Waves & Packets
Feb. 16, 2013

Supernova origin of galactic cosmic rays confirmed
Physics World
Despite wide agreement that supernova remnants are the sources of galactic cosmic rays (mostly protons), unequivocal evidence for the acceleration of protons in these objects has been lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. The first direct evidence that galactic cosmic rays are accelerated within supernova remnants has been provided by observations by the Fermi Large Area Telescope collaboration. The results, published in Science, make use of four years of data collected by the telescope observing two supernova remnants — IC 443 and W44. The observations fit very neatly with predictions of neutral pion decay.More

Breaking the Chandrasekhar mass limit may explain extremely bright supernova
Physics World
In a paper published in Physical Review Letters, a team of researchers are suggesting that magnetic fields play a role in white dwarfs that have mass beyond the "Chandrasekhar limit". In 1935 Chandrasekhar showed that stars with mass greater than 1.44 solar masses will not form a white dwarf. That is will not use all its hydrogen and helium and subsequently collapse into a highly dense state. Temperatures in stars more massive than this limit will instead rise to such a level that fusion reactions will be spontaneously triggered, destroying the star in seconds. The Chandrasekhar limit puts an upper limit on the brightness of exploding, white dwarfs, i.e., type Ia supernovae. But there are type Ia supernovae observations that are brighter than what the Chandrasekhar limit would allow. The researchers suggest that these "super- Chandrasekhar" white dwarfs were stabilized in their formation by magnetic fields on the order of 107-109 G in a process known as Landau quantization. Such fields, they reason, could stabilize a white dwarf of mass up to 2.58 solar masses, and this additional mass helps explain these super bright type Ia supernova. More

X-ray laser sees photosynthesis in action
Lightsources.org
Researchers at SLAC have for the first time used an x-ray laser to simultaneously look at the structure and function of Photosystem II, a protein complex in found plants, algae and some microbes. Photosystem II absorbs a photon and releases a proton and an electron, which provide the energy to link two water molecules, break them apart and release an oxygen molecule. Past x-ray studies on this protein had to use cryo-crystals as a hedge against radiation damage. Such crystals only showed the protein in a single chemical state. But with pulses on the order of 10-15 seconds, the SLAC x-ray laser can probe crystals at room temperature in a chemically active state, before any damage set in. As reported in Science, the research team was able to use both x-ray crystallography to determine the protein's structure, and x-ray emission spectroscopy to follow the position and flow of electrons in it. More

Vortex pinning could lead to superconducting breakthrough
Argonne National Lab
A multinational team of physicists discovered a way to efficiently freeze in place tiny magnetic vortices that interfere with superconductivity. This could in turn open up new vistas in applied superconductivity. Magnetic fields are the bane of superconductivity's existence. But in type II superconductors, magnetic fields form localized vortices around which superconductivity will persist. But in high magnetic fields the vortices will translate in the lattice, and eventually break down superconductivity in the material. Work along this line was the subject of the 2003 Nobel Prize in Physics. In new work reported in Nature Communications, researchers were able to immobilize vortices in geometric restrictions in a tungsten wire and in a titanium nitride perforated film. Though the present work was only on low-temperature superconductors, the researchers believe there is no reason why the approach should be restricted to just low-temperature superconductors. More

Researchers demonstrate Heisenberg uncertainty principle at macro level
Physorg.com
Physicists at the University of Colorado have demonstrated the Heisenberg uncertainty principle at the macro level. As described in their Science paper they built a 0.5mm square drum having a silicon frame and silicon nitride skin as the drum head. The drum was put in a chamber at 4K, subjected to laser pulses after being outfitted with mirrors to reflect the pulses. It was possible to measure the drum head displacements due to the laser shots. As more photons struck the drum, greater fluctuations occurred in the measurements recorded, distorting the readings, and proving that the Heisenberg uncertainty principle can indeed be demonstrated with objects large enough to be seen with the naked eye. More

New data suggests rare explosion created our galaxy's youngest black hole
NASA
New data from NASA's Chandra X-ray Observatory suggest a highly distorted supernova remnant, W49B, may contain the most recent black hole formed in the Milky Way galaxy. Most stellar explosions are generally symmetrical, with the stellar material blasting away more or less evenly in all directions. This remnant appears to be the product of a rare explosion in which matter is ejected at high speeds along the poles of a rotating star, more like the jets emanating from black holes. Most of the time a supernova remnant leads to a neutron star, which would normally be observable by both x-ray and radio telescopes. In this case there is no evidence of a neutron star, at least not in the Chanda data, which tends to imply that a black hole is forming instead of a neutron star. Observations like these, which are reported in the Astrophysical Journal, have been linked to gamma-ray bursts, which are thought to mark the birth of a black hole. There is no evidence that the W49B supernova produced a gamma-ray burst, but it may have properties — including being jet-driven and possibly forming a black hole — that overlap with such events. More

MOND used to predict key property in Andromeda's satellites
EurekAlert
Modified Newtonian Dynamics is a competing theory to the idea that dark matter is the reason why galaxies rotate faster than predicted by Newton's law of gravity. MOND protagonists argue that Newton's laws must be modified at accelerations that are eleven orders of magnitude lower than what we feel on the surface of the Earth. This they feel is a more satisfactory explanation for observations of velocity dispersion and other galactic properties than dark matter is. MOND vs dark matter is one of hottest debates in astrophysics. In a new paper to be published in the Astrophysical Journal, researchers have tested MOND by applying it to velocity dispersion within 17 dwarf spheroidal galaxies that are satellites of the nearby giant spiral galaxy Andromeda. These systems pose a strong test of MOND because their low stellar density predicts low accelerations. In 16 cases, the MOND predictions closely matched the velocity dispersions measured by others. In the 17th case the results were inconclusive because the observational errors are too large. The scientists also used MOND to predict velocity dispersions for 10 other faint dwarf galaxies in Andromeda. But as yet there are no observations to compare them to. More

Mosh pits teach us about the physics of collective behavior
Popular Science
A paper posted on arXiv by a Cornell graduate student has gone viral. Attending a heavy metal concert, the student somehow realized that in the mosh pit (apparently a requisite part of a heavy metal concert) there were curious patterns and collective behaviors in what had always felt to him like the epitome of chaos. He and his co-workers created a mosh pit simulator, where humans are reduced to two populations of spherical particles: one that are "self-propelled, experience flocking interactions...subject to random fluctuations in the forces they experience." The others prefer to remain stationary, and are not subject to flocking interactions or random forces. Though initially both populations are uniformly mixed, the team found that with sufficient time the flocking-interaction leads to a spontaneous phase separation with a dense population of the first population confined by the second. These results demonstrate how a non-equilibrium system can have equilibrium characteristics via the Central Limit Theorem. So while this work started off as a temporary break in the tether to the lab, and a fun exercise, it could actually enhance our understanding of collective motion in riots, protests, and panicked crowds, leading to new architectural safety design principles that limit the risk of injury at extreme social gatherings. More

NASA designs new space telescope optics
NASA Ames
Research scientists at NASA's Ames Research Center have developed a phase-induced amplitude apodization method to directly detect and photograph exoplanets. Telescopes based on this optical design will be able to directly image biomarkers of habitability. The design uses two specially designed non-spherical mirrors to reshape the light in the pupil of the telescope into a new "high-contrast" pupil pattern. This new high-contrast pupil has the special property of confining all diffraction and glare from the star into a small spot, which virtually blocks all the starlight without appreciably affecting the light from the planet. The deformable mirrors also correct aberrations with their wavefront control system. The design may be deployed in EXoplanetary Circumstellar Environments and Disk Explorer system. And if that is successful NASA may be capable of launching a telescope large enough to find and characterize basically all the habitable planets around our galactic neighborhood within the 2030 decade. More

Increase your options for graduate or REU program admissions
NSBP
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

Blood plasma is not a normal Newtonian fluid
American Physical Society
Blood is made of the solid cellular component and a liquid part called plasma. Researchers have thought that plasma is an ordinary fluid. In experiments reported in Physical Review Letters, researchers have now shown that that plasma has elasticity, something that would preclude it from being characterized as a normal fluid. Spin's fluid properties, but these new experiments use the separating-horizontal-plates method and a microfluidic method. Each eliminates confounding surface layer effects. What causes this elasticity at a molecular level could be very interesting from a molecular interactions standpoint as well as in designing synthetic substitutes for blood. More

National Society of Black Physicists jobs board postings
NSBP
Summer Undergraduate Researcher
Caribbean Science Foundation - Student Program for Innovation in Science and Engineering (SPISE)
Carl Albert Rouse Research Fellowship for Undergraduates
Victor M. Blanco Research Fellowship for Undergraduates
LIGO Summer Undergraduate Research Fellowship (SURF)
Vacuum Equipment Group Leader
Intern
Tenure-Track Faculty Position in Experimental Plasma Physics
NanoJapan: International Research Experience for Undergraduates
Research Experiences for Undergraduates: Materials Physics at the University of Florida
REU summer program on complex materials
REU Student
National Radio Astronomy Observatory Research Experience for Undergraduates
POSTDOCTORAL RESEARCH ASSOCIATE POSITIONS More

Latest research from Physics in Medicine and Biology
IOP Publishing
In vivo detection of Hirschsprung's disease by optical coherence tomography in rats

A method to remove residual signals in fibre optic luminescence dosimeters

Kinetic model optimization for characterizing tumour physiology by dynamic contrast-enhanced near-infrared spectroscopy

Three-dimensional fluorescence tomography of human breast tissues in vivo using a hand-held optical imager

Carotid wall volume quantification from magnetic resonance images using deformable model fitting and learning-based correction of systematic errors

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Latest research from Physics Reports
Elsevier
UV laser processing and multiphoton absorption processes in optical telecommunication fiber materials

The quantum adiabatic algorithm applied to random optimization problems: The quantum spin glass perspective

Models of few optical cycle solitons beyond the slowly varying envelope approximation

Shell models of magnetohydrodynamic turbulence

Multiple membranes in M-theory

Theoretical antineutrino detection, direction and ranging at long distances

Magnetic resonance imaging in laboratory petrophysical core analysis

Physics opportunities of a fixed-target experiment using LHC beams

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