Asymptotic expansion for reversible A + B <-> C reaction-diffusion process

We study long-time properties of reversible reaction-diffusion systems of type A + B C by means of perturbation expansion in powers of 1/t (inverse of time). For the case of equal diffusion coefficients we present exact formulas for the asymptotic forms of reactant concentrations and a complete, recursive expression for an arbitrary term of the expansions. Taking an appropriate limit we show that by studying reversible reactions one can obtain "singular" solutions typical of irreversible reactions.Comment: 6 pages, no figures, to appear in PR

Sea polarisation and the Drell-Hearn-Gerasimov sum-rule(s)

The Drell-Hearn-Gerasimov sum-rule is really two sum-rules: one for each of the valence and the sea/glue contributions to the nucleon wavefunction. The convergence of these sum-rules follows from the Froissart bound for spin dependent processes in QCD and is necessary for the consistency of the constituent quark model of low energy QCD. Some challenges for future polarised photoproduction experiments, for example at ELFE, are discussed.Comment: 10 pages, LaTe

x-Dependent Polarized Parton Distributions

Using QCD motivated and phenomenological considerations, we construct x- dependent polarized parton distributions, which evolve under GLAP evolution, satisfy DIS data and are within positivity constraints. Each flavor is done separately and the overall set can be used to predict polarization asymmetries for various processes. We perform our NLO analysis strictly in x space, avoiding difficulties in moment inversion. Small-x results and other physical considerations are discussed.Comment: 30 pages, 11 Postscript figure

Space-and time-resolved diffusion-limited binary reaction kinetics in capillaries: experimental observation of segregation, anomalous exponents, and depletion zone

An experimental investigation of one-dimensional, diffusion-limited A+B→C chemical reactions is reported. The persistence of reactant segregation and the formation of a depletion zone is observed and expressed in terms of the universal time exponents: α (motion of the boundary zone), β (width of instantaneous product formation zone), γ (rate of instantaneous local formation of product), δ (rate of instantaneous global formation of product), etc. There is good agreement with the recently predicted and/or simulated values: α =1/2, β =1/6, γ =2/3, δ =1/2, in contrast to classical predictions ( α =0, β =1/2, γ =0, δ =−1/2). Furthermore, classically the segregation would not be preserved and there would be no formation of a depletion zone and no motion (just dissipation) of the reaction zone. We also discuss the relations to electrode oxidation-reduction reactions, i.e., A+C→C where C is a catalyst, electrode, or “trap.”Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45162/1/10955_2005_Article_BF01049588.pd

Introduction to the special issue on the statistical mechanics of climate

We introduce the special issue on the Statistical Mechanics of Climate by presenting an informal discussion of some theoretical aspects of climate dynamics that make it a topic of great interest for mathematicians and theoretical physicists. In particular, we briefly discuss its nonequilibrium and multiscale properties, the relationship between natural climate variability and climate change, the different regimes of climate response to perturbations, and critical transitions

Lactobacillus plantarum 2142 prevents intestinal oxidative stress in optimized in vitro systems

Recently, there has been a growing interest to replace antibiotics’ administration with the application of probiotics. The aim of our investigations was to reveal the influence of spent culture supernatant of Lactobacillus plantarum 2142 on the response of enterocytes to oxidative stress, and the spent culture supernatant’s ability to protect them from oxidative injury. The experiments were performed on non-carcinogenic porcine epithelial cell line, IPEC-J2 isolated from a neonatal piglet and on human colon adenocarcinoma cell line, Caco-2. The cells cultured on membrane inserts were treated with millimolar hydrogen peroxide solution to provoke oxidative stress. The peroxide-triggered cell response profile was evaluated via determination of change in transepithelial electrical resistance, quantification of extent of cell death by 4’,6-diamidino-2 phenylindole (DAPI) staining and via estimation of proinflammatory cytokine, IL-8 production using ELISA technique. Non-starter lactobacilli supernatant-mediated inhibition of peroxide-triggered upregulation of IL-8 production confirmed the antiinflammatory properties of active metabolites produced by Lactobacillus plantarum 2142 in acute oxidative stress