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A feasibility analysis of bacterial chemotaxis under the influence of external noise  [cached]
Pratap R Patnaik
Journal of Biochemical Technology , 2009,
Abstract: Bacteria moving in response to chemical attractants are subject tonoise from the environment in addition to that within the cells.Environmental noise is observed typically through fluctuations inthe concentrations of the chemoattractant. Interactions between twoor more sources of noise may upset the chemotactic motility of thecells. This possibility is investigated here for Escherichia colithrough a pair of conditions derived earlier. These conditions relatethe tumbling time, the sensing time and the adaptation time of thecells. It is observed that chemotaxis is not feasible if the normalized variance of the external noise exceeds a critical value. This critical value does not depend on the expression of CheR, a key protein in the chemosensory system, and it agrees with similar values reported by others for intra-cellular noise. These observations indicate that stochastic resonance may be a prime factor enhancing chemotaxis in the presence of noise.
Black Holes under External Influence  [PDF]
Jiri Bicak
Physics , 2001, DOI: 10.1007/s12043-000-0161-7
Abstract: The work on black holes immersed in external fields is reviewed in both test-field approximation and within exact solutions. In particular we pay attention to the effect of the expulsion of the flux of external fields across charged and rotating black holes which are approaching extremal states. Recently this effect has been shown to occur for black hole solutions in string theory. We also discuss black holes surrounded by rings and disks and rotating black holes accelerated by strings.
Cellular Automata under the influence of noise  [PDF]
Luís Correia,Thomas Wehrle
Physics , 2006,
Abstract: Noise in the local transition function is compared to fluctuations in the updating times of the cells. Obtained results are shown to be quite different in both cases. In this extended abstract we briefly explain the problem and present results obtained and comment them.
Steady state work fluctuations of a dragged particle under external and thermal noise  [PDF]
A. Baule,E. G. D. Cohen
Physics , 2009,
Abstract: We consider a particle, confined to a moving harmonic potential, under the influence of friction and external asymmetric Poissonian shot noise (PSN). We study the fluctuations of the work done to maintain this system in a nonequilibrium steady state. PSN generalizes the usual Gaussian noise and can be considered to be a paradigm of external noise, where fluctuation and dissipation originate from physically independent mechanisms. We consider two scenarios: (i) the noise is given purely by PSN and (ii) in addition to PSN the particle is subject to white Gaussian noise. In both cases we derive exact expressions for the large deviation form of the work distribution, which are characterized by the time scales of the system. We show that the usual steady state fluctuation theorem is violated in our model and that in a certain parameter regime large negative work fluctuations are more likely to occur than the corresponding positive ones, though the average work is always positive.
Macro-Behaviour of Agents'' Opinion under Influence of an External Field
Macro-Behaviour of Agents' Opinion under Influence of an External Field

CHANG Yun-Feng,CAI Xu,
常云峰
,蔡勖

中国物理快报 , 2007,
Abstract: We propose a model to study the evolution of opinion under the influence of all external field on small world network. The maero-behaviour of agents' opinion and the relative change rate as time elapses are studied. The external field is found to play an important role in making the opinion s(t) balance or increase, and without the influence of the external field, the relative change rate γ(t) shows nonlinear increasing behaviour as time runs. What is more, this nonlinear increasing behaviour is independent of the initial condition, the strength of the external field and the time that we cancel the external field. The results may reflect some phenomena in our society, such as the function of the macro-control in China or the mass media in our society.
The macro-behavior of agents' opinion under the influence of an external field  [PDF]
YunFeng Chang,Long Guo,Xu Cai
Physics , 2006, DOI: 10.1088/0256-307X/24/8/075
Abstract: In this paper, a model about the evolution of opinion on small world networks is proposed. We studied the macro-behavior of the agents' opinion and the relative change rate as time elapses. The external field was found to play an important role in making the opinion $s(t)$ balance or increase, and without the influence of the external field, the relative change rate $\gamma(t)$ shows a nonlinear increasing behavior as time runs. What's more, this nonlinear increasing behavior is independent of the initial condition, the strength of the external field and the time that we cancel the external field. Maybe the results can reflect some phenomenon in our society, such as the function of the macro-control in China or the Mass Media in our society.
Models of population dynamics under the influence of external perturbations: mathematical results  [PDF]
Micka?l D. Chekroun,Lionel Roques
Mathematics , 2010,
Abstract: In this Note, we describe the stationary equilibria and the asymptotic behaviour of an heterogeneous logistic reaction-diffusion equation under the influence of autonomous or time-periodic forcing terms. We show that the study of the asymptotic behaviour in the time-periodic forcing case can be reduced to the autonomous one, the last one being described in function of the "size" of the external perturbation. Our results can be interpreted in terms of maximal sustainable yields from populations. We briefly discuss this last aspect through a numerical computation.
Decoherence and localization in tunneling process under influence of one external degree of freedom  [PDF]
Quanlin Jie,Bambi Hu,Guangjong Dong
Physics , 2006,
Abstract: We investigate numerically the tunneling effect under influence of another particle in a double well system. Such influence from only one degree of freedom makes decoherence and quantum-classical transition, i.e., suppression of the tunneling effect. The decoherence happens even for cases that the influence is from a particle of very small mass, and it has virtually no effect in the corresponding classical dynamics. There are cases similar to dynamical localization that the suppressed tunneling rate is several times smaller than the classical counterpart. This result is relevant for understanding quantitatively the dynamical process of decoherence and quantum to classical transition.
Inclusions in elasto-plastic solids under the influence of internal and external pressures  [cached]
Tapan Kumar Das,P. R. Sengupta,Lokenath Debnath
International Journal of Mathematics and Mathematical Sciences , 1995, DOI: 10.1155/s0161171295000743
Abstract: An attempt is made to study the problems of spherical and circular inclusions in elasto-plastic solids under the action of internal increasing pressure and external constant pressure, taking into consideration of the work-hardening effect. Particular attention is given to the linear work hardening effect on both problems. It is shown that results of this analysis are in good agreement with those of ideal plastic solids.
Entanglement dynamics of two qubits under the influence of external kicks and Gaussian pulses  [PDF]
Ferdi Altintas,Resul Eryigit
Mathematics , 2010, DOI: 10.1088/1751-8113/44/40/405302
Abstract: We have investigated the dynamics of entanglement between two spin-1/2 qubits that are subject to independent kick and Gaussian pulse type external magnetic fields analytically as well as numerically. Dyson time ordering effect on the dynamics is found to be important for the sequence of kicks. We show that "almost-steady" high entanglement can be created between two initially unentangled qubits by using carefully designed kick or pulse sequences.
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