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https://www.readbyqxmd.com/read/27911451/influence-of-specific-intermolecular-interactions-on-the-thermal-and-dielectric-properties-of-bulk-polymers-atomistic-molecular-dynamics-simulations-of-nylon-6
#1
N V Lukasheva, D A Tolmachev, V M Nazarychev, J M Kenny, S V Lyulin
Specific intermolecular interactions, in particular H-bonding, have a strong influence on the structural, thermal and relaxation characteristics of polymers. We report here the results of molecular dynamics simulations of Nylon 6 which provides an excellent example for the investigation of such an influence. To demonstrate the effect of proper accounting for H-bonding on bulk polymer properties, the AMBER99sb force field is used with two different parametrization approaches leading to two different sets of partial atomic charges...
December 2, 2016: Soft Matter
https://www.readbyqxmd.com/read/27910484/design-analysis-and-testing-of-kinematic-mount-for-astronomical-observation-instrument-used-in-space-camera
#2
Mingxin An, Lihao Zhang, Shuyan Xu, Jihong Dong
A statically determinate kinematic mount structure is designed for an astronomical observation instrument. The basic principle of the proposed kinematic mount is introduced in detail, including the design principle, its structure, and its degrees of freedom. The compliance equations for the single-axis right circle flexure hinge are deduced, and mathematical models of the compliances of the bipod in the X-axis and Z-axis directions are established. Based on the index requirements, the range of one design parameter (the hinge groove depth, R) for the kinematic mount is determined...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910444/synthetic-diagnostics-platform-for-fusion-plasmas-invited
#3
L Shi, E J Valeo, B J Tobias, G J Kramer, L Hausammann, W M Tang, M Chen
A Synthetic Diagnostics Platform (SDP) for fusion plasmas has been developed which provides state of the art synthetic reflectometry, beam emission spectroscopy, and Electron Cyclotron Emission (ECE) diagnostics. Interfaces to the plasma simulation codes GTC, XGC-1, GTS, and M3D-C(1) are provided, enabling detailed validation of these codes. In this paper, we give an overview of SDP's capabilities, and introduce the synthetic diagnostic modules. A recently developed synthetic ECE Imaging module which self-consistently includes refraction, diffraction, emission, and absorption effects is discussed in detail...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910290/radiation-therapy-staffing-model-2014
#4
Leigh J Smith, Rachel Kearvell, Anthony J Arnold, Kevina Choma, Aniko Cooper, Michael R Young, Donna L Matthews, Bronwyn Hilder, Debbie Howson, Katherine Fox, Katheryn Churcher
INTRODUCTION: In 2001, the Radiation Therapy Advisory Panel (RTAP) of the Australian Society of Medical Imaging and Radiation Therapy (ASMIRT) (formerly known as Australian Institute of Radiography) published a model for radiation therapist staffing in Australian radiation oncology departments. Between 2012-2013, the model was reviewed to ensure it reflected current radiation therapy practice, technology, and to facilitate forward planning of the radiation therapy workforce. METHOD: Twenty-four sites from all states participated and provided data on megavoltage simulation, planning and treatment delivery...
December 2016: Journal of Medical Radiation Sciences
https://www.readbyqxmd.com/read/27910162/effects-of-sample-size-and-distributional-assumptions-on-competing-models-of-the-factor-structure-of-the-panss-and-bprs
#5
Stephen J Tueller, Kiersten L Johnson, Kevin J Grimm, Sarah L Desmarais, Brian G Sellers, Richard A Van Dorn
Factor analytic work on the Positive and Negative Syndrome Scale (PANSS) and Brief Psychiatric Rating Scale (BPRS) has yielded varied and conflicting results. The current study explored potential causes of these discrepancies. Prior research has been limited by small sample sizes and an incorrect assumption that the items are normally distributed when in practice responses are highly skewed ordinal variables. Using simulation methodology, we examined the effects of sample size, (in)correctly specifying item distributions, collapsing rarely endorsed response categories, and four factor analytic models...
December 2, 2016: International Journal of Methods in Psychiatric Research
https://www.readbyqxmd.com/read/27909350/erosion-of-synchronization-coupling-heterogeneity-and-network-structure
#6
Per Sebastian Skardal, Dane Taylor, Jie Sun, Alex Arenas
We study the dynamics of network-coupled phase oscillators in the presence of coupling frustration. It was recently demonstrated that in heterogeneous network topologies, the presence of coupling frustration causes perfect phase synchronization to become unattainable even in the limit of infinite coupling strength. Here, we consider the important case of heterogeneous coupling functions and extend previous results by deriving analytical predictions for the total erosion of synchronization. Our analytical results are given in terms of basic quantities related to the network structure and coupling frustration...
June 1, 2016: Physica D. Nonlinear Phenomena
https://www.readbyqxmd.com/read/27908677/haemodynamic-variations-of-flow-to-renal-arteries-in-custom-made-and-pivot-branch-fenestrated-endografting
#7
J Ou, A Y S Tang, T L Chiu, K W Chow, Y C Chan, S W K Cheng
OBJECTIVE: This study aimed to investigate variation of blood flow to renal arteries in custom-made and pivot branch (p-branch) fenestrated endografting, using a computational fluid dynamics (CFD) technique. METHODS: Idealised models of custom-made and p-branch fenestrated grafting were constructed on a basis of a 26 mm stent graft. The custom-made fenestration was designed with a 6 mm diameter, while the 5 mm depth renal p-branch was created with a 6 mm inner and 15 mm outer fenestration...
November 28, 2016: European Journal of Vascular and Endovascular Surgery
https://www.readbyqxmd.com/read/27908486/an-inverse-method-to-determine-arterial-stiffness-with-guided-axial-waves
#8
Guo-Yang Li, Qiong He, Lin Jia, Ping He, Jianwen Luo, Yanping Cao
Many cardiovascular diseases can alter arterial stiffness; therefore, measurement of arterial wall stiffness can provide valuable information for both diagnosis of such diseases in the clinic and evaluation of the effectiveness of relevant drugs. However, quantitative assessment of the in vivo elastic properties of arterial walls in a non-invasive manner remains a great challenge. In this study, we found that the elastic modulus of the arterial wall can be extracted from the dispersion curve of the guided axial wave (GAW) measured using the ultrasound elastography method...
November 28, 2016: Ultrasound in Medicine & Biology
https://www.readbyqxmd.com/read/27908175/spatio-energetic-cross-talk-in-photon-counting-detectors-detector-model-and-correlated-poisson-data-generator
#9
Katsuyuki Taguchi, Christoph Polster, Okkyun Lee, Karl Stierstorfer, Steffen Kappler
PURPOSE: An x-ray photon interacts with photon counting detectors (PCDs) and generates an electron charge cloud or multiple clouds. The clouds (thus, the photon energy) may be split between two adjacent PCD pixels when the interaction occurs near pixel boundaries, producing a count at both of the pixels. This is called double-counting with charge sharing. (A photoelectric effect with K-shell fluorescence x-ray emission would result in double-counting as well). As a result, PCD data are spatially and energetically correlated, although the output of individual PCD pixels is Poisson distributed...
December 2016: Medical Physics
https://www.readbyqxmd.com/read/27908148/local-attenuation-curve-optimization-framework-for-high-quality-perfusion-maps-in-low-dose-cerebral-perfusion-ct
#10
Vincent Van Nieuwenhove, Geert Van Eyndhoven, K Joost Batenburg, Nico Buls, Jef Vandemeulebroucke, Jan De Beenhouwer, Jan Sijbers
PURPOSE: Cerebral perfusion x-ray computed tomography (PCT) is a powerful tool for noninvasive imaging of hemodynamic information throughout the brain. Conventional PCT requires the brain to be imaged multiple times during the perfusion process, and hence radiation dose is a major concern. The authors propose a PCT reconstruction algorithm that allows for lowering the dose while maintaining a high quality of the perfusion maps. It relies on an accurate estimation of the arterial input function (AIF), which in turn depends on the quality of the attenuation curves in the arterial region...
December 2016: Medical Physics
https://www.readbyqxmd.com/read/27908056/reconstruction-of-piano-hammer-force-from-string-velocity
#11
Antoine Chaigne
A method is presented for reconstructing piano hammer forces through appropriate filtering of the measured string velocity. The filter design is based on the analysis of the pulses generated by the hammer blow and propagating along the string. In the five lowest octaves, the hammer force is reconstructed by considering two waves only: the incoming wave from the hammer and its first reflection at the front end. For the higher notes, four- or eight-wave schemes must be considered. The theory is validated on simulated string velocities by comparing imposed and reconstructed forces...
November 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27908033/an-axisymmetric-time-domain-spectral-element-method-for-full-wave-simulations-application-to-ocean-acoustics
#12
Alexis Bottero, Paul Cristini, Dimitri Komatitsch, Mark Asch
The numerical simulation of acoustic waves in complex three-dimensional (3D) media is a key topic in many branches of science, from exploration geophysics to non-destructive testing and medical imaging. With the drastic increase in computing capabilities this field has dramatically grown in the last 20 years. However many 3D computations, especially at high frequency and/or long range, are still far beyond current reach and force researchers to resort to approximations, for example, by working in two dimensions (plane strain) or by using a paraxial approximation...
November 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27907999/leader-follower-consensus-and-synchronization-in-numerosity-constrained-networks-with-dynamic-leadership
#13
Subhradeep Roy, Nicole Abaid
In this work, we study leader-follower consensus and synchronization protocols over a stochastically switching network. The agents representing the followers can communicate with any other agent, whereas the agents serving as leaders are restricted to interact only with the other leaders. The model incorporates the phenomenon of numerosity, which limits the perceptual capacity of the agents while allowing for shuffling with whom each individual interacts at each time step. We derive closed form expressions for necessary and sufficient conditions for consensus, the rate of convergence to consensus, and conditions for stochastic synchronization in terms of the asymptotic convergence factor...
November 2016: Chaos
https://www.readbyqxmd.com/read/27907190/are-exam-questions-known-in-advance-using-local-dependence-to-detect-cheating
#14
Stefan Zimmermann, Dietrich Klusmann, Wolfgang Hampe
Cheating is a common phenomenon in high stakes admission, licensing and university exams and threatens their validity. To detect if some exam questions had been affected by cheating, we simulated how data would look like if some test takers possessed item preknowledge: Responses to a small number of items were set to correct for 1-10% of test takers. Item difficulty, item discrimination, item fit, and local dependence were computed using an IRT 2PL model. Then changes in these item properties from the non-compromised to the compromised dataset were scrutinized for their sensitivity to item preknowledge...
2016: PloS One
https://www.readbyqxmd.com/read/27907003/mapping-cholesterol-interaction-sites-on-serotonin-transporter-through-coarse-grained-molecular-dynamics
#15
Mariarosaria Ferraro, Matteo Masetti, Maurizio Recanatini, Andrea Cavalli, Giovanni Bottegoni
Serotonin transporter (SERT) modulates serotonergic signaling via re-uptake of serotonin in pre-synaptic cells. The inclusion in cholesterol-enriched membrane domains is crucial for SERT activity, suggesting a cross-talk between the protein and the sterol. Here, we develop a protocol to identify potential cholesterol interaction sites coupling statistical analysis to multi-microsecond coarse-grained molecular dynamics simulations of SERT in a previously validated raft-like membrane model. Six putative sites were found, including a putative CRAC motif on TM4 and a CARC motif on TM10...
2016: PloS One
https://www.readbyqxmd.com/read/27906472/long-term-clinical-impact-and-cost-effectiveness-of-obeticholic-acid-for-the-treatment-of-primary-biliary-cholangitis
#16
Sumeyye Samur, Matthew Klebanoff, Reiner Banken, Daniel S Pratt, Rick Chapman, Daniel A Ollendorf, Anne M Loos, Kathleen Corey, Chin Hur, Jagpreet Chhatwal
: Primary biliary cholangitis (PBC) is a chronic, progressive autoimmune liver disease that mainly affects middle-aged women. Obeticholic acid (OCA), which was recently approved by the Food and Drug Administration for PBC treatment, has demonstrated positive effects on biochemical markers of liver function. Our objective was to evaluate the long-term clinical impact and cost-effectiveness of OCA as a second-line treatment for PBC in combination with ursodeoxycholic acid (UDCA) in adults with an inadequate response to UDCA...
November 7, 2016: Hepatology: Official Journal of the American Association for the Study of Liver Diseases
https://www.readbyqxmd.com/read/27906468/optimal-timing-of-hepatitis-c-treatment-for-patients-on-the-liver-transplant-waiting-list
#17
Jagpreet Chhatwal, Sumeyye Samur, Brian Kues, Turgay Ayer, Mark S Roberts, Fasiha Kanwal, Chin Hur, Drew Michael S Donnell, Raymond T Chung
: The availability of oral direct-acting antiviral (DAAs) has altered the hepatitis C virus (HCV) treatment paradigm for both pre- and post-liver transplant (LT) patients. There is a perceived trade-off between pre- versus post-LT treatment of HCV-treatment may improve liver function but potentially decrease the likelihood of a necessary LT. Our objective was to identify LT-eligible patients with decompensated cirrhosis who would benefit (and not benefit) from pre-LT treatment based on their MELD scores...
November 5, 2016: Hepatology: Official Journal of the American Association for the Study of Liver Diseases
https://www.readbyqxmd.com/read/27906270/stochastic-model-for-quantum-noise-analysis-in-flat-panel-detectors-for-medical-imaging-applications
#18
Isao Yamada
A one-dimensional stochastic model is proposed to analyze the characteristics of quantum noise in flat-panel detectors (FPD) for medical imaging applications. The number of x-ray photons is modeled as a Poisson process, and explicit expressions for the autocorrelation function and noise power spectrum density (NPSD) are obtained in terms of the exposure dose, blur shape in the capture element, and pixel size. The results from the proposed model are validated with numerical simulations, and it is shown that this model can be used for the analysis of the noise properties of the FPD...
December 1, 2016: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
https://www.readbyqxmd.com/read/27905056/principal-covariates-clusterwise-regression-pccr-accounting-for-multicollinearity-and-population-heterogeneity-in-hierarchically-organized-data
#19
Tom Frans Wilderjans, Eva Vande Gaer, Henk A L Kiers, Iven Van Mechelen, Eva Ceulemans
In the behavioral sciences, many research questions pertain to a regression problem in that one wants to predict a criterion on the basis of a number of predictors. Although in many cases, ordinary least squares regression will suffice, sometimes the prediction problem is more challenging, for three reasons: first, multiple highly collinear predictors can be available, making it difficult to grasp their mutual relations as well as their relations to the criterion. In that case, it may be very useful to reduce the predictors to a few summary variables, on which one regresses the criterion and which at the same time yields insight into the predictor structure...
November 30, 2016: Psychometrika
https://www.readbyqxmd.com/read/27905055/a-multimethod-latent-state-trait-model-for-structurally-different-and-interchangeable-methods
#20
Tobias Koch, Martin Schultze, Jana Holtmann, Christian Geiser, Michael Eid
A new multiple indicator multilevel latent state-trait (LST) model for the analysis of multitrait-multimethod-multioccasion (MTMM-MO) data is proposed. The LST-COM model combines current CFA-MTMM modeling approaches of interchangeable and structurally different methods and LST modeling approaches. The model enables researchers to specify construct and method factors on the level of time-stable (trait) as well as time-variable (occasion-specific) latent variables and analyze the convergent and discriminant validity among different rater groups across time...
November 30, 2016: Psychometrika
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