SCIENCE & TECHNOLOGY

Fuel-efficient stoves
Radhakrishna Rao

For centuries, rural communities in India have been using highly inefficient, wasteful and pollution generating mud stoves for cooking. On the one hand they consume large volumes of firewood without producing commensurate volume of heat energy. On the other the uninterrupted smoke emitted by them causes indoor pollution, posing a serious threat to the health of the rural women.

Genetic tests: How useful?
Steve Connor

People who buy genetic tests from private companies offering to scan their entire genomes for genes linked to diseases such as Alzheimer’s or breast cancer are wasting their money, according to a panel of eminent scientists.

Spring time on Mars
On spring days on Mars, powerful geysers sometimes spew carbon dioxide "steam" and dust to great heights, a phenomenon unlike anything ever seen on earth, scientists said on Tuesday. These eruptions can be so strong that the falling dirt creates fan-shaped patterns extending hundreds of metres.

THIS UNIVERSE
PROF YASH PAL
Please explain the working of an atom bomb. How does it explode?
I can only talk of the principles of physics and engineering behind the making of the atom bomb. I cannot give you manufacturing details because I have never made any such bomb myself.

Prof Yash Pal
Prof Yash Pal

Trends
Dolphins say it with weeds

A man may bring flowers to impress women, but male Amazon river dolphins carry weeds to win over the opposite sex, British and Brazilian researchers say. The discovery comes from a three-year study of more than 6,000 groups of dolphins in Mamiraua, a flooded rainforest reserve in the Amazonian, British weekly New Scientist reports in its next issue.

Kangaroo that didn't hop
Evolution on fast forward


 


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Fuel-efficient stoves
Radhakrishna Rao

Philips stove
Philips stove

For centuries, rural communities in India have been using highly inefficient, wasteful and pollution generating mud stoves for cooking. On the one hand they consume large volumes of firewood without producing commensurate volume of heat energy. On the other the uninterrupted smoke emitted by them causes indoor pollution, posing a serious threat to the health of the rural women.

Of course, many government sponsored agencies, voluntary organisations and research institutions in India are engaged in designing, developing and popularising energy-efficient stoves that help cook food without causing serious indoor pollution. According to an estimate by WHO the pollution levels in rural Indian kitchens are 30 times higher than safe recommended levels.

Of late, corporate giants and multinationals too are contributing to the development and popularisation of energy efficient and ecofriendly stoves. For instance, Philips Research in Bangalore has developed a woodstove designed to use energy efficiently and also reduce smoke and toxic emissions. More importantly, this innovative stove reduces indoor pollution caused by smoke up to 90 per cent and organic volatile emission up to 98 per cent of the level of traditional cooking fire.

The most outstanding feature of this improved stove is an electronically controlled fan which forces air through the stove, leading to high temperature. Further, a thermoelectric generator using the heat from the burning wood produces electricity for the fan.

In addition, the generator is also equipped to power external equipment like radios or light bulbs. One conspicuous feature of this cooking stove is that it takes less time to heat up and also less time to reach cooking temperature. Philips Research plans to market and popularise this improved stove by roping in partners.

Not to be left behind, the UK-based Shell Foundation as part of its Breathing Space programme is planning to popularise clean and improved stoves in five countries, including India. To achieve this target, the Shell Foundation has joined hands with Envirofit International, a US-based NGO. With the funding and organisational support of Shell Foundation, Envirofit will design, develop and distribute clean cooking stoves that are specifically engineered to emit significantly, less toxic emissions and use less fuel.

“With half the world's population still cooking on wood, dung and other biomass burning stoves, the only way we are going to make a significant long- term impact and achieve the scale needed is by getting the private sector involved,” says Shell Foundation Director Kurt Hoffman.

Nearer home, the Mysore-based Centre for Appropriate Rural Technologies (CART) has come out with a highly efficient, smokeless bio residue gasifier stove. According to CART sources, this environmentally friendly stove is designed to exploit the bio residues available in abundance in rural areas of India. CART has named this stove as Anila. According to U.N. Ravikumar, Director of CART who innovated the concept and design of Anila, the biggest advantage of this stove is that the rural women will not inhale the smoke while cooking.

Anila, which has an efficiency level of around 40 per cent, uses bio-residues in the form of coconut frond, bagasse, groundnut shells, rice husk, areca waste and mulberry leaves. Incidentally, Anila remains hot for about half an hour after the burning stops. This can be used to retain the heat in the cooking vessels.
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Genetic tests: How useful?
Steve Connor

People who buy genetic tests from private companies offering to scan their entire genomes for genes linked to diseases such as Alzheimer’s or breast cancer are wasting their money, according to a panel of eminent scientists.

Several companies have begun offering genome-wide scans of a person’s DNA over the internet but potential customers have been warned that the science is still too preliminary to provide any meaningful information.

Medical specialists also warned there was a risk of people being misled about the results of such scans that could make them either over-anxious about being labelled “high risk”, or over-confident that they were at low risk of a particular disease.

“For people who are considering taking these tests, my simple message is, don’t,” said Christine Patch, a consultant genetics counsellor at Guy’s Hospital in London and a member of the Human Genetics Commission. “You are wasting your money.

“The risk is the anxiety caused but I also think there is a risk of false reassurance, for example to be told that you are at low risk of heart disease which may lead someone to carry on smoking. It’s not enough to say that these tests provide useful information because actually people taking these tests believe that the information they are getting are a genetic prediction.”

In the past year several companies have entered the market offering to scan a person’s complete genome for up to 500,000 genetic “markers” that can indicate anything from the risk of heart disease to ethnic origins.

DecodeMe, based in Iceland, offers a screening service for about 500 pounds which can scan for more than a dozen common diseases known to have a genetic component. Customers send cheek swabs through the post and have access to the information via a password-controlled website run by DecodeMe.

Two other companies, Navigenics, based in Silicon Valley, California, and 23andMe, set up by the wife of one of the founders of the internet giant Google, are to offer a similar service.

“These are significant companies with substantial backing. We are not talking about fringe players without any kind of presence or substance,” said Stuart Hogarth of the University of Nottingham who is calling for new rules to control how these firms can operate in the UK and Europe.

— The Independent
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Spring time on Mars

On spring days on Mars, powerful geysers sometimes spew carbon dioxide "steam" and dust to great heights, a phenomenon unlike anything ever seen on earth, scientists said on Tuesday.

These eruptions can be so strong that the falling dirt creates fan-shaped patterns extending hundreds of metres.

"Here's a place that looks wildly different than anything on earth," NASA scientist Candice Hansen said at a meeting of the American Geophysical Union.

Mars and earth are similar in that both are small, rocky planets with seasons caused by tilts in their axes, although the Martian year is twice as long as ours. But the seasonal geysers illustrate one result of their vast differences in climate.

In winter, the southern pole of Mars is minus 200 degrees F (minus 129 C), so cold that carbon dioxide in the atmosphere freezes to form a layer of dry ice about 20 inches thick.

On spring days, dry ice warmed by sunlight begins to turn into gas, some of which is trapped between the planet's surface and the remaining ice. When the pressure grows strong enough, the gas erupts through cracks or vents like a steamy jet, Hansen said.

As the day goes on and the planet's surface warms, the eruptions become larger. By midday, the gas also carries dust, which by evening has fallen on the surface in long fan-shaped patterns.

"I would call it a dust plume or a gas jet," Hansen said. "We've never actually caught one in action, but the fans that they leave behind are certainly impressive." — Reuters
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THIS UNIVERSE
PROF YASH PAL

Please explain the working of an atom bomb. How does it explode?

I can only talk of the principles of physics and engineering behind the making of the atom bomb. I cannot give you manufacturing details because I have never made any such bomb myself. In fact, even if I had I would not tell you because that would be wrong, against law and my personal principles. The physics goes like this:

From hydrogen to uranium there are 92 chemical elements that are stable enough to be found in sufficient quantity on earth. Everything we see is made of these elements. The chemical properties of the elements depend on the electron cloud of the atoms of these elements. The number of electrons in neutral atoms is equal to the number of protons in the nucleus of the atom. But the nucleus does not contain only protons, except for the hydrogen atom whose nucleus is just a single proton. If this were so the nucleus would break up because of the mutual repulsion between positively charged protons. To overcome this problem nature had made room for particles that have nuclear forces like the proton but are electrically neutral. These particles, called neutrons are put in the nucleus to provide a strong mutual attraction between the particles in the nucleus to overcome the repulsion between the charged protons. The requirements of stability necessitates that as we go towards heavier and heavier nuclei the number of neutrons overtakes the number of protons. (We have to remember that most of the mass of the atom is in its nucleus, because protons and neutrons are nearly 2000 times more massive than electrons.).

This competing operation of the long-range repulsive electrical forces and short-range attractive nuclear forces makes the nucleus a complicated balanced entity when the number of particles in it becomes large. It is this criticality that makes some of the heavier nuclei radioactive. This is true of the most abundant form of uranium and its daughter products.

The most significant facts that made a nuclear or atomic bomb possible are the following:

1). Nuclear physicists had already discovered that if one were to take a big nucleus and break it into two, the sum of masses of the two fragments would be slightly less than the mass of the original nucleus. The difference in mass would then result in a large energy release because of the famous result already derived by Einstein, E = mc2, where m is the mass that is converted and c the velocity of light. This energy is millions of time greater than the energies encountered in chemical processes like a coal or oil fire.

2). There should be a mechanism through which this process can be a started.

3). There should be a way that that makes the process into a chain reaction that results in an explosion.

In the case of ordinary chemical bombs the requirement 2) above is served by a detonator - a spark would do. The requirement 3) is then automatically ensured because the energy release in a tiny part of the chemical explosive quickly ignites all the other parts. For a nuclear bomb the process of ignition is entirely different. You cannot heat a kilogram of uranium 235 and get a bomb. In fact in uranium some of the nuclei are continuously breaking up, through the entry of stray neutrons from cosmic rays, or an implanted source of neutrons. Entry of a neutron in such a nucleus makes it unstable and breakup into smaller nuclei plus some energy. In this process some extra neutrons are also produced, which escape before they have a chance to split other nuclei. Therefore what one does is to have a critical mass of the fissile element deployed together in a relatively sparse manner. If this mass is suddenly compressed together the produced neutrons have a good chance of hitting other fissile nuclei and breaking them with production of energy and still more neutrons. Within microseconds or less the chain reaction takes over and a horrible weapon is exploded. Bombs that demolished Hiroshima and Nagasaki had energy release of about 10,000 tons of TNT each. Later on bombs have been developed that have more than a thousand times their destructive capacity. Luckily they have not been used so far on populations or people. It is horrible that science should have been used to produce monsters like these. We are clever but not yet humane enough.
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Trends

Dolphins say it with weeds

A man may bring flowers to impress women, but male Amazon river dolphins carry weeds to win over the opposite sex, British and Brazilian researchers say.

The discovery comes from a three-year study of more than 6,000 groups of dolphins in Mamiraua, a flooded rainforest reserve in the Amazonian, British weekly New Scientist reports in its next issue.

Of these groups, 221 included at least one dolphin, usually a male, that carried an object, such as weed, a stick or clay. The groups also usually contained an adult female. — AFP

Kangaroo that didn't hop

A 25-million-year-old fossil has revealed that a predecessor of Australia's iconic hopping kangaroo once galloped on all fours, had dog-like fangs and possibly climbed trees, scientists have reported.

"This is really the great, great, great, great grandfather of modern kangaroos," a member of the Australian team that analysed the bones, La Trobe University paleontologist Ben Kear, told The Age newspaper.

The near-complete skeleton of the prehistoric kangaroo was found in Queensland state in the 1990s and represents a new species called nambaroo gillespieae, Kear said. — AFP

Evolution on fast forward

Human evolution has been moving at breakneck speed in the past several thousand years, far from plodding along as some scientists had thought, researchers said on Monday.

In fact, people today are genetically more different from people living 5,000 years ago than those humans were different from the Neanderthals who vanished 30,000 years ago, according to anthropologist John Hawks of the University of Wisconsin. — Reuters


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