Hopping motion of lattice gases through nonsymmetric potentials under strong bias conditions

The hopping motion of lattice gases through potentials without mirror-reflection symmetry is investigated under various bias conditions. The model of 2 particles on a ring with 4 sites is solved explicitly; the resulting current in a sawtooth potential is discussed. The current of lattice gases in extended systems consisting of periodic repetitions of segments with sawtooth potentials is studied for different concentrations and values of the bias. Rectification effects are observed, similar to the single-particle case. A mean-field approximation for the current in the case of strong bias acting against the highest barriers in the system is made and compared with numerical simulations. The particle-vacancy symmetry of the model is discussed.Comment: 8 pages (incl. 6 eps figures); RevTeX 3.

General technique of calculating drift velocity and diffusion coefficient in arbitrary periodic systems

We develop a practical method of computing the stationary drift velocity V and the diffusion coefficient D of a particle (or a few particles) in a periodic system with arbitrary transition rates. We solve this problem both in a physically relevant continuous-time approach as well as for models with discrete-time kinetics, which are often used in computer simulations. We show that both approaches yield the same value of the drift, but the difference between the diffusion coefficients obtained in each of them equals V*V/2. Generalization to spaces of arbitrary dimension and several applications of the method are also presented.Comment: 12 pages + 2 figures, RevTeX. Submitted to J. Phys. A: Math. Ge

Performance of Certified Seed Lots of Dawson Alfalfa

Breeder, foundation, and certified seed lots of Dawson alfalfa, Medicago sativa L., were tested to determine stability in performance during three generations of seed increase under certification. Two field experiments were conducted, a seeded forage yield test and a space-planted test. Greenhouse experiments included separate tests for resistance to pea aphids, spotted alfalfa aphids, and bacterial wilt. Results obtained on certified Dawson alfalfa seed classes in field and greenhouse experiments were in agreement with the original variety description

Absence of self-averaging in the complex admittance for transport through random media

A random walk model in a one dimensional disordered medium with an oscillatory input current is presented as a generic model of boundary perturbation methods to investigate properties of a transport process in a disordered medium. It is rigorously shown that an admittance which is equal to the Fourier-Laplace transform of the first-passage time distribution is non-self-averaging when the disorder is strong. The low frequency behavior of the disorder-averaged admittance, $-1 \sim \omega^{\mu}$ where $\mu < 1$, does not coincide with the low frequency behavior of the admittance for any sample, $\chi - 1 \sim \omega$. It implies that the Cole-Cole plot of $$ appears at a different position from the Cole-Cole plots of $\chi$ of any sample. These results are confirmed by Monte-Carlo simulations.Comment: 7 pages, 2 figures, published in Phys. Rev.

Lattice gas model in random medium and open boundaries: hydrodynamic and relaxation to the steady state

We consider a lattice gas interacting by the exclusion rule in the presence of a random field given by i.i.d. bounded random variables in a bounded domain in contact with particles reservoir at different densities. We show, in dimensions $d \ge 3$, that the rescaled empirical density field almost surely, with respect to the random field, converges to the unique weak solution of a non linear parabolic equation having the diffusion matrix determined by the statistical properties of the external random field and boundary conditions determined by the density of the reservoir. Further we show that the rescaled empirical density field, in the stationary regime, almost surely with respect to the random field, converges to the solution of the associated stationary transport equation

Microscopic Model of Charge Carrier Transfer in Complex Media

We present a microscopic model of a charge carrier transfer under an action of a constant electric field in a complex medium. Generalizing previous theoretical approaches, we model the dynamical environment hindering the carrier motion by dynamic percolation, i.e., as a medium comprising particles which move randomly on a simple cubic lattice, constrained by hard-core exclusion, and may spontaneously annihilate and re-appear at some prescribed rates. We determine analytically the density profiles of the "environment" particles, as seen from the stationary moving charge carrier, and calculate its terminal velocity as the function of the applied field and other system parameters. We realize that for sufficiently small external fields the force exerted on the carrier by the "environment" particles shows a viscous-like behavior and define an analog of the Stokes formula for such dynamic percolative environments. The corresponding friction coefficient is also derived.Comment: appearing in Chem. Phys. Special Issue on Molecular Charge Transfer in Condensed Media - from Physics and Chemistry to Biology and Nano-Engineering, edited by A.Kornyshev (Imperial College London), M.Newton (Brookhaven Natl Lab) and J.Ulstrup (Technical University of Denmark

Alfalfa Insect Management Studies 1971-77

Three tests in southwestern Nebraska during 1971 and 1972 evaluated insecticides against the army cutworm. Adult alfalfa weevils did not damage new second growth alfalfa in a small plot study during a 3-year period (1973-1975) at Gothenburg, NE. However, excellent control of larval alfalfa weevils was obtained. These results indicated a need to establish economic threshold levels for the alfalfa weevil in Nebraska to prevent unnecessary use of insecticides. Four tests to control the alfalfa weevil with registered insecticides verified the efficacy of these materials under Nebraska conditions. A series of tests conducted during 1975 at the Mead Field Laboratory were designed to evaluate plant resistance, cultural practices and insecticides. The use of alfalfa varieties with resistance to various insect pests of alfalfa appeared to be an ideal control method. During 1975-1977, a test was conducted each year at the Mead Field Laboratory to evaluate new experimental insecticides against the alfalfa weevil and other pest insects of alfalfa grown for forage. A number of the new insecticides showed promise against the alfalfa weevil and the pea aphid

A Local Superlens

Superlenses enable near-field imaging beyond the optical diffraction limit. However, their widespread implementation in optical imaging technology so far has been limited by large-scale fabrication, fixed lens position, and specific object materials. Here we demonstrate that a dielectric lamella of subwavelength size in all three spatial dimensions behaves as a compact superlens that operates at infrared wavelengths and can be positioned to image any local microscopic area of interest on the sample. In particular, the lamella superlens may be placed in contact with any type of object and therefore enables examination of hard-to-scan samples, for example, with high topography or in liquids, without altering the specimen design. This lamella-based local superlens design is directly applicable to subwavelength light-based technology, such as integrated optics

Alfalfa Insect Management Studies 1971-77

Three tests in southwestern Nebraska during 1971 and 1972 evaluated insecticides against the army cutworm. Adult alfalfa weevils did not damage new second growth alfalfa in a small plot study during a 3-year period (1973-1975) at Gothenburg, NE. However, excellent control of larval alfalfa weevils was obtained. These results indicated a need to establish economic threshold levels for the alfalfa weevil in Nebraska to prevent unnecessary use of insecticides. Four tests to control the alfalfa weevil with registered insecticides verified the efficacy of these materials under Nebraska conditions. A series of tests conducted during 1975 at the Mead Field Laboratory were designed to evaluate plant resistance, cultural practices and insecticides. The use of alfalfa varieties with resistance to various insect pests of alfalfa appeared to be an ideal control method. During 1975-1977, a test was conducted each year at the Mead Field Laboratory to evaluate new experimental insecticides against the alfalfa weevil and other pest insects of alfalfa grown for forage. A number of the new insecticides showed promise against the alfalfa weevil and the pea aphid

Critical dimensions for random walks on random-walk chains

The probability distribution of random walks on linear structures generated by random walks in $d$-dimensional space, $P_d(r,t)$, is analytically studied for the case $\xi\equiv r/t^{1/4}\ll1$. It is shown to obey the scaling form $P_d(r,t)=\rho(r) t^{-1/2} \xi^{-2} f_d(\xi)$, where $\rho(r)\sim r^{2-d}$ is the density of the chain. Expanding $f_d(\xi)$ in powers of $\xi$, we find that there exists an infinite hierarchy of critical dimensions, $d_c=2,6,10,\ldots$, each one characterized by a logarithmic correction in $f_d(\xi)$. Namely, for $d=2$, $f_2(\xi)\simeq a_2\xi^2\ln\xi+b_2\xi^2$; for $3\le d\le 5$, $f_d(\xi)\simeq a_d\xi^2+b_d\xi^d$; for $d=6$, $f_6(\xi)\simeq a_6\xi^2+b_6\xi^6\ln\xi$; for $7\le d\le 9$, $f_d(\xi)\simeq a_d\xi^2+b_d\xi^6+c_d\xi^d$; for $d=10$, $f_{10}(\xi)\simeq a_{10}\xi^2+b_{10}\xi^6+c_{10}\xi^{10}\ln\xi$, {\it etc.\/} In particular, for $d=2$, this implies that the temporal dependence of the probability density of being close to the origin $Q_2(r,t)\equiv P_2(r,t)/\rho(r)\simeq t^{-1/2}\ln t$.Comment: LATeX, 10 pages, no figures submitted for publication in PR