 |
|
| SCIENCE & TECHNOLOGY |
|
|
Health impacts of Chernobyl accident
THIS UNIVERSE |
|
|
Health impacts of Chernobyl accident Twenty years ago, on April 26, 1986, the most serious nuclear accident occurred at the Chernobyl nuclear power station. On that day the nuclear engineers and technologists at the station attempted to do an experiment to test a newly designed backup power supply system to improve the safety of the reactor. Serious design flaws combined with unthinkably sloppy procedural lapses led to the accident. Dr Wilfried Kreisel, the WHO’s Executive Director in charge of Health and Environment, dismissed the claim as “fiction.” Some environmentalist groups quoted fatality figures of over 32,000. In 2000, BBC reported that Chernobyl had left 15,000 dead and 50,000 crippled by radiation! This authentic report estimated that as of mid-2005, fewer than 50 people died due to radiation exposure, almost all being highly exposed rescue workers. Many of these deaths occurred within months of the accident; some as late as late 2004. They included nine children who died of thyroid cancer out of about 4000 cases of thyroid cancer mainly in children and adolescents; all except these nine recovered. Other than these cancers, the specialists found no evidence for any increase in the incidence of leukemia and other cancers among the affected residents. Based on current knowledge, the international specialists made a statistical prediction that about 3940 deaths due to radiation exposure in the 600,000 exposed persons (including 200,000 emergency workers, 116,000 evacuees and 250,000 residents of the most contaminated areas) could occur due to the accident over their life time. Other learned bodies may challenge the estimate of 3940 deaths, which is based on a controversial radiation safety concept called Linear Non Threshold (LNT) hypothesis. There is a growing body of scientific evidence against this concept. Last year, the French Academy of Sciences severely criticised the LNT concept. In any population of 600,000, a quarter or about 150,000 people will eventually die from spontaneous cancer not related to radiation. Thus the report’s estimate for the eventual number of deaths from the accidents is far lower than the well-publicised speculations of tens of thousands of deaths. The confusion arose because thousands of people in the affected areas died of natural causes. The report noted some increase in particular cancers such as leukemia in the most highly exposed groups of emergency and recovery workers. The local residents tend to attribute all health problems to radiation exposure. They assumed that Chernobyl deaths were much higher than what they actually were. The UN report found that except the on-site reactor staff and emergency workers exposed on April 26, 1986, most workers and people living in contaminated areas received relatively low doses. Consequently, they did not find any evidence or likelihood of radiation related decreased fertility or congenital malformations among the population. But the relocation from affected areas proved to be a deeply traumatic experience for some 350,000 persons. Dr Burton Bennett, Chairman of the Forum, summarised the finding: “By and large... we have not found profound negative health impacts to the rest of the population in surrounding areas, nor have we found widespread contamination that would continue to pose a substantial threat to human health, with a few exceptional, restricted areas,”. Dr K. S. Parthasarathy is former Secretary, Atomic Energy Regulatory Board.
|
|
Tinkering with time What’s in half an hour? A lot more than only 30 minutes or 1,800 seconds - as Sri Lankans discovered last week. On April 14, the government adjusted Sri Lanka’s standard time to GMT+5:30 from GMT+6, which had been used since 1996. In doing so, the government completely ignored expert views of scientists and intellectuals. It listened instead to a vocal minority of nationalists, astrologers and Buddhist monks who had lobbied the newly elected president Mahinda Rajapaksa to “restore the clock to original Sri Lankan time”. SciDev.Net Strongest glue A bacterium that lives in rivers, streams and human aqueducts uses nature’s strongest glue to stay in one place, according to new research by Indiana University Bloomington and Brown University scientists reported in next week’s (April 11) Proceedings of the National Academy of Sciences. The scientists found they had to apply a force of about 1 micronewton to remove a single Caulobacter crescentus from a glass pipette. Because C. crescentus is so small, the pulling force of 1 micronewton generates a huge stress of 70 newtons per square millimeter. That stress, which the bacterial adhesions could sometimes withstand, is equivalent to five tons per square inch — three or four cars balanced atop a quarter. Not by lime juice
Researchers have concluded that using lemon or lime juice to protect women from HIV infection should be discouraged, as it could be unsafe. At a conference in Cape Town, South Africa, on April 24, scientists from the US-based CONRAD programme at the Eastern Virginia Medical School said it was unsafe for women to apply high concentrations of lime juice to their genitals to prevent HIV infection. SciDev.Net
|
|
THIS UNIVERSE If everything attracts everything else due to force of gravity, why don’t the planets fall into the Sun, or the Moon fall onto the Earth? The simple answer to this question would be that they do fall but keep missing their target because they are always in motion with respect to each other. The moon will definitely hit the earth if someone were to stop it from going around and suddenly release it. It is all the time falling towards the earth and keeps missing it. In fact, the combination of falling and the forward motion it got long ago keeps it going around in its orbit. The same is true of the satellites we launch. If we were to shoot our satellite straight up and leave it there it would fall down. That is why in order to make it go around the earth we take it up to a height and give it sufficient horizontal velocity so that it might go on trying to hit the earth while continuing to miss it! If a batsman were to hit a ball straight up it would come down and hit his head (or the bat, if he is a good marksman). But if he also gives the ball some horizontal velocity, he can get a sixer. If he were a superman he could actually put the ball into an orbit around the earth. How are minute quantities (like milligrams, micrograms, or nanograms) weighed? Down to milligrams one can use well-designed physical balances – indeed one can even go below one milligram if proper isolation from vibrations and other disturbances is ensured. But for going lower one needs to use other methods. We have to remember that our objective is to measure the mass, which is the quantity of material and not the amount of gravitational force. Mass is a measure of inertia. Inertia of an object is its intrinsic property that does not change whether the object is on earth, on the moon or orbiting in a weightless condition in earth orbit. One technique for measuring small masses that has become very current is to measure the change in resonant frequency of a quartz crystal on which the mass to be measured is deposited. Such crystals are piezoelectric, implying that a change in their dimension produces an electric potential across them. The reverse also happens; for example an oscillating electric field would introduce a physical oscillation of the crystal. The crystal, being mechanical in nature, also has a natural vibration frequency that depends on its dimensions and mass. If the electrical frequency is the same as the mechanical vibration frequency of the crystal there is a resonance that can be detected by a properly designed circuit. In this way the slightest change in the mass of the crystal can be measured. |
