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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
321

The Influence of Obliquely Propagating Monsoon Gravity Waves on the Polar Summer Mesosphere

Alexandre, David 01 July 2021 (has links)
The deep convection from monsoons is known to be a major source of gravity waves in the Earth's summer troposphere. While propagating through the middle atmosphere, these waves can carry their momentum up to the mesosphere, following either a vertical or an oblique path. This upward and oblique propagation of gravity waves refers to the latitudinal propagation, away from their low-latitude tropospheric source and towards the polar summer mesosphere. Their dissipation in this atmospheric region plays an important role in the global dynamical structure of the middle atmosphere and yet, the oblique propagation of gravity waves is not included in the present global models. Understanding the influence of the obliquely propagating monsoon gravity waves on the polar summer mesosphere, as well as the hemispheric and seasonal variations of this phenomenon, can improve the gravity-wave parameterization schemes used in the global models. My dissertation relies upon the atmosphere theory and the gravity-wave observations, first, to perform an observational analysis of the oblique propagation of gravity waves in the summer hemisphere. In response to temperature anomalies in the winter northern stratosphere, the distribution of the gravity-wave pseudomomentum flux in the opposite summer mesosphere appeared to be altered. This in turn changes the gravity-wave oblique propagation and its influence on the temperature variations seen in the polar mesospheric clouds. After the development of a 4-D non-hydrostatic ray-tracing model for the simulation of the gravity-wave propagation, my dissertation explores the hemispheric and seasonal differences in the propagation and dissipation of more than 40,000 gravity waves from the low-latitude troposphere. These ray-tracing simulations show the southern hemisphere to be more conducive to both the vertical and the oblique propagation of tropospheric to mesospheric gravity waves. This analysis also highlighted a strong wave filtering at the northern tropopause where a significant number of gravity waves were vertically reflected before reaching the stratosphere. / Doctor of Philosophy / The propagation of waves throughout the Earth's atmosphere is a key phenomenon to understanding the global atmosphere dynamics. These atmospheric waves are known to change the temperature, the pressure, the density and the composition of the middle atmosphere. As a wave propagates upward, the density of the atmospheric background exponentially decreases, resulting in an exponential increase in the wave amplitude and thus, an exponential increase in the energy carried by the wave. When the wave breaks, this energy is released and transferred to the background flow. Gravity waves are part of the atmospheric wave spectrum that is of interest to the scientific community. While small-scale gravity waves can form from tropospheric instabilities such as an unbalanced flow over the mountains or a deep convection from monsoon or thunderstorms, they can propagate up to the upper mesosphere where they can break and transfer a significant amount of energy to the background flow. Although the significant role of these gravity waves in the coupling mechanisms between atmospheric regions is without dispute, their horizontal scale is too small to be resolved by most of the global-scale atmospheric models. The deep convection from monsoon regions is known to be a major source of mesospheric GWs and previous studies on summer northern hemisphere have shown that monsoon GWs tend to propagate obliquely from the low-latitude stratopause up to the high-latitude mesopause. We focus the observational study on the summer southern hemisphere and the Inter-Hemispheric Coupling (IHC) between the summer mesopause, where Polar Mesospheric Clouds (PMCs) form, and the winter stratosphere where sudden warmings occur. PMCs are excellent indicators of atmospheric changes. Their correlations with wind, temperature and GW pseudomomentum flux highlight the consequences of anomalies in the winter stratosphere, such as warmings, on the oblique propagation of GWs that influence the PMC formation in the summer southern hemisphere. After the computation of a ray-tracing model for the simulation of the gravity-wave propagation, a hemispheric and seasonal comparison of the tropospheric to mesospheric gravity-wave propagation based on four simulations highlights the spectral nature of this phenomenon.
322

Determination of Surface Free Energies and Aspect Ratio of Talc

Lobato, Emilio Marcus de Castro 23 November 2004 (has links)
Microcalorimetric measurements and contact angle measurements were conducted to assess the surface chemistry of the mineral talc. The contact angles were performed on both flat and powdered samples and the results were used to determine the surface free energy components and parameters (SFEC) using the acid-base theory for solids, according to the van Oss-Chaudhury-Good approach. It was found that the surface hydrophobicity of talc increases with decreasing particle size up to a limit after which hydrophilicity (polarity) increases. The increase in hydrophobicity was attributed to the increase of the delamination of the lamellar talc particles. Delamination is a comminution mechanism that preferentially exposes talc's hydrophobic basal planes, while fracture is another mechanism that breaks the lamellae, rupturing covalent bonds thus exposing more hydrophilic edge surfaces. The decrease in hydrophobicity, beyond a given particle size, could be related to the prevail of fracture over delamination during grinding which generated more hydrophilic edge surfaces. The flow microcalorymetry combined with thin layer wicking allowed the separate estimation of the SFEC at the basal plane and edge surfaces of talc. The results suggested that the basal surface of talc is monopolar basic, while the edge surface is monopolar acidic, which are in agreement with the crystal structure of the mineral. The combination of two particle size distribution techniques, which are based on different physical principles, permitted the quantitative determination of the aspect ratio of highly anisometric particles, such as talc. The same trend obtained using flow microcalorimetry was observed for the evolution of the aspect ratio as a function of particle fineness, i.e. the fracture prevails over delamination after achieving a maximum aspect ratio value of about 35. The agreement between two distinct methods was considered rather encouraging. / Master of Science
323

Jean-Claude Izzo - "marseilleský polar" v českých překladech / Jean-Claude Izzo - "Marseillais polar" in the Czech translations

Šafrová, Zuzana January 2019 (has links)
This diploma thesis focuses on the most popular representative of the so-called "polar marseillais", which is Jean-Claude Izzo. The theoretical part briefly describes the development of the detective genre and the place of the detective novel in the framework of French literary production. It also deals with the position of the detective novel in the context of Czech literature and publishing. Secondly, Jean-Claude Izzo and his works will be presented in detail. Based on the information already presented, it will be possible to characterize the place of this author in connection to the French literary scene and to describe his function in the Czech environment. The main part of the work will be devoted to the translatological analysis and the critique of two Czech translations of Izzo's novels Totální chaos and Chourmo that together with Solea belong to his so-called 'Marseilles trilogy'.
324

Survie et pathogénicité des EHEC dans l'environnement digestif : Interactions avec le microbiote et l'épithélium intestinal. : Influence de l'administration de levures probiotiques. / Survival and Pathogenicity of Enterohemorrhagic Escherichia Coli in Digestive Environment : Interactions with the Microbiota and Intestinal Epithelium. : Influence of the Administration of Probiotic Yeasts.

Cordonnier, Charlotte 18 December 2015 (has links)
Les Escherichia coli entérohémorragiques (EHEC) sont des pathogènes majeurs pour l’homme responsables de toxi-infections alimentaires pouvant évoluer vers des complications potentiellement mortelles. La pathogénicité de ces souches est essentiellement due à la production de Shiga-toxines (Stx), même si d’autres facteurs semblent jouer un rôle important dans la virulence, comme des facteurs d’adhésion. La survie et la régulation des facteurs de virulence des EHEC dans l’environnement digestif humain sont des facteurs clés dans la pathogénicité bactérienne, mais restent à ce jour mal décrits, essentiellement en raison d’un manque de modèles d’étude adaptés. De plus, l’absence de traitement spécifique a conduit à s’intéresser à des moyens préventifs et/ou curatifs alternatifs, comme l’utilisation de probiotiques. L’objectif de ce travail de thèse est (i) de mieux comprendre le comportement de la souche de référence EHEC O157:H7 EDL933 dans l’environnement digestif humain simulé, et en particulier ses interactions avec le microbiote résident et l’épithélium intestinal, et (ii) d’évaluer l’effet antagoniste d’une souche de levure probiotique vis-à-vis de la survie, la virulence et l’interaction du pathogène avec l’épithélium intestinal, à l’aide d’approches in vitro et in vivo complémentaires. En modèles digestifs in vitro, la souche EHEC survit dans l’estomac, voire se multiplie dans les parties distales de l’intestin grêle, alors qu’elle ne se maintient pas dans l’environnement colique. Les gènes de virulence codant les Stx et des adhésines majeurs (intimine et « Long Polar Fimbriae » ou Lpf) sont surexprimés dès les parties hautes du tractus digestifs, et ce, même en absence de cellules épithéliales. Les conditions rencontrées dans le tractus digestif supérieur de l’enfant, comparativement à celui de l’adulte, conduisent à une survie et un niveau d’expression des gènes codant les Stx et les Lpf plus élevés chez l’enfant, ce qui peut contribuer à expliquer la grande sensibilité de cette population aux infections à EHEC. Enfin, les Lpf semblent jouent un rôle clé dans le ciblage spécifique des cellules M et le tropisme des EHEC pour les plaques de Peyer, et ce, à la fois in vitro (cellules M en culture) et in vivo (anses iléales murines). Même si elle ne modifie pas la survie du pathogène dans l’environnement colique, la levure probiotique S. cerevisiae CNCM I-3856 a montré des propriétés antagonistes intéressantes vis-à-vis d’EHEC O157:H7 en (i) modulant favorablement l’activité fermentaire du microbiote intestinal, (ii) diminuant significativement l’expression des gènes codant les Stx et (iii) inhibant la translocation bactérienne au travers des plaques de Peyer et les lésions hémorragiques associées. Par ailleurs, l’effet du pathogène et des probiotiques sur le microbiote colique est individu dépendant, confortant l’hypothèse que des facteurs associés à l’hôte, comme le microbiote, pourraient conditionner l’évolution clinique des infections à EHEC et l’efficacité d’une stratégie probiotique.Ce travail de thèse contribue à une meilleure compréhension du comportement des EHEC dans l’environnement digestif humain et confirme l’intérêt d’une stratégie probiotique dans la lutte contre le pathogène. Une étude plus approfondie du transcriptome du pathogène dans l’environnement digestif et une analyse par des méthodes haut débit du microbiote intestinal permettraient de continuer à mieux décrire la physiopathologie des infections à EHEC et comprendre les mécanismes associés à l’effet antagoniste des probiotiques. / The enterohemorrhagic Escherichia coli (EHEC) are major zoonotic pathogens responsible for food-borne infectionwhich leads to life-threatening complications in humans. The main virulence determinant of EHEC is the production of Shigatoxins (Stx), even if other factors seem to play an important role in virulence, such as adhesion factors. Survival and virulenceof EHEC strains in the human digestive environment are a key factor in bacterial pathogenesis but remains unclear owing tolack of relevant model. Moreover, no specific treatment has led to interest in preventative and / or curative alternatives, suchas using probiotics. The objective of this study is to better understand the behavior of the reference strain EHEC O157:H7EDL933 in the entire digestive tract, and in particular its interaction with the resident microbiota and the intestinal epithelium,and to evaluate the antagonistic effect of the probiotic yeast, Saccharomyces cerevisiae CNCM I-3856, using in vitro and in vivo complementary approaches.In vitro, bacterial mortality was noticed in the stomach, whereas bacterial growth resumption was observed in thedistal parts of the small intestine and the pathogen was not able to maintain in the human colonic conditions. Virulence genesencoding Stx and adhesins (intimin and “Long polar fimbriae”) are upregulated in the upper parts of the digestive tract. A ten-time higher amount of cells was found in the ileal effluents of infant compared to adult. stx genes were over-expressed (up to25-fold) in infant conditions compared to the adult ones. This results show that differences in digestive physicochemicalparameters of the upper gastrointestinal tract may partially explain why infants are more susceptible to EHEC infection thanadults. And finally, Lpf seem to play a key role in the interactions of EHEC with murine Peyer’s patches and are needed for anactive translocation of the pathogen across M cells, and both in vitro (M cells culture) and in vivo (murine ileal loops).S. cerevisiae had not effect on EHEC survival in the colonic environment but (i) favorably influenced gut microbiotaactivity through beneficial modulation of short chain fatty acid production, (ii) leading to significantly decrease stx expressionand (iii) significantly reduced EHEC translocation through M cells and inhibited in vivo interactions of the pathogen withPeyer’s patches and the associated hemorrhagic lesions. Probiotic had donor-dependent effect on the gut microbiota strengthenthe hypothesis that host-associated factors such as microbiota could influence the clinical evolution of EHEC infection and theeffectiveness of a probiotic strategy.This work contributes to a better understanding of the behavior of EHEC in the human digestive environment andconfirms the interest of probiotic strategy in controlling EHEC infections. Further transcriptome studies are warranted for thepathogen in the human digestive environment, with or without probiotics for the better understanding of the pathophysiologyof EHEC and so on the mechanisms involved in the antagonistic effect of probiotics.
325

Folheações infinitesimalmente polares / Infinitesimally polar foliations

Briquet, Rafael 29 April 2011 (has links)
O objetivo central desta dissertação é apresentar as folheações infinitesimalmente polares, fornecendo uma demonstração para o teorema que as caracteriza. Seguimos a abordagem original encontrada em Lytchak e Thorbergsson [25], de 2010. Diretamente da definição e do teorema principal obtem-se dois exemplos: folheações polares e folheações riemannianas singulares de codimensão 1 ou 2. Dedicamos especial atenção a um terceiro exemplo: folheações sem pontos horizontalmente conjugados. A demonstração deste resultado utiliza resultados obtidos anteriormente pelos mesmos autores em 2007, Lytchak e Thorbergsson [24]. Abordamos também, brevemente, as implicações do teorema caracterizador (que é um resultado local) sobre o quociente global de uma folheação infinitesimalmente polar. Variedades com folheações infinitesimalmente polares podem ser encaradas como um objeto que apresenta aspectos clássicos do teorema do toro maximal para grupos de Lie compactos, em um contexto mais amplo. / The present work aims at introducing infinitesimally polar foliations -- as defined by Lytchak and Thorbergsson [25] -- providing a proof for the classification theorem. Polar foliations and low codimension singular Riemannian foliations are two immediate examples. A third example is given by foliations without horizontally conjugate points. The proof of this assertion relies on previous results established by the same authors in Lytchak and Thorbergsson [24]. The classification theorem for infinitesimally polar foliations is a local result; we also derive from it some global consequences on the quotient space of such foliations. Infinitesimally polar foliations may be regarded as a generalised setting where one can find characteristic features from the maximal torus theorem for compact Lie groups.
326

Folheações infinitesimalmente polares / Infinitesimally polar foliations

Rafael Briquet 29 April 2011 (has links)
O objetivo central desta dissertação é apresentar as folheações infinitesimalmente polares, fornecendo uma demonstração para o teorema que as caracteriza. Seguimos a abordagem original encontrada em Lytchak e Thorbergsson [25], de 2010. Diretamente da definição e do teorema principal obtem-se dois exemplos: folheações polares e folheações riemannianas singulares de codimensão 1 ou 2. Dedicamos especial atenção a um terceiro exemplo: folheações sem pontos horizontalmente conjugados. A demonstração deste resultado utiliza resultados obtidos anteriormente pelos mesmos autores em 2007, Lytchak e Thorbergsson [24]. Abordamos também, brevemente, as implicações do teorema caracterizador (que é um resultado local) sobre o quociente global de uma folheação infinitesimalmente polar. Variedades com folheações infinitesimalmente polares podem ser encaradas como um objeto que apresenta aspectos clássicos do teorema do toro maximal para grupos de Lie compactos, em um contexto mais amplo. / The present work aims at introducing infinitesimally polar foliations -- as defined by Lytchak and Thorbergsson [25] -- providing a proof for the classification theorem. Polar foliations and low codimension singular Riemannian foliations are two immediate examples. A third example is given by foliations without horizontally conjugate points. The proof of this assertion relies on previous results established by the same authors in Lytchak and Thorbergsson [24]. The classification theorem for infinitesimally polar foliations is a local result; we also derive from it some global consequences on the quotient space of such foliations. Infinitesimally polar foliations may be regarded as a generalised setting where one can find characteristic features from the maximal torus theorem for compact Lie groups.
327

Estudo do fósforo sedimentar e de suas especiações químicas em dois sistemas costeiros e Plataforma Continental Sudeste (Brasil) e Baía do Almirantado (região antártica) considerando suas relações biogeoquímicas / Study of phosphorus and its chemical speciation in sediments in two coastal environments and southeasterns continental shelf (Brazil) and admiralty Bay (Antarctic region) considering its biogeochemical aspects

Berbel, Gláucia Bueno Benedetti 28 April 2008 (has links)
Este estudo tem como objetivo estudar o fósforo total e as especiações de fósforo nos sedimentos superficiais associados aos processos biogeoquímicos em dois sistemas estuarinos, na plataforma continental sudeste e na região polar antártica. Amostras de água de fundo foram coletadas em dois períodos sazonais (verão-inverno) nos estuários sob diferentes graus de impacto ambiental antrópico. A metodologia de extração das frações de (SEDEX) aplicada para obter as especiações químicas de fósforo foi testada com padrões certificados antes das análises. Os resultados foram reprodutivos e a eficiência da extração foi aceitável. As concentrações das espécies químicas de fósforo sedimentar nos dois estuários mostraram diferenças entre os setores seguindo as características granulométricas, influência da maré, condições redox das águas de fundo bem como, as ações antrópicas reveladas pelos dados quantitativos e qualitativos. Uma influência sazonal mínima foi observada. No caso da plataforma sudeste, altos valores de matéria orgânica foram observados em núcleos ao longo da plataforma, junto às estações externas das radiais de Santos e Ilha Grande mostrando uma diferenciação acompanhada pelas frações de fósforo orgânico e carbono orgânico. Nas demais radiais, altos valores de CaCO3 foram observados nas estações mais externas. Na Baía do Almirantado as frações predominantes foram P mineral, P detrítico, P-ligado à apatita autigênica, sendo que a forma orgânica foi baixa e associada a baixos valores de carbono orgânico. A quantificação e distribuição das espécies de fósforo nos sedimentos constituem importante ferramenta para compreender o ciclo biogeoquímico do fósforo e dos demais nutrientes nos ecossistemas marinhos. / This work aims to study the total and chemical species of phosphorus in the surface sediments associated to the biogeochemical processes in two estuarine systems, the southeastern continental shelf and Antarctic polar region. Bottom water samples were collected in two seasonal periods (summer-winter) in the estuaries under different degrees of environmental anthorpic impacts. The fraction extraction methodology (SEDEX) applied to obtain the chemical phosphorus species was tested in relation to the certified standards before analyses. The results were reproductive and the extraction efficiency was acceptable. The chemical species concentrations of sedimentary phosphorus in the two estuarine systems showed differences between sectors following the granulometric characteristics, tide influence, redox conditions of the bottom waters as well as anthropic actions revealed by quantitative and qualitative data. A minimum seasonal influence was observed. In the case of eastern continental shelf, high values of organic matter were found in nuclei distribution along the platform in the external stations of Santos and Ilha Grande radials showing a differentiation accompanied by organic phosphorus and C org., fractions. In the other radials high CaCO3 values were observed in the external stations. In the Admiralty Bay the predominant fractions were detrital apatite and authigenic/biogenic apatite, being that organic form was low, linked to low values of organic carbon. The quantification and distribution of P species in the sediments constitute important tools to understand the P and the other nutrient biogeochemical cycles in the sea ecosystems
328

Le détournement post-moderne du référent social dans le roman policier : fonctions et objectifs / Néant

Blancher, Marc 25 November 2013 (has links)
Ce travail est une étude des évolutions propres au roman policier rapportées au glissement de la modernité vers la postmodernité et de leur transposition dans la représentation du social propre à cette forme romanesque. Après deux premiers points préalables respectivement consacrés au développement genres que du roman policier – avec dans cet ordre le roman policier archaïque, le romanà énigme, le roman noir et enfin le néo-polar – depuis le milieu du XIXe siècle et à une mise en perspective des concepts de modernité et de postmodernité, il s’articule autour de trois axes choisis grâce auxquels pourra être établi le lien entre dimension évolutive du roman policier et substitution progressive de la modernité à la postmodernité. Ce lien n’est toutefois pas exclusif et il souligne un rapport d’interpénétration préalable entre les différents concepts.La première partie est consacrée à la notion de décomposition qu’elle étudie à différents niveaux : le premier est le niveau diégétique avec la décomposition narrative. Le roman policier est en effet souvent lié, par l’intermédiaire d’une énigme, à un mode de narration spécifique qui est explicité dans toute son ampleur et rapporté notamment à la notion de structure et de rapport au temps chronologique. Le deuxième point est consacré à la décomposition de la langue. C’est ainsi qu’il analyse les notions de langue au niveau diégétique et les relations entre parole et pouvoir au niveau intradiégétique, ainsi que les implications du pouvoir de la langue et de la parole sur l’image du social.Le troisième et dernier point de cette première partie est consacré à la décomposition du social que renvoie sa représentation via le prisme fictionnel. Il s’arrête plus spécifiquement, dans cet ordre, sur la représentation de l’autorité, sur les définitions des rapports sociaux et enfin sur son positionnement vis-à-vis du politique.La deuxième partie est consacrée aux mythologies du roman policier, aussi bien à celles qui lui sont propres qu’aux substrats qu’il réemploie, ce pour déterminer les modalités de repositionnement de ces éléments. Le premier est l’urbain : après une analyse des hypotextes mythologiques autour de l’urbain et de son rapport à l’humain, il est fait état des réalités socio-historiques liant urbanisation et criminalité avant que ne soit étudiée la redistribution de l’espace au sein de la sphère fictionnelle,notamment autour des concepts d’affect et d’appartenance. Le second est le social, qui est étudié aussi bien au niveau de son implantation idéologique que de son positionnement narratif, ainsi que des tensions sociales qui apparaissent dans la représentation, tensions qui culminent avec l’usage de la violence à différents niveaux. Enfin, le troisième élément est l’humain, qui bénéficie d’une évolution marquée dans son traitement via les figures humaines incarnées dans les personnages de la narration. / This paper is a study of the specific way in which the detective novel has evolved within thecontext of the shift from modernity to postmodernity, and of the manner in which its evolution isreflected within the social element that is peculiar to this fictional format. The paper tackles twoinitial aspects, the first being devoted to the development of the detective novel genre since the mid-nineteenth century, including that of its sub-genres, the roman policier archaïque, the whodunit, theroman noir and finally the neo-polar, and the second seeking to put into perspective the concepts ofmodernity and postmodernity. The focus then turns to three selected themes, which enables a link to beestablished between the evolution of the detective novel and the gradual shift from modernity topostmodernity. However, the link is not exclusive, and the paper emphasises the earlier interactionbetween the different concepts.The first section is devoted to the concept of deconstruction, which is studied at different levels,the first being the diegetic level including narrative deconstruction. In fact, the detective novel isfrequently associated with a specific method of narration, based on a conundrum, the full extent ofwhich is explained with particular reference to the concept of structure and relationship withchronological time. The second point deals with the deconstruction of the language. In doing so, itanalyses the concepts of language at a diegetic level and the relationships between the word andpower at an intradiegetic level, together with the implications of the power of language and the wordon the representation of the social context. The third and final point within this first section is devotedto the deconstruction of the social context that is reflected by its representation through the prism offiction. It focuses more specifically, in the following order, on the representation of authority, thedefinitions of social relationships and its position vis-à-vis politics.
329

Application of Hot-Melt Ink Jet Processes for Imaging at Offset Printing Form Cylinder

Abd El Kader, Magdy Ezzat 30 January 2004 (has links) (PDF)
The present work related to apply hot-melt ink-jet process for imaging at offset lithographic printing form, to utilise a reusable surface for many times and particularly related to validating thermal and ultrasonic erasing processes. This dissertation investigated systematically the role of certain factors towards affecting erasing image area process on print surfaces. Thermal erasing process approved to melt and suck the image area from the surface, the results were adopted by using contact angle measurements and scanning electron microscope. Ultrasonic erasing process permitted to solve the image area by choosing erasing chemistries, influence of selected erasing chemistries on printing surface, and evaluation the process, the results were tested by UV/Vis spectrometer, contact angle, profileometery and visual microscope. / Der Fortschritt im Bereich von Charakterisierung und Verständnis für Hot-melt Ink Jet Prozesse zur Bebilderung von Offsetdruckform-Zylindern ist ein Ergebnis dieser Forschung. Die Systematik dieser Arbeit basiert auf einem theoretischen Teil, um einen geeigneten Löschprozess auszuwählen. Der Löschprozess hängt von den Eigenschaften des Hot-melt Ink Jet Materials und der genutzten Aluminiumdruckoberfläche ab. Diese werden systematisch im Labormaßstab experimentell untersucht. Der thermische Prozess wurde einerseits durch Benetzbarkeitsprüfungen und anderseites durch Rasterelektronmikroskopaufnahmen bewertet.Der Ultraschallprozess ist ein nasser Löschprozess. Die Untersuchungen wurden in vier Stufen systematisch durchgeführt - Auswahl vom geeigneten Lösungsmitteln - Einflüsse von ausgewählten Lösungsmitteln auf nicht beschichtete und beschichtete Aluminium platten - Evaluation eines Ultraschalllöschprozesses - Validation eines Löschprozesses; zur Bewertung des Löschprozesses wurden mehrere Druckplattenproben bebildert und gelöscht Die Ergebnisse wurden durch UV/Vis Spektrometer, Kontaktwinkel, Profiliometrie und Visuelle Mikroskopie getestet.
330

Calibration and Application of Passive Sampling in Drinking Water for Perfluoroalkyl Substances / Kalibrering och tillämpning av passiv provtagning i dricksvatten för perfluoroalkylsubstanser

Persson, Caroline January 2015 (has links)
Perfluoroalkyl substances (PFASs) are global environmental contaminants and a need for monitoring levels has arisen due to their persistency and their ability to bioaccumulate. One relatively novel method of monitoring for both long and short time intervals and generating time-weighted average (TWA) concentrations is passive sampling for which no power, maintenance and supervision is required. The polar organic compound integrative sampler (POCIS) with a weak anion exchange (WAX) sorbent and the POCIS with a hydrophilic-lipophilic balance (HLB) adsorbent were calibrated for PFASs in a laboratory uptake experiment, and applied at a drinking water treatment plant (DWTP) in Stockholm, Sweden.   In the calibration study, all of the 14 studied PFASs were taken up by both passive samplers. Two and three out of the 14 studied PFASs had reached equilibrium after 28 days using POCIS WAX (PFBA and PFTeDA) and POCIS HLB (PFBA, PFPeA and PFTeDA), respectively. The sampling rate (Rs), which is the extracted water in liters per day, ranged between 0.003 and 0.10 L day-1 for the POCIS WAX and between 0.00052 and 0.13 L day-1 for the POCIS HLB. In general, Rs increased with increasing perfluorocarbon chain-length (C4 to C8) and for a perfluorocarbon chain-length longer than C8, Rs decreased with increasing perfluorocarbon chain-length (C8 to C13) for both passive samplers. FOSA had the highest Rs-value (0.10 and 0.13 L day-1) for both POCIS WAX and POCIS HLB, respectively. The POCIS WAX had a higher uptake for the short-chained PFASs PFBA (134 ng after 28 days), PFPeA (410 ng) and PFHxA (834 ng), compared to the POCIS HLB (0.5 ng, 58 ng, and 373 ng, respectively). For all other compounds, the accumulated amounts in the POCIS HLB were in the same range as in the POCIS WAX.   The application of the passive samplers at the DWTP showed that both passive samplers could detect ultra-trace (pg to ng L-1) levels of PFASs. A comparison of the TWA concentration showed that the two passive samplers had a good linear correlation (R2 = 0.63), but the TWA concentrations derived by POCIS WAX was approximately 40% higher compared to POCIS HLB. A comparison between the passive samplers and the grab samples did not show a correlation (R2 = 0.24 for POCIS WAX and R2 = 0.10 for POCIS HLB). The application also included a comparison of the removal efficiency in the conventional DWTP and a pilot plant with additional treatments steps of granulated activated carbon (GAC) and nanofiltration (NF). For the full-scale DWTP the average removal efficiency was 32% and high removal efficiency was observed for PFBA (81%). For the pilot plant, the removal efficiency was 100% for all the detected PFASs in the raw water. / Perfluoroalkylsubstanser (PFAS) har blivit uppmärksammade som globala miljöföroreningar, och ett behov av att övervaka dessa ämnens förekomst i miljön har uppkommit på grund av hög persistens i kombination med hög förmåga att bioackumulera. En relativt ny metod för tidsintegrerad provtagning är så kallad passiv provtagning. En adsorbent placeras i fält och ackumulerar PFAS från vattnet. Tillgång till elektricitet behövs inte, och behov av övervakning och underhåll är minimalt. I denna studie kalibrerades en så kallad ’polar organic compound integrative sampler’ (POCIS) för mätning av PFAS genom upptagsexperiment med två olika adsorbenter: en svag anjons adsorbent (WAX) och en hydrofil-lipofil balanserad adsorbent (HLB). Metodiken tillämpades sedan på vatten från ett dricksvattenverk i Stockholm, Sverige.   Upptagsexperimenten utfördes med 14 PFAS och samtliga togs upp av båda adsorbenterna. Två respektive tre av de studerade PFAS uppnådde jämvikt efter 28 dagar för WAX (PFBS och PFTeDA) samt HLB (PFBA, PFPeA och PFTeDA). Upptagshastigheten (Rs), det vill säga den volym som extraheras per dag, varierade mellan 0,003 och 0,1 L dag-1 för WAX och mellan 0,00052 och 0,13 L dag-1 för HLB. Generellt ökade Rs med en ökande längd på kedjan av perfluorerade kol upp till C8, för att sedan avta med ökande kedjelängd. FOSA hade det högsta Rs-värdet (0,10 och 0,13 L dag-1) för både WAX och HLB. WAX hade ett högre upptag (upp till 134, 410 och 834 ng) för PFAS med kort perfluorerad kolkedja (PFBA, PFPeA respektive PFHxA) jämfört med HLB (upp till 0,5, 58, och 373 ng). Den ackumulerade mängden för alla andra PFAS överensstämde väl mellan de båda provtagarna.   Mätning av PFAS halter i dricksvattenverket med hjälp av POCIS WAX och POCIS HLB visade att även PFAS kunde detekteras även vid miljörelevanta halter. En jämförelse mellan de båda passiva provtagarna visade på ett linjärt samband (R2 = 0,63), men där POCIS WAX hade en tendens att överskatta koncentrationen med ca 40%. En jämförelse mellan de passiva provtagarna och traditionell uppsamlingsprovtagning visade på låg överrensstämmelse (R2 = 0.24 för POCIS WAX och 0.10 för POCIS HLB). Vid tillämpningen gjordes även en beräkning för reningseffektiviteten av PFAS i dricksvattenverket och i en pilotanläggning där ytterligare rening med granulerat aktivt kol (GAC) och nanofiltration (NF) används. I dricksvattenverket var den genomsnittliga reningen 32%, med den högsta reningseffektiviteten för PFBA (81%). I pilotanläggningen var reningen 100% för alla upptäckta PFAS i råvattnet.

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