The role of argon in plasma-assisted deposition of indium nitride

Radiofrequency (RF) nitrogen plasma sources are commonly employed in the growth of group III-nitrides by molecular beam epitaxy and reactive evaporation. These sources produce atomic nitrogen and excited molecules (N₂*). In this work the relative flux of these two species produced by an RF source was studied by emission spectroscopy as a function of power, pressure, and argon dilution. Polycrystalline indium nitride thin films were synthesized under the same conditions. It was found that argon dilution had a strong influence on the production of active nitrogen, with maximum fluxes obtained around ∼40% N₂. Film properties, as measured by X-ray diffraction, atomic force microscopy and Hall effect, were also optimized at this condition. It was observed that the Hall mobility scaled with the sum of N and N₂* emission, suggesting that both species may be beneficial for InN growth.     

Kinetics of oxidation of some disaccharides in ammoniacal medium

Kinetics of oxidation of lactose, maltose, cellobiose and melibiose has been studied by hexacyanoferrate(III) in the presence of ammonia. A general mechanism involving the formation of intermediate enodiol anion has been suggested. The effects of dielectric constant and salts have been studied in detail. The oxidation products have been characterised by descending paper chromatography. Compensation effects have been observed.     

Order parameters of fluorophores in ground and excited states. Probe molecules in a lyotropic liquid crystal

Perylenc, 9,10-dimethylanthracene and 1,6-diphenyl-1,3,5-hexatriene (DPH) solubilized in a macroscopically aligned lyotropic nematic phase have been studied with linear dichroism (LD), steady-state and time-resolved fluorescence spectroscopy. From LD an order parameter of the fluorophore in its electronic ground state can be obtained, and from time-resolved polarized emission spectroscopy for its excited state. The order parameters of perylene in the ground and excited states are the same within experimental accuracy, but they are significantly different for 9,10-dimethylanthracene and DPH. It is concluded that the orientational distributions of fluorescent probe molecules in ground and excited states are generally not equal. Hence the order parameter of a fluorophore in a microscopically anisotropic and macroscopically isotropic system, e.g. a vesicle suspension, cannot generally be determined directly from the emission anisotropy.     

Low frequency Raman spectra of chalcogenide glasses

Low frequency (< 30 cm^-1) Raman scattering lineshapes for the chalcogenide glasses As₂S₃ and As₂Se₃ have been interpreted in terms of a model which explicitly includes acoustic (∼ ω2 density-of-states) and optic (rigid-layer like) vibrational modes.     

Study of Molecular Interactions in Binary Mixtures of Aniline with Carboxylic Acids at 293.15 K, 303.15 K and 313.15 K

Ultrasonic velocity, density, refractive index and viscosity of binary mixtures of aniline with acetic acid (AA) and propionic acid (PA) have been measured at 293.15, 303.15 and 313.15 K over the entire composition range. Further, the specific heat ratio, heat capacity, effective Debye temperature and pseudo-Gruensisen parameter and non-linearity parameter have been evaluated using ultrasonic absorption data. The deviation in isentropic compressibility, excess molar volume, excess intermolecular free length, deviation in molar refraction, deviation in viscosity, relaxation time, enthalpy, entropy and Gibbs energy of activation have been calculated from the experimental data and fitted with the Redlich-Kister polynomial equation. A comparative study has also been made between experimental and theoretically calculated values of densities using the HBT and Rackett density models. Mixing rules for the prediction of refractive index, e.g. Lorentz-Lorenz (L-L), Eykmen (Eyk), Weiner (W), Heller (H), Gladstone-Dale (G-D), Arago-Biot (A-B) and Newton (N) have been applied to these binary mixtures.     

Iron-catalyzed thioesterification of methylarenes with thiols in water

An iron-catalyzed coupling reaction of methylarenes with thiols leading to thioesters has been developed. The reactions were carried out in water with tert-butyl hydroperoxide (TBHP) as the oxidant and polyoxyethanyl α-tocopheryl sebacate (PTS) as the surfactant. The reaction medium is compatible with a series of functional groups and can be reused.     

6×n阶矩形网络等效电阻猜想的证明

任意k×n阶电阻网络等效电阻的公式研究属于科学难题,到目前为止已经获得了当k=1,2,…,5时的5种情形下的等效电阻公式,但对k≥6时的等效电阻的普适公式仅仅作为猜想给出.本文根据建立的任意k×n阶电阻网络等效电阻研究的方法,证明了k=6时的等效电阻公式的正确性,并且给出了其无穷网络的等效电阻公式,在对比验证时得到了一些新的三角恒等式.