Although several theoretical approaches consider general methods for dealing with shape, recent observations and experimental data show that embryos exhibit marked changes in the properties of the biological material involved in shape development and shape regulation capacity. In vivo experiments have shown that the amphibian embryo gradually develops from a situation in which it is not able to maintain its shape to one in which it can not only maintain its shape but also possesses a maximal tolerance towards deformation together (...) with a maximal shape regulation capacity. So far two especially clear conclusions have emerged: (i) the form of the embryo appears to be determined by cell activities intrinsic to each stage, and (ii) the morphogenetic programme can be executed normally within wide limits notwithstanding dramatic deformations of the embryo during quite a long period. Thus the hypothesis may be advanced that shape and morphogenesis to some extent become independent phenomena during embryonic development. (shrink)
The simple theory of resistivity originally applied to pure liquid metals (Ziman 1961, Bradley et al. 1962) is formally extended to liquid alloys. In dilute solutions, size difference between solute and solvent ions can be allowed for, approximately, by a modification of the pseudo-potential of the solute, in a manner reminiscent of the modification of solute valency suggested by Harrison and Blatt (1957) in dealing with the resistance of solid alloys. The theory explains qualitatively a number of interesting features of (...) the behaviour of liquid binary alloys, e.g. the failure of liquid solutions in polyvalent metals to obey the familiar rules of Nordheim and Linde. Some speculations on the anomalous behaviour of mercury amalgams are included. A bibliography of experimental results for both resistivity and density in liquid alloys is collected in Appendix II. (shrink)
Abstract The electrical resistivities of pure liquid tin and of liquid tin-gold alloys ranging in composition from 5 to 84 at. % Au have been measured as a function of temperature within the range 235?910°C using the d.c. four-point probe capillary technique; the overall error of the measurements was estimated to be less than ±0·25%. The temperature coefficient of resistivity increases progressively with increasing temperature for gold contents greater than 10 at. % and, for alloys containing between 63 and 80 (...) at. % Au, the temperature coefficient is negative at lower temperatures. No evidence was found for irregularities which were indicated at certain compositions by previous measurements using the a.c. rotating-field technique. The maximum in the resistivity composition isotherms lies between 72 and 75 at. % Au, depending on the temperature. Fairly good agreement is obtained between the experimental results and those predicted from the theory of Faber and Ziman using published structure data for this system and the simplified pseudo-potential form factors of Ashcroft. The relations between the electrical and thermodynamic properties of this system are briefly discussed. (shrink)
The electrical resistivity and absolute thermoelectric power of the liquid Cu x ?Bi(1? x ) system have been measured over the whole composition range from the liquidus to 1100°C. The thermal conductivity is deduced from measurements of these two properties. The experimental results are interpreted and discussed in term of the extended Faber?Ziman formula using the t-matrix formalism with hard-sphere structure factors. The concentration and energy dependence of the phase shifts have been taken into account for a complete conductivity (...) and thermopower calculation. (shrink)
The Venerable John Henry Cardinal Newman seemingly had the “Midas touch” in reverse. Oxford, Littlemore, Dublin were all sites of failures; the “Achilli Affair” was a humiliation; the quarrel with Faber was an embarrassment. Nonetheless, most people today think of Newman as a rousing success story. Why? Newman serves as an object lesson in living the Paschal Mystery, whereby each moment of crisis can be transformed into a moment of grace.