Boltzmann distribution illustrated with balls distributed on a hilly landscape. At positive temperatures (left), as they are common in everyday life, most balls lie in the valley around minimum potential energy. They barely move and therefore also possess minimum kinetic energy. At infinite temperature (center) the balls spread evenly over low and high energies in an identical landscape. Here, all energy states are equally probable. At negative temperatures (right), however, most balls wander on top of the hill, at the upper limit of potential energy. Also their kinetic energy is maximal. Energy states with large total energy are occupied more than those with small total energy, and the Boltzmann distribution is inverted. Credit: Max Planck Institute.
There a lot of great stuff going on:
Atoms at negative absolute temperature: The hottest systems in the world
On the absolute temperature scale that is used by physicists, the Kelvin scale, one cannot go below zero—at least not in the sense of getting colder than zero Kelvin. Physicists of the Ludwig-Maximilians University Munich and the Max Planck Institute of Quantum Optics, Garching, Germany, have now created an atomic gas in the lab that has nonetheless negative Kelvin values. These negative absolute temperatures lead to several striking consequences: Although the atoms in the gas attract each other and give rise to a negative pressure, the gas does not collapse, a behavior that is also postulated for dark energy in cosmology. Also supposedly impossible heat engines can be realized with the help of negative absolute temperatures, such as an engine with a thermodynamic efficiency above 100 percent. In order to bring water to the boil, energy needs to be added to the water. During heating up, the water molecules increase their kinetic energy over time and move faster on average. Yet, the individual molecules possess different kinetic energies, from very slow to very fast. In thermal equilibrium, low-energy states are more likely than high-energy states, i.e., only a few particles move really fast. In physics, this distribution is called Boltzmann distribution. Physicists led by Ulrich Schneider and Immanuel Bloch have now created a gas in which this distribution is inverted: Many particles possess large energies and only a few have small energies. This inversion of the energy distribution means that the particles have assumed a negative absolute temperature. “The inverted Boltzmann distribution is the hallmark of negative absolute temperature; and this is what we have achieved,” says Schneider. “Yet the gas is not colder than zero Kelvin, but hotter. It is even hotter than at any positive temperature. The temperature scale simply does not end at infinity, but jumps to negative values instead.”
‘Greenest street in America’ to provide data on smog-eating concrete
(GizMag) A streetscape that includes natural landscaping, bicycle lanes, wind powered lighting, storm water diversion for irrigation, drought-resistant native plants and innovative concrete has earned Cermak Road in Chicago the title of “Greenest Street in America” according to the Chicago Department of Transport (CDOT). The location runs through an industrial zone which links the state and US highways. The project will record quantifiable results through a set of equally aggressive sustainability goals charting eight performance areas such as storm water management, material reuse, energy reduction, and place making. The most anticipated data will be collected from the first commercial use of photocatalytic cement for the inside highway lanes. This “smog eating” cement contains nano particles of titanium dioxide and is designed to clean the surface of the road and remove nitrogen oxide from the surrounding air through a catalytic reaction driven by UV light. In addition CDOT used 30 percent recycled content in the sidewalk concrete.
Penn researchers show new level of control over liquid crystals
Researchers from the University of Pennsylvania have shown a new way to direct the assembly of liquid crystals, generating small features that spontaneously arrange in arrays based on much larger templates. “Liquid crystals naturally produce a pattern of close-packed defects on their surfaces,” says Shu Yang, leader of the study, “but it turns out that this pattern is often not that interesting for device applications. We want to arbitrarily manipulate that pattern on demand.” Electrical fields are often used to change the crystals’ orientation, as in the case with liquid crystal displays, but the Penn research team was interested in manipulating defects by using a physical template. Employing a class of liquid crystals that forms stacks of layers spaced in nanometers—known as “smectic” liquid crystals—the researchers set out to show that, by altering the geometry of the molecules on the bottommost layer, they could produce changes in the patterns of defects on the topmost. “The molecules can feel the geometry of the template, which creates a sort of elastic cue,” says another research, Kathleen Stebe. “That cue is transmitted layer by layer, and the whole system responds.” The researchers’ template was a series of microscopic posts arrayed like a bed of nails. By altering the size, shape, symmetry and spacing of these posts, as well as the thickness of the liquid crystal film, the researchers discovered they could make subtle changes in the patterns of the defects.
DARPA injected miracle foam could save lives on the battlefield
(Government Executive) DARPA has developed an injectable foam that shows promise in reducing death from internal bleeding, especially in situations involving noncompressible wounds. Two separate liquid compounds are injected in the body. When the two liquids mix, they react to form a foam coagulant that expands within the abdominal cavity-compressing the wound without sticking to vital organs. In tests, the compression was shown to reduce blood loss by six-fold and increase the three hour survival rate to 72 percent, up from just eight percent. DARPA Wound Stasis program manager Brian Holloway says, “If testing bears out, the foam technology could affect up to 50 percent of potentially survivable battlefield wounds.”
Inflatable private space stations: Bigelow’s big dream
NASA’s decision to buy an inflatable new room for the International Space Station may push the module’s builder—commercial spaceflight company Bigelow Aerospace—one step closer to establishing its own private stations in orbit. Last week, NASA announced that it will pay $17.8 million for the Nevada-based company’s Bigelow Expandable Activity Module (BEAM), which will be affixed to the huge orbiting lab as a technology demonstration.