8 Kemasan Mie Instant di Luar Negeri Ini Bikin Pengen Keliling Dunia

Researchers from Brown University have discovered another peculiar and potentially useful property of graphene, one-atom-thick sheets of carbon, that could be useful in guiding nanoscale self-assembly or in analyzing DNA or other biomolecules. A study published in Proceedings of the Royal Society A demonstrates mathematically what happens to stacks of graphene sheets under slight lateral compression -- a gentle squeeze from their sides. Rather than forming smooth, gently sloping warps and wrinkles across the surface, the researchers show that layered graphene forms sharp, saw-tooth kinks that turn out to have interesting electrical properties. "We call these quantum flexoelectric crinkles," said Kyung-Suk Kim, a professor in Brown's School of Engineering and the paper's senior author. "What's interesting about them is that each crinkle produces a remarkably thin line of intense electrical charge across the surface, which we think could be useful in a variety of applications." The charge, Kim says, is generated by the quantum behavior of electrons surrounding the carbon atoms in the graphene lattice. When the atomic layer is bent, the electron cloud becomes concentrated either above or below the layer plane. That electron concentration causes the bend to localize into a sharp point, and produces a line of electrical charge roughly one nanometer wide and running the length of the crinkle. The charge is negative across the tip of an upraised ridge and positive along the bottom of a valley. That electrical charge, Kim and his colleagues say, could be quite useful. It could, for example, be used to direct nanoscale self-assembly. The charged crinkles attract particles with an opposite charge, causing them to assemble along crinkle ridges or valleys. In fact, Kim says, particle assembly along crinkles has already been observed in previous experiments, but at the time the observations lacked a clear explanation. Those previous experiments involved graphene sheets and buckyballs -- soccer-ball-shaped molecules formed by 60 carbon atoms. Researchers dumped buckyballs onto different kinds of graphene sheets and observed how they dispersed. In most cases, the buckyballs spread out randomly on a layer of graphene like marbles dropped on smooth wooden floor. But on one particular type of multilayer graphene known as HOPG, the balls would spontaneously assemble into straight chains stretching across the surface. Kim thinks flexoelectric crinkles can explain that strange behavior. "We know that HOPG naturally forms crinkles when it's produced," Kim said. "What we think is happening is that the line charge created by the crinkles causes the buckyballs, which have an electric dipole near the line charge, to line up." Similarly, strange behaviors have been seen in experiments with biomolecules like DNA and RNA on graphene. The molecules sometimes arrange themselves in peculiar patterns rather than flopping out randomly as one might expect. Kim and colleagues think that these effects can be traced to crinkles as well. Most biomolecules have an inherent negative electrical charge, which causes them to line up along positively charged crinkle valleys. It might be possible to engineer crinkled surfaces to take full advantage of the flexoelectric effect. For example, Kim envisions a crinkled surface that causes DNA molecules to be stretched out in straight lines making them easier to sequence. "Now that we understand why these molecules line up the way they do, we can think about making graphene surfaces with particular crinkle patterns to manipulate molecules in specific ways," Kim said. Kim's lab at Brown has been working for years on nanoscale wrinkles, crinkles, creases and folds. They've shown that the formation of these structures can be carefully controlled, bolstering the possibility of crinkled graphene tailored to a variety of applications.

Limiting global warming to 2 degrees Celsius will require not only reducing emissions of carbon dioxide, but also active removal of carbon dioxide from the atmosphere. This has prompted heightened interest in 'negative emissions technologies.' A new study evaluates the potential for recently described methods that capture carbon dioxide from the atmosphere through an 'electrogeochemical' process that also generates hydrogen gas for use as fuel and creates by-products that can help counteract ocean acidification. Share: FULL STORY A new study evaluates the potential for recently described methods that capture carbon dioxide from the atmosphere through an "electrogeochemical" process that also generates hydrogen gas for use as fuel and creates by-products that can help counteract ocean acidification. Credit: © Francesco Scatena / Fotolia Limiting global warming to 2 degrees Celsius will require not only reducing emissions of carbon dioxide, but also active removal of carbon dioxide from the atmosphere. This conclusion from the Intergovernmental Panel on Climate Change has prompted heightened interest in "negative emissions technologies." A new study published June 25 in Nature Climate Change evaluates the potential for recently described methods that capture carbon dioxide from the atmosphere through an "electrogeochemical" process that also generates hydrogen gas for use as fuel and creates by-products that can help counteract ocean acidification. First author Greg Rau, a researcher in the Institute of Marine Sciences at UC Santa Cruz and visiting scientist at Lawrence Livermore National Laboratory, said this technology significantly expands the options for negative emissions energy production. The process uses electricity from a renewable energy source for electrolysis of saline water to generate hydrogen and oxygen, coupled with reactions involving globally abundant minerals to produce a solution that strongly absorbs and retains carbon dioxide from the atmosphere. Rau and other researchers have developed several related methods, all of which involve electrochemistry, saline water, and carbonate or silicate minerals. "It not only reduces atmospheric carbon dioxide, it also adds alkalinity to the ocean, so it's a two-pronged benefit," Rau said. "The process simply converts carbon dioxide into a dissolved mineral bicarbonate, which is already abundant in the ocean and helps counter acidification." The negative emissions approach that has received the most attention so far is known as "biomass energy plus carbon capture and storage" (BECCS). This involves growing trees or other bioenergy crops (which absorb carbon dioxide as they grow), burning the biomass as fuel for power plants, capturing the emissions, and burying the concentrated carbon dioxide underground. "BECCS is expensive and energetically costly. We think this electrochemical process of hydrogen generation provides a more efficient and higher capacity way of generating energy with negative emissions," Rau said. He and his coauthors estimated that electrogeochemical methods could, on average, increase energy generation and carbon removal by more than 50 times relative to BECCS, at equivalent or lower cost. He acknowledged that BECCS is farther along in terms of implementation, with some biomass energy plants already in operation. Also, BECCS produces electricity rather than less widely used hydrogen. "The issues are how to supply enough biomass and the cost and risk associated with putting concentrated carbon dioxide in the ground and hoping it stays there," Rau said. The electrogeochemical methods have been demonstrated in the laboratory, but more research is needed to scale them up. The technology would probably be limited to sites on the coast or offshore with access to saltwater, abundant renewable energy, and minerals. Coauthor Heather Willauer at the U.S. Naval Research Laboratory leads the most advanced project of this type, an electrolytic-cation exchange module designed to produce hydrogen and remove carbon dioxide through electrolysis of seawater. Instead of then combining the carbon dioxide and hydrogen to make hydrocarbon fuels (the Navy's primary interest), the process could be modified to transform and store the carbon dioxide as ocean bicarbonate, thus achieving negative emissions. "It's early days in negative emissions technology, and we need to keep an open mind about what options might emerge," Rau said. "We also need policies that will foster the emergence of these technologies."

California Institute of Technology have reported an inexpensive hybrid catalyst capable of splitting water to produce hydrogen, suitable for large-scale commercialization. Most systems to split water into its components -- hydrogen and oxygen -- require two catalysts, one to spur a reaction to separate the hydrogen and a second to produce oxygen. The new catalyst, made of iron and dinickel phosphides on commercially available nickel foam, performs both functions. Researchers said it has the potential to dramatically lower the amount of energy required to produce hydrogen from water while generating a high current density, a measure of hydrogen production. Lower energy requirements means the hydrogen could be produced at a lower cost. "It puts us closer to commercialization," said Zhifeng Ren, M.D. Anderson Chair Professor of physics at UH and lead author of a paper describing the new catalyst published Friday in Nature Communications. Hydrogen is considered a desirable source of clean energy, in the form of fuel cells to power electric motors or burned in internal combustion engines, along with a number of industrial uses. Because it can be compressed or converted to liquid, it is more easily stored than some other forms of energy, said Ren, who also is a researcher at the Texas Center for Superconductivity at UH. But finding a practical, inexpensive and environmentally friendly way to produce large amounts of hydrogen gas -- especially by splitting water into its component parts -- has been a challenge. Most hydrogen is currently produced through steam methane reforming and coal gasification; those methods raise the fuel's carbon footprint despite the fact that it burns cleanly. And while traditional catalysts can produce hydrogen from water, co-author Shuo Chen, assistant professor of physics at UH, said they generally rely on expensive platinum group elements. That raises the cost, making large-scale water splitting impractical. "In contrast, our materials are based on earth abundant elements and exhibit comparable performance with those of platinum group materials," she said. "It can be potentially scaled-up at low cost, which makes it very attractive and promising for the commercialization of water splitting." Researchers said the catalyst remained stable and effective through more than 40 hours of testing. The new catalyst, they wrote, "proves to be an outstanding bifunctional catalyst for overall water splitting, exhibiting both extremely high OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) activities in the same alkaline electrolyte. Indeed, it sets a new record in alkaline water electrolyzers (1.42 V to afford 10 mA cm-2), while at the commercially practical current density of 500 mA cm-2." Previous catalysts have used different materials to spur a reaction to produce the hydrogen than those that are used to produce the oxygen. Ren said the interaction between the iron phosphide particles and the dinickel phosphide particles boosted both reactions. "Somehow a joint effort of the two materials is better than any individual material," he said. In addition to Ren and Chen, other authors on the paper include Fang Yu, Haiqing Zhou and Jingying Sun, all with the UH Department of Physics; Fan Qin and Jiming Bao, with the Department of Electrical and Computer Engineering at UH; and Yufeng Huang and William A. Goddard III of the Materials and Process Simulation Center at the California Institute of Technology.

Carbon dioxide emissions from human activities must approach zero within several decades to avoid risking grave damage from the effects of climate change. This will require creativity and innovation, because some types of industrial sources of atmospheric carbon lack affordable emissions-free substitutes, according to a new paper in Science from team of experts led by University of California Irvine's Steven Davis and Carnegie's Ken Caldeira. In addition to heating, cooling, lighting, and powering individual vehicles -- subjects that are often the focus of the emissions discussion -- there are other major contributors to atmospheric carbon that are much more challenging to address. These tough nuts to crack include air travel; long-distance freight by truck, train, or ship; and the manufacture of steel and cement. "We wanted to look closely at the barriers and opportunities related to the most difficult-to-decarbonize services," said lead author Davis. The barriers they analyzed included: The expected increase in demand for air travel and freight shipping, sectors that already contribute about 6 percent of global emissions. The manufacture of cement and steel, which release 1.3 and 1.7 billion tons of carbon dioxide emissions into the atmosphere annually and are also expected to grow as infrastructure demands increase, particularly in the developing world. The necessity of generating and transmitting electricity with near 100 percent reliability, despite variability in renewable energy sources such as wind and solar. "Taken together these 'tough-nut' sources account for a substantial fraction of global emissions," Caldeira said. "To effectively address them, we will need to develop new processes and systems. This will require both development of new technologies and coordination and integration across industries." Possibilities that the team analyzed include, but aren't limited to, the synthesis of energy dense hydrogen or ammonia-based fuels for aviation and shipping, new furnace technologies in the manufacture of concrete and steel, and tools to capture and safely store hydrocarbon emissions. But the costs of implementing and scaling up these technologies to overhaul the transportation, construction, and energy storage industries will present hurdles, they warn. Plus, it will be necessary to overcome the inertia of existing systems and policies to create something new and better. "We don't have a crystal ball to foresee what technologies will exist a century from now," Caldeira continued. "But we know that people will want buildings, transportation, and other energy services and we can try to design our energy system so that it is able to take advantage of new inventions as they come along."

The U.S. oil and gas industry emits 13 million metric tons of the potent greenhouse gas methane from its operations each year, 60 percent more than estimated by the U.S. Environmental Protection Agency, according to a new study published today in the journal Science. Significantly, researchers found most of the emissions came from leaks, equipment malfunctions and other "abnormal" operating conditions. The climate impact of these leaks in 2015 was roughly the same as the climate impact of carbon dioxide emissions from all all U.S. coal-fired power plants operating in 2015, they found. "This study provides the best estimate to date on the climate impact of oil and gas activity in the United States," said co-author Jeff Peischl, a CIRES scientist working in NOAA's Chemical Sciences Division in Boulder, Colorado. "It's the culmination of 10 years of studies by scientists across the country, many of which were spearheaded by CIRES and NOAA." The new paper assessed measurements made at more than 400 well pads in six oil and gas production basins and scores of midstream facilities; measurements from valves, tanks and other equipment; and aerial surveys covering large swaths of the U.S. oil and gas infrastructure. The research was organized by the Environmental Defense Fund and drew on science experts from 16 research institutions including the University of Colorado Boulder and the University of Texas Austin. Methane, the main ingredient of natural gas, is a potent greenhouse gas that has more than 80 times the warming impact of carbon dioxide over the first 20 years after its release. The new study estimates total US emissions at 2.3 percent of production, enough to erode the potential climate benefit of switching from coal to natural gas over the past 20 years. The methane lost to leakage is worth an estimated $2 billion, according to the Environmental Defense Fund, enough to heat 10 million homes in the U.S. The assessment does suggest that repairing leaks and addressing other conditions that result in the accidental release of salrable methane could be effective. "Natural gas emissions can, in fact, be significantly reduced if properly monitored," said co-author Colm Sweeney, an atmospheric scientist in NOAA's Global Monitoring Division. "Identifying the biggest leakers could substantially reduce emissions that we have measured."