No description available.

No description available.

No description available.

While research on the environmental impacts of engineered nanoparticles (ENPs) is growing, the potential for them to be chemically transformed in the atmosphere has been largely ignored. The overall objective of this work was to assess the atmospheric transformation of carbonaceous nanoparticles (CNPs). The research focuses on C₆₀ fullerene because it is an important member of the carbonaceous nanoparticle (CNP) family and is used in a wide variety of applications. The first specific objective was to review the potential of atmospheric transformations to alter the environmental impacts of CNPs. We described atmospheric processes that were likely to physically or chemically alter aerosolized CNPs and demonstrated their relevance to CNP behavior and toxicity in the aqueous and terrestrial environment. In order to investigate the transformations of CNP aerosols under controlled conditions, we developed an aerosolization technique that produces nano-scale aerosols without using solvents, which can alter the surface chemistry of the aerosols. We demonstrated the technique with carbonaceous (C₆₀) and metal oxide (TiO₂, CeO₂) nanoparticle powders. All resulting aerosols exhibited unimodal size distributions and mode particle diameters below 100 nm. We used the new aerosolization technique to investigate the reaction between aerosolized C₆₀ and atmospherically realistic levels of ozone (O₃) in terms of reaction products, reaction rate, and oxidative stress potential. We identified C₆₀O, C₆₀O2, and C₆₀O3 as products of the C₆₀-O3 reaction. We demonstrated that the oxidative stress potential of C₆₀ may be enhanced by exposure to O3. We found the pseudo-first order reaction rate to be 9 x 10⁻⁶ to 2 x 10⁻⁵ s⁻¹, which is several orders of magnitude lower than the rate for several PAH species under comparable conditions. This research has demonstrated that a thorough understanding of atmospheric chemistry of ENPs is critical for accurate prediction of their environmental impacts. It has also enabled future research in that vein by developing a novel technique to produce nanoscale aerosols from nanoparticle powders. Results of this research will help guide the formulation of appropriate environmental policy concerning the regulation of ENPs. / Ph. D.

Dans un environnement urbain pollué, les altérations qui affectent les verres du patrimoine dépendent de facteurs intrinsèques, extrinsèques et temporels. Afin de caractériser les altérations atmosphériques résultant des interactions entre ces différents facteurs une stratégie de recherche prenant en compte un environnement multiphasique, le matériau (composition et surface) et le temps a été mise en place. Pour ce faire une étude complémentaire est menée sur des verres de vitraux exposés plusieurs centaines d'année et de verres modèles exposés en site réel et altéré artificiellement en laboratoire. Une approche multi-instrumentale et multi-échelle a été mise en place. Elle a permis d'identifier des mécanismes d'évolution de la couche d'altération (CA) notamment par la formation de lamines concentriques de ~10 nm (anciens fronts d'altération probables). L'exploration de l'impact des eaux de ruissellement montre que l'évolution de l'épaisseur de CA est dépendante à la fois d'une cinétique de diffusion (√t) et de dissolution (t). Enfin l'influence indirecte des produits néoformés sur l'altération semble jouer un rôle majeur à la fois en condition de ruissellement, avec la présence de CaCO3 qui précipite le détachement des écailles, et en milieu abrité, où la présence de K2CO3 est mise en cause dans la dissolution du réseau vitreux / In a polluted urban environment, alterations affecting heritage glasses depend on intrinsic and extrinsic factors as well as time. In order to characterize the atmospheric alteration resulting from the interactions occurring between these factors, a research strategy has been set up, taking into account the multi-phase environment, the material (composition and surface) and time. In order to do so, a complementary study was conducted on stained glasses displaying several hundred years of alterations and model-glasses exposed in-situ for a few years or artificially altered in the lab. A multi-instrument and multi-scale approach was used in this study. It allowed the identification of the mechanisms responsible for the evolution of the leached layer (LL), especially the presence of concentric 10nm thick laminae (probable traces of alteration front). The exploration of the run-off impact on alteration shows a dependency of LL thickness on both diffusion type kinetics (√t) and dissolution kinetics. Finally, the indirect impact of neoformed alteration products seems to take a major part both in run-off conditions, CaCO3 hastens the scaling, and in sheltered conditions, where K2CO3 can be cause for glass network dissolution

Thesis (Ph. D.)--Stony Brook University, 2003. / Includes bibliographical references (leaves 81-82).

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Qing Wang. Includes bibliographical references (p. 57-58). Also available online.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (p. 74-78).

No description available.

Under light wind conditions, the alternation of daytime heating and nighttime cooling creates a characteristic response in the oceanic boundary layer known as the diurnal cycle. The Mellor/Yamada Level II turbulence closure model is used to analyze this response pattern. The diurnal cycle has three phases. During morning and early afternoon, radiative solar heating produces stable stratification in the upper ocean, which inhibits the vertical transport of heat and momentum. Mean current speed at the surface increases as the effects of wind stress become confined to a shallow layer. This diurnal jet produces a mixed layer in the second phase, where turbulence generated by the vertical velocity shear balances the stabilizing buoyancy flux. At night, wind mixing and convective overturning due to surface cooling rapidly deepen the surface mixed layer during the third phase. / Graduation date: 1986