Cross-phase modulation in fiber links with multiple opticalamplifiers and dispersion compensators

We have theoretically and experimentally investigated the cross-phase modulation (XPM) effect in optical fiber links with multiple optical amplifiers and dispersion compensators. Our theory suggests that the XPM effect can be modeled as a phase modulator with inputs from the intensity of copropagating waves. The frequency response of the phase modulator corresponding to each copropagating wave depends on fiber dispersion, wavelength separation, and fiber length. The total XPM-induced phase shift is the integral of the phase shift contributions from all frequency components of copropagating waves. In nondispersive fibers, XPM is frequency-independent; in dispersive fibers, XPM's frequency response is approximately inversely proportional to the product of frequency, fiber dispersion, and wavelength separation. In an N-segment amplified link, the frequency response of XPM is increased N-fold, but only in very narrow frequency bands. In most other frequency bands, the amount of increase is limited and almost independent of N. However, in an N-segment amplified link with dispersion compensators, the frequency response of XPM is increased N-fold at all frequencies if the dispersion is compensated for within each fiber segment. Thus, the XPM-induced phase shift is smaller in systems employing lumped dispersion compensation than in systems employing distributed dispersion compensation     

Low-Temperature Synthesis of Ba(Mg1/3Ta2/3)O3 Ceramics from Ba-Mg-Ta Alkoxide Precursor

BMT perovskite ceramics were synthesized at low temperature (∼100°C) by chemical processing comprised of the hydrolysis of Ba-Mg-Ta alkoxide precursor. FT-IR and Raman spectroscopic studies of the Ba-Mg-Ta ethoxide precursor reveal that barium, magnesium, and tantalum ethoxides are bonded with each other via alkoxy bridging to form a trimetallic alkoxide. The hydrolysis of the Ba-Mg-Ta ethoxide with a large amount of water under refluxing results in the direct formation of a crystalline BMT phase with the pseudocubic perovskite structure at a low temperature of ∼100°C. The alkoxide-derived BMT powder has high sinterability to provide a high-density sintered body with a density of 94.0–98.0% at a low firing temperature of 1400°C.     

Immunological identification of Vibrioparahaemolyticus: Staphylococcal coagglutination test and enzyme-linked immunosorbent assay

The species-specific antigenicity of the lateral flagella of Vibrio parahaemolyticus was applied to techniques for immunological identification of the vibrio. One was a coagglutination test using staphylococcal cells sensitized with anti-lateral-flagella antibody bound to protein A located in the staphylococcal cell wall. The other technique was an enzyme-linked immunosorbent assay (ELISA) using a four-layer sandwich procedure. By means of the staphylococcal coagglutination technique, about 10⁶ vibrio cells or 60 ng of flagellar protein could be detected and the whole procedure was performed within 1 h. The sandwich ELISA procedure was more sensitive, but the time required for the whole procedure was about 8 h. Both techniques were specific for V. parahaemolyticus, because no cross-reactivity was observed with other related vibrios, and the tests were not inhibited by heterologous bacterial cells. These results suggest that both techniques are useful for the rapid identification of V. parahaemolyticus in complex samples.     

Preparation of thin films by sulfurizing sol–gel deposited precursors

Cu₂ZnSnS₄ (CZTS) thin films were prepared by sulfurizing precursors deposited by the sol–gel method. Copper (II) acetate monohydrate, zinc (II) acetate dihydrate and tin (II) chloride dihydrate were used as the starting materials of the sol–gel method, and 2-methoxyethanol and monoethanolamine were used as the solvent and the stabilizer, respectively. The solution was spin coated on soda lime glass substrates and dried at . The coated glasses were sulfurized by annealing at in a hydrogen sulfide-containing atmosphere. The annealed thin films showed X-ray diffraction peaks attributed to the single phase CZTS. The chemical composition of the films was almost stoichiometric and the band gap energy was at room temperature.     

Hierarchical structures of ZnO spherical particles synthesized solvothermally

We review the solvothermal synthesis, using a mixture of ethylene glycol (EG) and water as the solvent, of zinc oxide (ZnO) particles having spherical and flower-like shapes and hierarchical nanostructures. The preparation conditions of the ZnO particles and the microscopic characterization of the morphology are summarized. We found the following three effects of the ratio of EG to water on the formation of hierarchical structures: (i) EG restricts the growth of ZnO microcrystals, (ii) EG promotes the self-assembly of small crystallites into spheroidal particles and (iii) the high water content of EG results in hollow spheres.     

Characterization of rpoH in Acetobacter pasteurianus NBRC3283

The RpoH in Acetobacter pasteurianus NBRC3283 was characterized. It was revealed that the rpoH controls the expression of groEL, dnaKJ, grpE, and clpB to different extents. In addition, the rpoH disruption mutant became apt to be affected by heat, ethanol, and acetic acid, indicating its importance in acetic acid fermentation.     

Detection of CD133 (prominin‐1) in a human hepatoblastoma cell line (HuH‐6 clone 5)

We examined CD133 distribution in a human hepatoblastoma cell line (HuH‐6 clone 5). We directly observed the cultured cells on a pressure‐resistant thin film (silicon nitride thin film) in a buffer solution by using the newly developed atmospheric scanning electron microscope (ASEM), which features an open sample dish with a silicon nitride thin film window at its base, through which the scanning electron microscope beam scans samples in solution, from below. The ASEM enabled observation of the ventral cell surface, which could not be observed using standard SEM. However, observation of the dorsal cell surface was difficult with the ASEM. Therefore, we developed a new method to observe the dorsal side of cells by using Aclar® plastic film. In this method, cells are cultured on Aclar plastic film and the dorsal side of cells is in contact with the thin silicon nitride film of the ASEM dish. A preliminary study using the ASEM showed that CD133 was mainly localized in membrane ruffles in the peripheral regions of the cell. Standard transmission electron microscopy and scanning electron microscopy revealed that CD133 was preferentially concentrated in a complex structure comprising filopodia and the leading edge of lamellipodia. We also observed co‐localization of CD133 with F‐actin. An antibody against CD133 decreased cell migration. Methyl‐β‐cyclodextrin treatment decreased cell adhesion as well as lamellipodium and filopodium formation. A decrease in the cholesterol level may perturb CD133 membrane localization. The results suggest that CD133 membrane localization plays a role in tumor cell adhesion and migration. Microsc. Res. Tech. 76:844–852, 2013. © 2013 Wiley Periodicals, Inc.     

Sol-gel PZT thin films on nickel alloy electrodes

Abstract

The Ni alloy electrode was used for a bottom electrode of PZT thin films prepared by sol-gel process. Although PZT films were crystallized on soda–lime glass substrates with the alloy electrodes at a relatively low temperature of 500°C, second phases of Pb₃O₄ and ZrTiO₄ were produced on the electrode in addition to the perovskite PZT phase. In order to prevent the second phases forming, the heat treatment time of the electrode was increased to obtain the thicker Al₂O₃ layer on the alloy electrode. The second phases decreased with increasing the heat treatment time; however, the phases did not disappear. When BaTiO₃ films were inserted between the electrodes and PZT films, the PZT single phase was obtained. The tan δ of the films decreased with decreasing the amount of the second phases, finally it became 3.9%, the film of which possessed a remanent polarization of 20 μC/cm².     

Liposome-assisted activity of superoxide dismutase under oxidative stress

A biological membrane is the front line of defense for cells against various environmental stresses such as heat and reactive oxygen species (ROS) and is expected to play an important role in the antioxidant system with antioxidant enzymes, similarly to its chaperone-like function in cooperation with heat shock proteins. The oxidative stress response of superoxide dismutase (SOD), which is known to catalyze the dismutation of O(2)(-) to H(2)O(2), was investigated in the presence of artificial membranes, liposomes, in order to obtain fundamental information on the biological ROS scavenging system. SOD lost its activity in the presence of H(2)O(2) and was found to have two loops including one which contains an alpha-helix which presents the substrate O(2)(-) to the activity center of SOD (Cu(II)). From circular dichroism analysis of SOD in the presence of H(2)O(2), the contents of the alpha-helix in SOD were found to decrease in correspondence with the inactivation and conformational change of SOD, suggesting that the conformation of the alpha-helix loops affects SOD activity. In the presence of liposomes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), SOD was not inactivated in the presence of H(2)O(2) although the contents of its alpha-helix structure were decreased. The oxidized SOD was found to interact with the liposome surface under oxidative stress using dielectric dispersion analysis. Based on these results, a possible mechanism of SOD protection against ROS on liposomes was presented.     

Emergence of enterohemorrhagic Escherichia coli serovar O157 strains in clade 8 with highly similar pulsed-field gel electrophoresis patterns

Enterohemorrhagic Escherichia coli serovar O157 (O157) strains with highly similar pulsed-field gel electrophoresis (PFGE) patterns were isolated in Japan during 2007 and 2008. Several genetic features related to O157 evolution were investigated to indicate whether homoplasy might have contributed to the highly similar PFGE patterns in these strains. The O157 strains were classified in lineage I/II, as defined by a lineage-specific polymorphism assay-6 with an atypical allele in Z5935 (code: 231111). Analysis of the insertion sites of stx(2) phage in these strains showed that the sites were "occupied" in yehV and "intact" in wrbA, indicating that the strains were derived from "Cluster 1" of "Subgroup C." When a specific single-nucleotide polymorphism in ECs2357 in clade 8 strains was investigated, all of the strains in the present study were confirmed to be clade 8 strains. These results indicated that the O157 strains in this study had common genetic features, suggesting that the highly similar PFGE patterns of these strains were not due to homoplasy. Because no common source of these strains could be identified in 2007 to 2008 in Japan, these strains may have emerged from a unique O157 clade 8 clone and then spread by dissemination in Japan.