Coupled equations for Kähler metrics and Yang-Mills connections

We study equations on a principal bundle over a compact complex manifold coupling a connection on the bundle with a Kahler structure on the base. These equations generalize the conditions of constant scalar curvature for a Kahler metric and Hermite-Yang-Mills for a connection. We provide a moment map interpretation of the equations and study obstructions for the existence of solutions, generalizing the Futaki invariant, the Mabuchi K-energy and geodesic stability. We finish by giving some examples of solutions.Comment: 61 pages; v2: introduction partially rewritten; minor corrections and improvements in presentation, especially in Section 4; added references; v3: To appear in Geom. Topol. Minor corrections and improvements, following comments by referee

Spatial and temporal analysis of the seasonal and interannual variability in the tropical Pacific simulated with a coupled GCM

In the first part of this work, the dominant time scales that explain the tropical variability of the first SINTEX simulation (ECHAM4(T30)-ORCA) are identified through a spectral analysis. Higher order spectral analysis is used to examine the interactions among these time scales. The time series analyzed are an average of sea surface temperature over the Niño3 region. The time scales obtained are compared with those identified in another coupled GCM simulation (ECHAM4(T42)-OPYC3). The higher importance of the biannual time scale in this last is explained partly by the strength of the coupling between the annual and the biannual time scales. There is no such strong coupling in the SINTEX simulation. Important differences among the generation of the simulated warm (or cold) event suggest the need of a systematic classification to isolate their relevant features. Therefore in the second part of this work, we address this problem. A space-time cluster analysis is performed on a data set built by collecting the values of the heat content anomalies in the tropical Pacific region, in the fifteen months previous to a peak in the Niño3 Index that has been identified as a ‘warm’ (or ‘cold’) event. In the case of the warm events, three types of generation schemes are found. In two of them, there are anomalies of heat content in the west, north and south of the equator, more than nine months before the events start. In the third case, the anomalies appear and grow in the central equatorial Pacific. Only two types are needed to classify the generation of cold events. Negative sea level height anomalies appear six months before the Niño3 Index reaches the (local) minimum. They are located north of the equator in one of the groups, and south of it in the other. Some of these characteristic traits also appear in observations of warm and cold events

Storage requirements for PV power ramp-rate control

Short-term variability in the power generated by large grid-connected photovoltaic (PV) plants can negatively affect power quality and the network reliability. New grid-codes require combining the PV generator with some form of energy storage technology in order to reduce short-term PV power fluctuation. This paper proposes an effective method in order to calculate, for any PV plant size and maximum allowable ramp-rate, the maximum power and the minimum energy storage requirements alike. The general validity of this method is corroborated with extensive simulation exercises performed with real 5-s one year data of 500 kW inverters at the 38.5 MW Amaraleja (Portugal) PV plant and two other PV plants located in Navarra (Spain), at a distance of more than 660 km from Amaraleja

Burning in the management of heathlands of Erica ciliaris and Erica tetralix: effects on structure and diversity

Can controlled burning be used as a management tool of Erica ciliaris and Erica tetralix wet heathlands? Two E. ciliaris and E. tetralix communities were selected and two 5 x 5 m plots were established in each. These were then characterised on the basis of frequency and cover values and plant species composition. They were subjected to experimental burning, after which the plots were sampled twice a year during the following four and a half years. The results show that the cover of woody species very quickly attained the values of the Control Plots. Diversity and species composition did not suffer notable changes during this period, however, temporal heterogeneity indicates that the main changes occur in the first 18 months of secondary succession. The multivariate analysis showed that the samples registered during this time were grouped as a function of the cover values of the species, which shows that stages exist in the vegetation recovery of these communities. The damage produced by fire in the community is minor, as a rapid recovery of the vegetation was observed, so controlled burning is a useful tool in the management of these heathlands

Scale interactions in the tropical Atlanticvariability simulated with a coupled GCM

Warm and cold events in the Gulf of Guinea are an important feature in the interannual variability of the tropical Atlantic Ocean, and partly a manifestation of the equatorial Atlantic system's intrinsic variability. Due to the relatively reduced zonal extension of this ocean, the latter variability is comparatively weak and thus strongly modified by other factors at play, either local or remote, like the seasonal cycle or ENSO. We present here an analysis of the tropical Atlantic variability in a 100-year-long chunk of the output of a coupled GCM. Through it, we obtain a better understanding of this variability and of its interactions with the seasonal cycle and with the ENSO signal. Following hints in the observations, we separate warm or cold events of the simulation in a few types, according to their similarities and differences. This classification is carried out as a spatio-temporal cluster analysis of the values, from nine months before up to the peak of the event, of the heat content anomalies. This is an optimal variable to monitor the generation of the events. One of the warm event classes can be explained by ENSO interactions. One of the cold event types can be explained by this influence as well, while the seasonal interactions might explain the characteristics of another of them

Spatial and temporal analysis of the seasonal and interannual variability in the tropical Pacific simulated with a coupled GCM

In the first part of this work, the dominant time scales that explain the tropical variability of the first SINTEX simulation (ECHAM4(T30)-ORCA) are identified through a spectral analysis. Higher order spectral analysis is used to examine the interactions among these time scales. The time series analyzed are an average of sea surface temperature over the Niño3 region. The time scales obtained are compared with those identified in another coupled GCM simulation (ECHAM4(T42)-OPYC3). The higher importance of the biannual time scale in this last is explained partly by the strength of the coupling between the annual and the biannual time scales. There is no such strong coupling in the SINTEX simulation. Important differences among the generation of the simulated warm (or cold) event suggest the need of a systematic classification to isolate their relevant features. Therefore in the second part of this work, we address this problem. A space-time cluster analysis is performed on a data set built by collecting the values of the heat content anomalies in the tropical Pacific region, in the fifteen months previous to a peak in the Niño3 Index that has been identified as a ‘warm’ (or ‘cold’) event. In the case of the warm events, three types of generation schemes are found. In two of them, there are anomalies of heat content in the west, north and south of the equator, more than nine months before the events start. In the third case, the anomalies appear and grow in the central equatorial Pacific. Only two types are needed to classify the generation of cold events. Negative sea level height anomalies appear six months before the Niño3 Index reaches the (local) minimum. They are located north of the equator in one of the groups, and south of it in the other. Some of these characteristic traits also appear in observations of warm and cold events

Non-Abelian Vortices, Super-Yang-Mills Theory and Spin(7)-Instantons

We consider a complex vector bundle E endowed with a connection A over the eight-dimensional manifold R^2 x G/H, where G/H = SU(3)/U(1)xU(1) is a homogeneous space provided with a never integrable almost complex structure and a family of SU(3)-structures. We establish an equivalence between G-invariant solutions A of the Spin(7)-instanton equations on R^2 x G/H and general solutions of non-Abelian coupled vortex equations on R^2. These vortices are BPS solitons in a d=4 gauge theory obtained from N=1 supersymmetric Yang-Mills theory in ten dimensions compactified on the coset space G/H with an SU(3)-structure. The novelty of the obtained vortex equations lies in the fact that Higgs fields, defining morphisms of vector bundles over R^2, are not holomorphic in the generic case. Finally, we introduce BPS vortex equations in N=4 super Yang-Mills theory and show that they have the same feature.Comment: 14 pages; v2: typos fixed, published versio

Calibración de Microscopios Confocales

El microscopio confocal ha sido durante mucho tiempo un instrumento de observación tridimensional con múltiples aplicaciones especialmente dentro de la biología. Sin embargo en los últimos años ha comenzado a ser utilizado como instrumento de medida en diferentes áreas de la ingeniería. En la actualidad existen muchas especificaciones de productos (dimensionales, angulares, acabado superficial) en las escalas micrométricas y nanométricas que pueden o podrían ser verificadas utilizando este instrumento. Pero para que esta verificación sea válida dentro de un sistema de calidad el microscopio confocal debe ser trazable. Esta ponencia presenta una solución sencilla a este problema implementada en el Centro Láser de la Universidad Politécnica de Madrid (UPM) que ha permitido dotar de trazabilidad a las medidas dimensionales realizadas en el plano XY y en el eje Z de su microscopio confocal. The confocal microscope has been a three-dimensional observation instrument with multiple applications especially in biology. However in recent years has begun to be used as a measuring instrument contact in various engineering fields. At present there are many product specifications (size, angular, surface roughness) in the micrometer and nano scales that can or could be verified using this instrument. But this verification is only valid within a quality system if the confocal microscope is traceable. This paper presents a simple solution to this problem implemented in the Laser Centre of the Polytechnic University of Madrid (UPM). This solution provides traceablity to the size measurements made in the XY plane and the Z-axis

Leaders' sustainability competences and small and medium‐sized enterprises outcomes: the role of social entrepreneurial orientation

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe market for socially conscious products and services has grown exponentially in the last years. Consequently, adding social value is among the great challenges that companies have to face nowadays. In view of this, companies need leaders with a set of specific skills that prepares them to act and compete in this new environment. This is especially true for small and medium-sized enterprises (SMEs), which are even more dependent on their leaders' competences. The aim of this article is to analyse the influence of leaders' sustainability competences on the social entrepreneurial orientation of SMEs of the tourism sector, as well as the influence of this strategy on the firm's performance. The methodology used to validate the measurement scales is exploratory and confirmatory factor analysis and the structural equation modelling technique is applied to analyse the causal relationships proposed in the model. The results show that sustainability competences positively affect social entrepreneurial orientation; specifically, the social risk-taking and proactivity competence has a positive influence on the economic and social performance of SMEs, and in particular, on their green innovation performance. These results highlight the key role that leaders' competences have in SMEs' social orientation and thus, the importance of training in competences for sustainable development

Survival, dispersal and reproduction of headstarted Mona Island iguanas, Cyclura cornuta stejnegeri

The endemic Mona Island Iguana, Cyclura cornuta stejnegeri, is considered endangered, and exhibits relatively low population numbers and reduced recruitment of juveniles to adults. A headstarting program was initiated in 1999 to increase the effective population number. Two groups of headstarted iguanas were released in April and August 2002, after reaching a target size. Most of the released iguanas have since been observed to be active and in good health. Two females bred in 2004, the first certain record of reproduction by headstarted Cyclura iguanas in the wild. Eight radiotracked individuals had large dispersal ranges, with mean Minimum Convex Polygon (MCP) of 10.7 ha (range 2.6-22.2 ha) and mean distances covered of 288 m (range 471-6396 m).We discuss the future development of the headstarting program for Mona Island iguanas