130 research outputs found
A multi-scale tool for functionalization of polyolefins through radical grafting
Free radical induced grafting of polymers is an important synthesis strategy to improve the properties of the pristine polymer and to ensure compatibility in blends. In this contribution, a multi-scale modeling tool is presented that enables to describe the grafting kinetics with a detailed description at the molecular, micro- and meso-scale combined with a 1D macro-scale reactor model. The potential of the model is illustrated with polyolefins as polymer substrate, including model validation to lab-scale and industrial scale data. It is highlighted that the model is indispensable to achieve the optimal process conditions for improved process intensification and functionality/molecular control
Numerische und physikalische Modellierung von Ufererosion in KiesflĂŒssen
Bank erosion is a natural geomorphological process which affects a wide range of physical, ecological and socio-economic issues in the fluvial environment. Among the others, the impacts include loss of lands, damage to structure and infrastructures and dynamics of sediments, nutrients and contaminants. Hence, it is not surprising how riverbank retreat is closely related to the risk assessment.
Despite many progresses have been made in understanding and modelling bank erosion, further investigations are needed to better understand processes occurring on riverbank totally or partially composed of relatively coarse sediments. Therefore, the general aim of this study is to give a contribution in understanding and modelling processes, with particular focusing on gravel banks.
The study is organized to provide a general framework of analysis at different spatial scales, using as a reference study case the Cecina River (Pisa, Italy).
At the catchment scale, riverbank processes were studied with the specific aim to identify the variability of bank features (geometry and composition), the dominant mechanisms of retreat and their spatial distribution. Different methods to predict the lateral instabilities were also undertaken in order to pinpoint causes and factors which control the occurrence of different mechanisms of retreat.
At the reach scale, numerical models were employed with the aim of exploring methods for a combined analysis which couples different mechanisms of retreat, with particular focus on the inclusion of near-bank shear stresses. Moreover, based on results of the previous analyses, a framework for risk analysis due to bank erosion was developed.
The objective of the analyses carried out at the bank scale, was to better understand the basic processes occurring in relatively coarse bank sediments, in particular the occurrence of mass instability in the absence of fluvial erosion. In order to address the objective, a physical model of a bank composed by gravel and sand was built, and some experiments simulating the behaviour of the bank during a hydrograph were carried out. The tests allowed for the identification of different mechanisms of failure and for the analysis of the factor affecting non cohesive bank stability.Die Ufererosion stellt einen natĂŒrlichen geomorphologischen Prozess in fluvialen FlieĂgewĂ€ssern dar, der von groĂer Bedeutung fĂŒr verschiedene ingenieurtechnische, ökologische und sozio-ökonomische Fragestellungen ist. Sie stellt einen wichtigen Prozess im Hinblick auf die Dynamik von Sedimenten, NĂ€hrstoffen und Schadstoffen in FlieĂgewĂ€ssern dar und kann gleichzeitig aber auch zum Verlust von Land oder zur GefĂ€hrdung von Siedlungen und der Infrastruktur fĂŒhren. Deshalb ist es nicht erstaunlich, dass der mit der Ufererosion verbundene RĂŒckgang der Ufer in engem Zusammenhang mit der Risikobewertung steht.
Bis heute fĂŒhrten zahlreiche Untersuchungen zu einem verbesserten VerstĂ€ndnis der relevanten physikalischen Prozesse und somit zu einer verbesserten Modellierung der Ufererosion. Allerdings existieren, speziell im Hinblick auf die Erosion von relativ grobkörnigen Ufern, immer noch zahlreiche offene Fragestellungen. Das Ziel der Arbeit bestand deshalb darin, zum besseren VerstĂ€ndnis und zur verbesserten Modellierung der Erosion von Ufern aus kiesigem Material beizutragen.
Hierzu wurde anhand des ReferenzgewĂ€ssers des Cecina-Flusses in Italien ein ĂŒbergeordneter Rahmen fĂŒr die Analyse der relevanten Prozesse unter der BerĂŒcksichtigung verschiedener rĂ€umlicher Skalen geschaffen. Auf der Skala des Einzugsgebiets wurden die entsprechenden Prozesse mit dem spezifischen Ziel untersucht, die VariabilitĂ€t der Ufereigenschaften (Geometrie und Zusammensetzung), die dominanten Mechanismen fĂŒr den RĂŒckgang der Ufer als auch deren rĂ€umliche Verteilung zu identifizieren. Mittels verschiedener Methoden zur Vorhersage lateraler InstabilitĂ€ten wurden die relevanten Faktoren und Prozesse aufgezeigt, welche die verschiedenen Mechanismen der Ufererosion kontrollieren.
Auf der Flussabschnittsskala wurden anhand numerischer Modellierungen Methoden untersucht, die zu einer adĂ€quaten kombinierten Analyse der verschiedenen Erosionsmechanismen herangezogen werden können. Ein spezielles Augenmerk wurde hierbei auf die Schubspannungen in UfernĂ€he gelegt und es wurde ein Rahmen fĂŒr die Risikoanalyse im Hinblick auf die Ufererosion entwickelt.
Auf der Uferskala stand die Untersuchung der relevanten physikalischen Prozesse im Vordergrund, welche die Erosion von grobkörnigen Ufersedimenten und insbesondere das Auftreten von Uferrutschungen dominieren, wenn kein Sedimenttransport im GewĂ€sser vorliegt. Zu diesem Zweck wurde ein physikalisches Modell eines aus Kies und Sand bestehenden Ufers aufgebaut. Die Modelluntersuchungen, bei denen die StabilitĂ€t des Ufers infolge des Strömungsangriffs wĂ€hrend eines Hochwasserereignisses unter BerĂŒcksichtigung der Ganglinie untersucht wurde, fĂŒhrten zur Identifikation verschiedener Versagensmechanismen und wurden zur Analyse von Faktoren herangezogen, die die StabilitĂ€t von nicht kohĂ€siven Ufern beeinflussen
A tracking of the complete microstructural evolution of individual polymer chains during polymer modification reactions
Methyl jasmonate enhanced production of rosmarinic acid in cell cultures of Satureja khuzistanica in a bioreactor
The growing interest in rosmarinic acid (RA), an ester of caffeic acid and 3,4âdihydroxyphenyl lactic acid, is due to its biological activities, which include cognitiveâenhancing effects, slowing the development of Alzheimer's disease, cancer chemoprotection, and antiâinflammatory activity. Inspired by the challenge of meeting the growing demand for this plant secondary metabolite, we developed a biotechnological platform based on cell suspension cultures of Satureja khuzistanica. The high amounts of RA produced by this system accumulated mainly inside the cells. To further improve production, two elicitors, 100 ÎŒM methyl jasmonate (MeJA) and 40 mM cyclodextrin (CD), were tested, separately and together. MeJA increased RA productivity more than 3âfold, the elicited cultures achieving an RA production of 3.9 g Lâ1 without affecting biomass productivity. CD did not have a clear effect on RA production, and under the combined treatment of MeJA + CD only a small amount of RA was released to the medium. When the cell culture was transferred from a shake flask to a waveâmixed bioreactor, a maximum RA production of 3.1 g Lâ1 and biomass productivity of 18.7 g Lâ1 dâ1 was achieved under MeJA elicitation, demonstrating the suitability of S. khuzistanica cell suspensions for the biotechnological production of this bioactive plant secondary metabolite
New Insights on the Management of Wildlife Diseases Using Multi-State Recapture Models: The Case of Classical Swine Fever in Wild Boar
The understanding of host-parasite systems in wildlife is of increasing interest in relation to the risk of emerging diseases in livestock and humans. In this respect, many efforts have been dedicated to controlling classical swine fever (CSF) in the European Wild Boar. But CSF eradication has not always been achieved even though vaccination has been implemented at a large-scale. Piglets have been assumed to be the main cause of CSF persistence in the wild since they appeared to be more often infected and less often immune than older animals. However, this assumption emerged from laboratory trials or cross-sectional surveys based on the hunting bags.In the present paper we conducted a capture-mark-recapture study in free-ranging wild boar piglets that experienced both CSF infection and vaccination under natural conditions. We used multi-state capture recapture models to estimate the immunization and infection rates, and their variations according to the periods with or without vaccination. According to the model prediction, 80% of the infected piglets did not survive more than two weeks, while the other 20% quickly recovered. The probability of becoming immune did not increase significantly during the summer vaccination sessions, and the proportion of immune piglets was not higher after the autumn vaccination.Given the high lethality of CSF in piglets highlighted in our study, we consider unlikely that piglets could maintain the chain of CSF virus transmission. Our study also revealed the low efficacy of vaccination in piglets in summer and autumn, possibly due to the low palatability of baits to that age class, but also to the competition between baits and alternative food sources. Based on this new information, we discuss the prospects for the improvement of CSF control and the interest of the capture-recapture approach for improving the understanding of wildlife diseases
Mise au point sur les nouveaux syndromes et les syndromes connus dâintoxications par les champignons
International audienceLes champignons encore appelĂ©s MycĂštes ou Fungi appartiennent au rĂšgne fongique dĂ©fini par un ensemble de 7 caractĂšres fondamentaux. Lâidentification des espĂšces comestibles, toxiques ou mortelles passe par la connaissance de caractĂšres morphologiques, microscopiques voire chimiques. Quâen est-il des champignons dits comestibles ? Qui sait que Boletus edulis (CĂšpe de Bordeaux), Lactarius deliciosus (Lactaire dĂ©licieux) et Cantharellus cibarius (Girolle) peuvent dĂ©terminer un syndrome gastro-intestinal ? Qui suspecte que Auricularia auricula-judae (Oreille de Judas) et les morilles (Morchella sp.) peuvent ĂȘtre respectivement responsables du Purpura de Szechwan et dâun syndrome neurologique ? Quoi de nouveau sur Tricholoma equestre (Tricholome Ă©questre), un champignon comestible faisant partie des mĂ©langes forestiers, devenu mortel en 2001 car responsable dâune rhabdomyolyse ? Qui croirait encore dâactualitĂ© la confusion entre le mortel Cortinarius orellanus (Cortinaire Ă couleur de Rocou) et la Girolle (Cantharellus cibarius) ? Quel est le choix pharmaco-thĂ©rapeutique en 2011 quant au traitement de lâintoxication phalloĂŻdienne par Amanita phalloide
Les intoxications par les champignons. Partie I. Intoxications Ă long dĂ©lai dâapparition de la symptomatologie
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La classification des champignons
International audienceLa Mycologie est la science de lâĂ©tude des champignons. Elle comprend des Ă©tapes fondamentales qui sont : la taxonomie,la systĂ©matique et la nomenclature pour aboutir Ă un canevas gĂ©nĂ©ral de la classification des champignons
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