Development of photoactive ZnS-SiO composites on biogenic silica matrix for organic pollutant degradation.

Sulfide ZnS-SiO composite photocatalysts with biogenic silica matrix were prepared by sol-gel method based on wet gel and xerogel. FT-IR, SEM, XRD, EDXRF, UV-Vis, and XPS methods were systematically used to characterize the obtained materials. The use of support allowed to obtain stable porous (S = 79-105 m g; V = 0.

Global stability of an age-structured population model on several temporally variable patches.

We consider an age-structured density-dependent population model on several temporally variable patches. There are two key assumptions on which we base model setup and analysis. First, intraspecific competition is limited to competition between individuals of the same age (pure intra-cohort competition) and it affects density-dependent mortality.

Effect of density dependence on coinfection dynamics.

In this paper we develop a compartmental model of SIR type (the abbreviation refers to the number of Susceptible, Infected and Recovered people) that models the population dynamics of two diseases that can coinfect. We discuss how the underlying dynamics depends on the carrying capacity : from a simple dynamics to a more complex. This can also help in understanding the appearance of more complicated dynamics, for example, chaos and periodic oscillations, for large values of .

Exact solution of three-level model of excited state electron transfer symmetry breaking in quadrupolar molecules.

An analytical solution of a three-level model of symmetry breaking in excited A-D-A quadrupolar triads with an electron donor D and identical electron acceptors A and A is derived, in particular, an analytical expression for the dissymmetry parameter (difference in charges, in electron charge units, on the left and right arms of the molecule) is obtained. The model predicts the threshold dependence of the symmetry breaking degree on the parameters of the molecule and its interaction with the solvent. It is shown that for typical molecular parameters, symmetry breaking occurs as a charge transfer from one arm of the molecule to the other with nearly invariable donor charge.

Colloid transport of plutonium in the far-field of the Mayak Production Association, Russia.

Sorption of actinides, particularly plutonium, onto submicrometer-sized colloids increases their mobility, but these plutonium colloids are difficult to detect in the far-field. We identified actinides on colloids in the groundwater from the Mayak Production Association, Urals, Russia; at the source, the plutonium activity is approximately 1000 becquerels per liter. Plutonium activities are still 0.