Investigation of structural transition of regenerated silk fibroin aqueous solution by Rheo-NMR spectroscopy

In this study we applied Rheo-NMR to investigate the structural change of Bombyx mori silk fibroin in aqueous solution under shear. Monitoring the time dependence of 1H solution NMR spectra of silk fibroin subjected to constant shear strain, signal intensities of random coil decreased suddenly during shear while peaks from beta-sheet structure did not arise in the solution spectra. After these experiments, an aggregate of silk was found in the Couette flow cell and its secondary structure was determined as beta-sheet by 13C solid-state NMR. In conclusion the moderate shear applied here triggered the change in the secondary structure.     

Computer-generated line holograms using an xy plotter

A new method is presented for constructing a computer-generated Fourier-transformed line hologram using an xy plotter. Phase and amplitude of the complex amplitude in the hologram plane are represented by varying, respectively, the position and height of triangles formed in the cells composing the hologram. An image reconstructed optically from the hologram can be moved arbitrarily from the optical axis since the hologram contains information about the phase and amplitude of the complex amplitude in the hologram plane. A three-dimensional hologram from which an image was successfully reconstructed is also presented.     

Peak intensity variation in the partially coherent two-point resolution problem

The peak intensity variation in the two-point resolution problem is studied as functions of the two-point separation and the spatial coherence condition of illumination.     

Experimental and theoretical studies on thermodynamics and properties of tautomers of 2-substituted 6(4)-methyl-1,4(1,6)-dihydropyrimidine-5-carboxylates

Experimental and theoretical studies on the thermodynamics and properties of 2-substituted 6(4)-methyl-1,4(1,6)-dihydropyrimidine-5-carboxylates were undertaken by ¹H NMR measurements and DFT (density functional theory) calculations. The ratios of tautomers a/b of dihydropyrimidines (DPs) 1, 2, and 3 were determined under various conditions to reveal the effects of temperature, solvent, and concentration on the thermodynamic data. The observed results, the free energy differences (ΔG), enthalpy differences (ΔH), and entropy differences (ΔS), are discussed in terms of the molecular structures, dipole moments (DM), and the electrostatic potential maps calculated by the DFT to clarify the nature of the DPs.     

Dispersion Theory of Liquids Containing Optically Linear and Nonlinear Maxwell Garnett Nanoparticles

Kramers-Kronig relations and sum rules for effective linear permittivity of the Maxwell Garnett liquid-nanosphere system were obtained using complex analysis and general expression of the effective permittivity. When reflectance from optically linear and nonlinear Maxwell Garnett nanoparticles was calculated it was observed that the reflectance, in the case of attenuated total reflection, depends on the fill fraction of the nanospheres and their nonlinear susceptibility. According to simulations a good sensitivity of the nonlinear contribution on the reflectance can be obtained by using a probe wavelength corresponding to the resonance frequency of the nanosphere system. In Kretchmann#x0027;s configuration it was observed that the surface-plasmon-resonance angle depends on the fill fraction and on the intensity of the incident light. By using reflectance, it is possible to detect optically nonlinear nanospheres in liquids.     

Cationic Polymerization of N-Vinylcarbazole in the Presence of (+)-D-Camphor-10-sulfonic Acid

Optical rotation values of the polymers of N-vinylcarbazole (VCZ) obtained by a (+)-D-camphor-10-sulfonic acid (DCS) catalyst were found to increase linearly with an increase in the donor numbers of such solvents as 1,2-dichloroethane, dioxane, and tetrahydro-furan and such additives as N,N-dimethylformamide and tetra-methylurea. Asymmetric induction is considered to be caused by a stereoselective fixation of the growing VCZ cation with the optically active DCS anion, and fixation is assisted by nucleophilic solvation. No optically active VCZ polymer was obtained by using p-toluenesulfonic acid as the catalyst and (2s)-N,N′-carbonyl-N-cyclohexyl-aminomethyl pyrolizine as the additive.