Excitation profiles of resonance raman spectra in condensed media

A simple model, obtained by reducing a multimode system to a simple coordinate, is proposed to explain the broadening of RRS in liquid or solid media. It is shown that the coherent excitation of the near continuous background of low-frequency modes can cause homogeneous broadening of RRS profiles. The model is applied to the excitation profile of β-carotene.     

Cross-checking of nanoelectrospray ionization mass spectrometry and computer simulation for the evaluation of the interaction strength of non-covalently bound enkephalins in solution

Nanoelectrospray ionization mass spectrometry (nanoESI-MS) and computer simulation were applied to the characterization of non-covalent interactions of [Leu5]-enkephalin (LE) and its optical isomers, [D-Tyr1, Leu5]-enkephalin (Y-LE), [D-Phe4, Leu5]-enkephalin (F-LE) and [D-Tyr1, D-Phe4, Leu5]-enkephalin (YF-LE). The dimer formation tendencies of the optical isomers of LE were evaluated by nanoESI-MS using quadruply deuterated LE (H2N-Tyr-(2,2-d2)Gly-(2,2-d2)Gly-Phe-Leu-COOH, d4-LE) as an internal standard. The relative interaction strengths of the optical isomers of LE were estimated to be Y-LE < F-LE < LE < YF-LE. Geometry optimization calculations were performed for interactions in vacuo and in water using a semi-empirical SCF method (PM3). The initial coordinate of the dimer structure of LE was taken from that obtained from single-crystalline x-ray diffraction analysis. Estimates of the interaction strengths of the dimer complexes were based on the heats of formation of a dimer complex (Hd) and the corresponding monomers (Hm) using the equation DeltaH = Hd - 2Hm. The values of DeltaH obtained from the calculations for interactions in water decreased in the order Y-LE > F-LE > LE > YF-LE. Since the smaller values of DeltaH correspond to stronger interactions between peptides, the results from computer simulations were qualitatively consistent with those obtained from the nanoESI experiments. The possibility of cross-checking these independent techniques was demonstrated using medium-sized molecules of biological importance. The agreement of the results from the two techniques suggested that nanoESI experiments, at least qualitatively, reflected the relative interaction strengths of non-covalently bound enkephalins in aqueous solution.     

A new carbon—phosphorous bond forming reaction and synthesis of aminoalkylphosphonic acid derivatives

A new carbon—phosphorous bond forming reaction, that is, the reaction of α-methoxyurethanes with trialkyl phosphites in the presence of Lewis acid catalysts was studied on twelve examples.     

Frequency Dependence of ESR in Pristine Trans-Polyacetylene: Line Width

We measured a frequency dependence of ESR line width in (CH)x and (CD)x at frequencies 5～9,500 MHz. From a detailed analysis we could independently deduce 1-D diffusion rate of electron spin (neutral soliton) D_‖ /c_‖ ², and the trapped spin concentration C between 200 and 340 K.     

Evidence for Superconductivity in Nb2SC0.90 Carbosulfide

Abstract

Evidence for bulk superconductivity in Nb₂SC_0.90 carbosulfide is presented. Diamagnetic volume fraction of Nb₂SC_0.90 was precisely determined with low applied magnetic fields which were corrected by 6N lead rod as an internal standard. Based on magnetic field dependence of magnetic moment at several constant temperature's below T_C = 5 K, Nb₂SC_0.90 is found to be a type II superconductor with relatively high H _C2 and low H_C1.     

Interplay of Correlation,Randomness and Dimensionality Effects in Weakly-Coupled Half-Filled Random Hubbard Chains

Abstract

We study interplay of electronic correlation, randomness and dimensionality effects in half-filled random Hubbard chains weakly coupled via an interchain one-particle hopping. Based on the two-loop renormalization-group approach, phase diagrams are given in terms of temperature vs. strengths of the intrachain electron-electron umklapp scattering, the random scattering and the interchain one-particle hopping.     

High-performance organic field-effect transistors based on pi-extended tetrathiafulvalene derivatives

Aromatic ring-condensed TTF derivatives exhibited excellent p-type FET performances in thin films. Introduction of fused benzene and pyrazine rings to the TTF skeleton was effective to enhance the intermolecular interactions and stability to oxygen. Ordered molecular alignment was confirmed by XRD studies. A pi-stacking structure was observed in the single crystal of diquinoxalinoTTF.     

Magnetic and dielectric properties of YbFe2−xMnxO4 (0?x?1)

We have investigated the magnetic and dielectric properties of YbFe_2−xMn_xO₄ (0?x?1), which is an Fe-site-substituted system of new multiferroic oxides RFe₂O₄ (R=Y, Ho-Lu). X-ray diffraction measurements show that a solid solution is formed between YbFe₂O₄ (x=0) and YbFeMnO₄ (x=1) for 0?x?1, whereas only compounds with x=1 (i.e., RM₁M₂O₄; M₁ and M₂=trivalent and divalent cations, respectively) have been known for the Fe-site substitution in RFe₂O₄. The valence of the Mn ion is determined to be ∼2+, consistently with the suppression of low-temperature magnetization by the Mn substitution. The magnetic transition temperature (T_N) and the dielectric constant (ε′) decrease monotonically with increasing x. This result plausibly confirms that the magnetic and dielectric properties in oxides isostructural with RFe₂O₄ are governed by the electron transfer between Fe-site ions, unlike ordinary ferroelectrics and dielectrics, in which the ionic displacement plays a key role. The possibility for application is briefly discussed as well.