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When heated radiantly, head-body temperature gradients developed in both live and dead Tiliqua scincoides. The gradients were consistently larger in live than in dead individuals, indicating they were enhanced by a physiological component superimposed on the more basic physical components. Large gradients in the initial phases of heating represented a lag effect, the head core beginning to receive heat before the body core because it is closer to the heated surface. Once this lag effect subsided, the body heated more rapidly than the head because it presented a greater incident surface area per unit mass than did the head. Living lizards appeared to maintain head-body temperature differences until the maximum voluntary temperature was approached.
The abundance of Emydura krefftii in the nutrient-deficient dune lakes of Fraser Island, Australia, is explained in terms of the species' broad food habits and its ability to directly utilise foods of terrestrial origin. Small specimens of E. krefftii are carnivorous, relying principally on aquatic and terrestrial insects, and small crustaceans. As they grow, the turtles become omnivorous and eat larger varieties of insect and crustacean. The changes in diet with increasing turtle size are explained in terms of energetic efficiency, and by the fact that as the turtles grow, more robust food items become available to them. The diets of mature males and females of similar sizes do not differ appreciably.
A study of the reproduction of Krefft's river tortoise, Emydura krefftii, was conducted in the perched dune lakes of Fraser Island, Queensland. Mature male specimens exhibit a postnuptial pattern of spermatogenesis typical of temperate‐zone turtles elsewhere, with a peak in spermatogenic activity in autumn and a cessation of activity during the breeding season in spring and early summer. The spermatogenic cycle is paralleled by seasonal variation in testicular weight (standardized for body size) and in the diameter of the seminiferous tubules. Sperm are abundant in the epididymal canals throughout the year. Mating was observed in autumn, late winter and spring. Females have a cyclic reproductive pattern, with distinct phases of follicular enlargement, ovulation and oviducal period, and quiescence. Yolk begins to accumulate in the...
The aim of this dissertation was to explain why some people are indecisive, in the broadest sense of the term. First, a behavioral definition of indecisiveness was synthesized from the range of conceptions of indecision and indecisiveness found across different literatures. Indecisive behaviors were derived from the synthesized definition and used to develop a multi-dimensional, behavioral self-report scale. The scale was designed to capture the breadth of indecisive behaviors, without a priori attributing to them any causes. In three studies, the scale was developed, refined, validated, and used to test distinct mechanisms underlying indecisiveness. In Study 1 (N = 369), the initial scale was developed. Four types of indecisiveness were hypothesized to exist at distinct phases in the decision-making process: 1) before commitment, 2) ...
We study the anisotropic two-dimensional Hubbard model at and near half filling within a functional renormalization group method, focusing on the structure of momentum-dependent correlations which grow strongly upon approaching a critical temperature from above. We find that a finite nearest-neighbor interchain hopping is not sufficient to introduce a substantial momentum dependence of single-particle properties along the Fermi surface. However, when a sufficiently large second-nearest neighbor inter-chain hopping is introduced, the system is frustrated and we observe the appearance of so-called "hot spots", specific points on the Fermi surface around which scattering becomes particularly strong. We compare our results with other studies on quasi-one-dimensional systems.
Comment: 9 pages, preprint LPTENS 94/13
Les canaux potassiques voltage-dépendants forment des tétramères dont chaque sous-unité comporte six segments transmembranaires (S1 à S6). Le pore, formé des segments S5-S6 de chaque sous-unité, est entouré de quatre domaines responsables de la sensibilité au potentiel membranaire, les senseurs de voltage (VS; S1-S4). Lors d’une dépolarisation membranaire, le mouvement des résidus chargés situés dans le VS entraine un mouvement de charges détectable en électrophysiologie, le courant de « gating ». L’activation du VS conduit à l'ouverture du pore, qui se traduit par un changement de conformation en C-terminal du segment S6. Pour élucider les principes qui sous-tendent le couplage électromécanique entre ces deux domaines, nous avons étudié deux régions présumées responsables du couplage chez les canaux de type Shaker K+, soit la région ...
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