Guided ion beam studies of the reactions of O+, O 2 + , N+ and N 2 + with silane

Guided ion beam mass spectrometry is used to measure the cross sections as a function of kinetic energy for reaction of SiH₄ with O⁺(⁴S), O ₂ ⁺ (²Π_g,v=0), N⁺(³P), and N ₂ ⁺ (²Σ _g ⁺ ,v=0). All four ions react with silane by dissociative charge-transfer to form SiH _m ⁺ (m=0?3), and all but N ₂ ⁺ also form SiXH _m ⁺ products where (m=0?3) andX=O, O₂ or N. The overall reactivity of the O⁺, O ₂ ⁺ , and N⁺ systems show little dependence on kinetic energy, but for the case of N ₂ ⁺ , the reaction probability and product distribution relies heavily on the kinetic energy of the system. The present results are compared with those previously reported for reactions of the rare gas ions with silane [13] and are discussed in terms of vertical ionization from the 1t ₂ and 3a ₁ bands of SiH₄. Thermal reaction rates are also provided and dicussed.     

Fermentation Kinetics for Xylitol Production by a Pichia stipitis d-Xylulokinase Mutant Previously Grown in Spent Sulfite Liquor

Spent sulfite pulping liquor (SSL) contains lignin, which is present as lignosulfonate, and hemicelluloses that are present as hydrolyzed carbohydrates. To reduce the biological oxygen demand of SSL associated with dissolved sugars, we studied the capacity of Pichia stipitis FPL-YS30 (xyl3Δ) to convert these sugars into useful products. FPL-YS30 produces a negligible amount of ethanol while converting xylose into xylitol. This work describes the xylose fermentation kinetics of yeast strain P.stipitis FPL-YS30. Yeast was grown in rich medium supplemented with different carbon sources: glucose, xylose, or ammonia-base SSL. The SSL and glucose-acclimatized cells showed similar maximum specific growth rates (0.146 h⁻¹). The highest xylose consumption at the beginning of the fermentation process occurred using cells precultivated in xylose, which showed relatively high specific activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49). However, the maximum specific rates of xylose consumption (0.19 g_xylose/g_cel h) and xylitol production (0.059 g_xylitol/g_cel h) were obtained with cells acclimatized in glucose, in which the ratio between xylose reductase (EC 1.1.1.21) and xylitol dehydrogenase (EC 1.1.1.9) was kept at higher level (0.82). In this case, xylitol production (31.6 g/l) was 19 and 8% higher than in SSL and xylose-acclimatized cells, respectively. Maximum glycerol (6.26 g/l) and arabitol (0.206 g/l) production were obtained using SSL and xylose-acclimatized cells, respectively. The medium composition used for the yeast precultivation directly reflected their xylose fermentation performance. The SSL could be used as a carbon source for cell production. However, the inoculum condition to obtain a high cell concentration in SSL needs to be optimized. Prepared for 29th Symposium on Biotechnology for Fuels and Chemicals.     

Injectable,Interconnected, High‐Porosity Macroporous Biocompatible Gelatin Scaffolds Made by Surfactant‐Free Emulsion Templating

High‐porosity interconnected, thermoresponsive macroporous hydrogels are prepared from oil‐in‐water high internal phase emulsions (HIPEs) stabilized by gelatin‐graft‐poly(N‐isopropylacrylamide). PolyHIPEs are obtained by gelling HIPEs utilizing the thermoresponsiveness of the copolymer components. PolyHIPEs properties can be controlled by varying the aqueous phase composition, internal phase volume ratio, and gelation temperature. PolyHIPEs respond to temperature changes experienced during cell seeding, allowing fibroblasts to spread, proliferate, and penetrate into the scaffold. Encapsulated cells survive ejection of cell‐laden hydrogels through a hypodermic needle. This system provides a new strategy for the fabrication of safe injectable biocompatible tissue engineering scaffolds.

     

SOLUTION OF OPTIMAL TRANSPORTATION PROBLEMS USING A MULTIGRID LINEAR PROGRAMMING APPROACH

We compute and visualize solutions to the Optimal Transportation (OT) problem for a wide class of cost functions. The standard linear programming (LP) discretization of the continuous problem becomes intractable for moderate grid sizes. A grid refinement method results in a linear cost algorithm. Weak convergence of solutions is established and barycentric projection of transference plans is used to improve the accuracy of solutions. Optimal maps between nonconvex domains, partial OT free boundaries, and high accuracy barycenters are presented.     

SILEP-1 COMPUTER SYSTEM FOR MEASURING ELECTRICAL CONDUCTIVITY OF PLASMA IN THE CHANNELS OF MHD GENERATORS

Abstract

The development of devices capable of measuring the elctrical conductivity of plasma is a complex task that requires solution of a number of problems, including high flow velocities and high plasma temperatures, aggressive media, strong magnetic fields, and large Hall potentials. At the Institute for High Temperatures we have solved these problems in the course of developing we have solved these problems in the course of developing a computer system, SILEP-1, for measuring the electrical conductivity of plasma in the U-25B MHD generator.     

Duality and radiative corrections to leptonic widths in heavy quark systems

We use a duality argument to estimate the gluonic radiative corrections of orders α_s and α_s² to the leptonic widths for heavy quark systems.     

Decarboxylation of a benzo[b] thiophene-2-carboxylic acid

5-Hydroxy-3-methylbenzo[b]thiophene-2-carboxylic acid can be decarboxylated by refluxing with 48% hydrobromic acid for 30 minutes. Yield and quality of the product are better than for the previously used copper-quinoline decarboxylation. The 5-methoxy analog of the above acid is stable to decarboxylation under these conditions; however, it demethylates readily under the reaction conditions, and the phenol thus afforded decarboxylates.     

Mid-Infrared Transmission Spectroscopy of Sugar Solutions: Instrumentation and Analysis

Transmission studies on a specially designed scanning spectroprocessor for aqueous systems are reported for the first time. The nature of the absorption bands and the possibility of a universal isobestic point are discussed for a series of sugar solutions.