Gift-wrapped gas molecules

A group of scientists led by researchers at the Université de Versailles' Institut Lavoisier in France has worked out how to stably gift-wrap a chemical gas known as nitric oxide within metal-organic frameworks. Such an encapsulated chemical may allow doctors to administer nitric oxide in a more highly controlled way to patients, suggesting new approaches for treating dangerous infections and heart conditions with the biologically-active substance.

Not to be confused with the chemically-distinct anesthetic dentists use -- its cousin nitrous oxide (NO2), also known as laughing gas -- nitric oxide (NO) is one of very few gas molecules known to be involved in biological signaling pathways, the physiological gears that make the body tick at the microscopic level. It is very active biologically and can be found in bacteria, plant, animal and fungi cells.

In humans, NO is a powerful vasodilator, increasing blood flow and lowering vascular pressure. For this reason, gaseous NO is sometimes used to treat respiratory failure in premature infants. It also has strong antibacterial potency, owing to its molecular action as a biologically disruptive free radical, and cells in the human immune system naturally produce NO as a way of killing pathogenic invaders. Additionally, nitric oxide is believed to be the main vasoactive neurotransmitter regulating male erection, as aging nerves with reduced stimulation can inhibit the release of the molecule, thus causing erectile dysfunction. This, of course, can be mediated by taking nitric oxide supplements to achieve an erection.

While such activity would seem to make NO a prime candidate for drug design, the problem is delivery -- because it is a gas. In recent years, the gas storage capacity and biocompatibility of metal-organic-frameworks -- dissolvable compounds consisting of metal ions and rigid organic chemicals that can stably trap gas molecules -- have gained significant attention as candidates for delivering gas-based drugs. The new work extends this further than ever before, showing that these metal-organic frameworks can store and slowly deliver NO over an unprecedented amount of time, which is key for the drug's anti-thrombogenic action.

"This is an elegant and efficient method to store and deliver large amounts of NO for antibacterial purposes," said Christian Serre. "Or it can release controlled amounts of nitric oxide at the very low biological level for a prolonged period of time, in order to use it as a way to inhibit platelet aggregation." Serre is a CNRS research director at the Institut Lavoisier de Versailles, and also heads the institute's 'Porous Solids' research group.

Serre's consortium has previously reported the use of porous hybrid solids, such as metal-organic-frameworks, for the controlled delivery of nitric oxide gas. Their current paper on derivatives of iron polycarboxylates as framework candidate appears in the journal APL Materials, from AIP Publishing.

Serre and his group worked in collaboration with Russell Morris's team at the University of St Andrews in Scotland and researchers from Université de Basse-Normandie in France. The groups analyzed the NO adsorption and release properties of several porous biodegradable and biocompatible iron carboxylate metal-organic frameworks by use of infrared spectroscopy analysis, adsorption & desorption isotherms and water-triggered release tests.

In doing so, they confirmed the large nitric oxide absorption capacity of the iron frameworks, and that the NO was strongly bonding to the acidic metal sites on the molecules. Serre's group and coauthors also found that partially reducing the iron (III) into iron (II) enhances the affinity of the NO molecules for the framework. This strong interaction allows for a controlled release for a prolonged state of time -- days, at the biological level. This time scale depends on both the metal-organic framework structure and the oxidation state of iron, which can be carefully calibrated as needed for drug treatment.

These performances, associated with the biodegradable and low toxicity character of these metal-organic frameworks, might pave the way for their use in medical therapies or cosmetics formulation, which is one of the objectives of Serre's consortium in the near future. Current and forthcoming work includes using further spectroscopic experiments to understand the complex behavior of the iron frameworks once loaded with nitric oxide.

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Neutrinos can deliver not only full-on hits but also 'glancing blows'

In what they call a "weird little corner" of the already weird world of neutrinos, physicists have found evidence that these tiny particles might be involved in a surprising reaction.

Neutrinos are famous for almost never interacting. As an example, ten trillion neutrinos pass through your hand every second, and fewer than one actually interacts with any of the atoms that make up your hand. However, when neutrinos do interact with another particle, it happens at very close distances and involves a high-momentum transfer.

And yet a new paper, published in Physical Review Letters this week, shows that neutrinos sometimes can also interact with a nucleus but leave it basically untouched -- inflicting no more than a "glancing blow" -- resulting in a particle being created out of a vacuum.

Professor Kevin McFarland is a scientific co-spokesperson with the international MINERvA collaboration, which carries out neutrino scattering experiments at Fermilab McFarland, who also heads up the Rochester team that was primarily responsible for the analysis of the results, compares neutrino interactions to the firing of a bullet at a bubble, only to find the bubble was left intact.

"The bubble -- a carbon nucleus in the experiment -- deflects the neutrino 'bullet' by creating a particle from the vacuum," McFarland explains. "This effectively shields the bubble from getting blasted apart and instead the bullet only delivers a gentle bump to the bubble."

Producing an entirely new particle -- in this case a charged pion -- requires much more energy than it would take to blast the nucleus apart -- which is why the physicists are always surprised that the reaction happens as often as it does. McFarland adds that even painstakingly detailed theoretical calculations for this reaction "have been all over the map."

"The production of pions from this reaction had not been observed consistently in other experiments," McFarland said. By using a new technique, they were able to measure how much momentum and energy were transferred to the carbon nucleus -- showing that it remained undisturbed -- and the distribution of the pions that were created.

"After analyzing the results, we now have overwhelming evidence for the process," McFarland says.

The two members of the collaboration who were primarily responsible for analyzing the results were Aaron Higuera, at the time a postdoc at Rochester and now at the University of Houston, and Aaron Mislivec, one of McFarland's Ph.D. students.

Working with Higuera, Mislivec wrote the computer code that allowed them to sift through the results and get a picture of the reaction. "Our detector gave us access to the full information of exactly what was happening in this reaction," Mislivec explains. "Our data was consistent with the unique fingerprint of this reaction and determined how these interactions happen and how often." The key to identifying the reaction was finding undisturbed carbon nuclei and then studying the two resulting particles -- the pion, which is responsible for shielding the nucleus, and the muon.

Understanding this reaction, McFarland states, "is not going to make a better mousetrap, but it is exciting to learn that this weird reaction really does take place."

Researchers in the MINERvA collaboration measure low energy neutrino interactions both to support neutrino oscillation experiments and study the strong dynamics of the nucleon and nucleus that affect the interactions.

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A repulsive material: New hydrogel dominated by electrostatic repulsion

In a world-first achievement published in Nature, scientists from the RIKEN Center for Emergent Matter Science in Japan, along with colleagues from the National Institute of Material Science and the University of Tokyo, have developed a new hydrogel whose properties are dominated by electrostatic repulsion, rather than attractive interactions.

According to Yasuhiro Ishida, head of the Emergent Bioinspired Soft Matter Research Team, the work began from a surreptitious discovery, that when titanate nano-sheets are suspended in an aqueous colloidal dispersion, they align themselves face-to-face in a plane when subjected to a strong magnetic field. The field maximizes the electrostatic repulsion between them and entices them into a quasi-crystalline structure. They naturally orient themselves face to face, separated by the electrostatic forces between them.

To create the new material, the researchers used the newly discovered method to arrange layers of the sheets in a plane, and once the sheets were aligned in the plane, fixed the magnetically induced structural order by transforming the dispersion into a hydrogel using a procedure called light-triggered in-situ vinyl polymerization. Essentially, pulses of light are used to congeal the aqueous solution into a hydrogel, so that the sheets could no longer move.

By doing this, they created a material whose properties are dominated by electrostatic repulsion, the same force that makes our hair stand end when we touch a van generator.

Up to now, humanmade materials have not taken advantage of this phenomenon, but nature has. Cartilage owes its ability to allow virtually frictionless mechanical motion within joints, even under high compression, to the electrostatic forces inside it. Electrostatic repulsive forces are used in various places, such as maglev trains, vehicle suspensions and noncontact bearings, but up to now, materials design has focused overwhelmingly on attractive interactions.

The resultant new material, which contains the first example of charged inorganic structures that align co-facially in a magnetic flux, has interesting properties. It easily deforms when shear forces are applied parallel to the embedded nano-sheets, but strongly resists compressive forces applied orthogonally.

According to Ishida, "This was a surprising discovery, but one that nature has already made use of. We anticipate that the concept of embedding anisotropic repulsive electrostatics within a composite material, based on inspiration from articular cartilage, will open new possibilities for developing soft materials with unusual functions. Materials of this kind could be used in the future in various areas from regenerative medicine to precise machine engineering, by allowing the creation of artificial cartilage, anti-vibration materials and other materials that require resistance to deformation in one plane."

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Detecting extraterrestrial life through motion

Looking for life on other planets is not straightforward. It usually relies on chemical detection, which might be limited or even completely irrelevant to alien biology. On the other hand, motion is a trait of all life, and can be used to identify microorganisms without any need of chemical foreknowledge. EPFL scientists have now developed an extremely sensitive yet simple motion detector that can be built easily by adapting already-existent technology. The system has proven accurate with detecting bacteria, yeast, and even cancer cells, and is considered for the rapid testing of drugs and even the detection of extraterrestrial life. The work is published in the Proceedings of the National Academy of Sciences (PNAS).

Giovanni Dietler, Sandor Kasas and Giovanni Longo at EPFL have developed a motion detector that uses a nano-sized cantilever to detect motion. A cantilever is essentially a beam that is anchored only at one end, with the other end bearing a load. The cantilever design is often used with bridges and buildings, but here it is implemented on the micrometer scale, and about 500 bacteria can be deposited on it.

The idea comes from the technology behind an existing microscope, the atomic force microscope. This powerful microscope uses a cantilever to produce pictures of the very atoms on a surface. The cantilever scans the surface like the needle of a record player and its up-and-down movement is read by a laser to produce an image.

The motion sensor the Dietler and Kasas developed works the same way, but here the sample is attached on the cantilever itself. For example, a bacterium attaches to the cantilever. If the bacterium is alive, it will inevitably move in some way, e.g. move its flagellum or simply carry out normal biological functions. That motion also moves the much smaller and sensitive cantilever and it is captured by the readout laser as series of vibrations. The signal is taken as a sign of life.

The EPFL scientists successfully tested their novel system with isolated bacteria, yeast, mouse and human cells. They even tested soil from the fields around the EPFL campus and water from the nearby Sorge river. In each case, they were able to accurately detect and isolate vibration signatures from living cells. When they used drugs to kill anything alive, the motion signals stopped.

"The system has the benefit of being completely chemistry-free," says Dietler. "That means that it can be used anywhere -- in drug testing or even in the search for extraterrestrial life." The scientists envision a large array of cantilever sensors used in future space exploration probes like the Mars rover. As it relies on motion rather than chemistry, the cantilever sensor would be able to detect life forms in mediums that are native to other planets, such as the methane in the lakes of Titan.

However, the more immediate applications of the cantilever system are in drug development. Used in a larger array, the cantilevers could be covered with bacteria or cancer cells and incubated with various drug compounds. If the drugs are effective against the attached cells, the motion signals would decrease or stop altogether as the cells die off. This approach would be considerably quicker than current high-throughput systems used in by pharmaceutical companies when looking for candidate antibiotics or anticancer drugs.

"This is really the next step," says Dietler. "But we're still calling ESA and NASA to see if they're interested."

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Microscopy reveals how atom-high steps impede oxidation of metal surfaces

Low-energy electron microscopy images of the nickel-aluminum surface before and after oxidation. The faint lines before oxidation indicate the atom-high steps that separate flat terrace sections of the crystal surface. As oxidation begins at a point on one terrace, the oxide spreads in elongated stripes along that terrace, pushing steps out of the way and bunching them closer and closer together. Eventually the bunching of steps stops the growth of the oxide stripe and another begins to form, often at right angles, to produce a grid-like pattern.

Rust never sleeps. Whether a reference to the 1979 Neil Young album or a product designed to protect metal surfaces, the phrase invokes the idea that corrosion from oxidation -- the more general chemical name for rust and other reactions of metal with oxygen -- is an inevitable, persistent process. But a new study performed at the Center for Functional Nanomaterials (CFN) at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory reveals that certain features of metal surfaces can stop the process of oxidation in its tracks.

The findings, published in the Proceedings of the National Academy of Sciences, could be relevant to understanding and perhaps controlling oxidation in a wide range of materials -- from catalysts to the superalloys used in jet engine turbines and the oxides in microelectronics.

The experiments were performed by a team led by Guangwen Zhou of Binghamton University, in collaboration with Peter Sutter of the CFN, a DOE Office of Science User Facility. The team used a low-energy electron microscope (LEEM) to capture changes in the surface structure of a nickel-aluminum alloy as "stripes" of metal oxide formed and grew under a range of elevated temperatures.

"These microscopes are not that frequently found in ordinary research labs; there are only a handful around the U.S.," Sutter said. "We have a pretty lively 'user community' of scientists who come to the CFN just to use this type of instrument."

The metal Zhou wanted to study, nickel-aluminum, has a characteristic common to all crystal surfaces: a stepped structure composed of a series of flat terraces at different heights. The steps between terraces are only one atom high, but they can have a significant effect on material properties. Being able to see the steps and how they change is essential to understanding how the surface will behave in different environments, in this case in response to oxygen, Sutter said.

Said Zhou, "The acquisition of this kind of knowledge is essential for gaining control over the response of a metal surface to the environment."

Scientists have known for a while that the atoms at the edges of atomic steps are especially reactive. "They are not as completely surrounded as the atoms that are part of the flat terraces, so they are more free to interact with the environment," Sutter said. "That plays a role in the material's surface chemistry."

The new study showed that the aluminum atoms involved in forming aluminum oxide stripes came exclusively from the steps, not the terraces. But the LEEM images revealed even more: The growing oxide stripes could not "climb" up or down the steps, but were confined to the flat terraces. To continue to grow, they had to push the steps away as oxygen continued to grab aluminum atoms from the edges. This forced the steps to bunch closer and closer together, eventually slowing the rate of oxide stripe growth, and then completely stopping it.

"For the first time we show that atomic steps can slow surface oxidation at the earliest stages," Zhou said.

However, as one stripe stops growing, another begins to form. "As the oxide stripes grow along the two possible directions on the crystal, which are at right angles to one another, one ends up with these patterns of blocks and lines that are reminiscent of the grid-based paintings by Mondrian," Sutter said. "They are quite beautiful…" and persistent after all.

In fact, scientists who've studied a different "cut," or facet, of the crystalline nickel-aluminum alloy have observed that steps on that surface had no effect on oxide growth. In addition, on that surface, aluminum atoms throughout the bulk of the crystal could participate in the formation of aluminum oxide, and the oxide stripes could overrun the steps, Zhou said.

Still the details and differences of the two types of surfaces could offer new ways scientists might attempt to control oxidation depending on their purpose.

"Oxides are not all bad," Sutter said. "They form as a protective layer against corrosion attack. They play important roles in chemistry, for example in catalysis. Silicon oxide is the insulating material on microelectronic circuits, where it plays a central role in directing the flow of current."

Knowing which kind of surface a material has and its effects on oxidation -- or how to engineer surfaces with desired properties -- might improve the design of these and other materials.

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What you tweet when you go party can be useful for improving urban planning

Layout of businesses, nightlife and leisure areas in Madrid using Twitter are illustrated here. The uncolored part corresponds to residential areas.

Millions of Twitter users are constantly reporting where they are and what they are doing. With this information, two Spanish computer science experts suggest using geolocalized tweets for urban planning and land use. They have already done it in Manhattan, Madrid and London and have been able to identify, for example, nightlife areas of these large cities.

Every day millions of citizens around the world generate massive amounts of geolocalized content using mobile applications and social networks. Especially on Twitter, which could become a sensor of interactions between people and their environment and provide guidelines for planning life in the city.. A forgotten issue in urbanism is land use during the night time, with problems such as noise and dirt, which could be improved with this type of tool.

At least this is what Enrique and Vanessa Frías-Martínez believe, brother and sister and computer science researchers at Telefonica Research and the University of Maryland (USA) respectively, who have suggested using geolocalized tweets for urban planning and land use. Their study's results were published in 'Engineering Applications of Artificial Intelligence'.

As Enrique Frías-Martínez explained, "geolocalized tweets can be a very useful source of information for planning, since it is an activity carried out by a large number of people who provide information on where they are at a specific time and what they are doing."

The researcher points out that "thanks to the increased use of smartphones, social networks like Twitter and Facebook have made it possible to access and produce information ubiquitously."

Geolocation tags

These networks, he adds, generate tags with the event's geolocation. "For example, Twitter includes longitude-latitude information in the tweet if the user so desires. Amongst possible applications we have seen that this network could be highly suited to helping in urban planning, especially in identifying land use."

Using Twitter, says Enrique Frías-Martínez, "you can capture information on urban land use more efficiently and for a much larger number of people than with questionnaires. Moreover, this type of consultation, traditionally used until now in planning activities, are very costly and can cause problems due to the lack of accuracy of the answers."

The new technique "automatically determines land uses in urban areas by grouping together geographical regions with similar patterns of Twitter activity," says the researcher.

Using aggregate activity of tweets, the Frías-Martínez siblings have studied land use in Manhattan, Madrid and London. In the first two cases they identified four uses: residential, business, daytime leisure (mainly parks and tourist areas) and nightlife areas. In London, they also established industrial land uses. These results were validated with open data sources.

Nightlife

"One of the most interesting contributions of the study is the identification of nightlife areas, since this type of land use in not often specified in urban planning, despite the problems of noise, security and need for cleaning that this creates. Therefore, this information is very relevant," says Frías-Martínez.

In this respect, the study has determined that, in Madrid, night-time tweet activity is concentrated on weekends and in Manhattan, on weekdays. On the other hand, London is characterised by its tweeting activity in daytime leisure areas.

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New half-light half-matter quantum particles created

Prospects of developing computing and communication technologies based on quantum properties of light and matter may have taken a major step forward thanks to research by City College of New York physicists led by Dr. Vinod Menon.

In a pioneering study, Professor Menon and his team were able to discover half-light, half-matter particles in atomically thin semiconductors (thickness ~ a millionth of a single sheet of paper) consisting of two-dimensional (2D) layer of molybdenum and sulfur atoms arranged similar to graphene. They sandwiched this 2D material in a light trapping structure to realize these composite quantum particles.

"Besides being a fundamental breakthrough, this opens up the possibility of making devices which take the benefits of both light and matter," said Professor Menon.

For example one can start envisioning logic gates and signal processors that take on best of light and matter. The discovery is also expected to contribute to developing practical platforms for quantum computing.

Dr. Dirk Englund, a professor at MIT whose research focuses on quantum technologies based on semiconductor and optical systems, hailed the City College study.

"What is so remarkable and exciting in the work by Vinod and his team is how readily this strong coupling regime could actually be achieved. They have shown convincingly that by coupling a rather standard dielectric cavity to exciton-polaritons in a monolayer of molybdenum disulphide, they could actually reach this strong coupling regime with a very large binding strength," he said.

Professor Menon's research team included City College PhD students, Xiaoze Liu, Tal Galfsky and Zheng Sun, and scientists from Yale University, National Tsing Hua University (Taiwan) and Ecole Polytechnic -Montreal (Canada).

The study was funded by the U.S. Army Research Laboratory's Army Research Office and the National Science Foundation through the Materials Research Science and Engineering Center -- Center for Photonic and Multiscale Nanomaterials.

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A qubit candidate shines brighter

An array of microdisks and nanobeam photonic cavities formed from a single crystal diamond membrane. The scale bar indicates 2 microns.

In the race to design the world's first universal quantum computer, a special kind of diamond defect called a nitrogen vacancy (NV) center is playing a big role. NV centers consist of a nitrogen atom and a vacant site that together replace two adjacent carbon atoms in diamond crystal. The defects can record or store quantum information and transmit it in the form of light, but the weak signal is hard to identify, extract and transmit unless it is intensified.

Now a team of researchers at Harvard, the University of California, Santa Barbara and the University of Chicago has taken a major step forward in effectively enhancing the fluorescent light emission of diamond nitrogen vacancy centers -- a key step to using the atom-sized defects in future quantum computers. The technique, described in the journal Applied Physics Letters, from AIP Publishing, hinges on the very precise positioning of NV centers within a structure called a photonic cavity that can boost the light signal from the defect.

A Potential Qubit Power Couple

NV centers contain an unpaired electron that can store information in a property known as spin. Researchers can "read" the spin state of the electron by observing the intensity of particular frequencies of the light that the NV center emits when illuminated by a laser.

At room temperatures, this pattern of light emission couples to multiple "sideband" frequencies, making it difficult to interpret. To amplify the most important element of the signal researchers can use a structure called a photonic cavity, which consists of a pattern of nanoscale holes that serve to enhance the NV center's light emission at its main frequency.

"A photonic cavity that is properly matched to the NVs can substantially augment their capabilities," said Evelyn Hu, a researcher at Harvard whose group studies the optical and electronic behavior of materials that have been carefully sculpted at the nanoscale.

NV centers whose signal is enhanced by photonic cavities could act as qubits, the fundamental units of quantum information in a quantum computer.

Matchmaker, Matchmaker, Make Me a Match

Photonic cavities best enhance the signal of NV centers located in a "hot spot" where the cavities' resonant fields are strongest, but making sure an atom-sized defect's location matches up with this spot is extremely tricky.

"Strong spatial overlap is the hardest [task] to achieve in designing and fabricating a photonic cavity for NV centers," Hu said.

She compared the task to turning on a fixed small light beam in a dark room containing ultra-small transmitters that send out information once they are illuminated by the 'right' beam. If the match is right, the signal from the transmitter is returned strongly, but the challenge is that the chances of the light hitting the transmitter are very small.

Hu and her colleagues ultimately aim to make sure the beam (or field of the photonic cavity) will always hit the transmitter (or NV center), so that information will always be read out. They can do this by knowing the exact position of the tiny NV centers.

The team took an important first step toward this goal by controlling the depth of the diamond defects using a technique called delta doping. "Integrating a plane of spins into these structures enables us to engineering the spin-photon interaction and exploit quantum effects for future technologies," said David Awschalom, a researcher at the University of Chicago whose group grows and characterizes these systems. The technique confines the possible location of NV centers to a layer approximately 6 nanometers thick sandwiched inside a diamond membrane approximately 200 nanometers thick. The researchers then etched holes into the membrane to create the photonic cavities.

Using this method the researchers were able to increase the intensity of the light emitted by the NV centers by a factor of about 30 times.

The team believes they can further enhance the emission by also controlling the position of the defects in the horizontal plane and are currently working on possible ways to achieve full 3-D control.

Computers, Sensors and More

Nitrogen vacancy centers aren't the only candidate for qubits, but they have attracted a lot of interest because their electrons have long spin lifetimes at room temperature, meaning they can maintain quantum information for a relatively long time.

And the promise of NV centers doesn't stop at ultrafast computers. NV centers can also be used in non-computing applications, for examples as molecular-scale magnetic and temperature sensors that could measure the properties within single cells.

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American cities are many times brighter at night than German counterparts

Berlin at night, seen from the ISS.

German cities emit several times less light per capita than comparably sized American cities, according to a recent publication in the journal Remote Sensing. The size of the gap grew with city size, as light per capita increased with city size in the USA but decreased with city size in Germany. The study also examined regional differences, and surprisingly found that light emission per capita was higher in cities in the former East of Germany than from those in the former West.

The lead author, Dr. Christopher Kyba, studies visible light at night as a member of the Remote Sensing section of the German Research Center for Geosciences (GFZ). "The size of the difference in light emission is surprisingly large. This work will allow us to identify comparable cities in order to uncover the reasons behind the differences." These could include differences in the type of lamps, but also architectural factors like the width of the streets and the amount of trees. The LED lamps currently being installed in many cities are expected to greatly change the nighttime environment, for example by reducing the amount of light that shines upwards.

A main point of the study is to emphasize the great improvement in the quality of nighttime imagery of Earth since 2012. The European Space Agency's NightPod instrument has allowed astronauts to take high resolution images of individual cities. In addition, the entire world is now imaged nightly at 750 meter resolution by the Visible Infrared Imaging Radiometer Suite Day-Night Band onboard the Suomi National Polar-Orbiting Program weather satellite. This new imagery has made it possible to identify and measure the output of individual bright sources of light pollution for the first time. The study found that in Megacities in developing countries, the brightest light sources were typically airports or harbors. In contrast, the brightest areas in the capital cities of Europe are often associated with leisure, for example stadiums and city centers.

While artificial light at night is a problem for astronomers and nocturnal animals, it has the potential to be an important tool in understanding human activity. In order to make the most use out of it, the researchers say they will need to study urban light emissions in detail, including their spectrum, the directions in which light is emitted, and changes in light use and lit area over time.

The study demonstrated one practical use of the new data: since maps of nighttime light emission highlight the areas where light pollution is especially prevalent, they provide information about which areas can best be targeted for energy savings. Coauthor Dr. Franz Hölker from the Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) explains, "artificial light is responsible for a sizable portion of all nighttime electricity consumption. Identifying areas where light could be more efficiently used will make it possible to save energy, reduce costs, and reduce the impact of artificial light on the nighttime environment."

The study was performed at the Leibniz Institute of Freshwater Ecology and Inland Fisheries, the Free University of Berlin, and the Universidad Complutense de Madrid.

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Optogenetics captures neuronal transmission in live mammalian brain

This is a reconstruction of a pair of synaptically connected neurons.

Neurons, the cells of the nervous system, communicate by transmitting chemical signals to each other through junctions called synapses. This "synaptic transmission" is critical for the brain and the spinal cord to quickly process the huge amount of incoming stimuli and generate outgoing signals. However, studying synaptic transmission in living animals is very difficult, and researchers have to use artificial conditions that don't capture the real-life environment of neurons. Now, EPFL scientists have observed and measured synaptic transmission in a live animal for the first time, using a new approach that combines genetics with the physics of light. Their breakthrough work is published in Neuron.

Aurélie Pala and Carl Petersen at EPFL's Brain Mind Institute used a novel technique, "optogenetics," that has been making significant inroads in the field of neuroscience in the past ten years. This method uses light to precisely control the activity of specific neurons in living, even moving, animals in real time. Such precision is critical in being able to study the hundreds of different neuron types, and understand higher brain functions such as thought, behavior, language, memory -- or even mental disorders.

Activating neurons with light

Optogenetics works by inserting the gene of a light-sensitive protein into live neurons, from a single cell to an entire family of them. The genetically modified neurons then produce the light-sensitive protein, which sits on their outside, the membrane. There, it acts as an electrical channel -- something like a gate. When light is shone on the neuron, the channel opens up and allows electrical ions to flow into the cell; a bit like a battery being charged by a solar cell.

The addition of electrical ions changes the voltage balance of the neuron, and if the optogenetic stimulus is sufficiently strong it generates an explosive electrical signal in the neuron. And that is the impact of optogenetics: controlling neuronal activity by switching a light on and off.

Recording neuronal transmissions

Pala used optogenetics to stimulate single neurons of anesthetized mice and see if this approach could be used to record synaptic transmissions. The neurons she targeted were located in a part of the mouse's brain called the barrel cortex, which processes sensory information from the mouse's whiskers.

When Pala shone blue light on the neurons that contained the light-sensitive protein, the neurons activated and fired signals. At the same time, she measured electrical signals in neighboring neurons using microelectrodes that can record small voltage changes across a neuron's membrane.

Using these approaches, the researchers looked at how the light-sensitive neurons connected to some of their neighbors: small, connector neurons called "interneurons." In the brain, interneurons are usually inhibitory: when they receive a signal, they make the next neuron down the line less likely to continue the transmission.

The researchers recorded and analyzed synaptic transmissions from light-sensitive neurons to interneurons. In addition, they used an advanced imaging technique (two-photon microscopy) that allowed them to look deep into the brain of the live mouse and identify the type of each interneuron they were studying. The data showed that the neuronal transmissions from the light-sensitive neurons differed depending on the type of interneuron on the receiving end.

"This is a proof-of-concept study," says Aurélie Pala, who received her PhD for this work. "Nonetheless, we think that we can use optogenetics to put together a larger picture of connectivity between other types of neurons in other areas of the brain."

The scientists are now aiming to explore other neuronal connections in the mouse barrel cortex. They also want to try this technique on awake mice, to see how switching neuronal activity on and off with a light can affect higher brain functions.

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Shedding new light on diet of extinct animals

A herd of forest elephants in their natural environment in the La Lopé National Park, Gabon.

A study of tooth enamel in mammals living today in the equatorial forest of Gabon could ultimately shed light on the diet of long extinct animals, according to new research from the University of Bristol.

Reconstructing what extinct organisms fed on can be a real challenge. Scientists use a variety of methods including the structure of an animal's bones, analysis of its stomach contents and the patterns of wear left on the surface of its teeth. Geochemical methods have also proved useful but can be limited by poor preservation of the animal's remains.

Dr Jeremy Martin, formerly of Bristol's School of Earth Sciences and now at the Laboratoire de Géologie de Lyon: terre, planètes et environnement, University of Lyon/ENS de Lyon, and colleagues found that magnesium isotopes are particularly well suited to deciphering the diet of living mammals and, when used in conjunction with other methods such as carbon isotopes, they could open up new perspectives on the study of fossilised animals.

Dr Martin said: "Most chemical elements exist in distinct forms called isotopes which are characterized by different masses. Therefore, all the isotopes of an element will behave differently during a chemical reaction preferentially sorting out heavier ones from lighter ones."

As noted by Dr Balter, who took part in the study: "Biological processes such as digestion involve important isotopic fractionations of the various elements assimilated through food consumption so the stable isotope composition of an organism tends to reflect its diet -- we are what we eat."

Scientists know that the carbon and nitrogen isotopes preserved in bone collagen can give direct evidence about an animal's food intake. However, because of the rapid decay of organic matter, these inferences are limited to the recent past.

Dr Martin and colleagues explored the isotopic variability of one of the major elements that compose tooth apatite, the hardest biological structure to retain its pristine signal throughout the fossil record.

Teeth from various mammals living today in the equatorial forest of Gabon were purified for magnesium isotopes. The results show that the isotope ratios of magnesium 26 mg/24 mg increase from herbivore to higher-level consumers (such as carnivores) and, when used in conjunction with other geochemical proxies, serve as a strong basis to infer the diet of mammals.

Dr Martin said: "Many fossil groups do not have living analogues and inferring their diet is far from clear. Applying a new perspective to palaeoecology by using non-traditional isotopes (such as magnesium or calcium in conjunction with traditional approaches) holds great promise for our understanding of how such ancient organisms interacted with each other."

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Distribution of fish on northeast US shelf influenced by both fishing, climate

Summer flounder (Paralichthys dentatus).

Scientists studying the distribution of four commercial and recreational fish stocks in Northeast U.S. waters have found that climate change can have major impacts on the distribution of fish, but the effects of fishing can be just as important and occur on a more immediate time scale.

The four species studied -- black sea bass, scup, summer flounder, and southern New England/Mid-Atlantic Bight winter flounder -- have varied in abundance and have experienced heavy fishing pressure at times over the past 40 years. Scientists examined the distribution of the four species using Northeast Fisheries Science Center (NEFSC) research trawl survey data collected between 1972 and 2008. Generalized additive models were used to determine if the distributions of the four species had changed over time, and if these changes reflect changes in temperature or fishing pressure.

The researchers found that black sea bass, scup, and summer flounder exhibited significant poleward shifts in distribution in at least one season. The shifts in black sea bass and scup were related to temperature, while the shift in summer flounder was related to a decrease in fishing pressure and an expansion of the population age structure. The southern New England/Mid-Atlantic Bight stock of winter flounder showed no change in distribution.

"The study combined a range of resources at the Center, long-term oceanographic data and trawl survey data," said Richard Bell, a National Research Council research associate working at the NEFSC's Narragansett Laboratory in Rhode Island and lead author of the study. "Using these data, we demonstrated how a combination of fishing and climate can influence the distribution of marine fish. It is not one or the other."

Increasing ocean temperatures have significantly affected marine life, inducing shifts in distribution and changes in abundance. Climate change alters the distribution of suitable habitats, forcing organisms to move to a more favorable area of their range or attempt to survive under less than ideal conditions. Fishing reduces the abundance of marine populations and truncates their size and age structure, which can lead to range contractions or shifts.

Fishing typically removes the larger fish from a population. Larger, older summer flounder are typically found further north, and as exploitation reduced the numbers of summer flounder in the 1980s and 1990s, larger fish were preferentially harvested by the fishery. The remaining summer flounder population, dominated by smaller fish, subsequently became centered further south. The northward shift of the stock in recent decades was linked to an increase in the number of larger, older fish as the population has rebuilt.

"The fish were not shifting northward with warmer conditions, but simply re-colonizing their former habitat areas," said Bell.

Northerly shifts in scup and black sea bass are linked to increases in temperature and are more tied to climate than fishing.

The study suggests multiple factors specific to individual species need to be considered when developing management regulations for living marine resources. The management of each of the four species analyzed in this study is based on spatial allocations, and shifts in stock distributions can cause a mismatch between the distribution of fish and the catch allocations for different regions and states.

Findings from the study were published online in the ICES Journal of Marine Science.

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First scientific report shows police body-cameras can prevent unacceptable use-of-force

As Obama pledges investment in body-worn-camera technology for police officers, researchers say cameras induce 'self-awareness' that can prevent unacceptable uses-of-force seen to have tragic consequences in the US over the past year -- from New York to Ferguson -- but warn that cameras have implications for prosecution and data storage.

Researchers from the University of Cambridge's Institute of Criminology (IoC) have now published the first full scientific study of the landmark crime experiment they conducted on policing with body-worn-cameras in Rialto, California in 2012 -- the results of which have been cited by police departments around the world as justification for rolling out this technology.

The experiment showed that evidence capture is just one output of body-worn video, and the technology is perhaps most effective at actually preventing escalation during police-public interactions: whether that's abusive behaviour towards police or unnecessary use-of-force by police.

The researchers say the knowledge that events are being recorded creates "self-awareness" in all participants during police interactions. This is the critical component that turns body-worn video into a 'preventative treatment': causing individuals to modify their behaviour in response to an awareness of 'third-party' surveillance by cameras acting as a proxy for legal courts -- as well as courts of public opinion -- should unacceptable behaviour take place.

During the 12-month Rialto experiment, use-of-force by officers wearing cameras fell by 59% and reports against officers dropped by 87% against the previous year's figures.

However, the research team caution that the Rialto experiment is only the first step on a long road of evidence-gathering, and that more needs to be known about the impact of body-worn cameras in policing before departments are "steamrolled" into adopting the technology -- with vital questions remaining about how normalising the provision of digital video as evidence will affect prosecution expectations, as well as the storage technology and policies that will be required for the enormous amount of data captured.

President Obama recently promised to spend $263m of federal funds on body-worn-video to try and stem the haemorrhaging legitimacy of US police forces among communities across the United States after the killing of several unarmed black men by police caused nationwide anguish, igniting waves of protest.

But some in the US question the merit of camera technology given that the officer responsible for killing Eric Garner -- a 43-year-old black man suffocated during arrest for selling untaxed cigarettes -- was acquitted by a grand jury despite the fact that a bystander filmed the altercation on a mobile phone, with footage showing an illegal 'chokehold' administered on Garner who repeatedly states: "I can't breathe." (A medical examiner ruled the death a homicide).

For the Cambridge researchers, the Rialto results show that body-worn-cameras can mitigate the need for such evidence by preventing excessive use-of-force in the first place. Data from the Rialto experiment shows police officers are deterred from unacceptable uses-of-force -- indeed, from using force in general -- by the awareness that an interaction is being filmed; but this 'deterrence' relies on cognition of surveillance.

While the evidence provided by the video of Garner's death would suggest a heinous miscarriage of justice, say researchers, the filming itself by a bystander would not generate the self-awareness and consequent behaviour modification during the incident as observed during Rialto's institutionalised camera use.

"The 'preventative treatment' of body-worn-video is the combination of the camera plus both the warning and cognition of the fact that the encounter is being filmed. In the tragic case of Eric Garner, police weren't aware of the camera and didn't have to tell the suspect that he, and therefore they, were being filmed," said Dr Barak Ariel, from the Cambridge's IoC, who conducted the crime experiment with Cambridge colleague Dr Alex Sutherland and Rialto police chief Tony Farrar.

"With institutionalised body-worn-camera use, an officer is obliged to issue a warning from the start that an encounter is being filmed, impacting the psyche of all involved by conveying a straightforward, pragmatic message: we are all being watched, videotaped and expected to follow the rules," he said.

"Police subcultures of illegitimate force responses are likely to be affected by the cameras, because misconduct cannot go undetected -- an external set of behavioural norms is being applied and enforced through the cameras. Police-public encounters become more transparent and the curtain of silence that protects misconduct can more easily be unveiled, which makes misconduct less likely." In Rialto, police use-of-force was 2.5 times higher before the cameras were introduced.

The idea behind body-worn-video, in which small high-definition cameras are strapped to a police officers' torso or hat, is that every step of every police-public interaction -- from the mundane to those involving deadly force -- gets recorded to capture the closest approximation of actual events for evidence purposes, with only case-relevant data being stored.

In Rialto, an experimental model was defined in which all police shifts over the course of a year were randomly assigned to be either experimental (with camera) or control (without camera), encompassing over 50,000 hours of police-public interactions.

The dramatic reduction in both use-of-force incidents and complaints against the police during the experiment led to Rialto PD implementing an initial three-year plan for body-worn cameras. When the police force released the results, they were held up by police departments, media and governments in various nations as the rationale for camera technology to be integrated into policing.

Ariel and colleagues are currently replicating the Rialto experiment with over 30 forces across the world, from the West Yorkshire force and Northern Ireland's PSNI in the UK to forces in the United States and Uruguay, and aim to announce new findings at the IoC's Conference for Evidence-Based Policing in July 2015. Early signs match the Rialto success, showing that body-worn-cameras do appear to have significant positive impact on interactions between officers and civilians.

However, the researchers caution that more research is required, and urge police forces considering implementing body-worn-cameras to contact them for guidance on setting up similar experiments. "Rialto is but one experiment; before this policy is considered more widely, police forces, governments and researchers should invest further time and effort in replicating these findings," said Dr Sutherland.

Body-worn cameras appear to be highly cost-effective: analysis from Rialto showed every dollar spent on the cameras saved about four dollars on complaints litigations, and the technology is becoming ever cheaper. However, the sheer levels of data storage required as the cameras are increasingly adopted has the potential to become crippling.

"The velocity and volume of data accumulating in police departments -- even if only a fraction of recorded events turn into 'downloadable' recordings for evidentiary purposes -- will exponentially grow over time," said Ariel. "User licenses, storage space, 'security costs', maintenance and system upgrades can potentially translate into billions of dollars worldwide."

And, if body-worn cameras become the norm, what might the cost be when video evidence isn't available? "Historically, courtroom testimonies of response officers have carried tremendous weight, but prevalence of video might lead to reluctance to prosecute when there is no evidence from body-worn-cameras to corroborate the testimony of an officer, or even a victim," said Ariel.

"Body-worn-video has the potential to improve police legitimacy and enhance democracy, not least by calming situations on the front line of policing to prevent the pain and damage caused by unnecessary escalations of volatile situations. But there are substantial effects of body-worn-video that can potentially offset the benefits which future research needs to explore."

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Could playing Tchaikovsky's 'Nutcracker' and other music improve kids' brains?

Children who play the violin or study piano could be learning more than just Mozart. A University of Vermont College of Medicine child psychiatry team has found that musical training might also help kids focus their attention, control their emotions and diminish their anxiety.

Children who play the violin or study piano could be learning more than just Mozart. A University of Vermont College of Medicine child psychiatry team has found that musical training might also help kids focus their attention, control their emotions and diminish their anxiety. Their research is published in the Journal of the American Academy of Child & Adolescent Psychiatry.

James Hudziak, M.D., professor of psychiatry and director of the Vermont Center for Children, Youth and Families, and colleagues including Matthew Albaugh, Ph.D., and graduate student research assistant Eileen Crehan, call their study "the largest investigation of the association between playing a musical instrument and brain development."

The research continues Hudziak's work with the National Institutes of Health Magnetic Resonance Imaging (MRI) Study of Normal Brain Development. Using its database, the team analyzed the brain scans of 232 children ages 6 to 18.

As children age, the cortex -- the outer layer of the brain -- changes in thickness. In previous analysis of MRI data, Hudziak and his team discovered that cortical thickening or thinning in specific areas of the brain reflected the occurrence of anxiety and depression, attention problems, aggression and behavior control issues even in healthy kids -- those without a diagnosis of a disorder or mental illness. With this study, Hudziak wanted to see whether a positive activity, such as music training, would influence those indicators in the cortex.

The study supports The Vermont Family Based Approach, a model Hudziak created to establish that the entirety of a young person's environment -- parents, teachers, friends, pets, extracurricular activities -- contributes to his or her psychological health. "Music is a critical component in my model," Hudziak says.

The authors found evidence they expected -- that music playing altered the motor areas of the brain, because the activity requires control and coordination of movement. Even more important to Hudziak were changes in the behavior-regulating areas of the brain. For example, music practice influenced thickness in the part of the cortex that relates to "executive functioning, including working memory, attentional control, as well as organization and planning for the future," the authors write.

A child's musical background also appears to correlate with cortical thickness in "brain areas that play a critical role in inhibitory control, as well as aspects of emotion processing."

The findings bolster Hudziak's hypothesis that a violin might help a child battle psychological disorders even better than a bottle of pills. "We treat things that result from negative things, but we never try to use positive things as treatment," he says.

Such an approach may prove difficult to accomplish. According to the study's authors, research from the U.S. Department of Education indicates that three-quarters of U.S. high school students "rarely or never" take extracurricular lessons in music or the arts.

"Such statistics, when taken in the context of our present neuroimaging results," the authors write, "underscore the vital importance of finding new and innovative ways to make music training more widely available to youths, beginning in childhood."

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Mechanics of cells' long-range communication modeled by researchers

As fibrosis progresses, "bridges" of extracellular matrix appear between cells.

Interdisciplinary research at the University of Pennsylvania is showing how cells interact over long distances within fibrous tissue, like that associated with many diseases of the liver, lungs and other organs.

By developing mathematical models of how the collagen matrix that connects cells in tissue stiffens, the researchers are providing insights into the pathology of fibrosis, cirrhosis of the liver and certain cancers.

Tissue stiffness has long been know to be clinically relevant in these diseases, but the underlying changes that alter the mechanics of tissues are poorly understood. Consisting of a complex network of fibers, tissues have proven difficult to simulate and model beyond local, neighbor-to-neighbor interactions.

Developing a better understanding of the large-scale mechanical changes that occur over longer distances, specifically the process by which the extracellular matrix is pulled into compact, highly-aligned "bridges," could eventually form the basis of treatments for related diseases.

Vivek Shenoy, professor in the Department of Materials Science and Engineering in Penn's School of Engineering and Applied Science, has led an interdisciplinary research team to tackle this problem, authoring a pair of papers that were published in Biophysical Journal.

One, "Remodeling of Fibrous Extracellular Matrices by Contractile Cells: Predictions from Discrete Fiber Network Simulations" involved developing simulations that extrapolated the overall remodeling of the extracellular matrix based on the behavior of neighboring pairs of cells. The other, "Long Range Force Transmission in Fibrous Matrices Enabled by Tension-Driven Alignment of Fibers," took a more mathematical approach, producing a coarse-grained model of this remodeling that could be more broadly applied to fibrotic tissue.

"We're trying to understand how force is transmitted in tissues," Shenoy said. "Cells are the ones that generate force, and it has to be transmitted through what surrounds the cell, the extracellular matrix, or ECM. But imagine trying to model the ECM by trying to keep track of each collagen fibril in your liver; there are tens of millions of those. So we're taking what we learn from simulating those networks to turn it into a model that captures the main features with only a few parameters.

"The key here is the mechanics," he said. "In particular, how does ECM, as a fibrous material, differ from solids, gels and other materials that are better studied."

Rebecca Wells, an associate professor in Penn's Perelman School of Medicine and a co-author on the latter paper, provided insight into the clinical relevance of the mechanics that characterize ECM-related disorders.

"Fibrosis occurs when you have an injury and the tissue responds by depositing ECM, forming scar tissue," Wells said. "In liver fibrosis, the liver can stiffen by up to an order of magnitude, so measuring stiffness is a common diagnostic test for the disease. Increased stiffness also occurs in cancer, where tumors are typically stiffer than the surrounding tissue."

Existing experimental evidence showed that mechanical forces were at play in the changes in both fibrosis and cancer and that these forces were important to their development and progression but could not explain the long-ranging changes cells were able to produce to change their environments. When put in tissue-simulating gels, cells can deform their immediate surroundings but are unable to pull on more distant cells. In real, ECM-linked tissue, however, cells' range of influence can be up to 20 times their own diameter.

"If you look at a normal tissue," Shenoy said, "you see the cells are more rounded, and the network of ECM fibers is more random. But as cancer progresses, you see more elliptical cells, more ECM, and you see that the ECM fibers are more aligned. The cells are the ones generating force, so they're contracting and pulling the fibers, stretching them out into bridges."

"That's also the pathology of cirrhosis," Wells said. "My group had been looking at the early mechanical changes associated with liver fibrosis, which progresses to cirrhosis, but then, by collaborating with Vivek, we started to wonder if these large scale changes in the architecture of the liver could have a mechanical basis and if something similar to what is seen in gels might be occurring in the liver. This is a new way of approaching the problem, which has largely been thought of as biochemical in origin. And there are other tissues where it is probably the same thing, the lung, for example."

The researchers found that the critical difference between the existing models and ECM's long-range behavior was rooted in its elastic properties. Materials with linear elasticity cannot transmit force over the distances observed, but the team's simulations showed that nonlinear elasticity could arise from the ECM's fibrous structure.

"In our model, every component is linearly elastic," Shenoy said, "but the collective behavior is nonlinear; it emerges because of the connectivity. When you deform the network, it's easy to bend the 'sticks' that represent collagen fibers but hard to stretch them. When you deform it to a small extent, it's all the bending of the fibers, but, as you deform further, it can't accommodate bending any more and moves over to stretching, forming the bridges we see in the tissue."

Such simulations can't predict which fibers will end up in which bridge, necessitating the coarser-grained model the researchers described in their second paper. By showing the point at which linear elasticity gives way to its nonlinear counterpart, the team produced a more complete picture of how the alignment of collagen bridges under tension transmit force between distant cells.

Further studies are needed to elucidate the feedback loops between ECM stiffening and cell contraction strength. The team is conducting physical experiments to confirm and refine their in silico findings.

"Right now," Wells said," we're hypothesizing that the mechanical interactions modeled by the Shenoy lab explain aspects of cancer and fibrosis, and we're developing the experimental systems to confirm it with real cells."

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Sun sizzles in high-energy X-rays

For the first time, a mission designed to set its eyes on black holes and other objects far from our solar system has turned its gaze back closer to home, capturing images of our sun. NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has taken its first picture of the sun, producing the most sensitive solar portrait ever taken in high-energy X-rays.

"NuSTAR will give us a unique look at the sun, from the deepest to the highest parts of its atmosphere," said David Smith, a solar physicist and member of the NuSTAR team at University of California, Santa Cruz.

Solar scientists first thought of using NuSTAR to study the sun about seven years ago, after the space telescope's design and construction was already underway (the telescope launched into space in 2012). Smith had contacted the principal investigator, Fiona Harrison of the California Institute of Technology in Pasadena, who mulled it over and became excited by the idea.

"At first I thought the whole idea was crazy," says Harrison. "Why would we have the most sensitive high energy X-ray telescope ever built, designed to peer deep into the universe, look at something in our own back yard?" Smith eventually convinced Harrison, explaining that faint X-ray flashes predicted by theorists could only be seen by NuSTAR.

While the sun is too bright for other telescopes such as NASA's Chandra X-ray Observatory, NuSTAR can safely look at it without the risk of damaging its detectors. The sun is not as bright in the higher-energy X-rays detected by NuSTAR, a factor that depends on the temperature of the sun's atmosphere.

This first solar image from NuSTAR demonstrates that the telescope can in fact gather data about sun. And it gives insight into questions about the remarkably high temperatures that are found above sunspots -- cool, dark patches on the sun. Future images will provide even better data as the sun winds down in its solar cycle.

"We will come into our own when the sun gets quiet," said Smith, explaining that the sun's activity will dwindle over the next few years.

With NuSTAR's high-energy views, it has the potential to capture hypothesized nanoflares -- smaller versions of the sun's giant flares that erupt with charged particles and high-energy radiation. Nanoflares, should they exist, may explain why the sun's outer atmosphere, called the corona, is sizzling hot, a mystery called the "coronal heating problem." The corona is, on average, 1.8 million degrees Fahrenheit (1 million degrees Celsius), while the surface of the sun is relatively cooler at 10,800 Fahrenheit (6,000 degrees Celsius). It is like a flame coming out of an ice cube. Nanoflares, in combination with flares, may be sources of the intense heat.

If NuSTAR can catch nanoflares in action, it may help solve this decades-old puzzle.

"NuSTAR will be exquisitely sensitive to the faintest X-ray activity happening in the solar atmosphere, and that includes possible nanoflares," said Smith.

What's more, the X-ray observatory can search for hypothesized dark matter particles called axions. Dark matter is five times more abundant than regular matter in the universe. Everyday matter familiar to us, for example in tables and chairs, planets and stars, is only a sliver of what's out there. While dark matter has been indirectly detected through its gravitational pull, its composition remains unknown.

It's a long shot, say scientists, but NuSTAR may be able spot axions, one of the leading candidates for dark matter, should they exist. The axions would appear as a spot of X-rays in the center of the sun.

Meanwhile, as the sun awaits future NuSTAR observations, the telescope is continuing with its galactic pursuits, probing black holes, supernova remnants and other extreme objects beyond our solar system.

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Virginia. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley; Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Maryland; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, California; ATK Aerospace Systems, Goleta, California; and with support from the Italian Space Agency (ASI) Science Data Center.

NuSTAR's mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, California. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

For more information, visit:

• http://www nasa gov/nustar
• http://www nustar caltech.edu

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Maternal supplementation with multiple micronutrients compared with iron-folic acid

In Bangladesh, daily maternal supplementation of multiple micronutrients compared to iron-folic acid before and after childbirth did not reduce all-cause infant mortality to age 6 months, but did result in significant reductions in preterm birth and low birth weight, according to a study in the December 24/31 issue of JAMA.

Multiple micronutrient deficiencies are common among pregnant women in resource-poor regions of the world, especially in southern Asia. Coexisting with poor maternal nutrition across the region are excessive burdens of low birth weight (LBW), preterm birth, small size for gestational age, stillbirth, infant mortality, and maternal mortality. Gestational micronutrient deficiencies may contribute to avertable adverse birth outcomes. Data for effects of antenatal (before birth) multiple micronutrient (MM) supplementation on longer-term infant mortality are sparse for guiding policies in southern Asia, according to background information in the article.

Keith P. West Jr., Dr.P.H., of the Johns Hopkins Bloomberg School of Public Health, Baltimore, and colleagues conducted a study in which pregnant women in Bangladesh (n = 44,567) were randomly assigned to receive supplements containing 15 micronutrients or iron-folic acid alone, taken daily from early pregnancy to 12 weeks postpartum.

Among the 22,405 pregnancies in the multiple micronutrient group and the 22,162 pregnancies in the iron-folic acid group, there were 14,374 and 14,142 live-born infants, respectively, included in the analysis. At 6 months, multiple micronutrients did not significantly reduce infant mortality; there were 764 deaths (54.0 per 1,000 live births) in the iron-folic acid group and 741 deaths (51.6 per 1,000 live births) in the multiple micronutrient group.

Multiple micronutrient supplementation resulted in a non-statistically significant reduction in stillbirths (43.1 vs 48.2 per 1,000 births) and significant reductions in preterm births (18.6 vs 21.8 per 100 live births) and low birth weight (40.2 vs 45.7 per 100 live births).

"Our study's null finding is in agreement with a small number of trials that have provided an antenatal multiple micronutrient vs iron supplement, with or without folic acid, and found no effect on neonatal mortality," the authors write.

"Reasons for a null effect on postnatal survival after improvement in some birth outcomes with antenatal multiple micronutrient supplement use remain unknown but may reflect a complex interplay between maternal and newborn sizes and differential responses to supplementation by causes of death."

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Ultrasounds dance the 'moonwalk' in new metamaterial

Silicone beads embedded in a water-based gel (photograph is ~2 cm across).

Metamaterials have extraordinary properties when it comes to diverting and controlling waves, especially sound and light: for instance, they can make an object invisible, or increase the resolving power of a lens. Now, researchers at the Centre de Recherche Paul Pascal (CNRS) and the Institut de Mécanique et d'Ingénierie de Bordeaux (CNRS/Université de Bordeaux/Bordeaux INP/Arts et Métiers ParisTech) have developed the first three-dimensional metamaterials by combining physico-chemical formulation and microfluidics technology. This is a new generation of soft metamaterials that are easier to shape. In their experiment, the researchers got ultrasonic oscillations to move backwards while the energy carried by the wave moved forwards. Their work opens up new prospects, especially for high-resolution imaging (ultrasonography). It is published on 15 December 2014 in the journal Nature Materials.

Since the 2000s, the international scientific community has seen interest in metamaterials and their extraordinary properties grow exponentially. A metamaterial is a medium in which the phase velocity of light or sound waves can be negative (the material is said to have a negative refractive index).. In such a medium, the phase of the wave (the successive oscillations) and the energy carried by this same wave move in opposite directions. This property is not found in any natural homogeneous medium.

To obtain a metamaterial, it is necessary to make a heterogeneous medium that contains a large number of inclusions (known as microresonators). The usual way is to use micromechanical methods (etching, deposition, etc) to machine solid supports that will have the properties of metamaterials in one or two dimensions. However, this method cannot be used to work with soft matter at the micrometer scales required for ultrasounds, and the materials obtained remain limited to one or two dimensions.

In this study, the researchers developed a new type of metamaterial, in the fluid phase, formed of porous silicone microbeads embedded in a water-based gel. This metafluid is the first three-dimensional metamaterial to work at ultrasonic frequencies. In addition, due to its fluid nature, it can be made using physico-chemical processes and microfluidics technologies, which are much easier to implement than micromechanical methods.

One of the properties of porous media is that sound travels through them at very low speed (a few tens of meters per second) compared to water (1500 meters per second). Due to this sharp contrast, the whole suspension has the properties of a metamaterial provided the bead concentration is sufficient: when the researchers studied the propagation of ultrasonic waves through this medium, they directly measured a negative refractive index. Within such a metafluid, the energy carried by the wave travels from the emitter to the receiver, as expected, whereas the oscillations appear to move backwards in the opposite direction, rather like a dancer doing the 'moonwalk'.

These results open the way to numerous applications ranging from high-resolution ultrasound imaging to sound insulation and stealth in underwater acoustics. In addition, the soft-matter physico-chemical techniques used to make this metamaterial makes it possible to produce fluid or flexible materials with adaptable shapes, potentially at the industrial scale.

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