Thursday, November 12, 2009
Solar wind generated by the sun is probably driven by a process involving powerful magnetic fields, according to a new study led by UCL (University College London) researchers based on the latest observations from the Hinode satellite.
Scientists have long speculated on the source of solar winds. The Extreme Ultraviolet Imaging Spectrometer (EIS), on board the Japanese-UK-US Hinode satellite, is now generating unprecedented observations enabling scientists to provide a new perspective on the 50-year old question of how solar wind is driven. The collaborative study, published in this month's issue of Astrophysical Journal, suggests that a process called slipping reconnection may drive these winds.
Deb Baker, lead author from UCL Mullard Space Science Laboratory, says: "Solar wind is an outflow of million-degree gas and magnetic field that engulfs the Earth and other planets. It fills the entire solar system and links with the magnetic fields of the Earth and other planets. Changes in the Sun's million-mile-per-hour wind can induce disturbances within near-Earth space and our upper atmosphere and yet we still don't know what drives these outflows.
"However, our latest study suggests that it is the release of energy stored in solar magnetic fields which provides the additional driver for the solar wind. This magnetic energy release is most efficient in the brightest regions of activity on the Sun's surface, called active regions or sunspot groups, which are strong concentrations of magnetic field. We believe that this fundamental process happens everywhere on the Sun on virtually all scales."
Images taken in February 2007 from the EIS instrument showed that hot plasma outflows are due to a process called slipping reconnection. At the edges of active regions where this process can occur, a slow, continuous restructuring of the magnetic field leads to the release of energy and acceleration of particles in the Sun's hot outer atmosphere, known as the corona. Slipping reconnection is the first theory to explain how observed outflows from the Sun can be located over areas of a single magnetic sign, something previously considered improbable.
Computer models of the Sun's magnetic field were used to identify regions where slipping reconnection could occur. The locations proposed by the computer model were compared with measurements of the speed of the gas coming from the solar corona. The comparison showed the gas was moving outward at up to 100,000 mph, 1,000 times the wind speed in a hurricane, over the possible slipping reconnection regions.
University College London
"One of the big draws for an evolutionary biologist is that this species had a big influence on Darwin's ideas about how species evolve," said Graham Slater of the University of California, Los Angeles, noting that Darwin recognized differences between the East Falkland and West Falkland wolves as evidence that species are not fixed entities. But the wolves' circumstances were also just downright puzzling.
"It's really strange that the only native mammal on an island would be a large canid," Slater explained. "There are no other native terrestrial mammals—not even a mouse. It's even stranger when you consider that the Falklands are some 480 kilometers from the South American mainland. The question is, how did they get there?"
Possible explanations for the wolves' presence on the islands, which have never been connected to the South American mainland, range from dispersal by ice or logs to domestication and subsequent transport by Native Americans. Ultimately, the Falklands wolf died out because it was perceived as a threat to settlers and their sheep, although fur traders took out a lot of the population as well.
Biologists have also puzzled over the Falklands wolf's ancestry. It had been suggested that they were related to domestic dogs, North American coyotes, or South American foxes. Slater said the wolves were the size of a coyote, but much stockier, with fur the color of a red fox. They had short muzzles, just like gray wolves, and thick, wooly fur.
Slater's team now reports that the Falklands wolf's closest living relative is actually the maned wolf—an unusually long-legged, fox-like South American canid. The researchers also found that the four Falklands wolf samples that they examined shared a common ancestor at least 70,000 years ago, which suggests that they arrived on the islands before the end of the last ice age and before humans ever made it into the New World. That rules out the prevailing theory that Native Americans had anything to do with their presence on the islands.
"The biggest surprise was that the divergence of the Falklands wolf from its closest living relative, the maned wolf, occurred over 6 million years ago," Slater said. "Canids don't show up in the South American fossil record until 2.5 million years ago, which means these lineages must have evolved in North America. The problem is that there are no good fossils that can be assigned to the Falklands wolf lineage in North America."
Given that maned and Falklands wolves split so long ago, there should be fossils of their close relatives in South America, Slater said. And in fact, the researchers may have a candidate: a species from Patagonia called Dusicyon avus, which went extinct 6,000 to 8,000 years ago. Slater says that's a possibility that study coauthor Alan Cooper at the University of Adelaide in Australia is further investigating now.
That's because long-term space travel packs a one-two punch to astronauts: first it appears to weaken their immune systems; and second, it increases the virulence and growth of microbes. This combination of factors makes it vital for scientists to find tools that can help people cope with these microscopic hitchhikers before they lead to disease, especially since astronauts will not have the ability to return home to a hospital.
"When people think of space travel, often the vast distances are what come to mind first," said Jean-Pol Frippiat, one of the report's co-authors from Nancy-University in France, "but even after we figure out a way to cover these distances in a reasonable amount of time, we still need to figure out how astronauts are going to overcome disease and sickness."
Frippiat and colleagues based their conclusions on studies showing that immune systems of both people and animals in space flight conditions are significantly weaker than their grounded counterparts. They also reviewed studies that examined the effects of space flight conditions and altered gravity on virulence and growth of common pathogens such as Salmonella, E. coli and Staphylococcus. These studies show that these bacteria reproduce more rapidly in space flight conditions, leading to increased risk of contamination, colonization and serious infection.
"As clearly outlined by the researchers, we are unlikely to remain healthy when leaving earth for prolonged periods," said Luis Montaner, Editor-in-Chief of The Journal of Leukocyte Biology. "Unfortunately, because spacecraft technology is way ahead of our understanding of how to maintain human health, disease-free survival after reaching Mars or establishing a colony on the Moon may be problematic."
The remarkable eyes of a marine crustacean could inspire the next generation of DVD and CD players, according to a new study from the University of Bristol published today in Nature Photonics.
The mantis shrimps in the study are found on the Great Barrier Reef in Australia and have the most complex vision systems known to science. They can see in twelve colours (humans see in only three) and can distinguish between different forms of polarized light.
Special light-sensitive cells in mantis shrimp eyes act as quarter-wave plates – which can rotate the plane of the oscillations (the polarization) of a light wave as it travels through it. This capability makes it possible for mantis shrimps to convert linearly polarized light to circularly polarized light and vice versa. Manmade quarter-wave plates perform this essential function in CD and DVD players and in circular polarizing filters for cameras.
However, these artificial devices only tend to work well for one colour of light while the natural mechanism in the mantis shrimp’s eyes works almost perfectly across the whole visible spectrum – from near-ultra violet to infra-red.
Dr Nicholas Roberts, lead author of the Nature Photonics paper said: “Our work reveals for the first time the unique design and mechanism of the quarter-wave plate in the mantis shrimp’s eye. It really is exceptional – out-performing anything we humans have so far been able to create.”
Exactly why the mantis shrimp needs such exquisite sensitivity to circularly polarized light isn’t clear. However, polarization vision is used by animals for sexual signalling or secret communication that avoids the attention of other animals, especially predators. It could also assist in the finding and catching of prey by improving the clarity of images underwater. If this mechanism in the mantis shrimp provides an evolutionary advantage, it would be easily selected for as it only requires small changes to existing properties of the cell in the eye.
“What’s particularly exciting is how beautifully simple it is,” Dr Roberts continued. “This natural mechanism, comprised of cell membranes rolled into tubes, completely outperforms synthetic designs.
“It could help us make better optical devices in the future using liquid crystals that have been chemically engineered to mimic the properties of the cells in the mantis shrimp’s eye.”
This wouldn’t be the first time humans have looked to the natural world for new ideas, for example the lobster’s compound eye recently inspired the design of an X-ray detector for an astronomical telescope.
(Photo: Roy Caldwell, University of California, Berkeley)
University of Bristol
Scientists at the Technion-Israel Institute of Technology have developed a new, environmentally friendly silicon-air battery capable of supplying non-stop power for thousands of hours without needing to be replaced. The findings are published in the October 2009 issue of Electrochemistry Communications.
Created from oxygen and silicon (the second most plentiful element in the earth’s crust), such batteries would be lightweight, have an unlimited shelf life, and have a high tolerance for both humid and extremely dry conditions. Potential uses include medical applications (for example, powering diabetic pumps or hearing aids), sensors and microelectronics structured from silicon.
“Silicon-air batteries will be used like the ones already in use today,” says lead researcher Prof. Yair Ein-Eli of the Department of Materials Engineering. “But by using silicon – a safe, non-toxic, stable and more common material – we can create very lightweight batteries with infinite shelf life and high energy capacity.”
Silicon-air batteries would provide significant savings in cost and weight because they lack the built-in cathode of conventional batteries. The cathode in silicon-air (and metal-air) batteries is the oxygen that comes from the atmosphere through the membrane.
Prof. Ein-Eli estimates that in three to four years, silicon-air batteries can be made more powerful, as well as rechargeable. In 10 years, he says, it may be possible to build “electric car batteries made from silicon that will turn into sand that would be recycled into silicon and then into power again."
According to Prof. Ein-Eli, lightweight, long-lasting metal-air batteries are already used in hearing aids. There have also been attempts, he says, to upgrade such batteries for use in electric cars and portable electronic devices, and that interest in the matter was sparked recently when Toyota and Panasonic began joint efforts to adapt the zinc-air battery for future electronic cars.
American Society for Technion-Israel Institute of Technology
Deep brain stimulation may be a safe and effective treatment for Tourette syndrome, according to research published in the October 27, 2009, print issue of Neurology®, the medical journal of the American Academy of Neurology.
"Our findings hold promise for helping people with severe Tourette syndrome, who are in need of new treatment options to improve their quality of life," said study author Andrea Cavanna, MD, of the University of Birmingham, in the United Kingdom.
It is estimated that two million Americans are affected by Tourette syndrome, which is a neurological disorder characterized by uncontrolled movements and vocalizations, or tics, lasting more than a year. The first symptoms of Tourette syndrome are almost always noticed in childhood and some common tics include eye blinking, facial grimacing, shoulder shrugging and head or shoulder jerking. People who have Tourette syndrome often also have obsessive-compulsive disorder (OCD), depression, anxiety or attention deficit hyperactivity disorder (ADHD).
The study involved 15 people with severe Tourette syndrome and OCD who were an average age of 30 and continued to have severe symptoms after trying medications and psychobehavioral treatments. They also had high levels of depression and anxiety at the start of the study. The participants were followed and tested for two years after deep brain stimulation, which involves a surgically implanted brain pacemaker that sends electrical impulses to certain parts of the brain.
The study found that the participants experienced 52 percent fewer tics on average and a 26 to 33 percent improvement in the symptoms of OCD, depression and anxiety two years after deep brain stimulation began. Deep brain stimulation had no significant effect on thinking abilities in the study.
"Despite having only 15 patients in this study, it is the largest to date on the effectiveness of deep brain stimulation as a treatment for Tourette syndrome," said Cavanna. "The results showed that all 15 people who were assessed after two years' treatment experienced improvements in disabling tics and neurological problems, which is encouraging. Unfortunately three patients from the original group of 18 were no longer part of the study at follow up and this limits the ability to generalize our findings. More research needs to be done to confirm that deep brain stimulation is a safe and effective treatment for Tourette syndrome."
Deep brain stimulation is FDA approved for the treatment of essential tremor, Parkinson's disease and dystonia.
Tiny carbon nanotubes are being considered for use in everything from sports equipment to medical applications, but a great deal remains unknown about whether these materials cause respiratory or other health problems. Now a collaborative study from North Carolina State University, The Hamner Institutes for Health Sciences, and the National Institute of Environmental Health Sciences shows that inhaling these nanotubes can affect the outer lining of the lung, though the effects of long-term exposure remain unclear.
Using mice in an animal model study, the researchers set out to determine what happens when multi-walled carbon nanotubes are inhaled. Specifically, researchers wanted to determine whether the nanotubes would be able to reach the pleura, which is the tissue that lines the outside of the lungs and is affected by exposure to certain types of asbestos fibers which cause the cancer mesothelioma. The researchers used inhalation exposure and found that inhaled nanotubes do reach the pleura and cause health effects.
Short-term studies described in the paper do not allow conclusions about long-term responses such as cancer. However, the inhaled nanotubes “clearly reach the target tissue for mesothelioma and cause a unique pathologic reaction on the surface of the pleura, and caused fibrosis,” says Dr. James Bonner, associate professor of environmental and molecular toxicology at NC State and senior author of the study. The “unique reaction” began within one day of inhalation of the nanotubes, when clusters of immune cells (lymphocytes and monocytes) began collecting on the surface of the pleura. Localized fibrosis, or scarring on parts of the pleural surface that is also found with asbestos exposure, began two weeks after inhalation.
The study showed the immune response and fibrosis disappeared within three months of exposure. However, this study used only a single exposure to the nanotubes. “It remains unclear whether the pleura could recover from chronic, or repeated, exposures,” Bonner says. “More work needs to be done in that area and it is completely unknown at this point whether inhaled carbon nanotubes will prove to be carcinogenic in the lungs or in the pleural lining.”
The mice received a single inhalation exposure of six hours as part of the study, and the effects on the pleura were only evident at the highest dose used by the researchers – 30 milligrams per cubic meter (mg/m3). The researchers found no health effects in the mice exposed to the lower dose of one mg/m3.
North Carolina State University
Scientists at the University of California, Davis, have identified the dominant odor naturally produced in humans and birds that attracts the blood-feeding Culex mosquitoes, which transmit West Nile virus and other life-threatening diseases.
The groundbreaking research, published in the early online edition of the Proceedings of the National Academy of Sciences, explains why mosquitoes shifted hosts from birds to humans and paves the way for key developments in mosquito and disease control.
Entomology professor Walter Leal and postdoctoral researcher Zain Syed found that nonanal (sounds like NAWN-uh-nawl) is the powerful semiochemical that triggers the mosquitoes’ keen sense of smell, directing them toward a blood meal. A semiochemical is a chemical substance or mixture that carries a message.
“Nonanal is how they find us,” Leal said. “The antennae of the Culex quinquefasciatus are highly developed to detect even extremely low concentrations of nonanal.” Mosquitoes detect smells with the olfactory receptor neurons of their antennae.
Birds, the main hosts of mosquitoes, serve as the reservoir for the West Nile virus, Leal said. When infected mosquitoes take a blood meal, they transmit the virus to their hosts, which include birds, humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels and domestic rabbits. Since 1999, the U.S. Centers for Disease Control and Prevention have recorded 29,397 human cases and 1,147 fatalities in the United States alone.
The UC Davis researchers tested hundreds of naturally occurring compounds emitted by people and birds. They collected chemical odors from 16 adult human subjects, representing multiple races and ethnic groups.
“We then determined the specificity and sensitivity of the olfactory receptor neurons to the isolated compounds on the antennae of the mosquitoes,” Syed said.
Leal and Syed found that nonanal acts synergistically with carbon dioxide, a known mosquito attractant. “We baited mosquito traps with a combination of nonanal and carbon dioxide and we were drawing in as many as 2,000 a night in Yolo County, near Davis,” Syed said. “Nonanal, in combination with carbon dioxide, increased trap captures by more than 50 percent, compared to traps baited with carbon dioxide alone.”
(Photo: Kathy Garvey/UC Davis)
University of California, Davis
Researchers from Boston University and Tufts University near Boston recently demonstrated an infrared spectroscopy technique that can directly identify the "vibrational fingerprints" of extremely small quantities of proteins, the machinery involved in maintaining living organisms.
The new technique exploits nanotechnology to overcome several limitations of current, conventional techniques used to study biomolecules. "It allows identification of a protein by directly analyzing its vibrational fingerprint signatures," said team leader Hatice Altug, an assistant engineering professor at Boston University. "It may lead to a new toolkit for studying biomolecules."
The advance is reported in the Proceedings of the National Academy of Sciences. The National Science Foundation supports the research.
Previous bio-molecular study methods commonly use fluorescence spectroscopy, where biomolecules are labeled with very bright fluorescence tags to track how efficiently they interact with each other. Understanding interactions is important for medical drug research.
Fluorescence spectroscopy is quite sensitive at the single molecule level. However, the tags can be as big as the biomolecules themselves and interfere with the biomolecular interactions.
"There is currently a need to develop label-free bio-detection technologies," Altug said. "Infrared spectroscopy is a label-free method, because if you tune your ‘eye' to the infrared frequencies, you can directly see the bio-molecules without any labels."
Molecules consist of atoms bonded to each other with springs. Depending on the mass of atoms, how stiff these springs are, or how the atoms' springs are arranged, the molecules rotate and vibrate at specific frequencies similar to a guitar string that vibrates at specific frequencies depending on the string length. These resonant frequencies are molecule specific and they mostly occur in the infrared frequency range of the electromagnetic spectrum.
The sensitivity of infrared spectroscopy previously had been too low to detect these vibrations, particularly from small quantities of samples. The new method demonstrated by Altug's graduate student Ronen Adato and her post-doctoral fellow Ahmet Ali Yanik combines the strengths of nanotechnology and nanophotonics and overcomes the problems that prevented past use of infrared spectroscopy.
"We use arrays of tiny gold nanoparticles as efficient plasmonic nanoantennas to greatly amplify the ability to detect a molecule's inherent frequency," says Yanik. With their technique, the team obtained vibrational signatures from nearly 145 silk proteins deployed at the tip of each nanoantenna.
"Our technique gives researchers an ability to enhance inherent vibrational signatures more than 100,000 times," says Altug. "This allows us to sensitively study molecular structures and biological functions of extremely small quantities of molecules."
Altug anticipates that these new tools someday will help researchers design drugs, minimizing the complications of life-altering diseases such as cancer and Alzheimer's. "This advancement is fundamentally important for bio-chemistry," she says.
"Our plasmonic method is quite general and can also be adapted to enhance the infrared fingerprints of other molecules than proteins" said Altug. "It therefore provides a general purpose toolkit and may help amplify chemical sensing capabilities that are of particular concern to national defense."
(Photo: Hatice Altug, Electrical Engineering Department, Boston University)