A series of lab-scaled digestion studies including conventional mesophilic anaerobic digestion(MAD), thermophilic anaerobic digestion (TAD) at a range of treatment temperatures, and mesophilic high solids digestion of thermally pretreated wastewater sludge (THD) were carried out. Enhanced digestion performance in terms of solids destruction and methane generation by THD relative to MAD was achieved, and was largely attributable to the solubilization and subsequent biodegradation of energy-rich substrates within blended primary and secondary sludge. TAD was observed to underperform MAD, especially at elevated temperatures as methanogenic inhibition resulted in the accumulation of headspace hydrogen, thus resulting in poor removal of volatile fatty acids. The thermodynamics of fatty acid metabolism was favorable at each digestion temperature, thus it was concluded that microbial inhibition was the controlling factor in poor thermophilic performance. Inhibition by free unionized ammonia (NH₃) was characterized for THD and MAD biomass. Acetic acid degradation was equally affected over a range of NH₃ concentrations; however, methane generation by THD was less sensitive to ammonia inhibition, thus suggesting that methanogenesis by THD was less dependent on the NH₃-sensitive process of aceticlastic methanogenesis. Total ammonia nitrogen (TAN) and bicarbonate alkalinity were stoichiometrically produced from proteinaceous material during thermal hydrolytic pretreatment and subsequent high solids anaerobic digestion. Combined effects of TAN and high pH resulted in NH₃-inhibition during THD. Kinetic evaluations suggested that a growth rate reduction of approximately 65% was associated with in-situ NH₃ concentrations of the THD reactor. NH₃-inhibition was apparently responsible for a shift in dominant methanogenic community of the aceticlastic Methanosarcina barkeri in MAD to the hydrogenotrophic Methanoculleus bourgensis in THD. A similar shift in methanogenic community was observed between low temperature thermophilic digestion at 47°C, where the dominant order was Methanosarcinales, to high temperature thermophilic digestion at 59°C where the dominant order was Methanobacteriales. These findings support a process-driven pathway shift from aceticlastic to non-aceticlastic methanogenesis between 180 and 290 mg/L NH₃-N. Such a threshold is supported by previous literature related to ammonia tolerance of pure cultures of methanogens and has significant implications for the kinetic design of advanced anaerobic digestion processes. / Ph. D.

Master of Science

The purpose of this study was to describe the factors that determine the utilisation of VIA, and to investigate the socio-economic status of women who undergone VIA. A retrospective document analysis of 323 clinical records was conducted at a specific rural hospital in Zimbabwe. A retrospective, cross-sectional, non-experimental, descriptive, analysis of clinical records was conducted using a checklist to extract data from the records of women who have undergone VIA for cervical screening at the specific rural hospital. The results revealed that 70% (N=225) were from outside the catchment area, 73% (N=234) were poor, 54% (N=173) were of high parity, 85% (N=275) were ill with conditions that included lower back and abdominal pains, excessive vaginal discharge and vaginal bleeding after intercourse. The study further revealed that 72% (N=226) had no prior cervical cancer screening and 87% (N=277) were screened by chance. The conclusion drawn was that socio-economic and logistical constraints hinder cervical cancer screening among rural women. It is recommended that VIA screening and health education on cervical cancer be offered to all women visiting healthcare facilities. Furthermore, the government should consider funding in order to prioritise women’s health issues. / Health Studies / M.A. (Nursing Science)

Halogenierte Verbindungen treten in der Natur in einer großen Vielzahl auf. Ihre Funktionen können sehr vielfältig sein und reichen von antimikrobiellen Aktivitäten bis hin zu pflanzlichen Wachstumsregulatoren. Vor allem in Pilzen und Bakterien gibt es eine Reihe halogenierter Substanzen. Die Synthesewege und beteiligten Enzyme dieser Verbindungen sind weitestgehend aufgeklärt. Bei einer Klasse von halogenierenden Enzymen handelt es sich um Flavin-abhängige Tryptophan-Halogenasen, welche die Aminosäure Tryptophan regioselektiv und substratspezifisch an bestimmten Positionen des Indolrings halogenieren können. Tryptophan ist eine essenzielle Aminosäure, welche sehr vielfältige Funktionen innerhalb der Zellen besitzt. So wird diese in Polypeptidketten von Enzymen und Proteinen eingebaut und dient als Vorstufe für viele verschiedene Stoffwechselprodukte. Das Pflanzenhormon Indol-3-Essigsäure (IAA) leitet sich z. B. aus ebendieser Aminosäure ab. Pflanzenhormone haben sehr vielfältige Funktionen innerhalb der Pflanzen und spielen z. B. bei der Entwicklung, Differenzierung und Abwehr eine wichtige Rolle. In einigen Pflanzen konnte eine halogenierte Form von IAA, die 4-Chlorindol-3-Essigsäure, nachgewiesen werden. In verschiedenen Versuchen konnte gezeigt werden, dass diese Verbindung eine erhöhte Reaktivität gegenüber der nicht halogenierten Form aufweist. Die Wirkung dieser Substanz wurde in den letzten Jahrzehnten gut untersucht, über die an der Synthese beteiligten Enzyme dieses Pflanzenhormons ist jedoch kaum etwas bekannt. Im Rahmen dieser Arbeit wurden Gene von drei bakteriellen Tryptophan-Halogenasen (pyrH, thiH und prnA) in der Modellpflanze Arabidopsis thaliana exprimiert und die Bildung von chlorierten Substanzen genauer untersucht. Hauptaugenmerk wurde dabei auf mögliche chlorierte Metabolite gelegt, welche sich von der Aminosäure Tryptophan ableiten. Neben der Expression der bakteriellen Halogenasegene wurden diese zusätzlich für die Modellpflanze optimiert und unter der Kontrolle des 2× 35S-Promotors in Arabidopsis thaliana transformiert. Die heterologe Expression von AtpyrH, AtthiH, AtprnA, sowie der optimierten Gene AtpyrHopt, AtthiHopt und AtprnAopt konnte in verschiedenen transgenen Linien in den Pflanzen nachgewiesen werden. Die Expression der Halogenasegene variiert dabei in den untersuchten Linien. Durch die Optimierung konnte keine erhöhte Expression der Gene erzielt werden. Lediglich bei der Expression von AtpyrHopt zeigte sich ein erhöhtes Niveau der Genregulation im Vergleich zu AtpyrH. Der Nachweis, dass die transgenen Arabidopsis thaliana-Pflanzen, welche eines der Halogenasegene exprimieren, in der Lage sind die Aminosäure an der entsprechenden Position (5, 6 oder 7) zu halogenieren konnte für alle stabil transformierten Gene erbracht werden. Zusätzlich gelang es, die Halogenase-Enzyme aus transgenen Pflanzen von AtpyrH und AtpyrHopt anzureichern und deren Funktionsfähigkeit in einem Enzym-Test nachzuweisen. Es konnten ebenfalls weitere chlorierte Intermediate detektiert werden, welche u. a. Vorläufermoleküle des Hormons IAA aber auch weiterer Substanzen wie z. B. Camalexin sind. Für Arabidopsis thaliana-Wildtyp konnte die Möglichkeit zur Bildung von Cl-IAA durch die Zugabe von chloriertem Tryptophan gezeigt werden. Die an der Biosynthese beteiligten Enzyme können das chlorierte Substrat verwenden und dem Stoffwechsel zuführen. Die Bildung der chlorierten Verbindungen erfolgte in den transgenen Arabidopsis thaliana-Pflanzen ohne eine zusätzliche Expression einer Flavin-Reduktase. Das für die Halogenierungsreaktion notwendige FADH2 kann durch die Pflanzen selbst zur Verfügung gestellt werden. Die unterschiedliche Regulation der Gene führte bei den transgenen Linien nicht zu phänotypischen Unterschieden. Sowohl die Entwicklung der Pflanzen, als auch die Anzahl und Größe der Rosettenblätter entspricht dem Wildtyp und ist durch die Bildung chlorierter Verbindungen nicht beeinflusst. In verschiedenen Tests wurde die erhöhte Bioaktivität sowohl von chloriertem Tryptophan als auch chlorierter IAA in in vitro Experimenten mit verschiedenen Pflanzen bestätigt. Chlorierte IAA hemmte zusätzlich dazu das Wachstum des Bakteriums Pseudomonas syringae pv. tomato DC3000. In phytopathologischen Untersuchungen mit verschiedenen transgenen Pflanzen zeigte sich, dass Linien von AtthiHopt, AtprnA und AtprnAopt mitunter eine verbesserte Resistenz gegen bestimmte Pathogene aufweisen. Die Ergebnisse dieser Arbeit zeigen, dass die Bildung von chloriertem Tryptophan und chloriertem Indol-3-Acetonitril durch die heterologe Expression von Flavin-abhängigen Tryptophan-Halogenasen in Arabidopsis thaliana sowohl durch die ursprünglichen bakteriellen, als auch die optimierten Gene möglich ist.

Este trabalho descreve estudos eletroquímicos e espectroscópicos da eletrooxidação de etanol, acetaldeído e ácido acético sobre uma superfície de platina monocristalina de baixo índice de Miller 110 modificada por ósmio (Os). O eletrodo monocristalino de Pt(110) foi modificado por Os espontaneamente e pela aplicação de potencial. Os eletrodos foram caracterizados eletroquimicamente, de forma que foram obtidos valores baixos, intermediários e altos de Os sobre a superfície de Pt(110). A eletrooxidação de etanol sobre Pt(110) e Pt(110)/Os, analisada pelas técnicas de voltametria cíclica e cronoamperometria, mostrou que as densidades de corrente para essa reação foram maiores nos graus de recobrimento entre 0,51 – 0,61 ML. A partir dos resultados de FTIR in situ, verificou-se que a reação de oxidação de etanol difere em seus caminhos de acordo com o grau de recobrimento de Os. O caminho um sugere a quebra da ligação C—C com maior intensidade em graus de recobrimento entre 0,36 – 0,80 ML, formando espécies como COlinear, CHx e, posteriormente, CO2. O caminho dois mostra a formação de acetaldeído a partir de 0,4 V sobre os eletrodos Pt(110) e Pt(110)/Os, e que pode haver ainda a produção de CO e ácido acético a partir desse orgânico sobre eletrodos com HOs > 0,80 ML, a baixos potenciais. O estudo realizado com acetaldeído mostrou que o desempenho na oxidação desse orgânico foi sutilmente maior para os eletrodos modificados por Os. O caminho três apresenta a produção de CO2 proveniente da oxidação de etanol diretamente a ácido acético sobre eletrodos com alto grau de recobrimento. Durante a oxidação ocorre a formação a baixos potenciais de COlinear em grandes quantidades. Além disso, há produção de ácido acético e posteriormente de CO2. Ainda nos eletrodos espessos, a produção de CO2 ocorre sem que se observe a presença de COlinear, indicando a possibilidade da oxidação de ácido acético a CO2. A eletrooxidação de ácido acético sobre os diversos eletrodos de Pt(110)/Os mostra que ocorre a quebra dessa molécula para formar CO2, embora de forma menos expressiva que as demais moléculas estudadas. Sendo que parte do CO2 produzido provavelmente tem sua origem no grupo COO- que está adsorvido sobre a superfície do eletrodo. / This work reports the electrochemical and spectroscopic results of ethanol, acetaldehyde and acetic acid electrooxidation onto low index platinum single crystal surface (110) modified by osmium (Os). The Pt(110) electrode was modified by spontaneous and electroless Os deposition and checked electrochemically in order to obtain low, intermediate and high Os coverages on Pt(110). The ethanol electrooxidation on Pt(110) and Pt(110)/Os, which used voltammetric cycle and cronoamperometric techniques, showed higher currents toward this reaction on Os coverage between 0.51-0.61 ML. The FTIR results reveal that ethanol oxidation has different pathways according to Os coverage. The step one suggests that the cleavage of ethanol C—C bond occurs with major intensity forming species such as COlinaer and CHx when the reached coverage is 0.36 – 0.80 ML and further producing CO2. At the step two, acetaldehyde formation is improved above 0.4 V on Pt(110) and Pt(110)/Os, and at low potentials on HOs > 0.80 ML, this molecule can oxidize and form CO and acetic acid. Studies on acetaldehyde showed that the catalytic activity is slightly higher on electrodes modified by Os. The step three presents the CO2 production through acetic acid onto electrodes with high Os coverage. During the oxidation of this molecule, COlinear is produced in large quantities at low potentials; there is formation of acetic acid and thereupon CO2. Onto Os thick electrode, CO2 production occurs without the presence of COlinear, indicating the possibility of acetic acid oxidation directly to CO2. The acetic acid oxidation on various electrodes modified by Os is possible with cleavage of C—C bond to form CO2, though this process is less significant than others organic molecules studied. Since the amount of CO2 produced can arise through the acetate group once this specie is adsorbed onto the electrode surface.

As necessidades de energia global são, na sua maioria, dependentes de combustíveis fósseis. Hidrogênio é uma energia limpa alternativa a esses combustíveis fósseis. Bactérias fototróficas produzem hidrogênio a partir de compostos orgânicos por meio de processo anaeróbio dependente de luz. Assim, este trabalho visou avaliar o efeito das concentrações iniciais de ácido acético e biomassa, e a influência da intensidade luminosa, na produção de hidrogênio por bactéria fototrófica púrpura não-sulfurosa. Foram utilizados reatores em batelada de 2000 mL, com volume útil de 1000 mL e headspace de 1000 mL preenchido com hélio. Nos reatores foi adicionado ácido acético e glutamato de sódio (0,8 mmol/L) como fontes de carbono e nitrogênio, respectivamente, e cultura de bactéria fototrófica púrpura não-sulfurosa previamente purificada. O aumento da concentração inicial de ácido acético de 10 mmol/L para 17 mmol/L não promoveu mudanças significativas tanto no crescimento celular, quanto, na produção de hidrogênio (8,3 mL \'H IND.2\'/g massa seca.h e 8,8 mL \'H IND.2\'/g massa seca.h, respectivamente), para intensidade luminosa de 9000 - 10.000 lux. Nessa mesma intensidade luminosa, o aumento da concentração de biomassa inicial de 0,02 g/L para 0,04 g/L favoreceu o aumento da produção de hidrogênio de 8,8 mL \'H IND.2\'/g massa seca.h para 10,6 mL \'H IND.2\'/g massa seca.h, respectivamente. A produção de hidrogênio diminuiu acentuadamente de 10,6 mL \'H IND.2\'/g massa seca.h para 1,0 mL \'H IND.2\'/g massa seca.h com a diminuição da intensidade luminosa de 9000 - 10.000 lux para 4000 - 5000 lux. Na ausência de luz não ocorreu crescimento e produção de hidrogênio. A cultura manteve-se predominantemente avermelhada e as análise microscópicas mostraram a predominância de bacilos curvos, gram-negativos, aglomerados em formações de roseta; características típicas de alguns gêneros de bactérias fototróficas púrpuras não-sulfurosas. Todos os ensaios foram realizados à temperatura de 30 \'+ OU -\' 1 grau Celsius. A análise da estrutura da comunidade microbiana foi realizada por reação de polimerização em cadeia (PCR) de fragmentos de gene RNAr 16S, seguida de eletroforese em gel de gradiente desnaturante (DGGE), e revelou que não houve variações relevantes na estrutura das populações microbianas em função das diferentes condições de cultivo. / The global energy requirements are mostly dependent on fossil fuels. Hydrogen is a clean energy alternative to these fuels. Phototrophic bacteria produce hydrogen from organic compounds by an anaerobic light-dependent electron transfer process. Therefore, this study aimed at to evaluate the effect of the initial concentrations of acetic acid and biomass, and the influence of the light intensity on hydrogen production by purple non-sulfur phototrophic bacteria. The experiments were performed in batch operation, in reactors of 2000 mL, with culture volume of 1000 mL and headspace of 1000 mL, filled with helium. Acetic acid and sodium glutamate (0.8 mmol/L) were used as sources of carbon and nitrogen, respectively, and culture of purple non-sulfur phototrophic bacteria previously purifided. The increase of the initial acetic acid concentration from 10 mmol/L to 17 mmol/L did not promote significant changes in the cell growth and in the hydrogen production (8.3 mL \'H IND.2\'/g dry weight.h and 8.8 mL \'H IND.2\'/g dry weight.h, respectively), under a light intensity of 9000 - 10,000 lux. In this same light intensity, the increase of the initial biomass concentration from 0.02 g/L to 0.04 g/L resulted in an increase in the hydrogen production from 8.8 mL \'H IND.2\'/g dry weight.h to 10.6 mL \'H IND.2\'/g dry weight.h, respectively. The hydrogen production suddenly decreased from 10.6 mL \'H IND.2\'/g dry weigh.h to 1.0 mL \'H IND.2\'/g dry weight.h with the reduction of the light intensity from 9000 - 10,000 lux to 4000 - 5000 lux. Hydrogen production was not observed in absence of light. The culture remained predominantly purple and the microscopic analysis showed the predominance of rod-shaped cells, gram-negative, accumulated in formation of rosettes; typical characteristics of some types of purple non-sulfur phototrophic bacteria. The analysis of the structure of the microbial community was carried out by reaction of polymerization in chain (PCR) of the RNAr 16S, followed of denaturing gradient gel electrophoresis (DGGE), and reveled that the structure of the microbial populations did not change significantly in function of the different conditions of culture.

Lactobacillus buchneri é um microrganismo heterolático capaz de produzir quantidades significativas de ácido acético, que tem ação anti-fúngica e melhora a estabilidade aeróbia de silagens. Além de ácido acético, silagens inoculadas com L. buchneri tipicamente apresentam maiores teores de 1-propanol. Acredita-se que este álcool estaria associado à depressão de consumo de matéria seca (CMS). Assim, o objetivo deste trabalho foi avaliar o efeito da inoculação de silagens de milho com L. buchneri e da suplementação com 1-propanol no desempenho de vacas leiteiras. O experimento foi conduzido no Departamento de Zootecnia da Escola Superior de Agricultura \"Luiz de Queiroz\" (ESALQ/USP). A cultura do milho foi colhida com aproximadamente 35% de matéria seca (MS) e ensilada em bags com capacidade de 40 t. No momento da ensilagem, dois tratamentos foram impostos: controle (C) e L. buchneri 1 × 105 ufc/g (LB). Após 247 dias de armazenamento, os silos foram abertos e o ensaio de lactação foi iniciado. Vinte vacas Holandesas foram alocadas em sete Quadrados Latinos 3 × 3, com períodos de 21 dias (14 d adaptação). As dietas experimentais continham (% MS): 8% de caroço de algodão, 9,5% de polpa cítrica, 18% de farelo de soja, 9,0% de milho moído, 2,5% de premix mineral+vitaminas e 53% de silagem de milho C ou LB ou silagem de milho C + 1,0% de 1-propanol (PROP). O 1-propanol foi diluído em água (1:1) e aspergido na ração total durante a mistura, imediatamente antes da oferta das refeições. Parâmetros de fermentação e composição bromatológica das silagens foram realizadas nos períodos experimentais, assim como ensaio de estabilidade aeróbia. A taxa de desaparecimento de ácido acético, etanol e 1-propanol foram mensuradas em cada período durante a exposição das rações no cocho. O CMS, a produção e a composição de leite, a digestibilidade aparente no trato total, o comportamento ingestivo e o índice de seleção de partículas foram registrados entre os dias 15 e 21 de cada período experimental. Nos mesmos dias, foram realizadas coletas de fluido ruminal para determinação das concentrações de ácidos graxos voláteis e 1-propanol e, de sangue para avaliação das concentrações de glicose e ácidos graxos não esterificados (AGNE). Os dados foram submetidos à análise de variância e as médias comparadas pelo Teste de Tukey-Kramer (α=0,05), utilizando-se o procedimento MIXED do SAS. Os parâmetros de fermentabilidade e a estabilidade aeróbia das silagens foram semelhantes entre os tratamentos. O CMS, a produção e a composição do leite também não diferiram. Entretanto, a digestibilidade da matéria orgânica, foi menor para o tratamento LB. Animais alimentados com 1-propanol apresentaram maior concentração ruminal deste álcool, maior concentração sanguínea de glicose e menor de AGL. A inoculação das silagens com L. buchneri na dose 1 × 105 ufc/g não modifica a qualidade e a estabilidade aeróbia de silagens de milho. A inoculação com L. buchneri na dose 1 × 105 ufc/g e a adição de 1-propanol na dieta não alteraram o desempenho de vacas leiteiras. / L. buchneri is a heterolactic microorganism capable of producing significant amounts of acetic acid that has antifungal action and usually increase the aerobic stability of silage. In addition, silages inoculated with L. buchneri typically exhibit higher levels of 1-propanol. There is a clame that 1-propanol is associated with decreased dry matter intake (DMI). Thus, the objective of this work was to evaluate the effects of inoculating L. buchneri at corn ensiling and supplementing total mixed rations (TMR) with 1-propanol on the performance of lactating dairy cows. The experiment was conducted in the Department of Animal Science, College of Agriculture \"Luiz de Queiroz\" (ESALQ / USP). Corn crop was harvested at 35% DM and ensiled in farm scale bags (40 t/bag). At ensiling, treatments were: control (C) and L. buchneri 1 × 105 cfu/g (LB). After 247 d of storage, silos were opened and the lactation trial was carried out. Twenty Holstein cows housed in a Tie-stall barn were assigned to a replicated 3 × 3 Latin square design, with 21 d periods (14 d adaptation). Diets contained (DM basis): 8% whole cottonseed, 9.5% citrus pulp, 18% soybean meal, 9% dry ground corn, 2.5% premix mineral + vitamins, and 53% corn silage C or LB or corn silage C + 1% of 1-propanol (PROP). The 1-propanol was diluted in water (1:1) and sprayed onto the TMR during mixing, immediately before each feeding. Silage fermentation and chemical composition were evaluatedin each period, as well as the aerobic stability. Fractional disappearance rates of ethanol, acetic acid and 1-propanol were determined in TMR during feedbunk exposure. The DMI, milk yield and composition, total tract digestibility, ingestive behavior and particle sorting index were recorded from d-15 to d-21 in each period.. In addition, rumen fluid and blood were sampled to determine the concentrations of VFA and 1-propanool, and glucose and non-esterified fatty acids (NEFA), respectively. Analysis of variance was performed using the Mixed procedure of SAS and treatment means were compared by Tukey-Kramer test (α = 0.05). Silage fermentability and aerobic stability were similar between treatments. The DMI, milk yield and milk composition did not differ among treatments. However, the organic matter digestibility was lower for the treatment LB. Animals fed 1-propanol had higher ruminal concentration of this alcohol, higher blood glucose and lower blood NEFA. Inoculation of silage with L. buchneri at 1 × 105 cfu/g does not alter fermentation and is not sufficient to improve the aerobic stability of corn silages. The inoculation of silages with L. buchneri at 1 × 105 cfu/g and the supplementation of TMR with 1-propanol do not alter the performance of dairy cows.

The purpose of this research was to investigate the effects that aspirin (ASA) and its metabolites, salicylic acid (SA) and acetic acid (AA), have on the delivery of drugs across biological barriers when used in conjunction with electroporation. Electroporation is a technique used to enhance drug delivery across bio-membranes in which a transmembrane potential is induced into cellular membranes, resulting in the creation of aqueous pores that allow molecules to pass through the otherwise impermeable barrier. Aspirin is a widely used drug that has been used for over a century and has been proven relatively safe at normal doses as indicated by the low number of reports of poisoning cases it has been involved in. Components of aspirin are known to soften the cellular membranes by solubilizing the cell's surface proteins. B16F10 murine melanoma cancer cells were used in this investigation and treated with a 120µM buffered solution of calcein, a fluorescent indicator, in which the amount of delivered tracer molecules was measured using fluorescence. Identical concentrations of ASA and SA were investigated (1mM, 5mM, and 10mM) separately, focusing the effects concentration has electroporation delivery. Diluted acetic acid was also investigated at pH values of 6.42, 5.36, and 4.40. The concentration of acetic acid that had the lowest pH and ASA with the highest concentration had the greatest impacts on the augmentation of calcein delivery. Therefore, this demonstrates that aspirin and acetic acid have the potential to improve targeted molecular delivery in combination with electroporation.

In the present work, CO2 corrosion of API 5L X65 pipeline steel in the presence of acetic acid (HAc) was investigated. The objective of this research was to study a qualitative behaviour frequently found in the case of the so-called top-of-line corrosion (TLC). That is, increasing corrosion rates and steep shrinkage after certain - not predictable - time delay. The focus was on the role of HAc in the growth and stifling of localized attacks in CO2-containing media. The kinetic behaviours of carbon steel in such brines indicated that the overall effect of HAc is a balance between an enhanced cathodic reaction rate and a slightly inhibited anodic reaction rate. Results also showed that the active dissolution is not directly related to the presence of acetic acid but rather to what is generically referred to as CO2 corrosion. Zero resistance ammeter (ZRA) measurements on artificial pit electrode assembly, coupled to numerical simulation results, indicated that local HAc concentration gradients sustain the pit growth mechanism to a certain critical depth. Beyond this critical depth, the coupling current sharply drops off and the pit undergoes a process of stifling. However, a substantial effect of the purely ohmic drop on the pit stabilization process appeared unlikely in such conditions. Instead, initiated pits were shown to propagate and stifle mainly according to the counteracting depletions of HAc and CO2. On the basis of the obtained results, a complete scenario was therefore proposed for the morphological trend of localized attacks, which is in good agreement with field occurring TLC cases.

In the last few decades, numerous studies have been conducted on xenobiotic compounds due to their vast use in industries, households, etc. and consequently high exposure of these compounds. The main focus of this study is nonylphenol compounds such as nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), nonylphenoxy acetic acid (NP1EC) and nonylphenol (NP), which are among the harmful xenobiotic compounds that can cause endocrine disruption, cancer and other health problems and which are used widely in the production of surfactants and personal care products. In this study, laboratory scale aerobic semi continuous reactors containing Waste Activated Sludge (WAS) spiked with NP2EO were operated for a period of 91 days, to inspect the decomposition of NP2EO in solid and liquid phases. The results obtained on the final day of operation (91st day) showed that NP2EO degraded into product compounds among which NP1EC contributed to 90% of molar mass. In general, NP2EO showed a sharp degradation while NP1EC was produced rapidly. NP1EO also showed a steady degradation. However, NP was accumulated in the reactor. During the study, TS, VS, TSS and VSS degradation was also monitored and the percentage removals were found to be between 40-60%. COD removal on the other hand was between 64-66%.