|SCIENCE TRIBUNE||Thursday, October 18, Chandigarh, India|
Radioactivity in homes
Eric A. Cornell, Wolfgang Ketterle and Carl E. Wieman are jointly awarded the 2001 Nobel Prize in Physics. The Royal Swedish Academy of Sciences in Stockholm cited the three laureates "for their achievement of Bose-Einstein condensation in dilute gases of alkali atoms and for early fundamental studies of the properties of the condensates."
Cornell and Wieman of the University of Colorado at Boulder, USA along with Germany’s Wolfgang Ketterle won the prestigious $1 million prize for creating a new state of matter called as Bose-Einstein Condensate (BEC). The duo at Colorado had created the coldest place in the universe by building an "atomic trap" with magnetic fields to skim off hot atoms, thereby producing the BEC. Since its discovery in 1995, more than 2,000 scientific research papers have been published in this field.
Eric Cornell and Carl Wieman have succeeded in creating the BEC, a new state of matter, which was theorised about by an Indian scientist, Satyendra Nath Bose, and endorsed by world-renowned scientist Albert Einstein in 1920s. Satyendra Nath Bose at the Physics Department of the University of Calcutta did pioneering work in quantum theory, in particular on Max Planck’s black body radiation law. He presented an alternative derivation to Planck’s Law and sent his work to Einstein for his perusal. Einstein realised that Bose had removed a major objection against light quanta in Planck’ work. He translated the paper into German and developed the theory further, realising its potential. Einstein predicted that when a given a given number of the particles referred to by Bose came very close to each other and moved sufficiently slowly, they would convert to the lowest energy state. This phenomenon is called "Bose Einstein Condensate".
Beginning with a gas of room-temperature atoms, the JILA (Colorado) team first slowed the rubidium and captured it in a trap created by the light produced by diode lasers similar to ones used in compact disk players. The infrared lasers were aligned so that the atoms are bombarded by a steady stream of photons from all directions — front, back, left, right, up and down. The wavelength of the photons was so chosen that they interacted only with atoms that were moving towards the photons. This cooled the atoms to about 10 millionths of a degree above absolute zero. About 10 million of these cold atoms were captured in the light trap. Once the atoms were trapped, the lasers were turned off and the atoms were kept in place by a magnetic field. The atoms were further cooled in the magnetic trap by selecting the hottest atoms and kicking them out of the trap. In due course of time, JILA researchers became successful to cool the rubidium atoms to less than 170 billionth of a degree above absolute zero, thus causing them to condense into a "super atom" which behaved like a single entity. This effectively being a new form of matter has various possibilities.
Bose-Einstein condensation was first achieved at 10.54 a.m. on June 5, 1995. Scientists had sought to create the effect for more than 15 years. Cornell, Wieman and their team of researchers used laser and magnetic traps to create the Bose-Einstein condensate, a tiny ball of rubidium atoms, which was as stationary as the laws of quantum mechanics permitted. A diffuse cloud of normal rubidium atoms surrounded this ball. Made visible by a video this condensate was looking like the pit in a cherry except that it measured only about 20 microns in diameter or about one-fifth the thickness of a sheet of paper.
The condensate was formed inside a small glass cell surrounded by a tabletop array of magnets, lasers and computers, in a JILA laboratory. Within the atom trap were about 2,000 atoms of rubidium squeezed into a very small space at a very low temperature. The atoms within the condensate obeyed the laws of Quantum Physics and were fundamentally different from the normal atoms in the much less dense cloud surrounding it. To produce and photograph the condensate, the JILA team cooled the atoms to a temperature 300 times lower than that has ever been achieved in the scientific laboratories of the world. Even the most remote regions of interstellar space are a billion times warmer due to background radiation left over from the Big Bang.
The 2,000 rubidium atoms in the condensate existed in a strange condition, a kind of smeared-out, overlapping stew. The most of the properties of this condensate are still a big unknown. BEC is like an atomic counterpart to the laser because it puts a large number of atoms into the same quantum mechanical state, the scientists said. It is said that the condensate is to ordinary matter as laser light is to the light from a light bulb. "Atoms in a room temperature gas normally move about 1,000 miles per hour and slow down as temperatures drop." Cornell said. "The normal atoms at these low temperatures move about 3 feet per hour. The Bose-Einstein condensate atoms move a lot slower, too slow for us to measure yet."
"Since the apparatus to produce the BEC is not particularly exotic or expensive, so it is expected that a large number of people would replicate this work. It will provide physicists with a new way of studying quantum effects on a large scale, similar to the threshold effects observed in superconductivity and superfluidity," Wieman said.
Radioactivity in homes
The home of Stanley Waltras became famous. In 1984, on a cold December morning he set off radiation monitors as he entered the Limerick nuclear power plant in Boyertown, Philadelphia, (USA). It appeared that he carried some radioactive contamination into the reactor. Specialists found his home to be one of the most radioactive in USA. They confirmed the presence of large concentration of radon in his home. More extensive work nationwide revealed that radon is a very common pollutant in many homes. Radon story has been probably the most widely written about environmental theme over the past few years worldwide.
Radium present in trace quantities throughout earth’s crust and in building materials decays into radon. Other sources of radon are dissolved radon in water and that contained in liquid petroleum gas or natural gas. Radon and its decay products emit energetic alpha particle radiation and contribute large radiation doses to lung.
The US Surgeon General has warned that radon is the second leading cause of lung cancer in the USA. Only smoking causes more lung cancer deaths. The risk is larger if a smoker lives in a home, which has higher radon levels. The US Environmental Protection Agency and Surgeon General recommend testing all homes below third floor for radon. To focus attention on this important issue, the country organises National Radon Action Week from October 14-20, 2001. Do it-yourself radon test kits are available at supermarkets and hard ware stores.
The National Radiological Protection Board (NRPB), UK, estimates that over quarter a million or so British people live in homes with high radon levels. The lower end of the annual dose range to the people who live in homes with radon concentrations at or above 200 Bq per cubic metre of air is of the order of 10 mSv. The highest doses are well in excess of 100mSv. (Bq is a unit of radioactivity; in a radioactive material containing one Bq of radioactivity one atom disintegrates every sec; mSv is a unit of radiation dose; the skin dose in a chest x-ray examination is about one mSv; the average radiation dose to a worker in a modern nuclear power plant is a few mSv). In some areas of United Kingdom, persons in 5% of the homes are exposed to doses above 23.7 mSv/year. One per cent of the house shows dose values above 55.8 mSv/year. The highest estimated dose was 320 mSv/year in Cornwall.
The September, 2001, issue of the Radiological Protection Bulletin from NRPB refers to a booklet published by the British Parliamentary Office of Science and Technology (POST) in June, 2001, to educate the Members of Parliament about radon as a pollutant. POST provides independent and balanced analysis of public policy issues. The booklet covers the risks from radon, the control strategy, radon remedies in existing houses and radon prevention in new dwellings. The U.K. Government has recently started a new programme in partnership with 32 counties to address the problem.
One out of 15 homes in the USA have elevated radon levels. The problem is equally relevant in cold countries. Cost of heating home is high during winter. People save money by reducing ventilation. The decay products of radon build up in air. According to a Newsweek story, Gerald Nicholls, head of the New Jersey Bureau of Radiation Protection stated that many people in New Jersey and Pennsylvania get more radiation from radon in a week than anybody ever got at Three Mile Island. (Three Mile Island is the site at which the most serious nuclear reactor accident in America occurred.)
Radon in dwellings in India contributes less radiation dose because Indian homes are relatively well ventilated. In tropics air changes once every hour due to natural ventilation. The average individual dose after measurements in 1200 houses in various parts of India was estimated to be as low as 1.3 mSv per year.
Scientific evidence on the cancer-inducing potential of radon has been conflicting. R.W.Field and his co-workers found that as radon exposure increases, lung cancer rate also increases. (American Journal of Epidemiology, 2000). Even at the level at which the US Environmental Protection Agency recommends remedial action, 50 % increase in cancer rate was found. B.L. Cohen analysed lung cancer rates and radon levels in over 1600 counties in the USA and found that lung cancer rates decreased with radon levels! His database consisted of one million lung cancer deaths. Some specialists have disputed his findings.
Radiation doses from radon to millions of people in various countries are significantly greater than those from man made sources of exposures. The effort should be to reduce all types of controllable radiation doses. If it is practicable, the radon at home should be controlled as efficiently as radioactive discharges to the environment from nuclear power plants.
Dr K.S. Parthasarathy is Secretary to the Atomic Energy Regulatory Board
NEW PRODUCTS & DISCOVERIES
The Palm Cam Digital Camera from Panasonic uses breakthrough Super Disk technology to store up to 1500 images on one disk!
In addition to accepting standard floppies, this digital camera takes Super Disks, letting you store up to 1500 images on one removable 120MB disk. It would take 83 floppies to store the same amount of images.
If your PC is not equipped with a Super Disk Drive, you can still use the Supervises for storage and the included USB cable to quickly and easily transfer images to and from your camera directly to your computer.
The Panasonic Palm Cam has a .37" CCD that uses over 1.3 million pixels allowing you to capture sharp, crisp images in high resolution. Before and after you shoot an image, you can see what that image will look like on the camera’s 2.5" color LCD screen with 112,000 pixels. The LCD screen doubles as an on-screen menu that you can use to control various camera features and settings. You can produce incredible close-up shots by zooming in on the action using the built-in wide angle or telephoto settings.
The Palm Cam is equipped with a 3:1 optical zoom. For additional zoom options, use the camera’s 2x digital zoom feature to magnify the image to twice its normal size. A still image with audio can be recorded for five seconds so that when that photo is played back on your PC you can add corresponding audio.
Using Quick Time format, the camera also allows for motion image recording with audio. A total of 90 motion recording files can be stored on one Super Disk. Mac compatible. Price: approximately $ 495.
Rapid way to produce tools
Scientists in the USA have developed a new unconventional low cost technique for production of tools needed in large number in which a shape is created by spraying molten metal, reproducing the pattern’s shape, details and texture.
The Rapid Solidification Process reduces the lead times of producing tools. With it the tools can be produced in as little as three days and are suitable for both prototyping and production runs. Tools of virtually any common tooling alloy including steels, copper, aluminium, gray iron and Kirk site, can be produced using this technique.
The technique, developed by Idaho National Engineering and Environmental Laboratory, a US Department of Energy research lab, can be used to manufacture tools for variety of processes including injection molding, blow molding, die casting, stamping and forging.
Usually mass-produced items ranging from cell phones to automotive
parts are formed from molds or dies that require specialised machining and long
lead times to produce. Plastic injection molds, for example, can cost over
300,000 dollars and require three to six months to produce, followed by another
three months for tool checking and part qualification, a report in Mechanical
Engineering said. PTI
After studying the Malaysian woman who recently spent a month in a cage full of scorpions and survived their stings, researchers have concluded that she was protected by the very toxins that make the sting so painful.
Nor Malena Hassan spent a record-breaking 30 days in a glass cage with 2700 black scorpions in the town of Kota Baru in Malaysia. Although she was stung several times, she survived.
A team of researchers led by Now Hoon-Eng Khoo at the National University of Singapore analysed the venom from the black scorpion Heterometrus spinifer.
They found that the venom constricts blood vessels. This stops the venom from spreading throughout the body, so the sting causes only localised pain, a report in New Scientist said.
"The scorpion woman did receive painful stings, but as we have shown, the genus Heterometrus is unlikely to contain any potent neurotoxins," says Khoo. "So she was in no mortal danger."
Khoo’s team found that the active substances in black scorpion venom are acetylcholine and noradrenaline, two neurotransmitters found in mammals. Acetylcholine shuttles nerve signals form one cell to the next. The venom contains so much of it that it overstimulates nerve cells, causing intense pain.
Noradrenalin probably intensifies that pain by trapping the acetylcholine. But to do this it constricts blood vessels, stopping the venom from spreading further and protecting the victim, Khoo says. The findings, to be published in the forthcoming issue of the journal Biochemical Pharmacology, suggest that Heterometrus uses its sting primarily to defend itself rather than to paralyse or kill prey.
There are 1050 known species of scorpion. Most like H. Spinifer and its relatives, are relatively harmless. Only the most dangerous, such as the Chinese Buthus martensii Karsch, have venom that spreads through the body. This causes an overwhelming cascade of nerve signalling that can lead to heart failure or respiratory collapse. PTI