Community structure in mediterranean shallow lentic ecosystems: size-based vs. taxon-based approaches

The main environmental variables determining the community structure and the functioning of Mediterranean shallow lentic ecosystems are described. These ecosystems are characterized by the unpredictability of their water inputs and the high variability in their water level and physical and chemical composition. Variations in flooding, salinity, and water turnover are determinant in species composition and nutrient dynamics. Taxon-based and size-based approaches to the study of the community structure of aquatic organisms that colonise these ecosystems are also compared. The conventional taxonomic approach, based on the determination of species composition, has been used for the identification of patterns in species richness, distribution and temporal dynamics, and for ecological requirements of species and their potential use as ecological indicators. This taxonbased approach has been compared with a size-based approach, where individuals are classified by their size. Size-based approach gives complementary information about community structure and dynamics, especially when communities are dominated by a single species. The use of size diversity combined with species diversity is suggested for a more complete understanding of community structuring in this type of ecosystem. Detailed examples of two Mediterranean shallow lentic ecosystems, the salt marshes of the Empordà wetlands and the Espolla temporary karstic pond, which differ in hydrology and water origin, are used to discuss the suitability of these different approaches

Self-similar community structure in a network of human interactions

We propose a procedure for analyzing and characterizing complex networks. We apply this to the social network as constructed from email communications within a medium sized university with about 1700 employees. Email networks provide an accurate and nonintrusive description of the flow of information within human organizations. Our results reveal the self-organization of the network into a state where the distribution of community sizes is self-similar. This suggests that a universal mechanism, responsible for emergence of scaling in other self-organized complex systems, as, for instance, river networks, could also be the underlying driving force in the formation and evolution of social networks.

Political centralization and government accountability

This paper studies fiscal federalism when regions differ in voters' ability to monitor publicofficials. We develop a model of political agency in which rent-seeking politicians providepublic goods to win support from heterogeneously informed voters. In equilibrium, voterinformation increases government accountability but displays decreasing returns. Therefore,political centralization reduces aggregate rent extraction when voter information varies acrossregions. It increases welfare as long as the central government is required to provide publicgoods uniformly across regions. The need for uniformity implies an endogenous trade off between reducing rents through centralization and matching idiosyncratic preferences throughdecentralization. We find that a federal structure with overlapping levels of government canbe optimal only if regional differences in accountability are sufficiently large. The modelpredicts that less informed regions should reap greater benefits when the central governmentsets a uniform policy. Consistent with our theory, we present empirical evidence that lessinformed states enjoyed faster declines in pollution after the 1970 Clean Air Act centralizedenvironmental policy at the federal level.

XML-based information management environment for PE technologies

Printed electronics is an emerging concept in electronics manufacturing and it is in very early development stage. The technology is not stable, design kits are not developed, and flows and Computer Aided Design (CAD) tools are not fixed yet. The European project TDK4PE addresses all this issues and this PFC has been realized on this context. The goal is to develop an XML-based information system for the collection and management of information from the technology and cell libraries developed in TDK4PE. This system will ease the treatment of that information for a later generation of specific Design Kits (DK) and the corresponding documentation. This work proposes a web application to generate technology files and design kits in a formatted way; it also proposes a structure for them and a database implementation for storing the needed information. The application will allow its users to redefine the structure of those files, as well as export and import XML files, between other formats.

T-Coffee: a web server for the multiple sequence alignment of protein and RNA sequences using structural information and homology extension

This article introduces a new interface for T-Coffee, a consistency-based multiple sequence alignment program. This interface provides an easy and intuitive access to the most popular functionality of the package. These include the default T-Coffee mode for protein and nucleic acid sequences, the M-Coffee mode that allows combining the output of any other aligners, and template-based modes of T-Coffee that deliver high accuracy alignments while using structural or homology derived templates. These three available template modes are Expresso for the alignment of protein with a known 3D-Structure, R-Coffee to align RNA sequences with conserved secondary structures and PSI-Coffee to accurately align distantly related sequences using homology extension. The new server benefits from recent improvements of the T-Coffee algorithm and can align up to 150 sequences as long as 10 000 residues and is available from both http://www.tcoffee.org and its main mirror http://tcoffee.crg.cat.

Optimal capital structure: a trade-off model and its empirical testing

In the present research we have set forth a new, simple, Trade-Off model that would allow us to calculate how much debt and, by default, how much equity a company should have, using easily available information and calculating the cost of debt dynamically on the basis of the effect that the capital structure of the company has on the risk of bankruptcy; in an attempt to answer this question. The proposed model has been applied to the companies that make up the Dow Jones Industrial Average (DJIA) in 2007. We have used consolidated financial data from 1996 to 2006, published by Bloomberg. We have used simplex optimization method to find the debt level that maximizes firm value. Then, we compare the estimated debt with real debt of companies using statistical nonparametric Mann-Whitney. The results indicate that 63% of companies do not show a statistically significant difference between the real and the estimated debt.

Electron scattering in isotonic chains as a probe of the proton shell structure of unstable nuclei

Electron scattering on unstable nuclei is planned in future facilities of the GSI and RIKEN upgrades. Motivated by this fact, we study theoretical predictions for elastic electron scattering in the N=82, N=50, and N=14 isotonic chains from very proton-deficient to very proton-rich isotones. We compute the scattering observables by performing Dirac partial-wave calculations. The charge density of the nucleus is obtained with a covariant nuclear mean-field model that accounts for the low-energy electromagnetic structure of the nucleon. For the discussion of the dependence of scattering observables at low-momentum transfer on the gross properties of the charge density, we fit Helm model distributions to the self-consistent mean-field densities. We find that the changes shown by the electric charge form factor along each isotonic chain are strongly correlated with the underlying proton shell structure of the isotones. We conclude that elastic electron scattering experiments on isotones can provide valuable information about the filling order and occupation of the single-particle levels of protons.