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Space Center (space + center)
Selected AbstractsAn Empirical Study of the Effect of Knowledge Management Processes at Individual, Group, and Organizational Levels,DECISION SCIENCES, Issue 2 2003Rajiv Sabherwal ABSTRACT To enhance our understanding of knowledge management, this paper focuses on a specific question: How do knowledge management processes influence perceived knowledge management effectiveness? Prior literature is used to develop the research model, including hypotheses about the effects of four knowledge management processes (internalization, externalization, socialization, and combination) on perceived individual-level, group-level, and organizational-level knowledge management effectiveness. The study was conducted at the John F. Kennedy Space Center of the National Aeronautics and Space Administration using a survey of 159 individuals and two rounds of personal interviews. Structural equation modeling was performed to test measurement and structural models using the survey data. The emergent model suggests that internalization and externalization impact perceived effectiveness of individual-level knowledge management. Socialization and combination influence perceived effectiveness of knowledge management at group and organizational levels, respectively. The results also support the expected upward impact in perceived effectiveness of knowledge management, from individual to group level, as well as from group level to organizational level. The study's limitations and implications for practice and future research are described. [source] Molecular bacterial community analysis of clean rooms where spacecraft are assembledFEMS MICROBIOLOGY ECOLOGY, Issue 3 2007Christine Moissl Abstract Molecular bacterial community composition was characterized from three geographically distinct spacecraft-associated clean rooms to determine whether such populations are influenced by the surrounding environment or the maintenance of the clean rooms. Samples were collected from facilities at the Jet Propulsion Laboratory (JPL), Kennedy Space Flight Center (KSC), and Johnson Space Center (JSC). Nine clone libraries representing different surfaces within the spacecraft facilities and three libraries from the surrounding air were created. Despite the highly desiccated, nutrient-bare conditions within these clean rooms, a broad diversity of bacteria was detected, covering all the main bacterial phyla. Furthermore, the bacterial communities were significantly different from each other, revealing only a small subset of microorganisms common to all locations (e.g. Sphingomonas, Staphylococcus). Samples from JSC assembly room surfaces showed the greatest diversity of bacteria, particularly within the Alpha - and Gammaproteobacteria and Actinobacteria. The bacterial community structure of KSC assembly surfaces revealed a high presence of proteobacterial groups, whereas the surface samples collected from the JPL assembly facility showed a predominance of Firmicutes. Our study presents the first extended molecular survey and comparison of NASA spacecraft assembly facilities, and provides new insights into the bacterial diversity of clean room environments . [source] Airborne gravity tests in the Italian area to improve the geoid model of ItalyGEOPHYSICAL PROSPECTING, Issue 4 2009R. Barzaghi ABSTRACT Airborne gravimetry is an important method for measuring gravity over large unsurveyed areas. This technology has been widely applied in Canada, Antarctica and Greenland to map the gravity fields of these regions and in recent years, in the oil industry. In 2005, two tests in the Italian area were performed by ENI in cooperation with the Politecnico di Milano and the Danish National Space Center. To the knowledge of the authors, these were the first experiments of this kind in Italy and were performed over the Ionian coasts of Calabria and the Maiella Mountains. The Calabria test field is characterized by strong gravity variations due to the geophysical and topographic structure of the area. The ground gravity coverage is also quite dense. It was thus possible to compare airborne gravity with the ground observed values in order to check the precision of the airborne gravimetry. The second campaign was performed in an unsurveyed area centred on the Maiella Mountains, thus filling the data gap of this zone. Comparisons with existing ground data were also carried out in this area. After smoothing, the collected data have an accuracy of 2,3 mgal, as derived by cross-over analysis. Moreover, the collocation method applied to compare and merge ground-based and airborne data proved to be efficient and reliable. The standard deviation of the discrepancies between airborne data and collocation upward continued gravity is, in both cases, less than 8 mgal. In the Maiella test, the gravity field obtained by merging airborne and ground data using collocation also provides a more detailed description of the high-frequency pattern of the geopotential field in this area. [source] RELATING PHYTOPLANKTON DYNAMICS AND PRODUCTION TO SEDIMENT RESUSPENSION IN SOUTHERN LAKE MICHIGANJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Millie, D. F.1, Fahnenstiel, G. L.2, Carrick, H. J.3, Lohrenz, S. E.4, & Schofield, O. M. E.5 1USDA-Agricultural Research Service, Sarasota, FL 34236, USA, 2NOAA-Lake Michigan Field Station, Muskegon, MI 49441, USA, 3Institute of Marine Science, University of Southern Mississippi, Stennis Space Center, MS 39529, USA, 4Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY 14060, USA; 5Isttitute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road New Brunswick NJ 08901 USA, Sediment resuspension is an annually recurrent feature during spring holomixis in southern Lake Michigan. Relationships between resuspension events and phyt-oplankton biomass, compositional dynamics, and pro-duction were evaluated during 1998 and 1999. Increased water-column light attenuation (KPAR) and suspended particulate matter (SPM) concentrations corresponded with resuspension events within nearshore regions. However, neither KPAR nor SPM corresponded with chlorophyll (Chl) a concentrations, indicating no impact of resuspension on instantaneous biomass accumulation. Diatoms and cryptophytes dominated phytoplankton assemblages and together typically comprised greater than 85% of the Chl a. The associations of SPM/KPAR with diatom Chl a, and the inverse relationship between relative diatom and crypto-phyte Chl a corresponded with the dominance of diatoms and cryptophytes in near- and offshore waters, respectively. Moreover, a spatial variation in species composition occurred during resuspension events; small, centric diatoms exhibiting meroplanktonic life histories and large, pennate diatoms considered benthic in origin were associated with sediment resuspension whereas large, net diatoms and cryptophytes typically comprising phytoplankton of the annual spring bloom and of optically-clear, offshore waters were not. The presence of viable diatom photopigments and the abundance of small centric diatoms within the surficial sediments, established this layer as the source of meroplankton. Integral production was dramatically reduced within sediment-impacted waters; however, nearshore assemblages appeared to have greater photosynthetic capacities than offshore assemblages. Although resuspension dramatically influenced near-shore phytoplankton assemblages, it appeared to have little, if any relationship with the compositional development of the annual spring bloom. [source] Effects of cell structure and density on the properties of high performance polyimide foams,,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2-3 2005Martha K. Williams Abstract Activity at the NASA Langley Research Center (LaRC) has focused on developing low density polyimide foam and foam structures which are made using monomeric solutions or salt solutions formed from the reaction of a dianhydride and diamine dissolved in a mixture of foaming agents and alkyl alcohol at room temperature. Monomer blends may be used to make a variety of polyimide foams with varying properties. The first foaming process developed consisted of thermal cycling the polymer precursor residuum and allowing the inflation of the particles to interact to create the foam. This process has resulted in foam structures with higher percentages of open cell content. Another innovative foaming process has been developed that begins with partially inflated microspheres, "friable balloons", with incomplete polymer molecular weight gain, which when fully cured into a foam results in more closed cell structures. In a research study performed by NASA Kennedy Space Center (KSC) and LaRC, two closely related polyimide foams, TEEK-H series and TEEK-L series, (4,4,-oxydiphthalic anhydride/3,4,-oxydianiline and 3,3,,4,4,-benzophenonetetracarboxylic acid dianhydride/4,4,-oxydianiline) were investigated for density effects and closed versus open cell effects on the thermal, mechanical, and flammability properties. Thermal conductivity data under the full range of vacuum pressures indicate that these materials are effective insulators under cryogenic conditions. Contributing factors such as cell content, density, and surface area were studied to determine the effects on thermal conductivity. Cone calorimetry data indicated decreased peak heat release rates for the closed cell system, TEEK-H friable balloons, compared to the TEEK foams with higher open cell content. Mechanical properties including tensile strength and compressive strength indicated that the materials have good structural integrity. Foams with more open cell content resulted in greater tensile and compressive strengths than the closed cell foams. The maximum closed cell content achieved in the "friable balloon" system was 78% at a foam density of 0.048 gm/cm3. Published in 2005 by John Wiley & Sons, Ltd. [source] SUNRISE , Impressions from a successful science flightASTRONOMISCHE NACHRICHTEN, Issue 6 2010W. Schmidt Abstract SUNRISE is a balloon-borne telescope with an aperture of one meter. It is equipped with a filter imager for the UV wavelength range between 214 nm and 400 nm (SUFI), and with a spectro-polarimeter that measures the magnetic field of the photosphere using the Fe I line at 525.02 nm that has a Landé factor of 3. SUNRISE performed its first science flight from 8 to 14 June 2009. It was launched at the Swedish ESRANGE Space Center and cruised at an altitude of about 36 km and geographic latitudes between 70 and 74 degrees to Somerset Island in northern Canada. There, all data, the telescope and the gondola were successfully recovered. During its flight, Sunrise achieved high pointing stability during 33 hours, and recorded about 1.8 TB of science data. Already at this early stage of data processing it is clear that SUNRISE recorded UV images of the solar photosphere, and spectropolarimetric measurements of the quiet Sun's magnetic field of unprecedented quality (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Recessed elliptical-centric view-ordering for contrast-enhanced 3D MR angiography of the carotid arteriesMAGNETIC RESONANCE IN MEDICINE, Issue 3 2002R. Watts Abstract Fast arterial-venous transit in the carotid arteries requires accurate, reliable timing of the acquisition to the bolus transit to maximize arterial signal and minimize venous artifacts. The rising edge of the bolus is not utilized in conventional elliptical-centric view-ordering because the critical k -space center must be acquired with full arterial enhancement. In this study, a recessed elliptical-centric view-ordering scheme is introduced in which the k -space center is acquired a few seconds following scan initiation. The recessed view-ordering is shown to be more robust to timing errors than the conventional scheme in a study of 37 patients. Magn Reson Med 48:419,424, 2002. © 2002 Wiley-Liss, Inc. [source] | ||||||||||