The propagation of Mbar-range shock waves in low-density foam materials is of interest to target design in all approaches to inertial confinement fusion, high energy density physics, and laboratory astrophysics. We report absolute Hugoniot measurements for CH(1.72)N(0.086)O(0.37 )plastic foams with 73 and 94 mg/cm(3) densities in the 32-107 km/s shock velocity range. The experiments were performed on the shock compression platform developed on the NIKE KrF laser facility at the U.S. Naval Research Laboratory. NIKE's 4 or 8-ns long flat-top laser pulses drive steady shock waves into foam targets at the ablative pressures of 1-7 Mbar. The propagation of the ablation and shock fronts is tracked continuously in time using streaked side-on monochromatic x-ray imaging radiography. The straight x-t trajectories of the shock and ablation fronts in the recorded streak images confirmed their steadiness. The SESAME tabulated equation of state predictions generally agrees with our Hugoniot data within a 95% confidence band. The experimental uncertainty of the evaluated shock density compression ratios remains large, indicating the need for more experiments and improved theoretical understanding of the strong shock propagation mechanisms in dry foams.
The hydrodynamic growth of pre-imposed isolated rear-surface defects, specifically 9–20 μm deep by 8–20 μm wide laser-machined grooves on planar polystyrene foils, was investigated using the NIKE krypton-fluoride laser facility at the U.S. Naval Research Laboratory. High-resolution monochromatic x-ray radiography was employed to capture streaked face-on and two-dimensional side-on images of the defect evolution. The observed interfacial dynamics are consistent with the key characteristics of isolated-defect-triggered hydrodynamic perturbation growth first observed with front-surface defects by Zulick et al. [Phys. Rev. Lett. 125, 055001 (2020)] and Zulick et al. [Phys. Plasmas 27, 072706 (2020)]. These characteristics include an inherently multi-mode, phase-locked perturbation development, a monotonic increase in the lateral dimension of the perturbed region, and the oblique ejection of spikes during the nonlinear growth phase. Initially, material accelerated into the rear-surface groove forms a jet, which is subsequently overtaken by multi-mode bubble and spike Rayleigh–Taylor growth at the front surface. Experimental results demonstrated good agreement with both high-resolution fastrad3d simulations and analytical theoretical predictions.
This study evaluates the effectiveness of multimodal alarms in reducing inattentional blindness (i.e., the inability to detect unexpected visual stimuli), a critical safety concern in air traffic control (ATC). Two experiments were conducted: the first assessed the attention-capturing ability of multimodal alarms with visual, vibrotactile, and auditory alerting components in a simulated ATC task with 29 student controllers, using electroencephalography (EEG), questionnaires, and performance metrics. The second assessed the effectiveness of visual ambient alarms with reduced opacity and duration with 28 students. Results indicated that multimodal alarms significantly reduced missed alarms compared to the standard ATC alarm, but were perceived as more urgent and annoying. Notably, even low-opacity (5%) and brief (17 ms) visual ambient alarms were effective. These findings provide insights for optimizing alarm designs in safety-critical environments such as aviation, healthcare, and nuclear power.
Background: Alzheimer's Disease (AD), a type of dementia that interferes with memory, thinking, and behavior is the most common type of dementia. As a result, it is a leading contributor to death and disability for those over the age of 65. Therefore, future nurses must have the knowledge and skills to manage patients with AD in any setting spanning the healthcare continuum. Objective: The goal of this project was to evaluate perceptions of awareness, knowledge and sensitivity of future nurses concerning AD patients before and after participation in a simulated virtual reality dementia experience. Design/Participants. A quasi-experimental repeated measure pre-post design was used with a convenience sample of 163 undergraduate baccalaureate nursing students from three different courses at large public university in the Midwest. Methods: Students were placed in teams of four to participate in a 45-minute interactive simulated virtual reality dementia experience. Each session started with a 15-minute team pre-briefing session, followed by a 10-minute individual simulation, which was then followed by a 30-minute team debriefing session facilitated by faculty using the Plus/ Delta debriefing technique. The Dementia Attitudes Scale (DAS), The Knowledge About Memory Loss and Care Test (KAML-C), and the Healthcare Tour Survey were administered pre/post participation. Qualitative data was also collected from student reflections. Results: Statistically significant changes (p < 0.001) were noted in the pre/post DAS survey and the Healthcare Tour Survey. No significant change was noted on the KAML-C, although there was a trend towards improvement. No differences were noted between courses on any of the surveys. Conclusion: Using a virtual reality dementia experience proved to be a valuable strategy to increase student perceptions of awareness, knowledge, and sensitivity of AD. Further exploration is warranted to establish how these may be further facilitated to translate into improved care for those with AD.
Collisional and transport parameters for Cu are computed using the average atom model. Transition metals such as copper are difficult to model within the framework of the average atom model due to the presence of a narrow band of 3 d electrons that mix and hybridize with the broad 4 s band of nearly-free electrons. With electron temperature increasing, the 3 d electrons play a key role in the thermodynamics and transport properties of Cu (Lin et al 2008 Phys. Rev. B 77 075133), as well as the stability of the lattice (Loboda et al 2011 High Energy Density Phys. 7 361). In this work, the average atom model was used to track the average energy of the 3 d band and its evolution with electron temperature. At room temperature, its center is at ∼6 electron volts (eV), a few electron-volts below the Fermi energy, and with electron temperature increasing it sinks relative to it. At electron temperature of about 8 eV the 3 d electrons leave the conduction band and become bound. A long-standing problem related to the average ion charge observed by conduction band electrons is addressed and successfully resolved. A work-around has been found that predicts the correct average ion charge, Z ˉ , by formally introducing a third group of electrons: quasi-bound electrons. Benchmarking with published data is made that shows good agreement.
