Marks On Martian Dunes May Be Tracks of Dry-Ice Sleds

Several types of downhill flow features have been observed on Mars. This image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter is an example of a type called "linear gullies." (Credit: NASA/JPL-Caltech/Univ. of Arizona)

June 11, 2013 — NASA research indicates hunks of frozen carbon dioxide -- dry ice -- may glide down some Martian sand dunes on cushions of gas similar to miniature hovercraft, plowing furrows as they go.

Researchers deduced this process could explain one enigmatic class of gullies seen on Martian sand dunes by examining images from NASA's Mars Reconnaissance Orbiter (MRO) and performing experiments on sand dunes in Utah and California.

"I have always dreamed of going to Mars," said Serina Diniega, a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and lead author of a report published online by the journal Icarus. "Now I dream of snowboarding down a Martian sand dune on a block of dry ice."

The hillside grooves on Mars, called linear gullies, show relatively constant width -- up to a few yards, or meters, across -- with raised banks or levees along the sides. Unlike gullies caused by water flows on Earth and possibly on Mars, they do not have aprons of debris at the downhill end of the gully. Instead, many have pits at the downhill end.

"In debris flows, you have water carrying sediment downhill, and the material eroded from the top is carried to the bottom and deposited as a fan-shaped apron," said Diniega. "In the linear gullies, you're not transporting material. You're carving out a groove, pushing material to the sides."

Images from MRO's High Resolution Imaging Science Experiment (HiRISE) camera show sand dunes with linear gullies covered by carbon-dioxide frost during the Martian winter. The location of the linear gullies is on dunes that spend the Martian winter covered by carbon-dioxide frost. By comparing before-and-after images from different seasons, researchers determined that the grooves are formed during early spring. Some images have even caught bright objects in the gullies.

Scientists theorize the bright objects are pieces of dry ice that have broken away from points higher on the slope. According to the new hypothesis, the pits could result from the blocks of dry ice completely sublimating away into carbon-dioxide gas after they have stopped traveling.

"Linear gullies don't look like gullies on Earth or other gullies on Mars, and this process wouldn't happen on Earth," said Diniega. "You don't get blocks of dry ice on Earth unless you go buy them."

That is exactly what report co-author Candice Hansen, of the Planetary Science Institute in Tucson, Ariz., did. Hansen has studied other effects of seasonal carbon-dioxide ice on Mars, such as spider-shaped features that result from explosive release of carbon-dioxide gas trapped beneath a sheet of dry ice as the underside of the sheet thaws in spring. She suspected a role for dry ice in forming linear gullies, so she bought some slabs of dry ice at a supermarket and slid them down sand dunes.

That day and in several later experiments, gaseous carbon dioxide from the thawing ice maintained a lubricating layer under the slab and also pushed sand aside into small levees as the slabs glided down even low-angle slopes.

The outdoor tests did not simulate Martian temperature and pressure, but calculations indicate the dry ice would act similarly in early Martian spring where the linear gullies form. Although water ice, too, can sublimate directly to gas under some Martian conditions, it would stay frozen at the temperatures at which these gullies form, the researchers calculate.

"MRO is showing that Mars is a very active planet," Hansen said. "Some of the processes we see on Mars are like processes on Earth, but this one is in the category of uniquely Martian."

Hansen also noted the process could be unique to the linear gullies described on Martian sand dunes.

"There are a variety of different types of features on Mars that sometimes get lumped together as 'gullies,' but they are formed by different processes," she said. "Just because this dry-ice hypothesis looks like a good explanation for one type doesn't mean it applies to others."

The University of Arizona Lunar and Planetary Laboratory operates the HiRISE camera, which was built by Ball Aerospace & Technologies Corp. of Boulder, Colo. JPL, a division of the California Institute of Technology in Pasadena, manages MRO for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems, Denver, built the orbiter.

To see images of the linear gullies and obtain more information about MRO, visit: http://www.nasa.gov/mro .

For more about HiRISE, visit: http://hirise.lpl.arizona.edu .

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The above story is reprinted from materials provided byNASA/Jet Propulsion Laboratory.

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Journal Reference:

1. S. Diniega, C.J. Hansen, J.N. McElwaine, C.H. Hugenholtz, C.M. Dundas, A.S. McEwen, M.C. Bourke. A new dry hypothesis for the formation of martian linear gullies.Icarus, 2013; 225 (1): 526 DOI:10.1016/j.icarus.2013.04.006

Video Gamers Really Do See More: Gamers Capture More Information Faster for Visual Decision-Making

New research shows that playing video games trains the brain to make better and faster use of visual input. (Credit: © tomispin / Fotolia)

June 11, 2013 — Hours spent at the video gaming console not only train a player's hands to work the buttons on the controller, they probably also train the brain to make better and faster use of visual input, according to Duke University researchers.

"Gamers see the world differently," said Greg Appelbaum, an assistant professor of psychiatry in the Duke School of Medicine. "They are able to extract more information from a visual scene."

It can be difficult to find non-gamers among college students these days, but from among a pool of subjects participating in a much larger study in Stephen Mitroff's Visual Cognition Lab at Duke, the researchers found 125 participants who were either non-gamers or very intensive gamers.

Each participant was run though a visual sensory memory task that flashed a circular arrangement of eight letters for just one-tenth of a second. After a delay ranging from 13 milliseconds to 2.5 seconds, an arrow appeared, pointing to one spot on the circle where a letter had been. Participants were asked to identify which letter had been in that spot.

At every time interval, intensive players of action video games outperformed non-gamers in recalling the letter.

Earlier research by others has found that gamers are quicker at responding to visual stimuli and can track more items than non-gamers. When playing a game, especially one of the "first-person shooters," a gamer makes "probabilistic inferences" about what he's seeing -- good guy or bad guy, moving left or moving right -- as rapidly as he can.

Appelbaum said that with time and experience, the gamer apparently gets better at doing this. "They need less information to arrive at a probabilistic conclusion, and they do it faster."

Both groups experienced a rapid decay in memory of what the letters had been, but the gamers outperformed the non-gamers at every time interval.

The visual system sifts information out from what the eyes are seeing, and data that isn't used decays quite rapidly, Appelbaum said. Gamers discard the unused stuff just about as fast as everyone else, but they appear to be starting with more information to begin with.

The researchers examined three possible reasons for the gamers' apparently superior ability to make probabilistic inferences. Either they see better, they retain visual memory longer or they've improved their decision-making.

Looking at these results, Applebaum said, it appears that prolonged memory retention isn't the reason. But the other two factors might both be in play -- it is possible that the gamers see more immediately, and they are better able make better correct decisions from the information they have available.

To get at this question, the researchers will need more data from brainwaves and MRI imagery to see where the brains of gamers have been trained to perform differently on visual tasks.

This study, which appears in the June edition of the journalAttention, Perception and Psychophysics, was supported by grants from the Army Research Office (54528LS), the Department of Homeland Security (HSHQDC-08-C-00100), DARPA (D12AP00025-002) and Nike Inc.

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New Tasks Become as Simple as Waving a Hand With Brain-Computer Interfaces

This image shows the changes that took place in the brain for all patients participating in the study using a brain-computer interface. Changes in activity were distributed widely throughout the brain. (Credit: Jeremiah Wander, UW)

June 11, 2013 — Small electrodes placed on or inside the brain allow patients to interact with computers or control robotic limbs simply by thinking about how to execute those actions. This technology could improve communication and daily life for a person who is paralyzed or has lost the ability to speak from a stroke or neurodegenerative disease.

Now, University of Washington researchers have demonstrated that when humans use this technology -- called a brain-computer interface -- the brain behaves much like it does when completing simple motor skills such as kicking a ball, typing or waving a hand. Learning to control a robotic arm or a prosthetic limb could become second nature for people who are paralyzed.

"What we're seeing is that practice makes perfect with these tasks," said Rajesh Rao, a UW professor of computer science and engineering and a senior researcher involved in the study. "There's a lot of engagement of the brain's cognitive resources at the very beginning, but as you get better at the task, those resources aren't needed anymore and the brain is freed up."

Rao and UW collaborators Jeffrey Ojemann, a professor of neurological surgery, and Jeremiah Wander, a doctoral student in bioengineering, published their results online June 10 in theProceedings of the National Academy of Sciences.

In this study, seven people with severe epilepsy were hospitalized for a monitoring procedure that tries to identify where in the brain seizures originate. Physicians cut through the scalp, drilled into the skull and placed a thin sheet of electrodes directly on top of the brain. While they were watching for seizure signals, the researchers also conducted this study.

The patients were asked to move a mouse cursor on a computer screen by using only their thoughts to control the cursor's movement. Electrodes on their brains picked up the signals directing the cursor to move, sending them to an amplifier and then a laptop to be analyzed. Within 40 milliseconds, the computer calculated the intentions transmitted through the signal and updated the movement of the cursor on the screen.

Researchers found that when patients started the task, a lot of brain activity was centered in the prefrontal cortex, an area associated with learning a new skill. But after often as little as 10 minutes, frontal brain activity lessened, and the brain signals transitioned to patterns similar to those seen during more automatic actions.

"Now we have a brain marker that shows a patient has actually learned a task," Ojemann said. "Once the signal has turned off, you can assume the person has learned it."

While researchers have demonstrated success in using brain-computer interfaces in monkeys and humans, this is the first study that clearly maps the neurological signals throughout the brain. The researchers were surprised at how many parts of the brain were involved.

"We now have a larger-scale view of what's happening in the brain of a subject as he or she is learning a task," Rao said. "The surprising result is that even though only a very localized population of cells is used in the brain-computer interface, the brain recruits many other areas that aren't directly involved to get the job done."

Several types of brain-computer interfaces are being developed and tested. The least invasive is a device placed on a person's head that can detect weak electrical signatures of brain activity. Basic commercial gaming products are on the market, but this technology isn't very reliable yet because signals from eye blinking and other muscle movements interfere too much.

A more invasive alternative is to surgically place electrodes inside the brain tissue itself to record the activity of individual neurons. Researchers at Brown University and the University of Pittsburgh have demonstrated this in humans as patients, unable to move their arms or legs, have learned to control robotic arms using the signal directly from their brain.

The UW team tested electrodes on the surface of the brain, underneath the skull. This allows researchers to record brain signals at higher frequencies and with less interference than measurements from the scalp. A future wireless device could be built to remain inside a person's head for a longer time to be able to control computer cursors or robotic limbs at home.

"This is one push as to how we can improve the devices and make them more useful to people," Wander said. "If we have an understanding of how someone learns to use these devices, we can build them to respond accordingly."

The research team, along with the National Science Foundation's Engineering Research Center for Sensorimotor Neural Engineering headquartered at the UW, will continue developing these technologies.

This research was funded by the National Institutes of Health, the NSF, the Army Research Office and the Keck Foundation.

Story Source:

The above story is reprinted from materials provided byUniversity of Washington. The original article was written by Michelle Ma.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal Reference:

1. J. D. Wander, T. Blakely, K. J. Miller, K. E. Weaver, L. A. Johnson, J. D. Olson, E. E. Fetz, R. P. N. Rao, J. G. Ojemann. Distributed cortical adaptation during learning of a brain-computer interface task.Proceedings of the National Academy of Sciences, 2013; DOI: 10.1073/pnas.1221127110

Females Fend Off Gut Diseases -- At Least Among Mice

A microscopic image shows an inflamed intestine in a male mouse. MSU professor Laura McCabe and colleagues found that something about female mice seems to protect them from inflammatory bowel disease. (Credit: Image courtesy of Michigan State University)

June 11, 2013 — At least among mice, females have innate protection from certain digestive conditions, according to a new Michigan State University study.

While it's tricky to draw conclusions for human health, the findings could eventually help scientists better understand and treat the 1.4 million Americans suffering from inflammatory bowel diseases, or IBD.

Crohn's disease and colitis, the two most common forms of IBD, involve abnormal functioning of the immune system that can damage the digestive tract, causing inflammation, diarrhea, constipation, abdominal pain and other symptoms.

For the study, researchers induced colitis by giving mice with weakened immune systems a dose of bacteria that can cause digestive trouble. After six weeks, the males had significantly more severe symptoms than the females and had more of the bacteria left in their guts. The males also showed more deterioration of their bones, which studies have linked to gut inflammation.

"It seems females are protected from bad bacteria-induced bone loss, and it's because they have reduced gut inflammation," said co-author Laura McCabe, a professor in the MSU Departments of Physiology and Radiology. "When we looked at markers of inflammation in the male mice, they were really high, whereas the females didn't have that kind of bad response. They can somehow handle these nasty bacteria."

McCabe said while the new study is a step toward better understanding of IBD, it's not clear if women have the same kind of resistance to the condition as the female mice. Indeed, much is still unknown about IBD, including what causes it. The imbalance of good and bad gut bacteria that the experiment simulated is one possible cause.

"We want to know what it is about female mice allowing them to be protected," she said. "If we can understand that, we might have a potential therapeutic target for people with IBD."

The study was funded by the Crohn's and Colitis Foundation of America and appears in the journal Inflammatory Bowel Diseases.

McCabe's partners on the study from the Department of Physiology were Regina Irwin, research technologist; Tae Hyung Lee, research associate; and Narayanan Parameswaran, associate professor. Vincent Young from the University of Michigan also participated.

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Perfect Pitch May Not Be Absolute After All

A new study finds that exposure to music influences how people identify notes from their sound, rather than having the rare ability of perfect pitch at an early age. (Credit: © M. Schuppich / Fotolia)

June 11, 2013 — People who think they have perfect pitch may not be as in tune as they think, according to a new University of Chicago study in which people failed to notice a gradual change in pitch while listening to music.

When tested afterward, people with perfect, or absolute pitch, thought notes made out of tune at the end of a song were in tune, while notes that were in tune at the beginning sounded out of tune.

About one out of 10,000 people has absolute pitch, which means they can accurately identify a note by hearing it. They are frequently able, for instance, to replicate a song on a piano by simply hearing it. Absolute pitch has been "idealized in popular culture as a rare and desirable musical endowment, partly because several well-known composers, such as Mozart, Beethoven, Chopin and Handel, have been assumed to posses absolute pitch," the researchers write in "Absolute Pitch May Not Be So Absolute," in the current issue of Psychological Science.

The study showed that exposure to music influences how people identify notes from their sound, rather than having a rare, absolute ability at an early age. The research also demonstrates the malleability of the brain -- that abilities thought to be stable late in life can change with even a small amount of experience and learning.

One of the researchers, Stephen Hedger, a graduate student in psychology at UChicago, has absolute pitch, as determined by objective tests. Joining him in the study were postdoctoral scholar Shannon Heald and Howard Nusbaum, professor in psychology at UChicago.

Hedger and Heald decided to pursue the study after a session in which Heald tricked Hedger by covertly adjusting pitch on an electronic keyboard.

"Steve and I have talked about absolute pitch, and I thought it might be more malleable than people have thought," Heald said. While in the lab, Hedger began to play a tune, and Heald secretly changed the pitch with a wheel at the side of the keyboard.

Heald changed the tuning to make the music a third of a note flatter than it was at the beginning of the song. Hedger never noticed the change, which was gradual, and was later surprised to discover the music he was playing was actually out of tune at the end.

"I was astounded that I didn't notice the change," Hedger said. Working with Nusbaum, an expert on brain plasticity, they devised experiments to see if other people with absolute pitch would make the same mistake as Hedger.

The researchers recruited 27 people who were identified as having absolute pitch by standard tests and assigned them to two groups for two experiments. The subjects were tested on identifying notes at the beginning of the experiments, and each was able to correctly identify an in-tune note.

One group then listened to Johann Brahms' Symphony No. 1 in C Minor. In another experiment, a second group listened to music played on a French horn to determine whether individual instruments impact the ability to detect music going out of tune.

As the people listened to the symphony, the music was detuned during the first movement (about 15 minutes) to become flatter at the rate of two cents a minute. (The tonal distance between two notes, such as an A and G sharp, is measured as 100 cents).

By the end of the movement, the pitch had been detuned by 33 cents, a change none of the listeners detected, much like Hedger. The symphony was then played out of tune for the next three movements.

The listeners were then tested after listening to the detuned music, as they had been at the beginning of the session. They identified out-of-tune notes from the newly detuned music as being in tune, while reporting notes they heard in the pre-test were slightly out of tune.

Another test composed of only five notes, called phase music, equally found that people with absolute pitch changed what they determined was in tune after listening to the slightly out-of-tune music. That included notes not actually heard as detuned during the musical exposure.

In both tests, only the specific instruments used in the compositions were affected by the detuned nature of the listening experience. Neither the Brahms' Symphony nor the five-note compositions used a piano or French horn, and after listening to detuned music, notes played on these instruments were unaffected.

"Listening to detuned music significantly shifted the perceived intonation and generalized to notes that had not been heard in the detuned music," said Nusbaum. The researchers are now experimenting with people who have more limited pitch identification ability and are finding that their pitch identification can be improved.

"This is further evidence of how adaptable even the adult mind is for learning new skills. We are finding out more and more about how our brains are equipped to learn new things at any age and not limited by abilities previously thought to be available only from the time of birth," Nusbaum said.

Story Source:

The above story is reprinted from materials provided byUniversity of Chicago. The original article was written by William Harms.

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Modern Humans Did Not Settle in Asia Before Eruption of Sumatra Volcano 74,000 Years Ago, Study Finds

View of Lake Toba in Sumatra, Indonesia. (Credit: © 12ee12 / Fotolia)

June 11, 2013 — When did modern humans settle in Asia and what route did they take from humankind's African homeland? A University of Huddersfield professor has helped to provide answers to both questions. But he has also had to settle a controversy.

Professor Martin Richards, who heads the University's Archaeogenetics Research Group, co-authors a new article in the Proceedings of the National Academy of Sciences. It refutes a recent theory that there is archaeological evidence for the presence of modern humans in southern Asia before the super-eruption of the Mount Toba volcano in Sumatra. ‌One of the most catastrophic events since humans evolved, it happened approximately 74,000 years ago. In 2005, Professor Richards led research published in an article in the journalScience which used mitochondrial DNA evidence to show that anatomically modern humans dispersed from their Africa homeland via a "southern coastal route" from the Horn and through Arabia, about 60,000 years ago -- after the Toba eruption.‌

‌However, a team of archaeologists excavating in India then claimed to have found evidence that modern humans were there before the eruption -- possibly as early as 120,000 years ago, much earlier than Europe or the Near East were colonised. These findings, based on the discovery of stone tools below a layer of Toba ash, were published in Science in 2007.

Now Professor Richards -- working principally with the archaeologist Professor Sir Paul Mellars, of the University of Cambridge and the University of Edinburgh, with a team including Huddersfield University's Dr Martin Carr and colleagues from York and Porto -- has published his rebuttal of this theory. In doing so, they have been able to draw on a much greater body of DNA evidence that was available for the earlier article.

"One of the things we didn't have in 2005 was very much evidence from India in the way of mitochondrial sequences. Now, with a lot of people doing sequencing and depositing material in databases there are about 1,000 sequences from India," said Professor Richards.

‌By using the mitochondrial DNA of today's populations and working backwards, and by drawing on a wide variety of other evidence and research, the team was able to make much more precise estimates for the arrival of modern humans in India.

‌The evidence suggests dispersal from Africa and settlement in India no earlier than 60,000 years ago. "We also argue that close archaeological similarities between African and Indian stone-tool technologies after 70,000 years ago, as well as features such as beads and engravings, suggest that the slightly later Indian material had an African source," states Professor Richards.

"There were people in India before the Toba eruption, because there are stone tools there, but they could have been Neanderthals -- or some other pre-modern population," he adds.

"The replacement of the presumably archaic humans living previously in South Asia by modern people with these new technologies appears analogous to the replacement of Neanderthals by modern humans in Europe and western Asia 50-40,000 years ago."

Story Source:

The above story is reprinted from materials provided byUniversity of Huddersfield.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal References:

1. P. Mellars, K. C. Gori, M. Carr, P. A. Soares, M. B. Richards. Genetic and archaeological perspectives on the initial modern human colonization of southern Asia. Proceedings of the National Academy of Sciences, 2013; DOI: 10.1073/pnas.1306043110
2. Vincent Macaulay, Catherine Hill, Alessandro Achilli, Chiara Rengo, Douglas Clarke, William Meehan, James Blackburn, Ornella Semino, Rosaria Scozzari, Fulvio Cruciani, Adi Taha, Norazila Kassim Shaari, Joseph Maripa Raja, Patimah Ismail, Zafarina Zainuddin, William Goodwin, David Bulbeck, Hans-Jürgen Bandelt, Stephen Oppenheimer, Antonio Torroni, and Martin Richard. Single, Rapid Coastal Settlement of Asia Revealed by Analysis of Complete Mitochondrial Genomes. Science, 2005; 308 (5724): 1034 DOI: 10.1126/science.1109792
3. M. Petraglia, R. Korisettar, N. Boivin, C. Clarkson, P. Ditchfield, S. Jones, J. Koshy, M. M. Lahr, C. Oppenheimer, D. Pyle, R. Roberts, J.-L. Schwenninger, L. Arnold, K. White. Middle Paleolithic Assemblages from the Indian Subcontinent Before and After the Toba Super-Eruption. Science, 2007; 317 (5834): 114 DOI:10.1126/science.1141564

Master Regulator in Cancer Metastasis Discovered

Mammary epithelial cells that have undergone an epithelial-mesenchymal transition, exhibit a change in cell morphology with actin stress fibers (red) and with focused cell adhesion points (green). (Credit: Dr. Nathalie Meyer-Schaller, University of Basel)

June 10, 2013 — The predominant cause of death in cancer patients is metastasis, the formation of secondary tumors in other organs like the brain, liver, and lungs. Cancer cells detach from the original primary tumor and reach a single cell or group of cells in another organ. The cells of the body normally remain in place through adhering to an extracellular substance. However, cancer cells learn how to release themselves from these bonds and invade surrounding tissues, blood, and the lymphatic system.

The transformation of sedentary, specialized cells into wandering, invasive, and unspecialized cells is called epithelial-mesenchymal transition (EMT), which is central to metastasis. EMT is a multistage process, which is accompanied by a fundamental change in cell morphology and number of genetic programs. The molecular processes that govern EMT, however, are still poorly understood.

Main Switch Found

The research groups of Prof. Gerhard Christofori of the Department of Biomedicine at the University of Basel; Prof. Erik van Nimwegen from the Biozentrum, University of Basel; and Prof. Dirk Schuebeler from the Friedrich Miescher Institute have discovered a master regulator of EMT and metastasis: the transcription factor Sox4 is upregulated in its activity and triggers the expression of a number of genes that play an important role during EMT and metastasis.

In particular, Sox4 promotes the expression of the enzyme Ezh2, a methyltransferase, which generally influences methylation of specific proteins (histones), the packaging of the genetic material, and thus its readability and gene expression. Due to this change in genetic information, the behavior and function of cells are reprogrammed -- a process that is currently observed during metastasis. Such a change in gene expression is also found in patients with malignant cancer and metastasis and correlates with a poor prognosis.

These findings point to the possibility that the inhibition of the transcription factor Sox4 and especially the methyltransferase Ezh2 could hinder metastasis in cancer patients. Appropriate medications are currently being developed but they need to undergo clinical trials before being used in patients. The research was implemented within the framework of the SystemsX.ch-RTD Project "Cell Plasticity."

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The above story is reprinted from materials provided byUniversity of Basel, via EurekAlert!, a service of AAAS.

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Journal Reference:

1. Neha Tiwari, Vijay K. Tiwari, Lorenz Waldmeier, Piotr J. Balwierz, Phil Arnold, Mikhail Pachkov, Nathalie Meyer-Schaller, Dirk Schübeler, Erik van Nimwegen, Gerhard Christofori. Sox4 Is a Master Regulator of Epithelial-Mesenchymal Transition by Controlling Ezh2 Expression and Epigenetic Reprogramming. Cancer Cell, 2013; 23 (6): 768 DOI: 10.1016/j.ccr.2013.04.020