Dissolving grade eco-clean cellulose pulps by integrated fractionation of cardoon (Cynara cardunculus L.) stalk biomass

A biorefinery scheme with separate processing of the two main carbohydrate streams (cellulose and hemicellulose-derived) was employed to the energy crop cardoon (Cynara cardunculus L.) to fractionate the whole stalk material. A high quality xylose-enriched substrate was obtained after selective one-step dilute sulfuric acid hydrolysis of hemicelluloses, yielding 18.1 g of xylose per 100 g of dry biomass. The xylan-free solid residue was delignified by sulfur-free organosolv pulping to produce dissolving grade pulps having 93.8% of α-cellulose (33.1 g per 100 g dry initial biomass) and 79.5% degree of crystallinity. About 76% of crop lignin (13.8 g per 100 g dry initial biomass) was recovered from the spent pulping liquor as a high purity reactive precipitated organosolv lignin. Response surface methodology was used for statistical modeling and optimization of the applied separation processes. The central composite rotatable design was applied to assess the effects of the principal technological parameters on the main reaction outputs.     

Present status of the world and russian uranium mineral-raw material resources

The sharply higher demand for uranium for nuclear power during 2010–2050 and possibilities of modern mineral-material resources to meet these needs are evaluated on the basis of an analysis of IAEA information and other publications. Forecasts to 2030 show adequate reserves and resources for producing the required amount of uranium. New deposits will supply production expansion beyond 2030.     

Experimental study and modeling of holographic photonic crystals with defects of the spatial and band-gap structures

Results of experimental studies and modeling of holographic photonic crystals (PCs) with defects of their spatial and band-gap structures and also of studying quasi-crystals are presented. Thicklayer photopolymer materials with a hybrid matrix formed on the basis of the sol-gel technology are used for PC production. A method of obtaining delocalized defects is proposed and implemented. A code is written for computer modeling of the spatial PC structure, which offers a clear idea about the appearance of the synthesized crystal and the expected spectral characteristics.     

Suitability of automobile gasolines for prolonged storage

A new method of determination of chemical stability of automobile gasolines based on the proportion of absorbed oxygen (PAO) is proposed. Storage test results are used to formulate the chemical stability requirements for prolonged gasoline storage and to determine the standard PAO values.     

Study of the longitudinal stability of strip made of copper alloys during rolling in the vertical rolls of a strip mill

A method has been developed for experimentally studying the longitudinal stability of strip being rolled in vertical rolls on a strip mill with and without tension. The method makes it possible to study the effect of tension of the strip and reduction of its edges for different ratios of strip thickness to width. Quantitative results are obtained to evaluate the loss of stability and limiting state of strip when its edges undergo reduction.     

Polyoxometalate catalyzed ozonation of chemical pulps in organic solvent media

Polyoxometalate (POM) catalyzed ozonation of chemical pulps in organic solvent media was found to be particularly effective and selective environmentally benign bleaching approach providing a way for substantial increase in pulp brightness, viscosity and degree of delignification in comparison with other ozone-based bleaching techniques. A series of tested low-boiling polar aprotic and protic organic solvents showed a well-defined capacity for ozonation improvement in the presence of Keggin-type heteropolyanion [PMo₇V₅O₄₀]⁸⁻ (HPA-5). Even moderate solvent proportion of 6% (w/w) in the reaction solution caused additional gain in brightness up to 3.4% ISO with simultaneous increase in pulp viscosity up to 8.8% and lignin removal up to 18.9% after HPA-5 catalyzed ozonation (0.8% O₃; 0.5 mM HPA), as compared with the control solvent-free process. An aqueous acetone solution was found to be the preferred reaction medium in terms of pulp brightening and delignification. Under optimized conditions, the POM-catalyzed ozonation of eucalypt kraft pulp in acetone/water solution showed remarkable brightness improvement by 15.1% ISO with additional lignin removal by 39.4% and increase in intrinsic viscosity by 3% in comparison with pulp bleached in water media.     

Measurement of oxygen recombination rate constants by the piezoelectric method

The piezoelectric method is used to measure pressure in a gas flow within a nozzle, measurement results are compared with calculation, and values of the oxygen atom recombination rate constant are obtained for the temperature range 1680–3250°K.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 3, pp. 437–441, September, 1987.