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Modeling and Simulation

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https://www.readbyqxmd.com/read/28432960/molecular-dynamic-simulations-on-tkx-50-rdx-cocrystal
#1
Shuling Xiong, Shusen Chen, Shaohua Jin
Dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) is a newly synthesized energetic material with excellent comprehensive properties. Cyclotrimethylenetrinitramine (RDX) is currently one of the most widely used energetic materials in the world. TKX-50 and RDX supercell models and TKX-50/RDX cocrystal model were constructed based on their crystal cell parameters and the formation mechanism of cocrystal, respectively, then they were simulated by molecular dynamics (MD) simulations. The maximum trigger bond (NNO2) length(Lmax), binding energy (Ebind), radial distribution function (RDF), cohesive energy density(CED) and mechanical properties were simulated at different temperatures based on the simulated equilibrium structures of the models...
March 19, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28432953/new-and-practical-mathematical-model-of-membrane-fouling-in-an-aerobic-submerged-membrane-bioreactor
#2
Mst Fazana Rahman Zuthi, Wenshan Guo, Huu Hao Ngo, Duc Long Nghiem, Faisal I Hai, Siqing Xia, Jianxin Li, Jixiang Li, Yi Liu
This study aimed to develop a practical semi-empirical mathematical model of membrane fouling that accounts for cake formation on the membrane and its pore blocking as the major processes of membrane fouling. In the developed model, the concentration of mixed liquor suspended solid is used as a lumped parameter to describe the formation of cake layer including the biofilm. The new model considers the combined effect of aeration and backwash on the foulants' detachment from the membrane. New exponential coefficients are also included in the model to describe the exponential increase of transmembrane pressure that typically occurs after the initial stage of an MBR operation...
April 4, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28432909/source-receptor-relationships-for-pm2-5-during-typical-pollution-episodes-in-the-pearl-river-delta-city-cluster-china
#3
Yiming Liu, Yingying Hong, Qi Fan, Xuemei Wang, Pakwai Chan, Xiaoyang Chen, Anqi Lai, Mingjie Wang, Xunlai Chen
Located in the Southern China monsoon region, pollution days in Pearl River Delta (PRD) were classified into "Western type", "Central type" or "Eastern type", with a relative percentage of 67%, 24% and 9%, respectively. Using this classification system, three typical pollution events were selected for numerical simulations using the WRF-Chem model. The source sensitivity method for anthropogenic emissions of PM2.5 and its precursors was applied to identify the source-receptor relationships for PM2.5 among 9 cities in PRD...
April 19, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28432889/reducing-domestic-heating-demand-managing-the-impact-of-behavior-changing-feedback-devices-via-marketing
#4
Thorben Jensen, Émile J L Chappin
Feedback devices can be used to inform households about their energy-consumption behavior. This may persuade them to practice energy conservation. The use of feedback devices can also-via word of mouth-spread among households and thereby support the spread of the incentivized behavior, e.g. energy-efficient heating behavior. This study investigates how to manage the impact of these environmental innovations via marketing. Marketing activities can support the diffusion of devices. This study aims to identify the most effective strategies of marketing feedback devices...
April 19, 2017: Journal of Environmental Management
https://www.readbyqxmd.com/read/28432828/quantitative-contrast-enhanced-spectral-mammography-based-on-photon-counting-detectors-a-feasibility-study
#5
Huanjun Ding, Sabee Molloi
PURPOSE: To investigate the feasibility of accurate quantification of iodine mass thickness in contrast-enhanced spectral mammography. MATERIALS AND METHODS: A computer simulation model was developed to evaluate the performance of a photon-counting spectral mammography system in the application of contrast-enhanced spectral mammography. A figure-of-merit (FOM), which was defined as the decomposed iodine signal-to-noise ratio (SNR) with respect to the square root of the mean glandular dose (MGD), was chosen to optimize the imaging parameters, in terms of beam energy, splitting energy, and pre-filtrations for breasts of various thicknesses and densities...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432820/the-impact-of-small-motion-on-the-visualization-of-coronary-vessels-and-lesions-in-cardiac-ct-a-simulation-study
#6
Francisco Contijoch, J Webster Stayman, Elliot R McVeigh
PURPOSE: Coronary x-ray computed tomography angiography (CCTA) is used to non-invasively assess coronary artery geometry and has, combined with computational modeling, demonstrated the potential to identify physiologically significant lesions. These measurements require robust and accurate coronary imaging and delineation of vessels in the presence of small motion. This simulation study characterizes the impact of small, uncorrected vessel drifts during data acquisition on the assessment of vessel intensity, diameter, and shape...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432792/monte-carlo-study-of-the-chamber-phantom-air-gap-effect-in-a-magnetic-field
#7
Daniel J O'Brien, Gabriel O Sawakuchi
PURPOSE: The aim of this study was to examine the effect of sub-millimeter air gaps that may exist between an ionization chamber and solid phantoms when measurements are performed in a magnetic field. METHODS: Geant4 Monte Carlo simulations were performed using a model of a PTW 30013 Farmer chamber in a water phantom. Symmetrical and asymmetrical air gaps of various thicknesses were modeled surrounding the chamber, and the dose to the air cavity of the chamber was scored in each case...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432786/the-comprehensive-connectome-of-a-neural-substrate-for-on-motion-detection-in-drosophila
#8
Shin-Ya Takemura, Aljoscha Nern, Dmitri B Chklovskii, Louis K Scheffer, Gerald M Rubin, Ian A Meinertzhagen
Analysing computations in neural circuits often uses simplified models because the actual neuronal implementation is not known. For example, a problem in vision, how the eye detects image motion, has long been analysed using Hassenstein-Reichardt (HR) detector or Barlow-Levick (BL) models. These both simulate motion detection well, but the exact neuronal circuits undertaking these tasks remain elusive. We reconstructed a comprehensive connectome of the circuits of Drosophila's motion-sensing T4 cells using a novel EM technique...
April 22, 2017: ELife
https://www.readbyqxmd.com/read/28432656/collisional-cross-sections-with-t-wave-ion-mobility-spectrometry-without-experimental-calibration
#9
Daniel N Mortensen, Anna C Susa, Evan R Williams
A method for relating traveling-wave ion mobility spectrometry (TWIMS) drift times with collisional cross-sections using computational simulations is presented. This method is developed using SIMION modeling of the TWIMS potential wave and equations that describe the velocity of ions in gases induced by electric fields. The accuracy of this method is assessed by comparing the collisional cross-sections of 70 different reference ions obtained using this method with those obtained from static drift tube ion mobility measurements...
April 21, 2017: Journal of the American Society for Mass Spectrometry
https://www.readbyqxmd.com/read/28432489/design-development-and-clinical-validation-of-computer-aided-surgical-simulation-system-for-streamlined-orthognathic-surgical-planning
#10
REVIEW
Peng Yuan, Huaming Mai, Jianfu Li, Dennis Chun-Yu Ho, Yingying Lai, Siting Liu, Daeseung Kim, Zixiang Xiong, David M Alfi, John F Teichgraeber, Jaime Gateno, James J Xia
PURPOSE: There are many proven problems associated with traditional surgical planning methods for orthognathic surgery. To address these problems, we developed a computer-aided surgical simulation (CASS) system, the AnatomicAligner, to plan orthognathic surgery following our streamlined clinical protocol. METHODS: The system includes six modules: image segmentation and three-dimensional (3D) reconstruction, registration and reorientation of models to neutral head posture, 3D cephalometric analysis, virtual osteotomy, surgical simulation, and surgical splint generation...
April 21, 2017: International Journal of Computer Assisted Radiology and Surgery
https://www.readbyqxmd.com/read/28432423/note-on-the-coefficient-of-variations-of-neuronal-spike-trains
#11
Johannes Lengler, Angelika Steger
It is known that many neurons in the brain show spike trains with a coefficient of variation (CV) of the interspike times of approximately 1, thus resembling the properties of Poisson spike trains. Computational studies have been able to reproduce this phenomenon. However, the underlying models were too complex to be examined analytically. In this paper, we offer a simple model that shows the same effect but is accessible to an analytic treatment. The model is a random walk model with a reflecting barrier; we give explicit formulas for the CV in the regime of excess inhibition...
April 21, 2017: Biological Cybernetics
https://www.readbyqxmd.com/read/28432304/decreasing-temperature-enhances-the-formation-of-sixfold-hydrogen-bonded-rings-in-water-rich-water-methanol-mixtures
#12
Imre Bakó, László Pusztai, László Temleitner
The evolution of the structure of liquid water-methanol mixtures as a function of temperature has been studied by molecular dynamics simulations, with a focus on hydrogen bonding. The combination of the OPLS-AA (all atom) potential model of methanol and the widely used SPC/E water model has provided excellent agreement with measured X-ray diffraction data over the temperature range between 298 and 213 K, for mixtures with methanol molar fractions of 0.2, 0.3 and 0.4. Hydrogen bonds (HB-s) have been identified via a combined geometric/energetic, as well as via a purely geometric definition...
April 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28432206/identifying-factors-that-lead-to-the-persistence-of-imported-gonorrhoeae-strains-a-modelling-study
#13
Ben B Hui, David M Whiley, Basil Donovan, Matthew G Law, David G Regan
OBJECTIVE: The importation of Neisseria gonorrhoeae (NG) strains from overseas is believed to be the main source of antimicrobial resistance in Australia. With recent sporadic cases of ceftriaxone-resistant gonorrhoea reported in Australia and elsewhere, we sought to model the potential for imported NG strains to persist in the men who have sex with men (MSM) population in Australia. METHODS: We developed an individual-based model to simulate the transmission of NG in a population of urban MSM, and used this model to investigate factors contributing to the probability that an imported NG strain will persist...
May 2017: Sexually Transmitted Infections
https://www.readbyqxmd.com/read/28432139/feature-selective-attention-adaptively-shifts-noise-correlations-in-primary-auditory-cortex
#14
Joshua Downer, Brittany Rapone, Jessica Verhein, Kevin N O'Connor, Mitchell L Sutter
Sensory environments often contain an overwhelming amount of information, with both relevant and irrelevant information competing for neural resources. Feature attention mediates this competition by selecting the sensory features needed to form a coherent percept. How attention affects the activity of populations of neurons to support this process is poorly understood because population coding is typically studied through simulations in which one sensory feature is encoded without competition. Therefore, to study the effects of feature attention on population-based neural coding, investigations must be extended to include stimuli with both relevant and irrelevant features...
April 21, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28432039/simulation-training-evaluating-the-instructor-s-contribution-to-a-wizard-of-oz-simulator-in-obstetrics-and-gynecology-ultrasound-training
#15
Aric Katz, Ronnie Tepper, Avraham Shtub
BACKGROUND: Workplaces today demand graduates who are prepared with field-specific knowledge, advanced social skills, problem-solving skills, and integration capabilities. Meeting these goals with didactic learning (DL) is becoming increasingly difficult. Enhanced training methods that would better prepare tomorrow's graduates must be more engaging and game-like, such as feedback based e-learning or simulation-based training, while saving time. Empirical evidence regarding the effectiveness of advanced learning methods is lacking...
April 21, 2017: JMIR Medical Education
https://www.readbyqxmd.com/read/28431980/shear-stress-alterations-in-the-celiac-trunk-of-patients-with-a-continuous-flow-left-ventricular-assist-device-as-shown-by-in-silico-and-in-vitro-flow-analyses
#16
Francesco Scardulla, Salvatore Pasta, Leonardo D'Acquisto, Sergio Sciacca, Valentina Agnese, Christian Vergara, Alfio Quarteroni, Francesco Clemenza, Diego Bellavia, Michele Pilato
BACKGROUND: The use of left ventricular assist devices (LVADs) to treat advanced cardiac heart failure is constantly increasing, although this device leads to high risk for gastrointestinal bleeding. METHODS: Using in-silico flow analysis, we quantified hemodynamic alterations due to continuous-flow LVAD (HeartWare, Inc., Framingham, MA) in the celiac trunk and major branches of the abdominal aorta, and then explored the relationship between wall shear stress (WSS) and celiac trunk orientation...
March 24, 2017: Journal of Heart and Lung Transplantation
https://www.readbyqxmd.com/read/28431936/galectin-3-mediates-the-pulmonary-arterial-hypertension-induced-right-ventricular-remodeling-through-interacting-with-nadph-oxidase-4
#17
Jingni He, Xiaohui Li, Hui Luo, Tangzhiming Li, Lin Zhao, Qiangqiang Qi, Yuwei Liu, Zaixin Yu
Pulmonary arterial hypertension (PAH) is a progressive disorder that affects both pulmonary vasculature and the heart. The response of the right ventricle (RV) to the increased afterload is an important determinant of the PAH final outcome. Galectin-3 (Gal-3), a novel biomarker in left cardiac remodeling, takes part in multiple pathophysiological processes including the inflammation, fibrosis, immunity, and oxidative stress. The levels of Gal-3 are elevated in PAH patients, although the exact mechanisms underlie the PAH-induced right ventricular structural changes remain unclear...
March 27, 2017: Journal of the American Society of Hypertension: JASH
https://www.readbyqxmd.com/read/28431923/sources-of-racial-disparities-in-hiv-prevalence-in-men-who-have-sex-with-men-in-atlanta-ga-usa-a-modelling-study
#18
Steven M Goodreau, Eli S Rosenberg, Samuel M Jenness, Nicole Luisi, Sarah E Stansfield, Gregorio A Millett, Patrick S Sullivan
BACKGROUND: In the USA, men who have sex men (MSM) are at high risk for HIV, and black MSM have a substantially higher prevalence of infection than white MSM. We created a simulation model to assess the strength of existing hypotheses and data that account for these disparities. METHODS: We built a dynamic, stochastic, agent-based network model of black and white MSM aged 18-39 years in Atlanta, GA, USA, that incorporated race-specific individual and dyadic-level prevention and risk behaviours, network attributes, and care patterns...
April 18, 2017: Lancet HIV
https://www.readbyqxmd.com/read/28431748/a-benchtop-biorobotic-platform-for-in-vitro-observation-of-muscle-tendon-dynamics-with-parallel-mechanical-assistance-from-an-elastic-exoskeleton
#19
Benjamin D Robertson, Siddarth Vadakkeveedu, Gregory S Sawicki
We present a novel biorobotic framework comprised of a biological muscle-tendon unit (MTU) mechanically coupled to a feedback controlled robotic environment simulation that mimics in vivo inertial/gravitational loading and mechanical assistance from a parallel elastic exoskeleton. Using this system, we applied select combinations of biological muscle activation (modulated with rate-coded direct neural stimulation) and parallel elastic assistance (applied via closed-loop mechanical environment simulation) hypothesized to mimic human behavior based on previously published modeling studies...
March 21, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/28431740/getting-a-grip-on-reality-grasping-movements-directed-to-real-objects-and-images-rely-on-dissociable-neural-representations
#20
Erez Freud, Scott N Macdonald, Juan Chen, Derek J Quinlan, Melvyn A Goodale, Jody C Culham
In the current era of touchscreen technology, humans commonly execute visually guided actions directed to two-dimensional (2D) images of objects. Although real, three-dimensional (3D), objects and images of the same objects share high degree of visual similarity, they differ fundamentally in the actions that can be performed on them. Indeed, previous behavioral studies have suggested that simulated grasping of images relies on different representations than actual grasping of real 3D objects. Yet the neural underpinnings of this phenomena have not been investigated...
March 18, 2017: Cortex; a Journal Devoted to the Study of the Nervous System and Behavior
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