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  Mobile version   RSS   Subscribe   Unsubscribe   Archive   Media Kit Apr. 6, 2013
Volume: IV
Number: 12

National Society of Black Physicists    African Physical Society   South African Institute of Physics   African Astronomical Society  











 


Eagerly anticipated survey of cosmic-ray positrons reported in Physical Review Letters
American Physical Society

Via Physical Review Letters, the AMS Collaboration has reported its first results on the precision measurement of the positron fraction in primary cosmic rays for 0.5-350 GeV. The AMS results confirm prior results by the PAMELA mission and the Fermi Gamma-Ray Space Telescope, which both found a positron excess.

The positron fraction, i.e., the ratio of the number of positrons to the total number of electrons plus positrons, indicates an excess of positrons over what we expect from known galactic energetic phenomena. These processes create pions that eventually decay to electron-positron pairs. But most are expected to be annihilated before reaching Earth. Based on models of particle interactions and transport processes in the galaxy, particle astrophysicists predict a positron fraction (at Earth) that decreases, monotonically, at energies greater than 1 GeV. But the PAMELA and Fermi missions, as well as a few other earlier experiments found that the positron fraction increases at energies greater than 10 GeV. Amongst the possible interpretations is that there is an additional, unknown physical phenomena leading to an excess of antimatter. Alternatively it could be a signature of dark matter, i.e., positrons from annihilations of weakly interacting massive particles (WIMPS). The AMS results do not necessarily venture into that debate. They only reproduce the prior results from PAMELA and Fermi.

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DARPA, NIH and NSF embark on Brain Initiative
Medical News Today
President Barak Obama announced recently that he will ask for $100 million in his fiscal 2014 budget next week to sponsor the first year of the "BRAIN Initiative", a bold, new 10-year research effort to advance our understanding of the human brain and uncover new ways to treat, prevent and cure brain disorders like autism, epilepsy, traumatic brain injury, schizophrenia and Alzheimer's. With Congress keeping an eagle-eye on budget issues, it remains to be seen whether $100 million will be approved. But $100 million is not much in the gross scheme of the US science budget, and the funding scheme, $50 million DARPA, $40 million NIH, and $20M NSF, involves allocations of the expected topline authorizations of the agencies. Private corporations, e.g., the Allen Institute for Brain Science, the Kavli Institute and the Howard Hughes Medical Institute, are expected to be key contributors as well. Opportunities for physicists in this initiative include applications of microelectronics, optics and nanoscience, magnetoencephalography and theory to brain mapping, as well as quantum mechanical descriptions of single ion channels.
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Black hole seen eating piece of brown dwarf
Ars Technica
In 2011 astronomers using the INTEGRAL gamma ray telescope observed a strong source of emissions coming from the supermassive black hole at the center of galaxy NGC 4845. These emissions were unusual in that they fluctuated by a huge amount over a matter of days. Then after peaking, they faded over the course of a year. This indicated that perhaps the emission was from a one-time event, rather than the normal, steady consumption of matter normally seen at most black holes. Reporting in Astronomy and Astrophysics the researchers have concluded that a brown dwarf, i.e., a star-like object with insufficient mass to start hydrogen fusion in its core, drifted close to the black hole. The strong gravitational forces from the black hole overcame the brown dwarf's cohesion forces. About 10 percent of the brown dwarf tore off from the main body and fell into the black hole, creating a particularly bright but fluctuating accretion disk. It also made a corona-like cloud around the black hole, the first event of its kind ever observed. The rest of the brown dwarf eventually drifted away which explains the gradual fading of the emissions.
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New class of type I supernovae discovered
Physics World
Astronomers have already categorized two broad groups of supernovae: type Ia presumed to result from the complete disruption of a white dwarf, and type II, Ib, and Ic thought to explode when the core of giant star collapses. In a paper appearing in the Astrophysical Journal a team of astronomers has designated a new class of supernovae first thought to be an unusual variant of type Ia. Designated type Iax, this new class is less energetic and fainter than type Ia supernovae. In fact type Iax supernovae might be so weak that the white dwarf may even survive the explosion. Their faintness and variability make them unsuitable for use as standard cosmic candles. It remains to be studied how type Iax supernovae originate. One model suggests that come from a binary star system comprised of a white dwarf that gathers helium from a hydrogen-depleted companion star. Then either the helium envelope or the core ignites. Resolving these questions will teach us more about the nature of thermonuclear explosions.
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Pump-probe spectroscopy yields 1st direct observation of Cooper pair formation in cuprate
Ecole Polytechnique Federale de Lausanne
Physicists at the Laboratory for Ultrafast Microscopy and Electron Scattering (LUMES) at EPFL have reported the first direct observation of the formation of Cooper pairs in real time in a superconducting cuprate, and simultaneously determined how the process affects the material's optical properties. As described in the Proceedings of the National Academy of Sciences of the United States of America, the team cooled optimally doped La1.85Sr.85CuO4 to its superconducting temperature (40 K). Then they applied a technique coined coherent charge fluctuation spectroscopy, in which charge fluctuations are coherently generated by an optical pump pulse. Coherent excitations are subsequently probed by femtosecond-broad band reflectivity, allowing them to observe the breaking up of Cooper pairs into single electrons in real-time. As the Cooper pairs broke and re-formed, they caused a periodical change in the color spectrum of the superconductor. The color change gives some hints as to the orbitals involved in pair formation, while the breaking/recombination process invites a pseudospin analogy to NMR/ESR spectroscopy where T1 and *T2 relate to relaxations in the charge fluctuations. This experiment also opens up the possibility of coherent controlling the superconducting wave function.

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New insights into superconductivity of alkaline iron selenides
Rice University
Two Rice University physicists have offered a theoretical explanation of why some electrons in iron-based superconductors become frozen in place while electrons in neighboring orbitals continued to move. This behavior had been previously observed in an angle-resolved photoemission spectroscopy study. The theoretical analysis, published in Physical Review Letters, proposes a unified phase diagram for K1-xFe2-y Se2 that connects the superconducting phase to a phase that simultaneously exhibits metallic conducting and an insulating behavior, and further to a pure insulating phase. Their analysis centers on an orbital-selective Mott phase, and this is the first time an orbital-selective Mott phase has been identified in any model of iron-based superconductors.
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Hubble finds farthest type Ia supernova yet
NASA
The NASA/ESA Hubble Space Telescope has found the farthest supernova so far of the type used to measure cosmic distances. Supernova UDS10Wil, nicknamed SN Wilson after American President Woodrow Wilson, exploded more than 10 billion years ago. The discovery was part of a three-year Hubble program, begun in 2010, to survey faraway type Ia supernovae and determine whether they have changed during the 13.8 billion years since the explosive birth of the universe. This new distance record holder opens a window into the early universe, offering important new insights into how these stars explode. Finding remote supernovae also provides a powerful method to measure the universe's accelerating expansion due to dark energy. One of the debates surrounding type Ia supernovae is their mechanism of ignition. This latest detection adds credence to model where ignition caused by the explosive merger of two white dwarfs. This discovery is described in an Astrophysical Journal paper.
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How did objects from space kindle life on Earth?
University of Leeds
While it is generally accepted that some important ingredients for life came from meteorites bombarding the early Earth, scientists have not been able to explain how inanimate rock transformed into the building blocks of life. A new study, reported in Geochimica et Cosmochimica Acta, shows how adenosine triphosphate, a chemical found in all living cells and vital for generating biochemical energy, could have been created when meteorites containing phosphorus minerals landed in hot, acidic pools of liquids around volcanoes, which were likely to have been common across the early Earth. The early Earth was regularly bombarded by meteorites and interstellar dust rich in exotic minerals, including the the iron-nickel-phosphorus mineral, schreibersite. This mineral contains a highly reactive form of phosphorus. In a reactor that models the conditions of early Earth, acid hydrolysis of schreibersite yield pyrophosphate – the part of ATP responsible for energy transfer. Similar tests of phosphorus-containing minerals from other planets, say Mars, could indicate if life as we know it could be supported there.
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Getting your paper noticed
365 This webcast is all about making sure that your publication gets the attention it deserves. It gives some tips and tricks that can help you as an author, and explains what Elsevier as a publisher is doing to help. Listen Now.


What is behind Einstein's turbulence?
Max-Planck-Gesellschaft
Richard Feynman once described turbulence as "the most important unsolved problem of classical physics", because a description of the phenomenon from first principles does not exist. This is still regarded as one of the six most important problems in mathematics today. Despite its importance, extremely little is known about turbulence in the relativistic regime. For the first time, direct numerical simulations have provided relativistic calculations that give scientists a better understanding of universality and intermittency in turbulent flows that can be found in astrophysical phenomena. The results, published in Astrophysical Journal Letters, indicate that relativistic effects are able to significantly enhance the intermittency of the flow and affect the high-order statistics of the velocity field. The low-order statistics on the other hand are unchanged. They appear to be universal and in good agreement with the classical Kolmogorov theory.
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365 Days of Astronomy Podcast
365 Days of Astronomy Podcast publishes daily podcasts, five to 10 minutes in duration. They are written, recorded and produced by people around the world. We are looking for individuals, schools, companies and clubs to provide five to 10 podcasts. You can do as few as one episode or up to 12 episodes (one per month, subject, of course, to our editorial discretion). Our goal is to encourage people to sign up for a particular day (or days) of the year. For more information, see the 365 Days of Astronomy website.




National Society of Black Physicists jobs board postings
NSBP
Martin and Michele Cohen Dean of Science
Visiting Assistant Professor
Instructor of Physics - North Carolina School of Science and Mathematics
Wiess Instructorship in Physics and Astronomy
Upper School Physics Teacher
Full-time Lecturer in Experimental Physics
Summer Internship
Schuler Postdoctoral Fellowship
Postdoctoral Fellowship - Stanford Molecular Imaging Scholars Program
Summer Undergraduate Researcher
Research Experience for Undergraduates for Community College Students at Texas A&M University-Commerce Department of Physics & Astronomy
Postdoctoral Research Associate Positions
Lecturer/Sr. Lecturer

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Eagerly anticipated survey of cosmic-ray positrons reported in Physical Review Letters
American Physical Society
Via Physical Review Letters, the AMS Collaboration has reported its first results on the precision measurement of the positron fraction in primary cosmic rays for 0.5-350 GeV.

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ATRAP reports precise measurements of antiproton magnetic moment and proton spin flip
CERN Press Office
The Antihydrogen TRAP experiment at CERN's Antiproton Decelerator has reported via Physical Review Letters a new measurement of the antiproton magnetic moment made with an unprecedented uncertainty of 4.4 parts per million.

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Surviving your comprehensive exams
Dynamic Ecology
Quite likely the comprehensive exam (aka qualifying exam) is the most feared moment in an academic's life. This post should: a) be helpful to those who haven't, b) provide a place for survivors to share their advice in one place on the web, and c) help those of us who have students and have to help them navigate it.

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Latest research from Journal of Cosmology and Astroparticle Physics
IOP Publishing
Transition magnetic moments and collective neutrino oscillations: three-flavor effects and detectability

Searching for WISPy cold dark matter with a dish antenna

The 130 GeV gamma-ray line and Sommerfeld enhancements

Density perturbations from modulated decay of the curvaton

Global fits of the cMSSM and NUHM including the LHC Higgs discovery and new XENON100 constraints


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Latest research from Journal of Statistical Physics: Special Issue
Statistical Mechanics and Social Sciences

Springer
A Biased Review of Sociophysics

The Drastic Outcomes from Voting Alliances in Three-Party Democratic Voting (1990 → 2013)

Spatiotemporal Patterns of Urban Human Mobility

Value Production in a Collaborative Environment

Modeling Insurgent Dynamics Including Heterogeneity

Sustainable Development and Spatial Inhomogeneities

Crises and Collective Socio-Economic Phenomena: Simple Models and Challenges


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