Migration and capital accumulation: Evidence from rural Mexico

This paper studies the link between migration, remittances and productive assets accumulation for a panel of poor rural households in Mexico over the period 1997- 2006. In a context of financial markets imperfections, migration may act as a substitute for imperfect credit and insurance provision (through remittances from migrants) and, thus, exert a positive effect on investment. However, it may well be the case that remittances are channelled towards increasing consumption and leisure goods. Exploiting within family variation and an instrumental variable strategy, we show that migration indeed accelerates productive assets accumulation. Moreover, when we look at the effect of migration on consumption of non-productive assets (durable goods), we find instead a negative effect. Our results then suggest that poor rural families resort to migration as a way to mitigate constraints that prevent them from investing in productive assets.migration ; remittances ; capital accumulation ; rural poverty

Necrotrophic growth of periodontopathogens is a novel virulence factor in oral biofilms

The oral use of antimicrobial agents embedded in toothpastes and mouth rinses results in an oral microbial massacre with high amounts of dead bacteria in close proximity to few surviving bacteria. It was hypothesized that this provides the surviving pathogenic bacteria a large amount of dead microbial biomass as a nutritional source for growth (necrotrophy). This study demonstrated the necrotrophic growth of periodontal pathogens in the presence of different dead oral species. In addition, the presence of dead bacteria resulted in an outgrowth of several periodontal pathogens in complex multispecies biofilms. Additionally, upon contact with dead oral bacteria, virulence genes of P. intermedia and P. gingivalis were up-regulated (necrovirulence). This resulted in a more pronounced epithelial cytotoxicity (necrotoxicity). These findings indicate that presence of dead bacteria induce necrotrophy, necrovirulence and necrotoxicity in several oral pathogens

Optimización de la captación de corriente con catenaria rígida

La catenaria rígida presenta algunas características que la hacen especialmente apropiada para su montaje en líneas de metro, si bien el aumento del límite de velocidad de los vehículos destinados a las líneas modernas exige un diseño más eficiente para estos sistemas. En este trabajo se ha analizado el comportamiento dinámico de este tipo de sistemas de captación, a fin de diseñar un nuevo carril conductor con un comportamiento dinámico superior al de los ya existentes. Esto implica la posibilidad de aumentar la velocidad de circulación o la distancia entre soportes, con el consiguiente ahorro del coste de instalación. A tal fin, se ha modelizado un sistema pantógrafo-catenaria real, empleando técnicas avanzadas de modelado y simulación. Se ha realizado un estudio de sensibilidad, para analizar la influencia de cada variable de diseño sobre el comportamiento dinámico del conjunto, y se ha diseñado un carril conductor con mejores prestaciones que el actual

Migration and capital accumulation: Evidence from rural Mexico

This paper studies the link between migration, remittances and productive assets accumulation for a panel of poor rural households in Mexico over the period 1997- 2006. In a context of financial markets imperfections, migration may act as a substitute for imperfect credit and insurance provision (through remittances from migrants) and, thus, exert a positive effect on investment. However, it may well be the case that remittances are channelled towards increasing consumption and leisure goods. Exploiting within family variation and an instrumental variable strategy, we show that migration indeed accelerates productive assets accumulation. Moreover, when we look at the effect of migration on consumption of non-productive assets (durable goods), we find instead a negative effect. Our results then suggest that poor rural families resort to migration as a way to mitigate constraints that prevent them from investing in productive assets.Cet article analyse la relation entre migration et accumulation d'actifs sur des données de panel concernant des ménages ruraux au Mexique entre 1997 et 2006. Dans un contexte d'imperfection de marché, la migration peut constituer un substitut et avoir un effet positif sur l'investissement. Nous montrons que la migration encourage l'accumulation d'actifs productifs, au détriment d'actifs non-productifs. Nous illustrons nos résultats avec un modèle à deux périodes qui repose sur les décisions d'investissement et de migration pour des ménages en milieu rural avec des contraintes de crédit

In vitro increased respiratory activity of selected oral bacteria may explain competitive and collaborative interactions in the oral microbiome

Understanding the driving forces behind the shifts in the ecological balance of the oral microbiota will become essential for the future management and treatment of periodontitis. As the use of competitive approaches for modulating bacterial outgrowth is unexplored in the oral ecosystem, our study aimed to investigate both the associations among groups of functional compounds and the impact of individual substrates on selected members of the oral microbiome. We employed the Phenotype Microarray high-throughput technology to analyse the microbial cellular phenotypes of 15 oral bacteria. Multivariate statistical analysis was used to detect respiratory activity triggers and to assess similar metabolic activities. Carbon and nitrogen were relevant for the respiration of health-associated bacteria, explaining competitive interactions when grown in biofilms. Carbon, nitrogen, and peptides tended to decrease the respiratory activity of all pathobionts, but not significantly. None of the evaluated compounds significantly increased activity of pathobionts at both 24 and 48 h. Additionally, metabolite requirements of pathobionts were dissimilar, suggesting that collective modulation of their respiratory activity may be challenging. Flow cytometry indicated that the metabolic activity detected in the Biolog plates may not be a direct result of the number of bacterial cells. In addition, damage to the cell membrane may not influence overall respiratory activity. Our methodology confirmed previously reported competitive and collaborative interactions among bacterial groups, which could be used either as marker of health status or as targets for modulation of the oral environment

Improved design of an overhead rail current conductor for application in underground lines

Overhead rail current collector systems for railway traction offer certain features, such as low installation height and reduced maintenance, which make them predominantly suitable for use in underground train infrastructures. Due to the increased demands of modern catenary systems and higher running speeds of new vehicles, a more capable design of the conductor rail is needed. A new overhead conductor rail has been developed and its design has been patented [13]. Modern simulation and modelling techniques were used in the development approach. The new conductor rail profile has a dynamic behaviour superior to that of the system currently in use. Its innovative design permits either an increase of catenary support spacing or a higher vehicle running speed. Both options ensure savings in installation or operating costs. The simulation model used to optimise the existing conductor rail profile included both a finite element model of the catenary and a three-dimensional multi-body system model of the pantograph. The contact force that appears between pantograph and catenary was obtained in simulation. A sensitivity analysis of the key parameters that influence in catenary dynamics was carried out, finally leading to the improved design