A kinetic model for coagulation-fragmentation

The aim of this paper is to show an existence theorem for a kinetic model of coagulation-fragmentation with initial data satisfying the natural physical bounds, and assumptions of finite number of particles and finite $L^p$-norm. We use the notion of renormalized solutions introduced dy DiPerna and Lions, because of the lack of \textit{a priori} estimates. The proof is based on weak-compactness methods in $L^1$, allowed by $L^p$-norms propagation.Comment: 36 page

Regulation by protein kinase-C of putative P-type Ca channels expressed in Xenopus oocytes from cerebellar mRNA

AbstractXenopus oocytes injected with rat cerebellar mRNA expressed functional voltage-dependent Ca channels detected as an inward Ba current (IBa). The pharmacological resistance to dihydropyridines and ω-conotoxin together with the blockade obtained with Agelenopsis aperta venom suggest that these channels could be somehow assimilated to P-type Ca channels. The precise nature of the transplanted Ca channels was assessed by hybrid-arrest experiments using a specific oligonucleotide antisense-derivated from the recently cloned α1-subunit of P channels (BI-1 clone). In addition, we demonstrate that exogenous Ca channel activity was enhanced by two different PKC activators (a phorbol ester and a structural analog to diacylglycerol). The general electrophysiological and pharmacological properties of the stimulated Ca channels remain unchanged. This potentiation induced by PKC activators is antagonized by a PKC inhibitor (staurosporine) and by a monoclonal antibody directed against PKC. It is concluded that P-type Ca channels are potentially regulated by PKC phosphorylation and the functional relevance of this intracellular pathway is discussed

Un ancien lac au pied de l’<i>oppidum</i> de Gergovie (Puy-de-Dôme) : interactions sociétés-milieux dans le bassin de Sarliève à l’Holocène

International audienceZiel der seit 1997 im Becken von Sarliève, am Fuß des Oppidums von Gergovia (Puy-de-Dôme) durchgeführten Studien ist es, die wechselseitigen Beziehungen zwischen Mensch und Umwelt über einen langen Zeitraum aus einem systemischen und interdisziplinären Blickwinkel zu betrachten. Die Untersuchungen beziehen sich auf ein Niederschlagsgebiet mittlerer Größe in einer Region von eminenter geschichtlicher Bedeutung. Drei Untersuchungsachsen wurden definiert: •die Analyse der Entwicklung der Umwelt im Bereich dieses Niederschlagsgebietes in Hinsicht auf seine unterschiedlichen biophysikalischen Komponenten; •die Analyse der Geschichte der Flächennutzung und der Bewirtschaftung des Beckens durch die sich ablösenden Bevölkerungsgruppen; •die Analyse der durch den Menschen hervorgerufenen Umweltbelastung (Pflanzendecke, hydrosedimentäre Kräfte). Die Ergebnisse dieser Forschungen liefern die Elemente für die Erstellung eines sozialökologischen Modells, das das von 1970-1980 für die Grande Limagne ausgearbeitete Modell ablöst. Eine Abfolge von Agrarzyklen ist deutlich erkennbar. Diese stehen im Zusammenhang mit Phasen starker menschlicher Einflussnahme, die für das Mittelneolithikum, die Früh-und Spätbronzezeit, die ältere Eisenzeit, die späte Latène-und frühe Kaiserzeit, das Mittelalter und die Neuzeit erkannt wurden. Diese Zyklen sind eng verknüpft nicht nur mit der Entwicklung der Pflanzen und der Sedimentierungsdynamik, sondern auch mit den Schwankungen des Wasserstandes. In der Bronzezeit und im Mittelalter werden Transgressionsphasen mit besonders umfangreichen und einengenden Auswirkungen nachgewiesen. Der niedrige Pegel des Paläosees in der jüngeren Eisenzeit und der frühen Kaiserzeit begünstigt dagegen die Besiedlung der Uferregionen und sogar der Sohle des Beckens, das um die Zeitenwende durch ein Entwässerungssystem vollständig trocken gelegt wird. In der ersten Hälfte des 2. Jh. v. Chr. wird mit der starken Intensivierung der Siedlungstätigkeit in sämtlichen topographischen Kontexten eine deutliche quantitative Schwelle überschritten. Die Ergebnisse der archäologischen und paläoökologischen Untersuchungen lassen die methodische Erschließung der fruchtbarsten Böden im Zusammenhang mit einem stetigen wirtschaftlichen und demographischen Wachstum erkennen, das mit dem Bau großer als “zentrale Plätze“ interpretierter Siedlungen (La Grande Borne in Aulnat, Oppida von Corent, Gergovia und Gondole) zusammenfällt. In den ersten beiden Jahrhunderten unseres Zeitalters setzt sich diese Tendenz im Rahmen der Ökonomie der villae, die sich infolge der Gründung von Augustonemetum, der neuen Hauptstadt der avernischen civitas herausbildet, mit der von den Geländeformen unabhängigen Ausweitung der landwirtschaftlichen Nutzung auf das gesamte Becken fort. In der Spätantike und im frühen Mittelalter gewinnt der Sumpf in einem feuchteren Klima wieder an Boden, besonders durch die grundlegenden Veränderungen in der Art und Weise das Gebiet zu nutzen. Die mittelalterlichen Texte und die neuzeitliche Ikonographie bezeugen die Existenz eines Sees, der zu Beginn des 17. Jh. schließlich endgültig trockengelegt wird.The aim of the researches conducted since 1997 in the basin of Sarliève, at the foot of the oppidum of Gergovia (Puy-de-Dôme), is to detect in a systemic and interdisciplinary perspective the longlasting interactions societies/environment on the scale of a mediumsized basin located in a major area from an historical point of view. Three axes have been defined : * the characterization of the evolution of the environment on the scale of the basin inside its various biophysical components ; * the characterization of the history of land occcupation and of the exploitation of environment by successive populations settled in the basin ; * the characterization of the impact of human pressure on the environment (plant cover, hydro-sedimentary dynamics). Results provide elements of a new socioenvironmental model after the model completed in Limagne in the 1970'-1980'. A succession of land cycles has been detected and connected to phases of strong human pressure identified for Middle Neolithic, Early and Late Bronze Age, Early Iron Age, Early Empire, Middle Age and Modern period. These cycles are tightly connected with vegetation evolution and sedimentary dynamics but also with vertical variations of the lake level. Some phases of encroachment, particularly wide and constraining, have been revealed for Bronze Age and Middle Age. The low level of the lake during the Late Iron Age and the Early Empire in the other hand is favourable to the occupation of the edges and even at the bottom of the basin which is entirely drained due to a draining system at the turn of our era. A definite quantitative step, during the first half of the 2nd century BC, is represented by the high densification of the populated area in all kinds of physical units. Archaeological and environmental datas reveal a methodic exploitation of the most fertile lands in a context of continuous economic and demographic environment which coincides with the birth of towns identified as "central places" (such as la Grande Borne at Aulnat and the oppida of Corent at Veyre-Monton, Gergovia at La Roche-Blanche and Gondole at Le Cendre). This tendency goes on during the first two centuries AD, with the generalization of agrosystem to the whole basin, for any kind of relief, in the context of economic estates growing since the foundation of Augustonemetum, the new capital of the Arverni. The return of marsh in Late Antiquity and Early Middle Age is due to a more humid climate and to deep changes in the methods of environmental management. A real lake is attested by medieval sources and modern iconography and is definitely dried out at the beginning of the 17th century.Les recherches conduites depuis 1997 dans le bassin de Sarliève, au pied de l'oppidum de Gergovie (Puy-de-Dôme), visent à appréhender, dans une perspective systémique et interdisciplinaire, les interactions sociétés-milieux dans la longue durée, à l'échelle d'un bassin-versant de taille moyenne localisé dans une zone de première importance sur le plan historique. Trois axes de recherche ont été définis : * la caractérisation de l'évolution du milieu à l'échelle du bassin-versant dans ses différentes composantes biophysiques ; * la caractérisation de l'histoire de l'occupation du sol et de l'exploitation du milieu par les populations successives établies dans le bassin ; * la caractérisation de l'impact de la pression anthropique sur le milieu (couverture végétale, dynamiques hydrosédimentaires). Les résultats obtenus fournissent les éléments d'un modèle socio-environnemental qui renouvelle celui élaboré pour la Grande Limagne dans les années 1970-1980. Une succession de cycles agraires est clairement mise en évidence. Ceux-ci sont liés à des phases de forte pression humaine identifiées au Néolithique moyen, au Bronze ancien, au Bronze final, au premier âge du Fer, à La Tène finale, au Haut-Empire, au Moyen Âge et à l'époque moderne. Ces cycles sont étroitement corrélés avec l'évolution de la végétation et la dynamique sédimentaire, mais également avec les variations verticales du plan d'eau. Des phases de transgression particulièrement amples et contraignantes sont mises en évidence durant l'âge du Bronze et le Moyen Âge. Le bas niveau du paléolac durant le second âge du Fer et le Haut-Empire est, en revanche, propice à l'occupation des bordures et même du fond de la cuvette, qui est complètement asséchée grâce à un système de drainage aménagé aux environs du changement d'ère. Un seuil quantitatif très net est franchi dans la première moitié du IIe s. av. J.-C., avec la forte densification de l'habitat dans tous les types d'unités physiques. Les données archéologiques et paléoenvironnementales traduisent la mise en valeur méthodique des sols les plus fertiles, dans un contexte de croissance économique et démographique continue qui coïncide avec l'apparition de vastes agglomérations interprétées comme des " places centrales " (agglomération de la Grande Borne à Aulnat, oppida de Corent à Veyre-Monton, Gergovie à La Roche-Blanche et Gondole au Cendre). Cette tendance se poursuit durant les deux premiers siècles de notre ère, avec la généralisation de l'agrosystème à l'ensemble du bassin, quels que soient les types de reliefs, dans le cadre de l'économie domaniale qui se développe à la suite de la fondation d'Augustonemetum, nouvelle capitale de la cité arverne. La fin de l'Antiquité et le haut Moyen Âge voient le retour du marais à la faveur d'un climat plus humide et, surtout, de profonds changements dans les modalités de gestion du milieu. Un véritable lac est attesté par les textes médiévaux et par l'iconographie moderne. Il est définitivement asséché au début du XVIIe s

Estimating Attributable Mortality Due to Nosocomial Infections Acquired in Intensive Care Units

Background. The strength of the association between intensive care unit (ICU)-acquired nosocomial infections (NIs) and mortality might differ according to the methodological approach taken. Objective. TO assess the association between ICU-acquired NIs and mortality using the concept of population-attributable fraction (PAF) for patient deaths caused by ICU-acquired NIs in a large cohort of critically ill patients. Setting. Eleven ICUs of a French university hospital. Design. We analyzed surveillance data on ICU-acquired NIs collected prospectively during the period from 1995 through 2003. The primary outcome was mortality from ICU-acquired NI stratified by site of infection. A matched-pair, case-control study was performed. Each patient who died before ICU discharge was defined as a case patient, and each patient who survived to ICU discharge was denned as a control patient. The PAF was calculated after adjustment for confounders by use of conditional logistic regression analysis. Results. Among 8,068 ICU patients, a total of 1,725 deceased patients were successfully matched with 1,725 control Patients. The adjusted PAF due to ICU-acquired NI for patients who died before ICU discharge was 14.6% (95% confidence interval [CI], 14.4%—14.8%). Stratified by the type of infection, the PAF was 6.1% (95% CI, 5.7%-6.5%) for pulmonary infection, 3.2% (95% CI, 2.8%-3.5%) for central venous catheter infection, 1.7% (95% CI, 0.9%-2.5%) for bloodstream infection, and 0.0% (95% CI, -0.4% to 0.4%) for urinary tract infection. Conclusions. ICU-acquired NI had an important effect on mortality. However, the statistical association between ICU-acquired NI and mortality tended to be less pronounced in findings based on the PAF than in study findings based on estimates of relative risk. Therefore, the choice of methods does matter when the burden of NI needs to be assesse

A functional role for eicosanoid-lysophospholipids in activating monocyte signaling

Recently, eicosanoid-lysophospholipids were identified as novel metabolites generated from the direct cyclooxygenase- or lipoxygenase-catalyzed oxidation of 2-arachidonoyl-lysophospholipids produced from either phospholipase A(1)-mediated hydrolysis of diacyl arachidonoyl-phospholipids or through the cytochrome c-catalyzed oxidative hydrolysis of the vinyl ether linkage of arachidonoyl-plasmalogens. Although the metabolic pathways generating eicosanoid-lysophospholipids have been increasingly appreciated, the signaling functions of eicosanoid-lysophospholipids remain largely unknown. Herein, we demonstrate that 2-12(S)-HETE-lysophospholipids as well as nonesterified 12(S)-HETE are potent lipid mediators that activate THP-1 human monocytic cells to generate tumor necrosis factor α (TNFα) and interleukin 8 (IL8). Remarkably, low nanomolar concentrations of 12(S)-HETE-lysophospholipids, but not other oxidized signaling lipids examined activated THP-1 cells resulting in the production of large amounts of TNFα. Moreover, TNFα release induced by 12(S)-HETE-lysophospholipids was inhibited by the TNFα converting enzyme inhibitor TAPI-0 indicating normal processing of TNFα in THP-1 cells stimulated with these agonists. Western blotting analyses revealed that 12(S)-HETE-lysophospholipids activated the phosphorylation of NFκB p65, suggesting activation of the canonical NFκB signaling pathway. Importantly, activation of THP-1 cells to release TNFα was stereoselective with 12(S)-HETE favored over 12(R)-HETE. Furthermore, the EC(50) of 2-12(S)-HETE-lysophosphatidylcholine in activating THP-1 cells was 2.1 nm, whereas the EC(50) of free 12(S)-HETE was 23 nm. Additionally, lipid extracts of activated platelets were separated by RP-HPLC demonstrating the coelution of 12(S)-HETE with fractions initiating TNFα release. Collectively, these results demonstrate the potent signaling properties of 2-12(S)-HETE-lysophospholipids and 12(S)-HETE by their ability to release TNFα and activate NFκB signaling thereby revealing a previously unknown role of 2-12(S)-HETE-lysophospholipids in mediating inflammatory responses

A comparison of no-slip, stress-free and inviscid models of rapidly rotating fluid in a spherical shell

We investigate how the choice of either no-slip or stress-free boundary conditions affects numerical models of rapidly rotating flow in Earth's core by computing solutions of the weakly-viscous magnetostrophic equations within a spherical shell, driven by a prescribed body force. For non-axisymmetric solutions, we show that models with either choice of boundary condition have thin boundary layers of depth E^(1/2), where E is the Ekman number, and a free-stream flow that converges to the formally inviscid solution. At Earth-like values of viscosity, the boundary layer thickness is approximately 1m, for either choice of condition. In contrast, the axisymmetric flows depend crucially on the choice of boundary condition, in both their structure and magnitude (either E^(-1/2) or E^(-1)). These very large zonal flows arise from requiring viscosity to balance residual axisymmetric torques. We demonstrate that switching the mechanical boundary conditions can cause a distinct change of structure of the flow, including a sign-change close to the equator, even at asymptotically low viscosity. Thus implementation of stress-free boundary conditions, compared with no-slip conditions, may yield qualitatively different dynamics in weakly-viscous magnetostrophic models of Earth's core. We further show that convergence of the free-stream flow to its asymptotic structure requires E ≤10^(-5)