Browsing by Subject "AIC"
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Item Cyanide-catalyzed C-C bond formation: synthesis of novel compounds, materials and ligands for homogeneous catalysis(Texas A&M University, 2007-04-25) Reich, Blair Jesse EllynCyanide-catalyzed aldimine coupling was employed to synthesize compounds with 1,2-ene-diamine and ????-imine-amine structural motifs: 1,2,N,N'- tetraphenyletheylene-1,2-diamine (13) and (+/-)-2,3-di-(2-hydroxyphenyl)-1,2- dihydroquinoxaline (17), respectively. Single crystal X-ray diffraction provided solidstate structures and density functional theory calculations were used to probe isomeric preferences within this and the related hydroxy-ketone/ene-diol system. The enediamine and imine-amine core structures were calculated to be essentially identical in energy. However, additional effects-such as ???? conjugation-in 13 render an enediamine structure that is slightly more stable than the imine-amine tautomer (14). In contrast, the intramolecular hydrogen bonding present in 17 significantly favors the imine-amine isomer over the ene-diamine tautomer (18). Aldimine coupling (AIC) is the nitrogen analogue of the benzoin condensation and has been applied to dialdimines, providing the first examples of cyclizations effected by cyanide-catalyzed AIC. Sodium cyanide promoted the facile, intramolecular cyclization of several dialdimines in N,N-dimethylformamide, methanol, or dichloromethane/water (phase-transfer conditions) yielding a variety of six-membered heterocycles. Under aerobic conditions, an oxidative cyclization occurs to provide the diimine heterocycle. Cyanide-catalyzed aldimine coupling was employed as a new synthetic method for oligomerization. Nine rigidly spaced dialdimines were oxidatively coupled under aerobic conditions to yield conjugated oligoketimines and polyketimines with unprecedented structure and molecular weight (DP = 2 - 23, ~700 -8200 g/mol). The ????- diimine linkage was established based on IR spectroscopy, NMR spectroscopy, size exclusion chromatography, and X-ray crystallographic characterization of the model oxidized dimer of N-benzylidene-(p-phenoxy)-aniline. Cyclic voltammetry indicates ptype electrical conductivity, suggesting they are promising candidates for plastic electronic devices. The cyanide-catalyzed benzoin condensation reaction of 4-substituted benzaldehydes followed by oxidation to the diketone, and the Schiff Base condensation of two equivalents of o-aminophenol provides 2,3-(4-X-phenyl)2-1,4-(2- hydroxyphenyl)2-1,4-diazabutadiene. The ligand is given the moniker X-dabphol. These ligands are readily metallated to form M-X-dabphol complexes. The copper complexes catalytically fix CO2 with propylene oxide to yield propylene carbonate. DFT studies along with a comparison with Hammet parameters help validate and elaborate on the catalytic cycle and the catalytic results obtained. The nickel complex is competent for olefin epoxidation. Synthesis, characterization, X-ray structure, DFT analysis, and catalytic activity of the parent nickel dabphol complex are reported.Item Dynamic Relationships Between Immigrants and US Gross Domestic Product Using A Vector Error Correction Model (VECM)(2015-01-23) Regmi, GaneshDebate over immigration including the role visa policies and immigrants play in the US economy, especially effects on wages, gross domestic product (GDP), employment rate, and consumption remain unresolved. This study investigates the dynamic relationships among the selected economic variables and the number of immigrants to the United States. Variables included are annual total number of immigrants, US GDP, investment in education, national hourly wage rate, and energy consumption from 1964 to 2011. These variables are found to be non-stationary via augmented Dicky-Fuller tests and cointegrated with four cointegrating vectors. A vector error correction, therefore, is used in the analysis. Directed acyclic graphs are used to find contemporaneous causal relationships between the variables. DAGs showed, GDP and wage are source of information, energy both receives and provide information in the system, investment in education is only receiver of the information while immigrants are contemporaneously exogenous. Tests of exclusion find all the variables are in the cointegrating space suggesting all variables share long run relationships. Exogeneity test suggests that all variable responses to the perturbations in the long-run relationships. Result shows that in the short run, wage has a negative reaction to a shock in GDP. All variables except number of immigrants? response positively to one time innovations in investment in education. Increases in immigrants will has a negative effect on the other variables in short-run. The number of immigrants, in the short-run, do not respond in the innovations in the other variables. Similarly, any shock in energy consumption will not be responded by any the variables in short-run. Forecast error variance decompositions suggest in short-run a variable is mainly explained by itself; as one moves time ahead forecast the share of other variables becomes larger in explaining a variables forecast error. Wages explain a large amount of the variability in investment in education. All the variables are cointegrated and any policies implemented to increase or decrease a single variable has effect on other rest of the variables. So policy maker should consider the macroeconomic effect in the system.Item Factor Analysis for Skewed Data and Skew-Normal Maximum Likelihood Factor Analysis(2013-04-04) Gaucher, Beverly JaneThis research explores factor analysis applied to data from skewed distributions for the general skew model, the selection-elliptical model, the selection-normal model, the skew-elliptical model and the skew-normal model for finite sample sizes. In terms of asymptotics, or large sample sizes, quasi-maximum likelihood methods are broached numerically. The skewed models are formed using selection distribution theory, which is based on Rao?s weighted distribution theory. The models assume the observed variable of the factor model is from a skewed distribution by defining the distribution of the unobserved common factors skewed and the unobserved unique factors symmetric. Numerical examples are provided using maximum likelihood selection skew-normal factor analysis. The numerical examples, such as maximum likelihood parameter estimation with the resolution of the ?sign switching? problem and model fitting using likelihood methods, illustrate that the selection skew-normal factor analysis model better fits skew-normal data than does the normal factor analysis model.