Polytechnic University of Catalonia

About: Polytechnic University of Catalonia is a education organization based out in Barcelona, Spain. It is known for research contribution in the topics: Finite element method & Population. The organization has 16006 authors who have published 45325 publications receiving 949306 citations. The organization is also known as: UPC - BarcelonaTECH & Technical University of Catalonia.

Asymptotic enumeration and limit laws of planar graphs

Abstract: A graph is planar if it can be embedded in the plane, or in the sphere, so that no two edges cross at an interior point A planar graph together with a particular embedding is called a map There is a rich theory of counting maps, started by Tutte in the 1960's However, in this paper we are interested in counting graphs as combinatorial objects, regardless of how many nonequivalent topological embeddings they may have As we are going to see, this makes the counting considerably more difficult

Relaxation dynamics of fluid membranes.

Abstract: We study the effect of membrane viscosity in the dynamics of liquid membranes-possibly with free or internal boundaries-driven by conservative forces (curvature elasticity and line tension) and dragged by the bulk dissipation of the ambient fluid and the friction occurring when the amphiphilic molecules move relative to each other. To this end, we formulate a continuum model which includes a form of the governing equations for a two-dimensional viscous fluid moving on a curved, time-evolving surface. The effect of membrane viscosity has received very limited attention in previous continuum studies of the dynamics of fluid membranes, although recent coarse-grained discrete simulations suggest its importance. By applying our model to the study of vesiculation and membrane fusion in a simplified geometry, we conclude that membrane viscosity plays a dominant role in the relaxation dynamics of fluid membranes of sizes comparable to those found in eukaryotic cells, and is not negligible in many large synthetic systems of current interest.

Balances: a New Perspective for Microbiome Analysis.

Abstract: High-throughput sequencing technologies have revolutionized microbiome research by allowing the relative quantification of microbiome composition and function in different environments. In this work we focus on the identification of microbial signatures, groups of microbial taxa that are predictive of a phenotype of interest. We do this by acknowledging the compositional nature of the microbiome and the fact that it carries relative information. Thus, instead of defining a microbial signature as a linear combination in real space corresponding to the abundances of a group of taxa, we consider microbial signatures given by the geometric means of data from two groups of taxa whose relative abundances, or balance, are associated with the response variable of interest. In this work we present selbal, a greedy stepwise algorithm for selection of balances or microbial signatures that preserves the principles of compositional data analysis. We illustrate the algorithm with 16S rRNA abundance data from a Crohn's microbiome study and an HIV microbiome study. IMPORTANCE We propose a new algorithm for the identification of microbial signatures. These microbial signatures can be used for diagnosis, prognosis, or prediction of therapeutic response based on an individual's specific microbiota.

DiP: A Parallel Program Development Environment

Abstract: This paper describes an environment whose aim is to aid in the development and tuning of message passing applications before actually running them in a real system with a large number of processors. Our objective is not to eliminate tests on real machines but to be able to focus them in a more selective way and thereby minimize their number. The environment presented in this paper consists of three closely integrated tools: an instrumented communication library, a trace driven simulator (Dimemas) and a visualization/analysis tool (Paraver).

Measuring DEA efficiency in internet companies

Abstract: This paper uses Data Envelopment Analysis (DEA), a non-parametric approach to the estimation of production functions, in order to assess efficiency in dot corn firms. These firms have two objectives: to make an impact in the Internet and to obtain revenues from their activities. For this reason, the outputs have been two: unique visitors--a web metric--and revenues. DEA efficiencies have been obtained under various input/output combinations. A ranking of dot com firms in terms of relative efficiency has been obtained. A method based on multivariate analysis has been proven to be successful at showing the strengths and weaknesses of individual dot com firms. It is shown that there is a relationship between the type of e-business (e-tailers, search/portal, content/communities), and the way in which efficiency is obtained. The paper suggests a new approach to the problem of deciding which inputs and outputs the model should contain.