204 research outputs found

    Quadratic invariants for discrete clusters of weakly interacting waves

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    We consider discrete clusters of quasi-resonant triads arising from a Hamiltonian three-wave equation. A cluster consists of N modes forming a total of M connected triads. We investigate the problem of constructing a functionally independent set of quadratic constants of motion. We show that this problem is equivalent to an underlying basic linear problem, consisting of finding the null space of a rectangular M × N matrix with entries 1, −1 and 0. In particular, we prove that the number of independent quadratic invariants is equal to J ≡ N − M* ≥ N − M, where M* is the number of linearly independent rows in Thus, the problem of finding all independent quadratic invariants is reduced to a linear algebra problem in the Hamiltonian case. We establish that the properties of the quadratic invariants (e.g., locality) are related to the topological properties of the clusters (e.g., types of linkage). To do so, we formulate an algorithm for decomposing large clusters into smaller ones and show how various invariants are related to certain parts of a cluster, including the basic structures leading to M* < M. We illustrate our findings by presenting examples from the Charney–Hasegawa–Mima wave model, and by showing a classification of small (up to three-triad) clusters

    Capacitacion y desarrollo para el personal de Forestal Celco S.A.. Un enfoque al 2000

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    53 p.La presente investigación tiene por objetivo la elaboración de un Plan de Capacitación y Desarrollo para la empresa Forestal Celco S.A. en la perspectiva del año 2000. En primer lugar se identificaron los conceptos fundamentales descritos por autores con enfoques futuristas, lo cual sirvió como cimiento teórico para el estudio y construir los Factores Críticos del Éxito, a partir del análisis de frecuencias sobre los términos mas relevantes citados por cada uno de ellos. Se crearon paquetes de variables que fueron contrastadas con las actividades desarrolladas por la empresa, por nivel jerárquico, de las cuales nació una comparación entre las actividades de la descripción de cargos y las actividades efectivamente realizadas, definiendo a partir de esta confrontación árboles de decisión que contienen paquetes de actividades integradas; constituidas por herramientas, fundamentos e implementación. El Plan de Capacitación y Desarrollo para Forestal Celco S.A., fue construido a partir de las actividades mismas de la empresa y acompañado de los fundamentos de la formación conceptual básica por tipo de materia tratada, enfocado con instrumentos que dicen relación con las técnicas y herramientas utilizadas para la aplicación de los conceptos aprendidos, e implementar de acuerdo con el aprendizaje individual del personal de la empresa y entrenamiento personal para los mismos. El estudio proporciona un Plan de Capacitación adecuado a los equerimientos de cada una de las Sub Gerencias, al mismo tiempo programas de entrenamientos transversales por nivel jerárquico, atendiendo a las necesidades de la empresa investigada. Entre los hallazgos que derivan de las hipótesis, se encuentran el de confirmar que las variables de gestión relevantes por nivel jerárquico son diferentes entre si, al analizar el estudio de frecuencias de la descripción de cargos de la empresa. También se comprobó que las variables relevantes por nivel jerárquico son diferentes de las identificadas por cada una de las Sub Gerencias, al analizar el estudio de frecuencias de las actividades efectivamente realizadas por Forestal Celco S.A. Por ultimo, del análisis de correlaciones de las variables de gestión de la empresa en estudio, se desprenden paquetes de actividades que poseen un sentido lógico técnico, para desarrollar un Plan de Capacitación, en conjunto con los requerimientos de Forestal Celco S.A

    Polymer films containing chemically anchored diazonium salts with long-term stability as colorimetric sensors

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    We have prepared polymeric films as easy-to-handle sensory materials for the colorimetric detection and quantification of phenol derivatives (phenols) in water. Phenols in water resources result from their presence in pesticides and fungicides, among other goods, and are harmful ecotoxins. Colorless polymeric films with pendant diazonium groups attached to the acrylic polymer structure were designed and prepared for use as sensory matrices to detect phenol-derived species in water. Upon dipping the sensory films into aqueous media, the material swells, and if phenols are present, they react with the diazonium groups of the polymer to render a highly colored azo group, giving rise to the recognition phenomenon. The color development can be visually followed for a qualitative determination of phenols. Additionally, quantitative analysis can be performed by two different techniques: a) by using a UV–vis spectrophotometer (limit of detection of 0.12 ppm for 2-phenylphenol) and/or b) by using a smartphone with subsequent RGB analysis (limit of detection of 30 ppb for 2-phenylphenol)Fondo Europeo de Desarrollo Regional (FEDER) and the Spanish Agencia Estatal de Investigación (AEI) (MAT2017-84501-R

    Quaternion Solution for the Rock'n'roller: Box Orbits, Loop Orbits and Recession

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    We consider two types of trajectories found in a wide range of mechanical systems, viz. box orbits and loop orbits. We elucidate the dynamics of these orbits in the simple context of a perturbed harmonic oscillator in two dimensions. We then examine the small-amplitude motion of a rigid body, the rock'n'roller, a sphere with eccentric distribution of mass. The equations of motion are expressed in quaternionic form and a complete analytical solution is obtained. Both types of orbit, boxes and loops, are found, the particular form depending on the initial conditions. We interpret the motion in terms of epi-elliptic orbits. The phenomenon of recession, or reversal of precession, is associated with box orbits. The small-amplitude solutions for the symmetric case, or Routh sphere, are expressed explicitly in terms of epicycles; there is no recession in this case

    Pulmonary Abnormalities in Mice with Paracoccidioidomycosis: A Sequential Study Comparing High Resolution Computed Tomography and Pathologic Findings

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    Paracoccidioidomycosis (PCM) is a fungal infection caused by the dimorphic fungus Paracoccidioides brasiliensis. It occurs preferentially in rural workers in whom the disease is severe and may cause incapacitating pulmonary sequelae. Assessment of disease progression and treatment outcome normally includes chest x-rays or CT studies. Existing experimental PCM models have focused on several aspects, but none has done a radiologic or image follow-up evaluation of pulmonary lesions considered as the fungus primary target. In this study, the lungs of mice infected with fungal conidia were studied sequentially during the chronic stage of their experimental mycosis by noninvasive high resolution medical computed tomography, and at time of sacrifice, also by histopathology to characterize pulmonary abnormalities. Three basic lung lesion patterns were revealed by both techniques: nodular-diffuse, confluent and pseudo-tumoral which were located mainly around the hilus thus accurately reflecting the situation in human patients. The experimental design of this study decreases the need to sacrifice a large number of animals, and serves to monitor treatment efficacy by means of a more rational approach to the study of human pulmonary diseases. The findings we are reporting open new avenues for experimental research, increase our understanding of the mycosis pathogenesis and consequently have repercussions in patients' care

    Knockout of the dhfr-ts Gene in Trypanosoma cruzi Generates Attenuated Parasites Able to Confer Protection against a Virulent Challenge

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    Chagas disease is the clinical manifestation of the infection produced by the flagellate parasite Trypanosoma cruzi and currently there is no vaccine to prevent this disease. Therefore, different approaches or alternatives are urgently needed. Vaccination with live attenuated parasites has been used effectively in mice to reduce parasitemia and histological damage. However, the use of live parasites as inmunogens is controversial due to the risk of reversion to a virulent phenotype. In this work we genetically manipulated a naturally attenuated strain of T. cruzi in order to produce parasites with impaired replication and infectivity, using the mutation as a safety device against reversion to virulence. We show that genetically modified parasites display a lower proliferation rate in vitro and induced almost undetectable levels of T. cruzi specific CD8+ T cells when injected in mice. Furthermore, the immune response induced by these live mutant parasites confers protection against a subsequent virulent infection even a year after the original immunization

    Eco-bio-social determinants for house infestation by non-domiciliated Triatoma dimidiata in the Yucatan peninsula, Mexico

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    Background Chagas disease is a vector-borne disease of major importance in the Americas. Disease prevention is mostly limited to vector control. Integrated interventions targeting ecological, biological and social determinants of vector-borne diseases are increasingly used for improved control. Methodology/principal findings We investigated key factors associated with transient house infestation by T. dimidiata in rural villages in Yucatan, Mexico, using a mixed modeling approach based on initial null-hypothesis testing followed by multimodel inference and averaging on data from 308 houses from three villages. We found that the presence of dogs, chickens and potential refuges, such as rock piles, in the peridomicile as well as the proximity of houses to vegetation at the periphery of the village and to public light sources are major risk factors for infestation. These factors explain most of the intra-village variations in infestation. Conclusions/significance These results underline a process of infestation distinct from that of domiciliated triatomines and may be used for risk stratification of houses for both vector surveillance and control. Combined integrated vector interventions, informed by an Ecohealth perspective, should aim at targeting several of these factors to effectively reduce infestation and provide sustainable vector control

    Genetic polymorphisms located in genes related to immune and inflammatory processes are associated with end-stage renal disease: a preliminary study

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    Background Chronic kidney disease progression has been linked to pro-inflammatory cytokines and markers of inflammation. These markers are also elevated in end-stage renal disease (ESRD), which constitutes a serious public health problem. Objective To investigate whether single nucleotide polymorphisms (SNPs) located in genes related to immune and inflammatory processes, could be associated with ESRD development. Design and methods A retrospective case-control study was carried out on 276 patients with ESRD and 288 control subjects. Forty-eight SNPs were genotyped via SNPlex platform. Logistic regression was used to assess the relationship between each sigle polymorphism and the development of ESRD. Results Four polymorphisms showed association with ESRD: rs1801275 in the interleukin 4 receptor (IL4R) gene (OR: 0.66 (95%CI=0.46-0.95); p=0.025; overdominant model), rs4586 in chemokine (C-C motif) ligand 2 (CCL2) gene (OR: 0.70 (95%CI=0.54-0.90); p=0.005; additive model), rs301640 located in an intergenic binding site for signal transducer and activator of transcription 4 (STAT4) (OR: 1.82 (95%CI=1.17-2.83); p=0.006; additive model) and rs7830 in the nitric oxide synthase 3 (NOS3) gene (OR: 1.31 (95%CI=1.01-1.71); p=0.043; additive model). After adjusting for multiple testing, results lost significance. Conclusion Our preliminary data suggest that four genetic polymorphisms located in genes related to inflammation and immune processes could help to predict the risk of developing ESRD.This work was supported by grants from Instituto de Salud Carlos III (Ref: PI08/0738 and PI11/00245) to SR and Junta de Castilla y Leon (Ref: GRS 234/A/08) to ET. 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