Waves & Packets
Sep. 17, 2012

Room temperature superconductivity found in graphite grains
The Physicists arXiv Blog
Physicists in Germany have found curious and tantalizing evidence of superconductivity at the interface between grains of graphite after they have soaked in water and then dried out. The superconductivity seems to be only a surface effect, as it disappears when the grains are pressed into pellets. The authors show that the material's magnetic properties such as its magnetic moment change in a way that is consistent with the presence of superconducting vortices. But it is worth noting that this is only one of three conventionally necessary lines of evidence to show superconductivity. But the authors nevertheless point out the similarities in magnetic behavior in these grains with other previously studied granular superconducting oxides and carbon-based materials. They hypothesize that the water dopes the graphite surface with hydrogen and this plays some role in linking the grains together. They recall that a similar effect was demonstrated previously with wine and sake. The report is posted on arXiv, and the final peer-review paper appears in Advance Materials.More

Latest Planck results may resolve question about dark matter
Niels Bohr Institute
The latest results from the Planck Satellite may converge scientists' thinking on the origin of the mysterious microwave haze first observed in 2004 in the center of the Milky Way galaxy. The 2004 observation was made using the Wilkinson Microwave Anisotropy Probe. Since then, some astrophysicists have suggested that this haze is produced by annihilating dark-matter particles. But others are not so sure.

The Planck mission was launched by the European Space Agency in 2009 to meet several science objectives relating to the cosmic microwave background, the inflationary universe model, determining the Hubble constant and measurements of the Sunyaev-Zel'dovich effect. The more sensitive observations provided by Planck and reported in recent intermediate papers indicate that haze has the same form as that of synchrotron emission and it has some detailed structure to it. Researchers at the Niels Bohr institute believe that there is a quite strong indication that the haze could come from dark matter. But as usually the case in complex unknown physics, it may still be that no one model fully explains all the observations. More

On the role of a single spin in mechanical friction
American Physical Society
A team of researchers at the University of Hamburg and Ohio University has demonstrated how the magnetic moment of a single atom can influence slip friction between two metals. Slip friction between two surfaces is strongly dependent upon the chemical and physical properties of the two materials. On the atomic level discrete quantum effects become resolvable, especially when the materials are in a scanning tunneling microscope. In work reported in Physical Review Letters, the team used a spin-polarized STM to measure the friction for sliding a magnetic atom (cobalt) on an antiferromagnetic single layer of manganese atoms. Their work shows the importance of magnetic energy in sliding friction at the atomic scale (it is on par with chemical energy in some cases), and allows the comparison of friction parameters for magnetic and nonmagnetic nanocontacts. More

World's most stable laser created by NIST/JILA and German researchers
Laser Focus World
The world's most stable laser — with frequency variation of no more than 2 parts in 10,000 trillion — has been developed and tested by an international collaboration of scientists at NIST/JILA in Boulder, Colo., and a group at Physikalisch-Technische Bundesanstalt, the German counterpart of NIST. The work, reported in Nature Photonics, represents a new approach for constructing high-quality optical cavities that will bring more than an order of magnitude improvement over prior designs. In particular, it will accelerate progress in development of optical clocks, which operate at frequencies more than 10,000 times higher than the approximately 9.2 GHz microwaves used as the basis of the current worldwide time standard. Several new approaches led to the laser's superlative performance, most notably the substitution of single-crystal silicon for the ultralow expansion glass or fused silica customarily employed in the cavity mirrors and spacers. The system employed critical design measures to mitigate thermal and mechanical fluctuations.More

From frog's eye to quantum optical sensor
Physics World
Researchers in Singapore have reported in Physical Review Letters the use of a single rod photoreceptor cell taken from the eye of a frog to make an extremely sensitive detector. The fabricated detector is able to count individual photons and determine the coherence of extremely weak pulses of light. Photoreceptor cells from living organisms commonly outperform nonliving photon detectors. Human photo cells, for example, can register a single photon by setting off a set of chemical reactions and molecular conformation changes that ultimately change the electrical polarization of the cell, and hence causes a neural signal. In the current work, the researchers used rod cells from the eye of the African Clawed Frog to show that this species' eye will respond to just one photon as well, and can discriminate between coherent and noncoherent light pulses.More

Atomic force microscope measures strength of chemical bonds
Ars Technica
The exact strength and nature of chemical bonds between atoms depend of course on the identity of those atoms and the entire intra and inter-molecular environment. Basic level chemistry teaches that chemical bonds are either ionic or covalent, and the latter can be single, double or triple bonds. In reality the bond order is a complex and dynamic quantity due to fractional shared electrons. A consortium of researchers in Europe has figured out how to use a modified form of atomic force microscopy to examine the strength of chemical bonds in a single molecule. By modifying the tip of the AFM with a carbon monoxide molecule, they were able to detect differences in bond length (and by the Pauli expression, bond order) with exquisite resolution. This new method of molecular imaging could be used to study the structure of molecules and assemblies that do not readily crystalize. Their report appears in Science. More

X-rays unravel mysterious degradation of a Van Gogh painting
Deutsches Elektronen-Synchrotron
With a sophisticated X-ray analysis scientists have identified why parts of the Van Gogh painting "Flowers in a Blue Vase" have changed color over time: a supposedly protective varnish applied after the master's death has made some bright yellow flowers turn to an orange-grey color. The origin of this alteration is a hitherto unknown degradation process at the interface between paint and varnish, which studies at DESY´s X-ray source PETRA III and at the European Synchrotron Radiation Facility ESRF in Grenoble (France) have revealed for the first time. The cadmium yellow (cadmium sulphide, CdS) used by Van Gogh was a relatively new pigment, of which it has recently been discovered that in unvarnished paintings, it oxidizes with air (to cadmium sulphate; CdSO4) making the pigments lose color and luminosity. CdSO4 in turn reacted with Pb compounds, most likely from the varnish, to make PbSO4 other degradation products. This work will lead to better preservation and restoration techniques for some of the world's greatest art treasures. The scientific results are reported in Analytical Chemistry. More

Physicists patent nuclear waste-burning technology
R&D Magazine
A trio of physicists at the University of Texas at Austin has been been awarded a U.S. patent for a novel fusion-fission hybrid nuclear reactor that would use nuclear fusion and fission together to incinerate nuclear waste. The invention could someday be used to turn nuclear waste into fuel, thus removing the most dangerous forms of waste from the fuel cycle. The technology uses a tokamak device, which employs magnetic fields to produce fusion reactions. The device is driven by a transformational technology called the Super X Divertor, which has the capacity to safely divert the enormous amounts of heat out of the reactor core to keep the reactor producing energy. More

Graphene exhibits another quantum surprise
Physicists in the U.S. and Germany report via Science that graphene displays a fractional quantum Hall effect that is different to that seen in conventional materials. The FQHE occurs when charge carriers like electrons are confined to a 2-D plane, as in graphene, and are subjected to a perpendicular magnetic field in the Z-direction. If a current flows in the X-direction, a voltage — the Hall voltage — occurs in the Y-direction. At very low temperatures, this voltage is quantized in distinct steps or Hall states.

The researchers obtained their results by using a scanning single-electron transistor to probe samples of suspended graphene that were subject to an applied magnetic field. SETs measure the presence of energy gaps in the electronic spectrum of materials with a sensitivity that no other technique can match and is therefore ideal for exploring phenomena like the FQHE. They found unexpected fractional statistics that were a consequence of the underlying structural symmetry of graphene. These experiments confirm prior results on strong electron-electron interactions in graphene, and can be used in other 2-dimensional systems that exhibit exotic electronic behaviors.More

NASA orbiter observations point to 'dry ice' snowfall on Mars
NASA Jet Propulsion Laboratory
NASA's Mars Reconnaissance Orbiter data have given scientists the clearest evidence yet of carbon-dioxide snowfalls on Mars. This reveals the only known example of carbon-dioxide snow falling anywhere in our solar system. The snowfalls occurred from clouds around the Red Planet's south pole in winter. The presence of carbon-dioxide ice in Mars' seasonal and residual southern polar caps has been known for decades. The new data is from observations in the south polar region during Mars' southern winter in 2006-2007. It was collected by looking at clouds straight overhead and sideways with the Mars Climate Sounder, one of six instruments on the Mars Reconnaissance Orbiter. This instrument records brightness in nine wavebands of visible and infrared light as a way to examine particles and gases in the martian atmosphere. The data provides information about temperatures, particle sizes and density in carbon dioxide clouds. The analyses are presented in paper published in the Journal of Geophysical Research.More

Obama, Romney on science: Where the 2012 presidential candidates stand on key R&D issues
The Huffington Post
A 33-page report released by the Information Technology and Innovation Foundation concludes that neither candidate is crystal clear about how he would deal with a host of R&D issues, ranging from federal support for science to regulating the Internet. Both men talk up the importance of federal investments in basic research, but diverge on how government should approach more applied activities. President Barack Obama is seen as more willing to have the government be a partner with industry than Mitt Romney would. Obama would shield science agencies from spending rollbacks, while the Romney camp is reportedly silent on that particular point, though, like the Obama administration, Romney has proposed cuts in government spending. The report calls for more specificity from both sides. More

National Society of Black Physicists jobs board postings
Tenure-track Assistant Professor Position in Experimental Condensed Matter Physics at Rice University
Assistant Editor, Physical Review Letters
2 Tenure-track Faculty Positions in Astronomy/Astrophysics at Ohio University
Postdoctoral Positions in Cosmology at Lawrence Berkeley National Laboratory
Faculty Positions in Science, Technology, and Innovation
Tenure Track Assistant Professor in Evolution
Tenure Track Assistant Professor — Denison University
Assistant Professor Position in Experimental Nuclear Physics at Duke University
Assistant Professor in Experimental Condensed Matter Magnetism — Miami University of Ohio
Tenure Track Assistant Professor in Evolution
Faculty Opening Carnegie Mellon University McWilliams Center for Cosmology
Tenure-Track Faculty Position, Department of Physics, Emory University
Assistant Professor of Science, Technology, and Society and Physics
NASA Postdoctoral Fellowships
Assistant or Associate Professor — Gravitational wave and particle astrophysics / elementary particle physics
Faculty position in LCLS Science
Assistant Professor of Physics, tenure track
2-Year Full-Time Postdoctoral Fellowship in Acoustics
National Astrophysics and Space Science Program
Postdoctoral Research Associate PositionsMore

Latest research from New Journal of Physics
IOP Publishing
Quantum noise properties of multiphoton transitions in driven nonlinear resonators

Random matrix approach to the dynamics of stock inventory variations

Energy spectrum and Landau levels in bilayer graphene with spin–orbit interaction

On relating the genesis of cosmic baryons and dark matter

Carrier-envelope-phase tagging in measurements with long acquisition timesMore

Latest research from Optics Express
Optical Society of America
Gigabit NRZ, CAP and optical OFDM systems over POF links using LEDs

Polarization properties of surface plasmon enhanced photoluminescence from a single Ag nanowire

Serpentine low loss trapezoidal silica waveguides on silicon

Laser-written waveguides in KTP for broadband Type II second harmonic generation

Electro-optofluidics: achieving dynamic control on-chipMore