Tesi sul tema "Contamination"
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1
Owen, Michael Paul. "Scatterometer Contamination Mitigation". BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2310.
Testo completoAbstract (sommario):
Microwave scatterometers, which use radar backscatter measurements to infer the near-surface wind vector, are unique in their ability to monitor global wind vectors at high resolutions. However, scatterometer observations which are contaminated by land proximity or rain events produce wind estimates which have increased bias and variability, making them unreliable for many applications. Fortunately, the effects of these sources of contamination can be mitigated. Land contamination of backscatter measurements occurs when land partially fills the antenna illumination area. This reduces and masks the wind-induced backscatter signal. Land contamination is mitigated by quantifying the amount of contamination in a single observation using a metric referred to as the land contribution ratio (LCR). LCR levels which give rise to inadmissible levels of error in the wind estimates are determined and used to discard land-contaminated observations. Using this method results in contamination-free wind estimates which can be made as close to the coast as 5 km, an improvement of 25 km compared to previous methods. Rain contamination of scatterometer observations results from rain-induced scattering effects which modify the wind-induced backscatter. Rain backscatter effects are modeled phenomenologically to assess the impact of rain on the observed backscatter. Given the backscatter effects of wind and rain, there are three estimators: wind-only (WO), simultaneous wind and rain (SWR) and rain-only (RO), which have optimal performance in different wind and rain conditions. Rain contamination of wind estimates is mitigated using a new Bayes estimator selection (BES) technique which optimally selects WO, SWR, or RO estimates as they are most appropriate. BES is a novel adaptation of Bayes decision theory to operate on parameter estimates which may have different dimensions. The BES concept is extended to include prior selection and noise reduction techniques which generalizes BES to a wider variety of wind fields and further increase wind estimate accuracy. Overall, BES has wind estimation performance which surpasses that of either the WO or SWR wind estimates individually, and also provides a viable rain-impact flag.
2
Coughtrey, Anna. "Exploring the fear of contamination : mental contamination in obsessive compulsive disorder". Thesis, University of Reading, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542276.
Testo completo
3
Calderin, Morales Duriem. "Modeling of Loose Contamination Scenarios to Predict the Amount of Contamination Removed". FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/228.
Testo completoAbstract (sommario):
The objective of this research is to evaluate the influence of the factors identified by the Johnson, Kendall and Robert’s theory that affect the strength of the detachment force necessary to remove a particle of contaminant from a surface, and the roughness of the surface in which the contaminant is present, on predicting the efficiency of removal of loose contamination. Two methods were used to reach this objective: the first method consisted of quantifying the contamination by weight and the second method of quantifying the contamination by counting alpha and gamma particles. As a result, it was determined that for particles of 5 μm, the interaction between contaminant-wipe and contaminant-surface were significant. However, for particles between 37-149 μm, the contaminant-surface interaction was the only significant interaction affecting the amount of contamination removed. The results obtained were already used at a contaminated site, confirming the prediction of contamination removed
4
Scott-Fordsmand, Janeck James. "Biomarkers of soil contamination". Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265176.
Testo completo
5
Haner, Andrew Lloyd. "Iola, Kansas residential lead contamination". Thesis, Wichita State University, 2007. http://hdl.handle.net/10057/1536.
Testo completoAbstract (sommario):
In the late 1800’s and early 1900’s lead and zinc mining became prominent in Kansas, Oklahoma, and Missouri. With no knowledge of the effects that would impact the future, the mining companies continued to strip the land. With the discovery of lead and zinc ores in southeast Kansas, southwest Missouri, northeast Oklahoma in the late 1800’s a way to process the ores in a cheap way was needed. Natural gas in locations like Iola Kansas helped led to cheap ore processing and smelting. After the cheap fuel for the processing began to diminish in the early 1900’s, the multitude of smelters began to decrease. With the creation of the Environmental Protection Agency in 1970, concerns for the environment became a more than ever important issue. In the 1990’s, the EPA began to collect environmental impact data from areas potentially affected by mining, to access the effects of lead mining on residential areas in southeast Kansas and southwest Missouri. Thus, the methods of residential lead sampling were created. In Iola, Kansas the Kansas Department of Health and Environment performed tests to measure the extent that environmental impact from the smelters had on human residents of the town. With this evidence, the EPA was asked to conduct more testing, and to perform a cleanup of residential sites to help protect the environment and human health.Thesis [M.S]: Wichita State University, College of Liberal Arts and Science, Dept. of Geology
"December 2007."
6
Lee, Cheuk-hung, e 李卓雄. "Microbial contamination of enteral feeds". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31245596.
Testo completo
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Anderton, A. "Microbial contamination of enternal feeds". Thesis, University of Glasgow, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377156.
Testo completo
8
Fonseca, Viviane Grunert da. "Data contamination versus model deviation". Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299265.
Testo completo
9
Aguilar, Bobadilla Silvia E. "ECONOMIC ASPECTS OF HISTORICAL CONTAMINATION". Doctoral thesis, Vysoká škola ekonomická v Praze, 2008. http://www.nusl.cz/ntk/nusl-161826.
Testo completoAbstract (sommario):
The main scope of the work is to support a wider understanding of the achievements and limitations of economic analysis in historical contamination issues. The work describes how various schools of economics focus their study on environmental problems, specifically on Brownfields redevelopment. It presents the ideas of environmental economics, resource economics, free market environmentalism, institutional economics, political economy and ecological economics. The work includes a case study from the region of Ralsko in North Bohemia.
10
Haner, Andrew Lloyd Gries John. "Iola, Kansas residential lead contamination /". Thesis, A link to full text of this thesis in SOAR, 2007. http://hdl.handle.net/10057/1536.
Testo completo
11
Cotty, Peter J. "Aflatoxin Contamination: Variability and Management". College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/208346.
Testo completoAbstract (sommario):
Mapping aflatoxin contamination in the field reveals that most toxin occurs in relatively few, highly contaminated, bolls. Several studies suggest that protection of early bolls from pink bollworm damage will eliminate many of these highly contaminated bolls. Early harvest will also help reduce aflatoxin contamination. However, the crop must still be carefully managed after harvest because toxin content of mature bolls can increase very rapidly.
12
Cotty, P. J., D. R. Howell, C. Bock e A. Tellez. "Aflatoxin Contamination of Bt Cottonseed". College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/211132.
Testo completoAbstract (sommario):
Transgenic Bt cotton may have reduced susceptibility to aflatoxin contamination as a result of pink bollworm resistance. During 1995 and 1996, Bt cottonseed from several commercial fields in Arizona contained aflatoxin levels unacceptable for dairy use. Comparison of cottonseed with and without BGYF (bright-green-yellow fluorescence) from one highly contaminated (> 6,000 ppb aflatoxin Bj) Bt seed lot indicated that most contamination probably resulted from exposure of mature cotton to high humidity. Seed exhibiting BGYF was repeatedly detected in Bt cottonseed lots but, pink bollworm exit holes were not observed in the field. A field plot test in 1996 demonstrated high resistance among Bt cultivars to both pink bollworm damage and formation of BGYF seed cotton. These observations suggest that resistance to pink bollworm will result in reduced aflaaoxin contamination when pink bollworm pressure coincides with conditions conducive to Aspergillus flavus infection. However, Bt cultivars are not resistant to aflatoxin increases occurring after boll opening and large quantities aflatoxin can form during this period. If insect control provided by Bt cultivars leads growers to hold crops in the field longer, most advantages of Bt cotton in aflatoxin management may be lost. Combined use of Bt cultivars and atoxigenic strains of A. flavus may result in the most reliable control of aflatoxin contamination.
13
Coimbra-Lisboa, Paulo César. "On the contamination of confidence". reponame:Repositório Institucional do FGV, 2009. http://hdl.handle.net/10438/7728.
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Contaminação da confiança é um caso especial de incerteza Knightiana ou ambiguidade na qual o tomador de decisões está diante de não apenas uma única distribuição de probabilidades, mas sim de um conjunto de distribuições de probabilidades. A primeira parte desta tese tem o propósito de fornecer uma caracterização da contaminação da confiança e então apresentar um conjunto de axiomas comportamentais simples sob os quais as preferências de um tomador de decisões é representada pela utilidade esperada de Choquet com contaminação da confiança. A segunda parte desta tese apresenta duas aplicações econômicas de contaminação da confiança: a primeira delas generaliza o teorema de existência de equilíbrio de Nash de Dow e Werlang (o que permite apresentar uma solução explícita para o paradoxo segundo o qual os jogadores de um jogo do dilema dos prisioneiros com um número infinito de repetições não agem de acordo com o esperado pelo procedimento da indução retroativa) e a outra estuda o impacto da contaminação da confiança na escolha de portfolio.
Contamination of confidence is a special case of Knightian uncertainty or ambiguity in which the decision maker faces not simple probability measure but a set of probability measures. The first part of this thesis has the purpose to provide a characterization of the contamination of confidence and then present a simple set of behavioral axioms under which the decision maker’s preference is represented by the Choquet expected utility with contamination of confidence. The second part of this thesis presents two economic applications of the contamination of confidence: the first of them generalizes Dow and Werlang’s existence Theorem of Nash equilibrium under uncertainty (which enables to present an explicit solution to the paradox on which players in a finitely repeated prisoners’ dilemma breaks down backward induction) and the other studies the impact of the contamination of confidence in the portfolio choice.
14
Thomason, Jr Ernest Lowell. "Cross Contamination in Levered Endoscopes". ScholarWorks, 2018. https://scholarworks.waldenu.edu/dissertations/6138.
Testo completoAbstract (sommario):
Contamination is a prevalent issue with reprocessed levered endoscopes. The number of infections caused by resistant enterobacteriaceae in patients due to contaminated endoscopes increased to the point that the United States Food and Drug Administration released a safety alert to health care facilities that perform endoscopic retrograde cholangiopancreatography (ERCP). The purpose of this descriptive project was to evaluate if levered endoscopes used in ERCP procedures met high level disinfection criteria, were properly processed, and were germ free after reprocessing. The project was supported by 2 theories: the middle range theory of patient advocacy and the germ theory. Data (counts and percentages) were collected from testing 150 endoscopes at each of 4 facilities within an organization regarding the effectiveness of the reprocessing of the levered endoscopes. According to the project findings, there was a 7% average germ-free failure rate across the sites after the initial reprocessing. The cleaning process of the levered endoscopes allowed bacteria to remain on the scopes after the manufacturer-recommended cleaning was completed at the sites. Standardization of the organization's cleaning process and improvement in the national protocols were recommended. The project supported protecting the safety of endoscopy patients by identifying that the cleaning process could be improved to prevent introduction of infectious bacteria through a procedure. The results will be informative for laboratory staff who clean levered endoscopes, physicians who use the scopes in patient procedures, patients who undergo the procedures, and nurses who are tasked with improving patient safety in perioperative environments.
15
Bowling, Frank, Daryl Stickings, Valerie Edwards-Jones, David Armstrong e Andrew Boulton. "Hydrodebridement of wounds: effectiveness in reducing wound bacterial contamination and potential for air bacterial contamination". BioMed Central, 2009. http://hdl.handle.net/10150/610180.
Testo completoAbstract (sommario):
BACKGROUND:The purpose of this study was to assess the level of air contamination with bacteria after surgical hydrodebridement and to determine the effectiveness of hydro surgery on bacterial reduction of a simulated infected wound.METHODS:Four porcine samples were scored then infected with a broth culture containing a variety of organisms and incubated at 37degreesC for 24 hours. The infected samples were then debrided with the hydro surgery tool (Versajet, Smith and Nephew, Largo, Florida, USA). Samples were taken for microbiology, histology and scanning electron microscopy pre-infection, post infection and post debridement. Air bacterial contamination was evaluated before, during and after debridement by using active and passive methodsfor active sampling the SAS-Super 90 air sampler was used, for passive sampling settle plates were located at set distances around the clinic room.RESULTS:There was no statistically significant reduction in bacterial contamination of the porcine samples post hydrodebridement. Analysis of the passive sampling showed a significant (p < 0.001) increase in microbial counts post hydrodebridement. Levels ranging from 950 colony forming units per meter cubed (CFUs/m3) to 16780 CFUs/m3 were observed with active sampling of the air whilst using hydro surgery equipment compared with a basal count of 582 CFUs/m3. During removal of the wound dressing, a significant increase was observed relative to basal counts (p < 0.05). Microbial load of the air samples was still significantly raised 1 hour post-therapy.CONCLUSION:The results suggest a significant increase in bacterial air contamination both by active sampling and passive sampling. We believe that action might be taken to mitigate fallout in the settings in which this technique is used.
16
Croft, Richard G. "Remediation techniques for gas plant contamination". Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521955.
Testo completo
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MacDougall, Kenneth Alasdair. "Groundwater contamination : a risk based approach". Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366814.
Testo completo
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Lang, Adam. "Contamination and decontamination of steel components". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/contamination-and-decontamination-of-steel-components(32951cc3-b259-4e0b-b97e-fcc45c507bb7).html.
Testo completoAbstract (sommario):
Nuclear plant stainless steel can become contaminated by radionuclides during normal operation whereby the final disposition of these materials then becomes a major decommissioning challenge to address. Characterisation of the chemical and metallurgical processes that underpin contamination is essential in consideration of developing cost effective decontamination and prevention methods, as are in situ measurement techniques that allow assessment of contamination. To address these issues, contamination experiments to simulate the nitric acid-based reprocessing streams of the PUREX (Plutonium Uranium Redox Extraction) process, and alkaline spent fuel storage ponds were investigated. Solution and surface spectroscopic measurements were performed to characterise the sorption behaviour of stable analogues of two high yield fission products, Sr-90 and Cs-137, on as received and 30 % cold rolled AISI Type 304 stainless steel, respectively. In addition Laser Induced Breakdown Spectroscopy (LIBS) was also investigated as a standoff contamination assessment technique. Fission product accumulation was modelled to a second order kinetic fit that considers chemisorption, typically to a hydrous metal oxide surface, as rate controlling. This process is observed to be independent of solution composition and strain processing regime. This behaviour reflects complexation to the passivating surface chromium oxide film, and as determined by depth elemental analysis, effectively inhibits contaminant migration into the bulk material. Environment chemistry and microstructural variables that destabilise the Cr-rich passive film however reduces the passive layer capabilities to effectively inhibit fission product bulk diffusion. The importance of corrosion phenomena towards radionuclide sorption processes necessitates the consideration of metallurgical and chemical factors during the implementation of decontamination approaches to treat affected plant material at nuclear licenced sites. LIBS was found to be a satisfactory technique for measurement of Sr sorbed to steel but Cs could not be detected at the concentrations used in this experimentation. Furthermore, EDX and TOF-SIMS elemental mapping indicated ablated material may be redistributed into the crater profile during elemental analysis. This process has clear implications for the deployment of LIBS for in situ characterisation of nuclear materials as the uncontrolled redistribution of radioactive material certainly violates decommissioning principles.
19
Roth, Jake. "Bleed air oil contamination particulate characterization". Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/19022.
Testo completoAbstract (sommario):
Master of ScienceDepartment of Mechanical and Nuclear Engineering
Mohammad H. Hosni
Byron W. Jones
Gas turbine engine oil is contaminating the bleed air of an aircraft with enough frequency and intensity that health concerns are of public interest. While previous work measured micro particles and used only a simulator, this work mainly consists of measurements in the nanoparticle and ultrafine range using both the simulator and two different gas turbine engines. No previous research has been conducted using working jet engines to simulate a bleed air system and characterize the oil particulate contamination. Oil was injected into a bleed air simulator and an Allison 250 CC18 turbine engine in order to observe the particle size distributions resulting from thermal degradation and was measured with three particle sizing counters and an FTIR. The aerosol size distributions are given for various temperature and pressure ranges consistent with the process conditions associated with the bleed air in a commercial aircraft. Particle sizes of approximately 80nm to 100nm were observed at temperatures over 200°C while particles similar to injection distributions and smaller than measureable size were observed at lower power settings. Temperature is thought to be the controlling factor affecting particle size above 200°C while blade shear is likely the dominant factor for lower temperatures. The bleed air simulator produced results similar to the gas turbine engine results at higher temperatures, but did not replicate the size characteristics at lower temperatures. The observed particles are ultrafine and situated in the size range that may impact health safety more than larger particles.
20
Alexander, Barbara M. "Contamination of Firefighter Personal Protective Gear". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337885489.
Testo completo
21
Mahomed, N. "Finite element analysis of groundwater contamination". Master's thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/8294.
Testo completoAbstract (sommario):
Includes bibliographical references.The purpose of this study was to develop a computational Finite Element model, validated by experimentation, to assist in the understanding of groundwater contamination problems. It was mainly aimed at studying the extent and manner of travel of contaminants in the saturated soil of unconfined aquifers which may be pumped by of wells.
22
Lakies, Marcel. "Dynamic Cabin Air Contamination Calculation Theory". Aircraft Design and Systems Group (AERO), Department of Automotive and Aeronautical Engineering, Hamburg University of Applied Sciences, 2019. http://d-nb.info/1194940196.
Testo completoAbstract (sommario):
In this report an equation is derived to calculate the dynamic effect of primary and secondary aircraft cabin air contamination. The equation is applied in order to understand implications and hazards. Primary contamination is from an outside source in form of normal low level contamination or high level contamination in a failure case. Secondary contamination originates from deposited material released into the cabin by a trigger event. The dynamic effect is described as an initial value problem (IVP) of a system governed by a nonhomogeneous linear first order ordinary differential equation (ODE). More complicated excitations are treated as a sequence of IVPs. The ODE is solved from first principles. Spreadsheets are provided with sample calculations that can be adapted to user needs. The method is not limited to a particular principle of the environmental control system (ECS) or contamination substance. The report considers cabin air recirculation and several locations of contamination sources, filters, and deposit points (where contaminants can accumulate and from where they can be released). This is a level of detail so far not considered in the cabin air literature. Various primary and secondary cabin contamination scenarios are calculated with plausible input parameters taken from popular passenger aircraft. A large cabin volume, high air exchange rate, large filtered air recirculation rate, and high absorption rates at deposit points lead to low contamination concentration at given source strength. Especially high contamination concentrations would result if large deposits of contaminants are released in a short time. The accuracy of the results depends on the accuracy of the input parameters. Five different approaches to reduce the contaminant concentration in the aircraft cabin are discussed and evaluated. More effective solutions involve higher implementation efforts. The method and the spreadsheets allow predicting cabin air contamination concentrations independent of confidential industrial input parameters.
23
Green, Kemble. ""Nursing Contamination: Wearing Scrubs in Public"". Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/honors/238.
Testo completoAbstract (sommario):
Nurses are frequently seen in public in their “scrubs,” which could mean that contaminated clothing is being brought into the community, thereby posing an infection risk. The purpose of this study is to investigate if and which contaminants are present on the fabrics and the actions nurses are taking to eliminate contamination risks.
Eleven scrub tops were worn on hospital units over one twelve-hour shift. The contaminated scrubs and three control tops were then swabbed and used to inoculate agar plates. After incubation, colonies were counted, streaked onto nutrient and Mannitol-salt agar for isolation, and incubated. Using API Staph strips and Gram staining, the bacteria were identified. The nurses also completed a short survey on laundering and scrub care.
All scrub tops, except the controls, were contaminated with multiple species of bacteria including Staphylococcus species. Responses to the survey showed that no two nurses washed their scrubs in the same manner and many wear them in public. The results determined that bacteria can survive on clothing and pose the possibility of transmission throughout the hospital and public venues. The survey results indicate a need for employer laundering policies, public awareness of the risk for transmission of disease from contaminated clothing, and stricter regulations about employees wearing scrubs outside of health care facilities.
24
Spilsbury, Francis David. "Fish Fingerprints Signatures of Oil Contamination". Thesis, Curtin University, 2022. http://hdl.handle.net/20.500.11937/88429.
Testo completoAbstract (sommario):
A laboratory exposure trial investigating the effects of crude oil and heavy fuel oil on Lates calcarifer (barramundi, or Asian seabass), including analysis of biochemical biomarkers, gut microbiome studies, otolith microchemistry and geochemical biomarkers. This work has developed a novel, non-subjective method for the forensic identification of source oil in the event of a spill, using multivariate analysis of the ecotoxicological effects exhibited by fish exposed to petroleum hydrocarbons.
25
Lucas, Jean-Paul. "Contamination des logements par le plomb : prévalence des logements à risque et identication des déterminants de la contamination". Nantes, 2013. http://archive.bu.univ-nantes.fr/pollux/show.action?id=ee1e7f1b-e1e9-455c-afa8-ea7f68143c8e.
Testo completoAbstract (sommario):
Les niveaux en plomb (Pb) en milieu résidentiel ont été estimés pour la 1ère fois en France métropolitaine. Pour cela les outils de la théorie des sondages ont été appliqués aux données de l'enquête Plomb-Habitat (2008-2009). Un échantillon de 484 logements a été construit afin d'étudier la population de résidences principales (N = 3 581 991) abritant au moins un enfant âgé de 6 mois à 6 ans. Environ 2,9% des logements possèdent une concentration en Pb dans l'eau du robinet supérieure au seuil réglementaire (SR) de 10 µg/L ; dans 0,21% des logements et 4,1% des parties communes le SR américain de 430 µg/m² de Pb est dépassé dans les poussières intérieures ; 1,4% des sols des aires de jeu extérieures dépassent le SR américain de 300 mg/kg de Pb ; 24,5% des logements ont encore des peintures au Pb. Le Pb des poussières est connu comme étant le principal prédicteur des plombémies infantiles. Un modèle multi-niveaux à 2 niveaux a été construit afin d'expliquer les charges en Pb des poussières des 1834 pièces (niveau 1) investiguées dans les logements (niveau 2). Aucune pondération n'a été introduite dans la méthode d'estimation (pseudo vraisemblance) utilisée pour ce type de modèle sur données d'enquête. La poussière du palier est le principal contributeur à la contamination des poussières. Une étude de simulation a été réalisée à partir de nos données afin de comparer les différentes pondérations pour le niveau 2 d'un modèle multi-niveaux. Son résultat a permis de valider l'utilisation d'un modèle à 2 niveaux non pondéré pour expliquer les charges en Pb de la poussière. Jusqu'alors dans la littérature, seule la pondération au niveau 1 avait été étudiée pour ce type de modèleResidential lead levels were estimated for the first time in mainland France. For this, tools of the theory of survey sampling were applied to the data of the Plomb-Habitat survey (2008-2009). A sample of 484 dwelling was drawn to study the population (N = 3 581 991) of the main residences (as opposed to second home) where at least one child aged 6 months to 6 years was present. Approximately 2. 9% of housing units have a lead concentration in tap water higher or equal than the regulatory threshold (RT) of 10 µg/L; in approximately 0. 21% of dwellings and in 4. 1% of common areas the American RT of 430 µg/m² (40 µg/ft²) was exceeded for interior floor dust lead; 1. 4% of exterior play area soils exceed the American RT of 300 mg/kg of lead; 24. 5% of housing units have still lead-based paint. Lead in floor dust was pointed out as the main predictor of blood lead level in children. A multilevel model with 2 levels was fitted to explain the floor dust lead loadings of the 1834 rooms as level-1 units investigated in the homes considered as level-2 units. No weights was used in the estimation method (pseudolikelihood) used for this kind of modeling on survey data. Dust of the landing of an apartment is the main contributor to the contamination of dust by lead. A simulation study was carried out from our data to compare the different weights for the level-2 units of a multilevel model. Its result enabled us to confirm the fitting of an unweighted model to explain the dust lead loadings. Until now, only the level-1 weights had been studied in the literature for this kind of model
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Lucas, Jean-Paul. "Contamination des logements par le plomb : prévalences des logements à risque et identification des déterminants de la contamination". Phd thesis, Université de Nantes, 2013. http://tel.archives-ouvertes.fr/tel-00946167.
Testo completoAbstract (sommario):
Ce travail s'inscrit dans le domaine de la contamination des logements par le plomb. Il a consisté à estimer la prévalence des logements possédant un risque plomb et à identifier les déterminants de la contamination des poussières intérieures déposées au sol. Le travail s'est basé sur les données collectées dans 484 logements et 1834 pièces lors de la réalisation de l'enquête Plomb-Habitat (2008-2009). L'échantillon a été obtenu par un plan de sondage complexe à partir duquel un poids de sondage a été associé à chaque logement. La démarche s'est organisée en 4 temps. Elle a consisté tout d'abord à valider les données avant de réaliser les analyses statistiques. Puis elle a consisté dans un second temps à estimer les niveaux en plomb dans l'eau du robinet, dans les revêtements intérieurs, dans les aires de jeu extérieures des enfants ainsi que dans la poussière intérieure déposée au sol. Dans un troisième temps les contributions des sources potentielles pouvant contaminer cette poussière ont été estimées. Ceci a été réalisé par un modèle multi-niveaux sur données d'enquête, sans pondération ; le niveau 1 était constitué des pièces et le niveau 2 constitué des logements. Dans un quatrième temps, une simulation Monte Carlo a été réalisée afin de s'assurer de la pertinence du modèle ajusté à l'étape précédente. Ce travail a permis pour la première fois de réaliser un état de la contamination par le plomb dans les logements français. Il montre que concernant les niveaux en plomb dans l'eau du robinet, les poussières intérieures au sol, la peinture au plomb et les sols des aires de jeu extérieures, respectivement 2,5 %, 0,21 %, 24,5 % et 1,4 % des logements sont à risque dans la mesure où le seuil de référence respectif est dépassé. Ce travail met en évidence que les poussières du palier d'appartement sont le principal contributeur dans la contamination des poussières intérieures. Enfin ce travail a permis de montrer sur des données réelles d'enquête qu'une pondération non adéquate au niveau 2 d'un modèle multi-niveaux pouvait induire des estimateurs biaisés. Il serait intéressant à partir des résultats obtenus de définir le concept de logement à risque plomb et de proposer un diagnostic technique permettant de mettre aisément en évidence le risque plomb global d'un logement. Il serait en outre intéressant d'étudier plus précisément les voies de contamination entre les différents compartiments environnementaux et de généraliser les résultats concernant la pondération à utiliser dans une modélisation multi-niveaux sur données d'enquête.
27
Demmer, Rick. "Decontamination method comparison testing using simulated contamination". Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/80223/.
Testo completoAbstract (sommario):
Radiological decontamination of surfaces is challenging. Cleanup tasks are typically visual or even chemically measured, but radioactive contamination is invisible and measured at extremely low levels. Different contamination events have lead to the development of hundreds of decontamination processes. Their selection balances criteria such as cost effectiveness and waste minimization. While testing on the actual system where the contaminations arises (as "field" radioactive specimens) is appropriate, doing so is expensive and time consuming. Simulating contamination with substitute contaminants requires a unique understanding of the system. This provides a less expensive, more controlled and often more informative selection method. However, not all simulation methods are reliable, reproducible, have a useful range nor are relevant to the target activity. To address these needs, a range of simulated contamination systems have been developed: ·SIMCON 1 – to simulate loose contamination on stainless steel; ·SIMCON 2 – to simulate fixed contamination on oxide coated stainless steel; ·A radiological dispersal device (RDD) or so-called “dirty bomb” contaminant to simulate fixed contamination on urban material surfaces. Over 400 individual decontamination tests have been performed with these simulants, using a range of contaminants (Cs, Zr, Am, Sr, Co) and substrates (steel, concrete, marble, limestone, granite). Review and data mining of the results of these tests has allowed for the development of an understanding of the fundamental mechanisms of interaction between contamination and surface and their role in determining decontamination efficiency. Detailed analysis of the SIMCON results demonstrates that the availability of a deliberately designed contamination simulant system allows for the comparative assessment of a wide range of decontamination methods in a common frame of reference on a “level playing field”. Though somewhat intuitively obvious, the SIMCON methods evaluation unambiguously demonstrated that chemically different contaminants may behave quite differently during a decontamination action. The exact nature of this behavior depends upon the nature of applications (loose or fixed) and the decontamination method itself. If a wide range of decontamination methods are deployed on a well-designed contamination simulant, comparison of the results of the decontamination tests may provide insight into the mechanism of contamination e.g. how it is held (loose, fixed etc.), where it is held (on the surface, in a protective oxide layer etc.) and so forth. These conclusions are reinforced by detailed consideration of the urban RDD simulant decontamination data. With respect to the contaminants themselves, it is found that cations that exhibit a pH dependent speciation, such as americium or cobalt, can demonstrate radionuclide / material substrate specific chemistry that results in contaminant precipitation at the substrate surface, especially if the material has an intrinsically alkaline surface pH. For example, in the case of Am and Co, this results in the precipitation of Am and Co oxyhydroxide species at the outer surface of materials such as concrete with consequently high percentage removal efficiencies. For cationic radionuclides such as Cs+ that do not exhibit any nuclide/material surface specific chemistry the principal material property controlling the tenacity of that nuclide during decontamination from urban material substrates is the permeability of that substrate. For substrates of similar permeability, net surface negative charge on the material substrate plays a major role in determining the tenacity of non-reactive cations such as cesium; the larger the net negative charge on the substrate surface, the more tenacious the contamination. Finally, with respect to the decontamination agents themselves, harsh, high concentration chemical agents that utilize multiple decontamination processes (acids, bases, chelants) typically have an effectiveness advantage over more dilute, one component solutions. Strongly acidic solutions achieve the highest overall % removal decontamination results. This is partly because they tend to dissolve small amounts of the substrate surface and liberate imbibed contaminants. Finally, some strippable coating based methods are found to be surprisingly effective; likely because of their chelant/absorbtive character.
28
Conboy, Mary Jane. "Bacterial contamination of rural drinking water wells". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35790.pdf.
Testo completo
29
Bujatzeck, Baldur. "Decision support system for alleviating phosphorus contamination". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22032.
Testo completoAbstract (sommario):
The management of natural resources has greatly improved over the past decade. Despite advances in modelling the fate of nutrients or in modelling socio-economic effects of different farm management strategies, tools that integrate the advances made in these fields are still lacking. To develop a tool to overcome this gap, this research focused on the development of a multi-objective decision support system (MODSS) to alleviate phosphorus (P) contamination from agricultural fields and small watersheds. A decision supporting framework was designed to allow technical and public users to run the MODSS. The MODSS consists of the following elements: nonpoint source pollution models, an expert system to analyse the output of a qualitative P model, a scenario creation routine, a routine to estimate percentage and load based P reduction, a cost/benefits routine and a trade off analysis routine. Throughout the development of the MODSS, it was necessary to design a modified P Index for Southern Quebec. During the design process, the risk class 'controlled subsurface drainage' was introduced into the parameter subsurface drainage. The risk class was included due to findings that suggested that subsurface drainage is an important pathway for P loss in Southern Quebec. The modified P Index was coupled with a pre-screening routine to shorten the P Index analysis. The MODSS was applied to the Castor watershed, Quebec, Canada. The analysis showed that contributing distance, modified connectivity and P application rates are most likely probable causes for P movement from the fields in the Castor watershed. Additionally, the analysis showed that if BMP to reduce P loss are adopted the farmers could generate a surplus income.La gestion des ressources naturelles s'est considérablement améliorée pendant la décennie passée. Malgré les avances dans la modélisation du destin des nutriants ou dans le domaine de modélisation des effets socio-économiques de différentes stratégies de gestion agricole, il nous manque toujours les outils d'intégrer les avances dans ces domaines. Afin de créer un outil d'integration de ces avances, cette recherche s'est concentrée sur le développement d'un système de soutien à la décision à objectifs multiples pour alléger la contamination de phosphore (P) à partir des champs agricoles et des petites lignes de partage. Le système inclut une interface de soutien à la décision permettant aux utilisateurs techniques et au grand public d'utiliser le MODSS. Le MODSS est composé des éléments suivants: plusieurs modèles de pollution diffuse, un système spécialisé pour analyser le produit de sortie d'un modèle de phosphore qualitatif, une routine de création de scénario, une routine pour estimer la réduction du phosphore en termes de pourcentage et de charge, une routine d'analyse avantages-coûts et une routine d'analyse d'échanges. Le développement du MODSS nécessitait la proposition d'un index du phosphore adapté au sud du Québec. Une nouvelle classe de risques a été introduite dans le paramètre de drainage souterrain: le drainage souterrain contrôlé. Cette classe de risques a été ajoutée, puisque des résultats de recherche extérieurs suggéraient que le drainage souterrain constitue une voie importante de perte du phosphore dans le sud du Québec. L'index modifié du phosphore a été couplé avec une routine d'examens préliminaires afin de raccourcir l'analyse. Le MODSS a été appliqué au bassin-versant de Castor au Québec, Canada. L'analyse a démontré les causes probables du mouvement de phosphore provenant des champs du bassin-versant de Castor : la distance par rapport au point d'origine, la connectivité$
30
Braga, Maria Cristina Borba. "Surface water quality modelling of mercury contamination". Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396307.
Testo completo
31
Moles, Velázquez Andrés. "Autonomy, freedom of speech and mental contamination". Thesis, University of Warwick, 2007. http://wrap.warwick.ac.uk/2422/.
Testo completoAbstract (sommario):
The aim of the thesis is to rebut the dominant autonomy-based defence of hate speech within a liberal framework. The thesis argues that liberal egalitarianism is compatible with certain restrictions on free speech. I defend the view that liberal ideals such as equality and autonomy are, contrary to the arguments of many liberals, better achieved by imposing certain restrictions on what citizens are allowed to express. I examine the problem of freedom of expression in the context. of the public/private distinction. In particular, I explore the Rawlsian conception of this distinction, which is based on the idea that principles of justice apply only to the 'basic structure of society'. Citizens are required by justice to treat all others as free and equal citizens, but this seems to hold only when citizens deliberate about 'constitutional essentials and matters of basic justice'. In their private lives and other social contexts citizens are free to treat other people without equal respect and concern, provided that basic rights are not violated. This position is criticised by calling attention to recent developments in Social and Cognitive Psychology. Evidence suggests that much of our behaviour is triggered by features of�· the environment that bypass individuals' rational control: this includes social stereotypes, non-instrumental behaviour, and goal-oriented activity among others. I develop these ideas into a discussion of free speech and autonomy. I argue that autonomy defences of free speech need to assess how the environment directly affects rational processes. Moreover, I argue, given the structure of human cognition, there is no guarantee that attitudes and actions cultivated in the private sphere will not 'spillover' into the public sphere. For this reason, I suggest, political morality must also extend to the justice of our private practices. To the extent that autonomy and justice matter, I argue that we have reasons to limit the expression of certain views, in particular those which trigger processes that bypass rational control. Finally, despite the importance I attribute to the concept of autonomy, I reject the claim that my position endorses a form of liberal perfectionism. I do so by defending a conception of full publicity and demonstrating that the view I articulate is compatible with rejecting perfectionism.
32
Rivett, Michael Owen. "The organic contamination of the Birmingham aquifer". Thesis, University of Birmingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491197.
Testo completo
33
Poniger, S., H. Tochon-Danguy, H. Sachinidis, K. Alt, C. Hagemeyer e A. Scott. "Reducing metal contamination in Cu-64 production". Helmholtz-Zentrum Dresden - Rossendorf, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-166071.
Testo completoAbstract (sommario):
Introduction
In the past several years there has been a growing interest in the development of radiopharmaceuticals labeled with metallic radionuclides (Anderson et al. 1999). Of particular interest is the positron emitter Cu-64 (t½ = 12.7 h) for molecular imaging of small molecules as well as peptides and antibodies (Smith 2004). This has led us to the recent implementation of a solid target production facility using commercially available target irradiation station and chemistry modules. Routine production of Cu-64 was achieved with an average production yield of 0.32 mCi/μAh, however purification of Cu-64 has proven to be problematic; with several metallic contaminants compromising subsequent radiolabeling. We report in this work, the step by step procedure which led us to the successful production of low metal contaminant 64Cu with high specific activity and high labeling efficiency.
Material and Methods
Detailed implementation of our solid target was reported earlier (Poniger et al. 2012). A Nirta Solid Target from IBA was coupled to our 18/9 cyclotron using a 2-meter external beam line. A pneumatic solid target transfer system (STTS) designed by TEMA was use to deliver the irradiated target disks to a dedicated hotcell. Modules from IBA (Pinctada metal) were used for electroplating 64Ni onto a Ag disk and for acid dissolution and purification of the irradiated target. Typical irradiation parameters were 14.9 MeV at 35 μA for 5–6 hours with 64Ni plating’s ranging from 10–60 μm thickness at 6–12 mm. Radionuclidic purities were evaluated by gamma spectroscopy and traces of metallic impurities were determined by ICP-MS or ICP-AES. Labeling efficiency was evaluated by measuring the amount of 64Cu uptake per 20 μg of scFv-cage.
Results and Conclusion
Initial 64Cu purifications following the manufacturers recommended method resulted in high levels of Cu, Fe and Zn metal contaminants (see TABLE 1, ID 1). Note that little Ag contamination is observed nevertheless the 64Ni is plated directly on a Ag disk. After several productions, visual inspection of the module quickly revealed that the heater block used for heating the back of the Ag target disk was heavily corroded. Replacing the copper heater block with a PEEK heater block drastically reduced the levels of Cu and Fe contaminants.
Unfortunately unusually high levels of Zn were still observed regardless of the stringent conditions and ultrapure reagents used during the processing (see TABLE 1, ID 5). In our quest for answers, ICP-MS analysis of the 64Ni plating solution as well as critical stock reagents such as Milli-Q water (18 MΩ cm−1) and 30% HCl TraceSelect Ultra (Sigma) was performed (see TABLE 1, ID 2,3,4). The results were surprising, with high level of Zn found not only in the 64Ni plating solution, but as well in the HCl TraceSelect Ultra. It was hypothesized that the Pinctada’s glass bottles (Kay, 2004) used to store the reagents, especially concentrated acidic solutions were the source of Zn contamination and all glass bottles were replaced by LDPE or PFA types. Our hypothesis was confirmed by subsequent ICP-MS analysis of fresh samples of HCl TraceSelect Ultra and the 64Ni plating solution prepared/stored in plastic containers (see TABLE 1, ID 6,7). We also confirmed by ICP-MS analysis that no contamination occurred when performing a non-radioactive dissolution/purification sequence on the Pinctada module using a blank PTFE target disk in conjunction with the change to plastic reagent storage bottles (see TABLE 1, ID 8).
Initially the purification protocol was modified as described by Ometakova et al., 2012 to help reduce the co-elution of Zn contaminants with the 64Cu from the AG1-X8 resin. This change resulted in a significant amount of 64Cu eluting from the resin during the resin washing steps, so that protocol was abandoned and the protocol as described by Thieme et al., 2012 was adopted. By modifying the AG1-X8 resin washing protocol to this new method and eluting the 64Cu from with 0.1M HCl rather than Milli-Q water (see TABLE 1, ID 9), we were able to further reduce metal contaminants, especially Zn.
During the course of these experiments, the true specific activity of 64Cu increased from as low as 12 mCi/μmol of Cu (n = 2, TABLE 1, ID 1) to 649 mCi/μmol of Cu (n = 7, TABLE 1, ID 5) and finally to 4412 mCi/μmol of Cu (n = 3, TABLE 1, ID 9). In the same time, the effective specific activity increased from 0.03 ± 0.02 mCi per 20 μg of scFv-cage, to 3.7 ± 0.3 mCi per 20 g of scFv-cage with 64Cu.
In conclusion, a significant reduction in Cu, Fe and Zn contaminants was achieved when processing 64Cu using the Pinctada module: i) after replacement of the Cu heater block; ii) after elimination of glass reagent storage containers from the Pinctada module and procedures during preparation of the 64Ni plating solution and iii) after implementation of a new purification protocol (Thieme et al. 2012). Introduction of a 6M HCl wash-up cycle of the module prior to the dissolution procedure was also effective. However in recent 64Cu productions slightly elevated Ag levels have been observed and are under investigation (see TABLE 1, ID 9).
34
Largueche, Fatima-Zohra. "Assessment of ground contamination using Kriging techniques". Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320825.
Testo completo
35
Bailey, Susan K. "Tributyltin (TBT) contamination in Scottish coastal waters". Thesis, Edinburgh Napier University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292212.
Testo completo
36
Durrant, Christopher. "Effects of metal contamination on fish populations". Thesis, King's College London (University of London), 2010. http://kclpure.kcl.ac.uk/portal/en/theses/effects-of-metal-contamination-on-fish-populations(cd690b4f-265d-48cd-805e-c561e411b370).html.
Testo completo
37
Santana, Marina Ferreira Mourão. "Effects of microplastics contamination on marine biota". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/21/21134/tde-20032016-174906/.
Testo completoAbstract (sommario):
Microplastic pollution (particles < 5mm) is one of the most widespread impacts from modern society. Here, microplastic impacts were investigated through experimental assessments considering different exposure scenarios using mussels and micro-PVC as models. These aimed to investigate mussels\' physiological signs of stress under acute and chronic exposures and microplastics transference, assimilation and retention along food chains. In acute exposures, PVC intake affected mussels\' physiology over time, also influenced by plastics additives and particle concentration. Interactions among exposure factors (time, presence of additives and concentration) were more relevant than their individual effect, indicating the singularity of each contamination scenario. Long-term contact did not affect mussels, indicating the influence of time to acclimation. Microplastics were not assimilated and retained along food chains, but only biotransferred from prey tissues to predators\' tract, showing the influence of prey contamination on the effectiveness of microplastics biotransference. To evaluate risks in nature, microplastic ingestion was investigated in mussels from the Santos Estuary. Santos Estuary contained microplastics in 75% of sampled mussels, an issue of environmental and human concern. This study illustrated that microplastics impacts on mussels vary with microplastics characteristics, exposure scenario and species vulnerability, highlighting the need for more toxicological and risk evaluation studies.Os microplásticos (< 5mm) são um dos impactos mais difundidos da sociedade moderna. Aqui, eles foram estudados em ensaios experimentais, considerando diferentes composições de exposição de mexilhões à micro-PVCs. O objetivo foi investigar: sinais fisiológicos de estresse sob exposições aguda e crônica; e transferência, assimilação e retenção de microplásticos em cadeias tróficas. Para avaliar seus potenciais riscos na natureza, a ingestão por mexilhões também foi investigada no Estuário de Santos. As exposições agudas afetaram a fisiologia dos mexilhões, sendo influenciadas pelo tempo e concentração de exposição, e pela presença de aditivos plásticos. Interações entre esses fatores (tempo, concentração e aditivos) foram mais relevantes do que eles individualmente, sugerindo a singularidade dos cenários de poluição. A exposição de longo prazo não afetou os mexilhões, indicando a influência do tempo na aclimatação ao microplástico. O PVC não foi assimilado e retido nas cadeias tróficas, mas biotransferido do tecido das presas para o trato dos predadores, mostrando a influência do estado da presa na efetividade da biotransferência dos microplásticos. Dentre os mexilhões coletados, 75% estavam contaminados, revelando uma importante questão socioambiental. Esse trabalho ilustrou a complexidade dos impactos dos microplásticos para a biota marinha, ressaltando a necessidade de mais estudos sobre seus riscos.
38
Lavigne, Hélène. "Hémodialyse : contamination microbiologique et pyrogénique du dialysat". Bordeaux 2, 1992. http://www.theses.fr/1992BOR2P088.
Testo completo
39
Samoilenko, N., I. Yermakovych e L. Mårtensson. "Water contamination of urban areas by pharmaceuticals". Thesis, Белорусский государственный технологический университет; Vilnius Gediminas Technical University, 2014. http://repository.kpi.kharkov.ua/handle/KhPI-Press/25401.
Testo completoAbstract (sommario):
The occurrence and fate data of pharmaceuticals in the environment were described in the article. The main list of pharmaceuticals groups identified in surface and sewage waters was shown according to studies of laboratories in the U.S. and Europe. The main approaches for reduction of pharmaceuticals releasing into environment and monitoring of surface water were considered.
40
Babashova, Nazrin. "Detection of NORM contamination in LNG systems". Thesis, Linnéuniversitetet, Institutionen för byggd miljö och energiteknik (BET), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-95953.
Testo completoAbstract (sommario):
Naturally occurring radioactive material (NORM), which is present in the oil and gas industry, can pose a risk to the workers engaged in the activities in this field. Nevertheless, to our knowledge, there is no study on NORM presence and NORM measurement in liquefied natural gas (LNG) fuel systems and installations. Therefore, the question on whether NORM, particularly radon and radon progeny, can pose a risk to the health of employees, is still open. This study provides the initial base for further investigation and real NORM measurement. In this study, all stages of radon and radon decay products movement and deposition starting from natural gas production till the final destination are analyzed and reviewed. Several techniques for NORM detection and measurement are proposed. In the case if radon levels exceed the reference level, several actions towards radon reduction are proposed.
41
Luo, Yongshou. "Optimal monitoring and remediation of groundwater contamination". Case Western Reserve University School of Graduate Studies / OhioLINK, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=case1056479934.
Testo completo
42
Morehead, Donald. "Spatiotemporal Patterns of Contamination in Surface Water". University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1572879201471779.
Testo completo
43
Halstead, John Michael. "Managing ground water contamination from agricultural nitrates". Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54787.
Testo completoAbstract (sommario):
Ground water contamination from agricultural nitrates poses potential adverse health effects to a large segment of the rural population of the United States. Contamination is especially prevalent in livestock intensive areas, which produce large quantities of animal waste with substantial nitrogen content.
In this study, potential management strategies for reducing nitrate contamination of ground water from agricultural sources were examined using an economic-physical model of a representative dairy farm in Rockingham County, Virginia. A mixed integer programming model with stochastic constraints on nitrate loading to ground water and silage production was used to simulate the impacts of various nitrate loading reduction strategies on estimated farm level net returns over variable costs. A survey of all dairy operations in the county was conducted to assist in specifying the mathematical programming model, identify current nutrient management and quality issues, and gauge farmers’ attitudes toward ground water quality and agricultural chemical use.
Results of the model indicate that substantial reductions in current nitrate loadings are possible with relatively minor impacts on farmers’ net returns through the use of currently practiced approaches of cost sharing for manure storage facility construction and nutrient management planning. Greater loading reductions are achievable through presently untried policies of land use restrictions, bans on purchase of commercial fertilizer, and imposition of standards on loadings to ground water. These reductions are achieved, however, at higher costs in terms of reduced net returns.
Study results indicate that a wide range of policy options exist for reducing nitrate loading to ground water; these reductions, while varying in cost, do not appear to come at the expense of eliminating the economic viability of the county dairy sector. Model results indicate that reductions in nitrate loading of 40 to 70 percent (on average) could be achieved with reductions in farmers’ net returns of one to 19 percent, respectively, when cost sharing for manure storage construction was provided. Explicit consideration was given to the annual variability in nitrate loading due to weather and other factors. The result was higher policy costs than when average loadings alone were considered.Ph. D.
44
Borde, Yannick. "Gestion de la contamination en microélectronique avancée". Grenoble INPG, 2008. http://www.theses.fr/2008INPG0150.
Testo completoAbstract (sommario):
La performance globale d’un site de production peut directement dépendre de sa stratégie de prise en compte de la contamination et sa croissance et pérennité sont liées à sa capacité à faire face à de nouveaux contaminants. Les règles de lutte contre la contamination doivent autoriser une introduction rapide des technologies potentiellement perturbatrices tout en gardant des coûts associés le plus faible possible. Cette thèse apporte une meilleure compréhension du thème contamination en explorant des sujets pointus avec une approche scientifique novatrice par rapport à l’état de l’art en micro et nano électronique : étude de la dangerosité des éléments métalliques vis-à-vis du silicium et de l’oxyde de silicium, transfert de contaminants par contact physique ou par voie gazeuse. . . Elle se concrétise par la mise en place de règles de fonctionnement en égard à la contamination, cohérentes et fondées sur de réelles bases scientifiquesThe performance, the growth and the efficiency of a production line are related to its capacity to in the face of new contaminants. The contamination protocol must allow the introduction of potentially disturbing technologies while keeping the associated running costs as low as possible. Ln this thesis we provide a better understanding of contamination by taking the whole cycle into account and by investigating specific subjects with an innovative scientific approach which is applied to a to state of the art of micro and nano-electronics production line: seriousness study of metallic elements towards silicon and silicon oxide, transfer of contaminants via contact by solid objects or via gaseous phase. . . From the results contained in this thesis, the implementation of working rules have been established which are dedicated to the control of the contamination. These rules are consistent and founded from a sound scientific basis
45
Gelin, Martin, e Skogsberg Rikard Fridsén. "Water Contamination Detection With Artificial Neural Networks". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-295605.
Testo completoAbstract (sommario):
Drinking water is one of our most important re- sources, so the ability to reliably monitor harmful contaminations in our water distribution network is vital. In order to minimize false alarms for water monitoring, while keeping a high sensitivity, a machine learning approach was evaluated in this project. Measurement data captured with a new kind of sensor, an electronic tongue, was provided by Linköping university. The solution was an artificial neural network, in the structure of an Autoencoder, which could learn the dynamic behaviour of natural deviations and with a false alarm rate of approximately one false alarm per week. This was done by evaluating the data and assembling an input structure to account for daily cyclic phenomena, which then was used to train the neural network. The solution could detect anomalies as small as 1.5% by comparing the input with the reconstructed vector, and raise an alarm. In conclusion, an Autoencoder is a viable method for detecting anomalies in water quality.Drickvatten är en av våra mest värdefulla tillgångar, det är därför mycket viktigt att det finns sätt att pålitligt övervaka om dricksvattennätet blivit förorenat. För att kunna minimera antalet falsklarm och samtidigt ha hög känslighet mot dessa föroreningar undersöktes och implementerades en lösning med maskininlärningsalgoritmer. Mätdata tillhandahölls av Linköpings universitet och kom från en ny sensor kallad elektronisk tunga. Lösningen var ett artificiellt neuralt nätverk i form av en Autoencoder, som kunde lära sig det dynamiska beteende som ofarliga avvikelser utgjorde. Detta gav en lösning som i medel gav ett falsklarm per sju dagar. Detta gjordes genom att utvärdera rådata och konstruera en struktur på indata som tar hänsyn till dygnsbunda naturliga fenomen. Denna struktur användes sedan för att träna det neurala nätverket. Lösningen kunde upptäcka fel ner till 1.5% genom att jämföra indata med den rekonstruerade vektorn, och på så sätt ge ett alarm.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
46
Silva, Vera Alexandra Félix Graça. "Contamination by wildfires runoff: effects of biofiltration". Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/9858.
Testo completoAbstract (sommario):
Mestrado em Biologia Aplicada - Ecologia, Biodiversidade e Gestão de EcossistemasTodos os anos, vastas áreas da região Mediterrânea são devastadas por incêndios florestais. Estes podem causar sérios impactos nos ecossistemas, existindo um interesse crescente sobre os seus efeitos na qualidade da água e no biota aquático. A partir de extratos aquosos de cinzas, que se assumiu simularem escorrências de uma área ardida, determinaram-se analiticamente vários metais e dezasseis hidrocarbonetos aromáticos policíclicos (HAPs). Paralelamente, foi realizada uma avaliação ecotoxicológica desses extratos aquosos de cinzas com quatro espécies standard, representando diferentes grupos funcionais e níveis tróficos. Os extratos aquosos de cinzas induziram uma redução no crescimento dos produtores primários Pseudokirchneriella subcapitata e Lemna minor, e inibiram a luminescência da bactéria Vibrio fischeri, enquanto não se verificou uma imobilização significativa em ensaios com o cladócero zooplanctónico Daphnia magna. Estes resultados são concordantes com a inconsistência que se verifica existir na literatura relativamente aos efeitos deletérios dos incêndios no ecossistema aquático. Esta avaliação ecotoxicológica permitiu construir uma base de análise comparativa com vista a responder à questão essencial que motivou este estudo: a presença do bivalve invasor Corbicula fluminea nos sistemas afetados poderá apoiar a mitigação dos potenciais efeitos dos incêndios florestais nas comunidades aquáticas? Neste contexto, o potencial biofiltrador desta espécie foi testado ao longo de sete dias, utilizando como modelo experimental os extratos aquosos de cinzas simulando escorrências de incêndios. Ao longo da experiência verificou-se a diminuição de metais (redução acima dos 70% para o Mn e Zn) e PAHs (redução de 50% nos valores de naftaleno na água e a bioconcentração de alguns elementos nos tecidos moles (especialmente Cu e Zn) e conchas das amêijoas (especialmente Mn). Paralelamente foi efetuada a avaliação ecotoxicológica dos extratos aquosos após a biofiltração, utilizando a mesma bateria de organismos acima descrita, e de um modo geral, observou-se uma diminuição da toxicidade dos extratos. Aquando da exposição aos extractos aquosos filtrados observou-se uma menor inibição do crescimento dos produtores primários (estatisticamente significativa na taxa de crescimento e no incremento total da biomassa de L. minor) bem como uma menor inibição da luminescência of V. fischeri (ou mesmo estimulação da luminescência em várias das concentrações testadas) e não se registaram efeitos tóxicos em D. magna. Estes resultados sugerem que os efeitos ecológicos nefastos da presença da espécie invasora C. fluminea podem, em cenários particulares, ser compensados em alguma medida por serviços adicionais que a espécie poderá prestar ao ecossistema.
Every year, large areas of the Mediterranean region are devastated by wildfires. Wildfires can cause serious impacts on terrestrial ecosystems but there is also a growing concern about their effects on surface water quality and on the aquatic biota. Aqueous extracts of ashes (AEA) were used in this study as an alternative for the runoff from a burnt area. Various metals and sixteen polycyclic aromatic hydrocarbons (PAHs) were analytically determined in the extracts. Their ecotoxicological assessment followed with four standard species representing different functional groups and trophic levels. The aqueous extracts of ashes induced a reduction in the growth of the primary producers Pseudokirchneriella subcapitata and Lemna minor, and inhibited the luminescence of the bacteria Vibrio fischeri but did not produce a significant immobilization in the cladoceran zooplankter Daphnia magna. These results reflected the inconsistency found in the literature on the deleterious effects of wildfires on aquatic ecosystems. This assessment comprised the first step of this study, which had, as overarching research question, whether the invasive bivalve Corbicula fluminea could mitigate the potential effects of wildfires on aquatic species. The biofiltration potential of this species was tested by exposing it to aqueous extract of ashes during a 7-day period, and by using the filtered solution in a second battery of ecotoxicological tests. Throughout the experiment there was a reduction of the concentration of the metals (more than 70% for Mn and Zn) and PAHs (a loss of 50% in naphthalene in the aqueous extract and, at the same time, an increase in the concentration of some contaminants in the clam’s soft tissue (especially Cu and Zn) and shells (especially Mn). Generally, lower toxicity was observed after than before filtration by C. fluminea. When exposed to biofiltered AEA, a smaller inhibition on the growth of the primary producers was observed (statistical significant in both growth rate and yield of L. minor) as well as a much lower luminescence inhibition of V. fischeri (or even luminescence stimulation of several tested concentrations) and non toxic effects were reported in D. magna. Thus, the negative ecological effects resulting from the presence of the invasive species C. fluminea can eventually be somewhat compensated by additional services provided to the ecosystem.
47
Amaral, Maria José Aires do. "Lacertid lizards as bioindicators of agricultural contamination". Doctoral thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/8395.
Testo completoAbstract (sommario):
Doutoramento em Biologia - Ecotoxicologia e Biologia AmbientalApesar do recente aumento no número de estudos, os lagartos persistem como um dos grupos menos estudados em ecotoxicologia e o desconhecimento em relação à sua resposta à contaminação ambiental é enorme. A nível europeu, os lacertídeos têm sido identificados como potenciais espécies modelo para a ecotoxicologia com répteis. O principal objectivo deste projecto era determinar se um lacertídeo abundante pertencente ao género Podarcis, podia ser utilizado como bioindicador de exposição e toxicidade em zonas agrícolas. Para atingir este objectivo, utilizámos uma estratégia integrada com três fases. Numa primeira fase realizou-se um estudo de campo para documentar o tipo de exposição e parâmetros populacionais de populações de lacertídeos que ocorrem em zonas de uso intenso de pesticidas e zonas de agricultura orgânica. A segunda fase consistiu num estudo de mesocosmo em que se expuseram juvenis a um conjunto de pesticidas em condições controladas durante um período de um ano. Finalmente, a terceira fase incluiu um estudo laboratorial sobre os efeitos do clorpirifos, um dos insecticidas mais utilizado a nível global, em lagartixas. No término de cada um dos estudos, analisaram-se diversos biomarcadores e parâmetros de exposição e toxicidade a pesticidas nos diferentes indivíduos. Este conjunto abrangente de parâmetros foi analisado em diferentes níveis de organização biológica, incluindo parâmetros populacionais, bem como comportamentais, fisiológicos, bioquímicos e histológicos. Em geral, detectaram-se poucas diferenças estatísticas significativas entre as populações dos campos expostos a pesticidas e populações referência. Confirmando a dificuldade que existe em isolar os efeitos de diferentes contaminantes sobre as populações de outros factores locais, ciclos sazonais ou eventos estocásticos. As populações de P. bocagei parecem ser capazes de lidar com o nível observado de exposição a pesticidas. No entanto, indivíduos que vivem em locais expostos a pesticidas parecem estar menos adaptados ecologicamente do que aqueles que vivem em locais referência, apresentando um estado de depleção nutricional e sinais de stress metabólico. Os resultados obtidos com os animais da experiência de mesocosmo parecem reforçar estes resultados. Os animais prosperaram relativamente bem em todos os mesocosmos, independentemente do tratamento ou não com pesticidas, apresentando uma ampla gama de comportamentos naturais. A abordagem laboratorial confirmou P. bocagei como um valioso indicador de exposição sub-letal a doses ambientalmente realistas de clorpirifos. De acordo, com o conjunto d resultados obtidos, P. bocagei parece ser um bioindicador adequado de exposição a pesticidas.
Lizards are among the least studied groups in ecotoxicology and despite a recent increase in the number of studies, there is still a lack of knowledge regarding their response to environmental contamination. In Europe, lacertid lizards have been identified as potential model species for reptile ecotoxicology. The main question of this project was to assess if a highly abundant lacertid lizard belonging to the genus Podarcis, could be used as a bioindicator of pesticide exposure and toxicity in agricultural areas. To achieve this end, we used a three-stage tiered approach. The first tier took the form of a field survey to document the nature of the exposure and the population parameters of lacertids occurring in areas of intensive pesticide usage as well as areas of negligible pesticide usage. The second tier consisted of a mesocosm study in which naïve lizards were exposed to pesticides in a controlled experiment. Finally, the third tier included a laboratory approach to the effects of one of the most common insecticides used worldwide, chlorpyrifos. We assessed pesticide impact in individuals from the different tiers using a comprehensive set of biomarkers applied at different levels of biological organization, including population parameters as well as behavioral, physiological, biochemical and histological biomarkers. We detected few statistically significant differences between reference and exposed populations in the field study. Confirming the difficulty to isolate the effects of contaminants on natural populations where other local factors, natural cycles or stochastic events occur. P. bocagei populations seem to be able to compensate with the observed level of pesticide exposure. Nevertheless, individuals living in exposed sites seem to be less ecologically fit than those living in reference sites, presenting a depleted nutritional status and signs of metabolic stress. The results from the mesocosm setting reinforce these results. Lizards prospered relatively well in all enclosures, treated or not with pesticides, presenting a broad range of natural behaviors. The laboratory approach confirmed P. bocagei as valuable indicator of sub-lethal exposure to environmental realistic doses of chlorpyrifos. According to our results, P. bocagei seems to be a suitable bioindicator of pesticide exposure.
48
Nobliá, Matilda, e Christian Ryan. "Contamination Event Detection in Water Distribution Systems". Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214698.
Testo completoAbstract (sommario):
In any society, making sure that its citizens havea clean water supply is a fundamental issue. By modernizingthe way water distribution systems (WDSs) are monitored andcontrolled, the impact of contamination can be maintained andminimized. By using sensors that monitor relevant physicalparameters, a system that detects contamination and limitspopulation exposure can be designed. To achieve this, the workpresented in this report is focused on three main topics.Firstly, parameters for determining water quality are examined.This is the basis for choosing relevant sensors. Secondly,a study of contamination event detection (CED) is presented, inparticular a method to determine whether water is contaminatedor not based on sensor measurements is proposed. This iscompleted through the use of binary hypothesis testing as wellas examining existing sensors. Thirdly, the problem of optimalsensor placement in a WDS is studied. In extension, a greedyalgorithm is implemented to optimally place sensors in a modelof real-world network.
49
Kachapulula, Paul W., e Paul W. Kachapulula. "Aflatoxin-Producing Fungi and Contamination in Zambia". Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625642.
Testo completoAbstract (sommario):
Aflatoxins are cancer-causing, immuno-suppressive mycotoxins that frequently contaminate important staples in Zambia including maize and groundnut. Managing aflatoxins begins with understanding the distribution of aflatoxins across the target region. Seventeen percent of crops from markets contained aflatoxin concentrations above allowable levels in Zambia, with the frequency of contamination in groundnut and maize highest in warmest regions of the country.
Proper management of aflatoxin contamination requires a clear understanding of the etiologic agents of the observed contamination. Several species within Aspergillus section Flavi have been implicated as causal agents of aflatoxin contamination in Africa. In Zambia, A. parasiticus was the main etiologic agent of aflatoxin contamination of maize and groundnut, although fungi with S morphology also caused contamination. Aspergillus flavus L morphotype fungi were associated with reduced aflatoxins, suggesting natural biological control by atoxigenic strains may reduce aflatoxin contamination in Zambia.
In addition to maize and groundnut, wild insects, fruits and fish are important sources of food and incomes in Zambia. Unfortunately, both insects and wild plants are susceptible to aflatoxin contamination. To evaluate the safety of wild insects and fruit, concentrations of aflatoxins and presence of aflatoxin-producers were assessed. Some species of wild fruits and insects were found to have unsafe levels of aflatoxins suggesting mitigation efforts should target these important foods of Zambia in addition to crops such as groundnut and maize.
New lineages of aflatoxin-producing fungi have been described, and found associated with cases of aflatoxicoses in Kenya and elsewhere. Although A. parasiticus is highly frequent and an important etiologic agent of aflatoxin contamination, it is not known how this fungus is related to similar fungi elsewhere. A multigene phylogenetic analysis revealed at least two new groups divergent from known fungal species whose frequencies need to be modified if aflatoxin contamination of crops is to be reduced.
50
Probst, Claudia. "Fungi Associated with Aflatoxin Contamination in Africa". Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/201499.
Testo completoAbstract (sommario):
Aflatoxins are secondary metabolites produced by members of the fungal genus Aspergillus. Immunosuppressive and carcinogenic activities of these toxins negatively impact human health especially in developing countries. Severity of contamination is influenced by both fungal community structure and the environment to which the crop is exposed either prior to or after harvest. In 2004, a severe episode of lethal human aflatoxicosis occurred in the Eastern Province of Kenya. Analysis of fungal community structure revealed that this event was caused by a previously unknown fungal lineage closely resembling the S strain morphotype of Aspergillus flavus. Fungal communities associated with maize produced in affected regions of Kenya were invariably dominated by the new fungal lineage and its incidence was strongly correlated with maize aflatoxin content. Analyses of fungal communities of maize grown in adjacent Kenyan provinces showed that incidences of the new lineage are limited outside the Eastern Province where the aflatoxicoses outbreaks occurred. Multi-locus phylogenetic analyses suggest the newly identified Kenyan lineage is closely related to the B and G aflatoxin producing species A. minisclerotigenes, and more distantly related to both the A. flavus S strain and an unnamed taxon with similar morphology endemic in West Africa (strain SBG). Sequence analyses of the cypA aflatoxin biosynthesis gene identified a previously unknown 2.2 kb deletion unique to the Kenyan lineage and coherent with its phylogenetic placement. A polyphasic approach was used to study aflatoxin-producing fungal communities, with emphasis on occurrence of fungi with S strain morphology, in Sub-Saharan Africa. Four phylogenetically distinct groups of fungi with S strain morphology were identified with restrictions to West Africa (strain SBG) or Central and East Africa (A. flavus S strain, A. minisclerotigenes, the new lineage). Aflatoxin production in synthetic media was a poor predictor of aflatoxin production in viable maize grain. An in vitro assay was developed to predict the aflatoxin-producing potential of fungal isolates in maize. This screen was used to identify atoxigenic isolates of A. flavus with potential value for biological control within highly toxic Aspergillus communities associated with maize production in Kenya. These atoxigenic isolates have potential value for mitigating aflatoxin contamination in Kenya.