CLASSICAL SPLITTING OF FUNDAMENTAL STRINGS

We find exact solutions of the string equations of motion and constraints describing the {\em classical}\ splitting of a string into two. We show that for the same Cauchy data, the strings that split have {\bf smaller} action than the string without splitting. This phenomenon is already present in flat space-time. The mass, energy and momentum carried out by the strings are computed. We show that the splitting solution describes a natural decay process of one string of mass $M$ into two strings with a smaller total mass and some kinetic energy. The standard non-splitting solution is contained as a particular case. We also describe the splitting of a closed string in the background of a singular gravitational plane wave, and show how the presence of the strong gravitational field increases (and amplifies by an overall factor) the negative difference between the action of the splitting and non-splitting solutions.Comment: 27 pages, revtex

The Two-Dimensional Stringy Black-Hole: A New Approach and a Pathology

The string propagation in the two-dimensional stringy black-hole is investigated from a new approach. We completely solve the classical and quantum string dynamics in the lorentzian and euclidean regimes. In the lorentzian case all the physics reduces to a massless scalar particle described by a Klein-Gordon type equation with a singular effective potential. The scattering matrix is found and it reproduces the results obtained by coset CFT techniques. It factorizes into two pieces : an elastic coulombian amplitude and an absorption part. In both parts, an infinite sequence of imaginary poles in the energy appear. The generic features of string propagation in curved D-dimensional backgrounds (string stretching, fall into spacetime singularities) are analyzed in the present case. A new physical phenomenon specific to the present black-hole is found : the quantum renormalization of the speed of light. We find c_{quantum} = \sqrt{{k\o{k-2}}}~c_{classical}, where $k$ is the integer in front of the WZW action. This feature is, however, a pathology. Only for $k \to \infty$ the pathology disappears (although the conformal anomaly is present). We analyze all the classical euclidean string solutions and exactly compute the quantum partition function. No critical Hagedorn temperature appears here.Comment: 32 pages, uses phyzz

Apparent digestibility of fishing waste silage in red tilapia (oreochromis mossambicus x o. niloticus)

Mediante un diseño completamente aleatorizado con tres repeticiones, se determinó la digestibilidad in vivo de nutrientes y energía de los ensilajes de residuos pesqueros en tilapias rojas (Oreochromis mossambicus x O. niloticus). El ensilaje químico se preparo con ácido sulfúrico 98% (20 ml/kg) y ácido fórmico (10 ml/kg) y el ensilaje biológico con miel de caña (150 g/kg) y yogurt (Lactobacilus bulgaris y streptococcus acidophilus; 30 g/kg). Se usó oxido crómico como indicador y las heces se recolectaron por un sifón desde el fondo de los tanques. Se obtuvo que la digestibilidad aparente de algunos nutrientes difirió en función del tipo de ensilaje, entre tanto la proteína digestible fue mayor para el ensilaje químico y la materia seca, calcio y fósforo para el ensilaje biológico. Digestibilidades iguales (P>0,05) se presentó para los lípidos, cenizas y energía. Concluyendo que los ensilajes de residuos pesqueros presentan alto valor nutricional, lo que constituyen una fuente de proteína alternativa en la formulación de raciones para tilapias rojas.By means of a design completely randomized with three repetitions, in vivo digestibility of nutrients and energy in fishing waste silages were determined for red tilapia (Oreochromis mossambicus x O. niloticus). Chemical silage prepared with sulphuric acid 98% (20 ml/kg) and formic acid (10 ml/kg) and the biological with sugar cane molasses (150 g/kg) and of yogurt (Lactobacilus bulgaris and streptococcus acidophilus; 30 g/kg). The chromic oxide was used as inert indicator and fecal sample were recollected by siphon from the bottom of tanks. As a result, the apparent digestibility of some nutrients differed from silage type; meanwhile protein was bigger for the chemical silage and the dry matter, calcium and phosphorus for the biological silage. Similar digestibility (P>0,05) was presented for lipids, ashes and energy. In conclusion, all this showed that the fishing waste silages present high nutritional value, that constitute an alternative- protein source in the formulation of rations for red tilapias

Cartographic and geohistoric resources for the inventory of temporary wetlands and mediterranean desections

El presente artículo recopila y examina, desde una vertiente metodológica y geográfica, las fuentes o recursos cartográficos que se han analizado y utilizado para la realización del in-ventario de humedales temporales en el Medio Guadalquivir, y en el seno de nuestro proyecto de investigación. Estudiaremos fundamentalmente las fuentes cartográficas disponibles para el área citada, aunque en gran medida puedan ser extrapolables a la mayor parte de España. Se lleva a cabo una exposición de las líneas de trabajo y de los autores más representativos para el inventario de humedales temporales o desecados, mediante la investigación de la historia de los Archivos, de las Bibliotecas, de los Museos y de los Centros de Documentación convencionales y digitales actuales. En un segundo momento se aborda una propuesta metodológica para la investigación de esta faceta particular, acompañada por un nutrido apéndice en el que se recopilan las fuentes más significativas que venimos utilizando en nuestra investigación.This paper compiles and examines, from a methodological and geographical perspective, the sources or cartographic resources that have been analyzed and used for the realization of the inventory of temporary wetlands in the Middle Guadalquivir, and within our research project. We will study fundamentally the cartographic sources available for the mentioned area, although to a large extent they can be extrapolated to the greater part of Spain. An exposition of the lines of work and of the most representative authors for the inventory of temporary or dried wetlands is carried out, through the investigation of the History of Archives, of Libraries, of Museums and of Conventional Documentation Centers And digital technologies. In a second moment, a methodological proposal for the investigation of this particular facet is approached, accompanied by several appendices in which are collected the most significant sources that we have been using in our investigatio

Visita al Monumento Natural Sotos de la Albolafia (Córdoba, España)

Material docente del Máster en Gestión del Patrimonio desde el municipioEste recorrido tiene como escenario el paraje “Sotos de la Albolafia”, el único Monumento Natural de Europa que se encuentra en el interior de un casco urbano. Constituye un paisaje enmarcado en un casco histórico declarado Patrimonio de la Humanidad por la UNESCO, con la Mezquita-Catedral, Alcázar de los Reyes Cristianos, Torre de La Calahorra y Puente Romano.La actividad muestra la integración del Patrimonio Cultural y Ambiental a través de un enfoque etnográfico y didáctico del Monumento Natural, disfrutando a su vez de su alta biodiversidad con más de 180 especies: 120 especies de aves, a las que hay que sumar mamíferos como la nutria, reptiles, anfibios, peces, fauna invertebrada y una rica vegetación que mezcla especies de ribera y con otras propias de humedales y lagunas. Un itinerario que combina el conocimiento de los ecosistemas acuáticos y terrestres, la cultura del agua, el papel de la acción humana sobre el paisaje y la historia de los monumentos emblemáticos de la ciudad de Córdoba

Actividades humanas y espacios naturales protegidos: los humedales del sur de Córdoba

Presentación geográfica de un significativo conjunto de lagunas (de distinto tamaño y características) que, en la Campiña Alta de Córdoba, constituyen un valioso ejemplo de endorreísmo en la Andalucía interior. En ellas se da la doble circunstancia de una integra - ción secular en el espacio agrario circundante, del que históricamente han formado parte, y la conservación de unos valores ambientales que, a finales del siglo XX, atrajeron a los naturalistas, hasta el punto de convertir estas zonas húmedas en el paradigma de la necesidad urgente de medidas protectoras que salvaguardaran aquella riqueza biótica y, con posteriori - dad, paisajística. Contrapunto de gran valor ecológico en un entorno de potente agricultura de olivar, las singularidades paisajísticas y su biodiversidad fueron la base para su conversión en un conjunto destacado y singular del patrimonio natural andaluz. Todo ello sin que el entorno geográfico haya perdido su carácter de un intenso poblamiento y de un importante y significativo paisaje agrario. Desvelar las circunstancias y avatares acaecidos en este pro - ceso será el objetivo de nuestro estudio, con especial hincapié en las nuevas interrelaciones generadas entre espacios lagunares y la sociedad en que se inscriben a raíz de su declaración como Espacios Naturales Protegidos.The wetlands in Southern Cordoba are the geographical presentation of a meaningful group of lakes (with different sizes and features) that, in the Campiña Alta, constitute a valuable example of endorreism in inner Andalusia. They reunite an ancient integration within the surrounding agricultural areas, from which they have been historically part of, and the preservation of a set of environmental values that, at the end of the 20th century, attracted naturalists to the point of turning these wetlands into the epitome of the urgent need to pass protecting measures to shield that biotic wealth and, later, landscape richness. As a powerful environmentaly valuable counterpart of the mighty olive grove agriculture surroundings, the landscape singularities and its biodiversity were the ground for their turning into an outstanding and unique part of the natural Andalusian heritage. All without the loss of the dense settlement and the important and meaningful agrarian landscape, typical from this geographical setting. The goal of our study will be to unravel the circumstances and vicissitudes that took place during this process, paying special attention to the new interrelations created within the wetlands and the society they are part of since their proclamation as Natural Protected Areas

Effect of a DC Electric field on the melting temperature, nucleation and ice growth rate of the TIP4P/ICE water model

Understanding the effect of electric fields on the thermal stability and phase transitions of water could have potential applications in the food industry, cryopreservation, and environmental science. In this work, we investigate the effect of a static electric field on the melting temperature (Tm), ice nucleation and ice growth rate of two phases of ice, hexagonal ice (Ih) and ferroelectric cubic ice (Icf), for the TIP4P/ICE water model. By means of direct coexistence simulations, we establish that Tm of Ice Ih is shifted toward lower values, whereas Tm of Ice Icf grows, becoming the most stable ice phase for sufficiently largevalues of the applied electric field. We also investigate ice nucleation for both ice phases under an external electric field and find that, for a given supercooling with respect to Tm, while the field slows down the nucleation rate of ice Ih significantly, it barely affects that of ice Icf, due to the enhanced ability of water molecules to orient favorably along the direction of the field in the latter phase. In terms of absolute temperature, overall ice formation is promoted by the electric field because it increases the melting point of ice Icf. Finally, we show how the electric field slows down the crystal growth of Ice Ih and increases that of Ice Icf by a factor of about two