Photochemical properties of photosystem 1 immobilized in a mesoporous semiconductor matrix

The pigment-protein complex of photosystem 1 (PS1) isolated from cyanobacterium Synechocystis sp. PCC 6803 has been adsorbed on a solid mesoporous film made from TiO₂ nanoparticles. was on The TiO₂ film supported on a glass substrate with a surface area of 1 cm² adsorbs up to 0.045 nmol of PS1. PS1 molecules are distributed in the pores of the mesoporous support. Immobilization has an insignificant effect on the optical and photochemical properties of PS1. A reversible photoinduced EPR signal from the oxidized primary electron donor P700 of immobilized PS1 has been detected. It has been shown by photoelectrochemical methods that the photoexcitation of PS1 results in electron injection from PS1 to the conduction band of TiO₂.     

Influence of porous-coating thickness on the stability and transition of flat-plate supersonic boundary layer

In the present study, we examined, both experimentally and theoretically, the influence of porouscoating thickness on the stability and laminar-turbulent transition of flat-plate supersonic boundary layer at free-stream Mach number M_∞ = 2. A qualitative agreement between the data calculated by the linear theory of stability and the experimental data on the transition obtained for models with different porous-coating thicknesses was established. We show that with decreasing (within a certain interval) the porouscoating thickness the boundary layer becomes more stable to perturbations, and the laminar-turbulent transition, more delayed.     

Vibrational spectra of Fe<Subscript>3</Subscript>P and Fe<Subscript>2</Subscript>P metal-metalloid compound crystallites: Phonon and breather excitations

The spectra of small-amplitude single-phonon vibrations and large-amplitude nonlinear multiphonon vibrations of Fe₃P and Fe₂P metal-metalloid compound crystallites are investigated. The vibrational spectra of 3D crystallites of gradually increasing volumes are calculated within a microscopic approach using previously tested interatomic interaction potentials. The calculated energy of the main low-frequency peak is closer to its experimental value in comparison with previous calculations, which reduces the significant discordance between the experimental and theoretical spectra. The fine structure of the high-frequency part of the vibrational spectrum is discussed. A study of large-amplitude nonlinear vibrations (which determine the diffusion of atoms and dispersive processes in materials) showed that a specific nonlinear breather mode of vibration can be generated in the crystallites in question, which is a genetic precursor of nonlinear self-localized vibrations.     

Synthetic utilization of polynitroaromatic compounds. 2. Synthesis Of 4,6-dinitro-1,2-benzisothiazol-3-ones and 4,6-dinitro-1, 2-benzisothiazoles from 2-benzylthio-4,6-dinitrobenzamides

Cyclization of 2-benzylthio-4,6-dinitrobenzamides to 4,6-dinitro-1, 2-benzisothiazol-3-ones was achieved using SO(2)Cl(2) in CH(2)Cl(2) at room temperature. Alkylation of these heterocycles proceeded in a nonregioselective manner to yield a mixture of corresponding O- and N-alkylated products. Oxidation of 4,6-dinitro-1,2-benzisothiazoles (50% H(2)O(2) in AcOH) afforded the corresponding S-oxides and S, S-dioxides, depending on oxidation conditions. Unexpectedly, oxidation of a 3-methoxy derivative resulted in ring opening with the formation of the corresponding sulfamide. Chlorination of these 4,6-dinitro-1,2-benzisothiazol-3-ones (PCl(5)-POCl(3)) gave the expected 3-chloroisothiazoles.     

Triterpene glycosides and their genins from Thalictrum foetidum. III. The structure of cyclofoetoside A

A new glycoside of the cycloartane series — cyclofoetoside A — has been isolated from the epigeal part ofThalictrum foetidum L., and its structure has been established on the basis of chemical transformations and spectral characteristics as 24S-cycloartane-3,16,24,25-tetraol 3-0--L-arabinopyranoside 16-0-[0--L-rhamnopyranosyl-(16)--D-glucopyranoside].Pyatigorsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR; Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 66–71, January–February, 1986.     

Triterpene saponins fromThalictrum minus. VIII. Structure of thalicoside D

Thalicoside D — a new triterpene glycoside isolated fromThalictrum minus L. (Ranunculaceae) — has the structure of oleanolic acid 3-O-[O--L-rhamnopyranosyl-(12)-O--D-glucopyranosyl-(14)--L-arabinopyranoside 28-O-[O--D-glucopyranosyl-(16)--D-glucopyranoside]. This structure was established by the use of the results of acid and alkaline hydrolyses, SIMS spectra, and one- and two-dimensional NMR spectroscopy.Deceased.Irkutsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan [IKhRV AN RUz], Tashkent, FAX (3712) 62 73 48. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 398–403, May–June, 1994.     

Triterpene saponins fromThalictrum minus. IV. The structure of thalicoside A

The predominating saponin, which has been called thalicoside A, has been isolated from low meadow rue (Thalictrum minus). It has been established by chemical and spectral methods that thalicoside A is 3,16,22(S),29-tetrahydroxy-9,19-cyclo-20(S)-lanost-24-ene 3-O--D-galactopyranoside 29-O--D-glucopyranoside.Irkutsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 213–219, March–April, 1984.     

Furnace chemical vapor deposition bismuth-doped silica-core holey fiber

A bismuth-doped-pure-silica holey fiber is fabricated using a fiber preform made by the furnace chemical vapor deposition method. The spectroscopic properties of the fiber are studied, and laser action at λ=1450 nm with an efficiency of 12% is demonstrated.     

Novel mid-IR laser based on hybrid AlGaAsSb/InAs/CdMgSe heterostructure

We report on the development of a novel design of a mid-IR laser combining III–V and II–VI compounds in a “hybrid” double heterostructure. It possesses large (1.5 eV) potential barriers both for injected electrons and holes, suppressing their leakage from the active region, and provides strong optical confinement. An AlGaAsSb/InAs/CdMgSe laser diode with a III–V/II–VI heterovalent interface at the 0.6 μm-InAs active region has been grown by molecular beam epitaxy on an InAs substrate. Despite a far from optimal defect density at the CdMgSe/InAs interface and high losses inherent for bulk active region of the laser, the structure demonstrates lasing at 2.8 μm (up to 100 K) in the pulsed regime with a threshold current density of 3–4 kA/cm². Type II InSb monolayer insertions into an InAs layer show bright photoluminescence at 3.8 μm (77 K), confirming the great potential of the InAs-based nanostructure active region for longer wavelength applications.