Colorful Mix of Asteroids Discovered, May Aid Future Space Travel

New research from NASA's Spitzer Space Telescope reveals that asteroids somewhat near Earth, termed near-Earth objects, are a mixed bunch, with a surprisingly wide array of compositions.

This image, taken by NASA's Near Earth Asteroid 
Rendezvous mission in 2000, shows a close-up view 
of Eros, an asteroid with an orbit that takes it somew
hat close to Earth. NASA's Spitzer Space Telescope 
observed Eros and dozens of other near-Earth 
asteroids as part of an ongoing survey to study 
their sizes and compositions using 
infrared light. (Credit: NASA/JHUAPL)

Like the chocolates and fruity candies inside a piñata, these asteroids come in assorted colors and compositions. Some are dark and dull; others are shiny and bright. The Spitzer observations of 100 known near-Earth asteroids demonstrate that their diversity is greater than previously thought.

The findings are helping astronomers better understand near-Earth objects as a whole -- a population whose physical properties are not well known.

"These rocks are teaching us about the places they come from," said David Trilling, assistant professor of physics and astronomy at Northern Arizona University, and lead author of a new paper on the research appearing in the September issue of Astronomical Journal. "It's like studying pebbles in a streambed to learn about the mountains they tumbled down."

One of the mission's programs is to survey about 700 near-Earth objects, cataloguing their individual traits. By observing in infrared, Spitzer is helping to gather more accurate estimates of asteroids' compositions and sizes than what is possible with visible-light alone.

Trilling and his team have analyzed preliminary data on 100 near-Earth asteroids so far. They plan to observe 600 more over the next year. There are roughly 7,000 known near-Earth objects out of a population expected to number in the tens to hundreds of thousands.

"Very little is known about the physical characteristics of the near-Earth population," Trilling said. "Our data will tell us more about the population, and how it changes from one object to the next. This information could be used to help plan possible future space missions to study a near-Earth object."

The data show that some of the smaller objects have surprisingly high albedos (a measurement of how much sunlight an object reflects). Since asteroid surfaces become darker with time due to exposure to solar radiation, the presence of lighter, shinier surfaces for some asteroids may indicate that they are relatively young. This is evidence for the continuing evolution of the near-Earth object population.

In addition, the asteroids observed so far have a greater degree of diversity than expected, indicating that they might have different origins. Some might come from the main belt between Mars and Jupiter, and others could come from farther out in the solar system. This diversity also suggests that the materials that went into creating the asteroids -- the same materials that make up our planets -- were probably mixed together like a big solar-system soup very early on in its history.

The research complements that of NASA's Wide-field Infrared Survey Explorer, or WISE, an all-sky infrared survey mission up in space now. WISE has already observed more than 430 near-Earth objects. Of these, more than 110 are newly discovered.

In the future, both Spitzer and WISE will reveal even more about the "flavors" of near-Earth objects. This could reveal new clues about how the cosmic objects might have dotted our young planet with water and organics -- ingredients needed to jump-start life.

Other authors include Cristina Thomas, a post-doctoral scholar of physics and astronomy at NAU, and researchers from around the world.

How Brain Is Wired for Attention

University of Utah (U of U) medical researchers have uncovered a wiring diagram that shows how the brain pays attention to visual, cognitive, sensory, and motor cues. The research provides a critical foundation for the study of abnormalities in attention that can be seen in many brain disorders such as autism, schizophrenia, and attention deficit disorder.

University of Utah (U of U) medical researchers have 
uncovered a wiring diagram that shows how the brain 
pays attention to visual, cognitive, sensory, and motor
cues. The research provides a critical foundation for 
the study of abnormalities in attention that can be seen 
in many brain disorders such as autism, 
schizophrenia, and attention deficit disorder. 
(Credit: iStockphoto/Sebastian Kaulitzki)

The study appears Nov. 1, 2010, online in the Proceedings of the National Academy of Sciences (PNAS).
"This study is the first of its kind to show how the brain switches attention from one feature to the next," says lead researcher Jeffery S. Anderson, M.D., Ph.D., U of U assistant professor of radiology. Anderson and his team used MRI to study a part of the brain known as the intraparietal sulcus. "The brain is organized into territories, sort of like a map of Europe. There are visual regions, regions that process sound and areas that process sensory and motor information. In between all these areas is the intraparietal sulcus, which is known to be a key area for processing attention," Anderson says. "We discovered that the intraparietal sulcus contains a miniature map of all of these territories. We also found an organized pattern for how control regions of the brain connect to this map in the intraparietal sulcus. These connections help our brain switch its attention from one thing to another."
In addition, scientists discovered that this miniature map of all the things one can pay attention to is reproduced in at least 13 other places in the brain. They found connections between these duplicate maps and the intraparietal sulcus. Each copy appears to do something different with the information. For instance, one map processes eye movements while another processes analytical information. This map of the world that allows us to pay attention may be a fundamental building block for how information is represented in the brain.
"The research uncovers how we can shift our attention to different things with precision," says Anderson. "It's a big step in understanding how we organize information. Furthermore, it has important implications for disease. There are several diseases or disorders where attention processing is off, such as autism, attention deficit disorder, and schizophrenia, among others. This research gives us the information to test theories and see what is abnormal. When we know what is wrong, we can talk about strategies for treatment or intervention."
Deborah Yurgelun-Todd, Ph.D., professor of psychiatry in the U of U Schoold of Medicine and an investigator with the U of U Brain Institute and the Utah Science Technology and Research Initiative (USTAR), was the principal investigator and senior author of the study. The research was funded by a National Institutes of Health grant from the National Institute on Drug Abuse.

Blood group may affect woman's fertility

Researchers from Yale University and the Albert Einstein College of Medicine in New York studied over 560 women with an average age of 35, all of whom were undergoing fertility treatment in two different clinics. Blood samples were taken from each of the women and analyzed for blood group and the levels of the follicle stimulating hormone (FSH).

FSH is a known marker of fertility, with lower levels (less than 10) suggesting a woman will have better chances of conceiving than one with higher levels. High levels of FSH indicate a diminished ovarian reserve, which means egg quality is poor and the quantity of eggs remaining may be low. The ovarian reserve declines naturally from the middle to late 30s.

The results of the study showed that among women seeking fertility treatment, those with blood group O had double the likelihood of having an FSH level over 10 than women with any other blood type. This result remained true when the results were adjusted to take into account the woman’s age and other factors such as body mass index (BMI), and was true for women from both clinics. Women with blood group A were significantly less likely to have FSH levels over 10.

Leader of the research team, Dr. Edward Nejat from the Albert Einstein College of Medicine’s department of obstetrics and gynecology, said women with blood type A and the much less common AB — both of which have the A blood group gene — were protected in some way from a diminished ovarian reserve. He said the study included "a good mix of patients ethnically and racially."

Dr. Nejat said baseline FSH levels "gives us an idea of the quality and quantity of a woman's eggs," but they were only one marker of fertility. He said more studies were needed to see if blood group affects other hormone levels, and to see if the same effects were seen in the general population and not just women who were already seeking treatment for fertility problems. Nejat added that the woman’s age remained the most important factor in fertility.

The results of the research will be presented in Denver at the annual conference of the American Society for Reproductive Medicine (ASRM). President of the ASRM, Dr. William Gibbons, said studies such as this were needed to help us to better understand the "complexities of the human reproductive system."

Scientists develop method for detecting microRNA from living cells

Probe-microRNA duplexes translocate through thin nanopores. (Artwork: Robert Johnson)

MicroRNAs, or miRNAs, were initially identified in roundworms in 1993. Since then, biologists have discovered that microRNAs control gene expression, and therefore there is immense interest in these molecules as potential therapeutics for silencing cancer and disease-related genes.

The problem with microRNA detection is that the number of copies of microRNA in cells is so small that detection is quite challenging. The team developed a method to fabricate nanopores in the thinnest silicon nitride membranes reported to date, about 6 nm thick.

First, the team showed that these nanopores increase the signal resolution from reading DNA molecules as they pass through the pores. After demonstrating the enhanced sensitivity, the Penn team needed a method to isolate a specific microRNA from cells.

They teamed with a group headed by Larry McReynolds of New England Biolabs.

“Larry and co-workers had a neat trick: they use a viral protein called p19 to tightly bind duplex RNA molecules of the exact dimensions of microRNAs,” Meni Wanunu, a research associate at Penn, said. “So we devised a plan that uses this protein to isolate very small amounts of specific microRNAs that we can then quantify using our pores.”

The team focused on detecting miR122a, a liver-specific microRNA in mammals.

They first demonstrated that their nanopores are reliable enough to quantify the concentrations of these tiny molecules that are only 22 bases long, or 6 nm in length. After having made ultrathin membranes by locally etching silicon nitride, the group used electron beams to drill the nanopores in the thinned portion of the silicon nitride membranes.

“Using 3 nm diameter pores, these duplex RNA molecules just squeeze through the pores and in doing so, each molecule produces a nice electronic signal,” Wanunu said. “We were delighted, things worked out really nice. These are the smallest synthetic pores in all dimensions, and it is surprising how stable and robust they are. We now use them routinely for various investigations; they are our new state-of-the-art.”

The article, featured on the cover of the November 2010 issue of Nature Nanotechnology, shows a duplex microRNA molecule passing through a very thin nanopore made at Penn.

“It is wonderful to see the expected improvements in signal to noise ratios using these thin nanopores,” Marija Drndić, an associate professor of physics and the group leader on the project, said. “In spite of their being thin, they are quite robust, and they seem to function every time because they do not tend to trap hydrophobic contaminants and they allow unimpeded flow through them. All this makes them ideal candidates for various biophysical applications.”

The Penn team is now working on specific methods for detecting other smallmolecules, as well as integrating these nanopores with fluidic systems to improve sensitivity.

The research was conducted by Wanunu, Drndić Tali Dadosh and Vishva Ray of Penn, and Jingmin Jin and McReynolds of New England Biolabs.

Brain Regions Can Switch Functions in Young

A new paper from MIT neuroscientists, in collaboration with Alvaro Pascual-Leone at Beth Israel Deaconess Medical Center, offers evidence that it is easier to rewire the brain early in life. The researchers found that a small part of the brain's visual cortex that processes motion became reorganized only in the brains of subjects who had been born blind, not those who became blind later in life.

Scientists offer evidence that it is easier to rewire the 
brain early in life. Researchers found that a small part 
of the brain's visual cortex that processes motion became
reorganized only in the brains of subjects who had been 
born blind, not those who became blind later in life.
(Credit: iStockphoto/Vasiliy Yakobchuk)

The new findings, described in the Oct. 14 issue of the journal Current Biology, shed light on how the brain wires itself during the first few years of life, and could help scientists understand how to optimize the brain's ability to be rewired later in life. That could become increasingly important as medical advances make it possible for congenitally blind people to have their sight restored, said MIT postdoctoral associate Marina Bedny, lead author of the paper.

In the 1950s and '60s, scientists began to think that certain brain functions develop normally only if an individual is exposed to relevant information, such as language or visual information, within a specific time period early in life. After that, they theorized, the brain loses the ability to change in response to new input.

Animal studies supported this theory. For example, cats blindfolded during the first months of life are unable to see normally after the blindfolds are removed. Similar periods of blindfolding in adulthood have no effect on vision.

However, there have been indications in recent years that there is more wiggle room than previously thought, said Bedny, who works in the laboratory of MIT assistant professor Rebecca Saxe, also an author of the Current Biology paper. Many neuroscientists now support the idea of a period early in life after which it is difficult, but not impossible, to rewire the brain.

Bedny, Saxe and their colleagues wanted to determine if a part of the brain known as the middle temporal complex (MT/MST) can be rewired at any time or only early in life. They chose to study MT/MST in part because it is one of the most studied visual areas. In sighted people, the MT region is specialized for motion vision.

In the few rare cases where patients have lost MT function in both hemispheres of the brain, they were unable to sense motion in a visual scene. For example, if someone poured water into a glass, they would see only a standing, frozen stream of water.

Previous studies have shown that in blind people, MT is taken over by sound processing, but those studies didn't distinguish between people who became blind early and late in life.

In the new MIT study, the researchers studied three groups of subjects -- sighted, congenitally blind, and those who became blind later in life (age nine or older). Using functional magnetic resonance imaging (fMRI), they tested whether MT in these subjects responded to moving sounds -- for example, approaching footsteps.

The results were clear, said Bedny. MT reacted to moving sounds in congenitally blind people, but not in sighted people or people who became blind at a later age.

This suggests that in late-blind individuals, the visual input they received in early years allowed the MT complex to develop its typical visual function, and it couldn't be remade to process sound after the person lost sight. Congenitally blind people never received any visual input, so the region was taken over by auditory input after birth.

"We need to think of early life as a window of opportunity to shape how the brain works," said Bedny. "That's not to say that later experience can't alter things, but it's easier to get organized early on."

Bedny believes that by better understanding how the brain is wired early in life, scientists may be able to learn how to rewire it later in life. There are now very few cases of sight restoration, but if it becomes more common, scientists will need to figure out how to retrain the patient's brain so it can process the new visual input.

"The unresolved question is whether the brain can relearn, and how that learning differs in an adult brain versus a child's brain," said Bedny.

Bedny hopes to study the behavioral consequences of the MT switch in future studies. Those would include whether blind people have an advantage over sighted people in auditory motion processing, and if they have a disadvantage if sight is restored.

Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.

Research Shows: Risk of Marijuana’s ‘gateway effect’ Overblown

     New research from the University of New Hampshire shows that the “gateway effect” of marijuana – that teenagers who use marijuana are more likely to move on to harder illicit drugs as young adults – is overblown.

Whether teenagers who smoked pot will use other illicit drugs as young adults has more to do with life factors such as employment status and stress, according to the new research. In fact, the strongest predictor of whether someone will use other illicit drugs is their race/ethnicity, not whether they ever used marijuana.

Conducted by UNH associate professors of sociology Karen Van Gundy and Cesar Rebellon, the research appears in the September 2010, issue of the Journal of Health and Social Behavior in the article, “A Life-course Perspective on the ‘Gateway Hypothesis.’ “

“In light of these findings, we urge U.S. drug control policymakers to consider stress and life-course approaches in their pursuit of solutions to the ‘drug problem,’ ” Van Gundy and Rebellon say.

The researchers used survey data from 1,286 young adults who attended Miami-Dade public schools in the 1990s. Within the final sample, 26 percent of the respondents are African American, 44 percent are Hispanic, and 30 percent are non-Hispanic white.

The researchers found that young adults who did not graduate from high school or attend college were more likely to have used marijuana as teenagers and other illicit substances in young adulthood. In addition, those who used marijuana as teenagers and were unemployed following high school were more likely to use other illicit drugs.

However, the association between teenage marijuana use and other illicit drug abuse by young adults fades once stresses, such as unemployment, diminish.

“Employment in young adulthood can protect people by ‘closing’ the marijuana gateway, so over-criminalizing youth marijuana use might create more serious problems if it interferes with later employment opportunities,” Van Gundy says.

In addition, once young adults reach age 21, the gateway effect subsides entirely.

“While marijuana use may serve as a gateway to other illicit drug use in adolescence, our results indicate that the effect may be short-lived, subsiding by age 21. Interestingly, age emerges as a protective status above and beyond the other life statuses and conditions considered here. We find that respondents ‘age out’ of marijuana’s gateway effect regardless of early teen stress exposure or education, work, or family statuses,” the researchers say.

The researchers found that the strongest predictor of other illicit drug use appears to be race-ethnicity, not prior use of marijuana. Non-Hispanic whites show the greatest odds of other illicit substance use, followed by Hispanics, and then by African Americans.

New Artificial “Skin” Can Sense Pressure

    New artificial “skin” fashioned out of flexible semiconductor materials can sense touch, making it possible to create robots with a grip delicate enough to hold an egg, yet strong enough to grasp the frying pan, U.S. researchers said on Sunday.

Scientists have long struggled with a way to make robotic devices capable of adjusting the amount of force needed to hold and use different objects. The pressure-sensitive materials are designed to overcome that challenge.

“Humans generally know how to hold a fragile egg without breaking it,” said Ali Javey, an electrical engineer at theUniversity of California Berkeley, who led one of two teams reporting on artificial skin discoveries in the journal Nature Materials.

“If we ever wanted a robot that could unload the dishes, for instance, we’d want to make sure it doesn’t break the wine glasses in the process. But we’d also want the robot to be able to grip a stock pot without dropping it,” Javey said in a statement.

Javey’s team found a way to make ultra tiny “nanowires” from an alloy of silicon and germanium. Wires of this material were formed on the outside of a cylindrical drum, which was then rolled onto a sticky film, depositing the wires in a uniform pattern.

Sheets of this semiconductor film were then coated with a layer of pressure-sensitive rubber. Tests of the material showed it was able to detect a range of force, from typing on a keyboard to holding an object.

A second team led by Zhenan Bao, a chemical engineer at Stanford University in California, used a different approach, making a material so sensitive it can detect the weight of a butterfly resting on it.

Bao’s sensors were made by sandwiching a precisely molded, highly elastic rubber layer between two electrodes in a regular grid of tiny pyramids.

“We molded it into some kind of microstructure to incorporate some air pockets,” Bao said in a telephone interview. “If we introduce air pockets, then these rubber pieces can bounce back.”

When this material is stretched, the artificial skin measures the change in electrical activity. “The change in the thickness of the material is converted into an electrical signal,” she said.

Eventually, the teams hope artificial skin could be used to restore the sense of touch in people with prosthetic limbs, but scientists will first need a better understanding of how to integrate the system’s sensors with the human nervous system.

Javey’s artificial skin is the latest application of new ways of processing brittle, inorganic semiconductor materials such as silicon, into flexible electronics and sensors.

Earlier this year, a team at the California Institute of Technology in Pasadena devised a way to make flexible solar cells with silicon wires that are thin enough to be used in clothing.