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Monte Carlo simulation

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
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
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
E Andres Houseman, M Abbas Virji
Objective: Direct reading instruments are valuable tools for measuring exposure as they provide real-time measurements for rapid decision making. However, their use is limited to general survey applications in part due to issues related to their performance. Moreover, statistical analysis of real-time data is complicated by autocorrelation among successive measurements, non-stationary time series, and the presence of left-censoring due to limit-of-detection (LOD). A Bayesian framework is proposed that accounts for non-stationary autocorrelation and LOD issues in exposure time-series data in order to model workplace factors that affect exposure and estimate summary statistics for tasks or other covariates of interest...
August 1, 2017: Annals of Work Exposures and Health
Wook-Geun Shin, Mauro Testa, Hak Soo Kim, Jong Hwi Jeong, Se Byeong Lee, Yeon-Joo Kim, Chul Hee Min
For the independent validation of treatment plans, we developed a Monte Carlo (MC)-based patient dose calculation system with the tool for particle simulation (TOPAS) to enable routine and automatic dose recalculation for each patient. The proton beam nozzle was modeled with TOPAS to simulate the therapeutic beam, and MC commissioning was performed by comparing percent depth dose with the measurement. The beam set-up based on the prescribed beam range and modulation width was automated by modifying the vendor-specific method...
August 15, 2017: Physics in Medicine and Biology
James Z Hare, Shalabh Gupta, Thomas A Wettergren
This paper presents a distributed supervisory control algorithm that enables opportunistic sensing for energy-efficient target tracking in a sensor network. The algorithm called Prediction-based Opportunistic Sensing (POSE), is a distributed node-level energy management approach for minimizing energy usage. Distributed sensor nodes in the POSE network self-adapt to target trajectories by enabling high power consuming devices when they predict that a target is arriving in their coverage area, while enabling low power consuming devices when the target is absent...
August 11, 2017: IEEE Transactions on Cybernetics
Yong Dang, Wenyue Guo, Lianming Zhao, Houyu Zhu
Graphdiyne family has attracted a high degree of concern, because of its intriguing and promising properties. However, graphdiyne materials reported to date represent only a tiny fraction of the possible combinations. In this work, we demonstrate a computational approach to generate a series of conceivable graphdiyne-based frameworks (GDY-Rs and Li@GDY-Rs) by introducing a variety of functional groups (R = -NH2, -OH, -COOH, and -F) and doping metal (Li) in the molecular building blocks of graphdiyne without restriction of experimental conditions and rapidly screen the best candidates for the application of CO2 capture and sequestration (CCS)...
August 15, 2017: ACS Applied Materials & Interfaces
Yao Ai, Xiaobin Tang, Diyun Shu, Wencheng Shao, Chunhui Gong, Changran Geng, Xudong Zhang, Haiyan Yu
This work aims to determine the relationship between Cerenkov photon emission and radiation dose from internal radionuclide irradiation. Water and thyroid phantoms were used to simulate the distribution of Cerenkov photon emission and dose deposition through Monte Carlo method. The relationship between Cerenkov photon emission and dose deposition was quantitatively analyzed. A neck phantom was also used to verify Cerenkov photon detection for thyroid radionuclide therapy. Results show that Cerenkov photon emission and dose deposition exhibit the same distribution pattern in water phantom, and this relative distribution relationship also existed in the thyroid phantom...
August 14, 2017: Australasian Physical & Engineering Sciences in Medicine
Hendrik Schawe, Christoph Norrenbrock, Alexander K Hartmann
We perform Monte Carlo simulations to determine the critical temperatures of Ising Ferromagnets (IFM) on different types of two-dimensional proximity graphs, in which the distribution of their underlying node sets has been changed systematically by means of a parameter σ. This allows us to interpolate between regular grids and proximity graphs based on complete random placement of nodes. Each edge of the planar proximity graphs carries a weighted ferromagnetic coupling. The coupling strengths are determined via the Euclidean distances between coupled spins...
August 14, 2017: Scientific Reports
Fekade Bruck Sime, Uwe Hahn, Morgyn S Warner, Ing Soo Tiong, Michael S Roberts, Jeffrey Lipman, Sandra L Peake, Jason A Roberts
Changes in the pharmacokinetics of piperacillin in febrile neutropenic patients have been reported to result in sub-optimal exposures. This study aimed to develop a population pharmacokinetic model for piperacillin and perform dosing simulation to describe optimal dosing regimens for haematological malignancy patients with febrile neutropenia. Concentration-time data were obtained from previous prospective observational pharmacokinetic and interventional therapeutic drug monitoring studies. Non-parametric population pharmacokinetic analysis and Monte Carlo dosing simulations were performed with Pmetrics® package for R...
August 14, 2017: Antimicrobial Agents and Chemotherapy
Pascal Hauri, Uwe Schneider
PURPOSE: Long-term survivors of cancer who were treated with radiotherapy are at risk of a radiation-induced tumor. Hence, it is important to model the out-of-field dose resulting from a cancer treatment. These models have to be verified with measurements, due to the small size, the high sensitivity to ionizing radiation and the tissue-equivalent composition, LiF thermoluminescence dosimeters (TLD) are well-suited for out-of-field dose measurements. However, the photon energy variation of the stray dose leads to systematic dose errors caused by the variation in response with radiation energy of the TLDs...
August 11, 2017: Zeitschrift Für Medizinische Physik
Dave M Leathwick, Dongwen Luo
The concentration profile of anthelmintic reaching the target worms in the host can vary between animals even when administered doses are tailored to individual liveweight at the manufacturer's recommended rate. Factors contributing to variation in drug concentration include weather, breed of animal, formulation and the route by which drugs are administered. The implications of this variability for the development of anthelmintic resistance was investigated using Monte-Carlo simulation. A model framework was established where 100 animals each received a single drug treatment...
August 30, 2017: Veterinary Parasitology
Do Hyeon Yoo, Wook-Geun Shin, Jaekook Lee, Yeon Soo Yeom, Chan Hyeong Kim, Byung-Uck Chang, Chul Hee Min
After the Fukushima accident in Japan, the Korean Government implemented the "Act on Protective Action Guidelines Against Radiation in the Natural Environment" to regulate unnecessary radiation exposure to the public. However, despite the law which came into effect in July 2012, an appropriate method to evaluate the equivalent and effective doses from naturally occurring radioactive material (NORM) in consumer products is not available. The aim of the present study is to develop and validate an effective dose coefficient database enabling the simple and correct evaluation of the effective dose due to the usage of NORM-added consumer products...
August 9, 2017: Applied Radiation and Isotopes
Jennifer M Macleod, Josh Lipton-Duffin, Chaoying Fu, Tyler Taerum, Dmitrii F Perepichka, Federico Rosei
Two-dimensional (2D) molecular self-assembly allows for the formation of well-defined supramolecular layers with tailored geometrical, compositional and chemical properties. To date, random intermixing and entropic effects in these systems have largely been associated with crystalline disorder and glassy phases. Here we describe a 2D crystalline self-assembled molecular system that exhibits random incorporation of substitutional molecules. The lattice is formed from a mixture of trimesic acid (TMA) and terthienobenzenetricarboxylic acid (TTBTA), C3-symmetric hydrogen-bonding units of very different sizes (0...
August 14, 2017: ACS Nano
H A Mulder, H Rashidi
Response to infection in animals has 2 main mechanisms: resistance (ability to control pathogen burden) and tolerance (ability to maintain performance given the pathogen burden). Selection on disease resistance and tolerance to infections seems a promising avenue to increase productivity of animals in the presence of disease infections, but it is hampered by a lack of records of pathogen burden of infected animals. Selection on resilience (ability to maintain performance regardless of pathogen burden) may, therefore, be an alternative pragmatic approach, because it does not need records of pathogen burden...
August 2017: Journal of Animal Science
Wanyi Fu, Gregory M Sturgeon, Greeshma Agasthya, William Paul Segars, Anuj J Kapadia, Ehsan Samei
This study aimed to estimate the organ dose reduction potential for organ-dose-based tube current modulated (ODM) thoracic computed tomography (CT) with a wide dose reduction arc. Twenty-one computational anthropomorphic phantoms (XCAT) were used to create a virtual patient population with clinical anatomic variations. The phantoms were created based on patient images with normal anatomy (age range: 27 to 66 years, weight range: 52.0 to 105.8 kg). For each phantom, two breast tissue compositions were simulated: [Formula: see text] and [Formula: see text] (glandular-to-adipose ratio)...
July 2017: Journal of Medical Imaging
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