Molybdenum Carbide Synthesis Using Plasmas for Fuel Cells

DTIC Science & Technology

2013-06-01

S. A. Hong, I. H. Oh, and S. J. Shin, “Performance and life time analysis of the kW-class PEMFC stack,” Journal of Power Sources, vol. 106, pp. 295...pp. 591–596, 1998. [25] M. Gotz and H. Wendt, “Binary and ternary anode catalyst formulations including the elements W, Sn and Mo for PEMFCs ...and R. C. Urian, “Electrocatalysis of CO Tolerance by Carbon-Supported PtMo Electrocatalysts in PEMFCs ,” Journal of Electrochemical Society, vol

Binary metal oxide nanoparticle incorporated composite multilayer thin films for sono-photocatalytic degradation of organic pollutants

NASA Astrophysics Data System (ADS)

Gokul, Paramasivam; Vinoth, Ramalingam; Neppolian, Bernaurdshaw; Anandhakumar, Sundaramurthy

2017-10-01

We report reduced graphene oxide (rGO) supported binary metal oxide (CuO-TiO2/rGO) nanoparticle (NP) incorporated multilayer thin films based on Layer-by-Layer (LbL) assembly for enhanced sono-photocatalytic degradation of methyl orange under exposure to UV radiation. Multilayer thin films were fabricated on glass and quartz slides, and investigated using scanning electron microscopy and UV-vis spectroscopy. The loading of catalyst NPs on the film resulted in the change of morphology of the film from smooth to rough with uniformly distributed NPs on the surface. The growth of the control and NP incorporated films followed a linear regime as a function of number of layers. The%degradation of methyl orange as a function of time was investigated by UV-vis spectroscopy and total organic carbon (TOC) measurements. Complete degradation of methyl orange was achieved within 13 h. The amount of NP loading in the film significantly influenced the%degradation of methyl orange. Catalyst reusability studies revealed that the catalyst thin films could be repeatedly used for up to five times without any change in photocatalytic activity of the films. The findings of the present study support that the binary metal oxide catalyst films reported here are very useful for continuous systems, and thus, making it an option for scale up.

Single and multi-component adsorption of psychiatric pharmaceuticals onto alternative and commercial carbons.

PubMed

Calisto, Vânia; Jaria, Guilaine; Silva, Carla Patrícia; Ferreira, Catarina I A; Otero, Marta; Esteves, Valdemar I

2017-05-01

This work describes the adsorptive removal of three widely consumed psychiatric pharmaceuticals (carbamazepine, paroxetine and oxazepam) from ultrapure water. Two different adsorbents were used: a commercial activated carbon and a non-activated waste-based carbon (PS800-150-HCl), produced by pyrolysis of primary paper mill sludge. These adsorbents were used in single, binary and ternary batch experiments in order to determine the adsorption kinetics and equilibrium isotherms of the considered pharmaceuticals. For the three drugs and both carbons, the equilibrium was quickly attained (with maximum equilibrium times of 15 and 120 min for the waste-based and the commercial carbons, respectively) even in binary and ternary systems. Single component equilibrium data were adequately described by the Langmuir model, with the commercial carbon registering higher maximum adsorption capacities (between 272 ± 10 and 493 ± 12 μmol g -1 ) than PS800-150-HCl (between 64 ± 2 and 74 ± 1 μmol g -1 ). Multi-component equilibrium data were also best fitted by the single component Langmuir isotherm, followed by the Langmuir competitive model. Overall, competitive effects did not largely affect the performance of both adsorbents. Binary and ternary systems maintained fast kinetics, the individual maximum adsorption capacities were not lower than half of the single component systems and both carbons presented improved total adsorption capacities for multi-component solutions. Copyright © 2017 Elsevier Ltd. All rights reserved.

The use of nutshell carbons in drinking water filters for removal of trace metals.

PubMed

Ahmedna, Mohamed; Marshall, Wayne E; Husseiny, Abdo A; Rao, Ramu M; Goktepe, Ipek

2004-02-01

Filtration of drinking water by point-of-use (POU) or point-of-entry (POE) systems is becoming increasingly popular in the United States. Drinking water is filtered to remove both organic and inorganic contaminants. The objective of this study was to evaluate the use of granular activated carbon from nutshells (almond, English walnut, pecan) in a POU water filtration system to determine its effectiveness in removing select, potentially toxic metal ions, namely, copper (Cu2+), lead (Pb2+) or zinc (Zn2+) found in drinking water. The nutshell-based carbon system was designated "Envirofilter" and was compared to four commercial POU systems with brand names of BRITA, Omni Filter, PUR and Teledyne Water Pik. Eight prototype "Envirofilters", consisting of individual or binary mixtures of carbons made from acid-activated almond or pecan shells and steam-activated pecan or walnut shells were constructed and evaluated for adsorption of the three metal ions. The results indicated that a binary mixture of carbons from acid-activated almond and either steam-activated pecan or walnut shells were the most effective in removing these metals from drinking water of all the POU systems evaluated. Binary mixtures of acid-activated almond shell-based carbon with either steam-activated pecan shell- or walnut shell-based carbon removed nearly 100% of lead ion, 90-95% of copper ion and 80-90% of zinc ion. Overall the performance data on the "Envirofilters" suggest that these prototypes require less carbon than commercial filters to achieve the same metal adsorption efficiency and may also be a less expensive product.

Merger of a white dwarf-neutron star binary to 1029 carat diamonds: origin of the pulsar planets

NASA Astrophysics Data System (ADS)

Margalit, Ben; Metzger, Brian D.

2017-03-01

We show that the merger and tidal disruption of a carbon/oxygen (C/O) white dwarf (WD) by a neutron star (NS) binary companion provides a natural formation scenario for the PSR B1257+12 planetary system. Starting with initial conditions for the debris disc produced of the disrupted WD, we model its long-term viscous evolution, including for the first time the effects of mass and angular momentum loss during the early radiatively inefficient accretion flow (RIAF) phase and accounting for the unusual C/O composition on the disc opacity. For plausible values of the disc viscosity α ∼ 10-3-10-2 and the RIAF mass-loss efficiency, we find that the disc mass remaining near the planet formation radius at the time of solid condensation is sufficient to explain the pulsar planets. Rapid rocky planet formation via gravitational instability of the solid carbon dominated disc is facilitated by the suppression of vertical shear instabilities due to the high solid-to-gas ratio. Additional evidence supporting a WD-NS merger scenario includes (1) the low observed occurrence rate of pulsar planets (≲1 per cent of NS birth), comparable to the expected WD-NS merger rate; (2) accretion by the NS during the RIAF phase is sufficient to spin PSR B1257+12 up to its observed 6 ms period; (3) similar models of 'low angular momentum' discs, such as those produced from supernova fallback, find insufficient mass reaching the planet formation radius. The unusually high space velocity of PSR B1257+12 of ≳326 km s-1 suggests a possible connection to the calcium-rich transients, dim supernovae which occur in the outskirts of their host galaxies and were proposed to result from mergers of WD-NS binaries receiving supernova kicks. The C/O disc composition implied by our model likely results in carbon-rich planets with diamond interiors.

Method for retorting oil shale

DOEpatents

Shang, Jer-Yu; Lui, A.P.

1985-08-16

The recovery of oil from oil shale is provided in a fluidized bed by using a fluidizing medium of a binary mixture of carbon dioxide and 5 steam. The mixture with a steam concentration in the range of about 20 to 75 volume percent steam provides an increase in oil yield over that achievable by using a fluidizing gas of carbon dioxide or steam alone when the mixture contains higher steam concentrations. The operating parameters for the fluidized bed retorted are essentially the same as those utilized with other gaseous fluidizing mediums with the significant gain being in the oil yield recovered which is attributable solely to the use of the binary mixture of carbon dioxide and steam. 2 figs.

Innocent Bystanders and Smoking Guns: Dwarf Carbon Stars

NASA Astrophysics Data System (ADS)

Green, Paul J.

2014-01-01

As far as we know, most carbon throughout the Universe is created and dispersed by AGB stars. So it was at first surprising to find that the carbon stars most prevalent in the Galaxy are in fact dwarfs. We suspect that dC stars are most likely innocent bystanders in post-mass transfer binaries, and may be predominantly metal-poor. Among 1200 C stars found in the SDSS (Green 2013), we confirm 724 dCs, of which a dozen are DA/dC stars in composite spectrum binaries, quadrupling the total sample of these "smoking guns" for AGB binary mass transfer. The dCs likely span absolute magnitudes M_i from about 6.5 to 10.5. G-type dC stars with weak CN and relatively blue colors are probably the most massive dCs still cool enough to show C_2 bands. Eleven very red C stars with strong red CN bands appear to be N-type AGB stars at large Galactocentric distances, one likely a new discovery in the dIrr galaxy Le A. Two such stars within 30arcmin of each other may trace a previously unidentified dwarf galaxy or tidal stream at ~40 kpc. We describe follow-up projects to study the spatial, kinematic, and binary properties of these C-enriched dwarfs.

Comparing kinetic profiles between bifunctional and binary type of Zn(salen)-based catalysts for organic carbonate formation

PubMed Central

Martín, Carmen

2014-01-01

Summary Zn(salen) complexes have been employed as active catalysts for the formation of cyclic carbonates from epoxides and CO2. A series of kinetic experiments was carried out to obtain information about the mechanism for this process catalyzed by these complexes and in particular about the order-dependence in catalyst. A comparative analysis was done between the binary catalyst system Zn(salphen)/NBu4I and a bifunctional system Zn(salpyr)·MeI with a built-in nucleophile. The latter system demonstrates an apparent second-order dependence on the bifunctional catalyst concentration and thus follows a different, bimetallic mechanism as opposed to the binary catalyst that is connected with a first-order dependence on the catalyst concentration and a monometallic mechanism. PMID:25161742

Porous NiCo2O4 nanoarray-integrated binder-free 3D open electrode offers a highly efficient sensing platform for enzyme-free glucose detection.

PubMed

Luo, X; Huang, M; He, D; Wang, M; Zhang, Y; Jiang, P

2018-05-29

High electrical conductivity and the exposure to more active sites are crucial to boost the performance of a glucose sensor. A porous binary metal oxide nanoarray integrated on a binder-free 3D electrode is expected to offer a highly sensitive sensing platform. As a model, porous NiCo2O4 nanowire arrays supported on carbon cloth (NiCo2O4 NWA/CC) have been prepared and used for enzyme-free glucose sensing. NiCo2O4 NWA/CC shows larger effective surface area, superior electronic conductivity, and higher catalytic activity towards enzyme-free glucose sensing, with a linear range from 1 μM to 0.63 mM, a sensitivity of 4.12 mA mM-1 cm-2, and low detection limit of 0.5 μM. Moreover, NiCo2O4 NWA/CC also displays good selectivity and stability and thus, it can be reliable for glucose detection in human serum samples. These findings inspire the fabrication of a high-performance electrochemical sensing platform by preparing porous binary metal oxide nanoarrays supported on a 3D conductive substrate.

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

Eremenko, V.N.; Kosolapova, T.Ya.

Metallographic studies and chemical phase analysis of carbon-free nickel with titanium carbide, prepared by powder metallurgy and treated under various thermal conditions, showed no separation of free carbon and indicated that the TiC--Ni system is quasi-binary. (R.V.J.)

CXOGBS J173620.2-293338: A candidate symbiotic X-ray binary associated with a bulge carbon star

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

Hynes, Robert I.; Britt, C. T.; Johnson, C. B.

2014-01-01

The Galactic Bulge Survey (GBS) is a wide but shallow X-ray survey of regions above and below the Plane in the Galactic Bulge. It was performed using the Chandra X-ray Observatory's ACIS camera. The survey is primarily designed to find and classify low luminosity X-ray binaries. The combination of the X-ray depth of the survey and the accessibility of optical and infrared counterparts makes this survey ideally suited to identification of new symbiotic X-ray binaries (SyXBs) in the Bulge. We consider the specific case of the X-ray source CXOGBS J173620.2-293338. It is coincident to within 1 arcsec with a verymore » red star, showing a carbon star spectrum and irregular variability in the Optical Gravitational Lensing Experiment data. We classify the star as a late C-R type carbon star based on its spectral features, photometric properties, and variability characteristics, although a low-luminosity C-N type cannot be ruled out. The brightness of the star implies it is located in the Bulge, and its photometric properties are overall consistent with the Bulge carbon star population. Given the rarity of carbon stars in the Bulge, we estimate the probability of such a close chance alignment of any GBS source with a carbon star to be ≲ 10{sup –3}, suggesting that this is likely to be a real match. If the X-ray source is indeed associated with the carbon star, then the X-ray luminosity is around 9 × 10{sup 32} erg s{sup –1}. Its characteristics are consistent with a low luminosity SyXB, or possibly a low accretion rate white dwarf symbiotic.« less

Discovery of the Closest Hot Subdwarf Binary with White Dwarf Companion

NASA Astrophysics Data System (ADS)

Geier, S.; Marsh, T. R.; Dunlap, B. H.; Barlow, B. N.; Schaffenroth, V.; Ziegerer, E.; Heber, U.; Kupfer, T.; Maxted, P. F. L.; Miszalski, B.; Shporer, A.; Telting, J. H.; Ostensen, R. H.; O'Toole, S. J.; Gänsicke, B. T.; Napiwotzki, R.

2013-01-01

We report the discovery of an extremely close, eclipsing binary system. A white dwarf is orbited by a core He-burning compact hot subdwarf star with a period as short as ≃ 0.04987 d making this system the most compact hot subdwarf binary discovered so far. The subdwarf will start to transfer helium-rich material on short timescales of less than 50 Myr. The ignition of He-burning at the surface may trigger carbon-burning in the core although the WD is less massive than the Chandrasekhar limit (> 0.74 M⊙) making this binary a possible progenitor candidate for a supernova type Ia event.

Differentiation of Chemical Components in a Binary Solvent Vapor Mixture Using Carbon/Polymer Composite-Based Chemiresistors

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

Patel, Sanjay V.; Jenkins, Mark W.; Hughes, Robert C.

1999-07-19

We demonstrate a ''universal solvent sensor'' constructed from a small array of carbon/polymer composite chemiresistors that respond to solvents spanning a wide range of Hildebrand volubility parameters. Conductive carbon particles provide electrical continuity in these composite films. When the polymer matrix absorbs solvent vapors, the composite film swells, the average separation between carbon particles increases, and an increase in film resistance results, as some of the conduction pathways are broken. The adverse effects of contact resistance at high solvent concentrations are reported. Solvent vapors including isooctane, ethanol, dlisopropyhnethylphosphonate (DIMP), and water are correctly identified (''classified'') using three chemiresistors, their compositemore » coatings chosen to span the full range of volubility parameters. With the same three sensors, binary mixtures of solvent vapor and water vapor are correctly classified, following classification, two sensors suffice to determine the concentrations of both vapor components. Polyethylene vinylacetate and polyvinyl alcohol (PVA) are two such polymers that are used to classify binary mixtures of DIMP with water vapor; the PVA/carbon-particle-composite films are sensitive to less than 0.25{degree}A relative humidity. The Sandia-developed VERI (Visual-Empirical Region of Influence) technique is used as a method of pattern recognition to classify the solvents and mixtures and to distinguish them from water vapor. In many cases, the response of a given composite sensing film to a binary mixture deviates significantly from the sum of the responses to the isolated vapor components at the same concentrations. While these nonlinearities pose significant difficulty for (primarily) linear methods such as principal components analysis, VERI handles both linear and nonlinear data with equal ease. In the present study the maximum speciation accuracy is achieved by an array containing three or four sensor elements, with the addition of more sensors resulting in a measurable accuracy decrease.« less

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.

Aluminum-Mediated Formation of Cyclic Carbonates: Benchmarking Catalytic Performance Metrics.

PubMed

Rintjema, Jeroen; Kleij, Arjan W

2017-03-22

We report a comparative study on the activity of a series of fifteen binary catalysts derived from various reported aluminum-based complexes. A benchmarking of their initial rates in the coupling of various terminal and internal epoxides in the presence of three different nucleophilic additives was carried out, providing for the first time a useful comparison of activity metrics in the area of cyclic organic carbonate formation. These investigations provide a useful framework for how to realistically valorize relative reactivities and which features are important when considering the ideal operational window of each binary catalyst system. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular dynamics study of combustion reactions in supercritical environment. Part 1: Carbon dioxide and water force field parameters refitting and critical isotherms of binary mixtures

DOE PAGES

Masunov, Artem E.; Atlanov, Arseniy Alekseyevich; Vasu, Subith S.

2016-10-04

Oxy-fuel combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxycombustion the carbon dioxide and water are present in large concentrations in their transcritical state, and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and Molecular Dynamics with ReaxFF force field seem to be a suitable tool for such a study.more » Here we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several nonbonding parameters need adjustment. We report the new parameter set, capable to reproduce the critical temperatures and pressures. Furthermore, the critical isotherms of CO 2/H 2O binary mixtures are computationally studied here for the first time and their critical parameters are reported.« less

Molecular dynamics study of combustion reactions in supercritical environment. Part 1: Carbon dioxide and water force field parameters refitting and critical isotherms of binary mixtures

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

Masunov, Artem E.; Atlanov, Arseniy Alekseyevich; Vasu, Subith S.

Oxy-fuel combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxycombustion the carbon dioxide and water are present in large concentrations in their transcritical state, and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and Molecular Dynamics with ReaxFF force field seem to be a suitable tool for such a study.more » Here we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several nonbonding parameters need adjustment. We report the new parameter set, capable to reproduce the critical temperatures and pressures. Furthermore, the critical isotherms of CO 2/H 2O binary mixtures are computationally studied here for the first time and their critical parameters are reported.« less

Gas-liquid chromatography with a volatile "stationary" liquid phase.

PubMed

Wells, P S; Zhou, S; Parcher, J F

2002-05-01

A unique type of gas-liquid chromatography is described in which both mobile and "stationary" phases are composed of synthetic mixtures of helium and carbon dioxide. At temperatures below the critical point of the binary mixture and pressures above the vapor pressure of pure liquid carbon dioxide, helium and carbon dioxide can form two immiscible phases over extended composition ranges. A binary vapor phase enriched in helium can act as the mobile phase for chromatographic separations, whereas a CO2-rich liquid in equilibrium with the vapor phase, but condensed on the column wall, can act as a pseudostationary phase. Several examples of chromatographic separations obtained in "empty" capillary columns with no ordinary stationary liquid phase illustrate the range of conditions that produce such separations. In addition, several experiments are reported that confirm the proposed two-phase hypothesis. The possible consequences of the observed chromatographic phenomenon in the field of supercritical fluid chromatography with helium headspace carbon dioxide are discussed.

Largely enhanced dielectric properties of carbon nanotubes/polyvinylidene fluoride binary nanocomposites by loading a few boron nitride nanosheets

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

Yang, Minhao; Zhao, Hang; He, Delong

2016-08-15

The ternary nanocomposites of boron nitride nanosheets (BNNSs)/carbon nanotubes (CNTs)/polyvinylidene fluoride (PVDF) are fabricated via a combination of solution casting and extrusion-injection processes. The effects of BNNSs on the electrical conductivity, dielectric behavior, and microstructure changes of CNTs/PVDF binary nanocomposites are systematically investigated. A low percolation value (f{sub c}) for the CNTs/PVDF binary system is obtained due to the integration of solution and melting blending procedures. Two kinds of CNTs/PVDF binary systems with various CNTs contents (f{sub CNTs}) as the matrix are discussed. The results reveal that compared with CNTs/PVDF binary systems at the same f{sub CNTs}, the ternary BNNSs/CNTs/PVDFmore » nanocomposites exhibit largely enhanced dielectric properties due to the improvement of the CNTs dispersion state and the conductive network. The dielectric constant of CNTs/PVDF binary nanocomposite with 6 vol. % CNTs (f{sub CNTs} < f{sub c}) shows a 79.59% enhancement from 49 to 88 after the incorporation of 3 vol. % BNNSs. For the other CNTs/PVDF system with 8 vol. % CNTs (f{sub CNTs} > f{sub c}), it displays a 43.32% improvement from 1325 to 1899 after the addition of 3 vol. % BNNSs. The presence of BNNSs facilitates the formation of the denser conductive network. Meanwhile, the ternary BNNSs/CNTs/PVDF systems exhibit a low dielectric loss. The adjustable dielectric properties could be obtained by employing the ternary systems due to the microstructure changes of nanocomposites.« less

No double detonations but core carbon ignitions in high-resolution, grid-based simulations of binary white dwarf mergers

NASA Astrophysics Data System (ADS)

Fenn, D.; Plewa, T.; Gawryszczak, A.

2016-11-01

We study the violent phase of the merger of massive binary white dwarf systems. Our aim is to characterize the conditions for explosive burning to occur, and identify a possible explosion mechanism of Type Ia supernovae. The primary components of our model systems are carbon-oxygen (C/O) white dwarfs, while the secondaries are made either of C/O or of pure helium. We account for tidal effects in the initial conditions in a self-consistent way, and consider initially well-separated systems with slow inspiral rates. We study the merger evolution using an adaptive mesh refinement, reactive, Eulerian code in three dimensions, assuming symmetry across the orbital plane. We use a corotating reference frame to minimize the effects of numerical diffusion, and solve for self-gravity using a multigrid approach. We find a novel detonation mechanism in C/O mergers with massive primaries. Here, the detonation occurs in the primary's core and relies on the combined action of tidal heating, accretion heating, and self-heating due to nuclear burning. The exploding structure is compositionally stratified, with a reverse shock formed at the surface of the dense ejecta. The existence of such a shock has not been reported elsewhere. The explosion energy (1.6 × 1051 erg) and 56Ni mass (0.86 M⊙) are consistent with an SN Ia at the bright end of the luminosity distribution, with an approximated decline rate of Δm15(B) ≈ 0.99. Our study does not support double-detonation scenarios in the case of a system with a 0.6 M⊙ helium secondary and a 0.9 M⊙ primary. Although the accreted helium detonates, it fails to ignite carbon at the base of the boundary layer or in the primary's core.

An alternate metabolic hypothesis for a binary mixture of trichloroethylene and carbon tetrachloride: application of physiologically based pharmacokinetic (PBPK) modeling in rats.

EPA Science Inventory

Carbon tetrachloride (CC4) and trichloroethylene (TCE) are hepatotoxic volatile organic compounds (VOCs) and environmental contaminants. Previous physiologically based pharmacokinetic (PBPK) models describe the kinetics ofindividual chemical disposition and metabolic clearance fo...

The Evolution of Massive Close Binaries: Anomalous Relationship between Nitrogen Abundances and Rotational Velocities

NASA Astrophysics Data System (ADS)

Song, Hanfeng; Wang, Jiangtao; Song, Fen; Zhang, Ruiyu; Li, Zhi; Peng, Weiguo; Zhan, Qiong; Jing, Jianghong

2018-05-01

The combined effects of rotation and mass accretion on the evolution of binary systems are investigated in this work. Rotational binaries provide us with a promising channel that could explain the abnormal phenomenon of the nitrogen abundances in Groups 1 and 2 of the Galactic Hunter diagram. Group 1 contains fast-rotating but nitrogen-unenriched stars, whereas Group 2 includes apparently slowly rotating but nitrogen-enhanced stars. The donor star suffers from heavy mass loss that progressively exposes deep layers of nitrogen and corresponding angular momentum loss that can efficiently spin the star down. Rapid-rotation stars without nitrogen enrichment may be related to mass gainers that had accreted little matter from a close companion and then been spun up to rapid rotation. Nitrogen enrichment of mass gainers can be greatly suppressed by low accreting efficiency, which is induced by critical rotation, thermohaline mixing, and the gradient of mean molecular weight. Nitrogen enrichment due to mass accretion appears to be more efficient than that due to rotational mixing, because there exist thermohaline instabilities during Roche lobe overflow. The mixing in the enlarged convective core reduces carbon and nitrogen abundances but increases oxygen abundances in mass gainers. This process significantly triggers CNO cycling but does not support CN cycling. The orbital separation can be widened because of the nonconservative mass transfer, and this process gives rise to weak tidal torques. Therefore, invoking binaries has the potential to simultaneously explain the observed stars in Groups 1 and 2 of the Galactic Hunter diagram.

Effect of operational factors on bioregeneration of binary phenol and 4-chlorophenol-loaded granular activated carbon using PVA-immobilized biomass cryogels.

PubMed

Leong, Kwok-Yii; Adnan, Rohana; Lim, Poh-Eng; Ng, Si-Ling; Seng, Chye-Eng

2017-09-01

The effects of dry biomass density in cryogel beads, shaking speed and initial concentration ratio of phenol to 4-chlorophenol (4-CP) on the bioregeneration efficiencies of binary phenol and 4-CP-loaded granular activated carbon (GAC) for phenol and 4-CP, respectively, were investigated under the simultaneous adsorption and biodegradation approach. The results revealed higher bioregeneration efficiencies of binary-loaded GAC for phenol and 4-CP at higher dry biomass density but moderate shaking speed. The optimum dry biomass density in cryogel beads and shaking speed for use in bioregeneration were found to be 0.01 g/mL and 250 rpm, respectively. With respect to the initial phenol to 4-CP concentration ratio, the bioregeneration efficiencies were lower under increasing phenol and 4-CP initial concentrations, respectively, with the effect being more conspicuous under increasing 4-CP concentration. Higher bioregeneration efficiencies were achieved with the use of immobilized rather than suspended biomasses.

Refractive index, molar refraction and comparative refractive index study of propylene carbonate binary liquid mixtures.

PubMed

Wankhede, Dnyaneshwar Shamrao

2012-06-01

Refractive indices (n) have been experimentally determined for the binary liquid-liquid mixtures of Propylene carbonate (PC) (1) with benzene, ethylbenzene, o-xylene and p-xylene (2) at 298.15, 303.15 and 308.15 K over the entire mole fraction range. The experimental values of n are utilised to calculate deviation in refractive index (Δn), molar refraction (R) and deviation in molar refraction (ΔR). A comparative study of Arago-Biot (A-B), Newton (NW), Eyring and John (E-J) equations for determining refractive index of a liquid has been carried out to test their validity for all the binary mixtures over the entire composition range at 298.15 K. Comparison of various mixing relations is represented in terms of average deviation (AVD). The Δn and ΔR values have been fitted to Redlich-Kister equation at 298.15 K and standard deviations have been calculated. The results are discussed in terms of intermolecular interactions present amongst the components.

Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

PubMed Central

Mukundan, Vineetha; Yin, Jun; Joseph, Pharrah; Luo, Jin; Shan, Shiyao; Zakharov, Dmitri N; Zhong, Chuan-Jian; Malis, Oana

2014-01-01

Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2) alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C). The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering. PMID:27877663

Competitive adsorption of a binary CO2-CH4 mixture in nanoporous carbons: effects of edge-functionalization.

PubMed

Lu, Xiaoqing; Jin, Dongliang; Wei, Shuxian; Zhang, Mingmin; Zhu, Qing; Shi, Xiaofan; Deng, Zhigang; Guo, Wenyue; Shen, Wenzhong

2015-01-21

The effect of edge-functionalization on the competitive adsorption of a binary CO2-CH4 mixture in nanoporous carbons (NPCs) has been investigated for the first time by combining density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulation. Our results show that edge-functionalization has a more positive effect on the single-component adsorption of CO2 than CH4, therefore significantly enhancing the selectivity of CO2 over CH4, in the order of NH2-NPC > COOH-NPC > OH-NPC > H-NPC > NPC at low pressure. The enhanced adsorption originates essentially from the effects of (1) the conducive environment with a large pore size and an effective accessible surface area, (2) the high electronegativity/electropositivity, (3) the strong adsorption energy, and (4) the large electrostatic contribution, due to the inductive effect/direct interaction of the embedded edge-functionalized groups. The larger difference from these effects results in the higher competitive adsorption advantage of CO2 in the binary CO2-CH4 mixture. Temperature has a negative effect on the gas adsorption, but no obvious influence on the electrostatic contribution on selectivity. With the increase of pressure, the selectivity of CO2 over CH4 first decreases sharply and subsequently flattens out to a constant value. This work highlights the potential of edge-functionalized NPCs in competitive adsorption, capture, and separation for the binary CO2-CH4 mixture, and provides an effective and superior alternative strategy in the design and screening of adsorbent materials for carbon capture and storage.

The binary progenitors of short and long GRBs and their gravitational-wave emission

NASA Astrophysics Data System (ADS)

Rueda, J. A.; Ruffini, R.; Rodriguez, J. F.; Muccino, M.; Aimuratov, Y.; Barres de Almeida, U.; Becerra, L.; Bianco, C. L.; Cherubini, C.; Filippi, S.; Kovacevic, M.; Moradi, R.; Pisani, G. B.; Wang, Y.

2018-01-01

We have sub-classified short and long-duration gamma-ray bursts (GRBs) into seven families according to the binary nature of their progenitors. Short GRBs are produced in mergers of neutron-star binaries (NS-NS) or neutron star-black hole binaries (NS-BH). Long GRBs are produced via the induced gravitational collapse (IGC) scenario occurring in a tight binary system composed of a carbon-oxygen core (COcore) and a NS companion. The COcore explodes as type Ic supernova (SN) leading to a hypercritical accretion process onto the NS: if the accretion is sufficiently high the NS reaches the critical mass and collapses forming a BH, otherwise a massive NS is formed. Therefore long GRBs can lead either to NS-BH or to NS-NS binaries depending on the entity of the accretion. We discuss for the above compact-object binaries: 1) the role of the NS structure and the nuclear equation of state; 2) the occurrence rates obtained from X and gamma-rays observations; 3) the predicted annual number of detections by the Advanced LIGO interferometer of their gravitational-wave emission.

Multiclass Reduced-Set Support Vector Machines

NASA Technical Reports Server (NTRS)

Tang, Benyang; Mazzoni, Dominic

2006-01-01

There are well-established methods for reducing the number of support vectors in a trained binary support vector machine, often with minimal impact on accuracy. We show how reduced-set methods can be applied to multiclass SVMs made up of several binary SVMs, with significantly better results than reducing each binary SVM independently. Our approach is based on Burges' approach that constructs each reduced-set vector as the pre-image of a vector in kernel space, but we extend this by recomputing the SVM weights and bias optimally using the original SVM objective function. This leads to greater accuracy for a binary reduced-set SVM, and also allows vectors to be 'shared' between multiple binary SVMs for greater multiclass accuracy with fewer reduced-set vectors. We also propose computing pre-images using differential evolution, which we have found to be more robust than gradient descent alone. We show experimental results on a variety of problems and find that this new approach is consistently better than previous multiclass reduced-set methods, sometimes with a dramatic difference.

The population of single and binary white dwarfs of the Galactic bulge

NASA Astrophysics Data System (ADS)

Torres, S.; García-Berro, E.; Cojocaru, R.; Calamida, A.

2018-05-01

Recent Hubble Space Telescope observations have unveiled the white dwarf cooling sequence of the Galactic bulge. Although the degenerate sequence can be well fitted employing the most up-to-date theoretical cooling sequences, observations show a systematic excess of red objects that cannot be explained by the theoretical models of single carbon-oxygen white dwarfs of the appropriate masses. Here, we present a population synthesis study of the white dwarf cooling sequence of the Galactic bulge that takes into account the populations of both single white dwarfs and binary systems containing at least one white dwarf. These calculations incorporate state-of-the-art cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, for both white dwarfs with carbon-oxygen and helium cores, and also take into account detailed prescriptions of the evolutionary history of binary systems. Our Monte Carlo simulator also incorporates all the known observational biases. This allows us to model with a high degree of realism the white dwarf population of the Galactic bulge. We find that the observed excess of red stars can be partially attributed to white dwarf plus main sequence binaries, and to cataclysmic variables or dwarf novae. Our best fit is obtained with a higher binary fraction and an initial mass function slope steeper than standard values, as well as with the inclusion of differential reddening and blending. Our results also show that the possible contribution of double degenerate systems or young and thick-discbulge stars is negligible.

High-activity PtRuPd/C catalyst for direct dimethyl ether fuel cells.

PubMed

Li, Qing; Wen, Xiaodong; Wu, Gang; Chung, Hoon T; Gao, Rui; Zelenay, Piotr

2015-06-22

Dimethyl ether (DME) has been considered as a promising alternative fuel for direct-feed fuel cells but lack of an efficient DME oxidation electrocatalyst has remained the challenge for the commercialization of the direct DME fuel cell. The commonly studied binary PtRu catalyst shows much lower activity in DME than methanol oxidation. In this work, guided by density functional theory (DFT) calculation, a ternary carbon-supported PtRuPd catalyst was designed and synthesized for DME electrooxidation. DFT calculations indicated that Pd in the ternary PtRuPd catalyst is capable of significantly decreasing the activation energy of the CO and CH bond scission during the oxidation process. As evidenced by both electrochemical measurements in an aqueous electrolyte and polymer-electrolyte fuel cell testing, the ternary catalyst shows much higher activity (two-fold enhancement at 0.5 V in fuel cells) than the state-of-the-art binary Pt50 Ru50 /C catalyst (HiSPEC 12100). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organometallic Routes into the Nanorealms of Binary Fe-Si Phases

PubMed Central

Kolel-Veetil, Manoj K.; Keller, Teddy M.

2010-01-01

The Fe-Si binary system provides several iron silicides that have varied and exceptional material properties with applications in the electronic industry. The well known Fe-Si binary silicides are Fe3Si, Fe5Si3, FeSi, α-FeSi2 and β-FeSi2. While the iron-rich silicides Fe3Si and Fe5Si3 are known to be room temperature ferromagnets, the stoichiometric FeSi is the only known transition metal Kondo insulator. Furthermore, Fe5Si3 has also been demonstrated to exhibit giant magnetoresistance (GMR). The silicon-rich β-FeSi2 is a direct band gap material usable in light emitting diode (LED) applications. Typically, these silicides are synthesized by traditional solid-state reactions or by ion beam-induced mixing (IBM) of alternating metal and silicon layers. Alternatively, the utilization of organometallic compounds with reactive transition metal (Fe)-carbon bonds has opened various routes for the preparation of these silicides and the silicon-stabilized bcc- and fcc-Fe phases contained in the Fe-Si binary phase diagram. The unique interfacial interactions of carbon with the Fe and Si components have resulted in the preferential formation of nanoscale versions of these materials. This review will discuss such reactions.

Co-adsorption of Trichloroethylene and Arsenate by Iron-Impregnated Granular Activated Carbon.

PubMed

Deng, Baolin; Kim, Eun-Sik

2016-05-01

Co-adsorption of trichloroethylene (TCE) and arsenate [As(V)] was investigated using modified granular activated carbons (GAC): untreated, sodium hypochlorite-treated (NaClO-GAC), and NaClO with iron-treated GAC (NaClO/Fe-GAC). Batch experiments of single- [TCE or As(V)] and binary- [TCE and As(V)] components solutions are evaluated through Langmuir and Freundlich isotherm models and adsorption kinetic tests. In the single-component system, the adsorption capacity of As(V) was increased by the NaClO-GAC and the NaClO/Fe-GAC. The untreated GAC showed a low adsorption capacity for As(V). Adsorption of TCE by the NaClO/Fe-GAC was maximized, with an increased Freundlich constant. Removal of TCE in the binary-component system was decreased 15% by the untreated GAC, and NaClO- and NaClO/Fe-GAC showed similar efficiency to the single-component system because of the different chemical status of the GAC surfaces. Results of the adsorption isotherms of As(V) in the binary-component system were similar to adsorption isotherms of the single-component system. The adsorption affinities of single- and binary-component systems corresponded with electron transfer, competitive adsorption, and physicochemical properties.

Competitive adsorption of ibuprofen and amoxicillin mixtures from aqueous solution on activated carbons.

PubMed

Mansouri, Hayet; Carmona, Rocio J; Gomis-Berenguer, Alicia; Souissi-Najar, Souad; Ouederni, Abdelmottaleb; Ania, Conchi O

2015-07-01

This work investigates the competitive adsorption under dynamic and equilibrium conditions of ibuprofen (IBU) and amoxicillin (AMX), two widely consumed pharmaceuticals, on nanoporous carbons of different characteristics. Batch adsorption experiments of pure components in water and their binary mixtures were carried out to measure both adsorption equilibrium and kinetics, and dynamic tests were performed to validate the simultaneous removal of the mixtures in breakthrough experiments. The equilibrium adsorption capacities evaluated from pure component solutions were higher than those measured in dynamic conditions, and were found to depend on the porous features of the adsorbent and the nature of the specific/dispersive interactions that are controlled by the solution pH, density of surface change on the carbon and ionization of the pollutant. A marked roll-up effect was observed for AMX retention on the hydrophobic carbons, not seen for the functionalized adsorbent likely due to the lower affinity of amoxicillin towards the carbon adsorbent. Dynamic adsorption of binary mixtures from wastewater of high salinity and alkalinity showed a slight increase in IBU uptake and a reduced adsorption of AMX, demonstrating the feasibility of the simultaneous removal of both compounds from complex water matrices. Copyright © 2014 Elsevier Inc. All rights reserved.

Algorithm XXX : functions to support the IEEE standard for binary floating-point arithmetic.

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

Cody, W. J.; Mathematics and Computer Science

1993-12-01

This paper describes C programs for the support functions copysign(x,y), logb(x), scalb(x,n), nextafter(x,y), finite(x), and isnan(x) recommended in the Appendix to the IEEE Standard for Binary Floating-Point Arithmetic. In the case of logb, the modified definition given in the later IEEE Standard for Radix-Independent Floating-Point Arithmetic is followed. These programs should run without modification on most systems conforming to the binary standard.

IC 4663: The First Unambiguous [WN] Wolf-Rayet Central Star of a Planetary Nebula

NASA Astrophysics Data System (ADS)

Miszalski, B.; Crowther, P. A.; De Marco, O.; Köppen, J.; Moffat, A. F. J.; Acker, A.; Hillwig, T. C.

2013-01-01

Several [WC]-type central stars of planetary nebulae (PNe) are known to mimic the spectroscopic appearance of massive carbon-rich or WC-type Wolf-Rayet stars. In stark contrast, no [WN]-type central stars have yet been identified as clear-cut analogues of the common nitrogen-rich or WN-type Wolf-Rayet stars. We have identified the [WN3] central star of IC 4663 to be the first unambiguous example in PNe. The low luminosity nucleus and an asymptotic giant branch (AGB) halo surrounding the main nebula prove the bona-fide PN nature of IC 4663. Model atmosphere analysis reveals the [WN3] star to have an exotic chemical composition of helium (95%), hydrogen (<2%), nitrogen (0.8%), neon (0.2%) and oxygen (0.05%) by mass. Such an extreme helium-dominated composition cannot be predicted by current evolutionary scenarios for hydrogen deficient [WC]-type central stars. Only with the discovery of IC 4663 and its unusual composition can we now connect [WN] central stars to the O(He) central stars in a second H-deficient and He-rich evolutionary sequence, [WN]→O(He), that exists in parallel to the carbon-rich [WC]→PG1159 sequence. This suggests a simpler mechanism, perhaps a binary merger, can better explain H-deficiency in PNe and potentially other H-deficient/He-rich stars. In this respect IC 4663 is the best supported case for a possible merged binary central star of a PN.

Asymmetric supercapacitor based on flexible TiC/CNF felt supported interwoven nickel-cobalt binary hydroxide nanosheets

NASA Astrophysics Data System (ADS)

Zhou, Gangyong; Xiong, Tianrou; He, Shuijian; Li, Yonghong; Zhu, Yongmei; Hou, Haoqing

2016-06-01

Nanostructured nickel-cobalt binary hydroxide (NiCosbnd BH) is widely investigated as supercapacitor electrode material. However, the aggregation and poor electrical conductivity of NiCosbnd BH limit its practical application as a supercapacitor. In this work, a flexible free-standing hierarchical porous composite composed of NiCosbnd BH nanosheets and titanium carbide-carbon nanofiber (NiCosbnd BH@TiC/CNF) is fabricated through electrospinning and microwave assisted method. The as-prepared composites exhibit desirable electrochemical performances, including high specific capacitance, cycling stability, and rate capability. In particular, the NiCosbnd BH41@TiC/CNF composite electrode exhibits a maximum specific capacitance of 2224 F g-1 at the current density of 0.5 A g-1 and excellent cyclic stability of 91% capacity retention after 3000 cycles at 5.0 A g-1. To expand its practical application, an asymmetric supercapacitor (ASC) is fabricated using the NiCosbnd BH41@TiC/CNF composite as the positive electrode and active carbon as the negative electrode. The ASC exhibits a prominent energy density of 55.93 Wh kg-1 and a high power density of 18,300 W kg-1 at 5.0 A g-1. The superior electrochemical property is attributed to the uniform dispersion of NiCosbnd BH nanosheets on the TiC/CNF felt matrix. The TiC/CNF felt with uniformed TiC nanoparticles makes the fiber surface more suitable for growing NiCosbnd BH nanosheets and simultaneously enhances the conductivity of electrode.

HIGH-RESOLUTION CO OBSERVATION OF THE CARBON STAR CIT 6 REVEALING THE SPIRAL STRUCTURE AND A NASCENT BIPOLAR OUTFLOW

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

Kim, Hyosun; Liu, Sheng-Yuan; Hirano, Naomi

2015-11-20

CIT 6 is a carbon star in the transitional phase from the asymptotic giant branch (AGB) to the protoplanetary nebulae (pPNs). Observational evidences of two point sources in the optical, circumstellar arc segments in an HC{sub 3}N line emission, and a bipolar nebula in near-infrared provide strong support for the presence of a binary companion. Hence, CIT 6 is very attractive for studying the role of companions in the AGB–pPN transition. We have carried out high-resolution {sup 12}CO J = 2–1 and {sup 13}CO J = 2–1 observations of CIT 6 with the Submillimeter Array combined with the Submillimeter Telescopemore » (single-dish) data. The {sup 12}CO channel maps reveal a spiral-shell pattern connecting the HC{sub 3}N segments in a continuous form and an asymmetric outflow corresponding to the near-infrared bipolar nebula. Rotation of the {sup 12}CO channel peak position may be related to the inner spiral winding and/or the bipolar outflow. An eccentric orbit binary is suggested for the presence of an anisotropic mass loss to the west and a double spiral pattern. The lack of interarm emission to the west may indicate a feature corresponding to the periastron passage of a highly eccentric orbit of the binary. Spatially averaged radial and spectral profiles of {sup 12}CO J = 2–1 and {sup 13}CO J = 2–1 are compared with simple spherical radiative transfer models, suggesting a change of {sup 12}CO/{sup 13}CO abundance ratio from ∼30 to ∼50 inward in the CSE of CIT 6. The millimeter continuum emission is decomposed into extended dust thermal emission (spectral index ∼ −2.4) and compact emission from radio photosphere (spectral index ∼ −2.0)« less

Synergistic increase of oxygen reduction favourable Fe-N coordination structures in a ternary hybrid of carbon nanospheres/carbon nanotubes/graphene sheets.

PubMed

Zhang, Shiming; Liu, Bin; Chen, Shengli

2013-11-14

A Fe/N co-doped ternary nanocarbon hybrid, with uniform bamboo-like carbon nanotubes (CNTs) in situ grown on/between the single/few-layer graphene sheets interspaced by carbon nanosphere aggregates, was prepared through a one-pot heat treatment of a precursor mixture containing graphene oxide, Vulcan XC-72 carbon nanospheres, nitrogen rich melamine and small amounts of Fe ions. Physical characterization including electron microscopic images, N2 adsorption-desorption isotherms, pore size distribution, XPS, XRD, Mössbauer spectra, and EDX revealed that the 0-D/1-D/2-D ternary hybrid architecture not only offered an optimized morphology for high dispersion of each nanocarbon moiety, while the carbon nanosphere interspaced graphene sheets have provided a platform for efficient reaction between Fe ions and melamine molecules, resulting in uniform nucleation and growth of CNTs and formation of high density Fe-N coordination assemblies that have been believed to be the active centers for the oxygen reduction reaction (ORR) in carbon-based nonprecious metal electrocatalysts. In the absence of graphene oxides or carbon nanospheres, a similar heat treatment was found to result in large amounts of elemental Fe and Fe carbides and entangled CNTs with wide diameter distributions. As a result, the ternary Fe/N-doped nanocarbon hybrid exhibits ORR activity much higher than the Fe-N doped single or binary nanocarbon materials prepared under similar heat treatment conditions, and approaching that of the state-of-the-art carbon-supported platinum catalyst (Pt/C) in acidic media, as well as superior stability and methanol tolerance to Pt/C.

Experimental Evaluation of a Carbon Slurry Droplet Combustion Model

DTIC Science & Technology

1981-12-14

the increased mass and energy transport due to the flow percolating through the open porous structure of the carbon agglomerate. Two separate models...catalysts. Transport-rate enhancement factors were also employed in the carbon-agglomerate reaction analysis to account for the increased mass and energy ...D Effective binary diffusivity Ei Activation energy h Heat transfer coefficient H2 Diatomic hydrogen H20 Water i Enthalpy if Enthalpy of formation

Rapid synthesis of platinum-ruthenium bimetallic nanoparticles dispersed on carbon support as improved electrocatalysts for ethanol oxidation.

PubMed

Gu, Zhulan; Li, Shumin; Xiong, Zhiping; Xu, Hui; Gao, Fei; Du, Yukou

2018-07-01

Bimetallic nanocatalysts with small particle size benefit from markedly enhanced electrocatalytic activity and stability during small molecule oxidation. Herein, we report a facile method to synthesize binary Pt-Ru nanoparticles dispersed on a carbon support at an optimum temperature. Because of its monodispersed nanostructure, synergistic effects were observed between Pt and Ru and the PtRu/C electrocatalysts showed remarkably enhanced electrocatalytic activity towards ethanol oxidation. The peak current density of the Pt 1 Ru 1 /C electrocatalyst is 3731 mA mg -1 , which is 9.3 times higher than that of commercial Pt/C (401 mA mg -1 ). Furthermore, the synthesized Pt 1 Ru 1 /C catalyst exhibited higher stability during ethanol oxidation in an alkaline medium and maintained a significantly higher current density after successive cyclic voltammograms (CVs) of 500 cycles than commercial Pt/C. Our work highlights the significance of the reaction temperature during electrocatalyst synthesis, leading to enhanced catalytic performance towards ethanol oxidation. The Pt 1 Ru 1 /C electrocatalyst has great potential for application in direct ethanol fuel cells. Copyright © 2018 Elsevier Inc. All rights reserved.

THE HOT R CORONAE BOREALIS STAR DY CENTAURI IS A BINARY

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

Kameswara Rao, N.; Lambert, David L.; McArthur, Barbara

2012-11-20

The remarkable hot R Coronae Borealis (RCB) star DY Cen is revealed to be the first and only binary system to be found among the RCB stars and their likely relatives, including the extreme helium stars and the hydrogen-deficient carbon stars. Radial velocity determinations from 1982 to 2010 have shown that DY Cen is a single-lined spectroscopic binary in an eccentric orbit with a period of 39.67 days. It is also one of the hottest and most H-rich member of the class of RCB stars. The system may have evolved from a common envelope to its current form.

Self-supported Zn3P2 nanowire arrays grafted on carbon fabrics as an advanced integrated anode for flexible lithium ion batteries

NASA Astrophysics Data System (ADS)

Li, Wenwu; Gan, Lin; Guo, Kai; Ke, Linbo; Wei, Yaqing; Li, Huiqiao; Shen, Guozhen; Zhai, Tianyou

2016-04-01

We, for the first time, successfully grafted well-aligned binary lithium-reactive zinc phosphide (Zn3P2) nanowire arrays on carbon fabric cloth by a facile CVD method. When applied as a novel self-supported binder-free anode for lithium ion batteries (LIBs), the hierarchical three-dimensional (3D) integrated anode shows excellent electrochemical performances: a highly reversible initial lithium storage capacity of ca. 1200 mA h g-1 with a coulombic efficiency of up to 88%, a long lifespan of over 200 cycles without obvious decay, and a high rate capability of ca. 400 mA h g-1 capacity retention at an ultrahigh rate of 15 A g-1. More interestingly, a flexible LIB full cell is assembled based on the as-synthesized integrated anode and the commercial LiFePO4 cathode, and shows striking lithium storage performances very close to the half cells: a large reversible capacity over 1000 mA h g-1, a long cycle life of over 200 cycles without obvious decay, and an ultrahigh rate performance of ca. 300 mA h g-1 even at 20 A g-1. Considering the excellent lithium storage performances of coin-type half cells as well as flexible full cells, the as-prepared carbon cloth grafted well-aligned Zn3P2 nanowire arrays would be a promising integrated anode for flexible LIB full cell devices.We, for the first time, successfully grafted well-aligned binary lithium-reactive zinc phosphide (Zn3P2) nanowire arrays on carbon fabric cloth by a facile CVD method. When applied as a novel self-supported binder-free anode for lithium ion batteries (LIBs), the hierarchical three-dimensional (3D) integrated anode shows excellent electrochemical performances: a highly reversible initial lithium storage capacity of ca. 1200 mA h g-1 with a coulombic efficiency of up to 88%, a long lifespan of over 200 cycles without obvious decay, and a high rate capability of ca. 400 mA h g-1 capacity retention at an ultrahigh rate of 15 A g-1. More interestingly, a flexible LIB full cell is assembled based on the as-synthesized integrated anode and the commercial LiFePO4 cathode, and shows striking lithium storage performances very close to the half cells: a large reversible capacity over 1000 mA h g-1, a long cycle life of over 200 cycles without obvious decay, and an ultrahigh rate performance of ca. 300 mA h g-1 even at 20 A g-1. Considering the excellent lithium storage performances of coin-type half cells as well as flexible full cells, the as-prepared carbon cloth grafted well-aligned Zn3P2 nanowire arrays would be a promising integrated anode for flexible LIB full cell devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08467a

Influence of carbon on the formation of the surface layer in the process of electroerosion alloying of steel with tungsten

NASA Astrophysics Data System (ADS)

Vasil'eva, E. V.; Bochkov, V. E.; Mikheev, É. A.; Lyakishev, V. A.; Afanas'eva, T. N.

1983-10-01

With an increase in carbon content in the steel being treated, the thickness of the alloyed layer increases and its microhardness also increases. The carbon exerts a deoxidizing action on the layer being formed and promotes a reduction in the threshold of deerosion and also additional strengthening of the layer as the result of the formation of binary η-carbides.

Molecular Dynamics Simulation Study of the Capacitive Performance of a Binary Mixture of Ionic Liquids near an Onion-like Carbon Electrode.

PubMed

Li, Song; Feng, Guang; Fulvio, Pasquale F; Hillesheim, Patrick C; Liao, Chen; Dai, Sheng; Cummings, Peter T

2012-09-06

An equimolar mixture of 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C3mpy][Tf2N]), 1-methyl-1-butylpiperidinium bis(trifluoromethylsulfonyl)imide ([C4mpip][Tf2N]) was investigated by classic molecular dynamics (MD) simulation. Differential scanning calorimetry (DSC) measurements verified that the binary mixture exhibited lower glass transition temperature than either of the pure room-temperature ionic liquids (RTILs). Moreover, the binary mixture gave rise to higher conductivity than the neat RTILs at lower temperature range. In order to study its capacitive performance in supercapacitors, simulations were performed of the mixture, and the neat RTILs used as electrolytes near an onion-like carbon (OLC) electrode at varying temperatures. The differential capacitance exhibited independence of the electrical potential applied for three electrolytes, which is in agreement with previous work on OLC electrodes in a different RTILs. Positive temperature dependence of the differential capacitance was observed, and it was dominated by the electrical double layer (EDL) thickness, which is for the first time substantiated in MD simulation.

Adsorption and separation of binary and ternary mixtures of SO2, CO2 and N2 by ordered carbon nanotube arrays: grand-canonical Monte Carlo simulations.

PubMed

Rahimi, Mahshid; Singh, Jayant K; Müller-Plathe, Florian

2016-02-07

The adsorption and separation behavior of SO2-CO2, SO2-N2 and CO2-N2 binary mixtures in bundles of aligned double-walled carbon nanotubes is investigated using the grand-canonical Monte Carlo (GCMC) method and ideal adsorbed solution theory. Simulations were performed at 303 K with nanotubes of 3 nm inner diameter and various intertube distances. The results showed that the packing with an intertube distance d = 0 has the highest selectivity for SO2-N2 and CO2-N2 binary mixtures. For the SO2-CO2 case, the optimum intertube distance for having the maximum selectivity depends on the applied pressure, so that at p < 0.8 bar d = 0 shows the highest selectivity and at 0.8 bar < p < 2.5 bar, the highest selectivity belongs to d = 0.5 nm. Ideal adsorbed solution theory cannot predict the adsorption of the binary systems containing SO2, especially when d = 0. As the intertube distance is increased, the ideal adsorbed solution theory based predictions become closer to those of GCMC simulations. Only in the case of CO2-N2, ideal adsorbed solution theory is everywhere in good agreement with simulations. In a ternary mixture of all three gases, the behavior of SO2 and CO2 remains similar to that in a SO2-CO2 binary mixture because of the weak interaction between N2 molecules and CNTs.

Equilibrium isotherm and kinetic studies for the simultaneous removal of phenol and cyanide by use of S. odorifera (MTCC 5700) immobilized on coconut shell activated carbon

NASA Astrophysics Data System (ADS)

Singh, Neetu; Balomajumder, Chandrajit

2017-10-01

In this study, simultaneous removal of phenol and cyanide by a microorganism S. odorifera (MTCC 5700) immobilized onto coconut shell activated carbon surface (CSAC) was studied in batch reactor from mono and binary component aqueous solution. Activated carbon was derived from coconut shell by chemical activation method. Ferric chloride (Fecl3), used as surface modification agents was applied to biomass. Optimum biosorption conditions were obtained as a function of biosorbent dosage, pH, temperature, contact time and initial phenol and cyanide concentration. To define the equilibrium isotherms, experimental data were analyzed by five mono component isotherm and six binary component isotherm models. The higher uptake capacity of phenol and cyanide onto CSAC biosorbent surface was 450.02 and 2.58 mg/g, respectively. Nonlinear regression analysis was used for determining the best fit model on the basis of error functions and also for calculating the parameters involved in kinetic and isotherm models. The kinetic study results revealed that Fractal-like mixed first second order model and Brouser-Weron-Sototlongo models for phenol and cyanide were capable to offer accurate explanation of biosorption kinetic. According to the experimental data results, CSAC with immobilization of bacterium S. odorifera (MTCC 5700) seems to be an alternative and effective biosorbent for the elimination of phenol and cyanide from binary component aqueous solution.

Molten salt CO2 capture and electro-transformation (MSCC-ET) into capacitive carbon at medium temperature: effect of the electrolyte composition.

PubMed

Deng, Bowen; Chen, Zhigang; Gao, Muxing; Song, Yuqiao; Zheng, Kaiyuan; Tang, Juanjuan; Xiao, Wei; Mao, Xuhui; Wang, Dihua

2016-08-15

Electrochemical transformation of CO2 into functional materials or fuels (i.e., carbon, CO) in high temperature molten salts has been demonstrated as a promising way of carbon capture, utilisation and storage (CCUS) in recent years. In a view of continuous operation, the electrolysis process should match very well with the CO2 absorption kinetics. At the same time, in consideration of the energy efficiency, a molten salt electrochemical cell running at lower temperature is more beneficial to a process powered by the fluctuating renewable electricity from solar/wind farms. Ternary carbonates (Li : Na : K = 43.5 : 31.5 : 25.0) and binary chlorides (Li : K = 58.5 : 41.5), two typical kinds of eutectic melt with low melting points and a wide electrochemical potential window, could be the ideal supporting electrolyte for the molten salt CO2 capture and electro-transformation (MSCC-ET) process. In this work, the CO2 absorption behaviour in Li2O/CaO containing carbonates and chlorides were investigated on a home-made gas absorption testing system. The electrode processes as well as the morphology and properties of carbon obtained in different salts are compared to each other. It was found that the composition of molten salts significantly affects the absorption of CO2, electrode processes and performance of the product. Furthermore, the relationship between the absorption and electro-transformation kinetics are discussed based on the findings.

Role of precursor crystal structure on electrochemical performance of carbide-derived carbon electrodes

NASA Astrophysics Data System (ADS)

Palazzo, Benjamin; Norris, Zach; Taylor, Greg; Yu, Lei; Lofland, Samuel; Hettinger, Jeffrey

2015-03-01

Binary carbides with hexagonal and cubic crystal structures have been synthesized by reactive magnetron sputtering of vanadium and other transition metals in acetylene or methane gas mixed with argon. The binary carbides are converted to carbide-derived carbon (CDC) films using chlorine gas in a post-deposition process in an external vacuum reaction furnace. Residual chlorine has been removed using an annealing step in a hydrogen atmosphere. The CDC materials have been characterized by x-ray diffraction, x-ray fluorescence, and scanning electron microscopy. The performance of the CDC materials in electrochemical device applications has been measured with the hexagonal phase precursor demonstrating a significantly higher specific capacitance in comparison to that of the cubic phase. We report these results and pore-size distributions of these and similar materials.

Ternary phase equilibria in transition metal-boron-carbon-silicon systems. Part I. Related binary systems, Volume III. Systems Mo-B and W-B. Technical documentary report, 1 November 1964-1 June 1965

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

Rudy, E.; Windisch.

1965-07-01

On the basis of X-ray, melting point, metallographic, and differential thermoanalytical studies on molybdenum-boron and tungsten-boron alloys, constitution diagrams for both binary systems are presented. In the high temperature regions, the newly established phase diagrams differ significantly from previously reported systems. The results are discussed and compared with available literature data.

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

2016-09-27

Binary catalyst systems comprising a cationic Ru-CNC pincer complex and an alkali metal salt were developed for selective hydroboration of CO 2 utilizing pinacolborane at r.t. and 1 atm CO 2 , with the combination of [Ru(CNC Bn )(CO) 2 (H)][PF 6 ] and KOCO 2 t Bu producing formoxyborane in 76% yield. A bicyclic catalytic mechanism was proposed and discussed.

Formation Constraints Indicate a Black Hole Accretor in 47 Tuc X9

NASA Astrophysics Data System (ADS)

Church, Ross P.; Strader, Jay; Davies, Melvyn B.; Bobrick, Alexey

2017-12-01

The luminous X-ray binary 47 Tuc X9 shows radio and X-ray emission consistent with a stellar-mass black hole (BH) accreting from a carbon-oxygen white dwarf. Its location, in the core of the massive globular cluster 47 Tuc, hints at a dynamical origin. We assess the stability of mass transfer from a carbon-oxygen white dwarf onto compact objects of various masses, and conclude that for mass transfer to proceed stably, the accretor must, in fact, be a BH. Such systems can form dynamically by the collision of a stellar-mass BH with a giant star. Tidal dissipation of energy in the giant’s envelope leads to a bound binary with a pericenter separation less than the radius of the giant. An episode of common-envelope evolution follows, which ejects the giant’s envelope. We find that the most likely target is a horizontal-branch star, and that a realistic quantity of subsequent dynamical hardening is required for the resulting binary to merge via gravitational wave emission. Observing one binary like 47 Tuc X9 in the Milky Way globular cluster system is consistent with the expected formation rate. The observed 6.8-day periodicity in the X-ray emission may be driven by eccentricity induced in the ultra-compact X-ray binary’s orbit by a perturbing companion.

The durability of concrete containing a high-level of fly ash or a ternary blend of supplementary cementing materials

NASA Astrophysics Data System (ADS)

Gilbert, Christine M.

The research for this study was conducted in two distinct phases as follows: Phase 1: The objective was to determine the effect of fly ash on the carbonation of concrete. The specimens made for this phase of the study were larger in size than those normally used in carbonation studies and were are meant to more accurately reflect real field conditions. The results from early age carbonation testing indicate that the larger size specimens do not have a measured depth of carbonation as great as that of the smaller specimens typically used in carbonation studies at the same age and under the same conditions. Phase 2: The objective was to evaluate the performance of ternary concrete mixes containing a ternary cement blend consisting of Portland cement, slag and Type C fly ash. It was found that concrete mixtures containing the fly ash with the lower calcium (CaO) content (in binary or ternary blends) provided superior durability performance and resistance to ASR compared to that of the fly ash with the higher CaO content. Ternary blends (regardless of the CaO content of the fly ash) provided better overall durability performance than binary blends of cementing materials or the control.

Excess Volumes and Excess Isentropic Compressibilities of Binary Liquid Mixtures of Trichloroethylene with Esters at 303.15 K

NASA Astrophysics Data System (ADS)

Ramanaiah, S.; Rao, C. Narasimha; Nagaraja, P.; Venkateswarlu, P.

2015-11-01

Exces volumes, VE, and excess isentropic compressibilities, κSE, have been reported as a function of composition for binary liquid mixtures of trichloroethylene with ethyl acetate, n-propyl acetate, and n-butyl acetate at 303.15 K. Isentropic compressibilities are calculated using measured sound speeds and density data for pure components and for binary mixtures. Excess volumes and excess isentropic compressibilities are found to be negative for the three systems studied over the entire composition range at 303.15 K, whereas these values become more negative with an increase of carbon chain length. The results are discussed in terms of intermolecular interactions between unlike molecules.

Understanding the Phase Behavior of Tetrahydrofuran + Carbon Dioxide, + Methane, and + Water Binary Mixtures from the SAFT-VR Approach.

PubMed

Míguez, J M; Piñeiro, M M; Algaba, J; Mendiboure, B; Torré, J P; Blas, F J

2015-11-05

The high-pressure phase diagrams of the tetrahydrofuran(1) + carbon dioxide(2), + methane(2), and + water(2) mixtures are examined using the SAFT-VR approach. Carbon dioxide molecule is modeled as two spherical segments tangentially bonded, water is modeled as a spherical segment with four associating sites to represent the hydrogen bonding, methane is represented as an isolated sphere, and tetrahydrofuran is represented as a chain of m tangentially bonded spherical segments. Dispersive interactions are modeled using the square-well intermolecular potential. In addition, two different molecular model mixtures are developed to take into account the subtle balance between water-tetrahydrofuran hydrogen-bonding interactions. The polar and quadrupolar interactions present in water, tetrahydrofuran, and carbon dioxide are treated in an effective way via square-well potentials of variable range. The optimized intermolecular parameters are taken from the works of Giner et al. (Fluid Phase Equil. 2007, 255, 200), Galindo and Blas (J. Phys. Chem. B 2002, 106, 4503), Patel et al. (Ind. Eng. Chem. Res. 2003, 42, 3809), and Clark et al. (Mol. Phys. 2006, 104, 3561) for tetrahydrofuran, carbon dioxide, methane, and water, respectively. The phase diagrams of the binary mixtures exhibit different types of phase behavior according to the classification of van Konynenburg and Scott, ranging from types I, III, and VI phase behavior for the tetrahydrofuran(1) + carbon dioxide(2), + methane(2), and + water(2) binary mixtures, respectively. This last type is characterized by the presence of a Bancroft point, positive azeotropy, and the so-called closed-loop curves that represent regions of liquid-liquid immiscibility in the phase diagram. The system exhibits lower critical solution temperatures (LCSTs), which denote the lower limit of immiscibility together with upper critical solution temperatures (UCSTs). This behavior is explained in terms of competition between the incompatibility with the alkyl parts of the tetrahydrofuran ring chain and the hydrogen bonding between water and the ether group. A minimum number of unlike interaction parameters are fitted to give the optimal representation of the most representative features of the binary phase diagrams. In the particular case of tetrahydrofuran(1) + water(2), two sets of intermolecular potential model parameters are proposed to describe accurately either the hypercritical point associated with the closed-loop liquid-liquid immiscibility region or the location of the mixture lower- and upper-critical end-points. The theory is not only able to predict the type of phase behavior of each mixture, but also provides a reasonably good description of the global phase behavior whenever experimental data are available.

Accreting white dwarf models for type 1 supernovae. 1: Presupernova evolution and triggering mechanisms

NASA Technical Reports Server (NTRS)

Nomoto, K.

1981-01-01

As a plausible explosion model for a Type I supernova, the evolution of carbon-oxygen white dwarfs accreting helium in binary systems was investigated from the onset of accretion up to the point at which a thermonuclear explosion occurs. The relationship between the conditions in the binary system and the triggering mechanism for the supernova explosion is discussed, especially for the cases with relatively slow accretion rate. It is found that the growth of a helium zone on the carbon-oxygen core leads to a supernova explosion which is triggered either by the off-center helium detonation for slow and intermediate accretion rates or by the carbon deflagration for slow and rapid accretion rates. Both helium detonation and carbon deflagration are possible for the case of slow accretion, since in this case the initial mass of the white dwarf is an important parameter for determining the mode of ignition. Finally, various modes of building up the helium zone on the white dwarf, namely, direct transfer of helium from the companion star and the various types and strength of the hydrogen shell flashes are discussed in some detail.

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.

The ‘ideal selectivity’ vs ‘true selectivity’ for permeation of gas mixture in nanoporous membranes

NASA Astrophysics Data System (ADS)

He, Zhou; Wang, Kean

2018-03-01

In this study, we proposed and validated a novel and non-destructive experimental technology for measuring the permeation of binary gas mixture in nanoporous membranes. The traditional time lag rig was modified to examine the permeation characteristics of each gas component as well as that of the binary gas mixtures. The difference in boiling points of each species were explored. Binary gas mixtures of CO2/He were permeated through the nanoporous carbon molecular sieve membrane (CMSM). The results showed that, due to the strong interaction among different molecules and with the porous network of the membrane, the measured perm-selectivity or ‘true selectivity’ of a binary mixture can significantly deviate from the ‘ideal selectivity’ calculated form the permeation flux of each pure species, and this deviation is a complicated function of the molecular properties and operation conditions.

Competitive adsorption between benzene and ethylene dichloride on activated carbon: The importance of concentration

NASA Astrophysics Data System (ADS)

Miao, T.; Tang, H. M.; Cheng, Z. X.

2018-03-01

In this work we studied breakthroughs of binary mixtures of benzene and ethylene dichloride on fixed activated carbons bed. The results show a series of assault concentrations on activated carbon bed influences the nature of the adsorption competition mechanism. Assault concentration were used to determine how competition of compound distribution. The results are discussed in terms of competing energetic and the underlying molecular mechanisms. The ratio of assault concentrations is main reason for determining selectivity.

Kinetic Monte Carlo (kMC) simulation of carbon co-implant on pre-amorphization process.

PubMed

Park, Soonyeol; Cho, Bumgoo; Yang, Seungsu; Won, Taeyoung

2010-05-01

We report our kinetic Monte Carlo (kMC) study of the effect of carbon co-implant on the pre-amorphization implant (PAL) process. We employed BCA (Binary Collision Approximation) approach for the acquisition of the initial as-implant dopant profile and kMC method for the simulation of diffusion process during the annealing process. The simulation results implied that carbon co-implant suppresses the boron diffusion due to the recombination with interstitials. Also, we could compare the boron diffusion with carbon diffusion by calculating carbon reaction with interstitial. And we can find that boron diffusion is affected from the carbon co-implant energy by enhancing the trapping of interstitial between boron and interstitial.

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.

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

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.

High Resolution Imaging of Very Low Mass Spectral Binaries: Three Resolved Systems and Detection of Orbital Motion in an L/T Transition Binary

NASA Astrophysics Data System (ADS)

Bardalez Gagliuffi, Daniella C.; Gelino, Christopher R.; Burgasser, Adam J.

2015-11-01

We present high resolution Laser Guide Star Adaptive Optics imaging of 43 late-M, L and T dwarf systems with Keck/NIRC2. These include 17 spectral binary candidates, systems whose spectra suggest the presence of a T dwarf secondary. We resolve three systems: 2MASS J1341-3052, SDSS J1511+0607 and SDSS J2052-1609 the first two are resolved for the first time. All three have projected separations <8 AU and estimated periods of 14-80 years. We also report a preliminary orbit determination for SDSS J2052-1609 based on six epochs of resolved astrometry between 2005 and 2010. Among the 14 unresolved spectral binaries, 5 systems were confirmed binaries but remained unresolved, implying a minimum binary fraction of {47}-11+12% for this sample. Our inability to resolve most of the spectral binaries, including the confirmed binaries, supports the hypothesis that a large fraction of very low mass systems have relatively small separations and are missed with direct imaging. 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.

Three-Phase Melting Curves in the Binary System of Carbon Dioxide and Water

NASA Astrophysics Data System (ADS)

Abramson, E. H.

2017-10-01

Invariant, three-phase melting curves, of ice VI in equilibrium with solid CO2, of ice VII in equilibrium with solid CO2, and of solid CO2 in simultaneous equilibrium with a majority aqueous and a majority CO2 fluid, were explored in the binary system of carbon dioxide and water. Diamond-anvil cells were used to develop pressures of 5 GPa. Water exhibits a large melting temperature depression (73°C less than its pure melting temperature of 253°C at 5 GPa) indicative of large concentrations of CO2 in the aqueous solution. The melting point of water-saturated CO2 does not show a measureable departure from that of the pure system at temperatures lower than ∼200°C and only 10°C at 5 GPa (from 327°C).

Delayed Ionization in Transition Metal Carbon Clusters

NASA Astrophysics Data System (ADS)

Kooi, S. E.; Castleman, A. W., Jr.

1997-03-01

Mass spectrometric studies of several single and binary transition metal carbon cluster systems, produced in a laser vaporization source, reveal several species that undergo delayed ionization. Pulsed extraction and blocking electric fields, in a time-of-flight mass spectrometer, allow the study of delayed ionization over a time window after excitation with a pulsed laser. In systems where metallocarbohedrenes (Met-Cars) are produced, the Met-Cars are the dominate delayed species. Delayed ionization of binary metal Met-Cars Ti_xM_yC_12 (M=Zr,Nb,Y; x+y=8) is dependent on the ratio of the two metals. Delayed behavior is investigated over a range of photoionization wavelengths and fluences. In order to determine the degree to which the delayed ionization is thermionic in character, the experimental data have been compared to Klots's model for thermionic emission from small particles.

Carbon Isotopic Compositions in Carbon Dioxide Measured By Micro-Laser Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Li, J.-J.; Li, R.-X.; Dong, H.; Wang, Zh.-H.; Zhao, B.-S.; Wang, N.; Cheng, J.-H.

2017-05-01

We have prepared a series of 12CO2/13CO2 binary mixtures as standard samples at room temperature. Using microlaser Raman spectroscopy, it was found that the relationship between the 12CO2 mole fractions and the peak area ratios of 12CO2/13CO2 in the Raman spectra of CO2 binary mixtures showed a polynomial correlation. The establishment of the experimental working curve paves the way for estimating the mole fractions of each individual fluid inclusion and determining 13C/12C and δ13C u sing micro-Raman spectroscopy. The Raman spectra of 12CO2 and 13CO2 showed a characteristic peak at 1348 cm-1 with an argon laser at 785 nm, which is perhaps due to the formation of dimers.

Laser-induced phase separation of silicon carbide

PubMed Central

Choi, Insung; Jeong, Hu Young; Shin, Hyeyoung; Kang, Gyeongwon; Byun, Myunghwan; Kim, Hyungjun; Chitu, Adrian M.; Im, James S.; Ruoff, Rodney S.; Choi, Sung-Yool; Lee, Keon Jae

2016-01-01

Understanding the phase separation mechanism of solid-state binary compounds induced by laser–material interaction is a challenge because of the complexity of the compound materials and short processing times. Here we present xenon chloride excimer laser-induced melt-mediated phase separation and surface reconstruction of single-crystal silicon carbide and study this process by high-resolution transmission electron microscopy and a time-resolved reflectance method. A single-pulse laser irradiation triggers melting of the silicon carbide surface, resulting in a phase separation into a disordered carbon layer with partially graphitic domains (∼2.5 nm) and polycrystalline silicon (∼5 nm). Additional pulse irradiations cause sublimation of only the separated silicon element and subsequent transformation of the disordered carbon layer into multilayer graphene. The results demonstrate viability of synthesizing ultra-thin nanomaterials by the decomposition of a binary system. PMID:27901015

WR 148 and the not so compact companion

NASA Astrophysics Data System (ADS)

Munoz, Melissa; Moffat, Anthony J.; Hill, Grant M.; Shenar, Tomer; Richardson, Noel D.; Pablo, Herbert; St-Louis, Nicole; Ramiaramanantsoa, Tahina

2017-11-01

The objective is to determine the nature of the unseen companion of the single-lined spectroscopic binary, WR 148 (= WN7h+?). The absence of companion lines supports a compact companion (cc) scenario. The lack of hard X-rays favours a non-compact companion scenario. Is WR 148 a commonplace WR+OB binary or a rare WR+cc binary?

Eta Carinae: An Astrophysical Laboratory

NASA Technical Reports Server (NTRS)

Gull, T.

2008-01-01

In the 1840s, Eta Carinae, a massive binary near the end of its hydrogen burning cycle, ejected at least ten solar masses of material rich in nitrogen at the expense of carbon and oxygen. The resultant chemistry has led to a most peculiar mix of metals, molecules and dust. We identify thousands of nebular absorption lines of ions including Fe, Ni, V, Sr, Sc and molecules including H2, CH, OH, but no CO. Today we see a wind-enshrouded massive binary in the center of an expanding neutral hourglass and skirt. A similar ionized internal structure is associated with a lesser ejection of the 1890s. Both systems respond to the 5.54-year modulation of X-ray and ultraviolet radiation as the less massive, hotter companion plunges through the extended wind of the more massive, cooler primary. Observations and models are being brought together to understand the properties of the wind-enshrouded central binary. In turn we are learning much atomic spectroscopy, what molecules form in oxygen-and carbon-deprived environments and potentially about a dust that is quite different from the interstellar dust. As the next periastron occurs in January 2009, a number of observing teams are preparing to test these models with new observations.

Binary Hierarchical Porous Graphene/Pyrolytic Carbon Nanocomposite Matrix Loaded with Sulfur as a High-Performance Li-S Battery Cathode.

PubMed

Zhang, Hang; Gao, Qiuming; Qian, Weiwei; Xiao, Hong; Li, Zeyu; Ma, Li; Tian, Xuehui

2018-06-06

A N,O-codoped hierarchical porous nanocomposite consisting of binary reduced graphene oxide and pyrolytic carbon (rGO/PC) from chitosan is fabricated. The optimized rGO/PC possesses micropores with size distribution concentrated around 1.1 nm and plenty of meso/macropores. The Brunauer-Emmett-Teller specific surface area is 480.8 m 2 g -1 , and it possesses impressively large pore volume of 2.14 cm 3 g -1 . On the basis of the synergistic effects of the following main factors: (i) the confined space effect in the hierarchical porous binary carbonaceous matrix; (ii) the anchor effects by strong chemical bonds with codoped N and O atoms; and (iii) the good flexibility and conductivity of rGO, the rGO/PC/S holding 75 wt % S exhibits high performance as Li-S battery cathode. Specific capacity of 1625 mA h g -1 can be delivered at 0.1 C (1 C = 1675 mA g -1 ), whereas 848 mA h g -1 can be maintained after 300 cycles at 1 C. Even at high rate of 5 C, 412 mA h g -1 can be restrained after 1000 cycles.

Conversion of stranded waste-stream carbon and nutrients into value-added products via metabolically coupled binary heterotroph-photoautotroph system

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

Bohutskyi, Pavlo; Kucek, Leo A.; Hill, Eric

Metabolic flexibility and robustness of phototroph- heterotroph co-cultures provide a flexible binary engineering platform for a variety of biotechnological and environmental applications. Here, we metabolically coupled a heterotrophic bacterium Bacillus subtilis with astaxanthin producing alga Haematococcus pluvialis and successfully applied this binary co-culture for conversion of the starch-rich waste stream into valuable astaxanthin-rich biomass. Importantly, the implemented system required less mass transfer of CO2 and O2 due to in-situ exchange between heterotroph and phototroph, which can contribute to reduction in energy consumption for wastewater treatment. In addition, the maximum reduction in chemical oxygen demand, total nitrogen and phosphorus reached 65%,more » 55% and 30%, respectively. The preliminary economic analysis indicated that realization of produced biomass with 0.8% astaxanthin content may generate annual revenues of $3.2M (baseline scenario) from treatment of wastewater (1,090 m3/day) from a potato processing plant. Moreover, the revenues may be increased up to $18.2M for optimized scenario with astaxanthin content in algae of 2%. This work demonstrates a successful proof-of-principle for conversion of waste carbon and nutrients into targeted value-added products through metabolic connection of heterotrophic and phototrophic organisms. Utilization of heterotrophic-algal binary cultures opens new perspectives for designing highly-efficient production processes for feedstock biomass production as well as allows utilization of variety of organic agricultural, chemical, or municipal wastes.« less

Perfluorooctane sulfonate adsorption on powder activated carbon: Effect of phosphate (P) competition, pH, and temperature.

PubMed

Qian, Jin; Shen, Mengmeng; Wang, Peifang; Wang, Chao; Li, Kun; Liu, Jingjing; Lu, Bianhe; Tian, Xin

2017-09-01

Powdered activated carbon (PAC), as an adsorbent, was applied to remove perfluorooctane sulfonate (PFOS) from aqueous solution. Laboratory batch experiments were performed to investigate the influences of phosphate (P) competition, temperature, and pH for PFOS adsorption onto PAC. The results showed that higher temperature favored PFOS adsorption in single and binary systems. The kinetic data fitted very well to the pseudo second-order kinetic model. Thermodynamically, the endothermic enthalpy of the PFOS adsorption in single and binary systems were 125.07 and 21.25 kJ mol -1 , respectively. The entropy of the PFOS adsorption in single and binary systems were 0.479 and 0.092 kJ mol -1  K -1 , respectively. And the Gibbs constants were negative. These results indicated that the adsorption processes were spontaneous. The adsorption isotherms of PFOS agreed well with the Langmuir model. In the single system, PFOS adsorption decreased with increased pH value. The difference in the amount of PFOS adsorption between the single and binary systems increased at higher pH. Frustrated total internal reflection (FTIR) demonstrated that P competition increased the hydrophilicity of the PAC and the electrostatic repulsion between PFOS and PAC, then the PFOS adsorption amount decreased. It also demonstrated that, at higher temperature, increased PFOS adsorption was mainly due to the higher diffusion rate of PFOS molecules and greater number of active sites opened on the PAC surface. Copyright © 2017 Elsevier Ltd. All rights reserved.

Clustering and Dimensionality Reduction to Discover Interesting Patterns in Binary Data

NASA Astrophysics Data System (ADS)

Palumbo, Francesco; D'Enza, Alfonso Iodice

The attention towards binary data coding increased consistently in the last decade due to several reasons. The analysis of binary data characterizes several fields of application, such as market basket analysis, DNA microarray data, image mining, text mining and web-clickstream mining. The paper illustrates two different approaches exploiting a profitable combination of clustering and dimensionality reduction for the identification of non-trivial association structures in binary data. An application in the Association Rules framework supports the theory with the empirical evidence.

Adsorption of N-hexane, methanol and water vapor and binary mixtures of N-hexane/water vapor on super activated carbon nanoparticles

NASA Astrophysics Data System (ADS)

Prado, Jesus Antonio

Recent times have seen a large rise in the utilization of engineered nanomaterials (ENMs) within a wide variety of industries due to their unique properties. Consequently, the fabrication, application and disposal of ENMs will inevitably lead to their release to the environment. Once ENMs are in the environment, they may undergo atmospheric transformations, such the sorption of hazardous air pollutants (HAPs) or water vapor. These transformed ENMs may then affect the general public through inhalation -- or other pathways of exposure -- and those employed by the ever-growing nanotechnology sector are of particular vulnerability. As a result, it is important to evaluate the adsorption characteristics of a common carbon-based ENM under the presence of HAPs or water vapor which may adsorb onto them. This study investigated the unary and binary gas-phase adsorption of n-hexane, methanol and water vapor on super activated carbon nanoparticles (SACNPs) with a bench-scale adsorption system. Removal efficiencies, breakthrough tests, throughput ratios, adsorption capacities and kinetics modeling were completed to assess the adsorption behavior of the SACNPs.

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

Mukerjee, S.; McBreen, J.; Srinivasan, S.

Electrocatalysis for the oxygen reduction reaction (ORR) on five binary Pt alloy electrocatalysts (PtCr/C, PtMn/C, PtFe/C, PtCo/C and PtNi/C) supported on carbon have been investigated. The electrochemical characteristics for ORR in a proton conducting fuel cell environment has been correlated with the electronic and structural parameters determined under in situ conditions using XANES and EXAFS technique respectively. Results indicate that all the alloys possess higher Pt 5d band vacancies as compared to Pt/C. There is also evidence of lattice contraction in the alloys (supported by XRD results). Further, the Pt/C shows increase in Pt 5 d band vacancies during potentialmore » transitions from 0.54 to 0.84 V vs. RHE, which has been ration@ on the basis of OH type adsorption. In contrast to this, the alloys do not exhibit such an enhancement. Detailed EXAFS analysis supports the presence of OH species on Pt/C and its relative absence in the alloys. Correlation of the electrochemical results with bond distances and d-band vacancies show a volcano type behavior with the PtCr/C on top of the curve.« less

PtRu catalysts supported on heteropolyacid and chitosan functionalized carbon nanotubes for methanol oxidation reaction of fuel cells.

PubMed

Cui, Zhiming; Li, Chang Ming; Jiang, San Ping

2011-09-28

A simple self-assembly approach has been developed to functionalize carbon nanotubes (CNTs) with chitosan (CS) and heteropolyacids (HPAs) of phosphomolybdic acid (H(3)PMo(12)O(40), HPMo) and phosphotungstic acid (H(3)PW(12)O(40), HPW). The non-covalent functionalization method, which introduces homogenous surface functional groups with no detrimental effect on graphene structures of CNTs, can be carried out at room temperature without the use of corrosive acids. The PtRu nanoparticles supported on HPAs-CS-CNTs have a uniform distribution and much smaller size as compared to those of the PtRu nanoparticles supported on conventional acid treated CNTs (PtRu/AO-CNTs). The onset and peak potentials for CO(ad) oxidation on PtRu/HPAs-CS-CNTs catalysts are more negative than those on PtRu/AO-CNTs, indicating that HPAs facilitate the electro-oxidation of CO. The PtRu/HPMo-CS-CNTs catalyst has a higher electrocatalytic activity for methanol oxidation and higher tolerance toward CO poisoning than PtRu/HPW-CS-CNTs. The better electrocatalytic enhancement of HPMo on the PtRu/HPAs-CS-CNTs catalyst is most likely related to the fact that molybdenum-containing HPAs such as HPMo have more labile terminal oxygen to provide additional active oxygen sites while accelerating the CO and methanol oxidation in a similar way to that of Ru in the PtRu binary alloy system.

The white-dwarf cooling sequence of NGC 6791: a unique tool for stellar evolution

NASA Astrophysics Data System (ADS)

García-Berro, E.; Torres, S.; Renedo, I.; Camacho, J.; Althaus, L. G.; Córsico, A. H.; Salaris, M.; Isern, J.

2011-09-01

Context. NGC 6791 is a well-studied, metal-rich open cluster that is so close to us that it can be imaged down to luminosities fainter than that of the termination of its white-dwarf cooling sequence, thus allowing for an in-depth study of its white dwarf population. Aims: White dwarfs carry important information about the history of the cluster. We use observations of the white-dwarf cooling sequence to constrain important properties of the cluster stellar population, such as the existence of a putative population of massive helium-core white dwarfs, and the properties of a large population of unresolved binary white dwarfs. We also investigate the use of white dwarfs to disclose the presence of cluster subpopulations with a different initial chemical composition, and we obtain an upper bound to the fraction of hydrogen-deficient white dwarfs. Methods: We use a Monte Carlo simulator that employs up-to-date evolutionary cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, with carbon-oxygen and helium cores. The cooling sequences for carbon-oxygen cores account for the delays introduced by both 22Ne sedimentation in the liquid phase and by carbon-oxygen phase separation upon crystallization. Results: We do not find evidence for a substantial fraction of helium-core white dwarfs, and hence our results support the suggestion that the origin of the bright peak of the white-dwarf luminosity function can only be attributed to a population of unresolved binary white dwarfs. Moreover, our results indicate that if this hypothesis is at the origin of the bright peak, the number distribution of secondary masses of the population of unresolved binaries has to increase with increasing mass ratio between the secondary and primary components of the progenitor system. We also find that the observed cooling sequence appears to be able to constrain the presence of progenitor subpopulations with different chemical compositions and the fraction of hydrogen-deficient white dwarfs. Conclusions: Our simulations place interesting constraints on important characteristics of the stellar populations of NGC 6791. In particular, we find that the fraction of single helium-core white dwarfs must be smaller than 5%, that a subpopulation of stars with zero metallicity must be ≲12%, while if the adopted metallicity of the subpopulation is solar the upper limit is ~8%. Finally, we also find that the fraction of hydrogen-deficient white dwarfs in this particular cluster is surprinsingly small (≲6%).

Shear viscosity of binary mixtures: The Gay-Berne potential

NASA Astrophysics Data System (ADS)

Khordad, R.

2012-05-01

The Gay-Berne (GB) potential model is an interesting and useful model to study the real systems. Using the potential model, we intend to examine the thermodynamical properties of some anisotropic binary mixtures in two different phases, liquid and gas. For this purpose, we apply the integral equation method and solve numerically the Percus-Yevick (PY) integral equation. Then, we obtain the expansion coefficients of correlation functions to calculate the thermodynamical properties. Finally, we compare our results with the available experimental data [e.g., HFC-125 + propane, R-125/143a, methanol + toluene, benzene + methanol, cyclohexane + ethanol, benzene + ethanol, carbon tetrachloride + ethyl acetate, and methanol + ethanol]. The results show that the GB potential model is capable for predicting the thermodynamical properties of binary mixtures with acceptable accuracy.

Synthesis of Ultra-incompressible sp 3 -Hybridized Carbon Nitride with 1:1 Stoichiometry

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

Stavrou, Elissaios; Lobanov, Sergey; Dong, Huafeng

Search of materials with C-N composition hold a great promise in creating materials which would rival diamond hardness due to the very strong and relatively low-ionic C-N bond. Early experimental and theoretical works on C-N compounds were based on structural similarity with binary A 3B 4 structural types; however, the synthesis of C 3N 4 remains elusive. Here we explored an unbiased synthesis from the elemental materials at high pressures and temperatures. Using in situ synchrotron X-ray diffraction and Raman spectroscopy we demonstrate the synthesis of highly incompressible Pnnm CN compound with sp 3 hybridized carbon above 55 GPa andmore » 7000 K. This result is supported by first principles evolutionary search, which finds that Pnnm CN is the most stable compound above 10.9 GPa. On pressure release below 6 GPa the synthesized CN compound amorphizes reattaining its 1:1 stoichiometry as confirmed by Energy-Dispersive X-ray Spectroscopy. Here, this work underscores the importance of understanding of novel high-pressure chemistry rules and it opens a new route for synthesis of superhard materials.« less

Synthesis of Ultra-incompressible sp 3 -Hybridized Carbon Nitride with 1:1 Stoichiometry

DOE PAGES

Stavrou, Elissaios; Lobanov, Sergey; Dong, Huafeng; ...

2016-10-11

Search of materials with C-N composition hold a great promise in creating materials which would rival diamond hardness due to the very strong and relatively low-ionic C-N bond. Early experimental and theoretical works on C-N compounds were based on structural similarity with binary A 3B 4 structural types; however, the synthesis of C 3N 4 remains elusive. Here we explored an unbiased synthesis from the elemental materials at high pressures and temperatures. Using in situ synchrotron X-ray diffraction and Raman spectroscopy we demonstrate the synthesis of highly incompressible Pnnm CN compound with sp 3 hybridized carbon above 55 GPa andmore » 7000 K. This result is supported by first principles evolutionary search, which finds that Pnnm CN is the most stable compound above 10.9 GPa. On pressure release below 6 GPa the synthesized CN compound amorphizes reattaining its 1:1 stoichiometry as confirmed by Energy-Dispersive X-ray Spectroscopy. Here, this work underscores the importance of understanding of novel high-pressure chemistry rules and it opens a new route for synthesis of superhard materials.« less

The PyCBC search for binary black hole coalescences in Advanced LIGO's first observing run

NASA Astrophysics Data System (ADS)

Willis, Joshua; LIGO Scientific Collaboration

2017-01-01

Advanced LIGO's first observing run saw the first detections of binary black hole coalescences. We describe the PyCBC matched filter analysis, and the results of that search for binary systems with total mass up to 100 solar masses. This is a matched filter search for general-relativistic signals from binary black hole systems. Two signals, GW150914 and GW151226, were identified with very high significance, and a third possible signal, LVT151012, was found, though at much lower significance. Supported by NSF award PHY-1506254.

A survey of the Local Group of galaxies for symbiotic binary stars - I. First detection of symbiotic stars in M33

NASA Astrophysics Data System (ADS)

Mikołajewska, Joanna; Shara, Michael M.; Caldwell, Nelson; Iłkiewicz, Krystian; Zurek, David

2017-02-01

We present and discuss initial selection criteria and first results in M33 from a systematic search for extragalactic symbiotic stars. We show that the presence of diffuse ionized gas (DIG) emission can significantly contaminate the spectra of symbiotic star candidates. This important effect forces upon us a more stringent working definition of an extragalactic symbiotic star. We report the first detections and spectroscopic characterization of 12 symbiotic binaries in M33. We found that four of our systems contain carbon-rich giants. In another two of them, the giant seems to be a Zr-enhanced MS star, while the remaining six objects host M-type giants. The high number ratio of C to M giants in these binaries is consistent with the low metallicity of M33. The spatial and radial velocity distributions of these new symbiotic binaries are consistent with a wide range of progenitor star ages.

Tracing CNO exposed layers in the Algol-type binary system u Her

NASA Astrophysics Data System (ADS)

Kolbas, V.; Dervişoğlu, A.; Pavlovski, K.; Southworth, J.

2014-11-01

The chemical composition of stellar photospheres in mass-transferring binary systems is a precious diagnostic of the nucleosynthesis processes that occur deep within stars, and preserves information on the components' history. The binary system u Her belongs to a group of hot Algols with both components being B stars. We have isolated the individual spectra of the two components by the technique of spectral disentangling of a new series of 43 high-resolution échelle spectra. Augmenting these with an analysis of the Hipparcos photometry of the system yields revised stellar quantities for the components of u Her. For the primary component (the mass-gaining star), we find MA = 7.88 ± 0.26 M⊙, RA = 4.93 ± 0.15 R⊙ and Teff, A = 21 600 ± 220 K. For the secondary (the mass-losing star) we find MB = 2.79 ± 0.12 M⊙, RB = 4.26 ± 0.06 R⊙ and Teff, B = 12 600 ± 550 K. A non-local thermodynamic equilibrium analysis of the primary star's atmosphere reveals deviations in the abundances of nitrogen and carbon from the standard cosmic abundance pattern in accord with theoretical expectations for CNO nucleosynthesis processing. From a grid of calculated evolutionary models the best match to the observed properties of the stars in u Her enabled tracing the initial properties and history of this binary system. We confirm that it has evolved according to case A mass transfer. A detailed abundance analysis of the primary star gives C/N = 0.9, which supports the evolutionary calculations and indicates strong mixing in the early evolution of the secondary component, which was originally the more massive of the two. The composition of the secondary component would be a further important constraint on the initial properties of u Her system, but requires spectra of a higher signal-to-noise ratio.

Co-production of hydrogen and carbon nanotubes on nickel foam via methane catalytic decomposition

NASA Astrophysics Data System (ADS)

Ping, Dan; Wang, Chaoxian; Dong, Xinfa; Dong, Yingchao

2016-04-01

The co-production of COx-free hydrogen and carbon nanotubes (CNTs) was achieved on 3-dimensional (3D) macroporous nickel foam (NF) via methane catalytic decomposition (MCD) over nano-Ni catalysts using chemical vapor deposition (CVD) technique. By a simple coating of a NiO-Al2O3 binary mixture sol followed by a drying-calcination-reduction treatment, NF supported composite catalysts (denoted as NiyAlOx/NF) with Al2O3 transition-layer incorporated with well-dispersed nano-Ni catalysts were successfully prepared. The effects of Ni loading, calcination temperature and reaction temperature on the performance for simultaneous production of COx-free hydrogen and CNTs were investigated in detail. Catalysts before and after MCD were characterized by XRD, TPR, SEM, TEM, TG and Raman spectroscopy technology. Results show that increasing Ni loading, lowering calcination temperature and optimizing MCD reaction temperature resulted in high production efficiency of COx-free H2 and carbon, but broader diameter distribution of CNTs. Through detailed parameter optimization, the catalyst with a Ni/Al molar ratio of 0.1, calcination temperature of 550 °C and MCD temperature of 650 °C was favorable to simultaneously produce COx-free hydrogen with a growth rate as high as 10.3% and CNTs with uniform size on NF.

Electrolyte Engineering: Optimizing High-Rate Double-Layer Capacitances of Micropore- and Mesopore-Rich Activated Carbon.

PubMed

Chen, Ting-Hao; Yang, Cheng-Hsien; Su, Ching-Yuan; Lee, Tai-Chou; Dong, Quan-Feng; Chang, Jeng-Kuei

2017-09-22

Various types of electrolyte cations as well as binary cations are used to optimize the capacitive performance of activated carbon (AC) with different pore structures. The high-rate capability of micropore-rich AC, governed by the mobility of desolvated cations, can outperform that of mesopore-rich AC, which essentially depends on the electrolyte conductivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Circinus X-1: a Laboratory for Studying the Accretion Phenomenon in Compact Binary X-Ray Sources. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Robinson-Saba, J. L.

1983-01-01

Observations of the binary X-ray source Circinus X-1 provide samples of a range of spectral and temporal behavior whose variety is thought to reflect a broad continuum of accretion conditions in an eccentric binary system. The data support an identification of three or more X-ray spectral components, probably associated with distinct emission regions.

Numerical Simulations of Dynamical Mass Transfer in Binaries

NASA Astrophysics Data System (ADS)

Motl, P. M.; Frank, J.; Tohline, J. E.

1999-05-01

We will present results from our ongoing research project to simulate dynamically unstable mass transfer in near contact binaries with mass ratios different from one. We employ a fully three-dimensional self-consistent field technique to generate synchronously rotating polytropic binaries. With our self-consistent field code we can create equilibrium binaries where one component is, by radius, within about 99 of filling its Roche lobe for example. These initial configurations are evolved using a three-dimensional, Eulerian hydrodynamics code. We make no assumptions about the symmetry of the subsequent flow and the entire binary system is evolved self-consistently under the influence of its own gravitational potential. For a given mass ratio and polytropic index for the binary components, mass transfer via Roche lobe overflow can be predicted to be stable or unstable through simple theoretical arguments. The validity of the approximations made in the stability calculations are tested against our numerical simulations. We acknowledge support from the U.S. National Science Foundation through grants AST-9720771, AST-9528424, and DGE-9355007. This research has been supported, in part, by grants of high-performance computing time on NPACI facilities at the San Diego Supercomputer Center, the Texas Advanced Computing Center and through the PET program of the NAVOCEANO DoD Major Shared Resource Center in Stennis, MS.

One-pot synthesis of binary metal organic frameworks (HKUST-1 and UiO-66) for enhanced adsorptive removal of water contaminants.

PubMed

Azhar, Muhammad Rizwan; Abid, Hussein Rasool; Sun, Hongqi; Periasamy, Vijay; Tadé, Moses O; Wang, Shaobin

2017-03-15

In this study, binary metal organic frameworks (MOFs) with HKUST-1 and UiO-66 have been synthesized in a one-pot process. The synthesized MOFs were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), N 2 adsorption, and thermogravimetric analysis (TGA). The meso-porosity and thermal stability of the binary MOFs were higher than those of single HKUST-1 or UiO-66. The synthesized MOF hybrids were then tested for adsorptive removal of methylene blue (MB) from wastewater in terms of kinetic and isothermal adsorption as compared to a commercially available activated carbon (AC). All the synthesized MOFs showed significant removal of MB under a wide range of pH. The adsorption capacities of HKUST-1 are higher than UiO-66 and commercial AC while the binary MOFs presented an even higher adsorption capacity than single MOFs. This is the first time that binary HKUST-1 and UiO-66 MOFs have been successfully synthesized and demonstrated enhanced adsorptive removal of contaminants. Copyright © 2016 Elsevier Inc. All rights reserved.

Capture of trace sulfur gases from binary mixtures by single-walled carbon nanotube arrays: a molecular simulation study.

PubMed

Wang, Wenjuan; Peng, Xuan; Cao, Dapeng

2011-06-01

Adsorption of H(2)S and SO(2) pure gases and their selective capture from the H(2)S-CH(4), H(2)S-CO(2), SO(2)-N(2), and SO(2)-CO(2) binary mixtures by the single-walled carbon nanotubes (SWNT) are investigated via using the grand canonical Monte Carlo (GCMC) method. It is found that the (20, 20) SWNT with larger diameter shows larger capacity for H(2)S and SO(2) pure gases at T = 303 K, in which the uptakes reach 16.31 and 16.03 mmol/g, respectively. However, the (6,6) SWNT with small diameter exhibits the largest selectivity for binary mixtures containing trace sulfur gases at T = 303 K and P = 100 kPa. By investigating the effect of pore size on the separation of gas mixtures, we found that the optimized pore size is 0.81 nm for separation of H(2)S-CH(4), H(2)S-CO(2), and SO(2)-N(2) binary mixtures, while it is 1.09 nm for the SO(2)-CO(2) mixture. The effects of concentration and temperature on the selectivity of sulfide are also studied at the optimal pore size. It is found that the concentration (ppm) of sulfur components has little effect on selectivity of SWNTs for these binary mixtures. However, the selectivity decreases obviously with the increase of temperature. To improve the adsorption capacities, we further modify the surface of SWNTs with the functional groups. The selectivities of H(2)S-CO(2) and SO(2)-CO(2) mixtures are basically uninfluenced by the site density, while the increase of site density can improve the selectivity of H(2)S-CH(4) mixture doubly. It is expected that this work could provide useful information for sulfur gas capture.

Transition metal nitride coated with atomic layers of Pt as a low-cost, highly stable electrocatalyst for the oxygen reduction reaction

DOE PAGES

Tian, Xinlong; Adzic, Radoslav R.; Luo, Junming; ...

2016-02-10

Here, the main challenges to the commercial viability of polymer electrolyte membrane fuel cells are (i) the high cost associated with using large amounts of Pt in fuel cell cathodes to compensate for the sluggish kinetics of the oxygen reduction reaction, (ii) catalyst degradation, and (iii) carbon-support corrosion. To address these obstacles, our group has focused on robust, carbon-free transition metal nitride materials with low Pt content that exhibit tunable physical and catalytic properties. Here, we report on the high performance of a novel catalyst with low Pt content, prepared by placing several layers of Pt atoms on nanoparticles ofmore » titanium nickel binary nitride. For the ORR, the catalyst exhibited a more than 400% and 200% increase in mass activity and specific activity, respectively, compared with the commercial Pt/C catalyst. It also showed excellent stability/durability, experiencing only a slight performance loss after 10,000 potential cycles, while TEM results showed its structure had remained intact. The catalyst’s outstanding performance may have resulted from the ultrahigh dispersion of Pt (several atomic layers coated on the nitride nanoparticles), and the excellent stability/durability may have been due to the good stability of nitride and synergetic effects between ultrathin Pt layer and the robust TiNiN support.« less

Dielectric and spectroscopic study of binary mixture of Acrylonitrile with Chlorobenzene

NASA Astrophysics Data System (ADS)

Deshmukh, Snehal D.; Pattebahadur, K. L.; Mohod, A. G.; Undre, P. B.; Patil, S. S.; Khirade, P. W.

2018-05-01

In this paper, study of binary mixture of Acrylonitrile (ACN) with Chlorobenzene (CBZ) has been carried out at eleven concentrations at room temperature. The determined Dielectric Constant (ɛ0) Density (ρ) and Refractive index (nD) values of binary mixture are used to calculate the excess properties of mixture over the entire composition range and fitted to the Redlich-Kister equation. From the above parameters, intermolecular interaction and dynamics of molecules of binary mixture at molecular level are discussed. The Conformational analysis of the intermolecular interaction between Acrylonitrile and Chlorobenzene is supported by the FTIR spectra.

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.

X-ray Observations of Binary and Single Wolf-Rayet Stars with XMM-Newton and Chandra

NASA Technical Reports Server (NTRS)

Skinner, Stephen; Gudel, Manuel; Schmutz, Werner; Zhekov, Svetozar

2006-01-01

We present an overview of recent X-ray observations of Wolf-Rayet (WR) stars with XMM-Newton and Chandra. These observations are aimed at determining the differences in X-ray properties between massive WR + OB binary systems and putatively single WR stars. A new XMM spectrum of the nearby WN8 + OB binary WR 147 shows hard absorbed X-ray emission (including the Fe Ka line complex), characteristic of colliding wind shock sources. In contrast, sensitive observations of four of the closest known single WC (carbon-rich) WR stars have yielded only nondetections. These results tentatively suggest that single WC stars are X-ray quiet. The presence of a companion may thus be an essential factor in elevating the X-ray emission of WC + OB stars to detectable levels.

Evaluation of selected strapdown inertial instruments and pulse torque loops, volume 1

NASA Technical Reports Server (NTRS)

Sinkiewicz, J. S.; Feldman, J.; Lory, C. B.

1974-01-01

Design, operational and performance variations between ternary, binary and forced-binary pulse torque loops are presented. A fill-in binary loop which combines the constant power advantage of binary with the low sampling error of ternary is also discussed. The effects of different output-axis supports on the performance of a single-degree-of-freedom, floated gyroscope under a strapdown environment are illustrated. Three types of output-axis supports are discussed: pivot-dithered jewel, ball bearing and electromagnetic. A test evaluation on a Kearfott 2544 single-degree-of-freedom, strapdown gyroscope operating with a pulse torque loop, under constant rates and angular oscillatory inputs is described and the results presented. Contributions of the gyroscope's torque generator and the torque-to-balance electronics on scale factor variation with rate are illustrated for a SDF 18 IRIG Mod-B strapdown gyroscope operating with various pulse rebalance loops. Also discussed are methods of reducing this scale factor variation with rate by adjusting the tuning network which shunts the torque coil. A simplified analysis illustrating the principles of operation of the Teledyne two-degree-of-freedom, elastically-supported, tuned gyroscope and the results of a static and constant rate test evaluation of that instrument are presented.

Investigations on the system boron-carbon silicon

NASA Technical Reports Server (NTRS)

Kieffer, R.; Gugel, E.; Leimer, G.; Ettmayer, P.

1983-01-01

The above elements form with each other binary compounds which are very interesting from the point of view of their structure and their chemistry and which are important for technology. The present investigation is concerned with the three-component system and the behavior of the binary compounds occurring in it. Investigations employing various techniques, such as X-ray, chemical analysis, microscopy and fusion experiments showed that no ternary phase exists within the boundary of the ternary system. There is no compound with a higher abrasion capacity than boron carbide. The probable phase field divisions at two isothermic intersections and the fusion isotherms are indicated.

The Binary Pulsar: Gravity Waves Exist.

ERIC Educational Resources Information Center

Will, Clifford

1987-01-01

Reviews the history of pulsars generally and the 1974 discovery of the binary pulsar by Joe Taylor and Russell Hulse specifically. Details the data collection and analysis used by Taylor and Hulse. Uses this discussion as support for Albert Einstein's theory of gravitational waves. (CW)

Binary stars in the Galactic thick disc

NASA Astrophysics Data System (ADS)

Izzard, Robert G.; Preece, Holly; Jofre, Paula; Halabi, Ghina M.; Masseron, Thomas; Tout, Christopher A.

2018-01-01

The combination of asteroseismologically measured masses with abundances from detailed analyses of stellar atmospheres challenges our fundamental knowledge of stars and our ability to model them. Ancient red-giant stars in the Galactic thick disc are proving to be most troublesome in this regard. They are older than 5 Gyr, a lifetime corresponding to an initial stellar mass of about 1.2 M⊙. So why do the masses of a sizeable fraction of thick-disc stars exceed 1.3 M⊙, with some as massive as 2.3 M⊙? We answer this question by considering duplicity in the thick-disc stellar population using a binary population-nucleosynthesis model. We examine how mass transfer and merging affect the stellar mass distribution and surface abundances of carbon and nitrogen. We show that a few per cent of thick-disc stars can interact in binary star systems and become more massive than 1.3 M⊙. Of these stars, most are single because they are merged binaries. Some stars more massive than 1.3 M⊙ form in binaries by wind mass transfer. We compare our results to a sample of the APOKASC data set and find reasonable agreement except in the number of these thick-disc stars more massive than 1.3 M⊙. This problem is resolved by the use of a logarithmically flat orbital-period distribution and a large binary fraction.

Can Binary Population Synthesis Models Be Tested With Hot Subdwarfs ?

NASA Astrophysics Data System (ADS)

Kopparapu, Ravi Kumar; Wade, R. A.; O'Shaughnessy, R.

2007-12-01

Models of binary star interactions have been successful in explaining the origin of field hot subdwarf (sdB) stars in short period systems. The hydrogen envelopes around these core He-burning stars are removed in a "common envelope" evolutionary phase. Reasonably clean samples of short-period sdB+WD or sdB+dM systems exist, that allow the common envelope ejection efficiency to be estimated for wider use in binary population synthesis (BPS) codes. About one-third of known sdB stars, however, are found in longer-period systems with a cool G or K star companion. These systems may have formed through Roche-lobe overflow (RLOF) mass transfer from the present sdB to its companion. They have received less attention, because the existing catalogues are believed to have severe selection biases against these systems, and because their long, slow orbits are difficult to measure. Are these known sdB+cool systems worth intense observational effort? That is, can they be used to make a valid and useful test of the RLOF process in BPS codes? We use the Binary Stellar Evolution (BSE) code of Hurley et al. (2002), mapping sets of initial binaries into present-day binaries that include sdBs, and distinguishing "observable" sdBs from "hidden" ones. We aim to find out whether (1) the existing catalogues of sdBs are sufficiently fair samples of the kinds of sdB binaries that theory predicts, to allow testing or refinement of RLOF models; or instead whether (2) large predicted hidden populations mandate the construction of new catalogues, perhaps using wide-field imaging surveys such as 2MASS, SDSS, and Galex. This work has been partially supported by NASA grant NNG05GE11G and NSF grants PHY 03-26281, PHY 06-00953 and PHY 06-53462. This work is also supported by the Center for Gravitational Wave Physics, which is supported by the National Science Foundation under cooperative agreement PHY 01-14375.

Distances of Dwarf Carbon Stars

NASA Astrophysics Data System (ADS)

Harris, Hugh C.; Dahn, Conard C.; Subasavage, John P.; Munn, Jeffrey A.; Canzian, Blaise J.; Levine, Stephen E.; Monet, Alice B.; Pier, Jeffrey R.; Stone, Ronald C.; Tilleman, Trudy M.; Hartkopf, William I.

2018-06-01

Parallaxes are presented for a sample of 20 nearby dwarf carbon stars. The inferred luminosities cover almost two orders of magnitude. Their absolute magnitudes and tangential velocities confirm prior expectations that some originate in the Galactic disk, although more than half of this sample are halo stars. Three stars are found to be astrometric binaries, and orbital elements are determined; their semimajor axes are 1–3 au, consistent with the size of an AGB mass-transfer donor star.

Formation of wide binaries by turbulent fragmentation

NASA Astrophysics Data System (ADS)

Lee, Jeong-Eun; Lee, Seokho; Dunham, Michael M.; Tatematsu, Ken'ichi; Choi, Minho; Bergin, Edwin A.; Evans, Neal J.

2017-08-01

Understanding the formation of wide-binary systems of very low-mass stars (M ≤ 0.1 solar masses, M⊙) is challenging 1,2,3 . The most obvious route is through widely separated low-mass collapsing fragments produced by turbulent fragmentation of a molecular core4,5. However, close binaries or multiples from disk fragmentation can also evolve to wide binaries over a few initial crossing times of the stellar cluster through tidal evolution6. Finding an isolated low-mass wide-binary system in the earliest stage of formation, before tidal evolution could occur, would prove that turbulent fragmentation is a viable mechanism for (very) low-mass wide binaries. Here we report high-resolution ALMA observations of a known wide-separation protostellar binary, showing that each component has a circumstellar disk. The system is too young7 to have evolved from a close binary, and the disk axes are misaligned, providing strong support for the turbulent fragmentation model. Masses of both stars are derived from the Keplerian rotation of the disks; both are very low-mass stars.

Reduction from cost-sensitive ordinal ranking to weighted binary classification.

PubMed

Lin, Hsuan-Tien; Li, Ling

2012-05-01

We present a reduction framework from ordinal ranking to binary classification. The framework consists of three steps: extracting extended examples from the original examples, learning a binary classifier on the extended examples with any binary classification algorithm, and constructing a ranker from the binary classifier. Based on the framework, we show that a weighted 0/1 loss of the binary classifier upper-bounds the mislabeling cost of the ranker, both error-wise and regret-wise. Our framework allows not only the design of good ordinal ranking algorithms based on well-tuned binary classification approaches, but also the derivation of new generalization bounds for ordinal ranking from known bounds for binary classification. In addition, our framework unifies many existing ordinal ranking algorithms, such as perceptron ranking and support vector ordinal regression. When compared empirically on benchmark data sets, some of our newly designed algorithms enjoy advantages in terms of both training speed and generalization performance over existing algorithms. In addition, the newly designed algorithms lead to better cost-sensitive ordinal ranking performance, as well as improved listwise ranking performance.

Evaluating the Free Energies of Solvation and Electronic Structures of Lithium-Ion Battery Electrolytes.

PubMed

Shakourian-Fard, Mehdi; Kamath, Ganesh; Sankaranarayanan, Subramanian K R S

2016-09-19

Adaptive biasing force molecular dynamics simulations and density functional theory calculations were performed to understand the interaction of Li(+) with pure carbonates and ethylene carbonate (EC)-based binary mixtures. The most favorable Li carbonate cluster configurations obtained from molecular dynamics simulations were subjected to detailed structural and thermochemistry calculations on the basis of the M06-2X/6-311++G(d,p) level of theory. We report the ranking of these electrolytes on the basis of the free energies of Li-ion solvation in carbonates and EC-based mixtures. A strong local tetrahedral order involving four carbonates around the Li(+) was seen in the first solvation shell. Thermochemistry calculations revealed that the enthalpy of solvation and the Gibbs free energy of solvation of the Li(+) ion with carbonates are negative and suggested the ion-carbonate complexation process to be exothermic and spontaneous. Natural bond orbital analysis indicated that Li(+) interacts with the lone pairs of electrons on the carbonyl oxygen atom in the primary solvation sphere. These interactions lead to an increase in the carbonyl (C=O) bond lengths, as evidenced by a redshift in the vibrational frequencies [ν(C=O)] and a decrease in the electron density values at the C=O bond critical points in the primary solvation sphere. Quantum theory of atoms in molecules, localized molecular orbital energy decomposition analysis (LMO-EDA), and noncovalent interaction plots revealed the electrostatic nature of the Li(+) ion interactions with the carbonyl oxygen atoms in these complexes. On the basis of LMO-EDA, the strongest attractive interaction in these complexes was found to be the electrostatic interaction followed by polarization, dispersion, and exchange interactions. Overall, our calculations predicted EC and a binary mixture of EC/dimethyl carbonate to be appropriate electrolytes for Li-ion batteries, which complies with experiments and other theoretical results. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermodynamic models for vapor-liquid equilibria of nitrogen + oxygen + carbon dioxide at low temperatures

NASA Astrophysics Data System (ADS)

Vrabec, Jadran; Kedia, Gaurav Kumar; Buchhauser, Ulrich; Meyer-Pittroff, Roland; Hasse, Hans

2009-02-01

For the design and optimization of CO 2 recovery from alcoholic fermentation processes by distillation, models for vapor-liquid equilibria (VLE) are needed. Two such thermodynamic models, the Peng-Robinson equation of state (EOS) and a model based on Henry's law constants, are proposed for the ternary mixture N 2 + O 2 + CO 2. Pure substance parameters of the Peng-Robinson EOS are taken from the literature, whereas the binary parameters of the Van der Waals one-fluid mixing rule are adjusted to experimental binary VLE data. The Peng-Robinson EOS describes both binary and ternary experimental data well, except at high pressures approaching the critical region. A molecular model is validated by simulation using binary and ternary experimental VLE data. On the basis of this model, the Henry's law constants of N 2 and O 2 in CO 2 are predicted by molecular simulation. An easy-to-use thermodynamic model, based on those Henry's law constants, is developed to reliably describe the VLE in the CO 2-rich region.

Adsorption of Selected Pharmaceutical Compounds onto Activated Carbon in Dilute Aqueous Solutions Exemplified by Acetaminophen, Diclofenac, and Sulfamethoxazole.

PubMed

Chang, E-E; Wan, Jan-Chi; Kim, Hyunook; Liang, Chung-Huei; Dai, Yung-Dun; Chiang, Pen-Chi

2015-01-01

The adsorption of three pharmaceuticals, namely, acetaminophen, diclofenac, and sulfamethoxazole onto granular activated carbon (GAC), was investigated. To study competitive adsorption, both dynamic and steady-state adsorption experiments were conducted by careful selection of pharmaceuticals with various affinities and molecular size. The effective diffusion coefficient of the adsorbate was increased with decease in particle size of GAC. The adsorption affinity represented as Langmuir was consistent with the ranking of the octanol-water partition coefficient, K(ow). The adsorption behavior in binary or tertiary systems could be described by competition adsorption. In the binary system adsorption replacement occurred, under which the adsorbate with the smaller K(ow) was replaced by the one with larger K(ow). Results also indicated that portion of the micropores could be occupied only by the small target compound, but not the larger adsorbates. In multiple-component systems the competition adsorption might significantly be affected by the macropores and less by the meso- or micropores.

RUNAWAY DWARF CARBON STARS AS CANDIDATE SUPERNOVA EJECTA

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

Plant, Kathryn A.; Margon, Bruce; Guhathakurta, Puragra

2016-12-20

The dwarf carbon (dC) star SDSS J112801.67+004034.6 has an unusually high radial velocity, 531 ± 4 km s{sup −1}. We present proper motion and new spectroscopic observations which imply a large Galactic rest frame velocity, 425 ± 9 km s{sup −1}. Several other SDSS dC stars are also inferred to have very high galactocentric velocities, again each based on both high heliocentric radial velocity and also confidently detected proper motions. Extreme velocities and the presence of C {sub 2} bands in the spectra of dwarf stars are both rare. Passage near the Galactic center can accelerate stars to such extreme velocities, but the largemore » orbital angular momentum of SDSS J1128 precludes this explanation. Ejection from a supernova in a binary system or disruption of a binary by other stars are possibilities, particularly as dC stars are thought to obtain their photospheric C {sub 2} via mass transfer from an evolved companion.« less

An experimental study of adsorption interference in binary mixtures flowing through activated carbon

NASA Technical Reports Server (NTRS)

Madey, R.; Photinos, P. J.

1983-01-01

The isothermal transmission through activated carbon adsorber beds at 25 C of acetaldehyde-propane and acetylene-ethane mixtures in a helium carrier gas was measured. The inlet concentration of each component was in the range between 10 ppm and 500 ppm. The constant inlet volumetric flow rate was controlled at 200 cc (STP)/min in the acetaldehyde-propane experiments and at 50 cc (STP)/min in the acetaldehyde-ethane experiments. Comparison of experimental results with the corresponding single-component experiments under similar conditions reveals interference phenomena between the components of the mixtures as evidenced by changes in both the adsorption capacity and the dispersion number. Propane was found to displace acetaldehyde from the adsorbed state. The outlet concentration profiles of propane in the binary mixtures tend to become more diffuse than the corresponding concentration profiles of the one-component experiments. Similar features were observed with mixtures of acetylene and ethane; however, the displacement of acetylene by ethane is less pronounced.

Adsorption of Selected Pharmaceutical Compounds onto Activated Carbon in Dilute Aqueous Solutions Exemplified by Acetaminophen, Diclofenac, and Sulfamethoxazole

PubMed Central

Chang, E.-E.; Wan, Jan-Chi; Liang, Chung-Huei; Dai, Yung-Dun; Chiang, Pen-Chi

2015-01-01

The adsorption of three pharmaceuticals, namely, acetaminophen, diclofenac, and sulfamethoxazole onto granular activated carbon (GAC), was investigated. To study competitive adsorption, both dynamic and steady-state adsorption experiments were conducted by careful selection of pharmaceuticals with various affinities and molecular size. The effective diffusion coefficient of the adsorbate was increased with decease in particle size of GAC. The adsorption affinity represented as Langmuir was consistent with the ranking of the octanol-water partition coefficient, K ow. The adsorption behavior in binary or tertiary systems could be described by competition adsorption. In the binary system adsorption replacement occurred, under which the adsorbate with the smaller K ow was replaced by the one with larger K ow. Results also indicated that portion of the micropores could be occupied only by the small target compound, but not the larger adsorbates. In multiple-component systems the competition adsorption might significantly be affected by the macropores and less by the meso- or micropores. PMID:26078989

r-Process Nucleosynthesis in the Early Universe Through Fast Mergers of Compact Binaries in Triple Systems

NASA Astrophysics Data System (ADS)

Bonetti, Matteo; Perego, Albino; Capelo, Pedro R.; Dotti, Massimo; Miller, M. Coleman

2018-05-01

Surface abundance observations of halo stars hint at the occurrence of r-process nucleosynthesis at low metallicity ([Fe/H] < -3), possibly within the first 108 yr after the formation of the first stars. Possible loci of early-Universe r-process nucleosynthesis are the ejecta of either black hole-neutron star or neutron star-neutron star binary mergers. Here, we study the effect of the inclination-eccentricity oscillations raised by a tertiary (e.g. a star) on the coalescence time-scale of the inner compact object binaries. Our results are highly sensitive to the assumed initial distribution of the inner binary semi-major axes. Distributions with mostly wide compact object binaries are most affected by the third object, resulting in a strong increase (by more than a factor of 2) in the fraction of fast coalescences. If instead the distribution preferentially populates very close compact binaries, general relativistic precession prevents the third body from increasing the inner binary eccentricity to very high values. In this last case, the fraction of coalescing binaries is increased much less by tertiaries, but the fraction of binaries that would coalesce within 108 yr even without a third object is already high. Our results provide additional support to the compact-binary merger scenario for r-process nucleosynthesis.

Investigation of intermolecular interaction of binary mixture of acrylonitrile with bromobenzene

NASA Astrophysics Data System (ADS)

Deshmukh, S. D.; Pattebahadur, K. L.; Mohod, A. G.; Patil, S. S.; Khirade, P. W.

2018-04-01

In this paper, study of binary mixture of Acrylonitrile (ACN)with Bromobenzene(BB) has been carried out at eleven concentrations at room temperature. The determined density(ρ) and refractive index (nD) values of binary mixture are used to calculate the excess properties of mixture over the entire composition range. The aforesaid parameters are used to calculate excess parameters and fitted to the Redlich-Kister equation to determine the bj coefficients. From the above parameters, intermolecular interaction and dynamics of molecules of binary mixture at molecular level are discussed. The Conformational analysis of the intermolecular interaction between Acrylonitrile and Bromobenzene is supported by the FTIR spectra.

Electrocatalyst for alcohol oxidation in fuel cells

DOEpatents

Adzic, Radoslav R.; Marinkovic, Nebojsa S.

2001-01-01

Binary and ternary electrocatalysts are provided for oxidizing alcohol in a fuel cell. The binary electrocatalyst includes 1) a substrate selected from the group consisting of NiWO.sub.4 or CoWO.sub.4 or a combination thereof, and 2) Group VIII noble metal catalyst supported on the substrate. The ternary electrocatalyst includes 1) a substrate as described above, and 2) a catalyst comprising Group VIII noble metal, and ruthenium oxide or molybdenum oxide or a combination thereof, said catalyst being supported on said substrate.

The scent of mixtures: rules of odour processing in ants

PubMed Central

Perez, Margot; Giurfa, Martin; d'Ettorre, Patrizia

2015-01-01

Natural odours are complex blends of numerous components. Understanding how animals perceive odour mixtures is central to multiple disciplines. Here we focused on carpenter ants, which rely on odours in various behavioural contexts. We studied overshadowing, a phenomenon that occurs when animals having learnt a binary mixture respond less to one component than to the other, and less than when this component was learnt alone. Ants were trained individually with alcohols and aldehydes varying in carbon-chain length, either as single odours or binary mixtures. They were then tested with the mixture and the components. Overshadowing resulted from the interaction between chain length and functional group: alcohols overshadowed aldehydes, and longer chain lengths overshadowed shorter ones; yet, combinations of these factors could cancel each other and suppress overshadowing. Our results show how ants treat binary olfactory mixtures and set the basis for predictive analyses of odour perception in insects. PMID:25726692

Physical properties of organic fullerene cocrystals

NASA Astrophysics Data System (ADS)

Macovez, Roberto

2017-12-01

The basic facts and fundamental properties of binary fullerene cocrystals are reviewed, focusing especially on solvates and salts of Buckminsterfullerene (C60), and hydrates of hydrophilic C60 derivatives. The examined properties include the lattice structure and the presence of orientational disorder and/or rotational dynamics (of both fullerenes and cocrystallizing moieties), thermodynamic properties such as decomposition enthalpies, and charge transport properties. Both thermodynamic properties and molecular orientational disorder shed light on the extent of intermolecular interactions in these binary solid-state systems. Comparison is carried out also with pristine fullerite and with the solid phases of functionalized C60. Interesting experimental findings on binary fullerene cocrystals include the simultaneous occurrence of rotations of both constituent molecular species, crystal morphologies reminiscent of quasi-crystalline behaviour, the observation of proton conduction in hydrate solids of hydrophilic fullerene derivatives, and the production of super-hard carbon materials by application of high pressures on solvated fullerene crystals.

The effect of stellar evolution uncertainties on the rest-frame ultraviolet stellar lines of C IV and He II in high-redshift Lyman-break galaxies

NASA Astrophysics Data System (ADS)

Eldridge, John J.; Stanway, Elizabeth R.

2012-01-01

Young, massive stars dominate the rest-frame ultraviolet (UV) spectra of star-forming galaxies. At high redshifts (z > 2), these rest-frame UV features are shifted into the observed-frame optical and a combination of gravitational lensing, deep spectroscopy and spectral stacking analysis allows the stellar population characteristics of these sources to be investigated. We use our stellar population synthesis code Binary Population and Spectral Synthesis (BPASS) to fit two strong rest-frame UV spectral features in published Lyman-break galaxy spectra, taking into account the effects of binary evolution on the stellar spectrum. In particular, we consider the effects of quasi-homogeneous evolution (arising from the rotational mixing of rapidly rotating stars), metallicity and the relative abundance of carbon and oxygen on the observed strengths of He IIλ1640 Å and C IVλ1548, 1551 Å spectral lines. We find that Lyman-break galaxy spectra at z ˜ 2-3 are best fitted with moderately sub-solar metallicities, and with a depleted carbon-to-oxygen ratio. We also find that the spectra of the lowest metallicity sources are best fitted with model spectra in which the He II emission line is boosted by the inclusion of the effect of massive stars being spun-up during binary mass transfer so these rapidly rotating stars experience quasi-homogeneous evolution.

Non-covalent doping of graphitic carbon nitride with ultrathin graphene oxide and molybdenum disulfide nanosheets: an effective binary heterojunction photocatalyst under visible light irradiation.

PubMed

Hu, S W; Yang, L W; Tian, Y; Wei, X L; Ding, J W; Zhong, J X; Chu, Paul K

2014-10-01

A proof of concept integrating binary p-n heterojunctions into a semiconductor hybrid photocatalyst is demonstrated by non-covalent doping of graphite-like carbon nitride (g-C3N4) with ultrathin GO and MoS2 nanosheets using a facile sonochemical method. In this unique ternary hybrid, the layered MoS2 and GO nanosheets with a large surface area enhance light absorption to generate more photoelectrons. On account of the coupling between MoS2 and GO with g-C3N4, the ternary hybrid possesses binary p-n heterojunctions at the g-C3N4/MoS2 and g-C3N4/GO interfaces. The space charge layers created by the p-n heterojunctions not only enhance photogeneration, but also promote charge separation and transfer of electron-hole pairs. In addition, the ultrathin MoS2 and GO with high mobility act as electron mediators to facilitate separation of photogenerated electron-hole pairs at each p-n heterojunction. As a result, the ternary hybrid photocatalyst exhibits improved photoelectrochemical and photocatalytic activity under visible light irradiation compared to other reference materials. The results provide new insights into the large-scale production of semiconductor photocatalysts. Copyright © 2014 Elsevier Inc. All rights reserved.

High-resolution spectroscopic observations of the new CEMP-s star CD -50°776

NASA Astrophysics Data System (ADS)

Roriz, M.; Pereira, C. B.; Drake, N. A.; Roig, F.; Silva, J. V. Sales

2017-11-01

Carbon enhanced metal-poor (CEMP) stars are a particular class of low-metalicity halo stars whose chemical analysis may provide important contrains to the chemistry evolution of the Galaxy and to the models of mass-transfer and evolution of components in binary systems. Here, we present a detailed analysis of the CEMP star CD -50°776, using high resolution optical spectroscopy. We found that CD -50°776 has a metalicity [Fe/H] = -2.31 and a carbon abundance [C/Fe] = +1.21. Analysing the s-process elements and the europium abundances, we show that this star is actually a CEMP-s star, based on the criteria set in the literature to classify these chemically peculiar objects. We also show that CD -50°776 is a lead star, since it has a ratio [Pb/Ce] = +0.97. In addition, we show that CD -50°776 develops radial velocity variations that may be attributed to the orbital motion in a binary system. The abundance pattern of CD -50°776 is discussed and compared to other CEMP-s stars already reported in the literature to show that this star is a quite exceptional object among the CEMP stars, particularly due to its low nitrogen abundance. Explaining this pattern may require to improve the nucleosynthesis models, and the evolutionary models of mass transfer and binary interaction.

What the Computer Taught Me About My Students...or Is Binary Search "Natural"?

ERIC Educational Resources Information Center

Pasquino, Anne

1978-01-01

Several examples of student-written programs "teaching" a computer to guess systematically in finding a number between 0 and 10,000 are illustrated. These lend support to the contention that rather than being a "natural" application, using a binary search is a learned technique. (MN)

Physicochemical properties of binary solutions of propylene carbonate-acetonitrile in the range of 253.15-313.15 K

NASA Astrophysics Data System (ADS)

Tyunina, E. Yu.; Chekunova, M. D.

2017-05-01

The density, dynamic viscosity, and dielectric constant of propylene carbonate solutions with acetonitrile are measured over the composition of a mixed solvent at temperatures of 253.15, 273.15, 293.15, and 313.15 K. The molar volume, molar viscosity, and molar capacity of a mixture of propylene carbonate-acetonitrile and an excess amount of it are calculated. The effect the temperature and composition of the mixture have on the excess molar properties is discussed. A linear correlation is observed between the values of the molar fluidity, capacity, polarization, and molar volume of the studied system.

On the nature of the dwarf carbon star G77-61

NASA Technical Reports Server (NTRS)

Dearborn, D. S. P.; Liebert, J.; Aaronson, M.; Dahn, C. C.; Harrington, R.

1986-01-01

In the present study of astrometric, photometric, and spectrophotometric data for the low luminosity carbon star G77-61, radial velocity variations are detected which have a binary period of 245 days. The unseen companion is probably a cool white dwarf of much higher mass than the visible object. The most straightforward evolutionary hypothesis is that this star has an extremely metal-poor composition, and that it accreted a small amount of carbon-rich material when the now-unseen primary was at maximum radius. This may have inverted the C/O abundance of the secondary without achieving common envelope evolution and a sorter period.

Nanostructured iron(III)-copper(II) binary oxide: a novel adsorbent for enhanced arsenic removal from aqueous solutions.

PubMed

Zhang, Gaosheng; Ren, Zongming; Zhang, Xiwang; Chen, Jing

2013-08-01

To obtain a highly efficient and low-cost adsorbent for arsenic removal from water, a novel nanostructured Fe-Cu binary oxide was synthesized via a facile co-precipitation method. Various techniques including BET surface area measurement, powder XRD, SEM, and XPS were used to characterize the synthetic Fe-Cu binary oxide. It showed that the oxide was poorly crystalline, 2-line ferrihydrite-like and was aggregated with many nanosized particles. Laboratory experiments were performed to investigate adsorption kinetics, adsorption isotherms, pH adsorption edge and regeneration of spent adsorbent. The results indicated that the Fe-Cu binary oxide with a Cu: Fe molar ratio of 1:2 had excellent performance in removing both As(V) and As(III) from water, and the maximal adsorption capacities for As(V) and As(III) were 82.7 and 122.3 mg/g at pH 7.0, respectively. The values are favorable, compared to those reported in the literature using other adsorbents. The coexisting sulfate and carbonate had no significant effect on arsenic removal. However, the presence of phosphate obviously inhibited the arsenic removal, especially at high concentrations. Moreover, the Fe-Cu binary oxide could be readily regenerated using NaOH solution and be repeatedly used. The Fe-Cu binary oxide could be a promising adsorbent for both As(V) and As(III) removal because of its excellent performance, facile and low-cost synthesis process, and easy regeneration. Copyright © 2013 Elsevier Ltd. All rights reserved.

"I would have preferred more options": accounting for non-binary youth in health research.

PubMed

Frohard-Dourlent, Hélène; Dobson, Sarah; Clark, Beth A; Doull, Marion; Saewyc, Elizabeth M

2017-01-01

As a research team focused on vulnerable youth, we increasingly need to find ways to acknowledge non-binary genders in health research. Youth have become more vocal about expanding notions of gender beyond traditional categories of boy/man and girl/woman. Integrating non-binary identities into established research processes is a complex undertaking in a culture that often assumes gender is a binary variable. In this article, we present the challenges at every stage of the research process and questions we have asked ourselves to consider non-binary genders in our work. As researchers, how do we interrogate the assumptions that have made non-binary lives invisible? What challenges arise when attempting to transform research practices to incorporate non-binary genders? Why is it crucial that researchers consider these questions at each step of the research process? We draw on our own research experiences to highlight points of tensions and possibilities for change. Improving access to inclusive health-care for non-binary people, and non-binary youth in particular, is part of creating a more equitable healthcare system. We argue that increased and improved access to inclusive health-care can be supported by research that acknowledges and includes people of all genders. © 2016 John Wiley & Sons Ltd.

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.

Persulfate Oxidation of MTBE- and Chloroform-Spent Granular Activated Carbon

EPA Science Inventory

Activated persulfate (Na2S2O8) regeneration of methyl tert-butyl ether (MTBE) and chloroform-spent GAC was evaluated in this study. Thermal-activation of persulfate was effective and resulted in greater MTBE removal than either alkaline-activation or H2O2–persulfate binary mixtur...

Searching Ultra-compact Pulsar Binaries with Abnormal Timing Behavior

NASA Astrophysics Data System (ADS)

Gong, B. P.; Li, Y. P.; Yuan, J. P.; Tian, J.; Zhang, Y. Y.; Li, D.; Jiang, B.; Li, X. D.; Wang, H. G.; Zou, Y. C.; Shao, L. J.

2018-03-01

Ultra-compact pulsar binaries are both ideal sources of gravitational radiation for gravitational wave detectors and laboratories for fundamental physics. However, the shortest orbital period of all radio pulsar binaries is currently 1.6 hr. The absence of pulsar binaries with a shorter orbital period is most likely due to technique limit. This paper points out that a tidal effect occurring on pulsar binaries with a short orbital period can perturb the orbital elements and result in a significant change in orbital modulation, which dramatically reduces the sensitivity of the acceleration searching that is widely used. Here a new search is proposed. The abnormal timing residual exhibited in a single pulse observation is simulated by a tidal effect occurring on an ultra-compact binary. The reproduction of the main features represented by the sharp peaks displayed in the abnormal timing behavior suggests that pulsars like PSR B0919+06 could be a candidate for an ultra-compact binary of an orbital period of ∼10 minutes and a companion star of a white dwarf star. The binary nature of such a candidate is further tested by (1) comparing the predicted long-term binary effect with decades of timing noise observed and (2) observing the optical counterpart of the expected companion star. Test (1) likely supports our model, while more observations are needed in test (2). Some interesting ultra-compact binaries could be found in the near future by applying such a new approach to other binary candidates.

Dynamic mass exchange in doubly degenerate binaries. I - 0.9 and 1.2 solar mass stars

NASA Technical Reports Server (NTRS)

Benz, W.; Cameron, A. G. W.; Press, W. H.; Bowers, R. L.

1990-01-01

The dynamic mass exchange process in doubly degenerate binaries was investigated using a three-dimensional numerical simulation of the evolution of a doubly degenerate binary system in which the primary is a 1.2-solar-mass white dwarf and the Roche lobe filling secondary is a 0.9-solar-mass dwarf. The results show that, in a little more than two orbital periods, the secondary is completely destroyed and transformed into a thick disk orbiting about the primary. Since only a very small fraction of the mass (0.0063 solar mass) escapes the system, the evolution of the binary results in the formation of a massive object. This object is composed of three parts, the initial white dwarf primary, a very hot pressure-supported spherical envelope, and a rotationally supported outer disk. The evolution of the system can be understood in terms of a simple analytical model where it is shown that the angular momentum carried by the mass during the transfer and stored in the disk determines the evolution of the system.

Mechanistical studies on the formation of carbon dioxide in extraterrestrial carbon monoxide ice analog samples.

PubMed

Bennett, Chris J; Jamieson, Corey S; Kaiser, Ralf I

2009-06-07

Binary ice mixtures of two carbon monoxide isotopomers, (13)C(16)O and (12)C(18)O, were subjected at 10 K to energetic electrons to investigate the interaction of ionizing radiation with extraterrestrial, carbon monoxide bearing ices. The chemical modifications were monitored on line and in situ via absorption-reflection-absorption Fourier transform infrared spectroscopy as well as in the gas-phase via a quadrupole mass spectrometer. Detected products include two newly formed carbon monoxide isotopomers ((12)C(16)O and (13)C(18)O), carbon dioxide ((12)C(16)O(2), (12)C(18)O(16)O, (12)C(18)O(2), (13)C(16)O(2), (13)C(18)O(16)O, and (13)C(18)O(2)), and dicarbon monoxide ((12)C(13)C(16)O and (13)C(13)C(16)O). Kinetic profiles of carbon monoxide and of carbon dioxide were extracted and fit to derive reaction mechanisms and information on the decomposition of carbon monoxide and on the formation of carbon dioxide in extraterrestrial ice analog samples.

A near-infrared surface compositional analysis of blue straggler stars in open cluster M67.

NASA Astrophysics Data System (ADS)

Seifert, Richard; Gosnell, Natalie M.; Sneden, Chris

2017-01-01

Blue straggler stars (BSSs) are stars whose evolutions have been directly impacted by binary system interactions. By obtaining additional mass from a companion, BSSs are able to live prolonged lives on the main sequence. BSSs bring confusions to studies that rely on a standard stellar evolutionary track when modeling stellar populations, since the presence of BSSs can make a population appear younger than it actually is. It is important to have a better understanding of the mechanisms that drive BSS formation so that BSSs may be correctly accounted for in future studies.What we know about BSS formation is that they form in one of two ways. Either from a close binary system in which one star accretes mass from its companion star or from a hierarchical trinary system in which a close inner binary merges as a result of perturbations from a farther-orbiting third star. What we don’t know are the relative frequencies of these two formation mechanisms. To investigate this problem, We obtained IGRINS near-IR (H- & K-band) high resolution spectra of 6 BSSs and 12 red giant stars in open cluster M67. Using a grid of synthetic spectra obtained from the line analysis code MOOG, we identified and fit abundances for absorption lines of iron, carbon, nitrogen, and oxygen. The latter three elements can be affected by internal hydrogen fusion, mixing, and binary mass transfer. In the BSS mass accretion mechanism, there should be enhanced abundances of these elements on the surfaces of BSSs. By analyzing the abundances of these elements in our BSS spectra, we determine the formation mechanism for each member of our BSS sample.Funding for this research comes from the John W. Cox endowment for the Advanced Studies in Astronomy. For support of this work we acknowledge NSF grants AST-1211585 and AST-1616040 to CS. The successful development of the IGRINS spectrograph has resulted from the combined efforts of teams at the University of Texas at Austin and the Korea Astronomy and Space Science Institute; their work is gratefully acknowledged.

Defining a Materials Database for the Design of Copper Binary Alloy Catalysts for Electrochemical CO2 Conversion.

PubMed

Lee, Chan Woo; Yang, Ki Dong; Nam, Dae-Hyun; Jang, Jun Ho; Cho, Nam Heon; Im, Sang Won; Nam, Ki Tae

2018-01-24

While Cu electrodes are a versatile material in the electrochemical production of desired hydrocarbon fuels, Cu binary alloy electrodes are recently proposed to further tune reaction directionality and, more importantly, overcome the intrinsic limitation of scaling relations. Despite encouraging empirical demonstrations of various Cu-based metal alloy systems, the underlying principles of their outstanding performance are not fully addressed. In particular, possible phase segregation with concurrent composition changes, which is widely observed in the field of metallurgy, is not at all considered. Moreover, surface-exposed metals can easily form oxide species, which is another pivotal factor that determines overall catalytic properties. Here, the understanding of Cu binary alloy catalysts for CO 2 reduction and recent progress in this field are discussed. From the viewpoint of the thermodynamic stability of the alloy system and elemental mixing, possible microstructures and naturally generated surface oxide species are proposed. These basic principles of material science can help to predict and understand metal alloy structure and, moreover, act as an inspiration for the development of new binary alloy catalysts to further improve CO 2 conversion and, ultimately, achieve a carbon-neutral cycle. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon Nanomaterials in Direct Liquid Fuel Cells.

PubMed

Du, Huayun; Zhao, Cindy Xinxin; Lin, Jing; Guo, Jiang; Wang, Bin; Hu, Zhen; Shao, Qian; Pan, Duo; Wujcik, Evan K; Guo, Zhanhu

2018-04-19

Fuel cells have attracted more attentions due to many advantages they can provide, including high energy efficiency and low environmental burden. To form a stable, low cost and efficient catalyst, we presented here the state of the art of electrocatalyst fabrication approaches, involving carbon nanotubes and their multifunctional nanocomposites incorporated with noble metals, such as Pt, Pd, Au, their binary and ternary systems. Both fuel oxidation reactions and oxygen reduction reactions were emphasized with comprehensive examples and future prospects. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystallization of pure anhydrous polymorphs of carbamazepine by solution enhanced dispersion with supercritical fluids (SEDS).

PubMed

Edwards, A D; Shekunov, B Y; Kordikowski, A; Forbes, R T; York, P

2001-08-01

Pure anhydrous polymorphs of carbamazepine were prepared by solution-enhanced dispersion with supercritical fluids (SEDS). Crystallization of the polymorphs was studied. Mechanisms are proposed that consider the thermodynamics of carbamazepine, supersaturation in the SEDS process, and the binary phase equilibria of organic solvents and the carbon dioxide antisolvent. alpha-Carbamazepine was crystallized at high supersaturations and low temperatures, beta-carbamazepine crystallized from a methanol-carbon dioxide phase split, and gamma-carbamazepine crystallized via nucleation at high temperatures and low supersaturation. Copyright 2001 Wiley-Liss, Inc.

Synthesis, characterisation and applications of coiled carbon nanotubes.

PubMed

Hanus, Monica J; Harris, Andrew T

2010-04-01

Coiled carbon nanotubes are helical carbon structures formed when heptagonal and pentagonal rings are inserted into the hexagonal backbone of a 'straight' nanotube. Coiled carbon nanotubes have been reported with both regular and irregular helical structures. In this work the structure, growth mechanism(s), synthesis, properties and potential applications of coiled carbon nanotubes are reviewed. Published data suggests that coiled carbon nanotube synthesis occurs due to nonuniform extrusion of carbon from a catalyst surface. To date, coiled carbon nanotubes have been synthesised using catalyst modification techniques including: (i) the addition of S or P containing compounds during synthesis; (ii) the use of binary or ternary metal catalysts; (iii) the use of microwaves to create a local temperature gradient around individual catalyst particles and; (iv) the use of pH control during catalyst preparation. In most instances coiled carbon nanotubes are produced as a by-product; high yield and/or large-scale synthesis of coiled carbon nanotubes remains problematic. The qualitative analysis of coiled carbon nanotubes is currently hindered by the absence of specific characterisation data in the literature, e.g., oxidation profiles measured by thermogravimetric analysis and Raman spectra of pure coiled carbon nanotube samples.

Conversion of stranded waste-stream carbon and nutrients into value-added products via metabolically coupled binary heterotroph-photoautotroph system.

PubMed

Bohutskyi, Pavlo; Kucek, Leo A; Hill, Eric; Pinchuk, Grigoriy E; Mundree, Sagadevan G; Beliaev, Alexander S

2018-07-01

Growth of heterotrophic bacterium Bacillus subtilis was metabolically coupled with the photosynthetic activity of an astaxanthin-producing alga Haematococcus pluvialis for conversion of starch-containing waste stream into carotenoid-enriched biomass. The H. pluvialis accounted for 63% of the produced co-culture biomass of 2.2 g/L. Importantly, the binary system requires neither exogenous supply of gaseous substrates nor application of energy-intensive mass transfer technologies due to in-situ exchange in CO 2 and O 2 . The maximum reduction in COD, total nitrogen and phosphorus reached 65%, 55% and 30%, respectively. Conducted techno-economic assessment suggested that the astaxanthin-rich biomass may potentially offset the costs of waste treatment, and, with specific productivity enhancements (induction of astaxanthin to 2% and increase H. pluvialis fraction to 80%), provide and additional revenue stream. The outcome of this study demonstrates a successful proof-of-principle for conversion of waste carbon and nutrients into value-added products through metabolic coupling of heterotrophic and phototrophic metabolisms. Copyright © 2018. Published by Elsevier Ltd.

The mid-infrared spectrum of the carbon star HD 38218 and its possible relation to polycyclic aromatic hydrocarbons

NASA Technical Reports Server (NTRS)

Buss, Richard H., Jr.; Tielens, A. G. G. M.; Snow, Theodore P.

1991-01-01

The mid-infrared spectra of carbon giant stars with hot companions are investigated in order to search for infrared emission bands from polycyclic aromatic hydrocarbons (PAH) in the envelopes of the C giants. A strong 8-micron emission band found in TU Tau = HD 38218 is attributed to the binary A star companion. It is argued that if the 8-micron feature in HD 38218 arises from PAHs, they seem to be important constituents of the C-giant shell, and they might be large compared with some interstellar PAHs. It is suggested that because no other IR spectra of C giants show clear PAH features, the greater flux of hard radiation in the binary HD 38218 seems likely to be responsible for the 8-micron feature and for its absence in many other C giants. Thus, PAHs could be present in the same amounts relative to SiC grains in the shells of similar single C giants, and the formation of carbonaceous grains could proceed through the formation of PAHs in C giant shells.

Growth of normally-immiscible materials (NIMs), binary alloys, and metallic fibers by hyperbaric laser chemical vapor deposition

NASA Astrophysics Data System (ADS)

Maxwell, J. L.; Black, M. R.; Chavez, C. A.; Maskaly, K. R.; Espinoza, M.; Boman, M.; Landstrom, L.

2008-06-01

This work demonstrates that two or more elements of negligible solubility (and no known phase diagram) can be co-deposited in fiber form by hyperbaric-pressure laser chemical vapor deposition (HP-LCVD). For the first time, Hg-W alloys were grown as fibers from mixtures of tungsten hexafluoride, mercury vapor, and hydrogen. This new class of materials is termed normally-immiscible materials (NIMs), and includes not only immiscible materials, but also those elemental combinations that have liquid states at exclusive temperatures. This work also demonstrates that a wide variety of other binary and ternary alloys, intermetallics, and mixtures can be grown as fibers, e.g. silicon-tungsten, aluminum-silicon, boron-carbon-silicon, and titanium-carbon-nitride. In addition, pure metallic fibers of aluminum, titanium, and tungsten were deposited, demonstrating that materials of high thermal conductivity can indeed be grown in three-dimensions, provided sufficient vapor pressures are employed. A wide variety of fiber properties and microstructures resulted depending on process conditions; for example, single crystals, fine-grained alloys, and glassy metals could be deposited.

A binary main-belt comet.

PubMed

Agarwal, Jessica; Jewitt, David; Mutchler, Max; Weaver, Harold; Larson, Stephen

2017-09-20

Asteroids are primitive Solar System bodies that evolve both collisionally and through disruptions arising from rapid rotation. These processes can lead to the formation of binary asteroids and to the release of dust, both directly and, in some cases, through uncovering frozen volatiles. In a subset of the asteroids called main-belt comets, the sublimation of excavated volatiles causes transient comet-like activity. Torques exerted by sublimation measurably influence the spin rates of active comets and might lead to the splitting of bilobate comet nuclei. The kilometre-sized main-belt asteroid 288P (300163) showed activity for several months around its perihelion 2011 (ref. 11), suspected to be sustained by the sublimation of water ice and supported by rapid rotation, while at least one component rotates slowly with a period of 16 hours (ref. 14). The object 288P is part of a young family of at least 11 asteroids that formed from a precursor about 10 kilometres in diameter during a shattering collision 7.5 million years ago. Here we report that 288P is a binary main-belt comet. It is different from the known asteroid binaries in its combination of wide separation, near-equal component size, high eccentricity and comet-like activity. The observations also provide strong support for sublimation as the driver of activity in 288P and show that sublimation torques may play an important part in binary orbit evolution.

Thermodynamic Parameterization of Subduction-Zone Devolatilization and Application to Quantify Carbon Fluxes from Slab

NASA Astrophysics Data System (ADS)

Tian, M.; Katz, R. F.; Rees Jones, D. W.; May, D.

2017-12-01

Compared with other plate-tectonic boundaries, subduction zones (SZ) host the most drastic mechanical, thermal, and chemical changes. The transport of carbon through this complex environment is crucial to mantle carbon budget but remains the subject of active debate. Synthesis of field studies suggests that carbon subducted with the incoming slab is almost completely returned to the surface environment [Kelemen and Manning, 2015], whereas thermodynamic modelling indicates that a significant portion of carbon is retained in the slab and descends into the deep mantle [Gorman et al., 2006]. To address this controversy and quantify the carbon fluxes within SZs, it is necessary to treat the chemistry of fluid/volatile-rock interaction and the mechanics of porous fluid/volatile migration in a consistent modelling framework. This requirement is met by coupling a thermodynamic parameterization of de/re-volatilization with a two-phase flow model of subduction zones. The two-phase system is assumed to comprise three chemical components: rock containing only non-volatile oxides, H2O and CO2; the fluid phase includes only the latter two. Perple_X is used to map out the binary subsystems rock+H2O and rock+CO2; the results are parameterised in terms of volatile partition coefficients as a function of pressure and temperature. In synthesising the binary subsystems to describe phase equilibria that incorporate all three components, a Margules coefficient is introduced to account for non-ideal mixing of CO2/H2O in the fluid, such that the partition coefficients depend further on bulk composition. This procedure is applied to representative compositions of sediment, MORB, and gabbro for the slab, and peridotite for the mantle. The derived parameterization of each rock type serves as a lightweight thermodynamic module interfaceable with two-phase flow models of SZs. We demonstrate the application of this thermodynamic module through a simple model of carbon flux with a prescribed flow direction through (and out of) the slab. This model allows us to evaluate the effects of flow path and lithology on carbon storage within the slab.

Hierarchically self-assembled hexagonal honeycomb and kagome superlattices of binary 1D colloids.

PubMed

Lim, Sung-Hwan; Lee, Taehoon; Oh, Younghoon; Narayanan, Theyencheri; Sung, Bong June; Choi, Sung-Min

2017-08-25

Synthesis of binary nanoparticle superlattices has attracted attention for a broad spectrum of potential applications. However, this has remained challenging for one-dimensional nanoparticle systems. In this study, we investigate the packing behavior of one-dimensional nanoparticles of different diameters into a hexagonally packed cylindrical micellar system and demonstrate that binary one-dimensional nanoparticle superlattices of two different symmetries can be obtained by tuning particle diameter and mixing ratios. The hexagonal arrays of one-dimensional nanoparticles are embedded in the honeycomb lattices (for AB 2 type) or kagome lattices (for AB 3 type) of micellar cylinders. The maximization of free volume entropy is considered as the main driving force for the formation of superlattices, which is well supported by our theoretical free energy calculations. Our approach provides a route for fabricating binary one-dimensional nanoparticle superlattices and may be applicable for inorganic one-dimensional nanoparticle systems.Binary mixtures of 1D particles are rarely observed to cooperatively self-assemble into binary superlattices, as the particle types separate into phases. Here, the authors design a system that avoids phase separation, obtaining binary superlattices with different symmetries by simply tuning the particle diameter and mixture composition.

How important is thermodynamics for identifying elementary flux modes?

PubMed Central

Peres, Sabine; Jolicœur, Mario; Moulin, Cécile

2017-01-01

We present a method for computing thermodynamically feasible elementary flux modes (tEFMs) using equilibrium constants without need of internal metabolite concentrations. The method is compared with the method based on a binary distinction between reversible and irreversible reactions. When all reactions are reversible, adding the constraints based on equilibrium constants reduces the number of elementary flux modes (EFMs) by a factor of two. Declaring in advance some reactions as irreversible, based on reliable biochemical expertise, can in general reduce the number of EFMs by a greater factor. But, even in this case, computing tEFMs can rule out some EFMs which are biochemically irrelevant. We applied our method to two published models described with binary distinction: the monosaccharide metabolism and the central carbon metabolism of Chinese hamster ovary cells. The results show that the binary distinction is in good agreement with biochemical observations. Moreover, the suppression of the EFMs that are not consistent with the equilibrium constants appears to be biologically relevant. PMID:28222104

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.

Mass retention efficiencies of He accretion onto carbon-oxygen white dwarfs and type Ia supernovae

NASA Astrophysics Data System (ADS)

Wu, C.; Wang, B.; Liu, D.; Han, Z.

2017-07-01

Context. Type Ia supernovae (SNe Ia) play a crucial role in studying cosmology and galactic chemical evolution. They are thought to be thermonuclear explosions of carbon-oxygen white dwarfs (CO WDs) when their masses reach the Chandrasekar mass limit in binaries. Previous studies have suggested that He novae may be progenitor candidates of SNe Ia. However, the mass retention efficiencies during He nova outbursts are still uncertain. Aims: In this article, we aim to study the mass retention efficiencies of He nova outbursts and to investigate whether SNe Ia can be produced through He nova outbursts. Methods: Using the stellar evolution code Modules for Experiments in Stellar Astrophysics, we simulated a series of multicycle He-layer flashes, in which the initial WD masses range from 0.7 to 1.35 M⊙ with various accretion rates. Results: We obtained the mass retention efficiencies of He nova outbursts for various initial WD masses, which can be used in the binary population synthesis studies. In our simulations, He nova outbursts can increase the mass of the WD to the Chandrasekar mass limit and the explosive carbon burning can be triggered in the center of the WD; this suggests that He nova outbursts can produce SNe Ia. Meanwhile, the mass retention efficiencies in the present work are lower than those of previous studies, which leads to a lower birthrates of SNe Ia through the WD + He star channel. Furthermore, we obtained the elemental abundances distribution at the moment of explosive carbon burning, which can be used as the initial input parameters in studying explosion models of SNe Ia.

Organosilica Membrane with Ionic Liquid Properties for Separation of Toluene/H₂ Mixture.

PubMed

Hirota, Yuichiro; Maeda, Yohei; Yamamoto, Yusuke; Miyamoto, Manabu; Nishiyama, Norikazu

2017-08-03

In this study, we present a new concept in chemically stabilized ionic liquid membranes: an ionic liquid organosilica (ILOS) membrane, which is an organosilica membrane with ionic liquid-like properties. A silylated ionic liquid was used as a precursor for synthesis. The permselectivity, permeation mechanism, and stability of the membrane in the H₂/toluene binary system were then compared with a supported ionic liquid membrane. The membrane showed a superior separation factor of toluene/H₂ (>17,000) in a binary mixture system based on a solution-diffusion mechanism with improved durability over the supported ionic liquid membrane.

PatternCoder: A Programming Support Tool for Learning Binary Class Associations and Design Patterns

ERIC Educational Resources Information Center

Paterson, J. H.; Cheng, K. F.; Haddow, J.

2009-01-01

PatternCoder is a software tool to aid student understanding of class associations. It has a wizard-based interface which allows students to select an appropriate binary class association or design pattern for a given problem. Java code is then generated which allows students to explore the way in which the class associations are implemented in a…

The effect of vapor polarity and boiling point on breakthrough for binary mixtures on respirator carbon.

PubMed

Robbins, C A; Breysse, P N

1996-08-01

This research evaluated the effect of the polarity of a second vapor on the adsorption of a polar and a nonpolar vapor using the Wheeler model. To examine the effect of polarity, it was also necessary to observe the effect of component boiling point. The 1% breakthrough time (1% tb), kinetic adsorption capacity (W(e)), and rate constant (kv) of the Wheeler model were determined for vapor challenges on carbon beds for both p-xylene and pyrrole (referred to as test vapors) individually, and in equimolar binary mixtures with the polar and nonpolar vapors toluene, p-fluorotoluene, o-dichlorobenzene, and p-dichlorobenzene (referred to as probe vapors). Probe vapor polarity (0 to 2.5 Debye) did not systematically alter the 1% tb, W(e), or kv of the test vapors. The 1% tb and W(e) for test vapors in binary mixtures can be estimated reasonably well, using the Wheeler model, from single-vapor data (1% tb +/- 30%, W(e) +/- 20%). The test vapor 1% tb depended mainly on total vapor concentration in both single and binary systems. W(e) was proportional to test vapor fractional molar concentration (mole fraction) in mixtures. The kv for p-xylene was significantly different (p < or = 0.001) when compared according to probe boiling point; however, these differences were apparently of limited importance in estimating 1% tb for the range of boiling points tested (111 to 180 degrees C). Although the polarity and boiling point of chemicals in the range tested are not practically important in predicting 1% tb with the Wheeler model, an effect due to probe boiling point is suggested, and tests with chemicals of more widely ranging boiling point are warranted. Since the 1% tb, and thus, respirator service life, depends mainly on total vapor concentration, these data underscore the importance of taking into account the presence of other vapors when estimating respirator service life for a vapor in a mixture.

Probing the Milky Way electron density using multi-messenger astronomy

NASA Astrophysics Data System (ADS)

Breivik, Katelyn; Larson, Shane

2015-04-01

Multi-messenger observations of ultra-compact binaries in both gravitational waves and electromagnetic radiation supply highly complementary information, providing new ways of characterizing the internal dynamics of these systems, as well as new probes of the galaxy itself. Electron density models, used in pulsar distance measurements via the electron dispersion measure, are currently not well constrained. Simultaneous radio and gravitational wave observations of pulsars in binaries provide a method of measuring the average electron density along the line of sight to the pulsar, thus giving a new method for constraining current electron density models. We present this method and assess its viability with simulations of the compact binary component of the Milky Way using the public domain binary evolution code, BSE. This work is supported by NASA Award NNX13AM10G.

Hot gas, regenerative, supported H.sub.2 S sorbents

NASA Technical Reports Server (NTRS)

Voecks, Gerald E. (Inventor); Sharma, Pramod K. (Inventor)

1993-01-01

Efficient, regenerable sorbents for removal of H.sub.2 S from moderately high temperature (usually 200.degree. C.-550.degree.C.) gas streams comprise a porous, high surface area aluminosilicate support, suitably a zeolite, and most preferably a sodium deficient zeolite containing 1 to 20 weight percent of binary metal oxides. The binary oxides are a mixture of a Group VB or VIB metal oxide with a Group IB, IIB or VIII metal oxide such as V-Zn-O, V-Cu-O, Cu-Mo-O, Zn-Mo-O or Fe-Mo-O contained in the support. The sorbent effectively removes H.sub.2 S from the host gas stream in high efficiency and can be repetitively regenerated at least 10 times without loss of activity.

Adaptive Optics Imaging of the Circumbinary Disk around the T Tauri Binary UY Aurigae: Estimates of the Binary Mass and Circumbinary Dust Grain Size Distribution

NASA Astrophysics Data System (ADS)

Close, L. M.; Dutrey, A.; Roddier, F.; Guilloteau, S.; Roddier, C.; Northcott, M.; Ménard, F.; Duvert, G.; Graves, J. E.; Potter, D.

1998-05-01

We have obtained high-resolution (FWHM = 0.15") deep images of the UY Aur binary at J, H, and K' with the University of Hawaii adaptive optics instrument. We clearly detect an R ~ 500 AU circumbinary disk discovered with millimeter interferometry, making UY Aur the second young binary with a confirmed circumbinary disk. It appears that the disk is inclined ~42° from face on. We find that the near side of the disk is brighter than the far side by factors of 2.6, 2.7, and 6.5 times at K', H, and J, respectively. The original GG Tau circumbinary disk has been reexamined and is found to have similar flux ratios of 1.5, 2.6, and 3.6 at K', H, and J, respectively. A realistic power-law distribution (p = 4.7) of spherical dust aggregates (composed of silicates, amorphous carbon, and graphite) that reproduces the observed ISM extinction curve also predicts these observed flux ratios from Mie scattering theory. We find the observed preference of forward-scattering over back-scattering is well fitted (global χ2 minimization) by Mie scattering off particles in the range amin = 0.03 μm to amax = 0.5-0.6 μm. The existence of a significant population of grain radii larger than 0.6 μm is not supported by the scattering observations. Based on the observed disk inclination we derive an orbit for UY Aur where the mass for the binary is 1.6+0.47-0.67 M⊙. Based on the observed K7 and M0 spectral types for UY Aur A and B, accretion disk models for the inner disks around the central stars were constructed. The models suggest that small (lower limit R ~ 5-10 AU) inner disks exist around B and A. It appears that B is accreting ~5 times faster than A, and that both inner disks may be exhausted in ~102-103 yr without replenishment from the outer circumbinary disk. Our images suggest that these inner disks may indeed be resupplied with material through thin streamers of material that penetrate inside the circumbinary disk. Currently it appears that such a streamer may be a close to UY Aur B. Comparison of our IR images and the millimeter images of the gas clearly show that the dust seen in our IR images traces the gas in the circumbinary disk, as was also the case with GG Tau.

The unusual carbon star HD 59643 - Alternative models

NASA Technical Reports Server (NTRS)

Johnson, H. R.; Eaton, J. A.; Querci, F. R.; Querci, M.; Baumert, J. H.

1988-01-01

A binary model for the carbon star HD 59643 is discussed in which the secondary spectrum is formed in an accretion disk. If this hot, ultraviolet-emitting disk radiates like a 20,000 K black-body, it must be 0.03 solar radii or less across at minimum emission. Large widths of C IV multiplet UV1 on high-resolution spectra indicate its formation in the inner parts of a disk. The semiforbidden C III and Si III lines, however, are much narrower and could be formed in the outer parts of a disk or in the carbon star's chromosphere. The electron density in the region of formation of C III is about 10 to the 10th/cu cm.

Are some CEMP-s stars the daughters of spinstars?

NASA Astrophysics Data System (ADS)

Choplin, Arthur; Hirschi, Raphael; Meynet, Georges; Ekström, Sylvia

2017-11-01

Carbon-enhanced metal-poor (CEMP)-s stars are long-lived low-mass stars with a very low iron content as well as overabundances of carbon and s-elements. Their peculiar chemical pattern is often explained by pollution from an asymptotic giant branch (AGB) star companion. Recent observations have shown that most CEMP-s stars are in binary systems, providing support to the AGB companion scenario. A few CEMP-s stars, however, appear to be single. We inspect four apparently single CEMP-s stars and discuss the possibility that they formed from the ejecta of a previous-generation massive star, referred to as the "source" star. In order to investigate this scenario, we computed low-metallicity massive-star models with and without rotation and including complete s-process nucleosynthesis. We find that non-rotating source stars cannot explain the observed abundance of any of the four CEMP-s stars. Three out of the four CEMP-s stars can be explained by a 25M⊙ source star with vini 500 km s-1 (spinstar). The fourth CEMP-s star has a high Pb abundance that cannot be explained by any of the models we computed. Since spinstars and AGB predict different ranges of [O/Fe] and [ls/hs], these ratios could be an interesting way to further test these two scenarios.

Micro/nanostructured porous Fe-Ni binary oxide and its enhanced arsenic adsorption performances.

PubMed

Liu, Shengwen; Kang, Shenghong; Wang, Guozhong; Zhao, Huijun; Cai, Weiping

2015-11-15

A simple method is presented to synthesize micro/nano-structured Fe-Ni binary oxides based on co-precipitation and subsequent calcination. It has been found that the Fe-Ni binary oxides are composed of the porous microsized aggregates built with nanoparticles. When the atomic ratio of Fe to Ni is 2 to 1 the binary oxide is the micro-scaled aggregates consisting of the ultrafine NiFe2O4 nanoparticles with 3-6nm in size, and shows porous structure with pore diameter of 3nm and a specific surface area of 245m(2)g(-1). Such material is of abundant surface functional groups and has exhibited high adsorption performance to As(III) and As(V). The kinetic adsorption can be described by pseudo-second order model and the isothermal adsorption is subject to Langmuir model. The maximum adsorption capacity on such Fe-Ni porous binary oxide is up to 168.6mgg(-1) and 90.1mgg(-1) for As(III) and As(V), respectively, which are much higher than the arsenic adsorption capacity for most commercial adsorbents. Such enhanced adsorption ability for this material is mainly attributed to its porous structure and high specific surface area as well as the abundant surface functional groups. Further experiments have revealed that the influence of the anions such as sulfate, carbonate, and phosphate, which commonly co-exist in water, on the arsenic adsorption is insignificant, exhibiting strong adsorption selectivity to arsenic. This micro/nano-structured porous Fe-Ni binary oxide is hence of good practicability to be used as a highly efficient adsorbent for arsenic removal from the real arsenic-contaminated waters. Copyright © 2015 Elsevier Inc. All rights reserved.

UNDERSTANDING THE EVOLUTION OF CLOSE BINARY SYSTEMS WITH RADIO PULSARS

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

Benvenuto, O. G.; De Vito, M. A.; Horvath, J. E., E-mail: obenvenu@fcaglp.unlp.edu.ar, E-mail: adevito@fcaglp.unlp.edu.ar, E-mail: foton@astro.iag.usp.br

We calculate the evolution of close binary systems (CBSs) formed by a neutron star (behaving as a radio pulsar) and a normal donor star, which evolve either to a helium white dwarf (HeWD) or to ultra-short orbital period systems. We consider X-ray irradiation feedback and evaporation due to radio pulsar irradiation. We show that irradiation feedback leads to cyclic mass transfer episodes, allowing CBSs to be observed in between episodes as binary radio pulsars under conditions in which standard, non-irradiated models predict the occurrence of a low-mass X-ray binary. This behavior accounts for the existence of a family of eclipsingmore » binary systems known as redbacks. We predict that redback companions should almost fill their Roche lobe, as observed in PSR J1723-2837. This state is also possible for systems evolving with larger orbital periods. Therefore, binary radio pulsars with companion star masses usually interpreted as larger than expected to produce HeWDs may also result in such quasi-Roche lobe overflow states, rather than hosting a carbon-oxygen WD. We found that CBSs with initial orbital periods of P{sub i} < 1 day evolve into redbacks. Some of them produce low-mass HeWDs, and a subgroup with shorter P{sub i} becomes black widows (BWs). Thus, BWs descend from redbacks, although not all redbacks evolve into BWs. There is mounting observational evidence favoring BW pulsars to be very massive (≳ 2 M {sub ☉}). As they should be redback descendants, redback pulsars should also be very massive, since most of the mass is transferred before this stage.« less

The Lore of the Hair

NASA Astrophysics Data System (ADS)

Yunes, Nicolas; Yagi, Kent; Stein, Leo

2016-03-01

Stars can be hairy beasts, especially in theories that go beyond Einstein's. In the latter, a scalar field can be sourced and anchored to a neutron star, and if the later is in a binary system, the scalar field will emit dipole radiation. This radiation removes energy from the binary, forcing the orbit to adiabatically decay much more rapidly than due to the emission of gravitational waves as predicted in General Relativity. The detailed radio observation of binary pulsars has constrained the orbital decay of compact binaries stringently, so much so that theories that predict neutron stars with scalar hair are believed to be essentially ruled out. In this talk I will explain why this ``lore'' is actually incorrect, providing a counter-example in which scalar hair is sourced by neutron stars, yet dipole radiation is absent. I will then describe what binary systems need to be observed to constrain such theories with future astrophysical observations. I acknowledge support from NSF CAREER Grant PHY-1250636.

Finite-Size Effects of Binary Mutual Diffusion Coefficients from Molecular Dynamics

PubMed Central

2018-01-01

Molecular dynamics simulations were performed for the prediction of the finite-size effects of Maxwell-Stefan diffusion coefficients of molecular mixtures and a wide variety of binary Lennard–Jones systems. A strong dependency of computed diffusivities on the system size was observed. Computed diffusivities were found to increase with the number of molecules. We propose a correction for the extrapolation of Maxwell–Stefan diffusion coefficients to the thermodynamic limit, based on the study by Yeh and Hummer (J. Phys. Chem. B, 2004, 108, 15873−15879). The proposed correction is a function of the viscosity of the system, the size of the simulation box, and the thermodynamic factor, which is a measure for the nonideality of the mixture. Verification is carried out for more than 200 distinct binary Lennard–Jones systems, as well as 9 binary systems of methanol, water, ethanol, acetone, methylamine, and carbon tetrachloride. Significant deviations between finite-size Maxwell–Stefan diffusivities and the corresponding diffusivities at the thermodynamic limit were found for mixtures close to demixing. In these cases, the finite-size correction can be even larger than the simulated (finite-size) Maxwell–Stefan diffusivity. Our results show that considering these finite-size effects is crucial and that the suggested correction allows for reliable computations. PMID:29664633

BOREAS TGB-12 Soil Carbon and Flux Data of NSA-MSA in Raster Format

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Knapp, David E. (Editor); Rapalee, Gloria; Davidson, Eric; Harden, Jennifer W.; Trumbore, Susan E.; Veldhuis, Hugo

2000-01-01

The BOREAS TGB-12 team made measurements of soil carbon inventories, carbon concentration in soil gases, and rates of soil respiration at several sites. This data set provides: (1) estimates of soil carbon stocks by horizon based on soil survey data and analyses of data from individual soil profiles; (2) estimates of soil carbon fluxes based on stocks, fire history, drain-age, and soil carbon inputs and decomposition constants based on field work using radiocarbon analyses; (3) fire history data estimating age ranges of time since last fire; and (4) a raster image and an associated soils table file from which area-weighted maps of soil carbon and fluxes and fire history may be generated. This data set was created from raster files, soil polygon data files, and detailed lab analysis of soils data that were received from Dr. Hugo Veldhuis, who did the original mapping in the field during 1994. Also used were soils data from Susan Trumbore and Jennifer Harden (BOREAS TGB-12). The binary raster file covers a 733-km 2 area within the NSA-MSA.

Hydrodynamical Evolution of Merging Carbon-Oxygen White Dwarfs: Their Pre-supernova Structure and Observational Counterparts

NASA Astrophysics Data System (ADS)

Tanikawa, Ataru; Nakasato, Naohito; Sato, Yushi; Nomoto, Ken'ichi; Maeda, Keiichi; Hachisu, Izumi

2015-07-01

We perform smoothed particle hydrodynamics simulations for merging binary carbon-oxygen (CO) WDs with masses of 1.1 and 1.0 {M}⊙ , until the merger remnant reaches a dynamically steady state. Using these results, we assess whether the binary could induce a thermonuclear explosion, and whether the explosion could be observed as a type Ia supernova (SN Ia). We investigate three explosion mechanisms: a helium-ignition following the dynamical merger (“helium-ignited violent merger model”), a carbon-ignition (“carbon-ignited violent merger model”), and an explosion following the formation of the Chandrasekhar mass WD (“Chandrasekhar mass model”). An explosion of the helium-ignited violent merger model is possible, while we predict that the resulting SN ejecta are highly asymmetric since its companion star is fully intact at the time of the explosion. The carbon-ignited violent merger model can also lead to an explosion. However, the envelope of the exploding WD spreads out to ˜ 0.1 {R}⊙ ; it is much larger than that inferred for SN 2011fe (\\lt 0.1 {R}⊙ ) while much smaller than that for SN 2014J (˜ 1 {R}⊙ ). For the particular combination of the WD masses studied in this work, the Chandrasekhar mass model does not successfully lead to an SN Ia explosion. Besides these assessments, we investigate the evolution of unbound materials ejected through the merging process (“merger ejecta”), assuming a case where the SN Ia explosion is not triggered by the helium- or carbon-ignition during the merger. The merger ejecta interact with the surrounding interstellar medium and form a shell. The shell has a bolometric luminosity of more than 2× {10}35 {erg} {{{s}}}-1, lasting for ˜ 2× {10}4 years. If this is the case, the Milky Way should harbor about 10 such shells at any given time. The detection of the shell(s) can therefore rule out the helium-ignited and carbon-ignited violent merger models as major paths to SN Ia explosions.

Measurements of Physical Parameters of White Dwarfs: A Test of the Mass–Radius Relation

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

Bédard, A.; Bergeron, P.; Fontaine, G., E-mail: bedard@astro.umontreal.ca, E-mail: bergeron@astro.umontreal.ca, E-mail: fontaine@astro.umontreal.ca

We present a detailed spectroscopic and photometric analysis of 219 DA and DB white dwarfs for which trigonometric parallax measurements are available. Our aim is to compare the physical parameters derived from the spectroscopic and photometric techniques, and then to test the theoretical mass–radius relation for white dwarfs using these results. The agreement between spectroscopic and photometric parameters is found to be excellent, especially for effective temperatures, showing that our model atmospheres and fitting procedures provide an accurate, internally consistent analysis. The values of surface gravity and solid angle obtained, respectively, from spectroscopy and photometry, are combined with parallax measurementsmore » in various ways to study the validity of the mass–radius relation from an empirical point of view. After a thorough examination of our results, we find that 73% and 92% of the white dwarfs are consistent within 1 σ and 2 σ confidence levels, respectively, with the predictions of the mass–radius relation, thus providing strong support to the theory of stellar degeneracy. Our analysis also allows us to identify 15 stars that are better interpreted in terms of unresolved double degenerate binaries. Atmospheric parameters for both components in these binary systems are obtained using a novel approach. We further identify a few white dwarfs that are possibly composed of an iron core rather than a carbon/oxygen core, since they are consistent with Fe-core evolutionary models.« less

ThermoData Engine (TDE): software implementation of the dynamic data evaluation concept. 9. Extensible thermodynamic constraints for pure compounds and new model developments.

PubMed

Diky, Vladimir; Chirico, Robert D; Muzny, Chris D; Kazakov, Andrei F; Kroenlein, Kenneth; Magee, Joseph W; Abdulagatov, Ilmutdin; Frenkel, Michael

2013-12-23

ThermoData Engine (TDE) is the first full-scale software implementation of the dynamic data evaluation concept, as reported in this journal. The present article describes the background and implementation for new additions in latest release of TDE. Advances are in the areas of program architecture and quality improvement for automatic property evaluations, particularly for pure compounds. It is shown that selection of appropriate program architecture supports improvement of the quality of the on-demand property evaluations through application of a readily extensible collection of constraints. The basis and implementation for other enhancements to TDE are described briefly. Other enhancements include the following: (1) implementation of model-validity enforcement for specific equations that can provide unphysical results if unconstrained, (2) newly refined group-contribution parameters for estimation of enthalpies of formation for pure compounds containing carbon, hydrogen, and oxygen, (3) implementation of an enhanced group-contribution method (NIST-Modified UNIFAC) in TDE for improved estimation of phase-equilibrium properties for binary mixtures, (4) tools for mutual validation of ideal-gas properties derived through statistical calculations and those derived independently through combination of experimental thermodynamic results, (5) improvements in program reliability and function that stem directly from the recent redesign of the TRC-SOURCE Data Archival System for experimental property values, and (6) implementation of the Peng-Robinson equation of state for binary mixtures, which allows for critical evaluation of mixtures involving supercritical components. Planned future developments are summarized.

ON THE LIKELIHOOD OF PLANET FORMATION IN CLOSE BINARIES

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

Jang-Condell, Hannah, E-mail: hjangcon@uwyo.edu

2015-02-01

To date, several exoplanets have been discovered orbiting stars with close binary companions (a ≲ 30 AU). The fact that planets can form in these dynamically challenging environments implies that planet formation must be a robust process. The initial protoplanetary disks in these systems from which planets must form should be tidally truncated to radii of a few AU, which indicates that the efficiency of planet formation must be high. Here, we examine the truncation of circumstellar protoplanetary disks in close binary systems, studying how the likelihood of planet formation is affected over a range of disk parameters. If themore » semimajor axis of the binary is too small or its eccentricity is too high, the disk will have too little mass for planet formation to occur. However, we find that the stars in the binary systems known to have planets should have once hosted circumstellar disks that were capable of supporting planet formation despite their truncation. We present a way to characterize the feasibility of planet formation based on binary orbital parameters such as stellar mass, companion mass, eccentricity, and semimajor axis. Using this measure, we can quantify the robustness of planet formation in close binaries and better understand the overall efficiency of planet formation in general.« less

Modelling equilibrium adsorption of single, binary, and ternary combinations of Cu, Pb, and Zn onto granular activated carbon.

PubMed

Loganathan, Paripurnanda; Shim, Wang Geun; Sounthararajah, Danious Pratheep; Kalaruban, Mahatheva; Nur, Tanjina; Vigneswaran, Saravanamuthu

2018-03-30

Elevated concentrations of heavy metals in water can be toxic to humans, animals, and aquatic organisms. A study was conducted on the removal of Cu, Pb, and Zn by a commonly used water treatment adsorbent, granular activated carbon (GAC), from three single, three binary (Cu-Pb, Cu-Zn, Pb-Zn), and one ternary (Cu-Pb-Zn) combination of metals. It also investigated seven mathematical models on their suitability to predict the metals adsorption capacities. Adsorption of Cu, Pb, and Zn increased with pH with an abrupt increase in adsorption at around pH 5.5, 4.5, and 6.0, respectively. At all pHs tested (2.5-7.0), the adsorption capacity followed the order Pb > Cu > Zn. The Langmuir and Sips models fitted better than the Freundlich model to the data in the single-metal system at pH 5. The Langmuir maximum adsorption capacities of Pb, Cu, and Zn (mmol/g) obtained from the model's fits were 0.142, 0.094, and 0.058, respectively. The adsorption capacities (mmol/g) for these metals at 0.01 mmol/L equilibrium liquid concentration were 0.130, 0.085, and 0.040, respectively. Ideal Adsorbed Solution (IAS)-Langmuir and IAS-Sips models fitted well to the binary and ternary metals adsorption data, whereas the Extended Langmuir and Extended Sips models' fits to the data were poor. The selectivity of adsorption followed the same order as the metals' capacities and affinities of adsorption in the single-metal systems.

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

Sperauskas, J.; Začs, L.; Deveikis, V.

Yamashita has described a group of early carbon stars with enhanced lines of barium that resemble the CH stars but have low radial velocities. It is not clear whether they represent a class of stars separate from early R stars. Radial-velocity measurements and abundance analyses are applied in order to clarify the evolutionary status of CH-like stars. Radial-velocity monitoring was performed over a time interval of about 10 years. Abundance analysis was carried out using high-resolution spectra and the method of atmospheric models for three CH-like candidate stars. The radial-velocity monitoring confirmed regular variations for all of the classified CH-likemore » stars, except for two, in support of their binary nature. The calculated orbital parameters are similar to those observed for barium stars in the disk of the Galaxy and their counterparts in the halo, that is, the CH stars. The relatively low luminosity of CH-like stars and the overabundance of s -process elements in the atmospheres are in agreement with a mass-transfer scenario from the secondary—an AGB star in the past. The kinematic data and metallicities support the idea that CH-like stars are thin/thick-disk population objects.« less

TYCHO SN 1572: A NAKED Ia SUPERNOVA REMNANT WITHOUT AN ASSOCIATED AMBIENT MOLECULAR CLOUD

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

Tian, W. W.; Leahy, D. A., E-mail: tww@bao.ac.cn

The historical supernova remnant (SNR) Tycho SN 1572 originates from the explosion of a normal Type Ia supernova that is believed to have originated from a carbon-oxygen white dwarf in a binary system. We analyze the 21 cm continuum, H I, and {sup 12}CO-line data from the Canadian Galactic Plane Survey in the direction of SN 1572 and the surrounding region. We construct H I absorption spectra to SN 1572 and three nearby compact sources. We conclude that SN 1572 has no molecular cloud interaction, which argues against previous claims that a molecular cloud is interacting with the SNR. Thismore » new result does not support a recent claim that dust, newly detected by AKARI, originates from such an SNR-cloud interaction. We suggest that the SNR has a kinematic distance of 2.5-3.0 kpc based on a nonlinear rotational curve model. Very high energy {gamma}-ray emission from the remnant has been detected by the VERITAS telescope, so our result shows that its origin should not be an SNR-cloud interaction. Both radio and X-ray observations support that SN 1572 is an isolated Type Ia SNR.« less

Statistical studies in stellar rotation 2: A method of analyzing rotational coupling in double stars and an introduction to its applications

NASA Technical Reports Server (NTRS)

Bernacca, P. L.

1971-01-01

The correlation between the equatorial velocities of the components of double stars is studied from a statistical standpoint. A theory of rotational correlation is developed and discussed with regard to its applicability to existing observations. The theory is then applied to a sample of visual binaries which are the least studied for rotational coupling. Consideration of eclipsing systems and spectroscopic binaries is limited to show how the degrees of freedom in the spin parallelism problem can be reduced. The analysis lends support to the existence of synchronism in closely spaced binaries.

The Young Visual Binary Survey

NASA Astrophysics Data System (ADS)

Prato, Lisa; Avilez, Ian; Lindstrom, Kyle; Graham, Sean; Sullivan, Kendall; Biddle, Lauren; Skiff, Brian; Nofi, Larissa; Schaefer, Gail; Simon, Michal

2018-01-01

Differences in the stellar and circumstellar properties of the components of young binaries provide key information about star and disk formation and evolution processes. Because objects with separations of a few to a few hundred astronomical units share a common environment and composition, multiple systems allow us to control for some of the factors which play into star formation. We are completing analysis of a rich sample of about 100 pre-main sequence binaries and higher order multiples, primarily located in the Taurus and Ophiuchus star forming regions. This poster will highlight some of out recent, exciting results. All reduced spectra and the results of our analysis will be publicly available to the community at http://jumar.lowell.edu/BinaryStars/. Support for this research was provided in part by NSF award AST-1313399 and by NASA Keck KPDA funding.

Studies of Binary Pulsar Evolution Through Hubble Space Telescope Imaging of White Dwarf Companions

NASA Astrophysics Data System (ADS)

Lundgren, S. C.; Foster, R. S.; Camilo, F.

1995-12-01

In observations of six binary millisecond pulsars with the Hubble Space Telescope, we have discovered white dwarf companions to PSRs J0034-0534, J1022+1001, and J1713+0747 and improved photometry on PSRs J1640+2224 and J2145-0750. The companion to PSR J2019+2425 was not detected down to m_I=25.4. For the five companions detected, effective temperatures were estimated for the colors measured. Two of the white dwarfs, J0034-0534 and J1713+0747, are among the coolest and oldest known. Using distance estimates to the pulsars, the absolute luminosities were determined. Constrains on the masses and cooling times were obtained from the luminosities and temperatures. The results for each pulsar were related to expectations based on models for white dwarf cooling, Roche lobe overflow in the preceding low-mass X-ray binary phase, and mass accretion rate/neutron star spin period relations. Precision pulsar astrophysics at the Naval Research Laboratory is supported by the Office of Naval Research. SL is supported by a post-doctoral fellowship through the National Research Council. FC acknowledges support from NSF grant AST 91-15103 and a fellowship under the auspices of the European Commission.

Systematic Review of Life Cycle Greenhouse Gas Emissions from Geothermal Electricity

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

Eberle, Annika; Heath, Garvin A.; Carpenter Petri, Alberta C.

The primary goal of this work was to assess the magnitude and variability of published life cycle greenhouse gas (GHG) emission estimates for three types of geothermal electricity generation technologies: enhanced geothermal systems (EGS) binary, hydrothermal (HT) flash, and HT binary. These technologies were chosen to align the results of this report with technologies modeled in National Renewable Energy Laboratory's (NREL's) Regional Energy Deployment Systems (ReEDs) model. Although we did gather and screen life cycle assessment (LCA) literature on hybrid systems, dry steam, and two geothermal heating technologies, we did not analyze published GHG emission estimates for these technologies. Inmore » our systematic literature review of the LCA literature, we screened studies in two stages based on a variety of criteria adapted from NREL's Life Cycle Assessment (LCA) Harmonization study (Heath and Mann 2012). Of the more than 180 geothermal studies identified, only 29 successfully passed both screening stages and only 26 of these included estimates of life cycle GHG emissions. We found that the median estimate of life cycle GHG emissions (in grams of carbon dioxide equivalent per kilowatt-hour generated [g CO2eq/kWh]) reported by these studies are 32.0, 47.0, and 11.3 for EGS binary, HT flash, and HT binary, respectively (Figure ES-1). We also found that the total life cycle GHG emissions are dominated by different stages of the life cycle for different technologies. For example, the GHG emissions from HT flash plants are dominated by the operations phase owing to the flash cycle being open loop whereby carbon dioxide entrained in the geothermal fluids is released to the atmosphere. This is in contrast to binary plants (using either EGS or HT resources), whose GHG emissions predominantly originate in the construction phase, owing to its closed-loop process design. Finally, by comparing this review's literature-derived range of HT flash GHG emissions to data from currently operating geothermal plants, we found that emissions from operational plants exhibit more variability and the median of emissions from operational plants is twice the median of operational emissions reported by LCAs. Further investigation is warranted to better understand the cause of differences between published LCAs and estimates from operational plants and to develop LCA analytical approaches that can yield estimates closer to actual emissions.« less

The massive multiple system HD 64315

NASA Astrophysics Data System (ADS)

Lorenzo, J.; Simón-Díaz, S.; Negueruela, I.; Vilardell, F.; Garcia, M.; Evans, C. J.; Montes, D.

2017-10-01

Context. The O6 Vn star HD 64315 is believed to belong to the star-forming region known as NGC 2467, but previous distance estimates do not support this association. Moreover, it has been identified as a spectroscopic binary, but existing data support contradictory values for its orbital period. Aims: We explore the multiple nature of this star with the aim of determining its distance, and understanding its connection to NGC 2467. Methods: A total of 52 high-resolution spectra have been gathered over a decade. We use their analysis, in combination with the photometric data from All Sky Automated Survey and Hipparcos catalogues, to conclude that HD 64315 is composed of at least two spectroscopic binaries, one of which is an eclipsing binary. We have developed our own program to fit four components to the combined line shapes. Once the four radial velocities were derived, we obtained a model to fit the radial-velocity curves using the Spectroscopic Binary Orbit Program (SBOP). We then implemented the radial velocities of the eclipsing binary and the light curves in the Wilson-Devinney code iteratively to derive stellar parameters for its components. We were also able to analyse the non-eclipsing binary, and to derive minimum masses for its components which dominate the system flux. Results: HD 64315 contains two binary systems, one of which is an eclipsing binary. The two binaries are separated by 0.09 arcsec (or 500 AU) if the most likely distance to the system, 5 kpc, is considered. The presence of fainter companions is not excluded by current observations. The non-eclipsing binary (HD 64315 AaAb) has a period of 2.70962901 ± 0.00000021 d. Its components are hotter than those of the eclipsing binary, and dominate the appearance of the system. The eclipsing binary (HD 64315 BaBb) has a shorter period of 1.0189569 ± 0.0000008 d. We derive masses of 14.6 ± 2.3 M⊙ for both components of the BaBb system. They are almost identical; both stars are overfilling their respective Roche lobes, and share a common envelope in an overcontact configuration. The non-eclipsing binary is a detached system composed of two stars with spectral types around O6 V with minimum masses of 10.8 M⊙ and 10.2 M⊙, and likely masses ≈ 30 M⊙. Conclusions: HD 64315 provides a cautionary tale about high-mass star isolation and multiplicity. Its total mass is likely above 90M⊙, but it seems to have formed without an accompanying cluster. It contains one the most massive overcontact binaries known, a likely merger progenitor in a very wide multiple system. Based on observations obtained at the European Southern Observatory under programmes 078.D-0665(A), 082-D.0136 and 093.A-9001(A). 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 Astrofísica de Canarias.

Efficient Merge and Insert Operations for Binary Heaps and Trees

NASA Technical Reports Server (NTRS)

Kuszmaul, Christopher Lee; Woo, Alex C. (Technical Monitor)

2000-01-01

Binary heaps and binary search trees merge efficiently. We introduce a new amortized analysis that allows us to prove the cost of merging either binary heaps or balanced binary trees is O(l), in the amortized sense. The standard set of other operations (create, insert, delete, extract minimum, in the case of binary heaps, and balanced binary trees, as well as a search operation for balanced binary trees) remain with a cost of O(log n). For binary heaps implemented as arrays, we show a new merge algorithm that has a single operation cost for merging two heaps, a and b, of O(absolute value of a + min(log absolute value of b log log absolute value of b. log absolute value of a log absolute value of b). This is an improvement over O(absolute value of a + log absolute value of a log absolute value of b). The cost of the new merge is so low that it can be used in a new structure which we call shadow heaps. to implement the insert operation to a tunable efficiency. Shadow heaps support the insert operation for simple priority queues in an amortized time of O(f(n)) and other operations in time O((log n log log n)/f (n)), where 1 less than or equal to f (n) less than or equal to log log n. More generally, the results here show that any data structure with operations that change its size by at most one, with the exception of a merge (aka meld) operation, can efficiently amortize the cost of the merge under conditions that are true for most implementations of binary heaps and search trees.

A feature dictionary supporting a multi-domain medical knowledge base.

PubMed

Naeymi-Rad, F

1989-01-01

Because different terminology is used by physicians of different specialties in different locations to refer to the same feature (signs, symptoms, test results), it is essential that our knowledge development tools provide a means to access a common pool of terms. This paper discusses the design of an online medical dictionary that provides a solution to this problem for developers of multi-domain knowledge bases for MEDAS (Medical Emergency Decision Assistance System). Our Feature Dictionary supports phrase equivalents for features, feature interactions, feature classifications, and translations to the binary features generated by the expert during knowledge creation. It is also used in the conversion of a domain knowledge to the database used by the MEDAS inference diagnostic sessions. The Feature Dictionary also provides capabilities for complex queries across multiple domains using the supported relations. The Feature Dictionary supports three methods for feature representation: (1) for binary features, (2) for continuous valued features, and (3) for derived features.

129Xe nuclear magnetic resonance study of pitch-based activated carbon modified by air oxidation/pyrolysis cycles: a new approach to probe the micropore size.

PubMed

Romanenko, Konstantin V; Py, Xavier; d'Espinose de Lacaillerie, Jean-Baptiste; Lapina, Olga B; Fraissard, Jacques

2006-02-23

(129)Xe NMR has been used to study a series of homologous activated carbons obtained from a KOH-activated pitch-based carbon molecular sieve modified by air oxidation/pyrolysis cycles. A clear correlation between the pore size of microporous carbons and the (129)Xe NMR of adsorbed xenon is proposed for the first time. The virial coefficient delta(Xe)(-)(Xe) arising from binary xenon collisions varied linearly with the micropore size and appeared to be a better probe of the microporosity than the chemical shift extrapolated to zero pressure. This correlation was explained by the fact that the xenon collision frequency increases with increasing micropore size. The chemical shift has been shown to vary very little with temperature (less than 9 ppm) for xenon trapped inside narrow and wide micropores. This is indicative of a smooth xenon-surface interaction potential.

Automatic Carbon Dioxide-Methane Gas Sensor Based on the Solubility of Gases in Water

PubMed Central

Cadena-Pereda, Raúl O.; Rivera-Muñoz, Eric M.; Herrera-Ruiz, Gilberto; Gomez-Melendez, Domingo J.; Anaya-Rivera, Ely K.

2012-01-01

Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon dioxide-methane gas sensor based on the solubility of gases in water as the precursor of a sensor for biogas quality monitoring. The device described in this work was used for determining the composition of binary mixtures, such as carbon dioxide-methane, in the range of 0–100%. The design and implementation of a digital signal processor and control system into a low-cost Field Programmable Gate Array (FPGA) platform has permitted the successful application of data acquisition, data distribution and digital data processing, making the construction of a standalone carbon dioxide-methane gas sensor possible. PMID:23112626

Automatic carbon dioxide-methane gas sensor based on the solubility of gases in water.

PubMed

Cadena-Pereda, Raúl O; Rivera-Muñoz, Eric M; Herrera-Ruiz, Gilberto; Gomez-Melendez, Domingo J; Anaya-Rivera, Ely K

2012-01-01

Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon dioxide-methane gas sensor based on the solubility of gases in water as the precursor of a sensor for biogas quality monitoring. The device described in this work was used for determining the composition of binary mixtures, such as carbon dioxide-methane, in the range of 0-100%. The design and implementation of a digital signal processor and control system into a low-cost Field Programmable Gate Array (FPGA) platform has permitted the successful application of data acquisition, data distribution and digital data processing, making the construction of a standalone carbon dioxide-methane gas sensor possible.

High energy radiation precursors to the collapse of black holes binaries based on resonating plasma modes

NASA Astrophysics Data System (ADS)

Coppi, B.

2018-05-01

The presence of well organized plasma structures around binary systems of collapsed objects [1,2] (black holes and neutron stars) is proposed in which processes can develop [3] leading to high energy electromagnetic radiation emission immediately before the binary collapse. The formulated theoretical model supporting this argument shows that resonating plasma collective modes can be excited in the relevant magnetized plasma structure. Accordingly, the collapse of the binary approaches, with the loss of angular momentum by emission of gravitational waves [2], the resonance conditions with vertically standing plasma density and magnetic field oscillations are met. Then, secondary plasma modes propagating along the magnetic field are envisioned to be sustained with mode-particle interactions producing the particle populations responsible for the observable electromagnetic radiation emission. Weak evidence for a precursor to the binary collapse reported in Ref. [2], has been offered by the Agile X-γ-ray observatory [4] while the August 17 (2017) event, identified first by the LIGO-Virgo detection of gravitational waves and featuring the inferred collapse of a neutron star binary, improves the evidence of such a precursor. A new set of experimental observations is needed to reassess the presented theory.

Vulcan Identification of Eclipsing Binaries in the Kepler Field of View

NASA Astrophysics Data System (ADS)

Mjaseth, Kimberly; Batalha, N.; Borucki, W.; Caldwell, D.; Latham, D.; Martin, K. R.; Rabbette, M.; Witteborn, F.

2007-05-01

We report the discovery of 236 new eclipsing binary stars located in and around the field of view of the Kepler Mission. The binaries were identified from photometric light curves from the Vulcan exoplanet transit survey. The Vulcan camera is comprised of a modest aperture (10cm) f/2.8 Canon lens focusing a 7° x 7° field of view onto a 4096 x 4096 Kodak CCD. The system yields an hour-to-hour relative precision of 0.003 on 12th magnitude stars and saturates at 9th magnitude. The binaries have magnitudes in the range of 9.5 < V < 13.5 and periods ranging from 0.5 to 13 days. The milli-magnitude photometric precision allows detection of transits as shallow as 1%. The catalog contains a total of 273 eclipsing binary stars, including detached systems (high and low mass ratio), contact binaries, and triple systems. We present the derived orbital/transit properties, light curves, and stellar properties for selected targets. In addition, we summarize the results of radial velocity follow-up work. Support for this work came from NASA's Discovery Program and NASA's Origins of the Solar System Program.

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.

REMOVAL OF ADDED NITRATE IN THE SINGLE, BINARY, AND TERNARY SYSTEMS OF COTTON BURR COMPOST, ZEROVALENT IRON, AND SEDIMENT: IMPLICATIONS FOR GROUNDWATER NITRATE REMEDIATION USING PERMEABLE REACTIVE BARRIERS

EPA Science Inventory

Recent research has shown that carbonaceous solid materials and zerovalent iron (Fe0) may potentially be used as media in permeable reactive barriers (PRBs) to degrade groundwater nitrate via heterotrophic denitrification in the solid carbon system, and via abiotic reduction and ...

Physiologically-based pharmacokinetic (PBPK) modeling of two binary mixtures: metabolic activation of carbon tetrachloride by trichloroethylene and metabolic inhibition of chloroform by trichloroethylene.

EPA Science Inventory

The interaction between trichloroethylene (TCE) and chloroform (CHCI3) has been described as less than additive, with co-exposure to TCE and CHC13 resulting in less hepatic and renal toxicity than observed with CHCl3 alone. In contrast, the nonadditive interaction between TCE and...

Sulfur and nitrogen binary doped carbon dots derived from ammonium thiocyanate for selective probing doxycycline in living cells and multicolor cell imaging.

PubMed

Xue, Mingyue; Zhang, Liangliang; Zhan, Zhihua; Zou, Mengbing; Huang, Yong; Zhao, Shulin

2016-04-01

A novel sulfur and nitrogen binary doped carbon dots (S,N-CDs) was synthesized by one-step manner through the hydrothermal treatment of citric acid (CA) and ammonium thiocyanate, and the procedures for biomedical applications, including probing doxycycline in living cells and multicolor cell imaging were developed. The obtained S,N-CDs are stable in aqueous solution, possess a very high quantum yield (QY, 74.15%) and good photostability. The fluorescence of S,N-CDs can be specifically quenched by doxycycline, providing a convenient turn-off assay of doxycycline. This assay shows a wide linear detection range from 0.08 to 60 μM with a low detection limit of 20 nM. The present method also displays a good selectivity. More importantly, the S,N-CDs have an excellent biocompatibility and low cytotoxicity, allowing the multicolor cell imaging and doxycycline detection in living cells. Consequently, the developed doxycycline methods is facile, low-cost, biocompatible, sensitive and selective, which may hold the potential applications in the fields of food safety and environmental monitoring, as well as cancer therapy and related mechanism research. Copyright © 2015 Elsevier B.V. All rights reserved.

Testing the white dwarf mass-radius relationship with eclipsing binaries

NASA Astrophysics Data System (ADS)

Parsons, S. G.; Gänsicke, B. T.; Marsh, T. R.; Ashley, R. P.; Bours, M. C. P.; Breedt, E.; Burleigh, M. R.; Copperwheat, C. M.; Dhillon, V. S.; Green, M.; Hardy, L. K.; Hermes, J. J.; Irawati, P.; Kerry, P.; Littlefair, S. P.; McAllister, M. J.; Rattanasoon, S.; Rebassa-Mansergas, A.; Sahman, D. I.; Schreiber, M. R.

2017-10-01

We present high-precision, model-independent, mass and radius measurements for 16 white dwarfs in detached eclipsing binaries and combine these with previously published data to test the theoretical white dwarf mass-radius relationship. We reach a mean precision of 2.4 per cent in mass and 2.7 per cent in radius, with our best measurements reaching a precision of 0.3 per cent in mass and 0.5 per cent in radius. We find excellent agreement between the measured and predicted radii across a wide range of masses and temperatures. We also find the radii of all white dwarfs with masses less than 0.48 M⊙ to be fully consistent with helium core models, but they are on average 9 per cent larger than those of carbon-oxygen core models. In contrast, white dwarfs with masses larger than 0.52 M⊙ all have radii consistent with carbon-oxygen core models. Moreover, we find that all but one of the white dwarfs in our sample have radii consistent with possessing thick surface hydrogen envelopes (10-5 ≥ MH/MWD ≥ 10-4), implying that the surface hydrogen layers of these white dwarfs are not obviously affected by common envelope evolution.

Transport properties in mixtures involving carbon dioxide at low and moderate density: test of several intermolecular potential energies and comparison with experiment

NASA Astrophysics Data System (ADS)

Moghadasi, Jalil; Yousefi, Fakhri; Papari, Mohammad Mehdi; Faghihi, Mohammad Ali; Mohsenipour, Ali Asghar

2009-09-01

It is the purpose of this paper to extract unlike intermolecular potential energies of five carbon dioxide-based binary gas mixtures including CO2-He, CO2-Ne, CO2-Ar, CO2-Kr, and CO2-Xe from viscosity data and compare the calculated potentials with other models potential energy reported in literature. Then, dilute transport properties consisting of viscosity, diffusion coefficient, thermal diffusion factor, and thermal conductivity of aforementioned mixtures are calculated from the calculated potential energies and compared with literature data. Rather accurate correlations for the viscosity coefficient of afore-cited mixtures embracing the temperature range 200 K < T < 3273.15 K is reproduced from the present unlike intermolecular potentials energy. Our estimated accuracies for the viscosity are to within ±2%. In addition, the calculated potential energies are used to present smooth correlations for other transport properties. The accuracies of the binary diffusion coefficients are of the order of ±3%. Finally, the unlike interaction energy and the calculated low density viscosity have been employed to calculate high density viscosities using Vesovic-Wakeham method.

A new mechanism for selective adsorption of rubber on carbon black surface caused by nano-confinement in SBR/NBR solution

NASA Astrophysics Data System (ADS)

Kawazoe, Masayuki

A novel mechanism of selective adsorption of rubber molecules onto carbon black surface in a binary immiscible rubber blend solution has been proposed in this dissertation. The phenomenon leads to uneven distribution of carbon black to the specific polymer in the blend and the obtained electrically conductive composite showed drastic reduction of percolation threshold concentration (PTC). The mechanism and the feature of conductive network formation have much potential concerning both fundamental understanding and industrial application to improve conductive polymer composites. In chapter I, carbon black filled conductive polymer composites are briefly reviewed. Then, in chapter II, a mechanism of rubber molecular confinement into carbon black aggregate structure is introduced to explain the selective adsorption of a specific rubber onto carbon black surface in an immiscible rubber solution blend (styrene butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR) with toluene or chloroform). Next, in chapters III and IV, polymers with various radius of gyration (Rg) and carbon blacks with various aggregate structure are examined to verify the selective adsorption mechanism. Finally, in chapter V, the novel mechanism was applied to create unique meso-/micro-unit conductive network in carbon black dispersed SBR/NBR composites.

Water radiolysis by low-energy carbon projectiles from first-principles molecular dynamics

PubMed Central

Kohanoff, Jorge

2017-01-01

Water radiolysis by low-energy carbon projectiles is studied by first-principles molecular dynamics. Carbon projectiles of kinetic energies between 175 eV and 2.8 keV are shot across liquid water. Apart from translational, rotational and vibrational excitation, they produce water dissociation. The most abundant products are H and OH fragments. We find that the maximum spatial production of radiolysis products, not only occurs at low velocities, but also well below the maximum of energy deposition, reaching one H every 5 Å at the lowest speed studied (1 Bohr/fs), dissociative collisions being more significant at low velocity while the amount of energy required to dissociate water is constant and much smaller than the projectile’s energy. A substantial fraction of the energy transferred to fragments, especially for high velocity projectiles, is in the form of kinetic energy, such fragments becoming secondary projectiles themselves. High velocity projectiles give rise to well-defined binary collisions, which should be amenable to binary approximations. This is not the case for lower velocities, where multiple collision events are observed. H secondary projectiles tend to move as radicals at high velocity, as cations when slower. We observe the generation of new species such as hydrogen peroxide and formic acid. The former occurs when an O radical created in the collision process attacks a water molecule at the O site. The latter when the C projectile is completely stopped and reacts with two water molecules. PMID:28267804

Penning Ionization Electron Spectroscopy in Glow Discharge: A New Dimension for Gas Chromatography Detectors

NASA Technical Reports Server (NTRS)

Sheverev, V. A.; Khromov, N. A.; Kojiro, D. R.; Fonda, Mark (Technical Monitor)

2002-01-01

Admixtures to helium of 100 ppm and 5 ppm of nitrogen, and 100 ppm and 10 ppm of carbon monoxide were identified and measured in the helium discharge afterglow using an electrical probe placed into the plasma. For nitrogen and carbon monoxide gases, the measured electron energy spectra display distinct characteristic peaks (fingerprints). Location of the peaks on the energy scale is determined by the ionization energies of the analyte molecules. Nitrogen and carbon monoxide fingerprints were also observed in a binary mixture of these gases in helium, and the relative concentration analytes has been predicted. The technically simple and durable method is considered a good candidate for a number of analytical applications, and in particular, in GC and for analytical flight instrumentation.

Modeling CO2 mass transfer in amine mixtures: PZ-AMP and PZ-MDEA.

PubMed

Puxty, Graeme; Rowland, Robert

2011-03-15

The most common method of carbon dioxide (CO(2)) capture is the absorption of CO(2) into a falling thin film of an aqueous amine solution. Modeling of mass transfer during CO(2) absorption is an important way to gain insight and understanding about the underlying processes that are occurring. In this work a new software tool has been used to model CO(2) absorption into aqueous piperazine (PZ) and binary mixtures of PZ with 2-amino-2-methyl-1-propanol (AMP) or methyldiethanolamine (MDEA). The tool solves partial differential and simultaneous equations describing diffusion and chemical reaction automatically derived from reactions written using chemical notation. It has been demonstrated that by using reactions that are chemically plausible the mass transfer in binary mixtures can be fully described by combining the chemical reactions and their associated parameters determined for single amines. The observed enhanced mass transfer in binary mixtures can be explained through chemical interactions occurring in the mixture without need to resort to using additional reactions or unusual transport phenomena such as the "shuttle mechanism".

A Search for Nitrogen-enhanced Metal-poor Stars

NASA Astrophysics Data System (ADS)

Johnson, Jennifer A.; Herwig, Falk; Beers, Timothy C.; Christlieb, Norbert

2007-04-01

Theoretical models of very metal-poor intermediate-mass asymptotic giant branch (AGB) stars predict a large overabundance of primary nitrogen. The very metal-poor, carbon-enhanced, s-process-rich stars, which are thought to be the polluted companions of now extinct AGB stars, provide direct tests of the predictions of these models. Recent studies of the carbon and nitrogen abundances in metal-poor stars have focused on the most carbon-rich stars, leading to a potential selection bias against stars that have been polluted by AGB stars that produced large amounts of nitrogen and hence have small [C/N] ratios. We call these stars nitrogen-enhanced metal-poor (NEMP) stars and define them as having [N/Fe]>+0.5 and [C/N]<-0.5. In this paper we report on the [C/N] abundances of a sample of 21 carbon-enhanced stars, all but three of which have [C/Fe]<+2.0. If NEMP stars were made as easily as carbon-enhanced metal-poor (CEMP) stars, then we expected to find between two and seven NEMP stars. Instead, we found no NEMP stars in our sample. Therefore, this observational bias is not an important contributor to the apparent dearth of N-rich stars. Our [C/N] values are in the same range as values reported previously in the literature (-0.5 to +2.0), and all stars are in disagreement with the predicted [C/N] ratios for both low- and high-mass AGB stars. We suggest that the decrease in [C/N] from the low-mass AGB models is due to enhanced extramixing, while the lack of NEMP stars may be caused by unfavorable mass ratios in binaries or the difficulty of mass transfer in binary systems with large mass ratios. Based on observations obtained at Cerro Tololo Inter-American Observatory and Kitt Peak National Observatory, a division of the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.

Template-mediated, Hierarchical Engineering of Ordered Mesoporous Films and Powders

NASA Astrophysics Data System (ADS)

Tian, Zheng

Hierarchical control over pore size, pore topology, and meso/mictrostructure as well as material morphology (e.g., powders, monoliths, thin films) is crucial for meeting diverse materials needs among applications spanning next generation catalysts, sensors, batteries, sorbents, etc. The overarching goal of this thesis is to establish fundamental mechanistic insight enabling new strategies for realizing such hierarchical textural control for carbon materials that is not currently achievable with sacrificial pore formation by 'one-pot' surfactant-based 'soft'-templating or multi-step inorganic 'hard-templating. While 'hard'-templating is often tacitly discounted based upon its perceived complexity, it offers potential for overcoming key 'soft'-templating challenges, including bolstering pore stability, accommodating a more versatile palette of replica precursors, realizing ordered/spanning porosity in the case of porous thin films, simplifying formation of bi-continuous pore topologies, and inducing microstructure control within porous replica materials. In this thesis, we establish strategies for hard-templating of hierarchically porous and structured carbon powders and tunable thin films by both multi-step hard-templating and a new 'one-pot' template-replica precursor co-assembly process. We first develop a nominal hard-templating technique to successfully prepare three-dimensionally ordered mesoporous (3DOm) and 3DOm-supported microporous carbon thin films by exploiting our ability to synthesize and assemble size-tunable silica nanoparticles into scalable, colloidal crystalline thin film templates of tunable mono- to multi-layer thickness. This robust thin film template accommodates liquid and/or vapor-phase infiltration, polymerization, and pyrolysis of various carbon sources without pore contraction and/or collapse upon template sacrifice. The result is robust, flexible 3DOm or 3DOm-supported ultra-thin microporous films that can be transferred by stamp techniques to various substrates for low-cost counter-electrodes in dye-sensitized solar cells, as we demonstrate, or as potential high-flux membranes for molecular separations. Inspired by 'one-pot' 'soft'-templating approaches, wherein the pore forming agent and replica precursor are co-assembled, we establish how 'hard'-templating can be carried out in an analogous fashion. Namely, we show how pre-formed silica nanoparticles can be co-assembled from aqueous solutions with a carbon source (glucose), leading to elucidation of a pseudo-phase behavior in which we identify an operating window for synthesis of hierarchically bi-continuous carbon films. Systematic study of the association of carbon precursors with the silica particles in combination with transient coating experiments reveals mechanistic insight into how silica-adsorbed carbon precursor modulates particle assembly and ultimately controls template particle d-spacing. We uncover a critical d-spacing defining the boundary between ordered and disordered mesoporosity within the resulting films. We ultimately extend this thin-film mechanistic insight to realize 'one'-pot, bi-continuous 3DOm carbon powders. Through a combination of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and high-resolution transmission electron microscopy (HR-TEM), we elucidate novel synthesis-structure relations for template-mediated microstructuring of the 3DOm replica carbons. Attractive properties of the resulting bi-continuous porous carbons for applications, for example, as novel electrodes, include high surface areas, large mesopore volumes, and tunable graphitic content (i.e. >50%) and character. We specifically demonstrate their performance, in thin film form, as counter-electrodes in dye-sensitized solar cells. We also demonstrate how they can be exploited in powder form as high-performance supercapacitor electrodes exhibiting attractive retention and absolute capacitance. We conclude the thesis by demonstrating the versatility of both the thin-film and powder templating processes developed herein, for realizing ordered binary colloidal crystal templates and their bi-modal porous carbon replica films, expanding compositional diversity of the 'one-pot' thin film process beyond carbons to include an example of 3DOm ZrO2 films, and employing the hard-templating process as a strategy for realizing 3DOm carbon-supported nanocarbides.

Shaping planetary nebulae with jets in inclined triple stellar systems

NASA Astrophysics Data System (ADS)

Akashi, Muhammad; Soker, Noam

2017-08-01

We conduct three-dimensional hydrodynamical simulations of two opposite jets launched obliquely to the orbital plane around an asymptotic giant branch (AGB) star and within its dense wind, and demonstrate the formation of a 'messy' planetary nebula (PN), namely a PN lacking any type of symmetry (I.e. highly irregular). In building the initial conditions, we assume that a tight binary system orbits the AGB star and that the orbital plane of the tight binary system is inclined to the orbital plane of the binary system and the AGB star (the triple system plane). We further assume that the accreted mass on to the tight binary system forms an accretion disc around one of the stars and that the plane of the disc is tilted to the orbital plane of the triple system. The highly asymmetrical and filamentary structures that we obtain support the notion that messy PNe might be shaped by triple stellar systems.

Shaping planetary nebulae with jets in inclined triple stellar systems

NASA Astrophysics Data System (ADS)

Akashi, Muhammad; Soker, Noam

2017-10-01

We conduct three-dimensional hydrodynamical simulations of two opposite jets launched obliquely to the orbital plane around an asymptotic giant branch (AGB) star and within its dense wind, and demonstrate the formation of a `messy' planetary nebula (PN), namely, a PN lacking any type of symmetry (highly irregular). In building the initial conditions we assume that a tight binary system orbits the AGB star, and that the orbital plane of the tight binary system is inclined to the orbital plane of binary system and the AGB star. We further assume that the accreted mass onto the tight binary system forms an accretion disk around one of the stars, and that the plane of the disk is in between the two orbital planes. The highly asymmetrical lobes that we obtain support the notion that messy PNe might be shaped by triple stellar systems.

Characterization of the Ternary Compound Pd5Pt3Ni2 for PEMFC Cathode Electrocatalysts

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

Jarvis, Karalee; Zhao, J; Allard Jr, Lawrence Frederick

2010-01-01

Research on proton exchange membrane fuel cells (PEMFC) has increased over the last decade due to an increasing demand for alternative energy solutions. Most PEMFCs use Pt on carbon support as electrocatalysts for oxygen reduction reactions (ORR) [1]. Due to the high cost of Pt, there is a strong drive to develop less expensive catalysts that meet or exceed the performance of Pt. Binary and ternary Pt alloys with less expensive metals are a possible route [1]. In this work, a ternary alloy with composition Pd5Pt3Ni2 was studied as a potential cathode material. Preliminary results showed similar catalytic performance tomore » pure Pt in single-cell tests. However, to enhance its performance, it is necessary to understand how this ternary catalyst behaves during fuel cell operation. Various electron microscopy techniques were used to characterize the ternary Pd5Pt3Ni2 catalysts within the membrane-electrode assembly (MEA) both before and after fuel cell operation.« less

Visualising interacting binaries in 3D

NASA Astrophysics Data System (ADS)

Hynes, R. I.

2002-01-01

I have developed a code which allows images to be produced of a variety of interacting binaries for any system parameters. The resulting images are not only helpful in visualising the geometry of a given system but are also helpful in talks and educational work. I would like to acknowledge financial support from the Leverhulme Trust, and to thank Dan Rolfe for many discussions on how to represent interacting binaries and the users of BinSim who have provided valuable testing and feedback. BinSim would not have been possible without the efforts of Brian Paul and others responsible for the Mesa 3-D graphics library -- Mesa 3-D graphics .

Using Kepler K2 to Measure the Binary Fraction of PN Central Stars

NASA Astrophysics Data System (ADS)

Jacoby, George H.; Hillwig, Todd; De Marco, Orsola; Hurowitz, Jonathan; Jones, David; Kronberger, Matthias; Harmer, Dianne

2018-01-01

During the initial Kepler mission, 5 Planetary Nebula (PN) central stars were observed. The light curves for 4 of these central stars indicated a history of close binary interactions. That large fraction was suggestive that the actual fraction of PN harboring close binaries is much larger than the known lower limit of 20%, but that sample is far too small to be compelling. We have since acquired Kepler K2 data for Campaigns 0, 2, 7, and 11, hosting PN samples of 3, 4, 8, and 185 targets, respectively. We will provide an update on the number of binary candidates found in each field, and in particular, the Galactic Bulge field of Campaign 11. We also will discuss the challenges of working with Kepler observations in the crowded Campaign 11 field and the impact of those challenges on our ability to estimate the fraction of PN central stars that are binaries. This study was supported in part by NASA grants NNX17AE64G and NNX17AF80G.

Generation of two-dimensional binary mixtures in complex plasmas

NASA Astrophysics Data System (ADS)

Wieben, Frank; Block, Dietmar

2016-10-01

Complex plasmas are an excellent model system for strong coupling phenomena. Under certain conditions the dust particles immersed into the plasma form crystals which can be analyzed in terms of structure and dynamics. Previous experiments focussed mostly on monodisperse particle systems whereas dusty plasmas in nature and technology are polydisperse. Thus, a first and important step towards experiments in polydisperse systems are binary mixtures. Recent experiments on binary mixtures under microgravity conditions observed a phase separation of particle species with different radii even for small size disparities. This contradicts several numerical studies of 2D binary mixtures. Therefore, dedicated experiments are required to gain more insight into the physics of polydisperse systems. In this contribution first ground based experiments on two-dimensional binary mixtures are presented. Particular attention is paid to the requirements for the generation of such systems which involve the consideration of the temporal evolution of the particle properties. Furthermore, the structure of these two-component crystals is analyzed and compared to simulations. This work was supported by the Deutsche Forschungsgemeinschaft DFG in the framework of the SFB TR24 Greifswald Kiel, Project A3b.

SLoWPoKES-II: 100,000 WIDE BINARIES IDENTIFIED IN SDSS WITHOUT PROPER MOTIONS

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

Dhital, Saurav; West, Andrew A.; Schluns, Kyle J.

2015-08-15

We present the Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES)-II catalog of low-mass visual binaries identified from the Sloan Digital Sky Survey (SDSS) by matching photometric distances. The candidate pairs are vetted by comparing the stellar information. The candidate pairs are vetted by comparing the stellar density at their respective Galactic positions to Monte Carlo realizations of a simulated Milky Way. In this way, we are able to identify large numbers of bona fide wide binaries without the need for proper motions. Here, 105,537 visual binaries with angular separations of ∼1–20″ were identified, each with a probability ofmore » chance alignment of ≤5%. This is the largest catalog of bona fide wide binaries to date, and it contains a diversity of systems—in mass, mass ratios, binary separations, metallicity, and evolutionary states—that should facilitate follow-up studies to characterize the properties of M dwarfs and white dwarfs. There is a subtle but definitive suggestion of multiple populations in the physical separation distribution, supporting earlier findings. We suggest that wide binaries are composed of multiple populations, most likely representing different formation modes. There are 141 M7 or later wide binary candidates, representing a seven-fold increase over the number currently known. These binaries are too wide to have been formed via the ejection mechanism. Finally, we found that 6% of spectroscopically confirmed M dwarfs are not included in the SDSS STAR catalog; they are misclassified as extended sources due to the presence of a nearby or partially resolved companion. The SLoWPoKES-II catalog is publicly available to the entire community on the World Wide Web via the Filtergraph data visualization portal.« less

The respective roles of polar/nonpolar binary patterns and amino acid composition in protein regular secondary structures explored exhaustively using hydrophobic cluster analysis.

PubMed

Rebehmed, Joseph; Quintus, Flavien; Mornon, Jean-Paul; Callebaut, Isabelle

2016-05-01

Several studies have highlighted the leading role of the sequence periodicity of polar and nonpolar amino acids (binary patterns) in the formation of regular secondary structures (RSS). However, these were based on the analysis of only a few simple cases, with no direct mean to correlate binary patterns with the limits of RSS. Here, HCA-derived hydrophobic clusters (HC) which are conditioned binary patterns whose positions fit well those of RSS, were considered. All the HC types, defined by unique binary patterns, which were commonly observed in three-dimensional (3D) structures of globular domains, were analyzed. The 180 HC types with preferences for either α-helices or β-strands distinctly contain basic binary units typical of these RSS. Therefore a general trend supporting the "binary pattern preference" assumption was observed. HC for which observed RSS are in disagreement with their expected behavior (discordant HC) were also examined. They were separated in HC types with moderate preferences for RSS, having "weak" binary patterns and versatile RSS and HC types with high preferences for RSS, having "strong" binary patterns and then displaying nonpolar amino acids at the protein surface. It was shown that in both cases, discordant HC could be distinguished from concordant ones by well-differentiated amino acid compositions. The obtained results could, thus, help to complement the currently available methods for the accurate prediction of secondary structures in proteins from the only information of a single amino acid sequence. This can be especially useful for characterizing orphan sequences and for assisting protein engineering and design. © 2016 Wiley Periodicals, Inc.

The progenitors of supernovae Type Ia

NASA Astrophysics Data System (ADS)

Toonen, Silvia

2014-09-01

Despite the significance of Type Ia supernovae (SNeIa) in many fields in astrophysics, SNeIa lack a theoretical explanation. SNeIa are generally thought to be thermonuclear explosions of carbon/oxygen (CO) white dwarfs (WDs). The canonical scenarios involve white dwarfs reaching the Chandrasekhar mass, either by accretion from a non-degenerate companion (single-degenerate channel, SD) or by a merger of two CO WDs (double-degenerate channel, DD). The study of SNeIa progenitors is a very active field of research for binary population synthesis (BPS) studies. The strength of the BPS approach is to study the effect of uncertainties in binary evolution on the macroscopic properties of a binary population, in order to constrain binary evolutionary processes. I will discuss the expected SNeIa rate from the BPS approach and the uncertainties in their progenitor evolution, and compare with current observations. I will also discuss the results of the POPCORN project in which four BPS codes were compared to better understand the differences in the predicted SNeIa rate of the SD channel. The goal of this project is to investigate whether differences in the simulated populations are due to numerical effects or whether they can be explained by differences in the input physics. I will show which assumptions in BPS codes affect the results most and hence should be studied in more detail.

Innocent Bystanders: Carbon Stars from the Sloan Digital Sky Survey

NASA Astrophysics Data System (ADS)

Green, Paul

2013-03-01

Among stars showing carbon molecular bands (C stars), the main-sequence dwarfs, likely in post-mass transfer binaries, are numerically dominant in the Galaxy. Via spectroscopic selection from the Sloan Digital Sky Survey, we retrieve 1220 high galactic latitude C stars, ~5 times more than previously known, including a wider variety than past techniques such as color or grism selection have netted, and additionally yielding 167 DQ white dwarfs. Of the C stars with proper motion measurements, we identify 69% clearly as dwarfs (dCs), while ~7% are giants. The dCs likely span absolute magnitudes Mi from ~6.5 to 10.5. "G-type" dC stars with weak CN and relatively blue colors are probably the most massive dCs still cool enough to show C2 bands. We report Balmer emission in 22 dCs, none of which are G-types. We find 8 new DA/dC stars in composite spectrum binaries, quadrupling the total sample of these "smoking guns" for AGB binary mass transfer. Eleven very red C stars with strong red CN bands appear to be "N"-type AGB stars at large Galactocentric distances, one likely a new discovery in the dIrr galaxy Leo A. Two such stars within 30' of each other may trace a previously unidentified dwarf galaxy or tidal stream at ~40 kpc. We explore the multiwavelength properties of the sample and report the first X-ray detection of a dC star, which shows strong Balmer emission. Our own spectroscopic survey additionally provides the dC surface density from a complete sample of dwarfs limited by magnitude, color, and proper motion.

Experimental simulation of magma-carbonate interaction beneath Mt. Vesuvius, Italy

NASA Astrophysics Data System (ADS)

Jolis, E. M.; Freda, C.; Troll, V. R.; Deegan, F. M.; Blythe, L. S.; McLeod, C. L.; Davidson, J. P.

2013-11-01

We simulated the process of magma-carbonate interaction beneath Mt. Vesuvius in short duration piston-cylinder experiments under controlled magmatic conditions (from 0 to 300 s at 0.5 GPa and 1,200 °C), using a Vesuvius shoshonite composition and upper crustal limestone and dolostone as starting materials. Backscattered electron images and chemical analysis (major and trace elements and Sr isotopes) of sequential experimental products allow us to identify the textural and chemical evolution of carbonated products during the assimilation process. We demonstrate that melt-carbonate interaction can be extremely fast (minutes), and results in dynamic contamination of the host melt with respect to Ca, Mg and 87Sr/86Sr, coupled with intense CO2 vesiculation at the melt-carbonate interface. Binary mixing between carbonate and uncontaminated melt cannot explain the geochemical variations of the experimental charges in full and convection and diffusion likely also operated in the charges. Physical mixing and mingling driven by exsolving volatiles seems to be a key process to promote melt homogenisation. Our results reinforce hypotheses that magma-carbonate interaction is a relevant and ongoing process at Mt. Vesuvius and one that may operate not only on a geological, but on a human timescale.

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.

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.

Collapse and Fragmentation Models of Tidally Interacting Molecular Cloud Cores. IV. Initial Slow Rotation and Magnetic Field Support

NASA Astrophysics Data System (ADS)

Sigalotti, Leonardo Di G.; Klapp, Jaime

2000-03-01

Fragmentation has long been advocated as the primary mechanism for explaining the observed binary frequency among pre-main-sequence stars and, more recently, for explaining the emerging evidence for binary and multiple protostellar systems. The role of magnetic fields and ambipolar diffusion is essential to understand how dense cloud cores begin dynamic collapse and eventually fragment into protostars. Here we consider new numerical models of the gravitational collapse and fragmentation of slowly rotating molecular cloud cores, including the effects of magnetic support and ambipolar diffusion. The starting point of the evolution is provided by a magnetically stable (subcritical) condensation that results from adding a magnetic field pressure, B2/8π [with the field strength given by the scaling relation B=B0(ρ/ρ0)1/2], to a reference state consisting of a thermally supercritical (α~0.36), slowly rotating (β~0.037), Gaussian cloud core of prolate shape and central density ρ0. The effects of ambipolar diffusion are approximated by allowing the reference field strength B0 to gradually decrease over a timescale of 10 free-fall times. The models also include the effects of tidal interaction due to a gravitational encounter with another protostar, and so they may apply to low-mass star formation within a cluster-forming environment. The results indicate that the magnetic forces delay the onset of dynamic collapse, and hence of fragmentation, by an amount of time that depends on the initial central mass-to-flux ratio. Compared with previous magnetic collapse calculations of rapidly rotating (β=0.12) clouds, lower initial rotation (β~0.037) is seen to result in much shorter delay periods, thus anticipating binary fragmentation. In general, the results show that the models are still susceptible to fragment into binary systems. Intermediate magnetic support (η~0.285) and low tidal forces (τ<~0.201) may lead to final triple or quadruple protostellar systems, while increasing the size of η and τ always results in final binary protostellar cores. The formed binary systems have separations of ~200-350 AU, suggesting that the recently observed peaks around ~90 AU and 215 AU for T Tauri stars may be explained by the collapse and fragmentation of initially slowly rotating magnetic cloud cores with β<~0.04.

WIYN Open Cluster Study: Binary Orbits and Tidal Circularization in NGC 6819

NASA Astrophysics Data System (ADS)

Morscher, Meagan B.; Mathieu, R. D.; Kaeppler, S.; Hole, K. T.; Meibom, S.

2006-12-01

We are conducting a comprehensive stellar radial-velocity survey in NGC 6819, a rich, intermediate age ( 2.4 Gyr) open cluster with [Fe/H] -0.05. As of October 2006, we have obtained 7065 radial-velocity measurements of 1409 stars using the WIYN Hydra Multi-Object Spectrograph, with typical velocity measurement precisions of 0.4 km/s. Using an E/I criterion of 3, we have identified 282 velocity variables. In the past year we have expanded the number of final orbital solutions by 45 to a total of more than 80 solutions. In coeval stellar populations, circular binaries tend to have the shortest orbital periods, while longer period binaries show a distribution of non-zero eccentricities. The circularization of the shortest period orbits is the result of an exchange of stellar and orbital angular momentum due to tidal interactions. We defined a population’s tidal circularization period as the longest orbital period at which a binary of typical initial eccentricity has become circularized (e.g., has evolved to an eccentricity e = 0.01) over the lifetime of the cluster (Meibom & Mathieu, 2005, ApJ, 620, 970). We are studying the trend of increasing tidal circularization periods with population age. Preliminary results in NGC 6819 indicate a tidal circularization period of 7.5 days, which is consistent with this overall trend. We will recalculate the tidal circularization period in order to include the latest sample of orbital solutions. This comprehensive survey also allows us to investigate the relative spatial distributions of spectroscopic binaries and other constant-velocity cluster members of similar mass. We find the spectroscopic binaries to be more centrally concentrated at a statistically significant level, which we attribute to energy equipartition processes. MM was supported by REU NSF grant AST-0453442. RDM, SK, KTH, and SM were supported by NSF grant AST-0406615.

The chemical and catalytic properties of nanocrystalline metal oxides prepared through modified sol-gel synthesis

NASA Astrophysics Data System (ADS)

Carnes, Corrie Leigh

The goal of this research was to synthesize, characterize and study the chemical properties of nanocrystalline metal oxides. Nanocrystalline (NC) ZnO, CuO, NiO, Al2O3, and the binary Al2O 3/MgO and ZnO/CuO were prepared through modified sol gel methods. These NC metal oxides were studied in comparison to the commercial (CM) metal oxides. The samples were characterized by XRD, TGA, FTIR, BET, and TEM. The NC samples were all accompanied by a significant increase in surface area and decrease in crystallite size. Several chemical reactions were studied to compare the NC samples to the CM samples. One of the reactions involved a high temperature reaction between carbon tetrachloride and the oxide to form carbon dioxide and the corresponding metal chloride. A similar high temperature reaction was conducted between the metal oxide and hydrogen sulfide to form water and the corresponding metal sulfide. A room temperature gas phase adsorption was studied where SO2 was adsorbed onto the oxide. A liquid phase adsorption conducted at room temperature was the destructive adsorption of paraoxon (a toxic insecticide). In all reactions the NC samples exhibited greater activity, destroying or adsorbing a larger amount of the toxins compared to the CM samples. To better study surface area effects catalytic reactions were also studied. The catalysis of methanol was studied over the nanocrystalline ZnO, CuO, NiO, and ZnO/CuO samples in comparison to their commercial counterparts. In most cases the NC samples proved to be more active catalysts, having higher percent conversions and turnover numbers. A second catalytic reaction was also studied, this reaction was investigated to look at the support effects. The catalysis of cyclopropane to propane was studied over Pt and Co catalysts. These catalysts were supported onto NC and CM alumina by impregnation. By observing differences in the catalytic behavior, support effects have become apparent.

Synthesis and Characterization of CO-and H2S-Tolerant Electrocatalysts for PEM Fuel Cell

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

Shamsuddin Ilias

2005-12-22

The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary,more » ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. During this reporting period we synthesized four Pt-based electrocatalysts catalysts (Pt/Ru/Mo/Se, Pt/Ru/Mo/Ir, Pt/Ru/Mo/W, Ptr/Ru/Mo/Co) on Vulcan XG72 Carbon support by both conventional and ultra-sonication method. From current-voltage performance study, the catalytic activity was found in the increasing order of Pt/Ru/Mo/Ir > Pt/Ru/Mo/W > Pt/Ru/Mo/Co > Pt/Ru/MO/Se. Sonication method appears to provide better dispersion of catalysts on carbon support.« less

On multi-site damage identification using single-site training data

NASA Astrophysics Data System (ADS)

Barthorpe, R. J.; Manson, G.; Worden, K.

2017-11-01

This paper proposes a methodology for developing multi-site damage location systems for engineering structures that can be trained using single-site damaged state data only. The methodology involves training a sequence of binary classifiers based upon single-site damage data and combining the developed classifiers into a robust multi-class damage locator. In this way, the multi-site damage identification problem may be decomposed into a sequence of binary decisions. In this paper Support Vector Classifiers are adopted as the means of making these binary decisions. The proposed methodology represents an advancement on the state of the art in the field of multi-site damage identification which require either: (1) full damaged state data from single- and multi-site damage cases or (2) the development of a physics-based model to make multi-site model predictions. The potential benefit of the proposed methodology is that a significantly reduced number of recorded damage states may be required in order to train a multi-site damage locator without recourse to physics-based model predictions. In this paper it is first demonstrated that Support Vector Classification represents an appropriate approach to the multi-site damage location problem, with methods for combining binary classifiers discussed. Next, the proposed methodology is demonstrated and evaluated through application to a real engineering structure - a Piper Tomahawk trainer aircraft wing - with its performance compared to classifiers trained using the full damaged-state dataset.

Binary Sources and Binary Lenses in Microlensing Surveys of MACHOs

NASA Astrophysics Data System (ADS)

Petrovic, N.; Di Stefano, R.; Perna, R.

2003-12-01

Microlensing is an intriguing phenomenon which may yield information about the nature of dark matter. Early observational searches identified hundreds of microlensing light curves. The data set consisted mainly of point-lens light curves and binary-lens events in which the light curves exhibit caustic crossings. Very few mildly perturbed light curves were observed, although this latter type should constitute the majority of binary lens light curves. Di Stefano (2001) has suggested that the failure to take binary effects into account may have influenced the estimates of optical depth derived from microlensing surveys. The work we report on here is the first step in a systematic analysis of binary lenses and binary sources and their impact on the results of statistical microlensing surveys. In order to asses the problem, we ran Monte-Carlo simulations of various microlensing events involving binary stars (both as the source and as the lens). For each event with peak magnification > 1.34, we sampled the characteristic light curve and recorded the chi squared value when fitting the curve with a point lens model; we used this to asses the perturbation rate. We also recorded the parameters of each system, the maximum magnification, the times at which each light curve started and ended and the number of caustic crossings. We found that both the binarity of sources and the binarity of lenses increased the lensing rate. While the binarity of sources had a negligible effect on the perturbation rates of the light curves, the binarity of lenses had a notable effect. The combination of binary sources and binary lenses produces an observable rate of interesting events exhibiting multiple "repeats" in which the magnification rises above and dips below 1.34 several times. Finally, the binarity of lenses impacted both the durations of the events and the maximum magnifications. This work was supported in part by the SAO intern program (NSF grant AST-9731923) and NASA contracts NAS8-39073 and NAS8-38248 (CXC).

Phosphorization boosts the capacitance of mixed metal nanosheet arrays for high performance supercapacitor electrodes.

PubMed

Lan, Yingying; Zhao, Hongyang; Zong, Yan; Li, Xinghua; Sun, Yong; Feng, Juan; Wang, Yan; Zheng, Xinliang; Du, Yaping

2018-05-01

Binary transition metal phosphides hold immense potential as innovative electrode materials for constructing high-performance energy storage devices. Herein, porous binary nickel-cobalt phosphide (NiCoP) nanosheet arrays anchored on nickel foam (NF) were rationally designed as self-supported binder-free electrodes with high supercapacitance performance. Taking the combined advantages of compositional features and array architectures, the nickel foam supported NiCoP nanosheet array (NiCoP@NF) electrode possesses superior electrochemical performance in comparison with Ni-Co LDH@NF and NiCoO2@NF electrodes. The NiCoP@NF electrode shows an ultrahigh specific capacitance of 2143 F g-1 at 1 A g-1 and retained 1615 F g-1 even at 20 A g-1, showing excellent rate performance. Furthermore, a binder-free all-solid-state asymmetric supercapacitor device is designed, which exhibits a high energy density of 27 W h kg-1 at a power density of 647 W kg-1. The hierarchical binary nickel-cobalt phosphide nanosheet arrays hold great promise as advanced electrode materials for supercapacitors with high electrochemical performance.

Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells

PubMed Central

2014-01-01

Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li+Cl–), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li+Cl– catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA. PMID:24748912

Black-hole binaries as relics of gamma-ray burst/hypernova explosions

NASA Astrophysics Data System (ADS)

Moreno Mendez, Enrique

The Collapsar model, in which a fast-spinning massive star collapses into a Kerr black hole, has become the standard model to explain long-soft gamma-ray bursts and hypernova explosions (GRB/HN). However, stars massive enough (those with ZAMS mass ≳ (18--20) M⊙ ) to produce these events evolve through a path that loses too much angular momentum to produce a central engine capable of delivering the necessary energy. In this work I suggest that the soft X-ray transient sources are the remnants of GRBs/HNe. Binaries in which the massive primary star evolves a carbon-oxygen burning core, then start to transfer material to the secondary star (Case C mass transfer), causing the orbit to decay until a common-envelope phase sets in. The secondary spirals in, further narrowing the orbit of the binary and removing the hydrogen envelope of the primary star. Eventually the primary star becomes tidally locked and spins up, acquiring enough rotational energy to power up a GRB/HN explosion. The central engine producing the GRB/HN event is the Kerr black hole acting through the Blandford-Znajek mechanism. This model can explain not only the long-soft GRBs, but also the subluminous bursts (which comprise ˜ 97% of the total), the long-soft bursts and the short-hard bursts (in a neutron star, black hole merger). Because of our binary evolution through Case C mass transfer, it turns out that for the subluminous and cosmological bursts, the angular momentum O is proportional to m3/2D , where mD is the mass of the donor (secondary star). This binary evolution model has a great advantage over the Woosley Collapsar model; one can "dial" the donor mass in order to obtain whatever angular momentum is needed to drive the explosion. Population syntheses show that there are enough binaries to account for the progenitors of all known classes of GRBs.

Compact Binary Progenitors of Short Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Giacomazzo, Bruno; Perna, Rosalba; Rezzolla, Luciano; Troja, Eleonora; Lazzati, Davide

2013-01-01

In recent years, detailed observations and accurate numerical simulations have provided support to the idea that mergers of compact binaries containing either two neutron stars (NSs) or an NS and a black hole (BH) may constitute the central engine of short gamma-ray bursts (SGRBs). The merger of such compact binaries is expected to lead to the production of a spinning BH surrounded by an accreting torus. Several mechanisms can extract energy from this system and power the SGRBs. Here we connect observations and numerical simulations of compact binary mergers, and use the current sample of SGRBs with measured energies to constrain the mass of their powering tori. By comparing the masses of the tori with the results of fully general-relativistic simulations, we are able to infer the properties of the binary progenitors that yield SGRBs. By assuming a constant efficiency in converting torus mass into jet energy epsilon(sub jet) = 10%, we find that most of the tori have masses smaller than 0.01 Solar M, favoring "high-mass" binary NSs mergers, i.e., binaries with total masses approx >1.5 the maximum mass of an isolated NS. This has important consequences for the gravitational wave signals that may be detected in association with SGRBs, since "high-mass" systems do not form a long-lived hypermassive NS after the merger. While NS-BH systems cannot be excluded to be the engine of at least some of the SGRBs, the BH would need to have an initial spin of approx. 0.9 or higher.

Development of a Novel Vaccine Containing Binary Toxin for the Prevention of Clostridium difficile Disease with Enhanced Efficacy against NAP1 Strains.

PubMed

Secore, Susan; Wang, Su; Doughtry, Julie; Xie, Jinfu; Miezeiewski, Matt; Rustandi, Richard R; Horton, Melanie; Xoconostle, Rachel; Wang, Bei; Lancaster, Catherine; Kristopeit, Adam; Wang, Sheng-Ching; Christanti, Sianny; Vitelli, Salvatore; Gentile, Marie-Pierre; Goerke, Aaron; Skinner, Julie; Strable, Erica; Thiriot, David S; Bodmer, Jean-Luc; Heinrichs, Jon H

2017-01-01

Clostridium difficile infections (CDI) are a leading cause of nosocomial diarrhea in the developed world. The main virulence factors of the bacterium are the large clostridial toxins (LCTs), TcdA and TcdB, which are largely responsible for the symptoms of the disease. Recent outbreaks of CDI have been associated with the emergence of hypervirulent strains, such as NAP1/BI/027, many strains of which also produce a third toxin, binary toxin (CDTa and CDTb). These hypervirulent strains have been associated with increased morbidity and higher mortality. Here we present pre-clinical data describing a novel tetravalent vaccine composed of attenuated forms of TcdA, TcdB and binary toxin components CDTa and CDTb. We demonstrate, using the Syrian golden hamster model of CDI, that the inclusion of binary toxin components CDTa and CDTb significantly improves the efficacy of the vaccine against challenge with NAP1 strains in comparison to vaccines containing only TcdA and TcdB antigens, while providing comparable efficacy against challenge with the prototypic, non-epidemic strain VPI10463. This combination vaccine elicits high neutralizing antibody titers against TcdA, TcdB and binary toxin in both hamsters and rhesus macaques. Finally we present data that binary toxin alone can act as a virulence factor in animal models. Taken together, these data strongly support the inclusion of binary toxin in a vaccine against CDI to provide enhanced protection from epidemic strains of C. difficile.

Development of a Novel Vaccine Containing Binary Toxin for the Prevention of Clostridium difficile Disease with Enhanced Efficacy against NAP1 Strains

PubMed Central

Wang, Su; Doughtry, Julie; Xie, Jinfu; Miezeiewski, Matt; Rustandi, Richard R.; Horton, Melanie; Xoconostle, Rachel; Wang, Bei; Lancaster, Catherine; Kristopeit, Adam; Wang, Sheng-Ching; Christanti, Sianny; Vitelli, Salvatore; Gentile, Marie-Pierre; Goerke, Aaron; Skinner, Julie; Strable, Erica; Thiriot, David S.; Bodmer, Jean-Luc; Heinrichs, Jon H.

2017-01-01

Clostridium difficile infections (CDI) are a leading cause of nosocomial diarrhea in the developed world. The main virulence factors of the bacterium are the large clostridial toxins (LCTs), TcdA and TcdB, which are largely responsible for the symptoms of the disease. Recent outbreaks of CDI have been associated with the emergence of hypervirulent strains, such as NAP1/BI/027, many strains of which also produce a third toxin, binary toxin (CDTa and CDTb). These hypervirulent strains have been associated with increased morbidity and higher mortality. Here we present pre-clinical data describing a novel tetravalent vaccine composed of attenuated forms of TcdA, TcdB and binary toxin components CDTa and CDTb. We demonstrate, using the Syrian golden hamster model of CDI, that the inclusion of binary toxin components CDTa and CDTb significantly improves the efficacy of the vaccine against challenge with NAP1 strains in comparison to vaccines containing only TcdA and TcdB antigens, while providing comparable efficacy against challenge with the prototypic, non-epidemic strain VPI10463. This combination vaccine elicits high neutralizing antibody titers against TcdA, TcdB and binary toxin in both hamsters and rhesus macaques. Finally we present data that binary toxin alone can act as a virulence factor in animal models. Taken together, these data strongly support the inclusion of binary toxin in a vaccine against CDI to provide enhanced protection from epidemic strains of C. difficile. PMID:28125650

Orbital Characteristics of the Subdwarf-B and F V Star Binary EC 20117-4014 (=V4640 Sgr)

NASA Astrophysics Data System (ADS)

Otani, T.; Oswalt, T. D.; Lynas-Gray, A. E.; Kilkenny, D.; Koen, C.; Amaral, M.; Jordan, R.

2018-06-01

Among the competing evolution theories for subdwarf-B (sdB) stars is the binary evolution scenario. EC 20117-4014 (=V4640 Sgr) is a spectroscopic binary system consisting of a pulsating sdB star and a late F main-sequence companion; however, the period and the orbit semimajor axes have not been precisely determined. This paper presents orbital characteristics of the EC 20117-4014 binary system using 20 years of photometric data. Periodic observed minus calculated (O–C) variations were detected in the two highest-amplitude pulsations identified in the EC 20117-4014 power spectrum, indicating the binary system’s precise orbital period (P = 792.3 days) and the light-travel-time amplitude (A = 468.9 s). This binary shows no significant orbital eccentricity, and the upper limit of the eccentricity is 0.025 (using 3σ as an upper limit). This upper limit of the eccentricity is the lowest among all wide sdB binaries with known orbital parameters. This analysis indicated that the sdB is likely to have lost its hydrogen envelope through stable Roche lobe overflow, thus supporting hypotheses for the origin of sdB stars. In addition to those results, the underlying pulsation period change obtained from the photometric data was \\dot{P} = 5.4 (±0.7) × 10‑14 d d‑1, which shows that the sdB is just before the end of the core helium-burning phase.

The massive star binary fraction in young open clusters - II. NGC6611 (Eagle Nebula)

NASA Astrophysics Data System (ADS)

Sana, H.; Gosset, E.; Evans, C. J.

2009-12-01

Based on a set of over 100 medium- to high-resolution optical spectra collected from 2003 to 2009, we investigate the properties of the O-type star population in NGC6611 in the core of the Eagle Nebula (M16). Using a much more extended data set than previously available, we revise the spectral classification and multiplicity status of the nine O-type stars in our sample. We confirm two suspected binaries and derive the first SB2 orbital solutions for two systems. We further report that two other objects are displaying a composite spectrum, suggesting possible long-period binaries. Our analysis is supported by a set of Monte Carlo simulations, allowing us to estimate the detection biases of our campaign and showing that the latter do not affect our conclusions. The absolute minimal binary fraction in our sample is fmin = 0.44 but could be as high as 0.67 if all the binary candidates are confirmed. As in NGC6231 (see Paper I), up to 75 per cent of the O star population in NGC6611 are found in an O+OB system, thus implicitly excluding random pairing from a classical IMF as a process to describe the companion association in massive binaries. No statistical difference could be further identified in the binary fraction, mass-ratio and period distributions between NGC6231 and NGC 6611, despite the difference in age and environment of the two clusters.

The Orbit of the Gamma-Ray Binary 1FGL J1018.6−5856

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

Monageng, I. M.; McBride, V. A.; Kniazev, A. Y.

2017-09-20

Gamma-ray binaries are a small subclass of the high mass X-ray binary population that exhibit emission across the whole electromagnetic spectrum. We present the radial velocities of 1FGL J1018.6−5856 based on the observations obtained with the Southern African Large Telescope. We combine our measurements with those published in the literature to get a broad phase coverage. The mass function obtained supports a neutron star compact object, although a black hole mass is possible for the very low inclination angles. The improved phase coverage allows constraints to be placed on the orbital eccentricity ( e = 0.31 ± 0.16), which agreesmore » with the estimates from the high-energy data.« less

Compressed multi-block local binary pattern for object tracking

NASA Astrophysics Data System (ADS)

Li, Tianwen; Gao, Yun; Zhao, Lei; Zhou, Hao

2018-04-01

Both robustness and real-time are very important for the application of object tracking under a real environment. The focused trackers based on deep learning are difficult to satisfy with the real-time of tracking. Compressive sensing provided a technical support for real-time tracking. In this paper, an object can be tracked via a multi-block local binary pattern feature. The feature vector was extracted based on the multi-block local binary pattern feature, which was compressed via a sparse random Gaussian matrix as the measurement matrix. The experiments showed that the proposed tracker ran in real-time and outperformed the existed compressive trackers based on Haar-like feature on many challenging video sequences in terms of accuracy and robustness.

Mixing, diffusion, and percolation in binary supported membranes containing mixtures of lipids and amphiphilic block copolymers.

PubMed

Gettel, Douglas L; Sanborn, Jeremy; Patel, Mira A; de Hoog, Hans-Peter; Liedberg, Bo; Nallani, Madhavan; Parikh, Atul N

2014-07-23

Substrate-mediated fusion of small polymersomes, derived from mixtures of lipids and amphiphilic block copolymers, produces hybrid, supported planar bilayers at hydrophilic surfaces, monolayers at hydrophobic surfaces, and binary monolayer/bilayer patterns at amphiphilic surfaces, directly responding to local measures of (and variations in) surface free energy. Despite the large thickness mismatch in their hydrophobic cores, the hybrid membranes do not exhibit microscopic phase separation, reflecting irreversible adsorption and limited lateral reorganization of the polymer component. With increasing fluid-phase lipid fraction, these hybrid, supported membranes undergo a fluidity transition, producing a fully percolating fluid lipid phase beyond a critical area fraction, which matches the percolation threshold for the immobile point obstacles. This then suggests that polymer-lipid hybrid membranes might be useful models for studying obstructed diffusion, such as occurs in lipid membranes containing proteins.

Support-vector-machine tree-based domain knowledge learning toward automated sports video classification

NASA Astrophysics Data System (ADS)

Xiao, Guoqiang; Jiang, Yang; Song, Gang; Jiang, Jianmin

2010-12-01

We propose a support-vector-machine (SVM) tree to hierarchically learn from domain knowledge represented by low-level features toward automatic classification of sports videos. The proposed SVM tree adopts a binary tree structure to exploit the nature of SVM's binary classification, where each internal node is a single SVM learning unit, and each external node represents the classified output type. Such a SVM tree presents a number of advantages, which include: 1. low computing cost; 2. integrated learning and classification while preserving individual SVM's learning strength; and 3. flexibility in both structure and learning modules, where different numbers of nodes and features can be added to address specific learning requirements, and various learning models can be added as individual nodes, such as neural networks, AdaBoost, hidden Markov models, dynamic Bayesian networks, etc. Experiments support that the proposed SVM tree achieves good performances in sports video classifications.

Solitary waves in dimer binary collision model

NASA Astrophysics Data System (ADS)

Ahsan, Zaid; Jayaprakash, K. R.

2017-01-01

Solitary wave propagation in nonlinear diatomic (dimer) chains is a very interesting topic of research in the study of nonlinear lattices. Such waves were recently found to be supported by the essentially nonlinear granular lattice and Toda lattice. An interesting aspect of this discovery is attributed to the realization of a spectrum of the mass ratio (the only system parameter governing the dynamics) that supports the propagation of such waves corresponding to the considered interaction potential. The objective of this exposition is to explore solitary wave propagation in the dimer binary collision (BC) model. Interestingly, the dimer BC model supports solitary wave propagation at a discrete spectrum of mass ratios similar to those observed in granular and Toda dimers. Further, we report a qualitative and one-to-one correspondence between the spectrum of the mass ratio corresponding to the dimer BC model and those corresponding to granular and Toda dimer chains.

Influence of various carbon nano-forms as supports for Pt catalyst on proton exchange membrane fuel cell performance

NASA Astrophysics Data System (ADS)

Bharti, Abha; Cheruvally, Gouri

2017-08-01

In this study, we discuss the influence of various carbon supports for Pt on proton exchange membrane (PEM) fuel cell performance. Here, Pt supported on various carbon nano-forms [Pt/carbon black (Pt/CB), Pt/single-walled carbon nanotubes (Pt/SWCNT), Pt/multi-walled carbon nanotubes (Pt/MWCNT) and Pt/graphene (Pt/G)] are synthesized by a facile, single step, microwave-assisted, modified chemical reduction route. Their physical, chemical and electrochemical characteristics pertaining to oxygen reduction reaction (ORR) catalytic activity and stability in PEM fuel cell are studied in detail by various techniques and compared. The study shows that the different carbon supports does not significantly affect the Pt particle size during synthesis, but leads to different amount of defective sites in the carbon framework which influence both the availability of active metal nano-catalysts and metal-support interaction. In-situ electrochemical investigations reveal that the different carbon supports influence both ORR catalytic activity and stability of the catalyst. This is further corroborated by the demonstration of varying polarization characteristics on PEM fuel cell performance by different carbon supported Pt catalysts. This study reveals MWCNT as the most suitable carbon support for Pt catalyst, exhibiting high activity and stability for ORR in PEM fuel cell.

MERGERS OF UNEQUAL-MASS GALAXIES: SUPERMASSIVE BLACK HOLE BINARY EVOLUTION AND STRUCTURE OF MERGER REMNANTS

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

Khan, Fazeel Mahmood; Preto, Miguel; Berentzen, Ingo

Galaxy centers are residing places for supermassive black holes (SMBHs). Galaxy mergers bring SMBHs close together to form gravitationally bound binary systems, which, if able to coalesce in less than a Hubble time, would be one of the most promising sources of gravitational waves (GWs) for the Laser Interferometer Space Antenna. In spherical galaxy models, SMBH binaries stall at a separation of approximately 1 pc, leading to the 'final parsec problem' (FPP). On the other hand, it has been shown that merger-induced triaxiality of the remnant in equal-mass mergers is capable of supporting a constant supply of stars on themore » so-called centrophilic orbits that interact with the binary and thus avoid the FPP. In this paper, using a set of direct N-body simulations of mergers of initially spherically symmetric galaxies with different mass ratios, we show that the merger-induced triaxiality is also able to drive unequal-mass SMBH binaries to coalescence. The binary hardening rates are high and depend only weakly on the mass ratios of SMBHs for a wide range of mass ratios q. There is, however, an abrupt transition in the hardening rates for mergers with mass ratios somewhere between q {approx} 0.05 and 0.1, resulting from the monotonic decrease of merger-induced triaxiality with mass ratio q, as the secondary galaxy becomes too small and light to significantly perturb the primary, i.e., the more massive one. The hardening rates are significantly higher for galaxies having steep cusps in comparison with those having shallow cups at centers. The evolution of the binary SMBH leads to relatively shallower inner slopes at the centers of the merger remnants. The stellar mass displaced by the SMBH binary on its way to coalescence is {approx}1-5 times the combined mass of binary SMBHs. The coalescence timescales for SMBH binary with mass {approx}10{sup 6} M{sub Sun} are less than 1 Gyr and for those at the upper end of SMBH masses 10{sup 9} M{sub Sun} are 1-2 Gyr for less eccentric binaries whereas they are less than 1 Gyr for highly eccentric binaries. SMBH binaries are thus expected to be promising sources of GWs at low and high redshifts.« less

Experimental and theoretical study using DFT method for the competitive adsorption of two cationic dyes from wastewaters

NASA Astrophysics Data System (ADS)

Regti, Abdelmajid; Ayouchia, Hicham Ben El; Laamari, My Rachid; Stiriba, Salah Eddine; Anane, Hafid; Haddad, Mohammadine El

2016-12-01

The adsorption of cationic dyes, Basic Yellow (BY28) and Methylene Blue (MB) on a new activated carbon from medlar species were studied in both single and binary system. Some experimental parameters, namely, pH, amount of adsorbent and contact time are studied. Quantum chemical results indicate that the adsorption efficiency was directly related to the dye electrophilicity power. Some theorical parameters were calculated and proved that MB is more electrophilic than BY28, than greatest interaction with surface sites. Kinetic study showed that the adsorption follows the pseudo-second-order model and Freundlich was the best model to describe the phenomenon in the single and binary system. According to the local reactivity results using Parr functions, the sulphur and nitrogen atoms will be the main adsorption sites.

Application of a constant hole volume Sanchez-Lacombe equation of state to mixtures relevant to polymeric foaming.

PubMed

von Konigslow, Kier; Park, Chul B; Thompson, Russell B

2018-06-06

A variant of the Sanchez-Lacombe equation of state is applied to several polymers, blowing agents, and saturated mixtures of interest to the polymer foaming industry. These are low-density polyethylene-carbon dioxide and polylactide-carbon dioxide saturated mixtures as well as polystyrene-carbon dioxide-dimethyl ether and polystyrene-carbon dioxide-nitrogen ternary saturated mixtures. Good agreement is achieved between theoretically predicted and experimentally determined solubilities, both for binary and ternary mixtures. Acceptable agreement with swelling ratios is found with no free parameters. Up-to-date pure component Sanchez-Lacombe characteristic parameters are provided for carbon dioxide, dimethyl ether, low-density polyethylene, nitrogen, polylactide, linear and branched polypropylene, and polystyrene. Pure fluid low-density polyethylene and nitrogen parameters exhibit more moderate success while still providing acceptable quantitative estimations. Mixture estimations are found to have more moderate success where pure components are not as well represented. The Sanchez-Lacombe equation of state is found to correctly predict the anomalous reversal of solubility temperature dependence for low critical point fluids through the observation of this behaviour in polystyrene nitrogen mixtures.

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

Valle, Massimo Della; International Center for Relativistic Astrophysics Network, Piazzale della Repubblica 10, I-65122, Pescara

I’ll review the status of the Supernova/Gamma-Ray Burst connection. Several pieces of evidence suggest that long duration Gamma-ray Bursts are associated with bright SNe-Ic. However recent works suggest that GRBs might be produced in tight binary systems composed of a massive carbon-oxygen cores and a neutron star companion. Current estimates of the SN and GRB rates yield a ratio GRB/SNe-Ibc in the range ∼ 0.4% − 3%.

Combined NMR and molecular dynamics modeling study of transport properties in sulfonamide based deep eutectic lithium electrolytes: LiTFSI based binary systems.

PubMed

Pauric, Allen D; Halalay, Ion C; Goward, Gillian R

2016-03-07

The trend toward Li-ion batteries operating at increased (>4.3 V vs. Li/Li(+)) voltages requires the development of novel classes of lithium electrolytes with electrochemical stability windows exceeding those of LiPF6/carbonate electrolyte solutions. Several new classes of electrolytes have been synthesized and investigated over the past decade, in the search for LIB electrolytes with improved properties (increased hydrolytic stability, improved thermal abuse tolerance, higher oxidation voltages, etc.) compared with the present state-of-the-art LiPF6 and organic carbonates-based formulations. Among these are deep eutectic electrolytes (DEEs), which share many beneficial characteristics with ionic liquids, such as low vapor pressure and large electrochemical stability windows, with the added advantage of a significantly higher lithium transference number. The present work presents the pulsed field gradient NMR characterization of the transport properties (diffusion coefficients and cation transport numbers) of binary DEEs consisting of a sulfonamide solvent and lithium bis(trifluoromethanesulfonyl)imide salt. Insights into the structural and dynamical properties, which enable one to rationalize the observed ionic conductivity behavior were obtained from a combination of NMR data and MD simulations. The insights thus gained should assist the formulation of novel DEEs with improved properties for LIB applications.

A versatile strategy toward binary three-dimensional architectures based on engineering graphene aerogels with porous carbon fabrics for supercapacitors.

PubMed

Song, Wei-Li; Song, Kuo; Fan, Li-Zhen

2015-02-25

Graphene-based supercapacitors and related flexible devices have attracted great attention because of the increasing demands in the energy storage. As promising three-dimensional (3D) nanostructures in the supercapacitor electrodes, graphene-based aerogels have been paid dramatic attention recently, and numerous methods have been developed for enhancing their performance in energy storage. In this study, an exclusive strategy is presented toward directly in situ growing reduced graphene oxide (RGO) aerogels inside the 3D porous carbon fabrics for engineering the interfaces of the resulting binary 3D architectures. Such unique architectures have shown various advantages in the improvements of the nanostructures and chemical compositions, allowing them to possess much enhanced electrochemical properties (391, 229, and 195 F g(-1) at current densities of 0.1, 1, and 5 A g(-1), respectively) with excellent cycling stability in comparison with the neat RGO aerogels. The results of the performance in the flexible all-solid-state supercapacitors along with discussion on the related mechanisms in the electrochemical properties indicate the remaining issues and associated opportunities in the development of advanced energy storage devices. This strategy is relatively facile, versatile, and tunable, which highlights a unique platform for engineering various 3D porous structures in many fields.

New analytical technique for carbon dioxide absorption solvents

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

Pouryousefi, F.; Idem, R.O.

2008-02-15

The densities and refractive indices of two binary systems (water + MEA and water + MDEA) and three ternary systems (water + MEA + CO{sub 2}, water + MDEA + CO{sub 2}, and water + MEA + MDEA) used for carbon dioxide (CO{sub 2}) capture were measured over the range of compositions of the aqueous alkanolamine(s) used for CO{sub 2} absorption at temperatures from 295 to 338 K. Experimental densities were modeled empirically, while the experimental refractive indices were modeled using well-established models from the known values of their pure-component densities and refractive indices. The density and Gladstone-Dale refractive indexmore » models were then used to obtain the compositions of unknown samples of the binary and ternary systems by simultaneous solution of the density and refractive index equations. The results from this technique have been compared with HPLC (high-performance liquid chromatography) results, while a third independent technique (acid-base titration) was used to verify the results. The results show that the systems' compositions obtained from the simple and easy-to-use refractive index/density technique were very comparable to the expensive and laborious HPLC/titration techniques, suggesting that the refractive index/density technique can be used to replace existing methods for analysis of fresh or nondegraded, CO{sub 2}-loaded, single and mixed alkanolamine solutions.« less

Modelling of ceramide interactions with porous graphite carbon in non-aqueous liquid chromatography.

PubMed

West, C; Cilpa, G; Gaudin, K; Chaminade, P; Lesellier, E

2005-09-16

Interactions of solutes on porous graphitic carbon (PGC) with non-aqueous mobile phases are studied by the linear solvation energy relationship (LSER). Studies have been carried out with eight binary mixtures composed of a weak solvent (acetonitrile or methanol) and a strong solvent (tetrahydrofuran, n-butanol, CH2Cl2, 1,1,2-trichloro-2,2,1-trifluoroethane). The systematic analysis of a set of test compounds was performed for each solvent mixture in isocratic mode (50:50). The results were compared to those obtained on PGC with hydro-organic liquids and supercritical fluids. They were then correlated with the observed retention behaviour of lipid compounds, more particularly ceramides.

Multiplicity in Early Stellar Evolution

NASA Astrophysics Data System (ADS)

Reipurth, B.; Clarke, C. J.; Boss, A. P.; Goodwin, S. P.; Rodríguez, L. F.; Stassun, K. G.; Tokovinin, A.; Zinnecker, H.

Observations from optical to centimeter wavelengths have demonstrated that multiple systems of two or more bodies is the norm at all stellar evolutionary stages. Multiple systems are widely agreed to result from the collapse and fragmentation of cloud cores, despite the inhibiting influence of magnetic fields. Surveys of class 0 protostars with millimeter interferometers have revealed a very high multiplicity frequency of about 2/3, even though there are observational difficulties in resolving close protobinaries, thus supporting the possibility that all stars could be born in multiple systems. Near-infrared adaptive optics observations of class I protostars show a lower binary frequency relative to the class 0 phase, a declining trend that continues through the class II/III stages to the field population. This loss of companions is a natural consequence of dynamical interplay in small multiple systems, leading to ejection of members. We discuss observational consequences of this dynamical evolution, and its influence on circumstellar disks, and we review the evolution of circumbinary disks and their role in defining binary mass ratios. Special attention is paid to eclipsing PMS binaries, which allow for observational tests of evolutionary models of early stellar evolution. Many stars are born in clusters and small groups, and we discuss how interactions in dense stellar environments can significantly alter the distribution of binary separations through dissolution of wider binaries. The binaries and multiples we find in the field are the survivors of these internal and external destructive processes, and we provide a detailed overview of the multiplicity statistics of the field, which form a boundary condition for all models of binary evolution. Finally, we discuss various formation mechanisms for massive binaries, and the properties of massive trapezia.

Application of Pulsed-Field Gel Electrophoresis and Binary Typing as Tools in Veterinary Clinical Microbiology and Molecular Epidemiologic Analysis of Bovine and Human Staphylococcus aureus Isolates

PubMed Central

Zadoks, Ruth; van Leeuwen, Willem; Barkema, Herman; Sampimon, Otlis; Verbrugh, Henri; Schukken, Ynte Hein; van Belkum, Alex

2000-01-01

Thirty-eight bovine mammary Staphylococcus aureus isolates from diverse clinical, temporal, and geographical origins were genotyped by pulsed-field gel electrophoresis (PFGE) after SmaI digestion of prokaryotic DNA and by means of binary typing using 15 strain-specific DNA probes. Seven pulsed-field types and four subtypes were identified, as were 16 binary types. Concordant delineation of genetic relatedness was documented by both techniques, yet based on practical and epidemiological considerations, binary typing was the preferable method. Genotypes of bovine isolates were compared to 55 previously characterized human S. aureus isolates through cluster analysis of binary types. Genetic clusters containing strains of both human and bovine origin were found, but bacterial genotypes were predominantly associated with a single host species. Binary typing proved an excellent tool for comparison of S. aureus strains, including methicillin-resistant S. aureus, derived from different host species and from different databases. For 28 bovine S. aureus isolates, detailed clinical observations in vivo were compared to strain typing results in vitro. Associations were found between distinct genotypes and severity of disease, suggesting strain-specific bacterial virulence. Circumstantial evidence furthermore supports strain-specific routes of bacterial dissemination. We conclude that PFGE and binary typing can be successfully applied for genetic analysis of S. aureus isolates from bovine mammary secretions. Binary typing in particular is a robust and simple method and promises to become a powerful tool for strain characterization, for resolution of clonal relationships of bacteria within and between host species, and for identification of sources and transmission routes of bovine S. aureus. PMID:10790124

A binary origin for 'blue stragglers' in globular clusters.

PubMed

Knigge, Christian; Leigh, Nathan; Sills, Alison

2009-01-15

Blue stragglers in globular clusters are abnormally massive stars that should have evolved off the stellar main sequence long ago. There are two known processes that can create these objects: direct stellar collisions and binary evolution. However, the relative importance of these processes has remained unclear. In particular, the total number of blue stragglers found in a given cluster does not seem to correlate with the predicted collision rate, providing indirect support for the binary-evolution model. Yet the radial distributions of blue stragglers in many clusters are bimodal, with a dominant central peak: this has been interpreted as an indication that collisions do dominate blue straggler production, at least in the high-density cluster cores. Here we report that there is a clear, but sublinear, correlation between the number of blue stragglers found in a cluster core and the total stellar mass contained within it. From this we conclude that most blue stragglers, even those found in cluster cores, come from binary systems. The parent binaries, however, may themselves have been affected by dynamical encounters. This may be the key to reconciling all of the seemingly conflicting results found to date.

A New Quantum Gray-Scale Image Encoding Scheme

NASA Astrophysics Data System (ADS)

Naseri, Mosayeb; Abdolmaleky, Mona; Parandin, Fariborz; Fatahi, Negin; Farouk, Ahmed; Nazari, Reza

2018-02-01

In this paper, a new quantum images encoding scheme is proposed. The proposed scheme mainly consists of four different encoding algorithms. The idea behind of the scheme is a binary key generated randomly for each pixel of the original image. Afterwards, the employed encoding algorithm is selected corresponding to the qubit pair of the generated randomized binary key. The security analysis of the proposed scheme proved its enhancement through both randomization of the generated binary image key and altering the gray-scale value of the image pixels using the qubits of randomized binary key. The simulation of the proposed scheme assures that the final encoded image could not be recognized visually. Moreover, the histogram diagram of encoded image is flatter than the original one. The Shannon entropies of the final encoded images are significantly higher than the original one, which indicates that the attacker can not gain any information about the encoded images. Supported by Kermanshah Branch, Islamic Azad University, Kermanshah, IRAN

Dynamical Mass Segregation Versus Disruption of Binary Stars in Dense Stellar Systems

NASA Astrophysics Data System (ADS)

de Grijs, Richard; Li, C.; Deng, L.

2013-01-01

Upon their formation, dynamically cool (collapsing) star clusters will, within only a few million years, achieve stellar mass segregation for stars down to a few solar masses due to gravitational two-body encounters. Since binary systems are, on average, more massive than single stars, one would expect them to also rapidly mass segregate dynamically. Contrary to these expectations and based on high-resolution Hubble Space Telescope observations, we show that the compact, 15-30 Myr-old Large Magellanic Cloud cluster NGC 1818 is characterized by an increasing fraction of F-star binary systems (with combined masses of 1.3-1.6 solar masses) with increasing distance from the cluster center. This offers unprecedented support of the theoretically predicted but thus far unobserved dynamical disruption processes of the significant population of "soft" binary systems (with relatively low binding energies compared to the kinetic energy of their stellar members) in star clusters, which we could unravel by virtue of the cluster's unique combination of youth and high stellar density.

A Loader for Executing Multi-Binary Applications on the Thinking Machines CM-5: It's Not Just for SPMD Anymore

NASA Technical Reports Server (NTRS)

Becker, Jeffrey C.

1995-01-01

The Thinking Machines CM-5 platform was designed to run single program, multiple data (SPMD) applications, i.e., to run a single binary across all nodes of a partition, with each node possibly operating on different data. Certain classes of applications, such as multi-disciplinary computational fluid dynamics codes, are facilitated by the ability to have subsets of the partition nodes running different binaries. In order to extend the CM-5 system software to permit such applications, a multi-program loader was developed. This system is based on the dld loader which was originally developed for workstations. This paper provides a high level description of dld, and describes how it was ported to the CM-5 to provide support for multi-binary applications. Finally, it elaborates how the loader has been used to implement the CM-5 version of MPIRUN, a portable facility for running multi-disciplinary/multi-zonal MPI (Message-Passing Interface Standard) codes.

Carbon Stars Identified from LAMOST DR4 Using Machine Learning

NASA Astrophysics Data System (ADS)

Li, Yin-Bi; Luo, A.-Li; Du, Chang-De; Zuo, Fang; Wang, Meng-Xin; Zhao, Gang; Jiang, Bi-Wei; Zhang, Hua-Wei; Liu, Chao; Qin, Li; Wang, Rui; Du, Bing; Guo, Yan-Xin; Wang, Bo; Han, Zhan-Wen; Xiang, Mao-Sheng; Huang, Yang; Chen, Bing-Qiu; Chen, Jian-Jun; Kong, Xiao; Hou, Wen; Song, Yi-Han; Wang, You-Fen; Wu, Ke-Fei; Zhang, Jian-Nan; Zhang, Yong; Wang, Yue-Fei; Cao, Zi-Huang; Hou, Yong-Hui; Zhao, Yong-Heng

2018-02-01

In this work, we present a catalog of 2651 carbon stars from the fourth Data Release (DR4) of the Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST). Using an efficient machine-learning algorithm, we find these stars from more than 7 million spectra. As a by-product, 17 carbon-enhanced metal-poor turnoff star candidates are also reported in this paper, and they are preliminarily identified by their atmospheric parameters. Except for 176 stars that could not be given spectral types, we classify the other 2475 carbon stars into five subtypes: 864 C-H, 226 C-R, 400 C-J, 266 C-N, and 719 barium stars based on a series of spectral features. Furthermore, we divide the C-J stars into three subtypes, C-J(H), C-J(R), and C-J(N), and about 90% of them are cool N-type stars as expected from previous literature. Besides spectroscopic classification, we also match these carbon stars to multiple broadband photometries. Using ultraviolet photometry data, we find that 25 carbon stars have FUV detections and that they are likely to be in binary systems with compact white dwarf companions.

Acoustics of marine sediment under compaction: binary grain-size model and viscoelastic extension of Biot's theory.

PubMed

Leurer, Klaus C; Brown, Colin

2008-04-01

This paper presents a model of acoustic wave propagation in unconsolidated marine sediment, including compaction, using a concept of a simplified sediment structure, modeled as a binary grain-size sphere pack. Compressional- and shear-wave velocities and attenuation follow from a combination of Biot's model, used as the general framework, and two viscoelastic extensions resulting in complex grain and frame moduli, respectively. An effective-grain model accounts for the viscoelasticity arising from local fluid flow in expandable clay minerals in clay-bearing sediments. A viscoelastic-contact model describes local fluid flow at the grain contacts. Porosity, density, and the structural Biot parameters (permeability, pore size, structure factor) as a function of pressure follow from the binary model, so that the remaining input parameters to the acoustic model consist solely of the mass fractions and the known mechanical properties of each constituent (e.g., carbonates, sand, clay, and expandable clay) of the sediment, effective pressure, or depth, and the environmental parameters (water depth, salinity, temperature). Velocity and attenuation as a function of pressure from the model are in good agreement with data on coarse- and fine-grained unconsolidated marine sediments.

Laboratory Studies of Aedes aegypti Attraction to Ketones, Sulfides, and Primary Chloroalkanes Tested Alone and in Combination with L-Lactic Acid.

PubMed

Bernier, Ulrich R; Kline, Daniel L; Allan, Sandra A; Barnard, Donald R

2015-03-01

The attraction of female Aedes aegypti to single compounds and binary compositions containing L-lactic acid and an additional saturated compound from a set of ketones, sulfides, and chloroalkanes was studied using a triple-cage dual-port olfactometer. These chemical classes were studied because of their structural relation to acetone, dimethyl disulfide, and dichloromethane, which have all been reported to synergize attraction to L-lactic acid. Human odors, carbon dioxide, and the binary mixture of L-lactic acid and CO₂served as controls for comparison of attraction responses produced by the binary mixtures. All tested mixtures that contained chloroalkanes attracted mosquitoes at synergistic levels, as did L-lactic acid and CO₂. Synergism was less frequent in mixtures of L-lactic acid with sulfides and ketones; in the case of ketones, synergistic attraction was observed only for L-lactic acid combined with acetone or butanone. Suppression or inhibition of attraction response was observed for combinations that contained ketones of C7-C12 molecular chain length (optimum in the C8-C10 range). This inhibition effect is similar to that observed previously for specific ranges of carboxylic acids, aldehydes, and alcohols.

Study of different nanostructured carbon supports for fuel cell catalysts

NASA Astrophysics Data System (ADS)

Mirabile Gattia, Daniele; Antisari, Marco Vittori; Giorgi, Leonardo; Marazzi, Renzo; Piscopiello, Emanuela; Montone, Amelia; Bellitto, Serafina; Licoccia, Silvia; Traversa, Enrico

Pt clusters were deposited by an impregnation process on three carbon supports: multi-wall carbon nanotubes (MWNT), single-wall carbon nanohorns (SWNH), and Vulcan XC-72 carbon black to investigate the effect of the carbon support structure on the possibility of reducing Pt loading on electrodes for direct methanol (DMFC) fuel cells without impairing performance. MWNT and SWNH were in-house synthesised by a DC and an AC arc discharge process between pure graphite electrodes, respectively. UV-vis spectrophotometry, scanning and transmission electron microscopy, X-ray diffraction, and cyclic voltammetry measurements were used to characterize the Pt particles deposited on the three carbon supports. A differential yield for Pt deposition, not strictly related to the surface area of the carbon support, was observed. SWNH showed the highest surface chemical activity toward Pt deposition. Pt deposited in different forms depending on the carbon support. Electrochemical characterizations showed that the Pt nanostructures deposited on MWNT are particularly efficient in the methanol oxidation reaction.

Carbon nanotubes grown on bulk materials and methods for fabrication

DOEpatents

Menchhofer, Paul A [Clinton, TN; Montgomery, Frederick C [Oak Ridge, TN; Baker, Frederick S [Oak Ridge, TN

2011-11-08

Disclosed are structures formed as bulk support media having carbon nanotubes formed therewith. The bulk support media may comprise fibers or particles and the fibers or particles may be formed from such materials as quartz, carbon, or activated carbon. Metal catalyst species are formed adjacent the surfaces of the bulk support material, and carbon nanotubes are grown adjacent the surfaces of the metal catalyst species. Methods employ metal salt solutions that may comprise iron salts such as iron chloride, aluminum salts such as aluminum chloride, or nickel salts such as nickel chloride. Carbon nanotubes may be separated from the carbon-based bulk support media and the metal catalyst species by using concentrated acids to oxidize the carbon-based bulk support media and the metal catalyst species.

The formation of protostellar binaries in primordial minihalos

NASA Astrophysics Data System (ADS)

Riaz, R.; Bovino, S.; Vanaverbeke, S.; Schleicher, D. R. G.

2018-06-01

The first stars are known to form in primordial gas, either in minihalos with about 106 M⊙ or so-called atomic cooling halos of about 108 M⊙. Simulations have shown that gravitational collapse and disk formation in primordial gas yield dense stellar clusters. In this paper, we focus particularly on the formation of protostellar binary systems, and aim to quantify their properties during the early stage of their evolution. For this purpose, we combine the smoothed particle hydrodynamics code GRADSPH with the astrochemistry package KROME. The GRADSPH-KROME framework is employed to investigate the collapse of primordial clouds in the high-density regime, exploring the fragmentation process and the formation of binary systems. We observe a strong dependence of fragmentation on the strength of the turbulent Mach number M and the rotational support parameter β. Rotating clouds show significant fragmentation, and have produced several Pop. III proto-binary systems. We report maximum and minimum mass accretion rates of 2.31 × 10-1 M⊙ yr-1 and 2.18 × 10-4 M⊙ yr-1. The mass spectrum of the individual Pop III proto-binary components ranges from 0.88 M⊙ to 31.96 M⊙ and has a sensitive dependence on the Mach number M as well as on the rotational parameter β. We also report a range from ˜0.01 to ˜1 for the mass ratio of our proto-binary systems.

Where Planets Take up Residence

NASA Technical Reports Server (NTRS)

2007-01-01

This diagram illustrates that mature planetary systems like our own might be more common around twin, or binary, stars that are either really close together, or really far apart.

NASA's Spitzer Space Telescope observed that debris disks, which are signposts of mature planetary systems, are more abundant around the tightest and widest of binary stars it studied. Specifically, the infrared telescope found significantly more debris disks around binary stars that are 0 to 3 astronomical units apart (top panel) and 50 to 500 astronomical units apart (bottom panel) than binary stars that are 3 to 50 astronomical units apart (middle panel). An astronomical unit is the distance between Earth and the sun.

In other words, if two stars are as far apart from each other as the sun is from Jupiter (5 astronomical units) or Pluto (40 astronomical units), they would be unlikely to host a family of planetary bodies.

The Spitzer data also revealed that debris disks circle all the way around both members of a close-knit binary (top panel), but only a single member of a wide duo (bottom panel). This could explain why the intermediately spaced binary systems (middle panel) can be inhospitable to planetary disks: they are too far apart to support one big disk around both stars, and they are too close together to have enough room for a disk around just one star.

Quantitative Microbial Risk Assessment Tutorial: Publishing a Microbial Density Time Series as a Txt File

EPA Science Inventory

A SARA Timeseries Utility supports analysis and management of time-varying environmental data including listing, graphing, computing statistics, computing meteorological data and saving in a WDM or text file. File formats supported include WDM, HSPF Binary (.hbn), USGS RDB, and T...

The Role of Materialism on Social, Emotional and Behavioural Difficulties for British Adolescents

ERIC Educational Resources Information Center

Maras, Pam; Moon, Amy; Gupta, Taveeshi; Gridley, Nicole

2015-01-01

The relationship between materialism and social-emotional behavioural difficulties (SEBDs) was assessed by comparing a sample of adolescents receiving in-school behavioural support with adolescents not receiving any support. All participants completed the Youth Materialism Scale and the Strengths and Difficulties Questionnaire. Binary logistic…

Single wall carbon nanotube supports for portable direct methanol fuel cells.

PubMed

Girishkumar, G; Hall, Timothy D; Vinodgopal, K; Kamat, Prashant V

2006-01-12

Single-wall and multiwall carbon nanotubes are employed as carbon supports in direct methanol fuel cells (DMFC). The morphology and electrochemical activity of single-wall and multiwall carbon nanotubes obtained from different sources have been examined to probe the influence of carbon support on the overall performance of DMFC. The improved activity of the Pt-Ru catalyst dispersed on carbon nanotubes toward methanol oxidation is reflected as a shift in the onset potential and a lower charge transfer resistance at the electrode/electrolyte interface. The evaluation of carbon supports in a passive air breathing DMFC indicates that the observed power density depends on the nature and source of carbon nanostructures. The intrinsic property of the nanotubes, dispersion of the electrocatalyst and the electrochemically active surface area collectively influence the performance of the membrane electrode assembly (MEA). As compared to the commercial carbon black support, single wall carbon nanotubes when employed as the support for anchoring the electrocatalyst particles in the anode and cathode sides of MEA exhibited a approximately 30% enhancement in the power density of a single stack DMFC operating at 70 degrees C.

Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for Column CO2 Measurements

NASA Astrophysics Data System (ADS)

Campbell, J. F.; Lin, B.; Nehrir, A. R.; Obland, M. D.; Liu, Z.; Browell, E. V.; Chen, S.; Kooi, S. A.; Fan, T. F.

2015-12-01

Global and regional atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission and Atmospheric Carbon and Transport (ACT) - America airborne investigation are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity-Modulated Continuous-Wave (IM-CW) lidar techniques are being investigated as a means of facilitating CO2 measurements from space and airborne platforms to meet the mission science measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud returns. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of intervening optically thin clouds, thereby minimizing bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the Earth's surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques and provides very high (at sub-meter level) range resolution. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These techniques are used in a new data processing architecture to support the ASCENDS CarbonHawk Experiment Simulator (ACES) and ACT-America programs.

No rationale for 1 variable per 10 events criterion for binary logistic regression analysis.

PubMed

van Smeden, Maarten; de Groot, Joris A H; Moons, Karel G M; Collins, Gary S; Altman, Douglas G; Eijkemans, Marinus J C; Reitsma, Johannes B

2016-11-24

Ten events per variable (EPV) is a widely advocated minimal criterion for sample size considerations in logistic regression analysis. Of three previous simulation studies that examined this minimal EPV criterion only one supports the use of a minimum of 10 EPV. In this paper, we examine the reasons for substantial differences between these extensive simulation studies. The current study uses Monte Carlo simulations to evaluate small sample bias, coverage of confidence intervals and mean square error of logit coefficients. Logistic regression models fitted by maximum likelihood and a modified estimation procedure, known as Firth's correction, are compared. The results show that besides EPV, the problems associated with low EPV depend on other factors such as the total sample size. It is also demonstrated that simulation results can be dominated by even a few simulated data sets for which the prediction of the outcome by the covariates is perfect ('separation'). We reveal that different approaches for identifying and handling separation leads to substantially different simulation results. We further show that Firth's correction can be used to improve the accuracy of regression coefficients and alleviate the problems associated with separation. The current evidence supporting EPV rules for binary logistic regression is weak. Given our findings, there is an urgent need for new research to provide guidance for supporting sample size considerations for binary logistic regression analysis.

The most plausible explanation of the cyclic period changes in close binaries: the case of the RS CVn-type binary WW Dra

NASA Astrophysics Data System (ADS)

Liao, W.-P.; Qian, S.-B.

2010-07-01

Cyclic period changes are a fairly common phenomenon in close binary systems and are usually explained as being caused either by the magnetic activity of one or both components or by the light travel time effect (LTTE) of a third body. We searched the orbital period changes in 182 EA-type (including the 101 Algol systems used by Hall), 43 EB-type and 53 EW-type binaries with known mass ratio and spectral type of the secondary component. We reproduced and improved the diagram in Hall according to the new collected data. Our plots do not support the conclusion derived by Hall that cyclic period changes are restricted to binaries having a secondary component with spectral type later than F5. The presence of period changes among systems with a secondary component of early type indicates that magnetic activity is one, but not the only, cause of the period variation. It is discovered that cyclic period changes, probably resulting from the presence of a third body, are more frequent in EW-type binaries among close systems. Therefore, the most plausible explanation of the cyclic period changes is the LTTE through the presence of a third body. Using the century-long historical record of the times of light minimum, we analysed the cyclic period change in the Algol binary WW Dra. It is found that the orbital period of the binary shows a ~112.2-yr cyclic variation with an amplitude of ~0.1977d. The cyclic oscillation can be attributed to the LTTE by means of a third body with a mass no less than 6.43Msolar. However, no spectral lines of the third body were discovered, indicating that it may be a candidate black hole. The third body is orbiting the binary at a distance closer than 14.4 au and may play an important role in the evolution of this system.

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.

The Hot Horizontal-Branch Stars in omega Centauri

NASA Technical Reports Server (NTRS)

Moehler, S.; Dreizler, S.; Lanz, T.; Bono, G.; Sweigart, A. V.; Calamida, A.; Nonino, M.

2010-01-01

Context. UV observations of some massive globular clusters have revealed a significant population of stars hotter and fainter than the hot end of the horizontal branch (HB), the so-called blue hook stars. This feature might be explained either by the late hot flasher scenario where stars experience the helium flash while on the white dwarf cooling curve or by the progeny of the helium-enriched sub-population recently postulated to exist in some clusters. Previous spectroscopic analyses of blue hook stars in co Cen and NGC 2808 support the late hot flasher scenario, but the stars contain much less helium than expected and the predicted C, N enrichment could not be verified. Aims. We compare observed effective temperatures, surface gravities, helium abundances, and carbon line strengths (where detectable) of our targets stars to the predictions of the two scenarios. Methods. Moderately high resolution spectra of hot HB stars in the globular cluster omega-Cen were analysed for radial velocity variations, atmospheric parameters and abundances using LTE and non-LTE model atmospheres. Results. We find no evidence for close binaries among our target stars. All stars below 30 000 K are helium-poor and very similar to HB stars observed in that temperature range in other globular clusters. In the temperature range 30000 K to 50000 K we find that 28% of our stars are helium-poor (log ((sup n)He/(sup n )H)< - 1.6), while 72% have roughly solar or super-solar helium abundance (log ((sup n)He/(sup n )H) >/= -1.5). We also find carbon enrichment strongly correlated with helium enrichment, with a maximum carbon enrichment of 3% by mass. Conclusions. The strong carbon enrichment in tandem with helium enrichment is predicted by the late hot flasher scenario, but not by the helium-enrichment scenario. We conclude that the helium-rich HB stars in omega-Cen cannot be explained solely by the helium-enrichment scenario invoked to explain the blue main sequence.

Molecular Dynamics Simulations of the Initial-State Predict Product Distributions of Dediazoniation of Aryldiazonium in Binary Solvents.

PubMed

Cruz, Gustavo N; Lima, Filipe S; Dias, Luís G; El Seoud, Omar A; Horinek, Dominik; Chaimovich, Hernan; Cuccovia, Iolanda M

2015-09-04

The dediazoniation of aryldiazonium salts in mixed solvents proceeds by a borderline SN1 and SN2 pathway, and product distribution should be proportional to the composition of the solvation shell of the carbon attached to the -N2 group (ipso carbon). The rates of dediazoniation of 2,4,6-trimethylbenzenediazonium in water, methanol, ethanol, propanol, and acetonitrile were similar, but measured product distributions were noticeably dependent on the nature of the water/cosolvent mixture. Here we demonstrated that solvent distribution in the first solvation shell of the ipso carbon, calculated from classical molecular dynamics simulations, is equal to the measured product distribution. Furthermore, we showed that regardless of the charge distribution of the initial state, i.e., whether the positive charge is smeared over the molecule or localized on phenyl moiety, the solvent distribution around the reaction center is nearly the same.

Binary gas mixture adsorption-induced deformation of microporous carbons by Monte Carlo simulation.

PubMed

Cornette, Valeria; de Oliveira, J C Alexandre; Yelpo, Víctor; Azevedo, Diana; López, Raúl H

2018-07-15

Considering the thermodynamic grand potential for more than one adsorbate in an isothermal system, we generalize the model of adsorption-induced deformation of microporous carbons developed by Kowalczyk et al. [1]. We report a comprehensive study of the effects of adsorption-induced deformation of carbonaceous amorphous porous materials due to adsorption of carbon dioxide, methane and their mixtures. The adsorption process is simulated by using the Grand Canonical Monte Carlo (GCMC) method and the calculations are then used to analyze experimental isotherms for the pure gases and mixtures with different molar fraction in the gas phase. The pore size distribution determined from an experimental isotherm is used for predicting the adsorption-induced deformation of both pure gases and their mixtures. The volumetric strain (ε) predictions from the GCMC method are compared against relevant experiments with good agreement found in the cases of pure gases. Copyright © 2018 Elsevier Inc. All rights reserved.

Where are the Binaries? Results of a Long-term Search for Radial Velocity Binaries in Proto-planetary Nebulae

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

Hrivnak, Bruce J.; Lu, Wenxian; Steene, Griet Van de

We present the results of an expanded, long-term radial velocity search (25 years) for evidence of binarity in a sample of seven bright proto-planetary nebulae (PPNe). The goal is to investigate the widely held view that the bipolar or point-symmetric shapes of planetary nebulae (PNe) and PPNe are due to binary interactions. Observations from three observatories were combined from 2007 to 2015 to search for variations on the order of a few years and then combined with earlier observations from 1991 to 1995 to search for variations on the order of decades. All seven show velocity variations due to periodicmore » pulsation in the range of 35–135 days. However, in only one PPN, IRAS 22272+5435, did we find even marginal evidence for multi-year variations that might be due to a binary companion. This object shows marginally significant evidence of a two-year period of low semi-amplitude, which could be due to a low-mass companion, and it also displays some evidence of a much longer period of >30 years. The absence of evidence in the other six objects for long-period radial velocity variations due to a binary companion sets significant constraints on the properties of any undetected binary companions: they must be of low mass, ≤0.2 M {sub ⊙}, or long period, >30 years. Thus the present observations do not provide direct support for the binary hypothesis to explain the shapes of PNe and PPNe and severely constrains the properties of any such undetected companions.« less

Classification of octet AB-type binary compounds using dynamical charges: A materials informatics perspective

DOE PAGES

Pilania, G.; Gubernatis, J. E.; Lookman, T.

2015-12-03

The role of dynamical (or Born effective) charges in classification of octet AB-type binary compounds between four-fold (zincblende/wurtzite crystal structures) and six-fold (rocksalt crystal structure) coordinated systems is discussed. We show that the difference in the dynamical charges of the fourfold and sixfold coordinated structures, in combination with Harrison’s polarity, serves as an excellent feature to classify the coordination of 82 sp–bonded binary octet compounds. We use a support vector machine classifier to estimate the average classification accuracy and the associated variance in our model where a decision boundary is learned in a supervised manner. Lastly, we compare the out-of-samplemore » classification accuracy achieved by our feature pair with those reported previously.« less

The Algol-like binary TT Hydrae - The stars, circumstellar matter, and superionized plasma

NASA Technical Reports Server (NTRS)

Plavec, Mirek J.

1988-01-01

This paper reports on superionized UV emission lines discovered in TT Hydrae (HD 97528), a semidetached eclipsing binary system in the Southern-Hemisphere sky. The list of emission lines observed is typical for interacting nondegenerate binaries of the Algol type, but with system-specific relative-intensity characteristics. The primary component of the system is a B9.5 V main-sequence star with effective temperature of 9800 K. Its mass equals 2.25 solar masses; the radius is 1.9 solar radii; and surface gravity log g equals 4.23. The secondary star has a mass of 0.41 solar mass and fills its critical Roche lobe. Evidence obtained on mass interaction supports the conclusion that HD 97528 is a normal semidetached system.

A massive pulsar in a compact relativistic binary.

PubMed

Antoniadis, John; Freire, Paulo C C; Wex, Norbert; Tauris, Thomas M; Lynch, Ryan S; van Kerkwijk, Marten H; Kramer, Michael; Bassa, Cees; Dhillon, Vik S; Driebe, Thomas; Hessels, Jason W T; Kaspi, Victoria M; Kondratiev, Vladislav I; Langer, Norbert; Marsh, Thomas R; McLaughlin, Maura A; Pennucci, Timothy T; Ransom, Scott M; Stairs, Ingrid H; van Leeuwen, Joeri; Verbiest, Joris P W; Whelan, David G

2013-04-26

Many physically motivated extensions to general relativity (GR) predict substantial deviations in the properties of spacetime surrounding massive neutron stars. We report the measurement of a 2.01 ± 0.04 solar mass (M⊙) pulsar in a 2.46-hour orbit with a 0.172 ± 0.003 M⊙ white dwarf. The high pulsar mass and the compact orbit make this system a sensitive laboratory of a previously untested strong-field gravity regime. Thus far, the observed orbital decay agrees with GR, supporting its validity even for the extreme conditions present in the system. The resulting constraints on deviations support the use of GR-based templates for ground-based gravitational wave detectors. Additionally, the system strengthens recent constraints on the properties of dense matter and provides insight to binary stellar astrophysics and pulsar recycling.

A new study of the interacting binary star V356 Sgr

NASA Technical Reports Server (NTRS)

Polidan, R. S.

1988-01-01

Results on V356 Sgr from IUE and Voyager ultraviolet (500 to 3200 A) observations obtained in 1986 and 1987, primarily during 2 total eclipses are presented. The eclipse of Aug. 15, 1986 was fully covered with IUE low dispersion images and 9 hr of Voyager UVS data. The eclipse of Mar. 25, 1987 was covered with IUE low dispersion images and 1 high dispersion SWP image. During both eclipses the total strength of the emission lines is found to be invariant. An uneclipsed UV continuum is detected at wavelengths shorter than 1500 A. The high dispersion SWP spectrum reveals that the emission lines are extremely broad, almost symmetrical emissions with weak, slightly blue shifted absorption components. No evidence of carbon, C I, C II, C III, or C IV, is seen in the emission or absorption spectrum of V356 Sgr in eclipse. Models for this binary system are presented.

Discovery of very high velocity outflow in V Hydra - Wind from an accretion disk in a binary?

NASA Technical Reports Server (NTRS)

Sahai, R.; Wannier, P. G.

1988-01-01

High-resolution observations of lines from the CO v = 1-0 vibration-rotation band at 4.6 microns, taken with the FTS/KPNO 4-m telescope, are reported for the carbon-rich red giant V Hydra, which is surrounded by an extended expanding molecular envelope resulting from extensive mass loss. The spectrum shows, in addition to the expected absorption at the outflow velocity of the envelope, absorption extending up to 120 km/s bluewards of the stellar velocity. A comparison of the spectrum observed at two epochs shows that the high-velocity absorption features change with time. It is suggested that the observed high-velocity features in V Hydra arise in a high-velocity polar outflow from an accretion disk in a binary system, as proposed in the mass-loss model for bipolar envelopes by Morris (1988).

Extraction of purine alkaloids from maté (Ilex paraguariensis) using supercritical CO(2).

PubMed

Saldaña, M D; Mohamed, R S; Baer, M G; Mazzafera, P

1999-09-01

Experimental data for the supercritical CO(2) extraction of purine alkaloids (caffeine, theobromine, and theophylline) from ground herbal maté tea (Ilex paraguaryensis) using a high-pressure apparatus are presented. Caffeine, theophylline, and theobromine were identified in the extracted fractions using HPLC. Results indicated a much higher CO(2) selectivity for caffeine in comparison with those for theophylline and theobromine. Solubilities of pure compounds in carbon dioxide were also determined at 313.2, 323.2, 338.2, and 343.2 K, and pressures ranging from 14 to 24 MPa. Caffeine solubility exhibited a retrograde behavior with temperature while theophylline and theobromine manifested a normal behavior at conditions explored in this study. Solubilities in binary CO(2)/purine alkaloid model systems were much higher than those obtained during extraction of maté tea, demonstrating the difficulty of using binary data in predicting complex multicomponent behavior.

Invited Article: Mask-modulated lensless imaging with multi-angle illuminations

NASA Astrophysics Data System (ADS)

Zhang, Zibang; Zhou, You; Jiang, Shaowei; Guo, Kaikai; Hoshino, Kazunori; Zhong, Jingang; Suo, Jinli; Dai, Qionghai; Zheng, Guoan

2018-06-01

The use of multiple diverse measurements can make lensless phase retrieval more robust. Conventional diversity functions include aperture diversity, wavelength diversity, translational diversity, and defocus diversity. Here we discuss a lensless imaging scheme that employs multiple spherical-wave illuminations from a light-emitting diode array as diversity functions. In this scheme, we place a binary mask between the sample and the detector for imposing support constraints for the phase retrieval process. This support constraint enforces the light field to be zero at certain locations and is similar to the aperture constraint in Fourier ptychographic microscopy. We use a self-calibration algorithm to correct the misalignment of the binary mask. The efficacy of the proposed scheme is first demonstrated by simulations where we evaluate the reconstruction quality using mean square error and structural similarity index. The scheme is then experimentally tested by recovering images of a resolution target and biological samples. The proposed scheme may provide new insights for developing compact and large field-of-view lensless imaging platforms. The use of the binary mask can also be combined with other diversity functions for better constraining the phase retrieval solution space. We provide the open-source implementation code for the broad research community.

Colliding Winds and Tomography of O-Type Binaries

NASA Technical Reports Server (NTRS)

Gies, Dougles R.

1995-01-01

This grant was awarded in support of an observational study with the NASA IUE Observatory during the 15th episode (1992), and it subsequently also supported our continuing work in 16th (1994) and 18th (1995) episodes. The project involved the study of FUV spectra of massive spectroscopic binary systems containing hot stars of spectral type O. We applied a Doppler tomography algorithm to reconstruct the individual component UV spectra of stars in order to obtain improved estimates of the temperature, gravity, UV intensity ratio, and projected rotational velocity for stars in each system, and to make a preliminary survey for abundance anomalies through comparison with standard spectra. We also investigated the orbital phase-related variations in the UV stellar wind lines to probe the geometries of wind-wind collisions in these systems. The project directly supported two Ph.D. dissertations at Georgia State University (by Penny and Thaller), and we are grateful for this support. No inventions were made in the performance of this work. Detailed results are summarized in the abstracts listed in the following section.

The effect of activated carbon support surface modification on characteristics of carbon nanospheres prepared by deposition precipitation of Fe-catalyst

NASA Astrophysics Data System (ADS)

Kristianto, H.; Arie, A. A.; Susanti, R. F.; Halim, M.; Lee, J. K.

2016-11-01

In this study the effect of activated carbon support modification to synthesis of CNSs was observed. Modification of activated carbon was done by using nitric acid. The effect of modification was analyzed from its FTIR spectra. The Fe catalysts were deposited on to the support by using urea deposition precipitation method at various initial catalysts concentration. CNSs was synthesized by utilizing cooking palm oil as renewable carbon source, and pyrolized at 700°C for 1 hour under nitrogen atmosphere. The products obtained then analyzed using SEM-EDS, TEM, XRD, and Raman spectroscopy. The modification of activated carbon support had increased the oxygen functional group. This increase resulted on increase of metal catalysts deposited on activated carbon surface. Peak of C (100) was observed, while ID/IG of samples were obtained around 0.9, which is commonly obtained for CNSs. High catalysts loading on modified activated carbon support caused decomposition of CNSs and formation carbon onion.

a Gsa-Svm Hybrid System for Classification of Binary Problems

NASA Astrophysics Data System (ADS)

Sarafrazi, Soroor; Nezamabadi-pour, Hossein; Barahman, Mojgan

2011-06-01

This paperhybridizesgravitational search algorithm (GSA) with support vector machine (SVM) and made a novel GSA-SVM hybrid system to improve the classification accuracy in binary problems. GSA is an optimization heuristic toolused to optimize the value of SVM kernel parameter (in this paper, radial basis function (RBF) is chosen as the kernel function). The experimental results show that this newapproach can achieve high classification accuracy and is comparable to or better than the particle swarm optimization (PSO)-SVM and genetic algorithm (GA)-SVM, which are two hybrid systems for classification.

About decomposition approach for solving the classification problem

NASA Astrophysics Data System (ADS)

Andrianova, A. A.

2016-11-01

This article describes the features of the application of an algorithm with using of decomposition methods for solving the binary classification problem of constructing a linear classifier based on Support Vector Machine method. Application of decomposition reduces the volume of calculations, in particular, due to the emerging possibilities to build parallel versions of the algorithm, which is a very important advantage for the solution of problems with big data. The analysis of the results of computational experiments conducted using the decomposition approach. The experiment use known data set for binary classification problem.

Structural difference rule for amorphous alloy formation by ion mixing

NASA Technical Reports Server (NTRS)

Liu, B.-X.; Johnson, W. L.; Nicolet, M.A.; Lau, S. S.

1983-01-01

A rule is formulated which establishes a sufficient condition that an amorphous binary alloy will be formed by ion mixing of multilayered samples when the two constituent metals are of different crystalline structure, regardless of their atomic sizes and electronegativities. The rule is supported by the experimental results obtained on six selected binary metal systems, as well as by the previous data reported in the literature. The amorphization mechanism is discussed in terms of the competition between two different structures resulting in frustration of the crystallization process.

The formation mechanism of binary semiconductor nanomaterials: shared by single-source and dual-source precursor approaches.

PubMed

Yu, Kui; Liu, Xiangyang; Zeng, Qun; Yang, Mingli; Ouyang, Jianying; Wang, Xinqin; Tao, Ye

2013-10-11

One thing in common: The formation of binary colloidal semiconductor nanocrystals from single- (M(EEPPh2 )n ) and dual-source precursors (metal carboxylates M(OOCR)n and phosphine chalcogenides such as E=PHPh2 ) is found to proceed through a common mechanism. For CdSe as a model system (31) P NMR spectroscopy and DFT calculations support a reaction mechanism which includes numerous metathesis equilibriums and Se exchange reactions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Functionalized Natural Carbon-Supported Nanoparticles as Excellent Catalysts for Hydrocarbon Production.

PubMed

Sun, Jian; Guo, Lisheng; Ma, Qingxiang; Gao, Xinhua; Yamane, Noriyuki; Xu, Hengyong; Tsubaki, Noritatsu

2017-02-01

We report a one-pot and eco-friendly synthesis of carbon-supported cobalt nanoparticles, achieved by carbonization of waste biomass (rice bran) with a cobalt source. The functionalized biomass provides carbon microspheres as excellent catalyst support, forming a unique interface between hydrophobic and hydrophilic groups. The latter, involving hydroxyl and amino groups, can catch much more active cobalt nanoparticles on surface for Fischer-Tropsch synthesis than chemical carbon. The loading amount of cobalt on the final catalyst is much higher than that prepared with a chemical carbon source, such as glucose. The proposed concept of using a functionalized natural carbon source shows great potential compared with conventional carbon sources, and will be meaningful for other fields concerning carbon support, such as heterogeneous catalysis or electrochemical fields. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spacecraft On-Board Information Extraction Computer (SOBIEC)

NASA Technical Reports Server (NTRS)

Eisenman, David; Decaro, Robert E.; Jurasek, David W.

1994-01-01

The Jet Propulsion Laboratory is the Technical Monitor on an SBIR Program issued for Irvine Sensors Corporation to develop a highly compact, dual use massively parallel processing node known as SOBIEC. SOBIEC couples 3D memory stacking technology provided by nCUBE. The node contains sufficient network Input/Output to implement up to an order-13 binary hypercube. The benefit of this network, is that it scales linearly as more processors are added, and it is a superset of other commonly used interconnect topologies such as: meshes, rings, toroids, and trees. In this manner, a distributed processing network can be easily devised and supported. The SOBIEC node has sufficient memory for most multi-computer applications, and also supports external memory expansion and DMA interfaces. The SOBIEC node is supported by a mature set of software development tools from nCUBE. The nCUBE operating system (OS) provides configuration and operational support for up to 8000 SOBIEC processors in an order-13 binary hypercube or any subset or partition(s) thereof. The OS is UNIX (USL SVR4) compatible, with C, C++, and FORTRAN compilers readily available. A stand-alone development system is also available to support SOBIEC test and integration.

NuSTAR Observations of Two New Black Hole X-ray Binary Candidates within 1 pc of Sgr A*

NASA Astrophysics Data System (ADS)

Hord, Benjamin; Hailey, Charles; Mori, Kaya; Mandel, Shifra

2018-01-01

Remarkably, two new X-ray transients were discovered in outburst within ~1 pc of the Galactic Center by the Swift X-ray Telescope in the first half of 2016. A few weeks after each outburst began, NuSTAR ToO observations were triggered for both of the objects. These sources have no known counterparts at other energies. Both objects exhibit relativistically broadened Fe lines in their spectra and possible quasi-periodic oscillations (QPO) in their power spectra, which are features seen in many black hole X-ray binaries. Combined with the fact that there have been no previously observed large outbursts at these positions over the decade of the Swift X-ray Telescope galactic center monitoring campaign, these sources make for prime black hole binary candidates (BHC) rather than neutron star low-mass X-ray binaries (NS-LMXB), which have a known short (<~5 year) recurrence time. We will present 3-79 keV NuSTAR spectra and timing analysis of these sources that supports a black hole binary interpretation over a neutron star scenario. These new BHC, combined with at least one other previously discovered BHC near the Galactic Center, hint at a potentially substantive black hole population in the vicinity of the supermassive black hole at Sgr A*.

Thermodynamic functions, freezing transition, and phase diagram of dense carbon-oxygen mixtures in white dwarfs

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

Iyetomi, H.; Ogata, S.; Ichimaru, S.

1989-07-01

Equations of state for dense carbon-oxygen (C-O) binary-ionic mixtures (BIM's) appropriate to the interiors of white dwarfs are investigated through Monte Carlo simulations, by solution of relevant integral equations andvariational calculations in the density-functional formalism. It is thereby shown that the internal energies of the C-O BIM solids and fluids both obey precisely the linear mixing formulas. We then present an accurate calculation of the phase diagram associated with freezing transitions in such BIM materials, resulting in a novel prediction of an azeotropic diagram. Discontinuities of the mass density across the azeotropic phase boundaries areevaluated numerically for application to amore » study of white-dwarf evolution.« less

A Fast Optimization Method for General Binary Code Learning.

PubMed

Shen, Fumin; Zhou, Xiang; Yang, Yang; Song, Jingkuan; Shen, Heng; Tao, Dacheng

2016-09-22

Hashing or binary code learning has been recognized to accomplish efficient near neighbor search, and has thus attracted broad interests in recent retrieval, vision and learning studies. One main challenge of learning to hash arises from the involvement of discrete variables in binary code optimization. While the widely-used continuous relaxation may achieve high learning efficiency, the pursued codes are typically less effective due to accumulated quantization error. In this work, we propose a novel binary code optimization method, dubbed Discrete Proximal Linearized Minimization (DPLM), which directly handles the discrete constraints during the learning process. Specifically, the discrete (thus nonsmooth nonconvex) problem is reformulated as minimizing the sum of a smooth loss term with a nonsmooth indicator function. The obtained problem is then efficiently solved by an iterative procedure with each iteration admitting an analytical discrete solution, which is thus shown to converge very fast. In addition, the proposed method supports a large family of empirical loss functions, which is particularly instantiated in this work by both a supervised and an unsupervised hashing losses, together with the bits uncorrelation and balance constraints. In particular, the proposed DPLM with a supervised `2 loss encodes the whole NUS-WIDE database into 64-bit binary codes within 10 seconds on a standard desktop computer. The proposed approach is extensively evaluated on several large-scale datasets and the generated binary codes are shown to achieve very promising results on both retrieval and classification tasks.

Rotational Synchronization May Enhance Habitability for Circumbinary Planets: Kepler Binary Case Studies

NASA Astrophysics Data System (ADS)

Mason, Paul A.; Zuluaga, Jorge I.; Clark, Joni M.; Cuartas-Restrepo, Pablo A.

2013-09-01

We report a mechanism capable of reducing (or increasing) stellar activity in binary stars, thereby potentially enhancing (or destroying) circumbinary habitability. In single stars, stellar aggression toward planetary atmospheres causes mass-loss, which is especially detrimental for late-type stars, because habitable zones are very close and activity is long lasting. In binaries, tidal rotational breaking reduces magnetic activity, thus reducing harmful levels of X-ray and ultraviolet (XUV) radiation and stellar mass-loss that are able to erode planetary atmospheres. We study this mechanism for all confirmed circumbinary (p-type) planets. We find that main sequence twins provide minimal flux variation and in some cases improved environments if the stars rotationally synchronize within the first Gyr. Solar-like twins, like Kepler 34 and Kepler 35, provide low habitable zone XUV fluxes and stellar wind pressures. These wide, moist, habitable zones may potentially support multiple habitable planets. Solar-type stars with lower mass companions, like Kepler 47, allow for protected planets over a wide range of secondary masses and binary periods. Kepler 38 and related binaries are marginal cases. Kepler 64 and analogs have dramatically reduced stellar aggression due to synchronization of the primary, but are limited by the short lifetime. Kepler 16 appears to be inhospitable to planets due to extreme XUV flux. These results have important implications for estimates of the number of stellar systems containing habitable planets in the Galaxy and allow for the selection of binaries suitable for follow-up searches for habitable planets.

Close Binaries in the Orion Nebula Cluster: On the Universality of Stellar Multiplicity and the Origin of Field Stars

NASA Astrophysics Data System (ADS)

Duchene, Gaspard; Lacour, Sylvestre; Moraux, Estelle; Bouvier, Jerome; Goodwin, Simon

2018-01-01

While stellar multiplicity is an ubiquitous outcome of star formation, there is a clear dichotomy between the multiplicity properties of young (~1 Myr-old) stellar clusters, like the ONC, which host a mostly field-like population of visual binaries, and those of equally young sparse populations, like the Taurus-Auriga region, which host twice as many stellar companions. Two distinct scenarios can account for this observation: one in which different star-forming regions form different number of stars, and one in which multiplicity properties are universal at birth but where internal cluster dynamics destroy many wide binaries. To solve this ambiguity, one must probe binaries that are sufficiently close so as not to be destroyed through interactions with other cluster members. To this end, we have conducted a survey for 10-100 au binaries in the ONC using the aperture masking technique with the VLT adaptive optics system. Among our sample of the 42 ONC members, we discovered 13 companions in this range of projected separations. This is consistent with the companion frequency observed in the Taurus population and twice as high as that observed among field stars. This survey thus strongly supports the idea that stellar multiplicity is characterized by near-universal initial properties that can later be dynamically altered. On the other hand, this exacerbates the question of the origin of field stars, since only clusters much denser than the ONC can effectively destroyed binaries closer than 100 au.

Compositional Investigation of Binary Near-Earth Asteroid 66063 (1998 RO1): A Potentially Undifferentiated Assemblage

NASA Technical Reports Server (NTRS)

Abell, P. A.; Gaffey, M. J.; Landis, R. R.; Jarvis, K. S.

2005-01-01

It is now thought that approximately 16% of all asteroids among the near-Earth population may be binary objects. Several independent lines of evidence, such as the presence of doublet craters on the Earth and Moon [1, 2], complex lightcurves of near-Earth objects exhibiting mutual events [3], and radar images of near-Earth asteroids revealing distinct primary and secondary objects, have supported this conclusion [4]. To date at least 23 near-Earth objects have been discovered as binary systems with expectations that many more have yet to be identified or recognized. Little is known about the physical characteristics of binary objects except that they seem to have fairly rapid rotation rates, generally have primaries in the approx. 1 km diameter range with smaller secondaries on the order of a few hundred meters, and apart from a few exceptions, are in synchronous orbits [4, 5]. Previously only two of these binary near-Earth asteroids (1998 ST27 and 2003 YT1) have been characterized in terms of detailed mineralogical investigations [6, 7]. Such investigations are required to fully understand the formation mechanisms of these binary objects and their possible source regions. In addition, detailed knowledge of these objects may play an important role for planning future spacecraft missions and for the development of impact mitigation strategies. The work presented here represents a continued effort to characterize this particular sub-group of the near- Earth asteroid population.

Potential for a significant deep basin geothermal system in Tintic Valley, Utah

NASA Astrophysics Data System (ADS)

Hardwick, C.; Kirby, S.

2014-12-01

The combination of regionally high heat flow, deep basins, and permeable reservoir rocks in the eastern Great Basin may yield substantial new geothermal resources. We explore a deep sedimentary basin geothermal prospect beneath Tintic Valley in central Utah using new 2D and 3D models coupled with existing estimates of heat flow, geothermometry, and shallow hydrologic data. Tintic Valley is a sediment-filled basin bounded to the east and west by bedrock mountain ranges where heat-flow values vary from 85 to over 240 mW/m2. Based on modeling of new and existing gravity data, a prominent 30 mGal low indicates basin fill thickness may exceed 2 km. The insulating effect of relatively low thermal conductivity basin fill in Tintic Valley, combined with typical Great Basin heat flow, predict temperatures greater than 150 °C at 3 km depth. The potential reservoir beneath the basin fill is comprised of Paleozoic carbonate and clastic rocks. The hydrology of the Tintic Valley is characterized by a shallow, cool groundwater system that recharges along the upper reaches of the basin and discharges along the valley axis and to a series of wells. The east mountain block is warm and dry, with groundwater levels just above the basin floor and temperatures >50 °C at depth. The west mountain block contains a shallow, cool meteoric groundwater system. Fluid temperatures over 50 °C are sufficient for direct-use applications, such as greenhouses and aquaculture, while temperatures exceeding 140°C are suitable for binary geothermal power plants. The geologic setting and regionally high heat flow in Tintic Valley suggest a geothermal resource capable of supporting direct-use geothermal applications and binary power production could be present.

Robust Modeling of Stellar Triples in PHOEBE

NASA Astrophysics Data System (ADS)

Conroy, Kyle E.; Prsa, Andrej; Horvat, Martin; Stassun, Keivan G.

2017-01-01

The number of known mutually-eclipsing stellar triple and multiple systems has increased greatly during the Kepler era. These systems provide significant opportunities to both determine fundamental stellar parameters of benchmark systems to unprecedented precision as well as to study the dynamical interaction and formation mechanisms of stellar and planetary systems. Modeling these systems to their full potential, however, has not been feasible until recently. Most existing available codes are restricted to the two-body binary case and those that do provide N-body support for more components make sacrifices in precision by assuming no stellar surface distortion. We have completely redesigned and rewritten the PHOEBE binary modeling code to incorporate support for triple and higher-order systems while also robustly modeling data with Kepler precision. Here we present our approach, demonstrate several test cases based on real data, and discuss the current status of PHOEBE's support for modeling these types of systems. PHOEBE is funded in part by NSF grant #1517474.

Origin of the Elements

NASA Astrophysics Data System (ADS)

Truran, J. W., Jr.; Heger, A.

2003-12-01

Nucleosynthesis is the study of the nuclear processes responsible for the formation of the elements which constitute the baryonic matter of the Universe. The elements of which the Universe is composed indeed have a quite complicated nucleosynthesis history, which extends from the first three minutes of the Big Bang through to the present. Contemporary nucleosynthesis theory associates the production of certain elements/isotopes or groups of elements with a number of specific astrophysical settings, the most significant of which are: (i) the cosmological Big Bang, (ii) stars, and (iii) supernovae.Cosmological nucleosynthesis studies predict that the conditions characterizing the Big Bang are consistent with the synthesis only of the lightest elements: 1H, 2H, 3He, 4He, and 7Li (Burles et al., 2001; Cyburt et al., 2002). These contributions define the primordial compositions both of galaxies and of the first stars formed therein. Within galaxies, stars and supernovae play the dominant role both in synthesizing the elements from carbon to uranium and in returning heavy-element-enriched matter to the interstellar gas from which new stars are formed. The mass fraction of our solar system (formed ˜4.6 Gyr ago) in the form of heavy elements is ˜1.8%, and stars formed today in our galaxy can be a factor 2 or 3 more enriched (Edvardsson et al., 1993). It is the processes of nucleosynthesis operating in stars and supernovae that we will review in this chapter. We will confine our attention to three broad categories of stellar and supernova site with which specific nucleosynthesis products are understood to be identified: (i) intermediate mass stars, (ii) massive stars and associated type II supernovae, and (iii) type Ia supernovae. The first two of these sites are the straightforward consequence of the evolution of single stars, while type Ia supernovae are understood to result from binary stellar evolution.Stellar nucleosynthesis resulting from the evolution of single stars is a strong function of stellar mass (Woosley et al., 2002). Following phases of hydrogen and helium burning, all stars consist of a carbon-oxygen core. In the mass range of the so-called "intermediate mass" stars (1<˜M/M⊙<˜10), the temperatures realized in their degenerate cores never reach levels at which carbon ignition can occur. Substantial element production occurs in such stars during the asymptotic giant branch (AGB) phase of evolution, accompanied by significant mass loss, and they evolve to white dwarfs of carbon-oxygen (or, less commonly, oxygen-neon) composition. In contrast, the increased pressures that are experienced in the cores of stars of masses M>˜10M⊙ yield higher core temperatures that enable subsequent phases of carbon, neon, oxygen, and silicon burning to proceed. Collapse of an iron core devoid of further nuclear energy then gives rise to a type II supernova and the formation of a neutron star or black hole remnant (Heger et al., 2003). The ejecta of type IIs contain the ashes of nuclear burning of the entire life of the star, but are also modified by the explosion itself. They are the source of most material (by mass) heavier than helium.Observations reveal that binary stellar systems comprise roughly half of all stars in our galaxy. Single star evolution, as noted above, can leave in its wake compact stellar remnants: white dwarfs, neutron stars, and black holes. Indeed, we have evidence for the occurrence of all three types of condensed remnant in binaries. In close binary systems, mass transfer can take place from an evolving companion onto a compact object. This naturally gives rise to a variety of interesting phenomena: classical novae (involving hydrogen thermonuclear runaways in accreted shells on white dwarfs (Gehrz et al., 1998)), X-ray bursts (hydrogen/helium thermonuclear runaways on neutron stars (Strohmayer and Bildsten, 2003)), and X-ray binaries (accretion onto black holes). For some range of conditions, accretion onto carbon-oxygen white dwarfs will permit growth of the CO core to the Chandrasekhar limit MCh=1.4M⊙, and a thermonuclear runaway in to core leads to a type Ia supernova.In this chapter, we will review the characteristics of thermonuclear processing in the three environments we have identified: (i) intermediate-mass stars; (ii) massive stars and type II supernovae; and (iii) type Ia supernovae. This will be followed by a brief discussion of galactic chemical evolution, which illustrates how the contributions from each of these environments are first introduced into the interstellar media of galaxies. Reviews of nucleosynthesis processes include those by Arnett (1995), Trimble (1975), Truran (1984), Wallerstein et al. (1997), and Woosley et al. (2002). An overview of galactic chemical evolution is presented by Tinsley (1980).

Using an Iterative Fourier Series Approach in Determining Orbital Elements of Detached Visual Binary Stars

NASA Astrophysics Data System (ADS)

Tupa, Peter R.; Quirin, S.; DeLeo, G. G.; McCluskey, G. E., Jr.

2007-12-01

We present a modified Fourier transform approach to determine the orbital parameters of detached visual binary stars. Originally inspired by Monet (ApJ 234, 275, 1979), this new method utilizes an iterative routine of refining higher order Fourier terms in a manner consistent with Keplerian motion. In most cases, this approach is not sensitive to the starting orbital parameters in the iterative loop. In many cases we have determined orbital elements even with small fragments of orbits and noisy data, although some systems show computational instabilities. The algorithm was constructed using the MAPLE mathematical software code and tested on artificially created orbits and many real binary systems, including Gliese 22 AC, Tau 51, and BU 738. This work was supported at Lehigh University by NSF-REU grant PHY-9820301.

Sulfone-carbonate ternary electrolyte with further increased capacity retention and burn resistance for high voltage lithium ion batteries

NASA Astrophysics Data System (ADS)

Xue, Leigang; Lee, Seung-Yul; Zhao, Zuofeng; Angell, C. Austen

2015-11-01

Safety and high energy density are the two focus issues for current lithium ion batteries. For safety, it has been demonstrated that sulfone electrolytes are much less flammable than the prevailing all-carbonate type, and they are also promising for high voltage batteries due to the high oxidization resistance. However, the high melting points and viscosities greatly restricted their application. Based on our previous work on use of fluidity-enhancing cosolvents to make binary sulfone-carbonate electrolytes, we report here a three-component system that is more conductive and should be even less flammable while additionally having better low temperature stability. The conductivity-viscosity relations have been determined for this electrolyte and are comparable to those of the "standard" carbonate electrolyte. The additional component also produces much improved capacity retention for the LiNi0.5Mn1.5O4 cathode. As with carbonate electrolytes, increase of temperature to 55 °C leads to rapid capacity decrease during cycling, but the capacity loss is due to the salt, not the solvent. The high discharge capacity observed at 25 °C when LiBF4 replaces LiPF6, is fully retained at 55 °C.

Determination of Orbital Parameters for Visual Binary Stars Using a Fourier-Series Approach

NASA Astrophysics Data System (ADS)

Brown, D. E.; Prager, J. R.; DeLeo, G. G.; McCluskey, G. E., Jr.

2001-12-01

We expand on the Fourier transform method of Monet (ApJ 234, 275, 1979) to infer the orbital parameters of visual binary stars, and we present results for several systems, both simulated and real. Although originally developed to address binary systems observed through at least one complete period, we have extended the method to deal explicitly with cases where the orbital data is less complete. This is especially useful in cases where the period is so long that only a fragment of the orbit has been recorded. We utilize Fourier-series fitting methods appropriate to data sets covering less than one period and containing random measurement errors. In so doing, we address issues of over-determination in fitting the data and the reduction of other deleterious Fourier-series artifacts. We developed our algorithm using the MAPLE mathematical software code, and tested it on numerous "synthetic" systems, and several real binaries, including Xi Boo, 24 Aqr, and Bu 738. This work was supported at Lehigh University by the Delaware Valley Space Grant Consortium and by NSF-REU grant PHY-9820301.

Phase behaviors of binary mixtures composed of electron-rich and electron-poor triphenylene discotic liquid crystals

NASA Astrophysics Data System (ADS)

An, Lingling; Jing, Min; Xiao, Bo; Bai, Xiao-Yan; Zeng, Qing-Dao; Zhao, Ke-Qing

2016-09-01

Disk-like liquid crystals (DLCs) can self-assemble to ordered columnar mesophases and are intriguing one-dimensional organic semiconductors with high charge carrier mobility. To improve their applicable property of mesomorphic temperature ranges, we exploit the binary mixtures of electronic donor-acceptor DLC materials. The electron-rich 2,3,6,7,10,11-hexakis(alkoxy)triphenylenes (C4, C6, C8, C10, C12) and an electron-deficient tetrapentyl triphenylene-2,3,6,10-tetracarboxylate have been prepared and their binary mixtures have been investigated. The mesomorphism of the 1:1 (molar ratio) mixtures has been characterized by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and small angel x-ray scattering (SAXS). The self-assembled monolayer structure of a discogen on a solid-liquid interface has been imaged by the high resolution scanning tunneling microscopy (STM). The match of peripheral chain length has important influence on the mesomorphism of the binary mixtures. Project supported by the National Natural Science Foundation of China (Grant Nos. 51273133 and 51443004).

Planet Forming Protostellar Disks

NASA Technical Reports Server (NTRS)

Lubow, Stephen

1998-01-01

The project achieved many of its objectives. The main area of investigation was the interaction of young binary stars with surrounding protostellar disks. A secondary objective was the interaction of young planets with their central stars and surrounding disks. The grant funds were used to support visits by coinvestigators and visitors: Pawel Artymowicz, James Pringle, and Gordon Ogilvie. Funds were also used to support travel to meetings by Lubow and to provide partial salary support.

Mutual diffusion of binary liquid mixtures containing methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride

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

Guevara-Carrion, Gabriela; Janzen, Tatjana; Muñoz-Muñoz, Y. Mauricio

Mutual diffusion coefficients of all 20 binary liquid mixtures that can be formed out of methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride without a miscibility gap are studied at ambient conditions of temperature and pressure in the entire composition range. The considered mixtures show a varying mixing behavior from almost ideal to strongly non-ideal. Predictive molecular dynamics simulations employing the Green-Kubo formalism are carried out. Radial distribution functions are analyzed to gain an understanding of the liquid structure influencing the diffusion processes. It is shown that cluster formation in mixtures containing one alcoholic component has a significant impactmore » on the diffusion process. The estimation of the thermodynamic factor from experimental vapor-liquid equilibrium data is investigated, considering three excess Gibbs energy models, i.e., Wilson, NRTL, and UNIQUAC. It is found that the Wilson model yields the thermodynamic factor that best suits the simulation results for the prediction of the Fick diffusion coefficient. Four semi-empirical methods for the prediction of the self-diffusion coefficients and nine predictive equations for the Fick diffusion coefficient are assessed and it is found that methods based on local composition models are more reliable. Finally, the shear viscosity and thermal conductivity are predicted and in most cases favorably compared with experimental literature values.« less

Constraining the Type Ia Supernova Progenitor: The Search for Hydrogen in Nebular Spectra

NASA Astrophysics Data System (ADS)

Leonard, Douglas

2006-02-01

The progenitor systems of Type Ia supernovae (SNe Ia) are observationally unconstrained. Prevailing theory invokes a carbon- oxygen white dwarf accreting matter from a companion until a thermonuclear runaway ensues that incinerates the white dwarf. While models of exploding carbon-oxygen white dwarfs faithfully reproduce the main characteristics of SNe Ia, we are ignorant about the nature of the proposed companion star. Simulations resulting from this single- degenerate binary channel, however, demand the presence of low-velocity, H(alpha) emission in spectra taken in the nebular phase (250 - 400 days after maximum light), since a portion of the companion's envelope becomes entrained in the ejecta. This hydrogen has never been detected, and only generally weak limits have heretofore been set from ~ 6 SNe Ia observed during the nebular phase at low resolution and often with a low signal-to-noise ratio (S/N). We propose to remedy this situation through high S/N observations of two nearby, nebular-phase SNe Ia, with sufficient sensitivity and resolution to detect ~ 0.01 Msun of solar abundance material in the ejecta. The detection of late- time H(alpha) emission would be considered a ``smoking gun'' for the binary scenario. If H(alpha) is not detected, the limits will effectively rule out sub-giant, red giant, and all but the most widely separated main-sequence companions.

Perfluoro anion based binary and ternary ionic liquids as electrolytes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Lin, Hsi-Hsin; Peng, Jia-De; Suryanarayanan, V.; Velayutham, D.; Ho, Kuo-Chuan

2016-04-01

In this work, eight new ionic liquids (ILs) based on triethylammonium (TEA) or n-methylpiperidinium (NMP) cations and perfluoro carboxylate (PFC) anions having different carbon chain lengths are synthesized and their physico-chemical properties such as density, decomposition temperature, viscosity and conductivity are determined. Photovoltaic characteristics of dye-sensitized solar cells (DSSCs) with binary ionic liquids electrolytes, containing the mixture of the synthesized ILs and 1-methyl-3-propyl imidazolium iodide (PMII) (v/v = 35/65), are evaluated. Among the different ILs, solar cells containing NMP based ILs show higher VOC than that of TEA, whereas, higher JSC is noted for the DSSCs incorporated with the latter when compared to the former. Further, the photo-current of the DSSCs decreases with the increase of the carbon chain length of perfluoro carboxylate anionic group of ILs. The cell performance of the DSSC containing ternary ionic liquids-based electrolytes compose of NMP-2C/TEA-2C/PMII (v/v/v = 28/7/65) exhibits a JSC of 12.99 mA cm-2, a VOC of 639.0 mV, a FF of 0.72, and a cell efficiency of 6.01%. The extraordinary durability of the DSSC containing the above combination of electrolytes stored in dark at 50 °C is proved to be unfailing up to 1200 h.

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

Bradley, D. J.

The activity coefficient of carbon in nickel, nickel-titanium, nickel-titanium-chromium, nickel-titanium-molybdenum and nickel-titanium-molybdenum-chromium alloys has been measured at 900, 1100 and 1215/sup 0/C. The results indicate that carbon obeys Henry's Law over the range studied (0 to 2 at. percent). The literature for the nickel-carbon and iron-carbon systems are reviewed and corrected. For the activity of carbon in iron as a function of composition, a new relationship based on re-evaluation of the thermodynamics of the CO/CO/sub 2/ equilibrium is proposed. Calculations using this relationship reproduce the data to within 2.5 percent, but the accuracy of the calibrating standards used by manymore » investigators to analyze for carbon is at best 5 percent. This explains the lack of agreement between the many precise sets of data. The values of the activity coefficient of carbon in the various solid solutions are used to calculate a set of parameters for the Kohler-Kaufman equation. The calculations indicate that binary interaction energies are not sufficient to describe the thermodynamics of carbon in some of the nickel-based solid solutions. The results of previous workers for carbon in nickel-iron alloys are completely described by inclusion of ternary terms in the Kohler-Kaufman equation. Most of the carbon solid solution at high temperatures in nickel and nickel-titantium alloys precipitates from solution on quenching in water. The precipitate is composed of very small particles (greater than 2.5 nm) of elemental carbon. The results of some preliminary thermomigration experiments are discussed and recommendations for further work are presented.« less

Magnetic Fields and Multiple Protostar Formation

NASA Astrophysics Data System (ADS)

Boss, A. P.

2001-12-01

Recent observations of star-forming regions suggest that binary and multiple young stars are the rule rather than the exception, and implicate fragmentation as the likely mechanism for their formation. Most numerical hydrodynamical calculations of fragmentation have neglected the possibly deleterious effects of magnetic fields, in spite of ample evidence for the importance of magnetic support of pre-collapse clouds. We present here the first numerical hydrodynamical survey of the full effects of magnetic fields on the collapse and fragmentation of dense cloud cores. The models are calculated with a three dimensional, finite differences code which solves the equations of hydrodynamics, gravitation, and radiative transfer in the Eddington and diffusion approximations. Magnetic field effects are included through two simple approximations: magnetic pressure is added to the gas pressure, and magnetic tension is approximated by gravity dilution once collapse is well underway. Ambipolar diffusion of the magnetic field leading to cloud collapse is treated approximately as well. Models are calculated for a variety of initial cloud density profiles, shapes, and rotation rates. We find that in spite of the inclusion of magnetic field effects, dense cloud cores are capable of fragmenting into binary and multiple protostar systems. Initially prolate clouds tend to fragment into binary protostars, while initially oblate clouds tend to fragment into multiple protostar systems containing a small number (of order four) of fragments. The latter are likely to be subject to rapid orbital evolution, with close encounters possibly leading to the ejection of fragments. Contrary to expectation, magnetic tension effects appear to enhance fragmentation, allowing lower mass fragments to form than would otherwise be possible, because magnetic tension helps to prevent a central density singularity from forming and producing a dominant single object. Magnetically-supported dense cloud cores thus seem to be capable of collapsing and fragmenting into sufficient numbers of binary and multiple protostar systems to be compatible with observations of the relative rarity of single protostars. This work was partially supported by NSF grants AST-9983530 and MRI-9976645.

Collapse and Fragmentation of Molecular Cloud Cores. VII. Magnetic Fields and Multiple Protostar Formation

NASA Astrophysics Data System (ADS)

Boss, Alan P.

2002-04-01

Recent observations of star-forming regions suggest that binary and multiple young stars are the rule rather than the exception and implicate fragmentation as the likely mechanism for their formation. Most numerical hydrodynamic calculations of fragmentation have neglected the possibly deleterious effects of magnetic fields, despite ample evidence for the importance of magnetic support of precollapse clouds. We present here the first numerical hydrodynamic survey of the collapse and fragmentation of initially magnetically supported clouds that takes into account several magnetic field effects in an approximate manner. The models are calculated with a three-dimensional, finite differences code that solves the equations of hydrodynamics, gravitation, and radiative transfer in the Eddington and diffusion approximations. Magnetic field effects are included through two simple approximations: magnetic pressure is added to the gas pressure, and magnetic tension is approximated by gravity dilution once collapse is well underway. Ambipolar diffusion of the magnetic field leading to cloud collapse is treated approximately as well. Models are calculated for a variety of initial cloud density profiles, shapes, and rotation rates. We find that in spite of the inclusion of magnetic field effects, dense cloud cores are capable of fragmenting into binary and multiple protostar systems. Initially prolate clouds tend to fragment into binary protostars, while initially oblate clouds tend to fragment into multiple protostar systems containing a small number (of the order of 4) of fragments. The latter are likely to be subject to rapid orbital evolution, with close encounters possibly leading to the ejection of fragments. Contrary to expectation, magnetic tension effects appear to enhance fragmentation, allowing lower mass fragments to form than would otherwise be possible, because magnetic tension helps to prevent a central density singularity from forming and producing a dominant single object. Magnetically supported dense cloud cores thus seem to be capable of collapsing and fragmenting into sufficient numbers of binary and multiple protostar systems to be compatible with observations of the relative rarity of single protostars.

A Comprehensive Stellar Astrophysical Study of the Old Open Cluster M67 with Kepler

NASA Astrophysics Data System (ADS)

Mathieu, Robert D.; Vanderburg, Andrew; K2 M67 Team

2016-06-01

M67 is among the best studied of all star clusters. Being at an age and metallicity very near solar, at an accessible distance of 850 pc with low reddening, and rich in content (over 1000 members including main-sequence dwarfs, a well populated subgiant branch and red giant branch, white dwarfs, blue stragglers, sub-subgiants, X-ray sources and CVs), M67 is a cornerstone of stellar astrophysics.The K2 mission (Campaign 5) has obtained long-cadence observations for 2373 stars, both within an optimized central superaperture and as specified targets outside the superaperture. 1,432 of these stars are likely cluster members based on kinematic and photometric criteria.We have extracted light curves and corrected for K2 roll systematics, producing light curves with noise characteristics qualitatively similar to Kepler light curves of stars of similar magnitudes. The data quality is slightly poorer than for field stars observed by K2 due to crowding near the cluster core, but the data are of sufficient quality to detect seismic oscillations, binary star eclipses, flares, and candidate transit events. We are in the process of uploading light curves and various diagnostic files to MAST; light curves and supporting data will also be made available on ExoFOP.Importantly, several investigators within the M67 K2 team are independently doing light curve extractions and analyses for confirmation of science results. We also are adding extensive ground-based supporting data, including APOGEE near-infrared spectra, TRES and WIYN optical spectra, LCOGT photometry, and more.Our science goals encompass asteroseismology and stellar evolution, alternative stellar evolution pathways in binary stars, stellar rotation and angular momentum evolution, stellar activity, eclipsing binaries and beaming, and exoplanets. We will present early science results as available by the time of the meeting, and certainly including asteroseismology, blue stragglers and sub-subgiants, and newly discovered eclipsing binaries.This work is supported by NASA grant NNX15AW24A to the University of Wisconsin - Madison.

Crystallinity and compositional changes in carbonated apatites: Evidence from 31P solid-state NMR, Raman, and AFM analysis

NASA Astrophysics Data System (ADS)

McElderry, John-David P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M. Banaszak; Tecklenburg, Mary M. J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

2013-10-01

Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and 31P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse 31P NMR linewidth and inverse Raman PO43-ν1 bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3-10.3 wt% CO32- range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the 31P NMR chemical shift frequency and the Raman phosphate ν1 band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals.

Thermodynamic modelling of the C-U and B-U binary systems

NASA Astrophysics Data System (ADS)

Chevalier, P. Y.; Fischer, E.

2001-02-01

The thermodynamic modelling of the carbon-uranium (C-U) and boron-uranium (B-U) binary systems is being performed in the framework of the development of a thermodynamic database for nuclear materials, for increasing the basic knowledge of key phenomena which may occur in the event of a severe accident in a nuclear power plant. Applications are foreseen in the nuclear safety field to the physico-chemical interaction modelling, on the one hand the in-vessel core degradation producing the corium (fuel, zircaloy, steel, control rods) and on the other hand the ex-vessel molten corium-concrete interaction (MCCI). The key O-U-Zr ternary system, previously modelled, allows us to describe the first interaction of the fuel with zircaloy cladding. Then, the three binary systems Fe-U, Cr-U and Ni-U were modelled as a preliminary work for modelling the O-U-Zr-Fe-Cr-Ni multicomponent system, allowing us to introduce the steel components in the corium. In the existing database (TDBCR, thermodynamic data base for corium), Ag and In were introduced for modelling AIC (silver-indium-cadmium) control rods which are used in French pressurized water reactors (PWR). Elsewhere, B 4C is also used for control rods. That is why it was agreed to extend in the next years the database with two new components, B and C. Such a work needs the thermodynamic modelling of all the binary and pseudo-binary sub-systems resulting from the combination of B, B 2O 3 and C with the major components of TDBCR, O-U-Zr-Fe-Cr-Ni-Ag-In-Ba-La-Ru-Sr-Al-Ca-Mg-Si + Ar-H. The critical assessment of the very numerous experimental information available for the C-U and B-U binary systems was performed by using a classical optimization procedure and the Scientific Group Thermodata Europe (SGTE). New optimized Gibbs energy parameters are given, and comparisons between calculated and experimental equilibrium phase diagrams or thermodynamic properties are presented. The self-consistency obtained is quite satisfactory.

Mixed material formation and erosion

NASA Astrophysics Data System (ADS)

Linsmeier, Ch.; Luthin, J.; Goldstraß, P.

2001-03-01

The formation of mixed phases on materials relevant for first wall components of fusion devices is studied under well-defined conditions in ultra-high vacuum (UHV). This is necessary in order to determine fundamental parameters governing the basic processes of chemical reaction, material mixing and erosion. We examined the binary systems comprising of the wall materials beryllium, silicon, tungsten and titanium and carbon, the latter being both a wall material and a plasma impurity. Experiments were carried out to study the interaction of carbon in the form of a vapor-deposited component on clean, well-defined elemental surfaces. The chemical composition and the binding state are measured by X-ray photoelectron spectroscopy (XPS) after annealing treatments. For all materials, a limited carbide formation is found at room temperature. Annealing carbon films on elemental substrate leads to a complete carbidization of the carbon layer. The carbide layers on Be and Si are stable even at very high temperatures, whereas the carbides of Ti and W dissolve. The erosion of these two metals by sputtering is then identical to the pure metals, whereas for Be and Si a protective carbide layer can reduce the sputtering yields.

Advanced catalyst supports for PEM fuel cell cathodes

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

Du, Lei; Shao, Yuyan; Sun, Junming

2016-11-01

Electrocatalyst support materials are key components for polymer exchange membrane (PEM) fuel cells, which play a critical role in determining electrocatalyst durability and activity, mass transfer and water management. The commonly-used supports, e.g. porous carbon black, cannot meet all the requirements under the harsh operation condition of PEM fuel cells. Great efforts have been made in the last few years in developing alternative support materials. In this paper, we selectively review recent progress on three types of important support materials: carbon, non-carbon and hybrid carbon-oxides nanocomposites. A perspective on future R&D of electrocatalyst support materials is also provided.

The Fate of Neutron Star Binary Mergers

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

Piro, Anthony L.; Giacomazzo, Bruno; Perna, Rosalba, E-mail: piro@carnegiescience.edu

Following merger, a neutron star (NS) binary can produce roughly one of three different outcomes: (1) a stable NS, (2) a black hole (BH), or (3) a supramassive, rotationally supported NS, which then collapses to a BH following angular momentum losses. Which of these fates occur and in what proportion has important implications for the electromagnetic transient associated with the mergers and the expected gravitational wave (GW) signatures, which in turn depend on the high density equation of state (EOS). Here we combine relativistic calculations of NS masses using realistic EOSs with Monte Carlo population synthesis based on the massmore » distribution of NS binaries in our Galaxy to predict the distribution of fates expected. For many EOSs, a significant fraction of the remnants are NSs or supramassive NSs. This lends support to scenarios in which a quickly spinning, highly magnetized NS may be powering an electromagnetic transient. This also indicates that it will be important for future GW observatories to focus on high frequencies to study the post-merger GW emission. Even in cases where individual GW events are too low in signal to noise to study the post merger signature in detail, the statistics of how many mergers produce NSs versus BHs can be compared with our work to constrain the EOS. To match short gamma-ray-burst (SGRB) X-ray afterglow statistics, we find that the stiffest EOSs are ruled out. Furthermore, many popular EOSs require a significant fraction of ∼60%–70% of SGRBs to be from NS–BH mergers rather than just binary NSs.« less

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.

Photometric constraints on binary asteroid dynamics

NASA Astrophysics Data System (ADS)

Scheirich, Peter

2015-08-01

To date, about 50 binary NEAs, 20 Mars-crossing and 80 small MB asteroids are known. We observe also a population of about 200 unbound asteroid systems (asteroid pairs). I will review the photometric observational data we have for the best observed cases and compare them with theories of binary and paired asteroids evolution.The observed characteristics of asteroid systems suggest their formation by rotational fission of parent rubble-pile asteroids after being spun up by the YORP effect. The angular momentum content of binary asteroids is close to critical. The orientations of satellite orbits of observed binary systems are non-random; the orbital poles concentrate near the obliquities of 0 and 180 degrees, i.e., near the YORP asymptotic states.Recently, a significant excess of retrograde satellite orbits was detected, which is not yet explained characteristic.An evolution of binary system depend heavily on the BYORP effect. If BYORP is contractive, the primary and secondary could end in a tidal-BYORP equilibrium. Observations of mutual events between binary components in at least four apparitions are needed for BYORP to be revealed by detecting a quadratic drift in mean anomaly of the satellite. I will show the observational evidence of single-synchronous binary asteroid with tidally locked satellite (175706 1996 FG3), i.e, with the quadratic drift equal to zero, and binary asteroid with contracting orbit (88710 2001 SL9), with positive value of the quadratic drift (the solution for the quadratic drift is ambiguous so far, with possible values of 5 and 8 deg/yr2).The spin configuration of the satellite play a crucial role in the evolution of the system under the influence of the BYORP effect. I will show that the rotational lightcurves of the satellites show that most of them have small libration amplitudes (up to 20 deg.), with a few interesting exceptions.Acknowledgements: This work has been supported by the Grant Agency of the Czech Republic, Grant P209/12/0229, and by the Ministry of Education of the Czech Republic, Grant LG12001.

Electrochemical synthesis of elongated noble metal nanoparticles, such as nanowires and nanorods, on high-surface area carbon supports

DOEpatents

Adzic, Radoslav; Blyznakov, Stoyan; Vukmirovic, Miomir

2015-08-04

Elongated noble-metal nanoparticles and methods for their manufacture are disclosed. The method involves the formation of a plurality of elongated noble-metal nanoparticles by electrochemical deposition of the noble metal on a high surface area carbon support, such as carbon nanoparticles. Prior to electrochemical deposition, the carbon support may be functionalized by oxidation, thus making the manufacturing process simple and cost-effective. The generated elongated nanoparticles are covalently bound to the carbon support and can be used directly in electrocatalysis. The process provides elongated noble-metal nanoparticles with high catalytic activities and improved durability in combination with high catalyst utilization since the nanoparticles are deposited and covalently bound to the carbon support in their final position and will not change in forming an electrode assembly.

Development of a prototype regenerable carbon dioxide absorber

NASA Technical Reports Server (NTRS)

Onischak, M.

1976-01-01

Design information was obtained for a new, regenerable carbon dioxide control system for extravehicular activity life support systems. Solid potassium carbonate was supported in a thin porous sheet form and fabricated into carbon dioxide absorber units. Carbon dioxide and water in the life support system atmosphere react with the potassium carbonate and form potassium bicarbonate. The bicarbonate easily reverts to the carbonate by heating to 150 deg C. The methods of effectively packing the sorbent material into EVA-sized units and the effects of inlet concentrations, flowrate, and temperature upon performance were investigated. The cycle life of the sorbent upon the repeated thermal regenerations was demonstrated through 90 cycles.

Radio emission from RS CVn binaries. II - Polarization and spectral properties

NASA Technical Reports Server (NTRS)

Mutel, R. L.; Morris, D. H.; Doiron, D. J.; Lestrade, J. F.

1987-01-01

Multiepoch radio observations of circular polarization and spectral characteristics of several close, late-type stellar binaries are reported. The median luminosity of four well-studied systems ranged from 16.2 to 17.1 ergs/s/Hz. For individual systems, the fractional circular polarization decreases with increasing luminosity, particularly at frequencies above 5 GHz. Eclipsing binaries have significantly lower average circular polarization compared with noneclipsing systems. Helicity reversal is almost always observed between 1.4 and 4.9 GHz for systems with high orbital inclination. Comparison with ten years of previously published polarization observations for two RS CVn stellar systems show that the same helicity occurs at a given frequency for a given source, indicating a very stable, large-scale magnetic field geometry. These spectral and polarization characteristics strongly support a model of inhomogeneous gyrosynchrotron emission arising from electrons with power law energy spectra interacting with inhomogeneous magnetic fields.

A Search for Quiet Massive X-ray Binaries

NASA Astrophysics Data System (ADS)

McSwain, M. V.; Boyajian, T. S.; Grundstrom, E.; Gies, D. R.

2005-12-01

Wind accretion models of the X-ray luminosity in massive X-ray binaries (MXRBs) predict a class of "quiet" MXRBs in which the stellar wind is too weak to power a strong X-ray source. The first two candidates systems, HD 14633 and HD 15137, were recently detected. These O star + neutron star systems were ejected from the open cluster NGC 654, but although they both show evidence of a past supernova within the binary system, neither is a known X-ray emitter. These systems provide a new opportunity to examine the ejection mechanisms responsible for the OB runaway stars, and they can also provide key information about the evolution of spun-up, rejuvenated massive stars. We present here preliminary results from a search for other such quiet MXRBs. MVM is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-0401460.

The Search for Pre-Main Sequence Eclipsing Binary Stars in the Lagoon Nebula

NASA Astrophysics Data System (ADS)

Henderson, Calen B.; Stassun, K. G.

2009-01-01

We report time-series CCD I-band photometry for the pre-main-sequence cluster NGC 6530, located within the Lagoon Nebula. The data were obtained with the 4Kx4K imager on the SMARTS 1.0m telescope at CTIO on 36 nights over the summers of 2005 and 2006. In total we have light curves for 50,000 stars in an area 1 deg2, with a sampling cadence of 1 hour. The stars in our sample have masses in the range 0.25-4.0 Msun, assuming a distance of 1.25 kpc to the cluster. Our goals are to look for stars with rotation periods and to identify eclipsing binary candidates. Here we present light curves of photometrically variable stars and potential eclipsing binary star systems. This work has been supported by the National Science Foundation under Career grant AST-0349075.

Mergers of Black-Hole Binaries with Aligned Spins: Waveform Characteristics

NASA Technical Reports Server (NTRS)

Kelly, Bernard J.; Baker, John G.; vanMeter, James R.; Boggs, William D.; McWilliams, Sean T.; Centrella, Joan

2011-01-01

"We apply our gravitational-waveform analysis techniques, first presented in the context of nonspinning black holes of varying mass ratio [1], to the complementary case of equal-mass spinning black-hole binary systems. We find that, as with the nonspinning mergers, the dominant waveform modes phases evolve together in lock-step through inspiral and merger, supporting the previous model of the binary system as an adiabatically rigid rotator driving gravitational-wave emission - an implicit rotating source (IRS). We further apply the late-merger model for the rotational frequency introduced in [1], along with a new mode amplitude model appropriate for the dominant (2, plus or minus 2) modes. We demonstrate that this seven-parameter model performs well in matches with the original numerical waveform for system masses above - 150 solar mass, both when the parameters are freely fit, and when they are almost completely constrained by physical considerations."

Classification of skin cancer images using local binary pattern and SVM classifier

NASA Astrophysics Data System (ADS)

Adjed, Faouzi; Faye, Ibrahima; Ababsa, Fakhreddine; Gardezi, Syed Jamal; Dass, Sarat Chandra

2016-11-01

In this paper, a classification method for melanoma and non-melanoma skin cancer images has been presented using the local binary patterns (LBP). The LBP computes the local texture information from the skin cancer images, which is later used to compute some statistical features that have capability to discriminate the melanoma and non-melanoma skin tissues. Support vector machine (SVM) is applied on the feature matrix for classification into two skin image classes (malignant and benign). The method achieves good classification accuracy of 76.1% with sensitivity of 75.6% and specificity of 76.7%.

Assessment of various supervised learning algorithms using different performance metrics

NASA Astrophysics Data System (ADS)

Susheel Kumar, S. M.; Laxkar, Deepak; Adhikari, Sourav; Vijayarajan, V.

2017-11-01

Our work brings out comparison based on the performance of supervised machine learning algorithms on a binary classification task. The supervised machine learning algorithms which are taken into consideration in the following work are namely Support Vector Machine(SVM), Decision Tree(DT), K Nearest Neighbour (KNN), Naïve Bayes(NB) and Random Forest(RF). This paper mostly focuses on comparing the performance of above mentioned algorithms on one binary classification task by analysing the Metrics such as Accuracy, F-Measure, G-Measure, Precision, Misclassification Rate, False Positive Rate, True Positive Rate, Specificity, Prevalence.

The self-organization and functional activity of binary system based on erucyl amidopropyl betaine - alkylated polyethyleneimine

NASA Astrophysics Data System (ADS)

Gaynanova, Gulnara A.; Valiakhmetova, Alsu R.; Kuryashov, Dmitry A.; Kudryashova, Yuliana R.; Lukashenko, Svetlana S.; Syakaev, Victor V.; Latypov, Shamil K.; Bukharov, Sergey V.; Bashkirtseva, Natalia Yu.; Zakharova, Lucia Ya.

2013-11-01

The self-organization in individual and binary aqueous solutions of a zwitterionic surfactant erucyl amidopropyl betaine and alkylated polyethyleneimine is carried out with a wide range of physical and chemical methods, including tensiometry, conductometry, dynamic light scattering, pH-metry, spectrophotometry, and fluorescence spectroscopy. The data obtained strongly support the formation of nanosized aggregates in the systems and provide information on their structure and probable morphological transitions. High solubilization capacity and data on the contact angle showed a possibility of the application of these systems as nanocontainers or oil wetting agents in the oil recovery.

ROTATIONAL SYNCHRONIZATION MAY ENHANCE HABITABILITY FOR CIRCUMBINARY PLANETS: KEPLER BINARY CASE STUDIES

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

Mason, Paul A.; Zuluaga, Jorge I.; Cuartas-Restrepo, Pablo A.

2013-09-10

We report a mechanism capable of reducing (or increasing) stellar activity in binary stars, thereby potentially enhancing (or destroying) circumbinary habitability. In single stars, stellar aggression toward planetary atmospheres causes mass-loss, which is especially detrimental for late-type stars, because habitable zones are very close and activity is long lasting. In binaries, tidal rotational breaking reduces magnetic activity, thus reducing harmful levels of X-ray and ultraviolet (XUV) radiation and stellar mass-loss that are able to erode planetary atmospheres. We study this mechanism for all confirmed circumbinary (p-type) planets. We find that main sequence twins provide minimal flux variation and in somemore » cases improved environments if the stars rotationally synchronize within the first Gyr. Solar-like twins, like Kepler 34 and Kepler 35, provide low habitable zone XUV fluxes and stellar wind pressures. These wide, moist, habitable zones may potentially support multiple habitable planets. Solar-type stars with lower mass companions, like Kepler 47, allow for protected planets over a wide range of secondary masses and binary periods. Kepler 38 and related binaries are marginal cases. Kepler 64 and analogs have dramatically reduced stellar aggression due to synchronization of the primary, but are limited by the short lifetime. Kepler 16 appears to be inhospitable to planets due to extreme XUV flux. These results have important implications for estimates of the number of stellar systems containing habitable planets in the Galaxy and allow for the selection of binaries suitable for follow-up searches for habitable planets.« less

Growth of Vertically Aligned ZnO Nanowire Arrays Using Bilayered Metal Catalysts

DTIC Science & Technology

2012-01-01

12] J. P. Liu, C. X. Guo, C. M. Li et al., “Carbon-decorated ZnO nanowire array: a novel platform for direct electrochemistry of enzymes and...cited. Vertically aligned, high-density ZnO nanowires (NWs) were grown for the first time on c-plane sapphire using binary alloys of Ni/Au or Cu/Au as...deleterious to the ZnO NW array growth. Significant improvement of the Au adhesion on the substrate was noted, opening the potential for direct

Hans A. Bethe Prize: Cosmic Collisions Online - Compact Binary Mergers, Gravitational Waves and Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Shapiro, Stuart

2017-01-01

Hans A. Bethe elucidated our understanding of the fundamental forces of Nature by exploring and explaining countless phenomena occurring in nuclear laboratories and in stars. With the dawn of gravitational wave astronomy we now can probe compact binary mergers - Nature's cosmic collision experiments - to deepen our understanding, especially where strong-field gravitation is involved. In addition to gravitational waves, some mergers are likely to generate observable electromagnetic and/or neutrino radiation, heralding a new era of multimessenger astronomy. Robust numerical algorithms now allow us to simulate these events in full general relativity on supercomputers. We will describe some recent magnetohydrodynamic simulations that show how binary black hole-neutron star and neutron star-neutron star mergers can launch jets, lending support to the idea that such mergers could be the engines that power short gamma-ray bursts. We will also show how the magnetorotational collapse of very massive stars to spinning black holes immersed in magnetized accretion disks can launch jets as well, reinforcing the belief that such ``collapsars'' are the progenitors of long gamma-ray bursts. Computer-generated movies highlighting some of these simulations will be shown. We gratefully acknowledge support from NSF Grants 1300903 and 1602536 and NASA Grant NNX13AH44G.

Optical and X-ray studies of Compact X-ray Binaries in NGC 5904

NASA Astrophysics Data System (ADS)

Bhalotia, Vanshree; Beck-Winchatz, Bernhard

2018-06-01

Due to their high stellar densities, globular cluster systems trigger various dynamical interactions, such as the formation of compact X-ray binaries. Stellar collisional frequencies have been correlated to the number of X-ray sources detected in various clusters and we hope to measure this correlation for NGC 5904. Optical fluxes of sources from archival HST images of NGC 5904 have been measured using a DOLPHOT PSF photometry in the UV, optical and near-infrared. We developed a data analysis pipeline to process the fluxes of tens of thousands of objects using awk, python and DOLPHOT. We plot color magnitude diagrams in different photometric bands in order to identify outliers that could be X-ray binaries, since they do not evolve the same way as singular stars. Aligning previously measured astrometric data for X-ray sources in NGC 5904 from Chandra with archival astrometric data from HST will filter out the outlier objects that are not X-ray producing, and provide a sample of compact binary systems that are responsible for X-ray emission in NGC 5904. Furthermore, previously measured X-ray fluxes of NGC 5904 from Chandra have also been used to measure the X-ray to optical flux ratio and identify the types of compact X-ray binaries responsible for the X-ray emissions in NGC 5904. We gratefully acknowledge the support from the Illinois Space Grant Consortium.

DETECTABILITY OF EARTH-LIKE PLANETS IN CIRCUMSTELLAR HABITABLE ZONES OF BINARY STAR SYSTEMS WITH SUN-LIKE COMPONENTS

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

Eggl, Siegfried; Pilat-Lohinger, Elke; Haghighipour, Nader, E-mail: siegfried.eggl@univie.ac.at

2013-02-20

Given the considerable percentage of stars that are members of binaries or stellar multiples in the solar neighborhood, it is expected that many of these binaries host planets, possibly even habitable ones. The discovery of a terrestrial planet in the {alpha} Centauri system supports this notion. Due to the potentially strong gravitational interaction that an Earth-like planet may experience in such systems, classical approaches to determining habitable zones (HZ), especially in close S-type binary systems, can be rather inaccurate. Recent progress in this field, however, allows us to identify regions around the star permitting permanent habitability. While the discovery ofmore » {alpha} Cen Bb has shown that terrestrial planets can be detected in solar-type binary stars using current observational facilities, it remains to be shown whether this is also the case for Earth analogs in HZs. We provide analytical expressions for the maximum and rms values of radial velocity and astrometric signals, as well as transit probabilities of terrestrial planets in such systems, showing that the dynamical interaction of the second star with the planet may indeed facilitate the planets' detection. As an example, we discuss the detectability of additional Earth-like planets in the averaged, extended, and permanent HZs around both stars of the {alpha} Centauri system.« less

Microfluidic Synthesis Enables Dense and Uniform Loading of Surfactant-Free PtSn Nanocrystals on Carbon Supports for Enhanced Ethanol Oxidation.

PubMed

Wu, Fuxiang; Zhang, Dongtang; Peng, Manhua; Yu, Zhihui; Wang, Xiayan; Guo, Guangsheng; Sun, Yugang

2016-04-11

Developing new synthetic methods for carbon supported catalysts with improved performance is of fundamental importance in advancing proton exchange membrane fuel cell (PEMFC) technology. Continuous-flow, microfluidic reactions in capillary tube reactors are described, which are capable of synthesizing surfactant-free, ultrafine PtSn alloyed nanoparticles (NPs) on various carbon supports (for example, commercial carbon black particles, carbon nanotubes, and graphene sheets). The PtSn NPs are highly crystalline with sizes smaller than 2 nm, and they are highly dispersed on the carbon supports with high loadings up to 33 wt%. These characteristics make the as-synthesized carbon-supported PtSn NPs more efficient than state of the art commercial Pt/C catalysts applied to the ethanol oxidation reaction (EOR). Significantly enhanced mass catalytic activity (two-times that of Pt/C) and improved stability are obtained. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flexible all-carbon photovoltaics with improved thermal stability

NASA Astrophysics Data System (ADS)

Tang, Chun; Ishihara, Hidetaka; Sodhi, Jaskiranjeet; Chen, Yen-Chang; Siordia, Andrew; Martini, Ashlie; Tung, Vincent C.

2015-04-01

The structurally robust nature of nanocarbon allotropes, e.g., semiconducting single-walled carbon nanotubes (SWCNTs) and C60s, makes them tantalizing candidates for thermally stable and mechanically flexible photovoltaic applications. However, C60s rapidly dissociate away from the basal of SWCNTs under thermal stimuli as a result of weak intermolecular forces that "lock up" the binary assemblies. Here, we explore use of graphene nanoribbons (GNRs) as geometrically tailored protecting layers to suppress the unwanted dissociation of C60s. The underlying mechanisms are explained using a combination of molecular dynamics simulations and transition state theory, revealing the temperature dependent disassociation of C60s from the SWCNT basal plane. Our strategy provides fundamental guidelines for integrating all-carbon based nano-p/n junctions with optimized structural and thermal stability. External quantum efficiency and output current-voltage characteristics are used to experimentally quantify the effectiveness of GNR membranes under high temperature annealing. Further, the resulting C60:SWCNT:GNR ternary composites display excellent mechanical stability, even after iterative bending tests.

Simulation studies of chemical erosion on carbon based materials at elevated temperatures

NASA Astrophysics Data System (ADS)

Kenmotsu, T.; Kawamura, T.; Li, Zhijie; Ono, T.; Yamamura, Y.

1999-06-01

We simulated the fluence dependence of methane reaction yield in carbon with hydrogen bombardment using the ACAT-DIFFUSE code. The ACAT-DIFFUSE code is a simulation code based on a Monte Carlo method with a binary collision approximation and on solving diffusion equations. The chemical reaction model in carbon was studied by Roth or other researchers. Roth's model is suitable for the steady state methane reaction. But this model cannot estimate the fluence dependence of the methane reaction. Then, we derived an empirical formula based on Roth's model for methane reaction. In this empirical formula, we assumed the reaction region where chemical sputtering due to methane formation takes place. The reaction region corresponds to the peak range of incident hydrogen distribution in the target material. We adopted this empirical formula to the ACAT-DIFFUSE code. The simulation results indicate the similar fluence dependence compared with the experiment result. But, the fluence to achieve the steady state are different between experiment and simulation results.

Effective intermolecular potential and critical point for C60 molecule

NASA Astrophysics Data System (ADS)

Ramos, J. Eloy

2017-07-01

The approximate nonconformal (ANC) theory is applied to the C60 molecule. A new binary potential function is developed for C60, which has three parameters only and is obtained by averaging the site-site carbon interactions on the surface of two C60 molecules. It is shown that the C60 molecule follows, to a good approximation, the corresponding states principle with n-C8H18, n-C4F10 and n-C5F12. The critical point of C60 is estimated in two ways: first by applying the corresponding states principle under the framework of the ANC theory, and then by using previous computer simulations. The critical parameters obtained by applying the corresponding states principle, although very different from those reported in the literature, are consistent with the previous results of the ANC theory. It is shown that the Girifalco potential does not correspond to an average of the site-site carbon-carbon interaction.

Determinations of the {sup 12}C/{sup 13}C Ratio for the Secondary Stars of AE Aquarii, SS Cygni, and RU Pegasi

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

Harrison, Thomas E.; Marra, Rachel E., E-mail: tharriso@nmsu.edu, E-mail: rmarra@nmsu.edu

We present new moderate-resolution near-infrared spectroscopy of three CVs obtained using GNIRS on Gemini-North. These spectra covered three {sup 13}CO bandheads found in the K -band, allowing us to derive the isotopic abundance ratios for carbon. We find small {sup 12}C/{sup 13}C ratios for all three donor stars. In addition, these three objects show carbon deficits, with AE Aqr being the most extreme ([C/Fe] = −1.4). This result confirms the conjecture that the donor stars in some long-period CVs have undergone considerable nuclear evolution prior to becoming semi-contact binaries. In addition to the results for carbon, we find that themore » abundance of sodium is enhanced in these three objects, and the secondary stars in both RU Peg and SS Cyg suffer magnesium deficits. Explaining such anomalies appears to require higher mass progenitors than commonly assumed for the donor stars of CVs.« less

The s-Process Nucleosynthesis in Extremely Metal-Poor Stars as the Generating Mechanism of Carbon Enhanced Metal-Poor Stars

NASA Astrophysics Data System (ADS)

Suda, Takuma; Yamada, Shimako; Fujimoto, Masayuki Y.

The origin of carbon-enhanced metal-poor (CEMP) stars plays a key role in characterising the formation and evolution of the first stars and the Galaxy since the extremely-metal-poor (EMP) stars with [Fe/H] ≤ -2.5 share the common features of carbon enhancement in their surface chemical compositions. The origin of these stars is not yet established due to the controversy of the origin of CEMP stars without the enhancement of s-process element abundances, i.e., so called CEMP-no stars. In this paper, we elaborate the s-process nucleosynthesis in the EMP AGB stars and explore the origin of CEMP stars. We find that the efficiency of the s-process is controlled by O rather than Fe at [Fe/H] ≲ -2. We demonstrate that the relative abundances of Sr, Ba, Pb to C are explained in terms of the wind accretion from AGB stars in binary systems.

Multi-hazard evacuation route and shelter planning for buildings.

DOT National Transportation Integrated Search

2014-06-01

A bi-level, two-stage, binary stochastic program with equilibrium constraints, and three variants, are presented that : support the planning and design of shelters and exits, along with hallway fortification strategies and associated : evacuation pat...

Support vector machine as a binary classifier for automated object detection in remotely sensed data

NASA Astrophysics Data System (ADS)

Wardaya, P. D.

2014-02-01

In the present paper, author proposes the application of Support Vector Machine (SVM) for the analysis of satellite imagery. One of the advantages of SVM is that, with limited training data, it may generate comparable or even better results than the other methods. The SVM algorithm is used for automated object detection and characterization. Specifically, the SVM is applied in its basic nature as a binary classifier where it classifies two classes namely, object and background. The algorithm aims at effectively detecting an object from its background with the minimum training data. The synthetic image containing noises is used for algorithm testing. Furthermore, it is implemented to perform remote sensing image analysis such as identification of Island vegetation, water body, and oil spill from the satellite imagery. It is indicated that SVM provides the fast and accurate analysis with the acceptable result.

Nitrogen-doped carbon-supported cobalt-iron oxygen reduction catalyst

DOEpatents

Zelenay, Piotr; Wu, Gang

2014-04-29

A Fe--Co hybrid catalyst for oxygen reaction reduction was prepared by a two part process. The first part involves reacting an ethyleneamine with a cobalt-containing precursor to form a cobalt-containing complex, combining the cobalt-containing complex with an electroconductive carbon supporting material, heating the cobalt-containing complex and carbon supporting material under conditions suitable to convert the cobalt-containing complex and carbon supporting material into a cobalt-containing catalyst support. The second part of the process involves polymerizing an aniline in the presence of said cobalt-containing catalyst support and an iron-containing compound under conditions suitable to form a supported, cobalt-containing, iron-bound polyaniline species, and subjecting said supported, cobalt-containing, iron bound polyaniline species to conditions suitable for producing a Fe--Co hybrid catalyst.

Engineering catalytic activity via ion beam bombardment of catalyst supports for vertically aligned carbon nanotube growth

NASA Astrophysics Data System (ADS)

Islam, A. E.; Nikolaev, P.; Amama, P. B.; Zakharov, D.; Sargent, G.; Saber, S.; Huffman, D.; Erford, M.; Semiatin, S. L.; Stach, E. A.; Maruyama, B.

2015-09-01

Carbon nanotube growth depends on the catalytic activity of metal nanoparticles on alumina or silica supports. The control on catalytic activity is generally achieved by variations in water concentration, carbon feed, and sample placement on a few types of alumina or silica catalyst supports obtained via thin film deposition. We have recently expanded the choice of catalyst supports by engineering inactive substrates like c-cut sapphire via ion beam bombardment. The deterministic control on the structure and chemistry of catalyst supports obtained by tuning the degree of beam-induced damage have enabled better regulation of the activity of Fe catalysts only in the ion beam bombarded areas and hence enabled controllable super growth of carbon nanotubes. A wide range of surface characterization techniques were used to monitor the catalytically active surface engineered via ion beam bombardment. The proposed method offers a versatile way to control carbon nanotube growth in patterned areas and also enhances the current understanding of the growth process. With the right choice of water concentration, carbon feed and sample placement, engineered catalyst supports may extend the carbon nanotube growth yield to a level that is even higher than the ones reported here, and thus offers promising applications of carbon nanotubes in electronics, heat exchanger, and energy storage.

Stellar and Binary Evolution in Star Clusters

NASA Technical Reports Server (NTRS)

McMillan, Stephen L. W.

2001-01-01

This paper presents a final report on research activities covered on Stellar and Binary Evolution in Star Clusters. Substantial progress was made in the development and dissemination of the "Starlab" software environment. Significant improvements were made to "kira," an N-body simulation program tailored to the study of dense stellar systems such as star clusters and galactic nuclei. Key advances include (1) the inclusion of stellar and binary evolution in a self-consistent manner, (2) proper treatment of the anisotropic Galactic tidal field, (3) numerous technical enhancements in the treatment of binary dynamics and interactions, and (4) full support for the special-purpose GRAPE-4 hardware, boosting the program's performance by a factor of 10-100 over the accelerated version. The data-reduction and analysis tools in Starlab were also substantially expanded. A Starlab Web site (http://www.sns.ias.edu/-starlab) was created and developed. The site contains detailed information on the structure and function of the various tools that comprise the package, as well as download information, "how to" tips and examples of common operations, demonstration programs, animations, etc. All versions of the software are freely distributed to all interested users, along with detailed installation instructions.

A New Light Curve and Analysis of the Long Period Eclipsing Binary BF Draconis

NASA Astrophysics Data System (ADS)

Wolf, G. W.; Craig, L. E.; Caffey, J. F.

1999-01-01

The star BF Draconis was found to be an eclipsing binary by Strohmeier, Knigge and Ott (1962) and originally thought to be an Algol-type system with a period of 5.6 days. A spectrographic study by Imbert (1985) showed that the period was actually double this value and that the system consisted of two well-separated, almost-equal F-type stars in elliptical orbit. Diethelm, Wolf and Agerer (1993) later published a preliminary light curve of this system showing minima of unequal depth and width with a displaced secondary, confirming the elliptical orbit but disagreeing with Imbert on the specific orbital parameters. As a part of our long-term program of obtaining improved light curves of double-lined spectroscopic and eclipsing binaries, we have observed BF Draconis for the past four years using the 0.4 meter telescope at the Baker Observatory of Southwest Missouri State University. Complete light curves in the Cousins BVRI passbands have been obtained with our Photometrics CCD system, and a new model and orbital parameters for the binary have been determined using the Wilson-Devinney program. This research has been supported by NSF Grants AST-9315061 and AST-9605822 and NASA Grant NGT5-40060.

In search of a signature of binary Kuiper Belt Objects in the Pluto-Charon crater population

NASA Astrophysics Data System (ADS)

Zangari, Amanda Marie; Parker, Alex; Singer, Kelsi N.; Stern, S. Alan; Young, Leslie; Olkin, Catherine B.; Ennico, Kimberly; Weaver, Harold A.; New Horizons Geology, Geophysics and Imaging Science Theme Team

2016-10-01

In July 2015, New Horizons flew by Pluto and Charon, allowing mapping of the encounter hemisphere at high enough resolution to produce crater counts from the surfaces of the pair. We investigate the distribution of craters in search of a signature of binary impactors. The Kuiper Belt -- especially the cold classical region -- has a large fraction of binary objects, many of which are close-in, equal-mass binaries. We will present results on how the distribution of craters seen on Pluto and Charon compares to a random distribution of single body impactors on the surfaces of each. Examining the surfaces of Pluto and Charon proves challenging due to resurfacing, and the presence of tectonic and other geographic features. For example, the informally-named Cthulhu region is among the oldest on Pluto, yet it abuts a craterless region millions of years young. On Charon, chastmata divide the surface into regions informally named Vulcan Planum and Oz terra. In our statistics, we pay careful attention to the boundaries of where craters may appear, and the dependence of our results on crater size. This work was supported by NASA's New Horizons project.

Spectroscopy, MOST photometry, and interferometry of MWC 314: is it an LBV or an interacting binary?

NASA Astrophysics Data System (ADS)

Richardson, Noel D.; Moffat, Anthony F. J.; Maltais-Tariant, Raphaël; Pablo, Herbert; Gies, Douglas R.; Saio, Hideyuki; St-Louis, Nicole; Schaefer, Gail; Miroshnichenko, Anatoly S.; Farrington, Chris; Aldoretta, Emily J.; Artigau, Étienne; Boyajian, Tabetha S.; Gordon, Kathryn; Jones, Jeremy; Matson, Rachel; McAlister, Harold A.; O'Brien, David; Raghavan, Deepak; Ramiaramanantsoa, Tahina; Ridgway, Stephen T.; Scott, Nic; Sturmann, Judit; Sturmann, Laszlo; Brummelaar, Theo ten; Thomas, Joshua D.; Turner, Nils; Vargas, Norm; Zharikov, Sergey; Matthews, Jaymie; Cameron, Chris; Guenther, David; Kuschnig, Rainer; Rowe, Jason; Rucinski, Slavek; Sasselov, Dimitar; Weiss, Werner

2016-01-01

MWC 314 is a bright candidate luminous blue variable (LBV) that resides in a fairly close binary system, with an orbital period of 60.753 ± 0.003 d. We observed MWC 314 with a combination of optical spectroscopy, broad-band ground- and space-based photometry, as well as with long baseline, near-infrared interferometry. We have revised the single-lined spectroscopic orbit and explored the photometric variability. The orbital light curve displays two minima each orbit that can be partially explained in terms of the tidal distortion of the primary that occurs around the time of periastron. The emission lines in the system are often double-peaked and stationary in their kinematics, indicative of a circumbinary disc. We find that the stellar wind or circumbinary disc is partially resolved in the K'-band with the longest baselines of the CHARA Array. From this analysis, we provide a simple, qualitative model in an attempt to explain the observations. From the assumption of Roche Lobe overflow and tidal synchronization at periastron, we estimate the component masses to be M1 ≈ 5 M⊙ and M2 ≈ 15 M⊙, which indicates a mass of the LBV that is extremely low. In addition to the orbital modulation, we discovered two pulsational modes with the MOST satellite. These modes are easily supported by a low-mass hydrogen-poor star, but cannot be easily supported by a star with the parameters of an LBV. The combination of these results provides evidence that the primary star was likely never a normal LBV, but rather is the product of binary interactions. As such, this system presents opportunities for studying mass-transfer and binary evolution with many observational techniques.

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.

PAH Formation in O-rich Evolved Stars

NASA Astrophysics Data System (ADS)

Guzman-Ramirez, L.; Lagadec, E.; Jones, D.; Zijlstra, A. A.; Gesicki, K.

2015-08-01

Polycyclic aromatic hydrocarbons (PAHs) have been observed in O-rich planetary nebulae. This combination of oxygen-rich and carbon-rich material, known as dual-dust or mixed chemistry, is not expected to be seen around these objects. We recently proposed that PAHs could be formed from the photodissociation of CO in dense tori. Using VISIR/VLT, we spatially resolved the emission of the PAH bands and ionised emission from the [S IV] line, confirming the presence of dense central tori in all the observed O-rich objects. Furthermore, we show that for most of the objects, PAHs are located at the outer edge of these dense/compact tori, while the ionised material is mostly present in the inner parts, consistent with our hypothesis for the formation of PAHs in these systems. The presence of a dense torus has been strongly associated with the action of a central binary star and, as such, the rich chemistry seen in these regions may also be related to the formation of exoplanets in post-common-envelope binary systems.

Beowawe Bottoming Binary Unit - Final Technical Report for EE0002856

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

McDonald, Dale Edward

2013-02-12

This binary plant is the first high-output refrigeration based waste heat recovery cycle in the industry. Its working fluid is environmentally friendly and as such, the permits that would be required with a butane based cycle are not necessary. The unit is modularized, meaning that the unit’s individual skids were assembled in another location and were shipped via truck to the plant site. This project proves the technical feasibility of using low temperature brine The development of the unit led to the realization of low temperature, high output, and environmentally friendly heat recovery systems through domestic research and engineering. Themore » project generates additional renewable energy for Nevada, resulting in cleaner air and reduced carbon dioxide emissions. Royalty and tax payments to governmental agencies will increase, resulting in reduced financial pressure on local entities. The major components of the unit were sourced from American companies, resulting in increased economic activity throughout the country.« less

The economical utilization of geothermal energy

NASA Astrophysics Data System (ADS)

Rose, G.

1982-12-01

The geothermal energy which is stored in hot dry rock could be theoretically utilized for the generation of power. The hot-dry-rock procedure can provide a flow of hot water. The considered binary system can transform the obtained thermal energy into electrical energy. The system makes use of a Rankine cycle with a working fluid having a low boiling point. Heat from the hot water is transferred to the working fluid. The present investigation is concerned with the development of a method for the calculation of the entire process. The results obtained with the computational method are to provide a basis for the determination of the operational characteristics. The development method is used for the study of a process based on the use of carbon dioxide as working fluid. The economics of a use of the hot-dry-rock process with the binary system is also investigated. It is found that the considered procedure is not economical. Economical operation requires, in particular, hot water supplied at a much lower cost.

The progenitors of Type Ia supernovae with long delay times

NASA Astrophysics Data System (ADS)

Wang, Bo; Li, Xiang-Dong; Han, Zhan-Wen

2010-02-01

The nature of the progenitors of Type Ia supernovae (SNe Ia) is still unclear. In this paper, by considering the effect of the instability of accretion disc on the evolution of white dwarf (WD) binaries, we performed binary evolution calculations for about 2400 close WD binaries, in which a carbon-oxygen WD accretes material from a main-sequence (MS) star or a slightly evolved subgiant star (WD + MS channel), or a red-giant star (WD + RG channel) to increase its mass to the Chandrasekhar (Ch) mass limit. According to these calculations, we mapped out the initial parameters for SNe Ia in the orbital period-secondary mass (logPi - Mi2) plane for various WD masses for these two channels, respectively. We confirm that WDs in the WD + MS channel with a mass as low as 0.61Msolar can accrete efficiently and reach the Ch limit, while the lowest WD mass for the WD + RG channel is 1.0Msolar. We have implemented these results in a binary population synthesis study to obtain the SN Ia birthrates and the evolution of SN Ia birthrates with time for both a constant star formation rate and a single starburst. We find that the Galactic SN Ia birthrate from the WD + MS channel is ~1.8 × 10-3yr-1 according to our standard model, which is higher than the previous results. However, similar to the previous studies, the birthrate from the WD + RG channel is still low (~3 × 10-5yr-1). We also find that about one-third of SNe Ia from the WD + MS channel and all SNe Ia from the WD + RG channel can contribute to the old populations (>~1Gyr) of SN Ia progenitors.

Supported mesoporous carbon ultrafiltration membrane and process for making the same

DOEpatents

Strano, Michael; Foley, Henry C.; Agarwal, Hans

2004-04-13

A novel supported mesoporous carbon ultrafiltration membrane and process for producing the same. The membranes comprise a mesoporous carbon layer that exists both within and external to the porous support. A liquid polymer precursor composition comprising both carbonizing and noncarbonizing templating polymers is deposited on the porous metal support. The coated support is then heated in an inert-gas atmosphere to pyrolyze the polymeric precursor and form a mesoporous carbon layer on and within the support. The pore-size of the membranes is dependent on the molecular weight of the noncarbonizing templating polymer precursor. The mesoporous carbon layer is stable and can withstand high temperatures and exposure to organic chemicals. Additionally, the porous metal support provides excellent strength properties. The composite structure of the membrane provides novel structural properties and allows for increased operating pressures allowing for greater membrane flow rates. The invention also relates to the use of the novel ultrafiltration membrane to separate macromolecules from solution. An example is shown separating bovine serum albumin from water. The membrane functions by separating and by selective adsorption. Because of the membrane's porous metal support, it is well suited to industrial applications. The unique properties of the supported mesoporous carbon membrane also allow the membrane to be used in transient pressure or temperature swing separations processes. Such processes were not previously possible with existing mesoporous membranes. The present invention, however, possesses the requisite physical properties to perform such novel ultrafiltration processes.

Memristive effects in oxygenated amorphous carbon nanodevices

NASA Astrophysics Data System (ADS)

Bachmann, T. A.; Koelmans, W. W.; Jonnalagadda, V. P.; Le Gallo, M.; Santini, C. A.; Sebastian, A.; Eleftheriou, E.; Craciun, M. F.; Wright, C. D.

2018-01-01

Computing with resistive-switching (memristive) memory devices has shown much recent progress and offers an attractive route to circumvent the von-Neumann bottleneck, i.e. the separation of processing and memory, which limits the performance of conventional computer architectures. Due to their good scalability and nanosecond switching speeds, carbon-based resistive-switching memory devices could play an important role in this respect. However, devices based on elemental carbon, such as tetrahedral amorphous carbon or ta-C, typically suffer from a low cycling endurance. A material that has proven to be capable of combining the advantages of elemental carbon-based memories with simple fabrication methods and good endurance performance for binary memory applications is oxygenated amorphous carbon, or a-CO x . Here, we examine the memristive capabilities of nanoscale a-CO x devices, in particular their ability to provide the multilevel and accumulation properties that underpin computing type applications. We show the successful operation of nanoscale a-CO x memory cells for both the storage of multilevel states (here 3-level) and for the provision of an arithmetic accumulator. We implement a base-16, or hexadecimal, accumulator and show how such a device can carry out hexadecimal arithmetic and simultaneously store the computed result in the self-same a-CO x cell, all using fast (sub-10 ns) and low-energy (sub-pJ) input pulses.

C-Curves for Lengthening of Widmanstätten and Bainitic Ferrite

NASA Astrophysics Data System (ADS)

Yin, Jiaqing; Leach, Lindsay; Hillert, Mats; Borgenstam, Annika

2017-09-01

Widmanstätten ferrite and bainitic ferrite are both acicular and their lengthening rate in binary Fe-C alloys and low-alloyed steels under isothermal conditions is studied by searching the literature and through new measurements. As a function of temperature, the lengthening rate can be represented by a common curve for both kinds of acicular ferrite in contrast to the separate C-curves often presented in time-temperature-transformation (TTT) diagrams. The curves for Fe-C alloys with low carbon content show no obvious decrease in rate at low temperatures down to 623 K (350 °C). For alloys with higher carbon content, the expected decrease of rate as a function of temperature below a nose was observed. An attempt to explain the absence of a nose for low carbon contents by an increasing deviation from local equilibrium at high growth rates is presented. This explanation is based on a simple kinetic model, which predicts that the growth rates for Fe-C alloys with less than 0.3 mass pct carbon are high enough at low temperatures to make the carbon pileup, in front of the advancing tip of a ferrite plate, shrink below atomic dimensions, starting at about 600 K (323 °C).

KEY COMPARISON Final report on international comparison CCQM-K71: Measurement of stack gas

NASA Astrophysics Data System (ADS)

Nieuwenkamp, G.; van der Veen, A. M. H.; Wessel, R. M.; Qiao, Han; Oh, Sang-Hyub; Kim, Byung-Moon; Kim, Kwang-Sub; Pérez Castorena, Alejandro; Ramírez Nambo, Carlos; Koelliker Delgado, Jorge; Serrano Caballero, Victor M.; Rangel Murillo, Francisco; Avila Salas, Manuel de Jesus; Dias, Florbela; Baptista, Gonçalo; Konopelko, L. A.; Kustikov, Y. A.; Pankratov, V. V.; Selyukov, D. N.; Balandovich, V. S.; Vishnyakov, I. M.; Pavlov, M. V.; Maltsev, M. A.; Botha, Angelique; Valkova, Miroslava; Stovcik, Viliam; Musil, Stanislav; Milton, M. J. T.; Uprichard, I. J.; Vargha, G. M.; Guenther, F.; Gameson, L.; da Cunha, V.

2010-01-01

Industrial stack gas emission measurements are important for process control, control of air pollution, and for implementing legislation regarding carbon dioxide emission rights. Measurements are typically performed using a range of process analysers for carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), sulphur dioxide (SO2) and miscellaneous hydrocarbons. The calibration of these analysers is often performed using a series of binary mixtures of each component in nitrogen. For reasons of efficiency as well as a better match with true stack gas, the use of multi-component mixtures for this purpose would be preferred. The aim of this key comparison is to evaluate the measurement capabilities of national metrology institutes for carbon monoxide, carbon dioxide, nitrogen monoxide, sulphur dioxide and propane in nitrogen. Ten laboratories participated in the key comparison and one in the associated study. The key comparison reference value is based on the gravimetric preparation data. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Effect of air humidity on the removal of carbon tetrachloride from air using Cu-BTC metal-organic framework.

PubMed

Martín-Calvo, Ana; García-Pérez, Elena; García-Sánchez, Almudena; Bueno-Pérez, Rocío; Hamad, Said; Calero, Sofia

2011-06-21

We have used interatomic potential-based simulations to study the removal of carbon tetrachloride from air at 298 K, using Cu-BTC metal organic framework. We have developed new sets of Lennard-Jones parameters that accurately describe the vapour-liquid equilibrium curves of carbon tetrachloride and the main components from air (oxygen, nitrogen, and argon). Using these parameters we performed Monte Carlo simulations for the following systems: (a) single component adsorption of carbon tetrachloride, oxygen, nitrogen, and argon molecules, (b) binary Ar/CCl(4), O(2)/CCl(4), and N(2)/CCl(4) mixtures with bulk gas compositions 99 : 1 and 99.9 : 0.1, (c) ternary O(2)/N(2)/Ar mixtures with both, equimolar and 21 : 78 : 1 bulk gas composition, (d) quaternary mixture formed by 0.1% of CCl(4) pollutant, 20.979% O(2), 77.922% N(2), and 0.999% Ar, and (e) five-component mixtures corresponding to 0.1% of CCl(4) pollutant in air with relative humidity ranging from 0 to 100%. The carbon tetrachloride adsorption selectivity and the self-diffusivity and preferential sitting of the different molecules in the structure are studied for all the systems.

Saccharide-based graphitic carbon nanocoils as supports for PtRu nanoparticles for methanol electrooxidation

NASA Astrophysics Data System (ADS)

Sevilla, Marta; Lota, Grzegorz; Fuertes, Antonio B.

Highly graphitic carbon nanocoils were synthesised from the catalytic graphitization of carbon spherules obtained by the hydrothemal treatment of different saccharides (sucrose, glucose and starch). This nanostructured carbon was characterized by X-ray power diffraction, N 2 adsorption and microscopy techniques (SEM and TEM). The carbon nanocoils were used as a support for PtRu nanoparticles, which were well-dispersed over the carbon surface. This catalytic system was investigated for use as an electrocatalyst for methanol electrooxidation in an acid medium. The experiments were carried out at two working temperatures (25 °C and 60 °C). It was found that the carbon nanocoils supporting PtRu nanoparticles exhibit a high catalytic activity, which is even higher than that of conventional carbon supports (Vulcan XC-72R). We believe that the high electrocatalytic activity of the carbon nanocoils presented here is due to the combination of a good electrical conductivity, derived from their graphitic structure, and a wide porosity that allows the diffusional resistances of reactants/products to be minimized.

Quantifying Mass Transfer Processes in Groundwater as a Function of Molecular Structure Variation for Multicomponent NAPL Sources

NASA Astrophysics Data System (ADS)

Abbott, J. B., III; Tick, G. R.; Greenberg, R. R.; Carroll, K. C.

2017-12-01

The remediation of nonaqueous liquid (NAPL) contamination sources in groundwater has been shown to be challenging and have limited success in the field. The presence of multicomponent NAPL sources further complicates the remediation due to variability of mass-transfer (dissolution) behavior as a result of compositional and molecular structure variations between the different compounds within the NAPL phase. This study investigates the effects of the contaminant of concern (COC) composition and the bulk-NAPL components molecular structure (i.e. carbon chain length, aliphatic and aromatic) on dissolution and aqueous phase concentrations in groundwater. The specific COCs tested include trichloroethene (TCE), toluene (TOL), and perfluorooctanoic acid (PFOA). Each COC was tested in a series of binary batch experiments using insoluble bulk NAPL including n-hexane (HEX), n-decane (DEC), and n-hexadecane (HEXDEC). These equilibrium batch tests were performed to understand how different carbon-chain-length (NAPL) systems affect resulting COC aqueous phase concentrations. The experiments were conducted with four different COC mole fractions mixed within the bulk-NAPL derivatives (0.1:0.9, 0.05:0.95, 0.01:0.99, 0.001:0.999). Raoult's Law was used to assess the relative ideality of the mass transfer processes for each binary equilibrium dissolution experiment. Preliminary results indicate that as mole fraction of the COC decreases (composition effects), greater deviance from dissolution ideality occurs. It was also shown that greater variation in molecular structure (i.e. greater carbon chain length of bulk-NAPL with COC and aromatic COC presence) exhibited greater dissolution nonideality via Raoult's Law analysis. For instance, TOL (aromatic structure) showed greater nonideality than TCE (aliphatic structure) in the presence of the different bulk-NAPL derivatives (i.e. of various aliphatic carbon chains lengths). The results suggest that the prediction of aqueous phase concentration, from complex multicomponent NAPL sources, is highly dependent upon both composition and molecular structure variations of COC-NAPL mixtures, and such impacts should be taken into account when designing and evaluating a remediation strategy and/or predicting COC concentrations from a source zone region.

Far-UV Spectroscopy of Two Extremely Hot, Helium-Rich White Dwarfs

NASA Technical Reports Server (NTRS)

Werner, K.; Rauch, T.; Kruk, J. W.

2017-01-01

A large proportion of hot post-asymptotic giant branch stars and white dwarfs (WDs) are hydrogen-deficient. Two distinct evolutionary sequences have been identified. One of them comprises stars of spectral type [WC] and PG1159, and it originates from a late helium-shell flash, creating helium-rich stellar atmospheres with significant admixtures of carbon (up to about 50, mass fraction). The other sequence comprises stars of spectral type O(He) and luminous subdwarf O stars which possibly are descendants of RCrB stars and extreme helium stars. Their carbon abundances are significantly lower (of the order of 1 or less) and it is thought that they originate from binary-star evolution (through merger or common-envelope evolution). Here we investigate two of the three hottest known helium-rich (DO) WDs (PG 1034+001 and PG 0038+199). They are the only ones for which spectra were recorded with the Far Ultraviolet Spectroscopic Explorer and the Hubble Space Telescope, allowing a comprehensive ultraviolet spectral analysis. We find effective temperatures of T(eff) =115000 +/- 5000 K and 125000 +/- 5000 K, respectively, and a surface gravity of log g = 7 +/-0.5. In both stars, nitrogen is strongly oversolar while C and O are significantly subsolar. For all other assessed metals (Ne, Si, P, S, Ar, Fe, and Ni) we find abundances close to solar. We conclude that these WDs are immediate descendants of O(He) stars and, hence, result from close-binary evolution.

Using MOST to reveal the secrets of the mischievous Wolf-Rayet binary CV Ser

NASA Astrophysics Data System (ADS)

David-Uraz, Alexandre; Moffat, Anthony F. J.; Chené, André-Nicolas; Rowe, Jason F.; Lange, Nicholas; Guenther, David B.; Kuschnig, Rainer; Matthews, Jaymie M.; Rucinski, Slavek M.; Sasselov, Dimitar; Weiss, Werner W.

2012-11-01

The Wolf-Rayet (WR) binary CV Serpentis (= WR113, WC8d + O8-9IV) has been a source of mystery since it was shown that its atmospheric eclipses change with time over decades, in addition to its sporadic dust production. The first high-precision time-dependent photometric observations obtained with the Microvariability and Oscillations of STars (MOST) space telescope in 2009 show two consecutive eclipses over the 29-d orbit, with varying depths. A subsequent MOST run in 2010 showed a seemingly asymmetric eclipse profile. In order to help make sense of these observations, parallel optical spectroscopy was obtained from the Mont Megantic Observatory (2009, 2010) and from the Dominion Astrophysical Observatory (2009). Assuming these depth variations are entirely due to electron scattering in a β-law wind, an unprecedented 62 per cent increase in M⊙ is observed over one orbital period. Alternatively, no change in mass-loss rate would be required if a relatively small fraction of the carbon ions in the wind globally recombined and coaggulated to form carbon dust grains. However, it remains a mystery as to how this could occur. There also seems to be evidence for the presence of corotating interaction regions (CIR) in the WR wind: a CIR-like signature is found in the light curves, implying a potential rotation period for the WR star of 1.6 d. Finally, a new circular orbit is derived, along with constraints for the wind collision.

Detection of CI line emission towards the oxygen-rich AGB star omi Ceti

NASA Astrophysics Data System (ADS)

Saberi, M.; Vlemmings, W. H. T.; De Beck, E.; Montez, R.; Ramstedt, S.

2018-05-01

We present the detection of neutral atomic carbon CI(3P1-3P0) line emission towards omi Cet. This is the first time that CI is detected in the envelope around an oxygen-rich M-type asymptotic giant branch (AGB) star. We also confirm the previously tentative CI detection around V Hya, a carbon-rich AGB star. As one of the main photodissociation products of parent species in the circumstellar envelope (CSE) around evolved stars, CI can be used to trace sources of ultraviolet (UV) radiation in CSEs. The observed flux density towards omi Cet can be reproduced by a shell with a peak atomic fractional abundance of 2.4 × 10-5 predicted based on a simple chemical model where CO is dissociated by the interstellar radiation field. However, the CI emission is shifted by 4 km s-1 from the stellar velocity. Based on this velocity shift, we suggest that the detected CI emission towards omi Cet potentially arises from a compact region near its hot binary companion. The velocity shift could, therefore, be the result of the orbital velocity of the binary companion around omi Cet. In this case, the CI column density is estimated to be 1.1 × 1019 cm-2. This would imply that strong UV radiation from the companion and/or accretion of matter between two stars is most likely the origin of the CI enhancement. However, this hypothesis can be confirmed by high-angular resolution observations.

Adsorptive separation studies of ethane-methane and methane-nitrogen systems using mesoporous carbon.

PubMed

Yuan, Bin; Wu, Xiaofei; Chen, Yingxi; Huang, Jianhan; Luo, Hongmei; Deng, Shuguang

2013-03-15

Adsorptive separations of C(2)H(6)/CH(4) and CH(4)/N(2) binary mixtures are of paramount importance from the energy and environmental points of view. A mesoporous carbon adsorbent was synthesized using a soft template method and characterized with TEM, TGA, and nitrogen adsorption/desorption. Adsorption equilibrium and kinetics of C(2)H(6), CH(4), and N(2) on the mesoporous carbon adsorbent were determined at 278, 298, and 318 K and pressures up to 100 kPa. The adsorption capacities of C(2)H(6) and CH(4) on the mesoporous carbon adsorbent at 298 K and 100 kPa are 2.20 mmol/g and 1.05 mmol/g, respectively. Both are significantly higher than those of many adsorbents including pillared clays and ETS-10 at a similar condition. The equilibrium selectivities of C(2)H(6)/CH(4) and CH(4)/N(2) at 298 K are 19.6 and 5.8, respectively. It was observed that the adsorption of C(2)H(6), CH(4), and N(2) gases on the carbon adsorbent was reversible with modest isosteric heats of adsorption, which implies that this carbon adsorbent can be easily regenerated in a cyclic adsorption process. These results suggest that the mesoporous carbon studied in this work is a promising alternative adsorbent for the separations of C(2)H(6)/CH(4) and CH(4)/N(2) gas mixtures. Copyright © 2012 Elsevier Inc. All rights reserved.

Marine Carbonate Component in the Mantle Beneath the Southeastern Tibetan Plateau: Evidence From Magnesium and Calcium Isotopes

NASA Astrophysics Data System (ADS)

Liu, Fang; Li, Xin; Wang, Guiqin; Liu, Yufei; Zhu, Hongli; Kang, Jinting; Huang, Fang; Sun, Weidong; Xia, Xiaoping; Zhang, Zhaofeng

2017-12-01

Tracing and identifying recycled carbonates is a key issue to reconstruct the deep carbon cycle. To better understand carbonate subduction and recycling beneath the southeastern Tibetan Plateau, high-K cal-alkaline volcanic rocks including trachy-basalts and trachy-andesites from Tengchong were studied using Mg and Ca isotopes. The low δ26Mg (-0.31 ± 0.03‰ to -0.38 ± 0.03‰) and δ44/40Ca (0.67 ± 0.07‰ to 0.80 ± 0.04‰) values of these volcanic rocks compared to those of the mantle (-0.25 ± 0.07‰ and 0.94 ± 0.05‰, respectively) indicate the incorporation of isotopically light materials into the mantle source, which may be carbonate-bearing sediments with low δ26Mg and δ44/40Ca values. In addition, no correlations of δ26Mg and δ44/40Ca with either SiO2 contents or trace element abundance ratios (e.g., Sm/Yb and Ba/Y) were observed, suggesting that limited Mg and Ca isotopic fractionation occurred during cal-alkaline magmatic differentiation. A binary mixing model using Mg-Ca isotopes shows that 5-8% carbonates dominated primarily by dolostone were recycled back into the mantle. Since Tengchong volcanism is still active and probably related to ongoing plate tectonic movement, we propose that the recycled carbonates are derived from oceanic crust related to the ongoing subduction of the Indian plate.

Runoff-driven export of particulate organic carbon from soil in temperate forested uplands

NASA Astrophysics Data System (ADS)

Smith, Joanne C.; Galy, Albert; Hovius, Niels; Tye, Andrew M.; Turowski, Jens M.; Schleppi, Patrick

2013-03-01

We characterise the sources, pathways and export fluxes of particulate organic carbon (POC) in a headwater catchment in the Swiss Alps, where suspended sediment has a mean organic carbon concentration of 1.45%±0.06. By chemically fingerprinting this carbon and its potential sources using carbon and nitrogen elemental and isotopic compositions, we show that it derives from binary mixing between bedrock and modern biomass with a soil-like composition. The hillslope and channel are strongly coupled, allowing runoff to deliver recent organic carbon directly to the stream beyond a moderate discharge threshold. At higher flows, more biomass is mobilised and the fraction of modern carbon in the suspended load reaches 0.70, increased from 0.30 during background conditions. Significant amounts of non-fossil organic carbon are thus transferred from the hillslope without the need for extreme events such as landsliding. Precipitation is key: as soon as the rain stops, biomass supply ceases and fossil carbon again dominates. We use rating curves modelled using samples from five storm events integrated over 29-year discharge records to calculate long-term export fluxes of total POC and non-fossil POC from the catchment of 23.3±5.8 and 14.0±4.4 t km-2 yr-1 respectively. These yields are comparable to those from active mountain belts, yet the processes responsible are much more widely applicable. Such settings have the potential to play a significant role in the global drawdown of carbon dioxide via riverine biomass erosion, and their contribution to the global flux of POC to the ocean may be more important than previously thought.

Origin of the Excellent Performance of Ru on Nitrogen-Doped Carbon Nanofibers for CO2 Hydrogenation to CH4.

PubMed

Roldán, Laura; Marco, Yanila; García-Bordejé, Enrique

2017-03-22

Carbon materials have rarely been used as support for CO 2 methanation, which is usually carried out using catalysts supported on metal oxides. Here, it is shown that Ru nanoparticles supported on nitrogen-doped carbon nanofibers (NCNF) provide competitive CH 4 production rate and stability compared to Al 2 O 3 -supported catalysts. Contrary to the general belief about the inert nature of carbon supports, it is demonstrated that NCNF is a non-innocent spectator in CO 2 methanation due to its ability to store a high amount of CO ad reaction intermediates. This explains the excellent catalytic behaviour afforded by this unconventional catalyst support. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

MESA models for the evolutionary status of the epsilon Aurigae disk-eclipsed binary system

NASA Astrophysics Data System (ADS)

Stencel, Robert E.; Gibson, Justus

2018-06-01

The brightest member of the class of disk-eclipsed binary stars is the Algol-like long-period binary, epsilon Aurigae (HD 31964, F0Iap + disk, http://adsabs.harvard.edu/abs/2016SPIE.9907E..17S ). Using MESA (Modules for Experiments in Stellar Astrophysics, version 9575), we have made an evaluation of its evolutionary state. We sought to satisfy several observational constraints, including: (1) requiring evolutionary tracks to pass close to the current temperature and luminosity of the primary star; (2) obtaining a period near the observed value of 27.1 years; (3) matching a mass function of 3.0; (4) concurrent Roche lobe overflow and mass transfer; (5) an isotopic ratio 12C / 13C = 5 and, (6) matching the interferometrically determined angular diameter. A MESA model starting with binary masses of 9.85 + 4.5 solar masses, with a 100 day initial period, produces a 1.2 + 10.6 solar masses result having a 547 day period, plus a single digit 12C / 13C ratio. These values were reached near an age of 20 Myr, when the donor star comes close to the observed luminosity and temperature for epsilon Aurigae A, as a post-RGB/pre-AGB star. Contemporaneously, the accretor then appears as an upper main sequence, early B-type star. This benchmark model can provide a basis for further exploration of this interacting binary, and other long period binary stars. This report has been submitted to MNRAS, along with a parallel investigation of mass transfer stream and disk sub-structure. The authors are grateful to the estate of William Herschel Womble for the support of astronomy at the University of Denver.

CHARACTERIZATION OF SEVEN ULTRA-WIDE TRANS-NEPTUNIAN BINARIES

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

Parker, Alex H.; Kavelaars, J. J.; Petit, Jean-Marc

2011-12-10

The low-inclination component of the Classical Kuiper Belt is host to a population of extremely widely separated binaries. These systems are similar to other trans-Neptunian binaries (TNBs) in that the primary and secondary components of each system are of roughly equal size. We have performed an astrometric monitoring campaign of a sample of seven wide-separation, long-period TNBs and present the first-ever well-characterized mutual orbits for each system. The sample contains the most eccentric (2006 CH{sub 69}, e{sub m} = 0.9) and the most widely separated, weakly bound (2001 QW{sub 322}, a/R{sub H} {approx_equal} 0.22) binary minor planets known, and alsomore » contains the system with lowest-measured mass of any TNB (2000 CF{sub 105}, M{sub sys} {approx_equal} 1.85 Multiplication-Sign 10{sup 17} kg). Four systems orbit in a prograde sense, and three in a retrograde sense. They have a different mutual inclination distribution compared to all other TNBs, preferring low mutual-inclination orbits. These systems have geometric r-band albedos in the range of 0.09-0.3, consistent with radiometric albedo estimates for larger solitary low-inclination Classical Kuiper Belt objects, and we limit the plausible distribution of albedos in this region of the Kuiper Belt. We find that gravitational collapse binary formation models produce an orbital distribution similar to that currently observed, which along with a confluence of other factors supports formation of the cold Classical Kuiper Belt in situ through relatively rapid gravitational collapse rather than slow hierarchical accretion. We show that these binary systems are sensitive to disruption via collisions, and their existence suggests that the size distribution of TNOs at small sizes remains relatively shallow.« less

Comparison of age distributions estimated from environmental tracers by using binary-dilution and numerical models of fractured and folded karst: Shenandoah Valley of Virginia and West Virginia, USA

USGS Publications Warehouse

Yager, Richard M.; Plummer, Niel; Kauffman, Leon J.; Doctor, Daniel H.; Nelms, David L.; Schlosser, Peter

2013-01-01

Measured concentrations of environmental tracers in spring discharge from a karst aquifer in the Shenandoah Valley, USA, were used to refine a numerical groundwater flow model. The karst aquifer is folded and faulted carbonate bedrock dominated by diffuse flow along fractures. The numerical model represented bedrock structure and discrete features (fault zones and springs). Concentrations of 3H, 3He, 4He, and CFC-113 in spring discharge were interpreted as binary dilutions of young (0–8 years) water and old (tracer-free) water. Simulated mixtures of groundwater are derived from young water flowing along shallow paths, with the addition of old water flowing along deeper paths through the model domain that discharge to springs along fault zones. The simulated median age of young water discharged from springs (5.7 years) is slightly older than the median age estimated from 3H/3He data (4.4 years). The numerical model predicted a fraction of old water in spring discharge (0.07) that was half that determined by the binary-dilution model using the 3H/3He apparent age and 3H and CFC-113 data (0.14). This difference suggests that faults and lineaments are more numerous or extensive than those mapped and included in the numerical model.

Simultaneous voltammetric determination of dopamine and epinephrine in human body fluid samples using a glassy carbon electrode modified with nickel oxide nanoparticles and carbon nanotubes within a dihexadecylphosphate film.

PubMed

Figueiredo-Filho, Luiz C S; Silva, Tiago A; Vicentini, Fernando C; Fatibello-Filho, Orlando

2014-06-07

A simple and highly selective electrochemical method was developed for the single or simultaneous determination of dopamine (DA) and epinephrine (EP) in human body fluids using a glassy carbon electrode modified with nickel oxide nanoparticles and carbon nanotubes within a dihexadecylphosphate film using square-wave voltammetry (SWV) or differential-pulse voltammetry (DPV). Using DPV with the proposed electrode, a separation of ca. 360 mV between the peak reduction potentials of DA and EP present in binary mixtures was obtained. The analytical curves for the simultaneous determination of dopamine and epinephrine showed an excellent linear response, ranging from 7.0 × 10(-8) to 4.8 × 10(-6) and 3.0 × 10(-7) to 9.5 × 10(-6) mol L(-1) for DA and EP, respectively. The detection limits for the simultaneous determination of DA and EP were 5.0 × 10(-8) mol L(-1) and 8.2 × 10(-8) mol L(-1), respectively. The proposed method was successfully applied in the simultaneous determination of these analytes in human body fluid samples of cerebrospinal fluid, human serum and lung fluid.

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

NASA Astrophysics Data System (ADS)

Campo Bagatin, A.; Richardson, D. C.; Tsiganis, K.; Cheng, A. F.; Michel, P.

2017-09-01

The near-Earth asteroid (NEA) 65803 Didymos is a binary system and is the target of the proposed Asteroid Impact & Deflection Assessment (AIDA) mission, which combines an orbiter (Asteroid Impact Mission, AIM, or the reduced-scope AIM Deflection Demonstration, AIM-D2) [1, 2] and a kinetic impactor experiment (Double Asteroid Redirection Test, DART) planned to impact the secondary of the Didymos binary system in October, 2022 [3]. The Dynamical and Physical Properties of Didymos Working Group supports the AIDA mission by addressing questions related to understanding the dynamical state of the system and inferring the physical properties of the components

The virial coefficients of hard hypersphere binary mixtures

NASA Astrophysics Data System (ADS)

Enciso, E.; Almarza, N. G.; Gonzalez, M. A.; Bermejo, F. J.

The third, fourth and fifth virial coefficients of hard hypersphere binary mixtures with dimensionality d = 4, 5 have been calculated for size ratios R ≥0.1, R ı σ22 / σ11 , where σ ii is the diameter of component i . The composition independent partial virial coefficients have been evaluated by Monte Carlo integration of the corresponding Mayer modified star diagrams. The results are compared with the predictions of Santos, S., Yuste, S. B., and Lopez de Haro, M., 1999, Molec. Phys ., 96 , 1 of the equation of state of a multicomponent mixture of hard hyperspheres, and the good agreement gives strong support to the validity of that recipe.

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.

Ultraviolet spectroscopy of old novae and symbiotic stars

NASA Technical Reports Server (NTRS)

Lambert, D. L.; Slovak, M. H.; Shields, G. A.; Ferland, G. J.

1981-01-01

The IUE spectra are presented for two old novae and for two of the symbiotic variables. Prominent emission line spectra are revealed as a continuum whose appearance is effected by the system inclination. These data provide evidence for hot companions in the symbiotic stars, making plausible the binary model for these peculiar stars. Recent IUE spectra of dwarf novae provide additional support for the existence of optically thick accretion disks in active binary systems. The ultraviolet data of the eclipsing dwarf novae EX Hya and BV Cen appear flatter than for the noneclipsing systems, an effect which could be ascribed to the system inclination.

The Nature of the Enigmatic 10-Minute Accreting Binary System ES CET

NASA Technical Reports Server (NTRS)

Steeghs, Daniel

2005-01-01

ES Cet is one of the most compact binary systems known with an orbital period of only 10.3 minutes. Our allocated observations with the XMM-Newton X-ray satellite were performed in January and July 2004, with the data being delivered to the PI in August 2004. Preliminary results were presented by the PI in September 2004 and January 2005. We have also secured supporting optical observations of ES Ceti using the Magellan telescopes (November 2004). The team is currently performing a thorough and final analysis of the X-ray, UV and optical data sets with the latest XMM pipeline software and our own analysis packages.

Engineering catalytic activity via ion beam bombardment of catalyst supports for vertically aligned carbon nanotube growth

DOE PAGES

Islam, A. E.; Zakharov, D.; Stach, E. A.; ...

2015-09-16

Carbon nanotube growth depends on the catalytic activity of metal nanoparticles on alumina or silica supports. The control on catalytic activity is generally achieved by variations in water concentration, carbon feed, and sample placement on a few types of alumina or silica catalyst supports obtained via thin film deposition. We have recently expanded the choice of catalyst supports by engineering inactive substrates like c-cut sapphire via ion beam bombardment. The deterministic control on the structure and chemistry of catalyst supports obtained by tuning the degree of beam-induced damage have enabled better regulation of the activity of Fe catalysts only inmore » the ion beam bombarded areas and hence enabled controllable super growth of carbon nanotubes. A wide range of surface characterization techniques were used to monitor the catalytically active surface engineered via ion beam bombardment. The proposed method offers a versatile way to control carbon nanotube growth in patterned areas and also enhances the current understanding of the growth process. As a result, with the right choice of water concentration, carbon feed and sample placement, engineered catalyst supports may extend the carbon nanotube growth yield to a level that is even higher than the ones reported here, and thus offers promising applications of carbon nanotubes in electronics, heat exchanger, and energy storage.« less

Polymer network/carbon layer on monolith support and monolith catalytic reactor

DOEpatents

Nordquist, Andrew Francis; Wilhelm, Frederick Carl; Waller, Francis Joseph; Machado, Reinaldo Mario

2003-08-26

The present invention relates to an improved monolith catalytic reactor and a monolith support. The improvement in the support resides in a polymer network/carbon coating applied to the surface of a porous substrate and a catalytic metal, preferably a transition metal catalyst applied to the surface of the polymer network/carbon coating. The monolith support has from 100 to 800 cells per square inch and a polymer network/carbon coating with surface area of from 0.1 to 15 m.sup.2 /gram as measured by adsorption of N.sub.2 or Kr using the BET method.

Protected Amine Labels: A Versatile Molecular Scaffold for Multiplexed Nominal Mass and Sub-Da Isotopologue Quantitative Proteomic Reagents

PubMed Central

Ficarro, Scott B.; Biagi, Jessica M.; Wang, Jinhua; Scotcher, Jenna; Koleva, Rositsa I.; Card, Joseph D.; Adelmant, Guillaume; He, Huan; Askenazi, Manor; Marshall, Alan G.; Young, Nicolas L.; Gray, Nathanael S.; Marto, Jarrod A.

2014-01-01

We assemble a versatile molecular scaffold from simple building blocks to create binary and multiplexed stable isotope reagents for quantitative mass spectrometry. Termed Protected Amine Labels (PAL), these reagents offer multiple analytical figures of merit including, (i) robust targeting of peptide N-termini and lysyl side chains, (ii) optimal mass spectrometry ionization efficiency through regeneration of primary amines on labeled peptides, (iii) an amino acid-based mass tag that incorporates heavy isotopes of carbon, nitrogen, and oxygen to ensure matched physicochemical and MS/MS fragmentation behavior among labeled peptides, and (iv) a molecularly efficient architecture, in which the majority of hetero-atom centers can be used to synthesize a variety of nominal mass and sub-Da isotopologue stable isotope reagents. We demonstrate the performance of these reagents in well-established strategies whereby up to four channels of peptide isotopomers, each separated by 4 Da are quantified in MS-level scans with accuracies comparable to current commercial reagents. In addition we utilize the PAL scaffold to create isotopologue reagents in which labeled peptide analogs differ in mass based on the binding energy in carbon and nitrogen nuclei, thereby allowing quantification based on MS or MS/MS spectra. We demonstrate accurate quantification for reagents that support 6-plex labeling and propose extension of this scheme to 9-channels based on a similar PAL scaffold. Finally we provide exemplar data that extends the application of isotopologe-based quantification reagents to medium resolution, quadrupole time-of-flight mass spectrometers. PMID:24496597

A Chandra X-Ray Census of the Interacting Binaries in Old Open Clusters—Collinder 261

NASA Astrophysics Data System (ADS)

Vats, Smriti; van den Berg, Maureen

2017-03-01

We present the first X-ray study of Collinder 261 (Cr 261), which at an age of 7 Gyr is one of the oldest open clusters known in the Galaxy. Our observation with the Chandra X-Ray Observatory is aimed at uncovering the close interacting binaries in Cr 261, and reaches a limiting X-ray luminosity of {L}X≈ 4× {10}29 {erg} {{{s}}}-1 (0.3-7 keV) for stars in the cluster. We detect 107 sources within the cluster half-mass radius r h , and we estimate that among the sources with {L}X≳ {10}30 {erg} {{{s}}}-1, ˜26 are associated with the cluster. We identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have “straggled” from the main locus of Cr 261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, we estimate that Cr 261 has an approximate mass of 6500 M ⊙, roughly the same as the old open cluster NGC 6791. The X-ray emissivity of Cr 261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity.

Collision-induced absorption in the region of the ν2 + ν3 band of carbon dioxide

NASA Astrophysics Data System (ADS)

Baranov, Yu. I.

2018-03-01

The IR absorption spectra of pure carbon dioxide in the region of the forbidden ν2 + ν3 vibrational transition at 3004 cm-1 have been recorded using a Fourier-transform spectrometer. A multipass-optical cell with the path length of 100 m was used in the study. The data were taken at room temperature of 294.8 K with a resolution of 0.02 cm-1 over the spectral region 2500-3500 cm-1. A sample pressures varied from 207 to 463 kPa (2.04-4.57 atm). The measured binary absorption coefficients provide the band integrated intensity value of (2.39 ± 0.04) ∗ 10-4 cm-2 amagat-2. The result is compared with those from previous works. The observed band profile features are discussed.

Single-crystalline FeCo nanoparticle-filled carbon nanotubes: synthesis, structural characterization and magnetic properties.

PubMed

Ghunaim, Rasha; Scholz, Maik; Damm, Christine; Rellinghaus, Bernd; Klingeler, Rüdiger; Büchner, Bernd; Mertig, Michael; Hampel, Silke

2018-01-01

In the present work, we demonstrate different synthesis procedures for filling carbon nanotubes (CNTs) with equimolar binary nanoparticles of the type Fe-Co. The CNTs act as templates for the encapsulation of magnetic nanoparticles and provide a protective shield against oxidation as well as prevent nanoparticle agglomeration. By variation of the reaction parameters, we were able to tailor the sample purity, degree of filling, the composition and size of the filling particles, and therefore, the magnetic properties. The samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), superconducting quantum interference device (SQUID) and thermogravimetric analysis (TGA). The Fe-Co-filled CNTs show significant enhancement in the coercive field as compared to the corresponding bulk material, which make them excellent candidates for several applications such as magnetic storage devices.

A Fast Algorithm to Compute Conical Pockets in Proteins. Application to the Structural Characterization of γ-Carbonic Anhydrases.

PubMed

Petitjean, Michel

2017-10-01

Some major proteins families, such as carbonic anhydrases (CAs), have a conical cavity at the active site. No algorithm was available to compute conical cavities, so we needed to design one. The fast algorithm we designed let us show on a set of 717 CAs extracted from the PDB database that γ-CAs are characterized by active site cavity cone angles significantly larger than those of α-CAs and β-CAs: the generatrix-axis angles are greater than 60° for the γ-CAs while they are smaller than 50° for the other CAs. Free binaries of the CONICA software implementing the algorithm are available through a software repository at http://petitjeanmichel.free.fr/itoweb.petitjean.freeware.html. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impact of active phase chemical composition and dispersity on catalytic behavior in PROX reaction

NASA Astrophysics Data System (ADS)

Cherkezova-Zheleva, Z.; Paneva, D.; Todorova, S.; Kolev, H.; Shopska, M.; Yordanova, I.; Mitov, I.

2014-04-01

Iron and iron-platinum catalysts supported on activated carbon have been successfully synthesized by wet impregnation method and low-temperature treatment in inert atmosphere. The content of the supported phases corresponds to 10 wt % Fe and 0.5 wt % Pt. Four catalytic samples were synthesized: Sample A—activated carbon impregnated with Fe nitrate; Sample B—activated carbon impregnated with Pt salt; Sample C—activated carbon impregnated consequently with Fe and Pt salts; Sample D—activated carbon impregnated simultaneously with Fe and Pt salts. The as-prepared materials were characterized by Mössbauer spectroscopy, X-ray diffraction, infrared and X-ray photoelectron spectroscopy. The spectra show that the activated carbon support and the preparation procedure give rise to the synthesis of isolated metal Pt ions and ultradispersed Fe and Pt oxide species. Probably the presence of different functional groups of activated carbon gives rise to registered very high dispersion of loaded species on support. The catalytic tests were carried out in PROX reaction. A lower activity of bimetallic Pt-Fe samples was explained with the increase in surface oxygen species as a result of predomination of iron oxide on the support leading to the increase in selectivity to the H2 oxidation. Partial agglomeration of supported iron oxide phase was registered after catalytic tests.

Facile Fabrication of Platinum-Cobalt Alloy Nanoparticles with Enhanced Electrocatalytic Activity for a Methanol Oxidation Reaction

NASA Astrophysics Data System (ADS)

Huang, Huihong; Hu, Xiulan; Zhang, Jianbo; Su, Nan; Cheng, Jiexu

2017-03-01

Decreasing the cost associated with platinum-based catalysts along with improving their catalytic properties is a major challenge for commercial direct methanol fuel cells. In this work, a simple and facile strategy was developed for the more efficient preparation of multi-walled carbon nanotube (MWCNT) -supported Pt/CoPt composite nanoparticles (NPs) via solution plasma sputtering with subsequent thermal annealing. Quite different from general wet synthesis methods, Pt/CoPt composite NPs were directly derived from metal wire electrodes without any additions. The obtained Pt/CoPt/MWCNTs composite catalysts exhibited tremendous improvement in the electro-oxidation of methanol in acidic media with mass activities of 1719 mA mg-1Pt. This value is much higher than that of previous reports of Pt-Co alloy and commercial Pt/C (3.16 times) because of the many active sites and clean surface of the catalysts. The catalysts showed good stability due to the special synergistic effects of the CoPt alloy. Pt/CoPt/MWCNTs can be used as a promising catalyst for direct methanol fuel cells. In addition, this solution plasma sputtering-assisted synthesis method introduces a general and feasible route for the synthesis of binary alloys.

Facile Fabrication of Platinum-Cobalt Alloy Nanoparticles with Enhanced Electrocatalytic Activity for a Methanol Oxidation Reaction.

PubMed

Huang, Huihong; Hu, Xiulan; Zhang, Jianbo; Su, Nan; Cheng, JieXu

2017-03-30

Decreasing the cost associated with platinum-based catalysts along with improving their catalytic properties is a major challenge for commercial direct methanol fuel cells. In this work, a simple and facile strategy was developed for the more efficient preparation of multi-walled carbon nanotube (MWCNT) -supported Pt/CoPt composite nanoparticles (NPs) via solution plasma sputtering with subsequent thermal annealing. Quite different from general wet synthesis methods, Pt/CoPt composite NPs were directly derived from metal wire electrodes without any additions. The obtained Pt/CoPt/MWCNTs composite catalysts exhibited tremendous improvement in the electro-oxidation of methanol in acidic media with mass activities of 1719 mA mg -1 Pt . This value is much higher than that of previous reports of Pt-Co alloy and commercial Pt/C (3.16 times) because of the many active sites and clean surface of the catalysts. The catalysts showed good stability due to the special synergistic effects of the CoPt alloy. Pt/CoPt/MWCNTs can be used as a promising catalyst for direct methanol fuel cells. In addition, this solution plasma sputtering-assisted synthesis method introduces a general and feasible route for the synthesis of binary alloys.

NASA Tech Briefs, March 2005

NASA Technical Reports Server (NTRS)

2005-01-01

Topics covered include: Scheme for Entering Binary Data Into a Quantum Computer; Encryption for Remote Control via Internet or Intranet; Coupled Receiver/Decoders for Low-Rate Turbo Codes; Processing GPS Occultation Data To Characterize Atmosphere; Displacing Unpredictable Nulls in Antenna Radiation Patterns; Integrated Pointing and Signal Detector for Optical Receiver; Adaptive Thresholding and Parameter Estimation for PPM; Data-Driven Software Framework for Web-Based ISS Telescience; Software for Secondary-School Learning About Robotics; Fuzzy Logic Engine; Telephone-Directory Program; Simulating a Direction-Finder Search for an ELT; Formulating Precursors for Coating Metals and Ceramics; Making Macroscopic Assemblies of Aligned Carbon Nanotubes; Ball Bearings Equipped for In Situ Lubrication on Demand; Synthetic Bursae for Robots; Robot Forearm and Dexterous Hand; Making a Metal-Lined Composite-Overwrapped Pressure Vessel; Ex Vivo Growth of Bioengineered Ligaments and Other Tissues; Stroboscopic Goggles for Reduction of Motion Sickness; Articulating Support for Horizontal Resistive Exercise; Modified Penning-Malmberg Trap for Storing Antiprotons; Tumbleweed Rovers; Two-Photon Fluorescence Microscope for Microgravity Research; Biased Randomized Algorithm for Fast Model-Based Diagnosis; Fast Algorithms for Model-Based Diagnosis; Simulations of Evaporating Multicomponent Fuel Drops; Formation Flying of Tethered and Nontethered Spacecraft; and Two Methods for Efficient Solution of the Hitting- Set Problem.

Three-dimensional hollow-structured binary oxide particles as an advanced anode material for high-rate and long cycle life lithium-ion batteries

DOE PAGES

Wang, Deli; Wang, Jie; He, Huan; ...

2015-12-30

Transition metal oxides are among the most promising anode candidates for next-generation lithium-ion batteries for their high theoretical capacity. However, the large volume expansion and low lithium ion diffusivity leading to a poor charging/discharging performance. In this study, we developed a surfactant and template-free strategy for the synthesis of a composite of Co xFe 3–xO 4 hollow spheres supported by carbon nanotubes via an impregnation–reduction–oxidation process. The synergy of the composite, as well as the hollow structures in the electrode materials, not only facilitate Li ion and electron transport, but also accommodate large volume expansion. Using state-of-the-art electron tomography, wemore » directly visualize the particles in 3-D, where the voids in the hollow structures serve to buffer the volume expansion of the material. These improvements result in a high reversible capacity as well as an outstanding rate performance for lithium-ion battery applications. As a result, this study sheds light on large-scale production of hollow structured metal oxides for commercial applications in energy storage and conversion.« less

Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths.

PubMed

Soloviev, Sergiy O; Kapran, Andriy Y; Kurylets, Yaroslava P

2015-02-01

Binary oxide systems (CuCr2O4, CuCo2O4), deposited onto cordierite monoliths of honeycomb structure with a second support (finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine's gas exhausts (O2, NOx, H2O, CO2) and O3 as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO2. Oxidants used can be arranged with reference to decreasing their activity in a following series: O3≫NO2>H2O>NO>O2>CO2. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O3 occurs intensively (in the presence of copper chromite based catalyst) even at closing to ambient temperatures. Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem. Copyright © 2014. Published by Elsevier B.V.

Predicting Positive and Negative Relationships in Large Social Networks.

PubMed

Wang, Guan-Nan; Gao, Hui; Chen, Lian; Mensah, Dennis N A; Fu, Yan

2015-01-01

In a social network, users hold and express positive and negative attitudes (e.g. support/opposition) towards other users. Those attitudes exhibit some kind of binary relationships among the users, which play an important role in social network analysis. However, some of those binary relationships are likely to be latent as the scale of social network increases. The essence of predicting latent binary relationships have recently began to draw researchers' attention. In this paper, we propose a machine learning algorithm for predicting positive and negative relationships in social networks inspired by structural balance theory and social status theory. More specifically, we show that when two users in the network have fewer common neighbors, the prediction accuracy of the relationship between them deteriorates. Accordingly, in the training phase, we propose a segment-based training framework to divide the training data into two subsets according to the number of common neighbors between users, and build a prediction model for each subset based on support vector machine (SVM). Moreover, to deal with large-scale social network data, we employ a sampling strategy that selects small amount of training data while maintaining high accuracy of prediction. We compare our algorithm with traditional algorithms and adaptive boosting of them. Experimental results of typical data sets show that our algorithm can deal with large social networks and consistently outperforms other methods.

Automated characterisation of ultrasound images of ovarian tumours: the diagnostic accuracy of a support vector machine and image processing with a local binary pattern operator.

PubMed

Khazendar, S; Sayasneh, A; Al-Assam, H; Du, H; Kaijser, J; Ferrara, L; Timmerman, D; Jassim, S; Bourne, T

2015-01-01

Preoperative characterisation of ovarian masses into benign or malignant is of paramount importance to optimise patient management. In this study, we developed and validated a computerised model to characterise ovarian masses as benign or malignant. Transvaginal 2D B mode static ultrasound images of 187 ovarian masses with known histological diagnosis were included. Images were first pre-processed and enhanced, and Local Binary Pattern Histograms were then extracted from 2 × 2 blocks of each image. A Support Vector Machine (SVM) was trained using stratified cross validation with randomised sampling. The process was repeated 15 times and in each round 100 images were randomly selected. The SVM classified the original non-treated static images as benign or malignant masses with an average accuracy of 0.62 (95% CI: 0.59-0.65). This performance significantly improved to an average accuracy of 0.77 (95% CI: 0.75-0.79) when images were pre-processed, enhanced and treated with a Local Binary Pattern operator (mean difference 0.15: 95% 0.11-0.19, p < 0.0001, two-tailed t test). We have shown that an SVM can classify static 2D B mode ultrasound images of ovarian masses into benign and malignant categories. The accuracy improves if texture related LBP features extracted from the images are considered.

Intensity Modulation Techniques for Continuous-Wave Lidar for Column CO2 Measurements

NASA Astrophysics Data System (ADS)

Campbell, J. F.; Lin, B.; Obland, M. D.; Kooi, S. A.; Fan, T. F.; Meadows, B.; Browell, E. V.; Erxleben, W. H.; McGregor, D.; Dobler, J. T.; Pal, S.; O'Dell, C.

2017-12-01

Global and regional atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission and the Atmospheric Carbon and Transport (ACT) - America project are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity-Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space and airborne platforms to meet the ASCENDS and ACT-America science measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) and Linear Swept Frequency modulations to uniquely discriminate surface lidar returns from intermediate aerosol and cloud returns. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that take advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques and provides very high (at sub-meter level) range resolution. We compare BPSK to linear swept frequency and introduce a new technique to eliminate sidelobes in situations from linear swept frequency where the SNR is high with results that rival BPSK. We also investigate the effects of non-linear modulators, which can in some circumstances degrade the orthogonality of the waveforms, and show how to avoid this. These techniques are used in a new data processing architecture written in the C language to support the ASCENDS CarbonHawk Experiment Simulator (ACES) and ACT-America programs.

Improvement of oxygen-containing functional groups on olive stones activated carbon by ozone and nitric acid for heavy metals removal from aqueous phase.

PubMed

Bohli, Thouraya; Ouederni, Abdelmottaleb

2016-08-01

Recently, modification of surface structure of activated carbons in order to improve their adsorption performance toward especial pollutants has gained great interest. Oxygen-containing functional groups have been devoted as the main responsible for heavy metal binding on the activated carbon surface; their introduction or enhancement needs specific modification and impregnation methods. In the present work, olive stones activated carbon (COSAC) undergoes surface modifications in gaseous phase using ozone (O3) and in liquid phase using nitric acid (HNO3). The activated carbon samples were characterized using N2 adsorption-desorption isotherm, SEM, pHpzc, FTIR, and Boehm titration. The activated carbon parent (COSAC) has a high surface area of 1194 m(2)/g and shows a predominantly microporous structure. Oxidation treatments with nitric acid and ozone show a decrease in both specific surface area and micropore volumes, whereas these acidic treatments have led to a fixation of high amount of surface oxygen functional groups, thus making the carbon surface more hydrophilic. Activated carbon samples were used as an adsorbent matrix for the removal of Co(II), Ni(II), and Cu(II) heavy metal ions from aqueous solutions. Adsorption isotherms were obtained at 30 °C, and the data are well fitted to the Redlich-Peterson and Langmuir equation. Results show that oxidized COSACs, especially COSAC(HNO3), are capable to remove more Co(II), Cu(II), and Ni(II) from aqueous solution. Nitric acid-oxidized olive stones activated carbon was tested in its ability to remove metal ions from binary systems and results show an important maximum adsorbed amount as compared to single systems.

Deposition of platinum nanoparticles on carbon nanotubes by supercritical fluid method.

PubMed

Yen, Clive H; Cui, Xiaoli; Pan, Horng-Bin; Wang, Shaofen; Lin, Yuehe; Wai, Chien M

2005-11-01

Carbon nanotube-supported platinum nanoparticles with a 5-15 nm diameter size range can be synthesized by hydrogen reduction of platinum(ll) acetylacetonate in methanol modified supercritical carbon dioxide. X-ray photoelectron spectroscopy and X-ray diffraction spectra indicate that the carbon nanotubes contain zero-valent platinum metal and high-resolution transmission electron microscopy images show that the visible lattice fringes of platinum nanoparticles are crystallites. Carbon nanotubes synthesized with 25% by weight of platinum nanoparticles exhibit a higher activity for hydrogenation of benzene compared with a commercial carbon black platinum catalyst. The carbon nanotube-supported platinum nanocatalyst can be reused at least six times for the hydrogenation reaction without losing activity. The carbon nanotube-supported platinum nanoparticles are also highly active for electrochemical oxidation of methanol and for reduction of oxygen suggesting their potential use as a new electrocatalyst for proton exchange membrane fuel cell applications.

Development of a prototype regenerable carbon dioxide absorber for portable life support systems. [for astronaut EVA

NASA Technical Reports Server (NTRS)

Onischak, M.; Baker, B.

1977-01-01

The design and development of a prototype carbon dioxide absorber using potassium carbonate (K2CO3) is described. Absorbers are constructed of thin, porous sheets of supported K2CO3 that are spirally wound to form a cylindrical reactor. Axial gas passages are formed between the porous sheets by corrugated screen material. Carbon dioxide and water in an enclosed life support system atmosphere react with potassium carbonate to form potassium bicarbonate. The potassium carbonate is regenerated by heating the potassium bicarbonate to 150 C at ambient pressure. The extravehicular mission design conditions are for one man for 8 h. Results are shown for a subunit test module investigating the effects of heat release, length-to-diameter ratio, and active cooling upon performance. The most important effect upon carbon dioxide removal is the temperature of the potassium carbonate.

Accuracy and precision of gravitational-wave models of inspiraling neutron star-black hole binaries with spin: Comparison with matter-free numerical relativity in the low-frequency regime

NASA Astrophysics Data System (ADS)

Bhagwat, Swetha; Kumar, Prayush; Barkett, Kevin; Afshari, Nousha; Brown, Duncan A.; Lovelace, Geoffrey; Scheel, Mark A.; Szilagyi, Bela; LIGO Collaboration

2016-03-01

Detection of gravitational wave involves extracting extremely weak signal from noisy data and their detection depends crucially on the accuracy of the signal models. The most accurate models of compact binary coalescence are known to come from solving the Einstein's equation numerically without any approximations. However, this is computationally formidable. As a more practical alternative, several analytic or semi analytic approximations are developed to model these waveforms. However, the work of Nitz et al. (2013) demonstrated that there is disagreement between these models. We present a careful follow up study on accuracies of different waveform families for spinning black-hole neutron star binaries, in context of both detection and parameter estimation and find that SEOBNRv2 to be the most faithful model. Post Newtonian models can be used for detection but we find that they could lead to large parameter bias. Supported by National Science Foundation (NSF) Awards No. PHY-1404395 and No. AST-1333142.

Measurements of Aitken Visual Binary Stars: 2017 Report

NASA Astrophysics Data System (ADS)

Sérot, J.

2018-07-01

This paper is a continuation of that published in [1]. It presents the measurements of 136 visual binary stars discovered by R.G. Aitken and listed in the WDS catalog. These measurements were obtained between January and December 2017 with an 11" reflector telescope and two types of cameras : an ASI 290MM CMOS-based camera and a Raptor Kite EM-CCD. Binaries with a secondary component up to magnitude 15 and separation between 0.4 and 5 arcsec have been measured. The selection also includes pairs exhibiting a large difference in magnitude between components (up to ?m=6). Measurements were mostly obtained using the auto-correlation technique described in [1] but also, and this is a innovative aspect of the paper, using the so-called bispectrum reduction technique supported by the latest version of the SpeckelToolBox software. As for [1], a significant part of the observed pairs had not been observed in the previous decades and show significant movements compared to their last measurement.

Low-Luminosity AGN As Analogues of Galactic Black Holes in the Low/Hard State: Evidence from X-Ray Timing of NGC 4258

NASA Technical Reports Server (NTRS)

Markowitz, A.; Uttley, P.

2005-01-01

We present a broadband power spectral density function (PSD) measured from extensive RXTE monitoring data of the low-luminosity AGN NGC 4258, which has an accurate, maser-determined black hole mass of (3.9 plus or minus 0.1) x 10(exp 7) solar mass. We constrain the PSD break time scale to be greater than 4.5 d at greater than 90% confidence, which appears to rule out the possibility that NGC 4258 is an analogue of black hole X-ray binaries (BHXRBs) in the high/soft state. In this sense, the PSD of NGC 4258 is different to that of some more-luminous Seyferts, which appear similar to the PSDs of high/soft state X-ray binaries. This result supports previous analogies between LLAGN and X-ray binaries in the low/hard state based on spectral energy distributions, indicating that the AGN/BHXRB analogy is valid across a broad range of accretion rates.

CHROMOSPHERIC EMISSION OF PLANET CANDIDATE HOST STARS: A WAY TO IDENTIFY FALSE POSITIVES

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

Karoff, Christoffer; Knudsen, Mads Faurschou; Albrecht, Simon

2016-10-10

It has been hypothesized that the presence of closely orbiting giant planets is associated with enhanced chromospheric emission of their host stars. The main cause for such a relation would likely be enhanced dynamo action induced by the planet. We present measurements of chromospheric emission in 234 planet candidate systems from the Kepler mission. This ensemble includes 37 systems with giant-planet candidates, which show a clear emission enhancement. The enhancement, however, disappears when systems that are also identified as eclipsing binary candidates are removed from the ensemble. This suggests that a large fraction of the giant-planet candidate systems with chromosphericmore » emission stronger than the Sun are not giant-planet systems, but false positives. Such false-positive systems could be tidally interacting binaries with strong chromospheric emission. This hypothesis is supported by an analysis of 188 eclipsing binary candidates that show increasing chromospheric emission as function of decreasing orbital period.« less

Multiclass classification of microarray data samples with a reduced number of genes

PubMed Central

2011-01-01

Background Multiclass classification of microarray data samples with a reduced number of genes is a rich and challenging problem in Bioinformatics research. The problem gets harder as the number of classes is increased. In addition, the performance of most classifiers is tightly linked to the effectiveness of mandatory gene selection methods. Critical to gene selection is the availability of estimates about the maximum number of genes that can be handled by any classification algorithm. Lack of such estimates may lead to either computationally demanding explorations of a search space with thousands of dimensions or classification models based on gene sets of unrestricted size. In the former case, unbiased but possibly overfitted classification models may arise. In the latter case, biased classification models unable to support statistically significant findings may be obtained. Results A novel bound on the maximum number of genes that can be handled by binary classifiers in binary mediated multiclass classification algorithms of microarray data samples is presented. The bound suggests that high-dimensional binary output domains might favor the existence of accurate and sparse binary mediated multiclass classifiers for microarray data samples. Conclusions A comprehensive experimental work shows that the bound is indeed useful to induce accurate and sparse multiclass classifiers for microarray data samples. PMID:21342522

A 15.7-Minute AM CVn Binary Discovered in K2

NASA Astrophysics Data System (ADS)

Green, M. J.; Hermes, J. J.; Marsh, T. R.; Steeghs, D. T. H.; Bell, Keaton J.; Littlefair, S. P.; Parsons, S. G.; Dennihy, E.; Fuchs, J. T.; Reding, J. S.; Kaiser, B. C.; Ashley, R. P.; Breedt, E.; Dhillon, V. S.; Gentile Fusillo, N. P.; Kerry, P.; Sahman, D. I.

2018-04-01

We present the discovery of SDSS J135154.46-064309.0, a short-period variable observed using 30-minute cadence photometry in K2 Campaign 6. Follow-up spectroscopy and high-speed photometry support a classification as a new member of the rare class of ultracompact accreting binaries known as AM CVn stars. The spectroscopic orbital period of 15.65 ± 0.12 minutes makes this system the fourth-shortest period AM CVn known, and the second system of this type to be discovered by the Kepler spacecraft. The K2 data show photometric periods at 15.7306 ± 0.0003 minutes, 16.1121 ± 0.0004 minutes and 664.82 ± 0.06 minutes, which we identify as the orbital period, superhump period, and disc precession period, respectively. From the superhump and orbital periods we estimate the binary mass ratio q = M2/M1 = 0.111 ± 0.005, though this method of mass ratio determination may not be well calibrated for helium-dominated binaries. This system is likely to be a bright foreground source of gravitational waves in the frequency range detectable by LISA, and may be of use as a calibration source if future studies are able to constrain the masses of its stellar components.

A 15.7-minAM CVn binary discovered in K2

NASA Astrophysics Data System (ADS)

Green, M. J.; Hermes, J. J.; Marsh, T. R.; Steeghs, D. T. H.; Bell, Keaton J.; Littlefair, S. P.; Parsons, S. G.; Dennihy, E.; Fuchs, J. T.; Reding, J. S.; Kaiser, B. C.; Ashley, R. P.; Breedt, E.; Dhillon, V. S.; Gentile Fusillo, N. P.; Kerry, P.; Sahman, D. I.

2018-07-01

We present the discovery of SDSS J135154.46-064309.0, a short-period variable observed using 30-mincadence photometry in K2 Campaign 6. Follow-up spectroscopy and high-speed photometry support a classification as a new member of the rare class of ultracompact accreting binaries known as AM CVn stars. The spectroscopic orbital period of 15.65 ± 0.12 min makes this system the fourth-shortest-period AM CVn known, and the second system of this type to be discovered by the Kepler spacecraft. The K2 data show photometric periods at 15.7306 ± 0.0003 min, 16.1121 ± 0.0004 min, and 664.82 ± 0.06 min, which we identify as the orbital period, superhump period, and disc precession period, respectively. From the superhump and orbital periods we estimate the binary mass ratio q = M2/M1= 0.111 ± 0.005, though this method of mass ratio determination may not be well calibrated for helium-dominated binaries. This system is likely to be a bright foreground source of gravitational waves in the frequency range detectable by Laser Interferometer Space Antenna, and may be of use as a calibration source if future studies are able to constrain the masses of its stellar components.

Black holes, disks, and jets following binary mergers and stellar collapse: The narrow range of electromagnetic luminosities and accretion rates.

PubMed

Shapiro, Stuart L

2017-05-15

We have performed magnetohydrodynamic simulations in general relativity of binary neutron star and binary black hole-neutron star mergers, as well as the magnetorotational collapse of supermassive stars. In many cases the outcome is a spinnng black hole (BH) immersed in a magnetized disk, with a jet emanating from the poles of the BH. While their formation scenarios differ and their BH masses, as well as their disk masses, densities, and magnetic field strengths, vary by orders of magnitude, these features conspire to generate jet Poynting luminosities that all lie in the same, narrow range of ~10 52±1 erg s -1 . A similar result applies to their BH accretion rates upon jet launch, which is ~0.1-10 M ⊙ s -1 . We provide a simple model that explains these unanticipated findings. Interestingly, these luminosities reside in the same narrow range characterizing the observed luminosity distributions of over 400 short and long GRBs with distances inferred from spectroscopic redshifts or host galaxies. This result, together with the GRB lifetimes predicted by the model, supports the belief that a compact binary merger is the progenitor of an SGRB, while a massive, stellar magnetorotational collapse is the progenitor of an LGRB.

Swings between rotation and accretion power in a binary millisecond pulsar.

PubMed

Papitto, A; Ferrigno, C; Bozzo, E; Rea, N; Pavan, L; Burderi, L; Burgay, M; Campana, S; Di Salvo, T; Falanga, M; Filipović, M D; Freire, P C C; Hessels, J W T; Possenti, A; Ransom, S M; Riggio, A; Romano, P; Sarkissian, J M; Stairs, I H; Stella, L; Torres, D F; Wieringa, M H; Wong, G F

2013-09-26

It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion stage, the system is called a low-mass X-ray binary, and bright X-ray emission is observed. When the rate of mass transfer decreases in the later evolutionary stages, these binaries host a radio millisecond pulsar whose emission is powered by the neutron star's rotating magnetic field. This evolutionary model is supported by the detection of millisecond X-ray pulsations from several accreting neutron stars and also by the evidence for a past accretion disc in a rotation-powered millisecond pulsar. It has been proposed that a rotation-powered pulsar may temporarily switch on during periods of low mass inflow in some such systems. Only indirect evidence for this transition has hitherto been observed. Here we report observations of accretion-powered, millisecond X-ray pulsations from a neutron star previously seen as a rotation-powered radio pulsar. Within a few days after a month-long X-ray outburst, radio pulses were again detected. This not only shows the evolutionary link between accretion and rotation-powered millisecond pulsars, but also that some systems can swing between the two states on very short timescales.

Gravitational Conundrum? Dynamical Mass Segregation versus Disruption of Binary Stars in Dense Stellar Systems

NASA Astrophysics Data System (ADS)

de Grijs, Richard; Li, Chengyuan; Zheng, Yong; Deng, Licai; Hu, Yi; Kouwenhoven, M. B. N.; Wicker, James E.

2013-03-01

Upon their formation, dynamically cool (collapsing) star clusters will, within only a few million years, achieve stellar mass segregation for stars down to a few solar masses, simply because of gravitational two-body encounters. Since binary systems are, on average, more massive than single stars, one would expect them to also rapidly mass segregate dynamically. Contrary to these expectations and based on high-resolution Hubble Space Telescope observations, we show that the compact, 15-30 Myr old Large Magellanic Cloud cluster NGC 1818 exhibits tantalizing hints at the >~ 2σ level of significance (>3σ if we assume a power-law secondary-to-primary mass-ratio distribution) of an increasing fraction of F-star binary systems (with combined masses of 1.3-1.6 M ⊙) with increasing distance from the cluster center, specifically between the inner 10''-20'' (approximately equivalent to the cluster's core and half-mass radii) and the outer 60''-80''. If confirmed, then this will offer support for the theoretically predicted but thus far unobserved dynamical disruption processes of the significant population of "soft" binary systems—with relatively low binding energies compared to the kinetic energy of their stellar members—in star clusters, which we have access to here by virtue of the cluster's unique combination of youth and high stellar density.

Black holes, disks, and jets following binary mergers and stellar collapse: The narrow range of electromagnetic luminosities and accretion rates

PubMed Central

Shapiro, Stuart L.

2018-01-01

We have performed magnetohydrodynamic simulations in general relativity of binary neutron star and binary black hole-neutron star mergers, as well as the magnetorotational collapse of supermassive stars. In many cases the outcome is a spinnng black hole (BH) immersed in a magnetized disk, with a jet emanating from the poles of the BH. While their formation scenarios differ and their BH masses, as well as their disk masses, densities, and magnetic field strengths, vary by orders of magnitude, these features conspire to generate jet Poynting luminosities that all lie in the same, narrow range of ~1052±1 erg s−1. A similar result applies to their BH accretion rates upon jet launch, which is ~0.1–10 M⊙ s−1. We provide a simple model that explains these unanticipated findings. Interestingly, these luminosities reside in the same narrow range characterizing the observed luminosity distributions of over 400 short and long GRBs with distances inferred from spectroscopic redshifts or host galaxies. This result, together with the GRB lifetimes predicted by the model, supports the belief that a compact binary merger is the progenitor of an SGRB, while a massive, stellar magnetorotational collapse is the progenitor of an LGRB. PMID:29881790

Astroserver - Research Services in the Stellar Webshop

NASA Astrophysics Data System (ADS)

Németh, Péter

2017-12-01

A quick look at research and development in astronomy shows that we live in exciting times. Exoplanetary systems, supernovae, and merging binary black holes were far out of reach for observers two decades ago and now such phenomena are recorded routinely. This quick development would not have been possible without the ability for researchers to be connected, to think globally and to be mobile. Classical short-term positions are not always suitable to support these conditions and freelancing may be a viable alternative.We introduce the Astroserver framework, which is a new freelancing platform for scientists, and demonstrate through examples how it contributed to some recent projects related to hot subdwarf stars and binaries. These contributions, which included spectroscopic data mining, computing services and observing services, as well as artwork, allowed a deeper look into the investigated systems. The work on composite spectra binaries provided new details for the hypervelocity wide subdwarf binary PB 3877 and found diverse and rare systems with sub-giant companions in high-resolution spectroscopic surveys. The models for the peculiar abundance pattern of the evolved compact star LP 40-365 showed it to be a bound hypervelocity remnant of a supernova Iax event. Some of these works also included data visualizations to help presenting the new results. Such services may be of interest for many researchers.

Activity and Stability of Dispersed Multi Metallic Pt-based Catalysts for CO Tolerance in Proton Exchange Membrane Fuel Cell Anodes.

PubMed

Hassan, Ayaz; Ticianelli, Edson A

2018-01-01

Studies aiming at improving the activity and stability of dispersed W and Mo containing Pt catalysts for the CO tolerance in proton exchange membrane fuel cell (PEMFC) anodes are revised for the following catalyst systems: (1) a carbon supported PtMo electrocatalyst submitted to heat treatments; (2) Pt and PtMo nanoparticles deposited on carbon-supported molybdenum carbides (Mo2C/C); (3) ternary and quaternary materials formed by PtMoFe/C, PtMoRu/C and PtMoRuFe/C and; (4) Pt nanoparticles supported on tungsten carbide/carbon catalysts and its parallel evaluation with carbon supported PtW catalyst. The heat-treated (600 oC) Pt-Mo/C catalyst showed higher hydrogen oxidation activity in the absence and in the presence of CO and better stability, compared to all other Mo-containing catalysts. PtMoRuFe, PtMoFe, PtMoRu supported on carbon and Pt supported on Mo2C/C exhibited similar CO tolerances but better stability, as compared to as-prepared PtMo supported on carbon. Among the tungsten-based catalysts, tungsten carbide supported Pt catalyst showed reasonable performance and reliable stability in comparison to simple carbon supported PtW catalyst, though an uneven level of catalytic activity towards H2 oxidation in presence of CO is observed for the former as compared to Mo containing catalyst. However, a small dissolution of Mo, Ru, Fe and W from the anodes and their migration toward cathodes during the cell operation is observed. These results indicate that the fuel cell performance and stability has been improved but not yet totally resolved.

XPS and Raman studies of Pt catalysts supported on activated carbon

NASA Astrophysics Data System (ADS)

Tyagi, Deepak; Varma, Salil; Bharadwaj, S. R.

2018-04-01

Activated carbon is a widely used support for dispersing noble metals in addition to its many applications. We have prepared platinum catalyst supported on activated carbon for HI decomposition reaction of I-S thermochemical process of hydrogen generation. These catalysts were characterized by XPS and Raman before and after using for the reaction. It was observed that platinum is present in zero oxidation state, while carbon is present is both sp2 and sp3 hybridized forms along with some amount of it bonded to oxygen.

Campaign of AAVSO Monitoring of the CH Cyg Symbiotic System in Support of Chandra and HST Observations

NASA Astrophysics Data System (ADS)

Karovska, M.

2013-06-01

(Abstract only) CH Cyg is one of the most interesting interacting binaries in which a compact object, a white dwarf or a neutron star, accretes from the wind of an evolved giant or supergiant. CH Cyg is a member of the symbiotic systems group, and at about 250pc it is one of the closest systems. Symbiotic systems are accreting binaries, which are likely progenitors of a fraction of Pre-Planetary and Planetary Nebulae, and of a fraction of SN type Ia (the cosmic distance scale indicators). We carried out Chandra and HST observations of CH Cyg in March 2012 as part of a follow-up investigation of the central region of CH Cyg and its precessing jet, including the multi-structures that were discovered in 2008. I will describe here the campaign of multi-wavelength observations, including photometry and spectroscopy, that were carried out by AAVSO members in support of the space-based observations.

BigWig and BigBed: enabling browsing of large distributed datasets.

PubMed

Kent, W J; Zweig, A S; Barber, G; Hinrichs, A S; Karolchik, D

2010-09-01

BigWig and BigBed files are compressed binary indexed files containing data at several resolutions that allow the high-performance display of next-generation sequencing experiment results in the UCSC Genome Browser. The visualization is implemented using a multi-layered software approach that takes advantage of specific capabilities of web-based protocols and Linux and UNIX operating systems files, R trees and various indexing and compression tricks. As a result, only the data needed to support the current browser view is transmitted rather than the entire file, enabling fast remote access to large distributed data sets. Binaries for the BigWig and BigBed creation and parsing utilities may be downloaded at http://hgdownload.cse.ucsc.edu/admin/exe/linux.x86_64/. Source code for the creation and visualization software is freely available for non-commercial use at http://hgdownload.cse.ucsc.edu/admin/jksrc.zip, implemented in C and supported on Linux. The UCSC Genome Browser is available at http://genome.ucsc.edu.

Binary classification of aqueous solubility using support vector machines with reduction and recombination feature selection.

PubMed

Cheng, Tiejun; Li, Qingliang; Wang, Yanli; Bryant, Stephen H

2011-02-28

Aqueous solubility is recognized as a critical parameter in both the early- and late-stage drug discovery. Therefore, in silico modeling of solubility has attracted extensive interests in recent years. Most previous studies have been limited in using relatively small data sets with limited diversity, which in turn limits the predictability of derived models. In this work, we present a support vector machines model for the binary classification of solubility by taking advantage of the largest known public data set that contains over 46 000 compounds with experimental solubility. Our model was optimized in combination with a reduction and recombination feature selection strategy. The best model demonstrated robust performance in both cross-validation and prediction of two independent test sets, indicating it could be a practical tool to select soluble compounds for screening, purchasing, and synthesizing. Moreover, our work may be used for comparative evaluation of solubility classification studies ascribe to the use of completely public resources.

Effects of functionalization of carbon nanotubes on their dispersion in an ethylene glycol-water binary mixture--a molecular dynamics and ONIOM investigation.

PubMed

Balamurugan, Kanagasabai; Baskar, Prathab; Kumar, Ravva Mahesh; Das, Sumitesh; Subramanian, Venkatesan

2014-11-28

The present work utilizes classical molecular dynamics simulations to investigate the covalent functionalization of carbon nanotubes (CNTs) and their interaction with ethylene glycol (EG) and water molecules. The MD simulation reveals the dispersion of functionalized carbon nanotubes and the prevention of aggregation in aqueous medium. Further, residue-wise radial distribution function (RRDF) and atomic radial distribution function (ARDF) calculations illustrate the extent of interaction of -OH and -COOH functionalized CNTs with water molecules and the non-functionalized CNT surface with EG. As the presence of the number of functionalized nanotubes increases, enhancement in the propensity for the interaction with water molecules can be observed. However, the same trend decreases for the interaction of EG molecules. In addition, the ONIOM (M06-2X/6-31+G**:AM1) calculations have also been carried out on model systems to quantitatively determine the interaction energy (IE). It is found from these calculations that the relative enhancement in the interaction of water molecules with functionalized CNTs is highly favorable when compared to the interaction of EG.

Normal and outlying populations of the Milky Way stellar halo at [Fe/H] <–2

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

Cohen, Judith G.; Christlieb, Norbert; Thompson, Ian

2013-11-20

From detailed abundance analysis of >100 Hamburg/ESO candidate extremely metal-poor (EMP) stars we find 45 with [Fe/H] < –3.0 dex. We identify a heretofore unidentified group: Ca-deficient stars with sub-solar [Ca/Fe] ratios and the lowest neutron-capture abundances; the Ca-deficient group comprises ∼10% of the sample, excluding Carbon stars. Our radial velocity distribution shows that the carbon-enhanced stars with no s-process enhancements, CEMP-no, and which do not show C{sub 2} bands are not preferentially binary systems. Ignoring Carbon stars, approximately 15% of our sample are strong (≥5σ) outliers in one or more elements between Mg and Ni; this rises to ∼19%more » if very strong (≥10σ) outliers for Sr and Ba are included. Examples include: HE0305–0554 with the lowest [Ba/H] known; HE1012–1540 and HE2323–0256, two (non-velocity variable) C-rich stars with very strong [Mg,Al/Fe] enhancements; and HE1226–1149, an extremely r-process rich star.« less

XPS analysis of activated carbon supported ionic liquids: Enhanced purity and reduced charging

NASA Astrophysics Data System (ADS)

Foelske-Schmitz, A.; Weingarth, D.; Kötz, R.

2011-12-01

Herein we report on XPS measurements on five different [EMIM] based ionic liquids (IL) prepared on activated carbon and aluminium supports. The anions were [TFSI], [BF4], [FAP], [B(CN)4] and [EtOSO3]. The results show that impurities such as O, Si or hydrocarbons were significantly reduced or no longer detected when preparation was performed on the high surface area carbon support. All core level spectra were fitted and for [EMIM][FAP], [EMIM][B(CN)4] and [EMIM][EtOSO3] de-convolution procedures of the C 1s lines are suggested. Comparison of the determined binding energies with published data strongly suggests that sample charging is irrelevant when preparation is performed on the activated carbon support. This observation is supposed to refer to the high capacitance of the high surface area carbon.

Light Curve and Analysis of the Eclipsing Binary BF Centauri

NASA Astrophysics Data System (ADS)

Morris, M. A.; Wolf, G. W.

2003-12-01

The eclipsing binary star BF Centauri was observed photometrically by GWW in the uvby filter system from Mt. John Observatory in New Zealand during 1982, 1989 and 1998. It was also observed spectroscopically at 10 A/mm by W. A. Lawson in 1993 at Mt. Stromlo in Australia to obtain a radial velocity solution. The combined light curves and spectroscopic results have been analyzed using the 1998 version of Robert Wilson's WD light-curve programs. A consistent model for the system will be presented. This analysis was done as a part of a senior research project by MAM, who would like to acknowledge financial support from the Missouri Space Grant Consortium.

Moss and peat hydraulic properties are optimized to maximise peatland water use efficiency

NASA Astrophysics Data System (ADS)

Kettridge, Nicholas; Tilak, Amey; Devito, Kevin; Petrone, Rich; Mendoza, Carl; Waddington, Mike

2016-04-01

Peatland ecosystems are globally important carbon and terrestrial surface water stores that have formed over millennia. These ecosystems have likely optimised their ecohydrological function over the long-term development of their soil hydraulic properties. Through a theoretical ecosystem approach, applying hydrological modelling integrated with known ecological thresholds and concepts, the optimisation of peat hydraulic properties is examined to determine which of the following conditions peatland ecosystems target during this development: i) maximise carbon accumulation, ii) maximise water storage, or iii) balance carbon profit across hydrological disturbances. Saturated hydraulic conductivity (Ks) and empirical van Genuchten water retention parameter α are shown to provide a first order control on simulated water tensions. Across parameter space, peat profiles with hypothetical combinations of Ks and α show a strong binary tendency towards targeting either water or carbon storage. Actual hydraulic properties from five northern peatlands fall at the interface between these goals, balancing the competing demands of carbon accumulation and water storage. We argue that peat hydraulic properties are thus optimized to maximise water use efficiency and that this optimisation occurs over a centennial to millennial timescale as the peatland develops. This provides a new conceptual framework to characterise peat hydraulic properties across climate zones and between a range of different disturbances, and which can be used to provide benchmarks for peatland design and reclamation.

Bayesian Kernel Methods for Non-Gaussian Distributions: Binary and Multi-class Classification Problems

DTIC Science & Technology

2013-05-28

those of the support vector machine and relevance vector machine, and the model runs more quickly than the other algorithms . When one class occurs...incremental support vector machine algorithm for online learning when fewer than 50 data points are available. (a) Papers published in peer-reviewed journals...learning environments, where data processing occurs one observation at a time and the classification algorithm improves over time with new

Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions

EPA Science Inventory

Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds.

Removal of polybrominated diphenyl ethers by biomass carbon-supported nanoscale zerovalent iron particles: influencing factors, kinetics, and mechanism.

PubMed

Fu, Rongbing; Xu, Zhen; Peng, Lin; Bi, Dongsu

2016-12-01

In this study, nanoscale zerovalent iron (NZVI) immobilized on biomass carbon was used for the high efficient removal of BDE 209. NZVI supported on biomass carbon minimized the aggregation of NZVI particles resulting in the increased reaction performance. The proposed removal mechanism included the adsorption of BDE 209 on the surface or interior of the biomass carbon NZVI (BC-NZVI) particles and the subsequent debromination of BDE 209 by NZVI while biomass carbon served as an electron shuttle. BC-NZVI particles and the interaction between BC-NZVI particles and BDE 209 were characterized by TEM, XRD, and XPS. The removal reaction followed a pseudo-first-order rate expression under different reaction conditions, and the k obs was higher than that of other NZVI-supported materials. The debromination of BDE 209 by BC-NZVI was a stepwise process from nona-BDE to DE. A proposed pathway suggested that supporting NZVI on biomass carbon has potential as a promising technique for in situ organic-contaminated groundwater remediation.

Spiking Neural Classifier with Lumped Dendritic Nonlinearity and Binary Synapses: A Current Mode VLSI Implementation and Analysis.

PubMed

Bhaduri, Aritra; Banerjee, Amitava; Roy, Subhrajit; Kar, Sougata; Basu, Arindam

2018-03-01

We present a neuromorphic current mode implementation of a spiking neural classifier with lumped square law dendritic nonlinearity. It has been shown previously in software simulations that such a system with binary synapses can be trained with structural plasticity algorithms to achieve comparable classification accuracy with fewer synaptic resources than conventional algorithms. We show that even in real analog systems with manufacturing imperfections (CV of 23.5% and 14.4% for dendritic branch gains and leaks respectively), this network is able to produce comparable results with fewer synaptic resources. The chip fabricated in [Formula: see text]m complementary metal oxide semiconductor has eight dendrites per cell and uses two opposing cells per class to cancel common-mode inputs. The chip can operate down to a [Formula: see text] V and dissipates 19 nW of static power per neuronal cell and [Formula: see text] 125 pJ/spike. For two-class classification problems of high-dimensional rate encoded binary patterns, the hardware achieves comparable performance as software implementation of the same with only about a 0.5% reduction in accuracy. On two UCI data sets, the IC integrated circuit has classification accuracy comparable to standard machine learners like support vector machines and extreme learning machines while using two to five times binary synapses. We also show that the system can operate on mean rate encoded spike patterns, as well as short bursts of spikes. To the best of our knowledge, this is the first attempt in hardware to perform classification exploiting dendritic properties and binary synapses.

Raman Spectroscopy and Microphysics of Single PSC Precursor Particles Suspended in a Quadrupole Trap

NASA Astrophysics Data System (ADS)

Sonnenfroh, D. M.; Hunter, A. J.; Rawlins, W. T.

2001-12-01

Polar stratospheric clouds (PSCs) consist primarily of solid nitric acid trihydrate (NAT) particles, which are thought to nucleate via HNO3 uptake on background sulfuric acid particles at temperatures below 195 K. The mechanism for this process is uncertain, and depends on whether the sulfuric acid particles are solid or liquid at these temperatures. Previous results from laboratory and field measurements are mixed; our previous single-particle laboratory experiments showed that binary H2SO4/H2O particles at stratospheric compositions are essentially metastable in the liquid phase when cooled to PSC temperatures. Currently, we are investigating the detailed microphysics of binary (H2SO4/H2O) and ternary (HNO3/H2SO4/H2O) single particles suspended in an electrodynamic levitator, using optical elastic scattering and Raman spectroscopy to observe changes in phase and composition. Single-particle Raman spectra for supercooled binary particles exhibit spectral distributions which alter markedly with decreasing temperature down to 190 K. The variations signify increasing dissociation of HSO4(-) to SO4(-2) with decreasing temperature, consistent with measurements for bulk solutions. Upon gradual warming of supercooled liquid binary particles, some of them freeze briefly in a narrow "window" of the phase diagram, near 210 K and 60 weight per cent H2SO4. We will discuss the Raman spectroscopy and microphysical behavior of the liquid and frozen particles for both the binary and ternary systems. This research was supported by the NASA Atmospheric Effects of Aviation Program.

Corrosion-resistant catalyst supports for phosphoric acid fuel cells

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

Kosek, J.A.; Cropley, C.C.; LaConti, A.B.

High-surface-area carbon blacks such as Vulcan XC-72 (Cabot Corp.) and graphitized carbon blacks such as 2700{degree}C heat-treated Black Pearls 2000 (HTBP) (Cabot Corp.) have found widespread applications as catalyst supports in phosphoric acid fuel cells (PAFCs). However, due to the operating temperatures and pressures being utilized in PAFCs currently under development, the carbon-based cathode catalyst supports suffer from corrosion, which decreases the performance and life span of a PAFC stack. The feasibility of using alternative, low-cost, corrosion-resistant catalyst support (CRCS) materials as replacements for the cathode carbon support materials was investigated. The objectives of the program were to prepare high-surface-areamore » alternative supports and to evaluate the physical characteristics and the electrochemical stability of these materials. The O{sub 2} reduction activity of the platinized CRCS materials was also evaluated. 2 refs., 3 figs.« less

Correlation between mesopore volume of carbon supports and the immobilization of laccase from Trametes versicolor for the decolorization of Acid Orange 7.

PubMed

Ramírez-Montoya, Luis A; Hernández-Montoya, Virginia; Montes-Morán, Miguel A; Cervantes, Francisco J

2015-10-01

Immobilization of laccase from Trametes versicolor was carried out using carbon supports prepared from different lignocellulosic wastes. Enzymes were immobilized by physical adsorption. Taguchi methodology was selected for the design of experiments regarding the preparation of the carbon materials, which included the use of activating agents for the promotion of mesoporosity. A good correlation between the mesopore volumes of the carbon supports and the corresponding laccase loadings attained was observed. Specifically, the chemical activation of pecan nut shell with FeCl3 led to a highly mesoporous material that also behaved as the most efficient support for the immobilization of laccase. This particular laccase/carbon support system was used as biocatalyst for the decolorization of aqueous solutions containing Acid Orange 7. Mass spectrometry coupled to a liquid chromatograph allowed us to identify the products of the dye degradation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Reduced graphene oxide supported gold nanoparticles for electrocatalytic reduction of carbon dioxide

NASA Astrophysics Data System (ADS)

Saquib, Mohammad; Halder, Aditi

2018-02-01

Electrochemical reduction of carbon dioxide is one of the methods which have the capability to recycle CO2 into valuable products for energy and industrial applications. This research article describes about a new electrocatalyst "reduced graphene oxide supported gold nanoparticles" for selective electrochemical conversion of carbon dioxide to carbon monoxide. The main aim for conversion of CO2 to CO lies in the fact that the latter is an important component of syn gas (a mixture of hydrogen and carbon monoxide), which is then converted into liquid fuel via well-known industrial process called Fischer-Tropsch process. In this work, we have synthesized different composites of the gold nanoparticles supported on defective reduced graphene oxide to evaluate the catalytic activity of reduced graphene oxide (RGO)-supported gold nanoparticles and the role of defective RGO support towards the electrochemical reduction of CO2. Electrochemical and impedance measurements demonstrate that higher concentration of gold nanoparticles on the graphene support led to remarkable decrease in the onset potential of 240 mV and increase in the current density for CO2 reduction. Lower impedance and Tafel slope values also clearly support our findings for the better performance of RGOAu than bare Au for CO2 reduction.

Separation of methane-nitrogen mixtures using synthesis vertically aligned carbon nanotube membranes

NASA Astrophysics Data System (ADS)

Gilani, Neda; Daryan, Jafar Towfighi; Rashidi, Alimorad; Omidkhah, Mohammad Reza

2012-03-01

In this paper, capabilities of carbon nanotube (CNT) membranes fabricated in cylindrical pores of anodic aluminum oxide (AAO) substrate to separate the binary mixtures of CH4/N2 are studied experimentally. For this purpose, the permeability and selectivity of three CNT/AAO membranes with different growth time as 6 h, 12 h and 18 h are investigated. CNTs are grown vertically through holes of AAO with average pore diameter of 45 nm by chemical vapor deposition (CVD) of acetylene gas. CNT/AAO membranes with the same CNTs' outer diameters and different inner diameters are synthesized. The AAO are characterized by SEM analysis. In addition, SEM, TEM, BET N2 adsorption analysis and Raman spectroscopy are employed to characterize aligned CNTs. Study on permeability and selectivity of membranes for three binary mixtures of CH4/N2 showed that when the CNT inner diameters are 34 nm and 24 nm, viscous flow is the governing mechanism and insignificant selectivities of 1.2-1.24 are achieved. However, the membrane with CNT inner diameter and wall thickness of 8 nm and 16 nm respectively is considerably selective for CH4 over N2. It was also found that CH4 mole fraction in the feed and upstream feed pressure have major effect on permeability and selectivity. The membrane with 18 h synthesis time showed the selectivity is in the range of 1.8-3.85. The enhancement factor for N2 single gas diffusivity was also found to be about three times larger than that predicted by Knudsen diffusion model.

Far-UV spectroscopy of two extremely hot, helium-rich white dwarfs

NASA Astrophysics Data System (ADS)

Werner, K.; Rauch, T.; Kruk, J. W.

2017-05-01

A large proportion of hot post-asymptotic giant branch stars and white dwarfs (WDs) are hydrogen-deficient. Two distinct evolutionary sequences have been identified. One of them comprises stars of spectral type [WC] and PG1159, and it originates from a late helium-shell flash, creating helium-rich stellar atmospheres with significant admixtures of carbon (up to about 50%, mass fraction). The other sequence comprises stars of spectral type O(He) and luminous subdwarf O stars which possibly are descendants of RCrB stars and extreme helium stars. Their carbon abundances are significantly lower (of the order of 1% or less) and it is thought that they originate from binary-star evolution (through merger or common-envelope evolution). Here we investigate two of the three hottest known helium-rich (DO) WDs (PG 1034+001 and PG 0038+199). They are the only ones for which spectra were recorded with the Far Ultraviolet Spectroscopic Explorer and the Hubble Space Telescope, allowing a comprehensive ultraviolet spectral analysis. We find effective temperatures of Teff = 115 000 ± 5000 K and 125 000 ± 5000 K, respectively, and a surface gravity of log g= 7 ± 0.5. In both stars, nitrogen is strongly oversolar while C and O are significantly subsolar. For all other assessed metals (Ne, Si, P, S, Ar, Fe, and Ni) we find abundances close to solar. We conclude that these WDs are immediate descendants of O(He) stars and, hence, result from close-binary evolution. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer.

The carbon footprint of behavioural support services for smoking cessation.

PubMed

Smith, Anna Jo Bodurtha; Tennison, Imogen; Roberts, Ian; Cairns, John; Free, Caroline

2013-09-01

To estimate the carbon footprint of behavioural support services for smoking cessation: text message support, telephone counselling, group counselling and individual counselling. Carbon footprint analysis. Publicly available data on National Health Service Stop Smoking Services and per unit carbon emissions; published effectiveness data from the txt2stop trial and systematic reviews of smoking cessation services. Carbon dioxide equivalents (CO2e) per 1000 smokers, per lifetime quitter, and per quality-adjusted life year gained, and cost-effectiveness, including social cost of carbon, of smoking cessation services. Emissions per 1000 participants were 8143 kg CO2e for text message support, 8619 kg CO2e for telephone counselling, 16 114 kg CO2e for group counselling and 16 372 kg CO2e for individual counselling. Emissions per intervention lifetime quitter were 636 (95% CI 455 to 958) kg CO2e for text message support, 1051 (95% CI 560 to 2873) kg CO2e for telephone counselling, 1143 (95% CI 695 to 2270) kg CO2e for group counselling and 2823 (95% CI 1688 to 6549) kg CO2e for individual counselling. Text message, telephone and group counselling remained cost-effective when cost-effectiveness analysis was revised to include the environmental and economic cost of damage from carbon emissions. All smoking cessation services had low emissions compared to the health gains produced. Text message support had the lowest emissions of the services evaluated. Smoking cessation services have small carbon footprints and were cost-effective after accounting for the societal costs of greenhouse gas emissions.

BOREAS RSS-8 BIOME-BGC SSA Simulation of Annual Water and Carbon Fluxes

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); Kimball, John

2000-01-01

The BOREAS RSS-8 team performed research to evaluate the effect of seasonal weather and landcover heterogeneity on boreal forest regional water and carbon fluxes using a process-level ecosystem model, BIOME-BGC, coupled with remote sensing-derived parameter maps of key state variables. This data set contains derived maps of landcover type and crown and stem biomass as model inputs to determine annual evapotranspiration, gross primary production, autotrophic respiration, and net primary productivity within the BOREAS SSA-MSA, at a 30-m spatial resolution. Model runs were conducted over a 3-year period from 1994-1996; images are provided for each of those years. The data are stored in binary image format. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Ages of young star clusters, massive blue stragglers, and the upper mass limit of stars: Analyzing age-dependent stellar mass functions

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

Schneider, F. R. N.; Izzard, R. G.; Langer, N.

2014-01-10

Massive stars rapidly change their masses through strong stellar winds and mass transfer in binary systems. The latter aspect is important for populations of massive stars as more than 70% of all O stars are expected to interact with a binary companion during their lifetime. We show that such mass changes leave characteristic signatures in stellar mass functions of young star clusters that can be used to infer their ages and to identify products of binary evolution. We model the observed present-day mass functions of the young Galactic Arches and Quintuplet star clusters using our rapid binary evolution code. Wemore » find that the shaping of the mass function by stellar wind mass loss allows us to determine the cluster ages as 3.5 ± 0.7 Myr and 4.8 ± 1.1 Myr, respectively. Exploiting the effects of binary mass exchange on the cluster mass function, we find that the most massive stars in both clusters are rejuvenated products of binary mass transfer, i.e., the massive counterpart of classical blue straggler stars. This resolves the problem of an apparent age spread among the most luminous stars exceeding the expected duration of star formation in these clusters. We perform Monte Carlo simulations to probe stochastic sampling, which support the idea of the most massive stars being rejuvenated binary products. We find that the most massive star is expected to be a binary product after 1.0 ± 0.7 Myr in Arches and after 1.7 ± 1.0 Myr in Quintuplet. Today, the most massive 9 ± 3 stars in Arches and 8 ± 3 in Quintuplet are expected to be such objects. Our findings have strong implications for the stellar upper mass limit and solve the discrepancy between the claimed 150 M {sub ☉} limit and observations of four stars with initial masses of 165-320 M {sub ☉} in R136 and of supernova 2007bi, which is thought to be a pair-instability supernova from an initial 250 M {sub ☉} star. Using the stellar population of R136, we revise the upper mass limit to values in the range 200-500 M {sub ☉}.« less

Ages of Young Star Clusters, Massive Blue Stragglers, and the Upper Mass Limit of Stars: Analyzing Age-dependent Stellar Mass Functions

NASA Astrophysics Data System (ADS)

Schneider, F. R. N.; Izzard, R. G.; de Mink, S. E.; Langer, N.; Stolte, A.; de Koter, A.; Gvaramadze, V. V.; Hußmann, B.; Liermann, A.; Sana, H.

2014-01-01

Massive stars rapidly change their masses through strong stellar winds and mass transfer in binary systems. The latter aspect is important for populations of massive stars as more than 70% of all O stars are expected to interact with a binary companion during their lifetime. We show that such mass changes leave characteristic signatures in stellar mass functions of young star clusters that can be used to infer their ages and to identify products of binary evolution. We model the observed present-day mass functions of the young Galactic Arches and Quintuplet star clusters using our rapid binary evolution code. We find that the shaping of the mass function by stellar wind mass loss allows us to determine the cluster ages as 3.5 ± 0.7 Myr and 4.8 ± 1.1 Myr, respectively. Exploiting the effects of binary mass exchange on the cluster mass function, we find that the most massive stars in both clusters are rejuvenated products of binary mass transfer, i.e., the massive counterpart of classical blue straggler stars. This resolves the problem of an apparent age spread among the most luminous stars exceeding the expected duration of star formation in these clusters. We perform Monte Carlo simulations to probe stochastic sampling, which support the idea of the most massive stars being rejuvenated binary products. We find that the most massive star is expected to be a binary product after 1.0 ± 0.7 Myr in Arches and after 1.7 ± 1.0 Myr in Quintuplet. Today, the most massive 9 ± 3 stars in Arches and 8 ± 3 in Quintuplet are expected to be such objects. Our findings have strong implications for the stellar upper mass limit and solve the discrepancy between the claimed 150 M ⊙ limit and observations of four stars with initial masses of 165-320 M ⊙ in R136 and of supernova 2007bi, which is thought to be a pair-instability supernova from an initial 250 M ⊙ star. Using the stellar population of R136, we revise the upper mass limit to values in the range 200-500 M ⊙.

BD -22 5866: A Low-Mass, Quadruple-lined Spectroscopic and Eclipsing Binary

NASA Astrophysics Data System (ADS)

Shkolnik, Evgenya; Liu, Michael C.; Reid, I. Neill; Hebb, Leslie; Cameron, Andrew C.; Torres, Carlos A.; Wilson, David M.

2008-08-01

We report our discovery of an extremely rare, low-mass, quadruple-lined spectroscopic binary BD -22 5866 (=NLTT 53279, integrated spectral type = M0 V), found during an ongoing search for the youngest M dwarfs in the solar neighborhood. From the cross-correlation function, we are able to measure relative flux levels, estimate the spectral types of the components, and set upper limits on the orbital periods and separations. The resulting system is hierarchical, composed of a K7 + K7 binary and an M1 + M2 binary with semimajor axes of aAsin iA <= 0.06 and aBsin iB <= 0.30 AU. A subsequent search of the SuperWASP photometric database revealed that the K7 + K7 binary is eclipsing with a period of 2.21 days and at an inclination angle of 85°. Within uncertainties of 5%, the masses and radii of both components appear to be equal (0.59 M⊙, 0.61 R⊙). These two tightly orbiting stars (a = 0.035 AU) are in synchronous rotation, causing the observed excess Ca II, Hα, X-ray, and UV emission. The fact that the system was unresolved with published adaptive optics imaging, limits the projected physical separation of the two binaries at the time of the observation to dABlesssim 4.1 AU at the photometric distance of 51 pc. The maximum observed radial velocity difference between the A and B binaries limits the orbit to aABsin iAB <= 6.1 AU. As this tight configuration is difficult to reproduce with current formation models of multiple systems, we speculate that an early dynamical process reduced the size of the system, such as the interaction of the two binaries with a circumquadruple disk. Intensive photometric, spectroscopic, and interferometric monitoring, as well as a parallax measurement of this rare quadruple system, is certainly warranted. Based on observations collected at the W. M. Keck Observatory and the Canada-France-Hawaii Telescope (CFHT). The Keck Observatory is operated as a scientific partnership between the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. The CFHT is operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Electron Capture Supernovae from Close Binary Systems

NASA Astrophysics Data System (ADS)

Poelarends, Arend J. T.; Wurtz, Scott; Tarka, James; Cole Adams, L.; Hills, Spencer T.

2017-12-01

We present the first detailed study of the Electron Capture Supernova Channel (ECSN Channel) for a primary star in a close binary star system. Progenitors of ECSN occupy the lower end of the mass spectrum of supernova progenitors and are thought to form the transition between white dwarf progenitors and core-collapse progenitors. The mass range for ECSN from close binary systems is thought to be wider than the range for single stars, because of the effects of mass transfer on the helium core. Using the MESA stellar evolution code, we explored the parameter space of initial primary masses between 8 and 17 {M}⊙ , using a large grid of models. We find that the initial primary mass and the mass transfer evolution are important factors in the final fate of stars in this mass range. Mass transfer due to Roche lobe overflow during and after carbon burning causes the core to cool down so that it avoids neon ignition, even in helium-free cores with masses up to 1.52 {M}⊙ , which in single stars would ignite neon. If the core is able to contract to high enough densities for electron captures to commence, we find that, for the adopted Ledoux convection criterion, the initial mass range for the primary to evolve into an ECSN is between 13.5 and 17.6 {M}⊙ . The mass ratio, initial period, and mass-loss efficiency only marginally affect the predicted ranges.

SU-E-T-554: Monte Carlo Calculation of Source Terms and Attenuation Lengths for Neutrons Produced by 50–200 MeV Protons On Brass

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

Ramos-Mendez, J; Faddegon, B; Paganetti, H

2015-06-15

Purpose: We used TOPAS (TOPAS wraps and extends Geant4 for medical physicists) to compare Geant4 physics models with published data for neutron shielding calculations. Subsequently, we calculated the source terms and attenuation lengths (shielding data) of the total ambient dose equivalent (TADE) in concrete for neutrons produced by protons in brass. Methods: Stage1: The Bertini and Binary nuclear models available in Geant4 were compared with published attenuation at depth of the TADE in concrete and iron. Stage2: Shielding data of the TADE in concrete was calculated for 50– 200 MeV proton beams on brass. Stage3: Shielding data from Stage2 wasmore » extrapolated for 235 MeV proton beams. This data was used in a point-line-source analytical model to calculate the ambient dose per unit therapeutic dose at two locations inside one treatment room at the Francis H Burr Proton Therapy Center. Finally, we compared these results with experimental data and full TOPAS simulations. Results: At larger angles (∼130o) the TADE in concrete calculated with the Bertini model was about 9 times larger than that calculated with the Binary model. The attenuation length in concrete calculated with the Binary model agreed with published data within 7%±0.4% (statistical uncertainty) for the deepest regions and 5%±0.1% for shallower regions. For iron the agreement was within 3%±0.1%. The ambient dose per therapeutic dose calculated with the Binary model, relative to the experimental data, was a ratio of 0.93±0.16 and 1.23±0.24 for two locations. The analytical model overestimated the dose by four orders of magnitude. These differences are attributed to the complexity of the geometry. Conclusion: The Binary and Bertini models gave comparable results, with the Binary model giving the best agreement with published data at large angle. Shielding data we calculated using the Binary model is useful for fast shielding calculations with other analytical models. This work was supported by National Cancer Institute Grant R01CA140735.« less

The Discovery of a Low-Mass Binary Companion to HD130948

NASA Astrophysics Data System (ADS)

Potter, D. E.; Cushing, M. C.; Neuhauser, R.

2003-10-01

We report the discovery of a low mass binary companion to the nearby (17.9 pc) main sequence star HD130948 (HR5534, HIP 72567) using the Hokupa'a adaptive optics instrument mounted on the Gemini North 8 meter telescope. Both companions have the same common proper motion as the primary star as seen over a 4 month baseline. The JHK' photometry of the companions, when placed on a near-IR color-magnitude diagram and compared with theoretical models places them at the bottom of the M-dwarf sequence. Preliminary near IR spectra have been obtained with SpeX mounted on the NASA IRTF 3 meter telescope are consistent with the photometric results and show carbon monoxide bandheads and water absorption features indicative of an early L-late M spectral type. The X-ray activity and Lithium abundance of the primary star indicate that the system is probably less than 1 Gyr old. Assuming a young age, these objects are less than 80 Mjupiter. With further astrometric observations carried out over an estimated orbital period of 10-20 years, a dynamical mass will be obtained.

Predicting mixture phase equilibria and critical behavior using the SAFT-VRX approach.

PubMed

Sun, Lixin; Zhao, Honggang; Kiselev, Sergei B; McCabe, Clare

2005-05-12

The SAFT-VRX equation of state combines the SAFT-VR equation with a crossover function that smoothly transforms the classical equation into a nonanalytical form close to the critical point. By a combinination of the accuracy of the SAFT-VR approach away from the critical region with the asymptotic scaling behavior seen at the critical point of real fluids, the SAFT-VRX equation can accurately describe the global fluid phase diagram. In previous work, we demonstrated that the SAFT-VRX equation very accurately describes the pvT and phase behavior of both nonassociating and associating pure fluids, with a minimum of fitting to experimental data. Here, we present a generalized SAFT-VRX equation of state for binary mixtures that is found to accurately predict the vapor-liquid equilibrium and pvT behavior of the systems studied. In particular, we examine binary mixtures of n-alkanes and carbon dioxide + n-alkanes. The SAFT-VRX equation accurately describes not only the gas-liquid critical locus for these systems but also the vapor-liquid equilibrium phase diagrams and thermal properties in single-phase regions.

Improvement of N-phthaloylchitosan based gel polymer electrolyte in dye-sensitized solar cells using a binary salt system.

PubMed

Yusuf, S N F; Azzahari, A D; Selvanathan, V; Yahya, R; Careem, M A; Arof, A K

2017-02-10

A binary salt system utilizing lithium iodide (LiI) as the auxiliary component has been introduced to the N-phthaloylchitosan (PhCh) based gel polymer electrolyte consisting of ethylene carbonate (EC), dimethylformamide (DMF), tetrapropylammonium iodide (TPAI), and iodine (I 2 ) in order to improve the performance of dye-sensitized solar cell (DSSC) with efficiency of 6.36%, photocurrent density, J SC of 17.29mAcm -2 , open circuit voltage, V OC of 0.59V and fill factor, FF of 0.62. This efficiency value is an improvement from the 5.00% performance obtained by the DSSC consisting of only TPAI single salt system. The presence of the LiI in addition to the TPAI improves the charge injection rates and increases the iodide contribution to the total conductivity and both factors contribute to the increase in efficiency of the DSSC. The interaction behavior between polymer-plasticizer-salt was thoroughly investigated using EIS, FTIR spectroscopy and XRD. Copyright © 2016 Elsevier Ltd. All rights reserved.

Exclusion of a luminous red giant as a companion star to the progenitor of supernova SN 2011fe.

PubMed

Li, Weidong; Bloom, Joshua S; Podsiadlowski, Philipp; Miller, Adam A; Cenko, S Bradley; Jha, Saurabh W; Sullivan, Mark; Howell, D Andrew; Nugent, Peter E; Butler, Nathaniel R; Ofek, Eran O; Kasliwal, Mansi M; Richards, Joseph W; Stockton, Alan; Shih, Hsin-Yi; Bildsten, Lars; Shara, Michael M; Bibby, Joanne; Filippenko, Alexei V; Ganeshalingam, Mohan; Silverman, Jeffrey M; Kulkarni, S R; Law, Nicholas M; Poznanski, Dovi; Quimby, Robert M; McCully, Curtis; Patel, Brandon; Maguire, Kate; Shen, Ken J

2011-12-14

Type Ia supernovae are thought to result from a thermonuclear explosion of an accreting white dwarf in a binary system, but little is known of the precise nature of the companion star and the physical properties of the progenitor system. There are two classes of models: double-degenerate (involving two white dwarfs in a close binary system) and single-degenerate models. In the latter, the primary white dwarf accretes material from a secondary companion until conditions are such that carbon ignites, at a mass of 1.38 times the mass of the Sun. The type Ia supernova SN 2011fe was recently detected in a nearby galaxy. Here we report an analysis of archival images of the location of SN 2011fe. The luminosity of the progenitor system (especially the companion star) is 10-100 times fainter than previous limits on other type Ia supernova progenitor systems, allowing us to rule out luminous red giants and almost all helium stars as the mass-donating companion to the exploding white dwarf.

Carbon nanotubes/carbon fiber hybrid material: a super support material for sludge biofilms.

PubMed

Liu, Qijie; Dai, Guangze; Bao, Yanling

2017-07-16

Carbon fiber (CF) is widely used as a sludge biofilm support material for wastewater treatment. Carbon nanotubes/carbon fiber (CNTs/CF) hybrid material was prepared by ultrasonically assisted electrophoretic deposition (EPD). CF supports (CF without handling, CF oxidized by nitric acid, CNTs/CF hybrid material) were evaluated by sludge immobilization tests, bacterial cell adsorption tests and Derjaguin -Landau -Verwey -Overbeek (DLVO) theory. We found that the CNTs/CF hybrid material has a high capacity for adsorbing activated sludge, nitrifying bacterial sludge and pure strains (Escherichia coli and Staphylococcus aureus). CNTs deposited on CF surface easily wound around the curved surface of bacterial cell which resulted in capturing more bacterial cells. DLVO theory indicated the lowest total interaction energy of CNTs/CF hybrid material, which resulted in the highest bacteria cell adsorption velocity. Experiments and DLVO theory results proved that CNTs/CF hybrid material is a super support material for sludge biofilms.

Central Composite Design (CCD) applied for statistical optimization of glucose and sucrose binary carbon mixture in enhancing the denitrification process

NASA Astrophysics Data System (ADS)

Lim, Jun-Wei; Beh, Hoe-Guan; Ching, Dennis Ling Chuan; Ho, Yeek-Chia; Baloo, Lavania; Bashir, Mohammed J. K.; Wee, Seng-Kew

2017-11-01

The present study provides an insight into the optimization of a glucose and sucrose mixture to enhance the denitrification process. Central Composite Design was applied to design the batch experiments with the factors of glucose and sucrose measured as carbon-to-nitrogen (C:N) ratio each and the response of percentage removal of nitrate-nitrogen (NO3 --N). Results showed that the polynomial regression model of NO3 --N removal had been successfully derived, capable of describing the interactive relationships of glucose and sucrose mixture that influenced the denitrification process. Furthermore, the presence of glucose was noticed to have more consequential effect on NO3 --N removal as opposed to sucrose. The optimum carbon sources mixture to achieve complete removal of NO3 --N required lesser glucose (C:N ratio of 1.0:1.0) than sucrose (C:N ratio of 2.4:1.0). At the optimum glucose and sucrose mixture, the activated sludge showed faster acclimation towards glucose used to perform the denitrification process. Later upon the acclimation with sucrose, the glucose uptake rate by the activated sludge abated. Therefore, it is vital to optimize the added carbon sources mixture to ensure the rapid and complete removal of NO3 --N via the denitrification process.

Alternative solution model for the ternary carbonate system CaCO3 - MgCO3 - FeCO3 - I. A ternary Bragg-Williams ordering model

USGS Publications Warehouse

McSwiggen, P.L.

1993-01-01

The minerals of the ternary carbonate system CaCO3 - MgCO3 - FeCO3 represent a complex series of solid solutions and ordering states. An understanding of those complexities requires a solution model that can both duplicate the subsolidus phase relationships and generate correct values for the activities. Such a solution model must account for the changes in the total energy of the system resulting from a change in the ordering state of the individual constituents. Various ordering models have been applied to binary carbonate systems, but no attempts have previously been made to model the ordering in the ternary system. This study derives a new set of equations that allow for the equilibrium degree of order to be calculated for a system involving three cations mixing on two sites, as in the case of the ternary carbonates. The method is based on the Bragg-Williams approach. From the degree of order, the mole fractions of the three cations in each of the two sites can be determined. Once the site occupancies have been established, a Margules-type mixing model can be used to determine the free energy of mixing in the solid solution and therefore the activities of the various components. ?? 1993 Springer-Verlag.

Automated characterisation of ultrasound images of ovarian tumours: the diagnostic accuracy of a support vector machine and image processing with a local binary pattern operator

PubMed Central

Khazendar, S.; Sayasneh, A.; Al-Assam, H.; Du, H.; Kaijser, J.; Ferrara, L.; Timmerman, D.; Jassim, S.; Bourne, T.

2015-01-01

Introduction: Preoperative characterisation of ovarian masses into benign or malignant is of paramount importance to optimise patient management. Objectives: In this study, we developed and validated a computerised model to characterise ovarian masses as benign or malignant. Materials and methods: Transvaginal 2D B mode static ultrasound images of 187 ovarian masses with known histological diagnosis were included. Images were first pre-processed and enhanced, and Local Binary Pattern Histograms were then extracted from 2 × 2 blocks of each image. A Support Vector Machine (SVM) was trained using stratified cross validation with randomised sampling. The process was repeated 15 times and in each round 100 images were randomly selected. Results: The SVM classified the original non-treated static images as benign or malignant masses with an average accuracy of 0.62 (95% CI: 0.59-0.65). This performance significantly improved to an average accuracy of 0.77 (95% CI: 0.75-0.79) when images were pre-processed, enhanced and treated with a Local Binary Pattern operator (mean difference 0.15: 95% 0.11-0.19, p < 0.0001, two-tailed t test). Conclusion: We have shown that an SVM can classify static 2D B mode ultrasound images of ovarian masses into benign and malignant categories. The accuracy improves if texture related LBP features extracted from the images are considered. PMID:25897367

Searching for Extrasolar Trojan Planets: A Status Report

NASA Astrophysics Data System (ADS)

Caton, D. B.; Davis, S. A.; Kluttz, K. A.; Stamilio, R. J.; Wohlman, K. D.

2001-05-01

We are exploring the light curves of eclipsing binaries for the photometric signature of planets that may exist at the L4 and L5 Lagrange points of the stellar system. While no binaries are known to exist that strictly satisfy the stellar mass ratio constraint for the restricted three-body problem, the general solution would allow a planet formed at the L-point to remain there if there are no major perturbing bodies such as an additional planet. We have coined such objects "Trojan planets." The advantage of this approach is that the phases of the planetary eclipses are known. We picked systems with deep primary eclipses, to maximize the amount of system light eclipsed by the planet when in front of the hotter star. We also scanned the Finding List for Observers of Interactive Binary Stars, for G dwarf systems, but found only a few that were high inclination and detached. The target list includes QY Aql, YZ Aql, V442 Cas, SS Cet, S Cnc, VW Cyg, WW Cyg, RR Dra, RX Gem, RY Gem, VW Hya, Y Leo, TV Mon, BN Sct, UW Vir, AC UMa, and GSC 1657. We have concentrated on V442 Cas and YZ Aql, based on initial results that show anomalies in the light curves near the phases where a Trojan planet eclipse is expected. New work is being done on brighter systems by using a "spot filter," similar to that developed by Castellano (PASP 112, 821-6),2000), to allow longer exposures that provide brighter comparison stars. We will report on the observations made to date on several systems. We gratefully acknowledge the support of the National Science Foundation, through grants AST-9731062 and AST-0089248. We also appreciate the support of the Fund for Astrophysical Research. Gregory Shelton and Brenda Corbin, at the U.S. naval Observatory Library, have been indispensable in providing references for these binary systems. This research has made use of the Simbad database, operated at CDS, Strasbourg, France

Electrochemical durability of heat-treated carbon nanospheres as catalyst supports for proton exchange membrane fuel cells.

PubMed

Lv, Haifeng; Wu, Peng; Wan, Wei; Mu, Shichun

2014-09-01

Carbon nanospheres is wildly used to support noble metal nanocatalysts in proton exchange membrane (PEM) fuel cells, however they show a low resistance to electrochemical corrosion. In this study, the N-doped treatment of carbon nanospheres (Vulcan XC-72) is carried out in ammonia gas. The effect of heating treatment (up to 1000 degrees C) on resistances to electrochemical oxidation of the N-doped carbon nanospheres (HNC) is investigated. The resistance to electrochemical oxidation of carbon supports and stability of the catalysts are investigated with potentiostatic oxidation and accelerated durability test by simulating PEM fuel cell environment. The HNC exhibit a higher resistance to electrochemical oxidation than traditional Vulcan XC-72. The results show that the N-doped carbon nanospheres have a great potential application in PEM fuel cells.

Hydrodeoxygenation of phenols as lignin models under acid-free conditions with carbon-supported platinum catalysts.

PubMed

Ohta, Hidetoshi; Kobayashi, Hirokazu; Hara, Kenji; Fukuoka, Atsushi

2011-11-28

Carbon-supported Pt catalysts are highly active and reusable for the aqueous-phase hydrodeoxygenation of phenols as lignin models without adding any acids. It is suggested that Pt/carbon facilitates the hydrogenation of phenols and the hydrogenolysis of the resulting cyclohexanols.

75 FR 7931 - Airworthiness Directives; Airbus Model A380-841, -842, and -861 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-23

... addition, delamination has been observed within the monolithic Carbon Fibre Reinforced Plastic (CFRP... observed within the monolithic Carbon Fibre Reinforced Plastic (CFRP) structure around the pivot support... monolithic Carbon Fibre Reinforced Plastic (CFRP) structure around the pivot support-ring. This condition, if...

Mirror Support

NASA Technical Reports Server (NTRS)

Baron, Richard L. (Inventor)

2013-01-01

Disclosed herein is a method of making a mirror support comprising a composite, the composite comprising a plurality of carbon nanotubes, wherein at least two of the plurality of carbon nanotubes are bonded to each other through a bridging moiety bound to each of the two carbon nanotubes, and a laminate comprising the composite.

The Phases Differential Astrometry Data Archive. 5. Candidate Substellar Companions to Binary Systems

DTIC Science & Technology

2010-12-01

Mathematics and Astronomy , 105-24, California Institute of Technology, Pasadena, CA 91125, USA 5 Nicolaus Copernicus Astronomical Center, Polish Academy...Blind Test with support from NASA contract NAS7-03001 (JPL 1336910). PHASES is funded in part by the California Institute of Technol- ogy Astronomy

Beyond a Binary: The Lives of Gender-Nonconforming Youth

ERIC Educational Resources Information Center

Rankin, Sue; Beemyn, Genny

2012-01-01

The vast majority of college students, classroom faculty, student affairs educators, and administrators have a tremendous amount to learn about gender diversity. For this majority and for gender-nonconforming students and educators, opportunities are all but untapped to leverage this diversity to enhance learning, as well as to support and…

SALT reveals the barium central star of the planetary nebula Hen 2-39

NASA Astrophysics Data System (ADS)

Miszalski, B.; Boffin, H. M. J.; Jones, D.; Karakas, A. I.; Köppen, J.; Tyndall, A. A.; Mohamed, S. S.; Rodríguez-Gil, P.; Santander-García, M.

2013-12-01

Classical barium stars are binary systems which consist of a late-type giant enriched in carbon and slow neutron capture (s-process) elements and an evolved white dwarf (WD) that is invisible at optical wavelengths. The youngest observed barium stars are surrounded by planetary nebulae (PNe), ejected soon after the wind accretion of polluted material when the WD was in its preceding asymptotic giant branch (AGB) phase. Such systems are rare but powerful laboratories for studying AGB nucleosynthesis as we can measure the chemical abundances of both the polluted star and the nebula ejected by the polluter. Here, we present evidence for a barium star in the PN Hen 2-39 (PN G283.8-04.2) as one of only a few known systems. The polluted giant is very similar to that found in WeBo 1 (PN G135.6+01.0). It is a cool (Teff = 4250 ± 150 K) giant enhanced in carbon ([C/H] = 0.42 ± 0.02 dex) and barium ([Ba/Fe] = 1.50 ± 0.25 dex). A spectral type of C-R3 C24 nominally places Hen 2-39 amongst the peculiar early R-type carbon stars; however, the barium enhancement and likely binary status mean that it is more likely to be a barium star with similar properties, rather than a true member of this class. An AGB star model of initial mass 1.8 M⊙ and a relatively large carbon pocket size can reproduce the observed abundances well, provided mass is transferred in a highly conservative way from the AGB star to the polluted star (e.g. wind Roche lobe overflow). It also shows signs of chromospheric activity and photometric variability with a possible rotation period of ˜5.5 d likely induced by wind accretion. The nebula exhibits an apparent ring morphology in keeping with the other PNe around barium stars (WeBo 1 and A 70) and shows a high degree of ionization implying the presence of an invisible hot pre-WD companion that will require confirmation with UV observations. In contrast to A 70, the nebular chemical abundance pattern is consistent with non-Type I PNe, in keeping with the trend found from nebular s-process studies that non-Type I PNe are more likely to be s-process enhanced.

Amorphous carbon in the disk around the post-AGB binary HR 4049. Discerning dust species with featureless opacity curves

NASA Astrophysics Data System (ADS)

Acke, B.; Degroote, P.; Lombaert, R.; de Vries, B. L.; Smolders, K.; Verhoelst, T.; Lagadec, E.; Gielen, C.; Van Winckel, H.; Waelkens, C.

2013-03-01

Context. Infrared spectroscopy has been extensively used to determine the mineralogy of circumstellar dust. The identification of dust species with featureless opacities, however, is still ambiguous. Here we present a method to lift the degeneracy using the combination of infrared spectroscopy and interferometry. Aims: The binary post-AGB star HR 4049 is surrounded by a circumbinary disk viewed at a high inclination angle. Apart from gaseous emission lines and molecular emission bands of polycyclic aromatic hydrocarbons (PAH), diamonds, and fullerenes, the 2-25 μm infrared spectrum is featureless. The goal of the paper is to identify the dust species responsible for the smooth spectrum. Methods: We gathered high-angular-resolution measurements in the near- and mid-infrared with the VLTI interferometric instruments AMBER and MIDI. The data set is expanded with archival Geneva optical photometry, ISO-SWS and Spitzer-IRS infrared spectroscopy, and VISIR N-band images and spectroscopy. We computed a grid of radiative-transfer models of the circumbinary disk of HR 4049 using the radiative-transfer code MCMax. We searched for models that provide good fits simultaneously to all available observations. Results: We find that the variable optical extinction towards the primary star is consistent with the presence of very small (0.01 μm) iron-bearing dust grains or amorphous carbon grains. The combination of the interferometric constraint on the disk extent and the shape of the infrared spectrum points to amorphous carbon as the dominant source of opacity in the circumbinary disk of HR 4049. The disk is optically thick to the stellar radiation in the radial direction. At infrared wavelengths it is optically thin. The PAH emission is spatially resolved in the VISIR data and emanates from a region with an extent of several hundreds of AU, with a projected photocenter displacement of several tens of AU from the disk center. The PAHs most likely reside in a bipolar outflow. Conclusions: Dust species with featureless opacity curves, such as metallic iron and amorphous carbon, can be identified by combining infrared spectroscopy and high-angular-resolution measurements. In essence, this is because the temperatures of the dust species are notably different at the same physical distance to the star. Appendices A and B are available in electronic form at http://www.aanda.org

Tools to support GHG emissions reduction : a regional effort, part 1 - carbon footprint estimation and decision support.

DOT National Transportation Integrated Search

2010-09-01

Tools are proposed for carbon footprint estimation of transportation construction projects and decision support : for construction firms that must make equipment choice and usage decisions that affect profits, project duration : and greenhouse gas em...

Spectroscopy of Six Red Giants in the Draco Dwarf Spheroidal Galaxy

NASA Astrophysics Data System (ADS)

Smith, Graeme H.; Siegel, Michael H.; Shetrone, Matthew D.; Winnick, Rebeccah

2006-10-01

Keck Observatory LRIS-B (Low Resolution Imaging Spectrometer) spectra are reported for six red giant stars in the Draco dwarf spheroidal galaxy and several comparison giants in the globular cluster M13. Indexes that quantify the strengths of the Ca II H and K lines, the λ3883 and λ4215 CN bands, and the λ4300 G band have been measured. These data confirm evidence of metallicity inhomogeneity within Draco obtained by previous authors. The four brightest giants in the sample have absolute magnitudes in the range -2.6

Determination of the antileukemic drug mitoguazone and seven other closely related bis(amidinohydrazones) in human blood serum by high-performance liquid chromatography.

PubMed

Koskinen, M; Elo, H; Lukkari, P; Riekkola, M L

1996-10-11

A reversed-phase (C18) HPLC method with diode-array detection was developed for the separation and determination of methylglyoxal bis(amidinohydrazone) (mitoguazone) and seven closely related aliphatic analogs thereof, namely the bis(amidinohydrazones) of glyoxal, dimethylglyoxal, ethylmethylglyoxal, methylpropylglyoxal, butylmethylglyoxal, diethylglyoxal and dipropylglyoxal. The mobile phase consisted of a non-linear binary gradient of methanol and 0.03 M aqueous sodium acetate buffer (pH 4.3). Good separation of the eight congeners was achieved. On increasing the methanol content of the eluent, the bis(amidinohydrazones) eluted in the order of increasing number of carbon atoms in the side-chains. The method was also applied to the quantitative analysis of the compounds in aqueous solution and, combined with ultrafiltration, for the separation of the eight congeners in spiked human blood serum. A separate simplified method for the quantitative determination of each of the compounds in spiked human blood serum samples was also developed. The methods developed made for the first time possible the simultaneous HPLC analysis of more than one bis(amidinohydrazones). The results obtained indicate that the bis(amidinohydrazones) studied obviously have a distinct tendency to form ion associates with acetate ions and probably also other carboxylate ions in aqueous solution. This aspect may be of biochemical significance, especially concerning the intracellular binding of the compounds. Each one of the compounds studied invariably gave rise to one peak only, this result supporting the theory that the conventional synthesis of each of the compounds gives rise to one geometrical isomer only. This result is completely in agreement with the results of previous proton and carbon NMR spectroscopic as well as X-ray diffraction studies.

Elemental Metals or Oxides Distributed on a Carbon Substrate or Self-Supported and the Manufacturing Process Using Graphite Oxide as Template

NASA Technical Reports Server (NTRS)

Hung, Ching-Chen (Inventor)

1999-01-01

A process for providing elemental metals or metal oxides distributed on a carbon substrate or self-supported utilizing graphite oxide as a percursor. The graphite oxide is exposed to one or more metal chlorides to form an intermediary product comprising carbon, metal, chloride, and oxygen. This intermediary product can be further processed by direct exposure to carbonate solutions to form a second intermediary product comprising carbon, metal carbonate, and oxygen. Either intermediary product may be further processed: a) in air to produce metal oxide; b) in an inert environment to produce metal oxide on carbon substrate; c) in a reducing environment to produce elemental metal distributed on carbon substrate. The product generally takes the shape of the carbon precursor.

Elemental Metals or Oxides Distributed on a Carbon Substrate or Self-Supported and the Manufacturing Process Using Graphite Oxide as Template

NASA Technical Reports Server (NTRS)

Hung, Ching-Cheh (Inventor)

1999-01-01

A process for providing elemental metals or metal oxides distributed on a carbon substrate or self-supported utilizing graphite oxide as a precursor. The graphite oxide is exposed to one or more metal chlorides to form an intermediary product comprising carbon, metal, chloride, and oxygen. This intermediary product can be further processed by direct exposure to carbonate-solutions to form a second intermediary product comprising carbon, metal carbonate, and oxygen. Either intermediary product may be further processed: a) in air to produce metal oxide; b) in an inert environment to produce metal oxide on carbon substrate; c) in a reducing environment to produce elemental metal distributed on carbon substrate. The product generally takes the shape of the carbon precursor.

Predicting the enthalpies of melting and vaporization for pure components

NASA Astrophysics Data System (ADS)

Esina, Z. N.; Korchuganova, M. R.

2014-12-01

A mathematical model of the melting and vaporization enthalpies of organic components based on the theory of thermodynamic similarity is proposed. In this empirical model, the phase transition enthalpy for the homological series of n-alkanes, carboxylic acids, n-alcohols, glycols, and glycol ethers is presented as a function of the molecular mass, the number of carbon atoms in a molecule, and the normal transition temperature. The model also uses a critical or triple point temperature. It is shown that the results from predicting the melting and vaporization enthalpies enable the calculation of binary phase diagrams.

Multicomponent ionic liquid CMC prediction.

PubMed

Kłosowska-Chomiczewska, I E; Artichowicz, W; Preiss, U; Jungnickel, C

2017-09-27

We created a model to predict CMC of ILs based on 704 experimental values published in 43 publications since 2000. Our model was able to predict CMC of variety of ILs in binary or ternary system in a presence of salt or alcohol. The molecular volume of IL (V m ), solvent-accessible surface (Ŝ), solvation enthalpy (Δ solv G ∞ ), concentration of salt (C s ) or alcohol (C a ) and their molecular volumes (V ms and V ma , respectively) were chosen as descriptors, and Kernel Support Vector Machine (KSVM) and Evolutionary Algorithm (EA) as regression methodologies to create the models. Data was split into training and validation set (80/20) and subjected to bootstrap aggregation. KSVM provided better fit with average R 2 of 0.843, and MSE of 0.608, whereas EA resulted in R 2 of 0.794 and MSE of 0.973. From the sensitivity analysis it was shown that V m and Ŝ have the highest impact on ILs micellization in both binary and ternary systems, however surprisingly in the presence of alcohol the V m becomes insignificant/irrelevant. Micelle stabilizing or destabilizing influence of the descriptors depends upon the additives. Previous attempts at modelling the CMC of ILs was generally limited to small number of ILs in simplified (binary) systems. We however showed successful prediction of the CMC over a range of different systems (binary and ternary).

The circumbinary dusty disk around the hydrogen-deficient binary star υ Sagittarii

NASA Astrophysics Data System (ADS)

Netolický, M.; Bonneau, D.; Chesneau, O.; Harmanec, P.; Koubský, P.; Mourard, D.; Stee, P.

2009-06-01

Aims: The aim of this paper is to determine the properties of the dusty environment of the hydrogen-deficient binary system υ Sgr, whose binary properties and other characteristics are poorly known. Methods: We obtained the first mid-IR interferometric observations of υ Sgr using the instrument MIDI of the VLTI used with different pairs of 1.8 m and 8 m telescopes. The calibrated visibilities, the N band spectrum, and the SED were compared with disk models computed with the MC3D code to determine the geometry and chemical composition of the envelope. Results: υ Sgr is unresolved with an 8 m telescope at 8.7 μm. We propose a disk model that agrees with the measured visibilities and the SED, consisting of a geometrically thin disk with an inner radius R_in = 6.0+0.5-1.5 AU and a scale height h100 = 3.5+2.0-1.5 AU. The chemical composition of the dust is approximately 60% of carbon dust and 40% of silicate dust, as a consequence of several episodes of mass transfers, whose chemistry was imprinted in the dust composition. We also constrain the inclination of the disk i = 50°+10°-20° and its orientation position angle PA = 80°+10°-5°. Conclusions: The mid-infrared interferometric observations of the binary star υ Sgr allowed us to constrain the geometry of the circumbinary dusty envelope. By defining the inclination and PA of the system with better accuracy than before, these observations restrict the parameter space for the orbital parameters and thus the nature of the stars orbiting in this system. Based on observations made with the Very Large Telescope Interferometer at Paranal Observatory under program 079.D-0115. Visibility data are only available in electronic form at the CDS website.

System and method for controlling hydrogen elimination during carbon nanotube synthesis from hydrocarbons

DOEpatents

Reilly, Peter T. A.

2010-03-23

A system and method for producing carbon nanotubes by chemical vapor deposition includes a catalyst support having first and second surfaces. The catalyst support is capable of hydrogen transport from the first to the second surface. A catalyst is provided on the first surface of the catalyst support. The catalyst is selected to catalyze the chemical vapor deposition formation of carbon nanotubes. A fuel source is provided for supplying fuel to the catalyst.

Comparative study of different carbon-supported Fe2O3-Pt catalysts for oxygen reduction reaction.

PubMed

Tellez-Cruz, M M; Padilla-Islas, M A; Pérez-González, M; Solorza-Feria, O

2017-11-01

One of the challenges in electrocatalysis is the adequate dispersion of the catalyst on an appropriate porous support matrix, being up to now the most commonly used the carbon-based supports. To overcome this challenge, carbon supports must first be functionalized to guide the catalyst's nucleation, thereby, improving the dispersion and allowing the use of smaller amount of the catalyst material to achieve a higher electrochemically active surface area. This study present the effect of functionalized Vulcan carbon XC72 (FVC) and functionalized Black Pearl carbon (FBPC) as supports on the catalytic activity of decorated Fe 2 O 3 with Pt. Both carbons were functionalized with HNO 3 and subsequently treated with ethanolamine. Fe 2 O 3 nanoparticles were synthesized by chemical reduction and decorated with platinum by epitaxial growth. Pt and Fe 2 O 3 structural phases were identified by XRD and XPS; the Pt content was measured by XPS, and results showed to a high Pt content in Fe 2 O 3 -Pt/FBPC. TEM micrographs reveal nanoparticles with an average size of 2 nm in both supported catalysts. The Fe 2 O 3 -Pt/FVC catalyst presents the highest specific activity and mass activity, 0.21 mA cm -2 Pt and 140 mA mg Pt -1 , respectively, associated to the appropriate distribution of platinum on the Fe 2 O 3 nanoparticles.

Searching for Partners of Cool Senior Citizens

NASA Astrophysics Data System (ADS)

Jao, Wei-Chun; Henry, T. J.

2012-01-01

Mass is one of the most fundamental parameters in stellar astronomy. In order to measure dynamical masses, one needs to find nearby binary systems that can be resolved and monitored, ideally with orbital periods that completely wrap in a reasonable amount of time. Many surveys have been made of nearby main sequence dwarfs, and their mass-luminosity relation is well established. As part of our Cool Subdwarf Investigations (CSI) program, we are searching for subdwarf binaries of spectral types K and M within 60 parsecs to measure their multiplicity rate and to reveal binaries appropriate for mass determinations. Here we present results of our CSI work using HST's Fine Guidance Sensors. When combined with previous CSI work and results in the literature, we find the multiplicity rate of subdwarfs, 21%, to be surprisingly low compared to that of similar main sequence K and M stars, 37%. This work has several implications, including that the star formation and/or evolution history of subdwarfs is different than for dwarfs, and that ideal systems for subdwarf mass determinations are difficult to find. This work is supported by HST grant GO-11943.

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.

The Young Visual Binary Database

NASA Astrophysics Data System (ADS)

Prato, Lisa A.; Avilez, Ian; Allen, Thomas; Zoonematkermani, Saeid; Biddle, Lauren; Muzzio, Ryan; Wittal, Matthew; Schaefer, Gail; Simon, Michal

2017-01-01

We have obtained adaptive optics imaging and high-resolution H-band and in some cases K-band spectra of each component in close to 100 young multiple systems in the nearby star forming regions of Taurus, Ophiuchus, TW Hya, and Orion. The binary separations for the pairs in our sample range from 30 mas to 3 arcseconds. The imaging and most of our spectra were obtained with instruments behind adaptive optics systems in order to resolve even the closest companions. We are in the process of determining fundamental stellar and circumstellar properties, such as effective temperature, Vsin(i), veiling, and radial velocity, for each component in the entire sample. The beta version of our database includes systems in the Taurus region and provides plots, downloadable ascii spectra, and values of the stellar and circumstellar properties for both stars in each system. This resource is openly available to the community at http://jumar.lowell.edu/BinaryStars/. In this poster we describe initial results from our analysis of the survey data. Support for this research was provided in part by NSF award AST-1313399 and by NASA Keck KPDA funding.

Interaction between Saikosaponin D, Paeoniflorin, and Human Serum Albumin.

PubMed

Liang, Guo-Wu; Chen, Yi-Cun; Wang, Yi; Wang, Hong-Mei; Pan, Xiang-Yu; Chen, Pei-Hong; Niu, Qing-Xia

2018-01-27

Saikosaponin D (SSD) and paeoniflorin (PF) are the major active constituents of Bupleuri Radix and Paeonia lactiflora Pall , respectively, and have been widely used in China to treat liver and other diseases for many centuries. We explored the binding of SSD/PF to human serum albumin (HSA) by using fluorospectrophotometry, circular dichroism (CD) and molecular docking. Both SSD and PF produced a conformational change in HSA. Fluorescence quenching was accompanied by a blue shift in the fluorescence spectra. Co-binding of PF and SSD also induced quenching and a conformational change in HSA. The Stern-Volmer equation showed that quenching was dominated by static quenching. The binding constant for ternary interaction was below that for binary interaction. Site-competitive experiments demonstrated that SSD/PF bound to site I (subdomain IIA) and site II (subdomain IIIA) in HSA. Analysis of thermodynamic parameters indicated that hydrogen bonding and van der Waals forces were mostly responsible for the binary association. Also, there was energy transfer upon binary interaction. Molecular docking supported the experimental findings in conformation, binding sites and binding forces.

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.

Impact of Bayesian Priors on the Characterization of Binary Black Hole Coalescences

NASA Astrophysics Data System (ADS)

Vitale, Salvatore; Gerosa, Davide; Haster, Carl-Johan; Chatziioannou, Katerina; Zimmerman, Aaron

2017-12-01

In a regime where data are only mildly informative, prior choices can play a significant role in Bayesian statistical inference, potentially affecting the inferred physics. We show this is indeed the case for some of the parameters inferred from current gravitational-wave measurements of binary black hole coalescences. We reanalyze the first detections performed by the twin LIGO interferometers using alternative (and astrophysically motivated) prior assumptions. We find different prior distributions can introduce deviations in the resulting posteriors that impact the physical interpretation of these systems. For instance, (i) limits on the 90% credible interval on the effective black hole spin χeff are subject to variations of ˜10 % if a prior with black hole spins mostly aligned to the binary's angular momentum is considered instead of the standard choice of isotropic spin directions, and (ii) under priors motivated by the initial stellar mass function, we infer tighter constraints on the black hole masses, and in particular, we find no support for any of the inferred masses within the putative mass gap M ≲5 M⊙.

Doppler tomography of XTE J1118+480 revealing chromospheric emission from the secondary star

NASA Astrophysics Data System (ADS)

Zurita, C.; González Hernández, J. I.; Escorza, A.; Casares, J.

2016-08-01

Doppler tomography of emission lines in low-mass X-ray binaries allows us to investigate the structure and variability of the accretion discs as well as possible activity arising from the secondary stars. We present Doppler maps of the black hole binary XTE J1118+480 from spectra obtained using OSIRIS@GTC during quiescence on four different nights in 2011 and 2012. Doppler imaging of the Hα line shows, for the first time, a narrow component from the secondary star with observed equivalent widths varying in the range 1.2-2.9 Å but not correlated with the veiling of the accretion disc. The Hα flux of the secondary star is too large to be powered by X-ray irradiation, supporting chromospheric activity, possibly induced by rapid rotation, as the most likely origin of this feature in the black hole X-ray binary XTE J1118+480. In addition, we detect variations in the centroid of the Hα line on nightly basis. These are likely caused by a precessing accretion disc, although with a much lower amplitude (˜50 km s-1) than previously observed.

Impact of Bayesian Priors on the Characterization of Binary Black Hole Coalescences.

PubMed

Vitale, Salvatore; Gerosa, Davide; Haster, Carl-Johan; Chatziioannou, Katerina; Zimmerman, Aaron

2017-12-22

In a regime where data are only mildly informative, prior choices can play a significant role in Bayesian statistical inference, potentially affecting the inferred physics. We show this is indeed the case for some of the parameters inferred from current gravitational-wave measurements of binary black hole coalescences. We reanalyze the first detections performed by the twin LIGO interferometers using alternative (and astrophysically motivated) prior assumptions. We find different prior distributions can introduce deviations in the resulting posteriors that impact the physical interpretation of these systems. For instance, (i) limits on the 90% credible interval on the effective black hole spin χ_{eff} are subject to variations of ∼10% if a prior with black hole spins mostly aligned to the binary's angular momentum is considered instead of the standard choice of isotropic spin directions, and (ii) under priors motivated by the initial stellar mass function, we infer tighter constraints on the black hole masses, and in particular, we find no support for any of the inferred masses within the putative mass gap M≲5  M_{⊙}.

Nafion induced surface confinement of oxygen in carbon-supported oxygen reduction catalysts

DOE PAGES

Chlistunoff, Jerzy; Sansinena, Jose -Maria

2016-11-17

We studied the surface confinement of oxygen inside layers of Nafion self-assembled on carbon-supported oxygen reduction reaction (ORR) catalysts. It is demonstrated that oxygen accumulates in the hydrophobic component of the polymer remaining in contact with the carbon surface. Furthermore, the amount of surface confined oxygen increases with the degree of carbon surface graphitization, which promotes the self-assembly of the polymer. Planar macrocyclic ORR catalysts possessing a delocalized system of π electrons such as Co and Fe porphyrins and phthalocyanines have virtually no effect on the surface confinement of oxygen, in accordance with their structural similarity to graphitic carbon surfacesmore » where they adsorb. Platinum particles in carbon-supported ORR catalysts with high metal contents (20%) disrupt the self-assembly of Nafion and virtually eliminate the oxygen confinement, but the phenomenon is still observed for low Pt loading (4.8%) catalysts.« less

Embedded arrays of vertically aligned carbon nanotube carpets and methods for making them

DOEpatents

Kim, Myung Jong; Nicholas, Nolan Walker; Kittrell, W. Carter; Schmidt, Howard K.

2015-06-30

According to some embodiments, the present invention provides a system and method for supporting a carbon nanotube array that involve an entangled carbon nanotube mat integral with the array, where the mat is embedded in an embedding material. The embedding material may be depositable on a carbon nanotube. A depositable material may be metallic or nonmetallic. The embedding material may be an adhesive material. The adhesive material may optionally be mixed with a metal powder. The embedding material may be supported by a substrate or self-supportive. The embedding material may be conductive or nonconductive. The system and method provide superior mechanical and, when applicable, electrical, contact between the carbon nanotubes in the array and the embedding material. The optional use of a conductive material for the embedding material provides a mechanism useful for integration of carbon nanotube arrays into electronic devices.

Nafion induced surface confinement of oxygen in carbon-supported oxygen reduction catalysts

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

Chlistunoff, Jerzy; Sansinena, Jose -Maria

We studied the surface confinement of oxygen inside layers of Nafion self-assembled on carbon-supported oxygen reduction reaction (ORR) catalysts. It is demonstrated that oxygen accumulates in the hydrophobic component of the polymer remaining in contact with the carbon surface. Furthermore, the amount of surface confined oxygen increases with the degree of carbon surface graphitization, which promotes the self-assembly of the polymer. Planar macrocyclic ORR catalysts possessing a delocalized system of π electrons such as Co and Fe porphyrins and phthalocyanines have virtually no effect on the surface confinement of oxygen, in accordance with their structural similarity to graphitic carbon surfacesmore » where they adsorb. Platinum particles in carbon-supported ORR catalysts with high metal contents (20%) disrupt the self-assembly of Nafion and virtually eliminate the oxygen confinement, but the phenomenon is still observed for low Pt loading (4.8%) catalysts.« less

A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide

PubMed Central

Anthonysamy, Shahreen Binti Izwan; Afandi, Syahidah Binti; Khavarian, Mehrnoush

2018-01-01

Various types of carbon-based and non-carbon-based catalyst supports for nitric oxide (NO) removal through selective catalytic reduction (SCR) with ammonia are examined in this review. A number of carbon-based materials, such as carbon nanotubes (CNTs), activated carbon (AC), and graphene (GR) and non-carbon-based materials, such as Zeolite Socony Mobil–5 (ZSM-5), TiO2, and Al2O3 supported materials, were identified as the most up-to-date and recently used catalysts for the removal of NO gas. The main focus of this review is the study of catalyst preparation methods, as this is highly correlated to the behaviour of NO removal. The general mechanisms involved in the system, the Langmuir–Hinshelwood or Eley–Riedeal mechanism, are also discussed. Characterisation analysis affecting the surface and chemical structure of the catalyst is also detailed in this work. Finally, a few major conclusions are drawn and future directions for work on the advancement of the SCR-NH3 catalyst are suggested. PMID:29600136

A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide.

PubMed

Anthonysamy, Shahreen Binti Izwan; Afandi, Syahidah Binti; Khavarian, Mehrnoush; Mohamed, Abdul Rahman Bin

2018-01-01

Various types of carbon-based and non-carbon-based catalyst supports for nitric oxide (NO) removal through selective catalytic reduction (SCR) with ammonia are examined in this review. A number of carbon-based materials, such as carbon nanotubes (CNTs), activated carbon (AC), and graphene (GR) and non-carbon-based materials, such as Zeolite Socony Mobil-5 (ZSM-5), TiO 2 , and Al 2 O 3 supported materials, were identified as the most up-to-date and recently used catalysts for the removal of NO gas. The main focus of this review is the study of catalyst preparation methods, as this is highly correlated to the behaviour of NO removal. The general mechanisms involved in the system, the Langmuir-Hinshelwood or Eley-Riedeal mechanism, are also discussed. Characterisation analysis affecting the surface and chemical structure of the catalyst is also detailed in this work. Finally, a few major conclusions are drawn and future directions for work on the advancement of the SCR-NH 3 catalyst are suggested.

Hierarchical nanostructured hollow spherical carbon with mesoporous shell as a unique cathode catalyst support in proton exchange membrane fuel cell.

PubMed

Fang, Baizeng; Kim, Jung Ho; Kim, Minsik; Kim, Minwoo; Yu, Jong-Sung

2009-03-07

Hierarchical nanostructured spherical carbon with hollow macroporous core in combination with mesoporous shell has been explored to support Pt cathode catalyst with high metal loading in proton exchange membrane fuel cell (PEMFC). The hollow core-mesoporous shell carbon (HCMSC) has unique structural characteristics such as large specific surface area and mesoporous volume, ensuring uniform dispersion of the supported high loading (60 wt%) Pt nanoparticles with small particle size, and well-developed three-dimensionally interconnected hierarchical porosity network, facilitating fast mass transport. The HCMSC-supported Pt(60 wt%) cathode catalyst has demonstrated markedly enhanced catalytic activity toward oxygen reduction and greatly improved PEMFC polarization performance compared with carbon black Vulcan XC-72 (VC)-supported ones. Furthermore, the HCMSC-supported Pt(40 wt%) or Pt(60 wt%) outperforms the HCMSC-supported Pt(20 wt%) even at a low catalyst loading of 0.2 mg Pt cm(-2) in the cathode, which is completely different from the VC-supported Pt catalysts. The capability of supporting high loading Pt is supposed to accelerate the commercialization of PEMFC due to the anticipated significant reduction in the amount of catalyst support required, diffusion layer thickness and fabricating cost of the supported Pt catalyst electrode.

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.

The X-Ray Binary Population of the Nearby Dwarf Starburst Galaxy IC 10: Variable and Transient X-Ray Sources

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

Laycock, Silas; Cappallo, Rigel; Williams, Benjamin F.

We have monitored the Cassiopeia dwarf galaxy (IC 10) in a series of 10 Chandra ACIS-S observations to capture its variable and transient X-ray source population, which is expected to be dominated by High Mass X-ray Binaries (HMXBs). We present a sample of 21 X-ray sources that are variable between observations at the 3 σ level, from a catalog of 110 unique point sources. We find four transients (flux variability ratio greater than 10) and a further eight objects with ratios >5. The observations span the years 2003–2010 and reach a limiting luminosity of >10{sup 35} erg s{sup −1}, providingmore » sensitivity to X-ray binaries in IC 10 as well as flare stars in the foreground Milky Way. The nature of the variable sources is investigated from light curves, X-ray spectra, energy quantiles, and optical counterparts. The purpose of this study is to discover the composition of the X-ray binary population in a young starburst environment. IC 10 provides a sharp contrast in stellar population age (<10 My) when compared to the Magellanic Clouds (40–200 My) where most of the known HMXBs reside. We find 10 strong HMXB candidates, 2 probable background Active Galactic Nuclei, 4 foreground flare-stars or active binaries, and 5 not yet classifiable sources. Complete classification of the sample requires optical spectroscopy for radial velocity analysis and deeper X-ray observations to obtain higher S/N spectra and search for pulsations. A catalog and supporting data set are provided.« less

The Young L Dwarf 2MASS J11193254-1137466 Is a Planetary-mass Binary

NASA Astrophysics Data System (ADS)

Best, William M. J.; Liu, Michael C.; Dupuy, Trent J.; Magnier, Eugene A.

2017-07-01

We have discovered that the extremely red, low-gravity L7 dwarf 2MASS J11193254-1137466 is a 0.″14 (3.6 au) binary using Keck laser guide star adaptive optics imaging. 2MASS J11193254-1137466 has previously been identified as a likely member of the TW Hydrae Association (TWA). Using our updated photometric distance and proper motion, a kinematic analysis based on the BANYAN II model gives an 82% probability of TWA membership. At TWA’s 10 ± 3 Myr age and using hot-start evolutionary models, 2MASS J11193254-1137466AB is a pair of {3.7}-0.9+1.2 {M}{Jup} brown dwarfs, making it the lowest-mass binary discovered to date. We estimate an orbital period of {90}-50+80 years. One component is marginally brighter in K band but fainter in J band, making this a probable flux-reversal binary, the first discovered with such a young age. We also imaged the spectrally similar TWA L7 dwarf WISEA J114724.10-204021.3 with Keck and found no sign of binarity. Our evolutionary model-derived {T}{eff} estimate for WISEA J114724.10-204021.3 is ≈230 K higher than for 2MASS J11193254-1137466AB, at odds with the spectral similarity of the two objects. This discrepancy suggests that WISEA J114724.10-204021.3 may actually be a tight binary with masses and temperatures very similar to 2MASS J11193254-1137466AB, or further supporting the idea that near-infrared spectra of young ultracool dwarfs are shaped by factors other than temperature and gravity. 2MASS J11193254-1137466AB will be an essential benchmark for testing evolutionary and atmospheric models in the young planetary-mass regime.

Polymer system for gettering hydrogen

DOEpatents

Shepodd, Timothy Jon; Whinnery, LeRoy L.

2000-01-01

A novel composition comprising organic polymer molecules having carbon-carbon double bonds, for removing hydrogen from the atmosphere within enclosed spaces. Organic polymers molecules containing carbon-carbon double bonds throughout their structures, preferably polybutadiene, polyisoprene and derivatives thereof, intimately mixed with an insoluble catalyst composition, comprising a hydrogenation catalyst and a catalyst support, preferably Pd supported on carbon, provide a hydrogen getter composition useful for removing hydrogen from enclosed spaces even in the presence of contaminants such as common atmospheric gases, water vapor, carbon dioxide, ammonia, oil mists, and water. The hydrogen getter composition disclosed herein is particularly useful for removing hydrogen from enclosed spaces containing potentially explosive mixtures of hydrogen and oxygen.

Polymer formulations for gettering hydrogen

DOEpatents

Shepodd, Timothy Jon; Whinnery, LeRoy L.

1998-11-17

A novel composition comprising organic polymer molecules having carbon-carbon double bonds, for removing hydrogen from the atmosphere within enclosed spaces. Organic polymers molecules containing carbon-carbon double bonds throughout their structures, preferably polybutadiene, polyisoprene and derivatives thereof, intimately mixed with an insoluble catalyst composition, comprising a hydrogenation catalyst and a catalyst support, preferably Pd supported on carbon, provide a hydrogen getter composition useful for removing hydrogen from enclosed spaces even in the presence of contaminants such as common atmospheric gases, water vapor, carbon dioxide, ammonia, oil mists, and water. The hydrogen getter composition disclosed herein is particularly useful for removing hydrogen from enclosed spaces containing potentially explosive mixtures of hydrogen and oxygen.

N, P-codoped Mesoporous Carbon Supported PtCox Nanoparticles and Their Superior Electrochemical toward Methanol Oxidation

NASA Astrophysics Data System (ADS)

Cui, Hangjun; Li, Yueming; Liu, Shimin

2018-03-01

In this report, a novel strategy by using the N, P co-doped mesoporous carbon structure as catalyst support to enhance the electrochemical catalytic activity of Pt-based catalysts is proposed. The as-synthesized PtCox@N, P-doped mesoporous carbon nanocomposties have been studied as an anode catalyst toward methanol oxidation, exhibiting greatly improved electrochemical activity and stability compared with Pt@mesoporous carbon. The synergistic effects of N, P dual-doping and porous carbon structure help to achieve better electron transport at the electrode surface, which eventually leads to greatly enhanced catalytic activity compared to the pristine Pt/mesoporous carbon.…

Oxidation of CO and Methanol on Pd-Ni Catalysts Supported on Different Chemically-Treated Carbon Nanofibers

PubMed Central

Calderón, Juan Carlos; Rios Ráfales, Miguel; Nieto-Monge, María Jesús; Pardo, Juan Ignacio; Moliner, Rafael; Lázaro, María Jesús

2016-01-01

In this work, palladium-nickel nanoparticles supported on carbon nanofibers were synthesized, with metal contents close to 25 wt % and Pd:Ni atomic ratios near to 1:2. These catalysts were previously studied in order to determine their activity toward the oxygen reduction reaction. Before the deposition of metals, the carbon nanofibers were chemically treated in order to generate oxygen and nitrogen groups on their surface. Transmission electron microscopy analysis (TEM) images revealed particle diameters between 3 and 4 nm, overcoming the sizes observed for the nanoparticles supported on carbon black (catalyst Pd-Ni CB 1:2). From the CO oxidation at different temperatures, the activation energy Eact for this reaction was determined. These values indicated a high tolerance of the catalysts toward the CO poisoning, especially in the case of the catalysts supported on the non-chemically treated carbon nanofibers. On the other hand, apparent activation energy Eap for the methanol oxidation was also determined finding—as a rate determining step—the COads diffusion to the OHads for the catalysts supported on carbon nanofibers. The results here presented showed that the surface functional groups only play a role in the obtaining of lower particle sizes, which is an important factor in the obtaining of low CO oxidation activation energies. PMID:28335315

Spatially and size selective synthesis of Fe-based nanoparticles on ordered mesoporous supports as highly active and stable catalysts for ammonia decomposition.

PubMed

Lu, An-Hui; Nitz, Joerg-Joachim; Comotti, Massimiliano; Weidenthaler, Claudia; Schlichte, Klaus; Lehmann, Christian W; Terasaki, Osamu; Schüth, Ferdi

2010-10-13

Uniform and highly dispersed γ-Fe(2)O(3) nanoparticles with a diameter of ∼6 nm supported on CMK-5 carbons and C/SBA-15 composites were prepared via simple impregnation and thermal treatment. The nanostructures of these materials were characterized by XRD, Mössbauer spectroscopy, XPS, SEM, TEM, and nitrogen sorption. Due to the confinement effect of the mesoporous ordered matrices, γ-Fe(2)O(3) nanoparticles were fully immobilized within the channels of the supports. Even at high Fe-loadings (up to about 12 wt %) on CMK-5 carbon no iron species were detected on the external surface of the carbon support by XPS analysis and electron microscopy. Fe(2)O(3)/CMK-5 showed the highest ammonia decomposition activity of all previously described Fe-based catalysts in this reaction. Complete ammonia decomposition was achieved at 700 °C and space velocities as high as 60,000 cm(3) g(cat)(-1) h(-1). At a space velocity of 7500 cm(3) g(cat)(-1) h(-1), complete ammonia conversion was maintained at 600 °C for 20 h. After the reaction, the immobilized γ-Fe(2)O(3) nanoparticles were found to be converted to much smaller nanoparticles (γ-Fe(2)O(3) and a small fraction of nitride), which were still embedded within the carbon matrix. The Fe(2)O(3)/CMK-5 catalyst is much more active than the benchmark NiO/Al(2)O(3) catalyst at high space velocity, due to its highly developed mesoporosity. γ-Fe(2)O(3) nanoparticles supported on carbon-silica composites are structurally much more stable over extended periods of time but less active than those supported on carbon. TEM observation reveals that iron-based nanoparticles penetrate through the carbon layer and then are anchored on the silica walls, thus preventing them from moving and sintering. In this way, the stability of the carbon-silica catalyst is improved. Comparison with the silica supported iron oxide catalyst reveals that the presence of a thin layer of carbon is essential for increased catalytic activity.

Carbon corrosion of proton exchange membrane fuel cell catalyst layers studied by scanning transmission X-ray microscopy

NASA Astrophysics Data System (ADS)

Hitchcock, Adam P.; Berejnov, Viatcheslav; Lee, Vincent; West, Marcia; Colbow, Vesna; Dutta, Monica; Wessel, Silvia

2014-11-01

Scanning Transmission X-ray Microscopy (STXM) at the C 1s, F 1s and S 2p edges has been used to investigate degradation of proton exchange membrane fuel cell (PEM-FC) membrane electrode assemblies (MEA) subjected to accelerated testing protocols. Quantitative chemical maps of the catalyst, carbon support and ionomer in the cathode layer are reported for beginning-of-test (BOT), and end-of-test (EOT) samples for two types of carbon support, low surface area carbon (LSAC) and medium surface area carbon (MSAC), that were exposed to accelerated stress testing with upper potentials (UPL) of 1.0, 1.2, and 1.3 V. The results are compared in order to characterize catalyst layer degradation in terms of the amounts and spatial distributions of these species. Pt agglomeration, Pt migration and corrosion of the carbon support are all visualized, and contribute to differing degrees in these samples. It is found that there is formation of a distinct Pt-in-membrane (PTIM) band for all EOT samples. The cathode thickness shrinks due to loss of the carbon support for all MSAC samples that were exposed to the different upper potentials, but only for the most aggressive testing protocol for the LSAC support. The amount of ionomer per unit volume significantly increases indicating it is being concentrated in the cathode as the carbon corrosion takes place. S 2p spectra and mapping of the cathode catalyst layer indicates there are still sulfonate groups present, even in the most damaged material.

Digital image analysis to quantify carbide networks in ultrahigh carbon steels

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

Hecht, Matthew D.; Webler, Bryan A.; Picard, Yoosuf N., E-mail: ypicard@cmu.edu

A method has been developed and demonstrated to quantify the degree of carbide network connectivity in ultrahigh carbon steels through digital image processing and analysis of experimental micrographs. It was shown that the network connectivity and carbon content can be correlated to toughness for various ultrahigh carbon steel specimens. The image analysis approach first involved segmenting the carbide network and pearlite matrix into binary contrast representations via a grayscale intensity thresholding operation. Next, the carbide network pixels were skeletonized and parceled into braches and nodes, allowing the determination of a connectivity index for the carbide network. Intermediate image processing stepsmore » to remove noise and fill voids in the network are also detailed. The connectivity indexes of scanning electron micrographs were consistent in both secondary and backscattered electron imaging modes, as well as across two different (50 × and 100 ×) magnifications. Results from ultrahigh carbon steels reported here along with other results from the literature generally showed lower connectivity indexes correlated with higher Charpy impact energy (toughness). A deviation from this trend was observed at higher connectivity indexes, consistent with a percolation threshold for crack propagation across the carbide network. - Highlights: • A method for carbide network analysis in steels is proposed and demonstrated. • ImageJ method extracts a network connectivity index from micrographs. • Connectivity index consistent in different imaging conditions and magnifications. • Impact energy may plateau when a critical network connectivity is exceeded.« less

High-rate and long-life lithium-ion battery performance of hierarchically hollow-structured NiCo 2O 4/CNT nanocomposite

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

Wang, Jie; Wu, Jianzhong; Wu, Zexing

In this paper, 3D-transition binary metal oxides have been considered as promising anode materials for lithium-ion batteries with improved reversible capacity, structural stability and electronic conductivity compared with single metal oxides. Here, carbon nanotube supported NiCo 2O 4 nanoparticles (NiCo 2O 4/CNT) with 3D hierarchical hollow structure are fabricated via a simple one-pot method. The NiCo 2O 4 nanoparticles with interconnected pores are consists of small nanocrystals. When used as anode material for the lithium-ion battery, NiCo 2O 4/CNT exhibits enhanced electrochemical performance than that of Co 3O 4/CNT and NiO/CNT. Moreover, ultra-high discharge/charge stability was obtained for 4000 cyclesmore » at a current density of 5 A g –1. The superior battery performance of NiCo 2O 4 nanoparticles is probably attributed to the special structural features and physical characteristics, including integrity, hollow structure with interconnected pores, which providing sufficient accommodation for the volume change during charge/discharge process. Besides, the consisting of ultra-small crystals enhanced the utility of active material, and intimate interaction with CNTs improved the electron-transfer rate.« less

High-rate and long-life lithium-ion battery performance of hierarchically hollow-structured NiCo 2O 4/CNT nanocomposite

DOE PAGES

Wang, Jie; Wu, Jianzhong; Wu, Zexing; ...

2017-05-17

In this paper, 3D-transition binary metal oxides have been considered as promising anode materials for lithium-ion batteries with improved reversible capacity, structural stability and electronic conductivity compared with single metal oxides. Here, carbon nanotube supported NiCo 2O 4 nanoparticles (NiCo 2O 4/CNT) with 3D hierarchical hollow structure are fabricated via a simple one-pot method. The NiCo 2O 4 nanoparticles with interconnected pores are consists of small nanocrystals. When used as anode material for the lithium-ion battery, NiCo 2O 4/CNT exhibits enhanced electrochemical performance than that of Co 3O 4/CNT and NiO/CNT. Moreover, ultra-high discharge/charge stability was obtained for 4000 cyclesmore » at a current density of 5 A g –1. The superior battery performance of NiCo 2O 4 nanoparticles is probably attributed to the special structural features and physical characteristics, including integrity, hollow structure with interconnected pores, which providing sufficient accommodation for the volume change during charge/discharge process. Besides, the consisting of ultra-small crystals enhanced the utility of active material, and intimate interaction with CNTs improved the electron-transfer rate.« less

Multi-class SVM model for fMRI-based classification and grading of liver fibrosis

NASA Astrophysics Data System (ADS)

Freiman, M.; Sela, Y.; Edrei, Y.; Pappo, O.; Joskowicz, L.; Abramovitch, R.

2010-03-01

We present a novel non-invasive automatic method for the classification and grading of liver fibrosis from fMRI maps based on hepatic hemodynamic changes. This method automatically creates a model for liver fibrosis grading based on training datasets. Our supervised learning method evaluates hepatic hemodynamics from an anatomical MRI image and three T2*-W fMRI signal intensity time-course scans acquired during the breathing of air, air-carbon dioxide, and carbogen. It constructs a statistical model of liver fibrosis from these fMRI scans using a binary-based one-against-all multi class Support Vector Machine (SVM) classifier. We evaluated the resulting classification model with the leave-one out technique and compared it to both full multi-class SVM and K-Nearest Neighbor (KNN) classifications. Our experimental study analyzed 57 slice sets from 13 mice, and yielded a 98.2% separation accuracy between healthy and low grade fibrotic subjects, and an overall accuracy of 84.2% for fibrosis grading. These results are better than the existing image-based methods which can only discriminate between healthy and high grade fibrosis subjects. With appropriate extensions, our method may be used for non-invasive classification and progression monitoring of liver fibrosis in human patients instead of more invasive approaches, such as biopsy or contrast-enhanced imaging.

Facile Fabrication of Platinum-Cobalt Alloy Nanoparticles with Enhanced Electrocatalytic Activity for a Methanol Oxidation Reaction

PubMed Central

Huang, Huihong; Hu, Xiulan; Zhang, Jianbo; Su, Nan; Cheng, JieXu

2017-01-01

Decreasing the cost associated with platinum-based catalysts along with improving their catalytic properties is a major challenge for commercial direct methanol fuel cells. In this work, a simple and facile strategy was developed for the more efficient preparation of multi-walled carbon nanotube (MWCNT) -supported Pt/CoPt composite nanoparticles (NPs) via solution plasma sputtering with subsequent thermal annealing. Quite different from general wet synthesis methods, Pt/CoPt composite NPs were directly derived from metal wire electrodes without any additions. The obtained Pt/CoPt/MWCNTs composite catalysts exhibited tremendous improvement in the electro-oxidation of methanol in acidic media with mass activities of 1719 mA mg−1Pt. This value is much higher than that of previous reports of Pt-Co alloy and commercial Pt/C (3.16 times) because of the many active sites and clean surface of the catalysts. The catalysts showed good stability due to the special synergistic effects of the CoPt alloy. Pt/CoPt/MWCNTs can be used as a promising catalyst for direct methanol fuel cells. In addition, this solution plasma sputtering-assisted synthesis method introduces a general and feasible route for the synthesis of binary alloys. PMID:28358143

Binary ROCs in Perception and Recognition Memory Are Curved

ERIC Educational Resources Information Center

Dube, Chad; Rotello, Caren M.

2012-01-01

In recognition memory, a classic finding is that receiver operating characteristics (ROCs) are curvilinear. This has been taken to support the fundamental assumptions of signal detection theory (SDT) over discrete-state models such as the double high-threshold model (2HTM), which predicts linear ROCs. Recently, however, Broder and Schutz (2009)…

Reconsidering Children's Encounters with Nature and Place Using Posthumanism

ERIC Educational Resources Information Center

Malone, Karen

2016-01-01

This article explores and reconsiders the view of children's encounters with place as central to a place-based pedagogy that seeks to dismantle rather than support constructions of a nature-culture binary. I unpack the current fervour for reinserting the child in nature and nature-based education as a significant phenomenon in environmental and…

Gender classification from face images by using local binary pattern and gray-level co-occurrence matrix

NASA Astrophysics Data System (ADS)

Uzbaş, Betül; Arslan, Ahmet

2018-04-01

Gender is an important step for human computer interactive processes and identification. Human face image is one of the important sources to determine gender. In the present study, gender classification is performed automatically from facial images. In order to classify gender, we propose a combination of features that have been extracted face, eye and lip regions by using a hybrid method of Local Binary Pattern and Gray-Level Co-Occurrence Matrix. The features have been extracted from automatically obtained face, eye and lip regions. All of the extracted features have been combined and given as input parameters to classification methods (Support Vector Machine, Artificial Neural Networks, Naive Bayes and k-Nearest Neighbor methods) for gender classification. The Nottingham Scan face database that consists of the frontal face images of 100 people (50 male and 50 female) is used for this purpose. As the result of the experimental studies, the highest success rate has been achieved as 98% by using Support Vector Machine. The experimental results illustrate the efficacy of our proposed method.

The construction of support vector machine classifier using the firefly algorithm.

PubMed

Chao, Chih-Feng; Horng, Ming-Huwi

2015-01-01

The setting of parameters in the support vector machines (SVMs) is very important with regard to its accuracy and efficiency. In this paper, we employ the firefly algorithm to train all parameters of the SVM simultaneously, including the penalty parameter, smoothness parameter, and Lagrangian multiplier. The proposed method is called the firefly-based SVM (firefly-SVM). This tool is not considered the feature selection, because the SVM, together with feature selection, is not suitable for the application in a multiclass classification, especially for the one-against-all multiclass SVM. In experiments, binary and multiclass classifications are explored. In the experiments on binary classification, ten of the benchmark data sets of the University of California, Irvine (UCI), machine learning repository are used; additionally the firefly-SVM is applied to the multiclass diagnosis of ultrasonic supraspinatus images. The classification performance of firefly-SVM is also compared to the original LIBSVM method associated with the grid search method and the particle swarm optimization based SVM (PSO-SVM). The experimental results advocate the use of firefly-SVM to classify pattern classifications for maximum accuracy.

The Construction of Support Vector Machine Classifier Using the Firefly Algorithm

PubMed Central

Chao, Chih-Feng; Horng, Ming-Huwi

2015-01-01

The setting of parameters in the support vector machines (SVMs) is very important with regard to its accuracy and efficiency. In this paper, we employ the firefly algorithm to train all parameters of the SVM simultaneously, including the penalty parameter, smoothness parameter, and Lagrangian multiplier. The proposed method is called the firefly-based SVM (firefly-SVM). This tool is not considered the feature selection, because the SVM, together with feature selection, is not suitable for the application in a multiclass classification, especially for the one-against-all multiclass SVM. In experiments, binary and multiclass classifications are explored. In the experiments on binary classification, ten of the benchmark data sets of the University of California, Irvine (UCI), machine learning repository are used; additionally the firefly-SVM is applied to the multiclass diagnosis of ultrasonic supraspinatus images. The classification performance of firefly-SVM is also compared to the original LIBSVM method associated with the grid search method and the particle swarm optimization based SVM (PSO-SVM). The experimental results advocate the use of firefly-SVM to classify pattern classifications for maximum accuracy. PMID:25802511

TOPoS. IV. Chemical abundances from high-resolution observations of seven extremely metal-poor stars

NASA Astrophysics Data System (ADS)

Bonifacio, P.; Caffau, E.; Spite, M.; Spite, F.; Sbordone, L.; Monaco, L.; François, P.; Plez, B.; Molaro, P.; Gallagher, A. J.; Cayrel, R.; Christlieb, N.; Klessen, R. S.; Koch, A.; Ludwig, H.-G.; Steffen, M.; Zaggia, S.; Abate, C.

2018-04-01

Context. Extremely metal-poor (EMP) stars provide us with indirect information on the first generations of massive stars. The TOPoS survey has been designed to increase the census of these stars and to provide a chemical inventory that is as detailed as possible. Aims: Seven of the most iron-poor stars have been observed with the UVES spectrograph at the ESO VLT Kueyen 8.2 m telescope to refine their chemical composition. Methods: We analysed the spectra based on 1D LTE model atmospheres, but also used 3D hydrodynamical simulations of stellar atmospheres. Results: We measured carbon in six of the seven stars: all are carbon-enhanced and belong to the low-carbon band, defined in the TOPoS II paper. We measured lithium (A(Li) = 1.9) in the most iron-poor star (SDSS J1035+0641, [Fe/H] <-5.2). We were also able to measure Li in three stars at [Fe/H] -4.0, two of which lie on the Spite plateau. We confirm that SDSS J1349+1407 is extremely rich in Mg, but not in Ca. It is also very rich in Na. Several of our stars are characterised by low α-to-iron ratios. Conclusions: The lack of high-carbon band stars at low metallicity can be understood in terms of evolutionary timescales of binary systems. The detection of Li in SDSS J1035+0641 places a strong constraint on theories that aim at solving the cosmological lithium problem. The Li abundance of the two warmer stars at [Fe/H] -4.0 places them on the Spite plateau, while the third, cooler star, lies below. We argue that this suggests that the temperature at which Li depletion begins increases with decreasing [Fe/H]. SDSS J1349+1407 may belong to a class of Mg-rich EMP stars. We cannot assess if there is a scatter in α-to-iron ratios among the EMP stars or if there are several discrete populations. However, the existence of stars with low α-to-iron ratios is supported by our observations. Based on observations obtained at ESO Paranal Observatory, Programmes 189.D-0165,090.D-0306, 093.D-0136, and 096.D-0468.

Properties of an eclipsing double white dwarf binary NLTT 11748

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

Kaplan, David L.; Walker, Arielle N.; Marsh, Thomas R.

2014-01-10

We present high-quality ULTRACAM photometry of the eclipsing detached double white dwarf binary NLTT 11748. This system consists of a carbon/oxygen white dwarf and an extremely low mass (<0.2 M {sub ☉}) helium-core white dwarf in a 5.6 hr orbit. To date, such extremely low-mass white dwarfs, which can have thin, stably burning outer layers, have been modeled via poorly constrained atmosphere and cooling calculations where uncertainties in the detailed structure can strongly influence the eventual fates of these systems when mass transfer begins. With precise (individual precision ≈1%), high-cadence (≈2 s), multicolor photometry of multiple primary and secondary eclipsesmore » spanning >1.5 yr, we constrain the masses and radii of both objects in the NLTT 11748 system to a statistical uncertainty of a few percent. However, we find that overall uncertainty in the thickness of the envelope of the secondary carbon/oxygen white dwarf leads to a larger (≈13%) systematic uncertainty in the primary He WD's mass. Over the full range of possible envelope thicknesses, we find that our primary mass (0.136-0.162 M {sub ☉}) and surface gravity (log (g) = 6.32-6.38; radii are 0.0423-0.0433 R {sub ☉}) constraints do not agree with previous spectroscopic determinations. We use precise eclipse timing to detect the Rømer delay at 7σ significance, providing an additional weak constraint on the masses and limiting the eccentricity to ecos ω = (– 4 ± 5) × 10{sup –5}. Finally, we use multicolor data to constrain the secondary's effective temperature (7600 ± 120 K) and cooling age (1.6-1.7 Gyr).« less

The circumbinary dusty disk of upsilon Sgr revealed by mid-IR interferometric observations with the VLTI/MIDI

NASA Astrophysics Data System (ADS)

Bonneau, D.; Netolický, M.; Chesneau, O.; Harmanec, P.; Koubský, P.; Mourard, D.; Stee, P.

2008-11-01

The first mid-IR interferometric observations of a hydrogen-deficient binary star, υ Sgr, were carried out using the MIDI/VLTI instrument between April 2007 and May 2008. The dusty circumbinary envelope is resolved in the N band (8-13.5 μ m), and has a typical size of 20 x 14 mas. The calibrated fringe visibilities, the mid-IR spectrum and the SED were fitted using models computed with the radiative transfer code MC3D using several mixtures of carbon and silicate dust, in order to determine the geometry and chemical composition of the envelope. The best model we obtain is a geometrically thin and dense disk with an inner radius of R_{in} ≃ 6.0AU and a scale height h_{100} ≃ 3.5 AU. The inclination of the disk is i ≃ 50° and its position angle is PA ≃ 80°. The chemical composition of the dust is approximatelya ratio of 60% of carbon dust and 40% of silicate dust. We constrained for the first time the geometry and the chemistry of the circumbinary dusty envelope of υ Sgr. It is now clear that the components of υ Sgr are massive stars (> 10 M_⊙) and the results are compatible with evolutionary scenario proposed by Delgado & Thomas (1981) of a binary with massive components experiencing several phases of important mass transfer leading to the hydrogen-deficient primary star. However, complementary spectro-interferometric observations in the near infrared and the visible are mandatory to investigate the complex structure of the inner circumstellar environment and directly resolve the stellar components of the υ Sgr system.

Influence of Liquid Structure on Fickian Diffusion in Binary Mixtures of n-Hexane and Carbon Dioxide Probed by Dynamic Light Scattering, Raman Spectroscopy, and Molecular Dynamics Simulations.

PubMed

Klein, Tobias; Wu, Wenchang; Rausch, Michael Heinrich; Giraudet, Cédric; Koller, Thomas M; Fröba, Andreas Paul

2018-06-11

This study contributes to a fundamental understanding how the liquid structure in a model system consisting of weakly associative n-hexane ( n-C 6 H 14 ) and carbon dioxide (CO 2 ) influences the Fickian diffusion process. For this, the benefits of light scattering experiments and molecular dynamics (MD) simulations at macroscopic thermodynamic equilibrium were combined synergistically. Our reference Fickian diffusivities measured by dynamic light scattering (DLS) revealed an unusual trend with increasing CO 2 mole fractions up to a CO 2 concentration of about 70 mol%, which agrees with our simulation results. The molecular impacts on the Fickian diffusion were analyzed by MD simulations, where kinetic contributions related to the Maxwell-Stefan (MS) diffusivity and structural contributions quantified by the thermodynamic factor were studied separately. Both the MS diffusivity and the thermodynamic factor indicate the deceleration of Fickian diffusion compared to an ideal mixture behavior. Computed radial distribution functions as well as a significant blue-shift of the CH-stretching modes of n-C 6 H 14 identified by Raman spectroscopy show that the slowing-down of the diffusion is caused by a structural organization in the binary mixtures over a broad concentration range in the form of self-associated n-C 6 H 14 and CO 2 domains. These networks start to form close to the infinite dilution limits and seem to have their largest extent at a solute-solvent transition point at about 70 mol% of CO 2 . The current results not only improve the general understanding of mass diffusion in liquids, but also serve to develop sound prediction models for Fick diffusivities.

Membership, binarity, and rotation of F-G-K stars in the open cluster Blanco 1

NASA Astrophysics Data System (ADS)

Mermilliod, J.-C.; Platais, I.; James, D. J.; Grenon, M.; Cargile, P. A.

2008-07-01

Context: The nearby open cluster Blanco 1 is of considerable astrophysical interest for formation and evolution studies of open clusters because it is the third highest Galactic latitude cluster known. It has been observed often, but so far no definitive and comprehensive membership determination is readily available. Aims: An observing programme was carried out to study the stellar population of Blanco 1, and especially the membership and binary frequency of the F5-K0 dwarfs. Methods: We obtained radial-velocities with the CORAVEL spectrograph in the field of Blanco 1 for a sample of 148 F-G-K candidate stars in the magnitude range 10 < V < 14. New proper motions and UBVI CCD photometric data from two extensive surveys were obtained independently and are used to establish reliable cluster membership assignments in concert with radial-velocity data. Results: The membership of 68 stars is confirmed on the basis of proper motion, radial velocity, and photometric criteria. Fourteen spectroscopic- and suspected binaries (2 SB2s, 9 SB1s, 3 SB?) have been discovered among the confirmed members. Thirteen additional stars are located above the main sequence or close to the binary ridge, with radial velocities and proper motions supporting their membership. These are probable binaries with wide separations. Nine binaries (7 SB1 and 2 SB2) were detected among the field stars. The spectroscopic binary frequency among members is 20% (14/68); however, the overall binary rate reaches 40% (27/68) if one includes the photometric binaries. The cluster mean heliocentric radial velocity is +5.53 ± 0.11 km s-1 based on the most reliable 49 members. The V sin i distribution is similar to that of the Pleiades, confirming the age similarities between the two clusters. Conclusions: This study clearly demonstrates that, in spite of the cluster's high Galactic latitude, three membership criteria - radial velocity, proper motion, and photometry - are necessary for performing a reliable membership selection. Furthermore, even with accurate and extensive data, ambiguous cases still remain. Based on observations collected with the Danish 1.54-m and the Swiss telescopes at the European Southern Observatory, La Silla, Chile, and with the old YALO 1-m telescope at the Cerro Tololo InterAmerican Observatory, Chile. Table [see full textsee full textsee full textsee full textsee full textsee full text] is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/485/95

STABLE CONIC-HELICAL ORBITS OF PLANETS AROUND BINARY STARS: ANALYTICAL RESULTS

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

Oks, E.

2015-05-10

Studies of planets in binary star systems are especially important because it was estimated that about half of binary stars are capable of supporting habitable terrestrial planets within stable orbital ranges. One-planet binary star systems (OBSS) have a limited analogy to objects studied in atomic/molecular physics: one-electron Rydberg quasimolecules (ORQ). Specifically, ORQ, consisting of two fully stripped ions of the nuclear charges Z and Z′ plus one highly excited electron, are encountered in various plasmas containing more than one kind of ion. Classical analytical studies of ORQ resulted in the discovery of classical stable electronic orbits with the shape ofmore » a helix on the surface of a cone. In the present paper we show that despite several important distinctions between OBSS and ORQ, it is possible for OBSS to have stable planetary orbits in the shape of a helix on a conical surface, whose axis of symmetry coincides with the interstellar axis; the stability is not affected by the rotation of the stars. Further, we demonstrate that the eccentricity of the stars’ orbits does not affect the stability of the helical planetary motion if the center of symmetry of the helix is relatively close to the star of the larger mass. We also show that if the center of symmetry of the conic-helical planetary orbit is relatively close to the star of the smaller mass, a sufficiently large eccentricity of stars’ orbits can switch the planetary motion to the unstable mode and the planet would escape the system. We demonstrate that such planets are transitable for the overwhelming majority of inclinations of plane of the stars’ orbits (i.e., the projections of the planet and the adjacent start on the plane of the sky coincide once in a while). This means that conic-helical planetary orbits at binary stars can be detected photometrically. We consider, as an example, Kepler-16 binary stars to provide illustrative numerical data on the possible parameters and the stability of the conic-helical planetary orbits, as well as on the transitability. Then for the general case, we also show that the power of the gravitational radiation due to this planet can be comparable or even exceed the power of the gravitational radiation due to the stars in the binary. This means that in the future, with a progress of gravitational wave detectors, the presence of a planet in a conic-helical orbit could be revealed by the noticeably enhanced gravitational radiation from the binary star system.« less

Accretion of chemically fractionated material on a wide binary with a blue straggler

NASA Astrophysics Data System (ADS)

Desidera, S.; Gratton, R. G.; Lucatello, S.; Endl, M.; Udry, S.

2007-02-01

Context: The components of the wide binary HIP 64030 = HD 113984 show a large (about 0.25 dex) iron content difference (Desidera et al. 2006). The positions of the components on the color magnitude diagram suggest that the primary is a blue straggler. Aims: We studied the abundance difference of several elements besides iron, and we searched for stellar and substellar companions around the components to unveil the origin of the observed iron difference. Methods: A line-by-line differential abundance analysis for several elements was performed for iron, while suitable spectral synthesis was performed for C, N, and Li. High precision radial velocities obtained with the iodine cell were combined with available literature data. Results: The analysis of additional elements shows that the abundance difference for the elements studied increases with increasing condensation temperature, suggesting that accretion of chemically fractionated material might have occurred in the system. Alteration of C and N likely due to CNO processing is also observed. We also show that the primary is a spectroscopic binary with a period of 445 days and moderate eccentricity. The minimum mass of the companion is 0.17~M⊙. Conclusions: .Two scenarios were explored to explain the observed abundance pattern. In the first, all abundance anomalies arise on the blue straggler. If this is the case, the dust-gas separation may have been occurred in a circumbinary disk around the blue straggler and its expected white dwarf companion, as observed in several RV Tauri and post AGB binaries. In the second scenario, accretion of dust-rich material occurred on the secondary. This would also explain the anomalous carbon isotopic ratio of the secondary. Such a scenario requires that a substantial amount of mass lost by the central binary has been accreted by the wide component. Further studies to compare the two scenarios are proposed. Based on observations collected at the European Southern Observatory, Chile, using FEROS spectrograph (proposal ID: 70.D-0081), on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundacion Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, and on observations made at McDonald Observatory.

Discovery of carbon-vacancy ordering in Nb4AlC3–x under the guidance of first-principles calculations

PubMed Central

Zhang, Hui; Hu, Tao; Wang, Xiaohui; Li, Zhaojin; Hu, Minmin; Wu, Erdong; Zhou, Yanchun

2015-01-01

The conventional wisdom to tailor the properties of binary transition metal carbides by order-disorder phase transformation has been inapplicable for the machinable ternary carbides (MTCs) due to the absence of ordered phase in bulk sample. Here, the presence of an ordered phase with structural carbon vacancies in Nb4AlC3–x (x ≈ 0.3) ternary carbide is predicted by first-principles calculations, and experimentally identified for the first time by transmission electron microscopy and micro-Raman spectroscopy. Consistent with the first-principles prediction, the ordered phase, o-Nb4AlC3, crystalizes in P63/mcm with a = 5.423 Å, c = 24.146 Å. Coexistence of ordered (o-Nb4AlC3) and disordered (Nb4AlC3–x) phase brings about abundant domains with irregular shape in the bulk sample. Both heating and electron irradiation can induce the transformation from o-Nb4AlC3 to Nb4AlC3–x. Our findings may offer substantial insights into the roles of carbon vacancies in the structure stability and order-disorder phase transformation in MTCs. PMID:26388153

Thermal aging of electrolytes used in lithium-ion batteries - An investigation of the impact of protic impurities and different housing materials

NASA Astrophysics Data System (ADS)

Handel, Patricia; Fauler, Gisela; Kapper, Katja; Schmuck, Martin; Stangl, Christoph; Fischer, Roland; Uhlig, Frank; Koller, Stefan

2014-12-01

Thermal degradation products in lithium-ion batteries result mainly from hydrolysis sensitivity of lithium hexafluorophosphate (LiPF6). As organic carbonate solvents contain traces of protic impurities, the thermal decomposition of electrolytes is enhanced. Therefore, resulting degradation products are studied with nuclear magnetic resonance spectroscopy (NMR) and gas chromatography mass spectrometry (GC-MS). The electrolyte contains 1 M LiPF6 in a binary mixture of ethylene carbonate (EC) and diethylene carbonate (DEC) in a ratio of 1:2 (v/v) and is aged at ambient and elevated temperature. The impact of protic impurities, either added as deionized water or incorporated in positive electrode material, upon aging is investigated. Further, the influence of different housing materials on the electrolyte degradation is shown. Difluorophosphoric acid is identified as main decomposition product by NMR-spectroscopy. Traces of other decomposition products are determined by headspace GC-MS. Acid-base and coulometric titration are used to determine the total amount of acid and water content upon aging, respectively. The aim of this investigation is to achieve profound understanding about the thermal decomposition of one most common used electrolyte in a battery-like housing material.

Normal and Outlying Populations of the Milky Way Stellar Halo at [Fe/H] <-2

NASA Astrophysics Data System (ADS)

Cohen, Judith G.; Christlieb, Norbert; Thompson, Ian; McWilliam, Andrew; Shectman, Stephen; Reimers, Dieter; Wisotzki, Lutz; Kirby, Evan

2013-11-01

From detailed abundance analysis of >100 Hamburg/ESO candidate extremely metal-poor (EMP) stars we find 45 with [Fe/H] < -3.0 dex. We identify a heretofore unidentified group: Ca-deficient stars with sub-solar [Ca/Fe] ratios and the lowest neutron-capture abundances; the Ca-deficient group comprises ~10% of the sample, excluding Carbon stars. Our radial velocity distribution shows that the carbon-enhanced stars with no s-process enhancements, CEMP-no, and which do not show C2 bands are not preferentially binary systems. Ignoring Carbon stars, approximately 15% of our sample are strong (>=5σ) outliers in one or more elements between Mg and Ni; this rises to ~19% if very strong (>=10σ) outliers for Sr and Ba are included. Examples include: HE0305-0554 with the lowest [Ba/H] known; HE1012-1540 and HE2323-0256, two (non-velocity variable) C-rich stars with very strong [Mg,Al/Fe] enhancements; and HE1226-1149, an extremely r-process rich star. Based in part on observations obtained in part at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.

Physically unclonable cryptographic primitives using self-assembled carbon nanotubes.

PubMed

Hu, Zhaoying; Comeras, Jose Miguel M Lobez; Park, Hongsik; Tang, Jianshi; Afzali, Ali; Tulevski, George S; Hannon, James B; Liehr, Michael; Han, Shu-Jen

2016-06-01

Information security underpins many aspects of modern society. However, silicon chips are vulnerable to hazards such as counterfeiting, tampering and information leakage through side-channel attacks (for example, by measuring power consumption, timing or electromagnetic radiation). Single-walled carbon nanotubes are a potential replacement for silicon as the channel material of transistors due to their superb electrical properties and intrinsic ultrathin body, but problems such as limited semiconducting purity and non-ideal assembly still need to be addressed before they can deliver high-performance electronics. Here, we show that by using these inherent imperfections, an unclonable electronic random structure can be constructed at low cost from carbon nanotubes. The nanotubes are self-assembled into patterned HfO2 trenches using ion-exchange chemistry, and the width of the trench is optimized to maximize the randomness of the nanotube placement. With this approach, two-dimensional (2D) random bit arrays are created that can offer ternary-bit architecture by determining the connection yield and switching type of the nanotube devices. As a result, our cryptographic keys provide a significantly higher level of security than conventional binary-bit architecture with the same key size.

Physically unclonable cryptographic primitives using self-assembled carbon nanotubes

NASA Astrophysics Data System (ADS)

Hu, Zhaoying; Comeras, Jose Miguel M. Lobez; Park, Hongsik; Tang, Jianshi; Afzali, Ali; Tulevski, George S.; Hannon, James B.; Liehr, Michael; Han, Shu-Jen

2016-06-01

Information security underpins many aspects of modern society. However, silicon chips are vulnerable to hazards such as counterfeiting, tampering and information leakage through side-channel attacks (for example, by measuring power consumption, timing or electromagnetic radiation). Single-walled carbon nanotubes are a potential replacement for silicon as the channel material of transistors due to their superb electrical properties and intrinsic ultrathin body, but problems such as limited semiconducting purity and non-ideal assembly still need to be addressed before they can deliver high-performance electronics. Here, we show that by using these inherent imperfections, an unclonable electronic random structure can be constructed at low cost from carbon nanotubes. The nanotubes are self-assembled into patterned HfO2 trenches using ion-exchange chemistry, and the width of the trench is optimized to maximize the randomness of the nanotube placement. With this approach, two-dimensional (2D) random bit arrays are created that can offer ternary-bit architecture by determining the connection yield and switching type of the nanotube devices. As a result, our cryptographic keys provide a significantly higher level of security than conventional binary-bit architecture with the same key size.

Highly uniform distribution of Pt nanoparticles on N-doped hollow carbon spheres with enhanced durability for oxygen reduction reaction

DOE PAGES

Shi, Qiurong; Zhu, Chengzhou; Engelhard, Mark H.; ...

2017-01-19

Here, carbon-supported Pt nanostructures currently exhibited great potential in polymer electrolyte membrane fuel cells. Nitrogen-doped hollow carbon spheres (NHCSs) with extra low density and high specific surface area are promising carbon support for loading Pt NPs. The doped heteroatom of nitrogen could not only contribute to the active activity for the oxygen reduction reaction (ORR), but also shows a strong interaction with Pt NPs for entrapping them from dissolution/migration. This synergetic effect/interaction resulted in the uniform dispersion and strong combination of the Pt NPs on the carbon support and thus play a significant role in hindering the degradation of themore » catalytic activities of Pt NPs. As expected, the as-obtained Pt/NHCSs displayed improved catalytic activity and superior durability toward ORR.« less

A polyacrylonitrile copolymer-silica template for three-dimensional hierarchical porous carbon as a Pt catalyst support for the oxygen reduction reaction.

PubMed

Liu, Minmin; Li, Jian; Cai, Chao; Zhou, Ziwei; Ling, Yun; Liu, Rui

2017-08-01

Herein, we report a novel route to construct a hierarchical three-dimensional porous carbon (3DC) through a copolymer-silica assembly. In the synthesis, silica acts as a hard template and leads to the formation of an interconnected 3D macropore, whereas styrene-co-acrylonitrile polymer has been used as both a carbon source and a soft template for micro- and meso-pores. The obtained 3DC materials possess a large surface area (∼550.5 m 2 g -1 ), which facilitates high dispersion of Pt nanoparticles on the carbon support. The 3DC-supported Pt electrocatalyst shows excellent performance in the oxygen reduction reaction (ORR). The easy processing ability along with the characteristics of hierarchical porosity offers a new strategy for the preparation of carbon nanomaterials for energy application.