Monday, September 13, 2010

GLASPERLENSPIEL: NIST SCIENTISTS PROPOSE NEW TEST FOR GRAVITY

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A new experiment proposed by physicists at the National Institute of Standards and Technology (NIST) may allow researchers to test the effects of gravity with unprecedented precision at very short distances—a scale at which exotic new details of gravity's behavior may be detectable.

Of the four fundamental forces that govern interactions in the universe, gravity may be the most familiar, but ironically it is the least understood by physicists. While gravity's influence is well-documented on bodies separated by astronomical or human-scale distances, it has been largely untested at very close scales—on the order of a few millionths of a meter—where electromagnetic forces often dominate. This lack of data has sparked years of scientific debate.

"There are lots of competing theories about whether gravity behaves differently at such close range," says NIST physicist Andrew Geraci, "But it's quite difficult to bring two objects that close together and still measure their motion relative to each other very precisely."

In an attempt to sidestep the problem, Geraci and his co-authors have envisioned an experiment that would suspend a small glass bead in a laser beam "bottle," allowing it to move back and forth within the bottle. Because there would be very little friction, the motion of the bead would be exquisitely sensitive to the forces around it, including the gravity of a heavy object placed nearby.

According to the research team, the proposed experiment would permit the testing of gravity's effects on particles separated by 1/1,000 the diameter of a human hair, which could ultimately allow Newton's law to be tested with a sensitivity 100,000 times better than existing experiments.

Actually realizing the scheme—detailed in a new paper in Physical Review Letters—could take a few years, co-author Scott Papp says, in part because of trouble with friction, the old nemesis of short-distance gravity research. Previous experiments have placed a small object (like this experiment's glass bead) onto a spring or short stick, which have created much more friction than laser suspension would introduce, but the NIST team's idea comes with its own issues.

"Everything creates some sort of friction," Geraci says. "We have to make the laser beams really quiet, for one thing, and then also eliminate all the background gas in the chamber. And there will undoubtedly be other sources of friction we have not yet considered."

For now, Geraci says, the important thing is to get the idea in front of the scientific community.

"Progress in the scientific community comes not just from individual experiments, but from new ideas," he says. "The recognition that this system can lead to very precise force measurements could lead to other useful experiments and instruments."

(Photo: K. Talbott/NIST)

National Institute of Standards and Technology (NIST)

STUDY LINKS SHORTER SLEEP DURATIONS WITH GREATER RISKS OF MENTAL DISTRESS IN YOUNG ADULTS

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Young adults who get fewer than eight hours of sleep per night have greater risks of psychological distress, a combination of high levels of depressive and anxious symptoms, according to a study in the Sept. 1 issue of the journal SLEEP.

Using an average self-reported nightly sleep duration of eight to nine hours as a reference, the study found a linear association between sleep durations of less than eight hours and psychological distress in young adults between 17 and 24 years of age. The risk of psychological distress increased by 14 percent for each hour of nightly sleep loss, such that those sleeping less than six hours a night were twice as likely to be experiencing distress as average sleepers. A similar association was found between sleep duration and persistent psychological distress; the risk that a person with psychological distress at baseline would be distressed at the one-year follow-up increased by five percent for each hour of nightly sleep loss after adjusting for potential confounders (RR 1.05). Long sleep durations of more than nine hours showed no association with distress at any time point.

“In young adults already experiencing distress, the fewer hours they sleep the worse the outcome across the range of sleep hours,” said lead author Nick Glozier, MBBS, MRCPsych, PhD, associate professor of psychological medicine at the Brain and Mind Research Institute and the Centre for Integrated Research and Understanding of Sleep (CIRUS) at the University of Sydney in Australia.

The study also found that the risk for the onset of psychological distress was increased only in those young adults with extremely short sleep durations. Participants without psychological distress at baseline who reported sleeping five hours or less per night were three times more likely to be distressed one year later (RR 3.25).

“Short sleep duration increases the risk of a new onset of distress only among the very shortest sleepers, and doesn’t appear to have a psychological impact in young adults in good mental health with moderately short sleep durations, such as seven hours a night” said Glozier.

In 2007 the U.S. Substance Abuse and Mental Health Services Administration estimated that 17.9 percent of young adults between the ages of 18 and 25 years experienced serious psychological distress in the past year. The Australian Bureau of Statistics reported that 26 percent of all young people between 16 and 24 years of age had a mental disorder in 2007.

Conducted at The George Institute for Global Health of the University of Sydney, the DRIVE study involved 20,822 young adults in New South Wales, Australia. Participants completed a confidential survey, reporting the number of hours slept on both weekday and weekend nights during the past month. The data were weighted to determine respondents’ average nightly sleep duration. Thirty percent of participants slept for seven to eight hours per night, and 18 percent reported sleeping less than seven hours. Fewer than two percent of study subjects had an extremely short sleep duration of less than five hours per night.

Psychological distress was assessed using the Kessler Psychological Distress Scale (K10), a widely used 10-item screening instrument that evaluates a person’s mental health problems during the previous four weeks. It includes questions that ask about feeling tired, nervous, hopeless, restless, depressed, sad and worthless. A high score indicates that a person is likely to be suffering from a mental disorder. About 32.5 percent of young adults in the study had high levels of current psychological distress at baseline.

A randomly selected subsample of 2,937 participants completed a follow-up survey between 12 and 18 months after the baseline survey. A new onset of psychological distress was found in 239 of 1,992 participants (12 percent) who did not report psychological distress at baseline. Persistent psychological distress was found in 419 of 945 respondents (44 percent) who were distressed at baseline.

The authors noted that the relationship between sleep and psychological distress is complex. Although short sleep duration could be a real risk for distress, it is possible that sleep loss is a symptom of previous episodes of psychological distress that have got better, or that sleep disturbances reflect a comorbid condition that hinders distress from resolving. This study’s findings suggest that recent increases in the levels of distress reported by young adults may be related to changes in their sleep patterns.

“The increased reporting of stress seen in many countries over the past decade or two in this young adult population may reflect lifestyle or other changes that lead to too few hours of sleep,” Glozier said.

According to the authors, broad approaches to increase sleep duration in all young adults are unwarranted. Instead, interventions should target young adults who have either current distress or an extremely short sleep duration. Other studies show that potential targets for improving sleep in this age group include delaying school start times and reducing the amount of time at night that young adults spend watching TV, playing video games and using the Internet before going to bed.

American Academy of Sleep Medicine

FUEL-EFFICIENCY FORMULA NEEDS CARS WIRED WITH BETTER BRAINPOWER, LESS VROOM

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A University of Michigan researcher says it’s possible to triple fuel economy in gasoline-powered cars by 2035, but it’ll mean getting our automotive kicks from smart electronic technology and other forms of virtual performance rather than horsepower.

As federal regulators are poised to propose the next round of fuel economy mandates, John DeCicco, a senior lecturer at the School of Natural Resources and Environment and faculty fellow with the Michigan Memorial Phoenix Energy Institute, says the most cost-effective answer is steady progress in advanced combustion engines and hybrid drive---but stopping short of plugging in and requiring super batteries or gaseous fuels.

He finds that the solution is in our garages if Americans shift gears in terms of priorities. What DeCicco calls a “revolution by evolution” avoids politically trendy breakthrough technologies that will remain too expensive for most consumers.

“If we really prioritize efficiency, we can get just as far with less sticker shock,” he said. “Evolutionary change can be of profound consequence for cutting oil use and greenhouse gas emissions, and do so with manageable costs and minimal risks for automakers.”

DeCicco has completed a study for The Energy Foundation examining how far fuel economy can be taken if it becomes a top priority in product planning. See the study here.

His analysis shows that optimizing internal combustion engines plus rising adoption of grid-free hybrids will enable new fleet efficiency to reach 52 mpg by 2025 and 74 mpg by 2035.

Reaching such a horizon would entail cultural change in a gearhead world attuned to nuances of power performance. DeCicco identifies emerging trends for what he dubs “efficiency compatible” design strategies, enticing buyers away from brute force and toward smart technologies, intelligent safety features and svelte styling. Amenities like Bluetooth hookups, communication bandwidth and other information technology enhance customer value with minimal demands on power.

The report develops new interpretations of technology cost estimates that better depict the benefits of ongoing innovation while acknowledging the limits of how much consumers can spend. The analysis reflects the three-way trade-off among efficiency, performance and cost that the car market is likely to face in the years ahead.

“The fleet I’ve modeled for 2025 does not give up any of the performance and creature comforts consumers already enjoy,” he said. “You don’t have to go back to being Fred Flintstone, but you will see lower fuel costs instead of ever more mass and muscle.”
At the U-M, DeCicco teaches courses in sustainable energy and transportation energy policy and researches solutions to transportation energy and climate problems. Before returning to academia, he was the green world’s top vehicle technology expert, most recently as senior fellow for automotive strategies at the Environmental Defense Fund.

University of Michigan

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