The reaction between o-phenylenediamine and 2,3-dichloromaleic anhydride has been probed and found to give 2,3-dichloropyrrolo[1,2-a]- benzimidazol-1-one as the major product. Chlorine substitution in 2,3-dichloropyrrolo[1,2-a]benzimidazol-1-one by added benzylthiol occurs in the presence of pyridine to provide the corresponding monosulfide and disulfide derivatives. The first benzylthiol ligand undergoes reaction at the C-3 position of the five-membered pyrrolo-1-one ring, with the addition of the second benzylthiol ligand occurring at the remaining chlorine-substituted carbon. The mono- and disulfide derivatives have been isolated and characterized in solution by NMR, IR, and UV-vis spectroscopies, and the solid-state structure of 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one has been established by X-ray crystallography.

Two-dimensional molybdenum disulfide (MoS2) as a novel semiconducting material has drawn tremendous interest in the research field. As a van der Waals layered material, the weak interlayer binding enables the preparation of ultra-thin (few- or monolayer) samples. Due to its ultra-thin nature and advanced optical and electronic properties, it is considered as one of the promising candidates for flexible optoelectronic devices such as transistors, photodetectors and light emitting diodes. In the past decade, numerous progresses have been made to improve the performance of MoS2 devices, where developing doping techniques and lowering the contact resistance have been two major approaches under study. In this thesis, a novel method was created to prepare two-dimensional molybdenum nitrides via chemical conversion of MoS2. Molybdenum nitrides are highly conductive and robust. More importantly, the method we developed holds the promise to integrate ultrathin molybdenum nitrides with MoS2 in lateral heterostructures with atomically seamless connection. Such structures are promising to form low resistance contact for MoS2. In addition, a method to achieve the tunable n-type doping of MoS2 via surface adsorption of carbon species was also developed. With a high tunability and stability of dopant concentration, this method is expected to facilitate the fabrication of MoS2-based semiconductor devices.

The primary objective of this study was to examine changes in resource productivity and factor shares as irrigation was introduced on small rice farms using traditional management techniques. Average output on irrigated farms was double that of dry farms. This was because irrigated farms produced two crops as opposed to one crop on farms without irrigation. Examination of marginal products showed that farmers with irrigation could profitably use more land. Dry farmers could profitably use more labor. The low labor input and high MP of labor on dry farms occurs because these farmers are undercapitalized and are obliged to accept off-farm employment at crucial periods of the rice . growing season. On both farm types, irrigated and dry, factor shares of land were high suggesting that a redistribution of land would also redistribute income. This information provides criteria for formation of rice production policy in Ecuador.

A game theoretic approach is used to analyze an inventory problem with two products, random demand, and random supply. The supply chain analyzed includes two retailers that sell two substitutable products and two suppliers. Each retailer faces a stochastic demand for the product she sells and replenishes her inventory from her supplier. The supplier provides a random fraction of the quantity requested. A given percentage of customers with unmet demand will substitute the product sold by the other retailer. We assume that the two retailers who make ordering decisions are rational players. Since each retailer's decision affects the single period expected profit of the other retailer, game theory is used to find the order quantities when the retailers use a Nash strategy.

Most phylogenetic trees are inferred using time-reversible evolutionary models that assume that the relative rates of substitution for any given pair of nucleotides are the same regardless of the direction of the substitutions. However, there is no reason to assume that the underlying biochemical mutational processes that cause substitutions are similarly symmetrical. Here, we evaluate the effect on phylogenetic inference in empirical viral and simulated data of incorporating non-reversibility into models of nucleotide substitution processes. I consider two non-reversible nucleotide substitution models: (1) a 6-rate nonreversible model (NREV6) that is applicable to analyzing mutational processes in double-stranded genomes in that complementary substitutions occur at identical rates; and (2) a 12-rate non-reversible model (NREV12) that is applicable to analyzing mutational processes in single-stranded (ss) genomes in that all substitution types are free to occur at different rates. Using likelihood ratio and Akaike Information Criterion-based model tests, we show that, surprisingly, NREV12 provided a significantly better fit than the General Time Reversible (GTR) and NREV6 models to 21/31 dsRNA and 20/30 dsDNA datasets. As expected, however, NREV12 provided a significantly better fit to 24/33 ssDNA and 40/47 ssRNA datasets. I tested how non-reversibility impacts the accuracy with which phylogenetic trees are inferred. As simulated degrees of non-reversibility (DNR) increased, the tree topology inferences using both NREV12 and GTR became more accurate, whereas inferred tree branch lengths became less accurate. I conclude that while non-reversible models should be helpful in the analysis of mutational processes in most virus species, there is no pressing need to use these models for routine phylogenetic inference. Finally, I introduce a web application, RpNRM, that roots phylogenetic trees using a non-reversible nucleotide substitution model. The phylogenetic tree is rooted on every branch and the likelihoods of each rooting are determined and compared with the highest likelihood tree being identified as that with the most plausible rooting. The rooting accuracy of RpNRM was compared to that of the outgroup rooting method, the midpoint rooting method and another non-reversible model-based rooting method implemented in the program IQTREE. I find that although the RpNRM and IQTREE reversible model-based methods are not as accurate on their own as outgroup or midpoint rooting methods, they nevertheless provide an independent means of verifying the root locations that are inferred by these other methods.

<p> This thesis deals with 0-substituted carbenium ions. In particular, the relationship between the pattern of substitution and the nature of the charge distribution in the ion are probed by looking at the effects of systematic substituent change on bond distances.</p> <p> The model system employed in this investigation is the 1,3-dioxolan-2-ylium ion. A series of five ions were investigated by the preparation of single crystals which were studied using x-ray crystallography.</p> <p> The carbon oxygen bond distances around the five-membered dioxolanylium ring were found to be sensitive to changes in methyl substitution at position 4 of the ring. As methyl substitution at this position was increased systematically, an increase in the C4-03 carbon oxygen bond distance was observed.</p> <p> Changes in the substituent at position 2 of the dioxolanylium ring also had an effect on carbon oxygen bond distances but of a lesser magnitude than those brought about by methyl substitutions at position 4. The importance of these changes in structure are discussed in terms of the charge distribution in the cations.</p> / Thesis / Master of Science (MSc)

Macro lambda is a parameter for predicting the weight savings for using different material. Macro lambda approximates the response of a thin-walled structure to a change in material thickness. The relationship between macro lambda and weight savings for material substitution is given. The results of nine major joints for a car cab model are given. Two kinds of structural element for weight advantage of aluminum, magnesium and other light materials are given: curved beam in-plane bending, curved beam out-of-plane bending. Bulkhead reinforcement is given for a T-Joint model. The application shows a dramatic reduction of macro lambda for T-Joint x moment and y moment load, which means the weight advantage of light materials is reduced after the reinforcement applied. For the z moment load T-Joint model, adding center layer reinforcement gives the largest reduction of macro lambda and maximum von Mises stress. The bulkhead reinforcement is then used for two car cab joints: B-pillar to rocker joint and hinge pillar to rocker joint. The results indicate that the bulkhead reinforcement near the center area gives the biggest reduction for macro lambda. Micro lambda, which is a value for element level, is introduced. The relationship between micro lambda and force distribution is given. Then it is used for the analysis of the force distribution along curved beam model when the thickness of the model is doubled. The results indicate that the force is redistributed from the corner to center of the flange for the curved beam model. So for curved beam model, light material such as aluminum, magnesium, which is thicker, is more efficiently used than steel. Micro lambda is used for the analysis of B-pillar to rocker joint of a car cab. The result indicates that the maximum micro lambda area is just the area where we apply the optimum bulkhead reinforcement. Micro lambda is also used for the analysis of AISI PNGV bending model. The result shows that the C-pillar area is the major problem area. Several reinforcements for the C-pillar area are given. The result shows that layer 31172 is most important for increasing the stiffness.

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This dissertation describes two essays in empirical international trade, focusing on trade costs and the pattern of trade along the intensive and extensive margins. In the first essay, I study the barriers that impede international trade. In the second paper, I examine the growth of U.S. agricultural trade in detail describing how U.S. agriculture and food trade has expanded along the margins. The first chapter introduces a relatively straightforward, yet empirically powerful, manipulation of the gravity equation. The gravity model has been dubbed the work horse model of empirical trade, and thus is a suitable foundation from which to derive an indirect measure of largely unobservable 'iceberg' trade costs. In this paper, I solve a sector level version of the gravity equation and study the pattern of agricultural trade costs and factors that impede world agricultural trade growth over a long time series, 1986-2011. In addition, I estimate sector-specific elasticity of substitution which is a key parameter in the computation of trade cost. In the second essay, I examine the growth of world and U.S. agricultural exports along the intensive and extensive margins of international trade over the period 1986 to 2010. The purpose of this essay is to decompose the growth of world and U.S. agricultural trade using qualitative methods from the marketing literature (i.e., market expansion grids) but modified to fit bilateral trade relationships and a theoretical index to measure the margins of trade at a single point in time. In addition, we examine often overlooked channels by which U.S. agricultural exports have expanded using very detailed agricultural product lines. Using information related to the pattern of a trade rather than trade volume itself, I estimate how much starting a trade relationship with a new partner or in a new product variety matters to agricultural trade growth and then conclude with a set of stylized facts to inform current theory. / Ph. D.