2,953 research outputs found

    An American approach to anaesthesia research and a British perspective

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    The organisation of research in the Department of Anesthesiology at the University of Michigan is described and the comments of a British Senior Registrar working within the system are recorded.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74028/1/j.1365-2044.1981.tb08682.x.pd

    The Internet: An Assessment of Student Perceptions

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    REGIONAL IMPACT OF URBAN WATER USE ON IRRIGATED AGRICULTURE

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    Linear programming and regional input-output models were applied to estimate the impacts of increased pumping costs for irrigated agriculture due to groundwater depletion principally caused by the expanding urban area of San Antonio, Texas. A biophysical simulator was use to estimate linear programming coefficients of crop yield by irrigation level and timing. The results indicated significant local (county) economic impacts from groundwater mining but insignificant regional impacts. A major improvement on irrigation efficiency would be required to offset the increased pumping costs and reduce water availability associated with increased lifts due to urban expansion.Resource /Energy Economics and Policy,

    Spa47 is an oligomerization-activated type three secretion system (T3SS) ATPase from \u3cem\u3eShigella flexneri\u3c/em\u3e

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    Gram-negative pathogens often use conserved type three secretion systems (T3SS) for virulence. The Shigella type three secretion apparatus (T3SA) penetrates the host cell membrane and provides a unidirectional conduit for injection of effectors into host cells. The protein Spa47 localizes to the base of the apparatus and is speculated to be an ATPase that provides the energy for T3SA formation and secretion. Here, we developed an expression and purification protocol, producing active Spa47 and providing the first direct evidence that Spa47 is a bona fide ATPase. Additionally, size exclusion chromatography and analytical ultracentrifugation identified multiple oligomeric species of Spa47 with the largest greater than 8 fold more active for ATP hydrolysis than the monomer. An ATPase inactive Spa47 point mutant was then engineered by targeting a conserved Lysine within the predicted Walker A motif of Spa47. Interestingly, the mutant maintained a similar oligomerization pattern as active Spa47, but was unable to restore invasion phenotype when used to complement a spa47 null S. flexneri strain. Together, these results identify Spa47 as a Shigella T3SS ATPase and suggest that its activity is linked to oligomerization, perhaps as a regulatory mechanism as seen in some related pathogens. Additionally, Spa47 catalyzed ATP hydrolysis appears to be essential for host cell invasion, providing a strong platform for additional studies dissecting its role in virulence and providing an attractive target for anti-infective agents

    Balmer-dominated shocks in Tycho's SNR: omnipresence of CRs

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    We present wide-field, spatially and highly resolved spectroscopic observations of Balmer filaments in the northeastern rim of Tycho's supernova remnant in order to investigate the signal of cosmic-ray (CR) acceleration. The spectra of Balmer-dominated shocks (BDSs) have characteristic narrow (FWHM ∼\sim 10 kms−1^{-1}) and broad (FWHM ∼\sim 1000 kms−1^{-1}) Hα\alpha components. CRs affect the Hα\alpha-line parameters: heating the cold neutrals in the interstellar medium results in broadening of the narrow Hα\alpha-line width beyond 20 kms−1^{-1}, but also in reduction of the broad Hα\alpha-line width due to energy being removed from the protons in the post-shock region. For the first time we show that the width of the narrow Hα\alpha line, much larger than 20 kms−1^{-1}, is not a resolution or geometric effect nor a spurious result of a neglected intermediate (FWHM ∼\sim 100 kms−1^{-1}) component resulting from hydrogen atoms undergoing charge exchange with warm protons in the broad-neutral precursor. Moreover, we show that a narrow line width ≫\gg 20 kms−1^{-1} extends across the entire NE rim, implying CR acceleration is ubiquitous, and making it possible to relate its strength to locally varying shock conditions. Finally, we find several locations along the rim, where spectra are significantly better explained (based on Bayesian evidence) by inclusion of the intermediate component, with a width of 180 kms−1^{-1} on average.Comment: Proceeding for contributed talk at the IAU Symposium No. 331: "SN 1987A, 30 years later - Cosmic Rays and Nuclei from Supernovae and their Aftermaths", 2017, La Reunion Island; References correcte

    Balmer filaments in Tycho's supernova remnant: an interplay between cosmic-ray and broad-neutral precursors

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    We present Hα\alpha spectroscopic observations and detailed modelling of the Balmer filaments in the supernova remnant Tycho. We used Galaxy Hα\alpha Fabry-P\'erot Spectrometer on the William Herschel Telescope with a 3.4'×\times3.4' field-of-view, 0.2" pixel scale and \sigma_\rm{instr}=8.1 km/s resolution at 1" seeing for ∼10\sim10 hours, resulting in 82 spatial-spectral bins that resolve the narrow Hα\alpha line in the entire Tycho's northeastern rim. For the first time, we can mitigate artificial line broadening from unresolved differential motion, and probe Hα\alpha emission parameters in varying shock and ambient medium conditions. Broad Hα\alpha line remains unresolved within spectral coverage of 392 km/s. We employed Bayesian inference to obtain reliable parameter confidence intervals, and quantify the evidence for models with multiple line components. The median Hα\alpha narrow-line full-width at half-maximum of all bins and models is W_\rm{NL}=(54.8\pm1.8) km/s at the 95%95\% confidence level, varying within [35, 72] km/s between bins and clearly broadened compared to the intrinsic (thermal) ≈20\approx20 km/s. Possible line splits are accounted for, significant in ≈18%\approx18\% of the filament, and presumably due to remaining projection effects. We also find wide-spread evidence for intermediate-line emission of a broad-neutral precursor, with median W_\rm{IL}=(180\pm14) km/s (95%95\% confidence). Finally, we present a measurement of the remnant's systemic velocity, V_\rm{LSR}=-34 km/s, and map differential line-of-sight motions. Our results confirm the existence and interplay of shock precursors in Tycho's remnant. In particular, we show that suprathermal narrow-line emission is near-universal in Tycho and that, in absence of an alternative explanation, collisionless supernova remnant shocks constitute a viable acceleration source for Galactic TeV Cosmic-Ray protons.Comment: 36 pages, 17 figures, 5 tables, Paper accepted for publication in the Astrophysical Journal; References correcte
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