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A hot idea for cooling
Violence linked to screen images Scientists discover ‘drunk’ gene
Trends
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A hot idea for cooling NOWADAYS refrigeration is becoming increasingly important, especially for rural India. However, the high cost of compressor-based cooling machines (fridges) and unavailability or erratic supply of electricity are some of the bottlenecks that need to be removed, so that the benefits of refrigeration reach the common man. It is well known that the efficiency of a compressor-based cooling unit depends on its size, and when the size is reduced to a kitchen refrigerator, the compressor itself becomes less efficient. An approach to combining thermoelectrics with compressors sounds like a logical argument to increase cooling efficiency in domestic as well as commercial-scale refrigeration systems. In such a case, thermoelectric becomes increasingly more attractive. Thermoelectric cooling is based on the Peltier effect, in which current passes through a circuit of two dissimilar conductors and results in a temperature change at the junction. In this direction, a hybrid refrigerator can bring efficient, cheap cooling to rural India. A company based in Cambridge, MA, has developed a new solar-powered refrigeration system for food storage, which can prove to be a refrigeration boon to Indian villages that are off the grid. The design is a hybrid of conventional compressor-based refrigeration and thermoelectric materials—semiconductors that convert electricity into cooling and vice versa. In a thermoelectric module, voltage applied across a thermoelectric material sandwiched between two ceramic plates makes one side hot and the other cold. However, existing thermoelectrics, which are used in temperature-controlled car seats, lasers and portable picnic coolers, typically bismuth or lead telluride, are not efficient enough for large refrigerators. The new solar-powered refrigeration system combining thermoelectric- and compressor-based cooling could be used in off-grid villages in India. The refrigerating units would be cheaper than what is currently used in Indian villages, most of which are off the grid. In such villages, food distributors and processors store raw food products in traditional compressor-based cooling units that run on diesel generators. Developers of this project feel that even including the expense of the photovoltaic (PV) panels, this would cost the same or slightly less than the diesel-powered refrigeration units. More important, it would have no fuel costs, and almost no maintenance costs. According to the company’s initial calculations, using a compressor combined with thermoelectric modules would use 20 per cent less power to generate the same cooling as a compressor alone. The company estimates that the fridge costs 66 per cent less to operate because of the ability to remotely monitor and diagnose problems, as well as the need for fewer fossil fuels. The design uses off-the-shelf components: silicon PV panels, thermoelectric modules, and a compressor-based refrigeration unit. The company’s control system directs the two cooling components to work together, so that they utilise the solar panels to maximum capacity. Early in the morning and late in the afternoon, when the amount of sunlight is low, the solar panels won’t generate enough power to run the compressor. But there will be enough solar power to run the thermoelectric modules, which will generate cooling until the compressor takes on the job. Around midday, when the solar panels are working at full capacity to generate heat, the thermoelectric modules will use the extra heat that the compressor doesn’t need to provide additional cooling. The company (Promethean, USA) has already built a laboratory-scale 60-liter solar-assisted thermoelectric refrigerator and has plans to build a 500-liter prototype very soon. The standalone device is cooled by a hybrid compressor and three-to-five 180-watt solar panels. The refrigerator uses thermoelectric cooling instead of Freon and can reduce the dependence on diesel generators. The 60-liter prototype uses bismuth-telluride modules that are the most efficient cooling material known so far, but there is still room for improvement with new, possibly more-efficient thermoelectric materials in near future. The company also has future plans of using only thermoelectric modules hooked up to PV panels. Many advances in thermoelectric materials have come out of laboratories recently. Researchers have been successful to increase the efficiency of bismuth antimony telluride by 40 per cent by using nanocrystalline materials. The researchers are also tinkering with lead telluride and are starting to use silicon nanowires and silicon-germanium composites. The new technology, which has the potential to displace vapour-compressor refrigeration, can bring a revolution in the life of country’s rural masses by providing cheap, durable, problem/maintenance-free and eco-friendly refrigeration system. The writer is from the Department of Physics,
S.L.I.E.T., Longowal |
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Violence linked to screen images WaTCHING violent television programmes or video games can make teenage boys more prone to aggressive behaviour, according to a study that strengthens the case for curbing the amount of violence depicted in film and video. The research, published in Social Cognitive and Affective Neuroscience, used a medical scanner to investigate the brain activity of 22 boys aged between 14 and 17 while they viewed four-second video clips of violent scenes taken from 60 different videos. “We found that as the boys were exposed to more violent videos over time, their activation in brain regions concerned with emotional reactivity decreased and that was reflected in the data from the (brain scanner) and in the skin-conductance responses,” said Jordan Grafman who carried out the study at the US National Institute of Neurological Disorders and Stroke in Bethesda, Maryland. “The important new finding is that exposure to the most violent videos inhibits emotional reactions to similar aggressive videos over time,” Dr Grafman said. The study suggests that exposure to violent videos will make an adolescent less sensitive to violence, more accepting of violence, and more likely to commit aggressive acts, he added. —
The Independent |
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Scientists discover ‘drunk’ gene A gene that helps drink go to your head has been discovered by scientists. As well as providing a cheap night out, it is believed to protect against alcoholism.
Previous research has shown that people who react strongly to alcohol are less likely to become alcoholics. The gene, CYP2E1, provides the coded instructions for making an enzyme that breaks down alcohol. Scientists found that 10 to 20 per cent of the population possess a particular version of the gene that causes them to get drunk easily. The first few drinks during a night out will leave these individuals feeling more inebriated than their friends. Drugs that enhance the effect of CYP2E1 could in future be used to sensitise people to alcohol before an evening’s drinking—or even sober them up when they have had one too many, said the researchers. Scientists in the US investigated the genetics of 237 college student siblings who had one alcohol-dependent parent but were not alcoholics themselves. They homed in on an end region of chromosome 10 where the CYP2E1 gene resides. Participants’ response to drinking was linked to their genetic make-up. Students were given a mixture of grain alcohol and soda that was equivalent to about three average alcoholic drinks. At regular intervals they were then asked whether they felt drunk, sober, sleepy or awake. Senior study author Professor Kirk Wilhelmsen, from the University of North Carolina at Chapel Hill, said: “We have found a gene that protects against alcoholism, and on top of that, has a very strong effect. “But alcoholism is a very complex disease, and there are lots of complicated reasons why people drink. This may be just one of the reasons.” The findings were published in an early online edition of the journal Alcoholism: Clinical and Experimental Research. —
The Independent |
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Trends JERUSALEM: Scholars and anyone with an Internet connection will be able to take a new look into the Biblical past through an online archive of high-resolution images of the 2,000-year-old Dead Sea scrolls. Israel Antiquities Authority (IAA), the custodian of the scrolls that shed light on the life of Jews and early Christians at the time of Jesus, said it was collaborating with Google's research and development center in Israel to upload digitized images of the entire collection.
Osteoporosis drug regrows jaw bone
BOSTON: The osteoporosis drug Forteo can regrow bone in jaws damaged by severe bone-destroying conditions called osteonecrosis and periodontitis, doctors reported last week. The research, reported at the annual meeting of the American Society for Bone and Mineral Research in Toronto, suggests that the drug may spur growth in a damaged jaw, the researchers said.
Obama to appear on science show 'Mythbusters'
WASHINGTON: President Barack Obama said he was appearing on "Mythbusters", a television series that uses science to separate fact from fiction. Obama's appearance on the popular Discovery Channel show is part of a White House effort to highlight the importance of science, maths and engineering as experts warn that low interest in these subjects among the US students could hurt the economy.
German ‘heatball’
wheeze outwits EU light bulb ban
BERLIN: A German entrepreneur is bypassing a European Union ban on light bulbs of more than 60 watts by marketing his own brand as mini heaters. Siegfried Rotthaeuser and his brother-in-law have come up with a legal way of importing and distributing
75- and 100-watt light bulbs-by producing them in China, importing them as "small
heating devices" and selling them as "heatballs".
The problem with phthalates
BRUSSELS: Imagine a child sitting in his classroom, gazing through the window at the rain. He picks up his pencil and chews distractedly on the eraser at its top. Chemicals, classed in Europe as "toxic to reproduction," dissolve in his saliva and enter his body. It's a scenario that may not be unusual. A report published by a consortium of 140
environment groups shows that potentially risky chemicals (phthalates) are present in dozens of everyday plastic items for sale by European retailers-from shoes to erasers, from pencil cases to sex toys. — Reuters |
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S.S. Verma
