• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 40
  • 19
  • 18
  • 8
  • 4
  • 4
  • 2
  • 2
  • 1
  • Tagged with
  • 127
  • 68
  • 52
  • 36
  • 35
  • 34
  • 27
  • 25
  • 25
  • 18
  • 18
  • 17
  • 13
  • 12
  • 12
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Influência da estrutura da vegetação de áreas recuperadas pós-mineração em comunidades de aves no sul do Brasil / Communities of birds and influence of the structure of the vegetation in reclaimed areas after mining in the south of Brazil

Becker, Rafael Gustavo 27 February 2009 (has links)
Made available in DSpace on 2015-03-05T16:19:37Z (GMT). No. of bitstreams: 0 Previous issue date: 27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Atividades de mineração causam alterações nas paisagens, acarretando mudanças na vegetação e nas propriedades e topografia do solo que acabam por afetar a fauna. Para minimizar os efeitos da mineração, empresas mineradoras freqüentemente implementam procedimentos de recuperação ambiental exigidos por lei. O presente estudo aborda o efeito e a influência da estrutura da vegetação nas comunidades de aves em áreas recuperadas após processos de mineração em florestas no município de São Mateus do Sul, sudeste do Estado do Paraná e em áreas de campo em Candiota no Rio Grande do Sul No Paraná selecionei quatro áreas para as amostragens: três delas, com 5, 10 e 20 anos de recuperação vegetal (A05, A10 e A20, respectivamente) encontram-se na Unidade da Petrobrás (Superintendência de Industrialização de Xisto) e a quarta área de estudo é um fragmento florestal que não sofreu interferências de mineração (A50). Em Candiota selecionei três áreas com vegetação nativas nunca antes mineradas e três áreas recuperadas. Nos do / Mining activities cause severe alterations in natural landscapes, changing the vegetation and the properties and topography of the soil, and thus altering habitats and the associated fauna. To minimize the effects of mining, mining companies implement procedures of environmental recuperation demanded by law. The present study investigates the influence of vegetation structure on bird communities in reclaimed areas after mining in forest and grassland habitats in south Brazil. Forested areas were studied in the State of Paraná, while grasslands were studied in the Pampa biome in Rio Grande do Sul. In Paraná I sampled four areas, three of them (with 5, 10 and 20 years of vegetation recuperation named, respectively, A05, A10, and A20), were located in the Unit of Petrobrás, and the fourth was a forest fragment that did not suffer mining interferences (A50). In Rio Grande do Sul I selected six areas, three with native vegetation never mined before and three reclaimed areas. I sampled the avifauna using the point
22

Growth and Water Relations of Mountain Big Sagebrush on Reclaimed Mine Soils in Southwestern Wyoming

Carpenter, Alan T. 01 May 1985 (has links)
Mined-land reclamation practices in shrub-steppe ecosystems can be augmented by planting seedlings of locally dominant shrubs, e.g., mountain big sagebrush. Dispersion pattern could affect sagebrush performance by influencing amounts of windborne snow, soil and litter which accumulate around shrubs and by influencing water withdrawal by roots. Mountain big sagebrush seedlings were planted in plots on a reclaimed coal strip mine in two dispersion patterns: singly and in clumps of four at the same overall density. Performance of mountain big sagebrush was monitored during two growing seasons. Measures included plant survival, end-of-growing season aboveground biomass, leaf water potential components, soil water potential, twig and ephemeral leaf survival and reproductive allocation. Most measures of performance were similar for single and clumped plants. However, single plants had a greater twig elongation rate than clumped plants, and roots of plants in clumps removed less soil water to 50 cm than roots of single plants. In order for shrub dispersion pattern to affect plant performance via differential snow, soil or litter accumulation, the plants would have to respond to the added resources, probably water and nitrogen. An experiment was conducted to test if a small extra increment of water and nitrogen would affect mountain big sagebrush plants. The same plant performance indices listed above were monitored. The added water and nitrogen, either alone or in combination, had no effect except on reproduction. In 1983, there was a significant water* fertilizer interaction observed for some of the reproductive metrics, while in 1984 there was a significant water effect. While a significant main effect of nitrogen was expected under the prevailing wet conditions, the large reservoir of soil nitrogen evidently provided sufficient nitrogen. Reproduction was more sensitive to added water and nitrogen resources than was vegetative growth. The nearly equal performance of mountain big sagebrush in the two dispersion patterns may have resulted from several factors. Water availability to the experimental shrubs was very high throughout the study due to abnormally heavy precipitation and to removal of weeds from the plots. During drier years, dispersion pattern may have greater influence on the shrubs.
23

Enhancing Virus Surveillance through Metagenomics: Water Quality and Public Health Applications

Rosario-Cora, Karyna 28 October 2010 (has links)
Monitoring viruses circulating in the human population and the environment is critical for protecting public and ecosystem health. The goal of this dissertation was to incorporate a viral metagenomic approach into virus surveillance efforts (both clinical and water quality control programs) to enhance traditional virus detection methods. Clinical surveillance programs are designed to identify and monitor etiological agents that cause disease. However, the ability to identify viruses may be compromised when novel or unsuspected viruses are causing infection since traditional virus detection methods target specific known pathogens. Here we describe the successful application of viral metagenomics in a clinical setting using samples from symptomatic patients collected through the Enterovirus Surveillance (EVS) program in the Netherlands (Appendix A). Despite extensive PCR-based testing, the viruses in a small percentage of these samples (n = 7) remained unidentified for more than 10 years after collection. Viral metagenomics allowed the identification of viruses in all seven samples within a week using minimal sequencing, thus rapidly filling the diagnostic gap. The unexplained samples contained BK polyomavirus, Herpes simplex virus, Newcastle disease virus and the recently discovered Saffold viruses (SAFV) which dominated the unexplained samples (n = 4). This study demonstrated that metagenomic analyses can be added as a routine tool to investigate unidentified viruses in clinical samples in a public-health setting. In addition, metagenomic data gathered for SAFV was used to complete four genotype 3 SAFV (SAFV-3) genomes through primer walking, doubling the number of SAFV-3 full genomic sequences in public databases. In addition to monitoring viruses in symptomatic patients, it is also important to monitor viruses in wastewater (raw and treated) to protect the environment from biological contamination and prevent further spread of pathogens. To gain a comprehensive understanding of viruses that endure wastewater treatment, viral metagenomics was used to survey the total DNA and RNA viral community in reclaimed water (the reusable end-product of wastewater treatment) (Appendix B). Phages (viruses that infect bacteria) dominated the DNA viral community while eukaryotic viruses similar to known plant and insect viruses dominated RNA metagenomic libraries suggesting that highly stable viruses may be disseminated through this alternative water supply. A plant virus, the Pepper mild mottle virus (PMMoV), was identified as a potential indicator of wastewater contamination based on metagenomic data and quantitative PCR assays (Appendix C). The metagenomic analysis also revealed a wealth of novel single-stranded DNA (ssDNA) viruses in reclaimed water. Further investigation of sequences with low-level similarities to known ssDNA viruses led to the completion of ten novel ssDNA genomes from reclaimed water and marine environments (Appendix D). Unique genome architectures and phylogenetic analysis suggest that these ssDNA viruses belong to new viral genera and/or families. To further explore the ecology of the novel ssDNA viruses, a strategy was developed to take metagenomic analysis to the next level by combining expression analysis and immunotechnology (Appendix E). This dissertation made a significant contribution to current microbiological data regarding wastewater by uncovering viruses that endure the wastewater treatment and identifying a new viral bioindicator.
24

Water impacts on thermoelectric power generation

Stillwell, Ashlynn Suzanne 06 November 2013 (has links)
The energy-water nexus represents a complex system of correlated resources, with particular relevance to thermoelectric power plants. Since thermoelectric power plants typically depend on water for cooling, these facilities are prone to water-related challenges. At the same time, large water withdrawals for power plants can adversely impact other water users in a watershed. This work aims to evaluate water impacts on Texas power plant operations and the associated effects these power plants have on water availability. An evaluation of the water impacts on power generation in Texas was completed through four analyses: 1) water availability effects of changing cooling technologies, 2) economic value of drought resiliency through use of alternative cooling technologies, 3) dynamic impacts of reservoir storage on power generation operations, and 4) potential for reclaimed water as a cooling source. Based on the results of these analyses, the following general conclusions were drawn [bulleted list]: [bullet] Use of alternative cooling technologies decreases water withdrawals at the expense of additional energy and water consumption. However, the reduced withdrawals for power plants leaves more water in the stream for other water users, including instream flows. [bullet] Alternative cooling technologies incur additional capital costs, but gain value from reduced water withdrawals. The lower withdrawal requirements make such facilities more resilient to drought, which can have economic value from additional generation during possible drought-related curtailment or suspension. [bullet] Changing surface water reservoir storage at power plants has dynamic impacts on power generation operations, as well as other users in a river basin. Generally, decreasing power plant reservoir storage benefits other users in the basin. Instances arise where both beneficial and detrimental impacts are also observed. [bullet] Reclaimed water can be a technologically and economically feasible cooling source for many existing power plants. The future suitability of using reclaimed water for power plant cooling depends on water pipeline construction costs, reclaimed water flow, and water stress [end of bulleted list]. These general conclusions, along with further details, provide insight into the relationship between water resources and thermoelectric power plants. As resources become increasingly strained, understanding and responding to tradeoffs within the energy-water nexus, through such analyses, might become imperative for sustainable resource management. / text
25

Decentralized Urban Wastewater Reuse in China : - with Focus on Grey Water

Zhong, Ling January 2013 (has links)
Grey water reuse has attracted more and more attention among researchers and professionals in recent years. As most of the Chinese cities are undergoing the process of fast urbanization and economic development, many water-related problems have occurred and urban water resources management has become a strategic issue. The urge to reconsider the conventional ways of utilizing water and discharging the wastewater in cities is calling. As a relatively simple and flexible way, decentralized grey water reuse system can help to make the first step in achieving a sustainable urban water management. However, whether it is feasible in China is still a question. This paper aims at looking for the answer based on a survey and interviews with professionals in the fields from different Chinese cities. The result shows “reuse” as one of the solutions of solving water shortage and achieving sustainable water management is not as simple as one may think. In general, decentralized urban grey water / wastewater reuse is not easy to flourish in China in the near future though most of the respondents hold a positive attitude about reuse itself. To explain this difference between attitude and actual planning we need more historical, political and social-economic understanding with a touch of “Chinese characteristics”.
26

Detection Of Helminth Eggs And Protozoan Cysts In Wastewaters

Davutluoglu, Ayten 01 January 2005 (has links) (PDF)
The withdrawal of water sources concluded the reuse of treated wastewaters, especially for non-potable purposes. Agricultural use of the reclaimed wastewaters is one of the reuse options. However health considerations of the reuse of reclaimed wastewaters for public related purposes are underestimated, since wastewaters contain a variety of microbial pathogens, which may be transmitted to workers and consumers through the crops irrigated. Of these, parasitic eggs have a special place, as they are capable of surviving in the soil for months or even years, depending on environmental conditions. There is insufficient accumulated information on the health related criteria for the reuse of treated wastewaters in Turkey. The aim of this study was therefore to determine the helminthic eggs in raw sewage and in effluents of ASKi municipal wastewater treatment plant in Ankara. The study involved examining to decide whether these organisms exist in the wastewaters at all, and if so in what concentrations. Modified Bailenger&rsquo / s method, which published in the &ldquo / WHO Laboratory Manual of Parasitological and Bacteriological Techniques&rdquo / and &ldquo / U.S.EPA ICR Microbial Laboratory Manual&rdquo / were used in developing the specific methods used in this study.
27

Evaluation of cracking potential of superpave mixtures with high reclaimed asphalt pavement content

Ahmed, Ananna January 1900 (has links)
Master of Science / Civil Engineering / Mustaque A. Hossain / Approximately 89% of 11,000 miles of Kansas roads are surfaced with asphalt. Hundreds of thousands of tons of reclaimed asphalt pavement (RAP) are produced annually in the United States, including in Kansas. This bulk volume of RAP must be economically managed in order to achieve environmental friendliness. Recycling of RAP conserves natural resources and reduces landfill usage. However, many agencies have reported that increased RAP content produces drier hot-mix asphalt (HMA) mixtures than virgin mixtures that are susceptible to premature cracking. In this research, laboratory-produced Superpave HMA mixtures containing increased percentages (20, 30, and 40%) of RAP materials from three RAP sources (Shilling Construction Co., Konza Co., and the Kansas Department of Transportation’s project, US 73) were studied for cracking performance. Mix designs were produced using Superpave design criteria for 12.5-mm nominal maximum aggregate size mixture. The static and repetitive Semicircular Bending (SCB) test, the Texas Overlay Tester test, the dynamic modulus test, and Viscoelastic Continuum Damage (VECD) tests were performed on laboratory-prepared samples. In general, cracking performance decreased with increased RAP content. The RAP from the US 73 project performed most consistently compared to other two sources of RAPs. Test results were analyzed using two-way Analysis of Variance (ANOVA), proving that mixtures containing 4.5% to 4.9% binder performed the best against cracking. The RAP source was found to have more effect on cracking propensity than RAP content. Mixtures with RAP content up to 40% performed satisfactorily. Tukey’s pairwise comparison method was used to compare results from all tests; VECD was determined to be the most appropriate test to evaluate cracking propensity of HMA mixtures.
28

Métodos clássicos e moleculares para avaliação da qualidade virológica de lodo de esgoto e de água de reúso: determinação da eficiência e limites de detecção. / Standard and molecular methods for surveillance of human enteric viruses in sludge and reclaimed water: efficiency and detections limits.

Luana de Cássia Umeda 20 August 2012 (has links)
Os vírus entéricos humanos são encontrados no esgoto e em subprodutos dos processos de tratamento. Recentemente vem sendo recomendados como indicadores de qualidade microbiológica em normas da legislação brasileira e também nas de outros países, mas ainda com parâmetros a definir. O objetivo do estudo é a avaliação e a comparação entre métodos clássicos e moleculares aplicados à detecção de vírus entéricos em amostras de água de reúso e de lodo, visando subsidiar a legislação brasileira. Ensaios de semeadura experimental de protótipos de rotavírus e de adenovírus foram realizados nas matrizes ambientais e os vírus detectados por métodos clássicos (cultivo celular e reação de imunoperoxidase) e moleculares (PCR/nested-PCR, RT-PCR e ICC-PCR), determinando-se os limites de detecção de cada método para cada matriz. A pesquisa de rotavírus e adenovírus presentes naturalmente em 25 amostras de água de reúso e em 25 de lodo possibilitou a comparação dos métodos propostos. O ICC-PCR mostrou ser o método mais factível a ser aplicado na área de saneamento. / Human enteric viruses are common contaminants of raw sewage and subproducts of sewage treatment processes. In recent years, those viruses were recommend as new microbiological indicators in different matrices in Brazilian legislation and others countries, although some questions should be elucidated. At present, the aim was to evaluate and compare the efficiencies of standard and molecular virological methods for detection of human enteric viruses in sludge and reclaimed water samples. Rotavirus and adenovirus were experimentally spiked in the proposed matrices and virus recovery and detection limits established for each method and matrice. Viruses naturally presented in 25 samples of sludge and 25 samples of reclaimed water were assayed by all methods and results evaluated and compared for statistical significance. From all methods evaluated, ICC-PCR showed to be the most suitable for virus surveillance in sludge and reclaimed water.
29

Devulcanization of model compounds by a variety of diphenyldisulfides

Boyce, Annemè January 2017 (has links)
Improvements to the properties of recycled rubber, by developing a more selective breakdown process, is an important issue and a global challenge. Devulcanization is the most promising way to achieve this. It is a process which aims to totally or partially cleave monosulfidic (C-S-C), disulfidic (C-S-S-C) and polysulfidic (C-Sx-C) crosslinks of vulcanized rubber. In this study, the devulcanization of sulfur-vulcanized natural rubber with a variety of diphenyldisulfides has been studied using 2,3-dimethyl-2-butene and squalene as model compounds, vulcanized by sulfur and 2-bisbenzothiazole-2,2’-disulfide. 2-aminodiphenyldisulfide; 4-amino-diphenyldisulfide; bis(2-benzamido-)diphenyldisulfide and 2,2’-bithiosalicylic acid were used as aromatic disulfides devulcanization agents. Thermal analysis was used to investigate interactions between various combinations of curatives in the vulcanization systems in the absence of model compounds. Thermogravimetric analysis was used to detect mass changes during vulcanization and whether the samples decompose/evaporate so as not to contaminate differential scanning calorimetry instrumentation. Differential scanning calorimetry was used to investigate reactions occurring between curatives. Comparison of reversing and non-reversing signals in modulated experiments are suggestive of reactions between devulcanization agents and sulfur, and accelerators Vulcanization of the model compounds were performed in 10m evacuated sealed glass ampoules placed in an oil bath at 160 °C and agitated for the duration of vulcanization. After 60 min the ampoules were removed and quenched. These were then devulcanized by exposure to a devulcanization agent in a sealed ampoule at 180 for 60 min. Crosslinked 2,3-dimethyl-2-butene species were isolated and analysed by reversed phase high performance liquid chromatography. Particular attention was paid to changes in the number of sulfur atoms in the crosslinks. Results indicate that of the devulcanization agents tested 4-amino-diphenyldisulfide was the most effective. No detrimental effect on devulcanization efficiency was caused by the substitution of a basic amino group with an acidic carboxylic acid group Gel permeation chromatography was performed on devulcanized squalene crosslinks using a tetrahydrofuran eluent. GPC investigations with squalene were less effective than HPLC experiments with 2,3-dimethyl-2-butene at evaluating the relative efficiency of individual devulcanization agents. Results were, however, consistent with 4-amino-diphenyldisulfide again being the most efficient devulcanization agent.
30

Structure-Property Relationships to Understand Comprehensive Rejuvenation Mechanisms of Aged Asphalt Binder

January 2020 (has links)
abstract: This research focused on the structure-property relationships of a rejuvenator to understand the comprehensive rejuvenation mechanism of aged asphalt binder. Aged asphalt such as recycled asphalt shingles (RAS) and reclaimed asphalt pavement (RAP) contain various amounts of asphalt binder. However, the asphalt binder in RAS and RAP is severely aged and inferior in properties compared to a virgin binder. To address this issue, liquid additives have been used under the general title of rejuvenators. That poses an additional challenge associated with the lack of clear metrics to differentiate between softeners and rejuvenators. Therefore, there is a need for a thorough study of rejuvenators. In this study, diverse-sourced rejuvenators have been used in RAS and RAP-modified binders as well as laboratory-prepared aged binders. The properties of the rejuvenated aged binder were characterized at a macro-level and molecular level. The study showed that the performance of the RAS-modified binder was significantly improved after bio-modification by a bio-rejuvenator. This study further evaluated laboratory-prepared aged asphalt rejuvenated with different rejuvenators. The results found that oxidized bitumen became soft after adding rejuvenators, regardless of their source. Molecular dynamics simulation showed that the effective rejuvenator restored the molecular conformation and reduced the size of asphaltene nanoaggregates. The study results showed that due to the specific chemical composition of certain rejuvenators, they may negatively impact the durability of the mixture, especially about its resistance to moisture damage and aging. Computational analysis showed that while the restoration capacity of rejuvenators is related to their penetration into and peptizing of asphaltene nanoaggregates, the durability of the restored aged asphalt is mainly related to the polarizability values of the rejuvenator. Rejuvenators with lower polarizability showed better resistance to aging and moisture damage. In summary, this study develops the rheology-based indicators which relate to the molecular level phenomenon in the rejuvenation mechanism. The rheology-based indicators, for instance, crossover modulus and crossover frequency differentiated the rejuvenators from recycling agents. Moreover, the study found that rejuvenation efficiency and durability are depended on the chemistry of rejuvenators. Finally, based on the learning of chemistry, a chemically balanced rejuvenator is synthesized with superior rejuvenation properties. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2020

Page generated in 0.051 seconds