Rod-like liquid crystals of organic transition metal complexes. I. Reversible transformation between blue smectogen and red nematogen

Two novel types of transition-metal-containing liquid crystals, bis(p-n-koxydithiobenzoato)nickel(II) (abbreviated as (C_nO-DTB)₂Ni), and (p-n-alkoxydithiobenzoato)(p-n-alkoxyperthiobenzoato)nickel(II) (abbreviated as (C_nO-DTB)(C_nO-PTB)Ni), were synthesized. It was found that the (C_nO-DTB)₂Ni complex for n = 8 has smectic H and C mesophases, and that the (C_nO-DTB)₂Ni complexes for n = 4 and 8 easily transform into the corresponding monoperthio complexes, _nO-PTB)Ni, by heating at temperatures between 230°C and 285°C. It was confirmed that the transformation originates from an intermolecular reaction between the (C_nO-DTB)₂Ni complexes at high temperatures, and that the origin of the extra sulphurs in the resulting (C_nO-DTB)(C_nO-PTB)Ni complexes is the neighbouring (C_nO-DTB)₂Ni complexes. Interestingly, each of the (C_nO-DTB)(C_nO-PTB)Ni complexes (n = 4 and 8), has nematic mesophase and exhibits a unique double melting behaviour via the nematic phase, which is the first example in liquid crystals. The reversible transformation between the blue smectic rod-like (C_nO-DTB)₂Ni complex and the red nematic Λ-like (C_nO-DTB)(C_nO-PTB)Ni complex is possible.     

Self-assembly formation of the ordered nanostructure arrays induced by Be interaction with Si(1 1 1) surface

Formation of the beryllium (Be) submonolayers on the Si(1 1 1)7 × 7 surface has been studied using scanning tunneling microscopy. It has been found that Be interaction with Si(1 1 1) at 500-700 °C results in a self-assembly formation of the four various types of the highly-ordered nanostructure arrays. The nanostructure arrays develop on top of the “soft” silicide layer, which period and orientation alter with the nanostructure growth: the shorter the nanostructure period, the larger the rotation angle. The main structural parameters of the silicide layer and nanostructure arrays have been established.     

Zeta Functions of Graph Coverings

We give a decomposition formula for the zeta function of a group covering of a graph.     

Analysis of a time-limited service priority queueing system with exponential timer and server vacations

We consider a multi-class priority queueing system with a non-preemptive time-limited service controlled by an exponential timer and multiple (or single) vacations. By reducing the service discipline to the Bernoulli schedule, we obtain an expression for the Laplace-Stieltjes transform (LST) of the waiting time distribution via an iteration procedure, and a recursive scheme to calculate the first two moments. It is noted that we have to select embedded Markov points based on the service beginning epochs instead of the service completion epochs adopted for most of M/G/1 queueing analyses. Through the queue-length analysis, we obtain a decomposition form for the LST of the waiting time in each queue having the exhaustive service.      

Improvement of stability of phenacyloxycarbamidomethyl (Pocam) group,a cysteine protecting group removable with zinc reduction,under acidic conditions

In order to improve the stability of phenacyloxycarbamidomethyl (Pocam) group, a cysteine protecting group removable with zinc reduction, under acidic conditions, various alkyl substituents on the nitrogen atom of Pocam group were examined. As a result, attachment of an electron-withdrawing group improved the stability, and 2,2,2-trifluoroethyl (Tfe) group was most effective among four substituents tested. Tfe-Pocam group could be used in solid-phase peptide synthesis and peptide condensation reactions, and it was also useful for regioselective disulfide formation reactions.     

Pressure-induced structural transformations and the anomalous behavior of the viscosity in network chalcogenide and oxide melts

It is known that a number of compressed melts undergo structural phase transitions. Data on the structural changes at high pressures in chalcogenides (AsS, As₂S₃) and oxide (B₂O₃) melts with a network structure have been reviewed. Viscosity is one of the fundamental physical properties of a liquid. For various melts, it varies in a very wide range. Structural transformations in melts induce the corresponding changes in all physical properties, in particular viscosity. The measurements of the viscosity of a number of melts at high pressures and temperatures by the radiographic method have been reported. Changes in the viscosity by several orders of magnitude have been detected when the pressure is varied by several gigapascals. The diffusion mechanism in network-structure melts at various pressures has been analyzed. The prediction of the behavior of the viscosity of various melts at superhigh pressures is of high importance for the physics of glass transition, geophysics, and materials science.     

Piezo electric sensor for endocrine-disrupting chemicals using receptor-co-factor interaction.

In vitro screening assays are useful techniques for the determination of receptor-mediated activities in environmental samples. In order to define whether environmental chemicals act as an agonist or antagonist to the human estrogen receptor (hER), we have constructed a biosensor based on ligand-inducible interactions between hER and relative proteins on a quartz crystal microbalance (QCM). The his-tagged proteins, which were expressed in E. coli by recombinant DNA technology, were immobilized on an Au-electrode with Ni(II)-mediated chemisorption using the histidine tag and thiol-modified iminodiacetic acid. The resonance-frequency change of the protein-modified electrode was caused by association or dissociation with the hER relative proteins on the surface in the presence of estrogen. These results suggest that this sensor is applicable as a large-scale screening tool for estrogenic compounds.