Spread and transmission of bacterial pathogens in experimental populations of the nematode Caenorhabditis elegans.

Caenorhabditis elegans is frequently used as a model species for the study of bacterial virulence and innate immunity. In recent years, diverse mechanisms contributing to the nematode's immune response to bacterial infection have been discovered. Yet despite growing interest in the biochemical and molecular basis of nematode-bacterium associations, many questions remain about their ecology. Although recent studies have demonstrated that free-living nematodes could act as vectors of opportunistic pathogens in soil, the extent to which worms may contribute to the persistence and spread of these bacteria has not been quantified. We conducted a series of experiments to test whether colonization of and transmission between C. elegans nematodes could enable two opportunistic pathogens (Salmonella enterica and Pseudomonas aeruginosa) to spread on agar plates occupied by Escherichia coli. We monitored the transmission of S. enterica and P. aeruginosa from single infected nematodes to their progeny and measured bacterial loads both within worms and on the plates. In particular, we analyzed three factors affecting the dynamics of bacteria: (i) initial source of the bacteria, (ii) bacterial species, and (iii) feeding behavior of the host. Results demonstrate that worms increased the spread of bacteria through shedding and transmission. Furthermore, we found that despite P. aeruginosa's relatively high transmission rate among worms, its pathogenic effects reduced the overall number of worms colonized. This study opens new avenues to understand the role of nematodes in the epidemiology and evolution of pathogenic bacteria in the environment.Some C. elegans and bacteria strains were provided by the Caenorhabditis Genetics Centre, which is funded by NIH Office of Research Infrastructure Programs (P40 OD010440). We thank Andrew Grant and Craig Winstanley for providing strains and reagents. We thank Mark Viney and two anonymous reviewers for helpful comments on the manuscript. This research was funded by a grant from the Biotechnology and Biological Sciences Research Council (grant number BB/I012222/1) to OR. OR also acknowledges funding from the Royal Society (University Research Fellowship).This is the author accepted manuscript. The final published version can be found on the publisher's website at: http://aem.asm.org/content/early/2014/06/23/AEM.01037-14.long Copyright © 2014, American Society for Microbiology. All Rights Reserve

Counting discriminants of number fields

For each transitive permutation group G on n letters with n ≤ 4, we give without proof results, conjectures, and numer-ical computations on discriminants of number fields L of degree n over Q such that the Galois group of the Galois closure of L is isomorphic to G

Characterization of the Evapotranspiration flux on a Blue Green Solution (Blue Green Wave)

International audienceThe rapid growth of urban areas, jointly with the effects of climate change, is the major challenge to face the transition towards sustainable cities. Climate change leads to substantial modifications of the water cycle in cities, increasing the frequency of intense precipitation, drought and heat wave events. The replacement of natural surfaces by dark and impervious ones is the main cause of Urban Heat Islands (UHI) phenomenon. UHIs are microclimates characterized by significant temperature differences between inner cities and the surrounding rural areas. Part of a solution to tackle this issue is the re-naturalization of cities through the installation of Blue Green Solutions (BGS), such as green roofs, favoring the evapotranspiration (ET) process and thus reducing the air temperature. To benefit BGS implementation, it is crucial to understand the thermo-hydric processes that govern them. For this purpose, the ET process of a 1 ha green roof implemented in front of the Ecole de Ponts ParisTech (France) called Blue Green Wave (BGW) was studied to determine its possible cooling effect to mitigate UHIs. Therefore, three methods were tested and compared to estimate ET: (i) the water balance during dry periods through the difference on the soil moisture content measured via a wireless sensors network, (ii) the absolute humidity measured by a dynamic transpiration chamber, and (iii) a scintillometer to assess the sensible heat flux, which allows to deduce the latent heat flux by computing the energy balance. The wireless sensors demonstrated to assess correctly ET trends over long time periods, while the dynamic chamber allows to identify more precisely the ET behavior during shorter periods of measurement due to a better resolution. Indeed, ET computed via the water budget appeared significantly high compared to the values estimated by the dynamic chamber, and without showing an obvious daily pattern. In addition, ET trends estimated by both scintillometer and transpiration chamber methods were very close, but the corresponding values suffered from a significant difference. The divergence in ET flux computed by the three methods can be caused by: (1) errors in the sensible heat flux estimated by the scintillometer, leading overestimations of the latent heat flux; (2) noisy data of soil water content, induced by the rainfall events and the local soil characteristics where the sensors are implemented, and (3) modifications of the atmospheric conditions within the transpiration chamber. More generally, ET appeared higher in spring season and during the first days of summer, when high temperatures were reached and soil water content was enough to support ET without inducing a deficit for plants. Conversely, despite significant temperatures at the end of summer, ET rate was lower due to the lack of water content in the soil. This suggests that during summer, when the UHI intensity is stronger and the cooling effects of the green roofs are needed, the ET potential could not be sufficient. To go further in the space-time characterization of ET flux, additional experiments and multi-fractal analysis will be carried out soon

Diseño hidráulico y estructural de defensa ribereña en el río Moche, entre el tramo Bello Horizonte – Bello Lirio, Laredo - Trujillo 2019

La presenteinvestigación se realizó en el Rio Moche, entre el tramo Bello Horizonte–BelloLirio, donde las lluvias excesivas y el fenómeno del niño en el año 2017, produjeroninundaciones, erosiones y acumulaciones de arrastre de sedimentos, que llegaron a destruirzonas de cultivos, vías de comunicación, viviendas, etc. , afectando principalmente a la zonaagropecuaria, lo que significó el incremento de la crisis económica de la población, es porello que la presente tesis denominada “Diseño hidráulico y estructural de defensa ribereñaen el Rio Moche, entre el tramo Bello Horizonte–Bello Lirio, Laredo–Trujillo 2019”,consiste en plantear defensas ribereñas para ciertos puntos críticos que puedan protegeravenidas máximas para una población de 1062 habitantes. Como resultado obtuvimos que el levantamiento topográfico de una longitud de 9,083 kmtiene una topografía llana, esto significa que solo estamos considerando los desniveles queestán dentro del cauce del rio. Elestudiode mecánica desuelosde 6 muestrasen diferentespuntos nos permitió conocer el tipo de suelo, donde fue arena limosa sin plasticidad con un peso unitarioseco de promedio 1.229 g/cm3 y capacidad portante de 1.18 kg/cm2. Se ha calculadocaudales de diseño con tresmétodos: Gumbel, Nash y Levediev, teniendo como resultado34.351 m3/s, 28.647 m3/s, 32.744 m3/s, respectivamente. El diseño hidráulico se haconsiderado con un caudal de diseño 34.351m3/s, dado por el método de Gumbel con unperiodo de retorno de 50 años. El diseño estructural se consideró4.5metros de altura y 4metrosde base con respecto al muro de gavión, de acuerdo con los puntos críticos, en cuantoal muro de contención se consideró unabase de 3.65m con una altura de 4.90m.Los impactosambientales generados por el proyecto serán de bajas magnitudes y finalmente el costoreferencial del proyecto asciende a 29,088,676.64que incluye el costo directo, gastosgenerales, utilidad e IGV

PER-MARE: Adaptive Deployment of MapReduce over Pervasive Grids

International audienceMapReduce is a parallel programming paradigm successfully used to perform computations on massive amounts of data, being widely deployed on clusters, grid, and cloud infrastructures. Interestingly, while the emergence of cloud in- frastructures has opened new perspectives, several enterprises hesitate to put sensible data on the cloud and prefer to rely on internal resources. In this paper we introduce the PER- MARE initiative, which aims at proposing scalable techniques to support existent MapReduce data-intensive applications in the context of loosely coupled networks such as pervasive and desktop grids. By relying on the MapReduce programming model, PER-MARE proposes to explore the potential advan- tages of using free unused resources available at enterprises as pervasive grids, alone or in a hybrid environment. This paper presents the main lines that orient the PER-MARE approach and some preliminary results