Friday, September 24, 2010


0 comentarios

Though it was once believed that all asteroids are giant pieces of solid rock, later hypotheses have it that some are actually a collection of small gravel-sized rocks, held together by gravity. If one of these "rubble piles" spins fast enough, it's speculated that pieces could separate from it through centrifugal force and form a second collection — in effect, a second asteroid.

Now researchers at Tel Aviv University, in collaboration with an international group of scientists, have proved the existence of these theoretical "separated asteroid" pairs.

Ph.D. student David Polishook of Tel Aviv University's Department of Geophysics and Planetary Sciences and his supervisor Dr. Noah Brosch of the university's School of Physics and Astronomy say the research has not only verified a theory, but could have greater implications if an asteroid passes close to earth. Instead of a solid mountain colliding with earth's surface, says Dr. Brosch, the planet would be pelted with the innumerable pebbles and rocks that comprise it, like a shotgun blast instead of a single cannonball. This knowledge could guide the defensive tactics to be taken if an asteroid were on track to collide with the Earth.

A large part of the research for the study, recently published in the journal Nature, was done at Tel Aviv University's Wise Observatory, located deep in the Negev Desert — the first and only modern astronomical observatory in the Middle East.

According to Dr. Brosch, separated asteroids are composed of small pebbles glued together by gravitational attraction. Their paths are affected by the gravitational pull of major planets, but the radiation of the sun, he says, can also have an immense impact. Once the sun's light is absorbed by the asteroid, rotation speeds up. When it reaches a certain speed, a piece will break off to form a separate asteroid.

The phenomenon can be compared to a figure skater on the ice. "The faster they spin, the harder it is for them to keep their arms close to their bodies," explains Dr. Brosch.

As a result, asteroid pairs are formed, characterized by the trajectory of their rotation around the sun. Though they may be millions of miles apart, the two asteroids share the same orbit. Dr. Brosch says this demonstrates that they come from the same original asteroid source.

During the course of the study, Polishook and an international group of astronomers studied 35 asteroid pairs. Traditionally, measuring bodies in the solar system involves studying photographic images. But the small size and extreme distance of the asteroids forced researchers to measure these pairs in an innovative way.

Instead, researchers measured the light reflected from each member of the asteroid pairs. The results proved that in each asteroid pair, one body was formed from the other. The smaller asteroid, he explains, was always less than forty percent of the size of the bigger asteroid. These findings fit precisely into a theory developed at the University of Colorado at Boulder, which concluded that no more than forty percent of the original asteroid can split off.

With this study, says Dr. Brosch, researchers have been able to prove the connection between two separate spinning asteroids and demonstrate the existence of asteroids that exist in paired relationships.

(Photo: TAU)

Tel Aviv University


0 comentarios

The new Premier League season has begun and in Madrid the World Cup celebrations are barely over, yet according to research in WIREs Cognitive Science the world's best players may soon be facing a new challenge from football playing robots, which their creators claim will be able to play and beat a human team. The research reveals how building robots to play football is driving the development of artificial intelligence and robotic technology which can be used for roles including search and rescue and home help.

The author, Claude Sammut, from the ARC Centre of Excellence for Autonomous Systems in Sydney, reviewed the technology demonstrated at the RoboCup international robot soccer competition which this year took place in Singapore. Competitions have become a popular way for motivating innovations in robotics and provide teams of scientists with a way of comparing and testing new methods of programming artificial intelligence (AI).

"Football is a useful task for scientists developing robotic artificial intelligence because it requires the robot to perceive its environment, to use its sensors to build a model of that environment and then use that data to reason and take appropriate actions," said Sammut. "On a football pitch that environment is rapidly changing and unpredictable requiring a robot to swiftly perceive, reason, act and interact accordingly."

As with human players football also demands communication and cooperation between robotic players and crucially requires the ability to learn, as teams adjust their tactics to better take on their opponents.

Aside from football the competition also includes leagues for urban search and rescue and robotic home helpers which take place in areas simulating collapsed buildings and residential homes, revealing the multiple use of this technology.

While a football pitch layout is structured and known in advance, a search and rescue environment is highly unstructured and so the competition's rescue arena presents developers with a new set of challenges. On the football pitch the robots are able to localize and orientate themselves by recognising landmarks such as the goal post, yet in a rescue situation such localization is extremely difficult, meaning that the robot has to simultaneously map its environment while reacting and interacting to the surroundings.

In the home help competitions the robot is programmed to recognise appliances and landmarks which will be common in most homes, but in addition to orientating themselves they must react and interact with humans.

As the robotic technology continues to develop the rules of the competitions are altered and made harder to encourage innovation, it is the organisers' aim that this will drive the technology to a level where the football playing robots could challenge a human team.

"In 1968 John McCarthy and Donald Michie made a bet with chess champion David Levy that within 10 years a computer program could beat him," concluded Sammut. "It took a bit longer but eventually such programs came into being. It is in that same spirit of a great challenge that RoboCup aims, by the year 2050, to develop a team of fully autonomous robots that can win against the human world soccer champion team."

So while, for the moment, football players can focus on beating each other to lift silverware, tomorrow they may be facing a very different challenge.

(Photo: Aldebaran)



0 comentarios
In our dynamic 3D world, we can encounter a familiar face from any angle and still recognize that face with ease, even if the person has, for example, changed his hair style. This is because our brain has used the 2D snapshots perceived by our eyes (like a camera) to build and store a 3D mental representation of the face, which is resilient to such changes. This is an automatic process that most of us are not consciously aware of, and which appears to be a challenge for people with a particular type of face-blindness, as reported in the September 2010 issue of Elsevier's Cortex.

Prosopagnosia is a condition in which the ability to recognize faces is impaired; it can arise from damage to the brain or can also be present from early childhood, without any discernible brain damage. The latter is known as Developmental Prosopagnosia (DP) and in many cases it runs in families.

To investigate familial prosopagnosia, Drs. Yunjo Lee and Hugh Wilson at York University in Canada, together with colleagues from University College London and Harvard University, extensively assessed the face-processing abilities of three cases of DP within a single family. The participants, a father and two daughters, all have trouble recognizing faces, despite having otherwise normal visual sensory and intellectual abilities. All three are highly educated and socially well integrated; they know what a face looks like and can read facial expressions, attractiveness and gender from the face. One of the daughters is in fact a visual artist who frequently portrays faces with great detail in her sculptures, demonstrating her ability to process generic faces. However, the study showed that changes in lighting conditions and viewing angles affected their ability to recognize faces. For example, one of the daughters was able to detect subtle differences between two faces when looking at them from the same angle, but not when viewed from different angles.

The findings of this study suggest that some cases of familial DP result from an inability to form a robust mental representation of a face that can cope with changes in viewpoint or other conditions.



0 comentarios
Having a sibling, especially a twin, impacts your life. Your twin may be your best friend or your biggest rival, but throughout life you influence each other. However, a recent study published in Psychological Science, a journal of the Association for Psychological Science, shows that having an opposite-sex twin may impact you even before you are born: females with a male co-twin score higher on mental rotation task than females with a female co-twin.

Males, as young as three months of age, outperform females on mental rotation tasks, tests that require rotation of three dimensional objects in mental space. Testosterone has been suggested to account, at least partially, for sex differences in this task suggesting that females with exposure to higher levels of prenatal testosterone may perform better than females with lower levels of testosterone.

Eero Vuoksimaa from the University of Helsinki and co-authors assessed the possible prenatal masculinization of spatial ability in females with a male co-twin. “Earlier studies have tested the possible masculinization of females with a male co-twin, but the measures in those studies have not always been ideal,” says Vuoksimaa. “If prenatal masculinization does occur in female twins from opposite-sex pairs, it would be expected to be most evident in behaviors that are related to testosterone levels and show a large and robust male advantage, such as the mental rotation task.”

For the study, mental rotation task scores between twins from same-sex and opposite-sex pairs were compared. Not surprisingly males scored higher than females, but females with a male co-twin scored higher than did females with a female co-twin. In contrast, there was no difference in the mental rotation task performance of males from opposite-sex and same-sex pairs.

For females with a twin brother, determining if differences in performance are due to prenatal exposure to testosterone or due to their tendency to engage in more male-typical activities is still unclear. “While our results are consistent with the prenatal masculinization hypothesis,” says Vuoksimaa, “girls who grow up with a twin brother experience a different social world than girls growing up with a twin sister. We cannot exclude effects of post-birth socialization.”

However, the psychological scientists included a computer game task in their study, a possible indicator of practice effects. “Interestingly, computer game playing experience was not related to mental rotation test performance in our study,” says Vuoksimaa. This suggests that the results are not fully explained by postnatal environment, but the route for masculinization of mental rotation ability remains unknown. “More research is needed to disentangle the origins of the masculinization of mental rotation performance in females with a male co-twin.”

Association for Psychological Science


0 comentarios

Cancer is a difficult disease to treat because it's a personal disease. Each case is unique and based on a combination of environmental and genetic factors.

Conventional chemotherapy employs treatment with one or more drugs, assuming that these medicines are able to both "diagnose" and "treat" the affected cells. Many of the side effects experienced by chemotherapy patients are due to the fact that the drugs they are taking aren't selective enough. For instance, taking a drug that targets fast-growing tumor cells frequently results in hair loss, because cells in the hair follicle are among some of the fastest growing in the body. When it comes down to it, these drugs get the diagnosis wrong.

But what if we had cancer treatments that worked more like a computer program, which can perform actions based on conditional statements? Then, a treatment would kill a cell if--and only if--the cell had been diagnosed with a mutation. Only the defective cells would be destroyed, virtually eliminating unwanted side effects.

With support from the National Science Foundation (NSF), researchers at the California Institute of Technology have created conditional small RNA molecules to perform this task. Their strategy uses characteristics that are built into our DNA and RNA to separate the diagnosis and treatment steps.

"The molecules are able to detect a mutation within a cancer cell, and then change conformation to activate a therapeutic response in the cancer cell, while remaining inactive in cells that lack the cancer mutation," claims Niles Pierce, co-author of a recent study which appears in the September 6 issue of Proceedings of the National Academy of Sciences (PNAS).

This work is part of the Molecular Programming Project, funded by NSF's Directorate for Computer & Information Science & Engineering. One of the goals of the project is to increase understanding of how information can be stored and processed by molecules, and how we might create practical applications that utilize that information.

At the heart of this approach is ribonucleic acid or RNA, and all of the normal tasks it performs each and every day to keep our cells alive and healthy. RNA is the relatively short-lived counterpart of DNA, the coding system that stores full copies of our entire genome within almost every cell of our body. If we think of DNA as information stored on the hard drive of a computer, then RNA is like information stored on a more volatile kind of memory like RAM--which is erased when you switch off your computer.

RNAs perform all kinds of functions in a cell, acting as messengers and switches to communicate and monitor which genes are expressed in a cell at any given time. A particular class of RNAs, called small RNAs, is less than 30 base pairs in length (an average gene is thousands of base pairs long). These small bits of RNA are involved in many of the processes that maintain life. The treatment developed by Pierce and his colleagues relies on two separate small RNAs that structurally mimic those that occur naturally within our own cells. Because these molecules resemble small RNAs that are normally present, the researchers hope there will be few, if any side effects.

"By de-coupling diagnosis and treatment, we can create molecules that are both highly selective and highly effective in killing cancer cells," said Pierce. "Conceptually, small conditional RNAs have the potential to transform cancer treatment because they change what we can expect from a molecule. Many years of work remain to establish whether this conceptual promise can be realized in human patients."

Here's how it works: Treatment involves two different small RNAS. The first small RNA will open up if--and only if--it finds the cancer mutation. A positive "diagnosis" exposes a signal that was previously hidden within the small RNA. Once this small RNA is open, a second small RNA binds to it, setting off a chain reaction in which these RNA molecules continue to combine to form a longer chain. The length of the chain is an important part of the "treatment." Longer chains trick the cell into thinking it has been invaded by a virus, tripping a self-destruct response.

In the PNAS study, researchers demonstrated that this approach effectively eliminates lab-grown human brain, prostate and bone cancer cells in a mutation-specific manner. Future experiments will determine whether the treatment is effective on a larger scale.

(Photo: Suvir Venkataraman, William M. Clemons, Jr. and Niles A. Pierce (Caltech))

National Science Foundation


0 comentarios

Phosphorus, a mineral element found in rocks and bone, is a critical ingredient in fertilizers, pesticides, detergents and other industrial and household chemicals. Once phosphorus is mined from rocks, getting it into these products is hazardous and expensive, and chemists have been trying to streamline the process for decades.

MIT chemistry professor Christopher Cummins and one of his graduate students, Daniel Tofan, have developed a new way to attach phosphorus to organic compounds by first splitting the phosphorus with ultraviolet light. Their method, described in the Aug. 26 online edition of Angewandte Chemie, eliminates the need for chlorine, which is usually required for such reactions and poses health risks to workers handling the chemicals.

Guy Bertrand, chemistry professor at the University of California at Riverside, says the beauty of the discovery is its simplicity. “It is amazing to realize that nobody thought earlier about such a simple approach to incorporate phosphorus into organic molecules,” he says. “Such a synthetic approach to organophosphorus compounds is indeed urgent, since the old (chlorine)-based phosphorus chemistry has a lot of undesirable consequences on our environment.”

While the new reaction cannot produce the quantities needed for large-scale production of phosphorus compounds, it opens the door to a new field of research that could lead to such industrial applications, says Bertrand, who was not involved in the research.

Most natural phosphorus deposits come from fossilized animal skeletons, which are especially abundant in dried-up seabeds. Those phosphorus deposits exist as phosphate rock, which usually includes impurities such as calcium and other metals that must be removed.

Purifying the rock produces white phosphorus, a molecule containing four phosphorus atoms. White phosphorous is tetrahedral, meaning it resembles a four-cornered pyramid in which each corner atom is bound to the other three. Known as P4, white phosphorus is the most stable form of molecular phosphorus. (There are also several polymeric forms, the most common of which are black and red phosphorus, which consist of long chains of broken phosphorus tetrahedrons.)

For most industrial uses, phosphorus has to be attached one atom at a time, so single atoms must be detached from the P4 molecule. This is usually done in two steps. First, three of the atoms in P4 are replaced with chlorine, resulting in PCl3 — a phosphorus atom bound to three chlorine atoms.

Those chlorine atoms are then displaced by organic (carbon-containing) molecules, creating a wide variety of organophosphorus compounds such as those found in pesticides. However, this procedure is both wasteful and dangerous — chlorine gas was used as a chemical weapon during World War I — so chemists have been trying to find new ways to bind phosphorus to organic compounds without using chlorine.

Cummins has long been fascinated with phosphorus, in part because of its unusual tetrahedral P4 formation. Phosphorus is in the same column of the periodic table as nitrogen, whose most stable form is N2, so chemists expected that phosphorus might form a stable P2 structure. However, that is not the case.

For the past few years, Cummins’ research group has been looking for ways to break P4 into P2 in hopes of attaching the smaller phosphorus molecule to organic compounds. In the new study, Cummins drew inspiration from a long overlooked paper, published in 1937, which demonstrated that P4 could be broken into two molecules of P2 with ultraviolet light. In that older study, P2 then polymerized into red phosphorus.

Cummins decided to see what would happen if he broke apart P4 with UV light in the presence of organic molecules that have an unsaturated carbon-carbon bond (meaning those carbon atoms are able to grab onto other atoms and form new bonds). After 12 hours of UV exposure, he found that a compound called a tetra-organo diphosphane had formed, which includes two atoms of phosphorus attached to two molecules of the organic compound.

This suggests, but does not conclusively prove, that P2 forms and then immediately bonds to the organic molecule. In future studies, Cummins hopes to directly observe the P2 molecule, if it is indeed present.

Cummins also plans to investigate what other organophosphorus compounds can be synthesized with ultraviolet light, including metallic compounds. He has already created a nickel-containing organophosphorus molecule, which could have applications in electronics.

(Photo: MIT)



0 comentarios

Diet and exercise have long been the top two elements of effective weight loss. Now add a third: reading the labels on packaged foods.

Washington State University Economist Bidisha Mandal has found that middle-aged Americans who want to lose weight and who take up the label-reading habit are more likely to lose weight than those who don't. In some cases, label reading is even more effective than exercise.

"I'm finding that reading labels is useful," said Mandal, an assistant professor in the WSU School of Economic Sciences. "People who are trying to lose weight want to know what they're buying and preparing and many do better if they use labels to find what they need to know."

Writing in the latest Journal of Consumer Affairs, Mandal analyzes the responses of more than 3,700 people who regularly took a national survey asking about their label-reading habits while attempting to lose or control their weight. Among her findings:

* If you want to lose weight, you have a better chance of success if you read a food label when you first buy a product.
* People are more successful at losing weight when they add label reading to their exercise program.
* Label readers who do not exercise have a slightly greater chance of losing weight than those who exercise but do not read labels.
* Women are more likely to read food labels when they buy a product for the first time, possibly because they are responsible for buying food and cooking. They are also more successful than men in losing weight.
* In a case of good news and bad news, Mandal found that overweight and obese label readers are more likely to lose weight. But only a little more than one-third lost weight, while nearly half gained weight. This confirms what many middle-aged people know—losing weight is hard and often unsuccessful. But Mandal found overweight and obese people at least have a better chance if they read the label.

The analysis underscores the value of the U.S. Nutrition Labeling and Education Act, which has required standardized nutrition facts on packaged foods since 1994, Mandal said. She adds that the findings build the case for posting nutritional information on vending machines and in many restaurants, as planned under the new federal health care reform bill.

(Photo: WSU)

Washington State University


0 comentarios
New research findings from the Université de Montréal reveals that children as young as four are able to understand and use irony. This study, published recently in the British Journal of Developmental Psychology, may impact the way parents communicate with their family.

"Previous studies concluded that irony wasn't understood before the age of eight or ten," says Stephanie Alexander, a postdoctoral student at the Université de Montréal's Department of Social and Preventive Medicine and senior author of the study. "However, these studies were mostly done in a laboratory setting and mostly focused on sarcasm. We examined children at home and took into consideration four types of non-literal language: hyperbole, euphemism, sarcasm and rhetorical questions."

The study, which was done in collaboration with Holly Recchia from Concordia University, revealed that the children understood at least one ironic remark made by one of the parents. Although children can fully comprehend this language by age six, certain forms of irony such as hyperbole were understood at age four. In 22 of the 39 families studied, it was sarcasm that was best understood overall by the children.

Overall, hyperbole and sarcasm were most often used during positive interactions with children, while euphemisms and rhetorical questions were mostly used in situations of conflict. Also, mothers and fathers did not use irony in the same way. Mothers were more inclined to use rhetorical questions and fathers preferred sarcasm.

"Children's understanding of complex communication is more sophisticated than we believed in the past," says Alexander. "If parents are conscious that by age four a child can take a remark literally, especially in situations of conflict, using appropriate language can help defuse a potentially explosive situation."

Université de Montréal


0 comentarios

Evidence that a star has recently engulfed a companion star or a giant planet has been found using NASA's Chandra X-ray Observatory. The likely existence of such a "cannibal" star provides new insight into how stars and the planets around them may interact as they age.

The star in question, known as BP Piscium (BP Psc), appears to be a more evolved version of our Sun, but with a dusty and gaseous disk surrounding it. A pair of jets several light years long blasting out of the system in opposite directions has also been seen in optical data. While the disk and jets are characteristics of a very young star, several clues -- including the new results from Chandra -- suggest that BP Psc is not what it originally appeared to be.

Instead, astronomers have suggested that BP Psc is an old star in its so-called red giant phase. And, rather than being hallmarks of its youth, the disk and jets are, in fact, remnants of a recent and catastrophic interaction whereby a nearby star or giant planet was consumed by BP Psc.

When stars like the Sun begin to run of nuclear fuel, they expand and shed their outer layers. Our Sun, for example, is expected to swell so that it nearly reaches or possibly engulfs Earth, as it becomes a red giant star.

"It appears that BP Psc represents a star-eat-star Universe, or maybe a star-eat-planet one," said Joel Kastner of the Rochester Institute of Technology, who led the Chandra study. "Either way, it just shows it's not always friendly out there."

Several pieces of information have led astronomers to rethink how old BP Psc might be. First, BP Psc is not located near any star-forming cloud, and there are no other known young stars in its immediate vicinity. Secondly, in common with most elderly stars, its atmosphere contains only a small amount of lithium. Thirdly, its surface gravity appears to be too weak for a young star and instead matches up with one of an old red giant.

Chandra adds to this story. Young, low-mass stars are brighter than most other stars in X-rays, and so X-ray observations can be used as a sign of how old a star may be. Chandra does detect X-rays from BP Psc, but at a rate that is too low to be from a young star. Instead, the X-ray emission rate measured for BP Psc is consistent with that of rapidly rotating giant stars.

The spectrum of the X-ray emission -- that is how the amount of X-rays changes with wavelength -- is consistent with flares occurring on the surface of the star, or with interactions between the star and the disk surrounding it. The magnetic activity of the star itself might be generated by a dynamo caused by its rapid rotation. This rapid rotation can be caused by the engulfment process.

"It seems that BP Psc has been energized by its meal," said co-author Rodolfo (Rudy) Montez Jr., also from the Rochester Institute of Technology.

The star's surface is obscured throughout the visible and near-infrared bands, so the Chandra observation represents the first detection at any wavelength of BP Psc itself.

"BP Psc shows us that stars like our Sun may live quietly for billions of years," said co-author David Rodriguez from UCLA, "but when they go, they just might take a star or planet or two with them."

Although any close-in planets were presumably devastated when BP Psc turned into a giant star, a second round of planet formation might be occurring in the surrounding disk, hundreds of millions of years after the first round. A new paper using observations with the Spitzer Space Telescope has reported possible evidence for a giant planet in the disk surrounding BP Psc. This might be a newly formed planet or one that was part of the original planetary system.

"Exactly how stars might engulf other stars or planets is a hot topic in astrophysics today," said Kastner. "We have many important details that we still need to work out, so objects like BP Psc are really exciting to find."

(Photo: X-ray (NASA/CXC/RIT/J.Kastner et al), Optical (UCO/Lick/STScI/M.Perrin et al); Illustration: NASA/CXC/M.Weiss)

Chandra X-ray Center




Selected Science News. Copyright 2008 All Rights Reserved Revolution Two Church theme by Brian Gardner Converted into Blogger Template by Bloganol dot com