technique of holography was developed by theHungarian physicist Dennis Gabor in 1948 whenhe was working in the Research laboratory of theBritish Thomson-Houstan Company in Rugby,England. This discovery won him the 1971 NobelPrize in Physics.

In fact Gabor’s interest was to improve theresolving power of the electron microscope. Heused a two-step lensless imaging process thatinvolved interference between an object wave(emanating from the object) and a coherentbackground wave (called reference wave).Theresulting interference pattern was called a“hologram”, after the Greek word holos, meaningwhole as it contained the whole information. Thisis known as the recording process. Recorded inthe interference pattern is not only the amplitudedistribution but also the phase of the object wave.

HOLOGRAPHY– THE FASCINATING WORLDOF 3-D VIEWING

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The hologram has, however, little resemblance tothe object. It has in it a coded form of the objectwave. The second step in Gabor’s process, calledreconstruction process, involved reproduction ofthe image. The hologram was illuminated by anappropriate light beam which formed thereconstructed image of the object in its truethree-dimensional form.

Although the principle of holography was laiddown by Gabor in 1948, it attained practicalimportance in 1960 only after the advent of lasers.In 1962 Emmett N. Leith and Juris Upatnieks,working in the Radar Laboratory of the Universityof Michigan, succeeded in developing good qualityholograms using laser light.

In 1962, Yuri Nikolayevitch Denisyuk of Russiaintroduced a scheme for generating hologramsthat was conceptually similar to the early colourphotographic process of Gabriel Lippmann. Hesucceeded in producing a white light reflectionhologram which, for the first time, could beviewed in light from an ordinary incandescentlight bulb.

Another significant development in holographytook place in 1969 when Stephen A.Benton ofPolaroid Research Laboratories,Cambridge,Massachusetts, U.S.A. succeeded increating white light holograms. Depending on theviewing angle these holograms show all the sevencolours constituting white light and are called“rainbow” or Benton holograms. In fact, suchholograms are used on credit cards, magazinesand other commercial products to preventforgery. They find extensive use in the field ofadvertising, publishing and banking industries.

In 1972, Lloyd Cross developed a technique thatcombined white light transmission holographywith the conventional cinematography. In this wayhe was able to develop integral holograms, called“integrams” Looking through a transparentcylindrical drum, the three-dimensional imagescan be seen in motion. Such hologramsdescribing motion find applications in sciencefiction movies.

In 2008, optical scientists under leadership of TayPeyghambariam working at the University ofArizona College of Optical Sciences incollaboration with Nitto Denko TechnicalCorporation, Oceanside, California, U.S.A. couldmake 3-D holographic displays that could beerased and re-written in a matter of minutes.Their device consisted of a special plastic filmsandwiched between two pieces of glass eachcoated with a transparent electrode. In this devicethe images are “written” with the help of laserbeams and an externally applied electric field intothe light-sensitive plastic called ‘photorefractive’polymer. The holographic displays in this newtechnique are capable of showing a new imageevery few minutes.

Principle of Holography

Holography is actually a two stage process whichinvolves:

(i) Recording the hologram; and

(ii) Reconstruction of the image from the hologram.

For recording the hologram, a highly coherentlaser beam is divided by a beam splitter into twobeams, A and B. The beam A, known as thereference beam, hits the photographic plate

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directly. The beam B illuminates the object whosehologram is to be recorded .This gets scattered bythe object. The scattered beam, called the objectbeam, impinges on the photographic plate. Thesuperposition of the object beam and referencebeam produces an interference pattern which isrecorded on the photographic plate. Thehologram thus recorded is quite unintelligible andgives no idea about the image embedded in it.However, it contains all the information about theobject.

For viewing or reconstructing the image, thehologram is illuminated by the laser beam, whichis called the read-out beam. This beam is identicalwith the reference beam used during theformation of hologram. The points on thehologram act as diffraction grating. The wavesdiffracted through the hologram carry the phasesand amplitudes of the waves originally diffractedfrom the object during the formation ofhologram. The diffracted beam in general, givesrise to two images–one virtual and the other real.The virtual image has all the characteristics of the

object and can be seen on looking through thehologram. The real image, called pseudoscopicimage, can be photographed directly withoutusing a lens.

Instead of a conventional photographic film,holograms can also be recorded by using a digitaldevice, e.g. a charged-coupled device (CCD)camera. Known as digital holography, thereconstruction process in this case can be carriedout by digital processing of the recordedhologram using a standard computer. A three-dimensional image of the object can later bevisualized on a computer screen or TV set.

Applications of Holography

Holography has wide range of applications indiverse fields. We shall mention here some of theimportant applications of holography in scienceand technology.

An important application of holography is in thefield of information or data storage. The ability tostore large amount of information is of great

Fig. 1: Reading of a hologram Fig. 2: Reconstruction of the image

HOLOGRAPHY–THE FASCINATING WORLD OF 3-D VIEWING

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importance, as many electronic productsincorporate storage devices. The advantage ofholographic data storage is that the entire volumeof the recording media is used instead of just thesurface. Producing holographic CD storage isunder intense research and it is estimated that lTB(terarbite) data can be stored on a holographic CD.Certainly, holographic data storage seems to havethe potential of becoming the next generation ofpopular storage media.

Another major application of holography is in thecoding of information for security purposes andin preventing forgery. Holograms having securityfeatures are often used in credit and bank cards,books, DVDs, branded products, etc. Some Indianand foreign currency notes too carry the securityholograms.

Holographic microscopy is another potentialapplication of holography. As is known, aconventional microscope has a small depth offield (the range of depth over which an object is infocus at any microscopic setting).Biologicalspecimens, generally suspended in a fluid, moveabout making them sometimes in and sometimesout of focus of the microscope. However, thismotion can be “freezed” in a hologram takenthrough the microscope. The reconstructed 3-Dimage can then be studied at leisure.

Holographic interferometry is yet anothersignificant application of holography. lt can beused for testing stresses, strains and surfacedeformations in objects. Holographicinterferometry was actually a chance discoverymade in 1965 by a number of groups workingaround the world. R. L. Powell and K. A. Stetson atthe University of Michigan, Ann Arbor, made aninteresting discovery in that year. They found that

the holographic images of moving objects arewashed out. However, if double exposure is used,first with the object at rest and then in vibration,fringes will appear indicating the lines where thedisplacement amounted to multiples of a halfwavelength. In this way, Powell and Stetson couldreconstruct vibrational modes of a loudspeakermembrane and a guitar. The principle ofholographic interferometry by double exposurewas discovered simultaneously and independentlyin 1965 by Haines and Hildebrand of the Universityof Michigan, Ann Arbor and also by J.M. Burch inEngland and by G.W. Stroke and A. Lebeyrie inAnn Arbor, Michigan.

Non-destructive testing by holographicinterferometry is a very important industrialapplication of holography. The technique is able todetect even smallest defects. Applications ofholographic interferometry have, therefore, resultedin the improvement and reliability of products.

Medical diagnostics is a new and emerging field ofthe applications of holography. Some of theprominent fields of medical sciences in whichholographic technology is used are radiology,dentistry, urology, ophthalmology, orthopedics,pathology and so on. In the field ofophthalmology, for instance, any retinaldetachment or foreign body can easily bedetected.

Although holography has applications in diversefields it still is a relatively expensive procedure.However it is expected that with time we would beable to get over the cost factor and holographywill then have many more applications even ineveryday life. There is no gainsaying the fact thatpotential for holographic technology is indeedlimitless.

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O.P. AroraRegional Institute of EducationNational Council of Educational Research and TrainingBhopal

EPISODIC CONCEPTUALISATION–A POSSIBLE SOURCEOF ALTERNATIVE CONCEPTION ABOUT 'KINETIC ENERGY'AND 'WORK'

J.K. Mohapatra and B. K. ParidaRegional Institute of EducationNational Council of Educational Research and TrainingBhubanes war

In recent times, ‘Episodic Conceptualisation’ has been identified as one of the origins of pupils’ alternativeconceptions. It is hypothesized that the episodic format of the form, content, and mode of presentation of theconcepts ‘Kinetic Energy’ and ‘Work’ in the textbook as well as in the classroom by the teacher is likely togenerate in the minds of the pupils two isolated, mutually independent cognitive structures. It is conjectured thatany task, which demands conceptual and/or mathematical correlation between these two concepts, is likely tobring to the fore pupils’ alternative conceptions that are reflections of the above ‘Episodic Conceptualisation’. Theresults of the present study do indicate that there are enough evidences to put faith on our hypothesis andconjecture in the framework of these two concept labels.

Introduction

The form, structure and focus of pupils’alternative conceptions (hereafter referred asALCONs) in the recognizable cognitive structuresof pupils and their importance for the teaching-learning process have been well documented inthe last two decades through intensive andextensive researches on itemised concepts.Informative reference details in a discipline-wiseclassification format can be obtained from themonograph by Pfundt and Duit (1994). Thesestudies are interesting to researchers, informative

for curriculum framers, and educative forstudents of science education. But, in aframework of ‘research for teaching’ and‘teaching for research’, the full potential of thesefindings in helping the classroom practitioner toimprove /modify his/her teaching strategies sothat pupils can be helped to construct theirconcepts in a way the teacher expects them toconstruct, is yet to be realised. In fact, in an earlierpaper, Driver (1989) had commented that theefforts to optimise meaningful learning by usingthese findings in classroom situations haveresulted in partial to apparent success.

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We suggest that the functional limitation of theefforts could be due to the following reasons.

(1) The individualistic character of ALCONs hasremained the main hurdle that hasappreciably reduced the applicability of ourwealth of knowledge in this area. If, in a class,there are 30 pupils, then theoretically therewill be 30 independent ALCONs for each newconcept that is going to be taught. Thus, todiagnose these 30 ALCONs and then usethem meaningfully through cognitivenegotiation so as to help the pupils constructthe new concept becomes a Herculean taskfor the teacher. In some school systems, thenumber of pupils in a class is actuallymore than 30 thereby compounding theproblem further.

(2) All the techniques available in the literaturehave been used only to identify the ALCONsand not to diagnose their genesis. This is likeidentifying a disease without diagnosing itscause. Since it is acceptably true that anyprescription is as good as the quality ofdiagnosis about the cause, it is obvious thatsuggestions as well as efforts for the use ofthe research findings (about ALCONs) in aclassroom situation will have limited utility inthe absence of confirmed evidencesregarding the genesis of the ALCONs.

One possible way to remove the two limitations ata single stroke is to attempt to locate the genesis(thereby improving the functionality of aprescription) that is likely to produce a commonALCON in a group of pupils (thereby eliminatingthe problems created by the individualisticcharacter of the ALCONs).

Hence this study, which makes an effort toreconfirm Episodic Conceptualisation as apossible cause of group ALCONs as identifiedearlier by Mohapatra (1990), at least in Indiancondit ions.

Episodic Conceptualisation

Classroom teachers are often heard to say, “Wehave now finished ‘Mechanics’; in the next classwe move on to ‘Gravitation’”, or, similarstatements in other discipline areas. This‘atom ized’ view is seen in the school curric ulum,in teaching methods, and even in most of thetextbooks, at least in the Indian context. Acomprehensive example could be – in textbooks,‘Simpl e Harmonic Motion’ or ‘SHM’ is includedin the ‘Mechanic s’ chapter . ‘SHM’ is againdiscus sed with a different emphasis in thechapter on ‘Waves’. ‘SHM’ reappears withdiffer ent variables and thrusts in ‘A.C. Circuits’.And, finally, the principles of ‘SHM’ are againused and discus sed under wave theory of‘Optic s’. Each unit is treated as an is olatedepisode and sometimes even as a consumptionof identifiably different s ub-episodes. Forexampl e, in phys ics textbooks, the unit on‘Mechanics’ usually contains kinetics of linearmotion, uniform circular motion, and rotation ofrigid bodies as different sub-epis odes.

How is this episodic format likely to affectconceptualisation by pupils? In a Piagetian sense,each pupil internalises a concept by goingthrough the processes of assimilation,accommodation, and arriving at a state ofequilibration. In a Constructivist Framework(Glasersfeld, 1992(a); 1992(b); 1993) these three

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processes are controlled and effected by thepupil’s ALCONs, his/her ‘Cognitive Preference’(Tamir, 1985), his/her ‘Conceptual Categorisation’(Hewson and Thornley, 1989; Mohapatra, 1999),and finally result in a ‘Conceptual Change’ (Posneret al, 1982; Hewson and Thornley, 1989; Scott,Asoko and Driver, 1991; Mohapatra, 1997). With theacquisition of a new concept through conceptualchange leading to equilibration, one of fourpossibilities may occur:

(a) The boundary of the earlier equilibrationmay change to engulf the new concept. Thisis likely to happen when the pupil discoversa cognitive link between the new conceptand an extension of the already internalisedold concept (Conceptual integration:Hewson, 1981; Posner et al, 1982; Villani,1992; Mohapatra, 1997).

(b) The new concept may be accommodated inthe domain of the existing equilibration bydeveloping new substrates (Conceptualextension: Mohapatra, 1997).

(c) The new concept may be incorporatedstraight away in the existing structures(Conceptual capture: Hewson, 1981; Posneret al, 1982; Mohapatra, 1997).

(d) A new and different state of equilibrationmay start to be formed, if the new conceptpresented is intelligible, plausible andfruitful, but is in dissonance with theexisting structures (Villani, 1992; Mohapatra,1997).

The episodic format of the presentation ofdifferent units and sub-units in the textbooks andthe classroom is likely to induce the pupil to

develop pockets of isolated, unconnected statesof equilibration. This form of internalisation andinformation processing of concepts may be called‘Episodic Conceptualisation’ (EpiCon). Claxton(1984) calls concepts internalised by the pupils inthis process of conceptualisation as ‘mini-theories’ as it highlights the fact that the pupildoes not have a complete, comprehensive andcoherent theory, but has many little islands ofknowledge.

It is hypothesized (Mohapatra, 1990) that

(a) In the framework of such episodic cognitivestructures, if a pupil is asked a question thatneeds the simultaneous utilisation ofdifferent states of equilibration, then he/sheis likely to give responses which will becategorised as manifest ALCONs.

(b) Since such an EpiCon is likely to take placeinside a classroom, it will probably affect agroup of pupils simultaneously and in asimilar way. Hence an effective classroomstrategy can perhaps be designed to erase/modify the consequent ALCONs.

(c) Assuming the existence of the phenomenonof EpiCon it is proposed that, whenever asimultaneous application of more than oneepisode is demanded from the pupil, therewill be two processes through which theALCONs may manifest because of theEpiCon. First, the ‘process of misuse’ - thepupil may misuse one or more of the concepts.The misuse could be in the form, structure,and/or domain of validity of the concepts.Second, the ‘process of nonuse’- the pupil maynot use one or more of the relevant concepts

EPISODIC CONCEPTUALISATION–A POSSIBLE SOURCE OF ALTERNATIVE CONCEPTION ABOUT 'KINETIC ENERGY' AND 'WORK'

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and thus may arrive at a conclusion, which willbe regarded as an ALCON.

‘Kinetic energy’ and ‘Work’: theBackground

Children are exposed at a very early age to theterm ‘energy’, if not through textbooks, at leastthrough multimedia advertisements (Indiancontext), as “Beverage X is the source of myenergy.” Children see on the TV screen that theperson (model) drinks a cup of the beverage X andstarts running vigorously, ultimately securing firstposition in a race. Regular viewing of suchadvertisements obviously creates in the mind ofthe child an ‘anthropocentric’ framework (Watts,1983; Finegold and Trumper, 1989; Trumper,1990), i.e. ‘energy’ is associated with humanbeings. With this framework a cognitive imagewhere the term ‘energy’ seems to have closeassociation with a picture of vigorous expression/activity (a la kinetic energy) also gets embedded.Further, the child may also get reinforcement ofsuch an ideational structure from (Elkana, 1967)the Oxford English Dictionary, which defines‘energy’ as ‘force of vigour or expression’ andtraces it back to 1599.

In Indian schools, the concepts of ‘work’ and‘energy’ are included in Environmental Studies upto Class V in an informal way highlighting theeveryday meaning of these concepts rather thantheir formal scientific meaning. Again in Class VIthese concepts are presented in a mixed manneralong with ‘food’ in the chapter on Componentsof Food. In Classes VII and VIII, the concepts arealmost absent from the texts. The concepts of‘work’ and ‘energy’ are formally introduced in the

science textbook at Class IX in the chapter titled,Work and Energy. Starting with the everydaymeaning and scientific meaning of the term‘work’, work done by a constant force is definedas the product of the force and displacementoccurring in the direction of the force. ‘Energy’ isthen expressed in terms of ‘work’- “An objecthaving a capability to do work is said to possessenergy”. ‘Kinetic’ and ‘potential’ forms of energyare introduced next. Mathematical expression forkinetic energy possessed by a moving body isderived. Mathematical relation for computingpotential energy is also worked out for the case ofa body raised against gravity. Also discussed arethe transformation of energy from one form toanother and the law of conservation of energy (notthe law of conservation of energy and work).

Thus, by the end of Class IX, the pupils areexpected to have definite ALCONs about energy ingeneral and kinetic energy in particular as well asabout work. These ALCONs will ultimately control(Ausubel, 1968) their degree of meaningfullearning about ‘energy’ and ‘work’, taken inconjunction.

There have been a number of studies (Watts, 1983;Duit, 1984; Bliss & Ogborn, 1985; Gilbert & Pope,1982, 1986; Trumper, 1990, 1993, 1996, 1997;Finegold & Trumper, 1989) on pupils’ ALCONsabout energy. Attempts (Watts, 1983; Trumper,1997) have also been made to categorise theALCONs into classes. However, to the best of ourknowledge, no work is reported in the literaturewhich makes efforts to locate pupils’ ALCONs aswell as their genesis in the conceptual interfacebetween ‘kinetic energy’ and ‘work’, although thisis an important area since energy is defined as theability to do work.

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Episodes involving ‘Kinetic Energy’and ‘Work’

The following sub-episodes, involving kineticenergy and work, were identified by

• analysing the science textbooks (NCERT) ofclasses VI to X,

• observing actual classroom teaching,

• discussing with practicing teachers, and

• interviewing pupils of the above classes.

Each sub-episode is followed by a heading‘Result’, which indicates the thought process (asrevealed through interview) of the pupils becauseof the internalised sub-episode and alsohighlights the details of misuse and/or nonuse ofan episode by the pupils.

E1: Kinetic energy of a body depends on itsvelocity.

Result

(a) Velocity is the only key factor of kinetic energyof a body (This indicates misuse of E1).

(b) Some pupils are of the opinion that samekinetic energy means the same velocity (Thisindicates misuse of E1).

(c) Contribution of mass of a body to its kineticenergy is rarely taken note of (This indicatesnonuse of the fact that kinetic energy of abody depends also on its mass).

E2: Work is defined as the product of theapplied force and the displacement of the bodyin the direction of the force.

Result

(a) Work – Force ´ Distance traveled [Thisindicates (i) misuse of E2, (ii) nonuse of thevector property of force and displacement,and (iii) misusing ‘distance’ as synonymouswith ‘displacement’].

(b) As a corol lary of (a) above – If a body travelsthr ough a distanc e due to the applic ation ofa f orce, then work is done even if thedisplacement is zero or the angle betweenthe appl ied f orce and displac ement is 90°.

(c) For work to be done there m ust beapplication of a visible force like a push or apull ( This indicates nonuse of the statementthat ‘Energy is the ability to do wor k’ andconsequently, a body having energy c an dowork).

E3: Conversion of potential energy to kineticenergy in the case of vertic al free fall of abody.

Result

(a) Bodies released from the same height willattain the same velocity on reaching theground. So, they will have the same kineticenergy [This indicates misuse of E1 andeffects of ‘Result’ (b) and (c) of E1].

(b) If two different bodies ar e thrown vert ical lyup and have the sam e kinet ic ener gy at themoment of throw, they will rise to thesame height (This indicates misuse of E1and E3).

E4: Because of E3 the concept of gravity andgravitational force becomes a sub-episode in thecognitive domain of work and kinetic energy.


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Result

(a) Larger body means larger gravitational forceand hence larger velocity resulting in higherkinetic energy (This indicates misuse of E4).

E5: Because of E2, the concept of forcebecomes a sub-episode in the cognitive domainof wok and kinetic energy.

Result

(a) Same force acting for the same time leads tosame amount of work and same kineticenergy (This indicates misuse of E1 and E2).

(b) It is difficult to stop heavier bodies in motion(This indicates misuse of E2 and the conceptof force).

(c) As a subset of (b), above conclusions aboutthe effect of force of friction (introduced inClass VIII) are similar to (b) above.

E6: ‘Energy’, in general, and ‘kinetic energy’, inparticular, and ‘work’ are different episodes.

Result

(a) Difficult to conceive about the inter-conversion of kinetic energy and work (Thisindicates nonuse of E1, E2 and the conceptthat ‘Energy is the ability to do work’).

Method

Tool

The tool consists of six problems (Annexure – I).All of them are conceptual ones although some ofthem carry numerical data about masses ofobjects involved in motion. Each question hasthree choices as responses and the subjects wereasked to tick the one that in their opinion was the

correct response. Care was taken to provide somespace after every question, requesting thesubjects to write down the reasons for ticking anyparticular response. This provision was made toprobe their thought process. One (Q.4) out of theset of six questions was intentionally framed in aform similar to that in the prescribed textbookwith the intention of peeping into the stabilisedimprint in the minds of the pupils as produced bythe textbook. The tool was finalised after initial tryout on a sample of 50 pupils of Class X.

Sample

The sample consists of 334 pupils of Class Xdrawn from 5 schools, in and around the city ofBhopal. Care was taken to include governmentschools and schools run by private trusts. All theschools chosen were affiliated to the CentralBoard of Secondary Education (CBSE), New Delhi,India. This choice was prompted by the followingconsiderations.

• The medium of instruction in all theseschools is English. This uniformity is likelyto minimise differentiated ALCONs arisingout of linguistic differences.

• All the schools follow the same textbooksand hence the effects that are likely tomanifest due to different textbooks arealmost eliminated.

• As part of the conditions of affiliation, thescience teachers of all these schools aregraduates who have gone though at leastone year of professional teacher trainingprogramme. This is likely to bring somenormative effect on the teaching inputs andstyles of teaching science in these schools.

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• Even the physical facilities in these schoolsare above an optimal minimum, againbecause of the same affiliation conditions.

• Last, but not the least, the discipline in allthese schools is above satisfactory level and,as a result, rarely classes are droppedbecause of uncalled for reasons.

In Table 1, NCERT stands for National Council forEducational Research and Training, the apex bodyof the Government of India looking after thequality of school education, KVS acronym forKendriya Vidyalaya Sangathan, and JNVS is thatfor Jawaharlal Navodaya Vidyalaya Sangathan,

falling freely under gravity. Thinking this to bea similar phenomenon they may even tick thethird option, thereby forgetting that potentialenergy of a body raised to a height ‘h’ is massdependent because this potential energy isthe work done against the gravitational force.

(c) In the third question they are againconfronted with the situation of work beingconverted to kinetic energy. However, in thecontext of work, the concepts ‘force’ and‘distance’ are so deeply embedded in theirminds that they are likely to forget the role of

later two being the school systems also under theGovernment of India.

Administration

In the trial administration, it was observed thatpupils took about 30 minutes to complete thetest. Thus, the test was administered in a regularclass in presence of the class-teacher and in apupil friendly atmosphere.

Results and DiscussionsThe following can be easily discerned fromthe tool.

(a) The first question calls for the understandingof conversion of kinetic energy to workagainst the frictional forces of the brakes.But, from the pupils’ point of view, severalsub-episodes, like kinetic energy, work,frictional forces, their effects keeping in viewthe different masses of the two vehicles etc.come into play.

(b) The second question, though seems to befamiliar from the point of view of the pupils,is actually different in the sense that pupilsstudy the conversion of kinetic energy topotential energy only in the case of a body


Table 1: School-wise number of students of Class X constituting the sample

Name of the school No. of pupils Remark

Demonst ration Multi- purpose Schoo l (DMS) 57 Run by NCERT

Kendriya Vidyalaya No. 1 (KV 1) 74 Run by KVS

Kendriya Vidyalaya No. 2 (KV 2) 58 Run by KVS

Carmel Con vent (C C) 101 Run by pri vate trust

Jawaharlal Navo daya Vidyalaya (JNV) 44 Run by JNVS

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time interval here and be guided by theirepisodic conceptualisation [Refer ‘Result’ (a)of E5].

(d) Question 4 should be most familiar to themas it has a direct correspondence with what istaught in the class, but data regardingmasses will perhaps excite their mindsanother episode involving force and massapart from the episode of conversion of workto kinetic energy.

(e) Question 5 is again a variation of what theyhave studied and it brings into play theepisode of initial kinetic energy along with theepisode of free fall.

(f) Questions 1 and 6 have the same conceptualstructure but the situation in Q.1 is familiar tothe pupils and that in Q. 6, is unfamiliar. Thisunfamiliarity may activate different episodesin different pupils. Hence the pattern ofresponses of Q. 1 and Q. 6, though expectedto be similar, is likely to be different.

Percentage of pupils preferring particularresponses are presented in Table 2. In Table 2asteriked responses are the correct ones.

After the test was administered, the pupilspreferring incorrect responses were engaged ingroup discussions. The indications received fromwritten explanations by the pupils and the groupdiscussions about the interplay of episodes areshown in the last column in Table 2. In somecases it was discovered that pupils arrived at eventhe correct responses by employing wrongreasons, an example of which is given below.

Researcher : Against Q. 2 you have ticked theresponse (a) as correct.

Pupil : Yes, Sir.

Researcher : Congratulations, that is the correctanswer.

Pupil : Thank you, Sir.

Researcher : But let us discuss this a little more.How did you arrive at this answer?

Pupil : Sir, it is very simple.

Researcher : What is so simple about it?

Pupil : Sir, if the body is light, a force willproduce a greater velocity in it. (*)

Researcher : Greater velocity or greateracceleration?

Pupil : Sir, ultimately it amounts to thesame thing. (**)

Researcher : Then…………

Pupil : Sir, if the velocity is greater, then thebody will rise to a greater height.

Researcher : But in this case, the force which isacting due to gravity is downwardsand the body is moving upwards.

Pupil : (Thinks) … Sir … Yes … Sir … But …

Researcher : So, what is ‘But’?

Pupil : Sir, I do not know. But I know A’svelocity will be more and it will riseto a greater height. (***)

The response, (*), clearly shows the activation ofE2 and manifestation of an ALCON. Response,(**), is also an ALCON arising out of conceptual

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Table 2 : Percentage of pupils pref erring each re sponse, question-wise(The asteriked responses are the correct o nes)

1. a 21.0 40.5 39.6 51.5 45.4 41.0 E5, E6

b 50.8 43.2 37.9 27.7 27.3 36.8 E2, E6

c* 28.0 16.2 20.7 16.8 27.3 20.6

2. a* 73 .7 71.6 56.9 80.0 61.4 70 .6

b 26.3 17.6 25.8 14.8 31.8 21.5 E4, E5

c 1.8 13.5 17.2 3.0 6.8 8.1 E3

3. a 64 .9 48 .6 53.4 42.6 47.7 50.3 E1, E2

b* 26.3 28.4 22.4 28 .7 29.5 27.2

c 12.3 20.3 29.3 13.8 18.2 18.3 E2

4. a 15.8 44.6 13.8 34.6 34.1 29.9 E1, E2, E6

b 68 .4 40.5 55.1 34.6 45.4 46.7 E1, E2, E6

c* 15.8 13.5 31.0 31.7 13.6 22.4

5. a 70.0 40.5 48.3 60.4 43.2 53.3 E4, E5

b* 10.5 4.0 6.4 10.9 9.1 8.2

c 17.5 52.7 43.1 24.7 47.7 32.7 E4, E5

6. a 42.0 54.0 55.2 49.5 54.5 50.9 E2, E5, E6

b 52.6 23.0 24.1 31.7 25.0 31.1 E5, E6

c* 3.5 14.9 18 .9 16.8 20.4 14.9

Q. No. Suggestedresp onsesymbol

Percenta ge of pupils pr eferring each responseEp isod esinvolved

Various schools

DMS KV1 KV2 CC JNV All Schools

continuity (Mohapatra and Bhattacharya, 1989).The response, (***), shows an ad hoc element inthe conceptualisation scheme of the pupil.

Some of the identified key ALCONs arising out ofthe episodic nature of internalisation of theconcepts ‘kinetic energy’ and ‘work’ in this studyare the following.

• The loaded truck will travel a longer

distance because its mass is more and it willbe difficult to stop it.

• Two bodies of different masses thrownvertically upwards with the same kineticenergy will rise to the same height becausetheir kinetic energy is the same.

• If two bodies are acted upon by the sameforce for the same time they will have the

EPISODIC CONCEPTUALISATION : A POSSIBLE SOURCE OF ALTERNATIVE CONCEPTION ABOUT 'KINETIC ENERGY' AND 'WORK'

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same kinetic energy as the time for whichthe force acts is the same.

• If two bodies are acted upon by the sameforce until they travel the same distance,then the lighter body of the two will havegreater kinetic energy as its velocity will belarger.

• If two bodies are released from the sameheight with the same kinetic energy, thenboth will reach the earth’s surfacesimultaneously since the height of release isthe same.

At this time, it is worthwhile to look at theresponses to Q.4, which we thought was mostfamiliar to the pupils. Even in this case, about15per cent to 30 per cent pupils of variousschools and 22 per cent when all schools aretaken together, have ticked the correct response.For the rest 78 per cent their episodicconceptualisation has controlled their responses.This again indicates the strong effects of episodicconceptualisation. We also note in passing that insome cases the percentages do not add up to 100.This is so because in those cases some pupils didnot tick any of the responses.

Conclusion

By a fairly broad-based strategy we have identifiedin this study the structures of the episodes/sub-episodes in the minds of pupils in the domain ofinteraction of the concepts ‘kinetic energy’ and‘work’. Through discussions with the pupils andtheir written explanations, the possible ALCONsgenerated by these episodes/sub-episodes havebeen located. The interplay of the episodes/sub-

episodes (which are perhaps unconnectedstructures in the pupils’ comprehension domain)when more than one of them is simultaneouslyactivated, is then investigated to diagnosemanifest ALCONs. The tool used for thiscomprises six conceptual problems.Consequently, it did not put any demand on theskills of the pupils such as

• numerical computation,

• transforming symbols in formulae tonumbers by substituting the given data, and

• interpretation of the results, obtainedthrough numerical calculations.

Thus, any ALCONs, which are likely to arise out ofthe pupils’ deficiencies in these skills, have beenminimised.

To eliminate the ALCONs, the following strategiesare suggested, which can be used to promotemeaningful learning and reduce episodicconceptualisation, in this context, to theminimum.

• Enough emphasis be given on theinterchangeability of ‘energy’ and ‘work’, ingeneral and ‘kinetic energy’ and ‘work’, inparticular, keeping in view the accepteddefinition that energy is the ability to dowork.

• Activities be developed to demonstrate theabove interchangeability. As for example,pupils may be asked the following:

— We know that a duster on the table haspotential energy equal to mgh, where mis the mass of the duster and h is theheight of the table. Since ‘energy is the

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ability to do work’, design an experimentto show that the duster can do work.

— Thought provoking, interesting andchallenging conceptual problems maybe given. As for example,

— When a bow is taut, it is said that thebow has potential energy. Describe howthis energy is transformed to work.

— A steel ball is rolling on a table having

friction. After travelling some distanceit comes to rest. In the above processdescribe who is doing work.

Of course, each of the problems used here as testitems of the tool may also be used as problems ina classroom situation.

One of the authors is thankful to R. Trumper forproviding a few supportive literatures involving theconcept of energy.

References

AU SU BEL, D .P. 1968 . Ed ucat io nal Psycho lo gy : A C og ni ti ve V iew. Holt, R in eh art an dWinston, New York.

BLISS, J. and J. OGBORN, J. 1985. Children’s Choices of Uses of Energy, European Journal of ScienceEducation, 7, 195-203.

CLAXTON, G. L. 1984. Teaching and Acquiring Scientific Knowledge. In R. Keen and M. Pope (Eds.),Kelly in the Classroom: Ed ucatio nal App lications of Person al Con struct Psy cho log y.Cybersystems, Mon treal.

DRIVER, R. 1989. Students’ Conception and the Learning of Science. International Journal of ScienceEducation, 11(5), 481-190.

DUIT, R. 1984. Learning the Concept in School–Empirical results form the Philippines and WestGermany, Physics Education, 19, 55-66.

ELKANA, Y. 1967. The Emergence of the Energy Concept. Unpublished Doctoral Dissertation. BrandeisUniversity, Waltham, MA.

FINEGOLD, M. and R. TRUMPER. 1989. Categorising pupils’ Explanatory Frameworks in Energy as aMeans to the Development of Teaching Approach. Research in Science Education, 19, 97-110.

GILBERT, J. K. and POPE, M. 1982. School Children Discussing Energy. Report, Institute of EducationalDevelopment, University of Surrey.

GILBERT, J. K. and M. POPE. 1986. Small Group Discussions about Conceptions in Science. Researchin Science and Technology Education, 4, 61-76.

GLASERSFELD, E. von. 1992. a. A Constructivist’s View of Learning and Teaching. In R. Duit, F. Goldbergand H. Niedderer (Eds.), R esearch in Physics Learning: Theoretical Issues and EmpiricalStudies. Kiel, Germany: IPN at the University of Kiel.


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GLASERSFELD, E. V on. 1992 b . Constructivism Reconstructed: A Reply to Suchting. Science andEducation, 1, 379-384.

GLASERSFELD, E. VON. 1993. A constructivist Approach to Teaching. In L. Steffe and G. Gale (Eds.),Constructivism in Education. : Lawrence Earlbaum, Hillsdale, N. J.

HEWSON, P. 1981. A Conceptual Change Approach to Learning Science. European Journal of ScienceEducation, 3(4), 383-396.

HEWSON, P. W. and THORNLEY, R. 198 9. The Condition s of Conceptual Change in the Classroom.International Journal of Science Education, 11(5), 541-553.

MOH APATR A, J. K. 1990. Episodic Conceptualisat ion: a Po ssible Cau se o f Man ifest Alt ernat iveConceptions Amongst Group of Pupils in Some Indian Schools. International Journal of ScienceEducation, 12(4), 417-427.

MOHAPATRA, J. K. 1997. Taxonomy of Conceptual Change: Review of Two Anchoring InstructionalStrategies and a Functional Model of Teaching. Indian Educational Review, 32(1), 36-55.

MOHAPATRA, J. K. 1999. Taxonomy of Curriculum Designing: A Study of Inputs. Journal of IndianEducation, 15(3), 39-51.

MOHAPATRA, J. K. and S. BHATTACHARYA. 1989. Pupils,Teachers, Induced Incorrect Generalisations andthe Concept force. International Journal of Science Education, 11(4), 429-436.

PFUNDT, H. and R. DUIT. 1994. Bibliography: Students’ Alternative Frameworks and Science Education.IPN Reports in Brief. Kiel, West Germany: Institute for Science Education, University of Kiel.

POSNER, G. J., K. A. STRIKE, P. W. HEWSON and W. A. GERZOG. 1982. Accommodation of a Scientificconception: Towards a Theory of Conceptual Change. Science Education, 72(1), 103-113.

SCOTT, P. H., H. M. ASOKO and R. DRIVER. 1991. Teaching for Conceptual Change: A Review of Strategies.Pro ceed ings of the Bremen In tern atio nal Workshop on R esearch in Ph ysics Learning:Theoret ical Issues an d Empirical Studies.

TAMIR, P. 1985. Meta Analysis of Cognitive Preference and Learning. Journal of Research in ScienceTeaching, 22(1), 1-18.

TRUMPER, R. 1990. Being Constructive: An Alternative Approach to the Teaching of Energy Concept,Part I. International Journal of Science Education, 12, 343-354.

TRUMPER, R. 1993. Children’s Energy Concept: a Cross-age Study. International Journal of ScienceEducation, 15, 139-148.

TRUMP ER, R. 1996. A Survey of Israeli Physics Stud ents’ Co nceptio ns of En ergy in Pre-serviceTraining for High-school Teachers. Research in Science and Technology Education, 14, 179-192.

TRUMPER, R. 1997. The Need for Change in Elementary School Teacher Training: the Energy Conceptas an Example. Educational Research, 39(2), 157-174.

VILLANI, A. 1992. Conceptual Change in Science and Science Education. Science Education, 76(2),223-237.

WATTS, M. 1983. Some Alternative Views of Energy. Physics Education, 18, 213-217.

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Learning does not just mean studying for additionto qualifications or to improve job opportunities.It should be geared up to open up one's mentalabilities to explore a wide range of activities thatfacilitate widening the horizon of understandingnature and natural phenomena besides expandingscope for and physical opportunities. NCERT iscommitted to building a world-class educationand training framework. In order to accomplishits mandate for improving the quality of schooleducation it strives continuously to develop,upgrade and modernise school curriculum,assessments and examinations. Main objective ofthese interventions is to provide a coherent andintegrated curriculum and assessmentframework for schools, which, in turn, may raisestandard of achievement and widen educationalopportunity.

Nanoscience and nanotechnology has led to anunprecedented excitement in the scientific andengineering communities, especially during thelast decade. The recent revolutionary advances innanoscale phenomena open exciting, new avenues

for research and discovery. The potentialcontributions of advances in nanoscalephenomena to improve human health createdeven more excitement by envisioning newbiomaterials, devices and techniques forbiological detection and remediation. Thus, issuessuch as synthesis, fabrication andcharacterisation of functional nanomaterials andnanostructures for biomedical applications(molecular recognition, nanotubes, nanowires,nanoparticles, self-assembly, polymer-basednanomaterials, thin films, medical imaging,diagnosis and therapy, etc.) become veryimportant. In recognition of this potential, we areproposing a new curriculum at senior secondarylevel school education. We also provide a lessonplan that would help teachers in dealing with thistopic of interest.

Nanotechnology deals in the realm of the nearlyinvisible. The word comes from the Greek nanos,meaning “dwarf”. But by most accounts, thetechnology’s potential is anything but small.Scientists and engineers can now physically work

R. RavichandranRegional Institute of EducationNational Council of Educational Research and TrainingBhopal

P. SasikalaComputer Scie nce Department, Makhanla l ChaturvediNational Unive rsity, Bhopal

NANOSCIENCE CURRICULUM IN SCHOOL EDUCATIONINTEGRATING NANOSCIENCE INTO THE CLASSROOM

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with materials at the atomic level to create stain-proof fabrics, scratch-resistant paints and longer-lasting tennis balls. And researchers say newmedical diagnostic tools and smaller, moreefficient fuel cells and batteries based onnanoscience are on the way.

According to Chad Mirkin, Director of the Institutefor Nanotechnology at Northwestern University,“It has only been in recent times that we’ve had thetools that allow us to manipulate atoms andmolecules. There is a big shift here in the way weapproach science and the way we approachengineering and ultimately the way we approachmedicine. And I think in many respects it isrevolutionary.”

From computer chips invisible to the naked eye tomicroscopic machines that seek out and destroycancers inside the human body, many scientistscontend that the potential of nanotechnologycould be endless, but not without controversy.There are hundreds of nano-enhanced productsalready in the marketplace. But there are virtuallyno regulatory guidelines for their manufactureand distr ibution.

Nanotechnology Lesson Plan

This lesson plan has been prepared to serve as amodel to help senior secondary school scienceteachers to develop their own plan for anintroduction to nanotechnology in a classroomsetting.

Introduction to the Concepts of Nanotechnologyis the study and use of structures between 1nanometre and 100 nanometres in size.

A s k the s tudents : What is the smallest thing

you can imagine? Answers might include a humanhair, the head of a pin, or an atom.

Reading : Now have students read the following :

Introduction to Nanotechnology

Nanotechnology is defined as the study and use ofstructures between 1 nanometre and100 nanometres in size. To give you an idea ofhow small that is, it would take eight hundred100 nanometre particles side by side to match thewidth of a human hair.

Looking at Nanoparticle

Scientists have been studying and working withnanoparticles for centuries, but the effectivenessof their work has been hampered by their inabilityto see the structure of nanoparticles. In recentdecades the development of microscopes capableof displaying particles as small as atoms hasallowed scientists to see what they are workingwith.

Figure 1 provides a comparison of various objectsto help you begin to envision exactly how small ananometre is. The chart starts with objects thatcan be seen by the unaided eye, such as an ant, atthe top of the chart, and progresses to objectsabout a nanometre or less in size, such as theATP molecule that store energy from food inhumans.

Now that you have an idea of how small a scalenanotechnologists work with, consider thechallenge they face. Think about how difficult it isfor many of us to insert thread through the eye ofa needle. Such an image helps you imagine theproblem scientists have while working with the

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nanoparticles that can be as much as onemillionth the size of the thread. Only through theuse of powerful microscopes can they hope to‘see’ and manipulate these nano-sized particles.

The Nanotechnology Debate

There are many different points of view about thenanotechnology. These differences starts with thedefinition of nanotechnology. Some define it asany activity that involves manipulating materialsbetween one nanometre and 100 nanometres.However, the original definition ofnanotechnology involved building machines at themolecular scale and involves the manipulation ofmaterials on an atomic (about two-tenths of ananometre) scale.

The debate continues with varying opinions aboutexactly what nanotechnology can achieve. Someresearchers believe nanotechnology can be usedto significantly extend the human lifespan orproduce replicator-like devices that can createalmost anything from simple raw materials.Others see nanotechnology only as a tool to helpus do what we do now, but faster or better.

The third major area of debate concerns thetimeframe of nanotechnology-related advances.Will nanotechnology have a significant impact onour day-to-day lives in a decade or two, or willmany of these promised advances takeconsiderably longer to become realities?

Finally, all the opinions about whatnanotechnology can help us achieve echo withethical challenges. If nanotechnology helps us toincrease our lifespans or produce manufacturedgoods from inexpensive raw materials, what is themoral imperative about making such technologyavailable to all? Is there sufficient understanding

or regulation of nanotech based materials tominimise possible harm to us or ourenvironment?

Only time will tell how nanotechnology will affectour lives, the following topics will help youunderstand the possibilities and anticipate thefuture. The following section is dedicated toprovide clear and concise explanations ofnanotechnology applications.

Nanotechnology Applications

The ability to manipulate nano-sized materials hasopened up a world of possibilities in a variety ofindustries and scientific endeavors. Becausenanotechnology is essentially a set of techniquesthat allow manipulation of properties at a verysmall scale, it can have many applications, suchas:

D r ug del iver y: Today, most harmful side effectsof treatments such as chemotherapy are a resultof drug delivery methods that don’t pinpoint theirintended target cells accurately. Researchers atHarvard and MIT have been able to attach specialRNA strands, measuring about 10 nanometres indiametre, to nanoparticles and fill thenanoparticles with a chemotherapy drug. TheseRNA strands are attracted to cancer cells. Whenthe nanoparticle encounters a cancer cell itadheres to it and releases the drug into the cancercell. This directed method of drug delivery hasgreat potential for treating cancer patients whileproducing less side effects than those producedby conventional chemotherapy.

F abr ic s : The properties of familiar materials arebeing changed by manufacturers who are addingnano-sized components to conventional materials

NANOSCIENCE CURRICULUM IN SCHOOL EDUCATION–INTEGRATING NANOSCIENCE INTO THE CLASSROOM

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Fig. 1 The Scale of Things: Nanometres and more(Source: www. highlight healt h. com/... /2009/10/ telom ere.gif)

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to improve performance. For example, someclothing manufacturers are making water andstain repellent clothing using nano-sizedwhiskers in the fabric that cause water to bead upon the surface.

Making composite fabric with nano-sizedparticles or fibres allows improvement of fabricproperties without a significant increase inweight, thickness, or stiffness as might have beenthe case with previously used techniques.

Reac t iv ity of m ater ia l s : The properties ofmany conventional materials change when formedas nano-sized particles (nanoparticles). This isgenerally because nanoparticles have a greatersurface area per weight than larger particles; theyare therefore more reactive to some othermolecules. For example, studies have shown thatnanoparticles of iron can be effective in thecleanup of chemical in groundwater because theyreact more efficiently to those chemicals thanlarger iron particles.

S trength of Mater ia l s : Nano-sized particles ofcarbon, (for example nanotubes and bucky balls)are extremely strong. Nanotubes and bucky ballsare composed of only carbon and their strengthcomes from special characteristics of the bondsbetween carbon atoms. One proposed applicationthat illustrates the strength of nanosized particlesof carbon, is the manufacture of bullet proofvests made out of carbon nanotubes which weighas less as a T-shirt.

Mic ro/Nano El ectroMechanical System s :The ability to create gears, mirrors, sensorelements, as well as electronic circuitry in siliconsurfaces allows the manufacture of miniaturesensors such as those used to activate the airbags

in your car. This technique is called MEMS (Micro-Electro-Mechanical Systems). The MEMStechnique results in the integration of themechanical mechanism with the necessaryelectronic circuit on single silicon chip, similar tothe method used to produce computer chips.Using MEMS to produce a device reduces both thecost and size of the product, compared to similardevices made with conventional methods.MEMS is a stepping stone to NEMS orNanoElectroMechanical Systems. NEMS productsare being made by few companies, and will takeover as the standard, once manufactures makethe investment in the equipment needed toproduce nano-sized features.

Molec ul e Manuf ac tur ing : If you’re a Star Trekfan, you remember the replicator, a device thatcould produce anything from a space age guitarto a cup of Earl Grey tea. Your favourite characterjust programmed the replicator, and whatever heor she wanted appeared. Researchers are workingon developing a method called molecularmanufacturing that may someday make the StarTrek replicator a reality. The gadget these folksenvision is called a molecular fabricator; thisdevice would use tiny manipulators to positionatoms and molecules to build an object ascomplex as a desktop computer. Researchersbelieve that raw materials can be used to almostany inanimate object using this method.

Medic ine : Researchers are developingcustomised nanoparticle size of molecules thatcan deliver drugs directly to diseased cells in thebody. When it’s perfected, this method shouldgreatly reduce the damage treatment such aschemotherapy, does to a patient’s healthy cells.Nanomedicine refers to future developments in

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medicine that will be based on the ability to buildnanorobots. In the future these nanorobots couldactually be programmed to repair specificdiseased cells, functioning in a similar way toantibodies in our natural healing processes.

E l ec tr onic s : Nanotechnology holds someanswers for how we might increase thecapabilities of electronic devices while we reducetheir weight and power consumption.

S pac e : Nanotechnology may hold the key tomaking space-flight more practical. Advancementin nanomaterials make lightweight solar sails anda cable for the space elevator possible. Bysignificantly reducing the amount of rocket fuelrequired, these advances could lower the cost ofreaching orbit and travelling in space.

F ood : Nanotechnology is having an impact onseveral aspects of food science, from how food isgrown to how it is packaged. Companies aredeveloping nanomaterials that will make adifference not only in the taste of food, but also infood safety, and the health benefits that fooddelivers.

F uel Cel l s : Nanotechnology is being used toreduce the cost of catalysts used in fuel cells toproduce hydrogen ions from fuel such asmethanol and to improve the efficiency ofmembranes used in fuel cells to separatehydrogen ions from other gases as oxygen.

S ol ar Cell s : Researchers have developednanotech solar cells that can be manufactured atsignificantly lower cost than conventional solarcells.

Batter ies : Work is currently being done fordeveloping batteries using nanomaterials. One

such battery will be as good as new even afterremaining on the shelf for decades. Anotherbattery can be recharged significantly faster thanconventional batteries.

F uels : Nanotechnology can address theshortage of fossil fuels such as diesel andgasoline by making the production of fuels fromlow grade raw materials economical, increasingthe efficiency of engines, and making theproduction of fuels from normal raw materialsmore efficient.

Better A ir Qual ity : Nanotechnology canimprove the performance of catalysts used totransform fumes escaping from cars or industrialplants into harmless gases. That is becausecatalysts made from nanoparticles have a greatersurface area to interact with the reactingchemicals than the same quantity of catalystscomprising larger particles. The larger surfacearea allows more chemicals to interact with thecatalyst simultaneously, which makes the catalystsmore effective.

Cl eaner Water : Nanotechnology is being usedto develop solutions to three very differentproblems in water quality. One challenge is theremoval of industrial wastes, such as a cleaningsolvent called TCE, from groundwater.Nanoparticles can be used to convert thecontaminating chemical, through a chemicalreaction into harmless material. Studies haveshown that this method can be used successfullyto reach contaminates dispersed in undergroundponds and treat them at much lower cost thanconventional methods which require pumping thewater out of the ground for treatment.

Chem ic al S ens or s : Nanotechnology can

40


enable sensors to detect very small amounts ofchemical vapours. Various types of detectingelements, such as carbon nanotubes, zinc oxidenanowires or palladium nanoparticles can be usedin nanotechnology-based sensors. Because of thesmall size of nanotubes, nanowires, ornanoparticles, a few gas molecules are sufficientto change the electrical properties of the sensingelements. This allows the detection of a very lowconcentration of chemical vapours.

S por ts Goods : If you’re a tennis or golf player,you’ll be glad to hear that even sports goods haswandered into the nanotechnology applications inthe sports arena include increasing the strengthof tennis racquets, filling any imperfections inclub shaft materials and reducing the rate atwhich air leaks from tennis balls.

D is c uss ion : Hold a discussion in the classabout the basic concepts of nanotechnology,which might include issues like :

• You learned in this introduction that scientistshad to imagine the characteristics ofnanoparticles for years before they developedspecial microscopes that allowed them to seethem. What would it be like to work with amaterial you can’t see? Are there other fieldsof science where you work with things youcan’t see? (Radio waves, gravity, etc.)

• Whic h is bigger : A nanoparticle, an atom,or a molecule? Discuss the fact that,depending on the composition and numberof atoms in a molecule, it can vary from ananometre in diametre to hundreds ofnanometres in length. Similarly, differenttypes of atoms may have diametres rangingfrom a tenth of nanometre to 5 tenths of a

nanometre. Nanoparticles also vary in size,ranging up to 100 nanometres. All of thesecan be measured in nanometres, ameasurement with a constant size of onebillionth of a metre.

Explore an Application ofNanotechnology

D is c uss ion : Some scientific fields focus onone type of material or process, such asbiology that focuses on living organisms andmetreeology that focuses on the weather. Whatdoes nanotechnology focus on? Remind thestudents of the definition of nanotechnanotechnology; this study of structures ofsmall size can be applied in just about any field.Nanotechnology is currently being used inmedicine, the environment, to add strength tomaterials such as fabrics, space flight, and so on.

Reading : Have students search over as manyprocesses of information as possible includingthe internet and pick few pages to read.Encourage them to follow links on the site foradditional information, if they find it interesting.Have them create a brief report about what theyhave read and present it to the class.

The Future of Nanotechnology

Explain that nanotechnology has the potential tobe a disruptive technology, meaning that it couldcause extreme change in our society that couldhave a wide range of consequences. An exampleof this would be the industrial revolution, whichchanged the economy of most of our culturesfrom agrarian to manufacturing based.

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D is c uss ion : Pick one of these topics:

• The molecular replicator, once developed,could allow people to simply produce manyitems they need themselves with no need fora company to manufacture those products.What would this do to our economy as weknow it today? What if everybody couldproduce their own clothing, iPod, and shoes?Would it help poorer people or would it putpeople out of work? How would the worldchange?

• In the world of medicine nanotechnologycould change the human lifespan. Repairs atthe cellular level could stop and even reverseaging. If everybody could live hundreds ofyears, what would happen to our world?Would only an elite few get such treatmentand what consequences would that have? Ifnobody ever died, would people have to stophaving children to avoid overpopulation?What would that mean to our society?

One can hold a discussion with the entire class, orbreak up into smaller groups with some groupsmaking an argument for the benefits of thesechanges, and the other groups arguing the casethat such changes would bring more harm thangood to our society.

Opt ional A c t iv ity : Hold debates between thegroups on the above discussion topics.

Wrap up the lesson by pointing out thatnanotechnology offers great potential foradvancement, and that, as with any scientificbreakthrough, it also raises ethical andsocietal questions.

The following is a model syllabus onnanotechnology that it can be most suitable foradoption at senior secondary level. The proposedsyllabus is conceived for four semesters afterclass Xth. In semester format one can pursueissues more deeply and explore a wider variety ofquestions.

Nanoscience I• Biology• Algebra• Computer Literacy• Writing and Research

— Cell Structure— DNA Extraction— Gel Electrophoresis— Enzyme and Protein Structures— Tagging methods

Nanoscience II

• Chemistry• Physics• Mathematics• Communication

— Periodic Table— Molecules— Compounds— Physical properties— Electrical properties— Band structures— Computer Simulation— Basics of modelling programmes— Input requirement— Reliability— Variations

• Observational Internship


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Nanoscience III

• Nanoelectronics— Serve as an introduction to electrical

structures— Processor and memory device design and

fabrication— Emerging technologies: quantum,

photonics, nanowires, molecular• Nanobiotechnology

— Serve as an introduction to the field— Energy production and enzymatic

processes— Protein interactions

• Nanomaterials— Introduction to material properties and

manufacturing methodologies— Adhesion, tension, friction, viscosity, etc.,— Impact of manufacturing and operational

environments

Nanoscience IV• Advanced Fundamental Courses• Micro and Nano Fabrication• Thin Film Deposition• Introduction to Materials Characterisation• Principles and Applications of

Nanobiotechnology• Industry Internship

Picture on page 33 : Tiny nanogears may one day move microscopic machines through the humanbody in search of disease. (Source: www. highlighthealth. com/.../2009/10/telomere.gif)

Introduction

In 1986, Antoine Henri Becquerel, a Frenchphysicist, while working on phosphorescentmaterials such as uranium salts, found that theyemit radiations spontaneously. It was laterestablished that a magnetic or an electric fieldsplits such radiations into three beams. Theseradiations have been named after the first threeletters of the Greek alphabet, i.e., alpha (α), beta (β)and gamma (γ). The first two radiations arecorpuscles in nature so they are called particleswhereas the third, being electromagneticradiation, is called a ray. The elements, whichspontaneously emit such type of radiations, arecalled radioactive elements and the phenomenonis known as radioactivity. For discovery of theseradiations, Becquerel received Nobel Prize forPhysics jointly with Marie Curie and Pierre Curiein 1903.

Before going into detail of the phenomena it isimperative to understand the structure of anatom. An atom consists of a positively chargedcentral core, the nucleus, and negatively chargedelectrons which revolve round the nucleus in fixed

orbits. The nucleus contains positively chargedparticles protons and neutral particles neutrons.Either a proton or a neutron is called a nucleon. Inthe normal state of the atom, the number ofprotons is equal to the number of electrons, sothat the atom is electrically neutral. The number ofprotons is constant and unique to a particularatom and is called the atomic number (Z) whereasthe number of protons plus number of neutronsin the nucleus give the mass number (A). Sincelike charges repel one another, the protons withinthe nucleus are always trying to push each otherapart but they are held together by the attractivenuclear forces resulting from the combinedprotons and neutrons. When there is imbalancebetween the attractive nuclear forces and theelectrostatic repulsive forces (Coulomb replusion),the nucleus does not have enough binding energyto hold permanently the nucleons together, as aresult of which it becomes unstable. In unstablenuclei the binding energy per nucleon is very low.It is found that all nuclei with Z > 83 and A ≥ 210achieve greater stability by emittingspontaneously one or more α– particles (helium –4 nuclei), called

Prasanta Kumar PatraCentre for Science Education, NEHUShil lo ng

ENERGY AND ELECTRONIC CHARGE CONSERVATIONDURING ALPHA AND BETA EMISSION

44


α– particles (helium –4 nuclei), called α– emission.Again, it is observed that in stable nuclei the ratio

of neutron number to proton number

np is

usually between 1 and 1.5 (excluding the hydrogennucleus which consists of only one proton)(Marmier, 1969). So the nucleus becomes unstable

when it possesses either a higher np value than

that for stable nuclei by containing excess

neutrons or a lower np value by containing excess

protons. In the former case it emits an electron,called β–– emission, and in the latter case it emitsa positron called β+– emission, to dissipate excessenergy.

(A) Alpha Emission

After α– emission the original atom transformsinto a new atom of some other element whoseproton and neutron numbers each decreases byby 4 and 2 units respectively. In general this isrepresented as

4 42 2

A AZ ZX Y He Q− + +

−→ + + (1)

where X and Y are symbols for the parent and theresidual atoms respectively and Q, the decayenergy, is shared by the kinetic energy of theα– particle and the recoil energy of the resultingatom. From equation (1), it is clear thatα– emission is only possible if Q value is positive.

For example,

238 234 492 90 2 4.19 ,U Th He MeV++→ + + (2)

where mega electron volt (MeV) is the unit ofenergy (1 eV = 1.6 × 10–19 joule).

(i) Conservation of Energy during α–Emission

In equation (2), sum of masses of the products (athorium-234 and an α-particle) is less than massof the parent atom. The decrease in mass isconverted to energy according to Einstein's massenergy equivalence relation E = mc2, where E is thetotal energy, m the effective mass and c thevelocity of light in free space (c = 3 × 108m/s). Thisenergy is shared by the residual thorium atom andthe emitted α–particle. Since α–particle is quitelighter than thorium atom, most of the energyreleased is carried by the α-particle.

(ii) Conservation of Electronic Charge duringα–Emission

It appears from equation (2) that the electroniccharge is unbalanced although proton number isconserved in the equation. If we count thenumber of protons, neutrons and electronspresent in the parent and the residual atoms ofequation (2), we find that the parent atom has 92protons,146 neutrons and 92 electrons whereas theresidual atom will have 90 protons, 144 neutronsand 92 electrons as an α–particle contains twoprotons and two nuetrons only. This reveals thatthe residual atom has excess of two electronscompared to its total number of protons. Thus itis an ion. It is observed that at the time of decaythe residual atom as well as the α–particle is inionic form but subsequently they acquireneutrality. The question arises what happens tothese extra electrons in the residual thoriumatom? It appears that a continuous range ofvalues, ranging, from zero up to some maximum

44

45

value rather than a discrete value (Beiser, 2006;Evans, 1978). This is in apparent contradiction tothe law of conservation of energy. It has been agreat puzzle. A second problem is that theemitted electron does not usually travel in adirection opposite to that of the residual atom asin a two-body decay, which shows an apparentviolation of conservation of linear momentum. Athird problem is that spins of the neutron,proton and electron (in units of h/2p) are all ½,so the spins (and hence also angularmomentum) is not conserved in equation (3).

All these apparent discrepencies were accountedfor Wolfgang Pauli in 1931 (Beiser, 2006; Evans,1978). He suggested that in addition to electron,another extremely light particle is also emittedand these particles share the energy available in

147 N . This suggestion explains the observed

continuous energy spectrum of the emittedelectrons. This new particle has to be electricallyneutral to conserve charge and has spin of (1/2)(h/2π) to conserve angular momentum. EnricoFermi has named this particle as 'neutrino'("little neutral one" in Italian). Later it was

recognised as electron-antineutrino ( ev ) toconserve lepton number which must beconserved in weak interaction that causes betaemission. The lepton number is experimentallydeterminable just like electric charge and itsvalue is +1 for leptons such as electron, muon

(µ), tau (τ) and their associated neutrinos ( ev , µv

and τv ) and –1 for antileptons. The decay

equation (3) can thus be modified as

1 1 00 1 –1→ + + +en p e v Q (5)

The existence of neutrinos has beenexperimentally observed by Cowan and Reines(Cowan et al., 1956). The general transformationequation describing β– emission becomes

01 –1+→ + + +A A

Z Z eX Y e v Q (6)

The continuous energy carried by the electroncan be explained in the following way. In β– -emission, electron and electron-antineutrino areejected out of the nucleus and share themaximum energy of the emission in allproportions with each other, as they are much

lighter than the residual atom. When ev does not

get any energy, the electron carries all the energy

and in case ev grabs whole of the energy, the

electron is left without any energy. Further, theconservation of linear and angular momenta is

also satisfied because ev 's linear and angular

momenta exactly balance those of the emittedelectron and the residual atom as in three-bodydecay.

A fundamental level, each neutron consists of one'up' (u) quark and two 'down' (d) quarks whereaseach proton cunts of two u-quarks and one d-quark. The u-quark carries an amount of +2/3electronic charge and the d-quark carries anamount of –1/3 electronic charge. So, equation (5)is due to the conversion of a d-quark into a u-

quark by emission of a W– boson (Fig.1) due to theweak interaction (Griffiths, 1987). The W– bosonsubsequently decays into an electron and anelectron-antineutrino. So the transformation of aneutron into a proton takes place with theemission of an electron for charge conservationand an electron-antineutrino for energy andmomentum conservation.

ENERGY AND ELECTRONIC CHARGE CONSERVATION DURING ALPHA AND BETA EMISSION

46


The schematic diagram is given below :

Figure 1: Co nversion of a neutron i nto a proton

(ii) β+ - Emission

A positron is emitted from a nucleus in this case,this is possible only when a proton is convertedinto a neutron in the nucleus. in order to conserveenergy, linear and angular momenta, an electron-

neutrino ( ev ) is also emitted. Thus,

1 1 01 0 1+→ + + +ep n e v Q (7)

The general transformation equation ofβ+-emision can be written as

01 1− +→ + + +A A

Z Z eX Y e v Q (8)

Conservation of Energy during β+-Emission

Now the pertinent question is, 'how a protonwhich is smaller in mass than a neutron canconvert into a neutron and other particles'.Actually, a free proton, i.e., a proton outside thenucleus, cannot decay into a neutron, as there willbe violation of energy conservation. This alsoexplains that why a free proton is stable whereas afree neutron is unstable (half-life = 10 min 16 s)

(Beiser, 2006). However, this is possible inside anucleus as proton gets energy from the nucleusand is converted into a neutron by emitting apositron and an electron-neutrino. This can bewritten as

energy + 1 1 01 0 1+→ + + +ep n e v Q (9)

Since proton number decreases by one andneutron number increases by one, β+-emission

helps to increase np value.

Conservation of Electronic Chargeduring Beta (β+) Emission

Consider a tritium decay which spontaneouslygives helium –3 by emitting an electron and anelectron-antineutrino as follows:

3 3 01 2 1 18.6 V−→ + + +eH He e v Ke (10)

The number of protons, neutrons and electronspresent in a tritium atom is one, two and onerespectively whereas the residual helium–3 atomwill have two protons, one neutron and oneelectron. So the residual atom has insufficientnumber of electrons to balance its number ofprotons, i.e., it becomes helium ion (He+). Similarlyin β+-emission the residual atom will have oneelectron more. This implies that the residualatoms in both types of decay processes are ions atthe time of decay. It has been observed in earlyexperiments (Linder and Christian, 1952) that aneutral radioactive element gets charged afteremitting beta particles and gradually becomesneutral. It appears that the positively chargedhelium ion subsequently tries to acquire an extraelectron from one of the neighbouring atoms to

u un d d p

d u

→ → →

ev

−W −e

47

become neutral. And in β+-emission, the negativelycharged residual atom emits an electron to thesurrounding to become neutral. Again, in case ofβ–-emission, the emitted electron encountersnumerous collisions and finally stops. Then, it

usually attaches to an atom. On the other hand, inβ+-emission, the emitted positron (antiparticle)immediately collides with electron (particle) of thesurrounding produces energy which is carriedaway by two photons of gamma radiation.

ReferencesBEISER, A. 2006. Concepts of Modern Physics, 432-441 Tata McGraw-Hill, New Delhi.COWAN, C. L. et al. 1956. Detection of the Free Neutrino : a Confirmation. Science, 124, 103-104EVANS, R.D. 1978. The Atomic Nucleus, 47-48. Tata McGraw-Hill, New Delhi.GRIFFITHS D.1987. Introduction to Elementary Particles, 26-27, 67-68. John Wiley and Sons, New

York.LINDER, E.G. and S. M. CHRISTIAN. 1952. The use of Radioactive Material for the Generation of High

Voltage, 23, 1213-1216, J. Appl.MARMIER, P.S.E. 1969. Physics of Nucle i and Particles, Vol.1, 31-36, Academic Press, New York.

ENERGY AND ELECTRONIC CHARGE CONSERVATION DURING ALPHA AND BETA EMISSION

Introduction

Metacognitive knowledge involves knowledgeabout cognition in general, as well as awarenessof and knowledge about one’s own cognition. Theresearch on learning emphasis on helpingstudents become more knowledgeable of andresponsible for their own cognition and thinking[Flavell, J. 1979 , De Jager et.al. 2005]. Studentsbecome more aware of their own thinking as wellas more knowledgeable about cognition ingeneral. Furthermore, as they act on thisawareness they tend to learn better [Eylon, B. S.and Reif, F. 1984]. The labels for this generaldevelopmental trend vary from theory to theory,but they include the development of metacognitiveknowledge, metacognitive awareness, self-awareness, self-reflection, and self-regulation.Although there are many definitions and modelsof metacognition, an important distinction is onebetween (a) knowledge of cognition (Metacognitiveknowledge) and (b) the processes involving themonitoring, control, and regulation of cognition.

THE ROLE OF METACOGNITION INLEARNING AND TEACHING OF PHYSICSS. RajkumarResearch Scholar VOC Colle ge of Education, TuticorinMunicipal Girls Higher Secondary SchoolTiruneveli town

Metacognitive knowledge includes knowledge ofgeneral strategies that might be used for differenttasks, knowledge of the conditions under whichthese strategies might be used, knowledge of theextent to which the strategies are effective, andknowledge of the self. Metacognitive control andself regulatory processes are cognitive processesthat learners use to monitor, control, and regulatetheir cognition and learning. The metacognitiveand self-regulatory processes are wellrepresented in tasks such as checking, planning,and generating. Accordingly, on the knowledgedimension, ‘metacognitive knowledge’ categoriesrefer only to knowledge of cognitive strategies,not the actual use of those strategies.

Three Types of MetacognitiveKnowledge

In a classic article on metacognition, Flavell (1979)suggested that metacognition include knowledgeof strategy, task, and person variables. Flavell’smodel encourages students to consider how each

This article provides a brief overview of the theory of metacognition and its role in learning and teaching. Themetacognitive knowledge of strategy, task and personal variables enables students to perform better and learnmore. The instructional strategies that facilitate the construction of knowledge are discussed. Metacognitivestrategies for physics learning and teaching are given.

variable affects their own learning processes.Metacognitive knowledge could be categorizedunder three heads - Strategic Knowledge,Knowledge about cognitive task and Self-knowledge.

Strategic Knowledge

Strategic knowledge includes knowledge of thevarious strategies students might use tomemorise material, to extract meaning from text,and to comprehend what they hear in classroomsor what they read in books and other coursematerials. Although there are a large number ofdifferent learning strategies, they can be groupedinto three general categories: rehearsal,elaboration, and organisational [Isaacson andFujita 2006]. Rehearsal strategies refer to thestrategy of repeating words or terms to beremembered over and over to oneself, generallynot the most effective strategy for learning morecomplex cognitive processes. In contrast,elaboration strategies include various mnemonicsfor memory tasks, as well strategies such assummarising, paraphrasing, and selecting mainideas from texts. The elaboration strategies resultin deeper processing of the material to be learnedand lead to better comprehension and learningthan the rehearsal strategies. Finally,organisational strategies include various forms ofoutlining, concept mapping, and note taking,where the student makes connections betweenand among content elements. Like elaborationstrategies, these organisational strategies usuallyresult in better comprehension and learning thanrehearsal strategies.

Students can have knowledge of variousmetacognitive strategies that will be useful to

them in planning, monitoring, and regulating theirlearning and thinking. These strategies includethe ways in which individuals plan their cognition(e.g., set subgoals), monitor their cognition (e.g.,ask themselves questions as they read a piece oftext; check their answer to a problem inmathematics), and regulate their cognition.

Knowledge about cognitive task

In addition to knowledge about various strategies,individuals also accumulate knowledge aboutdifferent cognitive tasks. In recall task, theindividual must actively search memory andretrieve the relevant information; while in therecognition task, the emphasis is ondiscriminating among alternatives and selectingthe appropriate answer. As students develop their knowledge of different learning andthinking strategies and their use; this knowledgereflects the “what” and “how” of the differentstrategies. However, this knowledge maynot be enough for developing expertise inlearning. Students also must develop someknowledge about the “when” and “why” of usingthese strategies appropriately [Rajkumar 200),Shulman 1986]. Because not all strategies areappropriate for every situation, the learner mustdevelop some knowledge of the differentconditions and tasks where the differentstrategies could be used most appropriately.

Self-knowledge

Along with knowledge of different strategies andknowledge of cognitive tasks, Flavell (1979)proposed that self-knowledge was an importantcomponent of metacognition. Self-knowledgeincludes knowledge of one’s strengths and

THE ROLE OF METACOGNITION IN LEARNING AND TEACHING OF PHYSICS

49

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weaknesses. This self-awareness of the breadthand depth of one’s own knowledge base is animportant aspect of self-knowledge. Finally,individuals need to be aware of the different typesof strategies they are likely to rely on in differentsituations. An awareness that one relies more ona particular strategy when there may be betteralternative adaptive strategies for the task, couldlead to the possibility of a change in strategy use.

Implications for learning and teaching

Metacognitive knowledge can play an importantrole in student learning and, by implication, in theways students are taught and assessed in theclassroom [Nuthall, G. 1999]. First, as previouslynoted, metacognitive knowledge of strategies andtasks, as well as self-knowledge, is linked to howstudents will learn and perform in the classroom.Students who know about the different kinds ofstrategies for learning, thinking, and problemsolving are more likely be using them. After all, ifstudents do not know of a strategy, they will notbe able to use it. Students who do know aboutdifferent strategies for memory tasks, forexample, are more likely to use them to recallrelevant information. Similarly, students whoknow about different learning strategies are morelikely to use them while studying. And, studentswho know about general strategies for thinkingand problem solving are more likely to use themwhen confronting different classroom tasks.Metacognitive knowledge of all these differentstrategies enables students to perform better andlearn more. Many teachers assume that somestudents will be able to acquire metacognitiveknowledge on their own, while others lack theability to do so. Of course, some students do

acquire metacognitive knowledge throughexperience and with age, but many more fail to doso. It is not expected that teachers would teach formetacognitive knowledge in separate courses orseparate units.

It is more important that metacognitiveknowledge is embedded within the usual content-driven lessons in different subject areas. Generalstrategies for thinking and problem solving canbe taught in the context of English, mathematics,science, social studies, arts, music, and physicaleducation courses. Science teachers, for example,can teach general scientific methods andprocedures, but learning will likely be moreeffective when it is tied to specific science content,not as an abstract idea. The key is that teachersplan to include some goals for teachingmetacognitive knowledge in their regular unitplanning, and then actually try to teach and assessfor the use of this type of knowledge as they teachother content knowledge. One of the mostimportant aspects of teaching for metacognitiveknowledge is the explicit labelling of it forstudents.

Implication of physics learning

Metacognitive strategies refer to strategies forhelping learners become more aware ofthemselves as learners, and include ability tomonitor one’s understanding through self-regulation; ability to plan, monitor success andcorrect errors when desirable; and ability to assessone’s readiness for high level performance in thefield one is studying [Mestre and Touger 1989].Reflecting about one’s own learning is a majorcomponent of metacognition, and does not occurnaturally in the physics classroom, due to lack of

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opportunity and also because instructors often donot emphasize its importance. It is common tohear physics students comment, ‘I am stuck onthis problem’, but when asked for more specificityabout this condition of ‘stuckness’, students are ata loss to describe what we are sticking on thisproblem that has them stuck, and often just repeatthat they are just stuck and can’t proceed. If duringinstruction, we were to take the time to suggestwhy, and how, students should reflect about theirlearning, there would be fewer incidents of the‘stuck’ condition, since students would be able toidentify what they are missing that would allowthem to proceed. The contemporary view oflearning is that individuals actively construct theknowledge they possess.

Constructing knowledge is a lifelong, effortfulprocess requiring significant mental engagementfrom the learner. In contrast to the ‘absorbingknowledge in ready-to-use form from a teacheror textbook’ view of learning, the ‘constructingknowledge’ view has two important implicationsfor teaching. One is that the knowledge thatindividuals already possess affects their ability tolearn new knowledge. When new knowledgeconflicts with resident knowledge, the newknowledge will not make any sense to the learner,and is often constructed (or accommodated) inways that are not optimal for long-term recall orfor application in problem-solving contexts[Redish 2000 ].

The second implication is that instructionalstrategies that facilitate the construction ofknowledge should be favoured over those that donot. Sometimes this statement is interpreted tomean that we should abandon all lecturing andadopt instructional strategies where students are

actively engaged in their learning. Lecturing couldbe a very effective method for helping studentslearn, but wholesale lecturing is not an effectivemeans of getting the majority of studentsengaged in constructing knowledge during class-room instruction. Hence, instructionalapproaches where students are discussingphysics, doing physics, teaching each otherphysics and offering problem solution strategiesfor evaluation by peers will facilitate theconstruction of physics knowledge.

Implication of physics teaching

Largely missing from science classrooms,especially large lecture courses, is formativeassessment intended to provide feedback to bothstudents and instructors, so that students have anopportunity to revise and improve the quality oftheir thinking and instructors can tailorinstruction appropriately. The age-old techniqueof asking a question to the class, and asking for ashow of hands has been tried by most, but doesnot work well since few students participate in thehand-raising largely due to lack of anonymity. Inclasses having fewer number of students it is notdifficult to shape teaching so that two-waycommunication takes place between the teacherand the student. For example, one very effectivemethod of teaching physics to having classes withfewer number of students, perfected by Resnick(1983) involves class-wise discussions led by theteacher. Students offer their reasoning forevaluation by the other classmates and by theteacher, with the instructional format takingsomewhat the form of a debate among students,with the instructor moderating the discussion andleading it to desired certain direction by posing


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carefully crafted questions. In classes with largeenrollment, the advent of classroomcommunication systems allows the incorporationof a workshop atmosphere, with studentsworking collaboratively on conceptual orquantitative problems, entering answerselectronically via calculators, and viewing theresponse of entire class’s in the form of

histogram form for discussion [Mestre et. al.1989, Redish 2000]. With this approach, thehistogram serves as a springboard for a class-wise discussion in which students volunteer thereasoning that led to particular answers and therest of the class evaluates the arguments. Theteacher moderates, making sure that thediscussion leads to appropriate understanding.

DE JAG ER, B. M. JANSEN and G., REEZIGT. 2005. The Development of Metacognition in Primary S choolLearni ng Environments, Schoo l Effectiveness and School Improvement, Vol. 16, No. 2, pp.179- 196.

EYLON, B. S. and F. REIF. 1984. Effec ts of knowledge organisation on Task Performance Cogn.Instruct. 1 5 –44.

Metacognitive strategies in Physics teaching

The research reviewed above carries important implications for how instruction for teachers should bestructured. In this section I provide a list of desirable attributes for physics courses suggested byresearch on learning.

♦ Construction, and sense-making, of physics knowledge should be encouraged.

♦ The teaching of content should be a central focus.

♦ Ample opportunities should be available for learning ‘the process of doing science’.

♦ Ample opportunities should be provided for students to apply their knowledge flexibly across multiplecontexts.

♦ Helping students organise content knowledge according to some hierarchy should be a priority.

♦ Qualitative reasoning based on physics concepts should be encouraged.

♦ Metacognitive strategies should be taught to students.

♦ Formative assessment should be used frequently to monitor students understanding and to helptailor instruction to meet students’ needs.

♦ Teachers must provide students with opportunities to practice strategies they have been taught.

References

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FLAVEL L, J. 1979. Metacognition and Cognitive Monitor ing: A New area of Cognitive-DevelopmentalInquiry. American Psycholo gist, 34, 90 6-911.

ISAACSO N, R.M F. and FUJITA. 2 006. Metac ognitive Knowledge Monitor ing and S elf-RegulatedLearning: Academic Success and Reflections on Learning, Journal of the Scholarship ofTeaching and Learning, Vol. 6, No. 1, pp. 3 9 - 55.

MESTRE, J and J. TOU GER. 1989. Cogniti ve Research: W hat’s in it for Physics Teachers Phys. Teacher27, 44 7–56.

NUTHAL L, G. 1999. Learning How to Learn: The Evolution of Students’ Minds Through S ocialProcess es and Culture of the Classroom. Intern ational Jou rnal of Educational Research,31, 13 9–140.

RAJKUM AR S. 200 7. Knowledge Organisation in Physi cs Problem S olving, School Science,Vol. 45 , No.2,52-54.

REDISH, E. F. 200 0. Discipl ine-based Education and Education Research: The Case of Physics J . Appl.Developmental Psychol. ,2 1, 85–96.

RESNICK, L. B. 198 3. Mathematics and Science Learning: A New Conception Science, 220, 477–8.SHULMAN, L. 198 6. Thos e Who Understand: Knowledge Growth in Teaching. Educ . Researcher

15 (2), 4–14.


STUDENTS' SCIENCE RELATED EXPERIENCES, INTERESTIN SCIENCE TOPICS AND THEIR I NTERRELATIONSOME IMPLICATIONSK. Abdul Gafoor and Smitha NarayanDepartment o f EducationUniversity of Calicut, Calicut UniversityKerala

There are mounting evidences of decline in theinterest of young people in pursuing science. Thepolicy report of ninth meeting of Global ScienceForum (2003) found that there is steady decline inthe number of students in science andtechnology. In India also, there isa similar trend ofdecline in interest to pursue study of scienceinterest. National Science Survey (Shukla, 2005)has shown that interest in science as well assatisfaction with the quality of Science teachingdeclined as the age increased. One cannot take thedecline in interest in science lightly. Surveysacross the globe suggest that lack of interest inscience is mainly due to science being lessintrinsically motivating (Global Science Forum,2003; National Science Survey, Shukla, 2005),nature of science being cutoff from real world andits content being overloaded with mattersunrelated to the life of students (Hill and Wheeler,

1991; Osborne and Collins, 2001). One way ofmaking science relevant is to base science onexperiences in which pupils are interested andthose that can find applications in real life.

Recent studies on interest in science in India showthat there is a shift away from science at the plus-two and under-graduate level (Patil, 2003). Asinterest in science develops quite early in life(Gardner, 1975), decline in interest in science inlater years of life can be tackled to a certain extentby providing all the factors conducive to thedevelopment of interest in science interest fromquite early years itself. Exploration in the field ofinfluence of out-of-school science experiences oninterest in science is not substantial in India.

Present article is based on a study conducted bythe authors on 1473 students in 14 upper primaryschool students in Kozhikode district of Kerala.

Attempt was made to know the science-relatedactivities that children themselves choose withoutany external suggestion and the resultantinfluence these activities have on interest in thetopics that they learn in their science classes. Thefollowing are the broad findings, conclusions andthe implications derived from the study.

Extent and Nature of Science RelatedExperiences that Pupil Bring intoClassroom

The extent of out-of-school science experiencesof upper primary school pupils is moderate innature. Pupils have more out-of-schoolexperiences in biology compared to those inphysics and chemistry. This can be attributed tomany a reasons. Biology experiences are quiteevident and are quick to arouse curiosity of youngchildren. In addition, experiences related to healthand hygiene is a part of one’s daily life. In biology,maximum experience is through collection. Mostchildren collect leaves, feathers etc. for aestheticpurpose. It is quite strange that pupil derive leastexperience through observation. Theoretically,one can get lots of biological experience throughobservation. Nevertheless, active nature of youngchildren may not let them remain satisfied withobservation alone, which is a passive process.

Out-of-school chemistry experiences arecomparatively less among children. This may bebecause these experiences (e.g. different types oftaste and odour) are so common and so implicitthat children more often do not give specialattention to them. That is, they experience thembut they do not consider them as on ‘experience’.Observations and activities are comparatively

more in chemistry. This is quite natural as rapidchanges in the colour of things, domesticactivities like mixing liquid blue in water, makingpickles etc. are easily available to all. The extent ofexperimentation is comparatively low.Observations like removing paint using keroseneremoving nail polish, making transparencies orprinting of are rarely associated with applicationsof chemistry.

The extent of out-of-school experiences relatedto concepts of physics lie in between that ofbiology and chemistry. Physics experiences aremainly through observations. Children observethe sky, weather, shadows, etc rarely out ofcuriosity or for their aesthetic impact and often donot count it as an experience related to science.The least amount of experience is fromexperimentation. This is again strange, asexperiences like melting of ice, changes in lengthof shadow etc. are quite popular among youngchildren. One reason for this could be that werarely understand or project science as activity ofhuman beings as an attempt to understand natureand natural phenomena. It may be that childrenderive more experience from vicarious sourcesthan from direct ones.

Boys have more out-of-schoolexperiences in physics while girlshave them in chemistry

The extent and nature of out-of-school scienceexperiences differ among boys and girls. Boysusually have more experiences than girls. It maybe that boys get more opportunities for out-dooractivities. The difference is mainly due to theadvantage of boys in relation to out-of-school

STUDENTS' SCIENCE RELATED EXPERIENCES, INTEREST IN SCIENCE TOPICS AND THEIR INTERRELATION–SOME IMPLICATIONS

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relating to physics experiences. This finding issimilar to those from other parts of the world(Farenga and Joyce, 1997; Sjoberg, 2000;Christidou, 2006). Boys, world over, get moreinvolved in hands-on physical activities likerepairing things and opening up toys or otherthings to know the parts, activities typicallyconsidered as male-stereotype ones. It is a part ofthe sex-role expectations of the society (Johnson,1987; Farenga and Joyce, 1997). Girls usually havemore chemistry related out-of-schoolobservations and activity than the boys. Domesticsurroundings give easy access to chemistryrelated experiences like making of picklesobserving, changing in colour of fruits andvegetables, say, apples. Compared to girls, boysindulge more in biology related activities likelistening to the sound of birds, maintainingaquarium, rearing animals. Agriculture, fishingand similar other activities are typical maledominated activities in developing countries(Sjoberg, 2000). Biological activities also includethose related to health and hygiene. Due to theincreased interest in fitness in present times, boysindulge more in health care. Compared to boys,girls indulge more in collecting items like leavesand feathers, which can be for aesthetic purpose.Generally, boys, compared to girls, indulge morein active tasks while girls, compared to boys,indulge more in passive tasks like collection.Science is doing; hence, boys who indulge more inactive tasks will naturally have higher extent ofexperiences in science.

Urban pupils excel rural pupils inout-of-school science experiences

Urban and rural pupils differ in their out-of-school science experiences with urban pupils

having more experiences than rural pupilsespecially in Biology and Physics. The reason canbe the difference in opportunities. Rural pupils getopportunities for nature-related directexperiences. Even though this is less for urbanpupils, they receive indirect experiences through avisit to parks, zoological gardens, planetarium etc.Urban pupils have the added benefit of gettingmore vicarious experiences through computersand internet that can compensate for the lack ofdirect experiences.

Pupils in aided schools lag behindthose in government and unaidedschools in out-of-school scienceexperiences

Type of management also influences the extentand nature of out-of-school science experiences.Government school pupils have more experienceespecially in observations related to biologybesides physics, biology and chemistry relatedactivities as compared to children from both aidedand unaided schools. Biological activities arenature-related which are accessible to all butphysics related activities require mechanical andtechnological facilities, which are comparativelyavailable more to pupils in unaided schools. Theyhave more opportunity to be familiar withtelevision programmes, computers and internetmainly due to their more affluent background.Among the three groups, pupils from aidedschools are likely to have the least experiences,They may not be as familiar with technologicalactivities in comparison to pupil from unaidedschools, due to the difference in the domestic andschool environment. Nevertheless, they may notbe getting as much freedom as children in

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government schools get to explore theirsurroundings, due to the protective and restrictivenature in middle class families in third worldcountries. Further, research is required to explorehow out-of-school experiences vary for pupils indifferent types of schools.

Interest in Science Topics amongUpper Primary Pupils

The extent of interest in science of upper primarypupils is relatively high, which is a good indication,as science is an inevitable raw material oftechnology. Pupils have comparatively moreinterest in biology and physics. Interest in biologyis due to pupils’ desire to know about themselvesand other living forms in their surroundings.Physics can never remain behind in modernworld, as it is the basis for many popularprofessional courses like Engineering andComputer applications. Moreover, origin ofuniverse, space explorations etc. have always beena challenge to man, and to young curious minds.Study conducted elsewhere (Borrows, 2004) alsoshows lesser preference for chemistry amongpupils. The reason cited is that pupils considerchemistry as something that happens in thelaboratories. Topics like acids, recycling ofwastes, fertilisers, etc. may give the idea that theseare ‘jobs’ to be done in factories alone therebyreducing their appeal.

Girls are more interested in biologyand chemistry while boys are moreinterested in physics

The extent of interest in s cienc e is more forgir ls, owing m ainly due to their higher inter est

in biology and chemistry . Inc reased interest ofgir ls in biol ogy is sim ilar to the findings inprevious researches (Gardner, 1975; Sjoberg,2000; Uitto et al, 2006). The r eason cited is thatgirl s are more interes ted in peopl e and lifeoriented aspects of science like biology (Milleret al, 2006). The same reason is applicabl e tothe increased inter est in chemistr y as topicslike production of cooking gas, f oodpres ervation, preparation of m edicine etc. dealwith chemistry that infl uences lives of people.Boys are more interested in physics. Thisfinding also has s upport of previous researc hes(Ts abar i and Yarden, 2005; Christidou, 2006).Phys ics topics deal with abstr act concepts thatappeal girl s less (Tsabari and Yar den, 2005).Moreover, boys have more experiences inphysics; experiences have an influenc e oninterest (Johnson, 1987; Sjoberg, 2000).

Urban pupils have more interest inscience

Urban pupils are more interested in all the threefie lds of science than the rural pupils. Thissuggests societal inf luence on interest inscience. Urban pupils receive latest inform ationthr ough media , com puters and internet athom e. Fur ther, schools and computer institutesin urban locality hel p them devel op bet terunderstanding about scientific concepts . Betterunderstanding can increase interest in science.Lave and Wenger’s (1991 ) observation oflearning as contextualised and shaped byphys ical, s ocial and political landscape in whichit occur s to development of interes t can beapplied to development of inter est in scienceas well.

STUDENTS' SCIENCE RELATED EXPERIENCES, INTEREST IN SCIENCE TOPICS AND THEIR INTERRELATION– SOME IMPLICATIONS

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Pupils in aided schools have lesserextent of interest in science

Pupils in Government and unaided schools havemore interest in science than amongst those inGovernment aided schools. Difference in interestmight partially be due to difference in theirexperiences in day to day life. Apart from this,school facilities including access to internet andlibraries, learning environment, teaching styletogether with the difference in the socialbackground of the three strata influence theirinterest. Children in unaided schools, by andlarge, get better learning facilities, in their schoolas well as at home, while in government schoolsthey get them through the facilities provided bythe government. Children from aided schoolsremain wanting in both these aspects.

Out-of-School Science ExperiencesContributes to Interest in Science

The relationship between out-of-school scienceexperiences and interest in science is positive inall fields of science and in all categories ofexperiences. This also is in agreement with earlierstudies (Joyce and Farenga, 1999; Uitto et al, 2006,Zoldozoa, 2006). The relationship is substantial inbiology while in physics and chemistry, it iscomparatively low. This indicates that influence ofexperiences on interest is more in biology than inphysics and chemistry. This may be becausebiology is more life related. Among the categoriesof experiences, experimentation has more impacton interest. Experimentation is an act of discoverywhich in turn nurtures interest.

Gender difference exists inrelationship between out-of-schoolexperiences and interest in chemistry

Gender difference is evident only in the extent ofrelationship between out-of-school chemistryexperiences and interest in chemistry with boysexhibiting a stronger corelation than the girls.Even though girls have more experience inchemistry than the boys, they do not develop moreinterest in chemistry. These experiences, receivedmainly from domestic surroundings, may not behelping girls to find any learning opportunity inthem.

Not only urban pupils have more experiences, butthese experiences have higher influence on thedevelopment of their interest in science.

The extent of relationship between out-of-schoolscience experiences and interest in science showslocality-based differences. The extent ofrelationship is stronger for urban pupils in all thethree fields of science. Urban pupils have moreexposure to academic activities through indirectand vicarious means that enrich the scienceexperiences that they get. This also helps themutilise the experiences better to develop strongerinterest in science.

Out-of-school science experiences of pupils fromunaided schools have better influence on theirinterest in science.

The extent of relationship between out-of-schoolscience experiences and interest in science ismore for children from unaided schools, thanfrom both aided and government schools. Owingto the interventions and guidance from parents

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and teachers, students from unaided schools aremore orientated towards academics. They havebetter facilities at school like computer lab, richlibraries that enrich their experiences and givethem an opportunity to develop wider areas ofinterest.

Educational Implications

The findings bring to focus the fact that thenature and extent of out-of-school scienceexperiences and interest in science vary fordifferent strata of population. The study alsovalidated the person-object theory of interest byestablishing relationship between pupil’sexperience and her/his interest. Further, it wasrevealed that the extent of relationship betweenout-of-school science experiences and interest inscience differed among sub samples. Thesefindings render useful information that can bringabout some reformations in the educationalscenario.

1. Know about what pupils bring toclassroom

One cannot do much to control out-of-schoolexperiences, but knowing about what pupils bringto the classroom will help for providing bettereducational circumstances. For a constructivistteacher, knowledge of pupils’ out-of-schoolexperiences is invaluable as the presentexperiences are building blocks of the futureexperiences. Knowing students’ experiences alsoassists in providing those experiences that pupillack. Evidence of pupils’ experiential backgroundcan help a teacher to choose those experiencesthat can result in minimal dissonance with

existing experiences. In addition, teachers canknow how pupils use science in their daily life.Moreover, what people do is more important thanwhat they merely ‘know’.

2. Monitor interest from primaryclasses

Interest develops very early in life. So monitoringof interest should begin from primary schoolitself. Interest and attitude that one develops in thelower classes influence their future choices (Lloydand Contreras, 1984). Leaving nature of interestsand their fields unnoticed in the developing stagesof a child is detrimental as, no matter how hardwe try in the later stages, it would be quite difficultto make her/him get interested and people toappreciate science. Identifying pupils’ diverseinterests helps to nurture interest as well as tofind innovative means to make those fields ofscience in which they lack interest appealing. Thisproves helpful to alleviate transitional problems asthey reach secondary schools with diversifiedscience curriculum.

3. Relate classroom chemistry withchild’s life

An analysis of the extent of experiences andinterest showed that children generally have lesserextent of experience as well as interest inchemistry. Making children realise that chemistryis something that is going on all around andwithin us will help them see its significance.Extent of experience and interest in biology isrelatively high. Pupils need to see that the veryessence of biology rests on chemical reactions.This would help them appreciate the significance


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of chemistry in our lives. Once they understandthe utility of chemistry, they will get interested, aspupils need to feel the relevance of a concept intheir life to develop interest in it (Qualter, 1993).

4. Never ignore disparity in out-of-school experiences

The disparity in out-of-school experiences isnatural as personal choice and the social, culturaland economic background from which pupilscome determine these experiences. Still wecannot ignore the disparity in out-of-schoolexperiences, as a substantial positive correlationexists between out-of-school science experiencesand interest in science.

5. Girls have to be more accustomedto physics activities

Girls’ lesser extent of experience and interest inphysics reveals that irrespective of the vast culturaldifferences, girls all over the world remain elusiveonce it comes to physics. The reason citedelsewhere – sex-role socialisation- could be thecause for such gender differences in physics inKerala also. Even in the modern world, there stillexist male and female stereotype activities andpreferences. Physics is dominated by hands-onmechanical and technological activities, from whichgirls shy away or are kept away. Girls have to bemore accustomed to physics and made aware ofthe significance of physics lest they remain farbehind in the modern techno-savvy world.

6. Revamp rural schools

In the case of rural pupils, the environmentalfactors allow them to have nature related

experiences but when it comes to technologicalaspects, they do not get the facilities that theaffluent urban locale provides. Rural childrencome to school with an impoverished experientialbackground. The situation at school is notdifferent. A visit to rural schools can give us aglimpse of the poor infrastructural facilities thatpupils have. Disparity between urban and ruralschools can do nothing but contribute to thebackwardness of rural pupils. The solution lies ina complete revamping of rural schools. Morecomputers and better laboratory facilities,supplemented with trained teachers with enoughmotivation, frequent educational excursions toplaces of scientific interest and availability of otherresources might be one-step in this direction.

7. Pay special attention to the needs ofpupils in Government aided schools

The lack of exper ience and interest am ongst+pupils in Government aided schools is a seriousissue because in Keral a majority of schoolsbelong to this sector (Department of GeneralEducation, Ker ala, 2002-03 and 2003-04).Government provides necessary facilities forschool s in the public sector whereas unaidedschool s have the strong support of wealthymanagements, trusts and parents. Governmentaided schools, on the other hand, especiallyupper primary schools, are wanting in aids fromboth the government as well as management.This further aggravates the disadvantagedposit ion of pupils in these schools. Therefore,government and management have to pay specialattention to the needs of pupils a ided schools sothat their pupil can be on par w ith those fromgovernment and unaided schools.

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8. Personal autonomy is a crucialdeterminer of interest

The inequality in the magnitude of interest is not awelcome discovery, as over the years, governmenthas been diligently working towards reducing thediscrepancy in interest in science between variousstrata of population. A major landmark in thescience education was the introduction of theactivity-oriented learning. Nevertheless, thereexists a major distinction between out-of-schoollearning and classroom learning. Most oftenpupils undertake the activities as part of thecurricular requirements. Classroom learning,thus, becomes compulsory and extrinsicallymotivated. Moreover, all activities are timed andcollective. Scope for individual variations islimited. In contrast, out-of-school learning is oneof personal choices, giving ample freedom forexploration. The personal autonomy makes out-of-school experiences a crucial determiner ofinterest, as freedom to make decisions canenhance interest (Hanrahan, 1998). Activityoriented classrooms can be transformed for thebetter if teachers are willing to accommodate thisneed of pupils for liberty. Instead of directingthem to do exact prescription in the textbook,teacher can enquire about how they would dealwith a particular situation. This would not onlyallow the use of out-of-school experiences butalso bring students nearer to diverse ideas thatcan supplement classroom learning.

9. Using out-of-school experiencesindividualizes instruction

Out-of-school learning facilitates pupils’ inherentnature of individualised way of acquiringinformation. Using out-of-school experiences inscience classrooms thus individualisesinstruction.

The above discussion on the implications bringson certain recommendations to optimise sciencelearning. Conduct of science enrichmentprogrammes where pupils can implementscientific method under the guidance of resourcepersons will help create a ‘psychologicalmoratorium’ – an engaging and psychologicallysafe chance for learners to experiment with theidentity of self as scientist (Erikson, 1968). This notonly enhances interest but also gives enrichingexperiences to students who do not have accessto such experiences. Attempt needs to be made tomake pupils aware of the task value (Eccles andWigfield, 1995). Task value indicates the ability of atask to satisfy personal needs, which in turndepends on the interest, importance and utility ofthe task. Establishing educational guidance cells,especially in rural areas can help to developawareness about benefits of science therebynurturing interest in science. As experimentalactivities are better predicators of interest inscience, pupils need more opportunities forexperimental activities and club activities.


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BORROWS, P. 2004. Chemistry Trails. Cited in M. Braund and M. Reiss (2006), Towards a More Authentic ScienceCurriculum: The Contribution of Out-of-school Learning. International Journal of Science Education,28(12), 1373-1388.

CHRISTDOU, V. 2006. Greek Students’ Science-related Interest and Experiences: Gender Differences andCorrelations. International Journal of Science Education, 28 (10), 1181-1199.

Department of General Education, Kerala. 2003. Number of Schools Situated in Panchayath, Muncipalit andCorporation 2002-03. Retrieved, October 20, 2007, from http://www.kerala.gov.in/ dept_geneducation/5.11.pdf

ECCLES, J.S. and A. WIGFIELD. 1995. The Development of Achievement—Task Values: a Theoretical Analysis.Developmental Review, 12, 265-310.

ERIKSON, E. 1968. Identity, Youth and Crisis. Norton New York.

FARENGA, S.J. and B.A. JOYCE. 1997. What Children Bring to the Classroom: Learning Science from Experience.Retrieved, March 20, 2008, from http://www.findarticles.com.

Global Science Forum. 2003. Evolution of Student Interest in Science and Technology Studies. Policy Report.Retrieved, March 19, 2008, from http://www.oecd.org/dataoecd/16/30/36645825.pdf

GARDNER, P.L. 1975. Attitude to Science– A Review. Studies in Science Education, 2, 1-41.

JOHNSON, S. 1987. Gender Differences in Science: Parallels in Interest, Experien ce and Perfo rmance.International Journal of Science Education, 9 (4), 467-481.

JOYCE, B.A. and S. FAR ENGA. 1999. Informal Science Experiences, Attitudes and Future Interests in Science andGender Difference of High Ability Students. An Exploratory Study. Retrieved, March 20, 2008, from http://www.questia.com.

LAVE, J. and E. WEN GER. 1991. Situated L earning: Legitimat e Peripheral Participation. Cambridge UniversityPress, Cambridge.

LLYOD, C.V. and N.J. CONTRERAS. 1984. The Role of Experience in Learning Science Vocabulary. InternationalJournal of Science Education, 4, 275-283.

MILLER, P.H., J.S. BLESSING and S. SCHWARTZ. 2006. Gender Differences in High-school Students’ Views AboutScience. International Journal of Science Education, 28 (4), 363-381.

OSBORNE, J. and C. COLLINS. 2001. Pupils’ and Parents’ Views of the School Science Curriculum. InternationalJournal of Science Education, 23, 441- 467.

PATIL, R. 2003. Science Education in India. Retrieved, May 5, 2008, from http:// www.ias.ac.in/currsci/Aug102008/238.pdf.

QUALTER, A. 1993. I Would Like to Know More About That: A Study of the Interest Shown by Girls and Boys inScientific Topics. International Journal of Science Education, 15(3), 307-317.

References

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SHUKLA, R. 2005. India Science Report. Science Education, Human Resources and Public Attitude TowardsScience and Technology. Retrieved, May 10, 2008, from http://www.insaindia.org/ind%20science%20report-main.pdf.

SJOBERG, S. 2000. Science and Scientists. Pupils’ Experiences and Interests Relating to Science and Technology:Some Results from a Comparative Study in 21 Countries. Retrieved, March 19, 2008, from http://folk.uio.no/sveinj/.

TSABARI, AYELET-BARAM and A. YARDEN. 2005. Characterising Childrens’ Spontaneous Interests in Science andTechnology. International Journal of Science Education, 27, 803-826.

UITTO, A.J., K. JUUTI, J. LAVONEN and V. MEISSALO. 2006. Students’ Interests in Biology and Their Out-of-schoolExperiences. Journal of Biological Education, 40 (3), 124-129.

ZOLDOZOA, K. 2006. Education in the Field Influences Childrens’ Ideas and Interests Towards Science. Journal ofScience Education and Technology.

STUDENTS' SCIENCE RELATED EXPERIENCES, INTEREST IN SCIENCE TOPICS AND THEIR INTERRELATION: SOME IMPLICATIONS

COMPUTER AIDED LEARNINGPreety ChawlaSenior Lecturer, Citkara College of Education for WomenFatehpurgarhi, R ajpura, Patiala

With the advent and rapid expansion inInformation and Communication Technology, theaccess to higher education is being expandedenormously and fundamentally changing themodels of education. Today, with the use oftechnology, education has become more learner-centric, individualised, interactive and relevant tolearner’s needs, thus making it truly a life longlearning. Higher education can no longer beconsidered as a campus-based education forstudents. The arrival of computer and laterinternet has opened a much wider horizon foreducation. Computers have taken over everyconceivable field of operation today.

Computer Aided Learning (CAL) is based on theintegrative approach whereby a lecture or aninstruction is not replaced by the computerprogramme but it is introduced during the courseas a learning resource. It refers to the use ofcomputers to aid and support the education andtraining of the students. It is pedagogyempowered by digital technology. Computers arebeing increasingly employed for classroominstruction as also for individualised and distance

education. Computer- Based Instruction (CBI) isvariously known as Computer Aided Learning(CAL) in the U.K. and Computer Assisted Learning(CAI) in the USA. They both refer to on-line directinteractive learning experience through thecomputer. The synonyms for CAL are InternetBased Training (IBT) or web based Training (WBT),Multimedia Learning, Networked Learning andVirtual Education.

CAL is to convey vast amount information in a veryshort period of time. It is a powerful method ofreinforcing concepts and topics first introducedthrough the text book and discussion in theclassroom. CAL empowers us with a powerfultool to comprehend complex concepts. The use ofcomputers in education is basically a vision as ateaching and learning aid, besides it helps todevelop computer literacy amongst children.CAL helps to make the teaching-learning processjoyful, interesting and easy to understand throughaudio-visual media. It has potential to improvestudents’ performance by promoting activeparticipation, maintaining attention to tasks andenhancing problemsolving skills.

The psychological bases of using CAL are thatlearning could take place through hands onactivities and by providing opportunity to thelearner to construct her/his own knowledgebased on one’s experiences. The students becomean equal partner in the development of theknowledge. It reflects the true spirit of the age oldsaying, “Tell me and I will forget; Show me and Imight remember; But involve me and I willunderstand.

Instructional Applications ofComputers

CAL perhaps provides the best opportunity to thestudents for self-guided learning. It is self-pacedand self-planned, with the students themselveschoosing their own paths through the web ofinformation encompassed by the package. It canbe done in one of the many different modes ofinstruction, some of which are:

Tutorial Mode- In this mode, information ispresented in small units followed by a question.The student’s response is analysed by thecomputer and an appropriate feedback isprovided.

Drill and Practice Mode- In this mode, thelearner is provided with a number of gradedexamples on the concepts and principles learntearlier. The idea is to develop proficiency andfluency through doing. All the correct responsesare reinforced and the incorrect responses arediagnosed and corrected. The computercontinues the drill until mastery is achieved by thelearner.

In the Simulation mode, the learner is presentedwith scaled-down simulated situations bearing

correspondence with the real situations, e.g.simulation of an oscillating pendulum,propagation of waves, flight of an aeroplane,occurrence of a nuclear reaction, etc.

• In the D is cover y Mode, the inductiveapproach to teaching and learning isfollowed. The learner is encouraged toproceed through trial and error approach, i.e.by solving a given problem, realising, whereand how the things went wrong, trying againand finally solving the problem.

In the Gam ing Mode, the learner is engaged inplaying opposite the computer or a fellow learner.The extent of learning depends on the type of thegame. Games on spellings, names of places orgeneral knowledge games are some examples.

Advantages of Computer AidedLearning

The basic tenets of CAL offer the followingadvantages over other systems of instruction.

• Sc al ability

Many aspects of CAL are scalable, particularlywhen Internet derived technologies areutilised to produce a CA L package. Unlikeother educational media, a CAL package isdigita lly stored. Thus, it may be repr oducedwithout error as many tim es as required. Byproviding acces s to a CAL package over anetwork many students may us e a singleresour ce. Further , if the CA L package is madeaccessible via an Internet browser then itbecomes potentially available to a very widepopulation of learners using a large numberof computers.

COMPUTER AIDED LEARNING

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• Interac tiv ity

The importance of interaction to learning waseloquently summarised by Confuscius: “What Ihear I forget. What I see I remember. What I do Iremember always”. The nature of CAL lends itselfto involving the student with the learningprocesses with tasks requiring actions as alsothose dependent on feedback on the action thatthe student may receive leading to furtherappropriate tasks. This goal-action-feedbackcycle may be followed in a simple series ofinteractive questions, a complex case study oreven a computer simulation of a clinical situation.

• A utomat ion of A ss ess m ent

As a student interacts with a CAL exercise it ispossible to keep a record of each interaction onan identifiable log file. This provides a convenientoption to check on student performance bychecking on the correctness of response to theCAL exercise. Further, by building-up a profile ofhow a number of users interact with the system itis possible to identify weaknesses in the CALexercise itself. The automatic logs can thus helpdecrease both the burdens on assessingstudents and validating CAL exercises.

• Inf or mat ion inter connec t ivity

The information may be interconnected oncomputers, which allow users to click onhighlighted text to jump in a non-sequentialmanner to related information includingpictures, audio and video clips.

• Mul timedia

The incorporation of multimedia elementssuch as images, audio and v ideo clips in CAL

packages provide more than simplyenhancing the inter est of the l earner.Cognit ive psychol ogists suggest that learningis facilitated if the s tudent has to undertakeactive processing of presented infor mation,“mental roughage”. Diff erent individuals learnbetter in respons e to differ ent media, and ithas been suggested that learning may beimproved by providing information in morethan one form simultaneousl y such asanimat ion with s ound.

• S tudents ’ c onvenienc e

The convenience of the student is taken care ofin learning through CAT exercises. Eachstudent receives instruction at his own pace.

• Cont inuity

Each student responds continuously as she/hereceives instructions.

• Rapid F eedbac k

Each student receives rapid feedback. Thestudent gets has/his feedback for the previouscontent before reaching the next level.

• D ivis ion of Content

All units of learning are broken down intosubunits and small elements of learning. Thestudent gains mastery over the first subunitbefore moving to the next subunit.

• S tandar dis at ion of the Content

The same material is available to a largenumber of learners over a wide geographicalarea, which standardises the learningexperience whenever the learner logs on.

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• S er ves a l ar ge populat ion

A single programme can help thousands ofstudents to learn the content practically locatedanywhere on the globe.

• Nonver bal and Auditor y

It is possible to present the content innonverbal and auditory form other than thetext form.

Physical Obstacles to use of ComputerAssisted Learning

• The development of high-tech computer-assisted learning programs is labourintensive, requiring appropriate hardware,backup and frequent upgrading.

• A dedicated information technology staff isnecessary to provide practical advice andmaintenance of the software and hardware.

• Some people may be less inclined to useelectronic resources because of perceivedlack of computer literacy.

• There is a lack of adequate basicinfrastructure in schools.

• Lack of funds for operations andmaintenance makes it difficult to maintainhigh standards of Computer AssistedLearning.

• Lack of evaluation techniques and results oftools, makes it difficult to know theeffectiveness of the instruction.

• There are few learning resources forteachers in rural areas.

Teachers related issues

Many a time even if teachers had been trained inthe use of computer aided teaching, theintegration of ICT in the teaching/learningprocess is not sustainable. Some commonreasons could be:

• teacher overload as they have to prepare theprograms for Computer Assisted Learning,

• lack of incentives and motivation for theteachers,

• shortage of trained teachers,

• non-availability of latest Technology Hardwareand basic Infrastructure and

• non-availability of proper technical assistance.

Findings of the Research

The researches regarding use of CAL support thefollowing:

• The use of CAL as a supplement toconventional instruction produces higherachievement than the use of conventionalinstruction alone.

• Research is inconclusive regarding thecomparative effectiveness of conventionalinstruction vis a vis CAL.

• Computer-based education (CAL and othercomputer applications) produce higherachievement than conventional instructionalone.

• Use of word processors by the studentsfacilitates development of writing skills leading

COMPUTER AIDED LEARNING

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to higher-quality written work as compared toother methods employed for improving writingskills (paper and pencil, conventionaltypewriters).

• Students learn material faster with CAL thanwith conventional instruction alone.

• Students retain what they have learned better withCAL than with conventional instruction alone.

• The use of CAL leads to more positive attitudestoward computers, course content, quality ofinstruction, school in general, and self-as-learnerthan the use of conventional instruction alone.

• The use of CAL is associated with otherbeneficial outcomes, including greater internallocus of control, school attendance,motivation/time-on-task, and student-studentcooperation and collaboration than the use ofconventional instruction alone.

• CAL is more beneficial for younger studentsthan older ones.

• CAL is more beneficial with lower-achievingstudents than with higher-achieving ones.

• Economically disadvantaged students benefitmore from CAL than students from highersocio-economic backgrounds.

• CAL is more effective for teaching lower-cognitive material than higher-cognitivematerial.

• Most handicapped students, including learningdisabled, mentally retarded, hearing impaired,emotionally disturbed, and languagedisordered, achieve at higher levels with CALthan with conventional instruction alone.

• There are no significant differences in theeffectiveness of CAL as far as gender oflearners is concerned.

• Students’ fondness for CAL activities centreson the immediate, objective, and positivefeedback provided by these activities.

• CAL activities appear to be at least ascost-effective as — and sometimes more cost-effective than— other instructional methods,such as teacher-directed instruction andtutor ing.

Most programmes of computer-based instructionevaluated in the past have produced positive effectson student learning and attitudes. Furtherprogrammes for developing and implementingcomputer-based instruction should therefore beencouraged.

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FORMAL CHARGE — A NOVEL METHOD FOR TEACHINGTHEORETICAL INORGANIC CHEMISTRY

All atoms within a neutral molecule need not beneutral. The location of any charge is oftenimportant for understanding reactivity of themolecule. Ions bear a positive or negative charge.If the ion is polyatomic (i.e. constructed of morethan one atom), we might ask which atom (s) of ioncarry the charge? Thus knowledge of chargedistribution over the atoms in a molecule or ion(identification of atom that are electron rich orelectron poor) can be useful to interpret manyfacets of organic chemistry, including how and whyreactions occur (mechanisms) or how moleculesinteract with each other, a feature which stronglyinfluences physical and biological properties.

Chemists have developed a very simple bookkeeping method to determine if an atom within amolecule or ion is neutral, or bears a positive ornegative charge. The method provides integercharge only. Because this method provides someindication of charge distribution, it is an excellentstarting point for determining electrondistribution within a molecule or an ion, hencegives a starting point to predict chemical and

physical properties. These assigned integercharges are called formal charges. A formalcharge is a comparison of electrons owned by anatom in a Lewis structure versus the number ofelectrons possessed by the same atom in itsunbound, free atomic state. Also formal charge isway of counting electrons involved in bonding.

Formal charge is calculated as follows :

FC = GN – UE – 1/2BEFC = formal chargeGN = periodic table group number (number of

valence electrons in free, nonbondedatom)

UE = number of unshared electronsBE = number of electrons shared in covalent

bonds.OR FC= (number of valence electrons in the

neutral atom) – (number of electrons inlone pair) – (number of covalent bonds)

Thus for hydronium ion, (H3O+)

FC = 6 – 2 – ½(6) = +1

Bibhuti Narayan BiswalPrincipalSathya Sai Vidyaniketan, Ganeshvad Sisodra,Gujarat

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The formal charge on hydrogen is calculated asfollows. Hydrogen has one valence electron (GN =1),no unshared (UE = 0) and two shared electrons inthe oxygen - hydrogen covalent bond (BE = 2). Thusthe calculated formal charge on hydrogen is zero.

Because, each hydrogen atom in this molecule isidentical, each hydrogen atom has the same formalcharge of zero. Any hydrogen bearing one covalentbond always has a formal charge of zero.

Similarly, the formal charge on oxygen is calculatedas follows. Oxygen has six valence electrons (GN = 6),two unshared in one lone pair (UE = 2), a six sharedelectrons in three oxygen - hydrogen covalent bonds(BE = 6). Thus, the calculated formal charge on oxygenis +1. This indic ates the oxygen atom bears themajority of the positive charge of this ion.

In addition to above methods, it is also possible todeterm ine formal charge instinctively based oncomparing structure. The instinctive method is basedon comparing the structure with common, knownneutral structures. To do this it needs to recognisethe common neutral structures: that means 'C' has4 bonds; N has 3 bonds with one lone pair, O has2 bonds with two lone pair, F has one bond withthree lone pairs. For more clarity refer Table No.1.

- In the middle of the Table 1 are the neutralbonding situation for C, N, O and halogen F(Just think of each central atom bond beingto a hydrogen).

- To the left, a bond has been lost but convertedto a lone pair, so the central atom has gainedan electron and become (-ve).

- To the right, there are two scenarios : (i) Cand F has lost the shar ed electron of a bond,so losing one elec tron from the count tobecome positive (+ve) ( ii ) N and O haveconverted two unshar ed electrons into ashared pair of el ectrons in a bond, so losingone elec tron f rom the c ount to becomepositive (+ve).

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Thus, to find formal charge we follow the followingsteps:

(1) We count the valence electrons that belong to eachatom. For this it should be remembered that

- Unshared pairs belong entirely to the atomon which they reside.

- Shared pairs of electrons are equally betweenthe atoms by which they are shared: Half belongto one atom, and half belong to the other.

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(2) Compare the number of electrons that belongto each atom in a mol ecule or ion with thenumber of valence elec trons br ought intobonding by the neutral atom . That meanscarbon always bring 4 valence electrons intobonding, nitrogen brings five elec trons intobonding, oxygen br ings 6 e lectrons intobonding, hal ogens brings 7 el ectrons intobonding and hydrogen brings 1 electrons intobonding.

(3) If the number of valence electrons belonging tothe atom in a molecule or ion is different fromthe number that belong to the neutral atom,the atom has a formal charge. That means ifthe number of el ectrons that belong is onemore than the number in neutral atom, thenthe formal charge would be –1. If the number ofelectrons that belong to on atom in a moleculeor ion is one less than the number of electronson neutral atom, the formal charge is +1. If thenumber of electrons that belong is same as thenumber brought into bonding, the f orm alcharge is 0.

Selection of Reasonance Structures

Basing on formal charge it is possible to select theappropriate resonance structure of any moleculeout of several possible Lewis structures. Few tips todetermine appropriate Lewis structure as follows :

(1) The best Lew is s tr uc ture f or r es onancecontributing structure has the least number ofatoms with formal charge.

(2) Equivalent atoms have the same formal charge.For exam pl e, al l the hydrogen atom s ofmethane (CH4) are equivalent and therefore have

the same formal charge. All six hydrogen atomsin ethane (H3C-CH3) have the same formalcharge, as do the two carbon atoms.

(3) For mal charges other than +1, 0 or –1 areuncommon except for metals.

(4) If the sum of the formal charge is 0, the speciesis a molecule and if the sum of the formal chargeis not 0, then the species is an ion.

Resonance and Formal charge

Resonance structure often have formal chargesassociated with them. For instance NO2 moleculesformal charge can be calculated as:

In str ucture II the right hand oxygen has thr eenonbonding pairs, so this counts for six electrons.Then oxygen gets one of the two electrons in thebond with nitrogen. That's the number of electrons7, giving the O a minus one formal charge.

The other O has two nonbonding pairs of electronsand it also gets its shar e of 2 of four elec tronspresent in the double bond. That's six electrons,thus the left hand O has no formal charge.

The nitrogen gets its share of two electrons from

FORMAL CHARGE–A NOVEL METHOD FOR TEACHING THEORITICAL INORGANIC CHEMISTRY

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the double bond, one from the single bond and onefrom the half-filled orbital associated with it. That'sa total of electrons. This gives 'N' a +1 formal chargesince it needs 5 electrons to be neutral.

Similarly, consider the impor tant al lotr ope ofoxygen, ozone. This molecule is known to be bentbut not an equilateral triangle. It is also known thatit is symmetric with respect to the O-O bonds. (Itdoes in fact have a two-fold symmetry axis, and twoperpendicular symmetry planes i.e. C2v symmetry)The Lewis theory c annot predict this s tructurewithout assigning formal charges to res onancestructures. Ozone can be represented as:

To sum up, formal charge is an important tool insolving conceptual pr obl ems in c hem istr y i.e.stability, structure elucidation, reactivity, acidity, etc.of molec ules or ions. Al so, it offers reasonableexplanation to the following :

1. N2 is stable but isoelectronic CO is reactive.

2. HPO3 readily combines with water to f ormH3PO4 while HNO3 has no such tendency.

3. A cidic strength dec reas es in the or derHClO4 > HClO3 > HClO2 > HClO.

4. HNO3 is a stronger acid than HNO2.

5. Ozone is less stable than O2.

6. SO3, PO3 polymerise (linear chains), silicatespolymerise sharing corner, while NO3

– can't.

7. The plausible structure of formaldehyde isHCHO, i.e.

8. J. Ricci explained the acidic character of oxyacids in terms of formal charge as :

pK = 5.0-m (9.0) + n(4.0)

where m = formal charge on central atom,

n = number of non hydroxyl oxygen atoms inthe acids.

ReferencesDAVID G. DE WIT. 1994. J. Chem. Education, 71, 750B. BRUKE. W. EDWARD. 2002. J. Chem. Education, 2 (79) 155J. RICCI. 1948. J. Am. Chem. Soc.: 70, 109

In structure III, the two terminal oxygen possesses½ charges whereas the middle oxygen possessesone positive charge. It is however to be noted thatfor all resonating structures we can't write formalcharges. For instance benzene and its homologuebecaus e of the ir aromatic stabil is at ion anddelocalised pi (π) electronic cloud.

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“The stocks of petroleum, coal, propane, and natural gas will be consumed in a few years.” “Most of the observed increase in globally averaged temperatures since the mid-20th century is due to theobserved increase in anthropogenic greenhouse gas concentrations.”“The majority of the known petroleum reserves are located in the Middle East and thus worldwide fuelshortages would intensify the unrest that exists in the region, leading to further conflict and war.”

Gurkirat KaurLecturer, Chitkara College of Education for WomenFatehpurgarhi, R ajpura, Patiala

This concern and words of apprehensionregarding conventional petroleum products hasbeen starting the people all over the world since adecade. There is a growing anxiety due to generalenvironmental, economic, and geopoliticalmatters of sustainability of the petroleumproducts. Also the prices of the fossils fuels havebeen upsurging day-by-day. The only solution tothese problems is the identification and usage ofthe alternative fuels in industry, transportationand in economy of the world.

What are Alternative Fuels?

Alternative fuels are also known as non-conventional fuels and are substances that can be

ALTERNATIVE FUELS – A BOON FOR FUTUREGENERATIONS

used as fuels, other than conventional fuels.Conventional fuels include : fossil fuels (petroleum(oil), coal, propane, and natural gas), and nuclearmaterials such as uranium. An array of alternativefuels are there viz. biodiesel, bioalcohol (methanol,ethanol, butanol), chemically stored electricity(batteries and fuel cells), hydrogen, non-fossilmethane, non-fossil natural gas, vegetable oil andother biomass sources.

Why is there an increasing demandfor alternative fuels?

A variety of reasons contribute towards theincreased demand for alternative fuels,

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1. Environmental Concern - The majorenvironmental concern, according to an IPCCreport, is that “Most of the observed increasein globally averaged temperatures since themid-20th century is due to the observedincrease in anthropogenic greenhouse gasconcentrations.” Since burning fossil fuels isknown to increase greenhouse gasconcentrations in the atmosphere, they are alikely contributor to global warming.

2. Economic and Political Concern - The majorityof the known petroleum reserves are located inthe Middle East. There is general concern thatworldwide fuel shortage could intensify theunrest that exists in the region, leading tofurther conflict and war.

3. Limited Reserves of the Alternative fuels -Other important concern which have fuelleddemand revolve around the concept of peak oil,which predicts rising fuel costs as productionrates of petroleum enter a terminal decline.According to the Hubbert peak theory, whenthe production levels peak, demand for oil willexceed supply and without proper mitigationthis gap will continue to grow as productiondrops, which could cause a majorenergy crisis.

Biodiesel

Biodiesel refers to a vegetable oil - or animal fat-based diesel fuel consisting of long-chain alkyl(methyl, propyl or ethyl) esters. Biodiesel istypically made by chemically reacting lipids (e.g.,vegetable oil, animal fat (tallow) with an alcohol.Biodiesel is meant to be used in standard dieselengines alone, or blended with petrodiesel.

Biodiesel can be produced from a great variety offeedstocks like vegetable oils (soyabean,cottonseed, peanut, sunflower, coconut, etc.) andanimal fats (tallow) as well as waste oils (usedfrying oils).

The problem with the use of biodiesel includes theinherent higher price of the biodiesel, which inmany countries is offset by legislative andregulatory incentives or subsidies in the form ofreduced excise taxes, Slightly increased NOXexhaust emissions from biodiesel burning,oxidative stability, and Cold flow properties whichare especially relevant in cold countries.

Bioalcohol (Methanol and ethanol)

Ethanol is generally made from corn, biomass(agricultural crops and waste like rice straw), plantmaterial left from logging, and trash includingcellulose. Methanol can be made from variousbiomass resources like wood, as well as fromcoal. However, today nearly all methanol is madefrom natural gas, because it is cheaper.

Methanol and ethanol are not prim ary sourcesof energy; however, they are convenient fuels forstoring and transporting energy. These alcoholcan be used in internal combustion enginessuch as flexible fuel vehicles with m inormodifications.

The use of bioethanol in replacing fossil fuels invehicles is a matter of concern as large amount ofarable land is required for crops resulting inimbalance of environment and energy but recentdevelopments with cellulosic ethanol productionand commercialisation may assuage theseconcerns.

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Chemically stored electricity

Chemically stored electricity is used to run electriccars, T.V. and electrical appliances etc. Electricvehicles receive their power from various sources,including fossil fuels, nuclear power, andrenewable sources (tidal power, solar power, andwind power) or any combination of those. Aftergeneration, this energy is then transmitted to thevehicle through use of overhead lines, wirelessenergy transfer, or a direct connection through anelectrical cable. The electricity may then be storedonboard the vehicle using a battery, flywheel, supercapacitor, or fuel cell. A key advantage of electric orhybrid electric vehicles is their ability to recoverbraking energy as electricity to be restored to theon-board battery or sent back to the grid whereaswhen fossil fuel vehicles brake, they simply dumpthe energy into the environment as waste heat.

The problem with electric vehicles is of longrecharge times compared to the relatively fastprocess of refuelling a tank which is furthercomplicated by the current scarcity of publiccharging stations.

Hydrogen

Hydrogen is the lightest of all elements, easy toproduce through electrolysis, burns nearlypollution-free and being a non-carbon fuel, theexhaust is free of carbon dioxide.

Hydrogen as a fuel can be an asset but there is noaccessible natural reserve of uncombinedhydrogen, since what little there is resides inEarth’s outer atmosphere. Therefore, hydrogenfor use as fuel must first be produced usinganother energy source, making it a means totransport energy, rather than an energy source.

One existing method of hydrogen production issteam methane reformation; however, thismethod requires methane, which raisessustainability concerns. Another method ofhydrogen production is through electrolysis ofwater, in which electricity generated from anysource can be used. Photoelectrolysis,biohydrogen, and biomass or coal gasificationhave also been proposed as means to producehydrogen. Hydrogen has thus currently becomeimpractical to be used as an alternative fuel.

Alternative fossil fuels

Compressed natural gas (CNG) is a common fuelwhich comes from underground. However, naturalgas is a gas like air, rather a liquid like petroleum. Ithas been found to be one of the mostenvironmentally friendly fuels and is used to powera car or truck. Natural gas is made up of methane(95 per cent) and the other 5 per cent is made up ofvarious gases like butane, propane, ethane alongwith small amounts of water vapour. However,natural gas is a finite resource like all fossil fuels,and its production is expected to peak soon afteroil does.

Liquefied natural gas (LNG) is made byrefrigerating natural gas to –260° F to condense itinto a liquid (liquefaction) which removes most ofthe water vapour, butane, propane, and othertrace gases, that are usually included in ordinarynatural gas. The resulting LNG is usually morethan 98 per cent pure methane. The liquid form ismuch denser than natural gas or CNG and hasmuch more energy. LNG is good for large trucksthat need to go a long distance before they stopfor more fuel.

ALTERNATIVE FUELS – A BOON. FOR FUTURE GENERATIONS

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ReferencesKNOTHE. G. 2008. B iodiesel, Sci. Topics, Retrieved from http ://www.scitopics.com/Biodiesel.html

on 30 Augu st 2009.Alternative Fuels : Biodiesel, Retrieved from http://www.ep a.gov/smartway on 30 August 2009.Biodiesel, Retrieved from www.eere.energy.gov/veh iclesandfuels on 3 September, 2009.Alternative Fuels, R etrieved from http://en.wik ipedia.org/wiki/Alternative_fuel on 3 September

2009.Biodesel, Retrieved from http://en.wikipedia.org/wiki/Biodiesel on 12 September, 2009.Alternative Fuel Vehicles, Retrieved from www.ut ah.edu/unews o n 21 September, 2009.

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SCIENCE NEWS

Nanotechnology Used In BiofuelProcess

Dr James Palmer, Associate Professor ofchemical engineering at Louisiana TechUniversity, in collaboration with fellow professorsDr Yuri Lvov, Dr Dale Snow, and Dr Hisham Hegab,has developed the technology that wouldcapitalise the environmental and financial benefitsof “biofuels” by using nanotechnology to furtherimprove the cellulosic ethanol processes.

Biofuels are expected to play an important role insearch for sustainable fuels and energyproduction solutions for the future. The demandfor fuel in future, however, cannot be satisfiedwith traditional crops such as sugarcane or cornalone. Emerging technologies are allowingcellulosic biomass (wood, grass, stalks, etc.) to bealso converted into ethanol. Cellulosic ethanoldoes not compete with food production and hasthe potential to decrease emissions of greenhouse

gases (GHG) by 86 per cent over that of today’sfossil fuels. Current techniques for corn ethanolreduce greenhouse gases by only 19 per cent.

The nanotechnology processes developed atLouisiana Tech University, allows immobilisationof expensive enzymes used to convert cellulose tosugars, and thus makes them available for reuseseveral times over thereby significantly reducingthe overall cost of the process. Savings estimatesrange from approximately $32 million for eachcellulosic ethanol plant. This process can easily beapplied in large scale commercial environmentsand can immobilise in a wide variety or mixture ofenzymes production. (Source: Sc ience Daily online)

Giant Leap for Nerve Cell Repair

The repair of damaged nerve cells is a majorproblem in medicine today. A new study byDr David Colman, Director at the MontrealNeurological Institute and Hospital (The Neuro)

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and his research team, is a significant advancetowards a solution for neuronal repair. The studyfeatured first to show that nerve cells will growand make meaningful, functional contacts, orsynapses, the specialised junctions through whichneurons signal to each other with an artificialcomponent, in this case, plastic beads coated witha substance that encourages adhesion, andattracts the nerve cells.

Many therapies, most still in the conceptual stage,are aiming at to restore the connection betweenthe nerve cell and the severed nerve Fibres thatinnervate a target tissue, typically muscle.Traditional approaches to therapies would requirethe re-growth of a severed nerve fibre by adistance of up to one metre in order to potentiallyrestore function. The new approach, according toresearchers, bypasses the need to force nervecells to artificially grow these long distances, andeliminates the demand for two neurons to make asynapse, both of which are considerable obstaclesto neuronal repair in a damaged system.

The synapses generated in this research arevirtually identical to their natural counterpartsexcept the ‘receiving’ side of the synapse is anartificial plastic rather than another nerve cell orthe target tissue itself. This study is the first thatuses these particular devices, to show thatadhesion is a fundamental first step in triggeringsynaptic assembly.

In order to assess function that is transmission ofa signal from the synapse they stimulated thenerve cells with electricity, sending the signal, anaction potential, to the synapse. By artificiallystimulating nerve cells in the presence of dyes,

they could see that transmission had taken placeas the dyes were taken up by the synapses.

They believe that within the next five years, it willbe possible to have a fully functional device thatwill be able to directly convey natural nerve cellsignals from the nerve cell itself to an artificialmatrix containing a mini-computer that willcommunicate wirelessly with target tissues. Theseresults not only provide a model to understandhow neurons are formed which can be employedin subsequent studies but also provides hope forthose affected and potentially holds promise forthe use of artificial substrates in the repair ofdamaged nerves.

(Source: Sc ience Daily online)

New Mesozoic Mammal

Dr Zhe-Xi Luo, curator of vertebrate paleontologyand associate director of science and research atCarnegie Museum of Natural History and hiscolleagues have discovered a new species ofmammal that lived 123 million years ago inLiaoning Province in northeastern China. Thenewly discovered animal, Maotherium asiaticus,comes from famous fossil-rich beds of the YixianFormation.

Maotherium asiaticus is a symmetrodont,meaning that it has teeth with symmetricallyarranged cusps specialised for feeding on insectsand worms. It lived on the ground and had abody 15 cm long and weighing approximately70 to 80 g. By studying all features in thisexquisitely preserved fossil, researchers believeMaotherium to be more closely related tomarsupials and placentals than to monotremes

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primitive egg laying mammals of Australia andNew Guinea such as the platypus.

This new remarkably well preserved fossil, offersan important insight into how the mammalianmiddle ear evolved. The discoveries of suchexquisite dinosaur age mammals from Chinaprovide developmental biologists andpaleontologists with evidence of howdevelopmental mechanisms have impacted themorphological evolution of the earliest mammalsand sheds light on how complex structures canarise in evolution because of changes indevelopmental pathways.

Mammals have highly sensitive hearing, far betterthan the hearing capacity of all other vertebrates,and hearing is fundamental to the mammalianway of life. The mammalian ear evolution isimportant for understanding the origins of keymammalian adaptations. The intricate middle earstructure of mammals (including humans) hasmore sensitive hearing, discerning a wider rangeof sounds than other vertebrates. This sensitivehearing was a crucial adaptation, allowingmammals to be active in the darkness of the nightand to survive in the dinosaur dominatedMesozoic.

Mammalian hearing adaptation is made possibleby a sophisticated middle ear of three tiny bones,known as the hammer (malleus), the anvil (incus),and the stirrup (stapes), plus a bony ring for theeardrum (tympanic membrane). These mammalmiddle ear bones evolved from the bones of thejaw hinge in their reptilian relatives.Paleontologists have long attempted tounderstand the evolutionary pathway via whichthese precursor jawbones became separated

from the jaw and moved into the middle ear ofmodern mammals.

According to the Chinese and American scientistswho studied this new mammal, the middle earbones of Maotherium are partly similar to those ofmodern mammals; but Maotherium’s middle earhas an unusual connection to the lower jaw that isunlike that of adult modern mammals. Thismiddle ear connection, also known as the ossifiedMeckel’s cartilage, resembles the embryoniccondition of living mammals and the primitivemiddle ear of pre-mammalian ancestors. BecauseMaotherium asiaticus is preserved three-dimensionally, paleontologists were able toreconstruct how the middle ear attached to thejaw. This can be a new evolutionary feature,andcan be interpreted as having a “secondarilyreversal to the ancestral condition,” meaning thatthe adaptation is caused by changes indevelopment.

Modern developmental biology has shown thatdevelopmental genes and their gene network cantrigger the development of unusual middle earstructures, such as “re-appearance” of theMeckel’s cartilage in modern mice. The middle earmorphology in fossil mammal Maotherium of theCretaceous (145-65 million years ago) is verysimilar to the mutant morphology in the middleear of the mice with mutant genes. The scientificteam studying the fossil suggests that the unusualmiddle ear structure, such as the ossifiedMeckel’s cartilage, is actually the manifestation ofdevelopmental gene mutations in the deep timesof Mesozoic mammal evolution.


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Smaller and More Efficient NuclearBattery

Batteries can power anything from small sensorsto large systems. While scientists are finding waysto make them smaller but even more powerful,problems can arise when these batteries aremuch larger and heavier than the devicesthemselves. Jae Kwon, Assistant Professor ofelectrical and computer engineering at Universityof Missouri and his researcher team, aredeveloping a nuclear energy source that issmaller, lighter and more efficient. To provideenough power, it will need certain methods withhigh energy density. The radioisotope battery canprovide power density that is six orders ofmagnitude higher than chemical batteries.

Dr Kwon and his research team have beenworking on building a small nuclear battery,currently the size and thickness of a penny,intended to power various micro/nanoelectromechanical systems (M/NEMS).Although nuclear batteries can pose concerns,they are safe. However, nuclear power sourceshave already been safely powering a variety ofdevices, such as pace-makers, space satellites andunderwater systems. His innovation is not only inthe battery’s size, but also in its semiconductor.Kwon’s battery uses a liquid semiconductorrather than a solid semiconductor. The criticalpart of using a radioactive battery is that whenenergy is drawn from it, part of the radiationenergy can damage the lattice structure of thesolid semiconductor. By using a liquidsemiconductor, this problem will minimise.

In the future, they hope to increase the battery’spower, shrink its size and try with various other

materials. According to Kwon, the battery couldbe thinner than the thickness of human hair.


ALICE: New Aluminium-water RocketPropellant

Steven Son, associate professor of mechanicalengineering at Purdue University and hisResearch team have developed a new type ofrocket propellant made from a frozen mixture ofwater and “nanoscale aluminium” powder that ismore environmentally friendly than conventionalpropellants and could be manufactured on theMoon, Mars and other water-bearing bodies.

The aluminium-ice, or ALICE, propellant might beused to launch rockets into orbit and for long-distance space missions and also to generatehydrogen for fuel cells. ALICE developed on theAir Force Office of Scientific Research andPennsylvania State University, was used earlier tolaunch a 9-foot-tall (2.75 m) rocket. The vehiclereached an altitude of 1,300 feet (396 m). The tinysize of the aluminium particles, which have adiametre of about 80 nanomets, or billionths of ametre, is a key to the propellant’s performance.The nanoparticles combust more rapidly thanlarger particles and enable better control over thereaction and the rocket’s thrust.

ALICE provides thrust through a chemicalreaction between water and aluminium. As thealuminium ignites, water molecules provideoxygen and hydrogen to fuel the combustion untilall of the powder is burned. ALICE might one dayreplace some liquid or solid propellants, and,when perfected, might have a higher performance

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than conventional propellants. It is also extremelysafe while frozen because it is difficult to get itignited accidentally. It could be improved andturned into a practical propellant. Theoretically, italso could be manufactured in distant places likethe Moon or Mars instead of being transported athigh cost. Findings from spacecraft indicate thepresence of water on Mars and the Moon, andwater also may exist on asteroids, other moonsand bodies in space.

Manufacturers over the past decade have learned,how to make higher quality nano aluminiumparticles than was possible in the past. The fuelneeds to be frozen for two reasons: it must besolid to remain intact while subjected to theforces of the launch and also to ensure that itdoes not slowly react before it is used. Initially apaste, the fuel is packed into a cylindrical moldwith a metal rod running through the centre. Afterit is frozen, the rod is removed, leaving a cavityrunning the length of the solid fuel cylinder.A small rocket engine above the fuel is ignited,sending hot gasses into the central hole, causingthe ALICE fuel to ignite uniformly.

Other researchers previously have usedaluminium particles in propellants, but thosepropellants usually also contained larger, micron-size particles, whereas the new fuel containedpure nanoparticles. Future work will focus onperfecting the fuel and also may explore thepossibility of creating a gelled fuel using thenanoparticles. Such a gel would behave like aliquid fuel, making it possible to vary the rate atwhich the fuel is pumped into the combustionchamber to throttle the motor up and down andincrease the vehicle’s distance. A gelled fuel alsocould be mixed with materials containing larger

amounts of hydrogen and then used to runhydrogen fuel cells in addition to rocket motors.

The research is helping to train a new generationof engineers to work in academia, industry, forNASA and the military. It is unusual for studentsto get this kind of advanced and thorough trainingto go from a basic-science concept all the way to aflying vehicle that is ground tested and launched.This is the whole spectrum.


Does Moon have Water!

According to Dr Vincent Eke, in the Institute forComputational Cosmology, at Durham University,Crashing a rocket into the Moon will create “onemore dimple” on the lunar surface and could findwater ice on Earth’s nearest neighbour.

The Lunar Crater Observation and SensingSatellite (LCROSS) and its Centaur rocket wasmade to smash into a crater in the Cabeus regionof the Moon’s South Pole in the second week ofOctober 2009. This site has been chosen in view ofhigher concentration of hydrogen found in theregion which could be due to the hydrogen inwater present there as water ice. The rocket hasroughly the mass of a Transit van and it will hit theMoon at about 5,600 miles per hour (9 000 km/h).The energy of the collision has been estimated tobe roughly equivalent to two tonnes of TNT. It hasbeen estimated that the impact would hurlapproximately 350 tonnes of material up frommoon’s surface and will be propelled into thesunlight so that scientists can study itscomposition by using ground-based telescopes.

It may be recalled that in September 2009, India’sChandrayaan-1 probe had found that particles that

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make up the Moon’s soil are coated with smallamounts of H2O. It is contemplated that this waterin the form of ice could be found in the frozenconfines of the Moon’s polar craters wheretemperatures are in the vicinity of minus 170degrees Celsius. If it is so, then the Chandrayaan-1data would imply that the top metre of the surfacein these craters holds about 200,000 million litreof water.

According to Dr Eke, water ice could be stable forbillions of years on the Moon provided that it is coldenough. If ice is present in the permanently shadedlunar craters of the Moon then it could potentiallyprovide a water source for the eventualestablishment of a manned base on the Moon. Sucha base could be used as a platform for explorationinto the further reaches of our solar system.


Nobel Prize in Physics: Creators ofOptical Fibre Communication and CCDImage Sensor

The Royal Swedish Academy of Sciences hasdecided to award the Nobel Prize in Physics for2009 with one half to Charles K. Kao, StandardTelecommunication Laboratories, Harlow, UK,and Chinese University of Hong Kong “forgroundbreaking achievements concerning thetransmission of light in fibres for opticalcommunication, and the other half jointly to WillardS. Boyle and George E. Smith, Bell Laboratories,Murray Hill, NJ, USA “for the invention of animaging semiconductor circuit CCD sensor”.

This year’s Nobel Prize in Physics is awarded fortwo scientific achievements that have helped to

shape the foundations of today’s networkedsocieties. They have created many practicalinnovations for everyday life and provided newtools for scientific exploration.

In 1966, Charles K. Kao made a discovery that ledto a breakthrough in fibre optics. He carefullycalculated how to transmit light over longdistances via optical glass fibres. With a fibre ofpurest glass it would be possible to transmit lightsignals over 100 kilometres, compared to only 20metres for the fibres available in the 1960s. Kao’senthusiasm inspired other researchers to sharehis vision of the future potential of fibre optics.The first ultrapure fibre was successfullyfabricated just four years later, in 1970.

Today optical fibres make up the circulatory systemthat nourishes our communication society. Theselow-loss glass fibres facilitate global broadbandcommunication such as the Internet. Light flows inthin threads of glass, and it carries almost all of thetelephony and data traffic in each and everydirection. Text, music, images and video can betransferred around the globe in a split second.

If we were to unravel all of the glass fibres thatwind around the globe, we would get a singlethread over one billion kilometres long – which isenough to encircle the globe more than 25 000times – and is increasing by thousands ofkilometres every hour.

A large share of the traffic is made up of digitalimages, which constitute the second part of theaward. In 1969 Willard S. Boyle and George E.Smith invented the first successful imagingtechnology using a digital sensor, a CCD (Charge-Coupled Device). The CCD technology makes useof the photoelectric effect, as theorised by Albert

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Einstein and for which he was awarded the 1921year’s Nobel Prize. By this effect, light istransformed into electric signals. The challengewhen designing an image sensor was to gatherand read out the signals in a large number ofimage points, pixels, in a short time.

The CCD is the digital camera’s electronic eye. Itrevolutionised photography, as light could now becaptured electronically instead of on film. Thedigital form facilitates the processing anddistribution of these images. CCD technology isalso used in many medical applications, e.g.imaging the inside of the human body, both fordiagnostics and for microsurgery.

Digital photography has become an irreplaceabletool in many fields of research. The CCD hasprovided new possibilities to visualise thepreviously unseen. It has given us crystal clearimages of distant places in our universe as well asthe depths of the oceans.


Physicist Makes New High-resolutionPanorama of Milky Way

Cobbling together 3000 individual photographs, aphysicist Axel Mellinger, a professor at CentralMichigan University, has made a new high-resolution panoramic image of the full night sky,with the Milky Way galaxy as its centrepiece.

This panorama image shows stars 1000 timesfainter than the human eye can see, as well ashundreds of galaxies, star clusters and nebulae.Its high resolution makes the panorama useful forboth educational and scientific purposes.

Mellinger spent 22 months and travelled over26,000 miles (41, 800 km) to take digitalphotographs at dark sky locations in South Africa,Texas and Michigan. Each photograph is a two-dimensional projection of the celestial sphere. Assuch, each one contains distortions, in much thesame way that flat maps of the round Earth aredistorted. In order for the images to fit togetherseamlessly, those distortions had to be accountedfor that Mellinger used a mathematical model andhundreds of hours in front of a computer.

Due to artificial light pollution, natural air glow, aswell as sunlight scattered by dust in our solarsystem, it is virtually impossible to take a wide-field astronomical photograph that has a perfectlyuniform background. To fix this, he used datafrom the Pioneer 10 and 11 space probes. The dataallowed him to distinguish star light fromunwanted background light. He could then editout the varying background light in eachphotograph. That way they would fit togetherwithout looking patchy.

The result is an image of our home galaxy that nostar-gazer could ever see from a single spot onearth. Mellinger plans to make the giant648 megapixel image available to planetariumsaround the world.


New Evidence on Formation of Oil and Gas

Scientists in Washington, D.C. are reportinglaboratory evidence supporting the possibility thatsome of Earth’s oil and natural gas may haveformed in a way much different than thetraditional process.

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According to Anurag Sharma and colleagues thetraditional process involves biological processi.e. prehistoric plants died and c hanged into oiland gas while sandwiched between layers of rockin the hot, high-pressure environment deepbelow Earth’s surface. Some scientists, however,believe that oil and gas originated in other ways,including chemical reactions between carbondioxide and hydrogen below the Earth’s surf ace.

The genesis of the new study lies on the descriptionof the process suggested by famous Russianchemist Dimitri Mendeleev some time around 1877.Taking their clue from this the researcherscombined ingredients for this so-called abioticsynthesis of methane, the main ingredient innatural gas, in a diamond-anvil cell and monitoredin-situ the progress of the reaction. The diamondanvils can generate high pressures andtemperatures similar to those that occur deepbelow Earth’s surface and allow for in-situ opticalspectroscopy at the extreme environments.

The results strongly suggest that some methanecould form strictly from chemical reactions in avariety of chemical environments. This studyfurther highlights the role of reaction pathwaysand fluid immiscibility in the extent ofhydrocarbon formation at extreme conditionssimulating deep subsurface.


Mathematical Model to Explain Howthe Brain Might Stay in Balance

The human brain is made up of 100 billion ofneurons, acting like live wires, which must be keptin delicate balance to stabilise the world’s most

magnificent computing organ. Too muchexcitement and the network will slip into anapoplectic, uncomprehending chaos. Too muchinhibition and it will flat line. Marcelo O.Magnasco, Head of the Laboratory ofMathematical Physics at The RockefellerUniversity, and his colleagues have developed anew mathematical model that describes how thetrillions of interconnections among neuronscould maintain a stable but dynamic relationshipthat leaves the brain sensitive enough to respondto stimulation without veering into a blind seizure.

How such a massively complex and responsivenetwork, such as the brain, can balance theopposing forces of excitation and inhibition?According to Magnasco, neurons function togetherin localised groups to preserve stability. The definingcharacteristic of system is that the unit of behaviouris not the individual neuron or a local neural circuitbut rather groups of neurons that can oscillate insynchrony. The result is that the system is muchmore tolerant to faults, individual neurons may ormay not fire, individual connections may or may nottransmit information to the next neuron, but thesystem keeps functioning.

Magnasco’s model differs from traditional modelsof neural networks, which assume that each timea neuron fires and stimulates an adjoiningneuron, the strength of the connection betweenthe two increases. This is called the Hebbiantheory of synaptic plasticity and is the classicalmodel for learning. But the Magnasco system isanti-Hebbian. If the connections among anygroups of neurons are strongly oscillatingtogether, they are weakened because theythreaten homeostasis. Instead of trying to learn,our neurons are trying to forget. One advantage of

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this anti-Hebbian model is that it balances anetwork with a much larger number of degrees offreedom than classical models can accommodate,a flexibility that is likely required by a computer ascomplex as the brain.

Magnasco theorises that the connections thatbalance excitation and inhibition are continuallyflirting with instability. He compares the behaviourof neurons to a network of indefinitely largenumber of public address systems tweaked tothat critical point at which a flick of themicrophone brings on a screech of feedback thatthen fades to quiet with time.

This model of a balanced neural network isabstract; it does not try to recreate any specificneural function such as learning. But it requiresonly half of the network connections to establishthe homeostatic balance of exhibition andinhibition crucial to all other brain activity. Theother half of the network could be used for otherfunctions that may be compatible with moretraditional models of neural networks, includingHebbian learning.

Developing a systematic theory of how neuronscommunicate could provide a key to some of thebasic questions that researchers are exploringthrough experiments. This model could be one partof a better understanding. It has a large number ofinteresting properties that make it a suitablesubstrate for a large-scale computing device.


Genomes of Biofuel Yeasts Mapped

As global temperatures and energy costs continueto soar, renewable sources of energy will be key to

a sustainable future. An attractive replacement forgasoline is biofuel, and in two studies scientistshave analysed the genome structures ofbioethanol producing microorganisms,uncovering genetic clues that will be critical indeveloping new technologies needed toimplement production on a global scale.

Bioethanol is produced from the fermentation ofplant material, such as sugar cane and corn, bythe yeast Saccharomyces cerevisiae, just as in theproduction of alcoholic beverages. However, yeaststrains thriving in the harsh conditions ofindustrial fuel ethanol production are muchharder than their beer brewing counterparts, andsurprisingly little is known about how this yeastadapted to the industrial environment. Ifresearchers can identify the genetic changes thatunderlie this adaptation, new yeast strains couldbe engineered to help shift bioethanol productioninto high gear across the globe.

Two s tudies have taken a major step toward thisgoal, identifying genomic properties of indus trialfuel yeasts that likely gave rise to more robuststrains. In one of the studies , researcher LucasArgueso and colleagues from Duke U niversity atUSA and Br azil have sequenced and analysed thestruc ture of the entire genome of strain PE -2, aprominent indus trial stra in in Brazil. Their workrevealed that portions of the genome are plasticcompared to other yeast s trains, specifically theperipheral r egions of chromosomes, where theyobserved a number of s equencerearrangements.

Interestingly, these chromosomalrearrangements in PE-2 amplified genes involvedin str ess toleranc e, which likely contributed tothe adaptation of this s train to the indus trial

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environm ent. As PE-2 is amenable to geneticengineering, the authors believe that their workon PE-2 will open the door to developm ent ofnew technologies to boost bioethanolproduction.

In a s econd study conducted by Boris S tambukfrom Stanford Univer sity, USA and GavinSherlock Brazil, the two scientists have alsoanalysed the genome struc ture of industrialbioethanol yeas ts, searching for variations in thenumber of gene copies in five strains em ployedin Br azil, inc luding PE-2. Stambuk andcolleagues found that all five industrial strainsstudied harbour ampl ifications of genes involvedin the synthes is of vitamins B6 and B1compounds critic al for efficient growth andutilisation of sugar.

The group experimentally demonstrated that thegene amplifications confer robust growth inindustrial conditions, indicating that these yeastsare likely adapted to limited availability of vitaminsin the industrial process to gain a competitiveadvantage. Furthermore, the researchers suggestthat this knowledge can be utilised to engineernew strains of yeast capable of even more efficientbioethanol production, from a wider range ofagricultural stocks.

It is evident that an expanding human populationwill require more energy that exerts less impacton the environment, and the information gainedfrom these genomic studies of industrialbioethanol yeasts will be invaluable as biofuelresearchers optimise production and implementthe technology worldwide.


‘Ultra-primitive’ Particles Found InComet Dust

Interplanetary dust particles with presolar grains:Scanning electron images of two dust particles E1(panel A) and G4 (B) and secondary ion massspectrometry isotopic ratio maps (C—D). Oxygenisotope maps of particles E1 (C) and G4 (D) show fourand seven isotopically anomalous regions, indicated bycircles, which have been identified as presolar grains.The scale bars are 2 microns.

According to Larry Nittler and his colleagues,Department of Terrestrial Magnetism at CarnegieInstitution, dust samples collected by high-flyingaircraft in the upper atmosphere have yielded anunexpectedly rich trove of relics from the ancientcosmos. The stratospheric dust includes minutegrains that had formed inside stars that lived anddied long before the birth of our sun, as well asmaterial from molecular clouds in interstellarspace. This ultra-primitive material likely waftedinto the atmosphere after the Earth passedthrough the trail of an Earth crossing cometin 2003.

At high altitudes, most dust in the atmospherecomes from space, rather than the Earth’ssurface. Thousands of tons of interplanetary dustparticles (IDPs) enter the atmosphere each year.The only known cometary samples are those thatwere returned from comet 81P/Wild 2 by theStardust mission. The Stardust mission used aNASA-launched spacecraft to collect samples ofcomet dust, returning to Earth in 2006.

Comets are thought to be repositories ofprimitive, unaltered matter left over from theformation of the solar system. Material held foreons in cometary ice has largely escaped the

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heating and chemical processing that has affectedother bodies, such as the planets. However, theWild 2 dust returned by the Stardust missionincluded more altered material than expected,indicating that not all cometary material is highlyprimitive.

The IDPs used in the current study were collectedby NASA aircraft after the Earth passed throughthe dust trail of comet Grigg-Skjellerup. Theresearch team comprising Nittler, HennerBusemann, Ann Nguyen, George Cody, analysed asub-sample of the dust to determine thechemical, isotopic and micro-structuralcomposition of its grains. They are very differentfrom typical IDPs. They are more primitive, withhigher abundances of material whose originpredates the formation of the solar system. Thedistinctiveness of particles plus the timing of theircollection after the Earth’s passing throughthe comet trail, point to their source being theGrigg-Skjellerup comet.

This is exciting because it allows us to compareon a microscopic scale in the laboratory dustparticles from different comets. We can use themas tracers for different processes that occurred inthe solar system four-and-a-half billion years ago.

The biggest surprise for the researchers was theabundance of so-called pre-solar grains in thedust sample. Pre-solar grains are tiny dustparticles that formed in previous generations ofstars and in supernova explosions before theformation of the solar system. Afterwards, theywere trapped in our solar system as it wasforming and are found today in meteorites and inIDPs. Pre-solar grains are identified by havingextremely unusual isotopic compositionscompared to anything else in the solar system.

But pre-solar grains are generally extremely rare,with abundances of just a few parts per million ineven the most primitive meteorites, and a fewhundred parts per million in IDPs. In the IDPsassociated with comet Grigg-Skjellerup they areup to the per cent level. This is tens of timeshigher in abundance than other primitivematerials.

Also surprising is the comparison with thesamples from Wild 2 collected by the Stardustmission. Their samples seem to be much moreprimitive, much less processed, than the samplesfrom Wild 2. This may indicate that there is a hugediversity in the degree of processing of materialsin different comets.


New Hydrogen Storage Method

This schematic shows the structure of the new material,Xe(H2)7. Freely ro tating hydrogen mole cules (reddumbbells) surround xenon ato ms (yellow). (Cr edit:Image courtesy of Nature Chemistry)

Dr Maddury Somayazulu, a research scientist ofGeophysical Laboratory at Carnegie Institutionand his research team have found for the firsttime that high pressure can be used to make aunique hydrogen storage material. The discoverypaves the way for an entirely new way to approachthe hydrogen storage problem.

They found that the normally unreactive, noble gasxenon combines with molecular hydrogen (H2)under pressure to form a previously unknownsolid with unusual bonding chemistry. Theexperiments are the first time that has combinedthese elements to form a stable compound. The

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discovery debuts a new family of materials, whichcould boost new hydrogen technologies.

Xenon has some intriguing properties, includingits use as an anesthesia, its ability to preservebiological tissues, and its employment in lighting.Xenon is a noble gas, which means that it doesnot typically react with other elements.

According to Maddury Somayazulu, elementschange their configuration when placed underpressure, sort of like passengers readjustingthemselves as the elevator becomes full. Theysubjected a series of gas mixtures of xenon incombination with hydrogen to high pressures in adiamond anvil cell. At about 41,000 times thepressure at sea level (1 atm), the atoms becamearranged in a lattice structure dominated byhydrogen, but interspersed with layers of looselybonded xenon pairs. When we increasedpressure, like tuning a radio, the distancesbetween the xenon pairs changed the distancescontracted to those observed in dense metallicxenon.

The researchers imaged the compound at varyingpressures using X-ray diffraction, infrared andRaman spectroscopy. When they looked at thexenon part of the structure, they realised that theinteraction of xenon with the surroundinghydrogen was responsible for the unusual stabilityand the continuous change in xenon-xenondistances as pressure was adjusted from 41,000to 255,000 atmospheres.

They were taken off guard by both the structureand stability of this material by changes inelectron density at different pressures usingsingle-crystal diffraction. As electron density fromthe xenon atoms spreads towards the

surrounding hydrogen molecules, it seems tostabilise the compound and the xenon pairs.

It is very exciting to come up with new hydrogenrich compounds, not just for our interest insimple molecular systems, but because suchdiscoveries can be the foundation for importantnew technologies. This hydrogen-rich solidrepresents a new pathway to forming novelhydrogen storage compounds and the newpressure induced chemistry opens the possibilityof synthesising new energetic materials.


Bang on: Success for collider as firstatom is smashed

In Geneva, two circulating beams produced thefirst particle collisions in the world’s biggest atomsmasher, the Large Hadron Collider (LHC), threedays after its restart.

According to director general Rolf Heuer ofEuropean Organisation for Nuclear Research(CERN), two beams circulating simultaneously ledto collisions at all four detection points.According to scientists it is a great achievement tohave come this far in so short a time. In thecontrol rooms of the collider and of the four giantparticle detectors, built and staffed by thousandsof physicists who have the job of interpretingthe data from the beginning of time, there wereall-round cheers.

Scientists are looking to the collider inside a27 km tunnel on the Franco Swiss border tomimic the conditions that followed the Big Bangand help explain the origins of the universe. Theproject intended to study proton-proton collisions

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to create conditions following the big bang, is aglobal Endeavour. CERN has received supportfrom countries around the world, including India,in getting the LHC up and running again.

The LHC is back

On 20 November, 2009, particle beams were onceagain circulating in the world’s most powerfulparticle accelerator, CERN’s Large HadronCollider (LHC). A clockwise circulating beam wasestablished at 10 pm on that day. This has been animportant milestone on the road towards firstphysics experiment at the LHC, expected in 2010.

It may be recalled that the initial efforts tocirculate the beams at LHC in September 2008was abandoned within nine days, as it suffered aserious malfunction. A failure in an electricalconnection led to serious damage, and CERN hasto spend over a year in repairing andconsolidating the machine to ensure that such anincident cannot happen again.

Decommissioning the LHC began in the summerof 2010, and since then successive milestoneshave regularly been passed. On October, 8, theLHC reached its operating temperature of 1.9Kelvin, or about -271 °C. Particles were injectedon 23 October, but not circulated. On 7 November,a beam was steered through three octants of themachine and circulating beams werereestablished. The next expected importantmilestone has been low energy collisions. Thesewould give the experimental collaborations theirfirst collision data, enabling important calibrationwork to be carried out. This is significant, that allthe data they have recorded comes from cosmicrays. Ramping the beams to high energy followedin preparation for collisions at 7 TeV (3.5 TeV per

beam) and the first collision between circulatingbeams at LHC was accomplished after three daysof its restart.

For the first time on 23 November 2009, the LHCcirculated two beams simultaneously, allowing theoperators to test the synchronisation of thebeams and giving the experiments their firstchance to look for proton-proton collisions. Withjust one bunch of particles circulating in eachdirection, the beams can be made to cross in upto two places in the ring. From early in theafternoon, the beams were made to cross atpoints 1 and 5, home to the ATLAS and CMSdetectors, both of which were on the look out forcollisions. Later, beams crossed at points 2 and 8,ALICE and LHCb.

Beams were first tuned to produce collisions inthe ATLAS detector, which recorded its firstcandidate for collisions at 14:22 on that day. Later,the beams were optimised for CMS. In theevening, ALICE had the first optimisation,followed by LHCb.

These developments come just three days afterthe LHC restart, demonstrating the excellentperformance of the beam control system. Sincethe start-up, the operators have been circulatingbeams around the ring alternately in one directionand then the other at the injection energy of 450GeV. The beam lifetime has gradually beenincreased to 10 hours, and on November 23,2009, the beams were circulating simultaneouslyin both directions, still at the injection energy.

This undoubtedly marks the beginning of afantastic era of physics and hopefully discoveriesafter 20 years’ work by the international communityto build a machine and detectors of unprecedented

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complexity and performance. The events so farmark the start of the second half of this incrediblevoyage of discovery of the secrets of nature.

Next on the schedule is an intensecommissioning phase aimed at increasing thebeam intensity and accelerating the beams. Allbeing well, the LHC should reach 1.2 TeV perbeam by the end of 2009 and would haveprovided good quantities of c ollision data forthe experiments’ calibrations.

(Source: CERN Press release)

Harnessing Waste Heat from Lap topComp uters, Cell Phones May DoubleBattery Time

According to Peter Hagelstein, an associateprofessor of electrical engineering at MIT, USA,existing solid-state devices are not very efficient asfar as conversion of heat into electricity isconcerned. The major objective of the presentresearch carried out by Hagelstein, with hisresearch student Dennis Wu, has been to find asto how close realistic technology could come tothe theoretical limits for the efficiency of suchconversion. Theory says that such conversion ofenergy can never exceed a specific value called theCarnot Limit, based on a 19th-century formula fordetermining the maximum efficiency that anydevice can achieve in converting heat into work.But current commercial thermoelectric devicesonly achieve about one-tenth of that limit. Inearlier experiments involving a different newtechnology, thermal diodes, Hagelstein workedwith Yan Kucherov at Naval Research Laboratory,and coworkers to demonstrate the efficiency ashigh as 40 per cent of the Carnot Limit. Moreover,the calculations show that this new kind of systemcould ultimately reach as much as 90 per cent ofthat ceiling.

Hagelstein and coworkers started from scratchrather than trying to improve the performance ofexisting devices. They carried out their analysisusing a very simple system in which power wasgenerated by a single quantum dot device, a typeof semiconductor in which the electrons andholes, carry the electrical charges in the device,are very tightly confined in all three dimensions.By controlling all aspects of the device, they hopedto better understand how to design the idealthermal-to-electric converter.

According to Hagelstein, with present systems itis possible to efficiently convert heat into

In everything from computer processor chips to carengines to electric powerplants, the need to get rid ofexcess heat creates a major source of inefficiency. Butnew research points the way to a technology that mightmake it possible to harvest much of that wasted heatand turn it into usable electricity. (Credit: iStockphoto/Evgeny Kuklev)

The production and usage of electric energy isalways associated with some loss of energy in theform of heat. In everything from computerprocessor chips to car engines to electric powerplants, the need to get rid of excess heat creates amajor source of inefficiency. But new researchmight lead to a technology that may make itpossible to harvest much of that wasted heat andturn it into usable electricity. That kind of wasteenergy harvesting might, for example, lead tocellphones with double the talk time, laptopcomputers that can operate twice as long beforeneeding to be plugged in, or power plants that putout more electricity for a given amount of fuel.

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electricity, but with very little power. It is alsopossible to get plenty of electrical power. Youeither get high efficiency or high throughput, butthe team found that using their new system, itwould be possible to get both at once. A key to theimproved throughput was reducing theseparation between the hot surface and theconversion device. A recent research paper by MITprofessor Gang Chen reported on an analysisshowing that heat transfer could take placebetween very closely spaced surfaces at a rate thatis orders of magnitude higher than predicted bytheory.

The work on the development of this newtechnology is already in process. This technologycould produce a ten-fold improvement inthroughput power over existing photovoltaicdevices.

The first applications are likely to be in high-valuesystems such as computer chips, he says, butultimately it could be useful in a wide variety ofapplications, including cars, planes and boats. Alot of heat is generated in transport vehicles and alot of it is lost. If it could be recovered, thetransportation technology is going to get moreenergy efficient.


Crystalline sponge capture CO2

To sequester carbon dioxide as part of any climatechange mitigation strategy, the gas first has to becaptured from the flue at a power plant or othersource. The next step is just as important: the CO2

has to be released from whatever captured it sothat it can be pumped underground or otherwise

stored for the long term. That second step can becostly from an energy standpoint. Materialscurrently used to capture CO2 have to be heated torelease the gas. But chemists at University ofCalifornia, Los Angeles, have claimed that a newclass of materials developed by them, calledmetal-organic frameworks (MOFs), hold promisefor carbon capture. In the study, Omar Yaghidescribes the performance of one MOF, which canfree moss of the CO2

it captures at roomtemperature. Yaghi described a metal-organicframework as a “crystalline sponge”, a hybridlattice of organic compounds and metal atomsthat has a huge internal surface area where gasmolecules can be absorbed.

The MOF used in the study contains magnesiumatoms, which make just the right environment forbinding carbon dioxide. In experiments, thematerial separated out CO2 while allowingmethane to pass. What was really surprising,though, was that at room temperature 87 per centof the CO2 could be released.

(Source: Tim es of India)

Indians Succeed in Complete Mappingof the Human Genome: Genome Patriof an Indian Male

It took the US Human Genome Project more thana decade and $500 million to sequence genesdrawn from several volunteers. A team of Indianscientists at the Institute of Genomics andIntegrative Biology (IGIB), New Delhi, of theCouncil for Scientific and Industrial Research(CSIR) has reported mapping of the entire genomeof a 52-year-old Indian male from Jharkhand in

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just 10 months, at a cost of $30,000 or Rs 13.5lakh. With this achievement, India joins the ranksof the few countries – the US, UK, Canada, Chinaand South Korea, which have successfullysequenced the human genome. Earlier, CSIRscientists had mapped the genetic diversity of theIndian population and also completed thesequencing of genome of the zebra fish,commonly used in laboratories as a model forresearching human diseases.

There are greater chances of arriving at a betterunderstanding of the genetic make-up andpeculiarities of local populations with countriescreating their own DNA sequences; as suchknowledge is crucial in comprehending countryspecific health trends and genetic traits thatwould otherwise remain largely a mystery. Thiswill enrich knowledge of the different geneticvariations that occur in different populationgroups as well as enable the identification ofgenes that predispose some to certain diseases.The male, whose genome was decoded by CSIRscientists, is predisposed to heart disease andcancer, and this information has been gleanedfrom the sequencing of his DNA. The researchfinding inter alias suggests that Indians are moresusceptible to not just for heart diseases, butcertain kinds of cancer and mental disorders aswell. The technology, therefore, would beinvaluable in diagnostics and could be useful inmedical treatment as well. Drugs designed totarget the affected genes could be formulated,though at present to do so would involve highcosts and such an option would be out of reach ofthe average patient. However, as with all sci-techbreakthroughs, costs are bound to come down –as it has in the case of the genome mapping

technology and various computer models – and itis only a matter of time before they becomeaffordable.

According to Sridhar Sivasubbu, who l ed theprojec t along with Vinod S caria, they haveaccomplished mapping of entire genom e in afew months whereas the first human genomeproject which associated scientists from the US,UK, Fr ance, Germ any, Japan and China tooknearl y 13 years , from 1990 to 2003. Of course, thefirst time is always tough, as every attemptinvol ves trial and error , opined Sivasubbu whileelabor ating on their work. H owever, it wasn’teasy f or the two scientists who worked up to18 hours a day in the lab. We would never havebeen there, never done it without having a totallynew set of analytical and computational skills,which has been one of the biggest chal lengesbefore us, asserts Sivasubbu. Once this wasattained, ther e was no looking back. Accordingto Scaria s ince the genome technology wasreadily avail able to them, it took much less time.In spite of this, Sivasubbu and Sc aria toiled forlong hours on their mission to map the 310crore (3.1 billion) base pairs that constituted theJharkhand man’s DNA utilising the facilities of asupercomputer, c apable of analysing data at thespeed of four trillion operations per second, thattheir institute had acquired in 2006. Although thesupercomputer speeded up analysis by morethan 500 times com pared to or dinarycomputer s, scientists had to perform the manualwork of immobilising the sample on glass slide,adding one nucleot ide at a time andphotographing it using a high-res olution digitalcamera. Each nucleotide was identified bypeculiar colour it emits.

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Law and ethical resolutions tend to lag behindimplementation of scientific and technologicaladvances, and the relatively new field of DNAsequencing is no exception. What if an individual’sgenome patri (horoscope) were accessible toemployers and insurance companies who mightuse the information against the employee orclients? Should an individual choose to revealdetails of his genetic ‘horoscope’ to his family andfriends or keep it private? Would the knowledgeimpact the individual’s own perspective of life and

how he lives it? There are plenty of issues that maycrop up for debate, especially since predispositionto a disease does not mean it would actuallymanifest in the person.

(Source: Tim es of India)

Compiled and edited byR. JoshiDESM, NCERT, New Delhi

Archana SharmaJPF, DESM, NCERT, New Delhi

SCIENCE NEWS

WEB WATCH

In this Section, we present websites and a briefintroduction about them. Inclusion of a site doesnot imply that School Science endorses thecontent of the site. Sites have been suggestedon the basis of their possible utility toschool systems.

• Nanotechnologyhttp://www.crnano.org

This website o f Centre for Responsible N anotechno logy talk s about the meani ng ofnanotechnolo gy, four gener ations of nanotechnology deve lopm ent, nanotechnology asgener al purpo se technology and as dua l-use tec hnology. It provides links to re latedtopics , for exam ple, Nanotechnology Basics for students and other learners, Nano-sim ulatio ns, and the futur e of nanote chnolo gy.

• Nobel Prize s for 2009http://www.no belprize.org

This we bsite provides details, life and work of scientists awarded, Nobel P rize inPhysics , Chemistry, Phyisiology or Medicine for the year 2009. It als o has details aboutAlfred Nobel, No bel organis ation and l ife and wo rks of all Nobel Laur eates.

• Holographyhttp://www.holophile.com

This we bsite is good resource for holography. I t gives detai ls of the his tory ofholography, bi ography o f its inventor Dennis Gabor 's biogra phy, and the science ofho lo gra phy.

• Simple Ho lography - The Easiest way to make Holographshttp://www.ho lokits.com/ - a-simple_h olography.htm

This is a write-up by T. H. Jeong, Raymond Ro, Riley Aumiller and M. Iwasa ki withcontribution from J eff Blythe. It explains, in simple steps, how to make reflection andtransm ission holograms. It als o has a link to another useful write up by the a uthorson, "Teaching Hologr aphy in classroo ms."

• Misconcept ions in Scie ncehttp://www.indiana.edu

What ar e misconcepti ons? How do c hildren form m isconcepts? How can teache rs bestaddress students' s cience misco ncepion? All this and mor e are provided in this website.It also has many links that provi des a list of references of research studies onmisc oncepti ons.

Compiled and edited by

V.P. SrivastavaDESM, NCERT, New Delhi

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WEB WATCH

YOU'VE ASKED

1. Question: Conversion of milk into curd is dueto the reaction of micro organisms,but on adding chilly or lemon dropsto kilk, it is not counverted in tocurd? Whi is it so?

P.S.PoojaJawahar Navodaya VidyalayaGalibredu, Madikeri,KodaguKarnataka

Answer: The milk is converted into curd by theaction of bacteria calledLactobacillus. Lactobacillus is a kindof bacteria which can convert a sugarinto an alcohol and then into an acidby means of anaerobic respiration.When milk is heated to a temperatureof 30-40 degrees celsius and a smallamount of curd is added to it, thelactobacillus present in the curdsample get activated and multiply.These convert the lactose, a kind ofsugar, present in the milk into lacticacid, which imparts the sour taste tocurd. Thus, these bacteria increasethe acidity of milk and at the sametime cause the milk proteins (casein)to tangle into solid masses, or curds.On the other hand, when we put thelemon drops or chilli, the milk is notconverted into curd but the fatspresent in the milk get coagulated

?and its water content gets separated.The citric acid present in lemon juiceconverts unsaturated fats of milk intosaturated fats, which begin to formlumps. This process is known ascoagulation. Other solid (colloids)particles, such as those of proteinspresent in the milk, also get trappedin the process of formation of lumpsof fats and the resultant product iscommonly known as cottage cheeseor paneer.

2.Question: In places with hot climate it isadvised that outer walls of housesbe painted white. Explain.

M. Rama RaoS/O Shri DurgarajuD. No. 3-115 (near the Post office)Puwala StreetKothapalli 533 285Gokauaram (M), East Godawari, Andhra Pradesh

Answer: White or light coloured surfaces aregood refl ectors of light and heat.Since sunl ight carries both light andheat, the outer walls of a buildingexposed to sunlight becom e hot byabsorbing its heat and in turn roomsinside the building also get heated.However, if the outer wal ls of thebuilding are painted white or with alight shade, a greater part of the heatgets reflected back. This helps inkeeping inside of the buildingcomparatively cool, particularlyduring summers.

3. Question: Who publishes red data book?

Aishwarya JoshiB 285, Sector 20, NOI DAGautam Budh Nagar (U.P.)

Answer: Red Data Book provides the list ofendangered animal and plant species.At international level it is prepared bythe International Union ofConservation of Nature or NaturalResources (IUCN). For India the RedData Book for endangered animals ispublished by the Zoological Survey ofIndia, Kolkata while that for plants ispublished by Botanical Survey of India,Kolkata.

4.Question: Why the region above hills, the skyand the water in oceans and deeprivers/lakes looks blue from adistance?

Wangtum LowungClass VIC/o Principal

Ramakrishna Mission SchoolNarottam NagarArunachal Pradesh

Answer: You may be aware that sunlight orthe white light is a mixture of lightof seven different colours; namelyred, orange, yellow, green, blue,indigo and violet. When a ray oflight enters from one transparentmedium like air into another suchmedium like glass or water itbends from its straight line pathin the first medium and begins tomove in a different direction,although along a straight linepath, in the other medium. Thisphenomenon is called refraction.However, in the case of white lightor sunlight the extent to whichdifferent colours in a ray lightbend is different. As a result, athin beam of white light onentering a drop of water or aglass prism splits into itscomponent colours and gives riseto a spectrum on emerging outon the other side of it. Thisphenomenon is known asdispersion of light.However, if the size of the waterdrop is very small, say the size ofa dust particle, the light exhibitsanother phenomenon calledscattering. The light falling onsuch small particles is firstabsorbed by them and thenemitted. The process ofabsorption and emission of lighttakes place in less than a

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YOU'VE ASKED

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Form IV (See Rule 8)SCHOOL SCIENCEmicrosecond. However, the direction

in which the light gets reemitted isdifferent from its initial direction ofpropagation, the angle between theinitial direction of propagation andthat of scattered light is called angleof scattering. The brightness weobserve around us after sun rise evenif a place is not directly illuminated bysunlight, is due to scattering of lightby the dust particles present in air.The light of different colours presentin sunlight too gets scattered indifferent directions, angle ofscattering is different for light ofdifferent colours. But, we usually donot perceive it, as our eyes receivelight from all possible angles due toscattering by a large number ofparticles and the combined effect ofthese give us the impression of whitelight. The blue colour of the sky is oneof the most familiar examples toperceive the effect of difference in theangle of scattering for light ofdifferent colours. As the sunlightenters upper regions of atmosphere,the fine dust particles present therescatter light of different colours indifferent directions. The red light isscattered the largest angle while theviolet and blue are scattered least. Asa result, red, orange, yellow and greencomponents of sunlight get scattered

away while blue, indigo and violetcomponents get scattered towardsthe surface of the earth. As our eyesare more efficient to perceive bluecolour as compared to indigo andviolet, we see the sky as blue. Theregion above hills appears blue for asimilar reason though the scatteringin this case is by the fine droplets ofwater that evaporates from the soil ortranspires from the trees that cover it.

When sunlight falls on the surface ofwater in oceans or deep lakes/rivers, afraction of light gets reflected, a partgets refracted while rest of it getsabsorbed. Water absorbs more of thered light present in sunlight; the wateralso enhances the scattering of bluelight. The part of the sunlight thatpenetrates the water is scattered by itsparticles and also by ripples in thewater. In deep water, much of thesunlight is scattered by the oxygendissolved in the water, and thisscatters more of the blue light. That iswhy the water in oceans and deeplakes or rivers appears blue to us.This phenomenon inspiredChandrasekhar Venkata Raman toinvestigate scattering of light whichled to the discovery of thephenomenon now known as RamanEffect. Raman was awarded the NobelPrize in 1930 for his work on light.

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To Our Contributors

School Science is a journal published quarterly by the National Councilof Educational Research and Training, New Delhi. It aims at bringingwithin easy reach of teachers and students the recent developmentsin science and mathametics and their teaching, and serves as a usefulforum for the exchange of readers' views and experiences in scienceand mathametics education and science projects.Articles suitable to the objectives mentioned above are invited forpublication. An article sent for publication should normally not exceedten typed pages and it should be exclusive to this journal. A hard copy ofthe article including illustrations, if any, along with a soft copy shouldbe submitted in CD. Photographs (if not digital) should be at least ofpostcard size on glossy paper and should be properly packed to avoiddamage in transit. The publisher will not take any responsibility orliability for copy right infringement. The contributors therefore shouldprovide copy right permission, wherever applicable, and submit thesame along with the article.Manuscripts with illustrations, charts, graphs, etc. along with legends,neatly typed in double space on uniform sized paper, should be sentto Executive Editor, School Science, Department o f Education inScience and Mathematics, NCERT, Sri Aurobindo Marg, New Delhi110 016 or email at scho o l.science@yaho o .co.in

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