Transition Metal Ion-binding Properties of a 14-Membered N2O2S2- Macrobicyclic Ligand

The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N₂O₂S₂-macrobicycle. Metal picrates such as Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺,Cu²⁺ and Cd²⁺ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb²⁺ only among the other metals. The extraction constant (log K _ex) was determined to be 13.8 for Pb²⁺ complex.     

Production of123I on linear electron accelerator using highly-enriched124Xe

Highly enriched xenon¹²⁴Xe /99.85%/ has been used for the experimental production of iodine¹²³I by the /,n/ reaction. As the radiation source served a 30–45 MeV electron beam produced by a linear accelerator and converted by a tungsten converter to -radiation. The yield and radionuclidic purity of¹²³I have been estimated, the content of isotopic impurities /¹²⁴I and¹²⁵I/ being for 30 MeV irradiations lower than 4×10^–3%/.     

A Deodhar-type stratification on the double flag variety

We describe a partition of the double flag variety G/B⁺ × G/B^- of a complex semisimple algebraic group G analogous to the Deodhar partition on the flag variety G/B⁺. This partition is a refinement of the stratification into orbits both for B⁺ × B^- and for the diagonal action of G, just as Deodhar's partition refines the orbits of B⁺ and B^-. We give a coordinate system on each stratum, and show that all strata are coisotropic subvarieties. Also, we discuss possible connections to the positive and cluster geometry of G/B⁺ × G/B^-, which would generalize results of Fomin and Zelevinsky on double Bruhat cells and Marsh and Rietsch on double Schubert cells.     

Stability of a swarm of air bubbles in an oscillating liquid

The phenomenon of the formation of a swarm of air bubbles in a liquid executing vertical oscillations within a vertical tube is described. The explanation for the mechanism of air entry into the liquid and the behavior of the individual minute bubbles was given in [1], In the present paper we examine a swarm of bubbles—an air cushion; the stability of this swarm is studied. The results of experimental studies and theoretical calculations are compared.     

Dislocation glide in GaN films grown by the lateral-overgrowth method induced by low-energy electron-beam irradiation

The effect of irradiation on the dislocation structure of epitaxial GaN films, grown by the lateral-overgrowth method, is studied using the electron-beam-induced current mode in a scanning electron microscope. Low-energy electron-beam irradiation is found to lead to the gliding basal-plane dislocations even at very low excitation levels. Changes in the relative contrast of two segments of adjacent basal-plane dislocations may also indicate dislocation movement in the prismatic planes.     

Deep-level optical spectroscopy of ZnTe

The variation of the deep-level spectrum of stoichiometric ZnTe in the various stages of its purification and annealing in saturated Zn vapor has been studied by low-temperature photoluminescence and IR Fourier spectroscopy. The relation between the concentration of the main residual impurities with complex formation probability is analyzed. We have succeeded in observing for the first time Z center emission in ZnTe, as previously in CdTe and ZnSe. This center is shown to be a multicharged impurity in ZnTe. The activation energies of these levels have been determined. A comparison of the data obtained by chemical analysis with optical spectra has led to a conclusion that this center is associated with isolated oxygen present on the metalloid sublattice. While this emission exhibits the same specific features in a number of II–VI compounds (a high recombination rate, narrow emission lines, extremely weak electron-phonon coupling), the positions of the levels in the band gap and the characteristic charge state distinguish ZnTe from CdTe and ZnSe. As a rule, the Z center forms in a material in decomposition of various complexes (for instance, of the complex responsible for the 1.65-eV emission in ZnTe) and disappears when the material is doped leading to formation of the same complexes. An assumption is put forward that this center creates the main compensating deep levels and is an essential component of easily forming complexes with impurities. Its position in the lower half of the ZnTe band gap (in contrast to ZnSe and CdTe) makes preparation of the n material difficult. Fiz. Tverd. Tela (St. Petersburg) 40, 1010–1017 (June 1998)