Surface properties of TiFe and TiFe-Nb 6.8 at.% electrodes in aqueous solution

Even at ambient pressure and temperature TiFe and TiFe-Nb 6.8 at.% compounds display their outstanding abilities for absorbing hydrogen when cathodically polarized in an aqueous solution. Electrochemical reaction is also highly activated on electrodes made of these intermetallic compounds. This paper describes the results of electrochemical measurement and the surface properties of both TiFe and TiFe-Nb 6.8 at.% electrodes in comparison with those obtained using TiNi_n and TiCo_n (n = 1, 2, 3), emphasizing catalytic activity for the reaction of hydrogen evolution. It was concluded that the electrochemically active site of TiFe or TiFe-Nb 6.8 at.% electrode surface could be formed only after a specified area of the electrode had been covered with hydrogen of one or a few atomic layers. At the same time, this site acts as an entrance and exit for hydrogen into and out of the electrode.     

Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions

The tunnel magnetoresistance (TMR) effect in magnetic tunnel junctions (MTJs) is the key to developing magnetoresistive random-access-memory (MRAM), magnetic sensors and novel programmable logic devices. Conventional MTJs with an amorphous aluminium oxide tunnel barrier, which have been extensively studied for device applications, exhibit a magnetoresistance ratio up to 70% at room temperature. This low magnetoresistance seriously limits the feasibility of spintronics devices. Here, we report a giant MR ratio up to 180% at room temperature in single-crystal Fe/MgO/Fe MTJs. The origin of this enormous TMR effect is coherent spin-polarized tunnelling, where the symmetry of electron wave functions plays an important role. Moreover, we observed that their tunnel magnetoresistance oscillates as a function of tunnel barrier thickness, indicating that coherency of wave functions is conserved across the tunnel barrier. The coherent TMR effect is a key to making spintronic devices with novel quantum-mechanical functions, and to developing gigabit-scale MRAM.     

Schmelzlinienbestimmungsmodell zur vergleichenden Leistungsbeurteilung von Hochofenperioden

Vergleich von Hochofenbetriebsergebnissen mittels Leistungs-Faktor-Definition. Bestimmung der Lage und Form der Schmelzlinie im Hochofen durch Betriebsdaten. Wärmeeinbringen durch Blasform und deren Übertragung durch Konvektion und Strahlung. Einfluß der Wärmebedingungen im Unterofen auf die Lage der Schmelzlinie. Vergleich und Überprüfung der Modellprofile durch Betriebsmessungen. Einfluß verschiedener Unterofenparameter auf Hochofenbetrieb und Schmelzlinie. Schmelzgeschwindigkeit bei W- und ∧-Profilen in Abhängigkeit der Strahlungstemperatur. Untere kritische Höhenlage der Schmelzlinie und dynamisches Verhalten der Schmelzlinie.     

Land cover in East Asia classified using Terra MODIS and DMSP OLS products

Land cover is classified over East Asia using 250‐m Moderate Resolution Imaging Spectroradiometer (MODIS) land surface reflectance, MODIS snow cover and Operational Linescan System (OLS) human settlement data. The classification method includes a decision tree classification scheme that considers 11 kinds of land surface features derived from the OLS product and the time series of two MODIS products in 2000. The decision tree was defined manually based on the experiment because of insufficient training data, ease of tuning by visual interpretation, and extensibility to further research. The resulting classification is compared to three kinds of reference data, i.e. MODIS land cover product, Chinese digital land cover map, and Chinese census. The land cover classification can be input into a hydrological model applied to the Yellow River in China.     

Impact ionization rates in (100)Al0.48In0.52As

Impact ionization rates for electrons and holes in (100) Al_0.48In_0.52As were determined from photomultiplication measurements using AlInAs/GaInAs p⁺-i-n diodes grown by metalorganic vapor phase epitaxy (MOVPE). The impact ionization-rate ratio was derived as being 2.0~3.5 over the electric field range from 400 to 650 kV/cm. Ionization rates were found to be smaller than those previously reported. These results could be useful for designing AlInAs/GaInAs superlattice avalanche photodiodes with an electron-initiated configuration     

Secondary structural analysis in the solid state for analogous sequential polypeptides of glycine-rich sequence of spider dragline silk

Summary Four sequential copolypeptides poly(X-Gly-Gly) with X being Ala, Tyr, Gln, or Leu were prepared as a model of glycine-rich sequence of dragline spider silk produced by Nephila clavipes and their secondary structures in the solid state were characterized by FT-IR spectroscopy. Poly(Tyr-Gly-Gly), poly(Gln-Gly-Gly), and poly(Ala-Gly-Gly) form the β-sheet structures, whereas poly(Leu-Gly-Gly) existed as a disordered conformation as a cast film from formic acid. These results indicated that X-Gly-Gly sequences with Tyr, Gln, and Ala could contribute to the formation of the β-sheet structure in glycine-rich sequence. Received: 5 August 2000/Accepted: 24 August 2000     

Production of d-glucose from pseudo paper sludge with hydrothermal treatment

To convert cellulosic organics contained in industrial paper sludge into glucose, reaction of pseudo paper sludge composed of cellulose and inorganic compounds (calcium carbonate (CaCO₃), talc (Mg₃(Si₄O₁₀)(OH)₂), kaolin (Al₂(Si₂O₅)(OH)₄)) under hydrothermal conditions was studied. Significant amounts of glucose (ca. 23%) could be produced from cellulose in the absence of CaCO₃ for reaction in water at 523 K and 12 min reaction time. On the other hand, in the presence of CaCO3, most glucose decomposed over all conditions, whereas the addition of talc and kaolin to the mixtures increased the glucose yield to about 30%. For the case of chemical recycle of paper sludge with hydrothermal treatment to obtain d-glucose, it can be concluded that it is preferable to separate the calcium carbonate from the paper sludge before hydrothermal treatment.     

Phase diagram and Raman spectroscopy of EuCl2---NaCl binary mixtures

A phase diagram of the EuCl₂---NaCl system was determined by differential scanning calorimetry (DSC) and the activity coefficients of EuCl₂ and NaCl in this system were estimated under some assumptions. According to DSC measurement, it was found that there were two phase transitions at 1123.9 K and 1016.8 K. In order to specify the melting point of EuCl₂ we did Raman spectroscopy experiments. Thus, the melting point of EuCl₂ was evaluated to be 1016.8 K which was detected as the lower peak in the DSC curve. Raman spectroscopy of this system suggested that complex species were not formed clearly in the EuCl₂ poor system and the estimated activity coefficients of EuCl₂ also supported this suggestion.     

Effect of microstructures on dielectric breakdown strength of sintered reaction-bonded silicon nitride ceramics

Silicon nitride (Si₃N₄) was prepared from silicon by a sintered reaction-bonded silicon nitride method using yttria and magnesia as sintering additives. Post-sintering (PS) of nitrided compacts was carried out at 1850°C under a nitrogen pressure of 1 MPa. Effect of PS time on microstructure and dielectric breakdown strength (DBS) of the prepared Si₃N₄ ceramics was evaluated. The DBS was measured using specimens with four different thicknesses (0.30, 0.20, 0.10, and 0.05 mm) in order to examine the thickness dependence. The porosity of the sintered Si₃N₄ decreased by prolonging the PS time, and the full density could be achieved at the PS time of over 6 h. After full densification, rod-like β-Si₃N₄ grains grew up, and their maximum grain size increased from 45.1 to 154.7 μm by prolonging the PS time from 6 to 48 h. The DBS of the thick Si₃N₄ substrates (0.30 mm) showed little variation from 35.4 to 47.0 kV/mm, regardless of the PS time. On the other hand, that of the thin ones (0.05 mm) dramatically decreased from 99.5 to 9.8 kV/mm with increased the PS time from 6 to 48 h. Because the DBS sharply decreased at the thin substrate sintered for longer time in which some large-elongated grains might span the substrate thickness-wise throughout, it was inferred that the interface between β-Si₃N₄ grains and grain boundary phase/intergranular glassy films might be a path of the dielectric breakdown.     

Four-base codon-mediated incorporation of non-natural amino acids into proteins in a eukaryotic cell-free translation system

Various four-base codons have been shown to work for the introduction of non-natural amino acids into proteins in an Escherichia coli cell-free translation system. Here, a four-base codon-mediated non-natural mutagenesis was applied to a eukaryotic rabbit reticulocyte cell-free translation system. Mutated streptavidin mRNAs containing four-base codons were prepared and added to a rabbit reticulocyte lysate in the presence of tRNAs that were aminoacylated with a non-natural amino acid and had the corresponding four-base anticodons. A Western blot analysis of translation products indicated that the four-base codons CGGU, CGCU, CCCU, CUCU, CUAU, and GGGU were efficiently decoded by the aminoacyl-tRNAs having the corresponding four-base anticodons. In contrast, the four-base codons AGGU, AGAU, CGAU, UUGU, UCGU, and ACGU were not decoded. The stop codon-derived four-base codons UAGU, UAAU, and UGAU were found to be inefficient, whereas the amber codon UAG and opal codon UGA were efficient for the incorporation of non-natural amino acids. The application of the expanded genetic code in a eukaryotic cell-free system opens the possibility of a four-base codon-mediated incorporation of non-natural amino acids into proteins in living eukaryotic cells.