Infinite-dimensional representations of the rotation group and Dirac's monopole problem

Within the context of infinite-dimensional representations of the rotation group the Dirac monopole problem is studied in details. Irreducible infinite-dimensional representations, being realized in the indefinite metric Hilbert space, are given by linear unbounded operators in infinite-dimensional topological spaces, supplied with a weak topology and associated weak convergence. We argue that an arbitrary magnetic charge is allowed, and the Dirac quantization condition can be replaced by a generalized quantization rule yielding a new quantum number, the so-called topological spin, which is related to the weight of the Dirac string.Comment: JHEP style. Extended version of hep-th/0403146. Revised version, title and some notations are changed. References and Appendix B are adde

IDENTIDAD ETNICA COMO ELEMENTO PARA FOMENTAR EL DESARROLLO SOCIOECONÓMICO EN UNA COMUNIDAD MAZAHUA

Ethnic identity is a factor that determines the sense of belonging and the cultural values with regards to a particular native group. The objective of this study was to determine the degree of ethnic identity as an element for a socio-economic development strategy in a Mazahua community. A structured interview with ethnic identity characteristics was designed, it was applied to 57 individuals from the community of Rincón de los Pirules, Estado de México, in December 2016. The data were analyzed with a correlation and principal components analysis. The results showed that pride of belonging, knowledge and preservation of the native language were characteristics that explain the ethnic identity of the Mazahuapopulation studied. Four degrees of ethnic identity were identified, the most representative being G1 with strong ethnic identity and G2 with moderate ethnic identity, in 86% of the population. Therefore, to propose a socioeconomic strategy in the community of Rincón de los Pirules, it is convenient to consider ethnic identity as an element to facilitate its adoption and implementation.La identidad étnica es un factor que determina la pertenecía y los valores culturales con respecto a un grupo originario en particular. El objetivo del presente trabajo fue determinar el grado de Identidad Étnica como elemento para una estrategia de desarrollo socioeconómico en una comunidad mazahua. Se diseñó una encuesta estructurada con características de identidad étnica, que fue aplicada a 57 personas de la comunidad de Rincón de los Pirules, Estado de México. Los datos se analizaron mediante correlación y componentes principales. Los resultados mostraron que el orgullo de pertenencia, el conocimiento y conservación de la lengua originaria son características que explican la identidad étnica de lapoblación mazahua estudiada. Se identificaron cuatro grados de identidad, siendo los más representativos el G1 con fuerte identidad étnica y el G2 con moderada identidad étnica en 86% de la población. Es conveniente para el planteamiento de una estrategia socioeconómica en la comunidad deRincón de los Pirules, se considere a la identidad étnica como elemento para facilitar su adopción e implementación

COMPETENCIAS EN DIRECCIÓN DE PROYECTOS IDENTIFICADAS EN RECOLECTORES DE Liometopum apiculatum Mayr

The revaluation of natural resources is a result of the growing social pressure to generate profitable productive projects, particularly in regions that are agro-ecologically limited. A social intervention was carried out in four communities of the Potosino Zacatecano high plateau, which manage 28 694 ha, in order to identify the abilities that influence the success while collecting the escamolera ant larvae (Liometopum apiculatum Mayr) as economic activity. The behavior of the collectors was analyzedto identify current and required abilities to suggest the standardization of processes in the value chain. Six types of collectors were identified, according to their orientation in long-term collecting. The profiles reflected technical abilities (nest productivity, collection volumes, resources needed for the extraction, and quality standards of the escamol); of business survival (knowing where to commercialize); and of results-orientation (managing resources obtained, developing a collecting culture, and attaining an acceptable price per kilogram from their efforts). The interest of the collector is to continue taking advantage of the resource around planned projects, improving the presentation and fulfillment of requirements for innocuity as an ability that differentiates his/her product in the market.La revalorización de recursos naturales se debe a la creciente presión social por generar proyectos productivos rentables sobre todo en regiones limitadas agroecológicamente. Se realizó una intervención social en cuatro comunidades del altiplano Potosino Zacatecano, que manejan 28,694 ha, para identificar competencias que influyen en el éxito de recolecta de larvas de hormiga escamolera (Liometopum apiculatum Mayr) como actividad económica. Se analizó el comportamiento de recolectores, para identificar competencias actuales y requeridas para sugerir estandarización de procesos en la cadena de valor. Se identificaron seis tipos de recolectores de acuerdo a su orientación de recolección en el largo plazo. Los perfiles reflejaron competencias técnicas (productividad de nidos, volúmenes de recoleta, recursos requeridos para extracción y estándares de calidad de escamol); de sobrevivencia del negocio (saber dónde comercializar) y de orientación a resultados (administración de recursos obtenidos, desarrollo de cultura de recolecta, y lograr precio por kilogramo aceptable contra su esfuerzo). El interés del recolector es seguir aprovechando el recurso en torno a proyectos planificados, mejorar la presentación y cumplimiento de requisitos de inocuidad como competencia que diferencié su producto en el mercad

Fabricación y caracterización de composites de ácido poliláctico reforzados con madera de olivo

En esta investigación se ha reforzado el biopolímero ácido poliláctico con madera de olivo obteniéndose un composite que mejora las propiedades y a la vez cumple con los requisitos medioambientales. El proceso ha consistido en un mezclado automático del PLA, fibra de madera y 10% de aditivo, seguido de un proceso de inyección. El porcentaje de fibra de madera de olivo adicionada han sido del 20% y se ha empleado madera sin tratar y tratada con álcali. Se han determinado las propiedades mecánicas y térmicas de los composites y se ha evaluado la influencia de la exposición ultravioleta en el comportamiento mecánico

Paleocene seismic facies in the continental margin of Uruguay (South America)

In this contribution seismic facies of the Paleocene sequence are characterized in offshore basins of Uruguay through the study of a 2D seismic database. Seven seismic horizons were identified, limiting six sedimentary intervals with different characteristics. Hence, the complexity of the Paleocene sequence is greater than suggested by other studies. Seismic facies located in the basis of the sequence can be interpreted as sandy deposits related to the action of both turbidity and bottom currents. The identification of these deposits agrees with the expected Cretaceous source rocks, in addition to the importance of the overlying Paleocene shales as a regional seal. The results of this work open interesting exploratory perspectives in the continental margin of Uruguay

MIL-88A Metal-Organic Framework as a Stable Sulfur-Host Cathode for Long-Cycle Li-S Batteries

Lithium-sulfur (Li-S) batteries have received enormous interest as a promising energy storage system to compete against limited, non-renewable, energy sources due to their high energy density, sustainability, and low cost. Among the main challenges of this technology, researchers are concentrating on reducing the well-known “shuttle effect” that generates the loss and corrosion of the active material during cycling. To tackle this issue, metal-organic frameworks (MOF) are considered excellent sulfur host materials to be part of the cathode in Li-S batteries, showing efficient confinement of undesirable polysulfides. In this study, MIL-88A, based on iron fumarate, was synthesised by a simple and fast ultrasonic-assisted probe method. Techniques such as X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), and N2 adsorption/desorption isotherms were used to characterise structural, morphological, and textural properties. The synthesis process led to MIL-88A particles with a central prismatic portion and pyramidal terminal portions, which exhibited a dual micro-mesoporous MOF system. The composite MIL-88A@S was prepared, by a typical melt-diffusion method at 155 °C, as a cathodic material for Li-S cells. MIL-88A@S electrodes were tested under several rates, exhibiting stable specific capacity values above 400 mAh g−1 at 0.1 C (1C = 1675 mA g−1). This polyhedral and porous MIL-88A was found to be an effective cathode material for long cycling in Li-S cells, retaining a reversible capacity above 300 mAh g−1 at 0.5 C for more than 1000 cycles, and exhibiting excellent coulombic efficiency

Carbon aerogel supported platinum catalysts for selective hydrogenation of cinnamaldehyde

This paper describes the preparation and characterization of 1% wt. Pt catalysts supported in carbon aerogels for the application in the liquid-phase selective hydrogenation of cinnamaldehyde. Carbon aerogel supports with different textures were activated with hydrogen peroxide and ammonium peroxydisulfate leading to large amounts of surface groups but keeping unchanged their textural properties. After introducing Pt, the surface chemistry and morphology of the catalysts was characterized by analytical techniques like SEM, TPD, N2 adsorption isotherms, mercury porosimetry and H2 chemisorption. Catalysts prepared with activated aerogels exhibited good selectivity towards the desired product, cinnamyl alcohol. A high temperature post-treatment of the catalysts failed to enhance their selectivity, mainly leading to hydrocinnamaldehyde production

Formation Mechanism of Maghemite Nanoflowers Synthesized by a Polyol-Mediated Process

Magnetic nanoparticles are being developed as structural and functional materials for use in diverse areas, including biomedical applications. Here, we report the synthesis of maghemite (¿-Fe2O3) nanoparticles with distinct morphologies: single-core and multicore, including hollow spheres and nanoflowers, prepared by the polyol process. We have used sodium acetate to control the nucleation and assembly process to obtain the different particle morphologies. Moreover, from samples obtained at different time steps during the synthesis, we have elucidated the formation mechanism of the nanoflowers: the initial phases of the reaction present a lepidocrocite (¿-FeOOH) structure, which suffers a fast dehydroxylation, transforming to an intermediate "undescribed" phase, possibly a partly dehydroxylated lepidocrocite, which after some incubation time evolves to maghemite nanoflowers. Once the nanoflowers have been formed, a crystallization process takes place, where the ¿-Fe2O3 crystallites within the nanoflowers grow in size (from ~11 to 23 nm), but the particle size of the flower remains essentially unchanged (~60 nm). Samples with different morphologies were coated with citric acid and their heating capacity in an alternating magnetic field was evaluated. We observe that nanoflowers with large cores (23 nm, controlled by annealing) densely packed (tuned by low NaAc concentration) offer 5 times enhanced heating capacity compared to that of the nanoflowers with smaller core sizes (15 nm), 4 times enhanced heating effect compared to that of the hollow spheres, and 1.5 times enhanced heating effect compared to that of single-core nanoparticles (36 nm) used in this work