Orientational photorefractive effects observed in poly(vinyl alcohol)/liquid crystal composites

60 ) as a photoconductive sensitizer under an applied dc field. Orientational photorefractivity was demonstrated by observing Raman–Nath diffraction beams with an external dc field. The photorefractive gratings were partially memorized even in the absence of the applied dc field. Received: 12 January 1998/Revised version: 2 February 1998     

Effects of Dye‐Adsorption Solvent on the Performances of the Dye‐Sensitized Solar Cells Based on Black Dye

The effects of the dye‐adsorption solvent on the performances of the dye‐sensitized solar cells (DSSCs) based on black dye have been investigated. The highest conversion efficiency (10.6 %) was obtained in the cases for which 1‐PrOH and the mixed solvent of EtOH and tBuOH (3:1 v/v) were employed as dye‐adsorption solvents. The optimized value for the dielectric constant of the dye‐adsorption solvent was found to be around 20. The DSSCs that used MeOH as a dye‐adsorption solvent showed inferior solar‐cell performance relative to the DSSCs that used EtOH, 1‐PrOH, 2‐PrOH, and 1‐BuOH. Photo‐ and electrochemical measurements of black dye both in solution and adsorbed onto the TiO₂ surface revealed that black dye aggregates at the TiO₂ surface during the adsorption process in the case for MeOH. Both the shorter electron lifetime in the TiO₂ photoelectrode and the greater resistance in the TiO₂–dye–elecrolyte interface, attributed to the dye aggregation at the TiO₂ surface, cause the decrease in the solar‐cell performance of the DSSC that used MeOH as a dye adsorption solvent.     

Radial velocity profile reconstruction by Doppler spectroscopy measurements

An inversion method for plasma velocity determination was developed under the assumption of axial symmetry of plasmas. The specific right-hand side of equation (9) allows one to use experimental data without the need of differentiation which causes substantial reconstruction errors. The problem was formulated in the vorticity approach, and then Helmholtzs decomposition theorem for vector fields was used. Numerical simulation results for the algorithm verification, and real experimental data were applied for determination of radial velocity distribution.Received: 16 October 2002, Published online: 29 July 2003PACS: 07.05.Tp Computer modeling and simulation - 02.60.Cb Numerical simulation; solution of equations - 02.30.Zz Inverse Problems - 52.70.Kz Optical (ultraviolet, visible, infrared) measurementsA.L. Balandin: On leave from the Institute of System Dynamics and Control Theory, Irkutsk.     

Electrochemical synthesis of organosilicon compounds

Electrochemical reduction of allyl, vinyl, and aryl halides in the presence of a silylating agent (Me₃SiCl, HMe₂SiCl, or PhMe₂SiCl) afforded the corresponding organosilicon compounds offering a valuable method for introduction of a silyl group into organic molecules.     

Kinetic study of trifluoromethylation with s-(trifluoromethyl) dibenzothiophenium salts

The kinetic parameters were determined for C-trifluoromethylation of aniline with S-(trifluoromethyl)dibenzothiophenium triflate (1), its 3,7-dinitro derivative (2) and S-(trifluoromethyl)diphenylsulfonium triflate (3) in DMF-d₇. The higher reactivity of heterocyclic 1 compared with non-heterocyclic 3 could be explained on the basis of its greatly enhanced activation entropy (ΔS^≠: −11.2 cal mol ⁻¹ K⁻¹ for 1; −47.1 for 3), but not its enhanced activation enthalpy (ΔH^≠: 21.2 kcal mol⁻¹ for 1; 12.1 for 3). The aromatic delocalization of the heterocyclic ring may thus be only slightly disturbed by the S-trifluoromethyl substituent. The high reactivity of 2 was attributed to the great electron deficiency caused by two nitro groups in addition to the heterocyclic salt system (ΔH^≠ 17.0 kcal mol⁻¹, ΔS^≠ −9.1 cal mol⁻¹ K⁻¹ for 2). The reaction mechanism is discussed; the conventional S_N2 attack mechanism was ruled out and a mechanism for a side-on attack to the CF₃-S bond may possibly be applicable.     

Cotunneling effects in GaAs vertical double quantum dots

We report observation of Coulomb blockade lifting in GaAs vertical double quantum dot caused by cotunneling processes. One characteristic feature of investigated sample is relatively low potential barriers between dots and reservoirs, which makes cotunneling processes favorable. The measurement of current through the sample under variable bias and gate voltages was carried out at temperature of dilution refrigerator 10 mK. Several distinct features, specific to double dot, were observed and appropriate explanation for them was given.     

Rigorous bounds on quark masses within a nonrelativistic approach

By applying the Feynman-Hellmann theorem to \(q\bar q\) systems we find the following bounds on quark mass differences from the spectrum ofall quarkonium states $$\begin{gathered} 0.27 \leqq m_s - m_u \leqq 0.45GeV \hfill \\ 1.23 \leqq m_c - m_s \leqq 1.46GeV \hfill \\ 3.30 \leqq m_b - m_c \leqq 3.55GeV. \hfill \\ \end{gathered}$$ As best values we derive $$\begin{gathered} m_u = m_d = 0.31GeV,m_s = 0.62GeV, \hfill \\ m_c = 1.91GeV,m_b = 5.27GeV. \hfill \\ \end{gathered}$$      

Ircinamine B, bioactive alkaloid from marine sponge Dactylia sp.

Ircinamine B was isolated from the marine sponge Dactylia sp., which was collected at Cape Sada in Japan. Based on extensive spectral analysis, the structures of the isolated metabolites were established. This novel compound showed moderate activity against the murine leukemia cell line P388 (IC₅₀ 0.28 μg/mL).     

Hydro-Dehalogenation of α-Haloketones by Tin (II) Chloride and Sodium Hydrogen Sulfide

Aromatic and aliphatic α-haloketones were effectively dehalogenated by binary systems of sodium hydrogen sulfide (soft base) and a metal chloride such as tin (II) chloride, iron (II) chloride or chromium (III) chloride (hard acid).     

Blazed vector gratings fabricated using photosensitive polymer liquid crystals and control of polarization diffraction

The blazed vector grating possessing antisymmetric distributions of the birefringence were fabricated by exposing the line-focused linearly polarized ultraviolet light on the photosensitive polymer liquid crystals. The polarization states of the diffraction beams can be highly and widely controlled by designing the blazed structures, and the diffraction properties were well-explained by Jones calculus.