Fluctuations of the energy absorption of electron-photon radiation in a model with collision-grouping elements

In the present work, the general method proposed earlier for calculating the distribution density and moments of the absorbed energy in isolated sensitive regions of absorbers irradiated by ionizing particles is developed and made specific for the electron-photon problem. Electron transfer is considered within the framework of a model using grouping of excitations and slipping ionization; the presence of electron equilibrium in the vicinity of sensitive regions is assumed. Two similar methods of calculating these characteristics are developed. Both reduce the initial problem to two independent problems: determining the electron spectrum in the sensitive region (in one of the methods, the spectrum of electron sources is also needed) and calculating the coefficients characterizing electron transfer in the sensitive region and its immediate vicinity.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 89–94, September.     

Tests for extremality in a problem for quasiconformal mappings

Mathematical Notes -     

Narrow linewidth 2 μm optical parametric oscillation in periodically poled LiNbO<Subscript>3</Subscript> with volume Bragg grating outcoupler

An optical parametric oscillator using a periodically poled LiNbO₃ crystal and a volume Bragg grating output coupler is presented. Signal and idler wavelengths of 2008 and 2264 nm were generated from the 1064 nm Nd:YVO₄ pump laser. The Bragg grating was reflecting in a narrow band around 2008 nm, creating a purely singly resonant cavity. Signal and idler linewidths of approximately 0.44 and 0.72 nm, respectively, were measured. This is a reduction of 80 and 60 times compared to when using a mirror as output coupler. A total output energy of 156 μJ was measured with 47% slope efficiency. PACS 42.65.Yj; 42.72.Ai; 42.40.Eq     

Chaotic buffering and its mathematical models

We propose a general idea of obtaining different chains of coupled oscillators with chaotic buffering. As examples, we consider chains of diffusively coupled generalized cubic Schrödinger equations and nonlinear telegraph equations. We also give examples of systems that have an infinite-dimensional chaotic attractor.     

On Ramsey numbers of uniform hypergraphs with given maximum degree

For every ?>0 and every positive integers Δ and r, there exists C=C(?,Δ,r) such that the Ramsey number, R(H,H) of any r-uniform hypergraph H with maximum degree at most Δ is at most C|V(H)|^1+?.     

Generation of H− ions in a low-pressure xenon-hydrogen discharge. I

A theory of a low-pressure discharge in a xenon-molecular hydrogen mixture is developed. It is shown that, in such a discharge, at an interelectrode distance of L = 1 cm and a total plasma pressure of p ₀ ～ 1 Torr, the density of negative hydrogen ions produced via the dissociative attachment of thermal electrons to vibrationally excited molecules H₂ can reach a value as high as N_H ^? ≥ 10¹² cm^?3. According to calculations, the electron temperature in discharge operating regimes under study attains T _e ≈ 1?2 eV, which corresponds to the maximum of the e-v exchange rate constant of H₂ molecules. This ensures a relatively high rate of vibrational pumping of H₂ molecules in the discharge.     

Boric acid esters as thermal stabilizers and fungicidal additives for elastomers from natural rubber

New and previously synthesized boric acid esters were studied as thermal stabilizing and fungicidal additives to elastomers based on natural rubbers.     

Depolymerization of chitin and chitosan in the course of base deacetylation

Depolymerization of chitin and chitosan in the course of deacetylation in an alkaline medium was studied, and the influence exerted on the process by the nature and concentration of the alkali (NaOH, KOH) and salts (NaCl, NaI, KI) was examined.     

On the term “pH of the precipitation onset of heavy metal hydroxides”

It is suggested to take as pH of the precipitation onset of metal hydroxides the pH at which 10% of the initial amount of metal ions has precipitated. An equation for calculating this quantity is presented.