Effect of dynamic recrystallization on the importance of grain-boundary sliding during creep

During creep of polycrystalline materials at elevated temperatures, a certain amount of the strain is accommodated by grain-boundary sliding (GBS). The relative importance of GBS depends on the stress and grain size and sometimes temperature. During high-strain deformation, dynamic recrystallization often occurs with the resultant grain size only related to the stress. In this situation the importance of GBS is then dependent only upon stress and sometimes temperature. In dynamically recrystallized Magnox Al80 deformed atT>0.8T _m, 16 to 23% of the imposed strain is accommodated by GBS. A comparison has been made between the experimental results and some theoretical models for the importance of GBS during creep, modified to take account of recrystallization. The best fit to the data is obtained with the modified form of Langdons model. Deformation mechanism maps constructed with this model suggest that dynamic recrystallization can cause a switch of mechanism from dislocation creep to dominant GBS at intermediate temperature (T<673 K) and low stress. Deformation mechanism maps have also been constructed for calcite based on the data of Schmidet al. These suggest that GBS is an important mechanism in calcite deformed under geological conditions.     

Diffusion and transfer of antibody proteins from a sugar-based hydrogel

Diffusion of antibody protein from hydrogel films and hydrogel encapsulated in a microcapillary was studied. Thin hydrogel films were formed by crosslinking 6-acryloyl-B-O-methylgalactoside with N,N'-methylene-bis-acrylamide and the diffusive transport of monoclonal antimouse IgG-FITC into and out of the hydrate films was measured. Diffusion coefficients in 2 and 4% crosslinked hydrogel films were measured. The measured diffusion constants determined for IgG in both the 2 and 4% hydrogel films were comparable to the free diffusion of IgG in bulk water (Dmean approximately 10(-7) cm2/s). In addition, 2% crosslinked hydrogels were prepared in a capillary tube and the transport of antimouse IgG-FITC into and out of the hydrated hydrogel was measured. Kinetic analysis indicated that the protein transport through the capillary hydrogel was faster than would be expected for a simple diffusion process. Finally, by utilizing the diffusion of antibody from the capillary hydrogel, transfer of antibody to a silica surface was demonstrated. A capillary hydrogel loaded with antimouse IgG-FITC was used to transfer the protein to a silica surface forming a 30-micron spot of antibody, which was imaged using fluorescence microscopy. These results may lead to the development of a nonlithographic method of patterning antibodies on surfaces for use in integrated microimmunosensors.     

An evaluation of operator preference of diamond burs in coronal tooth preparation

Three postgraduate prosthodontic students served as clinicians/evaluators in a study rating their preferences for three different diamond cutting instruments from three manufacturers. Each evaluator prepared the axial walls of complete veneer crowns on extracted molar teeth and then ranked their preference of the instruments. To prepare nine teeth, each of the three instruments was used in random order and without knowledge of the specific manufacturer. The methodology for analyzing the evaluators' preferences and the results are discussed.     

Generation currents, noise and auger suppression in intrinsic diodes

The total diffusion-limited current and shot noise in intrinsic diodes do not depend explicitly on the detailed forms of the individual generation processes, but only on the current and noise of each process acting in isolation. Auger-like processes are relatively suppressed in high reverse bias.     

Effects of TCDD on Ah receptor, ARNT, EGF, and TGF-alpha expression in embryonic mouse urinary tract

Lipoprotein(a) [Lp(a)] biogenesis was examined in primary cultures of hepatocytes isolated from mice transgenic for both human apolipoprotein(a) [apo(a)] and human apoB. Steady-state and pulse-chase labeling experiments demonstrated that newly synthesized human apo(a) had a prolonged residence time (approximately 60 min) in the endoplasmic reticulum (ER) before maturation and secretion. Apo(a) was inefficiently secreted by the hepatocytes and a large portion of the protein was retained and degraded intracellularly. Apo(a) exhibited a prolonged and complex folding pathway in the ER, which included incorporation of apo(a) into high molecular weight, disulfide-linked aggregates. These folding characteristics could account for long ER residence time and inefficient secretion of apo(a). Mature apo(a) bound via its kringle domains to the hepatocyte cell surface before appearing in the culture medium. Apo(a) could be released from the cell surface by apoB-containing lipoproteins. These studies are consistent with a model in which the efficiency of post-translational processing of apo(a) strongly influences human plasma Lp(a) levels, and suggest that cell surface assembly may be one pathway of human Lp(a) production in vivo. Transgenic mouse hepatocytes thus provide a valuable model system with which to study factors regulating human Lp(a) biogenesis.     

Testing of total hip replacements: endurance tests and stress measurements. Part 2: Stress measurements

Brittle lacquer techniques and electric resistance strain gauge rosettes were used to measure strains on the stems of total hip replacements while loaded according to three standards. The stresses in these locations were also calculated and good agreement was found between the measured and calculated values. The Sines equation was used to calculate the endurance limit stress. Again good agreement was found with observed results. Suggestions are made regarding the endurance testing of hip prostheses.