Carbon monoxide laser emitting nanosecond pulses with 10 MHz repetition rate

Actively mode-locked electron-beam-sustained-discharge CO laser producing a train of ∼5-15 ns (FWHM) spikes following with repetition rate 10 MHz for both single-line and multiline mode of operation in the mid-IR range of ∼5 μm was experimentally studied. Total laser pulse duration was ∼0.5 ms for both mode-locked and free-running laser. Specific output energy in multiline CO laser mode of operation was up to 20 Jl⁻¹ Amagat⁻¹ and the laser efficiency up to 3.5%. The active mode-locking was achieved for single-line CO laser mode of operation in spectral range 5.2-5.3 μm. This sort of radiation can be used for pumping an optical parametric amplifier for optical stochastic cooling in relativistic heavy ion collider, for laser ablation, and for studying vibrational and rotational relaxation of CO and NO molecules.     

Formaldehyde Formation on Vanadium Oxide Surfaces V2O3(0001) and V2O5(001): How does the Stable Methoxy Intermediate Form?

Hydroxy‐mediated methoxy formation or stabilization is probably an important process in many methanol adsorption systems. Hydrogen atoms originating from the scission of the methanol O? H bond react with the substrate and form water. This process may result 1) in the production of additional surface defects as reactive centers for methoxy formation and 2) in the stabilization of methoxy groups by suppression of methanol formation.

     

The study of cyclooctene oxidation with molecular oxygen catalyzed by VSi2

The catalytic effect of VSi₂ on initial stages of the liquid-phase oxidation of cyclooctene by molecular oxygen was studied. The vanadium disilicide influences on the oxidation process in the presence of hydroperoxide. VSi₂ takes part in a radical formation stage by catalysis of hydroperoxide decomposition reaction. The catalyst was investigated before and after reaction using FTIR spectroscopy. From the data obtained, the kinetic model of the catalytic oxidation process was proposed and the equation for the reaction rate was derived. The equation has described all observed dependences of reaction rate on the concentration of reactants and content of catalyst.      

Inelastic behavior of the single domain of metal-ceramic composites with lamellar microstructure

Metal-ceramic composites are widely applied in the different brunches of industry. The composites are produced by squeeze-casting of the ceramic preform by molten aluminum alloy. The lamellar microstructure is obtained during freezing of ceramic suspension. The internal structure of the domains can be controlled via freeze-casting parameters. The material has high anisotropy level and its effective properties depend on lamella orientation. The aim of this study is numerical simulation of the inelastic behavior of the material and its verification by experiment. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Time-fractional radial heat conduction in a cylinder and associated thermal stresses

The theory of thermal stresses based on the heat conduction equation with the Caputo time-fractional derivative of order 0 < α ≤ 2 is used to investigate axisymmetic thermal stresses in a cylinder. The solution is obtained applying the Laplace and finite Hankel integral transforms. The Dirichlet and two types of Neumann problems with the prescribed boundary value of the temperature, the normal derivative of the temperature, and the heat flux are considered. Numerical results are illustrated graphically.     

Modification of Arabinogalactan Isolated from Larix sibirica Ledeb. into Sulfated Derivatives with the Controlled Molecular Weights

The process of sulfation of arabinogalactan—a natural polysaccharide from Larix sibirica Ledeb.—with sulfamic acid in 1,4-dioxane using different activators has been studied for the first time. The dynamics of the molecular weight of sulfated arabinogalactan upon variation in the temperature and time of sulfation of arabinogalactan with sulfamic acid in 1,4-dioxane has been investigated. It has been found that, as the sulfation time increases from 10 to 90 min, the molecular weights of the reaction products grow due to the introduction of sulfate groups without significant destruction of the initial polymer and sulfation products. Sulfation at 95 °C for 20 min yields the products with a higher molecular weight than in the case of sulfation at 85 °C, which is related to an increase in the sulfation rate; however, during the further process occurring under these conditions, sulfation is accompanied by the destruction and the molecular weight of the sulfated polymer decreases. The numerical optimization of arabinogalactan sulfation process has been performed. It has been shown that the optimal parameters for obtaining a product with a high sulfur content are a sulfamic acid amount of 20 mmol per 1 g of arabinogalactan, a process temperature of 85 °C, and a process time of 2.5 h.     

Packing congruent hyperspheres into a hypersphere

The paper considers a problem of packing the maximal number of congruent nD hyperspheres of given radius into a larger nD hypersphere of given radius where n = 2, 3, . . . , 24. Solving the problem is reduced to solving a sequence of packing subproblems provided that radii of hyperspheres are variable. Mathematical models of the subproblems are constructed. Characteristics of the mathematical models are investigated. On the ground of the characteristics we offer a solution approach. For n ≤ 3 starting points are generated either in accordance with the lattice packing of circles and spheres or in a random way. For n > 3 starting points are generated in a random way. A procedure of perturbation of lattice packings is applied to improve convergence. We use the Zoutendijk feasible direction method to search for local maxima of the subproblems. To compute an approximation to a global maximum of the problem we realize a non-exhaustive search of local maxima. Our results are compared with the benchmark results for n = 2. A number of numerical results for 2 ≤ n ≤ 24 are given.     

Express Method for Determination of Low Value of Trans-membrane Potential of Living Cells with Fluorescence Probe: Application on Haemocytes at Immune Responses

The method for measurement of trans-membrane potential of cell membrane was evaluated for the case of low potential value using fluorescence probe 4-(4-dimethylaminostyryl)-1-methylpyridinium, DSM. The method is based on comparative titration of cells with probe in buffers containing Na(+) or K(+). The apparent trans-membrane potential obtained with this way is a result of K(+)-Na(+) pump activity. The presented approach allowed measuring the low value of potential with 1-2?mV of accuracy without additional calibration procedures. The method was applied for investigation of potential of cell membrane of haemocytes of Galleria mellonella larvae. The value of potential of intact insect's haemocytes was found in the range from -10 to -20?mV. The change of potential value of haemocytes was investigated under model immune response and natural envenomation and parasitizing. The obtained deviations of cell membrane potential were in good correlation with changes of activity of main immune reactions, described in literature and obtained by us earlier.