Note that this page of links is assembled automatically via software
algorithm and sometimes it gets a little confused. Also, this is certainly NOT a complete list of resources, its just some of the ones that are easy to retrieve online.
Recent Physics-Related News Articles
These links point to recent Physics-related news articles from the popular press and more "physics oriented" sites.
Hacked E-Mail Is New Fodder for Climate Dispute (Sat Nov 21 4:24 am)
Private messages hacked from a British university are causing a stir among global warming skeptics, who say they show a climate science conspiracy.
Proton Beams Are on Track at Collider (Sat Nov 21 5:06 am)
The successful operation of the Large Hadron Collider marked the resumption of the world’s biggest and most expensive physics experiment.
Voracious Invader May Be Nearing Lake Michigan (Sat Nov 21 2:12 am)
Evidence of Asian carp, a fish that some fear could destroy the ecosystem of Lake Michigan, has been found beyond a barrier intended to keep the fish out.
Albert Crewe, First to Show a Single Atom, Is Dead at 82 (Sat Nov 21 1:47 am)
Dr. Crewe, a University of Chicago physicist, developed the high-resolution electron microscope that captured the first image of an individual atom.
New Data Shed Light on Large-Animal Extinction (Fri Nov 20 12:15 am)
A team from the University of Wisconsin uncovered a crucial sequence of events that rules out some explanations and severely constrains others.
Industrialized Nations Unveil Plans to Rein in Emissions (Fri Nov 20 1:55 am)
Prior to a climate change meeting scheduled for Copenhagen, industrialized countries, except the United States, are offering targets to curb greenhouse gases.
Proton Beams Are on Track at Collider (Sat Nov 21 3:23 am)
The successful operation of the Large Hadron Collider marked the resumption of a $9 billion quest to investigate the universe when it was less than a trillionth of a second old.
Little Progress in Freeing a Rover on Mars (Wed Nov 18 11:57 am)
Engineers tried to move the Spirit from a sand trap where it became stuck in May, but the maneuvers stopped after less than a second.
Shuttle Atlantis Lifts Off for 11-Day Mission (Wed Nov 18 8:48 pm)
Atlantis set off for the International Space Station, carrying spare parts and equipment as a hedge against failures after the shuttle fleet is retired next year.
Water Found on Moon, Researchers Say (Thu Nov 19 9:05 pm)
The discovery, which came out of a mission a month ago, confirmed scientists’ suspicions and could help explorers.
Setting Sail Into Space, Propelled by Sunshine (Tue Nov 10 2:49 pm)
Navigating the cosmos on winds of starlight is an ancient dream, and in about a year, a spacecraft called LightSail-1 may make it come true.
Former Astronaut Makes Plea Deal (Wed Nov 11 2:19 am)
Capt. Lisa Marie Nowak pleaded guilty on Tuesday to felony burglary of a car and misdemeanor battery as part of a plea bargain.
Qian Xuesen, Father of China’s Space Program, Dies at 98 (Wed Nov 4 12:29 am)
Mr. Qian was a rocket scientist who led China’s space and military rocketry efforts after he was drummed out of the U.S. during the redbaiting of the McCarthy era.
Circulation of LHC Beams Could Resume in Earnest over the Weekend (Fri Nov 20 2:50 pm)
The Large Hadron Collider , the world's most powerful particle accelerator, is drawing near to its long-awaited reboot. More than a year after the European collider's initial start-up was quashed by a helium leak caused by a faulty...
Novel Nova: Stellar Blast Powered by Helium May Leave a Tantalizing Remnant (Fri Nov 20 1:05 pm)
A stellar explosion known as a nova that was detected in 2000 formed a two-lobed shell of material ejected from the star. Shaped like a bow tie, it continues to swell at great velocity. But, curiously, the coat of ejecta flowing outward from...
Illuminating the Lilliputian: 10 Bioscapes Photo Contest Winners Revealed (Wed Nov 18 12:31 pm)
We are approaching the millennial anniversary of the first meaningful written description of how lenses and light could be used to magnify objects. It was in 1011 that Arab scientist Ibn al-Haytham (Alhazen) began writing the Book of Optics...
Ultrathin, Now Ultraflat: Ripple-Free Graphene May Hold Key to Material's Mysteries (Wed Nov 18 12:01 pm)
Graphene has been a hot topic in physics and materials science since its discovery five years ago . The sheets of carbon, just an atom thick, have a host of intriguing properties , including transparency, strength and a structure that lets...
Nanodevices Bend under the Force of Light (Sun Nov 15 12:01 pm)
A team of researchers has fabricated a micron-scale device that deforms significantly under the force of light, a technology that could form the basis for tiny light-actuated switches or filters in future optical devices. [More] ...
Heavy Metal: Researchers Try to Get the Lead out of Piezoelectronics (Thu Nov 12 3:50 pm)
Gadget makers often rely on piezoelectricity --the ability that some solids have to produce voltage when pressure is applied to them--to power tiny embedded systems, such as a BlackBerry Storm 2's touch screen or a car's airbag...
Planets May Affect the Chemistry of Their Stars (Wed Nov 11 12:01 pm)
Planets are, by and large, at the mercy of their stars. Not only do stars provide a ready energy source of radiated light and heat, but the mass and gravitational pull of stars flat-out dwarfs the summed masses and pulls of any orbiting companions....
Solar sail concept, like a phoenix, may rise again (Wed Nov 11 9:33 am)
It's only fitting that on what would have been Carl Sagan's 75th birthday, an organization started by the astronomer famous for his wondrous and elegant descriptions of the universe announced plans to test a wondrous and elegant...
GREAT RED SPOT NOT AS GREAT (Fri Feb 27 12:02 pm)
GREAT RED SPOT NOT AS GREAT The hurricanes that visit the Gulf and Caribbean in September and even the huge jetstream that dominates winter weath. . .
Ultrasound enhances noninvasive Down syndrome tests (Fri Nov 20 5:00 pm)
The addition of a "genetic sonogram" maximizes the accuracy of non-invasive testing for Down syndrome, said a Baylor College of Medicine researcher who was lead author of a landmark study in the current issue of Obstetrics and Gynecology.
High blood pressure easy to miss in children with kidney disease (Fri Nov 20 4:30 pm)
Spot blood pressure readings in children with chronic kidney disease often fail to detect hypertension - even during doctor's office visits - increasing a child's risk for serious heart problems, according to research from Johns Hopkins Children's...
Funeral industry workers exposed to formaldehyde face higher risk of leukemia (Fri Nov 20 4:10 pm)
Long durations of exposure to formaldehyde used for embalming in the funeral industry were associated with an increased risk of death from myeloid leukemia, according to a new study published online November 20 in the Journal of the National...
NJIT receives funding to improve Big Bear Telescope, study solar energy (Fri Nov 20 3:30 pm)
NJIT researchers are at work on many scientific and technological frontiers. The National Science Foundation has recently provided support that totals nearly $4.3 million for the diverse efforts of the following investigators under the American...
GE Scientists Developing Wearable RFID Sensors to Detect Airborne Chemical Agents (Fri Nov 20 3:30 pm)
GE Global Research, the technology development arm for the General Electric, today announced a $2 million award from the National Institute of Environmental Health Sciences to develop wearable RFID sensors to alert people to the presence of...
Termite creates sustainable monoculture fungus-farming (Fri Nov 20 3:20 pm)
(PhysOrg.com) -- Food production of modern human societies is mostly based on large-scale monoculture crops, but it now appears that advanced insect societies have the same practice. Our societies took just ten thousand years of (mainly cultural)...
B&N Nook sells out, too late for holiday orders (Fri Nov 20 3:10 pm)
(AP) -- Consumers who haven't yet ordered Barnes & Noble's electronic book reader, the Nook, won't see one before Christmas.
Elpida Completes Development of 1-Gigabit GDDR5 (Fri Nov 20 3:00 pm)
Elpida Memory, Japan's leading global supplier of Dynamic Random Access Memory, today announced that it had developed a 1-gigabit GDDR5 (product name: EDW1032BABG) that operates at a world-class high speed of 6Gbps.
Materials in extreme environments (Sun Nov 1 7:00 am)
The study of materials under harsh conditions is essential to meet a range of energy challenges—from creating better turbines, reactors, and batteries to developing future energy systems in dense plasmas.
Human-generated sound and marine mammals (Sun Nov 1 7:00 am)
Loud anthropogenic noises can alter the behavior of whales and other marine mammals, sometimes with fatal consequences
Paul Dirac: Engineer, mathematician, philosopher, physicist (Sun Nov 1 7:00 am)
Dirac practiced theoretical physics for almost 60 years with a unique style: a sometimes baffling combination of intuition, imagination, rectilinear logic, and steam-hammer mathematical power.
One of the things that sets science apart from many other fields of human-endeavor is that to prevent personal opinion from being represented as fact, articles that are submitted to scientific journals are "peer-reviewed", which means the paper is sent to a referee (possibly a scientific "competitor") who disects the article and makes sure its conclusions are valid based on the data presented. The process is not perfect, but it tends to drive a high level of scholarly quality in peer-reviewed journals.
USAGE NOTE: The symbol next to each feed item can be clicked in order to bring up the abstract from the article.
Author(s): Tyler R. Brosten, Sarah L. Codd, Robert S. Maier, and Joseph D. SeymourNuclear magnetic resonance measurements of scale dependent dynamics in a random solid open-cell foam reveal a characteristic length scale for transport processes in this novel type of porous medium. These measurements and lattice Boltzmann simulations for a model foam structure indicate dynamical be...[Phys. Rev. Lett. 103, 218001] Published Fri Nov 20, 2009
Author(s): Andreas Muller, Wei Fang, John Lawall, and Glenn S. SolomonIn typical epitaxial quantum dots (QDs) the ideally degenerate optical excitons are energy split, preventing the formation of two-photon entanglement in a biexciton decay. We use an external field, here a continuous-wave laser tuned to the QD in the ac Stark limit, to cancel the splitting and creat...[Phys. Rev. Lett. 103, 217402] Published Fri Nov 20, 2009
Author(s): G. Seibold, M. Grilli, and J. LorenzanaWe investigate a model where superconducting electrons are coupled to a frequency dependent charge-density wave order parameter Δ_{r} (ω). Our approach can reconcile the simultaneous existence of low-energy Bogoljubov quasiparticles and high energy electronic order as observed in scanning tunnelin...[Phys. Rev. Lett. 103, 217005] Published Fri Nov 20, 2009
Author(s): Kentaro Nomura, Shinsei Ryu, and Dung-Hai LeeAt the charge neutral point, graphene exhibits a very unusual high-resistance metallic state and a transition to a complete insulating phase in a strong magnetic field. We propose that the current carriers in this state are the charged vortices of the XY valley-pseudospin order parameter, a situatio...[Phys. Rev. Lett. 103, 216801] Published Fri Nov 20, 2009
Author(s): Thorben Kelling and Gerhard WurmIn laboratory experiments we observe dust aggregates from 100 μm to 1 cm in size composed of micrometer-sized grains levitating over a hot surface. Depending on the dust sample aggregates start to levitate at a temperature of 400 K. Levitation of dust aggregates is restricted to a pressure r...[Phys. Rev. Lett. 103, 215502] Published Fri Nov 20, 2009
Author(s): James Diorio, Yeunwoo Cho, James H. Duncan, and T. R. AkylasThe nonlinear wave pattern generated by a localized pressure source moving over a liquid free surface at speeds below the minimum phase speed (c_{min} ) of linear gravity-capillary waves is investigated experimentally and theoretically. At these speeds, freely propagating fully localized solitary...[Phys. Rev. Lett. 103, 214502] Published Fri Nov 20, 2009
Author(s): Paul von B?, Frank C. Meinecke, Franz C. Kir?, and Klaus-Robert M?rIdentifying temporally invariant components in complex multivariate time series is key to understanding the underlying dynamical system and predict its future behavior. In this Letter, we propose a novel technique, stationary subspace analysis (SSA), that decomposes a multivariate time series into i...[Phys. Rev. Lett. 103, 214101] Published Fri Nov 20, 2009
Author(s): Ivana Sersic, Martin Frimmer, Ewold Verhagen, and A. Femius KoenderinkWe present experimental observations of strong electric and magnetic interactions between split ring resonators (SRRs) in metamaterials. We fabricated near-infrared planar metamaterials with different inter-SRR spacings along different directions. Our transmission measurements show blueshifts and re...[Phys. Rev. Lett. 103, 213902] Published Fri Nov 20, 2009
Author(s): Manuel Kremer, Bettina Fischer, Bernold Feuerstein, Vitor L. B. de Jesus, Vandana Sharma, Christian Hofrichter, Artem Rudenko, Uwe Thumm, Claus Dieter Schr?, Robert Moshammer, and Joachim UllrichFully differential data for H_{2} dissociation in ultrashort (6 fs, 760 nm), linearly polarized, intense (0.44 PW/cm^{2} ) laser pulses with a stabilized carrier-envelope phase (CEP) were recorded with a reaction microscope. Depending on the CEP, the molecular orientation, and the kinetic ene...[Phys. Rev. Lett. 103, 213003] Published Fri Nov 20, 2009
Author(s): Peter M?r, Arnold J. Sierk, Ragnar Bengtsson, Hiroyuki Sagawa, and Takatoshi IchikawaTo determine which nuclei may exhibit shape isomerism, we use a well-benchmarked macroscopic-microscopic model to calculate potential-energy surfaces as functions of spheroidal (ϵ_{2} ), hexadecapole (ϵ_{4} ), and axial-asymmetry (γ) shape coordinates for 7206 nuclei from A=31 to A=290. We analyz...[Phys. Rev. Lett. 103, 212501] Published Fri Nov 20, 2009
Author(s): Pat Scott and Sofia SivertssonUltracompact minihalos have been proposed as a new class of dark matter structure. They would be produced by phase transitions in the early Universe or features in the inflaton potential, and constitute nonbaryonic massive compact halo objects today. We examine the prospects of detecting these minih...[Phys. Rev. Lett. 103, 211301] Published Fri Nov 20, 2009
Author(s): Runyao Duan, Yuan Feng, and Mingsheng YingWe provide a feasible necessary and sufficient condition for when an unknown quantum operation (quantum device) secretly selected from a set of known quantum operations can be identified perfectly within a finite number of queries, and thus complete the characterization of the perfect distinguishabi...[Phys. Rev. Lett. 103, 210501] Published Fri Nov 20, 2009
Author(s): M. Kormos, G. Mussardo, and A. TrombettoniWe present a novel method to compute expectation values in the Lieb-Liniger model both at zero and finite temperature. These quantities, relevant in the physics of one-dimensional ultracold Bose gases, are expressed by a series that has a remarkable behavior of convergence. Among other results, we s...[Phys. Rev. Lett. 103, 210404] Published Fri Nov 20, 2009
Author(s): Heiko Conrad, Felix Lehmk?r, Christian Sternemann, Arto Sakko, Dietmar Paschek, Laura Simonelli, Simo Huotari, Omid Feroughi, Metin Tolan, and Keijo H?l?enWe report on the formation of tetrahydrofuran clathrate hydrate studied by x-ray Raman scattering measurements at the oxygen K edge. A comparison of x-ray Raman spectra measured from water-tetrahydrofuran mixtures and tetrahydrofuran hydrate at different temperatures supports stochastic hydrate form...[Phys. Rev. Lett. 103, 218301] Published Thu Nov 19, 2009
Author(s): Christian Bick and Mikhail I. RabinovichThe capacity of working memory (WM), a short-term buffer for information in the brain, is limited. We suggest a model for sequential WM that is based upon winnerless competition amongst representations of available informational items. Analytical results for the underlying mathematical model relate ...[Phys. Rev. Lett. 103, 218101] Published Thu Nov 19, 2009
Author(s): Jens Koch, V. Manucharyan, M. H. Devoret, and L. I. GlazmanThe choice of impedance used to shunt a Josephson junction determines if the charge transferred through the circuit is quantized: a capacitive shunt renders the charge discrete, whereas an inductive shunt gives continuous charge. This discrepancy leads to a paradox in the limit of large inductances ...[Phys. Rev. Lett. 103, 217004] Published Thu Nov 19, 2009
Author(s): M. V. Milošević, A. Kanda, S. Hatsumi, F. M. Peeters, and Y. OotukaWe perform strategic current injection in a small mesoscopic superconductor and control the (non)equilibrium quantum states in an applied homogeneous magnetic field. In doing so, we realize a current-driven splitting of multiquanta vortices, current-induced transitions between states with different ...[Phys. Rev. Lett. 103, 217003] Published Thu Nov 19, 2009
Author(s): J. Sirker, R. G. Pereira, and I. AffleckIt has been conjectured that transport in integrable one-dimensional systems is necessarily ballistic. The large diffusive response seen experimentally in nearly ideal realizations of the S=1/2 1D Heisenberg model is therefore puzzling and has not been explained so far. Here, we show that, contrary ...[Phys. Rev. Lett. 103, 216602] Published Thu Nov 19, 2009
Author(s): K. A. Al-Hassanieh, C. D. Batista, G. Ortiz, and L. N. BulaevskiiWe report on a new electromagnetic phenomenon that emerges in Mott insulators. The phenomenon manifests as antiferromagnetic ordering due to orbital electric currents which are spontaneously generated from the coupling between spin currents and an external homogenous magnetic field. This novel spin-...[Phys. Rev. Lett. 103, 216402] Published Thu Nov 19, 2009
Author(s): Janghwan Cha, Seokho Lim, Cheol Ho Choi, Moon-Hyun Cha, and Noejung ParkWe investigate the mechanism of dihydrogen adsorption onto Ca cation centers, which has been the significant focus of recent research for hydrogen storage. We particularly concentrate on reliability of commonly used density-functional theories, in comparison with correlated wave function theories. I...[Phys. Rev. Lett. 103, 216102] Published Thu Nov 19, 2009
Author(s): D. H. Froula, C. E. Clayton, T. D?er, K. A. Marsh, C. P. J. Barty, L. Divol, R. A. Fonseca, S. H. Glenzer, C. Joshi, W. Lu, S. F. Martins, P. Michel, W. B. Mori, J. P. Palastro, B. B. Pollock, A. Pak, J. E. Ralph, J. S. Ross, C. W. Siders, L. O. Silva, and T. WangA laser wakefield acceleration study has been performed in the matched, self-guided, blowout regime producing 720±50 MeV quasimonoenergetic electrons with a divergence Δθ_{FWHM} of 2.85±0.15 mrad using a 10 J, 60 fs 0.8 μm laser. While maintaining a nearly constant plasma densi...[Phys. Rev. Lett. 103, 215006] Published Thu Nov 19, 2009
Author(s): L. L. Ji (吉亮亮), B. F. Shen (沈百飞), X. M. Zhang (张晓梅), F. C. Wang (王凤超), Z. Y. Jin (金张英), C. Q. Xia (夏长权), M. Wen (温猛), W. P. Wang (王文鹏), J. C. Xu (徐建彩), and M. Y. Yu (郁明阳)A scheme for producing nearly single-cycle relativistic laser pulses is proposed. When a laser pulse interacts with an overdense thin foil, because of self-consistent nonlinear modulation, the latter will be more transparent to the more intense part of the laser, so that a transmitted pulse can be m...[Phys. Rev. Lett. 103, 215005] Published Thu Nov 19, 2009
Author(s): Volkert van Steijn, Chris R. Kleijn, and Michiel T. KreutzerWe describe the breakup of a confined gas thread in a cross-flowing stream of liquid at capillary numbers Ca
Author(s): B. Aubert et al.We present an analysis of the decays B^{0} →K^{*0} (892)γ and B^{+} →K^{*+} (892)γ using a sample of about 383?0^{6} BB [over ¯] events collected with the BABAR detector at the PEP-II asymmetric energy B factory. We measure the branching fractions B(B^{0} →K^{*0} γ)=(4.47±0.10±0.16)?...[Phys. Rev. Lett. 103, 211802] Published Thu Nov 19, 2009
Author(s): Piotr Magierski, Gabriel Wlazłowski, Aurel Bulgac, and Joaqu?E. DrutWe calculate the one-body temperature Green’s (Matsubara) function of the unitary Fermi gas via quantum Monte Carlo, and extract the spectral weight function A(p,ω) using the methods of maximum entropy and singular value decomposition. From A(p,ω) we determine the quasiparticle spectrum, which ...[Phys. Rev. Lett. 103, 210403] Published Thu Nov 19, 2009
Author(s): K. Namikawa, M. Kishimoto, K. Nasu, E. Matsushita, R. Z. Tai, K. Sukegawa, H. Yamatani, H. Hasegawa, M. Nishikino, M. Tanaka, and K. NagashimaWe have developed a new method to investigate the relaxation time of the dipole moment in polarization clusters in BaTiO_{3} . Time correlation of speckle intensities was measured by the use of a double pulsed soft x-ray laser. The evolution of the relaxation time of the dipole moment near the Curie...[Phys. Rev. Lett. 103, 197401] Published Thu Nov 05, 2009
Author(s): William P. Putnam and Mehmet Fatih YanikWe propose the use of interaction-free quantum measurements with electrons to eliminate sample damage in electron microscopy. This might allow noninvasive molecular-resolution imaging. We show the possibility of such measurements in the presence of experimentally measured quantum decoherence rates a...[Phys. Rev. A 80, 040902] Published Fri Oct 23, 2009
Author(s): Thomas B. Schr?, Ulf R. Pedersen, Nicholas P. Bailey, S? Toxvaerd, and Jeppe C. DyreResults from molecular dynamics simulations of two viscous molecular model liquids—the Lewis-Wahnstr?odel of orthoterphenyl and an asymmetric dumbbell model—are reported. We demonstrate that the liquids have a “hidden” approximate scale invariance: equilibrium potential energy fluctuatio...[Phys. Rev. E 80, 041502] Published Tue Oct 13, 2009
Author(s): Daniel K. Shenfeld, Huafeng Xu, Michael P. Eastwood, Ron O. Dror, and David E. ShawIn computational thermodynamics, a sequence of intermediate states is commonly introduced to connect two equilibrium states. We consider two cases where the choice of intermediate states is particularly important: minimizing statistical error in free-energy difference calculations and maximizing ave...[Phys. Rev. E 80, 046705] Published Mon Oct 19, 2009
Author(s): Timothy E. Saunders and Martin HowardMorphogen profiles play a vital role in biology by specifying position in embryonic development. However, the factors that influence the shape of a morphogen profile remain poorly understood. Since morphogens should provide precise positional information, one significant factor is the robustness of ...[Phys. Rev. E 80, 041902] Published Fri Oct 02, 2009
Author(s): Richard S. Graham and Peter D. OlmstedWe perform kinetic Monte Carlo simulations of flow-induced nucleation in polymer melts with an algorithm that is tractable even at low undercooling. The configuration of the noncrystallized chains under flow is computed with a recent nonlinear tube model. Our simulations predict both enhanced nucle...[Phys. Rev. Lett. 103, 115702] Published Thu Sep 10, 2009
Author(s): G. Vogl, E. Partyka-Jankowska, M. Zając, and A. I. ChumakovWe study the structure of a model surface, i.e., an Fe monolayer on W(110) by nuclear resonant scattering of x rays. We conclude that at room temperature the structure is nearly perfect, whereas when increasing the temperature up to 770 K an increasing fraction of the Fe atoms feels the appearance o...[Phys. Rev. B 80, 115406] Published Fri Sep 04, 2009
Author(s): Christoph Freysoldt, Patrick Rinke, and Matthias SchefflerBy means of quasiparticle-energy calculations in the G_{0} W_{0} approach, we show for the prototypical insulator-semiconductor system NaCl/Ge(001) that polarization effects at the interfaces noticeably affect the excitation spectrum of molecules adsorbed on the surface of the NaCl films. The magnit...[Phys. Rev. Lett. 103, 056803] Published Fri Jul 31, 2009
Author(s): B. P. Abbott et al. LIGO Scientific CollaborationThis paper reports on an all-sky search for periodic gravitational waves from sources such as deformed isolated rapidly spinning neutron stars. The analysis uses 840 hours of data from 66 days of the fifth LIGO science run (S5). The data were searched for quasimonochromatic waves with frequencies ...[Phys. Rev. D 80, 042003] Published Tue Aug 11, 2009
Author(s): Xinguo Ren, Patrick Rinke, and Matthias SchefflerThe adsorption of CO on the Cu(111) surface is investigated in the random phase approximation (RPA) as formulated within the adiabatic connection fluctuation-dissipation theorem. The RPA adsorption energy is obtained by adding a “local exchange-correlation correction” that is extrapolated from c...[Phys. Rev. B 80, 045402] Published Thu Jul 02, 2009
Author(s): N. Bloembergen, C. K. Patel, P. Avizonis, R. G. Clem, A. Hertzberg, T. H. Johnson, T. Marshall, R. B. Miller, W. E. Morrow, E. E. Salpeter, A. M. Sessler, J. D. Sullivan, J. C. Wyant, A. Yariv, R. N. Zare, A. J. Glass, L. C. Hebel, G. E. Pake, M. M. May, W. K. Panofsky, A. L. Schawlow, C. H. Townes, and H. York APS Study Group Participants, APS Council Review Committee[Rev. Mod. Phys. 59, S1] Published Wed Jul 01, 1987
Author(s): Richard Wilson, Kamal J. Araj, Augustine O. Allen, Peter Auer, David G. Boulware, Fred Finlayson, Simon Goren, Clark Ice, Leon Lidofsky, Allen Lee Sessoms, Mary L. Shoaf, Irving Spiewak, Thomas Tombrello, Herbert S. Gutowsky, Andreas Acrivos, Herman Feshbach, and William A. Fowler APS Study Group Participants, APS Council Review Committee[Rev. Mod. Phys. 57, S1] Published Mon Jul 01, 1985
Author(s): Bernard R. Cooper, Wayne R. Gruner, Larry Anderson, Robert H. Davis, Paul Engelking, Jose D. Garcia, Edward Gerjuoy, Robert I. Jaffee, Philip G. Kosky, Leonidas Petrakis, Robert T. Poe, Richard Pollina, C. Dwight Prater, Robert L. Thomas, Sandor Trajmar, G. J. Dienes, Nancy M. O'Fallon, Harvey Brooks, William A. Fowler, Everett Gorin, Norman F. Ramsey, and M. D. Schlesinger APS Study Group Participants, Ex Officio Panel Members, APS Council Review Committee[Rev. Mod. Phys. 53, S1] Published Thu Oct 01, 1981
Author(s): L. Charles Hebel, Eldon L. Christensen, Fred A. Donath, Warren E. Falconer, Leon J. Lidofsky, Ernest J. Moniz, Thomas H. Moss, Robert L. Pigford, Thomas H. Pigford, Gene I. Rochlin, Robert H. Silsbee, McDonald E. Wrenn, Hans Frauenfelder, Theodore L. Cairns, W. K. Panofsky, and M. Gene Simmons APS Study Group Participants, APS Council Review CommitteeUtilization of nuclear fuels and management of nuclear wastes have become major topics of public discussion. Under the auspices of the American Physical Society this study was undertaken as an independent evaluation of technical issues in the use of fissionable materials in nuclear fuel cycles, toge...[Rev. Mod. Phys. 50, S1] Published Sun Jan 01, 1978
Author(s): H. W. Lewis, R. J. Budnitz, A. W. Castleman, D. E. Dorfan, F. C. Finlayson, R. L. Garwin, L. C. Hebel, S. M. Keeny, R. A. Muller, T. B. Taylor, G. F. Smoot, F. von Hippel, Hans Bethe, W. K. Panofsky, and V. F. Weisskopf APS Study Group Participants, APS Council Review CommitteeThe issue of light-water reactor (LWR) safety has been the subject of a part-time, year-long study sponsored by the American Physical Society. The goal of the study was the assessment of some of the technical aspects of the safety of large light-water nuclear power reactors typical of present commer...[Rev. Mod. Phys. 47, S1] Published Wed Jan 01, 1975
Author(s): F. L. Vook, H. K. Birnbaum, T. H. Blewitt, W. L. Brown, J. W. Corbett, J. H. Crawford, A. N. Goland, G. L. Kulcinski, M. T. Robinson, D. N. Seidman, F. W. Young, J. Bardeen, R. W. Balluffi, J. S. Koehler, and G. H. Vineyard APS Study Group Participants, APS Council Review Committee[Rev. Mod. Phys. 47, S1] Published Wed Jan 01, 1975
Author(s): David K. Barton, Roger Falcone, Daniel Kleppner, Frederick K. Lamb, Ming K. Lau, Harvey L. Lynch, David Moncton, David Montague, David E. Mosher, William Priedhorsky, Maury Tigner, and David R. VaughanThis issue of RMP has, as a special supplement, the report of an APS study group on the physics and engineering issues that must be addressed in designing a missile defense system capable of intercepting a hostile missile while it is still burning, the so-called “boost phase.” The challenges for...[Rev. Mod. Phys. 76, S1] Published Tue Oct 05, 2004
Author(s): Burton Richter, David Goldston, George Crabtree, Leon Glicksman, David Goldstein, David Greene, Dan Kammen, Mark Levine, Michael Lubell, Maxine Savitz, Daniel Sperling, Fred Schlachter, John Scofield, and James DawsonThe American Physical Society regularly produces reports on issues of public import that require technical understanding and for which an objective and authoritative analysis would be of particular use to the public and policy makers. This report, entitled Energy Future: Think Efficiency, is the lat...[Rev. Mod. Phys. 80, S1] Published Tue Dec 30, 2008
Author(s): Kaiichiro Ota, Masaki Nomura, and Toshio AoyagiWe demonstrate that the phase response curve (PRC) can be reconstructed using a weighted spike-triggered average of an injected fluctuating input. The key idea is to choose the weight to be proportional to the magnitude of the fluctuation of the oscillatory period. Particularly, when a neuron exhibi...[Phys. Rev. Lett. 103, 024101] Published Wed Jul 08, 2009
Author(s): Evan Monroig, Kazuyuki Aihara, and Yozo FujinoWe examine the problem of reconstructing input-output systems from time series data. Although the method of delays has already been used in the case where both input and output are measured, in some cases, the inputs cannot be measured, and hence, the method of delays cannot be used. On the basis of...[Phys. Rev. E 79, 056208] Published Fri May 08, 2009
Author(s): Johan M. Carlsson, Felix Hanke, Suljo Linic, and Matthias SchefflerWe study the oxidation of vacancies in graphene by ab initio atomistic thermodynamics to identify the dominant reaction mechanisms. Our calculations show that the low-temperature oxidation occurs via a two-step process: Vacancies are initially saturated by stable O groups, such as ether (C-O-C) and...[Phys. Rev. Lett. 102, 166104] Published Thu Apr 23, 2009
Author(s): Martin Gabl, Magdalena Bachmann, Norbert Memmel, and Erminald BertelSilver nanoclusters arranged in quasi-one-dimensional chains with a nearest-neighbor cluster-cluster distance of 1.4 nm were prepared on the R(15?2)-C/W(110) surface. The silver cluster chains form local thermodynamic equilibrium structures. Interactions between neighboring clusters are addressed ...[Phys. Rev. B 79, 153409] Published Mon Apr 27, 2009
Christophe Goupil We derive the principal contributions to energy flux and entropy flux in a thermoelectric material using a force-flux description. Using the reduced current u=J/kappa[del]T of the coupled thermal and electrical flows, we introduce the so-called thermoelectric potential Talpha+1/u. We show that this ... [J. Appl. Phys. 106, 104907 (2009)] published Fri Nov 20, 2009.
Tingkun Gu, Zhongchang Wang, Tomofumi Tada, and Satoshi Watanabe Electronic structures and transport properties of bulk TaO and Cu/TaO/Pt heterojunction have been studied from first principles. Of the two room-temperature phases of bulk TaO, beta-, and delta-TaO, our calculated results showed that the beta phase has much narrower band gap than the delta-TaO. For ... [J. Appl. Phys. 106, 103713 (2009)] published Fri Nov 20, 2009.
M. Frazier, J. G. Cates, J. A. Waugh, J. J. Heremans, M. B. Santos et al. We demonstrate the observation of spin-polarized photocurrent in InSb films grown on GaAs and InP substrates and InSb quantum wells where a nonequilibrium spin population has been achieved by using circularly polarized radiation. The characteristics of our observations indicated that the circular ph ... [J. Appl. Phys. 106, 103513 (2009)] published Fri Nov 20, 2009.
M. Nistor, F. Gherendi, N. B. Mandache, C. Hebert, J. Perriere et al. We report on the formation and transport properties of ZnO thin films which are grown by pulsed-electron beam deposition under a low residual oxygen pressure (10 mbar). ZnO films presenting metallic conductivity at room temperature, and a metal-semiconductor transition at low temperature, were epit ... [J. Appl. Phys. 106, 103710 (2009)] published Fri Nov 20, 2009.
Satoshi Awaji, Masafumi Namba, Kazuo Watnabe, Shun Ito, Eiji Aoyagi et al. Flux pinning properties on the ErBaCaO films with the nanoscaled and columnar-shaped BaMO (BMO,M=Zr,Sn) precipitates, i.e., nanorods, were investigated systematically based on the microstructure, critical current density J and irreversibility field B properties in high magnetic fields. We found that ... [J. Appl. Phys. 106, 103915 (2009)] published Fri Nov 20, 2009.
S. Olthof, W. Tress, R. Meerheim, B. Lussem, and K. Leo We investigate the doping behavior of the strongly electron accepting molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane coevaporated with the host molecule N,N,N,N-tetrakis(4-methoxyphenyl)-benzidine by photoemission spectroscopy and conductivity measurements. Using interface resolved me ... [J. Appl. Phys. 106, 103711 (2009)] published Fri Nov 20, 2009.
Vineet Kumar Rai, Cid B. de Araujo, Y. Ledemi, B. Bureau, M. Poulain et al. Optical properties of a neodymium (Nd) doped glass having composition based on the (GaS)(GeS) system are reported. Transition probabilities, radiative lifetimes, and branching ratios related to Nd levels were determined. Frequency upconversion (UC) luminescence due to nonresonant excitation at 1064 ... [J. Appl. Phys. 106, 103512 (2009)] published Fri Nov 20, 2009.
C. Pareige, C. Domain, and P. Olsson Atomistic kinetic Monte Carlo simulations based on the two-band semiempirical cohesive model for FeCr have revealed a body centered tetragonal FeCr ordered compound at very low temperatures. Density functional theory calculations have shown that this structure is more stable than the FeCr compound r ... [J. Appl. Phys. 106, 104906 (2009)] published Fri Nov 20, 2009.
Nicolas A. Shtin, Jose Mauricio Lopez Romero, and Eugene Prokhorov An accurate model for intrinsic dielectric loss in sapphire (alpha-AlO) is presented. The proposed model is based on a theory of electromagnetic field absorption governed by multiphonon relaxation processes influenced by a finite lifetime of thermal phonons. Expressions for anisotropic sapphire diel ... [J. Appl. Phys. 106, 104115 (2009)] published Fri Nov 20, 2009.
T. K. Sharma and E. Towe A simple method for calculating the ground state excitonic band gaps of strained wurtzite InGaN/GaN quantum wells (QWs) for the entire composition range is proposed. The modification of the electronic band structure due to strain becomes significant for high values of indium concentration. It is obs ... [J. Appl. Phys. 106, 104509 (2009)] published Fri Nov 20, 2009.
M. Filippi, B. Kundys, S. Agrestini, W. Prellier, H. Oyanagi et al. Charge ordering, dielectric permittivity, and local structure of LaSrNiO system have been explored by x-ray charge scattering, complex dielectric impedance spectroscopy, and extended x-ray absorption fine structure (EXAFS) measurements, made on the same single crystal sample. The local structure mea ... [J. Appl. Phys. 106, 104116 (2009)] published Fri Nov 20, 2009.
A. J. Smith, R. M. Gwilliam, V. Stolojan, A. P. Knights, P. G. Coleman et al. The concentration of vacancy-type defects in a silicon-on-insulator substrate consisting of a 110 nm silicon overlayer and a 200 nm buried oxide has been quantified using variable energy positron annihilation spectroscopy following 300 keV Si ion implantation to a dose of 1.5 x 10 cm and subsequent ... [J. Appl. Phys. 106, 103514 (2009)] published Fri Nov 20, 2009.
Tien-Kan Chung, Kin Wong, Scott Keller, Kang L. Wang, and Gregory P. Carman We report experimental results on electrical control of magnetic remanent states (i.e., nanoscale remanent domain patterns) in a magnetoelectric layered nanostructure, Ni nanobar/lead zirconate titanate film. First, with application of different external magnetic fields as a baseline characterizatio ... [J. Appl. Phys. 106, 103914 (2009)] published Fri Nov 20, 2009.
A. C. Pimentel, D. M. F. Prazeres, V. Chu, and J. P. Conde A comparative study of the performance of hydrogenated amorphous silicon photosensors based on two different device configurations for integration in a microarray platform for biomolecular detection is presented. A perpendicular contact p-i-n photodiode and a parallel contact intrinsic photoconducto ... [J. Appl. Phys. 106, 104904 (2009)] published Fri Nov 20, 2009.
P. Krone, D. Makarov, T. Schrefl, and M. Albrecht We present a systematic study on the magnetization reversal in square arrays of magnetic nanostructures. To account for the unavoidable inhomogeneities of the magnetic properties due to, i.e., template preparation, a distribution of magnetic anisotropy values was taken into account. We show that the ... [J. Appl. Phys. 106, 103913 (2009)] published Fri Nov 20, 2009.
Hemant Rao and Gijs Bosman Room temperature low frequency noise characteristics of gate and drain currents of an AlGaN/GaN high electron mobility transistor are reported. A Hooge parameter (alpha) ranging from 10 to 10 is extracted for drain current noise as a function of sheet carrier density. Gate current noise is simultane ... [J. Appl. Phys. 106, 103712 (2009)] published Fri Nov 20, 2009.
Ari Salmi, Lauri Salminen, and Edward Haeggstrom Papermaking, especially mechanical pulping, consumes much energy. To reduce this energy consumption one has to understand and exploit the phenomena present during the pulping. An important phenomenon to understand is wood fatigue. We quantitatively measure the fatigue generated during high strain ra ... [J. Appl. Phys. 106, 104905 (2009)] published Fri Nov 20, 2009.
Hans Christian Alt and Hans Edwin Wagner NO-related shallow donors in nitrogen-doped Czochralski silicon have been studied by infrared spectroscopy. Quasithermal equilibrium states were established by long-term thermal annealing in the temperature range from 600 to 1000 degrees C. By quantitative analysis of the 1s-->2p far-infrared el ... [J. Appl. Phys. 106, 103511 (2009)] published Fri Nov 20, 2009.
Jiagang Wu and John Wang Multiferroic BiFeO (BFO) thin films with (111), (100), (110) preferred, and random orientations were deposited by radio frequency magnetron sputtering on SrRuO-buffered SrTiO(111), SrTiO(100), SrTiO(110), and Pt(111)/Ti/SiO/Si(100) substrates, respectively. The orientation dependences of ferroelectr ... [J. Appl. Phys. 106, 104111 (2009)] published Thu Nov 19, 2009.
I. C. W. Chan and M. Beaudoin The Fernelius extension to the RosencwaigGersho theory for photothermal deflection spectroscopy (PDS) is modified to take into account multiple reflections and light trapping within a thin film-on-substrate system where both the thin film and the substrate can be absorbing. The extended model is use ... [J. Appl. Phys. 106, 103510 (2009)] published Thu Nov 19, 2009.
Changjun Jiang, Desheng Xue, Dangwei Guo, and Xiaolong Fan CoZr (40 nm) thin films with different Zr compositions were grown on silicon substrates by radio frequency magnetron sputtering. The coercivity decreased with an increase in the Zr composition. A uniaxial anisotropy existed in the CoZr films, and the anisotropy field of the films decreased from 55 t ... [J. Appl. Phys. 106, 103910 (2009)] published Thu Nov 19, 2009.
Vilas Shelke, V. N. Harshan, Sushma Kotru, and Arunava Gupta Epitaxial BiFeO thin films have been grown on (100)-oriented SrTiO and Nb-doped SrTiO substrates using the pulsed laser deposition technique under identical thermodynamic and variable kinetic conditions. The variation of growth kinetics through laser fluence and pulse repetition rate had minimal eff ... [J. Appl. Phys. 106, 104114 (2009)] published Thu Nov 19, 2009.
V. Franco, A. Conde, J. M. Romero-Enrique, Y. I. Spichkin, V. I. Zverev et al. The field dependence of the adiabatic temperature change DeltaT of second order phase transition materials is studied, both theoretically and experimentally. Using scaling laws, it is demonstrated that, at the Curie temperature, the field dependence of DeltaT is characterized by H. Therefore, as the ... [J. Appl. Phys. 106, 103911 (2009)] published Thu Nov 19, 2009.
U. Cvelbar, M. Mozetic, N. Hauptman, and M. Klanjsek-Gunde The degradation of Staphylococcus aureus bacteria during treatment with neutral oxygen atoms was monitored by scanning electron microscopy. Experiments were performed in an afterglow chamber made from borosilicate glass. The source of oxygen atoms was remote inductively coupled radiofrequency oxygen ... [J. Appl. Phys. 106, 103303 (2009)] published Thu Nov 19, 2009.
Tobias Niebling, Feng Zhang, Zulqurnain Ali, Wolfgang J. Parak, and Wolfram Heimbrodt Inorganic CdSe/ZnS core-shell quantum dots have been coated with amphiphilic polymers in order to enable their transfer to aqueous solutions. Additionally, ATTO-dye molecules have been embedded in the polymer shell. In this geometry ATTO dye acts as acceptor of the quantum dot donors' excitation. Th ... [J. Appl. Phys. 106, 104701 (2009)] published Thu Nov 19, 2009.
Photometric photoelectric data of the short-period close binary system, WZ Cephei, are presented. A new photometric analysis with the 2003 version of the Wilson-Devinney method confirmed that it is a shallow contact binary (f ~ 13.3%) with a high level of spot activity on the primary component. Combining new determined times of light minimum with the others published in the literature, the period change of the binary star is investigated. A periodic variation, with a period of 34.2 years and an amplitude of 0fd013, was discovered to be superimposed on a long-term period decrease (dP/dt = --8.8 ?10--8 days year--1). Both the secular period decrease and the shallow contact configuration suggest that this binary system is at the beginning of contact phase. It is on the way to evolving into a normal overcontact phase via secular angular momentum loss and/or mass transfer from the more massive component to the less massive one. The period oscillation can be explained either by the light-time effect due to the presence...
Using linear regression techniques and correlation analysis, the predictive power of Ohl's method is shown to satisfy one of the following relationships. Either a successful prediction of cycle amplitude can be obtained if the correlation between the minimum aa geomagnetic index in the declining phase of a solar cycle and the sunspot maximum of the succeeding cycle becomes stronger, or the prediction error exceeds the expected prediction error if the correlation becomes weaker. The correlation coefficient has a declining secular variation, which leads to a weakening trend in predictive power, as well as a 44 year periodicity that may explain why the prediction method did not work well for solar cycle 23. As this finding only emerged twice in the ~100 year period studied, this 44 year periodicity may occur with a degree of uncertainty and may therefore need to be checked in the future. Two quantities, namely a prediction parameter and the prediction index, are proposed to analyze predictive power. Using the above...
We present the results of an 8.4 GHz Very Large Array radio survey of early-type galaxies extracted from the sample selected by C?and collaborators for the Advanced Camera for Surveys Virgo Cluster Survey. The aim of this survey is to investigate the origin of radio emission in early-type galaxies and its link with the host properties in an unexplored territory toward the lowest levels of both radio and optical luminosities. Radio images, available for all 63 galaxies with B T < 14.4, show the presence of a compact radio source in 12 objects, with fluxes spanning from 0.13 mJy to 2700 mJy. The remaining 51 galaxies, undetected at a flux limit of ~0.1 mJy, have radio luminosities L lsim 4 ?1018 W Hz--1. The fraction of radio-detected galaxies are a strong function of stellar mass, in agreement with previous results: none of the 30 galaxies with M sstarf < 1.7 ?1010 M sun is detected, while 8 of the 11 most massive galaxies have radio cores. There appears to be no simple relation between the presence of a stellar...
Hubble Space Telescope/Advanced Camera for Surveys fields toward M31 and M32 were examined for the presence of possible star clusters. On the basis of stellar photometry, two intermediate-age clusters were found in the field that contains both M31 and M32 stars. One is approximately 200 Myr of age with a mass ~400 M sun, and the other is 1 Gyr old with mass ~8 ?104 M sun. Several other cluster candidates are identified, but their stellar populations are more similar to the field: old and slightly metal-poor.
We present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix), Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi) parallaxes with astrometric data from Fine Guidance Sensors FGS 1r and FGS 3, white-light interferometers on the Hubble Space Telescope. Proper motions, spectral classifications and VJHKT2M and DDO51 photometry of the stars comprising the astrometric reference frames provide spectrophotometric estimates of reference star absolute parallaxes. Introducing these into our model as observations with error, we determine absolute parallaxes for each PNN. Weighted averaging with previous independent parallax measurements yields an average parallax precision, sigmapi/pi = 5%. Derived distances are: d NGC 6853 = 405+28 --25 pc, d NGC 7293 = 216+14 --12 pc, d Abell 31 = 621+91 --70 pc, and d DeHt 5 = 345+19 --17 pc. These PNNi distances...
We present aperture synthesis observations in the 21 cm line of pointings centered on the Virgo Cluster region spirals NGC 4307, NGC 4356, NGC 4411B, and NGC 4492 using the Very Large Array (VLA) radio telescope in its CS configuration. These galaxies were identified in a previous study of the three-dimensional distribution of H I emission in the Virgo region as objects with a substantial dearth of atomic gas and Tully-Fisher (TF) distance estimates that located them well outside the main body of the cluster. We have detected two other galaxies located in two of our fields and observed bands, the spiral NGC 4411A and the dwarf spiral VCC 740. We provide detailed information of the gas morphology and kinematics for all these galaxies. Our new data confirm the strong H I deficiency of all the main targets but NGC 4411B, which is found to have a fairly normal neutral gas content. The VLA observations have also been used to discuss the applicability of TF techniques to the five largest spirals we have observed. We...
An important component of the Extragalactic Distance Database is a group of catalogs related to the measurement of H I line profile parameters. One of these is the All Digital H I catalog which contains an amalgam of information from new data and old. The new data result from observations with Arecibo and Parkes Telescopes and with the Green Bank Telescope, including continuing input since the award of the NRAO Cosmic Flows Large Program. The old data have been collected from archives, wherever available, particularly the Cornell University Digital H I Archive, the Nan? Telescope extragalactic H I archive, and the Australia Telescope H I archive. The catalog currently contains information on ~15, 000 profiles relating to ~13, 000 galaxies. The channel-flux per channel files, from whatever source, is carried through a common pipeline. The derived parameter of greatest interest is W m50, the profile width at 50% of the mean flux. After appropriate adjustment, the parameter Wmx is derived, the line width that statistically...
We have conducted a pilot survey for z > 3.5 quasars by combining the FIRST radio survey with the Sloan Digital Sky Survey (SDSS). While SDSS already targets FIRST sources for spectroscopy as quasar candidates, our survey includes fainter quasars and greatly improves the discovery rate by using strict astrometric criteria for matching the radio and optical positions. Our method allows for selection of high-redshift quasars with less color bias than with optical selection, as using radio selection essentially eliminates stellar contamination. We report the results of spectroscopy for 45 candidates, including 29 quasars in the range 0.37 < z < 5.2, with 7 having redshifts z > 3.5. We compare quasars selected using radio and optical criteria, and find that radio-selected quasars have a much higher fraction of moderately reddened objects. We derive a radio-loud quasar luminosity function at 3.5 < z < 4.0, and find that it is in good agreement with expectations from prior SDSS results.
Solutions of standard VR light curves for the eclipsing binary RT And were obtained using the PHOEBE program (ver. 0.3a). Absolute parameters of the stellar components were then determined, enabling them to be positioned on the mass-luminosity diagram. Times of minima data ("O -- C curve") were analyzed using the method of Kalimeris et al. A cyclic variation in the orbital period and brightness, with timescales of about 11.89 and 12.50 yr were found, respectively. This is associated with a magnetic activity cycle modulating the orbital period of RT And via the Applegate mechanism. To check the consistency of the Applegate model, we have estimated some related parameters of the RT And system. The calculated parameters were in accordance with those estimated by Applegate for other similar systems, except B, the subsurface magnetic field of which shows a rather high value for RT And.
One possible channel for the formation of dwarf galaxies involves birth in the tidal tails of interacting galaxies. We report the detection of a bright UV tidal tail and several young tidal dwarf galaxy (TDG) candidates in the post-merger galaxy NGC 4922 in the Coma cluster. Based on a two-component population model (combining young and old stellar populations), we find that the light of tidal tail predominantly comes from young stars (a few Myr old). The Galaxy Evolution Explorer ultraviolet data played a critical role in the parameter (age and mass) estimation. Our stellar mass estimates of the TDG candidates are ~106--7 M sun, typical for dwarf galaxies.
We present analysis of both the short-term optical and long-term multiwavelength variability of CTA 102. In 2004, this object was observed in an intense optical flaring state. Extensive R-band microvariability observations were carried out during this high state. In 2005, we obtained several weeks of contemporaneous radio, optical, and X-ray observations of CTA 102. These observations recorded distinct flaring activity in all three wavebands. Subsequent analysis revealed that this object may appear redder when in a brighter optical state, and that the X-ray, optical, and radio activity do not appear to be correlated. The shape of the observed spectral energy distributions suggests that both synchrotron-related and external inverse Compton processes may contribute to the X-ray emission. Our results are also compared to other results on this object and archival microvariability observations. It appears that more rapid, dramatic microvariability events occur when CTA 102 is in an elevated optical flux state.
We present the results of a search for occultation events by objects at distances between 100 and 1000 AU in light curves from the Taiwanese-American Occultation Survey. We searched for consecutive, shallow flux reductions in the stellar light curves obtained by our survey between 2005 February 7 and 2006 December 31 with a total of ~4.5 ?109 three-telescope simultaneous photometric measurements. No events were detected, allowing us to set upper limits on the number density as a function of size and distance of objects in Sedna-like orbits, using simple models.
We discuss the jet kinematics of a complete flux-density-limited sample of 135 radio-loud active galactic nuclei (AGNs) resulting from a 13 year program to investigate the structure and evolution of parsec-scale jet phenomena. Our analysis is based on new 2 cm Very Long Baseline Array (VLBA) images obtained between 2002 and 2007, but includes our previously published observations made at the same wavelength, and is supplemented by VLBA archive data. In all, we have used 2424 images spanning the years 1994-2007 to study and determine the motions of 526 separate jet features in 127 jets. The data quality and temporal coverage (a median of 15 epochs per source) of this complete AGN jet sample represent a significant advance over previous kinematics surveys. In all but five AGNs, the jets appear one-sided, most likely the result of differential Doppler boosting. In general, the observed motions are directed along the jet ridge line, outward from the optically thick core feature. We directly observe changes in speed...
In 1975, E. R. Robinson conducted the hallmark study of the behavior of classical nova light curves before eruption, and this work has now become part of the standard knowledge of novae. He made three points: 5 out of 11 novae showed pre-eruption rises in the years before eruption, one nova (V446 Her) showed drastic changes in the variability across eruptions, and all but one of the novae (excepting BT Mon) have the same quiescent magnitudes before and after the outburst. This work has not been tested since it came out. We have now tested these results by going back to the original archival photographic plates and measuring large numbers of pre-eruption magnitudes for many novae using comparison stars on a modern magnitude scale. We find in particular that four out of five claimed pre-eruption rises are due to simple mistakes in the old literature, that V446 Her has the same amplitude of variations across its 1960 eruption, and that BT Mon has essentially unchanged brightness across its 1939 eruption. Out of...
Using the IRAC images from the Spitzer c2d program, we have made a survey of mid-infrared outflows in the rho Ophiuchi molecular cloud. Extended objects that have prominent emission in IRAC channel 2 (4.5 mum) compared to IRAC channel 1 (3.6 mum) and stand out as green objects in the three-color images (3.6 mum in blue, 4.5 mum in green, 8.0 mum in red) are identified as mid-infrared outflows. As a result, we detected 13 new outflows in the rho Ophiuchi molecular cloud that have not been previously observed in either the optical or the near-infrared. In addition, at the positions of previously observed HH objects or near-infrared emission, we detected 31 mid-infrared outflows, among which seven correspond to previously observed HH objects and 30 to near-infrared emission. Most of the mid-infrared outflows detected in the rho Ophiuchi cloud are concentrated in the L1688 dense core region. In combination with the survey results for young stellar objects (YSOs) and millimeter and submillimeter sources, the distribution...
We present an initial survey of Mg II absorption characteristics in the halos of a carefully constructed, volume-limited subsample of galaxies embedded in the spectroscopic part of the Sloan Digital Sky Survey (SDSS). We observed quasars near sightlines to 20 low-redshift (z ~ 0.1), luminous (M r + 5log h = 0.3 - Mg II absorption at the galaxy's redshift, six systems have upper limits which preclude strong Mg II absorption, while the remaining observations rule out very strong (W eq(2796) >= 1-2 - absorption. The absorbers fall at higher impact parameters than many non-absorber sightlines, indicating a covering fraction fc lsim 0.4 for >=0.3 ?absorbers at z ~ 0.1, even at impact parameters
We present the results of a new VLA H I Imaging survey of Virgo galaxies, the VLA Imaging survey of Virgo galaxies in Atomic gas (VIVA). The survey includes high-resolution H I data of 53 carefully selected late type galaxies (48 spirals and five irregular systems). The goal is to study environmental effects on H I gas properties of cluster galaxies to understand which physical mechanisms affect galaxy evolution in different density regions, and to establish how far out the impact of the cluster reaches. As a dynamically young cluster, Virgo contains examples of galaxies experiencing a variety of environmental effects. Its nearness allows us to study each galaxy in great detail. We have selected Virgo galaxies with a range of star formation properties in low to high density regions (at projected distances from M87, d 87 = 0.3-3.3 Mpc). Contrary to previous studies, more than half of the galaxies in the sample (~60%) are fainter than 12 mag in BT . Overall, the selected galaxies represent the late type Virgo galaxies...
We present MASSCLEAN, a new, sophisticated and robust stellar cluster image and photometry simulation package. This visualization tool is able to create color-magnitude diagrams (CMDs) and standard FITS images in any of the traditional optical and near-infrared bands based on cluster characteristics input by the user, including but not limited to distance, age, mass, radius, and extinction. At the limit of very distant, unresolved clusters, we have checked the integrated colors created in MASSCLEAN against those from other simple stellar population models with consistent results. We have also tested models that provide a reasonable estimate of the field star contamination in images and CMDs. We demonstrate the package by simulating images and CMDs of well-known massive Milky Way clusters and compare their appearance to real data. Because the algorithm populates the cluster with a discrete number of tenable stars, it can be used as part of a Monte Carlo Method to derive the probabilistic range of characteristics...
In an effort to study Damped Lyalpha (DLA) galaxies at low redshift, we have been using the Sloan Digital Sky Survey (SDSS) to identify galaxies projected onto quasi-stellar object (QSO) sight lines and to characterize their optical properties. For low-redshift galaxies, the H I 21 cm emission line can be used as an alternate tool for identifying possible DLA galaxies, since H I-emitting galaxies typically exhibit H I columns that are larger than the classical DLA limit. Here, we report on follow-up H I 21 cm emission-line observations of two DLA candidates that are both low-redshift spiral galaxies, Mrk 1456 and SDSS J211701.26--002633.7. The observations were made using the Green Bank Telescope (GBT) and Arecibo telescope, respectively. Analysis of their H I properties reveal the galaxies to be about one and two M*H I galaxies, respectively, and to have average H I mass, gas richness, and gas-mass fraction for their morphological types. We consider Mrk 1456 and SDSS J211701.26--002633.7 to be candidate DLA...
A sample of 6188 nearby galaxy structures, complete to rF = 18fm3 and containing at least 10 members each, was the observational basis for an investigation of the alignment of bright galaxies with the major axes for the parent clusters. The distribution of position angles for galaxies within the clusters, specifically the brightest, the second brightest, the third, and the tenth brightest galaxies was tested for isotropy. Galaxy position angles appear to be distributed isotropically, as are the distributions of underlying cluster structure position angles. The characterization of galaxy structures according to richness class also appears to be isotropic. Characterization according to BM types, which are known for 1056 clusters, is more interesting. Only in the case of clusters of BM type I is there an alignment of the brightest cluster member with the major axis of the parent cluster. The effect is observed at the 2 significance level. In other investigated cases the distributions are isotropic. The results confirm...
In this work, we present the first results of our imaging campaign at Keck Observatory to identify the host galaxies of "dark" gamma-ray bursts (GRBs), events with no detected optical afterglow or with detected optical flux significantly fainter than expected from the observed X-ray afterglow. We find that out of a uniform sample of 29 Swift bursts rapidly observed by the Palomar 60 inch telescope through 2008 March (14 of which we classify as dark), all events have either a detected optical afterglow, a probable optical host-galaxy detection, or both. Our results constrain the fraction of Swift GRBs coming from very high redshift (z>7), such as the recent GRB 090423, to between 0.2% and 7% at 80% confidence. In contrast, a significant fraction of the sample requires large extinction columns (host-frame AV gsim 1 mag, with several events showing AV > 2-6 mag), identifying dust extinction as the dominant cause of the dark GRB phenomenon. We infer that a significant fraction of GRBs (and, by association, of high-mass...
We present the kinematical properties, distribution of spectroscopic subtypes, and stellar population subcomponents of the white dwarfs within 20 pc of the Sun. We find no convincing evidence of halo white dwarfs in the total 20 pc sample of 129 white dwarfs nor is there convincing evidence of genuine thick disk subcomponent members within 20 parsecs. Virtually, the entire 20 pc sample likely belongs to the thin disk. The total DA to non-DA ratio of the 20 pc sample is 1.6, a manifestation of deepening envelope convection which transforms DA stars with sufficiently thin H surface layers into non-DAs. The addition of five new stars to the 20 pc sample yields a revised local space density of white dwarfs of (4.9 ± 0.5) ?10--3 pc--3 and a corresponding mass density of (3.3 ± 0.3) ?10--3 M sun pc--3. We find that at least 15% of the white dwarfs within 20 parsecs of the Sun (the DAZ and DZ stars) have photospheric metals that possibly originate from accretion of circumstellar material (debris disks) around them....
Surface brightness profiles for 23 M31 star clusters were measured using images from the Wide Field Planetary Camera 2 on the Hubble Space Telescope, and fitted to two types of models to determine the clusters' structural properties. The clusters are primarily young (~108 yr) and massive (~104.5 M sun), with median half-light radius 7 pc and dissolution times of a few Gyr. The properties of the M31 clusters are comparable to those of clusters of similar age in the Magellanic Clouds. Simulated star clusters are used to derive a conversion from statistical measures of cluster size to half-light radius so that the extragalactic clusters can be compared to young massive clusters in the Milky Way. All three sets of star clusters fall approximately on the same age-size relation. The young M31 clusters are expected to dissolve within a few Gyr and will not survive to become old, globular clusters. However, they do appear to follow the same fundamental plane (FP) relations as old clusters; if confirmed with velocity...
We have obtained deep infrared J- and K-band observations of nine 4.9 ?4.9 arcmin fields in the Small Magellanic Cloud (SMC) with the ESO New Technology Telescope equipped with the SOFI infrared camera. In these fields, 34 RR Lyrae stars cataloged by the OGLE collaboration were identified. Using different theoretical and empirical calibrations of the infrared period-luminosity-metallicity relation, we find consistent SMC distance moduli, and find a best true distance modulus to the SMC of 18.97 ± 0.03 (statistical) ±0.12 (systematic) mag, which agrees well with most independent distance determinations to this galaxy, and puts the SMC 0.39 mag more distant than the Large Magellanic Cloud for which our group has recently derived, from the same technique, a distance of 18.58 mag. Based on observations obtained with the ESO NTT for programmes 082.D-0513(A) and 079.D-0482(A).
We present XMM-Newton observations of the type 1 active galactic nucleus (AGN) SDSS 1430 -- 0011 (z = 0.1032). The low signal-to-noise ratio spectrum of this source obtained in a snap shot Chandra observation showed an unusually flat continuum. With the follow-up XMM-Newton observations, we find that the source spectrum is complex; it either has an ionized absorber or a partially covering absorber. The underlying power law is in the normal range observed for AGNs. The low flux of the source during Chandra observations can be understood in terms of variations in the absorber properties. The X-ray and optical properties of this source are such that it cannot be securely classified as either a narrow-line Seyfert 1 or a broad-line Seyfert 1 galaxy, adding to the group of sources in the "in-between" class.
From a study of the editorial log for 251 manuscripts submitted in 2006, we learn that 6% are rejected, 5% are withdrawn, and 88% are eventually accepted for publication. Of the accepted articles, 30% are reviewed once, 58% twice, and 12% are reviewed 3-5 times. The mean time for the first review is 31 days and for the first revision is 44 days. The spread in total reviewing times (dispersion of 16 days) is much shorter than in total revision times (54 days). Important articles, those receiving 31-193 citations in 2 yr, are not reviewed more promptly than others nor revised more promptly. Only in the subfield of high-energy objects do the authors revise their manuscripts marginally more promptly than others.
We present an empirical model of Comptonization for fitting the spectra of X-ray binaries. This model, named simpl, has been developed as a package implemented in XSPEC. With only two free parameters, simpl is competitive as the simplest model of Compton scattering. Unlike the pervasive standard power-law model, simpl incorporates the basic features of Compton scattering of soft photons by energetic coronal electrons. Using a simulated spectrum, we demonstrate that simpl closely matches the behavior of physical Comptonization models that consider the effects of optical depth, coronal electron temperature, and geometry. We present fits to RXTE spectra of the black hole transient H1743-322 and a BeppoSAX spectrum of LMC X-3 using both simpl and the standard power-law model. A comparison of the results shows that simpl gives equally good fits, while eliminating the troublesome divergence of the standard power-law model at low energies. simpl is completely flexible and can be used self-consistently with any seed...
We present a means of characterizing and removing internal reflections between the CCD and other optical surfaces in an astronomical camera. The stellar reflections appear as out-of-focus images and are not necessarily axisymmetric about the star. Using long exposures of very bright stars as calibration images, we are able to measure the position, size, and intensity of reflections as a function of their position on the field. We also measure the extended stellar point-spread function out to 1°. Together this information can be used to create an empirical model of the excess light from bright stars and reduce systematic artifacts in deep surface photometry. We then reduce a set of deep observations of the Virgo cluster with our method to demonstrate its efficacy and to provide a comparison with other strategies for removing scattered light.
This tutorial presents a review of the analytical approach to obtain exact solutions for the populations of n-level ions, and summarizes the ideas behind detailed balance and the statistical physics of collisionally-excited ions. Seaton's analytical solution for the populations of the 3-level ion has been supplanted by matrix methods such as the master equation approach, which are now central to astronomy since there is a need to maintain a parity between improvements in quantum-mechanically calculated values for collision strengths and transition probabilities on the one hand, and three-dimensional (3D) photoionization codes used by astrophysicists for producing nebular diagnostics on the other. We show that the analytical method of solution to the problem using matrices and symbolic mathematics is straightforward, and we illustrate through theoretical, numerical, and empirical checks the validity of its results. First, we recast the equations of thermal statistical equilibrium for the energy level populations...
The repeated discovery of supermassive black holes (SMBHs) at the centers of galactic bulges, and the discovery of relations between the SMBH mass (M) and the properties of these bulges, have been fundamental in directing our understanding of both galaxy and SMBH formation and evolution. However, there are still many underlying questions surrounding the SMBH-galaxy relations. For example, are the scaling relations linear and constant throughout cosmic history, and do all SMBHs lie on the scaling relations? These fundamental questions can only be answered by further high quality direct M estimates from a wide range in redshift, before further refinements to galaxy evolution models can be made. In this article we determine the observational requirements necessary to directly determine SMBH masses, across cosmological distances, using current M modeling techniques. We also discuss the SMBH detection abilities of future facilities. We find that if different M modeling techniques, using different spectral features,...
High-contrast coronagraphic imaging is challenging for telescopes with central obstructions and thick spider vanes, such as the Subaru Telescope. We present in this article the first laboratory demonstration of a high-efficiency PIAA-type coronagraph on such a pupil, using coronagraphic optics which will be part of the Subaru Coronagraphic Extreme-AO (SCExAO) system currently under assembly. Lossless pupil apodization is performed by a set of aspheric PIAA lenses specifically designed to also remove the pupil's central obstruction, coupled with a spider removal plate (SRP) which removes spider vanes by translating four parts of the pupil with tilted plane-parallel plates. An "inverse-PIAA" system, located after the coronagraphic focal plane mask, is used to remove off-axis aberrations and deliver a wide field of view. Our results validate the concept adopted for the SCExAO system, and show that the Subaru Telescope pupil can be properly apodized for high-contrast coronagraphic imaging as close as≈1 lambda/D...
We are undertaking an astrometric search for gas giant planets and brown dwarfs orbiting nearby low-mass dwarf stars with the 2.5 m du Pont Telescope at the Las Campanas Observatory in Chile. We have built two specialized astrometric cameras, the Carnegie Astrometric Planet Search Cameras (CAPSCam-S and CAPSCam-N), using two Teledyne HAWAII-2RG HyViSI arrays, with the cameras' design having been optimized for high-accuracy astrometry of M dwarf stars. We describe two independent CAPSCam data reduction approaches and present a detailed analysis of the observations to date of one of our target stars, NLTT 48256. Observations of NLTT 48256 taken since 2007 July with CAPSCam-S imply that astrometric accuracies of around 0.3 mas hr are achievable, sufficient to detect a Jupiter-mass companion orbiting 1 AU from a late M dwarf 10 pc away with a signal-to-noise ratio (S/N) of about 4. We plan to follow about 100 nearby (primarily within about 10 pc) low-mass stars, principally late M, L, and T dwarfs, for 10 yr or more,...
The 6307 ?emission line in the spectrum of eta Car, found by Martin et al., is blue-shifted [S iii] lambda6313 emission originating from the outer wind structures of the massive binary system. We realized the identification while analyzing multiple forbidden emission lines not normally seen in the spectra of massive stars. The high spatial and moderate spectral resolutions of HST/STIS resolve forbidden lines of Fe, N, Fe, S, Ne, and Ar into spatially and velocity-resolved ropelike features originating from collisionally-excited ions photoionized by UV photons or collisions. While the [Fe ii] emission extends across a velocity range of ±500 km s out to 0.7", more highly ionized forbidden emissions ([N ii], [Fe iii], [S iii], [Ar iii], and [Ne iii]) range in velocity from -500 to +200 km s, but spatially extend out to only 0.4". The [Fe ii] defines the outer regions of the massive primary wind. The [N ii], [Fe iii] emissions define the the outer wind interaction regions directly photoionized by far-UV radiation....
BZ UMa is a cataclysmic variable star whose specific classification has eluded researchers since its discovery in 1968. It has outburst and spectral properties consistent with both U Gem class dwarf novae and intermediate polars. We present new photometric and polarimetric measurements of recent outbursts, including the first detected superoutburst of the system. Statistical analysis of these and archival data from outbursts over the past 40 years presents a case for BZ UMa as a nonmagnetic, U Gem class, SU UMa subclass dwarf nova.
We present the results of a search for periodic variables within 4078 time-series light curves and an analysis of the period-color plane for stars in the field of the open cluster NGC 2301. One hundred thirty-eight periodic variables were discovered, of which five are eclipsing binary candidates with unequal minima. The remaining 133 periodic variables appear to consist mainly of late-type stars whose variation is due to rotation modulated by star spot activity. The determined periods range from less than a day to over 14 days and have nearly unreddened B-R colors in the range of 0.8 to 2.8. The Barnes (2003) interpretation of the period-color plane of late type stars is tested with our data. Our data did not show distinct I and C sequences, likely due to nonmember field stars contaminating in the background, as we estimate the total contamination to be 43%. Using different assumptions, the gyrochronological age of the cluster is calculated to be 210±25 Myr, which falls in the range of age values (164-250 Myr)...
This article describes the assembly of an optical (RGB) all-sky mosaic image with an image scale of 36pixel, a limiting magnitude of approximately 14 mag, and an 18 bit dynamic range. Using a portable low-cost CCD camera system, 70 fields (each covering 40°?7°) were imaged over a time span of 22 months from dark-sky locations in South Africa, Texas, and Michigan. The fields were photometrically calibrated against standard catalog stars. Using sky background data from the Pioneer 10 and 11 space probes, gradients resulting from artificial light pollution, airglow, and zodiacal light were eliminated, while the large-scale galactic and extragalactic background resulting from unresolved sources was preserved. The 648 megapixel image is a valuable educational tool, being able to fully utilize the resolution and dynamic range of modern full-dome planetarium projection systems.
We have analyzed the light curves of 3C 279 at 22 GHz, 37 GHz, optical R band, and X-ray (2-10 KeV), and found evidence of quasi-periodic outbusts. The light curves show that 3C 279 is an extremely active object. A period of P=130.6±1.3 days was consistently confirmed by three methods: the power-spectrum method, the discrete correlation function (DCF) method, and the Jurkevich method. Based on the relationship between observed period P and the precession period P given by Rieger and our result, the precession period of jet in 3C 279 is P~=29.6 yr, which is completely consistent with the precession period of jet of about 30 yr obtained by Carrara et al.. This suggests that there is a precession jet in 3C 279 and the variability period of about 130.6 days that we obtained is most likely caused by the helical motion of the jet.
We discuss the critical importance of black hole mass indicators based on scaling relations in active galaxies. We highlight outstanding uncertainties in these methods and potential paths to substantial progress in the next decade.
We derive analytic expressions and approximate them in closed form, for the effective detection aperture for Cerenkov radio emission from ultra-high-energy neutrinos striking the Moon. The resulting apertures are in good agreement with recent Monte Carlo simulations and support the conclusion of James & Protheroe that neutrino flux upper limits derived from the GLUE search were too low by an order of magnitude. We also use our analytic expressions to derive scaling laws for the aperture as a function of observational and lunar parameters. We find that at low frequencies downward-directed neutrinos always dominate, but at higher frequencies, the contribution from upward-directed neutrinos becomes increasingly important, especially at lower neutrino energies. Detecting neutrinos from Earth near the Greisen-Zatsepin-Kuz'min regime will likely require radio telescope arrays with extremely large collecting area (Ae ~ 106 m2) and hundreds of hours exposure time. Higher-energy neutrinos are most easily detected using...
We develop an algorithm of separating the E and B modes of the cosmic microwave background (CMB) polarization from the noisy and discretized maps of Stokes parameters Q and U in a finite area. A key step of the algorithm is to take a wavelet-Galerkin discretization of the differential relation between the E, B and Q, U fields. This discretization allows derivative operator to be represented by a matrix, which is exactly diagonal in scale space, and narrowly banded in spatial space. We show that the effect of boundary can be eliminated by dropping a few discrete wavelet transform modes, located on or nearby the boundary. This method reveals that the derivative operators will cause large errors in the E and B power spectra on small scales if the Q and U maps contain Gaussian noise. It also reveals that if the Q and U maps are random, these fields lead to the mixing of E and B modes. Consequently, the B mode will be contaminated if the powers of E modes are much larger than that of B modes. Nevertheless, numerical...
We use Halpha and far-ultraviolet (FUV, 1539 - Galaxy Evolution Explorer (GALEX) data for a large sample of nearby objects to study the high-mass (m>= 2 M sun) star formation activity of normal late-type galaxies. The data are corrected for dust attenuation using the most accurate techniques available at present, namely the Balmer decrement for Halpha data and the total far-infrared to FUV flux ratio for GALEX data. The sample shows a highly dispersed distribution in the Halpha to FUV flux ratio (log f(Halpha)/f(FUV) = 1.10 ± 0.34 - indicating that two of the most commonly used star formation tracers give star formation rates (SFRs) with uncertainties up to a factor of 2-3. The high dispersion is partly due to the presence of active galactic nuclei, where the UV and the Halpha emission can be contaminated by nuclear activity, highly inclined galaxies, for which the applied extinction corrections are probably inaccurate, or starburst galaxies, where the stationarity in the star formation history required for...
We evaluate the achievable maximum energy of nuclei diffusively accelerated by shock wave in the jet of Cen A, based on an updated model involving the stochastic magnetic fields that are responsible for recent synchrotron X-ray measurements. For the maximum energy analysis, conceivable energy constraints from spatiotemporal scales are systematically considered for the jet-wide including discrete X-ray knots. We find that in the inner region within ~1 arcmin from galactic core, which includes knots AX and BX, proton and iron nucleus can be accelerated to 1019-1020 and 1021 eV (10-100 EeV and ZeV) ranges, respectively. The upper cutoff energy of the very energetic neutrinos produced via photopion interaction is also provided. These are essential for identifying the acceleration site of the ultra-high energy cosmic ray detected in the Pierre Auger Observatory, which signifies the arrival from nearby galaxies including Cen A.
We expand our study on the dispersion of polarization angles in molecular clouds. We show how the effect of signal integration through the thickness of the cloud as well as across the area subtended by the telescope beam inherent to dust continuum measurements can be incorporated in our analysis to correctly account for its effect on the measured angular dispersion and inferred turbulent to large-scale magnetic field strength ratio. We further show how to evaluate the turbulent magnetic field correlation scale from polarization data of sufficient spatial resolution and high enough spatial sampling rate. We apply our results to the molecular cloud OMC-1, where we find a turbulent correlation length of delta ≈ 16 mpc, a turbulent to large-scale magnetic field strength ratio of approximately 0.5, and a plane-of-the-sky large-scale magnetic field strength of approximately 760 muG.
We present the stellar and substellar mass function (MF) of the open cluster IC 2391, plus its radial dependence, and use this to put constraints on the formation mechanism of brown dwarfs (BDs). Our multi-band optical and infrared photometric survey with spectroscopic follow-up covers 11 deg2, making it the largest survey of this cluster to date. We observe a radial variation in the MF over the range 0.072-0.3 M sun, but no significant variation in the MF below the substellar boundary at the three cluster radius intervals is analyzed. This lack of radial variation for low masses is what we would expect with the ejection scenario for BD formation, although considering that IC 2391 has an age about three times older than its crossing time, we expect that BDs with a velocity greater than the escape velocity have already escaped the cluster. Alternatively, the variation in the MF of the stellar objects could be an indication that they have undergone mass segregation via dynamical evolution. We also observe a significant...
We present a study of the correlations between spectral, timing properties, and mass accretion rate observed in X-rays from the Galactic black hole (BH) binary GRS 1915+105 during the transition between hard and soft states. We analyze all transition episodes from this source observed with the Rossi X-ray Timing Explorer, coordinated with Ryle Radio Telescope observations. We show that broadband energy spectra of GRS 1915+105 during all these spectral states can be adequately presented by two bulk motion Comptonization (BMC) components: a hard component (BMC1, photon index Gamma1 = 1.7-3.0) with turnover at high energies and soft thermal component (BMC2, Gamma2 = 2.7-4.2) with characteristic color temperature
We estimate the fraction of mass that is composed of compact objects in gravitational lens galaxies. This study is based on microlensing measurements (obtained from the literature) of a sample of 29 quasar image pairs seen through 20 lens galaxies. We determine the baseline for no microlensing magnification between two images from the ratios of emission line fluxes. Relative to this baseline, the ratio between the continua of the two images gives the difference in microlensing magnification. The histogram of observed microlensing events peaks close to no magnification and is concentrated below 0.6 mag, although two events of high magnification, Deltam ~ 1.5, are also present. We study the likelihood of the microlensing measurements using frequency distributions obtained from simulated microlensing magnification maps for different values of the fraction of mass in compact objects, alpha. The concentration of microlensing measurements close to Deltam ~ 0 can be explained only by simulations corresponding to very...
We present a detailed multi-wavelength analysis and interpretation of the evolution of an M7.6 flare that occurred near the southeast limb on 2003 October 24. Pre-flare images at TRACE 195 'show that the bright and complex system of coronal loops already existed at the flaring site. The X-ray observations of the flare taken from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft reveal two phases of the flare evolution. The first phase is characterized by the altitude decrease of the X-ray looptop (LT) source for ~11 minutes. Such a long duration of the descending LT source motion is reported for the first time. The EUV loops, located below the X-ray LT source, also undergo contraction with similar speed (~15 km s--1) in this interval. During the second phase the two distinct hard X-ray footpoint (FP) sources are observed which correlate well with UV and Halpha flare ribbons. The X-ray LT source now exhibits upward motion as anticipated from the standard flare model. The RHESSI spectra...
BL Lac objects of the intermediate subclass (IBLs) are known to emit a substantial fraction of their power in the energy range 0.1-10 GeV. Detecting gamma-ray emission from such sources provides therefore a direct probe of the emission mechanisms and of the underlying powerhouse. The gamma-ray satellite, AGILE, detected the remarkable IBL S5 0716+714 (z sime 0.3) during a high state in the period from 2007 September-October, marked by two very intense flares reaching peak fluxes of 200 ?10--8 photons cm--2 s--1 above 100 MeV, with simultaneous optical and X-ray observations. We present here a theoretical model for the two major flares and discuss the overall energetics of the source. We conclude that 0716+714 is among the brightest BL Lac's ever detected at gamma-ray energies. Because of its high power and lack of signs for ongoing accretion or surrounding gas, the source is an ideal candidate to test the maximal power extractable from a rotating supermassive black hole via the pure Blandford-Znajek (BZ) mechanism....
Microstructure is observed on many lines of sight in the diffuse interstellar medium, mainly through variations in atomic line absorptions on timescales of a decade or less. This timescale implies that microstructure exists on a size scale comparable with that of the solar system; it is overpressured and transient. Both observations and theory confirm that a specific chemistry occurs in microstructure. We therefore explore a model of diffuse interstellar gas in which the chemistry in diffuse clouds is supplemented by chemistry in many transient and tiny perturbations. These perturbations are here assumed to be of unidentified origin, but it is assumed that ambipolar diffusion occurs within them. For plausible physical parameters, we find that this model can account for the range of molecular column densities observed in diffuse clouds, including species not usually accounted for by conventional models. Some molecular ions, predicted to be generated in the microstructure (including HS+, CH+ 2, CH+ 3, H2O+, and...
We present the Spectroscopic Imaging survey in the near-infrared (near-IR) with SINFONI (SINS) of high-redshift galaxies. With 80 objects observed and 63 detected in at least one rest-frame optical nebular emission line, mainly Halpha, SINS represents the largest survey of spatially resolved gas kinematics, morphologies, and physical properties of star-forming galaxies at z ~ 1-3. We describe the selection of the targets, the observations, and the data reduction. We then focus on the "SINS Halpha sample," consisting of 62 rest-UV/optically selected sources at 1.3 < z < 2.6 for which we targeted primarily the Halpha and [N II] emission lines. Only ≈30% of this sample had previous near-IR spectroscopic observations. The galaxies were drawn from various imaging surveys with different photometric criteria; as a whole, the SINS Halpha sample covers a reasonable representation of massive M sstarf gsim 1010 M sunstar-forming galaxies at z ≈ 1.5-2.5, with some bias toward bluer systems compared to pure K-selected...
Sagittarius A* is the source of near infrared, X-ray, radio, and (sub)millimeter emission associated with the supermassive black hole at the Galactic Center. In the submillimeter regime, Sgr A* exhibits time-variable linear polarization on timescales corresponding to
The distribution of protostar masses is studied for core-environment systems whose duration of infall follows a waiting-time distribution. Each core-environment system has a continuous density profile with no barrier to mass flow. The core is an isothermal sphere and the environment is a filament, a layer, or a uniform medium. The infall is terminated by gas dispersal due to outflows and turbulence. The distribution of infall durations is a declining exponential, the simplest waiting-time distribution. The resulting distribution of protostar masses closely resembles the initial mass function, provided the environment density is sufficiently high, and the distribution of initial core masses is sufficiently narrow. The high-mass tail of the mass function increases strongly with environment density and weakly with environment dimension. "Isolated" regions of low environment density form protostars of low mass from within the parent core. In contrast, "clustered" regions of high environment density form protostars...
We report the detection of gamma-ray pulsations (>=0.1 GeV) from PSR J2229+6114 and PSR J1048--5832, the latter having been detected as a low-significance pulsar by EGRET. Data in the gamma-ray band were acquired by the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope, while the radio rotational ephemerides used to fold the gamma-ray light curves were obtained using the Green Bank Telescope, the Lovell telescope at Jodrell Bank, and the Parkes Telescope. The two young radio pulsars, located within the error circles of the previously unidentified EGRET sources 3EG J1048--5840 and 3EG J2227+6122, present spin-down characteristics similar to the Vela pulsar. PSR J1048--5832 shows two sharp peaks at phases 0.15 ± 0.01 and 0.57 ± 0.01 relative to the radio pulse confirming the EGRET light curve, while PSR J2229+6114 presents a very broad peak at phase 0.49 ± 0.01. The gamma-ray spectra above 0.1 GeV of both pulsars are fit with power laws having exponential cutoffs near 3 GeV, leading to integral...
UV radiation from massive stars is thought to be the dominant heating mechanism of the nuclear interstellar medium (ISM) in the late stages of evolution of starburst galaxies, creating large photodissociation regions (PDRs) and driving a very specific chemistry. We report the first detection of PDR molecular tracers, namely HOC+ and CO+, and also confirm the detection of the PDR tracer HCO toward the starburst galaxy NGC 253, claimed to be mainly dominated by shock heating and in an earlier stage of evolution than M 82, the prototypical extragalactic PDR. Our CO+ detection suffers from significant blending to a group of transitions of 13CH3OH, tentatively detected for the first time in the extragalactic ISM. These species are efficiently formed in the highly UV-irradiated outer layers of molecular clouds, as observed in the late stage nuclear starburst in M 82. The molecular abundance ratios we derive for these molecules are very similar to those found in M 82. This strongly supports the idea that these molecules...
The "Mouse" (PWN G359.23--0.82) is a spectacular bow shock pulsar wind nebula, powered by the radio pulsar J1747--2958. The pulsar and its nebula are presumed to have a high space velocity, but their proper motions have not been directly measured. Here we present 8.5 GHz interferometric observations of the Mouse nebula with the Very Large Array, spanning a time baseline of 12 years. We measure eastward proper motion for PWN G359.23--0.82 (and hence indirectly for PSR J1747--2958) of 12.9 ± 1.8 mas yr--1, which at an assumed distance of 5 kpc corresponds to a transverse space velocity of 306 ± 43 km s--1. Considering pressure balance at the apex of the bow shock, we calculate an in situ hydrogen number density of approximately 1.0+0.4 --0.2 cm--3 for the interstellar medium through which the system is traveling. A lower age limit for PSR J1747--2958 of 163+28 --20 kyr is calculated by considering its potential birth site. The large discrepancy with the pulsar's spin-down age of 25 kyr is possibly explained by...
We revisit echelle spectra (spectral resolution R ≈ 40,000) of eight gamma-ray burst (GRB) afterglows to obtain the incidence (dN/dz) of weak intervening Mg II systems at a mean redshift of langzrang = 1.5. We show that dN/dz of systems having rest-frame equivalent widths 0.07 - \le W_r^{Mg\,\mathsc{ii}} < 1 'toward GRBs is statistically consistent with the incidence toward quasi-stellar objects (QSOs). Our result is in contrast to the results for Mg II systems having Wr >= 1 - where dN/dz toward GRBs has been found to be larger than toward QSOs by a factor of ≈4. We confirm the overdensity albeit at a factor of ≈3 only. This suggests that any explanation for the GRB/QSO discrepancy, be it intrinsic to the absorbers or a selection effect, should be inherent only to the galaxies that host strong absorbers in the line of sight to GRBs. We argue that, of all scenarios that have been proposed, lensing amplification is the one that could explain the strong Mg II enhancement while allowing for no significant...
The observable quantities in optical interferometry, which are the modulus and the phase of the complex visibility, may be corrupted by parasitic fringes superimposed on the genuine fringe pattern. These fringes are due to an interference phenomenon occurring from stray light effects inside an interferometric instrument. We developed an analytical approach to better understand this phenomenon when stray light causes cross talk between beams. We deduced that the parasitic interference significantly affects the interferometric phase and thus the associated observables including the differential phase and the closure phase. The amount of parasitic flux coupled to the piston between beams appears to be very influential in this degradation. For instance, considering a point-like source and a piston ranging from lambda/500 to lambda/5 in the L band (lambda = 3.5 mum), a parasitic flux of about 1% of the total flux produces a parasitic phase reaching at most one-third of the intrinsic phase. The piston, which can have...
We present new intermediate-band Str?en photometry based on more than 300 u, v, b, y images of the Galactic globular cluster omega Cen. Optical data were supplemented with new multiband near-infrared (NIR) photometry (350 J, H, Ks images). The final optical-NIR catalog covers a region of more than 20 ?20 arcmin squared across the cluster center. We use different optical-NIR color-color planes together with proper-motion data available in the literature to identify candidate cluster red-giant (RG) stars. By adopting different Str?en metallicity indices, we estimate the photometric metallicity for ≈4000 RGs, the largest sample ever collected. The metallicity distributions show multiple peaks ([Fe/H]phot = --1.73 ± 0.08, --1.29 ± 0.03, --1.05 ± 0.02, --0.80 ± 0.04, --0.42 ± 0.12, and --0.07 ± 0.08 dex) and a sharp cutoff in the metal-poor (MP) tail ([Fe/H]phot lsim --2 dex) that agree quite well with spectroscopic measurements. We identify four distinct subpopulations, namely, MP ([Fe/H]
We present a Chandra X-ray observation of the very high energy gamma-ray source HESS J1640 -- 465. We identify a point source surrounded by a diffuse emission that fills the extended object previously detected by XMM-Newton at the centroid of the HESS source, within the shell of the radio supernova remnant (SNR) G338.3 -- 0.0. The morphology of the diffuse emission strongly resembles that of a pulsar wind nebula (PWN) and extends asymmetrically to the southwest of a point source presented as a potential pulsar. The spectrum of the putative pulsar and compact nebula are well characterized by an absorbed power-law model which, for a reasonable N H value of 14 ?1022 cm--2, exhibit an index of 1.1 and 2.5 respectively, typical of Vela-like PWNe. We demonstrate that, given the H I absorption features observed along the line of sight, the SNR and the H II surrounding region are probably connected and lie between 8 kpc and 13 kpc. The resulting age of the system is between 10 and 30 kyr. For a 10 kpc distance (also...
We discuss acceleration measurements for a large sample of extragalactic radio jets from the Monitoring Of Jets in Active Galactic Nuclei with VLBA Experiments (MOJAVE) program, which studies the parsec-scale jet structure and kinematics of a complete, flux-density-limited sample of active galactic nuclei (AGNs). Accelerations are measured from the apparent motion of individual jet features or "components" which may represent patterns in the jet flow. We find that significant accelerations are common both parallel and perpendicular to the observed component velocities. Parallel accelerations, representing changes in apparent speed, are generally larger than perpendicular acceleration that represent changes in apparent direction. The trend for larger parallel accelerations indicates that a significant fraction of these changes in apparent speed are due to changes in intrinsic speed of the component rather than changes in direction to the line of sight. We find an overall tendency for components with increasing...
We present a study of an extended Lyalpha nebula located in a known overdensity at z ~ 2.38. The data include multiwavelength photometry covering the rest-frame spectral range from 0.1 to 250 mum, and deep optical spectra of the sources associated with the extended emission. Two galaxies are associated with the Lyalpha nebula. One of them is a dust enshrouded active galactic nucleus (AGN), while the other is a powerful starburst, forming stars at gsim400 M sun yr--1. We detect the He II emission line at 1640 ?in the spectrum of the obscured AGN, but detect no emission from other highly ionized metals (C IV or N V) as is expected from an AGN. One scenario that simultaneously reproduces the width of the detected emission lines, the lack of C IV emission, and the geometry of the emitting gas, is that the He II and the Lyalpha emission are the result of cooling gas that is being accreted on the dark matter halo of the two galaxies, Ly1 and Ly2. Given the complexity of the environment associated with our Lyalpha nebula...
We study the impact of correlated instrumental noise and non-circular antenna beam patterns on primordial non-Gaussianity analysis. The two systematic effects are reproduced in the case of the Planck mission, using Planck-like realistic simulations. The non-Gaussian analysis is conducted with different approaches. First we adopt a blind approach, using the Spherical Mexican Hat Wavelet and the Minkowski functionals, and then an f NL estimator. We look respectively for false primordial non-Gaussian detections and for bias or variance increase in the estimated f NL value. Even if some slight effects are present, we cannot observe any significant impact of the 1/f noise and the asymmetric beam on non-Gaussianity searches in the context of the Planck mission.
We present a new on-the-fly mapping of CO (J = 3-2) line emission with the Atacama Submillimeter Telescope Experiment toward the 8' ?8' (or 10.5 ?10.5 kpc at the distance of 4.5 Mpc) region of the nearby barred spiral galaxy M 83 at an effective resolution of 25''. Due to its very high sensitivity, our CO (J = 3 -- 2) map can depict not only spiral arm structures but also spur-like substructures extended in inter-arm regions. This spur-like substructures in CO (J = 3-2) emission are well coincident with the distribution of massive star-forming regions traced by Halpha luminosity and Spitzer/Infrared Array Camera 8 mum emission. We have identified 54 CO (J = 3-2) clumps as Giant Molecular-cloud Associations (GMAs) employing the CLUMPFIND algorithm, and have obtained their sizes, velocity dispersions, virial masses, and CO luminosity masses. We found that the virial parameter alpha, which is defined as the ratio of the virial mass to the CO luminosity mass, is almost unity for GMAs in spiral arms, whereas there...
Non Peer-Reviewed Preprints
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This article presents a study on different informative modalities of a percecptual supplementation device aiming at reducing overpressure at the buttock area. Visual, audio and tactile modalities are analysed and compared with a non-biofeedback session. In conclusion, modalities have a positive and equal effect, but they are not equally judged in term of comfort and disturbance with some other activities
We explain simple laboratory experiments for making quantitative measurements of the Doppler effect from sources with acceleration. We analyze the spectra and clarify the conditions for the Doppler effect to be experimentally measurable, which turn out to be non-trivial when acceleration is involved. The experiments use sources with gravitational acceleration, in free fall and in motion as a pendulum, so that the results can be checked against fundamental physics principles. The experiments can be easily set up from ``off the shelf'' components only. The experiments are suitable for a wide range of students, including undergraduates not majoring in science or engineering.
In a paper appearing in this issue of Physics Letters A, Kowalski raises some critical comments on the experiment [F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 1956] that we carried out by cavitating a solution of thorium-228. The experiment highlighted the anomalous decay of thorium, thus confirming the results previously obtained by Urutskoev et al. by explosion of titanium foils in solutions. In this Letter, we reply to these comments. We agree with Kowalski that critical comments are one of the key factors of the process to improve the quality of experiments and the interpretation of results. However we do hope that these comments together with the details provided in the replies will promote further and better experiments which are certainly worth performing in order to shed a brighter light on this issue, as Kowalski himself suggests in his comment.
A well known problem with EOP prediction is that a prediction strategy proved to be the best for some testing period and prediction length may not remain as such for other period of time. In this paper we consider possible strategies to combine EOP predictions made using different analysis technique to obtain a final prediction with the best accuracy corresponding to the least prediction error between input predictions. This approach can be used to improve the short-term real-time EOP forecast.
Many approaches are developed for the forecasting of the Earth rotation pa-rameters. In this work, we consider long-term vector prediction scheme realized on the artificial neural network. Learning set is formed on basis of the Taken' algorithm. Our approach allows us to obtain the vector of the parameter values and escape the expo-nential growth of the prediction errors. The versions of the prediction enhancement based on the using for nonlinear corrector are discussed.
For propagating and evanescent vector Bessel beams, we study the singularities of the Poynting vector (Poynting singularities), at which the energy flux density turns to zero. Poynting singularities include all the phase singularities and some of polarization ones (L- and C-points). We reveal the existence conditions and positions of singularities, which are located at cylindrical surfaces around the beam axis. We mark the special case of the evanescent Bessel beam in the form of cylindrical standing wave, that is singular at any spatial point.
In this paper, we apply transformation-based optics to the derivation of a general class of transparent metamaterial slabs. By means of analytical and numerical full-wave studies, we explore their image displacement/formation capabilities, and establish intriguing connections with configurations already known in the literature. Starting from these revisitations, we develop a number of nontrivial extensions, and illustrate their possible applications to the design of perfect radomes, anti-cloaking devices, and super-resolving lenses based on double-positive (possibly nonmagnetic) media. These designs show that such anomalous features may be achieved without necessarily relying on negative-index or strongly resonant metamaterials, suggesting more practical venues for the realization of these devices.
In particular, without the greenhouse effect, essential features of the atmospheric temperature profile as a function of height cannot be described, i.e., the existence of the tropopause above which we see an almost isothermal temperature curve, whereas beneath it the temperature curve is nearly adiabatic. The relationship between the greenhouse effect and observed temperature curve is explained and the paper by Gerlich and Tscheuschner [arXiv:0707.1161] critically analyzed. Gerlich and Tscheuschner called for this discussion in their paper.
We have considered an effect of atomic electrons due to the electronic bridge process on the nuclear $^{229m}$Th -- $^{229g}$Th transition in ^{229}$Th$^{3+}$. Based on a recent experimental result we assumed the energy difference between the isomeric and the ground nuclear states to be equal to 7.6 eV. We have calculated the ratios of the electronic bridge process probability Gamma_EB to the probability of the nuclear radiative transition (Gamma_N) for the electronic 5f_5/2 --> 6d_3/2,6d_5/2,7s and the 7s --> 7p_1/2,7p_3/2 transitions and found Gamma_EB/Gamma_N ~ 0.01-0.1 for the former and Gamma_EB/Gamma_N ~ 20 for the latter.
We investigate the quality factor Q for electrically small current distributions and practical antenna designs radiating the TE10 magnetic dipole field. The current distributions and the antenna designs employ electric currents on a spherical surface enclosing a magneto-dielectric material that serves to reduce the internal stored energy. Closed-form expressions for the internal and external stored energies as well as for the quality factor Q are derived. The influence of the sphere radius and the material permeability and permittivity on the quality factor Q is determined and verified numerically. It is found that for a given antenna size and permittivity there is an optimum permeability that ensures the lowest possible Q, and this optimum permeability is inversely proportional to the square of the antenna electrical radius. When the relative permittivity is equal to 1, the optimum permeability yields the quality factor Q that constitutes the lower bound for a magnetic dipole antenna with a magneto-dielectric...
We study the properties of the Google matrix of an Ulam network generated by intermittency maps. This network is created by the Ulam method which gives a matrix approximant for the Perron-Frobenius operator of dynamical map. The spectral properties of eigenvalues and eigenvectors of this matrix are analyzed. We show that the PageRank of the system is characterized by a power law decay with the exponent $\beta$ dependent on map parameters and the Google damping factor $\alpha$. Under certain conditions the PageRank is completely delocalized so that the Google search in such a situation becomes inefficient.
This chapter aims at introducing and discussing the techniques for the generation of 3D Finite Element Meshes of human organs. The field of computer assisted surgery is more specifically addressed.
We present a comprehensive study of semiclassical phase-space propagation in the Wigner representation, emphasizing numerical applications, in particular as an initial-value representation. Two semiclassical approximation schemes are discussed: The propagator of the Wigner function based on van Vleck's approximation replaces the Liouville propagator by a quantum spot with an oscillatory pattern reflecting the interference between pairs of classical trajectories. Employing phase-space path integration instead, caustics in the quantum spot are resolved in terms of Airy functions. We apply both to two benchmark models of nonlinear molecular potentials, the Morse oscillator and the quartic double well, to test them in a number of standard tasks such as computing autocorrelation functions and propagating coherent states. The performance of semiclassical Wigner propagation is very good even in the presence of marked quantum effects, e.g., in coherent tunneling and in propagating Schrodinger cat states. We suggest...
Spontaneous four-wave mixing can generate highly correlated photon pairs from atomic vapors. We show that multi-photon pumping of dipole-forbidden transitions in a recoil-free geometry can result in ultra-bright pair-emission in the full 4\pi solid angle, while strongly suppresses background Rayleigh scattering and associated atomic heating, Such a system can produce photon pairs at rates of ~ 10 ^12 per second, given only moderate optical depths of 10 ~ 100, or alternatively, the system can generate paired photons with sub-natural bandwidths at lower production rates. We derive a rate-equation based theory of the collective atomic population and coherence dynamics, and present numerical simulations for a toy model, as well as realistic model systems based on 133 Cs and 171 Yb level structures. Lastly, we demonstrate that dark-state adiabatic following (EIT) and/or timescale hierarchy protects the paired photons from reabsorption as they propagate through an optically thick sample.
We present a photoionization method to load single 40Ca ions in a linear Paul trap from an atomic beam. Neutral Ca I atoms are resonantly excited from the ground state to the intermediate 4s4p 1P_1-level using coherent 423nm radiation produced by single-pass second harmonic generation in a periodically poled KTiOPO_4 crystal pumped with an 120mW extended cavity diode laser. Ionization is then attained with a high-power light emitting diode imaged to the trap center, using an appropriately designed optical system composed of standard achromatic doublet lenses. The setup simplifies previous implementations at similar efficiency, and it hardly requires any maintenance at all.
We theoretically and numerically investigated the threshold network model with a generic weight function where there were a large number of nodes and a high threshold. Our analysis was based on extreme value theory, which gave us a theoretical understanding of the distribution of independent and identically distributed random variables within a sufficiently high range. Specifically, the distribution could be generally expressed by a generalized Pareto distribution, which enabled us to formulate the generic weight distribution function. By using the theorem, we obtained the exact expressions of degree distribution and clustering coefficient which behaved as universal power laws within certain ranges of degrees. We also compared the theoretical predictions with numerical results and found that they were extremely consistent.
The energy distributions of secondary electrons produced by energetic carbon ions (in the energy range used, e.g., in hadron therapy), incident on liquid water, are discussed. For low-energy ions, a new parameterization of the singly-differential ionization cross sections is introduced, based on tuning the position of the Bragg peak. The resulting parameterization allows a fast calculation of the energy spectra of secondary electrons at different depths along the ion's trajectory, especially near the Bragg peak. At the same time, this parameterization provides penetration depths for a broad range of initial-ion energies within the therapeutically-accepted error. For high-energy ions, the energy distribution is obtained with a use of the dielectric response function approach. Different models are compared and discussed.
An exact solution for the field of a charge in a uniformly accelerated noninertial frame of reference (NFR) alongside the "Equivalent Situation Postulate" allows one to find space-time structure as well as fields from arbitrarily shaped charged conductors, without using Einstein's equations. In particular, the space-time metric over a charged plane can be related to the metric being obtained from an exact solution to Einstein-Maxwell's equations. This solution describes an equilibrium of charged dust in parallel electric and gravitational fields. The field and metric outside a conducting ball have been found. The method proposed eliminates divergence of the proper energy and makes classical electrodynamics consistent at any sufficiently small distances. An experiment is proposed to verify the approach suggested.
Online music databases have increased signicantly as a consequence of the rapid growth of the Internet and digital audio, requiring the development of faster and more efficient tools for music content analysis. Musical genres are widely used to organize music collections. In this paper, the problem of automatic music genre classification is addressed by exploring rhythm-based features obtained from a respective complex network representation. A Markov model is build in order to analyse the temporal sequence of rhythmic notation events. Feature analysis is performed by using two multivariate statistical approaches: principal component analysis(unsupervised) and linear discriminant analysis (supervised). Similarly, two classifiers are applied in order to identify the category of rhythms: parametric Bayesian classifier under gaussian hypothesis (supervised), and agglomerative hierarchical clustering (unsupervised). Qualitative results obtained by Kappa coefficient and the obtained clusters corroborated the effectiveness...
Nanocluster impact on a free-standing graphene is performed by the molecular dynamics simulation, and the dynamical motion of the free-standing graphene is investigated. The graphene is bended by the incident nanocluster, and a transverse deflection wave isotropically propagated in the graphene is observed. We find that the time evolution of the deflection is semi-quantitatively described by the linear theory of elasticity.
Leading models of galaxy formation require large-scale energetic outflows to regulate the growth of distant galaxies and their central black holes. However, current observational support for this hypothesis at high redshift is mostly limited to rare z>2 radio galaxies. Here we present Gemini-North NIFS Intregral Field Unit (IFU) observations of the [O III]5007 emission from a z~2 ultraluminous infrared galaxy (ULIRG; L_IR>10^12 L_sol) with an optically identified Active Galactic Nucleus (AGN). The spatial extent (~4-8 kpc) of the high velocity and broad [O III] emission are consistent with that found in z>2 radio galaxies, indicating the presence of a large-scale energetic outflow in a galaxy population potentially orders of magnitude more common than distant radio galaxies. The low radio luminosity of this system indicates that radio-bright jets are unlikely to be responsible for driving the outflow. However, the estimated energy input required to produce the large-scale outflow signatures (of order...
We present the long-term monitoring of the High Mass X-ray Binary GX 301-2 performed with the SuperAGILE instrument on-board the AGILE mission. The source was monitored in the 20-60 keV energy band during the first year of the mission from 2007 July 17 to 2008 August 31, covering about one whole orbital period and three more pre-periastron passages for a total net observation time of about 3.7 Ms. The SuperAGILE dataset represents one of the most continuous and complete monitoring at hard X-ray energies of the 41.5 day long binary period available to date. The source behaviour was characterized at all orbital phases in terms of hard X-ray flux, spectral hardness, spin period history, pulsed fraction and pulse shape profile. We also complemented the SuperAGILE observations with the soft X-ray data of the RossiXTE/ASM. Our analysis shows a clear orbital modulation of the spectral hardness, with peaks in correspondence of the pre-periastron flare and near phase 0.25. The hardness peaks we found could be related...
We describe the procedure of the construction of a sample of distant ($z>0.3$) radio galaxies using the NED, SDSS, and CATS databases. We believe the sample to be free of objects with quasar properties. This paper is the second part of the description of the radio galaxies catalog we plan to use for cosmological tests. We report the photometric parameters for the objects of the list, and perform its preliminary statistical analysis including the construction of the Hubble diagrams.
We describe the procedure of the construction of a sample of distant ($z>0.3$) radio galaxies using the NED, CATS and SDSS databases for further use in various statistical tests. We believe the sample to be free of objects with quasar properties. This paper is the third part of the description of the radio galaxies catalog that we plan to use for cosmological tests. We report the results of the sample of angular sizes for the NVSS survey list objects, and its preliminary statistical analysis. Three-parameter diagrams "angular size-redshift-flux density" and "angular size-redshift-spectral index", and their two-parameter projections are constructed. Three subsamples of radio galaxies are separated in the "source size--flux density" diagram.
Radial metallicity gradients are observed in the disks of the Milky Way and in several other spiral galaxies. In the case of the Milky Way, many objects can be used to determine the gradients, such as HII regions, B stars, Cepheids, open clusters and planetary nebulae. Several elements can be studied, such as oxygen, sulphur, neon, and argon in photoionized nebulae, and iron and other elements in cepheids, open clusters and stars. As a consequence, the number of observational characteristics inferred from the study of abundance gradients is very large, so that in the past few years they have become one of the main observational constraints of chemical evolution models. In this paper, we present some recent observational evidences of abundance gradients based on several classes of objects. We will focus on (i) the magnitude of the gradients, (ii) the space variations, and (iii) the evidences of a time variation of the abundance gradients. Some comments on recent theoretical models are also given, in an effort...
We present $^{12}$CO(1--0) and $^{12}$CO(2--1) maps of the interacting Seyfert 2/LINER galaxy NGC 5953 obtained with the IRAM interferometer at resolutions of 2\farcs1 $\times$ 1\farcs4 and 1\farcs1 $\times$ 0\farcs7, respectively. The CO emission is distributed over a disk of diameter $\sim$16\arcsec ($\sim$2.2 kpc), within which are several, randomly distributed peaks. The strongest peak does not coincide with the nucleus, but is instead offset from the center, $\sim2-3^{\prime\prime}$ ($\sim$340 pc) toward the west/southwest. The kinematics of the molecular component are quite regular, as is typical of a rotating disk. We also compared the $^{12}$CO distribution of NGC 5953 with observations at other wavelengths in order to study correlations between different tracers of the interstellar medium. Using NIR images, we computed the gravity torques exerted by the stellar potential on the gas. The torques are predominantly positive in both $^{12}$CO(1--0) and $^{12}$CO(2--1), suggesting that gas is not flowing...
The velocity of the inner ejecta of stripped-envelope core-collapse supernovae (CC-SNe) is studied by means of an analysis of their nebular spectra. Stripped-envelope CC-SNe are the result of the explosion of bare cores of massive stars ($\geq 8$ M$_{\odot}$), and their late-time spectra are typically dominated by a strong [O {\sc i}] $\lambda\lambda$6300, 6363 emission line produced by the innermost, slow-moving ejecta which are not visible at earlier times as they are located below the photosphere. A characteristic velocity of the inner ejecta is obtained for a sample of 56 stripped-envelope CC-SNe of different spectral types (IIb, Ib, Ic) using direct measurements of the line width as well as spectral fitting. For most SNe, this value shows a small scatter around 4500 km s$^{-1}$. Observations ($< 100$ days) of stripped-envelope CC-SNe have revealed a subclass of very energetic SNe, termed broad-lined SNe (BL-SNe) or hypernovae, which are characterised by broad absorption lines in the early-time spectra,...
Gas and star velocity dispersions have been derived for eight circumnuclear star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC3310 using high resolution spectroscopy in the blue and far red. Stellar velocity dispersions have been obtained from the CaII triplet in the near-IR, using cross-correlation techniques, while gas velocity dispersions have been measured by Gaussian fits to the Hb 4861A and [OIII]5007A emission lines. The CNSFRs stellar velocity dispersions range from 31 to 73 km/s. These values, together with the sizes measured on archival HST images, yield upper limits to the dynamical masses for the individual star clusters between 1.8 and 7.1 x 10$^6$ M$_\odot$, for the whole CNSFR between 2 x 10$^7$ and 1.4 x 10$^8$ M$_\odot$, and 5.3 x 10$^7$ M$_\odot$ for the nucleus inside the inner 14.2 pc. The masses of the ionizing stellar population responsible for the HII region gaseous emission have been derived from their published Ha luminosities and are found to be between 8.7 x 10$^5$...
The procedure of the construction of a sample of distant ($z>0.3$) radio galaxies using NED, SDSS, and CATS databases for further application in statistical tests is described. The sample is assumed to be cleaned from objects with quasar properties. Primary statistical analysis of the list is performed and the regression dependence of the spectral index on redshift is found.
We report observations of Lyman Alpha Blob 1 (LAB1) in the SSA 22 protocluster region (z=3.09) with the integral-field spectrograph SAURON. We increased the signal-to-noise in the spectra by more than a factor three compared to our previous observations. This allows us to probe the structure of the LAB system in detail, examining its structure in the spatial and wavelength dimensions. We find that the emission from the system comes largely from five distinct blobs. Two of the emission regions are associated with Lyman Break Galaxies, while a third appears to be associated with a heavily obscured submillimeter galaxy. The fourth and fifth components do not appear to be associated with any galaxy despite the deep imaging that is available in this field. If we interpret wavelength shifts in the line centroid as velocity structure in the underlying gas, many of these emission systems show evidence of velocity shear. It remains difficult to distinguish between an underlying rotation of the gas and an outflow driven...
The three main methods currently in use for estimating the excitation class of planetary nebulae (PNe) central stars are compared and evaluated using 586 newly discovered and previously known PNe in the Large Magellanic Cloud (LMC). In order to achieve this we ran a series of evaluation tests using line ratios derived from de-reddened, flux calibrated spectra. Pronounced differences between the methods are exposed. Diagrams were created by comparing excitation classes with H-beta line fluxes. The best methods are then compared to published temperatures using the Zanstra method and assessed for their ability to reflect central star effective temperatures and evolution. As a result we call for a clarification of the term `excitation class' according to the different input parameters used. The first method, which we refer to as Exneb relies purely on the ratios of certain key emission lines. The second method, which we refer to as Ex* includes modeling to create a continuous variable and, for optically thick...
The determination of Saturn's atmospheric noble gas abundances are critical to understanding the formation and evolution of Saturn, and giant planets in general. These measurements can only be performed with an entry probe. A Saturn probe will address whether enhancement in heavy noble gases, as was found in Jupiter, are a general feature of giant planets, and their ratios will be a powerful constraint on how they form. The helium abundance will show the extent to which helium has phase separated from hydrogen in the planet's deep interior. Jupiter's striking neon depletion may also be tied to its helium depletion, and must be confirmed or refuted in Saturn. Together with Jupiter's measured atmospheric helium abundance, a consistent evolutionary theory for both planets, including "helium rain" will be possible. We will then be able to calibrate the theory of the evolution of all giant planets, including exoplanets. In addition, high pressure H/He mixtures under giant planet conditions are...
Recent X-ray observations of hot gas in the galaxy cluster MS 0735.6+7421 reveal huge radio-bright, quasi-bipolar X-ray cavities having a total energy ~10^{62} ergs, the most energetic AGN outburst currently known. We investigate the evolution of this outburst with two-dimensional axisymmetric gasdynamical calculations in which the cavities are inflated by relativistic cosmic rays. Many key observational features of the cavities and associated shocks are successfully reproduced. The radial elongation of the cavities indicates that cosmic rays were injected into the cluster gas by a (jet) source moving out from the central AGN. AGN jets of this magnitude must be almost perfectly identically bipolar. The relativistic momentum of a single jet would cause a central AGN black hole of mass 10^9 M_{sun} to recoil at ~6000 km s^{-1}, exceeding kick velocities during black hole mergers, and be ejected from the cluster-center galaxy. When the cavity inflation is complete, 4PV underestimates the total energy received by...
We investigate the fraction of starbursts, starburst-AGN composites, Seyferts, and LINERs as a function of infrared luminosity (L_IR) and merger progress for ~500 infrared-selected galaxies. Using the new optical classifications afforded by the extremely large data set of the Sloan Digital Sky Survey, we find that the fraction of LINERs in IR-selected samples is rare (< 5%) compared with other spectral types. The lack of strong infrared emission in LINERs is consistent with recent optical studies suggesting that LINERs contain AGN with lower accretion rates than in Seyfert galaxies. Most previously classified infrared-luminous LINERs are classified as starburst-AGN composite galaxies in the new scheme. Starburst-AGN composites appear to "bridge" the spectral evolution from starburst to AGN in ULIRGs. The relative strength of the AGN versus starburst activity shows a significant increase at high infrared luminosity. In ULIRGs (L_IR >10^12 L_odot), starburst-AGN composite galaxies dominate at early--intermediate...
(Abridged) The ammonia method, recently proposed to explore the electron-to-proton mass ratio, mu = m_e/m_p, is applied to nearby dark clouds in the Milky Way. This ratio, being measured in essentially different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter is supposed to vary in chameleon-like scalar field models which predict strong dependence of masses and coupling constants on the local matter density. High resolution spectral observations of molecular cores in lines of NH3 (J,K) = (1,1), HC3N J = 2-1, and N2H+ J = 1-0 have been carried out at three radio telescopes in order to measure the radial velocity offsets, DeltaV = V_rot - V_inv, between the inversion transition of NH3 (1,1) and rotational transitions of other molecules having different sensitivities to the parameter dmm = (mu_obs - mu_lab)/mu_lab. The measured values of DeltaV show a statistically significant velocity offset of 23 +/- 4_stat +/- 3_sys m/s. Being interpreted in terms of mu-variation,...
We investigate the validity of the quasar - radio galaxy unification scenario and determine the presence of dust tori among radio galaxies of various types. Actively accreting supermassive black holes in the centres of radio galaxies may be uncovered through their dust tori reradiating the optical and ultraviolet continuum in mid-infrared bands. Using VISIR on the VLT, we have obtained sub-arcsecond (~0.40") resolution N-band images, at a wavelength of 11.85 micron, of the nuclei of a sample of 27 radio galaxies of four types in the redshift range z=0.006-0.156. The sample consists of 8 edge-darkened, low-power Fanaroff-Riley class I (FR-I) radio galaxies, 6 edge-brightened, class II (FR-II) radio galaxies displaying low-excitation optical emission, 7 FR-IIs displaying high-excitation optical emission, and 6 FR-II broad emission line radio galaxies. Out of the sample of 27 objects, 10 nuclei are detected and several have constraining non-detections at 10 sigma sensitivities of 7 mJy. On the basis of the core...
[Abridged] We used the purely flux limited (17.5<=I<=24.0) VIMOS-VLT Deep Survey (VVDS) sample to produce a homogeneous and complete optically-selected group catalogue, with reliable group properties. Using mock catalogues extracted from the MILLENNIUM simulations, we first studied how many groups can potentially be found in a survey with the same sampling rate as the VVDS, and then we tested how well the virial line of sight velocity dispersion (s_los) of such groups can be measured using galaxy velocities. We verified that, given VVDS observational strategy, we are able to recover s_los when s_los >= 350 km/s. We then optimized our group-finding algorithm, based on the Voronoi-Delaunay method, training it on mocks mimicking all the VVDS survey strategies: we required the redshift and s_los distributions of the output groups (n(z) and n(s_los)) to be in agreement with those given by the group halos defined in the simulations. We also maximized the completeness (C) and purity (P) of the output group...
We report on two quantitative, morphological estimators of the filamentary structure of the Cosmic Web, the so-called global and local skeletons. The first, based on a global study of the matter density gradient flow, allows us to study the connectivity between a density peak and its surroundings, with direct relevance to the anisotropic accretion via cold flows on galactic halos. From the second, based on a local constraint equation involving the derivatives of the field, we can derive predictions for powerful statistics, such as the differential length and the relative saddle to extrema counts of the Cosmic web as a function of density threshold (with application to percolation of structures and connectivity), as well as a theoretical framework to study their cosmic evolution through the onset of gravity-induced non-linearities.
X-ray data analysis have recently revealed fairly complex structures in cluster centres to be more common than expected. Besides, great part of these structures resemble in morphology, presenting a spiral-like substructure. It is not yet well known how this specific pattern is formed or maintained. In particular, understanding the nature of these spiral-like feature at the centre of some clusters is the major motivation of this work. We analyse Chandra deep observation data of 15 nearby galaxy clusters (0.01 < z < 0.06). We used X-ray temperature and substructure maps to detect small features in the core of the clusters. We detect a spiral-like feature in the centre of 7 clusters: A85, A426, A496, Hydra A cluster, Centaurus, Ophiuchus and A4059. This particular pattern is similar to those found in numerical hydrodynamic simulations of cluster merger with non-zero impact parameter. In some clusters of our sample a strong radio source also occupies the inner region of the cluster, suggesting a possible connection...
The contribution of an extent component of source radio emission is estimated for quasars and galaxies. The consideration of source radio structures at kiloparsec scales is used at the decameter and the higher frequency bands. The determination of the contribution of an extent component to source radio emission as well as main physical parameters of sample sources is carried out. We found that especially extent sources, giant radio galaxies, have smaller luminosity of core region, weaker magnetic field and greater characteristic age in comparison with compact radio galaxies and quasars. As it follows from our examination, the extent component contribution to source emission may be the indicator of the radio source age.
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