Why we can see even in dim light

WASHINGTON (TIP): A new research by UC Davis researchers has discovered that the key chemical process that corrects for potential visual errors in low-light conditions. Understanding this fundamental step could lead to new treatments for visual deficits, or might one day boost normal night vision to new levels. Like the mirror of a telescope pointed toward the night sky, the eye’s rod cells capture the energy of photons – the individual particles that make up light. The interaction triggers a series of chemical signals that ultimately translate the photons into the light we see. The key light receptor in rod cells is a protein called rhodopsin. Each rod cell has about 100 million rhodopsin receptors, and each one can detect a single photon at a time. Scientists had thought that the strength of rhodopsin’s signal determines how well we see in dim light. But UC Davis scientists have found instead that a second step acts as a gatekeeper to correct for rhodopsin errors. The result is a more accurate reading of light under dim conditions. Individual rhodopsin errors are relatively small in magnitude – on the order of a few hundredths of a second – but even this much biological noise can affect how well the signal gets transmitted to the rest of the brain, the researchers said. The gatekeeper protects us from “seeing” more light than is actually there – a misreading that would have endangered an ice-age hunter, as it would a driver at dusk today. The correction may prevent the photon receptor from swamping the intricate chemical apparatus that leads to accurate light perception. “The rhodopsin receptor is the site where physics meets biology – where a photon of light from the physical world must get interpreted for the nervous system,” explained Marie Burns, professor of ophthalmology and vision science at UC Davis School of Medicine and lead author of the study. “Biology is messy. Rhodopsin does a remarkable but not perfect job,” she stated. Burns and her colleagues studied rod cells in the laboratory and discovered that calcium plays the gatekeeper role. They found that rhodopsin activity changed calcium levels in the cells and that over-active rhodopsins changed calcium levels at a faster rate than normal. This faster change led calcium to trigger a series of chemical steps to counter the over-active rhodopsin signal by producing an equal and opposite signal, thereby correcting false information before it gets sent on to the rest of the visual system. They uncovered this fundamental new level of control by measuring how long individual rhodopsin receptors remained active in response to flashes of light, and then determining how much calcium’s gatekeeping function modified the rhodopsin signals. “Basic research like ours often doesn’t translate to immediate clinical treatments for known diseases, but understanding fundamental processes has long-term significance,” Burns said. “In the case of our research, this understanding can prove essential for progress on a range of vision deficits that are currently poorly understood and untreatable,” she added. HARVARD SCIENTISTS SUGGEST MOON MADE FROM EARTH Anew theory put forward by Harvard scientists suggests the moon was once part of the earth that spun off after a giant collision with another body. In a paper published on Wednesday in the journal Science, Sarah Stewart and Matija uk said their theory would explain why the earth and moon have similar composition and chemistry.

The earth was spinning much faster at the time the Moon was formed, and a day lasted only two to three hours, they said. With the Earth spinning so quickly, a giant impact could have launched enough of the Earth’s material to form a moon, the scientists said in an explanation published on a Harvard website. www.fas.harvard.edu/~planets /sstewart/Moon.html According to the new theory, the Earth later reached its current rate of spinning through gravitational interaction between its orbit around the Sun and the Moon’s orbit around Earth.

The scientists noted that their proposition differed from the current leading theory, which holds that the Moon was created from material from a giant body that struck the Earth. Stewart is a professor of earth and planetary sciences at Harvard, and UK, an astronomer and an investigator at the SETI Institute, which supports research into the search for extraterrestrial life. The latter was conducting post-doctoral research at Harvard. LONDON (TIP): Nasa’s Curiosity rover on Mars is apparently littering on the Red planet.

Pictures beamed back by the rover show a bright object lying in the Martian dirt, and a closer look suggests the object is a piece of plastic wrapper that has fallen from the robot.

The discovery has put a twist on the rover’s current mission to scrub out its soil scoop and take its first sample of Martian dirt for analysis, the ‘New Scientist’ reported. However, more bright specks of unidentified matter in the soil – at first thought to be from Curiosity shedding – may actually be Martian in origin, although what they are is a mystery.

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Curiosity had been in the midst of preparing to feed soil into its Chemistry and Mineralogy (CheMin) instrument, which bounces thin beams of X-rays off a sample to read its mineral composition. This involved taking scoopfuls of soil, shaking them vigorously and then dumping them back out, to be sure that any lingering traces of Earthly particles didn’t make it into the science equipment. After the first scoop-and-shake revealed the unexpected object, Curiosity took a quick break to examine the find. It then got back on course, taking a second scoop of soil on October 12. Is Curiosity littering plastic on red planet

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