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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Dosimetric pre-treatment verification with an electronic portal imaging device

Wåhlin, Erik January 2006 (has links)
<p>A commercially available amorphous silicon electronic portal imaging device (EPID) was studied with regard to its dosimetric properties and to determine its usefulness as a tool for dosimetric pre-treatment verification of radiotherapy treatment fields. The dosimetric properties that were studied include reproducibility over time, linearity with dose, dose rate dependence and ghosting effects. The pre-treatment verification is performed by acquiring dosimetric images with the EPID and comparing these images with predicted images, calculated by the treatment planning system. This method for verification was evaluated. Also, the calibration and configuration of the treatment planning system and of the EPID for dosimetric verification was performed and is presented here.</p><p>The dosimetric properties of the EPID were found to be suitable for the measurements for which it is intended. It is linear with dose and does not show significant dose rate dependence or ghosting effects. As a pre-treatment verification system it is accurate within 3% and 3mm for ~99% of a region around the irradiated area of the image.</p>
22

Dosimetric pre-treatment verification with an electronic portal imaging device

Wåhlin, Erik January 2006 (has links)
A commercially available amorphous silicon electronic portal imaging device (EPID) was studied with regard to its dosimetric properties and to determine its usefulness as a tool for dosimetric pre-treatment verification of radiotherapy treatment fields. The dosimetric properties that were studied include reproducibility over time, linearity with dose, dose rate dependence and ghosting effects. The pre-treatment verification is performed by acquiring dosimetric images with the EPID and comparing these images with predicted images, calculated by the treatment planning system. This method for verification was evaluated. Also, the calibration and configuration of the treatment planning system and of the EPID for dosimetric verification was performed and is presented here. The dosimetric properties of the EPID were found to be suitable for the measurements for which it is intended. It is linear with dose and does not show significant dose rate dependence or ghosting effects. As a pre-treatment verification system it is accurate within 3% and 3mm for ~99% of a region around the irradiated area of the image.
23

Integration of Ozone and Ultrasound Activated Sludge Pre-Treatments into a Wastewater Treatment Whole-Plant Simulator

Musser, Jonathan January 2010 (has links)
Modern wastewater treatment provides great benefit to society by reducing the transmission of disease. In recent years computer simulation of whole plants has allowed for improved design and more economical consideration of alternatives. One new alternative for wastewater treatment is the pre-treatment of sludges, although this technology has not yet been adapted for computer simulation. This thesis describes research which was conducted to describe pre-treatments in terms appropriate for whole-plant computer models. Pre-treatment shows promise in terms of reducing sludge, a waste product the disposal of which can be costly depending on the applicable regulations. At the same time pre-treatment can improve the generation of biogas, which is readily converted to heat and/or electricity and can help to offset treatment energy requirements. Pre-treatments can be broadly categorized as physical, chemical, or thermal. For this study, ultrasound was selected as a model physical pre-treatment and ozone as a model chemical pre-treatment. The range of doses to be tested was obtained by reviewing earlier literature. Waste activated sludge was obtained from pilot reactors treating screened municipal wastewater. This sludge was subjected to a range of doses in batch reactors. Conventional laboratory analyses were used to determine the effects of pre-treatment on such parameters as chemical oxidant demand, solids, and various nitrogen fractions. As well, respirometry was utilized to estimate the biologically active and bioavailable fractions. A novel technique for analysis of respirometric data was developed, which consisted of fitting synthetic oxygen uptake rate curves to the measured data. Both ultrasound and ozone were observed to decrease the amount of active biomass present while increasing the amount of biodegradable material. The conversions between these fractions were modeled using simple functions of pre-treatment dose. For ultrasound, a conversion which exponentially decayed with respect to increasing ultrasound dose was used to relate these fractions. For ozone, the conversion from active biomass to slowly degradable material occurred more slowly than the conversion to rapidly degradable material; as such two conversions were modeled, each exponentially decaying with respect to dose but with different dose constants. The observed conversions were added to a whole-plant model and the implications of the models were considered for one simple wastewater treatment plant. Both pre-treatments showed a decrease in total sludge production and an increase in biogas production, as predicted by earlier research. Published full-scale results were not reported with sufficient detail to be replicated, and so a quantitative comparison was not possible.
24

Integration of Ozone and Ultrasound Activated Sludge Pre-Treatments into a Wastewater Treatment Whole-Plant Simulator

Musser, Jonathan January 2010 (has links)
Modern wastewater treatment provides great benefit to society by reducing the transmission of disease. In recent years computer simulation of whole plants has allowed for improved design and more economical consideration of alternatives. One new alternative for wastewater treatment is the pre-treatment of sludges, although this technology has not yet been adapted for computer simulation. This thesis describes research which was conducted to describe pre-treatments in terms appropriate for whole-plant computer models. Pre-treatment shows promise in terms of reducing sludge, a waste product the disposal of which can be costly depending on the applicable regulations. At the same time pre-treatment can improve the generation of biogas, which is readily converted to heat and/or electricity and can help to offset treatment energy requirements. Pre-treatments can be broadly categorized as physical, chemical, or thermal. For this study, ultrasound was selected as a model physical pre-treatment and ozone as a model chemical pre-treatment. The range of doses to be tested was obtained by reviewing earlier literature. Waste activated sludge was obtained from pilot reactors treating screened municipal wastewater. This sludge was subjected to a range of doses in batch reactors. Conventional laboratory analyses were used to determine the effects of pre-treatment on such parameters as chemical oxidant demand, solids, and various nitrogen fractions. As well, respirometry was utilized to estimate the biologically active and bioavailable fractions. A novel technique for analysis of respirometric data was developed, which consisted of fitting synthetic oxygen uptake rate curves to the measured data. Both ultrasound and ozone were observed to decrease the amount of active biomass present while increasing the amount of biodegradable material. The conversions between these fractions were modeled using simple functions of pre-treatment dose. For ultrasound, a conversion which exponentially decayed with respect to increasing ultrasound dose was used to relate these fractions. For ozone, the conversion from active biomass to slowly degradable material occurred more slowly than the conversion to rapidly degradable material; as such two conversions were modeled, each exponentially decaying with respect to dose but with different dose constants. The observed conversions were added to a whole-plant model and the implications of the models were considered for one simple wastewater treatment plant. Both pre-treatments showed a decrease in total sludge production and an increase in biogas production, as predicted by earlier research. Published full-scale results were not reported with sufficient detail to be replicated, and so a quantitative comparison was not possible.
25

Downstream Bioprocess Development for a Scalable Production of Pharmaceutical-grade Plasmid DNA

Zhong, Luyang January 2011 (has links)
The potential application of a hydrogel-based strong anion-exchange (Q) membrane to purify plasmid DNAs was evaluated. The maximum binding capacity of plasmid DNA was estimated to be 12.4 mg/ml of membrane volume with a plasmid DNA recovery of ~ 90%, which is superior to other commercially available anion-exchange resins and membranes. The membrane was able to retain its structural integrity and performance after multiple cycles of usage (> 30 cycles). The inherent properties of plasmid DNA, membrane adsorbent, and the ionic environment on membrane performance were identified as the factors affecting membrane performance and their effects were systematically investigated. Plasmid DNAs with smaller tertiary structure have shorter dynamic radius and/or lowersurface charge densities, which tended to have a better adsorption and recovery than those with larger tertiary structure. Environmental Scanning Electron Microscopy (ESEM) revealed that the hydrogel structure is more porous on one side of membrane than the other, and higher plasmid DNA adsorption and recovery capacities were observed if the more porous side of the membrane was installed upward of flow in the chromatographic unit. ESEM also revealed improved pore distribution and increased membrane porosity if membrane was pre-equilibrated in the buffer solution for 16 hours. The development of better flow through channel in the hydrogel membrane upon extensive soaking further improved plasmid DNA adsorption and recovery capacities. The ionic environment affects the tertiary size of plasmid DNA; and the optimal operating pH of membrane chromatography was different for the plasmid DNAs investigated in this study. The relative contribution of these factors to improve membrane chromatography of plasmid DNAs was analyzed using statistical modeling. It was found that the adsorption of plasmid DNA was mainly affected by the available adsorptive area associated with membrane porosity, whereas the recovery of plasmid DNAs was mainly affected by the environmental pH. A novel, RNase-free, and potentially scalable bioprocess was synthesized using the hydrogel membrane as the technology platform for the manufacturing of pharmaceutical-grade plasmid DNA. High bioprocess recovery and product quality were primarily associated with the optimal integration of impurity removal by calcium chloride precipitation and anion-exchange membrane chromatography and the implementation of isopropanol precipitation as a coupling step between the two impurity-removing steps. Complete removal of total cellular RNA impurity was demonstrated without the use of animal-derived RNase. High-molecular-weight (HMW) RNA and genomic DNA (gDNA) were removed by selective precipitation using calcium chloride at an optimal concentration. Complete removal of the remaining low-molecular-weight (LMW) RNA was achieved by membrane chromatography using the high-capacity and high-productive hydrogel membrane. The simultaneous achievement of desalting, concentrating and buffer exchange by the coupling step of isopropanol precipitation and the high efficiency and resolution of DNA-RNA separation by anion-exchange membrane chromatography significantly reduced the operating complexity of the overall bioprocess, increased the overall recovery of plasmid DNA, and enhanced product quality by removing trace amounts of impurities of major concern for biomedical applications, such as gDNA, proteins, and endotoxin.
26

Alternative Technologies for Inland Desalination

Corral, Andrea F. January 2014 (has links)
Water scarcity is one of the biggest issues we have to face as population and water consumption levels increase despite a fixed supply of renewable fresh water. Meeting the challenges that water scarcity poses to food production, ecosystem health, and political and social stability will require new approaches to using and managing water. Desalination already plays an essential role in water management. It constitutes a secure source of safe drinking water supply once demand management measures are fully implemented. Overcoming problems related to brine minimization and disposal is key to sustainable, efficient inland water desalination. The main focus of this was the investigation of technical limits and improvements for application in inland desalination. The first part of the dissertation covers the study of Membrane Distillation (MD) for desalination of water. The second part provides a broad perspective of Reverse Osmosis (RO), pretreatments -comparison of slow sand filtration and microfiltration-, post-mortem study of membranes to determining fouling and scaling causes, and RO brine minimization via Vibratory Shear Enhance Processing (VSEP®) for use in RO brine minimization. The study of Vacuum Membrane Distillation in a hollow fiber membrane was studied. Experimental work is supported by an original mathematical model to expose the physics of VMD and support predictions that extend VMD results beyond these generated in the laboratory. The advantages and disadvantages of each pretreatment, including their effects the effect on the performance of RO, a post-mortem membrane study and an economic analysis. The post-mortem study of membranes used during Yuma Desalting Plant operation. This work was used to identify the best pretreatment and more suitable membrane to treat saline water in the lower Colorado River. The work performed during the brine minimization study using VSEP®. This study included experimental data and an extensive economic analysis comparing Ion Exchange (IX) as pretreatment and VSEP® as post-treatment for RO.
27

USING ANAEROBIC CO-DIGESTION WITH ADDITION OF MUNICIPAL ORGANIC WASTES AND PRE-TREATMENT TO ENHANCE BIOGAS PRODUCTION FROM WASTEWATER TREATMENT PLANT SLUDGE

Li, CHENXI 20 September 2012 (has links)
In this project, by adding selected co-substrates and by incorporating optimum pre-treatment strategies, four experimental phases were conducted to assess the enhancement of biogas production from anaerobic co-digestion using wastewater treatment plant sludge as the primary substrate. In the first phase, the feasibility of using municipal organic wastes (synthetic kitchen waste (KW) and fat, oil and grease (FOG)) as co-substrates in anaerobic co-digestion was investigated. KW and FOG positively affected biogas production from anaerobic co-digestion, with ideal estimated substrate/inoculum (S/I) ratio ranges of 0.80-1.26 and 0.25-0.75, respectively. Combined linear and non-linear regression models were employed to represent the entire digestion process and demonstrated that FOG could be suggested as the preferred co-substrate. The effects of ultrasonic and thermo-chemical pre-treatments on the biogas production of anaerobic co-digestion with KW or FOG were investigated in the second phase. Non-linear regressions fitted to the data indicated that thermo-chemical pre-treatment could increase methane production yields from both FOG and KW co-digestion. Thermo-chemical pre-treatments of pH=10, 55°C provided the best conditions to increase methane production from FOG co-digestions. In the third phase, using the results obtained previously, anaerobic co-digestions with FOG were tested in bench-scale semi-continuous flow digesters at Ravensview Water Pollution Control Plant, Kingston, ON. The effects of hydraulic retention time (HRT), organic loading rate (OLR) and digestion temperature (37°C and 55°C) on biogas production were evaluated. The best biogas production rate of 17.4±0.86 L/d and methane content 67.9±1.46% was obtained with thermophilic (55°C) co-digestion at HRT=24 days and OLR=2.43±0.15 g TVS/L•d. In the fourth phase, with the suitable co-substrate, optimum pre-treatment method and operational parameters identified from the previous phases, anaerobic co-digestions with FOG were investigated in a two-stage thermophilic semi-continuous flow co-digestion system modified to incorporate thermo-chemical pre-treatment of pH=10 at 55°C. Overall, the modified two-stage co-digestion system yielded a 25.14±2.14 L/d (with 70.2±1.4% CH4) biogas production, which was higher than that obtained in the two-stage system without pre-treatment. The positive results could provide valuable information and original contribution to justify full-scale investigation in a continuing research program and to the field of research on anaerobic co-digestion of municipal organic wastes. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2012-09-20 09:00:09.719
28

I väntan på prostatacancer behandling : Copingprocessen för patienter med prostatacancerinnan medicinsk behandling / Waiting for prostate cancer treatment : The coping process for patients with prostate cancer before medical treatment

Lander, Jonathan, Johansson, Emil January 2014 (has links)
Varje år diagnostiseras 10 000 män med sjukdomen prostatacancer i Sverige. Att drabbas av sjukdomen prostatacancer är emotionellt ansträngande. Väntetiden vad gäller behandling för patienter med prostatacancer är lång. Detta gör att patienter med prostatacancer lever med sjukdomen prostata-cancer och känslorna kopplade till diagnosen prostatacancer under en lång tid. Syftet med den aktuella studien var att beskriva copingprocessen för patienter med prostatacancer innan medicinsk behandling. Metoden som använts till studien var en litteraturstudie baserad på 15 vetenskapliga artiklar. Resultatet visade att den kognitiva bedömningen av sjukdomen prostatacancer präglades av den information som patienter med prostata-cancer fick. Den kognitiva bedömningen av sjukdomen prostatacancer påverkades också av ålder och tid efter diagnos. Copingresurser som hade betydelse för patienter med prostatacancer var socialt stöd, personlighet och psykisk hälsa. De copingstrategier som användes av patienter med prostatacancer var främst emotionellt fokuserade. Patienter med prostatacancer är under stor emotionell belastning. Information och socialt stöd från vårdpersonal hjälper patienter med prostatacancer att hantera den emotionella belastningen. Ytterligare forskning krävs för att identifiera effektiva copingstrategier i ett tidigt stadium av diagnosen prostatacancer. / Every year 10 000 men are diagnosed with prostate cancer in Sweden. Affection of the disease is emotionally strenuous. The wait for treatment among patients diagnosed for prostate cancer is long. This result in patients diagnosed with prostate cancer living with the disease and the emotions associated with the diagnosis of prostate cancer for an extended time. The aim of the current study was to describe the coping process used by patients diagnosed with prostate cancer prior to treatment. The method of the current study was a literature study based on 15 scientific articles. The results indicated that appraisal of prostate cancer was influenced by the information that patients diagnosed with prostate cancer received. Furthermore appraisal of prostate cancer was affected by age and time since diagnosis. Social support, personality and mental health were coping resources that were of significance to patients diagnosed with prostate cancer. Emotion focused coping strategies were primarily used by patients diagnosed with prostate cancer. Patients with prostate cancer are emotionally distressed. Information and social support from healthcare personnel reduces the emotional distress. Further research should investigate what coping strategies are effective in an early stage of prostate cancer diagnosis.
29

Downstream Bioprocess Development for a Scalable Production of Pharmaceutical-grade Plasmid DNA

Zhong, Luyang January 2011 (has links)
The potential application of a hydrogel-based strong anion-exchange (Q) membrane to purify plasmid DNAs was evaluated. The maximum binding capacity of plasmid DNA was estimated to be 12.4 mg/ml of membrane volume with a plasmid DNA recovery of ~ 90%, which is superior to other commercially available anion-exchange resins and membranes. The membrane was able to retain its structural integrity and performance after multiple cycles of usage (> 30 cycles). The inherent properties of plasmid DNA, membrane adsorbent, and the ionic environment on membrane performance were identified as the factors affecting membrane performance and their effects were systematically investigated. Plasmid DNAs with smaller tertiary structure have shorter dynamic radius and/or lowersurface charge densities, which tended to have a better adsorption and recovery than those with larger tertiary structure. Environmental Scanning Electron Microscopy (ESEM) revealed that the hydrogel structure is more porous on one side of membrane than the other, and higher plasmid DNA adsorption and recovery capacities were observed if the more porous side of the membrane was installed upward of flow in the chromatographic unit. ESEM also revealed improved pore distribution and increased membrane porosity if membrane was pre-equilibrated in the buffer solution for 16 hours. The development of better flow through channel in the hydrogel membrane upon extensive soaking further improved plasmid DNA adsorption and recovery capacities. The ionic environment affects the tertiary size of plasmid DNA; and the optimal operating pH of membrane chromatography was different for the plasmid DNAs investigated in this study. The relative contribution of these factors to improve membrane chromatography of plasmid DNAs was analyzed using statistical modeling. It was found that the adsorption of plasmid DNA was mainly affected by the available adsorptive area associated with membrane porosity, whereas the recovery of plasmid DNAs was mainly affected by the environmental pH. A novel, RNase-free, and potentially scalable bioprocess was synthesized using the hydrogel membrane as the technology platform for the manufacturing of pharmaceutical-grade plasmid DNA. High bioprocess recovery and product quality were primarily associated with the optimal integration of impurity removal by calcium chloride precipitation and anion-exchange membrane chromatography and the implementation of isopropanol precipitation as a coupling step between the two impurity-removing steps. Complete removal of total cellular RNA impurity was demonstrated without the use of animal-derived RNase. High-molecular-weight (HMW) RNA and genomic DNA (gDNA) were removed by selective precipitation using calcium chloride at an optimal concentration. Complete removal of the remaining low-molecular-weight (LMW) RNA was achieved by membrane chromatography using the high-capacity and high-productive hydrogel membrane. The simultaneous achievement of desalting, concentrating and buffer exchange by the coupling step of isopropanol precipitation and the high efficiency and resolution of DNA-RNA separation by anion-exchange membrane chromatography significantly reduced the operating complexity of the overall bioprocess, increased the overall recovery of plasmid DNA, and enhanced product quality by removing trace amounts of impurities of major concern for biomedical applications, such as gDNA, proteins, and endotoxin.
30

Bioprocessing of Recalcitrant Substrates for Biogas Production

Kabir, Maryam M January 2015 (has links)
The application of anaerobic digestion (AD) as a sustainable waste management technology is growing worldwide, due to high energy prices as well as increasingly strict environmental regulations. The growth of the AD industry necessitates exploring new substrates for their utilisation in AD processes. The present work investigates the AD of two recalcitrant biomass: lignocelluloses and keratin-rich residues. The complex nature of these waste streams limits their biological degradation; therefore, suitable pre-processing is required prior to the AD process.In the first part of the study, the effects of organic solvent pre-treatments on bioconversion of lignocelluloses (straw and forest residues) to biogas were evaluated. Pre-treatment with N-methylmorpholine-N-oxide (NMMO) resulted in minor changes in the composition of the substrates, while their digestibility significantly increased. Furthermore, due to the high cost of the NNMO, the effect of pre-treatment with the recycled solvent was also explored. Since it was found that the presence of small traces of NMMO in the system after the treatment has inhibitory effects on AD, pre-treatments of forest residues using other organic solvents, i.e. acetic acid, ethanol, and methanol, were investigated too. Although pre-treatments with acetic acid and ethanol led to the highest methane yields, the techno-economical evaluation of the process showed that pre-treatment with methanol was the most viable economically, primarily due to the lower cost of methanol, compared to that of the other solvents.In the second part of the work, wool textile wastes were subjected to biogas production. Wool is mainly composed of keratin, an extremely strong and resistible structural protein. Thermal, enzymatic and combined treatments were, therefore, performed to enhance the methane yield. The soluble protein content of the pre-treated samples showed that combined thermal and enzymatic treatments had significantly positive effects on wool degradation, resulting in the highest methane yields, i.e. 10–20-fold higher methane production, compared to that obtained from the untreated samples.In the last part of this thesis work, dry digestion of wheat straw and wool textile waste, as well as their co-digestion were studied. The total solid (TS) contents applied in the digesters were between 6–30% during the investigations. The volumetric methane productivity was significantly enhanced when the TS was increased from 6 to 13–21%. This can be a beneficial factor when considering the economic feasibility of large-scale dry AD processes.

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