489 research outputs found

    Topology and quantum states: The electron-monopole system

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    This paper starts by describing the dynamics of the electronmonopole system at both classical and quantum level by a suitable reduction procedure. This suggests, in order to realise the space of states for quantum systems which are classically described on topologically non-trivial configuration spaces, to consider Hilbert spaces of exterior differential forms. Among the advantages of this formulation, we present—in the case of the group SU(2), how it is possible to obtain all unitary irreducible representations on such a Hilbert space, and how it is possible to write scalar Dirac-type operators, following an idea by K¨ahler

    Cognitive stimulation induces differential gene expression in octopus vulgaris: The key role of protocadherins

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    Octopuses are unique invertebrates, with sophisticated and flexible behaviors controlled by a high degree of brain plasticity, learning, and memory. Moreover, in Octopus vulgaris, it has been demonstrated that animals housed in an enriched environment show adult neurogenesis in specific brain areas. Firstly, we evaluated the optimal acclimatization period needed for an O. vulgaris before starting a cognitive stimulation experiment. Subsequently, we analyzed differential gene expression in specific brain areas in adult animals kept in tested (enriched environment), wild (naturally enriched environment), and control conditions (unenriched environment). We selected and sequenced three protocadherin genes (PCDHs) involved in the development and maintenance of the nervous system; three Pax genes that control cell specification and tissue differentiation; the Elav gene, an earliest marker for neural cells; and the Zic1 gene, involved in early neural formation in the brain. In this paper, we evaluated gene expression levels in O. vulgaris under different cognitive stimulations. Our data shows that Oct-PCDHs genes are upregulated in the learning and lower motor centers in the brain of both tested and wild animals (higher in the latter). Combining these results with our previous studies on O. vulgaris neurogenesis, we proposed that PCDH genes may be involved in adult neurogenesis processes, and related with their cognitive abilities

    Prostasome-like particles in stallion semen.

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    Human semen contains membranous vesicles called prosta- somes. They are secreted by the prostate gland and contain large amounts of cholesterol, sphingomyelin, and Ca2. Prostasomes enhance the motility of ejaculated spermatozoa and are in- volved in a number of additional biological functions. No prostasome-like vesicles have been described in horse se- men up to now. We have demonstrated the presence of pros- tasome-like vesicles in the equine semen and characterized them as to size, morphology, and lipid composition; we have found that they are similar to human prostasomes in many re- spects. We propose that these vesicles might be important for the fecundity of horse semen. This is of interest since the success of artificial insemination is limited by the fact that stallion sperm barely survive cryopreservation

    Tubulin nitration in human gliomas

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    Immunohistochem. and biochem. investigations showed that significant protein nitration occurs in human gliomas, esp. in grade IV glioblastomas at the level of astrocytes and oligodendrocytes and neurons. Enhanced alpha-tubulin immunoreactivity was co-present in the same elements in the glioblastomas. Proteomic methodologies were employed to identify a nitrated protein band at 55 kDa as alpha-tubulin. Peptide mass fingerprinting procedures demonstrated that tubulin is nitrated at Tyr224 in grade IV tumor samples but is unmodified in grade I samples and in non-cancerous brain tissue. These results provide the first characterization of endogenously nitrated tubulin from human tumor samples

    Causality in Schwinger's Picture of Quantum Mechanics

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    This paper begins the study of the relation between causality and quantum mechanics, taking advantage of the groupoidal description of quantum mechanical systems inspired by Schwinger’s picture of quantum mechanics. After identifying causal structures on groupoids with a particular class of subcategories, called causal categories accordingly, it will be shown that causal structures can be recovered from a particular class of non-selfadjoint class of algebras, known as triangular operator algebras, contained in the von Neumann algebra of the groupoid of the quantum system. As a consequence of this, Sorkin’s incidence theorem will be proved and some illustrative examples will be discussed.This researchwas funded by the Spanish Ministry of Economy and Competitiveness (MINECO), through the Severo Ochoa Programme for Centres of Excellence in RD (SEV-2015/0554), the MINECO research project PID2020-117477GB-I00, the Comunidad de Madrid project QUITEMAD+, S2013/ICE- 2801, the CONEX-Plus programme (University Carlos III of Madrid), Marie Sklodowska-Curie COFUND Action (H2020-MSCA-COFUND-2017-GA 801538). This work has been supported by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with UC3M in the line of “Research Funds for Beatriz Galindo Fellowships” (C&QIG-BG-CM-UC3M), and in the context of the V PRICIT (Regional Programme of Research and Technological Innovation)

    Giant Sigmoid Diverticulum: A Rare Presentation of a Common Pathology

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    Although colonic diverticulum is a common disease, affecting about 35% of patients above the age of 60, giant sigmoid diverticulum is an uncommon variant of which only relatively few cases have been described in the literature. We report on our experience with a patient affected by giant sigmoid diverticulum who was treated with diverticulectomy. Resection of the diverticulum is a safe surgical procedure, provided that the colon section close to the lesion presents no sign of flogosis or diverticula; in addition, recurrences are not reported after 6-year follow-up

    Isomorphisms of types in the presence of higher-order references (extended version)

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    We investigate the problem of type isomorphisms in the presence of higher-order references. We first introduce a finitary programming language with sum types and higher-order references, for which we build a fully abstract games model following the work of Abramsky, Honda and McCusker. Solving an open problem by Laurent, we show that two finitely branching arenas are isomorphic if and only if they are geometrically the same, up to renaming of moves (Laurent's forest isomorphism). We deduce from this an equational theory characterizing isomorphisms of types in our language. We show however that Laurent's conjecture does not hold on infinitely branching arenas, yielding new non-trivial type isomorphisms in a variant of our language with natural numbers
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