Of beta diversity, variance, evenness, and dissimilarity

The amount of variation in species composition among sampling units or beta diversity has become a primary tool for connecting the spatial structure of species assemblages to ecological processes. Many different measures of beta diversity have been developed. Among them, the total variance in the community composition matrix has been proposed as a single-number estimate of beta diversity. In this study, I first show that this measure summarizes the compositional variation among sampling units after nonlinear transformation of species abundances. Therefore, it is not always adequate for estimating beta diversity. Next, I propose an alternative approach for calculating beta diversity in which variance is substituted by a weighted measure of concentration (i.e., an inverse measure of evenness). The relationship between this new measure of beta diversity and so-called multiple-site dissimilarity measures is also discussed

The Doctor-Patient Relationship, Its Place in Modern Medicine -- A Dilemma

A medical student views the dilemmafaced in rendering modern, efficient medical services while striving to maintain the recognition and observance of the fact of each patient as individual

TRADE IN INTERMEDIATE GOODS IN ITALIAN MANUFACTURING INDUSTRIES

Due to the emergence of global value chains, trade has increased in intermediates goods. The first objective of the paper is to provide a picture of Italian intermediate imports by industry and over time. Moreover, this paper attempts to study three possible factors than can influence the import of intermediate goods - global sourcing, outsourcing and MNE networks - using pooled cross-section data for the period 1985-2004 for Italian industries. The econometric results point to a different relationship for high and medium-high technology industries and medium-low and low technology industries relative to the role of inward and outward FDI in explaining the imported intermediate demand. The results suggest that outsourcing is important in explaining intermediate imports for medium-low and low technology industries. On the contrary, for high and medium-high technology industries the data give support to the global-sourcing hypothesis while the evidence for the MNE network hypothesis is weak.Input-Output tables, Intermediate imports, Multinational firms

Statistics for low-lying zeros of symmetric power L-functions in the level aspect

We study one-level and two-level densities for low lying zeros of symmetric power L-functions in the level aspect. It allows us to completely determine the symmetry types of some families of symmetric power L-functions with prescribed sign of functional equation. We also compute the moments of one-level density and exhibit mock-Gaussian behavior discovered by Hughes & Rudnick.Comment: 45 page

The second moment of Dirichlet twists of Hecke LL-functions

Fix a Hecke cusp form $f$, and consider the $L$-function of $f$ twisted by a primitive Dirichlet character. As we range over all primitive characters of a large modulus $q$, what is the average behavior of the square of the central value of this $L$-function? Stefanicki proved an asymptotic valid only for $q$ having very few prime factors, and we extend this to almost all $q$.Comment: 9 page

A generalized framework for analyzing taxonomic, phylogenetic, and functional community structure based on presence-absence data

Community structure as summarized by presence–absence data is often evaluated via diversity measures by incorporating taxonomic, phylogenetic and functional information on the constituting species. Most commonly, various dissimilarity coefficients are used to express these aspects simultaneously such that the results are not comparable due to the lack of common conceptual basis behind index definitions. A new framework is needed which allows such comparisons, thus facilitating evaluation of the importance of the three sources of extra information in relation to conventional species-based representations. We define taxonomic, phylogenetic and functional beta diversity of species assemblages based on the generalized Jaccard dissimilarity index. This coefficient does not give equal weight to species, because traditional site dissimilarities are lowered by taking into account the taxonomic, phylogenetic or functional similarity of differential species in one site to the species in the other. These, together with the traditional, taxon- (species-) based beta diversity are decomposed into two additive fractions, one due to taxonomic, phylogenetic or functional excess and the other to replacement. In addition to numerical results, taxonomic, phylogenetic and functional community structure is visualized by 2D simplex or ternary plots. Redundancy with respect to taxon-based structure is expressed in terms of centroid distances between point clouds in these diagrams. The approach is illustrated by examples coming from vegetation surveys representing different ecological conditions. We found that beta diversity decreases in the following order: taxon-based, taxonomic (Linnaean), phylogenetic and functional. Therefore, we put forward the beta-redundancy hypothesis suggesting that this ordering may be most often the case in ecological communities, and discuss potential reasons and possible exceptions to this supposed rule. Whereas the pattern of change in diversity may be indicative of fundamental features of the particular community being studied, the effect of the choice of functional traits—a more or less subjective element of the framework—remains to be investigated