603 research outputs found
Westinghouse programs in pulsed homopolar power supplies
This document details Westinghouse's ongoing study of homopolar machines since 1929 with the major effort occurring in the early 1970's to the present. The effort has enabled Westinghouse to develop expertise in the technology required for the design, fabrication and testing of such machines. This includes electrical design, electromagnetic analysis, current collection, mechanical design, advanced cooling, stress analysis, transient rotor performance, bearing analysis and seal technology. Westinghouse is using this capability to explore the use of homopolar machines as pulsed power supplies for future systems in both military and commercial applications
Comparison of Three Physical Activity Measurement Tools to Assess Physical Activity Guideline Compliance in Children
Current physical activity recommendations suggest that children should have 60 minutes of moderate-to-vigorous physical activity (MVPA) per day. Purpose: The purpose of this study was to compare the ability of three different physical activity measurement tools to assess whether children were meeting physical activity recommendations. Methods: Physical activity was assessed for one week via accelerometer (ActiGraph GT3X), pedometer (New Lifestyles NL-1000), and for one day using a self report questionnaire (Self-Administered Physical Activity Checklist, or [SAPAC]) in thirty 5th-grade students. A total of 15 students, (11 ± 1 yrs; 11 female, 4 male) met compliance standards and were used for data comparisons. Minutes spent in MVPA per day were calculated from the SAPAC and accelerometer data using Sallis specifications and Freedson cut-points, respectively. Data from the SAPAC and accelerometers were compared with Centers for Disease Control and Prevention physical activity guidelines. Steps per day from the pedometers were compared with BMI referenced steps per day cut-point guidelines. All data are presented as mean ± SD. Results: SAPAC indicated MVPA of 460 ± 473 minutes per day. Accelerometer assessment indicated MVPA of 40 ± 15 minutes per day. Pedometer assessment indicated 8994 ± 3047 steps per day. Conclusions: Within this sample, 6% of subjects met minimum physical activity recommendations based on accelerometer data, whereas 20% met minimum physical activity recommendations using the pedometer. However, 100% of subjects met recommendations using the subjective self-report recall questionnaire. This pilot study indicates 5th-grade students dramatically over report estimated MVPA via self-report questionnaire. Therefore, objective physical activity assessment tools, such as accelerometers and pedometers may be better suited than self-report questionnaires to assess compliance with physical activity guidelines in 5th-grade students
Where Everybody Knows Your Name: Extraorganizational Clan-Building as Small Firm Strategy for Home Field Advantage
Small firms are comparatively resource disadvantaged when it comes to competing against scale-oriented competitors. However, one area where small firms may have a differential advantage is in building and nurturing highly personalized customer relationships. Drawing on extant work in external market, internal hierarchical, and internal clan coordinating mechanisms, we conceptualize an additional coordinating mechanism the extraorganizational clan, and hypothesize its relationship to small firm performance. We test our hypothesis, linking extraorganizational clan-building and firm performance, on a sample of over 300 small retail firms. Our findings show that selected aspects of clan-building behaviors have a positive effect on small firm performance. We conclude by reflecting on what our findings suggest for sustainable small firm competitive advantage
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Ecology of the northern subpopulation of northern anchovy (Engraulis mordax) in the California Current large marine ecosystem
Northern anchovy (Engraulis mordax) are a dominant forage fish in the California Current large marine ecosystem (CCLME). However, little is known about northern anchovy abundance, distribution, age structure, or population fluctuations relative to ocean conditions in the eastern boundary upwelling system off the U.S. West Coast. This thesis includes three primary studies of northern anchovy in the CCLME off Oregon and Washington using data collected during four National Marine Fisheries Service (NMFS) surveys (1977-2006): inter- and intra-annual variation in anchovy distribution and its relationship to oceanography, growth rates of larval and juvenile anchovy that indicate the timing of major spawning events and changes in mortality rates, and analysis of whole lipids and fatty acid profiles to determine food sources in years of contrasting oceanographic conditions. First, I quantified the relationship between northern anchovy abundance with environmental variables at two spatial and temporal scales: 1) mesoscale, including sea surface temperature (SST), salinity (SSS), density (SSD), chlorophyll a, distance from shore, and depth; and 2) macroscale, including Pacific Decadal Oscillation Index, Multivariate El Niño Southern Oscillation Index, timing of the Spring Transition, and abundance of cold-water zooplankton. Anchovy densities increased significantly from 1999-2004, and decreased significantly from 2005-2006. SST and proximity to shore were the most consistent parameters explaining anchovy distribution. Year-class strength was highly correlated with, and presumably driven by, the abundance of cold-water copepods. Second, I characterized recruitment for northern anchovy by conducting microstructure analysis of saggital otoliths from late larval and juvenile life history phases collected in September 2006. I identified a protracted spawning period for northern anchovy ranging from June-August 2006. Juveniles that were spawned and hatched early in the summer 2006 had higher growth rates, but smaller back-calculated sizes-at-age during the larval phase, when compared to congeners spawned later that summer. Finally, I determined total lipid content and fatty acid signatures of northern anchovy and three other forage fish species during two contrasting periods of oceanographic conditions (summers of 2005 and 2006): Pacific sardine (Sardinops sagax), Pacific herring (Clupea harengus pallasii), and whitebait smelt (Allosmerus elongatus). Forage fish lipid levels were lowest in 2005 and increased in 2006. Fatty acid biomarkers in 2005 indicated that the food web was based mainly on dinoflagellates, corroborating observations of delayed coastal upwelling and low primary productivity in the CCLME. In 2006, fatty acids reflected higher levels of diatom feeding and zooplankton carnivory. The results of these studies confirm that in the CCLME, northern anchovy are sensitive to even small environmental perturbations, which is important because this work provides metrics for evaluating climate-mediated, bottom-up ecological processes affecting anchovy survival.Keywords: anchovy, fatty acids, otolith microstructure, ecology, forage fish, regime shif
Where were they from? Modelling the source stock of dolphins stranded after the Deepwater Horizon oil spill using genetic and stable isotope data
Understanding the source stock of common bottlenose dolphins Tursiops truncatus that stranded in the northern Gulf of Mexico subsequent to the Deepwater Horizon oil spill was essential to accurately quantify injury and apportion individuals to the appropriate stock. The aim of this study, part of the Natural Resource Damage Assessment (NRDA), was to estimate the proportion of the 932 recorded strandings between May 2010 and June 2014 that came from coastal versus bay, sound and estuary (BSE) stocks. Four sources of relevant information were available on overlapping subsets totaling 336 (39%) of the strandings: genetic stock assignment, stable isotope ratios, photo-ID and individual genetic-ID. We developed a hierarchical Bayesian model for combining these sources that weighted each data source for each stranding according to a measure of estimated precision: the effective sample size (ESS). The photo- and genetic-ID data were limited and considered to potentially introduce biases, so these data sources were excluded from analyses used in the NRDA. Estimates were calculated separately in 3 regions: East (of the Mississippi outflow), West (of the Mississippi outflow through Vermilion Bay, Louisiana) and Western Louisiana (west of Vermilion Bay to the Texas-Louisiana border); the estimated proportions of coastal strandings were, respectively 0.215 (95% CI: 0.169-0.263), 0.016 (0.036-0.099) and 0.622 (0.487-0.803). This method represents a general approach for integrating multiple sources of information that have differing uncertainties.Publisher PDFPeer reviewe
Assigning stranded bottlenose dolphins to source stocks using stable isotope ratios following the Deepwater Horizon oil spill
The potential for stranded dolphins to serve as a tool for monitoring free-ranging populations would be enhanced if their stocks of origin were known. We used stable isotopes of carbon, nitrogen, and sulfur from skin to assign stranded bottlenose dolphins Tursiops truncatus to different habitats, as a proxy for stocks (demographically independent populations), following the Deepwater Horizon oil spill. Model results from biopsy samples collected from dolphins from known habitats (n = 205) resulted in an 80.5% probability of correct assignment. These results were applied to data from stranded dolphins (n = 217), resulting in predicted assignment probabilities of 0.473, 0.172, and 0.355 to Estuarine, Barrier Island (BI), and Coastal stocks, respectively. Differences were found west and east of the Mississippi River, with more Coastal dolphins stranding in western Louisiana and more Estuarine dolphins stranding in Mississippi. Within the Estuarine East Stock, 2 groups were identified, one predominantly associated with Mississippi and Alabama estuaries and another with western Florida. δ15N values were higher in stranded samples for both Estuarine and BI stocks, potentially indicating nutritional stress. High probabilities of correct assignment of the biopsy samples indicate predictable variation in stable isotopes and fidelity to habitat. The power of δ34S to discriminate habitats relative to salinity was essential. Stable isotopes may provide guidance regarding where additional testing is warranted to confirm demographic independence and aid in determining the source habitat of stranded dolphins, thus increasing the value of biological data collected from stranded individuals.Publisher PDFPeer reviewe
Direct, biomimetic synthesis of (+)-artemone via a stereoselective, organocatalytic cyclization
We present a four-step synthesis of (+)-artemone from (–)- linalool, featuring iminium organocatalysis of a doubly diastereoselective conjugate addition reaction. The strategy follows a proposed biosynthetic pathway, rapidly generates stereochemical complexity, uses no protecting groups, and minimizes redox manipulations
Effects of Variable Oceanographic Conditions on Forage Fish Lipid Content and Fatty Acid Composition in the Northern California Current
Lipids and fatty acids (FA) were investigated in 4 species of forage fish: northern anchovy Engraulis mordax, Pacific sardine Sardinops sagax, Pacific herring Clupea pallasi, and whitebait smelt Allosmerus elongatus, for their ability to serve as biological indicators of ocean conditions in the California Current large marine ecosystem (CCLME). Samples were collected during the oceanographically contrasting years of 2005 and 2006. Upwelling was severely curtailed in the spring and early summer of 2005, leading to delayed biological productivity, whereas upwelling was relatively normal in spring 2006. Principal components analysis described 78% of the variance within the lipid and FA dataset using the first 2 principal components. We found significant intra- and interspecific, interannual, and seasonal differences in lipid and FA profiles using univariate and permutation- based multivariate analysis of variance. Indicator species analysis showed distinct lipid and FA properties associated with each fish species. Using the ratio of docosahexaenoic acid (C22:6n-3) to eicosapentaeonic acid (C20:5n-3), we detected a transition from a diet composed primarily of dinoflagellate origin in early 2005 to a diet resulting from diatom-based productivity by late summer 2006. This shift was due to interannual differences in primary production, which was confirmed through phytoplankton sampling. Our study demonstrates that lipid and FA biomarkers in the forage fish community can provide information on ocean conditions and productivity that affect food web structure in the CCLME
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