265 research outputs found

    Berry Phase of a Resonant State

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    We derive closed analytical expressions for the complex Berry phase of an open quantum system in a state which is a superposition of resonant states and evolves irreversibly due to the spontaneous decay of the metastable states. The codimension of an accidental degeneracy of resonances and the geometry of the energy hypersurfaces close to a crossing of resonances differ significantly from those of bound states. We discuss some of the consequences of these differences for the geometric phase factors, such as: Instead of a diabolical point singularity there is a continuous closed line of singularities formally equivalent to a continuous distribution of `magnetic' charge on a diabolical circle; different classes of topologically inequivalent non-trivial closed paths in parameter space, the topological invariant associated to the sum of the geometric phases, dilations of the wave function due to the imaginary part of the Berry phase and others.Comment: 28 pages Latex, three uuencoded postcript figure

    Masculinity and feminity measurement in physical education teachers

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    Esta investigación tuvo por objetivo analizar las mediciones de masculinidad, feminidad, machismo y sumisión, características asociadas a la personalidad, de un grupo de docentes de Educación Física. Participaron en el estudio 53 docentes de nivel básico que laboran en un programa implementado por una institución gubernamental en la Ciudad de México. El muestreo fue de tipo no probabilístico. Se empleó como instrumento el Inventario de Masculinidad y Feminidad (IMAFE), instrumento confiable y válido en México, sujeto a prueba en otros países, en él se incluyen aspectos de los papeles de género tradicionales: machismo y sumisión. El análisis de los datos se efectúo mediante la prueba “t-Student” y el análisis de varianza de una clasificación, así como la comparación de medias de los resultados arrojados. Se concluye que no hay diferencias estadísticamente significativas en las cuatro escalas propuestas por el IMAFE y las variables de trabajo, sexo, edad y estado civil, en el grupo de docentes de Educación Física, en lo que respecta a las características asociadas a la personalidadThis research aimed to analyze the measurements of masculinity, femininity, machismo and submission features associated with the personality characteristics of a group of physical education teachers. Participated in the study53 basic level teachers working in a program implemented by a government institution in Mexico City. The sampling was not probabilistic type. As a tool for data collection was used the Inventory of Masculinity and femininity (IMAFE), reliable and valid instrument in Mexico, subject to testing in other countries, there aspects of traditional gender roles: machismo and submission. Data analysis undertaken using the “t-student” test and analysis of variance classification and comparison of the results obtained. It is concluded that no statistically significant differences in the four scales proposed by IMAFE and work variables sex, age and marital status in the group of physical education teachers in regard to the characteristics associated with personalit

    Pulmonary thromboembolism and alveolar hemorrhage as initial manifestations of systemic lupus erythematosus

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    Systemic lupus erythematosus (SLE) is an autoimmune disease that affects multiple organs. SLE can affect the lung, the pulmonary vasculature, and the pleura. A 38-year-old female with limb pain and ecchymosis who later developed pulmonary thromboembolism and alveolar hemorrhage is presented here. Clinical, imaging, laboratory, and histopathological evidence is presented. The patient met the European League Against Rheumatism (EULAR) and the American College of Rheumatology (ACR) criteria for SLE. Furthermore, the patient had a Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score of 35; thus, indicating severe disease. This case is an example of concomitant venous and arterial lung complications in an SLE patient

    Worldline path integral for the massive Dirac propagator : A four-dimensional approach

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    We simplify and generalize an approach proposed by Di Vecchia and Ravndal to describe a massive Dirac particle in external vector and scalar fields. Two different path integral representations for the propagator are derived systematically without the usual five-dimensional extension and shown to be equivalent due to the supersymmetry of the action. They correspond to a projection on the mass of the particle either continuously or at the end of the time evolution. It is shown that the supersymmetry transformations are generated by shifting and scaling the supertimes and the invariant difference of two supertimes is given for the general case. A nonrelativistic reduction of the relativistic propagator leads to a three-dimensional path integral with the usual Pauli Hamiltonian. By integrating out the photons we obtain the effective action for quenched QED and use it to derive the gauge-transformation properties of the general Green function of the theory.Comment: 27 pages, LaTeX, no figures, uses revtex.sty; note with omitted references added in proo

    Phase transitions in packet traffic on regular networks: a comparison of source types and topologies

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    Abstract We extend the packet traffic network models developed in recent years for rectangular grids to other regular networks, and to fragmented networks. The packet transfer mechanism is open-loop as before. The nodes of the network are either hosts or routers. Both can receive and transmit packets towards their destination; hosts can also create and receive packets. Long range dependent traffic with varying Hurst parameter is introduced at the host nodes of these networks, and comparative studies of the onset of congestion are carried out. Results show statistical robustness when the rectangular grid is adapted to form other regular networks. Qualitative behavior is the same, and simple mean field models accurately predict critical points as in the rectangular case. R/S-statistics show the presence of long range dependence even when sources are short range dependent. Results indicate that this long range dependence is closely linked to the queueing mechanism

    Linfangiectasia intestinal primaria: 20 años de experiencia en el Instituto Nacional de Pediatría

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    ResumenAntecedentesLa linfangiectasia intestinal primaria es una enfermedad congénita rara descrita por Waldmann en 1961, y que es consecuencia de una obstrucción del drenaje linfático del intestino delgado con dilatación secundaria de los vasos linfáticos, que distorsionan la arquitectura de las vellosidades ocasionando pérdida de linfa hacia la luz intestinal,dando como resultado una enteropatía perdedora de proteínas y malabsorción de nutrimentos.ObjetivoDescribir las características clínicas, bioquímicas, radiológicas, endoscópicas e histológicas en niños con linfangiectasia intestinal primaria.MétodoEstudio observacional, descriptivo, transversal y retrospectivo de niños con linfangiectasia intestinal primaria que fueron vistos en el Servicio de Gastroenterología y Nutrición del Instituto Nacional de Pediatría desde el 1 de enero de 1992 al 30 de septiembre de 2012, en donde se revisaron los expedientes clínicos de los niños con este diagnóstico.ResultadosSe encontraron 4 pacientes con linfangiectasia intestinal primaria, 3 de ellos diagnosticados antes de los 3 años; todos se presentaron con diarrea crónica, edema, linfopenia, hipocalcemia, hipoalbuminemia e hipogammaglobulinemia, y en 3 pacientes, con hipocolesterolemia, y con tránsito intestinal, endoscopia y biopsias intestinales características de esta enfermedad.ConclusionesLa linfangiectasia intestinal debe sospecharse ante un cuadro de diarrea crónica, enteropatía perdedora de proteínas, que se acompaña de edema a cualquier nivel, así como hipoalbuminemia, hipocalcemia, linfopenia, hipogammaglobulinemia e hipocolesterolemia como los principales hallazgos bioquímicos de esta entidad. Ante esta enfermedad debe realizarse estudio de serie esofagogastroduodenal con tránsito intestinal y endoscopia con toma de biopsias a nivel de duodeno. El tratamiento incluye dieta y administración periódica de albúmina y gammaglobulina.AbstractBackgroundPrimary intestinal lymphangiectasia is a rare congenital disease described by Waldmann in 1961 that is a consequence of obstruction of the lymphatic drainage of the small bowel with secondary lymph vessel dilation. This distorts the architecture of the villi and causes a leakage of lymph into the intestinal lumen, resulting in protein-losing enteropathy and malabsorption.AimTo describe the clinical, biochemical, radiologic, endoscopic, and histologic characteristics in children with primary intestinal lymphangiectasia.MethodA retrospective observational, descriptive, cross-sectional study was conducted that reviewed the case records of children diagnosed with primary intestinal lymphangiectasia that were seen at the Department of Gastroenterology and Nutrition of the Instituto Nacional de Pediatría within the time frame of January 1, 1992 to September 30, 2012.ResultsFour patients were found that presented with primary intestinal lymphangiectasia. Three of them had been diagnosed before 3 years of age. All the patients presented with chronic diarrhea, edema, lymphopenia, hypocalcemia, and hypogammaglobulinemia, and 3 patients presented with hypocholesterolemia. Bowel transit time, endoscopy, and intestinal biopsies were characteristic of this pathology.ConclusionsIntestinal lymphangiectasia should be suspected when there is a clinical picture of chronic diarrhea and protein-losing enteropathy accompanied with edema at any level, as well as hypoalbuminemia, hypocalcemia, lymphopenia, hypogammaglobulinemia, and hypocholesterolemia, which are the main biochemical findings of this pathology. All children presenting with intestinal lymphangiectasia should undergo an upper gastrointestinal series with bowel transit time and endoscopy with biopsies taken at the level of the duodenum. Treatment includes diet and the periodic administration of albumin and gamma globulin

    Visual 3-D SLAM from UAVs

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    The aim of the paper is to present, test and discuss the implementation of Visual SLAM techniques to images taken from Unmanned Aerial Vehicles (UAVs) outdoors, in partially structured environments. Every issue of the whole process is discussed in order to obtain more accurate localization and mapping from UAVs flights. Firstly, the issues related to the visual features of objects in the scene, their distance to the UAV, and the related image acquisition system and their calibration are evaluated for improving the whole process. Other important, considered issues are related to the image processing techniques, such as interest point detection, the matching procedure and the scaling factor. The whole system has been tested using the COLIBRI mini UAV in partially structured environments. The results that have been obtained for localization, tested against the GPS information of the flights, show that Visual SLAM delivers reliable localization and mapping that makes it suitable for some outdoors applications when flying UAVs

    Structural constraints in complex networks

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    We present a link rewiring mechanism to produce surrogates of a network where both the degree distribution and the rich--club connectivity are preserved. We consider three real networks, the AS--Internet, the protein interaction and the scientific collaboration. We show that for a given degree distribution, the rich--club connectivity is sensitive to the degree--degree correlation, and on the other hand the degree--degree correlation is constrained by the rich--club connectivity. In particular, in the case of the Internet, the assortative coefficient is always negative and a minor change in its value can reverse the network's rich--club structure completely; while fixing the degree distribution and the rich--club connectivity restricts the assortative coefficient to such a narrow range, that a reasonable model of the Internet can be produced by considering mainly the degree distribution and the rich--club connectivity. We also comment on the suitability of using the maximal random network as a null model to assess the rich--club connectivity in real networks.Comment: To appear in New Journal of Physics (www.njp.org
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