Receptive fields selection for binary feature description.

PubMed

Fan, Bin; Kong, Qingqun; Trzcinski, Tomasz; Wang, Zhiheng; Pan, Chunhong; Fua, Pascal

2014-06-01

Feature description for local image patch is widely used in computer vision. While the conventional way to design local descriptor is based on expert experience and knowledge, learning-based methods for designing local descriptor become more and more popular because of their good performance and data-driven property. This paper proposes a novel data-driven method for designing binary feature descriptor, which we call receptive fields descriptor (RFD). Technically, RFD is constructed by thresholding responses of a set of receptive fields, which are selected from a large number of candidates according to their distinctiveness and correlations in a greedy way. Using two different kinds of receptive fields (namely rectangular pooling area and Gaussian pooling area) for selection, we obtain two binary descriptors RFDR and RFDG .accordingly. Image matching experiments on the well-known patch data set and Oxford data set demonstrate that RFD significantly outperforms the state-of-the-art binary descriptors, and is comparable with the best float-valued descriptors at a fraction of processing time. Finally, experiments on object recognition tasks confirm that both RFDR and RFDG successfully bridge the performance gap between binary descriptors and their floating-point competitors.

Poynting-Flux-Driven Bubbles and Shocks Around Merging Neutron Star Binaries

NASA Astrophysics Data System (ADS)

Medvedev, M. V.; Loeb, A.

2013-04-01

Merging binaries of compact relativistic objects are thought to be progenitors of short gamma-ray bursts. Because of the strong magnetic field of one or both binary members and high orbital frequencies, these binaries are strong sources of energy in the form of Poynting flux. The steady injection of energy by the binary forms a bubble filled with matter with the relativistic equation of state, which pushes on the surrounding plasma and can drive a shock wave in it. Unlike the Sedov-von Neumann-Taylor blast wave solution for a point-like explosion, the shock wave here is continuously driven by the ever-increasing pressure inside the bubble. We calculate from the first principles the dynamics and evolution of the bubble and the shock surrounding it, demonstrate that it exhibits finite time singularity and find the corresponding analytical solution. We predict that such binaries can be observed as radio sources a few hours before and after the merger.

Matching asteroid population characteristics with a model constructed from the YORP-induced rotational fission hypothesis

NASA Astrophysics Data System (ADS)

Jacobson, Seth A.; Marzari, Francesco; Rossi, Alessandro; Scheeres, Daniel J.

2016-10-01

From the results of a comprehensive asteroid population evolution model, we conclude that the YORP-induced rotational fission hypothesis is consistent with the observed population statistics of small asteroids in the main belt including binaries and contact binaries. These conclusions rest on the asteroid rotation model of Marzari et al. ([2011]Icarus, 214, 622-631), which incorporates both the YORP effect and collisional evolution. This work adds to that model the rotational fission hypothesis, described in detail within, and the binary evolution model of Jacobson et al. ([2011a] Icarus, 214, 161-178) and Jacobson et al. ([2011b] The Astrophysical Journal Letters, 736, L19). Our complete asteroid population evolution model is highly constrained by these and other previous works, and therefore it has only two significant free parameters: the ratio of low to high mass ratio binaries formed after rotational fission events and the mean strength of the binary YORP (BYORP) effect. We successfully reproduce characteristic statistics of the small asteroid population: the binary fraction, the fast binary fraction, steady-state mass ratio fraction and the contact binary fraction. We find that in order for the model to best match observations, rotational fission produces high mass ratio (> 0.2) binary components with four to eight times the frequency as low mass ratio (<0.2) components, where the mass ratio is the mass of the secondary component divided by the mass of the primary component. This is consistent with post-rotational fission binary system mass ratio being drawn from either a flat or a positive and shallow distribution, since the high mass ratio bin is four times the size of the low mass ratio bin; this is in contrast to the observed steady-state binary mass ratio, which has a negative and steep distribution. This can be understood in the context of the BYORP-tidal equilibrium hypothesis, which predicts that low mass ratio binaries survive for a significantly longer period of time than high mass ratio systems. We also find that the mean of the log-normal BYORP coefficient distribution μB ≳10-2 , which is consistent with estimates from shape modeling (McMahon and Scheeres, 2012a).

Wind-driven angular momentum loss in binary systems. I - Ballistic case

NASA Technical Reports Server (NTRS)

Brookshaw, Leigh; Tavani, Marco

1993-01-01

We study numerically the average loss of specific angular momentum from binary systems due to mass outflow from one of the two stars for a variety of initial injection geometries and wind velocities. We present results of ballistic calculations in three dimensions for initial mass ratios q of the mass-losing star to primary star in the range q between 10 exp -5 and 10. We consider injection surfaces close to the Roche lobe equipotential surface of the mass-losing star, and also cases with the mass-losing star underfilling its Roche lobe. We obtain that the orbital period is expected to have a negative time derivative for wind-driven secular evolution of binaries with q greater than about 3 and with the mass-losing star near filling its Roche lobe. We also study the effect of the presence of an absorbing surface approximating an accretion disk on the average final value of the specific angular momentum loss. We find that the effect of an accretion disk is to increase the wind-driven angular momentum loss. Our results are relevant for evolutionary models of high-mass binaries and low-mass X-ray binaries.

Viscosity and diffusivity in melts: from unary to multicomponent systems

NASA Astrophysics Data System (ADS)

Chen, Weimin; Zhang, Lijun; Du, Yong; Huang, Baiyun

2014-05-01

Viscosity and diffusivity, two important transport coefficients, are systematically investigated from unary melt to binary to multicomponent melts in the present work. By coupling with Kaptay's viscosity equation of pure liquid metals and effective radii of diffusion species, the Sutherland equation is modified by taking the size effect into account, and further derived into an Arrhenius formula for the convenient usage. Its reliability for predicting self-diffusivity and impurity diffusivity in unary liquids is then validated by comparing the calculated self-diffusivities and impurity diffusivities in liquid Al- and Fe-based alloys with the experimental and the assessed data. Moreover, the Kozlov model was chosen among various viscosity models as the most reliable one to reproduce the experimental viscosities in binary and multicomponent melts. Based on the reliable viscosities calculated from the Kozlov model, the modified Sutherland equation is utilized to predict the tracer diffusivities in binary and multicomponent melts, and validated in Al-Cu, Al-Ni and Al-Ce-Ni melts. Comprehensive comparisons between the calculated results and the literature data indicate that the experimental tracer diffusivities and the theoretical ones can be well reproduced by the present calculations. In addition, the vacancy-wind factor in binary liquid Al-Ni alloys with the increasing temperature is also discussed. What's more, the calculated inter-diffusivities in liquid Al-Cu, Al-Ni and Al-Ag-Cu alloys are also in excellent agreement with the measured and theoretical data. Comparisons between the simulated concentration profiles and the measured ones in Al-Cu, Al-Ce-Ni and Al-Ag-Cu melts are further used to validate the present calculation method.

Thermal effects in rapid directional solidification - Linear theory

NASA Technical Reports Server (NTRS)

Huntley, D. A.; Davis, S. H.

1993-01-01

We study the morphological instability of the planar solid/liquid interface for a unidirectionally-solidified dilute binary mixture. We use a model developed by Boettinger et al. (1985, 1986), Aziz (1982), and Jackson et al. (1980), which allows for nonequilibrium effects on the interface through velocity-dependent segregation and attachment kinetics. Two types of instabilities are found in the linear stability analysis: (1) a cellular instability, and (2) an oscillatory instability driven by disequilibrium effects. Merchant and Davis (1990) characterized these instabilities subject to the frozen-temperature approximation (FTA). The present work relaxes the FTA by including the effects of latent heat and the full temperature distribution. Thermal effects slightly postpone the onset of the cellular instability but dramatically postpone the onset of the oscillatory instability; however, the absolute-stability conditions, at which at high speed the cellular and oscillatory instabilities are suppressed, remain unchanged from the FTA.

Temperature dependent structural and dynamical properties of liquid Cu80Si20 binary alloy

NASA Astrophysics Data System (ADS)

Suthar, P. H.; Shah, A. K.; Gajjar, P. N.

2018-05-01

Ashcroft and Langreth binary structure factor have been used to study for pair correlation function and the study of dynamical variable: velocity auto correlation functions, power spectrum and mean square displacement calculated based on the static harmonic well approximation in liquid Cu80Si20 binary alloy at wide temperature range (1140K, 1175K, 1210K, 1250K, 1373K, 1473K.). The effective interaction for the binary alloy is computed by our well established local pseudopotential along with the exchange and correction functions Sarkar et al(S). The negative dip in velocity auto correlation decreases as the various temperature is increases. For power spectrum as temperature increases, the peak of power spectrum shifts toward lower ω. Good agreement with the experiment is observed for the pair correlation functions. Velocity auto correlation showing the transferability of the local pseudopotential used for metallic liquid environment in the case of copper based binary alloys.

A Drosophila LexA Enhancer-Trap Resource for Developmental Biology and Neuroendocrine Research.

PubMed

Kockel, Lutz; Huq, Lutfi M; Ayyar, Anika; Herold, Emma; MacAlpine, Elle; Logan, Madeline; Savvides, Christina; Kim, Grace E S; Chen, Jiapei; Clark, Theresa; Duong, Trang; Fazel-Rezai, Vahid; Havey, Deanna; Han, Samuel; Jagadeesan, Ravi; Kim, Eun Soo Jackie; Lee, Diane; Lombardo, Kaelina; Piyale, Ida; Shi, Hansen; Stahr, Lydia; Tung, Dana; Tayvah, Uriel; Wang, Flora; Wang, Ja-Hon; Xiao, Sarah; Topper, Sydni M; Park, Sangbin; Rotondo, Cheryl; Rankin, Anne E; Chisholm, Townley W; Kim, Seung K

2016-10-13

Novel binary gene expression tools like the LexA-LexAop system could powerfully enhance studies of metabolism, development, and neurobiology in Drosophila However, specific LexA drivers for neuroendocrine cells and many other developmentally relevant systems remain limited. In a unique high school biology course, we generated a LexA-based enhancer trap collection by transposon mobilization. The initial collection provides a source of novel LexA-based elements that permit targeted gene expression in the corpora cardiaca, cells central for metabolic homeostasis, and other neuroendocrine cell types. The collection further contains specific LexA drivers for stem cells and other enteric cells in the gut, and other developmentally relevant tissue types. We provide detailed analysis of nearly 100 new LexA lines, including molecular mapping of insertions, description of enhancer-driven reporter expression in larval tissues, and adult neuroendocrine cells, comparison with established enhancer trap collections and tissue specific RNAseq. Generation of this open-resource LexA collection facilitates neuroendocrine and developmental biology investigations, and shows how empowering secondary school science can achieve research and educational goals. Copyright © 2016 Kockel et al.

An Introduction to the BFS Method and Its Use to Model Binary NiAl Alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Noebe, Ronald D.; Ferrante, J.; Amador, C.

1998-01-01

We introduce the Bozzolo-Ferrante-Smith (BFS) method for alloys as a computationally efficient tool for aiding in the process of alloy design. An intuitive description of the BFS method is provided, followed by a formal discussion of its implementation. The method is applied to the study of the defect structure of NiAl binary alloys. The groundwork is laid for a detailed progression to higher order NiAl-based alloys linking theoretical calculations and computer simulations based on the BFS method and experimental work validating each step of the alloy design process.

HST/FGS High Angular Resolution Observations of Binary Asteroids

NASA Astrophysics Data System (ADS)

Hestroffer, Daniel; Tanga, P.; Cellino, A.; Kaasalainen, M.; Torppa, J.; Marchis, F.; Richardson, D. C.; Elankumaran, P.; Berthier, J.; Colas, F.; Lounis, S.

2006-09-01

Binary or multiple asteroids are important bodies that provide insight into the physical properties of asteroids in general. The knowledge of the components orbit in a binary provides the total mass with high accuracy and generally permits a rough bulk-density estimate [1,2]. We have observed 10 selected binary or multiple asteroids (22 Kalliope, 45 Eugenia, 87 Sylvia, 90 Antiope, 107 Camilla, 121 Hermione, 283 Emma, 379 Huenna, 617 Patroclus, 762 Pulcova) with the HST/FGS interferometer in order to obtain high resolution data on the size and shape of their primaries (HST proposal ID 10614). All these systems except the Jupiter Trojan 617 Patroclus are located in the main-belt of asteroids. Combining these HST/FGS data to topographic models obtained from lightcurve inversion [3,4] yields the volume and hence the bulk density of these bodies with unprecedented accuracy [5]. This work will allow us to obtain important information on their internal structure, and insight into the possible gravitational re-accumulation process after a catastrophic disruptive collision [e.g. 6,7,8].In particular, one can see whether or not the surfaces of theses bodies closely follow an effective equipotential surface, and under what circumstances such a correspondence is or is not attained . We will present the preliminary results for the data reduction and the size and bulk density determination. [1] Merline et al. (2003). In: Asteroids III, pp 289. [2] Marchis et al. (2005) ACM 2005, Buzios, Brazil. [3] Kaasalainen et al. (2002) Icarus 159, 359. [4] Torppa et al. (2003) Icarus 164, 346. [5] Hestroffer et al. (2003) ACM 2002, ESA-SP 500, 493. [6] Michel et al. (2004) P&SS 52, 1109. [7] Durda et al. (2004) Icarus 167, 342. [8] Paolicchi et al. (1993) Cel. Mech., 57, 49.

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods.

PubMed

Chanbi, Daoud; Ogam, Erick; Amara, Sif Eddine; Fellah, Z E A

2018-05-07

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density.

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods

PubMed Central

Chanbi, Daoud; Amara, Sif Eddine; Fellah, Z. E. A.

2018-01-01

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density. PMID:29735946

Streaming potential method for characterizing interaction of electrical double layers between rice roots and Fe/Al oxide-coated quartz in situ.

PubMed

Liu, Zhao-Dong; Wang, Hai-Cui; Li, Jiu-Yu; Xu, Ren-Kou

2017-10-01

The interaction between rice roots and Fe/Al oxide-coated quartz was investigated through zeta potential measurements and column leaching experiments in present study. The zeta potentials of rice roots, Fe/Al oxide-coated quartz, and the binary systems containing rice roots and Fe/Al oxide-coated quartz were measured by a specially constructed streaming potential apparatus. The interactions between rice roots and Fe/Al oxide-coated quartz particles were evaluated/deduced based on the differences of zeta potentials between the binary systems and the single system of rice roots. The zeta potentials of the binary systems moved in positive directions compared with that of rice roots, suggesting that there were overlapping of diffuse layers of electric double layers on positively charged Fe/Al oxide-coated quartz and negatively charged rice roots and neutralization of positive charge on Fe/Al oxide-coated quartz with negative charge on rice roots. The greater amount of positive charges on Al oxide led to the stronger interaction of Al oxide-coated quartz with rice roots and the more shift of zeta potential compared with Fe oxide. The overlapping of diffuse layers on Fe/Al oxide-coated quartz and rice roots was confirmed by column leaching experiments. The greater overlapping of diffuse layers on Al oxide and rice roots led to more simultaneous adsorptions of K + and NO 3 - and greater reduction in leachate electric conductivity when the column containing Al oxide-coated quartz and rice roots was leached with KNO 3 solution, compared with the columns containing rice roots and Fe oxide-coated quartz or quartz. When the KNO 3 solution was replaced with deionized water to flush the columns, more K + and NO 3 - were desorbed from the binary system containing Al oxide-coated quartz and rice roots than from other two binary systems, suggesting that the stronger electrostatic interaction between Al oxide and rice roots promoted the desorption of K + and NO 3 - from the binary system and enhanced overlapping of diffuse layers on these oppositely charged surfaces compared with other two binary systems. In conclusion, the overlapping of diffuse layers occurred between positively charged Fe/Al oxides and rice roots, which led to neutralization of opposite charge and affected adsorption and desorption of ions onto and from the charged surfaces of Fe/Al oxides and rice roots.

WHITE-LIGHT FLARES ON CLOSE BINARIES OBSERVED WITH KEPLER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Qing; Xin, Yu; Liu, Ji-Feng

2016-06-01

Based on Kepler data, we present the results of a search for white light flares on 1049 close binaries. We identify 234 flare binaries, of which 6818 flares are detected. We compare the flare-binary fraction in different binary morphologies (“detachedness”). The result shows that the fractions in over-contact and ellipsoidal binaries are approximately 10%–20% lower than those in detached and semi-detached systems. We calculate the binary flare activity level (AL) of all the flare binaries, and discuss its variations along the orbital period ( P {sub orb}) and rotation period ( P {sub rot}, calculated for only detached binaries). Wemore » find that the AL increases with decreasing P {sub orb} or P {sub rot}, up to the critical values at P {sub orb} ∼ 3 days or P {sub rot} ∼ 1.5 days, and thereafter the AL starts decreasing no matter how fast the stars rotate. We examine the flaring rate as a function of orbital phase in two eclipsing binaries on which a large number of flares are detected. It appears that there is no correlation between flaring rate and orbital phase in these two binaries. In contrast, when we examine the function with 203 flares on 20 non-eclipse ellipsoidal binaries, bimodal distribution of amplitude-weighted flare numbers shows up at orbital phases 0.25 and 0.75. Such variation could be larger than what is expected from the cross section modification.« less

Properties of Neutrino-driven Ejecta from the Remnant of a Binary Neutron Star Merger: Pure Radiation Hydrodynamics Case

NASA Astrophysics Data System (ADS)

Fujibayashi, Sho; Sekiguchi, Yuichiro; Kiuchi, Kenta; Shibata, Masaru

2017-09-01

We performed general relativistic, long-term, axisymmetric neutrino radiation hydrodynamics simulations for the remnant formed after a binary neutron star merger, which consists of a massive neutron star and a torus surrounding it. As an initial condition, we employ the result derived in a three-dimensional, numerical relativity simulation for the binary neutron star merger. We investigate the properties of neutrino-driven ejecta. Due to the pair-annihilation heating, the dynamics of the neutrino-driven ejecta are significantly modified. The kinetic energy of the ejecta is about two times larger than that in the absence of pair-annihilation heating. This suggests that the pair-annihilation heating plays an important role in the evolution of merger remnants. The relativistic outflow, which is required for driving gamma-ray bursts, is not observed because the specific heating rate around the rotational axis is not sufficiently high, due to the baryon loading caused by the neutrino-driven ejecta from the massive neutron star. We discuss the condition for launching the relativistic outflow and the nucleosynthesis in the ejecta.

Single and binary adsorption of heavy metal ions from aqueous solutions using sugarcane cellulose-based adsorbent.

PubMed

Wang, Futao; Pan, Yuanfeng; Cai, Pingxiong; Guo, Tianxiang; Xiao, Huining

2017-10-01

A high efficient and eco-friendly sugarcane cellulose-based adsorbent was prepared in an attempt to remove Pb 2+ , Cu 2+ and Zn 2+ from aqueous solutions. The effects of initial concentration of heavy metal ions and temperature on the adsorption capacity of the bioadsorbent were investigated. The adsorption isotherms showed that the adsorption of Pb 2+ , Cu 2+ and Zn 2+ followed the Langmuir model and the maximum adsorptions were as high as 558.9, 446.2 and 363.3mg·g -1 , respectively, in single component system. The binary component system was better described with the competitive Langmuir isotherm model. The three dimensional sorption surface of binary component system demonstrated that the presence of Pb 2+ decreased the sorption of Cu 2+ , but the adsorption amount of other metal ions was not affected. The result from SEM-EDAX revealed that the adsorption of metal ions on bioadsorbent was mainly driven by coordination, ion exchange and electrostatic association. Copyright © 2017 Elsevier Ltd. All rights reserved.

First-principles study of intermetallic phase stability in the ternary Ti-Al-Nb alloy system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asta, M.; Ormeci, A.; Wills, J.M.

The stability of bcc-based phases in the Ti-Al-Nb alloy system has been studied from first-principles using a combination of ab-initio total energy and cluster variation method (CVM) calculations. Total energies have been computed for 18 binary and ternary bcc superstructures in order to determine low temperature ordering tendencies. From the results of these calculations a set of effective cluster interaction parameters have been derived. These interaction parameters are required input for CVM computations of alloy thermodynamic properties. The CVM has been used to study the effect of composition on finite-temperature ordering tendencies and site preferences for bcc-based phases. Strong orderingmore » tendencies are observed for binary Nb-Al and Ti-Al bcc phases as well as for ternary alloys with compositions near Ti{sub 2}AlNb. For selected superstructures we have also analyzed structural stabilities with respect to tetragonal distortions which transform the bcc into an fcc lattice. Instabilities with respect to such distortions are found to exist for binary but not ternary bcc compounds.« less

Acceptable aluminum additions for minimal environmental effect in iron-aluminum alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikka, V.K.; Viswanathan, S.; Vyas, S.

A systematic study of iron-aluminum alloys has shown that Fe-16 at. % Al alloys are not very sensitive to environmental embrittlement. The Fe-22 and -28 at. % Al alloys are sensitive to environmental embrittlement, and the effect can be reduced by the addition of chromium and through the control of grain size by additions of zirconium and carbon. The Fe-16 at. % Al binary, and alloys based on it, yielded over 20% room-temperature (RT) elongation even after high-temperature annealing treatments at 1100[degree]C. The best values for the Fe-22 and -28 at. % Al-base alloys after similar annealing treatments were 5more » and 10%, respectively. A multicomponent alloy, FAP, based on Fe- 16 at. % Al was designed, which gave an RT ductility of over 25%.« less

Acceptable aluminum additions for minimal environmental effect in iron-aluminum alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikka, V.K.; Viswanathan, S.; Vyas, S.

A systematic study of iron-aluminum alloys has shown that Fe-16 at. % Al alloys are not very sensitive to environmental embrittlement. The Fe-22 and -28 at. % Al alloys are sensitive to environmental embrittlement, and the effect can be reduced by the addition of chromium and through the control of grain size by additions of zirconium and carbon. The Fe-16 at. % Al binary, and alloys based on it, yielded over 20% room-temperature (RT) elongation even after high-temperature annealing treatments at 1100{degree}C. The best values for the Fe-22 and -28 at. % Al-base alloys after similar annealing treatments were 5more » and 10%, respectively. A multicomponent alloy, FAP, based on Fe- 16 at. % Al was designed, which gave an RT ductility of over 25%.« less

VizieR Online Data Catalog: Orbits based on SOAR speckle interferometry. II. (Tokovinin, 2017)

NASA Astrophysics Data System (ADS)

Tokovinin, A.

2018-01-01

We present new or updated orbits of 44 binary systems or subsystems. It is based on speckle interferometric measurements made at the 4.1m Southern Astrophysical Research (SOAR) telescope (Tokovinin et al. 2010, Cat. J/AJ/139/743; 2014, Cat. J/AJ/147/123; 2015, Cat. J/AJ/150/50; 2016, Cat. J/AJ/151/153; 2010PASP..122.1483T; Tokovinin 2012, Cat. J/AJ/144/56) combined with archival data collected in the Washington Double Star Catalog (WDS; Mason et al. 2001-2014, Cat. B/wds). It continues previous work on binary orbits resulting from the SOAR speckle program and follows the template of the Paper I (Tokovinin 2016, Cat. J/AJ/152/138), where the motivation is discussed. Briefly, the calculation of binary orbits is part of the astronomical infrastructure, and visual orbital elements are used in many areas. The state of the art is reflected in the Sixth Catalog of Visual Binary Orbits (VB6; Hartkopf et al. 2001AJ....122.3472H; http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6.html). (5 data files).

General relativistic dynamics of an extreme mass-ratio binary interacting with an external body

NASA Astrophysics Data System (ADS)

Yang, Huan; Casals, Marc

2017-10-01

We study the dynamics of a hierarchical three-body system in the general relativistic regime: an extreme mass-ratio inner binary under the tidal influence of an external body. The inner binary consists of a central Schwarzschild black hole and a test body moving around it. We discuss three types of tidal effects on the orbit of the test body. First, the angular momentum of the inner binary precesses around the angular momentum of the outer binary. Second, the tidal field drives a "transient resonance" when the radial and azimuthal frequencies are commensurable. In contrast with resonances driven by the gravitational self-force, this tidal-driven resonance may boost the orbital angular momentum and eccentricity (a relativistic version of the Kozai-Lidov effect). Finally, for an orbit-dynamical effect during the nonresonant phase, we calculate the correction to the innermost stable circular (mean) orbit due to the tidal interaction. Hierarchical three-body systems are potential sources for future space-based gravitational wave missions, and the tidal effects that we find could contribute significantly to their waveform.

Study of binary asteroids with three space missions

NASA Astrophysics Data System (ADS)

Kovalenko, Irina; Doressoundiram, Alain; Hestroffer, Daniel

Binary and multiple asteroids are common in the Solar system and encountered in various places going from Near-Earth region, to the main-belt, Trojans and Centaurs, and beyond Neptune. Their study can provide insight on the Solar System formation and its subsequent dynamical evolution. Binaries are also objects of high interest because they provide fundamental physical parameters such as mass and density, and hence clues on the early Solar System, or other processes that are affecting asteroid over time. We will present our current project on analysis of such systems based on three space missions. The first one is the Herschel space observatory (ESA), the largest infrared telescope ever launched. Thirty Centaurs and trans-Neptunian binaries were observed by Herschel and the measurement allowed to define size, albedo and thermal properties [1]. The second one is the satellite Gaia (ESA). This mission is designed to chart a three-dimensional map of the Galaxy. Gaia will provide positional measurements of Solar System Objects - including asteroid binaries - with unprecedented accuracy [2]. And the third one is the proposed mission AIDA, which would study the effects of crashing a spacecraft into an asteroid [3]. The objectives are to demonstrate the ability to modify the trajectory of an asteroid, to precisely measure its trajectory change, and to characterize its physical properties. The target of this mission is a binary system: (65803) Didymos. This encompasses orbital characterisations for both astrometric and resolved binaries, as well as unbound orbit, study of astrometric binaries, derivation of densities, and general statistical analysis of physical and orbital properties of trans-Neptunian and other asteroid binaries. Acknowledgements : work supported by Labex ESEP (ANR N° 2011-LABX-030) [1] Müller T., Lellouch E., Stansberry J. et al. 2009. TNOs are Cool: A Survey of the Transneptunian Region. EM&P 105, 209-219. [2] Mignard F., Cellino A., Muinonen K. et al. 2007. The Gaia Mission: Expected Applications to Asteroid Science. EM&P 1001, 97-125. [3] Galvez A., Carnelli I. et al. 2013. AIDA: The Asteroid Impact & Deflection Assessment Mission. EPSC 2013 - 1043.

High-resolution spectroscopy of extremely metal-poor stars from SDSS/Segue. II. Binary fraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aoki, Wako; Suda, Takuma; Beers, Timothy C.

2015-02-01

The fraction of binary systems in various stellar populations of the Galaxy and the distribution of their orbital parameters are important but not well-determined factors in studies of star formation, stellar evolution, and Galactic chemical evolution. While observational studies have been carried out for a large sample of nearby stars, including some metal-poor Population II stars, almost no constraints on the binary nature for extremely metal-poor (EMP; [Fe/H] <−3.0) stars have yet been obtained. Here we investigate the fraction of double-lined spectroscopic binaries and carbon-enhanced metal-poor (CEMP) stars, many of which could have formed as pairs of low-mass and intermediate-massmore » stars, to estimate the lower limit of the fraction of binary systems having short periods. The estimate is based on a sample of very metal-poor stars selected from the Sloan Digital Sky Survey and observed at high spectral resolution in a previous study by Aoki et al. That survey reported 3 double-lined spectroscopic binaries and 11 CEMP stars, which we consider along with a sample of EMP stars from the literature compiled in the SAGA database. We have conducted measurements of the velocity components for stacked absorption features of different spectral lines for each double-lined spectroscopic binary. Our estimate indicates that the fraction of binary stars having orbital periods shorter than 1000 days is at least 10%, and possibly as high as 20% if the majority of CEMP stars are formed in such short-period binaries. This result suggests that the period distribution of EMP binary systems is biased toward short periods, unless the binary fraction of low-mass EMP stars is significantly higher than that of other nearby stars.« less

Compact X-ray Binary Re-creation in Core Collapse: NGC 6397

NASA Astrophysics Data System (ADS)

Grindlay, J. E.; Bogdanov, S.; van den Berg, M.; Heinke, C.

2005-12-01

We report new Chandra observations of the core collapsed globular cluster NGC 6397. In comparison with our original Chandra observations (Grindlay et al 2001, ApJ, 563, L53), we now detect some 30 sources (vs. 20) in the cluster. A new CV is confirmed, though new HST/ACS optical observations (see Cohn et al this meeting) show that one of the original CV candidates is a background AGN). The 9 CVs (optically identified) yet only one MSP and one qLMXB suggest either a factor of 7 reduction in NSs/WDs vs. what we find in 47Tuc (see Grindlay 2005, Proc. Cefalu Conf. on Interacting Binaries) or that CVs are produced in the core collapse. The possible second MSP with main sequence companion, source U18 (see Grindlay et al 2001) is similar in its X-ray and optical properties to MSP-W in 47Tuc, which must have swapped its binary companion. Together with the one confirmed (radio) MSP in NGC 6397, with an evolved main sequence secondary, the process of enhanced partner swapping in the high stellar density of core collapse is implicated. At the same time, main sequence - main sequence binaries (active binaries) are depleted in the cluster core, presumably by "binary burning" in core collapse. These binary re-creation and destruction mechanisms in core collapse have profound implications for binary evolution and mergers in globulars that have undergone core collapse.

Sparse dynamical Boltzmann machine for reconstructing complex networks with binary dynamics

NASA Astrophysics Data System (ADS)

Chen, Yu-Zhong; Lai, Ying-Cheng

2018-03-01

Revealing the structure and dynamics of complex networked systems from observed data is a problem of current interest. Is it possible to develop a completely data-driven framework to decipher the network structure and different types of dynamical processes on complex networks? We develop a model named sparse dynamical Boltzmann machine (SDBM) as a structural estimator for complex networks that host binary dynamical processes. The SDBM attains its topology according to that of the original system and is capable of simulating the original binary dynamical process. We develop a fully automated method based on compressive sensing and a clustering algorithm to construct the SDBM. We demonstrate, for a variety of representative dynamical processes on model and real world complex networks, that the equivalent SDBM can recover the network structure of the original system and simulates its dynamical behavior with high precision.

Sparse dynamical Boltzmann machine for reconstructing complex networks with binary dynamics.

PubMed

Chen, Yu-Zhong; Lai, Ying-Cheng

2018-03-01

Revealing the structure and dynamics of complex networked systems from observed data is a problem of current interest. Is it possible to develop a completely data-driven framework to decipher the network structure and different types of dynamical processes on complex networks? We develop a model named sparse dynamical Boltzmann machine (SDBM) as a structural estimator for complex networks that host binary dynamical processes. The SDBM attains its topology according to that of the original system and is capable of simulating the original binary dynamical process. We develop a fully automated method based on compressive sensing and a clustering algorithm to construct the SDBM. We demonstrate, for a variety of representative dynamical processes on model and real world complex networks, that the equivalent SDBM can recover the network structure of the original system and simulates its dynamical behavior with high precision.

Enthalpies of mixing of liquid systems for lead free soldering: Al-Cu-Sn system.

PubMed

Flandorfer, Hans; Rechchach, Meryem; Elmahfoudi, A; Bencze, László; Popovič, Arkadij; Ipser, Herbert

2011-11-01

The present work refers to high-temperature drop calorimetric measurements on liquid Al-Cu, Al-Sn, and Al-Cu-Sn alloys. The binary systems have been investigated at 973 K, up to 40 at.% Cu in case of Al-Cu, and over the entire concentrational range in case of Al-Sn. Measurements in the ternary Al-Cu-Sn system were performed along the following cross-sections: x(Al)/x(Cu) = 1:1, x(Al)/x(Sn) = 1:1, x(Cu)/x(Sn) = 7:3, x(Cu)/x(Sn) = 1:1, and x(Cu)/x(Sn) = 3:7 at 1273 K. Experimental data were used to find ternary interaction parameters by applying the Redlich-Kister-Muggianu model for substitutional solutions, and a full set of parameters describing the concentration dependence of the enthalpy of mixing was derived. From these, the isoenthalpy curves were constructed for 1273 K. The ternary system shows an exothermic enthalpy minimum of approx. -18,000 J/mol in the Al-Cu binary and a maximum of approx. 4000 J/mol in the Al-Sn binary system. The Al-Cu-Sn system is characterized by considerable repulsive ternary interactions as shown by the positive ternary interaction parameters.

Search for Open binaries in the Southern Celestial Hemisphere using SPM4

NASA Astrophysics Data System (ADS)

Dávila, E.; Vieira, K.; Rosales, K.

2018-01-01

Open binaries' weak gravitational binding makes them vulnerable to any perturbation, turning them into excellent probes of the gravitational field where they are located. Currently there are only a few hundreds known or suspected open binaries, therefore a search for more of these systems is highly encouraging by looking for pairs of stars with common proper motions in an extensive, deep, and high quality astrometric catalog such as the SPM4 (Girard et al. 2011).

Synthetic Survey of the Kepler Field

NASA Astrophysics Data System (ADS)

Wells, Mark; Prša, Andrej

2018-01-01

In the era of large scale surveys, including LSST and Gaia, binary population studies will flourish due to the large influx of data. In addition to probing binary populations as a function of galactic latitude, under-sampled groups such as low mass binaries will be observed at an unprecedented rate. To prepare for these missions, binary population simulations need to be carried out at high fidelity. These simulations will enable the creation of simulated data and, through comparison with real data, will allow the underlying binary parameter distributions to be explored. In order for the simulations to be considered robust, they should reproduce observed distributions accurately. To this end we have developed a simulator which takes input models and creates a synthetic population of eclipsing binaries. Starting from a galactic single star model, implemented using Galaxia, a code by Sharma et al. (2011), and applying observed multiplicity, mass-ratio, period, and eccentricity distributions, as reported by Raghavan et al. (2010), Duchêne & Kraus (2013), and Moe & Di Stefano (2017), we are able to generate synthetic binary surveys that correspond to any survey cadences. In order to calibrate our input models we compare the results of our synthesized eclipsing binary survey to the Kepler Eclipsing Binary catalog.

Cerium-based, intermetallic-strengthened aluminum casting alloy: High-volume co-product development

DOE PAGES

Sims, Zachary C.; Weiss, David; McCall, S. K.; ...

2016-05-23

Here, several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanicalmore » properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.« less

Kinetically driven self-assembly of a binary solute mixture with controlled phase separation via electro-hydrodynamic flow of corona discharge.

PubMed

Jung, Hee Joon; Huh, June; Park, Cheolmin

2012-10-21

This feature article describes a new and facile process to fabricate a variety of thin films of non-volatile binary solute mixtures suitable for high performance organic electronic devices via electro-hydrodynamic flow of conventional corona discharge. Both Corona Discharge Coating (CDC) and a modified version of CDC, Scanning Corona Discharge Coating (SCDC), are based on utilizing directional electric flow, known as corona wind, of the charged uni-polar particles generated by corona discharge between a metallic needle and a bottom plate under a high electric field (5-10 kV cm(-1)). The electric flow rapidly spreads out the binary mixture solution on the bottom plate and subsequently forms a smooth and flat thin film in a large area within a few seconds. In the case of SCDC, the static movement of the bottom electrode on which a binary mixture solution is placed provides further control of thin film formation, giving rise to a film highly uniform over a large area. Interesting phase separation behaviors were observed including nanometer scale phase separation of a polymer-polymer binary mixture and vertical phase separation of a polymer-organic semiconductor mixture. Core-shell type phase separation of either polymer-polymer or polymer-colloidal nanoparticle binary mixtures was also developed with a periodically patterned microstructure when the relative location of the corona wind was controlled to a binary solution droplet on a substrate. We also demonstrate potential applications of thin functional films with controlled microstructures by corona coating to various organic electronic devices such as electroluminescent diodes, field effect transistors and non-volatile polymer memories.

Kinetically driven self-assembly of a binary solute mixture with controlled phase separation via electro-hydrodynamic flow of corona discharge

NASA Astrophysics Data System (ADS)

Jung, Hee Joon; Huh, June; Park, Cheolmin

2012-09-01

This feature article describes a new and facile process to fabricate a variety of thin films of non-volatile binary solute mixtures suitable for high performance organic electronic devices via electro-hydrodynamic flow of conventional corona discharge. Both Corona Discharge Coating (CDC) and a modified version of CDC, Scanning Corona Discharge Coating (SCDC), are based on utilizing directional electric flow, known as corona wind, of the charged uni-polar particles generated by corona discharge between a metallic needle and a bottom plate under a high electric field (5-10 kV cm-1). The electric flow rapidly spreads out the binary mixture solution on the bottom plate and subsequently forms a smooth and flat thin film in a large area within a few seconds. In the case of SCDC, the static movement of the bottom electrode on which a binary mixture solution is placed provides further control of thin film formation, giving rise to a film highly uniform over a large area. Interesting phase separation behaviors were observed including nanometer scale phase separation of a polymer-polymer binary mixture and vertical phase separation of a polymer-organic semiconductor mixture. Core-shell type phase separation of either polymer-polymer or polymer-colloidal nanoparticle binary mixtures was also developed with a periodically patterned microstructure when the relative location of the corona wind was controlled to a binary solution droplet on a substrate. We also demonstrate potential applications of thin functional films with controlled microstructures by corona coating to various organic electronic devices such as electroluminescent diodes, field effect transistors and non-volatile polymer memories.

Spectroscopy of Hot Horizontal Branch Stars in Globular Clusters

NASA Astrophysics Data System (ADS)

Moni-Bidin, C. M.

2006-06-01

We will present our latest results on spectroscopy of hot horizontal branch stars in globular clusters. This class of stars still presents many puzzling features, and many aspects of their formation and evolution are still unclear. Extreme Horizontal Branch (EHB) stars, also known as Subdwarf B (sdB) stars, are post-He flash stars with a He-burning core and high effective temperature (T_{eff} ≥ 20000 K). They originate from stars of low initial mass that during their evolution have lost great part of their external envelope. Many channel for the formation of these stars have been studied in literature. The scenarios involving dynamical interactions inside close binary systems, deeply investigated by Han et al. (2003, MNRAS, 341, 669), have been recently preferred, since between field sdB stars many close binary systems have been detected. (Morales-Rueda et al. 2003, MNRAS, 338, 752). Maxted et al. (2001, MNRAS, 326, 1391) estimated that 69+/-9% of field sdB stars are close binary systems. Latest results indicates that also this scenario presents some problems (Lisker et al. 2005, A&A, 430, 223), and Napiwotzki et al. (2004) found a lower fraction of binaries among their sample (42%). Moni Bidin et al. (2005, A&A, submitted) recently showed that in globular cluster NGC6752 the binary fraction among EHB stars is sensibly lower than what observed among field sdBs, estimating an upper limit of 20%. This difference between field and cluster sdBs is quite surprising. We are performing further investigation of these stars extending our search for close binary systems to other two clusters with a rich population of EHB stars. This will allow us to tell if the results on NGC6752 indicate a pecular cluster or the lack of binaries is a common trend of EHB stars in globular clusters. Moreover, with a larger sample we will be able to better estimate the binary fraction, or an upper limit for it. With our contribution we are going to show our results on this investigation that at the moment is still a work in progress.

EVOLUTION OF INTERMEDIATE-MASS X-RAY BINARIES DRIVEN BY THE MAGNETIC BRAKING OF AP/BP STARS. I. ULTRACOMPACT X-RAY BINARIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Wen-Cong; Podsiadlowski, Philipp, E-mail: chenwc@pku.edu.cn

2016-10-20

It is generally believed that ultracompact X-ray binaries (UCXBs) evolved from binaries consisting of a neutron star accreting from a low-mass white dwarf (WD) or helium star where mass transfer is driven by gravitational radiation. However, the standard WD evolutionary channel cannot produce the relatively long-period (40–60 minutes) UCXBs with a high time-averaged mass-transfer rate. In this work, we explore an alternative evolutionary route toward UCXBs, where the companions evolve from intermediate-mass Ap/Bp stars with an anomalously strong magnetic field (100–10,000 G). Including the magnetic braking caused by the coupling between the magnetic field and an irradiation-driven wind induced bymore » the X-ray flux from the accreting component, we show that intermediate-mass X-ray binaries (IMXBs) can evolve into UCXBs. Using the MESA code, we have calculated evolutionary sequences for a large number of IMXBs. The simulated results indicate that, for a small wind-driving efficiency f = 10{sup −5}, the anomalous magnetic braking can drive IMXBs to an ultra-short period of 11 minutes. Comparing our simulated results with the observed parameters of 15 identified UCXBs, the anomalous magnetic braking evolutionary channel can account for the formation of seven and eight sources with f = 10{sup −3}, and 10{sup −5}, respectively. In particular, a relatively large value of f can fit three of the long-period, persistent sources with a high mass-transfer rate. Though the proportion of Ap/Bp stars in intermediate-mass stars is only 5%, the lifetime of the UCXB phase is ≳2 Gyr, producing a relatively high number of observable systems, making this an alternative evolutionary channel for the formation of UCXBs.« less

TOPICAL REVIEW: Predictions for the rates of compact binary coalescences observable by ground-based gravitational-wave detectors

NASA Astrophysics Data System (ADS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Amador Ceron, E.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Antonucci, F.; Aoudia, S.; Arain, M. A.; Araya, M.; Aronsson, M.; Arun, K. G.; Aso, Y.; Aston, S.; Astone, P.; Atkinson, D. E.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Barker, D.; Barnum, S.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Bauchrowitz, J.; Bauer, Th S.; Behnke, B.; Beker, M. G.; Belczynski, K.; Benacquista, M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bigotta, S.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birindelli, S.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Blomberg, A.; Boccara, C.; Bock, O.; Bodiya, T. P.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bork, R.; Born, M.; Bose, S.; Bosi, L.; Boyle, M.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Budzyński, R.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet-Castell, J.; Burmeister, O.; Buskulic, D.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calloni, E.; Camp, J. B.; Campagna, E.; Campsie, P.; Cannizzo, J.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C.; Carbognani, F.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande Mottin, E.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, R.; Cook, D.; Corbitt, T. R.; Corda, C.; Cornish, N.; Corsi, A.; Costa, C. A.; Coulon, J. P.; Coward, D.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; D'Antonio, S.; Danzmann, K.; Dari, A.; Das, K.; Dattilo, V.; Daudert, B.; Davier, M.; Davies, G.; Davis, A.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; DeBra, D.; Degallaix, J.; del Prete, M.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Devanka, P.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Emilio, M. Di Paolo; Di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Dorsher, S.; Douglas, E. S. D.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Dueck, J.; Dumas, J. C.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Engel, R.; Etzel, T.; Evans, M.; Evans, T.; Fafone, V.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Flaminio, R.; Flanigan, M.; Flasch, K.; Foley, S.; Forrest, C.; Forsi, E.; Fotopoulos, N.; Fournier, J. D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gammaitoni, L.; Garofoli, J. A.; Garufi, F.; Gemme, G.; Genin, E.; Gennai, A.; Gholami, I.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gill, C.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hall, P.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Heefner, J.; Heitmann, H.; Hello, P.; Heng, I. S.; Heptonstall, A.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Howell, E.; Hoyland, D.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Jaranowski, P.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, C.; Kim, H.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kowalska, I.; Kozak, D.; Krause, T.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Królak, A.; Kuehn, G.; Kullman, J.; Kumar, R.; Kwee, P.; Landry, M.; Lang, M.; Lantz, B.; Lastzka, N.; Lazzarini, A.; Leaci, P.; Leong, J.; Leonor, I.; Leroy, N.; Letendre, N.; Li, J.; Li, T. G. F.; Lin, H.; Lindquist, P. E.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lu, P.; Luan, J.; Lubiński, M.; Lucianetti, A.; Lück, H.; Lundgren, A.; Machenschalk, B.; MacInnis, M.; Mackowski, J. M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Mak, C.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIvor, G.; McKechan, D. J. A.; Meadors, G.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menéndez, D. F.; Mercer, R. A.; Merill, L.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mino, Y.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moraru, D.; Moreau, J.; Moreno, G.; Morgado, N.; Morgia, A.; Morioka, T.; Mors, K.; Mosca, S.; Moscatelli, V.; Mossavi, K.; Mours, B.; MowLowry, C.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murray, P. G.; Nash, T.; Nawrodt, R.; Nelson, J.; Neri, I.; Newton, G.; Nishizawa, A.; Nocera, F.; Nolting, D.; Ochsner, E.; O'Dell, J.; Ogin, G. H.; Oldenburg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Pardi, S.; Pareja, M.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pedraza, M.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Persichetti, G.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Postiglione, F.; Prato, M.; Predoi, V.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabaste, O.; Rabeling, D. S.; Radke, T.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, P.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Röver, C.; Rogstad, S.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sakata, S.; Sakosky, M.; Salemi, F.; Sammut, L.; Sancho de la Jordana, L.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Santostasi, G.; Saraf, S.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Satterthwaite, M.; Saulson, P. R.; Savage, R.; Schilling, R.; Schnabel, R.; Schofield, R.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Somiya, K.; Sorazu, B.; Speirits, F. C.; Stein, A. J.; Stein, L. C.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Trummer, J.; Tseng, K.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vaishnav, B.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A.; Vinet, J.-Y.; Vocca, H.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Wanner, A.; Ward, R. L.; Was, M.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, L.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yeaton-Massey, D.; Yoshida, S.; Yu, P. P.; Yvert, M.; Zanolin, M.; Zhang, L.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

2010-09-01

We present an up-to-date, comprehensive summary of the rates for all types of compact binary coalescence sources detectable by the initial and advanced versions of the ground-based gravitational-wave detectors LIGO and Virgo. Astrophysical estimates for compact-binary coalescence rates depend on a number of assumptions and unknown model parameters and are still uncertain. The most confident among these estimates are the rate predictions for coalescing binary neutron stars which are based on extrapolations from observed binary pulsars in our galaxy. These yield a likely coalescence rate of 100 Myr-1 per Milky Way Equivalent Galaxy (MWEG), although the rate could plausibly range from 1 Myr-1 MWEG-1 to 1000 Myr-1 MWEG-1 (Kalogera et al 2004 Astrophys. J. 601 L179; Kalogera et al 2004 Astrophys. J. 614 L137 (erratum)). We convert coalescence rates into detection rates based on data from the LIGO S5 and Virgo VSR2 science runs and projected sensitivities for our advanced detectors. Using the detector sensitivities derived from these data, we find a likely detection rate of 0.02 per year for Initial LIGO-Virgo interferometers, with a plausible range between 2 × 10-4 and 0.2 per year. The likely binary neutron-star detection rate for the Advanced LIGO-Virgo network increases to 40 events per year, with a range between 0.4 and 400 per year.

A Semi-analytical Model for Wind-fed Black Hole High-mass X-Ray Binaries: State Transition Triggered by Magnetic Fields from the Companion Star

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yaji, Kentaro; Yamada, Shinya; Masai, Kuniaki

We propose a mechanism of state transition in wind-fed black hole (BH) binaries (high-mass X-ray binaries) such as Cyg X-1 and LMC X-1. Modeling a line-driven stellar wind from the companion by two-dimensional hydrodynamical calculations, we investigate the processes of wind capture by, and accretion onto, the BH. We assume that the wind acceleration is terminated at the He ii ionization front because ions responsible for line-driven acceleration are ionized within the front, i.e., the He iii region. It is found that the mass accretion rate inferred from the luminosity is remarkably smaller than the capture rate. Considering the difference,more » we construct a model for the state transition based on the accretion flow being controlled by magnetorotational instability. The outer flow is torus-like, and plays an important role to trigger the transition. The model can explain why state transition does occur in Cyg X-1, while not in LMC X-1. Cyg X-1 exhibits a relatively low luminosity, and then the He ii ionization front is located and can move between the companion and BH, depending on its ionizing photon flux. On the other hand, LMC X-1 exhibits too high luminosity for the front to move considerably; the front is too close to the companion atmosphere. The model also predicts that each state of high-soft or low-hard would last fairly long because the luminosity depends weakly on the wind velocity. In the context of the model, the state transition is triggered by a fluctuation of the magnetic field when its amplitude becomes comparable to the field strength in the torus-like outer flow.« less

A Study of Magnesium-Base Metallic Systems and Development of Principles for Creation of Corrosion-Resistant Magnesium Alloys

NASA Astrophysics Data System (ADS)

Mukhina, I. Yu.

2014-11-01

The effect of 26 alloying elements on the corrosion resistance of high-purity magnesium in a 0.5-n solution of sodium chloride and in a humid atmosphere (0.005 n) is studied. The Mg - Li, Mg - Ag, Mg - Zn, Mg - Cu, Mg - Gd, Mg - Al, Mg - Zr, Mg - Mn and other binary systems, which present interest as a base for commercial or perspective castable magnesium alloys, are studied. The characteristics of corrosion resistance of the binary alloys are analyzed in accordance with the group and period of the Mendeleev's periodic law. The roles of the electrochemical and volume factors and of the factor of the valence of the dissolved element are determined.

VizieR Online Data Catalog: Parameters of 529 Kepler eclipsing binaries (Kjurkchieva+, 2017)

NASA Astrophysics Data System (ADS)

Kjurkchieva, D.; Vasileva, D.; Atanasova, T.

2017-11-01

We reviewed the Kepler eclipsing binary catalog (Prsa et al. 2011, Cat. J/AJ/141/83; Slawson et al. 2011, Cat. J/AJ/142/160; Matijevic et al. 2012) to search for detached eclipsing binaries with eccentric orbits. (5 data files).

Ab initio studies on the adsorption and implantation of Al and Fe to nitride materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riedl, H., E-mail: helmut.riedl@tuwien.ac.at; Zálešák, J.; Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben

2015-09-28

The formation of transfer material products on coated cutting and forming tools is a major failure mechanism leading to various sorts of wear. To describe the atomistic processes behind the formation of transfer materials, we use ab initio to study the adsorption energy as well as the implantation barrier of Al and Fe atoms for (001)-oriented surfaces of TiN, Ti{sub 0.50}Al{sub 0.50}N, Ti{sub 0.90}Si{sub 0.10}N, CrN, and Cr{sub 0.90}Si{sub 0.10}N. The interactions between additional atoms and nitride-surfaces are described for pure adhesion, considering no additional stresses, and for the implantation barrier. The latter, we simplified to the stress required tomore » implant Al and Fe into sub-surface regions of the nitride material. The adsorption energies exhibit pronounced extrema at high-symmetry positions and are generally highest at nitrogen sites. Here, the binary nitrides are comparable to their ternary counterparts and the average adhesive energy is higher (more negative) on CrN than TiN based systems. Contrary, the implantation barrier for Al and Fe atoms is higher for the ternary systems Ti{sub 0.50}Al{sub 0.50}N, Ti{sub 0.90}Si{sub 0.10}N, and Cr{sub 0.90}Si{sub 0.10}N than for their binary counterparts TiN and CrN. Based on our results, we can conclude that TiN based systems outperform CrN based systems with respect to pure adhesion, while the Si-containing ternaries exhibit higher implantation barriers for Al and Fe atoms. The data obtained are important to understand the atomistic interaction of metal atoms with nitride-based materials, which is valid not just for machining operations but also for any combination such as interfaces between coatings and substrates or multilayer and phase arrangements themselves.« less

First-principles-based kinetic Monte Carlo studies of diffusion of hydrogen in Ni–Al and Ni–Fe binary alloys

DOE PAGES

Tafen, De Nyago

2015-02-14

The diffusion of dilute hydrogen in fcc Ni–Al and Ni–Fe binary alloys was examined using kinetic Monte Carlo method with input kinetic parameters obtained from first-principles density functional theory. The simulation involves the implementation of computationally efficient energy barrier model that describes the configuration dependence of the hydrogen hopping. The predicted hydrogen diffusion coefficients in Ni and Ni 89.4Fe 10.6 are compared well with the available experimental data. In Ni–Al, the model predicts lower hydrogen diffusivity compared to that in Ni. Overall, diffusion prefactors and the effective activation energies of H in Ni–Fe and Ni–Al are concentration dependent of themore » alloying element. Furthermore, the changes in their values are the results of the short-range order (nearest-neighbor) effect on the interstitial diffusion of hydrogen in fcc Ni-based alloys.« less

An X-ray look at the first head-trail nebula in an X-ray binary

NASA Astrophysics Data System (ADS)

Soleri, Paolo

2011-09-01

Head-tail trails are a common feature in active galactic nuclei and pulsar bow-shocks. Heinz et al. (2008) suggested that also X-ray binaries, being jet sources moving with high velocities in dense media, can leave trails of highly ionized plasma that should be detectable at radio frequencies. During bservations of faint-persistent X-ray binaries, we discovered an optical nebula around the X-ray binary SAX J1712.6-3739, consisting of a bow-shock ring-like nebula in front of the binary and two trails originating close to it. This is the first detection of such structure in a X-ray binary and it opens a new sub-field in the study of these objects. Observations with XMM-Newton and Chandra are now needed to investigate the properties of the surrounding nebula.

An X-ray look at the first head-trail nebula in an X-ray binary

NASA Astrophysics Data System (ADS)

Soleri, Paolo

2010-10-01

Head-tail trails are a common feature in active galactic nuclei and pulsar bow-shocks. Heinz et al. (2008) suggested that also X-ray binaries, being jet sources moving with high velocities in dense media, can leave trails of highly ionized plasma that should be detectable at radio frequencies. During observations of faint-persistent X-ray binaries, we discovered an optical nebula around the X-ray binary SAX J1712.6-3739, consisting of a bow-shock ring-like nebula ``in front'' of the binary and two trails originating close to it. This is the first detection of such structure in a X-ray binary and it opens a new sub-field in the study of these objects. Observations with XMM-Newton and Chandra are now needed to investigate the properties of the surrounding nebula.

Nominal vs. actual supersaturation of solutions

NASA Astrophysics Data System (ADS)

Borisenko, Alexander

2018-03-01

Following the formalism of the Classical Nucleation Theory beyond the dilute solution approximation, this paper considers a difference between the actual solute supersaturation (given by the present-to-saturated solute activity ratio) and the nominal supersaturation (given by the present-to-saturated solute concentration ratio) due to formation of subcritical transient solute clusters, called heterophase fluctuations. Based on their distribution function, we introduce an algebraic equation of supersaturation that couples the nominal supersaturation of a binary metastable solution with its actual supersaturation and a function of the specific interface energy and temperature. The applicability of this approach is validated by comparison to simulation data [(Clouet et al., Phys. Rev. B 69, 064109 (2004)] on nucleation of Al3Zr and Al3Sc in model binary Al alloys.

Evidence for Unresolved Exoplanet-hosting Binaries in Gaia DR2

NASA Astrophysics Data System (ADS)

Evans, Daniel F.

2018-05-01

This note describes an effort to detect additional stellar sources in known transiting exoplanet (TEP) systems, which are unresolved or barely resolved in the Gaia Data Release 2 (DR2) catalogue. The presence of multiple unresolved stars in photometric and spectroscopic observations of a transiting planetary system biases measurements of the planet's radius, mass, and atmospheric conditions. In addition to the effect on individual planetary systems, the presence of unresolved stars across the sample of known exoplanets biases our overall understanding of planetary systems, due to the systematic underestimation of both masses and radii. This work uses the Astrometric Goodness of Fit in the Along-Scan direction (GOF_AL) and the Astrometric Excess Noise as indicators of poorly-resolved binaries. Many known close binaries in the exoplanet host star sample have highly significant GOF_AL and Astrometric Excess Noise values, such as WASP-20AB with Astrometric Excess Noise significant at $4720\\sigma$ and GOF_AL=124.

Multi-Bit Quantum Private Query

NASA Astrophysics Data System (ADS)

Shi, Wei-Xu; Liu, Xing-Tong; Wang, Jian; Tang, Chao-Jing

2015-09-01

Most of the existing Quantum Private Queries (QPQ) protocols provide only single-bit queries service, thus have to be repeated several times when more bits are retrieved. Wei et al.'s scheme for block queries requires a high-dimension quantum key distribution system to sustain, which is still restricted in the laboratory. Here, based on Markus Jakobi et al.'s single-bit QPQ protocol, we propose a multi-bit quantum private query protocol, in which the user can get access to several bits within one single query. We also extend the proposed protocol to block queries, using a binary matrix to guard database security. Analysis in this paper shows that our protocol has better communication complexity, implementability and can achieve a considerable level of security.

The Orbital Parameters and Nature of the X-ray Pulsar IGR J16393-4643 Using Pulse Timing Analysis

NASA Astrophysics Data System (ADS)

Pearlman, Aaron B.; Corbet, R. H. D.; Pottschmidt, K.; Skinner, G. K.

2011-09-01

A 3.7 day orbital period was previously suggested for the 910 s X-ray pulsar IGR J16393-4643 from a pulse timing study of widely separated X-ray observations (Thompson et al., 2006), placing the system in the supergiant wind-fed region of the Ppulse-Porb diagram. However, orbital periods of 50.2 and 8.1 days could not be excluded. Nespoli et al. (2010) refute this wind-accreting high-mass X-ray binary classification and suggest a symbiotic X-ray binary (SyXB) designation based on infrared spectroscopy of the proposed counterpart and the potential 50.2 day orbital solution. SyXBs are low-mass X-ray binaries in which a neutron star accretes from the inhomogeneous medium around an M-type giant companion. We find that two statistically independent light curves of IGR J16393-4643, from the Swift Burst Alert Telescope (15-50 keV) and the Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) Galactic bulge scans (2-10 keV), show highly significant orbital modulation near 4.24 days. Making use of this precise orbital period, we present the results from pulse arrival time analysis on IGR J16393-4643 using RXTE PCA observations. We provide significantly improved phase-connected pulse timing results using archival observations presented in Thompson et al. (2006) and additional pulse timing data not included in their study to determine the orbital parameters of the system. The derived 7.5 M⊙ mass function is inconsistent with a SyXB identification.

The Interface Structure of High-Temperature Oxidation-Resistant Aluminum-Based Coatings on Titanium Billet Surface

NASA Astrophysics Data System (ADS)

Xu, Zhefeng; Rong, Ju; Yu, Xiaohua; Kun, Meng; Zhan, Zhaolin; Wang, Xiao; Zhang, Yannan

2017-10-01

A new type of high-temperature oxidation-resistant aluminum-based coating, on a titanium billet surface, was fabricated by the cold spray method, at a high temperature of 1050°C, for 8 h, under atmospheric pressure. The microstructure of the exposed surface was analyzed via optical microscopy, the microstructure of the coating and elemental diffusion was analyzed via field emission scanning electron microscopy, and the interfacial phases were identified via x-ray diffraction. The Ti-Al binary phase diagram and Gibbs free energy of the stable phase were calculated by Thermo-calc. The results revealed that good oxidation resistant 50-μm-thick coatings were successfully obtained after 8 h at 1050°C. Two layers were obtained after the coating process: an Al2O3 oxidation layer and a TiAl3 transition layer on the Ti-based substrate. The large and brittle Al2O3 grains on the surface, which can be easily spalled off from the surface after thermal processing, protected the substrate against oxidation during processing. In addition, the thermodynamic calculation results were in good agreement with the experimental data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Pei; Fang, Z. Zak; Koopman, Mark

Hydrogen has been investigated for decades as a temporary alloying element to refine the microstructure of Ti-6Al-4V, and is now being used in a novel powder metallurgy method known as "hydrogen sintering and phase transformation". Pseudo-binary phase diagrams of (Ti-6Al-4V)-xH have been studied and developed, but are not well established due to methodological limitations. In this paper, in situ studies of phase transformations during hydrogenation and dehydrogenation of (Ti-6Al-4V)-xH alloys were conducted using high-energy synchrotron X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The eutectoid phase transformation of β ↔ α + δ was observed in themore » (Ti-6Al-4V)-xH alloy via in situ synchrotron XRD at 211 °C with a hydrogen concentration of 37.5 at.% (measured using TGA-DSC). The relationships of hydrogen composition to partial pressure and temperature were investigated in the temperature range 450-900°C. Based on these results, a partial pseudo-binary phase diagram of (Ti-6Al-4V)-xH is proposed for hydrogen compositions up to 60 at.% in the temperature range 100-900°C. Using the data collected in real time under controlled parameters of temperature, composition and hydrogen partial pressure, this work characterizes relevant phase transformations and microstructural evolution for practical titanium-hydrogen technologies of Ti-6Al-4V.« less

Static and vibrational properties of equiatomic Na-based binary alloys

NASA Astrophysics Data System (ADS)

Vora, Aditya M.

2007-09-01

The computations of the static and vibrational properties of four equiatomic Na-based binary alloys viz. Na0.5Li0.5, Na0.5K0.5, Na0.5Rb0.5 and Na0.5Cs0.5, to second order in local model potential is discussed in terms of real-space sum of Born von Karman central force constants. The local field correlation functions due to Hartree (H), Ichimaru Utsumi (IU) and Sarkar et al. (S) are used to investigate the influence of the screening effects on the aforesaid properties. Results for the lattice constants C11, C12, C44, C12 C44, C12/C44 and bulk modulus B obtained using the H-local field correction function have higher values in comparison with the results obtained for the same properties using IU- and S-local field correction functions. The results for the Shear modulus (C‧), deviation from Cauchy's relation, Poisson's ratio σ, Young modulus Y, propagation velocity of elastic waves, phonon dispersion curves and degree of anisotropy A are highly appreciable for the four equiatomic Na-based binary alloys.

BRITE-Constellation reveals evidence for pulsations in the enigmatic binary η Carinae

NASA Astrophysics Data System (ADS)

Richardson, Noel D.; Pablo, Herbert; Sterken, Christiaan; Pigulski, Andrzej; Koenigsberger, Gloria; Moffat, Anthony F. J.; Madura, Thomas I.; Hamaguchi, Kenji; Corcoran, Michael F.; Damineli, Augusto; Gull, Theodore R.; Hillier, D. John; Weigelt, Gerd; Handler, Gerald; Popowicz, Adam; Wade, Gregg A.; Weiss, Werner W.; Zwintz, Konstanze

2018-04-01

η Car is a massive, eccentric binary with a rich observational history. We obtained the first high-cadence, high-precision light curves with the BRITE-Constellation nanosatellites over 6 months in 2016 and 6 months in 2017. The light curve is contaminated by several sources including the Homunculus nebula and neighbouring stars, including the eclipsing binary CPD -59°2628. However, we found two coherent oscillations in the light curve. These may represent pulsations that are not yet understood but we postulate that they are related to tidally excited oscillations of η Car's primary star, and would be similar to those detected in lower mass eccentric binaries. In particular, one frequency was previously detected by van Genderen et al. and Sterken et al. through the time period of 1974-1995 through timing measurements of photometric maxima. Thus, this frequency seems to have been detected for nearly four decades, indicating that it has been stable in frequency over this time span. These pulsations could help provide the first direct constraints on the fundamental parameters of the primary star if confirmed and refined with future observations.

Hard X-Ray Lightcurves of High Mass X-Ray Binaries

NASA Technical Reports Server (NTRS)

Laycock, S.; Coe, M. J.; Harmon, B. A.; Finger, M.; Wilson-Hodge, C.; Rose, M. Franklin (Technical Monitor)

2001-01-01

Using the 7.2 years of continuous data now available from the Burst And Transient Source Experiment (BATSE) aboard CGRO, we have measured orbital periods and produced folded lightcurves for 8 High Mass X-ray Binaries (HMXB). Given the length of the datasets, our determinations are based on many more binary orbits than previous investigations. Thus our source detections have high statistical significance and we are able to follow long-term trends in X-ray output. In particular we focus on two systems: A0538-668 and EXO2030+375 both HMXBs exhibiting Type I outbursts. Recent work on A0538-668 (Alcock et al 1999) reported a 16.65d optical variability due to the orbital period, but only seen during minima of a longer-term variability at 421d. We searched for this signal in the BATSE dataset using an ephemeris derived from Alcock et al ( 1999) & Skinner ( 1982). We found no evidence for such modulation and place an upper limit of 3.0 x 10(exp -3) photon/sq cm.s in the 20-70 keV BATSE energy band , based upon statistical modelling of the signal. EXO2030+375 has exhibited an X-ray active epoch, followed by a quiescent period lasting 2.5yr and since April 1996 has exhibited renewed activity. Previous observations (Reig et a 1998) using RXTE ASM data indicate secondary outbursts occur at apastron passage during the current epoch, but not in the former. We present a lightcurve for the earlier epoch showing convincing evidence for such apastron outbursts. We find apastron outbursts in 3 sources, all having orbital periods greater than 41d. No such signal is conclusively detected in the more rapidly orbiting systems studied.

30+ New & Known SB2s in the SDSS-III/APOGEE M Dwarf Ancillary Science Project Sample

NASA Astrophysics Data System (ADS)

Skinner, Jacob; Covey, Kevin; Bender, Chad; De Lee, Nathan Michael; Chojnowski, Drew; Troup, Nicholas; Badenes, Carles; Mahadevan, Suvrath; Terrien, Ryan

2018-01-01

Close stellar binaries can drive dynamical interactions that affect the structure and evolution of planetary systems. Binary surveys indicate that the multiplicity fraction and typical orbital separation decrease with primary mass, but correlations with higher order architectural parameters such as the system's mass ratio are less well constrained. We seek to identify and characterize double-lined spectroscopic binaries (SB2s) among the 1350 M dwarf ancillary science targets with APOGEE spectra in the SDSS-III Data Release 13. We quantitatively measure the degree of asymmetry in the APOGEE pipeline cross-correlation functions (CCFs), and use those metrics to identify a sample of 44 high-likelihood candidate SB2s. Extracting radial velocities (RVs) for both binary components from the CCF, we then measure mass ratios for 31 SB2s; we also use Bayesian techniques to fit orbits for 4 systems with 8 or more distinct APOGEE observations. The (incomplete) mass ratio distribution of this sample rises quickly towards unity. Two-sided Kolmogorov-Smirnov (K-S) tests find probabilities of 13.8% and 14.2% that the M dwarf mass ratio distribution is consistent with those measured by Pourbaix et al. (2004) and Fernandez et al. (2017), respectively. The samples analyzed by Pourbaix et al. and Fernandez et al. are dominated by higher-mass solar type stars; this suggests that the mass ratio distribution of close binaries is not strongly dependent on primary mass.

Phase-field modelling of β(Ti) solidification in Ti-45at.%Al: columnar dendrite growth at various gravity levels

NASA Astrophysics Data System (ADS)

Viardin, A.; Berger, R.; Sturz, L.; Apel, M.; Hecht, U.

2016-03-01

The effect of solutal convection on the solidification of γ titanium aluminides, specifically on β(Ti) dendrite growth, is not well known. With the aim of supporting directional solidification experiments under hyper-gravity using a large diameter centrifuge, 2D-phase field simulations of β(Ti) dendrite growth have been performed for the binary alloy Ti-45at.%Al and various gravity scenarios. Both, the direction and magnitude of the gravity vector were varied systematically in order to reveal the subtle interplay between the convective flow pattern and mushy zone characteristics. In this presentation, gravity effects are discussed for early dendrite growth. For selected cases the evolution on longer timescales is also analyse of and oscillatory modes leading to dynamically stable steady state growth are outlined. In a dedicated simulation series forced flow is superimposed, as to mimic thermally driven fluid flow expected to establish on the macroscopic scale (sample size) in the centrifugal experiments. Above a certain threshold this flow turns dominant and precludes solutally driven convective effects.

[delta] precipitation in an Al-Li-Cu-Mg-Zr alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prasad, K.S.; Mukhopadhyay, A.K.; Gokhale, A.A.

1994-05-15

AlLi based [delta] phase has an NaTl structure (i.e., a diamond cubic) with a = 0.637nm and is an equilibrium phase in the binary Al-Li system. In heat treated binary Al-Li alloys of appropriate compositions, [delta] phase can format grain boundaries as well as within the grains. In commercially heat treated Al-Li-Cu alloys of 2090 specification, the grain boundary precipitate [delta] of the binary Al-Li system is replaced by a combination of T[sub 2](Al[sub 6]CuLi[sub 3]), R(Al[sub 5]CuLi[sub 3]) and T[sub 1](Al[sub 2]CuLi) phases. In similarly treated Al-Li-Cu-Mg alloys of 8090 specification, the copper rich T[sub 2] phase, present inmore » the form of Al[sub 6]CuLi[sub 3[minus]x]Mg[sub x], is known to be the major coarse g.b. precipitate. The presence of an Al-Li-Cu-Mg based C phase at the grain boundaries of the commercially heat treated 8090 alloys has also been documented. No detailed study has yet been carried out to verify whether the [delta] phase can be present at the grain boundaries of the commercially heat treated 8090 alloys. Given the correlations between the g.b. phase morphology, g.b. phase chemistry, and the stress corrosion cracking resistance of these alloys, it is important that the g.b. precipitates be examined and identified. In this paper results using TEM are presented to show that the [delta] phase can be present in varying amounts at the grain boundaries in an 8090 alloy when heat treated in the temperature range of 170--350 C. An examination is also made of the [delta] precipitation within the grain to establish that the T[sub 2]/[alpha]-Al interface is the dominant nucleation site for the noncoherent [delta] phase.« less

Chandra Discovery of a Binary Active Galactic Nucleus in Mrk 739

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, Richard; Treister, Ezequiel; Veilleux, Sylvain; Vasudevan, Ranjan; Miller, Neal; Sanders, D. B.; Schawinski, Kevin; Trippe, Margaret

2011-07-01

We have discovered a binary active galactic nucleus (AGN) in the galaxy Mrk 739 using Chandra and Swift BAT. We find two luminous (L 2-10 keV = 1.1 × 1043 and 1.0 × 1042 erg s-1), unresolved nuclei with a projected separation of 3.4 kpc (5farcs8 ± 0farcs1) coincident with two bulge components in the optical image. The western X-ray source (Mrk 739W) is highly variable (× 2.5) during the 4 hr Chandra observation and has a very hard spectrum consistent with an AGN. While the eastern component was already known to be an AGN based on the presence of broad optical recombination lines, Mrk 739W shows no evidence of being an AGN in optical, UV, and radio observations, suggesting the critical importance of high spatial resolution hard X-ray observations (>2 keV) in finding these binary AGNs. A high level of star formation combined with a very low L [O III]/L 2-10 keV ratio cause the AGN to be missed in optical observations. 12CO observations of the (3-2) and (2-1) lines indicate large amounts of molecular gas in the system that could be driven toward the black holes during the violent galaxy collision and be key to fueling the binary AGN. Mrk 739E has a high Eddington ratio of 0.71 and a small black hole (log M BH = 7.05 ± 0.3) consistent with an efficiently accreting AGN. Other than NGC 6240, this stands as the nearest case of a binary AGN discovered to date.

Radial-velocity measures and the existence of astrophysical binaries in late-type dwarf stars

NASA Technical Reports Server (NTRS)

Bopp, B. W.; Meredith, R.

1986-01-01

Radial velocities with errors of 1-2 km/s are presented based on CCD scans obtained with the Kitt Peak National Observatory coude feed telescope between 1982 and 1985 of 48 dK-M stars that lack Balmer emission. Comparison with Gliese's (1969) values shows only two stars to be spectroscopic binary candidates with small velocity amplitudes. No evidence for any short period (less than 10 days) binaries is found, supporting the conclusions of Young et al. (1986) that there are no astrophysical binaries among these chromosherically inactive dM stars.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

DOE PAGES

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.; ...

2017-11-26

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300–360 °C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N 2 gas. Lastly, results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300–360 °C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N 2 gas. Lastly, results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300-360°C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N2 gas. Results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

Shapes and binary fractions of Jovian Trojans and Hildas through NEOWISE

NASA Astrophysics Data System (ADS)

Sonnett, S.; Mainzer, A.; Grav, T.; Bauer, J.; Masiero, J.; Stevenson, R.; Nugent, C.

2014-07-01

Jovian Trojans (hereafter, Trojans) and Hildas are indicative of planetary migration patterns since their capture and physical state must be explained by dynamical evolution models. Early models of minimal planetary migration necessitate that Trojans were dynamically captured from the giant planet region (e.g., Marzari & Scholl 1998). The Nice model instead suggests that Trojans were injected from the outer solar system during a period of significant giant planet migration (e.g., Morbidelli et al. 2005). A more recent version of the Nice model suggests that asymmetric scatterings and collisions would have taken place, producing dissimilar L4 and L5 clouds (Nesvorny et al. 2013). Each of these formation scenarios predicts a different origin and/or collisional evolution for Trojans, which can be inferred from rotation properties. Namely, the physical shape as a function of size helps determine the degree of collisional processing (Farinella et al. 1992). Also, the binary fraction as a function of separation between the two components can be used to determine the dominant binary formation mechanism and thus helps characterize the dynamical environment (e.g., Kern & Elliot 2006). Rotational variation usually corresponds to elongated shapes, but high amplitudes (> 0.9 magnitudes; Sheppard & Jewitt 2004) can only be explained by close or contact binaries. Therefore, rotational lightcurves can be used to infer both shape and the presence of a close companion. Motivated by the need for more observational constraints on solar system formation models and a poor understanding of the rotation properties and binary fraction of Trojans and Hildas, we are studying their rotational lightcurve amplitudes using infrared photometry from NEOWISE (Mainzer et al. 2011; Grav et al. 2011) in order to determine debiased rotational lightcurve amplitude distributions for various Trojan subpopulations and for Trojans compared to Hildas. Preliminary amplitude distributions show a large fraction of potential close or contact binaries (having Δ m > 0.9). These distributions can be used to constrain the collisional and dynamical history of solar system formation models.

Radar evidence for diverse shapes of the primaries among binary near-Earth asteroids

NASA Astrophysics Data System (ADS)

Brozovic, Marina; Benner, Lance; Ford, Thomas; Springmann, Alessondra; Taylor, Patrick; Shepard, Michael; Margot, Jean-Luc; Naidu, Shantanu; Nolan, Michael; Howell, Ellen; Busch, Michael; Giorgini, Jon; Magri, Christopher

2014-11-01

The Arecibo and Goldstone planetary radars have been exceptionally valuable instruments for the discovery of binary and triple asteroids in the near-Earth asteroid (NEA) population. To date, 34 out of 46 known binaries and two ternaries 71% objects total) have been discovered by radar. One of the first discovered and most well studied binary systems is (66391) 1999 KW4 (Ostro et al., 2006). This was the first system with radar evidence for a prominent equatorial bulge, sloped hemispheres, and polar flattening. 1999 KW4 Alpha became a “canonical shape model” for many theoretical studies and numerical simulations on the nature of the binary systems. As the number of binaries detected by radar grew, evidence mounted that not all primaries look like 1999 KW4 Alpha. In fact, (276049) 2002 CE26 (Shepard et al., 2006) and (285263) 1998 QE2 (Springmann et al., 2014) have very rounded shapes without an obvious presence of equatorial ridges. Furthermore, (164121) 2003 YT1 (Nolan et al., in prep.), (1862) Apollo (Ford et al., in prep.), and (363599) 2006 VV2 all have irregular, moderately elongated shapes that show the presence of a bulge at only selected longitudes. All three objects also show elongations of 1.2-1.3, which is still smaller than the mean elongation of ~1.5 in the NEA radar sample. Nevertheless, numerous other primaries have KW4-like shapes such as (185851) 2000 DP107 (Naidu et al., 2011), (311066) 2004 DC (Taylor et al, 2008), and (175706) 1996 FG3 (Benner et al., in prep.). We estimate the abundance of KW4-like objects to be at least 40% of the multiple system population, based on the 41 radar-detected cases. Our results only give the lower bound because not all the dataset have the sufficient SNRs and/or the rotational coverage. Recent Goldstone delay-Doppler images of 2013 WT44 were obtained at nearly pole-on subradar latitude and clearly show evidence of an equatorial bulge, sloped hemispheres, and polar flattening. This has provided one of the strongest arguments to date that KW4-like shapes are real and that they are not artifacts of the shape modeling algorithms. This does not come as a surprise given that KW4-like shapes are strongly motivated by the physics of the rapidly rotating rubble pile.

Tidal tearing of circumstellar disks in Be/X-ray and gamma-ray binaries

NASA Astrophysics Data System (ADS)

Okazaki, Atsuo T.

2017-11-01

About one half of high-mass X-ray binaries host a Be star [an OB star with a viscous decretion (slowly outflowing) disk]. These Be/X-ray binaries exhibit two types of X-ray outbursts (Stella et al. 1986), normal X-ray outbursts (L X~1036-37 erg s-1) and occasional giant X-ray outbursts (L X > 1037 erg s-1). The origin of giant X-ray outbursts is unknown. On the other hand, a half of gamma-ray binaries have a Be star as the optical counterpart. One of these systems [LS I +61 303 (P orb = 26.5 d)] shows the superorbital (1,667 d) modulation in radio through X-ray bands. No consensus has been obtained for its origin. In this paper, we study a possibility that both phenomena are caused by a long-term, cyclic evolution of a highly misaligned Be disk under the influence of a compact object, by performing 3D hydrodynamic simulations. We find that the Be disk cyclically evolves in mildly eccentric, short-period systems. Each cycle consists of the following stages: 1) As the Be disk grows with time, the initially circular disk becomes eccentric by the Kozai-Lidov mechanism. 2) At some point, the disk is tidally torn off near the base and starts precession. 3) Due to precession, a gap opens between the disk base and mass ejection region, which allows the formation of a new disk in the stellar equatorial plane (see Figure 1). 4) The newly formed disk finally replaces the precessing old disk. Such a cyclic disk evolution has interesting implications for the long-term behavior of high energy emission in Be/X-ray and gamma-ray binaries.

Commission 42: Close Binary Stars

NASA Astrophysics Data System (ADS)

Rucinski, Slavek M.; Ribas, Ignasi; Giménez, Alvaro; Harmanec, Petr; Hilditch, Ronald W.; Kaluzny, Janusz; Niarchos, Panayiotis; Nordström, Birgitta; Oláh, Katalin; Richards, Mercedes T.; Scarfe, Colin D.; Sion, Edward M.; Torres, Guillermo; Vrielmann, Sonja

Two meetings of interest to close binaries took place during the reporting period: A full day session on short-period binary stars mostly CV's (Milone et al. 2008) during the 2006 AAS Spring meeting in Calgary and the very broadly designed IAU Symposium No. 240 on Binary Stars as Critical Tools and Tests in Contemporary Astrophysics in Prague, 2006, with many papers on close binaries [Hartkopf et al. 2007]. In addition, the book by Eggleton (2006), which is a comprehensive summary of evolutionary processes in binary and multiple stars, was published.

Characterisation of phases in nanostructured, multilayered titanium alloys by analytical and high-resolution electron microscopy.

PubMed

Czyrska-Filemonowicz, A; Buffat, P A

2009-01-01

Surface processing of a Ti-6Al-4V alloy led to a complex multilayered microstructure containing several phases of the Ni-Ti-P-Al-O system, which improves the mechanical and tribological surface properties. The microstructure, chemical and phase compositions of the hard layer formed on the surface were investigated by LM, XRD, SEM as well as analytical/high-resolution TEM, STEM, EDS, electron diffraction and FIB. Phase identification based on electron diffraction, HRTEM and EDS microanalysis revealed the presence of several binary and ternary phases in the system Ti-Ni-P, sometimes with partial substitution of Ti by Al. However some phases, mainly nanoparticles, still remain not identified satisfactorily. Electron microscopy techniques used for identification of phases present in surface multilayers and some practical limits to their routine application are reminded here.

Using Blue Stragglers to Predict Retained Black Hole Population in Globular Clusters

NASA Astrophysics Data System (ADS)

Hermanek, Keith; Chatterjee, Sourav; Rasio, Frederic

2018-01-01

Large numbers of black holes (BHs) are expected to form in massive star clusters typical of the globular clusters (GCs). Sophisticated theoretical models suggest that many of these BHs can be retained in present-day GCs. Observations have also identified several BH candidates in Galactic and extragalactic GCs (e.g., Macarone et al. 2007; Irwin et al. 2010; Strader et al. 2012; Chomiuk et al. 2013; Miller-Jones et al. 2014). It has also been shown that high-mass and high-density clusters such as GCs are efficient factories of merging binary BHs similar to those observed by the LIGO observatories (Abbott et al. 2016a,b,c,d,e; Rodriguez et al. 2016). Understanding the formation rate and properties of binary BHs are dependent on a detailed understanding of how the BHs dynamically evolve within GCs. Nevertheless, directly detecting BHs in GCs is extremely challenging; BHs only in binaries with limited configurations can be directly detected by the detection of gravitational wave, X-ray, or radio emissions. We propose an indirect of inferring the number of undetected retained BHs in a GC by investigating the dynamical effects of a large number of BHs on the production of other tracer populations such as Blue Straggler Stars (BSS). Using a large grid of detailed GC models we show that there is a clear anti-correlation between the number of BSS in a cluster and the number of retained BHs. Being the most massive species, large numbers of retained BHs will dominate the core of the cluster as a result of mass-segregation driving away other low-mass species such as main-sequence stars from central high-density regions. BSS are expected to form from physical collisions between main-sequence (MS) stars mediated by binary encounters (e.g., Chatterjee et al. 2013) in cores of GCs. Production of BSS by collisions or mass transfer channels are suppressed if a large number of retained BHs in a cluster restrict the number of MS stars in the core. Extensive observational data exist on the number and radial distribution of BSS in GCs. Thus, this anti-correlation between the number of retained BHs and the number of BSS, once carefully calibrated by theoretical models, can be used to infer the population of undetected BHs in GCs.

Thermal Disk Winds in X-Ray Binaries: Realistic Heating and Cooling Rates Give Rise to Slow, but Massive, Outflows

NASA Astrophysics Data System (ADS)

Higginbottom, N.; Proga, D.; Knigge, C.; Long, K. S.

2017-02-01

A number of X-ray binaries exhibit clear evidence for the presence of disk winds in the high/soft state. A promising driving mechanism for these outflows is mass loss driven by the thermal expansion of X-ray heated material in the outer disk atmosphere. Higginbottom & Proga recently demonstrated that the properties of thermally driven winds depend critically on the shape of the thermal equilibrium curve, since this determines the thermal stability of the irradiated material. For a given spectral energy distribution, the thermal equilibrium curve depends on an exact balance between the various heating and cooling mechanisms at work. Most previous work on thermally driven disk winds relied on an analytical approximation to these rates. Here, we use the photoionization code cloudy to generate realistic heating and cooling rates which we then use in a 2.5D hydrodynamic model computed in ZEUS to simulate thermal winds in a typical black hole X-ray binary. We find that these heating and cooling rates produce a significantly more complex thermal equilibrium curve, with dramatically different stability properties. The resulting flow, calculated in the optically thin limit, is qualitatively different from flows calculated using approximate analytical rates. Specifically, our thermal disk wind is much denser and slower, with a mass-loss rate that is a factor of two higher and characteristic velocities that are a factor of three lower. The low velocity of the flow—{v}\\max ≃ 200 km s-1—may be difficult to reconcile with observations. However, the high mass-loss rate—15 × the accretion rate—is promising, since it has the potential to destabilize the disk. Thermally driven disk winds may therefore provide a mechanism for state changes.

Physical Structure of Four Symbiotic Binaries

NASA Technical Reports Server (NTRS)

Kenyon, Scott J. (Principal Investigator)

1997-01-01

Disk accretion powers many astronomical objects, including pre-main sequence stars, interacting binary systems, and active galactic nuclei. Unfortunately, models developed to explain the behavior of disks and their surroundings - boundary layers, jets, and winds - lack much predictive power, because the physical mechanism driving disk evolution - the viscosity - is not understood. Observations of many types of accreting systems are needed to constrain the basic physics of disks and provide input for improved models. Symbiotic stars are an attractive laboratory for studying physical phenomena associated with disk accretion. These long period binaries (P(sub orb) approx. 2-3 yr) contain an evolved red giant star, a hot companion, and an ionized nebula. The secondary star usually is a white dwarf accreting material from the wind of its red giant companion. A good example of this type of symbiotic is BF Cygni: our analysis shows that disk accretion powers the nuclear burning shell of the hot white dwarf and also manages to eject material perpendicular to the orbital plane (Mikolajewska, Kenyon, and Mikolajewski 1989). The hot components in other symbiotic binaries appear powered by tidal overflow from a very evolved red giant companion. We recently completed a study of CI Cygni and demonstrated that the accreting secondary is a solar-type main sequence star, rather than a white dwarf (Kenyon et aL 1991). This project continued our study of symbiotic binary systems. Our general plan was to combine archival ultraviolet and optical spectrophotometry with high quality optical radial velocity observations to determine the variation of line and continuum sources as functions of orbital phase. We were very successful in generating orbital solutions and phasing UV+optical spectra for five systems: AG Dra, V443 Her, RW Hya, AG Peg, and AX Per. Summaries of our main results for these systems appear below. A second goal of our project was to consider general models for the outbursts of symbiotic stars, with an emphasis on understanding the differences between disk-driven and nuclear-powered eruptions.

Electrical resistivity of Al-Cu liquid binary alloy

NASA Astrophysics Data System (ADS)

Thakor, P. P.; Patel, J. J.; Sonvane, Y. A.; Jani, A. R.

2013-06-01

Present paper deals with the electrical resistivity (ρ) of liquid Al-Cu binary alloy. To describe electron-ion interaction we have used our parameter free model potential along with Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. To see the influence of exchange and correlation effect, Hartree, Taylor and Sarkar et al local field correlation functions are used. From present results, it is seen that good agreements between present results and experimental data have been achieved. Lastly we conclude that our model potential successfully produces the data of electrical resistivity (ρ) of liquid Al-Cu binary alloy.

First-principles interatomic potentials for transition-metal aluminides. III. Extension to ternary phase diagrams

NASA Astrophysics Data System (ADS)

Widom, Mike; Al-Lehyani, Ibrahim; Moriarty, John A.

2000-08-01

Modeling structural and mechanical properties of intermetallic compounds and alloys requires detailed knowledge of their interatomic interactions. The first two papers of this series [Phys. Rev. B 56, 7905 (1997); 58, 8967 (1998)] derived first-principles interatomic potentials for transition-metal (TM) aluminides using generalized pseudopotential theory (GPT). Those papers focused on binary alloys of aluminum with first-row transition metals and assessed the ability of GPT potentials to reproduce and elucidate the alloy phase diagrams of Al-Co and Al-Ni. This paper addresses the phase diagrams of the binary alloy Al-Cu and the ternary systems Al-Co-Cu and Al-Co-Ni, using GPT pair potentials calculated in the limit of vanishing transition-metal concentration. Despite this highly simplifying approximation, we find rough agreement with the known low-temperature phase diagrams, up to 50% total TM concentration provided the Co fraction is below 25%. Full composition-dependent potentials and many-body interactions would be required to correct deficiencies at higher Co concentration. Outside this troublesome region, the experimentally determined stable and metastable phases all lie on or near the convex hull of a scatter plot of energy versus composition. We verify, qualitatively, reported solubility ranges extending binary alloys into the ternary diagram in both Al-Co-Cu and Al-Co-Ni. Finally, we reproduce previously conjectured transition-metal positions in the decagonal quasicrystal phase.

A study of binary Kuiper belt objects

NASA Astrophysics Data System (ADS)

Kern, Susan Diane

2006-06-01

About 10 5 bodies larger than 100km in diameter (Jewitt 1998) reside in the Kuiper Belt, beyond the orbit of Neptune. Since 1992 observational surveys have discovered over one thousand of these objects, believed to be fossil remnants of events that occurred nearly 4.5 billion years ago. Sixteen of these objects are currently known to be binaries, and many more are expected to be discovered. As part of the Deep Ecliptic Survey (DES) I have helped catalog nearly one third of the known Kuiper Belt object (KBO) population, and used that database for further physical studies. Recovery observations for dynamical studies of newly discovered objects with the Magellan telescopes and a high resolution imager, MagIC, revealed three binaries, 88611 (2001QT297), 2003QY90, and 2005EO304. One binary was found in the discovery observations, 2003UN284. Lightcurve measurements of these, and other non-binary KBOs, were obtained to look for unique rotational characteristics. Eleven of thirty-three objects, excluding the binaries, were found to have measurable variability. One of these objects, 2002GW32 has a particularly large amplitude (> 1 magnitude) of variability, and 2002GP32 has a relatively short (~3.3 hours, single-peaked) lightcurve. Among the binary population all the observed objects showed some level of variation. The secondary of 88611 was fit with a single-peaked period of 5.5±0.02 hours while the primary component appears to be non-variable above the measurement errors (0.05 magnitudes). Neither component appears to be color variable. The components of 2003QY90 are both highly variable yielding single- peaked rotation periods of 3.5±1.1 and 7.2±2.9 hours with amplitudes of 0.34±0.06 and 0.90±0.18 magnitudes, respectively. The rotation periods are comparable to those of other non-binary KBOs although distinct from that of an identified contact binary. Orbits and partial orbits for Kuiper belt binaries (KBBs) show a wide range of eccentricities, and an increasing number of binaries with decreasing binary semi-major axis. These characteristics exclude the formation models proposed by Funato et al. (2003) and Weidenschilling (2002), respectively. Conversely, the formation models of Astakhov et al. (2005) and Goldreich et al. (2002) appear to describe the observations, at least in part. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures

NASA Astrophysics Data System (ADS)

Islam, S. M.; Protasenko, Vladimir; Lee, Kevin; Rouvimov, Sergei; Verma, Jai; Xing, Huili Grace; Jena, Debdeep

2017-08-01

Deep ultraviolet (UV) optical emission below 250 nm (˜5 eV) in semiconductors is traditionally obtained from high aluminum containing AlGaN alloy quantum wells. It is shown here that high-quality epitaxial ultrathin binary GaN quantum disks embedded in an AlN matrix can produce efficient optical emission in the 219-235 nm (˜5.7-5.3 eV) spectral range, far above the bulk bandgap (3.4 eV) of GaN. The quantum confinement energy in these heterostructures is larger than the bandgaps of traditional semiconductors, made possible by the large band offsets. These molecular beam epitaxy-grown extreme quantum-confinement GaN/AlN heterostructures exhibit an internal quantum efficiency of 40% at wavelengths as short as 219 nm. These observations together with the ability to engineer the interband optical matrix elements to control the direction of photon emission in such binary quantum disk active regions offer unique advantages over alloy AlGaN quantum well counterparts for the realization of deep-UV light-emitting diodes and lasers.

Raman studies of nanocomposites catalysts: temperature and pressure effects of CeAl, CeMn and NiAl oxides

NASA Astrophysics Data System (ADS)

da Silva, Antonio N.; Neto, Antonio B. S.; Oliveira, Alcemira C.; Junior, Manoel C.; Junior, Jose A. L.; Freire, Paulo T. C.; Filho, Josué M.; Oliveira, Alcineia C.; Lang, Rossano

2018-06-01

High temperature and pressure effects on the physicochemical properties of binary oxides catalysts were investigated. The nanocomposites catalysts comprising of CeAl, CeMn and NiAl were characterized through various physicochemical techniques. A study of the temperature and pressure induced phenomena monitored by Raman spectroscopy was proposed and discussed. Spectral modifications of the Raman modes belonging to the CeMn suggest structural changes in the solid due to the MnO2 phase oxidation with increasing temperature. The thermal expansion and lattice anharmonicity effects were observed on CeMn due to lack of stability of the lattice vacancies. The CeAl and NiAl composites presented crystallographic stability at low temperatures however, undertake a phase transformation of NiO/Al2O3 into NiAl2O4, mostly without any deformation in its structure with increasing the temperature. It was also inferred that the binary oxides are more stables in comparison with monoxides. Detailed pressure-dependent Raman measurements of the T2g phonon mode of CeMn and NiAl revealed that the pressure contributes to modify bonds length and reduces the particles sizes of the solids. On the contrary, high pressure on CeAl sample improved the stability with addition of Al2O3 in the CeO2 lattice. The results then suggest a good stability of CeAl and NiAl composite catalysts at high pressure and low temperature and show how to prospect of tuning the catalysis for surface reactions entirely through in situ spectroscopic investigations means.

Synthesis and characterization of CdS-based ternary composite for enhanced visible light-driven photocatalysis

NASA Astrophysics Data System (ADS)

Singh, Arvind; Sinha, A. S. K.

2018-09-01

Active ternary graphite and alumina-supported cadmium sulphide (CdS) composite was synthesized by impregnation method followed by high-temperature solid-gas reaction and characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) techniques. The ternary CdS-graphite-alumina composite exhibited superior catalytic activity compared with the binary CdS-alumina composite due to its better visible-light absorption and higher charge separation. The ternary composite has a bed-type structure. It permits a greater interaction at the interface due to intimate contact between CdS and graphite in the ternary composite. This composite has a highly efficient visible light-driven photocatalytic activity for sustainable hydrogen production. It is also capable of degrading organic dyes in wastewater.

VizieR Online Data Catalog: SLoWPoKES-II catalog (Dhital+, 2015)

NASA Astrophysics Data System (ADS)

Dhital, S.; West, A. A.; Stassun, K. G.; Schluns, K. J.; Massey, A. P.

2015-11-01

We have identified the Sloan Low-mass Wide Pairs of Kinematically Equivalent Systems (SLoWPoKES)-II catalog of 105537 wide, low-mass binaries without using proper motions. We extend the SLoWPoKES catalog (Paper I; Dhital et al. 2010, cat. J/AJ/139/2566) by identifying binary systems with angular separations of 1-20'' based entirely on SDSS photometry and astrometry. As in Paper I, we used the Catalog Archive Server query tool (CasJobs6; http://skyserver.sdss3.org/CasJobs/) to select the sample of low-mass stars from the SDSS-DR8 star table as having r-i>=0.3 and i-z>=0.2, consistent with spectral types of K5 or later. Following Paper I (Dhital et al. 2010, cat. J/AJ/139/2566) we classified candidate pairs with a probability of chance alignment Pf{<=}0.05 as real binaries. We note that this limit does not have any physical motivation but was chosen to minimize the number of spurious pairs. This cut results in 105537 M dwarf (dM)+MS (see Table3), 78 white dwarf (WD)+dM (see Table5), and 184 sdM+sdM (see Table6) binary systems with separations of 1-20''. Of the dM+MS binaries, 44 are very low-mass (VLM) binary candidates (see Table4), with colors redder than the median M7 dwarf for both components. This represents a significant increase over the SLoWPoKES catalog of 1342 common proper motion (CPM) binaries that we presented in Paper I (Dhital et al. 2010, cat. J/AJ/139/2566). The SLoWPoKES and SLoWPoKES-II catalogs are available on the Filtergraph portal (http://slowpokes.vanderbilt.edu/). (4 data files).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujibayashi, Sho; Sekiguchi, Yuichiro; Kiuchi, Kenta

We performed general relativistic, long-term, axisymmetric neutrino radiation hydrodynamics simulations for the remnant formed after a binary neutron star merger, which consists of a massive neutron star and a torus surrounding it. As an initial condition, we employ the result derived in a three-dimensional, numerical relativity simulation for the binary neutron star merger. We investigate the properties of neutrino-driven ejecta. Due to the pair-annihilation heating, the dynamics of the neutrino-driven ejecta are significantly modified. The kinetic energy of the ejecta is about two times larger than that in the absence of pair-annihilation heating. This suggests that the pair-annihilation heating playsmore » an important role in the evolution of merger remnants. The relativistic outflow, which is required for driving gamma-ray bursts, is not observed because the specific heating rate around the rotational axis is not sufficiently high, due to the baryon loading caused by the neutrino-driven ejecta from the massive neutron star. We discuss the condition for launching the relativistic outflow and the nucleosynthesis in the ejecta.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briggs, Samuel A.; Edmondson, Philip D.; Littrell, Kenneth C.

Here, FeCrAl alloys are currently under consideration for accident-tolerant fuel cladding applications in light water reactors owing to their superior high-temperature oxidation and corrosion resistance compared to the Zr-based alloys currently employed. However, their performance could be limited by precipitation of a Cr-rich α' phase that tends to embrittle high-Cr ferritic Fe-based alloys. In this study, four FeCrAl model alloys with 10–18 at.% Cr and 5.8–9.3 at.% Al were neutron-irradiated to nominal damage doses up to 7.0 displacements per atom at a target temperature of 320 °C. Small angle neutron scattering techniques were coupled with atom probe tomography to assessmore » the composition and morphology of the resulting α' precipitates. It was demonstrated that Al additions partially destabilize the α' phase, generally resulting in precipitates with lower Cr contents when compared with binary Fe-Cr systems. The precipitate morphology evolution with dose exhibited a transient coarsening regime akin to previously observed behavior in aged Fe-Cr alloys. Similar behavior to predictions of the LSW/UOKV models suggests that α' precipitation in irradiated FeCrAl is a diffusion-limited process with coarsening mechanisms similar to those in thermally aged high-Cr ferritic alloys.« less

WR 20a Is an Eclipsing Binary: Accurate Determination of Parameters for an Extremely Massive Wolf-Rayet System

NASA Astrophysics Data System (ADS)

Bonanos, A. Z.; Stanek, K. Z.; Udalski, A.; Wyrzykowski, L.; Żebruń, K.; Kubiak, M.; Szymański, M. K.; Szewczyk, O.; Pietrzyński, G.; Soszyński, I.

2004-08-01

We present a high-precision I-band light curve for the Wolf-Rayet binary WR 20a, obtained as a subproject of the Optical Gravitational Lensing Experiment. Rauw et al. have recently presented spectroscopy for this system, strongly suggesting extremely large minimum masses of 70.7+/-4.0 and 68.8+/-3.8 Msolar for the component stars of the system, with the exact values depending strongly on the period of the system. We detect deep eclipses of about 0.4 mag in the light curve of WR 20a, confirming and refining the suspected period of P=3.686 days and deriving an inclination angle of i=74.5d+/-2.0d. Using these photometric data and the radial velocity data of Rauw et al., we derive the masses for the two components of WR 20a to be 83.0+/-5.0 and 82.0+/-5.0 Msolar. Therefore, WR 20a is confirmed to consist of two extremely massive stars and to be the most massive binary known with an accurate mass determination. Based on observations obtained with the 1.3 m Warsaw telescope at Las Campanas Observatory, which is operated by the Carnegie Institute of Washington.

Data-analysis driven comparison of analytic and numerical coalescing binary waveforms: Nonspinning case

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan Yi; Buonanno, Alessandra; McWilliams, Sean T.

2008-01-15

We compare waveforms obtained by numerically evolving nonspinning binary black holes to post-Newtonian (PN) template families currently used in the search for gravitational waves by ground-based detectors. We find that the time-domain 3.5PN template family, which includes the inspiral phase, has fitting factors (FFs) {>=}0.96 for binary systems with total mass M=10-20M{sub {center_dot}}. The time-domain 3.5PN effective-one-body template family, which includes the inspiral, merger, and ring-down phases, gives satisfactory signal-matching performance with FFs {>=}0.96 for binary systems with total mass M=10-120M{sub {center_dot}}. If we introduce a cutoff frequency properly adjusted to the final black-hole ring-down frequency, we find that themore » frequency-domain stationary-phase-approximated template family at 3.5PN order has FFs {>=}0.96 for binary systems with total mass M=10-20M{sub {center_dot}}. However, to obtain high matching performances for larger binary masses, we need to either extend this family to unphysical regions of the parameter space or introduce a 4PN order coefficient in the frequency-domain gravitational wave (GW) phase. Finally, we find that the phenomenological Buonanno-Chen-Vallisneri family has FFs {>=}0.97 with total mass M=10-120M{sub {center_dot}}. The main analyses use the noise-spectral density of LIGO, but several tests are extended to VIRGO and advanced LIGO noise-spectral densities.« less

Binary information propagation in circular magnetic nanodot arrays using strain induced magnetic anisotropy

NASA Astrophysics Data System (ADS)

Salehi-Fashami, M.; Al-Rashid, M.; Sun, Wei-Yang; Nordeen, P.; Bandyopadhyay, S.; Chavez, A. C.; Carman, G. P.; Atulasimha, J.

2016-10-01

Nanomagnetic logic has emerged as a potential replacement for traditional Complementary Metal Oxide Semiconductor (CMOS) based logic because of superior energy-efficiency (Salahuddin and Datta 2007 Appl. Phys. Lett. 90 093503, Cowburn and Welland 2000 Science 287 1466-68). One implementation of nanomagnetic logic employs shape-anisotropic (e.g. elliptical) ferromagnets (with two stable magnetization orientations) as binary switches that rely on dipole-dipole interaction to communicate binary information (Cowburn and Welland 2000 Science 287 1466-8, Csaba et al 2002 IEEE Trans. Nanotechnol. 1 209-13, Carlton et al 2008 Nano Lett. 8 4173-8, Atulasimha and Bandyopadhyay 2010 Appl. Phys. Lett. 97 173105, Roy et al 2011 Appl. Phys. Lett. 99 063108, Fashami et al 2011 Nanotechnology 22 155201, Tiercelin et al 2011 Appl. Phys. Lett. 99 , Alam et al 2010 IEEE Trans. Nanotechnol. 9 348-51 and Bhowmik et al 2013 Nat. Nanotechnol. 9 59-63). Normally, circular nanomagnets are incompatible with this approach since they lack distinct stable in-plane magnetization orientations to encode bits. However, circular magnetoelastic nanomagnets can be made bi-stable with a voltage induced anisotropic strain, which provides two significant advantages for nanomagnetic logic applications. First, the shape-anisotropy energy barrier is eliminated which reduces the amount of energy required to reorient the magnetization. Second, the in-plane size can be reduced (˜20 nm) which was previously not possible due to thermal stability issues. In circular magnetoelastic nanomagnets, a voltage induced strain stabilizes the magnetization even at this size overcoming the thermal stability issue. In this paper, we analytically demonstrate the feasibility of a binary ‘logic wire’ implemented with an array of circular nanomagnets that are clocked with voltage-induced strain applied by an underlying piezoelectric substrate. This leads to an energy-efficient logic paradigm orders of magnitude superior to existing CMOS-based logic that is scalable to dimensions substantially smaller than those for existing nanomagnetic logic approaches. The analytical approach is validated with experimental measurements conducted on dipole coupled Nickel (Ni) nanodots fabricated on a PMN-PT (Lead Magnesium Niobate-Lead Titanate) sample.

Structural and electronic properties of monolayer group III monochalcogenides

NASA Astrophysics Data System (ADS)

Demirci, S.; Avazlı, N.; Durgun, E.; Cahangirov, S.

2017-03-01

We investigate the structural, mechanical, and electronic properties of the two-dimensional hexagonal structure of group III-VI binary monolayers, M X (M =B , Al, Ga, In and X =O , S, Se, Te) using first-principles calculations based on the density functional theory. The structural optimization calculations and phonon spectrum analysis indicate that all of the 16 possible binary compounds are thermally stable. In-plane stiffness values cover a range depending on the element types and can be as high as that of graphene, while the calculated bending rigidity is found to be an order of magnitude higher than that of graphene. The obtained electronic band structures show that M X monolayers are indirect band-gap semiconductors. The calculated band gaps span a wide optical spectrum from deep ultraviolet to near infrared. The electronic structure of oxides (M O ) is different from the rest because of the high electronegativity of oxygen atoms. The dispersions of the electronic band edges and the nature of bonding between atoms can also be correlated with electronegativities of constituent elements. The unique characteristics of group III-VI binary monolayers can be suitable for high-performance device applications in nanoelectronics and optics.

A Periodically Varying Luminous Quasar at z = 2 from the Pan-STARRS1 Medium Deep Survey: A Candidate Supermassive Black Hole Binary in the Gravitational Wave-Driven Regime

NASA Astrophysics Data System (ADS)

Liu, Tingting; Gezari, Suvi

Supermassive black hole binaries (SMBHBs) should be an inevitable consequence of the hierarchical growth of massive galaxies through mergers and the strongest sirens of gravitational waves (GWs) in the cosmos. Yet, their direct detection has remained elusive due to the compact (sub-parsec) orbital separations of gravitationally bound SMBHBs. Here we exploit a theoretically predicted signature of SMBHBs in the time domain. We have begun a systematic search for SMBHB candidates in the Pan-STARRS1 Medium Deep Survey (MDS) and reported our first significant detection of such a candidate from our pilot study of MD09 in Liu et al. (2015). Our candidate PSO J334.2028+01.4075 has a detected period of 542 days, varying persistently over the available baseline. From its archival spectrum, we estimated the black hole mass of the z = 2.06 quasar to be ~1010 M⊙. The inferred ~7 R s binary separation therefore puts this candidate in the regime of GW-dominated orbital decay, opening up the exciting possibility of finding GW sources detectable by pulsar timing arrays (PTAs) in a wide-field optical synoptic survey.

A combined APT and SANS investigation of α' phase precipitation in neutron-irradiated model FeCrAl alloys

DOE PAGES

Briggs, Samuel A.; Edmondson, Philip D.; Littrell, Kenneth C.; ...

2017-03-01

Here, FeCrAl alloys are currently under consideration for accident-tolerant fuel cladding applications in light water reactors owing to their superior high-temperature oxidation and corrosion resistance compared to the Zr-based alloys currently employed. However, their performance could be limited by precipitation of a Cr-rich α' phase that tends to embrittle high-Cr ferritic Fe-based alloys. In this study, four FeCrAl model alloys with 10–18 at.% Cr and 5.8–9.3 at.% Al were neutron-irradiated to nominal damage doses up to 7.0 displacements per atom at a target temperature of 320 °C. Small angle neutron scattering techniques were coupled with atom probe tomography to assessmore » the composition and morphology of the resulting α' precipitates. It was demonstrated that Al additions partially destabilize the α' phase, generally resulting in precipitates with lower Cr contents when compared with binary Fe-Cr systems. The precipitate morphology evolution with dose exhibited a transient coarsening regime akin to previously observed behavior in aged Fe-Cr alloys. Similar behavior to predictions of the LSW/UOKV models suggests that α' precipitation in irradiated FeCrAl is a diffusion-limited process with coarsening mechanisms similar to those in thermally aged high-Cr ferritic alloys.« less

Contact binaries in the Trans-neptunian Belt

NASA Astrophysics Data System (ADS)

Thirouin, Audrey; Sheppard, Scott S.

2017-10-01

A contact binary is made up of two objects that are almost touching or in contact with each other. These systems have been found in the Near-Earth Object population, the main belt of asteroids, the Jupiter Trojans, the comet population and even in the Trans-neptunian belt.Several studies suggest that up to 30% of the Trans-Neptunian Objects (TNOs) could be contact binaries (Sheppard & Jewitt 2004, Lacerda 2011). Contact binaries are not resolvable with the Hubble Space Telescope because of the small separation between the system's components (Noll et al. 2008). Only lightcurves with a characteristic V-/U-shape at the minimum/maximum of brightness and a large amplitude can identify these contact binaries. Despite an expected high fraction of contact binaries, 2001 QG298 is the only confirmed contact binary in the Trans-Neptunian belt, and 2003 SQ317 is a candidate to this class of systems (Sheppard & Jewitt 2004, Lacerda et al. 2014).Recently, using the Lowell’s 4.3m Discovery Channel Telescope and the 6.5m Magellan Telescope, we started a search for contact binaries at the edge of our Solar System. So far, our survey focused on about 40 objects in different dynamical groups of the Trans-Neptunian belt for sparse or complete lightcurves. We report the discovery of 5 new potential contact binaries converting the current estimate of potential/confirmed contact binaries to 7 objects. With one epoch of observations per object, we are not able to model in detail the systems, but we derive estimate for basic information such as shape, size, density of both objects as well as the separation between the system’s components. In this work, we will present these new systems, their basic characteristics, and we will discuss the potential main reservoir of contact binaries in the Trans-neptunian belt.

The Nature of Double-peaked [O III] Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Fu, Hai; Yan, Lin; Myers, Adam D.; Stockton, Alan; Djorgovski, S. G.; Aldering, G.; Rich, Jeffrey A.

2012-01-01

Active galactic nuclei (AGNs) with double-peaked [O III] lines are suspected to be sub-kpc or kpc-scale binary AGNs. However, pure gas kinematics can produce the same double-peaked line profile in spatially integrated spectra. Here we combine integral-field spectroscopy and high-resolution imaging of 42 double-peaked [O III] AGNs from the Sloan Digital Sky Survey to investigate the constituents of the population. We find two binary AGNs where the line splitting is driven by the orbital motion of the merging nuclei. Such objects account for only ~2% of the double-peaked AGNs. Almost all (~98%) of the double-peaked AGNs were selected because of gas kinematics; and half of those show spatially resolved narrow-line regions that extend 4-20 kpc from the nuclei. Serendipitously, we find two spectrally unresolved binary AGNs where gas kinematics produced the double-peaked [O III] lines. The relatively frequent serendipitous discoveries indicate that only ~1% of binary AGNs would appear double-peaked in Sloan spectra and 2.2+2.5 -0.8% of all Sloan AGNs are binary AGNs. Therefore, the double-peaked sample does not offer much advantage over any other AGN samples in finding binary AGNs. The binary AGN fraction implies an elevated AGN duty cycle (8+8 -3%), suggesting galaxy interactions enhance nuclear accretion. We illustrate that integral-field spectroscopy is crucial for identifying binary AGNs: several objects previously classified as "binary AGNs" with long-slit spectra are most likely single AGNs with extended narrow-line regions (ENLRs). The formation of ENLRs driven by radiation pressure is also discussed. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Modeling the binary circumstellar medium of Type IIb/L/n supernova progenitors

NASA Astrophysics Data System (ADS)

Kolb, Christopher; Blondin, John; Borkowski, Kazik; Reynolds, Stephen

2018-01-01

Circumstellar interaction in close binary systems can produce a highly asymmetric environment, particularly for systems with a mass outflow velocity comparable to the binary orbital speed. This asymmetric circumstellar medium (CSM) becomes visible after a supernova explosion, when SN radiation illuminates the gas and when SN ejecta collide with the CSM. We aim to better understand the development of this asymmetric CSM, particularly for binary systems containing a red supergiant progenitor, and to study its impact on supernova morphology. To achieve this, we model the asymmetric wind and subsequent supernova explosion in full 3D hydrodynamics using the shock-capturing hydro code VH-1 on a spherical yin-yang grid. Wind interaction is computed in a frame co-rotating with the binary system, and gas is accelerated using a radiation pressure-driven wind model where optical depth of the radiative force is dependent on azimuthally-averaged gas density. We present characterization of our asymmetric wind density distribution model by fitting a polar-to-equatorial density contrast function to free parameters such as binary separation distance, primary mass loss rate, and binary mass ratio.

Strong disk winds traced throughout outbursts in black-hole X-ray binaries

NASA Astrophysics Data System (ADS)

Tetarenko, B. E.; Lasota, J.-P.; Heinke, C. O.; Dubus, G.; Sivakoff, G. R.

2018-02-01

Recurring outbursts associated with matter flowing onto compact stellar remnants (such as black holes, neutron stars and white dwarfs) in close binary systems provide a way of constraining the poorly understood accretion process. The light curves of these outbursts are shaped by the efficiency of angular-momentum (and thus mass) transport in the accretion disks, which has traditionally been encoded in a viscosity parameter, α. Numerical simulations of the magneto-rotational instability that is believed to be the physical mechanism behind this transport yield values of α of roughly 0.1–0.2, consistent with values determined from observations of accreting white dwarfs. Equivalent viscosity parameters have hitherto not been estimated for disks around neutron stars or black holes. Here we report the results of an analysis of archival X-ray light curves of 21 outbursts in black-hole X-ray binaries. By applying a Bayesian approach to a model of accretion, we determine corresponding values of α of around 0.2–1.0. These high values may be interpreted as an indication either of a very high intrinsic rate of angular-momentum transport in the disk, which could be sustained by the magneto-rotational instability only if a large-scale magnetic field threads the disk, or that mass is being lost from the disk through substantial outflows, which strongly shape the outburst in the black-hole X-ray binary. The lack of correlation between our estimates of α and the accretion state of the binaries implies that such outflows can remove a substantial fraction of the disk mass in all accretion states and therefore suggests that the outflows correspond to magnetically driven disk winds rather than thermally driven ones, which require specific radiative conditions.

Strong disk winds traced throughout outbursts in black-hole X-ray binaries.

PubMed

Tetarenko, B E; Lasota, J-P; Heinke, C O; Dubus, G; Sivakoff, G R

2018-02-01

Recurring outbursts associated with matter flowing onto compact stellar remnants (such as black holes, neutron stars and white dwarfs) in close binary systems provide a way of constraining the poorly understood accretion process. The light curves of these outbursts are shaped by the efficiency of angular-momentum (and thus mass) transport in the accretion disks, which has traditionally been encoded in a viscosity parameter, α. Numerical simulations of the magneto-rotational instability that is believed to be the physical mechanism behind this transport yield values of α of roughly 0.1-0.2, consistent with values determined from observations of accreting white dwarfs. Equivalent viscosity parameters have hitherto not been estimated for disks around neutron stars or black holes. Here we report the results of an analysis of archival X-ray light curves of 21 outbursts in black-hole X-ray binaries. By applying a Bayesian approach to a model of accretion, we determine corresponding values of α of around 0.2-1.0. These high values may be interpreted as an indication either of a very high intrinsic rate of angular-momentum transport in the disk, which could be sustained by the magneto-rotational instability only if a large-scale magnetic field threads the disk, or that mass is being lost from the disk through substantial outflows, which strongly shape the outburst in the black-hole X-ray binary. The lack of correlation between our estimates of α and the accretion state of the binaries implies that such outflows can remove a substantial fraction of the disk mass in all accretion states and therefore suggests that the outflows correspond to magnetically driven disk winds rather than thermally driven ones, which require specific radiative conditions.

High-Strength Nanotwinned Al Alloys with 9R Phase.

PubMed

Li, Qiang; Xue, Sichuang; Wang, Jian; Shao, Shuai; Kwong, Anthony H; Giwa, Adenike; Fan, Zhe; Liu, Yue; Qi, Zhimin; Ding, Jie; Wang, Han; Greer, Julia R; Wang, Haiyan; Zhang, Xinghang

2018-03-01

Light-weight aluminum (Al) alloys have widespread applications. However, most Al alloys have inherently low mechanical strength. Nanotwins can induce high strength and ductility in metallic materials. Yet, introducing high-density growth twins into Al remains difficult due to its ultrahigh stacking-fault energy. In this study, it is shown that incorporating merely several atomic percent of Fe solutes into Al enables the formation of nanotwinned (nt) columnar grains with high-density 9R phase in Al(Fe) solid solutions. The nt Al-Fe alloy coatings reach a maximum hardness of ≈5.5 GPa, one of the strongest binary Al alloys ever created. In situ uniaxial compressions show that the nt Al-Fe alloys populated with 9R phase have flow stress exceeding 1.5 GPa, comparable to high-strength steels. Molecular dynamics simulations reveal that high strength and hardening ability of Al-Fe alloys arise mainly from the high-density 9R phase and nanoscale grain sizes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficient common-envelope ejection through dust-driven winds

NASA Astrophysics Data System (ADS)

Glanz, Hila; Perets, Hagai B.

2018-04-01

Common-envelope evolution (CEE) is the short-lived phase in the life of an interacting binary-system during which two stars orbit inside a single shared envelope. Such evolution is thought to lead to the inspiral of the binary, the ejection of the extended envelope and the formation of a remnant short-period binary. However, detailed hydrodynamical models of CEE encounter major difficulties. They show that following the inspiral most of the envelope is not ejected; though it expands to larger separations, it remains bound to the binary. Here we propose that dust-driven winds can be produced following the CEE. These can evaporate the envelope following similar processes operating in the ejection of the envelopes of AGB stars. Pulsations in an AGB-star drives the expansion of its envelope, allowing the material to cool down to low temperatures thus enabling dust condensation. Radiation pressure on the dust accelerates it, and through its coupling to the gas it drives winds which eventually completely erode the envelope. We show that the inspiral phase in CE-binaries can effectively replace the role of stellar pulsation and drive the CE expansion to scales comparable with those of AGB stars, and give rise to efficient mass-loss through dust-driven winds.

"One-sample concept" micro-combinatory for high throughput TEM of binary films.

PubMed

Sáfrán, György

2018-04-01

Phases of thin films may remarkably differ from that of bulk. Unlike to the comprehensive data files of Binary Phase Diagrams [1] available for bulk, complete phase maps for thin binary layers do not exist. This is due to both the diverse metastable, non-equilibrium or instable phases feasible in thin films and the required volume of characterization work with analytical techniques like TEM, SAED and EDS. The aim of the present work was to develop a method that remarkably facilitates the TEM study of the diverse binary phases of thin films, or the creation of phase maps. A micro-combinatorial method was worked out that enables both preparation and study of a gradient two-component film within a single TEM specimen. For a demonstration of the technique thin Mn x Al 1- x binary samples with evolving concentration from x = 0 to x = 1 have been prepared so that the transition from pure Mn to pure Al covers a 1.5 mm long track within the 3 mm diameter TEM grid. The proposed method enables the preparation and study of thin combinatorial samples including all feasible phases as a function of composition or other deposition parameters. Contrary to known "combinatorial chemistry", in which a series of different samples are deposited in one run, and investigated, one at a time, the present micro-combinatorial method produces a single specimen condensing a complete library of a binary system that can be studied, efficiently, within a single TEM session. That provides extremely high throughput for TEM characterization of composition-dependent phases, exploration of new materials, or the construction of phase diagrams of binary films. Copyright © 2018 Elsevier B.V. All rights reserved.

Classification of binary intentions for individuals with impaired oculomotor function: ‘eyes-closed’ SSVEP-based brain-computer interface (BCI)

NASA Astrophysics Data System (ADS)

Lim, Jeong-Hwan; Hwang, Han-Jeong; Han, Chang-Hee; Jung, Ki-Young; Im, Chang-Hwan

2013-04-01

Objective. Some patients suffering from severe neuromuscular diseases have difficulty controlling not only their bodies but also their eyes. Since these patients have difficulty gazing at specific visual stimuli or keeping their eyes open for a long time, they are unable to use the typical steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) systems. In this study, we introduce a new paradigm for SSVEP-based BCI, which can be potentially suitable for disabled individuals with impaired oculomotor function. Approach. The proposed electroencephalography (EEG)-based BCI system allows users to express their binary intentions without needing to open their eyes. A pair of glasses with two light emitting diodes flickering at different frequencies was used to present visual stimuli to participants with their eyes closed, and we classified the recorded EEG patterns in the online experiments conducted with five healthy participants and one patient with severe amyotrophic lateral sclerosis (ALS). Main results. Through offline experiments performed with 11 participants, we confirmed that human SSVEP could be modulated by visual selective attention to a specific light stimulus penetrating through the eyelids. Furthermore, the recorded EEG patterns could be classified with accuracy high enough for use in a practical BCI system. After customizing the parameters of the proposed SSVEP-based BCI paradigm based on the offline analysis results, binary intentions of five healthy participants were classified in real time. The average information transfer rate of our online experiments reached 10.83 bits min-1. A preliminary online experiment conducted with an ALS patient showed a classification accuracy of 80%. Significance. The results of our offline and online experiments demonstrated the feasibility of our proposed SSVEP-based BCI paradigm. It is expected that our ‘eyes-closed’ SSVEP-based BCI system can be potentially used for communication of disabled individuals with impaired oculomotor function.

Classification of binary intentions for individuals with impaired oculomotor function: 'eyes-closed' SSVEP-based brain-computer interface (BCI).

PubMed

Lim, Jeong-Hwan; Hwang, Han-Jeong; Han, Chang-Hee; Jung, Ki-Young; Im, Chang-Hwan

2013-04-01

Some patients suffering from severe neuromuscular diseases have difficulty controlling not only their bodies but also their eyes. Since these patients have difficulty gazing at specific visual stimuli or keeping their eyes open for a long time, they are unable to use the typical steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) systems. In this study, we introduce a new paradigm for SSVEP-based BCI, which can be potentially suitable for disabled individuals with impaired oculomotor function. The proposed electroencephalography (EEG)-based BCI system allows users to express their binary intentions without needing to open their eyes. A pair of glasses with two light emitting diodes flickering at different frequencies was used to present visual stimuli to participants with their eyes closed, and we classified the recorded EEG patterns in the online experiments conducted with five healthy participants and one patient with severe amyotrophic lateral sclerosis (ALS). Through offline experiments performed with 11 participants, we confirmed that human SSVEP could be modulated by visual selective attention to a specific light stimulus penetrating through the eyelids. Furthermore, the recorded EEG patterns could be classified with accuracy high enough for use in a practical BCI system. After customizing the parameters of the proposed SSVEP-based BCI paradigm based on the offline analysis results, binary intentions of five healthy participants were classified in real time. The average information transfer rate of our online experiments reached 10.83 bits min(-1). A preliminary online experiment conducted with an ALS patient showed a classification accuracy of 80%. The results of our offline and online experiments demonstrated the feasibility of our proposed SSVEP-based BCI paradigm. It is expected that our 'eyes-closed' SSVEP-based BCI system can be potentially used for communication of disabled individuals with impaired oculomotor function.

Self-regulation of brain rhythms in the precuneus: a novel BCI paradigm for patients with ALS

NASA Astrophysics Data System (ADS)

Fomina, Tatiana; Lohmann, Gabriele; Erb, Michael; Ethofer, Thomas; Schölkopf, Bernhard; Grosse-Wentrup, Moritz

2016-12-01

Objective. Electroencephalographic (EEG) brain-computer interfaces (BCIs) hold promise in restoring communication for patients with completely locked-in stage amyotrophic lateral sclerosis (ALS). However, these patients cannot use existing EEG-based BCIs, arguably because such systems rely on brain processes that are impaired in the late stages of ALS. In this work, we introduce a novel BCI designed for patients in late stages of ALS based on high-level cognitive processes that are less likely to be affected by ALS. Approach. We trained two ALS patients via EEG-based neurofeedback to use self-regulation of theta or gamma oscillations in the precuneus for basic communication. Because there is a tight connection between the precuneus and consciousness, precuneus oscillations are arguably generated by high-level cognitive processes, which are less likely to be affected by ALS than processes linked to the peripheral nervous system. Main results. Both patients learned to self-regulate their precuneus oscillations and achieved stable online decoding accuracy over the course of disease progression. One patient achieved a mean online decoding accuracy in a binary decision task of 70.55% across 26 training sessions, and the other patient achieved 59.44% across 16 training sessions. We provide empirical evidence that these oscillations were cortical in nature and originated from the intersection of the precuneus, cuneus, and posterior cingulate. Significance. Our results establish that ALS patients can employ self-regulation of precuneus oscillations for communication. Such a BCI is likely to be available to ALS patients as long as their consciousness supports communication.

Application of computational thermodynamics in the study of magnsium alloys and bulk metallic glasses

NASA Astrophysics Data System (ADS)

Cao, Hongbo

In this thesis, the application of the computational thermodynamics has been explored on two subjects, the study of magnesium alloys (Chapter 1-5) and bulk metallic glasses (BMGs) (Chapter 6-9). For the former case, a strategy of experiments coupled with the CALPHAD approach was employed to establish a thermodynamic description of the quaternary system Mg-Al-Ca-Sr focusing on the Mg-rich phase equilibria. Multicomponent Mg-rich alloys based on the MgAl-Ca-Sr system are one of the most promising candidates for the high temperature applications in the transportation industry. The Mg-Al-Ca-Sr quaternary consists of four ternaries and six binaries. Thermodynamic descriptions of all constituent binaries are available in the literature. Thermodynamic descriptions of the two key ternaries, Mg-Al-Sr and Mg-Al-Ca, were obtained by an efficient and reliable methodology, combining computational thermodynamics with key experiments. The obtained thermodynamic descriptions were validated by performing extensive comparisons between the calculations and experimental information. Thermodynamic descriptions of the other two ternaries, MgCa-Sr and Al-Ca-Sr, were obtained by extrapolation. For the later case, a computational thermodynamic strategy was formulated to obtain a minor but optimum amount of additional element into a base alloy to improve its glass forming ability (GFA). This was done through thermodynamically calculating the maximum liquidus depressions caused by various alloying addition (or replacement) schemes. The success of this approach has been examined in two multicomponent systems, Zr-based Zr-Cu-Ni-Al-Ti and Cu-rich Cu-Zr-Ti-Y. For both cases, experimental results showed conclusively that the GFA increases more than 100% from the base alloy to the one with minor but optimal elemental addition. Furthermore, a thermodynamic computational approach was employed to identify the compositions of Zr-Ti-Ni-Cu-Al alloys exhibiting low-lying liquidus surfaces, which tend to favor the BMG formation. Guided by these calculations, several series of new Zr-based alloys with excellent GFA were synthesized. The approach using the thermodynamically calculated liquidus temperatures was proved to be robust in locating BMGs and can be considered as a universal method to predict novel BMGs not only of scientific interest but also potential technological applications.

Binary asteroid orbit evolution due to primary shape deformation

NASA Astrophysics Data System (ADS)

Hirabayashi, Masatoshi; Jacobson, Seth A.; Davis, Alex

2017-10-01

About a sixth of all small asteroid systems are binary [Margot et al., Science, 2002]. Many binary asteroids consist of an elongated synchronous secondary body orbiting a fast-rotating spheroidal primary body with ridges on its equator. The primary in such systems has experienced a long-term spin-up due to the YORP effect [Vokrouhlick'y et al., Asteroid IV, 2015]. This spin-up process can make the primary reach its spin barrier inducing shape deformation processes that ease the structural condition for failure inside the primary [e.g., Holsapple, Icarus, 2010]. Earlier works have shown that structural heterogeneities in the primary such as the shape and density distribution induce asymmetric deformation [Sánchez and Scheeres, Icarus, 2016]. Here, we investigate how asymmetric shape deformation in the primary affects the mutual motion of a binary system. We use a dynamics model for an irregularly shaped binary system that accounts for possible deformation of the primary [Hirabayashi et al., LPSC, 2017]. In this model, we consider asymmetric deformation that occurs based on structural failure in the primary and thus it modifies the location of the center of mass of the system. Using 1999 KW4 as an example, we study a hypothetical case in which the primary is initially identical to the current shape [Ostro et al., Science, 2006] with an aspect ratio (AR) of 0.83 and then suddenly changes its shape to an AR of 0.76. The results show that the asymmetric deformation process and the shift of the center of mass excite the eccentricity of the mutual orbit. Considering that the original mutual orbit has an eccentricity of 0.0004, after the primary shape change the eccentricity reaches values up to 0.15. Also, since the gravity field is modified after deformation, the secondary’s spin is desynchronized from the mutual orbit. Since synchronicity is a requirement for the binary YORP (BYORP) effect, which modifies the semi-major axis of binary asteroids, a primary shape change temporarily pauses the BYORP effect, in effect lengthening the effective BYORP timescale.

Subdwarf B Stars: Tracers Of Binary Evolution

NASA Astrophysics Data System (ADS)

Morales-Rueda, L.; Maxted, P. F. L.; Marsh, T. R.

2007-08-01

Subdwarf B stars are a superb stellar population to study binary evolution. In 2001, Maxted et al. (MNRAS, 326, 1391) found that 21 out of the 36 subdwarf B stars they studied were in short period binaries. These observations inspired new theoretical work that suggests that up to 90 per cent of subdwarf B stars are in binary systems with the remaining apparently single stars being the product of merging pairs. This high binary fraction added to the fact that they are detached binaries that have not changed significantly since they came out of the common envelope, make subdwarf B stars a perfect population to study binary evolution. By comparing the observed orbital period distribution of subdwarf B stars with that obtained from population synthesis calculations we can determine fundamental parameters of binary evolution such as the common envelope ejection efficiency. Here we give an overview of the fraction of short period binaries found from different surveys as well as the most up to date orbital period distribution determined observationally. We also present results from a recent search for subdwarf B stars in long period binaries.

Using LISA to Learn How Pairs of Black Holes Formed

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-11-01

Artists impression of the European Space Agencys Laser Interferometer Space Antenna, currently planned for a 2034 launch. [NASA]How are black-hole binaries built? Observations of gravitational waves from these systems made using the European Space Agencys upcoming mission, the Laser Interferometer Space Antenna (LISA) may be able to reveal their origins.Formation ChannelsThere are two primary placeswhere stellar-mass black-hole binaries are thought to form:In isolation in the galactic field, as the components of a stellar binary independently evolve into black holes but remain bound to each other.In dense stellar environments like globular clusters, where the high density of already-formed black holes can cause a pair to dynamically interact and form a binary before being ejected from the cluster.Can we differentiate between these origins based on future detections of gravitational waves from black-hole binaries? A team of scientists led by Katelyn Breivik (CIERA, Northwestern University) thinks that we can!The gravitational-wave spectrum and how we detect it (click for a closer look!). While ground-based interferometers like LIGO detect black-hole binaries in the final moments before merger, LISAs lower frequency band will allow it to detect binaries earlier in their inspiral. [NASA Goddard SFC]Differentiation by EccentricityBreivik and collaborators believe that the key clue is the binarys eccentricity. Gravitational-wave emission will eventually circularize all black-hole binaries during their inspiral. But in the first formation scenario, binary evolution processes like tidal circularization and mass transfer will reduce the binarys eccentricity early on whereas in the second scenario, the binaries that form in globular clusters may retain eccentricity in their orbits long enough that we can detect it.Ground-based interferometers wont be up to this task; by the time the binary orbits shrink enough to evolve into the LIGO frequency band, the orbits wont have measurable eccentricity anymore. But the upcoming space-based LISA mission, which will operate in a lower frequency band, might be able to pick up this signature.To determine if LISA can pull it off, Breivik and collaborators simulate two populations of binary black holes: one evolved in isolation in galactic fields, and the other formed dynamically in globular clusters and then ejected. The authors then explore the evolution of these populations masses and eccentricities as their orbits narrow into the LISA-detectable frequency band.Eccentricity evolution tracks as a function of gravitational-wave frequency for black-hole binaries formed in dynamical scenarios (black) and in isolation (blue for those with a common-envelope episode, green for those without). Eccentricities above 10-2 are measurable for all binaries; those above 10-3 are measurable for 90%. LISAs frequency band is shown in grey. [Breivik et al. 2016]Separating PopulationsBreivik and collaborators find that LISA will be able to make several important distinctions. First, if LISA detects binary black holes with eccentricities of e 0.01 at frequencies above 10-2 Hz, we can be fairly certainthat these originated from dynamical processes in dense stellar environments.For binary black holes detected with eccentricities of e 0.01 at lower frequencies, they could either have formed in dense stellar environments or they could have formed in isolation. Based on this studys results, however, those with measurable eccentricities that formed in isolation mostlikely originated from a common-envelope formation. Measuring eccentricities of such systems in the future could provide constraints on the physics of how this formation mechanism works.Though the field of gravitational-wave astronomy is only just beginning, its future is promising! Theoretical studies like this one will help us to extracta greater understanding from the observations we can expect down the road.BonusCheck out this beautiful simulationfrom Northwestern Visualization and Carl Rodriguez (a co-author on the above study) that shows what the formation of a binary black hole in a globular cluster might look like!http://aasnova.org/wp-content/uploads/2016/11/accelerated_nbody_hd.mp4CitationKatelyn Breivik et al 2016 ApJL 830 L18. doi:10.3847/2041-8205/830/1/L18

Phase-field-based lattice Boltzmann model for incompressible binary fluid systems with density and viscosity contrasts.

PubMed

Zu, Y Q; He, S

2013-04-01

A lattice Boltzmann model (LBM) is proposed based on the phase-field theory to simulate incompressible binary fluids with density and viscosity contrasts. Unlike many existing diffuse interface models which are limited to density matched binary fluids, the proposed model is capable of dealing with binary fluids with moderate density ratios. A new strategy for projecting the phase field to the viscosity field is proposed on the basis of the continuity of viscosity flux. The new LBM utilizes two lattice Boltzmann equations (LBEs): one for the interface tracking and the other for solving the hydrodynamic properties. The LBE for interface tracking can recover the Chan-Hilliard equation without any additional terms; while the LBE for hydrodynamic properties can recover the exact form of the divergence-free incompressible Navier-Stokes equations avoiding spurious interfacial forces. A series of 2D and 3D benchmark tests have been conducted for validation, which include a rigid-body rotation, stationary and moving droplets, a spinodal decomposition, a buoyancy-driven bubbly flow, a layered Poiseuille flow, and the Rayleigh-Taylor instability. It is shown that the proposed method can track the interface with high accuracy and stability and can significantly and systematically reduce the parasitic current across the interface. Comparisons with momentum-based models indicate that the newly proposed velocity-based model can better satisfy the incompressible condition in the flow fields, and eliminate or reduce the velocity fluctuations in the higher-pressure-gradient region and, therefore, achieve a better numerical stability. In addition, the test of a layered Poiseuille flow demonstrates that the proposed scheme for mixture viscosity performs significantly better than the traditional mixture viscosity methods.

Effect of Ag Addition on the Electrochemical Performance of Cu10Al in Artificial Saliva

PubMed Central

Salgado-Salgado, R. J.; Sotelo-Mazon, O.; Rodriguez-Diaz, R. A.; Salinas-Solano, G.

2016-01-01

In this work we proposed to evaluate the corrosion resistance of four different alloys by electrochemical techniques, a binary alloy Cu10Al, and three ternary alloys Cu10Al-xAg (x = 5, 10, and 15 wt.%) to be used like biomaterials in dental application. Biomaterials proposed were tested in artificial saliva at 37°C for 48 h. In addition, pure metals Cu, Al, Ag, and Ti as reference materials were evaluated. In general the short time tests indicated that the Ag addition increases the corrosion resistance and reduces the extent of localized attack of the binary alloy. Moreover, tests for 48 hours showed that the Ag addition increases the stability of the passive layer, thereby reducing the corrosion rate of the binary alloy. SEM analysis showed that Cu10Al alloy was preferably corroded by grain boundaries, and the Ag addition modified the form of attack of the binary alloy. Cu-rich phases reacted with SCN− anions forming a film of CuSCN, and the Ag-rich phase is prone to react with SCN− anions forming AgSCN. Thus, binary and ternary alloys are susceptible to tarnish in the presence of thiocyanate ions. PMID:27660601

Surface and cut-edge corrosion behavior of Zn-Mg-Al alloy-coated steel sheets as a function of the alloy coating microstructure

NASA Astrophysics Data System (ADS)

Oh, Min-Suk; Kim, Sang-Heon; Kim, Jong-Sang; Lee, Jae-Won; Shon, Je-Ha; Jin, Young-Sool

2016-01-01

The effects of Mg and Al content on the microstructure and corrosion resistance of hot-dip Zn-Mg-Al alloycoated steel sheets were investigated. Pure Zn and Zn-based alloy coatings containing Mg (0-5 wt%) and Al (0.2-55 wt%) were produced by a hot-dip galvanizing method. Mg and Al addition induced formation of intermetallic microstructures, like primary Zn, Zn/MgZn2 binary eutectic, dendric Zn/Al eutectoid, and Zn/Al/MgZn2/ternary eutectic structures in the coating layer. MgZn2-related structures (Zn/MgZn2, Zn/Al/MgZn2, MgZn2) played an important role in increasing the corrosion resistance of Zn-Mg-Al alloy-coated steel sheets. Zn-3%Mg-2.5%Al coating layer containing a large volume of lamellar-shaped Zn/MgZn2 binary eutectic structures showed the best cut-edge corrosion resistance. The analysis indicated that Mg dissolved from MgZn2 in the early stage of corrosion and migrated to the cathodic region of steel-exposed cut-edge area to form dense and ordered protective corrosion products, leading to prolonged cathodic protection of Zn-Mg-Al alloy-coated steel sheets.

Correlation between crystallographic anisotropy and dendritic orientation selection of binary magnesium alloys.

PubMed

Du, Jinglian; Guo, Zhipeng; Zhang, Ang; Yang, Manhong; Li, Mei; Xiong, Shoumei

2017-10-19

Both synchrotron X-ray tomography and EBSD characterization revealed that the preferred growth directions of magnesium alloy dendrite change as the type and amount of solute elements. Such growth behavior was further investigated by evaluating the orientation-dependent surface energy and the subsequent crystallographic anisotropy via ab-initio calculations based on density functional theory and hcp lattice structure. It was found that for most binary magnesium alloys, the preferred growth direction of the α-Mg dendrite in the basal plane is always [Formula: see text], and independent on either the type or concentration of the additional elements. In non-basal planes, however, the preferred growth direction is highly dependent on the solute concentration. In particular, for Mg-Al alloys, this direction changes from [Formula: see text] to [Formula: see text] as the Al-concentration increased, and for Mg-Zn alloys, this direction changes from [Formula: see text] to [Formula: see text] or [Formula: see text] as the Zn-content varied. Our results provide a better understanding on the dendritic orientation selection and morphology transition of magnesium alloys at the atomic level.

Electrical Transport Properties of Liquid Sn-Sb Binary Alloys

NASA Astrophysics Data System (ADS)

Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Jani, A. R.

2010-06-01

The study of electrical transport properties viz. electrical resistivity, thermo electrical power and thermal conductivity of liquid Sn-Sb binary alloys have been made by our well recognized single parametric model potential. In the present work, screening functions due to Hartree, Taylor, Ichimaru et al.. Farid et al.. and Sarkar et al.. have been employed to incorporate the exchange and correlation effects. The liquid alloy is studied as a function of its composition at temperature 823 K according to the Faber-Ziman model. Further, thermoelectric power and thermal conductivity have been predicted. The values of electrical resistivity of binary alloys computed with Ichimaru et al. and Farid et al.. screening function are in good agreement with the experimental data.

VizieR Online Data Catalog: ASAS, NSVS, and LINEAR detached eclipsing binaries (Lee, 2015)

NASA Astrophysics Data System (ADS)

Lee, C.-H.

2016-04-01

We follow the approach of Devor et al. (2008AJ....135..850D, Cat. J/AJ/135/850) to analyse the LC from ASAS (Pojmanski et al., Cat. II/264, NSVS (Wozniak et al., 2004AJ....127.2436W, and LINEAR (Palaversa et al., Cat. J/AJ/146/101) and extract the physical properties of the eclipsing binaries. (3 data files).

Relationships Between Abrasive Wear, Hardness, and Surface Grinding Characteristics of Titanium-Based Metal Matrix Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blau, Peter Julian; Jolly, Brian C

2009-01-01

The objective of this work was to support the development of grinding models for titanium metal-matrix composites (MMCs) by investigating possible relationships between their indentation hardness, low-stress belt abrasion, high-stress belt abrasion, and the surface grinding characteristics. Three Ti-based particulate composites were tested and compared with the popular titanium alloy Ti-6Al-4V. The three composites were a Ti-6Al-4V-based MMC with 5% TiB{sub 2} particles, a Ti-6Al-4V MMC with 10% TiC particles, and a Ti-6Al-4V/Ti-7.5%W binary alloy matrix that contained 7.5% TiC particles. Two types of belt abrasion tests were used: (a) a modified ASTM G164 low-stress loop abrasion test, and (b)more » a higher-stress test developed to quantify the grindability of ceramics. Results were correlated with G-ratios (ratio of stock removed to abrasives consumed) obtained from an instrumented surface grinder. Brinell hardness correlated better with abrasion characteristics than microindentation or scratch hardness. Wear volumes from low-stress and high-stress abrasive belt tests were related by a second-degree polynomial. Grindability numbers correlated with hard particle content but were also matrix-dependent.« less

Gemini and Keck Observations of Slowly Rotating, Bilobate Active Asteroid (300163)

NASA Astrophysics Data System (ADS)

Waniak, Waclaw; Drahus, Michal

2016-10-01

One of the most puzzling questions regarding Active Asteroids is the mechanism of their activation. While some Active Asteroids show protracted and often recurrent mass loss, consistent with seasonal ice sublimation, some other eject dust impulsively as a result of a catastrophic disruption (e.g. Jewitt et al. 2015, Asteroids IV, 221). It has been suggested that ice can be excavated from the cold near-surface interior by an impact (Hsieh & Jewitt 2006, Science 312, 561) or, for small objects susceptible to YORP torques, by near-critical spin rate (Sheppard & Trujillo 2014, AJ 149, 44). But impact and rapid spin can also cause a catastrophic disruption (e.g. Jewitt et al. 2015, Asteroids IV, 221). It therefore becomes apparent that the different types of mass loss observed in Active Asteroids can be best classified and understood based on the nucleus spin rates (Drahus et al. 2015, ApJL 802, L8), but unfortunately the rotation periods have been measured for a very limited number of these objects. With this in mind we have initiated a survey of light curves of small Active Asteroids on the largest ground-based optical telescopes. Here we present the results for (300163), also known as 288P and 2006 VW139, which is a small 2.6-km sized asteroid that exhibited a comet-like activity over 100 days in the second half of 2011 (Hsieh et al. 2012, ApJL 748, L15; Licandro et al. 2013, A&A 550, A17; Agarwal et al. 2016, AJ 151, 12). Using Keck/DEIMOS and Gemini/GMOS-S working in tandem on UT 2015 May 21-22 we have detected an inactive nucleus and measured a complete, dense, high-S/N rotational light curve. The light curve has a double-peaked period of 16 hours, an amplitude of 0.4 mag, and moderately narrow minima suggesting a bilobate or contact-binary shape. The long rotation period clearly demonstrates a non-rotational origin of activity of this object, consistent with an impact. Furthermore, among the five small Active Asteroids with known rotation periods (300163) is only the second object with a confirmed slow spin rate, the other three rotating rapidly, near the limit of rotational stability. This suggests that rotation- and impact-driven origin of activity can be comparably common among small asteroids.

Generation and Termination of Binary Decision Trees for Nonparametric Multiclass Classification.

DTIC Science & Technology

1984-10-01

O M coF=F;; UMBER2. GOVT ACCE5SION NO.1 3 . REC,PINS :A7AL:,G NUMBER ( ’eneration and Terminat_,on :)f Binary D-ecision jC j ik; Trees for Nonnararetrc...1-I . v)IAMO 0~I4 EDvt" O F I 00 . 3 15I OR%.OL.ETL - S-S OCTOBER 1984 LIDS-P-1411 GENERATION AND TERMINATION OF BINARY DECISION TREES FOR...minimizes the Bayes risk. Tree generation and termination are based on the training and test samples, respectively. 0 0 0/ 6 0¢ A 3 I. Introduction We state

Low Mach number fluctuating hydrodynamics of multispecies liquid mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donev, Aleksandar, E-mail: donev@courant.nyu.edu; Bhattacharjee, Amit Kumar; Nonaka, Andy

We develop a low Mach number formulation of the hydrodynamic equations describing transport of mass and momentum in a multispecies mixture of incompressible miscible liquids at specified temperature and pressure, which generalizes our prior work on ideal mixtures of ideal gases [Balakrishnan et al., “Fluctuating hydrodynamics of multispecies nonreactive mixtures,” Phys. Rev. E 89 013017 (2014)] and binary liquid mixtures [Donev et al., “Low mach number fluctuating hydrodynamics of diffusively mixing fluids,” Commun. Appl. Math. Comput. Sci. 9(1), 47-105 (2014)]. In this formulation, we combine and extend a number of existing descriptions of multispecies transport available in the literature. Themore » formulation applies to non-ideal mixtures of arbitrary number of species, without the need to single out a “solvent” species, and includes contributions to the diffusive mass flux due to gradients of composition, temperature, and pressure. Momentum transport and advective mass transport are handled using a low Mach number approach that eliminates fast sound waves (pressure fluctuations) from the full compressible system of equations and leads to a quasi-incompressible formulation. Thermal fluctuations are included in our fluctuating hydrodynamics description following the principles of nonequilibrium thermodynamics. We extend the semi-implicit staggered-grid finite-volume numerical method developed in our prior work on binary liquid mixtures [Nonaka et al., “Low mach number fluctuating hydrodynamics of binary liquid mixtures,” http://arxiv.org/abs/1410.2300 (2015)] and use it to study the development of giant nonequilibrium concentration fluctuations in a ternary mixture subjected to a steady concentration gradient. We also numerically study the development of diffusion-driven gravitational instabilities in a ternary mixture and compare our numerical results to recent experimental measurements [Carballido-Landeira et al., “Mixed-mode instability of a miscible interface due to coupling between Rayleigh–Taylor and double-diffusive convective modes,” Phys. Fluids 25, 024107 (2013)] in a Hele-Shaw cell. We find that giant nonequilibrium fluctuations can trigger the instability but are eventually dominated by the deterministic growth of the unstable mode, in both quasi-two-dimensional (Hele-Shaw) and fully three-dimensional geometries used in typical shadowgraph experiments.« less

Interactions of Organic Solvents at Graphene/α-Al 2 O 3 and Graphene Oxide/α-Al 2 O 3 Interfaces Studied by Sum Frequency Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Achtyl, Jennifer L.; Vlassiouk, Ivan V.; Dai, Sheng

2014-07-17

The adsorption of 1-hexanol from cyclohexane-d12 at single-layer graphene/α-Al2O3 interfaces was probed at mole percent values as low as 0.05 in the C–H stretching region using vibrational sum frequency generation (SFG). The SFG spectra are indiscernible from those obtained in the absence of graphene, and from those obtained in the presence of graphene oxide films prepared via oxygen plasma treatment of pristine single-layer graphene. A Langmuir adsorption model yields observed free adsorption energies of -19.9(5) to -20.9(3) kJ/mol for the three interfaces. The results indicate that the molecular structure of the hexanol alkyl chain is subject to the same orientationmore » distribution when graphene, oxidized or not, is present or absent at the α-Al2O3/cyclohexane-d12 interface. Moreover, it appears that the adsorption of 1-hexanol in this binary mixture is driven by hexanol interactions with the underlying oxide support, and that a single layer of graphene does not influence the extent of this interaction, even when defects are introduced to it. Finally, our structural and quantitative thermodynamic data provide important benchmarks for theoretical calculations and atomistic simulations of liquid/graphene interfaces. We hypothesize that defects emerging in graphene during operation of any device application that relies on layered solvent/graphene/oxide interfaces have little impact on the interfacial structure or thermodynamics, at least for the binary mixture and over the range of defect densities probed in our studies.« less

Binary Phase Diagrams and Thermodynamic Properties of Silicon and Essential Doping Elements (Al, As, B, Bi, Ga, In, N, P, Sb and Tl)

PubMed Central

Mostafa, Ahmad; Medraj, Mamoun

2017-01-01

Fabrication of solar and electronic silicon wafers involves direct contact between solid, liquid and gas phases at near equilibrium conditions. Understanding of the phase diagrams and thermochemical properties of the Si-dopant binary systems is essential for providing processing conditions and for understanding the phase formation and transformation. In this work, ten Si-based binary phase diagrams, including Si with group IIIA elements (Al, B, Ga, In and Tl) and with group VA elements (As, Bi, N, P and Sb), have been reviewed. Each of these systems has been critically discussed on both aspects of phase diagram and thermodynamic properties. The available experimental data and thermodynamic parameters in the literature have been summarized and assessed thoroughly to provide consistent understanding of each system. Some systems were re-calculated to obtain a combination of the best evaluated phase diagram and a set of optimized thermodynamic parameters. As doping levels of solar and electronic silicon are of high technological importance, diffusion data has been presented to serve as a useful reference on the properties, behavior and quantities of metal impurities in silicon. This paper is meant to bridge the theoretical understanding of phase diagrams with the research and development of solar-grade silicon production, relying on the available information in the literature and our own analysis. PMID:28773034

Zirconia toughened SiC whisker reinforced alumina composites small business innovation research

NASA Technical Reports Server (NTRS)

Loutfy, R. O.; Stuffle, K. L.; Withers, J. C.; Lee, C. T.

1987-01-01

The objective of this phase 1 project was to develop a ceramic composite with superior fracture toughness and high strength, based on combining two toughness inducing materials: zirconia for transformation toughening and SiC whiskers for reinforcement, in a controlled microstructure alumina matrix. The controlled matrix microstructure is obtained by controlling the nucleation frequency of the alumina gel with seeds (submicron alpha-alumina). The results demonstrate the technical feasibility of producing superior binary composites (Al2O3-ZrO2) and tertiary composites (Al2O3-ZrO2-SiC). Thirty-two composites were prepared, consolidated, and fracture toughness tested. Statistical analysis of the results showed that: (1) the SiC type is the key statistically significant factor for increased toughness; (2) sol-gel processing with a-alumina seed had a statistically significant effect on increasing toughness of the binary and tertiary composites compared to the corresponding mixed powder processing; and (3) ZrO2 content within the range investigated had a minor effect. Binary composites with an average critical fracture toughness of 6.6MPam sup 1/2, were obtained. Tertiary composites with critical fracture toughness in the range of 9.3 to 10.1 MPam sup 1/2 were obtained. Results indicate that these composites are superior to zirconia toughened alumina and SiC whisker reinforced alumina ceramic composites produced by conventional techniques with similar composition from published data.

Clustering for Binary Data Sets by Using Genetic Algorithm-Incremental K-means

NASA Astrophysics Data System (ADS)

Saharan, S.; Baragona, R.; Nor, M. E.; Salleh, R. M.; Asrah, N. M.

2018-04-01

This research was initially driven by the lack of clustering algorithms that specifically focus in binary data. To overcome this gap in knowledge, a promising technique for analysing this type of data became the main subject in this research, namely Genetic Algorithms (GA). For the purpose of this research, GA was combined with the Incremental K-means (IKM) algorithm to cluster the binary data streams. In GAIKM, the objective function was based on a few sufficient statistics that may be easily and quickly calculated on binary numbers. The implementation of IKM will give an advantage in terms of fast convergence. The results show that GAIKM is an efficient and effective new clustering algorithm compared to the clustering algorithms and to the IKM itself. In conclusion, the GAIKM outperformed other clustering algorithms such as GCUK, IKM, Scalable K-means (SKM) and K-means clustering and paves the way for future research involving missing data and outliers.

Strengthening by Substitutional Solutes and the Temperature Dependence of the Flow Stress in Ni3Al

DTIC Science & Technology

1989-05-26

stoichiometric composition in polycrystalline Ni3AI and Ni3Ga. 29 Fig. 3.1 The Ni-Al binary-alloy phase diagram in vacinity of Ni3A1 phase, as verified in...I <I- iai / I I- I I I I000 - - II 21 25 29 33 37 ATOMIC % Al Fig. 3.1 The Ni-Al binary-alloy phase diagram in vacinity of Ni3Al phase, as verified

Young Binaries and Early Stellar Evolution

NASA Astrophysics Data System (ADS)

Brandner, Wolfgang

1996-07-01

Most main-sequence stars are members of binary or multiple systems. The same is true for pre-main-sequence (PMS) stars, as recent surveys have shown. Therefore studying star formation means to a large extent studying the formation of binary systems. Similarly, studying early stellar evolution primarily involves PMS binary systems. In this thesis I have studied the binary frequency among ROSAT selected T Tauri stars in the Chamaeleon T association and the Scorpius-Centaurus OB association, and the evolutionary status of Hα-selected PMS binaries in the T associations of Chamaeleon, Lupus, and ρ Ophiuchi. The direct imaging and spectroscopic observations in the optical have been carried out under subarcsec seeing conditions at the ESO New Technology Telescope (NTT) at La Silla. Furthermore, high-spatial resolution images of selected PMS stars in the near infrared were obtained with the ESO adaptive optics system COME-ON+/ADONIS. Among 195 T Tauri stars observed using direct imaging 31 binaries could be identified, 12 of them with subarcsec separation. Based on statistical arguments alone I conclude that almost all of them are indeed physical (i.e. gravitationally bound) binary or multiple systems. Using astrometric measurements of some binaries I showed that the components of these binaries are common proper motion pairs, very likely in a gravitationally bound orbit around each other. The overall binary frequency among T Tauri stars with a range of separations between 120 and 1800 AU is in agreement with the binary frequency observed among main-sequence stars in the solar neighbourhood. However, within individual regions the spatial distribution of binaries is non-uniform. In particular, in Upper Scorpius, weak-line T Tauri stars in the vicinity of early type stars seem to be almost devoid of multiple systems, whereas in another area in Upper Scorpius half of all weak-line T Tauri stars have a companion in a range of separation between 0.''7 and 3.''0. For a sample of 14 spatially resolved PMS binaries (separations 0.''6 to 1.prime'7) located in the above mentioned T associations both photometric and spectroscopic information has been analyzed. All binaries (originally unresolved) were identified as PMS stars based on their strong Hα emission and their association with dark clouds. Using the spectral A index, which measures the strength of the CaH band at 697.5nm relative to the nearby continuum as a luminosity class indicator, I showed that the classical T Tauri stars in the sample tend to be close to luminosity class V. Eight out of the 14 pairs could be placed on an H--R diagram. When comparing with theoretical PMS evolutionary tracks the individual components of all pairs appear to be coeval within the observational errors. This result is similar to Hartigan et al. (1994) who found two thirds of the wider pairs with separations from 400 AU to 6000 AU to be coeval. However, unlike Hartigan et al.'s finding for the wider pairs, I find no non-coeval pairs. One of the presumed binaries in our sample (ESO Hα 281) turned out to be a likely chance projection with the ``primary'' showing neither Hα emission nor Li absorption. Finally, using adaptive optics at the ESO 3.6m telescope, diffraction-limited JHK images of the region around the Herbig AeBe star NX Pup were obtained. The close companion (sep. 0.''128) to NX Pup -- originally discovered by HST -- was clearly resolved and its JHK magnitudes were determined. A third object at a separation of 7.''0 from NX Pup was identified as a classical T Tauri star so that NX Pup may in fact form a hierarchical triple system. I discuss the evolutionary status of these stars and derive estimates for their spectral types, luminosities, masses, and ages. My conclusions are that binarity is established very early in stellar evolution, that the orbital parameters of wide binaries (a >= 120AU) remain virtually unchanged during their PMS evolution, and that the components of the wide binaries were formed at the same time --- perhaps either through collisional fragmentation or fragmentation of rotating filaments. (Copies of the thesis (written in German) and related pre-/reprints are available from the author upon request.)

High temperature structure in cool binary stars

NASA Technical Reports Server (NTRS)

Dupree, A. K.; Brickhouse, Nancy S.; Hanson, G. J.

1995-01-01

Strong high temperature emission lines in the EUVE spectra of binary stars containing cool components (Alpha Aur (Capella), 44 iota Boo, Lambda And, and VY Ari) provide the basis to define reliably the differential emission measure of hot plasma. The emission measure distributions for the short-period (P less than or equal to 13 d) binary systems show a high temperature enhancement over a relatively narrow temperature region similar to that originally found in Capella (Dupree et al. 1993). The emission measure distributions of rapidly rotating single stars 31 Com and AB Dor also contain a local enhancement of the emission measure although at different temperatures and width from Capella, suggesting that the enhancement in these objects may be characteristic of rapid rotation of a stellar corona. This feature might be identified with a (polar) active region, although its density and absolute size are unknown; in the binaries Capella and VY Ari, the feature is narrow and it may arise from an interaction region between the components.

Phase Composition and Hardening of Castable Al - Ca - Ni - Sc Alloys Containing 0.3% Sc

NASA Astrophysics Data System (ADS)

Belov, N. A.; Naumova, E. A.; Bazlova, T. A.; Doroshenko, V. V.

2017-05-01

The phase composition of aluminum alloys of the Al - Ca - Ni - Sc system containing 0.3 wt.% Sc is studied. It is shown that the aluminum solid solution may be in equilibrium not only with binary phases (Al4Ca, Al3Sc and Al3Ni) but also with a ternary Al9NiCa compound. The temperature of attainment of maximum hardening due to precipitation of nanoparticles of phase Al3Sc is determined for all the alloys studied. Principal possibility of creation of castable alloys based on an (Al) + Al4Ca + Al9NiCa eutectic, the hardening heat treatment of which does not require quenching, is substantiated.

Assisted stellar suicide: the wind-driven evolution of the recurrent nova T Pyxidis

NASA Astrophysics Data System (ADS)

Knigge, Ch.; King, A. R.; Patterson, J.

2000-12-01

We show that the extremely high luminosity of the short-period recurrent nova T Pyx in quiescence can be understood if this system is a wind-driven supersoft x-ray source (SSS). In this scenario, a strong, radiation-induced wind is excited from the secondary star and accelerates the binary evolution. The accretion rate is therefore much higher than in an ordinary cataclysmic binary at the same orbital period, as is the luminosity of the white dwarf primary. In the steady state, the enhanced luminosity is just sufficient to maintain the wind from the secondary. The accretion rate and luminosity predicted by the wind-driven model for T Pyx are in good agreement with the observational evidence. X-ray observations with Chandra or XMM may be able to confirm T Pyx's status as a SSS. T Pyx's lifetime in the wind-driven state is on the order of a million years. Its ultimate fate is not certain, but the system may very well end up destroying itself, either via the complete evaporation of the secondary star, or in a Type Ia supernova if the white dwarf reaches the Chandrasekhar limit. Thus either the primary, the secondary, or both may currently be committing assisted stellar suicide.

The NANOGrav Nine-Year Data Set: Limits on the Isotropic Stochastic Gravitational Wave Background

NASA Technical Reports Server (NTRS)

Arzoumanian, Z.; Brazier, A.; Burke-Spolaor, S.; Chamberlin, S. J.; Chatterjee, S.; Christy, B.; Cordes, J. M.; Cornish, N. J.; Crowter, K.; Demorest, P. B.;

The rapid size- and shape-controlled continuous hydrothermal synthesis of metal sulphide nanomaterials

NASA Astrophysics Data System (ADS)

Dunne, Peter W.; Starkey, Chris L.; Gimeno-Fabra, Miquel; Lester, Edward H.

2014-01-01

Continuous flow hydrothermal synthesis offers a cheap, green and highly scalable route for the preparation of inorganic nanomaterials which has predominantly been applied to metal oxide based materials. In this work we report the first continuous flow hydrothermal synthesis of metal sulphide nanomaterials. A wide range of binary metal sulphides, ZnS, CdS, PbS, CuS, Fe(1-x)S and Bi2S3, have been synthesised. By varying the reaction conditions two different mechanisms may be invoked; a growth dominated route which permits the formation of nanostructured sulphide materials, and a nucleation driven process which produces nanoparticles with temperature dependent size control. This offers a new and industrially viable route to a wide range of metal sulphide nanoparticles with facile size and shape control.Continuous flow hydrothermal synthesis offers a cheap, green and highly scalable route for the preparation of inorganic nanomaterials which has predominantly been applied to metal oxide based materials. In this work we report the first continuous flow hydrothermal synthesis of metal sulphide nanomaterials. A wide range of binary metal sulphides, ZnS, CdS, PbS, CuS, Fe(1-x)S and Bi2S3, have been synthesised. By varying the reaction conditions two different mechanisms may be invoked; a growth dominated route which permits the formation of nanostructured sulphide materials, and a nucleation driven process which produces nanoparticles with temperature dependent size control. This offers a new and industrially viable route to a wide range of metal sulphide nanoparticles with facile size and shape control. Electronic supplementary information (ESI) available: Experimental details, refinement procedure, fluorescence spectra of ZnS samples. See DOI: 10.1039/c3nr05749f

Amorphous and nanocrystalline phase formation in highly-driven Al-based binary alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalay, Yunus Eren

2009-01-01

Remarkable advances have been made since rapid solidification was first introduced to the field of materials science and technology. New types of materials such as amorphous alloys and nanostructure materials have been developed as a result of rapid solidification techniques. While these advances are, in many respects, ground breaking, much remains to be discerned concerning the fundamental relationships that exist between a liquid and a rapidly solidified solid. The scope of the current dissertation involves an extensive set of experimental, analytical, and computational studies designed to increase the overall understanding of morphological selection, phase competition, and structural hierarchy that occursmore » under far-from equilibrium conditions. High pressure gas atomization and Cu-block melt-spinning are the two different rapid solidification techniques applied in this study. The research is mainly focused on Al-Si and Al-Sm alloy systems. Silicon and samarium produce different, yet favorable, systems for exploration when alloyed with aluminum under far-from equilibrium conditions. One of the main differences comes from the positions of their respective T 0 curves, which makes Al-Si a good candidate for solubility extension while the plunging T 0 line in Al-Sm promotes glass formation. The rapidly solidified gas-atomized Al-Si powders within a composition range of 15 to 50 wt% Si are examined using scanning and transmission electron microscopy. The non-equilibrium partitioning and morphological selection observed by examining powders at different size classes are described via a microstructure map. The interface velocities and the amount of undercooling present in the powders are estimated from measured eutectic spacings based on Jackson-Hunt (JH) and Trivedi-Magnin-Kurz (TMK) models, which permit a direct comparison of theoretical predictions. For an average particle size of 10 {micro}m with a Peclet number of ~0.2, JH and TMK deviate from each other. This deviation indicates an adiabatic type solidification path where heat of fusion is reabsorbed. It is interesting that this particle size range is also consistent with the appearance of a microcellular growth. While no glass formation is observed within this system, the smallest size powders appear to consist of a mixture of nanocrystalline Si and Al. Al-Sm alloys have been investigated within a composition range of 34 to 42 wt% Sm. Gas atomized powders of Al-Sm are investigated to explore the morphological and structural hierarchy that correlates with different degrees of departure from full equilibrium conditions. The resultant powders show a variety of structural selection with respect to amount of undercooling, with an amorphous structure appearing at the highest cooling rates. Because of the chaotic nature of gas atomization, Cu-block melt-spinning is used to produce a homogeneous amorphous structure. The as-quenched structure within Al-34 to 42 wt% Sm consists of nanocrystalline fcc-Al (on the order of 5 nm) embedded in an amorphous matrix. The nucleation density of fcc-Al after initial crystallization is on the order of 10 22-10 23m -3, which is 10 5-10 6 orders of magnitude higher than what classical nucleation theory predicts. Detailed analysis of liquid and as-quenched structures using high energy synchrotron X-ray diffraction, high energy transmission electron microscopy, and atom probe tomography techniques revealed an Al-Sm network similar in appearance to a medium range order (MRO) structure. A model whereby these MRO clusters promote the observed high nucleation density of fcc-Al nanocrystals is proposed. The devitrification path was identified using high temperature, in-situ, high energy synchrotron X-ray diffraction techniques and the crystallization kinetics were described using an analytical Johnson-Mehl-Avrami (JMA) approach.« less

Engineering the switching dynamics of TiOx-based RRAM with Al doping

NASA Astrophysics Data System (ADS)

Trapatseli, Maria; Khiat, Ali; Cortese, Simone; Serb, Alexantrou; Carta, Daniela; Prodromakis, Themistoklis

2016-07-01

Titanium oxide (TiOx) has attracted a lot of attention as an active material for resistive random access memory (RRAM), due to its versatility and variety of possible crystal phases. Although existing RRAM materials have demonstrated impressive characteristics, like ultra-fast switching and high cycling endurance, this technology still encounters challenges like low yields, large variability of switching characteristics, and ultimately device failure. Electroforming has been often considered responsible for introducing irreversible damage to devices, with high switching voltages contributing to device degradation. In this paper, we have employed Al doping for tuning the resistive switching characteristics of titanium oxide RRAM. The resistive switching threshold voltages of undoped and Al-doped TiOx thin films were first assessed by conductive atomic force microscopy. The thin films were then transferred in RRAM devices and tested with voltage pulse sweeping, demonstrating that the Al-doped devices could on average form at lower potentials compared to the undoped ones and could support both analog and binary switching at potentials as low as 0.9 V. This work demonstrates a potential pathway for implementing low-power RRAM systems.

Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transformation temperature

NASA Technical Reports Server (NTRS)

Antolovich, Stephen D.; Saxena, Ashok; Cullers, Cheryl

1992-01-01

One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is considered a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems. More importantly though, probing the deformation mechanisms operating in fatigue will lead to a better understanding of NiAl's unique characteristics. Low cycle fatigue properties have been reported on binary NiAl in the past year, yet those studies were limited to two temperature ranges: room temperature and near 1000 K. Eventually, fatigue property data will be needed for a wide range of temperatures and compositions. The intermediate temperature range near the brittle-to-ductile transition was chosen for this study to ascertain whether the sharp change occurring in monotonic behavior also occurs under cyclic conditions. An effort was made to characterize the dislocation structures which evolved during fatigue testing and comment on their role in the deformation process.

Compositional origin of unusual β-relaxation properties in La-Ni-Al metallic glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Z. G.; Li, Y. Z.; Wang, Z.

2014-08-28

The β-relaxation of metallic glasses (MGs) bears nontrivial connections to their microscopic and macroscopic properties. In an effort to elucidate the mechanism of the β-relaxation, we studied by dynamical mechanical measurements the change of its properties on varying the composition of La{sub 60}Ni{sub 15}Al{sub 25} in various ways. The properties of the β-relaxation turn out to be very sensitive to the composition. It is found that the isochronal loss peak temperature of β-relaxation, T{sub β,peak}, is effectively determined by the total (La + Ni) content. When Cu is added into the alloy to replace either La, Ni, or Al, themore » T{sub β,peak} increases with decrease of the (La + Ni) content. The trend is in accordance with data of binary and ternary MGs formed from La, Ni, Al, and Cu. Binary La-Ni MGs have pronounced β-relaxation loss peaks, well separated from the α-relaxation. In contrast, the β-relaxation is not resolved in La-Al and La-Cu MGs, showing up as an excess wing. For the ternary La-Ni-Al MGs, increase of La or Ni content is crucial to lower the T{sub β,peak}. Keeping the Al content fixed, increase of La content lowers the T{sub β,peak} further, indicating the more important role La plays in lowering T{sub β,peak} than Ni. The observed effects on changing the composition of La{sub 60}Ni{sub 15}Al{sub 25} lead to the conclusion that the properties of the β-relaxation are mainly determined by the interaction between the largest solvent element, La, and the smallest element, Ni. From our data, it is further deduced that La and Ni have high mobility in the MGs, and this explains why the β-relaxation in this La-based MGs is prominent and well resolved from the α-relaxation as opposed to Pd- and Zr-based MGs where the solvent and largest atoms, Pd and Zr, are the least mobile.« less

Probing the clumpy winds of giant stars with high mass X-ray binaries

NASA Astrophysics Data System (ADS)

Grinberg, Victoria; Hell, Natalie; Hirsch, Maria; Garcia, Javier; Huenemoerder, David; Leutenegger, Maurice A.; Nowak, Michael; Pottschmidt, Katja; Schulz, Norbert S.; Sundqvists, Jon O.; Townsend, Richard D.; Wilms, Joern

2016-04-01

Line-driven winds from early type stars are structured, with small, overdense clumps embedded in tenuous hot gas. High mass X-ray binaries (HMXBs), systems where a neutron star or a black hole accretes from the line-driven stellar wind of an O/B-type companion, are ideal for studying such winds: the wind drives the accretion onto the compact object and thus the X-ray production. The radiation from close to the compact object is quasi-pointlike and effectively X-rays the wind.We used RXTE and Chandra-HETG observations of two of the brightest HMXBs, Cyg X-1 and Vela X-1, to decipher their wind structure. In Cyg X-1, we show that the orbital variability of absorption can be only explained by a clumpy wind model and constrain the porosity of the wind as well as the onion-like structure of the clumps. In Vela X-1 we show, using the newest reference energies for low ionization Si-lines obtained with LLNL’s EBIT-I, that the ionized phase of the circumstellar medium and the cold clumps have different velocities.

Orbital period changes in RW CrA, DX Vel and V0646 Cen

NASA Astrophysics Data System (ADS)

Volkov, I. M.; Chochol, D.; Grygar, J.; Mašek, M.; Juryšek, J.

2017-06-01

We aim to determine the absolute parameters of the components of southern Algol-type binaries with deep eclipses RW CrA, DX Vel, V0646 Cen and interpret their orbital period changes. The data analysis is based on a high quality Walraven photoelectric photometry, obtained in the 1960-70s, our recent CCD photometry, ASAS (Pojmanski, 2002), and Hipparcos (Perryman et al., 1997) photometry of the objects. Their light curves were analyzed using the PHOEBE program with fixed effective temperatures of the primary components, found from disentangling the Walraven (B-U) and (V-B) colour indices. We found the absolute parameters of the components of all three objects. All reliable observed times of minimum light were used to construct and analyze the Eclipse Time Variation (ETV) diagrams. We interpreted the ETV diagrams of the detached binary RW CrA and the semi-detached binary DX Vel by a LIght-Time Effect (LITE), estimated parameters of their orbits and masses of their third bodies. We suggest a long term variation of the inclination angle of both eclipsing binaries, caused by a non-coplanar orientation of their third body orbits. We interpreted the detected orbital period increase in the semi-detached binary V0646 Cen by a mass transfer from the less to more massive component with the rate M⊙ = 6.08×10-9 M⊙/yr.

Molecular dynamics simulations show altered secondary structure of clawless in binary complex with DNA providing insights into aristaless-clawless-DNA ternary complex formation.

PubMed

Kachhap, Sangita; Priyadarshini, Pragya; Singh, Balvinder

2017-05-01

Aristaless (Al) and clawless (Cll) homeodomains that are involved in leg development in Drosophila melanogaster are known to bind cooperatively to 5'-(T/C)TAATTAA(T/A)(T/A)G-3' DNA sequence, but the mechanism of their binding to DNA is unknown. Molecular dynamics (MD) studies have been carried out on binary, ternary, and reconstructed protein-DNA complexes involving Al, Cll, and DNA along with binding free energy analysis of these complexes. Analysis of MD trajectories of Cll-3A01, binary complex reveals that C-terminal end of helixIII of Cll, unwind in the absence of Al and remains so in reconstructed ternary complex, Cll-3A01-Al. In addition, this change in secondary structure of Cll does not allow it to form protein-protein interactions with Al in the ternary reconstructed complex. However, secondary structure of Cll and its interactions are maintained in other reconstructed ternary complex, Al-3A01-Cll where Cll binds to Al-3A01, binary complex to form ternary complex. These interactions as observed during MD simulations compare well with those observed in ternary crystal structure. Thus, this study highlights the role of helixIII of Cll and protein-protein interactions while proposing likely mechanism of recognition in ternary complex, Al-Cll-DNA.

Comparative study of blue laser diode driven cerium-doped single crystal phosphors in application of high-power lighting and display technologies

NASA Astrophysics Data System (ADS)

Balci, Mustafa H.; Chen, Fan; Cunbul, A. Burak; Svensen, Øyvind; Akram, M. Nadeem; Chen, Xuyuan

2018-02-01

Cerium-doped single crystals (Ce:LuAG, Ce:YAG, Ce:GAGG, Ce:GdYAG) have been investigated as stationary phosphor candidates for blue laser driven solid-state lighting without heat sink. The luminous properties of the single crystals are superior compared to the commercial ceramic powder phosphor wheels (Ce3+: Y3Al5O12). The high-power blue laser diode driven temperature increase of the crystals versus quantum efficiency is experimentally measured and discussed. We have carried out realistic measurements at high excitation power levels and at high temperatures. Limitation of phosphors as stationary sources is determined for commercial usage. The measurements were done without any heat sink to see the relative comparison of SCPs in the worst-case scenarios. The results indicate that Gd and Ga addition decreases the luminescence quenching temperature. Based on their superior properties, these single crystals can serve as potential phosphor candidates for high-power blue diode laser driven picture projectors for the green and red channels.

Investigating the Binary Offset Effect in the STIS CCD

NASA Astrophysics Data System (ADS)

Debes, John H.; Lockwood, Sean A.

2018-05-01

Recently, Boone et al., (2018) presented the "Binary Offset Effect" for the SNIFS instrument, which uses a CCD detector. The source of this uncertainty is related to the analog-to-digital readout process, which converts the analog electronic signal of the detector into a digital number as represented by binary bits. The Binary Offset Effect is due to cross-talk between the digital conversion process for a source or driver pixel and pixels read out after the driver. In the course of Boone et al.'s experimentation with this effect they identified a similar effect with the STIS CCD. The STIS team has independently investigated the Binary Offset Effect for a range of bias images currently used for scientific observations, broadly confirming that the effect exists. However, our preliminary investigation suggests that the impact is smaller than reported in Boone et al. (2018) for biases taken with Amplifier=D and GAIN=1, and a lesser effect exists for Amplifier=D and GAIN=4. There is a hint that the effect is time variable for the detector. We broadly assess the potential impact of this effect and make recommendations both for users and future directions of investigation.

Ab initio simulations of molten Ni alloys

NASA Astrophysics Data System (ADS)

Woodward, Christopher; Asta, Mark; Trinkle, Dallas R.; Lill, James; Angioletti-Uberti, Stefano

2010-06-01

Convective instabilities responsible for misoriented grains in directionally solidified turbine airfoils are produced by variations in liquid-metal density with composition and temperature across the solidification zone. Here, fundamental properties of molten Ni-based alloys, required for modeling these instabilities, are calculated using ab initio molecular dynamics simulations. Equations of state are derived from constant number-volume-temperature ensembles at 1830 and 1750 K for elemental, binary (Ni-X, X=Al, W, Re, and Ta) and ternary (Ni-Al-X, X=W, Re, and Ta) Ni alloys. Calculated molar volumes agree to within 0.6%-1.8% of available measurements. Predictions are used to investigate the range of accuracy of a parameterization of molar volumes with composition and temperature based on measurements of binary alloys. Structural analysis reveals a pronounced tendency for icosahedral short-range order for Ni-W and Ni-Re alloys and the calculations provide estimates of diffusion rates and their dependence on compositions and temperature.

Pulsar-irradiated stars in dense globular clusters

NASA Technical Reports Server (NTRS)

Tavani, Marco

1992-01-01

We discuss the properties of stars irradiated by millisecond pulsars in 'hard' binaries of dense globular clusters. Irradiation by a relativistic pulsar wind as in the case of the eclipsing millisecond pulsar PSR 1957+20 alter both the magnitude and color of the companion star. Some of the blue stragglers (BSs) recently discovered in dense globular clusters can be irradiated stars in binaries containing powerful millisecond pulsars. The discovery of pulsar-driven orbital modulations of BS brightness and color with periods of a few hours together with evidence for radio and/or gamma-ray emission from BS binaries would valuably contribute to the understanding of the evolution of collapsed stars in globular clusters. Pulsar-driven optical modulation of cluster stars might be the only observable effect of a new class of binary pulsars, i.e., hidden millisecond pulsars enshrouded in the evaporated material lifted off from the irradiated companion star.

HST spectrum and timing of the ultracompact X-ray binary candidate 47 Tuc X9

NASA Astrophysics Data System (ADS)

Tudor, V.; Miller-Jones, J. C. A.; Knigge, C.; Maccarone, T. J.; Tauris, T. M.; Bahramian, A.; Chomiuk, L.; Heinke, C. O.; Sivakoff, G. R.; Strader, J.; Plotkin, R. M.; Soria, R.; Albrow, M. D.; Anderson, G. E.; van den Berg, M.; Bernardini, F.; Bogdanov, S.; Britt, C. T.; Russell, D. M.; Zurek, D. R.

2018-05-01

To confirm the nature of the donor star in the ultracompact X-ray binary candidate 47 Tuc X9, we obtained optical spectra (3000-10 000 Å) with the Hubble Space Telescope / Space Telescope Imaging Spectrograph. We find no strong emission or absorption features in the spectrum of X9. In particular, we place 3σ upper limits on the H α and He II λ4686 emission line equivalent widths - EWH α ≲ 14 Å and -EW_{He {II}} ≲ 9 Å, respectively. This is much lower than seen for typical X-ray binaries at a similar X-ray luminosity (which, for L_2-10 keV ≈ 10^{33}-10^{34} erg s-1 is typically - EWH α ˜ 50 Å). This supports our previous suggestion, by Bahramian et al., of an H-poor donor in X9. We perform timing analysis on archival far-ultraviolet, V- and I-band data to search for periodicities. In the optical bands, we recover the 7-d superorbital period initially discovered in X-rays, but we do not recover the orbital period. In the far-ultraviolet, we find evidence for a 27.2 min period (shorter than the 28.2 min period seen in X-rays). We find that either a neutron star or black hole could explain the observed properties of X9. We also perform binary evolution calculations, showing that the formation of an initial black hole/ He-star binary early in the life of a globular cluster could evolve into a present-day system such as X9 (should the compact object in this system indeed be a black hole) via mass-transfer driven by gravitational wave radiation.

R144: a very massive binary likely ejected from R136 through a binary-binary encounter

NASA Astrophysics Data System (ADS)

Oh, Seungkyung; Kroupa, Pavel; Banerjee, Sambaran

2014-02-01

R144 is a recently confirmed very massive, spectroscopic binary which appears isolated from the core of the massive young star cluster R136. The dynamical ejection hypothesis as an origin for its location is claimed improbable by Sana et al. due to its binary nature and high mass. We demonstrate here by means of direct N-body calculations that a very massive binary system can be readily dynamically ejected from an R136-like cluster, through a close encounter with a very massive system. One out of four N-body cluster models produces a dynamically ejected very massive binary system with a mass comparable to R144. The system has a system mass of ≈355 M⊙ and is located at 36.8 pc from the centre of its parent cluster, moving away from the cluster with a velocity of 57 km s-1 at 2 Myr as a result of a binary-binary interaction. This implies that R144 could have been ejected from R136 through a strong encounter with another massive binary or single star. In addition, we discuss all massive binaries and single stars which are ejected dynamically from their parent cluster in the N-body models.

Relaxation near Supermassive Black Holes Driven by Nuclear Spiral Arms: Anisotropic Hypervelocity Stars, S-stars, and Tidal Disruption Events

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamers, Adrian S.; Perets, Hagai B., E-mail: hamers@ias.edu

Nuclear spiral arms are small-scale transient spiral structures found in the centers of galaxies. Similarly to their galactic-scale counterparts, nuclear spiral arms can perturb the orbits of stars. In the case of the Galactic center (GC), these perturbations can affect the orbits of stars and binaries in a region extending to several hundred parsecs around the supermassive black hole (SMBH), causing diffusion in orbital energy and angular momentum. This diffusion process can drive stars and binaries to close approaches with the SMBH, disrupting single stars in tidal disruption events (TDEs), or disrupting binaries, leaving a star tightly bound to themore » SMBH and an unbound star escaping the galaxy, i.e., a hypervelocity star (HVS). Here, we consider diffusion by nuclear spiral arms in galactic nuclei, specifically the Milky Way GC. We determine nuclear-spiral-arm-driven diffusion rates using test-particle integrations and compute disruption rates. Our TDE rates are up to 20% higher compared to relaxation by single stars. For binaries, the enhancement is up to a factor of ∼100, and our rates are comparable to the observed numbers of HVSs and S-stars. Our scenario is complementary to relaxation driven by massive perturbers. In addition, our rates depend on the inclination of the binary with respect to the Galactic plane. Therefore, our scenario provides a novel potential source for the observed anisotropic distribution of HVSs. Nuclear spiral arms may also be important for accelerating the coalescence of binary SMBHs and for supplying nuclear star clusters with stars and gas.« less

Forming spectroscopic massive protobinaries by disc fragmentation

NASA Astrophysics Data System (ADS)

Meyer, D. M.-A.; Kuiper, R.; Kley, W.; Johnston, K. G.; Vorobyov, E.

2018-01-01

The surroundings of massive protostars constitute an accretion disc which has numerically been shown to be subject to fragmentation and responsible for luminous accretion-driven outbursts. Moreover, it is suspected to produce close binary companions which will later strongly influence the star's future evolution in the Hertzsprung-Russel diagram. We present three-dimensional gravitation-radiation-hydrodynamic numerical simulations of 100 M⊙ pre-stellar cores. We find that accretion discs of young massive stars violently fragment without preventing the (highly variable) accretion of gaseous clumps on to the protostars. While acquiring the characteristics of a nascent low-mass companion, some disc fragments migrate on to the central massive protostar with dynamical properties showing that its final Keplerian orbit is close enough to constitute a close massive protobinary system, having a young high- and a low-mass components. We conclude on the viability of the disc fragmentation channel for the formation of such short-period binaries, and that both processes - close massive binary formation and accretion bursts - may happen at the same time. FU-Orionis-type bursts, such as observed in the young high-mass star S255IR-NIRS3, may not only indicate ongoing disc fragmentation, but also be considered as a tracer for the formation of close massive binaries - progenitors of the subsequent massive spectroscopic binaries - once the high-mass component of the system will enter the main-sequence phase of its evolution. Finally, we investigate the Atacama Large (sub-)Millimeter Array observability of the disc fragments.

Harnessing Active Fins to Segregate Nanoparticles from Binary Mixtures

NASA Astrophysics Data System (ADS)

Liu, Ya; Kuksenok, Olga; Bhattacharya, Amitabh; Ma, Yongting; He, Ximin; Aizenberg, Joanna; Balazs, Anna

2014-03-01

One of the challenges in creating high-performance polymeric nanocomposites for optoelectronic applications, such as bilayer solar cells, is establishing effective and facile routes for controlling the properties of interface and segregation of binary particles with hole conductor particles and electron conductor particles. We model nanocomposites that encompass binary particles and binary blends in a microchannel. An array of oscillating microfins is immersed in the fluid and tethered to the floor of the microchannel; the fluid containing mixture of nanoparticles is driven along the channel by an imposed pressure gradient. During the oscillations, the fins with the specific chemical wetting reach the upper fluid when they are upright and are entirely within the lower stream when they are tilted. We introduce specific interaction between the fins and particulates in the solution. Fins can selectively ``catch'' target nanoparticles within the upper fluid stream and then release them into the lower stream. We focus on different modes of fins motion to optimize selective segregation of particles within binary mixture. Our approach provides an effective means of tailoring the properties and ultimate performance of the composites.

Effects of Disk Warping on the Inclination Evolution of Star-Disk-Binary Systems

NASA Astrophysics Data System (ADS)

Zanazzi, J. J.; Lai, Dong

2018-04-01

Several recent studies have suggested that circumstellar disks in young stellar binaries may be driven into misalignement with their host stars due to secular gravitational interactions between the star, disk and the binary companion. The disk in such systems is twisted/warped due to the gravitational torques from the oblate central star and the external companion. We calculate the disk warp profile, taking into account of bending wave propagation and viscosity in the disk. We show that for typical protostellar disk parameters, the disk warp is small, thereby justifying the "flat-disk" approximation adopted in previous theoretical studies. However, the viscous dissipation associated with the small disk warp/twist tends to drive the disk toward alignment with the binary or the central star. We calculate the relevant timescales for the alignment. We find the alignment is effective for sufficiently cold disks with strong external torques, especially for systems with rapidly rotating stars, but is ineffective for the majority of star-disk-binary systems. Viscous warp driven alignment may be necessary to account for the observed spin-orbit alignment in multi-planet systems if these systems are accompanied by an inclined binary companion.

Effects of disc warping on the inclination evolution of star-disc-binary systems

NASA Astrophysics Data System (ADS)

Zanazzi, J. J.; Lai, Dong

2018-07-01

Several recent studies have suggested that circumstellar discs in young stellar binaries may be driven into misalignement with their host stars due to the secular gravitational interactions between the star, disc, and the binary companion. The disc in such systems is twisted/warped due to the gravitational torques from the oblate central star and the external companion. We calculate the disc warp profile, taking into account the bending wave propagation and viscosity in the disc. We show that for typical protostellar disc parameters, the disc warp is small, thereby justifying the `flat-disc' approximation adopted in previous theoretical studies. However, the viscous dissipation associated with the small disc warp/twist tends to drive the disc towards alignment with the binary or the central star. We calculate the relevant time-scales for the alignment. We find that the alignment is effective for sufficiently cold discs with strong external torques, especially for systems with rapidly rotating stars, but is ineffective for the majority of the star-disc-binary systems. Viscous warp-driven alignment may be necessary to account for the observed spin-orbit alignment in multiplanet systems if these systems are accompanied by an inclined binary companion.

The Multiplicity of Massive Stars: A High Angular Resolution Survey With The HST Fine Guidance Sensor

DTIC Science & Technology

2015-01-01

al. (2014), and of the Large Magellanic Cloud (LMC) Tarantula Nebula region by Sana et al. (2013b), demonstrate that the binary frequency may be »70...Monte-Carlo method to fit spectroscopic results for a large sample of O-type stars in the Tarantula Nebula region of the LMC, and they find a best fit

The Effectiveness of Al-Si Coatings for Preventing Interfacial Reaction in Al-Mg Dissimilar Metal Welding

NASA Astrophysics Data System (ADS)

Wang, Yin; Al-Zubaidy, Basem; Prangnell, Philip B.

2018-01-01

The dissimilar welding of aluminum to magnesium is challenging because of the rapid formation of brittle intermetallic compounds (IMC) at the weld interface. An Al-Si coating interlayer was selected to address this problem, based on thermodynamic calculations which predicted that silicon would change the reaction path to avoid formation of the normally observed binary Al-Mg IMC phases ( β-Al3Mg2 and γ-Al12Mg17). Long-term static heat treatments confirmed that a Si-rich coating will preferentially produce the Mg2Si phase in competition with the less stable, β-Al3Mg2 and γ-Al12Mg17 binary IMC phases, and this reduced the overall reaction layer thickness. However, when an Al-Si clad sheet was tested in a real welding scenario, using the Refill™ friction stir spot welding (FSSW) technique, Mg2Si was only produced in very small amounts owing to the much shorter reaction time. Surprisingly, the coating still led to a significant reduction in the IMC reaction layer thickness and the welds exhibited enhanced mechanical performance, with improved strength and fracture energy. This beneficial behavior has been attributed to the softer coating material both reducing the welding temperature and giving rise to the incorporation of Si particles into the reaction layer, which toughened the brittle interfacial IMC phases during crack propagation.

HYPERCRITICAL ACCRETION, INDUCED GRAVITATIONAL COLLAPSE, AND BINARY-DRIVEN HYPERNOVAE

DOE PAGES

Fryer, Chris L.; Rueda, Jorge A.; Ruffini, Remo

2014-09-16

We successfully, applied the induced gravitational collapse (IGC) paradigm to the explanation of GRB-SNe. The progenitor is a tight binary system composed of a CO core and a NS companion. Furthermore, the explosion of the SN leads to hypercritical accretion onto the NS companion, which reaches the critical mass, gravitationally collapsing to a BH with consequent emission of the GRB. The first estimates of this process were based on a simplified model of the binary parameters and the Bondi-Hoyle-Lyttleton accretion rate. We present the first full numerical simulations of the IGC process. We simulate the core-collapse, the SN explosion, andmore » the hydrodynamic evolution of the accreting material falling into the Bondi-Hoyle surface of the NS. For appropriate binary parameters, the IGC occurs in short timescale 102–103 s due to the combined action of photon trapping and neutrino cooling near the NS surface. We also address the observational features of this process.« less

Effects of grain size on the strength and ductility of Ni sub 3 Al and Ni sub 3 Al + boron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viens, D.V.; Weihs, T.P.; Baker, I.

Tensile and compression experiments have been performed on Ni{sub 3}Al and on Ni{sub 3}Al + B at 77K to 1023K at 1 {times} 10{sup {minus}4}s{sup {minus}1}. At low temperatures yielding occurs discontinuously and the yield strength obeys the relationship {sigma}{sub y} = {sigma}{sub i} + kd{sup {minus}3/4} where {sigma}{sub i} and k are constants. Grain refinement has little effect on the ductility of the binary alloy, but leads to a brittle to ductile transition in the alloy containing boron. At high temperatures, grain refinement weakens the material, owing to grain boundary sliding. Dynamic recrystalization occurs and leads to another brittlemore » to ductile transition upon refining the grains. Under all conditions investigated, fracture occurs intergranularly. An analysis based upon a work-hardening model is given for the d{sup {minus}3/4} dependence of the yield strength at low temperatures.« less

Nodding motions of accretion rings and disks - A short-term period in SS 433

NASA Technical Reports Server (NTRS)

Katz, J. I.; Anderson, S. F.; Grandi, S. A.; Margon, B.

1982-01-01

It is pointed out that accretion disks and rings in mass transfer binaries have been observed spectroscopically and calculated theoretically for many years. The present investigation is partly based on the availability of several years of spectroscopic observations of the Doppler shifts of the moving lines in SS433. A formalism is presented to compute frequencies and amplitudes of short-term 'nodding' motions in precessing accretion disks in close binary systems. This formalism is applied to an analysis of the moving-line Doppler shifts in SS433. The 35d X-ray cycle of Hercules X-1 is also discussed. In the considered model, the companion star exerts a gravitational torque on the disk rim. Averaged over the binary orbit, this yields a steady torque which results in the mean driven counterprecession of the disk.

Solidification of a binary alloy: Finite-element, single-domain simulation and new benchmark solutions

NASA Astrophysics Data System (ADS)

Le Bars, Michael; Worster, M. Grae

2006-07-01

A finite-element simulation of binary alloy solidification based on a single-domain formulation is presented and tested. Resolution of phase change is first checked by comparison with the analytical results of Worster [M.G. Worster, Solidification of an alloy from a cooled boundary, J. Fluid Mech. 167 (1986) 481-501] for purely diffusive solidification. Fluid dynamical processes without phase change are then tested by comparison with previous numerical studies of thermal convection in a pure fluid [G. de Vahl Davis, Natural convection of air in a square cavity: a bench mark numerical solution, Int. J. Numer. Meth. Fluids 3 (1983) 249-264; D.A. Mayne, A.S. Usmani, M. Crapper, h-adaptive finite element solution of high Rayleigh number thermally driven cavity problem, Int. J. Numer. Meth. Heat Fluid Flow 10 (2000) 598-615; D.C. Wan, B.S.V. Patnaik, G.W. Wei, A new benchmark quality solution for the buoyancy driven cavity by discrete singular convolution, Numer. Heat Transf. 40 (2001) 199-228], in a porous medium with a constant porosity [G. Lauriat, V. Prasad, Non-darcian effects on natural convection in a vertical porous enclosure, Int. J. Heat Mass Transf. 32 (1989) 2135-2148; P. Nithiarasu, K.N. Seetharamu, T. Sundararajan, Natural convective heat transfer in an enclosure filled with fluid saturated variable porosity medium, Int. J. Heat Mass Transf. 40 (1997) 3955-3967] and in a mixed liquid-porous medium with a spatially variable porosity [P. Nithiarasu, K.N. Seetharamu, T. Sundararajan, Natural convective heat transfer in an enclosure filled with fluid saturated variable porosity medium, Int. J. Heat Mass Transf. 40 (1997) 3955-3967; N. Zabaras, D. Samanta, A stabilized volume-averaging finite element method for flow in porous media and binary alloy solidification processes, Int. J. Numer. Meth. Eng. 60 (2004) 1103-1138]. Finally, new benchmark solutions for simultaneous flow through both fluid and porous domains and for convective solidification processes are presented, based on the similarity solutions in corner-flow geometries recently obtained by Le Bars and Worster [M. Le Bars, M.G. Worster, Interfacial conditions between a pure fluid and a porous medium: implications for binary alloy solidification, J. Fluid Mech. (in press)]. Good agreement is found for all tests, hence validating our physical and numerical methods. More generally, the computations presented here could now be considered as standard and reliable analytical benchmarks for numerical simulations, specifically and independently testing the different processes underlying binary alloy solidification.

Miscibility of amorphous ZrO2-Al2O3 binary alloy

NASA Astrophysics Data System (ADS)

Zhao, C.; Richard, O.; Bender, H.; Caymax, M.; De Gendt, S.; Heyns, M.; Young, E.; Roebben, G.; Van Der Biest, O.; Haukka, S.

2002-04-01

Miscibility is a key factor for maintaining the homogeneity of the amorphous structure in a ZrO2-Al2O3 binary alloy high-k dielectric layer. In the present work, a ZrO2/Al2O3 laminate thin layer has been prepared by atomic layer chemical vapor deposition on a Si (100) wafer. This layer, with artificially induced inhomogeneity (lamination), enables one to study the change in homogeneity of the amorphous phase in the ZrO2/Al2O3 system during annealing. High temperature grazing incidence x-ray diffraction (HT-XRD) was used to investigate the change in intensity of the constructive interference peak of the x-ray beams which are reflected from the interfaces of ZrO2/Al2O3 laminae. The HT-XRD spectra show that the intensity of the peak decreases with an increase in the anneal temperature, and at 800 °C, the peak disappears. The same samples were annealed by a rapid thermal process (RTP) at temperatures between 700 and 1000 °C for 60 s. Room temperature XRD of the RTP annealed samples shows a similar decrease in peak intensity. Transmission electronic microscope images confirm that the laminate structure is destroyed by RTP anneals and, just below the crystallization onset temperature, a homogeneous amorphous ZrAlxOy phase forms. The results demonstrate that the two artificially separated phases, ZrO2 and Al2O3 laminae, tend to mix into a homogeneous amorphous phase before crystallization. This observation indicates that the thermal stability of ZrO2-Al2O3 amorphous phase is suitable for high-k applications.

Neutron-star–black-hole binaries produced by binary-driven hypernovae

DOE PAGES

Fryer, Chris L.; Oliveira, F. G.; Rueda, Jorge A.; ...

2015-12-04

Here, binary-driven hypernovae (BdHNe) within the induced gravitational collapse paradigm have been introduced to explain energetic (E iso ≳10 52 erg), long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). The progenitor is a tight binary composed of a carbon-oxygen (CO) core and a neutron-star (NS) companion, a subclass of the newly proposed “ultrastripped” binaries. The CO-NS short-period orbit causes the NS to accrete appreciable matter from the SN ejecta when the CO core collapses, ultimately causing it to collapse to a black hole (BH) and producing a GRB. These tight binaries evolve through the SN explosion very differentlymore » than compact binaries studied in population synthesis calculations. First, the hypercritical accretion onto the NS companion alters both the mass and the momentum of the binary. Second, because the explosion time scale is on par with the orbital period, the mass ejection cannot be assumed to be instantaneous. This dramatically affects the post-SN fate of the binary. Finally, the bow shock created as the accreting NS plows through the SN ejecta transfers angular momentum, braking the orbit. These systems remain bound even if a large fraction of the binary mass is lost in the explosion (well above the canonical 50% limit), and even large kicks are unlikely to unbind the system. Indeed, BdHNe produce a new family of NS-BH binaries unaccounted for in current population synthesis analyses and, although they may be rare, the fact that nearly 100% remain bound implies that they may play an important role in the compact merger rate, important for gravitational waves that, in turn, can produce a new class of ultrashort GRBs.« less

Neutron-Star-Black-Hole Binaries Produced by Binary-Driven Hypernovae.

PubMed

Fryer, Chris L; Oliveira, F G; Rueda, J A; Ruffini, R

2015-12-04

Binary-driven hypernovae (BdHNe) within the induced gravitational collapse paradigm have been introduced to explain energetic (E_{iso}≳10^{52}  erg), long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). The progenitor is a tight binary composed of a carbon-oxygen (CO) core and a neutron-star (NS) companion, a subclass of the newly proposed "ultrastripped" binaries. The CO-NS short-period orbit causes the NS to accrete appreciable matter from the SN ejecta when the CO core collapses, ultimately causing it to collapse to a black hole (BH) and producing a GRB. These tight binaries evolve through the SN explosion very differently than compact binaries studied in population synthesis calculations. First, the hypercritical accretion onto the NS companion alters both the mass and the momentum of the binary. Second, because the explosion time scale is on par with the orbital period, the mass ejection cannot be assumed to be instantaneous. This dramatically affects the post-SN fate of the binary. Finally, the bow shock created as the accreting NS plows through the SN ejecta transfers angular momentum, braking the orbit. These systems remain bound even if a large fraction of the binary mass is lost in the explosion (well above the canonical 50% limit), and even large kicks are unlikely to unbind the system. Indeed, BdHNe produce a new family of NS-BH binaries unaccounted for in current population synthesis analyses and, although they may be rare, the fact that nearly 100% remain bound implies that they may play an important role in the compact merger rate, important for gravitational waves that, in turn, can produce a new class of ultrashort GRBs.

Neutron-Star-Black-Hole Binaries Produced by Binary-Driven Hypernovae

NASA Astrophysics Data System (ADS)

Fryer, Chris L.; Oliveira, F. G.; Rueda, J. A.; Ruffini, R.

2015-12-01

Binary-driven hypernovae (BdHNe) within the induced gravitational collapse paradigm have been introduced to explain energetic (Eiso≳1052 erg ), long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). The progenitor is a tight binary composed of a carbon-oxygen (CO) core and a neutron-star (NS) companion, a subclass of the newly proposed "ultrastripped" binaries. The CO-NS short-period orbit causes the NS to accrete appreciable matter from the SN ejecta when the CO core collapses, ultimately causing it to collapse to a black hole (BH) and producing a GRB. These tight binaries evolve through the SN explosion very differently than compact binaries studied in population synthesis calculations. First, the hypercritical accretion onto the NS companion alters both the mass and the momentum of the binary. Second, because the explosion time scale is on par with the orbital period, the mass ejection cannot be assumed to be instantaneous. This dramatically affects the post-SN fate of the binary. Finally, the bow shock created as the accreting NS plows through the SN ejecta transfers angular momentum, braking the orbit. These systems remain bound even if a large fraction of the binary mass is lost in the explosion (well above the canonical 50% limit), and even large kicks are unlikely to unbind the system. Indeed, BdHNe produce a new family of NS-BH binaries unaccounted for in current population synthesis analyses and, although they may be rare, the fact that nearly 100% remain bound implies that they may play an important role in the compact merger rate, important for gravitational waves that, in turn, can produce a new class of ultrashort GRBs.

A wavelet approach to binary blackholes with asynchronous multitasking

NASA Astrophysics Data System (ADS)

Lim, Hyun; Hirschmann, Eric; Neilsen, David; Anderson, Matthew; Debuhr, Jackson; Zhang, Bo

2016-03-01

Highly accurate simulations of binary black holes and neutron stars are needed to address a variety of interesting problems in relativistic astrophysics. We present a new method for the solving the Einstein equations (BSSN formulation) using iterated interpolating wavelets. Wavelet coefficients provide a direct measure of the local approximation error for the solution and place collocation points that naturally adapt to features of the solution. Further, they exhibit exponential convergence on unevenly spaced collection points. The parallel implementation of the wavelet simulation framework presented here deviates from conventional practice in combining multi-threading with a form of message-driven computation sometimes referred to as asynchronous multitasking.

The solidification behavior of calcium oxide-aluminum oxide slags

NASA Astrophysics Data System (ADS)

Prapakorn, Kritsada

The binary CaO-Al2O3 based slag and the ternary CaO-Al2O3-MgO based slag are common slags covering and inclusions that are found in calcium treated Al-killed, continuously cast steels. However, the effect of cooling conditions and chemistry on the solidification behavior of these slags is not well characterized. To better understand this phenomena, the solidification behavior of these slags was studied by using double hot thermocouple technique. TTT and CCT diagrams of these slags were determined to quantify the solidification behavior in both dry and humid atmospheres. In this work, these slag samples were easily undercooled and the solidification behavior of these slags was found to be a strong function of cooling conditions. The crystallization tendency of these slags follows the trends suggested by the phase diagram. In CaO-Al2O3 based slags, The eutectic composition (50%CaO) give the lowest crystallization tendency due to the lowest liquidus temperature. In a eutectic CaO-Al2O3 slag sample, dissolved water in the sample increases crystallization tendency and enhances the growth. It was also found that the crystalline phase that formed during cooling in both the dry and humid conditions is the mixture between 3CaO.Al2O 3 and CaO.Al2O3 phases. In CaO-Al2O3-MgO based slags, the crystallization tendency increases with MgO content because the high MgO content leads to the high liquidus temperature. The effect of dissolved of water on the crystallization of CaO-Al2O3-MgO based slags is not as prominent as in the eutectic CaO-Al2O3 slag. Thus, the addition of MgO to CaO-Al2O3 slags was seen to minimize or eliminate the effect of humidity on the solidification of CaO-Al2O3 based slags. In this work, Uhlmann's method was used to estimate the solid-liquid interfacial energy of CaO-Al2O3 based slag for the temperature between 1100--1250°C. The result is between 0.25--0.4 Joules/m 2.

Unusual Black Hole Binary LMC X-3: A Transient High-mass X-Ray Binary That Is Almost Always On?

NASA Astrophysics Data System (ADS)

Torpin, Trevor J.; Boyd, Patricia T.; Smale, Alan P.; Valencic, Lynne A.

2017-11-01

We have analyzed a rich, multimission, multiwavelength data set from the black hole X-ray binary (BHXB) LMC X-3, covering a new anomalous low state (ALS), during which the source flux falls to an unprecedentedly low and barely detectable level, and a more normal low state. Simultaneous X-ray and UV/optical monitoring data from Swift are combined with pointed observations from the Rossi X-ray Timing Explorer (RXTE) and X-ray Multi-Mirror Mission (XMM-Newton) and light curves from the Monitor of All-Sky X-ray Image (MAXI) instrument to compare the source characteristics during the ALS with those seen during the normal low state. An XMM-Newton spectrum obtained during the ALS can be modeled using an absorbed power law with {{Γ }}=1.41+/- 0.65 and a luminosity of 7.97× {10}33 erg s-1 (0.6-5 keV). The Swift X-ray and UV light curves indicate an X-ray lag of ˜8 days as LMC X-3 abruptly exits the ALS, suggesting that changes in the mass accretion rate from the donor drive the X-ray lag. The normal low state displays an asymmetric profile in which the exit occurs more quickly than the entry, with minimum X-ray flux a factor of ˜4300 brighter than during the ALS. The UV brightness of LMC X-3 in the ALS is also fainter and less variable than during normal low states. The existence of repeated ALSs in LMC X-3, as well as a comparison with other BHXBs, implies that it is very close to the transient/persistent X-ray source dividing line. We conclude that LMC X-3 is a transient source that is almost always “on.”

Unusual Black Hole Binary LMC X-3: A Transient High-Mass X-Ray Binary That Is Almost Always On?

NASA Technical Reports Server (NTRS)

Torpin, Trevor J.; Boyd, Patricia T.; Smale, Alan P.; Valencic, Lynne A.

2017-01-01

We have analyzed a rich, multimission, multiwavelength data set from the black hole X-ray binary (BHXB) LMC X-3, covering a new anomalous low state (ALS), during which the source flux falls to an unprecedentedly low and barely detectable level, and a more normal low state. Simultaneous X-ray and UV/optical monitoring data from Swift are combined with pointed observations from the Rossi X-ray Timing Explorer (RXTE) and X-ray Multi- Mirror Mission (XMM-Newton) and light curves from the Monitor of All-Sky X-ray Image (MAXI) instrument to compare the source characteristics during the ALS with those seen during the normal low state. An XMM-Newton spectrum obtained during the ALS can be modeled using an absorbed power law with Gamma = 1.41‚+/- 0.65 and a luminosity of 7.97 x 10(exp 33) erg/s (0.6-5 keV). The Swift X-ray and UV light curves indicate an X-ray lag of approx. 8 days as LMC X-3 abruptly exits the ALS, suggesting that changes in the mass accretion rate from the donor drive the X-ray lag. The normal low state displays an asymmetric profile in which the exit occurs more quickly than the entry, with minimum X-ray flux a factor of approx. 4300 brighter than during the ALS. The UV brightness of LMC X-3 in the ALS is also fainter and less variable than during normal low states. The existence of repeated ALSs in LMC X-3, as well as a comparison with other BHXBs, implies that it is very close to the transient/persistent X-ray source dividing line. We conclude that LMC X-3 is a transient source that is almost always "on."

Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albert, A.; André, M.; Anghinolfi, M.

The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV–EeV energy range using the Antares, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincidentmore » with the source were detected within ±500 s around the merger time. Additionally, no MeV neutrino burst signal was detected coincident with the merger. We further carried out an extended search in the direction of the source for high-energy neutrinos within the 14 day period following the merger, but found no evidence of emission. We used these results to probe dissipation mechanisms in relativistic outflows driven by the binary neutron star merger. The non-detection is consistent with model predictions of short GRBs observed at a large off-axis angle.« less

Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory

DOE PAGES

Albert, A.; André, M.; Anghinolfi, M.; ...

2017-11-29

The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV–EeV energy range using the Antares, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincidentmore » with the source were detected within ±500 s around the merger time. Additionally, no MeV neutrino burst signal was detected coincident with the merger. We further carried out an extended search in the direction of the source for high-energy neutrinos within the 14 day period following the merger, but found no evidence of emission. We used these results to probe dissipation mechanisms in relativistic outflows driven by the binary neutron star merger. The non-detection is consistent with model predictions of short GRBs observed at a large off-axis angle.« less

Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory

NASA Astrophysics Data System (ADS)

Albert, A.; André, M.; Anghinolfi, M.; Ardid, M.; Aubert, J.-J.; Aublin, J.; Avgitas, T.; Baret, B.; Barrios-Martí, J.; Basa, S.; Belhorma, B.; Bertin, V.; Biagi, S.; Bormuth, R.; Bourret, S.; Bouwhuis, M. C.; Brânzaş, H.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Celli, S.; Cherkaoui El Moursli, R.; Chiarusi, T.; Circella, M.; Coelho, J. A. B.; Coleiro, A.; Coniglione, R.; Costantini, H.; Coyle, P.; Creusot, A.; Díaz, A. F.; Deschamps, A.; De Bonis, G.; Distefano, C.; Di Palma, I.; Domi, A.; Donzaud, C.; Dornic, D.; Drouhin, D.; Eberl, T.; El Bojaddaini, I.; El Khayati, N.; Elsässer, D.; Enzenhöfer, A.; Ettahiri, A.; Fassi, F.; Felis, I.; Fusco, L. A.; Gay, P.; Giordano, V.; Glotin, H.; Grégoire, T.; Ruiz, R. Gracia; Graf, K.; Hallmann, S.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Hößl, J.; Hofestädt, J.; Illuminati, G.; James, C. W.; de Jong, M.; Jongen, M.; Kadler, M.; Kalekin, O.; Katz, U.; Kießling, D.; Kouchner, A.; Kreter, M.; Kreykenbohm, I.; Kulikovskiy, V.; Lachaud, C.; Lahmann, R.; Lefèvre, D.; Leonora, E.; Lotze, M.; Loucatos, S.; Marcelin, M.; Margiotta, A.; Marinelli, A.; Martínez-Mora, J. A.; Mele, R.; Melis, K.; Michael, T.; Migliozzi, P.; Moussa, A.; Navas, S.; Nezri, E.; Organokov, M.; Păvălaş, G. E.; Pellegrino, C.; Perrina, C.; Piattelli, P.; Popa, V.; Pradier, T.; Quinn, L.; Racca, C.; Riccobene, G.; Sánchez-Losa, A.; Saldaña, M.; Salvadori, I.; Samtleben, D. F. E.; Sanguineti, M.; Sapienza, P.; Schüssler, F.; Sieger, C.; Spurio, M.; Stolarczyk, Th.; Taiuti, M.; Tayalati, Y.; Trovato, A.; Turpin, D.; Tönnis, C.; Vallage, B.; Van Elewyck, V.; Versari, F.; Vivolo, D.; Vizzoca, A.; Wilms, J.; Zornoza, J. D.; Zúñiga, J.; ANTARES Collaboration; Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Samarai, I. Al; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Argüelles, C.; Auffenberg, J.; Axani, S.; Bagherpour, H.; Bai, X.; Barron, J. P.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Bourbeau, E.; Bourbeau, J.; Bradascio, F.; Braun, J.; Brayeur, L.; Brenzke, M.; Bretz, H.-P.; Bron, S.; Brostean-Kaiser, J.; Burgman, A.; Carver, T.; Casey, J.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cross, R.; Day, M.; de André, J. P. A. M.; De Clercq, C.; DeLaunay, J. J.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Dvorak, E.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eller, P.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Franckowiak, A.; Friedman, E.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Glauch, T.; Glüsenkamp, T.; Goldschmidt, A.; Gonzalez, J. G.; Grant, D.; Griffith, Z.; Haack, C.; Hallgren, A.; Halzen, F.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Hokanson-Fasig, B.; Hoshina, K.; Huang, F.; Huber, M.; Hultqvist, K.; Hünnefeld, M.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Kalaczynski, P.; Kang, W.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kheirandish, A.; Kim, J.; Kim, M.; Kintscher, T.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Köpke, L.; Kopper, C.; Kopper, S.; Koschinsky, J. P.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Kyriacou, A.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lauber, F.; Lesiak-Bzdak, M.; Leuermann, M.; Liu, Q. R.; Lu, L.; Lünemann, J.; Luszczak, W.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Maruyama, R.; Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Micallef, J.; Momenté, G.; Montaruli, T.; Moore, R. W.; Moulai, M.; Nahnhauer, R.; Nakarmi, P.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; O’Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Peiffer, P.; Pepper, J. A.; Pérez de los Heros, C.; Pieloth, D.; Pinat, E.; Plum, M.; Pranav, D.; Price, P. B.; Przybylski, G. T.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Rea, I. C.; Reimann, R.; Relethford, B.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk, D.; Sälzer, T.; Sanchez Herrera, S. E.; Sandrock, A.; Sandroos, J.; Santander, M.; Sarkar, S.; Sarkar, S.; Satalecka, K.; Schlunder, P.; Schmidt, T.; Schneider, A.; Schoenen, S.; Schöneberg, S.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soedingrekso, J.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stachurska, J.; Stamatikos, M.; Stanev, T.; Stasik, A.; Stettner, J.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strotjohann, N. L.; Stuttard, T.; Sullivan, G. W.; Sutherland, M.; Taboada, I.; Tatar, J.; Tenholt, F.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Tung, C. F.; Turcati, A.; Turley, C. F.; Ty, B.; Unger, E.; Usner, M.; Vandenbroucke, J.; Van Driessche, W.; van Eijndhoven, N.; Vanheule, S.; van Santen, J.; Vehring, M.; Vogel, E.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandler, F. D.; Wandkowsky, N.; Waza, A.; Weaver, C.; Weiss, M. J.; Wendt, C.; Werthebach, J.; Westerhoff, S.; Whelan, B. J.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wolf, M.; Wood, J.; Wood, T. R.; Woolsey, E.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Yuan, T.; Zoll, M.; IceCube Collaboration; Aab, A.; Abreu, P.; Aglietta, M.; Albuquerque, I. F. M.; Albury, J. M.; Allekotte, I.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arsene, N.; Asorey, H.; Assis, P.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Barbato, F.; Barreira Luz, R. J.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caruso, R.; Castellina, A.; Catalani, F.; Cataldi, G.; Cazon, L.; Chavez, A. G.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Cobos Cerutti, A. C.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Consolati, G.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; D’Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; Day, J. A.; de Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; Deligny, O.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D’Olivo, J. C.; Dorosti, Q.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Farmer, J.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Feldbusch, F.; Fenu, F.; Fick, B.; Figueira, J. M.; Filipčič, A.; Freire, M. M.; Fujii, T.; Fuster, A.; Gaïor, R.; García, B.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Golup, G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gorgi, A.; Gottowik, M.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Halliday, R.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Harvey, V. M.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Johnsen, J. A.; Josebachuili, M.; Jurysek, J.; Kääpä, A.; Kampert, K. H.; Keilhauer, B.; Kemmerich, N.; Kemp, J.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.; Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; Lago, B. L.; LaHurd, D.; Lang, R. G.; Lauscher, M.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lo Presti, D.; Lopes, L.; López, R.; López Casado, A.; Lorek, R.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Mariş, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Merenda, K.-D.; Michal, S.; Micheletti, M. I.; Middendorf, L.; Miramonti, L.; Mitrica, B.; Mockler, D.; Mollerach, S.; Montanet, F.; Morello, C.; Morlino, G.; Mostafá, M.; Müller, A. L.; Müller, G.; Muller, M. A.; Müller, S.; Mussa, R.; Naranjo, I.; Nellen, L.; Nguyen, P. 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G.; Scott, J.; Scott, S. M.; Seidel, E.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Shaddock, D. A.; Shaffer, T. J.; Shah, A. A.; Shahriar, M. S.; Shaner, M. B.; Shao, L.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Singer, L. P.; Singh, A.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, B.; Smith, J. R.; Smith, R. J. E.; Somala, S.; Son, E. J.; Sonnenberg, J. A.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Spencer, A. P.; Srivastava, A. K.; Staats, K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stevenson, S. P.; Stone, R.; Stops, D. J.; Strain, K. A.; Stratta, G.; Strigin, S. E.; Strunk, A.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Suresh, J.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Tait, S. C.; Talbot, C.; Talukder, D.; Tanner, D. B.; Tápai, M.; Taracchini, A.; Tasson, J. D.; Taylor, J. A.; Taylor, R.; Tewari, S. V.; Theeg, T.; Thies, F.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tonelli, M.; Tornasi, Z.; Torres-Forné, A.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trinastic, J.; Tringali, M. C.; Trozzo, L.; Tsang, K. W.; Tse, M.; Tso, R.; Tsukada, L.; Tsuna, D.; Tuyenbayev, D.; Ueno, K.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Varma, V.; Vass, S.; Vasúth, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Venugopalan, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Viets, A. D.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walet, R.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, J. Z.; Wang, W. H.; Wang, Y. F.; Ward, R. L.; Warner, J.; Was, M.; Watchi, J.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wessel, E. K.; Weßels, P.; Westerweck, J.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Whittle, C.; Wilken, D.; Williams, D.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Wofford, J.; Wong, K. W. K.; Worden, J.; Wright, J. L.; Wu, D. S.; Wysocki, D. M.; Xiao, S.; Yamamoto, H.; Yancey, C. C.; Yang, L.; Yap, M. J.; Yazback, M.; Yu, Hang; Yu, Haocun; Yvert, M.; Zadrożny, A.; Zanolin, M.; Zelenova, T.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, T.; Zhang, Y.-H.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, S. J.; Zhu, X. J.; Zucker, M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

2017-12-01

The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV–EeV energy range using the ANTARES, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincident with the source were detected within ±500 s around the merger time. Additionally, no MeV neutrino burst signal was detected coincident with the merger. We further carried out an extended search in the direction of the source for high-energy neutrinos within the 14 day period following the merger, but found no evidence of emission. We used these results to probe dissipation mechanisms in relativistic outflows driven by the binary neutron star merger. The non-detection is consistent with model predictions of short GRBs observed at a large off-axis angle.

The design and testing of a novel mechanomyogram-driven switch controlled by small eyebrow movements

PubMed Central

2010-01-01

Background Individuals with severe physical disabilities and minimal motor behaviour may be unable to use conventional mechanical switches for access. These persons may benefit from access technologies that harness the volitional activity of muscles. In this study, we describe the design and demonstrate the performance of a binary switch controlled by mechanomyogram (MMG) signals recorded from the frontalis muscle during eyebrow movements. Methods Muscle contractions, detected in real-time with a continuous wavelet transform algorithm, were used to control a binary switch for computer access. The automatic selection of scale-specific thresholds reduced the effect of artefact, such as eye blinks and head movement, on the performance of the switch. Switch performance was estimated by cued response-tests performed by eleven participants (one with severe physical disabilities). Results The average sensitivity and specificity of the switch was 99.7 ± 0.4% and 99.9 ± 0.1%, respectively. The algorithm performance was robust against typical participant movement. Conclusions The results suggest that the frontalis muscle is a suitable site for controlling the MMG-driven switch. The high accuracies combined with the minimal requisite effort and training show that MMG is a promising binary control signal. Further investigation of the potential benefits of MMG-control for the target population is warranted. PMID:20492680

The design and testing of a novel mechanomyogram-driven switch controlled by small eyebrow movements.

PubMed

Alves, Natasha; Chau, Tom

2010-05-21

Individuals with severe physical disabilities and minimal motor behaviour may be unable to use conventional mechanical switches for access. These persons may benefit from access technologies that harness the volitional activity of muscles. In this study, we describe the design and demonstrate the performance of a binary switch controlled by mechanomyogram (MMG) signals recorded from the frontalis muscle during eyebrow movements. Muscle contractions, detected in real-time with a continuous wavelet transform algorithm, were used to control a binary switch for computer access. The automatic selection of scale-specific thresholds reduced the effect of artefact, such as eye blinks and head movement, on the performance of the switch. Switch performance was estimated by cued response-tests performed by eleven participants (one with severe physical disabilities). The average sensitivity and specificity of the switch was 99.7 +/- 0.4% and 99.9 +/- 0.1%, respectively. The algorithm performance was robust against typical participant movement. The results suggest that the frontalis muscle is a suitable site for controlling the MMG-driven switch. The high accuracies combined with the minimal requisite effort and training show that MMG is a promising binary control signal. Further investigation of the potential benefits of MMG-control for the target population is warranted.

V and K-band Mass-Luminosity Relations for M Dwarf Stars

NASA Astrophysics Data System (ADS)

Benedict, George Frederick; Henry, Todd J.; McArthur, Barbara E.; Franz, Otto; Wasserman, Larry H.; Dieterich, Sergio

2015-08-01

Applying Hubble Space Telescope Fine Guidance Sensor astrometric techniques developed to establish relative orbits for binary stars (Franz et al. 1998, AJ, 116, 1432), determine masses of binary components (Benedict et al. 2001, AJ, 121, 1607), and measure companion masses of exoplanet host stars (McArthur et al. 2010, ApJ, 715, 1203), we derive masses with an average 2% error for 28 components of 14 M dwarf binary star systems. With these and other published masses we update the lower Main Sequence V-band Mass-Luminosity Relation first shown in Henry et al. 1999, ApJ, 512, 864. We demonstrate that a Mass-Luminosity Relation in the K-band has far less scatter. These relations can be used to estimate the masses of the ubiquitous red dwarfs (75% of all stars) to an accuracy of better than 5%.

Elevated Temperature Deformation of Fe-39.8Al and Fe-15.6Mn-39.4Al

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel

2004-01-01

The elevated temperature compressive properties of binary Fe-39.8 at % Al and Fe-15.6Mn-39.4Al have been measured between 1000 and 1300 K at strain rates between 10(exp 7) and 10(exp 3)/ s. Although the Mn addition to iron aluminide did not change the basic deformation characteristics, the Mn-modified alloy was slightly weaker. In the regime where deformation of FeAl occurs by a high stress exponent mechanism (n = 6), strength increases as the grain size decreases at least for diameters between approx. 200 and approx. 10 microns. Due to the limitation in the grain size-flow stress-temperature-strain rate database, the influence of further reductions of the grain size on strength is uncertain. Based on the appearance of subgrains in deformed iron aluminide, the comparison of grain diameters to expected subgrain sizes, and the grain size exponent and stress exponent calculated from deformation experiments, it is believed that grain size strengthening is the result of an artificial limitation on subgrain size as proposed by Sherby, Klundt and Miller.

Identification of the High-energy Gamma-Ray Source 3FGL J1544.6-1125 as a Transitional Millisecond Pulsar Binary in an Accreting State

NASA Astrophysics Data System (ADS)

Bogdanov, Slavko; Halpern, Jules P.

2015-04-01

We present X-ray, ultraviolet, and optical observations of 1RXS J154439.4-112820, the most probable counterpart of the unassociated Fermi-LAT source 3FGL J1544.6-1125. The optical data reveal rapid variability, which is a feature of accreting systems. The X-rays exhibit large-amplitude variations in the form of fast switching (within ˜10 s) between two distinct flux levels that differ by a factor of ≈10. The detailed optical and X-ray behavior is virtually identical to that seen in the accretion-disk-dominated states of the transitional millisecond pulsar (MSP) binaries PSR J1023+0038 and XSS J12270-4859, which are also associated with γ-ray sources. Based on the available observational evidence, we conclude that 1RXS J154439.4-112820 and 3FGL J1544.6-1125 are the same object, with the X-rays arising from intermittent low-luminosity accretion onto an MSP and the γ-rays originating from an accretion-driven outflow. 1RXS J154439.4-112820 is only the fourth γ-ray-emitting low-mass X-ray binary system to be identified and is likely to sporadically undergo transformations to a non-accreting rotation-powered pulsar system.

Effect of eccentricity on searches for gravitational waves from coalescing compact binaries in ground-based detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Duncan A.; Zimmerman, Peter J.

2010-01-15

Inspiralling compact binaries are expected to circularize before their gravitational-wave signals reach the sensitive frequency band of ground-based detectors. Current searches for gravitational waves from compact binaries using the LIGO and Virgo detectors therefore use circular templates to construct matched filters. Binary formation models have been proposed which suggest that some systems detectable by the LIGO-Virgo network may have non-negligible eccentricity. We investigate the ability of the restricted 3.5 post-Newtonian order TaylorF2 template bank, used by LIGO and Virgo to search for gravitational waves from compact binaries with masses M{<=}35M{sub {center_dot},} to detect binaries with nonzero eccentricity. We model themore » gravitational waves from eccentric binaries using the x-model post-Newtonian formalism proposed by Hinder et al.[I. Hinder, F. Hermann, P. Laguna, and D. Shoemaker, arXiv:0806.1037v1]. We find that small residual eccentricities (e{sub 0} < or approx. 0.05 at 40 Hz) do not significantly affect the ability of current LIGO searches to detect gravitational waves from coalescing compact binaries with total mass 2M{sub {center_dot}<}M<15M{sub {center_dot}.} For eccentricities e{sub 0} > or approx. 0.1, the loss in matched filter signal-to-noise ratio due to eccentricity can be significant and so templates which include eccentric effects will be required to perform optimal searches for such systems.« less

An experimental platform for pulsed-power driven magnetic reconnection

NASA Astrophysics Data System (ADS)

Hare, J. D.; Suttle, L. G.; Lebedev, S. V.; Loureiro, N. F.; Ciardi, A.; Chittenden, J. P.; Clayson, T.; Eardley, S. J.; Garcia, C.; Halliday, J. W. D.; Robinson, T.; Smith, R. A.; Stuart, N.; Suzuki-Vidal, F.; Tubman, E. R.

2018-05-01

We describe a versatile pulsed-power driven platform for magnetic reconnection experiments, based on the exploding wire arrays driven in parallel [Suttle et al., Phys. Rev. Lett. 116, 225001 (2016)]. This platform produces inherently magnetised plasma flows for the duration of the generator current pulse (250 ns), resulting in a long-lasting reconnection layer. The layer exists for long enough to allow the evolution of complex processes such as plasmoid formation and movement to be diagnosed by a suite of high spatial and temporal resolution laser-based diagnostics. We can access a wide range of magnetic reconnection regimes by changing the wire material or moving the electrodes inside the wire arrays. We present results with aluminium and carbon wires, in which the parameters of the inflows and the layer that forms are significantly different. By moving the electrodes inside the wire arrays, we change how strongly the inflows are driven. This enables us to study both symmetric reconnection in a range of different regimes and asymmetric reconnection.

A Wide-field Survey for Transiting Hot Jupiters and Eclipsing Pre-main-sequence Binaries in Young Stellar Associations

NASA Astrophysics Data System (ADS)

Oelkers, Ryan J.; Macri, Lucas M.; Marshall, Jennifer L.; DePoy, Darren L.; Lambas, Diego G.; Colazo, Carlos; Stringer, Katelyn

2016-09-01

The past two decades have seen a significant advancement in the detection, classification, and understanding of exoplanets and binaries. This is due, in large part, to the increase in use of small-aperture telescopes (<20 cm) to survey large areas of the sky to milli-mag precision with rapid cadence. The vast majority of the planetary and binary systems studied to date consists of main-sequence or evolved objects, leading to a dearth of knowledge of properties at early times (<50 Myr). Only a dozen binaries and one candidate transiting Hot Jupiter are known among pre-main-sequence objects, yet these are the systems that can provide the best constraints on stellar formation and planetary migration models. The deficiency in the number of well characterized systems is driven by the inherent and aperiodic variability found in pre-main-sequence objects, which can mask and mimic eclipse signals. Hence, a dramatic increase in the number of young systems with high-quality observations is highly desirable to guide further theoretical developments. We have recently completed a photometric survey of three nearby (<150 pc) and young (<50 Myr) moving groups with a small-aperture telescope. While our survey reached the requisite photometric precision, the temporal coverage was insufficient to detect Hot Jupiters. Nevertheless, we discovered 346 pre-main-sequence binary candidates, including 74 high-priority objects for further study. This paper includes data taken at The McDonald Observatory of The University of Texas at Austin.

X-Ray Binaries and Star Clusters in the Antennae: Optical Cluster Counterparts

NASA Astrophysics Data System (ADS)

Rangelov, Blagoy; Chandar, Rupali; Prestwich, Andrea; Whitmore, Bradley C.

2012-10-01

We compare the locations of 82 X-ray binaries (XRBs) detected in the merging Antennae galaxies by Zezas et al., based on observations taken with the Chandra X-Ray Observatory, with a catalog of optically selected star clusters presented by Whitmore et al., based on observations taken with the Hubble Space Telescope. Within the 2σ positional uncertainty of ≈0farcs8, we find 22 XRBs are coincident with star clusters, where only two to three chance coincidences are expected. The ages of the clusters were estimated by comparing their UBVI, Hα colors with predictions from stellar evolutionary models. We find that 14 of the 22 coincident XRBs (64%) are hosted by star clusters with ages of ≈6 Myr or less. All of the very young host clusters are fairly massive and have M >~ 3 × 104 M ⊙, with many having masses M ≈ 105 M ⊙. Five of the XRBs are hosted by young clusters with ages τ ≈ 10-100 Myr, while three are hosted by intermediate-age clusters with τ ≈ 100-300 Myr. Based on the results from recent N-body simulations, which suggest that black holes are far more likely to be retained within their parent clusters than neutron stars, we suggest that our sample consists primarily of black hole binaries with different ages.

Comparison of geothermal power conversion cycles

NASA Technical Reports Server (NTRS)

Elliott, D. G.

1976-01-01

Geothermal power conversion cycles are compared with respect to recovery of the available wellhead power. The cycles compared are flash steam, in which steam turbines are driven by steam separated from one or more flash stages; binary, in which heat is transferred from the brine to an organic turbine cycle; flash binary, in which heat is transferred from flashed steam to an organic turbine cycle; and dual steam, in which two-phase expanders are driven by the flashing steam-brine mixture and steam turbines by the separated steam. Expander efficiencies assumed are 0.7 for steam turbines, 0.8 for organic turbines, and 0.6 for two-phase expanders. The fraction of available wellhead power delivered by each cycle is found to be about the same at all brine temperatures: 0.65 with one stage and 0.7 with four stages for dual stream; 0.4 with one stage and 0.6 with four stages for flash steam; 0.5 for binary; and 0.3 with one stage and 0.5 with four stages for flash binary.

Experimental investigation of the phase equilibria and thermodynamic assessment in the U-Ga and U-Al-Ga systems

NASA Astrophysics Data System (ADS)

Moussa, Chantal; Berche, Alexandre; Barbosa, José; Pasturel, Mathieu; Stepnik, Bertrand; Tougait, Olivier

2018-02-01

The phase relations in the binary U-Ga and ternary U-Al-Ga systems were established as an isopleth section and two isothermal sections at 900 K and 1150 K for the whole concentration range, respectively. They were experimentally determined by means of powder and single crystal XRD, SEM-EDS analyses on both as-cast and heat-treated samples and DTA measurements. Both systems were thermodynamically assessed using the Calphad method based on the available data, i.e. phase relations and thermodynamic properties. The new description of the U-Ga phase diagram improves the composition-temperature description for most of invariant reactions. The U-Al-Ga system is characterized by large ternary extensions of the binary phases and the absence of ternary intermediate phase at both 900 K and 1150 K. These experimental results are nicely reproduced by the Calphad assessment, allowing to extract the thermodynamic parameters further used to calculate the liquidus projection and the invariant reactions along with their temperature.

Identification of Effective Teaching Behaviors

DTIC Science & Technology

1993-07-01

of proximal development reflects his two part theory of learning. Specifically, Vygotsky believes that learning has social and developmental components...which--in theory -- utilize artificial intelligence (Al) techniques to provide highly individualized instruction, much like that of a human tutor. The...this approach can produce acceptable instruction, it is not optimal. * Theory driven. Tutoring principles are based on some type of theory . Usually

Central structure of low-n Balmer lines in dense plasmas

NASA Technical Reports Server (NTRS)

Hey, J. D.; Griem, H. R.

1975-01-01

The investigation reported is concerned with disagreements between the computations of Kepple and Griem (1968) and the results of calculations based upon the 'unified theory' proposed by Vidal et al. (1973). Experiments were conducted with a high-pressure electromagnetically driven shock tube as the plasma source. The diagnostic methods used are discussed along with the experimental results and their significance.

Compressive creep behavior of alloys based on B2 FeAl

NASA Technical Reports Server (NTRS)

Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.

1986-01-01

Alloys based on FeAl are attractive alternate materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.

Compressive creep behavior of alloys based on B2 FeAl

NASA Technical Reports Server (NTRS)

Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.

1987-01-01

Alloys based on FeAl are attractive alternative materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.

Micromechanisms of Monotonic and Cyclic Subcritical Crack Growth in Advanced High Melting Point Low-Ductility Intermetallics

DTIC Science & Technology

1993-05-01

Advanced Structural Ceramics, MRS Symp. Proc., P. F. Becher et al . (eds.), MRS, Pittsburgh, PA (1986). 11) M. J. Reece, F. Guiu and M. F. R. Sammur...composites under study, listed in Table 2.1, were fabricated by phase blending -80 mesh y-TiAI (Ti-55 at.% Al , with small additions of Nb, Ta, C and 0...on phase transformations in the alloy system. In the case of the binary Nb- Al system, the peritectic reaction at 2060’C (Fig. 3.1), involving the

Acoustic emission from a solidifying aluminum-lithium alloy

NASA Technical Reports Server (NTRS)

Henkel, D. P.; Wood, J. D.

1992-01-01

Physical phenomena associated with the solidification of an AA2090 Al-Li alloy have been characterized by AE methods. Repeatable patterns of AE activity as a function of solidification time are recorded and explained for ultrahigh-purity (UHP) aluminum and an Al-4.7 wt pct Cu binary alloy, in addition to the AA2090 Al-Li alloy, by the complementary utilization of thermal, AE, and metallographic methods. One result shows that the solidification of UHP aluminum produces one discrete period of high AE activity as the last 10 percent of solid forms.

Alloy Design Data Generated for B2-Ordered Compounds

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Bozzolo, Guillermo; Abel, Phillip B.

2003-01-01

Developing alloys based on ordered compounds is significantly more complicated than developing designs based on disordered materials. In ordered compounds, the major constituent elements reside on particular sublattices. Therefore, the addition of a ternary element to a binary-ordered compound is complicated by the manner in which the ternary addition is made (at the expense of which binary component). When ternary additions are substituted for the wrong constituent, the physical and mechanical properties usually degrade. In some cases the resulting degradation in properties can be quite severe. For example, adding alloying additions to NiAl in the wrong combination (i.e., alloying additions that prefer the Al sublattice but are added at the expense of Ni) will severely embrittle the alloy to the point that it can literally fall apart during processing on cooling from the molten state. Consequently, alloying additions that strongly prefer one sublattice over another should always be added at the expense of that component during alloy development. Elements that have a very weak preference for a sublattice can usually be safely added at the expense of either element and will accommodate any deviation from stoichiometry by filling in for the deficient component. Unfortunately, this type of information is not known beforehand for most ordered systems. Therefore, a computational survey study, using a recently developed quantum approximate method, was undertaken at the NASA Glenn Research Center to determine the preferred site occupancy of ternary alloying additions to 12 different B2-ordered compounds including NiAl, FeAl, CoAl, CoFe, CoHf, CoTi, FeTi, RuAl, RuSi, RuHf, RuTi, and RuZr. Some of these compounds are potential high temperature structural alloys; others are used in thin-film magnetic and other electronic applications. The results are summarized. The italicized elements represent the previous sum total alloying information known and verify the computational method used to establish the table. Details of the computational procedures used to determine the preferred site occupancy can be found in reference 2. As further substantiation of the validity of the technique, and its extension to even more complicated systems, it was applied to two simultaneous alloying additions in an ordered alloy.

The region of formation of the ultraviolet high temperature resonance lines in the eclipsing binary Beta Persei (Algol)

NASA Technical Reports Server (NTRS)

Brandi, E.; Garcia, L. G.; Kondo, Y.; Sahade, J.

1989-01-01

A new series of IUE observations of Beta Persei has shown that the high temperature resonance lines of Si IV and C IV arise in a region that surrounds the brighter, early-type component of the system. The continuum spectrum corresponds to that of a B8V object, and the value of E(B-V) that yielded the best match between the two IUE regions was 0.06, the value quoted for Beta Per in Jamar et al.'s (1976) Catalog.

Generation of sub-gigabar-pressure shocks by a hyper-velocity impact in the collider driven by laser-induced cavity pressure

NASA Astrophysics Data System (ADS)

Badziak, J.; Kucharik, M.; Liska, R.

2018-02-01

The generation of high-pressure shocks in the newly proposed collider in which the projectile impacting a solid target is driven by the laser-induced cavity pressure acceleration (LICPA) mechanism is investigated using two-dimensional hydrodynamic simulations. The dependence of parameters of the shock generated in the target by the impact of a gold projectile on the impacted target material and the laser driver energy is examined. It is found that both in case of low-density (CH, Al) and high-density (Au, Cu) solid targets the shock pressures in the sub-Gbar range can be produced in the LICPA-driven collider with the laser energy of only a few hundreds of joules, and the laser-to-shock energy conversion efficiency can reach values of 10 - 20 %, by an order of magnitude higher than the conversion efficiencies achieved with other laser-based methods used so far.

A contact binary asteroid evolutionary cycle driven by BYORP & the classical Laplace plane

NASA Astrophysics Data System (ADS)

Rieger, Samantha; Scheeres, Daniel J.

2017-10-01

Several contact binaries have been observed to have high obliquities distributed around 90°. With this information, we explore the possibility of these high obliquities being a key characteristic that causes an evolutionary cycle of contact binary formation and separation.The contact binary cycle begins with a single asteroid that is spinning up due to the YORP effect. For the binary cycle we assume YORP will drive the obliquity to 90°. Eventually, the asteroid will reach a critical spin frequency that will cause the asteroid to fission into a binary. We assume that the mass-ratio, q, of the system is greater than 0.2. With a high q, the secondary will not escape/impact the primary but will evolve through tides into a stable circular double-synchronous orbit. The binary being synchronous will cause the forces from BYORP to have secular effects on the system. For this cycle, BYORP will need to expand the secondary away from the primary.As the system expands, we have found that the secondary will follow the classical Laplace plane. Therefore, the secondary’s orbit will increase in inclination with respect to the equator as the secondary’s orbit expands. The Laplace plane is a stable orbit to perturbations from J2 & Sun tides except for an instability region that exists for primaries with obliquities above 68.875° & a secondary orbital radius of 13.5-19.5 primary radii. Once BYORP expands the secondary into this instability region, the eccentricity of the secondary’s orbit will increase until the orbit intersects with the primary & causes an impact. This impact will create a contact binary with a new obliquity that will randomly range from 23°-150°. The cycle will begin again with YORP driving the contact binary to an obliquity of 90°.Our contribution will discuss the proposed contact binary cycle in more detail, including the mechanics of the system that drives the events given above. We will include investigations into how losing synchronous lock will disrupt the eccentricity growth in the Laplace plane instability region. We will also discuss the time scales of each event to help predict which part of the cycle we will most likely to be observing when discovering new contact binaries & binary systems.

Field-aligned currents and large scale magnetospheric electric fields

NASA Technical Reports Server (NTRS)

Dangelo, N.

1980-01-01

D'Angelo's model of polar cap electric fields (1977) was used to visualize how high-latitude field-aligned currents are driven by the solar wind generator. The region 1 and region 2 currents of Iijima and Potemra (1976) and the cusp field-aligned currents of Wilhjelm et al. (1978) and McDiarmid et al. (1978) are apparently driven by different generators, although in both cases the solar wind is their ultimate source.

Microstructure and Mechanical Properties of Al2O3/Er3Al5O12 Binary Eutectic Ceramic Prepared by Bridgman Method

PubMed Central

Song, Caiyu; Wang, Shunheng; Liu, Juncheng; Zhai, Shuoyan

2018-01-01

Directionally solidified Al2O3/Er3Al5O12 (EAG) eutectic ceramic was prepared via vertical Bridgman method with high-frequency induction heating. The effects of the growth rate on the microstructure and mechanical properties of the solidified ceramic were investigated. The experimental results showed that there were no pores or amorphous phases in the directionally solidified Al2O3/EAG eutectic ceramic. Al2O3 phase was embedded in the EAG matrix phase, and the two phases were intertwined with each other to form a typical binary eutectic “hieroglyphic” structure. With the increase of growth rate, the phase size and spacing of the solidified Al2O3/EAG ceramic both decreased, and the growth rate and phase spacing satisfied the λ2v ≈ 60 formula of Jackson-Hunt theory. The cross section microstructure of the solidified ceramic always exhibited an irregular eutectic growth, while the longitudinal section microstructure presented a directional growth. The mechanical properties of the solidified ceramic gradually increased with the increase of growth rate, and the maximum hardness and fracture toughness could reach 21.57 GPa and 2.98 MPa·m1/2 respectively. It was considered that the crack deflection and branching could enhance the toughness of the solidified ceramic effectively. PMID:29601545

Heats of Segregation of BCC Binaries from ab Initio and Quantum Approximate Calculations

NASA Technical Reports Server (NTRS)

Good, Brian S.

2004-01-01

We compare dilute-limit heats of segregation for selected BCC transition metal binaries computed using ab initio and quantum approximate energy methods. Ab initio calculations are carried out using the CASTEP plane-wave pseudopotential computer code, while quantum approximate results are computed using the Bozzolo-Ferrante-Smith (BFS) method with the most recent LMTO-based parameters. Quantum approximate segregation energies are computed with and without atomistic relaxation, while the ab initio calculations are performed without relaxation. Results are discussed within the context of a segregation model driven by strain and bond-breaking effects. We compare our results with full-potential quantum calculations and with available experimental results.

Modeling the Redshift Evolution of the Normal Galaxy X-Ray Luminosity Function

NASA Technical Reports Server (NTRS)

Tremmel, M.; Fragos, T.; Lehmer, B. D.; Tzanavaris, P.; Belczynski, K.; Kalogera, V.; Basu-Zych, A. R.; Farr, W. M.; Hornschemeier, A.; Jenkins, L.;

An evaluation of the various aspects of the progress in clinical applications of laser driven ionizing radiation

NASA Astrophysics Data System (ADS)

Hideghéty, K.; Szabó, E. R.; Polanek, R.; Szabó, Z.; Ughy, B.; Brunner, S.; Tőkés, T.

2017-03-01

There has been a vast development of laser-driven particle acceleration (LDPA) using high power lasers. This has initiated by the radiation oncology community to use the dose distribution and biological advantages of proton/heavy ion therapy in cancer treatment with a much greater accessibility than currently possible with cyclotron/synchrotron acceleration. Up to now, preclinical experiments have only been performed at a few LDPA facilities; technical solutions for clinical LDPA have been theoretically developed but there is still a long way to go for the clinical introduction of LDPA. Therefore, to explore the further potential bio-medical advantages of LDPA has pronounced importance. The main characteristics of LDPA are the ultra-high beam intensity, the flexibility in beam size reduction and the potential particle and energy selection whilst conventional accelerators generate single particle, quasi mono-energetic beams. There is a growing number of studies on the potential advantages and applications of Energy Modulated X-ray Radiotherapy, Modulated Electron Radiotherapy and Very High Energy Electron (VHEE) delivery system. Furthermore, the ultra-high space and/or time resolution of super-intense beams are under intensive investigation at synchrotrons (microbeam radiation and very high dose rate (> 40 Gy/s) electron accelerator flash irradiation) with growing evidence of significant improvement of the therapeutic index. Boron Neutron Capture Therapy (BNCT) is an advanced cell targeted binary treatment modality. Because of the high linear energy transfer (LET) of the two particles (7Li and 4He) released by 10BNC reaction, all of the energy is deposited inside the tumour cells, killing them with high probability, while the neighbouring cells are not damaged. The limited availability of appropriate neutron sources, prevent the more extensive exploration of clinical benefit of BNCT. Another boron-based novel binary approach is the 11B-Proton Fusion, which result in the release of three high LET alpha particles. These promising, innovative approaches for cancer therapy present huge challenges for dose calculation, dosimetry and for investigation of the biological effects. The planned LDPA (photons, VHEE, protons, carbon ions) at ELI facilities has the unique property of ultra-high dose rate (> Gy/s-10), short pulses, and at ELI-ALPS high repetition rate, have the potential to develop and establish encouraging novel methods working towards compact hospital-based clinical applications.

Fluorophore Metal-Organic Complexes: High-Throughput Optical Screening for Aprotic Electrochemical Systems.

PubMed

Park, Sung Hyeon; Choi, Chang Hyuck; Lee, Seung Yong; Woo, Seong Ihl

2017-02-13

Combinatorial optical screening of aprotic electrocatalysts has not yet been achieved primarily due to H + -associated mechanisms of fluorophore modulation. We have overcome this problem by using fluorophore metal-organic complexes. In particular, eosin Y and quinine can be coordinated with various metallic cations (e.g., Li + , Na + , Mg 2+ , Zn 2+ , and Al 3+ ) in aprotic solvents, triggering changes in their fluorescent properties. These interactions have been used in a reliable screening method to determine oxygen reduction/evolution reaction activities of 100 Mn-based binary catalysts for the aprotic Li-air battery.

Half-metallic Co-based quaternary Heusler alloys for spintronics: Defect- and pressure-induced transitions and properties

DOE PAGES

Enamullah, .; Johnson, D. D.; Suresh, K. G.; ...

2016-11-07

Heusler compounds offer potential as spintronic devices due to their spin polarization and half-metallicity properties, where electron spin-majority (minority) manifold exhibits states (band gap) at the electronic chemical potential, yielding full spin polarization in a single manifold. Yet, Heuslers often exhibit intrinsic disorder that degrades its half-metallicity and spin polarization. Using density-functional theory, we analyze the electronic and magnetic properties of equiatomic Heusler (L2 1) CoMnCrAl and CoFeCrGe alloys for effects of hydrostatic pressure and intrinsic disorder (thermal antisites, binary swaps, and vacancies). Under pressure, CoMnCrAl undergoes a metallic transition, while half-metallicity in CoFeCrGe is retained for a limited range.more » Antisite disorder between Cr-Al pair in CoMnCrAl alloy is energetically the most favorable, and retains half-metallic character in Cr-excess regime. However, Co-deficient samples in both alloys undergo a transition from half-metallic to metallic, with a discontinuity in the saturation magnetization. For binary swaps, configurations that compete with the ground state are identified and show no loss of half-metallicity; however, the minority-spin band gap and magnetic moments vary depending on the atoms swapped. For single binary swaps, there is a significant energy cost in CoMnCrAl but with no loss of half-metallicity. Although a few configurations in CoFeCrGe energetically compete with the ground state, the minority-spin band gap and magnetic moments vary depending on the atoms swapped. Furthermore, this information should help in controlling these potential spintronic materials.« less

Half-metallic Co-based quaternary Heusler alloys for spintronics: Defect- and pressure-induced transitions and properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Enamullah, .; Johnson, D. D.; Suresh, K. G.

Heusler compounds offer potential as spintronic devices due to their spin polarization and half-metallicity properties, where electron spin-majority (minority) manifold exhibits states (band gap) at the electronic chemical potential, yielding full spin polarization in a single manifold. Yet, Heuslers often exhibit intrinsic disorder that degrades its half-metallicity and spin polarization. Using density-functional theory, we analyze the electronic and magnetic properties of equiatomic Heusler (L2 1) CoMnCrAl and CoFeCrGe alloys for effects of hydrostatic pressure and intrinsic disorder (thermal antisites, binary swaps, and vacancies). Under pressure, CoMnCrAl undergoes a metallic transition, while half-metallicity in CoFeCrGe is retained for a limited range.more » Antisite disorder between Cr-Al pair in CoMnCrAl alloy is energetically the most favorable, and retains half-metallic character in Cr-excess regime. However, Co-deficient samples in both alloys undergo a transition from half-metallic to metallic, with a discontinuity in the saturation magnetization. For binary swaps, configurations that compete with the ground state are identified and show no loss of half-metallicity; however, the minority-spin band gap and magnetic moments vary depending on the atoms swapped. For single binary swaps, there is a significant energy cost in CoMnCrAl but with no loss of half-metallicity. Although a few configurations in CoFeCrGe energetically compete with the ground state, the minority-spin band gap and magnetic moments vary depending on the atoms swapped. Furthermore, this information should help in controlling these potential spintronic materials.« less

V and K-band Mass-Luminosity Relations for M dwarf Stars

NASA Astrophysics Data System (ADS)

Benedict, G. Fritz; Henry, Todd J.; McArthur, Barbara; Franz, Otto G.; Wasserman, Lawrence H.; Dieterich, Sergio

2015-01-01

Applying Hubble Space Telescope Fine Guidance Sensor astrometric techniques developed to establish relative orbits for binary stars (Franz et al. 1998, AJ, 116, 1432), determine masses of binary components (Benedict et al. 2001, AJ, 121, 1607), and measure companion masses of exoplanet host stars (McArthur et al. 2010, ApJ, 715, 1203), we derive masses with an average 2.1% error for 24 components of 12 M dwarf binary star systems. Masses range 0.08 to 0.40 solar masses. With these we update the lower Main Sequence V-band Mass-Luminosity Relation first shown in Henry et al. (1999, ApJ, 512, 864). We demonstrate that a Mass-Luminosity Relation in the K-band has far less scatter than in the V-band. For the eight binary components for which we have component magnitude differences in the K-band the RMS residual drops from 0.5 magnitude in the V-band to 0.05 magnitude in the K-band. These relations can be used to estimate the masses of the ubiquitous red dwarfs that account for 75% of all stars, to an accuracy of 5%, which is much better than ever before.

Full Phase Multi-Band Study of Eclipsing Binaries 1SWASP J061850.43+220511.9 and 2MASSJ07095549+3643564

NASA Astrophysics Data System (ADS)

Terheide, Rachel; Zhang, Liyun; Han, Xianming; Lu, Hongpeng

2018-01-01

We present full-phase VRI-band light curves for eclipsing binary 1SWASP J061850.43+220511.9, and full-phase BVRI-band light curves for eclipsing binary 2MASS J07095549+3643564. The observations were conducted using the 0.94-m Holcomb Observatory telescope located on Butler University Campus in Indianapolis, Indiana, and the 0.6-m SARA telescope located at the Cerro Tololo Inter-American Observatory in Chile. We obtained key system parameters for both eclipsing binaries. For 1SWASP J061850.43+220511.9, the period is 0.21482 ±0.00053 days compared to 0.21439 days from an older study (Lohr et. al), the system mass ratio is found as 2.50 and the system is classified as EW type. Similarly, for 2MASS J07095549+3643564, we obtained a linear ephemeris and a physical model for the first time. We found its period to be 0.22297 ±0.00032 days, as compared to 0.446092 days and 0.11152 days from previous research (Drake et. al 2014, Hartman et. al 2011). 2MASS J07095549+3643564 is classified as a W Uma type eclipsing binary.

Critical mingling and universal correlations in model binary active liquids

NASA Astrophysics Data System (ADS)

Bain, Nicolas; Bartolo, Denis

2017-06-01

Ensembles of driven or motile bodies moving along opposite directions are generically reported to self-organize into strongly anisotropic lanes. Here, building on a minimal model of self-propelled bodies targeting opposite directions, we first evidence a critical phase transition between a mingled state and a phase-separated lane state specific to active particles. We then demonstrate that the mingled state displays algebraic structural correlations also found in driven binary mixtures. Finally, constructing a hydrodynamic theory, we single out the physical mechanisms responsible for these universal long-range correlations typical of ensembles of oppositely moving bodies.

Deposition behavior of mixed binary metallic powders in cold spraying process

NASA Astrophysics Data System (ADS)

Zhou, X. L.; Mou, S. J.; Wu, X. K.; Zhang, J. S.

2011-10-01

In the present study, Zn/Al composite coating was selected for the typical case to study the deposition behavior and the deformation of binary mixing particles in cold spraying process by means of an experiment and numerical simulation. The experimental results demonstrated that the coating had a dense microstructure, and that Zn and Al were uniformly distributed in the coating. Al particles deformed more severely than Zn particles, and extensively deformed Al particles had a local jet-metallic mixing area. The steel substrate underwent a small amount of deformation when impacted by Zn particles, whereas the substrate did not deform when impacted by Al particles. XRD results show that the Zn/Al composite coating did not form a new phase, and only resulted in the mechanical mixing of Zn and Al, producing a pseudo-alloy coating. In addition, a binary Zn/Al multiparticle impact was first simulated using the finite element analysis software ANSYS/LS-DYNA. The effective plastic strain contour, which enabled the description of the particle deposit procedure, was demonstrated. The plastic deformation evolution of Zn and Al particles in the composite coating was analyzed individually, and the curves of effective plastic strain versus time of typical monitored elements at the edge of the Zn and Al particles were plotted. The simulations showed good concordance with the experimental results.

Accretion dynamics in pre-main sequence binaries

NASA Astrophysics Data System (ADS)

Tofflemire, B.; Mathieu, R.; Herczeg, G.; Ardila, D.; Akeson, R.; Ciardi, D.; Johns-Krull, C.

Binary stars are a common outcome of star formation. Orbital resonances, especially in short-period systems, are capable of reshaping the distribution and flows of circumstellar material. Simulations of the binary-disk interaction predict a dynamically cleared gap around the central binary, accompanied by periodic ``pulsed'' accretion events that are driven by orbital motion. To place observational constraints on the binary-disk interaction, we have conducted a long-term monitoring program tracing the time-variable accretion behavior of 9 short-period binaries. In this proceeding we present two results from our campaign: 1) the detection of periodic pulsed accretion events in DQ Tau and TWA 3A, and 2) evidence that the TWA 3A primary is the dominant accretor in the system.

Strong-field control and enhancement of chiral response in bi-elliptical high-order harmonic generation: an analytical model

NASA Astrophysics Data System (ADS)

Ayuso, David; Decleva, Piero; Patchkovskii, Serguei; Smirnova, Olga

2018-06-01

The generation of high-order harmonics in a medium of chiral molecules driven by intense bi-elliptical laser fields can lead to strong chiroptical response in a broad range of harmonic numbers and ellipticities (Ayuso et al 2018 J. Phys. B: At. Mol. Opt. Phys. 51 06LT01). Here we present a comprehensive analytical model that can describe the most relevant features arising in the high-order harmonic spectra of chiral molecules driven by strong bi-elliptical fields. Our model recovers the physical picture underlying chiral high-order harmonic generation (HHG) based on ultrafast chiral hole motion and identifies the rotationally invariant molecular pseudoscalars responsible for chiral dynamics. Using the chiral molecule propylene oxide as an example, we show that one can control and enhance the chiral response in bi-elliptical HHG by tailoring the driving field, in particular by tuning its frequency, intensity and ellipticity, exploiting a suppression mechanism of achiral background based on the linear Stark effect.

Solid state amorphization in the Al-Fe binary system during high energy milling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urban, P., E-mail: purban@us.es; Montes, J. M.; Cintas, J.

2013-12-16

In the present study, mechanical alloying (MA) of Al75Fe25 elemental powders mixture was carried out in argon atmosphere, using a high energy attritor ball mill. The microstructure of the milled products at different stages of milling was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results showed that the amorphous phase content increased by increasing the milling time, and after 50 hours the amorphization process became complete. Heating the samples resulted in the crystallization of the synthesized amorphous alloys and the appearance of the equilibrium intermetallic compounds Al{sub 5}Fe{submore » 2}.« less

HS 0705+6700: a New Eclipsing sdB Binary

NASA Astrophysics Data System (ADS)

Drechsel, H.; Heber, U.; Napiwotzki, R.; Ostensen, R.; Solheim, J.-E.; Deetjen, J.; Schuh, S.

HS 0705+6700 is a newly discovered eclipsing sdB binary system consisting of an sdB primary and a cool secondary main sequence star. CCD photometry obtained in October and November 2000 with the 2.5m Nordic (NOT) telescope (La Palma, Tenerife) in the B passband and with the 2.2m Calar Alto telescope (CAFOS, R filter) yielded eclipse light curves with complete orbital phase coverage at high time resolution. A periodogram analysis of 12 primary minimum times distributed over the time span from October 2000 to March 2001 allowed to derive the following exact period and linear ephemeris: prim. min. = HJD 2451822.759782(22) + 0.09564665(39) ṡ E A total of 15 spectra taken with the 3.5m Calar Alto telescope (TWIN spectrograph) on March 11-12, 2001, were used to establish the radial velocity curve of the primary star (K1 = 85.8 km/s) , and to determine its basic atmospheric parameters (Teff = 29300 K, log g = 5.47). The B and R light curves were solved using our Wilson-Devinney based light curve analysis code MORO (Drechsel et al. 1995, A&A 294, 723). The best fit solution yielded exact system parameters consistent with the spectroscopic results. Detailed results will be published elsewhere (Drechsel et al. 2001, A&A, in preparation).

PHOTOMETRIC PROPERTIES OF SELECTED ALGOL-TYPE BINARIES. III. AL GEMINORUM AND BM MONOCEROTIS WITH POSSIBLE LIGHT-TIME ORBITS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Y.-G.; Dai, H.-F.; Li, H.-L., E-mail: yygcn@163.com

We present the CCD photometry of two Algol-type binaries, AL Gem and BM Mon, observed from 2008 November to 2011 January. With the updated Wilson-Devinney program, photometric solutions were deduced from their EA-type light curves. The mass ratios and fill-out factors of the primaries are found to be q{sub ph} = 0.090({+-} 0.005) and f{sub 1} = 47.3%({+-} 0.3%) for AL Gem, and q{sub ph} = 0.275({+-} 0.007) and f{sub 1} = 55.4%({+-} 0.5%) for BM Mon, respectively. By analyzing the O-C curves, we discovered that the periods of AL Gem and BM Mon change in a quasi-sinusoidal mode, whichmore » may possibly result from the light-time effect via the presence of a third body. Periods, amplitudes, and eccentricities of light-time orbits are 78.83({+-} 1.17) yr, 0fd0204({+-}0fd0007), and 0.28({+-} 0.02) for AL Gem and 97.78({+-} 2.67) yr, 0fd0175({+-}0fd0006), and 0.29({+-} 0.02) for BM Mon, respectively. Assumed to be in a coplanar orbit with the binary, the masses of the third bodies would be 0.29 M{sub Sun} for AL Gem and 0.26 M{sub Sun} for BM Mon. This kind of additional companion can extract angular momentum from the close binary orbit, and such processes may play an important role in multiple star evolution.« less

Modelling Chemical Reasoning to Predict and Invent Reactions.

PubMed

Segler, Marwin H S; Waller, Mark P

2017-05-02

The ability to reason beyond established knowledge allows organic chemists to solve synthetic problems and invent novel transformations. Herein, we propose a model that mimics chemical reasoning, and formalises reaction prediction as finding missing links in a knowledge graph. We have constructed a knowledge graph containing 14.4 million molecules and 8.2 million binary reactions, which represents the bulk of all chemical reactions ever published in the scientific literature. Our model outperforms a rule-based expert system in the reaction prediction task for 180 000 randomly selected binary reactions. The data-driven model generalises even beyond known reaction types, and is thus capable of effectively (re-)discovering novel transformations (even including transition metal-catalysed reactions). Our model enables computers to infer hypotheses about reactivity and reactions by only considering the intrinsic local structure of the graph and because each single reaction prediction is typically achieved in a sub-second time frame, the model can be used as a high-throughput generator of reaction hypotheses for reaction discovery. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lattice misfits in four binary Ni-Base γ/γ1 alloys at ambient and elevated temperatures

NASA Astrophysics Data System (ADS)

Kamara, A. B.; Ardell, A. J.; Wagner, C. N. J.

1996-10-01

High-temperature X-ray diffractometry was used to determine the in situlattice parameters, a γ and a γ', and lattice misfits, δ = ( a γ', - a γ)/ a γ, of the matrix (γ) and dispersed γ'-type (Ni3X) phases in polycrystalline binary Ni-Al, Ni-Ga, Ni-Ge, and Ni-Si alloys as functions of temperature, up to about 680 °C. Concentrated alloys containing large volume fractions of the γ' phase (˜0.40 to 0.50) were aged at 700 °C to produce large, elastically unconstrained precipitates. The room-temperature misfits are 0.00474 (Ni-Al), 0.01005 (Ni-Ga), 0.00626 (Ni-Ge), and -0.00226 (Ni-Si), with an estimated error of ± 4 pct. The absolute values of the lattice constants of the γ and γ' phases, at compositions corresponding to thermodynamic equilibrium at about 700 °C, are in excellent agreement with data from the literature, with the exception of Ni3Ga, the lattice constant of which is much larger than expected. In Ni-Ge alloys, δ decreases to 0.00612 at 679 °C, and in Ni-Ga alloys, the decrease is to 0.0097. In Ni-Si and Ni-Al alloys, δ exhibits a stronger temperature dependence, changing to-0.00285 at 683 °C (Ni-Si) and to 0.00424 at 680 °C (Ni-Al). Since the times required to complete the high-temperature X-ray diffraction (XRD) scans were relatively short (2.5 hours at most), we believe that the changes in δ observed are attributable to differences between the thermal expansion coefficients of the γ and γ' phases, because the compositions of the phases in question reflect the equilibrium compositions at 700 δC. Empirical equations are presented that accurately describe the temperature dependences of a γ, a γ', and δ over the range of temperatures of this investigation.

Gravitational Waves from Stellar Black Hole Binaries and the Impact on Nearby Sun-like Stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopes, Ilídio; Silk, Joseph, E-mail: ilidio.lopes@tecnico.ulisboa.pt, E-mail: silk@astro.ox.ac.uk

We investigate the impact of resonant gravitational waves on quadrupole acoustic modes of Sun-like stars located nearby stellar black hole binary systems (such as GW150914 and GW151226). We find that the stimulation of the low-overtone modes by gravitational radiation can lead to sizeable photometric amplitude variations, much larger than the predictions for amplitudes driven by turbulent convection, which in turn are consistent with the photometric amplitudes observed in most Sun-like stars. For accurate stellar evolution models, using up-to-date stellar physics, we predict photometric amplitude variations of 1–10{sup 3} ppm for a solar mass star located at a distance between 1more » au and 10 au from the black hole binary and belonging to the same multi-star system. The observation of such a phenomenon will be within the reach of the Plato mission because the telescope will observe several portions of the Milky Way, many of which are regions of high stellar density with a substantial mixed population of Sun-like stars and black hole binaries.« less

Simulating Gravitational Radiation from Binary Black Holes Mergers as LISA Sources

NASA Technical Reports Server (NTRS)

Baker, John

2005-01-01

A viewgraph presentation on the simulation of gravitational waves from Binary Massive Black Holes with LISA observations is shown. The topics include: 1) Massive Black Holes (MBHs); 2) MBH Binaries; 3) Gravitational Wavws from MBH Binaries; 4) Observing with LISA; 5) How LISA sees MBH binary mergers; 6) MBH binary inspirals to LISA; 7) Numerical Relativity Simulations; 8) Numerical Relativity Challenges; 9) Recent Successes; 10) Goddard Team; 11) Binary Black Hole Simulations at Goddard; 12) Goddard Recent Advances; 13) Baker, et al.:GSFC; 13) Starting Farther Out; 14) Comparing Initial Separation; 15) Now with AMR; and 16) Conclusion.

Physical properties and catalog of EW-type eclipsing binaries observed by LAMOST

NASA Astrophysics Data System (ADS)

Qian, Sheng-Bang; He, Jia-Jia; Zhang, Jia; Zhu, Li-Ying; Shi, Xiang-Dong; Zhao, Er-Gang; Zhou, Xiao

2017-08-01

EW-type eclipsing binaries (hereafter called EWs) are strong interacting systems in which both component stars usually fill their critical Roche lobes and share a common envelope. Numerous EWs were discovered by several deep photometric surveys and there were about 40 785 EW-type binary systems listed in the international variable star index (VSX) by 2017 March 13. 7938 of them were observed with LAMOST by 2016 November 30 and their spectral types were identified. Stellar atmospheric parameters of 5363 EW-type binary stars were determined based on good spectroscopic observations. In the paper, those EWs are cataloged and their properties are analyzed. The distributions of orbital period (P), effective temperature (T), gravitational acceleration (log(g)), metallicity ([Fe/H]) and radial velocity (RV) are presented for these observed EW-type systems. It is shown that about 80.6% of sample stars have metallicity below zero, indicating that EW-type systems are old stellar populations. This is in agreement with the conclusion that EW binaries are formed from moderately close binaries through angular momentum loss via magnetic braking that takes a few hundred million to a few billion years. The unusually high metallicities of a few percent of EWs may be caused by contamination of material from the evolution of unseen neutron stars or black holes in the systems. The correlations between orbital period and effective temperature, gravitational acceleration and metallicity are presented and their scatters are mainly caused by (i) the presence of third bodies and (ii) sometimes wrongly determined periods. It is shown that some EWs contain evolved component stars and the physical properties of EWs mainly depend on their orbital periods. It is found that extremely short-period EWs may be older than their long-period cousins because they have lower metallicities. This reveals that they have a longer timescale of pre-contact evolution and their formation and evolution aremainly driven by angular momentum loss via magnetic braking.

Broadband white light emission from Ce:AlN ceramics: High thermal conductivity down-converters for LED and laser-driven solid state lighting

NASA Astrophysics Data System (ADS)

Wieg, A. T.; Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Garay, J. E.

2016-12-01

We introduce high thermal conductivity aluminum nitride (AlN) as a transparent ceramic host for Ce3+, a well-known active ion dopant. We show that the Ce:AlN ceramics have overlapping photoluminescent (PL) emission peaks that cover almost the entire visible range resulting in a white appearance under 375 nm excitation without the need for color mixing. The PL is due to a combination of intrinsic AlN defect complexes and Ce3+ electronic transitions. Importantly, the peak intensities can be tuned by varying the Ce concentration and processing parameters, causing different shades of white light without the need for multiple phosphors or light sources. The Commission Internationale de l'Eclairage coordinates calculated from the measured spectra confirm white light emission. In addition, we demonstrate the viability of laser driven white light emission by coupling the Ce:AlN to a readily available frequency tripled Nd-YAG laser emitting at 355 nm. The high thermal conductivity of these ceramic down-converters holds significant promise for producing higher power white light sources than those available today.

Aluminum silicide microparticles transformed from aluminum thin films by hypoeutectic interdiffusion

PubMed Central

2014-01-01

Aluminum silicide microparticles with oxidized rough surfaces were formed on Si substrates through a spontaneous granulation process of Al films. This microparticle formation was caused by interdiffusion of Al and Si atoms at hypoeutectic temperatures of Al-Si systems, which was driven by compressive stress stored in Al films. The size, density, and the composition of the microparticles could be controlled by adjusting the annealing temperature, time, and the film thickness. High-density microparticles of a size around 10 μm and with an atomic ratio of Si/Al of approximately 0.8 were obtained when a 90-nm-thick Al film on Si substrate was annealed for 9 h at 550°C. The microparticle formation resulted in a rapid increase of the sheet resistance, which is a consequence of substantial consumption of Al film. This simple route to size- and composition-controllable microparticle formation may lay a foundation stone for the thermoelectric study on Al-Si alloy-based heterogeneous systems. PMID:24994964

Aluminum silicide microparticles transformed from aluminum thin films by hypoeutectic interdiffusion.

PubMed

Noh, Jin-Seo

2014-01-01

Aluminum silicide microparticles with oxidized rough surfaces were formed on Si substrates through a spontaneous granulation process of Al films. This microparticle formation was caused by interdiffusion of Al and Si atoms at hypoeutectic temperatures of Al-Si systems, which was driven by compressive stress stored in Al films. The size, density, and the composition of the microparticles could be controlled by adjusting the annealing temperature, time, and the film thickness. High-density microparticles of a size around 10 μm and with an atomic ratio of Si/Al of approximately 0.8 were obtained when a 90-nm-thick Al film on Si substrate was annealed for 9 h at 550°C. The microparticle formation resulted in a rapid increase of the sheet resistance, which is a consequence of substantial consumption of Al film. This simple route to size- and composition-controllable microparticle formation may lay a foundation stone for the thermoelectric study on Al-Si alloy-based heterogeneous systems.

True ternary fission, the collinear cluster tripartition (CCT) of {sup 252}Cf

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oertzen, W. von; Pyatkov, Y. V.; Kamanin, D.

2012-10-20

In systematic work over the last decade (see Pyatkov et al. [12] and refs therein), the ternary fission decay of heavy nuclei, in {sup 235}U(n,fff) and {sup 252}Cf(sf) has been studied in a collinear geometry. The name used for this process is (CCT), with three fragments of similar size in a collinear decay, it is the true ternary fission. This decay has been observed in spontaneous fission as well as in a neutron induced reaction. The measurements are based on different experimental set-ups, with binary coincidences containing TOF and energy determinations. With two detector telescopes placed at 180 Degree-Sign ,more » the measurements of masses and energies of each of the registered two fragments, give complete kinematic solutions. Thus the missing mass events in binary coincidences can be determined, these events are obtained by blocking one of the lighter fragments on a structure in front of the detectors. The relatively high yield of CCT (more than 10{sup -3} per binary fission) is explained. It is due to the favourable Q-values (more positive than for binary) and the large phase space of the ternary CCT-decay, dominated by three (magic) clusters: e.g. isotopes of Sn, Ca and Ni, {sup 132}Sn+{sup 50}Ca+{sup 70}Ni. It is shown that the collinear (prolate) geometry has the favoured potential energy relative to the oblate shapes. The ternary fission is considered to be a sequential process. With this assumption the kinetic energies of the fragments have been calculated by Vijay et al.. The third fragments have very low kinetic energies (below 20 MeV) and have thus escaped their detection in previous work on 'ternary fission', where in addition an oblate shape and a triangle for the momentum vectors have been assumed.« less

Understanding AlN Obtaining Through Computational Thermodynamics Combined with Experimental Investigation

NASA Astrophysics Data System (ADS)

Florea, R. M.

2017-06-01

Basic material concept, technology and some results of studies on aluminum matrix composite with dispersive aluminum nitride reinforcement was shown. Studied composites were manufactured by „in situ” technique. Aluminum nitride (AlN) has attracted large interest recently, because of its high thermal conductivity, good dielectric properties, high flexural strength, thermal expansion coefficient matches that of Si and its non-toxic nature, as a suitable material for hybrid integrated circuit substrates. AlMg alloys are the best matrix for AlN obtaining. Al2O3-AlMg, AlN-Al2O3, and AlN-AlMg binary diagrams were thermodynamically modelled. The obtained Gibbs free energies of components, solution parameters and stoichiometric phases were used to build a thermodynamic database of AlN- Al2O3-AlMg system. Obtaining of AlN with Liquid-phase of AlMg as matrix has been studied and compared with the thermodynamic results. The secondary phase microstructure has a significant effect on the final thermal conductivity of the obtained AlN. Thermodynamic modelling of AlN-Al2O3-AlMg system provided an important basis for understanding the obtaining behavior and interpreting the experimental results.

Electrohydrodynamic Flows in Electrochemical Systems

NASA Technical Reports Server (NTRS)

Saville, D. A.

2005-01-01

Recent studies have established a new class of assembly processes with colloidal suspensions. Particles are driven together to form large crystalline structures in both dc and ac fields. The current work centers on this new class of flows in ac fields. In the research carried out under the current award, it was established that: (i) Small colloidal particles crystallize near an electrode due to electrohydrodynamic flows induced by an sinusoidally varying applied potential. (ii) These flows originate due to disturbances in the electrode polarization layer arising from the presence of the particles. Inasmuch as the charge and the field strength both scale on the applied field, the flows are proportional to the square of the applied voltage. (iii) Suspensions of two different sorts of particles can be crystallized and will form well-ordered binary crystals. (iv) At high frequencies the EHD flows die out. Thus, with a homogeneous system the particles become widely spaced due to dipolar repulsion. With a binary suspension, however, the particles may become attractive due to dipolar attraction arising from differences in electrokinetic dipoles. Consequently binary crystals form at both high and low frequencies.

Geomorphic Flood Area (GFA): a QGIS tool for a cost-effective delineation of the floodplains

NASA Astrophysics Data System (ADS)

Samela, Caterina; Albano, Raffaele; Sole, Aurelia; Manfreda, Salvatore

2017-04-01

The importance of delineating flood hazard and risk areas at a global scale has been highlighted for many years. However, its complete achievement regularly encounters practical difficulties, above all the lack of data and implementation costs. In conditions of scarce data availability (e.g. ungauged basins, large-scale analyses), a fast and cost-effective floodplain delineation can be carried out using geomorphic methods (e.g., Manfreda et al., 2011; 2014). In particular, an automatic DEM-based procedure has been implemented in an open-source QGIS plugin named Geomorphic Flood Area - tool (GFA - tool). This tool performs a linear binary classification based on the recently proposed Geomorphic Flood Index (GFI), which exhibited high classification accuracy and reliability in several test sites located in Europe, United States and Africa (Manfreda et al., 2015; Samela et al., 2016, 2017; Samela, 2016). The GFA - tool is designed to make available to all users the proposed procedure, that includes a number of operations requiring good geomorphic and GIS competences. It allows computing the GFI through terrain analysis, turning it into a binary classifier, and training it on the base of a standard inundation map derived for a portion of the river basin (a minimum of 2% of the river basin's area is suggested) using detailed methods of analysis (e.g. flood hazard maps produced by emergency management agencies or river basin authorities). Finally, GFA - tool allows to extend the classification outside the calibration area to delineate the flood-prone areas across the entire river basin. The full analysis has been implemented in this plugin with a user-friendly interface that should make it easy to all user to apply the approach and produce the desired results. Keywords: flood susceptibility; data scarce environments; geomorphic flood index; linear binary classification; Digital elevation models (DEMs). References Manfreda, S., Di Leo, M., Sole, A., (2011). Detection of Flood Prone Areas using Digital Elevation Models, Journal of Hydrologic Engineering, 16(10), 781-790. Manfreda, S., Nardi, F., Samela, C., Grimaldi, S., Taramasso, A. C., Roth, G., & Sole, A. (2014). Investigation on the Use of Geomorphic Approaches for the Delineation of Flood Prone Areas, Journal of Hydrology, 517, 863-876. Manfreda, S., Samela, C., Gioia, A., Consoli, G., Iacobellis, V., Giuzio, L., & Sole, A. (2015). Flood-prone areas assessment using linear binary classifiers based on flood maps obtained from 1D and 2D hydraulic models. Natural Hazards, Vol. 79 (2), pp 735-754. Samela, C. (2016), 100-year flood susceptibility maps for the continental U.S. derived with a geomorphic method. University of Basilicata. Dataset. Samela, C., Manfreda, S., Paola, F. D., Giugni, M., Sole, A., & Fiorentino, M. (2016). DEM-Based Approaches for the Delineation of Flood-Prone Areas in an Ungauged Basin in Africa. Journal of Hydrologic Engineering, 21(2), 1-10. Samela, C., Troy, T.J., Manfreda, S. (2017). Geomorphic classifiers for flood-prone areas delineation for data-scarce environments, Advances in Water Resources (under review).

The separation distribution and merger rate of double white dwarfs: improved constraints

NASA Astrophysics Data System (ADS)

Maoz, Dan; Hallakoun, Na'ama; Badenes, Carles

2018-05-01

We obtain new and precise information on the double white dwarf (DWD) population and on its gravitational-wave-driven merger rate by combining the constraints on the DWD population from two previous studies on radial velocity variation. One of the studies is based on a sample of white dwarfs (WDs) from the Sloan Digital Sky Survey (SDSS, which with its low spectral resolution probes systems at separations a < 0.05 au) and the other is based on the ESO-VLT Supernova-Ia Progenitor surveY (SPY, which with its high spectral resolution is sensitive to a < 4 au). From a joint likelihood analysis, the DWD fraction among WDs is fbin = 0.095 ± 0.020 (1σ, random) +0.010 (systematic) in the separation range ≲4 au. The index of a power-law distribution of initial WD separations (at the start of solely gravitational-wave-driven binary evolution), N(a)da ∝ aαda, is α = -1.30 ± 0.15 (1σ) +0.05 (systematic). The Galactic WD merger rate per WD is Rmerge = (9.7 ± 1.1) × 10-12 yr-1. Integrated over the Galaxy lifetime, this implies that 8.5-11 per cent of all WDs ever formed have merged with another WD. If most DWD mergers end as more-massive WDs, then some 10 per cent of WDs are DWD-merger products, consistent with the observed fraction of WDs in a `high-mass bump' in the WD mass function. The DWD merger rate is 4.5-7 times the Milky Way's specific Type Ia supernova (SN Ia) rate. If most SN Ia explosions stem from the mergers of some DWDs (say, those with massive-enough binary components) then ˜15 per cent of all WD mergers must lead to a SN Ia.

Room-temperature continuous-wave electrically injected InGaN-based laser directly grown on Si

NASA Astrophysics Data System (ADS)

Sun, Yi; Zhou, Kun; Sun, Qian; Liu, Jianping; Feng, Meixin; Li, Zengcheng; Zhou, Yu; Zhang, Liqun; Li, Deyao; Zhang, Shuming; Ikeda, Masao; Liu, Sheng; Yang, Hui

2016-09-01

Silicon photonics would greatly benefit from efficient, visible on-chip light sources that are electrically driven at room temperature. To fully utilize the benefits of large-scale, low-cost manufacturing foundries, it is highly desirable to grow direct bandgap III-V semiconductor lasers directly on Si. Here, we report the demonstration of a blue-violet (413 nm) InGaN-based laser diode grown directly on Si that operates under continuous-wave current injection at room temperature, with a threshold current density of 4.7 kA cm-2. The heteroepitaxial growth of GaN on Si is confronted with a large mismatch in both the lattice constant and the coefficient of thermal expansion, often resulting in a high density of defects and even microcrack networks. By inserting an Al-composition step-graded AlN/AlGaN multilayer buffer between the Si and GaN, we have not only successfully eliminated crack formation, but also effectively reduced the dislocation density. The result is the realization of a blue-violet InGaN-based laser on Si.

Effects of alloying elements (Mn, Co, Al, W, Sn, B, C and S) on biodegradability and in vitro biocompatibility of pure iron.

PubMed

Liu, B; Zheng, Y F

2011-03-01

Pure iron was determined to be a valid candidate material for biodegradable metallic stents in recent animal tests; however, a much faster degradation rate in physiological environments was desired. C, Mn, Si, P, S, B, Cr, Ni, Pb, Mo, Al, Ti, Cu, Co, V and W are common alloying elements in industrial steels, with Cr, Ni, Mo, Cu, Ti, V and Si being acknowledged as beneficial in enhancing the corrosion resistance of iron. The purpose of the present work (using Fe-X binary alloy models) is to explore the effect of the remaining alloying elements (Mn, Co, Al, W, B, C and S) and one detrimental impurity element Sn on the biodegradability and biocompatibility of pure iron by scanning electron microscopy, X-ray diffraction, metallographic observation, tensile testing, microhardness testing, electrochemical testing, static (for 6 months) and dynamic (for 1 month with various dissolved oxygen concentrations) immersion testing, cytotoxicity testing, hemolysis and platelet adhesion testing. The results showed that the addition of all alloying elements except for Sn improved the mechanical properties of iron after rolling. Localized corrosion of Fe-X binary alloys was observed in both static and dynamic immersion tests. Except for the Fe-Mn alloy, which showed a significant decrease in corrosion rate, the other Fe-X binary alloy corrosion rates were close to that of pure iron. It was found that compared with pure iron all Fe-X binary alloys decreased the viability of the L929 cell line, none of experimental alloying elements significantly reduced the viability of vascular smooth muscle cells and all the elements except for Mn increased the viability of the ECV304 cell line. The hemolysis percentage of all Fe-X binary alloy models were less than 5%, and no sign of thrombogenicity was observed. In vitro corrosion and the biological behavior of these Fe-X binary alloys are discussed and a corresponding mechanism of corrosion of Fe-X binary alloys in Hank's solution proposed. As a concluding remark, Co, W, C and S are recommended as alloying elements for biodegradable iron-based biomaterials. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A wide deep infrared look at the Pleiades with UKIDSS: new constraints on the substellar binary fraction and the low-mass initial mass function

NASA Astrophysics Data System (ADS)

Lodieu, N.; Dobbie, P. D.; Deacon, N. R.; Hodgkin, S. T.; Hambly, N. C.; Jameson, R. F.

2007-09-01

We present the results of a deep wide-field near-infrared survey of 12 deg2 of the Pleiades conducted as part of the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) Galactic Cluster Survey (GCS). We have extracted over 340 high-probability proper motion (PM) members down to 0.03 Msolar using a combination of UKIDSS photometry and PM measurements obtained by cross-correlating the GCS with data from the Two Micron All Sky Survey, the Isaac Newton Telescope and the Canada-France-Hawaii Telescope. Additionally, we have unearthed 73 new candidate brown dwarf (BD) members on the basis of five-band UKIDSS photometry alone. We have identified 23 substellar multiple system candidates out of 63 candidate BDs from the (Y - K, Y) and (J - K, J) colour-magnitude diagrams, yielding a binary frequency of 28-44 per cent in the 0.075-0.030 Msolar mass range. Our estimate is three times larger than the binary fractions reported from high-resolution imaging surveys of field ultracool dwarfs and Pleiades BDs. However, it is marginally consistent with our earlier `peculiar' photometric binary fraction of 50 +/- 10 per cent presented by Pinfield et al., in good agreement with the 32-45 per cent binary fraction derived from the recent Monte Carlo simulations of Maxted & Jeffries and compatible with the 26 +/- 10 per cent frequency recently estimated by Basri & Reiners. A tentative estimate of the mass ratios from photometry alone seems to support the hypothesis that binary BDs tend to reside in near equal-mass ratio systems. In addition, the recovery of four Pleiades members targeted by high-resolution imaging surveys for multiplicity studies suggests that half of the binary candidates may have separations below the resolution limit of the Hubble Space Telescope or current adaptive optics facilities at the distance of the Pleiades (a ~7 au). Finally, we have derived luminosity and mass functions from the sample of photometric candidates with membership probabilities. The mass function is well modelled by a lognormal peaking at 0.24Msolar and is in agreement with previous studies in the Pleiades. Based on observations made with the United Kingdom Infrared Telescope, operated by the Joint Astronomy Centre on behalf of the UK Particle Physics and Astronomy Research Council. E-mail: nlodieu@iac.es

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antolovich, S.D.; Saxena, A.; Cullers, C.

One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is consideredmore » a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems.« less

High-resolution urban flood modelling - a joint probability approach

NASA Astrophysics Data System (ADS)

Hartnett, Michael; Olbert, Agnieszka; Nash, Stephen

2017-04-01

The hydrodynamic modelling of rapid flood events due to extreme climatic events in urban environment is both a complex and challenging task. The horizontal resolution necessary to resolve complexity of urban flood dynamics is a critical issue; the presence of obstacles of varying shapes and length scales, gaps between buildings and the complex geometry of the city such as slopes affect flow paths and flood levels magnitudes. These small scale processes require a high resolution grid to be modelled accurately (2m or less, Olbert et al., 2015; Hunter et al., 2008; Brown et al., 2007) and, therefore, altimetry data of at least the same resolution. Along with availability of high-resolution LiDAR data and computational capabilities, as well as state of the art nested modelling approaches, these problems can now be overcome. Flooding and drying, domain definition, frictional resistance and boundary descriptions are all important issues to be addressed when modelling urban flooding. In recent years, the number of urban flood models dramatically increased giving a good insight into various modelling problems and solutions (Mark et al., 2004; Mason et al., 2007; Fewtrell et al., 2008; Shubert et al., 2008). Despite extensive modelling work conducted for fluvial (e.g. Mignot et al., 2006; Hunter et al., 2008; Yu and Lane, 2006) and coastal mechanisms of flooding (e.g. Gallien et al., 2011; Yang et al., 2012), the amount of investigations into combined coastal-fluvial flooding is still very limited (e.g. Orton et al., 2012; Lian et al., 2013). This is surprising giving the extent of flood consequences when both mechanisms occur simultaneously, which usually happens when they are driven by one process such as a storm. The reason for that could be the fact that the likelihood of joint event is much smaller than those of any of the two contributors occurring individually, because for fast moving storms the rainfall-driven fluvial flood arrives usually later than the storm surge (Divoky et al., 2005). Nevertheless, such events occur and in Ireland alone there are several cases of serious damage due to flooding resulting from a combination of high sea water levels and river flows driven by the same meteorological conditions (e.g. Olbert et al. 2015). A November 2009 fluvial-coastal flooding of Cork City bringing €100m loss was one such incident. This event was used by Olbert et al. (2015) to determine processes controlling urban flooding and is further explored in this study to elaborate on coastal and fluvial flood mechanisms and their roles in controlling water levels. The objective of this research is to develop a methodology to assess combined effect of multiple source flooding on flood probability and severity in urban areas and to establish a set of conditions that dictate urban flooding due to extreme climatic events. These conditions broadly combine physical flood drivers (such as coastal and fluvial processes), their mechanisms and thresholds defining flood severity. The two main physical processes controlling urban flooding: high sea water levels (coastal flooding) and high river flows (fluvial flooding), and their threshold values for which flood is likely to occur, are considered in this study. Contribution of coastal and fluvial drivers to flooding and their impacts are assessed in a two-step process. The first step involves frequency analysis and extreme value statistical modelling of storm surges, tides and river flows and ultimately the application of joint probability method to estimate joint exceedence return periods for combination of surges, tide and river flows. In the second step, a numerical model of Cork Harbour MSN_Flood comprising a cascade of four nested high-resolution models is used to perform simulation of flood inundation under numerous hypothetical coastal and fluvial flood scenarios. The risk of flooding is quantified based on a range of physical aspects such as the extent and depth of inundation (Apel et al., 2008) The methodology includes estimates of flood probabilities due to coastal- and fluvial-driven processes occurring individually or jointly, mechanisms of flooding and their impacts on urban environment. Various flood scenarios are examined in order to demonstrate that this methodology is necessary to quantify the important physical processes in coastal flood predictions. Cork City, located on the south of Ireland subject to frequent coastal-fluvial flooding, is used as a study case.

The first gravitational-wave burst GW150914, as predicted by the scenario machine

NASA Astrophysics Data System (ADS)

Lipunov, V. M.; Kornilov, V.; Gorbovskoy, E.; Tiurina, N.; Balanutsa, P.; Kuznetsov, A.

2017-02-01

The Advanced LIGO observatory recently reported (Abbott et al., 2016a) the first direct detection of gravitational waves predicted by Einstein (1916). The detection of this event was predicted in 1997 on the basis of the Scenario Machine population synthesis calculations (Lipunov et al., 1997b) Now we discuss the parameters of binary black holes and event rates predicted by different scenarios of binary evolution. We give a simple explanation of the big difference between detected black hole masses and the mean black hole masses observed in of X-ray Nova systems. The proximity of the masses of the components of GW150914 is in good agreement with the observed initial mass ratio distribution in massive binary systems, as is used in Scenario Machine calculations for massive binaries.

X-RAY BINARIES AND STAR CLUSTERS IN THE ANTENNAE: OPTICAL CLUSTER COUNTERPARTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rangelov, Blagoy; Chandar, Rupali; Prestwich, Andrea

2012-10-20

We compare the locations of 82 X-ray binaries (XRBs) detected in the merging Antennae galaxies by Zezas et al., based on observations taken with the Chandra X-Ray Observatory, with a catalog of optically selected star clusters presented by Whitmore et al., based on observations taken with the Hubble Space Telescope. Within the 2{sigma} positional uncertainty of Almost-Equal-To 0.''8, we find 22 XRBs are coincident with star clusters, where only two to three chance coincidences are expected. The ages of the clusters were estimated by comparing their UBVI, H{alpha} colors with predictions from stellar evolutionary models. We find that 14 ofmore » the 22 coincident XRBs (64%) are hosted by star clusters with ages of Almost-Equal-To 6 Myr or less. All of the very young host clusters are fairly massive and have M {approx}> 3 Multiplication-Sign 10{sup 4} M {sub Sun }, with many having masses M Almost-Equal-To 10{sup 5} M {sub Sun }. Five of the XRBs are hosted by young clusters with ages {tau} Almost-Equal-To 10-100 Myr, while three are hosted by intermediate-age clusters with {tau} Almost-Equal-To 100-300 Myr. Based on the results from recent N-body simulations, which suggest that black holes are far more likely to be retained within their parent clusters than neutron stars, we suggest that our sample consists primarily of black hole binaries with different ages.« less

Irradiation-driven Mass Transfer Cycles in Compact Binaries

NASA Astrophysics Data System (ADS)

Büning, A.; Ritter, H.

2005-08-01

We elaborate on the analytical model of Ritter, Zhang, & Kolb (2000) which describes the basic physics of irradiation-driven mass transfer cycles in semi-detached compact binary systems. In particular, we take into account a contribution to the thermal relaxation of the donor star which is unrelated to irradiation and which was neglected in previous studies. We present results of simulations of the evolution of compact binaries undergoing mass transfer cycles, in particular also of systems with a nuclear evolved donor star. These computations have been carried out with a stellar evolution code which computes mass transfer implicitly and models irradiation of the donor star in a point source approximation, thereby allowing for much more realistic simulations than were hitherto possible. We find that low-mass X-ray binaries (LMXBs) and cataclysmic variables (CVs) with orbital periods ⪉ 6hr can undergo mass transfer cycles only for low angular momentum loss rates. CVs containing a giant donor or one near the terminal age main sequence are more stable than previously thought, but can possibly also undergo mass transfer cycles.

The WFCAM Transit Survey: A Search for Rocky Planets Around Cool Stars

NASA Astrophysics Data System (ADS)

Birkby, J.; Hodgkin, S.; Pinfield, D.; WTS Consortium

2011-12-01

We report on the WFCAM Transit Survey which is a near-infrared photometric monitoring campaign designed primarily to test the predictions of planet formation theory. We monitor a statisically significant sample of ˜6,000 M-dwarfs (M<0.6M⊙) across 6 sq. deg of the sky, by taking advantage of the highly-efficient queue-scheduled operational mode of the 3.8m United Kingdom Infrared Telescope. Our light curves have RMS < 1% between 13 < J < 16 magnitudes and preliminary simulations indicate the survey is sensitive to at least Jupiter-like transits of M-dwarfs. The survey is approximately 25% complete and within this dataset we find i) no planet-like transit events, despite thorough and extensive follow-up this summer and ii) 32 new M-dwarf eclipsing binaries. We do not speculate on the planet fraction of M-dwarfs at this incomplete stage of our survey, but once we achieve 1,000 epochs of observation on our entire M-dwarf sample, we will have a significant observational constraint to place on occurrence of planets around M-dwarfs. We report masses and radii for three of our newly discovered eclipsing binary, with errors of 3-7%, which all show inflated radii when compared to stellar evolution models (e.g. Baraffe et al. (1998)). Our results support the growing body of observations with inflated M-dwarf radii, which may be caused by increased magnetic activity inhibiting the convection efficiency or increased star spot coverage (e.g. Chabrier et al. (2007); Jackson et al. (2009)). Finally, we present preliminary mass and radius estimates of a fourth new eclipsing binary, which is one of the lowest mass binary systems ever discovered and will provide a calibrating point in the desert of observations between 0.1-0.2M⊙.

Implicit Regularization for Reconstructing 3D Building Rooftop Models Using Airborne LiDAR Data

PubMed Central

Jung, Jaewook; Jwa, Yoonseok; Sohn, Gunho

2017-01-01

With rapid urbanization, highly accurate and semantically rich virtualization of building assets in 3D become more critical for supporting various applications, including urban planning, emergency response and location-based services. Many research efforts have been conducted to automatically reconstruct building models at city-scale from remotely sensed data. However, developing a fully-automated photogrammetric computer vision system enabling the massive generation of highly accurate building models still remains a challenging task. One the most challenging task for 3D building model reconstruction is to regularize the noises introduced in the boundary of building object retrieved from a raw data with lack of knowledge on its true shape. This paper proposes a data-driven modeling approach to reconstruct 3D rooftop models at city-scale from airborne laser scanning (ALS) data. The focus of the proposed method is to implicitly derive the shape regularity of 3D building rooftops from given noisy information of building boundary in a progressive manner. This study covers a full chain of 3D building modeling from low level processing to realistic 3D building rooftop modeling. In the element clustering step, building-labeled point clouds are clustered into homogeneous groups by applying height similarity and plane similarity. Based on segmented clusters, linear modeling cues including outer boundaries, intersection lines, and step lines are extracted. Topology elements among the modeling cues are recovered by the Binary Space Partitioning (BSP) technique. The regularity of the building rooftop model is achieved by an implicit regularization process in the framework of Minimum Description Length (MDL) combined with Hypothesize and Test (HAT). The parameters governing the MDL optimization are automatically estimated based on Min-Max optimization and Entropy-based weighting method. The performance of the proposed method is tested over the International Society for Photogrammetry and Remote Sensing (ISPRS) benchmark datasets. The results show that the proposed method can robustly produce accurate regularized 3D building rooftop models. PMID:28335486

Implicit Regularization for Reconstructing 3D Building Rooftop Models Using Airborne LiDAR Data.

PubMed

Jung, Jaewook; Jwa, Yoonseok; Sohn, Gunho

2017-03-19

With rapid urbanization, highly accurate and semantically rich virtualization of building assets in 3D become more critical for supporting various applications, including urban planning, emergency response and location-based services. Many research efforts have been conducted to automatically reconstruct building models at city-scale from remotely sensed data. However, developing a fully-automated photogrammetric computer vision system enabling the massive generation of highly accurate building models still remains a challenging task. One the most challenging task for 3D building model reconstruction is to regularize the noises introduced in the boundary of building object retrieved from a raw data with lack of knowledge on its true shape. This paper proposes a data-driven modeling approach to reconstruct 3D rooftop models at city-scale from airborne laser scanning (ALS) data. The focus of the proposed method is to implicitly derive the shape regularity of 3D building rooftops from given noisy information of building boundary in a progressive manner. This study covers a full chain of 3D building modeling from low level processing to realistic 3D building rooftop modeling. In the element clustering step, building-labeled point clouds are clustered into homogeneous groups by applying height similarity and plane similarity. Based on segmented clusters, linear modeling cues including outer boundaries, intersection lines, and step lines are extracted. Topology elements among the modeling cues are recovered by the Binary Space Partitioning (BSP) technique. The regularity of the building rooftop model is achieved by an implicit regularization process in the framework of Minimum Description Length (MDL) combined with Hypothesize and Test (HAT). The parameters governing the MDL optimization are automatically estimated based on Min-Max optimization and Entropy-based weighting method. The performance of the proposed method is tested over the International Society for Photogrammetry and Remote Sensing (ISPRS) benchmark datasets. The results show that the proposed method can robustly produce accurate regularized 3D building rooftop models.

EFFECTS OF CARBOXYLIC ACIDS ON LIQUID-PHASE ADSORPTION OF ETHANOL AND WATER BY HIGH-SILICA ZSM-5

EPA Science Inventory

Adsorption isotherms were measured for each compound adsorbed on commercially available ZSM-5 (Si/Al = 140) powder from binary and ternary liquid mixtures of ethanol, carboxylic acids, and water at room temperature. The amounts adsorbed were measured using a recently developed t...

Selective dry etching of III-V nitrides in Cl{sub 2}/Ar, CH{sub 4}/H{sub 2}/Ar, ICi/Ar, and IBr/Ar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vartuli, C.B.; Pearton, S.J.; MacKenzie, J.D.

1996-10-01

The selectivity for etching the binary (GaN, AlN, and InN) and ternary nitrides (InGaN and InAlN) relative to each other in Cl{sub 2}/Ar, CH{sub 4}/H{sub 2}/Ar, ICl/Ar, or IBr/Ar electron cyclotron resonance (ECR) plasmas, and Cl{sub 2}/Ar or CH{sub 4}/H{sub 2}/Ar reactive ion (RIE) plasmas was investigated. Cl-based etches appear to be the best choice for maximizing the selectivity of GaN over the other nitrides. GaN/AlN and GaN/InGaN etch rate ratios of {approximately} 10 were achieved at low RF power in Cl{sub 2}/Ar under ECR and RIE conditions, respectively. GaN/InN selectivity of 10 was found in ICl under ECR conditions.more » A relatively high selectivity (> 6) of InN/GaN was achieved in CH{sub 4}/H{sub 2}/Ar under ECR conditions at low RF powers (50 W). Since the high bond strengths of the nitrides require either high ion energies or densities to achieve practical etch rates it is difficult to achieve high selectivities.« less

A measurement of disorder in binary sequences

NASA Astrophysics Data System (ADS)

Gong, Longyan; Wang, Haihong; Cheng, Weiwen; Zhao, Shengmei

2015-03-01

We propose a complex quantity, AL, to characterize the degree of disorder of L-length binary symbolic sequences. As examples, we respectively apply it to typical random and deterministic sequences. One kind of random sequences is generated from a periodic binary sequence and the other is generated from the logistic map. The deterministic sequences are the Fibonacci and Thue-Morse sequences. In these analyzed sequences, we find that the modulus of AL, denoted by |AL | , is a (statistically) equivalent quantity to the Boltzmann entropy, the metric entropy, the conditional block entropy and/or other quantities, so it is a useful quantitative measure of disorder. It can be as a fruitful index to discern which sequence is more disordered. Moreover, there is one and only one value of |AL | for the overall disorder characteristics. It needs extremely low computational costs. It can be easily experimentally realized. From all these mentioned, we believe that the proposed measure of disorder is a valuable complement to existing ones in symbolic sequences.

IDENTIFICATION OF THE HIGH-ENERGY GAMMA-RAY SOURCE 3FGL J1544.6–1125 AS A TRANSITIONAL MILLISECOND PULSAR BINARY IN AN ACCRETING STATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogdanov, Slavko; Halpern, Jules P.

We present X-ray, ultraviolet, and optical observations of 1RXS J154439.4–112820, the most probable counterpart of the unassociated Fermi-LAT source 3FGL J1544.6–1125. The optical data reveal rapid variability, which is a feature of accreting systems. The X-rays exhibit large-amplitude variations in the form of fast switching (within ∼10 s) between two distinct flux levels that differ by a factor of ≈10. The detailed optical and X-ray behavior is virtually identical to that seen in the accretion-disk-dominated states of the transitional millisecond pulsar (MSP) binaries PSR J1023+0038 and XSS J12270–4859, which are also associated with γ-ray sources. Based on the available observationalmore » evidence, we conclude that 1RXS J154439.4–112820 and 3FGL J1544.6–1125 are the same object, with the X-rays arising from intermittent low-luminosity accretion onto an MSP and the γ-rays originating from an accretion-driven outflow. 1RXS J154439.4–112820 is only the fourth γ-ray-emitting low-mass X-ray binary system to be identified and is likely to sporadically undergo transformations to a non-accreting rotation-powered pulsar system.« less

An Interferometric Study of the Post-AGB Binary 89 Herculis. 1: Spatially Resolving the Continuum Circumstellar Environment at Optical and Near-IR Wavelengths with the VLTI, NPOI, IOTA, PTI, and the CHARA Array

DTIC Science & Technology

2013-01-01

evolution of binaries as well as the structure of circumstellar disks. Aims. A multiwavelength high angular resolution study of the prototypical object...optical to mid-IR wave- lengths. For YSOs this has led to the discovery of an empiri- cal size-luminosity relation (Millan-Gabet et al. 2001; Monnier...Millan-Gabet 2002), which in turn has led to the current paradigm (Dullemond & Monnier 2010) of a passive dusty disk with an optically thin cavity and the

A New Orbit for the Eclipsing Binary V577 Oph

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeffery, Elizabeth J.; Barnes, Thomas G. III; Montemayor, Thomas J.

Pulsating stars in eclipsing binary systems are unique objects for providing constraints on stellar models. To fully leverage the information available from the binary system, full orbital radial velocity curves must be obtained. We report 23 radial velocities for components of the eclipsing binary V577 Oph, whose primary star is a δ Sct variable. The velocities cover a nearly complete orbit and a time base of 20 years. We computed orbital elements for the binary and compared them to the ephemeris computed by Creevey et al. The comparison shows marginally different results. In particular, a change in the systemic velocitymore » by −2 km s{sup −1} is suggested by our results. We compare this systemic velocity difference to that expected due to reflex motion of the binary in response to the third body in the system. The systemic velocity difference is consistent with reflex motion, given our mass determination for the eclipsing binary and the orbital parameters determined by Volkov and Volkova for the three-body orbit. We see no evidence for the third body in our spectra, but we do see strong interstellar Na D lines that are consistent in strength with the direction and expected distance of V577 Oph.« less

Pulsed Accretion in the T Tauri Binary TWA 3A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tofflemire, Benjamin M.; Mathieu, Robert D.; Herczeg, Gregory J.

TWA 3A is the most recent addition to a small group of young binary systems that both actively accrete from a circumbinary disk and have spectroscopic orbital solutions. As such, it provides a unique opportunity to test binary accretion theory in a well-constrained setting. To examine TWA 3A’s time-variable accretion behavior, we have conducted a two-year, optical photometric monitoring campaign, obtaining dense orbital phase coverage (∼20 observations per orbit) for ∼15 orbital periods. From U -band measurements we derive the time-dependent binary mass accretion rate, finding bursts of accretion near each periastron passage. On average, these enhanced accretion events evolvemore » over orbital phases 0.85 to 1.05, reaching their peak at periastron. The specific accretion rate increases above the quiescent value by a factor of ∼4 on average but the peak can be as high as an order of magnitude in a given orbit. The phase dependence and amplitude of TWA 3A accretion is in good agreement with numerical simulations of binary accretion with similar orbital parameters. In these simulations, periastron accretion bursts are fueled by periodic streams of material from the circumbinary disk that are driven by the binary orbit. We find that TWA 3A’s average accretion behavior is remarkably similar to DQ Tau, another T Tauri binary with similar orbital parameters, but with significantly less variability from orbit to orbit. This is only the second clear case of orbital-phase-dependent accretion in a T Tauri binary.« less

VizieR Online Data Catalog: White dwarf candidates using LAMOST DR3 (Gentile Fusillo+, 2015)

NASA Astrophysics Data System (ADS)

Gentile Fusillo, N. P.; Rebassa-Mansergas, A.; Gansicke, B. T.; Liu, X.-W.; Ren, J. J.; Koester, D.; Zhan, Y.; Hou, Y.; Wang, Y.; Yang, M.

2016-01-01

We cross-matched all 65768 objects from the Gentile Fusillo et al. (2015, Cat. J/MNRAS/448/2260) catalogue with the list of the 4.6 million LAMOST spectra and retrieved 6101 spectra corresponding to 5173 unique objects. Thirty-five hundred of these have also received SDSS spectroscopic follow-up and 64 further objects had already been identified on the base of their LAMOST spectra as white dwarfs or white dwarf binaries by Zhang et al. (2013, Cat. J/AJ/146/34), Zhao et al. (2013AJ....145..169Z), Ren et al. (2014, Cat. J/A+A/570/A107) and Rebassa-Mansergas et al. (2015MNRAS.450..743R). (1 data file).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apellániz, J. Maíz; Sota, A.; Alfaro, E. J.

This is the third installment of the Galactic O-Star Spectroscopic Survey (GOSSS), a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R  ∼ 2500 digital observations selected from the Galactic O-Star Catalog. In this paper, we present 142 additional stellar systems with O stars from both hemispheres, bringing the total of O-type systems published within the project to 590. Among the new objects, there are 20 new O stars. We also identify 11 new double-lined spectroscopic binaries, 6 of which are of O+O type and 5 of O+B type, and an additional new tripled-lined spectroscopic binary of O+O+Bmore » type. We also revise some of the previous GOSSS classifications, present some egregious examples of stars erroneously classified as O-type in the past, introduce the use of luminosity class IV at spectral types O4-O5.5, and adapt the classification scheme to the work of Arias et al.« less

Spectral analysis of the binary nucleus of the planetary nebula Hen 2-428 - first results

NASA Astrophysics Data System (ADS)

Finch, Nicolle L.; Reindl, Nicole; Barstow, Martin A.; Casewell, Sarah L.; Geier, Stephan; Bertolami, Marcelo M. Miller; Taubenberger, Stefan

2018-04-01

Identifying progenitor systems for the double-degenerate scenario is crucial to check the reliability of type Ia supernovae as cosmological standard candles. Santander-Garcia et al. (2015) claimed that Hen 2-428 has a doubledegenerate core whose combined mass significantly exceeds the Chandrasekhar limit. Together with the short orbital period (4.2 hours), the authors concluded that the system should merge within a Hubble time triggering a type Ia supernova event. Garcia-Berro et al. (2016) explored alternative scenarios to explain the observational evidence, as the high mass conclusion is highly unlikely within predictions from stellar evolution theory. They conclude that the evidence supporting the supernova progenitor status of the system is premature. Here we present the first quantitative spectral analysis of Hen 2-428which allows us to derive the effective temperatures, surface gravities and helium abundance of the two CSPNe based on state-of-the-art, non-LTE model atmospheres. These results provide constrains for further studies of this particularly interesting system.

Valence and conduction band offsets of β-Ga2O3/AlN heterojunction

NASA Astrophysics Data System (ADS)

Sun, Haiding; Torres Castanedo, C. G.; Liu, Kaikai; Li, Kuang-Hui; Guo, Wenzhe; Lin, Ronghui; Liu, Xinwei; Li, Jingtao; Li, Xiaohang

2017-10-01

Both β-Ga2O3 and wurtzite AlN have wide bandgaps of 4.5-4.9 and 6.1 eV, respectively. We calculated the in-plane lattice mismatch between the (-201) plane of β-Ga2O3 and the (0002) plane of AlN, which was found to be 2.4%. This is the smallest mismatch between β-Ga2O3 and binary III-nitrides which is beneficial for the formation of a high quality β-Ga2O3/AlN heterojunction. However, the valence and conduction band offsets (VBO and CBO) at the β-Ga2O3/AlN heterojunction have not yet been identified. In this study, a very thin (less than 2 nm) β-Ga2O3 layer was deposited on an AlN/sapphire template to form the heterojunction by pulsed laser deposition. High-resolution X-ray photoelectron spectroscopy revealed the core-level (CL) binding energies of Ga 3d and Al 2p with respect to the valence band maximum in individual β-Ga2O3 and AlN layers, respectively. The separation between Ga 3d and Al 2p CLs at the β-Ga2O3/AlN interface was also measured. Eventually, the VBO was found to be -0.55 ± 0.05 eV. Consequently, a staggered-gap (type II) heterojunction with a CBO of -1.75 ± 0.05 eV was determined. The identification of the band alignment of the β-Ga2O3/AlN heterojunction could facilitate the design of optical and electronic devices based on these and related alloys.

The strength and ductility of polycrystalline NiAl in tension

NASA Technical Reports Server (NTRS)

Schulson, E. M.

1982-01-01

Experiments at temperatures from 20 C to 400 C at two strain rates (.0001/s and .000005/s) establish that: (1) at room temperatures, binary and microalloyed ( 1000 ppm La, Y, Mo, Ti) NiAl shows negligible ductility, independent of grain size over the range 5 to 140 micrometers; (2) at 295 C the tensile elongation of binary 51 Ni/49 Al increases from 1% to about 5% upon decreasing the grain size to below approximately 10 micrometers; (3) similarly, at 400 C the ductility increases from about 2% to 15% upon decreasing the grain size to below 15 micrometers; (4) the ductility of fine grained (7 micrometer) binary aggregates deformed at 295 C increases from approximately 5% to 12% upon decreasing the strain rate from .0001/s to .000005/s; (5) partial recrystallization (10% to 20%) of warm extruded binary and microalloyed material imparts 1% to 2% ductility at room temperature where fully recrystallized material is brittle; (6) the yield strength obeys a Hall-Petch relationship; and (7) when ductility is not observed, fracture coincides with yielding. The mechanisms underlying the flow and fracture of NiAl are discussed in terms of the nucleation and growth of microcracks. The concept of a critical grain size is considered in the light of the results.

Facile Fabrication of Binary Nanoscale Interface for No-Loss Microdroplet Transportation.

PubMed

Liang, Weitao; Zhu, Liqun; Li, Weiping; Xu, Chang; Liu, Huicong

2016-06-07

Binary nanoscale interfacial materials are fundamental issues in many applications for smart surfaces. A binary nanoscale interface with binary surface morphology and binary wetting behaviors has been prepared by a facile wet-chemical method. The prepared surface presents superhydrophobicity and high adhesion with the droplet at the same time. The composition, surface morphology, and wetting behaviors of the prepared surface have been systematic studied. The special wetting behaviors can be contributed to the binary nanoscale effect. The stability of the prepared surface was also investigated. As a primary application, a facile device based on the prepared binary nanoscale interface with superhydrophobicity and high adhesion was constructed for microdroplet transportation.

Elevated Temperature Compressive Strength Properties of Oxide Dispersion Strengthened NiAl After Cryo-milling and Roasting in Nitrogen

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Grahle, Peter; Arzt, Eduard; Hebsur, Mohan

1998-01-01

In an effort to superimpose two different elevated temperature strengthening mechanisms in NiAl, several lots of oxide dispersion strengthened (ODS) NiAl powder have been cryo-milled in liquid nitrogen to introduce AlN particles at the grain boundaries. As an alternative to cryo-milling, one lot of ODS NiAl was roasted in nitrogen to produce AlN. Both techniques resulted in hot extruded AlN-strengthened, ODS NiAl alloys which were stronger than the base ODS NiAl between 1200 and 1400 K. However, neither the cryo-milled nor the N2-roasted ODS NiAl alloys were as strong as cryo-milled binary NiAl containing like amounts of AlN. The reason(s) for the relative weakness of cryo-milled ODS NiAl is not certain; however the lack of superior strength in N2-roasted ODS NiAl is probably due to its relatively large AlN particles.

Outflow-driven Transients from the Birth of Binary Black Holes. II. Primary-induced Accretion Transients

NASA Astrophysics Data System (ADS)

Kimura, Shigeo S.; Murase, Kohta; Mészáros, Peter

2017-12-01

We discuss the electromagnetic radiation from newborn binary black holes (BBHs). As a consequence of the evolution of massive stellar binaries, a binary consisting of a primary black hole (BH) and a secondary Wolf–Rayet star is expected as a BBH progenitor system. We investigate optical transients from the birth of BBHs powered by the Bondi–Hoyle–Lyttleton accretion onto the primary BH, which occur ∼1–10 Gyr earlier than gravitational-wave signals at the BH–BH merger. When the secondary massive star collapses into a BH, it may eject a fraction of its outer material and may form a disk around the primary BH and induces a powerful disk wind. These primary-induced winds can lead to optical transients with a kinetic energy of ∼1047–3 × 1048 erg, an ejecta velocity of 108–109 cm s‑1, a duration of a few days, and an absolute magnitude ranging from about ‑11 to ‑14. The light curves and late-time spectra of these transients are distinctive from those of ordinary supernovae, and detection of this type of transient is possible by future optical transient surveys if the event rate of this transient is comparable to the merger rate of BBHs. This paper focuses on the emissions from disk-driven transients induced by the primary BH, different from Paper I, which focuses on wind-driven transients from the tidally locked secondary massive star.

Chemiluminescence analyzer of NOx as a high-throughput screening tool in selective catalytic reduction of NO

PubMed Central

Oh, Kwang Seok; Woo, Seong Ihl

2011-01-01

A chemiluminescence-based analyzer of NOx gas species has been applied for high-throughput screening of a library of catalytic materials. The applicability of the commercial NOx analyzer as a rapid screening tool was evaluated using selective catalytic reduction of NO gas. A library of 60 binary alloys composed of Pt and Co, Zr, La, Ce, Fe or W on Al2O3 substrate was tested for the efficiency of NOx removal using a home-built 64-channel parallel and sequential tubular reactor. The NOx concentrations measured by the NOx analyzer agreed well with the results obtained using micro gas chromatography for a reference catalyst consisting of 1 wt% Pt on γ-Al2O3. Most alloys showed high efficiency at 275 °C, which is typical of Pt-based catalysts for selective catalytic reduction of NO. The screening with NOx analyzer allowed to select Pt-Ce(X) (X=1–3) and Pt–Fe(2) as the optimal catalysts for NOx removal: 73% NOx conversion was achieved with the Pt–Fe(2) alloy, which was much better than the results for the reference catalyst and the other library alloys. This study demonstrates a sequential high-throughput method of practical evaluation of catalysts for the selective reduction of NO. PMID:27877438

An Extensive Census of Hubble Space Telescope Counterparts to Chandra X-Ray Sources in the Globular Cluster 47 Tucanae. II. Time Series and Analysis

NASA Astrophysics Data System (ADS)

Edmonds, Peter D.; Gilliland, Ronald L.; Heinke, Craig O.; Grindlay, Jonathan E.

2003-10-01

We report time series and variability information for the optical identifications of X-ray sources in 47 Tucanae reported in Paper I (at least 22 cataclysmic variables [CVs] and 29 active binaries). The radial distribution of the CVs is indistinguishable from that of the millisecond pulsars (MSPs) detected by Freire et al. A study of the eight CVs with secure orbital periods (two obtained from the Chandra study of Grindlay et al.) shows that the 47 Tuc CVs have fainter accretion disks, in the V band, than field CVs with similar periods. These faint disks and the faint absolute magnitudes (MV) of the 47 Tuc CVs suggests they have low accretion rates. One possible explanation is that the 47 Tuc objects may be a more representative sample of CVs, down to our detection threshold, than the CVs found in the field (where many low accretion rate systems are believed to be undiscovered), showing the advantages of deep globular cluster observations. The median FX/Fopt value for the 47 Tuc CVs is higher than that of all known classes of field CV, partly because of the faint MV values and partly because of the relatively high X-ray luminosities (LX). The latter are only seen in DQ Her systems in the field, but the 47 Tuc CVs are much fainter optically than most field DQ Her's. Previous work by Edmonds et al. has shown that the four brightest CVs in NGC 6397 have optical spectra and broadband colors that are consistent with DQ Her's having lower than average accretion rates. Some combination of magnetic behavior and low accretion rates may be able to explain our observations, but the results at present are ambiguous, since no class of field CV has distributions of both LX and MV that are consistent with those of the 47 Tuc CVs. The radial distribution of the X-ray detected active binaries is indistinguishable from that of the much larger sample of optical variables (eclipsing and contact binaries and BY Dra variables) detected in previous Wide Field Planetary Camera 2 (WFPC2) studies by Albrow et al. The X-ray properties of these objects (luminosity, hardness ratios, and variability) are consistent with those of active binaries found in field studies, and the FX/Fopt distribution is significantly different from those of the CVs and the MSPs that are detected (or possibly detected) in the optical. Despite these results, we examine the possibility that a few of the active binaries are MSPs with main-sequence companions resulting from double exchanges in the crowded core of 47 Tuc. No solid evidence is found for a significant population of such objects, and therefore, using the methods of Grindlay et al., we estimate that the number of MSPs in 47 Tuc with luminosities above 1030 ergs s-1 is ~30-40, near the previous lower limit. We present the results of a new, deeper search for faint low-mass X-ray binaries (LMXBs) in quiescence. One reasonable and one marginal candidate for optical identification of a quiescent LMXB was found (one is already known). Finally, it is shown that the periods of the blue variables showing little or no evidence for X-ray emission are too long for Roche lobe filling (if the variations are ellipsoidal). These blue variables also show no evidence for the large flickering levels seen in comparably bright CVs. At present we have no satisfactory explanation for these objects, although some may be detached white dwarf-main-sequence star binaries. Based on observations with the NASA/ESA Hubble Space Telescope obtained at STScI, which is operated by AURA, Inc. under NASA contract NAS 5-26555.

Dual-sensitivity profilometry with defocused projection of binary fringes.

PubMed

Garnica, G; Padilla, M; Servin, M

2017-10-01

A dual-sensitivity profilometry technique based on defocused projection of binary fringes is presented. Here, two sets of fringe patterns with a sinusoidal profile are produced by applying the same analog low-pass filter (projector defocusing) to binary fringes with a high- and low-frequency spatial carrier. The high-frequency fringes have a binary square-wave profile, while the low-frequency binary fringes are produced with error-diffusion dithering. The binary nature of the binary fringes removes the need for calibration of the projector's nonlinear gamma. Working with high-frequency carrier fringes, we obtain a high-quality wrapped phase. On the other hand, working with low-frequency carrier fringes we found a lower-quality, nonwrapped phase map. The nonwrapped estimation is used as stepping stone for dual-sensitivity temporal phase unwrapping, extending the applicability of the technique to discontinuous (piecewise continuous) surfaces. We are proposing a single defocusing level for faster high- and low-frequency fringe data acquisition. The proposed technique is validated with experimental results.

Self-assembly of metal nanostructures on binary alloy surfaces

PubMed Central

Duguet, T.; Han, Yong; Yuen, Chad; Jing, Dapeng; Ünal, Barış; Evans, J. W.; Thiel, P. A.

2011-01-01

Deposition of metals on binary alloy surfaces offers new possibilities for guiding the formation of functional metal nanostructures. This idea is explored with scanning tunneling microscopy studies and atomistic-level analysis and modeling of nonequilibrium island formation. For Au/NiAl(110), complex monolayer structures are found and compared with the simple fcc(110) bilayer structure recently observed for Ag/NiAl(110). We also consider a more complex codeposition system, (Ni + Al)/NiAl(110), which offers the opportunity for fundamental studies of self-growth of alloys including deviations for equilibrium ordering. A general multisite lattice-gas model framework enables analysis of structure selection and morphological evolution in these systems. PMID:21097706

IRAS 16253–2429: THE FIRST PROTO-BROWN DWARF BINARY CANDIDATE IDENTIFIED THROUGH THE DYNAMICS OF JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsieh, Tien-Hao; Lai, Shih-Ping; Belloche, Arnaud

2016-07-20

The formation mechanism of brown dwarfs (BDs) is one of the long-standing problems in star formation because the typical Jeans mass in molecular clouds is too large to form these substellar objects. To answer this question, it is crucial to study a BD in the embedded phase. IRAS 16253–2429 is classified as a very low-luminosity object (VeLLO) with an internal luminosity of <0.1 L {sub ⊙}. VeLLOs are believed to be very low-mass protostars or even proto-BDs. We observed the jet/outflow driven by IRAS 16253–2429 in CO (2–1), (6–5), and (7–6) using the IRAM 30 m and Atacama Pathfinder Experimentmore » telescopes and the Submillimeter Array (SMA) in order to study its dynamical features and physical properties. Our SMA map reveals two protostellar jets, indicating the existence of a proto-binary system as implied by the precessing jet detected in H{sub 2} emission. We detect a wiggling pattern in the position–velocity diagrams along the jet axes, which is likely due to the binary orbital motion. Based on this information, we derive the current mass of the binary as ∼0.032 M{sub ⊙}. Given the low envelope mass, IRAS 16253–2429 will form a binary that probably consist of one or two BDs. Furthermore, we found that the outflow force as well as the mass accretion rate are very low based on the multi-transition CO observations, which suggests that the final masses of the binary components are at the stellar/substellar boundary. Since IRAS 16253 is located in an isolated environment, we suggest that BDs can form through fragmentation and collapse, similar to low-mass stars.« less

Density, Molar Volume, and Surface Tension of Liquid Al-Ti

NASA Astrophysics Data System (ADS)

Wessing, Johanna Jeanette; Brillo, Jürgen

2017-02-01

Al-Ti-based alloys are of enormous technical relevance due to their specific properties. For studies in atomic dynamics, surface physics and industrial processing the precise knowledge of the thermophysical properties of the liquid phase is crucial. In the present work, we systematically measure mass density, ρ (g cm-3), and the surface tension, γ (N m-1), as functions of temperature, T, and compositions of binary Al-Ti melts. Electromagnetic levitation in combination with the optical dilatometry method is used for density measurements and the oscillating drop method for surface tension measurements. It is found that, for all compositions, density and surface tension increase linearly upon decreasing temperature in the liquid phase. Within the Al-Ti system, we find the largest values for pure titanium and the smallest for pure aluminum, which amount to ρ(L,Ti) = 4.12 ± 0.04 g cm-3 and γ(L,Ti) = 1.56 ± 0.02 N m-1; and ρ(L,Al) = 2.09 ± 0.01 g cm-3 and γ(L,Al) = 0.87 ± 0.06 N m-1, respectively. The data are analyzed concerning the temperature coefficients, ρ T and γ T, excess molar volume, V E, excess surface tension, γ E, and surface segregation of the surface active component, Al. The results are compared with thermodynamic models. Generally, it is found that Al-Ti is a highly nonideal system.

EXTRASOLAR BINARY PLANETS. II. DETECTABILITY BY TRANSIT OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, K. M.; Ida, S.; Ochiai, H.

2015-05-20

We discuss the detectability of gravitationally bound pairs of gas-giant planets (which we call “binary planets”) in extrasolar planetary systems that are formed through orbital instability followed by planet–planet dynamical tides during their close encounters, based on the results of N-body simulations by Ochiai et al. (Paper I). Paper I showed that the formation probability of a binary is as much as ∼10% for three giant planet systems that undergo orbital instability, and after post-capture long-term tidal evolution, the typical binary separation is three to five times the sum of the physical radii of the planets. The binary planets aremore » stable during the main-sequence lifetime of solar-type stars, if the stellarcentric semimajor axis of the binary is larger than 0.3 AU. We show that detecting modulations of transit light curves is the most promising observational method to detect binary planets. Since the likely binary separations are comparable to the stellar diameter, the shape of the transit light curve is different from transit to transit, depending on the phase of the binary’s orbit. The transit durations and depth for binary planet transits are generally longer and deeper than those for the single planet case. We point out that binary planets could exist among the known inflated gas-giant planets or objects classified as false positive detections at orbital radii ≳0.3 AU, propose a binary planet explanation for the CoRoT candidate SRc01 E2 1066, and show that binary planets are likely to be present in, and could be detected using, Kepler-quality data.« less

X-Ray Probes of Cosmic Star-Formation History

NASA Technical Reports Server (NTRS)

Ghosh, Pranab; White, Nicholas E.

2001-01-01

In a previous paper we point out that the X-ray luminosity L(sub x) of a galaxy is driven by the evolution of its X-ray binary population and that the profile of L(sub x) with redshift can both serve as a diagnostic probe of the Star Formation Rate (SFR) profile and constrain evolutionary models for X-ray binaries. We update our previous work using a suite of more recently developed SFR profiles that span the currently plausible range. The first Chandra deep imaging results on L(sub x)-evolution are beginning to probe the SFR profile of bright spirals and the early results are consistent with predictions based on current SFR models. Using these new SFR profiles the resolution of the "birthrate problem" of lowmass X-ray binaries (LMXBs) and recycled, millisecond pulsars in terms of an evolving global SFR is more complete. We also discuss the possible impact of the variations in the SFR profile of individual galaxies.

Mechanical property, biocorrosion and in vitro biocompatibility evaluations of Mg-Li-(Al)-(RE) alloys for future cardiovascular stent application.

PubMed

Zhou, W R; Zheng, Y F; Leeflang, M A; Zhou, J

2013-11-01

Mg-Li-based alloys were investigated for future cardiovascular stent application as they possess excellent ductility. However, Mg-Li binary alloys exhibited reduced mechanical strengths due to the presence of lithium. To improve the mechanical strengths of Mg-Li binary alloys, aluminum and rare earth (RE) elements were added to form Mg-Li-Al ternary and Mg-Li-Al-RE quarternary alloys. In the present study, six Mg-Li-(Al)-(RE) alloys were fabricated. Their microstructures, mechanical properties and biocorrosion behavior were evaluated by using optical microscopy, X-ray diffraction, scanning electronic microscopy, tensile tests, immersion tests and electrochemical measurements. Microstructure characterization indicated that grain sizes were moderately refined by the addition of rare earth elements. Tensile testing showed that enhanced mechanical strengths were obtained, while electrochemical and immersion tests showed reduced corrosion resistance caused by intermetallic compounds distributed throughout the magnesium matrix in the rare-earth-containing Mg-Li alloys. Cytotoxicity assays, hemolysis tests as well as platelet adhesion tests were performed to evaluate in vitro biocompatibilities of the Mg-Li-based alloys. The results of cytotoxicity assays clearly showed that the Mg-3.5Li-2Al-2RE, Mg-3.5Li-4Al-2RE and Mg-8.5Li-2Al-2RE alloys suppressed vascular smooth muscle cell proliferation after 5day incubation, while the Mg-3.5Li, Mg-8.5Li and Mg-8.5Li-1Al alloys were proven to be tolerated. In the case of human umbilical vein endothelial cells, the Mg-Li-based alloys showed no significantly reduced cell viabilities except for the Mg-8.5Li-2Al-2RE alloy, with no obvious differences in cell viability between different culture periods. With the exception of Mg-8.5Li-2Al-2RE, all of the other Mg-Li-(Al)-(RE) alloys exhibited acceptable hemolysis ratios, and no sign of thrombogenicity was found. These in vitro experimental results indicate the potential of Mg-Li-(Al)-(RE) alloys as biomaterials for future cardiovascular stent application and the worthiness of investigating their biodegradation behaviors in vivo. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

New Approaches to the Computer Simulation of Amorphous Alloys: A Review.

PubMed

Valladares, Ariel A; Díaz-Celaya, Juan A; Galván-Colín, Jonathan; Mejía-Mendoza, Luis M; Reyes-Retana, José A; Valladares, Renela M; Valladares, Alexander; Alvarez-Ramirez, Fernando; Qu, Dongdong; Shen, Jun

2011-04-13

In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe 2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus) temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total) are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties.

New Approaches to the Computer Simulation of Amorphous Alloys: A Review

PubMed Central

Valladares, Ariel A.; Díaz-Celaya, Juan A.; Galván-Colín, Jonathan; Mejía-Mendoza, Luis M.; Reyes-Retana, José A.; Valladares, Renela M.; Valladares, Alexander; Alvarez-Ramirez, Fernando; Qu, Dongdong; Shen, Jun

2011-01-01

In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus) temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total) are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties. PMID:28879948

Robust surface roughness indices and morphological interpretation

NASA Astrophysics Data System (ADS)

Trevisani, Sebastiano; Rocca, Michele

2016-04-01

Geostatistical-based image/surface texture indices based on variogram (Atkison and Lewis, 2000; Herzfeld and Higginson, 1996; Trevisani et al., 2012) and on its robust variant MAD (median absolute differences, Trevisani and Rocca, 2015) offer powerful tools for the analysis and interpretation of surface morphology (potentially not limited to solid earth). In particular, the proposed robust index (Trevisani and Rocca, 2015) with its implementation based on local kernels permits the derivation of a wide set of robust and customizable geomorphometric indices capable to outline specific aspects of surface texture. The stability of MAD in presence of signal noise and abrupt changes in spatial variability is well suited for the analysis of high-resolution digital terrain models. Moreover, the implementation of MAD by means of a pixel-centered perspective based on local kernels, with some analogies to the local binary pattern approach (Lucieer and Stein, 2005; Ojala et al., 2002), permits to create custom roughness indices capable to outline different aspects of surface roughness (Grohmann et al., 2011; Smith, 2015). In the proposed poster, some potentialities of the new indices in the context of geomorphometry and landscape analysis will be presented. At same time, challenges and future developments related to the proposed indices will be outlined. Atkinson, P.M., Lewis, P., 2000. Geostatistical classification for remote sensing: an introduction. Computers & Geosciences 26, 361-371. Grohmann, C.H., Smith, M.J., Riccomini, C., 2011. Multiscale Analysis of Topographic Surface Roughness in the Midland Valley, Scotland. IEEE Transactions on Geoscience and Remote Sensing 49, 1220-1213. Herzfeld, U.C., Higginson, C.A., 1996. Automated geostatistical seafloor classification - Principles, parameters, feature vectors, and discrimination criteria. Computers and Geosciences, 22 (1), pp. 35-52. Lucieer, A., Stein, A., 2005. Texture-based landform segmentation of LiDAR imagery. International Journal of Applied Earth Observation and Geoinformation 6, 261-270. Ojala, T., Pietikäinen, M. & Mäenpää, T. 2002. "Multiresolution gray-scale and rotation invariant texture classification with local binary patterns", IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 24, no. 7, pp. 971-987. Smith, M.W. 2014. "Roughness in the Earth Sciences", Earth-Science Reviews, vol. 136, pp. 202-225. Trevisani, S., Cavalli, M. & Marchi, L. 2012. "Surface texture analysis of a high-resolution DTM: Interpreting an alpine basin", Geomorphology, vol. 161-162, pp. 26-39. Trevisani, S., Rocca, M. 2015. MAD: robust image texture analysis for applications in high resolution geomorphometry. Comput. Geosci. 81, 78-92. doi:10.1016/j.cageo.2015.04.003.

Applications of High Intensity Proton Accelerators

NASA Astrophysics Data System (ADS)

Raja, Rajendran; Mishra, Shekhar

2010-06-01

Superconducting radiofrequency linac development at Fermilab / S. D. Holmes -- Rare muon decay experiments / Y. Kuno -- Rare kaon decays / D. Bryman -- Muon collider / R. B. Palmer -- Neutrino factories / S. Geer -- ADS and its potential / J.-P. Revol -- ADS history in the USA / R. L. Sheffield and E. J. Pitcher -- Accelerator driven transmutation of waste: high power accelerator for the European ADS demonstrator / J. L. Biarrotte and T. Junquera -- Myrrha, technology development for the realisation of ADS in EU: current status & prospects for realisation / R. Fernandez ... [et al.] -- High intensity proton beam production with cyclotrons / J. Grillenberger and M. Seidel -- FFAG for high intensity proton accelerator / Y. Mori -- Kaon yields for 2 to 8 GeV proton beams / K. K. Gudima, N. V. Mokhov and S. I. Striganov -- Pion yield studies for proton driver beams of 2-8 GeV kinetic energy for stopped muon and low-energy muon decay experiments / S. I. Striganov -- J-Parc accelerator status and future plans / H. Kobayashi -- Simulation and verification of DPA in materials / N. V. Mokhov, I. L. Rakhno and S. I. Striganov -- Performance and operational experience of the CNGS facility / E. Gschwendtner -- Particle physics enabled with super-conducting RF technology - summary of working group 1 / D. Jaffe and R. Tschirhart -- Proton beam requirements for a neutrino factory and muon collider / M. S. Zisman -- Proton bunching options / R. B. Palmer -- CW SRF H linac as a proton driver for muon colliders and neutrino factories / M. Popovic, C. M. Ankenbrandt and R. P. Johnson -- Rapid cycling synchrotron option for Project X / W. Chou -- Linac-based proton driver for a neutrino factory / R. Garoby ... [et al.] -- Pion production for neutrino factories and muon colliders / N. V. Mokhov ... [et al.] -- Proton bunch compression strategies / V. Lebedev -- Accelerator test facility for muon collider and neutrino factory R&D / V. Shiltsev -- The superconducting RF linac for muon collider and neutrino factory - summary of working group 2 / J. Galambos, R. Garoby and S. Geer -- Prospects for a very high power CW SRF linac / R. A. Rimmer -- Indian accelerator program for ADS applications / V. C. Sahni and P. Singh -- Ion accelerator activities at VECC (particularly, operating at low temperature) / R. K. Bhandari -- Chinese efforts in high intensity proton accelerators / S. Fu, J. Wang and S. Fang -- ADSR activity in the UK / R. J. Barlow -- ADS development in Japan / K. Kikuchi -- Project-X, SRF, and very large power stations / C. M. Ankenbrandt, R. P. Johnson and M. Popovic -- Power production and ADS / R. Raja -- Experimental neutron source facility based on accelerator driven system / Y. Gohar -- Transmutation mission / W. S. Yang -- Safety performance and issues / J. E. Cahalan -- Spallation target design for accelerator-driven systems / Y. Gohar -- Design considerations for accelerator transmutation of waste system / W. S. Yang -- Japan ADS program / T. Sasa -- Overview of members states' and IAEA activities in the field of Accelerator Driven Systems (ADS) / A. Stanculescu -- Linac for ADS applications - accelerator technologies / R. W. Garnett and R. L. Sheffield -- SRF linacs and accelerator driven sub-critical systems - summary working groups 3 & 4 / J. Delayen -- Production of Actinium-225 via high energy proton induced spallation of Thorium-232 / J. Harvey ... [et al.] -- Search for the electric dipole moment of Radium-225 / R. J. Holt, Z.-T. Lu and R. Mueller -- SRF linac and material science and medicine - summary of working group 5 / J. Nolen, E. Pitcher and H. Kirk.

Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transition temperature

NASA Technical Reports Server (NTRS)

Cullers, Cheryl L.; Antolovich, Stephen D.

1993-01-01

The intermetallic compound NiAl is one of many advanced materials which is being scrutinized for possible use in high temperature, structural applications. Stoichiometric NiAl has a high melting temperature, excellent oxidation resistance, and good thermal conductivity. Past research has concentrated on improving monotonic properties. The encouraging results obtained on binary and micro-alloyed NiAl over the past ten years have led to the broadening of NiAl experimental programs. The purpose of this research project was to determine the low cycle fatigue properties and dislocation mechanisms of stoichiometric NiAl at temperatures near the monotonic brittle-to-ductile transition. The fatigue properties were found to change only slightly in the temperature range of 600 to 700 K; a temperature range over which monotonic ductility and fracture strength increase markedly. The shape of the cyclic hardening curves coincided with the changes observed in the dislocation structures. The evolution of dislocation structures did not appear to change with temperature.

International Conference on Integrated Optical Circuit Engineering, 1st, Cambridge, MA, October 23-25, 1984, Proceedings

NASA Astrophysics Data System (ADS)

Ostrowsky, D. B.; Sriram, S.

Aspects of waveguide technology are explored, taking into account waveguide fabrication techniques in GaAs/GaAlAs, the design and fabrication of AlGaAs/GaAs phase couplers for optical integrated circuit applications, ion implanted GaAs integrated optics fabrication technology, a direct writing electron beam lithography based process for the realization of optoelectronic integrated circuits, and advances in the development of semiconductor integrated optical circuits for telecommunications. Other subjects examined are related to optical signal processing, optical switching, and questions of optical bistability and logic. Attention is given to acousto-optic techniques in integrated optics, acousto-optic Bragg diffraction in proton exchanged waveguides, optical threshold logic architectures for hybrid binary/residue processors, integrated optical modulation and switching, all-optic logic devices for waveguide optics, optoelectronic switching, high-speed photodetector switching, and a mechanical optical switch.

WIYN Open Cluster Study. XXXVI. Spectroscopic Binary Orbits in NGC 188

DTIC Science & Technology

2009-04-01

2000; Pleiades , Mermilliod et al. 1992; M67, Mathieu et al. 1990). Today, the advent of multi-object spectrographs permits surveys of larger stellar...open clusters (e.g., M67, Mathieu et al. (1990); Praesepe, Mermilliod et al. (1994); Pleiades , Bouvier et al. (1997); Hyades, Patience et al. (1998

FIRST, a fibered aperture masking instrument: Results of the Lick observing campaign

NASA Astrophysics Data System (ADS)

Bordwell, Baylee; Duchene, Gaspard; Huby, Elsa; Goebel, Sean; Marchis, Franck; Perrin, Guy; Lacour, Sylvestre; Kotani, Takayuki; Gates, Elinor L.; Choquet, Elodie

2015-01-01

FIRST is a prototype instrument aimed at achieving high dynamic range and angular resolution in ground-based images at visible wavelengths near the diffraction limit. FIRST utilizes an aperture masking-like technique that makes use of single-mode fibers and pupil remapping to maximize the area of the telescope mirror in use. While located at Lick observatory in 2011 and 2012, FIRST observed 25 binary systems with the Shane 3m telescope, with separations ranging from 20 to 200 mas, comparable to the 50 mas diffraction limit for our central wavelength. Huby et al. (2013) has reported results for the Capella system that established the utility of FIRST for characterizing stellar binaries using the directly measured spectral flux ratio. Using an improved data analysis pipeline, we obtained closure phase measurements for a majority of the targets observed at Lick, and derived angular separations and spectral flux ratios. From the spectral flux ratios we obtained spectra for the companions over at least 600-850 nm with R~300. Finally, by obtaining results for many binary systems we have better constrained the current performance of FIRST, which has an exciting future ahead at its current location behind SCExAO at the Subaru 8.2 m telescope, where it will eventually become available for general use by the astronomical community.

Both size-frequency distribution and sub-populations of the main-belt asteroid population are consistent with YORP-induced rotational fission

NASA Astrophysics Data System (ADS)

Jacobson, S.; Scheeres, D.; Rossi, A.; Marzari, F.; Davis, D.

2014-07-01

From the results of a comprehensive asteroid-population-evolution model, we conclude that the YORP-induced rotational-fission hypothesis has strong repercussions for the small size end of the main-belt asteroid size-frequency distribution and is consistent with observed asteroid-population statistics and with the observed sub-populations of binary asteroids, asteroid pairs and contact binaries. The foundation of this model is the asteroid-rotation model of Marzari et al. (2011) and Rossi et al. (2009), which incorporates both the YORP effect and collisional evolution. This work adds to that model the rotational fission hypothesis (i.e. when the rotation rate exceeds a critical value, erosion and binary formation occur; Scheeres 2007) and binary-asteroid evolution (Jacobson & Scheeres, 2011). The YORP-effect timescale for large asteroids with diameters D > ˜ 6 km is longer than the collision timescale in the main belt, thus the frequency of large asteroids is determined by a collisional equilibrium (e.g. Bottke 2005), but for small asteroids with diameters D < ˜ 6 km, the asteroid-population evolution model confirms that YORP-induced rotational fission destroys small asteroids more frequently than collisions. Therefore, the frequency of these small asteroids is determined by an equilibrium between the creation of new asteroids out of the impact debris of larger asteroids and the destruction of these asteroids by YORP-induced rotational fission. By introducing a new source of destruction that varies strongly with size, YORP-induced rotational fission alters the slope of the size-frequency distribution. Using the outputs of the asteroid-population evolution model and a 1-D collision evolution model, we can generate this new size-frequency distribution and it matches the change in slope observed by the SKADS survey (Gladman 2009). This agreement is achieved with both an accretional power-law or a truncated ''Asteroids were Born Big'' size-frequency distribution (Weidenschilling 2010, Morbidelli 2009). The binary-asteroid evolution model is highly constrained by the modeling done in Jacobson & Scheeres, and therefore the asteroid-population evolution model has only two significant free parameters: the ratio of low-to-high-mass-ratio binaries formed after rotational fission events and the mean strength of the binary YORP (BYORP) effect. Using this model, we successfully reproduce the observed small-asteroid sub-populations, which orthogonally constrain the two free parameters. We find the outcome of rotational fission most likely produces an initial mass-ratio fraction that is four to eight times as likely to produce high-mass-ratio systems as low-mass-ratio systems, which is consistent with rotational fission creating binary systems in a flat distribution with respect to mass ratio. We also find that the mean of the log-normal BYORP coefficient distribution B ≈ 10^{-2}.

State-change in the "transition" binary millisecond pulsar J1023+0038

NASA Astrophysics Data System (ADS)

Stappers, B. W.; Archibald, A.; Bassa, C.; Hessels, J.; Janssen, G.; Kaspi, V.; Lyne, A.; Patruno, A.; Hill, A. B.

2013-10-01

We report a change in the state of PSR J1023+0038, a source which is believed to be transitioning from an X-ray binary to an eclipsing binary radio millisecond pulsar (Archibald et al. 2009, Science, 324, 1411). The system was known to contain an accretion disk in 2001 but has shown no signs of it, or of accretion, since then, rather exhibiting all the properties of an eclipsing binary millisecond radio pulsar (MSP).

Characteristic electron variations across simple high-speed solar wind streams

NASA Technical Reports Server (NTRS)

Feldman, W. C.; Asbridge, J. R.; Bame, S. J.; Gosling, J. T.; Lemons, D. S.

1978-01-01

The paper deals with electron variations across simple high-speed streams. Comprehensive scans of the shapes of electron distributions measured at the highest bulk speeds confirm the results of Rosenbauer et al. (1976, 1977) and show that the electron velocity distributions can be broken down into a low-energy or core component and a high-energy strongly beamed component. The low-energy component displays many characteristics expected from a fluid: the internal particle coupling necessary to maintain this state must result from both binary Coulomb collisions and wave-particle interactions. The high-energy or halo component displays many characteristics expected to develop in the absence of collisions beyond a certain base radius. These electrons appear to evolve under the primary influence of static interplanetary magnetic and electric fields and, therefore, develop very anisotropic velocity distributions.

Development of a HTSMA-Actuated Surge Control Rod for High-Temperature Turbomachinery Applications

NASA Technical Reports Server (NTRS)

Padula, Santo, II; Noebe, Ronald; Bigelow, Glen; Culley, Dennis; Stevens, Mark; Penney, Nicholas; Gaydosh, Darrell; Quackenbush, Todd; Carpenter, Bernie

2007-01-01

In recent years, a demand for compact, lightweight, solid-state actuation systems has emerged, driven in part by the needs of the aeronautics industry. However, most actuation systems used in turbomachinery require not only elevated temperature but high-force capability. As a result, shape memory alloy (SMA) based systems have worked their way to the forefront of a short list of viable options to meet such a technological challenge. Most of the effort centered on shape memory systems to date has involved binary NiTi alloys but the working temperatures required in many aeronautics applications dictate significantly higher transformation temperatures than the binary systems can provide. Hence, a high temperature shape memory alloy (HTSMA) based on NiTiPdPt, having a transformation temperature near 300 C, was developed. Various thermo-mechanical processing schemes were utilized to further improve the dimensional stability of the alloy and it was later extruded/drawn into wire form to be more compatible with envisioned applications. Mechanical testing on the finished wire form showed reasonable work output capability with excellent dimensional stability. Subsequently, the wire form of the alloy was incorporated into a benchtop system, which was shown to provide the necessary stroke requirements of approx.0.125 inches for the targeted surge-control application. Cycle times for the actuator were limited to 4 seconds due to control and cooling constraints but this cycle time was determined to be adequate for the surge control application targeted as the primary requirement was initial actuation of a surge control rod, which could be completed in approximately one second.

PSR J0538+2817 As The Remnant Of The First Supernova Explosion in a Massive Binary

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.

2006-08-01

It is generally accepted that the radio pulsar PSR J0538+2817 is associated with the supernova remnant (SNR) S147. The only problem for the association is the obvious discrepancy (Kramer et al. 2003) between the kinematic age of the system of ~30 kyr (estimated from the angular offset of the pulsar from the geometric center of the SNR and pulsar's proper motion) and the characteristic age of the pulsar of ~600 kyr. To reconcile these ages one can assume that the pulsar was born with a spin period close to the present one (Kramer et al. 2003; Romani & Ng 2003). We propose an alternative explanation of the age discrepancy based on the fact that PSR J0538+2817 could be the stellar remnant of the first supernova explosion in a massive binary system and therefore could be as old as indicated by its characteristic age. Our proposal implies that S147 is the diffuse remnant of the second supernova explosion (that disrupted the binary system) and that a much younger second neutron star (not necessarily manifesting itself as a radio pulsar) should be associated with S147. We use the existing observational data on the system PSR J0538+2817/SNR S147 to suggest that the progenitor of the supernova that formed S147 was a Wolf-Rayet star (so that the supernova explosion occurred within a wind bubble surrounded by a massive shell) and to constrain the parameters of the binary system. We also restrict the magnitude and direction of the kick velocity received by the young neutron star at birth and find that the kick vector should not strongly deviate from the orbital plane of the binary system.

Binding Thermodynamics of Ferredoxin:NADP+ Reductase: Two Different Protein Substrates and One Energetics

PubMed Central

Martínez-Júlvez, Marta; Medina, Milagros; Velázquez-Campoy, Adrián

2009-01-01

Abstract The thermodynamics of the formation of binary and ternary complexes between Anabaena PCC 7119 FNR and its substrates, NADP+ and Fd, or Fld, has been studied by ITC. Despite structural dissimilarities, the main difference between Fd and Fld binding to FNR relates to hydrophobicity, reflected in different binding heat capacity and number of water molecules released from the interface. At pH 8, the formation of the binary complexes is both enthalpically and entropically driven, accompanied by the protonation of at least one ionizable group. His299 FNR has been identified as the main responsible for the proton exchange observed. However, at pH 10, where no protonation occurs and intrinsic binding parameters can be obtained, the formation of the binary complexes is entropically driven, with negligible enthalpic contribution. Absence of the FMN cofactor in Fld does not alter significantly the strength of the interaction, but considerably modifies the enthalpic and entropic contributions, suggesting a different binding mode. Ternary complexes show negative cooperativity (6-fold and 11-fold reduction in binding affinity, respectively), and an increase in the enthalpic contribution (more favorable) and a decrease in the entropic contribution (less favorable), with regard to the binary complexes energetics. PMID:19527656

Microstructure and mechanical behavior of metal injection molded Ti-Nb binary alloys as biomedical material.

PubMed

Zhao, Dapeng; Chang, Keke; Ebel, Thomas; Qian, Ma; Willumeit, Regine; Yan, Ming; Pyczak, Florian

2013-12-01

The application of titanium (Ti) based biomedical materials which are widely used at present, such as commercially pure titanium (CP-Ti) and Ti-6Al-4V, are limited by the mismatch of Young's modulus between the implant and the bones, the high costs of products, and the difficulty of producing complex shapes of materials by conventional methods. Niobium (Nb) is a non-toxic element with strong β stabilizing effect in Ti alloys, which makes Ti-Nb based alloys attractive for implant application. Metal injection molding (MIM) is a cost-efficient near-net shape process. Thus, it attracts growing interest for the processing of Ti and Ti alloys as biomaterial. In this investigation, metal injection molding was applied to the fabrication of a series of Ti-Nb binary alloys with niobium content ranging from 10wt% to 22wt%, and CP-Ti for comparison. Specimens were characterized by melt extraction, optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Titanium carbide formation was observed in all the as-sintered Ti-Nb binary alloys but not in the as-sintered CP-Ti. Selected area electron diffraction (SAED) patterns revealed that the carbides are Ti2C. It was found that with increasing niobium content from 0% to 22%, the porosity increased from about 1.6% to 5.8%, and the carbide area fraction increased from 0% to about 1.8% in the as-sintered samples. The effects of niobium content, porosity and titanium carbides on mechanical properties have been discussed. The as-sintered Ti-Nb specimens exhibited an excellent combination of high tensile strength and low Young's modulus, but relatively low ductility. © 2013 Elsevier Ltd. All rights reserved.

An auditory oddball brain-computer interface for binary choices.

PubMed

Halder, S; Rea, M; Andreoni, R; Nijboer, F; Hammer, E M; Kleih, S C; Birbaumer, N; Kübler, A

2010-04-01

Brain-computer interfaces (BCIs) provide non-muscular communication for individuals diagnosed with late-stage motoneuron disease (e.g., amyotrophic lateral sclerosis (ALS)). In the final stages of the disease, a BCI cannot rely on the visual modality. This study examined a method to achieve high accuracies using auditory stimuli only. We propose an auditory BCI based on a three-stimulus paradigm. This paradigm is similar to the standard oddball but includes an additional target (i.e. two target stimuli, one frequent stimulus). Three versions of the task were evaluated in which the target stimuli differed in loudness, pitch or direction. Twenty healthy participants achieved an average information transfer rate (ITR) of up to 2.46 bits/min and accuracies of 78.5%. Most subjects (14 of 20) achieved their best performance with targets differing in pitch. With this study, the viability of the paradigm was shown for healthy participants and will next be evaluated with individuals diagnosed with ALS or locked-in syndrome (LIS) after stroke. The here presented BCI offers communication with binary choices (yes/no) independent of vision. As it requires only little time per selection, it may constitute a reliable means of communication for patients who lost all motor function and have a short attention span. 2009 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Cellular-dendritic transition in directionally solidified binary alloys

NASA Technical Reports Server (NTRS)

Tewari, S. N.; Laxmanan, V.

1987-01-01

The microstructural development of binary alloys during directional solidification is studied. Cellular growth data for the Al-Cu and Pb-Sn binary alloy systems are analyzed in order evaluate the criteria of Kurz and Fisher (1981) and Trivedi (1984) for cellular-dendritic transition. It is observed that the experimental growth values do not correlate with the Kurz and Fisher or Trivedi data.

Relaxation dynamics in a binary hard-ellipse liquid.

PubMed

Xu, Wen-Sheng; Sun, Zhao-Yan; An, Li-Jia

2015-01-21

Structural relaxation in binary hard spherical particles has been shown recently to exhibit a wealth of remarkable features when size disparity or mixture composition is varied. In this paper, we test whether or not similar dynamical phenomena occur in glassy systems composed of binary hard ellipses. We demonstrate via event-driven molecular dynamics simulation that a binary hard-ellipse mixture with an aspect ratio of two and moderate size disparity displays characteristic glassy dynamics upon increasing density in both the translational and the rotational degrees of freedom. The rotational glass transition density is found to be close to the translational one for the binary mixtures investigated. More importantly, we assess the influence of size disparity and mixture composition on the relaxation dynamics. We find that an increase of size disparity leads, both translationally and rotationally, to a speed up of the long-time dynamics in the supercooled regime so that both the translational and the rotational glass transition shift to higher densities. By increasing the number concentration of the small particles, the time evolution of both translational and rotational relaxation dynamics at high densities displays two qualitatively different scenarios, i.e., both the initial and the final part of the structural relaxation slow down for small size disparity, while the short-time dynamics still slows down but the final decay speeds up in the binary mixture with large size disparity. These findings are reminiscent of those observed in binary hard spherical particles. Therefore, our results suggest a universal mechanism for the influence of size disparity and mixture composition on the structural relaxation in both isotropic and anisotropic particle systems.

Physical Properties of the LMC Eclipsing Binary Stars

NASA Astrophysics Data System (ADS)

Prsa, Andrej; Devinney, E. J.; Guinan, E. F.; Engle, S. G.; DeGeorge, M.

2009-01-01

To date, three independent studies have devised an automatic procedure to analyse and extract the principal parameters of 2581 detached eclipsing binary stars from the OGLE photometric survey of the Large Magellanic Cloud (LMC): Devor (2005), Tamuz et al. (2006), and Prsa et al. (2008). For time efficiency, Devor used a simple model of two spherical, limb-darkened stars without tidal or reflection physics. Tamuz et al.'s approach employs a more realistic EBOP model, which is still limited in handling proximity physics. Our study used a back-propagating neural network that was trained on the light curves computed by a modern Wilson-Devinney code. The three approaches are confronted and correlations in the results are sought that indicate the degree of reliability of the obtained results. A database of solutions consistent across all three studies is presented. We assess the suitability of each method for other morphology types (i.e. semi-detached and overcontact binaries) and we overview the practical limitations of these methods for the upcoming survey data. This research is supported by NFS/RUI Grant No. AST-05-07542, which we gratefully acknowledge.

CHANDRA AND SWIFT X-RAY OBSERVATIONS OF THE X-RAY PULSAR SMC X-2 DURING THE OUTBURST OF 2015

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, K. L.; Hu, C.-P; Lin, L. C. C.

2016-09-10

We report the Chandra /HRC-S and Swift /XRT observations for the 2015 outburst of the high-mass X-ray binary pulsar in the Small Magellanic Cloud, SMC X-2. While previous studies suggested that either an O star or a Be star in the field is the high-mass companion of SMC X-2, our Chandra /HRC-S image unambiguously confirms the O-type star as the true optical counterpart. Using the Swift /XRT observations, we extracted accurate orbital parameters of the pulsar binary through a time of arrivals analysis. In addition, there were two X-ray dips near the inferior conjunction, which are possibly caused by eclipsesmore » or an ionized high-density shadow wind near the companion’s surface. Finally, we propose that an outflow driven by the radiation pressure from day ∼10 played an important role in the X-ray/optical evolution of the outburst.« less

Dynamical and Physical Properties of 65803 Didymos, the Proposed AIDA Mission Target

NASA Astrophysics Data System (ADS)

Richardson, Derek C.; Barnouin, Olivier S.; Benner, Lance A. M.; Bottke, William; Campo Bagatin, Adriano; Cheng, Andrew F.; Eggl, Siegfried; Hamilton, Douglas P.; Hestroffer, Daniel; Hirabayashi, Masatoshi; Maurel, Clara; McMahon, Jay W.; Michel, Patrick; Murdoch, Naomi; Naidu, Shantanu P.; Pravec, Petr; Rivkin, Andrew S.; Rosenblatt, Pascal; Sarid, Gal; Scheeres, Daniel J.; Scheirich, Peter; Tsiganis, Kleomenis; Zhang, Yun; AIDA Dynamical and Physical Properties of Didymos Working Group

2016-10-01

Binary near-Earth asteroid (NEA) 65803 Didymos is the proposed Asteroid Impact & Deflection Assessment (AIDA) mission target, combining an orbiter [1] and a kinetic impactor for a planned encounter in fall 2022 [2]. The Dynamical and Physical Properties of Didymos Working Group supports this mission by addressing questions related to understanding the dynamical state of the system and inferring physical properties. Didymos is an Apollo-class NEA that likely reached its current orbit by exiting the inner main belt near or within the nu-6 resonance (> 82% chance) [3]. Remote observations [4] show Didymos is spectroscopically most consistent with ordinary chondrites. The diameters of the binary components are measured to be about 780 and 160 m [5]. A model of the short-term binary dynamics suggests possible librations of the secondary with up to ~10-deg amplitude, depending on its axial ratio. However, an equilibrium orbital and rotational solution is consistent with a libration amplitude of only ~1 deg. The primary, with an estimated 2.1 g/cc bulk density (uncertainty 30%) has a possibly super-critical rotation period of 2.26 h that may imply a cohesive strength of several tens of Pa. At this rate, perturbed regolith material may go through take-off/landing cycles and cause loss of fines due to solar radiation pressure. Based on a continuum analysis [6], the internal structure would likely fail before the equatorial region. A discrete analysis [7,8] shows that a minimum of 2.5 g/cc bulk density is needed for the structure to hold without cohesion. The system may be subject to weak thermal radiation forces (BYORP) with a period drift of no greater than 1 s/yr [9]. Experiments using the ISAE-SUPAERO drop tower [10] are underway to model the possible deployment of a lander on the secondary. References: [1] Michel et al. 2016, ASR 57, 2529; [2] Cheng et al. 2016, P&SS 127, 27; [3] Granvik et al. 2015, DPS 47, 214.07; [4] Dunn et al. 2013, LPSC 44, 1719; [5] Osip et al. 2016, this meeting; [6] Hirabayashi & Scheeres 2015, IAU 29, 2256185; [7] Barnouin et al. 2015, DPS 47, 402.09; [8] Zhang et al. 2016, this meeting; [9] McMahon et al. 2016, LPSC 47, 1903; [10] Sunday et al. 2016, Rev. Sci. Instr., accepted.

The Blazar PG 1553+113 as a Binary System of Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Tavani, M.; Cavaliere, A.; Munar-Adrover, Pere; Argan, A.

2018-02-01

The BL Lac PG 1553+113 has been continuously monitored in gamma-rays with Fermi-LAT for over 9 years. Its updated light curve now includes five iterations of a main pattern comprising a high peak and a longer trough, with a period P≃ 2.2 {year}. Our analysis of 2015–2017 data confirms the occurrence in 2017 January of a new peak fitting in with the previous trend. In addition, we identify secondary peaks (“twin peaks”) that occur in closely symmetric pairs on both sides of most main peaks, including the last one; their occurrence is supported by correlated X-ray outbursts. We stress that the above features strongly point to binary dynamics in a system of two black holes (BHs) of some 108 and {10}7 {M}ȯ . At periastron the smaller BH periodically stresses the jet j 1 launched by the heavier companion, and triggers MHD–kinetic tearing instabilities. These lead to magnetic reconnections and to acceleration of electrons that produce synchrotron emission from the optical to X-ray bands, and inverse Compton scattering into the GeV range. We discuss two possible origins of the twin peaks : a single-jet model, based on added instabilities induced in j 1 by the smaller companion BH on its inner orbital arc; and a two-jet model with the smaller BH supporting its own, precessing jet j 2 that contributes lower, specific GeV emissions. Such behaviors combining time stability with amplitude variations betray plasma instabilities driven in either jet by binary dynamics, and can provide a double signature of the long-sought supermassive BH binaries.

General relativistic viscous hydrodynamics of differentially rotating neutron stars

NASA Astrophysics Data System (ADS)

Shibata, Masaru; Kiuchi, Kenta; Sekiguchi, Yu-ichiro

2017-04-01

Employing a simplified version of the Israel-Stewart formalism for general-relativistic shear-viscous hydrodynamics, we perform axisymmetric general-relativistic simulations for a rotating neutron star surrounded by a massive torus, which can be formed from differentially rotating stars. We show that with our choice of a shear-viscous hydrodynamics formalism, the simulations can be stably performed for a long time scale. We also demonstrate that with a possibly high shear-viscous coefficient, not only viscous angular momentum transport works but also an outflow could be driven from a hot envelope around the neutron star for a time scale ≳100 ms with the ejecta mass ≳10-2 M⊙ , which is comparable to the typical mass for dynamical ejecta of binary neutron-star mergers. This suggests that massive neutron stars surrounded by a massive torus, which are typical outcomes formed after the merger of binary neutron stars, could be the dominant source for providing neutron-rich ejecta, if the effective shear viscosity is sufficiently high, i.e., if the viscous α parameter is ≳10-2. The present numerical result indicates the importance of a future high-resolution magnetohydrodynamics simulation that is the unique approach to clarify the viscous effect in the merger remnants of binary neutron stars by the first-principle manner.

Interactions in Massive Colliding Wind Binaries

NASA Technical Reports Server (NTRS)

Corcoran, M.

2012-01-01

The most massive stars (M> 60 Solar Mass) play crucial roles in altering the chemical and thermodynamic properties of their host galaxies. Stellar mass is the fundamental stellar parameter that determines their ancillary properties and which ultimately determines the fate of these stars and their influence on their galactic environs. Unfortunately, stellar mass becomes observationally and theoretically less well constrained as it increases. Theory becomes uncertain mostly because very massive stars are prone to strong, variable mass loss which is difficult to model. Observational constraints are uncertain too. Massive stars are rare, and massive binary stars (needed for dynamical determination of mass) are rarer still: and of these systems only a fraction have suitably high orbital inclinations for direct photometric and spectroscopic radial-velocity analysis. Even in the small number of cases in which a high-inclination binary near the upper mass limit can be identified, rotational broadening and contamination of spectral line features from thick circumstellar material (either natal clouds or produced by strong stellar wind driven mass loss from one or both of he stellar components) biases the analysis. In the wilds of the upper HR diagram, we're often left with indirect and circumstantial means of determining mass, a rather unsatisfactory state of affairs.

Simultaneous Transformation of Commingled Trichloroethylene, Tetrachloroethylene, and 1,4-Dioxane by a Microbially Driven Fenton Reaction in Batch Liquid Cultures.

PubMed

Sekar, Ramanan; Taillefert, Martial; DiChristina, Thomas J

2016-11-01

Improper disposal of 1,4-dioxane and the chlorinated organic solvents trichloroethylene (TCE) and tetrachloroethylene (also known as perchloroethylene [PCE]) has resulted in widespread contamination of soil and groundwater. In the present study, a previously designed microbially driven Fenton reaction system was reconfigured to generate hydroxyl (HO˙) radicals for simultaneous transformation of source zone levels of single, binary, and ternary mixtures of TCE, PCE, and 1,4-dioxane. The reconfigured Fenton reaction system was driven by fed batch cultures of the Fe(III)-reducing facultative anaerobe Shewanella oneidensis amended with lactate, Fe(III), and contaminants and exposed to alternating anaerobic and aerobic conditions. To avoid contaminant loss due to volatility, the Fe(II)-generating, hydrogen peroxide-generating, and contaminant transformation phases of the microbially driven Fenton reaction system were separated. The reconfigured Fenton reaction system transformed TCE, PCE, and 1,4-dioxane either as single contaminants or as binary and ternary mixtures. In the presence of equimolar concentrations of PCE and TCE, the ratio of the experimentally derived rates of PCE and TCE transformation was nearly identical to the ratio of the corresponding HO˙ radical reaction rate constants. The reconfigured Fenton reaction system may be applied as an ex situ platform for simultaneous degradation of commingled TCE, PCE, and 1,4-dioxane and provides valuable information for future development of in situ remediation technologies. A microbially driven Fenton reaction system [driven by the Fe(III)-reducing facultative anaerobe S. oneidensis] was reconfigured to transform source zone levels of TCE, PCE, and 1,4-dioxane as single contaminants or as binary and ternary mixtures. The microbially driven Fenton reaction may thus be applied as an ex situ platform for simultaneous degradation of at least three (and potentially more) commingled contaminants. Additional targets for ex situ and in situ degradation by the microbially driven Fenton reaction developed in the present study include multiple combinations of environmental contaminants susceptible to attack by Fenton reaction-generated HO˙ radicals, including commingled plumes of 1,4-dioxane, pentachlorophenol (PCP), PCE, TCE, 1,1,2-trichloroethane (TCA), and perfluoroalkylated substances (PFAS). Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Simultaneous Transformation of Commingled Trichloroethylene, Tetrachloroethylene, and 1,4-Dioxane by a Microbially Driven Fenton Reaction in Batch Liquid Cultures

PubMed Central

Sekar, Ramanan; Taillefert, Martial

2016-01-01

ABSTRACT Improper disposal of 1,4-dioxane and the chlorinated organic solvents trichloroethylene (TCE) and tetrachloroethylene (also known as perchloroethylene [PCE]) has resulted in widespread contamination of soil and groundwater. In the present study, a previously designed microbially driven Fenton reaction system was reconfigured to generate hydroxyl (HO˙) radicals for simultaneous transformation of source zone levels of single, binary, and ternary mixtures of TCE, PCE, and 1,4-dioxane. The reconfigured Fenton reaction system was driven by fed batch cultures of the Fe(III)-reducing facultative anaerobe Shewanella oneidensis amended with lactate, Fe(III), and contaminants and exposed to alternating anaerobic and aerobic conditions. To avoid contaminant loss due to volatility, the Fe(II)-generating, hydrogen peroxide-generating, and contaminant transformation phases of the microbially driven Fenton reaction system were separated. The reconfigured Fenton reaction system transformed TCE, PCE, and 1,4-dioxane either as single contaminants or as binary and ternary mixtures. In the presence of equimolar concentrations of PCE and TCE, the ratio of the experimentally derived rates of PCE and TCE transformation was nearly identical to the ratio of the corresponding HO˙ radical reaction rate constants. The reconfigured Fenton reaction system may be applied as an ex situ platform for simultaneous degradation of commingled TCE, PCE, and 1,4-dioxane and provides valuable information for future development of in situ remediation technologies. IMPORTANCE A microbially driven Fenton reaction system [driven by the Fe(III)-reducing facultative anaerobe S. oneidensis] was reconfigured to transform source zone levels of TCE, PCE, and 1,4-dioxane as single contaminants or as binary and ternary mixtures. The microbially driven Fenton reaction may thus be applied as an ex situ platform for simultaneous degradation of at least three (and potentially more) commingled contaminants. Additional targets for ex situ and in situ degradation by the microbially driven Fenton reaction developed in the present study include multiple combinations of environmental contaminants susceptible to attack by Fenton reaction-generated HO˙ radicals, including commingled plumes of 1,4-dioxane, pentachlorophenol (PCP), PCE, TCE, 1,1,2-trichloroethane (TCA), and perfluoroalkylated substances (PFAS). PMID:27542932

Einstein@Home Finds a Double Neutron Star

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

Have you been contributing your computer idle time to the Einstein@Home project? If so, youre partly responsible for the programs recent discovery of a new double-neutron-star system that will be key to learning about general relativity and stellar evolution.The 305-m Arecibo Radio Telescope, built into the landscape at Arecibo, Puerto Rico. [NOAO/AURA/NSF/H. Schweiker/WIYN]The Hunt for PulsarsObserving binary systems containing two neutron stars and in particular, measuring the timing of the pulses when one or both companions is a pulsar can provide highly useful tests of general relativity and binary stellar evolution. Unfortunately, these systems are quite rare: of 2500 known radio pulsars, only 14 of them are in double-neutron-starbinaries.To find more systems like these, we perform large-scale, untargeted radio-pulsar surveys like the ongoing Pulsar-ALFA survey conducted with the enormous 305-m radio telescope at Arecibo Observatory in Puerto Rico. But combing through these data for the signature of a highly accelerated pulsar (the acceleration is a clue that its in a compact binary) is very computationally expensive.PSR J1913+1102s L-band pulse profile, created by phase-aligning and summing all observations. [Adapted from Lazarus et al. 2016]To combat this problem, the Einstein@Home project was developed. Einstein@Home allows anyone to volunteer their personal computers idle time to help run the analysis of survey data in the search for pulsars. In a recent publication led by Patrick Lazarus (Max Planck Institute for Radio Astronomy), the Einstein@Home team announced the discovery of the pulsar PSR J1913+1102 a member of what seems to be a brand new double-neutron-starsystem.An Intriguing DiscoveryLazarus and collaborators followed up on the discovery to obtain timing measurements of the pulsar, which they found to have a spin period of 27.3 ms. They measured PSR J1913+1102 to be in a 4.95-hr, nearly circular (e 0.09) binary orbit with a massive companion that, based on its properties, is most likely another neutron star. The team wasnt able to detect pulsations from the companion, but that could mean that its beam doesnt cross the Earth, or its very faint, or its simply no longer active as a pulsar.Orbital evolution of the six known double-neutron-star systems that will coalesce within a Hubble time, including J1913+1102 (black solid line). They move toward the origin as they lose energy to gravitational waves and approach merger. Shown are current positions (black dots), estimates of the positions when the compact binaries were formed (grey dots), and future evolution. [Lazarus et al. 2016]Lazarus and collaborators use their observations of the system to arguethat PSR J1913+1102 waslikely spun up (recycled) by accretion of matter from its companions progenitor. The companion then exploded in the second supernova of the system, providing a very small kick hence the low eccentricity of the system and resulting in the current double-neutron-starbinary we observe.Lessons from PSR J1913+1102Observations of compact binaries such as this one can reveal a wealth of information. Besides providing clues about how the binary evolved, precise timing measurements (now being made) will also allow powerful tests of general relativity.One of the measurements that may be possible by the end of this year will provide information about the orbital decay of the binary expected to continue for 0.5 Gyr until the system merges due to the emission of gravitational waves.In the meantime, you can bet that Einstein@Home will continue hunting for more systems like PSR J1913+1102 and its companion!CitationP. Lazarus et al 2016 ApJ 831 150. doi:10.3847/0004-637X/831/2/150

On the enhancement of p-11B fusion reaction rate in laser-driven plasma by α → p collisional energy transfer

NASA Astrophysics Data System (ADS)

Belloni, Fabio; Margarone, Daniele; Picciotto, Antonino; Schillaci, Francesco; Giuffrida, Lorenzo

2018-02-01

The possibility of triggering an avalanche reaction in laser-driven p-11B fusion by the effect of collisional energy transfer from α particles to protons has recently been debated, especially in connection to the high yield of α particles (4 × 108 per laser shot) achieved on engineered targets at the Prague Asterix Laser System (PALS), with a pulse of 500 J, 0.3 ns FWHM. We elucidate this controversial subject within the framework of a simple two-population model for protons, based on the binary collision theory in a plasma. We find an avalanche characteristic time of almost 1 μs for the 675 keV fusion cross section resonance in typical PALS plasma, upon idealized confinement conditions. This avalanche time is one order of magnitude higher than previously reported, meaning that no such process can substantially develop in plasma at the PALS on the 675 keV resonance, not even in the most optimistic confinement scenarios. Nevertheless, we put forward for further investigation that more realistic conditions for setting up the avalanche regime could rather be attained by suitably targeting the narrow 163 keV resonance in the fusion cross section, also in connection to recently proposed laser-driven magnetic trapping techniques.

α-Al2O3/Ga2O3 superlattices coherently grown on r-plane sapphire

NASA Astrophysics Data System (ADS)

Oshima, Takayoshi; Kato, Yuji; Imura, Masataka; Nakayama, Yoshiko; Takeguchi, Masaki

2018-06-01

Ten-period binary α-Al2O3/Ga2O3 superlattices were fabricated on r-plane sapphire substrates by molecular beam epitaxy. By systematic variation of α-Ga2O3 thickness and evaluation through X-ray reflectivity and diffraction measurements and scanning transmission electron microscopy, we verified that the superlattice with α-Ga2O3 thickness up to ∼1 nm had coherent interfaces without misfit dislocation in spite of the large lattice mismatches. This successful fabrication of coherent α-Al2O3/Ga2O3 superlattices will encourage further development of α-(Al x Ga1‑ x )2O3-based heterostructures including superlattices.

Spherical hashing: binary code embedding with hyperspheres.

PubMed

Heo, Jae-Pil; Lee, Youngwoon; He, Junfeng; Chang, Shih-Fu; Yoon, Sung-Eui

2015-11-01

Many binary code embedding schemes have been actively studied recently, since they can provide efficient similarity search, and compact data representations suitable for handling large scale image databases. Existing binary code embedding techniques encode high-dimensional data by using hyperplane-based hashing functions. In this paper we propose a novel hypersphere-based hashing function, spherical hashing, to map more spatially coherent data points into a binary code compared to hyperplane-based hashing functions. We also propose a new binary code distance function, spherical Hamming distance, tailored for our hypersphere-based binary coding scheme, and design an efficient iterative optimization process to achieve both balanced partitioning for each hash function and independence between hashing functions. Furthermore, we generalize spherical hashing to support various similarity measures defined by kernel functions. Our extensive experiments show that our spherical hashing technique significantly outperforms state-of-the-art techniques based on hyperplanes across various benchmarks with sizes ranging from one to 75 million of GIST, BoW and VLAD descriptors. The performance gains are consistent and large, up to 100 percent improvements over the second best method among tested methods. These results confirm the unique merits of using hyperspheres to encode proximity regions in high-dimensional spaces. Finally, our method is intuitive and easy to implement.

PRS J0045-7319: A massive SMC binary

NASA Astrophysics Data System (ADS)

Bell, J. F.

1994-04-01

The existence of X-ray binary systems shows that neutron stars are found in orbit around massive stars. Before these systems enter the mass accretion phase, one would expect the neutron star might be detectable as a radio pulsar. The discovery of PSR B1259-63 by Johnston et al. (1992, Astrophys. J. Lett, 387, L37), which is in orbit around the Be star SS2883, provided the first evidence for such systems. PSR J0045-7319 was discovered in a systematic search of the Magellanic Clouds for radio pulsars by McConnell et al. (1991, Mon. Not. R. Astron. Soc., 249, 645). Its dispersion measure of 105 pc/cu cm assures its association with the Small Magellanic Cloud making it the only known pulsar in the SMC. The discovery of regular Doppler shifts of the pulse period of PSR J0045-7319 implies that the pulsar is in a highly eccentric 51-day binary orbit, making it the most luminous binary pulsar known (Kaspi et al., 1993, submitted to Astrophys. J.). The observed Keplerian orbital parameters show that the companion mass is greater the 4 solar mass. Optical observations of the field reveal a 16th magnitude, 11 solar mass, B1 main-sequence star, which we conclude is the pulsar's companion. The timing observations imply that this pulsar has not been spun up by accretion from the companion. This suggests that, like the PSR B1259-63 binary system, the PSR J0045-7319 system is a progenitor of an X-ray binary system. At periastron the pulsar approaches to within six stellar radii of the companion.

Geomorphic Flood Area (GFA): a DEM-based tool for flood susceptibility mapping at large scales

NASA Astrophysics Data System (ADS)

Manfreda, S.; Samela, C.; Albano, R.; Sole, A.

2017-12-01

Flood hazard and risk mapping over large areas is a critical issue. Recently, many researchers are trying to achieve a global scale mapping encountering several difficulties, above all the lack of data and implementation costs. In data scarce environments, a preliminary and cost-effective floodplain delineation can be performed using geomorphic methods (e.g., Manfreda et al., 2014). We carried out several years of research on this topic, proposing a morphologic descriptor named Geomorphic Flood Index (GFI) (Samela et al., 2017) and developing a Digital Elevation Model (DEM)-based procedure able to identify flood susceptible areas. The procedure exhibited high accuracy in several test sites in Europe, United States and Africa (Manfreda et al., 2015; Samela et al., 2016, 2017) and has been recently implemented in a QGIS plugin named Geomorphic Flood Area (GFA) - tool. The tool allows to automatically compute the GFI, and turn it into a linear binary classifier capable of detecting flood-prone areas. To train this classifier, an inundation map derived using hydraulic models for a small portion of the basin is required (the minimum is 2% of the river basin's area). In this way, the GFA-tool allows to extend the classification of the flood-prone areas across the entire basin. We are also defining a simplified procedure for the estimation of the river depth, which may be helpful for large-scale analyses to approximatively evaluate the expected flood damages in the surrounding areas. ReferencesManfreda, S., Nardi, F., Samela, C., Grimaldi, S., Taramasso, A. C., Roth, G., & Sole, A. (2014). Investigation on the use of geomorphic approaches for the delineation of flood prone areas. J. Hydrol., 517, 863-876. Manfreda, S., Samela, C., Gioia, A., Consoli, G., Iacobellis, V., Giuzio, L., & Sole, A. (2016). Flood-prone areas assessment using linear binary classifiers based on flood maps obtained from 1D and 2D hydraulic models. Nat. Hazards, Vol. 79 (2), pp 735-754. Samela, C., Manfreda, S., Paola, F. D., Giugni, M., Sole, A., & Fiorentino, M. (2016). DEM-Based Approaches for the Delineation of Flood-Prone Areas in an Ungauged Basin in Africa. J. Hydrol. Eng,, 06015010. Samela, C., Troy, T. J., & Manfreda, S. (2017a). Geomorphic classifiers for flood-prone areas delineation for data-scarce environments. Adv. Water Resour., 102, 13-28.

On the Induced Gravitational Collapse

NASA Astrophysics Data System (ADS)

Becerra, Laura M.; Bianco, Carlo; Fryer, Chris; Rueda, Jorge; Ruffini, Remo

2018-01-01

The induced gravitational collapse (IGC) paradigm has been applied to explain the long gamma ray burst (GRB) associated with type Ic supernova, and recently the Xray flashes (XRFs). The progenitor is a binary systems of a carbon-oxygen core (CO) and a neutron star (NS). The CO core collapses and undergoes a supernova explosion which triggers the hypercritical accretion onto the NS companion (up to 10-2 M⊙s-1). For the binary driven hypernova (BdHNe), the binary system is enough bound, the NS reach its critical mass, and collapse to a black hole (BH) with a GRB emission characterized by an isotropic energy Eiso > 1052 erg. Otherwise, for binary systems with larger binary separations, the hypercritical accretion onto the NS is not sufficient to induced its gravitational collapse, a X-ray flash is produced with Eiso < 1052 erg. We're going to focus in identify the binary parameters that limits the BdHNe systems with the XRFs systems.

Learning moment-based fast local binary descriptor

NASA Astrophysics Data System (ADS)

Bellarbi, Abdelkader; Zenati, Nadia; Otmane, Samir; Belghit, Hayet

2017-03-01

Recently, binary descriptors have attracted significant attention due to their speed and low memory consumption; however, using intensity differences to calculate the binary descriptive vector is not efficient enough. We propose an approach to binary description called POLAR_MOBIL, in which we perform binary tests between geometrical and statistical information using moments in the patch instead of the classical intensity binary test. In addition, we introduce a learning technique used to select an optimized set of binary tests with low correlation and high variance. This approach offers high distinctiveness against affine transformations and appearance changes. An extensive evaluation on well-known benchmark datasets reveals the robustness and the effectiveness of the proposed descriptor, as well as its good performance in terms of low computation complexity when compared with state-of-the-art real-time local descriptors.

Accreting binary population synthesis and feedback prescriptions

NASA Astrophysics Data System (ADS)

Fragos, Tassos

2016-04-01

Studies of extagalactic X-ray binary populations have shown that the characteristics of these populations depend strongly on the characteristics of the host galaxy's parent stellar population (e.g. star-formation history and metallicity). These dependencies not only make X-ray binaries promising for aiding in the measurement of galaxy properties themselves, but they also have important astrophysical and cosmological implications. For example, due to the relatively young stellar ages and primordial metallicities in the early Universe (z > 3), it is predicted that X-ray binaries were more luminous than today. The more energetic X-ray photons, because of their long mean-free paths, can escape the galaxies where they are produced, and interact at long distances with the intergalactic medium. This could result in a smoother spatial distribution of ionized regions, and more importantly in an overall warmer intergalactic medium. The energetic X-ray photons emitted from X-ray binaries dominate the X-ray radiation field over active galactic nuclei at z > 6 - 8, and hence Χ-ray binary feedback can be a non-negligible contributor to the heating and reionization of the inter-galactic medium in the early universe. The spectral energy distribution shape of the XRB emission does not change significantly with redshift, suggesting that the same XRB subpopulation, namely black-hole XRBs in the high-soft state, dominates the cumulative emission at all times. On the contrary, the normalization of the spectral energy distribution does evolve with redshift. To zeroth order, this evolution is driven by the cosmic star-formation rate evolution. However, the metallicity evolution of the universe and the mean stellar population age are two important factors that affect the X-ray emission from high-mass and low-mass XRBs, respectively. In this talk, I will review recent studies on the potential feedback from accreting binary populations in galactic and cosmological scales. Furthermore, I will discuss which are the next steps towards a more physically realisitc modelling of accreting compact object populations in the early Universe.

Evolution of an electron-positron plasma produced by induced gravitational collapse in binary-driven hypernovae

NASA Astrophysics Data System (ADS)

Melon Fuksman, J. D.; Becerra, L.; Bianco, C. L.; Karlica, M.; Kovacevic, M.; Moradi, R.; Muccino, M.; Pisani, G. B.; Primorac, D.; Rueda, J. A.; Ruffini, R.; Vereshchagin, G. V.; Wang, Y.

2018-01-01

The binary-driven hypernova (BdHN) model has been introduced in the past years, to explain a subfamily of gamma-ray bursts (GRBs) with energies Eiso ≥ 1052 erg associated with type Ic supernovae. Such BdHNe have as progenitor a tight binary system composed of a carbon-oxigen (CO) core and a neutron star undergoing an induced gravitational collapse to a black hole, triggered by the CO core explosion as a supernova (SN). This collapse produces an optically-thick e+e- plasma, which expands and impacts onto the SN ejecta. This process is here considered as a candidate for the production of X-ray flares, which are frequently observed following the prompt emission of GRBs. In this work we follow the evolution of the e+e- plasma as it interacts with the SN ejecta, by solving the equations of relativistic hydrodynamics numerically. Our results are compatible with the Lorentz factors estimated for the sources that produce the flares, of typically Γ ≲ 4.

Primary Surface Particle Motion as a Mechanism for YORP-Driven Binary Asteroid Evolution

NASA Astrophysics Data System (ADS)

Fahnestock, Eugene G.; Scheeres, D. J.

2008-09-01

Within the largest class of binary asteroid systems -- asynchronous binaries typified by 1999 KW4 -- we hypothesize continued YORP spin-up of the rapidly rotating primary leads to recurring episodic lofting motion of primary equator regolith. We theorize this is a mechanism for transporting YORP-injected angular momentum from primary spin into the mutual orbit. This both enables binary primaries to continue to spin at near surface fission rates and produces continued orbit expansion on time scales several times faster than expansion predicted by tidal dissipation alone. This is distinct from the Binary Yorp (BYORP) phenomenon, not studied in this work but to be added to it later. We evaluate our hypotheses using a combination of techniques for an example binary system. First high-fidelity dynamic simulation of surface-originating particles in the full-detail gravity field of the binary components, themselves propagated according to the full two body problem, gives particle final disposition (return impact, transfer impact, escape). Trajectory end states found for regolith lofted at different initial primary spin rates and relative poses are collected into probability matrices, allowing probabilistic propagation of surface particles for long durations at low computational cost. We track changes to mass, inertia dyad, rotation state, and centroid position and velocity for each component in response to this mapped particle motion. This allows tracking of primary, secondary, and mutual orbit angular momenta over time, clearly demonstrating the angular momentum transfer mechanism and validating our hypotheses. We present current orbit expansion rates and estimated orbit size doubling times consistent with this mechanism, for a few binary systems. We also discuss ramifications of this type of rapid binary evolution towards separation, including the frequency with which "divorced binaries" on similar heliocentric orbits are produced, formation of triple systems such as 2001 SN263, and separation timescale dependence on heliocentric distance.

Shapes, rotation, and pole solutions of the selected Hilda and Trojan asteroids

NASA Astrophysics Data System (ADS)

Gritsevich, Maria; Sonnett, Sarah; Torppa, Johanna; Mainzer, Amy; Muinonen, Karri; Penttilä, Antti; Grav, Thomas; Masiero, Joseph; Bauer, James; Kramer, Emily

2017-04-01

Binary asteroid systems contain key information about the dynamical and chemical environments in which they formed. For example, determining the formation environments of Trojan and Hilda asteroids (in 1:1 and 3:2 mean-motion resonance with Jupiter, respectively) will provide critical constraints on how small bodies and the planets that drive their migration must have moved throughout Solar System history, see e.g. [1-3]. Therefore, identifying and characterizing binary asteroids within the Trojan and Hilda populations could offer a powerful means of discerning between Solar System evolution models. Dozens of possibly close or contact binary Trojans and Hildas were identified within the data obtained by NEOWISE [4]. Densely sampled light curves of these candidate binaries have been obtained in order to resolve rotational light curve features that are indicative of binarity (e.g., [5-7]). We present analysis of the shapes, rotation, and pole solutions of some of the follow-up targets observed with optical ground-based telescopes. For modelling the asteroid photometric properties, we use parameters describing the shape, surface light scattering properties and spin state of the asteroid. Scattering properties of the asteroid surface are modeled using a two parameter H-G12 magnitude system. Determination of the initial best-fit parameters is carried out by first using a triaxial ellipsoid shape model, and scanning over the period values and spin axis orientations, while fitting the other parameters, after which all parameters were fitted, taking the initial values for spin properties from the spin scanning. In addition to the best-fit parameters, we also provide the distribution of the possible solution, which should cover the inaccuracies of the solution, caused by the observing errors and model. The distribution of solutions is generated by Markov-Chain Monte Carlo sampling the spin and shape model parameters, using both an ellipsoid shape model and a convex model, Gaussian curvature of which is defined as a spherical harmonics series [8]. References: [1] Marzari F. and Scholl H. (1998), A&A, 339, 278. [2] Morbidelli A. et al. (2005), Nature, 435, 462. [3] Nesvorny D. et al. (2013), ApJ, 768, 45. [4] Sonnett S. et al. (2015), ApJ, 799, 191. [5] Behrend R. et al. (2006), A&A, 446, 1177. [6] Lacerda P. and Jewitt D. C. (2007), AJ, 133, 1393. [7] Oey J. (2016), MPB, 43, 45. [8] Muinonen et al., ACM 2017.

Electro-acoustic sensors based on AlN thin film: possibilities and limitations

NASA Astrophysics Data System (ADS)

Wingqvist, Gunilla

2011-06-01

The non-ferroelectric polar wurtzite aluminium nitride (AlN) material has been shown to have potential for various sensor applications both utilizing the piezoelectric effect directly for pressure sensors or indirectly for acoustic sensing of various physical, chemical and biochemical sensor applications. Especially, sputter deposited AlN thin films have played a central role for successful development of the thin film electro-acoustic technology. The development has been primarily driven by one device - the thin film bulk acoustic resonator (FBAR or TFBAR), with its primary use for high frequency filter applications for the telecom industry. AlN has been the dominating choice for commercial application due to compatibility with the integrated circuit technology, low acoustic and dielectric losses, high acoustic velocity in combination with comparably high (but still for some applications limited) electromechanical coupling. Recently, increased piezoelectric properties (and also electromechanical coupling) in the AlN through the alloying with scandium nitride (ScN) have been identified both experimentally and theoretically. Inhere, the utilization of piezoelectricity in electro-acoustic sensing will be discussed together with expectation on acoustic FBAR sensor performance with variation in piezoelectric material properties in the parameter space around AlN due to alloying, in view of the ScxAl1-xN (0

Jet creation in post-AGB binaries: the circum-companion accretion disk around BD+46°442

NASA Astrophysics Data System (ADS)

Bollen, Dylan; Van Winckel, Hans; Kamath, Devika

2017-11-01

Aims: We aim at describing and understanding binary interaction processes in systems with very evolved companions. Here, we focus on understanding the origin and determining the properties of the high-velocity outflow observed in one such system. Methods: We present a quantitative analysis of BD+46°442, a post-AGB binary that shows active mass transfer that leads to the creation of a disk-driven outflow or jet. We obtained high-resolution optical spectra from the HERMES spectrograph, mounted on the 1.2 m Flemish Mercator Telescope. By performing a time-series analysis of the Hα profile, we identified the different components of the system. We deduced the jet geometry by comparing the orbital phased data with our jet model. In order to image the accretion disk around the companion of BD+46°442, we applied the technique of Doppler tomography. Results: The orbital phase-dependent variations in the Hα profile can be related to an accretion disk around the companion, from which a high-velocity outflow or jet is launched. Our model shows that there is a clear correlation between the inclination angle and the jet opening angle. The latitudinally dependent velocity structure of our jet model shows a good correspondence to the data, with outflow velocities higher than at least 400 km s-1. The intensity peak in the Doppler map might be partly caused by a hot spot in the disk, or by a larger asymmetrical structure in the disk. Conclusions: We show that BD+46°442 is a result of a binary interaction channel. The origin of the fast outflow in this system might be to a gaseous disk around the secondary component, which is most likely a main-sequence star. Our analysis suggests that the outflow has a rather wide opening angle and is not strongly collimated. Our time-resolved spectral monitoring reveals the launching site of the jet in the binary BD+46°442. Similar orbital phase-dependent Hα profiles are commonly observed in post-AGB binaries. Post-AGB binaries provide ideal test beds to study jet formation and launching mechanisms over a wide range of orbital conditions. Based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemmish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A60

Ab initio atomistic thermodynamics study on the oxidation mechanism of binary and ternary alloy surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Shi-Yu, E-mail: buaasyliu@gmail.com; Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong; Liu, Shiyang

Utilizing a combination of ab initio density-functional theory and thermodynamics formalism, we have established the microscopic mechanisms for oxidation of the binary and ternary alloy surfaces and provided a clear explanation for the experimental results of the oxidation. We construct three-dimensional surface phase diagrams (SPDs) for oxygen adsorption on three different Nb-X(110) (X = Ti, Al or Si) binary alloy surfaces. On the basis of the obtained SPDs, we conclude a general microscopic mechanism for the thermodynamic oxidation, that is, under O-rich conditions, a uniform single-phase SPD (type I) and a nonuniform double-phase SPD (type II) correspond to the sustainedmore » complete selective oxidation and the non-sustained partial selective oxidation by adding the X element, respectively. Furthermore, by revealing the framework of thermodynamics for the oxidation mechanism of ternary alloys through the comparison of the surface energies of two separated binary alloys, we provide an understanding for the selective oxidation behavior of the Nb ternary alloy surfaces. Using these general microscopic mechanisms, one could predict the oxidation behavior of any binary and multi-component alloy surfaces based on thermodynamics considerations.« less

Optimization of Capsule Symmetry in Z-Pinch Driven Hohlraums

NASA Astrophysics Data System (ADS)

Vesey, R. A.; Cuneo, M.; Hanson, D.; Porter, J.; Mehlhorn, T.; Ruggles, L.; Simpson, W.; Vargas, M.; Hammer, J.; Landen, O.

1999-11-01

The uniformity of the radiation flux incident on the capsule is a critical issue for indirect drive fusion using the z-pinch driven hohlraum high-yield concept(J.H. Hammer et al., Phys. Plas. 6), 2129 (1999).. Experiments on the Z accelerator at Sandia have demonstrated the ability to diagnose the uniformity of the flux striking a foam ball (surrogate capsule)(P.A. Amendt et al., Phys. Plas. 4), 1862 (1997); S.G. Glendinning et al. Rev. Sci. Instrum. 70, 536 (1999).. These single-sided drive experiments have been modeled using radiosity and radiation-hydrodynamics codes, yielding agreement with the measured ablation rate vs. angle on the foam ball. Flux uniformity at the 1-2% level needed for high-convergence capsule implosions requires a 2-sided drive (top and bottom z-pinch) configuration. Constrained optimization methods have identified hohlraum geometries with improved symmetry.

Leveraging the Polar Cap: Ground-Based Measurements of the Solar Wind

NASA Astrophysics Data System (ADS)

Urban, K. D.; Gerrard, A. J.; Weatherwax, A. T.; Lanzerotti, L. J.; Patterson, J. D.

2016-12-01

In this study, we look at and identify relationships between solar wind quantities that have previously been shown to have direct access into the very high-latitude polar cap as measured by ground-based riometers and magnetometers in Antarctica: ultra-low frequency (ULF) power in the interplanetary magnetic field (IMF) Bz component and solar energetic proton (SEP) flux (Urban [2016] and Patterson et al. [2001], respectively). It is shown that such solar wind and ground-based observations can be used to infer the hydromagnetic structure and magnetospheric mapping of the polar cap region in a data-driven manner, and that high-latitude ground-based instrumentation can be used to infer concurrent various state parameters of the geospace environment.

Yb-doped aluminophosphosilicate ternary fiber with high efficiency and excellent laser stability

NASA Astrophysics Data System (ADS)

Li, Yuwei; Peng, Kun; Zhan, Huan; Liu, Shuang; Ni, Li; Wang, Yuying; Yu, Juan; Wang, Xiaolong; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

2018-03-01

By using chelate precursor doping technique and traditional modified chemical vapor deposition system, we fabricated Yb-doped aluminophosphosilicate (Al2O3-P2O5-SiO2, ternary Yb-APS) large-mode-area fiber and reported on its laser performance. The fiber preform was doped with Al, P and Yb with concentration of ∼8000 ppm, ∼1700 ppm and ∼400 ppm in molar percent, respectively. Tested with master oscillator power amplifier system, the home-made Yb-APS fiber was found to present 1.02 kW at 1061.1 nm with a high slope efficiency of 81.2% and excellent laser stability with power fluctuation less than ±1.1% for over 10 h. Compared with Yb-doped aluminosilicate (Al2O3-SiO2, binary Yb-AS) fiber, the introduction of P2O5 effectively suppressed photodarkening effect even the P/Al ratio is much less than 1, indicating that Yb-APS fiber is a better candidate for high power fiber lasers.

The rapid size- and shape-controlled continuous hydrothermal synthesis of metal sulphide nanomaterials.

PubMed

Dunne, Peter W; Starkey, Chris L; Gimeno-Fabra, Miquel; Lester, Edward H

2014-02-21

Continuous flow hydrothermal synthesis offers a cheap, green and highly scalable route for the preparation of inorganic nanomaterials which has predominantly been applied to metal oxide based materials. In this work we report the first continuous flow hydrothermal synthesis of metal sulphide nanomaterials. A wide range of binary metal sulphides, ZnS, CdS, PbS, CuS, Fe(1-x)S and Bi2S3, have been synthesised. By varying the reaction conditions two different mechanisms may be invoked; a growth dominated route which permits the formation of nanostructured sulphide materials, and a nucleation driven process which produces nanoparticles with temperature dependent size control. This offers a new and industrially viable route to a wide range of metal sulphide nanoparticles with facile size and shape control.

Adaptive optics imaging of the MBM 12 association. Seven binaries and an edge-on disk in a quadruple system

NASA Astrophysics Data System (ADS)

Chauvin, G.; Ménard, F.; Fusco, T.; Lagrange, A.-M.; Beuzit, J.-L.; Mouillet, D.; Augereau, J.-C.

2002-11-01

We report adaptive optics (AO) observations of the young and nearby association MBM 12 obtained with the Canada-France-Hawaii Telescope. Our main observational result is the discovery of six new binary systems, LkHα 264, E 0255+2018, RX J0255.4+2005, S18, MBM 12-10, RX J0255.3+1915, and the confirmation of HD 17332, already known as a binary. We also detected a possible quadruple system. It is composed of the close binary LkHα 263 AB (separation of ~ 0.41''), of LkHα 262 located ~ 15.25'' from LkHα 263 A, and of LkHα 263 C, located ~ 4.1'' from LkHα 263 A. A preliminary study of the binary fraction suggests a binary excess in the MBM 12 association as compared to the field and IC 348. Because of the high binarity rate, previous estimations of spectral types and measurements of IR excesses for several candidate members of MBM 12 have to be revised. LkHα 263 C is a nebulous object that we interpret as a disk oriented almost perfectly edge-on and seen in scattered light. This object has already been reported by Jayawardhana et al. (\\cite{Jayawardhana2002}). Scattered light models allow us to estimate some of the structural parameters (i.e. inclination, diameter and to a lesser extent dust mass) of the circumstellar disk. We find an inclination of 89o and a outer radius for the disk, ~ 165 AU if the distance to MBM 12 is 275 pc. With the present data set, we do not attempt to re-assess the distance to MBM 12. We estimate however that the distance to the candidate member RX J0255.3+1915 is d > 175 pc. Based on data collected at the Canada-France-Hawaii Telescope. The CFHT corporation is funded by the Governments of Canada and France, and by the University of Hawaii.

A practical, intuitive brain-computer interface for communicating ‘yes’ or ‘no’ by listening

NASA Astrophysics Data System (ADS)

Hill, N. Jeremy; Ricci, Erin; Haider, Sameah; McCane, Lynn M.; Heckman, Susan; Wolpaw, Jonathan R.; Vaughan, Theresa M.

2014-06-01

Objective. Previous work has shown that it is possible to build an EEG-based binary brain-computer interface system (BCI) driven purely by shifts of attention to auditory stimuli. However, previous studies used abrupt, abstract stimuli that are often perceived as harsh and unpleasant, and whose lack of inherent meaning may make the interface unintuitive and difficult for beginners. We aimed to establish whether we could transition to a system based on more natural, intuitive stimuli (spoken words ‘yes’ and ‘no’) without loss of performance, and whether the system could be used by people in the locked-in state. Approach. We performed a counterbalanced, interleaved within-subject comparison between an auditory streaming BCI that used beep stimuli, and one that used word stimuli. Fourteen healthy volunteers performed two sessions each, on separate days. We also collected preliminary data from two subjects with advanced amyotrophic lateral sclerosis (ALS), who used the word-based system to answer a set of simple yes-no questions. Main results. The N1, N2 and P3 event-related potentials elicited by words varied more between subjects than those elicited by beeps. However, the difference between responses to attended and unattended stimuli was more consistent with words than beeps. Healthy subjects’ performance with word stimuli (mean 77% ± 3.3 s.e.) was slightly but not significantly better than their performance with beep stimuli (mean 73% ± 2.8 s.e.). The two subjects with ALS used the word-based BCI to answer questions with a level of accuracy similar to that of the healthy subjects. Significance. Since performance using word stimuli was at least as good as performance using beeps, we recommend that auditory streaming BCI systems be built with word stimuli to make the system more pleasant and intuitive. Our preliminary data show that word-based streaming BCI is a promising tool for communication by people who are locked in.

Simulations of material mixing in laser-driven reshock experiments

NASA Astrophysics Data System (ADS)

Haines, Brian M.; Grinstein, Fernando F.; Welser-Sherrill, Leslie; Fincke, James R.

2013-02-01

We perform simulations of a laser-driven reshock experiment [Welser-Sherrill et al., High Energy Density Phys. (unpublished)] in the strong-shock high energy-density regime to better understand material mixing driven by the Richtmyer-Meshkov instability. Validation of the simulations is based on direct comparison of simulation and radiographic data. Simulations are also compared with published direct numerical simulation and the theory of homogeneous isotropic turbulence. Despite the fact that the flow is neither homogeneous, isotropic nor fully turbulent, there are local regions in which the flow demonstrates characteristics of homogeneous isotropic turbulence. We identify and isolate these regions by the presence of high levels of turbulent kinetic energy (TKE) and vorticity. After reshock, our analysis shows characteristics consistent with those of incompressible isotropic turbulence. Self-similarity and effective Reynolds number assessments suggest that the results are reasonably converged at the finest resolution. Our results show that in shock-driven transitional flows, turbulent features such as self-similarity and isotropy only fully develop once de-correlation, characteristic vorticity distributions, and integrated TKE, have decayed significantly. Finally, we use three-dimensional simulation results to test the performance of two-dimensional Reynolds-averaged Navier-Stokes simulations. In this context, we also test a presumed probability density function turbulent mixing model extensively used in combustion applications.

Control of broadband optically generated ultrasound pulses using binary amplitude holograms.

PubMed

Brown, Michael D; Jaros, Jiri; Cox, Ben T; Treeby, Bradley E

2016-04-01

In this work, the use of binary amplitude holography is investigated as a mechanism to focus broadband acoustic pulses generated by high peak-power pulsed lasers. Two algorithms are described for the calculation of the binary holograms; one using ray-tracing, and one using an optimization based on direct binary search. It is shown using numerical simulations that when a binary amplitude hologram is excited by a train of laser pulses at its design frequency, the acoustic field can be focused at a pre-determined distribution of points, including single and multiple focal points, and line and square foci. The numerical results are validated by acoustic field measurements from binary amplitude holograms, excited by a high peak-power laser.

Microstructure evolution of a dissimilar junction interface between an Al sheet and a Ni-coated Cu sheet joined by magnetic pulse welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Itoi, Takaomi, E-mail: itoi@faculty.chiba-u.jp

An Al sheet and a Ni-coated Cu sheet were lap joined by using magnetic pulse welding (MPW). Tensile tests were performed on the joined sheets, and a good lap joint was achieved at a discharge energy of > 0.9 kJ. The weld interface exhibited a wavy morphology and an intermediate layer along the weld interface. Microstructure observations of the intermediate layer revealed that the Ni coating region consisted of a Ni–Al binary amorphous alloy and that the Al sheet region contained very fine Al nanograins. Ni fragments indicative of unmelted residual Ni from the coating were also observed in partsmore » of the intermediate layer. Formation of these features can be attributed to localize melting and a subsequent high rate cooling of molten Al and Ni confined to the interface during the MPW process. In the absence of an oxide film, atomic-scale bonding was also achieved between the intermediate layer and the sheet surfaces after the collision. MPW utilises impact energy, which affects the sheet surfaces. From the obtained results, good lap joint is attributed to an increased contact area, the anchor effect, work hardening, the absence of an oxide film, and suppressed formation of intermetallic compounds at the interface. - Highlights: •Good lap joint of an Al sheet and a Ni-coated Cu sheet was achieved by using magnetic pulse welding. •A Ni–Al binary amorphous alloy was formed as an intermediate layer at weld interface. •Atomic-scale bonding was achieved between the intermediate layer and the sheet surfaces.« less

Ostwald ripening of faceted Si particles in an Al-Si-Cu melt

DOE PAGES

Shahani, A. J.; Xiao, X.; Skinner, K.; ...

2016-07-04

The microstructural evolution of an Al-Si-Cu alloy during Ostwald ripening is imaged via synchrotron-based, four-dimensional (i.e., space and time resolved) X-ray tomography. Samples of composition Al-32 wt%Si-15 wt%Cu were annealed isothermally at 650 °C, in the two-phase solid-liquid regime, while tomographic projections were collected in situ over the course of five hours. Advances in experimental methods and computational approaches enable us to characterize the local interfacial curvatures and velocities during ripening. The sequence of three-dimensional reconstructions and interfacial shape distributions shows highly faceted Si particles in a copper-enriched liquid, that become increasingly isotropic or rounded over time. In addition, wemore » find that the coarsening rate constant is approximately the same in the binary and ternary systems. By coupling these experimental measurements with CALPHAD modeling and ab initio molecular dynamics simulation, we assess the influence of Cu on the coarsening process. Lastly, we find the unusual “pinning” of microstructure at the junction between rough and smooth interfaces and suggest a mechanism for this behavior.« less

Monsoon-Driven Biogeochemical Processes in the Arabian Sea

DTIC Science & Technology

2005-08-03

ffir Meereskunde, Universitat Kiel. Kumar, S. P., Madhupratap, M., Kumar, M. D., Muraleedharan , P. M., de Souza, S. N., Gauns, M., et al. (2001a). High...1638. Kumar, S. P., Ramaiah, N., Gauns, M., Sarma, V., Muraleedharan , P. M., Raghukumar, S., et al. (2001b). Physical forcing of biological

Crack-resistant Al2O3-SiO2 glasses.

PubMed

Rosales-Sosa, Gustavo A; Masuno, Atsunobu; Higo, Yuji; Inoue, Hiroyuki

2016-04-07

Obtaining "hard" and "crack-resistant" glasses have always been of great important in glass science and glass technology. However, in most commercial glasses both properties are not compatible. In this work, colorless and transparent xAl2O3-(100-x)SiO2 glasses (30 ≤ x ≤ 60) were fabricated by the aerodynamic levitation technique. The elastic moduli and Vickers hardness monotonically increased with an increase in the atomic packing density as the Al2O3 content increased. Although a higher atomic packing density generally enhances crack formation in conventional oxide glasses, the indentation cracking resistance increased by approximately seven times with an increase in atomic packing density in binary Al2O3-SiO2 glasses. In particular, the composition of 60Al2O3 • 40SiO2 glass, which is identical to that of mullite, has extraordinary high cracking resistance with high elastic moduli and Vickers hardness. The results indicate that there exist aluminosilicate compositions that can produce hard and damage-tolerant glasses.

Contributions of phase and structural transformations in multicomponent Al-Mg alloys to the linear and nonlinear mechanisms of anelasticity

NASA Astrophysics Data System (ADS)

Golovin, I. S.; Bychkov, A. S.; Mikhailovskaya, A. V.; Dobatkin, S. V.

2014-02-01

The effects of the processes of severe plastic deformation (SPD), recrystallization, and precipitation of the β phase in multicomponent alloys of the Al-5Mg-Mn-Cr and Al-(4-5%)Mg-Mn-Zn-Sc systems on the mechanisms of grain-boundary relaxation and dislocation-induced microplasticity have been studied in some detail. To stabilize the ultrafine-grained structure and prevent grain growth, dispersed Al-transition-metal particles, such as Al3Zr, Al6Mn, Al7Cr, Al6(Mn,Cr), Al18Cr2Mg3 have been used. We have special interest in alloys with additions of scandium, which forms compounds of the Al3Sc type and favors the precipitation of finer particles compared to the aluminides of other transition metals. After SPD, Al-(4-5%)Mg-Mn-Zr-Sc alloys exhibit an enhanced recrystallization temperature. The general features of the dislocation and grain-boundary anelasticity that have been established for the binary Al-Mg alloys are retained; i.e., (1) the decrease in the dislocation density in the process of recrystallization of cold-worked alloys leads to the formation of a pseudo-peak in the curves of the temperature dependences of internal friction (TDIF) and to a decrease in the critical amplitude of deformation corresponding to the onset of dislocation motion in a stress field; (2) the precipitation of the β phase suppresses the grain-boundary relaxation; (3) the dissolution of the β phase, the passage of the magnesium atoms into the solid solution, and the precipitation of the β' phase upon heating hinder the motion of dislocations; (4) the coarsening of the highly dispersed particles containing Zr and Sc increases the dislocation mobility. The grain-boundary relaxation and dislocation-impurity interaction and their temperature dependences, as well as processes of the additional alloying of the binary alloys by Mn, Cr, Zr, and Sc, have been estimated quantitatively.

Using Dopants to Tune Oxygen Vacancy Formation in Transition Metal Oxide Resistive Memory.

PubMed

Jiang, Hao; Stewart, Derek A

2017-05-17

Introducing dopants is an important way to tailor and improve electronic properties of transition metal oxides used as high-k dielectric thin films and resistance switching layers in leading memory technologies, such as dynamic and resistive random access memory (ReRAM). Ta 2 O 5 has recently received increasing interest because Ta 2 O 5 -based ReRAM demonstrates high switching speed, long endurance, and low operating voltage. However, advances in optimizing device characteristics with dopants have been hindered by limited and contradictory experiments in this field. We report on a systematic study on how various metal dopants affect oxygen vacancy formation in crystalline and amorphous Ta 2 O 5 from first principles. We find that isoelectronic dopants and weak n-type dopants have little impact on neutral vacancy formation energy and that p-type dopants can lower the formation energy significantly by introducing holes into the system. In contrast, n-type dopants have a deleterious effect and actually increase the formation energy for charged oxygen vacancies. Given the similar doping trend reported for other binary transition metal oxides, this doping trend should be universally valid for typical binary transition metal oxides. Based on this guideline, we propose that p-type dopants (Al, Hf, Zr, and Ti) can lower the forming/set voltage and improve retention properties of Ta 2 O 5 ReRAM.

Surface Segregation in Multicomponent Systems: Modeling of Surface Alloys and Alloy Surfaces

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John; Noebe, Ronald D.; Good, Brian; Honecy, Frank S.; Abel, Phillip

1999-01-01

The study of surface segregation, although of great technological importance, has been largely restricted to experimental work due to limitations associated with theoretical methods. However, recent improvements in both first-particle and semi-empirical methods are opening, the doors to an array of new possibilities for surface scientists. We apply one of these techniques, the Bozzolo, Ferrante and Smith (BFS) method for alloys, which is particularly suitable for complex systems, to several aspects of the computational modeling of surfaces and segregation, including alloy surface segregation, structure and composition of alloy surfaces, and the formation of surface alloys. We conclude with the study of complex NiAl-based binary, ternary and quaternary thin films (with Ti, Cr and Cu additions to NiAl). Differences and similarities between bulk and surface compositions are discussed, illustrated by the results of Monte Carlo simulations. For some binary and ternary cases, the theoretical predictions are compared to experimental results, highlighting the accuracy and value of this developing theoretical tool.

Density Measurements of Low Silica CaO-SiO2-Al2O3 Slags

NASA Astrophysics Data System (ADS)

Muhmood, Luckman; Seetharaman, Seshadri

2010-08-01

Density measurements of a low-silica CaO-SiO2-Al2O3 system were carried out using the Archimedes principle. A Pt 30 pct Rh bob and wire arrangement was used for this purpose. The results obtained were in good agreement with those obtained from the model developed in the current group as well as with other results reported earlier. The density for the CaO-SiO2 and the CaO-Al2O3 binary slag systems also was estimated from the ternary values. The extrapolation of density values for high-silica systems also showed good agreement with previous works. An estimation for the density value of CaO was made from the current experimental data. The density decrease at high temperatures was interpreted based on the silicate structure. As the mole percent of SiO2 was below the 33 pct required for the orthosilicate composition, discrete {text{SiO}}4^{4 - } tetrahedral units in the silicate melt would exist along with O2- ions. The change in melt expansivity may be attributed to the ionic expansions in the order of {text{Al}}^{ 3+ } - {text{O}}^{ 2- } < {text{Ca}}^{ 2+ } - {text{O}}^{ 2- } < {text{Ca}}^{ 2+ } - {text{O}}^{ - } Structural changes in the ternary slag also could be correlated to a drastic change in the value of enthalpy of mixing.

Kepler eclipsing binaries with δ Scuti components and tidally induced heartbeat stars

NASA Astrophysics Data System (ADS)

Guo, Zhao; Gies, Douglas R.; Matson, Rachel A.

δ Scuti stars are generally fast rotators and their pulsations are not in the asymptotic regime, so the interpretation of their pulsation spectra is a very difficult task. Binary stars, especially eclipsing systems, offer us the opportunity to constrain the space of fundamental stellar parameters. Firstly, we show the results of KIC9851944 and KIC4851217 as two case studies. We found the signature of the large frequency separation in the pulsational spectrum of both stars. The observed mean stellar density and the large frequency separation obey the linear relation in the log-log space as found by Suarez et al. (2014) and García Hernández et al. (2015). Second, we apply the simple `one-layer model' of Moreno & Koenigsberger (1999) to the prototype heartbeat star KOI-54. The model naturally reproduces the tidally induced high frequency oscillations and their frequencies are very close to the observed frequency at 90 and 91 times the orbital frequency.

A Pulsar and White Dwarf in an Unexpected Orbit

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-11-01

Astronomers have discovered a binary system consisting of a low-mass white dwarf and a millisecond pulsar but its eccentric orbit defies all expectations of how such binaries form.Observed orbital periods and binary eccentricities for binary millisecond pulsars. PSR J2234+0511 is the furthest right of the green stars that mark the five known eccentric systems. [Antoniadis et al. 2016]Unusual EccentricityIt would take a low-mass (0.4 solar masses) white dwarf over 100 billion years to form from the evolution of a single star. Since this is longer than the age of the universe, we believe that these lightweights are instead products of binary-star evolution and indeed, we observe many of these stars to still be in binary systems.But the binary evolution that can create a low-mass white dwarf includes a period of mass transfer, in which efficient tidal dissipation damps the systems orbital eccentricity. Because of this, we would expect all systems containing low-mass white dwarfs to have circular orbits.In the past, our observations of low-mass white dwarfmillisecond pulsar binaries have all been consistent with this expectation. But a new detection has thrown a wrench in the works: the unambiguous identification of a low-mass white dwarf thats in an eccentric (e=0.13) orbit with the millisecond pulsar PSR J2234+0511. How could this system have formed?Eliminating Formation ModelsLed by John Antoniadis (Dunlap Institute at University of Toronto), a team of scientists has used newly obtained optical photometry (from the Sloan Digital Sky Survey) and spectroscopy (from the Very Large Telescope in Chile) of the white dwarf to confirm the identification of this system.Antoniadis and collaborators then use measurements of the bodies masses (0.28 and 1.4 solar masses for the white dwarf and pulsar, respectively) and velocities, and constraints on the white dwarfs temperature, radius and surface gravity, to address three proposed models for the formation of this system.The 3D motion of the pulsar (black solid lines; current position marked with diamond) in our galaxy over the past 1.5 Gyr. This motion is typical for low-mass X-ray binary descendants, favoring a binary-evolution model over a 3-body-interaction model. [Antoniadis et al. 2016]In the first model, the eccentric binary was created via adynamic three-body formation channel. This possibility is deemed unlikely, as the white-dwarf properties and all the kinematic properties of the system point to normal binary evolution.In the secondmodel, the binary system gains its high eccentricity after mass transfer ends, when the pulsar progenitor experiences a spontaneous phase transition. The authors explore two options for this: one in which the neutron star implodes into a strange-quark star, and the other in which an over-massive white dwarf suffers a delayed collapse into a neutron star. Both cases are deemed unlikely, because the mass inferred for the pulsar progenitor is not consistent with either model.In the third model, the system forms a circumbinary disk fueled by material escaping the proto-white dwarf. After mass transfer has ended, interactions between the binary and its disk gradually increase the eccentricity of the system, pumping it up to what we observe today. All of the properties of the system measured by Antoniadis and collaborators are thus far consistent with this model.Further observations of this system and systems like it (several others have been detected, though not yet confirmed) will help determine whether binary evolution combined with interactions with a disk can indeed explain the formation of this unexpectedly eccentricsystem.CitationJohn Antoniadis et al 2016 ApJ 830 36. doi:10.3847/0004-637X/830/1/36

Surface and interface engineering of anatase TiO2 anode for sodium-ion batteries through Al2O3 surface modification and wise electrolyte selection

NASA Astrophysics Data System (ADS)

Li, Tao; Gulzar, Umair; Bai, Xue; Monaco, Simone; Longoni, Gianluca; Prato, Mirko; Marras, Sergio; Dang, Zhiya; Capiglia, Claudio; Proietti Zaccaria, Remo

2018-04-01

In the present study, Al2O3 is utilized for the first time as coating agent on nanostructured anatase TiO2 in order to investigate its effect on sodium-ion batteries performance. Our results show that the Al2O3 coating, introduced by a facile two-step approach, provides beneficial effects to the TiO2-based anodes. However, the coated TiO2 still suffers of capacity fading upon cycling when using 1.0 M of NaClO4 in propylene carbonate (PC) as electrolyte. To address this issue, the influence of different electrolytes (NaClO4 salt in various solvents) is further studied. It is found that the modified TiO2 exhibits significant improvements in cycling performance using binary ethylene carbonate (EC) and PC solvent mixture without the need of the commonly used fluoroethylene carbonate (FEC) additive. Under the best configuration, our battery could deliver a high reversible capacity of 188.1 mAh g-1 at 0.1C after 50 cycles, good rate capability up to 5C, and remarkable long-term cycling stability at 1C rate for 650 cycles. This excellent performance can be ascribed to the synergistic effects of surface and interface engineering enabling the formation of a stable and highly ionic conductive interface layer in EC:PC based electrolyte which combines the native SEI film and an 'artificial' SEI layer of irreversibly formed Na-Al-O.

Numerically Simulating Collisions of Plastic and Foam Laser-Driven Foils

NASA Astrophysics Data System (ADS)

Zalesak, S. T.; Velikovich, A. L.; Schmitt, A. J.; Aglitskiy, Y.; Metzler, N.

2007-11-01

Interest in experiments on colliding planar foils has recently been stimulated by (a) the Impact Fast Ignition approach to laser fusion [1], and (b) the approach to a high-repetition rate ignition facility based on direct drive with the KrF laser [2]. Simulating the evolution of perturbations to such foils can be a numerical challenge, especially if the initial perturbation amplitudes are small. We discuss the numerical issues involved in such simulations, describe their benchmarking against recently-developed analytic results, and present simulations of such experiments on NRL's Nike laser. [1] M. Murakami et al., Nucl. Fusion 46, 99 (2006) [2] S. P. Obenschain et al., Phys. Plasmas 13, 056320 (2006).

The Effect of Impurities on the Processing of Aluminum Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zi-Kui Liu; Shengjun Zhang; Qingyou Han

2007-04-23

For this Aluminum Industry of the Future (IOF) project, the effect of impurities on the processing of aluminum alloys was systematically investigated. The work was carried out as a collaborative effort between the Pennsylvania State University and Oak Ridge National Laboratory. Industrial support was provided by ALCOA and ThermoCalc, Inc. The achievements described below were made. A method that combines first-principles calculation and calculation of phase diagrams (CALPHAD) was used to develop the multicomponent database Al-Ca-K-Li-Mg-Na. This method was extensively used in this project for the development of a thermodynamic database. The first-principles approach provided some thermodynamic property data thatmore » are not available in the open literature. These calculated results were used in the thermodynamic modeling as experimental data. Some of the thermodynamic property data are difficult, if not impossible, to measure. The method developed and used in this project allows the estimation of these data for thermodynamic database development. The multicomponent database Al-Ca-K-Li-Mg-Na was developed. Elements such as Ca, Li, Na, and K are impurities that strongly affect the formability and corrosion behavior of aluminum alloys. However, these impurity elements are not included in the commercial aluminum alloy database. The process of thermodynamic modeling began from Al-Na, Ca-Li, Li-Na, K-Na, and Li-K sub-binary systems. Then ternary and higher systems were extrapolated because of the lack of experimental information. Databases for five binary alloy systems and two ternary systems were developed. Along with other existing binary and ternary databases, the full database of the multicomponent Al-Ca-K-Li-Mg-Na system was completed in this project. The methodology in integrating with commercial or other aluminum alloy databases can be developed. The mechanism of sodium-induced high-temperature embrittlement (HTE) of Al-Mg is now understood. Using the thermodynamic database developed in this project, thermodynamic simulations were carried out to investigate the effect of sodium on the HTE of Al-Mg alloys. The simulation results indicated that the liquid miscibility gap resulting from the dissolved sodium in the molten material plays an important role in HTE. A liquid phase forms from the solid face-centered cubic (fcc) phase (most likely at grain boundaries) during cooling, resulting in the occurrence of HTE. Comparison of the thermodynamic simulation results with experimental measurements on the high-temperature ductility of an Al-5Mg-Na alloy shows that HTE occurs in the temperature range at which the liquid phase exists. Based on this fundamental understanding of the HTE mechanism during processing of aluminum alloy, an HTE sensitive zone and a hot-rolling safe zone of the Al-Mg-Na alloys are defined as functions of processing temperature and alloy composition. The tendency of HTE was evaluated based on thermodynamic simulations of the fraction of the intergranular sodium-rich liquid phase. Methods of avoiding HTE during rolling/extrusion of Al-Mg-based alloys were suggested. Energy and environmental benefits from the results of this project could occur through a number of avenues: (1) energy benefits accruing from reduced rejection rates of the aluminum sheet and bar, (2) reduced dross formation during the remelting of the aluminum rejects, and (3) reduced CO2 emission related to the energy savings. The sheet and extruded bar quantities produced in the United States during 2000 were 10,822 and 4,546 million pounds, respectively. It is assumed that 50% of the sheet and 10% of the bar will be affected by implementing the results of this project. With the current process, the rejection rate of sheet and bar is estimated at 5%. Assuming that at least half of the 5% rejection of sheet and bar will be eliminated by using the results of this project and that 4% of the aluminum will be lost through dross (Al2O3) during remelting of the rejects, the full-scale industrial implementation of the project results would lead to energy savings in excess of 6.2 trillion Btu/year and cost savings of $42.7 million by 2020.« less

VizieR Online Data Catalog: Stellar rotation in h Per (Moraux+, 2013)

NASA Astrophysics Data System (ADS)

Moraux, E.; Artemenko, S.; Bouvier, J.; Irwin, J.; Ibrahimov, M.; Magakian, T.; Grankin, K.; Nikogossian, E.; Cardoso, C.; Hodgkin, S.; Aigrain, S.; Movsessian, T. A.

2013-10-01

List of periodic objects ordered by periodogram peak power. The binary flag is set to 2 if the object has been identified as a binary in the i'CFHT, i'CFHT-K CMD and to 1 otherwise. The V and IC magnitudes as well as the membership flag (column before last) are from Currie et al. (2010, Cat. J/ApJS/186/191). The near infrared photometry has been obtained with WIRCam at CFHT and is from Cardoso et al. (in prep.). The last column indicates whether the object has been detected in Hα (Currie et al., 2007, Cat. J/ApJ/659/599) and/or in X-rays (Currie et al., 2009, Cat. J/AJ/137/3210; C. Argiroffi, priv. com). (1 data file).

Actuation and transduction of resonant vibrations in GaAs/AlGaAs-based nanoelectromechanical systems containing two-dimensional electron gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shevyrin, A. A., E-mail: shevandrey@isp.nsc.ru; Pogosov, A. G.; Bakarov, A. K.

2015-05-04

Driven vibrations of a nanoelectromechanical system based on GaAs/AlGaAs heterostructure containing two-dimensional electron gas are experimentally investigated. The system represents a conductive cantilever with the free end surrounded by a side gate. We show that out-of-plane flexural vibrations of the cantilever are driven when alternating signal biased by a dc voltage is applied to the in-plane side gate. We demonstrate that these vibrations can be on-chip linearly transduced into a low-frequency electrical signal using the heterodyne down-mixing method. The obtained data indicate that the dominant physical mechanism of the vibrations actuation is capacitive interaction between the cantilever and the gate.

Density and refractive index data of binary and ternary mixtures of imidazolium-based ionic liquids, n-hexane and organic compounds involved in the kinetic resolution of rac-2-pentanol.

PubMed

Montalbán, Mercedes G; Collado-González, Mar; Lozano-Pérez, A Abel; Baños, F Guillermo Díaz; Víllora, Gloria

2018-08-01

This data article is related to the subject of the research article "Extraction of Organic Compounds Involved in the Kinetic Resolution of rac-2-Pentanol from n-Hexane by Imidazolium-based Ionic Liquids: Liquid-Liquid Equilibrium" (Montalbán et al., 2018) [1]. It contains experimental data of density and refractive index of binary and ternary mixtures of imidazolium-based ionic liquids, n -hexane and organic compounds involved in the kinetic resolution of rac -2-pentanol ( rac -2-pentanol, vinyl butyrate, rac -2-pentyl butyrate or butyric acid) measured at 303.15 K and 1 atm. These data are presented as calibration curves which help to determine the composition of the ionic liquid-rich phase knowing its density or refractive index.

A DATA-DRIVEN MODEL FOR SPECTRA: FINDING DOUBLE REDSHIFTS IN THE SLOAN DIGITAL SKY SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsalmantza, P.; Hogg, David W., E-mail: vivitsal@mpia.de

2012-07-10

We present a data-driven method-heteroscedastic matrix factorization, a kind of probabilistic factor analysis-for modeling or performing dimensionality reduction on observed spectra or other high-dimensional data with known but non-uniform observational uncertainties. The method uses an iterative inverse-variance-weighted least-squares minimization procedure to generate a best set of basis functions. The method is similar to principal components analysis (PCA), but with the substantial advantage that it uses measurement uncertainties in a responsible way and accounts naturally for poorly measured and missing data; it models the variance in the noise-deconvolved data space. A regularization can be applied, in the form of a smoothnessmore » prior (inspired by Gaussian processes) or a non-negative constraint, without making the method prohibitively slow. Because the method optimizes a justified scalar (related to the likelihood), the basis provides a better fit to the data in a probabilistic sense than any PCA basis. We test the method on Sloan Digital Sky Survey (SDSS) spectra, concentrating on spectra known to contain two redshift components: these are spectra of gravitational lens candidates and massive black hole binaries. We apply a hypothesis test to compare one-redshift and two-redshift models for these spectra, utilizing the data-driven model trained on a random subset of all SDSS spectra. This test confirms 129 of the 131 lens candidates in our sample and all of the known binary candidates, and turns up very few false positives.« less

The Orion Bullets: New GEMS MCAO images

NASA Astrophysics Data System (ADS)

Ginsburg, Adam; Bally, John; Youngblood, Allison

2013-07-01

The Orion A molecular cloud (OMC1) is the nearest site of massive star formation at a distance of 414 pc. The BN/KL region within it contains signs of a massive explosion triggered 500 years ago by decay of a non- hierarchical multiple system of massive stars. We present observations of the OMC1 core at high spatial resolution (<0.1") in narrow-band [Fe II] 1.64um and H2 S(1) 1-0 2.12um filters. The new data reveal compact (0.1" to 0.5") knots with unique excitation and chemical properties, unveiling new details about the three-dimensional structure of the explosion. Bright H2 emission from these compact, high proper-motion knots and compact [Fe II] features are consistent with scenario proposed by Bally et al. (2011) in which they are interpreted to be high density (n > 10^8 cm^{-3}) disk fragments launched from within a few AU of a massive star by a > three-body dynamical interaction that led to the ejection of the BN objects and the formation of a compact (separation < few AU) binary, most likely radio source I. The proper motions are as high as 400 km/s, hinting at the enormous energy unleashed in the explosion. The data also unveiled a population of obscured close binary systems. This new population will allow a comparison of embedded young binary systems with the older, un-obscured, visual binary population to test models of the evolution of multiplicity statistics in the Orion Nebula Cluster.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hora, H.; Korn, G.; Eliezer, S.

Measured highly elevated gains of proton–boron (HB11) fusion (Picciottoet al., Phys. Rev. X4, 031030 (2014)) confirmed the exceptional avalanche reaction process (Lalousiset al., Laser Part. Beams 32, 409 (2014); Horaet al., Laser Part. Beams33, 607 (2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh accelerationabovemore » $$10^{20}~\\text{cm}~\\text{s}^{-2}$$ for plasma blocks was theoretically and numerically predicted since 1978 (Hora,Physics of Laser Driven Plasmas(Wiley, 1981), pp. 178 and 179) and measured (Sauerbrey, Phys. Plasmas3, 4712 (1996)) in exact agreement (Horaet al., Phys. Plasmas14, 072701 (2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell’s stress tensor by the dielectric properties of plasma leading to the nonlinear (ponderomotive) force $$f_{\\text{NL}}$$ resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. Finally, this is supported also by other experiments with very high HB11 reactions under different conditions (Labauneet al., Nature Commun.4, 2506 (2013)).« less

Cognitive Effects of Mindfulness Training: Results of a Pilot Study Based on a Theory Driven Approach

PubMed Central

Wimmer, Lena; Bellingrath, Silja; von Stockhausen, Lisa

2016-01-01

The present paper reports a pilot study which tested cognitive effects of mindfulness practice in a theory-driven approach. Thirty-four fifth graders received either a mindfulness training which was based on the mindfulness-based stress reduction approach (experimental group), a concentration training (active control group), or no treatment (passive control group). Based on the operational definition of mindfulness by Bishop et al. (2004), effects on sustained attention, cognitive flexibility, cognitive inhibition, and data-driven as opposed to schema-based information processing were predicted. These abilities were assessed in a pre-post design by means of a vigilance test, a reversible figures test, the Wisconsin Card Sorting Test, a Stroop test, a visual search task, and a recognition task of prototypical faces. Results suggest that the mindfulness training specifically improved cognitive inhibition and data-driven information processing. PMID:27462287

Cognitive Effects of Mindfulness Training: Results of a Pilot Study Based on a Theory Driven Approach.

PubMed

Wimmer, Lena; Bellingrath, Silja; von Stockhausen, Lisa

2016-01-01

The present paper reports a pilot study which tested cognitive effects of mindfulness practice in a theory-driven approach. Thirty-four fifth graders received either a mindfulness training which was based on the mindfulness-based stress reduction approach (experimental group), a concentration training (active control group), or no treatment (passive control group). Based on the operational definition of mindfulness by Bishop et al. (2004), effects on sustained attention, cognitive flexibility, cognitive inhibition, and data-driven as opposed to schema-based information processing were predicted. These abilities were assessed in a pre-post design by means of a vigilance test, a reversible figures test, the Wisconsin Card Sorting Test, a Stroop test, a visual search task, and a recognition task of prototypical faces. Results suggest that the mindfulness training specifically improved cognitive inhibition and data-driven information processing.

GenAlEx 6.5: genetic analysis in Excel. Population genetic software for teaching and research--an update.

PubMed

Peakall, Rod; Smouse, Peter E

2012-10-01

GenAlEx: Genetic Analysis in Excel is a cross-platform package for population genetic analyses that runs within Microsoft Excel. GenAlEx offers analysis of diploid codominant, haploid and binary genetic loci and DNA sequences. Both frequency-based (F-statistics, heterozygosity, HWE, population assignment, relatedness) and distance-based (AMOVA, PCoA, Mantel tests, multivariate spatial autocorrelation) analyses are provided. New features include calculation of new estimators of population structure: G'(ST), G''(ST), Jost's D(est) and F'(ST) through AMOVA, Shannon Information analysis, linkage disequilibrium analysis for biallelic data and novel heterogeneity tests for spatial autocorrelation analysis. Export to more than 30 other data formats is provided. Teaching tutorials and expanded step-by-step output options are included. The comprehensive guide has been fully revised. GenAlEx is written in VBA and provided as a Microsoft Excel Add-in (compatible with Excel 2003, 2007, 2010 on PC; Excel 2004, 2011 on Macintosh). GenAlEx, and supporting documentation and tutorials are freely available at: http://biology.anu.edu.au/GenAlEx. rod.peakall@anu.edu.au.

TX Cnc AS A MEMBER OF THE PRAESEPE OPEN CLUSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, X. B.; Deng, L.; Lu, P.

2009-08-15

We present B-, V-, and I-band CCD photometry of the W UMa-type binary system TX Cnc, which is a member star of the Praesepe open cluster. Based on the observations, new ephemeris and a revised photometric solution of the binary system were derived. Combined with the results of the radial velocity solution contributed by Pribulla et al., the absolute parameters of the system were determined. The mass, radius, and luminosity of the primary component are derived to be 1.35 {+-} 0.02 M {sub sun}, 1.27 {+-} 0.04 R {sub sun}, and 2.13 {+-} 0.11 L {sub sun}. Those for themore » secondary star are computed as 0.61 {+-} 0.01 M {sub sun}, 0.89 {+-} 0.03 R {sub sun}, and 1.26 {+-} 0.07 L {sub sun}, respectively. Based on these results, a distance modulus of (m - M) {sub V} = 6.34 {+-} 0.05 is determined for the star. It confirms the membership of TX Cnc to the Praesepe open cluster. The evolutionary status and the physical nature of the binary system are discussed compared with the theoretical model.« less

Achievable Information Rates for Coded Modulation With Hard Decision Decoding for Coherent Fiber-Optic Systems

NASA Astrophysics Data System (ADS)

Sheikh, Alireza; Amat, Alexandre Graell i.; Liva, Gianluigi

2017-12-01

We analyze the achievable information rates (AIRs) for coded modulation schemes with QAM constellations with both bit-wise and symbol-wise decoders, corresponding to the case where a binary code is used in combination with a higher-order modulation using the bit-interleaved coded modulation (BICM) paradigm and to the case where a nonbinary code over a field matched to the constellation size is used, respectively. In particular, we consider hard decision decoding, which is the preferable option for fiber-optic communication systems where decoding complexity is a concern. Recently, Liga \\emph{et al.} analyzed the AIRs for bit-wise and symbol-wise decoders considering what the authors called \\emph{hard decision decoder} which, however, exploits \\emph{soft information} of the transition probabilities of discrete-input discrete-output channel resulting from the hard detection. As such, the complexity of the decoder is essentially the same as the complexity of a soft decision decoder. In this paper, we analyze instead the AIRs for the standard hard decision decoder, commonly used in practice, where the decoding is based on the Hamming distance metric. We show that if standard hard decision decoding is used, bit-wise decoders yield significantly higher AIRs than symbol-wise decoders. As a result, contrary to the conclusion by Liga \\emph{et al.}, binary decoders together with the BICM paradigm are preferable for spectrally-efficient fiber-optic systems. We also design binary and nonbinary staircase codes and show that, in agreement with the AIRs, binary codes yield better performance.

Performance of iron-chromium-aluminum alloy surface coatings on Zircaloy 2 under high-temperature steam and normal BWR operating conditions

NASA Astrophysics Data System (ADS)

Zhong, Weicheng; Mouche, Peter A.; Han, Xiaochun; Heuser, Brent J.; Mandapaka, Kiran K.; Was, Gary S.

2016-03-01

Iron-chromium-aluminum (FeCrAl) coatings deposited on Zircaloy 2 (Zy2) and yttria-stabilized zirconia (YSZ) by magnetron sputtering have been tested with respect to oxidation weight gain in high-temperature steam. In addition, autoclave testing of FeCrAl-coated Zy2 coupons under pressure-temperature-dissolved oxygen coolant conditions representative of a boiling water reactor (BWR) environment has been performed. Four different FeCrAl compositions have been tested in 700 °C steam; compositions that promote alumina formation inhibited oxidation of the underlying Zy2. Parabolic growth kinetics of alumina on FeCrAl-coated Zy2 is quantified via elemental depth profiling. Autoclave testing under normal BWR operating conditions (288 °C, 9.5 MPa with normal water chemistry) up to 20 days demonstrates observable weight gain over uncoated Zy2 simultaneously exposed to the same environment. However, no FeCrAl film degradation was observed. The 900 °C eutectic in binary Fe-Zr is addressed with the FeCrAl-YSZ system.

On the accuracy of the interdiffusion coefficient measurements of high-temperature binary mixtures under ISS conditions

NASA Astrophysics Data System (ADS)

Saez, Núria; Ruiz, Xavier; Pallarés, Jordi; Shevtsova, Valentina

2013-04-01

An accelerometric record from the IVIDIL experiment (ESA Columbus module) has exhaustively been studied. The analysis involved the determination of basic statistical properties as, for instance, the auto-correlation and the power spectrum (second-order statistical analyses). Also, and taking into account the shape of the associated histograms, we address another important question, the non-Gaussian nature of the time series using the bispectrum and the bicoherence of the signals. Extrapolating the above-mentioned results, a computational model of a high-temperature shear cell has been performed. A scalar indicator has been used to quantify the accuracy of the diffusion coefficient measurements in the case of binary mixtures involving photovoltaic silicon or liquid Al-Cu binary alloys. Three different initial arrangements have been considered, the so-called interdiffusion, centred thick layer and the lateral thick layer. Results allow us to conclude that, under the conditions of the present work, the diffusion coefficient is insensitive to the environmental conditions, that is to say, accelerometric disturbances and initial shear cell arrangement.

Structure of high alumina content Al2O3-SiO2 composition glasses.

PubMed

Weber, Richard; Sen, Sabyasachi; Youngman, Randall E; Hart, Robert T; Benmore, Chris J

2008-12-25

The structure of binary aluminosilicate glasses containing 60-67 mol % Al2O3 were investigated using high-resolution 27Al NMR and X-ray and neutron diffraction. The glasses were made by aerodynamic levitation of molten oxides. The 67% alumina composition required a cooling rate of approximately 1600 degrees C s(1-) to form glass from submillimeter sized samples. NMR results show that the glasses contain aluminum in 4-, 5-, and 6-fold coordination in the approximate ratio 4:5:1. The average Al coordination increases from 4.57 to 4.73 as the fraction of octahedral Al increases with alumina content. The diffraction results on the 67% composition are consistent with a disordered Al framework with Al ions in a range of coordination environments that are substantially different from those found in the equilibrium crystalline phases. Analysis of the neutron and X-ray structure factors yields an average bond angle of 125 +/- 4 degrees between an Al ion and the adjoining cation via a bridging oxygen. We propose that the structure of the glass is a "transition state" between the alumina-rich liquid and the equilibrium mullite phase that are dominated by 4- and 6-coordinated aluminum ions, respectively.

Local Multi-Grouped Binary Descriptor With Ring-Based Pooling Configuration and Optimization.

PubMed

Gao, Yongqiang; Huang, Weilin; Qiao, Yu

2015-12-01

Local binary descriptors are attracting increasingly attention due to their great advantages in computational speed, which are able to achieve real-time performance in numerous image/vision applications. Various methods have been proposed to learn data-dependent binary descriptors. However, most existing binary descriptors aim overly at computational simplicity at the expense of significant information loss which causes ambiguity in similarity measure using Hamming distance. In this paper, by considering multiple features might share complementary information, we present a novel local binary descriptor, referred as ring-based multi-grouped descriptor (RMGD), to successfully bridge the performance gap between current binary and floated-point descriptors. Our contributions are twofold. First, we introduce a new pooling configuration based on spatial ring-region sampling, allowing for involving binary tests on the full set of pairwise regions with different shapes, scales, and distances. This leads to a more meaningful description than the existing methods which normally apply a limited set of pooling configurations. Then, an extended Adaboost is proposed for an efficient bit selection by emphasizing high variance and low correlation, achieving a highly compact representation. Second, the RMGD is computed from multiple image properties where binary strings are extracted. We cast multi-grouped features integration as rankSVM or sparse support vector machine learning problem, so that different features can compensate strongly for each other, which is the key to discriminativeness and robustness. The performance of the RMGD was evaluated on a number of publicly available benchmarks, where the RMGD outperforms the state-of-the-art binary descriptors significantly.

Glass formation, ionic conductivity, and conductivity/viscosity decoupling, in LiAlCl{sub 4} + LiClO{sub 4} and LiAlCl{sub 4} + LiAlCl{sub 3}{center_dot}imide solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Videa, M.; Angeli, C.A.

As part of a search for chemically and electrochemically stable ambient temperature molten lithium salt systems the authors have investigated the properties of solutions of LiAlCl{sub 4} with various second components. In this paper they review the factors which determine the ambient temperature conductivity and report results for two systems, one of which satisfies the stability requirements although failing to provide the high conductivities which are needed for a successful ambient temperature Li battery electrolyte. These ionic solutions appear to be very fragile liquids. Evidence is found for a mixing incompatibility of polarizable and nonpolarizable components of binary melts.

The `Henry Problem' of `density-driven' groundwater flow versus Tothian `groundwater flow systems' with variable density: A review of the influential Biscayne aquifer data.

NASA Astrophysics Data System (ADS)

Weyer, K. U.

2017-12-01

Coastal groundwater flow investigations at the Biscayne Bay, south of Miami, Florida, gave rise to the concept of density-driven flow of seawater into coastal aquifers creating a saltwater wedge. Within that wedge, convection-driven return flow of seawater and a dispersion zone were assumed by Cooper et al. (1964) to be the cause of the Biscayne aquifer `sea water wedge'. This conclusion was based on the chloride distribution within the aquifer and on an analytical model concept assuming convection flow within a confined aquifer without taking non-chemical field data into consideration. This concept was later labelled the `Henry Problem', which any numerical variable density flow program must be able to simulate to be considered acceptable. Both, `density-driven flow' and Tothian `groundwater flow systems' (with or without variable density conditions) are driven by gravitation. The difference between the two are the boundary conditions. 'Density-driven flow' occurs under hydrostatic boundary conditions while Tothian `groundwater flow systems' occur under hydrodynamic boundary conditions. Revisiting the Cooper et al. (1964) publication with its record of piezometric field data (heads) showed that the so-called sea water wedge has been caused by discharging deep saline groundwater driven by gravitational flow and not by denser sea water. Density driven flow of seawater into the aquifer was not found reflected in the head measurements for low and high tide conditions which had been taken contemporaneously with the chloride measurements. These head measurements had not been included in the flow interpretation. The very same head measurements indicated a clear dividing line between shallow local fresh groundwater flow and saline deep groundwater flow without the existence of a dispersion zone or a convection cell. The Biscayne situation emphasizes the need for any chemical interpretation of flow pattern to be supported by head data as energy indicators of flow fields. At the Biscayne site density-driven flow of seawater did and does not exist. Instead this site and the Florida coast line in general are the end points of local fresh and regional saline groundwater flow systems driven by gravity forces and not by density differences.

Wide binaries in Tycho-Gaia II: metallicities, abundances and prospects for chemical tagging

NASA Astrophysics Data System (ADS)

Andrews, Jeff J.; Chanamé, Julio; Agüeros, Marcel A.

2018-02-01

From our recent catalogue based on the first Gaia data release (TGAS), we select wide binaries in which both stars have been observed by the Radial Velocity Experiment (RAVE) or the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Using RAVE and LAMOST metallicities and RAVE Mg, Al, Si, Ti and Fe abundances, we find that the differences in the metallicities and elemental abundances of components of wide binaries are consistent with being due to observational uncertainties, in agreement with previous results for smaller and more restricted samples. The metallicity and elemental abundance consistency between wide binary components presented in this work confirms their common origin and bolsters the status of wide binaries as 'mini-open clusters'. Furthermore, this is evident that wide binaries are effectively co-eval and co-chemical, supporting their use for, e.g. constraining age-activity-rotation relations, the initial-final mass relation for white dwarfs and M-dwarf metallicity indicators. Additionally, we demonstrate that the common proper motion, common parallax pairs in TGAS with the most extreme separations (s ≳ 0.1 pc) typically have inconsistent metallicities, radial velocities or both and are therefore likely to be predominantly comprised of random alignments of unassociated stars with similar astrometry, in agreement with our previous results. Finally, we propose that wide binaries form an ideal data set with which we can test chemical tagging as a method to identify stars of common origin, particularly because the stars in wide binaries span a wide range of metallicities, much wider than that spanned by nearby open clusters.

Frontal lobe function and behavioral changes in amyotrophic lateral sclerosis: a study from Southwest China.

PubMed

Wei, QianQian; Chen, XuePing; Zheng, ZhenZhen; Huang, Rui; Guo, XiaoYan; Cao, Bei; Zhao, Bi; Shang, Hui-Fang

2014-12-01

Despite growing interest, the frequency and characteristics of frontal lobe functional and behavioral deficits in Chinese people with amyotrophic lateral sclerosis (ALS), as well as their impact on the survival of ALS patients, remain unknown. The Chinese version of the frontal assessment battery (FAB) and frontal behavioral inventory (FBI) were used to evaluate 126 sporadic ALS patients and 50 healthy controls. The prevalence of frontal lobe dysfunction was 32.5%. The most notable impairment domain of the FAB was lexical fluency (30.7%). The binary logistic regression model revealed that an onset age older than 45 years (OR 5.976, P = 0.002) and a lower educational level (OR 0.858, P = 0.002) were potential determinants of an abnormal FAB. Based on the FBI score, 46.0% of patients showed varied degrees of frontal behavioral changes. The most common impaired neurobehavioral domains were irritability (25.4%), logopenia (20.6%) and apathy (19.0%). The binary logistic regression model revealed that the ALS Functional Rating Scale-Revised scale score (OR 0.127, P = 0.001) was a potential determinant of an abnormal FBI. Frontal functional impairment and the severity of frontal behavioral changes were not associated with the survival status or the progression of ALS by the cox proportional hazard model and multivariate regression analyses, respectively. Frontal lobe dysfunction and frontal behavioral changes are common in Chinese ALS patients. Frontal lobe dysfunction may be related to the onset age and educational level. The severity of frontal behavioral changes may be associated with the ALSFRS-R. However, the frontal functional impairment and the frontal behavioral changes do not worsen the progression or survival of ALS.

Explosively Driven Particle Fields Imaged Using a High-Speed Framing Camera and Particle Image Velocimetry

DTIC Science & Technology

2011-08-01

inert steel particles and by Frost et al. (2005, 2007) with reactive aluminum and magnesium particles. All used sensitized nitromethane and were...particles in a spherical or cylindrical charge case was used with sensitized nitromethane . Frost et al. (2002), determined that for a given charge

The Spot Variability and Related Brightness variations of the Solar Type PreContact W UMa Binary System V1001 Cas

NASA Astrophysics Data System (ADS)

Samec, Ronald George; Koenke, Sam S.; Faulkner, Danny R.

2015-08-01

A new classification of eclipsing binary has emerged, Pre Contact WUMa Binaries (PCWB’s, Samec et al. 2012). These solar-type systems are usually detached or semidetached with one or both components under filling their critical Roche lobes. They usually have EA or EB-type light curves (unequal eclipse depths, indicating components with substantially different temperatures). The accepted scenario for these W UMa binaries is that they are undergoing steady but slow angular momentum losses due to magnetic braking as stellar winds blow radially away on stiff bipolar field lines. These binaries are believed to come into stable contact and eventually coalesce into blue straggler type, single, fast rotating A-type stars (Guinan and Bradstreet,1988). High precision 2012 and 2009 light curves are compared for the very short period (~0.43d) Precontact W UMa Binary (PCWB), V1001 Cassiopeia. This is the shortest period PCWB found so far. Its short period, similar to the majority of W UMa’s, in contrast to its distinct Algol-type light curve, make it a very rare and interesting system. Our solutions of light curves separated by some three years give approximately the same physical parameters. However the spots radically change, in temperature, area and position causing a distinctive variation in the shape of the light curves. We conclude that spots are very active on this solar type dwarf system and that it may mimic its larger cousins, the RS CVn binaries.

Binary Star Orbits. 4. Orbits of 18 Southern Interferometric Pairs

DTIC Science & Technology

2010-09-01

Horch et al. 2010; Balega et al. 2007; Docobo et al. 2008; Hartkopf & Mason 2009; McAlister et al. 1996; Prieur et al. 2009), their southern...Kubat, J. 1997, A&A, 322, 565 Horch , E. P., Falta, D., Anderson, L. M., DeSousa, M. D., Miniter, C. M., Ahmed, T., & van Altena, W. F. 2010, AJ, 139, 205

al3c: high-performance software for parameter inference using Approximate Bayesian Computation.

PubMed

Stram, Alexander H; Marjoram, Paul; Chen, Gary K

2015-11-01

The development of Approximate Bayesian Computation (ABC) algorithms for parameter inference which are both computationally efficient and scalable in parallel computing environments is an important area of research. Monte Carlo rejection sampling, a fundamental component of ABC algorithms, is trivial to distribute over multiple processors but is inherently inefficient. While development of algorithms such as ABC Sequential Monte Carlo (ABC-SMC) help address the inherent inefficiencies of rejection sampling, such approaches are not as easily scaled on multiple processors. As a result, current Bayesian inference software offerings that use ABC-SMC lack the ability to scale in parallel computing environments. We present al3c, a C++ framework for implementing ABC-SMC in parallel. By requiring only that users define essential functions such as the simulation model and prior distribution function, al3c abstracts the user from both the complexities of parallel programming and the details of the ABC-SMC algorithm. By using the al3c framework, the user is able to scale the ABC-SMC algorithm in parallel computing environments for his or her specific application, with minimal programming overhead. al3c is offered as a static binary for Linux and OS-X computing environments. The user completes an XML configuration file and C++ plug-in template for the specific application, which are used by al3c to obtain the desired results. Users can download the static binaries, source code, reference documentation and examples (including those in this article) by visiting https://github.com/ahstram/al3c. astram@usc.edu Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Resolving the structure and properties of τ1-Cr-Ni-Al for high temperature protective applications

NASA Astrophysics Data System (ADS)

Simonson, J. W.; Nicasio, J. E.; Ilyas, H.; Pabla, J.; Horvat, K.; Misuraca, J. C.

Increasing the temperature of the steam in turbine power plants enhances thermal efficiency while reducing CO2 emissions. Exposed steel components, however, must be coated to withstand the harsh environments present in next-generation advanced ultra-supercritical plants. Proposed coating materials must exhibit low density, high hardness, high toughness, excellent oxidation resistance, and low thermal conductivity. With an eye towards satisfying this diverse array of requirements, we report the properties of the so-called τ1 phase of Cr-Ni-Al. We resolve the previously controversial composition and crystal structure of this material. The complex structure is composed of distorted icosahedra and octahedra of Al, with nearest-neighbor transition metal-Al bond lengths as short as 2.4 Å, far shorter than typical distances in Ni-Al and Cr-Al binaries. Accordingly, Vickers hardness is 6 . 88 +/- 0 . 13 GPa, as hard as extra-high-hardness armor plating at only 45% the density. We discuss these properties in light of the result of transport and oxidation resistance measurements. The apparent dependencies of these properties on crystal structure suggests new criteria for materials research. Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund, for support of this research under contract 56764-UNI10.

Data-driven inference of network connectivity for modeling the dynamics of neural codes in the insect antennal lobe

PubMed Central

Shlizerman, Eli; Riffell, Jeffrey A.; Kutz, J. Nathan

2014-01-01

The antennal lobe (AL), olfactory processing center in insects, is able to process stimuli into distinct neural activity patterns, called olfactory neural codes. To model their dynamics we perform multichannel recordings from the projection neurons in the AL driven by different odorants. We then derive a dynamic neuronal network from the electrophysiological data. The network consists of lateral-inhibitory neurons and excitatory neurons (modeled as firing-rate units), and is capable of producing unique olfactory neural codes for the tested odorants. To construct the network, we (1) design a projection, an odor space, for the neural recording from the AL, which discriminates between distinct odorants trajectories (2) characterize scent recognition, i.e., decision-making based on olfactory signals and (3) infer the wiring of the neural circuit, the connectome of the AL. We show that the constructed model is consistent with biological observations, such as contrast enhancement and robustness to noise. The study suggests a data-driven approach to answer a key biological question in identifying how lateral inhibitory neurons can be wired to excitatory neurons to permit robust activity patterns. PMID:25165442

Primordial main equence binary stars in the globular cluster M71

NASA Technical Reports Server (NTRS)

Yan, Lin; Mateo, Mario

1994-01-01

We report the identification of five short-period variables near the center of the metal-rich globular cluster M71. Our observations consist of multiepoch VI charge coupled device (CCD) images centered on the cluster and covering a 6.3 min x 6.3 min field. Four of these variables are contact eclipsing binaries with periods between 0.35 and 0.41 days; one is a detached or semidetached eclipsing binary with a period of 0.56 days. Two of the variables were first identified as possible eclipsing binaries in an earlier survey by Hodder et al. (1992). We have used a variety of arguments to conclude that all five binary stars are probable members of M71, a result that is consistent with the low number (0.15) of short-period field binaries expected along this line of sight. Based on a simple model of how contact binaries evolve from initially detached binaries, we have determined a lower limit of 1.3% on the frequency of primordial binaries in M71 with initial orbital periods in the range 2.5 - 5 days. This implies that the overall primordial binary frequency, f, is 22(sup +26)(sub -12)% assuming df/d log P = const ( the 'flat' distribution), or f = 57(sup +15)(sub -8)% for df/d log P = 0.032 log P + const as observed for G-dwarf binaries in the solar neighborhood (the 'sloped' distribution). Both estimates of f correspond to binaries with initial periods shorter than 800 yr since any longer-period binaries would have been disrupted over the lifetime of the cluster. Our short-period binary frequency is in excellent agreement with the observed frequency of red-giant binaries observed in globulars if we adopt the flat distribution. For the sloped distribution, our results significantly overestimate the number of red-giant binaries. All of the short-period M71 binaries lie within 1 mag of the luminosity of the cluster turnoff in the color-magnitude diagram despite the fact we should have easily detected similar eclipsing binaries 2 - 2.5 mag fainter than this. We discuss the implications of this on our estimates of the binary frequency in M71 and on the formation of blue stragglers.

Faint AGN in z ≳ 6 Lyman-break galaxies powered by cold accretion and rapid angular momentum transport

NASA Astrophysics Data System (ADS)

Muñoz, Joseph A.; Furlanetto, Steven

2012-11-01

We develop a radiation pressure-balanced model for the interstellar medium of high-redshift galaxies that describes many facets of galaxy formation at z ≳ 6, including star formation rates and distributions and gas accretion on to central black holes. We first show that the vertical gravitational force in the disc of such a model is dominated by the disc self-gravity supported by the radiation pressure of ionizing starlight on gas. Constraining our model to reproduce the UV luminosity function of Lyman-break galaxies (LBGs), we limit the available parameter space to wind mass-loading factors one to four times the canonical value for momentum-driven winds. We then focus our study by exploring the effects of different angular momentum transport mechanisms in the galactic disc and find that accretion driven by gravitational torques, such as from linear spiral waves or non-linear orbit crossings, can build up black hole masses by z = 6 consistent with the canonical M-σ relation with a duty cycle of unity, while accretion mediated by a local viscosity such as in an α-disc results in negligible black hole (BH) accretion. Both gravitational torque models produce X-ray emission from active galactic nuclei (AGN) in high-redshift LBGs in excess of the estimated contribution from high-mass X-ray binaries. Using a recent analysis of deep Chandra observations by Cowie et al., we can already begin to rule out the most extreme regions of our parameter space: the inflow velocity of gas through the disc must either be less than one per cent of the disc circular velocity or the X-ray luminosity of the AGN must be substantially obscured. Moderately deeper future observations or larger sample sizes will be able to probe the more reasonable range of angular momentum transport models and obscuring geometries.

A Structural Molar Volume Model for Oxide Melts Part I: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 Melts—Binary Systems

NASA Astrophysics Data System (ADS)

Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

2016-04-01

A structural molar volume model was developed to accurately reproduce the molar volume of molten oxides. As the non-linearity of molar volume is related to the change in structure of molten oxides, the silicate tetrahedral Q-species, calculated from the modified quasichemical model with an optimized thermodynamic database, were used as basic structural units in the present model. Experimental molar volume data for unary and binary melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system were critically evaluated. The molar volumes of unary oxide components and binary Q-species, which are model parameters of the present structural model, were determined to accurately reproduce the experimental data across the entire binary composition in a wide range of temperatures. The non-linear behavior of molar volume and thermal expansivity of binary melt depending on SiO2 content are well reproduced by the present model.

Conference on Binary Optics: An Opportunity for Technical Exchange

NASA Technical Reports Server (NTRS)

Cole, Helen J. (Editor); Pittman, William C. (Editor)

1993-01-01

The papers herein were presented at the Conference on Binary Optics held in Huntsville, AL, February 23-25, 1993. The papers were presented according to subject as follows: modeling and design, fabrication, and applications. Invited papers and tutorial viewgraphs presented on these subjects are included.

High-Precision Studies of Compact Variable Stars

NASA Astrophysics Data System (ADS)

Bloemen, Steven

2014-10-01

This book, which is a reworked and updated version of Steven Bloemen's original PhD thesis, reports on several high-precision studies of compact variable stars. Its strength lies in the large variety of observational, theoretical and instrumentation techniques that are presented and used and paves the way towards new and detailed asteroseismic applications of single and binary subdwarf stars. Close binary stars are studied using high cadence spectroscopic datasets collected with state of the art electron multiplying CCDs and analysed using Doppler tomography visualization techniques. The work touches upon instrumentation, presenting the calibration of a new fast, multi-colour camera installed at the Mercator Telescope on La Palma. The thesis also includes theoretical work on the computation of the temperature range in which stellar oscillations can be driven in subdwarf B-stars. Finally, the highlight of the thesis is the measurement of velocities of stars using only photometric data from NASA's Kepler satellite. Doppler beaming causes stars to appear slightly brighter when they move towards us in their orbits, and this subtle effect can be seen in Kepler's brightness measurements. The thesis presents the first validation of such velocity measurements using independent spectroscopic measurements. Since the detection and validation of this Doppler beaming effect, it has been used in tens of studies to detect and characterize binary star systems, which are key calibrators in stellar astronomy.

Prediction of A2 to B2 Phase Transition in the High Entropy Alloy Mo-Nb-Ta-W

NASA Astrophysics Data System (ADS)

Huhn, William; Widom, Michael

2014-03-01

In this talk we show that an effective Hamiltonian fit with first principles calculations predicts an order/disorder transition occurs in the high entropy alloy Mo-Nb-Ta-W. Using the Alloy Theoretic Automated Toolset, we find T=0K enthalpies of formation for all binaries containing Mo, Nb, Ta, and W, and in particular we find the stable structures for binaries at equiatomic concentrations are close in energy to the associated B2 structure, suggesting that at intermediate temperatures a B2 phase is stabilized in Mo-Nb-Ta-W. Our ``hybrid Monte Carlo/molecular dynamics'' results for the Mo-Nb-Ta-W system are analyzed to identify certain preferred chemical bonding types. A mean field free energy model incorporating nearest neighbor bonds will be presented, allowing us to predict the mechanism of the order/disorder transition. We find the temperature evolution of the system is driven by strong Mo-Ta bonding. Comparison of the free energy model and our MC/MD results suggest the existence of additional low-temperature phase transitions in the system likely ending with phase segregation into binary phases. We would like to thank DOD-DTRA for funding this research under contract number DTRA-11-1-0064.

On The Origin Of Hyper-Fast Pulsars

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.

2006-08-01

Recent proper motion and parallax measurements for the pulsar PSR B1508+55 gave the highest (transverse) velocity (~1100 km/s) ever measured for a neutron star (Chatterjee et al. 2005). The spin-down characteristics of PSR B1508+55 (typical of non-recycled pulsars) imply that the high velocity of this pulsar cannot be solely due to disruption of a tight massive binary system. A possible way to account for the high velocity of PSR B1508+55 is to assume that at least a part of this velocity is due to a natal or post-natal kick (Chatterjee et al. 2005). We propose an alternative explanation for the origin of hyper-fast pulsars. We suggest that PSR B1508+55 could be the remnant of a (symmetric) supernova explosion of the helium core of a massive star expelled at high velocity from the dense core of a young massive stellar cluster by an intermediate-mass (binary) black hole. The maximum peculiar velocity of the helium core is limited by the parabolic velocity on its surface and could be as large as ~2000 km/s. Thus, one can account not only for the high velocity measured for PSR B1508+55, but also for the even higher velocity of ~1600 km/s inferred for the pulsar PSR B2224+65 (Guitar; Chatterjee & Cordes 2004) on the basis of its proper motion and the dispersion measure distance estimate.

LLE Review 116 (July-September 2008)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marozas, J.A., editor

2010-03-12

This issue has the following articles: (1) Optimizing Electron-Positron Pair Production on kJ-Class High-Intensity Lasers for the Purpose of Pair-Plasma Creation; (2) Neutron Yield Study of Direct-Drive, Low-Adiabat Cryogenic D2 Implosions on OMEGA; (3) Al 1s-2p Absorption Spectroscopy of Shock-Wave Heating and Compression in Laser-Driven Planar Foil; (4) A Measurable Lawson Criterion and Hydro-Equivalent Curves for Inertial Confinement Fusion; (5) Pulsed-THz Characterization of Hg-Based, High-Temperature Superconductors; (6) LLE's Summer High School Research Program; (7) FY08 Laser Facility Report; and (8) National Laser Users Facility and External Users Programs.

The Orbital and Physical Parameters, and the Distance of the Eclipsing Binary System OGLE-LMC-ECL-25658 in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Elgueta, S. S.; Graczyk, D.; Gieren, W.; Pietrzyński, G.; Thompson, I. B.; Konorski, P.; Pilecki, B.; Villanova, S.; Udalski, A.; Soszyński, I.; Suchomska, K.; Karczmarek, P.; Górski, M.; Wielgórski, P.

2016-08-01

We present an analysis of a new detached eclipsing binary, OGLE-LMC-ECL-25658, in the Large Magellanic Cloud (LMC). The system consists of two late G-type giant stars on an eccentric orbit with an orbital period of ˜200 days. The system shows total eclipses and the components have similar temperatures, making it ideal for a precise distance determination. Using multi-color photometric and high resolution spectroscopic data, we have performed an analysis of light and radial velocity curves simultaneously using the Wilson-Devinney code. We derived orbital and physical parameters of the binary with a high precision of \\lt 1%. The masses and surface metallicities of the components are virtually the same and equal to 2.23+/- 0.02 {M}⊙ and [{Fe}/{{H}}]\\=\\-0.63+/- 0.10 dex. However, their radii and rates of rotation show a distinct trace of differential stellar evolution. The distance to the system was calculated using an infrared calibration between V-band surface brightness and (V-K) color, leading to a distance modulus of (m-M)\\=\\18.452+/- 0.023 (statistical) ± 0.046 (systematic). Because OGLE-LMC-ECL-25658 is located relatively far from the LMC barycenter, we applied a geometrical correction for its position in the LMC disk using the van der Marel et al. model of the LMC. The resulting barycenter distance to the galaxy is {d}{{LMC}}\\=\\50.30+/- 0.53 (stat.) kpc, and is in perfect agreement with the earlier result of Pietrzyński et al.

OGLE II Eclipsing Binaries In The LMC: Analysis With Class

NASA Astrophysics Data System (ADS)

Devinney, Edward J.; Prsa, A.; Guinan, E. F.; DeGeorge, M.

2011-01-01

The Eclipsing Binaries (EBs) via Artificial Intelligence (EBAI) Project is applying machine learning techniques to elucidate the nature of EBs. Previously, Prsa, et al. applied artificial neural networks (ANNs) trained on physically-realistic Wilson-Devinney models to solve the light curves of the 1882 detached EBs in the LMC discovered by the OGLE II Project (Wyrzykowski, et al.) fully automatically, bypassing the need for manually-derived starting solutions. A curious result is the non-monotonic distribution of the temperature ratio parameter T2/T1, featuring a subsidiary peak noted previously by Mazeh, et al. in an independent analysis using the EBOP EB solution code (Tamuz, et al.). To explore this and to gain a fuller understanding of the multivariate EBAI LMC observational plus solutions data, we have employed automatic clustering and advanced visualization (CAV) techniques. Clustering the OGLE II data aggregates objects that are similar with respect to many parameter dimensions. Measures of similarity for example, could include the multidimensional Euclidean Distance between data objects, although other measures may be appropriate. Applying clustering, we find good evidence that the T2/T1 subsidiary peak is due to evolved binaries, in support of Mazeh et al.'s speculation. Further, clustering suggests that the LMC detached EBs occupying the main sequence region belong to two distinct classes. Also identified as a separate cluster in the multivariate data are stars having a Period-I band relation. Derekas et al. had previously found a Period-K band relation for LMC EBs discovered by the MACHO Project (Alcock, et al.). We suggest such CAV techniques will prove increasingly useful for understanding the large, multivariate datasets increasingly being produced in astronomy. We are grateful for the support of this research from NSF/RUI Grant AST-05-75042 f.

Multiple Absorption Components in the Post-Periastron He I P Cygni Absorption Troughs of Eta Carinae

NASA Technical Reports Server (NTRS)

Richardson, Noel D.; Damineli, Augusto; Gull, Ted; Moffat, Anthony; Groh, Jose; St.-Jean, Lucas; Walter, Frederick M.; Teodoro, Mairan; Madura, Tom; Corcoran, Michael;

Terrestrial Planet Formation in Binary Star Systems

NASA Technical Reports Server (NTRS)

Lissauer, J. J.; Quintana, E. V.; Adams, F. C.; Chambers, J. E.

2006-01-01

Most stars reside in binary/multiple star systems; however, previous models of planet formation have studied growth of bodies orbiting an isolated single star. Disk material has been observed around one or both components of various young close binary star systems. If planets form at the right places within such disks, they can remain dynamically stable for very long times. We have simulated the late stages of growth of terrestrial planets in both circumbinary disks around 'close' binary star systems with stellar separations ($a_B$) in the range 0.05 AU $\\le a_B \\le$ 0.4 AU and binary eccentricities in the range $0 \\le e \\le 0.8$ and circumstellar disks around individual stars with binary separations of tens of AU. The initial disk of planetary embryos is the same as that used for simulating the late stages of terrestrial planet growth within our Solar System and around individual stars in the Alpha Centauri system (Quintana et al. 2002, A.J., 576, 982); giant planets analogous to Jupiter and Saturn are included if their orbits are stable. The planetary systems formed around close binaries with stellar apastron distances less than or equal to 0.2 AU with small stellar eccentricities are very similar to those formed in the Sun-Jupiter-Saturn, whereas planetary systems formed around binaries with larger maximum separations tend to be sparser, with fewer planets, especially interior to 1 AU. Likewise, when the binary periastron exceeds 10 AU, terrestrial planets can form over essentially the entire range of orbits allowed for single stars with Jupiter-like planets, although fewer terrestrial planets tend to form within high eccentricity binary systems. As the binary periastron decreases, the radial extent of the terrestrial planet systems is reduced accordingly. When the periastron is 5 AU, the formation of Earth-like planets near 1 AU is compromised.

Correction: A binary catalyst system of a cationic Ru-CNC pincer complex with an alkali metal salt for selective hydroboration of carbon dioxide.

PubMed

Ng, Chee Koon; Wu, Jie; Hor, T S Andy; Luo, He-Kuan

2016-12-22

Correction for 'A binary catalyst system of a cationic Ru-CNC pincer complex with an alkali metal salt for selective hydroboration of carbon dioxide' by Chee Koon Ng et al., Chem. Commun., 2016, 52, 11842-11845.

Glass viscosity calculation based on a global statistical modelling approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fluegel, Alex

2007-02-01

A global statistical glass viscosity model was developed for predicting the complete viscosity curve, based on more than 2200 composition-property data of silicate glasses from the scientific literature, including soda-lime-silica container and float glasses, TV panel glasses, borosilicate fiber wool and E type glasses, low expansion borosilicate glasses, glasses for nuclear waste vitrification, lead crystal glasses, binary alkali silicates, and various further compositions from over half a century. It is shown that within a measurement series from a specific laboratory the reported viscosity values are often over-estimated at higher temperatures due to alkali and boron oxide evaporation during the measurementmore » and glass preparation, including data by Lakatos et al. (1972) and the recently published High temperature glass melt property database for process modeling by Seward et al. (2005). Similarly, in the glass transition range many experimental data of borosilicate glasses are reported too high due to phase separation effects. The developed global model corrects those errors. The model standard error was 9-17°C, with R^2 = 0.985-0.989. The prediction 95% confidence interval for glass in mass production largely depends on the glass composition of interest, the composition uncertainty, and the viscosity level. New insights in the mixed-alkali effect are provided.« less

Speckle imaging with the MAMA detector: Preliminary results

NASA Technical Reports Server (NTRS)

Horch, E.; Heanue, J. F.; Morgan, J. S.; Timothy, J. G.

1994-01-01

We report on the first successful speckle imaging studies using the Stanford University speckle interferometry system, an instrument that uses a multianode microchannel array (MAMA) detector as the imaging device. The method of producing high-resolution images is based on the analysis of so-called 'near-axis' bispectral subplanes and follows the work of Lohmann et al. (1983). In order to improve the signal-to-noise ratio in the bispectrum, the frame-oversampling technique of Nakajima et al. (1989) is also employed. We present speckle imaging results of binary stars and other objects from V magnitude 5.5 to 11, and the quality of these images is studied. While the Stanford system is capable of good speckle imaging results, it is limited by the overall quantum efficiency of the current MAMA detector (which is due to the response of the photocathode at visible wavelengths and other detector properties) and by channel saturation of the microchannel plate. Both affect the signal-to-noise ratio of the power spectrum and bispectrum.

Towards a user-friendly brain-computer interface: initial tests in ALS and PLS patients.

PubMed

Bai, Ou; Lin, Peter; Huang, Dandan; Fei, Ding-Yu; Floeter, Mary Kay

2010-08-01

Patients usually require long-term training for effective EEG-based brain-computer interface (BCI) control due to fatigue caused by the demands for focused attention during prolonged BCI operation. We intended to develop a user-friendly BCI requiring minimal training and less mental load. Testing of BCI performance was investigated in three patients with amyotrophic lateral sclerosis (ALS) and three patients with primary lateral sclerosis (PLS), who had no previous BCI experience. All patients performed binary control of cursor movement. One ALS patient and one PLS patient performed four-directional cursor control in a two-dimensional domain under a BCI paradigm associated with human natural motor behavior using motor execution and motor imagery. Subjects practiced for 5-10min and then participated in a multi-session study of either binary control or four-directional control including online BCI game over 1.5-2h in a single visit. Event-related desynchronization and event-related synchronization in the beta band were observed in all patients during the production of voluntary movement either by motor execution or motor imagery. The online binary control of cursor movement was achieved with an average accuracy about 82.1+/-8.2% with motor execution and about 80% with motor imagery, whereas offline accuracy was achieved with 91.4+/-3.4% with motor execution and 83.3+/-8.9% with motor imagery after optimization. In addition, four-directional cursor control was achieved with an accuracy of 50-60% with motor execution and motor imagery. Patients with ALS or PLS may achieve BCI control without extended training, and fatigue might be reduced during operation of a BCI associated with human natural motor behavior. The development of a user-friendly BCI will promote practical BCI applications in paralyzed patients. Copyright 2010 International Federation of Clinical Neurophysiology. All rights reserved.

High Frequency Vibration Based Fatigue Testing of Developmental Alloys

NASA Astrophysics Data System (ADS)

Holycross, Casey M.; Srinivasan, Raghavan; George, Tommy J.; Tamirisakandala, Seshacharyulu; Russ, Stephan M.

Many fatigue test methods have been previously developed to rapidly evaluate fatigue behavior. This increased test speed can come at some expense, since these methods may require non-standard specimen geometry or increased facility and equipment capability. One such method, developed by George et al, involves a base-excited plate specimen driven into a high frequency bending resonant mode. This resonant mode is of sufficient frequency (typically 1200 to 1700 Hertz) to accumulate 107 cycles in a few hours. One of the main limitations of this test method is that fatigue cracking is almost certainly guaranteed to be surface initiated at regions of high stress. This brings into question the validity of the fatigue test results, as compared to more traditional uniaxial, smooth-bar testing, since high stresses are subjecting only a small volume to fatigue damage. This limitation also brings into question the suitability of this method to screen developmental alloys, should their initiation life be governed by subsurface flaws. However, if applicable, the rapid generation of fatigue data using this method would facilitate faster design iterations, identifying more quickly, material and manufacturing process deficiencies. The developmental alloy used in this study was a powder metallurgy boron-modified Ti-6Al-4V, a new alloy currently being considered for gas turbine engine fan blades. Plate specimens were subjected to fully reversed bending fatigue. Results are compared with existing data from commercially available Ti-6Al-4V using both vibration based and more traditional fatigue test methods.

Creep Behavior of Near-Stoichiometric Polycrystalline Binary NiAl

NASA Technical Reports Server (NTRS)

Raj, S. V.

2002-01-01

New and published constant load creep and constant engineering strain rate data on near-stoichiometric binary NiAl in the intermediate temperature range 700 to 1300 K are reviewed. Both normal and inverse primary creep curves are observed depending on stress and temperature. Other characteristics relating to creep of NiAl involving grain size, stress and temperature dependence are critically examined and discussed. At stresses below 25 MPa and temperatures above 1000 K, a new grain boundary sliding mechanism was observed with n approx. 2, Qc approx. 100 kJ/ mol and a grain size exponent of about 2. It is demonstrated that Coble creep and accommodated grain boundary sliding models fail to predict the experimental creep rates by several orders of magnitude.

AN EXTENDED AND MORE SENSITIVE SEARCH FOR PERIODICITIES IN ROSSI X-RAY TIMING EXPLORER/ALL-SKY MONITOR X-RAY LIGHT CURVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levine, Alan M.; Bradt, Hale V.; Chakrabarty, Deepto

2011-09-01

We present the results of a systematic search in {approx}14 years of Rossi X-ray Timing Explorer All-Sky Monitor (ASM) data for evidence of periodicities. Two variations of the commonly used Fourier analysis search method have been employed to significantly improve upon the sensitivity achieved by Wen et al. in 2006, who also searched for periodicities in ASM data. In addition, the present search is comprehensive in terms of sources studied and frequency range covered, and has yielded the detection of the signatures of the orbital periods of eight low-mass X-ray binary systems and of ten high-mass X-ray binaries not listedmore » in the tables of Wen et al. Orbital periods, epochs, signal amplitudes, modulation fractions, and folded light curves are given for each of these systems. Seven of the orbital periods are the most precise reported to date. In the course of this work, the 18.545 day orbital period of IGR J18483-0311 was co-discovered, and the first detections in X-rays were made of the {approx}3.9 day orbital period of LMC X-1 and the {approx}3.79 hr orbital period of 4U 1636-536. The results inform future searches for orbital and other periodicities in X-ray binaries.« less

An X-ray excited wind in Centaurus X-3

NASA Technical Reports Server (NTRS)

Day, C. S. R.; Stevens, Ian R.

1993-01-01

We propose a new interpretation of the behavior of the notable X-ray binary source Centaurus X-3. Based on both theoretical and observational arguments (using EXOSAT data), we suggest that an X-ray excited wind emanating from the O star is present in this system. Further, we suggest that this wind is responsible for the mass transfer in the system rather than Roche-lobe overflow or a normal radiatively driven stellar wind. We show that the ionization conditions in Cen X-3 are too extreme to permit a normal radiatively driven wind to emanate from portions of the stellar surface facing toward the neutron star. In addition, the flux of X-rays from the neutron star is strong enough to drive a thermal wind from the O star with sufficient mass-flux to power the X-ray source. We find that this model can reasonably account for the long duration of the eclipse transitions and other observed features of Cen X-3. If confirmed, this will be the first example of an X-ray excited wind in a massive binary. We also discuss the relationship between the excited wind in Cen X-3 to the situation in eclipsing millisecond pulsars, where an excited wind is also believed to be present.

Assessment of microalloying effects on the high temperature fatigue behavior of NiAl

NASA Technical Reports Server (NTRS)

Noebe, R. D.; Lerch, B. A.; Rao, K. B. S.

1995-01-01

Binary NiAl suffers from a lack of strength and poor creep properties at and above 1000 K. Poor creep resistance in turn affects low cycle fatigue (LCF) lives at low strain ranges due to the additional interactions of creep damage. One approach for improving these properties involved microalloying with either Zr or N. As an integral part of a much larger alloying program the low cycle fatigue behavior of Zr and N doped nickel aluminides produced by extrusion of prealloyed powders has been investigated. Strain controlled LCF tests were performed in air at 1000 K. The influence of these microalloying additions on the fatigue life and cyclic stress response of polycrystalline NiAl are discussed.

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

NASA Astrophysics Data System (ADS)

Bozzo, E.; Oskinova, L.; Feldmeier, A.; Falanga, M.

2016-05-01

The accretion of the stellar wind material by a compact object represents the main mechanism powering the X-ray emission in classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. In this work we present the first attempt to simulate the accretion process of a fast and dense massive star wind onto a neutron star, taking into account the effects of the centrifugal and magnetic inhibition of accretion ("gating") due to the spin and magnetic field of the compact object. We made use of a radiative hydrodynamical code to model the nonstationary radiatively driven wind of an O-B supergiant star and then place a neutron star characterized by a fixed magnetic field and spin period at a certain distance from the massive companion. Our calculations follow, as a function of time (on a total timescale of several hours), the transitions of the system through all different accretion regimes that are triggered by the intrinsic variations in the density and velocity of the nonstationary wind. The X-ray luminosity released by the system is computed at each time step by taking into account the relevant physical processes occurring in the different accretion regimes. Synthetic lightcurves are derived and qualitatively compared with those observed from classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. Although a number of simplifications are assumed in these calculations, we show that taking into account the effects of the centrifugal and magnetic inhibition of accretion significantly reduces the average X-ray luminosity expected for any neutron star wind-fed binary. The present model calculations suggest that long spin periods and stronger magnetic fields are favored in order to reproduce the peculiar behavior of supergiant fast X-ray transients in the X-ray domain.

Crack-resistant Al2O3–SiO2 glasses

PubMed Central

Rosales-Sosa, Gustavo A.; Masuno, Atsunobu; Higo, Yuji; Inoue, Hiroyuki

2016-01-01

Obtaining “hard” and “crack-resistant” glasses have always been of great important in glass science and glass technology. However, in most commercial glasses both properties are not compatible. In this work, colorless and transparent xAl2O3–(100–x)SiO2 glasses (30 ≤ x ≤ 60) were fabricated by the aerodynamic levitation technique. The elastic moduli and Vickers hardness monotonically increased with an increase in the atomic packing density as the Al2O3 content increased. Although a higher atomic packing density generally enhances crack formation in conventional oxide glasses, the indentation cracking resistance increased by approximately seven times with an increase in atomic packing density in binary Al2O3–SiO2 glasses. In particular, the composition of 60Al2O3•40SiO2 glass, which is identical to that of mullite, has extraordinary high cracking resistance with high elastic moduli and Vickers hardness. The results indicate that there exist aluminosilicate compositions that can produce hard and damage-tolerant glasses. PMID:27053006

Crack-resistant Al2O3-SiO2 glasses

NASA Astrophysics Data System (ADS)

Rosales-Sosa, Gustavo A.; Masuno, Atsunobu; Higo, Yuji; Inoue, Hiroyuki

2016-04-01

Obtaining “hard” and “crack-resistant” glasses have always been of great important in glass science and glass technology. However, in most commercial glasses both properties are not compatible. In this work, colorless and transparent xAl2O3-(100-x)SiO2 glasses (30 ≤ x ≤ 60) were fabricated by the aerodynamic levitation technique. The elastic moduli and Vickers hardness monotonically increased with an increase in the atomic packing density as the Al2O3 content increased. Although a higher atomic packing density generally enhances crack formation in conventional oxide glasses, the indentation cracking resistance increased by approximately seven times with an increase in atomic packing density in binary Al2O3-SiO2 glasses. In particular, the composition of 60Al2O3•40SiO2 glass, which is identical to that of mullite, has extraordinary high cracking resistance with high elastic moduli and Vickers hardness. The results indicate that there exist aluminosilicate compositions that can produce hard and damage-tolerant glasses.

A GDP-driven model for the binary and weighted structure of the International Trade Network

NASA Astrophysics Data System (ADS)

Almog, Assaf; Squartini, Tiziano; Garlaschelli, Diego

2015-01-01

Recent events such as the global financial crisis have renewed the interest in the topic of economic networks. One of the main channels of shock propagation among countries is the International Trade Network (ITN). Two important models for the ITN structure, the classical gravity model of trade (more popular among economists) and the fitness model (more popular among networks scientists), are both limited to the characterization of only one representation of the ITN. The gravity model satisfactorily predicts the volume of trade between connected countries, but cannot reproduce the missing links (i.e. the topology). On the other hand, the fitness model can successfully replicate the topology of the ITN, but cannot predict the volumes. This paper tries to make an important step forward in the unification of those two frameworks, by proposing a new gross domestic product (GDP) driven model which can simultaneously reproduce the binary and the weighted properties of the ITN. Specifically, we adopt a maximum-entropy approach where both the degree and the strength of each node are preserved. We then identify strong nonlinear relationships between the GDP and the parameters of the model. This ultimately results in a weighted generalization of the fitness model of trade, where the GDP plays the role of a ‘macroeconomic fitness’ shaping the binary and the weighted structure of the ITN simultaneously. Our model mathematically explains an important asymmetry in the role of binary and weighted network properties, namely the fact that binary properties can be inferred without the knowledge of weighted ones, while the opposite is not true.

Searching for Solar System Wide Binaries with Pan-STARRS-1

NASA Astrophysics Data System (ADS)

Holman, Matthew J.; Protopapas, P.; Tholen, D. J.

2007-10-01

Roughly 60% of the observing time of the Pan-STARRS-1 (PS1) telescope will be dedicated to a "3pi steradian" survey with an observing cadence that is designed for the detection of near-Earth asteroids and slow-moving solar system bodies. Over this course of its 3.5 year cience mission, this unprecedented survey will discover nearly every asteroid, Trojan, Centaur, long-period comet, short-period comet, and trans-neptunian object (TNO) brighter than magnitude R=23. This census will be used to address a large number of questions regarding the physical and dynamical properties of the various small body populations of the solar system. Roughly 1-2% of TNOs are wide binaries with companions at separations greater than 1 arcsec and brightness differences less than 2 magnitudes (Kern & Elliot 2006; Noll et al 2007). These can be readily detected by PS1; we will carry out such a search with PS1 data. To do so, we will modify the Pan-STARRS Moving Object Processing System (MOPS) such that it will associate the components of resolved or marginally resolved binaries, link such pairs of detections obtained at different epochs, and the estimate the relative orbit of the binary. We will also determine the efficiency with which such binaries are detected as a function of the binary's relative orbit and the relative magnitudes of the components. Based on an estimated 7000 TNOs that PS1 will discover, we anticipate finding 70-140 wide binaries. The PS1 data, 60 epochs over three years, is naturally suited to determining the orbits of these objects. Our search will accurately determine the binary fraction for a variety of subclasses of TNOs.

Early dynamical evolution of substructured stellar clusters

NASA Astrophysics Data System (ADS)

Dorval, Julien; Boily, Christian

2015-08-01

It is now widely accepted that stellar clusters form with a high level of substructure (Kuhn et al. 2014, Bate 2009), inherited from the molecular cloud and the star formation process. Evidence from observations and simulations also indicate the stars in such young clusters form a subvirial system (Kirk et al. 2007, Maschberger et al. 2010). The subsequent dynamical evolution can cause important mass loss, ejecting a large part of the birth population in the field. It can also imprint the stellar population and still be inferred from observations of evolved clusters. Nbody simulations allow a better understanding of these early twists and turns, given realistic initial conditions. Nowadays, substructured, clumpy young clusters are usually obtained through pseudo-fractal growth (Goodwin et al. 2004) and velocity inheritance. Such models are visually realistics and are very useful, they are however somewhat artificial in their velocity distribution. I introduce a new way to create clumpy initial conditions through a "Hubble expansion" which naturally produces self consistent clumps, velocity-wise. A velocity distribution analysis shows the new method produces realistic models, consistent with the dynamical state of the newly created cores in hydrodynamic simulation of cluster formation (Klessen & Burkert 2000). I use these initial conditions to investigate the dynamical evolution of young subvirial clusters, up to 80000 stars. I find an overall soft evolution, with hierarchical merging leading to a high level of mass segregation. I investigate the influence of the mass function on the fate of the cluster, specifically on the amount of mass loss induced by the early violent relaxation. Using a new binary detection algorithm, I also find a strong processing of the native binary population.

Prevalence and predictors of thyroid functional abnormalities in newly diagnosed AL amyloidosis.

PubMed

Muchtar, E; Dean, D S; Dispenzieri, A; Dingli, D; Buadi, F K; Lacy, M Q; Hayman, S R; Kapoor, P; Leung, N; Russell, S; Lust, J A; Lin, Yi; Warsame, R; Gonsalves, W; Kourelis, T V; Go, R S; Chakraborty, R; Zeldenrust, S; Kyle, R A; Rajkumar, S Vincent; Kumar, S K; Gertz, M A

2017-06-01

Data on the effect of systemic immunoglobulin light chain amyloidosis (AL amyloidosis) on thyroid function are limited. To assess the prevalence of hypothyroidism in AL amyloidosis patients and determine its predictors. 1142 newly diagnosed AL amyloidosis patients were grouped based on the thyroid-stimulating hormone (TSH) measurement at diagnosis: hypothyroid group (TSH above upper normal reference; >5 mIU L -1 ; n = 217, 19% of study participants) and euthyroid group (n = 925, 81%). Predictors for hypothyroidism were assessed in a binary multivariate model. Survival between groups was compared using the log-rank test and a multivariate analysis. Patients with hypothyroidism were older, more likely to present with renal and hepatic involvement and had a higher light chain burden compared to patients in the euthyroid group. Higher proteinuria in patients with renal involvement and lower albumin in patients with hepatic involvement were associated with hypothyroidism. In a binary logistic regression model, age ≥65 years, female sex, renal involvement, hepatic involvement, kappa light chain restriction and amiodarone use were independently associated with hypothyroidism. Ninety-three per cent of patients in the hypothyroid group with free thyroxine measurement had normal values, consistent with subclinical hypothyroidism. Patients in the hypothyroid group had a shorter survival compared to patients in the euthyroid group (4-year survival 36% vs 43%; P = 0.008), a difference that was maintained in a multivariate analysis. A significant proportion of patients with AL amyloidosis present with hypothyroidism, predominantly subclinical, which carries a survival disadvantage. Routine assessment of TSH in these patients is warranted. © 2017 The Association for the Publication of the Journal of Internal Medicine.

Metabolic Syndrome and Associated Factors in a Population-Based Sample of Schoolchildren in Colombia: The FUPRECOL Study.

PubMed

Ramírez-Vélez, Robinson; Anzola, Alejandro; Martinez-Torres, Javier; Vivas, Andres; Tordecilla-Sanders, Alejandra; Prieto-Benavides, Daniel; Izquierdo, Mikel; Correa-Bautista, Jorge Enrique; Garcia-Hermoso, Antonio

2016-11-01

In contrast to the definition of metabolic syndrome (MetS) in adults, there is no standard definition of MetS in pediatric populations. We aimed at assessing the differences in the prevalence of MetS in children and adolescents aged 9-17 years using four different operational definitions for these age groups and at examining the associated variables. A total of 675 children and 1247 adolescents attending public schools in Bogota (54.4% girls; age range 9-17.9 years) were included. The prevalence of MetS was determined by the definitions provided by the International Diabetes Federation (IDF) and three published studies by Cook et al., de Ferranti et al., and Ford et al. In addition, we further examined the associations between each definition of MetS in the total sample and individual risk factors using binary logistic regression models adjusted for gender, age, pubertal stage, weight status, and inflammation in all participants. The prevalence of MetS was 0.3%, 6.3%, 7.8%, and 11.0% according to the definitions by IDF, Cook et al., Ford et al., and de Ferranti et al., respectively. The most prevalent components were low high-density lipoprotein cholesterol and high triglyceride levels, whereas the least prevalent components were higher waist circumference and hyperglycemia. Overall, the prevalence of MetS was higher in obese than in non-obese schoolchildren. MetS diagnoses in schoolchildren strongly depend on the definition chosen. These findings may be relevant to health promotion efforts for Colombian youth to develop prospective studies and to define which cut-offs are the best indicators of future morbidity.

Pluto-Charon: a test of the astrometric approach for finding asteroid satellites

NASA Astrophysics Data System (ADS)

Kikwaya, J.-B.; Thuillot, W.; Berthier, J.

2003-05-01

The astrometric method to find asteroid satellites is based on the search for the reflex effect on the primary object due to the orbital motion of a possible satellite (Monet & Monet 1998, Kikwaya et al. 2002). As reported by Kikwaya et al. (2003), the astrometric signature of a satellite of 146 Lucina may reach several mas. Spectral analysis might then detect the signal under good conditions of signal/noise ratio, with high quality astrometric measurements and large coverage by different sites of observation. However, the astrometric method cannot be applied to any binary system of asteroids. It depends strongly on the mass ratio of the two bodies and the distance between them (Kikwaya et al. 2002). Pluto-Charon provides a good test of this method. Previous works based on direct imaging of Charon show that its period is 6.357 days and the mass ratio is 0.122 (Wasserman et al. 2000), putting this system into the range that can be observed by our method. Using archived photographic observations (1914-1995) and CCD observations from US Naval Observatory, Flagstaff station (1995-1998), Bordeaux observatory (1996-1997) and Mc Donald Observatory (1997), we are analyzing the position of Pluto to see if its wobble effect due to Charon (amplitude around 95 mas) can be detected and if the orbital period of Charon can be recovered through a spectral analysis. If successful, this will reinforce the ability of our astrometric method to find asteroid satellites.

The Three-body System δ Circini

NASA Astrophysics Data System (ADS)

Mayer, Pavel; Harmanec, Petr; Sana, Hugues; Le Bouquin, Jean-Baptiste

2014-12-01

Delta Cir is known as an O7.5 III eclipsing and spectroscopic binary with an eccentric orbit. Penny et al. discovered the presence of a third component in the IUE spectra. The eclipsing binary and the third body revolve around a common center of gravity with a period of 1644 days in an eccentric orbit with a semimajor axis of 10 AU. We demonstrate the presence of apsidal-line rotation with a period of ≈141 yr, which is considerably longer than its theoretically predicted value, based on the published radii of the binary components derived from the Hipparchos H p light curve. However, our new solution of the same light curve resulted in smaller radii and better agreement between the observed and predicted period of the apsidal-line advance. There are indications that the third body is a binary. The object was resolved by VLTI using the PIONIER combiner; in 2012 June, the separation was 3.78 mas with magnitude difference in the H region 1.ͫ75. This result means that (assuming a distance of 770 pc) the inclination of the long orbit is 87.°7. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programs ID 65.N-0577, 67.B-0504, 074D-0300, 178.D-0361, 182.D-0356, 083.D-0589, 185.D-0056, 086.D-0997, and 087D-0946.

Outflow from the outer Lagrangian point - Observations and models of 4U 2127 + 12 in M15

NASA Technical Reports Server (NTRS)

Bailyn, Charles D.; Garcia, Michael R.; Grindlay, Jonathan

1989-01-01

MMT observations of AC 211, the optical counterpart of the high-luminosity X-ray source in globular cluster M15, are presented. The observation of Naylor et al. (1988) that the He I absorption is blueshifted by more than 100 km/s with respect to the mean velocity of the cluster is confirmed. It is shown that if the absorption occurs in a stream of gas outflowing from the L2 point of a binary system, as might be expected for a common envelope binary, both the blueshift and the unexpectedly low velocity variations of the He I lines can be understood. The model predicts that the He I velocity curve is not sinusoidal.

Collaborative designing and job satisfaction of airplane manufacturing engineers: A case study

NASA Astrophysics Data System (ADS)

Johnson, Michael David, Sr.

The group III-nitride system of materials has had considerable commercial success in recent years in the solid state lighting (SSL) and power electronics markets. The need for high efficient general lighting applications has driven research into InGaN based blue light emitting diodes (LEDs), and demand for more efficient power electronics for telecommunications has driven research into AlGaN based high electron mobility transistors (HEMTs). However, the group III-nitrides material properties make them attractive for several other applications that have not received as much attention. This work focuses on developing group III-nitride based devices for novel applications. GaN is a robust, chemically inert, piezoelectric material, making it an ideal candidate for surface acoustic wave (SAW) devices designed for high temperature and/or harsh environment sensors. In this work, SAW devices based on GaN are developed for use in high temperature gas or chemical sensor applications. To increase device sensitivity, while maintaining a simple one-step photolithography fabrication process, devices were designed to operate at high harmonic frequencies. This allows for GHz regime operation without sub-micron fabrication. One potential market for this technology is continuous emissions monitoring of combustion gas vehicles. In addition to SAW devices, high electron mobility transistors (HEMTs) were developed. The epitaxial structure was characterized and the 2-D electron gas concentrations were simulated and compared to experimental results. Device fabrication processes were developed and are outlined. Fabricated devices were electrically measured and device performance is discussed.

VizieR Online Data Catalog: Binary white dwarfs atmospheric parameters (Gianninas+, 2014)

NASA Astrophysics Data System (ADS)

Gianninas, A.; Dufour, P.; Kilic, M.; Brown, W. R.; Bergeron, P.; Hermes, J. J.

2017-04-01

The sample that we analyze includes a total of 61 ELM WD binaries from the ELM Survey (Brown et al. 2013, J/ApJ/769/66). The bulk of this sample is comprised of the 58 ELM WDs listed in Table 3 of Brown et al. (2013, J/ApJ/769/66), but also includes three additional ELM WDs that have been published in separate papers since then. The spectra of these 61 ELM WDs were obtained using five distinct setups on two different telescopes. A total of 57 targets were observed with the 6.5m MMT telescope with the Blue Channel spectrograph (Schmidt et al. 1989PASP..101..713S). The four remaining targets were observed using the Fred Lawrence Whipple Observatory's (FLWO) 1.5m Tilinghast telescope equipped with the FAST spectrograph (Fabricant et al. 1998PASP..110...79F) and the 600 line/mm grating. (2 data files).

General Relativistic Simulations of Magnetized Plasmas Around Merging Supermassive Black Holes

NASA Technical Reports Server (NTRS)

Giacomazzo, Bruno; Baker, John G.; Miller, M. Coleman; Reynolds, Christopher S.; van Meter, James R.

2012-01-01

Coalescing supermassive black hole binaries are produced by the mergers of galaxies and are the most powerful sources of gravitational waves accessible to space-based gravitational observatories. Some such mergers may occur in the presence of matter and magnetic fields and hence generate an electromagnetic counterpart. In this paper we present the first general relativistic simulations of magnetized plasma around merging supermassive black holes using the general relativistic magnetohydrodynamic code Whisky. By considering different magnetic field strengths, going from non-magnetically dominated to magnetically dominated regimes, we explore how magnetic fields affect the dynamics of the plasma and the possible emission of electromagnetic signals. In particular we observe, total amplification of the magnetic field of approx 2 orders of magnitude which is driven by the accretion onto the binary and that leads to stronger electromagnetic signals than in the force-free regime where such amplifications are not possible.

A Spectroscopic Orbit for the Late-type Be Star β CMi

NASA Astrophysics Data System (ADS)

Dulaney, Nicholas A.; Richardson, Noel D.; Gerhartz, Cody J.; Bjorkman, J. E.; Bjorkman, K. S.; Carciofi, Alex C.; Klement, Robert; Wang, Luqian; Morrison, Nancy D.; Bratcher, Allison D.; Greco, Jennifer J.; Hardegree-Ullman, Kevin K.; Lembryk, Ludwik; Oswald, Wayne L.; Trucks, Jesica L.

2017-02-01

The late-type Be star β CMi is remarkably stable compared to other Be stars that have been studied. This has led to a realistic model of the outflowing Be disk by Klement et al. These results showed that the disk is likely truncated at a finite radius from the star, which Klement et al. suggest is evidence for an unseen binary companion in orbit. Here we report on an analysis of the Ritter Observatory spectroscopic archive of β CMi to search for evidence of the elusive companion. We detect periodic Doppler shifts in the wings of the Hα line with a period of 170 days and an amplitude of 2.25 km s-1, consistent with a low-mass binary companion (M ≈ 0.42 M ⊙). We then compared small changes in the violet-to-red peak height changes (V/R) with the orbital motion. We find weak evidence that it does follow the orbital motion, as suggested by recent Be binary models by Panoglou et al. Our results, which are similar to those for several other Be stars, suggest that β CMi may be a product of binary evolution where Roche lobe overflow has spun up the current Be star, likely leaving a hot subdwarf or white dwarf in orbit around the star. Unfortunately, no direct sign of this companion star is found in the very limited archive of International Ultraviolet Explorer spectra.

Precision X-ray Timing of RX J0806.3+1527 with CHANDRA: Evidence for Gravitational Radiation from an Ultracompact Binary

NASA Technical Reports Server (NTRS)

Strohymayer, Tod E.

2004-01-01

RX J0806.3+1527 is a candidate double degenerate binary with possibly the shortest known orbital period. The source shows an approximately equal to 100% X-ray intensity modulation at the putative orbital frequency of 3.11 mHz (321.5 s). If the system is a detached, ultracompact binary gravitational radiation should drive spin-up with a magnitude of nu(sup dot) approximately 10(exp -16) Hz per second. Efforts to constrain the X-ray frequency evolution to date have met with mixed success, principally due to the sparseness of earlier observations. Here we describe the results of the first phase coherent X-ray monitoring campaign on RX J0806.3+1527 with Chandra. We obtained a total of 70 ksec of exposure in 6 epochs logarithmically spaced over 320 days. With these data we conclusively show that the X-ray frequency is increasing at a rate of 3.77 plus or minus 0.8 x 10(exp -16) Hz per second. Using the ephemeris derived from the new data we are able to phase up all the earlier Chandra and ROSAT data and show they are consistent with a constant nu(sup dot) = 3.63 plus or minus 0.06 x 10(exp -16) Hz per second over the past decade. This value appears consistent with that recently derived by Israel et al. largely from monitoring of the optical modulation, and is in rough agreement with the solutions reported initially by Hakala et al., based on ground-based optical observations. The large and stable nu(sup dot) over a decade is consistent with gravitational radiation losses driving the evolution. An intermediate polar (IP) scenario where the observed X-ray period is the spin period of an accreting white dwarf appears less tenable because the observed nu(sup dot) requires an m(sup dot) approximately equal to 4 x 10 (exp -8) solar mass yr(sup -l), that is much larger than that inferred from the observed X-ray luminosity (although this depends on the uncertain distance and bolometric corrections), and it is difficult to drive such a high m(sup dot) in a binary system with parameters consistent with all the multiwavelength data. If the ultracompact scenario is correct, then the X-ray flux cannot be powered by stable accretion which would drive the components apart, suggesting a new type of energy source (perhaps electromagnetic) may power the X-ray flux.

Generation of an infectious clone of a new Korean isolate of apple chlorotic leaf spot virus (ACLSV) driven by dual 35S and T7 promoters in a versatile binary vector

USDA-ARS?s Scientific Manuscript database

The full-length sequence of a new isolate of Apple chlorotic leaf spot virus (ACLSV) from Korea was divergent, but most closely related to the Japanese isolate A4, at 84% nucleotide identity. The full-length cDNA of the Korean isolate of ACLSV was cloned into a binary vector downstream of the bacter...

New Pleiades Eclipsing Binaries and a Hyades Transiting System Identified by K2

NASA Astrophysics Data System (ADS)

David, Trevor J.; Conroy, Kyle E.; Hillenbrand, Lynne A.; Stassun, Keivan G.; Stauffer, John; Rebull, Luisa M.; Cody, Ann Marie; Isaacson, Howard; Howard, Andrew W.; Aigrain, Suzanne

2016-05-01

We present the discovery in Kepler’s K2 mission observations and our follow-up radial velocity (RV) observations from Keck/HIRES for four eclipsing binary (EB) star systems in the young benchmark Pleiades and Hyades clusters. Based on our modeling results, we announce two new low mass ({M}{tot}\\lt 0.6 {M}⊙ ) EBs among Pleiades members (HCG 76 and MHO 9) and we report on two previously known Pleiades binaries that are also found to be EB systems (HII 2407 and HD 23642). We measured the masses of the binary HCG 76 to ≲2.5% precision, and the radii to ≲4.5% precision, which together with the precise effective temperatures yield an independent Pleiades distance of 132 ± 5 pc. We discuss another EB toward the Pleiades that is a possible but unlikely Pleiades cluster member (AK II 465). The two new confirmed Pleiades systems extend the mass range of Pleiades EB components to 0.2-2 {M}⊙ . Our initial measurements of the fundamental stellar parameters for the Pleiades EBs are discussed in the context of the current stellar models and the nominal cluster isochrone, finding good agreement with the stellar models of Baraffe et al. at the nominal Pleiades age of 120 Myr. Finally, in the Hyades, we report a new low mass eclipsing system (vA 50) that was concurrently discovered and studied by Mann et al. We confirm that the eclipse is likely caused by a Neptune-sized transiting planet, and with the additional RV constraints presented here we improve the constraint on the maximum mass of the planet to be ≲1.2 MJup.

PSR J0538+2817 as the remnant of the first supernova explosion in a massive binary

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.

It is generally accepted that the radio pulsar PSR J 0538 2817 is associated with the supernova remnant SNR S 147 The only problem for the association is the obvious discrepancy Kramer et al 2003 between the kinematic age of the system of sim 30 kyr estimated from the angular offset of the pulsar from the geometric center of the SNR and pulsar s proper motion and the characteristic age of the pulsar of sim 600 kyr To reconcile these ages one can assume that the pulsar was born with a spin period close to the present one Kramer et al 2003 Romani Ng 2003 We propose an alternative explanation of the age discrepancy based on the fact that PSR J 0538 2817 could be the stellar remnant of the first supernova explosion in a massive binary system and therefore could be as old as indicated by its characteristic age Our proposal implies that S 147 is the diffuse remnant of the second supernova explosion that disrupted the binary system and that a much younger second neutron star not necessarily manifesting itself as a radio pulsar should be associated with S 147 We use the existing observational data on the system PSR J 0538 2817 SNR S 147 to suggest that the progenitor of the supernova that formed S 147 was a Wolf-Rayet star so that the supernova explosion occurred within a wind bubble surrounded by a massive shell and to constrain the parameters of the binary system We also restrict the magnitude and direction of the kick velocity received by the young neutron star at birth and find that the kick vector

The First Detection of (O IV) from an Ultraluminous X-Ray Source with Spitzer. 2. Evidence for High Luminosity in Holmberg II ULX

DTIC Science & Technology

2010-01-01

from the accretion disk of the binary system and inconsistent with narrow beaming. We show that the emission nebula is matter- bounded both in the line...making them very dif- ficult to characterize. The ionization nebulae surrounding some ULXs have become critical for understanding the properties of...Abolmasov et al. 2007). It is located inside an ionized nebula (the “Foot nebula ”), and shows high- ionization optical emission lines coincident with

First-principles study on the thermal expansion of Ni-X binary alloys based on the quasi-harmonic Debye model

NASA Astrophysics Data System (ADS)

Shin, Yongjin; Jung, Woo-Sang; Lee, Young-Su

2016-11-01

In this study, we use the quasi-harmonic Debye model to predict the coefficient of thermal expansion of Ni- X binary alloys. The method bridges between the macroscopic elastic behavior and thermodynamic properties of materials without an expensive calculation of the volume dependence of the phonon density of states. Furthermore, the Grüneisen parameter is derived from the volume dependence of the Debye temperature, which is calculated from the first-principles elastic stiffness constants. The experimental coefficient of thermal expansion (CTE) of pure nickel is well reproduced, especially in the low temperature region. Among the few alloying elements tested, Al is predicted to slightly decrease the CTE whereas Mo and W are more effective in reducing the CTE. For the cases of Ni-X binary alloy systems, where the variation in the CTE is relatively small, the method used here appears to perform better than certain other formulations that rely entirely on the energy vs. volume relationship.

Spectra disentangling applied to the Hyades binary θ2 Tauri AB: new orbit, orbital parallax and component properties

NASA Astrophysics Data System (ADS)

Torres, K. B. V.; Lampens, P.; Frémat, Y.; Hensberge, H.; Lebreton, Y.; Škoda, P.

2011-01-01

Aims: θ^2 Tau is a detached and single-lined interferometric-spectroscopic binary as well as the most massive binary system of the Hyades cluster. The system revolves in an eccentric orbit with a periodicity of 140.7 days. Its light curve furthermore shows a complex pattern of δ Scuti-type pulsations. The secondary has a similar temperature but is less evolved and fainter than the primary. In addition, it is rotating more rapidly. Since the composite spectra are heavily blended, the direct extraction of radial velocities over the orbit of component B was hitherto unsuccessful. Our aim is to reveal the spectrum of the fainter component and its corresponding Doppler shifts in order to improve the accuracy of the physical properties of this important “calibrator” system. Methods: Using high-resolution spectroscopic data recently obtained with the Elodie (Observatoire de Haute-Provence, France) and Hermes (Roque de Los Muchachos, La Palma, Spain) spectrographs, and applying a spectra disentangling algorithm to three independent data sets including CfA spectra (Oak Ridge Observatory, USA), we derived an improved spectroscopic orbit. We next used a code based on simulated annealing and general least-squares minimization to refine the orbital solution by performing a combined astrometric-spectroscopic analysis based on the new spectroscopy and the long-baseline data from the Mark III optical interferometer. Results: As a result of the performed disentangling, and notwithstanding the high degree of blending, the velocity amplitude of the fainter component is obtained in a direct and objective way. Major progress based on this new determination includes an improved computation of the orbital parallax (still consistent with previous values). Our mass ratio is in good agreement with the older estimates of Peterson et al. (1991, 1993), but the mass of the primary is 15-25% higher than the more recent estimates by Torres et al. (1997) and Armstrong et al. (2006). Conclusions: The evolutionary status of both components is re-evaluated in the light of the revisited properties of θ^2 Tau AB. Due to the strategic position of the components in the turnoff region of the cluster, the new determinations imply stricter constraints for the age and the metallicity of the Hyades cluster. We conclude that the location of component B can be explained by current evolutionary models, but the location (and the status) of the more evolved component A is not trivially explained and requires a detailed abundance analysis of its disentangled spectrum. The improved accuracy (at the 2% level) on the stellar masses provides a useful basis for the comparison of the observed pulsation frequencies with suitable theoretical models. Based on observations obtained at the 1.93-m telescope of the Observatoire de Haute Provence, the 1.2-m Mercator telescope at the Roque de los Muchachos Observatory (in the framework of the Hermes Consortium) and the 1.5-m Wyeth telescope at Oak Ridge Observatory.Full Table 4 is only available in electronic form at http://www.aanda.org

Constraining the Radiation and Plasma Environment of the Kepler Circumbinary Habitable-zone Planets

NASA Astrophysics Data System (ADS)

Zuluaga, Jorge I.; Mason, Paul A.; Cuartas-Restrepo, Pablo A.

2016-02-01

The discovery of many planets using the Kepler telescope includes 10 planets orbiting eight binary stars. Three binaries, Kepler-16, Kepler-47, and Kepler-453, have at least one planet in the circumbinary habitable zone (BHZ). We constrain the level of high-energy radiation and the plasma environment in the BHZ of these systems. With this aim, BHZ limits in these Kepler binaries are calculated as a function of time, and the habitability lifetimes are estimated for hypothetical terrestrial planets and/or moons within the BHZ. With the time-dependent BHZ limits established, a self-consistent model is developed describing the evolution of stellar activity and radiation properties as proxies for stellar aggression toward planetary atmospheres. Modeling binary stellar rotation evolution, including the effect of tidal interaction between stars in binaries, is key to establishing the environment around these systems. We find that Kepler-16 and its binary analogs provide a plasma environment favorable for the survival of atmospheres of putative Mars-sized planets and exomoons. Tides have modified the rotation of the stars in Kepler-47, making its radiation environment less harsh in comparison to the solar system. This is a good example of the mechanism first proposed by Mason et al. Kepler-453 has an environment similar to that of the solar system with slightly better than Earth radiation conditions at the inner edge of the BHZ. These results can be reproduced and even reparameterized as stellar evolution and binary tidal models progress, using our online tool http://bhmcalc.net.

CONSTRAINING THE RADIATION AND PLASMA ENVIRONMENT OF THE KEPLER CIRCUMBINARY HABITABLE-ZONE PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuluaga, Jorge I.; Mason, Paul A.; Cuartas-Restrepo, Pablo A.

The discovery of many planets using the Kepler telescope includes 10 planets orbiting eight binary stars. Three binaries, Kepler-16, Kepler-47, and Kepler-453, have at least one planet in the circumbinary habitable zone (BHZ). We constrain the level of high-energy radiation and the plasma environment in the BHZ of these systems. With this aim, BHZ limits in these Kepler binaries are calculated as a function of time, and the habitability lifetimes are estimated for hypothetical terrestrial planets and/or moons within the BHZ. With the time-dependent BHZ limits established, a self-consistent model is developed describing the evolution of stellar activity and radiation propertiesmore » as proxies for stellar aggression toward planetary atmospheres. Modeling binary stellar rotation evolution, including the effect of tidal interaction between stars in binaries, is key to establishing the environment around these systems. We find that Kepler-16 and its binary analogs provide a plasma environment favorable for the survival of atmospheres of putative Mars-sized planets and exomoons. Tides have modified the rotation of the stars in Kepler-47, making its radiation environment less harsh in comparison to the solar system. This is a good example of the mechanism first proposed by Mason et al. Kepler-453 has an environment similar to that of the solar system with slightly better than Earth radiation conditions at the inner edge of the BHZ. These results can be reproduced and even reparameterized as stellar evolution and binary tidal models progress, using our online tool http://bhmcalc.net.« less

Demixing, surface nematization, and competing adsorption in binary mixtures of hard rods and hard spheres under confinement

NASA Astrophysics Data System (ADS)

Wu, Liang; Malijevský, Alexandr; Avendaño, Carlos; Müller, Erich A.; Jackson, George

2018-04-01

A molecular simulation study of binary mixtures of hard spherocylinders (HSCs) and hard spheres (HSs) confined between two structureless hard walls is presented. The principal aim of the work is to understand the effect of the presence of hard spheres on the entropically driven surface nematization of hard rod-like particles at surfaces. The mixtures are studied using a constant normal-pressure Monte Carlo algorithm. The surface adsorption at different compositions is examined in detail. At moderate hard-sphere concentrations, preferential adsorption of the spheres at the wall is found. However, at moderate to high pressure (density), we observe a crossover in the adsorption behavior with nematic layers of the rods forming at the walls leading to local demixing of the system. The presence of the spherical particles is seen to destabilize the surface nematization of the rods, and the degree of demixing increases on increasing the hard-sphere concentration.

Demixing, surface nematization, and competing adsorption in binary mixtures of hard rods and hard spheres under confinement.

PubMed

Wu, Liang; Malijevský, Alexandr; Avendaño, Carlos; Müller, Erich A; Jackson, George

2018-04-28

A molecular simulation study of binary mixtures of hard spherocylinders (HSCs) and hard spheres (HSs) confined between two structureless hard walls is presented. The principal aim of the work is to understand the effect of the presence of hard spheres on the entropically driven surface nematization of hard rod-like particles at surfaces. The mixtures are studied using a constant normal-pressure Monte Carlo algorithm. The surface adsorption at different compositions is examined in detail. At moderate hard-sphere concentrations, preferential adsorption of the spheres at the wall is found. However, at moderate to high pressure (density), we observe a crossover in the adsorption behavior with nematic layers of the rods forming at the walls leading to local demixing of the system. The presence of the spherical particles is seen to destabilize the surface nematization of the rods, and the degree of demixing increases on increasing the hard-sphere concentration.

The Beta Pictoris Phenomenon in Young Stars With Accreting Gas

NASA Technical Reports Server (NTRS)

Grady, Carol A.

1999-01-01

Program Hae2BPIC resulted in usable ISO spectra of three young, Herbig Ae stars: HR 5999 (A7e, t=0.6 Myr), SV Cep (al-2e, t=1-3 Myr), and MW Vul (Al-2e, t=1-3 Myr). While too small a sample to pursue our original goal of surveying the silicate emission in these young, protoplanetary disk systems, comparison of these data with ground-based IR spectra, and published ISO observations of other HAe stars (especially the posters at PPIV) reveals the following: The known binary stars in the sample show signatures of partially crystal line silicate features by t=0.6 Myr, at an epoch when ostensibly single Herbig Ae stars have substantially stronger silicate emission dominated by amorphous grains. The known binary stars also show deficits in the optically thick continuum flux relative to coeval single stars. Comparison of ISO spectra indicates that the flux deficit seen in WD 163296 over 10-100 microns relative to AB Aur reflects a real deficit of material interior to 300.

Blue supergiant progenitors from binary mergers for SN 1987A and other Type II-peculiar supernovae

NASA Astrophysics Data System (ADS)

Menon, Athira; Heger, Alexander

2017-11-01

We present results of a systematic and detailed stellar evolution study of binary mergers for blue supergiant (BSG) progenitors of Type II supernovae, particularly for SN 1987A. We are able to reproduce nearly all observational aspects of the progenitor of SN 1987A, Sk -69 °202, such as its position in the HR diagram, the enrichment of helium and nitrogen in the triple-ring nebula and its lifetime before its explosion. We build our evolutionary model based on the merger model of Podsiadlowski et al. (1992), Podsiadlowski et al. (2007) and empirically explore an initial parameter consisting of primary masses, secondary masses and different depths up to which the secondary penetrates the He core during the merger. The evolution of the post-merger star is continued until just before iron-core collapse. Of the 84 pre-supernova models (16 M⊙ - 23 M⊙) computed, the majority of the pre-supernova models are compact, hot BSGs with effective temperature >12 kK and 30 R⊙ - 70 R⊙ of which six match nearly all the observational properties of Sk -69 °202.

Non-binary LDPC-coded modulation for high-speed optical metro networks with backpropagation

NASA Astrophysics Data System (ADS)

Arabaci, Murat; Djordjevic, Ivan B.; Saunders, Ross; Marcoccia, Roberto M.

2010-01-01

To simultaneously mitigate the linear and nonlinear channel impairments in high-speed optical communications, we propose the use of non-binary low-density-parity-check-coded modulation in combination with a coarse backpropagation method. By employing backpropagation, we reduce the memory in the channel and in return obtain significant reductions in the complexity of the channel equalizer which is exponentially proportional to the channel memory. We then compensate for the remaining channel distortions using forward error correction based on non-binary LDPC codes. We propose non-binary-LDPC-coded modulation scheme because, compared to bit-interleaved binary-LDPC-coded modulation scheme employing turbo equalization, the proposed scheme lowers the computational complexity and latency of the overall system while providing impressively larger coding gains.

Heterogeneity of Multimedia Exposures to Neurotoxic Elements (Al, As, Cd, Pb, Mn, and Hg) in Breastfed Infants from Porto Velho, Brazil.

PubMed

Bastos, Wanderley R; Vieira, Solange M; Manzatto, Ângelo G; Dórea, José G; Rubira, Marcelo C; de Souza, Victor Francisco P; da Costa Junior, Walkimar A; Souza Bastos, Maria T

2017-10-01

Infant exposure to neurotoxic elements is a public health issue that needs monitoring with regard to breast milk composition. We studied six neurotoxic elements in breast milk samples at different stages of lactation in mothers from Porto Velho, Brazil. We used a flow-injection mercury system (FIMS) to determine total Hg concentrations and an inductively coupled plasma optical emission spectrometer (ICP-OES) to determine the concentrations of Al, As, Cd, Pb, and Mn in 106 donors of a human milk bank. Association rules analyses were applied to determine the pattern of binary and ternary mixtures of the measured exposants. The metal concentration was mostly below the limit of detection (LOD) for Cd (99%), Pb (84%), and Hg (72%), and it was above the LOD for As (53%), Mn (60%), and Al (82%), respectively. Median concentrations (dry weight) of Al, As, Hg, Mn, and Pb were 1.81 μg/g, 13.8 ng/g, 7.1 ng/g, 51.1 ng/g, and 0.43 μg/g, respectively. Al is singly the most frequent element to which infants are exposed. Occurring binary combination (> LOD) was 56% for Al-Mn, 41% for Al-As, 22% for Al-Hg, and 13% for Al-Pb. In 100% of neonates, exposure to Al-ethylmercury (EtHg) occurred through immunization with thimerosal-containing vaccines (TCV). Association rules analysis revealed that Al was present in all of the multilevel combinations and hierarchical levels and that it showed a strong link with other neurotoxic elements (especially with Mn, As, and Hg). (a) Nursing infants are exposed to combinations of neurotoxicants by different routes, dosages, and at different stages of development; (b) In breastfed infants, the binary exposures to Al and total Hg can occur through breast milk and additionally through TCV (EtHg and Al); (c) The measured neurotoxic elements were found at low frequencies in breast milk and at concentrations that pose no public health concerns for milk banking.

A fast method for finding bound systems in numerical simulations: Results from the formation of asteroid binaries

NASA Astrophysics Data System (ADS)

Leinhardt, Zoë M.; Richardson, Derek C.

2005-08-01

We present a new code ( companion) that identifies bound systems of particles in O(NlogN) time. Simple binaries consisting of pairs of mutually bound particles and complex hierarchies consisting of collections of mutually bound particles are identifiable with this code. In comparison, brute force binary search methods scale as O(N) while full hierarchy searches can be as expensive as O(N), making analysis highly inefficient for multiple data sets with N≳10. A simple test case is provided to illustrate the method. Timing tests demonstrating O(NlogN) scaling with the new code on real data are presented. We apply our method to data from asteroid satellite simulations [Durda et al., 2004. Icarus 167, 382-396; Erratum: Icarus 170, 242; reprinted article: Icarus 170, 243-257] and note interesting multi-particle configurations. The code is available at http://www.astro.umd.edu/zoe/companion/ and is distributed under the terms and conditions of the GNU Public License.

Stability of binaries. Part II: Rubble-pile binaries

NASA Astrophysics Data System (ADS)

Sharma, Ishan

2016-10-01

We consider the stability of the binary asteroids whose members are granular aggregates held together by self-gravity alone. A binary is said to be stable whenever both its members are orbitally and structurally stable to both orbital and structural perturbations. To this end, we extend the stability analysis of Sharma (Sharma [2015] Icarus, 258, 438-453), that is applicable to binaries with rigid members, to the case of binary systems with rubble members. We employ volume averaging (Sharma et al. [2009] Icarus, 200, 304-322), which was inspired by past work on elastic/fluid, rotating and gravitating ellipsoids. This technique has shown promise when applied to rubble-pile ellipsoids, but requires further work to settle some of its underlying assumptions. The stability test is finally applied to some suspected binary systems, viz., 216 Kleopatra, 624 Hektor and 90 Antiope. We also see that equilibrated binaries that are close to mobilizing their maximum friction can sustain only a narrow range of shapes and, generally, congruent shapes are preferred.

The Growth of Stellar Mass Black Hole Binaries Trapped in the Accretion Disks of Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Yi, Shu-Xu; Cheng, K. S.; Taam, Ronald E.

2018-06-01

Among the four black hole (BH) binary merger events detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO), six progenitor BHs have masses greater than 20 M ⊙. The existence of such massive BHs suggests that extreme metal-poor stars are the progenitors. An alternative possibility, that a pair of stellar mass BHs each with mass ∼7 M ⊙ increases to >20 M ⊙ via accretion from a disk surrounding a supermassive BH (SMBH) in an active galactic nucleus (AGN), is considered. The growth of mass of the binary and the transfer of orbital angular momentum to the disk accelerates the merger. Based on the recent numerical work of Tang et al., it is found that, in the disk of a low-mass AGN with mass ∼106 M ⊙ and Eddington ratio >0.01, the mass of an individual BH in the binary can grow to >20 M ⊙ before coalescence, provided that accretion takes place at a rate more than 10 times the Eddington value. This mechanism predicts a new class of gravitational wave (GW) sources involving the merger of two extreme Kerr black holes associated with AGNs and a possible electromagnetic wave counterpart.

Flux amplification and sustainment of ST plasmas by multi-pulsed coaxial helicity injection on HIST

NASA Astrophysics Data System (ADS)

Higashi, T.; Ishihara, M.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

2010-11-01

The Helicity Injected Spherical Torus (HIST) device has been developed towards high-current start up and sustainment by Multi-pulsed Coaxial Helicity Injection (M-CHI) method. Multiple pulses operation of the coaxial plasma gun can build the magnetic field of STs and spheromak plasmas in a stepwise manner. So far, successive gun pulses on SSPX at LLNL were demonstrated to maintain the magnetic field of spheromak in a quasi-steady state against resistive decay [1]. The resistive 3D-MHD numerical simulation [2] for STs reproduced the current amplification by the M-CHI method and confirmed that stochastic magnetic field was reduced during the decay phase. By double pulsed operation on HIST, the plasma current was effectively amplified against the resistive decay. The life time increases up to 10 ms which is longer than that in the single CHI case (4 ms). The edge poloidal fields last between 0.5 ms and 6 ms like a repetitive manner. During the second driven phase, the toroidal ion flow is driven in the same direction as the plasma current as well as in the initial driven phase. At the meeting, we will discuss a current amplification mechanism based on the merging process with the plasmoid injected secondly from the gun. [1] B. Hudson et al., Phys. Plasmas Vol.15, 056112 (2008). [2] Y. Kagei et al., J. Plasma Fusion Res. Vol.79, 217 (2003).

GenAlEx 6.5: genetic analysis in Excel. Population genetic software for teaching and research—an update

PubMed Central

Peakall, Rod; Smouse, Peter E.

2012-01-01

Summary: GenAlEx: Genetic Analysis in Excel is a cross-platform package for population genetic analyses that runs within Microsoft Excel. GenAlEx offers analysis of diploid codominant, haploid and binary genetic loci and DNA sequences. Both frequency-based (F-statistics, heterozygosity, HWE, population assignment, relatedness) and distance-based (AMOVA, PCoA, Mantel tests, multivariate spatial autocorrelation) analyses are provided. New features include calculation of new estimators of population structure: G′ST, G′′ST, Jost’s Dest and F′ST through AMOVA, Shannon Information analysis, linkage disequilibrium analysis for biallelic data and novel heterogeneity tests for spatial autocorrelation analysis. Export to more than 30 other data formats is provided. Teaching tutorials and expanded step-by-step output options are included. The comprehensive guide has been fully revised. Availability and implementation: GenAlEx is written in VBA and provided as a Microsoft Excel Add-in (compatible with Excel 2003, 2007, 2010 on PC; Excel 2004, 2011 on Macintosh). GenAlEx, and supporting documentation and tutorials are freely available at: http://biology.anu.edu.au/GenAlEx. Contact: rod.peakall@anu.edu.au PMID:22820204

Water-based binary polyol process for the controllable synthesis of silver nanoparticles inhibiting human and foodborne pathogenic bacteria

USDA-ARS?s Scientific Manuscript database

The polyol process is a widely used strategy for producing nanoparticles from various reducible metallic precursors; however it requires a bulk polyol liquid reaction with additional protective agents at high temperatures. Here, we report a water-based binary polyol process using low concentrations ...

Binaries in Transneptunian Resonances: Evidence for Slow Migration of Neptune?

NASA Technical Reports Server (NTRS)

Noll, Keith

2012-01-01

A distinguishing feature of trans neptunian objects (TNO) is the high fraction that arc binary. This is particularly true for the Cold Classicals (CC), objects in lowe and low i orbits concentrated between the 3:2 and 2: 1 mean-motion resonances. CCs have other physical markers: red colors, high albedos, and equal-mass binaries. The CCs appear to be a coherent and physically distinct population of planetesimals that has survived to the present with their physical properties relatively unaltered. Their spatial concentration between 39.4 and 47.7 AU has made identification of the CCs as a physical group possible. However, objects that started out as CCs arc almost certainly 1101 limited to this one dynamical niche. We can, therefore, use the measurable physical properties of CCs as tracers of Neptune-driven dynamical mixing in the Kuiper Belt. As Neptune migrated, its mean-motion resonances preceded it into the planetesimal disk. The efficiency of capture into mean motion resonances depends on the smoothness of Neptune's migration and the local population available to be captured. The two strongest resonances, the 3:2 at 39.4 AU and 2: 1 at 47.7 AU, straddle the core repository of the physically distinct CCs, providing a unique opportunity to test the details of Neptune's migration. Smooth migration should result in a measurable difference between the 3:2 and 2:1 with low inclination 2:1s having a red, binary population mirroring that of the CC itself while the 3:2 will be less contaminated. Alternative models with rapid migration would generate a more homogeneous result.

Avalanche boron fusion by laser picosecond block ignition with magnetic trapping for clean and economic reactor

DOE PAGES

Hora, H.; Korn, G.; Eliezer, S.; ...

2016-10-11

Measured highly elevated gains of proton–boron (HB11) fusion (Picciottoet al., Phys. Rev. X4, 031030 (2014)) confirmed the exceptional avalanche reaction process (Lalousiset al., Laser Part. Beams 32, 409 (2014); Horaet al., Laser Part. Beams33, 607 (2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh accelerationabovemore » $$10^{20}~\\text{cm}~\\text{s}^{-2}$$ for plasma blocks was theoretically and numerically predicted since 1978 (Hora,Physics of Laser Driven Plasmas(Wiley, 1981), pp. 178 and 179) and measured (Sauerbrey, Phys. Plasmas3, 4712 (1996)) in exact agreement (Horaet al., Phys. Plasmas14, 072701 (2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell’s stress tensor by the dielectric properties of plasma leading to the nonlinear (ponderomotive) force $$f_{\\text{NL}}$$ resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. Finally, this is supported also by other experiments with very high HB11 reactions under different conditions (Labauneet al., Nature Commun.4, 2506 (2013)).« less

Sizing Up Red-Giant Twins

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-02-01

In KIC 9246715, two red-giant stars twins in nearly every way circle each other in a 171-day orbit. This binary pair may be a key to learning about masses and radii of stars with asteroseismology, the study of oscillations in the interiors of stars.Two Ways to MeasureIn order to understand a stars evolution, it is critical that we know its mass and radius. Unfortunately, these quantities are often difficult to pin down!One of the few cases in which we can directly measure stars masses and radii is in eclipsing binaries, wherein two stars eclipse each other as they orbit. If we have a well-sampled light curve for the binary, as well as radial velocities for both stars, then we can determine the stars complete orbital information, including their masses and radii.But there may be another way to obtain stellar mass and radius: asteroseismology. In asteroseismology, oscillations inside stars are used to characterize the stellar interiors. Conveniently, if a star with a convective envelope exhibits solar-like oscillations, these oscillations can be directly compared to those of the Sun. Mass and radius scaling relations which use the Sun as a benchmark and scale based on the stars temperature can then be used to derive the mass and radius of the star.Test Subjects from KeplerSolar-like oscillations from KIC 9246715 are shown in red across different resonant frequencies. The oscillations of a single red-giant star with similar properties are shown upside down in grey for reference. [Rawls et al. 2016]Of course, scaling relations are only useful if we can test them! A team of scientists including Meredith Rawls (New Mexico State University) has identified 18 red-giant eclipsing binaries in the Kepler field of view that also exhibit solar-like oscillations perfect for testing the scaling relations.In a recent study led by Rawls, the team analyzed the first of these binaries, KIC 9246715. Using the Kepler light curves in addition to radial velocity measurements from high-resolution ground-based spectroscopy at the Fred Lawrence Whipple Observatory and Apache Point Observatory, Rawls and collaborators established that the two stars have masses of 2.17 and 2.15 solar masses, and radii of 8.4 and 8.3 solar radii.Not Quite Twins?Intriguingly, when the authors measured the stellar oscillations from the binary, they were only able to pick out one signal. Using the scaling relations, their measurements reveal that the star producing the oscillations has a mass of 2.17 solar masses and radius of 8.3 radii consistent with both red giants in the system, within error bars. This provides excellent confirmation of the scaling relations for obtaining mass and radius, but it also raises a new question: why is only one star of this twin system producing oscillations?Rawls and collaborators have an idea: one star might be more magnetically active than the other, causing the suppression of oscillations in the more active star. The authors observations and detailed modeling support this idea, but similar analyses of the rest of the red-giant eclipsing binaries identified in the Kepler field will help to determine if KIC 9246715 is unusual, or if this behavior is common among such systems.CitationMeredith L. Rawls et al 2016 ApJ 818 108. doi:10.3847/0004-637X/818/2/108

Candidate Binary Trojan and Hilda Asteroids from Rotational Light Curves

NASA Astrophysics Data System (ADS)

Sonnett, Sarah M.; Mainzer, Amy K.; Grav, Tommy; Masiero, Joseph R.; Bauer, James M.; Kramer, Emily A.

2017-10-01

Jovian Trojans (hereafter, Trojans) are asteroids in stable orbits at Jupiter's L4 and L5 Lagrange points, and Hilda asteroids are inwards of the Trojans in 3:2 mean-motion resonance with Jupiter. Due to their special dynamical properties, observationally constraining the formation location and dynamical histories of Trojans and HIldas offers key input for giant planet migration models. A fundamental parameter in assessing formation location is the bulk density - with low-density objects associated with an ice-rich formation environment in the outer solar system and high-density objects typically linked to the warmer inner solar system. Bulk density can only be directly measured during a close fly-by or by determining the mutual orbits of binary asteroid systems. With the aim of determining densities for a statistically significant sample of Trojans and Hildas, we are undertaking an observational campaign to confirm and characterize candidate binary asteroids published in Sonnett et al. (2015). These objects were flagged as binary candidates because their large NEOWISE brightness variations imply shapes so elongated that they are not likely explained by a singular equilibrium rubble pile and instead may be two elongated, gravitationally bound asteroids. We are obtaining densely sampled rotational light curves of these possible binaries to search for light curve features diagnostic of binarity and to determine the orbital properties of any confirmed binary systems by modeling the light curve. We compare the We present an update on this follow-up campaign and comment on future steps.

Assisted stellar suicide in V617 Sagittarii

NASA Astrophysics Data System (ADS)

Steiner, J. E.; Oliveira, A. S.; Cieslinski, D.; Ricci, T. V.

2006-02-01

Context: .V617 Sgr is a V Sagittae star - a group of binaries thought to be the galactic counterparts of the Compact Binary Supersoft X-ray Sources - CBSS. Aims: .To check this hypothesis, we measured the time derivative of its orbital period. Methods: .Observed timings of eclipse minima spanning over 30 000 orbital cycles are presented. Results: .We found that the orbital period evolves quite rapidly: P/dot{P} = 1.1×106 years. This is consistent with the idea that V617 Sgr is a wind driven accretion supersoft source. As the binary system evolves with a time-scale of about one million years, which is extremely short for a low mass evolved binary, it is likely that the system will soon end either by having its secondary completely evaporated or by the primary exploding as a supernova of type Ia. Conclusions: .

Planetary Systems Dynamics Eccentric patterns in debris disks & Planetary migration in binary systems

NASA Astrophysics Data System (ADS)

Faramaz, V.; Beust, H.; Augereau, J.-C.; Bonsor, A.; Thébault, P.; Wu, Y.; Marshall, J. P.; del Burgo, C.; Ertel, S.; Eiroa, C.; Montesinos, B.; Mora, A.

2014-01-01

We present some highlights of two ongoing investigations that deal with the dynamics of planetary systems. Firstly, until recently, observed eccentric patterns in debris disks were found in young systems. However recent observations of Gyr-old eccentric debris disks leads to question the survival timescale of this type of asymmetry. One such disk was recently observed in the far-IR by the Herschel Space Observatory around ζ2 Reticuli. Secondly, as a binary companion orbits a circumprimary disk, it creates regions where planet formation is strongly handicapped. However, some planets were detected in this zone in tight binary systems (γ Cep, HD 196885). We aim to determine whether a binary companion can affect migration such that planets are brought in these regions and focus in particular on the planetesimal-driven migration mechanism.

Featured Image: Making a Rapidly Rotating Black Hole

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-10-01

These stills from a simulation show the evolution (from left to right and top to bottom) of a high-mass X-ray binary over 1.1 days, starting after the star on the right fails to explode as a supernova and then collapses into a black hole. Many high-mass X-ray binaries like the well-known Cygnus X-1, the first source widely accepted to be a black hole host rapidly spinning black holes. Despite our observations of these systems, however, were still not sure how these objects end up with such high rotation speeds. Using simulations like that shown above, a team of scientists led by Aldo Batta (UC Santa Cruz) has demonstrated how a failed supernova explosion can result in such a rapidly spinning black hole. The authors work shows that in a binary where one star attempts to explode as a supernova and fails it doesnt succeed in unbinding the star the large amount of fallback material can interact with the companion star and then accrete onto the black hole, spinning it up in the process. You can read more about the authors simulations and conclusions in the paper below.CitationAldo Batta et al 2017 ApJL 846 L15. doi:10.3847/2041-8213/aa8506

Exploring X-Ray Binary Populations in Compact Group Galaxies With Chandra

NASA Technical Reports Server (NTRS)

Tzanavaris, P.; Hornschemeier, A. E..; Gallagher, S. C.; Lenkic, L.; Desjardins, T. D.; Walker, L. M.; Johnson, K. E.; Mulchaey, J. S.

2016-01-01

We obtain total galaxy X-ray luminosities, LX, originating from individually detected point sources in a sample of 47 galaxies in 15 compact groups of galaxies (CGs). For the great majority of our galaxies, we find that the detected point sources most likely are local to their associated galaxy, and are thus extragalactic X-ray binaries (XRBs) or nuclear active galactic nuclei (AGNs). For spiral and irregular galaxies, we find that, after accounting for AGNs and nuclear sources, most CG galaxies are either within the +/-1s scatter of the Mineo et al. LX-star formation rate (SFR) correlation or have higher LX than predicted by this correlation for their SFR. We discuss how these "excesses" may be due to low metallicities and high interaction levels. For elliptical and S0 galaxies, after accounting for AGNs and nuclear sources, most CG galaxies are consistent with the Boroson et al. LX-stellar mass correlation for low-mass XRBs, with larger scatter, likely due to residual effects such as AGN activity or hot gas. Assuming non-nuclear sources are low- or high-mass XRBs, we use appropriate XRB luminosity functions to estimate the probability that stochastic effects can lead to such extreme LX values. We find that, although stochastic effects do not in general appear to be important, for some galaxies there is a significant probability that high LX values can be observed due to strong XRB variability.

Tertiary particle physics with ELI: from challenge to chance (Conference Presentation)

NASA Astrophysics Data System (ADS)

Drska, Ladislav

2017-05-01

nteraction of high-intensity laser pulses with solid state targets results in generation of intense pulses of secondary particles via electromagnetic interaction : electrons, ions, hard x-rays. The beams of these particles can be used to produce various types of third-generation particles, beyond electromagnetic also other types of fundamental interactions can be involved in this process [1]. As the most interesting tertiary particles could be mentioned positrons, neutron, muons. This paper shall extend our previous analysis of this topic [2]: it discusses selected technical problems of design and realization of applicable sources of these particles and presents some more elaborated proposals for potential meaningful / hopefuly realistic exploitations of this technology. (1)Tertiary Sources (TS) : First Development Steps. This part of the presentation includes the topics as follows: (11) Pulsed positron sources: Verified solutions of laser-driven positron sources [3] [4] [5], development towards applicable facilities. Some unconventional concepts of application of lasers for positron production [6]. Techniques for realization of low/very-low energy positrons. (12) Taylored neutron sources [7]: Neutron sources with demanded space distribution, strongly beamed and isotropic solutions [8] [9]. Neutron generation with taylored energy distribution. Problem of the direct production of neutrons with very low energy [10] [11]. (13) Potential muon sources: Proof-of-principle laser experiment on electron / photon driven muon production [12] [13]. Study of the possibility of effective generation of surface muons. Problems of the production of muons with very low energy. (2) Fundamental & Applied Physics with TS: This part of the talk presents the themes: (21) Diagnostic potential of TS: Lepton emission as a signature of processes in extreme systems. Passive and active diagnostics using positrons, problems of detection and evaluation. Potential diagnostic applications of muons. Concrete application study: muon tomography. (22) Antilepton gravity studies [14]: Possibility of antimattter gravity research using positronium and muonium [15] [16]. Lepton / antilepton gravity studiesactive with relativistic particle beams [17]. First-phase practical application : positron production for filling (commertial) particle traps, development base for multiple microtrap systems. (23) Hidden world searching [18] : Potential laser-based production / detection of selected dark mattter particles - axions, hidden photons [19] [20]. Search for hidden particles in nuclear decay processes [21]. Potential application output: intense positronium source. Conclusion: The extensive feasibility study confirms the potential of ELI to contribute to the solution of Grand Challenge Problems of physics. Laser-produced tertiary particles will play important role in this effort. : References [1] L.Drska et al.: Physics of Extreme Systems. Course ATHENS CTU18, Prague 12 - 19 Nov., 2016. http://vega.fjfi.cvut.cz/docs/athens2016/ [2] L.Drska : Lepton Diagnostics and Antimatter Physics. In: SPIE Optics+Optoelectronics, Prague, April 13 - 16, 2015 . [3] H. Chen et al.: Scaling the Yield of Laser-Driven Electron-Positron Jets to Laboratory Astrophysics Applications. Rep. LLNL-JRNL-665381, Dec. 11, 2014. [4] E Liang et al.: High e+ / e- Ratio Dense Pair Creation with 1022 W.cm-2 Laser Irradiating Solid Targets. Scientific Reports, Sept. 14, 2015. www.nature.com/scientificreports [5] G. Sarri et al.: Spectral and Spatial Characterization of Laser-driven Positron Beams. Plasma Phys. Control. Fusion 59 (2017) 014015. [6] B. Schoch: A Method to Produce Intense Positron Beams via Electro Pair Production on Electrons. arXiv:1607.03847v1 [physics.acc-ph] [7] I. Pomerantz: Laser Generation of Neutrons: Science and Applications. In: ELI-NP Summer School, Magurele, Sept. 21 - 25, 2015. http://www.eli-np.ro/2015-summer-school/presentations/23.09/Pomerantz_Eli-NP-Summer-school-2015.pdf [8] V.P. Kovalev: Secondary Radiation of Electron Accelerators (in Russian). Atomizdat 1969. [9] M. Lebois et al.: Development of a Kinematically Focused Neutron Source with p(Li7,n)Be7 Inverse Reaction. Nucl. Instr. Meth. Phys. Res. A 735 (2014), 145. [10] D. Habs et al.: Neutron Halo Isomers in Stable Nuclei and their Possible Application for the Production of Low Energy, Pulsed, Polarized Neutron Beams of High Intensity and High Brilliance. Appl. Phys B103 (2011),485. [11] T. Masuda et al.: A New Method of Creating High/Intensity Neutron Source. arXiv:1604.02818v1[nucl-ex] [12] A.I. Titov et al.: Dimuon Production by Laser-wakefield Accelerated Electrons. Phys. Rev. ST Accel. Beams 12 (2009) 111301. [13] W. Dreesen et al.: Detection of Petawatt Laser-Induced Muon Source for Rapid High-Gamma Material Detection. DOE/NV/25946-2262. [14] F. Castelli: Positronium and Fundamental Physics: What Next ? In: What Next, Florence 2015. [15] G. Dufour et al. : Prospects for Studies of the Free Fall and Gravitation Quantum States of Antimatter. Advances in High Energy Physics 2015 (2015) 379642. [16] D.M. Kaplan et al.. Antimatter Gravity with Muonium. IIT-CAPP-16-1. arXiv:1601.07222v2 [physics.ins-det] [17] T. Kalaydzhyan: Gravitational Mass of Positron from LEP Synchrotron Losses. arXiv:1508.04377v3 [hep-ph] [18] J. Alexander et al.: Dark Sector 2016 Workshop: Community Report. arXiv:1608.08632[hep-ph] [19] M.A. Wahud et al.: Axion-like Particle Production in a Laser-Induced Dynamical Spacertime. arXiv:1612.07743v1 [hep-ph] [20] V. Kozhuharov et al: New Projects on Dark Photon Search. arXiv:1610.04389v1 [hep-ex] [21] A.J. Krasznahorkay et al.: Observation of Anomalous Internal Pair Creation in Be8: A Possible Signature of a Light, Neutral Boson. arXiv:1504.01527v1 [nucl-ex

The nature of the laning transition in two dimensions

NASA Astrophysics Data System (ADS)

Glanz, T.; Löwen, H.

2012-11-01

If a binary colloidal mixture is oppositely driven by an external field, a transition towards a laned state occurs at sufficiently large drives, where particles driven alike form elongated structures (‘lanes’) characterized by a large correlation length ξ along the drive. Here we perform extensive Brownian dynamics computer simulations on a two-dimensional equimolar binary Yukawa system driven by a constant force that acts oppositely on the two species. We systematically address finite-size effects on lane formation by exploring large systems up to 262 144 particles under various boundary conditions. It is found that the correlation length ξ along the field depends exponentially on the driving force (or Peclet number). Conversely, in a finite system, ξ reaches a fraction of the system size at a driving force which is logarithmic in the system size, implying massive finite-size corrections. For a fixed finite drive, ξ does not diverge in the thermodynamic limit. Therefore, though laning has a signature as a sharp transition in a finite system, it is a smooth crossover in the thermodynamic limit.

Particle acceleration and transport at a 2D CME-driven shock using the HAFv3 and PATH Code

NASA Astrophysics Data System (ADS)

Li, G.; Ao, X.; Fry, C. D.; Verkhoglyadova, O. P.; Zank, G. P.

2012-12-01

We study particle acceleration at a 2D CME-driven shock and the subsequent transport in the inner heliosphere (up to 2 AU) by coupling the kinematic Hakamada-Akasofu-Fry version 3 (HAFv3) solar wind model (Hakamada and Akasofu, 1982, Fry et al. 2003) with the Particle Acceleration and Transport in the Heliosphere (PATH) model (Zank et al., 2000, Li et al., 2003, 2005, Verkhoglyadova et al. 2009). The HAFv3 provides the evolution of a two-dimensional shock geometry and other plasma parameters, which are fed into the PATH model to investigate the effect of a varying shock geometry on particle acceleration and transport. The transport module of the PATH model is parallelized and utilizes the state-of-the-art GPU computation technique to achieve a rapid physics-based numerical description of the interplanetary energetic particles. Together with a fast execution of the HAFv3 model, the coupled code gives us a possibility to nowcast/forecast the interplanetary radiation environment.

The evolution of photoevaporating viscous discs in binaries

NASA Astrophysics Data System (ADS)

Rosotti, Giovanni P.; Clarke, Cathie J.

2018-02-01

A large fraction of stars are in binary systems, yet the evolution of protoplanetary discs in binaries has been little explored from the theoretical side. In this paper, we investigate the evolution of the discs surrounding the primary and secondary components of binary systems on the assumption that this is driven by photoevaporation induced by X-rays from the respective star. We show how for close enough separations (20-30 au for average X-ray luminosities) the tidal torque of the companion changes the qualitative behaviour of disc dispersal from inside out to outside in. Fewer transition discs created by photoevaporation are thus expected in binaries. We also demonstrate that in close binaries the reduction in viscous time leads to accelerated disc clearing around both components, consistent with unresolved observations. When looking at the differential disc evolution around the two components, in close binaries discs around the secondary clear first due to the shorter viscous time-scale associated with the smaller outer radius. In wide binaries instead the difference in photoevaporation rate makes the secondaries longer lived, though this is somewhat dependent on the assumed scaling of viscosity with stellar mass. We find that our models are broadly compatible with the growing sample of resolved observations of discs in binaries. We also predict that binaries have higher accretion rates than single stars for the same disc mass. Thus, binaries probably contribute to the observed scatter in the relationship between disc mass and accretion rate in young stars.

Low-mass X-ray binaries from black hole retaining globular clusters

NASA Astrophysics Data System (ADS)

Giesler, Matthew; Clausen, Drew; Ott, Christian D.

2018-06-01

Recent studies suggest that globular clusters (GCs) may retain a substantial population of stellar-mass black holes (BHs), in contrast to the long-held belief of a few to zero BHs. We model the population of BH low-mass X-ray binaries (BH-LMXBs), an ideal observable proxy for elusive single BHs, produced from a representative group of Milky Way GCs with variable BH populations. We simulate the formation of BH binaries in GCs through exchange interactions between binary and single stars in the company of tens to hundreds of BHs. Additionally, we consider the impact of the BH population on the rate of compact binaries undergoing gravitational wave driven mergers. The characteristics of the BH-LMXB population and binary properties are sensitive to the GCs structural parameters as well as its unobservable BH population. We find that GCs retaining ˜1000 BHs produce a galactic population of ˜150 ejected BH-LMXBs, whereas GCs retaining only ˜20 BHs produce zero ejected BH-LMXBs. Moreover, we explore the possibility that some of the presently known BH-LMXBs might have originated in GCs and identify five candidate systems.

Binary to Octal and Octal to Binary Code Converter Using Mach-Zehnder Interferometer for High Speed Communication

NASA Astrophysics Data System (ADS)

Pal, Amrindra; Kumar, Santosh; Sharma, Sandeep

2017-05-01

Binary to octal and octal to binary code converter is a device that allows placing digital information from many inputs to many outputs. Any application of combinational logic circuit can be implemented by using external gates. In this paper, binary to octal and octal to binary code converter is proposed using electro-optic effect inside lithium-niobate based Mach-Zehnder interferometers (MZIs). The MZI structures have powerful capability to switching an optical input signal to a desired output port. The paper constitutes a mathematical description of the proposed device and thereafter simulation using MATLAB. The study is verified using beam propagation method (BPM).

Oxidation Kinetics of Cast TiAl3

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Humphrey, D. L.

1992-01-01

The isothermal oxidation kinetics of the TiAl3 compound over a wide temperature range is documented, and these rates are related to exclusive alpha-Al2O3 scale growth. The specific weight change vs time curves are shown. Two abnormalities are immediately apparent. One is that a rapid initial uptake of oxygen occurs at times less than 5 h, followed by a lower oxidation rate at longer times, for tests at 900 C and below. The other is that the final weight changes for the 700, 800, and 900 C tests are not in the sequence expected with respect to temperature. Isothermal oxidation of drop cast TiAl above 1000 C was found to exhibit parabolic oxidation controlled by protective alpha-Al2O3 scale formation. TiAl is the only phase in the binary Ti-Al system that forms exclusive scales of alpha-Al2O3 in isothermal oxidation. High anomalous rates at short times and at temperatures below 1000 C resulted from the internal oxidation of a second phase of aluminum.

An adjoint-based framework for maximizing mixing in binary fluids

NASA Astrophysics Data System (ADS)

Eggl, Maximilian; Schmid, Peter

2017-11-01

Mixing in the inertial, but laminar parameter regime is a common application in a wide range of industries. Enhancing the efficiency of mixing processes thus has a fundamental effect on product quality, material homogeneity and, last but not least, production costs. In this project, we address mixing efficiency in the above mentioned regime (Reynolds number Re = 1000 , Peclet number Pe = 1000) by developing and demonstrating an algorithm based on nonlinear adjoint looping that minimizes the variance of a passive scalar field which models our binary Newtonian fluids. The numerical method is based on the FLUSI code (Engels et al. 2016), a Fourier pseudo-spectral code, which we modified and augmented by scalar transport and adjoint equations. Mixing is accomplished by moving stirrers which are numerically modeled using a penalization approach. In our two-dimensional simulations we consider rotating circular and elliptic stirrers and extract optimal mixing strategies from the iterative scheme. The case of optimizing shape and rotational speed of the stirrers will be demonstrated.

Sawtooth events and O+ in the plasma sheet and boundary layer: CME- and SIR-driven events

NASA Astrophysics Data System (ADS)

Lund, E. J.; Nowrouzi, N.; Kistler, L. M.; Cai, X.; Liao, J.

2017-12-01

The role of ionospheric ions in sawtooth events is an open question. Simulations[1,2,3] suggest that O+ from the ionosphere produces a feedback mechanism for driving sawtooth events. However, observational evidence[4,5] suggest that the presence of O+ in the plasma sheet is neither necessary nor sufficient. In this study we investigate whether the solar wind driver of the geomagnetic storm has an effect on the result. Building on an earlier study[4] that used events for which Cluster data is available in the plasma sheet and boundary layer, we perform a superposed epoch analysis for coronal mass ejection (CME) driven storms and streaming interaction region (SIR) driven storms separately, to investigate the hypothesis that ionospheric O+ is an important contributor for CME-driven storms but not SIR-driven storms[2]. [1]O. J. Brambles et al. (2011), Science 332, 1183.[2]O. J. Brambles et al. (2013), JGR 118, 6026.[3]R. H. Varney et al. (2016), JGR 121, 9688.[4]J. Liao et al. (2014), JGR 119, 1572.[5]E. J. Lund et al. (2017), JGR, submitted.

Photo-degradation of basic green 1 and basic red 46 dyes in their binary solution by La2O3-Al2O3nanocomposite using first-order derivative spectra and experimental design methodology.

PubMed

Fahimirad, Bahareh; Asghari, Alireza; Rajabi, Maryam

2017-05-15

In this work, the lanthanum oxide-aluminum oxide (La 2 O 3 -Al 2 O 3 ) nanocomposite is introduced as an efficient photocatalyst for the photo-degradation of the dyes basic green 1 (BG1) and basic red 46 (BR46) in their binary aqueous solution under the UV light irradiation. The properties of this catalyst are determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and UV-visible spectrophotometry. The first-order derivative spectra are used for the simultaneous analysis of the dyes in their binary solution. The screening investigations indicate that five parameters including the catalyst dosage, concentration of the dyes, irradiation time, and solution pH have significant effects on the photo-degradation of the dyes. The effects of these variables together with their interactions in the photo-degradation of the dyes are studied using the Box-Behnken design (BBD). Under the optimum experimental conditions, obtained via the desirability function, the photo-catalytic activities of La 2 O 3 -Al 2 O 3 and pure Al 2 O 3 are also investigated. The results obtained show an enhancement in the photo-catalytic activity when La 2 O 3 nanoparticles are loaded on the surface of Al 2 O 3 nanoparticles. Copyright © 2017 Elsevier B.V. All rights reserved.

An Investigation of the Interatomic Bonding Characteristics of a Ti - 51at.% Al Alloy by X-Ray Diffraction

DTIC Science & Technology

1991-06-01

GROUP SUBGROUP X-ray Diffraction, XRD, TiAI, titanium , aluminum, bonding characteristics, titanium aluminides , Debye-Waller temperature factor...XRD Powder Particles (575X) .............. 47 viii I. INTRODUCTION Titanium aluminides are recognized for their high specific strength, particularly at...bonding characteristics of binary titanium aluminides . Upon the introduction of a third element to the system, a rearrangement of the valence

VizieR Online Data Catalog: Excess CaII H&K emission in active binaries (Montes+, 1996)

NASA Astrophysics Data System (ADS)

Montes, D.; Fernandez-Figueroa, M. J.; Cornide, M.; de Castro, E.

1996-05-01

In this work we analyze the behaviour of the excess CaII H & K and H_epsilon emissions in a sample of 73 chromospherically active binary systems (RS CVn and BY Dra classes), of different activity levels and luminosity classes. This sample includes the 53 stars analyzed by Fernandez-Figueroa et al. (1994) and the observations of 28 systems described by Montes et al. (1995). By using the spectral subtraction technique (subtraction of a synthesized stellar spectrum constructed from reference stars of spectral type and luminosity class similar to those of the binary star components) we obtain the active-chromosphere contribution to the CaII H & K lines in these 73 systems. We have determined the excess CaII H & K emission equivalent widths and converted them into surface fluxes. The emissions arising from each component were obtained when it was possible to deblend both contributions. (4 data files).

Thermodynamics of Liquid Alkali Metals and Their Binary Alloys

NASA Astrophysics Data System (ADS)

Thakor, P. B.; Patel, Minal H.; Gajjar, P. N.; Jani, A. R.

2009-07-01

The theoretical investigation of thermodynamic properties like internal energy, entropy, Helmholtz free energy, heat of mixing (ΔE) and entropy of mixing (ΔS) of liquid alkali metals and their binary alloys are reported in the present paper. The effect of concentration on the thermodynamic properties of Ac1Bc2 alloy of the alkali-alkali elements is investigated and reported for the first time using our well established local pseudopotential. To investigate influence of exchange and correlation effects, we have used five different local field correction functions viz; Hartree(H), Taylor(T), Ichimaru and Utsumi(IU), Farid et al. (F) and Sarkar et al. (S). The increase of concentration C2, increases the internal energy and Helmholtz free energy of liquid alloy Ac1Bc2. The behavior of present computation is not showing any abnormality in the outcome and hence confirms the applicability of our model potential in explaining the thermodynamics of liquid binary alloys.

Laser driven supersonic flow over a compressible foam surface on the Nike lasera)

NASA Astrophysics Data System (ADS)

Harding, E. C.; Drake, R. P.; Aglitskiy, Y.; Plewa, T.; Velikovich, A. L.; Gillespie, R. S.; Weaver, J. L.; Visco, A.; Grosskopf, M. J.; Ditmar, J. R.

2010-05-01

A laser driven millimeter-scale target was used to generate a supersonic shear layer in an attempt to create a Kelvin-Helmholtz (KH) unstable interface in a high-energy-density (HED) plasma. The KH instability is a fundamental fluid instability that remains unexplored in HED plasmas, which are relevant to the inertial confinement fusion and astrophysical environments. In the experiment presented here the Nike laser [S. P. Obenschain et al., Phys. Plasmas 3, 2098 (1996)] was used to create and drive Al plasma over a rippled foam surface. In response to the supersonic Al flow (Mach=2.6±1.1) shocks should form in the Al flow near the perturbations. The experimental data were used to infer the existence and location of these shocks. In addition, the interface perturbations show growth that has possible contributions from both KH and Richtmyer-Meshkov instabilities. Since compressible shear layers exhibit smaller growth, it is important to use the KH growth rate derived from the compressible dispersion relation.

Reliable binary cell-fate decisions based on oscillations

NASA Astrophysics Data System (ADS)

Pfeuty, B.; Kaneko, K.

2014-02-01

Biological systems have often to perform binary decisions under highly dynamic and noisy environments, such as during cell-fate determination. These decisions can be implemented by two main bifurcation mechanisms based on the transitions from either monostability or oscillation to bistability. We compare these two mechanisms by using stochastic models with time-varying fields and by establishing asymptotic formulas for the choice probabilities. Different scaling laws for decision sensitivity with respect to noise strength and signal timescale are obtained, supporting a role for oscillatory dynamics in performing noise-robust and temporally tunable binary decision-making. This result provides a rationale for recent experimental evidences showing that oscillatory expression of proteins often precedes binary cell-fate decisions.

Compact Objects In Binary Systems: Formation and Evolution of X-ray Binaries and Tides in Double White Dwarfs

NASA Astrophysics Data System (ADS)

Valsecchi, Francesca

Binary star systems hosting black holes, neutron stars, and white dwarfs are unique laboratories for investigating both extreme physical conditions, and stellar and binary evolution. Black holes and neutron stars are observed in X-ray binaries, where mass accretion from a stellar companion renders them X-ray bright. Although instruments like Chandra have revolutionized the field of X-ray binaries, our theoretical understanding of their origin and formation lags behind. Progress can be made by unravelling the evolutionary history of observed systems. As part of my thesis work, I have developed an analysis method that uses detailed stellar models and all the observational constraints of a system to reconstruct its evolutionary path. This analysis models the orbital evolution from compact-object formation to the present time, the binary orbital dynamics due to explosive mass loss and a possible kick at core collapse, and the evolution from the progenitor's Zero Age Main Sequence to compact-object formation. This method led to a theoretical model for M33 X-7, one of the most massive X-ray binaries known and originally marked as an evolutionary challenge. Compact objects are also expected gravitational wave (GW) sources. In particular, double white dwarfs are both guaranteed GW sources and observed electromagnetically. Although known systems show evidence of tidal deformation and a successful GW astronomy requires realistic models of the sources, detached double white dwarfs are generally approximated to point masses. For the first time, I used realistic models to study tidally-driven periastron precession in eccentric binaries. I demonstrated that its imprint on the GW signal yields constrains on the components' masses and that the source would be misclassified if tides are neglected. Beyond this adiabatic precession, tidal dissipation creates a sink of orbital angular momentum. Its efficiency is strongest when tides are dynamic and excite the components' free oscillation modes. Accounting for this effect will determine whether our interpretation of current and future observations will constrain the sources' true physical properties. To investigate dynamic tides I have developed CAFein, a novel code that calculates forced non-adiabatic stellar oscillations using a highly stable and efficient numerical method.

Shell-binary nanoparticle materials with variable electrical and electro-mechanical properties.

PubMed

Zhang, P; Bousack, H; Dai, Y; Offenhäusser, A; Mayer, D

2018-01-18

Nanoparticle (NP) materials with the capability to adjust their electrical and electro-mechanical properties facilitate applications in strain sensing technology. Traditional NP materials based on single component NPs lack a systematic and effective means of tuning their electrical and electro-mechanical properties. Here, we report on a new type of shell-binary NP material fabricated by self-assembly with either homogeneous or heterogeneous arrangements of NPs. Variable electrical and electro-mechanical properties were obtained for both materials. We show that the electrical and electro-mechanical properties of these shell-binary NP materials are highly tunable and strongly affected by the NP species as well as their corresponding volume fraction ratio. The conductivity and the gauge factor of these shell-binary NP materials can be altered by about five and two orders of magnitude, respectively. These shell-binary NP materials with different arrangements of NPs also demonstrate different volume fraction dependent electro-mechanical properties. The shell-binary NP materials with a heterogeneous arrangement of NPs exhibit a peaking of the sensitivity at medium mixing ratios, which arises from the aggregation induced local strain enhancement. Studies on the electron transport regimes and micro-morphologies of these shell-binary NP materials revealed the different mechanisms accounting for the variable electrical and electro-mechanical properties. A model based on effective medium theory is used to describe the electrical and electro-mechanical properties of such shell-binary nanomaterials and shows an excellent match with experiment data. These shell-binary NP materials possess great potential applications in high-performance strain sensing technology due to their variable electrical and electro-mechanical properties.

Precision Ephemerides for Gravitational-wave Searches. I. Sco X-1

NASA Astrophysics Data System (ADS)

Galloway, Duncan K.; Premachandra, Sammanani; Steeghs, Danny; Marsh, Tom; Casares, Jorge; Cornelisse, Rémon

2014-01-01

Rapidly rotating neutron stars are the only candidates for persistent high-frequency gravitational wave emission, for which a targeted search can be performed based on the spin period measured from electromagnetic (e.g., radio and X-ray) observations. The principal factor determining the sensitivity of such searches is the measurement precision of the physical parameters of the system. Neutron stars in X-ray binaries present additional computational demands for searches due to the uncertainty in the binary parameters. We present the results of a pilot study with the goal of improving the measurement precision of binary orbital parameters for candidate gravitational wave sources. We observed the optical counterpart of Sco X-1 in 2011 June with the William Herschel Telescope and also made use of Very Large Telescope observations in 2011 to provide an additional epoch of radial-velocity measurements to earlier measurements in 1999. From a circular orbit fit to the combined data set, we obtained an improvement of a factor of 2 in the orbital period precision and a factor of 2.5 in the epoch of inferior conjunction T 0. While the new orbital period is consistent with the previous value of Gottlieb et al., the new T 0 (and the amplitude of variation of the Bowen line velocities) exhibited a significant shift, which we attribute to variations in the emission geometry with epoch. We propagate the uncertainties on these parameters through to the expected Advanced LIGO-Virgo detector network observation epochs and quantify the improvement obtained with additional optical observations. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 087.D-0278.

CLOSE BINARIES WITH INFRARED EXCESS: DESTROYERS OF WORLDS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matranga, M.; Drake, J. J.; Kashyap, V. L.

2010-09-10

We present the results of a Spitzer photometric investigation into the IR excesses of close binary systems. In a sample of 10 objects, excesses in Infrared Array Camera and MIPS24 bands implying the presence of warm dust are found for 3. For two objects, we do not find excesses reported in earlier IRAS studies. We discuss the results in the context of the scenario suggested by Rhee and co-workers, in which warm dust is continuously created by destructive collisions between planetary bodies. A simple numerical model for the steady-state distribution of dust in one IR excess system shows a centralmore » clearing of radius 0.22 AU caused by dynamical perturbations from the binary star. This is consistent with the size of the central clearing derived from the Spitzer spectral energy distribution. We conclude that close binaries could be efficient 'destroyers of worlds' and lead to destabilization of the orbits of their planetary progeny by magnetically driven angular momentum loss and secular shrinkage of the binary separation.« less

Chemical abundances of primary stars in the Sirius-like binary systems

NASA Astrophysics Data System (ADS)

Kong, X. M.; Zhao, G.; Zhao, J. K.; Shi, J. R.; Kumar, Y. Bharat; Wang, L.; Zhang, J. B.; Wang, Y.; Zhou, Y. T.

2018-05-01

Study of primary stars lying in Sirius-like systems with various masses of white dwarf (WD) companions and orbital separations is one of the key aspects to understand the origin and nature of barium (Ba) stars. In this paper, based on high-resolution and high-S/N spectra, we present systematic analysis of photospheric abundances for 18 FGK primary stars of Sirius-like systems including six giants and 12 dwarfs. Atmospheric parameters, stellar masses, and abundances of 24 elements (C, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Ba, La, Ce, and Nd) are determined homogeneously. The abundance patterns in these sample stars show that most of the elements in our sample follow the behaviour of field stars with similar metallicity. As expected, s-process elements in four known Ba giants show overabundance. A weak correlation was found between anomalies of s-process elemental abundance and orbital separation, suggesting that the orbital separation of the binaries could not be the main constraint to differentiate strong Ba stars from mild Ba stars. Our study shows that the large mass (>0.51 M⊙) of a WD companion in a binary system is not a sufficient condition to form a Ba star, even if the separation between the two components is small. Although not sufficient, it seems to be a necessary condition since Ba stars with lower mass WDs in the observed sample were not found. Our results support that [s/Fe] and [hs/ls] ratios of Ba stars are anti-correlated with the metallicity. However, the different levels of s-process overabundance among Ba stars may not be dominated mainly by the metallicity.

X-Ray Probes of Cosmic Star Formation History

NASA Technical Reports Server (NTRS)

Ghosh, Pranab; White, Nicholas E.

2001-01-01

We discuss the imprints left by a cosmological evolution of the star formation rate (SFR) on the evolution of X-ray luminosities Lx of normal galaxies, using the scheme earlier proposed by us, wherein the evolution of LX of a galaxy is driven by the evolution of its X-ray binary population. As indicated in our earlier work, the profile of Lx with redshift can both serve as a diagnostic probe of the SFR profile and constrain evolutionary models for X-ray binaries. We report here the first calculation of the expected evolution of X-ray luminosities of galaxies, updating our work by using a suite of more recently developed SFR profiles that span the currently plausible range. The first Chandra deep imaging results on Lx evolution are beginning to probe the SFR profile of bright spiral galaxies; the early results are consistent with predictions based on current SFR models. Using these new SFR profiles, the resolution of the "birthrate problem" of low-mass X-ray binaries and recycled, millisecond pulsars in terms of an evolving global SFR is more complete. We discuss the possible impact of the variations in the SFR profile of individual galaxies and galaxy types.

Demixing in symmetric supersolid mixtures

NASA Astrophysics Data System (ADS)

Jain, Piyush; Moroni, Saverio; Boninsegni, Massimo; Pollet, Lode

2013-09-01

The droplet crystal phase of a symmetric binary mixture of soft-core bosons is studied by computer simulation. At high temperature each droplet comprises on average equal numbers of particles of either component, but the two components demix below the supersolid transition temperature, i.e., droplets mostly consist of particles of one component. Clustering of droplets of the same component is also observed. Demixing is driven by quantum tunneling of particles across droplets over the system and does not take place in an insulating crystal. This effect provides an unambiguous experimental signature of supersolidity.

X-rays from the eclipsing pulsar 1957+20

NASA Technical Reports Server (NTRS)

Fruchter, A. S.; Bookbinder, J.; Garcia, M. R.; Bailyn, C. D.

1992-01-01

The detection of soft X-rays of about 1 keV energy from the eclipsing pulsar PSR1957+20 is reported. This high-energy radiation should be a valuable diagnostic of the wind in this recycled pulsar system. Possible sources of the X-ray emission are the interstellar nebula driven by the pulsar wind, the interaction between the pulsar and its evaporating companion, and the pulsar itself. The small apparent size of the X-ray object argues against the first of these possibilities and suggests that the X-rays are produced within the binary.

High-Contrast 3.8 Micron Imaging of the Brown Dwarf/Planet-Mass Companion to GJ 758

NASA Technical Reports Server (NTRS)

Currie, Thayne; Bailey, Vanessa; Fabrycky, Daniel; Murray-Clay, Ruth; Rodigas, Timothy; Hinz, Phil

2010-01-01

We present L' band (3.8 Micron) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to have one -- possibly two-- faint comoving companions (GJ 7588 and "C", respectively). GJ 758B is detected in two distinct datasets. Additionally, we report a \\textit(possible) detection of the object identified by Thalmann et al as "GJ 758C" in our more sensitive dataset, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 758B has a H-L'color redder than nearly all known L--T8 dwarfs. Based on comparisons with the COND evolutionary models, GJ 758B has Te approx. 560 K (+150 K, -90 K) and a mass ranging from approx. 10-20 Mj if it is approx. 1 Gyr old to approx. 25-40 Mj if it is 8.7 Gyr old. GJ 758B is likely in a highly eccentric orbit, e approx. 0.73 (+0.12,-0.21), with a semimajor axis of approx. 44 AU (+32 AU, -14 AU). Though GJ 758B is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of jovian-mass planets.

The Araucaria project. The distance to the small Magellanic Cloud from late-type eclipsing binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graczyk, Dariusz; Pietrzyński, Grzegorz; Gieren, Wolfgang

2014-01-01

We present a distance determination to the Small Magellanic Cloud (SMC) based on an analysis of four detached, long-period, late-type eclipsing binaries discovered by the Optical Gravitational Lensing Experiment (OGLE) survey. The components of the binaries show negligible intrinsic variability. A consistent set of stellar parameters was derived with low statistical and systematic uncertainty. The absolute dimensions of the stars are calculated with a precision of better than 3%. The surface brightness-infrared color relation was used to derive the distance to each binary. The four systems clump around a distance modulus of (m – M) = 18.99 with a dispersionmore » of only 0.05 mag. Combining these results with the distance published by Graczyk et al. for the eclipsing binary OGLE SMC113.3 4007, we obtain a mean distance modulus to the SMC of 18.965 ± 0.025 (stat.) ± 0.048 (syst.) mag. This corresponds to a distance of 62.1 ± 1.9 kpc, where the error includes both uncertainties. Taking into account other recent published determinations of the SMC distance we calculated the distance modulus difference between the SMC and the Large Magellanic Cloud equal to 0.458 ± 0.068 mag. Finally, we advocate μ{sub SMC} = 18.95 ± 0.07 as a new 'canonical' value of the distance modulus to this galaxy.« less

Lubrication model for evaporation of binary sessile drops

NASA Astrophysics Data System (ADS)

Williams, Adam; Sáenz, Pedro; Karapetsas, George; Matar, Omar; Sefiane, Khellil; Valluri, Prashant

2017-11-01

Evaporation of a binary mixture sessile drop from a solid substrate is a highly dynamic and complex process with flow driven both thermal and solutal Marangoni stresses. Experiments on ethanol/water drops have identified chaotic regimes on both the surface and interior of the droplet, while mixture composition has also been seen to govern drop wettability. Using a lubrication-type approach, we present a finite element model for the evaporation of an axisymmetric binary drop deposited on a heated substrate. We consider a thin drop with a moving contact line, taking also into account the commonly ignored effects of inertia which drives interfacial instability. We derive evolution equations for the film height, the temperature and the concentration field considering that the mixture comprises two ideally mixed volatile components with a surface tension linearly dependent on both temperature and concentration. The properties of the mixture such as viscosity also vary locally with concentration. We explore the parameter space to examine the resultant effects on wetting and evaporation where we find qualitative agreement with experiments in both these areas. This enables us to understand the nature of the instabilities that spontaneously emerge over the drop lifetime. EPSRC - EP/K00963X/1.

Thermodynamic model for solution behavior and solid-liquid equilibrium in Na-Al(III)-Fe(III)-Cr(III)-Cl-H2O system at 25°C

NASA Astrophysics Data System (ADS)

André, Laurent; Christov, Christomir; Lassin, Arnault; Azaroual, Mohamed

2018-03-01

The knowledge of the thermodynamic behavior of multicomponent aqueous electrolyte systems is of main interest in geo-, and environmental-sciences. The main objective of this study is the development of a high accuracy thermodynamic model for solution behavior, and highly soluble M(III)Cl3(s) (M= Al, Fe, Cr) minerals solubility in Na-Al(III)-Cr(III)-Fe(III)-Cl-H2O system at 25°C. Comprehensive thermodynamic models that accurately predict aluminium, chromium and iron aqueous chemistry and M(III) mineral solubilities as a function of pH, solution composition and concentration are critical for understanding many important geochemical and environmental processes involving these metals (e.g., mineral dissolution/alteration, rock formation, changes in rock permeability and fluid flow, soil formation, mass transport, toxic M(III) remediation). Such a model would also have many industrial applications (e.g., aluminium, chromium and iron production, and their corrosion, solve scaling problems in geothermal energy and oil production). Comparisons of solubility and activity calculations with the experimental data in binary and ternary systems indicate that model predictions are within the uncertainty of the data. Limitations of the model due to data insufficiencies are discussed. The solubility modeling approach, implemented to the Pitzer specific interaction equations is employed. The resulting parameterization was developed for the geochemical Pitzer formalism based PHREEQC database.

Building an Unusual White-Dwarf Duo

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-09-01

A new study has examined how the puzzling wide binary system HS 2220+2146 which consists of two white dwarfs orbiting each other might have formed. This system may be an example of a new evolutionary pathway for wide white-dwarf binaries.Evolution of a BinaryMore than 100 stellar systems have been discovered consisting of two white dwarfs in a wide orbit around each other. How do these binaries form? In the traditional picture, the system begins as a binary consisting of two main-sequence stars. Due to the large separation between the stars, the stars evolve independently, each passing through the main-sequence and giant branches and ending their lives as white dwarfs.An illustration of a hierarchical triple star system, in which two stars orbit each other, and a third star orbits the pair. [NASA/JPL-Caltech]Because more massive stars evolve more quickly, the most massive of the two stars in a binary pair should be the first to evolve into a white dwarf. Consequently, when we observe a double-white-dwarf binary, its usually a safe bet that the more massive of the two white dwarfs will also be the older and cooler of the pair, since it should have formed first.But in the case of the double-white-dwarf binary HS 2220+2146, the opposite is true: the more massive of the two white dwarfs appears to be the younger and hotter of the pair. If it wasnt created in the traditional way, then how did this system form?Two From Three?Led by Jeff Andrews (Foundation for Research and Technology-Hellas, Greece and Columbia University), a team of scientists recently examined this system more carefully, analyzing its spectra to confirm our understanding of the white dwarfs temperatures and masses.Based on their observations, Andrews and collaborators determined that there are no hidden additional companions that could have caused the unusual evolution of this system. Instead, the team proposed that this unusual binary might be an example of an evolutionary channel that involves three stars.The authors proposed formation scenario for H220+2146. In this picture, the inner binary merges to form a blue straggler. This star and the remaining main-sequence star then evolve independently into white dwarfs, forming the system observed today. [Andrews et al. 2016]An Early MergerIn the model the authors propose for HS 2220+2146, the binary system began as a hierarchical triple system of main-sequence stars. The innermost binary then merged to form a large star known as a blue straggler a star that, due to the merger, will evolve more slowly than its larger mass implies it should.The blue straggler and the remaining main-sequence star, still in a wide orbit, then continued to evolve independently of each other. The smaller star ended its main-sequence lifetime and became a white dwarf first, followed by the more massive but slowly evolving blue straggler thus forming the system we observe today.If the authors model is correct, then HS 2220+2146 would be the first binary double white dwarf known to have formed through this channel. ESAs Gaia mission, currently underway, is expected to discover up to a million new white dwarfs, many of which will likely be in wide binary systems. Among these, we may well find many other systems like HS 2220+2146 that formed in the same way.CitationJeff J. Andrews et al 2016 ApJ 828 38. doi:10.3847/0004-637X/828/1/38

Fabrication of biodegradable Zn-Al-Mg alloy: Mechanical properties, corrosion behavior, cytotoxicity and antibacterial activities.

PubMed

Bakhsheshi-Rad, H R; Hamzah, E; Low, H T; Kasiri-Asgarani, M; Farahany, S; Akbari, E; Cho, M H

2017-04-01

In this work, binary Zn-0.5Al and ternary Zn-0.5Al-xMg alloys with various Mg contents were investigated as biodegradable materials for implant applications. Compared with Zn-0.5Al (single phase), Zn-0.5Al-xMg alloys consisted of the α-Zn and Mg 2 (Zn, Al) 11 with a fine lamellar structure. The results also revealed that ternary Zn-Al-Mg alloys presented higher micro-hardness value, tensile strength and corrosion resistance compared to the binary Zn-Al alloy. In addition, the tensile strength and corrosion resistance increased with increasing the Mg content in ternary alloys. The immersion tests also indicated that the corrosion rates in the following order Zn-0.5Al-0.5Mg

Adsorption behavior of the (+/-)-Tröger's base enantiomers in the phase system of a silica-based packing coated with amylose tri(3,5-dimethyl carbamate) and 2-propanol and molecular modeling interpretation.

PubMed

Mihlbachler, Kathleen; De Jesús, Marco A; Kaczmarski, Krzysztof; Sepaniak, Michael J; Seidel-Morgenstern, Andreas; Guiochon, Georges

2006-04-28

The binary adsorption isotherms of the enantiomers of Tröger's base in the phase system made of Chiral Technologies ChiralPak AD [a silica-based packing coated with amylose tri(3,5-dimethyl carbamate)] as the chiral stationary phase (CSP) and 2-propanol as the mobile phase were measured by the perturbation method. The more retained enantiomer exhibits a S-shaped adsorption isotherm with a clear inflection point, the concentration of the less retained enantiomer having practically no competitive influence on this isotherm: In the entire range of concentrations studied, dq2/dC1 approximately 0. By contrast, the less retained enantiomer has a Langmuir adsorption isotherm when pure. At constant mobile phase concentrations, however, its equilibrium concentration in the adsorbed phase increases with increasing concentration of the more retained enantiomer and dq1/dC2 > 0. This cooperative adsorption behavior, opposed to the classical competitive behavior, is exceedingly rare but was clearly demonstrated in this case. Two adsorption isotherm equations that account for these physical observations were derived. They are based on the formation of an adsorbed multi-layer, as suggested by the isotherm data. The excellent agreement between the experimental overloaded elution profiles of binary mixtures and the profiles calculated with the equilibrium-dispersive model validates this binary isotherm model. The adsorption energies calculated by molecular mechanics (MM) and by molecular dynamics (MD) indicate that the chiral recognition arising from the different interactions between the functional groups of the CSP and the molecules of the Tröger's base enantiomers are mainly driven by their Van der Waals interactions. The MD data suggest that the interactions of the (-)-Tröger's base with the CSP are more favored by 8+/-(5) kJ/mol than those of (+)-Tröger's base. This difference seems to be a contributing factor to the increased retention of the - enantiomer on this chromatographic system. The modeling of the data also indicates that both enantiomers can form high stoichiometry complexes while binding onto the stationary phase, in agreement with the results of the equilibrium isotherm studies.

High hardness and superlative oxidation resistance in a pseudo-icosahehdral Cr-Al binary

NASA Astrophysics Data System (ADS)

Simonson, J. W.; Rosa, R.; Antonacci, A. K.; He, H.; Bender, A. D.; Pabla, J.; Adrip, W.; McNally, D. E.; Zebro, A.; Kamenov, P.; Geschwind, G.; Ghose, S.; Dooryhee, E.; Ibrahim, A.; Aronson, M. C.

Improving the efficiency of fossil fuel plants is a practical option for decreasing carbon dioxide emissions from electrical power generation. Present limits on the operating temperatures of exposed steel components, however, restrict steam temperatures and therefore energy efficiency. Even as a new generation of creep-resistant, high strength steels retain long term structural stability to temperatures as high as ~ 973 K, the low Cr-content of these alloys hinders their oxidation resistance, necessitating the development of new corrosion resistant coatings. We report here the nearly ideal properties of potential coating material Cr55Al229, which exhibits high hardness at room temperature as well as low thermal conductivity and superlative oxidation resistance at 973 K, with an oxidation rate at least three times smaller than those of benchmark materials. These properties originate from a pseudo-icosahedral crystal structure, suggesting new criteria for future research.

A Nonmetal Plasmonic Z-Scheme Photocatalyst with UV- to NIR-Driven Photocatalytic Protons Reduction.

PubMed

Zhang, Zhenyi; Huang, Jindou; Fang, Yurui; Zhang, Mingyi; Liu, Kuichao; Dong, Bin

2017-05-01

Ultrabroad-spectrum absorption and highly efficient generation of available charge carriers are two essential requirements for promising semiconductor-based photocatalysts, towards achieving the ultimate goal of solar-to-fuel conversion. Here, a fascinating nonmetal plasmonic Z-scheme photocatalyst with the W 18 O 49 /g-C 3 N 4 heterostructure is reported, which can effectively harvest photon energies spanning from the UV to the nearinfrared region and simultaneously possesses improved charge-carrier dynamics to boost the generation of long-lived active electrons for the photocatalytic reduction of protons into H 2 . By combining with theoretical simulations, a unique synergistic photocatalysis effect between the semiconductive Z-scheme charge-carrier separation and metal-like localized-surface-plasmon-resonance-induced "hot electrons" injection process is demonstrated within this binary heterostructure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

1550-nm Driven ErAs:In(Al)GaAs Photoconductor-Based Terahertz Time Domain System with 6.5 THz Bandwidth

NASA Astrophysics Data System (ADS)

Nandi, U.; Norman, J. C.; Gossard, A. C.; Lu, H.; Preu, S.

2018-04-01

ErAs:In(Al)GaAs superlattice photoconductors are grown using molecular beam epitaxy (MBE) with excellent material characteristics for terahertz time-domain spectroscopy (TDS) systems operating at 1550 nm. The transmitter material (Tx) features a record resistivity of 3.85 kΩcm and record breakdown field strength of 170 ± 40 kV/cm (dark) and 130 ± 20 kV/cm (illuminated with 45 mW laser power). Receivers (Rx) with different superlattice structures were fabricated showing very high mobility (775 cm2/Vs). The TDS system using these photoconductors features a bandwidth larger than 6.5 THz with a laser power of 45 mW at Tx and 16 mW at Rx.

Development of Return Period Inundation Maps In A Changing Climate Using a Systems of Systems Approach

NASA Astrophysics Data System (ADS)

Bilskie, M. V.; Hagen, S. C.; Alizad, K.; Passeri, D. L.; Irish, J. L.

2016-12-01

Worldwide, coastal land margins are experiencing increased vulnerability from natural and manmade disasters [Nicholls et al., 1999]. Specifically, coastal flooding is expected to increase due to the effects of climate change, and sea level rise (SLR) in particular. A systems of systems (SoS) approach has been implemented to better understand the dynamic and nonlinear effects of SLR on tropical cyclone-induced coastal flooding along a low-gradient coastal landscape (northern Gulf of Mexico [NGOM]). The backbone of the SoS framework is a high-resolution, physics-based, tide, wind-wave, and hurricane storm surge model [Bilskie et al., 2016a] that includes systems of SLR scenarios [Parris et al., 2012], shoreline morphology [Passeri et al., 2016; Plant et al., 2016], marsh evolution [Alizad et al., 2016], and population dynamics driven by carbon emission scenarios [Bilskie et al., 2016b]. Prior to considering future conditions, the storm surge model was comprehensively validated for present-day conditions [Bilskie et al., 2016a]. The present-day model was then modified to represent the potential future landscape based on four SLR scenarios prescribed by Parris et al. [2012] linked to carbon emissions scenarios for the year 2100. Numerical simulations forced by hundreds of synthetic tropical cyclones were performed and the results facilitate the development of return period inundation maps across the NGOM that reflect changes to the coastal landscape. The SoS approach allows new patterns and properties to emerge (i.e. nonlinear and dynamic effects of SLR) that would otherwise be unobserved using a static SLR model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Hongfei; Yang, Zhenhua; Pan, Cheng

Here, we report that the addition of a non-photoactive tertiary polymer phase in the binary bulk heterojunction (BHJ) polymer solar cell leads to a self-assembled columnar nanostructure, enhancing the charge mobilities and photovoltaic efficiency with surprisingly increased optimal active blend thicknesses over 300 nm, 3–4 times larger than that of the binary counterpart. Using the prototypical poly(3-hexylthiophene) (P3HT):fullerene blend as a model BHJ system, we discover that the inert poly(methyl methacrylate) (PMMA) added in the binary BHJ blend self-assembles into vertical columns, which not only template the phase segregation of electron acceptor fullerenes but also induce the out-of-plane rotation ofmore » the edge-on-orientated crystalline P3HT phase. Using complementary interrogation methods including neutron reflectivity, X-ray scattering, atomic force microscopy, transmission electron microscopy, and molecular dynamics simulations, we show that the enhanced charge transport originates from the more randomized molecular stacking of the P3HT phase and the spontaneous segregation of fullerenes at the P3HT/PMMA interface, driven by the high surface tension between the two polymeric components. The results demonstrate a potential method for increasing the thicknesses of high-performance polymer BHJ solar cells with improved photovoltaic efficiency, alleviating the burden of stringently controlling the ultrathin blend thickness during the roll-to-roll-type large-area manufacturing environment.« less

Origin of Pre-Coronal-Jet Minifilaments: Flux Cancellation

NASA Technical Reports Server (NTRS)

Panesar, Navdeep K.; Sterling, Alphonse; Moore, Ronald L.

2017-01-01

Coronal jets are frequent magnetically channeled narrow eruptions. All coronal jets observed in EUV and X-ray images show a bright spire with a base brightening, also known as jet bright point (JBP). Recent studies of jets show that coronal jets are driven by small-scale filament eruptions (e.g. Hong et al. 2011, Shen et al. 2012, Adams et al. 2014, Sterling et al. 2015). We recently investigated the triggering mechanism of ten on-disk quiet-region coronal jet eruptions and found that magnetic flux cancellation at the neutral line of minifilaments is the main cause of quiet-region jet eruptions (Panesar et al.2016).

Buyer and seller data from pay what you want and name your own price laboratory markets.

PubMed

Krämer, Florentin; Schmidt, Klaus M; Spann, Martin; Stich, Lucas

2017-06-01

Pay What You Want (PWYW) and Name Your Own Price (NYOP) are customer-driven pricing mechanisms that give customers (some) pricing power and that have been used in service industries with high fixed costs to price discriminate without setting a reference price. This paper describes buyer and seller data in a series of induced-value laboratory experiments that compare PWYW and NYOP in monopoly and competitive situations. Sellers are in a one-shot interaction with buyers. Sellers using customer-driven pricing mechanisms may exogenously or endogenously receive additional promotional benefits, for instance through word-of-mouth effects. The major findings based on the data presented here are reported in the paper "Delegating Pricing Power to Customers: Pay What You Want or Name Your Own Price?" (Krämer et al., 2017) [3].

Gravitational influences on the liquid-state homogenization and solidification of aluminum antimonide. [space processing of solar cell material

NASA Technical Reports Server (NTRS)

Ang, C.-Y.; Lacy, L. L.

1979-01-01

Typical commercial or laboratory-prepared samples of polycrystalline AlSb contain microstructural inhomogeneities of Al- or Sb-rich phases in addition to the primary AlSb grains. The paper reports on gravitational influences, such as density-driven convection or sedimentation, that cause microscopic phase separation and nonequilibrium conditions to exist in earth-based melts of AlSb. A triple-cavity electric furnace is used to homogenize the multiphase AlSb samples in space and on earth. A comparative characterization of identically processed low- and one-gravity samples of commercial AlSb reveals major improvements in the homogeneity of the low-gravity homogenized material.

A Spectroscopic Orbit for the Late-type Be Star β CMi

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dulaney, Nicholas A.; Richardson, Noel D.; Gerhartz, Cody J.

The late-type Be star β CMi is remarkably stable compared to other Be stars that have been studied. This has led to a realistic model of the outflowing Be disk by Klement et al. These results showed that the disk is likely truncated at a finite radius from the star, which Klement et al. suggest is evidence for an unseen binary companion in orbit. Here we report on an analysis of the Ritter Observatory spectroscopic archive of β CMi to search for evidence of the elusive companion. We detect periodic Doppler shifts in the wings of the H α linemore » with a period of 170 days and an amplitude of 2.25 km s{sup −1}, consistent with a low-mass binary companion ( M ≈ 0.42 M {sub ⊙}). We then compared small changes in the violet-to-red peak height changes ( V / R ) with the orbital motion. We find weak evidence that it does follow the orbital motion, as suggested by recent Be binary models by Panoglou et al. Our results, which are similar to those for several other Be stars, suggest that β CMi may be a product of binary evolution where Roche lobe overflow has spun up the current Be star, likely leaving a hot subdwarf or white dwarf in orbit around the star. Unfortunately, no direct sign of this companion star is found in the very limited archive of International Ultraviolet Explorer spectra.« less

Bit-Table Based Biclustering and Frequent Closed Itemset Mining in High-Dimensional Binary Data

PubMed Central

Király, András; Abonyi, János

2014-01-01

During the last decade various algorithms have been developed and proposed for discovering overlapping clusters in high-dimensional data. The two most prominent application fields in this research, proposed independently, are frequent itemset mining (developed for market basket data) and biclustering (applied to gene expression data analysis). The common limitation of both methodologies is the limited applicability for very large binary data sets. In this paper we propose a novel and efficient method to find both frequent closed itemsets and biclusters in high-dimensional binary data. The method is based on simple but very powerful matrix and vector multiplication approaches that ensure that all patterns can be discovered in a fast manner. The proposed algorithm has been implemented in the commonly used MATLAB environment and freely available for researchers. PMID:24616651

Three-dimensional orbit and physical parameters of HD 6840

NASA Astrophysics Data System (ADS)

Wang, Xiao-Li; Ren, Shu-Lin; Fu, Yan-Ning

2016-02-01

HD 6840 is a double-lined visual binary with an orbital period of ˜7.5 years. By fitting the speckle interferometric measurements made by the 6 m BTA telescope and 3.5 m WIYN telescope, Balega et al. gave a preliminary astrometric orbital solution of the system in 2006. Recently, Griffin derived a precise spectroscopic orbital solution from radial velocities observed with OPH and Cambridge Coravel. However, due to the low precision of the determined orbital inclination, the derived component masses are not satisfying. By adding the newly collected astrometric data in the Fourth Catalog of Interferometric Measurements of Binary Stars, we give a three-dimensional orbit solution with high precision and derive the preliminary physical parameters of HD 6840 via a simultaneous fit including both astrometric and radial velocity measurements.

Hydrodynamical and Spectral Simulations of HMXB Winds

NASA Astrophysics Data System (ADS)

Mauche, Christopher W.; Liedahl, D. A.; Plewa, T.

2006-09-01

We describe the results of a research program to develop improved models of the X-ray spectra of cosmic sources such as X-ray binaries, CVs, and AGN in which UV line-driven mass flows are photoionized by an X-ray source. Work to date has focused on high-mass X-ray binaries (HMXBs) and on Vela X-1 in particular, for which there are high-quality Chandra HETG spectra in the archive. Our research program combines FLASH hydrodynamic calculations, XSTAR photoionization calculations, HULLAC atomic data, improved calculations of the line force multiplier, X-ray emission models appropriate to X-ray photoionized plasmas, and Monte Carlo radiation transport. We will present movies of the relevant physical quantities (density, temperature, ionization parameter, velocity) from a FLASH two-dimensional time-dependent simulation of Vela X-1, maps showing the emissivity distributions of the X-ray emission lines, and a preliminary comparison of the resulting synthetic spectra to the Chandra HETG spectra. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

SPIN–SPIN COUPLING IN THE SOLAR SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batygin, Konstantin; Morbidelli, Alessandro, E-mail: kbatygin@gps.caltech.edu

The richness of dynamical behavior exhibited by the rotational states of various solar system objects has driven significant advances in the theoretical understanding of their evolutionary histories. An important factor that determines whether a given object is prone to exhibiting non-trivial rotational evolution is the extent to which such an object can maintain a permanent aspheroidal shape, meaning that exotic behavior is far more common among the small body populations of the solar system. Gravitationally bound binary objects constitute a substantial fraction of asteroidal and TNO populations, comprising systems of triaxial satellites that orbit permanently deformed central bodies. In thismore » work, we explore the rotational evolution of such systems with specific emphasis on quadrupole–quadrupole interactions, and show that for closely orbiting, highly deformed objects, both prograde and retrograde spin–spin resonances naturally arise. Subsequently, we derive capture probabilities for leading order commensurabilities and apply our results to the illustrative examples of (87) Sylvia and (216) Kleopatra asteroid systems. Cumulatively, our results suggest that spin–spin coupling may be consequential for highly elongated, tightly orbiting binary objects.« less

High Energy Interactions in Massive Binaries: An Application to a Most Mysterious Binary

NASA Technical Reports Server (NTRS)

Corcoran, Michael

2013-01-01

Extremely massive stars (50M and above) are exceedingly rare in the local Universe but are believed to have composed the entire first generation of stars, which lived fast, died young and left behind the first generation of black holes and set the stage for the formation of lower mass stars suitable to support life. There are significant uncertainties about how this happened (and how it still happens), mostly due to our poor knowledge of how stars change mass as they evolve. Extremely massive stars give mass back to the ISM via strong radiatively-driven winds and sometimes through sporadic eruptions of the most massive and brightest stars. Such mass loss plays an important role in the chemical and dynamical evolution of the local interstellar medium prior to the supernova explosion. Below we discuss how high energy thermal (and, in some cases, non-thermal) emission, along with modern simulations in 2 and 3 dimensions, can be used to help determine a physically realistic picture of mass loss in a well-studied, mysterious system.

Stability of Buoyancy-Driven Gas Flow: Visualization of Coherent and Incoherent Gas Flow Patterns and Capillary Trapping

NASA Astrophysics Data System (ADS)

Geistlinger, H. W.; Samani, S.; Pohlert, M.; Jia, R.; Lazik, D.

2009-12-01

There are several mechanisms by which the CO2 can be stored: (1) In hydrodynamic trapping, the buoyant CO2 remains as a mobile fluid but is prevented from flowing back to the surface by an impermeable cap rock. (2) In solution trapping, CO2 dissolves into the brine, possibly enhanced by gravity instabilities due to the larger density of the brine-CO2 liquid mixture. (3) In mineral trapping, geochemical binding to the rock due to mineral precipitation. (4) In capillary trapping, the CO2 phase is disconnected into a coherent, mobile phase and an incoherent, immobile (trapped) phase. Recent analytical and numerical investigations [Juanes et al., 2006, 2009; Hesse et al., 2007 ] of buoyant-driven CO2-plume along a sloped aquifer are based on the following conceptual process model: (1) During the injection period, the less wetting CO2 displaces the more wetting brine in a drainage-like process. It is assumed that no capillary trapping occurs and that the CO2-network is coherent and driven both by the injection pressure and the buoyant pressure. Because of this coherence assumption a generalized Darcy-law can be used for the dynamics of the mobile, gaseous CO2-phase. (2) After injection the buoyant CO2 migrates laterally and upward, and water displaces CO2 at the trailing edge of the plume in an imbibition-like process. During this process, there are several physical mechanisms by which the water can displace the CO2 [Lenormand et al., 1983]. In addition to piston-type displacement, core-annular flow (also called: cooperative pore-body filling) may occur, i.e. the wetting phase moves along the walls and under certain conditions the CO2-core flow becomes unstable (snap-off). For water wet rocks, snap-off is the dominant mechanism [Al-Futaisi and Patzek, 2003; Valvatne and Blunt, 2004]. There seems to be consensus that the capillary trapping mechanism has a huge impact on the migration and distribution of CO2 which, in turn, affects the effectiveness of the other sequestration mechanisms. In order to investigate the stability of buoyancy-driven gas flow and the transition between coherent flow, incoherent flow, and their correlation to capillary trapping, we conducted high-resolution optical bench scale experiments. We observed a grain-size (dk) - and flow-rate (Q) dependent transition from incoherent to coherent flow. Based on core-annular flow (= cooperative pore-body filling), we propose a dynamic stability criterion that could describe our experimental results. Our experimental results for vertical gas flow support the experimental results by Lenormand et al. [1983] obtained for horizontal flow, if one takes into account that gravity leads to more unstable flow conditions. Our main results, which are in strong contradiction to the accepted conceptual model of the sloped aquifer, are: (1) Capillary Trapping can already occur during injection and at the front of the plume [Lazik et al., 2008] (2) Gas clusters or bubbles can be mobile (incoherent gas flow) and immobile (capillary trapping), and (3) Incoherent gas flow can not be described by a generalized Darcy law [Geistlinger et al., 2006, 2009].

Seismic Velocity Structure of the Pacific Upper Mantle in the NoMelt Region from Finite-Frequency Traveltime Tomography

NASA Astrophysics Data System (ADS)

Hung, S. H.; Lin, P. Y.; Gaherty, J. B.; Russell, J. B.; Jin, G.; Collins, J. A.; Lizarralde, D.; Evans, R. L.; Hirth, G.

2017-12-01

Surface wave dispersion and magnetotelluric survey from the NoMelt Experiment conducted on 70 Ma central Pacific seafloor revealed an electrically resistive, high shear wave velocity lid of 80 km thick underlain by a non-highly conductive, low-velocity layer [Sarafian et al., 2015; Lin et al., 2016]. The vertical structure of the upper mantle consistent with these observational constraints suggests a plausible convection scenario, where the seismically fast, dehydrated lithosphere preserving very strong fossil spreading fabric moves at a constant plate speed over the hydrated, melt-free athenospheric mantle with the presence of either pressure-driven return flow or thermally-driven small scale circulation. To explore 3-D variations in compressional shear wave velocities related to the lithospheric and asthenospheric mantle dynamics, we employ a multichannel cross correlation method to measure relative traveltime residuals based on the vertical P and traverse S waveforms filtered at 10-33 s from telseismic earthquakes at epicentral distance between 30 and 98 degrees. The obtained P and S residuals show on average peak-to-peak variations of ±0.5 s and ±1 s, respectively, across the NoMelt OBS array. Particularly, the P residuals for most of the events display an asymmetrical pattern with respect to an axis oriented nearly N-S to NE-SW through the array. Preliminary ray-based P tomography results reveal similar asymmetric variations in the uppermost 100 km mantle. To verify the resulting structural features, we will further perform both the P and S traveltime tomography and resolution tests based on a multiscale finite-frequency approach which properly takes into account both the 3D off-path sensitivities of the measured residuals and data-adaptive resolution of the model.

Inferring Binary and Trinary Stellar Populations in Photometric and Astrometric Surveys

NASA Astrophysics Data System (ADS)

Widmark, Axel; Leistedt, Boris; Hogg, David W.

2018-04-01

Multiple stellar systems are ubiquitous in the Milky Way but are often unresolved and seen as single objects in spectroscopic, photometric, and astrometric surveys. However, modeling them is essential for developing a full understanding of large surveys such as Gaia and connecting them to stellar and Galactic models. In this paper, we address this problem by jointly fitting the Gaia and Two Micron All Sky Survey photometric and astrometric data using a data-driven Bayesian hierarchical model that includes populations of binary and trinary systems. This allows us to classify observations into singles, binaries, and trinaries, in a robust and efficient manner, without resorting to external models. We are able to identify multiple systems and, in some cases, make strong predictions for the properties of their unresolved stars. We will be able to compare such predictions with Gaia Data Release 4, which will contain astrometric identification and analysis of binary systems.

Atomistic Modeling of Diffusion and Phase Transformations in Metals and Alloys

NASA Astrophysics Data System (ADS)

Purja Pun, Ganga Prasad

Dissertation consists of multiple works. The first part is devoted to self-diffusion along dislocation cores in aluminum followed by the development of embedded atom method potentials for Co, NiAl, CoAl and CoNi systems. The last part focuses on martensitic phase transformation (MPT) in Ni xAl1--x and Al xCoyNi1-- x--y alloys. New calculation methods were developed to predict diffusion coefficients in metal as functions of temperature. Self-diffusion along screw and edge dislocations in aluminum was studied by molecular dynamic (MD) simulations. Three types of simulations were performed with and without (intrinsic) pre-existing vacancies and interstitials in the dislocation core. We found that the diffusion along the screw dislocation was dominated by the intrinsic mechanism, whereas the diffusion along the edge dislocation was dominated by the vacancy mechanism. The diffusion along the screw dislocation was found to be significantly faster than the diffusion along the edge dislocation, and the both diffusivities were in reasonable agreement with experimental data. The intrinsic diffusion mechanism can be associated with the formation of dynamic Frenkel pairs, possibly activated by thermal jogs and/or kinks. The simulations show that at high temperatures the dislocation core becomes an effective source/sink of point defects and the effect of pre-existing defects on the core diffusivity diminishes. First and the foremost ingredient needed in all atomistic computer simulations is the description of interaction between atoms. Interatomic potentials for Co, NiAl, CoAl and CoNi systems were developed within the Embedded Atom Method (EAM) formalism. The binary potentials were based on previously developed accurate potentials for pure Ni and pure Al and pure Co developed in this work. The binaries constitute a version of EAM potential of AlCoNi ternary system. The NiAl potential accurately reproduces a variety of physical properties of the B2-NiAl and L12--Ni3Al phases. The potential is expected to be especially suitable for simulations of hetero-phase interfaces and mechanical behavior of NiAl alloys. Apart from properties of the HCP Co, the new Co potential is accurate enough to reproduce several properties of the FCC Co which were not included in the potential fit. It shows good transferability property. The CoAl potential was fitted to the properties of B2-CoAl phase as in the NiAl fitting where as the NiCo potential was fitted to the ab initio formation energies of some imaginary phases and structures. Effect of chemical composition and uniaxial mechanical stresses was studied on the martensitic phase transformation in B2 type Ni-rich NiAl and AlCoNi alloys. The martensitic phase has a tetragonal crystal structure and can contain multiple twins arranged in domains and plates. The twinned martensites were always formed under the uniaxial compression where as the single variant martensites were the results of the uniaxial tension. The transformation was reversible and characterized by a significant temperature hysteresis. The magnitude of the hysteresis depends on the chemical composition and stress.

υ-driven winds from the remnant of binary neutron star mergers

NASA Astrophysics Data System (ADS)

Perego, A.

2018-01-01

We present a 3D hydrodynamic study of the neutrino-driven winds that emerge from the remnant of a neutron star merger, represented by a thick accretion disc orbiting around a massive neutron star. This strong baryonic wind is blown out by neutrino absorption on free baryons inside the disc. It expands within a few tens of ms along the original binary rotation axis. If the central object survives for at least 200ms, the mass ejected in the wind can reach 5% of the initial mass of the accretion disc. Due to the intense neutrino irradiation, matter ejected in the wind increases its electron fraction between 0.3 and 0.4, producing weak r-process nucleosynthesis yields. We predict a distinct UV/optical transient associated with the wind ejecta that peaks from a few hours to a few days after the merger.

Protograph LDPC Codes Over Burst Erasure Channels

NASA Technical Reports Server (NTRS)

Divsalar, Dariush; Dolinar, Sam; Jones, Christopher

2006-01-01

In this paper we design high rate protograph based LDPC codes suitable for binary erasure channels. To simplify the encoder and decoder implementation for high data rate transmission, the structure of codes are based on protographs and circulants. These LDPC codes can improve data link and network layer protocols in support of communication networks. Two classes of codes were designed. One class is designed for large block sizes with an iterative decoding threshold that approaches capacity of binary erasure channels. The other class is designed for short block sizes based on maximizing minimum stopping set size. For high code rates and short blocks the second class outperforms the first class.

X-ray nova and LMXB V404 Cyg in rare outburst

NASA Astrophysics Data System (ADS)

Waagen, Elizabeth O.

2015-06-01

V404 Cyg, an X-ray nova and a low mass X-ray binary (LMXB) with black hole component, is undergoing its first reported X-ray and optical outburst since 1989. Large scale, rapid variations are being reported in wavelengths from X-ray to radio by professional and amateur astronomers worldwide. Satellite and ground-based observations have been and are continuing to be made by many members of the professional community, including S. D. Barthelmy et al. (GCN Circular 17929, 15 June 2015, Swift BAT initial detection); H. Negoro et al. (ATel #7646, 17 Jun 2015); E. Kuulkers et al. (ATel #7647, 17 June 2015, Swift observations); K. Gazeas et al. (ATel #7650, 17 June 2015, optical photometry); R. M. Wagner et al. (ATel #7655, 18 June, optical spectroscopy); K. Mooley et al. (ATel #7658, 18 June, radio observations). T. Munoz-Darias et al. report P Cyg profiles were seen on 18 Jun 2015 (ATel #7659). They note that P-Cyg profiles were also observed during the 1989 outburst (Casares et al. 1991, MNRAS, 250, 712), and that V404 Cyg is so far the only black hole X-ray transient that has shown this phenomenology. Observations in all bands are requested. Filtered observations are preferred. Please use a cadence as high as possible while obtaining a suitable s/n. If spectroscopy is possible with your equipment, it is requested. Finder charts with sequence may be created using the AAVSO Variable Star Plotter (https://www.aavso.org/vsp). Observations should be submitted to the AAVSO International Database. Precise observing instructions and other details are given in the full Alert Notice.

Beta Decay Half-Life of 84Mo

NASA Astrophysics Data System (ADS)

Stoker, J. B.; Mantica, P. F.; Bazin, D.; Bickley, A.; Becerril, A.; Crawford, H.; Cruse, K.; Estrade, A.; Mosby, M.; Guess, C. J.; Hitt, G. W.; Lorusso, G.; Matos, M.; Meharchand, R.; Minamisono, K.; Montes, F.; Pereira, J.; Perdikakis, G.; Pinter, J. S.; Schatz, H.; Vredevoogd, J.; Zegers, R. G. T.

2008-10-01

The β-decay half-life ^84Mo governs leakage out of the Zr-Nb cycle, a high temperature rp-process endpoint in x-ray binaries [1]. Treatment of the background and the poor statistics accumulated during the previous half-life measurement leave questions about statistical and systematic errors. We have remeasured the half-life of ^84Mo using a concerted setup of the NSCL β-Counting System [3] and 16 detectors from the Segmented Germanium Array [4]. We will report the half-life for ^84Mo, deduced using 40 times the previous sample size. The application of the NSCL RF Fragment Separator to remove unwanted isotopes, and hence reduce background for the half-life measurement, will also be discussed. [1] H. Schatz et al., Phys. Rep. 294, 167 1998 [2] P. Kienle et al., Prog. Part. Nuc. Phys. 46, 73 2001 [3] J. Prisciandaro et al., NIM A 505, 140 2003 [4] W. Mueller et al., NIM A 466, 492 2001 [5] D. Gorelov et al. PAC 2005, Knoxville, TN, May 16-20

Excited-state proton transfer dynamics of firefly's chromophore D-luciferin in DMSO-water binary mixture.

PubMed

Kuchlyan, Jagannath; Banik, Debasis; Roy, Arpita; Kundu, Niloy; Sarkar, Nilmoni

2014-12-04

In this article we have investigated intermolecular excited-state proton transfer (ESPT) of firefly's chromophore D-luciferin in DMSO-water binary mixtures using steady-state and time-resolved fluorescence spectroscopy. The unusual behavior of DMSO-water binary mixture as reported by Bagchi et al. (J. Phys. Chem. B 2010, 114, 12875-12882) was also found using D-luciferin as intermolecular ESPT probe. The binary mixture has given evidence of its anomalous nature at low mole fractions of DMSO (below XD = 0.4) in our systematic investigation. Upon excitation of neutral D-luciferin molecule, dual fluorescence emissions (protonated and deprotonated form) are observed in DMSO-water binary mixture. A clear isoemissive point in the time-resolved area normalized emission spectra further indicates two emissive species in the excited state of D-luciferin in DMSO-water binary mixture. DMSO-water binary mixtures of different compositions are fascinating hydrogen bonding systems. Therefore, we have observed unusual changes in the fluorescence emission intensity, fluorescence quantum yield, and fluorescence lifetime of more hydrogen bonding sensitive anionic form of D-luciferin in low DMSO content of DMSO-water binary mixture.

Orbital Period Variations in the NY Vir System, Revisited in the Light of New Data

NASA Astrophysics Data System (ADS)

Baştürk, Özgür; Esmer, Ekrem Murat

2018-02-01

NY Virginis is an eclipsing binary system with a subdwarf B primary and an M type dwarf secondary. Recent studies (Qian et al. 2012; Lee et al. 2014) suggested the presence of two circumbinary planets with a few Jovian masses within the system. Lee et al. (2014) examined the orbital stabilities of the suggested planets, using the best-fit parameters derived from their eclipse timing variation analysis. They found that the outer companion should be ejected from the system in about 800 000 years. An observational report from Pulley et al. (2016) pointed out that the recent mideclipse times of the binary deviate significantly from the models suggested by Lee et al. (2014). In fact, variations in the orbital period of the system had already been recognized by many authors, but the parameters of these variations vary significantly as new data accumulate. Here, we analyze the eclipse timing variations of the NY Vir system, using new mid-eclipse times that we have obtained together with earlier published measurements in order to understand the nature of the system and constrain its parameters.

Preferential site occupancy of alloying elements in TiAl-based phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holec, David, E-mail: david.holec@unileoben.ac.at; Reddy, Rajeev K.; Klein, Thomas

2016-05-28

First principles calculations are used to study the preferential occupation of ternary alloying additions into the binary Ti-Al phases, namely, γ-TiAl, α{sub 2}-Ti{sub 3}Al, β{sub o}-TiAl, and B19-TiAl. While the early transition metals (TMs, group IVB, VB, and VIB elements) prefer to substitute for Ti atoms in the γ-, α{sub 2}-, and B19-phases, they preferentially occupy Al sites in the β{sub o}-TiAl. Si is, in this context, an anomaly, as it prefers to sit on the Al sublattice for all four phases. B and C are shown to prefer octahedral Ti-rich interstitial positions instead of substitutional incorporation. The site preferencemore » energy is linked with the alloying-induced changes of energy of formation, hence alloying-related (de)stabilisation of the phases. We further show that the phase-stabilisation effect of early TMs on β{sub o}-phase has a different origin depending on their valency. Finally, an extensive comparison of our predictions with available theoretical and experimental data (which is, however, limited mostly to the γ-phase) shows a consistent picture.« less

PSEUDO-BINARY SYSTEMS INVOLVING RARE EARTH LAVES PHASES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wernick, J.H.; Haszko, S.E.; Dorsi, D.

1962-06-01

The phase relations in a number of pseudo-binary systems involving rare earth Laves phases were determined. Complete series of cubic solid-solutions occur in the DyMn/sub 2/HoMn/sub 2/, HoMn/sub 2/-HoFe/sub 2/, DyMn/sub 2/-DyFe/ sub 2/, HoMn/sub 2/-HoAl/ sub 2/, TbMn/sub 2/TbAl/sub 2/, and DyMn/sub 2/-DyAl/ sub 2/ pseudobinary systems. Deviations from linearity in the lattice constants with composition occur in all these systems. Complete series of cubic solidsolutions also exist in the GdAl/sub 2/-ErAl/sub 2/, GdAl/sub 2/-PrAl/sub 2/ , GdAl/sub 2/-NdAl/sub 2/, GdAl/sub 2/-DyAl/sub 2/, TbAl/sub 2/-NdAl/sub 2/, and T bAl/sub 2/-DyAl/sub 2/ systems. For these systems, no deviation from linearitymore » occurs in the lattice constants. For the DyFe/sub 2/-DyAl/sub 2/ and DyCo/sub 2/- DyAl/sub 2/ systems, two new ternary phases, DyFeAl and DyCoAl, form and have the MgZn/sub 2/ structure. Their structures were determined from x-ray powder data only. The electronic state giving rise to the formation of these ternary phases is discussed qualitatively. For the DyMn/sub 2/TmMn/sub 2/ system, the range of composition in which the cubic MgCu/sub 2/ and hexagonal MgZn/sub 2/ structures exist are reported. No complete series of solid solutions or intermediate phases are formed in the DyNi/sub 2/-DyAl/sub 2/ system. (auth)« less

Dynamics of quadruple systems composed of two binaries: stars, white dwarfs, and implications for Ia supernovae

NASA Astrophysics Data System (ADS)

Fang, Xiao; Thompson, Todd A.; Hirata, Christopher M.

2018-05-01

We investigate the long-term secular dynamics and Lidov-Kozai (LK) eccentricity oscillations of quadruple systems composed of two binaries at quadrupole and octupole orders in the perturbing Hamiltonian. We show that the fraction of systems reaching high eccentricities is enhanced relative to triple systems, over a broader range of parameter space. We show that this fraction grows with time, unlike triple systems evolved at quadrupole order. This is fundamentally because with their additional degrees of freedom, quadruple systems do not have a maximal set of commuting constants of the motion, even in secular theory at quadrupole order. We discuss these results in the context of star-star and white dwarf-white dwarf (WD) binaries, with emphasis on WD-WD mergers and collisions relevant to the Type Ia supernova problem. For star-star systems, we find that more than 30 per cent of systems reach high eccentricity within a Hubble time, potentially forming triple systems via stellar mergers or close binaries. For WD-WD systems, taking into account general relativistic and tidal precession and dissipation, we show that the merger rate is enhanced in quadruple systems relative to triple systems by a factor of 3.5-10, and that the long-term evolution of quadruple systems leads to a delay-time distribution ˜1/t for mergers and collisions. In gravitational wave-driven mergers of compact objects, we classify the mergers by their evolutionary patterns in phase space and identify a regime in about 8 per cent of orbital shrinking mergers, where eccentricity oscillations occur on the general relativistic precession time-scale, rather than the much longer LK time-scale. Finally, we generalize previous treatments of oscillations in the inner binary eccentricity (evection) to eccentric mutual orbits. We assess the merger rate in quadruple and triple systems and the implications for their viability as progenitors of stellar mergers and Type Ia supernovae.

WIYN OPEN CLUSTER STUDY. XXXVI. SPECTROSCOPIC BINARY ORBITS IN NGC 188

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geller, Aaron M.; Mathieu, Robert D.; Harris, Hugh C.

2009-04-15

We present 98 spectroscopic binary orbits resulting from our ongoing radial velocity survey of the old (7 Gyr) open cluster NGC 188. All but 13 are high-probability cluster members based on both radial velocity and proper motion membership analyses. Fifteen of these member binaries are double lined. Our stellar sample spans a magnitude range of 10.8 {<=}V{<=} 16.5 (1.14-0.92 M {sub sun}) and extends spatially to 17 pc ({approx}13 core radii). All of our binary orbits have periods ranging from a few days to on the order of 10{sup 3} days, and thus are hard binaries that dynamically power themore » cluster. For each binary, we present the orbital solutions and place constraints on the component masses. Additionally, we discuss a few binaries of note from our sample, identifying a likely blue straggler-blue straggler binary system (7782), a double-lined binary with a secondary star which is underluminous for its mass (5080), two potential eclipsing binaries (4705 and 5762), and two binaries which are likely members of a quadruple system (5015a and 5015b)« less

The 2001 U.S. Naval Observatory Double Star CD-Rom. III. The Third Catalog of Interferometric Measurements of Binary Stars

DTIC Science & Technology

2001-12-01

CHARA southern speckle program from 1989 to 1996 (cf. Hartkopf et al. 1996), and by the more recent speckle e†orts of Horch and colleagues (cf. Horch ...Mason, B. D. 2001, Third Catalog of Interferometric Measurements of Binary Stars (CHARA Contrib. No. 4) (Atlanta : Georgia State Univ.) Horch , E

Constituent Redistribution in U-Zr Metallic Fuel Using the Advanced Fuel Performance Code BISON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galloway, Jack D.; Unal, Cetin; Matthews, Christopher

2016-09-30

Previous work done by Galloway, et. al. on EBR-II ternary (U-Pu-Zr) fuel constituent redistribution yielded accurate simulation data for the limited data sets of Zr redistribution. The data sets included EPMA scans of two different irradiated rods. First, T179, which was irradiated to 1.9 at% burnup, was analyzed. Second, DP16, which was irradiated to 11 at% burnup, was analyzed. One set of parameters that most accurately represented the zirconium profiles for both experiments was determined. Since the binary fuel (U-Zr) has previously been used as the driver fuel for sodium fast reactors (SFR) as well as being the likely drivermore » fuel if a new SFR is constructed, this same process has been initiated on the binary fuel form. From limited binary EPMA scans as well as other fuel characterization techniques, it has been observed that zirconium redistribution also occurs in the binary fuel, albeit at a reduced rate compared to observation in the ternary fuel, as noted by Kim et. al. While the rate of redistribution has been observed to be slower, numerous metallographs of U-Zr fuel show distinct zone formations.« less

Microstructure and mechanical properties of a single crystal NiAl alloy with Zr or Hf rich G-phase precipitates

NASA Technical Reports Server (NTRS)

Locci, I. E.; Noebe, R. D.; Bowman, R. R.; Miner, R. V.; Nathal, M. V.; Darolia, R.

1991-01-01

The possibility of producing NiAl reinforced with the G-phase (Ni16X6Si7), where X is Zr or Hf, has been investigated. The microstructure of these NiAl alloys have been characterized in the as-cast and annealed conditions. The G-phases are present as fine cuboidal precipitates (10 to 40 nm) and have lattice parameters almost four times that of NiAl. They are coherent with the matrix and fairly resistant to coarsening during annealing heat treatments. Segregation and nonuniform precipitate distribution observed in as-cast materials were eliminated by homogenization at temperatures near 1600 K. Slow cooling from these temperatures resulted in large plate shaped precipitates, denuded zones, and a loss of coherency in some of the large particles. Faster cooling produced a homogeneous fine distribution of cuboidal G-phase particles in the matrix. Preliminary mechanical properties for the Zr-doped alloy are presented and compared to binary single crystal NiAl. The presence of these precipitates appears to have an important strengthening effect at temperatures not less than 1000 K compared to binary NiAl single crystals.

View subspaces for indexing and retrieval of 3D models

NASA Astrophysics Data System (ADS)

Dutagaci, Helin; Godil, Afzal; Sankur, Bülent; Yemez, Yücel

2010-02-01

View-based indexing schemes for 3D object retrieval are gaining popularity since they provide good retrieval results. These schemes are coherent with the theory that humans recognize objects based on their 2D appearances. The viewbased techniques also allow users to search with various queries such as binary images, range images and even 2D sketches. The previous view-based techniques use classical 2D shape descriptors such as Fourier invariants, Zernike moments, Scale Invariant Feature Transform-based local features and 2D Digital Fourier Transform coefficients. These methods describe each object independent of others. In this work, we explore data driven subspace models, such as Principal Component Analysis, Independent Component Analysis and Nonnegative Matrix Factorization to describe the shape information of the views. We treat the depth images obtained from various points of the view sphere as 2D intensity images and train a subspace to extract the inherent structure of the views within a database. We also show the benefit of categorizing shapes according to their eigenvalue spread. Both the shape categorization and data-driven feature set conjectures are tested on the PSB database and compared with the competitor view-based 3D shape retrieval algorithms.

The Fate of Merging Neutron Stars

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-08-01

A rapidly spinning, highly magnetized neutron star is one possible outcome when two smaller neutron stars merge. [Casey Reed/Penn State University]When two neutron stars collide, the new object that they make can reveal information about the interior physics of neutron stars. New theoretical work explores what we should be seeing, and what it can teach us.Neutron Star or Black Hole?So far, the only systems from which weve detected gravitational waves are merging black holes. But other compact-object binaries exist and are expected to merge on observable timescales in particular, binary neutron stars. When two neutron stars merge, the resulting object falls into one of three categories:a stable neutron star,a black hole, ora supramassive neutron star, a large neutron star thats supported by its rotation but will eventually collapse to a black hole after it loses angular momentum.Histograms of the initial (left) and final (right) distributions of objects in the authors simulations, for five different equations of state. Most cases resulted primarily in the formation of neutron stars (NSs) or supramassive neutron stars (sNSs), not black holes (BHs). [Piro et al. 2017]Whether a binary-neutron-star merger results in another neutron star, a black hole, or a supramassive neutron star depends on the final mass of the remnant and what the correct equation of state is that describes the interiors of neutron stars a longstanding astrophysical puzzle.In a recent study, a team of scientists led by Anthony Piro (Carnegie Observatories) estimated which of these outcomes we should expect for mergers of binary neutron stars. The teams results along with future observations of binary neutron stars may help us to eventually pin down the equation of state for neutron stars.Merger OutcomesPiro and collaborators used relativistic calculations of spinning and non-spinning neutron stars to estimate the mass range that neutron stars would have for several different realistic equations of state. They then combined this information with Monte Carlo simulations based on the mass distribution of neutron-star binaries in our galaxy. From these simulations, Piro and collaborators could predict the distribution of fates expected for merging neutron-star binaries, given different equations of state.The authors found that the fate of the merger could vary greatly depending on the equation of state you assume. Intriguingly, all equations of state resulted in a surprisingly high fraction of systems that merged to form a neutron star or a supramassive neutron star in fact, four out of the five equations of state predicted that 80100% of systems would result in a neutron star or a supermassive neutron star.Lessons from ObservationsThe frequency bands covered by various current and planned gravitational wave observatories. Advanced LIGO has the right frequency coverage to be able to explore a neutron-star remnant if the signal is loud enough. [Christopher Moore, Robert Cole and Christopher Berry]These results have important implications for our future observations. The high predicted fraction of neutron stars resulting from these mergers tells us that its especially important for gravitational-wave observatories to probe 14 kHz emission. This frequency range will enable us to study the post-merger neutron-star or supramassive-neutron-star remnants.Even if we cant observe the remnants behavior after it forms, we can still compare the distribution of remnants that we observe in the future to the predictions made by Piro and collaborators. This will potentially allow us to constrain the neutron-star equation of state, revealing the physics of neutron-star interiors even without direct observations.CitationAnthony L. Piro et al 2017 ApJL 844 L19. doi:10.3847/2041-8213/aa7f2f

Fast optical and X-ray variability in the UCXB 4U0614+09

NASA Astrophysics Data System (ADS)

Hakala, P. J.; Charles, P. A.; Muhli, P.

2011-09-01

We present results from several years of fast optical photometry of 4U0614+091 (V1055 Orionis), a candidate ultracompact X-ray binary most likely consisting of a neutron star and a degenerate secondary. We find evidence for strong accretion-driven variability at all epochs, which manifests itself as red noise. This flickering produces transient peaks in the observed power spectrum in the 15-65 min period range. Only in one of our 12 optical data sets can we see evidence for a period that cannot be reproduced using the red noise model. This period of 51 min coincides with the strongest period detected by Shahbaz et al. and can thus be taken as the prime candidate for the orbital period of the system. Furthermore, we find some tentative evidence for the X-ray versus optical flux anticorrelation discovered by Machin et al. using our data together with the all-sky X-ray monitoring data from RXTE/All Sky Monitor. We propose that the complex time series behaviour of 4U0614+09 is a result of drastic changes in the accretion disc geometry/structure on time-scales from hours to days. Finally, we want to draw attention to the interpretation of moderately strong peaks in the power spectra of especially accreting sources. Many of such 'periods' can probably be attributed to the presence of red noise (i.e. correlated events) in the data. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Uses results provided by the ASM/RXTE teams at MIT and at the RXTE SOF and GOF at NASA's GSFC.

X-ray Spectral Formation In High-mass X-ray Binaries: The Case Of Vela X-1

NASA Astrophysics Data System (ADS)

Akiyama, Shizuka; Mauche, C. W.; Liedahl, D. A.; Plewa, T.

2007-05-01

We are working to develop improved models of radiatively-driven mass flows in the presence of an X-ray source -- such as in X-ray binaries, cataclysmic variables, and active galactic nuclei -- in order to infer the physical properties that determine the X-ray spectra of such systems. The models integrate a three-dimensional time-dependent hydrodynamics capability (FLASH); a comprehensive and uniform set of atomic data, improved calculations of the line force multiplier that account for X-ray photoionization and non-LTE population kinetics, and X-ray emission-line models appropriate to X-ray photoionized plasmas (HULLAC); and a Monte Carlo radiation transport code that simulates Compton scattering and recombination cascades following photoionization. As a test bed, we have simulated a high-mass X-ray binary with parameters appropriate to Vela X-1. While the orbital and stellar parameters of this system are well constrained, the physics of X-ray spectral formation is less well understood because the canonical analytical wind velocity profile of OB stars does not account for the dynamical and radiative feedback effects due to the rotation of the system and to the irradiation of the stellar wind by X-rays from the neutron star. We discuss the dynamical wind structure of Vela X-1 as determined by the FLASH simulation, where in the binary the X-ray emission features originate, and how the spatial and spectral properties of the X-ray emission features are modified by Compton scattering, photoabsorption, and fluorescent emission. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Was the nineteenth century giant eruption of Eta Carinae a merger event in a triple system?

NASA Astrophysics Data System (ADS)

Portegies Zwart, S. F.; van den Heuvel, E. P. J.

2016-03-01

We discuss the events that led to the giant eruption of Eta Carinae, and find that the mid-nineteenth century (in 1838-1843) giant mass-loss outburst has the characteristics of being produced by the merger event of a massive close binary, triggered by the gravitational interaction with a massive third companion star, which is the current binary companion in the Eta Carinae system. We come to this conclusion by a combination of theoretical arguments supported by computer simulations using the Astrophysical Multipurpose Software Environment. According to this model the ˜90 M⊙ present primary star of the highly eccentric Eta Carinae binary system is the product of this merger, and its ˜30 M⊙ companion originally was the third star in the system. In our model, the Homunculus nebula was produced by an extremely enhanced stellar wind, energized by tidal energy dissipation prior to the merger, which enormously boosted the radiation-driven wind mass-loss. The current orbital plane is then aligned with the equatorial plane of the Homunculus, and the symmetric lobes are roughly aligned with the argument of periastron of the current Eta Carina binary. The merger itself then occurred in 1838, which resulted in a massive asymmetric outflow in the equatorial plane of the Homunculus. The 1843 outburst can in our model be attributed to the subsequent encounter when the companion star (once the outermost star in the triple system) plunges through the bloated envelope of the merger product, once when it passed periastron again. We predict that the system has an excess space velocity of order 50 km s-1 in the equatorial plane of the Homunculus. Our triple model gives a viable explanation for the high runaway velocities typically observed in LBVs.

Ab initio modeling of zincblende AlN layer in Al-AlN-TiN multilayers

DOE PAGES

Yadav, S. K.; Wang, J.; Liu, X. -Y.

2016-06-13

An unusual growth mechanism of metastable zincblende AlN thin film by diffusion of nitrogen atoms into Al lattice is established. Using first-principles density functional theory, we studied the possibility of thermodynamic stability of AlN as a zincblende phase due to epitaxial strains and interface effect, which fails to explain the formation of zincblende AlN. We then compared the formation energetics of rocksalt and zincblende AlN in fcc Al through direct diffusion of nitrogen atoms to Al octahedral and tetrahedral interstitials. Furthermore, the formation of a zincblende AlN thin film is determined to be a kinetically driven process, not a thermodynamicallymore » driven process.« less

Binary-disk interaction. II. Gap-opening criteria for unequal-mass binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Del Valle, Luciano; Escala, Andrés, E-mail: ldelvalleb@gmail.com

We study the interaction of an unequal-mass binary with an isothermal circumbinary disk, motivated by the theoretical and observational evidence that after a major merger of gas-rich galaxies, a massive gaseous disk with a supermassive black hole binary will be formed in the nuclear region. We focus on the gravitational torques that the binary exerts on the disk and how these torques can drive the formation of a gap in the disk. This exchange of angular momentum between the binary and the disk is mainly driven by the gravitational interaction between the binary and a strong nonaxisymmetric density perturbation thatmore » is produced in the disk, in response to the presence of the binary. Using smoothed particle hydrodynamics numerical simulations, we test two gap-opening criteria, one that assumes the geometry of the density perturbation is an ellipsoid/thick spiral and another that assumes a flat spiral geometry for the density perturbation. We find that the flat spiral gap-opening criterion successfully predicts which simulations will have a gap in the disk and which will not. We also study the limiting cases predicted by the gap-opening criteria. Since the viscosity in our simulations is considerably smaller than the expected value in the nuclear regions of gas-rich merging galaxies, we conclude that in such environments the formation of a circumbinary gap is unlikely.« less

Experimental evidence of space charge driven resonances in high intensity linear accelerators

DOE PAGES

Jeon, Dong -O

2016-01-12

In the construction of high intensity accelerators, it is the utmost goal to minimize the beam loss by avoiding or minimizing contributions of various halo formation mechanisms. As a halo formation mechanism, space charge driven resonances are well known for circular accelerators. However, the recent finding showed that even in linear accelerators the space charge potential can excite the 4σ = 360° fourth order resonance [D. Jeon et al., Phys. Rev. ST Accel. Beams 12, 054204 (2009)]. This study increased the interests in space charge driven resonances of linear accelerators. Experimental studies of the space charge driven resonances of highmore » intensity linear accelerators are rare as opposed to the multitude of simulation studies. This paper presents an experimental evidence of the space charge driven 4σ ¼ 360° resonance and the 2σ x(y) – 2σ z = 0 resonance of a high intensity linear accelerator through beam profile measurements from multiple wire-scanners. Moreover, measured beam profiles agree well with the characteristics of the space charge driven 4σ = 360° resonance and the 2σ x(y) – 2σ z = 0 resonance that are predicted by the simulation.« less

Featured Image: Stars from Broken Clouds and Disks

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-04-01

This still from a simulation captures binary star formation in action. Researchers have long speculated on the processes that lead to clouds of gas and dust breaking up into smaller pieces to form multiple-star systems but these take place over a large range of scales, making them difficult to simulate. In a new study led by Leonardo Sigalotti (UAM Azcapotzalco, Mexico), researchers have used a smoothed-particle hydrodynamics code to model binary star formation on scales of thousands of AU down to scales as small as 0.1 AU. In the scene shown above, a collapsing cloud of gas and dust has recently fragmented into two pieces, forming a pair of disks separated by around 200 AU. In addition, we can see that smaller-scale fragmentation is just starting in one of these disks, Disk B. Here, one of the disks spiral arms has become unstable and is beginning to condense; it will eventually form another star, producing a hierarchical system: a close binary within the larger-scale binary. Check out the broaderprocessin the four panels below (which show the system as it evolves over time), or visitthe paper linked below for more information about what the authors learned.Evolution of a collapsed cloud after large-scale fragmentation into a binary protostar: (a) 44.14 kyr, (b) 44.39 kyr, (c) 44.43 kyr, and (d) 44.68 kyr. The insets show magnifications of the binary cores. [Adapted from Sigalotti et al. 2018]CitationLeonardo Di G. Sigalotti et al 2018 ApJ 857 40. doi:10.3847/1538-4357/aab619

Magnetic field response of doubly clamped magnetoelectric microelectromechanical AlN-FeCo resonators

NASA Astrophysics Data System (ADS)

Bennett, S. P.; Baldwin, J. W.; Staruch, M.; Matis, B. R.; LaComb, J.; van't Erve, O. M. J.; Bussmann, K.; Metzler, M.; Gottron, N.; Zappone, W.; LaComb, R.; Finkel, P.

2017-12-01

Magnetoelectric (ME) cantilever resonators have been successfully employed as magnetic sensors to measure low magnetic fields; however, high relative resolution enabling magnetometry in high magnetic fields is lacking. Here, we present on-chip silicon based ME microelectromechanical (MEMS) doubly clamped resonators which can be utilized as high sensitivity, low power magnetic sensors. The resonator is a fully suspended thin film ME heterostructure composed of an active magnetoelastic layer (Fe0.3Co0.7), which is strain coupled to a piezoelectric signal/excitation layer (AlN). By controlling uniaxial stress arising from the large magnetoelastic properties of magnetostrictive FeCo, a magnetically driven shift of the resonance frequency of the first fundamental flexural mode is observed. The theoretical intrinsic magnetic noise floor of such sensors reaches a minimum value of 35 p T /√{H z }. This approach shows a magnetic field sensitivity of ˜5 Hz/mT in a bias magnetic field of up to 120 mT. Such sensors have the potential in applications required for enhanced dynamic sensitivity in high-field magnetometry.

EVOLUTION OF A RING AROUND THE PLUTO–CHARON BINARY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bromley, Benjamin C.; Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu

We consider the formation of satellites around the Pluto–Charon binary. An early collision between the two partners likely produced the binary and a narrow ring of debris, out of which arose the moons Styx, Nix, Kerberos, and Hydra. How the satellites emerged from the compact ring is uncertain. Here we show that a particle ring spreads from physical collisions and collective gravitational scattering, similar to migration. Around a binary, these processes take place in the reference frames of “most circular” orbits, akin to circular ones in a Keplerian potential. Ring particles damp to these orbits and avoid destructive collisions. Dampingmore » and diffusion also help particles survive dynamical instabilities driven by resonances with the binary. In some situations, particles become trapped near resonances that sweep outward with the tidal evolution of the Pluto–Charon binary. With simple models and numerical experiments, we show how the Pluto–Charon impact ring may have expanded into a broad disk, out of which grew the circumbinary moons. In some scenarios, the ring can spread well beyond the orbit of Hydra, the most distant moon, to form a handful of smaller satellites. If these small moons exist, New Horizons will find them.« less

A New Method for the Quick Determination of S-Type and P-Type Habitable Zones in Binary Systems

NASA Astrophysics Data System (ADS)

Wang, Zhaopeng; Cuntz, Manfred

2017-01-01

More than 3500 exoplanets have been confirmed nowadays, including a very large number of planets discovered by the Kepler mission. Additional exoplanets are expected to be found by ongoing missions as, e.g., K2 as well as future missions such as TESS. Exoplanets, especially terrestrial planets, located in stellar habitable zones are drawing great attention from the community and the public at large due to their potential for hosting alien life - a prospect that makes the adequate determination of stellar habitable zones an important goal of exoplanetary research. In the local Galactic neighborhood, binary systems occur relatively frequently. Thus, it is the aim of my presentation to offer a method for the quick determination for the existence of habitable zones in binaries. Therefore, fitting formulas for binary habitable zones regarding both S-type and P-type star-planet configurations are provided. Based on previous work in the literature, a joint constraint regarding radiative habitable zones and planetary orbital stability limits is used. Models of stellar habitable zones utilize updated computations for planetary climate models as given by Kopparapu et al. (2013, 2014) [ApJ 765, 131; ApJL 787, L29]. Cases studies showing the quality of the fit formulas, as well as applications to observed systems, are presented as well.

Phonon Dispersion in Amorphous Ni-Alloys

NASA Astrophysics Data System (ADS)

Vora, A. M.

2007-06-01

The well-known model potential is used to investigate the longitudinal and transverse phonon dispersion curves for six Ni-based binary amorphous alloys, viz. Ni31Dy69, Ni33Y67, Ni36Zr64, Ni50Zr50, Ni60 Nb40, and Ni81B19. The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves. The theoretical approach given by Hubbard-Beeby is used in the present study to compute the phonon dispersion curves. Five local field correction functions proposed by Hartree, Taylor, Ichimaru-Utsumi, Farid et al. and Sarkar et al. are employed to see the effect of exchange and correlation in the aforesaid properties.

Neutral Beam Driven Neoclassical Transport in NSTX

NASA Astrophysics Data System (ADS)

Houlberg, W. A.; Shaing, K. C.; Callen, J. D.

2002-11-01

We re-examine the particle and heat flows driven by neutral beam injection in tokamak plasmas. These appear as inward pinches for co-injection and outward for counter injection. We derive the parallel friction and heat friction forces exerted on the thermal species by the energetic beam ions by extending the early analysis of Callen, et al. [1], which are then used as external forces in the moments formulation of neoclassical transport in NCLASS [2]. NCLASS is based on the multiple species treatment of Hirshman and Sigmar [3]. Of particular interest is the ion energy flux driven by the heat friction term. It scales as the beam energy, while the particle and electron heat terms scale as the thermal plasma temperature. In NSTX the high beam energy to plasma temperature ratio may lead to a net negative ion heat flux with strong co-injection. Limtations to the theory, such as the large fast ion orbit size relative to the radius of the flux surface, are discussed. Comparisons are made with earlier works by Hinton and Kim [4] and Stacey [5], who evaluated only the beam-thermal friction. [1] J.D. Callen, et al, 5th IAEA, Tokyo (1974), Vol 1, 645 [2] W.A. Houlberg, K.C. Shaing, S.P. Hirshman, M.C. Zarnstorff, Phys. Plasmas 4 (1997) 3230 [3] S.P. Hirshman, D.J. Sigmar, Nucl. Fusion 21 (1981) 1079 [4] F.L. Hinton, Y.-B. Kim, Phys. Fluids B 5 (1993) 3012 [5] W.M. Stacey, Phys. Fluids B 5 (1993) 4505

Analog Computer-Aided Detection (CAD) information can be more effective than binary marks.

PubMed

Cunningham, Corbin A; Drew, Trafton; Wolfe, Jeremy M

2017-02-01

In socially important visual search tasks, such as baggage screening and diagnostic radiology, experts miss more targets than is desirable. Computer-aided detection (CAD) programs have been developed specifically to improve performance in these professional search tasks. For example, in breast cancer screening, many CAD systems are capable of detecting approximately 90% of breast cancer, with approximately 0.5 false-positive detections per image. Nevertheless, benefits of CAD in clinical settings tend to be small (Birdwell, 2009) or even absent (Meziane et al., 2011; Philpotts, 2009). The marks made by a CAD system can be "binary," giving the same signal to any location where the signal is above some threshold. Alternatively, a CAD system presents an analog signal that reflects strength of the signal at a location. In the experiments reported, we compare analog and binary CAD presentations using nonexpert observers and artificial stimuli defined by two noisy signals: a visible color signal and an "invisible" signal that informed our simulated CAD system. We found that analog CAD generally yielded better overall performance than binary CAD. The analog benefit is similar at high and low target prevalence. Our data suggest that the form of the CAD signal can directly influence performance. Analog CAD may allow the computer to be more helpful to the searcher.

Visible-Light-Driven BiOI-Based Janus Micromotor in Pure Water.

PubMed

Dong, Renfeng; Hu, Yan; Wu, Yefei; Gao, Wei; Ren, Biye; Wang, Qinglong; Cai, Yuepeng

2017-02-08

Light-driven synthetic micro-/nanomotors have attracted considerable attention due to their potential applications and unique performances such as remote motion control and adjustable velocity. Utilizing harmless and renewable visible light to supply energy for micro-/nanomotors in water represents a great challenge. In view of the outstanding photocatalytic performance of bismuth oxyiodide (BiOI), visible-light-driven BiOI-based Janus micromotors have been developed, which can be activated by a broad spectrum of light, including blue and green light. Such BiOI-based Janus micromotors can be propelled by photocatalytic reactions in pure water under environmentally friendly visible light without the addition of any other chemical fuels. The remote control of photocatalytic propulsion by modulating the power of visible light is characterized by velocity and mean-square displacement analysis of optical video recordings. In addition, the self-electrophoresis mechanism has been confirmed for such visible-light-driven BiOI-based Janus micromotors by demonstrating the effects of various coated layers (e.g., Al 2 O 3 , Pt, and Au) on the velocity of motors. The successful demonstration of visible-light-driven Janus micromotors holds a great promise for future biomedical and environmental applications.

Title: Detection of a 31.6 s pulse period for the supernova impostor SN 2010da in NGC 300, observed in ULX state

NASA Astrophysics Data System (ADS)

Carpano, S.; Haberl, F.; Maitra, C.

2018-01-01

The supernova impostor SN 2010da located in NGC 300, later identified as a likely Supergiant B[e] High-mass X-ray binary (Lau et al. 2016, ApJ, 830, 142 and Villar et al. 2016, ApJ, 830, 11), was observed in outburst during two long (139 and 82 ks) XMM-Newton observations performed on 2016 December 17 to 20. We report the discovery of a strong periodic modulation in the X-ray flux with a pulse period of 31.6 s and a very rapid spin-up, and confirm therefore that the compact object is a neutron star.

Friction and wear of iron-base binary alloys in sliding contact with silicon carbide in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Multipass sliding friction experiments were conducted with various iron base binary alloys in contact with a single crystal silicon carbide surface in vacuum. Results indicate that the atomic size and concentration of alloy elements play important roles in controlling the transfer and friction properties of iron base binary alloys. Alloys having high solute concentration produce more transfer than do alloys having low solute concentration. The coefficient of friction during multipass sliding generally increases with an increase in the concentration of alloying element. The change of friction with succeeding passes after the initial pass also increases as the solute to iron, atomic radius ratio increases or decreases from unity.

Designing defect-based qubit candidates in wide-gap binary semiconductors for solid-state quantum technologies

NASA Astrophysics Data System (ADS)

Seo, Hosung; Ma, He; Govoni, Marco; Galli, Giulia

2017-12-01

The development of novel quantum bits is key to extending the scope of solid-state quantum-information science and technology. Using first-principles calculations, we propose that large metal ion-vacancy pairs are promising qubit candidates in two binary crystals: 4 H -SiC and w -AlN. In particular, we found that the formation of neutral Hf- and Zr-vacancy pairs is energetically favorable in both solids; these defects have spin-triplet ground states, with electronic structures similar to those of the diamond nitrogen-vacancy center and the SiC divacancy. Interestingly, they exhibit different spin-strain coupling characteristics, and the nature of heavy metal ions may allow for easy defect implantation in desired lattice locations and ensure stability against defect diffusion. To support future experimental identification of the proposed defects, we report predictions of their optical zero-phonon line, zero-field splitting, and hyperfine parameters. The defect design concept identified here may be generalized to other binary semiconductors to facilitate the exploration of new solid-state qubits.

VizieR Online Data Catalog: Minima of 41 binaries from entire Kepler mission (Gies+, 2015)

NASA Astrophysics Data System (ADS)

Gies, D. R.; Matson, R. A.; Guo, Z.; Lester, K. V.; Orosz, J. A.; Peters, G. J.

2016-06-01

We embarked on a search for eclipse timing variations among a subset of 41 eclipsing binaries that were identified prior to the start of Kepler observations (see our first paper, Gies et al. 2012, cat. J/AJ/143/137). Our first paper documented the eclipse times in observations made over quarters Q0-Q9 (2009.3-2011.5). Now with the Kepler mission complete with observations through Q17 (ending 2013.4), we present here the eclipse timings for our sample of 41 binaries over the entire duration of the mission. The associated times given in our first paper were based upon UTC (Coordinated Universal Time) while the current set uses TDB (Barycentric Dynamical Time), and here we report the times in reduced Barycentric Julian Date (BJD-2400000 days). We used the Simple Aperture Photometry (SAP) flux except in the case of KIC04678873. The list of targets appears in Table1. The eclipse timing measurements were made in almost the same way as described in our first paper. Our measurements appear in Table2. (2 data files).

How can we make stable linear monoatomic chains? Gold-cesium binary subnanowires as an example of a charge-transfer-driven approach to alloying.

PubMed

Choi, Young Cheol; Lee, Han Myoung; Kim, Woo Youn; Kwon, S K; Nautiyal, Tashi; Cheng, Da-Yong; Vishwanathan, K; Kim, Kwang S

2007-02-16

On the basis of first-principles calculations of clusters and one dimensional infinitely long subnanowires of the binary systems, we find that alkali-noble metal alloy wires show better linearity and stability than either pure alkali metal or noble metal wires. The enhanced alternating charge buildup on atoms by charge transfer helps the atoms line up straight. The cesium doped gold wires showing significant charge transfer from cesium to gold can be stabilized as linear or circular monoatomic chains.

Determination of 200 °C Isothermal Section of Al-Ag-Ga Phase Diagram by Microanalysis, X-ray Diffraction, Hardness and Electrical Conductivity Measurements

NASA Astrophysics Data System (ADS)

Premović, Milena; Tomović, Milica; Minić, Duško; Manasijević, Dragan; Živković, Dragana; Ćosović, Vladan; Grković, Vladan; Đorđević, Aleksandar

2017-04-01

Ternary Al-Ag-Ga system at 200 °C was experimentally and thermodynamically assessed. Isothermal section was extrapolated using optimized thermodynamic parameters for constitutive binary systems. Microstructure and phase composition of the selected alloy samples were analyzed using light microscopy, scanning electron microscopy combined with energy-dispersive spectrometry and x-ray powder diffraction technique. The obtained experimental results were found to be in a close agreement with the predicted phase equilibria. Hardness and electrical conductivity of the alloy samples from four vertical sections Al-Ag80Ga20, Al-Ag60Ga40, Ag-Al80Ga20 and Ag-Al60Ga40 of the ternary Al-Ag-Ga system at 200 °C were experimentally determined using Brinell method and eddy current measurements. Additionally, hardness of the individual phases present in the microstructure of the studied alloy samples was determined using Vickers microhardness test. Based on experimentally obtained results, isolines of Brinell hardness and electrical conductivity were calculated for the alloys from isothermal section of the ternary Al-Ag-Ga system at 200 °C.

Perceptually relevant grouping of image tokens on the basis of constraint propagation from local binary patterns

NASA Astrophysics Data System (ADS)

Behlim, Sadaf Iqbal; Syed, Tahir Qasim; Malik, Muhammad Yameen; Vigneron, Vincent

2016-11-01

Grouping image tokens is an intermediate step needed to arrive at meaningful image representation and summarization. Usually, perceptual cues, for instance, gestalt properties inform token grouping. However, they do not take into account structural continuities that could be derived from other tokens belonging to similar structures irrespective of their location. We propose an image representation that encodes structural constraints emerging from local binary patterns (LBP), which provides a long-distance measure of similarity but in a structurally connected way. Our representation provides a grouping of pixels or larger image tokens that is free of numeric similarity measures and could therefore be extended to nonmetric spaces. The representation lends itself nicely to ubiquitous image processing applications such as connected component labeling and segmentation. We test our proposed representation on the perceptual grouping or segmentation task on the popular Berkeley segmentation dataset (BSD500) that with respect to human segmented images achieves an average F-measure of 0.559. Our algorithm achieves a high average recall of 0.787 and is therefore well-suited to other applications such as object retrieval and category-independent object recognition. The proposed merging heuristic based on levels of singular tree component has shown promising results on the BSD500 dataset and currently ranks 12th among all benchmarked algorithms, but contrary to the others, it requires no data-driven training or specialized preprocessing.

Influence of alloying elements on the oxidation behavior of NbAl3

NASA Technical Reports Server (NTRS)

Hebsur, M. G.; Stephens, J. R.; Smialek, J. L.; Barrett, C. A.; Fox, D. S.

1988-01-01

NbAL3 is one candidate material for advanced aeropropulsion systems because of its high melting point, low density, and good oxidation resistance. Although NbAl3 has the lowest oxidation rate among the binary Nb-Al alloys, it does not form exclusive layers of protective Al2O3 scales. Recently Perkin et al., have shown the feasibility of forming alumina scales on Nb-Al alloys at greatly reduced Al contents. However, the objective was to maintain the high Al content, and hence low density, while achieving the capability of growing protective alumina scales. Alloy development followed approaches similar to those used successfully for superalloys and oxidation resistant MCrAlY coatings. Among the three elements examined (Ti, Si, and Cr) as ternary additions to Nb-Al3, Cr was the most effective in favoring the selective oxidation of Al. Nb-41Al-8Cr formed exclusive layers of alumina and had a k sub p value of 0.22 mg squared/cm (sup 4)/hr at 1200 C. The addition of 1 wt percent Y to this alloy was also beneficial, resulting in nearly an order of magnitude decrease in K sub p at 1200 C. Further improvements were achieved by adding about 1 wt percent Si to the quaternary alloy. The k sub p value of 0.012 mg squared/cm (sup 4)/hr for Nb-40Al-8Cr-1Y-1Si at 1200 C was identical to the best NiAl + Zr alloys. These NbAl3 alloys also exhibited excellent cyclic oxidation resistance for 100 hr at 1200 C, being nearly equivalent to NiAl + Zr.

The Effect of Single, Binary and Ternary Anions of Chloride, Carbonate and Phosphate on the Release of 2,4-Dichlorophenoxyacetate Intercalated into the Zn-Al-layered Double Hydroxide Nanohybrid

NASA Astrophysics Data System (ADS)

Hussein, Mohd Zobir; Jaafar, Adila Mohamad; Yahaya, Asmah Hj.; Zainal, Zulkarnain

2009-11-01

Intercalation of beneficial anion into inorganic host has lead to an opportunity to synthesize various combinations of new organic-inorganic nanohybrids with various potential applications; especially, for the controlled release formulation and storage purposes. Investigation on the release behavior of 2,4-dichlorophenoxyacetate (2,4-D) intercalated into the interlayer of Zn-Al-layered double hydroxide (ZAN) have been carried out using single, binary and ternary aqueous systems of chloride, carbonate and phosphate. The release behavior of the active agent 2,4-D from its double-layered hydroxide nanohybrid ZANDI was found to be of controlled manner governed by pseudo-second order kinetics. It was found that carbonate medium yielded the highest accumulated release of 2,4-D, while phosphate in combination with carbonate and/or nitrate speeds up the release rate of 2,4-D. These results indicate that it is possible to design and develop new delivery system of latex stimulant compound with controlled release property based on 2,4-D that is known as a substance to increase latex production of rubber tree, Hevea brasiliensis.

Semiconductor lasers driven by self-sustained chaotic electronic oscillators and applications to optical chaos cryptography.

PubMed

Kingni, Sifeu Takougang; Mbé, Jimmi Hervé Talla; Woafo, Paul

2012-09-01

In this work, we numerically study the dynamics of vertical cavity surface emitting laser (VCSEL) firstly when it is driven by Chua's oscillator, secondly in case where it is driven by a broad frequency spectral bandwidth chaotic oscillator developed by Nana et al. [Commun. Nonlinear Sci. Numer. Simul. 14, 2266 (2009)]. We demonstrated that the VCSEL generated robust chaotic dynamics compared to the ones found in VCSEL subject to a sinusoidally modulated current and therefore it is more suitable for chaos encryption techniques. The synchronization characteristics and the communication performances of unidirectional coupled VCSEL driven by the broad frequency spectral bandwidth chaotic oscillators are investigated numerically. The results show that high-quality synchronization and transmission of messages can be realized for suitable system parameters. Chaos shift keying method is successfully applied to encrypt a message at a high bitrate.

Temperature driven evolution of thermal, electrical, and optical properties of Ti-Al-N coatings.

PubMed

Rachbauer, Richard; Gengler, Jamie J; Voevodin, Andrey A; Resch, Katharina; Mayrhofer, Paul H

2012-03-01

Monolithic single phase cubic (c) Ti 1- x Al x N thin films are used in various industrial applications due to their high thermal stability, which beneficially effects lifetime and performance of cutting and milling tools, but also find increasing utilization in electronic and optical devices. The present study elucidates the temperature-driven evolution of heat conductivity, electrical resistivity and optical reflectance from room temperature up to 1400 °C and links them to structural and chemical changes in Ti 1- x Al x N coatings. It is shown that various decomposition phenomena, involving recovery and spinodal decomposition (known to account for the age hardening phenomenon in c-Ti 1- x Al x N), as well as the cubic to wurtzite phase transformation of spinodally formed AlN-enriched domains, effectively increase the thermal conductivity of the coatings from ∼3.8 W m -1  K -1 by a factor of three, while the electrical resistivity is reduced by one order of magnitude. A change in the coating color from metallic grey after deposition to reddish-golden after annealing to 1400 °C is related to the film structure and discussed in terms of film reflectivity.

Resampling to accelerate cross-correlation searches for continuous gravitational waves from binary systems

NASA Astrophysics Data System (ADS)

Meadors, Grant David; Krishnan, Badri; Papa, Maria Alessandra; Whelan, John T.; Zhang, Yuanhao

2018-02-01

Continuous-wave (CW) gravitational waves (GWs) call for computationally-intensive methods. Low signal-to-noise ratio signals need templated searches with long coherent integration times and thus fine parameter-space resolution. Longer integration increases sensitivity. Low-mass x-ray binaries (LMXBs) such as Scorpius X-1 (Sco X-1) may emit accretion-driven CWs at strains reachable by current ground-based observatories. Binary orbital parameters induce phase modulation. This paper describes how resampling corrects binary and detector motion, yielding source-frame time series used for cross-correlation. Compared to the previous, detector-frame, templated cross-correlation method, used for Sco X-1 on data from the first Advanced LIGO observing run (O1), resampling is about 20 × faster in the costliest, most-sensitive frequency bands. Speed-up factors depend on integration time and search setup. The speed could be reinvested into longer integration with a forecast sensitivity gain, 20 to 125 Hz median, of approximately 51%, or from 20 to 250 Hz, 11%, given the same per-band cost and setup. This paper's timing model enables future setup optimization. Resampling scales well with longer integration, and at 10 × unoptimized cost could reach respectively 2.83 × and 2.75 × median sensitivities, limited by spin-wandering. Then an O1 search could yield a marginalized-polarization upper limit reaching torque-balance at 100 Hz. Frequencies from 40 to 140 Hz might be probed in equal observing time with 2 × improved detectors.