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Passive
smoking linked to DNA damage and birth defects What
keeps the Earth cooking Prof Yash
Pal This Universe Trends |
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Passive smoking linked to DNA damage PASSIVE smoking can cause genetic damage to sperm cells that may result in birth defects, miscarriages and other reproductive problems which make it difficult to father a healthy child, scientists have found. A study involving laboratory mice discovered that sperm cells are vulnerable to DNA damage caused by side-stream tobacco smoke, which is composed of about 4,000 chemicals, including about 60 known cancer-causing substances. Researchers believe that similar DNA changes in boys or men exposed regularly to passive smoke could lead to reproductive problems such as infertility or a higher risk of fathering children with congenital defects. Scientists led by Carole Yauk, of Health Canada in Ottawa, found that when mice were exposed to the side-stream smoke from a burning cigarette, they suffered a significant increase in the number of DNA mutations within the “germ cells” of the testes which are responsible for making sperm. “Our data suggests that paternal exposure to second-hand smoke may have reproductive consequences that go beyond the passive smoker,” the researchers write in the journal Proceedings of the National Academy of Sciences. They say their work on laboratory mice provides “compelling evidence” to support the argument that passive smoking should be regarded as a potential mutation-causing behaviour in human sperm cells. “Consistent with data for first-hand smoke, male exposure to second-hand smoke before fertilisation is likely to have detrimental reproductive consequences that go beyond the passive smoker,” they say. A separate study of more than 1,500 American teenagers found that exposure to passive smoking in early childhood increased the risk of developing hearing problems that could impair a child’s educational development. It is the first time that passive smoking has been linked directly with hearing loss and will almost certainly be used to justify greater efforts to protect the estimated two million children in the UK who live in households where they are regularly exposed to the tobacco smoke of parents or relatives. The scientists found that the degree of hearing loss was linked to the amount of nicotine breakdown products found in the bloodstream of the teenagers, indicating that passive smoking was actually causing the problem rather then merely being associated with it. Professor Anil Lalwani, of New York University School of Medicine, said many children were exposed to second-hand smoke in the home, and discovering a connection with hearing loss in teenagers had huge health implications. “We need to evaluate how we deal with smoking in public places and at home, as well as how often and when we screen children for hearing loss,” Professor Lalwani said.
— The Independent
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WE all know that the Earth runs on massive amounts of heat — enough to melt iron in the outer core, create magnetic field, spread the sea floors and move the continents. However, where all this heat comes from was a mystery until now. According to a new research, only about half of our planet’s internal heat stems from natural radioactivity. The rest is primordial heat left over from the planet’s formation, and possibly others. Geologists have used temperature measurements from more than 20,000 boreholes around the world to estimate that some 44 terawatts (44 trillion watts) of heat is constantly flowing out of the Earth’s interior into space. But, where does it come from? Geologists relied on temperature measurements from more than 20,000 boreholes around the world. Radioactive decay of uranium, thorium, and potassium in Earth’s crust and mantle is a principal source, and in 2005 scientists in the KamLAND collaboration, based in Japan, first showed that there was a way to measure the contribution directly. Using the Kamioka Liquid-scintillator Antineutrino Detector (KamLAND) located under a mountain in Japan, they analysed geoneutrinos — emitted by decaying radioactive materials within the Earth. “As a detector of geoneutrinos, KamLAND has distinct advantages,” said Stuart Freedman of the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), which is a major contributor to KamLAND. “KamLAND was specifically designed to study antineutrinos. We are able to discriminate them from background noise and detect them with very high sensitivity,” added Freedman, a member of Berkeley Lab’s Nuclear Science Division and a professor in the Department of Physics at the University of California at Berkeley, leads US participation. KamLAND scientists have now published new figures for heat energy from radioactive decay. Based on the improved sensitivity of the KamLAND detector, plus several years’ worth of additional data, the new estimate is not merely “consistent” with the predictions of accepted geophysical models but is precise enough to aid in refining those models. Antineutrinos are produced not only in the decay of uranium, thorium, and potassium isotopes but in a variety of others, including fission products in nuclear power reactors. In fact, reactor-produced antineutrinos were the first neutrinos to be directly detected (neutrinos and antineutrinos are distinguished from each other by the interactions in which they appear). All models of the inner Earth depend on indirect evidence. Leading models of the kind known as bulk silicate Earth (BSE) assume that the mantle and crust contain only lithophiles (“rock-loving” elements) and the core contains only siderophiles (elements that “like to be with iron”). Thus, all the heat from radioactive decay comes from the crust and mantle – about eight terawatts from uranium 238 (238U), another eight terawatts from thorium 232 (232Th), and four terawatts from potassium 40 (40K). Additional factors that have to be taken into account include how the radioactive elements are distributed (whether uniformly or concentrated in a “sunken layer” at the core-mantle boundary), variations due to radioactive elements in the local geology (in KamLAND’s case, less than 10 per cent of the expected flux), antineutrinos from fission products, and how neutrinos oscillate as they travel through the crust and mantle. Alternate theories were also considered, including the speculative idea that there may be a natural nuclear reactor somewhere deep inside the Earth, where fissile elements have accumulated and initiated a sustained fission reaction. This is more heat energy than the popular BSE model suggests, but still far less than Earth’s total. Said Freedman, “One thing we can say with near certainty is that radioactive decay alone is not enough to account for Earth’s heat energy. Whether the rest is primordial heat or comes from some other source is an unanswered question.” The study is detailed in Nature Geoscience.
— ANI
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This Universe When
we take a blood test, just a little blood is extracted from a vein in the arm using a needle. But when we get the test report, we come to know the total amount of blood present in our body. Please explain. The laboratory report on a small sample of blood does not contain information about the total amount of blood in the body; as you very rightly say, that information would be impossible to determine from the sample. What the report does contain instead is the concentration of either blood cells (in cells/unit volume) or biomolecules (in grams or moles)/unit volume). For example, the concentration of glucose in blood may help a doctor determine whether a patient has diabetes and the concentration of white blood cells could shed light on the health of the immune system. When there is adequate lighting in a room considering dark outside, reading in the room doesn’t strain our eyes. But during daytime, when there is much sunshine outside, the same lighting appears to be inadequate. Why? When you are in a room with adequate lighting and it is dark outside, the iris of your eyes is appropriately adjusted for comfortable reading. If there is sunshine outside, general lighting in the room might increase a little, but your eyes also turn occasionally to the brightness of the sun outside. This tends to reduce the aperture of your eyes. This is slightly less than what it was earlier. As a result, you feel that you need to brighten the room some more for comfortable reading.
Readers wanting to ask Prof Yash Pal a question can e-mail him at palyash.pal@gmail.com
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Trends WASHINGTON: The Hubble Space Telescope has discovered a tiny fourth moon orbiting the distant icy dwarf planet Pluto, NASA said on Wednesday. The space telescope was searching for rings around the planetary oddball at the edge of our solar system when it came across P4, the temporary name for the newly discovered moon.
US wants to talk outer space with China
WASHINGTON: The US wants to open a regular dialogue with China on outer space in an effort to create "rules for the road" and reduce the risk of misunderstandings, a US defence official said. China is making major investments in space and, unlike in the US, distinguishing between China's civil and military space sectors is difficult because "the two are essentially one," Gregory Schulte, deputy assistant secretary of defence for space policy, said.
— Reuters |
Steve
Connor
