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Proc Math Phys Eng Sci 2019 Mar 20;475(2223):20180898. Epub 2019 Mar 20.

Department of Mathematics and Statistics, Memorial University, St John's, Canada A1C 5S7.

For delayed non-local reaction-diffusion equations arising from population biology, selection mechanisms of the speed sign for the bistable travelling wavefront have not been found. In this paper, based on the theory of asymptotic speeds of spread for monotone semiflows, we firstly provide an interval of values of wave speed and a novel general condition for determining the speed sign by applying the comparison principle and the globally asymptotic stability of the bistable travelling wave. Moreover, through constructing novel upper/lower solutions, we give explicit conditions for the speed sign to be positive or negative. Read More

Proc Math Phys Eng Sci 2019 Mar 20;475(2223):20180816. Epub 2019 Mar 20.

Department of Mathematical Sciences, University of Liverpool, Liverpool L69 3BX, UK.

A new model is proposed for elastic waves induced by a pulsating flow in a stenotic artery containing several stents. Dispersion properties of the waves depend on the stent structure-this feature is addressed in the present paper. Several vascular stenting procedures include overlapping stents; this configuration is also included in the model. Read More

Proc Math Phys Eng Sci 2019 Mar 13;475(2223):20180761. Epub 2019 Mar 13.

Institut für Mathematik, MA 7-1, Technische Universität Berlin, Straße des 17. Juni 136, 10623 Berlin, Germany.

Kahan discretization is applicable to any quadratic vector field and produces a birational map which approximates the shift along the phase flow. For a planar quadratic canonical Hamiltonian vector field, this map is known to be integrable and to preserve a pencil of cubic curves. Generically, the nine base points of this pencil include three points at infinity (corresponding to the asymptotic directions of cubic curves) and six finite points lying on a conic. Read More

Proc Math Phys Eng Sci 2019 Mar 20;475(2223):20180547. Epub 2019 Mar 20.

Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Twin Cities, MN, USA.

In this study, we establish an inclusive paradigm for the homogenization of scalar wave motion in periodic media (including the source term) at finite frequencies and wavenumbers spanning the first Brillouin zone. We take the eigenvalue problem for the unit cell of periodicity as a point of departure, and we consider the projection of germane Bloch wave function onto a suitable eigenfunction as descriptor of effective wave motion. For generality the finite wavenumber, finite frequency homogenization is pursued in via second-order asymptotic expansion about the apexes of 'wavenumber quadrants' comprising the first Brillouin zone, at frequencies near given (acoustic or optical) dispersion branch. Read More

Proc Math Phys Eng Sci 2019 Mar 6;475(2223):20180358. Epub 2019 Mar 6.

School of Mathematics and Statistics, University of Sydney, Sydney, New South Wales 2006, Australia.

We derive Edgeworth expansions that describe corrections to the Gaussian limiting behaviour of slow-fast systems. The Edgeworth expansion is achieved using a semi-group formalism for the transfer operator, where a Duhamel-Dyson series is used to asymptotically determine the corrections at any desired order of the time-scale parameter . The corrections involve integrals over higher-order auto-correlation functions. Read More

Auton Robots 2019 Feb 29;43(2):345-357. Epub 2018 Jun 29.

University of North Carolina at Chapel Hill, Chapel Hill, NC, USA,

In highly constrained settings, e.g., a tentaclelike medical robot maneuvering through narrow cavities in the body for minimally invasive surgery, it may be difficult or impossible for a robot with a generic kinematic design to reach all desirable targets while avoiding obstacles. Read More

Clin Hemorheol Microcirc 2019 Apr 16. Epub 2019 Apr 16.

U1046 INSERM, UMR 9214 CNRS « Physiopathologie & Médecine Expérimentale du Cœur et des Muscles - PHYMEDEXP », Unité d'Explorations Métaboliques (CERAMM), Université de Montpellier, Département de Physiologie Clinique, Hôpital Lapeyronie CHRU Montpellier, France.

 The ideal hematocrit is the hematocrit (Hct) value resulting in the highest value of Hct/viscosity (h/η) ratio and can thus be predicted from viscometric measurements with the use of equations such as Quemada's one which yield the determination of the bell-shaped curve of h/η as a function of Hct. In a series of recent papers we applied this approach to various populations, using viscometry at high shear rate (1000 s-1). However the shape of this curve has been reported to be dependent on the shear rate, resulting in a right-shift in this top value when Hct increase. Read More

J Chem Phys 2019 Apr;150(15):154902

Theoretical Quantum Physics Laboratory, RIKEN Cluster for Pioneering Research, Wako-shi, Saitama 351-0198, Japan.

We investigate the one- and two-dimensional diffusion limited reactions A + A → 0 and A + B → 0 with A active Janus particles and B passive particles in thermal equilibrium. We show that by increasing the self-propulsion time of the A particles, the reactant densities decay faster, at least for time transients of potential interest for chemical applications, e.g. Read More

Neural Netw 2019 Apr 4;116:35-45. Epub 2019 Apr 4.

School of Mathematical Sciences, Ocean University of China, Qingdao 266100, China. Electronic address:

In this paper, we study stochastic impulsive reaction-diffusion neural networks with S-type distributed delays, aiming to obtain the sufficient conditions for global exponential stability. First, an impulsive inequality involving infinite delay is introduced and the asymptotic behaviour of its solution is investigated by the truncation method. Then, global exponential stability in the mean-square sense of the stochastic impulsive reaction-diffusion system is studied by constructing a simple Lyapunov-Krasovskii functional where the S-type distributed delay is handled by the impulsive inequality. Read More

Phys Rev E 2019 Mar;99(3-1):032224

Université de Caen Normandie, ESIX Cherbourg, ABTE EA4651-ToxEMAC, 14000 Caen, France.

The dynamics of a weakly dissipative Hamiltonian system submitted to stochastic perturbations has been investigated by means of asymptotic methods. The probability of noise-induced separatrix crossing, which drastically changes the fate of the system, is derived analytically in the case where noise is an additive Kubo-Anderson process. This theory shows how the geometry of the separatrix, as well as the noise intensity and correlation time, affect the statistics of crossing. Read More

Phys Rev E 2019 Mar;99(3-1):032127

Department of Physics, Tokyo University of Science, Noda, Chiba 278-8510, Japan.

We study the relaxation behavior of the Ornstein-Uhlenbeck (OU) process with time-dependent and fluctuating diffusivity. In this process, the dynamics of the position vector is modeled by the Langevin equation with a linear restoring force and a fluctuating diffusivity (FD). This process can be interpreted as a simple model of relaxational dynamics with internal degrees of freedom or in a heterogeneous environment. Read More

Phys Rev E 2019 Mar;99(3-1):033110

Université Côte d'Azur, CNRS, LJAD, Nice 06108, France.

The dynamics of Rayleigh-Taylor turbulence convection in the presence of an alternating, time-periodic acceleration is studied by means of extensive direct numerical simulations of the Boussinesq equations. Within this framework, we discover a mechanism of relaminarization of turbulence: the alternating acceleration, which initially produces a growing turbulent mixing layer, at longer times suppresses turbulent fluctuation and drives the system toward an asymptotic stationary configuration. Dimensional arguments and linear stability theory are used to predict the width of the mixing layer in the asymptotic state as a function of the period of the acceleration. Read More

Phys Rev E 2019 Mar;99(3-1):032140

Departamento de Física, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil.

Circular KPZ interfaces spreading radially in the plane have Gaussian unitary ensemble (GUE) Tracy-Widom (TW) height distribution (HD) and Airy_{2} spatial covariance, but what are their statistics if they evolve on the surface of a different background space, such as a bowl, a mountain, or any surface of revolution? To give an answer to this, we report here extensive numerical analyses of several one-dimensional KPZ models on substrates whose size enlarges as 〈L(t)〉=L_{0}+ωt^{γ}, while their mean height 〈h〉 increases as usual [〈h〉∼t]. We show that the competition between the L enlargement and the correlation length (ξ≃ct^{1/z}) plays a key role in the asymptotic statistics of the interfaces. While systems with γ>1/z have HDs given by GUE and the interface width increasing as w∼t^{β}, for γ<1/z the HDs are Gaussian, in a correlated regime where w∼t^{αγ}. Read More

Stat Med 2019 Apr 17. Epub 2019 Apr 17.

Canadian Cancer Trials Group, Queen's University, Kingston, Canada.

The analysis of quality of life (QoL) data can be challenging due to the skewness of responses and the presence of missing data. In this paper, we propose a new weighted quantile regression method for estimating the conditional quantiles of QoL data with responses missing at random. The proposed method makes use of the correlation information within the same subject from an auxiliary mean regression model to enhance the estimation efficiency and takes into account of missing data mechanism. Read More

BMC Med Res Methodol 2019 Apr 16;19(1):79. Epub 2019 Apr 16.

MINT UMR INSERM 1066, CNRS 6021, Université d'Angers, UFR Santé, 16 Boulevard Davier, Angers Cedex, 49085, France.

Background: In medical research, explanatory continuous variables are frequently transformed or converted into categorical variables. If the coding is unknown, many tests can be used to identify the "optimal" transformation. This common process, involving the problems of multiple testing, requires a correction of the significance level. Read More

IEEE Trans Neural Netw Learn Syst 2019 Apr 11. Epub 2019 Apr 11.

This paper focuses on developing a distributed leader-following fault-tolerant tracking control scheme for a class of high-order nonlinear uncertain multiagent systems. Neural network-based adaptive learning algorithms are developed to learn unknown fault functions, guaranteeing the system stability and cooperative tracking even in the presence of multiple simultaneous process and actuator faults in the distributed agents. The time-varying leader's command is only communicated to a small portion of follower agents through directed links, and each follower agent exchanges local measurement information only with its neighbors through a bidirectional but asymmetric topology. Read More

IEEE Trans Med Imaging 2019 Apr 12. Epub 2019 Apr 12.

In OCT angiography (OCTA), decorrelation computation has been widely used as a local motion index to identify dynamic flow from static tissues, but its dependence on SNR severely degrades the vascular visibility, particularly in low- SNR regions. To mathematically characterize the decorrelation-SNR dependence of OCT signals, we developed a multi-variate time series (MVTS) model. Based on the model, we derived a universal asymptotic linear relation of decorrelation to inverse SNR (iSNR), with the variance in static and noise regions determined by the average kernel size. Read More

Ecol Evol 2019 Mar 21;9(6):3651-3660. Epub 2019 Feb 21.

Department of Biological and Environmental Science University of Jyväskylä Jyväskylä Finland.

Body size determines key ecological and evolutionary processes of organisms. Therefore, organisms undergo extensive shifts in resources, competitors, and predators as they grow in body size. While empirical and theoretical evidence show that these size-dependent ontogenetic shifts vastly influence the structure and dynamics of populations, theory on how those ontogenetic shifts affect the structure and dynamics of ecological networks is still virtually absent. Read More

Optica 2018 May 15;5(5):624-627. Epub 2018 May 15.

Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA.

The ability to simultaneously recover multiple fluorophores within biological tissue (multiplexing) can have important applications for tracking parallel disease processes . Here we present a novel method for rapid and quantitative multiplexing within a scattering medium, such as biological tissue, based on fluorescence lifetime contrast. This method employs a tomographic inversion of the asymptotic (late) portion of time-resolved spatial frequency (SF) domain measurements. Read More

Random Struct Algorithms 2019 May 12;54(3):444-498. Epub 2018 Nov 12.

Department of Mathematics and Computer Science Eindhoven University of Technology Eindhoven The Netherlands.

It is well known that many random graphs with infinite variance degrees are ultra-small. More precisely, for configuration models and preferential attachment models where the proportion of vertices of degree at least k is approximately k with τ ∈ (2,3), typical distances between pairs of vertices in a graph of size n are asymptotic to and , respectively. In this paper, we investigate the behavior of the diameter in such models. Read More

Lifetime Data Anal 2019 Apr 12. Epub 2019 Apr 12.

Department of Biostatistics and Bioinformatics, Duke University School of Medicine, Durham, NC, 27705, USA.

We discuss the multivariate (2L-variate) correlation structure and the asymptotic distribution for the group-sequential weighted logrank statistics formulated when monitoring two correlated event-time outcomes in clinical trials. The asymptotic distribution and the variance-covariance for the 2L-variate weighted logrank statistic are derived as available in various group-sequential trial designs. These methods are used to determine a group-sequential testing procedure based on calendar times or information fractions. Read More

Phys Rev Lett 2019 Mar;122(12):122701

Institute for Nuclear Theory and Department of Physics, University of Washington, Seattle, Washington 98195, USA.

We consider quarkyonic matter to naturally explain the observed properties of neutron stars. We argue that such matter might exist at densities close to that of nuclear matter, and at the onset, the pressure and the sound velocity in quarkyonic matter increase rapidly. In the limit of large number of quark colors N_{c}, this transition is characterized by a discontinuous change in pressure as a function of baryon number density. Read More

Theor Popul Biol 2019 Apr 8. Epub 2019 Apr 8.

Goethe University, Institute of Mathematics, 60629 Frankfurt am Main, Germany. Electronic address:

We revisit the model by Wiser et al. (2013), which describes how the mean fitness increases over time due to beneficial mutations in Lenski's long-term evolution experiment. We develop the model further both conceptually and mathematically. Read More

Stat Med 2019 Apr 10. Epub 2019 Apr 10.

Department of Statistics and Actuarial Science, University of Waterloo, Waterloo, Canada.

A mixture model is described, which accommodates different Markov processes governing disease progression in a finite set of latent classes. We give special attention to the setting in which individuals are examined intermittently and transition times are consequently interval censored. A score test is developed to identify genetic markers associated with class membership. Read More

J Math Biol 2019 Apr 9. Epub 2019 Apr 9.

Ecole Normale Supérieure, 46 rue d'Ulm, 75005, Paris, France.

We study here the bulk electro-diffusion properties of micro- and nanodomains containing a cusp-shaped structure in three-dimensions when the cation concentration dominates over the anions. To determine the consequences on the voltage distribution, we use the steady-state Poisson-Nernst-Planck equation with an integral constraint for the number of charges. A non-homogeneous Neumann boundary condition is imposed on the boundary. Read More

Psychol Res Behav Manag 2019 21;12:195-208. Epub 2019 Mar 21.

Department of Clinical Epidemiology, Shengjing Hospital of China Medical University, Shenyang, China,

Purpose: Although the mental health status of doctoral students deserves attention, few scholars have paid attention to factors related to their mental health problems. We aimed to investigate the prevalence of depression and anxiety in doctoral students and examine possible associated factors. We further aimed to assess whether mentoring relationships mediate the association between research self-efficacy and depression/anxiety. Read More

Polymers (Basel) 2018 Jul 30;10(8). Epub 2018 Jul 30.

Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany.

The conformational and rheological properties of active filaments/polymers exposed to shear flow are studied analytically. Using the continuous Gaussian semiflexible polymer model extended by the activity, we derive analytical expressions for the dependence of the deformation, orientation, relaxation times, and viscosity on the persistence length, shear rate, and activity. The model yields a Weissenberg-number dependent shear-induced deformation, alignment, and shear thinning behavior, similarly to the passive counterpart. Read More

Polymers (Basel) 2019 Mar 14;11(3). Epub 2019 Mar 14.

School of Mathematical, Physical and Computational Sciences, University of Reading, Reading RG6 6AX, UK.

Dynamical properties of branched polymer melts are determined by the polymer molecular weights and architectures containing junction points. Relaxation of entangled symmetric star polymers proceeds via arm-retraction and constraint release (CR). In this work, we investigate arm-retraction dynamics in the framework of a single-chain slip-spring model without CR effect where entanglements are treated as binary contacts, conveniently modeled as virtual "slip-links", each involving two neighboring strands. Read More

Stat Med 2019 Apr 7. Epub 2019 Apr 7.

Division of Cancer Epidemiology and Genetics, NIH National Cancer Institute, Rockville, MD.

We propose an extension of Harrell's concordance (C) index to evaluate the prognostic utility of biomarkers for diseases with multiple measurable outcomes that can be prioritized. Our prioritized concordance index measures the probability that, given a random subject pair, the subject with the worst disease status as of a time τ has the higher predicted risk. Our prioritized concordance index uses the same approach as the win ratio, by basing generalized pairwise comparisons on the most severe or clinically important comparable outcome. Read More

J Mol Spectrosc 2019 Feb;356:7-20

Group of Molecular Astrophysics, IFF-CSIC. C/Serrano 121, 28006 Madrid, Spain.

This article provides an overview of recent astronomical studies and a closely coordinated laboratory program devoted to the study of the physics and chemistry of carbon rich Asymptotic Giant Branch (AGB) stars. The increased sensitivity and angular resolution of high altitude ground-based millimeter-wave interferometers in the past few years has enabled molecular astronomers to determine the excitation and spatial distribution of molecules within a few stellar radii of the central star where the molecular seeds of dust are formed, and to critically assess the physicochemical mechanisms of dust formation and growth. However the astronomical studies are crucially dependent on precise laboratory measurements of the rotational spectra - both in the ground and vibrationally excited states of the normal and rare isotopic species - of the principal molecules in the inner region which appear to contain only two or three heavy atoms Much remains to be done by laboratory spectroscopists as evidenced by the large number of unassigned millimeters-wave rotational lines that are observed in the inner envelope of carbon rich AGB stars. Read More

ISA Trans 2019 Mar 28. Epub 2019 Mar 28.

School of Astronautics, Harbin Institute of Technology, Harbin 150001, China.

This paper addresses the problems of robust stability analysis and L-gain controller synthesis for uncertain impulsive positive systems. First, by employing the idea of impulse interval partitioning, an impulse-time-dependent discretized copositive Lyapunov function is proposed to analyze the robust stability and L-gain performance of the considered system without control inputs, and several stability conditions and L-gain criteria are respectively derived. Subsequently, a sufficient condition is formulated for the existence of state-feedback controllers with which not only the positivity and robust uniform asymptotic stability of the resulting closed-loop system are guaranteed, but also a prescribed L-gain performance is satisfied simultaneously. Read More

J Chem Phys 2019 Apr;150(13):134105

State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China and Center for Advanced Chemical Physics and 2011 Frontier Centre for Quantum Science and Technology, University of Science and Technology of China, 96 Jinzhai Road, Hefei 230026, China.

A single set of coordinates, which is optimal for both asymptotic product and reactant, is difficult to find in a state-to-state reactive scattering calculation using the quantum wave packet method. An interaction-asymptotic region decomposition (IARD) method was proposed in this work to solve this "coordinate problem." In the method, the interaction region and asymptotic regions are applied with the local optimal coordinate system, i. Read More

Prev Vet Med 2019 Mar 12. Epub 2019 Mar 12.

Section of Epidemiology, Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA. Electronic address:

Multidrug resistance is a serious problem raising the specter of infections for which there is no treatment. One of the most important tools in combating multidrug resistance is large scale monitoring programs, because they track resistance over large geographic areas and time scales. This large scope, however, can also introduce variability into the data. Read More

Stat Med 2019 Apr 4. Epub 2019 Apr 4.

Division of Biostatistics, Weill Cornell Medicine, New York, New York.

The consistency of doubly robust estimators relies on the consistent estimation of at least one of two nuisance regression parameters. In moderate-to-large dimensions, the use of flexible data-adaptive regression estimators may aid in achieving this consistency. However, n -consistency of doubly robust estimators is not guaranteed if one of the nuisance estimators is inconsistent. Read More

Sci Rep 2019 Apr 4;9(1):5630. Epub 2019 Apr 4.

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

The distributions of the diagonal elements of the Wigner's reaction [Formula: see text] matrix for open systems with violated time reversal T invariance in the case of large absorption are for the first time experimentally studied. The Wigner's reaction matrix links the properties of chaotic systems with the scattering processes in the asymptotic region. Microwave networks consisting of microwave circulators were used in the experiment to simulate quantum graphs with violated T invariance. Read More

Math Biosci Eng 2019 02;16(3):1654-1682

Department of Mathematics, Harbin Institute of Technology, Harbin 150001, P.R. China.

In this paper, we studied an SVIR epidemic model with nonlocal dispersal and delay, and we find that the existence of traveling wave is determined by the basic reproduction number ℜ₀ and minimal wave speed c. By applying Schauder's fixed point theorem and Lyapunov functional, the existence and boundary asymptotic behaviour of traveling wave solutions is investigated for ℜ₀>1 and c>c. The existence of traveling waves is obtained for ℜ₀>1 and c=c by employing a limiting argument. Read More

Math Biosci Eng 2019 02;16(3):1554-1574

Department of Mathematics, Swinburne University of Technology, Hawthorn, VIC 3122 Australia.

In this study, we propose an n-species stochastic model which considers the influences of the competitions and delayed diffusions among populations on dynamics of species. We then investigate the stochastic dynamics of the model, such as the persistence in mean of the species, and the asymptotic stability in distribution of the model. Then, by using the Hessian matrix and theory of optimal harvesting, we investigate the optimal harvesting problem, obtaining the optimal harvesting effort and the maximum of expectation of sustainable yield (ESY). Read More

Math Biosci Eng 2019 02;16(3):1525-1553

Laboratoire d'Analyse Nonlinéaire et Mathématiques Appliquées, University of Tlemcen, Tlemcen 13000, Algeria.

In this paper, we focus on the study of the dynamics of a certain age structured epidemic model. Our aim is to investigate the proposed model, which is based on the classical SIR epidemic model, with a general class of nonlinear incidence rate with some other generalization. We are interested to the asymptotic behavior of the system. Read More

Math Biosci Eng 2019 02;16(3):1471-1488

Library, Guizhou University of Finance and Economics, Guiyang, Guizhou 550025, China.

In this work, dynamical behaviors of discrete time Beverton-Holt population model with fuzzy parameters are studied. It provides a flexible model to fit population data. For three different fuzzy parameters and fuzzy initial conditions, according to a generalization of division (g-division) of fuzzy number, it can represent dynamical behaviors including boundedness, global asymptotical stability and persistence of positive solution. Read More

IEEE Trans Neural Netw Learn Syst 2019 Mar 29. Epub 2019 Mar 29.

This paper presents an online kinodynamic motion planning algorithmic framework using asymptotically optimal rapidly-exploring random tree (RRT*) and continuous-time Q-learning, which we term as RRT-Q*. We formulate a model-free Q-based advantage function and we utilize integral reinforcement learning to develop tuning laws for the online approximation of the optimal cost and the optimal policy of continuous-time linear systems. Moreover, we provide rigorous Lyapunov-based proofs for the stability of the equilibrium point, which results in asymptotic convergence properties. Read More

Stat Methods Med Res 2019 Apr 4:962280219839427. Epub 2019 Apr 4.

4 Department of Preventive Medicine, Northwestern Feinberg School of Medicine, Chicago, IL, USA.

Tracking a subject's risk factors or health status over time is an important objective in long-term epidemiological studies with repeated measurements. An important issue of time-trend tracking is to define appropriate statistical indices to quantitatively measure the tracking abilities of the targeted risk factors or health status over time. We present a number of local and global statistical tracking indices based on the rank-tracking probabilities, which are derived from the conditional distribution functions, and propose a class of kernel-based nonparametric estimation methods. Read More

BMC Bioinformatics 2019 Apr 2;20(1):165. Epub 2019 Apr 2.

Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.

Background: Log-linear and multinomial modeling offer a flexible framework for genetic association analyses of offspring (child), parent-of-origin and maternal effects, based on genotype data from a variety of child-parent configurations. Although the calculation of statistical power or sample size is an important first step in the planning of any scientific study, there is currently a lack of software for genetic power calculations in family-based study designs. Here, we address this shortcoming through new implementations of power calculations in the R package Haplin, which is a flexible and robust software for genetic epidemiological analyses. Read More

J Colloid Interface Sci 2019 Mar 28;547:87-91. Epub 2019 Mar 28.

Key Laboratory of Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, 100084 Beijing, China.

Hypothesis: Although the static flotation of elongated cylinders is well understood, their flotation behavior under dynamic conditions after contacting a liquid surface, such as in situations experienced by water-walking insects, still need to be revealed.

Methodology: The motion of elongated horizontal cylinders after zero-velocity contact with a liquid surface is considered, and the motion equation of the cylinder is established and solved to obtain the dynamic flotation conditions.

Findings: The limiting density ratios for the dynamic flotation of elongated cylinders with different Bond numbers and contact angles are determined. Read More

Phys Rev E 2019 Feb;99(2-1):023112

Lawrence Livermore National Laboratory, Livermore, California 94551, USA.

We consider Rayleigh-Taylor and Richtmyer-Meshkov instabilities at the interface between two fluids, one or both of which may be viscous. We derive exact analytic expressions for the amplitude η(t) in the linear regime when only one of the fluids is viscous. The more general case is solved numerically using Laplace transforms. Read More

Phys Rev E 2019 Feb;99(2-1):022212

SUPA and Department of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland, EU.

Localized and pinned discrete breathers in Bose-Einstein condensates in optical lattices or in arrays of optical waveguides oscillate with frequencies which are much higher than those present in the spectrum of the background. Hence, the interaction between localized breathers and their surroundings is extremely weak leading to a multiple-time-scale perturbation expansion. We identify the leading order in the asymptotic expansion of the breather amplitude which does not average to zero after one full oscillation. Read More

Phys Rev E 2019 Feb;99(2-1):022803

Physics Department, TU Dortmund University, 44221 Dortmund, Germany.

We study the axisymmetric response of a complete spherical shell under homogeneous compressive pressure p to an additional point force. For a pressure p below the classical critical buckling pressure p_{c}, indentation by a point force does not lead to spontaneous buckling but an energy barrier has to be overcome. The states at the maximum of the energy barrier represent a subcritical branch of unstable stationary points, which are the transition states to a snap-through buckled state. Read More

Phys Rev E 2019 Feb;99(2-1):022103

School of Chemistry, University of Hyderabad, Gachibowli 500046, Hyderabad, India.

In this study we used a nonequilibrium simulation method to investigate the temperature dependent divergence of thermal conductivity in a one-dimensional momentum conserving system with an asymmetric double well nearest-neighbor interaction potential. We show that across all temperatures thermal conductivity exhibits power-law divergence with the chain length and the value of the divergence exponent (α) depends on the temperature of the system. At low and high temperatures α reaches close to ∼0. Read More

Phys Rev E 2019 Feb;99(2-1):022113

Institute for Soft and Bio Matter Science, Changwon National University, Changwon 51140, Korea.

We investigate, via spin-flip kinetic Monte Carlo simulations, the entire growth kinetic process of the two-dimensional kinetic Ising model cooled to zero temperature with finite cooling rates. A new slow dynamics, suppressed, and unseen in the instantaneous quench emerges and eventually crosses over to the asymptotic standard coarsening behavior. We present a numerical observation of the excess defect number density that provides direct information on the generated defects due to the critical slowing down. Read More

J Phys Chem B 2019 Apr 15. Epub 2019 Apr 15.

Department of Chemistry , University of Wisconsin , 1101 University Avenue , Madison , Wisconsin 53706 , United States.

The properties of room-temperature ionic liquids (ILs) may be viewed as resulting from a balance of electrostatic interactions that can be tuned at short range but constrained to satisfy universal, asymptotic screening conditions. Short-range interactions and ion packing provide ample opportunity for chemical tunability, while asymptotic sum rules dictate that the long-range structure and charge oscillation be similar to those of molten alkali halide salts. In this work, we study the structure factors and long-range electrostatic interactions in six ILs. Read More

IEEE Trans Pattern Anal Mach Intell 2019 Mar 26. Epub 2019 Mar 26.

We consider estimation and inference of precision matrices in sparse tensor graphical models. To facilitate study, data is assumed to follow a tensor normal distribution whose covariance has a Kronecker product structure. A critical challenge in both estimation and inference of this model is that its penalized maximum likelihood estimation involves minimizing a non-convex objective function. Read More