Friday, March 30, 2018

Russians Create Synthetic Chameleon Skin

An international team of researchers including Dmitry Ivanov, the head of laboratory of functional soft-matter systems, MSU, announced the development of a synthetic chameleon skin. Similar to its biological analogue, the synthetic skin reacts to mechanical stimuli by changing its stiffness and color. The scientists see their development as quite promising. The work was published in the recent issue of the Science journal.

Having worked in academic institutions in Europe for 25 years, Dmitry Ivanov founded a laboratory of functional soft-matter systems at the Faculty of Physical and Chemical Engineering, MSU. To take the direction of the new laboratory, he left the direction of a French Institute of Materials Sciences operating under the French National Center for Scientific Research. Today Dmitry Ivanov actively involves his Moscow colleagues into international projects, one of which is the development of the chameleon skin.

Naturally, this is not exactly skin and it doesn't belong to a chameleon. The scope of the development is active camouflage, although camouflaging is not the only property of this novel material. Generally, chameleon is not the only animal able to change the colour of its skin depending on its state. The means of active camouflage are also used by some cephalopods and amphibians.

This is a synthetic chameleon skin.

Credit: Dmitry Ivanov

In addition, under external mechanical stimuli their soft skin quickly becomes stiff to prevent premature rupture. Scientists have been trying for a long time to create synthetic materials with similar properties, however all polymers that have been developed by now showed by far smaller changes in mechanical stiffness under deformation than living tissues. As for a material that could stiffen under stretching and change colour at the same time, no one dared even dream about it. Still, now it exists.

The development of the team is based on the so-called copolymers, i.e. polymers that consist of several different constituent parts. According to Dmitry Ivanov, the copolymer created by the authors of the article is substantially different from conventional linear macromolecules. The new macromolecule resembles a dumbbell with a hairy hand. The center of the construct is formed by an element with densely grafted branches that looks like a bottle brush. What is interesting about such a molecular brush initially developed in the USA, some years ago, is that the macromolecular backbone with branches is very stiff. A material consisting of such brushes may be initially quite soft but rapidly stiffens upon deformation.

Moreover, the new polymers are capable of molecular self-assembly -- a property that is being actively studied in Ivanov's Moscow lab. In certain conditions such a system is able to assemble into a complex hierarchical structure from the basic elements -- macromolecules. The final structure will have completely different characteristics than the basic elements in the initial non-organized state. During this process, nanometer-sized particles transform into a material with targeted properties and functionality.

The international team of researchers participating in this project was the first to code all properties required for practical use (e.g., the full stress-strain curve) in the molecular structure of such polymers. The whole deformation behavior may be coded in a specific way to make it completely identical to that of the living tissues. Among the prospects opened by this material Dmitry Ivanov emphasizes its use in medicine, in particular in the manufacture of biological implants where it will eliminate the issue of mechanical inconsistency. Each biological implant should have mechanical properties very similar to those of surrounding tissues, otherwise the patient may be hurt. The figure shows sample stress-strain curves of pig skin compared to those of the developed polymers. One can see that the new materials reproduce the mechanical properties of living skin with high accuracy.

Another important element of the synthesized molecular dumbbells are their end pieces. In the course of self-assembly they form nanosized spheres creating an active camouflage effect, as the distances between the spheres satisfy the conditions for diffraction of visible light. Mechanical deformation of such a structure changes the conditions of diffraction and results in a blue shift of the iridescent sample colour. Therefore, the new materials can reproduce not only the stress-strain curves of living tissues but also their coloration created by a purely physical phenomenon - light diffraction.

Ivanov explains: "Our materials may be programmed to cover a wide range of mechanical and colour characteristics. The only thing you have to do is set out the necessary structural parameters of the molecular "brushes". This approach is similar to coding our hereditary information in DNA strands."

Contacts and sources:
Yana Khlyustova
Lomonosov Moscow State University

Citation: Chameleon-like elastomers with molecularly encoded strain-adaptive stiffening and coloration

Bacteria "Breathes" Rocks by Growing Electric Nanowires

A nanowire structure and electron transfer process of a unique bacterium could provide a foundation for sustainable energy.

Could a unique bacterium be nature's microscopic power plant?

Scientist Moh El-Naggar and his team think it's possible. They work with the Shewanella oneidensis species of bacteria, one of a group of microbes that essentially "breathe" rocks.

As part of their metabolism, the bacteria have developed a way to transfer electrons from the interior of the cell across their outer membrane to a receiving surface in the outside world.

The process is akin to the way humans use oxygen to breathe. The body takes electrons from food and, ultimately, transfers those electrons to oxygen inhaled by the lungs.

Scientist Moh El-Naggar studies bacteria that construct membrane wires to 'breathe' rock. This three-dimensional construct depicts a wire composed of spherical vesicles containing electron-transporting proteins (red and green).

Credit: Sahand Pirbadian of USC Dornsife and Poorna Subramanian of Caltech

The organism was discovered nearly 30 years ago by Kenneth Nealson, now Wrigley Chair in Environmental Studies and professor of Earth sciences and biological sciences at USC Dornsife. Scientists have more recently been interested in learning exactly how the bacteria pull off such an exceptional biological trick.

El-Naggar,associate professor of physics, biological sciences, and chemistry at USC Dornsife, and a collaborative team from USC and Caltech think they have the answer. Their paper published on March 22 by the Proceedings of the National Academy of Sciences highlights research that offers a new understanding of how these bacteria may use "nanowires" to accomplish the electronic feat.

Micro machines

Harnessing energy from living, organic sources holds tremendous potential for new sustainable technology. A microbial fuel cell, for example, could generate electricity by capturing electrons from the bacteria on electrodes instead of the rocks that these organisms evolved to breathe.

"Microbes are highly evolved machines," El-Naggar said. "And what we have here is a class that is really good at converting energy and interacting with the abiotic world."

Another advantage to using "electric bacteria" is already being explored at USC -- wastewater treatment. Microbes feed on the waste, oxidizing the organic substances and producing a small amount of electricity.

Aside from myriad practical applications, these organisms could exemplify the kinds of life that exist in environments where little or no oxygen exists, such as the deep ocean or under the Martian surface.

Depositing electrons outside the cell is how they survive, said El-Naggar, who holds the Robert D. Beyer ('81) Early Career Chair in Natural Sciences. "If one were to shut down the ability to transfer the electron out of their system, they would not be able to make energy. The bacteria would basically suffocate."

Wired for survival

Under the microscope, scientists can see what appear to be filaments projecting from these cells. For years, the prevailing hypothesis was that these were a form of tiny hairs called pili, similar to those found on other types of bacteria.

But in 2013, a research scientist in El-Naggar's laboratory, Sahand Pirbadian, discovered that these projections, referred to as "nanowires," were actually extensions of the cell membrane covered in cytochromes -- proteins containing iron that facilitate electron transport. These nanowires allow the bacteria to connect with surfaces much further away than one would expect.

Through light microscopy imaging, the team had an idea of the nanowires' basic composition. But they were curious as to whether the cytochromes were close enough together to transport electrons along the wire. If the density were high enough, they thought a bridge could form along the membrane that would allow an electron to cross onto external surfaces.

Insane in the membrane

For the current study, El-Naggar and Pirbadian collaborated with Grant Jensen and Poorna Subramanian at Caltech, experts in the use of electron cryotomography, or ECT. Using ECT, researchers can instantly freeze cells, preserving them in a form that is extremely close to their natural state, and then image them with nanoscale resolution in three dimensions.

Subramanian and Pirbadian were able to capture life-like images of the bacteria and their nanowires. What they found was intriguing.

"These are not simple tubes," El-Naggar said. "They turned out to be more like a chain of membrane pearls, strung together."

With the images produced by ECT, the team was the first to see how electron transport proteins were distributed in the membrane to form the nanowires. While some were touching each other, many were further apart -- up to 30 nanometers -- a range too far for an electron to jump. With this new information, the team proposed that the proteins float within the membrane. This creates just enough collisions to allow electrons to exchange from one to the next until they reach the end of the nanowire and transfer to the rock or metal surface.

Their next step is to confirm these collisions are, in fact, happening.

While there is much that remains to be learned, El-Naggar is excited about where the research might lead.

"My lab is driven by the idea that we could develop new machines, where living cells are functioning as part of a hybrid biotic-abiotic system," he said. "We are trying build the foundations of a new generation of living electronics."

Contacts and sources:
Jim Key
University of Southern California

Authors on the study include Mohamed Y. El-Naggar and Sahand Pirbadian from the University of Southern California, and Grant J. Jensen and Poorna Subramanian from Caltech.

Water Harvesting from Air with Microengineered SRS Could Aid Billions of People

A slippery rough surface (SRS) inspired by both pitcher plants and rice leaves outperforms state-of-the-art liquid-repellent surfaces in water harvesting applications, according to a team of researchers at Penn State and the University of Texas at Dallas.

The team reports their work online today (March 30) in Science Advances, an open-access journal.

"With an estimated 4 billion people living in a situation of water scarcity during at least some part of the year, an inexpensive method for harvesting water from water vapor or from fog droplets in air could have enormous practical applications, and will help alleviate the water scarcity issues in many regions of the world," said the project's leader, Tak-Sing Wong, who is the Wormley Family Early Career Professor in Engineering and assistant professor of mechanical engineering, Penn State.

In the image, the left panel is a directional slippery rough surface (SRS, this study), the middle panel is a slippery liquid-infused porous surface (SLIPS) and the right panel is a superhydrophobic surface. This image shows a comparison of water harvesting performance of SRS vs other state-of-the-art liquid repellent surfaces.

Credit: Xianming Dai/Nan Sun/Jing Wang/Tak-Sing Wong, Penn State

Many water-harvesting technologies are not as efficient, because when water is attracted to a hydrophilic surface, the water tends to form a sheet and clings to the surface, making it hard to remove. But Wong's post-doctoral scholar, Simon Dai, now an assistant professor at UT Dallas, was looking at combining different biological strategies to create a slippery solution for water harvesting.

"With SRS, we combined the slippery interface of a pitcher plant with the surface architecture of a rice leaf, which has micro/nanoscale directional grooves on its surface that allows water to be removed very easily in one direction but not the other," said Dai.

Dai developed a pitcher plant-inspired slippery surface with hydrophilic chemistry. At the same time, he added the directional grooves and gave the new surface a microscale roughness that increased the surface area. The rate of water and fog harvesting are directly proportional to the amount of surface area on which droplets can form. The rice leaf-inspired grooves whisk the water droplets away through capillary action or gravity.

Through experiments carried out at Penn State, the team showed that these surfaces can collect tiny water droplets from air at a rate faster than many state-of-the-art surfaces. Molecular dynamics simulations carried out at UT Dallas by Dai's colleague, Steven Nielson, explained why the hydrophilic surface was particularly good at water harvesting.

"If the SRS material is produced at scale, we estimate that we can collect over 120 liters of water per square meter of the surface per day, and we can further increase the water harvesting rate by optimizing the SRS," said Nan Sun, graduate student in Wong's group and coauthor of the paper, titled "Hydrophilic Directional Rough Surfaces for Water Harvesting."

Wong's team is currently working on optimizing and scaling up the SRS with the goal to create highly efficient water harvesting systems for providing clean water in water scarcity regions.

Contacts and sources:
A'ndrea Elyse Messer
Penn State

Artificial Intelligence Search NASA Data for Planets Hospitable to Life

As part of an effort to identify distant planets hospitable to life, NASA has established a crowdsourcing project in which volunteers search telescopic images for evidence of debris disks around stars, which are good indicators of exoplanets.

Using the results of that project, researchers at MIT have now trained a machine-learning system to search for debris disks itself. The scale of the search demands automation: There are nearly 750 million possible light sources in the data accumulated through NASA’s Wide-Field Infrared Survey Explorer (WISE) mission alone.

In tests, the machine-learning system agreed with human identifications of debris disks 97 percent of the time. The researchers also trained their system to rate debris disks according to their likelihood of containing detectable exoplanets. In a paper describing the new work in the journal Astronomy and Computing, the MIT researchers report that their system identified 367 previously unexamined celestial objects as particularly promising candidates for further study.

A young sun-like star encircled by its planet-forming disk of gas and dust.
A young sun-like star encircled by its planet-forming disk of gas and dust.
Image: NASA/JPL-Caltech

The work represents an unusual approach to machine learning, which has been championed by one of the paper’s coauthors, Victor Pankratius, a principal research scientist at MIT’s Haystack Observatory. Typically, a machine-learning system will comb through a wealth of training data, looking for consistent correlations between features of the data and some label applied by a human analyst — in this case, stars circled by debris disks.

But Pankratius argues that in the sciences, machine-learning systems would be more useful if they explicitly incorporated a little bit of scientific understanding, to help guide their searches for correlations or identify deviations from the norm that could be of scientific interest.

“The main vision is to go beyond what A.I. is focusing on today,” Pankratius says. “Today, we’re collecting data, and we’re trying to find features in the data. You end up with billions and billions of features. So what are you doing with them? What you want to know as a scientist is not that the computer tells you that certain pixels are certain features. You want to know ‘Oh, this is a physically relevant thing, and here are the physics parameters of the thing.’”

Classroom conception

The new paper grew out of an MIT seminar that Pankratius co-taught with Sara Seager, the Class of 1941 Professor of Earth, Atmospheric, and Planetary Sciences, who is well-known for her exoplanet research. The seminar, Astroinformatics for Exoplanets, introduced students to data science techniques that could be useful for interpreting the flood of data generated by new astronomical instruments. After mastering the techniques, the students were asked to apply them to outstanding astronomical questions.

For her final project, Tam Nguyen, a graduate student in aeronautics and astronautics, chose the problem of training a machine-learning system to identify debris disks, and the new paper is an outgrowth of that work. Nguyen is first author on the paper, and she’s joined by Seager, Pankratius, and Laura Eckman, an undergraduate majoring in electrical engineering and computer science.

From the NASA crowdsourcing project, the researchers had the celestial coordinates of the light sources that human volunteers had identified as featuring debris disks. The disks are recognizable as ellipses of light with slightly brighter ellipses at their centers. The researchers also used the raw astronomical data generated by the WISE mission.

To prepare the data for the machine-learning system, Nguyen carved it up into small chunks, then used standard signal-processing techniques to filter out artifacts caused by the imaging instruments or by ambient light. Next, she identified those chunks with light sources at their centers, and used existing image-segmentation algorithms to remove any additional sources of light. These types of procedures are typical in any computer-vision machine-learning project.

Coded intuitions

But Nguyen used basic principles of physics to prune the data further. For one thing, she looked at the variation in the intensity of the light emitted by the light sources across four different frequency bands. She also used standard metrics to evaluate the position, symmetry, and scale of the light sources, establishing thresholds for inclusion in her data set.

In addition to the tagged debris disks from NASA’s crowdsourcing project, the researchers also had a short list of stars that astronomers had identified as probably hosting exoplanets. From that information, their system also inferred characteristics of debris disks that were correlated with the presence of exoplanets, to select the 367 candidates for further study.

“Given the scalability challenges with big data, leveraging crowdsourcing and citizen science to develop training data sets for machine-learning classifiers for astronomical observations and associated objects is an innovative way to address challenges not only in astronomy but also several different data-intensive science areas,” says Dan Crichton, who leads the Center for Data Science and Technology at NASA’s Jet Propulsion Laboratory. “The use of the computer-aided discovery pipeline described to automate the extraction, classification, and validation process is going to be helpful for systematizing how these capabilities can be brought together. The paper does a nice job of discussing the effectiveness of this approach as applied to debris disk candidates. The lessons learned are going to be important for generalizing the techniques to other astronomy and different discipline applications.”

“The Disk Detective science team has been working on its own machine-learning project, and now that this paper is out, we’re going to have to get together and compare notes,” says Marc Kuchner, a senior astrophysicist at NASA’s Goddard Space Flight Center and leader of the crowdsourcing disk-detection project known as Disk Detective. “I’m really glad that Nguyen is looking into this because I really think that this kind of machine-human cooperation is going to be crucial for analyzing the big data sets of the future.”

Cpntacts and sources:
Sara Remus
Massachusetts Institute of Technology (MIT)

Life in the Clouds for Venus? Search for Extraterrestrial Life in the Neighborhood

In the search for extraterrestrial life, scientists have turned over all sorts of rocks.

Mars, for example, has geological features that suggest it once had — and still has — subsurface liquid water, an almost sure prerequisite for life. Scientists have also eyed Saturn’s moons Titan and Enceladus as well as Jupiter’s moons Europa, Ganymede and Callisto as possible havens for life in the oceans under their icy crusts.

Now, however, scientists are dusting off an old idea that promises a new vista in the hunt for life beyond Earth: the clouds of Venus.

In a paper published online today (March 30, 2018) in the journal Astrobiology, an international team of researchers led by planetary scientist Sanjay Limaye of the University of Wisconsin–Madison’s Space Science and Engineering Center lays out a case for the atmosphere of Venus as a possible niche for extraterrestrial microbial life.

A composite image of the planet Venus as seen by the Japanese probe Akatsuki. The clouds of Venus could have environmental conditions conducive to microbial life.

Image from the Akatsuki Orbiter, built by Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency

“Venus has had plenty of time to evolve life on its own,” explains Limaye, noting that some models suggest Venus once had a habitable climate with liquid water on its surface for as long as 2 billion years. “That’s much longer than is believed to have occurred on Mars.”

On Earth, terrestrial microorganisms — mostly bacteria — are capable of being swept into the atmosphere, where they have been found alive at altitudes as high as 41 kilometers (25 miles) by scientists using specially equipped balloons, according to study co-author David J. Smith of NASA’s Ames Research Center.

There is also a growing catalog of microbes known to inhabit incredibly harsh environments on our planet, including the hot springs of Yellowstone, deep ocean hydrothermal vents, the toxic sludge of polluted areas, and in acidic lakes worldwide.

“On Earth, we know that life can thrive in very acidic conditions, can feed on carbon dioxide, and produce sulfuric acid,” says Rakesh Mogul, a professor of biological chemistry at California State Polytechnic University, Pomona, and a co-author on the new paper. He notes that the cloudy, highly reflective and acidic atmosphere of Venus is composed mostly of carbon dioxide and water droplets containing sulfuric acid.

Sanjay Limaye
Credit: University of Wisconsin–Madison

The habitability of Venus’ clouds was first raised in 1967 by noted biophysicist Harold Morowitz and famed astronomer Carl Sagan. Decades later, the planetary scientists David Grinspoon, Mark Bullock and their colleagues expanded on the idea.

Supporting the notion that Venus’ atmosphere could be a plausible niche for life, a series of space probes to the planet launched between 1962 and 1978 showed that the temperature and pressure conditions in the lower and middle portions of the Venusian atmosphere — altitudes between 40 and 60 kilometers (25–27 miles) — would not preclude microbial life. The surface conditions on the planet, however, are known to be inhospitable, with temperatures soaring above 450 degrees Celsius (860 degrees Fahrenheit).

Limaye, who conducts his research as a NASA participating scientist in the Japan Aerospace Exploration Agency’s Akatsuki mission to Venus, was eager to revisit the idea of exploring the planet’s atmosphere after a chance meeting at a teachers’ workshop with paper co-author Grzegorz Słowik of Poland’s University of Zielona Góra. Slowik made him aware of bacteria on Earth with light-absorbing properties similar to those of unidentified particles that make up unexplained dark patches observed in the clouds of Venus. Spectroscopic observations, particularly in the ultraviolet, show that the dark patches are composed of concentrated sulfuric acid and other unknown light-absorbing particles.

Those dark patches have been a mystery since they were first observed by ground-based telescopes nearly a century ago, says Limaye. They were studied in more detail by subsequent probes to the planet.

“Venus shows some episodic dark, sulfuric rich patches, with contrasts up to 30–40 percent in the ultraviolet, and muted in longer wavelengths. These patches persist for days, changing their shape and contrasts continuously and appear to be scale dependent,” says Limaye.

“Venus has had plenty of time to evolve life on its own,” explains Limaye, noting that some models suggest Venus once had a habitable climate with liquid water on its surface for as long as 2 billion years. “That’s much longer than is believed to have occurred on Mars.”

The particles that make up the dark patches have almost the same dimensions as some bacteria on Earth, although the instruments that have sampled Venus’ atmosphere to date are incapable of distinguishing between materials of an organic or inorganic nature.

The patches could be something akin to the algae blooms that occur routinely in the lakes and oceans of Earth, according to Limaye and Mogul — only these would need to be sustained in the Venusian atmosphere.

Limaye, who has spent his career studying planetary atmospheres, was further inspired to revisit the idea of microbial life in the clouds of Venus by a visit to Tso Kar, a high-altitude salt lake in northern India where he observed the powdery residue of sulfur-fixing bacteria concentrated on decaying grass at the edge of the lake being wafted into the atmosphere.

Limaye notes, however, that a part of the equation that isn’t known is when Venus’ liquid water evaporated — extensive lava flows in the last billion years likely have either destroyed or covered up the planet’s earlier terrestrial history.

In the hunt for extraterrestrial life, planetary atmospheres other than Earth’s remain largely unexplored.

A Venus Atmospheric Maneuverable Platform, or VAMP. The aircraft, which would fly like a plane and float like a blimp, could help explore the atmosphere of Venus, which has temperature and pressure conditions that do not preclude the possibility of microbial life.

Credit: Northrop Grumman

One possibility for sampling the clouds of Venus, says Limaye, is on the drawing board: VAMP, or Venus Atmospheric Maneuverable Platform, a craft that flies like a plane but floats like a blimp and could stay aloft in the planet’s cloud layer for up to a year gathering data and samples.

Such a platform could include instruments like Raman Lidar, meteorological and chemical sensors, and spectrometers, says Limaye. It could also carry a type of microscope capable of identifying living microorganisms.

“To really know, we need to go there and sample the clouds,” says Mogul. “Venus could be an exciting new chapter in astrobiology exploration.”

The Wisconsin scientist and his colleagues remain hopeful that such a chapter can be opened as there are ongoing discussions about possible NASA participation in Russia’s Roscosmos Venera-D mission, now slated for the late 2020s. Current plans for Venera-D might include an orbiter, a lander and a NASA-contributed surface station and maneuverable aerial platform.

Contacts and sources:
Sanjay Limaye  
University of Wisconsin–Madison

Hear Like Cats, Better than Dogs, With Device Tens of Trillions Times Smaller Than Human Eardrum

Case Western Reserve University researchers achieve cat-like 'hearing' with device 10,000,000,000,000 times smaller than human eardrum.

 Researchers at Case Western Reserve University (CWRU)  are developing atomically thin "drumheads" able to receive and transmit signals across a radio frequency range far greater than what we can hear with the human ear.

But the drumhead is tens of trillions times (10 followed by 13 zeros) smaller in volume and 100,000 times thinner than the human eardrum.

The advances will likely contribute to making the next generation of ultralow-power communications and sensory devices smaller and with greater detection and tuning ranges.

llustration of ultrasensitive optical interrogation of the motions of atomically thin drumhead nanoelectromechanical resonators (made of atomic layers of MoS2 semiconductor crystals).

Credit: CWRU

"Sensing and communication are key to a connected world," said Philip Feng, an associate professor of electrical engineering and computer science and corresponding author on a paper about the work published March 30 in the journal Science Advances. "In recent decades, we have been connected with highly miniaturized devices and systems, and we have been pursuing ever-shrinking sizes for those devices."

The challenge with miniaturization: Also achieving a broader dynamic range of detection, for small signals, such as sound, vibration, and radio waves.

"In the end, we need transducers that can handle signals without losing or compromising information at both the 'signal ceiling' (the highest level of an undistorted signal) and the 'noise floor' (the lowest detectable level)," Feng said.

While this work was not geared toward specific devices currently on the market, researchers said, it was focused on measurements, limits and scaling which would be important for essentially all transducers.

Those transducers may be developed over the next decade, but for now, Feng and his team have already demonstrated the capability of their key components-the atomic layer drumheads or resonators-at the smallest scale yet.

The work represents the highest reported dynamic range for vibrating transducers of their type. To date, that range had only been attained by much larger transducers operating at much lower frequencies-like the human eardrum, for example.

Comparison of dynamic ranges and frequency bands of the eardrums of humans, other animals, and atomically thin drumheads.

Credit: CWRU

"What we've done here is to show that some ultimately miniaturized, atomically thin electromechanical drumhead resonators can offer remarkably broad dynamic range, up to ~110dB, at radio frequencies (RF) up to over 120MHz," Feng said. "These dynamic ranges at RF are comparable to the broad dynamic range of human hearing capability in the audio bands."

New dynamic standard

Feng said the key to all sensory systems-from naturally occurring sensory functions in animals to sophisticated devices in engineering-is that desired dynamic range.

Dynamic range is the ratio between the signal ceiling over the noise floor and is usually measured in decibels (dB).

Human eardrums normally have dynamic range of about 60 to 100dB in the range of 10Hz to 10kHz, and our hearing quickly decreases outside this frequency range. Other animals, such as the common house cat or beluga whale (see illustration), can have comparable or even wider dynamic ranges in higher frequency bands.

The vibrating nanoscale drumheads developed by Feng and his team are made of atomic layers of semiconductor crystals (single-, bi-, tri-, and four-layer MoS2 flakes, with thickness of 0.7, 1.4, 2.1, and 2.8 nanometers), with diameters only about 1 micron.

They construct them by exfoliating individual atomic layers from the bulk semiconductor crystal and using a combination of nanofabrication and micromanipulation techniques to suspend the atomic layers over micro-cavities pre-defined on a silicon wafer, and then making electrical contacts to the devices.

Further, these atomically thin RF resonators being tested at Case Western Reserve show excellent frequency "tunability," meaning their tones can be manipulated by stretching the drumhead membranes using electrostatic forces, similar to the sound tuning in much larger musical instruments in an orchestra, Feng said.

The study also reveals that these incredibly small drumheads only need picoWatt (pW, 10^-12 Watt) up to nanoWatt (nW, 10^-9 Watt) level of RF power to sustain their high frequency oscillations.

"Not only having surprisingly large dynamic range with such tiny volume and mass, they are also energy-efficient and very 'quiet' devices", Feng said, "We 'listen' to them very carefully and 'talk' to them very gently."

Contacts and sources:
Mike Scott
Case Western Reserve University (CWRU) 

The paper's co-authors were: Jaesung Lee, a Case Western Reserve post-doctoral research associate; Max Zenghui Wang, a former research associate now at the University of Electronic Science and Technology of China (UESTC), Chengdu, China; Keliang He, a former graduate student in physics, now a senior engineer at Nvidia; Rui Yang, a former graduate student and now a post-doctoral scholar at Stanford University; and Jie Shan, a former physics professor at Case Western Reserve now at Cornell University.

The work has been financially supported by the National Academy of Engineering Grainger Foundation Frontiers of Engineering Award (Grant: FOE 2013-005) and the National Science Foundation CAREER Award (Grant: ECCS-1454570).

Highest Known Sea Levels Create the Iconic Shape of Mount Etna?

The iconic cone-like structure of Mount Etna could have been created after water levels in the Mediterranean Sea rose following an extended period of deglaciation, according to new research.

A study by Iain Stewart, Professor of Geoscience Communication at the University of Plymouth, explores changes in the volcano’s structures which began around 130,000 years ago.

Scientists have previously said the switch from a fissure-type shield volcano to an inland cluster of nested stratovolcanoes was caused by a tectonically driven rearrangement of major border faults.

However Professor Stewart, writing in Episodes, has suggested the change coincides closely with a period of particularly high sea levels that could have triggered the fundamental change in Mount Etna’s magmatic behaviour.

He also believes such a phenomenon could also explain changes at other volcanic sites across the world including the similarly iconic Stromboli, just off the north coast of Sicily, and even the volcano on Montserrat in the Caribbean.

Mount Etna
Credit:  Flickr/Wikimedia Commons

Professor Stewart, who fronted the BBC documentary Volcano Live in 2013, said: “Mount Etna is arguably one of the most iconic volcanoes on the planet, but 100,000 years ago there would have been no cone-like structure such as you see today. I had always been interested to know what prompted that to happen but I believe the dates of sea levels rising – and how they correspond to the volcano physically changing – offer a potential explanation. The precise sensitivities of the plumbing beneath Etna has always been something of a mystery, but exploring how sea levels interact with its fault lines could shed new light on its creation and future.”

Mount Etna’s eruptive history began around 500,000 years ago with submarine volcanism. But this changed around 220,000 years ago into fissure type activity which built a north-south chain of eruptive centres along the present coastline.

This ultimately created a broad shield volcano immediately east of Etna’s coastline, which ceased around 130,000 years ago at the same time as the sea reached its highest levels following a period of deglaciation starting almost 12,000 years earlier.

However, Professor Stewart believes that over a few millennia those sea level rises could have caused the fault system beneath and around Mount Etna to completely change in behaviour, sealing up old lava flows and ultimately forcing them to emerge elsewhere on the island. This ultimately created the iconic cone structure visible today, with Europe’s most active volcano still continuing to erupt tens of thousands of years later.

This new research has been published days after another study showed that Etna is edging towards the Mediterranean at a rate of around 14mm per year.

Professor Stewart added: “The latest measurements of Etna’s seaward slide give us a much better understanding of just how unstable Europe’s biggest volcano is. But the big question remains: what is driving that instability? For me, the fact that Etna’s dramatic switches in eruptive behaviour coincide with past abrupt changes in ocean levels implies that Etna’s antics are at least in part orchestrated by fluctuating waters of the Mediterranean Sea.”

Contacts and sources:
Alan Williams
University of Plymouth

The full study – Did sea-level change cause the switch from fissure-type to central-type volcanism at Mount Etna, Sicily? by Iain S Stewart – is published in Episodes (Journal of International Geoscience), DOI: 10.18814/epiiugs/2018/v41i1/018002.

Rewritable Paper Thin LCD Is Flexible, Light and Tought

Optoelectronic engineers in China and Hong Kong have manufactured a special type of liquid crystal display (LCD) that is paper-thin, flexible, light and tough. With this, a daily newspaper could be uploaded onto a flexible paperlike display that could be updated as fast as the news cycles. It sounds like something from the future, but scientists estimate it will be cheap to produce, perhaps only costing $5 for a 5-inch screen. The new optically rewritable LCD design was reported this week in Applied Physics Letters, from AIP Publishing.

The team focused on two key innovations for achieving highly flexible designs. The first is the recent development of optically rewritable LCDs. Like conventional LCD displays, the display is structured like a sandwich, with a liquid crystal filling between two plates. Unlike conventional liquid crystals where electrical connections on the plates create the fields required to switch individual pixels from light to dark, optically rewritable LCDs coat the plates with special molecules that realign in the presence of polarized light and switch the pixels. This removes the need for traditional electrodes, reduces the structure’s bulk and allows more choices in the type and thickness of plates. 

Consequently, optically rewritable LCDs are thinner than traditional LCDs, at less than half a millimeter thick, can be made from flexible plastic, and weigh only a few grams. “It’s only a little thicker than paper,” said Jiatong Sun, a co-author from Donghua University in China.

Optically rewritable LCDs are durable and cheap to manufacture because of their simple structure. Moreover, like an electronic paper screen in an e-book, energy is only required to switch display images or text. Therefore, running costs are low because these new LCDs don’t need power to sustain an image once it is written on the screen. 

Combined flexible blue optically rewritable LCD

Credit:  Zhang et al.

The second innovation involves the spacers that create the separation of the plastic or glass plates. “We put spacers between glass layers to keep the liquid crystal layer uniform,” Sun said. Spacers are used in all LCDs to determine the thickness of the liquid crystal. A constant thickness is necessary for good contrast ratio, response time and viewing angle. However, when plates bends, it forces the liquid crystal away from the impact site and leaves sections of the screen blank and so alterations in spacer design are critical to prevent liquid crystal in flexible LCDs from moving excessively. Developing a flexible design that overcomes this barrier has proven challenging.

The researchers tried three different spacer designs and found that a meshlike spacer prevented liquid crystal from flowing when their LCD was bent or hit. This innovation enabled them to create the first flexible optically rewritable LCD.

An additional innovation involved improved color rendering. The scientists report that until this study, optically rewritable LCDs had only been able to display two colors at a time. Now, their optically rewritable LCD simultaneously displays the three primary colors. They achieved this by placing a special type of liquid crystal behind the LCD, which reflected red, blue and green. To make this into a commercial product, Sun wants to improve the resolution of the flexible optically rewritable LCD.

“Now we have three colours but for full colour we need to make the pixels too small for human eyes to see,” Sun said.

Contacts and sources:
Julia Majors
American Institute of Physics

Citation: A flexible optically re-writable color liquid crystal display. Authors: Yihong Zhang, Jiatong Sun, Yang Liu, Jianhua Shang, Hao Liu, Huashan Liu, Xiaohui Gong, Vladimir Chigrinov, Hoi Sing Kowk. Applied Physics Letters, 2018; 112 (13): 131902 DOI: 10.1063/1.5021619

Thursday, March 29, 2018

Sahara Desert Grew 10% since 1920 Says New NSF Study

The Sahara Desert has expanded by about 10 percent since 1920, according to a new study by National Science Foundation (NSF)-funded scientists at the University of Maryland (UMD).

The research is the first to assess century-scale changes to the boundaries of the world's largest desert. It suggests that other deserts could be expanding as well. The study is published today in the Journal of Climate.

"The trends in Africa of hot summers getting hotter and rainy seasons drying out are linked with factors that include increasing greenhouse gases and aerosols in the atmosphere," says Ming Cai, a program director in NSF's Division of Atmospheric and Geospace Sciences, which funded the research. "These trends have a devastating effect on the lives of African people, who depend on agriculture-based economies."

Satellite image showing the Sahara Desert (beige) and savannas to the south (green).

Credit: NASA

Deserts defined

Deserts are defined by low average annual rainfall -- usually 100 millimeters (less than 4 inches) of rain per year or less. The researchers analyzed annual rainfall data recorded throughout Africa from 1920 to 2013 and found that the Sahara, which occupies much of the northern part of the continent, expanded by 10 percent during this period.

When the scientists looked at seasonal trends over the same period, the most notable expansion of the Sahara occurred in summer, resulting in a nearly 16 percent increase in the desert's average area over the 93-year span covered by the study.

Africa's Sahara Desert is expanding, encroaching on savanna ecosystems.

Credit: Luca Galuzzi

"Our results are specific to the Sahara, but they likely have implications for the world's other deserts," said Sumant Nigam, an atmospheric and ocean scientist at UMD, and the senior author of the study.

Why the expansion?

The results suggest that human-caused climate change, as well as natural climate cycles, caused the desert's expansion. The geographic pattern of expansion varied from season to season, with the largest differences along the Sahara's northern and southern boundaries.

"Deserts usually form in the subtropics because of what's called Hadley circulation, through which air rises at the equator and descends in the subtropics," Nigam said. That circulation has a drying effect. "Climate change is likely to widen this Hadley circulation, causing the northward advance of subtropical deserts," said Nigam. "The southward creep of the Sahara suggests that additional mechanisms are at work."

The Sahara is the world's largest warm-weather desert, roughly equal in size to the contiguous United States.

A seemingly endless sea of sand, the Sahara stretches to the horizon.

Credit: Wikimedia

Like all deserts, the boundaries of the Sahara fluctuate with the seasons, expanding in the dry winter and contracting during the wetter summer.

The southern border of the Sahara adjoins the Sahel, the semi-arid transition zone that lies between the Sahara and fertile savannas farther south.

The Sahara expands as the Sahel retreats, disrupting the region's fragile savanna ecosystems and human societies. Lake Chad, which sits at the center of this transition zone, serves as a bellwether for changing conditions in the Sahel.

"The entire Chad Basin falls in the region where the Sahara has crept southward, and the lake is drying out," Nigam explained. "It's a very visible footprint of reduced rainfall not just locally, but across the whole region. It's an indicator of declining water in the Chad Basin."

Natural climate cycles, or climate change?

Natural climate cycles can affect rainfall in the Sahara and the Sahel. The researchers concluded that these climate cycles accounted for about two-thirds of the total expansion of the Sahara.

The remaining one-third can be attributed to human-caused climate change, but the authors note that longer climate records that extend across several climate cycles are needed to reach definitive conclusions.

An intense Saharan dust storm sends a massive dust plume northwestward over the Atlantic Ocean.

Credit: NASA

"Many previous studies have documented trends in rainfall in the Sahara and Sahel, but our study is unique in that we use these trends to infer changes in the desert expanse on a century timescale," said researcher Natalie Thomas of UMD, lead author of the paper.

The results have far-reaching implications for the future of the Sahara and other subtropical deserts. As the world's population continues to grow, a reduction in land with adequate rainfall to support crops could have devastating consequences.

"Our priority was to document long-term trends in rainfall and temperature in the Sahara," said Thomas. "Our next step will be to look at what's driving these trends, for the Sahara and elsewhere.

"We've already started looking at seasonal temperature trends over North America, for example. Here, winters are getting warmer but summers are about the same. In Africa, it's the opposite -- winters are holding steady but summers are getting warmer. So the stresses in Africa are already more severe."

 Contacts and sources: 
Cheryl Dybas, NSF,
Matt Wright, University of Maryland,

What Stops Mass Extinctions?

Black plague killed between 30 to 50 percent of people worldwide. The cause, Yersinia pestis, is still around, but people are not dying of the plague. An even more devastating modern disease caused by the chytrid fungus wiped entire frog and salamander populations off the map. New results from work at the Smithsonian Tropical Research Institute (STRI) in Panama published in the Mar. 29 edition of Science, reveal the outcomes of the chytridiomycosis epidemic and their implications for diseases of mass destruction.

"Imagine a deadly disease that affects not only humans but other mammal species like dogs, cats and cows," said Roberto Ibáñez, STRI staff scientist and in-country director of the Panama Amphibian Rescue and Conservation Project. "Chytridiomycosis kills off most of the individuals in many different species of amphibians, but for some species it stops short of driving them to complete extinction."

"We were lucky that Karen Lips, now at the University of Maryland in College Park and colleagues saw this epidemic coming into Panama from Costa Rica, and researchers were able to study both the frogs and the disease before, during and after the peak of the epidemic," Ibañez said.

STRI staff scientist and in-country director of the Panama Amphibian Rescue and Conservation Project, Roberto Ibañez, collecting frogs for captive breeding.

Credit: Sean Mattson, STRI

Disease outbreaks rarely annihilate the host species, because pathogens need their hosts in order to survive and reproduce.

"Because we have pathogen and host samples from before, during and after the epidemic, we can ask whether some frogs survived because the pathogen grew weaker through time, or because the frogs' immune systems or resistance increased through time," said Jamie Voyles, disease ecologist at the University of Nevada, Reno, and first author of the paper.

This Panamanian frog demonstrates a very wide range of color patters, thus its name, Atelopus varius.
Credit: Brian Gratwicke

The authors tracked changes in amphibian species numbers and communities, infection patterns, host resistance and pathogen virulence for several decades hoping to see evidence of a weaker pathogen and/or of host resistance. The disease-causing fungus, Batrachochytrium dendrobatidis, appeared in El Cope, Panama, in 2004, in El Valle in 2006 and in Campana National Park in 2007. Between five and 13 years after the epidemic, the authors saw evidence of some recovery in nine species, but the fungus was still present. However, not all frog species rebounded, some species are still missing.

There was no evidence that the pathogen grew more slowly, responded differently to skin secretions from the frogs or became less virulent.

This Panamanian frog demonstrates a very wide range of color patters, thus its name, Atelopus varius.

Credit: Brian Gratwicke

However, skin secretions from wild frogs that survived the epidemic inhibited growth of the fungus significantly more than secretions from frogs moved into captive breeding programs before the disease arrived. Researchers think that wild frogs became more resistant to the disease.

"The Panama Amphibian Rescue and Conservation Project collected healthy frogs before the outbreak," Ibañez said. "We learned to breed them in captivity and are now releasing Atelopus varius in areas where the epidemic has passed, so it is extremely important for us to realize that the defenses of these frogs may be weaker than the defenses of frogs that survived the epidemic in the wild. Captive breeding programs must consider breeding and releasing frogs with stronger defenses, and testing their skin secretions against the fungus is one useful tool to see which frogs are more resistant."

As in other pathogens that infect multiple species, the chytrid fungus poses a threat to amphibians, the cytrid fungus poses a threat to amphibians, increasing the likelihood of extinction of some species. It is vital to understand how disease transitions work--from outbreak, to epidemic, to coexistence--and our results have implications for a skyrocketing human population facing emerging diseases with the potential to cause global pandemics," said Ibañez.

Contacts and sources:
Beth King
The Smithsonian Tropical Research Institute

Citation:  Voyles J., Woodhams, D.C., Saenz, V et al. 2018. Shifts in disease dynamics in a tropical amphibian assemblage are not due to pathogen attenuation. Science. 10.1126/science.aao4806

Author affiliations include: the Smithsonian Tropical Research Institute; the University of Nevada, Reno; the University of Pittsburgh; the University of California, Berkeley; the New Mexico Institute of Mining and Technology; the Arizona Game and Fish Department; Vanderbilt University; Sistema Nacional de Investigación, Panama; La Mica Biological Station and the Fundación Centro de Conservación de Anfibios, Panama.

Your Ultra-Slow Brain Waves Link Directly to the State of Consciousness

Very slow brain waves, long considered an artifact of brain scanning techniques, may be more important than anyone had realized. Researchers at Washington University School of Medicine in St. Louis have found that very slow waves are directly linked to state of consciousness and may be involved in coordinating activity across distant brain regions.

Credit: Washington University School of Medicine

If you keep a close eye on an MRI scan of the brain, you’ll see a wave pass through the entire brain like a heartbeat once every few seconds. This ultra-slow rhythm was recognized decades ago, but no one quite knew what to make of it. MRI data are inherently noisy, so most researchers simply ignored the ultra-slow waves.

But by studying electrical activity in mouse brains, researchers at Washington University School of Medicine in St. Louis have found that the ultra-slow waves are anything but noise. They are more like waves in the sea, with everything the brain does taking place in boats upon that sea. Research to date has been focused on the goings-on inside the boats, without much thought for the sea itself. But the new information suggests that the waves play a central role in how the complex brain coordinates itself and that the waves are directly linked to consciousness.

“Your brain has 100 billion neurons or so, and they have to be coordinated,” said senior author Marcus Raichle, MD, the Alan A. and Edith L. Wolff Distinguished Professor of Medicine and a professor of radiology at Mallinckrodt Institute of Radiology at the School of Medicine. “These slowly varying signals in the brain are a way to get a very large-scale coordination of the activities in all the diverse areas of the brain. When the wave goes up, areas become more excitable; when it goes down, they become less so.”

The study is published March 29 in the journal Neuron.

In the early 2000s, Raichle and others discovered patterns of brain activity in people as they lay quietly in MRI machines, letting their minds wander. These so-called resting-state networks challenged the assumption that the brain quiets itself when it’s not actively engaged in a task. Now we know that even when you feel like you’re doing nothing, your brain is still humming along, burning almost as much energy daydreaming as solving a tough math problem.

Using resting-state networks, other researchers started searching for – and finding – brain areas that behaved differently in healthy people than in people with brain diseases such as schizophrenia and Alzheimer’s. But even as resting-state MRI data provided new insights into neuropsychiatric disorders, they also consistently showed waves of activity spreading with a slow regularity throughout the brain, independently of the disease under study. Similar waves were seen on brain scans of monkeys and rodents.

Some researchers thought that these ultra-slow waves were no more than an artifact of the MRI technique itself. MRI gauges brain activity indirectly by measuring the flow of oxygen-rich blood over a period of seconds, a very long timescale for an organ that sends messages at one-tenth to one-hundredth of a second. Rather than a genuinely slow process, the reasoning went, the waves could be the sum of many rapid electrical signals over a relatively long time.

First author Anish Mitra, PhD, and Andrew Kraft, PhD – both MD/PhD students at Washington University – and colleagues decided to approach the mystery of the ultra-slow waves using two techniques that directly measure electrical activity in mice brains. In one, they measured such activity on the cellular level. In the other, they measured electrical activity layer by layer along the outer surface of the brain.

They found that the waves were no artifact: Ultra-slow waves were seen regardless of the technique, and they were not the sum of all the faster electrical activity in the brain.

Instead, the researchers found that the ultra-slow waves spontaneously started in a deep layer of mice’s brains and spread in a predictable trajectory. As the waves passed through each area of the brain, they enhanced the electrical activity there. Neurons fired more enthusiastically when a wave was in the vicinity.

Moreover, the ultra-slow waves persisted when the mice were put under general anesthesia, but with the direction of the waves reversed.

“There is a very slow process that moves through the brain to create temporary windows of opportunity for long-distance signaling,” Mitra said. “The way these ultra-slow waves move through the cortex is correlated with enormous changes in behavior, such as the difference between conscious and unconscious states.”

The fact that the waves’ trajectory changed so dramatically with state of consciousness suggests that ultra-slow waves could be fundamental to how the brain functions. If brain areas are thought of as boats bobbing about on a slow-wave sea, the choppiness and direction of the sea surely influences how easily a message can be passed from one boat to another, and how hard it is for two boats to coordinate their activity.

The researchers now are studying whether abnormalities in the trajectory of such ultra-slow waves could explain some of the differences seen on MRI scans between healthy people and people with neuropsychiatric conditions such as dementia and depression.

“If you look at the brain of someone with schizophrenia, you don’t see a big lesion, but something is not right in how the whole beautiful machinery of the brain is organized,” said Raichle, who is also a professor of biomedical engineering, of neurology, of neuroscience and of psychological and brain sciences. “What we’ve found here could help us figure out what is going wrong. These very slow waves are unique, often overlooked and utterly central to how the brain is organized. That’s the bottom line.”

This work was funded by the National Institutes of Health (NIH), grant numbers F30MH106253, NS080675, Q1 R01NS084028, R01NS085419, R01NS094692, F31NS089135, MH102471, R01 NS099429 and R01 NS078223; and the McDonnell Center for Systems Neuroscience.

Contacts and sources:
Tamara Bhandari
Washington University School of Medicine

Citation:  Mitra A, Kraft A, Wright P, Acland B, Snyder AZ, Rosenthal Z, Czerniewski L, Bauer A, Snyder L, Culver J, Lee J-M, Raichle ME. Spontaneous Infra-Slow Brain Activity has Unique Spatiotemporal Dynamics and Laminar Structure. Neuron. March 29, 2018.

Dining Out More Dangerous Than Eating at Home Says Study

Dining out more at restaurants, cafeterias and fast-food outlets may boost total levels of potentially health-harming chemicals called phthalates in the body, according to a study out today. Phthalates, a group of chemicals used in food packaging and processing materials, are known to disrupt hormones in humans and are linked to a long list of health problems.
Credit: The Milken Institute School of Public Health

The study is the first to compare phthalate exposures in people who reported dining out to those more likely to enjoy home-cooked meals. People who reported consuming more restaurant, fast food and cafeteria meals had phthalate levels that were nearly 35 percent higher than people who reported eating food mostly purchased at the grocery store, according to the study.

"This study suggests food prepared at home is less likely to contain high levels of phthalates, chemicals linked to fertility problems, pregnancy complications and other health issues," says senior author Ami Zota, ScD, MS, an assistant professor of environmental and occupational health at Milken Institute School of Public Health (Milken Institute SPH) at the George Washington University. "Our findings suggest that dining out may be an important, and previously under-recognized source of exposure to phthalates for the U.S. population."

Lead author Julia Varshavsky, PhD, MPH, who did the work while she was at the University of California, Berkeley, School of Public Health, Zota, and their colleagues used data from the National Health and Nutrition Examination Survey (NHANES) collected between 2005 and 2014. The 10,253 participants in the study were asked to recall what they ate and where their food came from in the previous 24 hours. The researchers then analyzed the links between what people ate and the levels of phthalate break-down products found in each participant's urine sample.

The team found that 61 percent of the participants reported dining out the previous day. In addition, the researchers found:

The association between phthalate exposure and dining out was significant for all age groups but the magnitude of association was highest for teenagers;

Adolescents who were high consumers of fast food and other food purchased outside the home had 55 percent higher levels of phthalates compared to those who only consumed food at home;

Certain foods, and especially cheeseburgers and other sandwiches, were associated with increased levels of phthalates--but only if they were purchased at a fast-food outlet, restaurant or cafeteria. The study found that sandwiches consumed at fast food outlets, restaurants or cafeterias were associated with 30 percent higher phthalate levels in all age groups.

"Pregnant women, children and teens are more vulnerable to the toxic effects of hormone-disrupting chemicals, so it's important to find ways to limit their exposures," says Varshavsky, who is now a postdoctoral scientist at the University of California, San Francisco. "Future studies should investigate the most effective interventions to remove phthalates from the food supply."

A previous study by Zota and colleagues suggested that fast food may expose consumers to higher levels of phthalates. That study found that people who ate the most fast food, burgers, fries and other foods, had phthalate levels that were as much as 40 percent higher than people who rarely ate such foods

The new study looked more broadly at dining out--not just at fast-food outlets--and found that it was significantly associated with increased exposure to phthalates. The authors say the findings are worrisome because two-thirds of the U.S. population eats at least some food outside the home daily.

Additional authors of the study include Rachel Morello-Frosch at the University of California, Berkeley, and Tracey Woodruff at the University of California, San Francisco.

The team used an innovative method of assessing real-world exposures to multiple phthalates, called cumulative phthalate exposure, which takes into account evidence that some phthalates are more toxic than others. The National Academies of Sciences has weighed in twice on phthalates--first in a 2008 report, they recommended using cumulative risk assessments in order to estimate the human health risk posed by this class of chemicals; and then in 2017 with a report finding that certain phthalates are presumed to be reproductive hazards to humans.

Many products contain phthalates, including take-home boxes, gloves used in handling food, food processing equipment and other items used in the production of restaurant, cafeteria and fast food meals. Previous research suggests these chemicals can leach from plastic containers or wrapping into food.

If verified by additional research, the findings from this study suggest that people who love dining out are getting a side of phthalates with their entrée.

Home-cooked meals may be one way to limit exposure to these harmful chemicals. "Preparing food at home may represent a win-win for consumers," adds Zota. "Home cooked meals can be a good way to reduce sugar, unhealthy fats and salt. And this study suggests it may not have as many harmful phthalates as a restaurant meal."

At the same time, phthalate contamination of the food supply also represents a larger public health problem, one that must be addressed by policymakers. Zota and Woodruff's previous research shows that policy actions, such as bans, can help reduce human exposure to harmful phthalates.

Contacts and sources:
Kathy Fackelmann
George Washington University

Citation:  Dietary sources of cumulative phthalates exposure among the U.S. general population in NHANES 2005-2014. Julia Varshavsky et al. Environment International, 2018

Monkeys Synchronize Brains When They Collaborate To Perform Motor Tasks

Though their purpose and function are still largely unknown, mirror neurons in the brain are believed by some neuroscientists to be central to how humans relate to each other. Deficiencies in mirror neurons might also play a role in autism and other disorders affecting social skills.

Scientists have previously shown that when one animal watches another performing a motor task, such as reaching for food, mirror neurons in the motor cortex of the observer’s brain start firing as though the observer were also reaching for food.

a computer screen shows brain waves
Credit: Duke University

New Duke research published March 29 in the journal Scientific Reports suggests mirroring in monkeys is also influenced by social factors, such as proximity to other animals, social hierarchy and competition for food.

The Duke team found that when pairs of monkeys interacted during a social task, the brains of both animals showed episodes of high synchronization, in which pools of neurons in each animal’s motor cortex tended to fire at the same time. This phenomenon is known as interbrain cortical synchronization.

“We believe our study has the potential to open a complete new field of investigation in modern neuroscience by demonstrating that even the simplest functions of the motor cortex, such as creating body movements, are heavily influenced by the type of social relationships among the animals participating,” said senior author Miguel Nicolelis, M.D., Ph.D.

Previously, neuroscientists had limited their studies to recording brain activity in one animal at a time. What makes this research unique, Nicolelis said, is that the Duke team created a multi-channel wireless system to record the electrical activity of hundreds of neurons in the motor cortices of two monkeys simultaneously as they interacted in the same space.

“For decades, researchers suspected that cortical synchrony may play roles in perceptive and cognitive functions," said Daofen Chen, Ph.D., at the National Institute of Neurological Disorders and Stroke (NINDS), one of the funders of the research. "This study introduced a new paradigm, and opens the door to understanding a new social dimension of brain circuitry function behind that synchrony."

During one task, one monkey, called the passenger, sat in an electronic wheelchair programmed to reach a reward across the room, a fresh grape. A second monkey, the observer, was also in the room watching the first monkey’s trajectory toward the reward. Electrical activity in the motor cortex of each monkey’s brain was recorded simultaneously. An analysis showed that when the passenger traveled across the room under the attentive gaze of the observer, pools of neurons in their motor cortices showed episodes of synchronization.

The researchers found these episodes of interbrain cortical synchronization (ICS) could predict the location of the passenger’s wheelchair in the room, as well its velocity. The brain activity could also predict how close the animals were to each other, as well as the passenger’s proximity to the reward.

The most compelling finding, they said, was that ICS could predict another key social parameter -- the rank of the monkeys in the colony.

Miguel Nicolelis, M.D., Ph.D. “This could be valuable for any social task that requires the synchronization of many individuals to improve social cohesion.”

Credit: Duke University

During tasks when the colony’s most dominant monkey was traveling toward the reward under the observation of a lower-ranking animal, the magnitude of ICS grew steadily as the passenger approached the observer. Synchronization peaked when the animals were about three feet apart -- close enough that one might be able to stretch out an arm to groom the other, or attack.

But when a lower-ranking monkey was the passenger and the dominant monkey was observing, ICS did not increase as the monkeys got closer, suggesting social rank plays a role in brain synchronization.

The researchers believe episodes of ICS were generated by the simultaneous activation of mirror-neurons in both the passenger’s and observer’s brains. They propose similar correlations between brain synchrony and social interaction might take place during human social interactions, as well.

The findings could lead to new diagnostics or treatments for conditions where neuronal mirroring might not follow typical patterns, as has been suggested in autism, they said. Measuring ICS in humans could also reveal how well groups work together, and even what types of training improve their brain synchrony and teamwork.

“Using a non-invasive version of this approach, we may be able to quantify how well professional athletes, musicians or dancers are working together, or if an audience is engaged in what they’re seeing, listening or imagining,” Nicolelis said. “This could be valuable for any social task that requires the synchronization of many individuals to improve social cohesion.”

Nicolelis plans to explore brain synchrony in people through future trials at Duke using functional MRI and electrode caps.

In addition to Nicolelis, study authors included Po-He Tseng, Sankaranarayani Rajangam, Gary Lehew, and Mikhail A. Lebedev.

The research was supported by The Hartwell Foundation, NINDS (R01NS073952) and the National Institute of Mental Health (DP1MH099903), both part of the National Institutes of Health.

Contacts and sources:
Samiha Khanna
Duke University Medical Center 

Citation: Interbrain cortical synchronization encodes multiple aspects of social interactions in monkey pairs. Authors:   Po-He Tseng, Sankaranarayani Rajangam, Gary Lehew, Mikhail A. Lebedev, Miguel A. L. Nicolelis. Scientific Reports, 2018; 8 (1) DOI: 10.1038/s41598-018-22679-x

Polymers Mimic Chameleon Skin, Change Colors When Flexed or Stretched

In the future, body tight clothing may change colors like a chameleon 's skin as an athlete, dancer or consumer moves. 

Biological tissues have complex mechanical properties – soft-yet-strong, tough-yet-flexible – and are difficult to reproduce using synthetic materials. 

Now an international team has managed to produce a biocompatible synthetic material that replicates tissue mechanics and alters color when it changes shape, like chameleon skin. These results, to which researchers from CNRS, Université de Haute-Alsace1 and ESRF, the European Synchrotron, have contributed with colleagues in the US (University of North Carolina at Chapel Hill, University of Akron), are published on March 30, 2018 in Science. They promise new materials for biomedical devices.

To produce a medical implant, we need to select materials with similar mechanical properties to those in biological tissues, so as to mitigate inflammation or necrosis. A number of tissues including the skin, the intestinal wall, and the heart muscle, have the particularity of being soft yet stiffening when they are stretched. Until now, it has been impossible to reproduce this behavior with synthetic materials. 

Top – left: molecular structure of a plastomer synthesized in this work; right: supramolecular structure formed by the assembly of identical plastomers.

Bottom – left: stress-strain curves for plastomers (“M300-2” and “M300-3”) that mimic the mechanical behavior of pig skin samples (“porcine”, in transversal or longitudinal cross-section); right: image showing the iridescent color of the plastomers. The edges are less blue because they receive the light at a different angle.

Credit:  © D.A. Ivanov and S.S. Sheiko

The researchers have attempted to achieve this with a unique triblock copolymer2. They have synthesized a physically cross-linked elastomer composed of a central block onto which side chains are grafted (like a bottle brush) and with linear terminal blocks at each end (See figure). The researchers have found that by carefully selecting the polymer's structural parameters, the material followed the same strain curve as a biological tissue, in this case pig skin. It is also biocompatible, since it does not require additives, e.g. solvent, and remains stable in the presence of biological fluids.

Another property of the material appeared during the experiments: its color change upon deformation. As the scientists have shown, this is a purely physical phenomenon, which is caused by light scattering from the polymer structure. Atomic force microscopy and X-ray diffraction experiments have shown that the terminal blocks of these polymers assemble in nanometer spheres, distributed in a brush-polymer matrix. Light interferes with this microphase-separated structure to produce color according to the distance between the spheres; so when the material is stretched it changes color. It is the same mechanism that explains – in large part – how chameleons change color.

The researchers have therefore succeeded in encoding in a unique synthetic polymer both mechanical properties (flexibility, strain profile) and optical properties, which had never previously been achieved. By adjusting the length or density of the “brush's” various side chains, these properties can be modulated. This discovery could lead to medical implants or more personalized prostheses (vascular implants, intraocular implants, replacement of intervertebral discs), and also to materials with completely new strain profiles, and applications that have not yet been imagined.

Contacts and sources:

Citation: Chameleon-like elastomers with molecularly encoded strain-adaptive stiffening and coloration. Authors: Mohammad Vatankhah-Varnosfaderani, Andrew N. Keith, Yidan Cong, Heyi Liang, Martin Rosenthal, Michael Sztucki, Charles Clair, Sergei Magonov, Dimitri A. Ivanov, Andrey V. Dobrynin, Sergei S. Sheiko. Science, 2018; 359 (6383): 1509 DOI: 10.1126/science.aar5308

Invisibility Cloak Inspired by Squids and "Jurassic World" Could Protect Soldiers and Structures

Materials inspired by disappearing Hollywood dinosaurs and real-life shy squid have been invented by UCI engineers, according to new findings in Science this Friday.

The thin swatches can quickly change how they reflect heat, smoothing or wrinkling their surfaces in under a second after being stretched or electrically triggered. That makes them invisible to infrared night vision tools or lets them modulate their temperatures.

“Basically, we’ve invented a soft material that can reflect heat in similar ways to how squid skin can reflect light,” said corresponding author Alon Gorodetsky, an engineering professor. “It goes from wrinkled and dull to smooth and shiny, essentially changing the way it reflects the heat.”

UCI engineering professor Alon Gorodetsky and doctoral student Chengyi Xu have achieved a breakthrough, inventing a stretchy new material modeled after both squid skin and Hollywood dinosaurs with remarkable properties. 
Associate Professor of Chemical Engineering & Materials Science Alon Gorodetsky and grad student Chengyi X
Credit: Steve Zylius / UCI

Potential uses include better camouflage for troops and insulation for spacecraft, storage containers, emergency shelters, clinical care, and building heating and cooling systems.

“We were inspired both by science fiction and science fact – seeing dinosaurs disappear and reappear under an infrared camera in ‘Jurassic World’ and seeing squid filmed underwater do similar things,” said Gorodetsky. “So we decided to merge those concepts to design a really unique technology.”

Made of sandwiches of aluminum, plastic, and sticky tape, the material transforms from a wrinkled grey to a glossy surface when it is either pulled manually or zapped with voltage.

Products that reflect heat, such as emergency blankets, have existed for decades. But in the past several years, inventors in Gorodetsky’s lab and others have pushed to create dramatically improved versions via bio-inspired engineering. One focus has been to imitate how squid and other cephalopods can nearly instantaneously change their skin to blend into their surrounding environment.

Now, he and his team have done it, creating prototypes that can next be scaled up into large sheets of commercially useable material. Patents are pending.

“It was hard, especially the first phase when we were learning how to work with the sticky material,” said doctoral student Chengyi Xu, lead author. After trial-and-error processes involving thousands of attempts, he and postdoctoral scholar George Stiubianu finally saw the mirror-like coating change when they pulled it sideways.

“The whole project was so exciting.” he said.

Gorodetsky praised his team, saying, “These are exactly the type of graduate students and postdocs that UCI should be recruiting. They’re amazing.”

Contacts and sources:
Janet Wilson
University of California, Irvine

Anti-aging pill? It's on the Horizon

Sharply restricting calories can fend off signs of aging, but for many people it’s not practical.  Nicotinomide riboside (NR) mimics caloric restriction, kick-starting the same pathways responsible for its health benefits. In some people, NR lowers blood pressure and reduces arterial stiffness.

Scientists have long known that restricting calories can fend off physiological signs of aging, with studies in fruit flies, roundworms, rodents and even people showing that chronically slashing intake by about a third can reap myriad health benefits and, in some cases, extend lifespan.

From a public health perspective, that advice would be impractical for many and dangerous for some.

But a new CU Boulder study published today indicates that when people consume a natural dietary supplement called nicotinomide riboside (NR) daily, it mimics caloric restriction, aka “CR,” kick-starting the same key chemical pathways responsible for its health benefits.

Credit:  University of Colorado at Boulder

Supplementation also tends to improve blood pressure and arterial health, particularly in those with mild hypertension, the study found.

“This was the first ever study to give this novel compound to humans over a period of time,” said senior author Doug Seals, a professor and researcher in the Department of Integrative Physiology. “We found that it is well tolerated and appears to activate some of the same key biological pathways that calorie restriction does.”

For the study, published in the journal Nature Communications, Seals and lead author Chris Martens, then a postdoctoral fellow at CU Boulder, included 24 lean and healthy men and women ages 55 to 79 from the Boulder area.

Half were given a placebo for six weeks, then took a 500 mg twice-daily dose of nicotinamide riboside (NR) chloride (NIAGEN). The other half took NR for the first six weeks, followed by placebo.

The researchers took blood samples and other physiological measurements at the end of each treatment period.

Participants reported no serious adverse effects.

The researchers found that 1,000 mg daily of NR boosted levels of another compound called nicotinamide adenine dinucleotide (NAD+) by 60 percent. NAD+ is required for activation of enzymes called sirtuins, which are largely credited with the beneficial effects of calorie restriction. It’s involved in a host of metabolic actions throughout the body, but it tends to decline with age.

Research suggests that as an evolutionary survival mechanism, the body conserves NAD+ when subjected to calorie restriction. But only recently have scientists begun to explore the idea of supplementing with so-called “NAD+-precursors” like NR to promote healthy aging.

Nicotinomide riboside structural formula

Credit:  University of Colorado at Boulder

“The idea is that by supplementing older adults with NR, we are not only restoring something that is lost with aging (NAD+), but we could potentially be ramping up the activity of enzymes responsible for helping protect our bodies from stress,” Martens said.

The new study also found that in 13 participants with elevated blood pressure or stage 1 hypertension (120–139/80–89 mmHg), systolic blood pressure was about 10 points lower after supplementation. A drop of that magnitude could translate to a 25 percent reduction in heart attack risk.

“If this magnitude of systolic blood pressure reduction with NR supplementation is confirmed in a larger clinical trial, such an effect could have broad biomedical implications,” the authors note.

Ultimately, the authors say, such CR-mimicking compounds could provide an additional option—alongside the dietary changes and exercise currently recommended—for people whose blood pressure is not yet high enough to warrant medication but who are still at risk for a heart attack.

They stress that the study was small and “pilot in nature.”

“We are not able to make any definitive claims that this compound is safe or going to be effective for specific segments of the population,” said Martens, now an assistant professor at the University of Delaware. “What this paper provides us with is a really good stepping stone for future work.”

Martens and Seals have applied for a grant to conduct a larger clinical trial looking specifically at the impact of NR supplementation on blood pressure and arterial health. Martens is also launching a separate trial looking at the impact NR has on older adults with mild cognitive impairment, a precursor to Alzheimer’s disease.

The study was partially funded by grants from the National Institutes of Health and the American Federation for Aging Research. ChromaDex, the maker of NIAGEN provided supplements and some financial support.

Contacts and sources:
Lisa Marshall.
University of Colorado at Boulder 

Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD in healthy middle-aged and older adults. Authors: Christopher R. Martens, Blair A. Denman, Melissa R. Mazzo, Michael L. Armstrong, Nichole Reisdorph, Matthew B. Mcqueen, Michel Chonchol, Douglas R. Seals. Nature Communications, 2018; DOI: 10.1038/s41467-018-03421-7

A.I. To Control Air Flow in Underground Smart Complex “Santica”

Artificial intelligence will reduce energy costs by predicting the movement of people in underground complex “Santica”

Underground complex “Santica” in the heart of Kobe is the target of a 3-year initiative to develop an airflow control system based on AI sensors that detect the movement of people and air currents. The project was commissioned by Japan’s Ministry of Environment as a Low Carbon Technology Research and Development Program. It is a collaboration between Kobe University, Nikken Sekkei Research Institute (NSRI), Sohatsu Systems Laboratory Inc., and Kobe Chikagai Co., Ltd. (location provider).

The airflow control system

Credit: Kobe University

For 3 years from 2017 to 2019, Kobe University is working with NSRI and Sohatsu Systems Laboratory Inc. to reduce energy costs by developing the next generation of heating, cooling and ventilation technology: controlling air currents based on predicting people’s movements. The goal is a 50% cut in energy and CO2 emissions in the Santica underground area. Nippon Telegraph and Telephone Corporation (NTT) provides technology support for this project by developing the AI that predicts human movement, and contributing technology for optimization and regulation. Kobe City is also a participant, offering support with the aim of troubleshooting and providing services for Kobe’s citizens.

The Sannomiya area in the heart of Kobe city is undergoing large-scale renovations, and the “Santica” underground complex is in a key location. We aim to use this underground-based initiative as a catalyst for making the entire city center “smart”.

Developing the next generation of airflow technology

Stations, airports and partially-open underground complexes have particularly high heating and cooling costs compared to regular buildings. Due to the complex nature of human movement in these areas, effective heating, cooling and ventilation methods are yet to be established. However, recent developments in IoT technology have made it possible to obtain more detailed data about these environments. This enables new airflow controls and creates new possibilities for reducing CO2 emissions.

Fresh air is directed to the busy (high density) areas

Credit: Kobe University

In addition to controlling airflow around entrances and exits based on the season and time of day, this initiative also understands and predicts the environment (movement and behavior of people, heat data etc.) of the underground complex using sensors for air currents and movement of people. Through smart control of airflow based on this data we aim to minimize heating and cooling costs, saving electricity and reducing CO2 emissions by approximately 50% in the Santica area.

Testing the effectiveness of AI-controlled airflow

Heating, cooling and ventilation is traditionally provided equally throughout a space. In contrast, the technology developed in this initiative will calculate the necessary heating, cooling and ventilation for each area, minimizing energy output. This will add a pleasant fan effect to the air currents. Through this project, we are testing the effectiveness of AI-based real-time data collection, analysis and regulation in predicting human movement and controlling our environment.

Contacts and sources:
Kobe University 

Wednesday, March 28, 2018

Supernova Likely ‘Burped’ Before Exploding

The slow fade of radioactive elements following a supernova allows astrophysicists to study them at length. But the universe is packed full of flash-in-the pan transient events lasting only a brief time, so quick and hard to study they remain a mystery.

Only by increasing the rate at which telescopes monitor the sky has it been possible to catch more Fast-Evolving Luminous Transients (FELTs) and begin to understand them.

According to a new study in Nature Astronomy, researchers say NASA's Kepler Space Telescope captured one of the fastest FELTs to date. Peter Garnavich, professor and department chair of astrophysics and cosmology physics at the University of Notre Dame and co-author of the study, described the event as "the most beautiful light curve we will ever get for a fast transient."

The FELT, captured in 2015, rose in brightness over just 2.2 days and faded completely within 10 days.

Credit: NASA/JPL-Caltech

"We think these might actually be very common, these flashes, and we have just been missing them in the past because they are so fast," Garnavich said. "The fact that one occurred in the small area of the sky being monitored by Kepler means they are probably fairly common."

The FELT, captured in 2015, rose in brightness over just 2.2 days and faded completely within 10 days. Most supernovae can take 20 days to reach peak brightness and weeks to become undetectable.

Researchers debated what could be causing these particularly fast events but ultimately settled on a simple explanation: The stars "burp" before exploding and don't generate enough radioactive energy to be seen later. As the supernova runs into the gas expelled in the burp, astrophysicists observe a flash. The supernova then fades beyond their ability to detect it.

"Our conclusion was that this was a massive star that exploded, but it had a mass loss -- a wind -- that started a couple of years before it exploded," Garnavich described. "A shock ran into that wind after the explosion, and that's what caused this big flash. But it turns out to be a rather weak supernova, so within a couple of weeks we don't see the rest of the light."

The only visible activity is from the quick collision of the gas and the exploding star, where some of the kinetic energy is converted to light. One mystery that remains is why the "burp" would happen such a short time before the supernova explosion. Astrophysicists want to know how the outside of the star reacts to what's happening deep in the core, Garnavich said.

While the Kepler telescope and its K2 mission is expected to run out of fuel and end in the coming months, NASA's Transiting Exoplanet Survey Satellite (TESS) is planned for launch following the K2 mission. Garnavich said data retrieved during the TESS mission could also be used to study FELTs.

The study was funded by NASA.

The study was led by Armin Rest at the Space Telescope Science Institute. Co-authors include Giovanni Strampelli, also at the Space Telescope Science Institute; David Khatami and Daniel Kasen at the University of California Berkeley and Lawrence Berkeley National Laboratory; Brad E. Tucker, research fellow at the Research School of Astronomy and Astrophysics, Mount Stromlo Observatory and the ARC Centre of Excellence for All-Sky Astrophysics; Edward J. Shaya, Robert P. Olling and Richard Mushotzky at the University of Maryland; Alfredo Zenteno and R. Chris Smith at the Cerro Tololo Inter-American Observatory; Steve Margheim at the Gemini Observatory; David James and Victoria A. Villar at the Harvard-Smithsonian Center for Astrophysics; and Francisco Förster at the University of Chile.

Contacts ad sources:
Jessica Sieff 
University of Notre Dame