The aim of the masterâs thesis is to design a hydraulically controlled dozer for nonhomogeneous materials. The proposed dozer of non-homogeneous materials is attached to a telehandler. The thesis is divided into a theoretical and practical part. In the theoretical part contains a summary of similar machinery, a description of a telehandler and a summary of possible non-homogeneous materials. The practical part deals with the structural design of the proposed dozer. The design includes selection and justification of the chosen concept, important technical calculations, a scheme of the hydraulic circuit, strength check calculations, and drawing documentation.

Pour répondre aux enjeux économiques et sociaux modernes, le développement de catalyseurs organométalliques à base de métaux abondants et bon marché, comme alternatives aux catalyseurs historiques basés sur les métaux précieux, connaît un essor constant depuis deux décennies. L’objectif du présent travail doctoral a été de développer des catalyseurs à base de manganèse, troisième métal de transition le plus abondant après le fer et le titane, et précédemment principalement utilisé en oxydation, pour les réactions de (dé)-hydrogénation. / To meet modern economic and social challenges, the development of inexpensive and abundant metal-based organometallic catalysts, as alternatives to historical catalysts based on precious metals, has been growing steadily for two decades. The aim of this doctoral work was to develop catalysts based on manganese, which is the third most abundant transition metal after iron and titanium, and previously mainly used in oxidation, for (de)-hydrogenation reactions.

MSc (Mathematics) / Department of Mathematics

The primary result from this dissertation is following inequality: d(B) ≤ min(2^< wd(B),sup{λ^c(B): λ < wd(B)}) in ZFC, where B is a homogeneous complete Boolean algebra, d(B) is the density, wd(B) is the weak density, and c(B) is the cellularity of B. Chapter II of this dissertation is a general overview of homogeneous complete Boolean algebras. Assuming the existence of a weakly inaccessible cardinal, we give an example of a homogeneous complete Boolean algebra which does not attain its cellularity. In chapter III, we prove that for any integer n > 1, wd_2(B) = wd_n(B). Also in this chapter, we show that if X⊂B is κ—weakly dense for 1 < κ < sat(B), then sup{wd_κ(B):κ < sat(B)} = d(B). In chapter IV, we address the following question: If X is weakly dense in a homogeneous complete Boolean algebra B, does there necessarily exist b € B\{0} such that {x∗b: x ∈ X} is dense in B|b = {c € B: c ≤ b}? We show that the answer is no for collapsing algebras. In chapter V, we give new proofs to some well known results concerning supporting antichains. A direct consequence of these results is the relation c(B) < wd(B), i.e., the weak density of a homogeneous complete Boolean algebra B is at least as big as the cellularity. Also in this chapter, we introduce discernible sets. We prove that a discernible set of cardinality no greater than c(B) cannot be weakly dense. In chapter VI, we prove the main result of this dissertation, i.e., d(B) ≤ min(2^< wd(B),sup{λ^c(B): λ < wd(B)}). In chapter VII, we list some unsolved problems concerning this dissertation.

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Single levitated microdroplets of sodium chloride, potassium chloride, and natural seawater are investigated under conditions similar to that in the troposphere by using the electrodynamic balance technique. The thermodynamics and the kinetics of liquid-to-solid phase transitions have been investigated as a function of temperature and humidity. The temperature dependence of the critical partial pressure of water vapor over aqueous supersaturated aerosol droplets allows us to determine negative values for the integral heat of solution of KCl, NaCl and Mediterranean Sea droplets. In addition, the rates of homogeneous nucleation from supersaturated solution droplets are reported, where the data are fitted with three exponential functions to give three values for the nucleation rates. The phase transition processes which occur on different time scales are identified. The investigation of natural sea salt aerosol droplets collected from the Mediterranean Sea, Atlantic Ocean, Pacific Ocean, North Sea, and Suez Canal show that the phase change (liquid-to-solid) can occur at relative humidities that are greater than 33% RH, where the deliquescence humidity of MgCl2 is known to occur. It is found that there are slight variations (either a decrease or an increase) in water vapor pressure over the supersaturated aerosol droplets due to the change in water salinity, organic components that are present in the water sample, the depth, where the water sample is gathered, and its geographic location. The experimental results show that the presence of the organic substances in the aerosol particles affects the crystallization process depending on the amount and the type of the organic substance. It is observed that adding 1-heptanol to a NaCl droplet increases the crystallization diameter, which is attributed to the formation of a layer of the organic substance on the droplet surface, so that water evaporation cannot efficiently occur.

To meet the educational needs and acceleration of talented and gifted (TAG) students, it is important to determine the best learning environment to afford optimal academic success during their educational experience. A study at a Bartow County school district in Georgia has been conducted in order to establish this best learning environment. This study investigated if Lexile scores (ability) and academic averages (performance) differ for 6th grade TAG students in homogeneous classes compared to TAG students in heterogeneous settings. Vygotsky's theory of social constructivism, which proposes that students need to feel socially and cognitively supported by their environment, was the theoretical foundation of this study. Using a time series, quasi-experimental, between-group comparison, and a 2-group, nonequivalent control group design, this study analyzed archival data for reading, language arts, and social studies from sixth grade middle school TAG students (n = 43) who were enrolled in both homogenous and heterogeneous settings depending on the scheduling of the courses. The results revealed no significant differences in either the reading or language arts classes but did reveal a significant difference (p = .03) in the level of academic performance for social studies in homogeneous classes compared to students in heterogeneous classes. The findings may contribute to positive social change by informing educators about the utility of specific curricular content for TAG students in a particular setting.

With its unrivaled versatility and atom economy, olefin metathesis is arguably the most powerful catalyst methodology now known for the construction of carbon-carbon bonds. When compared to palladium-catalyzed cross-coupling methodologies, however, catalyst productivity lags far behind, even for the “robust” ruthenium metathesis catalysts. Unexpected limitations to the robustness of these catalysts were first widely publicized by reports describing the implementation of metathesis in pharmaceutical manufacturing. Recurring discussion centered on low catalyst productivity resulting from decomposition of the Ru catalysts by impurities, including ppm-level contaminants in the technical-grade solvent. Over the past 7 years, a series of mechanistic studies from the Fogg group has uncovered the pathways by which common contaminants (or indeed reagents) trigger catalyst decomposition. Two principal pathways were identified: abstraction of the alkylidene or methylidene ligand by nucleophiles, and deprotonation of the metallacyclobutane intermediate by Bronsted base. Emerging applications, however, notably in chemical biology, highlight new challenges to catalyst productivity. The first part of this thesis emphasizes the need for informed mechanistic insight as a guide to catalyst redesign. The widespread observation of a cyclometallated N-heterocyclic carbene (NHC) motif in crystal structures of catalyst decomposition products led to the presumption that activation of a C-H bond in the NHC ligand initiates catalyst decomposition. Reducing NHC bulk has therefore been proposed as critical to catalyst redesign. In experiments designed to probe the viability of this solution, the small NHC ligand IMe4 (tetramethylimidazol-2-ylidene) was added to the resting-state methylidene complexes formed in metathesis by the first- and second-generation Grubbs catalysts (RuCl2(PCy3)2(=CH2) GIm or RuCl2(H2IMes)(PCy3)(=CH2) GIIm, respectively). The intended product, a resting-state methylidene species bearing a truncated NHC, was not formed, owing to immediate loss of the methylidene ligand. Methylidene loss is now shown to result from nucleophilic attack by the NHC – a small, highly potent nucleophile – on the methylidene. Density functional calculations indicate that IMe4 abstracts the methylidene, generating the N-heterocyclic olefin H2C=IMe4. The latter is an even more potent nucleophile, which attacks a second methylidene, resulting in liberation of [EtIMe4]Cl. These findings report indirectly on the original question concerning the impact of ligand truncation. The ease with which a small, potent nucleophile can abstract the key methylidene ligand from GIm and GIIm underscores the importance of increasing steric protection at the [Ru]=CH2 site. This chemistry also suggests intriguing possibilities for efficient, selective, controlled methylidene abstraction to terminate metathesis activity while leaving the “RuCl2(H2IMes)(PCy3)” core intact. This could prove an enabling strategy for tandem catalysis applications in which metathesis is the first step. The second part of this thesis, inspired by the potential of olefin metathesis in chemical biology, focuses on the impact of hydroxide ion and water on the productivity of phosphine-free metathesis catalysts. In reactions with the important second-generation Hoveyda catalyst HII, hydroxide anion is found to engage in salt metathesis with the chloride ligands, rather than nucleophilic attack. The resulting Ru-hydroxide complex is unreactive toward any olefins larger than ethylene, while ethylene itself causes rapid decomposition. Proposed as the decomposition pathway is bimolecular coupling promoted by the strong H-bonding character of the hydroxide ligands. Lastly, the impact of the water on Ru-catalyzed olefin metathesis is examined. In a survey of normally facile metathesis reactions using state-of-the-art catalysts, even trace water (0.1% v/v) is found to be highly detrimental. The impact of water is shown to be greater at room temperature than previously established at 60 °C. Preliminary evidence strongly suggests that the mechanism by which water induces decomposition is temperature-dependent. Thus, at high temperature, decomposition of the metallacyclobutane intermediate appears to dominate, but this pathway is ruled out at ambient temperatures. Instead, water is proposed to promote bimolecular decomposition. Polyphenol resin, which can sequester water by H-bonding, is shown to offer an interim solution to the presence of trace water in organic media. These findings suggest that major avenues of investigation aimed at reducing intrinsic catalyst decomposition may likewise be relevant to the development of water-tolerant catalysts.

Cyclopropyl-containing substrates have been frequently utilized as "probes" for the detection of SET pathways in organic and biorganic systems. These reactions are based on the cyclorpropylcarbinyl → homoallyl rearrangement, which is fast and essentially irreversible. The implicit assumption in such studies is that if a "radical" species is produced, it will undergo ring opening. We have found that there are two important factors to consider in the design of SET probes: 1) ring strain, the thermodynamic driving force for the rearrangement, and 2) resonance energy, which may help or hinder rearrangement, depending on the specific system. Delocalization of spin and charge were found to be important factors pertaining to substituent effects on the rates of radical anion rearrangements. Previous studies from our lab have centered on highly conjugated phenyl cyclopropyl ketones. This work considers a series of compounds varying in their conjugative components from a highly conjugated spiro[2.5]octa-4,7-dien-6-one and derivatives to simple aliphatic ketones. Utilizing cyclic, linear sweep voltammetry, and preparative electrolysis techniques, it was discovered that all substrates yielded ring opened products with rates and selectivities that will prove useful and informative in the design of mechanistic probes based on the cyclorpropylcarbinyl → homoallyl rearrangement. Rates of homogeneous electron transfer from a series of hydrocarbon mediators to substrates were measured using homogeneous catalysis techniques. Standard reduction potentials and reorganization energies of substrates were derived using Marcus theory. Conjugative interactions with the cyclopropyl group are discussed. / Ph. D.

Two series of stable palladium and silver complexes ligated to hemilabile ligands were prepared. The stability and applicability of these well-defined complexes in promoting various reactions (cycloaddition, hydroamination, cross-coupling reactions, etc.) was investigated. Structure-activity studies with a series of related ligands led us to find a pronounced ligand effect on these reactions. The dichotomous reactivity of triethyl phosphonium hydrobromide salt with dialkyl acetals was used for the synthesis of alkoxy phosphonium salts. Reactivity and applications of these phosphonium salts were described for the synthesis of the biologically active cinnamyl triazoles and ethyl indole-2-carboxylates. Total synthesis of the natural product nostodione A, was developed in eight chemical steps and with 21.6% overall yield from ethyl-2-indolecarboxylates. The synthesis of a mini-panel of structural analogs allowed for the discovery of anti-parasitic biological activity of nostodione A and its analogues for the first time. / Thesis / Doctor of Science (PhD)