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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.
791

Acute Modulation of Endothelial Cell Glucose Transport: A Dissertation

Cura, Anthony J. 15 October 2010 (has links)
Studies have demonstrated that under conditions of chronic metabolic stress, GLUT1-mediated sugar transport is upregulated at the blood-brain barrier by a number of mechanisms. Although acute metabolic stress has also been shown to increase GLUT1-mediated transport, the mechanisms underlying this regulation remain unclear. This work attempts to explain how GLUT1-mediated sugar uptake is increased during acute metabolic stress, as well as explore the factors involved in this modulation of sugar transport in blood-brain barrier endothelial cells. Glucose depletion, KCN and FCCP were applied to brain microvascular endothelial cell line bEnd.3 in order to induce acute metabolic stress by ATP depletion. Kinetic sugar uptake measurements in combination with qPCR, whole cell lysate western blots, and cell-surface biotinylation were employed to probe for changes in GLUT1-mediated sugar uptake, GLUT1 expression levels, and GLUT1 localization during metabolic stress. Finally, the role of AMP-activated kinase (AMPK) in the bEnd.3 cell response to acute stress was examined using the specific AMPK activator AICAR and inhibitor Compound C. The data presented in this thesis supports the following two conclusions: 1. GLUT1-mediated sugar transport in bEnd.3 cells during acute metabolic stress is increased 3-7 fold due to translocation of intracellular GLUT1 to the plasma membrane, with no change in expression of total GLUT1 protein, and 2. AMPK plays a direct role in modulating increases in GLUT1-mediated sugar transport in bEnd.3 cells during acute metabolic stress by regulating trafficking of GLUT1 to the plasma membrane.
792

Synthesis and evaluation of selectin antagonists targeting acute inflammation

Simard, Ryan 04 1900 (has links)
L’accumulation excessive de leucocytes conduisant à un dysfonctionnement de la réponse immunitaire est caractéristique de plusieurs maladies inflammatoires. La première étape du recrutement des leucocytes aux sites d’inflammation est tributaire de l’interaction entre le tétrasaccharide sialyl LewisX (sLeX) et les protéines d’adhésion sélectines P et E, qui sont exprimés sur les cellules endothéliales des parois vasculaires. Par conséquent, les sélectines sont des cibles thérapeutiques importantes. Ainsi, la conception d’antagonistes des sélectines est une stratégie prometteuse pour traiter l'inflammation aiguë. Par exemple, l’administration d’analogues du sLeX chez les patients hospitalisés souffrant de crises vaso-occlusives ou de syndrome de détresse respiratoire aiguë (SDRA) peut atténuer les enjeux d'accumulation de cellules immunitaires. Tout en se basant sur la première génération d'antagonistes des sélectines développées par notre laboratoire, l’objectif de ce travail était de synthétiser et d'évaluer l’activité biologique d’une nouvelle série d’analogues du sLeX ciblant l'inflammation aiguë. Ce travail établit deux nouvelles stratégies qui permettent d'accéder à des analogues du sLeX incorporant un motif galactopyranoside bicyclique avec une fonctionnalité carboxylate ayant une conformation restreinte. Dans la première approche, l’intermédiaire bicyclique clé est formé en 13 étapes à partir du D-galactose pentaacétate avec un rendement global de 19 %. Indépendamment de la stéréochimie des précurseurs, une réaction de cyclisation intramoléculaire a permis de générer l’intermédiaire clé avec le carboxylate en position axiale. Un contrôle cinétique Curtin-Hammett serait à l'origine de la stéréosélectivité, une hypothèse supportée par une étude expérimentale et par calculs théoriques DFT. La série des carboxylates équatoriales a également été préparée par une stratégie de désilylation basée sur la migration d'un ester β,γ-insaturé. La deuxième approche implique une stratégie de double glycosidation orthogonale qui est influencée par la conformation restreinte du bicycle. L'intermédiaire bicyclique, portant un groupement nitrile en C9 (alpha), a été préparé en 12 étapes avec un rendement global de 53 %. Cette approche a mené à une série d'antagonistes des sélectines incorporant des modifications d'amide, d'amine et de tétrazole, ainsi qu'un analogue incorporant un C6-benzamide. Cette approche modulaire peut être exploitée pour préparer d’autres isostères d'acide carboxylique. Un analogue hybride a été préparé en combinant le galactopyranoside bicyclique avec la fonctionnalisation de la chaîne latérale qui se retrouve sur l’espaceur à base de tartrate. Cette voie de synthèse a également été conçue afin d'accéder aux analogues du sLeX portant une sonde de photoaffinité. Cet analogue servira comme outil dans le marquage par photoaffinité des sélectines pour élucider les résidus clés du site actif. Les analogues de la deuxième génération ont été évalués pour leur capacité à se lier aux sélectines et d’empêcher les cellules immunitaires d’adhérer. Une méthode qualitative permettant de classer l’affinité de nos composés aux sélectines à l'aide de la spectroscopie SPR ainsi qu'une expérience préliminaire d'inhibition compétitive en solution ont été développées. Les principaux composés ont également été évalués à l'aide de tests in vitro d'adhésion de cellules HL-60 et de roulement par imagerie des cellules vivantes. Un essai de migration cellulaire par lavage péritonéal in vivo a été utilisé pour valider l’activité de nos composés principaux et leur capacité à inhiber le recrutement des neutrophiles dans un modèle d'inflammation aiguë. Nos résultats démontrent l’augmentation de la puissance et de l’activité de nos analogues de deuxième génération comparativement à la première. La série de galactopyranosides a démontré une spécificité pour l'inhibition de la P-sélectine, alors que la série des arabinopyranosides, incorporant un motif tétrazole, a démontré une activité remarquable vers la E-sélectine. La combinaison des deux modifications ont produit une activité pan-sélectines exceptionnelle qui justifie une enquête plus approfondie. / The first step for leukocyte adhesion and rolling along the vascular endothelium during the immune system inflammatory response involves the recognition of the tetrasaccharide sialyl LewisX (sLeX) by selectin glycoproteins. Dysfunction of the immune response, a consequence of several pathologies of inflammatory disease, leads to an excessive influx of leukocytes that necessitates therapeutic intervention. The development of glycomimetics, small molecule therapeutics that imitate complex glycans, is a promising strategy for treating inflammation. Specifically, a targeted approach amenable to severe acute inflammation, such as in hospitalized patients suffering from vaso-occlusive crises (VOC) or acute respiratory distress syndrome (ARDS). Building off the first generation of selectin antagonists developed by our laboratory, the aim of this work was to synthesize and evaluate the potency of a new class of sLeX glycomimetics for use as selectin antagonists targeting acute inflammation. This work describes the development of two novel strategies for sLeX glycomimetics incorporating a challenging trans-bicyclo[4.4.0] 3-O,4-C-fused galactopyranoside scaffold with a conformationally restricted carboxylate moiety. In the first approach, the key bicyclic galactopyranoside intermediate was accessed through a 13-step sequence with 19% overall yield from D-galactose pentaacetate. An unprecedented intramolecular cyclization reaction provided the desired axially configured bicyclic intermediate independent of the precursor stereochemistry. The origin of stereoselectivity was proposed to be under Curtin-Hammett kinetic control; a hypothesis supported by an experimental study and theoretical DFT calculations. The equatorial carboxylate series was also prepared using a desilylation strategy capitalizing on the migration of an β,γ-unsaturated ester. The second approach is highlighted by an orthogonal dual-glycosidation strategy that takes advantage of the conformationally restricted scaffold. The key bicyclic intermediate, bearing an α-configured C9 nitrile moiety, was prepared in 12 steps with a 53% overall yield. This approach led to a series of selectin antagonists incorporating axially-locked amide, amine, and tetrazole modifications at the C9 position, as well as an analogue incorporating a C6-benzamide. The modular galactopyranoside framework achieved using this approach can be exploited to prepare additional carboxylic acid bioisosteres for future SAR studies. A hybrid analogue was prepared, that combines the bicyclic galactopyranoside scaffold and a synthetic approach to selectin antagonists incorporating sidechain modifications to the first-generation tartrate diester. This synthetic route was also elaborated to access sLeX glycomimetics bearing a benzophenone-based photoaffinity probe. This analogue will serve as a valuable tool in the photoaffinity labeling of selectin proteins to elucidate key active site residues. The second-generation analogues were evaluated for their ability to inhibit selectin adhesion. A qualitative method to rank the binding strength towards recombinant P- and E-selectin proteins using SPR biosensor technology was developed, as well as a preliminary competitive inhibition in solution experiment with immobilized PSGL-1. Several compounds were also evaluated using an in vitro HL-60 cell adhesion assay, and a live-cell imaging experiment. An in vivo peritoneal lavage cellular migration assay was used to validate the potency of our lead compounds at inhibiting neutrophil recruitment in an acute inflammation model. Key results from the biological evaluations include an improvement in activity by restricting the conformation of the carboxylate moiety to the axial configuration, as well as an enhancement in potency over the lead compound from the first-generation series. Remarkably, specificity for P-selectin inhibition was observed with the galactopyranoside series, while the arabinopyranoside series, incorporating a tetrazole bioisostere, displayed significant activity towards E-selectin. The combination of the two modifications yielded remarkable pan-selectin activity that warrants further investigation.
793

Responses of oaks to mammal and insect herbivory

Perkovich, Cynthia L. 23 April 2021 (has links)
No description available.
794

Evaluation of the nutritional quality of feed supplements utilized by communal cattle farmers during the dry season at Ga-Matlala, Limpopo Province, South Africa

Monkwe, Thapelo Rosina January 2022 (has links)
Thesis (M.Sc. Agriculture (Animal Production)) -- University of Limpopo, 2022 / Refer to document / National Research Foundation (NRF)
795

Carbohydrates in the Arctic and the Southern Ocean – Chemical Analysis, Transfer from the Sea to the Atmosphere and Potential Relevance for Cloud Formation

Zeppenfeld, Sebastian 05 October 2022 (has links)
Primär emittierte marine Aerosolpartikel haben einen wichtigen Einfluss auf den Strahlungshaushalt der Erde, indem sie unter anderem als Kondensations (CCN)- oder Eiskeime (INP) für die Bildung von Wolken wirken. In den ozeanisch geprägten Polarregionen dominieren diese marinen Aerosolpartikel in der Luft und können dort eine bedeutende bzw. sich noch verändernde Rolle im Rahmen des Klimawandels einnehmen. Sie entspringen vordergründig aus dem ozeanische Oberflächenwasser und dem hauchdünnen Oberflächenfilm, dem sogenannte sea surface microlayer (SML), und werden durch das Platzen von durch Wind eingetragene Luftblasen freigesetzt. Primär emittierte marine Aerosolpartikel bestehen aus anorganischem Meersalz und organischen Kohlenstoffverbindungen, deren relative Anteile sich stark in Abhängigkeit vom Aerosoldurchmessers unterscheiden. In diesem Zusammenhang stellen die marinen Kohlenhydrate eine wichtige organische Stoffgruppe dar, deren ozeanische Quellen, Übergang vom Ozean in die Atmosphäre, Veränderungen in der Atmosphäre als auch deren Beitrag bei der Kondensation und Eiskeimbildung noch nicht ausreichend verstanden sind. Dieser begrenzte Kenntnisstand ist unter anderem auf das mangelnde Vorhandensein analytischer Methoden zurückzuführen, die eine zuverlässige Bestimmung von Kohlenhydraten in den stark salzhaltigen Matrices bei sehr niedrigen Massekonzentrationen mit hohen Wiederfindungsraten gewährleisten. Im Rahmen dieser Doktorarbeit wurde durch Kombination der Hochleistungs-Anionenaustauschchromatographie mit gepulster amperometrischer Detektion (HPAEC-PAD) und einer Entsalzung durch Elektrodialyse eine analytische Methode entwickelt, welche die Bestimmung eines breiten Spektrums an gelösten Kohlenhydraten in freier (als Monosaccharide) und gebundener (als Oligo- oder Polysaccharide) Form in Meerwasser und anderen salzhaltigen Matrices ermöglicht. Mithilfe dieser neuen Methode wurde ein biogeochemischer Zusammenhang zwischen dem Vorkommen von freier Glucose und der eiskeimbildenden Aktivität im arktischen SML beobachtet. Außerdem wurde im meereisfreien Teil des Südlichen Ozeans der primäre Transfer von Kohlenhydraten vom Ozean über den SML in die Atmosphäre und deren sekundäre atmosphärische Veränderungen erforscht. Die umfangreichen Untersuchungen mariner Kohlenhydrate in polarem Meerwasser und Aerosolpartikeln zeigen Indizien einer bisher noch unterschätzten atmosphärischen Bedeutung mikrobiologischer Prozesse auf.:1. Introduction ............................................................................................................................................... 1 1.1 The Polar Oceans ................................................................................................................................. 3 1.1.1 Geographical Definitions and Characteristics.......................................................................... 3 1.1.2 Role in Earth’s Climate System ................................................................................................ 5 1.1.3 Changing Climate and Consequences ...................................................................................... 6 1.2 Sea Spray Aerosol over the Polar Oceans ........................................................................................... 9 1.2.1 Production Mechanisms of Sea Spray Aerosol ........................................................................ 9 1.2.2 Chemo-Selective Sea-Air Transfer and Atmospheric Aging ................................................... 10 1.2.3 Impact on Earth’s Radiation Budget ...................................................................................... 12 1.3 The Surface of the Polar Oceans ....................................................................................................... 15 1.3.1 The Sea Surface Microlayer ................................................................................................... 15 1.3.2 Selective Enrichment of Chemical Compounds ..................................................................... 15 1.3.3 Atmospheric Relevance for Atmospheric Chemistry and Cloud Microphysics ..................... 24 1.4 Marine Carbohydrates....................................................................................................................... 26 1.4.1 Chemical Structures ............................................................................................................... 26 1.4.2 Microbial Role ........................................................................................................................ 28 1.4.3 Marine Carbohydrates in the Atmosphere ............................................................................ 30 1.4.4 Chemical Analysis and Sea Salt Interference ......................................................................... 31 2. Results and Discussions ........................................................................................................................... 35 2.1 First Publication ................................................................................................................................. 35 2.1.1 Glucose as a Potential Chemical Marker for Ice Nucleating Activity in Arctic Seawater and Melt Pond Samples ......................................................................................................................... 35 2.1.2 Supporting Information ......................................................................................................... 47 2.2 Second Publication ............................................................................................................................ 55 A protocol for quantifying mono-and polysaccharides in seawater and related saline matrices by electro-dialysis (ED) – combined with HPAEC-PAD ........................................................................ 55 2.3 Third Publication ............................................................................................................................... 70 2.3.1 Aerosol Marine Primary Carbohydrates and Atmospheric Transformation in the Western Antarctic Peninsula ......................................................................................................................... 70 2.3.2 Supporting Information ......................................................................................................... 88 3. Atmospheric Implications ........................................................................................................................ 95 4. Summary ................................................................................................................................................ 98 5. References ............................................................................................................................................. 101 List of Abbreviations .................................................................................................................................. 121 List of Figures ............................................................................................................................................. 123 List of Tables .............................................................................................................................................. 124 Curriculum Vitae ........................................................................................................................................ 125 / Primary marine aerosol particles impact Earth’s radiation budget by acting, among other things, as cloud condensation nuclei (CCN) or ice nucleating particles (INP) for the formation of clouds. Over the polar oceans, primary marine aerosol emissions dominate the atmospheric particles and can play a significant and changing role there in the context of climate change. These particles are primarily emitted from the oceanic surface water and a thin surface film, the so-called sea surface microlayer (SML), by the bursting of air bubbles entrained by the wind. They consist of inorganic sea salt and organic matter (OM), whose relative proportions differ greatly depending on the aerosol diameter. In this context, the marine carbohydrates represent an important group of OM, whose oceanic sources, their transition from the sea to the atmosphere, atmospheric aging and contribution to the condensation of water droplets and ice nucleation are not well understood. This limited level of knowledge is due, among other things, to the lack of analytical methods that enable a reliable determination of carbohydrates at very low mass concentrations with high recovery rates in the salty matrices. Within the framework of this PhD thesis, an analytical method was developed by combining high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and a prior desalination by electro-dialysis (ED), which enables the determination of a wide range of dissolved carbohydrates in their free (as monosaccharides) and combined (as oligo- or polysaccharides) forms in seawater and other saline matrices. With this new method, a biogeochemical connection between the presence of free glucose and the ice nucleating activity in the Arctic SML could be observed. In addition, the primary transfer of carbohydrates from the ocean via the SML into the atmosphere and subsequent secondary atmospheric transformations were investigated in the sea ice-free part of the Southern Ocean. Consequently, the extensive investigations of marine carbohydrates in seawater and aerosol particles indicate an atmospheric importance of microbiological processes that has been underestimated until now.:1. Introduction ............................................................................................................................................... 1 1.1 The Polar Oceans ................................................................................................................................. 3 1.1.1 Geographical Definitions and Characteristics.......................................................................... 3 1.1.2 Role in Earth’s Climate System ................................................................................................ 5 1.1.3 Changing Climate and Consequences ...................................................................................... 6 1.2 Sea Spray Aerosol over the Polar Oceans ........................................................................................... 9 1.2.1 Production Mechanisms of Sea Spray Aerosol ........................................................................ 9 1.2.2 Chemo-Selective Sea-Air Transfer and Atmospheric Aging ................................................... 10 1.2.3 Impact on Earth’s Radiation Budget ...................................................................................... 12 1.3 The Surface of the Polar Oceans ....................................................................................................... 15 1.3.1 The Sea Surface Microlayer ................................................................................................... 15 1.3.2 Selective Enrichment of Chemical Compounds ..................................................................... 15 1.3.3 Atmospheric Relevance for Atmospheric Chemistry and Cloud Microphysics ..................... 24 1.4 Marine Carbohydrates....................................................................................................................... 26 1.4.1 Chemical Structures ............................................................................................................... 26 1.4.2 Microbial Role ........................................................................................................................ 28 1.4.3 Marine Carbohydrates in the Atmosphere ............................................................................ 30 1.4.4 Chemical Analysis and Sea Salt Interference ......................................................................... 31 2. Results and Discussions ........................................................................................................................... 35 2.1 First Publication ................................................................................................................................. 35 2.1.1 Glucose as a Potential Chemical Marker for Ice Nucleating Activity in Arctic Seawater and Melt Pond Samples ......................................................................................................................... 35 2.1.2 Supporting Information ......................................................................................................... 47 2.2 Second Publication ............................................................................................................................ 55 A protocol for quantifying mono-and polysaccharides in seawater and related saline matrices by electro-dialysis (ED) – combined with HPAEC-PAD ........................................................................ 55 2.3 Third Publication ............................................................................................................................... 70 2.3.1 Aerosol Marine Primary Carbohydrates and Atmospheric Transformation in the Western Antarctic Peninsula ......................................................................................................................... 70 2.3.2 Supporting Information ......................................................................................................... 88 3. Atmospheric Implications ........................................................................................................................ 95 4. Summary ................................................................................................................................................ 98 5. References ............................................................................................................................................. 101 List of Abbreviations .................................................................................................................................. 121 List of Figures ............................................................................................................................................. 123 List of Tables .............................................................................................................................................. 124 Curriculum Vitae ........................................................................................................................................ 125
796

Is sugar as sweet to the palate asseeds are appetizing to the belly? : Taste responsiveness to seven sweet-tastingsubstances in white-faced sakis (Pithecia pithecia)

Redin Hurtado, Mikel January 2023 (has links)
Differences in taste perception between species are thought to reflect evolutionaryadaptations to dietary specializations such as seed predation. By employing a two-bottlepreference test, the purpose of the current study was to evaluate the taste responsiveness forfive food-associated carbohydrates and two steviol glycosides in four adult white-faced sakis(Pithecia pithecia). The taste preference thresholds were found to be 10 mM for sucrose, 10-40 mM for fructose, 20-30 mM for glucose and maltose, and 30-40 mM for lactose. The sakisalso showed a clear preference for rebaudioside A and stevioside over tap water atconcentrations as low as 0.04 and 0.2-0.5 mM, respectively. When given the choice betweenall binary combinations of the five carbohydrates at equimolar concentrations of 100, 200,and 300 mM, respectively, the sakis displayed the following preference pattern: sucrose >fructose > glucose ≥ maltose = lactose. The obtained taste preference thresholds for foodassociated carbohydrates fall into the lower range of values among primates, suggesting acomparatively high sweet-taste sensitivity in the sakis. The pattern of relative preferenceswas consistent with that reported in most tested primates. Altogether, the responsivenesstowards the sweet-tasting substances obtained in this seed predator resembles the resultsobtained in primates which act as seed dispersers. However, these results might reflect anevolutionary adaptation of white-faced sakis to exploit resources containing low sugarconcentrations such as unripe fruits and seeds.
797

The effect of Trinexapac Ethyl and three Nitrogen sources on creeping bentgrass (<i>Agrostis stolonifera</i>) grown under three light environments

Nangle, Edward J. 19 March 2008 (has links)
No description available.
798

Probing bacterial uptake of glycosylated ciprofloxacin conjugates

Milner, S.J., Carrick, C. ., Kerr, Kevin G., Snelling, Anna M., Thomas, G.H., Duhme-Klair, A-K., Routledge, A. January 2014 (has links)
No / Mono- and disaccharide-functionalised conjugates of the fluoroquinolone antibiotic ciprofloxacin have been synthesised and used as chemical probes of the bacterial uptake of glycosylated ciprofloxacin. Their antimicrobial activities against a panel of clinically relevant bacteria were determined: the ability of these conjugates to inhibit their target DNA gyrase and to be transported into the bacteria was assessed by using in vivo and in vitro assays. The data suggest a lack of active uptake through sugar transporters and that although the addition of monosaccharides is compatible with the inhibition of DNA gyrase, the addition of a disaccharide results in a significant decrease in antimicrobial activity.
799

Synthèse d'une nouvelle classe d'inhibiteurs potentiels d'enzymes à base de phosphore

Rogel, Olivier 10 1900 (has links)
Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal. / Les carbohydrates sont des composés importants au niveau biologique. De nombreux analogues contenant un hétéroatome autre que l'oxygène sur le cycle hémiacétallique existent dans la nature et ont fait l'objet de nombreuses synthèses dans de nombreux groupes de recherche depuis près de 40 ans. Cependant les hétéroatomes présents sur le cycle hémiacétallique sont essentiellement les atomes d'azote et de soufre et il existe peu de carbohydrates contenant la liaison carbone-phosphore. Quant aux analogues concernant le remplacement du carbone anomérique par un hétéroatome, ils sont très peu nombreux. Nous avons synthétisé un nouveau type d'analogue les phostones. Les phostones sont des analogues de carbohydrates où le carbone anomérique est remplacé par un atome de phosphore pentacovalent. Nous avons synthétisé différents analogues dans quatre projets. Notre premier projet concerne la synthèse des L-fucophostones, des analogues du L-fucose. Plusieurs oligosaccharides présents à la surface des cellules contiennent une unité L-fucose. Ces oligosaccharides sont aussi communs à de nombreux cancers dont ceux du foie, de l'ovaire et du sein. La modification de son carbone anomérique pourrait mener à une activité inhibitrice sur les enzymes concernées par le L-fucose tel que les fucosidases et les fucosyltransférases. Nous avons utilisé le L-fucose comme produit de départ afin de conserver au maximum sa stéréochimie. Quant aux N-acétyl-D-glucosaminophostone et N-acétyl-D-mannosaminophostone, elles sont des analogues des N-acétyl-D-glucosamine et N-acétyl-D-mannosamine. Ces saccharides sont des composants essentiels de nombreuses glycoprotéines. Ces glycoprotéines sont une classe de produits naturels jouant un rôle crucial dans les phénomènes de reconnaissance moléculaire. Nous avons pu effectuer pour la première fois la réaction d'Abramov sur une oxime, ce qui a généré les phosphonates cycliques avec une fonction alkoxy amine en a du phosphore. Le troisième projet concerne le phosphoramidon qui est un puissant inhibiteur d'une métalloprotéase à zinc jouant un rôle particulièrement important au niveau des cellules endothéliales, l'enzyme de conversion de l'endothéline (ECE). Cette enzyme est impliquée dans la régulation du flux sanguin et son dérèglement est reconnu comme un important facteur déclenchant dans de nombreuses maladies. L'analogue en phostone du phosphoramidon modifie la structure du phosphoramidon en incorporant la fonction phosphonamide à l'intérieur du L-rhamnose et en supprimant la fonction acide phosphonique. En dépit des progrès considérables faits dans la compréhension du mécanisme d'action et de la biologie du virus de la grippe, celui-ci continue d'être la plus importante cause de mortalité au niveau des maladies respiratoires. Le mécanisme unique de propagation du virus de la grippe a permis aux chercheurs d'identifier un certain nombre de cibles potentielles dont l'hémagglutinine et la neuraminidase, les deux glycoprotéines de surface les plus importantes impliquées dans la propagation du virus. L'activité enzymatique des neuraminidases repose sur la coupure du lien a.2,3 entre l'acide sialique et le carbohydrate auquel il est lié. Dans ce dernier projet, nous avons synthétisé les sialophostones, des analogues de l'acide sialique où l'action de l'acide carboxylique et de l'hydroxyle anomérique est remplacé par un acide phosphonique.
800

Nucleation, milk and membranes as modifications to enhance biological phosphorus removal in activated sludge

Van Lierde, Patrick G. January 2015 (has links)
Enhanced biological phosphorus removal (EBPR) was researched from the performance of a modified University of Cape Town (UCT), anaerobic-anoxic/nitrifying-aerobic process. The work focussed on high P influent where milk was compared to carbohydrates as exogenous added carbon and typical settled sewage. The results confirmed that at equal COD load in the influent (minimum COD:P (250:5) ratio for EBPR), milk always provided sufficient soluble substrate than the carbohydrate mix, but also improved the EBPR performance. The laboratory scale treated 10L/day where 2 parallel treatment trains for milk and an equivalent carbohydrate mix as supplement to compare and study the P sequestration from hypothesised P ligands in milk and easily assimilable carbon (AOM) after fermentation for biological P uptake. The aerobic bioreactors used submerged flat sheet membranes (AeMBR) to improve the effluent quality and reduce the suspended solid residues. The results suggested extra benefits from adding calcium chloride (CaCl2) (200 ml at 250 mM/day or 200 mg/L treated) to form P complexes both in the anaerobic and aerobic zones (100 ml CaCl2 250mM/zone/day). To complete P removal a calcium phosphate (CaPO4) further treatment stage (post membrane final effluent (F.E.)) was added for nucleation. The combination of, A2O-N, exogenous carbon and calcium addition improved the performance of the EBPR, and enabled the laboratory units to achieve less than the 1 mg/L P required by the EU Directive. The process was tested at higher than normal P loads (maximum 100 mg/L) (domestic wastewater influent 15 mg/L). Experiments with influent P load ≤ 50mg/L, with 1% milk as AOM were compared to the carbohydrate mix and could remove soluble P to less than 1mg/L above 97% and less than 2 mg/L more than 99% of the in the time respectively. With an influent P load of 60mg/L (maximum 100 mg/L), the soluble P in the F.E. with milk was below 5 mg/L and below 8 mg/L with carbohydrates mix. The results showed that most of the phosphorus was retained by the sludge during the anoxic-aerobic phases. The remaining phosphate in the F.E. was able to pass through AeMBR pore size (0.4 μm) and needed to be chelated by the nucleation process. The results indicated this A2O-N modifications achieved stable nutrient removal and also offered the potential for more sustainable phosphorus recovery. The EBPR without AOM was 25% less efficient compared to milk and never achieved the E.U standard of 1mg/L in final effluent. The flat sheet membrane always achieved a NTU final effluent below 1 and the TOC always greater than 90% removal or less than the EU 125 standard regardless of the feeding COD/P ratio.

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