Unifying model of driven polymer translocation

We present a Brownian dynamics model of driven polymer translocation, in which non-equilibrium memory effects arising from tension propagation (TP) along the cis side subchain are incorporated as a time-dependent friction. To solve the effective friction, we develop a finite chain length TP formalism, expanding on the work of Sakaue [Sakaue, PRE 76, 021803 (2007)]. The model, solved numerically, yields results in excellent agreement with molecular dynamics simulations in a wide range of parameters. Our results show that non-equilibrium TP along the cis side subchain dominates the dynamics of driven translocation. In addition, the model explains the different scaling of translocation time w.r.t chain length observed both in experiments and simulations as a combined effect of finite chain length and pore-polymer interactions.Comment: 7 pages, 3 figure

Analysis of Oil Production Behavior for the Fractured Basement Reservoir Using Hybrid Discrete Fractured Network Approach

Unlike naturally fractured reservoir, fractured basement reservoir (FBR) has almost non-permeable matrix and flow is strongly dependent upon fracture network. This might cause the rapid changing behavior on oil production whether fracture near wellbore is saturated with either oil or water. In this aspect, realistic representation of fracture network is essential in FBR. Therefore the simulation of FBR is generally applied by dual-porosity (DP) continuum approach because discrete fractured network (DFN) simulator with multiphase flow is not commercially available except in-house model. In this paper, hybrid DFN approach is applied, which is continuum model coupled with local grid refinement (LGR). LGR is adapted at the cells which are passing through fractures, in order to represent fracture width less than 0.1 ft. Up to now, LGR is mostly used for well block rather than the fracture. In this approach, well control volume can not be described by LGR cell, thus, four-leg horizontal well concept substitutes the vertical well with the use of equivalent wellbore radius for overcoming the numerical convergence problem. The application of hybrid DFN approach for FBR is discussed about investigation of the possibility for drastic change on oil production. Based on the results, in fractured reservoir using hybrid DFN approach, oil production is not found to be proportional to the magnitude of matrix permeability, not as in porous system with dual-porosity approach. Also, we realized that oil production is once dropped it can not be recovered back to previous level in FBR. This is because oil-saturated fracture near well is once changed to water-saturated, then, there was not anymore changes occurred within the same fracture.Key words: Dual-porosity; Hybrid DFN; Fractured basement reservoir; Local grid refinemen

UBVI Surface Photometry of the Spiral Galaxy NGC 300 in the Sculptor Group

We present UBVI surface photometry for 20.'5 X 20.'5 area of a late-type spiral galaxy NGC 300. In order to understand the morphological properties and luminosity distribution characteristics of NGC 300, we have derived isophotal maps, surface brightness profiles, ellipticity profiles, position angle profiles, and color profiles. By merging the I-band data of our surface brightness measurements with those of Boeker et al. (2002) based on Hubble Space Telescope observations, we have made combined I-band surface brightness profiles for the region of 0."02 < r < 500" and decomposed the profiles into three components: a nucleus, a bulge, and an exponential disk.Comment: 16 pages(cjaa209.sty), Accepted by the Chinese J. Astron. Astrophys., Fig 2 and 8 are degraded to reduce spac

Influence of non-universal effects on dynamical scaling in driven polymer translocation

We study the dynamics of driven polymer translocation using both molecular dynamics (MD) simulations and a theoretical model based on the non-equilibrium tension propagation on the cis side subchain. We present theoretical and numerical evidence that the non-universal behavior observed in experiments and simulations are due to finite chain length effects that persist well beyond the relevant experimental and simulation regimes. In particular, we consider the influence of the pore-polymer interactions and show that they give a major contribution to the non-universal effects. In addition, we present comparisons between the theory and MD simulations for several quantities, showing extremely good agreement in the relevant parameter regimes. Finally, we discuss the potential limitations of the present theories.Peer reviewe

Exact solutions of charged wormhole

In this paper, the backreaction to the traversable Lorentzian wormhole spacetime by the scalar field or electric charge is considered to find the exact solutions. The charges play the role of the additional matter to the static wormhole which is already constructed by the exotic matter. The stability conditions for the wormhole with scalar field and electric charge are found from the positiveness and flareness for the wormhole shape function.Comment: 9 pages, Revtex, no figures, to appear in Phys. Rev. D(2001

The Localization Transition of the Two-Dimensional Lorentz Model

We investigate the dynamics of a single tracer particle performing Brownian motion in a two-dimensional course of randomly distributed hard obstacles. At a certain critical obstacle density, the motion of the tracer becomes anomalous over many decades in time, which is rationalized in terms of an underlying percolation transition of the void space. In the vicinity of this critical density the dynamics follows the anomalous one up to a crossover time scale where the motion becomes either diffusive or localized. We analyze the scaling behavior of the time-dependent diffusion coefficient D(t) including corrections to scaling. Away from the critical density, D(t) exhibits universal hydrodynamic long-time tails both in the diffusive as well as in the localized phase.Comment: 13 pages, 7 figures

Coarse-graining the dynamics of coupled oscillators

We present an equation-free computational approach to the study of the coarse-grained dynamics of {\it finite} assemblies of {\it non-identical} coupled oscillators at and near full synchronization. We use coarse-grained observables which account for the (rapidly developing) correlations between phase angles and oscillator natural frequencies. Exploiting short bursts of appropriately initialized detailed simulations, we circumvent the derivation of closures for the long-term dynamics of the assembly statistics.Comment: accepted for publication in Phys. Rev. Let

Approximate String Matching Using a Bidirectional Index

International audienceWe study strategies of approximate pattern matching that exploit bidirectional text indexes, extending and generalizing ideas of [5]. We introduce a formalism, called search schemes, to specify search strate-gies of this type, then develop a probabilistic measure for the efficiency of a search scheme, prove several combinatorial results on efficient search schemes, and finally, provide experimental computations supporting the superiority of our strategies

Anomalous microwave conductivity coherence peak in c-axis MgB2 thin film

The temperature dependence of the real part of the microwave complex conductivity at 17.9 GHz obtained from surface impedance measurements of two c-axis oriented MgB2 thin films reveals a pronounced maximum at a temperature around 0.6 times the critical temperature. Calculations in the frame of a two-band model based on Bardeen-Cooper-Schrieffer (BCS) theory suggest that this maximum corresponds to an anomalous coherence peak resembling the two-gap nature of MgB2. Our model assumes there is no interband impurity scattering and a weak interband pairing interaction, as suggested by bandstructure calculations. In addition, the observation of a coherence peak indicates that the pi-band is in the dirty limit and dominates the total conductivity of our filmsComment: 10 pages, 4 figures, to be published in Phys. Rev. Let