Since their accidental introduction into the Great Lakes in mid- to late-1980s, the freshwater zebra mussels, Dreissena polymorpha, have colonized most lakes and waterways across eastern North America. Their rapid spread is partly attributed to their ability to tenaciously attach to hard substrates via an adhesive apparatus called the byssus, resulting in serious environmental and economic impacts. A detailed ultrastructural study of the bysuss revealed a 10 nm adhesive layer at the attachment interface. Distributions of the main adhesive amino acid, 3,4-dihydroxyphenylalanine (DOPA), and its oxidizing (cross-linking) enzyme, catechol oxidase, were determined histochemically. It was found that, upon aging, DOPA levels remained high in the portion of the byssus closest to the interface, consistent with an adhesive role. In contrast, reduced levels of DOPA corresponded well with high levels of catechol oxidase in the load-bearing component of the byssus, presumably forming cross-links and increasing the cohesive strength.

Since their accidental introduction into the Great Lakes in mid- to late-1980s, the freshwater zebra mussels, Dreissena polymorpha, have colonized most lakes and waterways across eastern North America. Their rapid spread is partly attributed to their ability to tenaciously attach to hard substrates via an adhesive apparatus called the byssus, resulting in serious environmental and economic impacts. A detailed ultrastructural study of the bysuss revealed a 10 nm adhesive layer at the attachment interface. Distributions of the main adhesive amino acid, 3,4-dihydroxyphenylalanine (DOPA), and its oxidizing (cross-linking) enzyme, catechol oxidase, were determined histochemically. It was found that, upon aging, DOPA levels remained high in the portion of the byssus closest to the interface, consistent with an adhesive role. In contrast, reduced levels of DOPA corresponded well with high levels of catechol oxidase in the load-bearing component of the byssus, presumably forming cross-links and increasing the cohesive strength.

This project examined multiple aspects of the reproductive biology of the wetland invasive species, purple loosestrife (<i>Lythrum salicaria</i> L.), in central Saskatchewan. An examination of insect taxa visiting the three floral morphs of <i>Tristylous</i> L. <i>salicaria</i>, as well as a ranking of the pollination efficiency of individual insect species, an apparent first for L salicaria, was undertaken. Surface features of the floral nectary of L. <i>salicaria</i>, as well as floral nectar secretion dynamics, were also investigated. This project also re-visited some of the previous work done on this invasive species, including various floral organ morphometrics in relation to heterostyly, and aspects of the tristylous breeding system including self-fertilization, and fertilization potential of both illegitimate pollination and legitimate pollination.<p>The trimorphic nature of the sexual floral organs of L. <i>salicaria</i> were well defined in Saskatchewan. Significant differences in length (long-, intermediate- and short-style lengths) exist between all three floral morphs. Lengths of the staminal filaments (long, intermediate, and short) were also significantly different. Also the floral nectary in L. <i>salicaria</i> is located in a depression formed at the interface of the hypanthium and the gynoecium. Several stomata are located at regular intervals along the nectary surface, and may constitute the escape route for floral nectar. No morphological differences in nectary structure were apparent among the three floral morphs.<p>Nectar secretion dynamics of L. <i>salicaria</i> were examined between the three floral morphs throughout two summer days in 2006. Peak average nectar volumes and nectar sugar quantities were detected at 3:00 pm, and, interestingly, no significant differences were detected between floral morphs, in accordance with nectary morphology. The estimated secretion rates for L. <i>salicaria</i> ranged from 61 83 µg of nectar sugar per flower per hour.<p>Hand-pollination experiments carried out over the summers of 2006 and 2007 at three field sites in and around Saskatoon have verified the strong self-incompatibility in the breeding system of this tristylous species. Intramorph pollination, using illegitimate pollen, did not result in fertilisation, whereas legitimate hand-pollination experiments yielded multiple pollen tubes at the style base, without exception.<p><i>Lythrum salicaria</i> in central Saskatchewan was visited by several bee taxa including honeybees (<i>Apis mellifera</i> L.), bumblebees (Bombus spp.), leafcutter bees (Megachile spp.), and sweat bees (Lasioglossum spp.). A single visit by <i>Anthophora furcata</i> (Panzer) was also recorded in 2007. Generally, bee visits led to high levels of pollination success as determined by fluorescence microscopy of pollen tubes following single insect visits to previously-unvisited flowers. However, most visits by hoverflies (Syrphidae) were non-pollinating. Visits by Pieris rapae (L.), yellowjacket wasps (Vespidae) and some non-syrphid flies (Diptera) also yielded no pollen tubes at the style base.<p>A study of the ultrastructure and development of the floral nectary of the purple loosestrife cultivar Morden Gleam (<i>Lythrum virgatum</i> L. x L. alatum Pursh.) showed that starch build up in pre-secretory nectary tissues declined throughout secretion, and is virtually absent in post-secretory nectary tissues. The lack of a direct vascular supply to the floral nectary suggests that the starch breakdown products likely make up most of the floral nectar carbohydrates. Surface features of the floral nectary in Morden Gleam closely resembled those of L. salicaria, located in the valley formed between the hypanthium and gynoecium. Nectary stomata, occasionally in pairs, likely serve as outlets for nectar in this cultivar.

Mechanical property and thermal stability of Zr-Si-N films of varying silicon contents deposited on Al2O3 (0001) substrates are characterized. All films provided for characterization were deposited by reactive DC magnetron sputter deposition technique from elemental Zr and Si targets in a N2/Ar plasma at 800 oC. The hardness and microstructures of the as deposited films and post-annealed films up to 1100 oC are evaluated by means of nanoindentation, X-ray diffractometry and transmission electron microscopy. The Zr-Si-N films with 9.4 at.% Si exhibit hardness as high as 34 GPa and a strong (002) texture within which vertically elongated ZrN crystallites are embedded in a Si3N4 matrix. The hardness of these two dimensional nanocomposite films remains stable up to 1000 oC annealing temperatures which is in contrast to ZrN films where hardness degradation occurs already above 800 oC. The enhanced thermal stability is attributed to the presence of Si3N4 grain boundaries which act as efficient barriers to hinder the oxygen diffusion. X-ray amorphous or nanocrystalline structures are observed in Zr-Si-N films with silicon contents &gt; 13.4 at.%. After the annealing treatments, crystalline phases such as ZrSi2, ZrO2 and Zr2O are formed above 1000 oC in the Si-containing films while only zirconia crystallites are observed at 800 oC in pure ZrN films because oxygen acts as artifacts in the vacuum furnace. The structural, compositional and hardness comparison of as-deposited and annealed films reveal that the addition of silicon enhances the thermal stability compared to pure ZrN films and the hardness degradation stems from the formation of oxides at elevated temperatures.

In-situ polymerization is one of the most efficient methods for production of polymer clay nanocomposites. In-situ polymerization of olefins using coordination catalysts is a type of heterogeneous polymerization. In order to achieve acceptable clay nanolayer dispersion in the polyolefin matrix, the clay layer exfoliation and particle break up during the polymerization are essential requirements. A literature review on polyolefin/clay nanocomposite is given in Chapter 2. In Chapter 3, we present a new mathematical model, which is as an extension of the multigrain model (MGM), to describe the intercalative polymerization and expansion of clay interlayer spaces during polymerization using clay-supported metallocenes. The results from the model show that, under the studied conditions, mass transfer is not a strong factor controlling clay exfoliation and particle break up. If the polymerization active sites are supported uniformly on all clay surfaces, effective exfoliation will be achieved after a relative short polymerization time. In practice, obtaining good dispersion of clay nanolayers with uniform properties requires that the active sites be exclusively located on the clay nanolayer surfaces, and not extracted by the solvent to form a homogeneous solution. Factors favouring active site extraction would result in nanocomposites with poor properties. In addition, high polymerization activities, stable polymerization runs, and ease of supporting are other criteria for a successful in-situ polymerization. For this purpose we established a catalyst supporting method by which most of these requirements were met. In this method, the water content on the clay surface, which is considered as poison for the metallocene catalyst, was used to produce MAO upon reaction with trimethylaluminum (TMA). Using this method, polymerization was highly active in absence of MAO cocatalyst, knowing that MAO cocatalyst promotes active site extraction from the clay surface and results in poor powder morphology. Chapter 4 describes the development of this supporting methodology. Chapter 4 also investigates the effect of the organic modification type existing on the clay surface on the success of catalyst supporting and in-situ polymerization. We found that using the proposed supporting procedure, only tertiary ammonium type modification enhanced the in-situ polymerization, whereas the quaternary ammonium worsened the catalyst supporting efficiency and led to catalyst with poor or no polymerization activity. It is suggested that, in addition to enhancing clay surface-organic solvent compatibility (which facilitates catalyst supporting), the tertiary ammonium cation reacts with the in-situ produced MAO and increases the stability of the cocatalyst bonded to the clay surface. The effect of different polymerization conditions on the polymerization behavior and nanocomposite structural properties, such as catalyst loading during supporting, polymerization temperature and triisobutylaluminum (TIBA) concentration, were studied in Chapter 5. It was found that TIBA acts merely as scavenger. High polymerization activities were obtained with low Al/Zr ratios (Al from TIBA) and increased Al concentration decreased the polymerization activity and also the quality of powder morphology. Catalyst loading in the supporting step showed to have an important role in determining the final properties. The clay particles with higher catalyst loading resulted in better exfoliation and powder morphologies The effect of solvent type during catalyst supporting and polymerization was studied in Chapter 6. It was shown that catalyst supporting in n-hexane resulted in polymerizations with higher activities and polymers with higher molecular weight were produced. Polymerization with catalyst supported in hexane showed different ethylene uptake profiles, suggesting different mechanism of exfoliation. It is suggested that using this catalyst, the clay is mostly exfoliated before polymerization started. Similar to the original clay, the catalyst supporting efficiency on the organically modified clay was close to 100 percent. However, comparing the polymerization activities of these catalysts to those that were supported directly in the reactor just before the polymerization (in-reactor, or in-situ, supported catalysts) shows that a considerable fraction of the active sites are deactivated during the prolonged contact between catalyst and clay support surface. In Chapter 5, it was shown that the in-reactor supported catalyst had considerably higher polymerization activities, up to 40 percent of that of the homogeneous catalyst. Nanocomposites made with in-reactor supported catalysts had powder morphology and nanaolayer dispersion comparable to those made with clay-supported catalysts.

This project examined multiple aspects of the reproductive biology of the wetland invasive species, purple loosestrife (<i>Lythrum salicaria</i> L.), in central Saskatchewan. An examination of insect taxa visiting the three floral morphs of <i>Tristylous</i> L. <i>salicaria</i>, as well as a ranking of the pollination efficiency of individual insect species, an apparent first for L salicaria, was undertaken. Surface features of the floral nectary of L. <i>salicaria</i>, as well as floral nectar secretion dynamics, were also investigated. This project also re-visited some of the previous work done on this invasive species, including various floral organ morphometrics in relation to heterostyly, and aspects of the tristylous breeding system including self-fertilization, and fertilization potential of both illegitimate pollination and legitimate pollination.<p>The trimorphic nature of the sexual floral organs of L. <i>salicaria</i> were well defined in Saskatchewan. Significant differences in length (long-, intermediate- and short-style lengths) exist between all three floral morphs. Lengths of the staminal filaments (long, intermediate, and short) were also significantly different. Also the floral nectary in L. <i>salicaria</i> is located in a depression formed at the interface of the hypanthium and the gynoecium. Several stomata are located at regular intervals along the nectary surface, and may constitute the escape route for floral nectar. No morphological differences in nectary structure were apparent among the three floral morphs.<p>Nectar secretion dynamics of L. <i>salicaria</i> were examined between the three floral morphs throughout two summer days in 2006. Peak average nectar volumes and nectar sugar quantities were detected at 3:00 pm, and, interestingly, no significant differences were detected between floral morphs, in accordance with nectary morphology. The estimated secretion rates for L. <i>salicaria</i> ranged from 61 83 µg of nectar sugar per flower per hour.<p>Hand-pollination experiments carried out over the summers of 2006 and 2007 at three field sites in and around Saskatoon have verified the strong self-incompatibility in the breeding system of this tristylous species. Intramorph pollination, using illegitimate pollen, did not result in fertilisation, whereas legitimate hand-pollination experiments yielded multiple pollen tubes at the style base, without exception.<p><i>Lythrum salicaria</i> in central Saskatchewan was visited by several bee taxa including honeybees (<i>Apis mellifera</i> L.), bumblebees (Bombus spp.), leafcutter bees (Megachile spp.), and sweat bees (Lasioglossum spp.). A single visit by <i>Anthophora furcata</i> (Panzer) was also recorded in 2007. Generally, bee visits led to high levels of pollination success as determined by fluorescence microscopy of pollen tubes following single insect visits to previously-unvisited flowers. However, most visits by hoverflies (Syrphidae) were non-pollinating. Visits by Pieris rapae (L.), yellowjacket wasps (Vespidae) and some non-syrphid flies (Diptera) also yielded no pollen tubes at the style base.<p>A study of the ultrastructure and development of the floral nectary of the purple loosestrife cultivar Morden Gleam (<i>Lythrum virgatum</i> L. x L. alatum Pursh.) showed that starch build up in pre-secretory nectary tissues declined throughout secretion, and is virtually absent in post-secretory nectary tissues. The lack of a direct vascular supply to the floral nectary suggests that the starch breakdown products likely make up most of the floral nectar carbohydrates. Surface features of the floral nectary in Morden Gleam closely resembled those of L. salicaria, located in the valley formed between the hypanthium and gynoecium. Nectary stomata, occasionally in pairs, likely serve as outlets for nectar in this cultivar.

In this thesis, carbon supported platinum nanoparticles have been prepared by using PtCl4 as a starting material and 1-octanethiol, 1-decanethiol, 1-dodecanethiol and 1-hexadecanethiol as surfactants for methanol, ethanol and 2-propanol oxidation reactions. The structure, particle sizes and surface morphologies of the platinum were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). XRD and TEM results indicate that all prepared catalysts have a face centered cubic structure and are homogeneously dispersed on the carbon support with a narrow size distribution (2.0 to 1.3 nm). X-ray photoelectron spectra of the catalysts were examined and it was found that platinum has two different oxidation state, Pt (0) and Pt (IV), oxygen and sulfur compounds are H2Oads and OHads, bounded and unbounded thiols. The electrochemical and electrocatalytic properties of those catalysts were investigated towards C1 to C3 alcohol oxidations by cyclic voltammetry (CV) and chronoamperometry (CA). The highest electrocatalytic activity was obtained from catalyst I which was prepared with 1-octanethiol. This may be attributed to decrease in the ratio of bounded to unbounded thiol species and increase in Pt (0)/Pt (IV), H2Oads/OHads ratios, electrochemical surface area, CO tolerance and percent platinum utility.

Bacterial cell wall proteins (S-layer) are - due to both the capability to self-assemble into two-dimensional crystals and their distinct chemical and structural properties - suitable for the deposition of metallic particles at their surface . The cluster growth is subject of this thesis. The binding of metal complexes to S-layers of Bacillus sphaericus and Sporosarcina ureae and their subsequent reduction leads to the formation of regularly arranged platinum or palladium cluster arrays on the biomolecular template. A heterogeneous nucleation mechanism is proposed for this process consisting of the binding of metal complexes and their subsequent reduction. The kinetics of the process and the binding of the complexes to the protein are characterized by UV/VIS spectroscopy. This thesis focuses on structural investigations by means of transmission electron microscopy, electron holography, scanning force microscopy, image analysis, and image processing. Preferred cluster-deposition sites are determined by correlation averaging. A more precise determination and quantification is obtained by Multivariate Statistical Analysis. Furthermore a method for the electron beam induced formation of highly-ordered metallic cluster arrays in the transmission electron microscope and a fast screening method for surface layers of Gram-positive bacteria are presented. / Bakterielle Zellhüllenproteine (S-Layer) eignen sich durch ihre Fähigkeit zur Selbstassemblierung zu zweidimensionalen Kristallen und durch ihre besonderen chemischen und strukturellen Eigenschaften zur Abscheidung regelmäßiger metallischer Partikel auf ihrer Oberfläche. In dieser Arbeit wird das Clusterwachstum auf S-Layern untersucht. Die Anbindung von Metallkomplexen an S-Layer von Bacillus sphaericus und Sporosarcina ureae und deren Reduktion führt zur Abscheidung periodisch angeordneter metallischer Platin- bzw. Palladiumcluster auf dem Biotemplat. Für diese Clusterbildung wird ein heterogener Keimbildungsmechanismus vorgeschlagen, bestehend aus Komplexanbindung und Reduktion. Die Bestimmung der Prozeßkinetik und die Charakterisierung der Anbindung der Komplexe an das Protein erfolgt mittels UV/VIS-Spektroskopie. Den Schwerpunkt dieser Arbeit bilden strukturelle Untersuchungen mit Hilfe der Transmissionselektronenmikroskopie, der Elektronenholographie, der Rasterkraftmikroskopie und der Bildanalyse und Bildverarbeitung. Durch Korrelationsmittelung werden Strukturinformationen gewonnen, die eine Bestimmung der lateral bevorzugten Clusterpositionen ermöglichen. Für die auf S-Layern erzeugten Clusterarrays wird die Belegung der einzelnen Positionen mittels Multivariater Statistischer Analyse genauer quantifiziert. Außerdem werden eine Methode zur Erzeugung hochgeordneter metallischer Partikelarrays unter dem Einfluß des Elektronenstrahles im Transmissionselektronenmikroskop und eine Methode zum schnellen Test Gram-positiver Bakterienstämme auf die Existenz von S-Layern vorgestellt.

The structural evolution of carbon:transition metal (C:TM) nanocomposite thin films is investigated in two regimes: (i) surface diffusion governed regime occurring during the film growth and (ii) bulk diffusion dominated regime occurring during the post-deposition thermal annealing. C:V, C:Co, and C:Cu nanocomposite films were grown by ion beam co-sputtering. The influence of the metal type, metal content (15-40 at.%), substrate temperature (RT-500°C), and annealing temperature (300-700°C) on the structure and morphology of the composite is studied by the means of elastic recoil detection analysis, X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Vanadium (copper) is in carbidic (metallic) state in the whole temperature range of the study. In contrast, cobalt is in carbidic state up to 300°C and becomes metallic at higher growth temperatures. The nanoparticles in C:V films exhibit a globular shape at RT-500°C, whereas in C:Co and C:Cu films a growth transition from globular to elongated nanoparticles occurs around 300°C. The comparison of the Raman spectroscopy results from carbon reference and C:TM thin films shows that the presence of the metal during growth significantly enhances the formation of sixfold ring carbon clusters at temperatures as low as RT. The enhancement occurs independently of the nanoparticle size, shape, and phase, and metal content, and is related to processes taking place on the nanoparticle surface of the growing film rather than in the bulk. The degree of enhancement depends on the TM type and content. Post-deposition annealing of C:Co and C:Cu films at 700°C causes the metal segregation at the film surface, while no changes upon annealing occur in C:V films. In addition, cobalt brings about the carbon graphitization by a dissolution-diffusion-precipitation mechanism, similar to the metal-mediated crystallization of amorphous silicon or germanium. No graphitization upon annealing occurs in C:V, C:Cu, and carbon reference films. / Die Strukturentwicklung in Kohlenstoff-Übergangsmetall-Nanokompositschichten wird in zwei Bereichen untersucht: (i) im oberflächendiffusionsgesteuerten Bereich während des Schichtwachstums und (ii) im bulkdiffusionsdominierten Bereich während des nachträglichen Temperns. C:V, C:Co und C:Cu Nanokompositschichten wurden durch Ionenstrahl Co-Sputtern hergestellt. Der Einfluss des Metalltyps, des Metallgehalts (15-40 at.%), der Substrattemperatur (RT-500°C) und der Temperatur beim Tempern (300-700°C) auf die Struktur und Morphologie des Komposits wird mittels elastischer Rückstoßteilchen-Analyse, Röntgenbeugung, Transmissionselektronenmikroskopie und Ramanspektroskopie untersucht. Vanadium (Kupfer) ist im gesamten Temperaturbereich der Studie in karbidischem (metallischen) Zustand. Im Gegensatz dazu befindet sich Kobalt bis zu einer Temperatur von 300°C in karbidischem Zustand und wird bei höheren Abscheidetemperaturen metallisch. Die Nanopartikel in C:V Filmen besitzen eine runde Form im Temperaturbereich von RT bis 500°C wohingegen bei den C:Co und C:Cu Filmen ein Übergang von runden zu länglichen Partikeln bei etwa 300°C zu beobachten ist. Der Vergleich der Ramanspektroskopieresultate der Kohlenstoffreferenzproben und der Nanokompositschichten zeigt, dass die Anwesenheit des Metalls während des Schichtwachstums die Bildung von sechsatomigen Kohlenstoffringclustern bei Temperaturen so niedrig wie Raumtemperatur deutlich fördert. Die Erhöhung tritt unabhängig von der Partikelgröße, -form und phase und unabhängig vom Metallgehalt auf, und betrifft eher Prozesse, die auf der Oberfläche der Nanopartikel während des Schichtwachstums stattfinden als im Bulk. Der Grad der Erhöhung hängt vom Metalltyp und -gehalt ab. Nachträgliches Tempern der C:Co und C:Cu Filme bei 700°C führt zur Segregation des Metalls an der Schichtoberfläche während in den C:V Filmen keine Veränderungen durch das Tempern auftreten. Des weiteren kommt es in den C:Co Filmen zur Graphitisierung des Kohlenstoffs durch einen „Lösungs-Diffusions-Ablagerungs“ Mechanismus ähnlich der metallvermittelten Kristallisierung in amorphem Silizium und Germanium. In den C:V, C:Cu und Kohlenstoffreferenzfilmen findet keine Graphitisierung während des Temperns statt.

Corrosion protection performance of a completely soluble polyaniline-dodecylbenzenesulfonic acid salt (PANI-DBSA) on C45 steel has been studied with electrochemical impedance and potentiodynamic measurements. Chloroform is the most suitable solvent to process the pristine PANI-DBSA because of negligible interaction of the solvent with the polyaniline (PANI) backbone. An anodic shift in the corrosion potential (<img src="http://scitation.aip.org/stockgif3/Dgr.gif" alt="Delta" align="bottom" border="0"><i>E</i>=~70&nbsp;&nbsp;mV), a decrease in the corrosion current and a significant increase in the charge transfer resistance indicate a significant anti-corrosion performance of the soluble PANI deposited on the protected steel surface. Corrosion protection follows the mechanism of formation of a passive oxide layer on the surface of C45 steel. In situ UV-Vis spectroscopy was used to investigate the differences in permeability of aqueous anions into PANI-DBSA. Preliminary results of electron diffraction studies show that PANI-DBSA possesses an orthorhombic type of crystal structure. An increase in the feed ratio of DBSA to aniline increases the tendency of aggregation of spherical particles of PANI obvious in transmission electron microscopy. PANI-DBSA slowly loses its electrochemical activity in acid free electrolyte without undergoing degradation.