Using acoustic emission for the analysis of wear processes during sliding friction

The acoustic response of two friction pairs, in which brittle fracture and intense plastic deformation take place during friction, has been studied. The acoustic signals have been analyzed by calculating median frequencies using the window Fourier transform technique.     

Improving the cutting mechanism of a disk-type wood chipper

Methods of waste-free woodchip production are verified. This permits improvement in the cutting mechanism of a disk-type wood chipper.     

Edge contact in conical transmissions with round gear teeth

Conical drives with large tooth inclination are considered. The contact spot in edge contact is considered by analogy with the profile components and central impacts in an equivalent cylindrical transmission.     

Low-temperature structural studies of Tl2Ba2CaCu2O x

Low-temperature x-ray diffraction studies of superconducting Tl-2212 ceramics revealed anomalies in thec cell parameter andc-axis thermal expansion coefficient near the superconducting transition. Air and vacuum anneals in the range 400–550‡C demonstrate that these anomalies correlate with the superconducting properties of the material. The anomalous temperature variation of thermal expansion suggests that the superconducting transition is accompanied by significant changes in the phonon spectrum.     

Histidine-containing dipeptides as endogenous regulators of the activity of sarcoplasmic reticulum Ca-release channels

We have recently published an experimental method useful for causing discrete cerebral microischemic foci in rabbits. In that study it was shown that on reaching the brain, plastic beads (with an average diameter of 80 or 110 microns) give rise to foci of increased [14C]2-deoxyglucose accumulation, indicating anaerobic glycolysis. Further, it was suggested that the relatively low accumulation of [14C]2-deoxyglucose, as observed in the center of some of the ischemic foci located in areas which are thought to have a poor collateral blood supply, was an indication of glucose depletion. This work is intended to be a useful approach for the study of diffusion-limited consumption of glucose and oxygen in microischemic regions, located in endarterial regions. It is shown that a mathematical model with reasonable parameters can be fitted to a measured [14C]2-deoxyglucose profile. The results of this study are compatible with the view that the glucose concentration in the ischemic center is very low and limits the rate of energy turnover. Together with animal experiments, this mathematical model may impart new information of importance for evaluating the treatment of subcortical infarctions in humans.     

Ca-release channels (ryanodine receptors) of sarcoplasmic reticulum: structure and properties. A review

Recent data on characteristics of the structure, function, and regulation of sarcoplasmic reticulum Ca-release channels (ryanodine receptors) from various types of muscles are summarized. The history of identification and purification of Ca-release channels, the properties of isoforms expressed in various tissues, their electric characteristics, and regulation by endogenous and exogenous compounds are described. The phosphorylation of Ca-release channels by protein kinases and their interaction with various intracellular regulatory proteins are discussed. The proposed mechanisms of excitation-contraction coupling and the role of the Ca-release channels in this process are analyzed.     

Unit for welding housings of apparatus

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 5, pp. 28–29, May, 1990.