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Can nuclear fusion be achieved? Video games not all bad Stem cells may protect brain Melting Greenland glacier Realistic time machine?
New Products and Discoveries Prof Yash
Pal
PROF YASH PAL |
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Can nuclear fusion be achieved? Dr Steven Cutts assesses prospects of our matching the immense energy output of the sun now that a $ 5 billion experimental thermonuclear reactor is to be built
But now Europe, the US, China and Japan propose to establish an International Thermonuclear Experimental Reactor costing a staggering five billion dollars in a massive bid to achieve the breakthrough which has so far eluded science’s best efforts to duplicate the incredible energy output of the sun. Some bitter squabbles over ITER’s location have yet to be resolved but it seems likely that the reactor will be sited on the Mediterranean coast of France. In the aftermath of World War II the breathless pace of nuclear science continued unabated and the US led the way with the successful detonation of the first hydrogen bombs. Apart from scaring the collective hell out of most of the people on the planet, this achievement begged a question: How did the successful scientists manage to produce the extreme temperature needed to make fusion possible? In fact, they used an atomic bomb as a detonator. Limitless power The news wasn’t all bad. If one hydrogen bomb could wipe out a major city, surely the same kind of nuclear fission could provide limitless electrical power. How to control the process would be the problem. The fusion reactor needed is a receptacle in which hydrogen gas is heated until its atoms fuse and give off energy but the temperature at which hydrogen atoms begin to fuse is so high that any kind of material container would melt long before fusion occurred. The Russians managed to get around that problem with a cunning doughnut-shaped device, Tokamak, which uses magnetic fields to enclose hydrogen gas superheated into an electrically charged plasma that never touches its container. Since the 1950s the US has spent over $15 billion on fusion research, yet still can’t make it work, though in the late 80s a pair of maverick scientists claimed an unexpected breakthrough. They believed they’d managed to fuse hydrogens in a liquid-filled tube at room temperature in a process called cold fusion which sent shock waves through the entire scientific world. A Nobel prize seemed almost guaranteed up to the point when it became obvious that the fusion process was not
occurring at all. The scientists involved had misinterpreted their own data and foolishly arranged a press conference before bothering to publish details of their findings in scientific journals for expert scrutiny. Cold fusion was a non-starter. The term was established without reason and the men responsible for it rapidly sank into obscurity. It was just another episode in the suspenseful story of excitement and disappointment surrounding the dream of fusion nuclear power. Now another chapter in the history of fusion research begins with the planned construction of the ITER reactor worth 10 billion euros, the second most expensive scientific project to date after the international space station. It seems destined to spend the next 20 to 30 years perfecting our handing of superheated plasma before another reactor built 20 years from now might actually produce usable power. Apart from the associated international prestige involved, what drives governments to fund such work is the promise of limitless energy produced without risk of atmospheric pollution and catastrophic climate change; energy produced through a nuclear process free from the risk of nuclear weapons proliferation. The fuel source will be the oceans and is essentially inexhaustible. Disposal of radioactive waste will not involve the timescales required of
conventional fission nuclear power. Despite all setbacks and cost overruns this force that drives the stars — the holy grail of energy research — still beckons. Just because nuclear fusion is still a dream doesn’t mean it is not going to happen. Scientific miracles are not unknown. A hundred generations watched the birds with envy before the Wright brothers proved that we too could take to the air. Yet many of us ask why when nuclear fusion is so difficult to harness here on earth do we bother trying to do it at all when there is a readymade reactor working perfectly 93 million miles over our heads. To convert its energy into electricity we need only photovoltaic solar panels. So should we not be concentrating our efforts on producing those at prices everyone on earth can afford?
— AF
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Parents
take note — video games are not all bad. In young children and adolescents they can lead to excessive use and aggressive behaviour but a leading expert said last week that the games ease pain, distract patients undergoing chemotherapy for cancer and help to develop dexterity. “The degree of attention needed to play such a game can distract the player from the sensation of pain,” Professor Mark Griffiths, of Nottingham University in England, said in an editorial in the British Medical Journal. In patients with arm injuries, the games have been used to increase strength and dexterity while children with learning disabilities have played them to develop spatial ability. “Therapeutic benefits have also been reported for a variety of adult populations including wheelchair users with spinal cord injuries, people with severe burns and people with muscular dystrophy,” according to Griffiths. Although the reported negative effects, which include wrist pain, hallucinations and repetitive strain injuries, have been widely reported, Griffiths said they tend to be temporary and could be caused by other factors. “Some of these adverse effects seem to be rare and many resolve when the patients no long play the games,” he added. Griffiths, a professor of gambling studies, called for more studies into the long-term effects of video games and what constitutes excessive use. “Further research should examine factors within games such as novelty, users’ preferences, and relative levels of challenge and should compare video games with other potentially distracting activities,” he added. — Reuters
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STEM cells may protect the brain and nervous system against damage from tumours and conditions such as multiple sclerosis, researchers at Milan’s San Raffaele Scientific Institute have found. Experiments with mice with a disease similar to multiple sclerosis showed that stem cells injected into the blood stream migrated to inflamed areas in the brain and spinal cord, killing inflammatory cells, the researchers said. This means a single injection of stem cells could be used to treat many different areas of damage in the body, reducing the clinical signs of the disease. “There is a therapeutic potential in this discovery, but it’s still too early to talk about a cure for humans,” head of research Gianvito Martino told a news conference. Mice treated with stem cells at the onset of the disease started to recover between one or two months, the team reported. Stem cells are primitive cells that can transform themselves into many specialised forms, such as blood cells. Their potential of regenerating organs or tissue has given hope to sufferers from nervous diseases such as multiple sclerosis. The researchers said the stem cells could also potentially be used as a natural anti-inflammatory drug to treat damage by diseases such as stroke, brain tumours, and spinal cord injuries. “With this discovery, we are moving closer to a targeted use of stem cell therapy without sideeffects,” researcher Stefano Pluchino said. “The interesting thing is that adult stem cells grow in vitro without becoming specialised, they are injected and they find the damaged organ by themselves and decide autonomously how to treat it.” The results of the study will be published in Nature magazine.
— Reuters
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Melting Greenland glacier Scientists monitoring a glacier in Greenland have found it is moving into the sea three times faster than a decade ago. Satellite measurements of the Kangerdlugssuaq glacier show that, as well as moving more rapidly, the glacier’s boundary is shrinking dramatically — probably because of melting brought about by climate change. The Kangerdlugssuaq glacier on Greenland’s east coast is one of several that drains the huge Greenland ice sheet. The glacier’s movements are considered critical in understanding the rate at which the ice sheet is melting. Kangerdlugssuaq is about 1,000 metres (3,280ft) thick, about 4.5 miles wide, extends for more than 20 miles into the ice sheet and drains about 4 per cent of the ice from the Greenland ice sheet. Experts believe any change in the rate at which the glacier transports ice from the ice sheet into the ocean has important implications for increases in sea levels around the world. If the entire Greenland ice sheet were to melt into the ocean it would raise sea levels by up to seven metres (23ft), inundating vast areas of low-lying land, including London and much of eastern England. Computer models suggest that this would take at least 1,000 years but even a sea-level rise of a metre would have a catastrophic impact on coastal plains where more than two-thirds of the world’s population live. Measurements taken in 1988 and in 1996 show the glacier was moving at a rate of between 3.1 and 3.7 miles per year. The latest measurements taken this summer show it is now moving at 8.7 miles a year. Gordon Hamilton, professor of earth sciences at Maine University, who made the measurements using global positioning system (GPS) satellites, said the velocity measurements were accurate to within about 45 metres of movement per year and that Kangerdlugssuaq is probably the fastest-moving glacier in the world. “This is a dramatic discovery. There is concern that the acceleration of this and similar glaciers and the associated discharge of ice is not described in current ice-sheet models of the effects of climate change,” Professor Hamilton said. — By arrangement with
The Independent, London
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THE laws of physics seem to allow time travel, but no one has had much hope of building an actual time machine because it would take such exotic conditions and materials. Now, physicist Amos Ori of the Technion Israel Institute of Technology in Haifa has come up with a potentially more practical time machine design. Unlike most previous proposals, this one requires only normal matter and the vacuum known to exist in space, says Ori. One type of time travel occurs routinely here and now: our inexorable one-way drift into the future. Einstein’s special theory of relativity revealed the possibility of accelerated travel into the future. Suppose a person spends a year in a rocket that’s traveling slightly less than the speed of light. Because motion at such enormous speeds drastically slows the clock for the traveler, that person could return to Earth to find that many years had elapsed at home. In that way, a traveler could leap into the future. Retreating into the past is another matter, but one that relativity theory also suggests might be possible. The theory shows that gravity curves space-time and slows clocks. That’s why time-travel theorists have proposed that regions of space-time might naturally, or by human intervention, be made to curve back onto themselves. Someone moving around such a loop could travel back in time. A new version of such a loop is what Ori proposes in the July 8 Physical Review Letters. The loop would form within an empty, donut-shaped region of space-time enveloped by a sphere of normal matter, he says. The distortion of space-time in the central donut would result from other huge nearby masses, perhaps including a black hole, or from interference of gravity waves propagating through the donut. To return to the past, a traveller in a rocket would zip around inside the donut, receding a little further into the past with each orbit, Ori says. Ken D. Olum of Tufts University in Medford, Mass., is skeptical that Ori’s concept could succeed. Until now, scientists have called for using prodigious amounts of an exotic entity known as negative energy, which theorists expect to exist only in minuscule quantities, for time machines. In 1992, Stephen W. Hawking of Cambridge University in England proved a theorem that rules out time machines built without negative energy, Olum notes. Ori counters that Hawking’s analysis involves certain conditions that don’t apply to his concept. Igor D. Novikov of the Niels Bohr Institute in Copenhagen finds Ori’s concept of a donut-shaped core “very original and probably without unrealistic parts.” The new proposal “is a valuable contribution to studies of potential time machines,” he says.
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New Products and Discoveries
Scientists have deciphered the DNA of the parasites responsible for three deadly diseases: African sleeping sickness, Chagas’ disease, and leishmaniasis. This information could open new routes to preventing and treating these conditions, which collectively kill more than one million people worldwide each year. The diseases are caused by related protozoa in a group known as trypanosomatids-single-celled organisms that are transmitted back and forth between at least two hosts, often a blood-eating insect and a person. African sleeping sickness, caused by Trypanosoma brucei, gradually brings on devastating neurological symptoms that affect the sleep cycle. Chagas’ disease, caused by Trypanosoma cruzi, critically damages the heart, stomach, and brain. Leishmaniasis, caused by various species of Leishmania protozoa, can lethally enlarge the spleen and liver. Meat-eating caterpillar A newly named species of Hawaiian caterpillar sneaks up on a resting snail and quickly spins silk strands around it, lashing it to the spot. The caterpillar then reaches into the snail shell’s opening and has lunch. These larvae of a small moth, newly named Hyposmocoma molluscivora, are the first mollusk-eating caterpillars that scientists have officially described, says Daniel Rubinoff of the University of Hawaii at Manoa. A few other snail eaters have been spotted in Hawaii but not yet studied. Larger trout Trout with three chromosome sets grew faster than fish with two sets, so the industry tries to breed fish with three sets for meat production. Rainbow trout with three sets of chromosomes grow faster because they are unable to reproduce. The energy from the food they eat is shifted from reproduction to growth. Mirror images When a capuchin monkey looks at its own image in a mirror, something strange happens. The diminutive creature reacts not as if it sees a stranger, as many researchers had assumed. Instead, the reflection gets treated as a special phenomenon, generally eliciting curiosity and friendly overtures from females and a mix of distress and fear from males, a new study finds. Capuchins’ reactions signal an intermediate self-awareness that lies somewhere between seeing the mirror image as another individual and recognizing the reflected figure as self, according to a team led by psychologist Frans B.M. de Waal of Emory University in Atlanta. |
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PROF YASH PAL AS a bush walker and a pilot, if I wish to travel from point A to point B, I can follow a magnetic heading on my compass to get there. What mechanism do astronauts or automatic probes in space use to ensure that spacecraft are going the right way? This question can open up a discussion on many different fronts. While it is true that a compass is useful because the earth’s magnetic field is such as would be produced by a bar magnet with its north and south poles approximately close to the earth’s geographical poles. That is why the magnetic needle of the compass points north south. It is true that we can tell the east and west, and therefore all other directions by looking at the direction of sunrise and sunset, but the magnetic needle is more accurate because the direction of sunrise and sunset varies with the change of seasons. For near earth satellites and rockets where the earth’s magnetic field is still substantially felt magnetometers, which are more sophisticated instruments than compasses, are still used for direction finding and, indeed, for studying the strength and direction of the field. But there are other methods that have been traditionally used. In this connection I will like to start with the method that has been used to define positions on earth. We do it by giving the polar coordinates of the point in question — in other words the latitude and longitude which you see drawn on the globe, or the atlas you use. How are they determined and more particularly, if you were on a ship out in the ocean how you would determine where you are? Latitude is easy. If you have a simple theodolite you can measure the altitude of the pole star. You know that pole star happens to lie in the direction of the earth axis pointing north. This direction remains the same as the earth rotates. At the equator the latitude would be zero degrees and on the North Pole the pole star would be at 90 degrees — right overhead. But knowing the latitude of your position is not enough. In order to know the longitude you need to do more. You have to be able to measure accurately the time of transit of the sun or a star and find out how much this time differs from that measured at a point on the zero meridian, a meridian passing through Greenwich in England! In practice you could have a table of transit times for a number of stars at Greenwich measured on an accurate clock, carry a synchronised clock with you to the place whose longitude you want to know and determine the time of transit of any of the stars. The time difference between the Greenwich measurement and that at your unknown location will give you the longitude because you know that the earth rotates by 15 degrees every hour (360 degrees every 24 hours). This is the way the coordinates were determined by early explorers. You would recall that at that time we did not have accurate digital watches of today; therefore considerable mechanical ingenuity had to be expended to design and build accurate and reliable “chronometers”, as these clocks were called. Historically that is considered an important technological achievement, because the great explorations of that era would have been difficult without this innovation. Let me refer to navigation in moving vehicles, rockets and space. There also very accurate position determination is by measuring directions of a number of distant stars (these stars are so far that to a first approximation they can be considered as fixed light sources in the sky). It is interesting that whether on earth or out in space our locations are accurately defined only when we make use of the nearly fixed coordinates of our distant stellar inhabitants in the sky. However in recent years a wonderful new system has become available, thanks to space technology. We have developed a system in which a significant number of artificially produced stars have been installed in the sky, for observing which we do not need fancy telescopes or cumbersome chronometers. These artificial stars are satellites placed in extremely well defined orbits around the earth. Each of them carries an atomic clock and keeps broadcasting its time and identity. Specially designed receivers at any location on the ground, in a rocket or another satellite note the time of reception of the pulse from different satellites. Since the velocity of travel is the velocity of light we immediately know the distance to a number of satellites whose position is accurately known. It is then a simple job for a computer in the receiving equipment to convert the information into coordinates of the receiver. These coordinates are extremely accurate. We know not only the longitude and latitude but also the altitude. The equipment can also plot the coordinates on maps that are present in its memory. This system is popularly known as Global Positioning System (GPS). It is beginning to be used very widely both by military and civilian sectors, for mapping, targeting, navigation of vehicles and boats and also for geophysical research. Perhaps I should also mention the use of inertial guidance systems. They are so named because except for initial velocity and position they are entirely self-contained and depend only on inertial dynamics. These systems use gyroscopes and accelerometers. A gyroscope defines an inertial direction, very much like a spinning top. Direction of motion is measured with respect to that direction. Rate of change in velocity is determined by accelerometers. If at every moment of time you know the velocity, its change with respect to time and directions of change you know exactly where you will end up after a certain amount of time. Such systems are essential for most rockets and space vehicles. They can be supplemented by terminal guidance systems using optical and other sensors. Let me end by pointing out one more method of finding out our location and navigation used by many living creatures. This is through our capability to sense and recognise molecules through our noses and other means. This is very useful for locating a good “dhaba” to eat in, or a girl- friend wearing a perfume we recognise. Snakes can track a field mouse to its hiding place by collecting the molecules it has shed during its flight, using its forked tongue and two sensors in its mouth. Dogs can track criminals or friends by moving their noses left to right. And I have no time left to talk of the remarkable tracking and guidance capabilities of birds who can travel thousands of kilometres across mountains and oceans to the spot where they would spend their winter and raise their young. |
HAD Indiana Jones turned his hand to physics rather than archaeology, he would have set out in search of fusion nuclear power, the elusive holy grail of energy research. Ever since the I950s scientists have seemingly been on the verge of producing electricity from it and governments around the world have pumped huge funds into their efforts — but not one functional kilowatt of power has yet emerged. Nuclear fusion remains a mirage that recedes as fast as we approach it and many technicians in the field question whether we will ever obtain viable power output from the process.
Bigger rainbow trout for consumers is the goal of Agricultural Research Service (ARS) scientists who are working with industry on genetic methods to more efficiently produce fish that grow faster. William K. Hershberger, research leader at the ARS National Center for Cool and Cold Water Aquaculture in Kearneysville, W.Va., and his colleagues have developed a more effective way to produce rainbow trout that have three sets of chromosomes instead of the usual two sets.