Wednesday, September 15, 2010

PERSONAL CUSHION OF AIR

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Plans for Orion — the capsule that resembles the Apollo program’s spacecraft and was supposed to send humans to the moon by 2020 as part of NASA’s Constellation program — were changed in February when President Obama canceled Constellation, and then announced two months later that NASA would continue to develop Orion as an escape vehicle to be docked at the International Space Station for emergencies.

While it appears that Orion will eventually take flight, NASA continues to struggle with one crucial aspect of its design: minimizing the violent impact that astronauts would experience during landing. Although NASA initially designed Orion’s crew seats to be mounted onto a stiff structure supported by shock absorbers — essentially the same technology used to cushion Apollo’s water landings — this 1,100-pound structure would be too heavy to cushion astronauts if the vehicle landed on land. Whereas the Apollo capsule was designed to land in water, and Orion would likely do the same, NASA wants to make sure that Orion can land on land in case of an emergency.

A graduate student in MIT’s Department of Aeronautics and Astronautics has helped design a smaller alternative: a reusable, 700-pound air-bag system that could inflate during launch and landing, deflate for storage purposes, and partially inflate to provide seating while the vehicle is in space. Not only would the system be lighter than the one NASA originally proposed, but it would also be entirely mechanical, meaning not controlled by computers.

This is important because “the vast majority of accidents and failures in engineering systems” can be traced to computers misinterpreting situations, says Sydney Do, who helped design the air-bag system and spent several weeks in August testing a full-sized prototype designed to protect one astronaut. “Our goal was to see if it was possible to design a landing system that was purely mechanical.”

According to a paper presented at the American Institute of Aeronautics and Astronautics Space 2009 conference by Do and his thesis adviser, Olivier de Weck, an associate professor of aeronautics and astronautics and engineering systems, the air-bag system was inspired by the structure of seeds. Just as a fluid surrounds the embryo in seeds to provide protection as the seed is distributed, the Orion air-bag system would surround each astronaut in “a personal cushion of air,” according to current NASA astronaut Charlie Camarda, who seeks to develop more innovative space-engineering concepts that veer from the traditional. In 2008, Camarda helped organize a group of students from Pennsylvania State University and MIT, including Do, to explore how the physics of seeds could be applied to engineering principles. Do’s design for an Orion air-bag system, Camarda says, represents “a very novel” approach to mechanical design that could inspire more biological-based solutions in engineering.

NASA’s Engineering and Safety Center agreed to fund the study by the Penn State and MIT students to explore the feasibility of an air-bag system that Orion astronauts could inflate before reentering Earth’s atmosphere. The students’ first step was to conduct tests to observe how the inflated bags behave when they are dropped from increasing one-foot increments while supporting an object that weighs about the same as an average male head — such drops simulate the impact velocity that an astronaut would feel upon landing.

These tests revealed how important timing is in terms of releasing gas from an air bag. Unlike car air bags, which inflate when hot gas is injected into them upon impact, the inflated Orion air bags already contain gas upon impact. If the air bags are either not big enough or don’t have enough air in them, the astronaut’s seat will directly impact the ground. Alternatively, if there is enough gas inside the bag, but it’s not released before the seat hits the ground, the impact will cause the seat to bounce upward, which could injure the astronaut. That’s because as an astronaut falls into the bag during the landing, the kinetic energy created from this motion is combined with the energy of the gas molecules moving inside the bags. This increases the pressure of the gas inside the bag, which could cause bouncing.

To prevent this bounce, enough gas needs to be vented between the point at which the floor of Orion impacts the ground and the point at which the seat and the astronaut impact the ground so that the kinetic energy caused by the falling seat and occupant have been removed. But even after some of this gas is vented, there still needs to be enough gas remaining in the bags to prevent direct impact between the seat and the ground. To get this balance right, the students decided to design valves that are triggered to open at a low pressure, which would allow gas to vent as soon as Orion’s floor comes to rest, but before the seat can impact the ground.

When NASA decided to fund the research for another year last spring, Do took over the research for his master’s thesis and began testing a valve for the system. He then developed a computer model to analyze how certain variables, such as air-bag size, would affect the risk of astronaut injury upon impact. This helped him configure a prototype seat that would have four air bags — each about one foot long by two feet wide — containing two rectangular valves about six inches wide. Do then built the air bags from vectran, a high-strength material that was used to make the air bags for several rovers that landed on Mars.

Earlier this month, he tested the prototype through a series of drop tests conducted from as high as 10 feet involving a crash dummy that measured the acceleration of each drop. While Do still needs to analyze those results before presenting his final design to NASA later this fall, he says that the fact that the system survived dozens of drops suggests that certain variables he chose for the prototype, such as the material and manufacturing of the air bags, are adequate for an Orion landing. According to Camarda, future research could explore ways to ensure “a robust and fail-safe” system in the event that a valve malfunctions.

Do cautions that the air-bag system has one drawback: It’s likely only effective for vertical drops, meaning that the air bags could tip over if Orion descended at a sideways angle. But he says this might not be an issue if Orion is designed to land vertically. Although whatever NASA decides to do with Do’s research ultimately depends on the future of human spaceflight, he is hopeful that even if Orion never takes flight, his research could be used to guide designs of similar capsule-type spacecraft that commercial companies might be interested in building.

(Photo: William Litant)

Massachusetts Institute of Technology

ARCHAEOLOGICAL STUDY SHOWS HUMAN ACTIVITY MAY HAVE BOOSTED SHELLFISH SIZE

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In a counter-intuitive finding, new research from North Carolina State University shows that a species of shellfish widely consumed in the Pacific over the past 3,000 years has actually increased in size, despite – and possibly because of – increased human activity in the area.

“What we’ve found indicates that human activity does not necessarily mean that there is going to be a negative impact on a species – even a species that people relied on as a major food source,” says Dr. Scott Fitzpatrick, associate professor of sociology and anthropology at NC State and co-author of the study. “The trends we see in the archaeological record in regard to animal remains are not always what one would expect.”

At issue is the humped conch, Strombus gibberulus, a small mollusk that has been a food source in the Pacific islands for thousands of years. The researchers dated and measured more than 1,400 humped conch shells found at an archaeological site on the island of Palau in the western Pacific. They expected the size of the conchs to decrease over time, based on the conventional wisdom that an expanding human population would result in the conchs being harvested before they could achieve their maximum size.

Instead, the researchers were surprised to find that the average size of the conchs actually increased in conjunction with a growing human population. Specifically, the length of the average conch increased by approximately 1.5 millimeters (mm) over the past 3,000 years. That may not sound like much, but it is significant when you consider the conchs are only around 30 mm long – which means the conchs are now almost 5 percent larger than they used to be.

Fitzpatrick believes the size increase is likely related to an increase in nutrients in the conch’s waters, stemming from increased agriculture and other human activities.

“In the big picture,” Fitzpatrick says, “this study tells us to focus on the physical evidence and beware of conventional wisdom. It also tells us that using a large number of samples is important. Previous studies had shown a decline in conch size at Pacific archaeological sites – but they used smaller sample sizes. Maybe that is a factor in their findings.”

The study was co-authored by Fitzpatrick, Christina Giovas of the University of Washington, and two NC State undergraduates, Meagan Clark and Mira Abed. A paper describing the study, “Evidence for size increase in an exploited mollusk: humped conch (Strombus gibberulus) at Chelechol ra Orrak, Palau from ca. 3000-0 BP,” will be published in a forthcoming issue of the Journal of Archaeological Science. The samples used in the study were collected as part of a National Science Foundation-funded research initiative.

(Photo: NCSU)

North Carolina State University

BODY CLOCK DRUGS COULD EASE PSYCHIATRIC DISORDERS AND JET LAG

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University of Manchester researchers have successfully used a drug to reset and restart the natural 24-hour body clock of mice in the lab. The ability to do this in a mammal opens up the possibility of dealing with a range of human difficulties, including some psychiatric disorders, jet lag and the health impacts of shift work.

The work, funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and the Medical Research Council (MRC), was led by Professor Andrew Loudon, in Manchester’s Faculty of Life Sciences, and Dr Mick Hastings, of the MRC Laboratory of Molecular Biology in Cambridge, working with a multi-disciplinary team of scientists from Pfizer led by Dr Travis Wager. The study is published today in PNAS.

Professor Loudon said: “It can be really devastating to our brains and bodies when something happens to disrupt the natural rhythm of our body clocks. This can be as a result of disease or as a consequence of jet lag or frequent changing between day and night shifts at work.

“We’ve discovered that we can control one of the key molecules involved in setting the speed at which the clock ticks and in doing so we can actually kick it into a new rhythm.”

Most living creatures and plants have an internal body timing system – called the circadian clock. This is a complex system of molecules in every cell that drives the rhythmicity of everything from sleep in mammals to flowering in plants. Light and the day and night cycle are very important for resetting the clock and the fine adjustments are made through the action of several enzymes, including one called casein kinase 1, which has been the centre of this project.

Professor Loudon continued: “The circadian clock is linked to the 24-hour day-night cycle and the major part of the clock mechanism 'ticks' once per day. If you imagine each 'tick' as represented by the rise and fall of a wave over a 24-hour period, as you go up there is an increase in the amount of proteins in the cell that are part of the clock mechanism, and as you go down, these substances are degraded and reduce again. What casein kinase 1 does is to facilitate the degradation part.

“So you can imagine that the faster casein kinase 1 works, the steeper the downward part of the wave and the faster the clock ticks - any change in casein kinase 1 activity, faster or slower, would adjust the 'ticking' from 24 hours to some other time period. Consider that if your body suddenly starts working on a 23-hour or 25-hour clock, many of your natural processes, such as sleeping and waking could soon become out of step with day and night.”

The team found a drug that slows casein kinase 1 down and used it in mice where the circadian rhythm has ceased i.e. the clock has stopped ticking all together. In live mice and also in cells and tissue samples from mice, they were able to re-establish the ticking of the clock by using the drug to inhibit the activity of casein kinase 1.

Professor Loudon concluded: “We’ve shown that it’s possible to use drugs to synchronise the body clock of a mouse and so it may also be possible to use similar drugs to treat a whole range of health problems associated with disruptions of circadian rhythms. This might include some psychiatric diseases and certain circadian sleep disorders. It could also help people cope with jet lag and the impact of shift work.”

Professor Janet Allen, BBSRC Director of Research, said: “The most effective way to develop drugs to treat a health problem is to understand the basic biology that underpins what is going on in our bodies. In this case, by understanding the basic biology of the enzyme controlling biological clocks the research team have been able to identify potential drug-based solutions to a range of issues that affect many people’s health and quality of life.”

Dr Michel Goedert, Head of the Neurobiology Division at Medical Research Council Laboratory of Molecular Biology, said: “We’re all familiar with jet-lag and that sense of being disoriented in time. What is probably less widely understood is how this effect can impact on those with certain mental illnesses. It is crucial to find out what can go wrong at the molecular and cellular level in the brain if we are to determine what treatments will work for patients. If further studies in humans confirm what this study has shown in mice, this could eventually lead to an entirely new approach to treating mental illnesses such as bipolar disorder.”

Dr Wager, Associate Research Fellow, Pfizer, added: “It is amazing what can be accomplished when first-rate academic groups and pharmaceutical discovery units team up. Leveraging each other’s talents we now have a deeper understanding of the role casein kinase plays within biological systems. Having the ability to entrain or re-entrain an arrhythmic system opens the door to new treatment option for circadian rhythm disorders. Targeting the inhibition of casein kinase with small molecules may lead to the discovery of novel drugs for the treatment of bipolar depression and other circadian rhythm disorders. The burden of these disorders is enormous and new treatment options are needed.”

University of Manchester

HOW MUCH SMOKING IS SAFE? THE ANSWER APPEARS TO BE NONE

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Smokers often wonder if smoking less might be safe for their health. The answer appears to be no. Occasional smoking, and even second-hand smoke, create biological changes that may increase the risks of lung disease and cancer, according to a new study.

Even at the lowest detectable levels of nicotine in urine, the genes most sensitive to tobacco smoke in cells lining the lungs' airways begin to function differently, reports a study authored by Cornell and NewYork-Presbyterian Hospital/Weill Cornell Medical Center (NYPH/WCMC) researchers and published Aug. 20 in the American Journal of Respiratory and Critical Care Medicine.

This is the first study to show that even minimal exposure to tobacco smoke triggers signs of detectable smoking stress in the genomewide gene expression profile of the lung. The technique developed for the study, which analyzed some 372 genes known to be sensitive to smoking, could potentially be used to detect the onset of a number of other nonsmoking related diseases.

To diagnose the start of lung disease, "you'd have to follow someone who smokes for many years, but what we have here is a signal that shows up at very low levels," said Larsson Omberg, a postdoctoral researcher in biological statistics and computational biology (BSCB) and one of the paper's lead authors.

As a technique applicable to nonsmoking related diseases, "it's a foundation that we can build on," added co-author Jason Mezey, an assistant professor in BSCB, whose lab directed the statistical analysis.

Dr. Ronald Crystal, senior author of the study and chief of pulmonary and critical care medicine at NYPH/WCMC, analyzed the urine (for nicotine and cotinine, the chemical into which the liver breaks down nicotine) and cells from the small airways of the lung of 121 individuals. Urine nicotine and cotinine levels were used to categorize volunteers as nonsmokers or occasional or heavy smokers.

Omberg, Mezey and colleagues drew upon various methods for analyzing genes quantified by microarray analysis. By combining methods, they created a new process that allowed them to see the effects of smoking on single genes as well as the entire genome at very low levels of exposure.

The researchers found that in the volunteers with "low exposure" to smoking, more than one-third of the 372 genes sensitive to smoking were triggered. (Some genes have lower expression and some genes have higher expression when exposed to tobacco smoke). This smoke stress was observed even when urine nicotine was below detectable levels, and when urine cotinine was just barely above detectable levels.

Also, the study found, heavy smokers triggered more of these genes and the expression of individual genes increased accordingly.

"The model allows us to predict, based on nicotine and cotinine levels, how much a gene may be expressing," said Omberg. The method also allowed them to analyze all genes across the genome as one function. "Using genomewide data, one can extract more subtle patterns of the effects of low levels of exposure," added Mezey.

Cornell University

RESEARCHERS DISCOVER HOW TO CONDUCT FIRST TEST OF UNTESTABLE STRING THEORY

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Researchers describe how to carry out the first experimental test of string theory in a paper published in Physical Review Letters.

String theory was originally developed to describe the fundamental particles and forces that make up our universe. The new research, led by a team from Imperial College London, describes the unexpected discovery that string theory also seems to predict the behaviour of entangled quantum particles. As this prediction can be tested in the laboratory, researchers can now test string theory.

Over the last 25 years, string theory has become physicists’ favourite contender for the ‘theory of everything’, reconciling what we know about the incredibly small from particle physics with our understanding of the very large from our studies of cosmology. Using the theory to predict how entangled quantum particles behave provides the first opportunity to test string theory by experiment.

“If experiments prove that our predictions about quantum entanglement are correct, this will demonstrate that string theory ‘works’ to predict the behaviour of entangled quantum systems,” said Professor Mike Duff FRS, lead author of the study from the Department of Theoretical Physics at Imperial College London.

“This will not be proof that string theory is the right ‘theory of everything’ that is being sought by cosmologists and particle physicists. However, it will be very important to theoreticians because it will demonstrate whether or not string theory works, even if its application is in an unexpected and unrelated area of physics,” added Professor Duff.

Professor Duff recalled sitting in a conference in Tasmania where a colleague was presenting the mathematical formulae that describe quantum entanglement: “I suddenly recognised his formulae as similar to some I had developed a few years earlier while using string theory to describe black holes. When I returned to the UK I checked my notebooks and confirmed that the maths from these very different areas was indeed identical.”

The discovery that string theory seems to make predictions about quantum entanglement is completely unexpected, but because quantum entanglement can be measured in the lab, it does mean that at last researchers can test predictions based on string theory. There is no obvious connection to explain why a theory that is being developed to describe the fundamental workings of our universe is useful for predicting the behaviour of entangled quantum systems. “This may be telling us something very deep about the world we live in, or it may be no more than a quirky coincidence”, concluded Professor Duff. “Either way, it’s useful."

(Photo: ICL)

Imperial College London

SILICON OXIDE CIRCUITS BREAK BARRIER

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Rice University scientists have created the first two-terminal memory chips that use only silicon, one of the most common substances on the planet, in a way that should be easily adaptable to nanoelectronic manufacturing techniques and promises to extend the limits of miniaturization subject to Moore's Law.

Last year, researchers in the lab of Rice Professor James Tour showed how electrical current could repeatedly break and reconnect 10-nanometer strips of graphite, a form of carbon, to create a robust, reliable memory "bit." At the time, they didn't fully understand why it worked so well.

Now, they do. A new collaboration by the Rice labs of professors Tour, Douglas Natelson and Lin Zhong proved the circuit doesn't need the carbon at all.

Jun Yao, a graduate student in Tour's lab and primary author of the paper that appears today in the online edition of Nano Letters, confirmed his breakthrough idea when he sandwiched a layer of silicon oxide, an insulator, between semiconducting sheets of polycrystalline silicon that served as the top and bottom electrodes.

Applying a charge to the electrodes created a conductive pathway by stripping oxygen atoms from the silicon oxide and forming a chain of nano-sized silicon crystals. Once formed, the chain can be repeatedly broken and reconnected by applying a pulse of varying voltage.

The nanocrystal wires are as small as 5 nanometers (billionths of a meter) wide, far smaller than circuitry in even the most advanced computers and electronic devices.

"The beauty of it is its simplicity," said Tour, Rice's T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science. That, he said, will be key to the technology's scalability. Silicon oxide switches or memory locations require only two terminals, not three (as in flash memory), because the physical process doesn't require the device to hold a charge.

It also means layers of silicon-oxide memory can be stacked in tiny but capacious three-dimensional arrays. "I've been told by industry that if you're not in the 3-D memory business in four years, you're not going to be in the memory business. This is perfectly suited for that," Tour said.

Silicon-oxide memories are compatible with conventional transistor manufacturing technology, said Tour, who recently attended a workshop by the National Science Foundation and IBM on breaking the barriers to Moore's Law, which states the number of devices on a circuit doubles every 18 to 24 months.

"Manufacturers feel they can get pathways down to 10 nanometers. Flash memory is going to hit a brick wall at about 20 nanometers. But how do we get beyond that? Well, our technique is perfectly suited for sub-10-nanometer circuits," he said.

Austin tech design company PrivaTran is already bench testing a silicon-oxide chip with 1,000 memory elements built in collaboration with the Tour lab. "We're real excited about where the data is going here," said PrivaTran CEO Glenn Mortland, who is using the technology in several projects supported by the Army Research Office, National Science Foundation, Air Force Office of Scientific Research, and the Navy Space and Naval Warfare Systems Command Small Business Innovation Research (SBIR) and Small Business Technology Transfer programs.

"Our original customer funding was geared toward more high-density memories," Mortland said. "That's where most of the paying customers see this going. I think, along the way, there will be side applications in various nonvolatile configurations."

Yao had a hard time convincing his colleagues that silicon oxide alone could make a circuit. "Other group members didn't believe him," said Tour, who added that nobody recognized silicon oxide's potential, even though it's "the most-studied material in human history."

"Most people, when they saw this effect, would say, 'Oh, we had silicon-oxide breakdown,' and they throw it out," he said. "It was just sitting there waiting to be exploited."

In other words, what used to be a bug turned out to be a feature.

Yao went to the mat for his idea. He first substituted a variety of materials for graphite and found none of them changed the circuit's performance. Then he dropped the carbon and metal entirely and sandwiched silicon oxide between silicon terminals. It worked.

"It was a really difficult time for me, because people didn't believe it," Yao said. Finally, as a proof of concept, he cut a carbon nanotube to localize the switching site, sliced out a very thin piece of silicon oxide by focused ion beam and identified a nanoscale silicon pathway under a transmission electron microscope.

"This is research," Yao said. "If you do something and everyone nods their heads, then it’s probably not that big. But if you do something and everyone shakes their heads, then you prove it, it could be big.

"It doesn't matter how many people don't believe it. What matters is whether it's true or not."

Silicon-oxide circuits carry all the benefits of the previously reported graphite device. They feature high on-off ratios, excellent endurance and fast switching (below 100 nanoseconds).

They will also be resistant to radiation, which should make them suitable for military and NASA applications. "It's clear there are lots of radiation-hardened uses for this technology," Mortland said.

Silicon oxide also works in reprogrammable gate arrays being built by NuPGA, a company formed last year through collaborative patents with Rice University. NuPGA's devices will assist in the design of computer circuitry based on vertical arrays of silicon oxide embedded in "vias," the holes in integrated circuits that connect layers of circuitry. Such rewritable gate arrays could drastically cut the cost of designing complex electronic devices.

Rice University

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