2,617 research outputs found
Directory of aerospace safety specialized information sources
Directory aids safety specialists in locating information sources and individual experts in engineering-related fields. Lists 170 organizations and approximately 300 individuals who can provide safety-related technical information in form of documentation, data, and consulting expertise. Information on hazard and failure cause identification, accident analysis, and materials characteristics are covered
Cepheid Masses: FUSE Observations of S Mus
S Mus is the Cepheid with the hottest known companion. The large ultraviolet
flux means that it is the only Cepheid companion for which the velocity
amplitude could be measured with the echelle mode of the HST GHRS.
Unfortunately, the high temperature is difficult to constrain at wavelengths
longer than 1200 \AA because of the degeneracy between temperature and
reddening. We have obtained a FUSE spectrum in order to improve the
determination of the temperature of the companion. Two regions which are
temperature sensitive near 16,000 K but relatively unaffected by H
absorption (940 \AA, and the Ly wings) have been identified. By
comparing FUSE spectra of S Mus B with spectra of standard stars, we have
determined a temperature of 17,000 500 K. The resultant Cepheid mass is
6.0 0.4 M. This mass is consistent with main sequence
evolutionary tracks with a moderate amount of convective overshoot.Comment: accepted to Ap
Border Zone Mass Transit Demad in Brownsville and Laredo
This study examines whether economic conditions in Mexico influence public transportation ridership levels in the border cities of Brownsville and Laredo, Texas. Besides the standard variables generally utilized to model bus ridership, additional indicators included in the empirical analysis are northbound pedestrian traffic and the real exchange rate index. Seemingly unrelated regression parameter estimates suggest that the volume of pedestrian border crossings in both cities is positively related to changes in ridership. The real exchange rate index in Laredo is negatively related to fluctuations in ridership, implying that peso appreciation increases transit utilization in this border city
Temperature dependence of the switching field distributions in all-perpendicular spin-valve nanopillars
We present temperature dependent switching measurements of the Co/Ni
multilayered free element of 75 nm diameter spin-valve nanopillars. Angular
dependent hysteresis measurements as well as switching field measurements taken
at low temperature are in agreement with a model of thermal activation over a
perpendicular anisotropy barrier. However, the statistics of switching (mean
switching field and switching variance) from 20 K up to 400 K are in
disagreement with a N\'{e}el-Brown model that assumes a temperature independent
barrier height and anisotropy field. We introduce a modified N\'{e}el-Brown
model thats fit the experimental data in which we take a dependence
to the barrier height and the anisotropy field due to the temperature dependent
magnetization and anisotropy energy.Comment: 5 pages, 4 figure
Mexico Evidence on the Regional Retail Impacts of Violent Crime
Prior research reports mixed results regarding the economic impacts of crime. This study employs data from all regions of Mexico, including border regions in both the north and the south, to examine the effects of homicides on retail activity across Mexico during a period of escalating violence. The results indicate that one additional homicide within a municipality eliminates one retail establishment and one paid job in the retail sector. Furthermore, the negative consequences of violent crime for retailers are augmented by proximity to an international border. This is consistent with previous research findings that cross-border shopping is a key feature of commerce along the international boundaries of Mexico. It suggests that crime waves may disproportionately impact border city retail activity by partially diverting customer traffic to stores located in neighboring countries. This result is also consistent with the finding of recent research that violent conflict in northern Mexico resulted in increased retail activity in some United States border cities
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