Syntheses and X-ray structures of mixed benzenethiolato-sulfido and -selenido trinuclear nickel clusters

The reaction between NiCl₂, NaSPh and NaEH (E = S, Se) in a mixture of acetonitrile and acetone gave trinuclear clusters [Ni₃(μ₃-E)(μ-SPh)₃(SPh)₃]²⁻(E = S, Se) and the previously characterized mononuclear complex [Ni(SPh)₄]²⁻. The X-ray structures of the trinuclear clusters are similar to each other except for the Ni₃E (E = S, Se) sections, and the Ni---E (E = S, E = S, Se) frameworks planes which are condensed via adjacent edges to form planar NiS₄ or NiS₃Se coordination planes which are condensed via adjacent edges to form cyclic systems with a triply bridging sulfido or selenido ion in the centre.     

Visualization of 50 MHz Surface Acoustic Wave Propagation Using Stroboscopic Phase-Shift Interferometry

A Stroboscopic phase-shift interferometry has been developed to visualize surface acoustic wave (SAW) propagation on SAW devices quantitatively. The developed interferometry is a Fizeau-type one with a multi-mode semiconductor laser diode and an optical isolator. With the laser light illuminating stroboscopically, observed interference intensity gives information about average displacements of the vibrations. Fifty MHz SAW propagation on the surface of the SAW device has been measured with the interferometry. Distribution of the SAW along the propagation path has been observed, whose amplitude is 3 nm (p-p). Repetition accuracy evaluated with the root mean square method is 1/2500 of the laser wavelength. The system is useful for estimating and improving performances of micro-devices.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27-29, Saitama, Japan.     

On thefg-coloring of graphs

This paper introduces a new type of edge-coloring of multigraphs, called anfg-coloring, in which each color appears at each vertexv no more thanf(v) times and at each set of multiple edges joining verticesv andw no more thang(vw) times. The minimum number of colors needed tofg-color a multigraphG is called thefg-chromatic index ofG. Various upper bounds are given on thefg-chromatic index. One of them is a generalization of Vizing's bound for the ordinary chromatic index. Our proof is constructive, and immediately yields a polynomial-time algorithm tofg-color a given multigraph using colors no more than twice thefg-chromatic index.     

Preparation and phase behavior of poly(4‐trimethylsilylstyrene)‐block‐polyisoprene

Three poly(4‐trimethylsilylstyrene)‐block‐polyisoprenes (TIs), the molecular weights of which were 82,000, 152,000 and 291,000 (TI‐82K, TI‐152K, and TI‐291K), were synthesized by sequential anionic polymerizations. The component polymers were a miscible pair that presented a lower critical solution temperature phase diagram if blended. The TI phase behavior was investigated with transmission electron microscopy. The order–disorder transition could be observed at a temperature between 200 °C (the ordered state) and 150 °C (the disordered state) for the block copolymer TI‐152K. The block copolymer TI‐82K presented the disordered state at 200 °C, whereas TI‐291K was in the ordered state at 150 °C. With the Flory–Huggins interaction parameter between poly(4‐trimethylsilylstyrene) and polyisoprene, which was evaluated by small‐angle neutron scattering for the block copolymers, the TI phase behavior could be reasonably explained by mean‐field theory. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1214–1219, 2005     

Real-time Adaptive Optics with a Twisted Nematic Liquid Crystal Light Modulator Controlled by the Wave Front Reconstruction Sensor

We propose adaptive optics constructed with a new principle. In this system, numerical phase reconstruction algorithm is incorporated with the Hartmann wave front sensor and the phase compensator is driven to the conjugate of the input phase distortion at each time step. The computer simulation shows a sufficient robustness and swiftness of the wave front reconstruction sensor. Then, the experimental system is configured putting special emphasis on the simplicity and feasibility of the system. A small 2-dimensional grid mask is used in the Hartmann sensor, and a twisted nematic phase modulator with a response time of 30 ms is used as the phase compensator. The control system has a simple open loop setup using a phase reconstruction algorithm. This experimental system was effective not only for static phase distortion, but also for the dynamic phase perturbation induced by a thermal convection.     

Effect of the silanization conditions on chromatographic behavior of an open-tubular capillary column coated with a modified silica-gel thin layer.

The performance of an open-tubular capillary column coated with a modified silica-gel thin layer was investigated, particularly concerning the effect of the silanization process on it. Although the increase in the octadecyltriethoxysilane (ODTES) concentration in the silanization process could enhance the retention factor of naphthalene, its theoretical plate number was significantly reduced (ODTES, 5 to 50%; k, 0.2 to 4.3; N, 79600 to 2600 m(-1)). Namely, the increase in the retention factor was accompanied by a decrease in the theoretical plate number. A similar phenomenon was also observed when octadecyldimethylchlorosilane (ODCS) was used as the silanization regent. However, increases in both the retention factor and the theoretical plate number could be achieved (sample, naphthalene; k, 0.05 to 0.09; N, 149000 to 220000 m(-1)) by a NaOH treatment to the fabricated thin porous silica-gel layer before silanization with ODCS. The electrochromatographic separation of proteins and peptides by using the NaOH-treated column could obtain more peaks than electrophoretic separation.     

Conformational studies on poly(ethacrylic acid) in aqueous salts by potentiometric,viscometric, optical and1H-NMR measurements

The conformation of poly(ethacrylic acid) was studied in aqueous salts by means of potentiometric, viscometric, optical and¹H-NMR measurements. The modified potentiometric titration curves in aqueous NaCl at ionic strengths 0.01–0.3 and 5–35 °C indicated the pH-induced conformational transition from the compact to extended coil. The standard free energy changes and the difference in molar heat capacity between the two conformers were estimated from the potentiometric data. The viscometric and optical behaviours did also show the existence of the compact form at acid pH's and the pH-induced conformational transition to the extended coil in aqueous NaCl and NaClO₄. From comparison with the data for poly(methacrylic acid), the results were concluded to be consistent with the existence of the compact form stabilized by hydrophobic interaction between ethyl groups. The methyl widths in 400 MHz¹H-NMR spectra indicated that the side chains in the polymer in the compact form are in a more restricted motional state than in the coil form. Intermolecular aggregations were found at very low degrees of ionization of carboxyl groups.     

Phase transition in the family LaxBi4−xTi3O12: In relation to lattice symmetry and distortion

The ferroelectric phase transition in the family La_xBi_4?xTi₃O₁₂ was investigated by X-ray diffractometry and differential scanning calorimetry. The crystal symmetry is orthorhombic in the range of 1 > x ≥ 0 and tetragonal in x ? 1. It was found that the shift of the phase-transition temperature is closely related to crystallographic symmetry and lattice distortion. (1) As the value of x increases, the ratio of lattice parameters, $\text{a}\text{b}$, decreases toward 1. (2) In the range of 1 > x ≥ 0, the lattice distortion increases with increasing x; just before x exceeds about 1, the distortion reaches a maximum. (3) As x exceeds about 1, the distortion decreases distinctively. (4) In the orthorhombic region, the phase-transition temperature decreases with increasing x. (5) In the tetragonal region, the transition does not occur. (6) The relation of transition temperature T_c to x is represented by a nonlinear function.