The Diffuse Nature of Stromgren Spheres

In this Letter, we argue that the standard analytical derivations of properties of HII regions, such as the speed, shape and asymptotic position of ionisation fronts require a more precise treatment. These derivations use the on the spot approximation, which in effect ignores the diffuse component of the radiation field. We show that, in fact, HII regions are diffusion dominated. This has as a result that the morphology of inhomogeneous HII regions will be drastically different, because shadowing effects have a less profound impact on the apparent shape. Moreover, it will have influence on the propagation speed of ionisation fronts. We quantify our claims by analytically deriving the internal radiation structure of HII regions, taking diffusion fully into account for several different cosmologically relevant density distributions.Comment: 4 pages, 2 figures, accepted for publication in A&A Letter

Educación de la libertad. un nuevo acercamiento para comprender la relación valores-educación en el contexto de pluralidad e incertidumbre del mundo actual

El horizonte de crisis-cambio-globalización en que se encuentra el mundo hace que el tema de los valores en la educación y sus concreciones en la llamada “educación en valores” adquieran cada vez mayor relevancia. El cambio de época que vivimos, justifica la preocupación por el tema pero este contexto mundial está marcado por dos elementos que se deben tomar en cuenta para plantear programas eficaces de educación moral y programas más pertinentes de investigación sobre el tema. Estos dos elementos son la incertidumbre y la pluralidad. En un contexto como este, es necesario buscar nuevos enfoques de formación e investigación sobre el tema de los valores que respondan al sujeto humano de hoy. Una distinción filosófica que puede ayudar a esta búsqueda es la que hacen Zubiri y Aranguren entre “moral como contenido” y “moral como estructura”. Una persona puede vivir al margen de los contenidos morales de su sociedad, pero ningún ser humano puede evitar ser “estructuralmente moral”. La propuesta de este trabajo consiste en que una educación moral para los tiempos de incertidumbre y pluralidad que hoy vivimos debe ser una propuesta basada en la “moral como estructura” y no, como la mayoría de los programas actuales, en la “moral como contenido”

Rumen-protected rice bran to induce the adaptation of calcium metabolism in dairy cows

Dairy cows suffer from hypocalcaemia in the days around calving, which may result in a condition generally known as milk fever. Calcium metabolism sharply shifts at the start of lactation, because Ca needs suddenly become much greater than at the end of gestation. Calcium metabolism is able to adapt to different physiological situations, but adaptation requires several days to be effective, resulting in this transient hypocalcaemia. A way to prevent milk fever is to induce adaptation of Ca metabolism weeks before calving by reducing dietary availability of Ca, to prepare Ca metabolism for calving. Rice bran contains a very low level of Ca and a high level of phytic acid, which is a well-know dietary antagonist of Ca in monogastric species. Preventing the ruminal degradation of phytic acid, rice bran can reduce the nutritional availability of dietary Ca in cows. In this thesis, fat coating and formaldehyde treatment proved effective to protect phytic acid in rice bran from ruminal degradation. Formaldehyde treatment was chosen as the preferred method, because it had no detrimental effects on voluntary feed intake. Feeding rumen-protected rice bran reduced dietary Ca availability, thereby inducing the adaptation of Ca metabolism. Furthermore, the product, fed before calving to multiparous cows, improved calcaemia for the first three days after calving. Rumen-protected rice bran, fed in the last weeks of gestation, could represent a practical dietary strategy to prevent milk fever

Scattering of surface plasmons by one-dimensional periodic nanoindented surfaces

In this work, the scattering of surface plasmons by a finite periodic array of one-dimensional grooves is theoretically analyzed by means of a modal expansion technique. We have found that the geometrical parameters of the array can be properly tuned to achieve optimal performance of the structure either as a Bragg reflector or as a converter of surface plasmons into light. In this last case, the emitted light is collimated within a few degrees cone. Importantly, we also show that a small number of indentations in the array are sufficient to fully achieve its functional capabilities.Comment: 5 pages, 5 figures; changed sign convention in some definition

Resonant tunneling through a small quantum dot coupled to superconducting leads

We address the problem of non-linear transport through discrete electronic levels in a small quantum dot coupled to superconducting electrodes. In our approach the low temperature I-V characteristics can be calculated including all multiple quasi-particle and Andreev processes. The limit of very weak coupling to the leads and large charging energies is briefly analyzed comparing the calculated lineshapes of the I-V curves with recent experimental results. When the coupling to the leads increases and Coulomb blockade effects can be neglected, the combination of multiple Andreev processes and resonant transmission gives rise to a rich subgap structure which largely differs from the one found in the more studied S-N-S systems. We show how multiple processes can be included within a simple sequential tunneling picture qualitatively explaining the subgap structure. We suggest an experimental set-up where the predicted effects could be observed.Comment: 11 pages, 4 postscript figures, to be published in Phys. Rev. B (rapid communications

Discurso del Sr. Decano Dr. Martín J. Casey

Fil: Casey, Martín J. Universidad de Buenos Aires. Facultad de Derecho. Buenos Aires, ArgentinaFil: López, Mario Justo. Universidad de Buenos Aires. Facultad de Derecho. Cátedra Teoría del Estado. Buenos Aires, ArgentinaCon: Discurso del Sr. Profesor Emérito Dr. Mario Justo López\nTemas de Derecho Penal I

Pregabalin in the treatment of inferior alveolar nerve paraesthesia following overfilling of endodontic sealer

A case of orofacial pain and inferior alveolar nerve (IAN) paraesthesia after extrusion of endodontic sealer within the mandibular canal treated with prednisone and pregabalin is described. A 36-year-old woman underwent root canal treatment of the mandibular second right premolar tooth. Post-operative panoramic radiograph revealed the presence of radiopaque canal sealer in the mandibular canal. Damage to IAN consecutive to extrusion of endodontic sealer was diagnosed. Non-surgical management was decided, including: 1 mg/kg/day prednisone 2 times/day, once-daily regimen, and 150 mg/day pregabalin, two doses per day, monitoring the progress with periodic follow-up visits. Six weeks after the incident the signs and symptoms were gone. The complete resolution of paraesthesia and the control of pain achieved suggest that a non-surgical approach, combining prednisone and the GABA analogue pregabalin, is a good option in the management of the IAN damage subsequent to endodontic sealer extrusion

Origen y evolución de la imagen geográfica del centro histórico de Córdoba: investigación para su caracterización

En el Plan de Ordenación del Territorio de Andalucía2 (en adelante POTA), las Estrategias de Desarrollo Territorial constituyen su núcleo central, pues contienen las líneas de actuación necesarias para la consecución del Modelo propuesto. Uno de los cuatro grandes bloques en que se contienen estas estrategias hace referencia al llamado Sistema Regional de Protección del Territorio, siendo el Sistema del Patrimonio Territorial una de sus principales líneas maestras. Componentes de dicho Sistema son, entre otros, las ciudades históricas protegidas como Conjuntos Históricos, cual es el caso de la ciudad de Córdoba, parte de cuyo casco fue declarado en 1994 Patrimonio de la Humanidad por la UNESCO. Uno de los retos actuales de los centros históricos es hacer convivir sus señas de identidad seculares con los embates del sector turístico, y con las corrientes que abogan por una “modernización” y adaptación a los momentos actuales. El objeto de nuestro trabajo es, en primer lugar, perfilar los rasgos esenciales de la imagen geográfica que, en el pasado, el centro histórico de Córdoba despertó en viajeros y visitantes para contrastar, en un segundo momento, esta realidad con aquellos elementos que los habitantes del centro histórico de Córdoba perciben en la actualidad como claves para preservar su carácter y tradición histórica. Al respecto presentamos el estudio que se está realizando para caracterizar dicha imagen. Para ello proponemos como marco epistemológico el de la Geografía de la Percepción que, desde los años 60 del s. XX, aportara Kevin Lynch, convencidos de su aplicabilidad como apoyo a la redacción de los documentos de planeamiento vinculados con los bienes patrimoniales. La oportunidad del estudio se deriva de las anunciadas intenciones del Ayuntamiento de Córdoba de modificar el Plan Especial de Protección del Conjunto Histórico de la ciudad. Ocasión, por tanto, inmejorable para intentar contrastar los resultados que se deriven de la tramitación oficial, con los que se presentarían aplicando dicha metodología.In the Spatial Planning Plan of Andalusia (POTA, approved by Decree 206/2006, of 28 November), the Territorial Development Strategies constitute the core, because it comprises the necessary action lines in order to attain the proposed model. One of the four blocks which they are contained in, make reference to the so-called Regional System of Territorial Protection, being the Territorial Heritage System one of the main points. Components of the mentioned System are, between others, the historic cities considered as Cultural Heritage, which is the case of Cordoba, whose old quarter was declared World Heritage in 1994 by the UNESCO. One of the challenges of these old quarters is living together in accordance with their age-old hallmarks and the ravages of the tourism sector, and also with the currents that plead for a “modernization” and an adaptation to new times. The aim of the essay is, first of all, shaping the essential features of the image -geographical image- that travellers and visitors could have in the past from the old quarter of Cordoba, to contrast them with the elements perceived by their residents, as keys to maintain its nature and historical tradition. On this matter, the ongoing study is being presented to characterize this image. We suggest an epistemological framework developed by Kevin Lynch from the 60’s to the present day called Geography of Perception. We are convinced of its applicability in the drafting of documents as a support to Planning linked to patrimonial assets. The opportunity of the study derives from the intentions expressed by the City Council of Cordoba of modifying the Specific Plan made for the Old Quarter of the city. This is, therefore, an excellent opportunity to contrast the results which were obtained by the official proceedings using the methodology indicated above