The chemistry of copper sulfate dosing for effective algal kill was investigated in laboratory studies with Selenastrum capricornutum and Microcystis aeruginosa. The goal was to give practical information for water treatment plants operators who often must apply copper sulfate for algae control in impoundments. Research focused on the theoretical relationships involved in copper dosing, with emphasis on the applicability of these relationships to Virginia freshwater. Concentrations of alkalinity and humic acid were varied to study their effect on percentages of ionic copper available. Long-term (2 weeks) growth-rate studies were performed to study the effect of humic acid on the toxicity of ionic copper to algae. Some protection of algae from copper by humic acid was observed. As the humic acid concentration was increased, more ionic copper was complexed and, thus, was unavailable for algal kill. The only case in which humic acid was not demonstrably protective was at a low concentration (4 mg/L TOC). It is possible that in a long-term test, low humic acid levels may not protect algae, because the copper may be released from the humic acid complex. Alkalinity and the humic acid concentration (TOC) both complex ionic copper, however alkalinity appears to be more important in determining available ionic copper in freshwater. At alkalinities greater than 10 mg/L (as CaCO₃) and humic acid less than 8.0 mg/L, alkalinity predominated in determining available ionic copper. A short term (4-hour) procedure involving measurement of oxygen production by algae exposed to copper was also used to determine the effect of humic acid on ionic copper toxicity to algae. The data showed that short-term tests were best used to predict trends shown in the long-term tests. Both Selenastrum capricornutum (a green alga) and Microcystis aeruginosa (a blue-green alga) were protected from ionic copper by humic acid. Oxygen production was found to be best used to approximate toxic concentrations of a suspect compound, as opposed to being used to precisely determine toxic concentrations. / Master of Science

The object of this research was to investigate and evaluate three methods for determination of sulfate and to use the obtained information as a guide in selecting an accurate analytical method with which to conduct a complete analysis of calcium sulfate deposits. The investigation of the analytical methods revealed that the gravimetric method is most accurate for high sulfate concentrations. This method was selected for all analytical work conducted in the study of the deposited material and in the development of a sodium hydroxide-alcohol-water solution for the removal of the calcium sulfate deposits. The initial phases of the development of the sodium hydroxide-alcohol-water solution were discouraging in that the results were inconsistent and could not be reproduced. It was believed that such inconsistencies resulted, primarily, from the method of mixing the solutions, since all mixing was done by weight percentages. The method of mixing was revised, and all subsequent mixing was governed by titration of the solution in order to determine the sodium hydroxide concentration. The alcohol was added after the solution was adjusted to the desired sodium hydroxide concentration. The investigation revealed that, following the immersion period, “air drying" the material had an effect upon the behavior of the sample during the second immersion period. It was seen that the disintegration of more resistant materials could be facilitated by employing such a period for drying the material before a second immersion period. A cost study revealed that application of the proposed method for removal of calcium sulfate deposits from treatment facilities is economically sound and that the cost of application of the method is very small compared to the cost of replacement of facilities. / Master of Science

The nature of chemical reactions taking place during the titration of dilute Al solutions in the presence of either chloride or sulfate were examined by refining the apparent Al hydrolysis products assuming the presence of solution species with n (OH/Al mole ratio) equal to 1, 2, 2.5, 3 and 4. The second and third hydrolysis products for Al were refined by comparison of calculated titration patterns to those observed for 10⁻³, 10⁻⁴ and 10⁻⁵ M Al in 1 M, 0.1 M and 0.01 M KCl. A large degree of polynuclear character of Al solutions was found even at Al concentrations as low as 10⁻⁵ M. The n value and size of the polynuclear complexes are affected by Al concentration. The concentration constant, pQ₁₃ is found to be at least 17.4-17.7. It is concluded that the mononuclear Al(OH)₂ species is never significant. Use of statistical analysis of the data and graphical methods did not result in consistent data for polymer size determinations. The lower pQ values for mononuclear Al hydrolysis are explained by the structural instability of the mononuclear complexes. The bond strengths required for the bonds in the second and third hydrolysis complexes are often larger than those allowed for octahedral coordination. For that reason, the pQ values would be lower than calculated by extrapolation between the stable first and fourth hydrolysis constants. A new polynuclear complexation mechanism for Al is proposed to account for the high concentration of high n value polynuclear species in the titration refinements. The proposed linear l double chain structure has a structure consistent with boehmite and diaspore. This structure differs from the linear single chain and ring based polynuclear structures by the presence of rows of three coordinated oxygens in the bond central chain and rows of two and one coordinated oxygens along the plane edges. A rearrangement of internal charge in this structure is proposed in which part of the charge is removed from the three coordinated oxygens to result in an uncharged hydroxyl with the charge shifted to the one coordinated site neutralizing the hydroxyl. This results in a general formula for the polynuclear structure of (Al(OH)₃)_x(Al(OH)₂)₂²⁺. This structure results in a higher n value for a lower number of Al than does the other polynuclear complexation schemes and therefore explains the presence of high n value polymers in unaged Al solutions which would have required polymers of greater than a hundred Al cations. The observed presence of a second Al plateau on titration patterns with Al concentrations greater than 5 x10⁻⁵ M could not be the result of the onset of precipitation as earlier proposed. It is proposed that at a pH in the 6 to 7 range, a change of some of the one coordinated sites on the edge of the larger polynuclear and precipitant structures from water to hydroxyls results in a change in net edge charge from net positive to net negative which causes an increased rate of crystal growth due to the unlike charge between the edges and the smaller polynuclear and mononuclear complexes. The refinement of Al titration data in K₂SO₄, provide pQ values one to three pQ units lower than those obtained from equivalent KCl solutions. A catalytic mechanism is proposed in which Al polymerization is facilitated by the formation of mononuclear Al hydroxy sulfate complexes which combine together to form nonsulfate containing polynuclear complexes. The increased hydrolyzed concentration and lower ionic charge resulting from these complexes would increase the rate of polymerization in these systems. Evidence for the presence of mononuclear hydroxy sulfate complexes comes from the better fit for titration patterns in sulfate systems which would not have been observed for increased polymerization alone. / Ph. D.

The net present replacement value of all publicly and privately owned potable water pipes in the U.S. is on the order of $2.4 trillion dollars, and costs associated with deteriorating iron pipes is billions of dollars per year. Problems arising from iron corrosion include reduced lifetime of the material, scale buildup and energy loss, nonuniform corrosion and leaks, catastrophic failure, "red water," disinfectant loss and bacterial re-growth. Iron corrosion is a very complicated process and is affected by many factors. This research focused on the effect of disinfectant type, sulfate/chloride ratios, nitrate concentration, and magnesium hardness on iron corrosion. For the waters tested, chlorine better controlled red water and microbial activity in the bulk solution than chloramine. Changes in the sulfate/chloride ratio did not have a large effect on iron corrosion. High levels of nitrate increased the rate of chlorine decay as a result of free ammonia formation, and also increased the release of iron. Increased magnesium and zinc decreased the red water caused by high silicate. Microbiological activity is important in iron corrosion, and control of re-growth in water distribution systems is a major challenge for water utilities. A separate study examined the inter-relationship between iron corrosion and bacterial re-growth, with a special focus on the potential of iron pipe to serve as a source of phosphorus. Under some circumstances corroding iron and steel may serve as a source for all macronutrients necessary for bacterial re-growth including fixed carbon, fixed nitrogen and phosphorus. Conceptual models and experimental data illustrate that levels of phosphorus released from corroding iron are significant relative to that necessary to sustain high levels of biofilm bacteria. Consequently, it may be more difficult to limit re-growth on iron surfaces by limiting phosphorus in the bulk water. / Master of Science

The process of symbiotic nitrogen fixation (SNF) in legume root nodules requires the channeling and exchange of nutrients within and between the host plant cells and between the plant cells and their resident rhizobia. Using a forward genetics approach in the Medicago truncatula Tnt1 mutant population followed by whole genome sequencing, two putative sulfate transporter genes, MtSULTR3;5 and MtSULTR3;4b, were identified. To support the hypothesis that the defective putative sulfate transporter genes were the causative mutation for the mutants' phenotypes, the M. truncatula Tnt1 population was successfully reverse screened to find other mutant alleles of the genes. The F2 progeny of mutants backcrossed with wildtype R108 demonstrated co-segregation of mutant phenotypes with the mutant alleles confirming that the mutated mtsultr3;5 and mtsultr3;4b genes were the cause of defective SNF in the mutant lines mutated in the respective genes. This finding was further established for mtsultr3;4b by successful functional complementation of a mutant line defective in the gene with the wildtype copy of MtSULTR3;4b. A MtSULTR3;4b promoter-GUS expression experiment indicated MtSULTR3;4b expression in the vasculature and infected and uninfected plant cells of root nodules. MtSULTR3;4b was found to localize to the autophagosome membrane when expressed in Nicotiana benthamiana. A transcriptomics study on the mutant nodules revealed the probable impact of mutated mtsultr3;5 and mtsultr3;4b on expression of genes involved in N fixation and on other biological processes, including possible effects of the mutated genes on the transcriptional regulation of sulfate assimilation pathway in the respective mutants' nodules. The RNAseq study also demonstrated the mis-regulation of nodule zone-specific genes in mtsultr3;5 and mtsultr3;4b mutants. A PCR-based approach was used to study the transcription of MtSULTR3;5 and MtSULTR3;4b in the respective mutant lines. The study demonstrated formation of readthrough chimeric gene-Tnt1 transcripts in mtsultr3;5 mutant alleles and truncated chimeric gene-Tnt1 transcripts and aberrantly spliced transcripts or no transcripts in mtsultr3;4b mutant alleles. Gene expression analysis of all MtSULTR genes using qRT-PCR was carried out in wildtype M. truncatula R108 nodules at a time course to evaluate the MtSULTR genes for their potential involvement in the SNF process.

Les cathéters veineux centraux (CVC) sont largement utilisés pour administrer des chimiothérapies, des hémodialyses et d'autres traitements. Généralement fabriqués en polydiméthylsiloxane (PDMS), ces dispositifs médicaux présentent un risque intrinsèque d'infection en raison de la formation possible d'un biofilm, augmentant ainsi le risque de complications, également connues sous le nom d'infections sanguines associées aux cathéters centraux (CLABSI). Les revêtements polymères libérant des médicaments constituent une stratégie bien connue pour lutter contre la formation de biofilms. Toutefois, la stabilité du revêtement sur le substrat au fil du temps constitue un défi majeur. Par conséquent, ce travail vise à développer un revêtement à base de chitosane conçu pour avoir une adhérence et une stabilité maximales afin d'assurer une libération soutenue des médicaments et des propriétés antibactériennes au fil du temps. Un revêtement composé de chitosane (CS) comme vecteur de médicament, d'acide caféique (CA) et de sulfate de cuivre (Cu) comme réticulants, et de moxifloxacine (Mox) comme antibiotique, a été déposé par un processus de coulée et de revêtement par immersion sur une surface de PDMS fonctionnalisée. Un facteur crucial pour la stabilité du revêtement est l'environnement dans lequel il sera implanté. À notre connaissance, l'étude de la stabilité du revêtement sous écoulement (c'est-à-dire sous contrainte de cisaillement) et en présence d'un milieu pseudo-physiologique qui imite le plasma humain dans de telles conditions n'a pas encore été abordée dans la littérature. Les résultats ont montré que le chitosane sans la présence de réticulants (formulation de contrôle) n'est pas en mesure d'assurer une libération contrôlée et une activité antibactérienne prolongée contre *E. coli* et *S. aureus*. En revanche, la formulation optimisée a pu démontrer une activité antibactérienne pendant 21 jours, sans toxicité pour les fibroblastes dermiques humains, et a montré une plus grande force d'adhésion que la formulation de contrôle. En comparant la formulation de contrôle à la formulation optimisée, il est évident qu'en optimisant l'enrobage à base de chitosane, sa stabilité dans le temps a également été optimisée par rapport à la formulation de contrôle. Ces résultats encouragent donc l'application de la technologie développée ici pour produire des revêtements antibactériens à base de chitosane pour les CVC en PDMS afin de lutter contre les infections nosocomiales à répétition, ainsi qu'une méthode originale développée pour vérifier la stabilité des revêtements *in vitro*, reproduisant certaines des conditions soumis *in vivo*. / Central venous catheters (CVCs) are largely used to administer chemotherapy, hemodialysis, and other treatments. Mostly made of polydimethylsiloxane (PDMS), these medical devices present an intrinsic risk of infection due to the possible formation of biofilm, thus increasing the risk of complications, also known as Central line-associated bloodstream infection (CLABSI). Drug-releasing polymer coatings are a well-recognized strategy for combating biofilm formation. However, the coating's stability on the substrate throughout time is a major challenge. Therefore, this work aims to develop a chitosan-based coating designed to have maximum adhesion and stability to ensure sustained drug release and antibacterial properties over time. A coating composed of chitosan (CS) as a drug carrier, caffeic acid (CA) and copper sulphate (Cu) as crosslinkers, and moxifloxacin (Mox) as an antibiotic, was deposited through a casting and dip-coating process onto functionalized PDMS surface. A crucial factor for the stability of the coating is the environment in which it will be implanted. As far as we know, the study of coating stability under flow (i.e. shear stress) and in the presence of a pseudo-physiological medium that mimics human plasma under such conditions has not yet been addressed in the literature. The results showed that chitosan without the presence of crosslinkers (control formulation) is not able to provide controlled release and prolonged antibacterial activity against *E. coli* and *S. aureus*. On the other hand, the optimized formulation was able to demonstrate antibacterial activity for up to 21 days, without demonstrating toxicity to human dermal fibroblasts and showed greater adhesion strength than the control formulation. By comparing the control formulation with the optimized formulation, it was evident that the later had increased stability over time. Thus, these results encourage the application of the technology developed here to produce antibacterial coatings based on chitosan for CVCs made of PDMS to control CLABSI, as well as an original method developed for checking the stability of coatings *in vitro*, mimicking some of the conditions reported *in vivo*.

En Europe de l’Ouest, S est devenu un élément limitant pour la croissance des plantes. Ainsi, des carences en S apparaissent de plus en plus fréquemment sur des cultures tel que le colza. Dans le sol, 95% de S est sous formes organiques, non disponibles pour les plantes. L’intervention de la microflore est indispensable pour assurer la minéralisation du S organique en sulfates, assimilables par la plante. Nos objectifs ont été de caractériser la communauté fongique impliquée dans la minéralisation des esters de S, forme majoritaire de S organique, via une activité arylsulfatase (ARS), dans les rhizosphères de colza et d’orge. La communauté fongique est composée de plusieurs genres affiliés principalement aux Ascomycètes. Chez les souches fongiques isolées de la rhizosphère de colza et d’orge, une activité ARS a été détectée dans différents compartiments cellulaires. La régulation de ces activités ARS semble dépendante du taxon considéré. Nous avons par ailleurs montré que l’environnement rhizosphérique n’influence pas toujours la taille de la communauté fongique ARS. Dans les sols, si les activités ARS totale et intracellulaire semblent négativement corrélées avec les quantités de sulfates, l’activité ARS extracellulaire semble indépendante de la disponibilité en sulfates. En conclusion, l’ensemble des expérimentations suggère que la communauté fongique fonctionnelle joue un rôle dans la dynamique du S dans les sols agricoles. Des approches d’écologie fonctionnelle permettraient de mieux cerner leur implication dans la disponibilité en S minéral pour la plante / In Western Europe, sulfur (S) deficiency occurs in certain crops, including crucifers and cereals. Therefore, S becomes limiting for crop production and plants exhaust S mainly from soil organic S. In soil, 95% of S is in organic form that is not readily available for plants. This organic form containing principally ester S requires microbial mineralization to sulfate by arylsulfatase (ARS) enzyme. Our objectives were to characterize the fungal community having the ARS activity in the rhizosphere of rape versus that of barley. Functional fungal community comprised several genera principally belonging to Ascomycota. In different fungal strains, ARS activity was detected in different cellular compartments. The regulation of ARS was mostly dependent on microbial taxa. The density of the functional fungal community was not influenced by rhizospheric compartment.In soils, total and intracellular ARS activities were negatively correlated with soil sulfates whereas soil extracellular ARS activity was independent of sulfates. The overall results suggest that the functional fungal community could play a role in the dynamics of S in agricultural soils. Further approaches should be developed to allow a better understanding of their potential involvement in S nutrition of crops

En accordance avec son haut prévalence dans le monde, parmi tous les cas de démence, la maladie d'Alzheimer (MA) est considérée comme la principal pathologie affectant les personnes plus âgées que 65 ans. Depuis son première description en 1907, de la recherche important et des observations innovants ont été faites concernant des aspects histopathologiques et moléculaires la neurodégénération associée à la maladie. Cependant, les mécanismes moléculaires de la pathogenèse et de la progression de la MA restent toujours partiellement compris. Outre, des stratégies thérapeutiques efficaces soit pour la prévention, soit pour l'arrêt de la progression de la maladie ne sont pas encore développées. Il semble donc crucial le développement de la recherche dans des domaines émergeants, nés à partir des concepts innovants et basés sur des approches mécanistiques novateurs à fin de découvrir des aspects dans la physiopathologie de la neurodégénérescence qui puissent conduire à des stratégies thérapeutiques pour soigner ces maladies.Les études présentées ici sont centrées dans le rôle des héparanes sulfates (HS), un membre particulier de la famille des glycosaminoglycannes, dans la physiopathologie des troubles neurodégénératifs, tels que la MA et démences associées, nommées taupathies. Ce travail de recherche, basé sur plusieurs observations isolées suggérant une association entre la pathologie de tau caractéristique des taupathies et les HS, explore par des moyens de études moléculaires, cellulaires et animaux les implications pathologiques de telle interaction. Comme résultat, je montre ici des évidences suggérant une participation clé des HS dans les évènements pathologiques de tau, tels que la phosphorylation anormale, la formation des inclusions intracellulaires, et la propagation des amas de tau.Globalement, le travail présenté ici dévoile une implication importante des HS hautement sulfatés dans la pathologie de tau associée à la MA, et au même temps ouvre une gamme de voies de recherche novatrices pour approfondir dans la caractérisation de l'interaction tau/HS et ses consequences physiopathologiques. De plus, ceci suggère des cibles pharmacologiques alternatives qui puisèrent donner d'espoir pour trouver un traitement effectif pour la MA. / According to its higher prevalence worldwide among all dementia cases, Alzheimer's disease (AD) is placed as the first pathology affecting people aged of more than 65 years old. Since it first description in 1907, profound research and groundbreaking observations have been made concerning the histopathological and molecular aspects of its associated neurodegeneration. However, the molecular mechanisms of AD pathogenesis and progression remain still poorly understood. In addition, an efficient therapeutic approach to either prevent or stop the disease progression has not yet been developed. It becomes hence crucial to develop research in emerging areas raising from groundbreaking concepts and supported by new mechanistic approaches in order to unveil novel aspects of the physiopathology of neurodegeneration and therefore design new therapeutic approaches to treat these pathologies.The present study is focused on the role of heparan sulfate (HS), a particular member of the glycosaminoglycan family, in the physiopathology of neurodegenerative disorders, such as AD and related dementias, termed tauopathies. Based on numerous separate observations suggesting an association between tau pathology characteristic of tauopathies and HS, this research explores the pathological implications of such interaction by the means of molecular, cellular, and animal studies. As a result, I hereby present evidence suggesting a crucial involvement of HS in tau pathological events, such as abnormal phosphorylation, inclusion formation, and assembly propagation.Globally, the present work unveils a strong implication of highly sulfated HS in tau pathology associated to AD and related tauopathies, and opens a wide array of novel research pathways to deepen into the characterization of tau /HS interplay and its pathophysiologic consequences. In addition, it suggests alternative pharmacological targets that could bring some hope in finding an effective treatment for AD.

O presente trabalho tem por objetivo investigar e propor uma metodologia rápida e eficaz de avaliação da reatividade do cimento Portland frente ao ataque por sulfatos. O método consiste na utilização de amostras de pasta de cimento hidratada em pó, colocadas em contato direto com soluções concentradas de Na2SO4 e MgSO4, em temperatura elevada (65ºC), para acelerar o ataque. Apesar dos cimentos estudados possuírem composição química parecida, os resultados de SO3 combinado mostraram que o cimento Classe G foi pouco menos suscetível ao ataque por sulfatos em função do maior teor de Fe2O3 presente. Da TG e DRX observou-se a formação de etringita no ataque por ambos os sais de sulfato; e formação de gipsita no ataque por MgSO4. Enquanto havia disponibilidade de portlandita na pasta hidratada, o cimento com adição mineral incorporada apresentou mesma taxa de ataque que os demais (sem adição), entretanto a partir do momento que toda a portlandita foi consumida, iniciou-se um processo de descalcificação do C-S-H, observado pela DRX. / The main point of this research is to propose a fast and effective method of evaluation of the cement reactivity to sulfate attack. Resistance to sulfate attack was measured by determining the combined sulfate in cement paste samples with exposure to Na2SO4 and MgSO4 solution, at high temperature (65°C). The samples of cement paste was triturated (powdered) in the proposed method. The results of combined SO3 showed that the Class G cement was little less susceptible to the sulfate attack because it has larger amount of Fe2O3. The ettringite formation was observed in the attack for both sulfate salts; and gypsum formation in the attack for MgSO4 (results of TG and XRD). The blended cement presented same results that the others, however when the Ca(OH)2 was totally consumed, it observed the decalcification of the C-S-H, by XRD.

Les protéines solubles sont généralement faiblement immunogènes, ce qui constitue unelimite pour le développement de vaccins sous unitaires à base de protéines. Mes travaux de thèseont eu pour objectif de décrypter certains mécanismes moléculaires et cellulaires qui contribuent àl’immunogénicité et d’en tirer partie pour développer des approches originales permettantd’améliorer la capacité des protéines à déclencher la réponse immunitaire. Pour cela, j’aiprincipalement utilisé le transactivateur transcriptionnel (Tat) du VIH-1. J’ai montré quel’oligomérisation de Tat permet à un mécanisme de collaboration B-TH-2 d’induire la réponseimmunitaire en absence d’adjuvant. J’ai identifié le déterminant minimal responsable de l’effet etmontré qu’il confère la propriété adjuvante à d’autres antigènes. J’ai ensuite montré que laprésentation aux cellules T restreinte aux CMH I et CMH II est accrue lorsque les protéines sontdotées de la capacité à lier des sucres sulfatés d’expression ubiquitaire: les héparanes sulfate. Cestravaux ont permis de définir de nouvelles approches pour améliorer l’immunogénicité de protéinessusceptibles d’être intégrées dans des préparations vaccinales. / Soluble proteins are usually poorly immunogenic, which is a limit to the development ofsubunit vaccines based on proteins. My thesis work aimed to decipher some molecular and cellularmechanisms that contribute to the immunogenicity and to exploit them to develop innovativeapproaches to improve the ability of proteins to trigger the immune response. For this purpose, Imainly used the transcriptional transactivator (Tat) of HIV-1. I showed that the oligomerization of Tatenables a B-TH-2 collaborative mechanism to induce the immune response in the absence ofadjuvant. I identified the minimum region determining the effect and showed that it confers the selfadjuvantingproperty to other antigens. In the second part of my work, I showed that the MHC I andMHC II restricted presentation to T cells is increased when the proteins are endowed with the abilityto bind ubiquitous sulfated polysaccharides: heparan sulfates. This work helped to define newapproaches to improve the immunogenicity of proteins that are likely to be included in vaccinepreparations.