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Biological clock could help estimate time of death Most individuals carry the gene activity ‘clock’ in their brain . —
Thinkstockphotos Western Indian Ocean earthquake risk underestimated Trends Prof Yash
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Biological clock could help estimate time of death PEOPLE with severe depression have a disrupted “biological clock” that makes it seem as if they are living in a different time zone to the rest of the healthy population living alongside them, a study has found. It is the first time that depression has been linked unequivocally to the internal circadian clock of the human brain, which regulates the body’s day-and-night cycle over a 24-hour period, scientists said. The researchers found that they could estimate a healthy person’s time of death to within a few hours by analysing the activity levels of a set of genes — whether they are switched on ‘high’ or ‘low’ — within certain regions of the deceased brain. However, this correlation broke down when they analysed the autopsied brains of people who had suffered from depression. Their gene activity bore little relationship to the hour of death, which indicated they suffered a severely disrupted sleeping pattern, the scientists found. The findings suggest that patients with severe depression could be better treated if there was some way of improving the relationship between the daily cycle of gene activity of the brain with the actual time of day or night, they said. “We think the depressed individuals are more likely to be out-of-sync with the regular wake-sleep timing,” said Jun Li of the University of Michigan, the lead author of the study published in the journal Proceedings of the National Academy of Sciences. “Our data also suggests that their daily cycles are not only shifted, but also disrupted. That is, they sleep by the wrong clock, and when they do sleep, the quality [of sleep] could be different from normal sleep,” Dr Li said. “If we can understand how depression and poor sleep reinforce each other, we may be able to find better treatment, perhaps by finding better ways to break the cycle,” he said. The scientists screened nearly 12,000 genes for daily activity rhythms in six regions of the brain from 55 deceased individuals who had no history of psychiatric or neurological illness. The same was done on the brains of 34 deceased people with severe depression — some of whom had committed suicide. To their surprise, the scientists found that with the healthy brains they could estimate to within a couple of hours the time of a person’s death, based on which of about 100 genes were active or dormant over a 24-hour period. “Most of our subjects were awake on the day of their death, due to last-hour medical emergencies, or, in the case of some depression cases, due to suicide attempt,” Dr Li said. “But we were able to show that most individuals carry the gene activity ‘clock’ in their brain. This suggested to us that such a clock is quite stable upon one-day disturbance, and this is consistent with the common knowledge that it takes many days to recover from jet-lag,” he said. The genes that respond to the time of day appear to be part of the complex biological machinery of the body that helps it to cope with the different demands of the 24-hour cycle — regulating when to sleep and when to be awake. “There really was a moment of discovery. It was when we realised that many of the genes that show 24-hour cycles in the normal individuals were well-known circadian-rhythm genes,” Dr Li said. “People with depression were not synchronised to the usual solar day in terms of this gene activity. It’s as if they were living in a different time zone than the one they died in,” he said. There has been much research on the circadian clock, both in animals and humans, but this is the first time that such an elaborate network of genes have been studied in such detail, said Huda Akil, a co-author of the study. “Hundreds of new genes that are very sensitive to circadian rhythms emerged from this research — not just the primary clock genes that have been studied in animals or cell cultures, but other genes whose activity rises and falls throughout the day,” Dr Akil said. “We were truly able to watch the daily rhythm play out in a symphony of biological activity, by studying where the clock had stopped at the time of death. And then, in depressed people, we could see how this was disrupted,” she said. “In depressed people, [a disrupted biological clock] can become part of a vicious cycle. Therefore, one can speculate that re-setting the clock for instance with light or physical activity, is a reasonable, concrete target to aim for in the treatment of severe depression,” Dr Akil added.
— The Independent
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Western Indian Ocean earthquake risk underestimated EARTHQUAKES similar to the devastating 9.1-magnitude Sumatra quake of 2004 could occur in an area beneath the Western Indian Ocean, threatening the coastlines of India and Pakistan, a new study has warned. Scientists from the University of Southampton suggest that the risk from undersea earthquakes and associated tsunami in this area of the Arabian Sea at the Makran subduction zone — which could threaten the coastlines of Pakistan, Iran, Oman, India and potentially further afield — has been previously underestimated. The results highlight the need for further investigation of pre-historic earthquakes and should be fed into hazard assessment and planning for the region. Subduction zones are areas where two of the Earth’s tectonic plates collide and one is pushed beneath the other. When a quake occurs here, the seabed moves horizontally and vertically as the pressure is released, displacing large volumes of water that can result in a tsunami. The Makran subduction zone has shown little earthquake activity since a magnitude 8.1 earthquake in 1945 and magnitude 7.3 in 1947. Because of its relatively low seismicity and limited recorded historic earthquakes, it has often been considered incapable of generating major earthquakes. Plate boundary faults at subduction zones are expected to be prone to rupture generating earthquakes at temperatures of between 150 and 450°C. Scientists used this relationship to map out the area of the potential fault rupture zone beneath the Makran by calculating the temperatures where the plates meet. Larger fault rupture zones result in larger magnitude earthquakes. “Thermal modelling suggests that the potential earthquake rupture zone extends a long way northward, to a width of up to 350 km which is unusually wide relative to most other subduction zones,” said Gemma Smith, lead author from the University of Southampton School of Ocean and Earth Science, based at the National Oceanography Centre Southampton . The team also found that the thickness of the sediment on the subducting plate could be a contributing factor to the magnitude of an earthquake and tsunami there. — PTI
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Trends OSLO: A melt of ice on Greenland and Antarctica is likely to be less severe than expected this century, limiting sea level rise to a maximum of 69 cm (27 inches), an international study said. Even so, such a rise could dramatically change coastal environments in the lifetimes of people born today with ever more severe storm surges and erosion, according to the ice2sea project by 24, mostly European, scientific institutions.
Boeing demonstrator breaks hypersonic flight record WASHINGTON: Boeing Co’s X-51A Waverider made history when it achieved the longest hypersonic flight by a jet fuel-powered aircraft, flying for 3-1/2 minutes at five times the speed of sound, the US Air Force said. The last of four unmanned experimental military aircraft built by Boeing flew for at a top speed of Mach 5.1 over the Pacific Ocean, the Air Force said. The total flight covered 230 nautical miles in just over six minutes before the hypersonic cruiser plunged into the ocean. Soyuz space capsule returns to Earth ALMATY/CAPE CANAVERAL, Florida: Canadian astronaut Chris Hadfield who became a music sensation when his zero-gravity version of David Bowie’s “Space Oddity” went viral on the Web returned to Earth along with his American and Russian colleagues this week after a five-month stint on the International Space Station. Their Soyuz space capsule descended under an orange parachute and raised clouds of dust as it ignited an engine to cushion its landing about 150 km southeast of the town of Zhezkazgan. — Reuters
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THIS UNIVERSE Pressure is an intensive property. Suppose we take 2 gm in one container and 2,000 gm in another container (same size) of the same gas under similar conditions, in the second container the probability of number of collisions would be greater as compared to the first one due to the increased number of molecules. Going by this, the pressure should be greater in the second container that makes pressure an extensive one, which is contradiction to the given fact. Please explain. You have confused me a little. Your second cylinder is a different case. It is a different, separate cylinder. If it has a larger number of gas molecules in the same volume, it has a right to have a greater pressure. I do not know what principle is being violated. There is no need to be confused by extraneous philosophical deliberation. Why do planets orbit around stars? Imagine two celestial bodies, one a star, much bigger than another, which we will call a planet because it is much smaller than the star. Wandering about in space, they happen to come within mutual gravitational hailing distance. It is clear that being attracted towards each other; they will collide only if they do not have initial transverse velocity with respect to each other. Since this is very unlikely, they will pass by and from now on they will come closer but only on an orbital path. If there is no resistance, the two will start going around each other, the planet being called the satellite of the star.
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PEOPLE with severe depression have a disrupted “biological clock” that makes it seem as if they are living in a different time zone to the rest of the healthy population living alongside them, a study has found.
It is the first time that depression has been linked unequivocally to the internal circadian clock of the human brain, which regulates the body’s day-and-night cycle over a 24-hour period, scientists said.
