Proton-transfer reactions are one of the most fundamental chemical reactions. However, the chemical dynamics of these processes remain elusive due to the difficulty of modeling these reactions. Establishing an experimental model system and using infrared absorption and two-dimensional infrared (2D IR) spectroscopies as means for detection, the chemical dynamics of the protonation states that are involved in a ground-electronic-state proton-transfer reaction in solution can be determined. In this study, experimental models are established with formic acid and nitrogenous bases in a low dielectric solvent. A hydrogen bond forms between the acid and the base, which will allow for the proton to transfer between the two molecules to form the neutral and the ion-pair protonation states. The carbon-deuterium (C-D) stretch and the carbonyl (C=O) stretch of the formic acid molecule are used as the reporter groups for the 2D IR measurements. The results of the C-D stretch demonstrate that there is a high sensitivity to the deprotonation, vibrational coupling, and vibrational dynamics trends that are linked to the solute-solvent interactions. The results of the C=O stretch demonstrate a sensitivity to the deprotonation and conformational disorder in which the position of the C=O changes the dynamics of the protonation state. Although, a proton-transfer is not detected, the experimental model system provides an understanding of the features that govern the chemical dynamics of proton-transfer reactions.

Electron transfer is one of the fundamental process occurring in many chemical reactions. Electron transfer process has been under intensive study for many applications, for example artificial photosynthesis, where electrons from photo-excited chromophore molecules are harnessed to produce solar fuels in various forms. Transition metal complexes, such as ruthenium and rhenium complexes, play an important role in the continuing development of artificial photosynthetic devices. The electron transfer process in chromophores involving transition metal complexes often occurs on an ultrafast time scale from sub-ps to ns. To resolve such dynamics, ultrafast spectroscopic techniques are required. A variety of ultrafast techniques, such as time-resolved infrared spectroscopy and multi-pulse transient absorption spectroscopy, were used in this study to unravel the excited state electron transfer dynamics in a series of Re(I) complexes. Transition metal complexes often feature excited states that involve only partial electron transfer between the electron donating and accepting ligands, even for ligands with strong electron donating and accepting properties. It is often difficult to design a compact complex feature a full electron transfer excited state. Therefore, part of the work presented in this thesis was dedicated to the study of the electron transfer extent in the excited states of a series of [Re(N,N)(CO)3L]+ compounds, where N,N stands for electron accepting and L stands for electron donating ligands. By carefully designing the structure and redox properties of both the electron donor and acceptor, we demonstrated that essentially a full-electron charge transfer excited state can be prepared, while the designed Re(I) complex is still compact. To further extend the understanding of the electron transfer in transition metal complexes, modulation of the electron transfer rate in a compact Re(I) complex was studied. By perturbing the electron transfer process with a femtosecond mid-IR pulse, we showed that a 28% increase of the electron transfer rate was achieved. This study demonstrated the possibility of using a small energy mid-IR quanta to change the energy conversion process in a chromophore. Vibrational energy transfer in molecules is another important process in nature. Detailed understanding of the vibrational energy transfer on a molecule level is fundamentally important and essential for the development of molecular optical devices. It was recently discovered that the transport of vibrational energy in molecules can be fast and efficient due to its ballistic character. To understand the mechanism of the ballistic energy transport, experiments with several series of oligomers were performed using a relaxation-assisted two-dimensional infrared method. The energy transport speed was found to be dependent on transport initiation method and the transport pathways for different cases of initiation were identified. Detailed analysis on the chain band structure, group velocity and vibrational relaxation dynamics is presented. / acase@tulane.edu

An analytical dispersion model has been derived to determine the distribution of velocities and concentrations of a tracer in a two-dimensional jet in a coflowing ambient fluid. The particular novelty of this model is that it bridges the gap between near-field (where initial momentum dominates behaviour) and far-field (where ambient turbulence is more important) domains. We describe this domain as the ???intermediate field???. In a literature review of coflowing jets we find several laboratory studies and models which can predict the velocities (and in some cases concentrations) in a 2D jet, however they all have shortcomings. None could fully account for ambient turbulence, and all were strictly near-field, i.e. they are unable to describe behaviour when ambient turbulence dominates the initial shear. A brief review of analytical far-field models was also undertaken. There are standard solutions for the dispersion of a 2D continuous source but none that allow for an initial source momentum or non-uniform velocity. As opposed to the near-field coflow approach used by other researchers we start from the far-field, modifying the simple diffusion models by perturbing the governing equations to allow for the initial momentum. Models are developed for both along-stream velocity and the concentration field of a tracer. From the velocity model, a comparison is made with experimental data available from one researcher (Wang, 1996) and an existing near-field coflow model PJCMERG (Davidson, 1989). The initial conditions (width and excess velocity) for our model are determined by Gaussian curve fitting to an arbitrary point in the near-field. The diffusivity parameter is used to adjust (tune) the model until the centreline velocity profile matches. We can always achieve this match and to a much closer degree than PJCMERG. There are no available laboratory or field data for concentrations of a tracer in a 2D coflowing jet although the near-field model PJCMERG does have a tracer component. We demonstrate how PJCMERG cannot converge to any far-field model, while our model provides a neat transition between the near-field and far-field. We have started the extension of the 2D model to the more common 3D situation although we have yet to carry out any comparisons with other models or data. The model development is included in an appendix for other researchers to pick up.

Coupled two-dimensional HPLC systems were developed for the separation of complex sample matrices. Low molecular weight polystyrene oligomers were used as model compounds for the development of these systems since the sample dimensionality of oligostyrenes could be defined and classified according to two sample characteristics. That is, oligostyrenes could be classed as a two-dimensional sample, where one sample dimension is the variation in the number of monomers that make up oligomeric units determining the weight of the polymer, with a second sample dimension being the variation in stereoisomerism of each oligomer. During this study it was found that by combining two separation dimensions consisting of C18 and carbon clad zirconia (CCZ) phases separation of oligostyrenes according to molecular weight and stereochemistry was possible in coupled two-dimensional systems. The C18 phase separated the sample according to molecular weight, while the CCZ phase separated the sample according to the stereochemistry. The stereoisomer separations of the oligostyrenes reported on the CCZ surface were far superior to those previously reported in the literature. The efficiency of the separation process in a coupled two-dimensional system was then evaluated by studying the variation in band variance of a test probe. The results of the study indicated that the performance of a two-dimensional separation process was highly dependent upon the mobile phase compatibility, even when solvents were completely miscible and of similar polarities. Extracts from 17 species of Australian native plants were examined for xanthine oxidase inhibitory activity, the enzyme responsible for the formation of the disease gout. Chromatographic separation was conducted on plant extracts found to possess significant inhibitory activity against xanthine oxidase, with an extract from the species Clerodendrum floribundum R. Br. found to possess the greatest activity of the species examined. A two-dimensional separation of a crude extract from Clerodendrum floribundum R. Br. was conducted using one of the developed HPLC systems, to illustrate the use of such a system for the separation of a non-model complex sample mixture / Doctor of Philosophy (PhD)

An analytical dispersion model has been derived to determine the distribution of velocities and concentrations of a tracer in a two-dimensional jet in a coflowing ambient fluid. The particular novelty of this model is that it bridges the gap between near-field (where initial momentum dominates behaviour) and far-field (where ambient turbulence is more important) domains. We describe this domain as the ???intermediate field???. In a literature review of coflowing jets we find several laboratory studies and models which can predict the velocities (and in some cases concentrations) in a 2D jet, however they all have shortcomings. None could fully account for ambient turbulence, and all were strictly near-field, i.e. they are unable to describe behaviour when ambient turbulence dominates the initial shear. A brief review of analytical far-field models was also undertaken. There are standard solutions for the dispersion of a 2D continuous source but none that allow for an initial source momentum or non-uniform velocity. As opposed to the near-field coflow approach used by other researchers we start from the far-field, modifying the simple diffusion models by perturbing the governing equations to allow for the initial momentum. Models are developed for both along-stream velocity and the concentration field of a tracer. From the velocity model, a comparison is made with experimental data available from one researcher (Wang, 1996) and an existing near-field coflow model PJCMERG (Davidson, 1989). The initial conditions (width and excess velocity) for our model are determined by Gaussian curve fitting to an arbitrary point in the near-field. The diffusivity parameter is used to adjust (tune) the model until the centreline velocity profile matches. We can always achieve this match and to a much closer degree than PJCMERG. There are no available laboratory or field data for concentrations of a tracer in a 2D coflowing jet although the near-field model PJCMERG does have a tracer component. We demonstrate how PJCMERG cannot converge to any far-field model, while our model provides a neat transition between the near-field and far-field. We have started the extension of the 2D model to the more common 3D situation although we have yet to carry out any comparisons with other models or data. The model development is included in an appendix for other researchers to pick up.

An analytical dispersion model has been derived to determine the distribution of velocities and concentrations of a tracer in a two-dimensional jet in a coflowing ambient fluid. The particular novelty of this model is that it bridges the gap between near-field (where initial momentum dominates behaviour) and far-field (where ambient turbulence is more important) domains. We describe this domain as the ???intermediate field???. In a literature review of coflowing jets we find several laboratory studies and models which can predict the velocities (and in some cases concentrations) in a 2D jet, however they all have shortcomings. None could fully account for ambient turbulence, and all were strictly near-field, i.e. they are unable to describe behaviour when ambient turbulence dominates the initial shear. A brief review of analytical far-field models was also undertaken. There are standard solutions for the dispersion of a 2D continuous source but none that allow for an initial source momentum or non-uniform velocity. As opposed to the near-field coflow approach used by other researchers we start from the far-field, modifying the simple diffusion models by perturbing the governing equations to allow for the initial momentum. Models are developed for both along-stream velocity and the concentration field of a tracer. From the velocity model, a comparison is made with experimental data available from one researcher (Wang, 1996) and an existing near-field coflow model PJCMERG (Davidson, 1989). The initial conditions (width and excess velocity) for our model are determined by Gaussian curve fitting to an arbitrary point in the near-field. The diffusivity parameter is used to adjust (tune) the model until the centreline velocity profile matches. We can always achieve this match and to a much closer degree than PJCMERG. There are no available laboratory or field data for concentrations of a tracer in a 2D coflowing jet although the near-field model PJCMERG does have a tracer component. We demonstrate how PJCMERG cannot converge to any far-field model, while our model provides a neat transition between the near-field and far-field. We have started the extension of the 2D model to the more common 3D situation although we have yet to carry out any comparisons with other models or data. The model development is included in an appendix for other researchers to pick up.

Les éléments de diffraction sont largement utilises aujourd'hui dans un nombre grandissant d'applications grâce à la progression des technologies de micro-structuration dans le sillage de la microélectronique. Pour un design optimal de ces éléments, des méthodes de modélisation précises sont nécessaires. Plusieurs méthodes ont été développées et sont utilisées avec succès pour des réseaux de diffraction unidimensionnel de différents types. Cependant, les méthodes existantes pour les réseaux deux dimensionnel ne couvrent pas tous types de structures possibles. En particulier, le calcul de l'efficacité de diffraction sur les réseaux métalliques à deux dimensionnel avec parois verticales représente encore une grosse difficulté pour les méthodes existantes. Le présent travail a l'objectif le développement d'une méthode exacte de calcul de l'efficacité de diffraction de tels réseaux qui puisse servir de référence. La méthode modale développée ici - dénommée -true-mode" en anglais - exprime le champ électromagnétique sur la base des vrais modes électromagnétiques satisfaisant les conditions limites de la structure 2D à la différence d'une méthode modale où les modes sont ceux d'une structure approchée obtenue, par exemple, par développement de Fourier. L'identification et la représentation de ces vrais modes 'a deux dimensions restait 'a faire et ce n'est pas le moindre des résultats du présent travail que d'y avoir conduit. Les expressions pour la construction du champ sont données avec des exemples de résultats concrets. Sont aussi fournies les équations pour le calcul des intégrales de recouvrement et des éléments de la matrice de diffusion.

This study evaluates a 1D and a 2D method for analyzing the combined effect of inland rainfall and hurricane-induced storm surge on a coastal floodplain. Horsepen Bayou near Clear Lake, southeast of Houston, Texas is vulnerable to storm surge, which can travel upstream into the Bayou and exacerbate flooding outside the designated floodplain. However, the current 100-year floodplain for this area is delineated using a 1D model without direct storm surge inputs. Additionally, floodplains with flat topography, like Horsepen, could be modeled more accurately using 2D models, instead of the traditional 1D approach. A 1D HEC-RAS model and a 2D XPSWMM model are used to compare the resulting floodplain from three historical storms and one synthetic storm. When compared to actual FEMA flood claims, the floodplains calculated by the 2D model are more representative of inundation hazard in Horsepen and therefore a better tool for evaluating flooding in the area.

Membrane proteins are involved in a number of disease pathologies and thus comprise a large number of drug targets. Determination of the high-resolution three-dimensional structure is essential for rational drug design, but several hurdles need to be overcome, primarily the over-expression and purification of said membrane proteins. Human leukotriene C4 synthase (hLTC4S), an 18 kDa integral membrane protein localized in the outer nuclear membrane of eosinophils and basophils, catalyzes the conjugation of LTA4 and reduced glutathione to produce LTC4. LTC4 and its metabolites LTD4 and LTE4 are the cysteinyl leukotrienes implicated in bronchoconstriction and inflammation pathways. The focus of my project involves optimizing the over-expression and purification of hLTC4S, which was heterologously expressed in Schizosaccharomyces pombe, purified by immobilized affinity chromatography, and finally "polished" with a buffer exchange step to remove excess co-purified lipids. The optimized protocol yielded ~1 mg of ~90% homogenous, pure protein per liter of cell culture. The finalized purified protein can then be used for further investigation of two-dimensional crystals by electron crystallography with the overall goal of structure determination.

No description available.