>Magister Scientiae - MSc / Water is essential for life, yet access to safe drinking water is still a major concern worldwide due to waterborne diseases. The current study proposes silver nanoparticles (AgNPs) as an antibacterial agent. Silver nanoparticles were synthesised using different reductants and stabilisers, and the resulting structures were characterised with Ultra-violet visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS) analysis. The antibacterial properties of the AgNPs were tested against a panel of 5 indicator organisms: Cupriavidus metallidurans, Staphylococcus epidermidis, Mycobacterium smegmatis, Bacillus cereus and a multi-drug resistant Escherichia coli 1699. Spherical AgNPs that absorbed at around 400 nm, with diameters ranging between 18.8-26.4 nm or 5.4-13.1 nm were prepared by ascorbic acid or sodium borohydride respectively. The optimum processing conditions that produced 6±1.8 nm spherical nanoparticles included maintaining the temperature at 0 ⁰C, the pH at 9.78 and the NaBH4/Ag/PVP ratio at 16:1:10. Exposing AgNPs to light for 6 hours did not alter the particle size rather it changed the particles shape from spherical to icosahedral. Stirring caused particles to agglomerate, however, no agitation resulted in the formation of irregular structures of different sizes. Sensitivity to the AgNPs ranged between 25 % and 100 % reduced bacterial growth depending on the strains used and the concentration of the AgNPs. The Gram negative bacteria were more sensitive to AgNPs than Gram positive bacteria. However silver ions were more toxic than AgNPs for all but one of the strains tested, B. cereus was completely resistant to both Ag+ and AgNPs. C. metallidurans and E.coli (1699) showed a dose dependent sensitivity to AgNPs and the minimum inhibitory concentrations were established at 50 and 20 mg/L AgNPs respectively. C. metallidurans and E.coli (1699) were also eradicated by 10 mg/L Ag+. The E. coli TEM images showed accumulation of AgNPs within the cells, cell shrinking and leakage of cellular components. This suggests that AgNPs have a similar toxicity effect on bacterial cells as Ag+.

In January 2010, a magnitude 7.0 earthquake devastated Haiti, one of the poorest countries in the Western Hemisphere. Haiti’s weak sanitation infrastructure and limitations in the public health system made the country susceptible to the spread of waterborne diseases. Following the earthquake, cholera rapidly spread through Haiti, killing 4,672 people in 5 months and leaving thousands hospitalized (MSNBC, 2010). Cholera is an infectious diarrheal disease caused by the pathogen, Vibrio cholerae, which results in severe dehydration with a high mortality risk. The source of the epidemic was traced to the Artibonite River, the island’s longest and most essential drinking water source (Encyclopaedia Britannica. n.d.). The origin of the contamination was later discovered to be unsanitary conditions left from United Nations peacekeepers from Nepal. Eight years later, cholera cases are still prevalent, although numbers have declined recently due to aid from private organizations (Dowell, S.F. et al 2011, Katz, J.M. 2013). However, with climate-related increases in ocean water temperatures, scientists expect hurricanes to intensify and increase damage to developing countries (Center for Climate and Energy Solutions. n.d.). Natural disasters promote the spread of waterborne illness by isolating people from safe drinking water and destroying public health infrastructure such as happened with the cholera outbreak in Haiti (Funari, E. et al 2013). To prevent future waterborne disease epidemics in such areas with limited resources, it would be beneficial to improve environmental surveillance through development of rapid, reliable, and portable detection methods for waterborne pathogens. The advent of high-throughput sequencing technologies has enabled the detection and characterization of microbial communities in their natural environments, an approach known as metagenomics. Metagenomic sequencing, unlike more traditional PCR methodologies, is capable of sequencing thousands of organisms in a sample. This metagenomic shotgun sequencing approach detects the abundance of microbes and bacterial diversity in the environment (Illumina, n.d.). The Oxford Nanopore MinION is a shotgun sequencing device that is optimal for portable, rapid detection of the microbial diversity in an environmental sample (Oxford MinION, n.d.). This handheld device has enormous potential for field use in emergency preparedness and disease response, particularly in developing countries where more advanced analytical equipment may be inaccessible due to lack of facilities or damaged infrastructure. Having access to quick, infield assessment technology for rapidly emerging outbreaks would be beneficial to a disease-specific public health response. Current protocols recommend that DNA is extracted from environmental samples as rapidly as possible after collection. If cooling is available with an insulated ice chest, samples may be transported/stored for periods ranging from 6 to 24 hours. The shorter timeframes minimize unwanted shifts in microbial structure (U.S. Geological Survey, 1997, WHO, n.d.). Access to cold storage in remote areas is unlikely, and the use of liquid preservation methods could assist in maintaining quality of DNA, and hence produce more accurate data in metagenomic analyses. In the absence of cold storage facilities, infield filtration coupled with preservation techniques are necessary to maintain samples integrity for transport to laboratory facilities. This thesis aimed to develop an infield filtration and sequencing protocol, coupled with the Oxford Nanopore MinION sequencing platform, to identify the potential bacteria, viruses, protozoa, fungi, antimicrobial resistance (AMR), pathogenic strains, and virulence associated genes for use in remote locations. Five locations across Lake Warner, Massachusetts were used for method development, coupled with Millipore Sterivex filters for field filtration to determine the most effective method for sample preparation in remote locations. Additionally, a chemical preservation method was assessed using dimethyl sulfoxide, disodium EDTA, and saturated NaCl (DESS). A study by Gray et al, found that liquid preservation methods (DNAgard, RNAlater, and DESS) outperformed the card-based preservatives (FTA cards and FTA Elute cards) in terms of bacterial recovery (Gray, M.A., et al 2013). DESS was selected for investigation in this thesis because of the low cost compared to the other liquid-based preservatives. Lake Warner in Hadley, Massachusetts, which is heavily used for fishing and boating activities, flows into the Connecticut River via the Mill River. Historically, the lake experienced high Escherichia coli (E. coli) levels due to pollution from primary effluent released in the 1950s from the Amherst Wastewater Treatment Plant (Johnson, J., 2015). Similar to Vibrio cholerae, E.coli spp is a waterborne bacteria caused by fecal contamination. Although most E.coli are natural inhabitants of the gastrointestinal tract, pathogenic serotypes can result in severe complications in vulnerable populations such as kidney failure in children and the elderly adults. (Todar, K., 2012). Lake Warner was chosen for the method development because of its history of E. coli pollution and recreational traffic as well as its general accessibility for study. Designing a methodology for rapid detection of pathogenic bacteria using a metagenomic approach could help improve surveillance for environmental pathogens that pose future epidemic risk. These tools are becoming increasingly important for prediction and response to waterborne diseases as climate impacts increase the frequency, intensity, and duration of extreme weather events that damage critical infrastructure for vulnerable populations (van Aalst, M.K. 2006).

The transmission of human pathogens by faecally contaminated fruit and vegetables is well established, but the burden of disease caused by foodborne pathogens is unknown. Fresh produce can be contaminated through the use of polluted irrigation water or by the handling of the produce by infected individuals either pre- or post harvest. There is very little known regarding the extent of viral contamination of irrigation water and fresh produce in South Africa. Noroviruses (NoV) and hepatitis A virus (HAV) are recognized as leading causes of foodborne viral disease. These viruses are transmitted predominantly via the faecal–oral route, primarily person-to-person by direct contact with an infected person, or indirectly by ingestion of contaminated food and water. The detection of enteric viruses in food or water is problematical and complex as many foodborne viruses, including HAV and NoV, cannot be readily isolated in cell culture. The aim of this investigation was to develop and optimise simple and efficient methods for the concentration and detection of NoV GII and HAV in irrigation water and fresh produce. These methods would then be applied to field samples of irrigation water and fresh produce to try and establish a link between viral contamination detected in irrigation water and that on associated irrigated fresh produce. The efficiency of different commercial real-time reverse transcriptase-polymerase chain reaction amplification kits for the realtime detection of HAV, NoV GI and NoV GII was assessed, and standard curves for the quantitative detection of these viruses were constructed using the most appropriate kit. Using two types of fresh produce, three different elution buffers, each at two pHs, with two different elution times were compared to establish which buffer was the most efficient for the extraction of viruses from the fresh produce. The tris-glycine beef extract buffer (pH 9.5) with an elution time of 20 minutes most efficient for the extraction of the selected enteric viruses from fresh produce. From April 2008 to November 2009, 86 irrigation water and 72 fresh produce samples were collected from commercial and subsistence farms, street vendors and commercial outlets. All the irrigation water and fresh produce samples were analysed for HAV, NoV GI and NoV GII. Overall, 16.3 % (13/86) and 12.5 % (9/72) of irrigation water and fresh produce samples tested positive for one or more human pathogenic viruses, namely NoV GII and HAV, respectively. Nucleotide sequence and phylogenetic analysis of the HAV and NoV GII strains identified clinically relevant viruses in the irrigation water and on the fresh produce. A direct link between contaminated irrigation water and contamination of fresh produce could not be established, but irrigation water was identified as a possible source of contamination of the fresh produce. The results also suggested that food handlers contributed significantly to the viral contamination of the fresh produce. This study highlights the potential health risk posed by fresh produce to consumers in South Africa and highlights the need for further in depth studies to quantify the risk to consumers. This study represents new data on the occurrence of enteric viruses in food and water in South Africa and is crucial for the development of effective intervention and control strategies for food safety in South Africa. Copyright / Dissertation (MSc)--University of Pretoria, 2011. / Medical Virology / unrestricted

Replacing solventborne coating with waterborne can reduce emission of VOC from paint shops, and decrease the amount of CO2 released from after-burners. The chemistry of 2K WB urethane coatings includes complex kinetics, with a selectivity which is highly dependent on application and curing conditions. To be able to design a coating process producing stable high quality coatings, it is important to know what factors affect the material properties. In this project, the effect of variations in temperature during curing of 2K WB and 2K SB topcoats have been evaluated in order to determine if there are any measurable effects on the material. The significance of these difference have also been evaluated to substantiate the need for thorough design of the curing process. After evaluation of visual, mechanical and chemical properties, as well as the durability of the cured topcoats, it was found that the effect of curing temperature on the level of gloss on 2K WB topcoats could be seen with the naked eye. Effects on colour, hardness, flexibility, adhesion and durability could also be measured, and revealed apparent changes in the material. Increased curing temperature had effects on both cross-linking density and isocyanate conversion. The heightened temperature contributed to the formation of topcoats with significantly decreased level of gloss and reduced stone-chip resistance, but also increased hardness and chemical resistance to an extent that was deemed significant. Varied curing temperature was found to give variations in durability, which with time may give different ageing properties of parts coated under different conditions. Before implementation of this type of waterborne topcoat, it is recommended that several properties be further evaluated, such as the effect of humidity and wet paint viscosity on the material properties. / Genom att ersätta lösningsmedelsburna ytbehandlingar med vattenburna kan man kraftigt reducera utsläppen av VOC från lackeringsverkstäder och minska mängden CO2som frigörs från efterbrännare. Kemin för 2K WB uretanlacker innefattar komplex kinetik med selektivitet som är starkt beroende av applicerings- och härdningsbetingelser. För att kunna konstruera en ytbehandlingsprocess som producerar stabila högkvalitativa ytbehandlingar är det viktigt att känna till vilka faktorer påverkar materialegenskaperna. I detta projekt har effekten av variationer i temperatur under härdning av 2K WB och 2K SB topplack utvärderats för att fastställa om det resulterar i mätbara effekter på den färdiga topplacken. Även signifikansen av dessa skillnader har utvärderats för att bedöma behovet av noggrann utformning av härdningsprocessen. Efter utvärdering av visuella, mekaniska och kemiska egenskaper samt hållbarheten hos de härdade lackerna, fanns det att effekten av härdningstemperaturen på nivån av glans för 2K WB topplacker kunde ses med blotta ögat. Effekter på färg, hårdhet, flexibilitet, vidhäftning och hållbarhet visades också mätbara, och visade på tydliga förändringar i materialet. Förhöjd härdningstemperatur visade sig ha effekter på både tvärbindningsdensiteten och omsättning av isocyanater hos härdaren. En förhöjd härdningstemperatur påvisades även bidra till bildandet av en topplack med avsevärt minskad glansnivå och visst minskad stenskottsbeständighet, men även ökad hårdhet och kemikalietålighet i en omfattning som fanns signifikant. Varierad härdningstemperatur visade sig ge variationer i hållfasthet, som med tiden riskerar att ge olika åldringsegenskaper hos komponenter belagda under olika förhållanden. Innan denna typ av vattenburen täckfärg implementeras i produktion rekommenderas att ytterligare egenskaper utvärderas, såsom inverkan av fukt och våtfärgsviskositet på ytbehandlingens slutegenskaper

Research is presented which encompasses a study of epoxies based on diglycidyl ether of bisphenol A (DGEBA) cured with 2-ethyl-4-methylimidazole (EMI-24) in the presence of the nonionic surfactant Triton X-100. Interest in this epoxy system is due partially to the potential application as a waterborne replacement for solvent cast epoxies in E-glass laminated printed circuit boards. This research has revealed that the viscoelastic behavior of the cured epoxy is altered when serving as the matrix in a glass composite. The additional constraining and coupling of the E-glass fibers to the segmental motion of the epoxy matrix results in an increased level of viscoelastic cooperativity. Current research has determined that the cooperativity of an epoxy/E-glass composite is also sensitive to the surface chemistry of the glass fibers. Model single-ply epoxy/E-glass laminates were constructed in which the glass was pretreated with either 3-aminopropyltriethoxysilane (APS) or 3-glycidoxypropyltrimethoxysilane (GPS) coupling agents. Dynamic mechanical analysis (DMA) was then used to create master curves of the storage modulus (E') in the frequency domain. The frequency range of the master curves and resulting cooperativity plots clearly varied depending on the surface treatment of the glass fibers. It was determined that the surfactant has surprisingly little effect in the observed trends in cooperativity of the composites. However, the changes in cooperativity due to the surface pretreatment of the glass were lessened by the aqueous phase of the waterborne resin. Moisture uptake experiments were also performed on epoxy samples that were filled with spherical glass beads as well as multi-ply laminated composites. No increases in the diffusion constant could be attributed to the surfactant. However, the surfactant did enhance the final equilibrium moisture uptake levels. These equilibrium moisture uptake levels were also sensitive to the surface pretreatment of the E-glass. / Ph. D.

No description available.

Yes / Aeromonas hydrophila is a well-known waterborne pathogen that recently was found to infect humans. Here, we report the draft genome of a freshwater isolate from a Malaysian waterfall, A. hydrophila strain M023, which portrays N-acylhomoserine lactone-dependent quorum sensing. / University of Malaya via High Impact Research Grants (UM C/625/1/HIR/MOHE/CHAN/01, A-000001-50001, and UM C/625/1/HIR/MOHE/CHAN/14/1, H-50001-A000027)

Climate change is increasing the frequency and intensity of (extra-) tropical cyclones including hurricanes and winter storms worldwide. Waterborne diseases, resulting from flood-related impacts, affect public health and are of major concern for society. Previous research studies have highlighted a statistically significant linear correlation between waterborne diseases and climate variables, especially precipitation and temperature. However, to the best of our knowledge, no studies have explored nonlinear models (e.g., machine learning) to predict waterborne disease outbreaks in the aftermath of hurricanes and winter storms. Here, we aim at predicting waterborne disease counts as well as disease outbreaks using historic climate demographic, and public health data of Florida, U.S. that date back to 1992. For this, we first predicted diseases in aggregated coastal counties using multiple linear (MLR) and random forest regression (RFR) models. Then, we developed a binary random forest classifier (RFC) model to predict waterborne disease outbreaks (e.g., 0: no outbreak and 1: outbreak). Results of this study showed that the highest coefficient of determination (R2) for the MLR model was 0.65 for two aggregated county groups, namely St. Johns-Duval-Nassau and Sarasota-Charlotte-Lee. The RFR model showed the highest R2 of 0.69 for the county group Sarasota-Charlotte-Lee. The highest Root Mean Square Error (RMSE) was found for the county group Miami Dade-Broward- Palm Beach with a value of 15 and 16 people for both the MLR and RFR models. St. Johns-Duval-Nassau and Sarasota-Charlotte-Lee groups achieved the highest Kling-Gupta Efficiency (KGE) of 0.76 for the MLR model. Sarasota-Charlotte-Lee also performed the best in terms of KGE for the RFR model with a score of 0.69. On the other hand, the binary RFC model for Pinellas-Hillsborough-Manatee achieved a model's accuracy of 0.93 and f1-score of 0.48. We anticipate that the models' performance can substantially be improved with access to higher spatial resolution climate data as well as longer demographic and public health records. Nevertheless, we here provide a solid methodology that can inform local authorities about imminent public health impacts and mitigate negative effects on society, economy, and environment. / Master of Science / Climate change is increasing the frequency and intensity of tropical storms, which include hurricanes and winter storms worldwide. Extreme weather events have been shown to increase the risk of waterborne disease outbreaks (i.e. diseases that are transmitted by water), especially due to increased flooding. Previous studies showed a correlation between climate factors, such as precipitation and temperature, and waterborne diseases, but no concrete models have been developed to predict these outbreaks. Advanced prediction models can help predict where disease outbreaks are most likely to occur and can help in preparing for and mitigating the severity of these outbreaks to help save lives, protect the environment, and reduce the damage done to infrastructure. Our research focused on developing a model framework using climate and demographic data from coastal Florida counties dating back to 1992 to predict Salmonellosis, a common waterborne bacterial infection, after a hurricane event. We created two regression models, one a multiple linear regression (MLR) and the other a random forest regression (RFR) to predict the number of Salmonellosis cases. Additionally, we created a random forest classifier model (RFC) to predict whether an outbreak would occur. After running analyses for these three models on groups of three counties, we found that the MLR and RFR showed similar accuracies at predicting cases, with the MLR performing slightly better for most counties. For the Sarasota-Charlotte-Lee county group, the RFR performed the best. The RFC model performed the best with the highest accuracy of 93% for Pinellas-Hillsborough-Manatee. Future improvements can help make these models more reliable, such as using better and more data, along with adding more variables.

Synthèse de nouveaux WPU (waterborne polyurethane) cationiques à partir du caoutchouc naturel (NR), et évaluation de leurs propriétés adhésives pour des surfaces de type cuir. Ces WPU ont été obtenus par réaction du caoutchouc liquide hydroxy téléchélique (HTNR), de toluene-2,4-diisocyanate (TDI), N-methyl diethanol amine (NMDEA, en tant qu’émulsifiant) et d’éthylène glycol (EG, extenseur de chaîne). Ces structures biosourcés sont développés comme alternatives aux WPU issus des ressources fossiles à fort impact environnemental. Les effets de cinq paramètres ont été étudiés, à savoir la quantité d'émulsifiant (de 0 à 2,25 mole), celle d’éthylène glycol (de 0 à 3 moles), le Mn du HTNR (de 100 à 3000 g/mole), l'indice NCO (de 100 à 150) et le taux d’époxydation des HTNR précurseurs (de 0 à 30%). Il a été en outre démontré que la stabilité des dispersions aqueuses pour les formulations optimales dépassait les 10 mois. La géométrie des particules dispersées a été étudiée, démontrant un aspect sphérique et une taille à l'échelle nanométrique. Ainsi, plusieurs facteurs ont été étudiés pour évaluer les propriétés adhésives optimales sur bandes de cuir (Mn, pourcentage d’'époxyde). Des tests standard (Peel test et Lap Shear test) ont été utilisés et les valeurs obtenues comparées avec celles issus de formulations adhésives commerciales avec ou sans solvants. Au bilan, une formulation optimale a été déterminée (Mn = 3000 g/mole, LR epoxydation = 10%, NMDEA 5.67%wt, NCO index de 100 et 1 mole d’EG) avec cuisson préalable des systèmes à 70°C. Ce WPU a montré une force d’'adhésion supérieure à toutes les formulations commerciales testées. / Novel cationic waterborne polyurethane (cWPU) based on natural rubber (NR) have been prepared by the polymerization reaction of hydroxyl telechelic natural rubber (HTNR), toluene-2,4-diisocyanate (TDI), N-methyl diethanol amine (NMDEA, as emulsifier), and ethylene glycol (EG, chain extender). The polyol structures have been developed as alternative to produce cWPUs derived from a renewable resource. The effects of five parameters were studied – amount of NMDEA (0 – 2.25 mole), amount of EG (0 – 3 mole), molecular weight of HTNR (~1000 – 3000 g/mole), NCO index (100 – 150), and epoxide content on eHTNR soft segment (0 – 30%). The appearance of cWPU dispersion was milky-blue with long shelf life time, more than 10 months. Particle of prepared cWPU were spherical shape in the nano range size. The adhesive properties of cWPUs on the real leather surface, taking into account of the different molecular weights of HTNR and different degree of epoxide content on HTNR, were tested by lap shear test and 180 degree peel test and compared with commercial adhesives. Overall, to balance the stability and adhesive strength, the best conditions for preparing cWPU adhesive for leather application in this study was from the composition of HTNR3000 with epoxide content of 10%, NMDEA 5.67%wt, NCO index of 100 and 1 mole of EG. in condition of curing at 70 °C. In comparison to non-solvent based and solvent based commercial adhesives, the adhesive strengths of these synthesized cWPU adhesive were superior.

Clean drinking and recreational water is essential for human survival and contaminated water cause 1.4 million deaths worldwide every year. Both developing and developed countries suffer as a consequence of unsafe water that cause waterborne diseases. The Great Lakes region, located in the United States is no exception. Climate change is predicted to cause an increase in waterborne disease outbreaks, worldwide, in the future. To adapt to this public health threat, vulnerability assessments are necessary. This literature study includes a vulnerability assessment that describes the main factors that affect the spreading of waterborne diseases in the Great Lakes region. Future climate scenarios in the region, and previous outbreaks are also described. The study also includes a statistical analysis where mean temperature and precipitation is plotted against waterborne disease cases. The main conclusion drawn is that the Great Lakes region is at risk of becoming more vulnerable to waterborne diseases in the future, if it does not adapt to climate change.