Processing sodium tellurite melts in low gravity drop shaft: Part II Melt solidification and glass formation

The effect of gravity on glass formation and crystallization of the Na₂Ocdot;8TeO₂ (NT₈) and Na₂O4TeO₂ (NT₄) melts were investigated using the low gravity drop shaft at the Japan Microgravity Center (JAMIC). This drop shaft produces a low gravity of <10^–3 g for 10 s during free-fall and about 8 to 10 g for 5 s during deceleration of the capsule. The glass initially adhered to a small platinum heating coil was re-melted in low gravity. The melt detached from the heating coil during the high-g period and solidified after being splattered on a plate (substrate) located 4 cm below the heating coil. The parameters that were varied for the drop shaft experiments were the melt temperature and the substrate material on which the melt splattered. Like what was observed at 1-g (ground), the NT₈ splatters from the drop shaft experiments always formed glass, being independent of the melt temperature and the substrate material used. The splatters from the NT₄ melts partially crystallized in all the drop shaft experiments, even though this melt is an excellent glass former at 1-g. The splatter on a substrate of higher cooling ability such as copper had a smaller amount of crystals than the splatter on a substrate of smaller cooling ability such as glass or alumina. The glass transition temperature, heat capacity in the glass transition region, activation energy for crystallization and the infrared (IR) spectra for the drop shaft splatters were not significantly different from those for the similar splatters prepared at 1-g. However, the crystallization temperature of all the drop shaft splatters was 5 to 10°C lower than that of their 1-g counterparts. This result suggests that the NT₈ and NT₄ melts solidified under drop shaft conditions are less resistant to crystallization than the similar melts solidified at 1-g.     

Characterization and tribological behavior of cast In-Situ Al (Mg,Mo)-Al2O3 (MoO3) composite

Aluminum alloy—based cast in-situ composite has been synthesized by dispersion of externally added molybdenum trioxide particles (MoO₃) in molten aluminum at the processing temperature of 850 °C. During processing, the displacement reaction between molten aluminum and MoO₃ particles results in formation of alumina particles in situ and also releases molybdenum into molten aluminum. A part of this molybdenum forms solid solution with aluminum and the remaining part reacts with aluminum to form intermetallic phase Mo(Al_1−x Fe _x )₁₂ of different morphologies. Magnesium (Mg) is added to the melt in order to help wetting of alumina particles generated in situ, by oxidation of molten aluminum by molybdenum trioxide, and helps to retain these particles inside the melt. The mechanical properties of the cast in-situ composite, as indicated by ultimate tensile stress, yield stress, percentage elongation, and hardness, are relatively higher than those observed either in cast commercial aluminum or in cast Al-Mo alloy. The wear and friction of the resulting cast in-situ Al(Mg,Mo)-Al₂O₃(MoO₃) composites have been investigated using a pin-on-disc wear testing machine under dry sliding conditions at different normal loads of 9.8N, 14.7N, 19.6N, 24.5N, 29.4N, 34.3N, and 39.2 N and a constant sliding speed of 1.05 m/s. The results of the current investigation indicate that the cumulative volume loss and wear rate of cast in-situ composites are significantly lower than those observed either in cast commercial aluminum or in cast Al-Mo alloy, under similar load and sliding conditions. Beyond about 30 to 35 N loads, there appears to be a higher rate of increase in the wear rate in the cast in-situ composite as well as in cast commercial aluminum and cast Al-Mo alloy. For a given normal load, the coefficient of friction of cast in-situ composite is significantly lower than those observed either in cast commercial aluminum or in cast Al-Mo alloy. The coefficient of friction of cast in-situ composite increases gradually with increasing normal load while those observed in cast commercial aluminum or in cast Al-Mo alloy remain more or less the same. Beyond a critical normal load of about 30 to 35 N, the coefficient of friction decreases with increasing normal load in all the three materials.     

Analysis of dependencies in advanced transaction models

Transactional dependencies play an important role in coordinating and executing the subtransactions in advanced transaction processing models, such as, nested transactions and workflow transactions. Researchers have formalized the notion of transactional dependencies and have shown how various advanced transaction models can be expressed using different kinds of dependencies. Incorrect specification of dependencies can result in unpredictable behavior of the advanced transaction, which, in turn, can lead to unavailability of resources and information integrity problems. In this work, we focus on how to correctly specify dependencies in an advanced transaction. We enumerate the different kinds of dependencies that may be present in an advanced transaction and classify them into two broad categories: event ordering and event enforcement dependencies. Different event ordering and event enforcement dependencies in an advanced transaction often interact in subtle ways resulting in conflicts and redundancies. We describe the different types of conflicts that can arise due to the presence of multiple dependencies and describe how one can detect such conflicts. An advanced transaction may also contain redundant dependencies—these are dependencies that can be logically derived from other dependencies. We show how such extraneous dependencies can be eliminated to get an equivalent set of dependencies that has the same effect as the original set. Our dependency analysis is done in the context of a generalized advanced transaction model that is capable of expressing different kinds of advanced transactions. Recommended by: Amit Sheth     

Classification of a bacterial isolate, from pozol, exhibiting antimicrobial activity against several gram-positive and gram-negative bacteria, yeasts, and molds

A bacterial isolate, designated CS93, capable of producing a broad-spectrum antimicrobial compound(s) effective against gram-positive and gram-negative bacteria, yeasts, and molds was isolated from pozol, a fermented maize product. This strain was phenotypically similar to another pozol isolate that was previously designated as Agrobacterium azotophilium by other investigators. By using biochemical, phenotypic, and 16S rRNA sequence analysis, both pozol isolates were identified as members of the genus Bacillus, possibly a variant of Bacillus subtilis. While the antimicrobial compound(s) was initially produced only on a solid medium, parameters were identified for production in broth. The compound(s) was heat stable (121 degrees C for 15 min), exhibited activity over a wide pH range (pH 3 to pH 11), and was inactivated by pronase E. The antimicrobial compound(s) was bactericidal and bacteriolytic against Escherichia coli V517, bacteriostatic against Micrococcus luteus, and fungistatic against Saccharomyces cerevisiae. The inhibitory compound(s) could possibly serve as a food biopreservative.     

High Performance CMOS Analog Arithmetic Circuits

Unique designs for CMOS analog arithmetic circuits are presented which perform addition (V₁ + V₂), subtraction (V₂ – V₁), add/invert –(V₁ + V₂), and multiply (V₁ × V₂). The circuit operation is based on the inherent square law of MOS transistor drain current when operating in the saturation region. Key features include: good linearity and accuracy, single ended voltage inputs and output, wide input and output range and no input bias voltages. The circuits can be directly coupled (no buffer) and serve as basic building blocks for analog signal processing implementations such as analog filters and adaptive equalizers. All circuits were implemented in 1.2 m CMOS technology.     

Determination of K Id at or below NDTT using instrumented drop-weight testing

Two kinds of surface cracked specimens are numerically analyzed by the three dimensional elastic-plastic FEM. Near tip regions are divided into fine elements, and the stress and displacement fields at the crack tip are compared with HRR solutions.At first, surface cracked specimens subjected to bending are analyzed by changing the aspect ratio and depth/thickness ratio. The effect of the loading condition, crack shape and the crack depth on the stress and displacement fields are discussed. Then the pipe with surface crack subjected to bending is analyzed and the availability of the J-integral concept to the LBB analysis is discussed.In every specimen, it is shown that in the regions very near to the crack tip, the displacement field is similar to HRR solutions of plane strain. In the outer regions, however, the stress and displacement fields depend strongly on the shape, thickness, and loading conditions.     

Grain size estimation in anisotropic materials

The need for an efficient sampling technique for estimation of grain size in anisotropic materials is addressed through statistical analysis of quantitative metallographic data on a series of iron specimens cold rolled to different extents. The data are utilized to arrive at the most efficient procedure for measuring grain size in anisotropic materials. The analysis reveals that, for cold-rolled materials, design-based intersection counting on a single longitudinal metallographic plane is sufficient to reliably and efficiently estimate the average grain size.     

Specific binding of L-triiodothyronine modulates Na(+)-K(+)-ATPase activity in adult rat cerebrocortical synaptosomes

Interactions of L-triiodothyronine (T3) in adult rat cerebrocortical synaptosomes were studied in vitro. Scatchard plot analysis revealed two sets of T3 binding sites. The degree of saturation of T3 binding sites (putative receptor) correlated well with the dose-dependent inhibition of Na(+)-K(+)-ATPase activity in synaptosomes. The relative binding affinities and relative inhibition of enzyme activities for different TH analogues were L-T3 > T3-amine > TRIAC = L-T4 > r-T3 > T2 and L-T3 > T3-amine > TRIAC > L-T4 > r-T3 > T2, respectively. The present study demonstrates the nature of inhibition of synaptosomal Na(+)-K(+)-ATPase activity may be as a function of T3 occupancy of synaptosomal receptor sites in adult mammalian brain.