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New results conclusively show muon neutrinos transform to electron neutrinos
The T2K Experiment
The T2K collaboration has announced a definitive observation of muon neutrino to electron neutrino transformation. In 2011, the collaboration announced the first indication of this process, which was then a new type of neutrino oscillation; now, with 3.5 times more data, this transformation is firmly established. Neutrino oscillation is a manifestation of a long-range quantum mechanical interference. Observation of this new type of neutrino oscillation leads the way to new studies of CP violation which provides a distinction between physical processes involving matter and antimatter. CP violation in neutrinos in the very early universe may be the reason that the observable universe today is dominated by matter and contains no an insignificant amount of antimatter. Now with T2K firmly establishing this form of neutrino oscillation that is sensitive to CP violation, a search for CP violation in neutrinos becomes a major scientific quest in the coming years.
B-mode polarization detected in the cosmic microwave background for 1st time
The South Pole Telescope collaboration has measured for the first time B-mode polarization of the Cosmic Microwave Background (CMB). B-mode polarization is a subtle change in the rotation or curl of CMB photons. This is analogous to classical electrodynamics where the electric field (E-field) has a vanishing curl and the magnetic field (B-field) has a vanishing divergence. While B-mode polarization of the CMB has been long predicted, this is the first experimental detection. It produces temperature variations in the CMB of only about one part in 10 million, or 0.4 μK. The Planck results from earlier this year showed CMB fluctuations on the scale of μKs as well. B-mode polarization is postulated to be due to gravitation fields of massive bodies in the universe, i.e., gravitational lensing. B-mode polarization from gravitational lensing can help set constraints on the amount of matter in the Universe. And if the signals are subtracted from polarization maps of the CMB, that result can be used to detect gravitational waves, a key component of Einstein’s General Theory of Relativity. The results are reported in paper posted on arXiv.
Attractive force arises from black-body radiation
Black-body radiation can give rise to a net attractive force between tiny objects. The Stark effect shifts and splits electronic states due to a static electric field. An atom in such a field will have its ground state lowered by radiation that does not correspond to its electron transition frequency. Thus it will be attracted to the field source. This is the basis of optical tweezers. Work reported in Physical Review Letters follows from the question of whether or not an attractive optical potential for atoms could be created from blackbody radiation. It turns out the first atomic hydrogen transition frequency is in the UV, while the blackbody radiation at 100K gives frequencies in the IR. So via the Stark effect, this blackbody radiation does produce an attractive force for hydrogen atoms. The force falls off rapidly with distance. But in interplanetary space it can be 108 times the potential caused by gravity, which means that its presence could have important effects on the behavior of clouds of gas and dust in space. This bridge-building result has important implications in stellar and galactic evolution as well as fundamental matter-radiation interaction.
Helical microcurrents could explain optical properties of cuprate superconductors
American Physical Society
Experiments have shown that polarized light reflected from the surface of a cuprate superconducting material in the pseudogap phase has a slightly rotated angle of polarization. The effect, called Kerr rotation, occurs in magnetic materials. Microscopes use it to distinguish magnetic domains. But in a magnet, which has a distinct north and south pole, the Kerr rotation angle changes sign when the sample is flipped on its back. In cuprates, this sign change is absent, an effect that has been difficult to explain. New results reported in Physical Review Letters show that the peculiar Kerr effect is explicable if the light is interacting with local magnetic fields that twist by 90 degrees from one copper-oxide layer to the next. These fields could come from microscopic loops of current near each copper atom—an idea that has been proposed to explain the physics of the pseudogap phase. The key physical insight is that electrons between different copper-oxide planes interact, as opposed to those interactions being confined to just one plane.
IBM IR detector reveals fundamental photoconductivity properties of graphene
Earlier this year IBM researchers demonstrated that graphene photoconductivity could either be positive or negative depending on its gate bias. The positive is due to a photovoltaic effect and the negative is due to a bolometric effect. The bolometric effect couples photons to electron-phonon scattering, and then to photocurrent flowing in the opposite direction of the source-drain current. The IBM team has explored ways to amplify this bolometric effect. In new work reported in Nature Communications and Nature Photonics, they report some fundamental properties about dispersion and damping in optically driven plasmons in graphene. Graphene’s optical properties in the IR and THz regions can be tailored and enhanced by patterning graphene into periodic metamaterials with sub-wavelength feature sizes. The absorption in a single layer of graphene that utilizes its intrinsic plasmons can be as high as 40 percent in the THz, and the window of high absorption can be moved into the mid-IR by patterning the material and harvesting the plasmons. This points to photodectectors that yield an order of magnitude improvement in the device’s photo-responsivity in comparison to their non-plasmonic counterparts.
Could regulating cell voltage treat cancer?
Medical Physics Web
The link between voltage and cancer goes back to the late 1930s, when a new-fangled device called a voltmeter to show that tumor tissue has different electrical properties from normal tissue. In the early 1970s a biophysicist at NASA Langley traced this difference to a disparity in cell polarization, or how much more negatively charged the inside of a cell is compared with its outside, suggesting that electric polarization might somehow be a regulator of cancer and other cell proliferation. In new experiments reported in Disease Models and Mechanisms, researchers have shown this interpretation to be correct. They found that a lowered polarization inhibits the function of a transporter protein that draws in the signaling molecule butyrate, which, through various enzymes, controls the expression of growth genes. With less butyrate in the cell, these genes are free to instigate abnormally high, cancerous growth. The challenge is to find ways to lower tumor cell polarization as an effective cancer treatment. The results indicate that if this is done cancer cells will die. This work also has implications in biological pattern formation, wound healing, and on the notion that electronic devices such as mobile phones can cause cancer.
Physicists offer novel insight into experimental cancer treatment
Magnetic hyperthermia is as an attractive approach for the treatment of certain cancers as it has no known side effects compared to more conventional therapies. Ferromagnetic nanoparticles are especially interesting for this application because they show superparamagnetism. This is the capacity for nanoparticles to align and respond to a magnetic field, and, when the field is removed, the thermal motion is high enough to randomly reorient them, leaving no residual magnetization. In work recently reported in the International Journal of Nanomedicine for example, magnetic hyperthermia completely ablated tumor cells without affecting surrounding tissue, and the organ returned to normal morphology and function. Research recently reported in the Journal of Physics D: Applied Physics, demonstrates that the mechanism and amount of heat generated by magnetic nanoparticles can be understood when both the physical and hydrodynamic size distributions for the samples are known to high accuracy. This understanding is critical to produce particles with optimized properties for specific applications at minimal dose.
New model sheds further light on the Grotthuss mechanism
Johannes Gutenberg University Mainz
The Grotthuss mechanism, named after its discoverer, Theodor Grotthus, is how protons in solvated in water move very rapidly from one water molecule to the next. It is why the conductivity of water is relatively high. The Grottus mechanism is based on the assumption that it is not that a single specific proton moving from one molecule to another; instead, there is 'bucket line' where the bond to a proton bond is cleaved, the 'liberated proton' joins to another water molecule, making a hydronium ion (H3O+), which can grow to H5O2+ and H9O4+ mini-clusters. Then perhaps a different proton leaves to be transported along some loose chain of water molecules. Though the mechanism has been known for 200 years, but new work published in the Proceedings of the National Academy of Sciences of the United States of America sheds new light on the mechanism’s exact details. The water chain provides a ‘road’ for protons to follow. Proton hopping is intermittent, i.e., the diffusion of protons and hydroxide ions occurs during periods of intense activity involving concerted proton hopping, followed by periods of rest. The water molecules 'dance' around each other until they achieve an energetically favorable state. Only then will a proton hop along the ‘road’ to another molecule.
Making heavy elements by colliding neutron stars
Over the last 10 years astronomers have connected short duration gamma-ray burst with the collision of neutron stars, and they have assigned the bursts as signatures of new neutron-rich elements being produced in the aftermath of the explosion. In work to be published in Astrophysical Journal Letters, astronomers at the Harvard-Smithsonian Center for Astrophysics have now identified a red point of light at the same location as gamma-ray burst, GRB 130603B. This is the first identification of an optical counterpart to this type of gamma-ray burst. Assuming the red point was actually part of the same event as the GRB, the astronomers considered two possibilities: either it was the afterglow of an explosion or it was light emitted by the production of new heavy nuclei. The researchers compared the light output from the optical/IR counterpart to models and found it most strongly agreed with the collision between two objects of roughly equal mass, along with the nuclear processes forming heavy elements.
Study by the American Institute of Physics finds that all-male faculties not necessarily due to hiring bias
A study by the American Institute of Physics asserts that bias in hiring does not explain why more than half of US physics departments have all-male faculties. Rather, they say, rigorous statistical analysis suggests that the real reason female physics faculty members are rare is simply that physics departments have a small number of positions, and so few women are getting physics degrees. The report also notes that the proportion of women who are assistant professors is higher than that of recent PhD graduates. Though the report has touch off a fire storm of criticism, many commentators have missed that the analysis only answers a very narrow question, i.e., can the existence of all-male faculties be pinned on bias in hiring. The results of this study argue that the answer is no, and that the reasons are more complicated. And that even in a world where half of all physics Ph.D. graduates are women, there would still be all-male faculties.
Why do physicists gravitate towards jobs in finance?
According to a report published last year by the UK's Institute of Physics, of those in employment one year after graduation, a job in "finance" was second only in popularity to a job in "education". Trailing behind those two are jobs in "scientific and technical industries", in "government" and in "energy and the environment". Furthermore, many of those who stay on to PhD level and beyond eventually leave academia to work in the financial sector, often at senior levels in investment banks. It is not suprising that many physicists end up working in the financial sector. After all, they are good at using mathematics to solve real-world problems and the money is good. The March 2013 edition of Nature Physics was devoted to the latest academic research into the links between physics and finance. Understanding the behavior of complex financial markets can be done with the tools and understanding of statistical physics. The most famous equation in finance, the Black-Scholes equation, is a parabolic reaction-diffusion equation. A lot of new methods use the emerging area of "complex networks". The recent financial crisis has highlighted the need to better understand how the global markets work. Theoretical developments in statistical physics and complex systems may be able to help.
National Society of Black Physicists jobs board postings
Scholar Scientist in Experimental Condensed Matter Physics and Materials Science
Director of DC Magnet Program Experimental Condensed Matter Physics and Materials Science
Visiting Assistant Professor of Physics & Astronomy, non-tenure track
Stanford Synchrotron Radiation Lightsource Director
Linac Coherent Light Source
Postdoctoral position in Astrophysics/Astroparticle Physics
POSTDOCTORAL RESEARCH ASSOCIATE POSITIONS
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