Setting properties of alginate impression materials in dynamic viscoelasticity

The viscoelastic properties of three alginate impression materials were investigated. A landmark of working time was calculated using a raw phase-time curve. A landmark of setting time was calculated from an inflection point of the divided difference of the first order in the share modulus-time curve. As a result, the working time was common at the point of delta = 45 degrees in variable frequencies. The mean value was obtained with less deviation. The setting times obtained were similar for variable frequencies. The mean values showed a distinct difference for each impression material.     

Is the intracellular pH threshold an anaerobic threshold from the view point of intracellular events?: a brief review

Intracellular biochemical changes could be monitored noninvasivery and continuously by using nuclear magnetic resonance (NMR). In about the last decade, intracellular behavior of phosphorus compounds and pH during muscle contraction in man have been studied by 31P nuclear magnetic resonance spectroscopy (31P-MRS). During incremental load, lactic acidosis was followed by a decline in intracellular pH. 31P-MRS studies has been definitely proved that this change in intracellular pH shows the threshold behavior. Some reports discussed the intracellular pH threshold (pHT) as an anaerobic threshold (AT) from the view point of intracellular events. However, our studies revealed that pHT did not reflect the onset of lactate production. In this article, studies of intracellular pH of working muscle were reviewed in relation to an anaerobic threshold.     

Purification and characterization of pili of a Vibrio cholerae non-O1 strain

Pili of the Vibrio cholerae non-O1 strain V10 were purified and characterized. The V10 pili were physicochemically and immunologically different from those of the previously reported V. cholerae non-O1 strain S7, although the pili of the two strains had homologous N-terminal amino acid sequences. V10 plus antigen was detected only in V. cholerae non-O1 strains.     

Ionic conductivity and morphology of complexes formed by polyurethanes and lithium perchlorate

Summary Segmented polyether urethane (SEU) and urethaneurea (SEUU) were synthesized using ABA type triblock copolymer as a prepolymer, where A stands for poly(oxyethylene) and B stands for poly(oxytetramethylene). Lithium perchlorate was dissolved in SEU or SEUU to prepare LiC10₄ complexes (SEU/LiC10₄ and SEUU/LiC10₄) in film form. The highest conductivities observed here were 5.13x10^-6 S cm^-1 at 30°C and 3.34x10^-5 S cm^-1 at 50°C for LiC10₄/SEUU (oxyethylene-units content, 31 mol%). The ionic conductivity of these complexes was found to show the Arrhenius type temperature dependency. The effect of lithium perchlorate dissolution on the morphology of SEU and SEUU were also discussed.     

Analysis of CYP2D6 substrate interactions by computational methods

Cytochrome P450 CYP2D6 is involved in the oxidation of well over 150 drugs and, in general, those which contain a basic nitrogen atom in the molecule. To clarify how the residues of CYP2D6 are utilized for orientating a wide range of its specific substrates and distinguishing them from a variety of other organic compounds, docking studies by AutoDock and molecular dynamics (MD) simulations were conducted. Specific ligands were docked to both the homology model and crystal structures optimally to estimate the site of reaction on the ligand molecule and the binding energy for the complex, which were generally in good agreement with the experimental data. MD simulation for the CYP2D6-propranolol complex was then carried out to reveal the amino acid residues interacting with the substrate at the active site. Phe-120, Glu-216, Asp-301, and Phe-483 are identified as the substrate-binding residues in agreement with previously reported site-directed mutagenesis data and the crystal structure reported recently (PDB code: 2F9Q). As well as these residues, our theoretical prediction suggests that Phe-219 and Glu-222 are also important residues for mediating oxidation of substrates, especially propranolol.     

Observation of secondary particles grown on crystal surfaces of silicon carbide

Pressureless sintering of ultrafine SiC powder containing a large amount of free Si was carried out with the aid of boron. Epitaxial growth of secondary particles was observed by scanning electron microscopy (SEM) on some hexagonal-shaped surfaces of -SiC cube-octahedra. The other hexagonal-shaped surfaces were seen to be entirely smooth. The two-fold symmetry of the [100] axes for the appearance of secondary particles certainly reflects the polarity of -SiC. When the sintering was repeated again, coalescence growth of secondary particles was remarkable on the former surfaces and layered growth was predominant on the latter surfaces.     

Sol-Gel Processing and Conduction Mechanism of RuO2-Glass Thick-Film Resistors

Sol-gel processing was used to study the conduction mechanism in RuO₂-glass thick-film resistors (TFRs). The relation between resistance and conductive particle concentration was studied on TFRs with uniformly dispersed RuO₂ particles in lead silicate glass. The resistance-concentration relation was best expressed by the percolation theory, whereas conventional TFRs showed a marked deviation. Conductivity measurements and Auger spectroscopy of glass films heated in contact with RuO₂ films revealed appreciable dissolution of RuO₂ in glass. Summarizing the experimental results, a percolation theory has been proposed as a possible conduction mechanism.     

One‐component epoxy resin with imine as water‐initiated latent hardener: Improvement of the mechanical and adhesive properties by the addition of methacrylate copolymer

The effect of addition of methacrylate polymer into a one‐component epoxy resin, containing Epikote 828 and diimine as a water‐initiated hardener, was examined. Although the cured epoxy resin in the presence of methyl methacrylate–butyl acrylate (MMA–BA) copolymer was very brittle, the resin containing MMA–BA–[γ‐(methacryloxy)propyl]trimethoxysilane (TMSMA) copolymer showed good mechanical and adhesive properties. The adhesive strength of the cured epoxy resin containing MMA–BA–TMSMA copolymer was much higher than that without its polymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1943–1949, 2005     

Improvement of Water Lubricity of Titanium Nitride–Titanium Composite by Hydrophilic Silane Coupling Agent

To improve the lubricity of titanium nitride–titanium (TiN–Ti) composite in water, a hydrophilic silane coupling agent was added to the water. The tribological characteristics of the TiN–Ti composite in distilled water and in aqueous solutions of the silane coupling agent ranging in concentration from 0.001 to 0.1 mol/L were investigated. The silane coupling agent effectively inhibited the formation of a thick titanium oxide layer, which degrades the water lubricity of Ti-based materials, on the sliding surface. The lubricity of the TiN–Ti composite in the aqueous solutions of the silane coupling agent was much better than that in distilled water.