Polylactic acid (PLA) resins of various molecular weights and molecular weight distributions were synthesized. Linear, narrow molecular weight distribution (MWD) PLA resins were synthesized, as well as resins containing both high molecular weight branched structures and low molecular weight chains and oligomers. Narrow MWD resins were synthesized for use as adhesives for corrugated paperboard and broad MWD resins were synthesized for use as a waterborne coating. PLA resins were dispersed for use as a waterborne coating. Success has been made at forming films utilizing various plasticizers and surfactants as well as polyvinyl alcohol as dispersing agents. A cold dispersion procedure realized the most success, as a 15% PLA waterborne formulation was achieved. Standard test methods show a high degree of grease resistance for the formulated coatings. A hot melt adhesive was also formulated utilizing blends of narrow MWD resins of various molecular weights. The hot melt adhesive showed a high degree of success as failure occurred at the substrate for the materials tested.

The global market for waterborne coatings will continue to grow because alternative solventborne coatings emit environmentally hazardous volatile organic compounds (VOCs). However, most waterborne coatings are softer than solventborne crosslinked thermoset coatings because they feature thermoplastic polymer dispersions. To overcome these challenges, in this thesis we suggest a novel crosslinkable aqueous dispersion system that incorporates epoxy and amine particles into poly(methyl methacrylate) (PMMA); the particles will react when water (the solvent) evaporates, offering a potential one-component (1K) reactive system. Emulsion polymerization was used to synthesize the particles with the help of surfactants. Epoxy and amine particles were successfully incorporated during the synthesis of PMMA and formed a two-component (2K) aqueous dispersion. In this process, a non-ionic surfactant, Triton X405 (TX405), was used to prevent interactions with the amine particles. Nuclear magnetic resonance (NMR) was used to determine the actual incorporation ratios of epoxy and amine and we found an epoxy incorporation plateau. Dynamic light scattering (DLS) was used to determine the particle size distributions and a uniform distribution was observed. The pendulum test and the pencil test were used for coating hardness, which surpassed currently marketed waterborne coatings. The resulting aqueous dispersions could be cured under facile conditions, i.e., in air and at low temperatures. An increase in Tg was observed after crosslinking. Different mechanical properties were observed when the coatings were cured at different temperatures, 25°C, 70°C, and 100°C. These results suggest that we have successfully formed crosslinked coatings that contain our epoxy and amine incorporated particles, with mechanical properties comparable to the traditional solventborne coatings.

No description available.

The primary differences between the solventborne and waterborne epoxy printed circuit board (PCB) impregnating resins arise from the distinct physical compositions and drying characteristics of the polymer solution and the latex emulsion. The presence of residual surfactant from the waterborne epoxy emulsion poses a concern for dielectric performance and adhesive durability. Another problem involves the crystallization of insoluble solid dicyandiamide (DICY), which is significantly different in morphology than that found in solution cast resins. A two-stage drying model was employed to gain a better understanding the drying and coalescence processes. The process of surface DICY crystal formation during the drying of glass prepreg sheet was related to a threshold concentration of the curing agent in the impregnating latex resin formulation. Conditions favoring faster drying lead to the rapid formation of a coalesced skin layer of latex resin, thereby trapping the curing agent in the bulk and reducing the surface deposition of DICY by percolating water. Surfactant is believed to remain concentrated in a receding wet zone until it is driven to the surfaces of the glass fibers upon the completion of drying. The copper foil/laminate interface was evaluated by a 90° peel test as part of two different studies: an analysis of the viscoelastic response of the interface during peel and a study of the thermal durability of the copper/laminate interfacial peel strength. The surfactant acted as a plasticizer to toughen the fiber/matrix interphase, resulting in larger observed peel strengths in the latex resin impregnated materials relative to the solventborne system. Surfactant segregated to the fiber surface during coalescence to form a plasticized fiber/matrix interphase; surfactant migrated into the bulk during postcure to yield a more homogeneously plasticized epoxy matrix. Dielectric measurements of neat resin and laminate materials revealed that the dielectric constants of the model resin-impregnated laminates met the performance criteria for PCB substrates of their class, regardless of surfactant content. Overall, the adhesive performance, adhesive durability, and dielectric properties of PCB systems fabricated with model latex epoxy resin, containing native surfactant (5 wt %), met or exceeded the performance of an equivalent solventborne resin impregnated system. / Ph. D.

Pathogen contamination, typically quantified by elevated levels of fecal indicator bacteria (FIB), remains the leading cause of surface water-quality impairments in the United States. Continuous watershed-scale models are typically employed to facilitate Total Maximum Daily Load (TMDL) restoration efforts. Due to limited understanding of microbial fate and transport, predictions of FIB concentrations are associated with considerable uncertainty relative to other water-quality contaminants. By focusing on a data-rich instrumented urban watershed, this study aims to improve understanding of microbial fate and transport processes. Weekly FIB concentrations in both the water column and streambed sediments were monitored for one year, and statistical correlations with hydrometeorological and physicochemical variables were identified. An intensive six storm intra-sampling campaign quantified and contrasted loading trends of both traditional regulatory FIB and emerging Microbial Source Tracking (MST) markers. Together, these intensive monitoring efforts facilitated evaluation of the impacts of bacteria-sediment interactions on the predictions of daily FIB concentrations in Hydrological Simulation Program-Fortran (HSPF) over multiple years. While superior overall model performance was demonstrated as compared to earlier efforts, the inclusion of bacteria-sediment interactions did not improve performance. Large wet-weather microbial loading appears to have dwarfed the effects of FIB release and resuspension from sediment. Although wet-weather loading is generally considered as a primary source of waterbody microbial loads, dry-weather periods are more directly associated with public health concern, which may be a more suitable area for future model-refinement efforts. Site evaluation is critical to determine whether the added model complexity and effort associated with partitioning phases of FIB can be sufficiently offset by gains in predictive capacity. Finally, a stochastic framework to translate simulated daily FIB concentrations into estimates of human illness risks is presented that can be can be readily integrated into existing TMDLs. As even small concentrations of FIB from human sources are associated with great risk, and monitoring efforts indicated moderate/high levels of human-associated MST marker in this watershed, remediation efforts to protect public health would be best directed toward infrastructure improvements. Uncertainty analysis indicates more site-specific knowledge of pathogen presence and densities would best improve the estimation of illness risks. / Ph. D.

The analysis of potentially harmful biological particles is imperative for the mitigation of disease. As a result, there is a growing need for tools which can characterize, detect, and separate biological particles for the alleviation of a multitude of disease. One powerful technique for the analysis of cells is the use of dielectrophoresis (DEP) forces for the manipulation of particle movement. DEP is a particle transport phenomenon, induced by the presence of non-uniform electric fields. The dependence on intrinsic electrical properties of cells, have enabled DEP force to be utilized for numerous biological analyses. This thesis presents the investigation of breast cancer, pathogen, neuronal and glial cells and their DEP profiles. The drug response of various breast cancer cell lines when exposed to a variety of chemical stimuli were analyzed using shifts in their DEP profiles in relation to control groups. These results were supplemented with gene expression analysis to identify biophysical changes which could contribute to the DEP shifts. Additional experiments were conducted for the monitoring of pathogens. Live/dead bacteria mixtures were evaluated using an integrated system with DEP enrichment and impedance spectroscopy. Another application of DEP which was investigated was the separation of heterogeneous mixtures. Through the use of a novel microfluidic channel design, the separation of simulated circulating tumor cells (CTCs) from diluted blood and neuron cells from glial cells was demonstrated. The wide range of applications examined in this thesis highlights the versatility of DEP and the flexibility of the reported devices. / MS / Microscale technology can be utilized for the identification, characterization and sorting of biological material in a plethora of biomedical applications. One promising technique which is capable of cell manipulation is dielectrophoresis (DEP). DEP is a microscale force which causes particles to be attracted or repelled by specific geometries in microchannels. The DEP force is produced by the application of electric fields and can be utilized to analysis biological cell populations. This is because biological particles have unique electrical properties based on their cell morphology. Distinctions in their external protrusions and internal structures contribute to their electrical properties and can be identified in their DEP profiles. Based on this concept a variety of biomedical applications of DEP was explored. Chapter 2 and 3 describe the investigation of cells when exposed to various drugs. Drug induced responses were characterized based on their shifts in their DEP profiles. Chapter 4 presents the a rapid and low-cost live/dead assay for bacteria in aqueous samples through DEP and impedance spectroscopy. In chapter 5, the development of a DEP platform for cell sorting is reported. The wide range of biomedical applications which were explored demonstrate the useful nature of the DEP phenomenon.

Yes / This study examines the feasibility of using colloidal silica nanoparticles as active agents in high concentration waterborne polymer latex formulations. We showed that distributing the silica throughout the waterborne emulsion formed a composite coating material with a hydrophilic surface that consequently reduced exterior dirt pickup. Two grades of silica nanoparticles were studied, one using sodium stabilisation and another using epoxysilane modification to introduce glycidox-ypropyltrimethoxysilane surface functionality. Rheological study of the waterborne latex on mixing showed that there was an immediate pH responsive interaction between the silica sols and the polymer latex. Once loading of sodium charge stabilised silica NPs exceeded the volume required for heteroflocculation to occur the mixture demonstrated the potential to gel on standing – a process which took weeks, or months, to occur depending on the pH and relative concentrations used. At least fifty percent silane modification to the NP surface was found to be necessary to maintain a stable colloidal dispersion for long term storage of the waterborne latex. Despite this both grades of silica were found to imbue reductions in dirt pickup when applied to exterior masonry concrete studies over a 3-month weathering test / This work was supported by the Royal Society of Chemistry [E21-8346952505].

The spread of antibiotic-resistant microorganisms in the environment is recognized widely as an important public health issue, with concerns about future ability to treat infectious diseases. The main risk to public health is that the resistance genes are transferred from environmental bacteria to human pathogens. Safe water is one of the most important needs in public health in the twenty first century. The major health threat posed by drinking unsafe water is the transmission of infectious diseases, which are the leading causes of mortality and morbidity for children under the age of 5 and it is estimated to cause 1.5 million deaths annually in developing countries. In addition to the wide spread cases of water-borne diseases resulting from the contamination of water sources, concerns have been raised when these diseases fail to be cured due to development of resistance to most prescribed antibiotics by the contaminating microorganisms. It is now a well-established fact that E.coli is a significant cause of diarrheal illnesses both in infants and adults in many parts of the world. Data on clinical isolates is plenty while less attention has been given to environmental isolates of these enteric pathogens. Samples from the environment such as water may serve as probable reservoirs of these pathogens; this is compounded by the entry of functional compounds of antibiotics into waterways, through humans and animals that have ingested antibiotics. This is because antibiotics are not completely metabolized and may enter waterways through the waste products of these humans or animals.Studies on antimicrobial resistance is important in order to detect changes in patterns of resistance, implement control measures on the use of antimicrobial agents, and to prevent the spread of multidrug-resistant strains of bacteria. It also provides surveillance data for antibiotic resistances, necessary to define or update guidelines for empirical treatment, as well as a guide for appropriate antibiotic supplies. Study objectives: The objectives of this research were: (i) to determine the total and faecal coliform status of drinking water sources, as an indication of quality; (ii) to determine the bacteriological profile of bacteria flora in the drinking water sources; (iii) to determine prevalence and susceptibility profiles of antibiotic resistant water-borne E.coli; (iv) to investigate the virulence genes associated with multiple antibiotic resistant E. coli isolates; (v) to compare three laboratory based techniques: PCR, API 20E, and Culture based methods used for detection of E.coli and (vi) to determine the association between multiple antibiotic resistance and radiation sensitivity (D10). © University of South Africa 2014 VII Methodology: Four hundred and sixty four (464) water samples were collected for assessment between June 2011 and May 2012. The samples were collected from 57 sampling sites, from six different water sources including: boreholes (10), a canal (1), dams (15), hand-dug wells (15), a river (1), and streams (15). Total coliforms, faecal coliforms, and E. coli analysis were done by the MPN method. Bacteria isolation and identification were done using API 20E, conventional methods, and a PCR based DNA STRIP technology that allows simultaneous detection of virulence genes and confirmation of E. coli isolates. Antibiotic susceptibility testing was also conducted using the Kirby-bauer method. Radiation sensitivity was done using a cobalt 60 source. Results: The results obtained indicated that all the water sources were of poor quality in terms of microbial distributions with total coliform and faecal coliform counts ranging between 0 to 2.4x103 MPN/100ml. E. coli counts ranged between 10 to 7.9x101MPN/100ml. Disease risk assessment of the various water sources indicated that dam water sources presented a high disease risk, while borehole water sources had a low disease risk. A total of five hundred and twenty bacterial isolates (520) were obtained during the period of study. Three hundred and five (305) isolates representing 58.65% of the total were obtained during the dry season, as against (205) representing 41.35% in the rainy season. The most commonly occurring bacteria in the water samples was Klebsiella spp constituting 20%. The next most occurring organism was E. coli (18.7%). This was followed by Pseudomonas aeruginosa (15.61%), Enterobacter spp. (15.4%), Proteus vulgaris (13.1%), and Enterococcus faecalis (9.2%). The least isolated bacteria were Vibrio cholerae (1.2%) and Shigella spp. (1.2%). The prevalence of multi drug resistance E. coli was 49.48 %. E. coli isolates showed a high sistance patterns to the tested antibiotics. They were most resistant to penicillin (32.99%), cefuroxime (28.87%), erythromycin (23.71%), and tetracycline (21.45%). In contrast, they were susceptible to nitrofurantoin (93.8%), cefotaxime and amikacin (91.75%), gentamicin (90.7%), nalidixic acid (89.65%), ciprofloxacin (74.2%), chloramphenicol (69.07%), pipemidic acid (65.97%) and cefuroxime (52.58%). Sixty-three percent (63%) of the multidrug resistant E. coli strains recorded a multiple antibiotic resistance (MAR) index value of >0.2. Six (6%) percent of he multiple antibiotic resistant were eae virulence genes producing however, none of the E. coli isolates produced the stx1 and stx2 virulent gene. The analytical profile index (API) recorded specificity and sensitivity of 99.7% and 98.50 % respectively for the detection of E. coli. The © University of South Africa 2014 VIII culture/ biochemical based methods for detection of E coli recorded specificity of 81.82% and a sensitivity of 96.91%. There was no association (P> 0.05) between radiation sensitivity (D10) and antibiotic resistances. Conclusion: The study has confirmed that majority of the water sources used for drinking and domestic purposes in the study area are highly contaminated with high levels of faecal coliforms above the recommended standards. There were also resence of bacteria of public health importance in the water sources. Both animals and humans could be sources of faecal bacteria contamination of the drinking water sources. The study confirmed a high prevalence of multiple antibiotic resistances in E. coli isolates. The eae virulence gene was associated with some of the multiple resistant E. coli isolates. The study also concludes that API 20E has a high specificity and sensitivity close to that of the PCR. Lastly, There is no association between multiple antibiotic resistant indexes and radiation sensitivity (D10) of antibiotic resistant E. coli. / School of Environmental Sciences / D. Phil. (Environmental Science)

Submitted in fulfilment of the requirements for the Master of Technology Degree: Environmental Health, Durban University of Technology, 2012. / Waterborne diseases represent substantial global burden of disease and children under the age of five are more susceptible to these diseases compared to adults. The aim of this study was to determine the microbiological quality of Nyabarongo River water used for domestic purposes, women’s knowledge, attitudes and practices (KAP) on water usage and waterborne diseases and its link to the diarrhoea outbreaks experienced in two rural communities: Rusheshe and Ayabaraya of Masaka in Rwanda. A total of 35water samples were collected from Nyabarongo River and from study households which used slow sand filtration (SSF) or Sûr’Eau as treatment methods and analyzed for total coliform and faecal coliform indicators. For household samples turbidity was also analyzed. Retrospective records from Masaka Health Centre were reviewed to determine the prevalence of waterborne diseases from the study areas during 2010. Further, a structured questionnaire was administered to 324 women residents of the study areas to elicit information on their KAP on water handling and waterborne diseases. SPSS Predictive Analytic Software (PASW) Statistics version 18.0 (IBM, Somers, NY) and STATA Release (Version 11.0, College Station, Texas USA) were used for data analysis. Results showed that the mean values of total and faecal coliforms of river and household water samples were above the WHO and Rwandan recommended guidelines. The mean values of total coliform and faecal coliform were significantly lower (p ≤ 0.05) in both filtered and Sûr’Eau treated water than in river water. No statistical differences of means were observed for both total coliform and faecal coliform counts between samples taken from filtered and Sûr’Eau treated water containers (p=0.80 (TC) and p = 0.56 (FC). However, turbidity values were significantly lower in filtered water using SSF than in Sûr’Eau treated water samples (p =0.002). Out of 2814 records form Masaka Health Centre during 2010, 160 cases were identified as having diarrhoeal diseases. Furthermore, respondents who used Nyabarongo River as source of water were more likely to have symptoms of diarrhoea (OR =5.35; CI: 2.12 - 14.46; p <0.05). The frequency of diarrhoea were significantly higher among people who did not wash hands before food preparation (p = 002) and after using a toilet (p = 0.007) than among those who did. There was a statistically significant association of level of education levels and drinking water treatment practices at the household level (p < 0.05). Respondents with primary school education only and those with high school education were more likely to wash their hands after using a toilet (OR= 5.24, CI 1.42-19.38, p =0.01 and OR = 7.15, CI = 1.79 -28.62, p=0.01, respectively) than those who did not attend school. No significant associations were identified between educational levels and washing hands before food preparation. The findings of this study points to the facts that water sourced from Nyabarongo River is unsafe for human consumption even after prescribed treatment, such as the use of SSF and Sûr’Eau, and could increase the prevalence of waterborne diseases and therefore calls for urgent provision of potable water. Women in the study areas had limited knowledge regarding water storage practices for prevention of household water contamination and this; underscore the need for more water handling practices and hygiene education in rural communities. / Durban University of Technology.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Waterborne sewage system design and expansion objectives are often focused on minimising initial investment while increasing system capacity and meeting hydraulic requirements. Although these objectives make good sense in the short term, the solutions obtained might not represent the optimal cost-effective solution to the complete useful life of the system. Maintenance and operation of any system can have a significant impact on the life-cycle cost. The costing process needs to be better understood, which include maintenance and operation criteria in the design of a sewer system. Together with increasing public awareness regarding global warming and environmental degradation, environmental impact, or carbon cost, is also an important factor in decisionmaking for municipal authorities. This results in a multiplicity of different objectives, which can complicate the decisions faced by waterborne sewage utilities. Human settlement and migration is seen as the starting point of expansion problems. An investigation was conducted into the current growth prediction models for municipal areas in order to determine their impact on future planning and to assess similarities between the models available. This information was used as a platform to develop a new method incorporating indirect costs into models for planning waterborne sewage systems. The need to balance competing objectives such as minimum cost, optimal reliability, and minimum environmental impact was identified. Different models were developed to define the necessary criteria, thus minimising initial investment, operating cost and environmental impact, while meeting hydraulic constraints. A non-dominated sorting genetic algorithm (NSGA-II) was applied to certain waterborne sewage system (WSS) scenarios that simulated the evolutionary processes of genetic selection, crossover, and mutation to find a number of suitable solutions that balance all of the given objectives. Stakeholders could in future apply optimisation results derived in this thesis in the decision making process to find a solution that best fits their concerns and priorities. Different models for each of the above-mentioned objectives were installed into a multi-objective NSGA and applied to a hypothetical baseline sewer system problem. The results show that the triple-objective optimisation approach supplies the best solution to the problem. This approach is currently not applied in practice due to its inherent complexities. However, in the future this approach may become the norm. / AFRIKAANSE OPSOMMING: Spoelafvoering rioolstelsel ontwerp en uitbreiding doelwitte is dikwels gefokus op die vermindering van aanvanklike belegging, terwyl dit die verhoging van stelsel kapasiteit insluit en ook voldoen aan hidrouliese vereistes. Alhoewel hierdie doelwitte goeie sin maak in die kort termyn, sal die oplossings verkry dikwels nie die optimale koste-effektiewe oplossing van die volledige nuttige lewensduur van die stelsel verteenwoordig nie. Bedryf en instandhouding van 'n stelsel kan 'n beduidende impak op die lewensiklus-koste hê, en die kostebepalings proses moet beter verstaan word en die nodige kriteria ingesluit word in die ontwerp van 'n rioolstelsel. Saam met 'n toenemende openbare bewustheid oor aardverwarming en die agteruitgang van die omgewing, is omgewingsimpak, of koolstof koste, 'n belangrike faktor in besluitneming vir munisipale owerhede. As gevolg hiervan, kan die diversiteit van die verskillende doelwitte die besluite wat munisipale besluitnemers in die gesig staar verder bemoeilik. Menslike vestiging en migrasie is gesien as die beginpunt van die uitbreiding probleem. 'n Ondersoek na die huidige groeivoorspelling modelle vir munisipale gebiede is van stapel gestuur om hul impak op die toekomstige beplanning te bepaal, en ook om die ooreenkomstes tussen die modelle wat beskikbaar is te asesseer. Hierdie inligting is gebruik as 'n platform om ‘n nuwe metode te ontwikkel wat indirekte kostes inkorporeer in die modelle vir die beplanning van spoelafvoer rioolstelsels. Die behoefte is geïdentifiseer om meedingende doelwitte soos minimale aanvanklike koste, optimale betroubaarheid en minimum invloed op die omgewing te balanseer. Verskillende modelle is ontwikkel om die bogenoemde kriteria te definiëer, in die strewe na die minimaliseering van aanvanklike belegging, bedryfskoste en omgewingsimpak, terwyl onderhewig aan hidrouliese beperkinge. ‘n Nie-gedomineerde sorteering genetiese algoritme (NSGA-II), istoegepas op sekere spoelafvoering rioolstelsel moontlikhede wat gesimuleerde evolusionêre prosesse van genetiese seleksie, oorplasing, en mutasie gebruik om 'n aantal gepaste oplossings te balanseer met inagname van al die gegewe doelwitte. Belanghebbendes kan in die toekoms gebruik maak van die resultate afgelei in hierdie tesis in besluitnemings prosesse om die bes-passende oplossing vir hul bekommernisse en prioriteite te vind. Verskillende modelle vir elk van die bogenoemde doelwitte is geïnstalleer in die nie-gedomineerde sorteering genetiese algoritme en toegepas op 'n hipotetiese basislyn rioolstelsel probleem. Die resultate toon dat die drie-objektief optimalisering benadering die beste oplossing vir die probleem lewer. Hierdie benadering word tans nie in die praktyk toegepas nie, as gevolg van sy inherente kompleksiteite. Desnieteenstaande, kan hierdie benadering in die toekoms die norm word.