Construction of chlorophyll assemblies based on zinc complexes of triazole–chlorin conjugates

A series of triazole–chlorin conjugates were prepared by Huisgen reactions of a C3–ethynylated chlorophyll derivative with azido compounds. Dimerization behaviour of their zinc complexes was investigated based on UV–vis, circular dichroism, and ¹H NMR spectroscopies as well as molecular modelling calculation.     

Proposal of a new optical system for prism-based surface-plasmon-resonance imaging

Optical Review - We propose a new prism-based surface-plasmon-resonance microscope (PB-SPRM) with a diffraction grating. Unlike the conventional PB-SPRM, the proposed one is free from distortion...     

Synthesis of Quinoline Derivatives by [4+2]Cycloaddition Reaction

Synthesis of quinoline derivatives by Lewis acid catalyzed [4+2]cycloaddition was investigated.     

A structural investigation of calcium fluorosilicate glasses

The structure of x CaF₂(1?x)CaOSiO₂ glasses was investigated by X-ray photoelectron, F K_α emission X-ray and infrared absorption spectroscopies and ionic refraction of fluorine. A maximum in F_1s binding energy and a minimum in chemical shift of F K_α X-ray were found in the region of 7–10 mol% CaF₂, indicating that the state of fluorine changes. The ionic refraction of fluorine increased with increasing CaF₂ content up to 7 mol% CaF₂ and was nearly constant for compositions with more than 7 mol% CaF₂. There was practically no change in $\text{Ca}{}_{\mathrm{<mtext>2</mtext><mtext>p</mtext><mtext>(</mtext><mtext>3</mtext><mtext>2</mtext><mtext>)</mtext>}}$ binding energy for compositions with less than 7 mol% CaF₂. These data suggest that the fluorine ion bonds with a silicon predominantly for a CaF₂ content of less than 7 mol% and bonds with a calcium ion for increased CaF₂ content. Further, partial charges of fluorine, calcium and silicon, calculated by the modified Sanderson method could explain the chance of F_1s and $\text{Ca}{}_{\mathrm{<mtext>2</mtext><mtext>p</mtext><mtext>3</mtext><mtext>2</mtext>}}$ binding energies with composition. It is suggested that when the CaF₂ content is more than 7 mol%, the coordination number of fluorine increases and that of calcium decreases with increasing CaF₂ content.     

Growth kinetics of amorphous hydrogenated silicon studied by pulsed rf discharge

The growth rate and hydrogen bonding configuration of a-Si:H prepared by a pulsed rf discharge technique were measured as a function of repetition frequency. The result was compared with the case of the gas-phase polymerization of monomers C₂H₂, C₂H₄, and C₂H₆ in a pulsed rf discharge. From distinct difference between the pulsed-plasma depositions of a-Si:H and C:H films, it is concluded that the growth of a-Si:H proceeds through the heterogeneous reactions among chemical species on the substrate surface.     

X‐ray microtomographic visualization of Escherichia coli by metalloprotein overexpression

This paper reports X‐ray microtomographic visualization of the microorganism Escherichia coli overexpressing a metalloprotein ferritin. The three‐dimensional distribution of linear absorption coefficients determined using a synchrotron radiation microtomograph with a simple projection geometry revealed that the X‐ray absorption was homogeneously distributed, suggesting that every E. coli cell was labeled with the ferritin. The ferritin‐expressing E. coli exhibited linear absorption coefficients comparable with those of phosphotungstic acid stained cells. The submicrometer structure of the ferritin‐expressing E. coli cells was visualized by Zernike phase contrast using an imaging microtomograph equipped with a Fresnel zone plate. The obtained images revealed curved columnar or bunching oval structures corresponding to the E. coli cells. These results indicate that the metalloprotein overexpression facilitates X‐ray visualization of three‐dimensional cellular structures of biological objects.     

Phase Transition and Structure Change of Urea Adducts with n-Paraffins and Paraffin-type Compounds

The phase transition temperatures of urea adducts with many n-paraffins and several paraffin-type compounds were measured by differential thermal analysis and the general structure change causing the phase transitions was revealed by X-ray structure analysis. The ordinary hexagonal adducts (high-temperature form) transform commonly into orthorhombic adducts (low-temperature form) except for a few adducts with guest molecules possessing cylindrical shapes. The phase transition can be regarded as an order-disorder transition with respect to the orientation of the guest molecules about the urea channel axis with a cooperative deformation of the urea channels resulting in the orderly orientation of guest molecules below the transition temperatures. The changes in orientation and motion of the guest molecules through the phase transitions are discussed on the basis of X-ray analysis, potential energy and broad-line NMR.     

Hume-Rothery electron concentration rule across a whole solid solution range in a series of gamma-brasses in Cu–Zn,Cu–Cd,Cu–Al,Cu–Ga,Ni–Zn and Co–Zn alloy systems

The aim of the present work is to examine if the Hume-Rothery stabilisation mechanism holds across whole solid solution ranges in a series of gamma-brasses with especial attention to the role of vacancies introduced into the large unit cell. The concentration dependence of the number of atoms in the unit cell, N, for gamma-brasses in the Cu–Zn, Cu–Cd, Cu–Al, Cu–Ga, Ni–Zn and Co–Zn alloy systems was determined by measuring the density and lattice constants at room temperature. The number of itinerant electrons in the unit cell, e/uc, is evaluated by taking a product of N and the number of itinerant electrons per atom, e/a, for the transition metal element deduced earlier from the full-potential linearised augmented plane wave (FLAPW)-Fourier analysis. The results are discussed within the rigid-band model using as a host the density of states (DOS) derived earlier from the FLAPW band calculations for the stoichiometric gamma-brasses Cu₅Zn₈, Cu₉Al₄ and TM₂Zn₁₁ (TM = Co and Ni). A solid solution range of gamma-brasses in Cu–Zn, Cu–Cd, Cu–Al, Cu–Ga and Ni–Zn alloy systems is found to fall inside the existing pseudogap at the Fermi level. This is taken as confirmation of the validity of the Hume-Rothery stability mechanism for a whole solute concentration range of these gamma-brasses. An exception to this behaviour was found in the Co–Zn gamma-brasses, where orbital hybridisation effects are claimed to play a crucial role in stabilisation.     

ESR investigation of sucrose radicals produced by particle irradiation

We investigated sucrose radicals produced by heavy-ion irradiation with various linear energy transfer (LETs) and the possibility for a sucrose electron spin resonance (ESR) dosimeter. The impact of heavy ions on sucrose produced sucrose radicals, which were measured by ESR. The obtained spectral pattern was the same as that for helium (He) ions, carbon (C) ions, neon (Ne) ions, iron (Fe) ions, and gamma-ray irradiation. Identical spectra were measured after 1 year, but the initial intensities decreased by a few percent when the samples were kept in ESR tubes with the caps at ambient temperature. The total spin concentration obtained by heavy-ion irradiation had a linear relation with the absorbed dose, and correlated logarithmically with the LET. Qualitative ESR analyses showed that the production of sucrose radicals depended on both the particle identity and the LET at the same dose. The production of spin concentration by He ions was the most sensitive to LET. Empirical relations between the LET and the spin yield for various particles imply that the LET at a certain dose can be estimated by the spin concentration. Therefore, the present ESR results imply that sucrose can be used to monitor the absorbed dose and the LET of particle irradiation.