The rheology of suspensions of titanate fibers in polymer solution

The, Theological properties of suspensions of relatively small amounts of titanate fibers in polystyrene solution have been measured by means of a Weissenberg rheogoniometer. The titanate fibers employed have diameters smaller than 0.5 micron and aspect ratios higher than 40. It has been found that the rheological properties of the suspensions are markedly time dependent; the steady-flow shearing stress increases with increasing time when the rate of shear is changed abruptly from an initial high value to a considerably lower final value. This behavior can be attributed to the re-formation of a structure formed by the dispersed fibers and broken at higher shear rates. The dynamic storage modulus G′ also depends strongly upon the re-formation of the structure. Although the structure reformation process under shear appears too complicated to be analyzed satisfactorily, an attempt has been made to generalize the experimental data with a simple equation.     

Ionotropic and metabotropic glutamate receptor agonist-induced [Ca2+]i increase in isolated rat supraoptic neurons

Although a number of studies have shown that various free fatty acids (FFAs) and monoacylglycerides (MGs) have bactericidal properties in vitro, the role of these compounds in vivo has not been determined. This study evaluated the antibacterial properties of medium-chain MGs and FFAs for different bacterial enteropathogens with an in-vitro bacterial killing assay and an in-vivo model of intestinal colonisation. Incubation of test bacteria with medium-chain MGs for 4 h led to 100-10,000-fold reductions in numbers of viable cells of Vibrio cholerae, Salmonella typhi, Shigella sonnei and enterotoxigenic Escherichia coli (ETEC). Lauric acid was the only medium-chain FFA to show comparable in-vitro bactericidal activity. The ability of dietary MGs to reduce or eliminate bacterial colonisation of the intestinal tract was evaluated in mice that were predisposed to bacterial colonisation by treatment with streptomycin (STR+). Mice were treated with streptomycin, challenged intragastrically with V. cholerae or ETEC, and given monocaprin (C10:0 MG) either concurrently or as part of the daily diet. Control mice given STR+ without MGs and challenged with V. cholerae or ETEC showed high numbers of challenged bacteria in gastrointestinal contents by 1 h after administration. Concurrent administration of V. cholerae and C10:0 MG (2.5 mg/ml) caused > 1000-fold reduction in numbers of V. cholerae recovered from the gastrointestinal tracts of STR+ mice. Concurrent administration of C10:0 MG with ETEC did not cause a reduction in the number of viable ETEC present in the intestinal tract of STR+ mice. Administration of C10:0 MG in the diet had no effect on the number of viable V. cholerae or ETEC associated with caecal or ileal tissue of STR+ mice when C10:0 MG in the diet was started 1 day before, the same day, or 2 days after bacterial challenge. Collectively, these results suggested that dietary MGs may prevent intestinal colonisation by bacterial enteropathogens if administered at the time of exposure, but have little effect on established intestinal infections.     

Electroconductivity of sintered bodies of α-Al2O3-TiN composite prepared by CVD reaction in a fluidized bed

α-Al₂O₃ particles whose primary size is ca. 450 nm are smoothly fluidized by forming agglomerates of ca. 200 μm and are coated with TiN crystallites generated by a chemical vapour deposition (CVD) reaction of TiCl₄ and NH₃ at 973 K. The α-Al₂O₃-TiN composite particles and those obtained by mechanically mixing constituent particles are sintered at 1873 K in a nitrogen atmosphere, and the electroconductivity of sintered bodies is measured at 298 K. The electroconductivity of the CVD-hybridized composites is higher than that of mechanically mixed ones. This shows the effectiveness of fluidized-bed CVD processing in the preparation of composite ceramic particles.     

Preparation of nickel and Ni-Zn ferrite films by thermal decomposition of metal acetylacetonates

Nickel and Ni-Zn ferrite (Ni_1–x Zn _x Fe₂O₄) films were prepared on various substrates (quartz glass, MgO single crystal, etc.) by thermal decomposition of metal acetylacetonates (Ni (acac)₂ · 2H₂O, Zn (acac)₂ · 2H₂O and Fe (acac)₃). Typical decomposition and heat treatment conditions for obtaining a single phase of NiFe₂O₄ film were as follows: evaporation temperature of Ni-Fe complexes: 230°C, the mole concentration of Fe (acac)₃,R (%) = Fe (acac)₃/(Fe (acac)₃ + Ni (acac)₂ · 2H₂O) = 33, substrate temperature: 330 to 550° C, and heat treatment of the as-grown film: 800 to 1000° C, 1 h. Ni_1–x Zn _x Fe₂O₄ films were obtained by controlling the compositionR in Ni-Fe complexes and the evaporation temperature of Zn (acac)₂ · 2H₂O. The Ni-Zn ferrite film at the compositionx = 0.37 (Ni_0.63Zn_0.37Fe₂O₄) gave the maximum saturation magnetization _s = 60 emu g^–1 and the coercive forceHc 25 Oe. These films showed a magnetic anisotropy which makes the magnetization easy parallel to film surface.     

High temperature and pressure preparation and properties of iron carbides Fe7C3 and Fe3C

The formation regions of Fe₇C₃ and Fe₃C were determined at high temperature and high pressure in the iron-graphite system. Fe₇C₃ formed at relatively higher pressures and Fe₃C at lower pressures. Both Fe₇C₃ and Fe₃C were isolated from coexisting excess carbon powders by a magnetic method. Fe₇C₃ had a Curie point of 250° C and a saturation magnetization of 120 emu g^–1 at room temperature and Fe₃C had those of 210° C and 125 emu g^–1. Fe₇C₃ decomposed to Fe₃C and carbon at 600° C, but to -Fe and carbon at 700° C at atmospheric pressure, and Fe₃C to -Fe and carbon at 700° C. The substitution of other metals (Cr, Mo and W) for iron in these carbides leads to changes in the thermal stabilities and the magnetic properties.     

Synthesis of barium hexaferrite for magnetic recording media using the KCl flux system

Individual and fine crystals of barium hexaferrite were prepared by a modified flux method using the KCI flux system. Co²⁺-Ti⁴⁺-substituted barium hexaferrite with a homogeneous composition was synthesized at 950° C for 5 h or at 1000° C for 1 h from a mixture of BaCO₃, Fe₂O₃, CoO and TiO₂ with 30 wt% KCI added. Laboratory-prepared fine Fe₂O₃, was preferred because it gave ferrite particles with diameters of 0.2 to 0.4m. Magnetic properties were controlled by the Co-Ti content in hexaferrite crystals. Coercive force and Curie temperature decreased with the degree of Co-Ti substitution with saturation magnetization held at high value. The present process, from which individual and fine barium hexaferrite crystals can be prepared by using the KCI flux system, is recommended as a means of mass-production of ferrite powders with controlled magnetic properties for use in magnetic recording media.     

Involvement of catalyst materials in nonthermal plasma chemical processing of hazardous air pollutants

Catalytic effects of metal oxides in nonthermal plasma chemical processing of hazardous air pollutants (HAPs) are discussed, relevant to their activities for the oxidation of HAPs in nonthermal plasma media and their selective control of active oxygen species derived from background O₂. In ferroelectric packed-bed reactors, the oxidation power of barium titanate (BaTiO₃) is not strong enough to oxidize HAPs and their carbon intermediates to CO₂. Only nitrous oxide (N₂O) was formed from background N₂ and lattice oxygen atoms in BaTiO₃. The catalytic effect of BaTiO₃ is negligible under aerated conditions. On the other hand, ozone (O₃) is formed from background O₂ in much higher concentrations in a silent discharge plasma reactor. Manganese dioxide (MnO₂)-catalyzed decomposition of O₃ promotes decomposition of benzene, which is less reactive than trichloroethylene and tetrachloroethylene. The acceleration of benzene consumption rate is ascribed to the promotion of its oxidative decomposition by the triplet oxygen atom. Catalytic control of in situ active oxygen species could be one of the most effective approaches to increase the energy efficiency of the nonthermal plasma reactor and to achieve the complete oxidation of the carbon atoms in HAPs.     

Multilevel-type multilayer X-ray lens (Fresnel zone plate) by sputter deposition

We have developed a multilevel-type multilayer X-ray lens (Fresnel zone plate, FZP) using sputter deposition. Such a multilevel-type FZP can attain high diffraction efficiency which results in the reduction of radiation damage to biological specimens and the simplification of the X-ray optical system because unwanted diffraction orders are considerably suppressed. Previously, we have reported the effectiveness (i.e., realizing high diffraction efficiency) of a multilevel multilayer FZP with 4-step structure. This paper presents two experimental results on the FZP: (1) the focusing test of a multilayer FZP with 6-step structure in order to realize higher efficiency and (2) the change over time of the focusing characteristic of the FZP with 4-step structure. For (1), the diffraction efficiency of the 1st order focus and the focused beam size measured by knife-edge scanning were found to be more than 50% and 0.8 μm, respectively, at 41.3 keV, and superior to the previous results. For (2), no significant differences have been observed: it can be said that the multilevel FZP is stable at least for 9 months.     

Cloning of a novel prolidase gene from Aureobacterium esteraromaticum

The prolidase gene from Aureobacterium esteraromaticum was cloned and expressed in Escherichia coli. The cloned enzyme had the same enzymatic properties as the wild-type enzyme. Kinetic analysis of the enzyme indicated that the best substrate was Pro-Hyp, which was not hydrolyzed by other prolidases. Interestingly, there was no homology between the deduced amino acid sequence of A. esteraromaticum prolidase and those of the other sources such as human E. coli and Lactobacillus. However, homology was seen with the yeast hypothetical protein YJL213w, the function of which is unknown. These findings indicate that the A. esteraromaticum prolidase is a novel enzyme different from other prolidases reported to date.