Physics Today Daily Edition
Ars Technica: Creating specific shapes from nanoparticles can be difficult, but a new technique to create molds from DNA may provide a way to scale up the production of nanomaterial structures. In DNA, the patterns of the base pairs determine the shape that the molecule folds into. Computational modeling allowed researchers to create self-assembling DNA molecules that fold into 3D structures. Those structures then serve as molds for nanometals. A tube and two lids were made out of DNA. Then a gold nanoparticle was attached to the inside of the tube, which was sealed with the lids. Placed in a solution with dissolved gold atoms, the nanoparticle grows until it fills the tube. Then, silver nitrate and ascorbic acid were added to the solution, which caused the silver to bind to the gold inside the mold. The result was three silver cuboids. Further work created complex structures including a sandwich of silver trapped between two quantum dots, which could couple with electromagnetic radiation at wavelengths larger than the structure.
Nature: The Sun had been thought to be the primary warming influence on the water in shallow coastal areas, from coral reefs to Arctic shorelines to popular beaches. However, using data gathered from buoys and sensors, Gregory Sinnett and Falk Feddersen of the Scripps Institution of Oceanography in La Jolla, California, have found that ocean waves contain more heat than they expected. Although the Sun is responsible for a lot of it—particularly in places like southern California, where Scripps is located—breaking waves generate a surprising amount of heat, which results from the energy created by the forces of friction. Even in predominantly cloudy areas like the Pacific Northwest, considerable heat can still be imparted to the water by the stronger wave action. The unexpected heat source, some researchers suggest, may be exacerbating the coastal erosion that is occurring in Arctic Alaska, where loss of sea ice and more open water have led to more wave action.
New Scientist: To help monitor the health of the International Space Station's crew, researchers have developed a device that will allow the astronauts to check their bone and muscle mass while on board. Because of the large and powerful magnets required to scan the entire human body, conventional magnetic resonance imaging (MRI) machines can weigh more than a ton. Now Gordon Sarty at the University of Saskatchewan in Canada and colleagues have shrunk the size of the magnets to create a magnetic field across just a small area of the body, such as the wrist. They presented their device, called TRASE (transmit array spatial encoding), on 3 October at the International Astronautical Congress held in Toronto.
Science: In September, the Department of Energy's Fusion Energy Sciences Advisory Committee (FESAC) outlined a 10-year plan for fusion research in the US. The plan called for immediately shutting down one and later maybe a second of the three current midsize fusion projects to allow for the construction of new facilities and the alteration or upgrading of projects at other existing facilities. Most significantly, it changed nothing in regard to the US's contribution to ITER. Most of the criticisms the report has received have been about the process behind the drafting of the document. The short time that was allotted for the creation of the report meant that the panel, which included no researchers from major fusion projects, had very little time to collect input from the fusion research community. The amount of time given to the community to then review the document was very short, which led to a delay in the committee's vote on the report. And for the FESAC vote, 14 of the 23 members recused themselves because they were connected to either a major fusion lab or another lab that would benefit from the proposals in the report.
Sydney Morning Herald: Three years ago Jason Brand used a weather balloon to loft a toy chicken 33 km above New South Wales, Australia. Now, at the age of 12, he is designing a remote-controlled glider that he believes could break the sound barrier. As with the chicken, he plans to use a balloon to lift the 9-kg, 2.5-m craft before releasing it. Unlike the chicken, he'll be in control of the glider and its descent via remote; he'll be able to see the glider with a pair of virtual-reality goggles linked to a camera in the glider's nose. With his father's help, he is running a Kickstarter campaign to raise the $80 000 they estimate it will cost to obtain the necessary equipment. In Jason's free time, he is also a student representative on a team competing for a Google Lunar XPrize to land a robot on the Moon.
BBC: A ministerial report has revealed that Italy will soon require a portion of all gasoline and diesel to contain advanced biofuels, which are made from waste material. Using advanced biofuels instead of traditional biofuels will reduce the amount of farmland being devoted to growing nonfood crops. Italy will require 0.6% of all fuel to be advanced biofuels by 2018, with an increase to 1% by 2022. That will make Italy the first European nation to have such a requirement. The European Union had attempted to set a similar goal for all member countries, but the final version was nonbinding. Last year the world's first plant that makes biofuel from straw opened near Turin, Italy, and there are plans to open three more similar plants in the southern part of the country.
MIT Technology Review: Materials that alter their shape in response to changes in electrical charge, temperature, or air pressure have been in use for decades. But they have not been widely employed in airplanes because of the extreme stresses they would be exposed to. Now Skylar Tibbets of MIT and his colleagues have partnered with Airbus to develop shape-shifting carbon-fiber composites that can be used in aircraft. The researchers are using unusual carbon-fiber materials—they are not rigid like normal carbon-fiber ones—from a startup named Carbitex. They use a 3D printer to add layers of shape-changing polymers to the carbon-fiber sheets. The resulting carbon-fiber composites can change shape in response to specific stimuli. The first application for the materials will likely be on air intake valves, which change size as a plane changes altitude, but they could potentially replace hydraulic actuators and hinges.
Nature: NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft entered Martian orbit in September and began taking pictures of the planet using a UV spectrograph. Bruce Jakosky of the University of Colorado Boulder and his team have released the first of those images, which reveal that the solar wind is stripping hydrogen, oxygen, and carbon atoms from Mars's atmosphere. The carbon and oxygen atoms stay relatively close to the planet, but the hydrogen atoms, being much lighter, are sprayed into space. The images provide some direct evidence about the process that has slowly eroded the Martian atmosphere over billions of years.
BBC: One of the variables that climate models include is a measure of how much atmospheric carbon dioxide is absorbed by plants. According to a new study of the absorption process by Lianhong Gu of Oak Ridge National Laboratory and his colleagues, the amount plants absorbed between 1901 and 2010 was actually 16% higher than most models had estimated. To reach that conclusion, Gu's team studied mesophyll diffusion—the way that CO2 spreads within leaves. Their analysis of several climate models has also led them to believe that the amount of atmospheric CO2 has been overestimated by 17%. They say their finding regarding plants' CO2 absorption would account for that discrepancy. Although the researchers' work may lead to an adjustment of climate models, it is unlikely to alter the general implications of increasing levels of atmospheric CO2 on climate change.
Guardian: Over the past century, global sea levels have risen drastically. According to a recent study published in the Proceedings of the National Academy of Sciences, that rise stands in stark contrast with most of the current interglacial period, which extends back some 6000 years. Over most of that time, sea levels have not changed by more than 20 cm. Since the start of the 20th century, however, they have already risen by that much and show no sign of stopping. The researchers attribute the rise in sea levels to global warming brought on by ever-increasing anthropogenic carbon emissions. They based their study on remnants of tree roots and sea mollusks found in sea-floor sediments, which indicate which areas were covered by water and when. That evidence has shed light on some 35 000 years of the geologic record. Because of Earth’s slow dynamic response, the researchers predict that sea levels will continue to rise for the next several centuries, even if Earth’s governments manage to keep carbon emissions at present-day levels.
Los Angeles Times: The reionization epoch is the stage in the formation of the universe when the hydrogen atoms filling space were ionized and the universe became transparent to low-energy light. To achieve that ionization, highly energetic radiation was necessary, but where it came from is uncertain. One possibility is that early galaxies released large amounts of radiation in the extreme UV or higher—a range known as Lyman continuum radiation. However, galaxies trap most of the radiation in that range, with only a very few leaking as much 2% of the extremely high-energy radiation they produce. To initiate the reionization process, it is estimated that the early galaxies would have needed to release at least 20% of their extreme radiation. Now, researchers using the Hubble Space Telescope have found a galaxy that is leaking 21% of the radiation it produces in the Lyman continuum radiation. The galaxy, J0921+4509, is producing new stars at a massive rate of 50 solar masses per year, an order of magnitude greater than that of the Milky Way. It is possible that this rate of star creation is related to the amount of radiation escaping.
Ars Technica: Cosmic rays are constantly bombarding Earth. Trying to detect them to study their origins has proven to be a challenge because as they strike Earth’s atmosphere, they break up into showers of secondary particles. Even the largest detectors can only capture a few traces of the high-energy photons and other particles that manage to reach Earth’s surface. Now researchers at the University of California's Davis and Irvine campuses have proposed a novel design for a vast detector array that takes advantage of the global proliferation of smartphones. Their CRAYFIS (cosmic rays found in smartphones) app would make use of the digital sensors in the phones’ high-resolution cameras to watch for the high-energy particles—but only when the phone is inactive and plugged in for charging. Anyone interested can sign on for the beta testing of either the Android or iOS version.