Waves & Packets
Oct. 20, 2012

Physicists show path to more ferroelectric materials
American Physical Society
Ferroelectrics exhibit a spontaneous electric polarization that can be reversed by an applied electric field. The term and physical behavior is completely analogous to ferromagnetism, which refers to materials that have a permanent magnetic moment that can be reversed by an external magnetic field. Ferroelectrics are of profound interest for sensor, switching and capacitor applications; especially materials where the "polarization flip" has a suitably low energy barrier.

Like ferromagnetism, ferroelectricity is related not only to chemical composition, but also to the nanostructure of the material lattice. Using density functional theory calculations, a team of American physicists has explored the ferroelectric properties of several dozen triatomic compounds that exhibit a hexagonal crystal lattice, including 18 existing nonrare-earth compounds and 70 hypothetical compounds that have never been synthesized. Their results, reported in Physical Review Letters, show that eight compounds, LiBeP, LiCaBi, NaMgP, NaMgAs, NaZnSb, NaMgBi, KMgSb and KMgBi have polarizations in the range favorable for ferroelectric switching, and therefore are promising candidates for new ferroelectric materials. More

Fine-tuning frictional forces with electric fields
American Physical Society
In a paper in Physical Review Letters, a physicist in France has demonstrated how electric fields can modify the frictional force between surfaces. The system in question involved polyelectrolytes absorbed on smooth mica. The surfaces are called "polymer brushes" as they resemble the bristles on a toothbrush. When two surfaces brought together, the polymers inter-digitate, and the number of molecular, and even atomic contacts can be controlled by an applied electric field. Conformational responses, thus electrical contacts, are shown to be electric field frequency dependent, as well as dependent on hydrodynamic properties of the medium and polymer chain length. Several applications can ensue from this work, e.g., wear reduction in water-based environments, surface patterning and real-time control of tactile sensations, since electrical signals are relatively easy to produce and control.More

Increase your options for graduate or REU program admissions
The NSBP GradApps and REUApps services are open to all students and allows them to upload all the elements of an admissions application, including academic and work history, transcripts, letters of recommendation and a personal statement. Graduate and REU programs can subscribe to these databases to increase the programs' applicant pool, while at the same time allowing students can put their credentials in front of more programs than to which they would otherwise apply. More

Nanoadhesion leads to negative coefficient of friction
National Institute of Science and Technology
Researchers at the National Institutes of Standards and Technology have reported in paper published in Nature Physics that when a gold tip is contacted to a graphene surface, that it actually becomes harder to slide the tip across the surface after contact is broken. The explanation is that the graphene is deformed by indentation at the point of contact. And when pulled away, the graphene atoms adhere to the tip, deforming the surface in perhaps a different direction. Eventually the graphene-tip system reaches a fracture point; all of this happening on the nanometer length scale in piconewton force scale. But in a macroscopic view, the phenomenon appears as a surprising increase in the coefficient of friction as the normal force decreases. But demonstration of nano-indentations and nano-adhesion at atomic force microscope tips was demonstrated in 1990 by Uzi Landman and his co-workers.More

Cosmic rays used to examine the damaged cores of the Fukushima Daiichi nuclear reactors
Los Alamos National Laboratory
In work reported in Physical Review Letters, researchers at Los Alamos National Lab compared two methods for using cosmic-ray radiography to gather images of nuclear material within the core of a reactor similar to Fukushima Daiichi Reactor No. 1. Cosmic rays (made mostly of protons) produce muons (negatively charged particles) when they collide with atmospheric molecules. Muons can penetrate deeply into materials (on the order of meters). In 1969, Nobel Laureate Luis Alvarez used muon radiography to search for hidden chambers in the Egyptian pyramids of Giza. In the current application, the Los Alamos team found that scattering cosmic-ray radiography was far superior to the traditional transmission method for capturing high-resolution image data of potentially damaged nuclear material.More

High-resolution infrared images from Keck reveal new planetary weather features on Uranus
University of Wisconsin
In 1986, when Voyager swept past Uranus, the probe's portraits of the planet were "notoriously bland," disappointing scientists, yielding few new details of the planet and its atmosphere. Now a new technique is revealing features that were before buried in the noise. Uranus' atmosphere is made up mostly of hydrogen, helium and methane, has winds of up 560 miles per hour, and temperatures as cold as minus 360-degree Fahrenheit range, cold enough to freeze methane. But what is intriguing is that the atmosphere has copious dynamics that would need an energy supply. Uranus has no detectable internal energy source, but the sun is 900 times weaker there than on Earth because it is 30 times further from the sun. Planetary scientists and astronomers will surely be occupied for years to come by further elucidating the hydrodynamic features of the planet's atmosphere, and finding possible energy sources for them. More

Earth-sized planet found just outside solar system
R D Magazine
European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth. It is also the least massive exoplanet ever discovered around a star like the sun. The planet was detected using the High Accuracy Radial velocity Planet Searcher instrument on the 3.6-meter telescope at the European Southern Observatory's La Silla station in Chile. The observation is detailed in Nature. The Alpha Centauri system is only 4.3 light years away. One of the brightest star systems in the galaxy, it is actually a trio of stars. The wobble technique signal for the newly discovered planet is characterized as small, but real. The data indicates that the planet orbits 1 of the 3 stars every 3.2 days. Though proximity and similarity to Earth has made some think of an eventual voyage to this newly discovered planet, the close orbit around its star probably makes it much too hot for life as we know it.More

Nuclear pastas in supernovae
American Physical Society
Neutron stars are the universe's gift to physicists. They provide nuclear, condensed matter and astro-physicists one of the most robust systems to explore a number of different natural phenomena. When a star goes supernova its core is compressed to extreme pressures and densities. Physicists have proposed that, at a certain stage of the collapse, matter self-organizes into what is known as "nuclear pasta," a collection of bizarre structures, such as rods, slabs, and cylindrical and spherical holes (bubbles), which may constitute 10 to 20 percent of the inner core of the collapsing star.

New Skyrme-Hartree-Fock calculations, reported in Physical Review Letters, yield a pressure-temperature phase diagram showing both the onset of nuclear pasta in inhomogeneous matter, and the ultimate dissolution into a homogeneous neutron, proton and electron liquid. This is the first time this has been done in a fully self-consistent manor in such a robust model. The calculations hinted at a new phase structure in the pasta. Moreover, during the transition the core becomes a frustrated system, where the competing forces of nuclear attraction and Coulomb repulsion prevent the system from finding a stable equilibrium, driving it to fluctuate between degenerate states. More

Editorial: Meet a science committee that doesn't get science
Ars Technica
Two members of the Committee on Science, Space and Technology in the U.S. House of Representatives have made news recently with their statements that were at odds with even the most basic scientific evidence. First, there was Todd Akin of Missouri with his suggestion that women can consciously and cognitively "shut down" a pregnancy if they were victims of a "legitimate rape." The congressman did not offer any physiological evidence for such an ability. Then Georgia Representative Paul Broun, an actual medical doctor with a degree from the Medical College of Georgia and a BS in chemistry from the University of Georgia, declared that everything he was taught about evolution and embryology and the Big Bang Theory are all "...lies straight from the pit of Hell." Last year, the committee chair, Rep. Ralph Hall from Texas, in a statement expressing his skepticism over global warming, impugned the integrity of climate scientists by suggesting that they receive at least indirect payments of $5,000 for every report they publish that indicates that human activity and greenhouse gases has led to global warming. The House Science Committee is the authorizing committee for the NSF, NASA and NIST. Besides its agency authorization work, the committee has jurisdiction over several important policy challenges facing the physics community. More

Report: 1 million UK jobs depend on physics
Institute of Physics
A new report from the Institute of Physics shows that 4 percent of employees in the U.K. work in companies that would not exist without the physics base, or without employees that have an advanced understanding of physics.More

National Society of Black Physicists jobs board postings
Post Doctoral Research Associate - Space Telescope Science Institute
Tenure-Track Faculty Position, Physics
Assistant Professor, Experimental Physics
Tenure-track Position Applied Physics — #18557
Tenure-Track Assistant Professor - University of Maryland Baltimore County
Assistant Professor, Astrophysics
Cornell University Tenure Track Assistant Professor in Experimental Physics
Experimental Particle Physics Faculty
National Radio Astronomy Observatory Jansky Fellowship Program
Tenure Track Faculty Position in Experimental Particle Physics
Faculty Positions in Science, Technology and Innovation
Tenure-track faculty position in physics at Middlebury College
AAAS Science & Technology Policy Fellow
Assistant Professor of Physics and Astronomy
Faculty Position in Theoretical Polymer Physics
Tenure-Track Faculty Position in Astronomy
Assistant ProfessorMore

Latest research from Reports on Progress in Physics
IOP Publishing
Orbital upper critical field and its anisotropy of clean 1- and 2-band superconductors

Physically based principles of cell adhesion mechanosensitivity in tissues

Torsional electromechanical systems based on carbon nanotubes

Physics of lateral triple quantum-dot molecules with controlled electron numbers

Overview on the physics and materials of the new superconductor KxFe2−ySe2More

Latest research from Physical Review X
American Physical Society
Topological Code Autotune

Fractionalizing Majorana Fermions: Non-Abelian Statistics on the Edges of Abelian Quantum Hall States

Energy Spectra of Vortex Distributions in 2-Dimensional Quantum Turbulence

Loops and Self-Reference in the Construction of Dictionaries

Demonstration Scheme for a Laser-Plasma-Driven Free-Electron LaserMore