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Monte carlo

E M Gavilán Arriazu, B A López de Mishima, O A Oviedo, E P M Leiva, O A Pinto
Herein, a Monte Carlo study within the canonical assembly has been applied to elucidate the lithium-ion phase transition order of a stage II lithium-graphite intercalation compound (LiC12) around the critical point. The results reveal a weakly first-order phase transition at 354.6 ± 0.5 K via measurements that follows the power laws with effective exponents. The graphite-lithium system was emulated within a lattice-gas model, comprising specific insertion sites arranged in four parallel planes with a triangular geometry...
August 18, 2017: Physical Chemistry Chemical Physics: PCCP
Pratik P Dholabhai, Enrique Martínez, Nicholas T Brown, Blas Pedro Uberuaga
In the quest to develop new materials with enhanced ionic conductivity for battery and fuel cell applications, nano-structured oxides have attracted attention. Experimental reports indicate that oxide heterointerfaces can lead to enhanced ionic conductivity, but these same reports cannot elucidate the origin of this enhancement, often vaguely referring to pipe diffusion at misfit dislocations as a potential explanation. However, this highlights the need to understand the role of misfit dislocation structure at semi-coherent oxide heterointerfaces in modifying carrier mobilities...
August 18, 2017: Physical Chemistry Chemical Physics: PCCP
Nicole L Ackerman, Federico Boschi, Antonello E Spinelli
There is experimental evidence for the production of non-Cerenkov radioluminescence in a variety of materials, including tissue. We constructed a Geant4 Monte Carlo simulation of the radiation from P32 and Tc99m interacting in chicken breast and used experimental imaging data to model a scintillation-like emission. The same radioluminescence spectrum is visible from both isotopes and cannot otherwise be explained through fluorescence or filter miscalibration. We conclude that chicken breast has a near-infrared scintillation-like response with a light yield three orders of magnitude smaller than BGO...
August 2017: Journal of Biomedical Optics
Feng Zhu, Weizhang Wu, Fuhai Zhu, Yong Wang, Yingjie Wang, Tingyi Xia
The main purpose of our investigation was to quantify the dosimetric influence of intravenous contrast agent for pancreatic cancer radiotherapy treatment. This study focused on complex modulated irradiation techniques of tomotherapy (TOMO) and volumetric-modulated arc therapy (VMAT) to investigate if novel conformal treatment methods could reduce the influence of contrast agent. In our study, patients with pancreatic cancer were enrolled to have 2 computed tomography (CT) scans in the same position without and with intravenous contrast agent for treatment planning...
August 14, 2017: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
Liang Li, Yi Zhang, Lian Ma, Ping Ji, Sarah Yim, Badrul A Chowdhury, Suresh Doddapaneni, Jiang Liu, Yaning Wang, Chandrahas Sahajwalla
Population pharmacokinetic/pharmacodynamic (PK/PD) models were developed to quantitate the exposure-response relationships using continuous longitudinal data on American College of Rheumatology (ACR) subcomponents, that is, tender-joint count (TJC), swollen-joint count (SJC), C-reactive protein, patient's assessment of pain, patient's global assessment of disease activity, physician's global assessment of disease activity, and patient's assessment of physical function for 5 biologics approved for use in rheumatoid arthritis...
September 2017: Journal of Clinical Pharmacology
Natalia Saltybaeva, Hatem Alkadhi
PURPOSE: The objective of our study was to assess the effect of patient vertical off-centering on organ dose in chest CT with tube current modulation. METHODS: For this purpose, anthropomorphic phantoms representing adult male, female and overweight male were scanned on 192-slice CT scanner at eleven different vertical positions (maximal off-centering ± 5 cm). Monte Carlo simulations were performed for each of the investigated setup, using tube current values extracted from the raw data, in order to obtain 3D dose distributions...
August 17, 2017: Medical Physics
Robert K Merrill, Steven J McAnany, Todd J Albert, Sheeraz A Qureshi
STUDY DESIGN: Cost-effectiveness analysis. OBJECTIVE: Investigate the 7-year cost-effectiveness of two-level cervical disc replacement (CDR) and anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: CDR and ACDF are both effective treatment strategies for managing degenerative conditions of the cervical spine. CDR has been shown to be a more-cost effective intervention in the short term, but the long-term cost-effectiveness has not been established...
August 14, 2017: Spine
Vijitha Periyasamy, Manojit Pramanik
Monte Carlo (MC) simulation for light propagation in tissue is the gold standard for studying the light propagation in biological tissue and has been used for years. Interaction of photons with a medium is simulated based on its optical properties. New simulation geometries, tissue-light interaction methods, and recording techniques are designed recently. Applications, such as whole mouse body simulations for fluorescence imaging, eye model for blood vessel imaging, skin model for terahertz imaging, human head model for sinus imaging, have emerged...
August 14, 2017: IEEE Reviews in Biomedical Engineering
Hsin-Yun Liu, Ching-Tzu Yang, Yu-Nu Wang, Wen-Chuin Hsu, Tzu-Hsin Huang, Yueh-E Lin, Chin-Yi Liu, Yea-Ing L Shyu
AIMS: To examine the role of balancing competing needs in the relationship between caregiving demand and caregiving outcomes (caregivers' role strain and depressive symptoms). BACKGROUND: Caregivers who do not balance competing needs are more likely to experience negative caregiving outcomes, suggesting that balance mediates between caregiving demand and caregiving outcomes. Identifying a mediator of negative caregiving effects may help in developing tailored interventions for family caregivers of persons with dementia...
August 17, 2017: Journal of Advanced Nursing
Maria Petropoulou, Dimitris Mavridis
When we synthesize research findings via meta-analysis, it is common to assume that the true underlying effect differs across studies. Total variability consists of the within-study and between-study variances (heterogeneity). There have been established measures, such as I(2) , to quantify the proportion of the total variation attributed to heterogeneity. There is a plethora of estimation methods available for estimating heterogeneity. The widely used DerSimonian and Laird estimation method has been challenged, but knowledge of the overall performance of heterogeneity estimators is incomplete...
August 16, 2017: Statistics in Medicine
Daniel Lecina, Joan F Gilabert, Victor Guallar
Modeling the dynamic nature of protein-ligand binding with atomistic simulations is one of the main challenges in computational biophysics, with important implications in the drug design process. Although in the past few years hardware and software advances have significantly revamped the use of molecular simulations, we still lack a fast and accurate ab initio description of the binding mechanism in complex systems, available only for up-to-date techniques and requiring several hours or days of heavy computation...
August 16, 2017: Scientific Reports
Michael David Clark, Kenneth R Morris, Maria Silvina Tomassone
We present a novel simulation-based investigation of the nucleation of nanodroplets from solution and from vapor. Nucleation is difficult to measure or model accurately, and predicting when nucleation should occur remains an open problem. Of specific interest is the "metastable limit", the observed concentration at which nucleation occurs spontaneously, which cannot currently be estimated a priori. To investigate the nucleation process, we employ Gauge Cell Monte Carlo simulations to target spontaneous nucleation and measure thermodynamic properties of the system at nucleation...
August 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Michael Fischer
Zeolites and structurally related materials (zeotypes) have received considerable attention as potential adsorbents for selective carbon dioxide adsorption. Within this group, zeotypes with aluminophosphate composition (AlPOs) could be an interesting alternative to the more frequently studied aluminosilicate zeolites. So far, however, only a few AlPOs have been characterised experimentally in terms of their CO2 adsorption properties. In this study, force-field based grand-canonical Monte Carlo (GCMC) simulations were used to evaluate the potential of AlPOs for CO2/N2 separation, a binary mixture that constitutes a suitable model system for the removal of carbon dioxide from flue gases...
August 16, 2017: Physical Chemistry Chemical Physics: PCCP
Daniel M Goldenholz, Joseph Tharayil, Robert Moss, Evan Myers, William H Theodore
BACKGROUND: The placebo response in epilepsy randomized clinical trials (RCTs) has recently been shown to largely reflect underlying natural variability in seizure frequency. Based on this observation, we sought to explore the parameter space of RCT design to optimize trial efficiency and cost. METHODS: We used one of the world's largest patient reported seizure diary databases, to derive virtual patients for simulated RCTs. We ran 1000 randomly generated simulated trials using bootstrapping (sampling with replacement) for each unique combination of trial parameters, sweeping a large set of parameters in durations of the baseline and test periods, number of patients, eligibility criteria, drug effect size, and patient dropout...
August 2017: Annals of Clinical and Translational Neurology
Daniel Adyro Martínez-Bello, Antonio López-Quílez, Alexander Torres Prieto
BACKGROUND: Dengue is a high incidence arboviral disease in tropical countries around the world. Colombia is an endemic country due to the favourable environmental conditions for vector survival and spread. Dengue surveillance in Colombia is based in passive notification of cases, supporting monitoring, prediction, risk factor identification and intervention measures. Even though the surveillance network works adequately, disease mapping techniques currently developed and employed for many health problems are not widely applied...
August 15, 2017: International Journal of Health Geographics
Tingting Wang, Yi-Ping Phoebe Chen, Iona M MacLeod, Jennie E Pryce, Michael E Goddard, Ben J Hayes
BACKGROUND: Using whole genome sequence data might improve genomic prediction accuracy, when compared with high-density SNP arrays, and could lead to identification of casual mutations affecting complex traits. For some traits, the most accurate genomic predictions are achieved with non-linear Bayesian methods. However, as the number of variants and the size of the reference population increase, the computational time required to implement these Bayesian methods (typically with Monte Carlo Markov Chain sampling) becomes unfeasibly long...
August 15, 2017: BMC Genomics
Kyle S Gustafson, Guoxi Xu, Karl F Freed, Jian Qin
The multiple-scattering theory for the electrostatics of many-body systems of monopolar spherical particles, embedded in a dielectric medium, is generalized to describe the electrostatics of these particles with embedded dipoles and multipoles. The Neumann image line construction for the electrostatic polarization produced by one particle is generalized to compute the energy, forces, and torques for the many-body system as functions of the positions of the particles. The approach is validated by comparison with direct numerical calculation, and the convergence rate is analyzed and expressed in terms of the discontinuity in dielectric contrast and particle density...
August 14, 2017: Journal of Chemical Physics
Markus Schröder, Hans-Dieter Meyer
We propose a Monte Carlo method, "Monte Carlo Potfit," for transforming high-dimensional potential energy surfaces evaluated on discrete grid points into a sum-of-products form, more precisely into a Tucker form. To this end we use a variational ansatz in which we replace numerically exact integrals with Monte Carlo integrals. This largely reduces the numerical cost by avoiding the evaluation of the potential on all grid points and allows a treatment of surfaces up to 15-18 degrees of freedom. We furthermore show that the error made with this ansatz can be controlled and vanishes in certain limits...
August 14, 2017: Journal of Chemical Physics
Praveen Kumar Bommineni, Sudeep N Punnathanam
Co-crystal formation from fluid-mixtures is quite common in a large number of systems. The simplest systems that show co-crystal (also called substitutionally ordered solids) formation are binary hard sphere mixtures. In this work, we study the nucleation of AB2 type solid compounds using Monte Carlo molecular simulations in binary hard sphere mixtures with the size ratio of 0.55. The conditions chosen for the study lie in the region where nucleation of an AB2 type solid competes with that of a pure A solid with a face-centered-cubic structure...
August 14, 2017: Journal of Chemical Physics
Hsiu-Yu Yu, Zahera Jabeen, David M Eckmann, Portonovo S Ayyaswamy, Ravi Radhakrishnan
We have studied the microstructure of a flow-driven hardsphere suspension inside a cylinder using dynamical density functional theory and Monte Carlo simulations. In order to be representative of various physical conditions that may prevail in experiments, we investigate the problem using both the grand canonical ($\mu VT$) ensemble and the canonical ($NVT$) ensemble. In both ensembles, the hydrodynamic effect on the suspension mediated by the presence of the confining wall is implemented in a mean-field fashion by incorporating the thermodynamic work done by the inertial lift force on the particle given the average flow field...
August 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
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