Kinetic study of the reaction between molybdenum trioxide and gaseous carbon tetrachloride

The kinetics of the chlorination reaction of molybdenum trioxide with gaseous carbon tetrachloride has been studied at temperatures between 713 and 753 K. The effects of temperature, reaction time, residence time and gaseous reactant concentration on conversion were studied throughout the reaction. In all cases, there was an increase in conversion when the above operating variables were increased. The kinetic model proposed is consistent with and correlates the experimental data. In the range studied for the different variables, the step that controls the rate of reaction is the surface chemical reaction. Values of the rate constant and the activation energy were estimated.     

Comparison of demineralized allogeneic bone matrix grafting (the Urist procedure) and the Ilizarov procedure in large diaphyseal defects in sheep

The bone inductive capability of the Urist and Ilizarov procedures was compared in the repair of large diaphyseal defects in sheep. In 30 animals, a 4 cm segmental defect was created in the middle portion of the right femur and was stabilized with an external fixator. The sheep were divided into four groups according to the type of reconstruction of the defect. In group 1, a demineralized allogeneic bone matrix (DABM) cylinder was used; in group 2, DABM chips; and in group 3, gradual transport of a piece of bone detached from the proximal femoral fragment was used to fill the defect. Group 4 served as a control (the defect was left empty). New bone formation was assessed by serial radiographs until the time of death at 2 or 4 months. Postmortem specimens were analyzed with respect to bone mineral content, uptake of isotopes (45Ca and 3H-proline), and histology. The first signs of new bone formation were radiographically evident at 4 weeks. In the two groups in which reconstruction involved DABM (Urist procedures), new bone failed to form in eight of the 13 animals. Full bridging of the defect was observed at 8 weeks in one animal with a DABM cylinder and two with DABM chips. No decisive difference in bone yield could be demonstrated between the two Urist procedures. In the group treated with the Ilizarov procedure, new bone formation consistently occurred at a high rate; full bridging of the defect was observed in seven of the eight animals. Bone mineral scanning and histologic analysis essentially confirmed the radiographic results. Uptake of isotopes was selectively analyzed in two sheep from each experimental group in which new bone formation was exhibited in the defect; new bone formation was increased compared with that in the contralateral femur but was equal among the three experimental groups. Our study shows that gradual transport of a detached piece of autogeneic bone (Ilizarov procedure) is more effective than implantation of DABM (Urist procedure) in eliciting new bone formation in large diaphyseal defects in sheep. The variable bone induction by DABM may be explained by differences in host immune responses to the implants.     

STATISTICAL ASSOCIATION LEARNING OF THE MARKOV DECISION PROCESS

A neural computing approach to the Markov decision problem is presented. The method makes use of historical records of rewards as inputs and average long-run incomes per epoch as targets for training a backpropagation network to associate the two quantities, without a priori knowledge of the state transition probabilities. Estimation of the long-run income, given a new reward matrix as input, is interpreted as a statistical-association learning problem. Following the training, the relevant functional relationship between the income (output) and the reward (input), that has been learned by the network, can be used to compute an unknown expected income. The present study examines network generalization to new inputs, considering the effects of different topological designs and the characteristics of training samples on neural computing accuracy. Successful performance of the best design, which is determined directly from the underlying mathematical model of the Markov decision problem, is demonstrated by a computer simulation experiment.     

Contributing authors

Contributing authors     

Preparation of fibrous ion-exchangers containing guanidine groups

Conclusions -- The reaction of guanidine with grafted polyglysodylmethacrylate has been investigated. Basic kinetic parameters of the process have been determined.-- Fibrous chemisorbents have been prepared based on graft PCA-PGMA or Cell-PGMA copolymers which have been aminated with guanidine; the content of amino nitrogen was up to 2% by wt.Translated from Khimicheskie Volokna, No. 1, pp. 29–31, January–February, 1991.     

Thermal layers near a friction surface of bodies in high-velocity slip

Thermal layers generated when one body slips over the surface of another are considered. Exactness of the solutions obtained by the methods of the boundary layer theory is analyzed.Institute of New Physical and Applied Problems of the Ukrainian Academy of Sciences, Kiev. Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 63, No. 6, pp. 760–766, December, 1992.