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Updated: 15 min 46 sec ago

Tiniest particles melt and then turn into ‘Jell-O’

8 hours 53 min ago

The fact that microscopic particles known as polymers and colloids will melt as temperatures rise was no surprise to scientists.

But raise the temperature a little more and the particles will re-solidify. The new solid is a substance like Jell-O, with the polymers adhering to the colloids and gluing them together.

The discovery points to new ways to create “smart materials,” cutting-edge materials that adapt to their environment by taking new forms, and to sharpen the detail of 3D printing.

“These findings show the potential to engineer the properties of materials using not only temperature, but also by employing a range of methods to manipulate the smallest of particles,” explains Lang Feng, the study’s lead author and an NYU doctoral student at the time it was conducted.

The research, which appears in the journal Nature Materials, reveals that the well-known Goldilocks Principle, which posits that success is found in the middle rather than at extremes, doesn’t necessarily apply to the smallest of particles.

The study focuses on polymers and colloids—particles as small as one-billionth and one-millionth of a meter in size, respectively.

Paint, milk, glass

These materials, and how they form, are of notable interest to scientists because they are the basis for an array of consumer products. For instance, colloidal dispersions comprise such everyday items as paint, milk, gelatin, glass, and porcelain and for advanced engineering such as steering light in photonics.

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By better understanding polymer and colloidal formation, scientists have the potential to harness these particles and create new and enhanced materials—possibilities that are now largely untapped or are in relatively rudimentary form.

In the Nature Materials study, the researchers examined polymers and larger colloidal crystals at temperatures ranging from room temperature to 85 degrees C.

At room temperature, the polymers act as a gas bumping against the larger particles and applying a pressure that forces them together once the distance between the particles is too small to admit a polymer.

In fact, the colloids form a crystal using this process known as the depletion interaction—an attractive entropic force, which is a dynamic that results from maximizing the random motion of the polymers and the range of space they have the freedom to explore.

As usual, the crystals melt on heating, but, unexpectedly, on heating further they re-solidify. The solid is much softer, more pliable, and more open than the crystal.

This result, the researchers observe, reflects enthalpic attraction—the adhesive energy generated by the higher temperatures and stimulating bonding between the particles. By contrast, at the mid-level temperatures, conditions were too warm to accommodate entropic force, yet too cool to bring about enthalpic attraction.

Lang, now a senior researcher at ExxonMobil, observes that the finding may have potential in 3D printing.

Currently, this technology can create 3D structures from two-dimensional layers. However, the resulting structures are relatively rudimentary in nature. By enhancing how particles are manipulated at the microscopic level, these machines could begin creating objects that are more detailed, and realistic, than is currently possible.

The National Science Foundations, NASA, and the Department of Energy funded the work.

Source: NYU

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Why some ‘green’ buildings have stinky water

9 hours 1 min ago

Cost and environmental impact are two reasons to install plastic pipes in buildings, but research shows they can put chemicals in drinking water and cause unpleasant odors.

Buildings are being plumbed with many types of plastic drinking water pipes. These include crosslinked polyethylene (PEX), high-density polyethylene (HDPE), polyvinylchloride (PVC), chlorinated PVC (cPVC), and polypropylene (PP) pipes, says Andrew Whelton, an assistant professor of civil engineering in Purdue University’s Lyles School of Civil Engineering and Division of Environmental and Ecological Engineering.

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Plastic pipes are generally less expensive, lighter, and easier to install than metal pipes. A 2012 comparison showed PEX pipe was the least expensive among plastic pipes, costing just 43 cents per foot compared to the most expensive metal, copper pipe, at $2.55 per foot.

Thousands of dollars can be saved during construction by installing plastic instead of metal plumbing systems, and proponents assert plastic pipes require less energy to manufacture—generating less carbon dioxide compared to metal pipes—ostensibly making them a good fit for green buildings.

“Little is known about the degree to which plastic pipes sold in the US affect drinking water quality,” says Whelton, who will prsent the findings at the 2014 US Green Building Council’s Greenbuild International Conference & Exposition on Friday in New Orleans.

Six kinds of PEX pipe

Some testing results appear online in September in the journal Water Research. There, the researchers describe drinking water impacts caused by six brands of PEX pipes available in the United States.

For the Water Research study, researchers tested drinking water from a PEX plumbing system in a “net-zero energy” building in Maryland six months after the system had been installed.

The testing revealed the presence of 11 chemicals that were PEX pipe ingredients and ingredient degradation products. Research with PEX pipes in the laboratory also showed that six brands caused drinking water to exceed the US Environmental Protection Agency’s maximum recommended drinking water odor limit, Whelton says.

The US EPA’s maximum drinking water odor limit is a “threshold odor number” of 3, or 3 TON. Compliance is voluntary because the standard is based on aesthetic, not health, considerations.

Chlorine in the water

Odor and chemical levels were monitored with and without chlorine treatment over a 30-day period for the six pipe brands. Chlorine, the most popular disinfectant chemical used in the United States, protects drinking water from disease-causing organisms as it travels to the tap.

When chlorine reacted with chemicals leached by the plastic pipes, odor levels for one brand of PEX pipe tripled. While the total mass of chemicals leached by PEX pipes was found to decline after 30 days of testing, odors generally continued as the pipes aged, Whelton says.

A general assumption in the United States is that chemicals responsible for drinking water odors pose no health dangers. Although, several chemicals found in the plumbing research have regulated health limits, and one PEX pipe brand caused drinking water to exceed the ethyl-tert-butyl ether (ETBE) drinking water health standard. ETBE is a PEX pipe manufacturing byproduct with drinking water standards in New Hampshire and New York state.

When establishing the ETBE limit in New Hampshire, public health officials specifically added a 10-fold reduction to allow for its suspected carcinogenic potential. However, no federal drinking water standard exists, Whelton says.

The researchers found ETBE drinking water levels as high as 175 parts per billion (ppb) during the first three days of PEX pipe use and then 74 ppb after 30 days of use when the testing ended. New Hampshire has the most stringent drinking water health standard of 40 ppb. Michigan also has an ETBE standard, but it is based on limiting drinking water odor caused by ETBE.

Smells like gasoline

The presence of drinking water odor can prompt homeowners to avoid their drinking water altogether.

“A contractor who installed PEX in parts of a million-dollar home in Oklahoma asked us for help because the homeowners reported gasoline-like odors in a bathroom’s tap water,” Whelton says. “The homeowners refused to take showers in the PEX-plumbed bathroom because they were concerned about their health.”

By testing tap water from the home, Whelton’s team discovered that toluene, a solvent used for plastic resin synthesis and ETBE were present above levels where odors would be detected. Neither toluene nor ETBE exceeded health standards, however. The gasoline smelling water was safe to use.

The research also shows that there are differences in the quality of PEX products on the market, and different brands cause different odor and chemical-leaching impacts.

The team plans to continue the work and release additional results from the study over the next several months. Findings show some chemicals released by plumbing pipes can be transformed into carcinogenic chemicals regulated by the EPA; chemicals leached by certain plastics are conducive to bacterial growth; and plumbing system cleaning practices described in some, but not all, plumbing codes can cause PEX pipe chemical leaching to worsen.

The work is funded by an NSF grant.

Source: Purdue University

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Aches after exercise might predict chronic pain

9 hours 47 min ago

Scientists know that exercise helps the body tolerate pain. But some feel more benefits than others.

A new study reports that rats displaying the least sensitivity after running on a treadmill are also less likely to develop pain after a nerve injury.

The results, published in Journal of Pain, suggest that exercise could be a valuable component in helping doctors predict susceptibility to pain, particularly following injury or surgery, says Junad Khan, assistant professor of diagnostic sciences at Rutgers, who led the study with former faculty member Eli Eliav, now dean for oral health at University of Rochester School of Medicine and Dentistry.

Patient profiling

“We could use it as a form of patient profiling,” Khan says. “We hope that the finding from this study could support the development of individual pain management plans.”

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The phenomenon of pain reduction after exercise is known as “exercise-induced hypoanalgesia” or (EIH).  Researchers say that an individual’s capacity for EIH, or their EIH profile, can indicate how efficiently their body modulates pain, meaning how it manages both the sensation and suppression of pain.

Chronic pain conditions such as fibromyalgia, migraine, low back pain, and temporomandibular disorder have been shown to be associated with faulty pain modulation.

In the study, researchers determined each rats’ EIH profile based on their response to painful stimuli, before and after a treadmill run.  Those same rats were then given a procedure that caused nerve injury. Rats with a high EIH profile  meaning they felt less pain after exercise—developed less pain from the injury than rats with a low EIH profile.

Khan, who specializes in orofacial pain, is hoping that the work will provide greater insight into how pain is transmitted and perceived, in addition to the best ways to relieve it.

Source: Rutgers

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Web app is like ‘Google maps’ for the brain

9 hours 58 min ago

A new online tool for scientists and doctors called Golgi makes it easy to explore the brain of a rat.

The web app, unveiled today, offers details at the click of a button about how the regions of the brain communicate and interact.

Rat brains are close enough to human brains to offer valuable insights but are far easier to study and therefore represent a larger pool of research data.

“We have a big advantage because we’re the only group—really in the world—that has a flat map of the brain,” says Larry Swanson, professor of biological sciences at USC Dornsife.

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Swanson collaborated with USC grad student Ramsay Brown, who designed the program as an undergraduate working in Swanson’s lab.

To display the brain’s 3D structure on 2D screens, Swanson and Brown used the embryonic brain—which begins as a flat sheet of cells—as a guide. This flattens the brain and keeps related portions of the brain located close together. Flattening the brain lets users click around and display connectome and other data directly on regions they’re interested in learning about for research or treatment.

“We designed a really intuitive way to explore the more nuanced details about the brain and connectome,” Brown says. “Making this data easy and accessible will improve how scientists and doctors explore, explain, and treat human conditions and restore quality of life—and that’s really special to us.”

Brown and Swanson think this program is just the beginning. Connectomics, the subfield of neuroscience that studies and maps the brain’s wiring, is advancing quickly and providing better maps as the technique evolves.

Programs like Golgi will help doctors and researchers make sense of these new maps and make better medical and scientific decisions faster.

“Many people now think that understanding these neurological diseases is going to require understanding the circuitry of the brain,” Swanson says.

The National Institutes of Health supported the project.

Source: USC

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You’d be lost without your ‘mental compass’

10 hours 18 sec ago

New research shows how our brains anchor the “mental compass.” Without this complex system for keeping track of which direction you’re facing as you move around, remembering how to get around would be impossible.

The findings provide a neurological basis for something that psychologists have long observed about navigational behavior: people use geometrical relationships to orient themselves.

The research, which is related to the work that won this year’s Nobel Prize in Physiology or Medicine, adds new dimensions to our understanding of spatial memory and how it helps us to build memories of events.

Russell Epstein, a professor of psychology at University of Pennsylvania, and postdoctoral fellow Steven Marchette led the study, which appears in Nature Neuroscience.

“Imagine coming out of a subway stop,” says Marchette. “You know exactly where you are in the world, but you still have the experience of looking around to figure out which way you are facing. You might think, ‘I’m looking at city hall, so I must be facing east.’ It takes a second before it clicks.

“We’re interested in how people are able to reset their sense of direction in the world and what cues they rely upon in the environment to do that.”

In the virtual museums

To test how the brain makes these inferences, the researchers designed an experiment in which they introduced participants to a virtual environment, a set of four museums in a park, and had the participants memorize the location of the everyday objects on display in those museums.

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They then scanned their brains while asking them to recall the spatial relationships between those objects, such as whether the bicycle was to the left or the right of the cake.

In the scans, using a technique that measures blood flow to different regions of the brain known as fMRI, the researchers focused on a region known as the retrosplenial complex. People who have severe injuries to this region are able to recognize landmarks in their environments but are unable to recall how to get from one to another, suggesting that it plays a specific role in the type of memory used in navigation and orientation.

“The retrosplenial complex is very much underexplored,” Epstein says. “While we don’t have the ability to go in and look at individual neurons, like O’Keefe and the Mosers did in their Nobel Prize-winning work, one of the nice things about fMRI is that we didn’t have to decide beforehand which areas of the brain to record from.”

Three possibilities

There are three ways the retrosplenial complex could conceivably encode this type of information and serve as part of a mental compass.

One way would be a “global” system, in which the brain tracks the absolute direction one is facing regardless of visual cues in the environment. In fact, there is good evidence that such a system exists in the brain, but the Penn team doubted that the retrosplenial complex was the central component of it.

An “idiosyncratic” system, in which the brain keeps tracks of direction for each environment independently, was another possibility. In such a system, remembering that your desk is on the north wall of your office would involve recalling the room itself and picking out the relevant features.

Finally, they considered a “geometric” system that is based on more generalized relationships between features in an environment. There, remembering that your desk is on the north wall of your office would involve recalling the relationship between the desk and the door—say, the desk is on the left when I enter the room—without having to specifically recall the room itself.

North, south, east, or west?

The architecture of the team’s virtual park was critical for being able to distinguish which of these three types of systems participants were using to orient themselves in regards to the objects.

The park’s four museums were laid out in a cloverleaf pattern around a central plaza, which itself could only be approached from the south. Each museum had a single door, all of which faced the center of the plaza. Each museum was visually distinct but all were identical in layout: a single room containing eight unique objects, two on each wall. The objects were contained in niches, such that participants could only see them from straight ahead.

“We designed it this way so that it was clear to the participants that each museum’s back wall pointed in one of the cardinal directions,” says Marchette. “And by placing the objects in the niches, we ensured that they could only see them when they were looking due north, south, east, or west.”

After being allowed to freely roam around the virtual environment, participants were tested about the locations of the objects. They were asked to return to the lab a day or two later, where they were given the opportunity to refresh their memories about the layout of the objects before entering the MRI scanner. There, they were shown words representing a pair of objects that were found in one of the museums and asked whether the second object was to the left or the right of the first.

The researchers used half of a participant’s responses to calibrate their measurement of that participant’s retrosplenial complex and then compared the activation patterns they saw there to responses in that participant’s other half.

“If the retrosplenial complex supported a global system,” Marchette says, “then it shouldn’t matter whether people are imagining facing the back wall or the left wall; if you’re looking north in one museum and north in the other, the activation patterns should be similar. As we expected, that doesn’t happen.

“Likewise, for an idiosyncratic system, we would expect that remembering the back walls of two different museums would produce dissimilar patterns, since you would be remembering the room itself. That doesn’t happen either.”

A ‘floor plan’ in the brain

Instead, the patterns look similar when participants imagined looking at objects that have the same geometric relationship to the surrounding room, regardless of the “true” direction the participant was facing. For example, remembering objects on the back walls of two different museums produced similar activation patterns, even though the back wall is north in one museum and east in the other.

“We can even reconstruct the location the participant is remembering based on those similarities,” Epstein says. “Once we know what we are looking for based on the first half of a participant’s responses, we can estimate the location of a given view entirely from the fMRI data, and they are reasonably close to where the views actually are.

“That’s a pretty cool result. It’s as if we can read out a ‘floor plan’ of the museums from each person’s brain. And because the museums are geometrically identical, the retrosplenial complex uses the same ‘floor plan’ for all of them”

The team’s research provides a more complete picture of what is happening in the brain when people navigate from one place to another.

“Psychologists have long surmised that geometry is important for this kind of memory,” Epstein says, “but this is beginning to show the neurological basis for it. We hope this opens the door for a deeper look at this region of the brain.”

The National Institutes of Health and the National Science Foundation supported the research.

Source: Penn

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‘Starfish’ crystals could lead to 3D-printed pills

11 hours 34 min ago

Engineers have figured out how to make rounded crystals with no facets, a design that mimics the hard-to-duplicate texture of starfish shells.

The discovery could one day lead to 3D-printed medications that absorb better into the body.

Both the crystals’ shape and the way they’re made—using organic vapor jet printing—have other promising applications, researchers say. The geometry could potentially be useful to guide light in advanced LEDs, solar cells, and nonreflective surfaces.

These rounded crystals with no facets have a structure occasionally found in nature but one that is difficult to produce in a lab. (Credit: Max Shtein)

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“We call them nanolobes. They look like little hot air balloons that are rising from the surface,” says Olga Shalev, a doctoral student in materials science and engineering at University of Michigan.

The nanoscale shapes are made out of boron subphthalocyanine chloride, a material often used in organic solar cells.

It’s in a family of small molecular compounds that tend to make either flat films or faceted crystals with sharp edges, says Max Shtein, associate professor of materials science and engineering, macromolecular science, and engineering, chemical engineering, and art and design.

“In my years of working with these kinds of materials, I’ve never seen shapes that looked like these. They’re reminiscent of what you get from biological processes,” Shtein says. “Nature can sometimes produce crystals that are smooth, but engineers haven’t been able to do it reliably.”

Echinoderm sea creatures such as brittle stars have ordered rounded structures on their bodies that work as lenses to gather light into their rudimentary eyes. But in a lab, crystals composed of the same minerals tend either to be faceted with flat faces and sharp angles, or smooth, but lacking molecular order.

Made by accident

Researchers made the curved crystals by accident several years ago. They’ve since traced their steps and figured out how to do it on purpose.

In 2010, Shaurjo Biswas, then a doctoral student, was making solar cells with the organic vapor jet printer. He was recalibrating the machine after switching between materials. Part of the recalibration process involves taking a close look at the fresh layers of material, of films, printed on a plate.

Biswas X-rayed several films of different thicknesses to observe the crystal structure and noticed that the boron subphthalocyanine chloride, which typically does not form ordered shapes, started to do so once the film got thicker than 600 nanometers. He made some thicker films to see what would happen. At 800 nanometers thick, the repeating nanolobe pattern emerged every time.

“At first, we wondered if our apparatus was functioning properly,” Shtein says. For a long while, the blobs were lab curiosities. Researchers were focused on other things.

Spray painting with gas

Then doctoral student Shalev got involved. She was fascinated by the structures and wanted to understand the reason for the phenomenon. She repeated the experiments in a modified apparatus that gave more control over the conditions to vary them systematically.

Shalev collaborated with physics professor Roy Clarke to gain a better understanding of the crystallization, and mechanical engineering professor Wei Lu to simulate the evolution of the surface. She’s first author of the new paper that is published in the current edition of Nature Communications. “As far as we know, no other technology can do this,” she says.

The organic vapor jet printing process the researchers use is a technique Shtein helped to develop when he was in graduate school. He describes it as spray painting, but with a gas rather than with a liquid. It’s cheaper and easier to do for certain applications than competing approaches that involve stencils or can only be done in a vacuum.

The researchers are especially hopeful about the prospects for this technique to advance emerging 3D-printed pharmaceutical concepts.

For example, the method offers a precise way to control the size and shape of medicine particles, for easier absorption into the body. It could also allow drugs to be attached directly to other materials and it doesn’t require solvents that might introduce impurities.

The US Department of Energy, the National Science Foundation, and the Air Force Office of Scientific Research provided funding for the study.

Source: University of Michigan

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Signs of autism by 18 months in younger siblings

13 hours 13 min ago

About 20 percent of children who have older siblings with autism also develop the disorder. Of those children, 57 percent show symptoms as early as 18 months.

The findings stress the need for early and repeated screening in the first three years of life so that, if necessary, intervention can begin as soon as possible.

A large-scale study has identified specific social-communicative behaviors that distinguish infants with autism spectrum disorder (ASD) from their typically and atypically developing high-risk peers as early as 18 months of age.

“While the majority of siblings of children with ASD will not develop the condition themselves, for those who do, one of the key priorities is finding more effective ways of identifying and treating them as early as possible,” says Katarzyna Chawarska, associate professor in the Child Study Center and the Department of Pediatrics at Yale University School of Medicine.

“Our study reinforces the need for repeated diagnostic screening in the first three years of life to identify individual cases of ASD as soon as behavioral symptoms are apparent.”

Patterns of behavior

For the study, published in the Journal of the American Academy of Child & Adolescent Psychiatry, researchers pooled data from eight sites participating in the Autism Speaks Baby Siblings Research Consortium. The team closely examined social, communicative, and repetitive behaviors in 719 infants when they were 18 months old.

The team looked for patterns that might predict a later diagnosis of ASD. They then followed up when the participants were age 3.

“Our research suggests that approximately half of the siblings who are later diagnosed with ASD display signs suggestive of ASD at 18 months, and in those who appeared asymptomatic at 18 months, symptoms appeared between 18 and 36 months,” Chawarska says.

What was most interesting to the research team was that different patterns of behaviors at 18 months may be predictive of ASD later on. In about 50 percent of siblings, a combination of poor eye contact and lack of communicative gestures or imaginative play is most strongly associated with later ASD diagnosis.

In a small percentage of those later diagnosed with ASD, eye contact may be relatively normal, but they begin to display early signs of repetitive behaviors and have limited non-verbal communication skills.

“So not only do the behavioral symptoms appear at different ages, but different combinations of early symptoms may predict the diagnostic outcome,” Chawarska says.

“Linking these developmental dynamics with underlying neurobiology may advance our understanding of causes of ASD and further efforts to personalize treatment for ASD by tailoring it to specific clinical profiles and their developmental dynamics.”

Source: Yale University

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Volcanoes offer ‘time-lapse’ clues to early Earth

13 hours 39 min ago

Samoan volcanoes have yielded evidence of the planet’s early formation still trapped inside the Earth.

Known as hotspots, volcanic island chains such as Samoa can have ancient primordial signatures from the early solar system that have somehow survived billions of years.

Matthew Jackson, an associate professor in the department of Earth science at University of California, Santa Barbara, and colleagues utilized high-precision lead and helium isotope measurements to unravel the chemical composition and geometry of the deep mantle plume feeding Samoa’s volcanoes. Their findings appear in Nature.

Where the mantle melts

In most cases, volcanoes are located at the point where two tectonic plates meet, and are created when those plates collide or diverge. Hotspot volcanoes, however, are not located at plate boundaries but rather represent the anomalous melting in the interior of the plates.

Such intraplate volcanoes form above a plume-fed hotspot where the Earth’s mantle is melting. The plate moves over time—at approximately the rate human fingernails grow (three inches a year)—and eventually the volcano moves off the hotspot and becomes extinct. Another volcano forms in its place over the hotspot and the process repeats itself until a string of volcanoes evolves.

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“So you end up with this linear trend of age-progressive volcanoes,” Jackson says. “On the Pacific plate, the youngest is in the east and as you go to the west, the volcanoes are older and more deeply eroded. Hawaii has two linear trends of volcanoes—most underwater—which are parallel to each other. There’s a southern trend and a northern trend.”

Because the volcanic composition of parallel Hawaiian trends is fundamentally different, Jackson and his team decided to look for evidence of this in other hotspots.

In Samoa, they found three volcanic trends exhibiting three different chemical configurations as well as a fourth group of a late-stage eruption on top of the third trend of volcanoes. These different groups exhibit distinct compositions.

“Our goal was to figure out how we could use this distribution of volcano compositions at the surface to reverse-engineer how these components are distributed inside this upwelling mantle plume at depth,” Jackson says.

Primordial material

Each of the four distinct geochemical compositions, or endmembers, that the scientists identified in Samoan lavas contained low Helium-3 (He-3) and Helium-4 (He-4) ratios. The surprising discovery was that they all exhibited evidence for mixing with a fifth, rare primordial component consisting of high levels of He-3 and He-4.

“We have really strong evidence that the bulk of the plume is made of the high Helium-3, -4 component,” Jackson says.

“That tells us that most of this plume is primordial material and there are other materials hosted inside of this plume with low Helium-3, -4, and these are likely crustal materials sent into the mantle at ancient subduction zones.”

The unique isotopic topology revealed by the researchers’ analysis showed that the four low-helium endmembers do not mix efficiently with one another. However, each of them mixes with the high He-3 and He-4 component.

“This unique set of mixing relationships requires a specific geometry for the four geochemical flavors within the upwelling plume: They must be hosted within a matrix that is composed of the rare fifth component with high He-3,” Jackson explains.

“This new constraint on plume structure has important implications for how deep mantle material is entrained in plumes, and it gives us the clearest picture yet for the chemical structure of an upwelling mantle plume.”

Coauthors of the paper are from the Woods Hole Oceanographic Institution, the University of Hawaii, and the California Institute of Technology. The National Science Foundation funded the work.

Source: UC Santa Barbara

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How energy loss can make lasers more intense

13 hours 39 min ago

Energy loss in optical systems, such as lasers, is a chief hindrance to their performance and efficiency and it occurs on an ongoing, frustrating basis.

To help laser systems overcome loss, operators often pump the system with an overabundance of photons, or light packets, to achieve optical gain.

“This turns the conventional textbook understanding of lasers upside down.”

But now scientists have demonstrated a more effective—yet counterintuitive—way to reap energy gains: they add loss to the laser system. In other words, they’ve invented a way to win by losing.

“Too much of something can be really detrimental,” says Sahin Kaya Ozdemir, a research scientist at Washington University in St. Louis. “If you pump in more energy to get more laser intensity, and it’s too strong, you can get a sudden drop in the laser performance.

“It is counterintuitive and paradoxical to see that the lasing starts and its output power becomes higher and higher when more loss is introduced, that is, less pumping is used,” adds Ozdemir. “This turns the conventional textbook understanding of lasers upside down.”

The results were published recently in the journal Science.

Three experiments

In the first experiment, an international team showed they could change the coupling between two microresonators by changing their distance and introduce on-demand loss controllably to one of them.

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In a second experiment, by varying the loss, they manipulated the coupling regimes and estimated the intensity of light in the two resonators and surprisingly found an initial decrease in total intensity of the two resonators followed by an increase, and finally a rebirth of strong light intensity as the loss was increased.

“The loss added beyond a critical value increased the total light intensity and its distribution between the resonators,” says Bo Peng, a graduate student.

In a third experiment, the researchers report achieving two nonlinear phenomena, the Thermal Effect and a Raman gain in silica despite increasing loss.

“Light intensity is a very important parameter in optical systems, and here we have provided a new route to increase light intensity by modulating loss in the system,” says Lan Yang, an associate professor in electrical and systems engineering. “Instead of the standard method of adding more energy into the system, we’re offering a more energy-efficient method.”

Beyond lasers

Yang says that in addition to lasing improvements, their findings could lead to new schemes and techniques for controlling and reversing the effects of loss in various other physical systems, such as in photonic crystal activities, plasmonic structures, and metamaterials.

The experimental system that the researchers used consists of two tiny directly coupled silica microtoroid (doughnut-shaped) resonators, each coupled to a different fiber-taper coupler that aids in guiding light from a laser diode to photodetectors; the fiber is tapered in the middle so that light can between the fibers and the resonators.

Yang says the concept will work in any coupled physical system.

Loss is delivered to one of the microresonators by a tiny device, a chromium-coated silica nanotip, whose position within the evanescent field (leaked-out light) of one of the resonator was controlled by a nanopositioner that operates at a minuscule 20-nanometer resolution.

“Chromium is used because it’s a strongly absorbing material at a wavelength of 1550 nanometers, and it gives a good dose of loss,” Peng explains.

The ‘exceptional point’

Another nanopositioner controls the coupling strength between the resonators by tuning their distance.

The loss-gain phenomenon occurs near a feature called the exceptional point, which has a dramatic effect on a system’s properties. The exceptional point has contributed to a number of counterintuitive activities and results in recent physics studies.

“When we steer the system through the exceptional point, the symmetric distribution of the fields between two resonators become asymmetric,” Ozdemir says. “Asymmetric distribution leads to field localization, increasing the light intensity in one of the resonators, in this case the resonator with less loss.

“As a result, all nonlinear processes, which depend on the intensity of light, in that subsystem become affected.”

“The beauty of this work is in how we came to provide new schemes and techniques to engineer a physical system by controlling loss,” Yang adds. “Normally, loss is considered bad, but we actually take advantage of this and reverse the bad effect. We used the laser to show it.”

The Presidential Early Career Award for Scientists and Engineers, Army Research Office, US Department of Energy, RIKEN iTHES Project, MURI Center for Dynamic Magneto-Optics, Grant-in-Aid for Scientific Research, Vienna Science and Technology Fund, and the Austrian Science Fund supported the project, which also included researchers from RIKEN in Japan and the Vienna University of Technology in Austria.

Source: Washington University in St. Louis

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Staph bacteria gang up to outsmart antibiotics

14 hours 36 min ago

Relatively harmless bacteria can turn deadly when they start sharing resources with their “friends,” new research shows.

One way that Staphylococcus aureus and other pathogens can become resistant to antibiotics is to change the way they generate energy and become small and weak “colony variants,” says Eric Skaar, professor of pathology, microbiology, and immunology at Vanderbilt University.

“The question has been: how do bacteria that are less fit and grow poorly in the laboratory cause such persistent infections in humans?”

Current studies support the notion that antibiotic-resistant staph bacteria, including methicillin-resistant (MRSA) strains, can exchange nutrients with each other and even with other bacterial species, including the “normal” microbes of the microbiome, to increase their virulence during an infection.

The new findings, published in the journal Cell Host & Microbe, challenge infectious disease dogma, Skaar says.

“The thinking has been that if an infection becomes resistant to antibiotics, then the resistant organisms appeared clonally, meaning they’re all genetically the same.”

Swap molecules

Skaar and colleagues wondered if perhaps instead “there are a bunch of organisms that became resistant in different ways and that can exchange the molecules they’re each individually missing.”

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Researchers tested this hypothesis by mixing together two different small colony variant strains of staph—one that can’t produce heme and the other that can’t make menaquinone. They found that in culture, these strains exchanged the two metabolites and grew as if they were wild-type staph.

Next, they tested the idea in a mouse model of the bone infection osteomyelitis. Antibiotic-resistant small colony variant S. aureus is the cause of chronic and difficult to treat osteomyelitis and also of lung infections in patients with cystic fibrosis (CF).

The investigators demonstrated that either staph strain alone (heme- or menaquinone-deficient) caused only minimal bone infection, but mixed together, they caused a fully virulent and bone-destroying infection.

“In bone, these bacteria are trading molecules,” Skaar says.

Big bunch of bullies

Researchers then isolated samples of staph small colony variants and normal bacteria from the lungs of CF patients.

When individual CF staph small colony variants were mixed together in culture, they grew like wild-type bacteria. Likewise, co-culture of CF staph small colony variants with normal microbiome bacterial species also enhanced the growth of staph in culture.

“The microbiome of a cystic fibrosis patient’s lungs can provide nutrients to these small colony variants and revert them to wild-type behavior,” Skaar says.

“Our findings show that these antibiotic-resistant infections are not what we thought they were—they’re not a single strain of bacteria with a single lesion leading to the small colony variant phenotype. Instead, they’re a mixed population of organisms that are sharing nutrients.

“They act like a big group of bullies until you hit them with drugs, then they stop sharing resources and are resistant. When the drugs go away, they start sharing resources again and get even tougher.

“We’re now a little bit smarter about how these organisms are behaving in an infection, which I think we can use to inform new treatment approaches,” Skaar says.

Preventing the nutrient exchange, for example, may offer a new therapeutic strategy against these antibiotic-resistant organisms.

The National Institutes of Health supported the research.

Source: Vanderbilt University

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Does IBS cause men more social trouble?

15 hours 12 min ago

A new study suggests that irritable bowel syndrome (IBS) causes more interpersonal difficulties for men than for women. The findings challenged the investigators’ expectations.

“Our findings underscore the significance of studying gender-based differences in how people experience the same disease or condition,” says Jeffrey Lackner, professor of medicine in the University at Buffalo School of Medicine and Biomedical Sciences.

IBS is among the most common, disabling, and intractable gastrointestinal disorders. Symptoms include abdominal pain, diarrhea, and/or constipation. It is estimated to affect between 25 million and 50 million Americans.

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Because IBS is twice as common among women as men, far less is known about how men experience the disease.

The new study reveals little difference between men and women in the severity of their gastrointestinal symptoms.

Previous psychological research findings had suggested that males with IBS take on stereotypically feminine traits, including passive and accommodating behaviors, according to Lackner and his coauthors.

But this study finds that men report feeling cold and detached, and as though they have a need to dominate their relationships with others. Men, not women, report having more difficulties in interpersonal relationships.

“That discrepancy underscores our need to move beyond clinical intuition and anecdote, and systematically study the different ways that each gender experiences disease in general,” says Lackner.

The findings may have relevance to the ways that male IBS patients interact with their doctors, he says. “Patients who have a domineering and distant interpersonal style may need to work more closely with the physicians,” says Lackner.

Coauthors are from Wayne State, Northwestern University, and University of Wisconsin-Parkside. National Institutes of Health funded the work.

The study was part of a poster session yesterday at the American College of Gastroenterology (ACG) annual meeting in Philadelphia.

Source: University at Buffalo

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The internet isn’t broken. It’s asleep

15 hours 12 min ago

The internet runs pretty much 24 hours a day in some parts of the world, but in other places—notably in Asia, South America, and Eastern Europe—the internet “sleeps.”

Researchers say knowing more about that pattern will help them avoid confusing a sleeping internet with a broken one. It will also help them develop better systems to measure and track internet outages, such as those that struck the New York area after Hurricane Sandy.

“The internet is important in our lives and businesses, from streaming movies to buying online. Measuring network outages is a first step to improving internet reliability,” says John Heidemann, research professor at the USC Viterbi School of Engineering’s Information Sciences Institute.

Heidemann collaborated with USC’s Lin Quan and Yuri Pradkin on the study, which will be presented at the 2014 ACM Internet Measurements Conference on November 5.

Their study found that the richer a country is, the more likely it is that the internet will be up and running 24/7.

“This work is one of the first to explore how networking policies affect how the network is used,” Heidemann says.

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There are 4 billion IPv4 internet addresses. Heidemann and his team pinged about 3.7 million address blocks (representing about 950 million addresses) every 11 minutes over the span of two months, looking for daily patterns.

“This data helps us establish a baseline for the internet—to understand how it functions, so that we have a better idea of how resilient it is as a whole, and can spot problems quicker,” Heidemann says.

“We have grown our coverage to 4 million blocks [more than 1 billion addresses] as internet use grows,” Heidemann adds.

He hopes that long-term observations will help guide internet operation.

The Department of Homeland Security, Science and Technology Directorate; HSARPA, Cyber Security Division via the Air Force Research Laboratory, Information Directorate and SPAWAR funded the research.

Source: USC

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Is red the color of love for monkeys, too?

Fri, 10/17/2014 - 10:30

When researchers showed pictures of monkey rear ends to other monkeys, they found females showed a preference for males if their backsides were surrounded by the color red.

While past studies have suggested the color red can intensify feelings of attraction and anger in people, the findings with monkeys suggest biology may help explain the “red effect.”

“Previous research shows that the color red in a mating context makes people more attractive, and in the fighting context makes people seem more threatening and angry,” says Benjamin Y. Hayden, a coauthor of the study and professor in brain and cognitive sciences at the University of Rochester.

Hayden, whose research often involves primates, and Andrew J. Elliot, a professor of psychology at Rochester who has published several articles on humans and the red effect and coauthor of the study, sought to uncover what causes humans’ response to the color.

Is it triggered simply by repeated cultural exposures, or is there is a biological basis that may help explain why the color tends to amplify human emotions?

As Hayden put it, “is this just because every year on Valentine’s Day we see these red things everywhere and it creates a link for us between the color red and romance, or is it really a fundamental thing rooted in our biology?”

Why monkeys?

One way to test for biological influence would be to assess reactions in individuals who have not been conditioned to associate the color red with romance, Hayden says.

“What if we could test this in someone who is not even human, but was exposed to a lot of the same evolutionary pressures? Well, that would be a monkey,” he says. “So, we conducted experiments to see if monkeys would have similar biases as humans, and in a nutshell the answer is, yes, it seems like they do.”

The new study, which appears in the journal Evolution and Human Behavior, involved rhesus monkeys (Macaca mulatta) from a free-ranging population of approximately 1,000 residing at the Cayo Santiago field site in Puerto Rico. The animals live in naturally formed social groups and are habituated to human observation.

The researchers conducted two trials that measured the amount of time the primates looked at black and white images of the hindquarters of adult monkeys. The stimuli, which included images of both sexes, were surrounded by an “extraneous” color, framed by either red or blue. The researchers also used an image of a common shell found on the island as a control data point.

Red and rear ends

Hayden notes that a standard measure to gauge interest in those who don’t have language—primates or babies, for example—is by how long they look at a given object. The longer the gaze indicates a greater amount of interest.

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In the first trial, the researchers displayed sequential images of male hindquarters surrounded—in random order—by frames of red or blue, to adult monkeys of both sexes. They were also presented with the shell image.

The researchers found a significant female bias toward the images of male hindquarters, but only when a red frame surrounded the image. “To our knowledge,” the researchers say, “this is the first demonstration of an extraneous color effect in non-human primates.”

In a second trial, the researchers displayed images of female hindquarters surrounded, again by either a red or blue frame. Female monkeys did not show a preference for other female hindquarters, regardless of the color of the surrounding frame.

But, surprising to the researchers, male monkeys did not show a preference for the female hindquarters, either, even when surrounded by the color red.

The researchers say additional work is needed to understand why males did not respond to the extraneous colors. One possibility is that the reproductive state of females is reflected in facial color changes rather than changes in the hindquarters. Images of females, which were restricted to the hindquarter region, may have been too limited to elicit male responses.

That female rhesus monkeys’ interest in images of the opposite sex appears to be influenced by extraneous color suggests that the “red effect” is not unique to humans. Instead, the researchers argued, it appears to be supported by an “evolved biological mechanism.”

Neither males nor females displayed a bias toward the shell image regardless of the color of its frame.

Kelly D. Hughes, a doctoral candidate at the University of Rochester, is lead author of the study. James P. Higham, an assistant professor of anthropology at New York University, and William L. Allen, a postdoctoral fellow in anthropology at the University of Hull, are coauthors.

The Sloan Foundation, NIDA, and two Reach fellowships from the University of Rochester to undergraduate research assistants supported the work. The population of rhesus monkeys at Cayo Santiago is currently supported by the National Center for Research Resources, the Office of Research Infrastructure Programs of the National Institute of Health, and the Medical Science Campus of the University of Puerto Rico.

Source: University of Rochester

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Terrified prey change where plants grow in savannas

Fri, 10/17/2014 - 09:46

The classic food chain on the savanna may be more complicated than prey eats plants and predator eats prey.

Researchers conducted fieldwork at the Mpala Research Centre in Laikipia, Kenya, 100 kilometers north of the equator in a savanna.

“Where the prey do and do not go, it turns out, strongly influences the types of plants you find in these habitats.”

The team looked at three components of the ecosystem: the predators, including leopards and wild dogs; the leaf-eating impala; and two species of acacia trees, one defended by more thorns than the other.

“We’d like to know if the forage that impala don’t eat in dangerous areas can be used to save people’s livestock, especially in drought years. It would be very interesting to understand these types of linkages among carnivores, their prey, and people,” says Todd Palmer, associate professor pf biology at University of Florida.

“The work is essentially about the importance of predators in Africa in shaping the ecosystems in which they live. In a nutshell, predators create a landscape of fear, where their prey are too frightened to go into places where predators like to hang out.

“And where the prey do and do not go, it turns out, strongly influences the types of plants you find in these habitats.”

Claws, teeth, and thorns

For the study, published in the journal Science, the team using GPS telemetry to follow the movement of both predators and prey. They observed that impala preferred to feed in less-risky, more open areas populated by herds of their kin, including other African ungulates such as dik-dik and elephants.

In these less risky areas, the impala suppress the abundance of their favorite, less thorny, food plants. As a result, the acacia trees in these areas are better defended with an abundance of thorns, and thus, less appealing to the herbivores.

“If you walked into an area in the African bush and found it characterized by very thorny and well defended plants, you might never think that the “thorniness” of the area was a result of where predators like to stalk prey,” Palmer says. “Yet, that’s exactly what we show.”

Basically, these herbivores “are caught between a rock and a hard place. They must avoid the claws and teeth of their predators and the thorns and chemicals of their food.”

Ultimately, the question the researchers want to answer is what kinds of widespread effects do humans have by driving the decline of top predators and their habitats?

Researchers say the findings could have broad implications for the habitats in which animals live.

One benefit might be for the people who live in these areas, says Palmer. “Because it’s a human-occupied landscape, we are interested in learning more about how people interact with this food chain.”

Adam T. Ford, a doctoral student at the University of British Columbia is the study’s lead author.

Source: University of Florida

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Diving birds at risk without fish for dinner

Fri, 10/17/2014 - 07:57

Diving birds that winter in the Salish Sea (between British Columbia and Washington) were 11 times more likely to be in decline than non-diving birds, a new study finds.

Also, populations of diving birds that rely on forage fish, such as Pacific herring, are 16 times more likely to decline than those with more varied diets.

The study lends credence to what scientists have long suspected: “If you want to recover birds, you need to recover the food that they’re eating,” says coauthor Joe Gaydos, a wildlife veterinarian at School of Veterinary Medicine at the University of California, Davis.

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“This could help puffins, western grebes, common murres, and other diving species recover.”

Wildlife agencies from the US and Canada have separately monitored wintering marine birds in the Salish Sea. Yet birds living there do not recognize its borders. So UC Davis Wildlife Health Center scientists combined 17 years of wintering bird data from both Washington and British Columbia, as well as Audubon Christmas Bird Counts, to develop a risk assessment for the birds and better understand what is driving declines across the entire region.

“For example, from looking at years of public health trends we know that humans can have certain behaviors that make them more likely to develop adult diabetes,” says lead author Ignacio Vilchis, a postdoctoral research fellow with the UC Davis Wildlife Health Center at the time of the study and now a research scientist at Scripps Institution of Oceanography.

“You can interpret wildlife trends similarly, except that habits that place certain wildlife species at risk of decline are the result of much longer time pressures, like natural selection and evolution.

“So it becomes clear that environmental changes are the actual threat. We therefore think the smoking gun here is that there must be less forage fish available in the Salish Sea for diving birds.”

The fish factor

The researchers found 148 bird species that frequent the Salish Sea during winter. Of those, 39 were considered the core wintering marine bird community. The scientists separated the birds into two groups: those experiencing declining populations and those that were not. They then looked for shared risk factors and found that diving and diet were the main ecological traits driving the decline.

The study concludes that a combination of reasons is probably making diving birds more at risk of declines—they get entangled in fishing gear, are more vulnerable to oil spills, and require more calories than most non-diving birds.

But the researchers propose that long-term changes in the availability of forage fish are pushing the declines. Half of all Pacific herring stocks in Puget Sound are low, as are herring stocks throughout the Salish Sea.

Pacific herring and other forage fish, like surf smelt and Pacific sand lance that spawn in coastal habitats may also be negatively affected by changes in Puget Sound, where 93 percent of the coastline has been altered by dredging, seawalls, and removal of vegetation.

“Now that we have a much better idea what is going on, we can hopefully address it,” Vilchis says.

Gaydos is also director of the SeaDoc Society, a program of the UC Davis Karen C. Drayer Wildlife Health Center.

The SeaDoc Society, Canadian Wildlife Service, and Washington state funded the work, which appears in the journal Conservation Biology.

Source: UC Davis

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We still have no clue what Super-Earths are made of

Fri, 10/17/2014 - 07:46

Despite discovering hundreds of exoplanets known as “super-Earths,” astronomers still don’t know what they’re made of.

They’re larger than Earth but smaller than Nepture, and appear to be the most common type of exoplanet identified so far.

A super-Earth could be just that: a bigger version of Earth—mostly rocky, with an atmosphere. Then again, it could be a mini-Neptune, with a large rock-ice core encapsulated in a thick envelope of hydrogen and helium.

Or it could be a water world—a rocky core enveloped in a blanket of water and perhaps an atmosphere composed of steam (depending on the temperature of the planet).

“It’s really interesting to think about these planets because they could have so many different compositions, and knowing their composition will tell us a lot about how planets form,” says Heather Knutson, assistant professor of planetary science at California Institute of Technology (Caltech).

Exoplanet GJ 1214b has been a popular target for the Hubble Space Telescope since its discovery in 2009. (Credit: NASA/ESA/D. Aguilar, Harvard-Smithsonian Center for Astrophysics)

For example, because planets in this size range acquire most of their mass by pulling in and incorporating solid material, water worlds initially must have formed far away from their parent stars, where temperatures were cold enough for water to freeze. Most of the super-Earths known today orbit very close to their host stars. If water-dominated super-Earths turn out to be common, it would indicate that most of these worlds did not form in their present locations but instead migrated in from more distant orbits.

In addition to thinking about exoplanets, researchers use space-based observatories like the Hubble and Spitzer Space Telescopes to learn more about the distant worlds. For example, they analyze the starlight that filters through a planet’s atmosphere as it passes in front of its star to learn about the composition of the atmosphere.

Molecular species present in the planet’s atmosphere absorb light at particular wavelengths. Therefore, by using Hubble and Spitzer to view the planet and its atmosphere at a number of different wavelengths, the researchers can determine which chemical compounds are present.

To date, nearly two dozen planets have been characterized with this technique. These observations have shown that the enormous gas giant exoplanets known as hot-Jupiters have water, carbon monoxide, hydrogen, helium—and potentially carbon dioxide and methane—in their atmospheres.

Too cloudy

However, right now super-Earths are the hot topic. Unfortunately, although hundreds of super-Earths have been found, only a few are close enough and orbiting bright enough stars for astronomers to study in this way using currently available telescopes.

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The first super-Earth that the astronomical community targeted for atmospheric studies was GJ 1214b, in the constellation Ophiuchus. Based on its average density (determined from its mass and radius), it was clear from the start that the planet was not entirely rocky.

However, its density could be equally well matched by either a primarily water composition or a Neptune-like composition with a rocky core surrounded by a thick gas envelope. Information about the atmosphere could help astronomers determine which one it was: a mini-Neptune’s atmosphere should contain lots of molecular hydrogen, while a water world’s atmosphere should be water dominated.

GJ 1214b has been a popular target for the Hubble Space Telescope since its discovery in 2009.

Disappointingly, after a first Hubble campaign led by researchers at the Harvard-Smithsonian Center for Astrophysics, the spectrum came back featureless—there were no chemical signatures in the atmosphere. After a second set of more sensitive observations led by researchers at the University of Chicago returned the same result, it became clear that a high cloud deck must be masking the signature of absorption from the planet’s atmosphere.

“It’s exciting to know that there are clouds on the planet, but the clouds are getting in the way of what we actually wanted to know, which is what is this super-Earth made of?” explains Knutson.

Atmosphere without hydrogen?

Now Knutson’s team has studied a second super-Earth: HD 97658b, in the constellation Leo. The new findings are reported in the Astrophysical Journal.

The researchers used Hubble to measure the decrease in light when the planet passed in front of its parent star over a range of infrared wavelengths in order to detect small changes caused by water vapor in the planet’s atmosphere.

However, again the data came back featureless. One explanation is that HD 97658b is also enveloped in clouds. However, Knutson says, it is also possible that the planet has an atmosphere that is lacking hydrogen. Because such an atmosphere could be very compact, it would make the telltale fingerprints of water vapor and other molecules very small and hard to detect.

“Our data are not precise enough to tell whether it’s clouds or the absence of hydrogen in the atmosphere that’s causing the spectrum to be flat,” she says. “This was just a quick first look to give us a rough idea of what the atmosphere looked like. Over the next year, we will use Hubble to observe this planet again in more detail. We hope those observations will provide a clear answer to the current mystery.”

It appears that clouds are going to continue to pose a real challenge in studies of super-Earths, so Knutson and other researchers are working to understand the composition of the clouds around these planets and the conditions under which they form. The hope is that they will get to the point where they can predict which worlds will be shrouded in clouds.

“If we can then target planets that we think should be cloud-free, that will help us make optimal use of Hubble’s time,” she says.

There is only one more known super-Earth that can be targeted for atmospheric studies with current telescopes, Knutson says. But new surveys, such as NASA’s extended Kepler K2 mission and the Transiting Exoplanet Survey Satellite (TESS), slated for launch in 2017, should identify a large sample of new targets.

While astronomers would love to study exoplanets the size of Earth, these worlds are just a bit too small and too difficult to observe with Hubble and Spitzer. NASA’s James Webb Space Telescope, which is scheduled for launch in 2018, will provide the first opportunity to study more Earth-like worlds.

“Super-Earths are at the edge of what we can study right now,” Knutson says. “But super-Earths are a good consolation prize—they’re interesting in their own right, and they give us a chance to explore new kinds of worlds with no analog in our own solar system.”

Source: Caltech

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Alpine butterflies survived by working their ‘net’

Fri, 10/17/2014 - 07:00

Good connections helped alpine butterflies survive a serious population crash in 2003 that killed off more than 60 percent of the population.

The alpine butterfly lives in high-altitude meadows of the Rocky Mountains. A new study focused on a network of them living along three ridge tops in Alberta, Canada.

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The butterflies’ lives revolve around access to their host plants, the lanceleaf stonecrop and ledge stonecrop. Mother butterflies lay their eggs near these plants, where the larvae overwinter. A certain amount of snow cover is required to regulate the eggs’ temperature before hatching.

But in the winter of 2003, the amount of snow needed didn’t come.

Here’s where things could have gotten very bad for this population of alpine butterfly.

But it didn’t, at least not for the long term. Enough patches of butterfly activity remained that could easily connect with each other, allowing the population to make a rebound.

“The population crashed, but it was through their connectivity that they were able to maintain genetic diversity,” says Serena Caplins, a doctoral student of population biology at University of California, Davis and lead author of the study published in the journal Proceedings of the Royal Society B.

Scientists from the University of Alberta and University of Cincinnati had been collecting data on this network of alpine butterflies since 1995. This gave researchers an ideal opportunity to compare genetic differences in the butterflies before and after the 2003 population crash.

Isolated butterflies

Caplins and colleagues found that patches with low connectivity lost more genetic diversity than those with high connectivity. In short, the easier it was for the butterflies to find each other, the more genetic diversity remained.

Yet forests responding to warming weather are encroaching on the butterflies’ meadow habitat, making them more isolated from each other. For the butterflies, these growing, warming forests are akin to an interstate through a mountain—fragmenting their habitat and cutting them off from other alpine butterflies. If they continue to separate and there’s another population crash, it could be harder for them to restore genetic diversity.

The study provides insight into the importance of providing connections—either through greenbelts or greater habitat protection—so populations can rebound and maintain genetic diversity in the face of climate change and other stressors. Genetic diversity, in turn, can lead to healthier populations that are more prepared to weather environmental impacts.

“Overall this was positive,” says Caplins of the results. “It suggests some of these populations may be more robust than we thought, but it is a warning that if things continue to get worse, and connectivity decreases, it could be a problem down the road.”

Researchers from University of British Columbia, Trent University, University of Alberta, and the University of Cincinnati were coauthors of the study.

The National Science Foundation, National Sciences and Engineering Research Council of Canada, Canada Research Chairs and Canadian Foundation for Innovation funded the study. Collaboration among several institutions was supported by a Distributed Graduate Seminar in Landscape Genetics from the National Center for Ecological Analysis and Synthesis.

Source: UC Davis

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Food or sex? It’s a no-brainer for male worms

Fri, 10/17/2014 - 06:32

Male nematodes will ignore food when it’s time to find a mate, a behavior not seen in their female counterparts.

The results, which appear today in the journal Current Biology, may point to how subtle changes in the brain’s circuitry dictate differences in behavior between males and females.

“While we know that human behavior is influenced by numerous factors, including cultural and social norms, these findings point to basic biological mechanisms that may not only help explain some differences in behavior between males and females, but why different sexes may be more susceptible to certain neurological disorders,” says Douglas Portman, an associate professor in the department of biomedical genetics and Center for Neural Development and Disease at the University of Rochester and lead author of the study.

The findings were made in experiments involving C. elegans, a microscopic roundworm that has long been used by researchers to understand fundamental mechanisms in biology—including human biology.

C. elegans is particularly useful in the study of the nervous system, and scientists understand in great detail the development, function, and multiple connections of its entire neural network.

Wandering males

The study focuses on the activity of a single pair of neurons found in C. elegans—called AWA—that control smell. Smell, along with taste and touch, are critical sensory factors that dictate how C. elegans understands and navigates its environment, including finding food, avoiding danger, and locating a mate.

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There are two sexes of C. elegans, males and hermaphrodites. Though the hermaphrodites are able to self-fertilize, they are also mating partners for males, and are considered to be modified females.

It has been previously observed that males and hermaphrodites act differently when exposed to food. If placed at a food source, the hermaphrodites tend to stay there. Males, however, will leave the food source and “wander”—scientist believe they do this because they are in search of a mate.

The researchers discovered that the sensory mechanisms—called chemoreceptors—of the AWA neurons were regulated by the sexual identity of these cells, which, in turn, controls the expression of a receptor called ODR-10. These receptors bind to a chemical scent that is given off by food and other substances.

In hermaphrodites, more of the ODR-10 receptors are produced, making the worms more sensitive—and thereby attracted—to the presence of food.

In males, fewer of these receptors are active, essentially suppressing their ability—and perhaps desire—to find food. However, when males were deprived of food, they produced dramatically higher levels of this receptor, allowing them to temporarily focus on finding food.

Worms in a petri dish

To confirm the role of these genetic differences between the sexes on behavior, the researchers designed a series of experiments in which they observed the activity of C. elegans when placed in a petri dish and confronted with the option to either feed or go in search of a mate. The hermaphrodites were place in the center of the dish at a food source and, as expected, they stayed put.

The males were placed in their own individual food sources at the periphery of the dish. As a further obstacle between the males and their potential mates, an additional ring of food surrounded the hermaphrodites in the center of the dish.

The males in the experiment consisted of two categories, one group with a normal genetic profile and another group that had been engineered by the researchers to overexpress the ODR-10 receptor, essentially making them more sensitive to the smell of food.

The researchers found that the normal worms left their food source and eventually made their way to the center of the dish where they mated with the hermaphrodites.

Strange behavior

The genetically engineered males were less successful at finding a mate, presumably because they were more interested in feeding. By examining the genetic profile of the resulting offspring, the scientists observed that the normal males out-produced the genetically engineered males by 10 to one.

In separate experiments, the researchers were also able to modify the behavior of the hermaphrodites by suppressing the ODR-10 receptors, causing them to act like males and abandon their food source.

“These findings show that by tuning the properties of a single cell, we can change behavior,” says Portman. “This adds to a growing body of evidence that sex-specific regulation of gene expression may play an important role in neural plasticity and, consequently, influence differences in behaviors—and in disease susceptibility—between the sexes.”

Additional researchers from Rochester and Brandeis University collaborated on the study, which was funded by the National Institute of General Medical Sciences, the National Science Foundation, the Human Frontiers Science Program, and the National Alliance for Autism Research /Autism Speaks.

Source: University of Rochester

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Do cadavers make the best anatomy teachers?

Fri, 10/17/2014 - 05:46

Computer simulations are an increasingly popular way to teach anatomy in college, but students learn better with human cadavers, according to new research.

Cary Roseth, associate professor of educational psychology at Michigan State University, says the study suggests cadaver-based instruction should continue in undergraduate human anatomy, a gateway course to medical school, nursing, and other health and medical fields.

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In the United States, most anatomy courses still emphasize the use of cadavers, although in many cases digital technologies supplement the instruction. Yet there is a growing debate over whether cadavers are needed at all—some medical schools in Australia and the United Kingdom have stopped using cadavers to teach anatomy altogether.

The research, which appears in the September/October issue of Anatomical Sciences Education, is the only known scientific study to directly compare the effects of cadaver-based and computer-simulation instruction on students’ learning of cadaver-based structures.

“Our findings indicate that educational technology can enhance anatomy instruction but is unlikely to fully replace cadavers,” says Roseth, a coauthor of the study.

A better question, Roseth says, is how to properly balance the use of digital technologies with cadaver instruction in anatomy classrooms. The controversy has intensified in recent years as the increasing costs of cadaver instruction goes up against the decreasing costs and increasing capabilities of modern technologies.

Roseth’s coauthors are Andrew Saltarelli, a former Michigan State doctoral student who’s now an instructional designer at Stanford University, and William Saltarelli, an anatomy professor at Central Michigan University.

Higher grades

The researchers studied a semester-long undergraduate anatomy lecture course with 233 students who were assigned to one of 14 labs. One group of students learned on a cadaver and was tested on a cadaver. Another group of students learned on a multimedia learning system and also was tested on a cadaver.

The students were tested on two things: identifying parts of the body and explaining how they worked.

On identification, the students who learned on a cadaver scored, on average, about 16 percent higher than those who learned on the simulated system.

On explanation, the students who learned on a cadaver scored about 11 percent higher. This finding was particularly surprising, Roseth says, given that one of the benefits of the multimedia program is that it can show how parts of the body work—such as blood flow through carotid arteries—while a cadaver cannot.

The difference in the average scores, Roseth notes, was essentially the difference between one grade.

“When it comes to learning actual—rather than simulated—human anatomy, the digital representations, even with all of their additional affordances, did not work as well as the cadaver,” Roseth says.

Source: Michigan State University

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How 60 of the weirdest birds are related

Fri, 10/17/2014 - 04:42

A family called cotingas include some of the loudest, weirdest-looking, brightest, least-understood birds on the planet. Some have bulbous crests, long fleshy wattles, or Elvis-worthy pompadours. Others have shockingly bright feathers—electric blue, deep purple, or screaming orange.

How did they get that way? What twisting evolutionary path resulted in the origin of more than 60 species that barely seem to be related each other?

A new phylogeny, or evolutionary “tree of life,” makes finding answers to these questions possible. The findings make possible new discoveries about the cotingas, which are native to Central and South America.

“They are so variable that even defining just what a cotinga is has been a difficult question,” says lead author Jake Berv, a PhD student in the Fuller Evolutionary Biology Lab at the Cornell Lab of Ornithology.

This circular rendition of the “tree of life” shows nearly all the sizes, colors, and adaptations for the continga family of birds radiating outward from the center and its common ancestor. Both males and females are shown except where plumage for both is the same. View larger. (Credit: Courtesy of the Handbook of the Birds of the World. Vol. 9. Cotingas to Pipits and Wagtails, Lynx Edicions 2004)

“Our study provides comprehensive insight into how nearly all the cotinga species are related to each other going all the way back to their common ancestor. No previous attempts to understand the evolutionary history of this group have included genetic samples from nearly all the existing species,” says Berv.

Berv began sequencing DNA samples and compiling data in late 2010 while working as a lab technician at Yale University with coauthor Rick Prum, a leading expert on cotingas. For species whose DNA had never been sequenced before, the researchers took small tissue samples from the toe pads of museum specimens.

Understanding how one species is related to another within this group allows scientists to trace the evolution of specific traits and behaviors.

Many mates, brighter colors?

For example, Berv and Prum wanted to learn if the evolution of differently colored males and females in this bird group (known as sexual dimorphism) is directly linked to a breeding system in which males have multiple mates (known as polygyny—a fairly widespread practice in some birds, including the familiar Red-winged Blackbird).

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Darwin first theorized that the increased pressure of sexual selection in polygynous birds spurred the development of color differences between the sexes. That is to say, in situations where males have the chance to mate with many female birds, there’s pressure for them to step up their game by adopting brilliant colors. This appears to be true for many species—but not the cotingas.

When Berv and Prum examined patterns of evolution for these two traits across their new tree of life, there was no significant match. There have been many more evolutionary changes in color than there have been for breeding system. Berv says these traits may be evolutionarily “decoupled” in the cotingas.

However, sexual selection appears to have played a role in the evolution of sexual differences other than color in some cotingas.

“In one case, the Screaming Piha, the males and females look alike but the male sings one of the loudest songs on the planet,” says Yale’s Rick Prum. “That means male-female plumage difference alone is not evidence for sexual selection because sexual selection is also driving other traits such as voice and behavior.”

Crazy colors

Though the researchers didn’t find a link between the coloration of males and females and the evolution of polygynous breeding systems, Prum says some form of sexual selection almost certainly did play a role in the eye-popping colors some cotingas display.

Some species have evolved a variety of colors seen only in this group of birds, such as the glowing orange cowl of the Andean Cock-of-the-Rock, the fluorescence of the Turquoise Cotinga, or the blue-and-maroon combo of the Banded Cotinga.

“Some cotinga colors are not produced by pigments,” Berv explains. “Some of these birds have evolved cool nanoscale feather structures made with feather protein molecules. The nanostructures scatter light and produce visible color the birds use in sexual signaling.”

Figuring out how these feather structures evolved is an area of future study. In fact, “the sky’s the limit,” according to Prum, who notes other areas of study could include the evolution of elaborate courtship displays, clutch sizes, or the vocal organs that produce the ear-splitting sounds of the raucous bellbirds and pihas. Even the color question can be studied on a much more refined scale.

Beyond ‘yes or no’

“Rather than just asking whether males and females of a species are dimorphic, yes or no, we will next measure various color patches and quantify brilliance,” says Prum.

“For example, male and female robins look different, so that would be a ‘yes’ for dimorphism. But they’re not as different as the male and female Scarlet Tanager. On the ‘yes-no’ scale they would be scored the same. If we actually measure the colors we’d be able to say ‘Wow, males and females of one species are really a lot more different than the other.’ That would reflect the impact of sexual selection a lot better.”

“One of the biggest analytical differences between what we’ve done and past work is that we used a ‘species tree’ approach, which is potentially more accurate than what is typically applied to genetic data,” Berv says.

“We ran our data through more traditional types of analyses as well, and all of them strongly supported a consistent evolutionary ‘tree of life.’ We hope other scientists who are interested in these birds take our phylogeny and do all sorts of great things with it.”

The paper appears in Molecular Phylogenetics and Evolution.

W. R. Coe funds from Yale University supported the work, as did the facilities and staff of the Yale University Faculty of Arts and Sciences High Performance Computing Center. The DNA work was performed at Yale; Berv did the data analysis and writing at the Cornell Lab.

Source: Cornell University

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