• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 142
  • 59
  • 24
  • 17
  • 16
  • 11
  • 5
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • Tagged with
  • 336
  • 124
  • 83
  • 68
  • 63
  • 44
  • 38
  • 38
  • 29
  • 24
  • 22
  • 21
  • 20
  • 20
  • 18
  • 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.
121

Effect of charge-modifying coatings on the antibacterial effect of silver nanoparticles for Escherichia coli

Martín Pardo, Reinaldo Román 09 1900 (has links)
L'émergence de bactéries multirésistantes dues à une utilisation abusive d'antibiotiques est devenue l'une des menaces les plus dangereuses pour la santé publique. Le développement de nouveaux médicaments et la recherche d'agents antibactériens non traditionnels ont conduit à la nanotechnologie en tant que solution potentielle à ce problème. Les nanoparticules d'argent (NPs d’Ag) sont largement connues pour leur effet antibactérien. Cette étude vise à synthétiser des NPs d’Ag avec différents revêtements et à relier leurs propriétés physico-chimiques à leurs activités biocides, en mettant l'accent sur la façon dont leur charge de surface (estimée par leur potentiel zêta) affecte leurs efficacités antibactériennes et anti-biofilm. Les NPs d’Ag ont été synthétisées en utilisant du citrate comme agent de stabilisation et du polyvinylpyrrolidone, du polyéthylène glycol, de la chitosane et du polyéthylèneimine comme revêtements. La Spectroscopie de Masse à Plasma Inductif de Particule Unique, la Diffusion de Lumière Dynamique et les mesures de potentiel zêta ont été utilisées pour caractériser les NPs d’Ag préparées. La caractérisation des formulations de nanoparticules a montré qu'elles avaient des diamètres similaires d'environ 10 nm et des charges allant de -46 mV à 16 mV. Les comptages de plaques d'agar et les tests de micro dilution ont montré que les NPs d’Ag synthétisées étaient très efficaces pour empêcher la croissance des cellules bactériennes Escherichia coli. Des biofilms d'E. coli ont été cultivés et exposés aux NPs d’Ag, puis vérifiés à l'aide d'une microscopie à balayage laser confocal montrant que les formulations de NP avec un potentiel zêta négatif avaient plus d'activité anti-biofilm que les NP chargées neutres ou positives. / The emergence of multidrug resistant bacteria due to the misuse of antibiotics has become one of the most dangerous threats to public health. Development of new drugs and the search for non-traditional antibacterial agents have led to nanotechnology as a potential solution to this problem. Silver nanoparticles (Ag NPs) are widely known for their antibacterial effect. This study aims to synthesize Ag NPs with different coatings and relate their physicochemical properties with their biocidal activities, with special emphasis on how their surface charge (estimated via their zeta potential) affects their antibacterial and antibiofilm efficacies. Ag NPs were synthesized using citrate as a stabilizing agent and polyvinyl pyrrolidone, polyethylene glycol, chitosan and polyethyleneimine were used as coatings. Single Particle Inductively Coupled Plasma Mass Spectroscopy, Dynamic Light Scattering, and zeta potential measurements were used to characterize the prepared Ag NPs. Characterization of the nanoparticle formulations showed that they had similar diameters of around 10 nm and charges ranging from -46 mV to 16 mV. Agar Plate Counts and microdilution assays showed that the synthesized Ag NPs were very effective in preventing growth of Escherichia coli bacterial cells. E. coli biofilms were grown and exposed to the Ag NPs and checked afterwards with a confocal laser scanning microscopy showing that NP formulations with a negative zeta potential had more anti-biofilm activity than neutral or positive charged NPs.
122

Evaluation of Dissolved Air Flotation for Water Purification: With Focus on Floc Characteristics and PFAS / Utvärdering av Flotationprocess för Vattenrening: Med Fokus på Flockkaraktär och PFAS

Löf, Ludwig January 2021 (has links)
I detta projekt har experiment utförts med mål att förse kommunalförbundet Norrvatten med data som kan användas som underlag för beslutsfattande angående om deras fällningslinjer i vattenreningsprocessen ska köras i flotation eller sedimentering. För detta ändamål har koncentrationen av poly- och perfluorerade alkylsubstanser (PFAS) samt karaktär av agglomererade partiklar (flockar) undersökts och jämförts mellan fällningslinjer som körs i olika konfigurationer. För flockkaraktär har skapandet och stabiliteten av flockar varit av intresse, eftersom flotation har ett mer turbulent flöde där flockarna riskerar att brista. Partikelstorlek, storleksfördelning och zeta potential identifierades som egenskaper som reflekterar flockarnas karaktär, dessa analyserades i en zetasizer. Koncentrationen av elva vanligt förekommande PFAS ämnen analyserades i projektet. Resultatet av flockkaraktär tyder på att det ej fanns någon större skillnad i skapandet av flockar samt deras stabilitet mellan de olika fällningslinjerna som undersökts. Detta eftersom zeta potentialen var identisk (-6.45 mV) för de analyserade proverna från respektive process. Analyserna och provberedningen bedömdes ha en hög mätosäkerhet, och några förbättringar som föreslås för att öka säkerheten är genomförande av komplementerande fotoanalys för att bekräfta likheter i utseende mellan flockar, samt att genomföra mer analyser så att en statistisk giltighet av analysen kan kvantifieras. För PFAS koncentrationen så var koncentrationen av PFAS lägre i utgående vatten från fällningslinje som körs i sedimentation (7.5 ng/l), jämfört med prov från linje som körs i flotation (9.2 ng/l). För fällningslinjen som kördes i flotation så skapades skum med höga koncentrationer av PFAS (3800 ng/l) jämfört med analyserade vattenprover (5.5–9.2 ng/l), detta identifierades som en potentiell källa för PFAS-avlägsning. Resultaten av PFAS baserades endast på en provtagningsserie, och förbättringar av validitet kan åstadkommas genom samling av mer analysdata för samma processer, och genom att analysera ett av proverna i två olika instrument, som båda analyserar PFAS koncentration. / In this project, attempts have been made to collect data that allows the municipal association Norrvatten in the decision-making process on the  flotation/ sedimentation step of their water treatment process. In this sense, poly- and perfluorinated alkyl substances (PFAS) concentration and the characteristics of agglomerated particles (flocs) have been investigated and compared between the two modes that the process can be operated. For the floc characteristics, the creation and stability of the flocs were investigated, and the particle size, size distribution and zeta potential was identified as important properties and thereafter analysed using the instrument zetasizer. The concentration of eleven different PFAS compounds were analysed. The results of floc characteristics show that there is no major difference in creation and breakage of flocs in the two investigated modes, since the analysed samples had the same zeta potential, -6.45 mV. The results were deemed uncertain because of varying results, and improvement suggestions include using photoanalysis to confirm similar floc appearances and to produce more data so a statistical validity can be quantified. As for the PFAS concentration, the concentration of PFAS were slightly lower in the treatment step in which sedimentation was utilized (7.5 ng/l) compared to when flotation was utilized (9.2 ng/l). The flotation mode did, however, create foam with a high PFAS concentration (3800 ng/l) compared to the liquid samples (5.5-9.2 ng/l), so a potential PFAS removal source was identified. The results were based on one sample series, so improvements of validity can be achieved by gathering more data, analysing more samples, and analysing the same sample in two different instruments measuring PFAS concentrations.
123

Laboratory-scale evaluation of different aspects related to Ceratium hirundinella removal during simulation of a conventional water treatment plant which includes sedimentation / Hendrik Ewerts

Ewerts, Hendrik January 2015 (has links)
The freshwater dinoflagellate species, Ceratium hirundinella (C. hirundinella) possesses unique characteristics, such as a thecal-plate cell covering of cellulose, spines and flagella. Unlike most other algae and cyanobacteria, C. hirundinella cells are relatively large in size (up to 450 μm in length and 50 μm in width). These unique characteristics (e.g. cell covering and flagella) and adaptations (e.g. spines) give the dinoflagellate cells the ability to reduce their sinking rate from the euphotic zone and to migrate easily through the water column. When source water contains high concentrations of C. hirundinella cells, water treatment problems and poor aesthetic water quality can be expected. These water treatment problems may include 1) the disruption of coagulation and flocculation, 2) clogging of sand filters and 3) taste and odour problems when cells penetrate into the final water. In Chapter 9 of this study, a list of operational guidelines (including alert levels) and recommendations to assist managers and operators of plants when C. hirundinella cells are causing water treatment problems. During events of high C. hirundinella concentrations in source water, managers and operators of conventional water treatment plants need strategies to optimize coagulants and unit processes. Thus when source water contains motile nuisance algae, such as C. hirundinella, in moderate or abundant quantities, it is advisable to conduct jar stirring test experiments using both turbidity and total photosynthetic pigment (or chlorophyll-a) analyses as indicators of appropriate coagulant choice and dosages. The aims of this study are summarized as follows:  To optimize coagulants and conventional water treatment processes by implementing relevant algal removal strategies and indicators during jar stirring test experiments,  To investigate the changes in surface charge (known as zeta potential) on C. hirundinella cells before and after adding coagulants as part of the treatment processes,  To investigate the physical and chemical impacts on the morphology of C. hirundinella cells after coagulation, flocculation and sedimentation,  To identify organic compounds that may be responsible for taste and odour problems associated with C. hirundinella,  To investigate the efficiency of pre-chlorination on the removal C. hirundinella cells when dosing various coagulants, and  Give recommendations and operational guidelines relevant for a conventional water treatment plant to improve C. hirundinella removal A combined water treatment system (Phipps and Bird Model), consisting of a six paddle jar test apparatus and six sand filter columns, was used to simulate conventional processes (coagulation, flocculation, sedimentation and rapid sand filtration). Source water samples containing relatively high C. hirundinella concentrations (> 500 cell/mℓ) were collected from Benoni Lake (26º10’50.40’’S; 28º17’50.11’’ E) in plastic containers and stored as a homogenous sample in a 200 litre container under laboratory conditions (± 22 °C). Samples were collected from the source water as well as after sedimentation (from the supernatant or sludge) to determine turbidity, total photosynthetic pigment analyses (chlorophyll) and for phytoplankton analyses. Flocs (containing C. hirundinella cells) were collected from the sludge or sediment for scanning electron microscopy investigations and to perform zeta potential analyses. Concentrated C. hirundinella samples were frozen at -80 °C according to the proposed sampling protocol for organic compound analyses. Results obtained from this study proved that using the relevant indicators to determine the appropriate coagulant dosages during jar stirring tests may generally improve the removal of problem-causing algae, such as C. hirundinella cells. Improved algal removal efficiencies will subsequently ensure final water with good aesthetic quality. The surface charge (zeta potential) on C. hirundinella cells can be used to evaluate the best coagulation conditions within an operating window of -10 mV to +3 mV when dosing various coagulants. Scanning electron microscopy investigations revealed major damaging effects to C. hirundinella cells when dosing high Ca(OH)2 concentrations. However, when dosing lower Ca(OH)2 concentrations, in combination with organic polymer, better C. hirundinella cell removal efficiencies with less damaging effects to cells was observed. This study also indicated that the pre-chlorination, without causing cell lyses, can be applied to render the highly motile cells immobile which will subsequently assist the coagulation unit process. The aesthetic quality (e.g. tastes and odours) of drinking water may be influenced when C. hirundinella cells release organic material into the water as a result of cell lyses. Organic compounds, such as fatty acids and dicarboxylic acids can lead to taste and odour problems which associate with the presence of C. hirundinella. Organic compounds also serve as precursors for the formation of harmful chlorine by-products formed during chlorination. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
124

Laboratory-scale evaluation of different aspects related to Ceratium hirundinella removal during simulation of a conventional water treatment plant which includes sedimentation / Hendrik Ewerts

Ewerts, Hendrik January 2015 (has links)
The freshwater dinoflagellate species, Ceratium hirundinella (C. hirundinella) possesses unique characteristics, such as a thecal-plate cell covering of cellulose, spines and flagella. Unlike most other algae and cyanobacteria, C. hirundinella cells are relatively large in size (up to 450 μm in length and 50 μm in width). These unique characteristics (e.g. cell covering and flagella) and adaptations (e.g. spines) give the dinoflagellate cells the ability to reduce their sinking rate from the euphotic zone and to migrate easily through the water column. When source water contains high concentrations of C. hirundinella cells, water treatment problems and poor aesthetic water quality can be expected. These water treatment problems may include 1) the disruption of coagulation and flocculation, 2) clogging of sand filters and 3) taste and odour problems when cells penetrate into the final water. In Chapter 9 of this study, a list of operational guidelines (including alert levels) and recommendations to assist managers and operators of plants when C. hirundinella cells are causing water treatment problems. During events of high C. hirundinella concentrations in source water, managers and operators of conventional water treatment plants need strategies to optimize coagulants and unit processes. Thus when source water contains motile nuisance algae, such as C. hirundinella, in moderate or abundant quantities, it is advisable to conduct jar stirring test experiments using both turbidity and total photosynthetic pigment (or chlorophyll-a) analyses as indicators of appropriate coagulant choice and dosages. The aims of this study are summarized as follows:  To optimize coagulants and conventional water treatment processes by implementing relevant algal removal strategies and indicators during jar stirring test experiments,  To investigate the changes in surface charge (known as zeta potential) on C. hirundinella cells before and after adding coagulants as part of the treatment processes,  To investigate the physical and chemical impacts on the morphology of C. hirundinella cells after coagulation, flocculation and sedimentation,  To identify organic compounds that may be responsible for taste and odour problems associated with C. hirundinella,  To investigate the efficiency of pre-chlorination on the removal C. hirundinella cells when dosing various coagulants, and  Give recommendations and operational guidelines relevant for a conventional water treatment plant to improve C. hirundinella removal A combined water treatment system (Phipps and Bird Model), consisting of a six paddle jar test apparatus and six sand filter columns, was used to simulate conventional processes (coagulation, flocculation, sedimentation and rapid sand filtration). Source water samples containing relatively high C. hirundinella concentrations (> 500 cell/mℓ) were collected from Benoni Lake (26º10’50.40’’S; 28º17’50.11’’ E) in plastic containers and stored as a homogenous sample in a 200 litre container under laboratory conditions (± 22 °C). Samples were collected from the source water as well as after sedimentation (from the supernatant or sludge) to determine turbidity, total photosynthetic pigment analyses (chlorophyll) and for phytoplankton analyses. Flocs (containing C. hirundinella cells) were collected from the sludge or sediment for scanning electron microscopy investigations and to perform zeta potential analyses. Concentrated C. hirundinella samples were frozen at -80 °C according to the proposed sampling protocol for organic compound analyses. Results obtained from this study proved that using the relevant indicators to determine the appropriate coagulant dosages during jar stirring tests may generally improve the removal of problem-causing algae, such as C. hirundinella cells. Improved algal removal efficiencies will subsequently ensure final water with good aesthetic quality. The surface charge (zeta potential) on C. hirundinella cells can be used to evaluate the best coagulation conditions within an operating window of -10 mV to +3 mV when dosing various coagulants. Scanning electron microscopy investigations revealed major damaging effects to C. hirundinella cells when dosing high Ca(OH)2 concentrations. However, when dosing lower Ca(OH)2 concentrations, in combination with organic polymer, better C. hirundinella cell removal efficiencies with less damaging effects to cells was observed. This study also indicated that the pre-chlorination, without causing cell lyses, can be applied to render the highly motile cells immobile which will subsequently assist the coagulation unit process. The aesthetic quality (e.g. tastes and odours) of drinking water may be influenced when C. hirundinella cells release organic material into the water as a result of cell lyses. Organic compounds, such as fatty acids and dicarboxylic acids can lead to taste and odour problems which associate with the presence of C. hirundinella. Organic compounds also serve as precursors for the formation of harmful chlorine by-products formed during chlorination. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
125

Three topics in algebraic curves over finite fields / Três tópicos em curvas algébricas sobre corpos finitos

Coutinho, Mariana de Almeida Nery 14 March 2019 (has links)
In the present work is presented a brief data collection about the history of prime numbers and how this subject is shown in the new scenario brought by BNCC (Common Curricular National Base) . It was proved the Fundamental Arithmetic Theorem and it was presented two important ways to calculate that are the Congruence and the Fermet Theorem. It is given a teaching method and a differentiated material to be used in class. / Neste trabalho é apresentado um breve levantamento da história dos números primos e de que maneira o assunto acerca desses números aparecem no novo cenário trazido pela BNCC. Provamos o Teorema Fundamental da Aritmética e apresentamos duas ferramentas importantes de cálculo, que são as Congruências e o Pequeno Teorema de Fermat. Apresentamos ainda uma proposta didática e um material diferenciado para ser utilizado em sala de aula.
126

Généralisations du critère d’indépendance linéaire de Nesterenko / Generalisations of Nesterenko's linear independence criterion

Dauguet, Simon 10 June 2014 (has links)
Cette thèse s'inscrit dans le prolongement du résultat d'Apéry donnant l'irrationalité de ζ (3) et de celui de Ball-Rivoal prouvant qu'il existe une infinité d'entiers impairs en lesquels la fonction zêta de Riemann prend des valeurs irrationnelles. Un outil crucial dans la démonstration de Ball-Rivoal est le critère d'indépendance linéaire de Nesterenko, qui a été généralisé par Fischler et Zudilin pour exploiter sous des hypothèses très restrictives la présence de diviseurs communs aux coefficients des formes linéaires. Une généralisation ultérieure due à Fischler s'applique lorsqu'on dispose d'approximations simultanées des nombres réels en question (et non plus de combinaisons Z-linéaires petites de ces nombres).Dans cette thèse, on améliore ce dernier résultat en affaiblissant considérablement les hypothèses sur les diviseurs. On démontre aussi un critère d'indépendance linéaire analogue, dans l'esprit de celui de Siegel. Dans une autre partie en commun avec Zudilin, on construit, en utilisant des identités hypergéométriques, des approximations simultanées de ζ (2) et ζ (3) qui permettent de démontrer en même temps l'irrationalité de ces deux nombres. En appliquant essentiellement le critère démontré précédemment, on en déduit une minoration des combinaisons Z-linéaires de 1, ζ 2) et ζ (3), sous des hypothèses de divisibilité très fortes sur les coefficients (si bien que l'indépendance linéaire sur Q de ces trois nombres est toujours conjecturale). / This Ph.D. thesis lies in the path opened by Apéry who proved the irrationality of ζ(3) andalready followed by Ball-Rivoal who proved that there are infinitely many odd integers at which Riemann zeta function takes irrational values. A fundamental tool in the proof of Ball-Rivoal is Nesterenko’s linear independence criterion. This criterion has been generalized by Fischler and Zudilin to use common divisors of the coefficients of linear forms, under some restrictive assumptions. Then Fischler gave another generalization for simultaneous approximations (instead of small Z-linear combinations).In this Ph.D. thesis, we improve this last result by greatly weakening the assumption on thedivisors. We prove also an analogous linear independence criterion in the spirit of Siegel. Inanother part joint with Zudilin, we construct simultaneous linear approximations to ζ(2) and ζ(3) using hypergeometric identitites. These linear approximations allow one to prove at thesame time the irrationality of ζ(2) and that of ζ(3). Then, using a criterion from the previouspart, we deduce a lower bound on Z-linear combinations of 1, ζ(2) and ζ(3), under somestrong divisibility hypotheses on the coefficients (so that the Q-linear independence of thesethree numbers still remains an open problem).
127

O efeito do cimento composto de sulfato de cálcio e beta fosfato tricálcico com controle de potencial zeta sobre o reparo de defeitos ósseos críticos em calvária de ratos / The effect of calcium sulfate and beta-tricalcium phosphate composite with zeta potential control on the healing process of bone critical defects in rats

Daniel Falbo Martins de Souza 02 July 2015 (has links)
Nos defeitos bucomaxilofaciais, a intervenção cirúrgica utilizando enxertos ou substi-tutos ósseos é indicada para reestabelecer a forma e a função perdidas. Nesse con-texto, enxertos auto?genos e alo?genos te?m sido substituídos por biomateriais osteo-condutores e reabsorvíveis. O objetivo deste trabalho foi avaliar por meio de micro-tomografia e dos aspectos histológicos do reparo ósseo, se um novo cimento bifási-co composto por sulfato de cálcio e beta fosfato tricálcico com controle de potencial zeta, poderia induzir ou conduzir a neoformação óssea em defeitos críticos, produzi-dos em calvárias de ratos. Foi realizado um defeito crítico de 8mm de diâmetro na calvária de 40 ratos Wistar machos. No grupo teste (n=20) os defeitos foram preen-chidos pelo cimento. No grupo controle (n=20) os defeitos não foram preenchidos e permaneceram apenas com o coágulo. Os animais sofreram eutanásia em 7, 14, 21 e 42 dias do pós operatório. Espécimes da região da ferida foram microtomografa-dos e posteriormente as amostras foram preparadas para análise histológica. A aná-lise histomorfológica incluiu a avaliação morfológica da histopatologia do reparo, a avaliação morfométrica da área de formação das trabéculas ósseas comparativa-mente entre os grupos. Realizamos ainda a coloração com fosfatase tartrato-resistente (TRAP) para identificação de osteoclastos. Os resultados mostraram que os defeitos preenchidos pelo cimento não apresentaram diminuição significativa da área de acordo com a progressão dos períodos pós-operatórios, pelo contrário, em alguns animais, o defeito aparentemente aumentou. A histomorfologia do reparo mostrou agrupamentos mais expressivos de células gigantes no grupo teste suge-rindo resposta a corpo estranho e osso neoformado mais maduro no grupo controle No grupo teste houve permanência do material e resposta corpo estranho até os úl-timos períodos de observação. Na histomorfometria, a área total de neoformação óssea na região da ferida foi significativamente maior e crescente com o passar do tempo experimental no grupo controle do que no grupo teste. As células gigantes apresentaram expressão histoquímica positiva para TRAP e não foram identificados osteoclastos. Concluímos que neste modelo de estudo, o cimento cerâmico não in-duziu ou conduziu a neoformação óssea de defeitos ósseos críticos criados em cal-vária de ratos sob o ponto de vista microtomográfico e histológico. / Surgical intervention employing grafts and bone substitutes is the best choice in oral and maxillofacial bone defects reconstruction for structural and functional lost. Re-garding this, autogenous and alogenous grafts have been used as osteocondutive and resorbable biomaterials. The aim of this study was to evaluate if a new bone bi-phasic composite of calcium sulfate and beta tricalcium phosphate with zeta potential control could induce or conduct bone formation in rats\' calvarias critical defects mod-el. Forty male Wistar rats underwent 8mm diameter calvaria perforation under gen-eral anesthesia. Animals were randomly allocated to group test (n=20), when the de-fects were filled with the biphasic phosphate and group control (n=20) when the wound was left just with blood clot. Animals underwent euthanasia 7, 14, 21 and 42 days after surgery. Bone calvaria specimens underwent microtomography and histo-logical processing for analysis. Histomorphological and histomorphometry were per-formed regarding aspects of bone healing evolution and new bone total area within the defect. Additionally, histological samples were tartrate-resistant phosphatase (TRAP) stained for osteoclasts identification. The results showed that defects filled by the composite did not present significant bone formation considering postoperative evolution, on the contrary it seemed that the defect area increased in some animals. The bone repair histomorphology in test-group showed expressive giant cells nests involving the ceramic material suggesting foreign body reaction. A mature bone tis-sue neoformation was significantly more intense in the control-group. In the test-group the permanence of the exogenous material caused the sustained foreign body reaction until the last observational periods. Histomorphometric analysis showed that in control-group the total area of bone formation was significantly greater and pro-gressive along the experiment than the test-group. Osteoclasts were not identified but the giant cells presented positive reaction to TRAP. It was possible to conclude that the biphasic ceramic with zeta potential control was not capable to induce or conduct bone neoformation in critical defects created in rats\' calvaria.
128

Influência da velocidade cross-flow na câmara de flotação na eficiência de unidades de flotação por ar dissolvido tratando água para abastecimento / The influence of cross-flow velocity in the flotation chamber on efficiency of a dissolved air flotation unit treating drinking water

Araújo, Cláudio Júnior 07 October 2010 (has links)
O reator de FAD deve propiciar condições adequadas para contato entre as micro-bolhas e os flocos formados no pré-tratamento e também condições para que o conjunto floco/bolha possa ser direcionado ao topo do reator, e assim ser removido. O projeto de pesquisa visou estudar condições hidrodinâmicas proporcionadas pela variação da Velocidade Cross-Flow (VCF) e assim verificar a influência na eficiência de uma estação piloto de flotação por ar dissolvido. A VCF é importante parâmetro para concepção de unidades de FAD e é função da vazão de entrada no tanque de flotação e da área entre o nível d\'água no tanque de flotação e o anteparo que separa a zona de contato da zona de separação. A velocidade cross-flow constitui um parâmetro de grande importância para projetos de unidades de flotação. Nesta região de transição entre a zona de contato e a zona de separação, ocorre a passagem do conjunto floco/bolha, e turbulência excessiva pode causar o rompimento do conjunto e assim comprometer a eficiência da flotação. Além disso, o padrão de escoamento observado na zona de separação dos flotadores, onde ocorre a separação dos aglomerados \"flocos + bolhas\", depende fortemente do valor médio da velocidade cross-flow, conforme comentado por Lundh et al. (2000 e 2002) e por Reali e Patrizzi (2007). Daí a necessidade de se investigar mais profundamente a influência da VCF na eficiência da clarificação por flotação. O projeto de pesquisa foi dividido em duas etapas. Para realização das etapas foi estudado um tipo de água preparada em laboratório, através da adição de substância húmica e caulinita, para obtenção de cor aparente e turbidez, respectivamente. A água estudada possui cor aparente e turbidez moderada (1 mg/L de substância húmica e 8,5 mg/L de caulinita) resultando em valores de turbidez por volta de 7 NTU e cor aparente por volta de 40 UH. A etapa 1 consistiu na determinação do par, pH de coagulação e dosagem de coagulante (sulfato de alumínio), gradiente médio de floculação e tempo médio de floculação adequado para a água de estudo. Para realização da etapa 1 foi utilizado equipamento de flotação de bancada de regime de batelada (Flotateste), que se encontra nas dependências do Laboratório de Tratamento Avançado e Reuso de Águas - LATAR/SHS/EESC/USP. Foram mantidos fixos os seguintes parâmetros: \'T IND.MR\', \'G IND.MR\', \'T IND.F\', \'G IND.F\', \'P IND.SAT\', \'T IND.REC\', \'V IND.FLOT\'. Conforme preconizado por Reali et al (2007), foi variada a dosagem de coagulante. Após determinado o melhor par pH e dosagem de coagulante foram realizados ensaios visando determinar o melhor \'G IND.F\' e \'T IND.F\' para a água em estudo. Para a água de estudo foram escolhidas duas condições de potencial Zeta, determinados na etapa 1 do projeto de pesquisa. A primeira condição o potencial Zeta permaneceria com valor próximo de 0 mV e na segunda condição o potencial Zeta seria positivo, por volta de +12 mV. A etapa 2 consistiu em variar a velocidade cross-flow, através da variação da altura do vertedor de saída da água flotada de uma unidade piloto de flotação, de forma a se obter diferentes valores de VCF (mantendo-se constantes os valores de tempo de contato e taxa de aplicação superficial na zona de contato), para dois valores de Taxas de Aplicação Superficial (TAS) (7,67 m/h e 15 m/h) na zona de separação e os dois valores de potencial Zeta (PZ), e com isto avaliar a sua influencia na eficiência de remoção de sólidos suspensos totais, cor e turbidez da instalação piloto retangular de FAD. / The reactor DAF should provide adequate conditions for contact between the micro-bubbles and the flakes formed in the pretreatment conditions and also for the aggregate flocs/bubble can be directed to the top of the reactor, and thus be removed. The research project aimed at studying hydrodynamic conditions provided by the variation of Cross-Flow Velocity (VCF) and thus checks the influence on the efficiency of a pilot plant of dissolved air flotation. The VCF is an important parameter to design units of DAF and is a function of input flow in the flotation tank and the area between the water level in the flotation tank and the bulkhead that separates the contact zone of the zone of separation. The cross-flow velocity is a parameter of great importance to projects of flotation units. In this region of the transition zone between the contact zone and the separation zone, occurs the passage of the aggregate flocs/bubble, and excessive turbulence can cause disruption of the aggregate and thereby harm the flotation efficiency. Moreover, the pattern of flow observed in the flotation separation zone, which occurs the separation of aggregates \"flakes + bubbles\", depends strongly on the average value of cross-flow velocity as described by Lundh et al. (2000 and 2002) and Reali and Patrizzi (2007). Hence the needs to investigate further the influence of VCF on the clarification efficiency by flotation. The research project was divided into two steps. To perform the steps has been studied a type of water prepared in the laboratory, through the addition of humic substances and kaolin, to obtain apparent color and turbidity, respectively. The study water has moderate turbidity and apparent color (1 mg/L of humic substance and 8.5 mg/L of kaolin) resulting in turbidity values around 7 NTU and color apparent by 40 HU. Step 1 consisted in the determination of the pair, coagulation pH and coagulant dosage (aluminum sulfate), flocculation gradient and time flocculation suitable for the study water. For the implementation of step 1 was used bench batch flotation system equipment (Flotatest), located on the Laboratory for Advanced Treatment and Reuse Water - LATAR / SHS / EESC / USP. Were kept fixed the following parameters: \'T IND.MR\', \'G IND.MR\', \'T IND.F\', \'G IND.F\', \'P IND.SAT\', \'T IND.REC\', \'V IND.FLOT\'. As predicted by Reali et al (2007), was varied the dosage of coagulant. After determined the best pair of coagulant dosage and pH coagulation the tests were performed to determine the best \'G IND.F\' and \'T IND.F\' for the study water. For the study water were chosen two conditions of Zeta potential values, determined in the step 1 of the research project, where the first condition the Zeta potential value kept near 0 mV and the second condition kept a positive value of Zeta potential, around +12 mV. The step 2 consisted of varying the cross-flow velocity, by varying the height of the outlet weir of the clarified water of the flotation pilot plant to obtain different values of VCF (keeping constant the values of time contact and application rate on the contact zone) for two values of superficial application rates (7.67 m/h and 15 m/h) in the zone of separation and the two values of Zeta potential (PZ) and then was availed the influence on removal efficiency of total suspended solids, colour and turbidity of the rectangular pilot plant of DAF.
129

Números e polinômios de Bernoulli

Mirkoski, Maikon Luiz 19 October 2018 (has links)
Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-11-29T18:07:06Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Maikon Luiz.pdf: 959643 bytes, checksum: aaf472f5b8a9a29532793d01234788a9 (MD5) / Made available in DSpace on 2018-11-29T18:07:06Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Maikon Luiz.pdf: 959643 bytes, checksum: aaf472f5b8a9a29532793d01234788a9 (MD5) Previous issue date: 2018-10-19 / Neste trabalho,estudamos os números e os polinomios de Bernoulli,bem como algumas de suas aplicações mais importantes em Teoria dos Números. Com base em uma caracterização ao simples, os polinômios de Bernoulli são introduzidos e, posteriormente, os números de Bernoulli. As séries de Fourier dos polinomios de Bernoulli são utilizadas na demonstração da equação funcional da função teta. Esta equação, por sua vez, é utilizada na demonstração da celebre equação funcional da função zeta, que tem importância central na teoria da distribuição dos números primos. Além das conexões com a funções especiais zeta e teta, discutimos também, em detalhe,conexões entre os números e os polinomios de Bernoulli com a função gama. Essas relações são então exploradas para produzir belas fórmulas para certos valores da função zeta, entre outras aplicações. / In this work we study Bernoulli numbers and Bernoulli polynomials, as well as some of its most important applications in Number Theory. Based on a simple characterization, the Bernoulli polynomials are introduced and, later, the Bernoulli numbers. The Fourier series of the Bernoulli polynomials are used to demonstrate the functional equation of the theta function. This equation, in turn, is used in the proof of the famous functional equation of the zeta function, which is central to the theory of prime number distribution. In addition to the connections with the special functions zeta and theta, we also discuss, in detail, connections between the Bernoulli numbers and Bernoulli polynomials with the gamma function. These relations are then explored to produce beautiful formulas for certain values of the zeta function,among other applications.
130

Interação da porfirina catiônica meso-tetrakis (4-N-metilpiridil) com vesículas de fosfolipídio nos estados gel e líquido cristalino / Interaction of the cationic meso-tetrakis (4-N-methylpyridyl) porphyrin with gel and liquid state phospholipid vesicles

Sousa Neto, Diógenes de 23 April 2014 (has links)
Este estudo reúne os principais resultados de fluorescência estática e resolvida no tempo sobre a interação da porfirina meso-tetrakis (4-metilpiridil), na forma de base livre (TMPyP) e complexada com Zn2+ (ZnTMPyP), com vesículas de fosfolipídio. Adicionalmente foram utilizadas as técnicas de potencial zeta e espalhamento de luz dinâmico (DLS, do inglês \"dynamic light scattering\"). As vesículas de fosfolipídio foram formadas por dois conjuntos de fosfolipídios: saturados e insaturados. O primeiro grupo é formado pela mistura dos fosfolipídios zwiteriônico 1,2-dipalmitoil-sn-glicero-3-fosfocolina (DPPC) e aniônico 1,2-dipalmitoil-sn-3-glicero-[fosfo-rac-(1- glicerol)] (DPPG), a diferentes razões molares. Os estudos utilizando tais sistemas foram realizados abaixo (25oC) e acima (50oC) da temperatura de transição de fase gel-líquido cristalino destes fosfolipídios (~ 41oC). O segundo grupo é formado pela mistura dos fosfolipídios zwiteriônico 1-palmitoil-2-oleoil-sn-glicero-3-fosfocolina (POPC) e aniônico 1-palmitoil-2-oleoil-sn-glicero-3-fosfo(1-rac-glicerol) (POPG). Como a transição de fase destes dois fosfolipídios ocorre a temperaturas negativas, todos os experimentos foram realizados a 25oC (vesículas no estado líquido cristalino). Todos os sistemas foram preparados através do método de extrusão para a obtenção de vesículas grandes unilamelares (LUV, do inglês \"large unilamellar vesicles\"). As análises dos dados de fluorescência indicaram que a atração eletrostática entre os substituíntes (positivamente carregados) das porfirinas TMPyP e ZnTMPyP e o grupo das cabeças polares (camada de Stern) das vesículas de fosfolipídio desempenha um papel fundamental na associação da porfirina. A distribuição da TMPyP entre o meio aquoso (tampão) e as vesículas de fosfolipídio foi evidenciada pela coexistência de um tempo de vida de fluorescência mais curto (~ 5 ns) e outro mais longo (~ 9-11 ns), respectivamente. Baseado nos valores das constantes pré-exponenciais, estudos adicionais mostram que a distribuição acima é afetada pela concentração de sal na solução. Os resultados de supressão de fluorescência com o supressor iodeto de potássio (KI) indicaram que ambas porfirinas estão localizadas, preferencialmente, na região da camada de Stern. Este resultado foi confirmado pelos estudos de potencial zeta e de DLS, os quais mostraram uma neutralização parcial das cargas negativas na superfície das vesículas devido à associação da porfirina. / This study presents time-resolved and steady-state fluorescence results on the interaction of the meso-tetrakis (4-methylpyridil) porphyrin, in free base form (TMPyP), and complexed with Zn2+ (ZnTMPyP), with phospholipid vesicles. Zeta potential and dynamic light scattering (DLS) techniques were also used. Phospholipid vesicles were formed by two phospholipid systems: saturated and unsaturated. The first group is a mixture of zwiterionic dipalmitoyl-sn-glycero-3-phosphocoline (DPPC) and anionic 1,2-dipalmitoyl-sn-3-glycero-[phospho-rac-(1-glycerol)] (DPPG) phospholipids, at different molar ratios. Measurements were performed bellow (25oC) and above (50oC) the main gel-liquid crystalline phase transition temperature (~ 41oC). The second group is constituted by a mixture of zwiterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocoline (POPC) and anionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho(1-rac-glycerol) (POPG) phospholipids, at different molar ratios. Since the gel-liquid crystalline phase transition of these phospholipids occurs at a very low temperature value, all experiments were performed at 25oC (liquid crystalline state vesicles). All phospholipid systems were prepared through the extrusion method in order to obtain large unilamellar vesicles (LUV). The fluorescence data analyses indicated that the electrostatic attraction between the porphyrin substituents (positively charged) and the polar head groups of the phospholipid vesicles (Stern layer) plays an important role on the porphyrin binding affinity. The distribution of TMPyP between the aqueous medium (buffer) and the phospholipid vesicles was characterized by the coexistence of a shorter (~ 5 ns) and a longer (~ 9-11 ns) fluorescence lifetimes, respectively. Based on the pre- exponential values, additional time-resolved experiments showed a redistribution of the porphyrin at increasing salt concentration. The quenching studies, using potassium iodide (KI) as quencher, indicated that both TMPyP and ZnTMPyP are preferentially located at the Stern layer region. This result is in agreement with the zeta potential and DLS findings, which demonstrated a partial neutralization of the negative charges at the vesicle surface due to the porphyrin association.

Page generated in 0.0367 seconds