Study of optical response of spinel oxide by utilizing IR-THz spectromicroscopy

We performed a spectromicroscopic measurement on LiV₂O₄ in IR-THz (25 meV–1.5 eV) from 6–300 K under high pressures up to 20 GPa by using a DAC at the spectromicroscopy station (BL43IR) at SPring-8. At 40 K, a clear metal–insulator change was observed above 6 GPa in the optical conductivity spectra. The newly developed peak structure around 1 eV reflects the pseudo-gap forming under pressure at 40 K.     

Catalytic Pauson-Khand-type reaction using aldehydes as a CO source

[reaction: see text]. Rhodium complex-catalyzed carbonylative alkene-alkyne coupling proceeds using aldehydes as a CO source. Cinnamaldehyde is the best CO donor, and various cyclopentenones were provided in high isolated yields by a solvent-free system.     

Classification of extremal contractions from smooth fourfolds of -type

We investigate divisorial contractions of extremal rays from
smooth fourfolds. When the exceptional divisor is contracted to a curve, we prove that the divisor is a -bundle or quadric bundle over a smooth curve and the contraction is the blowing up along the curve. Furthermore we determine the local analytic structure of the contraction.

     

Calorimetric determination of enthalpies,gibbs energies,and entropies of inclusion of some alcohols into α- and β-cyclodextrins in aqueous solutions

The enthalpies of transfer of cyclohexanol from aqueous to aqueous - or -cyclodextrin solutions have been measured at various mole fractions at 298.15 K on a rocking twin-microcalorimeter of heat-conduction type and the molar enthalpies, Gibbs energies, and entropies of inclusion in the aqueous solutions have been determined by the method proposed by the authors [Netsu Sokutei 10, 103 (1983)], to elucidate the driving force of the molecular inclusion. Discussions are given for all the systems obtained by the authors, concluding that the driving force is the enhancement of the entropy.Calorimetric studies on molecular inclusion V.     

Avenic acid,a new amino acid possessing an iron chelating activity

A new amino acid derivative possessing an iron chelating activity was isolated from root washings of water cultured $\text{Avena sativa}$ under iron deficient conditions. The structure of this compound, avenic acid A has been determined as 2(S),3′(S),3″(S)-N-[3-(3-hydroxy-3-carboxypropylamino)-3-carboxypropyl]-homoserine (1) on the basis of chemical and spectroscopic evidence.     

Novel soft chemical method for optically transparent Ru(bpy)3-K4Nb6O17 thin film

A unique guest-guest ion exchange method was developed for preparing a thin film of a nano-layered K(4)Nb(6)O(17).3H(2)O that possesses both (1) optical transparency and (2) ion-exchangeability under ambient conditions without calcination at high temperature. An optically transparent Ru(bpy)(3)(2+)-K(4)Nb(6)O(17) hybrid thin film, a photoresponsive electrode, was successfully prepared by the guest-guest exchange method by use of the intercalation compound MV(2+)-K(4)Nb(6)O(17) as a precursor. The optically transparent Ru(bpy)(3)(2+)-K(4)Nb(6)O(17) hybrid thin films have been characterized by X-ray diffraction, SEM, AFM, IR, and UV spectroscopies, as well as elemental analysis. The electrochemical behavior of the ITO/Ru(bpy)(3)(2+)-K(4)Nb(6)O(17) hybrid thin film electrode was studied; it also exhibits swift photoresponse in the visible region.     

Spectroscopic observation of bipolaronic point defects in Ba(1-x)KxBiO3

An infrared-absorption band centered at 0.85 eV, which is below the big optical absorption at the charge-density-wave (CDW) gap energy of 1.85 eV, has been observed for semiconducting single crystalline Ba(1-x)KxBiO3. With substituting K for Ba, the spectral weight of the new band increases with x, while that of the CDW-gap excitation decreases. Since the impurity state with the K substitution is known to be nonmagnetic at low temperatures, Bi3+ the state with 6s2 electrons surrounded by the six Bi5+ ions forms a small bipolaron by losing a pair of electrons in the Rice-Sneddon model. The new band is assigned to a transition from the lower-Peierls band to a state of the bipolaronic point defect.