In situ x-ray diffraction studies of iron under shock conditions confirm unambiguously a phase change from the bcc (alpha) to hcp (epsilon) structure. Previous identification of this transition in shock-loaded iron has been inferred from the correlation between shock-wave-profile analyses and static high-pressure x-ray measurements. This correlation is intrinsically limited because dynamic loading can markedly affect the structural modifications of solids. The in situ measurements are consistent with a uniaxial collapse along the [001] direction and shuffling of alternate (110) planes of atoms, and are in good agreement with large-scale nonequilibrium molecular dynamics simulations.
The Military Suicide Research Consortium (MSRC) developed a 57-item questionnaire assessing suicide risk factors, referred to as the Common Data Elements (CDEs), in order to facilitate data sharing and improve collaboration across independent studies. All studies funded by MSRC are required to include the CDEs in their assessment protocol. The CDEs include shortened measures of the following: current and past suicide risk, lethality and intent of past suicide attempts, hopelessness, thwarted belongingness, anxiety sensitivity, posttraumatic stress disorder symptoms, traumatic brain injury, insomnia, and alcohol abuse. This study aimed to evaluate the psychometric properties of the CDE items drawn from empirically validated measures. Exploratory factor analysis was used to examine the overall structure of the CDE items, and confirmatory factor analyses were used to evaluate the distinct properties of each scale. Internal consistencies of the CDE scales and correlations with full measures were also examined. Merged data from 3,140 participants (81.0% military service members, 75.6% male) across 19 MSRC-funded studies were used in analyses. Results indicated that all measures exhibited adequate internal consistency, and all CDE shortened measures were significantly correlated with the corresponding full measures with moderate to strong effect sizes. Factor analyses indicated that the shortened CDE measures performed well in comparison with the full measures. Overall, our findings suggest that the CDEs are not only brief but also provide psychometrically valid scores when assessing suicide risk and related factors that may be used in future research. (PsycINFO Database Record
Solid state experiments at extreme pressures (10-100 GPa) and strain rates (~10 6 -10 8 s occur at shock strengths of ~20 GPa, whereas the corresponding transition for Cu shocked along the [134] direction occurs at higher shock strengths. This slip-twinning threshold also depends on the stacking fault energy (SFE), being lower for low SFE-
Ripple induced thermal loss effect on plasma rotation is investigated in a set of Ohmic L-mode plasmas performed in Tore Supra, and comparisons with neoclassical predictions including ripple are performed. Adjusting the size of the plasma, the ripple amplitude has been varied from 0.5% to 5.5% at the plasma boundary, keeping the edge safety factor constant. The toroidal flow dynamics is understood as being likely dominated by turbulence transport driven processes at low ripple amplitude, while the ripple induced toroidal friction becomes dominant at high ripple. In the latter case, the velocity tends remarkably towards the neoclassical prediction (counter-current rotation). The radial electric field is not affected by the ripple variation and remains well described by its neoclassical prediction. Finally, the poloidal velocity is fairly close to the neoclassical prediction at high ripple amplitude, but significantly departs from it at low ripple.
Monocrystalline copper samples with orientations of [001] and [221] were shocked at pressures ranging from 20 GPa to 60 GPa using two techniques: direct drive lasers and explosively driven flyer plates. The pulse duration for these techniques differed substantially: 40 ns for the laser experiments at 0.5 mm into the sample and 1.1 ~1.4 µs for the flyer-plate experiments at 5 mm into the sample. The residual microstructures were dependent on orientation, pressure, and shocking method. The much shorter pulse duration in the laser driven shock yielded microstructures closer to the ones generated at the shock front. For the flyer-plate experiments, the longer pulse duration allows shockgenerated defects to reorganize into lower energy configurations. Calculations show that the post-shock cooling for the laser driven shock is 10 3 ~ 10 4 faster than that for plateimpact shock, propitiating recovery and recrystallization conditions for the latter. At the higher pressure level, extensive recrystallization was observed in the plate-impact samples, while it was absent in the laser driven shock. An effect that is proposed to contribute significantly to the formation of recrystallized regions is the existence of micro-shear-bands, which increase the local temperature beyond the prediction from adiabatic compression.
Solid-state dynamics experiments at very high pressures and strain rates are becoming possible with highpower laser facilities, albeit over brief intervals of time and spatially small scales. To achieve extreme pressures in the solid state requires that the sample be kept cool, with T sample Ͻ T melt . To this end, a shockless, plasma-piston "drive" has been developed on the Omega laser, and a staged shock drive was demonstrated on the Nova laser. To characterize the drive, velocity interferometer measurements allow the high pressures of 10 to 200 GPa (0.1 to 2 Mbar) and strain rates of 10 6 to 10 8 s Ϫ1 to be determined. Solid-state strength in the sample is inferred at these high pressures using the Rayleigh-Taylor (RT) instability as a "diagnostic." Lattice response and phase can be inferred for single-crystal samples from time-resolved X-ray diffraction. Temperature and compression in polycrystalline samples can be deduced from extended X-ray absorption fine-structure (EXAFS) measurements. Deformation mechanisms and residual melt depth can be identified by examining recovered samples. We will briefly review this new area of laser-based materials-dynamics research, then present a path forward for carrying these solid-state experiments to much higher pressures, P Ͼ 10 3 GPa (10 Mbar), on the National Ignition Facility (NIF) laser at Lawrence Livermore National Laboratory.
Laser-based shock experiments have been conducted in thin Si and Cu crystals at pressures above the published Hugoniot Elastic Limit ͑HEL͒ for these materials. In situ x-ray diffraction has been used to directly measure the response of the shocked lattice during shock loading. Static film and x-ray streak cameras recorded x rays diffracted from lattice planes both parallel and perpendicular to the shock direction. In addition, experiments were conducted using a wide-angle detector to record x rays diffracted from multiple lattice planes simultaneously. These data showed uniaxial compression of Si ͑100͒ along the shock direction and three-dimensional compression of Cu ͑100͒. In the case of the Si diffraction, there was a multiple wave structure observed. This is evaluated to determine whether there is a phase transition occurring on the time scale of the experiments, or the HEL is much higher than previously reported. Results of the measurements are presented.
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