Evidence for the formation of two types of oxygen interstitials in neutron-irradiated α-Al2O3 single crystals.

Due to unique optical/mechanical properties and significant resistance to harsh radiation environments, corundum (α-Al2O3) is considered as a promising candidate material for windows and diagnostics in forthcoming fusion reactors. However, its properties are affected by radiation-induced (predominantly, by fast neutrons) structural defects. In this paper, we analyze thermal stability and recombination kinetics of primary Frenkel defects in anion sublattice - the F-type electronic centers and complementary oxygen interstitials in fast-neutron-irradiated corundum single crystals. Combining precisely measured thermal annealing kinetics for four types of primary radiation defects (neutral and charged Frenkel pairs) and the advanced model of chemical reactions, we have demonstrated for the first time a co-existence of the two types of interstitial defects - neutral O atoms and negatively charged O- ions (with attributed optical absorption bands peaked at energies of 6.5 eV and 5.6 eV, respectively). From detailed analysis of interrelated kinetics of four oxygen-related defects, we extracted their diffusion parameters (interstitials serve as mobile recombination partners) required for the future prediction of secondary defect-induced reactions and, eventually, material radiation tolerance.

Atomic, electronic and magnetic structure of an oxygen interstitial in neutron-irradiated Al2O3 single crystals.

A single radiation-induced superoxide ion [Formula: see text] has been observed for the first time in metal oxides. This structural defect has been revealed in fast-neutron-irradiated (6.9×1018 n/cm2) corundum (α-Al2O3) single crystals using the EPR method. Based on the angular dependence of the EPR lines at the magnetic field rotation in different planes and the determined g tensor components, it is shown that this hole-type [Formula: see text] center (i) incorporates one regular and one interstitial oxygen atoms being stabilized by a trapped hole (S = 1/2), (ii) occupies one oxygen site in the (0001) plane being oriented along the a axis, and (iii) does not contain any other imperfection/defect in its immediate vicinity. The thermal stepwise annealing (observed via the EPR signal and corresponding optical absorption bands) of the [Formula: see text] centers, caused by their destruction with release of a mobile ion (tentatively the oxygen ion with the formal charge -1), occurs at 500-750 K, simultaneously with the partial decay of single F-type centers (mostly with the EPR-active F+ centers). The obtained experimental results are in line with the superoxide defect configurations obtained via density functional theory (DFT) calculations employing the hybrid B3PW exchange-correlation functional. In particular, the DFT calculations confirm the [Formula: see text] center spin S = 1/2, its orientation along the a axis. The [Formula: see text] center is characterized by a short O-O bond length of 1.34 Å and different atomic charges and magnetic moments of the two oxygens. We emphasize the important role of atomic charges and magnetic moments analysis in order to identify the ground state configuration.

Distinctive features of diffusion-controlled radiation defect recombination in stoichiometric magnesium aluminate spinel single crystals and transparent polycrystalline ceramics.

MgAl2O4 spinel is important optical material for harsh radiation environment and other important applications. The kinetics of thermal annealing of the basic electron (F, F+) and hole (V) centers in stoichiometric MgAl2O4 spinel irradiated by fast neutrons and protons is analyzed in terms of diffusion-controlled bimolecular reactions. Properties of MgAl2O4 single crystals and optical polycrystalline ceramics are compared. It is demonstrated that both transparent ceramics and single crystals, as well as different types of irradiation show qualitatively similar kinetics, but the effective migration energy Ea and pre-exponent D0 are strongly correlated. Such correlation is discussed in terms of the so-called Meyer-Neldel rule known in chemical kinetics of condensed matter. The results for the irradiated spinel are compared with those for sapphire, MgO and other radiation-resistant materials.

[Glycosilated derivatives of substituted hydroxylamine. II. Phase transfer synthesis and investigation of glycosyl transfer reaction of glucosaminides of substituted hydroxylavine].

1-(2-Acetamido-3,4,6,-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyloxy)-benzotriazole reacted in boiling dichloromethane, in the presence of Luis acids as a promotors with primary and secondary aliphatic and cycloaliphatic alcohols and diisopropilidene galactose with alkyl-O-1,2-trans-glucosaminides formation. It was shown that the other glucosaminides of substituted hydroxylamine are not participated in this reaction. Structures of glucosaminides were identify by 1H-NMR-spectroscopy and comparison with known compounds.

Thermoluminescence centres created selectively in MgO crystals by fast neutrons.

A possibility of using the thermoluminescent detection of collision-created interstitial centres in MgO by the TL peak at 700 K, arising at the radiative recombination of anion interstitials with F+ centres, for the selective detection of fast neutrons in mixed neutron-gamma fields, is examined. Selectivity and sensitivity of such a detector are discussed. For the present time, the sensitivity of the thermoluminescent detection of anion interstitials created by neutron irradiation is comparable to that of the EPR detection of F+ centres, the main limitations of the thermoluminescence method being connected with the background thermoluminescence and absence of suitable luminescence centres in this temperature region, when undoped and untreated MgO crystals are used. Possible ways to overcome these shortcomings are discussed.

[Accumulation of anomalous glycopolymers in the walls of main lymphatic vessels of the extremities in patients with chronic lymphedema]. / Nakoplenie anomal'nykh glikopolimerov v stenke magistral'nykh limfaticheskikh sosudov konechnostei cheloveka pri khronicheskoi limfedeme.

Redistribution of lectin receptor sites in the mam-lymphatics of human extremities in primary and secondary lymphedema in comparison with normal lymphatics has been investigated using conjugates to peroxidase of LCA, PNA, RCA, SBA, WGA and LAA. Chronic lymphedema caused no essential differences in lectin binding to tissue structures of intima and adventitia: endotheliocytes were strong reactive both with LCA, PNA, WGA and LAA; all lectins used bound fibrillary structures in subendothelial layer and adventitia. On the opposite, tunica media of main lymphatics in primary lymph stasis displayed accumulation of LCA-, PNA-, SBA- and LAA-binding deposits round smooth myocytes. When PNA used, the appearance of a specific "wide loop shaped reticulum" within lymphatics media in lymph stasis was observed. We consider, that lectin receptor sites accumulation phenomenon reflects some changes in smooth myocytes metabolism, possibly caused by dystrophia of these cell population with consequent incomplete glycosylation of synthesized glycopolymers.

[Effect of mineral-ammonium preparation MP-15 on nitrogen metabolism and performance of young bulls in press fattening]. / Vliianie mineral'no-ammoniinogo preparata MP-15 na azotistyi obmen i produktivnost' bychkov pri otkorme na zhome.

Introduction of the mineral-ammonium preparation MP-15 to the diet of fattings during 140 days of the experiment resulted in 10.5% rise of their performance. The preparation MP-15 is shown to activate nitrogen metabolism, increases the buffer capacity and concentration in blood of calcium and phosphorus.

[Carboxylation processes in cattle with different levels of productivity]. / Osoblyvosti protsesiv karboksyliuvannia u velykoï rohatoï khudoby riznoho rivnia produktyvnosti

The experiments were conducted on bulls-analogs of the black-piebald and Simmental breed which differ from each other in the intensity of live weight gain (18-31%) as well as on lactating cows-analogs of the black-piebald breed which differ in the level of milk productivity (41-80%). The intensity of the carboxylation processes (CO2 fixation) as well as of protein and lipids biosynthesis in the liver of the bulls from a heavy-producing group (the second group) is shown to be considerably higher than in the low-producing animals (the first group). In venous blood plasm of the second group bulls the content of urea and citrate was higher (by 29-141 and 33%, respectively) than in the first group animals. Blood plasma of the lactating cows from a heavy-producing group contains more urea (57-70%), citrate (146-80%) and total protein (10-14%) than that of animals with low milk productivity. Similar regularity is also observed as to the amount of urea and citrate of milk of cows with a higher milk productivity (by 40-50 and 51-53% higher respectively, than in the low-productive animals).