Probing Multiscale Structure of Mineral and Nanoporous Kerogen Phase in Organic-Rich Source and Neutron Scattering

International audienceSource rocks are expected to become increasingly important in the upcoming years for oil and gas production as well as for the storage of greenhouse gases. These rocks are bedded and heterogeneous media, composed of minerals, kerogen, and pore space. One of the most challenging issues is to better define the pore space, including pore size distribution, pore volume fraction, pore connectivity, and pore affinity for various fluids. The aim of this study is to achieve such relevant parameters using X-ray and neutron scattering technique complementarity. Rock thin blades cut normal to the bedding plane preserve sample integrity and allow their measurements in both techniques. Two-dimensional scattering patterns show anisotropy, due to preferential orientation of lamellar minerals, which allows us to assess an order parameter. This parameter is a valuable tool for mechanical and transport properties. A model based on a three-phase system (minerals, kerogen, and pores) is developed through the study of scattering length density of each component within both radiations. The model allows us to fit both X-ray and neutron 1D data using the same model parameters. This latter is then considered as selective. It allows us to extract the kerogen mass density, the kerogen pore size distribution and its associated volume fraction, and the chemical nature of kerogen pore content. This methodology has been applied to a series of five source rocks of increasing maturities from Barnett Shale Play and Montney-Doig formations. Mature samples show a kerogen density of ∼1.6 g·cm–3, a pore radius distribution centered on 0.5–0.7 nm accounting for a pore volume fraction of ∼0.01–0.04. These kerogen nanopores are filled with light condensed hydrocarbons. However, the overmature kerogen exhibits a mass density of 1.74 g·cm–3, an additional pore radius distribution centered around 3.5 nm with a pore volume fraction of 0.002, and an empty pore space. All these parameters are in agreement with Rock-Eval pyrolysis measurements and literature data on similar source rocks. These results pointed out that the three-phase model associated with X-ray and neutron complementarity could be applied to in situ studies

Structural Iron (II) of Basaltic Glass as an Energy Source for Zetaproteobacteria in an Abyssal Plain Environment, Off the Mid Atlantic Ridge

International audienceTo explore the capability of basaltic glass to support the growth of chemosynthetic microorganisms, complementary in situ and in vitro colonization experiments were performed. Microbial colonizers containing synthetic tholeitic basaltic glasses, either enriched in reduced or oxidized iron, were deployed off-axis from the Mid Atlantic Ridge on surface sediments of the abyssal plain (35 • N; 29 • W). In situ microbial colonization was assessed by sequencing of the 16S rRNA gene and basaltic glass alteration was characterized using Scanning Electron Microscopy, micro-X-ray Absorption Near Edge Structure at the Fe-K-edge and Raman microspectroscopy. The colonized surface of the reduced basaltic glass was covered by a rind of alteration made of iron-oxides trapped in a palagonite-like structure with thicknesses up to 150 μm. The relative abundance of the associated microbial community was dominated (39% of all reads) by a single operational taxonomic unit (OTU) that shared 92% identity with the iron-oxidizer Mariprofundus ferrooxydans PV-1. Conversely, the oxidized basaltic glass showed the absence of iron-oxides enriched surface deposits and correspondingly there was a lack of known iron-oxidizing bacteria in the inventoried diversity. In vitro, a similar reduced basaltic glass was incubated in artificial seawater with a pure culture of the iron-oxidizing M. ferrooxydans DIS-1 for 2 weeks, without any additional nutrients or minerals. Confocal Laser Scanning Microscopy revealed that the glass surface was covered by twisted stalks characteristic of this iron-oxidizing Zetaproteobacteria. This result supported findings of the in situ experiments indicating that the Fe(II) present in the basalt was the energy source for the growth of representatives of Zetaproteobacteria in both the abyssal plain and the in vitro experiment. In accordance, the surface alteration rind observed on the reduced basaltic glass incubated in situ could at least partly result from their activity

Le sol social mexicain porte-t-il encore des communs ?: Ejidos et lotissements d’intérêt social dans la périphérie de Mexico

International audienceCe research paper vise à présenter le résultat d’un travail de recherche mené en 2018-2019 sur le thème des transformations des communs fonciers urbains pour l’habitat dans le cas de la périphérie de la zone métropolitaine de Mexico. Deux processus majeurs sont ici questionnés et croisés : d’une part, l’évolution d’un système de propriété collective spécifique au Mexique qu’est l’ejido, dont la privatisation progressive est permise depuis les années 1990 ; d’autre part, la croissance urbaine spectaculaire de lotissements de logements d’intérêt social, qualifiables d’abordables dans le contexte latino-américain. Si ces deux tendances ne s’expliquent pas en se réduisant l’une à l’autre, des relations fortes sont à mettre en lumière.Les communs fonciers urbains constituent une alternative majeure pour la revendication du droit à la ville dans un contexte de transition urbaine et, dans le cas de Mexico comme dans celui d’autres métropoles, ces communs ont été perturbés par leur marchandisation partielle et les pratiques informelles liées à leur situation urbaine ou périurbaine. La double approche de cette étude par les communs et par le logement de masse permet de se concentrer, non pas sur la ressource foncière de l’ejido en tant que telle, mais sur les rapports qui régissent son fonctionnement et qui questionnent les alternatives à la propriété privée pour l’habitat. Dans le contexte mexicain comme dans d’autres contextes, ces communs fonciers urbains pour l’habitat peuvent être des vecteurs d’un accès à un logement abordable, mais aussi de logiques ségrégatives.Pour ce faire, l’ejido et le commun seront interrogés dans leur maintien et dans la forme de leurs mutations. A partir de bases de données publiques et d’un travail de terrain mené en 2019, il s’agira d’analyser les mécanismes de production de logements, les rapports entre les acteurs de ce processus. Une première partie de la démonstration présente le processus qui a permis la privatisation du sol social et la production sur ce même foncier d’un modèle de grands lotissements d'intérêt social. Une seconde partie vise à comprendre la construction d’un nouveau jeu d'acteurs institutionnels et privés qu'a instauré une gouvernance qui a mené à la déstructuration des ejidos et à la financiarisation de la production du logement. Une troisième et dernière partie aborde les conséquences territoriales et sociales de cette politique qui transforme le sol social en logements d'intérêt social

Linking current river pollution to historical pesticide use: Insights for territorial management?

International audiencePersistent organic pollutants like organochlorine pesticides continue to contaminate large areas worldwide raising questions concerning their management. We designed and tested a method to link soil and water pollution in the watershed of the Galion River in Martinique. We first estimated the risk of soil contamination by chlordecone by referring to past use of land for banana cultivation and took 27 soil samples. We then sampled surface waters at 39 points and groundwater at 16 points. We tested three hypotheses linked to the source of chlordecone pollution at the watershed scale: (i) soils close to the river, (ii) soils close to the sampling point, (iii) throughout the sub-watershed generated at the sampling point. Graphical and statistical analysis showed that contamination of the river increased when it passed through an area with contaminated plots and decreased when it passed through area not contaminated by chlordecone. Modeling showed that the entire surface area of the watershed contributed to river pollution, suggesting that the river was mainly being contaminated by the aquifers and groundwater flows. Our method proved to be a reliable way to identify areas polluted by chlordecone at the watershed scale and should help stakeholders focus their management actions on both hot spots and the whole watershed. (C) 2016 Elsevier B.V. All rights reserved

Salmonella enterica serovars Panama and Arechavaleta: Risk Factors for Invasive Non-Typhoidal Salmonella Disease in Guadeloupe, French West Indies

International audienceA retrospective study was conducted to identify the risk factors associated with Salmonella enterica bac-teremia in infants and children in Guadeloupe, French West Indies. The 171 patients with S. enterica infection seen between 2010 and 2014 included 155 (90.6%) with acute gastroenteritis, of whom 42 (27.1%) had concomitant bac-teremia, and 16 (9.4%) with primary bacteremia. Most cases (97.7%) were in infants and children with no underlying health condition. Two subspecies were recovered: enterica (N = 161, 94.2%) and houtenae (N = 10, 5.8%). All but one (serovar Typhi) were non-typhoidal Salmonella. The most common serovars were Panama (N = 57, 33.3% of isolates) and Arechavaleta (N = 28, 16.4%). Univariate analysis showed a strong association only between age > 6 months and infection with the Panama or Arechavaleta serovar (P = 0.002). The rate of resistance to all classes of antibiotics during the study period was low ( 5 days (P = 0.01), vomiting (P = 0.001), and increased respiratory rate (P = 0.001) contributed independently to bacteremia in the multivariate analysis. Thus, if non-typhoidal infection is suspected, blood should be cultured and antibiotic treatment initiated in all patients who meet these criteria

Population perception of mandatory childhood vaccination programme before its implementation, France, 2017

International audienceBackgroundVaccination policy in France was previously characterised by the coexistence of eight recommended and three mandatory vaccinations for children younger than 2 years old. These 11 vaccines are now mandatory for all children born after 1 January 2018.AimTo study the French population’s opinion about this new policy and to assess factors associated with a positive opinion during this changing phase.MethodsA cross-sectional survey about vaccination was conducted from 16 November–19 December 2017 among the GrippeNet.fr cohort. Data were weighted for age, sex and education according to the French population. Univariate and multivariate analyses were performed to identify factors associated with a favourable opinion on mandatory vaccines’ extension and defined in the ‘3Cs’ model by the World Health Organization Strategic Advisory Group of Experts working group on vaccine hesitancy.ResultsOf the 3,222 participants (response rate 50.5%) and after adjustment, 64.5% agreed with the extension of mandatory vaccines. It was considered a necessary step by 68.7% of the study population, while 33.8% considered it unsafe for children and 56.9% saw it as authoritarian. Factors associated with a positive opinion about the extension of mandatory vaccines were components of the confidence, complacency and convenience dimensions of the ‘3Cs’ model.ConclusionsIn our sample, two thirds of the French population was in favour of the extension of mandatory vaccines for children. Perception of vaccine safety and benefits were major predictors for positive and negative opinions about this new policy

Evidence for a Continuous Drift of the HIV-1 Species towards Higher Resistance to Neutralizing Antibodies over the Course of the Epidemic

<div><p>We compared the neutralization sensitivity of early/transmitted HIV-1 variants from patients infected by subtype B viruses at 3 periods of the epidemic (1987–1991, 1996–2000, 2006–2010). Infectious pseudotyped viruses expressing envelope glycoproteins representative of the viral quasi-species infecting each patient were tested for sensitivity to neutralization by pools of sera from HIV-1 chronically infected patients and by an updated panel of 13 human monoclonal neutralizing antibodies (HuMoNAbs). A progressive significantly enhanced resistance to neutralization was observed over calendar time, by both human sera and most of the HuMoNAbs tested (b12, VRC01, VRC03, NIH45-46^G54W, PG9, PG16, PGT121, PGT128, PGT145). Despite this evolution, a combination of two HuMoNAbs (NIH45-46^G54W and PGT128) still would efficiently neutralize the most contemporary transmitted variants. In addition, we observed a significant reduction of the heterologous neutralizing activity of sera from individuals infected most recently (2003–2007) compared to patients infected earlier (1987–1991), suggesting that the increasing resistance of the HIV species to neutralization over time coincided with a decreased immunogenicity. These data provide evidence for an ongoing adaptation of the HIV-1 species to the humoral immunity of the human population, which may add an additional obstacle to the design of an efficient HIV-1 vaccine.</p></div

Decreasing immunogenicity of clade B HIV-1 variants in term of NAbs induction over the course of the epidemic.

<p>[A and B] Comparison of the frequencies of detection of NAbs [A] and of NAbs titers [B] against 6 heterologous subtype B isolates (BX08, 92BR020, QH0692.42, AC10.0.29, RHPA4259.7 and REJO4541.67) in sera from clade B chronically infected patients at the two extreme periods of the study i.e. 1987–1991 (n = 30) and 2003–2007 (n = 30). Differences in the frequency of detection and the titers of NAbs among sera from the two groups of patients were compared by Chi² or ANOVA tests after adjustment for the strain, respectively. [C] Comparison of the neutralization breadth between the sera of the two periods. Each point represents the value for one serum. [D] Comparison of the potency scores (see methods) between the sera of the two periods. Box plots show the distribution of potency scores of each group of sera; the horizontal lines represent the 10^th, median and 90^th percentiles. Differences between breadth and potency score between the two groups of sera were evaluated using a Wilcoxon signed ranked test.</p

Enhanced resistance of clade B early/transmitted HIV-1 variants to neutralization by HuMoNAbs over the course of the epidemic.

<p>[A to E] Comparison of the neutralization sensitivity of Env-pseudotyped viruses derived from historical patients (HP, n = 11), intermediate patients (IP, n = 15) and contemporary patients (CP, n = 14) by b12, VRC01, VRC03 and NIH45-46G54W [A], PG9, PG16 and PGT145 [B], PGT121, PGT128, PGT135 and 2G12 [C] and 2F5 and 4E10 [D]. Box plots show the distribution of antibody titers (IC₅₀) of each HuMoNAb towards pseudotyped viruses of each period; the horizontal lines represent the 10^th, median and 90^th percentiles. Each data represents the mean value of the assay performed in duplicate. Differences of neutralization sensitivity between viruses over calendar time were evaluated using a Jonckheere-Terpstra test. [E] Comparison of the neutralization coverage of each HuMoNabs used at various concentrations (IC₅₀≤10 µg/mL, ≤1 µg/mL or ≤0.01 µg/mL) towards pseudotyped viruses from HP, IP and CP. Differences of neutralization coverage of viruses from HP to CP were evaluated using a Chi² test for trend.</p