Optimal bounds for POD approximations of infinite horizon control problems based on time derivatives

In this paper we consider the numerical approximation of infinite horizon problems via the dynamic programming approach. The value function of the problem solves a Hamilton-Jacobi-Bellman (HJB) equation that is approximated by a fully discrete method. It is known that the numerical problem is difficult to handle by the so called curse of dimensionality. To mitigate this issue we apply a reduction of the order by means of a new proper orthogonal decomposition (POD) method based on time derivatives. We carry out the error analysis of the method using recently proved optimal bounds for the fully discrete approximations. Moreover, the use of snapshots based on time derivatives allow us to bound some terms of the error that could not be bounded in a standard POD approach. Some numerical experiments show the good performance of the method in practice

Septal thrombus formation after subcutaneous implantable cardioverter shock in a young female with dilated cardiomyopathy.

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Effects of Previous Land-Use on Plant Species Composition and Diversity in Mediterranean Forests

At some point in their history, most forests in the Mediterranean Basin have been subjected to intensive management or converted to agriculture land. Knowing how forest plant communities recovered after the abandonment of forest-management or agricultural practices (including livestock grazing) provides a basis for investigating how previous land management have affected plant species diversity and composition in forest ecosystems. Our study investigated the consequences of historical “land management” practices on present-day Mediterranean forests by comparing species assemblages and the diversity of (i) all plant species and (ii) each ecological group defined by species’ habitat preferences and successional status (i.e., early-, mid-, and late-successional species). We compared forest stands that differed both in land-use history and in successional stage. In addition, we evaluated the value of those stands for biodiversity conservation. The study revealed significant compositional differentiation among stands that was due to among-stand variations in the diversity (namely, species richness and evenness) of early-, intermediate-, and late-successional species. Historical land management has led to an increase in compositional divergences among forest stands and the loss of late-successional forest species

Plant β-diversity i in human-altered forest ecosystems: the importance of the structural, spatial, and topographical characteristics of stands in patterning plant species assemblages

An understanding of spatial patterns of plant species diversity and the factors that drive those patterns is critical for the development of appropriate biodiversity management in forest ecosystems. We studied the spatial organization of plants species in human- modified and managed oak forests (primarily, Quercus faginea) in the Central Pre- Pyrenees, Spain. To test whether plant community assemblages varied non-randomly across the spatial scales, we used multiplicative diversity partitioning based on a nested hierarchical design of three increasingly coarser spatial scales (transect, stand, region). To quantify the importance of the structural, spatial, and topographical characteristics of stands in patterning plant species assemblages and identify the determinants of plant diversity patterns, we used canonical ordination. We observed a high contribution of ˟-diversity to total -diversity and found ˟-diversity to be higher and ˞-diversity to be lower than expected by random distributions of individuals at different spatial scales. Results, however, partly depended on the weighting of rare and abundant species. Variables expressing the historical management intensities of the stand such as mean stand age, the abundance of the dominant tree species (Q. faginea), age structure of the stand, and stand size were the main factors that explained the compositional variation in plant communities. The results indicate that (1) the structural, spatial, and topographical characteristics of the forest stands have the greatest effect on diversity patterns, (2) forests in landscapes that have different land use histories are environmentally heterogeneous and, therefore, can experience high levels of compositional differentiation, even at local scales (e.g., within the same stand). Maintaining habitat heterogeneity at multiple spatial scales should be considered in the development of management plans for enhancing plant diversity and related functions in human-altered forest

The asymmetric temporal rhythms of anti-consumption

This research draws upon qualitative data to empirically examine a theorisation of the temporal dimensions of social practices, and how anti-consumption destabilises and is destabilised by five dimensions: duration, tempo, sequence, synchronisation, and periodicity. Our analytical facets highlight the emergence of what we term dissonant intervals, that is, temporal glitches that manifest in these temporal dimensions of social practices that are unsettled by anti-consumption. Where the social coordination of temporalities becomes challenging or even impossible due to the accrual of these dissonant intervals, this generates a micro-level asymmetric (that is, uneven, unsettled) socio-temporal rhythm in daily life. We contribute the novel concepts of dissonant interval and asymmetric socio-temporal rhythm to sociological research on the temporalities of social practices. The significance of these concepts lies in their expansion of existing temporality vocabularies and imaginaries, their generative potential for future research and their implications for the promotion of environmentally sustainable practices

The asymmetric temporal rhythms of anti-consumption

This research draws upon qualitative data to empirically examine a theorisation of the temporal dimensions of social practices, and how anti-consumption destabilises and is destabilised by five dimensions: duration, tempo, sequence, synchronisation, and periodicity. Our analytical facets highlight the emergence of what we term dissonant intervals, that is, temporal glitches that manifest in these temporal dimensions of social practices that are unsettled by anti-consumption. Where the social coordination of temporalities becomes challenging or even impossible due to the accrual of these dissonant intervals, this generates a micro-level asymmetric (that is, uneven, unsettled) socio-temporal rhythm in daily life. We contribute the novel concepts of dissonant interval and asymmetric socio-temporal rhythm to sociological research on the temporalities of social practices. The significance of these concepts lies in their expansion of existing temporality vocabularies and imaginaries, their generative potential for future research and their implications for the promotion of environmentally sustainable practices

Stressed interbank markets: evidence from the European financial and sovereign debt crisis

This paper documents stress in the unsecured overnight interbank market in the euro area over the course of the financial and sovereign debt crisis in Europe. We find that stress i) leads some banks to borrow in the market at rates that are higher than the rate of the marginal lending facility of the ECB, ii) leads to less cross-border transactions and contributes to the fragmentation of the euro area money market. A triple-difference estimate shows that the borrowing of banks in the periphery from banks in the core almost disappears in the second half of 2011. Domestic borrowing, however, replaces the loss of cross-border borrowing. Our findings document the severe malfunctioning of the market for liquidity caused by asymmetric information problems in crisis times. We exploit euro area payments data to construct a novel dataset of interbank lending and borrowing. We verify the validity of our approach using the post-trading structure MID, maintained at Banco de España. Based on our results, we conclude that MID is a very high quality source of Spanish interbank market data for research and policy purposes

Effect of positioning on the accuracy of decision making of association football top-class referees and assistant referees during competitive matches

The aim of this study was to examine the effect of positioning on the correctness of decision making of top-class referees and assistant referees during international games. Match analyses were carried out during the Fe´de´ration Internationale de Football Association (FIFA) Confederations Cup 2009 and 380 foul play incidents and 165 offside situations were examined. The error percentage for the referees when indicating the incidents averaged 14%. The lowest error percentage occurred in the central area of the field, where the collaboration of the assistant referee is limited, and was achieved when indicating the incidents from a distance of 11–15 m, whereas this percentage peaked (23%) in the last 15-min match period. The error rate for the assistant referees was 13%. Distance of the assistant referee to the offside line did not have an impact on the quality of the offside decision. The risk of making incorrect decisions was reduced when the assistant referees viewed the offside situations from an angle between 46 and 608. Incorrect offside decisions occurred twice as often in the second as in the first half of the games. Perceptual-cognitive training sessions specific to the requirements of the game should be implemented in the weekly schedule of football officials to reduce the overall error rate

Teorema de Hasse-Minkowski

Clasificación de las formas cuadráticas en el cuerpo de los racionales. Por lo tanto introducimos los números p-ádicos y la clasificación de las formas cuadráticas en dichos cuerpos también