Search

The growth of three-dimensional perturbations subject to the Crow instability along a vortex dipole resulting from the passage of a shock wave through a heavy gaseous cylinder is examined numerically. A linear stability analysis is performed based on geometric parameters extracted from two-dimensional simulations to determine the range of unstable wavenumbers, which is found to extend from 0.0 to 1.3 when normalized by the core separation distance. The analysis is then verified by comparison to three-dimensional simulations, which clearly show the development of the instability and the pinch-off of the vortex dipole into isolated vortex rings, which manifest as clumps of the original cylinder material. A scaling law is developed to determine the relevant spatiotemporal scales of the instability development, which is then used to assess the feasibility of a high-energy-density experiment visualizing clump formation. Specifically, a shocked cylinder with an initial diameter of 100 μm consisting of a perturbation of approximate wavelength and amplitude of 600 and 10 μm, respectively, is expected to form clumps resulting from the Crow instability approximately 40 ns after it is shocked, with dynamics which can be readily visualized on the Omega EP laser facility. [ABSTRACT FROM AUTHOR]

In Parkinson’s disease (PD) patients, verbal suggestions have been shown to modulate motor and clinical outcomes in treatment with subthalamic deep brain stimulation (DBS). Furthermore, DBS may alleviate pain in PD. However, it is unknown if verbal suggestions influence DBS’ effects on pain.

Thermal transport of uniformly laser-irradiated spheres of various materials is investigated computationally. One-dimensional simulations of low- to mid-Z materials (Be, Al, and Cu) are performed to evaluate the impact of nonlocal electron transport on experimental observables under laser intensities of relevance to direct-drive inertial confinement fusion. We compare thermal transport models of different levels of fidelity: flux-limited Spitzer–Harm diffusion, the Schurtz–Nicolai–Busquet (SNB) reduced-order nonlocal model, and a Fokker–Planck description. Spitzer–Harm diffusion with different flux-limiter factors are compared with different implementations of the SNB model in the HYDRA radiation hydrodynamics code. Under the conditions of interest, the peak heat flux in the thermal front with the SNB model shows good agreement with Fokker–Planck calculations, with the largest errors below 10% at 1015 W/cm2 laser intensity. From HYDRA-SNB simulations, two experimentally relevant effects are observed from nonlocal heat transport when compared to flux-limited Spitzer–Harm modeling: coronal temperatures are cooler due to reduced heat fluxes in the expanding plasma and (for mid-Z materials) x-ray emissions are enhanced due to preheating in the dense plasma. [ABSTRACT FROM AUTHOR]

ISAV is the causative agent of the infectious salmon anaemia (ISA), a disease listed by the OIE that has caused important economic losses to the Atlantic salmon (Salmo salar) industry. ISAV variants are identified as pathogenic or non‐pathogenic based on the presence or absence of a deletion in the highly polymorphic region (HPR) of segment 6 (S6). HPRΔ variants (pathogenic) are the only forms of the virus known to grow in cell culture. This is the first report of a HPR0 variant isolated in cell culture. The isolate is, however, atypical as it shows a marker of virulent variants on another segment (S5), which has never been reported for any other HPR0 variants. The significance of this finding remains unclear until more in‐depth work is carried out but does challenge current knowledge. [ABSTRACT FROM AUTHOR]

We present a set of high explosive driven Rayleigh-Taylor strength experiments for beryllium to produce data to distinguish predictions by various strength models. Design simulations using existing strength model parameterizations from Steinberg-Lund and Preston-Tonks-Wallace (PTW) suggested an optimal design that would delineate between not just different strength models, but different parameters sets of the PTW model. Application of the models to the post-shot results, however, suggests growth consistent with little material strength. We focus mostly on efforts to simulate the data using published strength models as well as the more recent RING relaxation model developed at VNIIEF. The results of the strength experiments indicate weak influence of strength in mitigating the growth with the RING model coming closest to predicting the material behavior. Finally, we present shock and ramp-loading recovery experiments. [ABSTRACT FROM AUTHOR]

We consider hydrodynamic instabilities produced by the interaction of an oblique shock with a perturbed material interface under high-energy-density (HED) conditions. During this interaction, a baroclinic torque is generated along the interface due to the misalignment between the density and pressure gradients, thus leading to perturbation growth. Our objective is to understand the competition between the impulsive acceleration due to the normal component of the shock velocity, which drives the Richtmyer–Meshkov instability, and the shear flow across the interface due to the tangential component of the shock velocity, which drives the Kelvin–Helmholtz instability, as well as its relation to perturbation growth. Since the vorticity resulting from the shock-interface interaction is confined to the interface, we describe the perturbation growth using a two-dimensional vortex-sheet model. We demonstrate the ability of the vortex-sheet model to reproduce roll-up dynamics for non-zero Atwood numbers by comparing to past laser-driven HED experiments. We determine the dependence of the interface dynamics on the tilt angle and propose a time scaling for the perturbation growth at early time. Eventually, this scaling will serve as a platform for the design of future experiments. This study is the first attempt to incorporate into a vortex-sheet model the time-dependent interface decompression and the deceleration (as well as the corresponding Rayleigh–Taylor instability) arising from laser turn-off. [ABSTRACT FROM AUTHOR]

Summarizes data on developmental patterns in constructive play--play in which children use play materials to make something. Reviews knowledge about developmental correlates and effects of constructive play behavior and examines methodological and theoretical issues. (NH)

The dynamics of bubbles inertially collapsing in water near solid objects have been the subject of numerous studies in the context of cavitation erosion. While non-spherical bubble collapse, re-entrant jet dynamics and emitted shock waves have received significant interest, less is known about the temperatures thereby produced and their possible connection to damage. In this article, we use highly resolved numerical simulations of a single bubble inertially collapsing near a rigid surface to measure the temperatures produced in the fluid and estimate those in the solid, as well as to identify the responsible mechanisms. In particular, we find that elevated temperatures along the wall can be produced by one of two mechanisms, depending on the initial stand-off distance of the bubble from the wall and the driving pressure: for bubbles initially far from the wall, the shock generated by the bubble collapse is the source of the high temperature, while bubbles starting initially closer migrate towards the wall and eventually come into contact with it. A scaling is introduced to describe the maximum fluid temperature along the wall as a function of the initial stand-off distance and driving pressure. To predict the temperature of the solid, we develop a semianalytical heat transfer model, which supports recent experimental observations that elevated temperatures achieved during collapse could play a role in cavitation damage to soft heat-sensitive materials. [ABSTRACT FROM AUTHOR]

Background: Childhood trauma (CT) is a potential risk factor in psychosis, and the prevalence of CT may be higher in patients with psychosis compared to other mental health disorders. The aim of the study was to investigate the potential specificity of CT in psychosis. Methods: The sample consisted of 52 patients with schizophrenia spectrum disorders and 52 matched patients with other mental health disorders. CT was measured by the CTQ-SF. The groups were compared on CTQ-SF sum and subscale scores indicating rates of CT, in addition to rates of none/low vs. moderate/severe levels of CT. Results: The psychosis group had significantly higher CTQ-SF sum scores, and reported significantly higher levels of, and more severe, physical and sexual abuse and physical neglect. Also, 67.3% of the psychosis group reported ≥ 1 CT above the cut-off, compared to 38.5% in the non-psychosis group. No patients in the non-psychosis group reported ≥ 4 CT, compared to 9.6% in the psychosis group. Conclusions: Patients with psychosis reported more severe and frequent CT compared to non-psychotic patients. Our results may indicate some specificity for moderate and severe levels of physical and sexual abuse, and physical neglect, in schizophrenia spectrum disorders. [ABSTRACT FROM PUBLISHER]

In a variety of recently developed medical procedures, bubbles are formed directly in soft tissue and may cause damage. While cavitation in Newtonian liquids has received significant attention, bubble dynamics in tissue, a viscoelastic medium, remains poorly understood. To model tissue, most previous studies have focused on Maxwell-based viscoelastic fluids. However, soft tissue generally possesses an original configuration to which it relaxes after deformation. Thus, a Kelvin–Voigt-based viscoelastic model is expected to be a more appropriate representation. Furthermore, large oscillations may occur, thus violating the infinitesimal strain assumption and requiring a nonlinear/finite-strain elasticity description. In this article, we develop a theoretical framework to simulate spherical bubble dynamics in a viscoelastic medium with nonlinear elasticity. Following modern continuum mechanics formalism, we derive the form of the elastic forces acting on a bubble for common strain-energy functions (e.g. neo-Hookean, Mooney–Rivlin) and incorporate them into Rayleigh–Plesset-like equations. The main effects of nonlinear elasticity are to reduce the violence of the collapse and rebound for large departures from the equilibrium radius, and increase the oscillation frequency. The present approach can readily be extended to other strain-energy functions and used to compute the stress/deformation fields in the surrounding medium. [ABSTRACT FROM PUBLISHER]

In this work, we examine the hydrodynamics of high-energy-density (HED) shear flows. Experiments, consisting of two materials of differing density, use the OMEGA-60 laser to drive a blast wave at a pressure of ~50 Mbar into one of the media, creating a shear flow in the resulting shocked system. The interface between the two materials is Kelvin-Helmholtz unstable, and a mixing layer of growing width develops due to the shear. To theoretically analyze the instability's behavior, we rely on two sources of information. First, the interface spectrum is well-characterized, which allows us to identify how the shock front and the subsequent shear in the post-shock flow interact with the interface. These observations provide direct evidence that vortex merger dominates the evolution of the interface structure. Second, simulations calibrated to the experiment allow us to estimate the time-dependent evolution of the deposition of vorticity at the interface. The overall result is that we are able to choose a hydrodynamic model for the system, and consequently examine how well the flow in this HED system corresponds to a classical hydrodynamic description. [ABSTRACT FROM AUTHOR]

Merluccius capensis and M. paradoxus are morphologically very similar and cannot be registered separately by species in the Namibian commercial hake catches. This prevents a biologically plausible single-species stock assessment from being carried out. Here, species-separated data from an observer programme and scientific surveys are used to model the spatio-temporal overlap of the two species, which are then used to predict the catch by species in each commercial trawl. The study presents a method that compensates for both the escapement and codend retention differences in the survey and commercial trawls. The accuracy with which species were identified was found to be considerably higher during scientific surveys compared with that obtained from observers, whereas the seasonal coverage of the observer data was much better than that of the surveys. The estimated spatio-temporal model parameters from each of these two data sources were similar, however, despite these differences. In support of previous findings, M. capensis had a shallower and more northerly distribution than M. paradoxus with depth and latitude together explaining 51% and 85% of the residuals in the models produced from observer and survey data respectively. Model outputs suggest that during the period 1998–2007, M. paradoxus has dominated the annual hake catches. Even though our method is unable to account for abrupt and unexpected changes in the species’ geographical distribution, it does open the way for the establishment of a single-species hake assessment in Namibia. [ABSTRACT FROM AUTHOR]

Infectious salmon anaemia virus (ISAV) surveillance in the Bay of Fundy has identified the existence of a large number of genetically distinct ISAV isolates which appear to be of variable virulence. Genetically distinct isolates are currently being designated based on sequencing of the hyper polymorphic region (HPR) of genomic segment 6, which encodes the haemagglutinin–esterase protein, but it has been difficult to elucidate a clear association between these molecular variations and variations in virulence. This has hampered the establishment of proactive management decisions regarding infected fish, and ISAV infections, regardless of type, must be treated as one. Field data of ISAV infections is difficult to collect and to compare between infections because of a wide range of confounding factors including time of year, fish stock, cage site location, mitigating factors and stressors. An important tool in determining the relationship between molecular differences and virulence comes from analysis of quarantine studies. The goal of this study was to compare the virulence, by co-habitation and intraperitoneal injection, of four regionally common and recent ISAV isolates in a controlled environment. We found significant differences in mortality between ISAV molecular isolates, and present data showing that survival of ISAV infection confers significant resistance to re-infection with a different ISAV isolate. These findings, if borne out in field studies, will significantly alter the way ISAV infections are managed in the Bay of Fundy and elsewhere. [ABSTRACT FROM AUTHOR]

Johnsen, E., and Godø, O. R. 2007. Diel variations in acoustic recordings of blue whiting (Micromesistius poutassou). – ICES Journal of Marine Science, 64: 1202–1209. Annual landings of blue whiting (Micromesistius poutassou) in the northeast Atlantic have exceeded 2 million metric tonnes in recent years, and overexploitation is an increasing concern in terms of the sustainability of the fishery. The most important fisheries-independent dataset used for tuning the analytical stock assessment comes from the Norwegian surveys of blue whiting west off the British Isles. The survey is carried out in March/April during peak spawning, and improving its quality will have a direct positive effect on stock assessment. Here, we analyse diel effects on the abundance and vertical distribution as recorded by acoustics in 1995 and 1996 and from 1998 to 2002, and evaluate the potential effects on the survey estimates. On average, the acoustic density of blue whiting was ∼20% higher by day than by night. However, the diel bias varied considerably among years, and surprisingly, the acoustic density in shallow water (<350 m) was in general highest at night, when the blue whiting were distributed higher in the water column and more dispersed. The span in the vertical depth range increased considerably with bottom depth in water shallower than 550 m. In deeper water, where blue whiting had little or no bottom association, the day–night differences in vertical distribution were smaller and not affected by bottom depth. The inconsistency of the diel effect from year to year negatively affects the time-series used during annual stock assessments. [ABSTRACT FROM PUBLISHER]

Since the introduction of chlorpromazine, an increasing number of drugs have been added to the list of antipsychotics (neuroleptics). These drugs can be further classified as either first-generation antipsychotics (FAPs) or second-generation antipsychotics (SAPs), depending on their ability to antagonize serotonine in addition to dopamine. The efficacy of various drugs is generally equal, whereas both pharmacological profiles and side-effects differ. Antipsychotic drug therapy recommendations are available both in Norway and internationally, and the purpose of this cross-sectional survey was to register the use of these drugs in representative mental hospitals (A and B), and compare our findings to the recommendations. Medical prescriptions were registered, and data further analysed. In hospital A, a total of 149 patients' prescriptions were registered. Antipsychotics were received voluntarily by 117 patients. Eighty-two of these used one antipsychotic drug, and in this group, 65% received SAPs. Antipsychotic combination therapy was received by 35 patients, and was associated with higher prescription rates of both anticholinergics and benzodiazepines. SAPs were not associated with increased use of benzodiazepines, compared to FAPs. Antipsychotics were frequently combined with mood stabilizers and antidepressants. Our findings in hospital A concerning therapy practices of antipsychotics, were confirmed in hospital B, where 64 patients' medical prescriptions were registered. We conclude that FAPs are still commonly prescribed. Antipsychotic combination therapy is used despite of lack of evidence for efficacy, and is associated with increased prescription rates of anticholinergics and benzodiazepines. [ABSTRACT FROM AUTHOR]

In this paper we introduce and evaluate a method for eliciting a representative sample of total personal networks. First names were used as a cue to elicit a sample of 14 alters from 712 respondents through a telephone interview. Network characteristics for each respondent were calculated as averages and proportions across the 14 alters. These were compared to other studies using more specialized network generators. Our method produced results which are logically consistent with those expected from a generator that elicits a sample from the total rather than a specialized subset of the total network. The proportions of kin relations, average tie strength and frequency of contacts are found to be lower than network generators designed to elicit networks of social support. Given our conclusion that the sample is representative of the total network, we examine the varying characteristics of respondents and their networks based on the domination of a particular relation type in their network. This analysis provides answers to such questions as "What characteristics of respondents account for the proportion of family relations in their network?' and 'What are the similarities between respondents whose networks are made up of mostly work-related relations?' [ABSTRACT FROM AUTHOR]

This study investigated the relationship between the duration of indoor free play periods and the social and cognitive levels of preschoolers' play. The play of thirty-four 4- and 5-year-old children in two preschool class-rooms was observed during 15 and 30 minute play periods over an 8-week period using Rubin's social-cognitive scale. It was hypothesized that the children would exhibit a higher percentage of mature play categories relative to other forms of play during the longer play periods than during the shorter ones. Wilcoxon signed ranks tests confirmed this hypothesis, with subjects being found to engage in significantly higher percentages of group play, constructive play and group-dramatic play in the long periods. [ABSTRACT FROM PUBLISHER]

Introduction: Use of antipsychotic drugs is common in nonpsychotic disorders such as depression, anxiety, autism spectrum disorders, and insomnia. But exposure to antipsychotic drugs has been associated with a range of serious adverse events from arrythmias to diabetes. There is a need for detailed information on current practice and trends in the utilization of this drug class to guide future initiatives on the rational use of antipsychotic drugs. Objectives: To investigate trends in dosing and prevalence of antipsychotic prescriptions in Scandinavia. Methods:Weretrieved data on antipsychotic use between 2006 and 2016 from Danish, Norwegian and Swedish national prescription registers. For each antipsychotic, we calculated prevalence of use and mean doses, overall and for specific age groups. Results: Antipsychotic use in Scandinavia increased from 16.5 to 17.2 users/1,000 inhabitants between 2006 and 2016 (+2.4%, p=0.02). In 2006, chlorprothixene and levomepromazine were the most commonly used antipsychotics. By 2016, quetiapine was the most used antipsychotic in all three countries and across all age groups, with an overall one-year prevalence of 4.05 to 9.97 users/1,000 inhabitants. Mean doses of quetiapine decreased markedly during the 11-year study period (0.46 to 0.28 DDD/user/day), while mean doses for clozapine and olanzapine remained high (0.90-1.07 resp. 0.66-0.88DDD/user/day). Conclusions: We found an increasing prevalence of antipsychotic prescriptions that coincides with low and/or decreasing mean doses of the majority of commonly used antipsychotics in Scandinavia. Of all antipsychotics, this development was most pronounced for quetiapine. Reasons for and consequences of increased antipsychotic use that lasts shorter periods of time requires further study. [ABSTRACT FROM AUTHOR]

Abstract Background This study examines the patients' need for information and guidance in the selection of dialysis modality, and in establishing and practicing home dialysis. The study focuses on patients' experiences living with home dialysis, how they master the treatment, and their views on how to optimize communication with health services and the potential of telemedicine. Methods We used an inductive research strategy and conducted semi-structured interviews with eleven patients established in home dialysis. Our focus was the patients' experiences with home dialysis, and our theoretical reference was patients' empowerment through telemedicine solutions. Three informants had home haemodialysis (HHD); eight had peritoneal dialysis (PD), of which three had automated peritoneal dialysis (APD); and five had continuous ambulatory peritoneal dialysis (CAPD). The material comprises all PD-patients in the catchment area capable of being interviewed, and all known HHD-users in Norway at that time. Results All of the interviewees were satisfied with their choice of home dialysis, and many experienced a normalization of daily life, less dominated by disease. They exhibited considerable self-management skills and did not perceive themselves as ill, but still required very close contact with the hospital staff for communication and follow-up. When choosing a dialysis modality, other patients' experiences were often more influential than advice from specialists. Information concerning the possibility of having HHD, including knowledge of how to access it, was not easily available. Especially those with dialysis machines, both APD and HHD, saw a potential for telemedicine solutions. Conclusions As home dialysis may contribute to a normalization of life less dominated by disease, the treatment should be organized so that the potential for home dialysis can be fully exploited. Pre-dialysis information should be unbiased and include access to other patients' experiences. Telemedicine may potentially facilitate a communication-based follow-up and improve safety within the home setting, making it easier to choose and live with home dialysis.