Université catholique de Louvain

About: Université catholique de Louvain is a education organization based out in Louvain-la-Neuve, Belgium. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 25319 authors who have published 57360 publications receiving 2172080 citations. The organization is also known as: University of Louvain & UCLouvain.

An Analysis of the Greedy Algorithm for the Submodular Set Covering Problem

Abstract: We consider the problem: min $$\{ \mathop \Sigma \limits_{j \in s} f_j :z(S) = z(N),S \subseteqq N\} $$ wherez is a nondecreasing submodular set function on a finite setN. Whenz is integer-valued andz(O)=0, it is shown that the value of a greedy heuristic solution never exceeds the optimal value by more than a factor $$H(\mathop {\max }\limits_j z(\{ j\} ))$$ where $$H(d) = \sum\limits_{i = 1}^d {\frac{1}{i}} $$ . This generalises earlier results of Dobson and others on the applications of the greedy algorithm to the integer covering problem: min {fy: Ay ≧b, y e {0, 1}} wherea ij ,b i } ≧ 0 are integer, and also includes the problem of finding a minimum weight basis in a matroid.

The curse of dimensionality in data mining and time series prediction

Abstract: Modern data analysis tools have to work on high-dimensional data, whose components are not independently distributed. High-dimensional spaces show surprising, counter-intuitive geometrical properties that have a large influence on the performances of data analysis tools. Among these properties, the concentration of the norm phenomenon results in the fact that Euclidean norms and Gaussian kernels, both commonly used in models, become inappropriate in high-dimensional spaces. This papers presents alternative distance measures and kernels, together with geometrical methods to decrease the dimension of the space. The methodology is applied to a typical time series prediction example.

Aquaporins Constitute a Large and Highly Divergent Protein Family in Maize

Abstract: Aquaporins (AQPs) are an ancient family of channel proteins that transport water and neutral solutes through a pore and are found in all eukaryotes and most prokaryotes. A comparison of the amino acid sequences and phylogenetic analysis of 31 full-length cDNAs of maize (Zea mays) AQPs shows that they comprise four different groups of highly divergent proteins. We have classified them as plasma membrane intinsic proteins (PIPs), tonoplast intrinsic proteins, Nod26-like intrinsic proteins, and small and basic intrinsic proteins. Amino acid sequence identities vary from 16% to 100%, but all sequences share structural motifs and conserved amino acids necessary to stabilize the two loops that form the aqueous pore. Most divergent are the small and basic integral proteins in which the first of the two highly conserved Asn-Pro-Ala motifs of the pore is not conserved, but is represented by alanine-proline-threonine or alanine-proline-serine. We present a model of ZmPIP1-2 based on the three-dimensional structure of mammalian AQP1. Tabulation of the number of times that the AQP sequences are found in a collection of databases that comprises about 470,000 maize cDNAs indicates that a few of the maize AQPs are very highly expressed and many are not abundantly expressed. The phylogenetic analysis supports the interpretation that the divergence of PIPs through gene duplication occurred more recently than the divergence of the members of the other three subfamilies. This study opens the way to analyze the function of the proteins in Xenopus laevis oocytes, determine the tissue specific expression of the genes, recover insertion mutants, and determine the in planta function.

Intestinal permeability, gut-bacterial dysbiosis, and behavioral markers of alcohol-dependence severity

Abstract: Alcohol dependence has traditionally been considered a brain disorder. Alteration in the composition of the gut microbiota has recently been shown to be present in psychiatric disorders, which suggests the possibility of gut-to-brain interactions in the development of alcohol dependence. The aim of the present study was to explore whether changes in gut permeability are linked to gut-microbiota composition and activity in alcohol-dependent subjects. We also investigated whether gut dysfunction is associated with the psychological symptoms of alcohol dependence. Finally, we tested the reversibility of the biological and behavioral parameters after a short-term detoxification program. We found that some, but not all, alcohol-dependent subjects developed gut leakiness, which was associated with higher scores of depression, anxiety, and alcohol craving after 3 wk of abstinence, which may be important psychological factors of relapse. Moreover, subjects with increased gut permeability also had altered composition and activity of the gut microbiota. These results suggest the existence of a gut-brain axis in alcohol dependence, which implicates the gut microbiota as an actor in the gut barrier and in behavioral disorders. Thus, the gut microbiota seems to be a previously unidentified target in the management of alcohol dependence.

Selective attention to angry faces in clinical social phobia.

Abstract: This study investigated the time course of attentional responses to emotional facial expressions in a clinical sample with social phobia. With a visual probe task, photographs of angry, happy, and neutral faces were presented at 2 exposure durations: 500 and 1250 ms. At 500 ms, the social phobia group showed enhanced vigilance for angry faces, relative to happy and neutral faces, in comparison with normal controls. In the 1250-ms condition, there were no significant attentional biases in the social phobia group. Results are consistent with a bias in initial orienting to threat cues in social anxiety. Findings are discussed in relation to recent cognitive models of anxiety disorders.