Bacterial biofilm infection is a common (~ 2 to 4%) complication for recipients of surgically implanted medical devices. Due to the tremendous increase in antibiotic resistance when these bacteria enter the biofilm phenotype, present treatment requires explantation and replacement of the device, often with multiple surgeries and always with much longer patient recovery time. The specific objective of this study was to quantify the degree of biofilm deactivation from exposure to thermal shock for varying temperature and time durations. While extreme temperature (>150˚C) is routinely used to sterilize (e.g. autoclaves), such temperatures have a severe cost within the body. Despite extensive studies on thermal deactivation of bacteria in the planktonic phenotype over a wide range of temperatures (e.g., pasteurization protocols), surprisingly little is known about the thermal deactivation of biofilms except under extreme conditions. Here, the deactivation of Pseudomonas aeruginosa biofilms is reported. These biofilms were cultured at 37°C for 24 hours in a drip-flow reactor and subjected to heat shocks on the range of 50°C to 80°C for durations of 1 to 30 minutes. Heat shocks were delivered by immersion in thermostatted media for the prescribed time and the resulting concentration of colony forming units (CFU/mL) were quantified using direct enumeration. Up to 6.6 orders of magnitude reduction in CFU concentration was observed, indicating that thermal deactivation is a reasonable approach to biofilm mitigation. Integrating this approach with a magnetic nanoparticle implant coating will result in an innovative treatment for implant infections in situ without explantation or device replacement.

The inhibiting and deactivating effects of basic nitrogen species present in gas oils on catalyst active sites has been well recognized over the years; however, recent studies have shown comparable inhibiting and deactivating effects exhibited by non-basic nitrogen species. A novel pre-treatment technique employing the heterogeneously cross-linked macroporous polymer poly(glycidyl methacrylate) (PGMA) as the hydrophilic support coupled with organic compound tetranitrofluorenone has shown promising results for the selective elimination of non-basic nitrogen heterocyclic species from bitumen derived heavy gas oil (HGO). Characterization techniques such as Scanning electron microscopy (SEM), low temperature N2 adsorption–desorption (BET), CHNOS elemental analysis, fourier transform infrared spectroscopy (FT-IR), epoxy content titration, and thermo gravimetry/differential thermal analyzer (TG/DTA) were employed for determining the optimum parameters during each step of the polymer synthesis. Step 1 comprised of direct polymerization of the monomers under the determined optimum conditions, with specific surface area of 34.7 m2/g and epoxy content of 5.8 wt% for the PGMA polymer support. Step 2 comprised of substitution of the epoxy ring with the acetone oxime functionality; FT-IR results indicated characteristics peaks at 1650 cm-1 which ascertained the presence of acetone oxime on the polymer, with epoxy content titration indicating a decrease of up to 33% of the epoxy content due to the substitution. Coupling of the organic compound tetranitrofluorenone with the polymer was performed in the final step, with TGA and DTG results indicating highest weight loss of approximately 126.9 μg, which signified that sample T had the greatest amount of organic compound present in comparison to the other samples (sample N to Sample S). The optimized polymer (sample T) was capable of removing nitrogen up to 6.7%, while having little to no influence on the sulphur or aromatic species. These results were in agreement with step 4 TGA analysis that showed sample T had the highest presence of the organic compound. Reusability of the polymer multiple times with consistent removal is another known advantage of such a pre-treatment technique; hence reusability studies were performed, and showed that the polymer was indeed capable of multiple uses, with consistent removal of nitrogen compounds at approximately 6.5% from fresh heavy gas oil feedstocks. Kinetic studies were performed as the final phase in order to evaluate the performance of the treated HGO in comparison to non-treated HGO. The effect of parameters such as temperature and LHSV were determined, with higher temperatures resulting in higher conversion of HDS and HDN. Similarly, as the LHSV was decreased, the conversions were increased for both HDS and HDN due to longer contact time between the feed and the catalyst. The highest obtained conversions were at an LHSV of 0.5 hr-1 and temperature of 395°C with treated HGO having HDS of 97.5% and HDN of 90.3%; while non-treated HGO having HDS of 94.9% and HDN of 78.3%. Employing the power law model, the results indicated that for treated HGO the reaction order for both HDS and HDN was 1.50; while for non-treated HGO the reaction order for HDS was 2.25 and for HDN was 2.00. The activation energies were then calculated with 141.4 kJ/mol being obtained for HDS and 113.8 kJ/mol for HDN for treated HGO; while for non-treated HGO the activation energy for HDS was 150.4 kJ/mol and for HDN was 121.4 kJ/mol. It was observed that the conversion of both HDS and HDN were higher and the activation energies were lower for treated HGO, indicating that the removal of non-basic nitrogen species prior to hydrotreatment had a positive impact on catalyst performance and consequently the level of conversion.

Protein stability plays an important role in a wide variety of settings ranging from industrial processes where proteins are used as biocatalysts to medical settings where misfolded proteins are implicated in disease. Understanding protein stability will allow design of improved bioprocess and pharmaceutical formulations as well as aid in the development of therapies for protein-based diseases. The effects of dissolved salts on protein kinetic stability are studied here. We find that ion-solvent interactions, characterized by the Jones-Dole B-viscosity coefficient, are strong indicators of salt effects on protein deactivation. This finding is used to develop a model for predicting protein deactivation in salt solutions in terms of two competing processes. Since protein unfolding and aggregation can lead to a number of protein misfolding diseases, we test the applicability of our model for describing salt effects on transthyretin aggregation. As the factors contributing to protein stability become more understood, the use of enzymes as biocatalyst for industrial process will increase, and the need for enzymes active in a wide range of reaction media will increase. We have developed a process using an enzyme in combination with organic-aqueous tunable solvents (OATS) which allows for monophasic reaction of the enzyme with hypdrophobic substrates. The reaction mixture can be separated into two phases by the addition of carbon dioxide pressure. This separation allows for both convenient recovery of the hydrophobic reaction product from the organic phase as well as recycle of the enzyme in the aqueous phase. Overall reaction conversions of 80% and little enzyme activity loss are observed after six reaction cycles.

O controle da superfície química em colunas capilares abertas é de fundamental importância para atingir um alto desempenho na análise cromatográfica, sendo muito estudada ao longo das décadas de 70 e 80, mas tendo pouco destaque nos últimos anos por parte dos pesquisadores. A atividade da superfície de uma coluna capilar é causada por grupos silanol (Si-OH) e impurezas como metais, por exemplo. A presença destes grupos silanol faz com que alguns compostos sofram adsorção, principalmente pela formação de pontes de hidrogênio, originando picos com longas caudas no cromatograma. Por isso, a eliminação dos sítios ativos faz-se necessária quando uma amostra apresenta interação com a superfície da coluna. Esta desativação pode ser feita por meio de agentes silanizantes que reagem com os grupos hidroxila. Visto que a maioria dos artigos publicados sobre este assunto envolve colunas de vidro, o presente trabalho estudou os efeitos de cada fase do pré-tratamento de tubos aplicado para as colunas atuais de sílica fundida, verificando os agentes silanizantes HMDS, DPTMDS e TPDMDS que seriam mais adequados para suportar as fases estacionárias OV-73 e OV-17. Também se avaliou o uso de filmes finos de 0,01 , 0,05 e 0,10 ?m de polietileno glicol (PEG) como alternativa para a desativação da parede interna do capilar, o qual mostrou resultados satisfatórios de estabilidade e inatividade. / The control of the inner surface in open tubular capillary columns has fundamental importance to reach a high performance in gas chromatography analysis. It was very studied during 1970´s and 1980´s, but has not interested the researches along last years, not excluding also, the possibility of commercial secrets regarding column preparation. The activity on the surface of capillary column is mainly caused by silanol groups (Si-OH) and impurities such as metal ions and water. These groups favours reversible and irreversible adsorption of polar compounds, which results in tailed peak shapes and incomplete elution from the column. Therefore, the elimination of the active sites is necessary. The deactivation procedures are based on blocking of silanol groups by means of chemical reaction. This present work studied the effects of the surface pretreatment steps applied to fused silica capillary columns. Some silylating agents such as HMDS, DPTMDS and TPDMDS were valued. The coating behavior using OV-73 and OV-17 stationary phases was studied too. Film thickness of 0,01 , 0,05 and 0,10 ?m of poly(ethylene glycol) (PEG) was applied as alternative procedure, showing good stability and column deactivation.

Abstract The aim of this thesis is the knowledge of the most relevant deactivation mechanisms of Pd/Rh three-way catalysts under different ageing conditions, the deactivation correlation of laboratory scale ageing and engine bench/vehicle ageings, and the evaluation of the deactivation correlation. In the literature review, the phenomena involved in the three-way catalyst operation and its deactivation are considered. In the experimental section, ageing-induced phenomena in the catalyst are studied and deactivation correlations between laboratory scale and engine bench/vehicle ageings are presented, based on the results of several surface characterization techniques. The effects of ageing atmosphere and temperature, and time are considered in particular. Fresh and aged catalysts used in this study were metallic monoliths designed for Euro IV emission limits. Thermal ageings were carried out in the reductive, oxidative and inert atmospheres in the temperature range of 800°C to 1200°C, and in the presence of water vapour (hydrothermal ageing). The engine ageing was carried out in the exhaust gas stream of a V8 engine during a 40 hour period. The ageing procedure composed of rich and stoichiometric air-to-fuel ratios carried out consecutively. The vehicle ageing was accomplished under real driving conditions (100 000 kilometres). According to the results, deactivation of a Pd/Rh monolith is a combination of several ageing phenomena. The most important deactivation mechanisms are the sintering of active phase, the collapse in surface area and ageing-induced solid-solid phase transitions in the bulk washcoat. Furthermore, poisoning is a relevant deactivation mechanism of the vehicle-aged catalyst. High ageing temperature, gas phase composition and exposure time are essential variables to the deactivation of a Pd/Rh three-way catalyst. This thesis presents an approach to discover the deactivation correlation between the laboratory scale ageing and under the vehicle's operation in an engine bench or on-road. Based on the characterization results, the accelerated laboratory scale air ageing does not correspond to the ageing-induced changes in the catalyst under the vehicle's operation. Therefore, there is a need for a modified ageing cycle and according to the results, a deactivation correlation between the laboratory scale ageing and the engine bench ageing can be presented as a function of ageing temperature and atmosphere, and time. Instead, after the vehicle operation, the deactivation correlation cannot be presented based solely on the studied variables because, after 100 000 kilometres of driving, the role of poisoning should be taken into account in the ageing cycle. The results of this thesis can be utilized and applied in the development of laboratory scale ageing cycles, which corresponds closely to the ageing-induced changes in the catalyst during the vehicle operation. This enables a rather fast testing of the catalyst's performance and reduces the cost during the manufacturing of catalysts.

A titania-supported nickel catalyst was prepared and tested in methanation in order to evaluate its catalytic properties (activity, selectivity and specially, activity loss), and compare it with an alumina-supported nickel catalyst. The titania-supported catalyst did not only show higher stability than alumina, but also presented a different cause of deactivation, carbon formation. In addition, a kinetic model was obtained for the titania-supported catalyst, and a study of the effect of different operating conditions (temperature, composition and partial pressures of synthesis gas and water) on the deactivation rate and carbon formation of this catalyst was performed. / <p><strong></strong> </p>

The aim of the study is to evaluate the ability of non-noble metal catalysts to function as the commercially used noble metal catalyst. The exhaust gas that was used in the project is generated from a heater developed by ReformTech AB with diesel as fuel. The compound that was focused on is carbon monoxide that has a concentration of 300-750 ppm. The catalysts that were tested are MnO/CeO2, CuO/CeO2 and a Pt/CeO2 catalyst used to compare the non-noble metal catalyst with. The sensitivity against sulfur poisoning was also analyzed by mixing sulfur into the fuel. Analysis of the exhaust gas was done with a micro-GC and the catalysts were also analyzed with SEM before and after exposure of sulfur.   The manganese catalyst with a loading of 7 wt-% did not show any activity against carbon monoxide oxidation. The copper catalysts contained two different loadings of active material, 7 and 14 wt-% and monoliths with 400 and 600 cpsi were used. Both loadings showed good activity against carbon monoxide oxidation.   The most prominent catalyst was the 14 wt-% CuO/CeO2 catalyst with a 600 cpsi monolith because of an increase in surface area. The SEM analysis showed that sulfur was present on the surface when the heater was using diesel with 300 ppm sulfur. The sulfur caused complete deactivation of the non-noble metal catalysts and a small decrease in activity was shown on the noble metal Pt catalyst.

System architecture analyses of distributed ship systems offer a practical view of system behavior over all operational states; however, the effectiveness of these analyses can be bound by limited computational performance or capability. Deactivation diagrams provide an alternative view to conventional system architecture descriptions, allowing for rapid analysis of system connectivity and flow based on precomputed single-state system descriptions. This thesis explores the development of system deactivation diagrams and their use in early-stage naval ship system design. Software tools developed in C++ and VBA as part of this research support the Virginia Tech (VT) Naval Ship Design Concept and Requirements Exploration (CandRE) process and tools utilizing the U.S. Navy's Leading-Edge Architecture for Prototyping Systems (LEAPS) framework database. These tools incorporate automated path-finding algorithms developed based on proven network theory and effective computational methods for use in performing ship system deactivation analysis. Data drawn from the results of this approach possess extensible applicability towards studies in naval ship system vulnerability, flow optimization, network architecture, and other system analyses. Supplementary work on interfacing the LEAPS framework libraries with deactivation analyses has demonstrated the capability for generating deactivation diagrams from complex LEAPS ship system databases and paved the way for future incorporation of LEAPS into research work at Virginia Tech. / Master of Science / As the development of new ships becomes more technically complex due to the increased incorporation of redundant and interdependent ship systems, there is a greater need for advanced tools to support future ship system design. Ship operational capabilities rely on the resiliency of onboard systems in all situations, included damaged conditions, and require comprehensive design evaluation to identify weaknesses in system concepts. This thesis details the development of a computational approach to ship system analysis using precomputed deactivation diagrams for early-stage naval ship system design. Deactivation diagrams are a unique way of looking at the interconnectivity of system components and offer a consolidated view of complex network architecture to significantly simplify and accelerate subsequent analyses. Developments in computational algorithms for ship system connectivity presented in this thesis aid in the automated development of deactivation diagrams and support system flow and vulnerability analyses with particular regard to ongoing work on the Virginia Tech (VT) Naval Ship Design Concept and Requirements Exploration (C&RE) process. Additional thesis development work referencing the U.S. Navy’s Leading-Edge Architecture for Prototyping Systems (LEAPS) database framework has demonstrated the capability for generating deactivation diagrams from complex LEAPS ship system databases and paved the way for future incorporation of LEAPS into research work at VT.

Yes / The deactivation of the oxidative desulfurization (ODS) catalysts is a challenge and is a major concern in industrial catalytic processes. In this work, an activated carbon (AC) was prepared from agricultural waste and modified to withstand the ODS activity loss over time. The AC was impregnated with manganese and coated with aluminum oxide to prolong the activity lifetime. The catalysts were characterized by nitrogen adsorption-desorption, scanning electron microscope, energy dispersive X-ray, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and transition electron microscope (TEM). The BET surface areas of the examined AC materials were 814.48 m2/g, 784.76 m2/g, and 755.03 m2/g for the AC, Mn/AC, and coated Mn/AC catalysts, respectively with a dominance of microporous pore size. The TGA showed that the coating layer retards the degradation of the active metal and suppresses phase transitions. XRD showed no change in the structure of the catalyst with a coating layer, and from the TEM analysis, the coating layer thickness was 3.6 nm. The kinetics of the ODS catalysts were investigated. It was shown that the ODS reaction follows the first-order kinetics and is not influenced by the coating layer. The activity decay was also investigated. It is found that the activation energy of the deactivation reaction over the coated catalyst was higher than the uncoated catalyst.

Various distillates are treated with hydrogen gas during hydrotreatment in the presence of catalyst in order to reduce the sulfur and aromatic content of the product. Optimal hydrotreater performance is essential for producing Nynas specialty oils, in order to fulfill the planned production volume and to meet the product specification. Loss of catalyst activity is inevitable during the production. To adjust for the impact of catalyst deactivation, different process variables are manipulated. Different distillates affect the catalyst in different ways due to the variation in distillate composition. Distillates with higher organic nitrogen content and running at a lower temperature tend to deactivate the catalyst more due to the adsorption of nitrogen compounds on the active sites of the catalyst and their slow nature of desorption. In this master thesis, different catalyst deactivation mechanisms with a focus on nitrogen deactivation have been studied. Since nitrogen is not normally measured at Nynas, nitrogen content of different distillates and products and how these values change during operation was not known. Different distillates, blend of distillates and different products were measured to estimate roughly the typical nitrogen value of the distillates and products. The temperature data inside the reactors were analyzed to calculate and plot WABT (weighted average bed temperature) during different product runs and to see whether there is a correlation between the nitrogen content of the feed and operation severity (increase in WABT). Historical process data from hydrotreater unit 2 (mostly from 2013-2014) were analyzed with a view to finding out signs of catalyst deactivation. Similar product runs were also analyzed and compared to see how the catalysts performed at different periods of time. A kinetic model, based on HDS kinetics, has been used for following up two product runs. To do so, sulfur content of the feed and product were measured. Aromatic content of the product was also measured to see whether the product was on specification. .From the calculation and plotting of WABTs, it could be seen that there is an increase in WABT during the product runs operating at lower temperatures and with higher nitrogen content. From the comparison of two P3 product runs at two different time periods, it could be seen that ∆T development over one bed (amount of reaction over the bed) was much lower at one time. This can possibly be a sign of catalyst deactivation since it contributed to lesser amount of reaction over the bed. From the calculations by using the kinetic model, it could be seen that the actual temperatures were higher than the predicted temperatures. The increase in WABTs could also be noticed. These observations can possibly be coupled with nitrogen deactivation of the catalysts.  However, more tests are required to verify whether the temperature differences were significant or not. Other parameters which are also important from product selling point of view such as viscosity, color, flash point, acid number etc. and have not been covered in this degree project need to be taken into consideration before making further conclusions.