Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 133-141).

Thesis (Ph.D.)--Ohio University, June, 2009. / Release of full electronic text on OhioLINK has been delayed until June 1, 2010. Includes bibliographical references (leave 107)

Thesis (Ph.D.)--Ohio University, June, 2009. / Title from PDF t.p. Release of full electronic text on OhioLINK has been delayed until June 1, 2010. Includes bibliographical references (leave 107)

Spatial correlation functions, which quantify spatial relationships among porphyroblasts over a range of length scales, can be used in combination with other techniques of quantitative textural analysis to constrain crystallization mechanisms in metamorphic rocks. The utility, reliability, and robustness of these functions, however, depend critically upon correct methods of calculation and application to geological samples. Application of the L' -function, Pair Correlation Function, and Mark Correlation Function (Stoyan and Stoyan, 1994) to artificial arrangements of crystals yields results consistent with their predetermined ordering and clustering qualities. These results serve as a foundation for the interpretation of more complex simulated and natural crystal arrays. Analysis of artificial and simulated crystal arrays in which ordering signals are obscured in various ways (displacing crystals in an ordered array by increasing amounts, reducing the number of crystals, and increasing the sample's aspect ratio) demonstrates that these scale-dependent functions are robust indicators of effects diagnostic of certain crystallization mechanisms, even in complex circumstances. The effects of clustering of nucleation sites, however, can strongly obscure any underlying signal that might reveal crystallization mechanisms. The L' -function and the Pair Correlation Function are sensitive to short-range ordering of crystals, which may reflect suppression of nucleation in the vicinity of growing porphyroblasts. The Mark Correlation Function is sensitive to size-isolation correlations, which may reflect retardation of growth among crystals competing for nutrients. Interpretation of these functions, however, requires careful attention to proper calculation of Monte Carlo simulations, which are used to identify values of the functions that constitute a null-hypothesis region for comparison to samples with unknown ordering and clustering characteristics. To yield functional values commensurate with those calculated for a particular natural rock specimen, each simulation must match as closely as possible several critical features of the natural rock, including the set of crystal radii, limitations on the observability of crystals, and the shape and size of the bounding surface of the sample. Crystallization mechanisms in seven previously studied garnetiferous rocks from three localities (Carlson et al., 1995; Denison and Carlson, 1997) have been re-assessed using both scale-dependent correlation functions and single-valued spatial statistics, both evaluated by comparison to rigorously computed null-hypothesis regions. The results confirm previous inferences that the nucleation and growth rates of the garnet porphyroblasts in these specimens were governed by rates of diffusion through the intergranular medium. / text

The Dynamic Model for Aerosol Nucleation (DMAN) is a model which simulates nucleation, gas-phase chemistry, coagulation and condensation/evaporation for a multi-component atmospheric aerosol population. We developed an updated version of DMAN which includes the condensation of organic vapors on nanoparticles, using the recently developed Volatility Basis Set framework, and simulates the gas phase chemistry using the chemical mechanism SAPRC-99. The simulations were performed for two locations with different organic sources; Hyytiala (Finland) and Finokalia (Greece). Initially, we compared the results of the extended DMAN model with the old version which does not include the condensation of organics. The condensation of organics neglecting the Kelvin effects resulting in an approximate doubling of the growth rate of new particles. The number predicted concentration of particles above 3 nm (N3) and 100 (N100) increased at both locations. The increase of surface tension decreased dramatically the growth rate and the diameter that the new particles reached. The predicted concentration of N100 decreased at Hyytiala but increased at Finokalia, while the concentration of N3 decreased in both locations. Condensation of semi-volatile organic vapors, assuming realistic values of the organic surface energy, cannot explain the observed growth rates in Hyytiala during typical nucleation events. The simulations with production and condensation of low-volatility organics and a surface tension of 0.025 N m-1 indicate that the model can reproduce well the field measurements. The addition of chemical aging reactions converting semi-volatile organic aerosol (OA) to low volatility compounds helped the model to better reproduce the observed growth of the fresh particles. At Hyytiala, the organics are the major components during the growth process of new particles. The low-volatility secondary OA helps the growth initially, but after a few hours most of the growth is due to semi-volatile secondary OA components. At Finokalia, the simulation shows that the organic components have a complementary role for the growth contributing 45% of the total mass of new particles. / Το Δυναμικό Μοντέλο Πυρηνογένεσης Σωματιδίων (DMAN) είναι ένα μοντέλο το όποιο προσομοιώνει την πυρηνογένεση, την χημεία στην αέρια φάση, την συσσωμάτωση και την συμπύκνωση/εξάτμιση για ένα πολυσυστατικό πληθυσμό σωματιδίων. Εμείς αναπτύξαμε μια ανανεωμένη έκδοση του DMAN, το όποιο περιλαμβάνει και την συμπύκνωση των οργανικών ατμών πάνω στα νανοσωματίδια, χρησιμοποιώντας την πρόσφατη προσέγγιση Volatility Basis Set και προσομοιώνοντας την αέρια χημεία με την χρήση του χημικού μηχανισμού SAPRC-99. Οι προσομοιώσεις πραγματοποιήθηκαν για δυο τοποθεσίες με διαφορετικές πήγες οργανικών: Hyytiala (Φινλανδία) και Φινοκαλιά (Ελλάδα). Αρχικά, εμείς συγκρίναμε τα αποτελέσματα του εκτεταμένου DMAN μοντέλου με την παλιά έκδοση, η όποια δεν περιλαμβάνει την συμπύκνωση των οργανικών. Η συμπύκνωση των οργανικών παραμελώντας το Kelvin effect έχει σαν αποτέλεσμα τον διπλασιασμό του ρυθμού ανάπτυξης των νέων σωματιδίων. Η προβλεπόμενη συγκέντρωση αριθμού των σωματιδίων πάνω από 3 nm (N3) και 100 (N100) αυξήθηκε και στις δύο τοποθεσίες. Η αύξηση της επιφανειακής τάσης μειώνει δραματικά το ρυθμό ανάπτυξης και την διάμετρο που φτάνουν τα νέα σωματίδια. Η προβλεπόμενη συγκέντρωση των N100 μειώθηκε στη Hyytiala αλλά αυξήθηκε στην Φινοκαλιά, ενώ η συγκέντρωση του Ν3 μειώθηκε και στις δύο περιοχές. Η συμπύκνωση των ημι-πτητικών οργανικών ατμών, θεωρώντας ρεαλιστικές τιμές της επιφανειακής ενέργειας των οργανικών ατμών, δεν μπορεί να εξηγήσει το παρατηρούμενο ρυθμό ανάπτυξης στην Hyytiala κατά τη διάρκεια μιας τυπικής μέρας με πυρηνογένεση. Οι προσομοιώσεις με παραγωγή και συμπύκνωση οργανικών με χαμηλή πτητικότητα και επιφανειακή τάση 0.025 N m-1 δείχνουν ότι το μοντέλο μπορεί να αναπαράγει καλά τις μετρήσεις πεδίου. Η προσθήκη των χημικών αντιδράσεων γήρανσης μετατρέπουν τα ημι-πτητικά οργανικά αεροζόλ (ΟΑ) σε ενώσεις με χαμηλή πτητικότητα, αυτές βοηθούν το μοντέλο να αναπαράγει καλύτερα την παρατηρούμενη ανάπτυξη των φρέσκων σωματιδίων. Στην Hyytiala, τα οργανικά είναι τα κύρια συστατικά κατά τη διαδικασία της ανάπτυξης νέων σωματιδίων. Τα χαμηλής πτητικότητας δευτερογενή ΟΑ βοηθά στην ανάπτυξη αρχικά, αλλά μετά από μερικές ώρες το μεγαλύτερο μέρος της αύξησης οφείλεται στα ημι-πτητικά δευτερογενή ΟΑ. Στη Φινοκαλιά, η προσομοίωση δείχνει ότι τα οργανικά συστατικά έχουν ένα συμπληρωματικό ρόλο για την ανάπτυξη συμβάλλοντας 45% της συνολικής μάζας των νέων σωματιδίων.

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This thesis is about "nano-cellular" polymer foams, i.e., to understand nano-bubble nucleation and growth mechanisms, we used Self-Consistent Field Theory(SCFT) for the research.\\ Classical Nucleation Theory (CNT) is often used to calculate nucleation rates, but CNT has assumptions which break down for a nano-sized bubble: it assumes planar sharp interfaces and bulk phases inside bubbles. Therefore, since the size of a nano-sized bubble is comparable to the size of the polymer molecule, we assumed that a bubble surface is a curved surface, and we ivestigated effects of curvature on the nucleation barrier. SCFT results show that sharper curvatures of smaller s cause a higher polymer configurational entropy and lower internal energy, and also the collapse of the bulk phase for smaller bubbles causes low internal energy. Consequently, the homogenous bubble nucleation barrier for curved surfaces is much smaller than flat surface (CNT prediction).\\ We calculated direct predictions for maximum possible cell densities as a function of bubble radius without calculation of nucleation barrier or nucleation rates in CNT. Our results show higher cell densities at higher solvent densities and lower temperatures. Moreover, our cell density prediction reveals that rather than surface tension, the volume free energy, often labelled as a pressure difference in CNT, is the dominant factor for both cell densities and cell sizes. This is not predicted by CNT.\\ We also calculated direct predictions for the maximum possible cell densities as a function of system volume in compressible systems. With an assumption that system pressure has an optimal pressure which gives the maximal density of good quality foams (bulk phase inside bubble), we calculated the inhomogeneous system pressure, the homogeneous system, and cell density as a function of system volume.\\ Maximal cell prediction in compressible system shows the incompressible system prediction is the upperbound maximal cell density, and qualitatively consistent with the compressible system results - higher cell densities at low temperatures and high solvent densities.\\ In addition, our results show a bigger expansion as well as a high cell density at low temperature and high solvent density, but temperature is a more dominant factor than the solvent density. From our results, we assume that a quick pressure dropping is required to get a better quality foam of a higher cell density.

Doctor of Philosophy(PhD) / Particle formation in RAFT-mediated emulsion polymerization has been studied using reaction calorimetry. By measuring the heat flow during controlled feed ab-initio emulsion polymerization in the presence of amphipathic RAFT agents, particle formation by self-assembly of these species could be observed. Two different monomer systems, i.e. styrene and n-butyl acrylate, and various degrees of hydrophobicity of the initial macro-RAFT agents have been studied and compared. The different macro-RAFT agents were synthesized by first forming a hydrophilic block of poly(acrylic acid) that would later on act as the electrosteric stabilizing group for the particles. Subsequently, different lengths of hydrophobic blocks were grown at the reactive end of the poly(acrylic acid) hydrophilic block via the RAFT-mediated controlled radical polymerization, either comprised of n-butyl acrylate or styrene. Two processes govern particle formation: adsorption of macro-RAFT agents onto growing particles and formation of new particles by initiation of micellar aggregates or by homogeneous nucleation. Competition between these processes could be observed when monomers with a relatively high (n-butyl acrylate) or low (styrene) propagation rate coefficient were used. A model describing particle formation has been developed and the results of model calculations are compared with experimental observations. Preliminary modeling results based on a set of reasonable physico-chemical parameters already showed good agreement with the experimental results. Most parameters used have been verified experimentally. The development of the molecular weight distribution of the macro-RAFT agents has been analyzed by different techniques. Quantification of the particle formation process by analytical techniques was difficult, but qualitative insights into the fundamental steps governing the nucleation process have been obtained. The amount of macro-RAFT agents initially involved in particle formation could be determined from the increase of molecular weight. The particle size distribution has been measured by capillary hydrodynamic fractionation, transmission electron microscopy and dynamic light scattering. From the data obtained from these particle-sizing techniques, the number of particles during the reaction could be monitored, leading to an accurate estimate for the particle formation time. Upon implementation of the experimental data obtained for the surface active macro-RAFT systems, the model demonstrated to be very sensitive towards the “headgroup” area of the macro-RAFT species. Three nucleation cases based on the initial surface activity of the macro-RAFT species in the aqueous phase are proposed to explain the deviations from the assumptions of the nucleation model. Even though the macro-RAFT species have a narrow molecular weight distribution, they are nevertheless made up of a distribution of block lengths of polystyrene upon a distribution of block lengths of poly(acrylic acid). The resulting differences in initial surface activity are the most probable reason for the observed differences between model calculations and experimental results for the nucleation time and particle size distribution of the final latex product. With the procedure described above, latexes have been synthesized without using conventional surfactants and the mechanisms involved in the particle formation for these systems have been elucidated. The results of this work enable production of latex systems with well defined molecular mass distributions and narrow particle size distributions. Furthermore, the technique based on the application of amphipathic RAFT agents is promising for the production of complex polymeric materials in emulsion polymerization on a technical scale.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.