• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 674
  • 400
  • 118
  • 45
  • 39
  • 23
  • 18
  • 12
  • 12
  • 12
  • 12
  • 12
  • 12
  • 11
  • 8
  • Tagged with
  • 1797
  • 1797
  • 461
  • 388
  • 337
  • 241
  • 217
  • 188
  • 175
  • 164
  • 162
  • 152
  • 150
  • 145
  • 144
  • 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.
211

Deposicao de aerossois em acidentes postulados em reatores nucleares

FERNANDES, ALMIR 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:41:00Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:53Z (GMT). No. of bitstreams: 1 04012.pdf: 7834222 bytes, checksum: b31bfdc345cffdd5ddde533b9f81ccae (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
212

Disconnected: Investigating the Social and Political Conditions Shaping Mexico City’s Air Quality Regulatory Environment

January 2018 (has links)
abstract: Mexico City has an ongoing air pollution issue that negatively affects its citizens and surroundings with current structural disconnections preventing the city from improving its overall air quality. Thematic methodological analysis reveals current obstacles and barriers, as well as variables contributing to this persistent problem. A historical background reveals current programs and policies implemented to improve Mexico’s City air quality. Mexico City’s current systems, infrastructure, and policies are inadequate and ineffective. There is a lack of appropriate regulation on other modes of transportation, and the current government system fails to identify how the class disparity in the city and lack of adequate education are contributing to this ongoing problem. Education and adequate public awareness can potentially aid the fight against air pollution in the Metropolitan City. / Dissertation/Thesis / Masters Thesis Justice Studies 2018
213

Deposicao de aerossois em acidentes postulados em reatores nucleares

FERNANDES, ALMIR 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:41:00Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:53Z (GMT). No. of bitstreams: 1 04012.pdf: 7834222 bytes, checksum: b31bfdc345cffdd5ddde533b9f81ccae (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
214

Nuclear based methods of analysis in bioenvironmental studies

Altaf, Waleed J. January 1989 (has links)
The use of neutron and charged particle induced reactions is briefly discussed and the experimental facilities employed in this work are described. The qualitative elemental composition of human lung tissues, taken from individuals deceased from non-lung-related causes, was determined by prompt gamma-ray neutron activation analysis (PGNAA), cyclic neutron activation analysis (CNAA), conventional neutron activation and proton induced X-ray emission analyses. In addition elemental concentrations were determined by CNAA and conventional activation. Concentration values for elements previously not extensively reported in the literature, Ce, Cl, F, Hf and Sc were obtained as well as values for 18 other elements. Fingernail samples were investigated in order to study the uptake of Se and Zn supplementation. The effect of the rate of excretion through fingernails of Se and Zn on the level of Na is described. The variations in the elemental concentrations from finger to finger are shown for Se, Cl, Na and K and the variations from hand to hand, of a control, are shown for Br, Cl, K, Mg, Na, Rb, S, Se and Zn. Concentration values for Br, Ce, S, and Se, for which values available in the literature are very few , are presented. Bone biopsy samples were collected from the iliac crest of subjects, divided into four groups depending on the length of dialysis treatment, aluminium levels in blood and bone pathology in terms of osteoporosis. Fluorine concentration in the samples were determined by CNAA and proton Induced gamma-ray emission (PIGE) in conjunction with Rutherford backscattering (RBS). The relation between the A1 levels in the system and the F concentrations in the bone samples was investigated and the existence of a positive correlation between A1 and F was found. The effect of mass fractionation was tested for small and large sample fractions of Bowen's kale and the detection sensitivities were determined in counts/mg of sample. The concept of the sampling factor in CNAA was established for the comparative determination of elemental concentrations and the representative mass of Bowen's kale required for the determination of Br, Ca, Cl, K, Mg, Na, Rb, S, Se, Sm and V were found. Following the Chernobyl reactor accident, measurements of University of Surrey students returning from Kiev and Minsk were conducted for the neck region and the chest region. The activity of iodine (I-131) in the thyroid and the effective dose equivalent were calculated. The activities in the chest region for Cs-137, Zr-95 and the annihilation radiation were determined using a chest water-phantom. Measurement of radioactive particulates in air filters, collected from air ventilation units in the London area, a month after the radioactive cloud from Chernobyl had passed over the U.K., was carried out and the concentrations of 17 fission products in the atmosphere were calculated.
215

Scots pine needle longevity and other shoot characteristics along pollution gradients

Lamppu, J. (Jukka) 14 December 2002 (has links)
Abstract Branches of adult Scots pine (Pinus sylvestris L.) trees were sampled from boreal dry pine forests to study needle longevity, its variation and its relation to other shoot characteristics. The stands studied were located along transects from two smelters and one city, e.g. along gradients of pollution impact. Constant needle age structures were assumed and static life-tables generated. Mean needle longevity was calculated as the sum of the proportions of living needle fascicles on the successive annual shoots. It fully incorporated the information of the static life-tables and was preferred to median or maximum ages because of its significantly lower variation. The first half of the shedding span, the duration of the period when the needle survival gradually dropped from 90 to 50 %, proved to validly reflect the changes in the needle age structure. Needle longevity decreased 15-40 % towards the pollution sources along the transects studied. Near the smelters, needle longevity decreased with the increasing needle Fe, or Fe, Ni and Cu concentration that represented the main constituents of the airborne particle emissions. Near the city, needle longevity decreased with the increasing needle N and P concentrations, annual needle mass and needle mass packing and decreasing needle area packing. In the urban forests, needle Mg, P and K concentrations decreased linearly with the decreasing needle survival from the second to the fourth needle age class. Concentrations in the living needles of the fourth age class stayed over 80 % of the average for all the age classes, though needle survival dropped below 50 %. A decreasing needle Mn concentration was detected towards all the emission sources. Leaching, especially from the soil, as a possible cause was discussed. Needle longevity had the lowest variation among the shoot characteristics, which increases its value as a tool in ecological monitoring. Low plasticity in needle longevity could be an acclimation to the ambient environmental conditions and length of the growing season and to maximise the carbon gain per time. Needle longevity decreased and annual needle mass and leaf mass per area increased upwards in the crowns of mature Scots pines, reflecting the acclimation to irradiance.
216

Assessing atmospheric composition impacts using a chemical climatology framework : case studies at the UK monitoring supersites

Malley, Christopher Stuart January 2016 (has links)
In the mid-1800s, monitoring networks were established to investigate atmospheric composition impacts, and the conditions giving rise to them. The development of these networks, in terms of coordination and standardisation between contributing sites, has resulted in large advances in knowledge of the nature of atmospheric composition. Currently thousands of sites collect high quality atmospheric composition measurements globally. This thesis contends that in order to maximise the information derived from these measurements, a further advancement in standardisation is required to encompass the interpretation of monitoring network data. Currently there are limited examples of a common interpretation of data applied across all sites in a monitoring network, especially in relation to specific atmospheric composition impacts. In this thesis, a ‘chemical climatology’ framework is outlined which provides a common basis for targeting analysis towards identifying the linkage between a specific atmospheric composition impact and its causal drivers. Case studies apply the chemical climatology framework to demonstrate its utility in deriving scientific and policy relevant conclusions using measurement data from the UK monitoring supersites located at Harwell and Auchencorth. Prior to this, the representativeness of each site is quantified through the application of cluster analysis to ozone data at 100 rural European sites to identify groupings of sites with similar ozone variation. Harwell was representative of rural locations within 120 km of London, while Auchencorth was representative of a larger, transboundary spatial domain including the remainder of the rural UK. The first case study links the impact of ozone on human health (quantified by SOMO10 and SOMO35 metrics) and vegetation (flux-based PODY) to meteorological and emissions drivers. Between 1990 and 2013 at Harwell, there was a significant decrease in the contribution of European ozone to determining the impacts. Improvement in the human health impact was heavily dependent on the choice of metric (SOMO35 decreased, no change in SOMO10), and the vegetation impacts had not improved as high ozone episodes frequently coincided with plant conditions which reduced ozone uptake. These chemical climates emphasise the need for ozone mitigation on larger (hemispheric) scales than currently implemented. Secondly, the impact of 27 measured VOCs on the extent of the regional ozone increment is assessed. The photochemical loss of VOCs is then linked to reported gridded VOC emissions using air mass back trajectory analysis. Ethene and m+p-xylene had the largest diurnal photochemical loss during maximum monthly regional ozone increment, but the key conclusion was the limitation introduced through the reporting of gridded VOC emissions in heavily aggregated source sectors. Finally, the conditions producing the long term health impact of particulate matter (quantified by annual average PM10 and PM2.5 concentrations) at each site are derived through integration of measurements of PM10 and PM2.5 with measurements of PM constituents. It is shown that the frequent, moderate PM10 and PM2.5 concentrations made a larger contribution to annual average values compared to the relatively infrequent high, episodic concentrations. The contribution of PM constituents and the contribution of local vs regional emissions to the range of PM concentrations is investigated. It was concluded that similar reductions in the contribution of secondary inorganic aerosol to the moderate PM10 and PM2.5 concentrations could be achieved from both the reduction of frequently traversed, smaller emissions sources, and less frequently traversed, larger emissions sources. The final chapter demonstrates the benefits from the extension of this framework to an entire monitoring network. It is envisioned that for each atmospheric composition impact, a standard set of statistics would be calculated which quantify the ‘impact’, ‘state’ and ‘drivers’ of that chemical climate. Calculation of ozone human health chemical climates across 100 European monitoring sites demonstrate this concept. This standardised interpretation of monitoring network data not only allows consistent comparison of an impact, but the common basis for determining how the impact is derived allows for the consideration of novel mitigation strategies and their spatial applicability.
217

Lead exposure of children attending pre-school facilities in certain geographical areas of Pretoria, in relation to their activity patterns : a cross-sectional study

John, Juanette 19 September 2005 (has links)
Please read the abstract in the section 00front of this document / Dissertation (MSc)--University of Pretoria, 2005. / School of Health Systems and Public Health (SHSPH) / Unrestricted
218

Effect of ambient air pollution on development of childhood asthma

Clark, Nina Annika 11 1900 (has links)
Asthma prevalence is increasing worldwide and the causes of this increase are largely unknown. There is increasing recognition of the importance of early environmental exposures in childhood asthma development. Outdoor air pollution has been shown to trigger asthma symptoms but its role in incident disease remains controversial. To address these questions, I investigated the effect of in utero and first year of life exposure to ambient air pollution on risk of asthma diagnosis in a nested case-control study. All children born in Southwestern British Columbia in 1999 and 2000 (N=37,401) were assessed for incidence of asthma diagnosis at age 3 - 4 years using hospitalization and primary physician records. Exposure to ambient air pollution was estimated for the gestational period and first year of life using high-resolution pollution surfaces derived from government monitoring station data as well as land use regression models adjusted for temporal variation. Conditional logistic regression analyses were used to estimate effects of CO, NO, NO₂, PM₁₀, PM₂.₅, O₃, SO₂, black carbon, wood smoke and proximity to roads and point sources on asthma diagnosis. Elevated risks of asthma diagnosis were observed with increased early life exposure to CO, NO, NO₂, PM₁₀, SO₂, black carbon and proximity to point sources. Effects were generally larger for first year exposures than in utero exposures, and larger for girls than boys. The results indicate that early life exposure to air pollution is associated with increased risk of asthma diagnosis in early childhood. Although the effect sizes are small, air pollution exposure in urban areas is ubiquitous so may have significant effects at the population level. These results should be confirmed when children are older and asthma diagnosis is more robust. / Medicine, Faculty of / Population and Public Health (SPPH), School of / Graduate
219

The Impact of Exposure to Ambient Air Pollution on Educational Outcomes

Zhang, Yanjiao January 2017 (has links)
In this study, I examine if higher levels of ambient air pollution impact educational outcomes. According to the literature review, CO, O3, PM10 and PM2.5 are found to be four pollutants that could have an impact on cognitive ability, so I focus on these air pollutants. I analyze provincial test results for the province of British Columbia, and Secondary School Literacy Test results from the province of Ontario (OSSLT) with air pollution and weather data corresponding to the locations and dates in which tests took place. A longitudinal approach is used, in which test results are compared within a school over time with a fixed effects model chosen to control for school and year fixed effects. Correlations are found among the four pollutants in the two provinces, therefore, an integrated Air Quality Index (AQI) is calculated to further examine the relationship between air pollution and educational outcomes. In British Columbia, I find that there is a negative impact of ambient air pollution on student’s test results: a one standard deviation increase in AQI leads to a 0.23 percentage points decrease in student average grade. Furthermore, I find that in BC, air pollution’s impact on students with special needs experience about 3.4 times of the average impact of other students. In Ontario, I do not find significant association between OSSLT results and the AQI, and this might be because of not having enough observations in Ontario school dataset and lots of missing data in air pollution dataset. However, the association between ambient air pollution and OSSLT results is found to be negative overall, congruent with results from BC.
220

Industrial location planning: a means to control atmospheric pollution

Buchanan, Donald Maclachlan January 1965 (has links)
There appears to be a need for communication between community and regional planners and air pollution control specialists since atmospheric pollution has become one of the chief problems of the present day. A number of professions have approached the study of air pollution and its control in unique ways. The hypothesis is advanced that the control of industrial location by all levels of government in a cooperative manner, taking into account the applicable meteorological factors, would significantly reduce potential atmospheric pollution. Air pollution existed from the earliest times, but it was not until 1273 that legal control was recognized as necessary. After the industrial revolution and a series of acute health episodes in the twentieth century the various effects of atmospheric contamination were discovered. The physical planner has not sufficiently recognized the problem, and should strive to make clean air a goal towards which the planning process is directed. In Canada the British North America Act allocates the responsibility for atmospheric pollution control between the federal and provincial jurisdictions. Engineering control aspects may be given legal force by either government depending on the pollutant source, though the provincial authority appears much broader in scope. Technical abatement methods are complex and costly, and are particularly difficult for both the odourless and detectable gases. Costs of recovery may limit abatement solutions beyond 95% indicating that other methods are required. Performance standards are an attempt to enforce the use of such methods through municipal zoning by-laws, though there is some question as to whether they are necessary with good general regulation of emissions. The national and provincial (or state) governments have been chiefly concerned with industrial location from the socio-economic point of view. Local government has continued to be concerned with physical planning through zoning which both protects residents of the area and guides industrial growth. This power derives from the provincial legislatures in Canada, and not from court interpretations of the extent of community power as in the United States. Air zoning is an attempt to employ meteorological data in larger areas, recognizing that urban complexes themselves have a tremendous effect on climate, and that many factors have to be quantified and assessed. Detailed knowledge of area microclimates is considered to be most important in air zoning decisions. The metropolitan areas of Los Angeles and Edmonton illustrate the approach advocated to control atmospheric pollution. Los Angeles has not yet effectively integrated its air pollution control and planning control administrations, the county being responsible for the former and 70 different authorities for the latter. In Edmonton the administrations have been partially integrated, but in the field of major rezoning decisions no liaison exists. An investigation of the hypothesis by means of a quantifiable method, depending on wind direction and distance variables, reveals that locating air pollutant industries in accordance with meteorological factors could significantly lower potential pollution levels. The hypothesis is deficient in that it does not recognize the complementary need for engineering abatement controls. Many other factors are considered in industrial location planning besides air pollution control, the problem really being that it is not usually considered as a factor. The various aspects of the hypothesis are assessed in order to formulate policy recommendations for research, legislation, and control measures. Federal government leadership manifested through a Canada Air Pollution Control Act is advocated, with accompanying provincial Acts making for a total cooperative approach. The goal of clean air would, therefore, be given substance on a national basis. / Applied Science, Faculty of / Community and Regional Planning (SCARP), School of / Graduate

Page generated in 0.1089 seconds