Abrasion Resistance of Field-Assisted Ion-Exchanged Glass

The fracture strength of HF-etched samples was measured as a function of field-assisted K-Na ion exchange depth, as well as the severity of abrasion. As expected, the more severe the abrasion, the greater the depth required to make the strength insensitive to abrasion. An abrasion-independent weakening mechanism that increased with exchange depth was also found to be operative.     

Toughening by Metallic Lamina in Nickel/Alumina Composites

Tape casting and hot-pressing were used to produce metal/ alumina laminate composites. The mechanical behavior of these laminates was characterized. The strength and toughness of the laminates were greatly improved in comparison to that of monolithic alumina. Indentation strength values of the laminates remained approximately constant for indent loads between 10 and 100 N. Thus, this type of laminate appears to be a good candidate for damage-tolerant composite material design.     

Structural Aspects of the Lattice Thermal Expansion of Hexagonal Cordierite

The mechanism of lattice thermal expansion in pure hexagonal cordierite prepared by glass devitrification was investigated by time-of-flight neutron powder diffraction at temperatures from 22° to 750°C under vacuum. Full matrix least-squares refinement of the diffraction spectra was carried out in space group P6/mcc using the Rietveld method. The structural data from the refinements were resolved into components parallel and normal to the c axis. The negative c axis expansion results from two effects: (1) increasing distortion of the T₂ tetrahedral (ring tetrahedra) with temperature, primarily due to displacement of the T₂ cations toward the c-axis channels in the structure; (2) decreasing distortion of the T₁/M tetrahedra/ octahedra with increasing temperature, due to octahedral I (M-O₁) bond expansion and an associated decrease in torsional distortion of the T₁ tetrahedra.     

Processing and Properties of Particulate Composites from Coated Powders

A method is described for sintering of highly loaded (≤20 vol%) alumina matrix/silicon carbide whisker or platelet composites to closed porosity. The method uses controlled heterogeneous precipitation in a suspension of whiskers or platelets. The suspension-coated particles are calcined to produce a free-flowing composite powder which can be hot-pressed or free-sintered to high density. The results of consolidation and mechanical property testing are reported.     

Suitability of commercial cottonseed for producing edible high protein flours by liquid classification

The 1976 and 1977 crops of glanded cottonseed from oil mills located in 7 major U.S. cottonbelt growing areas were evaluated as to their suitability for processing into edible, high-protein flours. Both the physical and chemical characteristics of fuzzy seed samples were studied. Ginned seed samples were hulled, dried, comminuted, slurried with hexane and liquid classified by both a laboratory differential settling test (DST) and pilot plant liquid cyclone process (LCP). Liquid cyclone operating data and extensive analytical data of the kernels, flour and meals produced are shown. A free gossypol level of 1.10% or less in full fat kernels was the determining factor for producing edible flours from glanded seed by the LCP. The Lower Rio Grande Valley area was the only area from which liquid classified cottonseed flour consistently exceeded the current maximal free gossypol standard of 450 ppm. Ca. 94% of the total U.S. cottonseed production is suitable for producing edible, high-protein flours by liquid classification.     

Mixed-Mode Fracture in Soda-Lime Glass Using Indentation Flaws

Mixed-mode failure of soda-lime glass under inert and fatigue test conditions was studied using Knoop indentation flaws. For annealed cracks (residual stress-free) crack extension (catastrophic or subcritical) is by an abrupt transition from the initial crack plane to a noncoplanar crack plane followed by a reorientation of the crack normal to the applied stress. Although fatigue strength of these inclined flaws increased linearly with respect to orientation of the flaws to the applied stress up to an angle of 60°, this increase was considerably less than what was predicted by existing theories. It is believed that subcritical crack growth causes the crack to be realigned perpendicular to the applied stress before failure for all orientations; hence, fatigue strength does not show the dramatic increase at orientation angles as predicted by theory. For as-indented cracks the contact residual stress causes the crack extension to be less inclined to the initial crack plane than for annealed cracks, but in this case also, the crack realigns itself perpendicular to the applied stress. Again, fatigue strength is relatively insensitive to the orientation angle as predicted by theory and subcritical crack growth is believed to play a primary role in determining this strength dependency.     

Quantitative estimation of sucrose esters of plamitic acid

Thin layer chromatography was adapted for direct quantitative estimation of sucrose esters of palmitic acid. Urea-phosphoric acid spray was used to detect the sucrose moiety of the various esters. The photometrically metermined density density of each spot on the thin layer plate was found to be proportional to its sucrose content. Ester content was then obtained by multiplying sucrose found by the factor, mol. wt. ester/mol. wt. sucrose. Ester mixtures were prepared by interesterifying sucrose with various proportions of methyl palmitate in dimethylformamide solution. Positional isomers were observed at each level of substitution but could not be adequately separated from each other for quantitative evaluation. Presented at the AOCS Meeting, Minneapolis, October 1969. So. Utiliz. Res. Dev. Div., ARS, USDA.     

Effects of experimental endogenous hyperlipemia on circulating leukocytes and erythrocytes

Effects of hyperlipemia on circulating leukocytes and erythrocytes were studied in dogs which were given repeated, intravenous injections of a nonionic detergent, Triton WR-1339. Erythrocyte lipid concentrations increased from 3.6±0.9 mg/10¹⁰ cells in control animals to 9.3±1.5 mg in the hyperlipemic group. This increase was accompanied by a shift in the distribution of total fatty acids toward a higher percentage of saturated and monounsaturated acids. In contrast to the changes observed in erythrocytes, the leukocyte lipid content remained unaltered in dogs with serum cholesterol levels ranging from 500 to more than 2,000 mg/100 ml. Leukocyte counts rose whereas hematocrit values, hemoglobin concentrations, and erythrocyte counts decreased. Oxygen utilization studies showed no significant metabolic differences between leukocytes which were isolated from hyperlipemic or control animals. Circulating leukocytes in dogs with an endogenously induced hyperlipemia were shown therefore to maintain normal lipid concentrations and did not participate in lipophage formation, as reported for certain diet-induced lipemias.     

A review of the unique features of HDL apoproteins

The human plasma high density lipoproteins (HDL) are a heterogeneous ensemble of five proteins associated with both neutral and polar lipids. The sequences of all five proteins are known. ApoA-I and apoA-II are the major protein components; apoC-I, apoC-II and apoC-III are the minor protein components. All these apoproteins spontaneously recombine with phospholipids to give stable lipid-protein complexes and freely exchange between the two major HDL subclasses, HDL₂ and HDL₃. In addition, ApoC-I, apoC-II, and apoC-III exchange between HDL and very low density lipoproteins. Furthermore, certain HDL apoproteins are activators for plasma enzymes that are important in lipid metabolism. ApoA-I and apoC-I activate lecithin/cholesterol acyltransferase; apoC-II is an activator of lipoprotein lipase. The regions of apoC-I and apoC-II that are involved in the activation of these enzymes have been localized with synthetic peptides. Studies of synthetic and native fragments of apoA-II, apoC-I, apoC-II, and apoC-III as well as model lipid-binding peptides have identified specific regions with structural features common to lipid-binding proteins. These special properties, which include helical potential, sequences with a critical amphipathic length, and high hydrophobicity of the nonpolar side of the amphipathic helix, are the determinants of HDL structure and metabolism.     

Separation and determination of mono-, Di-, and triglycerides in monoglyceride concentrates

Summary Monoglyceride concentrates are quantitatively separated into mono-, di-, and triglyceride components on silica gel columns by an adsorption chromatographic technique. The separated glycerides are determined gravimetrically. The adsorption on silica gel is dependent on the number of hydroxyl groups in the molecule, and the influence of unsaturation and chain length is minimized. Combinations of benzene and ethyl ether are used for elution, thus preventing isomerization, which frequently results when polar solvents such as alcohols are used. The procedure for the chromatographic separation is simple and straightforward. The equipment used is easily obtainable. The silica gel adsorbent requires only adjustment of its water content before use. Mixtures of both saturated and unsaturated glycerides and those having different fatty acid chain length have been separated. Known mixtures have also been analyzed. For a known mixture containing 15% tripalmitin, 45% distearin, and 38% monopalmitin the average deviations from the calculated values were 0.4%, 0.2%, and 0.6%, respectively