Non Parametric Instrumental Regression

The focus of the paper is the nonparametric estimation of an instrumental regression function ϕ defined by conditional moment restrictions stemming from a structural econometric model: E [Y − ϕ (Z) | W] = 0, and involving endogenous variables Y and Z and instruments W . The function ϕ is the solution of an ill-posed inverse problem and we propose an estimation procedure based on Tikhonov regularization. The paper analyses identification and overidentification of this model and presents asymptotic properties of the estimated nonparametric instrumental regression function.

Nonparametric Instrumental Regression

The focus of the paper is the nonparametric estimation of an instrumental regression function P defined by conditional moment restrictions stemming from a structural econometric model : E[Y-P(Z)|W]=0 and involving endogenous variables Y and Z and instruments W. The function P is the solution of an ill-posed inverse problem and we propose an estimation procedure based on Tikhonov regularization. The paper analyses identification and overidentification of this model and presents asymptotic properties of the estimated nonparametric instrumental regression function.Nous nous intéressons à l'estimation non paramétrique d'une fonction de régression instrumentale P . Cette fonction est définie à l'aide de conditions de moment provenant d'un modèle économétrique structurel de la forme E[Y-P(Z)|W]=0 où les Y et Z sont des variables endogènes et les W des instruments. La fonction P est alors la solution d'un problème inverse mal posé, et nous proposons une procédure d'estimation utilisant la régularisation de Tikhonov. Le papier analyse l'identification et la suridentification du modèle et donne les propriétés asymptotiques de l'estimateur de la régression instrumentale non paramétrique

Editorial:Omics and Systems Approaches to Study the Biology and Applications of Lactic Acid Bacteria

Editorial on the Research Topic Omics and Systems Approaches to Study the Biology and Applications of Lactic Acid Bacteri

Non Parametric Instrumental Regression

The focus of the paper is the nonparametric estimation of an instrumental regression function ϕ defined by conditional moment restrictions stemming from a structural econometric model: E [Y − ϕ (Z) | W] = 0, and involving endogenous variables Y and Z and instruments W . The function ϕ is the solution of an ill-posed inverse problem and we propose an estimation procedure based on Tikhonov regularization. The paper analyses identification and overidentification of this model and presents asymptotic properties of the estimated nonparametric instrumental regression function

Design of formal specifications by normal logic programs : merging formal text and good comments

Projet CHLOEFormal specifications are a kind of art : they mixture formal text and informal comments in an unstructured manner. We present a method based on logic programming in which formal text and comments can be also formally related through proofs. The paper is focused on the description of the proofs system used in the design of such specifications. The specification language uses normal clauses (definite clauses with possibly negative literals in the body) for its formal part and is aimed at defining relations. The comments are expressed as logic formulas written with some of the specified relations and define some local properties that the relations must satify. They introduce some redundancy which helps to understand the specification. The proofs are partial and partly automatized. They are not aimed at complete validation of the specification, but rather at debuging it and improving the comments such that its understanding is facilitated. This approach is illustrated by the example of the design of draft standard Prolog on which this methodology is currently applied

Genomics of Streptococcus macedonicus: moving from pathogenicity to adaptation to the dairy environment

Background: Lactic acid bacteria (LAB constitute a significant group of microorganisms found in foods, but also contribute to human health. The Streptococcus bovis/ Streptococcus equinus complex within LAB includes members that have been implicated in human diseases, like endocarditis and colon cancer. Objectives: In this study we compared the three available genome sequences of Streptococcus macedonicus strains isolated from dairy products. Only one strain has its genome complete sequenced and previous analysis showed diminished pathogenic potential and adaptation to the milk environment. Here we present the in silico analysis of these strains, in order to better understand the S. macedonicus species. Methods: Chromosomal maps were constructed using DNA Plotter and whole genome sequence alignments were performed by progressiveMAUVE and Webact in order to visualize conserved genomic regions or chromosomal rearrangements. Genomic islands were identified and visualized by IslandViewer, potential bacteriocins were predicted by BAGEL3 and CRISPRs were analyzed by the tools available in the CRISPRcompar web-service. Conclusions: The analysis revealed that the strains have lost genes involved in the catabolism of complex plant carbohydrates, in the adhesion to the host’s cells and in haemolysis. On the other hand, an extra lactose operon and a proteolytic system characteristic of LAB were identified. Even though our whole genome analysis of S. macedonicus shows adaptation traits to the nutrient-rich dairy environment, analysis of additional S. macedonicus genomes, including non-dairy isolates, may be necessary to clarify its pathogenic potential

Characterization of the dairy Streptococcus thermophilus ACA-DC 29 strain through comparative genomics

Background: Although the Streptococcus genus includes mainly pathogenic species, Streptococcus thermophilus is a widely used dairy starter culture of great economic importance for the food industry. S. thermophilus has been adapted to milk probably through a degenerative evolution process that has led to the loss of typical streptococcal pathogenic traits. Objectives: The genome sequence of the yogurt isolate S. thermophilus ACA-DC 29 was analyzed for assessing the technological potential of this strain. Comparative genomics analysis was also performed between the genome of ACA-DC 29 and the existing complete genome sequences of S. thermophilus. Methods:The genome sequence of ACA-DC 29 was annotated using online annotation tools. Full chromosome alignments were calculated with Progressive Mauve. The pangenome, the core genome and the unique genes were predicted with the GView Server. The genomic islands, the CRISPRs and the antimicrobial peptides were predicted with IslandViewer, CRISPRcompar and BAGEL3, respectively. Conclusions:The analysis of the S. thermophilus ACA-DC 29 genome sequence revealed the absence of pathogenic features. Genes related to the adaptation to milk were identified. Full chromosome alignments showed a high degree of synteny among the different strains. The pangenome of the ten strains comprised of approximately 2,300 genes. Concerning the ACA-DC 29 strain, approximately 250 unique genes involved in various biological processes were also identified. Further analysis indicated that several of them may have been acquired through horizontal gene transfer. Five potential antimicrobial peptides and two CRISPR systems, which may confer resistance against phages, were also predicted