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Monte Carlo simulation

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https://www.readbyqxmd.com/read/28432792/monte-carlo-study-of-the-chamber-phantom-air-gap-effect-in-a-magnetic-field
#1
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/28431338/the-design-and-fabrication-of-beta-sensor-system-for-in-situ-diffusion-tests-in-mudstone-in-france
#2
Zhenhua Lin, Olivier Tillement, Marie-Genevieve Blanchin, Vivek Jindal, Agnès Vinsot, Romain V H Dagnelie, Virginie Blin, Yanick Lettry, Benoit Hautefeuille
Long term in situ diffusion experiments in the Callovian-Oxfordian mudstone (France) are designed in the context of nuclear waste management. β-emitters HTO and (36)Cl radiotracers are representative of neutral and anionic species in these experiments. Studies have been carried out to design an in situ beta monitoring system in order to quantify tracer migration in the rock pore water over time. The development, design and calibration of β-emitter radiation sensors were performed. An optimised geometry was calculated for the detection chamber of (36)Cl in solution (Ø×L=30×2mm(2)) via Monte-Carlo N-Particle transport simulation tools...
April 1, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28430705/disparities-in-female-breast-cancer-stage-at-diagnosis-in-new-jersey-a-spatial-temporal-analysis
#3
Lisa M Roche, Xiaoling Niu, Antoinette M Stroup, Kevin A Henry
BACKGROUND: Despite improvements in early detection of breast cancer, disparities persist in stage at diagnosis, which is an important prognostic factor. METHODS: We used the space-time scan statistic in SaTScan to identify geographic areas and time periods with significantly elevated proportions of female breast cancer diagnosed at the in situ or distant stage in New Jersey. The analyses were conducted with census tracts as the geographic unit of analysis, elliptical spatial windows, 3-year temporal windows, and Poisson models...
December 22, 2016: Journal of Public Health Management and Practice: JPHMP
https://www.readbyqxmd.com/read/28430505/excitation-gap-scaling-near-quantum-critical-three-dimensional-antiferromagnets
#4
M Lohöfer, S Wessel
By means of large-scale quantum Monte Carlo simulations, we examine the quantum critical scaling of the magnetic excitation gap (the triplon gap) in a three-dimensional dimerized quantum antiferromagnet, the bicubic lattice, and identify characteristic multiplicative logarithmic scaling corrections atop the leading mean-field behavior. These findings are in accord with field-theoretical predictions that are based on an effective description of the quantum critical system in terms of an asymptotically free field theory, which exhibits a logarithmic decay of the renormalized interaction strength upon approaching the quantum critical point...
April 7, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28430475/amplitude-mode-in-three-dimensional-dimerized-antiferromagnets
#5
Yan Qi Qin, B Normand, Anders W Sandvik, Zi Yang Meng
The amplitude ("Higgs") mode is a ubiquitous collective excitation related to spontaneous breaking of a continuous symmetry. We combine quantum Monte Carlo (QMC) simulations with stochastic analytic continuation to investigate the dynamics of the amplitude mode in a three-dimensional dimerized quantum spin system. We characterize this mode by calculating the spin and dimer spectral functions on both sides of the quantum critical point, finding that both the energies and the intrinsic widths of the excitations satisfy field-theoretical scaling predictions...
April 7, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28430156/zero-sum-matrix-game-with-payoffs-of-dempster-shafer-belief-structures-and-its-applications-on-sensors
#6
Xinyang Deng, Wen Jiang, Jiandong Zhang
The zero-sum matrix game is one of the most classic game models, and it is widely used in many scientific and engineering fields. In the real world, due to the complexity of the decision-making environment, sometimes the payoffs received by players may be inexact or uncertain, which requires that the model of matrix games has the ability to represent and deal with imprecise payoffs. To meet such a requirement, this paper develops a zero-sum matrix game model with Dempster-Shafer belief structure payoffs, which effectively represents the ambiguity involved in payoffs of a game...
April 21, 2017: Sensors
https://www.readbyqxmd.com/read/28430132/celestial-object-imaging-model-and-parameter-optimization-for-an-optical-navigation-sensor-based-on-the-well-capacity-adjusting-scheme
#7
Hao Wang, Jie Jiang, Guangjun Zhang
The simultaneous extraction of optical navigation measurements from a target celestial body and star images is essential for autonomous optical navigation. Generally, a single optical navigation sensor cannot simultaneously image the target celestial body and stars well-exposed because their irradiance difference is generally large. Multi-sensor integration or complex image processing algorithms are commonly utilized to solve the said problem. This study analyzes and demonstrates the feasibility of simultaneously imaging the target celestial body and stars well-exposed within a single exposure through a single field of view (FOV) optical navigation sensor using the well capacity adjusting (WCA) scheme...
April 21, 2017: Sensors
https://www.readbyqxmd.com/read/28427337/treatment-seeking-behaviour-in-low-and-middle-income-countries-estimated-using-a-bayesian-model
#8
Victor A Alegana, Jim Wright, Carla Pezzulo, Andrew J Tatem, Peter M Atkinson
BACKGROUND: Seeking treatment in formal healthcare for uncomplicated infections is vital to combating disease in low- and middle-income countries (LMICs). Healthcare treatment-seeking behaviour varies within and between communities and is modified by socio-economic, demographic, and physical factors. As a result, it remains a challenge to quantify healthcare treatment-seeking behaviour using a metric that is comparable across communities. Here, we present an application for transforming individual categorical responses (actions related to fever) to a continuous probabilistic estimate of fever treatment for one country in Sub-Saharan Africa (SSA)...
April 20, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28427153/comparison-between-proton-boron-fusion-therapy-pbft-and-boron-neutron-capture-therapy-bnct-a-monte-carlo-study
#9
Joo-Young Jung, Do-Kun Yoon, Brendan Barraclough, Heui Chang Lee, Tae Suk Suh, Bo Lu
The aim of this study is to compare between proton boron fusion therapy (PBFT) and boron neutron capture therapy (BNCT) and to analyze dose escalation using a Monte Carlo simulation. We simulated a proton beam passing through the water with a boron uptake region (BUR) in MCNPX. To estimate the interaction between neutrons/protons and borons by the alpha particle, the simulation yielded with a variation of the center of the BUR location and proton energies. The variation and influence about the alpha particle were observed from the percent depth dose (PDD) and cross-plane dose profile of both the neutron and proton beams...
February 25, 2017: Oncotarget
https://www.readbyqxmd.com/read/28427044/on-the-reverse-micelle-effect-in-liquid-scintillation-counting
#10
Youcef Nedjadi, Jean-Pascal Laedermann, François Bochud, Claude Bailat
This work looks into the tracks of electrons in nanoemulsive scintillating media using the Monte Carlo Geant4-DNA code which simulates event-by-event interactions of electrons in liquid water down to the eV, without resorting to the condensed history method. It demonstrates that the average number of micelles in which electrons deposit energy is quite large, increasing with their emission energy, decreasing with micelle size, and rising with micelle concentration. The probability of an electron ending its track in a micelle is found to be rather large and micelle size-dependent below 1keV, and approximating the aqueous fraction at higher energies...
April 12, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28426674/tribological-investigations-of-the-load-temperature-and-time-dependence-of-wear-in-sliding-contact
#11
Matthew David Marko, Jonathan P Kyle, Yuanyuan Sabrina Wang, Elon J Terrell
An effort was made to study and characterize the evolution of transient tribological wear in the presence of sliding contact. Sliding contact is often characterized experimentally via the standard ASTM D4172 four-ball test, and these tests were conducted for varying times ranging from 10 seconds to 1 hour, as well as at varying temperatures and loads. A numerical model was developed to simulate the evolution of wear in the elastohydrodynamic regime. This model uses the results of a Monte Carlo study to develop novel empirical equations for wear rate as a function of asperity height and lubricant thickness; these equations closely represented the experimental data and successfully modeled the sliding contact...
2017: PloS One
https://www.readbyqxmd.com/read/28426209/channel-assisted-proton-conduction-behavior-in-hydroxyl-rich-lanthanide-based-magnetic-metal-organic-frameworks
#12
Soumava Biswas, Jayita Chakraborty, Vijay Singh Parmar, Siba Prasad Bera, Nirmal Ganguli, Sanjit Konar
Two new lanthanide-based 3D metal-organic frameworks (MOFs), {[Ln(L)(Ox)(H2O)]n·xH2O} [Ln = Gd(3+) and x = 3 (1) and Dy(3+) and x = 1.5 (2); H2L = mucic acid; OxH2 = oxalic acid] showing interesting magnetic properties and channel-mediated proton conduction behavior, are presented here. Single-crystal X-ray structure analysis shows that, in complex 1, the overall structure originates from the mucate-bridged gadolinium-based rectangular metallocycles. The packing view reveals the presence the two types of hydrophilic 1D channels filled with lattice water molecules, which are strongly hydrogen-bonded with coordinated water along the a and b axes, whereas for complex 2, the 3D framework originates from a carboxylate-bridged dysprosium-based criss-cross-type secondary building block...
April 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28426204/parameter-optimization-for-interaction-between-c-terminal-domains-of-hiv-1-capsid-protein
#13
Hao Sha, Fangqiang Zhu
HIV-1 capsid proteins (CAs) assemble into a capsid that encloses the viral RNA. The binding between a pair of C-terminal domains (CTDs) constitutes a major interface in both the CA dimers and the large CA assemblies. Here we attempt to use a general residue-level coarse-grained model to describe the interaction between two isolated CTDs in Monte Carlo simulations. With the standard parameters that depend only on the residue types, the model predicts a much weaker binding in comparison to the experiments. Detailed analysis reveals that some Lennard-Jones parameters are not compatible with the experimental CTD dimer structure, thus resulting in an unfavorable interaction energy...
April 20, 2017: Journal of Chemical Information and Modeling
https://www.readbyqxmd.com/read/28423966/linear-energy-transfer-distributions-in-the-brainstem-depending-on-tumour-location-in-intensity-modulated-proton-therapy-of-paediatric-cancer
#14
Lars Fredrik Fjæra, Zuofeng Li, Kristian S Ytre-Hauge, Ludvig P Muren, Daniel J Indelicato, Yasmin Lassen-Ramshad, Grete May Engeseth, Marianne Brydøy, Andrea Mairani, Stella Flampouri, Olav Dahl, Camilla H Stokkevåg
BACKGROUND: For tumours near organs at risk, there is concern about unintended increase in biological dose from elevated linear energy transfer (LET) at the distal end of treatment fields. The objective of this study was therefore to investigate how different paediatric posterior fossa tumour locations impact LET and biological dose to the brainstem during intensity-modulated proton therapy (IMPT). MATERIAL AND METHODS: Multiple IMPT plans were generated for four different simulated tumour locations relative to the brainstem for a five-year-old male patient...
April 19, 2017: Acta Oncologica
https://www.readbyqxmd.com/read/28422503/predicting-protein-interactions-of-concentrated-globular-protein-solutions-using-colloidal-models
#15
Mahlet Asfaw Woldeyes, Cesar Calero-Rubio, Eric M Furst, Christopher J Roberts
Protein interactions of α-chymotrypsinogen A (aCgn) were quantified using light scattering from low to high protein concentrations. Static light scattering (SLS) was used to determine the excess Rayleigh ratio (R(ex)) and osmotic second virial coefficients (B22) as a function of pH and total ionic strength (TIS). Repulsive (attractive) protein-protein interactions (PPI) were observed at pH 5 (pH 7), with decreasing repulsions (attractions) upon increasing TIS. Simple colloidal potential-of-mean force models (PMF) that account for short-range non-electrostatic attractions and screened electrostatic interactions were used to fit model parameters from data for B22 vs TIS at both pH values...
April 19, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28422397/a-novel-radiation-protection-device-based-on-tungsten-functional-paper-for-application-in-interventional-radiology
#16
Hajime Monzen, Mikoto Tamura, Kohei Shimomura, Yuichi Onishi, Shinichi Nakayama, Takahiro Fujimoto, Kenji Matsumoto, Kohei Hanaoka, Takeshi Kamomae
Tungsten functional paper (TFP), which contains 80% tungsten by weight, has radiation-shielding properties. We investigated the use of TFP for the protection of operators during interventional or therapeutic angiography. The air kerma rate of scattered radiation from a simulated patient was measured, with and without TFP, using a water-equivalent phantom and fixed C-arm fluoroscopy. Measurements were taken at the level of the operator's eye, chest, waist, and knee, with a variable number of TFP sheets used for shielding...
April 19, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28421417/estimation-of-qt-interval-prolongation-through-model-averaging
#17
Peter L Bonate
The current method to analyze concentration-QT interval data, which is based on predictions conditional on a best model, fails to take into account the uncertainty of the model. Previous studies have suggested that failure to take into account model uncertainty using a best model approach can result in confidence intervals that are overly optimistic and may be too narrow. Theoretically, more realistic estimates are obtained using model-averaging where the overall point estimate and confidence interval are a weighted-average from a set of candidate models, the weights of which are equal to each model's Akaike weight...
April 18, 2017: Journal of Pharmacokinetics and Pharmacodynamics
https://www.readbyqxmd.com/read/28419533/a-new-approach-for-radiosynoviorthesis-a-dose-optimized-planning-method-based-on-monte-carlo-simulation-and-synovial-measurement-using-3d-slicer-and-mri
#18
Mirta Bárbara Torres Berdeguez, Sylvia Thomas, Patricia Rafful, Tiago Arruda Sanchez, Susie Medeiros Oliveira Ramos, Marta Souza Albernaz, Lidia Vasconcellos de Sá, Sergio Augusto Lopes de Souza, Felix Mas Milian, Ademir Xavier da Silva
PURPOSE: Recently, there has been a growing interest in a methodology for dose planning in radiosynoviorthesis to substitute fixed activity. Clinical practice based on fixed activity frequently does not embrace radiopharmaceutical dose optimization in patients. The aim of this paper is to propose and discuss a dose planning methodology considering the radiological findings of interest obtained by three-dimensional magnetic resonance imaging combined with Monte Carlo simulation in radiosynoviorthesis treatment applied to hemophilic arthropathy...
April 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28419332/new-model-for-mines-and-transportation-tunnels-external-dose-calculation-using-monte-carlo-simulation
#19
Kh A Allam
In this work, a new methodology is developed based on Monte Carlo simulation for tunnels and mines external dose calculation. Tunnels external dose evaluation model of a cylindrical shape of finite thickness with an entrance and with or without exit. A photon transportation model was applied for exposure dose calculations. A new software based on Monte Carlo solution was designed and programmed using Delphi programming language. The variation of external dose due to radioactive nuclei in a mine tunnel and the corresponding experimental data lies in the range 7...
April 13, 2017: Radiation Protection Dosimetry
https://www.readbyqxmd.com/read/28419323/monte-carlo-simulation-used-to-calculate-energy-correction-factor-for-thermoluminescent-dosimeters-used-by-occupational-workers-on-pediatric-exams
#20
G Hoff, D Filipov, S Paschuk, H R Schelin, V Denyak
The main objective of this work is to simulate the X-ray scattered spectra by different pediatric phantoms (simulation of children subjected to barium meal procedures) to calculate an energy correction factor (ECF) to the reading of thermoluminescent dosimeters (TLDs). To perform this evaluation, the TLDs were positioned over three areas in two occupational workers: eyes, thyroid and hands. The Geant4 toolkit was used to define the spectra collected by TLDs, making possible to calculate the ECF. This work was developed in two stages: (1) evaluation of scattered spectra by different standard phantoms (newborn, 1, 5 and 10 years old); (2) definition of the ECF to the absorbed energy by each TLD...
April 13, 2017: Radiation Protection Dosimetry
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