1,837 research outputs found

    Development of design allowable data for Celion 6000/LARC-160, graphite/polyimide composite laminates

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    A design allowables test program was conducted on Celion 6000/LARC-160 graphite polyimide composite to establish material performance over a 116 K (-250 F) to 589 K (600 F) temperature range. Tension, compression, in-plane shear and short beam shear properties were determined for uniaxial, quasi-isotropic and + or - 45 deg laminates. Effects of thermal aging and moisture saturation on mechanical properties were also evaluated. Celion 6000/LARC-160 graphite/polyimide can be considered an acceptable material system for structural applications to 589 K (600 F)

    Observation of coasting beam at the HERA Proton--Ring

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    We present data collected with the HERA-B wire target which prove the existence of coasting beam at the HERA proton storage ring. The coasting beam is inherently produced by the proton machine operation and is not dominated by target effects.Comment: 17 pages (Latex), 12 figures (Enc. Postscript

    Enhanced relativistic-electron beam collimation using two consecutive laser pulses

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    The double laser pulse approach to relativistic electron beam (REB) collimation has been investigated at the LULI-ELFIE facility. In this scheme, the magnetic field generated by the first laser-driven REB is used to guide a second delayed REB. We show how electron beam collimation can be controlled by properly adjusting laser parameters. By changing the ratio of focus size and the delay time between the two pulses we found a maximum of electron beam collimation clearly dependent on the focal spot size ratio of the two laser pulses and related to the magnetic field dynamics. Cu-K alpha and CTR imaging diagnostics were implemented to evaluate the collimation effects on the respectively low energy ( MeV) components of the REB

    On the energetics of P-P bond dissociation of sterically strained tetraamino-diphosphanes

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    The homolytic P-P bond fission in a series of sterically congested tetraaminodiphosphanes (R2N)(2)P-P-(NR2)(2) ({4}(2)-{9}(2), two of which were newly synthesized and fully characterized) into diaminophosphanyl radicals (R2N)(2)P-center dot (4-9) was monitored by VT EPR spectroscopy. Determination of the radical concentration from the EPR spectra permitted to calculate free dissociation energies Delta G(Diss)(295) as well as dissociation enthalpies Delta H-Diss and entropies Delta S-Diss, respectively. Large positive values of Delta G(Diss)(295) indicate that the degree of dissociation is in most cases low, and the concentration of persistent radicals - even if they are spectroscopically observable at ambient temperature - remains small. Appreciable dissociation was established only for the sterically highly congested acyclic derivative {9}(2). Analysis of the trends in experimental data in connection with DFT studies indicate that radical formation is favoured by large entropy contributions and the energetic effect of structural relaxation (geometrical distortions and conformational changes in acyclic derivatives) in the radicals, and disfavoured by attractive dispersion forces. Comparison of the energetics of formation for CC-saturated N-heterocyclic diphosphanes and the 7 pi-radical 3c indicates that the effect of energetic stabilization by pi-electron delocalization in the latter is visible, but stands back behind those of steric and entropic contributions. Evaluation of spectroscopic and computational data indicates that diaminophosphanyl radicals exhibit, in contrast to aminophosphenium cations, no strong energetic preference for a planar arrangement of the (R2N)(2)P unit.Peer reviewe

    Extreme flood response to short-duration convective rainfall in South-West Germany

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    The 2 June 2008 flood-producing storm on the Starzel river basin in South-West Germany is examined as a prototype for organized convective systems that dominate the upper tail of the precipitation frequency distribution and are likely responsible for the flash flood peaks in Central Europe. The availability of high-resolution rainfall estimates from radar observations and a rain gauge network, together with indirect peak discharge estimates from a detailed post-event survey, provided the opportunity to study in detail the hydrometeorological and hydrological mechanisms associated with this extreme storm and the ensuing flood. Radar-derived rainfall, streamgauge data and indirect estimates of peak discharges are used along with a distributed hydrologic model to reconstruct hydrographs at multiple locations. Observations and model results are combined to examine two main questions, (i) assessment of the distribution of the runoff ratio for the 2008 flash flood and how it compares with other less severe floods; and (ii) analysis of how the spatial and temporal distribution of the extreme rainfall, and more specifically storm motion, controls the flood response. It is shown that small runoff ratios (less than 20 %) characterized the runoff response and that these values are in the range of other, less extreme, flood events. The influence of storm structure, evolution and motion on the modeled flood hydrograph is examined by using the “spatial moments of catchment rainfall”. It is shown that downbasin storm motion (in the range of 0.7–0.9ms−1) had a noticeable impact on flood response by increasing the modeled flood peak by 13 %

    The use of data in resource limited settings to improve quality of care

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    Quality improvement is driven by benchmarking between and within institutions over time and the collaborative improvement efforts that stem from these comparisons. Benchmarking requires systematic collection and use of standardized data. Low- and middle-income countries (LMIC) have great potential for improvements in newborn outcomes but serious obstacles to data collection, analysis, and implementation of robust improvement methodologies exist. We review the importance of data collection, internationally recommended neonatal metrics, selected methods of data collection, and reporting. The transformation from data collection to data use is illustrated by several select data system examples from LMIC. Key features include aims and measures important to neonatal team members, co-development with local providers, immediate access to data for review, and multidisciplinary team involvement. The future of neonatal care, use of data, and the trajectory to reach global neonatal improvement targets in resource-limited settings will be dependent on initiatives led by LMIC clinicians and experts

    A physical model describing the interaction of nuclear transport receptors with FG nucleoporin domain assemblies

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    The permeability barrier of nuclear pore complexes (NPCs) controls bulk nucleocytoplasmic exchange. It consists of nucleoporin domains rich in phenylalanine-glycine motifs (FG domains). As a bottom-up nanoscale model for the permeability barrier, we have used planar films produced with three different end-grafted FG domains, and quantitatively analyzed the binding of two different nuclear transport receptors (NTRs), NTF2 and Importin b, together with the concomitant film thickness changes. NTR binding caused only moderate changes in film thickness; the binding isotherms showed negative cooperativity and could all be mapped onto a single master curve. This universal NTR binding behavior –a key element for the transport selectivity of the NPC –was quantitatively reproduced by a physical model that treats FG domains as regular, flexible polymers, and NTRs as spherical colloids with a homogeneous surface, ignoring the detailed arrangement of interaction sites along FG domains and on the NTR surface
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