Microstructure and superconducting current ofIn situ Nb3Sn superconducting wire

The diffusion of elemental tin and the morphological change of niobium filaments inin situ Nb₃Sn superconducting composite wires and their influences on critical current were studied. When the amount of tin plated on the samples was high, the diffusion of elemental tin was enhanced. The critical current increased with increasing tin concentration but the increase became sluggish at high tin contents. The niobium filaments were initially ribbon-like but they became rod-like and then sausage-like after annealing treatment. Such a morphological change acted to reduce superconducting current capacity. When the amount of niobium was low, the filaments spheroidized by high-temperature and long-term annealing, resulting in serious reduction in critical current and upper critical magnetic field. High niobium contents led to high critical current and high upper critical magnetic field due to retainment of continuity of the filaments after annealing, effective proximity effect and a high amount of Nb₃Sn formed in comparison with low niobium content amount. The titanium addition raised the upper critical magnetic field, resulting in improvement in critical current at high magnetic fields.     

Mitral valve protrusion assessed by use of B-mode echocardiography in dogs with mitral regurgitation

OBJECTIVES: The purpose of this study ws to assess whether a community program begun in March 1988 that organized multiple city departments and private citizens could reduce alcohol-impaired driving, related driving risks, and traffic deaths and injuries. METHODS: Trends in fatal crashes and injuries per 100 crashes were compared in Saving Lives Program cities and the rest of Massachusetts from March 1984 through February 1993. In annual roadside surveys conducted at randomly selected locations, safety belt use among occupants of 54577 vehicles and travel speeds of 118442 vehicles were observed. Four statewide telephone surveys (n = 15188) monitored self-reported driving after drinking. RESULTS: In program cities relative to the rest of Massachusetts during the 5 program years in comparison with the previous 5 years, fatal crashes declined 25%, from 178 to 120, and fatal crashes involving alcohol decreased 42%, from 69 to 36. Visible injuries per 100 crashes declined 5%, from 21.1 to 16.6. The proportions of vehicles observed speeding and teenagers who drove after drinking were cut in half. CONCLUSIONS: Interventions organized by multiple city departments and private citizens can reduce driving after drinking, related driving risks, and traffic deaths and injuries.     

Estimation of interfacial shear strength between superconducting oxides and silver sheath from multiple- fracture phenomenon of the oxide

The influences of interfacial shear strength between superconducting Y-Ba-Cu-O and silver and that between Bi-Pb-Sr-Ca-Cu-O and silver on the multiple fracture of the oxides embedded in silver-sheathed composite wires, prepared by a powder-in-tube method, on the multiple fracture of the oxides was analyzed. The stress distribution in the oxide was calculated based on the proposed method, and the multiple-fracture phenomenon was simulated by means of a Monte Carlo simulation method. From the comparison of the experimental results with those obtained by the simulation, the interfacial shear strength between Y-Ba-Cu-O and silver and that between Bi-Pb-Sr-Ca-Cu-O and silver were estimated to be nearly 30 and 40 MPa, respectively.     

Stress concentration at a notch tip in unidirectional metal matrix composites

A method to calculate static stress concentration factors in the fibers at the tip of a rectangular notch in unidirectional metal matrix composites was presented based on the shear lag analysis for a two-dimensional (2-D) model. By using this method, the influences of matrix yielding, width and size of notch, and size of specimen on the stress concentration factors were described. Furthermore, this method was applied successfully to describe the load-COD curve and tensile strength of notched-boron/aluminum and alumina/aluminum composites.     

Disruption of three phosphatidylinositol-polyphosphate 5-phosphatase genes from Saccharomyces cerevisiae results in pleiotropic abnormalities of vacuole morphology, cell shape, and osmohomeostasis

We have shown previously that switching of the alpha v-associated beta1 and beta5 integrin subunits during differentiation of myelin-forming oligodendrocytes may regulate important aspects of cell behaviour such as migration (Milner et al., 1996: J Neurosci 16:7240-7252). In this study we have examined the developmental regulation of other alpha v-associated beta subunits in oligodendroglial cell cultures and also the control of their expression by neurons, using xenocultures to distinguish glial and neuronal integrins. We have found that oligodendroglia express alpha vbeta8 in addition to the previously-described alpha vbeta1, alpha vbeta3, and alpha vbeta5. Beta8 and beta3 together comprise the 80kD band seen in alpha v immunoprecipitations that represents the most abundant alpha v-associated beta subunit and show reciprocal patterns of expression during development. Alpha vbeta8 is expressed at high levels on oligodendrocyte precursors and differentiated oligodendrocytes but diminishes during the intermediate stages of differentiation. Alpha vbeta3, in contrast, shows an opposite pattern of expression, with the highest levels seen at the intermediate stages of differentiation and little expression on either oligodendrocyte precursors and differentiated oligodendrocytes. The expression of alpha vbeta3 is not altered by coculture with neurons, unlike that of alpha vbeta8, in which the decrease seen at the intermediate stages of differentiation is less marked in the presence of neurones. Our results confirm that switching of alpha v-associated beta subunits is an important feature of oligodendrocyte differentiation and suggest that alpha vbeta8 and alpha vbeta3 have distinct functions during myelination.     

Stenosis of Carpentier-Edwards pericardial bioprosthesis in the tricuspid position caused by adhesion of native valve cusps to the bioprosthesis

We experienced a case of dysfunction of Carpentier-Edwards pericardial bioprosthesis in the tricuspid position. Explanted bioprosthesis showed overgrowth of neointima from ring to cusps and adhesion to remnants of native cusps. This restricted the motion of the pericardial leaflets resulting in orifice stenosis. Care must be taken in such valve replacement by this prosthesis leaving native valve tissue.