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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.
491

Problematika farmak v podzemních vodách / Pharmaceuticals issues in groundwaters

Šrot, Martin January 2016 (has links)
Main objective of the diploma thesis was to observe the concentrations of selected types of drugs in the environment around the area of the village Horní Beřkovice. This goal was achieved by monitoring of the drugs concentration in surface and ground waters at Horní Beřkovice site. Monitoring system allowed to detect the passage of pollution from the source of the contamination, through sewage treatment plant, the unsaturated zone and aquifer to a potential user of contaminated groundwater. The diploma thesis is based on the field data from TACR project. I have analyzed data from the six samplings at the area of the village Horní Beřkovice with regard to the observed drugs or their residues in surface and ground waters. I have compared the results with data from the sewage treatment plants in the river basin of Želivka. Keywords: ground water, surface water, sewage treatment plant, drugs, contamination
492

Chitosan nanoparticles functionalized with plant extracts for the inhibition of the toxic effects of aflatoxin B1 and Ochratoxin A

Mhlongo, Jatro Kulani 01 July 2014 (has links)
M.Sc. (Nanoscience) / Ochratoxin A and Aflatoxin B1 are important food contaminates as they are known to be mutagenic, genotoxic, nephrotoxic, hepatotoxic, immunosuppressive and teratogenic to both animals and humans. These mycotoxins are associated with the contamination of food stuff such as grapes, maize, red pepper, meat, milk, beans and processed products from contaminated raw material. Current physical, biological and chemical methods employed to improve the safety of food often compromise the nutritional value and result in huge losses. The alternative to these treatments are addition of supplements with protective properties to reduce the toxicity of mycotoxins or prevent their formation. The work presented in this dissertation reports an attempt to develop such materials to prevent damage caused by ochratoxin A and aflatoxin B1. This was done through the synthesis; characterisation and cytotoxicity study of chitosan nanoparticles with methanolic plant extracts (L. leonurus, M. longifolia and A. montanus). Inhibition of cellular damage due to mycotoxins for possible application in prevention of cellular damage by mycotoxins also presented. Chitosan nanoparticles were synthesised using an ionic gelation method with sodium triphosphate as the cross linker. The methanolic medicinal plants extracts were incorporated into the chitosan solution before synthesising nanoparticles, and nanoparticle synthesis initiated by the addition of sodium triphosphate solution. The synthesised products were characterised using zetasizer, transmission electron microscopy, x-ray diffraction and Fourier-transform infrared spectroscopy. The extracts’ antioxidant ability was evaluated before incorporation into chitosan using 2, 2-diphenyl- 1-picrylhydrazy (DPPH) radical scavenging assay. This assay was performed using UVvis spectroscopy. The cytotoxicity of the synthesised nanoparticles was assessed using a Vero cell line and by evaluating the cell viability with an MTS assay. The nanoparticles were successfully synthesised and showed the presence of different functional groups as expected. Plain chitosan nanoparticles were roughly spherical shaped and had smooth surfaces, nanoparticles containing extracts similarly were spherical in shape as well but had rougher surfaces when visualised under TEM. All nanoparticles had positive zeta potentials between 26 – 28 mV. The average particle sizes ranged between 31 – 65 nm as measured using TEM and average particle sizes obtained using zetasiser was 78 – 190 nm. The cytotoxicity studies of plain nanoparticles and nanoparticles with extract showed that the synthesised nanomaterials were not toxic even at concentration of 500 μg/ml and less than 20% of the Vero cells were affected under these conditions.
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493

A comparative study of fungi and mycotoxin contamination in animal products from selected rural and urban areas of South Africa with particular reference to the impact of this on the health of rural black people

Mwanza, Mulunda 24 October 2012 (has links)
D.Tech. (Biomedical technology) / The majority of the South African rural black population remain is exposed to HIV/ AIDS and other chronic diseases, tuberculosis, malaria and cancer. The effect of single and combined mycotoxins on their health and particularly their immune system is unknown and remain of concern as these populations are on daily basis exposed more than one mycotoxin at once. The aim of this study was to evaluate the exposure of South African rural black populations to mycotoxins via animal products in comparison to urban populations and to assess the effect of the major mycotoxins (fumonisin B1 (FB1), aflatoxin B1 (AFB1) and ochratoxin A (OTA)) mostly present in their food on human and animals (pigs) mononuclear cells and by extrapolation, evaluate possibilities of these mycotoxins on the immune system. To achieve this, animal feed and animal products (milk, serum, and tissues) obtained from selected rural and commercial farms in selected areas of South Africa were analysed for fungal and mycotoxins contamination. It was found in this study that almost all of the samples from both areas were contaminated with the major mycotoxin producing fungal strains (Fusarium, Aspergillus and Penicillium spp.) with the most prominent among them being Aspergillus flavus (87%), A. parasiticus (43%), A. niger (69%), A. ochraceus (42%), A. candidus (23%), F. verticillioides (98%) F. graminearum (67%) and P. Verrucosum (48.9%) and in commercial samples A. flavus (98%), A. parasiticus (51%), A. ochraceus (65%), A. niger (31%), A. candidus (21%), F. verticillioides (F. moniliforme) (68%), F. graminearum (43%) and P. verrucosum (7%). While, the three main mycotoxins were also present and contaminated most samples with fumonisins (FBs) 0in rural and commercial samples at 90.6% and 93.3% respectively with respective means values of 10136.4 ppb and 1045.4 ppb. Aflatoxins (AFs) contamination was of 92.0% in rural samples and 96.2% in commercial samples with means concentrations of 168.8 ppb and 294.1 ppb respectively. While 85.4% and 83.7% of rural and commercial samples respectively were contaminated with ochratoxin A (OTA), with mean concentrations of 67.6 ppb and 89.4 ppb respectively. Zearalenone (ZEA) concentrations were of 43.6 ppb in rural samples and 62.7 ppb in commercial samples with respective contamination of 50.6% and 55.3%. In addition, a co-occurrence of fungi and mycotoxins contaminations was found in both rural and commercial samples. It was found that, 50.5% of rural and 53% of commercial samples were contaminated with all four analyzed mycotoxins. (FBs, AFs, OTA and ZEA), whereas, 81.2% and 79.5% of samples respectively from rural and commercial farms were contaminated with FBs, AFs and OTA mycotoxins simultaneously. The above-obtained results are of significance in this study as they confirm the hypothesis of fungal contamination and mycotoxin co-occurrence in South African feed and their possible combined effects on consumers.
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494

Impacts of selected leguminous tree species and kaolinite pre-amendment on oil-contaminated soil for bioremediation in the oil-bearing region of Nigeria

Oyedeji, Ayodele A. January 2016 (has links)
This study investigates the impacts of selected Leguminous Tree Species (LTS) and kaolinite pre-amendment on oil-contaminated soil. It covered assessment of different levels of contamination (0, 25, 50, 75 and 100 ml in 4000 g soil; which represents the degree of light crude oil spillage concentration as 0.0, 0.63, 1.25, 1.88 and 2.5 %v/w) on the growth performance of Albizia adianthifolia, Albizia odoratissima, Bauhinia monandra, Delonix regia, Peltophorum pterocarpum and Tetrapleura tetraptera LTS investigated. Percentage germination, seedling height, seedling girth, number of leaves and number of nodules decreased as the concentrations of crude oil in soil samples increased. LTS affected soil physicochemical properties. Soil acidity decreased; soil organic matter, carbon content and exchangeable ions increased. N, P and K were altered in the LTS planted soil as compared to controls, but there were no significant (P > 0.05) differences. There were increased microbial counts in the crude oil-contaminated soil planted with LTS as compared with non-LTS planted soils. Hydrocarbon removal was significantly higher (P < 0.05, n = 3) in LTS planted soil than in non-planted soil. D. regia planted soils had most hydrocarbon removal and had significantly more growth in terms of plant height, girth and leaf production in the field. Kaolinite (10 and 20 g samples) applications were suitable and effective sorbent agents for oil-contamination at the different oil concentrations. The sorption potential of kaolinite increased with the increase in kaolinite to 20 g. The potential re-usability of kaolinite after the initial use for oil sorption was analysed and 10 g of burnt kaolinite sorbed 43.62%, while 20 g sorbed 58.90%. The rate of oil sorption by fresh kaolinite was significantly higher than burnt kaolinite. Results show the considerable potential of phytoremediation protocols with LTS and kaolinite as combined remediating agents for oil spill remediation in the humid tropics.
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495

Persistent organic pollutants in foodstuffs and human samples from Hong Kong

Tsang, Hin Long 01 January 2008 (has links)
No description available.
496

Vattenkvalitet i enskilda dricksvattenbrunnar i ett omvandlingsområde : En undersökning av enskilda dricksvattenbrunnar i delar av Hertsölandet i Luleå kommun, utifrån ett hälsoskyddsperspektiv / Water quality in private groundwater wells in a conversion area : A survey of private groundwater supplies in parts of Hertsölandet in Luleå municipality, from a health protection perspective

Boqvist, Lisa January 2017 (has links)
Good quality of drinking water is the foundation of a functioning society. Many Swedish municipals investigates ways to protect water supplies in convention areas. The purpose of this study was to investigate the risks of microbiological contamination of drinking water by private sewers and geothermal heat pumps. The purpose was also to investigate the risks of contamination associated with safety distances from energy wells and private sewers. Water samples were taken from private groundwater wells in the convention area of Hertsölandet in Luleå municipal, to test for microbiological contamination. To investigate safety distances, maps were made to locate private sewers, private groundwater wells and energy wells in the area. The result indicated that the groundwater wells was not contaminated by wastewater but that individual weaknesses in the groundwater wells contributed to microorganisms in the drinking water. However, too few samples were taken to provide a reliable result. The samples were taken at spring time and it should possibly had been more representative to take the samples after the summer season, when the use of water and production of wastewater has increased. Contaminations associated with safety distances to geothermal heat pumps and other groundwater wells could not be detected. The results shown that several groundwater wells were located too close to sewers according to safety distance. It is possible that the risks will increase as more people moves permanently to this area.
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497

Transport and fate of chemical and microbial tracers at University of Western Cape (UWC) campus site, Cape Flats aquifer of South Africa

Haricombe, Erin January 2016 (has links)
>Magister Scientiae - MSc / Extreme weather events in combination with geographical changes in groundwater utilization, groundwater availability, aquifer recharge, and ultimately changes in the quality of water resources, are expected in the future. As a consequence of changing weather patterns and urbanization the demand for groundwater is likely to increase in certain areas. We know that most waterborne pathogenic health epidemics are associated with contamination of farm water and wastewater. There is however limited understanding of the nature and extent of chemical, physical and biological processes that control the fate and transport of the microorganisms in primary and secondary aquifers. In this thesis, transport results are reported, where E. coli and PDR1 were selected as the biological tracers transported through a primary aquifer at the University of the Western Cape. In conjunction with the microbes salt and Rhodamine (chemical tracers) were injected to compare their fate and transport mechanism in the primary aquifer medium. A series of controlled Darcy experiments under laboratory and field conditions were conducted. Each provided a different data and information. The results from laboratory studies were used to improve design of the field studies. In both cases, the data collected provided information on fate and transport of microbes in groundwater. The field design phase of the experiment was an up-scaling of the laboratory phase of this project. The amount of chemical tracers injected into the aquifer was increased in proportion to the size of the research site. Tracer tests using chemical and microbial tracers were conducted simultaneously. Results of laboratory tests demonstrate a 5 times slower transport of microbes, compared to tests with salts during the laboratory phase. The salts at field scale show a breakthrough occurring after 2 days whereas the microbes –did not break through during the 28 days of the observation period. A new borehole was drilled closer to the pumping borehole to eliminate distance or travel time, but this had no effect on field results for the microbes. / National Research Foundation
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498

Social and economic factors influencing under-five mortality in Zimbabwe during 1996-2005

Kembo, Joshua 15 March 2010 (has links)
This study addressed important issues on infant and child mortality in Zimbabwe. The broad objective of the study is to establish levels and trends of under-5 mortality and to determine the impact of maternal, socioeconomic and environmental contamination variables on infant and child mortality. Data from four DHS surveys conducted in Zimbabwe were used. It was found that mortality at all ages below 5 years old remained more or less constant from the period 1990-1994 to the period 1995-1999 and declined from the period 1995-1999 to 2001-2005. Mortality below 5 years old declined from 102 deaths per 1,000 live births during 1995-1999 to 82 deaths in 2001-2005. This decline was unexpected and it is argued that this decline is probably not genuine. Various types of evidence are provided to support the view that this decline in mortality probably did not take place. Analysis of ZDHS 2005- 06 showed that births of order 6+ and short preceding interval (intervals of less than or equal to 18 months) had the highest infant mortality risk. Infants with these characteristics were significantly more likely (2.75 times) to die in infancy relative to births of order 2-5 and long preceding birth interval (p<0.001). The infant mortality risk associated with multiple births was 2.08 times more relative to singleton births (p<0.001). The results indicated that socioeconomic variables did not have a distinct impact on infant mortality. Determinants of child mortality were different in relative importance from those of infant mortality. The effect of maternal education, though not significant, implied a decline in child mortality with increasing maternal schooling. The provision of piped drinking water and flush toilets to the households had a stronger impact on child mortality than infant mortality. Including HIV prevalence in the models elevated the odds of dying in infancy and childhood stages by 10 percent and 63 percent, respectively. This suggests that HIV/AIDS directly and/or indirectly influences the current levels of under-5 mortality in Zimbabwe. This study supports health policy initiatives stimulating use of family planning methods to increase birth intervals. Family planning programmes should be aimed at educating women and men with low educational levels and those in rural areas about the potential benefits of long-term birth spacing. These and other results are expected to assist policy makers and programme managers in the child health sector to formulate appropriate strategies to improve the situation of under-5 children in Zimbabwe. / Thesis (PhD)--University of Pretoria, 2010. / School of Health Systems and Public Health (SHSPH) / PhD / Unrestricted
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499

New approaches to the control of contamination in biofuel ethanol fermentations

Spencer, Christopher Andrew January 2014 (has links)
The production of biofuels and in particular bioethanol has increased rapidly since the early 1990’s. The advantages of biofuels include reduced CO2 production, a decrease in fuel importation for many nations (notably the US and Brazil), and comparatively simple blending with fossil fuels. The production of basic fuel ethanol (1st generation) involves the use of an energy crop feedstock (corn in US and sugar cane in Brazil). The feedstock is processed via simple mechanical methods to release the simple carbohydrates, mixed with water and fermented anaerobically via S. cerevisiae yeast into ethanol and CO2. Due to the low market value of fuel ethanol, profit margins are restrictive, and as a result sterilisation and aseptic techniques are not economically viable, and contamination by environmental organisms is commonplace. The current system of biocontrol involves the addition of antibiotics, primarily penicillin and virginiamycin, to the fermentation. While these antibiotics are broad spectrum and highly effective in reducing the impact of contamination, the negative environmental impacts of antibiotic usage are well known. In order to reduce the impact of contamination and reduce reliance on antibiotics an alternative system of biocontrol is required. In this thesis various biocontrol agents are assessed, including bacteriophage, hop acids, chitosan, onion oil extract, copper and silver ions. The effect of these agents on the growth of various contaminant bacteria and a strain of S. cerevisiae is assessed and fermentations are carried out under sterile and controlled contaminated conditions to generate data on the effect of the contaminant and the various methods of biocontrol. Other possibilities investigated include the insertion of plasmids containing heat shock proteins into S. cerevisiae to enhance thermo-tolerance.
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500

Application of catalysts and nanomaterials in the design of an electrochemical sensor for ochratoxin A

Flanagan, Shane Patrick 06 December 2010 (has links)
Ochratoxin A is the most potent chlorinated derivative of the ochratoxin group, consisting of a 5'-chlorinated dihydroisocoumarin moiety linked by an amide bond to l-phenylalanine. Produced as a secondary fungal metabolite by several species of Aspergillus and Penicillium, ochratoxin A has been shown to readily contaminate a large variety of commodities including cereals, groundnuts, dried fruit, spices and coffee. This has led to widespread contamination of ochratoxin in wine, beer, milk and meat products. As ochratoxin A is a potent nephrotoxin exhibiting teratogenic and carcinogenic properties, the development of a rapid screening platform for the cost effective control of ochratoxin A content in foodstuffs is therefore required. The evaluation of metallophthalocyanine and carbon nanotube electrode modification toward the development of a nanostructured biosensor capable of enhancing the electrochemical detection of ochratoxin A in complex media is presented. Cyclic voltammetry at a glassy carbon electrode allowed for the optimization of detection parameters including pH and type of supporting electrolyte. Britton-Robinson buffer was found to be the most suitable supporting electrolyte in terms of sensitivity and reproducibility obtaining a LOD of 0.28 μM as determined by differential pulse voltammetry. Subsequent analysis determined the dependence of OTA oxidation on pH in acidic media which proceeds with the transfer of two electrons to form a quinone/hydroquinone couple shown to adsorb to the electrode surface. Passivation of the electrode through adsorption of oxidation products was shown to severely limit the detection of OTA upon successive detection cycles. Comparison of various metallophthalocyanine modifiers showed an increase in sensitivity toward the detection of OTA at phthalocyanine complexes with metal based redox processes. However with the exception of NiPc and CoTCPc complexes, phthalocyanine modification was limited by the increase in deviation of current response and extent of fouling. NiPc modification showed an increase in sensitivity by two fold with fouling characteristics comparable to an unmodified electrode while low improvements in fouling was observed at CoTCPc modified electrodes with sensitivity in detection comparable to an unmodified electrode.Modification of the electrode with multi- and single walled carbon nanotubes produced a significant increase in sensitivity toward the detection of ochratoxin A. The electrocatalytic activity of nanotube modifiers was attributed to the increase in surface area and to the addition of oxygenated functional groups upon acid treatment as confirmed by Raman spectroscopy. Acid functionalization of the carbon nanotubes for a period of two hours produced the greatest increase in sensitivity obtaining a respective LOD of 0.09 μM and 0.03 μM for analysis of ochratoxin A at multi- and single walled carbon nanotube modified electrodes. Centrifugal purification of carbon nanotubes was deemed necessary to improve the electrocatalytic activity of the nanotube modifiers through the removal of carbonaceous impurities as visualized by atomic force microscopy. Furthermore, a crude lipase preparation, lipase A, was investigated as a potential biological recognition element for selective detection of ochratoxin A in complex media. Lipase A enabled the hydrolysis of ochratoxin A to the electroactive species ochratoxin α as confirmed by thin layer chromatography and voltammetric analysis. Additional isolation of a pure hydrolase from the lipase A preparation is required prior to utilization within a nanostructured biosensor platform capable of detecting ochratoxin A in complex media.
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