SCIENCE TRIBUNE Thursday, March 29, 2001, Chandigarh, India

Meeting the challenge of climate change
Pravin Kumar
UST a few degrees change of temperature may mean a major climate swing all over the world — greater than any seen in the past 10,000 years — which we humans and a number of life-forms may find difficult to endure.

Chance discovery of immortal skin
OUND healing and other areas of medical research are poised for a major boost with the discovery of "immortal human skin" by scientists.

Evidence for discrete nature of space
B.R. Sood
INSTEIN'S theory of relativity considers three dimensional space at par with time. In fact, in the theory of relativity, time is taken to be the fourth dimension along with three dimensions of space and it is customary to consider space-time together for all purposes.

Pulsed neutrons for advanced research
HE Spaliation Neutron Source is a high intensity pulsed neutron facility for use in condensed matter research using slow neutron scattering techniques. Negative hydrogen ions are injected from a 70 MeV linear accelerator into the synchrotron vacuum chamber where they are stripped of their two electrons to become protons.





Meeting the challenge of climate change
Pravin Kumar

JUST a few degrees change of temperature may mean a major climate swing all over the world — greater than any seen in the past 10,000 years — which we humans and a number of life-forms may find difficult to endure. All the available evidence suggests that human activity is putting into the atmosphere various gases, which create a "greenhouse" effect, sending the mean global temperature upwards.

The U.N. sponsored talks held at The Hague last November failed signally to bring about a global agreement over cutting down the emission of "greenhouse gases", or gases which are held responsible for heating the atmosphere to never-before levels.

It was a re-play of the April, 1995, Berlin conference on climate change. The principal accused, as always, was the United States, which has 5 per cent of the world’s population but emits one-fourth of all the greenhouse gases. The Hague talks were to have sought ways to implement the 1997 agreement in Kyoto (Japan) by which developed countries would reduce the emission of greenhouse gases to 5.2 per cent below 1990 levels by 2012.

The air is merely one component of a coupled, interacting system. The temperature of the earth’s surface is determined by the air, but the components of the air that influence the temperature the most are, not the major ones but the few "trace components" — the heat-trapping gases like carbon dioxide (CO2), methane and water-vapour, which occur in parts per million by volume.

Every day, 20 million tonnes of carbon dioxide (CO2) is put into the atmosphere by human activities — chiefly by the burning of fossil fuels like coal and petroleum. The average person is responsible for the addition of one tonne of carbon (or four tonnes of CO2) to the atmosphere every year. In the course of a year, 7 gigatonnes of greenhouse gases are put into the atmosphere. (1 gigatonne=1000 million tonnes.) The gases remain there for 50 to 2000 years because the natural "sinks", like the oceans, take up the gases slowly. Carbon dioxide (CO2) contributes more than half of the man-made "greenhouse" effect, which is due to the fact that carbon dioxide is opaque to infrared radiation: it lets in sunlight but traps the infrared radiation given by the earth. This is not altogether a bad thing, for in its absence, the earth would be too cold to sustain life. However, the evidence from Greenland ice-cores (samples) and tree-rings indicated that the natural sinks have kept the atmospheric carbon dioxide at a constant 250 parts per million (PPM) for 1000 years before the Industrial Revolution... By 1955 however, the CO2 level had risen to about 320 PPM. The current level is about 350 PPM.

The report (1990) of the Inter-governmental Panel on Climate Change (IPCC) noted that, at the present rate of increase (about 1.3 per cent annually), CO2 will reach a level of 400 PPM by 2015 and 600 PPMby 2076. Some of the added CO2 is soaked up by the oceans, but not all of it.

CO2 is not the only culprit. Measurements show that methane, another greenhouse gas, given off from rice fields and by cattle during digestion, is increasing about twice as fast as CO2. Yet another greenhouse gas is nitrous oxide. Scientists at the National Institute of Oceanography, Dona Paula, Goa, recently presented evidence in the scientific journal Nature that fertiliser run-off into the Arabian Sea may be intensifying oxygen depletion, leading to the production of nitrous oxide. This effect is likely to be heightened as nitrogenous fertilisers are increasingly used to step up food production.

The next two gases on the list are CFC-11 and CFC-12 — used extensively in refrigeration (which are also accused of destroying the ozone layer of the stratosphere, which is responsible for shielding the earth from the harmful ultraviolet component of sunlight). Ozone is also classified as an infrared absorbing gas; it is released into the troposphere by a range of human activities, from driving cars to raising livestock. However, the CFCs have been the subject of an international agreement (the Montreal Protocol) which may slow down their growth over the next 20 years.

Water-vapour is also a powerful absorber of infrared radiation. As the surface air heats up, owing to the added trace gases, more water is sucked up from the oceans: This makes the surface warmer still. There is some uncertainty in this scenario, due to natural factors like volcanic eruptions and due to the fact that the amount of water vapour varies with the location. The most troublesome weakness of even the most sophisticated models of climatic heating is in the way they simulate clouds, for clouds affect the radiative balance. Nevertheless, the balance of evidence clearly suggests a human hand in climate change.

The "mid-range" scenario of the IPCC’s models project an increase of global temperatures (relative to 1990) of about 2 degrees C. by 2100, and 5 degrees C in the "worst case" scenario. The rate of heating is estimated to have a range of 0.2 — 0.5 degree per decade. The climate heating would be greater at high latitudes than near the equator. The Northern hemisphere, which contains most of the Earth’s land area, will warm up faster than the Southern Hemisphere, which has most of the oceans.

We do not know how civilisation will adapt to such changes, which would be greater than any seen in the last 10,000 years. Just a few degrees change in the average temperature may mean a major climate change. As a result of the warming, much of the ice that was left over at the end of the last Ice Age will start melting. This, along with the thermal expansion of the upper layers of the oceans, will bring about a rise in the sea level. Data from global tidal gauges suggests that the global sea level has risen by 10 to 15 cm during the past century. At the end of the 21st century, it is expected to be a metre higher than it is today. Sea level would continue to rise even if the greenhouse gases were to be stabilised at the present level. At the climate talks held at The Hague in November last, scientists warned that even if delegates implemented in full the proposals before them, this would cut only 1/600 degree of the 5 degree temperature rise expected by 2100.Top



Chance discovery of immortal skin

WOUND healing and other areas of medical research are poised for a major boost with the discovery of "immortal human skin" by scientists.

While doing a routine study on the life span of human skin cells, University of Wisconsin-Madison research team witnessed a rare spontaneous mutstion when a small cluster of cells in petri dish continued to actively divide. The scientists continued to grow this unique cell line over the course of a year without the cells showing any signs of slowing down.

A new UW-Madison spin-off company called Stratatech, housed at University Research Park in Madison has patented "immortal human skin" and is studying the prospect of using it for treatment of severe burn patient. "There are a lot of opportunities dovetailing out of this single basic discovery that are very exciting," says Lynnn Allen-Hoffmann, a professor of pathology in the UW-Madison Medical School and Managing director of Stratatech. "It would be a career dream come true to develop some kind of off-the-shelf product that would be available to doctors," he adds.

First animal tests have confirmed that the novel skin will cover and heal superficial wounds. Most importantly, Allen-Hoffmann says the cells grow into distinct stratified layers to become essentially no different from normal skin. "That was the really big finding in all this, the critical piece of information we needed to prove," she says. "These cells proved to be incredibly normal. "The unique tissue is comprised entirely of keratinocyte cells, which make up the vast majority of human skin cells.

The cells can be genetically engineered to fit different medical or research needs like consumer products testing. By using the Stratatech product, the company can prove its products are safe for humans without the need for animal testing. Another promising use for the cell line, called NIKS (for Near-diploid immortalized Keratinocyte skin is in drug discovery. Scientists can engineer different diseases of human skin, such as cancer or viral infections, and be able to test drugs with that "normal" tissue environment.

But the technology’s value to burn medicine may be most dramatic.

The need for burn treatment alternatives is acute, with a large number of burn hospitalisations each year requiring extensive skin grafting. A key milestone remains in proving the tissue would not be rejected by human patients.

Stratatech has plans to move quickly toward possible medical uses, with clinical trials and work with regulatory agencies leading to initial human trials by 2002. Allen-Hoffmann says a number of basic research projects at UW-Madison and elsewhere also are likely to capitalize on this new found ability to develop realistic models of human skin disease.

Allen-Hoffmann notes that what exactly happened to create these cell remains shrouded in mystery. They arose from a 1996 project in which her research team was studying aging of human skin. The skin used for the experience was from discarded foreskin from a circumcision. Lab manager Sandy Schlosser co-discover of the NIKS cells, noticed tiny cluster of cells emerged in a petri dish of dead skin cells and ultimately "wound-healed" across the entire dish. The researchers known how these cells differ genetically, in that they have a duplication of one section of the long arm of chromosome eight. Beyond that they are remarkably similar to the parent cells. But the group tried to regenerate the same cell line in experiments and were unable to do so.

Allen-Hoffman says these types of mutations are one in million in science. There are only four other documented example of "immortal" cells developed out of laboratory work and all of those cases have caveats that limit their usefulness. PTITop



Evidence for discrete nature of space
B.R. Sood

EINSTEIN'S theory of relativity considers three dimensional space at par with time. In fact, in the theory of relativity, time is taken to be the fourth dimension along with three dimensions of space and it is customary to consider space-time together for all purposes. Further, it is conjectured in the Big Bang theory of the creation of the universe that space-time were created at the precise moment of the Big Bang. One of the premises of the theory of relativity is that both space and time are not absolute entities and take on values that depend upon the speed of the observer with respect to the object about which measurements of distances and time spans are being made.

Leaving the relativity of space-time apart, relativity theory presumes space-time to form a continuum. By that what is meant is that space-time vary in a continuous manner. To make this point clear, consider the motion of the seconds hand of a digital clock. Seconds hand moves in units of one second. This is as if time is discrete and the unit of discreteness is one second in this case. In a similar manner, discrete nature of space can be visualised. Discrete nature of space-time forms the basis of quantum theory which is more fundamental and explains phenomenon at the atomic and the sub-atomic scales. So far, there has been theoretical speculation about space-time not being continuous but there has been no experimental evidence for space-time being discrete. Lack of experimental evidence is due to the fact that picture of smooth space falls apart on tiny scale of 10-43 (one divided by one followed by 35 zeroes) metre and that of time around 10-43 (one divided by one followed by 43 zeroes) second.

However, the situation changed recently with some new observations on the high energy radiations emanating from distant galaxy (named "Markarian 501" after the astronomer Markarian). High energy radiation from Markarian 501 is in the form of gamma rays. The galaxy is so far off that it takes gamma rays, travelling at a speed of 10 million kilometres in a year, 300 million years to reach the earth. Thus, Markarian 501 is three billion trillion (three followed by 21 zeroes) km away from earth.

From the known facts that space is filled with low energy radiation in the form of infra-red rays and that gamma rays during their long passage can interact with infrared rays and get annihilated giving rise to material particles in the form of electron-positron pairs, it is very surprising that gamma rays make it to the earth. The fact that gamma rays from galaxy Markarian 501 do reach the earth points to the fact that something unusual is taking place. Gamma rays should have been slowly mopped up by the sea of all pervading infrared radiation.

Two possible models have been suggested for this unusual observation. One is based on the manner in which gamma rays are produced in the galaxy. It is conjectured that if the nature of gamma rays originating from Markarian 501 is similar to the light in a super efficient laser than any built so far on earth, then gamma rays moving in tandem would travel the long distances for 300 million years without getting annihilated on the way. However, natural gamma ray lasers sound like an outlandish explanation.

The other model proposed for the strange behaviour of gamma rays from Markarian 501 opens up an entirely new kind of physics. It has been predicted earlier that on tiny scales, our picture of continuous space-time falls apart giving way to a seething froth of quantum gravity fluctuation dubbed space-time foam. It is only high energy gamma rays that can feel the bumps of discrete space and hence are slowed down. Slow travelling gamma rays avoid interaction with infrared radiation and are saved from annihilation. Thus, the fact that high energy gamma rays from Markarian 501 travel all the way to the earth after traversing for 300 million years through space gives an indirect evidence for space being discrete.

By anology, it is certain that if space is discrete, time must also be discrete. The new observations have given impetus to the theories that have for long talked of discreteness of space-time. With this explanation for the observation of strange behaviour of very high energy gamma rays another paradox about the long distance travelling of extremely high energy protons has been resolved. Protons with energy which is about a billion times more than the highest energy of protons accelerated in the laboratory and whose source is distant active galaxies should have been devoured by infrared radiation on their long voyage to the earth. Very high energy protons, like high energy gamma rays, can also feel the bumps of discrete space and are slowed down. Slowing down of protons acts as an impediment for their destruction by the sea of low energy radiation. Above mentioned observations and their explanation is definitely going to change the thinking of the scientists about space-time.Top



Pulsed neutrons for advanced research

THE Spaliation Neutron Source (SNS) is a high intensity pulsed neutron facility for use in condensed matter research using slow neutron scattering techniques.

Negative hydrogen ions are injected from a 70 MeV linear accelerator into the synchrotron vacuum chamber where they are stripped of their two electrons to become protons. Around the synchrotron ring are quadrupole focusing magnets, dipole bending magnets and six radio frequency stations where the beam of protons is given energy boosts to accelerate it still further.

When its velocity reaches about nine-tenths of the speed of light — an energy of 800 MeV — the beam will be extracted from the ring to the target station containing the heavy water cooled uranium target. The 800 MeV proton beam will strike the target to produce bursts of fast neutrons which, when slowed by four moderators, yield slow neutrons with a variety of energy and time structures.

The slow neutrons leave the stainless steel target void vessel through 18 beam ports leading to up to 25 simultaneous research projects in the experimental hall. These include molecular spectroscopy, a liquid and amorphous materials diffractometer, a high resolution powder diffractometer and a high energy transfer spectrometer.

Funded by Britain’s Science and Engineering Research Council, the Spaliation Neutron Source is a centre for international scientific cooperation and provides research facilities for university experiments. This highest intensity source of pulsed neutrons accommodates advanced studies in physics, chemistry, biology and materials science and makes possible many new experiments, for example, on minute specimens, the study of transient effects, and in the observation of electron energy levels in semiconductors. NFTop



1. This British geologist invented the Seismograph (an instrument for recording earthquakes) and thus laid the foundations of seismology. Name this author of books “Earthquakes” (1883) and “Seismology” (1898).

2. A new probe, called MAP, to be launched by the USA shortly, will examine the various kinds of matter in the universe with a view of solving the Big Bang puzzle. What is the full name of MAP?

3. The rate of chirping of this insect depends upon the temperature of the environment and thus the temperature can be estimated by counting this rate. Which is this insect?

4. Plastics are generally insulators but a few plastics act as electrical semiconductors under suitable conditions. When voltage is applied to them, they emit light of different colours. Can you think for which type of technology can such materials offer immense possibilities?

5. We all assume Newton’s laws of motion to be normally valid?

6. The atoms of some non-metallic elements have the property of linking of one another to form covalently bonded chains. What is this phenomenon called which is most predominant in case of carbon?

7. What is the name given to pressure in the blood vessles when the heart contracts (beats) and pushes blood through the circulatory system? What is this pressure called when the heart is resting (that is, between beats)?

8. What is a communication system comprising two devices called, each device containing a short range radio transmitter and a receiver?

9. This instrument is the best hearing aid for a completely deaf ear. In it a sensitive receiver put into the inner ear catches sound signals, converts these into electrical signals, amplifies these and then transmits these to the brain. Which is this instrument?

10. The latest science centre, where concepts of science are explained by interesting like exhibits, models, panels etc., was inaugurated by our Prime Minister recently. Where is it located?


1. John Miline
2. Microwave Anistropy Probe 
3. Cricket 
4. Display technology 
5. When the velocities of the objects become comparable to the velocity of light 
6. Catenation 
7. Systolic (high) and diastolic (low) blood pressure 
8. Walkie-talkie 
9. Cochlear implant 
10. At Kurukshetra (Haryana).