A newly discovered method for making two-dimensional materials could lead to new and extraordinary properties, particularly in a class of materials called nitrides, say the Penn State materials scientists who discovered the process. This first-ever growth of two-dimensional gallium nitride using graphene encapsulation could lead to applications in deep ultraviolet lasers, next-generation electronics and sensors.
"These experimental results open up new avenues of research in 2D materials," says Joshua Robinson, associate professor of materials science and engineering. "This work focuses on making 2D gallium nitride, which has never been done before."
Gallium nitride in its three-dimensional form is known to be a wide-bandgap semiconductor. Wide-bandgap semiconductors are important for high frequency, high power applications. When grown in its two-dimensional form, gallium nitride transforms from a wide-bandgap material to an ultrawide-bandgap material, effectively tripling the energy spectrum it can operate in, including the whole ultraviolet, visible and infrared spectrum. This work will have a particular impact on electro-optic devices that manipulate and transmit light.
"This is a new way of thinking about synthesizing 2D materials," said Zak Al Balushi, a Ph.D. candidate coadvised by Robinson and Joan Redwing, professor of materials science and engineering and electrical engineering. Al Balushi is lead author on a paper appearing online today (Aug.29) in the journal Nature Materials titled "Two-Dimensional Gallium Nitride Realized via Graphene Encapsulation."
New research by scientists at The University of Akron (UA) shows that a nanometer-thin layer of water between two charged surfaces exhibits ice-like tendencies that allow it to withstand pressures of hundreds of atmospheres. The discovery could lead to better ways to minimize friction in a variety of settings.
Why water between two surfaces does not always simply squeeze out when placed under severe pressure had never been fully understood. The UA researchers discovered that naturally-occurring charges between two surfaces under intense pressure traps the water, and gives it ice-like qualities. It is this ice-like layer of water—occurring at room temperature—that then lessens the friction between the two surfaces.
"For the first time we have a basic understanding of what happens to water under these conditions and why it keeps two surfaces apart," says Professor Ali Dhinojwala. "We had suspected something was happening at the molecular level, and now we have proof."
"This discovery could lead to improved designs where low friction surfaces are critic
Using the world's most powerful telescopes, an international team of astronomers has found a massive galaxy that consists almost entirely of dark matter.
The galaxy, Dragonfly 44, is located in the nearby Coma constellation and had been overlooked until last year because of its unusual composition: It is a diffuse "blob" about the size of the Milky Way, but with far fewer stars.
"Very soon after its discovery, we realized this galaxy had to be more than meets the eye. It has so few stars that it would quickly be ripped apart unless something was holding it together," said Yale University astronomer Pieter van Dokkum, lead author of a paper in the Astrophysical Journal Letters.
Van Dokkum's team was able to get a good look at Dragonfly 44 thanks to the W.M. Keck Observatory and the Gemini North telescope, both in Hawaii. Astronomers used observations from Keck, taken over six nights, to measure the velocities of stars in the galaxy. They used the 8-meter Gemini North telescope to reveal a halo of spherical clusters of stars around the galaxy's core, similar to the halo that surrounds our Milky Way galaxy.
Star velocities are an indication of the galaxy's mass, the researchers noted. The faster the stars move, the more mass its galaxy will have.
You might not think of bacteria as technologically state-of-the-art, but some use some amazing tricks—like propellers powered by tiny self-assembling electric motors—to swim in their environment, as Dr Karl Kruszelnicki explains.
Astronomers using ALMA surveyed dozens of young stars - some Sun-like and others approximately double that size - and discovered that the larger variety have surprisingly rich reservoirs of carbon monoxide gas in their debris disks. In contrast, the lower-mass, Sun-like stars have debris disks that are virtually gas-free.
MIT biological engineers have devised a way to record complex histories in the DNA of human cells, allowing them to retrieve "memories" of past events, such as inflammation, by sequencing the DNA.
This analog memory storage system—the first that can record the duration and/or intensity of events in human cells—could also help scientists study how cells differentiate into various tissues during embryonic development, how cells experience environmental conditions, and how they undergo genetic changes that lead to disease.
"To enable a deeper understanding of biology, we engineered human cells that are able to report on their own history based on genetically encoded recorders," says Timothy Lu, an associate professor of electrical engineering and computer science, and of biological engineering. This technology should offer insights into how gene regulation and other events within cells contribute to disease and development, he adds.
Lu, who is head of the Synthetic Biology Group at MIT's Research Laboratory of Electronics, is the senior author of the new study, which appears in the Aug. 18 online edition of Science. The paper's lead authors are Samuel Perli SM '10, PhD '15 and graduate student Cheryl Cui.
A new concept could bring highly efficient solar power by combining three types of technologies that convert different parts of the light spectrum and also store energy for use after sundown.
Combining the technologies could make it possible to harness and store far more of the spectrum of sunlight than is possible using any one of the technologies separately.
"Harvesting the full spectrum of sunlight using a hybrid approach offers the potential for higher efficiencies, lower power production costs, and increased power grid compatibility than any single technology by itself," said Peter Bermel, an assistant professor in Purdue University's School of Electrical and Computer Engineering. "The idea is to use technologies that, for the most part exist now, but to combine them in a creative way that allows us to get higher efficiencies than we normally would."
The approach combines solar photovoltaic cells, which convert visible and ultraviolet light into electricity, thermoelectric devices that convert heat into electricity, and steam turbines to generate electricity. The thermoelectric devices and steam turbines would be driven by heat collected and stored using mirrors to focus sunlight onto a newly designed "selective solar absorber and reflector."
"This is a spectrally selective system, so it is able to efficiently make use of as much of the spectrum as possible," he said. "The thermal storage allows for significant flexibility in the time of power generation, so the system can produce power for hours after sunset, providing a consistent source of power throughout the day."
Findings from the research are detailed in a paper with an advance online publication date of Aug. 15, and the paper is scheduled to appear in a future print issue of the journal Energy & Environmental Science.
Archaeologists believe they have identified a new way of putting accurate dates to great events of prehistory. Rare and spectacular storms on the sun appear to have left their mark in forests and fields around the planet over the past 5,000 years.
Michael Dee, of Oxford University’s research laboratory for archaeology and the history of art, thinks evidence of such solar storms could help put precise years to some of the great uncertainties of history: the construction of Egypt’s Great Pyramid of Giza, the collapse of the ancient Mayan civilisation in Central America, and perhaps even the arrival of the Vikings in the Americas. Lost cities #7: how Nasa technology uncovered the 'megacity' of Angkor Read more
Every tree maintains its own almanac in the form of annual growth rings. For decades dendrochronologists have been using tree-ring evidence and radiocarbon dating to build a timetable of events that confirm historical accounts, even those predating the first written chronicles.
Humans living in the pre-Hispanic Mexican city of Teotihuacan may have bred rabbits and hares for food, fur and bone tools, according to a study published Aug. 17, 2016, in the open-access journal PLOS ONE by Andrew Somerville from the University of California San Diego, US, and colleagues.
Physicists are hunting for a particle that they hope could clue us in on some of the biggest mysteries in the universe. Questions like: Why the heck do we exist?
But after scouring an entire year’s worth of data from the largest particle detector on the planet, scientists at IceCube Neutrino Observatory have some bleak news. They're 99% sure the particle doesn’t exist.
Researchers have discovered a mechanism of intercellular communication that helps explain how biological systems and actions - ranging from a beating heart to the ability to hit a home run - function properly most of the time, and in some scenarios quite remarkably.
The findings are an important basic advance in how cell sensory systems function, they shed light on the poorly-understood interaction between cells - and they also suggest that some of the damage done by cancer cells can be seen as a "failure to communicate."
The work was reported today in Proceedings of the National Academy of Sciences by physicists from Oregon State University and Purdue University, done with support from the National Science Foundation and the Simons Foundation.
Scientists have long known that cells have various types of sensory abilities that are key to their function, such as sensing light, heat, nerve signals, damage, chemicals or other inputs.
In this process, a chemical stimulus called ATP functions as a signaling molecule, which in turn causes calcium levels in a cell to rise and decline, and tells a cell it's time to do its job - whether that be sending a nerve impulse, seeing a bird in flight or repairing a wound. These sensing processes are fundamental to the function of life.
"We've understood for some time the basics of cellular sensory function and how it helps a cell respond to its environment," said Bo Sun, an assistant professor of physics in the College of Science at Oregon State University, and a corresponding author on this study.
Violent thunderstorms can often cause torrential rain, which pose a threat for both humans and the infrastructure. Until now such extreme weather phenomena have been very poorly understood. However, using advanced simulations for cloud systems, researchers also from the Niels Bohr Institute have determined how complex cloud systems build up in the atmosphere, which then interact with each other and strengthen the further build up of heavy rain and severe thunderstorms. The results are published in the scientific journal, Nature Geoscience.
Using high-resolution cloud models, researchers from the Max Planck Institute for Meteorology in Hamburg, the Swedish Meteorological and Hydrological Institute in Norrköping and the Niels Bohr Institute at the University of Copenhagen analysed how heavy rainfall is affected by rising temperatures. The simulations were performed over an area that typically constitutes a single field area in climate models, that is, an area of 200 km x 200 km. In the high-resolution cloud model the area is divided into smaller areas of 200 meters, resulting in a 1000 times greater resolution. The high resolution made it possible for the researchers to uncover the processes taking place in the atmosphere, which are only included in global climate models to a very approximate degree.
"To detect the physical process that form, for example, storm clouds, we use simulations that are capable of revealing local thermal and moisture variations, which give rise to so-called 'convective' clouds. Convection is the process that forms, for example, thunderstorm clouds. Due to the heating of the surface in connection with sufficient humidity, a warm updraft is released in the atmosphere. Traditional climate models do not see these processes to an adequate degree. It is interesting how systematically convective clouds occur. Where two clouds collide, new and stronger clouds often appear," explains Jan O. Haerter, researcher at the Niels Bohr Institute at the University of Copenhagen.
The cost of solar power is beginning to reach price parity with cheaper fossil fuel-based electricity in many parts of the world, yet the clean energy source still accounts for just slightly more than 1 percent of the world'
A nanoscale wireless communication system developed by researchers at Boston College uses plasmonic antennas to produce greater control and increased efficiency to an approach eyed for next-generation 'on-chip' communications technologies.
Electronic components have become faster and faster over the years, thus making powerful computers and other technologies possible. Researchers at ETH Zurich have now investigated how fast electrons can ultimately be controlled with electric fields. Their insights are of importance for the petahertz electronics of the future.
How genes in our DNA are expressed into traits within a cell is a complicated mystery with many players, the main suspects being chemical. However, a new study by University of Illinois researchers and collaborators in China has demonstrated that external mechanical force can directly regulate gene expression. The study also identified the pathway that conveys the force from the outside of the cell into the nucleus.
Identifying the ways mechanical forces send signals within cells has applications not only in fundamental cell biology, but also for cancer, stem cells and regenerative medicine, said mechanical science and engineering professor Ning Wang, who led the study with cell and developmental biology professor Andrew Belmont. The researchers published their work in the journal Nature Materials.
"Each cell in your body has the same DNA, but tissues behave very differently because genes are expressed differently," Wang said. "There is so much we don't know about gene expression. I think this work is the beginning to unravel some of the unknowns."
Researchers have long known that forces, both external and internal, can affect cell behavior. But the question loomed as to whether the forces themselves triggered changes in gene expression, or if the forces triggered a chemical-signaling pathway within the cell.
"Cells only have two 'senses' to interact with their environment," Wang said. "They cannot see or hear, but they can 'feel' mechanical forces and 'taste' chemical signals. Many studies have detailed chemical-signaling pathways, but it's important to understand how the mechanical forces affect the cell as well. Mechanical signaling is as important as chemical signaling, and this study shows it's a direct pathway."
When you hear a sound, only some of the neurons in the auditory cortex of your brain are activated. This is because every auditory neuron is tuned to a certain range of sound, so that each neuron is more sensitive to particular types and levels of sound than others. In a new study, researchers have designed a neuromorphic ("brain-inspired") computing system that mimics this neural selectivity by using artificial level-tuned neurons that preferentially respond to specific types of stimuli.
In the future, level-tuned neurons may help enable neuromorphic computing systems to perform tasks that traditional computers cannot, such as learning from their environment, pattern recognition, and knowledge extraction from big data sources.
The researchers, Angeliki Pantazi et al., at IBM Research-Zurich and École Polytechnique Fédérale de Lausanne, both in Switzerland, have published a paper on the new neuromorphic architecture in a recent issue of Nanotechnology.
Like all neuromorphic computing architectures, the proposed system is based on neurons and their synapses, which are the junctions where neurons send signals to each other. In this study, the researchers physically implemented artificial neurons using phase-change materials. These materials have two stable states: a crystalline, low-resistivity state and an amorphous, high-resistivity state. Just as in traditional computing, the states can be switched by the application of a voltage. When the neuron's conductance reaches a certain threshold, the neuron fires.
"We have demonstrated that phase-change-based memristive devices can be used to create artificial neurons and synapses to store and process data," coauthor Evangelos Eleftheriou at IBM Research-Zurich told Phys.org. "A phase-change neuron uses the phase configuration of the phase-change material to represent its internal state, the membrane potential. For the phase-change synapse, the synaptic weight—which is responsible for the plasticity—is encoded by the conductance of the nanodevice."
Researchers at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley have created a sort of nanoscale display case that enables new atomic-scale views of hard-to-study chemical and biological samples.
Their work, published online Aug. 18 in the journal Science, could help to reveal new structural details for a range of challenging molecules—including complex chemical compounds and potentially new drugs—by stabilizing them inside sturdy structures known as metal-organic frameworks (MOFs).
The researchers introduced a series of different molecules that were chemically bound inside these porous MOFs, each measuring about 100 millionths of a meter across, and then used X-ray techniques to determine the precise molecular structure of the samples inside the MOFs.
The samples ranged from a simple alcohol to a complex plant hormone, and the new method, dubbed "CAL" for covalent alignment (the molecules form a type of chemical bond known as a covalent bond in the MOFs), enables researchers to determine the complete structure of a molecule from a single MOF crystal that contains the sample molecules in its pores.
The MOFs in the study, which are identical and are easy to manufacture in large numbers, provided a sort of backbone for the sample molecules that held them still for the X-ray studies—the molecules otherwise can be wobbly and difficult to stabilize. The researchers prepared the samples by dipping the MOFs into solutions containing different molecular mixes and then heating them until they crystallized.
University of Adelaide research has for the first time statistically proven that the earliest standing stone monuments of Britain, the great circles, were constructed specifically in line with the movements of the Sun and Moon, 5000 years ago.
Jeff Steinhauer, a physicist at Technion University in Israel, has created an acoustic black hole and observed particles slipping out of its grasp, providing the strongest evidence to date of one of Stephen Hawking's most famous predictions.
In 1974, Stephen Hawking predicted that black holes might not be the bottomless pits we imagine them to be. According to Hawking's calculations, some information might escape black holes in the form of energy, or Hawking radiation.
Here's how it works: Throughout the universe, matter-antimatter pairs of particles are constantly flickering in and out of existence (because matter and antimatter quickly annihilate each other).
But if one of these particles is dragged into the event horizon of a black hole — the point where not even light can escape — before the pair annihilates, the other particle might slip away as Hawking radiation.
The universe is governed by four fundamental forces.
There’s gravity and electromagnetism, and then the lesser known weak and nuclear forces.
But a group of theoretical physicists at the University of California, Irvine (UCI) thinks there might just be a fifth fundamental force lurking in the shadows.
And this force could revolutionize our understanding of physics, unlocking the mysterious dark universe and potentially even leading to a holy grail of physics: a Grand Unified Theory that merges all of the fundamental forces into one. The researchers explain their findings in a paper published August 11 in the journal Physical Review Letters.
“The four known forces have very obvious jobs holding our universe together,” Jonathan Feng, one of the study’s authors, told Business Insider. “That’s how we discovered them. Gravity holds the planets in orbit around the sun. You see electricity and magnetism in lightning and magnets. The role of this force is going to be much more subtle. If it weren’t, we would have found it a long time ago.”
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