Global ETD Search

511	Electron Transfer and Other Reactions Using Atomic Metal Anions Butson, Jeffery M. January 2014 (has links) The atomic metal anions Rb-, Cs-, Cu-, Ag- and Fe- have been generated in the gas phase and reacted with various neutral reactants in a triple quadrupole mass spectrometer. The metal anions were formed via electrospray ionization of the metal-oxalate solutions and form in gas phase between the capillary and the first quadrupole. Neutral gas phase reactants investigated include NO, NO2, SO2, C6F5OH, C6F5NH2, C6F6, E-octafluoro-butene and 1,2,3/1,2,4/1,3,5 trifluoro-benzene. When possible, CBS-4M methods were used to suggest the lowest energy products based on relative energy. Observed reactions of atomic metal anions with the aforementioned neutral species include electron transfer and dissociative electron transfer to the neutral gas phase reactants. In addition, hydrogen abstraction and fluorine abstraction forming a neutral metal hydride or fluoride as well as the formation of multiply substituted metal-oxide/fluoride anions was also observed. Metal-complex anions observed from the gas phase reactions include CuF-,CuF2-,CuO-,CuO2-, FeO-, FeO2-, FeO3-, FeF-, FeF2-, FeF3-, CsF- and CsF2-. Metal Anion Metal Anion Atomic Atomic Metal Anion Atomic Metals Atomic Metal Anions Anions Metals Mass Spectrometer Triple Quadrupole Rb Cs Fe Cu Ag Cs- Rb- Fe- Cu- Ag- pentafluoroaniline pentafluorophenol nitrogen dioxide sulfur dioxide nitrogen oxide nitrogen monoxide oxygen oxalic oxalic acid gas phase electrospray ionization electrospray ionization electro-spray ionization electro-spray hexafluorobenzene 1,2,3-trifluorobenzene 1,2,4-trifluorobenzene 1,3,5-trifluorobenzene fluorine E-octafluoro-butene octafluoro-butene octafluoro butene CBS-4M abstraction hydrogen abstraction fluorine abstraction hydride fluoride metal hydride metal fluoride caesium fluoride rubidium fluoride iron fluride copper fluoride rubidium caesium iron copper silver iron anion copper anion rubidium anion caesium anion silver anion cesium cesium anion atomic caesium anion atomic cesium anion atomic rubidium anion atomic iron anion atomic copper anion atomic silver anion 1,2,3 trifluorobenzene 1,2,4 trifluorobenzene 1,3,5 trifluorobenzene copper fluoride anion iron fluoride anion copper difluoride copper difluoride anion iron difluoride iron difluoride anion iron trifluoride iron trifluoride anion cesium fluoride cesium fluoride anion caesium difluoride anion caesium difluoride cesium difluoride cesium difluoride anion caesium fluoride anion nitrogen monoxide anion sulfur dioxide anion nitrogen dioxide anion copper oxide copper oxide anion copper dioxide copper dioxide anion iron oxide iron oxide anion iron dioxide iron dioxide anion iron trioxide iron trioxide anion electron transfer
512	Hypervalent diorganoantimony(III) fluorides via diorganoantimony(III) cations – a general method of synthesis Preda, Ana Maria, Raţ, Ciprian I., Silvestru, Cristian, Lang, Heinrich, Rüffer, Tobias, Mehring, Michael 18 February 2016 (has links) (PDF) Novel diorganoantimony(III) fluorides containing ligands with pendant arms, R2SbF (5), (R)PhSbF (6) [R = 2-(2′,6′-iPr2C6H3N[double bond, length as m-dash]CH)C6H4], R′′2SbF (7) and (R′′)PhSbF (8) [R′′ = 2-(Me2NCH2)C6H4], were prepared via the ionic derivatives [R2Sb]+[PF6]− (1), [(R)PhSb]+[PF6]− (2), [R′′2Sb]+[SbF6]− (4) and [(R′′)PhSb]+[SbF6]− (obtained in situ) by treatment with [Bu4N]F·3H2O. The ionic species used as starting materials as well as [R′2Sb]+[PF6]− (3) [R′ = 2-(2′,4′,6′-Me3C6H2N[double bond, length as m-dash]CH)C6H4] were obtained from the corresponding bromides or chlorides and Tl[PF6] or Ag[SbF6]. The compounds were investigated by multinuclear NMR spectroscopy in solution, MS and IR spectroscopy in the solid state. The molecular structures of the ionic species 1·2CH2Cl2 and 3·2CHCl3 as well as of the fluorides 5–8 were determined by single-crystal X-ray diffraction. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich. Antimon Fluorid Organoantimonverbindungen Hypervalente Verbindungen Ionogene Verbindungen Strukturanalyse antimony fluoride organoantimony compounds hypervalent compounds ionic species structure analysis ddc:540 Antimon Hypervalentes Molekül Strukturanalyse
513	Essays on Cognitive Development and Medical Care Öhman, Mattias January 2016 (has links) This thesis consists of four self-contained papers. Essay I (with Linuz Aggeborn): Fluoridation of the drinking water is a public policy whose aim is to improve dental health. Although the evidence is clear that fluoride is good for dental health, concerns have been raised regarding potential negative effects on cognitive development. We study the effects of fluoride exposure through the drinking water in early life on cognitive and non-cognitive ability, education and labor market outcomes in a large-scale setting. We use a rich Swedish register dataset for the cohorts born 1985-1992, together with drinking water fluoride data. To estimate the effects, we exploit intra-municipality variation of fluoride, stemming from an exogenous variation in the bedrock. First, we investigate and confirm the long-established positive relationship between fluoride and dental health. Second, we find precisely estimated zero-effects on cognitive ability, non-cognitive ability and education for fluoride levels below 1.5 mg/l. Third, we find evidence that fluoride improves later labor market outcomes, which indicates that good dental health is a positive factor on the labor market. Essay II: I study the associations between cognitive and non-cognitive abilities and mortality using a population-wide dataset of almost 700,000 Swedish men born between 1950 and 1965. The abilities were measured at the Swedish military enlistment at age 18-20. In addition, I investigate if income and education are good proxies for the abilities. The results suggest that both cognitive and non-cognitive abilities are strongly associated with mortality, but that non-cognitive ability is a stronger predictor. The associations are only partly mediated through income and education. For middle and high income earners and individuals with a college education there are no associations with mortality. However, for low income earners and individuals without a college education, both abilities are strongly associated with mortality. The associations are mainly driven by the bottom of the distributions. Essay III (with Matz Dahlberg, Kevin Mani and Anders Wanhainen): We examine how health information affects individuals' well-being using a regression discontinuity design on data from a screening program for an asymptomatic disease, abdominal aortic aneurysm (AAA). The information provided to the individuals is guided by the measured aorta size and its relation to pre-determined levels. When comparing individuals that receive information that they are healthy with those that receive information that they are in the risk zone for AAA, we find no effects. However, when comparing those that receive information that they have a small AAA, and will be under increased surveillance, with those who receive information that they are in the risk zone, we find a weak positive effect on well-being. This indicates that the positive information about increased surveillance may outweigh the negative information about worse health. Essay IV: I estimate the effect of SSRI antidepressants on the risk of mortality for myocardial infarction (MI) patients using Propensity Score Matching on individual health variables such as pharmaceutical drug prescription, patient history and severity of the MI. The effect of antidepressants on mortality is a heavily debated topic. MI patients have an elevated risk of developing depression, and antidepressants are among the most common treatments for depression and anxiety. However, there are indications that some classes of antidepressants may have drug-induced cardiovascular effects and could be harmful for individuals with heart problems, but there is a lack of large-scale studies using credible identification strategies. My findings indicate no increased risk of two-year mortality for MI patients using SSRI. The results are stable for several specifications and robustness checks. Fluoride Cognitive ability Non-cognitive ability Income Education Employment Dental health Mortality Information Health Screening Abdominal aortic aneurysm Myocardial infarction Antidepressants SSRI Propensity score matching
514	Essays on Politics and Health Economics Aggeborn, Linuz January 2016 (has links) Essay I (with Mattias Öhman): Fluoridation of the drinking water is a public policy whose aim is to improve dental health. Although the evidence is clear that fluoride is good for dental health, concerns have been raised regarding potential negative effects on cognitive development. We study the effects of fluoride exposure through the drinking water in early life on cognitive and non-cognitive ability, education and labor market outcomes in a large-scale setting. We use a rich Swedish register dataset for the cohorts born 1985-1992, together with drinking water fluoride data. To estimate the effect we exploit intra-municipality variation of fluoride, stemming from an exogenous variation in the bedrock. First, we investigate and confirm the long-established positive relationship between fluoride and dental health. Second, we find precisely estimated zero effects on cognitive ability, non-cognitive ability and education. We do not find any evidence that fluoride levels below 1.5 mg/l have negative effects. Third, we find evidence that fluoride improves labor market outcome later in life, which indicates that good dental health is a positive factor on the labor market. / Essay II: Motivated by the intense public debate in the United States regarding politicians’ backgrounds, I investigate the effects of electing a candidate with earlier experience from elective office to the House of Representatives. The U.S. two-party-system with single-member election districts enables me to estimate the causal effect in a RD design where the outcomes are measured at the election district level. I find some indications that candidates with earlier elective experience are more likely to be members of important congressional committees. I also find some indications that directed federal spending (pork barrel spending) is higher in those districts were the elected representative had earlier elective experience prior of being elected to the House, but the effect manifests itself some years after the election. In contrast, I find no robust or statistically significant effects for personal income per capita or unemployment rate in the home district. / Essay III: This paper uses Swedish and Finnish municipal data to investigate the effect of changes in voter turnout on the tax rate, public spending and vote-shares. A reform in Sweden in 1970, which overall lowered the cost of voting, is applied as an instrument for voter turnout in local elections. The reform increased voter turnout in Sweden. The higher voter turnout resulted in higher municipal taxes and greater per capita local public spending. There are also indications that higher turnout decreased the vote share for right-wing parties. I use an individual survey data set to conclude that it was in particular low income earners that began to vote to a greater extent after the reform. / Essay IV (with Lovisa Persson): In a theoretical model where voters and politicians have different preferences for how much to spend on basic welfare services contra reception services for asylum seekers, we conclude that established politicians that are challenged by right-wing populists will implement a policy with no spending on asylum seekers if the cost is high enough. Additionally, adjustment to right-wing populist policy is more likely when the economy is in a recession. Voters differ in their level of private consumption in such a way that lower private consumption implies higher demand for basic welfare services at the expense of reception of asylum seekers, and thus stronger disposition to support right-wing populist policies. We propose that this within-budget-distributional conflict can arise as an electorally decisive conflict dimension if parties have converged to the median voter on the size-of-government issue. Fluoride Cognitive ability Non-cognitive ability Income Education Employment Dental health Political Leadership American politics Regression discontinuity Voter turnout Local public finance Sweden Finland Right-wing populism welfare chauvinism
515	Influence d’un rince-bouche fluoré sur la corrosion galvanique entre un fil NiTi ou un fil CuNiTi et différents boîtiers orthodontiques : incidence sur les propriétés mécaniques des fils Benguira, David M. 04 1900 (has links) Objectif : il a été rapporté que l’utilisation d’agents prophylactiques fluorés pouvait favoriser la corrosion galvanique au sein des alliages de titane. L’objectif de la présente étude était d’évaluer l’effet d’un rince-bouche fluoré sur les propriétés mécaniques de fils en nickel-titane (NiTi) et de fils en cuivre-nickel-titane (CuNiTi) lorsque ces derniers sont couplés à des boîtiers de compositions différentes (boîtiers de marques Smartclip, Clarity, et Sprint). Matériels et Méthodes : 90 segments de fils en NiTi et 90 segments de fils en CuNiTi ont été chacun couplés à 2 boîtiers de chaque marque. Chaque assemblage fil-boîtiers a été par la suite incubé pendant 3 heures à 37°C, soit dans une solution de fluore neutre (Fluorinse™ 0,05% NaF), soit dans une solution de salive artificielle (solution contrôle). Suite à l’incubation, les échantillons étaient nettoyés avec de l’eau déshydrogénée, les fils séparés des boîtiers et montés sur un support pour subir un test de pliage en trois points en milieu humide (salive artificielle) à 37°C. Les modules d’élasticité ainsi que les limites conventionnelles d’élasticité en activation et en désactivation ont été mesurés et comparés. Des analyses de Variance (ANOVA) et des comparaisons post-hoc avec la correction de Bonferronni ont été utilisées pour comparer les groupes entre eux (α = 0,05). Résultats : L’utilisation d’un rince-bouche fluoré a produit une réduction du module d’élasticité et de la limite conventionnelle d’élasticité en activation et en désactivation pour les fils en NiTi ; cependant, cet effet a été modulé par le type de boîtier auquel le fil a été couplé. Les propriétés mécaniques de fils en CuNiTi n’ont pas été affectées par le fluor, ou par le type de boîtier utilisé. Conclusions : L’utilisation d’un rince-bouche fluoré modifie les propriétés mécaniques des fils en NiTi seulement. Cet effet est modulé par le boîtier auquel le fil en NiTi est couplé. A la différence des autres études publiées dans la littérature, nos résultats ne nous permettent pas de conclure que la modification des propriétés mécaniques des fils en NiTi entrainerait obligatoirement un allongement de la durée du traitement orthodontique. Mots clés : Fluor, fils nickel-titane, boîtiers orthodontiques, corrosion galvanique, propriétés mécaniques. / Aim: it has been reported that the use of fluoride prophylactic agents can cause galvanic corrosion of the titanium based alloys used in orthodontics. The purpose of the present study was to investigate the effects of a fluoride mouthrinse on the mechanical properties of nickel-titanium (NiTi) and copper–nickel-titanium (CuNiTi) orthodontic archwires that have been coupled with different types of orthodontic brackets (Smartclip, Clarity, and Sprint brackets). Materials and Methods: 90 segments of NiTi and 90 segments of CuNiTi archwires were tested. Every segment was coupled with 2 brackets of each brand. The wire–bracket assembly obtained was incubated, at 37°C for three hours either in a solution of a commercially available mouthwash (Fluorinse™ 0,05% NaF), or in a solution of artificial saliva (control). Following the incubation, the wires were separated from the brackets, rinsed, mounted on a stainless steel support and placed in a waterbath of artificial saliva at 37°C. A 3-point bending test was made to calculate the loading and unloading elastic modulus and yield strength of the wires. Analysis of variance (ANOVA) and post hoc comparisons were made using Bonferronni’s correction to identify the statistically significant differences (α = 0,05). Results: The use of a fluoridated mouthrinse reduced the loading and unloading elastic modulus and yield strength of the NiTi wires. This reduction, however, varies with the type of bracket that was coupled with the wire. The mechanical properties of the CuNiTi wires were not modified by the use of the fluoride rinse or by the type of bracket to which they were coupled. Conclusions : The use of a fluoride mouthrinse alters the mechanical properties of NiTi wires only. This effect varies with the type of bracket that was in contact with the wire. However our results do not allow us to conclude that the alteration of the mechanical properties of the wires would necessarily imply a prolongation of the orthodontic treatment time. Key words: Fluoride, nickel-titanium archwires, galvanic corrosion, mechanical properties,orthodontic brackets. Fluor Corrosion galvanique Fils nickel-titane Boîtiers orthodontiques Propriétés mécaniques Fluoride Nickel-titanium archwires Galvanic corrosion Mechanical properties Orthodontic brackets
516	Le cycle hydrosocial et la fluoration de l'eau : la production des eaux fluorées Amado Rohten, Rodrigo 04 1900 (has links) La fluoration artificielle de l’eau est une méthode employée en tant que moyen de prévention de la carie dentaire. Il s’agit d’un traitement de l’eau dont le but est d’ajuster de façon « optimale » la concentration en fluorure dans l’eau potable pour la prévention de la carie dentaire, par l’ajout d’un composé fluoré. La fluoration de l’eau fait l’objet d’un débat de société depuis le début des années 1950. La théorie du cycle hydrosocial nous invite à réfléchir sur la manière dont l’eau et la société se définissent et se redéfinissent mutuellement dans le temps et dans l’espace. Cette théorie nous permet d’aborder l’étude du sujet de la fluoration avec une nouvelle perspective d’analyse. Il y a peu d’études en sciences sociales qui portent sur le sujet de la fluoration, généralement abordé d’un point de vue des sciences de la santé. Nous proposons de décrire le processus de production des eaux fluorées dans un contexte hydrosocial. Ce mémoire est structuré en quatre chapitres. Nous commençons par familiariser le lecteur avec la théorie du cycle hydrosocial. Ensuite, nous faisons une mise en contexte de la fluoration de l’eau, d’une part en présentant un état des lieux, et d’autre part en présentant ce en quoi consiste la pratique de la fluoration de l’eau. Après avoir familiarisé le lecteur avec les thèmes généraux concernant la fluoration de l’eau, nous proposons de reconstituer une histoire hydrosociale de la fluoration. Cette histoire nous permet de mettre en évidence les relations hydrosociales desquelles découle la production des eaux fluorées. L’histoire hydrosociale de la fluoration comporte une phase contemporaine que nous abordons en présentant les principales idées de l’opposition à la fluoration artificielle de l’eau à l’aide notamment d’une analyse iconographique d’images portant sur le thème de la fluoration. Finalement, nous discutons des implications de la théorie du cycle hydrosocial pour étudier la problématique de la fluoration. / Artificial water fluoridation is a method used as a way of preventing tooth decay. It is a water treatment that consists in adjusting the fluoride concentration in water to a “optimal” level in order for it to work in preventing tooth decay. Water fluoridation has been subject to social debate since the early 50’s. The theory of the hydrosocial cycle brings us to think about the ways water and society are mutually defined and redefined by one another in time and space. This theory allows us to study the subject of water fluoridation with a new perspective. There are few works in social sciences that are about water fluoridation, a subject which is generally approached by a health science point of view. We are proposing to describe the production process of fluoridated waters in a hydrosocial context. This research is organized in four chapters. First, we start by introducing the reader to the theory of the hydrosocial cycle by presenting the literature on the matter. Next, we put into context the practice of water fluoridation by first presenting the current state of affairs in regards to water fluoration programs across the world, and second by presenting the technical aspects of water fluoridation. After the reader has been presented with the general themes covered by the subject of water fluoridation, we propose to rebuild a hydrosocial of fluoridation. This story allows us to bring forward the hydrosocial relations from which stems the production process of fluoridated waters. The hydrosocial history of fluoridation includes a contemporary historical phase in which we introduce some key ideas about the opposition to artificial water fluoration. Furthermore, we try to illustrate some of the hydrosocial principles of fluoridation that are representative of the contemporary narratives by doing an iconographic analysis of images on the subject of fluoridation. Finally, we discuss about the implications of the hydrosocial cycle theory on the study of the fluoridation problem. Cycle hydrosocial Fluoration de l'eau Histoire de la fluoration Eau fluorée Fluorure Hydrosocial cycle Water fluoridation History of fluoridation Fluoridated water Fluoride
517	Molecular Probes for Biologically Important Molecules: A Study of Thiourea, Hydroxyl radical, Peroxynitrite and Hypochlorous acid Chakraborty, Sourav 14 May 2010 (has links) Numerous chemical species are important to the health of biological systems. Some species can be beneficial at low doses and harmful at high doses. Other species are highly reactive and trigger serious cell damage. Improved methods to detect the presence and activity of such species are needed. In this work, several biologically important species were studied using appropriate analytical techniques. Fluoride is an important species in human physiology. It strengthens teeth and gives protection against dental caries. However, elevated concentrations of fluoride in the body can lead to health problems such as dental and skeletal fluorosis. Reported fluoride sensors used fluorescence quenching methods in determining fluoride concentration. Our study explored synthesis and characterization of 1,8-bis(phenylthioureido) naphthalene (compound 1) as a fluoride sensing molecule. Compound 1 showed a remarkable 40 fold enhancement in fluorescence with 5 eq of fluoride addition. Compound 1 also showed possibility of visual colorimetric sensing with fluoride. Free radical mediated oxidations of biomolecules are responsible for different pathological conditions in the human body. Superoxide is generated in cells and tissues during oxidative burst. Moderately reactive superoxide is converted to peroxyl, alkoxyl and hydroxyl radicals by various enzymatic, chemical, and biochemical processes. Hydroxyl radical imparts rapid, non specific oxidative damage to biomolecules such as proteins and lipids. Superoxide also reacts with nitric oxide in cells to yield peroxynitrite, which is highly reactive and damages biomolecules. Both hydroxyl radical and peroxynitrite readily react with amino acids containing aromatic side chains. Low density lipoprotein (LDL) carries cholesterol in the human body. Elevated concentration of LDL is a potential risk factor for atherosclerosis. Previous research drew a strong correlation between oxidized low density lipoprotein (ox-LDL) and plaque formation in the arterial wall. More importantly, oxidative damage causes structural changes to the LDL protein (apo B-100) which might facilitate the uptake of LDL by macrophages. In this study LDL was exposed to various concentrations of hydroxyl radical peroxynitrite and hypochlorite. Thereafter oxidized amino acid residues in apo B-100 were mapped by LC-MS/MS methods. We found widely distributed oxidative modifications in the apo B-100 amino acid sequence. fluoride fluorescence enhancement thiourea chromogenic sensing low density lipoproteins (LDL) Fenton Chemistry free radicals hydroxyl radical peroxynitrite hypochlorus acid surface mapping proteomics LC-MS/MS natural variants
518	Performances des procédés physico-chimiques et membranaires pour l'élimination des ions fluorure dans les eaux de forage : application aux eaux tunisiennes / Performances of physico-chemical and membranes processes for the elimination of fluoride ions in drilling waters : application to tunisian waters Ben Nasr, Anis 04 October 2013 (has links) La problématique de l’élimination de l’excès d’ions fluorure présents dans les eaux de forage destinées à la consommation humaine peut être résolue en utilisant plusieurs méthodes. Dans cette thèse, les procédés testés sont : l’adsorption sur des particules d’os de seiche, l’adsorption sur des particules de calcite en présence d’acide acétique, la nanofiltration et l’échange d’ions. L’objectif est d’optimiser les différents procédés pour des solutions modèles en ions fluorure, puis de réaliser pour ces conditions optimales le traitement d’une eau de forage tunisienne. La concentration limite en ions fluorure imposée par la WHO est de 1.5 mg.L-1. Les essais d’adsorption en utilisant l’os de seiche, disponible en Tunisie, sont simples à mettre en œuvre et permettent des traitements à petite échelle avec des coûts très compétitifs en utilisant un matériau non toxique. La défluoration de l'eau souterraine avec l’os de seiche présente une concentration résiduaire en fluorure de 1,3 mg.L-1 (TR = 61,5%). Dans le cas de la précipitation des ions fluorures sous forme de fluorite suivi de microfiltration, l’addition d’acide acétique aux particules de calcite (CaCO3) favorise l’élimination des ions fluorure. La défluoration de l'eau souterraine montre que l’eau traitée présente une concentration résiduaire en fluorure de 1,24 mg.L-1 (TR = 53,7%). En utilisant une résine échangeuse d’ions Purolite A520E, la défluoration de l'eau souterraine montre que l’eau traitée présente une concentration résiduaire en fluorure de 1,2 mg.L-1 (TR = 54%). La nanofiltration permet de traiter des volumes importants d’eau et les taux de rétention des ions fluorure sont satisfaisants (88% et 57%) / The issue of the removal of excess fluoride ions present in well water for human consumption can be solved using several methods. In this PhD thesis, four processes have been tested: adsorption using cuttlefish bone particles, adsorption on calcite particles with acid acetic addition, nanofiltration and ion exchange. The aim is to optimize the different processes by using model solutions of fluoride ions, and to treat a Tunisian groundwater at these optimal conditions. The limiting concentration given by the WHO is 1,5 mg.L-1. The adsorption using cuttlefish bone, available in Tunisia, is simple to implement and provides treatment at small scale with very competitive costs by using a non-toxic material. Defluorination of groundwater shows that the water treated with cuttlefish bones has a residual fluoride concentration of 1.3 mg L-1 (TR = 61.5%). In the case of precipitation of fluoride ions in the form of fluorite followed by microfiltration, the addition of acetic acid to the particles of calcite (CaCO3) promotes the removal of fluoride. Defluorination groundwater shows that the treated water has a residual fluoride concentration of 1.24 mg L-1 (TR = 53.7 %). Using a ion exchange resin Purolite A520E, defluorination groundwater shows that water treated has a residual fluoride concentration of 1.2 mg L-1 (TR = 54%). Nanofiltration is particularly interesting as it allows the treatment of large volumes. The retention of fluoride ions are again satisfactory (88% and 57%) Ions fluorure Procédé physicochimique Traitement des eaux Eaux tunisiennes Procédé membranaire Adsorption Précipitation Nanofiltration Fluoride ions Physicochemical process Water treatment Tunisian waters Membrane process Adsorption Precipitation Nanofiltration 628.1
519	Síntese de membranas planas compostas de PVDF e nanopartículas de argila. / Synthesis of flat sheet membrane using PVDF and clay nanoparticles. Morihama, Ana Carolina Daniel 30 March 2016 (has links) Esta pesquisa foi desenvolvida no laboratório do Centro Internacional de Referência em Reúso de Água (CIRRA), vinculado ao Departamento de Engenharia Hidráulica e Ambiental da Escola Politécnica da Universidade de São Paulo (USP). O projeto de pesquisa teve como objetivo principal a síntese de membranas planas compostas, utilizando o polímero fluoreto de polivinilideno (PVDF), nanopartículas inorgânicas de argila (montmorilonita hidrofílica) e óxido de polietileno (PEO). As membranas foram sintetizadas pelo processo de inversão de fases, utilizando 18% em massa de PVDF, n-metil-pirrolidona como solvente e água como o não solvente. Avaliou-se a influência da introdução de diferentes concentrações de nanopartículas de argila e PEO. As membranas sintetizadas foram submetidas a testes de avaliação de desempenho (permeabilidade, capacidade de separação, potencial de depósitos) e de caracterização (morfologia e características físicas). Os resultados obtidos indicam que a adição de nanopartículas inorgânicas de argila e o formador de poros PEO melhoraram o desempenho e as características físicas das membranas. As membranas Kynar 761 6% argila 0% PEO (K6-0), Kynar 761 0% argila 4% PEO (K0-4) e Kynar 761 6% argila 4% PEO (K6-4) apresentaram as melhores permeabilidades com um aumento, respectivamente, de 520%, 1.250% e 1.100%, em relação à membrana pura. Além disso, observa-se uma melhora de 55%, 60% e 41% na redução do potencial de depósito, respectivamente, para as membranas K6-0, K0-4 e K6-4, quando comparada a membrana de controle. A melhora da permeabilidade e do potencial de depósito das membranas compostas está relacionada à melhoria da hidrofilicidade e da carga superficiail. A morfologia interna das membranas sintetizadas com argila pode ser caracterizada com uma camada superficial com poros conectados verticalmente aos poros em formas de canais da camada intermediária. A camada inferior possui uma morfologia esponjosa com micro-poros. O aumento da quantidade e tamanho dos poros superficiais é proporcional ao aumento da concentração de argila, assim como a diminuição de bloqueios horizontais entre a camada superficial e os poros em formas de canais da camada intermediária. A morfologia interna das membranas sintetizadas com PEO pode ser caracterizada por uma camada superficial densa com poros e uma camada inferior com uma morfologia esponjosa densa com micro-poros. A camada intermediaria tem uma morfologia densa com poros em forma de canais com diâmetros maiores se comprado às membranas sem adição de PEO. A adição de PEO diminui o tamanho médio dos micro-poros, se comparado com as membranas onde apenas argila é adicionada. Foi constatado que a melhoria da permeabilidade está associada à alteração na morfologia interna das membranas compostas. O aumento dos poros superficiais conectados aos poros em forma de canais mais longos e uma camada inferior menor, proporciona uma redução da resistência interna da membrana, devido à formação de caminhos livres, facilitando a passagem da água. Pelas análises de espectrômetro de raios X por dispersão de energia (EDS), foram identificadas nanopartículas de argila dispersas na superfície e na matriz transversal da membrana. Os resultados indicam que a introdução de nanopartículas de argila na solução polimérica é uma técnica de modificação da membrana promissora no melhoramento do desempenho da membrana para o tratamento de água e efluentes. / This research was developed in the International Reference Center for Water Reuse (IRCWR) laboratory inside to the Departamento de Engenharia Hidráulica e Ambiental da Escola Politécnica da Universidade de São Paulo (USP). The main objective of this research is the synthesis of ultrafiltration flat sheet membrane, using polyvinylidene fluoride (PVDF) polymer, clay (montmorillonite hydrophilic) inorganic nanoparticles and polyethylene oxide (PEO). Membranes were synthesized by phase inversion process, using 18% PVDF, mass based, in n-methylpyrrolidone as solvent and water as the non-solvent in the coagulation bath. The influence of different concentrations of clay nanoparticles and PEO was evaluated. Permeability, separation capability, and foulling potential tests were conducted to evaluate membranes performance and morphology analysis and physical characteristics were used for membranes characterization. Results indicated that clay nanoaprticles and PEO addiction can improve membrane permeability and morphology. The Kynar 761 6% clay 0% PEO (K6-0), Kynar 761 0% clay 4% PEO (K0-4) and Kynar 761 6% clay 4% PEO (K6-4) membranes showed the best permeability results, with an increase, respectively of 520%, 1,250% and 1,100%, compared to pure membrane. Furthermore, there is an improvement of 55%, 60% and 41% in the foulling potential reduction, respectively, for K6-0, K0-4 and K6-4 membranes, compared to the control membrane. It was verified that membrane permeability improvement and fouling potential reduction with the addition of clay nanoparticles is related with the improvement of membranes hydrophilicity and surface charge. The internal morphology of the membranes synthesized with clay can be characterized by a surface layer with pores interconnected with finger-like pores in the intermediate layer. The bottom layer has a sponge-like morphology with micro-pores. The increasing number and size of surface pores and also the reduction of horizontal blocks between the surface layer and the finger-like pores in the intermediate layer, is observed with increasing dosage of clay. The internal morphology of the membranes synthesized with PEO can be characterized by a dense surface layer and a bottom layer with dense sponge morphology with micro-pores. The intermediate layer has a dense morphology with finger-like pores with larger diameters if compared to the membranes without addition of PEO. The PEO addition decreases the average size of micro-pores, compared with membranes only clay is added. It was observed that change in composite membranes internal morphology, resulted in the water permeability improvement. The increasing superficial pores connected to longer finger-like pores and a thin bottom layer resulted in an internal pore structure with a lower resistance due to free paths formation, facilitating the flow passage. Using Energy Dispersive X-ray Spectroscopy (EDS) analysis it was possible to observed clay nanoparticles dispersed on membrane surface and in its cross-section matrix. These preliminary results indicate that clay nanoclay addiction in polymeric solution is a promising membrane modification technique for improving membrane performance for water and wastewater treatment. Argilas Clay nanoparticles Efluentes (Tratamento) Fluoreto de polivinilideno (PVDF) Membranas modificadas Modified membranes Morfologia Morphology Nanopartículas Permeabilidade Permeability Poly(vinylidene fluoride) (PVDF) Reuso da água Tratamento de água Water treatment
520	Comparação do potencial erosivo de duas fontes ácidas sobre o esmalte e avaliação de métodos de controle da erosão dental / Comparison of the erosive potential of two acidic sources in enamel and evaluation of treatments for prevention of dental erosion Braga, Sheila Regina Maia 01 September 2009 (has links) Erosão dental é definida como a perda irreversível de tecido duro dental por um processo químico que não envolve bactérias. O objetivo deste trabalho foi comparar in vitro o potencial erosivo de duas fontes ácidas e avaliar métodos de controle da erosão dental em esmalte. Para a comparação das fontes ácidas, coroas de 5 molares inclusos foram seccionadas em quatro, totalizando 20 espécimes. Nos espécimes, uma superfície de esmalte (janela) de 3 x 3 mm foi delimitada. Os espécimes foram submetidos ao desafio erosivo em suco gástrico (obtido durante endoscopia) (n=10), ou suco de laranja (industrializado) (n=10), como segue: 5 minutos em 3 ml de solução ácida, enxágue com água destilada e armazenagem em saliva artificial por 3 horas. Este ciclo foi repetido 4 vezes ao dia por 14 dias. O cálcio (Ca) eliminado dos espécimes na solução ácida foi quantificado por Espectrometria de emissão atômica. A presença de carbonato (CO) e fosfato (PO) foi avaliada nos espécimes antes e após o desafio erosivo pela Espectroscopia FT-Raman. Para a avaliação dos métodos de controle da erosão quarenta espécimes de esmalte de molares inclusos foram distribuídos para cada um dos métodos propostos (n=10): gel de flúor fosfato acidulado (APF 1,23%), laser de Nd:YAG (100 mJ, 1 W, 10 Hz), associação flúor + laser e laser + flúor. Os métodos de controle foram aplicados 1 hora antes do desafio erosivo já descrito, realizado com ácido clorídrico (0,01 M/pH 2,2) como fonte ácida. O flúor foi mantido por 4 minutos sobre a superfície de esmalte. A superfície foi irradiada, com contato, após aplicação de um fotoabsorvedor. As associações foram feitas utilizando o flúor e o laser como descrito anteriormente. A perda de Ca dos espécimes foi quantificada por Espectrometria de emissão atômica e a rugosidade superficial dos espécimes (Ra) foi avaliada antes e após o desafio erosivo. Na comparação das fontes ácidas, os espécimes submetidos à erosão perderam: 12,74 ± 3,33 mg/L de Ca (suco gástrico) e 7,07 ± 1,44 mg/L de Ca (suco de laranja) (p=0,0003). A análise em Espectroscopia FT-Raman não detectou alteração significativa na razão CO/PO após o desafio ácido. Os valores CO/PO antes e depois do desafio foram: 0,16/0,17 (suco gástrico) (p=0,37) e 0,18/0,14 (suco de laranja) (p=0,16). Na avaliação dos métodos de controle da erosão, as perdas de Ca foram (mg/L): APF 1,707a (± 0,113), Nd:YAG 1,638a (±0,080), APF + Nd:YAG 1,385b (±0,078), Nd:YAG + APF 1,484b (±0,068). A rugosidade média inicial dos espécimes foi de 0,14 m. Após o desafio erosivo a rugosidade apresentou significativo aumento (p<0,01): APF 0,69bc (±0,091), Nd:YAG 0,87a (±0,119), APF + Nd:YAG 0,61c (±0,090) e Nd:YAG + APF 0,72b (±0,069). Foi possível concluir que o suco gástrico apresentou potencial erosivo ao esmalte maior que o suco de laranja. A associação entre flúor e laser apresentou-se mais eficaz no controle da erosão dental do que os métodos isoladamente. / Dental erosion is defined as irreversible loss of dental hard tissue due to chemical processes without the involvement of microorganisms. The aim of this study was to compare in vitro the erosive potential of two acidic sources and evaluate the effectiveness of treatments for prevention of dental erosion. To compare the acidic sources, crowns of 5 unerupted human third molars were sectioned in four, totalizing 20 enamel slabs. In the slabs, a test surface (window) of 3 x 3 mm was delimited. The specimens were submitted to erosive challenge into gastric juice (from endoscopy exam) (n=10), or orange juice (industrialized) (n=10), as follows: 5 minutes in 3 ml of acidic solution, rinse with distilled water and stored in artificial saliva for 3 hours. This cycle was repeated for four times a day during 14 days. Calcium (Ca) loss after acid exposure was determined by atomic emission spectroscopy. The presence of carbonate (CO) and phosphate (PO) in the specimens was evaluated before and after the erosive challenge by FT-Raman spectroscopy. To evaluate the treatments for prevention of dental erosion, forty enamel specimens of unerupted human third molars were distributed according to the following treatments (n=10): acidic phosphate fluoride gel (APF 1.23%), Nd:YAG laser (100 mJ, 1 W, 10 Hz), and the associations fluoride + laser and laser + fluoride. These treatments were applied 1 hour before the erosive challenge, which, in this phase was made with hydrochloric acid only (0.01 M/pH 2.2). The fluoride was applied on the enamel surfaces for 4 minutes. The irradiation of enamel surface was made in the contact mode after coating with a photo-activator. The associations were done using fluoride and laser like describe before. The Ca loss was determined by atomic emission spectroscopy and superficial roughness (Ra) was measured before and after the erosive challenge. In the comparison of the acidic sources, the mean loss of Ca were: 12.74 ± 3.33 mg/L Ca (gastric juice) and 7.07 ± 1.44 mg/L Ca (orange juice) (p=0.0003). The FT-Raman spectroscopy found no statistically significant difference in the ratio CO/PO after the erosive challenge. The CO/PO ratios values before and after the challenge were: 0.16/0.17 (gastric juice) (p=0.37) and 0.18/0.14 (orange juice) (p=0.16). In the evaluation of the treatments, the mean Ca loss were (mg/L): APF 1.707a (± 0.113), Nd:YAG 1.638a (±0.080), APF + Nd:YAG 1.385b (±0.078), Nd:YAG + APF 1.484b (±0.068). The mean initial roughness of specimens was 0.14 m. After the erosive challenge the roughness showed a significant increase (p<0.01): APF 0.69bc (±0.091), Nd:YAG 0.87a (±0.119), APF + Nd:YAG 0.61c (±0.090) and Nd:YAG + APF 0.72b (±0.069). It was concluded that gastric juice has higher erosive potential to enamel than orange juice and the association between fluoride and laser was more efficient for the prevention of dental erosion than both methods separately. Análise espectral Raman Desmineralização do dente Erosão dentária Espectrometria Flúor Fluoride Lasers Lasers Prevenção & controle Prevention & control Spectrometry Spectrum analysis Raman Tooth demineralization Tooth erosion

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