Optimal control models and elicitation of attitudes towards climate damages

This paper examines the consequences of various attitudes towards climate damages through a family of stochastic optimal control models (RESPONSE): cost-efficiency for a given temperature ceiling; cost-benefit analysis with a "pure preference for current climate regime" and full cost-benefit analysis. The choice of a given proxy of climate change risks is actually more than a technical option. It is essentially motivated by the degree of distrust regarding the legitimacy of an assessment of climate damages and the possibility of providing in due time reliable and non controversial estimates. Our results demonstrate that a) for early decades abatement, the difference between various decision-making frameworks appears to matter less than the difference between stochastic and non stochastic approach given the cascade of uncertainty from emissions to damages; b) in a stochastic approach, the possibility of non-catastrophic singularities in the damage function is sufficient to significantly increase earlier optimal abatements; c) a window of opportunity for action exists up to 2040: abatements further delayed may induce significant regret in case of bad news about climate response or singularities in damages.Cost-efficiency; Cost-benefit; Climate sensitivity; Climate change damages; Uncertainty; Optimal climate policy; Decision making frameworks

Business Cycles, Bifurcations and Chaos in a Neo-Classical Model with Investment Dynamics

This paper presents a non-equilibrium dynamic model (NEDyM) that introduces investment dynamics and non-equilibrium effects into a Solow growth model. NEDyM can reproduce several typical economic regimes and, for certain ranges of parameter values, exhibits endogenous business cycles with realistic characteristics. The cycles arise from the investment-profit instability and are constrained by the increase in labor costs and the inertia of production capacity. For other parameter ranges, the model exhibits chaotic behavior. These results show that complex variability in the economic system may be due to deterministic, intrinsic factors, even if the long-term equilibrium is neo-classical in nature

Climate policies as a hedge against the uncertainty on future oil supply

International audienceDespite the inextricable link between oil scarcity and climate change, the interplay between these two issues is paradoxically an underworked area. This article uses a global energy-economy model to address the link between future oil supply and climate change and assesses in a common framework both the costs of climate policies and oil scarcity. It shows that, in the context of a limited and uncertain amount of ultimately recoverable oil resources, climate policies reduce the world vulnerability to peak oil. Climate policies, therefore, appear as a hedging strategy against the uncertainty on oil resources, in addition to their main aim of avoiding dangerous climate change. This co-benefit is estimated at the net present value of US$11,500 billion. Eventually, reducing the risk of future economic losses due to oil scarcity may appear as a significant side-benefit of climate policies to many decision-makers

Methylobacterium Genome Sequences: A Reference Blueprint to Investigate Microbial Metabolism of C1 Compounds from Natural and Industrial Sources

Methylotrophy describes the ability of organisms to grow on reduced organic compounds without carbon-carbon bonds. The genomes of two pink-pigmented facultative methylotrophic bacteria of the Alpha-proteobacterial genus Methylobacterium, the reference species Methylobacterium extorquens strain AM1 and the dichloromethane-degrading strain DM4, were compared. Methodology/Principal Findings The 6.88 Mb genome of strain AM1 comprises a 5.51 Mb chromosome, a 1.26 Mb megaplasmid and three plasmids, while the 6.12 Mb genome of strain DM4 features a 5.94 Mb chromosome and two plasmids. The chromosomes are highly syntenic and share a large majority of genes, while plasmids are mostly strain-specific, with the exception of a 130 kb region of the strain AM1 megaplasmid which is syntenic to a chromosomal region of strain DM4. Both genomes contain large sets of insertion elements, many of them strain-specific, suggesting an important potential for genomic plasticity. Most of the genomic determinants associated with methylotrophy are nearly identical, with two exceptions that illustrate the metabolic and genomic versatility of Methylobacterium. A 126 kb dichloromethane utilization (dcm) gene cluster is essential for the ability of strain DM4 to use DCM as the sole carbon and energy source for growth and is unique to strain DM4. The methylamine utilization (mau) gene cluster is only found in strain AM1, indicating that strain DM4 employs an alternative system for growth with methylamine. The dcm and mau clusters represent two of the chromosomal genomic islands (AM1: 28; DM4: 17) that were defined. The mau cluster is flanked by mobile elements, but the dcm cluster disrupts a gene annotated as chelatase and for which we propose the name “island integration determinant” (iid).Conclusion/Significance These two genome sequences provide a platform for intra- and interspecies genomic comparisons in the genus Methylobacterium, and for investigations of the adaptive mechanisms which allow bacterial lineages to acquire methylotrophic lifestyles.Organismic and Evolutionary Biolog

Dégradation du dichlorométhane et adaptation à la production intracellulaire d'acide chez Methylobacterium

Nous étudions la dégradation microbienne du dichlorométhane (DCM), un solvant chloré toxique d origine industrielle. Notre modèle expérimental est la souche M. dichloromethanicum DM4, dont le métabolisme du DCM a déjà été caractérisé. L objectif de mon travail a consisté à identifier et caractériser les modes de résistance à la toxicité du DCM. Nous avons mis en évidence une résistance accrue à un stress acide intracellulaire de la souche DM4 après croissance sur le DCM. En parallèle, nous avons développé une stratégie mettant en jeu un gène rapporteur de fluorescence, pour identifier les gènes impliqués dans le métabolisme du DCM et à la résistance à ce composé. Cette approche expérimentale a été renforcée par l analyse des séquences génomiques de M. dichloromethanicum DM4 et de la souche de référence M. extorquens AM1, incapable de croître avec le DCM, afin d identifier de manière globale les modes de résistance à la toxicité du DCM dans ce modèle microbien.Dichloromethane (DCM) is a toxic chloridic solvent, mainly of anthropogenic origin. The metabolism of dichloromethane degradation by the strain Methylobacterium dichloromethanicum DM4 was characterised in detail. The aim of this study was to identify and characterise different resistance pathways to dichloromethane toxicity in the DM4 strain. At the physiological level the adaptive response to intracellular acid produced during microbial DCM degradation was analysed. This study provided evidence that DCM metabolism by DM4 strain is accompanied by an increased resistance to intracellular acid. A strategy involving random transposon mutagenesis using a fluorescent reporter system was used to identify genes specifically induced by dichloromethane. These experimental approaches were reinforced by the subsequent analysis and comparison of the complete genome sequences of M. dichlorometanicum DM4 and the reference strain, M. extorquens AM1, which is incapable of growth on DCM.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Les thermes de Chassenon (Charente), transformations et réoccupation aux IVe-VIe s. p.C.

International audienc

Approche de la synthèse de la saraïne A fondée sur une hypothèse biogénétique

Les alcaloïdes de la famille des manzamines, isolés d'éponges marines, possèdent des structures polycycliques complexes ainsi que des activités biologiques prometteuses. L'étude de leur biogenèse pourrait permettre d'accéder efficacement à ces structures ou à leurs analogues. Dans le cadre d'une hypothèse biogénétique générale, une réaction de Mannich intramoléculaire a été proposée comme ultime étape du processus biologique permettant la formation du cœur tricyclique de la saraïne A. L'obtention du précurseur postulé a alors été envisagée selon deux scénarios principaux faisant intervenir le malonaldéhyde. L'évaluation du premier repose sur l'étude de l'addition de dérivés d'acides aminés sur les composés obtenus selon des réactions de Knoevenagel impliquant le malonaldéhyde et ses dérivés. L'obtention de précurseurs simplifiés pouvant servir d'intermédiaires dans la synthèse de la saraïne A a été réalisée suivant des additions de Michael de type 5-endo-trig, mais ces méthodologies ne semblent pas pouvoir être appliquées aux autres alcaloïdes de la famille. Le second scénario fait intervenir une addition de Michael intramoléculaire permettant la cyclisation d'aminoacroléines poly-insaturées. Les pyrrolines obtenues possèdent des structures proches de celles des intermédiaires proposés dans notre hypothèse, ce qui devrait permettre de pouvoir effectuer l'étude de la réaction de Mannich intramoléculaire finale.Manzamines alkaloids, isolated from marine sponges, present complex polycyclic structures and promising biological activities. A better comprehension of their biogenesis should allow an effective access to these structures or to analogues. More specifically, the biosynthesis of sarain A may be achieved through an intramolecular Mannich process and two pathways were then proposed to explain the synthesis of the putative precursor. The valuation of the first one relied on the study of the Knoevenagel reaction starting from malonaldehyde and its derivatives. Further addition of aminoacids onto the resulting adducts were also performed to yield useful pyrrolidinone intermediates as a result of 5-endo-trig Michael reactions. The second scenario involves an intramolecular Michael addition allowing the cyclisation of polyunsaturated aminoacroleins which leads to functionalized pyrrolines. This strategy appears to be promising and versatile and we are currently trying to set up the final Mannich reaction.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Les thermes de Chassenon (Charente) : transformation et réoccupation (IVe-VIe s. p.C.)

The recent excavations (1998-2000) of the Longeas thermal baths (Chassenon, Charente) help us to understand the evolution, both private and civil, and reoccupation of this construction from the 4th to the 6th century AD. Here we follow the transformation of a gallo-roman public building, in the heart of an peri-urban sanctuary into a rural hamlet composed of juxtaposed workshops and living quarters. Reconstructed at the beginning of the 4th century, the thermal baths were reoccupied without prior destruction or abandon, as early as the first third of the 5th century by a series of large dwellings linked to storage and grain preparation areas. From the end of the 5th century to the beginning of the 6th century, a second phase, richer and better structured, corresponds to the last occupation of the site, after nearly 500 years of continuous occupation. This evolution should certainly be interpreted in the more general context of Christianisation and the Visigothic settlement in this region during the 5th century AD.Les fouilles récentes (1998-2000) des thermes de Longeas (Chassenon, Charente) permettent d’appréhender l'évolution et la réoccupation privative et domestique de cet édifice du IVe au VIe s. p.C. On y suit la transformation d’un bâtiment public gallo-romain, au cœur d’un sanctuaire périurbain, en un hameau rural composé de cellules d’habitat et d’artisanat juxtaposées. Reconstruits au début du IVe s., les thermes sont réoccupés, sans destruction ni abandon préalables, dès le premier tiers du Ve s. par une série de grandes habitations, liées à des zones de stockage et de préparation des grains. De la fin du Ve s. au début du VIe s., une seconde phase, plus riche et mieux structurée, correspond à la dernière occupation du site, après presque 500 ans d’utilisation continue de celui-ci. Il convient sans doute d’interpréter cette évolution dans le contexte plus général de la christianisation et de l’implantation wisigothique dans cette région au cours du Ve s. p.C.Hourcade David, Lebreton Stéphane. Les thermes de Chassenon (Charente) : transformation et réoccupation (IVe-VIe s. p.C.). In: Aquitania : une revue inter-régionale d'archéologie, tome 18, 2001. pp. 111-135