The Causal Boundary of spacetimes revisited

We present a new development of the causal boundary of spacetimes, originally introduced by Geroch, Kronheimer and Penrose. Given a strongly causal spacetime (or, more generally, a chronological set), we reconsider the GKP ideas to construct a family of completions with a chronology and topology extending the original ones. Many of these completions present undesirable features, like those appeared in previous approaches by other authors. However, we show that all these deficiencies are due to the attachment of an ``excessively big'' boundary. In fact, a notion of ``completion with minimal boundary'' is then introduced in our family such that, when we restrict to these minimal completions, which always exist, all previous objections disappear. The optimal character of our construction is illustrated by a number of satisfactory properties and examples.Comment: 37 pages, 10 figures; Definition 6.1 slightly modified; multiple minor changes; one figure added and another replace

The causal boundary of wave-type spacetimes

A complete and systematic approach to compute the causal boundary of wave-type spacetimes is carried out. The case of a 1-dimensional boundary is specially analyzed and its critical appearance in pp-wave type spacetimes is emphasized. In particular, the corresponding results obtained in the framework of the AdS/CFT correspondence for holography on the boundary, are reinterpreted and very widely generalized. Technically, a recent new definition of causal boundary is used and stressed. Moreover, a set of mathematical tools is introduced (analytical functional approach, Sturm-Liouville theory, Fermat-type arrival time, Busemann-type functions).Comment: 41 pages, 1 table. Included 4 new figures, and some small modifications. To appear in JHE

Identificación de técnicas de manufactura y funcionalidad de vasijas cerámicas en estudios de lámina

Sin resume

DISEÑO DE ZANJAS CON VELOCIDAD DE INFILTRACIÓN VARIABLE PARA CONSERVACIÓN DE AGUAS Y SUELOS DE LA CUENCA DEL RÍO PURAPEL (CHILE)

Se desarrolló un procedimiento para dimensionar zanjas de infiltración dependiendo de un balance hídrico en la ladera, el cual está focalizado en dos elementos centrales; eventos extremos de precipitación y capacidad de infiltración variable. Este modelo de infiltración incorpora el análisis regional de frecuencia, técnicas geoestadísticas, la ecuación de infiltración de Green- Ampt para superficies con pendientes y un modelo de balance hídrico propuesto por Akan (2002). Los resultados del modelo de zanjas de infiltración con tasas variables de infiltración y diferentes texturas del suelo, permitieron obtener mediante métodos numéricos, los parámetros de diseño de una zanja: altura máxima de agua (calado) y el tiempo de almacenamiento. Este estudio proporciona una extensión práctica de las relaciones intensidad-duración frecuencia para zonas sin registro continuo de la lluvia y con escasez de datos hidrológicos y climatológicos, con el propósito de dimensionar estructuras de conservación de aguas y suelo. El modelo fue aplicado a la cuenca del Río Purapel en Chile central, para demostrar la facilidad del procedimiento sugerido

Effect of Melengestrol Acetate (Mga) on the Metabolic Profile in Heifers

AbstractFrom the analysis of 21 Cebu-Swiss heifers healthy, developing, with 235.55 ± 17.81kg of body weight (BW), 118.62 ± 3.97cm and 2.58 ± 0.35 of body condition (BC) scale of 1-5. They were divided into two groups: MGA (n = 10) and control (n = 11). For 55 days were given a constant diet (including 15 days of adaptation), based on concentrate and sorghum straw. The contribution of daily intake was 599.08g of crude protein and 12.18 Mcal. Blood samples were obtained every 5 days. The concentrations of cholesterol, triglyceride, high-density lipoprotein, low-density lipoprotein, urea, total protein and glucose were measured for spectrophotometric using the enzyme-colorimetric technique in plasma. The daily gain was balanced PV of 603.5 to 232.5 grams and height stopped from day 25. The CC did not show significant changes (P> 0.01). The mean concentration of plasma cholesterol was 107.59 ± 13.38 vs. 109.61 ± 11.72mg/dl (MGA and control, respectively) with a downward trend more pronounced from day 25. The concentration of triglycerides was 12.61 ± 6.91 vs. 16.19 ± 8.86mg/dl (MGA and control), no trend in the first 20 days and from day 25 there was an increase compared to the average of the previous days. The concentrations of HDL 63.73 ± 3.26 vs. 63.79 ± 10.27mg/dl (MGA and control) and 43.56 ± 6.24 vs. LDLc. 46.54 ± 14.89mg/dl (MGA and control) were irregular, but within normal ranges. The values of total protein were 5.70 ± 0.40 vs. 5.22 ± 0.31mg/dl (MGA and control), no trend the first 15 days and from day 20 increased in concentration compared to previous surveys. Urea levels were 14.79 ± 5.22 vs. 14.13 ± 4.8mg/dl (MGA and control) with a tendency to discharge. Glucose levels were 60.06 ± 7.62 vs. 58.24 ± 5.43mg/dl (MGA and control), with an irregular behavior in the normal range. The consumption of 0.5mg/dl of MGA for 40 days increased plasma concentrations of triglycerides and total protein, but did not affect cholesterol levels, HDL and LDL cholesterol, urea and glucose

Fusion of 8He with 206Pb around Coulomb barrier energies

5th International Conference FUSION11The experimental study of the fusion of light neutron-rich nucleus 8He with 206Pb is reported in this work. A fusion stack of 206Pb targets has been used for this study. The most prominent evaporation residue (210Po), which has half-life of 138 days and decays by alpha emission, is populated in the reaction. Radiochemical analysis technique is used to extract the yield of this evaporation residueMinisterio Español de Ciencia e Innovación FPA2007-6307

Parámetros de calidad de la canal y la carne de cabritos lechales de raza payoya en sistema de explotación convencional

En el trabajo se han elegido 24 cabritos pertenecientes a la raza Payoya, 12 machos y 12 hembras con el objeto de comparar los parámetros de la calidad de la canal y de la carne. Los resultados nos muestran que aunque existen algunas diferencias en algunas medidas de calidad de la carne (pH, CRA, L*, a*, b*, C y Hº), el resto de los parámetros estudiados no presentaron diferencias significativas entre los dos sexos

Modeling Optical and Electronic Properties of Silica Nano-Clusters in Silicon Rich Oxide Films

Quantum effects are very important in nano scale systems such as molecules and clusters constituted of particles from a few to hundreds or a few thousands of atoms. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these molecules or clusters are bonded. Generally, these nano-structures display optical and electronic properties significantly different of the bulk materials. Silica agglomerates expected in Silicon Rich Oxide (SRO) films have optical properties, which depend directly on size, and their rationalization can lead to new applications with a potential impact on many fields of science and technology. On the other hand, the room temperature photoluminescence (PL) of Si : SiO2 or Si : SiOx structures usually found in SRO has recently generated an enormous interest due to their possible applications in optoelectronic devices. However, the understanding of the emission mechanism is still under debate. In this research, we employed the Density Functional Theory with a functional B3LYP and a basis set 6-31 G* to calculate the electronic and optical properties of molecules and clusters of silicon dioxide. With the theoretical calculation of the structural and optical properties of silicon dioxide clusters is possible to evaluate the contribution of silica in the luminescent emission mechanism experimentally found in thin SRO films. It was found that silica contribution to the luminescent phenomenon in SRO thin films is less important than that of the silicon monoxide agglomerates because the number of silica structures, which may show emission in the visible spectrum, is much lower [1], compared to the number of silicon monoxide structures which emit in this region. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3192