18,029 research outputs found

    Gravitational waves from binary systems in circular orbits: Convergence of a dressed multipole truncation

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    The gravitational radiation originating from a compact binary system in circular orbit is usually expressed as an infinite sum over radiative multipole moments. In a slow-motion approximation, each multipole moment is then expressed as a post-Newtonian expansion in powers of v/c, the ratio of the orbital velocity to the speed of light. The bare multipole truncation of the radiation consists in keeping only the leading-order term in the post-Newtonian expansion of each moment, but summing over all the multipole moments. In the case of binary systems with small mass ratios, the bare multipole series was shown in a previous paper to converge for all values v/c < 2/e, where e is the base of natural logarithms. In this paper, we extend the analysis to a dressed multipole truncation of the radiation, in which the leading-order moments are corrected with terms of relative order (v/c)^2 and (v/c)^3. We find that the dressed multipole series converges also for all values v/c < 2/e, and that it coincides (within 1%) with the numerically ``exact'' results for v/c < 0.2.Comment: 9 pages, ReVTeX, 1 postscript figur

    Investigation of warm fog properties and fog modification concepts

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    Warm fog seeding to determine potential of various sized and unsized hygroscopic chemicals for fog dissipatio

    A target for production of radioxenons

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    A liquid cesium target has been developed which allows the production and separate identification of the neutron deficient isotopes of xenon. The present report describes irradiations utilizing 34 to 41 MeV protons to produce millicurie quantities of Xe-127 and Xe-129m. At higher energies, however, the target could be used without modification to produce xenon isotopes as light as 119

    Nonlinear dynamic analysis of structures Final report

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    Dynamic response of initially stressed inflatable thin membrane shell

    The Use of Commercial Bacterial Soil Inoculant Regime in an Urban Prairie Restoration

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    For successful grassland restoration, commercial soil inoculants are often recommended to increase establishment success. In spring 2009, a 0.94-ha tract was targeted for restoration at Phil Hardberger Park, a 126-ha park in the heart of San Antonio, Texas. Woody species, mainly Texas persimmon (Diospyros texana Scheele), and Ashe juniper (Juniperus asheiiBuchholz), were removed and the area was divided into 10 subplots measuring 911 m2 on average. In September 2009, over 40,000 plugs of seven native grass species were planted. In addition, native prairie seed mixes, including various grass and forb seeds, were sown into the site at a rate of 11.26 kg/ha. Half of the native grass plants were treated with a soil bacteria inoculant plus additional nutrients (IN) (BioGensis IIITM DS Tainio Technology and Technique Inc.), and half were left as controls (C). Soil samples from the plots were taken in February 2010 and 2011 and analyzed for soil nutrients, bacteria, protozoa, and fungi. Vegetation data were collected October 2010 and May and October 2011 to assess differences in percent cover between the treatments. The IN treatment resulted in significantly higher percent cover in the second growing season of three native grasses,Eriochloa sericea (Scheele) Munro ex Vasey, Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths, and B. curtipendula (Michx.) Torr; however, no significant differences were found between the IN and C plots for measures of overall native species abundance, soil resources, or the presence of soil microbes. We concluded that commercial soil inoculants may not have been necessary for the successful establishment of a native grassland community

    Investigation of a direction sensitive sapphire detector stack at the 5 GeV electron beam at DESY-II

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    Extremely radiation hard sensors are needed in particle physics experiments to instrument the region near the beam pipe. Examples are beam halo and beam loss monitors at the Large Hadron Collider, FLASH or XFEL. Currently artificial diamond sensors are widely used. In this paper single crystal sapphire sensors are considered as a promising alternative. Industrially grown sapphire wafers are available in large sizes, are of low cost and, like diamond sensors, can be operated without cooling. Here we present results of an irradiation study done with sapphire sensors in a high intensity low energy electron beam. Then, a multichannel direction-sensitive sapphire detector stack is described. It comprises 8 sapphire plates of 1 cm^2 size and 525 micro m thickness, metallized on both sides, and apposed to form a stack. Each second metal layer is supplied with a bias voltage, and the layers in between are connected to charge-sensitive preamplifiers. The performance of the detector was studied in a 5 GeV electron beam. The charge collection efficiency measured as a function of the bias voltage rises with the voltage, reaching about 10 % at 950 V. The signal size obtained from electrons crossing the stack at this voltage is about 22000 e, where e is the unit charge. The signal size is measured as a function of the hit position, showing variations of up to 20 % in the direction perpendicular to the beam and to the electric field. The measurement of the signal size as a function of the coordinate parallel to the electric field confirms the prediction that mainly electrons contribute to the signal. Also evidence for the presence of a polarisation field was observed.Comment: 13 pages, 7 figures, 3 table

    Estimation of stratospheric input to the Arctic troposphere: 7Be and 10Be in aerosols at Alert, Canada

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    Concentrations of 7Be and 210Pb in 2 years of weekly high-volume aerosol samples collected at Alert, Northwest Territories, Canada, showed pronounced seasonal variations. We observed a broad winter peak in 210Pb concentration and a spring peak in 7Be. These peaks were similar in magnitude and duration to previously reported results for a number of stations in the Arctic Basin. Beryllium 10 concentrations (determined only during the first year of this study) were well correlated with those of 7Be; the atom ratio 10Be/7Be was nearly constant at 2.2 throughout the year. This relatively high value of 10Be/7Be indicates that the stratosphere must constitute an important source of both Be isotopes in the Arctic troposphere throughout the year. A simple mixing model based on the small seasonal variations of 10Be/7Be indicates an approximately twofold increase of stratospheric influence in the free troposphere in late summer. The spring maxima in concentrations of both Be isotopes at the surface apparently reflect vertical mixing in rather than stratospheric injections into the troposphere. We have merged the results of the Be-based mixing model with weekly O3 soundings to assess Arctic stratospheric impact on the surface O3 budget at Alert. The resulting estimates indicate that stratospheric inputs can account for a maximum of 10-15% of the 03 at the surface in spring and for less during the rest of the year. These estimates are most uncertain during the winter. The combination of Be isotopic measurements and O3 vertical profiles could allow quantification of the contributions of O3 from the Arctic stratosphere and lower latitude regions to the O3 budget in the Arctic troposphere. Although at present the lack of a quantitative understanding of the temporal variation of O3 lifetime in the Arctic troposphere precludes making definitive calculations, qualitative examples of the power of this approach are given

    Gaussian-Charge Polarizable Interaction Potential for Carbon Dioxide

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    A number of simple pair interaction potentials of the carbon dioxide molecule are investigated and found to underestimate the magnitude of the second virial coefficient in the temperature interval 220 K to 448 K by up to 20%. Also the third virial coefficient is underestimated by these models. A rigid, polarizable, three-site interaction potential reproduces the experimental second and third virial coefficients to within a few percent. It is based on the modified Buckingham exp-6 potential, an anisotropic Axilrod-Teller correction and Gaussian charge densities on the atomic sites with an inducible dipole at the center of mass. The electric quadrupole moment, polarizability and bond distances are set to equal experiment. Density of the fluid at 200 and 800 bars pressure is reproduced to within some percent of observation over the temperature range 250 K to 310 K. The dimer structure is in passable agreement with electronically resolved quantum-mechanical calculations in the literature, as are those of the monohydrated monomer and dimer complexes using the polarizable GCPM water potential. Qualitative agreement with experiment is also obtained, when quantum corrections are included, for the relative stability of the trimer conformations, which is not the case for the pair potentials.Comment: Error in the long-range correction fixed and three-body dispersion introduced. 32 pages (incl. title page), 7 figures, 9 tables, double-space
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