• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 438
  • 84
  • 60
  • 55
  • 47
  • 25
  • 15
  • 11
  • 11
  • 11
  • 11
  • 11
  • 11
  • 9
  • 8
  • Tagged with
  • 979
  • 85
  • 72
  • 64
  • 63
  • 49
  • 46
  • 44
  • 44
  • 41
  • 41
  • 39
  • 38
  • 37
  • 37
  • 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.
201

Koncentrace tuhé znečišťující látky uvnitř stáje velkochovu drůbeže v závislosti na stáří drůbeže

DVOŘÁK, David January 2018 (has links)
This thesis deals with the issue of air pollution, emission of solid substance in the large-scale poultry. Compares the level of surface contamination inside the breeding facility, depending on the age of the poultry. The measurements were carried out in accordance with the applicable methodology for the evaluation and the determination of the concentration of dust particles PM10 in the selected large-scale poultry. Measurement was carried out in a large-scale broiler Farma u lesa in Sudoměřice u Bechyně. The aim of this work was to obtain a measurement and then evaluate the data obtained. The measurements were carried out in two rounds to measure two size fractions of solid pollutants. The DUST TRAK 8530, borrowed by the faculty, was used to measure the solid dust particles in bulge. Further, the thesis also describes description and measurement methodology with this device.
202

Avaliação do ambiente domiciliar e da sensibilidade cutanea imediata de pacientes atopicos e a prevalencia de acaros em amostras de poeira coletadas de colchões de camas e berços na cidade de Londrina-PR / Prevalence of mites in dust samples from mattress surfaces from single beds or cribs and evaluation of the home environment and sensitivity to mites in atopic patients residing in the south Brazilian city of Londrina

Silva, Dagoberto Ribeiro da 27 June 2007 (has links)
Orientadores: Eduardo Mello de Capitani, Celso Henrique de Oliveira / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-10T11:51:23Z (GMT). No. of bitstreams: 1 Silva_DagobertoRibeiroda_D.pdf: 7786104 bytes, checksum: 79d077434edacc262627179e99b88b50 (MD5) Previous issue date: 2007 / Resumo: A prevenção e tratamento de sintomas referidos como asma e rinite alérgica devem incluir o controle ambiental de aeroalérgenos, tais como ácaros e baratas. O objetivo desse estudo foi investigar a fauna acarina em amostras de poeira de colchões de berços e camas em Londrina, estado do Paraná, sul do Brasil, e avaliar a correlação entre fatores e métodos de controle ambientais e a sensibilidade acarina de pacientes atópicos. Crianças atópicas pré-escolares (n=24) e escolares e adultos (n=21) e o grupo-controle, com crianças sem atopia, pré-escolares (n=15), escolares e adultos (n=15) responderam a um questionário de perguntas específicas sobre as condições estruturais e ambientais de residências na cidade de Londrina/PR. Testes de puntura para ácaros e poeira domiciliar foram realizados na maioria dos pacientes para avaliar a sensibilidade imediata. Foram aspirados uma única vez, 133 amostras de poeira das faces superior e inferior de colchões e estrados de 38 residências (18 berços e 21 camas) e um berçário (6 berços). A análise estatística foi realizada para analisar a correlação dos resultados obtidos. O adequado controle ambiental foi raramente observado nas residências. Os testes de puntura mostraram uma alta sensibilidade para os extratos de poeira domiciliar e os ácaros D. pteronyssinus, D. farinae, e B. tropicalis, também em crianças. Não foi observada correlação entre sensibilização e os diversos fatores ou métodos de controle ambiental analisados. Um total de 758 corpos de ácaros foram contados em 133 amostras analisadas; 233 (30,7%) em amostras de berços e 525 (69,3%) nas amostras das camas (p<0,0001). Ácaros da poeira domiciliar, principalmente Dermatophagoides pteronyssinus, representaram 72% e 84% do total de ácaros contados em amostras de poeira de berços e camas, respectivamente. A média de concentração estimada de corpos de ácaros da poeira domiciliar em amostras de berços e camas foi de 289,9 ± 136,7 e 875,0 ± 183,6 ácaros/g, respectivamente. A análise estatística demonstrou uma contagem significativamente maior de corpos de ácaros na face inferior dos colchões quando comparado com a face superior, somente nas amostras das camas (p=0,025). O estudo sugere que ácaros são importantes alérgenos para atópicos na cidade de Londrina. Os resultados aqui obtidos demonstram que os colchões de berços têm suficiente corpos de ácaros para causar sensibilização em humanos. Esforços adicionais devem ser realizados para melhorar a conscientização da população local quanto ao uso de métodos de controle de alérgenos, tais como o uso de capas de revestimento em travesseiros e colchões de berços e camas para evitar a exposição alergênica / Abstract: The prevention and treatment of symptoms related to asthma and allergic rhinitis must include the environmental control of aeroallergens such as mites and cockroaches. The aim of this study was to investigate mites in mattress dust samples from cribs or beds in the southern Brazilian city of Londrina, State of Paraná as well as to evaluate the possible interrelation between environmental factors and control methods, and mite sensitivity of atopic patients. Atopic pre-school children (n=24), school-age children and adults (n=21) and group-control with non-atopic pre-school children (n=15), school-age children and adults (n=15) completed a questionnaire on the structural and environmental conditions of Londrina/PR. Skin prick tests for mites and house dust extracts were performed in most patients to evaluate immediate sensitivity. Dust samples from 133 top and bottom mattress surfaces, and bed frames from 38 dwellings (18 cribs and 21 beds), and one day nursery (6 cribs) were vacuumed. Statistical analysis was also performed. Adequate environmental control was rarely seen in dwellings. Skin prick test results showed a high sensitivity for the extracts of house dust, and the mites D. pteronyssinus, D. farinae, and B. tropicalis, also in children. Sensitivity and environmental factors or control method correlation was not observed. A total of 758 mite bodies were counted in slides; 233 (30.7%) from cribs and 525 (69.3%) from beds (p<0.001). House dust mites- mainly Dermatophagoides pteronyssinus, represented 72% and 84% of total mite count in crib and bed dust samples, respectively. The estimated mean HDM body concentration in crib or bed slides were 289.9 ± 136.7 and 875.0 ± 183.6 mites/g, respectively. Statistical analysis showed a significantly higher mite body count on bottom mattress surfaces compared to top surface in bed samples only (p=0.025). The study suggests which mites are important allergens for atopic patients in Londrina. Data herein show that cribs like mattresses have sufficient mite bodies to cause sensitization to humans. Local communities should be informed about allergen control methods such as the use of mattress and pillow covers for cribs and beds to avoid allergen exposure / Doutorado / Clinica Medica / Doutor em Clínica Médica
203

Risk factors precipitating exacerbations in adult asthma patients presenting at Kalafong Hospital, Pretoria

Geyser, Maria Magdalena 19 August 2008 (has links)
Objective. To determine if poor compliance with asthma treatment is independently associated with exacerbations requiring emergency room visits in adult patients seen at Kalafong Hospital, a secondary regional- and teaching hospital affiliated to the University of Pretoria. Methods. A matched case-control study was undertaken - matched on age and gender, between December 2003 and May 2005. Known asthma patients with exacerbations presenting at the hospital's emergency unit were chosen as cases. Controls were stable asthma patients recruited from the outpatient departments. A structured questionnaire was used to interview patients concerning their possible exposure to certain triggers and risk factors. Univariate and multivariate analysis with conditional logistic regression was done to determine any significant exposures. Participants were between 18 ¬65 years of age. Results. Three hundred and fifty-six patients were evaluated. Fifty cases and 100 controls were enrolled. Cases were shown to be more non-compliant than controls (OR = 2.18; 95% CI 1.09 to 4.38, p = 0.03). Missing follow-up doctor appointments for the last six months was statistically significant with an OR of 2.39 (95% CI 1.08 to 5.27) and p = 0.03. Cases had more bacterial respiratory infections than controls (OR = 5.00; 95% CI 1.57 to 15.94, p = 0.01). More controls (50%) were exposed to dust- and environmental pollution than cases (38%) (OR = 0.60; 95% CI 0.29 to 1.23, p = 0.16). There was also an interaction between non-compliance and dust- and environmental pollution. Conclusion. Non-compliance and bacterial respiratory infections were strong predictors of exacerbations in adult asthma patients at Kalafong Hospital. / Dissertation (MPh)--University of Pretoria, 2008. / School of Health Systems and Public Health (SHSPH) / MPh / Unrestricted
204

Improvement of physical, mechanical and strength behavior of cohesive soils with natural pozzolana and brick dust

Chang, E., Chang, E., Villalta, J., Fernandez, C., Duran, G. 28 February 2020 (has links)
This research project seeks to improve soil properties through experimentation with geotechnical purposes. For this, will be used natural volcanic pozzolana in 5%, 10%, 15% and brick dust in 10% giving it a second reuse. The soil improvement will be analyzed with the proposed additions and its influence on the results. It is concluded that the addition improves the behavior of the soil by decreasing its plasticity index, increases the compaction index and improves the geotechnical parameters.
205

Geochemistry, Weathering and Diagenesis of the Bermuda Paleosols:

Frisch, Joel A. January 2020 (has links)
Thesis advisor: Rudolph Hon / Pleistocene-age terra rossa paleosols are situated on and are intercalated with eolianite and marine carbonate units across the Bermuda Islands. These clay-rich soils were originally thought to the derived from weathering of the volcanic seamount and/or from dissolution of the carbonate units, the paleosols are now believed to be primarily the result of atmospheric dust deposition from Saharan North Africa and the Sahel via long range transport, with some local inputs. If so, these soil units are mixtures of atmospheric deposition during one or more glacial- interglacial cycles. Previous investigations have been conducted on the paleosols to determine their provenance, age, and to identify unique characteristics for island wide mapping. We conducted comprehensive geochemical analyses to determine the degree of chemical weathering and diagenesis, and to identify processes responsible for their formation and development. The paleosols were found to be geochemically similar across all ages, and to show an increased degree of alteration with age rather than with their duration of subaerial exposure, indicating diagenesis by infiltrating meteoric waters as well subaerial weathering. Evidence of paleosol diagenesis suggests vadose flow across the island may not be limited to preferential pathways and that while flow through the limestones is complex, infiltrating waters appear to have allowed for additional alteration of the soils. In addition to the paleosols, clay-rich deposits with paleosol-like textures were identified during coring operations in Harrington Sound and Hungry Bay, beneath present-day sea level. The source and development histories of these materials were previously unknown. Since these clay deposits are situated beneath present-day sea level it is likely that they were deposited and chemically weathered exclusively during glacial low-sea level climate conditions. Geochemical analyses were conducted on the submarine clay samples to determine if they were related to the above-sea level paleosol and to identify their sources. Major and trace element signatures showed the submarine clay deposits to be chemically similar to the paleosols and to be derived from a similar upper continental crust-like parent. Trace element fingerprinting showed the samples to be derived from a parent similar to that of the paleosols; primarily atmospheric dust with some volcanic contributions. These findings provide additional evidence that trade wind vectors for dust transport were present during Pleistocene glacial climate conditions. Weathering indicators reveal the submarine clay samples to be somewhat less weathered than paleosols of similar age and comparable periods of exposure. Like the paleosols, the submarine clays underwent an initial period of rapid subaerial weathering which suggests warm humid climate conditions during glacial low sea level periods. However, the submarine clays did not experience extended periods of diagenesis, which may explain the somewhat lower degree of weathering. Evidence of inputs from the volcanic platform to the paleosols was limited, but comparisons with shallow volcanic rock and highly weathered volcanic residual known as the Primary Red Clay showed some similarities, suggesting that in-situ chemical weathering of the volcanic platform could produce a laterite with some characteristics similar to the Bermuda paleosols. Geochemical analysis of volcanic sands collected at Whalebone Bay showed the igneous fragments to be a result of mechanical weathering and sorting of heavy refractory minerals and we interpret these sediments to be best described as a beach placer deposit. These materials are enriched in insoluble trace elements and REE, and their contribution to the paleosols is limited. / Thesis (MS) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.
206

Hut lung : a study of domestically acquired pneumoconiosis in rural women

Grobbelaar, Johannes P 20 July 2017 (has links)
Pneumoconiosis in rural Transkeian women termed "Transkei Silicosis" has been thought to be caused by silica inhaled while grinding maize by traditional methods (Palmer and Daynes, 1967). This study was undertaken to investigate the features and causes of hut lung. The range of clinical, radiologic, histologic, pulmonary physiologic and broncho-alveolar lavage features in patients meeting the following criteria was assessed: i) rural women practising traditional cooking methods ii) with a diffuse nodularity on chest x-ray iii) and lung biopsy evidence of pneumoconiosis iv) and without occupational exposure v) or evidence of active tuberculosis. Smoke and dust levels were measured in rural dwellings during cooking and maize grinding and ground maize and grinding rocks were analysed. 25 patients were studied. 17 were non-smokers, 5 were pipe smokers and 3 smoked 10 or less cigarettes per day. 7 had evidence of previous tuberculosis. The radiological findings ranged from a diffuse fine miliary pattern through coarse nodules with coalescence, to extensive fibrosis resembling PMF. The histologic features revealed simple "anthracosis" in 12, anthracosis with macules in 6 and mixed dust fibrosis in 7, of which 2 had silicotic nodules and 1 PMF. No such findings were observed in the control lung biopsy specimens obtained at post-mortem from city dwelling Xhosa females. Mild to moderate airflow limitation (defined as an FEV1/FVC ratio of &lt; 65% and/or RV&gt; 145% of predicted) was present in 73% while a reduced T'LCO (&lt; 80% predicted) was found in 76% of the patients. Cell numbers and differential counts in BAL fluid were normal but&gt; 80% of the macrophages were heavily laden with inorganic inclusions. The mean smoke level during indoor open fire cooking was 30mg/m³. Respirable dust and quartz concentrations ranging from 3,03 to 5, 82mg/m³ and 0,097 to 0,186mg/m³ respectively were found during hand grinding with sandstone (100% quartz), but were lower (ranging from 2,62 to 3,40mg/m³ and 0,024mg/m³ respectively) when non-quartz containing dolerite was used. Calculated cumulative equivalent time-weighted average respirable dust concentrations were shown to be similar to those found in an average South African gold mine while calculated equivalent respirable quartz concentrations were well below those found in the worst exposed gold miners and well within the recommended threshold limit values of the National Institute for Occupational Safety and Health (NIOSH) and the World Health Organisation (WHO). Respirable quartz exposure alone was not sufficient to explain the changes found. Respirable non-quartz containing nuisance dust and intense smoke exposure were shown to be significant. It was concluded that: i) hut lung can be defined as a domestic pneumoconiosis that occurs in rural women who practise primitive cooking methods ii) hut lung typically occurs in rural maize grinding Transkeian women but can occur in other rural women iii) there is a wide clinical, spectrum radiological and histologic iv) the pulmonary physiological changes are predominantly those of airflow limitation with some CO transfer factor reduction v) cigarette and pipe smoking do not contribute to the aetiology or pulmonary physiological abnormalities vi) the bronchoalveolar lavage features may help differentiate this condition from miliary tuberculosis vi) the aetiology of hut lung is multifactorial with exposure to respirable quartz and non-quartz containing dust together with smoke particles from biomass fuelled fires all playing a significant role while previous tuberculosis may be a contributing factor.
207

Circumstellar Environments of Supernovae / 星周環境から迫る超新星爆発

Nagao, Takashi 25 March 2019 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21573号 / 理博第4480号 / 新制||理||1643(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 前田 啓一, 准教授 上田 佳宏, 教授 嶺重 慎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM
208

Scattering properties of dust in Orion and Epsilon Eridani exoplanetary system

Mendillo, Christopher B. 22 January 2016 (has links)
Dust grain properties were investigated in two very different Galactic environments: the interstellar medium and an exoplanetary system. Two sounding rocket missions were developed to study these regions. Wide-field observations of the Orion OB stellar association were performed in the far-ultraviolet using the Spectrograph for Photometric Imaging with Numeric Reconstruction (SPINR) sounding rocket. These observations reveal the diffuse signature of starlight scattering off interstellar dust grains. The spectral-imaging data were used along with a three-dimensional radiative transfer model to measure the dust scattering parameters: the grain albedo (a) and the scattering asymmetry (g). The measured parameters are consistent with previous measurements made toward Orion. A sharp increase in albedo was measured at 〜1330 A. This feature is not explained by current grain models. The constructed three-dimensional model of Orion includes a two-component dust distribution. The foreground distribution is responsible for the small amount of visible reddening measured toward the bright stars in the Orion constellation.The background distribution represents the Orion Molecular Cloud, which dominates observations of dust emission in the infrared. This model was used to show that backscattered light from the molecular cloud alone cannot produce the observed scattered light distribution. The foreground dust, though optically thin in the visible, significantly contributes to the scattered light in the far-ultraviolet. This suggests that observations of Orion in the infrared and far-ultraviolet may probe entirely different dust populations. The Planetary Imaging Concept Testbed Using a Rocket Experiment (PICTURE) sounding rocket was developed to characterize dust grains in the nearby Epsilon Eridani exoplanetary system. This is a young, dusty system with a Jupiter-massed planet orbiting at 〜3.4 AU (astronomical units). PICTURE sought to capture a direct, visible-light image of dust-scattered starlight in this system with the aid of a high-contrast nulling coronagraph. The design and laboratory testing of the PICTURE science payload is presented. Although the mission returned no science data, several important technological advances were made to enable future direct imaging missions. Most notably, PICTURE demonstrated 5.1 milliarcsecond pointing stability using a fast optical tracking system.
209

Characterising South Africa’s major dust sources

Bekiswa, Sisanda Ongeziwe 24 February 2020 (has links)
The study investigates the surface controls of major dust emissions and determines the patial distribution of major dust source in South Africa. This study follows a multi-disciplinary approach where primary and secondary data were used. The main objective of the study is to determine the spatial distribution of South Africa's Major Dust Sources. Meteosat Second Generation (MSG) satellite imagery, land use and land cover maps were used to achieve the first and the second objectives of the study. Primary data involved sampling 30 soil samples in the field in order to achieve the third objective of the study. The crust, soil moisture, soil texture and grain size are all controls of dust emission. This investigation is however focused predominantly on grain size characteristics. GIS methods were also used to determine soil type from the African soil map. Soil samples in both provinces were then collected to assess the Particle Size Distribution (PSD) of the soils. The particle size was determined based on a sieve analysis for grain sizes that were greater than 2mm and laser diffractometry, MasterSizer (Malvern) was used to achieve this. The results from the Malvern were later put to R Statistics where they were clustered into eight clusters to determine similarities and difference of the grain size. Because there is no uniqueness in the soil types found in the study area, there were no solid conclusions made based in them. The results show that the soil types are found across South Africa but not the same amount of dust activity was detected in the other parts of the country. Previous studies show that global significant dust sources are natural sources such as lakes, pans and depressions. However, results demonstrate that South African dust sources are anthropogenic sources resulting from commercial agriculture in semi-arid regions. This study has demonstrated that surface sediments suitable for dust production are a mixture of fine material, silt (50µm) and coarse material, sand (2000µm) and it appears that all clusters in this study all contained both mixtures and all have potential to emit dust.
210

The influence of turbulence on dust and gas explosions in closed vessels /

Bond, Jean-François January 1985 (has links)
No description available.

Page generated in 0.045 seconds