Formation of Pillars at the Boundaries between H II Regions and Molecular Clouds

We investigate numerically the hydrodynamic instability of an ionization front (IF) accelerating into a molecular cloud, with imposed initial perturbations of different amplitudes. When the initial amplitude is small, the imposed perturbation is completely stabilized and does not grow. When the initial perturbation amplitude is large enough, roughly the ratio of the initial amplitude to wavelength is greater than 0.02, portions of the IF temporarily separate from the molecular cloud surface, locally decreasing the ablation pressure. This causes the appearance of a large, warm HI region and triggers nonlinear dynamics of the IF. The local difference of the ablation pressure and acceleration enhances the appearance and growth of a multimode perturbation. The stabilization usually seen at the IF in the linear regimes does not work due to the mismatch of the modes of the perturbations at the cloud surface and in density in HII region above the cloud surface. Molecular pillars are observed in the late stages of the large amplitude perturbation case. The velocity gradient in the pillars is in reasonably good agreement with that observed in the Eagle Nebula. The initial perturbation is imposed in three different ways: in density, in incident photon number flux, and in the surface shape. All cases show both stabilization for a small initial perturbation and large growth of the second harmonic by increasing amplitude of the initial perturbation above a critical value.Comment: 21 pages, 8 figures, accepted for publication in ApJ. high resolution figures available upon reques

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

Scaling Extreme Astrophysical Phenomena to the Laboratory

High-energy-density (HED) physics refers broadly to the study of macroscopic collections of matter under extreme conditions of temperature and density. The experimental facilities most widely used for these studies are high-power lasers and magnetic-pinch generators. The HED physics pursued on these facilities is still in its infancy, yet new regimes of experimental science are emerging. Examples from astrophysics include work relevant to planetary interiors, supernovae, astrophysical jets, and accreting compact objects (such as neutron stars and black holes). In this paper, we review a selection of recent results in this new field of HED laboratory astrophysics and provide a brief look ahead to the coming decade

Lack of Correlation of WAIS Digit Span with Clox 1 and the Dementia Rating Scale in MCI

Individuals with MCI declined in performance over 6 months in the Clock-drawing (Clox 1) and the WAIS Digit Span tests, but not in the Dementia Rating Scale (DRS). Individual performance on Clox 1 and Digit Span did not correlate after 6 months. Performance on the Digit Span Test also did not correlate with the DRS, but performance on Clox 1 correlated with the DRS. Performance in Clox 1 was, therefore, not a predictor of performance in the Digit Span Test. These findings support the use of a test battery containing the Digit Span test to detect and track cognitive decline in MCI

Loneliness in autistic adults: A systematic review

In this systematic review, we examined quantitative, qualitative and mixed methods studies on loneliness in autistic adults. A total of 1460 articles were identified, and 34 of these met inclusion criteria. Results demonstrated that (1) there is a paucity of qualitative data providing first-hand descriptions of loneliness from autistic adults; (2) few empirical studies have used reliable/valid measures of loneliness developed specifically for autistic adults, and in just one study was a measure of loneliness developed for, and validated in, autistic adults; (3) the collective dimension of loneliness (i.e. belonging in society) has been described by autistic adults, yet has not been investigated as frequently as the intimate (i.e. romantic relationships) or relational (i.e. friend/family relationships) dimensions of loneliness; (4) the factors associated with increased loneliness in autistic adults include autistic characteristics, anxiety, depression and suicidal ideation, negative experiences and learned helplessness, a lack of autism understanding and acceptance, sensory avoidance, camouflaging and unemployment; and (5) the factors associated with decreased loneliness in autistic adults include having relationships, participation in social skill interventions and/or experiencing fewer difficulties with social skills, positive views and acceptance of oneself, being female and time spent engaging in activities (e.g. online gaming). Directions for future research are considered

Designing a Heat Sink for Lithium-ion Battery Packs in Electric Vehicles

This report addresses the concepts and implementation of fluid cooled heat sink designs for an electric or hybrid vehicle battery. To determine the battery’s temperature and heat flux profile, testing was performed by measuring these values at multiple locations on a lithium-ion pouch battery using heat flux sensors and thermocouples during the charge and discharge cycles of the battery. Once the data was collected and analyzed, trendlines were fit to the heat flux data then used to create equations for the heat flux profile during the discharging stage. Each equation represented a specific region on the battery geometry. Four heat sink designs were modeled in COMSOL Multiphysics to optimize cooling. The third model concept (Model 3) was chosen as the best model because it cooled the battery to the lowest temperature with the lowest pressure drop

Optimizing Laboratory Experiments for Dynamic Astrophysical Phenomena

To make a laboratory experiment an efficient tool for the studying the dynamical astrophysical phenomena, it is desirable to perform them in such a way as to observe the scaling invariance with respect to the astrophysical system under study. Several examples are presented of such scalings in the area of magnetohydrodynamic phenomena, where a number of scaled experiments have been performed. A difficult issue of the effect of fine-scale dissipative structures on the global scale dissipation-free flow is discussed. The second part of the paper is concerned with much less developed area of the scalings relevant to the interaction of an ultra-intense laser pulse with a pre-formed plasma. The use of the symmetry arguments in such experiments is also considered

Cognitive testing for dementia is adversely affected by administration in a foreign location

BACKGROUND: It is colloquially considered that cognitive tests can be adversely affected by administration in a foreign location. However, a definitive demonstration of this is lacking in the literature. To determine whether or not this is the case, we compared the results of cognitive testing in a familiar versus foreign environment by single test administrator of individuals diagnosed with Alzheimer\u27s disease randomized to placebo in a multi-site clinical study. FINDINGS: Cognitive tests were administered to 6 long-term residents of an assisted living facility at their residence (the Familiar cohort). The identical tests were administered to a newly admitted resident and to 2 community-dwelling individuals who drove to the administrator\u27s office for the first time (the Foreign cohort). Secondary testing was administered 3 months later at the same respective locations. Caregivers of participants completed reports of mood, behavior and activities of daily living. The Familiar cohort performed equally well at both visits. The Foreign cohort performed significantly worse than the Familiar cohort at baseline. They improved statistically, and matched Familiar cohort performance, by their second visit. Caregiver reports for both cohorts were unchanged between visits. CONCLUSIONS: These findings support the notion that a foreign location can adversely affect performance on cognitive tests, and therefore support cognitive testing in a familiar location