Anisotropic transport of microalgae Chlorella vulgaris in microfluidic channel

In this work, we study the regional dependence of transport behavior of microalgae Chlorella vulgaris inside microfluidic channel on applied fluid flow rate. The microalgae are treated as spherical naturally buoyant particles. Deviation from the normal diffusion or Brownian transport is characterized based on the scaling behavior of the mean square displacement(MSD) of the particle trajectories by resolving the displacements in the streamwise(flow) and perpendicular directions.The channel is divided into three different flow regions, namely center region of the channel and two near-wall boundaries and the particle motions are analyzed at different flow rates. We use the scaled Brownian motion to model the transitional characteristics in the scaling behavior of the MSDs. We find that there exist anisotropic anomalous transports in all the three flow regions with mixed sub-diffusive, normal and super-diffusive behavior in both longitudinal and transverse directions.     

Modified signed-digit trinary addition using synthetic wavelet filter

The modified signed-digit (MSD) number system has been a topic of interest as it allows for parallel carry-free addition of two numbers for digital optical computing. In this paper, harmonic wavelet joint transform (HWJT)-based correlation technique is introduced for optical implementation of MSD trinary adder implementation. The realization of the carry-propagation-free addition of MSD trinary numerals is demonstrated using synthetic HWJT correlator model. It is also shown that the proposed synthetic wavelet filter-based correlator shows high performance in logic processing. Simulation results are presented to validate the performance of the proposed technique.     

分子动力学模拟压水反应堆中氢气对水的影响

通过分子动力学方法模拟了在常温常压下(1 atm, 298 K)和在压水堆环境下(155 atm, 626 K), 水分子数为256, 氢分子数为0, 25, 50, 75和100等不同数目时, 粒子系统的动力学性质和微观结构, 分析了不同氢气对水中溶解氧的影响. 从模拟结果可知, 在常温常压和压水堆环境下, 当氢粒子数分别为0, 25, 50, 75和100时, 粒子系统的均方位移会随氢分子数增加而增加, 并且常温常压下的增长幅度远小于压水堆环境下的增长幅度, 如压水堆环境下氢分子数为75时系统的均方位移约是常温常压下氢分子数为75时系统的均方位移的6.02倍, 比压水堆环境下氢分子数0时系统的均方位移增加了131.88%. 此外, 粒子系统的微观结构, 从径向分布函数看, 在常温常压下随着氢分子数目的增加而小幅度增加, 这与常温常压下因氢气溶解在水中增大了氧离子周围的粒子密度相符合. 而在压水堆环境下, 氢分子数为75, 50, 25与为0时的水比较, 其径向分布均不会有太大的变化, 而分子数为100时会出现明显增加, 与为0时的水比较其径向分布增加了22.00%. 模拟结果表明, 往压水堆中的水加入氢气能明显地抑制水中的溶解氧.     

分子动力学模拟压水反应堆中联氨对水的影响

本文采用分子动力学方法模拟在常温常压下(1 atm,298 K)和在压水堆环境下(155 atm,626 K),水分子数为256,联氨(N₂H₄)分子数为0,25,50,75等不同数目时,水和联氨粒子系统的动力性质和微观结构.同时探讨了联氨分子的引入对水中溶解氧的影响.从模拟结果可知,在常温常压下,当联氨的分子数为0,25,50,75时,粒子系统的均方位移会随联氨分子数的增加而增加;联氨分子数为0与为25,50,75比较时会少一个数量级;压水堆环境下,联氨分子数 关键词： 分子动力学 压水堆 联氨     

Dynamics and spatial organization of endosomes in mammalian cells

We combine particle tracking and stochastic simulations to analyze the dynamics and organization of early endocytic vesicles in mammalian cells. At short time scales (<10(1) sec) vesicles exhibit 1D symmetric bidirectional motor-driven transport on microtubules such that the mean squared displacement (MSD) scales as t3/2, but the MSD shows a crossover to facilitated diffusion at longer times (>10(1) sec). Facilitated diffusion results in rapid equilibration of vesicles on microtubules. The asterlike organization of microtubules causes perinuclear accumulation of vesicles despite symmetric transport.     

A multilayer scintillation detector of high-energy particles for satellite experiments

We describe the detecting system of a high-energy charged particle telescope spectrometer for a space experiment to be performed on the outer surface of the Russian section of the International Space Station and other spacecraft, including small satellites. The spectrometer’s detecting system is a multilayer scintillation detector (MSD) of polystyrene plates scanned by photomultipliers. It allows high-intensity fluxes of electrons (up to ～10⁵ cm^?2 s^?1) several milliseconds long with energies of 3 to 30 MeV to be measured with an accuracy of ～1 μs, along with time profiles and the evolution of particle energy spectra. The MSD is characterized by an energy resolution no worse than 10%, an angular resolution of ～10 degrees, a geometric factor of ～40 cm² sr, and a trigger system time resolution of ～20 ns.     

Quasi-elastic neutron scattering study of dynamics in condensed matter

Quasi-elastic neutron scattering (QENS) technique, known to study stochastic motions has been successfully used to elucidate the molecular motions and physical properties related to them, in a variety of systems. QENS is a unique technique that provides information on the time-scale of the motion as well as the geometry of the motions. In this paper, results of some of the systems studied using the facility available at Dhruva, Trombay and other mega-facilities are discussed. Emphasis is given on the results obtained from three different systems studied using QENS, namely, (1) alkyl chain motions in monolayer protected metal clusters, (2) molecular motions of propane in Na-Y zeolitic systems and (3) the study of reorientational motions of liquid crystal innO.m series in different mesophases.     

Geodesic Motions in 2 + 1-Dimensional Charged Black Holes

We study the geodesic motions of a test particle around 2 + 1-dimensional charged black holes. We obtain a class of exact geodesic motions for the massless test particle when the ratio of its energy and angular momentum is given by the square root of the cosmological constant. The other geodesic motions for both massless and massive test particles are analyzed using the numerical method.     

Dielectrophoretic motions of a single particle in the vicinity of a planar wall under a direct-current electric field

We have numerically investigated two-dimensional dielectrophoretic motions of one particle induced due to interactions with a nearby planar wall under uniform electric field. Results show that the motions depend strongly on the gap between the particle and wall and their conductivity combination while the motion direction is determined uniquely by the wall conductivity. The particle is repelled to move farther away from the wall less conductive than the fluid, and vice versa. The motions become strengthened as either conductivity of the particle or wall deviates further from that of the fluid. Finally, the mechanism for the wall-induced DEP motions is examined.     

Parallel Modified Signed-Digit Computing for Large-Scale Two Dimensional Data Array

We propose a novel parallel algorithm of modified signed-digit (MSD) computing, in which MSD digits are encoded to three bit plane (BP) patterns. The addition of two MSD data arrays is performed with two steps: calculating nine intermediate patterns from encoded BP patterns and calculating three BP patterns with the nine intermediate patterns. A system module constucted with nine beam splitter cubes is developed for optical demonstration. Preliminary experimental results are given.     

Optoelectronic symbolic substitution based canonical modified signed-digit arithmetic

A single-step optoelectronics symbolic substitution scheme to handle parallel modified signed-digit (MSD) arithmetic operations is proposed. Conversion algorithms from MSD numbers into a canonical MSD representation are provided. The canonical MSD numbers have the property that no two consecutive digits are non-zero. The addition operation of two CMSD numbers is performed in one step. It will be shown that through the use of CMSD representation, the number of symbolic substitution rules in an optical content-addressable memory (CAM) based system is significantly reduced. The number of symbolic substitution rules can be further reduced to an optimum value through a proposed shared content-addressable memory optical set-up. Further, the proposed optical scheme doubles the storage efficiency of the shared content-addressable memory.     

On mean square displacement behaviors of anomalous diffusions with variable and random orders

Mean square displacement (MSD) is used to characterize anomalous diffusion. Recently, models of anomalous diffusion with variable-order and random-order were proposed, but no MSD analysis has been given so far. The purpose of this Letter is to offer a concise derivation of MSD functions for the variable-order model and the random-order model. Numerical results are presented to illustrate the analytical results. In addition, we show how to establish a variable-random-order model for a given MSD function which has clear application potentials.     

室内可吸入颗粒物运动特性的格子 Boltzmann方法模拟

为探究室内可吸入颗粒物的运动特性,使用格子Boltzmann方法,在颗粒物运动概率模型的基础上考虑布朗力对颗粒物的作用,利用改良的LB-CA（Lattice Boltzmann-cellular automata）模型,模拟了Re数分别为400、1 000和2 000时粒径为0.01 μm、0.1 μm和1 μm的颗粒物在上送上回和上送侧回两种回风形式中的运动特性.结果显示：颗粒物的空间分布范围随着Re数的增大而增大,小粒径的颗粒物受到气流湍动和扩散作用的影响更明显;颗粒物的均方位移（mean square displacement,MSD）与Re数、颗粒物粒径的大小成反比,而同样的Re数下,颗粒物在上送侧回的回风形式中其MSD较大.总体上看上送侧回的回风形式具有较低的悬浮颗粒数和更高的室内空气品质.     

How well do we know atomic motions of simple liquids?

Microscopic motions in molten potassium spanning three frequency decades are studied by neutron-scattering techniques. These comprise well-defined density oscillations and stochastic particle rearrangements and both are modeled on microscopic grounds. While vibratory motions are shown to share characteristics with those of their parent crystals, dynamic correlations between a diffusing particle and its neighbors can be accounted for only semiquantitatively.     

A Charged Erez-Rosen Spacetime and Gravitational Repulsion

An Erez–Rosen spacetime having a highly-charged source (e> m) is presented. Motions of a neutral particle along the symmetry axis and in the median plane are shown to exhibit repulsion near the source. The absence of frame-dragging effects in this static spacetime permits radial motions and allows for a comparison of motions along these special geodesics.     

Lévy Walk with Multiple Internal States

Lévy walk with multiple internal states can effectively model the motion of particles that don’t immediately move back to the directions or areas which they come from. When the Lévy walk behaves superdiffusion, it is discovered that the non-immediately-repeating property, characterized by the constructed transition matrix, has no influence on the particle’s mean square displacement (MSD) or Pearson coefficient. This is a kind of stable property of Lévy walk. However, if the Lévy walk shows the dynamical behaviors of normal diffusion, then the effect of non-immediately-repeating emerges. For the Lévy walk with some particular transition matrices, it may display nonsymmetric dynamics; in these cases, the behaviors of their variances are detailedly discussed, especially some comparisons with the ones of the continuous time random walks are made (a striking difference is the changes of the exponents of the variances). The first passage time distribution and its average of Lévy walks are simulated, the results of which turn out that the first passage time can distinguish Lévy walks with different transition matrices, while the MSD can not.

     

System Plus Reservoir Approach to Quantum Brownian Motion of a Rod-Like Particle

Quantum Brownian motion of a rod-like particle is investigated in the frame work of system plus reservoir model. The quantum mechanical and classical limit for both translational and rotational motions are discussed. Correlation functions, fluctuation-dissipation relations and mean squared values of translational and rotational motions are obtained.     

Ultra-fast all-optical polarization-encoded modified signed-digit addition using terahertz-optical-asymmetric-demultiplexer (TOAD) switches

In this paper, enhanced designs for ultra-fast all-optical circuits based on the terahertz-optical-asymmetric-demultiplexer (TOAD) adders are proposed. The high speed is achieved due to the use of the nonlinear optical materials and the nonbinary modified signed-digit (MSD) number representation. The proposed all-optical circuits use polarized light to present the trinary digits of the MSD numbers. It will be shown that the polarization-encoded MSD adder uses much less TOADs switches (37.5% less) and it is faster by 33.33% compared to the intensity-encoded ones.     

Bifurcation in a complex-valued wave-field model

The travelling-wave solutions of a model Lagrangian density for a complex-valued scalar field (with possible applications related to charge density waves, magnetic domain walls and particle physics) are explored by means of the slow-fluctuation technique. There are three main wave types, with the amplitudes modulated periodically and the complex amplitude vector either librating or precessing. They are separated by two bifurcations, one with respect to a system parameter, the other due to initial conditions. In addition, there are several classes of degenerate waves, including some with purely harmonic, stable, straight-line or circular motions of the amplitude vector. Beyond the range of the slow-fluctuation approximation there are several soliton solutions which all lack stability.     

A Study of Resuspended Particles from a Line Bed at the Wall of a Fluid Flow. Statistical Aspects

A statistical analysis of the dynamic behaviour of a bed of particles on the wall of a fluid flow is presented. By applying the different forces acting on each particle, i.e. fluid forces, adhesion to the wall and autohesion forces, conditions needed to obtain possible motions are determined and motions of the last downstream particle are described. It is shown that, above a critical value, increasing flow rate will promote the re-entrainment process along the wall, whereas increasing adhesion and autohesion forces will maintain the line bed stationary. Moreover, in some circumstances, starting particles execute some small jumps before rolling and/or sliding along the wall, which reduces the residence time of the particle on the wall. These results confirms some published hypotheses.