Dynamical evolution of unstable self-gravitating scalar solitons

Recently, static and spherically symmetric configurations of globally regular self-gravitating scalar solitons were found. These configurations are unstable with respect to radial linear perturbations. In this paper we study the dynamical evolution of such configurations and show that, depending on the sign of the initial perturbation, the solitons either collapse to a Schwarzschild black hole or else ``explode'' into an outward moving domain wall.Comment: 11 pages, 16 figures, submitted to Phys. Rev.

Generalized harmonic spatial coordinates and hyperbolic shift conditions

We propose a generalization of the condition for harmonic spatial coordinates analogous to the generalization of the harmonic time slices introduced by Bona et al., and closely related to dynamic shift conditions recently proposed by Lindblom and Scheel, and Bona and Palenzuela. These generalized harmonic spatial coordinates imply a condition for the shift vector that has the form of an evolution equation for the shift components. We find that in order to decouple the slicing condition from the evolution equation for the shift it is necessary to use a rescaled shift vector. The initial form of the generalized harmonic shift condition is not spatially covariant, but we propose a simple way to make it fully covariant so that it can be used in coordinate systems other than Cartesian. We also analyze the effect of the shift condition proposed here on the hyperbolicity of the evolution equations of general relativity in 1+1 dimensions and 3+1 spherical symmetry, and study the possible development of blow-ups. Finally, we perform a series of numerical experiments to illustrate the behavior of this shift condition.Comment: 18 pages and 12 figures, extensively revised version explaining in the new Section IV how the shift condition can be made 3-covarian

A quantitative analysis of cold water for human consumption in hospitals in Spain

An estimation of the water used for human consumption in hospitals is essential to determine possible savings and to fix criteria to improve the design of new water consumption models.The present work reports on cold water for human consumption (CWHC) in hospitals in Spain and determines the possible savings. In the period of 2005–2012, 80 Eco-Management and Audit Schemes (EMAS) from20 hospitals were analysed. The results conclude that the average annual consumption of CWHC is 1.59m3/m2 (with a standard deviation of 0.48 m3/m2), 195.85 m3/bed (standard deviation 70.07 m3/bed), or 53.69 m3/worker (standard deviation 16.64 m3/worker). The results demonstrate the possibility of saving 5,600,000m3 of water per year. Assuming the cost of water as approximately 1.22 €/m3, annual savings are estimated as 6,832,000 €. Furthermore, 2,912MWh of energy could be saved, and the emission of 22,400 annual tonnes of CO2 into the atmosphere could be avoided

VARGAS VILA, MÁS ALLÁ DE LA HIPÉRBOLE

Vargas Vila, más allá de la hipérbol

Corneal biomechanical properties in different ocular conditions and new measurement techniques

Several refractive and therapeutic treatments as well as several ocular or systemic diseases might induce changes in the mechanical resistance of the cornea. Furthermore, intraocular pressure measurement, one of the most used clinical tools, is also highly dependent on this characteristic. Corneal biomechanical properties can be measured now in the clinical setting with different instruments. In the present work, we review the potential role of the biomechanical properties of the cornea in different fields of ophthalmology and visual science in light of the definitions of the fundamental properties of matter and the results obtained from the different instruments available. The body of literature published so far provides an insight into how the corneal mechanical properties change in different sight-threatening ocular conditions and after different surgical procedures. The future in this field is very promising with several new technologies being applied to the analysis of the corneal biomechanical properties

A century of limnological evolution and interactive threats in the Panama Canal: Long-term assessments from a shallow basin

Large tropical river dam projects are expected to accelerate over the forthcoming decades to satisfy growing demand for energy, irrigation and flood control. When tropical rivers are dammed the immediate impacts are relatively well studied, but the long-term (decades-centuries) consequences of impoundment remain poorly known. We combined historical records of water quality, river flow and climate with a multi-proxy (macrofossils, diatoms, biomarkers and trace elements) palaeoecological approach to reconstruct the limnological evolution of a shallow basin in Gatun Lake (Panama Canal, Panama) and assess the effects of multiple linked factors (river damming, forest flooding, deforestation, invasive species, pollution and hydro-climate) on the study area. Results show that a century after dam construction, species invasion, deforestation and salt intrusions have forced a gradual change in the study basin from a swamp-type environment towards a more saline lake-governed system of benthic–littoral production likely associated with the expansion of macrophyte stands. Hydrology still remains the most important long-term (decades) structural factor stimulating salinity intrusions, primary productivity, deposition of minerals, and reduction of water transparency during wet periods. During dry periods, physical-chemical conditions are in turn linked to clear water and aerobic conditions while nutrients shift to available forms for the aquatic biota in the detrital-rich reductive sediments. Our study suggests that to preserve the natural riverine system functioning of this area of the Panama Canal, management activities must address long-term ecosystem structural drivers such as river flow, runoff patterns and physical-chemical conditions

Complexity of Instances for Combinatorial Optimization Problems

Non

Industry 4.0-based dynamic Social Organizational Life Cycle Assessment to target the social circular economy in manufacturing

Nowadays in manufacturing, the topic of sustainability plays a key role. However, over the years, economic crises and the climate change debate have focused the attention of scholars, industrialists and policy makers mainly on environmental sustainability, putting social sustainability on the back burner. This is also evident in the scientific literature which highlights several knowledge gaps. The digital transition of factories and Industry 4.0 technologies have not yet been fully exploited to correlate production and social metrics. As a result, there is a lack of adequate tools for monitoring social performance in the factory environment. In this context, the social dimension of the circular economy is still an under-researched topic. This study aims to fill these gaps by integrating Social Organizational Life Cycle Assessment (SO-LCA) and Industry 4.0 technologies in a blended methodological approach designed to dynamically monitor the social performance of a major manufacturing industry. Using primary data, a set of site-specific social indicators and indexes were created to assess the organization's social impact against key stakeholder categories and subcategories. Finally, within that set, those social metrics that the organization considers essential to moving toward the circular economy were identified. Therefore, this study, has contributed to fill the literature gaps by demonstrating that the digitization of production processes, not only enables the assessment of environmental impact, but can also play a key role in knowing the social performance of a manufacturing organization and to identify the hidden social dimension in the circular economy

Test Anxiety: Associations with personal and family variables

La ansiedad ante los exámenes es un comportamiento muy frecuente, sobre todo entre la población escolar que afronta una presión social muy centrada en la obtención de un gran éxito académico. Pocos estudios han analizado las relaciones entre la ansiedad ante los exámenes, la postergación académica (academic procrastination), variables personales y familiares y las notas en matemáticas. En este trabajo se analiza el impacto de variables sociopersonales tales como el nivel de estudios de la madre y del padre, el número de hermanos y el número de cursos suspensos utilizando ANOVAS en dos muestras independientes de 533 y 796 sujetos de los 3 primeros cursos de la Educación Secundaria Obligatoria. Los datos, similares en los dos estudios, revelan que la ansiedad ante los exámenes es superior en las chicas y disminuye con el aumento del nivel de estudios de la madre y del padre, del número de cursos suspensos y de las notas en matemáticas. La ansiedad ante los exámenes y la conducta de postergación se correlacionan positiva y significativamente. Los resultados son discutidos en función de los hallazgos de las investigaciones previas. Se analizan las implicaciones para la práctica educativa.Test anxiety is a common behavior among students facing social pressure centered on mastery. Only a few studies have analyzed the relations between test anxiety, academic procrastination, personal and family variables and math grades. This work focus on the analysis of the impact of students’ social-personal variables such as parents’ education level, number of siblings and under-achievement by performing ANOVAs in two samples of 533 and 796 students from junior high-school. Corroborating the findings in other studies, the data stress that test anxiety is higher in girls and decreases when students’ parents have higher educational levels, with the number of courses flunked, and when students’ math grades were lower. Test anxiety and procrastination correlate positive and significantly. Findings are discussed and compared with those of previous researches. The implications for teaching practice are also analyzed

Hyperbolicity of the Kidder-Scheel-Teukolsky formulation of Einstein's equations coupled to a modified Bona-Masso slicing condition

We show that the Kidder-Scheel-Teukolsky family of hyperbolic formulations of the 3+1 evolution equations of general relativity remains hyperbolic when coupled to a recently proposed modified version of the Bona-Masso slicing condition.Comment: 4 pages. Several changes. Main corrections are in eqs. 4.9 and 4.1