683 research outputs found
A global simulation for laser driven MeV electrons in -diameter fast ignition targets
The results from 2.5-dimensional Particle-in-Cell simulations for the
interaction of a picosecond-long ignition laser pulse with a plasma pellet of
50- diameter and 40 critical density are presented. The high density
pellet is surrounded by an underdense corona and is isolated by a vacuum region
from the simulation box boundary. The laser pulse is shown to filament and
create density channels on the laser-plasma interface. The density channels
increase the laser absorption efficiency and help generate an energetic
electron distribution with a large angular spread. The combined distribution of
the forward-going energetic electrons and the induced return electrons is
marginally unstable to the current filament instability. The ions play an
important role in neutralizing the space charges induced by the the temperature
disparity between different electron groups. No global coalescing of the
current filaments resulted from the instability is observed, consistent with
the observed large angular spread of the energetic electrons.Comment: 9 pages, 6 figures, to appear in Physics of Plasmas (May 2006
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Electronic Clinical Quality Measures of Health Information Technology and Hospital Performance: Evidence of U.S. Hospitals
Electronic clinical quality measures (eCQMs) are an integral part of health information technology (HIT). This study explores the effect of eCQM implementation on hospital performance. The study proposes hospital profitability, efficiency, and quality to measure hospital performance. Based on the literature, this research hypothesizes that implementing eCQMs would positively impact hospital profitability, efficiency, and quality. The sample data are drawn from the 2017 American Hospital Association (AHA) U.S. Hospital Survey datasets (N = 6282), the 2017 AHA U.S. Hospital I.T. Survey dataset (N = 3451), and the 2017 Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) datasets (N = 4345). This paper also analyzes the effect of four control variables in the profitablity models – hospital bed size, location, ownership, and teaching status. The study uses multiple regression models to test the hypotheses. Data strongly supports Hypothesis 1 (profitability), moderately supports Hypothesis 2 (efficiency), and does not support Hypothesis 3 (quality). Control variables show mixed results. Both theoretical and practical implications are discussed. Implications and future directions for this research shed light on the potential benefits of implementing eCQMs in hospitals
Validating 3D two-parameter fracture mechanics models for structural integrity assessments
In-situ fracture tests were carried out on the I12 beamline at the Diamond Light Source. Four Al-Ti metal-matrix composites (MMCs), with two crack lengths, were studied to assess for the impact of in-plane constraint. Synchrotron X-ray computed tomography and synchrotron X-ray diffraction were used to measure total strain and elastic strain respectively. In this work, the measured elastic strains in the samples are detailed as a function of applied load and compared against those predicted from a 3D elastic-plastic finite element model. The modelled strains increased asymptotically towards the tip of the electro discharge machined notch. The experimental results do not highlight the same response, which is due to a combination of blunting and low experimental spatial resolution. Far field experimental and measured strain fields converged, notably in the test piece containing a long notch (a/W = 0.5) and higher levels of constraint
Coagulated Mineral Adsorbents for Dye Removal, and Their Process Intensification Using an Agitated Tubular Reactor (ATR)
The aim of this study was to understand the efficacy of widely available minerals as dual-function adsorbers and weighter materials, for the removal of toxic azo-type textile dyes when combined with coprecipitation processes. Specifically, the adsorption of an anionic direct dye was measured on various mineral types with and without the secondary coagulation of iron hydroxide (‘FeOOH’) in both a bench-scale stirred tank, as well as an innovative agitated tubular reactor (ATR). Talc, calcite and modified bentonite were all able to remove 90–95% of the dye at 100 and 200 ppm concentrations, where the kinetics were fitted to a pseudo second-order rate model and adsorption was rapid (99% of the dye was achieved for all the coagulated systems, where additionally, they produced significantly enhanced settling rates and bed compression. The greatest settling rate (9 mm min−1) and solids content increase (450% w/w) were observed for the calcium carbonate system, which also displayed the most homogenous distribution. This system was selected for scale-up and benchmarking in the ATR. Dye removal and sediment dispersion in the ATR were enhanced with respect to the bench scale tests, although lower settling rates were observed due to the relatively high shear rate of the agitator. Overall, results highlight the applicability of these cost-effective minerals as both dye adsorbers and sludge separation modifiers to accelerate settling and compression in textile water treatment. Additionally, the work indicates the suitability of the ATR as a flexible, modular alternative to traditional stirred tank reactors
Elemental signatures of Australopithecus africanus teeth reveal seasonal dietary stress
Reconstructing the detailed dietary behaviour of extinct hominins is challenging1\u2014particularly for a species such as Australopithecus africanus, which has a highly variable dental morphology that suggests a broad diet2,3. The dietary responses of extinct hominins to seasonal fluctuations in food availability are poorly understood, and nursing behaviours even less so; most of the direct information currently available has been obtained from high-resolution trace-element geochemical analysis of Homo sapiens (both modern and fossil), Homo neanderthalensis4 and living apes5. Here we apply high-resolution trace-element analysis to two A. africanus specimens from Sterkfontein Member 4 (South Africa), dated to 2.6\u20132.1 million years ago. Elemental signals indicate that A. africanus infants predominantly consumed breast milk for the first year after birth. A cyclical elemental pattern observed following the nursing sequence\u2014comparable to the seasonal dietary signal that is seen in contemporary wild primates and other mammals\u2014indicates irregular food availability. These results are supported by isotopic evidence for a geographical range that was dominated by nutritionally depauperate areas. Cyclical accumulation of lithium in A. africanus teeth also corroborates the idea that their range was characterized by fluctuating resources, and that they possessed physiological adaptations to this instability. This study provides insights into the dietary cycles and ecological behaviours of A. africanus in response to food availability, including the potential cyclical resurgence of milk intake during times of nutritional challenge (as observed in modern wild orangutans5). The geochemical findings for these teeth reinforce the unique place of A. africanus in the fossil record, and indicate dietary stress in specimens that date to shortly before the extinction of Australopithecus in South Africa about two million years ago
One-to-one direct modeling of experiments and astrophysical scenarios: pushing the envelope on kinetic plasma simulations
There are many astrophysical and laboratory scenarios where kinetic effects
play an important role. These range from astrophysical shocks and plasma shell
collisions, to high intensity laser-plasma interactions, with applications to
fast ignition and particle acceleration. Further understanding of these
scenarios requires detailed numerical modelling, but fully relativistic kinetic
codes are computationally intensive, and the goal of one-to-one direct
modelling of such scenarios and direct comparison with experimental results is
still difficult to achieve. In this paper we discuss the issues involved in
performing kinetic plasma simulations of experiments and astrophysical
scenarios, focusing on what needs to be achieved for one-to-one direct
modeling, and the computational requirements involved. We focus on code
efficiency and new algorithms, specifically on parallel scalability issues,
namely on dynamic load balancing, and on high-order interpolation and boosted
frame simulations to optimize simulation performance. We also discuss the new
visualization and data mining tools required for these numerical experiments
and recent simulation work illustrating these techniques is also presented.Comment: 10 pages, 5 figure
Ability and disability in autism spectrum disorder:a systematic literature review employing the International Classification of Functioning, Disability and Health-Children and Youth version
Objective: This study is the first in a series of four empirical investigations to develop International Classification of Functioning, Disability and Health (ICF) Core Sets for Autism Spectrum Disorder (ASD). The objective was to use a systematic review approach to identify, number, and link functional ability and disability concepts used in the scientific ASD literature to the nomenclature of the ICF-CY (Children and Youth version of the ICF, covering the life span). Methods: Systematic searches on outcome studies of ASD were carried out in Medline/PubMed, PsycINFO, ERIC and Cinahl, and relevant functional ability and disability concepts extracted from the included studies. These concepts were then linked to the ICF-CY by two independent researchers using a standardized linking procedure. New concepts were extracted from the studies until saturation of identified ICF-CY categories was reached. Results: Seventy-one studies were included in the final analysis and 2475 meaningful concepts con tained in these studies were linked to 146 ICF-CY categories. Of these, 99 categories were considered most relevant to ASD (i.e., identified in at least 5% of the studies), of which 63 were related to Activities and Participation, 28 were related to Body functions, and 8 were related to Environmental factors. The five most frequently identified categories were basic interpersonal interactions (51%), emotional functions (49%), complex interpersonal interactions (48%), attention functions (44%), and mental functions of language (44%). Conclusion: The broad variety of ICF-CY categories identified in this study reflects the heterogeneity of functional differences found in ASD—both with respect to disability and exceptionality—and underlines the potential value of the ICF-CY as a framework to capture an individual's functioning in all dimensions of life. The current results in combination with three additional preparatory studies (expert survey, focus groups, and clinical study) will provide the scientific basis for defining the ICF Core Sets for ASD for multipurpose use in basic and applied research and every day clinical practice of ASD. Autism Res 2015, 8: 782–794. © 2015 The Authors Autism Research published by Wiley Periodicals, Inc. on behalf of International Society for Autism Research
Ultrafast Structural Dynamics of BlsA, a Photoreceptor from the Pathogenic Bacterium Acinetobacter baumannii
Acinetobacter baumannii is an important human pathogen that can form biofilms and persist under harsh environmental conditions. Biofilm formation and virulence are modulated by blue light, which is thought to be regulated by a BLUF protein, BlsA. To understand the molecular mechanism of light sensing, we have used steady-state and ultrafast vibrational spectroscopy to compare the photoactivation mechanism of BlsA to the BLUF photosensor AppA from Rhodobacter sphaeroides. Although similar photocycles are observed, vibrational data together with homology modeling identify significant differences in the β5 strand in BlsA caused by photoactivation, which are proposed to be directly linked to downstream signaling
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