Physics Today Daily Edition
NPR: As the most severe Ebola epidemic ever unfolds in West Africa, some researchers are studying it through the use of computer simulations. The goal is to see how the outbreak might spread and which public health measures could prove most effective in containing it. The effort is complicated by a number of factors, including the uncertainty in the total number of dead and infected people, how many infected people stay at home rather than go to hospitals, and how burial practices can spread the infection. Although the situation is too complex for computer models to come up with definitive answers on how many people will ultimately die and exactly when the epidemic will end, they do underscore the need to act quickly before the Ebola outbreak becomes too large to contain.
Climate Progress: Among the developed countries of the world, Germany is proving to be very successful at making the switch to renewable energy sources for its electricity production. That effort was reflected in the first half of 2014, when the country managed to generate one-third of its electrical power from renewables. That is a remarkable accomplishment in view of the fact that most renewables are inherently intermittent: The Sun only shines during the day, and the wind doesn’t always blow. Moreover, Germany's electrical power grid has proven to be very reliable: Since 2008 the average number of minutes that electricity was lost per customer each year has been less than 16—far less than in any other country in Europe or the US. However, the switch has not come without a price: Germans pay more for their electricity. Regardless, the country remains committed to getting 80% of its power from renewables by 2050.
BBC: Researchers have built a swarm of more than 1000 small robots that can shuffle around on three spindly legs to form two-dimensional shapes. Although the 3-cm-sized robots are fed the same computer program, they modify their movements based on what their neighbors are doing. Modeled on the swarm behavior of living organisms such as ants and birds, the so-called Kilobots could one day be used to develop self-assembling tools and structures. The tiny robots are not fast, however: Each shape can take 6 to 12 hours. "Actually watching the experiment run is like watching paint dry,” says Michael Rubenstein of Harvard University, coauthor of the group’s study published in Science.
Telegraph: NASA’s Stardust spacecraft was launched 15 years ago to collect dust samples from the coma of comet Wild 2 and from the outer reaches of space. Fitted with collectors made of a silica-based aerogel, Stardust returned to Earth in 2006 with at least a million particles in separate sets of detectors. One set was open when the craft passed through Wild 2 and then closed, the other closed through the comet's passage and kept open in a region of space suspected to have interstellar particles. To help sort the vast amounts of data, NASA turned to crowdsourcing, in which citizen scientists used their home computers to scan the collectors for the tracks left as particles hit the aerogel and became embedded. Scientists say that seven of the particles in the second set may be interstellar dust from outside our solar system.
MIT Technology Review: Being made of plastic, organic LEDs are intrinsically flexible. Although OLEDs could be used for displays that can be bent or rolled, it's challenging to protect the material from the few molecules of oxygen or water vapor that suffice to degrade performance. Kateeva, a startup in Menlo Park, California, has devised a solution to the protection problem. By using inkjet technology, the company can coat OLED displays faster and more cheaply than can current processes. Meanwhile, another startup, Canatu of Helsinki, Finland, has resolved a problem that besets flexible touch-sensitive displays. The flat, rigid screens of tablet computers and smartphones rely on tin-doped indium oxide, which is too brittle for use on a flexible screen. For its displays, Canatu replaces the oxide with a thin, flexible film covered with a layer of carbon nanobuds—that is, carbon nanotubes topped with spheres of carbon atoms.
New Scientist: Asteroids are agglomerations of rubble. The smallest have so little gravity that if they were to spin with a period shorter than 2.2 hours, they would fly apart. That limit, derived in 1996 by Alan Harris of the Space Science Institute in Boulder, Colorado, has been breached by a 1.1-kilometer-wide near-Earth asteroid known as (29075) 1950 DA. Ben Rozitis of the University of Tennessee and his collaborators argue in a paper published this week in Nature that a type of weak intermolecular interaction known as the van der Waals force holds 1950 DA together. Although the asteroid poses no threat to Earth, its integrity remains weak. If such an asteroid were on target to hit Earth, deflecting it would have to be done in such a way as to avoid breaking it up and creating a swarm of smaller, yet still deadly fragments that continue toward our planet.
Nature: When midges swarm, they do not execute the dramatic collective swoops and turns of flocks of starlings or schools of fish. Nevertheless, by tightly confining their individual flight patterns, the small flying insects do exhibit collective, self-organized behavior. Nicholas Ouellette and James Puckett of Yale University used high-speed video cameras to investigate the statistics of swarming. In a paper published this week in Journal of the Royal Society Interface, the pair reports that just 10 midges are needed to trigger the onset of self-organized behavior. Their results will constrain generic models that seek to mimic swarming based on interactions among the swarm's members.
BBC: A new and powerful surveillance satellite was launched into Earth orbit yesterday from Vandenberg Air Force Base in California. Known as WorldView-3 and owned by DigitalGlobe of Colorado, the satellite can image Earth's topography with a spatial resolution of 31 cm and in 29 spectral bands, some of which enable the orbiter to peer through clouds. From its Sun-synchronous, 612-km-high orbit, WorldView-3 can identify certain minerals and the species and relative health of plants. Before the satellite's launch, only military satellites had such imaging capability.
Nature: The European Union plans to spend €12 million ($16 million) over three years to evaluate the effects of extracting valuable minerals from the vicinity of hydrothermal vents in the ocean floor. The vents are attractive to mining companies because they provide a means for manganese nodules, rare-earth elements, and other commercially attractive materials to escape from the underlying crust. But those same vents support specialized and possibly fragile ecosystems. In the first study undertaken so far, French researchers released plumes of sulfite particles near the Azores islands. Such plumes are likely from mining operations. No deep-sea mining projects are currently under way, but several concessions in the Pacific Ocean have already been granted.
BBC: David Mitlin of Clarkson University in New York and his colleagues have made supercapacitors—energy storage devices that can charge and discharge quickly—from an unlikely material: the fibrous inner bark of hemp plants. Hemp, which lacks the hallucinogenic properties of its cousin, cannabis, is grown worldwide as a textile crop. The inner bark is usually discarded during milling. Mitlin found, however, that the bark's fibers can be processed to create thin, carbon-rich layers that function as efficient cathodes. When combined with an electrolyte, the hemp-based cathodes form capacitors that can sustain power densities up to 20 kW/kg.
Ars Technica: Using data from the US Census Bureau, researchers from Washington University in St. Louis have sought to determine the impact of rigorous science standards that have been implemented in schools in some US states. The study period ran from 1980 to 1999 and encompassed graduation requirements that ranged from zero mandatory science courses to six. Once all the other influences were accounted for, the researchers found that the states with the highest math and science requirements had dropout rates up to one percentage point higher than those with the lowest requirements. Science standards also influence students' college careers. Although high math and science standards depressed college attendance, they also raised college graduation rates. The boost was strongest—three percentage points—for black women.
New York Times: Every four years the International Mathematical Union awards its top prize, the Fields Medal, to two, three, or four mathematicians under the age of 41. Among the four recipients of the 2014 medal is Stanford University's Maryam Mirzakhani, who becomes the first woman and first Iranian to receive the honor in its 78-year history. Mirzakhani's research is concerned with dynamics, which is also the subject area of two of her fellow laureates, Artur Avila of the National Institute of Pure and Applied Mathematics in Brazil and Martin Hairer of Warwick University in the UK. The other laureate, Manjul Bhargava of Princeton University, studies the geometry of numbers.
Science: When photons scatter off a molecule, about one in a million of them incur a characteristic drop in energy that can be used to identify the molecule. Known as the Raman effect, the phenomenon can in principle be used to identify the chemical makeup of a distant sample by firing a powerful laser at it and measuring the reflected spectrum. The weakness of the Raman effect has precluded that application—until now. Marlan Scully of Texas A&M University and his colleagues have discovered that random lasing, a phenomenon that occurs in disordered materials, can be exploited to boost the Raman signal. Thanks to that boost, Scully and his team could identify the Raman signature of an explosive after the photons embodying it had bounced back and forth between mirrors for a distance of 400 meters. In that test, the laser was close to the sample. Proving the technique's practicality will entail illuminating the sample from afar.
Ars Technica: The Moon's gravitational pull on Earth, as evidenced by the oceans’ tides, has long been recognized; however, Earth also exerts a reciprocal pull on the Moon. That pull creates seismic waves, which must dissipate in the Moon’s interior. Scientists have attempted to calculate the effects of Earth’s tidal forces on the Moon, but until recently none of the calculations had proven satisfactory. In a new study published in Nature Geoscience, researchers propose that the Moon has a zone of low viscosity located at its core–mantle boundary. That partially melted zone helps dissipate the heat created by the seismic-wave action. Although the model goes a long way toward matching simulations with observations, more refinements are needed, the scientists say. Their research could prove important to furthering our understanding of how planetary bodies formed.
BBC: Researchers have developed a method to create very pure samples of silicon-28, whose lack of nuclear spin makes it ideal for a certain type of quantum computation. Purity is paramount, because the presence of other naturally occurring isotopes, such as silicon-29, can shorten the lifetime of electron-based qubits. Obtaining pure silicon-28 has proven a difficult and expensive process. Now the researchers have shown that an analytical chemistry technique—mass spectrometry—common in most laboratories can be used to identify and separate the different silicon isotopes. Although the method can produce only a very small amount of silicon-28, it is enough to work with as long as quantum computing remains in the research phase. Ultrapure silicon-28 is also an ingredient of the Avogadro Project, an international initiative to develop a new, artifact-free standard for the kilogram based on Avogadro's number.