Search results for "modelos"
showing 10 items of 199 documents
Geometric inequivalence of metric and Palatini formulations of General Relativity
2020
Projective invariance is a symmetry of the Palatini version of General Relativity which is not present in the metric formulation. The fact that the Riemann tensor changes nontrivially under projective transformations implies that, unlike in the usual metric approach, in the Palatini formulation this tensor is subject to a gauge freedom, which allows some ambiguities even in its scalar contractions. In this sense, we show that for the Schwarzschild solution there exists a projective gauge in which the (affine) Kretschmann scalar, K≡R R , can be set to vanish everywhere. This puts forward that the divergence of curvature scalars may, in some cases, be avoided by a gauge transformation of the …
Modelos de gestión en áreas comerciales urbanas: centros comerciales abiertos en España
2014
Los partenariados públicos-privados (PPP) en áreas comerciales urbanas son proyectos de cooperación entre la administración pública y los comerciantes locales que persiguen un mismo objetivo: la recuperación funcional y económica de una determinada área urbana. Desde su nacimiento en Norteamérica, los PPP han ido adaptándose a la estructura empresarial, cultural y política de su entorno regional. España, que adoptó este tipo de proyectos de PPP más recientemente, se encuentra en la actualidad en un momento decisivo para replantear la fórmula de gestión y financiación de sus proyectos ya consolidados.
A high dietary glycemic index increases total mortality in a Mediterranean population at high cardiovascular risk
2014
© 2014 Castro-Quezada et al. Objective: Different types of carbohydrates have diverse glycemic response, thus glycemic index (GI) and glycemic load (GL) are used to assess this variation. The impact of dietary GI and GL in all-cause mortality is unknown. The objective of this study was to estimate the association between dietary GI and GL and risk of all-cause mortality in the PREDIMED study. Material and Methods: The PREDIMED study is a randomized nutritional intervention trial for primary cardiovascular prevention based on community-dwelling men and women at high risk of cardiovascular disease. Dietary information was collected at baseline and yearly using a validated 137-item food freque…
Herramientas para la generación y evaluación ex-ante de modelos de negocio
2015
El trabajo de investigación recogido en esta Tesis construye sobre dos líneas de investigación que han recibido un notable impulso en los últimos años. Se trata de dos líneas enmarcadas en el extenso ámbito de la innovación empresarial, con especial aplicación al mundo de la iniciativa emprendedora. Se trata de: • la creación de oportunidades y mercados, como concepto que amplía el tradicional descubrimiento de oportunidades, y lo sustituye como origen de la iniciativa emprendedora (Alvarez and Barney, 2007; Dew et al., 2011), y • la innovación en modelos de negocio, como herramienta competitiva que amplía los espacios tradicionales de aplicación de la innovación al ámbito de la concepción …
Stellar structure models in modified theories of gravity: Lessons and challenges
2019
The understanding of stellar structure represents the crossroads of our theories of the nuclear force and the gravitational interaction under the most extreme conditions observably accessible. It provides a powerful probe of the strong field regime of General Relativity, and opens fruitful avenues for the exploration of new gravitational physics. The latter can be captured via modified theories of gravity, which modify the Einstein-Hilbert action of General Relativity and/or some of its principles. These theories typically change the stellar structure equations, thus having a large impact on the astrophysical properties of the corresponding stars and opening a new window to constrain these …
An infinite class of exact rotating black hole metrics of modified gravity
2022
We build an infinite class of exact axisymmetric solutions of a metric-affine gravity theory, namely, Eddington-inspired Born-Infeld gravity, coupled to an anisotropic fluid as a matter source. The solution-generating method employed is not unique of this theory but can be extended to other Ricci-Based Gravity theories (RBGs), a class of theories built out of contractions of the Ricci tensor with the metric. This method exploits a correspondence between the space of solutions of General Relativity and that of RBGs, and is independent of the symmetries of the problem. For the particular case in which the fluid is identified with non-linear electromagnetic fields we explicitly derive the corr…
New scalar compact objects in Ricci-based gravity theories
2019
Taking advantage of a previously developed method, which allows to map solutions of General Relativity into a broad family of theories of gravity based on the Ricci tensor (Ricci-based gravities), we find new exact analytical scalar field solutions by mapping the free-field static, spherically symmetric solution of General Relativity (GR) into quadratic $f(R)$ gravity and the Eddington-inspired Born-Infeld gravity. The obtained solutions have some distinctive feature below the would-be Schwarzschild radius of a configuration with the same mass, though in this case no horizon is present. The compact objects found include wormholes, compact balls, shells of energy with no interior, and a new …
A Contribution to the analysis of the first Spanish public-private partnership in primary and specialized maternity care: a social network analysis a…
2021
The La Ribera University Hospital (Alzira, Valencia) was the first experience of public-private partnership in the Spanish National Health System. In addition to the need to coordinate two levels of health care (primary/specialised), two models of human resource management (public/private) had to be coordinated. To illustrate this complexity, the group of midwives in the health area has been taken, analysing their relational patterns through the methodological approach of Social Network Analysis. In terms of results, out of a population of 31 midwives, those of the public model occupy peripheral positions and cooperate poorly, both internally and externally. However, those of the private mo…
Estimación mediante programación genética de los patrones del suelo humectantes para el riego por goteo
2012
Drip irrigation is considered as one of the most efficient irrigation systems. Knowledge of the soil wetted perimeter arising from infiltration of water from drippers is important in the design and management of efficient irrigation systems. To this aim, numerical models can represent a powerful tool to analyze the evolution of the wetting pattern during irrigation, in order to explore drip irrigation management strategies, to set up the duration of irrigation, and finally to optimize water use efficiency. This paper examines the potential of genetic programming (GP) in simulating wetting patterns of drip irrigation. First by considering 12 different soil textures of USDA–SCS soil texture t…
Predictors of short- and long-term adherence with a Mediterranean-type diet intervention: the PREDIMED randomized trial.
2016
Background: Dietary intervention success requires strong participant adherence, but very few studies have examined factors related to both short-term and long-term adherence. A better understanding of predictors of adherence is necessary to improve the design and execution of dietary intervention trials. This study was designed to identify participant characteristics at baseline and study features that predict short-term and long-term adherence with interventions promoting the Mediterranean-type diet (MedDiet) in the PREvencion con DIeta MEDiterranea (PREDIMED) randomized trial. Methods: Analyses included men and women living in Spain aged 55-80 at high risk for cardiovascular disease. Part…