Dynamics of Filament Formation in Laser Produced Collisional Magnetoplasma

The paper presents an investigation of growth dynamics of spike in a collisional magneto plasma in the presence of externally applied magnetic field. We have set up and solved the non‐linear differential equations for growth and width of the laser spikes. We have considered the mechanism of nonuniform heating of carriers along the wavefront which is important in collisional plasmas. The effect of intensity of main beam and magnetic field on growth dynamics of spikes is studied (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Nonequilibrium Approach to Temperature Calibration for Tungsten Filament Atomic Spectrometry

A nonequilibrium approach to voltamperometric temperature measurement for tungsten filament atomizers was developed to facilitate the transfer of thermal conditions between instruments that possess different power supply regulation modes and filaments. Large differences in the equilibrium and instantaneous temperatures were found during the pyrolysis and atomization steps of cadmium atomic absorption spectroscopy (AAS) analysis. By using the instantaneous temperature, the pyrolysis and atomization behaviors of cadmium were shown to be equivalent regardless of the power supply regulation mode. The pyrolysis conditions optimized for a 15-V filament were readily and accurately transferred to a 12-V filament by applying the nonequilibrium voltamperometric temperature model.     

A Numerical Study of the Dynamics of Vector-Born Viral Plant Disorders Using a Hybrid Artificial Neural Network Approach

Most plant viral infections are vector-borne. There is a latent period of disease inside the vector after obtaining the virus from the infected plant. Thus, after interacting with an infected vector, the plant demonstrates an incubation time before becoming diseased. This paper analyzes a mathematical model for persistent vector-borne viral plant disease dynamics. The backpropagated neural network based on the Levenberg—Marquardt algorithm (NN-BLMA) is used to study approximate solutions for fluctuations in natural plant mortality and vector mortality rates. A state-of-the-art numerical technique is utilized to generate reference data for obtaining surrogate solutions for multiple cases through NN-BLMA. Curve fitting, regression analysis, error histograms, and convergence analysis are used to assess accuracy of the calculated solutions. It is evident from our simulations that NN-BLMA is accurate and reliable.     

Theoretical investigation of photoprocesses in complex organic compounds upon high-power laser excitation

A procedure of theoretical investigations into the dynamics of energy level populations of organic molecules upon high-power laser excitation is developed that allows information on stimulated emission of molecules, gain and lasing spectra, dynamics of lasing pulses, populations of the ground and excited states, and influence of the induced absorption on lasing of the organic molecules to be obtained. Laws of changing of the above-indicated processes are established for two pyran substitutes. Results of theoretical and experimental investigations are well correlated. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 51–60, March, 2009.     

A Boltzmann Equation Approach to the Dynamics of the Simple Piston

The evolution of a simple piston under a constant external force is investigated from a microscopic approach. Using Boltzmann's equation and simplifying assumptions it is shown that the system evolves towards equilibrium according to the macroscopic laws of thermodynamics: entropy production is positive and Onsager's relations are verified near equilibrium. Numerical simulations are presented which show that the evolution takes place in two stages: first a deterministic approach to the equilibrium position and then a stochastic motion around the equilibrium position. It also shows that the damping is not correctly described with these simplifying assumptions and a quantitative explanation of this effect remains an open problem.     

A Simple Approach to Analyzing Protein Side-Chain Dynamics fromC NMR Relaxation Data

A simple approach to deriving motional dynamics information of protein and peptide side chains by using¹³C NMR relaxation data is presented. By using linear approximation of internal rotational correlation functions, simple equations for relating side-chain conformation, bond rotational amplitudes, and rotational correlation coefficients with different NMR relaxation parameters have been obtained. Auto- and cross-correlation spectral densities are considered, and it is shown that proton-coupled¹³C NMR relaxation measurements allow detailed motional information to be obtained.     

A Non-Variational Approach to Nonlinear Stability in Stellar Dynamics Applied to the King Model

In previous work by Y. Guo and G. Rein, nonlinear stability of equilibria in stellar dynamics, i.e., of steady states of the Vlasov-Poisson system, was accessed by variational techniques. Here we propose a different, non-variational technique and use it to prove nonlinear stability of the King model against a class of spherically symmetric, dynamically accessible perturbations. This model is very important in astrophysics and was out of reach of the previous techniques.     

Protrusion of a Virtual Model Lamellipodium by Actin Polymerization: A Coarse-Grained Langevin Dynamics Model

We report the development of a coarse-grained Langevin dynamics model of a lamellipodium featuring growing F-actin filaments in order to study the effect of stiffness of the F-actin filament, the G-actin monomer concentration, and the number of polymerization sites on lamellipodium protrusion. The virtual lamellipodium is modeled as a low-aspect-ratio doubly capped cylinder formed by triangulated particles on its surface. It is assumed that F-actin filaments are firmly attached to a lamellipodium surface where polymerization sites are located, and actin polymerization takes place by connecting a G-actin particle to a polymerization site and to the first particle of a growing F-actin filament. It is found that there is an optimal number of polymerization sites for rapid lamellipodium protrusion. The maximum speed of lamellipodium protrusion is related to competition between the number of polymerization sites and the number of available G-actin particles, and the degree of pulling and holding of the lamellipodium surface by non-polymerizing actin filaments. The lamellipodium protrusion by actin polymerization displays saltatory motion exhibiting pseudo-thermal equilibrium: the lamellipodium speed distribution is Maxwellian in two dimensions but the lamellipodium motion is biased so that the lamellipodium speed in the direction of the lamellipodium motion is much larger than that normal to the lamellipodium motion.     

A Spatial Stochastic Model for Virus Dynamics

We introduce a spatial stochastic model for virus dynamics. We show that if the death rate of infected cells increases too fast with the virus load the virus dies out. This is in sharp contrast with what happens in the (non-spatial deterministic) basic model for virus dynamics. AMS 1991 Subject Classification: 60K35     

Quantum Trajectory Approach to Molecular Dynamics Simulation with Surface Hopping

In this work we propose a quantum trajectory approach to the powerful molecular dynamics simulation with surface hopping, from an insight that an effective “observation” is actually implied in the simulation through tracking the forces experienced, just like checking the meter's result in quantum measurement process. This treatment can build the nonadiabatic surface hopping on a physical foundation, instead of the usual fictitious and conceptually inconsistent hopping algorithms. The effects and advantages of the proposed scheme are preliminarily illustrated by a two-surface model system.     

Quantum Trajectory Approach to Molecular Dynamics Simulation with Surface Hopping

In this work we propose a quantum trajectory approach to the powerful molecular dynamics simulation with surface hopping,from an insight that an efectiveobservationis actually implied in the simulation through tracking the forces experienced,just like checking the meter’s result in quantum measurement process.This treatment can build the nonadiabatic surface hopping on a physical foundation,instead of the usual fictitious and conceptually inconsistent hopping algorithms.The efects and advantages of the proposed scheme are preliminarily illustrated by a two-surface model system.     

基于辐射的温度测量方程的构造研究

基于辐射的温度测量方程，以采用选择不同的波长，不同的温度和不同的谱色（滤色片子以技术实现）等方法进行构造，依据这些方法获得的测量数据彼此之间线性无关，从而可以将被测物体发射率函数的具体形式和温度予以确定。     

An Approach to Linear Scalable DH-PHEMT Model for Millimeterwave Application

This paper describes a scalable small-signal equivalent circuit for 0.25 m gatelength Double Heterojunction delta-doped PHEMTs. The scaling rules for all elements except the pad capacitances and bondwire inductances have been determined. Good agreement is obtained between simulation results and measured results for 2 times 20 m , 2 times 40 m, 2 times 60 m, 2 times 100 m gate width (number of gate fingers times unit gate width) DH PHEMT.     

Spot Size Technique: A Theoretical Approach To Optimize Dispersion Compensated

Using a spot size based optimization technique, a bend loss versus dispersion diagram has been obtained theoretically for the most widely used step-index disper sion compensated optical fibers (DCF). The Rayleigh scattering loss can be incorpo rated with bend loss to calculate figure of merit (FOM), thus giving an FOM versus dispersion curve on a single diagram. The plot of the FOM-dispersion curve on a single diagram is useful from the designer's point of view, as it provides a quick reference for choosing the best suitable DCF, which should have large negative dispersion as well as maximum possible value of FOM. The effect of fiber manufac turing losses such as absorption loss on the maximum value of FOM has also been estimated.     

A New Approach to the Design of Hybrid Lenses for Integrated Optics

The Fresnel lens is one of the most extensively studied components in both classical and integrated optics. This structure is free from axial spherical aberration, but is heavily affected by both off-axis and chromatic aberrations. The latter can be compensated by introducing a refractive component, whose chromatic behavior is the opposite of that of the diffractive lens. This hybrid refractive-diffractive structure, however, is not able to deal effectively with off-axis aberrations, namely, with coma. In this work, a novel methodology for the design of corrected hybrid lenses is proposed which allows for correction of both chromatism and coma. The design method is based on a ray-optics variational approach which provides a range of possible achromatic solutions. An optimization procedure is performed by means of a series of beam propagation method numerical calculations which make it possible to simulate the lens operation and thus to find the best solution.     

端到端网络流量的混合估计方法(英文)

利用主成分分析法获取端到端网络流量的主要特征分量并获得其初始估计结果.为克服其初值敏感性将估计结果作为遗传算法的初始值、链路流量估计偏差作为遗传算法的适应度函数,通过构建合适的交叉和变异概率函数来控制遗传算法的交叉和变异过程.采用合适的约束迭代函数,利用遗传算法通过迭代寻优获得端到端流量的估计结果,仿真结果表明所提出的方法是可行的.     

Modeling the Dynamics of T-Cell Development in the Thymus

The thymus hosts the development of a specific type of adaptive immune cells called T cells. T cells orchestrate the adaptive immune response through recognition of antigen by the highly variable T-cell receptor (TCR). T-cell development is a tightly coordinated process comprising lineage commitment, somatic recombination of Tcr gene loci and selection for functional, but non-self-reactive TCRs, all interspersed with massive proliferation and cell death. Thus, the thymus produces a pool of T cells throughout life capable of responding to virtually any exogenous attack while preserving the body through self-tolerance. The thymus has been of considerable interest to both immunologists and theoretical biologists due to its multi-scale quantitative properties, bridging molecular binding, population dynamics and polyclonal repertoire specificity. Here, we review experimental strategies aimed at revealing quantitative and dynamic properties of T-cell development and how they have been implemented in mathematical modeling strategies that were reported to help understand the flexible dynamics of the highly dividing and dying thymic cell populations. Furthermore, we summarize the current challenges to estimating in vivo cellular dynamics and to reaching a next-generation multi-scale picture of T-cell development.     

Geometric and Algebraic Approach to Classical Dynamics of a Particle with Spin

We investigate the Frenkel equation and alternative approaches aimed to describe classically the dynamics of a particle with a spin degree of freedom. For all those theories unphysical solutions are shown to exist but to be removable via formal use of geometric perturbation theory. With an Clifford algebraic representation of the employed geometric concepts we put forward the modified Frenkel equation as more intuitive as alternative approaches.     

An Alternative Approach to the Classical Dynamics of an Extended Charged Particle

In this paper the analysis of the classical dynamics of a charged particle is carried out without considering that the electromagnetic field necessarily goes to zero at infinity. A quite general non-linear equation of motion is obtained for an extended charged particle valid for any distribution of charge in the particle and for an electromagnetic field satisfying any boundary conditions. Some common approximations are analyzed with detail to determine how the usual difficulties arise.     

Multiple-Photon Dynamics in Molecules: A New Approach to High Resolution Spectroscopy of Highly Excited Vibrational States

Multi-photon transitions with two simultaneously interacting IR laser fields lead to final excited states with frequenciesnν = n₁ν₁+ n₂ν₂, withnthe total number of photons absorbed and (n,n₁,n₂) = (2, 1, 1), (3, 2, 1), (4, 1, 3), etc. The nature of the actual transition is determined by shift measurements, where the lasers are frequency-tuned by δν_iin opposite directions keeping the sum frequency,nν, resonant with the molecular transition. This technique opens a new spectral range for multi-photon transitions and a unique identification of the observed features. Forn₁andn₂both positive the excitation will lead to a “normal” up–up multi-photon transition. Many three- and four-photon transitions in the ν₃vibrational ladder of SF₆could be resolved with a resolution of 1 MHz, as well as four new two-photon transitions. As long asn₁+ n₂≥ 0, one of the twon_imay be negative resulting in an, e.g., up–down excitation pathway with its particular selection rules. The up–down excitations are demonstrated both for one- and two-photon transitions using the frequency shift technique. The different possible excitation schemes which meet the resonance condition for these transitions lead to interference effects and local couplings to highly excited states. Changes in resonance frequency for a one-photon transition (n= 1), due to these effects, are demonstrated. Evidently, the radiative coupling of participating levels to high-lying or quasi-continuum states may drastically change for different δν_ileading both to ac Stark shift and transition probability variations.