457 research outputs found

    The charged particle radiation environment for AXAF

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    The Advanced X Ray Astrophysics Facility (AXAF) will be subjected to several sources of charged particle radiation during its 15-year orbital lifetime: geomagnetically-trapped electrons and protons, galactic cosmic ray particles, and solar flare events. These radiation levels are presented for the AXAF orbit for use in the design of the observatory's science instruments

    A near-infrared study of the luminous merging galaxies NGC 2623 and ARP 148

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    As part of an investigation of the physical mechanisms which produce large infrared luminosities in interacting systems, multicolor near-infrared maps were obtained of the long tailed galaxy NGC 2623 and the ring galaxy Arp 148. The near-infrared broadband spectrum was decomposed to obtain the contribution of four processes: emission from evolved stars, nebular continuum emission, thermal reradiation, and extinction. This multicolor analysis, along with 2 micrometer maps and 10 micrometer measurements, is used to determine the structure of these interacting galaxies and to delineate regions of star formation

    Innovation Adoption In Industrial Sales Organizations: A Field Study Of The Post-adoption Phase In The Case Of Telemarketing

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    Telemarketing is an increasingly popular innovation in industrial salesforces in North America. In spite of rising popularity, the incidence of problems severe enough to cause discontinuance has been estimated at about 40%. The purpose of this study was to formulate and test a model of organizational factors leading to successful adoption of the telemarketing innovation. Data to test the model were collected by interviewing two key informants in each of 110 industrial salesforces that had adopted telemarketing in the recent past. Structural equation modeling as implemented by LISREL was used to test the fit of the model to the data and to test the hypotheses developed from the model.;The overall model was a moderately good fit and support was found for many of the individual hypotheses in the model. To summarize, organization centralization was positively associated with success; formalization was negatively related to success. Resolution of implementation issues, sales rep support of telemarketing and core use of telemarketing were all positively associated with success. Division of labor, differentiation, and management support of telemarketing were positively related to resolution of implementation issues; sales rep support of innovation and innovation compatibility were both positively related to sales rep support of telemarketing. Sales management support of innovation was positively related to management support of telemarketing.;Because the causal model was tested on cross-sectional data, the findings must be viewed as tentative at this point. However, preliminary conclusions were drawn for theory and marketing management. The study contributes to innovation theory by specifically modeling variables in the post-adoption phase of organization innovation adoption. Because the model is specifically formulated for the sales organization setting, it also contributes to sales management theory--especially the growing body of theory on marketing organization structure. The major theoretical contribution is the successful modeling of interrelationships among constructs that had been previously found to relate to innovation on individual bases.;Given the relatively high proportion of variance in adoption success explained by the model (.44), useful conclusions and implications for marketing managers were also drawn. In conclusion, the model provides a good start for needed future work on post-innovation adoption in organizations

    Chandra Measurements of a Complete Sample of X-ray Luminous Galaxy Clusters: the Gas Mass Fraction

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    We present Chandra X-ray measurements of the gas mass fraction out to r500 for a complete sample of the 35 most luminous clusters from the Brightest Cluster Sample and the Extended Brightest Cluster Sample at redshift z=0.15-0.30. The sample includes relaxed and unrelaxed clusters, and the data were analysed independently using two pipelines and two different models for the gas density and temperature. We measure an average of fgas(r500) = 0.163 +/- 0.032, which is in agreement with the cosmic baryon fraction (Omega_b / Omega_M = 0.167 +/- 0.006) at the 1-sigma level, after adding the stellar baryon fraction. Earlier studies reported gas mass fractions significantly lower than the cosmic baryon fraction at r500, and in some cases higher values that are consistent with the cosmic baryon fraction towards the virial radius.In this paper we show that the most X-ray luminous clusters in the redshift range z=0.15-0.30 have a gas mass fraction that is consistent with the cosmic value at r500.Comment: MNRAS submitted, comments welcome; 23 pages, 57 figure

    Optical BVRI Photometry of Common Proper Motion F/G/K+M Wide Separation Binaries

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    We present optical (BVRI) photometric measurements of a sample of 76 common proper motion wide separation main sequence binary pairs. The pairs are composed of a F-, G-, or K-type primary star and an M-type secondary. The sample is selected from the revised NLTT catalog and the LSPM catalog. The photometry is generally precise to 0.03 mag in all bands. We separate our sample into two groups, dwarf candidates and subdwarf candidates, using the reduced proper motion (RPM) diagram constructed with our improved photometry. The M subdwarf candidates in general have larger V−RV-R colors than the M dwarf candidates at a given V−IV-I color. This is consistent with an average metallicity difference between the two groups, as predicted by the PHOENIX/BT-Settl models. The improved photometry will be used as input into a technique to determine the metallicities of the M-type stars.Comment: 26 pages, 8 figures, accepted for publication in A

    A near infrared spectroscopic study of the interstellar gas in the starburst core of M82

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    Researchers used the McDonald Observatory Infrared Grating Spectrometer, to complete a program of spatially resolved spectroscopy of M82. The inner 300 pc of the starburst was observed with 4 inch (50 pc) resolution. Complete J, H and K band spectra with resolution 0.0035 micron (lambda/delta lambda=620 at K) were measured at the near-infrared nucleus of the galaxy. Measurements of selected spectral features including lines of FeII, HII and H2 were observed along the starburst ridge-line, so the relative distribution of the diagnostic features could be understood. This information was used to better define the extinction towards the starburst region, the excitation conditions in the gas, and to characterize the stellar populations there

    Microfocus/Polycapillary-Optic Crystallographic X-Ray System

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    A system that generates an intense, nearly collimated, nearly monochromatic, small-diameter x-ray beam has been developed for use in macromolecular crystallography. A conventional x-ray system for macromolecular crystallography includes a rotating-anode x-ray source, which is massive (.500 kg), large (approximately 2 by 2 by 1 m), and power-hungry (between 2 and 18 kW). In contrast, the present system generates a beam of the required brightness from a microfocus source, which is small and light enough to be mounted on a laboratory bench, and operates at a power level of only tens of watts. The figure schematically depicts the system as configured for observing x-ray diffraction from a macromolecular crystal. In addition to the microfocus x-ray source, the system includes a polycapillary optic . a monolithic block (typically a bundle of fused glass tubes) that contains thousands of straight or gently curved capillary channels, along which x-rays propagate with multiple reflections. This particular polycapillary optic is configured to act as a collimator; the x-ray beam that emerges from its output face consists of quasi-parallel subbeams with a small angular divergence and a diameter comparable to the size of a crystal to be studied. The gap between the microfocus x-ray source and the input face of the polycapillary optic is chosen consistently with the focal length of the polycapillary optic and the need to maximize the solid angle subtended by the optic in order to maximize the collimated x-ray flux. The spectrum from the source contains a significant component of Cu K (photon energy is 8.08 keV) radiation. The beam is monochromatized (for Cu K ) by a nickel filter 10 m thick. In a test, this system was operated at a power of 40 W (current of 897 A at an accelerating potential of 45 kV), with an anode x-ray spot size of 41+/-2 microns. Also tested, in order to provide a standard for comparison, was a commercial rotating-anode x-ray crystallographic system with a pyrolytic graphite monochromator and a 250-micron pinhole collimator, operating at a power of 3.15 kW (current of 70 mA at an accelerating potential of 45 kV). The flux of collimated Cu K radiation in this system was found to be approximately 16 times that in the rotatinganode system. Data on x-ray diffraction from crystals of tetragonal form of lysozyme (protein) in this system were found to be of high quality and to be reducible by use of standard crystallographic software
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