Temperature and frequency dependence of the spin-lattice relaxation times of E′1 centers in neutron-irradiated quartz glass

Results are reported for measurements of the spin-lattice relaxation times of E′₁ centers in quartz glass, produced by neutron irradiation, with the measurements made at two frequencies 9.25 and 24.0 GHz over a wide temperature interval 1.5–300 K. The experimental data are interpreted on the basis of interaction mechanisms of the spins with two-level systems with excitation energies ∼6, ∼26, and ∼420 cm⁻¹. A small modification of the existing theory allows us to explain a number of features of the observed temperature and frequency dependence of the relaxation rate. The results are compared with the data available in the literature on spin-lattice relaxation of irradiation centers in crystalline quartz and quartz glass. Fiz. Tverd. Tela (St. Petersburg) 39, 1335–1337 (August 1997)     

Electron-impact mass spectra of natural phenylethanoids

The electron-impact mass spectra of a number of phenylpropanoids and iridoid glycosides containing a phenylethanoid fragment in their structure have been studied. This has revealed features of the formation of fragments of 4-hydroxyphenylethyl and 3,4-dihydroxyphenylethyl alcohols and also of fragments of phenylethylamine and indolylethylamine derivatives present in the structures of the compounds investigated.     

NMR excitation by an electric field as a dynamic manifestation of magnetoelectric and antiferroelectric interactions

The possibility of excitation of NMR signals by an ac electric field in magnetically ordered crystals is discussed. Such signals can be recorded using the time-dependent component of the electric polarization vector. It is assumed that the electric and magnetic characteristics are coupled to each other through magnetoelectric and antiferroelectric interactions. Several types of magnetic structures are analyzed in which these interactions are not forbidden by symmetry. Such structures include two-sublattice single-position ferro-and antiferromagnetic phases in centrosymmetrical crystals, two-sublattice magnetic crystals without a center of symmetry (such as KNiPO₄), and four-sublattice antiferromagnetic crystals with three types of antiferromagnetism vectors (such as Cr₂O₃ and α-Fe₂O₃).     

Conditions of stability of magnetic sublattices at exchange mixing of states with different spins

The conditions of compatibility of the magnetic sublattice hypothesis with the requirements of quantum theory have been derived. These conditions imply the presence of (even weak) magnetic anisotropy and a macroscopic number of spins in the sublattice.     

Glycosides of cinnamyl alcohol from the rhizomes ofRhodiola rosea

Three new cinnamyl alcohol glycosides have been isolated for the first time from the rhizomes of roseroot stonecropRhodiola rosea L. (Sedum rosea). On the basis of chemical transformations and the results of UV, IR, PMR, and mass spectroscopy the following structures are proposed for the compounds isolated: rozin — trans-cinnamyl O-β-D-glucopyranoside; rozavin — transcinnamyl O-(6′-O-α-L-arabinopyranosyl-β-D-glucopyranoside); and rozarin — trans-cinnamyl O-(6′-O-α-L-arabinofuranosyl-β-glucopyranoside).     

Fischer-Tropsch Catalysts Based on Zr-Fe Intermetallides Encapsulated in an Al2O3/Al Matrix

ZrFe and ZrFe₂ intermetallides in an Al₂O₃/Al cermet matrix are reported as catalysts for the fixed-bed Fischer-Tropsch synthesis, and the effects of some preparation conditions on their texture, structural, mechanical, and catalytic properties are discussed. A nonmonotonic dependence of their catalytic activity on the size of interametallide particles is observed. The selectivity, activity, and mechanical strength of the composites depend on the calcination temperature and on the place of the hydriding step in the catalyst preparation procedure. In terms of volumetric efficiency, the catalysts prepared are comparable with bulk, unencapsulated intermetallides and are among the most efficient iron-containing catalysts known to date.     

Flavonoids of the peel of the fruit ofCitrus unshiu

Institute of Biochemistry, Academy of Sciences of the Georgian Republic, Tbilisi, and Samara Medical Institute, Russia. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 821–822, November–December, 1994.     

Flavonoids of the buds of Populus balsamifera

D. I. Ul'yanov Kuibyshev Medical Institute. All-Union Scientific-Research Institute of Medicinal Plants Scientific-Industrial Association Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 272–273, March–April, 1990.     

Synthesis of Nonracemic 9-(1-Methoxycarbonylethyl)-1,2,3,4-tetrahydrocarbazole

A new approach has been proposed to the synthesis of indole derivatives containing a chiral substituent at the nitrogen atom, comprizing Fischer indolization of phenylhydrazines with a chiral substituent at the -nitrogen atom. The initial hydrazines were obtained by the alkylation (Mitsunobu reaction applying optically active esters of lactic acid) of anilines containing an electron-accepting substituent at the amino group. Subsequent removal of the activating acceptor grouping was realized by nitrosation of the chiral secondary aniline followed by reduction of the corresponding N-nitroso compound.