Increasing the force with which a shock wave discharged from the channel acts on an obstacle by way of converting a normal pressure shock to a system of oblique shocks

The results are given of experimental and numerical investigations of the effect produced on an obstacle by shock waves discharged from channels of different cross-sectional shapes (circle, square, cross). The pressure distribution on an obstacle mounted normally to the flow axis is measured. The experimental results are compared to the data of numerical calculation for determining the optimal modes as regards the duration of calculation and the cell size that produce the least difference between the experimental and numerical data. Calculations are performed of the gas flow behind a shock wave discharged from a channel of X-shaped cross section, and the distribution of pressure and temperature over the obstacle surface is plotted. It is found that the force with which a flow acts on an obstacle when discharged from a channel of X-shaped cross section is much greater than in the case of being discharged from a channel of round or square cross section. Shadow photographs show that this is due to the reduction of the loss of total pressure in the flow because of the conversion of the normal pressure shock to a system of oblique shocks.Translated from Teplofizika Vysokikh Temperatur, Vol. 42, No. 6, 2004, pp. 900–907.Original Russian Text Copyright © 2004 by T. V. Bazhenova, V. V. Golub, A. L. Kotelnikov, A. S. Chizhikov, M. V. Bragin, and S. B. Shcherbak.     

Biochemical markers of strophanthin arrhythmia

The increase of the concentration of fatty acids, the reduction in the concentration of serotonin, the lowering of the activity of glucose-6-phosphate dehydrogenase and transketolase, and the development of compensated metabolic acidosis were discovered in the stage that preceded strophanthine arrhythmia. These characteristics may be recommended for a wider use on the clinical basis for predicting arrhythmias in the treatment of cardiac glycosides.     

Effect of hypoxemia on the erythropoietic activity of organs during perfusion

Hypoxemia (45-minute) influence in vivo on erythropoietic activity of the kidney, liver, spleen, and sternum was studied by normoxemic perfusion of the isolated organs. The erythropoietic activity proved to increase after 6-hour perfusion of the liver; this confirmed the participation of this organ in the extrarenal secretion of the erythropoietic factor.     

Choledocholithiasis after cholecystectomy

Concrements were found in the ducts of 172 patients subjected to secondary surgical interventions on bile ducts. The detailed analysis of the data failed to answer the question whether the stones could be formed immediately in the ducts without such conditions as a mechanical obstacle for the outflow of bile, the presence of foreign bodies and a big stump of the cystic duct. Such a formation of stones can take place in very few cases. The authors have shown that control cholangiography and especially choledochoscopy can reduce the danger to leave the stones in the ducts, but does not eliminate the danger completely. Nevertheless they think that now it is possible to lessen the indications for biliodigestive anastomoses in choledocholithiasis since the retained stones can be revealed within the first days after surgery and, as a rule, removed with instruments or by other methods using the drainage left in the ducts.     

Metrological support for composition and quality control of sheet float glass

The key tasks related to provision of metrological support for the quality control of thermally polished glass at factories are discussed. This involves the creation of a state (national) standard sample, a unified set of certified calibration samples, state (national) standards for determination of float-glass composition and properties, and metrological certification of measuring apparatus based on a set of standard samples. Translated from Steklo i Keramika, No. 3, pp. 22–24, March. 1997.     

Epileptic afterdischarge in the hippocampal-entorhinal system: current source density and unit studies

The contribution of the various hippocampal regions to the maintenance of epileptic activity, induced by stimulation of the perforant path or commissural system, was examined in the awake rat. Combination of multiple-site recordings with silicon probes, current source density analysis and unit recordings allowed for a high spatial resolution of the field events. Following perforant path stimulation, seizures began in the dentate gyrus, followed by events in the CA3-CA1 regions. After commissural stimulation, rhythmic bursts in the CA3-CA1 circuitry preceded the activation of the dentate gyrus. Correlation of events in the different subregions indicated that the sustained rhythmic afterdischarge (2-6 Hz) could not be explained by a cycle-by-cycle excitation of principal cell populations in the hippocampal-entorhinal loop. The primary afterdischarge always terminated in the CA1 region, followed by the dentate gyrus, CA3 region and the entorhinal cortex. The duration and pattern of the hippocampal afterdischarge was essentially unaffected by removal of the entorhinal cortex. The emergence of large population spike bursts coincided with a decreased discharge of interneurons in both CA1 and hilar regions. The majority of hilar interneurons displayed a strong amplitude decrement prior to the onset of population spike phase of the afterdischarge. These findings suggest that (i) afterdischarges can independently arise in the CA3-CA1 and entorhinal dentate gyrus circuitries, (ii) reverberation of excitation in the hippocampal-entorhinal loop is not critical for the maintenance of afterdischarges and (iii) decreased activity of the interneuronal network may release population bursting of principal cells.