Irreversible helix rearrangement from Cis‐transoid to Cis‐cisoid in poly(p‐n‐hexyloxyphenylacetylene) induced by heat‐treatment in solid phase

Polymerization of p‐n‐hexyloxyphenylacetylene (pHPA) by using a [Rh(norbornadine)Cl]₂‐triethylamine catalyst was carried out at room temperature to afford stereoregular helical poly(p‐n‐hexyloxyphenylacetylene)s (PpHPAs). When ethanol and n‐hexane were used as polymerization solvents, a bright yellow PpHPAs, poly( Y ) with M_n = 8.5 × 10⁴ and its purple red polymer, poly( R ) with M_n = 5.3 × 10⁴ were obtained in 95% yields and 84% yields, respectively. Diffuse reflective UV–vis spectra of poly( Y ) and poly( R ) in solid phase showed different broad absorption peaks at 445 and 575 nm, respectively. X‐Ray diffraction patterns of poly( Y ) and poly( R ) showed typical columnar structures assignable to cis‐transoid and cis‐cisoid structures, respectively, which were also supported by molecule mechanics calculation. Poly( Y ) was irreversibly transformed to a reddish‐black polymer, poly( Y‐B ), which columnar diameter was nearly the same as that of poly( R ). Further, poly( Y ) showed an exothermic peak in the differential scanning calorimetry trace at 80 °C for 1 h in N₂ gas. Thus, these findings suggest a thermally irreversible rearrangement from an unstable cis‐transoid form, poly( Y ) with a stretched cis‐transoid helix to a stable cis‐cisoid form, poly( R ), with a contracted cis‐cisoid helix in the solid phase to give poly( Y → B ) with the cis‐cisoid form. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

An Entropy-Based Tool to Help the Interpretation of Common-Factor Spaces in Factor Analysis

This paper proposes a method for deriving interpretable common factors based on canonical correlation analysis applied to the vectors of common factors and manifest variables in the factor analysis model. First, an entropy-based method for measuring factor contributions is reviewed. Second, the entropy-based contribution measure of the common-factor vector is decomposed into those of canonical common factors, and it is also shown that the importance order of factors is that of their canonical correlation coefficients. Third, the method is applied to derive interpretable common factors. Numerical examples are provided to demonstrate the usefulness of the present approach.     

Novel superconducting phases in copper oxides and iron-oxypnictides: NMR studies

We reexamine the novel phase diagrams of antiferromagnetism (AFM) and high-T_c superconductivity (HTSC) for a disorder-free CuO₂ plane based on an evaluation of local hole density (p) by site-selective Cu-NMR studies on multilayered copper oxides. Multilayered systems provide us with the opportunity to research the characteristics of the disorder-free CuO₂ plane. The site-selective NMR is the best and the only tool used to extract layer-dependent characteristics. Consequently, we have concluded that the uniform mixing of AFM and SC is a general property inherent to a single CuO₂ plane in an underdoped regime of HTSC. The T=0 phase diagram of AFM constructed here is in quantitative agreement with the theories in a strong correlation regime which is unchanged even with mobile holes. This Mott physics plays a vital role for mediating the Cooper pairs to make T_c of HTSC very high. By contrast, we address from extensive NMR studies on electron-doped iron-oxypnictides La1111 compounds that the increase in T_c is not due to the development of AFM spin fluctuations, but because the structural parameters, such as the bond angle α of the FeAs₄ tetrahedron and the a-axis length, approach each optimum value. Based on these results, we propose that a stronger correlation in HTSC than in FeAs-based superconductors may make T_c higher significantly.     

Effects of the molecular properties of mixed solvents on the elution of alkyl benzoates in RPLC.

The retention behavior and mechanism of methyl, ethyl, propyl, isopropyl, buthyl and isobuthyl benzoates have been studied at different eluent compositions of aqueous mixtures with water-soluble organic solvents (methanol, ethanol, 1-propanol, 2-propanol, acetonitrile (AN), 1,4-dioxane and tetrahydrofuran (THF)) in RPLC. The retention of the solutes is discussed based on the solvent composition, solvent polarity (ETN value), preferential solvation, hydrogen bonding and solvent clusters of the eluents. The smaller ETN values and the larger preferential solvation of the mixed solvent eluted the solutes faster. The IR spectra of HDO suggested that the solvents, except for methanol and ethanol, break the hydrogen bonding between water molecules, resulting in fast elution of the solutes. Based upon the results, we chose an optimum solvent composition for the separation of benzoates and applied it to the determination of the benzoates in clove.     

Use of various types of column reactors for flow-injection analysis.

Two or three different kinds of immobilized enzymes can be aligned in a minireactor so that sequential enzymatic reactions are carried out from upstream to downstream during flow-injection analysis. A lactate oxidase-catalase reactor, used as precolumn for removing pre-existing lactate in serum before the lactose dehydrogenase (LDH) reactions, was useful for the determination of serum LDH activity, which did not require any blank correction. A sequential glutamate dehydrogenase-glutamate oxidase reactor was also useful for a novel chemiluminometric determination of ammonia. On the other hand, a co-immobilized creatininase-creatinase-sarcosine oxidase reactor, in spite of containing creatininase which catalyses the reversible reaction, was the most efficient for the determination of serum creatinine.     

An upper bound approach on yield surfaces of porous materials

Summary Triaxial deformation of a porous material is analyzed. A material model is proposed where the material consists of spherical cells each of which has a spherical pore in the center of the matrix. The velocity field in the matrix is assumed and the upper bound approach is attempted. The yield surfaces of the porous materials with various volume fractions of pores v _f are obtained as ellipsoids whose axes become smaller with increasing v _f.They coincide with the yield surfaces which have been proposed by the authors earlier.

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Ein Obere-Schranken-Ansatz für den Fließort von porösem Material

Übersicht Analysiert wird die dreiachsige Deformation eines porösen Werkstoffs, der durch kugelförmige Zellen mit sphärischen Löchern im Zentrum der Matrix modelliert wird. Für die Anwendung des Obere-Schranken-Satzes wird ein Geschwindigkeitsfeld in der Matrix angesetzt. Damit erhält man als Fließort von porösen Werkstoffen mit verschiedenen Porenvolumen-Anteilen v _fEllipsoide, deren Hauptachsen mit zunehmendem v _fkleiner werden. Sie stimmen mit den Fließorten, welche die Autoren schon früher halbexperimentell und halb-analytisch ermittelt haben, überein.

     

Atropisomerism observed in indometacin derivatives

To elucidate the active conformation of indometacin that differentiates between cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), the stereochemistry around the N-benzoylated indole moiety of indometacin was studied. Resolution of stable atropisomers as representative conformations was found to be possible by restricting rotation about the N-C7' and/or C7'-C1' bond. Only the aR-isomer showed specific inhibition of COX-1, and COX-2 was not inhibited by either atropisomer.     

A mathematical modeling approach to the formation of urban and rural areas: Convergence of global solutions of the mixed problem for the master equation in sociodynamics

Urban and rural areas are formed by human migration from thinly populated areas to densely populated areas. It is known in sociodynamics that human migration is described by a nonlinear integro-partial differential equation whose unknown function denotes the population density. This equation is called the master equation. The master equation has its origin in statistical physics, and is regarded as one of the most fundamental equations in natural sciences, as its name suggests. We describe the formation of urban and rural areas by making use of global solutions of the mixed problem for this equation. In this paper we prove sufficient conditions for the mixed problem to have a unique global solution that converges to a two-tier step function as the time variable tends to infinity. This step function is a stationary solution of the master equation, and the higher (lower, respectively) step represents a stationary urban (rural, respectively) area. This result mathematically describes the formation of urban and rural areas in the real world.