The Full Cost of High-Speed Rail: An Engineering Approach

This paper examines the full costs, defined as the sum of private and social costs, of a high speed rail system proposed for a corridor connecting Los Angeles and San Francisco in California. The full costs include infrastructure, fleet capital and operating expenses, the time users spend on the system, and the social costs of externalities, such as noise, pollution, and accidents. Comparing these full costs to those of other competing modes contributes to the evaluation of the feasibility of high speed rail in the corridor. The paper concludes that high speed rail is significantly more costly than expanding existing air service, and marginally more expensive than auto travel. This suggests that high speed rail is better positioned to serve shorter distance markets where it competes with auto travel than longer distance markets where it substitutes for air. .

Reliable ABC model choice via random forests

Approximate Bayesian computation (ABC) methods provide an elaborate approach to Bayesian inference on complex models, including model choice. Both theoretical arguments and simulation experiments indicate, however, that model posterior probabilities may be poorly evaluated by standard ABC techniques. We propose a novel approach based on a machine learning tool named random forests to conduct selection among the highly complex models covered by ABC algorithms. We thus modify the way Bayesian model selection is both understood and operated, in that we rephrase the inferential goal as a classification problem, first predicting the model that best fits the data with random forests and postponing the approximation of the posterior probability of the predicted MAP for a second stage also relying on random forests. Compared with earlier implementations of ABC model choice, the ABC random forest approach offers several potential improvements: (i) it often has a larger discriminative power among the competing models, (ii) it is more robust against the number and choice of statistics summarizing the data, (iii) the computing effort is drastically reduced (with a gain in computation efficiency of at least fifty), and (iv) it includes an approximation of the posterior probability of the selected model. The call to random forests will undoubtedly extend the range of size of datasets and complexity of models that ABC can handle. We illustrate the power of this novel methodology by analyzing controlled experiments as well as genuine population genetics datasets. The proposed methodologies are implemented in the R package abcrf available on the CRAN.Comment: 39 pages, 15 figures, 6 table

Heme rescues a two-component system Leptospira biflexa mutant

<p>Abstract</p> <p>Background</p> <p>Heme is typically a major iron source for bacteria, but little is known about how bacteria of the <it>Leptospira </it>genus, composed of both saprophytic and pathogenic species, access heme.</p> <p>Results</p> <p>In this study, we analysed a two-component system of the saprophyte <it>Leptospira biflexa</it>. <it>In vitro </it>phosphorylation and site-directed mutagenesis assays showed that Hklep is a histidine kinase which, after autophosphorylation of a conserved histidine, transfers the phosphate to an essential aspartate of the response regulator Rrlep. Hklep/Rrlep two-component system mutants were generated in <it>L. biflexa</it>. The mutants could only grow in medium supplemented with hemin or δ-aminolevulinic acid (ALA). In the pathogen <it>L. interrogans</it>, the <it>hklep </it>and <it>rrlep </it>orthologous genes are located between <it>hemE </it>and <it>hemL </it>genes, which encode proteins involved in heme biosynthesis. The <it>L. biflexa hklep </it>mutant could be complemented with a replicative plasmid harbouring the <it>L. interrogans </it>orthologous gene, suggesting that these two-component systems are functionally similar. By real-time quantitative reverse transcription-PCR, we also observed that this two-component system might influence the expression of heme biosynthetic genes.</p> <p>Conclusion</p> <p>These findings demonstrate that the Hklep/Rrlep regulatory system is critical for the <it>in vitro </it>growth of <it>L. biflexa</it>, and suggest that this two-component system is involved in a complex mechanism that regulates the heme biosynthetic pathway.</p

Comportements socio-démographiques des individus atteints de dystrophie myotonique

Une recherche empirique sur les conditions de vie des individus atteints de dystrophie myotonique a été réalisée au Saguenay-Lac-Saint-Jean. S’agissant d’une maladie héréditaire dominante, il est important de comprendre les comportements de nuptialité et de fécondité des individus atteints. En matière de nuptialité, nous observons une très nette différenciation entre les comportements des femmes et des hommes atteints. En matière de fécondité, la population atteinte de DM suit globalement les mêmes tendances que la population québécoise. Cette recherche démontre l’utilité des sciences sociales pour dégager les structures socio-culturelles sous-jacentes au problème d’épidémiologie génétique que représente une maladie héréditaire.An empirical research on the living conditions of individuals with myotonic distrophy has been conducted in the Saguenay-Lac-Saint-Jean region of Quebec. The disease being hereditary dominant, it is important to understand the nuptiality and fertility behavior of these individuals. As far as nuptiality is concerned a clear difference in female and male behavior has been observed. Fertility trends are similar for the population affected with the disease and for the total population of Quebec. This kind of research shows how social sciences may be useful in making apparent the socio-cultural structures underlying the problem of genetic epidemiology produced by hereditary diseases.Una investigación empírica sobre las condiciones de vida de los individuos afectados de distrofía miotónica fue realizada en Saguenay-Lac-Saint-Jean. Tratándose de una enfermedad hereditaria dominante, es importante entender los comportamientos de nupcialidad y fecundidad de los individuos afectados. Con respecto a la nupcialidad se observa una diferencia demarcada entre el comportamiento de los hombres y de las mujeres. Con respecto a la fecundidad, la población afectada de DM sigue globalmente las mismas tendencias que la población quebequense. Esta investigación demuestra la utilidad de las ciencias sociales para distinguir las estructuras socio-culturales subjacentes al problema de epidemiología genetica que representa una enfermedad hereditaria

La social-démocratie des années 2000

Notes de la Fondation Jean JaurèsCette contribution fait le point sur l'état de la social-démocratie depuis les années 2000, après l'élargissement à l'Est et l'éclatement d'une grande crise du capitalisme. Elle se base largement sur des résultats collectés dans le "Handbook of Social Democracy in the European Union" (2013), publié aux éditions Palgrave Macmillan et soutenu par la Fondation Jean-Jaurès

Répartition géographique de la maladie d’Alzheimer au Saguenay-Lac-Saint-Jean, Québec (Projet IMAGE) : résultats préliminaires

La maladie d'Alzheimer (MA) est une affection neurodégénérative du cerveau dont l'étiologie demeure encore inconnue. Il s'agit de la forme de démence la plus commune chez la personne âgée car environ 60 % des cas de démence sénile présentent des lésions anatomo-pathologiques caractéristiques de la MA. Le taux de prévalence de la MA serait d'environ 5 % chez les individus âgés de 65 ans et plus. Les premiers symptômes apparaissent généralement après 60 ans et le risque d'être atteint augmente avec l'âge. En raison du phénomène de vieillissement de nos populations, le nombre de cas de MA devrait augmenter de façon significative dans l'avenir.Notre article a pour objectif de présenter les premières données du Projet IMAGE sur la répartition géographique de la MA, selon le lieu résidentiel des cas, au sein d'une région spécifique de la province de Québec. Nous faisons également état de nos premières mesures sur les variations entre les milieux urbain et rural. Le registre IMAGE de cas Alzheimer est en édification depuis 1986 sur l'ensemble du territoire du Saguenay—Lac-Saint-Jean; 221 cas « définitifs », « probables » et « possibles » sont répertoriés actuellement. En travaillant sur la base de six sphères géographiques de recensement prédéfinies, la variation des taux de prévalence standardisés n'apparaît pas statistiquement significative. Seules les sphères d'Alma et de La Baie, avec un indice comparatif de prévalence supérieur à l'unité, présentent une tendance au surnombre de cas, sans pour autant être statistiquement significative. Par ailleurs, la proportion de cas recensés dans la sphère d'Alma est en grande partie rurale.Alzheimer's disease (AD) is a neurodegenerative disorder of the brain; its etiology remains unknown. It represents the most common form of dementia among the elderly, since over 60 % of the cases of senile dementia show the characteristic anatomo-pathological features of AD. The prevalence rate of AD is approximately 5 % amongst individuals aged 65 and over. The disease onset is generally after 60 and the risk of developing AD increases with age. In view of the phenomenon of ageing of our populations, the number of cases of AD should increase significantly in the future.The objective of this paper is to present the preliminary findings of the IMAGE Project on the geographical distribution of AD cases, based on their place of residence in one specific region of the province of Québec. We also present our initial measurements on the variations in prevalence rates between urban and rural areas. The establishment of the IMAGE registry of AD cases has been in progress since 1986 over the entire Saguenay—Lac-Saint-Jean territory; 221 possible, probable and definite cases have actually been screened. Working on the basis of six predefined geographical spheres of screening, the variation of standardized prevalence rates does not appear to be statistically significant. Only the spheres of Alma and of La Baie, with a comparative prevalence index greater than 1,0, show a trend for more cases, albeit not statistically significant. Moreover, the proportion of cases found in the sphere of Alma is largely rural

ABC random forests for Bayesian parameter inference

This preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (http://dx.doi.org/10.24072/pci.evolbiol.100036). Approximate Bayesian computation (ABC) has grown into a standard methodology that manages Bayesian inference for models associated with intractable likelihood functions. Most ABC implementations require the preliminary selection of a vector of informative statistics summarizing raw data. Furthermore, in almost all existing implementations, the tolerance level that separates acceptance from rejection of simulated parameter values needs to be calibrated. We propose to conduct likelihood-free Bayesian inferences about parameters with no prior selection of the relevant components of the summary statistics and bypassing the derivation of the associated tolerance level. The approach relies on the random forest methodology of Breiman (2001) applied in a (non parametric) regression setting. We advocate the derivation of a new random forest for each component of the parameter vector of interest. When compared with earlier ABC solutions, this method offers significant gains in terms of robustness to the choice of the summary statistics, does not depend on any type of tolerance level, and is a good trade-off in term of quality of point estimator precision and credible interval estimations for a given computing time. We illustrate the performance of our methodological proposal and compare it with earlier ABC methods on a Normal toy example and a population genetics example dealing with human population evolution. All methods designed here have been incorporated in the R package abcrf (version 1.7) available on CRAN.Comment: Main text: 24 pages, 6 figures Supplementary Information: 14 pages, 5 figure

Assessing groundwater resources in coastal area: a case study in Myanmar

Coastal aquifers are of a great relevance for human needs because coastal areas are often densely populated. To meet the needs of the people living in coastal area and to assess the groundwater resources for the future, we need to know the main characteristics of these aquifers. A preliminary hydrogeological assessment is conducted in order to point out the main questions encountered. Then, a geophysical survey is designed to answer these questions. Finally, the economical impact of integrated hydro-geophyscial approach is calculated. This paper presents the main results of a survey conducted in Myanmar. We found that the joint use of hydrogeological data (boreholes and pumping tests) with appropriate geophysics (magnetic resonance sounding and electrical resistively measurements) improves significantly the knowledge of coastal groundwater resources. The presence of groundwater, its available quantity but also its salinity can be reasonably estimated from surface geophysical measurements