2,993 research outputs found

    A program for computing shock-tube gas dynamic properties

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    Computer program calculates thermodynamic properties from basic spectroscopic data. Program capacity is a mixture of 100 different species composed of ten different elements. The output is a complete thermodynamic and chemical description of the gas

    Shock-tube thermochemistry tables for high- temperature gases, 90% carbon dioxide and 10% nitrogen, volume 2

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    Shock tube tabulated computer equilibrium thermodynamic properties for carbon dioxide and nitrogen mixtur

    A database for the industrial trawl fishery of Cote d'Ivoire

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    Fishery statistics for the industrial trawl fishery of Cote d'Ivoire have been well documented since 1968. However, data processing has changed significantly with time and some of the data files have been lost. In 1997, the Centre de Recherches Oceanologiques d'Abidjan decided to retrieve and process all trawl data available from different sources. This paper gives an overview of the database covering the period 1968 to 1997 and describes its coverage, format, structure and use. The database was developed using MS ACCESS and is a powerful tool for storing information about this fishery, and for analysis of its dynamics over a period of 30 years

    A deep, wide-field search for substellar members in NGC 2264

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    We report the first results of our ongoing campaign to discover the first brown dwarfs (BD) in NGC 2264, a young (3 Myr), populous star forming region for which our optical studies have revealed a very high density of potential candidates - 236 in << 1 deg2^2 - from the substellar limit down to at least ∼\sim 20 MJup_{\rm Jup} for zero reddening. Candidate BD were first selected using wide field (I,zI,z) band imaging with CFH12K, by reference to current theoretical isochrones. Subsequently, 79 (33%) of the I,zI,z sample were found to have near-infrared 2MASS photometry (JHKsJHK_s ±\pm 0.3 mag. or better), yielding dereddened magnitudes and allowing further investigation by comparison with the location of NextGen and DUSTY isochrones in colour-colour and colour-magnitude diagrams involving various combinations of II,JJ,HH and KsK_s. We discuss the status and potential substellarity of a number of relatively unreddened (Av_{\rm v} << 5) likely low-mass members in our sample, but in spite of the depth of our observations in I,zI,z, we are as yet unable to unambiguously identify substellar candidates using only 2MASS data. Nevertheless, there are excellent arguments for considering two faint (observed II ∼\sim 18.4 and 21.2) objects as cluster candidates with masses respectively at or rather below the hydrogen burning limit. More current candidates could be proven to be cluster members with masses around 0.1 M⊙_{\odot} {\it via} gravity-sensitive spectroscopy, and deeper near-infrared imaging will surely reveal a hitherto unknown population of young brown dwarfs in this region, accessible to the next generation of deep near-infrared surveys.Comment: 10 pages, 12 figures, accepted by A&

    Proximity effect between two superconductors spatially resolved by scanning tunneling spectroscopy

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    We present a combined experimental and theoretical study of the proximity effect in an atomic-scale controlled junction between two different superconductors. Elaborated on a Si(111) surface, the junction comprises a Pb nanocrystal with an energy gap of 1.2 meV, connected to a crystalline atomic monolayer of lead with a gap of 0.23 meV. Using in situ scanning tunneling spectroscopy we probe the local density of states of this hybrid system both in space and in energy, at temperatures below and above the critical temperature of the superconducting monolayer. Direct and inverse proximity effects are revealed with high resolution. Our observations are precisely explained with the help of a self-consistent solution of the Usadel equations. In particular, our results demonstrate that in the vicinity of the Pb islands, the Pb monolayer locally develops a finite proximity-induced superconducting order parameter, well above its own bulk critical temperature. This leads to a giant proximity effect where the superconducting correlations penetrate inside the monolayer a distance much larger than in a non-superconducting metal.Comment: 13 pages, 14 figures, accepted for publication in Physical Review

    Shock-tube thermochemistry tables for high-temperature gases. Volume 5: Carbon dioxide

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    Equilibrium thermodynamic properties and species concentrations for carbon dioxide are tabulated for moving, standing, and reflected shock waves. Initial pressures range from 6.665 to 6665 N/sq m (0.05 to 50.0 torr), and temperatures from 2,000 to over 80,000K. In this study, 20 molecular and atomic species were considered

    Shock-tube thermochemistry tables for high-temperature gases. Volume 4 - Nitrogen

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    Shock tube thermochemistry tables for high temperature gase

    Gravitational Lensing as Signal and Noise in Lyman-alpha Forest Measurements

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    In Lyman-alpha forest measurements it is generally assumed that quasars are mere background light sources which are uncorrelated with the forest. Gravitational lensing of the quasars violates this assumption. This effect leads to a measurement bias, but more interestingly it provides a valuable signal. The lensing signal can be extracted by correlating quasar magnitudes with the flux power spectrum and with the flux decrement. These correlations will be challenging to measure but their detection provides a direct measure of how features in the Lyman-alpha forest trace the underlying mass density field. Observing them will test the fundamental hypothesis that fluctuations in the forest are predominantly driven by fluctuations in mass, rather than in the ionizing background, helium reionization or winds. We discuss ways to disentangle the lensing signal from other sources of such correlations, including dust, continuum and background residuals. The lensing-induced measurement bias arises from sample selection: one preferentially collects spectra of magnified quasars which are behind overdense regions. This measurement bias is ~0.1-1% for the flux power spectrum, optical depth and the flux probability distribution. Since the effect is systematic, quantities such as the amplitude of the flux power spectrum averaged across scales should be interpreted with care.Comment: 22 pages, 8 figures; v2: references added, discussion expanded, matches PRD accepted versio

    Surface and Bulk Structural Properties of Single Crystalline Sr3Ru2O7

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    We report temperature and thermal-cycling dependence of surface and bulk structures of double-layered perovskite Sr3Ru2O7 single crystals. The surface and bulk structures were investigated using low-energy electron diffraction (LEED) and single-crystal X-ray diffraction (XRD) techniques, respectively. Single-crystal XRD data is in good agreement with previous reports for the bulk structure with RuO6 octahedral rotation, which increases with decreasing temperature (~ 6.7(6)degrees at 300 K and ~ 8.1(2) degrees at 90 K). LEED results reveal that the octahedra at the surface are much more distorted with a higher rotation angle (~ 12 degrees between 300 and 80 K) and a slight tilt ((4.5\pm2.5) degrees at 300 K and (2.5\pm1.7) degrees at 80 K). While XRD data confirms temperature dependence of the unit cell height/width ratio (i.e. lattice parameter c divided by the average of parameters a and b) found in a prior neutron powder diffraction investigation, both bulk and surface structures display little change with thermal cycles between 300 and 80 K.Comment: 25 pages, 5 figures, 5 tables, to appear in Physical Review
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