691 research outputs found

    Oxygen impurities in NiAl: Relaxation effects

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    We have used a full-potential linear muffin-tin orbital method to calculate the effects of oxygen impurities on the electronic structure of NiAl. Using the supercell method with a 16-atom supercell we have investigated the cases where an oxygen atom is substitutionally placed at either a nickel or an aluminum site. Full relaxation of the atoms within the supercell was allowed. We found that oxygen prefers to occupy a nickel site over an aluminum site with a site selection energy of 138 mRy (21,370 K). An oxygen atom placed at an aluminum site is found to cause a substantial relaxation of its nickel neighbors away from it. In contrast, this steric repulsion is hardly present when the oxygen atom occupies the nickel site and is surrounded by aluminum neighbors. We comment on the possible relation of this effect to the pesting degradation phenomenon (essentially spontaneous disintegration in air) in nickel aluminides.Comment: To appear in Phys. Rev. B (Aug. 15, 2001

    Far infrared luminosity function of local galaxies in the AKARI Deep Field South

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    We present the first far-infrared luminosity function in the AKARI Deep Field South, a premier deep field of the AKARI Space Telescope, using spectroscopic redshifts obtained with AAOmega. To date, we have found spectroscopic redshifts for 389 galaxies in this field and have measured the local (z<0.25) 90 ÎĽm luminosity function using about one-third of these redshifts. The results are in reasonable agreement with recent theoretical predictions

    Space Vehicle Terrestrial Environment Design Requirements Guidelines

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    The terrestrial environment is an important driver of space vehicle structural, control, and thermal system design. NASA is currently in the process of producing an update to an earlier Terrestrial Environment Guidelines for Aerospace Vehicle Design and Development Handbook. This paper addresses the contents of this updated handbook, with special emphasis on new material being included in the areas of atmospheric thermodynamic models, wind dynamics, atmospheric composition, atmospheric electricity, cloud phenomena, atmospheric extremes, and sea state. In addition, the respective engineering design elements are discussed relative to terrestrial environment inputs that require consideration. Specific lessons learned that have contributed to the advancements made in the application and awareness of terrestrial environment inputs for aerospace engineering applications are presented

    Probing Ion-Ion and Electron-Ion Correlations in Liquid Metals within the Quantum Hypernetted Chain Approximation

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    We use the Quantum Hypernetted Chain Approximation (QHNC) to calculate the ion-ion and electron-ion correlations for liquid metallic Li, Be, Na, Mg, Al, K, Ca, and Ga. We discuss trends in electron-ion structure factors and radial distribution functions, and also calculate the free-atom and metallic-atom form-factors, focusing on how bonding effects affect the interpretation of X-ray scattering experiments, especially experimental measurements of the ion-ion structure factor in the liquid metallic phase.Comment: RevTeX, 19 pages, 7 figure

    Comparison of some Reduced Representation Approximations

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    In the field of numerical approximation, specialists considering highly complex problems have recently proposed various ways to simplify their underlying problems. In this field, depending on the problem they were tackling and the community that are at work, different approaches have been developed with some success and have even gained some maturity, the applications can now be applied to information analysis or for numerical simulation of PDE's. At this point, a crossed analysis and effort for understanding the similarities and the differences between these approaches that found their starting points in different backgrounds is of interest. It is the purpose of this paper to contribute to this effort by comparing some constructive reduced representations of complex functions. We present here in full details the Adaptive Cross Approximation (ACA) and the Empirical Interpolation Method (EIM) together with other approaches that enter in the same category

    Dynamical properties of liquid Al near melting. An orbital-free molecular dynamics study

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    The static and dynamic structure of liquid Al is studied using the orbital free ab-initio molecular dynamics method. Two thermodynamic states along the coexistence line are considered, namely T = 943 K and 1323 K for which X-ray and neutron scattering data are available. A new kinetic energy functional, which fulfills a number of physically relevant conditions is employed, along with a local first principles pseudopotential. In addition to a comparison with experiment, we also compare our ab-initio results with those obtained from conventional molecular dynamics simulations using effective interionic pair potentials derived from second order pseudopotential perturbation theory.Comment: 15 pages, 12 figures, 2 tables, submitted to PR

    Obesity is associated with worse quality of life in women with gynecologic malignancies: An opportunity to improve patient-centered outcomes

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    BACKGROUND: The objective of the current study was to evaluate the effect of obesity on pretreatment quality of life (QoL) in gynecologic oncology patients. METHODS: The authors analyzed collected data from an institution-wide cohort study of women with gynecologic cancers enrolled from August 2012 to June 2013. The Functional Assessment of Cancer Therapy-General, site-specific symptom scales, and the National Institutes of Health Patient-Reported Outcomes Measurement Information System (PROMIS) global mental and physical health tools were administered. Survey results were linked to clinical data abstracted from medical records (demographics and comorbid conditions). Bivariate tests and multivariate linear regression models were used to evaluate factors associated with QoL scores. RESULTS: A total of 182 women with ovarian, uterine, cervical, and vulvar/vaginal cancers were identified; of these, 152 (84%) were assessed before surgery. Mean body mass index was 33.5 kg/m2 and race included white (120 patients [79%]), black (22 patients [15%]), and other (10 patients [6.5%]). A total of 98 patients (64.5%) were obese (body mass index ≥30). On multivariate analysis, subscales for functional (17 vs 19; P=.04), emotional (16 vs 19; P=.008), and social (22 vs 24; P=.02) well-being as well as overall Functional Assessment of Cancer Therapy-General scores (77 vs 86; P5.002) and Patient-Reported Outcomes Measurement Information System global physical health scores (45 vs 49; P=.003) were found to be significantly lower in obese versus nonobese patients. CONCLUSIONS: Before cancer treatment, obese patients with gynecologic malignancies appear to have worse baseline QoL than their normal-weight counterparts. Emerging models of QoL-based cancer outcome measures may disproportionately affect populations with a high obesity burden. The potential disparate impact of cancer therapy on longitudinal QoL in the obese versus nonobese patients needs to be evaluated

    Active Galactic Nuclei at the Crossroads of Astrophysics

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    Over the last five decades, AGN studies have produced a number of spectacular examples of synergies and multifaceted approaches in astrophysics. The field of AGN research now spans the entire spectral range and covers more than twelve orders of magnitude in the spatial and temporal domains. The next generation of astrophysical facilities will open up new possibilities for AGN studies, especially in the areas of high-resolution and high-fidelity imaging and spectroscopy of nuclear regions in the X-ray, optical, and radio bands. These studies will address in detail a number of critical issues in AGN research such as processes in the immediate vicinity of supermassive black holes, physical conditions of broad-line and narrow-line regions, formation and evolution of accretion disks and relativistic outflows, and the connection between nuclear activity and galaxy evolution.Comment: 16 pages, 5 figures; review contribution; "Exploring the Cosmic Frontier: Astrophysical Instruments for the 21st Century", ESO Astrophysical Symposia Serie

    Planck 2015 results. XXVII. The Second Planck Catalogue of Sunyaev-Zeldovich Sources

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    We present the all-sky Planck catalogue of Sunyaev-Zeldovich (SZ) sources detected from the 29 month full-mission data. The catalogue (PSZ2) is the largest SZ-selected sample of galaxy clusters yet produced and the deepest all-sky catalogue of galaxy clusters. It contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data-sets, and is the first SZ-selected cluster survey containing > 10310^3 confirmed clusters. We present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. Using simulations, we find that the Y5R500 estimates are robust to pressure-profile variation and beam systematics, but accurate conversion to Y500 requires. the use of prior information on the cluster extent. We describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical and X-ray data-sets, and which places emphasis on the robustness of the counterpart match. We discuss the physical properties of the new sample and identify a population of low-redshift X-ray under- luminous clusters revealed by SZ selection. These objects appear in optical and SZ surveys with consistent properties for their mass, but are almost absent from ROSAT X-ray selected samples
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