• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • 1
  • Tagged with
  • 4
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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.
1

Ozone concentration profile retrieval from ground-based high-resolution thermal infrared spectra.

Van Delst, Paul F. January 1996 (has links)
Simulations of the Atmospheric Emitted Radiance Interferometer (AERI), a ground-based, high-resolution infrared detection system, are used to produce retrieved atmospheric ozone concentration profiles. A line-by-line transmittance model, FASCD3P, is used for the forward model and a maximum likelihood retrieval scheme is employed for the inverse model. An a priori data set consisting of 83 midlatitude winter ozone sondes is used to condition the inversion. Three iterations are required to reduce the radiance residuals to less than the instrument noise. The retrieval accuracy below 300mb is within 25% of truth. Above 300mb, variance within the a priori data is the dominant source of retrieval error. This is due to the number of retrieved layers (27) being higher than the amount of independent information present in the radiance spectra (approximately 4) so much of the retrieval information above 300mb comes from the a priori data.
2

Trumpalaikė ozono koncentracijos kaita atmosferos pažemio sluoksnyje / Short-term variations of the ground-level ozone concentration

Pletkutė, Lina 01 July 2010 (has links)
Baigiamajame magistro darbe nagrinėjama trumpalaikė ozono koncentracijos kaita ir jos priklausomybė nuo meteorologinių parametrų. Literatūros apžvalgoje aptariama ozono susidarymas, cheminės savybės, poveikis žmogaus sveikatai ir augalams. Atlikta 2000-2009 metais Preilos monitoringo stotyje gautų duomenų (vienos valandos vidurkiai) analizė. 2009 metų šiltuoju sezonu atliktas eksperimentas, sudaryta dešimties ir dviejų minučių vidurkių ozono koncentracijos ir meteorologinių parametrų duomenų bazė. Parametrų tarpusavio priklausomybė nustatyta panaudojant tiesinės regresijos metodą, apskaičiuoti koreliacijos koeficientai. Pasinaudojant Furje metodu atlikta ozono bei meteorologinių parametrų spektrinė analizė. Buvo rasti pagrindiniai dažnių pikai, kurie labiausiai išryškėja. Darbą sudaro 6 dalys: įvadas, literatūros apžvalga, matavimo prietaisai ir metodika, eksperimentinių tyrimų rezultatai, išvados ir literatūros sąrašas. Darbo apimtis – 57 p. teksto be priedų, 38 paveikslai., 3 lentelės, 53 bibliografiniai šaltiniai. Atskirai pridedami darbo priedai. / In master final work the variation of short-term ozone concentration variations were analyzed. Ozone formation, chemical characteristics, impact on human health and plants were described. The study of the short- and long-term ozone concentration variations dependence on meteorological parameters is presented. The data of hourly parameters obtained at the monitoring station Preila during 2000-2009 years were analyzed. The 2 and 10 minutes average values of the ozone concentration and meteorological parameters were collected during experiment in warm season of 2009 year. The regression analysis was applied for the determination of the correlation coefficients between variables. The strongest relationship from the long-term variations was found between ozone concentration and temperature. The strongest relationship from the short-term variations was found between ozone concentration and wind speed. Structure: introduction, literary review, measurements instruments and methodology, experimental research results, conclusions and references. Thesis consists of: 57 p. text without appendixes, 38 pictures, 3 tables, 53 bibliographical entries. Appendixes included.
3

Investigations on the respiratory effects of ozone in the rodent / Cornelius Jacon Lotriet

Lotriet, Cornelius Jacob January 2010 (has links)
Ozone, being an unstable molecule, is believed to be one of the strongest oxidant agents known to man. Rapid growth in the application of ozone — both as disinfectant and as form of alternative medicine — led to questions about the effects of uncontrolled ozone exposure and inhalation, whether intentional or unintentional, on the human body. This study specifically focussed on examining, identifying and substantiating the respiratory effect of acute exposure (10 min or less) to considerably higher ozone concentrations than reported on before (19.5 ± 0.5 ppm). Respiratory tissue of rodents (Duncan–Hartley guinea pigs of both sexes and Male Wistar rats) was subjected to ozone by utilising three distinctly diverse models of ozone introduction: (a) in vitro exposure, (b) in vivo exposure, and (c) ex vivo by employing an isolated lung perfusion model which allows for real–time, breath–by–breath data acquisition of ozone’s effect on respiratory mechanics. The effect of ozone on the isolated trachea in the presence of various drugs with well–known effects, including methacholine, isoproterenol and ascorbic acid was also examined. The results found in this study identified two direct effects on the isolated trachea due to ozone exposure: (1) a definite contraction of the isolated trachea immediately after exposure to ozone, and (2) a clearly visible and significant hyper responsiveness of the isolated trachea to irritants, e.g. methacholine. Although ozone has a negative effect on the trachea, it was concluded that ozone has no adverse effect on muscarinic acetylcholine receptors. An apparent EC50 value of ozone on the trachea was established by two different methods as (2.77 ± 0.02) x 10–3 M and (2.10 ± 0.03) x 10–3 M, respectively. Ozone furthermore displayed an attenuation of the beneficial pharmacological response of –sympathomimetic drugs (i.e. isoproterenol), while isoproterenol itself has a relaxing effect on the ozone–induced contraction of the isolated trachea. Indomethacin pre–treatment of isolated tracheal tissue significantly (77%) reduced the ozone–induced contraction of tracheal smooth muscle, suggesting that COXproducts of arachidonic acid play a prominent role in the development of pulmonary function decrements consequent to acute high–dose ozone exposure. Ascorbic acid exhibited a meaningful prophylactic effect on ozone–induced contraction of both isolated tracheal tissue and in the isolated lung perfusion model, emphasising the major role antioxidants play in both the epithelium lining fluid (ELF) of the respiratory system and in plasma throughout the body in protecting against the destructive effects of ozone. Surprisingly, pre–treatment with ascorbic acid did not prevent hyper responsiveness of isolated tracheal preparations to methacholine after a 10 min ozone (19.5 ± 0.5 ppm) exposure. In the lung perfusion model, the presence of ascorbic acid in the perfusion medium did, however, significantly reduce the magnitude and rate of decline in lung compliance after ozone exposure (46% decline with ascorbic acid versus 96% in the control study without ascorbic acid). Examination of a lung perfusion model exposed to ozone (19.5 ± 0.5 ppm O3; 5 seconds) presented a significant decline in lung compliance (95.6% within 2 min), tidal volume (70%) and maximum inspiratory flow (71.2%), with an ensuing reduction in lung elasticity and severely hampered breathing pattern. Microscopic examination after acute high–dose inhalation studies did not display any significant cellular damage, oedema or inflammation after acute high–dose ozone exposure. This suggests that significant cellular injury and inflammation is possibly not the causative factor of early breathing difficulty experienced after acute high–dose ozone inhalation, as these symptoms and particularly the result of inflammatory precursors, is believed to probably only set in at a later stage. Although the potential advantages of ozone in certain fields of medicine are not disputed, ozone, depending on its concentration and cumulative dose, can be either therapeutic or toxic. Observations in this study emphasised that even short bursts of high–dose ozone inhalation have deleterious effects on respiratory health and care should be taken not to jump to conclusions regarding ozone’s medical application without relevant scientific evidence. It must be stressed that high–dose inhalation of ozone should be avoided at all cost – especially by those with existing airway diseases. / Thesis (Ph.D. (Pharmacology))--North-West University, Potchefstroom Campus, 2011.
4

Investigations on the respiratory effects of ozone in the rodent / Cornelius Jacon Lotriet

Lotriet, Cornelius Jacob January 2010 (has links)
Ozone, being an unstable molecule, is believed to be one of the strongest oxidant agents known to man. Rapid growth in the application of ozone — both as disinfectant and as form of alternative medicine — led to questions about the effects of uncontrolled ozone exposure and inhalation, whether intentional or unintentional, on the human body. This study specifically focussed on examining, identifying and substantiating the respiratory effect of acute exposure (10 min or less) to considerably higher ozone concentrations than reported on before (19.5 ± 0.5 ppm). Respiratory tissue of rodents (Duncan–Hartley guinea pigs of both sexes and Male Wistar rats) was subjected to ozone by utilising three distinctly diverse models of ozone introduction: (a) in vitro exposure, (b) in vivo exposure, and (c) ex vivo by employing an isolated lung perfusion model which allows for real–time, breath–by–breath data acquisition of ozone’s effect on respiratory mechanics. The effect of ozone on the isolated trachea in the presence of various drugs with well–known effects, including methacholine, isoproterenol and ascorbic acid was also examined. The results found in this study identified two direct effects on the isolated trachea due to ozone exposure: (1) a definite contraction of the isolated trachea immediately after exposure to ozone, and (2) a clearly visible and significant hyper responsiveness of the isolated trachea to irritants, e.g. methacholine. Although ozone has a negative effect on the trachea, it was concluded that ozone has no adverse effect on muscarinic acetylcholine receptors. An apparent EC50 value of ozone on the trachea was established by two different methods as (2.77 ± 0.02) x 10–3 M and (2.10 ± 0.03) x 10–3 M, respectively. Ozone furthermore displayed an attenuation of the beneficial pharmacological response of –sympathomimetic drugs (i.e. isoproterenol), while isoproterenol itself has a relaxing effect on the ozone–induced contraction of the isolated trachea. Indomethacin pre–treatment of isolated tracheal tissue significantly (77%) reduced the ozone–induced contraction of tracheal smooth muscle, suggesting that COXproducts of arachidonic acid play a prominent role in the development of pulmonary function decrements consequent to acute high–dose ozone exposure. Ascorbic acid exhibited a meaningful prophylactic effect on ozone–induced contraction of both isolated tracheal tissue and in the isolated lung perfusion model, emphasising the major role antioxidants play in both the epithelium lining fluid (ELF) of the respiratory system and in plasma throughout the body in protecting against the destructive effects of ozone. Surprisingly, pre–treatment with ascorbic acid did not prevent hyper responsiveness of isolated tracheal preparations to methacholine after a 10 min ozone (19.5 ± 0.5 ppm) exposure. In the lung perfusion model, the presence of ascorbic acid in the perfusion medium did, however, significantly reduce the magnitude and rate of decline in lung compliance after ozone exposure (46% decline with ascorbic acid versus 96% in the control study without ascorbic acid). Examination of a lung perfusion model exposed to ozone (19.5 ± 0.5 ppm O3; 5 seconds) presented a significant decline in lung compliance (95.6% within 2 min), tidal volume (70%) and maximum inspiratory flow (71.2%), with an ensuing reduction in lung elasticity and severely hampered breathing pattern. Microscopic examination after acute high–dose inhalation studies did not display any significant cellular damage, oedema or inflammation after acute high–dose ozone exposure. This suggests that significant cellular injury and inflammation is possibly not the causative factor of early breathing difficulty experienced after acute high–dose ozone inhalation, as these symptoms and particularly the result of inflammatory precursors, is believed to probably only set in at a later stage. Although the potential advantages of ozone in certain fields of medicine are not disputed, ozone, depending on its concentration and cumulative dose, can be either therapeutic or toxic. Observations in this study emphasised that even short bursts of high–dose ozone inhalation have deleterious effects on respiratory health and care should be taken not to jump to conclusions regarding ozone’s medical application without relevant scientific evidence. It must be stressed that high–dose inhalation of ozone should be avoided at all cost – especially by those with existing airway diseases. / Thesis (Ph.D. (Pharmacology))--North-West University, Potchefstroom Campus, 2011.

Page generated in 0.1505 seconds