Ag2O-Doped Bi2Sr2Ca1Cu2Ox Superconductors Prepared via Melt-Quenching

Ag₂O-doped superconducting Bi₂Sr₂Ca₁Cu₂O _x ceramics were prepared by a melt-quenching–reheating method. It is found that the Ag₂O-doped, as-cast specimens exhibit superconductivity ( T _c= around 80 K) by heat treatment at temperatures around 800°C even in an evacuated and sealed silica glass tube, while the undoped specimens do not and vaporize by the corresponding heat treatment. Conversion of the Ag₂O-doped, as-cast specimens into superconducting ceramics when heated in an evacuated vessel is explained in terms of the oxygen donor of Ag₂O in the specimen. This finding enables us to fabricate a desired shape of superconducting Bi₂Sr₂Ca₁Cu₂O _x ceramics sealed in metals or glasses. The addition of Ag₂O to Bi₂Sr₂Ca₁Cu₂O _x melt, however, had deleterious influences on the superconducting properties ( T _c and J _c) of the resultant ceramics when obtained by heat treatment in air.     

Enzymatic assay method for measuring mizoribine levels in serum

A sensitive and specific method for assaying serum mizoribine levels that can be applied to general automatic clinical analyzers was developed. Regression analysis of the enzymatic assay (y) vs. the HPLC method (x) produced the following relation: y=0.964x+0.090 (n=262, Sy, x=6.37 ng/mL).     

Humectants improve myosin extractability and water activity of raw, cured intermediate moisture meats

Glycerol, propylene glycol and sorbitol were incorporated into salt-based intermediate moisture meats manufactured from porcine M. longissimus thoracis and bovine M. biceps femoris by dry curing and air drying at 4°C. Moisture content and water activity (a(w)) in cured pork were reduced by the addition of propylene glycol and sorbitol. Propylene glycol was more effective than sorbitol in lowering a(w). The extractability of myosin heavy chain, used as an index of alteration of myofibrillar protein, decreased in intermediate moisture porcine meats with the addition of salt and was unaffected by sorbitol. However, use of glycerol and propylene glycol in cured and air-dried pork increased the extractability of myosin heavy chain. Whereas intact myofibrils could not be extracted from salt-cured, air-dried beef, myofibrils could be made from air-dried beef cured in the presence of 10% glycol, 5% propylene glycol and 4% sorbitol. Such myofibrils contracted immediately on addition of Mg(2+)-ATP. In addition, even after storafe for 5 months, including 30 days at 25°C, myosin heavy chain could be extracted from meat cured with this combination of humectants. In comparison with salt curing alone, curing meat with the above three humectants together, plus salt, results in intermediate moisture meats more like fresh meat.     

Synthesis and thermal properties of poly(urethane)s containing soft and flexible chain as the diols part

Summary α,ω-Diols with long carbon chains, HO(CH₂)₁₂O(CH₂)₁₂OH, HO(CH₂)₁₂O(CH₂)₁₂O(CH₂)₁₂OH, and HO(CH₂)_mOC₆H₄O(CH₂)_mOH (m =6, 12), reacted with diisocyanates to give the corresponding poly(urethane)s in 87–99% yields. Structure of the polyurethane was confirmed by ¹H and ¹³C NMR spectroscopy. IR absorbance due to ν(C=O) vibration of the polymers obtained from hexamethylene diisocyanate was observed at lower wavenumber than that of the polymers from aromatic diisocyanates. Melting point of the poly(urethane)s decreased with increase in flexibility of the polymer chain. Received: 20 April 1998/Revised version: 1 May 1998/Accepted: 22 May 1998     

Chemical Reactions of Ultraphosphate Glasses with Water at Various Temperatures

The chemical reactions between P₂O₅-ZnO-H₂O ultraphosphate glasses and water were characterized between room temperature and 500°C, using thermogravimetry, differential scanning calorimetry, X-ray diffraction, and ³¹P nuclear magnetic resonance. Water adsorption and hydrolysis reactions of the glass leads to the formation of H₃PO₄ and crystalline ZnH₂P₂O₇ below 200°C. The rate of water adsorption increases, owing to the hygroscopicity of the hydrolysis products of the glass. Devitrification occurs at 250°C via surface reactions. The microstructure of the devitrified glass consists of crystalline Zn₂P₄O₁₂ and a liquid phase containing hydrolysis products of P₂O₅ like metaphosphoric acid (HPO₃) _n. Devitrification is finally followed by water desorption at higher temperatures.     

Photocatalytic inactivation and removal of algae with TiO<Subscript>2</Subscript>-coated materials

The capabilities of TiO₂-coated materials for the inactivation and removal of algae were investigated. As supports for TiO₂, non-woven fabric and Ni foam were chosen. To evaluate the ability of noble metal cocatalyst additions to facilitate the photocatalytic algal inhibition of TiO₂-coated materials, Pd nanoparticles were deposited on non-woven fabric-supported TiO₂ by photoelectrochemical deposition. The fabric-supported Pd/TiO₂ showed higher inhibition activity for algal growth compared to the fabric-supported TiO₂ without Pd. In addition, Ni foam-supported TiO₂ also showed high inhibition activity, both in laboratory-scale tests and open-air tests. Therefore, TiO₂-coated materials with suitable coating methods such as the use of cocatalysts or large surface area can substantially inhibit algal growth. The ability of the TiO₂-coated materials to inhibit algae correlated well with their activity for the photocatalytic decolorization of methylene blue, suggesting a nonspecific mechanism in the breakdown of cellular structures.     

Morphological Effects of Grinding on Bismuth-Based Cuprate Superconductors

Morphological changes of bismuth-based cuprate superconductors, such as the 2223 phase, via a small mechanical force were studied mainly by means of high-resolution transmission electron microscopy and atomic force microscopy. Even light mechanical grinding of the sintered 2223 samples led to the formation of superfine particles that had a width of ∼5 nm. Moreover, we found first that the superfine particles had a discrete thickness of odd numbers of a half unit length c /2 of the 2223 phase, e.g. 1.9 nm, 5.6 nm, and so on. The formation of the superfine particles was due to cleavage at Bi—O double layers that were bound weakly to each other in a unit cell.     

Highly Active Titania Photocatalyst Particles of Controlled Crystal Phase, Size, and Polyhedral Shapes

Mesoscopic crystalline anatase particles of titanium(IV) oxide (titania) with decahedral morphology and with octahedral morphology were synthesized by gas-phase reaction of titanium(IV) chloride with oxygen and hydrothermal reaction of titanate nanowires in an alkaline medium, respectively, and their photocatalytic activities in relation with their crystal morphology were investigated.     

Adsorption mechanism of heavy-metal ion by microspherical tannin resin

The spherical tannin resin (STR) resulting from the reaction between Mimosa (Acacia Mollissima) tannin (condensed-type tannin) and formaldehyde was very porous. The specific surface area of the STR made from 37.5% of tannin was 139.2 m²/g (1 g of the resin in this is wet resin corresponding to 1 g of dried resin). Properties such as specific surface area and average pore radius could be controlled by adjusting the tannin concentration. The apparent activation energy of Cu²⁺ ion adsorption by STR was 3 kcal/mol, and that of Cr⁶⁺ ion was 2 kcal/mol. Since the energy was small, we concluded that the adsorption of metal ions was not influenced significantly by the adsorption temperature. The heat of adsorption for Cu²⁺ ions was only 1.6 kcal/mol, which suggests that the adsorption was a physical phenomenon. It was thought that the diffusion of heavy-metal ions into the porous resin was the rate-determining step of the adsorption since the elution profile of the column method was analogous to the profile of active carbon, which adsorbs physically, the heavy metal ions gradually leaking through the column. The surface and cross section of the STR were observed before and after Cu²⁺ ion adsorption with the scanning electron microscope. The pores of the spherical resin were clogged with adsorbed copper, suggesting that the Cu²⁺ ions were adsorbed during the formation of a multimolecular layer. The adsorption may therefore have been due to physical attractive forces. The rate of adsorption and adsorption isotherms of Cu²⁺ ions from copper salts having various anions was found to vary depending on the type of anion. These phenomena were not thought to be due to the properties of the spherical resin but to differences in the hydration state of copper ions.     

Electrical Conduction at the Interface between Insulating van der Waals Materials

Emergent properties of 2D materials attract considerable interest in condensed matter physics and materials science due to their distinguished features that are missing in their bulk counterparts. A mainstream in this research field is to broaden the scope of material to expand the horizons of the research area, while developing functional interfaces between different 2D materials is another indispensable research direction. Here, the emergence of electrical conduction at the interface between insulating 2D materials is demonstrated. A new class of van der Waals heterostructures consisting of two sets of insulating transition‐metal dichalcogenides, group‐VI WSe₂ and group‐IV TMSe₂ (TM = Zr, Hf), is developed via molecular‐beam epitaxy, and it is found that those heterostructures are highly conducting although all the constituent materials are highly insulating. The WSe₂/ZrSe₂ interface exhibits more conducting behavior than the WSe₂/HfSe₂ interface, which can be understood by considering the band alignments between constituent materials. Moreover, by increasing Se flux during heterostructure fabrication, the WSe₂/ZrSe₂ interface becomes more conducting, reaching nearly metallic behavior. Further improvement of the crystalline quality as well as exploring different material combinations are expected to lead to metallic conduction, providing a novel functionality emerging at van der Waals heterostructures.