2,145 research outputs found
Who leads Research Productivity Change? Guidelines for R&D policy makers
Relying on efficiency analysis we evaluate to what extent policy makers have been able to promote the establishment of consolidated and comprehensive research groups to contribute to the implementation of a successful innovation system for the Spanish food technology sector, oriented to the production of knowledge based on an application model. Using data envelopment analysis techniques and Malmquist productivity indices we find pervasive levels of inefficiency and a typology of different research strategies. Among these, in contrast to what has been assumed, established groups do not play the pre-eminent benchmarking role; rather, partially oriented, specialized and "shooting star" groups are the most common patterns. These results correspond with an infant innovation system, where the fostering of higher levels of efficiency and promotion of the desired research patterns are ongoing.Innovation Policy; Management; Productivity Change; Malmquist Index; Distance Function
Type I vacuum solutions with aligned Papapetrou fields: an intrinsic characterization
We show that Petrov type I vacuum solutions admitting a Killing vector whose
Papapetrou field is aligned with a principal bivector of the Weyl tensor are
the Kasner and Taub metrics, their counterpart with timelike orbits and their
associated windmill-like solutions, as well as the Petrov homogeneous vacuum
solution. We recover all these metrics by using an integration method based on
an invariant classification which allows us to characterize every solution. In
this way we obtain an intrinsic and explicit algorithm to identify them.Comment: 14 pages; v2: added new section, references and tabl
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Past and present potential distribution of the Iberian Abies species: A phytogeographic approach using pollen data and species distribution models
This is the accepted version of the following article: Alba-Sánchez, F., López-Sáez, J. A., Pando, B. B.-d., Linares, J. C., Nieto-Lugilde, D. and López-Merino, L. (2010), Past and present potential distribution of the Iberian Abies species: a phytogeographic approach using fossil pollen data and species distribution models. Diversity and Distributions, 16: 214–228, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/j.1472-4642.2010.00636.x/abstract.Aim - Quaternary palaeopalynological records collected throughout the Iberian Peninsula and species distribution models (SDMs) were integrated to gain a better understanding of the historical biogeography of the Iberian Abies species (i.e. Abies pinsapo and Abies alba). We hypothesize that SDMs and Abies palaeorecords are closely correlated, assuming a certain stasis in climatic and topographic ecological niche dimensions. In addition, the modelling results were used to assign the fossil records to A. alba or A. pinsapo, to identify environmental variables affecting their distribution, and to evaluate the ecological segregation between the two taxa.
Location - The Iberian Peninsula.
Methods - For the estimation of past Abies distributions, a hindcasting process was used. Abies pinsapo and A. alba were modelled individually, first calibrating the model for their current distributions in relation to the present climate, and then projecting it into the past—the last glacial maximum (LGM) and the Middle Holocene periods—in relation to palaeoclimate simulations. The resulting models were compared with Iberian-wide fossil pollen records to detect areas of overlap.
Results - The overlap observed between past Abies refugia—inferred from fossil pollen records—and the SDMs helped to construct the Quaternary distribution of the Iberian Abies species. SDMs yielded two well-differentiated potential distributions: A. pinsapo throughout the Baetic mountain Range and A. alba along the Pyrenees and Cantabrian Range. These results propose that the two taxa remained isolated throughout the Quaternary, indicating a significant geographical and ecological segregation. In addition, no significant differences were detected comparing the three projections (present-day, Mid-Holocene and LGM), suggesting a relative climate stasis in the refuge areas during the Quaternary.
Main conclusions - Our results confirm that SDM projections can provide a useful complement to palaeoecological studies, offering a less subjective and spatially explicit hypothesis concerning past geographic patterns of Iberian Abies species. The integration of ecological-niche characteristics from known occurrences of Abies species in conjunction with palaeoecological studies could constitute a suitable tool to define appropriate areas in which to focus proactive conservation strategies.The Andalusian Innovation,
Science, and Industry Regional Ministry and the National Plan of the Spanish Government
Conformational transitions of membrane-bound HIV-1 fusion peptide
AbstractThe human immunodeficiency virus type-1 (HIV-1) fusion peptide (FP) functions as a non-constitutive membrane anchor that translocates into membranes during envelope glycoprotein-induced fusion. Here, by means of infrared spectroscopy (IR) and of various bilayer-perturbation assays, we describe the peptide conformations that are accessible to its membrane-bound state and the transitions occurring between them. The peptide underwent a conformational transition from a predominantly α-helical structure to extended β-type strands by increasing peptide concentration in 1-palmitoyl-2-oleoylphosphatidylglycerol (POPG) vesicles. A comparable transition was observed at a fixed 1:100 peptide-to-lipid ratio when calcium was added to vesicles containing prebound α-helical peptide. Cation binding induced an increase in the amount of H-bonded carbonyls within the interfacial region of POPG. Calcium-promoted α→β conversion in membranes correlated with the closure of preformed lytic pores and took place in dispersed (nonaggregated) vesicles doped with poly(ethylene glycol)–lipid conjugates, showing that the conformational transition was independent of vesicle aggregation. We conclude that the target membrane conditions modulate the eventual structure adopted by the HIV-1 FP. Conformational polymorphism of the inserted peptide may contribute to the flexibility of the fusogenic complex during the fusion reaction cycle, and/or may be related to target membrane perturbation at the fusion locus
Regenerating the strength of thermally recycled glass fibres using hot sodium hydroxide
Results are presented from the ReCoVeR project on the regeneration of the strength of thermally conditioned glass fibres. Thermal recycling of end-of-life glass fibre reinforced composites or composite manufacturing waste delivers fibres with virtually no residual strength or value. Composites produced from such fibres also have extremely poor mechanical performance. Data is presented showing that a short hot sodium hydroxide solution treatment of such recycled fibres can more than triple their strength and restore their ability to act as an effective reinforcement in second life composite materials. The implications of these results for real materials reuse of recycled glass fibres as replacement for pristine reinforcement fibres are discussed
Regeneration of thermally recycled glass fibre for cost-effective composite recycling : increasing the strength of thermally conditioned glass fibres using cost effective recover treatments
The paper reports an extensive study on the regenerating performance of thermally treated glass fibres using two different chemically based treatments routes. The effectiveness of these two different treatments was investigated on strength recovery of glass fibres thermally treated with the conditions imitating composite recycling technology. The regenerated strength levels of these ReCoVeRed fibres must also be further protected and maintained by the use of standard fibre sizing technology similar to standard glass fibre products. Consequently, the effect on fibre strength of the combination of our ReCoVeR treatments with the standard silane coatings was also studied. Significant increase of fibre strength was obtained through the ReCoVeR and coatings treatments, achieving up to 200% increase in fibre strength in comparison with the glass fibre thermally treated
Mutual fund performance attribution and market timing using portfolio holdings
We propose a novel performance attribution model for equity fund portfolios. The model analyses investment decisions based on portfolio holdings and measures the value added from different sources of performance such as past return strategies, security selection, market timing and passive timing. The model was tested for a sample of mutual funds. Empirical results show that security selection is the main contributor to fund performance regardless of the sample period considered or the asset pricing model used. The evidence of timing ability is mixed with low significance. Nevertheless there are noticeable differences between the timing ability of the best and worst performing funds, especially in crisis periods. Analysing the relationship between mutual fund performance (and its different components) and fund characteristics, we find that top funds are significantly smaller and more concentrated than other funds. Finally, we also examine the persistence in the performance and in its components finding evidence of positive persistence in past return strategies and picking skills although this persistence is not shown in the overall performance
Spatio-temporal variability of bovine tuberculosis eradication in Spain (2006-2011)
A. Garcia-Saenz et al.In this study we analyzed the space–time variation of the risk of bovine tuberculosis (bTB) in cattle between 2006 and 2011. The results indicated that at country level, there were no significant temporal changes between years, but, at county level bTB evolution was more heterogeneous. In some counties, between some years, the prevalence and the incidence of the disease was higher as compared to the global rate in the rest of the counties of Spain. The analysis of potential risk factors indicated that both, a large number of movements from counties with high incidence (>1%), and presence of bullfighting cattle herds increased bTB risk. Red deer abundance, number of goats and number of mixed cattle-goat farms were not significantly associated with the prevalence/incidence of bTB.This research was supported by a Grant from the Ministerio de Ciencia e Innovación of Spain (AGL-2010-21098). PhD studies of Garcia-Saenz A, are funded by a FPI Grant from Ministerio de Ciencia e Innovación of Spain (BES-2011-043628) and PhD studies of Guta S., are funded by Agencia Española de Cooperación Internacional para el Desarrollo (AECID). Acevedo P., was supported by a Beatriu de Pinós fellowship funded by ‘Comissionat per a Universitats i Recerca del Departament d’Innovació, Universitats i Empresa’ of the Generalitat de Catalunya, and the COFUND Programme – Marie Curie Actions under 7th Framework Programme of the European Community. He is currently funded from the SFRH/BPD/90320/2012 post-doctoral Grant by Portuguese Fundação para a Ciência e a Tecnologia (FCT) and European Social Fund.Peer Reviewe
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