581 research outputs found
Multiscale Kinetic Monte-Carlo for Simulating Epitaxial Growth
We present a fast Monte-Carlo algorithm for simulating epitaxial surface
growth, based on the continuous-time Monte-Carlo algorithm of Bortz, Kalos and
Lebowitz. When simulating realistic growth regimes, much computational time is
consumed by the relatively fast dynamics of the adatoms. Continuum and
continuum-discrete hybrid methods have been developed to approach this issue;
however in many situations, the density of adatoms is too low to efficiently
and accurately simulate as a continuum. To solve the problem of fast adatom
dynamics, we allow adatoms to take larger steps, effectively reducing the
number of transitions required. We achieve nearly a factor of ten speed up, for
growth at moderate temperatures and large D/F.Comment: 7 pages, 6 figures; revised text, accepted by PR
Penerapan Model Pembelajaran Kooperatif TIME Token Untuk Meningkatkan Prestasi Belajar Siswa Pada Pokok Bahasan Reaksi Reduksi Oksidasi Di Kelas X SMA Negeri 2 Siak Hulu
Research on the application of cooperative learning model Time Token has been conducted to improve student learning achievement on the topic stoichiometry at class X SMAN 2 Siak Hulu. This research is experimental research with randomized control group pretest-posttest design. The sample took in the month February â maret 2013. The sample consisted of two class, X3 class as control class. Experimental class is the with cooperative learning model Time Token and Control Class is the class with cooperative learning model Time Token. Analyze of data by used t-test formula. Result of data processing obtained t count>t table is 2,07 > 1,67. It means that the application of cooperative learning model Time Token can improve student achievement on the topic redoks at class X SMAN 2 Siak Hulu with the increasing percentage of 6,299%
Characterising white matter in Huntington's disease
Background:
Investigating early white matter (WM) change in Huntingtonâs Disease (HD) can improve our understanding of the way in which disease spreads from the striatum.
Objectives:
Here, we provide a detailed characterisation of pathology-related WM change in HD. We first examined WM microstructure using diffusion-weighted imaging, then investigated both underlying biological properties of WM and products of WM damage including iron, myelin plus neurofilament light (NfL), a biofluid marker of axonal degeneration â in parallel with the mutant huntingtin protein (mHTT).
Methods:
We examined WM change in HD gene-carriers from the HD-CSF cohort, baseline visit. We used standard diffusion MRI to measure metrics including fractional anisotropy (FA), a marker of WM integrity, and diffusivity; a novel diffusion model (NODDI) to measure axonal density and organisation; T1 and T2 weighted structural MRI images to derive proxy iron content and myelin-contrast measures; and biofluid concentrations of NfL (in CSF and plasma) and mHTT (in CSF).
Results:
HD gene-carriers displayed reduced FA and increased diffusivity compared to controls, both of which were also associated with disease progression, CSF and mHTT levels. HD gene-carriers also displayed proxy measures of reduced myelin-contrast and iron in the striatum.
Conclusion:
Collectively, these findings present a more complete characterisation of HD-related microstructural brain changes. Correlation between reduced FA, increased axonal orientation and biofluid markers suggest that axonal breakdown is associated with increased WM degeneration, while higher quantitative T2 signal and lower myelin-contrast may indicate a process of demyelination limited to the striatum
Low Myoâinositol indicating astrocytic damage in a case series of neuromyelitis optica
Astrocytic necrosis is a prominent pathological feature of neuromyelitis optica (NMO) lesions and is clinically relevant. We report 5 NMOârelated cases, all with longitudinally extensive lesions in the upper cervical cord, who underwent cervical cord 1Hâmagnetic resonance spectroscopy. Lower myoâinositol/creatine values, suggesting astrocytic damage, were consistently found within the NMO lesions when compared with healthy controls and patients with multiple sclerosis (MS), who showed at least 1 demyelinating lesion at the same cord level. Therefore, the in vivo quantification of myoâinositol may distinguish NMO from MS. This is an important step toward developing imaging markers for clinical trials in NMO
The Heavy Photon Search test detector
The Heavy Photon Search (HPS), an experiment to search for a hidden sector photon in fixed target electroproduction, is preparing for installation at the Thomas Jefferson National Accelerator Facility (JLab) in the Fall of 2014. As the first stage of this project, the HPS Test Run apparatus was constructed and operated in 2012 to demonstrate the experimentŚłs technical feasibility and to confirm that the trigger rates and occupancies are as expected. This paper describes the HPS Test Run apparatus and readout electronics and its performance. In this setting, a heavy photon can be identified as a narrow peak in the e+eâ invariant mass spectrum above the trident background or as a narrow invariant mass peak with a decay vertex displaced from the production target, so charged particle tracking and vertexing are needed for its detection. In the HPS Test Run, charged particles are measured with a compact forward silicon microstrip tracker inside a dipole magnet. Electromagnetic showers are detected in a PbW04 crystal calorimeter situated behind the magnet, and are used to trigger the experiment and identify electrons and positrons. Both detectors are placed close to the beam line and split top-bottom. This arrangement provides sensitivity to low-mass heavy photons, allows clear passage of the unscattered beam, and avoids the spray of degraded electrons coming from the target. The discrimination between prompt and displaced e+eâ pairs requires the first layer of silicon sensors be placed only 10 cm downstream of the target. The expected signal is small, and the trident background huge, so the experiment requires very large statistics. Accordingly, the HPS Test Run utilizes high-rate readout and data acquisition electronics and a fast trigger to exploit the essentially 100% duty cycle of the CEBAF accelerator at JLab
Influences of alignment and obesity on knee joint loading in osteoarthritic gait
To determine the influences of frontal plane knee alignment and obesity on knee joint loads in older, overweight and obese adults with knee osteoarthritis
Why don't hospital staff activate the rapid response system (RRS)? How frequently is it needed and can the process be improved?
Abstract
Background
The rapid response system (RRS) is a process of accessing help for health professionals when a patient under their care becomes severely ill. Recent studies and meta-analyses show a reduction in cardiac arrests by a one-third in hospitals that have introduced a rapid response team, although the effect on overall hospital mortality is less clear. It has been suggested that the difficulty in establishing the benefit of the RRS has been due to implementation difficulties and a reluctance of clinical staff to call for additional help. This assertion is supported by the observation that patients continue to have poor outcomes in our institution despite an established RRS being available. In many of these cases, the patient is often unstable for many hours or days without help being sought. These poor outcomes are often discovered in an ad hoc fashion, and the real numbers of patients who may benefit from the RRS is currently unknown. This study has been designed to answer three key questions to improve the RRS: estimate the scope of the problem in terms of numbers of patients requiring activation of the RRS; determine cognitive and socio-cultural barriers to calling the Rapid Response Team; and design and implement solutions to address the effectiveness of the RRS.
Methods
The extent of the problem will be addressed by establishing the incidence of patients who meet abnormal physiological criteria, as determined from a point prevalence investigation conducted across four hospitals. Follow-up review will determine if these patients subsequently require intensive care unit or critical care intervention. This study will be grounded in both cognitive and socio-cultural theoretical frameworks. The cognitive model of situation awareness will be used to determine psychological barriers to RRS activation, and socio-cultural models of interprofessional practice will be triangulated to inform further investigation. A multi-modal approach will be taken using reviews of clinical notes, structured interviews, and focus groups. Interventions will be designed using a human factors analysis approach. Ongoing surveillance of adverse outcomes and surveys of the safety climate in the clinical areas piloting the interventions will occur before and after implementation
Measurement of the Polarized Structure Function for in the Resonance Region
The polarized longitudinal-transverse structure function
has been measured using the reaction in the
resonance region at and 0.65 GeV. No previous
data exist for this reaction channel. The kinematically
complete experiment was performed at Jefferson Lab with the CEBAF Large
Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at an
energy of 1.515 GeV. A partial wave analysis of the data shows generally better
agreement with recent phenomenological models of pion electroproduction
compared to the previously measured channel. A fit to both
and channels using a unitary isobar model suggests the unitarized
Born terms provide a consistent description of the non-resonant background. The
-channel pion pole term is important in the channel through a
rescattering correction, which could be model-dependent.Comment: 6 pages, LaTex, 5 eps figures: Submitted to PRC/Brief Reports v2:
Updated referenc
Measurement of Deeply Virtual Compton Scattering with a Polarized Proton Target
The longitudinal target-spin asymmetry A_UL for the exclusive
electroproduction of high energy photons was measured for the first time in
p(e,e'p\gamma). The data have been accumulated at Jefferson Lab with the CLAS
spectrometer using 5.7 GeV electrons and a longitudinally polarized NH_3
target. A significant azimuthal angular dependence was observed, resulting from
the interference of the Deeply Virtual Compton Scattering and Bethe-Heitler
processes. The amplitude of the sin(phi) moment is 0.252 +/- 0.042(stat) +/-
0.020(sys). Theoretical calculations are in good agreement with the magnitude
and the kinematic dependence of the target-spin asymmetry, which is sensitive
to the generalized parton distributions H and H-tilde.Comment: Modified text slightly, added reference
Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV
The three-body photodisintegration of 3He has been measured with the CLAS
detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV
and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first
time to cover a wide momentum and angular range for the two outgoing protons.
Three kinematic regions dominated by either two- or three-body contributions
have been distinguished and analyzed. The measured cross sections have been
compared with results of a theoretical model, which, in certain kinematic
ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications:
removed 2 figures, improvements on others, a few minor modifications to the
tex
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