1,611 research outputs found

    Discovery of a Dicephalic Western Diamondback Rattlesnake, Crotalus atrox (Serpentes: Viperidae), from Texas, with a Summary of Dicephalism Among Members of the Genus Crotalus

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    We document the fourth record of a dicephalic western diamondback rattlesnake, Crotalus atrox, collected on 17 September 2005 in Tom Green County, Texas, along with features of its external and internal anatomy, which are compared with normal C. atrox neonates. This is only the second reported case of complete anatomical duplication of the respiratory system and nearly complete duplication of the circulatory and digestive systems in dicephalic snakes. In addition, we present a summary of dicephalism among 10 species within the genus Crotalus

    Description of a papillate tactile organ in the Typhlopidae

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    In a unique specimen of Rhinotyphlops, the rostrum supports approximately 250 elongate, flexible papillae. Each papilla consists of a tubular shaft and an expanded hair-like bulb weakly embedded in the epidermis. Immediately deep to the base of each papilla is a small cluster of neuronal cells and a vascular supply. Although this Rhinotyphlops is presumed to be fossorial, the morphology of these soft papilla suggest they function as mechanoreceptors

    Berezin transform on the quantum unit ball

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    We introduce and study, in the framework of a theory of quantum Cartan domains, a q-analogue of the Berezin transform on the unit ball. We construct q-analogues of weighted Bergman spaces, Toeplitz operators and covariant symbol calculus. In studying the analytical properties of the Berezin transform we introduce also the q-analogue of the SU(n,1)-invariant Laplace operator (the Laplace-Beltrami operator) and present related results on harmonic analysis on the quantum ball. These are applied to obtain an analogue of one result by A.Unterberger and H.Upmeier. An explicit asymptotic formula expressing the q-Berezin transform via the q-Laplace-Beltrami operator is also derived. At the end of the paper, we give an application of our results to basic hypergeometric q-orthogonal polynomials.Comment: 38 pages, accepted by Journal of Mathematical Physic

    Homogenisation of carnivorous mammal ensembles caused by global range reductions of large-bodied hypercarnivores during the late Quaternary

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    Carnivorous mammals play crucial roles in ecosystems by influencing prey densities and behaviour, and recycling carrion. Yet, the influence of carnivores on global ecosystems has been affected by extinctions and range contractions throughout the Late Pleistocene and Holocene (~130 000 years ago to the current). Large-bodied mammals were particularly affected, but how dietary strategies influenced species’ susceptibility to geographic range reductions remains unknown. We investigated 1) the importance of dietary strategies in explaining range reductions of carnivorous mammals (≄5% vertebrate meat consumption), and 2) differences in functional diversity of continental carnivore ensembles by comparing current, known ranges to current, expected ranges under a present-natural counterfactual scenario. The present-natural counterfactual estimates current mammal ranges had modern humans not expanded out of Africa during the Late Pleistocene and were not a main driver of extinctions and range contractions, alongside changing climates. Ranges of large-bodied hypercarnivorous mammals are currently smaller than expected, compared to smaller-bodied carnivorous mammals that consume less vertebrate meat. This resulted in consistent differences in continental functional diversity, whereby current ensembles of carnivorous mammals have undergone homogenisation through structural shifts towards smaller-bodied insectivorous and herbivorous species. The magnitude of ensemble structural shift varied among continents, with Australia experiencing the greatest difference. Weighting functional diversity by species’ geographic range sizes caused a three-fold greater shift in ensemble centroids than when using presence-absence alone. Conservation efforts should acknowledge current reductions in the potential geographic ranges of large-bodied hypercarnivores and aim to restore functional roles in carnivore ensembles, where possible, across continents

    Branching laws for discrete Wallach points

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    We consider the (projective) representations of the group of holomorphic automorphisms of a symmetric tube domain V⊕iΩV\oplus i\Omega that are obtained by analytic continuation of the holomorphic discrete series. For a representation corresponding to a discrete point in the Wallach set, we find the decomposition under restriction to the identity component of GL(Ω)GL(\Omega). Using Riesz distributions, an explicit intertwining operator is constructed as an analytic continuation of an integral operator. The density for the Plancherel measure involves quotients of Γ\Gamma-functions and the cc-function for a symmetric cone of smaller rank.Comment: 22 page

    Harnessing Higher-Order (Meta-)Logic to Represent and Reason with Complex Ethical Theories

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    The computer-mechanization of an ambitious explicit ethical theory, Gewirth's Principle of Generic Consistency, is used to showcase an approach for representing and reasoning with ethical theories exhibiting complex logical features like alethic and deontic modalities, indexicals, higher-order quantification, among others. Harnessing the high expressive power of Church's type theory as a meta-logic to semantically embed a combination of quantified non-classical logics, our work pushes existing boundaries in knowledge representation and reasoning. We demonstrate that intuitive encodings of complex ethical theories and their automation on the computer are no longer antipodes.Comment: 14 page