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| Unravelling El-Nino mystery by Radhakrishna Rao Refrigerators of the future By B. R. Sood Science notebook On bombs and planets by Rajesh Kochhar |
Towards a cashless world by Dinesh Kumar New products & discoveries Save rain water by S.P. Malhotra Science Quiz by J.P. Garg |
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Unravelling El-Nino mystery |
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| Refrigerators of the future By B. R. Sood REFRIGERATORS in use at present have two main drawbacks. First, freon-12 gas is used in the compressor of the refrigerator and this gas is responsible for depletion of the ozone layer. Ozone layer in the upper atmosphere prevents ultraviolet radiation, coming from the sun, from reaching the earth. It is because of ozone layer that incidence of skin cancer amongst the human race is at a low level. Depletion of ozone layer is bound to change the scenario for the worst. Under the UN climate change convention, to which India is party, all nations are expected to switch over to ozone friendly refrigerants by year 2005. The second drawback is that moving parts in a refrigerator restrict its lifespan. Costly repair work is needed. It would be wonderful if a refrigerator without these two drawbacks is designed and marketed. Obviously, a refrigerator without a compressor is the answer. Making use of the phenomenon of thermoelectricity, it is indeed possible to have such a refrigerator. Refrigerator based on thermoelectric materials (TEM) which are akin to solid state electronic devices have no moving parts, are very convenient and extremely reliable and their technology is environmentally cleaner. However, their efficiency of cooling at present is about one-third the value that for conventional compressor based refrigerators. For this reason, thermoelectric refrigerators are used in specialised applications where reliability and convenience is more important than economy. These applications are varied and include spot cooling of a computer’s chip or an infra-red detector or a beverage cooler powered by a battery in a car. Thermoelectricity was discovered by Seebeck and it is the appearance of a voltage difference across a material whose two ends are kept at different temperatures. This results in an electric current flowing under the influence of a temperature difference and hence the name thermoelectricity. Voltage difference across a thermoelectric material of unit length whose ends are kept at a temperature difference of one degree is known as Seeback coefficient (or thermoelectirc power). A thermocouple is a device formed by joining two wires of thermoelectric materials having varied thermoelectric properties. When a current is passed in a device having two junctions one junction gets could and the other gets heated. Reversal of current flow leads to hot junction becoming cold and vice versa. Since in a thermoelectric material both the current flow (due to potential difference) and the heat flow (due to temperature difference) are involved, the efficiency of a material for use in a thermoelectric device would depend on their thermoelectric power, electric and thermal conductivities. It is convenient to define a figure of merit parameter (FMP) for thermoelectric materials. FMP is product of the square of the thermoelectric power, temperature and the ratio of electrical and thermal conductivities. It is desirable to have a high value of FMP and for that it is imperative that the material be a good conductor of electricity and a bad conductor of heat. Till about a decade back semiconductor materials like Bismuth Telluride and Antimony Telluride were though to be the best materials. These materials had a FMP around 1. However for thermoelectric refrigerators to find wide applications a desirable value of FMP is around 3. More recently a number of materials with FMP greater than one have been explored and that has given a boost to the research activity in this field. Theoretically, it has been found that FMP values of around 10 is feasible. More research work is needed before such high values of FMP are achieved and full potential of thermolectric refrigerators, the refrigerators of the future, is realised. Currently materials under study which have the possibility of having high FMP values are CoFe3 CoSb12, LaFe3 CoSb12 which are formed by starting from the material CoSb3. Another possible candidate with better future is a structure consisting of alternate thin film layers of PbTe and Pb 0.927- Eu 0.073 Such finely tuned structures have given FMP value of around 2 which is a very encouraging sing for the future refrigerator based on thermoelectric materials. The writer is Professor of Physics, Punjabi University, Patiala.  |
| Towards a cashless world by Dinesh Kumar Forget fat wallets and heavier pockets weighed down with small change. Forget also the bother of trying to buy a small thing when all you are carrying is hundred rupee notes. The world is moving on to paying electronically, through smart cards. They promise to make your pocket lighter and give you all the convenience of not carrying cash. You can forget being the victim of shopkeepers who are perpetually conspiring to palm off their dirty and torn currency notes to you! The cash card is not a credit card, though it may look like one. In the case of credit cards, one buys things on credit and a bill is received in the subsequent month. If the amount is not settled or is settled partially, interest must be paid on the balance amount, which may be as high as 2.5 to 3 per cent per month. In the cash card, one uses one’s own money. Just as one withdraws money from a savings bank, one will have the card filled electronically and go about paying for purchases at different shops, downloading cash again once the balance is exhausted. The technology has been successful in Europe. Experimental cards have already been tried out all over the world over and now in India as well. In Delhi, the supermarket Nanz has its own smart cards. A similar card is available in Hyderabad also. Because of the convenience that it promises, smart cards are the cash of the future and it is only a matter of time before they invade Chandigarh too. It will, however, be some time before the cards find wide acceptability. How the technololgy works is simple. The cards carry an electronic chip which stores an amount electronically. The retailer must have a machine that can read the card. Once inserted in it, the machine debits the price of the newspaper of coffee from it, leaving the balance intact. Security is ensured through a Personal Identification Number (PIN), which the user must not disclose to the retailer. If you have a fear of losing money, the cards are particularly useful, since they cannot be used by anybody who does not know your PIN. In the case of loss, of course, all one has to do is to inform the bank. The cards can be disposable, to be thrown away once their balance is finished, or they can be rechargeable, to be used again and again by loading cash on them. Both technologies are being tried out. Already, pre-paid cards are being used for public telephones and transport systems in Europe and some mobile phone companies in India have introduced such cards here as well. Smart cards were tried out in the Atlanta Olympics. Each athlete was given a card, which could be used throughout the Olympic area to pay for goods or services. Others could buy prepaid cards. But the scheme failed in Atlanta, because not all stores accepted the cards and one had to search for a place where the card could be used. That is not stopping the companies. In Australia. the USA and England, companies are trying out various types of smart cards. An Australian company has gone a step further. It has designed a watch which does the functions of a smart card. The watch has a small antenna in the form of a ring circling the watch face. The wearer just has to wave his wrist in front of electronic readers to make a purchase or pay for the bus fare. Users are encouraged to use the system through discounts offered on purchases. Transactions on the watch are also secured through the PIN that must be used every time by the user. The cards and the watches represent a big advantage as they do away with the need for handling large amounts of cash. Petrol pumps and restaurants will be less susceptible to robberies. They are a step better than a credit card, since no vouchers have to be signed and no confirmation has to be obtained from the credit card company. There are two limitations to the technology. First, it requires that a large number of retailers start accepting the cards. The value of any card is limited if it is not accepted in the city. Second, banks may charge a little fee for issuing the cards and downloading cash on them. Will the customers be willing to pay? Banks will also have to agree on a single terminal that can use all cards. If each bank goes separately, retailers will find it cumbersome to install a number of machines. A common technology has already been agreed upon by companies in Europe. Cash cards are still to catch up in India, but there is little doubt that it is the technology of the future. With Indian companies already launching smart cards, banks cannot be far behind. The nationalised banks will of course find it difficult to adapt to the new technology, given their lethargic staff, but the new-generation private banks might spearhead the change towards a cashless world. |
| Save rain water by S.P. Malhotra Farmers of Haryana do not have any history for agitations, much less for the violent ones. On the other hand they are known to be generally peaceful; they have been tolerating the numerous shortcomings in their canals which seldom had a satisfactory water supply. But today, they are on a war path. To blame it on Punjab’s decision of making water and electricity free, or the instigation of some political party, would be an oversimplification of a complex problem. Here is a professional’s assessment regarding the genesis of the present Orisis as well as a solution for the same. It was somewhere in the sixties when the government formulated schemes inviting farmers for installing their private electric tubewells for making use of the water from the hitherto unexploited underground reservoir. The response from the farmers was overwhelming and today, there are over five lakh such tubewells. These have proved to be the backbone of the green revolution in this state. The cost of working a tubewell depends upon the depth from which it has to lift water and this plays a crucial role in the economics of its performance. Because of this, the government had to see that the level of the groundwater did not go so low as to make its working uneconomical. To guard against this, the government took great precautions for working out, as carefully as possible, the extent of the annual recharge which could be expected through the natural resources like the rainfall and the seepage through the canals and drains. The withdrawals by the tubewells was planned to remain below this recharge. Despite this precaution, something went wrong somewhere; the levels of the groundwater started falling as early as in the seventies and have been steadily going down since then. Even the more than average rainfall during the last 10 consecutive years has failed to make any difference. What shall be its fate 20 years late? Obviously the recharge had been overestimated. This was a man-made mistake and not a natural calamity. Not only the state government has done nothing to neutralise the effects of this mistake, the issue is not even on its agenda. All that it did was to devise a formula for giving some relief to farmers; the Electricity Board was asked to supply electricity to farmers on reduced rates not for the actual units consumed but on the basis of the horsepower of the motor installed. As the fall in the levels of the groundwater continued, farmers had to keep on installing motors of bigger and bigger HP and thus pay more and more for the same quantity of water pumped year after year. Thus this formula did not prove to be a damage control measure. This is the crux of the present agitation by farmers. The one and the only long-term solution of this problem is first to arrest the decline in the levels of the groundwater and then to raise these to the safe limits. This can be done by diverting the huge quantity of rain water, now going waste via its numerous drains into the rivers like the Yamuna and the Ghaggar, into the underground reservoir. At present Haryana does not have the requisite technology for this. As it is highly situation specific, it cannot be borrowed from outside and, therefore, it has to be developed after some research. In this age of knowledge explosion it should not be difficult to do so. Such a technology is a question of life and death for these tubewells and consequently for Haryana, should not the farmer-friendly goverment of Haryana pay immediate attention to this vital question? The writer is a former Engineer-in-Chief, Haryana Irrigation Department. |
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products & discoveries Genes hold key to fight ageing The secret to fight ageing may lie in one’s genes, according to a Banaras-based scientist who says genetic manipulation may defer ageing by about 20 years. Ageing is a progressive change taking place in an organism after adulthood, leading to death. According to M.S. Kanungo from the department of Zoology at the Banaras Hindu University (BHU), ageing is a “genetically controlled” process which occurs in organisms over a period of time due to reduced functions of various organs of the body. The facts that individuals of similar species have a fixed life span, identical twins have similar longevity, progency of long-live members live longer and changes within organisms appear well-timed indicate that ageing has a genetic basis. Kanungo reported in the journal Current Science. But Kanungo rules out the possibility of a “single master gene” responsible for ageing as different organs are controlled by different genes, and each organ follows its own specific pattern of ageing. Different organs age at different times and at different rates. According to his “gene regulation theory” of ageing, the depletion of certain “nuclear proteins or factors” responsible for keeping essential genes active leads to depressed functions of organs. If one can design ways to reverse this effect. “It would prolong the youthful period in humans by 20 years or more”, the report says.Apart from prolonging life, it would “postpone onset of old-age diseases like heart and brain disorders, arthritis, cancer and Alzheimer’s disease” that set in after the age of 50, the report says. Cameras that see the invisible Though sunflowers appear yellow to the naked eye, it may soon be possible to view an invisible green pattern at the centre of sunflower petals, thanks to two new colour television (CTV) cameras developed by Japanese researchers that can capture pictures invisible to the human eye. The pattern is called “nectar guide” which according to scientists tells insects where the nectar lies. It is amongst a host of other phenomena which can be viewed using the cameras, according to a report in IEEE Transactions on Broadcasting. The TV cameras can be applied in various fields like science, art, medicine and industry and are of immense help to producers of science programmes. An ordinary CTV camera shoots images within the range of visible light — wavelength from 380 nanometres (nm) to 780 nm. The new cameras, developed with joint efforts of Fuji Photo Optical Company Ltd. and Hitachi Denshi Ltd. reproduce information using visible light and the invisible ranges of ultraviolet (UV) and infrared (IR) light, the report says. New material for lithium battery Material scientists at Masssachusetts institute of Technology (MIT) USA, have come up with a family of less expensive and potentially better performing candidates to replace the electrode material currently used in lithium batteries. When a device like laptop computer or cellular phone, powered by lithium batteries, is switched on, positively charged particles of lithium (ions) travel from the positive electode (anode) of the cell to the negative electrode (cathode) to insert themselves in the crystal structure of the cathode material, reports Chemical & Engineering News. To balance the positive charge, negatively-charged electrons released from lithium travel in the opposite direction and get exchanged at the positive electrode. Based on their calculation, the MIT team has predicted that coating of aluminium on lithium cobaltoxide electrodes can enhance the activity of the cell by forcing oxygen to play a larger role in the electron exchange process. But though participation of oxygen in the exchange process increases the operating voltage of the battery, higher voltage degrade the electrolyte solution of the cell thereby shortening a battery’s lifetime. Researchers are currently busy in improving the short comings associated with this new material. Hydrogen from water and light Using light as the only energy input, U.S. researchers have created a combined photovoltaic-photoelectrochemical cell that splits water into hydrogen and oxygen at an efficiency almost twice as high as reported earlier. The work, which could have major implications for the generation of renewable energy, was carried out by scientists at the National Renewable Energy Laboratory (NREL), Colorado, reports Chemical and Engineering News. According to the scientists, the machine is able to split water for the first time with such high efficiency. Earlier, scientists had tasted success in developing a photoelectrochemical cell that could split water just as efficiently but those cells required application of an external potential in addition to light. In the NREL device, additional potential is provided by its built-in photovoltaic component. Hydrogen is an ideal fuel from an environmental standpoint, because the only by-product of its combustion is water. But producing hydrogen from renewable resources is currently very expensive and economically unviable. The new device demonstrates that it may eventually be possible to generate hydrogen — a non-polluting and totally recyclable energy carrier — directly and efficiently out of two of our planet’s most abundant natural resources, sunlight and water. The device can produce hydrogen directly from light with 12.4 per cent efficiency. It is a unique combination of a gallium indium phosphide photo-electrochemical cell and a gallium arsenide photovoltaic cell. The photovoltaic component provides the voltage boost needed to electrolyse water efficiently. |
| Science notebook On bombs and planets by Rajesh Kochhar IF you are a poet or a playwright you may assert that there is nothing in a name. You would perhaps argue that what matters is how a thing looks or smells rather than what it is called. However, if you are a student of science, you would notice that nomenclature itself can provide some useful contextual information.Take the case of two fissionable elements recently in news: uranium and plutonium. A tale indeed hangs by their name. Both are named after planets. The five planets, from Mercury to Saturn, are visible to the unaided eye. They therefore were known to all cultures who independently gave them names of their choice. In 1780 a planet beyond Saturn was discovered telescopically. The discoverer, William Herschel, wanted to name it after his king. Fortunately, better sense prevailed and, instead, the name Uranus from Greek mythology was adopted. Nine years later, in 1789 M.H. Klaproth discovered new element uranium. It was isolated from the ore pitchblende. The fact that Uranus and uranium were discovered close together, in the 18th century itself, tells us that uranium occurs naturally. The discovery of radioactivity itself had to wait for another 100 years. In 1896, the French physicist Henry Bacquerel discovered the uranium continuously emitted radiations of great penetrating power which were independent of external energy sources. In 1940, Edwin McMillan and Philip Abelson bombarded uranium with neutrons and obtained a new element, a man-made one. It was named neptunium. The name in fact suggested itself. In 1846, planet Neptune that lies beyond Uranus had been discovered. It was only natural to name an element obtained from uranium after the planet following Uranus. The planet after Neptune, Pluto, (discovered in the 1930s) lent its name to yet another element plutonium, produced in 1940 by bombarding and isotope of uranium (U-238) with deuteron (heavy hydrogen). Unlike uranium, which does have a stable isotope, all isotopes of plutonium are radioactive. The most important is plutonium — 239 because, it is fissionable and can be readily produced in large quantities in breeder reactors by neutron bombardment of uranium-238 which is easily available but is itself non-fissionable. Most elements were produced in the laboratory, but the solar system had run out of planets. These elements were named after America, California, Einstein, etc. Scientists and Hiroshima It was the greatest regret of Albert Einstein’s life that he lent his name to an appeal for making nuclear bomb. It is however not very well known that the decision to drop the bomb in Japan was taken with the explicit approval of US scientists. In April, 1945, the USA appointed an Interim Committee for “advising the President on the various questions raised by our apparently imminent success in developing and atomic weapon”. This eight-member committee included three scientists who were the presidents (vice-chancellors) of Carnegie Institution, MIT and Harvard University, besides holding advisory positions in the government. This committee in turn was assisted in its work by as Scientific panel comprising four well known nuclear scientists. A.H. Compton, Enrico Fermi, E.O. Lawrence and J.R. Oppenheimer. The Interim Committee and the Scientific panel recommended that the bomb be used against Japan as soon as possible and that no prior warning be given of the nature of the new weapon. There was only one dissenting voice which objective to the no-warning clause. The objection came not from a scientist but from the under secretary of the navy! |
| Science Quiz by J.P. Garg 1. America is strongly protesting the recent deal regarding sale of nuclear power reactors by Russia to India. Earlier, the USA had successfully stalled the sale of special engines needed for ASLV (Augmented Satellite Launch Vehicle), which India is now on the threshold of developing indigenously. What are these type of engines called? 2. Which country has conducted the maximum number of nuclear tests till now? How many? When did it conduct its first nuclear test? 3. Man has already created animal-animal hybrids. Now there is a move to create human-animal hybrids, which is being strongly resisted by some right thinking scientists. What is the general name of such hybrids? 4. Prolonged use of mosquito repellents can lead to harmful side-effects. Which ingredient is there in these repellents that can cause headache, itching of nose and throat, eye burning, asthma or even damage to liver? 5. Acetylsalicylic acid is used as a medicine in aches and pains. What is its common name? 6. “Mericks” has been in the news recently. What is it and what does it do? 7. What is a fathometer used for? 8. What are the remains of past plant or animal life preserved in earth’s crust called? 9. Name of the world’s oldest working steam locomotive. Between which two stations does it run a tourist train? 10. Who synthesised water from oxygen and hydrogen for the first time? ANSWERS 1. Cryogenic engines 2. USA; 1032; on July 16, 1945, in Alamogarda 3. Chimera 4. Pyrethrines 5. Aspirin 6. It is a disease that kills chickens 7. To measures depth of sea 8. Fossils 9. Fairy Queen; Delhi and Alwar 10. English chemist and physicist Henry Cavendish. |
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