No description available.

<p>This study has shown that OH˙ radicals can be generated in an Fe/O2 cell from the electrode products via Fenton&rsquo / s reaction and used for water disinfection. The cell system in which the experiments were carried out was open and undivided and contained two electrodes with iron (Fe) as the anode and oxygen (O2) gas diffusion electrode. Typically, 100 ml of Na2SO4.10H2O (0.5M) solution was used as a background electrolyte. OH˙ radicals were produced in-situ in an acidic solution aqueous by oxidation of iron (II), formed by dissolving of the anode, with hydrogen peroxide (H2O2). The H2O2 was electrogenerated by reduction of oxygen using porous reticulated vitreous carbon (RVC) as a catalyst.</p>

<p>A comparative study of electrolysers using different anodic materials for the electrolysis of brine (sodium chloride) for the production of sodium hypochlorite as a source of available chlorine for disinfection of rural water supplies has been undertaken. The electrolyser design used was tubular in form, having two chambers i.e. anode inside and cathode outside, separated by a tubular inorganic ceramic membrane. The anode was made of titanium rod coated with a thin layer of platinum and a further coat of metal oxide. The cathode was made of stainless steel wire. An assessment of these electrolysers was undertaken by studying the effects of some variable parameters i.e.current, voltage and sodium chloride concentration. The cobalt electrolyser has been shown to be superior as compared to the ruthenium dioxide and manganese dioxide electrolysers in terms of hypochlorite generation. Analysis of hydroxyl radicals was undertaken since there were claims that these are produced during brine electrolysis. Hydroxyl radical analysis was not successful, since sodium hypochlorite and hypochlorous acid interfere using the analytical method described in this study.</p>

To avoid the spread of disease from sewage treatment effluents, pathogenic microorganisms present must be destroyed by one or a combination of disinfection methods. Chlorine remains the predominant disinfectant used although it consumes considerable amounts of energy and has associated exposure risks from production, transportation and storage of this poisonous gas. In addition to bacteria and other objectionable microorganisms, color, suspended and colloidal solids also require removal from water for reuse. Aluminum and iron additions have been used to coagulate and remove non-settleable solids. By electrically dissolving aluminum to form solids-bridging aluminum hydroxide, the water itself can also be disinfected by the effects of electrical fields and its reactions to form disinfectant chemicals and direct destruction of microorganisms in the water. This research investigated the effects of electrical current, time, and chloride concentration on the electrochemical disinfection of sewage treatment plant effluent using aluminum electrodes to substitute for chlorine disinfection.

O objetivo deste estudo foi investigar, longitudinalmente, o efeito de cinco soluções desinfetantes sobre a microdureza e rugosidade superficial de uma resina acrílica termopolimerizável e três materiais reembasadores rígidos. Um total de 240 corpos de prova circulares (30 X 6mm) foram fabricados, utilizando um material para base de dentaduras (Lucitone 550; n=60), e três materiais rígidos, para reembasamento (Jet; n=60, Kooliner; n=60, Tokuyama rebase II fast; n=60), os quais foram imersos em água (controle), e em cinco soluções desinfetantes (hipoclorito de sódio a 1%, hipoclorito de sódio a 2%, hipoclorito de sódio a 5,25%, glutaraldeído a 2% e gluconato de clorexidina a 4%), e testados para avaliação de microdureza Knoop (KHN) e rugosidade superficial (Ra-µm) em diferentes intervalos (antes das imersões, após 30, 90 e 180 ciclos de desinfecção. Em cada condição experimental foram utilizados 10 corpos de prova de cada material estudado. Os dados foram analisados através de esquema fatorial (6X4) e as médias foram analisadas por meio de análise de variância, seguida por teste de Tukey a 5%. Para as resinas Lucitone 550 (20,61 ± 1,36 a 15,44 ± 1,26 KHN), Jet (18,74 ± 0,47 a 13,75 ± 0,95 KNH), Kooliner (14,09 ± 1,63 a 7,52 ± 0,88 KHN) e Tokuyama rebase II fast (12,57 ± 0,94 a 8,28 ± 0,39 KHN), foi observada uma diminuição significativa dos valores de microdureza, independente da solução utilizada, após 180 ciclos de imersão. Não foi observada interação significativa para a rugosidade da resina Kooliner. Para a resina Lucitone 550 (0,06 ± 0,01 a 0,20 ± 0,02µm) e Jet (0,07 ± 0,01 a 0,23 ± 0,04µm), foi observado aumento significativo dos valores de rugosidade superficial, independente da solução desinfetante utilizada, e a após 180 ciclos de imersão em água, estes materiais mantiveram valores semelhantes ao da avaliação inicial. A resina Tokuyama rebase II fast não mostrou diferenças significativas nos valores de rugosidade superficial quando imersa em água, hipoclorito de sódio a 2%, 5,25% e glutaraldeído a 2%, durante o período do estudo. Ao final da avaliação (180 ciclos), conclui-se que, embora todas as soluções tenham causado redução da microdureza da resina Lucitone 550, os espécimes submetidos às imersões em H5,25% e H2% apresentaram menores valores, no entanto, não ocorreu diferença significante entre os desinfetantes para as resinas autopolimerizáveis. As soluções H1%, H2% e GC4% causaram maior alteração na rugosidade superficial da resina Lucitone 550. Estas mesmas soluções, além de H5,25%, promoveram maior rugosidade na resina Jet, enquanto que, para a resina Tokuyama Rebase II fast, não houve diferença entre os desinfetantes. / The aim of this study was to investigate the longitudinal effect of five disinfection solutions on the hardness and roughness of one heat-polymerizing denture base acrylic resin and three hard chairside resins. A total of 240 circular specimens (30 X 6mm) were fabricated using one denture base material (Lucitone 550; n=60) and three hard chairside reliners (Jet; n=60, Kooliner; n=60, Tokuyama rebase II fast; n=60), which were immersed in water (control), and five disinfecting solutions (1% sodium hypochlorite; 2% sodium hypochlorite; 5,25% sodium hypochlorite, 2% glutaraldehyde; 4% chlorhexidine gluconate) that were tested for knoop hardness (KHN) and roughness (Ra-µm) for different times (before immersions, after 30, 90 and 180 immersion cycles). For each experimental condition, 10 specimens were used from each material. Data was analyzed by factorial scheme (6 X 4) and the means were analyzed by The Variance Analysis which was followed by Tukey\'s test 5%. For Lucitone 550 (from 20,61 ± 1,36 to 15,44 ± 1,26 KHN), Jet (from 18,74 ± 0,47 to 13,75 ± 0,95 KHN), Kooliner (from 14,09 ± 1,63 to 7,52 ± 0,88 KHN), Tokuyama rebase II fast (from 12,57 ± 0,94 to 8,28 ± 0,39 KHN) significant decrease in hardness was observed regardless of the solution used, after 180 immersion cycles. No significant interactions were observed for Kooliner roughness. Between Lucitone (from 0,06 ± 0,01 to 0,20 ± 0,02µm) and Jet, (from 0,07 ± 0,01 to 0,23 ± 0,04µm) there was a significant increase in roughness regardless of the disinfectant solution used; Jet showed significant increase in roughness after immersion in water for 180 cycles. Tokuyama rebase II fast showed no significant differences in roughness when immersed in water, 2% sodium hypochlorite, 5.25% sodium hypochlorite, and 2% glutaraldehyde after 180 cycles. In conclusion, this study showed that Lucitone 550 specimens exhibited significant decrease in hardness regardless of the disinfection solution used, and the specimens immersed in H5,25% and H2% showed lower hardness values; However, no significant differences were noted between all disinfectants solution, for hard chairside resins. The solutions H1%, H2% and GC4% caused more alteration in roughness of Lucitone 550. These solutions along with H5,25% caused an increase in the roughness of Jet, while with the Tokuyama rebase II fast there was no difference between the disinfection solutions.

O objetivo desse estudo foi investigar longitudinalmente, o efeito de sucessivos ciclos de desinfecção sobre as propriedades de microdureza e rugosidade superficial de 4 diferentes resinas acrílicas. Foram confeccionados 200 corpos de prova, utilizando um material para base de dentaduras (Lucitone 550) e três materiais rígidos para reembasamento (Jet, Kooliner e Tokuyama Rebase II Fast), os quais foram divididos, para cada resina, em cinco grupos: imersos em água (controle) e submetidos à irradiação por microondas em quatro combinações diferentes de potência-tempo. Esses grupos foram avaliados em relação à rugosidade superficial (Ra-µm) e microdureza Knoop (KHN) em um período anterior às desinfecções e após 30, 90 e 180 ciclos de desinfecção. Os dados foram submetidos à análise de variância, seguida por teste de Tukey a 5%. As principais alterações nos valores de microdureza (diminuição) e rugosidade superficial (aumento) ocorreram após 30 ciclos de desinfecção em microondas. Após esse período existiu uma tendência para a estabilização dos valores dessas propriedades, mesmo quando ciclos adicionais (90 e 180 ciclos) foram realizados. Os tratamentos empregados para os diferentes grupos experimentais (diferentes combinações de potência-tempo) não foram os principais fatores que tiveram influência sobre a propriedade de microdureza. É provável que a redução dos valores de microdureza tenha sido mais dependente da sorpção de água do que da energia de microondas por si só. O principal efeito sobre a microdureza através da irradiação por microondas parece ser o efeito da água. A exposição da prótese a fluidos como água e saliva é uma condição que não pode ser evitada. Esse comportamento não foi observado para a rugosidade superficial. Os tratamentos empregados para os diferentes grupos experimentais (diferentes combinações de potência-tempo) tiveram influência sobre a propriedade de rugosidade superficial. De maneira geral observou-se que os valores de rugosidade superficial dos espécimes somente imersos em água foram menores do que os valores dos espécimes irradiados. Apesar da rugosidade de alguns espécimes ter ficado acima de 0.2 um, isso não parece contra-indicar a desinfecção por microondas. As técnicas convencionais de acabamento e polimento aplicadas para as outras superfícies dificilmente atingem níveis de rugosidade superficial inferiores a 0,2 µm. Dessa maneira parece ser prudente a afirmação de que a desinfecção através da energia de microondas pode ser utilizada para a desinfecção de próteses. / The objective of this study was to investigate the longitudinal effect of microwave disinfection on the hardness and roughness of one heat-polymerizing denture base acrylic resin and three hard chairside resins. A total of 200 specimens were fabricated using one denture base material (Lucitone 550; n=50) and three hard chairside reliners (Jet; n=50, Kooliner; n=50, Tokuyama Rebase II Fast; n=50), which were immersed in water (control), and submitted to microwave disinfection at four different arrangements of power and time. These specimens were tested for knoop hardness (KHN) and roughness (Ra-µm) for different times (before disinfection, after 30, 90 and 180 disinfection cycles). Data were analyzed by Variance Analysis which was followed by the Turkey\'s test at a level of 5%. The principal alterations on hardness (reduction) and on roughness (elevation) occurred after 30 disinfection cycles. Both of the properties remained stable after this period, even after 90 and 180 disinfection cycles. The different arrangements of power and time carried out for the experimental groups did not have influence on hardness. It is possible that this property was more affected from water sorption than microwave energy only. During its clinical use, the denture is exposed to water and saliva and it seems that this condition cannot be prevented. This fact was not observed for roughness. The different arrangements of power and time carried out for the experimental groups had influence on roughness. It was observed that the control group had lower roughness values when compared to the experimental groups. The roughness values of some specimens were greater than 0.2 um. However, this fact does not compromise the indication of microwave disinfection. The finishing and polishing techniques commonly used for the other surfaces of the denture do not get roughness values below 0.2 um. Therefore, it is very likely that microwave disinfection could be recommended for the disinfection of dentures.

Tang Hung Yuk. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 71-79). / Abstracts in English and Chinese. / ABSTRACT --- p.i / DECLARATION --- p.iii / ACKNOWLEDGEMENT --- p.iv / TABLE OF CONTENTS --- p.v / LIST OF TABLES --- p.viii / LIST OF FIGURES --- p.ix / Chapter CHAPTER ONE: --- INTRODUCTION --- p.1 / Chapter 1.1 --- Fundamentals of TiO2 --- p.1 / Chapter 1.2 --- Application of TiO2 --- p.5 / Chapter 1.3 --- Scope of Work --- p.11 / Chapter CHAPTER TWO: --- DISINFECTION BY UV IRRADIATED TiO2 --- p.14 / Chapter 2.1 --- Introduction --- p.14 / Chapter 2.2 --- Experimental --- p.19 / Chapter 2.2.1 --- Materials --- p.19 / Chapter 2.2.2 --- Preparation of TiO2 films --- p.19 / Chapter 2.2.3 --- Culture of microorganisms --- p.20 / Chapter 2.2.4 --- Bactericidal activities --- p.21 / Chapter 2.2.5 --- Photocatalytic experiment to degrade acetone in gas phase --- p.21 / Chapter 2.2.6 --- Photocatalytic experiment to degrade rhodamine B in aqueous phase --- p.22 / Chapter 2.2.7 --- Characterization --- p.23 / Chapter 2.3 --- Results and Discussions --- p.25 / Chapter 2.3.1 --- Bactericidal activity --- p.25 / Chapter 2.3.2 --- Photocatalytic activity --- p.34 / Chapter 2.3.3 --- Thickness and transmittance of Ti〇2 films --- p.37 / Chapter 2.3.4 --- Surface morphology and roughness of thin films --- p.40 / Chapter 2.3.5 --- Crystalline phase and crystallite size of thin films --- p.42 / Chapter 2.3.6 --- XPS study --- p.43 / Chapter CHAPTER THREE: --- DISINFECTION BY VISIBLE IRRADIATED TiO2 --- p.47 / Chapter 3.1 --- Introduction --- p.47 / Chapter 3.2 --- Experimental --- p.58 / Chapter 3.2.1 --- Materials --- p.58 / Chapter 3.2.2 --- Preparation of TiO2 films --- p.58 / Chapter 3.2.3 --- Culture of microorganisms --- p.59 / Chapter 3.2.4 --- Bactericidal activity --- p.60 / Chapter 3.3 --- Results and discussions --- p.61 / Chapter 3.3.1 --- Dye adsorbed TiO2 film stability --- p.61 / Chapter 3.3.2 --- Bactericidal activity of the dye-sensitized TiO2 films --- p.62 / Chapter 3.3.3 --- Bactericidal mechanism of the films under irradiation --- p.64 / Chapter CHAPTER FOUR: --- CONSLUSIONS --- p.68 / REFERENCES --- p.71

在過去的幾十年中，人們越來越關心由致病微生物引起的水傳播疾病的爆發。作為一種綠色技術，太陽能光催化在不引起二次污染的殺滅各種致病微生物方面引起了廣泛關注。但是，目前最廣泛應用的TiO₂光催化劑僅在紫外光激發範圍內有效，而紫外光僅占太陽光譜的4%。因為太陽光譜中有45%是可見光，所以新型可見光催化劑的開發是現今光催化技術亟待解決的問題。另一方面，目前對於光催化殺菌機理的研究報導非常稀少而且主要集中于紫外-TiO₂光催化系統中，而對於可見光催化系統中的殺菌機理研究還鮮有報導。 / 本研究介紹三種新型可見光催化劑的殺菌性能。它們是B,Ni共摻TiO₂微米球（BNT），BiVO₄納米管（BV-NT）和CdIn₂S₄微米球（CIS）。其中一種是修飾的TiO₂催化劑，另兩種是新型的非TiO₂基催化劑。採用加入各種湮滅劑結合一種分離裝置的研究方法系統研究了三種催化劑的可見光殺菌機理。首先，研究發現當用BNT作為光催化劑的時候，可見光催化降解染料和殺菌之間存在巨大的差異。對於光催化降解染料，光催化反應主要發生在催化劑的表面，是由表面活性物質如h⁺, ・OHs和・O₂⁻參與，而細菌可以被擴散物種如・OH[subscript b]和H₂O₂，以不直接接觸催化劑表面的方式被殺死。可擴散的H₂O₂在這種殺菌過程中起了最重要的作用，而它可以在催化劑價帶以・OH[subscript b]溶液體相耦合和・OH[subscript s]催化劑表面耦合兩種方式產生。 / 其次，在用BV-NT作為光催化劑可見光殺滅大腸桿菌的過程中，光生空穴（h⁺）以及由空穴產生的氧化物種，如・OH[subscript s], H₂O₂和・HO₂/・O₂⁻，是主要的活性物種。但是這個殺菌過程只有很少量的H₂O₂可以擴散到溶液中，導致有效殺菌需要細菌和光催化表面直接接觸。研究還發現，細菌本身可以捕獲光生電子（e⁻）來降低空穴-電子複合率，這個作用在無氧氣參與的殺菌過程中尤為明顯。透射電鏡顯示，細菌的破壞是由細胞壁開始從外到內的被破壞。研究認為，表面羥基・OH[subscript s]比溶液體相羥基・OH[subscript b]更加重要，並且很難從BV-NT表面擴散進容易中。 / 最後，研究還發現CIS也具有不接觸細菌而有效可見光催化殺滅大腸桿菌的能力，這也歸結為可擴散H₂O₂，而不是・OH的作用。H₂O₂可以通過・O₂⁻從催化劑導帶和價帶同時產生。本研究提供了幾種具有應用前景的高效可見光催化殺菌催化劑，並對其光催化機理提出了新的思路，指出可見光催化殺菌機理與使用的光催化劑是密切相關的。更重要的是，本研究建立了一種簡便易行的研究方法，可用於對其他各種可見光催化殺菌系統進行深入的機理研究。 / During the last few decades, there has been an increasing public concern related to the outbreak of waterborne diseases caused by pathogenic microorganisms. As a green technology, solar photocatalysis has attracted much attention for the disinfection of various microorganisms without secondary pollution. However, the most commonly used TiO₂ photocatalyst is only active under UV irradiation which accounts for only 4% of the solar spectrum. Therefore, new types of photocatalysts that can be excited by visible light (VL) are highly needed, as 45% of the solar spectrum is covered by VL. In addition, existing reports on the mechanisms of photocatalytic bacterial disinfection are rather limited and mostly based on TiO₂-UV irradiated systems, thus the mechanisms in visible-light-driven (VLD) photocatalystic disinfection systems are far from fully understandable. / In this study, three different kinds of VLD photocatalysts were discovered for the photocatalytic bacterial disinfection. They were B-Ni-codoped TiO₂ microsphere (BNT), bismuth vanadate nanotube (BV-NT), and cadmium indium sulfide (CIS). One was modified TiO₂-based photocatalyst, and the other two were new types of non-TiO₂ based photocatalyst. The mechanisms of VLD photocatalytic disinfection were investigated by multiple scavenging studies combined with a partition system. Firstly, significant differences between VLD photocatalytic dye decolorization and bacterial disinfection were found in the case of BNT as the photocatalyst. For photocatalytic dye decolorization, the reaction mainly occurred on the photocatalyst surface with the aid of surface-bounded reactive species (h⁺, ・OH[subscript s] and ・O₂⁻), while bacterial cell could be inactivated by diffusing reactive oxidative species such as ・OH[subscript b] and H₂O₂ without the direct contact with the photocatalyst. The diffusing H₂O₂ played the most important role in the photocatalytic disinfection, which could be produced both by the coupling of ・OH[subscript b] in bulk solution and ・OH[subscript s] on the surface of photocatalyst at the valence band. / Secondly, when using BV-NT as the photocatalyst for Escherichia coli K-12 inactivation, the photogenerated h⁺ and reactive oxidative species derived from h⁺, such as ・OH[subscript s], H₂O₂ and ・HO₂/・O₂⁻, were the major reactive species. However, the inactivation requires close contact between the BV-NT and bacterial cells, as only a limited amount of H₂O₂ can diffuse into the solution to cause the inactivation. The bacterial cells can trap e⁻ in order to minimize e⁻-h⁺ recombination, especially under anaerobic condition. Transmission electron microscopic study indicated the destruction process of bacterial cell began from the cell wall to other cellular components. The ・OH[subscript s] was postulated to be more important than ・OH[subscript b] and was not supposed to be released very easily from BV-NT surface. / Finally, it was found that E. coli cells could be effectively inactivated without the direct contact with CIS, which was attributed to the function of diffusing H₂O₂ rather than ・OH. H₂O₂ was produced from both conduction and valance bands with the involvement of ・O₂⁻, which were detected by ESR spin-trap with DMPO trapping technology. While this study provided promising candidates of efficient VLD photocatalysts for water disinfection as well as deep insights into the disinfection mechanisms, it was notable that the photocatalytic disinfection mechanisms were quite dependent on the selected photocatalysts. Nevertheless, the research methodology established in this study was proved to be facile and versatile for the in-depth investigation of mechanisms in different VLD photocatalyst systems. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Wang, Wanjun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 140-170). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Acknowledgements --- p.i / Abstract --- p.vi / List of Figures --- p.xvi / List of Plates --- p.xxiii / List of Tables --- p.xxiv / List of Equations --- p.xxv / Abbreviations --- p.xxvii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Water disinfection --- p.1 / Chapter 1.2 --- Traditional water disinfection methods --- p.2 / Chapter 1.2.1 --- Chlorination --- p.2 / Chapter 1.2.2 --- Ozonation --- p.3 / Chapter 1.2.3 --- UV irradiation --- p.4 / Chapter 1.3 --- Advanced oxidation process --- p.5 / Chapter 1.4 --- Photocatalysis --- p.6 / Chapter 1.4.1 --- Fundamental mechanism for TiO₂ photocatalysis --- p.7 / Chapter 1.4.2 --- Photocatalytic water disinfection --- p.12 / Chapter 1.5 --- Visible-light-driven photocatalysts for water disinfection --- p.16 / Chapter 1.5.1 --- Modified TiO₂ photocatalysts --- p.16 / Chapter 1.5.1.1 --- Surface modication of TiO₂ by noble metals --- p.16 / Chapter 1.5.1.2 --- Ion doped TiO₂ --- p.18 / Chapter 1.5.1.3 --- Dye-sensitized TiO₂ --- p.19 / Chapter 1.5.1.4 --- Composite TiO₂ --- p.20 / Chapter 1.5.2 --- Non-TiO₂ based photocatalysts --- p.22 / Chapter 1.5.2.1 --- Metal oxides --- p.22 / Chapter 1.5.2.2 --- Metal sulfides --- p.24 / Chapter 1.5.2.3 --- Bismuth metallates --- p.25 / Chapter 1.6 --- Photocatalystic disinfection mechanisms --- p.27 / Chapter 2 --- Objectives --- p.30 / Chapter 3 --- Comparative Study of Visible-light-driven Photocatalytic Mechanisms of Dye Decolorization and Bacterial Disinfection by B-Ni-codoped TiO₂ Microspheres --- p.32 / Chapter 3.1 --- Introduction --- p.32 / Chapter 3.2 --- Experimental --- p.35 / Chapter 3.2.1 --- Materials --- p.35 / Chapter 3.2.2 --- Characterizations --- p.36 / Chapter 3.2.3 --- Photocatalytic decolorization of RhB --- p.36 / Chapter 3.2.4 --- Photocatalytic disinfection of E. coli K-12 --- p.37 / Chapter 3.2.5 --- Partition system --- p.40 / Chapter 3.2.6 --- Scavenging study --- p.41 / Chapter 3.2.7 --- Analysis of ・OH and ・O₂⁻ --- p.42 / Chapter 3.2.8 --- Analysis of H₂O₂ --- p.43 / Chapter 3.3 --- Results and Discussion --- p.44 / Chapter 3.3.1 --- XRD and SEM images --- p.44 / Chapter 3.3.2 --- Photocatalytic decolorization of RhB --- p.46 / Chapter 3.3.2.1 --- Role of reactive species --- p.46 / Chapter 3.3.2.2 --- Partition system for dye decolorization --- p.49 / Chapter 3.3.3 --- Photocatalytic bacterial disinfection --- p.51 / Chapter 3.3.3.1 --- Role of reactive species --- p.51 / Chapter 3.3.3.2 --- Partition system for bacterial disinfection --- p.54 / Chapter 3.3.3.3 --- pH effects --- p.58 / Chapter 3.3.3.4 --- Role of H₂O₂ --- p.60 / Chapter 3.3.4 --- Role of ・O₂⁻ in RhB decolorization and bacterial disinfection --- p.67 / Chapter 3.4 --- Conclusions --- p.75 / Chapter 4. --- Visible-light-driven Photocatalytic Inactivation of E. coli K-12 by Bismuth Vanadate Nanotubes: Bactericidal Performance and Mechanism --- p.76 / Chapter 4.1 --- Introduction --- p.76 / Chapter 4.2 --- Experimental --- p.78 / Chapter 4.2.1 --- Materials --- p.78 / Chapter 4.2.2 --- Photocatalytic bacterial inactivation --- p.80 / Chapter 4.2.3 --- Bacterial regrowth ability test --- p.82 / Chapter 4.2.4 --- Analysis of reactive species --- p.82 / Chapter 4.2.5 --- Preparation procedure for bacterial TEM study --- p.83 / Chapter 4.2.6 --- Analysis of bacterial catalase activity --- p.84 / Chapter 4.2.7 --- Analysis of potassium ion leakage --- p.84 / Chapter 4.3 --- Results and Discussion --- p.85 / Chapter 4.3.1 --- Photocatalytic bacterial inactivation --- p.85 / Chapter 4.3.2 --- Mechanism of photocatalytic inactivation --- p.87 / Chapter 4.3.2.1 --- Role of primary reactive species --- p.87 / Chapter 4.3.2.2 --- Role of direct contact effect --- p.96 / Chapter 4.3.3 --- Destruction model of bacterial cells --- p.98 / Chapter 4.3.4 --- Analysis of radical production --- p.104 / Chapter 4.4 --- Conclusions --- p.109 / Chapter 5 --- CdIn₂S₄ Microsphere as an Efficient Visible-light-driven Photocatalyst for Bacterial Inactivation: Synthesis, Characterizations and Photocatalytic Inactivation Mechanisms --- p.111 / Chapter 5.1 --- Introduction --- p.111 / Chapter 5.2 --- Experimental --- p.113 / Chapter 5.2.1 --- Synthesis --- p.113 / Chapter 5.2.2 --- Characterizations --- p.114 / Chapter 5.2.3 --- Photocatalytic bacterial inactivation --- p.116 / Chapter 5.3 --- Results and Discussion --- p.117 / Chapter 5.3.1 --- Characterizations of Photocatalyst --- p.117 / Chapter 5.3.2 --- Photocatalytic bacterial inactivation and mechanism --- p.121 / Chapter 5.3.3 --- Destruction process of bacterial cell --- p.128 / Chapter 5.3.4 --- Analysis of radical generation --- p.131 / Chapter 5.4 --- Conclusions --- p.133 / Chapter 6 --- General Conclusions --- p.135 / Chapter 7 --- References --- p.140

In this thesis I developed and analysed several mathematical models that describe the dynamics of infectious diseases spreading in a population simultaneously with people becoming aware of the presence of the disease and thus modifying their behaviour. This is achieved using compartmental models, with further extensions to models with time delays and the administration of vaccines. Resulting mathematical models were analysed using the techniques of dynamical systems and bifurcations theory, complemented by direct numerical simulations. Design of optimal strategies maximising the reduction of infection rates subject to logistical constraints were studied within the new modelling framework and with a view to be used in realistic contexts. Of particular interest is the design and analysis of the impact of local and global awareness campaigns, as well as the administration of vaccines to minimise the spread of infections.

Resumo: Este estudo teve por objetivo avaliar a efetividade da irradiação por microondas na esterilização de próteses totais. Para isso, oitenta próteses totais padronizadas foram confeccionadas e submetidas à esterilização com óxido de etileno. As próteses foram então individualmente inoculadas (107 ufc/mL) com meio de cultura de Tryptic Soy Broth (TSB) contendo um dos seguintes microrganismos: C.albicans, S. aureus, B. subtilis e P. aeruginosa. Após 48 horas de incubação a 37oC, 40 amostras foram imersas em 200 mL de água e irradiadas a 650 W por 6 minutos. Quarenta amostras não irradiadas foram utilizadas como controle. A seguir, 25 uL da suspensão resultante das diluições seriadas de 10-1 a 10-6, foram semeados em placas de Petri contendo os meios de cultura seletivos para cada microrganismo. Todas as placas foram incubadas a 37oC por 48 horas. Após a incubação, as colônias foram quantificadas em ufc/mL. Para verificação da efetividade exposição às microondas em longo prazo as amostras irradiadas foram imersas em meio de cultura e incubadas a 37oC por 7 dias. A esterilização foi obtida, após 48 horas, para as próteses contaminadas com C.albicans, S. aureus e B. subtilis. Um pequeno número de colônias foi observado em 2 placas de Petri para o microrganismo P. aeruginosa. Após 7 dias de incubação a 37oC houve crescimento microbiológico em 3 culturas de TSB, sendo 2 para P. aeruginosa e um para B. subtilis. Todas as próteses totais do grupo controle apresentaram crescimento microbiano nas placas de Petri, após 48 horas de incubação a 37oC. A irradiação por microondas por 6 minutos a 650 W provou ser um método rápido e efetivo para desinfecção das próteses totais contaminadas com P. aeruginosa e B. subtilis além, de promover a esterilização das inoculadas com C. albicans e S. aureus. / Abstract: The aim of this study was to evaluate the effectiveness of microwave irradiation on the sterilization of complete dentures contaminated with individual suspension of 3 bacterias (P. aeruginosa, S. aureus and B. subtilis) and one fungus (C. albicans). Eighty simulated maxillary complete dentures were fabricated in a standardized procedure and subjected to ethylene oxide sterilization. The dentures were individually inoculated (107 cfu/mL) with Tryptic Soy Broth (TSB) media containing one of the tested microorganisms. After incubation at 37°C for 48 hours, forty dentures were immersed in 200 mL of distilled water and submitted to microwave irradiation at 650 W for 6 minutes. Forty non - irradiated dentures were used as positive controls. Using 0.9% sodium chlorine solution as diluent, tenfold serial dilutions 10-1 - 10-6 were plated onto 4 selective media appropriate for each organism: Manitol Salt Agar for S. aureus, Miller Hinton for P. aeruginosa, Sabourand Agar containing 5 μg/mL gentamicin for C.albicans, and Tryptic Soy Agar for B. subtilis. All plates were incubated at 37°C for 48 hours and colonies counts of each plate were quantified (cfu/mL). To verify the long - term effectiveness ofmicrowave sterilization, the TSB beakers with the microwave specimens were incubated at 37°C for 7 days. Data were statistically analyzed by Kruskal - Wallis's test (α=0.05). Irradiated dentures showed consistent sterilization of S. aureus, B. subtilis and C. albicans after 48 hours. Compared to P. aeruginosa control, a very low number of colonies were detected only in two plates. Turbidity was observed in three broth beakers, two from P. aeruginosa and one from B. subtilis, after 7 days incubation at 37°C. All control dentures showed microbial...(Complete abstract, click electronic access below) / Orientador: Carlos Eduardo Vergani / Coorientador: Denise Madalena Palomari Spolidorio / Banca: Ana Cláudia Pavarina / Banca: Dalva Cruz Laganá / Mestre