1,160 research outputs found
Theory of Second and Higher Order Stochastic Processes
This paper presents a general approach to linear stochastic processes driven
by various random noises. Mathematically, such processes are described by
linear stochastic differential equations of arbitrary order (the simplest
non-trivial example is , where is not a Gaussian white
noise). The stochastic process is discretized into time-steps, all possible
realizations are summed up and the continuum limit is taken. This procedure
often yields closed form formulas for the joint probability distributions.
Completely worked out examples include all Gaussian random forces and a large
class of Markovian (non-Gaussian) forces. This approach is also useful for
deriving Fokker-Planck equations for the probability distribution functions.
This is worked out for Gaussian noises and for the Markovian dichotomous noise.Comment: 35 pages, PlainTex, accepted for publication in Phys Rev. E
Conductance and localization in disordered wires: role of evanescent states
This paper extends an earlier analytical scattering matrix treatment of
conductance and localization in coupled two- and three Anderson chain systems
for weak disorder when evanescent states are present at the Fermi level. Such
states exist typically when the interchain coupling exceeds the width of
propagating energy bands associated with the various transverse eigenvalues of
the coupled tight-binding systems. We calculate reflection- and transmission
coefficients in cases where, besides propagating states, one or two evanescent
states are available at the Fermi level for elastic scattering of electrons by
the disordered systems. We observe important qualitative changes in these
coefficients and in the related localization lengths due to ineffectiveness of
the evanescent modes for transmission and reflection in the various scattering
channels. In particular, the localization lengths are generally significantly
larger than the values obtained when evanescent modes are absent. Effects
associated with disorder mediated coupling between propagating and evanescent
modes are shown to be suppressed by quantum interference effects, in lowest
order for weak disorder
Response of Soybean Insects to Foliar Applications of a Chitin Synthesis Inhibitor TH 6040
The activity of TH 6040, a chitin synthesis inhibitor, was determined against velvetbean caterpillar, Anticarsia gemmatalis Hübner, and other soybean defoliators in field tests in Georgia, South Carolina, and Brazil. Single applications at rates as low as 75 g AI/ha afforded adequate initial and excellent residual control of A. gemmatalis and some suppression of low populations of Plusia spp. Two applications at higher rates gave significant control of soybean looper, Pseudoplusia includens (Walker), and showed promise against green cloverworm, Plathypena scabra (F.), and Mexican bean beetle, Epilachna varivestis Mulsant. Populations of geocorids and nabids were lower in 1 test, possibly because of insecticidal activity, scarcity of prey, or both
Irreversible nucleation in molecular beam epitaxy: From theory to experiments
Recently, the nucleation rate on top of a terrace during the irreversible
growth of a crystal surface by MBE has been determined exactly. In this paper
we go beyond the standard model usually employed to study the nucleation
process, and we analyze the qualitative and quantitative consequences of two
important additional physical ingredients: the nonuniformity of the
Ehrlich-Schwoebel barrier at the step-edge, because of the existence of kinks,
and the steering effects, due to the interaction between the atoms of the flux
and the substrate. We apply our results to typical experiments of second layer
nucleation.Comment: 11 pages. Table I corrected and one appendix added. To be published
in Phys. Rev. B (scheduled issue: 15 February 2003
Response of Soybean Insects to Foliar Applications of a Chitin Synthesis Inhibitor TH 6040
The activity of TH 6040, a chitin synthesis inhibitor, was determined against velvetbean caterpillar, Anticarsia gemmatalis Hübner, and other soybean defoliators in field tests in Georgia, South Carolina, and Brazil. Single applications at rates as low as 75 g AI/ha afforded adequate initial and excellent residual control of A. gemmatalis and some suppression of low populations of Plusia spp. Two applications at higher rates gave significant control of soybean looper, Pseudoplusia includens (Walker), and showed promise against green cloverworm, Plathypena scabra (F.), and Mexican bean beetle, Epilachna varivestis Mulsant. Populations of geocorids and nabids were lower in 1 test, possibly because of insecticidal activity, scarcity of prey, or both
Odor Evaluation and Gas Emission from Manure of Dairy Heifers Fed High/Low - Forage Quality and High/Low-Concentrate Diets
A heifer feeding trial evaluated the impact of high/low forage quality and high/low concentrate level nutrient-balanced diets on simultaneous odor and gas emissions from the manure. Gas concentration was determined using an infrared photoacoustic analyzer over a 24-hour period using a steady-state flux chamber setup containing urine:feces as-excreted from eight individual heifers. Odorous air samples were collected from chamber headspace and evaluated by six human assessors for pleasantness, intensity and detection threshold using a forced-choice dynamic olfactometer. Ammonia emission ranged from 0.64 to 3.94 mg NH3 cm-2 d-1 across diets. Average ammonia emission from the low concentrate (80% forage) diets (2.11 mg NH3 cm-2 d-1) was larger than the high concentrate (20% forage) diets (1.69 mg NH3 cm-2 d-1), but not significantly different. Carbon dioxide emission was significantly higher (p= 0.0143) in the low concentrate diets. There was a linear increase of methane emission as reduced quality forage (corn stover) was increased in the low-concentrate diet (p = 0.030). Nitrous oxide emissions were similar and low in all diets. Highest average odor emission (8.58 OU m-2 sec-1) was from the low concentrate, high forage quality (80% corn silage) diet while lowest emission (5.01 OU m-2 sec-1) was measured when forage quality was reduced (32% silage; 48% stover). Odor emission tended to be reduced with lower quality forage diets, but with no significant difference. The volume of feces produced from the high concentrate diet was about half that from the low concentrate diet heifers. But total manure produced by the high concentrate diet heifers was 23% higher due to increased urine production
Localization-delocalization transition in the quasi-one-dimensional ladder chain with correlated disorder
The generalization of the dimer model on a two-leg ladder is defined and
investigated both, analytically and numerically. For the closed system we
calculate the Landauer resistance analytically and found the presence of the
point of delocalization at the band center which is confirmed by the numerical
calculations of the Lyapunov exponent. We calculate also analytically the
localization length index and present the numerical investigations of the
density of states (DOS). For the open counterpart of this model the
distribution of the Wigner delay times is calculated numerically. It is shown
how the localization-delocalization transition manifest itself in the behavior
of the distribution.Comment: 9 pages, 10 figures, Revte
Diffusion in disordered systems under iterative measurement
We consider a sequence of idealized measurements of time-separation onto a discrete one-dimensional disordered system. A connection with Markov
chains is found. For a rapid sequence of measurements, a diffusive regime
occurs and the diffusion coefficient is analytically calculated. In a
general point of view, this result suggests the possibility to break the
Anderson localization due to decoherence effects. Quantum Zeno effect emerges
because the diffusion coefficient vanishes at the limit .Comment: 8 pages, 0 figures, LATEX. accepted in Phys.Rev.
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