Two-dimensional diffraction study of ice crystallisation in polymer gels

Ice crystallisation in crosslinked dextran (Sephadex) gels was studied by the method of two-dimensional X-ray diffraction (XRD) in combination with the simultaneous measurement of differential scanning calorimetry (DSC). With a Sephadex G25 gel where an exotherm due to ice crystallisation is observed in the DSC rewarming trace, it was indicated by the XRD pattern that small ice crystals less than approximately 10 microns in diameter are readily formed during freezing, and that the endothermic trend prior to the exotherm is not due to the glass transition but due to the melting of the small ice crystals. Moreover, the diffraction pattern observed with frozen Sephadex gels depended on the density of crosslink indicating that ice crystals of different size and dimension are formed in the gels.     

Self-ordering of nanofacets on vicinal SiC surfaces

Vicinal 4H and 6H-SiC(0001) surfaces have been investigated using atomic force microscopy and cross-sectional high-resolution transmission electron microscopy. We observed the characteristic self-ordering of nanofacets on any surface, regardless of polytypes and vicinal angles, after gas etching at high temperature. Two facet planes are typically revealed: (0001) and high index (112;n) that are induced by equilibrium surface phase separation. A (112;n) plane may have a free energy minimum due to attractive step-step interactions. The differing ordering distances in 4H and 6H polytypes imply the existence of SiC polytypic dependence on nanofaceting. Thus, it should be possible to control SiC surface nanostructures by selecting a polytype, a vicinal angle, and an etching temperature.     

Screening effect diverts the swimming directions from diaphototactic to positive phototactic in a disk-shaped green flagellate Mesostigma viride

We found diaphototactic behavior (i.e. the cells swim perpendicularly with respect to the incident light) in a strain with colorless eyespot of a unicellular disk-shaped green flagellate Mesostigma viride. Lacking pigments completely in the eyespot, the screening effect in this strain was due only to the central part of the chloroplast whose cross section was thin. The diaphototaxis was most obvious when unilateral green stimulus light (520-580 nm) was given, whereas positive phototaxis appeared when given blue light (430-490 nm). The choice between diaphototaxis and (ordinary) phototaxis depended entirely on the transmission (%T) of the cell body against each wavelength of the stimulus: the green light penetrated well (%T > 90%), whereas the blue light was considerably shaded by the chloroplast (50% < %T < 70%). The fraction of positive phototactically behaving cells against each wavelength was in proportion to the front-to-back contrast value obtained at each individual wavelength. The fraction of diaphototaxis was inversely proportional to it. In addition, bilateral stimulus irradiations to wild-type cell with colored eyespot provided useful information about the principle of the diaphototactic steering.     

Krafft temperature and enthalpy of solution of<Emphasis Type="Italic"> N</Emphasis>-acyl amino acid surfactants and their racemic modifications: effect of the counter ion

The Krafft temperatures and enthalpies of solution of N-hexadecanoyl alaninate and valinate, and N-tetradecanoyl phenylalaninate were obtained from differential scanning calorimetry. The Krafft temperature of N-acyl amino acid surfactant increased with decreasing size of the counter ion, with some exceptions. The enthalpy of solution was endothermic and increased with decreasing size of the counter ion except for the cases of lithium salt. The results showed that the L-L interaction in the solid state of N-hexadecanoyl amino acid surfactant salt was superior to the D-L interaction for both the alanine and valine systems when the counter ion size increased. However, the D-L interaction was still advantageous for the phenylalanine system with Cs⁺ as a counter ion. Both Fourier transform infrared spectroscopy studies and theoretical calculations suggested that the difference in magnitudes of the interactions between peptide and counter ion was a dominant factor for the chiral effect.     

Free Field Construction for the ABF Models in Regime II

The Wakimoto construction for the quantum affine algebra U $_q$ ( $(\widehat{\mathfrak{s}\mathfrak{l}_2 })$ ) admits a reduction to the q-deformed parafermion algebras. We interpret the latter theory as a free field realization of the Andrews–Baxter–Forrester models in regime II. We give multi-particle form factors of some local operators on the lattice and compute their scaling limit, where the models are described by a massive field theory with $\mathbb{Z}$ $_k$ symmetric minimal scattering matrices.     

Measurement Accuracy in Phase-Shifting Point Diffraction Interferometer with Two Optical Fibers

A phase-shifting point diffraction interferometer (PS/PDI) with point sources of two single mode optical fibers has been developed, which will be appropriate for the surface figure measurement of large aperture optics on a sub-nanometer scale. To reduce the measurement error factors, a fiber optic plate (FOP) is used as a projection plane for interference pattern. Errors caused by imperfection of optical alignment, such as position of point sources and tilt of FOP, are minimized by analyzing the measured phase data with an original method. Measurement accuracy in the PS/ PDI is estimated with the interference pattern produced by the two optical fiber sources. If inhomogeneity of the FOP and a systematic error of the PS/PDI are eliminated, the measurement accuracy of the present system is estimated to be less than 4nm P-V and 0.7nm rms, respectively, at a measurement wavelength of 632.8 nm.     

Peumusolide A, unprecedented NES non-antagonistic inhibitor for nuclear export of MEK

A new polyketide peumusolide A was disclosed as an unprecedented NES non-antagonistic inhibitor for nuclear export of MEK, a promising scaffold for antitumor agents with novel mechanism of action, from Peumus boldus Molina. The absolute stereostructure as well as optical purity was established by use of the two synthesized enantiomeric model lactones. In addition, the Δε values in their CD spectra were demonstrated to be the conclusive index for determination of not only configuration at C-3 but also optical purity of natural congeneric polyketides. Peumusolide A was revealed to show NES non-antagonistic action by the biotinylated probe and to inhibit proliferation of MEK-activated tumor cells selectively.