High-Temperature Strength and Creep Behavior of Melt-Infiltrated SiC-Mo≤5Si3C≤1 Composites

Molybdenum carbosilicide composites (SiC-Mo_≤5Si₃C_≤1) were fabricated via the melt-infiltration process. The fracture behavior of the composites was studied from room temperature up to 1800°C in 1 atm (∼10⁵ Pa) of argon. The bend strength of the composites slightly increased at ∼1200°C, because of the brittle-ductile transition of the intermetallic phase. The composites retained ∼90% of their room-temperature strength, even at 1700°C. Compressive creep tests were performed over a temperature range of 1760°-1850°C and a stress range of 200–250 MPa. The creep rate of the SiC-Mo_≤5Si₃C_≤1 composites was approximately an order of magnitude higher than that of reaction-bonded SiC.     

The ac superposition method,a new hot‐line diagnostic method for 6‐kV XLPE power cables

Water trees are the most hazardous factor affecting the life of XLPE distribution cables and the major cause of insulation failure. It is well known that insulation failure causes stoppages in electrical service and requires extensive repair work. Up to now, deterioration of cable insulation has been diagnosed mainly by the dc leakage current method. However, application of this method for diagnostic measurements requires interruption of electrical service. Several types of hot‐line diagnostic methods (including the dc component current and dc superposition methods) were developed to detect water tree deterioration. However, these methods have some shortcomings, such as being subject to effects of stray currents and the accuracy of measurements not being sufficiently high. Therefore, we have attempted to develop a new hot‐line diagnostic method. We investigated whether the signals produced by superposition of voltages of various frequencies to the cover layer of energized cables were correlated with deterioration by the water treeing. As a result, we found that a deterioration signal of 1 Hz was observed when we superposed an ac voltage (commercial frequency × 2 +1 Hz) on the cover layer of cable where the water tree had occurred in the insulation. © 1999 Scripta Technica, Electr Eng Jpn, 130(2): 49–58, 2000     

Purification, characterization, and gene cloning of glycerol dehydrogenase from Hansenula ofunaensis, and its expression for production of optically active diol

Optically active alcohol is an important building block as a versatile chiral synthon for the asymmetric synthesis of pharmaceuticals and agrochemicals. We purified and characterized glycerol dehydrogenase from Hansenula ofunaensis and prepared optically active 1,2-octanediol using a recombinant Escherichia coli harboring the glycerol dehydrogenase gene. The deduced amino acid sequence was investigated for identities with those of other alcohol dehydrogenases in the NCBI databank. The identification of the unknown product of a resting-cell reaction was performed by GC-MS. In the deduced amino acid sequence composed of 376 residues, the NAD(H) binding pattern and cysteine residues that correspond to the cysteine ligands at the zinc atom were conserved as they are in alcohol dehydrogenases from other origins. Glycerol dehydrogenase from Hansenula polymorpha DL-1 (Pichia angusta, DDBJ/EMBL/GenBank accession no. BAD32688) had the highest identity to our enzyme, showing 73% identity. Our glycerol dehydrogenase catalyzed the NAD(+)-dependent oxidation of long-chain secondary alcohols such as 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol. Activities toward 2,4-pentanediol and 2,5-hexanediol were hardly detected. From these results, it was confirmed that our enzyme requires two hydroxyl groups on adjacent carbon atoms for oxidation. 2,3-Pentanedione, 2,3-hexanedione, and 3,4-hexanedione were significantly reduced. The transformants oxidized only (R)-1,2-octanediol in 50 mM racemate (R:S=52:48), and produced (S)-1,2-octanediol (24 mM, <99.9% e.e.) after 24 h of incubation. The reaction product was suggested to be 1-hydroxy-2-octanone by GC-MS, which showed secondary hydroxyl groups oxidized. Glycerol dehydrogenase from H. ofunaensis could be useful for the production of long-chain optically active secondary alcohols.     

Processing of Al/SiC composites in continuous solid–liquid co-existent state by SPS and their thermal properties

Silicon carbide (SiC)-particle-dispersed-aluminum (Al) matrix composites were fabricated in a unique fabrication method, where the powder mixture of SiC, pure Al and Al–5mass% Si alloy was uniquely designed to form continuous solid–liquid co-existent state during spark plasma sintering (SPS) process. Composites fabricated in such a way can be well consolidated by heating during SPS processing in a temperature range between 798 K and 876 K for a heating duration of 1.56 ks. Microstructures of the composites thus fabricated were examined by scanning electron microscopy and no reaction was detected at the interface between the SiC particle and the Al matrix. The relative packing density of the Al–matrix composite containing SiC was higher than 99% in a volume fraction range of SiC between 40% and 55%. Thermal conductivity of the composite increased with increasing the SiC content in the composite at a SiC fraction range between 40 vol.% and 50 vol.%. The highest thermal conductivity was obtained for Al–50 vol.% SiC composite and reached 252 W/mK. The coefficient of thermal expansion of the composites falls in the upper line of Kerner’s model, indicating strong bonding between the SiC particle and the Al matrix in the composite.     

Exploring urban students’ constructions about school, work, race, and ethnicity.

This qualitative study is an exploration of 32 urban high school students’ narratives about the connection between school, work, and societal expectations of their future success related to their racial and ethnic background. The sample varied along 2 contextual dimensions: participation in a psychoeducational intervention (Tools for Tomorrow) and developmental status (i.e., half the sample were 9th-grade students and the other half were 12th-grade students). Using consensual qualitative research, the narratives revealed 3 major domains: future orientation; students’ perceptions of society’s expectations based on race and ethnicity; and students’ perception of the role of their race and ethnicity in future success. Results reveal that the majority of students endorse a connection between school and work, believe that society holds low expectations for them based on their racial and ethnic background, and cannot predict their future success based on their background. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Molecular Analysis of the Polymeric Glutenins with Gliadin‐Like Characteristics That Were Produced by Acid Dispersion of Wheat Gluten

We had earlier shown that the dispersion of wheat gluten in acetic acid solution conferred gliadin‐like characteristics to the polymeric glutenins. To elucidate the molecular behavior of its polymeric glutenins, the characteristics of gluten powder prepared from dispersions with various types of acid were investigated in this study. Mixograph measurements showed that the acid‐treated gluten powders, regardless of the type of acid, had dough properties markedly weakened in both resistance and elasticity properties, as though gliadin was supplemented. The polymeric glutenins extracted with 70% ethanol increased greatly in all acid‐treated gluten powders. Size exclusion HPLC and SDS‐PAGE indicated that the behavior of polymeric glutenins due to acid treatment was attributed to their subunit composition rich in high molecular weight glutenin subunit (HMW‐GS) and not their molecular size. The gluten prepared with the addition of NaCl in acid dispersion had properties similar to those of the control gluten. The results suggest that ionic repulsion induced by acid dispersion made the polymeric glutenins rich in HMW‐GS disaggregate, and therefore, act like gliadins.     

Lipoglycoprotein of Gelatin

Abstract

Solvent extracts were compared with the parent gelatins by means of TLC and HPLC. The photographic effects of the various protein fractions are discussed.     

Some Properties of Oxidized Gelatin

Alkali processed inert type gelatin has been oxidized in a controlled stepivise fashion using H₂,0₂. The difference between oxidation degree of gelatin was detected by a simple physical ripening test and potentiometric titration with AgNO₃. The physical ripening was very influenced by pH and the variety of halide. The titration curve has an inflection point and the plot of pAg vs. logarithm of Ag ion concentration gives a straight line.     

Mechanical Defects Deriving from the Manufacturing Process of High-Density Electronic Boards: Experimental Analysis of Critical Factors

Current market demand calls for electronic boards that are increasingly sophisticated, of high technological content, with high standards of quality and reliability, and cost as low as possible. The high-density electronic boards produced for applications in the biomedical, aerospace, telecommunications, and automation industries are designed using sophisticated procedures that yield optimum results with regard to electronic performances. However, the physical/mechanical and thermal aspects involved in the practical realization of the boards are still based on technological processes that are not as well controlled or as well known with regard to sensitivity to the various characteristic parameters. This results in a high rate of defects occurring in the case of particularly critical boards, due to which finished boards are frequently rejected at inspection or even in service, with significant financial loss. A study has been conducted focusing on qualitative and quantitative analysis of the deformation, and on twisting deformation in particular, of semifinished products during the manufacturing process. A specific procedure has been developed for making measurements and acquiring experimental data, in a research activity commissioned by an Italian company which manufactures electronic boards. Processing of the data and subsequent analysis of the results has made it possible to analyze the production stages having the greatest influence of the extent of the final deformation.     

Dispersion in the Presence of Acetic Acid or Ammonia Confers Gliadin‐Like Characteristics to the Glutenin in Wheat Gluten

Spray‐dried gluten has unique properties and is commercially available in the food industry worldwide. In this study, we examined the viscoelastic properties of gluten powder prepared by dispersion in the presence of acetic acid or an ammonia solvent and then followed by lyophilization instead of a spray drying. Mixograph measurements showed that the acid‐ and ammonia‐treated gluten powders had marked decreases in the time to peak dough resistance when compared with the control gluten powder. The integrals of the dough resistance and bandwidth for 3 min after peak dough resistance decreased in both treated gluten powders. Similar phenomena were observed when gliadin was supplemented to gluten powders. Basic and acidic conditions were applied to the acid‐ and ammonia‐treated gluten powders, respectively, and the viscoelastic behaviors were found to depend on the pH in the gluten dispersion just before lyophilization. These behaviors suggest that gluten may assume a reversible change in viscoelasticity by a fluctuation in pH during gluten dispersion. SDS‐PAGE showed that the extractable proteins substantially increased in some polymeric glutenins including the low molecular weight‐glutenin subunit (LMW‐GS) when the ammonia‐treated gluten powder was extracted with 70% ethanol. In contrast, the extractable proteins markedly increased in many polymeric glutenins including the high molecular weight‐glutenin subunit and/or the LMW‐GS when the acid‐treated gluten powder was extracted with 70% ethanol. It thus follows that the extractability of polymeric glutenin to ethanol increases similarly to gliadin when gluten is exposed to an acidic or a basic pH condition; therefore, glutenin adopts gliadin‐like characteristics.