Thermal conductivity of crystalline chrysotile asbestos

The thermal conductivity of crystalline chrysotile asbestos made up of hollow tubular Mg₃Si₂O₅(OH)₄ filaments is measured in the range 5–300 K. The paper discusses the possibility of using this material in studies of the thermal conductivity of thin filaments of metals and semiconductors incorporated into the channels of crystalline chrysotile asbestos tubes.     

Long-wavelength optical phonons in the ZnTe/Zn<Subscript>0.8</Subscript>Cd<Subscript>0.2</Subscript>Te superlattice

The lattice IR reflection spectra of a ZnTe/Zn_0.8Cd_0.2Te superlattice measured at temperatures of 300 and 10 K are analyzed. The ZnTe/Zn_0.8Cd_0.2Te superlattice is grown by molecular-beam epitaxy on a GaAs substrate with a ZnTe buffer layer. It is found that the lattice IR reflection spectra of the studied structure exhibit only one reflection band. Dispersion analysis of the experimental spectrum has revealed the presence of one lattice TO mode close in frequency to the mode of pure ZnTe. This result is explained by a shift in the frequency of the lattice modes of the ZnTe and Zn_0.8Cd_0.2Te layers of the superlattice toward each other. In turn, this shift is caused by internal elastic stresses in the superlattice due to a mismatch between the lattice parameters of the materials of these layers.     

Beryllium (boron) clustering quest in relativistic multifragmentation (BECQUEREL Project)

A physical program of irradiation of emulsions in beams of relativistic nuclei named the BECQUEREL Project is reviewed. It is destined to study in detail the processes of relativistic fragmentation of light radioactive and stable nuclei. The expected results would make it possible to answer some topical questions concerning the cluster structure of light nuclei. Owing to the best spatial resolution, the nuclear emulsions would enable one to obtain unique and evident results. The most important irradiations will be performed in the secondary beams of He, Be, B, C, and N radioactive nuclei formed on the basis of JINR Nuclotron beams of stable nuclei. We present results on the charged state topology of relativistic fragmentation of the ¹⁰B nucleus at low energy-momentum transfers as the first step of the research.     

Polyaniline/12-phosphotungstic acid/V<Subscript>2</Subscript>O<Subscript>5</Subscript> nanocomposite and its platinum analog as oxygen reduction electrocatalysts

A guest-host nanocomposite based on electroconducting polyaniline doped with 12-phosphotungstic acid and V₂O₅ as well as its bifunctional analog containing not more than 5 mass% nanosized platinum were obtained. A study was carried out on the structure of these nanocomposites, their redox characteristics, and electrocatalytic activity in the reduction of oxygen. These nanocomposites were found to display catalytic properties in the electrochemical reduction of oxygen, while the presence of even a slight amount of nanosized platinum in the bifunctional composite leads to a significant increase in its electrocatalytic activity. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 307–314, September–October, 2007.     

Five Novel Taccalonolides from the Roots of the Vietnamese Plant Tacca paxiana

Chemical investigation of the roots of the Vietnamese plant Tacca paxiana resulted in the isolation of five new steroidal compounds, taccalonolide R ( 6 ), S ( 7 ), T ( 8 ), U ( 9 ), and V ( 10 ). Their structures were established on the basis of NMR and mass‐spectral data. In addition, the five known taccalonolides A ( 1 ), B ( 2 ), E ( 3 ), K ( 4 ), and N ( 5 ) were also isolated and identified.     

Zur maassanalytischen Bestimmung der Phosphors?ure mit Uranl?sung

Ohne Zusammenfassung     

Study of the dissolution and growth of salt single crystals in inhomogeneous acoustic fields: I. A standing acoustic wave

The growth of the isolated (100) face of a KDP crystal at exposure of the phase boundary to the initial ultrasound field and a standing acoustic wave has been investigated. A significant growth response of this face, exposed to sound normally along the acoustic axis in the near zone of a piston-like half-wave vibrator with f = 20 kHz and tangentially in the pulsed two-frequency (f = 600 and 900 kHz) standing-wave mode, has been revealed. It is shown that the mechanisms of mass exchange enhancement in these acoustic modes are different. The results obtained show a fundamental possibility of controlling crystal growth and dissolution by varying the parameters of inhomogeneous acoustic field.     

Doping of KDP single crystals with cerium: Growth and optical properties

The features of doping of KDP crystals with cerium ions and organocerium complexes with alizarin complexon and arsenazo III have been investigated. It is established that “direct” doping by introducing cerium salts into the initial solution cannot be implemented. The effect of organometallic complexes of cerium on the crystal growth has been studied. Organocerium complexes predominantly enter the prismatic or pyramidal growth sectors. It is shown that the complex arsenazo III + Ce blocks the growth of the prismatic sector. Cerium-doped KDP crystals exhibit a photoluminescence band peaking at the wavelength λ_max= 350 nm.