Embrittlement of low-alloy structural steel by neutron irradiation

The radiation embrittlement of reactor vessel materials is a complex process, which depends on the conditions of irradiation and the microstructure and chemical composition of the steel. It is universally acknowledged that phosphorus, copper, and nickel intensify the radiation embrittlement of vessel material the most. It is believed that Mn, N, C, Mo, Si, As, Sn, V, and other elements also influence radiation embrittlement, but their effect has not been definitely established and is much less than the effect of phosphorus, copper, and nickel. The presence of a synergetic interaction of elements in the irradiation process and the complex interaction of metallurgical factors and the irradiation conditions make it difficult to determine the degree to which impurities and alloying elements influence radiation embrittlement. The effect of the chemical composition of steel, as one of the most important parameters determining the radiation service life of vessel material, on radiation embrittlement is studied, 5 figures, 1 table, 20 references. Translated from Atomnaya énergiya. Vol. 88, No. 4, pp. 271–276, April, 2000.     

Synthesis of lanthanum chromite using the sol-gel method

Synthesis of lanthanum chromite using the sol-gel method is considered. The effect of the amount of gel-forming agent and the heat treatment time and temperature on the completion of synthesis is investigated. The optimum parameters of the process are presented. The possibility of replacing the powder obtained by vibration crushing of electrically melted lanthanum chromite with powder synthesized by the sol-gel method in the production of miniature ceramic articles is demonstrated. Translated from Steklo i Keramika, No. 6, pp. 15 – 17, June, 1998.     

Novel spray-dried PHA microparticles for antitumor drug release

The production of poly-3-hydroxybutyrate (P3HB) and poly-3-hydroxybutyrate/polyethylene glycol (PEG)-based microparticles, loaded with antitumor drugs paclitaxel (PTX) and 5-Fluorouracil (5-FU) by spray-drying technique, was investigated. The average diameter of microparticles was found to be 3.4?±?0.5?µm and zeta potential was about ?44?mV. The addition of surfactant PEG did not show any effect on the morphological characteristics of the particles. But the chemical structure of drug influenced on the properties. Microparticles had heterogeneous pores on the surface when the hydrophobic PTX was encapsulated. It was established that the addition of surfactant positively influenced on the properties of particles and led to the loading of 5-FU directly into the matrix. This is confirmed by the results of electron microscopy and dynamics of drug release in vitro. As a whole, the release profiles of PTX and 5-FU from composite P3HB/PEG microparticles were less than from P3HB microparticles. The results of the morphological evaluation of Hela cells demonstrated that the use of cytostatic drugs loaded in P3HB microparticles induces morphological changes associated with apoptosis (chromatin condensation, core fragmentation, margination of nucleus). Thus, the obtained results can serve as the basis for the development of new antitumor drugs of prolonged action, intended for various modes of administration.     

Two-electron exchange between neutral and ionized negative-<Emphasis Type="Italic">U</Emphasis> tin centers in lead chalcogenides

Two-electron exchange between neutral and doubly ionized negative-U tin centers in PbS and PbSe has been studied by Mössbauer emission spectroscopy. The activation energy for this process in PbS is 0.11(2) eV, which is comparable to the depth of tin levels in the band gap of PbS, whereas the activation energy for this process in PbSe, 0.05(1) eV, is comparable to the correlation energy of negative-U donor tin centers in PbSe. The exchange occurs through simultaneous transfer of two electrons and involves valence band states.     

Liquidus Temperatures of Cryolite Melts With Low Cryolite Ratio

The effect of calcium fluoride on liquidus temperatures of the cryolite melts with a low cryolite ratio (CR) was studied. The systems KF-NaF-AlF₃ and KF-LiF-AlF₃ with CRs of 1.3, 1.5, and 1.7 have been investigated. The liquidus curves of systems containing CaF₂ are different and depend on the K/(K + Na) and K/(K + Li) ratios. In potassium cryolite with CRs of 1.3 and 1.5, the calcium fluoride solubility is low and increases with NaF (LiF) concentration.     

The characteristics of neuroendocrine regulatory disorders in acute myocardial infarct in relation to the severity of the course of the disease

A total of 45 patients aged 35 to 73 years who had sustained acute myocardial infarction (MI) were studied in a special cardiological unit. On days 1, 5, 14, 28 of hospital stay, each patient underwent measurements of cortisol, insulin, T3 and T4 and calculations of the mathematical clinic severity index after G.I. Marchuk et al. In acute MI, there were elevated plasma levels of cortisol depending on the MI severity with a small repeated peak of its increase on day 14 and its subsequent decrease, except deaths. In severe acute MI there were impairments of reciprocal cortisol/insulin ratios. This was particularly pronounced in patients with lethal outcomes. By the end of hospital rehabilitation, patients with acute MI displayed lower levels of thyroidal hormones. The maximum decrease in T3 and T4 was found in patients with lethal outcomes. There was a direct correlation between the mathematical clinical severity index of the natural history of acute MI and the levels of cortisole triidothyronine at the hospital stage of observation. In the course of the study it was found that the Marchuk clinical severity index serves as an informative severity index of MI course whose determination in its acute period allows one to predict the course of acute MI and to choose a differential therapy of and to make a diagnosis of possible complications.