Vertical segregation among pathways mediating nitrogen loss (N2 and N2O production) across the oxygen gradient in a coastal upwelling ecosystem

Indexación: ScopusThe upwelling system off central Chile (36.5 S) is seasonally subjected to oxygen (O2)-deficient waters, with a strong vertical gradient in O2 (from oxic to anoxic conditions) that spans a few metres (30-50€m interval) over the shelf. This condition inhibits and/or stimulates processes involved in nitrogen (N) removal (e.g. anammox, denitrification, and nitrification). During austral spring (September 2013) and summer (January 2014), the main pathways involved in N loss and its speciation, in the form of N2 and/or N2O, were studied using 15N-tracer incubations, inhibitor assays, and the natural abundance of nitrate isotopes along with hydrographic information. Incubations were developed using water retrieved from the oxycline (25€m depth) and bottom waters (85€m depth) over the continental shelf off Concepción, Chile. Results of 15N-labelled incubations revealed higher N removal activity during the austral summer, with denitrification as the dominant N2-producing pathway, which occurred together with anammox at all times. Interestingly, in both spring and summer maximum potential N removal rates were observed in the oxycline, where a greater availability of oxygen was observed (maximum O2 fluctuation between 270 and 40€μmol€L'1) relative to the hypoxic bottom waters ( < €20€μmol€O2€L'1). Different pathways were responsible for N2O produced in the oxycline and bottom waters, with ammonium oxidation and dissimilatory nitrite reduction, respectively, as the main source processes. Ammonium produced by dissimilatory nitrite reduction to ammonium (DNiRA) could sustain both anammox and nitrification rates, including the ammonium utilized for N2O production. The temporal and vertical variability of /15N-NO3' confirms that multiple N-cycling processes are modulating the isotopic nitrate composition over the shelf off central Chile during spring and summer. N removal processes in this coastal system appear to be related to the availability and distribution of oxygen and particles, which are a source of organic matter and the fuel for the production of other electron donors (i.e. ammonium) and acceptors (i.e. nitrate and nitrite) after its remineralization. These results highlight the links between several pathways involved in N loss. They also establish that different mechanisms supported by alternative N substrates are responsible for substantial accumulation of N2O, which are frequently observed as hotspots in the oxycline and bottom waters. Considering the extreme variation in oxygen observed in several coastal upwelling systems, these findings could help to understand the ecological and biogeochemical implications due to global warming where intensification and/or expansion of the oceanic OMZs is projected.https://www.biogeosciences.net/14/4795/2017

Bifurcation behavior of a superlattice model

We present a complete description of the stationary and dynamical behavior of semiconductor superlattices in the framework of a discrete drift model by means of numerical continuation, singular perturbation analysis, and bifurcation techniques. The control parameters are the applied DC voltage (φ) and the doping (ν) in nondimensional units. We show that the organizing centers for the long time dynamics are Takens–Bogdanov bifurcation points in a broad range of parameters and we cast our results in a φ-ν phase diagram. For small values of the doping, the system has only one uniform solution where all the variables are almost equal. For high doping we find multistability corresponding to domain solutions and the stationary solutions may exhibit chaotic spatial behavior. In the intermediate regime of ν the solution can be time-periodic depending on the bias. The oscillatory regions are related to the appearance and disappearance of Hopf bifurcation tongues which can be sub- or supercritical. These results are in good agreement with most of the experimental observations and also predict new interesting dynamical behavior.Junta de Andalucía PB97-008

Novel types of anti-ecloud surfaces

In high power RF devices for space, secondary electron emission appears as the main parameter governing the multipactor effect and as well as the e-cloud in large accelerators. Critical experimental activities included development of coatings with low secondary electron emission yield (SEY) for steel (large accelerators) and aluminium (space applications). Coatings with surface roughness of high aspect ratio producing the so-call secondary emission suppression effect appear as the selected strategy. In this work a detailed study of the SEY of these technological coatings and also the experimental deposition methods (PVD and electrochemical) are presented. The coating-design approach selected for new low SEY coatings include rough metals (Ag, Au, Al), rough alloys (NEG), particulated and magnetized surfaces, and also graphene like coatings. It was found that surface roughness also mitigate the SEY deterioration due to aging processes.Comment: 4 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Italy; CERN Yellow Report CERN-2013-002, pp.153-15

A vision-based monitoring system for very early automatic detection of forest fires

Trabajo presentado a la "I International Conference on Modelling, Monitoring and Management of Forest Fires" celebrada en Toledo del 17 al 19 de Septiembre de 2008.International Conference on Modelling, Monitoring and Management of Forest Fires I This paper describes a system capable of detecting smoke at the very beginning of a forest fire with a precise spatial resolution. The system is based on a wireless vision sensor network. Each sensor monitors a small area of vegetation by running on-site a tailored vision algorithm to detect the presence of smoke. This algorithm examines chromaticity changes and spatio-temporal patterns in the scene that are characteristic of the smoke dynamics at early stages of propagation. Processing takes place at the sensor nodes and, if that is the case, an alarm signal is transmitted through the network along with a reference to the location of the triggered zone - without requiring complex GIS systems. This method improves the spatial resolution on the surveilled area and reduces the rate of false alarms. An energy efficient implementation of the sensor/processor devices is crucial as it determines the autonomy of the network nodes. At this point, we have developed an ad hoc vision algorithm, adapted to the nature of the problem, to be integrated into a single-chip sensor/processor. As a first step to validate the feasibility of the system, we applied the algorithm to smoke sequences recorded with commercial cameras at real-world scenarios that simulate the working conditions of the network nodes. The results obtained point to a very high reliability and robustness in the detection process.This work is funded by Junta de Andalucía (CICE) through project 2006-TIC-2352.Peer Reviewe

Methodological issues in the measurement of alcohol consumption: The importance of drinking patterns

Medir correctamente el consumo de alcohol es fundamental para investigar de forma fiable sus efectos en salud. Sin embargo, ésta estimación resulta enormemente compleja, tanto por la diversidad de formas de consumo de alcohol existente como por la gran heterogeneidad en su clasificación. Además, cada patrón de consumo de alcohol puede asociarse a efectos muy diferente sobre la salud, por lo que no tenerlos en consideración cuando estimamos la ingesta de alcohol puede ocultar o confundir su importancia en estos efectos. Todo ello dificulta las comparaciones entre estudios y el establecimiento de asociaciones consistentes que permitan comprender los verdaderos efectos del consumo de alcohol, tanto globales como específicos de cada patrón de bebida. Este trabajo revisa los principales métodos y fuentes de información disponibles en España para estimar los aspectos más relevantes del consumo de alcohol, así como las dificultades y problemas metodológicos más frecuentes en la medición y clasificación de cada uno de estos indicadoresMeasurement of alcohol consumption is essential for proper investigation of its effects on health. However, its estimation is extremely complex, because of the diversity of forms of alcohol consumption and their highly heterogeneous classification. Moreover, each form may have different effects on health; therefore, not considering the most important drinking patterns when estimating alcohol in take could mask the important role of consumption patterns in these effects. All these issues make it very difficult to compare the results of different studies and to establish consistent associations for understanding the true effects of alcohol consumption, both overall and specific to each drinking pattern. This article reviews the main methods and sources of information available in Spain for estimating the most important aspects of alcohol consumption, as well as the most frequent methodological problems encountered in the measurement and classification of drinking patterns.Este estudio se realizó en el marco del Grupo de Trabajo sobre Alcohol de la Sociedad Española de Epidemiología con la ayuda económica del Plan Nacional sobre Drogas que ha contribuido a su funcionamiento (órdenes SSI 2800/2012 y 131/2013

¿Para qué acumulas? Gestionar los recursos no utilizados ante una recesión económica generalizada

Research to date has shown that a company can accumulate slack resources for a variety of reasons. But how do managers use this excess of resources in a general economic crisis? This study aims to ascertain how companies apply these resources when faced with a financial crisis and economic meltdown, in order to provide answers to the underexplored questions regarding the ways in which firms consume their slack resources. Through the analysis of a sample of 449 Spanish industrial companies during the 2006-2017period, and the application of Latent Growth Modelling, the evolution of the different slack and performance indicators is observed for the identification of disparate behaviour between companies with high and lowinitial endowments of slack resources. The results also show that each type of slack serves a differentpurpose and, therefore, their consumption or use shows clear divergences.Las investigaciones realizadas hasta la fecha han demostrado que una empresa puede acumular un exceso de recursos por diversas razones. Pero, ¿cómo utilizan los directivos este exceso de recursos en una crisis económica generalizada? Este estudio pretende averiguar cómo aplican las empresas estos recursos cuando se enfrentan a una crisis financiera y a un colapso económico, con el fin de dar respuesta a las cuestiones poco exploradas sobre las formas en que las empresas consumen sus recursos holgados. Mediante el análisis de una muestra de 449 empresas industriales españolas durante el periodo 2006-2017, y la aplicación de la Modelización Latente del Crecimiento, se observa la evolución de los distintos indicadores de holgura y rendimiento para la identificación de comportamientos dispares entre empresas con altas y bajas dotaciones iniciales de recursos de holgura. Los resultados también muestran que cada tipo de holgura sirve a un propósito diferente y, por tanto, su consumo o utilización muestra claras divergencias

Con qué evalúan los estudiantes de Magisterio en formación

Presentamos en este trabajo los instrumentos de evaluación propuestos por estudiantes de 2º curso del Grado de Educación Primaria mientras cursaban la asignatura de Didáctica de las Ciencias Experimentales en la Universidad de Sevilla. El desarrollo del curso se ha realizado a partir de una propuesta de enseñanza de las ciencias por investigación escolar, diseñada en el seno de un Proyecto de I+D+i1. A partir del análisis del contenido de las tres propuestas de enseñanza que los estudiantes elaboran a lo largo del curso, resulta: 1) un replanteamiento de la propuesta inicial. 2) diversificación de instrumentos. 3) escaso uso de instrumentos de evaluación para favorecer la autonomía del estudiante.Ministerio de Ciencia e Innovación EDU2011-2355