Effets de voisinage et localisation : la ségrégation urbaine est-elle inéluctable ?

URL des Documents de travail : http://centredeconomiesorbonne.univ-paris1.fr/documents-de-travail-du-ces/Documents de travail du Centre d'Economie de la Sorbonne 2008.72 - ISSN : 1955-611XIn this paper, we provide a theoretical framework for exploring the consequences of neighborhood informational effects - identified as role models - so as to deduce the urban configuration. With this aim, we have developed an overlapping generations model of community formation. When young, an individual must choose whether to invest in education or not. The crucial feature of our framework is that children assess the economic pay-off of education by observing the experience of the older generation residing in their neighborhood. When an adult, an individual who cares about her offspring's income must choose the family's location. We show that there exist two urban configurations. (i) An integrated city may occur where the socio-economic composition of each neighborhood makes its inhabitants well informed and therefore willing to invest in education. (ii) A segregated city may emerge where socio-economic segregation makes the inhabitants of poor communities be misinformed about the benefits of education.Cet article développe un modèle théorique d'économie urbaine qui étudie les conséquences d'effets de voisinage informationnels sur l'organisation de la ville. Il s'agit, en particulier, d'examiner l'impact de tels effets de voisinage sur le processus de ségrégation urbaine. Pour ce faire, nous développons un modèle à générations imbriquées avec choix individuel d'éducation et de localisation. Lorsqu'il est jeune, un individu décide de son effort d'éducation. L'hypothèse centrale est de dire que les jeunes évaluent les rendements de l'investissement scolaire en observant les résultats obtenus par la génération précédente du quartier. Lorsqu'il atteint l'âge adulte, un individu doit décider du lieu de résidence de la famille. A la différence des résultats obtenus dans la littérature, nous montrons que, sous certaines conditions, deux types de ville existent et sont stables. (i) Une ville intégrée peut émerger dans laquelle les quartiers sont composés d'une population hétérogène et présentent les mêmes incitations à l'éducation. (ii) Une ville ségrégée est possible qui comporte un ghetto de pauvres avec une mauvaise information sur l'intérêt de l'éducation et un taux d'éducation faible. Enfin, il n'y a pas unanimité parmi les individus pour préférer l'un des deux équilibres

Effets de voisinage et localisation : la ségrégation urbaine est-elle inéluctable ?

Cet article développe un modèle théorique d'économie urbaine qui étudie les conséquences d'effets de voisinage informationnels sur l'organisation de la ville. Il s'agit, en particulier, d'examiner l'impact de tels effets de voisinage sur le processus de ségrégation urbaine. Pour ce faire, nous développons un modèle à générations imbriquées avec choix individuel d'éducation et de localisation. Lorsqu'il est jeune, un individu décide de son effort d'éducation. L'hypothèse centrale est de dire que les jeunes évaluent les rendements de l'investissement scolaire en observant les résultats obtenus par la génération précédente du quartier. Lorsqu'il atteint l'âge adulte, un individu doit décider du lieu de résidence de la famille. A la différence des résultats obtenus dans la littérature, nous montrons que, sous certaines conditions, deux types de ville existent et sont stables. (i) Une ville intégrée peut émerger dans laquelle les quartiers sont composés d'une population hétérogène et présentent les mêmes incitations à l'éducation. (ii) Une ville ségrégée est possible qui comporte un ghetto de pauvres avec une mauvaise information sur l'intérêt de l'éducation et un taux d'éducation faible. Enfin, il n'y a pas unanimité parmi les individus pour préférer l'un des deux équilibres.Croyances, effets informationnels, inégalités, segmentation sociale.

High resolution, on-line identification of strains from the Mycobacterium tuberculosis complex based on tandem repeat typing

BACKGROUND: Currently available reference methods for the molecular epidemiology of the Mycobacterium tuberculosis complex either lack sensitivity or are still too tedious and slow for routine application. Recently, tandem repeat typing has emerged as a potential alternative. This report contributes to the development of tandem repeat typing for M. tuberculosis by summarising the existing data, developing additional markers, and setting up a freely accessible, fast, and easy to use, internet-based service for strain identification. RESULTS: A collection of 21 VNTRs incorporating 13 previously described loci and 8 newly evaluated markers was used to genotype 90 strains from the M. tuberculosis complex (M. tuberculosis (64 strains), M. bovis (9 strains including 4 BCG representatives), M. africanum (17 strains)). Eighty-four different genotypes are defined. Clustering analysis shows that the M. africanum strains fall into three main groups, one of which is closer to the M. tuberculosis strains, and an other one is closer to the M. bovis strains. The resulting data has been made freely accessible over the internet to allow direct strain identification queries. CONCLUSIONS: Tandem-repeat typing is a PCR-based assay which may prove to be a powerful complement to the existing epidemiological tools for the M. tuberculosis complex. The number of markers to type depends on the identification precision which is required, so that identification can be achieved quickly at low cost in terms of consumables, technical expertise and equipment

Time scales of regional circulation of saline fluids in continental aquifers (Armorican massif, Western France)

International audienceIn recent decades, saline fluids have been sampled worldwide at great depths in continental basements. Although some of them have been attributed to marine transgressions the mechanisms allowing their circulation is not understood. In this paper, we describe the horizontal and vertical distribution of moderately saline fluids (60 to 1400 mg L−1) sampled at depths ranging from 41 to 200 m in aquifers at the regional scale of the Armorican Massif (northwestern France). The horizontal and vertical distributions of high chloride concentrations are in good agreement with both the altitudinal and vertical limits and succession of the three major transgressions between the Mio-Pliocene and Pleistocene ages. The mean chloride concentration for each transgression area is exponentially related to the time spanned until present. It defines the potential laws of leaching of marine waters by fresh meteoric waters. The results of the Armorican aquifers provide the first observed constraints for the time scales of seawater circulation in the continental basement and the subsequent leaching by fresh meteoric waters. The general trend of increasing chloride concentration with depth and the time frame for the flushing process provide useful information to develop conceptual models of the paleo-functionning of Armorican aquifers

Tribute to Jean-Yves Jaffray July 22, 1939 - February 26, 2009

International audienceTribute to Jean-Yves Jaffray by the French Group of Decision TheoryHommage à Jean-Yves Jaffray par le groupe français de Théorie de la Décisio

Натечные карбонатные новообразования набережной реки Туры: особенности строения и процессы формирования

International audienc

Biochemical markers of ongoing joint damage in rheumatoid arthritis - current and future applications, limitations and opportunities

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease associated with potentially debilitating joint inflammation, as well as altered skeletal bone metabolism and co-morbid conditions. Early diagnosis and aggressive treatment to control disease activity offers the highest likelihood of preserving function and preventing disability. Joint inflammation is characterized by synovitis, osteitis, and/or peri-articular osteopenia, often accompanied by development of subchondral bone erosions, as well as progressive joint space narrowing. Biochemical markers of joint cartilage and bone degradation may enable timely detection and assessment of ongoing joint damage, and their use in facilitating treatment strategies is under investigation. Early detection of joint damage may be assisted by the characterization of biochemical markers that identify patients whose joint damage is progressing rapidly and who are thus most in need of aggressive treatment, and that, alone or in combination, identify those individuals who are likely to respond best to a potential treatment, both in terms of limiting joint damage and relieving symptoms. The aims of this review are to describe currently available biochemical markers of joint metabolism in relation to the pathobiology of joint damage and systemic bone loss in RA; to assess the limitations of, and need for additional, novel biochemical markers in RA and other rheumatic diseases, and the strategies used for assay development; and to examine the feasibility of advancement of personalized health care using biochemical markers to select therapeutic agents to which a patient is most likely to respond

MLVA-16 typing of 295 marine mammal Brucella isolates from different animal and geographic origins identifies 7 major groups within Brucella ceti and Brucella pinnipedialis

<p>Abstract</p> <p>Background</p> <p>Since 1994, <it>Brucella </it>strains have been isolated from a wide range of marine mammals. They are currently recognized as two new <it>Brucella </it>species, <it>B. pinnipedialis </it>for the pinniped isolates and <it>B. ceti </it>for the cetacean isolates in agreement with host preference and specific phenotypic and molecular markers. In order to investigate the genetic relationships within the marine mammal <it>Brucella </it>isolates and with reference to terrestrial mammal <it>Brucella </it>isolates, we applied in this study the Multiple Loci VNTR (Variable Number of Tandem Repeats) Analysis (MLVA) approach. A previously published assay comprising 16 loci (MLVA-16) that has been shown to be highly relevant and efficient for typing and clustering <it>Brucella </it>strains from animal and human origin was used.</p> <p>Results</p> <p>294 marine mammal <it>Brucella </it>strains collected in European waters from 173 animals and a human isolate from New Zealand presumably from marine origin were investigated by MLVA-16. Marine mammal <it>Brucella </it>isolates were shown to be different from the recognized terrestrial mammal <it>Brucella </it>species and biovars and corresponded to 3 major related groups, one specific of the <it>B. ceti </it>strains, one of the <it>B. pinnipedialis </it>strains and the last composed of the human isolate. In the <it>B. ceti </it>group, 3 subclusters were identified, distinguishing a cluster of dolphin, minke whale and porpoise isolates and two clusters mostly composed of dolphin isolates. These results were in accordance with published analyses using other phenotypic or molecular approaches, or different panels of VNTR loci. The <it>B. pinnipedialis </it>group could be similarly subdivided in 3 subclusters, one composed exclusively of isolates from hooded seals (<it>Cystophora cristata</it>) and the two others comprising other seal species isolates.</p> <p>Conclusion</p> <p>The clustering analysis of a large collection of marine mammal <it>Brucella </it>isolates from European waters significantly strengthens the current view of the population structure of these two species, and their relative position with respect to the rest of the <it>Brucella </it>genus. MLVA-16 is confirmed as being a rapid, highly discriminatory and reproducible method to classify <it>Brucella </it>strains including the marine mammal isolates. The <it>Brucella2009 </it>MLVA-16 genotyping database available at <url>http://mlva.u-psud.fr/</url> is providing a detailed coverage of all 9 currently recognized <it>Brucella </it>species.</p

Perspectives for integrating human and environmental risk assessment and synergies with socio-economic analysis

International audienceFor more than a decade, the integration of human and environmental risk assessment (RA) has become an attractive vision. At the same time, existing European regulations of chemical substances such as REACH (EC Regulation No. 1907/2006), the Plant Protection Products Regulation (EC regulation 1107/2009) and Biocide Regulation (EC Regulation 528/2012) continue to ask for sector-specific RAs, each of which have their individual information requirements regarding exposure and hazard data, and also use different methodologies for the ultimate risk quantification. In response to this difference between the vision for integration and the current scientific and regulatory practice, the present paper outlines five medium-term opportunities for integrating human and environmental RA, followed by detailed discussions of the associated major components and their state of the art. Current hazard assessment approaches are analyzed in terms of data availability and quality, and covering non-test tools, the integrated testing strategy (ITS) approach, the adverse outcome pathway (AOP) concept, methods for assessing uncertainty, and the issue of explicitly treating mixture toxicity. With respect to exposure, opportunities for integrating exposure assessment are discussed, taking into account the uncertainty, standardization and validation of exposure modeling as well as the availability of exposure data. A further focus is on ways to complement RA by a socio-economic assessment (SEA) in order to better inform about risk management options. In this way, the present analysis, developed as part of the EU FP7 project HEROIC, may contribute to paving the way for integrating, where useful and possible, human and environmental RA in a manner suitable for its coupling with SEA

MLVA polymorphism of Salmonella enterica subspecies isolated from humans, animals, and food in Cambodia

<p>Abstract</p> <p>Background</p> <p><it>Salmonella </it>(<it>S</it>.) <it>enterica </it>is the main cause of salmonellosis in humans and animals. The epidemiology of this infection involves large geographical distances, and strains related to an episode of salmonellosis therefore need to be reliably discriminated. Due to the limitations of serotyping, molecular genotyping methods have been developed, including multiple loci variable number of tandem repeats (VNTR) analysis (MLVA). In our study, 11 variable number tandem-repeats markers were selected from the <it>S. enterica </it>Typhimurium LT2 genome to evaluate the genetic diversity of 206 <it>S. enterica </it>strains collected in Cambodia between 2001 and 2007.</p> <p>Findings</p> <p>Thirty one serovars were identified from three sources: humans, animals and food. The markers were able to discriminate all strains from 2 to 17 alleles. Using the genotype phylogeny repartition, MLVA distinguished 107 genotypes clustered into two main groups: <it>S. enterica </it>Typhi and other serovars. Four serovars (Derby, Schwarzengrund, Stanley, and Weltevreden) were dispersed in 2 to 5 phylogenic branches. Allelic variations within <it>S. enterica </it>serovars was represented using the minimum spanning tree. For several genotypes, we identified clonal complexes within the serovars. This finding supports the notion of endemo-epidemic diffusion within animals, food, or humans. Furthermore, a clonal transmission from one source to another was reported. Four markers (STTR3, STTR5, STTR8, and Sal20) presented a high diversity index (DI > 0.80).</p> <p>Conclusions</p> <p>In summary, MLVA can be used in the typing and genetic profiling of a large diversity of <it>S. enterica </it>serovars, as well as determining the epidemiological relationships of the strains with the geography of the area.</p