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Monte carlo

Philippe Glorennec, Jean-Paul Lucas, Anne-Camille Mercat, Alain-Claude Roudot, Barbara Le Bot
Children are exposed to toxic metals and metalloids via their diet and environment. Our objective was to assess the aggregate chronic exposure of children aged 3-6years, living in France, to As, Cd, Cr, Cu, Mn, Pb, Sb, Sr, and V present in diet, tap water, air, soil and floor dust in the years 2007-2009. Dietary data came from the French Total Diet Study, while concentrations in residential tap water, soil and indoor floor dust came from the 'Plomb-Habitat' nationwide representative survey on children's lead exposure at home...
October 19, 2016: Environment International
Subhasree Pradhan
Spinless, interacting electrons on a finite size triangular lattice moving in an extremely strong perpendicular magnetic field are studied in comparison to a square lattice. Using a Falicov-Kimball model, the effects of Coulomb correlation, magnetic field and finite system size on their energy spectrum are observed. Exact diagonalization and Monte Carlo simulation methods (based on a modified Metropolis algorithm) have been employed to examine the recursive structure of the Hofstadter spectrum in the presence of several electronic correlation strengths for different system sizes...
October 21, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Tobias Dornheim, Simon Groth, Travis Sjostrom, Fionn D Malone, W M C Foulkes, Michael Bonitz
We perform ab initio quantum Monte Carlo (QMC) simulations of the warm dense uniform electron gas in the thermodynamic limit. By combining QMC data with the linear response theory, we are able to remove finite-size errors from the potential energy over the substantial parts of the warm dense regime, overcoming the deficiencies of the existing finite-size corrections by Brown et al. [Phys. Rev. Lett. 110, 146405 (2013)]. Extensive new QMC results for up to N=1000 electrons enable us to compute the potential energy V and the exchange-correlation free energy F_{xc} of the macroscopic electron gas with an unprecedented accuracy of |ΔV|/|V|,|ΔF_{xc}|/|F|_{xc}∼10^{-3}...
October 7, 2016: Physical Review Letters
Junki Yoshitake, Joji Nasu, Yukitoshi Motome
Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that the precursor of quantum spin liquids appears in the spin dynamics in the paramagnetic state over a wide temperature range. Using the cluster dynamical mean-field theory and the continuous-time quantum Monte Carlo method, which are newly developed in the Majorana fermion representation, we calculate the dynamical spin structure factor, relaxation rate in nuclear magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model whose ground state is a canonical example of the quantum spin liquid...
October 7, 2016: Physical Review Letters
Dominic Woolf, Johannes Lehmann, David R Lee
Restricting global warming below 2 °C to avoid catastrophic climate change will require atmospheric carbon dioxide removal (CDR). Current integrated assessment models (IAMs) and Intergovernmental Panel on Climate Change scenarios assume that CDR within the energy sector would be delivered using bioenergy with carbon capture and storage (BECCS). Although bioenergy-biochar systems (BEBCS) can also deliver CDR, they are not included in any IPCC scenario. Here we show that despite BECCS offering twice the carbon sequestration and bioenergy per unit biomass, BEBCS may allow earlier deployment of CDR at lower carbon prices when long-term improvements in soil fertility offset biochar production costs...
October 21, 2016: Nature Communications
Astha Garg, Charles A Cartier, Kyle J M Bishop, Darrell Velegol
The zeta potential of a particle characterizes its motion in an electric field and is often thought to be negligible at high ionic strength (several moles per liter) due to thinning of the electrical double layer (EDL). Here, we describe zeta potential measurements on polystyrene latex (PSL) particles at monovalent salt concentrations up to saturation (~ 5 M NaCl) using electrophoresis in sinusoidal electric fields and high-speed video microscopy. Our measurements reveal that the zeta potential remains finite at even the highest concentrations...
October 21, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Sandipan Dawn, A K Bakshi, Deepa Sathian, T Palani Selvam
Neutron scatter contributions as a function of distance along the transverse axis of (241)Am-Be source were estimated by three different methods such as shadow cone, semi-empirical and Monte Carlo. The Monte Carlo-based FLUKA code was used to simulate the existing room used for the calibration of CR-39 detector as well as LB6411 doseratemeter for selected distances from (241)Am-Be source. The modified (241)Am-Be spectra at different irradiation geometries such as at different source detector distances, behind the shadow cone, at the surface of the water phantom were also evaluated using Monte Carlo calculations...
October 7, 2016: Radiation Protection Dosimetry
Kihong Son, Jin Sung Kim, Hoyeon Lee, Seungryong Cho
This study investigates dose distribution due to kV cone-beam computed tomography (CBCT) for the patients undergoing CBCT-based image-guided radiation therapy (IGRT). The kV-CBCT provides an efficient image-guidance tool for acquiring the latest volumetric image of a patient's anatomy, and has been being routinely used in clinics for an accurate treatment setup. Imaging radiation doses resulting from six different acquisition protocols of the on-board imager (OBI) were calculated using a Geant4 Application for Tomographic Emission (GATE) Monte Carlo simulation toolkit, and the absorbed doses by various organs were analyzed for the adult and pediatric numerical XCAT phantoms in this study...
October 20, 2016: Radiation Protection Dosimetry
Teresa M Attina, Russ Hauser, Sheela Sathyanarayana, Patricia A Hunt, Jean-Pierre Bourguignon, John Peterson Myers, Joseph DiGangi, R Thomas Zoeller, Leonardo Trasande
BACKGROUND: Endocrine-disrupting chemicals (EDCs) contribute to disease and dysfunction and incur high associated costs (>1% of the gross domestic product [GDP] in the European Union). Exposure to EDCs varies widely between the USA and Europe because of differences in regulations and, therefore, we aimed to quantify disease burdens and related economic costs to allow comparison. METHODS: We used existing models for assessing epidemiological and toxicological studies to reach consensus on probabilities of causation for 15 exposure-response relations between substances and disorders...
October 17, 2016: Lancet Diabetes & Endocrinology
Sven Dirkmann, Mirko Hansen, Martin Ziegler, Hermann Kohlstedt, Thomas Mussenbrock
In this work we report on the role of ion transport for the dynamic behavior of a double barrier quantum mechanical Al/Al2O3/NbxOy/Au memristive device based on numerical simulations in conjunction with experimental measurements. The device consists of an ultra-thin NbxOy solid state electrolyte between an Al2O3 tunnel barrier and a semiconductor metal interface at an Au electrode. It is shown that the device provides a number of interesting features such as an intrinsic current compliance, a relatively long retention time, and no need for an initialization step...
October 20, 2016: Scientific Reports
Jeffrey A Walker
BACKGROUND: Self-contained tests estimate and test the association between a phenotype and mean expression level in a gene set defined a priori. Many self-contained gene set analysis methods have been developed but the performance of these methods for phenotypes that are continuous rather than discrete and with multiple nuisance covariates has not been well studied. Here, I use Monte Carlo simulation to evaluate the performance of both novel and previously published (and readily available via R) methods for inferring effects of a continuous predictor on mean expression in the presence of nuisance covariates...
2016: PeerJ
Hideki Kato, Keita Sakai, Mizuki Uchiyama, Kentaro Suzuki
The diagnostic reference levels (DRLs) of the general X-ray radiography are defined by the absorbed dose of air at the entrance surface with backscattered radiation from a scattering medium. Generally, the entrance surface dose of the general X-ray radiography is calculated from measured air kerma of primary X-ray multiplied by a backscatter factor (BSF). However, the BSF data employed at present used water for scattering medium, and was calculated based on the water-absorbed dose by incident primary photons and backscattered photons from the scattering medium...
2016: Nihon Hoshasen Gijutsu Gakkai Zasshi
Uwe Schneider, Fabiano Vasi, Jürgen Besserer
BACKGROUND AND PURPOSE: When fractionation schemes for hypofractionation and stereotactic body radiotherapy are considered, a reliable cell survival model at high dose is needed for calculating doses of similar biological effectiveness. An alternative to the LQ-model is the track-event theory which is based on the probabilities for one- and two two-track events. A one-track-event (OTE) is always represented by at least two simultaneous double strand breaks. A two-track-event (TTE) results in one double strand break...
2016: PloS One
Jianfei Yang, Dirk H J Poot, Matthan W A Caan, Tanja Su, Charles B L M Majoie, Lucas J van Vliet, Frans M Vos
PURPOSE: This paper presents and studies a framework for reliable modeling of diffusion MRI using a data-acquisition adaptive prior. METHODS: Automated relevance determination estimates the mean of the posterior distribution of a rank-2 dual tensor model exploiting Jeffreys prior (JARD). This data-acquisition prior is based on the Fisher information matrix and enables the assessment whether two tensors are mandatory to describe the data. The method is compared to Maximum Likelihood Estimation (MLE) of the dual tensor model and to FSL's ball-and-stick approach...
2016: PloS One
Peter Brommesson, Uno Wennergren, Tom Lindström
The structure of contacts that mediate transmission has a pronounced effect on the outbreak dynamics of infectious disease and simulation models are powerful tools to inform policy decisions. Most simulation models of livestock disease spread rely to some degree on predictions of animal movement between holdings. Typically, movements are more common between nearby farms than between those located far away from each other. Here, we assessed spatiotemporal variation in such distance dependence of animal movement contacts from an epidemiological perspective...
2016: PloS One
Josseanne Maria Teixeira, Maria do Carmo De Carvalho Martins, Luanne Fortes Monte Soares, Ana Lina De Carvalho Cunha Sales, Daiane Cristina Ferreira Damasceno, Francisco Valmor Macedo Cunha, Regina Célia De Assis, José Carlos Santos Júnior, Nivea Maria Da Costa Sousa
INTRODUCTION: Food and dietetic components have received considerable attention as auxiliary feeding resources on controlling of chronic non-transmissible diseases, among them diabetes. This study evaluated the effect of supplementary diet with multimixture based on linseed, sesame, oats and sunflower seeds on the hepatic function and antioxidant activity of diabetic rats. METHODS: Male rats were distributed on groups of seven animals: diabetic control (DC), diabetics subject to multimixture diet (DM), diabetic with insulin (DI), and normal control (NC)...
September 20, 2016: Nutrición Hospitalaria: Organo Oficial de la Sociedad Española de Nutrición Parenteral y Enteral
Vahid Sokhanvaran, Saeid Yeganegi
The quantum mechanics (QM) method and Grand Canonical Monte Carlo (GCMC) simulations were performed to study the effect of lithium cation doping on the adsorption and separation of CO2, CH4 and H2 on 2-fold interwoven metal-organic framework (MOF) Zn2(NDC)2(diPyNI). The second order Moller-Plesset (MP2) calculations on the (Li+-diPyNI) cluster model showed that the energetically most favorable lithium binding site is above the pyridine ring side and at a distance of 1.817 Å from the oxygen atom. The results revealed that the adsorption capacity of Zn2(NDC)2(diPyNI) for carbon dioxide is higher than that of hydrogen and methane at room temperature...
October 19, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Heewon Park, Atsushi Niida, Seiya Imoto, Satoru Miyano
Driver gene selection is crucial to understand the heterogeneous system of cancer. To identity cancer driver genes, various statistical strategies have been proposed, especially the L1-type regularization methods have drawn a large amount of attention. However, the statistical approaches have been developed purely from algorithmic and statistical point, and the existing studies have applied the statistical approaches to genomic data analysis without consideration of biological knowledge. We consider a statistical strategy incorporating biological knowledge to identify cancer driver gene...
October 19, 2016: Journal of Computational Biology: a Journal of Computational Molecular Cell Biology
Claudia Baumung, Jürgen Rehm, Heike Franke, Dirk W Lachenmeier
Nicotine was not included in previous efforts to identify the most important toxicants of tobacco smoke. A health risk assessment of nicotine for smokers of cigarettes was conducted using the margin of exposure (MOE) approach and results were compared to literature MOEs of various other tobacco toxicants. The MOE is defined as ratio between toxicological threshold (benchmark dose) and estimated human intake. Dose-response modelling of human and animal data was used to derive the benchmark dose. The MOE was calculated using probabilistic Monte Carlo simulations for daily cigarette smokers...
October 19, 2016: Scientific Reports
Zhiyong Yang, Aihua Chai, Peicong Zhou, Ping Li, Yongfu Yang
We study the process of a semiflexible polymer chain adsorption onto planar surface by the dynamic Monte Carlo method, based on the three-dimension off-lattice model. Both the strength of attractive monomer-surface interaction εa and bending energy b have pronounced effect on the adsorption and shape of semiflexible polymer chain. The semiflexible polymer can just fully adsorb onto the surface at certain εa which is defined as critical εa The essential features of the semiflexible polymer adsorption onto surface are that (i) the critical εa increases with increase of b ; (ii) the shape of the fully adsorbed semiflexible polymer chain is film-like toroid, and the toroid becomes more and more perfect with increase of b In addition, the size of toroid and the number of turns of toroid can be controlled by the b and εa...
October 18, 2016: Bioscience Reports
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