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  Mobile version   RSS   Subscribe   Unsubscribe   Archive   Media Kit Feb. 23, 2013
Volume: IV
Number: 6

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











 

Evidence for new spin-spin interaction may be in the Earth's crust
Physics World    Share    Share on FacebookTwitterShare on LinkedinE-mail article
In 2007 physicists proposed the existence of unparticles, and ways to find them, that could mediate spin-spin interaction over long distances. Yet laboratory investigations with specially polarized spins have not revealed any such forces or particles. In new work published in Science, a team of physicists have investigated the problem using spin-spin interactions in the iron-rich Earth's core. What the new experiment gives up in distance between the spins and the detector, it more than makes up in the sheer number (~1042) of spins. The team did not find any unparticles. But they did make a map of the Earth's polarized electron spins. And they were able to reduce, by a factor of 106, the upper limit of the spin-spin forces associated unparticles, as well as with particles known as axial bosons, which in the world of precision metrology is a fairly significant advance. More



Astronomers find smallest known planet
NASA    Share    Share on FacebookTwitterShare on LinkedinE-mail article
Astronomers have reported via Nature finding a planetary system, Kepler-37, with three planets. The planets were discovered using data from NASA's Kepler space telescope. Two of them are smaller than Earth, and one of these is smaller than Mercury and is about the size of Earth's moon. This is the first finding of a planet that is smaller than any in our solar system. This small planet, dubbed, Kepler-37b, is probably rocky with no atmosphere or water, owing to its extremely small size and highly irradiated surface. Finding small planets depends upon the ability to discern minute changes in the brightness of the host star. One type of change is caused by the transit of planets between the star and the telescope. But fainter and higher frequency brightness changes are caused by acoustic waves generated by boiling in the star's interior. These variations indicate the star's size, and this then allows astronomers to determine the orbiting planet's size. Finding this small planet is therefore a key milestone in exoplanet searches and the Kepler mission specifically, as it evidences increased abilities discern changes in stellar brightness. More



Dopant atoms in iron pnictide lead to anisotropic scattering and Cooper pair formation
Brookhaven National Lab    Share    Share on FacebookTwitterShare on LinkedinE-mail article
A team of physicists has used spectroscopic imaging scanning tunneling microscopy to directly visualize the electronic structure of Ca(Fe1−x Cox)2As2 that was doped by substituting Co for Fe atoms. Previously it was thought that dopants work by just adding more electrons. But in this study, reported in Nature Physics, the investigators found that around 8 percent doping, the cobalt atoms qualitatively change the electronic structure in a way that allows some electrons to join into "Cooper pairs", and the material becomes a superconductor. Moreover they found that in underdoped cases, the cobalt atoms specifically introduce asymmetric scattering states where electrons can move along one axis in the material, but experience heavy resistance in a cross-wise axis. This is the first time the impurity scattering associated with dopant atoms has been observed experimentally, and the reason for the geometry of the scattering is an interesting problem that begs for a theoretical explanation. More

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X-rays reveal persistent spin waves in iron pnictide superconductors
Paul Sherrer Institute    Share    Share on FacebookTwitterShare on LinkedinE-mail article
Several years ago scientists demonstrated that in some materials magnetism may co-exist with superconductivity. Using resonant inelastic X-ray scattering, physicists at the Paul Sherrer Institute have shown this fact in samples of potassium doped BaFe2As2. Doping this material with potassium atoms transitions it to a superconducting phase. X-rays excite spin waves, which are easily detected in the undoped material. These new results, reported in Nature Communication, demonstrate that the optimally-doped superconducting Ba0.6K0.4Fe2As2 retains well-defined spin waves of almost the same intensity. This suggests that the spin fluctuations in Fe-pnictide superconductors originate from a distinctly correlated spin state. This result connects pnictide superconductors with cuprate superconductors, which also display spin waves in superconducting states despite the two types of materials having fundamentally different electronic structures. More



Why are isotope ratios in interplanetary dust and meteorites different from those on Earth?
Lawrence Berkeley Laboratory    Share    Share on FacebookTwitterShare on LinkedinE-mail article
For many years scientists have been investigating if photochemistry could explain some of the differences in isotope ratios between Earth and what's found in meteorites and interplanetary dust particles. The idea is that wavelength dependent chemical reaction branching can help identify the radiation state of the Universe, and that can then be mapped to cosmic evolution. So what scientists do is look at isotope ratios of samples collected from various sources, and then try to mimic cosmic photochemical reactors in laboratory cells.

One theory that has come out of this work suggests that CO clouds in the early stages of our solar system's formation would have preferentially absorbed certain wavelengths of UV radiation, and this would affect isotope ratios via mass effects of the isotopes. This self-shielding theory has been observed in molecular clouds far out in space. But the theory does not resolve why oxygen-16 is less prevalent meteorite samples from the primitive time of our solar system than it is in the Sun. So another theory looks deeper into the physics of the photochemical reactions for mass-independent processes.

Isotope ratios of sulfur atoms also tell a story of when and where an object formed in our solar system. In work recently published in the Proceedings of the National Academy of Sciences scientists determined the branching ratios in the photodissociation of hydrogen sulfide exposed to various solar vacuum UV wavelengths. The results exhibited mass-independent sulfur isotopic compositions that take place through wavelength-dependent predissociative channels. Therefore it is possible, and quite plausible, that sulfur isotope ratios can be mapped directly to the photophysical environment, thus location, of where a meteorite sample was formed.
More



Physicists develop 'tractor beam' to pull particles instead of pushing them
Optics and Photonics News    Share    Share on FacebookTwitterShare on LinkedinE-mail article
For two decades, scientists have used optical tweezers to trap tiny beads, molecules and even atoms in a small space and to push them around with radiation pressure. But researchers can now pull these nanoscale particles with a beam of green light — eerily reminiscent of the Star Trek "tractor beam". As reported in Nature Photonics, scientists made the tractor beam by shining a wide Gaussian beam of 532-nm linearly polarized laser light onto a reflective mirror. By changing the beam's orientation from p-polarization to s-polarization, the researchers pushed and pulled the small polystyrene beads around in different directions and clustered them in small groups. The simple setup is easily attached to optical microscopes, and the research team will use it to explore the self-organization and self-sorting behavior of nanoparticles as they interact with light. More



Bees and electric fields
Ars Technica    Share    Share on FacebookTwitterShare on LinkedinE-mail article
As they travel through the air, bumblebees lose electrons, accumulating a small positive electrical charge. Flowers, meanwhile, are generally negatively charged at the top, thanks to a slight positive charge in the air around them. As a bee approaches a flower, a tiny electric field is created between plant and pollinator. In experiments reported in Science, researchers created a field of fake flowers that they could manipulate. Half the flowers were positively charged, and these flowers held a tiny bit of sugar solution as a reward for the bees. The remaining flowers had no charge and held a bitter quinine drink. The bees exhibited the ability to sense the magnitude and geometry of electric fields. It is unclear exactly how bees can sense these electrical fields. The mechanism can involve simple electrostatics like the venerable old van der Graff demonstration, or it could be something more intricate like the quantum mechanical (radical pair) mechanism of magnetoreception in birds. More



Neutrinos, the Standard Model misfits
Symmetry Magazine    Share    Share on FacebookTwitterShare on LinkedinE-mail article
For years, scientists thought that neutrinos fit perfectly into the Standard Model. But they don't. By better understanding these strange, elusive particles, scientists seek to better understand the workings of the Universe, one discovery at a time. More



New acoustic imaging technique will help oil recovery, medical therapy, materials science, more
American Physical Society    Share    Share on FacebookTwitterShare on LinkedinE-mail article
Previously a team of researchers reported a method to reconstruct an acoustic image of a material from sensors embedded in the medium where the wave reflections are recast as being from a single virtual source. However, multiple reflections and the fact that the method required some much idealized assumptions, e.g., isotropy of the sound speed, uniform layer thicknesses and shapes, etc, lead to major inaccuracies. The team has now reported via Physical Review Letters a more general method that works on an arbitrary number of layers, made of any material, and with interfaces of any shape. Applying this method to a highly variable geological system, the team was able to construct an acoustic profile with a high level of accuracy. More



Increase your options for graduate or REU program admissions
NSBP    Share    Share on FacebookTwitterShare on LinkedinE-mail article
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

Journal of Women and Minorities in Science and Engineering
Designed as a unique and much-needed resource for educators, managers and policymakers, the Journal of Women and Minorities in Science and Engineering publishes original, peer-reviewed papers that report innovative ideas and programs for classroom teachers, scientific studies and formulation of concepts related to the education, recruitment and retention of underrepresented groups in science and engineering.

Access now available to NSBP members at www.nsbp.org.


Policy updates: Sequestration, rare materials, RHIC, open access, political targeting of research
Waves and Packets    Share    Share on FacebookTwitterShare on LinkedinE-mail article
Last October we presented eight U.S. policy issues that every physicist should follow. The re-election President Barack Obama has not yet really resolved any of them. The Helium Stewardship of Act of 2012 died in the last Congress, and has not yet been introduced in the current Congress. Measures to stabilize the supply of Mo-99 and other rare earths have not been addressed. The wolf of deep across-the-board budget cuts is still at our door and many agencies have communicated draconian measures to deal with the required spending cuts. Owing to more general budget woes, the Nuclear Science Advisory Board recommended that RHIC be closed down. Last week identical bills were introduced in the House and the Senate concerning open access to government funded research. Open-access supporters applauded the introduction of the Fair Access to Science and Technology Research Act. Publishers generally oppose the bill, calling more onerous than bill proposed in the past. And finally, GOP House members have again called for the end of government funding of social science research. Physicists should channel Lewis Branscomb and defend social science research as he did during his stint as chair of the National Science Board, because attacks against certain areas of physics research are sure to follow. More

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    Share    Share on FacebookTwitterShare on LinkedinE-mail article
Postdoctoral Fellowship - Stanford Molecular Imaging Scholars Program
Physics Academic Coordinator I/Lecturer
Summer Undergraduate Researcher
Intern
Tenure-Track Faculty Position in Experimental Plasma Physics
REU summer program on complex materials
REU Student
National Radio Astronomy Observatory Research Experience for Undergraduates
POSTDOCTORAL RESEARCH ASSOCIATE POSITIONS




Latest research from Europhysics Letters
IOP Publishing    Share    Share on FacebookTwitterShare on LinkedinE-mail article
Structure-dependent vibrational properties of metallic nanoclusters

Higgs to μ ∓ τ ± decay in supersymmetry without R-parity

Ergodicity breaking in a model showing many-body localization

Conformal invariance: From Weyl to SO(2,d)

Theoretical framework for nanoparticle uptake and accumulation kinetics in dividing cell populations

More

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Latest research from International Journal of Modern Physics D: Special Issue on Gravitational Wave Detection and Fundamental Physics in Space
World Scientific    Share    Share on FacebookTwitterShare on LinkedinE-mail article
http://www.worldscientific.com/worldscinet/ijmpd

Electromagnetic Counterparts of Gravitational Wave Sources: Mergers of Compact Objects

The LISA Pathfinder Mission

DECIGO Pathfinder

ASTROD-GW: Overview and Progress

Implications of Galactic and Solar Particle Measurements on Board Interferometers for Gravitational

Wave Detection in Space

Pulsar Searching and Timing

ASTROSAT: Some Key Science Prospects

IndIGO and LIGO-India: Scope and Plans for Gravitational Wave Research and Precision Metrology in India

More


 
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