Energy transfer between Yb3+ and Er3+ ions in an Er,Yb:YAl3(BO3)4 crystal

The electron-excitation energy transfer between Er³⁺ and Yb³⁺ ions in Er,Yb:YAl₃(BO₃)₄ crystals has been investigated. Crystals with different concentrations of active ions have been grown, and their luminescence decay kinetics in the spectral range near 1 μm have been experimentally measured. The energy-transfer microparameters have been calculated. It is shown that, to correctly describe the energy transfer in Er,Yb:YAl₃(BO₃)₄ crystals, one must take into account the interactions of higher orders than dipole-dipole interactions.     

Optical spectroscopy and efficient continuous-wave operation near 2 μm for a Tm, Ho:KYW laser crystal

The growth, spectroscopy and lasing performance of a novel Tm,?Ho:KY(WO₄)₂ crystal are reported. The peak emission cross-section of the Ho^{3+ 5}I₇→⁵I₈ transition and lifetime of the ⁵I₇ excited state were determined to be 4.8×10^?20 cm² and 1.8 ms, respectively, in a spectral range at around 2060 nm. Using a Ti:sapphire laser as a pump source at 802 nm, a maximum slope efficiency of up to 44% has been achieved with a corresponding output power of 460 mW at 2056 nm during continuous-wave operation of a Tm,?Ho:KY(WO₄)₂ laser at room temperature. A tuning range of 1890–2080 nm has been demonstrated.     

Double-β decay of116Cd

The NEMO-2 tracking detector located in the Fréjus Underground Laboratory was designed as a prototype of the detector NEMO-3 to study 0ν and 2ν double-beta decay (ββ) physics. After ten months of nearly continuous running with an enriched cadmium source (0.92 mol·y of¹¹⁶Cd) aββ2ν half-life ofT _1/2=(3.75±0.35(stat)±0.21(syst))·10¹⁹ y was measured. Limits with 90% CL on the¹¹⁶Cd half-lives of 5.0·10²¹ y forββ0ν decay and of 1.2·10²¹ y forββ0νχ ⁰ decay with a Majoron (χ ⁰) were obtained. Theoretical predictions for 0ν and 2ν decays of¹¹⁶Cd are also presented.     

Study of the effect of ammonium sulfate additives on the structure and photocatalytic activity of titanium dioxide

Thermal hydrolysis of titanium hydrochloride in the presence of ammonium sulfate added in a Ti: SO ₄ ^2? = 20: 1 ratio was used to obtain samples of mesoporous titanium dioxide with anatase structure, stable in a wide temperature range. The phase composition, porous structure, and morphology of the synthesized titanium dioxide powders were examined by X-ray phase analysis, IR spectroscopy, scanning electron microscopy, and low-temperature adsorption of nitrogen. The role played by sulfate ions in how the microstructure of titanium dioxide is formed was determined. The effect of the hydrolysis temperature on the structure of titanium dioxide being obtained and on its photocatalytic activity in the reaction of decomposition of Methyl Orange dye was examined.     

Elastic and moisture-resistant compounds based on mixtures of oligotetraurethane diepoxide,epoxy-diane resin,and aromatic diamine

Elastic and cold-resistant compounds based on oligodiene tetraurethane diepoxide and ED-20 epoxy-diane resin were obtained. The structure of compounds formed upon curing of the reaction mixture with aromatic diamine was studied. The advantages of new compounds in terms of physicomechanical and adhesion properties compared to a compound containing no ED-20 resin are demonstrated.     

Substrate requirements of phospholipase D from Streptomyces netropsis in the transphosphatidylation synthesis of phospolipids

The effect of the structure of the phospholipid substrate on the yield of phosphatidyl-5′-thymidine by transphosphatidylation catalyzed by phospholipase D from Streptomyces netropsis was studied. The reaction and product yield depended on the structures of the polar and nonpolar parts, the hydrophobic-hydrophilic balance, and the degree of unsaturation of the fatty-acids in the phospholipid substrate. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 26–29, January–February, 2006.     

Effect of structure of polar head of phospholipids on their fragmentation during γ-irradiation of model membranes

The ability of phospholipids with different structures of the polar head (phosphatidylpropandiol, phosphatidylglycerol, phosphatidylinositol, and cardiolipin) to sustain radiation-induced fragmentation was studied. It was shown by thin-layer chromatography and MALDI-TOF mass spectroscopy that all test lipids entering the composition of model membranes subjected to γ-irradiation suffered fragmentation yielding phosphatidic acid. The radiation-chemical yield of phosphatidic acid increased in this phospholipid series on passing from phosphatidylpropanediol to cardiolipin.     

Condensed Isoquinolines. 14. Spirocyclic Systems Containing a Benzo[5,6][1,2,4]thiadiazino[4,3-b]isoquinoline Ring

We propose a convenient preparative method for synthesis of derivatives of novel heterospirane systems with a benzo[5,6][1,2,4]thiadiazino[4,3-b]isoquinoline ring, based on the reaction of 1-(2-bromomethylphenyl)-1-cyclopentanecarbonitrile and 4-(2-bromomethylphenyl)-3,4,5,6-tetrahydro-2H-pyran-4-carbonitrile with o-aminobenzenesulfamide.     

Yb3+:KY(WO4)2 laser with a fast saturable absorber

Quantum-well semiconductor structures with superlattice barriers and reduced recovery time of absorption are designed and manufactured. A saturable absorption mirror based on such a structure is used in the Yb³⁺:KY(WO₄)₂ laser. The mode locking at a repetition rate of 70 MHz yields an almost bandwidth-limited pulse with a duration of about 115 fs. The maximum mean power (1.57 W) is comparable with a CW power of 1.62 W, which indicates a relatively low level of nonsaturable loss in the saturable absorption mirror.     

Molecular simulation of LiCl aqueous solutions

Non-primitive LiCl aqueous electrolyte solutions were studied at 1.0, 5.0 and 10.0 M concentrations by molecular dynamics simulations. It was observed that the ion hydration structure is progressively lost with increasing concentration. The ions are aggregated in small clusters at C = 1.0 M. However, at this concentration, two large clusters were detected that are an initial step in an aggregation process. At C = 5.0 M, the highly unstable ion clustering seems to correspond to an intermediary state between low concentration states with poor aggregation and states where the ions are highly aggregated, as observed at C = 10.0 M where almost all the ions are clustered in one cluster. This cluster does not present a crystal-like structure. The high solubility of LiCl in aqueous solutions can consequently be explained as a result of the large radii difference between the anion and the cation that results in the instability of the ionic aggregates, which makes the formation of crystal seeds difficult.