Low-Temperature Sintering of Aluminum Oxide

A fine-sized (∼0.1 μm), agglomerate-free Al₂O₃ dispersion was used to prepare homogeneous green bodies with ∼69% relative density and ∼10-nm median pore radius. Samples could be sintered at 1150°C to a relative density >99.5% and an average grain size of 0.25 μm.     

Suspension Processing of Al2O3/SiC Whisker Composites

Homogeneous Al₂O₃ powder/SiC whisker compacts were prepared by suspension processing. By optimizing the conditions for particle/whisker codispersion, castable suspensions could be prepared at total-solids concentrations 50 vol%. Green bodies with high relative density (∼66% to 70%) were obtained with SiC whisker contents in the range of 5 to 30 vol%. Although densification was severely inhibited by the SiC whiskers, significantly higher sintered densities were obtained by suspension processing compared to dry processing.     

Thermal Conductivity of Anisotropic Solids at High Temperatures—The Thermal Conductivity of Molded and Pyrolytic Graphites

A method has been developed for the determination of the thermal conductivities of anisotropic solids under conditions of two–dimensional, steady–state heat conduction in a cylinder of finite length heated in vacuum by high–frequency induction and radiating heat to the surroundings. The method has been used to determine the radial thermal conductivity, K_r , and the axial thermal conductivity, K_z , of molded ZT-type and pyrolytic graphite in the temperature range 1260° to 2200°K. For ZT-type graphite, K_z/K_r =–0.101 + 2.002 × 10⁻⁴± T (1260°K < T < 2200°K); for pyrolytic graphite, K_z/K_r = 0.0376 at 1817°K.     

Clay-Particle Dispersion by Ultrasons

The dispersion of 1.0% kaolin suspensions in water was studied utilizing ultrasonic vibrational energy. The effect of time of exposure to ultra-sons was examined microscopically and turbidi-metrically by means of a spectrophotometer. Complete deagglomeration and dispersion were accomplished in 10 minutes of exposure to ultra-sons without any apparent deleterious effects on the primary particle size of the kaolin. The effects of two accepted methods of dispersion were compared with the ultrasonic method.     

ELEMENTAL ANALYSIS OF GRASSES AND LEGUMES GROWING ON SOIL COVERING COAL FLY ASH LANDFILL SITES

Forage grasses and legumes growing in the soil covering four coal fly ash landfill sites in Central New York were sampled and analyzed for 20 elements. Selenium, boron and molybdenum were most consistently higher in concentration in these crops than the corresponding control plants sampled from adjacent upwind locations. Legumes absorbed greater amounts of these elements than grasses probably owing to their deep-rooted penetration of the fly ash layer below. Factors affecting the extent of absorption of these elements by the crops and the agricultural significance as related to grazing farm animals are discussed.     

THE THROMBORESISTANCE OF A HEPARIN-POLYVINYL ALCOHOL HYDROGEL†

Heparin immobilized onto polyvinyl alcohol (PVA) by action of glutaraldehyde has been shown to be biologically active in a novel parallel flow arteriovenous shunt in dogs. The hepann-PVA hydrogel originally devised by Merrill and his collaborators was applied as a coaling to chromic acid etched polyethylene lubing. A pair of Y-connectors was used to divert < 2% of the flow in the AV shunt through the heparinized tube, which remained patent for longer Ihan two hours while a control tube without heparin was occluded within 30 minutes at a main shunt flow rate of ～l50mL/min. This enhanced patency was achieved without significant release from the surface, consistent with earlier experiments attributing the thromboresistance of the heparin-PVA hydrogel to the formation of a surface bound inactive thrombin-antithrombin III complex. Radiolabelled thrombin adsorbed onto beads made from the gel was readily displaced by arvinized plasma, indicating that the inactive complex was not itself permanently bound to the surface.

These results demonstrate the utility of Merrill's hydrogel for preparing materials with potential long lerm thromboresistance and for testing the validity of the hypothesized limitations to the long term use of immobilized heparin.     

Perceptually Grounded Language Learning: Part 2—DETE: A Neural/Procedural Model

In Part 1 of this two-part series, we introduced Katamic memory—a neural network architecture capable of robust sequence learning and recognition. In Part 2, we introduce the Blobs World taskjdomain for language learning and describe the DETE language learning system, which is composed of over 50 Katamic memory modules. DETE currently learns small subsets of English and Spanish via association with perceptual! motor inputs. In addition to Kaiamic memory, DETE employs several other novel features: (1) use of feature planes, to encode visual shapes, spatial relationships and the motions of objects, (2) phase-locking of neural firing, in order to represent focus of atention and to bind objects across multiple feature planes, and (3) a method for encoding temporal relationships, so that DETE can learn utterances involving the immediate past and future. We compare DETE to related models and discuss the implications of this approach for language-learning research.     

Supercritical CO2 Extraction of Annatto (Bixa orellana) Pigments and Some Characteristics of the Color Extracts

Supercritical CO₂ (SC-CO₂) was used to extract natural food colors from Annatto (Bixa orellana) seeds with different pressures and temperatures. Results from the reverse thin-layer chromatographic separation and GC/MS revealed that SC-CO₂ extracts were composed mainly of bixin, geranylgeraniol and norbixin. Differences in absolute values of solubility parameters (SPD) between these main compounds and SC-CO₂ indicated bixin was more easily extracted than norbixin under conditions used. A higher yield of total pigments was obtained at extraction pressure above 310 bar than at 210 bar and 50°C.     

Effect of Hydrogen Peroxide and Phenolic Compounds on Horseradish Peroxidase-Catalyzed Decolorization of Betalain Pigments

The effect of hydrogen peroxide and phenolic compounds on the decolorization of betanin and a betaxanthin preparation by horse-radish peroxidase (HRP) was examined. Betanin was decolorized at a greater rate than the betaxanthm pigments and both reactions were H₂O²-dependent. Betaxanthin was more prone to oxidatic decolorization than betanin. 2,4-Dichlorophenol, resorcinol and o-toluidine stimulated the decolorization of both pigments. Guaiacol enhanced the peroxidatic decolorization of both pigments to a small extent, but inhibited the oxidatic breakdown of betaxanthin. Possible implications of these results are discussed.