Diffusion-controlled annihilation A+B→0A + B \to 0 with initially separated reactants: The death of an AA particle island in the BB particle sea

We consider the diffusion-controlled annihilation dynamics $A+B\to 0$ with equal species diffusivities in the system where an island of particles $A$ is surrounded by the uniform sea of particles $B$. We show that once the initial number of particles in the island is large enough, then at any system's dimensionality $d$ the death of the majority of particles occurs in the {\it universal scaling regime} within which $\approx 4/5$ of the particles die at the island expansion stage and the remaining $\approx 1/5$ at the stage of its subsequent contraction. In the quasistatic approximation the scaling of the reaction zone has been obtained for the cases of mean-field ($d \geq d_{c}$) and fluctuation ($d < d_{c}$) dynamics of the front.Comment: 4 RevTex pages, 1 PNG figure and 1 EPS figur

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

La variation des indicateurs bactériens et des flux de MES dans les systèmes séparatifs d'eaux pluviales à Östersund, en Suède - Résultats préliminaires

Faecal bacteria are a major pollution threat of water bodies designated for multipurpose use including drinking water sources or recreational purposes. Even though stormwater discharges may contribute significantly to microbiological pollution, they have not been fully investigated in the European context. We have studied the presence of indicator bacteria and total suspended solids (TSS) in stormwater discharged from four urban catchments, with areas between 5 and 40 ha, in Östersund, Sweden. The aim was to determine local variation of standard bacteria strains and TSS in Swedish urban catchments with specific land uses. Further, intra event variations were investigated. During dry weather, indicator bacteria concentrations in sewers conveying baseflow did not exceed 100 CFU/100 mL. During storm runoff, total coliform and int. enterococci concentrations increased 102 to 103 times, compared to those in baseflow. Compared to these two parameters, considerably lower concentrations were observed for E. coli and C. perfringens. Bacteria concentrations differed significantly among the sampling sites and partly, a first flush phenomenon was observed. Partly, significant correlations between TSS and indicator bacteria were observed. These were catchment specific and need a more detailed assessment. Further research will focus on seasonal variations and influential factors.Godkänd; 2013; 20130821 (helgal)</p

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