Waves & Packets

Black holes turn up the heat for the universe

18 May 2012 14:16:53 CDT

Until recently, astrophysicists thought that supermassive black holes can only influence their immediate surroundings. But recent results to be published in the Astrophysical Journal and the Monthly Notices of the Royal Astronomical Society reveal a process where gamma-ray emitting, supermassive black holes can influence the formation and growth of entire galaxies.

Christoph Pfrommer, one of the co-authors, explained to Waves and Packets that "the energetic TeV photons from blazers essentially annihilate on the sea of ordinary photons (optical light) that fill the universe. This annihilation is possible because the photons are so energetic that they can pair-produce electrons and positrons in this process. The pairs of electrons and positrons produced in this way initially continue to fly in the direction of the original gamma ray photon, but not for long. Plasma instabilities let the electron-positron beam become unstable. As a result, it gets dissipated quickly in the local gas, such that the original energy of the TeV photons becomes available for heating up the gas and can be observed as an additional broadening of the lines in quasar spectra."

The research team was able to quantitatively match observed spectra to spectra predicted through cosmological hydrodynamical simulations. The phenomena postulated in this work, i.e., blazar heating, may hold the key to some long-standing puzzles in galaxy evolution.

An unmistakable signal that could rewrite the Standard Model

18 May 2012 14:16:53 CDT

At the Sanford Underground Research Facility researchers are close to kicking off the MAJORANA DEMONSTRATOR experiment. The experiment's major science question is, are neutrinos their own antiparticles? A yes answer would be indicated by neutrino-less double-beta decay of an isotope like ⁷⁶Ge. And if the answer is yes, then one of the basic principles of the Standard Model, i.e., conservation of lepton number, would be violated. The MAJORANA experiment therefore seeks to observe neutrino-less double-beta decay in ⁷⁶Ge. (There are other experiments that use isotopes of tellurium, xenon, neodymium or other elements.) With a half-life of 100 trillion times the age of the universe, ⁷⁶Ge decay is an extremely rare event. And background cosmic radiation of course includes neutrinos and anti-neutrinos. So to make this experiment work researchers need lots of ⁷⁶Ge, lots of shielding from background radiation, and very sensitive detectors.

Physicists control liquid oxygen drops with fridge magnets

18 May 2012 14:16:53 CDT

A team of scientists in France has demonstrated trajectory control of a drop of liquid oxygen by a simple magnet at room temperature. The work could help with the development of highly hydrophobic materials and also with the study of very low-friction mechanical systems. The researchers created a liquid oxygen drops that exhibit the Leidenfrost effect, i.e., when a liquid comes in contact with a surface that is at a significantly higher temperature than the liquid's boiling point. A vapor surrounds the droplet that keeps it from evaporating quickly, and at the same time keeps it from direct contact with the surface. The result is a liquid drop that is levitated over the surface. In the current work, reported in Physical Review E, the drop was made of paramagnetic liquid oxygen. The drop's paramagnetism rendered it controllable by an external magnetic field, which in this case was provided by a common refrigerator magnet. Besides the industrial applications, this result provide some very interesting physics demonstration opportunities.

Timing quantum tunneling to attosecond precision

18 May 2012 14:16:53 CDT

A multinational team of physicists has measured electron tunneling times in two separate cases, when recombining with a helium atom and when recombining with a carbon dioxide molecule. In the experiments, reported in Nature, the researchers first used a weak field to one electron ionize either the He or CO₂ substrate. They could then optically guide the electron back to its original point. Then by switching to a stronger field laser they lowered the ionization energy barrier. In the case of CO₂ they could even access more stable lower-lying orbitals. The photon color resulting from the electron recombination allowed the researchers to connect barrier "size" to tunneling time. This result can also be taken as another verification of quantum mechanics, as their tunneling time results did match the real part of the predicted quantum mechanical time, but not at all the predictions coming from a classical treatment of the electron.

Looking into a metallic glass

18 May 2012 14:16:53 CDT

A metallic glass may be coming to smart phone near you. Metallic glasses are metals. They can be strong, corrosion- and wear-resistant, yet break abruptly. But scientists are just now getting a glimpse into the molecular structure these "glasses" well enough to understand their properties. Through electron fluctuation microscopy experiments researchers have revealed that Zr₅₀Cu₄₅A_l5 bulk metallic glass has a semi-ordered structure. The results are reported in Physical Review Letters. These particular samples exhibited local clusters of atoms with fivefold symmetric pentagonal or icosahedron structures surrounding a central atom. Materials with such symmetry tend shatter rather than stretch or bend under stress, like metallic glasses. So this metallic glass, at least, does not have exactly perfect crystalline structure. But it certainly does not have the same level of disorder as a normal glass. With local clusters seemingly confirmed, it may be possible to determine if groups of clusters pack into larger nanoscale crystalline arrangements.

New type of paper is made of graphene and protein fibrils

18 May 2012 14:16:53 CDT

In a recent article in Nature Nanotechnology, researchers in Switzerland describe their creation of a new kind paper made of alternating layers of protein and graphene. This novel nanocomposite is entirely biodegradable. As a biosensor this paper could be used to precisely measure the activity of enzymes. But it might be possible to see it one day as wound-healing adjuvant, or as an electrodynamic modality for targeted drug delivery.

Graduate school burnout quantified

18 May 2012 14:16:53 CDT

A recent study published in an online, open-access journal, PloS One, shows how graduate students' career aspirations evolve over time. Most starting physics graduate students are attracted to a more research-focused career rather than teaching, government work, or science outreach and writing. But as time moves on, students begin to realize that such a career is not in the cards for most Ph.D. physicists, and most will never attain a tenure-track position at a university. The report points out that advisors do not discuss alternative career paths with their students, probably because they do not have any more knowledge about that than the student does. But the authors of the study suggest that universities should be more upfront about career prospects in research before admitting students, which they say would cut down on enrollments but also the number of disillusioned students in the future.

Newfound exoplanet may turn to dust

18 May 2012 14:16:53 CDT

Researchers at MIT, NASA and elsewhere have detected a possible planet, some 1,500 light years away, that appears to be evaporating under the blistering heat of its parent star. The group's findings, published in the Astrophysical Journal, are based on data from the NASA's Kepler Observatory. A long tail of debris, like the tail of a comet, is following the planet. That debris trail might tell the story of the planet's disintegration. The planet is small, only about the size of Mercury, and it is orbiting close to its star, having a surface temperature of 3,600° F. This might be hot enough to vaporize metals of the planet, which then condense into dust. Or the debris might be ash from surface volcanos. In any event, the researchers calculated that the planet will be entirely disintegrated within 100 million years.

Photoacoustics screen for breast cancer without X-rays

18 May 2012 14:16:53 CDT

A team of Dutch researchers have reported in the Optics Express the preliminary proof-of-concept results demonstrating that photoacoustics rather than ionizing radiation (such as X-rays) can detect and visualize breast tumors. Optical mammography is possible because hemoglobin readily absorbs in the IR. Tumors are more blood-vessel dense, thus contain more hemoglobin, than normal tissue. So tumors are clearly distinguishable from normal tissue. The researchers combined the optical system's ability to distinguish between benign and malignant tissue with ultrasound to achieve superior targeting ability.

Draft of Next Generation Science Standards released

18 May 2012 14:16:53 CDT

The science component of the Common Core School Standards Initiative was recently released. The "Common Core" is a project of the National Governors Association and the Council of Chief State School Officers to standardize learning standards across the United States. The mathematics and English Language Arts components were released in 2010. An understanding of the Framework for K-12 Science Education is crucial to be able to critically review the Next Generation Science Standards. This framework was developed by a National Academy of Sciences panel chaired by former American Physical Society president, Helen Quinn. The NGSS are consistent with and thus seem to implicitly support the curricular strategy of "Physics First" in high schools, even if the exact text is explicitly silent about specific curricular structures. This first draft of the new science standards will be online for public comment until June 1.

National Society of Black Physicists jobs board postings

18 May 2012 14:16:53 CDT

Advanced Topics in Astrostatistics
Biophotonic Solutions 2012 MIIPS Ultrafast Pulse Shaping Workshop
SKA Project Scientist
Women's Business Enterprise National Council Student Program
3x Senior Astronomers — SKA Africa
Nanoscale Measurements For Soft Matter Systems
Kenyon College 1-year Visiting Assistant Professor of Physics
NASA Postdoctoral Fellowships
National Astrophysics and Space Science Program
Postdoctoral Research Associate Positions

Latest research from Measurement Science and Technology

18 May 2012 14:16:53 CDT

Measuring protein dynamics with ultrafast 2-dimensional infrared spectroscopy

Wavelet-transform-based time–frequency domain reflectometry for reduction of blind spot

Calibration of the scales of areal surface topography measuring instruments: Part 2. Amplification, linearity and squareness

Characterization of Bessel beams generated by polymeric microaxicons

A new sensor-based self-configurable bandstop filter for reducing the energy leakage in industrial microwave ovens

Latest research from Measurement

18 May 2012 14:16:53 CDT

An optical noncontact measurement method for hot-state size of cylindrical shell forging

Suppressing harmonic powerline interference using multiple-notch filtering methods with improved transient behavior

Autonomous estimation of angle random walk of fiber optic gyro in attitude determination system of satellite

Study of cutting force and surface roughness in the turning of polytetrafluoroethylene composites with a polycrystalline diamond tool

Decomposition of process damping ratios and verification of process damping model for chatter vibration