Small-Angle X-Ray Scattering Analysis of Nucleation in Glass: II, Selenium Ruby Glasses

Nucleation studies were conducted on several selenium ruby glasses, of different colorant concentrations, using the technique of small-angle X-ray scattering. The glass rnicrostructure increased from homogeneous to 6-nm (60-Å) precipitating particles as the colors changed from colorless through yellow and orange to red. The glasses showed little difference in particle morphology despite differences in color, supporting the explanation of ruby color formation as due to energy band-gap phenomena. Matrix intensities, particle volume concentrations, and interfacial surface areas were also determined.     

Effect of Surface Finish on Structural Ceramic Failure

The relation between fracture strength and surface finish of brittle nonmetallic materials was examined and related to surface-crack theory. Specimens used in an experimental illustration were made of a commercially available 96%-pure alumina with an average grain size of 3.8 μm and a porosity of about 6%. Several groups of specimens, each having a different surface finish, were used in a biaxial ball-and-ring     

EFFECT OF POSTMORTEM AGE OF FLOUNDER SARCOPLASMIC RETICULUM ON INHIBITION OF ENZYMIC LIPID PEROXIDATION BY CYTOSOL

On aging in situ or in vitro, flounder muscle sarcoplasmic reticulum became less sensitive to inhibition by the soluble fraction of the muscle tissue. This decrease in sensitivity to inhibition was the result of the change in balance between the response to a dialyzable inhibitor and a large molecular weight activator found in the soluble fraction. With aging, the sarcoplasmic reticulum became more sensitive to the stimulatory activity of the large molecular weight activator.     

SOME CHARACTERISTICS OF THE NAD(P)H-DEPENDENT LIPID PEROXIDATION SYSTEM IN THE MICROSOMAL FRACTION OF CHICKEN BREAST MUSCLE

Incubation of the microsomal fraction isolated from chicken breast muscle in the presence of NADPH, ADP and Fe⁺⁺⁺ ions was shown to result in lipid peroxidation. NADH was able to replace NADPH as the source of reducing equivalents but was less efficient. The pH optimum for malonaldehyde (MDA) production was found to be around pH 6. 7. Oxygen uptake by the system was shown to have a pH optimum of 5.5. Oxygen uptake was approximately linearly dependent on temperature but malonaldehyde production exhibited a sharp increase between 25°C and 37°C. Inhibitor studies and the virtual absence of cytochromes indicate that this system is not similar to that isolated from rat liver microsomes. The activity of the lipid peroxidation system was maintained after storage for 7 days at pH 7.25 and 4°C. At pH 5.6 a reduction in activity was noted after 7 days.     

HYDROXYL RADICAL MODIFICATION OF FISH MUSCLE PROTEINS

A xanthine oxidase-based system was used to generate hydroxyl free radicals in washed, minced cod muscle. Oxidation of protein was measured by increase in protein carbonyl content; the system used produced approximately 0.1 mol of carbonyl groups per 10⁵ g of protein. This degree of oxidation had only minor effects on the SDS-PAGE patterns of the muscle proteins. The solubility of the proteins was not affected by this amount of oxidation unless they were also subjected to a freeze/thaw cycle. With a freeze/thaw cycle, a highly significant decrease in protein solubility occurred compared to that which took place in a sample not exposed to the free radical system. Lowering the pH from 6.8 or 6.5 to 6.0 or 5.5 had a strong negative impact on protein solubility. Protein oxidation appeared in two phases in washed cod mince, an initial rapid increase followed by a second phase that may have been linked to oxidation of the small amount of lipid in the sample. Comparison of protein carbonyl formation in stored mackerel fillets or mince indicated that the range of oxidation studied in the cod model system was similar to what occurs in stored mackerel muscle postmortem.