Chemistry and application of organic isocyanates,IX. Conversion of tolylene-2,4-diisocyanate into urethane derivatives by means of heptane-1,4,7-triol

Investigations on the conversion of tolylene-2,4-diisocyanate (2,4-TDI or TDI) with heptane-1,4,7-triol 1,4,7-HPT or HPT) at 55–85°C and various molar ratios of starting materials are described. By means of mass spectroscopic analysis and gel permeation chromatography, molecular weights of six oligomers and their percent contents in the products have been estimated. Moreover, a scheme of the formation of all prepared isocyanate prepolymers has been proposed. It has been shown, that apart from oligomers having the structures resulting from the reaction of 1,4,7-HPT with the isocyanate group in the position “4”, reaction products contained oligomers, which confirmed the reactivity of isocyanate group in the position “2”, too.     

The assessment of therapeutic effectiveness of paravertebral blockades in patients with painful radicular syndromes in discopathy and in lumbar spine spondylosis

A group of 103 patients were examined for radicular painful syndromes in lumbar discopathy and lumbar spondylosis. Fifty-eight were treated by placing them in spine-decompressing position, traction and therapeutic exercises. The group of 45 patients had additionally paravertebral blockade (steroid + a local anaesthetic). In the blockade group the therapeutic effects were better, with rapid reduction of acute pain, with wellbeing improvement and better comfort, which facilitated further stages of the treatment. This made possible shortening of hospital stay by 20%, on average, as compared with the group without blockade. In patients with shorter lasting radicular pains (below 2 months) the results after paravertebral blockade were significantly better than in cases with longer duration of pains (2-6 months).     

Freeze-fracture electron microscopic and low temperature X-ray scattering studies of the effect of cryofixation upon serum low density lipoprotein structure

We report here a correlated X-ray diffraction and freeze-fracture electron microscope study of the effects of several cryofixation procedures upon human serum low density lipoprotein (LDL₂) structure. Only when the LDL₂ solutions contained 75%, by weight, glycerol were the room temperature and post cryofixation low temperature LDL₂ X-ray scattering curves indistinguishable from one another. Other cryofixation procedures, slow or rapid, with or without glycerol, resulted in differences between the room temperature and low temperature LDL₂ X-ray scattering curves, in part due to the effect of quenching upon the solvent. Freezeetching electron microscopy of the slowly cryofixed LDL₂ showed marked aggregation of the particles and an unusual morphological appearance. In contrast, after rapid cryofixation or cryofixation in the presence of glycerol, freeze-etch electron microscopy revealed well-isolated particles which had a knobby morphology. The results demonstrate that under certain conditions (in the presence of 75% glycerol) cryofixation results in minimal, if any, structural alteration of, at least, the LDL₂ lipid moiety. Further, this study underlines the more general conclusion that any high resolution structural study employing a cryofixation step must be interpreted with caution and the effect of cryofixation upon the sample structure need be evaluated by independent means.     

Determination of copper in water by means of chalcocite copper ion-selective electrode

The possibility of determination of copper in natural waters was tested by direct potentiometry with chalcocite copper sensitive ion selective electrode. This can be carried out for the copper concentration down to 6 μg l⁻¹ when the standard additions procedure is used. The electrode characteristics was investigated and as a medium was proposed a TFB solution containing Tris, potassium fluoride and potassium nitrate. However at the extreme low concentrations of copper the water samples after addition of TFB should be heated to boiling. In these conditions the accuracy of determination for the average of five measurements is not worse than 25%, and precision is of the order of 20%.     

Analytical function for lidar geometrical compression form-factor calculations

A simple model of image formation in a Newtonian telescope was used for calculating an analytical formula, that describes the geometric compression form factors of coaxial and biaxial lidars. Calculations were successfully validated by comparison with real measurements, confirming the accuracy of our approach. The need for different alignment of coaxial and biaxial systems to increase the overlap between the lidar emitter and receiver is also discussed.     

Harmonische Analyse des Magnetisierungsstromes von Drehstromasynchronmotoren

Übersicht Es werden die von der Eisensättingung stammenden Oberwellen des Luftspaltfeldes, des Magnetisierungsstromes und der Strangspannung analysiert. Nach der Vorstellung des physikalischen Bildes dieser Oberwellen bei Stern- und Dreieckschaltung der Ständerwicklung werden die Ergebnisse der Messungen an speziell gebauten Käfigläufermotoren mit hoher Sättigung entweder der Ständerzähne oder des Ständerjoches berichtet.

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Contents Saturation harmonics of magnetic field in the air-gap, of the magnetizing current and of the phase voltage in three-phase induction motors are analysed. The physical picture of these harmonics is presented and the results of tests executed on specially manufactured squirrel-cage motors with highly saturated stator teeth or stator yoke are reported.

     

Effect of molybdenum on the kinetics of phase transformation of undercooled austenite in high-speed steels under continuous cooling

The aim of these investigations was to determine the effect of the ratio % Mo to % W in the austenite of high-speed steels on the kinetics of its transformation under continuous cooling. The investigations were carried out on model alloys. Three CCT curves were drawn. Also the influence of cooling velocity on the volume fraction of retained austenite in high-speed steels was evaluated. It was determined that with the increase of the Mo content in the high-speed steel matrix the M_S temperature decreases and the fraction of retained austenite increases, the development of the bainite transformation decreases and the stability of austenite increases in the range of diffusion transformations. With an increased cooling rate, the volume fraction of retained austenite decreases at first and then it increases. These changes are caused by the precipitation of carbides from undercooled austenite and can give rise to the differences in the content of retained austenite on the cross-section of quenched tools.