An accurate SVD algorithm for 2 by 2 triangular matrices

Using a fine accuracy analysis and the results from cite{har-mat-09}, a new accurate algorithm for computing the singular value decomposition of 2 by 2 triangular matrices is constructed. It is obtained by combining the new algorithm which is derived in cite{har-mat-09} and the algorithm which is coded as an xLASV2 computational routine of LAPACK. Relative error bounds for the output data of the hybrid algorithm are equal to or smaller than the same bounds for any of these two algorithms

An investigation on the skewness patterns and fractal nature of research productivity distributions at field and discipline level

The paper provides an empirical examination of how research productivity distributions differ across scientific fields and disciplines. Productivity is measured using the FSS indicator, which embeds both quantity and impact of output. The population studied consists of over 31,000 scientists in 180 fields (10 aggregate disciplines) of a national research system. The Characteristic Scores and Scale technique is used to investigate the distribution patterns for the different fields and disciplines. Research productivity distributions are found to be asymmetrical at the field level, although the degree of skewness varies substantially among the fields within the aggregate disciplines. We also examine whether the field productivity distributions show a fractal nature, which reveals an exception more than a rule. Differently, for the disciplines, the partitions of the distributions show skewed patterns that are highly similar

Diversity dynamics in Nymphalidae butterflies: Effect of phylogenetic uncertainty on diversification rate shift estimates

The family Nymphalidae is the largest family within the true butterflies and has been used to develop hypotheses explaining evolutionary interactions between plants and insects. Theories of insect and hostplant dynamics predict accelerated diversification in some scenarios. We investigated whether phylogenetic uncertainty affects a commonly used method (MEDUSA, modelling evolutionary diversity using stepwise AIC) for estimating shifts in diversification rates in lineages of the family Nymphalidae, by extending the method to run across a random sample of phylogenetic trees from the posterior distribution of a Bayesian run. We found that phylogenetic uncertainty greatly affects diversification rate estimates. Different trees from the posterior distribution can give diversification rates ranging from high values to almost zero for the same clade, and for some clades both significant rate increase and decrease were estimated. Only three out of 13 significant shifts found on the maximum credibility tree were consistent across more than 95% of the trees from the posterior: (i) accelerated diversification for Solanaceae feeders in the tribe Ithomiini; (ii) accelerated diversification in the genus Charaxes, and (iii) deceleration in the Danaina. By using the binary speciation and extinction model (BISSE), we found that a hostplant shift to Solanaceae or a codistributed character is responsible for the increase in diversification rate in Ithomiini, and the result is congruent with the diffuse cospeciation hypothesis. A shift to Apocynaceae is not responsible for the slowdown of diversification in Danaina. Our results show that taking phylogenetic uncertainty into account when estimating diversification rate shifts is of great importance, and relying on the maximum credibility tree alone potentially can give erroneous results.Comment: 23 pages, 7 figures, 2 tables and 12 supplementary material files. Both authors contributed equally to this wor

Methods and Models for Environmental Conflicts Analysis and Resolution

This thesis is a description of a particular approach to the analysis and resolution of environmental conflicts. Within this framework we have presented a certain number of models as well as a certain number of methods and procedures with an heavy descriptive value but also with some normative value. On the other hand, this thesis is not a general and exhaustive description of the methods for the analysis and resolution of environmental conflicts nor it contains a full and exhaustive analysis of the literature in this area. Moreover this thesis is not a collection of turnkey recipes that can be used to analyze and resolve a particular environmental problem. An outline of the thesis The present thesis is composed by seven chapters and three short appendices. The first chapter presents the general frameworks of the thesis, defines its motivations and aims, frames some basic concepts and describes both the adopted attitudes and the proposed narratives. The second chapter is devoted essentially to an analysis of the various types of actors and of their interrelations as well as to a presentation of the various perspectives that represent the families of models we discuss in chapters 5 and 6. In the third chapter we provide a detailed critical analysis of System Dynamics as a cognitive tool that acts as a background of the whole thesis though it is mentioned explicitly only in chapter 6. The fourth chapter contains a presentation of two family of protocols (auctions and barters) that we propose both as autonomous tools and as ancillary tools of other protocols. The fifth chapter contains the analysis of the ways through which a coalition of heterogeneous deciders may form in order to define a solution to a common problem. The chapter contains an iterative procedure made of two phases (a static setting phase and a dynamic setting phase) that can be executed repeatedly by the deciders until they reach a satisfactory solution. The sixth chapter contains a description of the procedures and methods through which two or more deciders can enter into competition among themselves on two or more competing projects in order to possibly select one of them and, lastly, share among themselves the costs and benefits associated to the selected project. In the seventh chapter we draw some conclusions, list some open problems and underline some topics worth of further research efforts. The appendices aim at making this thesis as self contained as possible and therefore they contain some of the concepts we refer to in the main chapters but that we preferred to put there so to avoid cluttering too much those chapters. For these reasons we put a brief analysis of some concepts of System Dynamics in Appendix A, a description of some concepts of Decision Theory in Appendix B and a small bunch of concepts of Game Theory in Appendix C

Do interdisciplinary research teams deliver higher gains to science?

The present paper takes its place in the stream of studies that analyze the effect of interdisciplinarity on the impact of research output. Unlike previous studies, in this study the interdisciplinarity of the publications is not inferred through their citing or cited references, but rather by identifying the authors' designated fields of research. For this we draw on the scientific classification of Italian academics, and their publications as indexed in the WoS over a five-year period (2004-2008). We divide the publications in three subsets on the basis the nature of co-authorship: those papers coauthored with academics from different fields, which show high intensity of inter-field collaboration ("specific" collaboration, occurring in 110 pairings of fields); those papers coauthored with academics who are simply from different "non-specific" fields; and finally co-authorships within a single field. We then compare the citations of the papers and the impact factor of the publishing journals between the three subsets. The results show significant differences, generally in favor of the interdisciplinary authorships, in only one third (or slightly more) of the cases. The analysis provides the value of the median differences for each pair of publication subsets