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Monte Carlo simulation

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https://www.readbyqxmd.com/read/28643833/modelling-critical-casimir-force-induced-self-assembly-experiments-on-patchy-colloidal-dumbbells
#1
Arthur C Newton, T Anh Nguyen, Sandra J Veen, Daniela J Kraft, Peter Schall, Peter G Bolhuis
Colloidal particles suspended in a binary liquid mixture can interact via solvent mediated interactions, known as critical Casimir forces. For anisotropic colloids this interaction becomes directional, which leads to rich phase behavior. While experimental imaging and particle tracking techniques allow determination of isotropic effective potentials via Boltzmann inversion, the modeling of effective interaction in anisotropic systems is non-trivial precisely because of this directionality. Here we extract effective interaction potentials for non-spherical dumbbell particles from observed radial and angular distributions, by employing reference interaction site model (RISM) theory and direct Monte Carlo simulations...
June 23, 2017: Soft Matter
https://www.readbyqxmd.com/read/28643753/dosimetric-characteristic-of-physical-wedge-versus-enhanced-dynamic-wedge-based-on-monte-carlo-simulations
#2
Seied Rabie Mahdavi, Ghazale Geraily, Ahmad Mostaar, Arman Zia, Golbarg Esmaili, Somayeh Farahani
AIM OF STUDY: Physical wedges (PWs) are widely used in radiotherapy to obtain tilted isodose curves, but they alter beam quality. Dynamic wedges (DWs) using moving collimator overcome this problem, but measuring their beam data is not simple. The main aim of this study is to obtain all dosimetric parameters of DWs produced by Varian 2100CD with Monte Carlo simulation and compare them to those from PWs. SUBJECTS AND METHODS: To simulate 6 MV photon beams equipped with PW and DW, BEAMnrc code was used...
April 2017: Journal of Cancer Research and Therapeutics
https://www.readbyqxmd.com/read/28643157/effect-of-variance-ratio-on-anova-robustness-might-1-5-be-the-limit
#3
María J Blanca, Rafael Alarcón, Jaume Arnau, Roser Bono, Rebecca Bendayan
Inconsistencies in the research findings on F-test robustness to variance heterogeneity could be related to the lack of a standard criterion to assess robustness or to the different measures used to quantify heterogeneity. In the present paper we use Monte Carlo simulation to systematically examine the Type I error rate of F-test under heterogeneity. One-way, balanced, and unbalanced designs with monotonic patterns of variance were considered. Variance ratio (VR) was used as a measure of heterogeneity (1.5, 1...
June 22, 2017: Behavior Research Methods
https://www.readbyqxmd.com/read/28642681/%C3%AE-1-containing-gaba-a-receptors-cluster-at-synapses-where-they-mediate-slower-synaptic-currents-than-%C3%AE-2-containing-gaba-a-receptors
#4
Christine L Dixon, Pankaj Sah, Angelo Keramidas, Joseph W Lynch, Nela Durisic
GABA-A receptors (GABAARs) are pentameric ligand-gated ion channels that are assembled mainly from α (α1-6), β (β1-3) and γ (γ1-3) subunits. Although GABAARs containing γ2L subunits mediate most of the inhibitory neurotransmission in the brain, significant expression of γ1 subunits is seen in the amygdala, pallidum and substantia nigra. However, the location and function of γ1-containing GABAARs in these regions remains unclear. In "artificial" synapses, where the subunit composition of postsynaptic receptors is specifically controlled, γ1 incorporation slows the synaptic current decay rate without affecting channel deactivation, suggesting that γ1-containing receptors are not clustered and therefore activated by diffuse neurotransmitter...
2017: Frontiers in Molecular Neuroscience
https://www.readbyqxmd.com/read/28642571/pharmacokinetic-and-pharmacodynamic-modeling-of-cyadox-against-clostridium-perfringens-in-swine
#5
Lei Yan, Shuyu Xie, Dongmei Chen, Yuanhu Pan, Yanfei Tao, Wei Qu, ZhenLi Liu, Zonghui Yuan, Lingli Huang
The purpose of this study was to evaluate the activity of cyadox against Clostridium perfringens in swine and optimize the dosage regimen using ex vivo pharmacokinetic-pharmacodynamic (PK-PD) modeling. After oral administration, the ileum fluid of pigs containing the free cyadox was collected by implanted ultrafiltration probes. The Tmax, AUC24h, and CL/F of free cyadox in the ileum fluid were 1.96 h, 106.40 μg/h/mL, and 0.27 L/kg/h, respectively. Cyadox displayed a concentration-dependent killing action against C...
June 22, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28642456/predicting-conformational-ensembles-and-genome-wide-transcription-factor-binding-sites-from-dna-sequences
#6
Munazah Andrabi, Andrew Paul Hutchins, Diego Miranda-Saavedra, Hidetoshi Kono, Ruth Nussinov, Kenji Mizuguchi, Shandar Ahmad
DNA shape is emerging as an important determinant of transcription factor binding beyond just the DNA sequence. The only tool for large scale DNA shape estimates, DNAshape was derived from Monte-Carlo simulations and predicts four broad and static DNA shape features, Propeller twist, Helical twist, Minor groove width and Roll. The contributions of other shape features e.g. Shift, Slide and Opening cannot be evaluated using DNAshape. Here, we report a novel method DynaSeq, which predicts molecular dynamics-derived ensembles of a more exhaustive set of DNA shape features...
June 22, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28641969/determining-3d-kinematics-of-the-hip-using-video-fluoroscopy-guidelines-for-balancing-radiation-dose-and-registration-accuracy
#7
Fabio D'Isidoro, Patrik Eschle, Thomas Zumbrunn, Christian Sommer, Stephan Scheidegger, Stephen J Ferguson
BACKGROUND: Video fluoroscopy is a technique currently used to retrieve the in vivo three-dimensional kinematics of human joints during activities of daily living. Minimization of the radiation dose absorbed by the subject during the measurement is a priority and has not been thoroughly addressed so far. This issue is critical for the motion analysis of the hip joint, because of the proximity of the gonads. The aims of this study were to determine the x-ray voltage and the irradiation angle that minimize the effective dose and to achieve the best compromise between delivered dose and accuracy in motion retrieval...
May 25, 2017: Journal of Arthroplasty
https://www.readbyqxmd.com/read/28641669/effect-of-biological-and-mass-transfer-parameter-uncertainty-on-n%C3%A2-o-emission-estimates-from-wrrfs
#8
Kang Song, Willie F Harper, Yuki Takeuchi, Masaaki Hosomi, Akihiko Terada
  This research used the detailed activated sludge model (ASM) to investigate the effect of parameter uncertainty on nitrous oxide (N2O) emissions from biological wastewater treatment systems. Monte Carlo simulations accounted for uncertainty in the values of the microbial growth parameters and in the volumetric mass transfer coefficient for dissolved oxygen (kLaDO), and the results show that the detailed ASM predicted N2O emission of less than 4% (typically 1%) of the total influent <inline-graphic xmlns:xlink="http://www...
July 1, 2017: Water Environment Research: a Research Publication of the Water Environment Federation
https://www.readbyqxmd.com/read/28641188/risk-assessment-of-triclosan-released-from-sewage-treatment-plants-in-european-rivers-using-a-combination-of-risk-quotient-methodology-and-monte-carlo-simulation
#9
Vasiliki S Thomaidi, Christos Matsoukas, Athanasios S Stasinakis
Ιn this study a probabilistic risk assessment was applied to investigate the environmental risks for the European aquatic environment associated with triclosan (TCS) occurrence in treated wastewater. The concentrations of TCS in effluents of European Sewage Treatment Plants (STPs) were recorded through literature review, while toxicity data was collected for three groups of aquatic organisms (algae, Daphnia magna and fish). The ratio of Measured Environmental Concentration (MEC) and Predicted No Effect Concentration (PNEC), expressed as a Risk Quotient (RQ), was calculated for risk characterization, while Monte Carlo simulation was applied to quantify the associated uncertainty...
June 19, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28640184/a-carrier-estimation-method-based-on-mle-and-kf-for-weak-gnss-signals
#10
Hongyang Zhang, Luping Xu, Bo Yan, Hua Zhang, Liyan Luo
Maximum likelihood estimation (MLE) has been researched for some acquisition and tracking applications of global navigation satellite system (GNSS) receivers and shows high performance. However, all current methods are derived and operated based on the sampling data, which results in a large computation burden. This paper proposes a low-complexity MLE carrier tracking loop for weak GNSS signals which processes the coherent integration results instead of the sampling data. First, the cost function of the MLE of signal parameters such as signal amplitude, carrier phase, and Doppler frequency are used to derive a MLE discriminator function...
June 22, 2017: Sensors
https://www.readbyqxmd.com/read/28639869/economic-burden-of-inpatient-admission-of-ankle-fractures
#11
Justin D Stull, Suneel B Bhat, Justin M Kane, Steven M Raikin
BACKGROUND: Ankle fractures are among the most prevalent traumatic orthopaedic injuries. A large proportion of patients sustaining operative ankle fractures are admitted directly from the emergency department prior to operative management. In the authors' experience, however, many closed ankle injuries may be safely and effectively managed on an outpatient basis. The aim of this study was to characterize the economic impact of routine inpatient admission of ankle fractures. METHODS: A retrospective review of all outpatient ankle fracture surgery performed by a single foot and ankle fellowship-trained surgeon at a tertiary level academic center in 2012 was conducted to identify any patients requiring postoperative inpatient admission...
June 1, 2017: Foot & Ankle International
https://www.readbyqxmd.com/read/28638169/organ-and-effective-dose-reduction-for-region-of-interest-roi-cbct-and-fluoroscopy
#12
Zhenyu Xiong, Sarath Vijayan, Stephen Rudin, Daniel R Bednarek
In some medical-imaging procedures using CBCT and fluoroscopy, it may be needed to visualize only the center of the field-of-view with optimal quality. To reduce the dose to the patient as well as enable increased contrast in the region of interest (ROI) during CBCT and fluoroscopy procedures, a 0.7 mm thick Cu ROI attenuator with a circular aperture 12% of the FOV was used. The aim of this study was to quantify the dose-reduction benefit of ROI imaging during a typical CBCT and interventional fluoroscopy procedures in the head and torso...
February 11, 2017: Proceedings of SPIE
https://www.readbyqxmd.com/read/28636805/a-hybrid-phantom-system-for-patient-skin-and-organ-dosimetry-in-fluoroscopically-guided-interventions
#13
David Borrego, Daniel Siragusa, Stephen Balter, Wesley E Bolch
To investigate calibrations for improved estimates of skin dose and to develop software for computing absorbed organ doses for fluoroscopically guided interventions (FGIs) with the use of radiation dose structured reports (RDSR) and the UF/NCI family of hybrid computational phantoms METHODS AND MATERIALS: Institutional review board approval was obtained for this retrospective study in which ten RDSRs were selected for their high cumulative reference air kerma values. Skin doses were computed using the University of Florida's rapid in-clinic peak skin dose algorithm (or UF-RIPSA)...
June 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28636792/mtf-and-dqe-enhancement-using-an-apodized-aperture-x-ray-detector-design
#14
Tomi F Nano, Terenz Escartin, Elina Ismailova, Karim S Karim, Jan Lindstrȍm, Ho Kyung Kim, Ian A Cunningham
PURPOSE: Acquisition of high-quality x-ray images using low patient exposures requires detectors with high detective quantum efficiency (DQE). We describe a novel apodized-aperture pixel (AAP) design that increases high-frequency modulation transfer function (MTF) and DQE values. The AAP design makes a separation of physical sensor elements from image pixels by using very small sensor elements (e.g. 0.010-0.025 mm) to synthesize desired larger image pixels (e.g. 0.1-0.2 mm). METHODS: A cascaded systems model of signal and noise propagation is developed to describe the benefits of the AAP approach in terms of the MTF, Wiener noise power spectrum (NPS) and DQE...
June 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28636763/sensitive-volume-effects-on-monte-carlo-calculated-ion-chamber-response-in-magnetic-fields
#15
Victor N Malkov, David W O Rogers
PURPOSE: The development of magnetic resonance guided radiation therapy (MR-gRT) necessitates accurate Monte Carlo (MC) models of ion chambers for computing ion chamber corrections to compensate for the presence of the magnetic field. This study evaluates the sensitivity of the ion chamber dose response in a magnetic field on the collection volume used in the MC simulation METHODS: The EGSnrc system's egs_chamber application is used with a recently developed and validated magnetic field transport code...
June 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28636625/comparison-study-of-exhaust-plume-impingement-effects-of-small-mono-and-bipropellant-thrusters-using-parallelized-dsmc-method
#16
Kyun Ho Lee
A space propulsion system is important for the normal mission operations of a spacecraft by adjusting its attitude and maneuver. Generally, a mono- and a bipropellant thruster have been mainly used for low thrust liquid rocket engines. But as the plume gas expelled from these small thrusters diffuses freely in a vacuum space along all directions, unwanted effects due to the plume collision onto the spacecraft surfaces can dramatically cause a deterioration of the function and performance of a spacecraft. Thus, aim of the present study is to investigate and compare the major differences of the plume gas impingement effects quantitatively between the small mono- and bipropellant thrusters using the computational fluid dynamics (CFD)...
2017: PloS One
https://www.readbyqxmd.com/read/28636564/radiation-dosimetry-in-magnetic-fields-with-farmer-type-ionization-chambers-determination-of-magnetic-field-correction-factors-for-different-magnetic-field-strengths-and-field-orientations
#17
Claudia Katharina Spindeldreier, Oliver Schrenk, Anna Bakenecker, Iwan Kawrakow, Lucas Norberto Burigo, Christian P Karger, Steffen Greilich, Asja Pfaffenberger
The aim of this work was to determine magnetic field correction factors that are needed for dosimetry in hybrid devices for MR-guided radiotherapy for Farmer-type ionization chambers for different magnetic field strengths and field orientations. The response of six custom-built Farmer-type chambers irradiated at a 6 MV linac was measured in a water tank positioned in a magnet with magnetic field strengths between 0.0 T and 1.1 T. Chamber axis, beam and magnetic field were perpendicular to each other and both magnetic field directions were investigated...
June 21, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28634725/analyzing-individual-growth-with-clustered-longitudinal-data-a-comparison-between-model-based-and-design-based-multilevel-approaches
#18
Hsien-Yuan Hsu, John J H Lin, Susan T Skidmore
To prevent biased estimates of intraindividual growth and interindividual variability when working with clustered longitudinal data (e.g., repeated measures nested within students; students nested within schools), individual dependency should be considered. A Monte Carlo study was conducted to examine to what extent two model-based approaches (multilevel latent growth curve model - MLGCM, and maximum model - MM) and one design-based approach (design-based latent growth curve model - D-LGCM) could produce unbiased and efficient parameter estimates of intraindividual growth and interindividual variability given clustered longitudinal data...
June 20, 2017: Behavior Research Methods
https://www.readbyqxmd.com/read/28634333/atomic-rearrangement-of-a-sputtered-mos2-film-from-amorphous-to-a-2d-layered-structure-by-electron-beam-irradiation
#19
Bong Ho Kim, Hyun Ho Gu, Young Joon Yoon
We synthesised a crystalline MoS2 film from as-sputtered amorphous film by applying an electron beam irradiation (EBI) process. A collimated electron beam (60 mm dia.) with an energy of 1 kV was irradiated for only 1 min to achieve crystallisation without an additional heating process. After the EBI process, we observed a two-dimensional layered structure of MoS2 about 4 nm thick and with a hexagonal atomic arrangement on the surface. A stoichiometric MoS2 film was confirmed to grow well on SiO2/Si substrates and include partial oxidation of Mo...
June 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28634292/monte-carlo-sampling-for-stochastic-weight-functions
#20
Daan Frenkel, K Julian Schrenk, Stefano Martiniani
Conventional Monte Carlo simulations are stochastic in the sense that the acceptance of a trial move is decided by comparing a computed acceptance probability with a random number, uniformly distributed between 0 and 1. Here, we consider the case that the weight determining the acceptance probability itself is fluctuating. This situation is common in many numerical studies. We show that it is possible to construct a rigorous Monte Carlo algorithm that visits points in state space with a probability proportional to their average weight...
June 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
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