On the existence of a single temperature in continuum thermodynamics

Summary A global hypothesis involving the heat flux and the entropy flux is shown to be equivalent to the existence of temperature.

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Zusammenfassung Es wird gezeigt, dass eine globale Hypothese für die Wärmezufuhr und Entropiezufuhr mit der Existenze der Temperatur äquivalent ist.

     

Thermodynamic influences on the growth of one-dimensional shock waves in materials with memory

In this paper we study one-dimensional shock waves in materials with memory, including thermodynamic influences. In particular, we derive a differential equation relating the strain and strain gradient behind the shock, and give criteria under which the wave will grow or decay.

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Zusammenfassung In dieser Arbeit werden eindimensionale Stoßwellen mit Berücksichtigung thermodynamischer Einflüsse in Werkstoffen mit Gedächtnis untersucht. Speziell wird eine Differentialgleichung abgeleitet, die das Verhältnis zwischen Spannungs- und Verzerrungsgradienten hinter der Stoßwelle herstellt. Ferner werden Bedingungen für Anwuchs und Abfall der Welle angegeben.

     

Equipresence and constitutive equations for rigid heat conductors

Zusammenfassung Die Autoren diskutieren neuere Anwendungen des Äquipräsenzprinzips auf Konstitutionsgleichungen ruhender Wärmeleiter und entwickeln sodann eine Theorie, in welcher die Beeinflussung der freine Energie, der Entropie und des Wärmeflusses durch die Geschichte nicht nur der Temperatur, sondern auch des Temperaturgradienten zugelassen ist. Sie formulieren für starre Körper dieser Art notwendige und hinreichende Bedingungen für die Gültigkeit der Clausius-Duhemschen Ungleichung in allen glatten Wärmeprozessen.     

Phases of elastic materials

Zusammenfassung Es wird eine Methode beschrieben für die Charakterisierung von Stoff-Phasen durch Angabe der Symmetrie-Gruppe als Funktion der Deformation und Temperatur. Wenn in einem elastischen Stoff die Phase durch Dichte und Temperatur bestimmt wird, dann gelten die meisten der üblichen Resultate für die Gesamt-Symmetrie-Gruppe auch für die Gruppe, die einer gegebenen Phase entspricht.     

Semiconducting polymers based on charge-transfer complexes. IV. Electrical properties and structure of polymeric charge-transfer complexes

Model electron donor molecules, 10-methylphenothiazine and 4-(methylthio)anisole, and polymeric electron donors which contained these molecules on the side chains of N-acyl-substituted polyethylenimines, were complexed with the electron acceptors, dichlorodicyanoquinone (DDQ), tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE), and tetranitrofluorenone (TNF). The model donors formed 1:1 complexes with all the acceptors except TCNE. The polymeric donors formed amorphous complexes with DDQ, TCNQ, and TCNE. Crystalline complexes were formed with TNF which had low melting points (lower than the model complexes and the pure polymer). This is apparently due to poor lateral packing of the polymer chains. Electrical resistivities were lower for all the polymer complexes than for the corresponding model complexes. Electrical resistivity also decreased with increase in complex crystallinity. In the best case the polymer complex was two hundred times as conducting as the model. The concentration of unpaired electrons measured by EPR was nearly independent of temperature. Most of the electrons seen are trapped and do not participate in conduction. Thermal activation energies for conduction were in the range of 0.5–1.8 eV and were nearly equal for the model and corresponding polymeric complexes. Elongation of polymer complex with TCNQ by rolling produces a decrease in resistivity in the roll direction, although the complex is amorphous. This reinforces the hypothesis that conduction is parallel to the polymer backbone. A polymer–tetranitrofluorenone complex was photoconducting, though the photoconductivity was smaller than the dark conductivity at the level of illumination used. Dember and Seebeck effects indicated that the major carrier in the complex was holes.     

Trefoil Knots without Tritangent Planes

A quick proof is given that trefoil knots constructed explicitlyas (3,2) curves on a torus by stereographic projection fromS³ have no tritangent planes.     

Island models and the catalytic oxidation of carbon monoxide and carbon monoxide-olefin mixtures

Simple kinetic models which take account of the formation of islands of adsorbate on a catalyst surface are proposed, and are compared with an elementary step model for CO oxidation and oxidation of a CO-butene or CO-propylene mixture. The island models give fits to data from step change transient experiments which are comparable with the elementary step model, and give better fits to steady-state and continuously oscillating data (the latter with hydrocarbon present). Theoretical predictions of chaotic behaviour in CO oxidation can be obtained with the island models. Comparisons between island models suggest that islands of CO have the most significant effect on simulations at the experimental conditions.