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https://www.readbyqxmd.com/read/29151271/development-of-spin-orbit-coupling-for-stochastic-configuration-interaction-techniques
#1
Paul Murphy, Jeremy P Coe, Martin J Paterson
To perform spin-orbit coupling calculations on atoms and molecules, good zeroth-order wavefunctions are necessary. Here, we present the software development of the Monte Carlo Configuration Interaction (MCCI) method, to enable calculation of such properties, where MCCI iteratively constructs a multireference wavefunction using a stochastic procedure. In this initial work, we aim to establish the efficacy of this technique in predicting the splitting of otherwise degenerate energy levels on a range of atoms and small diatomic molecules...
November 19, 2017: Journal of Computational Chemistry
https://www.readbyqxmd.com/read/29150815/score-based-tests-of-differential-item-functioning-via-pairwise-maximum-likelihood-estimation
#2
Ting Wang, Carolin Strobl, Achim Zeileis, Edgar C Merkle
Measurement invariance is a fundamental assumption in item response theory models, where the relationship between a latent construct (ability) and observed item responses is of interest. Violation of this assumption would render the scale misinterpreted or cause systematic bias against certain groups of persons. While a number of methods have been proposed to detect measurement invariance violations, they typically require advance definition of problematic item parameters and respondent grouping information...
November 17, 2017: Psychometrika
https://www.readbyqxmd.com/read/29150714/stochastic-lotka-volterra-food-chains
#3
Alexandru Hening, Dang H Nguyen
We study the persistence and extinction of species in a simple food chain that is modelled by a Lotka-Volterra system with environmental stochasticity. There exist sharp results for deterministic Lotka-Volterra systems in the literature but few for their stochastic counterparts. The food chain we analyze consists of one prey and [Formula: see text] predators. The jth predator eats the [Formula: see text]th species and is eaten by the [Formula: see text]th predator; this way each species only interacts with at most two other species-the ones that are immediately above or below it in the trophic chain...
November 17, 2017: Journal of Mathematical Biology
https://www.readbyqxmd.com/read/29150680/potential-landscape-of-high-dimensional-nonlinear-stochastic-dynamics-with-large-noise
#4
Ying Tang, Ruoshi Yuan, Gaowei Wang, Xiaomei Zhu, Ping Ao
Quantifying stochastic processes is essential to understand many natural phenomena, particularly in biology, including the cell-fate decision in developmental processes as well as the genesis and progression of cancers. While various attempts have been made to construct potential landscape in high dimensional systems and to estimate transition rates, they are practically limited to the cases where either noise is small or detailed balance condition holds. A general and practical approach to investigate real-world nonequilibrium systems, which are typically high-dimensional and subject to large multiplicative noise and the breakdown of detailed balance, remains elusive...
November 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29149377/multi-patch-and-multi-group-epidemic-models-a-new-framework
#5
Derdei Bichara, Abderrahman Iggidr
We develop a multi-patch and multi-group model that captures the dynamics of an infectious disease when the host is structured into an arbitrary number of groups and interacts into an arbitrary number of patches where the infection takes place. In this framework, we model host mobility that depends on its epidemiological status, by a Lagrangian approach. This framework is applied to a general SEIRS model and the basic reproduction number [Formula: see text] is derived. The effects of heterogeneity in groups, patches and mobility patterns on [Formula: see text] and disease prevalence are explored...
November 17, 2017: Journal of Mathematical Biology
https://www.readbyqxmd.com/read/29149077/rna-virus-evolution-via-a-quasispecies-based-model-reveals-a-drug-target-with-a-high-barrier-to-resistance
#6
Richard J Bingham, Eric C Dykeman, Reidun Twarock
The rapid occurrence of therapy-resistant mutant strains provides a challenge for anti-viral therapy. An ideal drug target would be a highly conserved molecular feature in the viral life cycle, such as the packaging signals in the genomes of RNA viruses that encode an instruction manual for their efficient assembly. The ubiquity of this assembly code in RNA viruses, including major human pathogens, suggests that it confers selective advantages. However, their impact on viral evolution cannot be assessed in current models of viral infection that lack molecular details of virus assembly...
November 17, 2017: Viruses
https://www.readbyqxmd.com/read/29148964/twenty-five-years-of-the-binary-power-law-for-characterizing-heterogeneity-of-disease-incidence
#7
Laurence V Madden, Gareth Hughes, Wanderson Bucker Moraes, Xiangming Xu, William W Turechek
Spatial pattern, an important epidemiological property of plant diseases, can be quantified at different scales using a range of methods. The spatial heterogeneity (or overdispersion) of disease incidence among sampling units is an especially important measure of small-scale pattern. As an alternative to Taylor's power law for the heterogeneity of counts with no upper bound, the binary power law (BPL) was proposed in 1992 as a model to represent the heterogeneity of disease incidence (number of plant units diseased out of n observed in each sampling unit, or the proportion diseased in each sampling unit)...
November 17, 2017: Phytopathology
https://www.readbyqxmd.com/read/29148818/dissociation-constants-of-cytochrome-p450-2c9-cytochrome-p450-reductase-complexes-in-a-lipid-bilayer-membrane-depend-on-nadph-a-single-protein-tracking-study
#8
Carlo Barnaba, Evan Taylor, James A Brozik
Cytochrome P450-Reductase (CPR) is a versatile NADPH-dependent electron donor located in the cytoplasmic side of the endoplasmic reticulum. It is an electron transferase that is able to deliver electrons to a variety of membrane-bound oxidative partners, including the drug-metabolizing enzymes of the cytochrome P450s (P450). CPR is also stoichiometrically limited compared to its oxidative counterparts and hypotheses have arisen about possible models that can overcome the stochiometric imbalance, including quaternary organization of P450 and diffusion-limited models...
November 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29148325/characteristics-of-high-and-low-efficiency-hospitals
#9
Michael Rosko, Herbert S Wong, Ryan Mutter
We compared performance, operating characteristics, and market environments of low- and high-efficiency hospitals in the 37 states that supplied inpatient data to the Healthcare Cost and Utilization Project from 2006 to 2010. Hospital cost-inefficiency estimates using stochastic frontier analysis were generated. Hospitals were then grouped into the 100 most- and 100 least-efficient hospitals for subsequent analysis. Compared with the least efficient hospitals, high-efficiency hospitals tended to have lower average costs, higher labor productivity, and higher profit margins...
January 1, 2017: Medical Care Research and Review: MCRR
https://www.readbyqxmd.com/read/29145538/association-between-socioeconomic-determinants-and-the-metabolic-syndrome-in-the-german-health-interview-and-examination-survey-for-adults-degs1-a-mediation-analysis
#10
Diego Montano
BACKGROUND: Metabolic syndrome and different socioeconomic characteristics including education and occupational status have been found to be associated in previous research. Nonetheless, theoretical models defining core variables and causal processes accounting for these associations are lacking. OBJECTIVES: The main objectives of the present investigation are (1) to present a theoretical model integrating physiological, biochemical, and psychosocial factors determining metabolic syndrome prevalence and (2) to corroborate the hypothesis that socioeconomic determinants are (partially) mediated by health-related behaviors, health risks, and dietary habits...
July 2017: Review of Diabetic Studies: RDS
https://www.readbyqxmd.com/read/29145393/estimating-the-probabilities-of-rare-arrhythmic-events-in-multiscale-computational-models-of-cardiac-cells-and-tissue
#11
Mark A Walker, Viatcheslav Gurev, John J Rice, Joseph L Greenstein, Raimond L Winslow
Ectopic heartbeats can trigger reentrant arrhythmias, leading to ventricular fibrillation and sudden cardiac death. Such events have been attributed to perturbed Ca2+ handling in cardiac myocytes leading to spontaneous Ca2+ release and delayed afterdepolarizations (DADs). However, the ways in which perturbation of specific molecular mechanisms alters the probability of ectopic beats is not understood. We present a multiscale model of cardiac tissue incorporating a biophysically detailed three-dimensional model of the ventricular myocyte...
November 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/29144733/a-mechanism-for-symmetry-breaking-and-shape-control-in-single-crystal-gold-nanorods
#12
Michael J Walsh, Wenming Tong, Hadas Katz-Boon, Paul Mulvaney, Joanne Etheridge, Alison M Funston
The phenomenon of symmetry breaking-in which the order of symmetry of a system is reduced despite manifest higher-order symmetry in the underlying fundamental laws-is pervasive throughout science and nature, playing a critical role in fields ranging from particle physics and quantum theory to cosmology and general relativity. For the growth of crystals, symmetry breaking is the crucial step required to generate a macroscopic shape that has fewer symmetry elements than the unit cell and/or seed crystal from which it grew...
November 16, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/29143842/wrinkling-formation-in-simply-supported-graphenes-under-tension-and-compression-loadings
#13
Ch Androulidakis, E N Koukaras, M G Pastore Carbone, M Hadjinicolaou, C Galiotis
Wrinkles in supported graphenes can be formed either by uniaxial compression or uniaxial tension beyond a certain critical load depending on the mode of loading. In the first case, the wrinkling direction is normal to the compression axis whereas in tension, wrinkles of the same pattern are formed parallel to the loading direction due to Poisson's (lateral) contraction. Herein we show by direct AFM observations that in simply-supported graphenes such instabilities appear as periodic wrinkles over existing stochastic undulations caused by the underlying-substrate-roughness...
November 16, 2017: Nanoscale
https://www.readbyqxmd.com/read/29142351/development-of-a-simple-image-processing-application-that-makes-abdominopelvic-tumor-visible-on-positron-emission-tomography-computed-tomography-image
#14
Anil Kumar Pandey, Kartik Saroha, Param Dev Sharma, Chetan Patel, Chandrashekhar Bal, Rakesh Kumar
Introduction: In this study, we have developed a simple image processing application in MATLAB that uses suprathreshold stochastic resonance (SSR) and helps the user to visualize abdominopelvic tumor on the exported prediuretic positron emission tomography/computed tomography (PET/CT) images. Methods: A brainstorming session was conducted for requirement analysis for the program. It was decided that program should load the screen captured PET/CT images and then produces output images in a window with a slider control that should enable the user to view the best image that visualizes the tumor, if present...
October 2017: Indian Journal of Nuclear Medicine: IJNM: the Official Journal of the Society of Nuclear Medicine, India
https://www.readbyqxmd.com/read/29142096/novel-ca-2-dependent-mechanisms-regulate-spontaneous-release-at-excitatory-synapses-onto-ca1-pyramidal-cells
#15
Walter E Babiec, Thomas J O'Dell
Although long thought to simply be a source of synaptic noise, spontaneous, action-potential independent release of neurotransmitter from presynaptic terminals has multiple roles in synaptic function. We explored whether and to what extent the two predominantly proposed mechanisms for explaining spontaneous release, stochastic activation of voltage-gated Ca(2+) channels (VGCCs) or activation of Ca(2+)-sensing receptors (CaSRs) by extracelluar Ca(2+), played a role in the sensitivity of spontaneous release to the level of extracellular Ca(2+) concentration at excitatory synapses at CA1 pyramidal cells of the adult, male mouse hippocampus...
November 15, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/29141416/perturbation-expansions-of-stochastic-wavefunctions-for-open-quantum-systems
#16
Yaling Ke, Yi Zhao
Based on the stochastic unravelling of the reduced density operator in the Feynman path integral formalism for an open quantum system in touch with harmonic environments, a new non-Markovian stochastic Schrödinger equation (NMSSE) has been established that allows for the systematic perturbation expansion in the system-bath coupling to arbitrary order. This NMSSE can be transformed in a facile manner into the other two NMSSEs, i.e., non-Markovian quantum state diffusion and time-dependent wavepacket diffusion method...
November 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29140577/herbivory-and-drought-generate-short-term-stochasticity-and-long-term-stability-in-a-savanna-understory-community
#17
Corinna Riginos, Lauren M Porensky, Kari E Veblen, Truman P Young
Rainfall and herbivory are fundamental drivers of grassland plant dynamics, yet few studies have examined long-term interactions between these factors in an experimental setting. Understanding such interactions is important, as rainfall is becoming increasingly erratic and native wild herbivores are being replaced by livestock. Livestock grazing and episodic low rainfall are thought to interact, leading to greater community change than either factor alone. We examined patterns of change and stability in herbaceous community composition through four dry periods, or droughts, over 15 years of the Kenya Long-term Exclosure Experiment (KLEE), which consists of six different combinations of cattle, native wild herbivores (e...
November 15, 2017: Ecological Applications: a Publication of the Ecological Society of America
https://www.readbyqxmd.com/read/29140407/targeted-treatment-of-yaws-with-household-contact-tracing-how-much-do-we-miss
#18
Louise Dyson, Michael Marks, Oliver M Crook, Oliver Sokana, Anthony W Solomon, Alex Bishop, David C W Mabey, T Déirdre Hollingsworth
Yaws is a disabling bacterial infection primarily found in warm and humid tropical areas. The World Health Organisation strategy mandates an initial round of total community treatment (TCT) with single-dose azithromycin followed either by further TCT or active case finding and treatment of cases and their contacts (the Morges strategy). We wish to investigate the effectiveness of the Morges strategy. We employ a stochastic household model to study the transmission of infection using data collected from a pre-TCT survey conducted in the Solomon Islands...
November 13, 2017: American Journal of Epidemiology
https://www.readbyqxmd.com/read/29139317/a-gamma-process-modeling-approach-for-the-comparison-of-dissolution-profiles
#19
H K T Ng, M H Ling, P S Chan
In this paper, we propose a stochastic gamma process model for assessing the similarity of two dissolution profiles. Based on the proposed stochastic model, we utilize the difference factor and similarity factor to test the similarity of two dissolution profiles based on bootstrap confidence intervals. The performances of the proposed methods are compared with a multivariate test procedure via Monte Carlo simulation studies. The proposed testing methods are shown to be powerful and effectively controlling the error rate...
November 15, 2017: Drug Development and Industrial Pharmacy
https://www.readbyqxmd.com/read/29138408/both-nodal-signalling-and-stochasticity-select-for-prospective-distal-visceral-endoderm-in-mouse-embryos
#20
Katsuyoshi Takaoka, Hiromi Nishimura, Hiroshi Hamada
Anterior-posterior (A-P) polarity of mouse embryos is established by distal visceral endoderm (DVE) at embryonic day (E) 5.5. Lefty1 is expressed first at E3.5 in a subset of epiblast progenitor cells (L1(epi) cells) and then in a subset of primitive endoderm cells (L1(dve) cells) fated to become DVE. Here we studied how prospective DVE cells are selected. Lefty1 expression in L1(epi) and L1(dve) cells depends on Nodal signaling. A cell that experiences the highest level of Nodal signaling begins to express Lefty1 and becomes an L1(epi) cell...
November 14, 2017: Nature Communications
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