The Relativistic Factor in the Orbital Dynamics of Point Masses

There is a growing population of relativistically relevant minor bodies in the Solar System and a growing population of massive extrasolar planets with orbits very close to the central star where relativistic effects should have some signature. Our purpose is to review how general relativity affects the orbital dynamics of the planetary systems and to define a suitable relativistic correction for Solar System orbital studies when only point masses are considered. Using relativistic formulae for the N body problem suited for a planetary system given in the literature we present a series of numerical orbital integrations designed to test the relevance of the effects due to the general theory of relativity in the case of our Solar System. Comparison between different algorithms for accounting for the relativistic corrections are performed. Relativistic effects generated by the Sun or by the central star are the most relevant ones and produce evident modifications in the secular dynamics of the inner Solar System. The Kozai mechanism, for example, is modified due to the relativistic effects on the argument of the perihelion. Relativistic effects generated by planets instead are of very low relevance but detectable in numerical simulations

Branching rate expansion around annihilating random walks

We present some exact results for branching and annihilating random walks. We compute the nonuniversal threshold value of the annihilation rate for having a phase transition in the simplest reaction-diffusion system belonging to the directed percolation universality class. Also, we show that the accepted scenario for the appearance of a phase transition in the parity conserving universality class must be improved. In order to obtain these results we perform an expansion in the branching rate around pure annihilation, a theory without branching. This expansion is possible because we manage to solve pure annihilation exactly in any dimension.Comment: 5 pages, 5 figure

Selective Realism and the Framework/Interaction Distinction: A Taxonomy of Fundamental Physical Theories

Following the proposal of a new kind of selective structural realism that uses as a basis the distinction between framework and interaction theories, this work discusses relevant applications in fundamental physics. An ontology for the different entities and properties of well-known theories is thus consistently built. The case of classical field theories --including General Relativity as a classical theory of gravitation-- is examined in detail, as well as the implications of the classification scheme for issues of realism in Quantum Mechanics. These applications also shed light on the different range of applicability of the ontic and epistemic versions of structural realism

Primordial Earth mantle heterogeneity caused by the Moon-forming giant impact

The giant impact hypothesis for Moon formation successfully explains the dynamic properties of the Earth-Moon system but remains challenged by the similarity of isotopic fingerprints of the terrestrial and lunar mantles. Moreover, recent geochemical evidence suggests that the Earth's mantle preserves ancient (or "primordial") heterogeneity that predates the Moon-forming giant impact. Using a new hydrodynamical method, we here show that Moon-forming giant impacts lead to a stratified starting condition for the evolution of the terrestrial mantle. The upper layer of the Earth is compositionally similar to the disk, out of which the Moon evolves, whereas the lower layer preserves proto-Earth characteristics. As long as this predicted compositional stratification can at least partially be preserved over the subsequent billions of years of Earth mantle convection, the compositional similarity between the Moon and the accessible Earth's mantle is a natural outcome of realistic and high-probability Moon-forming impact scenarios. The preservation of primordial heterogeneity in the modern Earth not only reconciles geochemical constraints but is also consistent with recent geophysical observations. Furthermore, for significant preservation of a proto-Earth reservoir, the bulk composition of the Earth-Moon system may be systematically shifted towards chondritic values.Comment: Comments are welcom

On the 2-point function of the O(N) model

The self-energy of the critical 3-dimensional O(N) model is calculated. The analysis is performed in the context of the Non-Perturbative Renormalization Group, by exploiting an approximation which takes into account contributions of an infinite number of vertices. A very simple calculation yields the 2-point function in the whole range of momenta, from the UV Gaussian regime to the scaling one. Results are in good agreement with best estimates in the literature for any value of N in all momenta regimes. This encourages the use of this simple approximation procedure to calculate correlation functions at finite momenta in other physical situations

Floral biology of Salvia stachydifolia, a species visited by bees and birds: Connecting sexual phases, nectar dynamics and breeding system to visitors' behaviour

Adaptive convergence in floral phenotype among plants sharing a pollinator guild has been acknowledged in the concept of pollination syndrome. However, many plants display traits associated with a given syndrome, but are visited by multiple pollinators. This situation may indicate the beginning of a pollinator shift or may result in a stable situation with adaptations to different pollinators. In Salvia stachydifolia, a previous study suggested that flower shape is optimized to maximize the contribution to pollination of bees and hummingbirds. Here, we studied three additional aspects of its floral biology: sexual phases, nectar dynamics and breeding system, and examined their connection with pollinators' behaviour to explore the presence of adaptations to bee and/or hummingbird pollination. Methods: Using a greenhouse population, we applied five pollination treatments to characterize breeding system. To determine sexual phases, we recorded flower opening, anther dehiscence, corolla fall and stigma receptivity. Additionally, we characterized nectar volume and concentration dynamics along the day. Finally, to determine pollinator assemblage and visitation patterns, we performed field observations and recorded pollinators' behaviour. Important Findings: Salvia stachydifolia was partially protandrous and self-compatible, but open-pollinated plants attained the highest reproductive success, suggesting that reproduction is mainly dependent on pollinator activity. Bombus opifex bumblebees were the most frequent visitors, but Sappho sparganura hummingbirds dominated visits early in the morning and at dusk. Nectar was typical of bumblebee pollination. We suggest that the bee-hummingbird mixed visitation constitutes an unstable evolutionary situation, making S. stachydifolia an ideal system to understand the ecological circumstances in which pollination shifts occur.Fil: Barrionuevo, Camila Nerea. Universidad Nacional de Córdoba. Facultad de Medicina. Departamento de Fisiología Humana y Física Biomedica. Cátedra de Física Biomedica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Benitez-Vieyra, Santiago Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Sazatornil, Federico David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin

Efeito na motilidade gástrica em ratos de Equisetum giganteum L. n.v. cola de caballo, Cortaderia selloana (Schult & Schltz. f.) n.v. cortadera, Anthemis cotula L. n.v. manzanilla amarga e Atriplex undulata D. Dietr. n.v. zampa blanca

Previous studies determined that the oral administration of hydroalcoholic extracts obtained from the aerial parts of Equisetum giganteum L. n.v. cola de caballo, Cortaderia selloana (Schult & Schultz. f.) n.v. cortadera, Anthemis cotula L. n.v. manzanilla amarga y Atriplex undulata D. Dietr. n.v. zampa blanca prevent gastric ulcers induced by hypothermia and immobilization in mice. The formation of gastric ulcers in this experimental model is caused by a decrease in cytoprotective factors and by a mechanical erosive effect produced in the mucosa by increased gastric motility. In order to determine whether these extracts produce a decrease in gastric motility, in this study gastric emptying of a radiopaque substance was observed by taking radiographs at 0, 60, 100 and 160 minutes after the start of the test. A delay in gastric emptying time with respect to the control group animals was interpreted as a decrease in motility. The results of this work allow us to conclude that all the extracts of Atriplex undulata, Equisetum giganteum, Cortaderia Selloana and Anthemis cotula show an inhibitory effect on gastric motility from higher to lower respectivelyEstudios previos determinaron que la administración oral de extractos hidroalcohólicos obtenidos a partir de partes aéreas de Equisetum giganteum L. n.v. cola de caballo, Cortaderia selloana (Schultz&Schultz. f.) n.v. cortadera, Anthemis cotula L. n.v. manzanilla amarga y Atriplex undulata D. Dietr. n.v. zampa blanca, previenen las úlceras gástricas inducidas por hipotermia e inmovilización en ratones. La formación de las úlceras gástricas por estrés en este modelo experimentales provocada por una disminución de los factores citoprotectores y por un efecto erosivo mecánico producido en la mucosa por aumento de la motilidad gástrica. Con el objetivo de determinar si estos extractos producen una disminución de la motilidad gástrica, en este trabajo se observó el vaciado gástrico de una sustancia radiopaca tomando radiografías a los 0,60, 100 y 160 minutos de iniciado el ensayo. Un retraso en el tiempo de vaciado gástrico con respecto a los animales del grupo testigo se interpretó como una disminución de la motilidad. Los resultados de este trabajo permiten concluir que todos los extractos de Atriplex undulata, Equisetum giganteum, Cortaderia selloana y Anthemis cotula exhiben efecto inhibitorio sobre la motilidad gástrica de mayor a menor respectivamente.Estudos anteriores determinaram que a administração oral de extratos hidroalcoólicos obtidos das partes aéreas de Equisetum giganteum L. n.v. cola de caballo, Cortaderia selloana (Schult & Schltz. f.) n.v. cortadera, Anthemis cotula L. n.v. manzanilla amarga e Atriplex undulata D. Dietr. n.v. zampa blanca, previnem úlceras gástricas induzidas por hipotermia e imobilização em camundongos. A formação de úlceras gástricas devido ao estresse neste modelo experimental é causada pela diminuição dos fatores citoprotetores e por um efeito erosivo mecânico produzido na mucosa pelo aumento da motilidade gástrica. A fim de determinar se esses extratos produzem uma diminuição na motilidade gástrica, neste estudo, o esvaziamento gástrico de uma substância radiopaca foi observado por meio de radiografias em 0,60, 100 e 160 minutos após o início do ensaio. Um atraso no tempo de esvaziamento gástrico em relação aos animais do grupo controle foi interpretado como diminuição da motilidade. Os resultados deste trabalho permitem concluir que todos os extratos de Atriplex undulata, Equisetum giganteum, Cortaderia selloana e Anthemis cotula apresentam efeito inibitório na motilidade gástrica de maior para menor, respectivamente.respectivamente

Distancias ecológicas en el ambiente de polinización explican la divergencia entre poblaciones de Salvia stachydifolia Benth

La adaptación local en rasgos florales puede originarse como resultado de las diferencias en la abundancia o en la efectividad de diferentes polinizadores en distintas poblaciones. Las diferencias resultantes por la adaptación, eventualmente, podrían generar aislamiento reproductivo y especiación incipiente. Salvia stachydifolia Benth (Lamiaceae), es una especie de los pastizales de neblina de las Yungas y posee una gran diversidad de formas y tamaños florales lo que nos llevó a preguntarnos si estos procesos son responsables de las diferencias entre poblaciones. Para ello, estudiamos 8 poblaciones de la especie en el Noroeste de Argentina y extrajimos esquejes que fueron cultivados en un jardín común. En cada población, caracterizamos la variabilidad en la forma de la corola utilizando técnicas de morfometría geométrica; el volumen y concentración de néctar y en el ensamble de polinizadores. S. stachydifolia presenta poblaciones visitadas principalmente por colibríes, por abejas o por colibríes, abejas y moscas. Encontramos diferencias entre poblaciones en la concentración y volumen de néctar y en la forma de la corola, relacionadas a los visitantes más frecuentes en cada población. Con los datos obtenidos se calcularon para las poblaciones naturales y jardín común matrices de distancias fenotípicas, ecológicas (debida a diferentes ensambles de polinizadores) y geográficas entre las poblaciones y luego analizamos las correlaciones entre dichas matrices. Las distancias fenotípicas y ecológicas se encuentran positivamente correlacionadas, mientras que la correlación con la distancia geográfica es menor, sugiriendo adaptación local de S. stachydifolia a sus visitantes más frecuentes.Fil: Izquierdo, Juliana Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Costas, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Sazatornil, Federico David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Benitez-Vieyra, Santiago Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina1 Congreso Latinoamericano de EvoluciónVirtualChileSociedad Chilena de EvoluciónAsociación Colombiana de Biología EvolutivaSociedad Argentina de Biología Evolutiv

Climatización por ciclo abierto por desecado y humidificación

Se presentan los resultados del análisis técnico económico del equipo de refrigeración de un sistema de climatización para climas cálidos y húmedos operado por energía solar. Se seleccionó un ciclo abierto de humidificación con deshumidificación adiabática previa mediante gel de sílice regenerada por energía solar, con enfriamiento de la corriente de aire mediante un intercambio de calor con aire exterior saturado de humedad. En base al comportamiento termodinámico del ciclo y a una carga térmica de 1745 W se determinó que el gel de sílice debe adsorber 1,7 gr s⁻¹ de agua, para regenerar esta masa de agua se debe aportar 10000 W al aire de regeneración con un colector de placa plana de cubierta de vidrio simple de 30 m². Se efectuó el cómputo de materiales y presupuesto y se determinó que el costo del equipo sería de $8410 con una incidencia del colector del 50%.Facultad de Arquitectura y Urbanism