Image and Coherence Transfer in the Stimulated Down-conversion Process

The intensity transverse profile of the light produced in the process of stimulated down-conversion is derived. A quantum-mechanical treatment is used. We show that the angular spectrum of the pump laser can be transferred to the stimulated down-converted beam, so that images can also be transferred from the pump to the down-converted beam. We also show that the transfer can occur from the stimulating beam to the down-converted one. Finally, we study the process of diffraction through an arbitrarily shaped screen. For the special case of a double-slit, the interference pattern is explicitly obtained. The visibility for the spontaneous emitted light is in accordance with the van Cittert - Zernike theorem for incoherent light, while the visibility for the stimulated emitted light is unity. The overall visibility is in accordance with previous experimental results

On Logical Depth and the Running Time of Shortest Programs

The logical depth with significance $b$ of a finite binary string $x$ is the shortest running time of a binary program for $x$ that can be compressed by at most $b$ bits. There is another definition of logical depth. We give two theorems about the quantitative relation between these versions: the first theorem concerns a variation of a known fact with a new proof, the second theorem and its proof are new. We select the above version of logical depth and show the following. There is an infinite sequence of strings of increasing length such that for each $j$ there is a $b$ such that the logical depth of the $j$th string as a function of $j$ is incomputable (it rises faster than any computable function) but with $b$ replaced by $b+1$ the resuling function is computable. Hence the maximal gap between the logical depths resulting from incrementing appropriate $b$'s by 1 rises faster than any computable function. All functions mentioned are upper bounded by the Busy Beaver function. Since for every string its logical depth is nonincreasing in $b$, the minimal computation time of the shortest programs for the sequence of strings as a function of $j$ rises faster than any computable function but not so fast as the Busy Beaver function.Comment: 12 pages LaTex (this supercedes arXiv:1301.4451

Experimental determination of multipartite entanglement with incomplete information

Multipartite entanglement is very poorly understood despite all the theoretical and experimental advances of the last decades. Preparation, manipulation and identification of this resource is crucial for both practical and fundamental reasons. However, the difficulty in the practical manipulation and the complexity of the data generated by measurements on these systems increase rapidly with the number of parties. Therefore, we would like to experimentally address the problem of how much information about multipartite entanglement we can access with incomplete measurements. In particular, it was shown that some types of pure multipartite entangled states can be witnessed without measuring the correlations [M. Walter et al., Science 340, 1205 (2013)] between parties, which is strongly demanding experimentally. We explore this method using an optical setup that permits the preparation and the complete tomographic reconstruction of many inequivalent classes of three- and four-partite entangled states, and compare complete versus incomplete information. We show that the method is useful in practice, even for non-pure states or non ideal measurement conditions.Comment: 12 pages, 7 figures. Close to published versio

Axillary bud viability and dry matter production of Poa ligularis in Patagonian grasslands

Poa ligularis Nees is one of the dominant perennial grass species in Patagonian grasslands. This is the first field study which investigated the effects of defoliation frequency on its number of viable axillary buds, and subsequent dry matter production during one growing season. Experiments were arranged in a randomized complete block design. Treatments included one defoliation height (10 cm), from one to five times a year, and undefoliated controls. Bud respiratory activity was examined usingthe tetrazolium test and the vital stain Evan's blue. At the end of the growing season, plants that have been defoliated more than three times showed significatively (p<0.05) lower number of respiratory active buds than unclipped controls. A high defoliation frequency increased bud death in stem bases. Both defoliated and undefoliated plants produced more (p<0.05) axillary buds at the periphery than at their center. Defoliation treatments increased shoot weight by 13.4% on average compared with undefoliated controls, but reduced in by 10% the average number of metabolically active axillary buds. This indicates that this reduction, however, was not high enough to constrain dry matter production.It appears that Poa ligularis could tolerate moderate grazing frequency and intensity without compromising its potential regrowth capacity. Longer-term studies of the effects of defoliation on dry matter production and bud metabolic activity are needed to understand the cumulative effects of grazing of P. ligularis in natural grasslands.Poa ligularis Nees es una de las especies de gramíneas perennes dominantes en los pastizales naturales de la Patagonia. Este es el primer estudio que investigó los efectos de la frequencia de defoliación sobre su número de yemas axilares viables, y subsiguiente producción de materia seca durante una estación de crecimiento. Los estudios se efectuaron utilizando un diseño de bloques completamente al azar. Los tratamientos incluyeron una altura de defoliación (10 cm), de una a cinco veces por año, además de controles no defoliados. La actividad respiratoria de las yemas fue examinada usando el método del tetrazolio y el colorante vital azul de Evans.Hacia el final de la estación de crecimiento, las plantas que habían sido defoliadas más de tres veces mostraron un número significativamente menor (p<0.05) de yemas con actividad respiratoria que los controles no defoliados. Una alta frecuencia de defoliación incrementó la muerte de yemas en las bases de tallos. Todas las plantas- defoliadas o no, produjeron más (p<0.05) yemas axilares en su periferia que en su centro. La defoliación incrementó 13.4% el peso de los tallos en promedio, pero redujo en 10% el número promedio de yemas axilares metabólicamente activas. Esto indica que esta reducción , sin embargo, no fue suficiente como para limitar la producción de materia seca. Parece que P. ligularis toleraría una frecuencia e intensidad moderada de pastoreo sin comprometer su capacidad potencial de rebrote. Se necesitan estudios a más largo plazo de los efectos de la defoliación en la producción de materia seca y actividad metabólica de las yemas para entender los efectos acumulativos del pastoreo de Poa ligularis en los pastizales naturales.Fil: Souto, Cintia Paola. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Becker, G. F.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; ArgentinaFil: Siffredi, G. L.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; ArgentinaFil: Busso, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Sterberg, M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentin

Classificação de redes pedonais para pessoas com mobilidade reduzida

O presente trabalho analisa alguns dos factores que condicionam a mobilidade pedonal de uma parte da população, as pessoas com mobilidade reduzida. No âmbito da realidade portuguesa, o objectivo foi determinar se as características físicas de um determinado espaço urbano respeitam as exigências do Decreto-Lei 163/2006. Neste enquadramento, um modelo de avaliação do grau de conformidade dos espaços com as normas vigentes foi idealizado com o intuito de gerar uma classificação dos locais estudados. Este modelo estabelece a normalização dos valores levantados para os itens considerados e a sua agregação para a obtenção de um índice que exprime o grau de conformidade do espaço avaliado. O modelo foi integrado num SIG para permitir a representação dos resultados alcançados em mapas de classificação e aplicada a um caso de estudo na cidade de Braga, Portugal

Comparison of experimental and numerical sloshing loads in partially filled tanks

Sloshing phenomenon consists in the movement of liquids inside partially filled tanks, whichgenerates dynamic loads on the tank structure. Resulting impact pressures are of great importance in assessingstructural strength, and their correct evaluation still represents a challenge for the designer due to the highnonlinearities involved, with complex free surface deformations, violent impact phenomena and influence of airtrapping. In the present paper a set of two-dimensional cases for which experimental results are available areconsidered to assess merits and shortcomings of different numerical methods for sloshing evaluation, namely twocommercial RANS solvers (FLOW-3D and LS-DYNA), and two own developed methods (Smoothed ParticleHydrodynamics and RANS). Impact pressures at different critical locations and global moment induced by watermotion for a partially filled tank with rectangular section having a rolling motion have been evaluated and resultsare compared with experiments

Aplicación del plasma en la industria textil

El plasma, medio extremadamente reactivo con una mezcla de iones, electrones y radicales libres, permite hacer modificaciones en la estructura de los materiales poliméricos, sobretodo en la superficie, empleando solamente energía eléctrica (eventualmente con la adición de gases) sin necesitar de agua ni de productos químicos. Hay dos grandes tipos de posibilidades: tratamiento a baja presión (“glow discharge”), lo cual necesita todavía de una cámara cerrada dificultando el tratamiento en continuo, y el tratamiento a presión atmosférica (“Corona”), menos reactivo pero con la ventaje de permitir su inclusión en una línea continua de ennoblecimiento textil. El tratamiento plasma puede ahorrar una etapa de tratamiento convencional en húmedo, por ejemplo para mejorar las propiedades de humectabilidad y de adhesión de las superficies textiles, y también permite por si solo la obtención de efectos de acabado “tradicionales” (como por ejemplo la reducción del enfieltrado de los tejidos de lana) ó más innovadores (para textiles técnicos, como por ejemplo para filtraciones selectivas o el crecimiento de tejidos biológicos). En esta comunicación se presentan algunos resultados de proyectos desarrolhados en la Universidad de Miño con la descarga Corona en tejidos de algodón. Los resultados muestran que un tratamiento Corona de un tejido de algodón permite obtener efectos muy variados, tales como: eliminar el uso de humectantes en el desencolado, mercerizado, blanqueo, tintura, un mejor efecto de mercerizado e de acabado con resinas (en este caso con una reducción del formaldehído libre), un mejor rendimiento, penetración y solidez al frote de estampados con pigmentos, etc. En este momento está funcionando en una empresa de producción de textiles para el hogar un prototipo industrial integrado en la línea de pretratamiento, con interesantes resultados. El tratamiento plasma tiene grandes potencialidades de aplicación industrial en el ennoblecimiento textil, con vantages ecológicas, económicas y permitiendo la obtención de nuevos efectos en las superficies textiles. Es una de las tecnologías a considerar en la implementación de la Directiva Europeia sobre la Prevención y Control Integrado de la Polución en empresas textiles del ramo del agua