Comparison of M. longissimus dorsi pigment concentration from implanted and control Angus and Limousin bulls and steers

M. longissimus dorsi total pigment concentration, visual color score and 24-h pH values were evaluated in a 2(3) factorial design that included bulls versus steers, Zeranol implants versus control and Angus versus Limousin comparisons. Bulls had greater total pigment concentration than steers (3.25 versus 2·90 mg/g; P < 0·01) and darker colored lean (P < 0·01). Twenty-four hour pH values did not differ between bulls and steers. Zeranol implanting and breed had no effect on total pigment concentration or visual color score; however, Limousin had higher (P < 0·05) 24-h pH values than Angus. The initial slaughter group (N = 10; average age = 256 days) had 34% less total pigment than the final slaughter group (N = 48; average age = 458 days). The correlation between visual color score and total pigment concentration was -0·65. These results indicate that the darker colored lean from bulls is due in part to an increase in pigment concentration.     

Silicon carbide filaments: Microstructure

The microstructure of chemically vapour deposited silicon carbide filaments has been examined using transmission electron microscopy. The filament bulk consisted of heavily faulted columnar subgrains of-SiC which were preferentially oriented such that {1 1 1} planes were parallel to the surface of the carbon fibre substrate. The protective coating on the filament surface was characterized by several microstructurally distinct layers, all of which consisted primarily of carbon. The first layers of the coating contained small crystallites of SiC in addition to turbostratic carbon, while the outer layers showed no evidence of SiC. Implications of the filament microstructure with respect to mechanical properties are discussed.     

Applications of dynamic fracture mechanics for the prediction of crack arrest in engineering structures

The compatibility of the static and dynamic approaches to crack propagation and arrest is investigated. For clarity, the term kinetic is introduced for analyses that focus on the entire crack initiation/propagation/arrest process — as opposed to static analyses which consider only the end points — as dynamic effects are not always significant in a crack run/arrest event. The importance of integrating experimental and computational work in this field is also discussed and a differentiation is given between the ways in which this can be done. An example computation on a thermal shock problem where dynamic effects are minimal, i.e., where the static and kinetic approaches are nearly the same, and a computation for a DCB specimen where significant differences occur between the two approaches are described. It is concluded that the static and kinetic approaches are entirely compatible as long as reflected stress waves do not reach the crack tip prior to crack arrest. But, when this is not the case, it is the kinetic approach that must be used. Similarly, when inelastic effects are important, only the kinetic approach can properly admit them.

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Résumé On étudie la compatibilité des approches statiques et dynamiques pour la propagation et l'arrêt d'une fissure. Pour des raisons de clarification, le terme cinétique est introduit dans une analyse qui couvre l'entièreté du processus d'amorçage, propagation et arrêt d'une fissure, par opposition à l'analyse statique qui ne considère que les points terminals et dans la mesure où les effets dynamiques ne sont pas toujours appréciables dans un processus de course et d'arrêt d'une fissure. On discute également l'importance d'intéger le travail expérimental et le travail par calculs dans ce domaine et l'on établit une différence entre les différentes voies qui peuvent être suivies. A titre d'exemple, on établit le calcul pour un problème de choc termique où les effets dynamiques sont minimes, c'est-à-dire où les approches statiques et cinétiques sont à peu près les mêmes et un calcul pour une éprouvette Cantilever où des différences significatives surviennent entre les deux approches. On conclut que les approches statiques et cinétiques sont entièrement compatibles pour autant que les ondes de contrainte réfléchies n'atteignent pas l'extrémité de la fissure avant que ne se produisent son arrêt. Cependant, comme lorsque cela n'est pas le cas, c'est l'approche cinétique qui doit être utilisée. De même, lorsque les effets inélastiques sont importants, seule l'approche cinétique peut les prendre en compte.

     

Superconductivity effects near the metal-insulator transition in granular indium films

The paper reports on an investigation of the electric resistance as a function of temperatureT, magnetic fieldH, and applied voltageV in granular indium films when approaching the metal-insulator transition (MIT) due to increased thickness of the oxide layers between granules. The dependences are shown to be governed atT5 K by competition of the hopping conductivity and the Josephson tunneling of electrons, sometimes giving rise to a resistance minimum inR(T) associated with superconductivity. It was also found that even when the intergranular Josephson tunneling is totally suppressed, transition of granules to the superconducting state influences essentially the dependencesR(T, H), changing the functional form ofR(T) and resulting in anomalously high negative magnetoresistance. This is shown to stem from the change of the character of activated electron tunneling as the granules become superconducting.