Modeling of the transient behavior of a slurry bubble column reactor for CO2 methanation, and comparison with a tube bundle reactor

In this publication, the performance of a slurry bubble column reactor (SBCR) and a tube bundle reactor (TBR) are compared for steady-state and transient Power-to-Gas (PtG) operation. Transient PtG conditions are modeled using gas load step changes between 25 and 100% of the reactor maximum capacities in 1 s. For steady-state operation the TBR facilitates much higher gas hourly space velocities (GHSV) as compared to the SBCR. A sensitivity analysis shows that the TBR is limited by heat transfer, while the SBCR is limited by gas/liquid mass transfer. For transient PtG operation the TBR undergoes significant temperature changes within a short time resulting in out of specification product gas qualities and unacceptable temperature hot spots; the SBCR temperature shows marginal changes upon transient operating conditions, and the outlet gas composition sticks to the gas quality requirements. Finally, measures to improve the efficiency of both reactors are proposed considering dimensionless numbers. The GHSV of the SBCR can be enhanced by increasing the specific interfacial area controlling gas/liquid mass transfer, while the transient behavior of the TBR can be improved by reducing the catalyst concentration/activity or by mixing the catalyst with high heat capacity inert material in detriment of the GHSV

Une nouvelle ère pour l'intermédiation en immobilier résidentiel : fondements, digitalisation et limites

Why, during the digital era, individuals still prefer transaction operations through an estate agent? What do the Internet perspectives offer to the intermediation actors? And what are the Limits of this digital transformation?The work developed in this dissertation aim to provide answers elements to those questions to estate professionals wishing to understand better the behavior of their customers and the market today. The objective of this dissertation is to contribute to the comprehension of improving the intermediation systems, and particularly what brings buyers and sellers to use these services on the real estate French market.Pourquoi à l’ère du digital, les particuliers préfèrent-ils encore opérer des transactions immobilières avec un intermédiaire ? Quelles sont les perspectives qu’offre Internet aux acteurs de l’intermédiation ? Et quelles sont les limites de cette transformation digitale ? Les travaux développés dans la présente thèse visent à apporter des éléments de réponses à ces questions aux professionnels de l’immobilier résidentiel souhaitant mieux appréhender le comportement de leurs clients et du marché aujourd’hui. L’objectif de cette thèse est de contribuer à améliorer la compréhension des systèmes d’intermédiation, et en particulier de ce qui amène les acheteurs et les vendeurs à utiliser ces services, sur le marché immobilier résidentiel français

Greening the Common Agricultural Policy: a behavioral perspective and lab-in-the-field experiment in Germany

This study investigates the behavioral economic underpinnings of current policy approaches to integrate environmental objectives into the Common Agricultural Policy. We conduct an economic lab-in-the-field experiment with farmers in Germany. We analyze the impact of the following policy design features on farmers’ decisions to adopt sustainable agricultural practices: (i) framing of the policy: whether farmers perceive themselves as being part of the problem or the solution, (ii) degree of control: mandatory vs. voluntary policy (iii) framing of incentives as either losses or gains. All policy designs tested result in a significant increase in hectares conserved compared to a baseline scenario without policy. Also behavioral factors do significantly affect farmers’ behavior at the individual level. Only framing is found to significantly affect policy effectiveness

Plasmodium Purine Metabolism and Its Inhibition by Nucleoside and Nucleotide Analogues

International audienceMalaria still affects around 200 million people and is responsible for more than 400,000 deaths per year, mostly children in subequatorial areas. This disease is caused by parasites of the Plasmodium genus. Only a few WHO-recommended treatments are available to prevent or cure plasmodial infections, but genetic mutations in the causal parasites have led to onset of resistance against all commercial antimalarial drugs. New drugs and targets are being investigated to cope with this emerging problem, including enzymes belonging to the main metabolic pathways, while nucleoside and nucleotide analogues are also a promising class of potential drugs. This review highlights the main metabolic pathways targeted for the development of potential antiplasmodial therapies based on nucleos(t)ide analogues, as well as the different series of purine-containing nucleoside and nucleotide derivatives designed to inhibit Plasmodium falciparum purine metabolism.

From speciation to introgressive hybridization: the phylogeographic structure of an island subspecies of termite, Reticulitermes lucifugus corsicus

<p>Abstract</p> <p>Background</p> <p>Although much research has been carried out into European <it>Reticulitermes </it>taxonomy in recent years, there is still much discussion about phylogenetic relationships. This study investigated the evolution from intra- to interspecific phylogeny in the island subspecies <it>Reticulitermes lucifugus corsicus </it>and threw new light on this phenomenon. An integrative approach based on microsatellites and mitochondrial and nuclear DNA sequences was used to analyze samples taken from a wide area around the Tyrrhenian sea and showed how the subspecies evolved from its origins to its most recent form on continental coasts.</p> <p>Results</p> <p>According to mitochondrial phylogeny and molecular clock calculations, island and continental taxa diverged significantly by vicariance in the Pleistocene glacial period. However, more recently, numerous migrations, certainly human-mediated, affected the structure of the populations. This study provided evidence of direct hybridization and multiple introgressions which occurred in several hybrid areas. Analysis using STRUCTURE based on microsatellite data identified a population in Provence (France) which differed considerably (Fst = 0.477) from populations on the island of Corsica and in Tuscany in the Italian peninsula. This new population, principally distributed in urban areas, is highly heterogeneous especially within the ITS2 regions where homogenization by concerted evolution does not appear to have been completed.</p> <p>Conclusion</p> <p>This study provides an unusual picture of genetic interaction between termite populations in the Tyrrhenian area and suggests that more attention should be paid to the role of introgression and human impact on the recent evolution of European termites.</p

Paleontology in France: 200 years in the footsteps of Cuvier and Lamarck

International audienceDue to its richness in fossil localities and Fossil-Lagerstätten, France played a major role in the 18th and 19th centuries in establishing paleontology and biostratigraphy as scientific disciplines. The French naturalist and zoologist Cuvier (1769-1832) established the fields of comparative anatomy and paleontology, and proposed the concept of 'catastrophism' in geology. The naturalist Lamarck (1744-1829) is considered the founder of invertebrate paleontology and biostratigraphy and an early pioneer in the studies of evolution, developing the idea of 'transformism' and creating the word 'fossil', while his successor Blainville (1777-1850) was the first to use the word 'paleontology'. Based on this rich heritage, numerous French scientists strengthened paleontology as an important discipline during the 19th and 20th centuries. Paleontology was present at the universities of most major French cities, as documented by the rich collections in over 50 natural history museums and university collections. The most significant paleontological collection is that housed in the Muséum National d'Histoire Naturelle (MNHN) at Paris that currently hosts the largest research unit in paleontology of France with over 100 scientists, curators and technicians. The second largest collection (and the largest in terms of invertebrate fossils) is housed at the University of Lyon1, where the most important university paleontology research team is present. About 250 professional paleontologists are currently working in research units that are mostly affiliated to the Centre National de Recherche Scientifique (CNRS), in public or private museums, or in the numerous natural parcs. A significant generation change took place in the early 2000s, with the retirement of the paleontologists recruited in the 1960s and 1970s, that were often specialized in alpha-taxonomy and stratigraphy, and the arrival of a young generation of scientists that attempts to answer more 'modern' questions, such as global (climate) change, biodiversity, or evolution. This new generation of paleontologists faces modified funding schemes with project-based supporting structures in a more and more competitive environment. In the present paper we attempt to summarize the current situation of paleontology as a discipline in the very complex academic and scientific context of France. After a short overview on the history of French paleontology in the last centuries, a synopsis on institutions and funding agencies is presented briefly. The major research departments and their research themes are then described, together with the most important collections, the paleontological associations, journals, and databases, etc. Paleontological training possibilities and job opportunities, in particular in academia, are next documented, concluding with a summary of the prospects of the discipline

Protocadherins Mediate Dendritic Self-Avoidance in the Mammalian Nervous System

Dendritic arbors of many neurons are patterned by a process called self-avoidance, in which branches arising from a single neuron repel each other. By minimizing gaps and overlaps within the arbor, self-avoidance facilitates complete coverage of a neuron’s territory by its neurites. Remarkably, some neurons that display self-avoidance interact freely with other neurons of the same subtype, implying that they discriminate self from non-self. Here, we demonstrate roles for the clustered protocadherins (Pcdhs) in dendritic self-avoidance and self/non-self discrimination. The Pcdh locus encodes ~60 related cadherin-like transmembrane proteins, at least some of which exhibit isoform-specific homophilic adhesion in heterologous cells and are expressed stochastically and combinatorially in single neurons. Deletion of all 22 Pcdhs in the mouse gamma subcluster (Pcdhgs) disrupts self-avoidance of dendrites in retinal starburst amacrine cells (SACs) and cerebellar Purkinje cells. Further genetic analysis of SACs showed that Pcdhgs act cell-autonomously during development, and that replacement of the 22 Pcdhgs with a single isoform restores self-avoidance. Moreover, expression of the same single isoform in all SACs decreases interactions among dendrites of neighboring SACs (heteroneuronal interactions). These results suggest that homophilic Pcdhg interactions between sibling neurites (isoneuronal interactions) generate a repulsive signal that leads to self-avoidance. In this model, heteroneuronal interactions are normally permitted because dendrites seldom encounter a matched set of Pcdhgs unless they emanate from the same soma. In many respects, our results mirror those reported for Dscam1 in Drosophila: this complex gene encodes thousands of recognition molecules that exhibit stochastic expression and isoform-specific interactions, and mediate both self-avoidance and self/non-self discrimination. Thus, although insect Dscams and vertebrate Pcdhs share no sequence homology, they appear to underlie similar strategies for endowing neurons with distinct molecular identities and patterning their arbors.Molecular and Cellular Biolog

Establishment of the Variation of Vitamin K Status According to Vkorc1 Point Mutations Using Rat Models

International audienceVitamin K is crucial for many physiological processes such as coagulation, energy metabolism, and arterial calcification prevention due to its involvement in the activation of several vitamin K-dependent proteins. During this activation, vitamin K is converted into vitamin K epoxide, which must be re-reduced by the VKORC1 enzyme. Various VKORC1 mutations have been described in humans. While these mutations have been widely associated with anticoagulant resistance, their association with a modification of vitamin K status due to a modification of the enzyme efficiency has never been considered. Using animal models with different Vkorc1 mutations receiving a standard diet or a menadione-deficient diet, we investigated this association by measuring different markers of the vitamin K status. Each mutation dramatically affected vitamin K recycling efficiency. This decrease in recycling was associated with a significant alteration of the vitamin K status, even when animals were fed a menadione-enriched diet suggesting a loss of vitamin K from the cycle due to the presence of the Vkorc1 mutation. This change in vitamin K status resulted in clinical modifications in mutated rats only when animals receive a limited vitamin K intake totally consistent with the capacity of each strain to recycle vitamin K