2,179 research outputs found
XUV Opacity of Aluminum between the Cold-Solid to Warm-Plasma Transition
We present calculations of the free-free XUV opacity of warm, solid-density
aluminum at photon energies between the plasma frequency at 15 eV and the
L-edge at 73 eV, using both density functional theory combined with molecular
dynamics and a semi-analytical model in the RPA framework with the inclusion of
local field corrections. As the temperature is increased from room temperature
to 10 eV, with the ion and electron temperatures equal, we calculate an
increase in the opacity in the range over which the degree of ionization is
constant. The effect is less pronounced if only the electron temperature is
allowed to increase. The physical significance of these increases is discussed
in terms of intense XUV-laser matter interactions on both femtosecond and
picosecond time-scales.Comment: 4 pages, 3 figure
Measurement of nuclear effects in neutrino interactions with minimal dependence on neutrino energy
We present a phenomenological study of nuclear effects in neutrino
charged-current interactions, using transverse kinematic imbalances in
exclusive measurements. Novel observables with minimal dependence on neutrino
energy are proposed to study quasielastic scattering, and especially resonance
production. They should be able to provide direct constraints on nuclear
effects in neutrino- and antineutrino-nucleus interactions.Comment: 7 pages, 9 figures, accepted version by PR
Plastic Deformation in Laser-Induced Shock Compression of Monocrystalline Copper
Copper monocrystals were subjected to shock compression at pressures of 10–60 GPa by a short (3 ns initial) duration laser pulse. Transmission electron microscopy revealed features consistent with previous observations of shock-compressed copper, albeit at pulse durations in the µs regime. The results suggest that the defect structure is generated at the shock front. A mechanism for dislocation generation is presented, providing a realistic prediction of dislocation density as a function of pressure. The threshold stress for deformation twinning in shock compression is calculated from the constitutive equations for slip, twinning, and the Swegle-Grady relationship
A Coordinated Radio Afterglow Program
We describe a ground-based effort to find and study afterglows at centimeter
and millimeter wavelengths. We have observed all well-localized gamma-ray
bursts in the Northern and Southern sky since BeppoSAX first started providing
rapid positions in early 1997. Of the 23 GRBs for which X-ray afterglows have
been detected, 10 have optical afterglows and 9 have radio afterglows. A
growing number of GRBs have both X-ray and radio afterglows but lack a
corresponding optical afterglow.Comment: To appear in Proc. of the 5th Huntsville Gamma-Ray Burst Symposium, 5
pages, LaTe
Optimization of double pulse pumping for Ni-like Sm x-ray lasers
We report a systematic study of double pulse pumping of the Ni-like Sm x-ray laser at 73 Angstrom, currently the shortest wavelength saturated x-ray laser. It is found that the Sm x-ray laser output can change by orders of magnitude when the intensity ratio of the pumping pulses and their relative delay are varied. Optimum pumping conditions are found and interpreted in terms of a simple model. (C) 1999 American Institute of Physics. [S0021-8979(99)07102-9]
Transient x-ray diffraction used to diagnose shock compressed Si crystals on the Nova laser
Transient x-ray diffraction is used to record time-resolved information about the shock compression of materials. This technique has been applied on Nova shock experiments driven using a hohlraum x-ray drive. Data were recorded from the shock release at the free surface of a Si crystal, as well as from Si at an embedded ablator/Si interface. Modeling has been done to simulate the diffraction data incorporating the strained crystal rocking curves and Bragg diffraction efficiencies. Examples of the data and post-processed simulations are presented
Experimental Status of Neutrino Physics
After a fascinating phase of discoveries, neutrino physics still has a few
mysteries such as the absolute mass scale, the mass hierarchy, the existence of
CP violation in the lepton sector and the existence of right-handed neutrinos.
It is also entering a phase of precision measurements. This is what motivates
the NUFACT 11 conference which prepares the future of long baseline neutrino
experiments. In this paper, we report the status of experimental neutrino
physics. We focus mainly on absolute mass measurements, oscillation parameters
and future plans for oscillation experiments
Influenza Vaccine Effectiveness against Hospitalisation with Confirmed Influenza in the 2010-11 Seasons: A Test-negative Observational Study
Immunisation programs are designed to reduce serious morbidity and mortality from influenza, but most evidence supporting the effectiveness of this intervention has focused on disease in the community or in primary care settings. We aimed to examine the effectiveness of influenza vaccination against hospitalisation with confirmed influenza. We compared influenza vaccination status in patients hospitalised with PCR-confirmed influenza with patients hospitalised with influenza-negative respiratory infections in an Australian sentinel surveillance system. Vaccine effectiveness was estimated from the odds ratio of vaccination in cases and controls. We performed both simple multivariate regression and a stratified analysis based on propensity score of vaccination. Vaccination status was ascertained in 333 of 598 patients with confirmed influenza and 785 of 1384 test-negative patients. Overall estimated crude vaccine effectiveness was 57% (41%, 68%). After adjusting for age, chronic comorbidities and pregnancy status, the estimated vaccine effectiveness was 37% (95% CI: 12%, 55%). In an analysis accounting for a propensity score for vaccination, the estimated vaccine effectiveness was 48.3% (95% CI: 30.0, 61.8%). Influenza vaccination was moderately protective against hospitalisation with influenza in the 2010 and 2011 seasons
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