The nature of lignin from steam explosion/enzymatic hydrolysis of softwood

Effective utilization of the lignin by-product is a prerequisite to the commercial viability of ethanol production from softwood wastes using a steam explosion (SE)/enzymatic hydrolysis (EH)/fermentation process. Changes in the chemical composition of Douglas fir wood on SO₂-catalyzed SE followed by EH were assessed using conventional analytical methods and new halogen-probetechniques. A significant solubilization of hemicelluloses was observed in the SE stage, the severity of which affected subsequent fermentation of cellulose and sorption of enzymes. SE of softwood resulted in dramatic changes in the chemical structure of lignin in the residual material involving chemical reactions via the benzyl cation. This leads to a more condensed lignin with partly blocked α-reaction centres. Possible uses for this lignin are discussed.     

Studying the start-up scenario for a pulsed gyrotron with a relativistic electron beam

We present the results of studying the start-up scenario for a high-power pulsed gyrotron operated at the TE₅₃ mode for two variants of the current–voltage characteristic of a three-electrode magnetron-injection electron gun. In the standard variant of feeding the voltage to the first anode from the resistive divider, sequential generation of the TE₇₃ and TE₆₃ modes, and, finally, the operating TE₅₃ mode was observed at the edge of the pulse. The current–voltage characteristic for which only the operating mode is excited is obtained by decreasing the growth rate of the voltage applied to the first anode.     

13C NMR study of the dissociation of tartaric and citric acids

The dissociation of tartaric and citric acid was studied by the ¹³C NMR method. All four dissociation constants of tartrate and citrate were determined directly from the pH-dependent shift of signals of carbon atoms making the composition of the hydroxy acids. It was shown that on successive splitting off of protons in tartaric acid, rings are formed between the carboxy and hydroxy groups, while in citric acid such rings are not formed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 6, pp. 706–710, November–December, 1990.     

Three-Component Synthesis of 5-Arylmethylene-3-benzoylmethylenepiperazine-2,6-diones

Russian Journal of General Chemistry -     

Unique effective action in two dimensional induced quantum gravity

The gauge dependence of the effective action in two dimensional induced gravity with non-local action is investigated. The unique effective action in this theory on flat background is also discussed. The configuration-space metric dependence of the unique effective action is studied.On leave from Tomsk Pedagogical Inst., Tomsk, Russia Address after 1.08.92: Dept. of Physics, Hiroshima Univ., Higashi-Hiroshima 724, Japan     

Description of the algebra of infinitesimal automorphisms of quadrics of codimension two and their classification

This research was accomplished with the financial support of the Russian Foundation for Fundamental Research, Grant No. 93-011-225.     

Condensation of ketoximes with phenylacetylene

2-Methyl-5-phenyl- and 2,5-diphenylpyrrole and 2-phenyl-, Z-[1-(2-phenylvinyl)]-3-phenyl-, and 4,5,6,7-tetrahydroindole, and 2,4-diphenyl-3,3-dimethyl-5-hydroxypyrroline have been obtained from the reaction of ketoximes with phenylacetylene, catalyzed by KOH-DMSO.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 485–488, April, 1992.