Improvement of thermochromic property at low temperatures of CuMo0.94W0.06O4 by Zn substitution

Zinc-doped copper molybdenum oxide, Zn-doped CuMo_0.94W_0.06O₄, was synthesized, and the effects of the Zn doping on the thermochromic property of CuMo_0.94W_0.06O₄ were investigated at low temperatures. X-ray diffractometry and diffuse reflectance UV–Vis spectroscopy clarified that Zn doping for CuMo_0.94W_0.06O₄ promoted the structural phase transition of the γ-phase to the α-phase of CuMo_0.94W_0.06O₄ at low temperatures and Zn-doped CuMo_0.94W_0.06O₄ exhibited a drastic color change in the temperature range of 30–70 °C. Differential scanning calorimetry also confirmed that Zn doping changed the phase transition temperature of CuMo_0.94W_0.06O₄. Consequently, Cu_1?xZn_xMo_0.94W_0.06O₄ with x?=?0.01 exhibited a larger thermal change in the diffuse reflectance spectrum in the visible light range, compared with CuMo_0.94W_0.06O₄. An appropriate Zn-doping ratio was effective for enhancing the thermochromic property of the CuMo_0.94W_0.06O₄ pigment in the visible region in the temperature range of 30–70 °C.

     

Molecular-shape imprinting and immobilization of biomolecules on a polymer containing azo dye

We demonstrate a novel technique for molecular imprinting and immobilization on a surface of a polymer containing azo dyes (azopolymer). The azopolymer was found to be capable of immobilizing micrometer- and nanometer-scale macromolecules (e.g., lambda-DNA, immunoglobulin G (IgG), bacterial protease, and 1-mum polystyrene particles) through photoirradiation with blue-wavelength light. Fluorescence and atomic force microscopy studies revealed that the azopolymer surface deformed along with the shape of the macromolecules, holding them in place after photoirradiation. The desorption of the immobilized macromolecules from the azopolymer surface in an aqueous medium was observed to be very slow, on the time scale of 10 min to weeks, depending on the photoirradiation time. Immunological and enzymatic studies showed that IgG and bacterial protease immobilized on the azopolymer surface retained their original functionality. These results suggest that the azopolymer physically, not chemically, binds the macromolecules because of the increase in contact area between the macromolecules and the azopolymer surface after photoirradiation.     

Density-ratio matching under the Bregman divergence: a unified framework of density-ratio estimation

Estimation of the ratio of probability densities has attracted a great deal of attention since it can be used for addressing various statistical paradigms. A naive approach to density-ratio approximation is to first estimate numerator and denominator densities separately and then take their ratio. However, this two-step approach does not perform well in practice, and methods for directly estimating density ratios without density estimation have been explored. In this paper, we first give a comprehensive review of existing density-ratio estimation methods and discuss their pros and cons. Then we propose a new framework of density-ratio estimation in which a density-ratio model is fitted to the true density-ratio under the Bregman divergence. Our new framework includes existing approaches as special cases, and is substantially more general. Finally, we develop a robust density-ratio estimation method under the power divergence, which is a novel instance in our framework.     

Polycyclic N-hetero compounds. XXXVII. A convenient synthesis and evaluation of anti-platelet aggregation activity of 1,2,4,5-tetrahydro[1]- benzothiepino[4,5-e]imidazo[1,2-c]pyrimidine and its related compounds

A simple and highly efficient methodology for the synthesis of 1,2,4,5-tetrahydro[1]benzothiepino[4,5-e]-imidazo[1,2-c]pyrimidine ( XI ) having a novel ring system via 4-substituted 5,6-dihydro[1]benzothiepino-[5,4-d]pyrimidines VII-X is described. The anti-platelet aggregation activity for it and its related compounds against collagen-induced aggregation of rabbit blood platelets in vitro was found.     

Evaluation of asymmetrical structure dialysis membrane by tortuous capillary pore diffusion model

The tortuous capillary pore diffusion model (TCPDM) has been used for estimating diffusive and pure water permeability from simple structure parameters such as pore diameter, surface porosity, wall thickness and tortuosity. The validity of this model for evaluation of homogeneous membrane has been already confirmed. Recently, there is a trend toward the use of asymmetrical dialysis membranes made of synthetic polymer such as poly(acrylonitrile) (PAN), polysulfone (PS) and a polyethersulfone polyarylate (PEPA) blend polymer. The purpose of the present study is to apply the TCPDM to evaluation of commercially available hollow-fiber dialysis membranes with asymmetrical structures by simplifying them to a double-layer membrane. The TCPDM is capable of estimating pore tortuosity of asymmetrical dialysis membranes having skin and supporting layers from data on membrane thickness, pore diameter, pure water permeability and water content. Values for diffusive permeability obtained by the TCPDM are in a good agreement with experimental data. This TCPDM model is useful for evaluation of not only homogeneous membrane but also asymmetrical membrane.     

Folding Dynamics of 10‐Residue β‐Hairpin Peptide Chignolin

Short peptides that fold into β‐hairpins are ideal model systems for investigating the mechanism of protein folding because their folding process shows dynamics typical of proteins. We performed folding, unfolding, and refolding molecular dynamics simulations (total of 2.7 μs) of the 10‐residue β‐hairpin peptide chignolin, which is the smallest β‐hairpin structure known to be stable in solution. Our results revealed the folding mechanism of chignolin, which comprises three steps. First, the folding begins with hydrophobic assembly. It brings the main chain together; subsequently, a nascent turn structure is formed. The second step is the conversion of the nascent turn into a tight turn structure along with interconversion of the hydrophobic packing and interstrand hydrogen bonds. Finally, the formation of the hydrogen‐bond network and the complete hydrophobic core as well as the arrangement of side‐chain–side‐chain interactions occur at approximately the same time. This three‐step mechanism appropriately interprets the folding process as involving a combination of previous inconsistent explanations of the folding mechanism of the β‐hairpin, that the first event of the folding is formation of hydrogen bonds and the second is that of the hydrophobic core, or vice versa.     

Polycyclic N-hetero compounds. XXXV. Syntheses and anti-platelet aggregation activity of 5,6-Dihydro-4H-benzo[3,4]cyclohept[1,2-e]imidazo[1,2-c]pyrimidines with an oxygen function at the 1-position

Various 6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-d][pyrimidines bearing amino acid group at the 4-position of the skeleton were synthesized by the reaction of 4-chloro-6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-d]-pyrimidine with some amino acid, which were cyclized to 5,6-dihydro-4H-benzo[3,4]cyclohept[1,2-e]imidazo-[1,2-c]pyrimidines, corresponding to B-homo-11,13,15-triazasteroids. Their inhibitory activities against platelet aggregation induced by collagen were also investigated.