Preparation of surfactant-free vinyl polymers by conventional emulsion polymerization using hydrolysable emulsifiers

Emulsion polymerizations of several vinyl monomers, styrene, methyl methacrylate, butyl methacrylate, butyl acrylate, and vinyl acetate, in water using alkali–hydrolysable cationic surfactants with a betaine ester group (1-alkoxycarbonylmethyl)trimethylammonium chlorides, as emulsifiers were carried out and properties of the resulting latices and the polymers recovered by hydrolysis and salting out were investigated. There were little influences of the surfactants and monomers used here on the polymerizations, forming stable and monodisperse latices with a mean diameter of ca. 70 nm and giving a high molecular weight of polymers at high yields. All polymers were precipitated and recovered by adding a small amount of sodium hydroxide into the latex solutions contained little amount of ionic species. Solvent-cast films of the polymers were found to have surfaces as hydrophobic as those for the corresponding pure polymers prepared by bulk polymerization.     

Ce3+-activated fluoride crystals as prospective activemedia for widely tunable ultraviolet ultrafast lasers with direct 10-nspumping

New possibilities have been investigated for recently developed solid-state tunable ultraviolet (UV) laser materials such as Ce³⁺ ion-activated LuLiF₄ (LLF) and LiCaAlF₆ (LiCAF). With their broad-gain width, demonstrated reliability, and high efficiency, they are attractive for ultrashort pulse generation and amplification. To prove that, we have demonstrated UV picosecond-pulse amplification using Ce:LLF. For such new laser materials, we proposed a passive self-injection seeding scheme for the direct generation of short-pulse trains, which does not require CW operation capability or an external short-pulse seeding laser, Using this simple scheme, a UV sub-nanosecond pulse train is directly and passively generated from Ce:LLF pumped by a standard 10-ns KrF excimer laser, and Ce:LiCAF pumped by the fourth harmonic of a conventional 10-ns Q-switched Nd:YAG laser     

Effects of additives on prebreakdown phenomena in n-hexane

Prebreakdown phenomena in n-hexane are observed in detail for positive and negative polarities by using simultaneously a high speed schlieren technique and an LED current measuring system, when an impulse voltage (1.1/225 μs) is applied to a point-to-plane electrode gap. Furthermore, the effects of several additives on the streamer propagation are investigated. Especially the effects of electron-trapping additives on negative streamer propagation and of low ionization potential additives on the positive streamer propagation, are examined, as is a correlation between the shape and the propagation velocity of the streamers     

Expression of Human DNAJ (Heat Shock Protein-40) B3 in Humanized UDP-glucuronosyltransferase 1 Mice

The human DNAJB3 gene encodes a DNAJ (Heat shock protein 40; Hsp40) homolog, subfamily B, member 3 chaperone protein (DNAJB3), which can be down-regulated in disease conditions, as observed in decreased expression of DNAJB3 mRNA in peripheral blood mononuclear cells (PBMC) of obese patients. Recently, humanized UDP-glucuronosyltransferase (UGT) 1 mice (hUGT1 mice) were developed, in which the introduced human UGT1 gene contained a gene encoding human DNAJB3. In the present study, we analyzed the expression of human DNAJB3 mRNA in hUGT1 mice. Among the examined tissues, the testis had the highest expression of human DNAJB3 mRNA, while the lowest expression was observed in the liver. We found that the pattern of tissue-specific expression of mouse Dnajb3 in hUGT1 mice was very similar to that of human DNAJB3. We further demonstrated that the expression of human DNAJB3 in the liver was significantly reduced in high-fat-diet-fed hUGT1 mice compared to the expression level in the control mice, indicating that the expression of human DNAJB3 in hUGT1 mice could be similarly regulated in disease conditions such as obesity. Humanized UGT1 mice might therefore be useful to investigate the physiological role of human DNAJB3 in vivo.     

Repeatable change in electrical resistance of Si surface by mechanical and electrical nanoprocessing

The properties of mechanically and electrically processed silicon surfaces were evaluated by atomic force microscopy (AFM). Silicon specimens were processed using an electrically conductive diamond tip with and without vibration. After the electrical processing, protuberances were generated and the electric current through the silicon surface decreased because of local anodic oxidation. Grooves were formed by mechanical processing without vibration, and the electric current increased. In contrast, mechanical processing with vibration caused the surface to protuberate and the electrical resistance increased similar to that observed for electrical processing. With sequential processing, the local oxide layer formed by electrical processing can be removed by mechanical processing using the same tip without vibration. Although the electrical resistance is decreased by the mechanical processing without vibration, additional electrical processing on the mechanically processed area further increases the electrical resistance of the surface.     

Improvement of a Measurement System for Surface Loss Rate of Ozone

Ozone molecules present in high-purity oxygen as a feed gas interact with surfaces and oxygen molecules in an enclosed container. Therefore, some of the ozone molecules are destroyed and the density of ozone decreases with time. An experimental system has been constructed to monitor the temporal decrease in ozone density in a container based on the HgI 254 nm photoabsorption method. Our investigation is focused on the dependence of the effective lifetime of ozone on the wall material at various gas pressures. During the experiments, distortion of the measured decay curves often caused by instabilities in the mercury lamp intensity. We thus attempted to build a simple setup that eliminates the effect of long-term intensity drift. This setup is based on light source intensity monitoring by a separate photodetector and data correction software. This article describes the setup of the experimental apparatus, the results including some preliminary experiments and the temporal variation of the surface loss rate of ozone by repeated measurement along with inspections of the wall surface by Auger electron spectroscopy.     

Euphorbia tirucalli β-Amyrin Synthase: Critical Roles of Steric Sizes at Val483 and Met729 and the CH–π Interaction between Val483 and Trp534 for Catalytic Action

The functions of Val483, Trp534, and Met729 in Euphorbia tirucalli β-amyrin synthase were revealed by comparing the enzyme activities of site-directed mutants against that of the wild type. The Gly and Ala variants with a smaller bulk size at position 483 predominantly afforded monocyclic camelliol C, which suggested that the orientation of the (3S)-2,3-oxidosqualene substrate was not appropriately arranged in the reaction cavity as a result of the decreased bulk size, leading to failure of its normal folding into the chair–chair–chair–boat–boat conformation. The Ile variant, with a somewhat larger bulk, afforded β-amyrin as the dominant product. Intriguingly, various variants of Trp534 exhibited significantly decreased enzymatic activities and provided no aberrantly cyclized products, although the aromatic Phe and Tyr residues were incorporated and the steric sizes of the aliphatic residues were altered. Therefore, the Trp534 residue does not stabilize the transient cation through a cation–π interaction. Furthermore, the Trp residue, with the largest steric bulk among all natural amino acids, is essential for high enzymatic activity. Robust CH–π complexation between the Val483 and Trp534 residues is proposed herein. Altering the steric bulk at the Met729 position afforded the pentacyclic skeletons. Thus, Met729 is positioned at the E-ring formation site. More detailed insights into the functions of the Val483, Trp534, and Met729 residues are provided by homology modeling.