DSC Studies on Polytetrahydrofurans with Various Molecular Masses, Their Blends and Their Cured Samples

DSC studies are given for polytetrahydrofurans with molecular masses equal to 650, 1400, and 2900, for their blends, and for their cured samples. The samples were stored, annealed, and quenched to obtain the samples with different thermal histories. Two or more endothermic peaks appear in the DSC curves for the stored samples, even for the non-blended samples. A hyperbolic curve forced the plot of the highest melting temperature vs. the molecular mass to asymptote to about 50°C. The relationship between the highest melting temperature and the composition for the blended samples is suitable to linear or Fox’s relation. A peak and a shoulder appear in the DSC curves of the cured samples. As the samples are cooled at the faster rates in the thermal treatment, the shoulder appears at the lower temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determining anomalous dynamic patterns in price indexes of the London Metal Exchange by data synchronization

Data synchronization based on the Kuramoto model for collective synchronization and hypothesis testing based on the rank test combined with the random shuffling surrogate method are applied to finding major feature patterns of weekly nonferrous metal returns from the time series of daily spot and futures price indexes in the London Metal Exchange since 1989. Our results suggest the existence of day-of-the-week anomalies in the metal returns. We conjecture that such anomalies are large-scale manifestations of synchronously accumulated risk-aversive actions of individual market players.     

Automated precolumn derivatization system for analyzing physiological amino acids by liquid chromatography/mass spectrometry

An automated method for high‐throughput amino acid analysis, using precolumn derivatization high‐performance liquid chromatography/electrospray mass spectrometry (HPLC/ESI‐MS), was developed and evaluated. The precolumn derivatization step was performed in the reaction port of a home‐built auto‐sampler system. Amino acids were derivatized with 3‐aminopyridyl‐N‐hydroxysuccinimidyl carbamate, and a 3 μm Wakosil‐II 3C8‐100HG column (100 × 2.1 mm i.d.) was used for separation. To achieve a 13 min cycle for each sample, the derivatization and separation steps were performed in parallel. The results of the method evaluation, including the linearity, and the intra‐ and inter‐precision, were sufficient to measure physiological amino acids in human plasma samples. The relative standard deviations of typical amino acids in actual human plasma samples were below 10%. Copyright © 2009 John Wiley & Sons, Ltd.     

Structures and electronic transport on silicon surfaces

By utilizing a variety of surface superstructures formed on silicon surfaces and atomic layers grown on them, close correlations between the atomic-scale structures and electrical conduction phenomena at the surfaces have been revealed. State-of-art techniques for analyzing and controlling atomic/electronic structures of surfaces are leading to an understanding of the novel electronic transport properties at surfaces. For example, the electrical conduction through surface-state bands, which are inherent in the surface superstructure, has been confirmed in in-situ measurements. An important phenomenon has also been found, where adatoms donate carriers into the surface-state band, resulting in a remarkable enhancement in electrical conductance. The nucleation of the adatoms diminishes such a doping effect. Furthermore, electrical conduction through atomic layers grown on the surfaces, whose growth structures are sensitive to the substrate surface structures, will be also discussed. In this review, we emphasize that the surface electronic transport properties are closely related to the atomic structures and atomistic dynamics on surfaces. The ultimate two-dimensional electron systems, consisting of the surface-state bands and grown atomic layers, are expected to provide a new stage in surface physics, as well as a precursory stage leading to atomic-scale electronics devices.     

Polar antiferromagnets produced with orbital order

Polar states are realized in pseudocubic manganite films fabricated on high-index substrates, in which a Jahn-Teller (JT) distortion remains an active variable. Several types of orbital orders (OOs) were found to develop large optical second harmonics, signaling broken-inversion symmetry distinct from their bulk forms and films on (100) substrates. The observed symmetry lifting and first-principles calculation both indicate that the modified JT q2 mode drives Mn-site off centering, which can be controlled by a magnetic-field-induced phase transition via a coupling of OO and spin orders.     

Synthesis and binding studies of novel bisthiacalix[4]arenes with diimime linkages

A series of novel bisthiacalix[4]arenes with diimine linkages of different aromatic or heteroaromatic dialdehydes have been synthesized. The structure of one of the bisthiacalixarene has been analyzed by X-ray crystallography. These molecules quantitatively extract silver ion from aqueous into organic phase under neutral conditions.     

Basic study on the determination of total boron by conversion to tetrafluoroborate ion (BF4) followed by ion chromatography

The basic study on the determination of tetrafluoroborate ion (BF₄⁻) by ion chromatography, and total boron by conversion of boric acid to BF₄⁻ followed by ion chromatography of BF₄⁻ has been carried out. The results of thermodynamic calculations for the system of boric acid (H₃BO₃)-F⁻-H⁺ showed that the mole fraction of BF₄⁻ was higher than 99% at pH lower than 3.5 and 4.5 when the total free fluoride concentration (2[H₂F₂] + 2[HF₂⁻] + [HF] + [F⁻]) was as high as 0.1 and 1.0 M, respectively. The fraction of BF₄⁻ increased with increasing total free fluoride concentration. BF₄⁻ fraction values were higher than 99% at pH 0.75 and at total free fluoride concentration of 0.05 M or higher. BF₄⁻ was hardly formed at pH > 7 even when the total free fluoride concentration was as high as 1.0 M. According to the experimental results, the fraction of BF₄⁻ at pH 0.7-0.8 was 51.2, 95.6 and 96.7% when the total fluoride concentration (2[H₂F₂] + 2[HF₂⁻] + [HF] + [F⁻] + 3[BF₃OH⁻] + 4[BF₄⁻]) was 0.2, 1.0 and 3.3 M, respectively. The formation reaction of BF₄⁻ from boric acid reached an equilibrium state within 20 min regardless of reaction temperature, in the range of 20-50 °C, when the total boron and total fluoride concentrations were 66.7 mM and 1.0 M, respectively. Although BF₄⁻ was formed only under acidic conditions, BF₄⁻, once formed, was very stable under alkaline conditions at least for several hours. We have concluded that BF₄⁻ could be analyzed by ion chromatography using sodium hydroxide solution as an eluent because BF₄⁻ was stable under chromatographic conditions. BF₄⁻ solution prepared from boric acid could be used as a standard solution in the ion chromatographic analysis of BF₄⁻ instead of the sodium tetrafluoroborate (NaBF₄) reagent available commercially, if a discrepancy of about 4-5% was allowed.     

Design of a silicon-based plasmonic optical sensor for magnetic field monitoring in the infrared

Surface plasmon resonance (SPR) sensor chip is proposed for magnetic field monitoring in the infrared wavelength region. The structure is based on silicon substrate and gold as SPR-active metal used with an appropriate magnetic fluid film. The angular interrogation method has been used to study the sensor’s performance in terms of large shift and small width of the SPR curve for a wide range of magnetic field between 30 and 220 Oe. The effect of field incidence angle is also studied on the proposed sensor’s performance, and it is observed that the field should be incident as parallel to the magnetic fluid surface as possible. Any possibility of oxidation problem to the proposed SPR sensor is addressed by using a stable buffer layer. All the performance parameters were found to be significantly large for the above field incidence condition. The proposed sensor is able to achieve a resolution of the order as high as 0.18 Oe for magnetic field detection.     

Novel orbital ordering induced by anisotropic stress in a manganite thin film

A novel structure of orbital ordering is found in a Nd0.5Sr0.5MnO3 thin film, which exhibits a clear first-order transition, by synchrotron x-ray diffraction measurements. Lattice parameters vary drastically at the metal-insulator transition at 170 K (= T(MI)), and superlattice reflections appear below 140 K (= T(CO)). The electronic structure between T(MI) and T(CO) is identified as A-type antiferromagnetic with a d(x2-y2) ferro-orbital ordering. The new type of antiferro-orbital ordering characterized by the wave vector (1/4 1/4 1/2) in cubic notation emerges below T(CO). The accommodation of the large lattice distortion at the first-order phase transition and the appearance of the novel orbital ordering are brought about by the anisotropy in the substrate, a new parameter for the phase control.     

Anomalous scattering from dielectric bispheres in the specular direction

Resonant scattering from dielectric bispheres in the specular direction (the so-called specular resonance), previously known only in the microwave range, has been observed at the optical wavelength. Systematic experiments with micrometer-sized dielectric bispheres assembled by micromanipulation, together with rigorous numerical calculations, reveal that this scattering is a precursor of the classical rainbow and is a general phenomenon observed in the wide range of size parameters (>5 for n=1.59) for various refractive indices.