Temperature dependence of the lowest-direct-bandgap energy in the ternary chalcopyrite semiconductor AgInSe<Subscript>2</Subscript>

Photoreflectance spectra have been measured on the ternary chalcopyrite semiconductor AgInSe₂ at T = 15–300 K. The direct-bandgap energies, E _0A, E _0B, and E _0C, of AgInSe₂ show unusual temperature dependence at low temperatures. The resultant temperature coefficients \({\partial E_{0\alpha}/\partial T}\) \(({\alpha=\hbox{A, B, C}})\) are positive at T below ～100 K and negative above ～100 K. These results are successfully explained by taking into account the negative lattice thermal expansion at low temperatures. The spin–orbit and crystal-field parameters Δ_so and Δ_cf are also found to show small temperature variations.     

Fabrication and interfacial electronic structure studies on polypyrrole/TiO2 nano hybrid systems for photovoltaic aspects

The progress in studying the interfacial electronic structures of the developing new class of hybrid organic/inorganic material systems have envisaged a new dimension into the field of photovoltaics, which could be of great help in understanding the nature of charge transfer in them. In this regard, electropolymerization of pyrrole monomers have been carried out at room temperature on the surface of TiO2 working electrodes (assisted by UV radiations) and their interfacial electronic structure has been studied as a function of the applied photo anodic potentials. The formation of polypyrrole deposits has been ensured using FT-IR and Raman spectroscopy. Surface analysis of the hybrid matrix revealed the tendency of polymer molecules to cover up the spherical surface of TiO2 nanoparticles that could help in improving the light absorption rate. Signals (bands) corresponding to pyrrole molecules observed in the ultraviolet photoelectron spectroscopy measurements have been correlated with the polaronic states formed and identified to shift as a function of the applied photo anodic potentials, revealing the decrease in work function of the hybrid system to take place (confirmed using cyclic voltammetry measurements). The decreasing trend in the work function elucidates the adjustment in electronic structure of the system (hybrid materials possessing smaller work functions are generally preferred for photovoltaic studies). The aforementioned behavioural aspects have been reasoned with the increase in overpotential values for polarization, from the decrease in up-take rate of the anionic dopant, which increases the current density values, thereby modifying the conductivity of the systems.     

Unified surface anchoring strength from the splay elastic deformation in nematic slabs

Film thickness dependences of the unified surface anchoring strengths from the splay deformation for nematic cells were discussed. Thin nematic parallel (d = 2-50 μm) and wedge (d = 0.3-5 μm) cells with the same solid surface were prepared to evaluate the surface anchoring strength. The surface anchoring strengths from the splay deformations for two kinds of liquid crystals were measured by using the saturation method. The nematogens used were 4-pentyl-4′-cyanobiphenyl and mixture compound ZLI-4792 (Merck Japan Co., Ltd.) with positive dielectric anisotropy. Film thickness dependence of the surface anchoring strength was elucidated on the basis of the conventional ionic surface polarization. It was also discussed that a surface anchoring strength from the splay deformation is to be an intrinsic value defined at an interfacial region and not a value changing with the film thickness.     

A Simple Determination Method of Adsorption Kinetics from a Liquid Phase Fixed‐Bed Breakthrough Curve

The mass transfer zone (MTZ) method using the linear driving force (LDF) approximation is the most common and frequently used technique for the analysis of adsorption kinetics from a fixed‐bed breakthrough curve and for adsorptive process design. However, the adsorption kinetics obtained by the MTZ method includes approximations and estimation errors. This report describes a new analytical method for determining the intraparticle diffusivity (D_S) and the fluid‐film mass transfer coefficient (k_F) from an experimental breakthrough curve without using the LDF approximation and empirical correlations for estimating k_F . The proposed method has the advantage of less trial and error on the curve‐fitting process and helps better determine D_S and k_F . The estimation procedure of the Biot number that represents the ratio of D_S to k_F is the key of this method. The values of D_S and k_F for the adsorption of phenols onto activated carbon were determined from experimental breakthrough curves using the new analytical method. The results indicate that the method presented in this study yields reliable values.     

Plastic Forming of High‐Tc YBa2Cu3O7−x Bulk Superconductors

The large bulk high‐T_c YBa₂Cu₃O_7?x (YBCO) superconductor samples were prepared by plastic‐forming method. We examined the effects of the solvent and the crystallinity of YBCO powder on the composition, crystallinity, and superconducting properties of YBCO sheet samples (sample size: 50 mm × 50 mm× 3 mm). By changing the solvent from water to turpentine oil, the leaching of Ba²⁺ ions from YBa₂Cu₃(OH)_y multimetallic hydroxide particles used as an inorganic binder and the YBCO powder were reduced. This results in the composition of the grain boundaries of fired YBCO sheet samples to be the same as the composition of YBa₂Cu₃(OH)_y multimetallic hydroxide particles. Changing nondoped YBCO powder prepared by sintering to 5 wt% Pt‐doped YBCO powder prepared by melt texturing, J_c value of YBCO sheet samples changed from about 700 to 6,106 A/cm² at 77 K.     

Structure and reactivity of MoO3-MgO catalysts

Surface of OH groups on reduced MoO₂-MgO catalysts such as $$ - - Mg - - O - - \begin{array}{*{20}c} {||} \\ {Mo} \\ | \\ \end{array} - - OH$$ may act as an active site for hydrogenation of propene. The surface hexa-coordinated Mo⁵⁺ ion (MO _6c ⁵⁺ ) was reduced to a lower number of cation such as Mo⁴⁺ or Mo³⁺ which act as an active site for metathesis of propene.     

Hybrid Planar Wiggler with a Period of 2 cm for Higher Harmonic FEL Lasing

A hybrid planar wiggler with a period of 20 mm has been studied as the simplest one which gives the strong field including some higher harmonic components by selecting proper sizes of the ferromagnetic and the permanent magnet. Small gap length of the wiggler and small width of permendur satisfy these conditions to a certain degree. Gain analysis of FEL suggests that for high wiggler field of K>1 ～ 1.6, higher harmonic gains are improved primarily due to its strong field, and for low wiggler field of K< 1 ～ 1.6, they are mainly due to the modification of the wiggler field distribution.     

Effects of free fatty acids on the binding of steroid hormones to bovine serum albumin

The effects of binding of free fatty acids (FFA) to bovine serum albumin (BSA) on steroid hormone binding to BSA were examined. The FFA studied included myristic, palmitic, stearic, oleic and linoleic acids. The binding coefficient K was estimated from the changes in the equilibrium partition coefficient between the aqueous and the hexane phase caused by the addition to BSA to the aqueous phase. A noticeable effect of FFA binding (molar ratio FFA/BSA, 2∶1) on the affinities of α-estradiol, ethynylestradiol and dehydroisoandrosterone to BSA was not observed: however, the affinities of progesterone, androsterone and testosterone were distinctly enhanced by FFA binding. Furthermore, the elution profiles of gel filtration chromatography clearly showed that progesterone and testosterone are easily liberated from the hormone/BSA complexes and that stronger binding of these hormones to BSA is caused by binding of FFA to BSA. The affinity of ethynylestradiol to BSA is stronger than that of progesterone and testosterone and is not affected by palmitic acid binding to BSA.