Catálogo de los meteoritos hallados en territorio argentino

Es presentado aquí el primer catálogo de meteoritos argentinos. El listado actualizado incluye varios especímenes no reportados previamente. En total se mencionan setenta y cuatro ejemplares, caídos ó encontrados. Fueron omitidos deliberadamente otros seis, de dudosa existencia, más siete pseudometeoritos. Este catálogo brinda las informaciones básicas de cada especímen tales como su procedencia (ubicación geográfica en coordenadas históricas y mapa), clasificación, imagen, peso total, custodios y si fue visto caer ó encontrado casualmente. El trabajo entrega asimismo una completa bibliografía en cada caso. Por otra parte, se anuncia que, con el objeto de impedir el contrabando de meteoritos, el 14 de noviembre de 2007 fue sancionada la Ley Nacional n° 26.306. Gracias a ella, los meteoritos caídos en territorio argentino han sido declarados bienes culturales de la Nación y su comercialización está expresamente prohibida. En las conclusiones se menciona una realidad evidente, que el mayor avistamiento de meteoroides se ha producido en las zonas más pobladas del país, con la excepción de la Provincia de Buenos Aires, donde es comparable al de Patagonia.The first Catalogue of Meteorites from Argentina is presented here. The updated list includes many new specimens previously never reported. The total number of specimens mentioned is seventy four (74), fallen or found. Six doubtful specimens and seven pseudometeorites were deliberately omitted. The catalogue gives the basic information about each specimen, including its provenience (in historical co-ordinates and map), classification, image, total weight, the institution who keeps it, and if it was seen to fall or was found. Our work brings also a complete bibliography about each specimen. We also remark, with the aim to stop the illegal trade of meteorites, that in November 14, 2007, it was dictated a new law, Ley Nacional number 26.306. This law declares that all the meteorites are considered cultural properties of the Argentina’s Nation and their commercial trade is totally forbidden. In the conclusions we indicate that the largest numbers of sightseers of meteoroids were placed in the most populated zones of the country, with the exception of Buenos Aires province in which they were like those of Patagonia’s.Fil: Acevedo, Rogelio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Rocca, Maximiliano. Fundacion de Historia Natural Felix de Azara; Argentin

A very unusual cluster of multiple small impact craters probably created by the impact of a split cometary nucleus in Patagonia

Se hace aquí un análisis detallado del evento de impacto cósmico de Bajada del Diablo (S 42º 45’, W 67º 30’). El evento ocurrió probablemente en el Pleistoceno Medio (780.000 a 130.000 años atrás), y originalmente unos 550 cráteres de impacto de menos de 400 metros de diámetro fueron creados simultáneamente en unárea de 480 kilómetros cuadrados en Bajada del Diablo, Chubut, Patagonia central. Hoy solo sobreviven a los procesos erosivos que han actuado desde el evento de impacto unos 200 cráteres de impacto. La ausencia de una clara elipse de impacto en la distribución de planta de los cráteres de impacto evidencia el impacto de un objeto que ya venía muy fragmentado antes de entrar en la atmósfera terrestre. La ausencia en el sitio mismo de fragmentos de meteoritos (tanto pétreos como metálicos) apunta a que el objeto que impacto estaba principalmente compuesto por hielos, y probablemente era un núcleo helado de cometa fragmentado. Luego de un análisis lógico se favorece el origen de estos cráteres de impacAn analysis of the impact event that created the Bajada del Diablo (S 42º 45’, W 67º 30’) impact crater strewn field is presented. At mid Pleistocene (780,000 to 130,000 years ago), about 550 impact craters of less than 400 meters in diameter were created simultaneously in an area of about 480 square kilometres at Bajada del Diablo in central Patagonia. Absence in the maps of craters of a clear dispersion ellipsoid in the area points toward the idea of the impact of a very fragmented small cosmic object. Cosmic impactor could have been: 1) a “rubble pile” type Near Earth Asteroid or 2) a small split cometary nucleus. The absence of meteorites in the area is in conflict with the hypothesis of the impact of a rocky Near Earth Asteroid. More probably, an ice comet nucleus was the responsible of the impact since the impact of such an icy object would not have left visible traces of itself after more than 130,000 years. After some analysis the impact of a small 200 meters wide split ice comet nucleus is presented as the most probable scenario.Fil: Rocca, Maximiliano. No especifíca;Fil: Acevedo, Rogelio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Quantization of a six-dimensional Wess-Zumino model

We examine a six-dimensional Wess-Zumino model. The equations of motion are of the fourth order, implying two modes of propagation; a normal bradyonic mode and a tachyonic mode. The conserved fermion current is constructed. The component fields are quantized in such a way that the operator representing the supercharge is the generator of supersymmetry transformations. The quantization is complemented by the definition of the vacuum for both modes. The evaluation of vacuum expectation values leads to a Feynman propagator for the normal mode and a half-advanced and half-retarded propagator for the tachyon mode. Convolutions between these propagators show consistency with unitarity.Departamento de Físic

Quantization of a 4th-Order Wave Equation

The quantization of a scalar field obeying a fourth-order wave equation is described. Faster-than-light particles appearing in the process are treated as ghosts, with the wrong relation between spin and statistics. In this way, positive energy spectrum, as well as positive metric in Fock space are obtained. Finally, some implications of an interaction described by a Lagrangian symmetrized in the scalar fields are briefly discussed.Facultad de Ciencias ExactasComisión de Investigaciones Científicas de la provincia de Buenos Aire

Tandem RNA affinity purifications to study an essential snoRNA in ribosome assembly

Eukaryotic ribosome assembly is an essential process involving many protein and RNA assembly factors. Mutations of genes encoding ribosomal proteins or assembly factors can result in diseases in humans. The upregulation of ribosome assembly is also a hallmark of many cancers. snR30 is an interesting assembly factor due to its role as an unusual and essential H/ACA small nucleolar RNA and as it is one of only three essential RNA assembly factors. Here, I have developed a system for the co-expression of aptamer-tagged variants of snR30 and truncations of ribosomal RNA in Saccharomyces cerevisiae. Next, I optimized the tandem purifications of the snR30-bound pre-ribosomes utilizing these aptamers. In conclusion, my system will allow for in-depth characterization of the composition and structure of snR30-bound ribosome precursors. This characterization will improve the understanding of the essential activity of snR30 for ribosome assembly in yeast and inform future studies on the function of the homologous U17 RNA in humans

Survey-based naming conventions for use in OBO Foundry ontology development

A wide variety of ontologies relevant to the biological and medical domains are available through the OBO Foundry portal, and their number is growing rapidly. Integration of these ontologies, while requiring considerable effort, is extremely desirable. However, heterogeneities in format and style pose serious obstacles to such integration. In particular, inconsistencies in naming conventions can impair the readability and navigability of ontology class hierarchies, and hinder their alignment and integration. While other sources of diversity are tremendously complex and challenging, agreeing a set of common naming conventions is an achievable goal, particularly if those conventions are based on lessons drawn from pooled practical experience and surveys of community opinion. We summarize a review of existing naming conventions and highlight certain disadvantages with respect to general applicability in the biological domain. We also present the results of a survey carried out to establish which naming conventions are currently employed by OBO Foundry ontologies and to determine what their special requirements regarding the naming of entities might be. Lastly, we propose an initial set of typographic, syntactic and semantic conventions for labelling classes in OBO Foundry ontologies. Adherence to common naming conventions is more than just a matter of aesthetics. Such conventions provide guidance to ontology creators, help developers avoid flaws and inaccuracies when editing, and especially when interlinking, ontologies. Common naming conventions will also assist consumers of ontologies to more readily understand what meanings were intended by the authors of ontologies used in annotating bodies of data

Factores que influyen en el crecimiento de la biomasa algal

La biomasa algal, según su composición química, puede destinarse a la producción de alimentos para consumo humano o animal, suplementos nutricionales, cosméticos, biofertilizantes, pigmentos, antioxidantes, especialidades químicas, etc. Tanto la producción de biomasa microalgal como la de sus productos derivados pueden ser optimizadas mediante una adecuada modificación de las condiciones físicas y la composición de los medios nutrientes utilizados para sus cultivos. Este trabajo se centra en el estudio de los parámetros que tienen influencia sobre la producción de la biomasa microalgal de Spirulina Platensis. Con respecto a la influencia de los factores fisicoquímicos se analizan la incidencia de la concentración inicial de inóculo, la intensidad lumínica y el método de agitación. La optimización de estos parámetros y otros como la temperatura, el pH, los ciclos de luz y oscuridad, resultan determinantes en la explotación comercial de biomasa y/o sus productos secundarios (metabolitos) de interés. Disponer de información sistemática sobre estas tecnologías constituye un desafío tecnológico fundamental en relación a la matriz productiva de nuestro país.According to its chemical composition, algal biomass could be used to produce food, feed, nutritional supplements, cosmetics, biofertilizers, pigments, antioxidants, fine chemicals, etc. Both the production of microalgal biomass and its derivatives can be optimized by a proper modification of physical conditions and nutrient media composition applied when their cultures. This work is focused on the study of parameters relevant to Spirulina Platensis microalgal biomass production. Related to the physical and chemical factors, influence of inoculum initial concentration, light intensity and stirring method were analyzed. Optimization of said parameters, including also others like temperature, pH, light-dark cycles, is critical for the commercial exploitation of biomass and/or its valuable secondary products (metabolites). The achievement of meaningful information on these technologies is a significant challenge regarding the productive matrix of our country.Fil: Argumedo Moix, Maximiliano. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Álvarez, Paola. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Mateucci, Ricardo. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Busto, Víctor Daniel. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; ArgentinaFil: Rocca, Patricia Della. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentin

Overcoming the Ontology Enrichment Bottleneck with Quick Term Templates

The developers of the Ontology of Biomedical Investigations (OBI) primarily use Protégé for editing. However, adding many classes with similar patterns of logical definition is time consuming, error prone, and requires the editor to have some expertise in OWL. Therefore, the process is poorly suited for a large number of domain experts who have limited experience Protégé and ontology development. We have developed a procedure to ease this task and allow such domain experts to add terms to the ontology in a way that both effectively includes complex logical definitions yet requires minimal manual intervention by OBI developers. The procedure is based on editing a Quick Term Template in a spreadsheet format which is subsequently converted into an OWL file. This procedure promises to be a robust and scalable approach for ontology enrichment

Diseño de concreto empleando fibra de coco para mejorar las propiedades mecánicas, en una vivienda multifamiliar, Lamas 2021

El presente trabajo de investigación “Diseño de Concreto Empleando Fibra de Coco para Mejorar las Propiedades Mecánicas, en una Vivienda Multifamiliar, Lamas 2021” propone determinar de qué manera el empleo de fibra de coco en el diseño de concreto mejora las propiedades mecánicas en una vivienda multifamiliar, con el empleo de distintos porcentajes de fibra de coco, como fueron agregados desde un 0% , 1%, 1.5% y 2%, para un tiempo de curado de 3, 7, 14 y 28 días y así demostrar así la efectividad en aumento de la resistencia del concreto en sus propiedades mecánicas. Para realizar el diseño del concreto, fue diseñado bajo la normal ACI, para la elaboración de un concreto 210 kg/cm2 se utilizó cemento hidráulico, dado al ambiente al cual estará expuesto. Los resultados obtenidos a los 28 días de las 112 probetas de 4”x 8”, demostraron que la fibra de coco influye en aumento la resistencia a partir de 1.5% y 2% cortados a 3 cm de longitud, se realizaron muestras de concreto patrón, para poder comparar las resistencias. Se concluyó que el empleo de la fibra de coco mejora las propiedades mecánicas del diseño de concreto en una vivienda multifamiliar

Two-color quantum memory in double-Λ media

We propose a quantum memory for a single-photon wave packet in a superposition of two different colors, i.e., two different frequency components, using the electromagnetically induced transparency technique in a double-Λ system. We examine a specific configuration in which the two frequency components are able to exchange energy through a four-wave mixing process as they propagate, so the state of the incident photon is recovered periodically at certain positions in the medium. We investigate the propagation dynamics as a function of the relative phase between the coupling beams and the input single-photon frequency components. Moreover, by considering time-dependent coupling beams, we numerically simulate the storage and retrieval of a two-frequency-component single-photon qubit