Statistical model of internal energy dissipation in composition materials

A model of the theoretical evaluation of normalized losses of elastic-vibration energy in matrix-type composition materials with spherical inclusions as a function of the probability of the development of plastic deformations in microvolumes of the matrix is proposed. The distribution function of maximum shear stresses in the matrix in the vicinity of an inclusion is constructed on the basis of Muskhelishvili's relationships with allowance for the effect of neighboring inclusions. The effect of the volume percentage of inclusions and the ratio of the shear moduli of the inclusions and matrix on the level of energy losses associated with microlocalized plastic deformations of the matrix is analyzed.Translated from Problemy Prochnosti, No. 7, pp. 94–98, July, 1990.     

Inherited chemical inhomogeneity in oxide layers deposited by the method of microarc oxidizing on hypereutectic silumins

The effect of the size and of the kind of distribution of silicon in Al-Si alloys with hypereutectic composition on the characteristics of the oxide layer formed by microarc oxidizing (MAO) is studied. It is shown that the inhomogeneity of the distribution of silicon in the oxide layers is inherited from the initial structure of the alloys. The mechanism of the effect of silicon on the structure of oxide layers and the processes of their formation due to MAO of hypereutectic silumins are discussed. It is shown that it is principally possible to use the method of microarc oxidizing for obtaining hardened layers with controlled distribution of silicon. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 23–27, March, 2007.     

A purinergic component of the excitatory postsynaptic current mediated by P2X receptors in the CA1 neurons of the rat hippocampus

The pyramidal neurons in the CA1 area of hippocampal slices from 17- to 19-day-old rats have been investigated by means of patch clamp. Excitatory postsynaptic currents (EPSCs) were elicited by stimulating the Schaffer collateral at a frequency below 0.2 Hz. It was found that inhibition of glutamatergic transmission by 20 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 100 microM 2-amino-5-phosphonovaleric acid (D-APV) left a small component of the EPSC uninhibited. The amplitude of this residual EPSC (rEPSC) comprised 25 +/- 11% of the total EPSC when measured at a holding potential of -50 mV. The rEPSC was blocked by selective P2 blocker pyridoxal phosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS) 10 microM and bath incubation with non-hydrolysable ATP analogues, ATP-gamma-S and alpha, beta-methylene-ATP at 50 and 20 microM, respectively. The rEPSC was dramatically potentiated by external Zn2+ (10 microM). In another series of experiments exogenous ATP was applied to the CA1 neurons in situ. An inward current evoked by ATP was inhibited by PPADS to the same extent as the rEPSC. It is concluded that, depending on membrane voltage, about one-fifth to one-quarter of the EPSC generated by the excitatory synaptic input to the hippocampal CA1 neurons of rat is due to the activity of P2X receptors.