13,110 results match your criteria Asymptotic Analysis[Journal]


Adaptive Fuzzy Asymptotic Tracking for Nonlinear Systems With Nonstrict-Feedback Structure.

IEEE Trans Cybern 2020 Jul 3;PP. Epub 2020 Jul 3.

In this article, the tracking control problems of the nonlinear nonstrict-feedback systems are considered. By combining the backstepping technique and bound estimation method, a novel nonlinear adaptive asymptotical control law is proposed, which offsets the effect of the unknown virtual control parameters and the uncertain nonlinearities. Correspondingly, an improved Lyapunov function by introducing the lower bounds of control parameters has been devised in this article. Read More

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http://dx.doi.org/10.1109/TCYB.2020.3002242DOI Listing

Chaos and periodicities in a climatic time series of the Iberian Margin.

Chaos 2020 Jun;30(6):063126

Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Armilla, 18100 Granada, Spain.

We analyze the time series of the temperature of the sedimentary core MD01-2443 originating from the Iberian Margin with a duration of 420 kyr. The series has been tested for unit-root and a long term trend is estimated. We identify four significant periodicities together with a low climatic activity every 100 kyr, and these were associated with internal and external forcings. Read More

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http://dx.doi.org/10.1063/1.5123509DOI Listing

Elastic properties of self-assembled bilayer membranes: Analytic expressions via asymptotic expansion.

J Chem Phys 2020 Jun;152(24):244121

Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada.

Bilayer membranes self-assembled from amphiphilic molecules are ubiquitous in biological and soft matter systems. The elastic properties of bilayer membranes are essential in determining the shape and structure of bilayers. A novel method to calculate the elastic moduli of the self-assembled bilayers within the framework of the self-consistent field theory is developed based on an asymptotic expansion of the order parameters in terms of the bilayer curvature. Read More

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http://dx.doi.org/10.1063/5.0009734DOI Listing

The chord-length distribution of a polyhedron.

Acta Crystallogr A Found Adv 2020 Jul 1;76(Pt 4):474-488. Epub 2020 Jun 1.

Dipartimento di Fisica G. Galilei, Università di Padova, via Marzolo 8, I-35131 Padova, Italy.

The chord-length distribution function [γ''(r)] of any bounded polyhedron has a closed analytic expression which changes in the different subdomains of the r range. In each of these, the γ''(r) expression only involves, as transcendental contributions, inverse trigonometric functions of argument equal to R[r, Δ], Δ being the square root of a second-degree r polynomial and R[x, y] a rational function. As r approaches δ, one of the two end points of an r subdomain, the derivative of γ''(r) can only show singularities of the forms |r - δ| and |r - δ|, with n and m appropriate positive integers. Read More

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http://dx.doi.org/10.1107/S2053273320004519DOI Listing

Stabilization of Interval Type-2 Fuzzy-Based Reliable Sampled-Data Control Systems.

IEEE Trans Cybern 2020 Jun 30;PP. Epub 2020 Jun 30.

This article investigates the stabilization problem of the Takagi-Sugeno (T-S) fuzzy-based interval type-2 (IT-2) reliable sampled-data control system. Different from the existing studies, the information for the entire sampling interval with a relation of the augmented state vectors is considered for designing the reliable sampled-data control of IT-2 T-S fuzzy systems. In this regard, we construct the suitable looped Lyapunov-Krasovskii functional (LKF) with the information of the fuzzy membership function that feeds back the time derivative of the membership function to derive sufficient conditions. Read More

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http://dx.doi.org/10.1109/TCYB.2020.3001609DOI Listing

Understanding surface charge regulation in silica nanopores.

Phys Chem Chem Phys 2020 Jun 29. Epub 2020 Jun 29.

Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521, USA.

Nanoporous silica is used in a wide variety of applications, ranging from bioanalytical tools and materials for energy storage and conversion as well as separation devices. The surface charge density of nanopores is not easily measured by experiment yet plays a vital role in the performance and functioning of silica nanopores. Herein, we report a theoretical model to describe charge regulation in silica nanopores by combining the surface-reaction model and the classical density functional theory (CDFT). Read More

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http://dx.doi.org/10.1039/d0cp02152kDOI Listing

Nonparametric hyperrectangular tolerance and prediction regions for setting multivariate reference regions in laboratory medicine.

Stat Methods Med Res 2020 Jun 29:962280220933910. Epub 2020 Jun 29.

Department of Mathematics and Statistics, University of Maryland Baltimore County, Baltimore, MD, USA.

Reference regions are widely used in clinical chemistry and laboratory medicine to interpret the results of biochemical or physiological tests of patients. There are well-established methods in the literature for reference limits for univariate measurements; however, limited methods are available for the construction of multivariate reference regions, since traditional multivariate statistical regions (e.g. Read More

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http://dx.doi.org/10.1177/0962280220933910DOI Listing

Nonparametric testing of lack of dependence in functional linear models.

PLoS One 2020 26;15(6):e0234094. Epub 2020 Jun 26.

School of Statistics, Capital University of Economics and Business, Beijing, China.

An important inferential task in functional linear models is to test the dependence between the response and the functional predictor. The traditional testing theory was constructed based on the functional principle component analysis which requires estimating the covariance operator of the functional predictor. Due to the intrinsic high-dimensionality of functional data, the sample is often not large enough to allow accurate estimation of the covariance operator and hence causes the follow-up test underpowered. Read More

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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0234094PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7319281PMC

Improved Kaplan-Meier Estimator in Survival Analysis Based on Partially Rank-Ordered Set Samples.

Comput Math Methods Med 2020 29;2020:7827434. Epub 2020 May 29.

Professor Alborzi Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.

This study presents a novel methodology to investigate the nonparametric estimation of a survival probability under random censoring time using the ranked observations from a Partially Rank-Ordered Set (PROS) sampling design and employs it in a hematological disorder study. The PROS sampling design has numerous applications in medicine, social sciences and ecology where the exact measurement of the sampling units is costly; however, sampling units can be ordered by using judgment ranking or available concomitant information. The general estimation methods are not directly applicable to the case where samples are from rank-based sampling designs, because the sampling units do not meet the identically distributed assumption. Read More

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http://dx.doi.org/10.1155/2020/7827434DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7296468PMC

Model-free approach to quantifying the proportion of treatment effect explained by a surrogate marker.

Biometrika 2020 Mar 24;107(1):107-122. Epub 2019 Dec 24.

Department of Biostatistics, Harvard University, 655 Huntington Avenue, Boston, Massachusetts 02115, U.S.A.

In randomized clinical trials, the primary outcome, , often requires long-term follow-up and/or is costly to measure. For such settings, it is desirable to use a surrogate marker, , to infer the treatment effect on , Δ. Identifying such an and quantifying the proportion of treatment effect on explained by the effect on are thus of great importance. Read More

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http://dx.doi.org/10.1093/biomet/asz065DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7315285PMC

Vitamin D Serum Levels in the UK Population, including a Mathematical Approach to Evaluate the Impact of Vitamin D Fortified Ready-to-Eat Breakfast Cereals: Application of the NDNS Database.

Nutrients 2020 Jun 23;12(6). Epub 2020 Jun 23.

Kellogg's Europe, Orange Tower, Media City UK, Salford, Manchester M50 2HF, UK.

Vitamin D status is relatively poor in the general population, potentially leading to various conditions. The present study evaluates the relationship between vitamin D status and intake in the UK population and the impact of vitamin D fortified ready-to-eat cereals (RTEC) on this status via data from the National Diet and Nutrition Survey (NDNS: 2008-2012). Four cohorts were addressed: ages 4-10 ( = 803), ages 11-18 ( = 884), ages 19-64 ( = 1655) and ages 65 and higher ( = 428). Read More

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http://dx.doi.org/10.3390/nu12061868DOI Listing

Modeling the role of macrophages in HIV persistence during antiretroviral therapy.

J Math Biol 2020 Jun 24. Epub 2020 Jun 24.

Department of Mathematics, University of Florida, Gainesville, FL, 32611, USA.

HIV preferentially infects activated CD4+ T cells. Current antiretroviral therapy cannot eradicate the virus. Viral infection of other cells such as macrophages may contribute to viral persistence during antiretroviral therapy. Read More

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http://dx.doi.org/10.1007/s00285-020-01513-xDOI Listing

Mixture distributions in a stochastic gene expression model with delayed feedback: a WKB approximation approach.

J Math Biol 2020 Jun 24. Epub 2020 Jun 24.

University of Delaware, Newark, DE, USA.

Noise in gene expression can be substantively affected by the presence of production delay. Here we consider a mathematical model with bursty production of protein, a one-step production delay (the passage of which activates the protein), and feedback in the frequency of bursts. We specifically focus on examining the steady-state behaviour of the model in the slow-activation (i. Read More

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http://dx.doi.org/10.1007/s00285-020-01512-yDOI Listing

Generalized Regression Estimators with High-Dimensional Covariates.

Stat Sin 2020 Jul;30(3):1135-1154

School of Statistics and Data Science & LPMC, Nankai University, Tianjin 300071, China.

Data from a large number of covariates with known population totals are frequently observed in survey studies. These auxiliary variables contain valuable information that can be incorporated into estimation of the population total of a survey variable to improve the estimation precision. We consider the generalized regression estimator formulated under the model-assisted framework in which a regression model is utilized to make use of the available covariates while the estimator still has basic design-based properties. Read More

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http://dx.doi.org/10.5705/ss.202017.0384DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7313320PMC

Scanning-Chain Formation Control for Multiple Unmanned Surface Vessels to Pass Through Water Channels.

IEEE Trans Cybern 2020 Jun 24;PP. Epub 2020 Jun 24.

For scenarios to pass through narrow and irregular channels, we develop a pragmatic distributed flexible formation protocol for multiple unmanned surface vessel systems (Multi-USVs). Therein, for path tracking with two leaders USVs, we propose a model predictive trajectory tracking scheme. Specifically, we design a scanning-formation controller with a trajectory state estimator for the followers to follow the leaders in order to efficiently fulfill the passing-through mission. Read More

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http://dx.doi.org/10.1109/TCYB.2020.2997833DOI Listing

Semiparametric copula-based analysis for treatment effects in the presence of treatment switching.

Stat Med 2020 Jun 24. Epub 2020 Jun 24.

Center for Drug Evaluation, Taipei, Taiwan.

In controlled trials, "treatment switching" occurs when patients in one treatment group switch to alternative treatments during the trial, and poses challenges to treatment effect evaluation owing to crossover of the treatments groups. In this work, we assume that treatment switching can occur after some disease progression event and view the progression and death events as two semicompeting risks. The proposed model consists of a copula model for the joint distribution of time-to-progression (TTP) and overall survival (OS) up to the earlier of the two events, as well as a conditional hazard model for OS subsequent to progression. Read More

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http://dx.doi.org/10.1002/sim.8585DOI Listing

Dynamic buckling of an inextensible elastic ring: Linear and nonlinear analyses.

Phys Rev E 2020 May;101(5-1):053002

Mathematical Institute, University of Oxford, Woodstock Rd, Oxford, OX2 6GG, United Kingdom.

Slender elastic objects such as a column tend to buckle under loads. While static buckling is well understood as a bifurcation problem, the evolution of shapes during dynamic buckling is much harder to study. Elastic rings under normal pressure have emerged as a theoretical and experimental paradigm for the study of dynamic buckling with controlled loads. Read More

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http://dx.doi.org/10.1103/PhysRevE.101.053002DOI Listing

Hearing Euler characteristic of graphs.

Phys Rev E 2020 May;101(5-1):052320

Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warsaw, Poland.

The Euler characteristic χ=|V|-|E| and the total length L are the most important topological and geometrical characteristics of a metric graph. Here |V| and |E| denote the number of vertices and edges of a graph. The Euler characteristic determines the number β of independent cycles in a graph while the total length determines the asymptotic behavior of the energy eigenvalues via Weyl's law. Read More

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http://dx.doi.org/10.1103/PhysRevE.101.052320DOI Listing

Kinetic roughening of the urban skyline.

Phys Rev E 2020 May;101(5-1):050301

Physics Department, Rutherford Building, 3600 rue University, McGill University, Montréal, Québec, Canada H3A 2T8.

We analyze the morphology of the modern urban skyline in terms of its roughness properties. This is facilitated by a database of 10^{7} building heights in cities throughout the Netherlands which allows us to compute the asymptotic height difference correlation function in each city. We find that in cities for which the height correlations display power-law scaling as a function of distance between the buildings, the corresponding roughness exponents are commensurate to the Edwards-Wilkinson and Kardar-Parisi-Zhang equations for kinetic roughening. Read More

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http://dx.doi.org/10.1103/PhysRevE.101.050301DOI Listing

Streaming-potential-mediated pressure-driven transport of Phan-Thien-Tanner fluids in a microchannel.

Authors:
Sandip Sarkar

Phys Rev E 2020 May;101(5-1):053104

Department of Mechanical Engineering, Jadavpur University, Kolkata 700 032, India.

Streaming potential mediated pressure driven electrokinetic transport of Phan-Thien-Tanner fluids in a slit type parallel plate microchannel is studied analytically and semianalytically. Without adopting the traditional considerations of Debye-Hückel linearization approximation for low surface potentials, exact analytical solutions are obtained for the electrostatic potential distribution, velocity, and volumetric flow rates taking into account the full Poisson-Boltzmann equation. The influences of interfacial electrokinetics and viscoelasticity on the streaming potential development, polymeric stress components, shear viscosity, and the hydroelectric energy conversion efficiency are incorporated concurrently. Read More

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http://dx.doi.org/10.1103/PhysRevE.101.053104DOI Listing

Quantum diffusion in spin chains with phase space methods.

Phys Rev E 2020 May;101(5-1):052120

Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA.

Connecting short-time microscopic dynamics with long-time hydrodynamics in strongly correlated quantum systems is one of the outstanding questions. In particular, it is hard to determine various hydrodynamic coefficients such as the diffusion constant or viscosity starting from a microscopic model: exact quantum simulations are limited to either small system sizes or to short times, which are insufficient to reach asymptotic behavior and so various approximations must be applied. We show that these difficulties, at least for particular models, can be circumvented by using the cluster truncated Wigner approximation (CTWA), which maps quantum Hamiltonian dynamics into classical Hamiltonian dynamics in auxiliary high-dimensional phase space. Read More

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http://dx.doi.org/10.1103/PhysRevE.101.052120DOI Listing

Caloric curves of classical self-gravitating systems in general relativity.

Phys Rev E 2020 May;101(5-1):052105

Laboratoire de Physique Théorique, Université de Toulouse, CNRS, UPS, France.

We determine the caloric curves of classical self-gravitating systems at statistical equilibrium in general relativity. In the classical limit, the caloric curves of a self-gravitating gas depend on a unique parameter ν=GNm/Rc^{2}, called the compactness parameter, where N is the particle number and R the system's size. Typically, the caloric curves have the form of a double spiral. Read More

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http://dx.doi.org/10.1103/PhysRevE.101.052105DOI Listing

High-temperature ion-thermal behavior from average-atom calculations.

Phys Rev E 2020 May;101(5-1):053201

Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545, USA.

Atom-in-jellium calculations of the Einstein frequency were used to calculate the mean displacement of an ion over a wide range of compression and temperature. Expressed as a fraction of the Wigner-Seitz radius, the displacement is a measure of the asymptotic freedom of the ion at high temperature, and thus of the change in heat capacity from six to three quadratic degrees of freedom per atom. A functional form for free energy was proposed based on the Maxwell-Boltzmann distribution as a correction to the Debye free energy, with a single free parameter representing the effective density of potential modes to be saturated. Read More

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http://dx.doi.org/10.1103/PhysRevE.101.053201DOI Listing

Oscillations and negative velocity autocorrelation emerging from a Brownian particle model with hydrodynamic interactions.

Phys Rev E 2020 May;101(5-1):052140

CRUB, Universidad Nacional del Comahue, Quintral 1250, 8400 Bariloche, Río Negro, Argentina.

We study the dynamics of a particle in a fluid from a generalized Langevin equation (GLE) with a frictional exponential memory kernel and hydrodynamic interactions. By using Laplace analysis we obtain the analytical expressions for the velocity autocorrelation function (VACF) and mean square displacement (MSD) of the particle. Our results show that, in the strictly asymptotic time limit, the dynamics of the particle correspond to a particle ruled by a GLE with a Dirac delta friction memory kernel and hydrodynamic interactions. Read More

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http://dx.doi.org/10.1103/PhysRevE.101.052140DOI Listing

A new Lyapunov functional for stability analysis of neutral-type Hopfield neural networks with multiple delays.

Authors:
Ozlem Faydasicok

Neural Netw 2020 Jun 16;129:288-297. Epub 2020 Jun 16.

Department of Mathematics, Faculty of Science, Istanbul University, Vezneciler, Istanbul, Turkey. Electronic address:

This research paper conducts an investigation into the stability issue for a more general class of neutral-type Hopfield neural networks that involves multiple time delays in the states of neurons and multiple neutral delays in the time derivatives of the states of neurons. By constructing a new proper Lyapunov functional, an alternative easily verifiable algebraic criterion for global asymptotic stability of this type of Hopfield neural systems is derived. This new stability condition is entirely independent of time and neutral delays. Read More

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http://dx.doi.org/10.1016/j.neunet.2020.06.013DOI Listing

Interference of a resonance state with itself: a route to control its dynamical behaviour.

Authors:
A García-Vela

Phys Chem Chem Phys 2020 Jun 23. Epub 2020 Jun 23.

Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain.

It is demonstrated both numerically and mathematically that the dynamical behavior of an isolated resonance state, which comprises the resonance decay lifetime and the asymptotic fragment state distribution produced upon resonance decay, can be extensively controlled by means of quantum interference induced by a laser field in the weak-field regime. The control scheme applied is designed to induce interference between amplitudes excited at two different energies of the resonance line shape, namely the resonance energy and an additional energy. This scheme exploits the resonance property of possessing a nonzero energy width, which makes it possible that a resonance state may interfere with itself, and thus allows interference between the amplitudes excited at the two energies of the resonance width. Read More

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http://dx.doi.org/10.1039/d0cp00392aDOI Listing

Subcarrier wave continuous variable quantum key distribution with discrete modulation: mathematical model and finite-key analysis.

Sci Rep 2020 Jun 22;10(1):10034. Epub 2020 Jun 22.

ITMO University, Kronverkskiy, 49, Saint Petersburg, 197101, Russia.

In this paper we report a continuous-variable quantum key distribution protocol using multimode coherent states generated on subcarrier frequencies of the optical spectrum. We propose a coherent detection scheme where power from a carrier wave is used as a local oscillator. We compose a mathematical model of the proposed scheme and perform its security analysis in the finite-size regime using fully quantum asymptotic equipartition property technique. Read More

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http://dx.doi.org/10.1038/s41598-020-66948-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7308325PMC

A nonlinear epidemiological model considering asymptotic and quarantine classes for SARS CoV-2 virus.

Chaos Solitons Fractals 2020 Sep 4;138:109953. Epub 2020 Jun 4.

Department of Mathematics, National Institute of Technology, Hamirpur 177001, India.

In this article, we develop a mathematical model considering susceptible, exposed, infected, asymptotic, quarantine/isolation and recovered classes as in case of COVID-19 disease. The facility of quarantine/isolation have been provided to both exposed and infected classes. Asymptotic individuals either recovered without undergo treatment or moved to infected class after some duration. Read More

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http://dx.doi.org/10.1016/j.chaos.2020.109953DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7269963PMC
September 2020

A Markovian influence graph formed from utility line outage data to mitigate large cascades.

IEEE Trans Power Syst 2020 Jul 30;35(4):3224-3235. Epub 2020 Jan 30.

KZ, ID, ZW are with Electrical and Computer Engineering dept., Iowa State University, Ames IA USA; AR is with Statistics dept., Texas A&M University, College Station TX USA; APG is with Statistics dept., Iowa State University.

We use observed transmission line outage data to make a Markovian influence graph that describes the probabili- ties of transitions between generations of cascading line outages. Each generation of a cascade consists of a single line outage or multiple line outages. The new influence graph defines a Markov chain and generalizes previous influence graphs by including multiple line outages as Markov chain states. Read More

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http://dx.doi.org/10.1109/TPWRS.2020.2970406DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7304557PMC

A simplified math approach to predict ICU beds and mortality rate for hospital emergency planning under Covid-19 pandemic.

Comput Chem Eng 2020 Sep 4;140:106945. Epub 2020 Jun 4.

Anesthesia and ICU Department Maggiore Hospital, ASST Lodi, Lodi, Italy.

The different stages of Covid-19 pandemic can be described by two key-variables: ICU patients and deaths in hospitals. We propose simple models that can be used by medical doctors and decision makers to predict the trends on both short-term and long-term horizons. Daily updates of the models with real data allow forecasting some key indicators for decision-making (an Excel file in the Supplemental material allows computing them). Read More

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http://dx.doi.org/10.1016/j.compchemeng.2020.106945DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7271874PMC
September 2020

Probing bulk viscosity in relativistic flows.

Philos Trans A Math Phys Eng Sci 2020 Jul 22;378(2175):20190409. Epub 2020 Jun 22.

Università di Ferrara and INFN-Ferrara, 44122 Ferrara, Italy.

We derive an analytical connection between kinetic relaxation rate and bulk viscosity of a relativistic fluid in spatial dimensions, all the way from the ultra-relativistic down to the near non-relativistic regime. Our derivation is based on both Chapman-Enskog asymptotic expansion and Grad's method of moments. We validate our theoretical results against a benchmark flow, providing further evidence of the correctness of the Chapman-Enskog approach; we define the range of validity of this approach and provide evidence of mounting departures at increasing Knudsen number. Read More

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http://dx.doi.org/10.1098/rsta.2019.0409DOI Listing

Dynamic growth models for Caragana korshinskii shrub biomass in China.

J Environ Manage 2020 Sep 22;269:110675. Epub 2020 May 22.

Research Institute of Desertification Control, Ningxia Academy of Agriculture and Forestry Science, Yinchuan, PR China. Electronic address:

The Caragana korshinskii shrub is a widely distributed plant found in arid regions and plays an important role in ecological environment protection. Accurate estimations of shrub biomass are particularly important for natural resource management decision making. 114 individual C. Read More

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http://dx.doi.org/10.1016/j.jenvman.2020.110675DOI Listing
September 2020

Graphical approaches for the control of generalized error rates.

Stat Med 2020 Jun 17. Epub 2020 Jun 17.

Statistical Methodology, Novartis Pharma AG, Basel, Switzerland.

When simultaneously testing multiple hypotheses, the usual approach in the context of confirmatory clinical trials is to control the familywise error rate (FWER), which bounds the probability of making at least one false rejection. In many trial settings, these hypotheses will additionally have a hierarchical structure that reflects the relative importance and links between different clinical objectives. The graphical approach of Bretz et al (2009) is a flexible and easily communicable way of controlling the FWER while respecting complex trial objectives and multiple structured hypotheses. Read More

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http://dx.doi.org/10.1002/sim.8595DOI Listing

Power Divergence Family of Statistics for Person Parameters in IRT Models.

Psychometrika 2020 Jun 16. Epub 2020 Jun 16.

Teachers College, Columbia University, New York, USA.

We generalize the power divergence (PD) family of statistics to the two-parameter logistic IRT model for the purpose of constructing hypothesis tests and confidence intervals of the person parameter. The well-known score test statistic is a special case of the proposed PD family. We also prove the proposed PD statistics are asymptotically equivalent and converge in distribution to [Formula: see text]. Read More

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http://dx.doi.org/10.1007/s11336-020-09712-7DOI Listing

The inverse-probability-of-censoring weighting (IPCW) adjusted win ratio statistic: an unbiased estimator in the presence of independent censoring.

J Biopharm Stat 2020 Jun 17:1-18. Epub 2020 Jun 17.

Department of Population and Quantitative Health Sciences, University of Massachusetts Medical School , Worcester, Massachusetts, USA.

The win ratio method has received much attention in methodological research, ad hoc analyses, and designs of prospective studies. As the primary analysis, it supported the approval of tafamidis for the treatment of cardiomyopathy to reduce cardiovascular mortality and cardiovascular-related hospitalization. However, its dependence on censoring is a potential shortcoming. Read More

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http://dx.doi.org/10.1080/10543406.2020.1757692DOI Listing

Estimation and inference for semi-competing risks based on data from a nested case-control study.

Stat Methods Med Res 2020 Jun 17:962280220926219. Epub 2020 Jun 17.

Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA, USA.

In semi-competing risks, the occurrence of some non-terminal event is subject to a terminal event, usually death. While existing methods for semi-competing risks data analysis assume complete information on all relevant covariates, data on at least one covariate are often not readily available in practice. In this setting, for standard univariate time-to-event analyses, researchers may choose from several strategies for sub-sampling patients on whom to collect complete data, including the nested case-control study design. Read More

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http://dx.doi.org/10.1177/0962280220926219DOI Listing

AdaptiveBandit: A Multi-armed Bandit Framework for Adaptive Sampling in Molecular Simulations.

J Chem Theory Comput 2020 Jun 30. Epub 2020 Jun 30.

Computational Science Laboratory, Universitat Pompeu Fabra, 08003 Barcelona, Spain.

Sampling from the equilibrium distribution has always been a major problem in molecular simulations due to the very high dimensionality of the conformational space. Over several decades, many approaches have been used to overcome the problem. In particular, we focus on unbiased simulation methods such as parallel and adaptive sampling. Read More

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http://dx.doi.org/10.1021/acs.jctc.0c00205DOI Listing

Compound optimal allocations for survival clinical trials.

Biom J 2020 Jun 15. Epub 2020 Jun 15.

Unit of Biostatistics and Clinical Trials, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, FC, Italy.

The aim of the present paper is to provide optimal allocations for comparative clinical trials with survival outcomes. The suggested targets are derived adopting a compound optimization strategy based on a subjective weighting of the relative importance of inferential demands and ethical concerns. The ensuing compound optimal targets are continuous functions of the treatment effects, so we provide the conditions under which they can be approached by standard response-adaptive randomization procedures, also guaranteeing the applicability of the classical asymptotic inference. Read More

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http://dx.doi.org/10.1002/bimj.201900232DOI Listing

Oscillatory Carreau flows in straight channels.

R Soc Open Sci 2020 May 13;7(5):191305. Epub 2020 May 13.

Institute of Mechanics, Bulgarian Academy of Sciences, Sofia, Bulgaria.

The present paper studies the oscillatory flow of Carreau fluid in a channel at different Womersley and Carreau numbers. At high and low Womersley numbers, asymptotic expansions in small parameters, connected with the Womersley number, are developed. For the intermediate Womersley numbers, theoretical bounds for the velocity solution and its gradient, depending on the problem parameters, are proven and explicitly given. Read More

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http://dx.doi.org/10.1098/rsos.191305DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7277286PMC

Unruh-like effects: effective temperatures along stationary worldlines.

J High Energy Phys 2020 9;2020(6):59. Epub 2020 Jun 9.

Department of Physics, Nazarbayev University, Nur-Sultan, Kazakhstan 010000.

We study the detailed balance temperatures recorded along all classes of stationary, uniformly accelerated worldlines in four-dimensional Minkowski spacetime, namely along (i) linear uniform acceleration, (ii) cusped, (iii) circular, (iv) catenary, and (v) helix worldlines, among which the Unruh temperature is the particular case for linear uniform acceleration. As a measuring device, we employ an Unruh-DeWitt detector, modeled as a qubit that interacts for a long time with a massless Klein-Gordon field in the vacuum state. The temperatures in each case (i) - (v) are functions of up to three invariant quantities: curvature or proper acceleration, , torsion, , and hypertorsion, , and except for the case (i), they depend on the transition frequency difference of the detector, . Read More

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http://dx.doi.org/10.1007/JHEP06(2020)059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7282697PMC

In Vitro Gas Production from Batch Cultures of Stomach and Hindgut Digesta of Horses Adapted to a Prebiotic Dose of Fructooligosaccharides and Inulin.

J Equine Vet Sci 2020 Jul 9;90:103020. Epub 2020 Apr 9.

Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle, Germany. Electronic address:

Fructooligosaccharides (FOS) and inulin may modulate hindgut fermentation. It was tested if digesta batch cultures taken from horses adapted to FOS and inulin show different fermentation compared with such taken from nonsupplemented horses. Six horses received 0. Read More

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http://dx.doi.org/10.1016/j.jevs.2020.103020DOI Listing

Modeling the Effects of Meteorological Factors and Unreported Cases on Seasonal Influenza Outbreaks in Gansu Province, China.

Bull Math Biol 2020 Jun 12;82(6):73. Epub 2020 Jun 12.

Department of Applied Mathematics, Lanzhou University of Technology, Lanzhou, 730050, Gansu, People's Republic of China.

Influenza usually breaks out seasonally in temperate regions, especially in winter, infection rates and mortality rates of influenza increase significantly, which means that dry air and cold temperatures accelerate the spread of influenza viruses. However, the meteorological factors that lead to seasonal influenza outbreaks and how these meteorological factors play a decisive role in influenza transmission remain unclear. During the epidemic of infectious diseases, the neglect of unreported cases leads to an underestimation of infection rates and basic reproduction number. Read More

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http://dx.doi.org/10.1007/s11538-020-00747-6DOI Listing

Statistical mechanical analysis of the electromechanical coupling in an electrically-responsive polymer chain.

Soft Matter 2020 Jun 12. Epub 2020 Jun 12.

Department of Civil and Environmental Engineering, Carnegie Mellon University, USA. and Center for Nonlinear Analysis, Carnegie Mellon University, USA. and Department of Materials Science and Engineering, Carnegie Mellon University, USA.

Polymeric materials that couple deformation and electrostatics have the potential for use in soft sensors and actuators with applications ranging from robotic, biomedical, energy, aerospace and automotive technologies. In contrast to the mechanics of polymers that has been studied using statistical mechanics approaches for decades, the coupled response under deformation and electrical field has largely been modeled only phenomenologically at the continuum scale. In this work, we examine the physics of the coupled deformation and electrical response of an electrically-responsive polymer chain using statistical mechanics. Read More

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http://dx.doi.org/10.1039/d0sm00845aDOI Listing

Adsorption inhibition by swollen micelles may cause multistability in active droplets.

Authors:
Matvey Morozov

Soft Matter 2020 Jun;16(24):5624-5632

Nonlinear Physical Chemistry Unit, Faculté des Sciences, Université libre de Bruxelles (ULB), CP231, 1050 Brussels, Belgium.

Experiments indicate that microdroplets undergoing micellar solubilization in the bulk of surfactant solution may excite Marangoni flows and self-propel spontaneously. Surprisingly, self-propulsion emerges even when the critical micelle concentration is exceeded and the Marangoni effect should be saturated. To explain this, we propose a novel model of a dissolving active droplet that is based on two fundamental assumptions: (a) products of the solubilization may inhibit surfactant adsorption; (b) solubilization prevents the formation of a monolayer of surfactant molecules at the droplet interface. Read More

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http://dx.doi.org/10.1039/d0sm00662aDOI Listing

Generalized mean residual life models for case-cohort and nested case-control studies.

Lifetime Data Anal 2020 Jun 11. Epub 2020 Jun 11.

Department of Population Health, New York University School of Medicine, New York, NY, 10016, USA.

Mean residual life (MRL) is the remaining life expectancy of a subject who has survived to a certain time point and can be used as an alternative to hazard function for characterizing the distribution of a time-to-event variable. Inference and application of MRL models have primarily focused on full-cohort studies. In practice, case-cohort and nested case-control designs have been commonly used within large cohorts that have long follow-up and study rare diseases, particularly when studying costly molecular biomarkers. Read More

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http://dx.doi.org/10.1007/s10985-020-09499-wDOI Listing

Psychological Capital Mediates the Association Between Perceived Organizational Support and Work Engagement Among Chinese Doctors.

Front Public Health 2020 22;8:149. Epub 2020 May 22.

Department of Social Medicine, School of Public Health, China Medical University, Shenyang, China.

As experts studying occupational health psychology know, low level of work engagement leads to higher turnover intentions. Some researchers have put a focus on the association between organizational support and work engagement. However, little has been done concerning the mediating effect of psychological capital (PsyCap) on the association between perceived organizational support (POS) and work engagement (vigor, dedication, absorption) among Chinese doctors. Read More

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http://dx.doi.org/10.3389/fpubh.2020.00149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7256625PMC

An imputation approach for fitting two-part mixed effects models for longitudinal semi-continuous data.

Stat Methods Med Res 2020 Jun 11:962280220927720. Epub 2020 Jun 11.

Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, MD, USA.

Two-part mixed effects models are often used for analyzing longitudinal data with many zeros. Typically, these models are formulated with binary and continuous components separately with random effects that are correlated between the two components. Researchers have developed maximum-likelihood and Bayesian approaches for fitting these models that often require using particular software packages or very specialized software. Read More

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http://dx.doi.org/10.1177/0962280220927720DOI Listing

A refined dynamic finite-strain shell theory for incompressible hyperelastic materials: equations and two-dimensional shell virtual work principle.

Proc Math Phys Eng Sci 2020 May 27;476(2237):20200031. Epub 2020 May 27.

Department of Mathematics, City University of Hong Kong, Kowloon Tong, Hong Kong, People's Republic of China.

Based on previous work for the static problem, in this paper, we first derive one form of dynamic finite-strain shell equations for incompressible hyperelastic materials that involve three shell constitutive relations. In order to single out the bending effect as well as to reduce the number of shell constitutive relations, a further refinement is performed, which leads to a refined dynamic finite-strain shell theory with only two shell constitutive relations (deducible from the given three-dimensional (3D) strain energy function) and some new insights are also deduced. By using the weak formulation of the shell equations and the variation of the 3D Lagrange functional, boundary conditions and the two-dimensional shell virtual work principle are derived. Read More

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http://dx.doi.org/10.1098/rspa.2020.0031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7277122PMC

From a discrete model of chemotaxis with volume-filling to a generalized Patlak-Keller-Segel model.

Proc Math Phys Eng Sci 2020 May 13;476(2237):20190871. Epub 2020 May 13.

School of Mathematics and Statistics, University of St Andrews, St Andrews KY16 9SS, UK.

We present a discrete model of chemotaxis whereby cells responding to a chemoattractant are seen as individual agents whose movement is described through a set of rules that result in a biased random walk. In order to take into account possible alterations in cellular motility observed at high cell densities (i.e. Read More

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http://dx.doi.org/10.1098/rspa.2019.0871DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7277129PMC

A pseudo-likelihood method for estimating misclassification probabilities in competing-risks settings when true-event data are partially observed.

Biom J 2020 Jun 10. Epub 2020 Jun 10.

Family AIDS Care and Education Services (FACES), Research Care and Training Program (RCTP), Kenya Medical Research Institute (KEMRI), Kisumu, Kenya.

Outcome misclassification occurs frequently in binary-outcome studies and can result in biased estimation of quantities such as the incidence, prevalence, cause-specific hazards, cumulative incidence functions, and so forth. A number of remedies have been proposed to address the potential misclassification of the outcomes in such data. The majority of these remedies lie in the estimation of misclassification probabilities, which are in turn used to adjust analyses for outcome misclassification. Read More

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http://dx.doi.org/10.1002/bimj.201900198DOI Listing