Direct hydrocarbon fuel cells are fuel cells than use hydrocarbons directly as fuel instead of the most commonly used fuel in a fuel cell, hydrogen. Studies are being done on direct hydrocarbon fuel cells because they have the potential to be energetically more efficient than hydrogen fuel cells. There are many different hydrocarbons that are available to use as a feed stock and each one reacts at different reaction rates. As the current density of a fuel cell is linked to the reaction rate, it is important to know the energetics of an oxidation reaction that is occurring. Density Functional Theory (DFT) is a technique that can be used to predict the energy states of intermediate reaction steps in a given mechanism. The focus of this study is the using DFT to explore the energetics of the oxidation of ethane to ethylene in a nickel-anode catalyst fuel cell. DFT was used in adsorption runs to optimize the geometries beginning (adsorbed ethane) and end (adsorbed ethylene) of the oxidation reaction. DFT was then used to calculate the energy of transition states by varying bond lengths. It was determined the removal of the second hydrogen from the ethyl radical is the most energy intensive step and, thus, the rate limiting step. Hydrogen, ethane, and ethylene were all explored in this study. The heats of adsorption varied from largest to smallest in the order of ethylene, hydrogen, and ethane. It was determined that the heat of adsorption of hydrogen is sufficient to meet the energy requirements for the dissociation reaction. This may help explain why hydrogen reacts so readily in fuel cells. Conversely, the heats of adsorption for the hydrocarbons did not meet the energy requirements for the dissociation reactions. This may help explain why ethane and ethylene react more slowly in a fuel cell as compared to hydrogen. Also, the oxidation of ethane to ethylene requires two large activation energies. These two additional activation energies may help explain why ethylene reacts more readily than ethane in a fuel cell.

Parkinson's disease (PD) is a progressive neurodegenerative and movement disorder that involves specific loss of dopaminergic neurons in the substantia nigra of the brain. Exact causes of PD are unknown. However, cells affected in PD are centers of dopamine (DA) synthesis, storage, and metabolism, which implicate DA as an endogenous neurotoxin that contributes to PD. Furthermore, DA is known to undergo oxidation to radicals and quinones. These reactive species exert deleterious effects on cells through a variety of mechanisms that are relevant to the pathogenesis of PD. Another potential mechanism of toxicity for DA is metabolism to 3,4-dihydroxyphenylacetaldehyde (DOPAL). This reactive metabolite is significantly more toxic than the parent DA. DOPAL has several demonstrated mechanisms of toxicity, including formation of protein-adducts via reaction with amine-type cellular nucleophiles. However, known toxicity mechanisms do not fully account for DOPAL's high toxicity. Oxidation of DOPAL to a reactive quinone or radical could help explain its high toxicity. Therefore, the hypothesis of this work is that DOPAL is capable of undergoing oxidation that leads to increased protein modification and nucleophilic reactivity. Experimentally, oxidation of DOPAL results in formation of a semi-quinone radical and an ortho-quinone, as confirmed by electron paramagnetic resonance spectroscopy and nuclear magnetic resonance spectroscopy, respectively. In agreement with the stated hypothesis, oxidation of DOPAL enhanced its ability to induce protein cross-linking of a model protein (glyceraldehyde 3-phosphate dehydrogenase) as indicated by polyacrylamide gel-electrophoresis. Also, the presence of anti-oxidants (ascorbate, N-acetyl cysteine) attenuated the reactivity of DOPAL with the model aminenucleophile N-acetyl lysine. These results indicate that DOPAL oxidation enhances both protein cross-linking and nucleophilic reactivity. This work resulted in several other important findings. DOPAL is shown to undergo carbonyl-hydration in aqueous media, and spontaneous oxidation of DOPAL results in formation of superoxide. Furthermore, DOPAL is shown to be susceptible to oxidation by cyclooxygenase-2, an enzyme known to be involved in PD. This provides a potential mechanism for formation of the oxidized products identified here. As DA metabolism and oxidation occur in cells affected by PD, the experimental results demonstrated here are likely relevant for understanding the pathogenesis of PD.

Ab Initio calculations suggest that partially lithiated layered LixMnO₂ transforms to spinel in a two-stage process. In the first stage, a significant fraction of the Mn and Li ions rapidly occupy tetrahedral sites, forming a metastable intermediate. The second stage involves a more difficult coordinated rearrangement of Mn and Li ions to form spinel. This behavior is contrasted to LixCoO₂. The susceptibility of Mn for migration into the Li layer is found to be controlled by oxidation state which suggests various means of inhibiting the transformation. These strategies could prove useful in the creation of superior Mn based cathode materials. / Singapore-MIT Alliance (SMA)

Replacement of thymidine in DNA by halopyrimidines, such as bromodeoxyuridine (BrdU) and iododeoxyuridine (IdU), has long been known to enhance DNA damage and cell death induced by ionizing/UV radiation, but the mechanism of action of halopyrimidines at the molecular level is poorly understood. We have applied advanced time-resolved femtosecond laser spectroscopy to this molecular system of biological, chemical and medical significance. We obtained the first real-time observations of the transition states of the ultrafast electron transfer (UET) reactions of halopyrimidines with the ultrashort-lived precursor to the hydrated electron, which is a general product in ionizing/UV radiation. Our results provide a mechanistic understanding of these photo-/radiosensitizing drugs at the molecular level. We found that the UET reaction of BrdU is completed within 0.2 picosecond (ps) after the electronic exciataion, leading to the formation of the transition state BrdU* with a lifetime of ~1.5 ps that then dissociates into Br and a high reactive radical dU•. We have also demonstrated that the reaction efficiency for the formation of the reactive radical dU• to cause DNA damage and cell death is in the order of IdU>>BrdU>CldU>>FdU. This is due to the availability of two precursor states of ~0.2 ps and ~ 0.54 ps lifetimes for dissociative electron attachment (DEA) to IdU, of one precursor state of ~0.2 ps lifetime for DEAs to BrdU and CldU, and no precursors for DEA to FdU. This explains why BrdU and IdU were found to be effective radio-/photosensitizers and indicates that IdU should be explored as the most effective radiosensitizer among halopyrimidines. Moreover, as a by-product of this project, these halopyrimidines have been employed as quantum-state-specific molecular probes to resolve a long-standing controversy about the nature and lifetimes of prehydrated electrons. These findings also have a broader significance as they indicated that nonequilibrium precursor electrons may play an important role in electron-initiated reactions in many biological, chemical and environmental systems. We have also demonstrated UET reactions of nucleotides with the precursor to the hydrated electrons. Our results indicate that among DNA bases, adenine is the most efficient electron trapper and an effective electron transfer promoter, while guanine is the most effective in dissociative electron attachment. These results not only primarily explain the sequence selectivity of duplex DNA containing BrdU/IdU, but imply that the DEA of guanine is an important mechanism for radiation-induced DNA damage in ionizing radiation and radiotherapy of cancer.

Replacement of thymidine in DNA by halopyrimidines, such as bromodeoxyuridine (BrdU) and iododeoxyuridine (IdU), has long been known to enhance DNA damage and cell death induced by ionizing/UV radiation, but the mechanism of action of halopyrimidines at the molecular level is poorly understood. We have applied advanced time-resolved femtosecond laser spectroscopy to this molecular system of biological, chemical and medical significance. We obtained the first real-time observations of the transition states of the ultrafast electron transfer (UET) reactions of halopyrimidines with the ultrashort-lived precursor to the hydrated electron, which is a general product in ionizing/UV radiation. Our results provide a mechanistic understanding of these photo-/radiosensitizing drugs at the molecular level. We found that the UET reaction of BrdU is completed within 0.2 picosecond (ps) after the electronic exciataion, leading to the formation of the transition state BrdU* with a lifetime of ~1.5 ps that then dissociates into Br and a high reactive radical dU•. We have also demonstrated that the reaction efficiency for the formation of the reactive radical dU• to cause DNA damage and cell death is in the order of IdU>>BrdU>CldU>>FdU. This is due to the availability of two precursor states of ~0.2 ps and ~ 0.54 ps lifetimes for dissociative electron attachment (DEA) to IdU, of one precursor state of ~0.2 ps lifetime for DEAs to BrdU and CldU, and no precursors for DEA to FdU. This explains why BrdU and IdU were found to be effective radio-/photosensitizers and indicates that IdU should be explored as the most effective radiosensitizer among halopyrimidines. Moreover, as a by-product of this project, these halopyrimidines have been employed as quantum-state-specific molecular probes to resolve a long-standing controversy about the nature and lifetimes of prehydrated electrons. These findings also have a broader significance as they indicated that nonequilibrium precursor electrons may play an important role in electron-initiated reactions in many biological, chemical and environmental systems. We have also demonstrated UET reactions of nucleotides with the precursor to the hydrated electrons. Our results indicate that among DNA bases, adenine is the most efficient electron trapper and an effective electron transfer promoter, while guanine is the most effective in dissociative electron attachment. These results not only primarily explain the sequence selectivity of duplex DNA containing BrdU/IdU, but imply that the DEA of guanine is an important mechanism for radiation-induced DNA damage in ionizing radiation and radiotherapy of cancer.

Mitochondrial dysfunction plays a pivotal role in the development of aging phenotypes and aging-associated neurodegenerative disorders, such as Alzheimer’s disease (AD), Parkinson’s disease (PD) and Amyotrophic lateral sclerosis (ALS). Strategies that restore mitochondrial dysfunction may rescue the deficits of central metabolism in these disorders and improve cell survival. For example, we found that modulating the mTOR signaling pathway in a tissue culture model of aging-induced mitochondrial DNA mutation enhanced mitochondrial function as evidenced by increased oxygen consumption. Our previous melatonin studies also led us to hypothesize that caloric restriction and the hormone melatonin would reverse brain mitochondrial dysfunction in animal models of AD. Although caloric restriction did not improve mitochondrial function in a transgenic P301L tau model of AD, novel insight into the regulation of F0-F1 ATP synthase activity under CR was gained that may help explain the protective effects of CR in other disease models. In addition, we determined the effects of melatonin treatment on brain mitochondrial cytochrome c oxidase (COX) activity using the transgenic APPSWE mouse model of AD bred to double melatonin receptor (MT1 and MT2) knockout mice. COX activity declined with aging in control mice, but increased with aging in AD mice, most likely as a response to mitochondrial reactive oxygen species (ROS) induced by amyloid-beta generated through APP proteolysis. Both effects were blunted by melatonin treatment. The effects of melatonin were partially dependent on the G-protein coupled melatonin receptors. We also used PD models to identify therapies that restore mitochondrial dysfunction. We showed that overexpression of wild-type alpha synuclein (α-syn) in human neuroblastoma M17 cells resulted in mitochondrial oxygen consumption deficits; similar to the levels observed when PD mutant forms (A30P α-syn, E46K α-syn, and, A53T α-syn) were overexpressed. Mitochondria from cells overexpressing α-syn were more sensitive to a high iron environment, mimicking the physiological conditions in which dopaminergic neurons are found. Diethyl oxaloacetate, succinate, and several amino acids were protective, suggesting the possibility for effective dietary interventions for PD. Lastly, we delineated the level of mitochondrial complex IV activity between gray and white matter in human cervical and lumbar spinal cord, as well as mitochondrial aggregation in the entire neurovascular units (NVU) as a consequence of ALS. At the conclusion of these projects a better understanding of the molecular mechanisms leading to mitochondrial dysfunction in AD, PD, ALS, and aging was gained and promising strategies to delay or reverse these dysfunctions were developed.

Defining and measuring the quality of customer service has been a major challenge for business-to-business marketers. This research addresses the question whether an established instrument for consumer markets (SERVQUAL) can be used for understanding the role of customer service in the European nylon intermediates industry. To accomplish this objective, an in-depth literature review is accomplished followed by several expert panels adopting the instrument slightly. Based on a survey sample of 110 industry members collected with the 'drop and collect technique' the appropriateness of the tool to verify the anticipated structure is examined using reliability tests as well as exploratory and confirmatory factor analysis. The findings suggest that even though various criteria for reliability and validity are met, the five-dimensional structure of the instrument cannot be recovered. The research questions the usefulness of the instrument for the European nylon intermediates industry despite it being originally anticipated to be applicable. However, the research emphasises that the instrument is a useful indicator for understanding the role of customer service based on individual items rather than on the instrument's dimensionality. It is demonstrated how the implementation in the nylon intermediates industry enables an organization to develop a greater awareness of customer service quality and how an enterprise gains an initial instrument to comprehend and improve this element of the offering. The thesis concludes by linking the results of the research with the discussion on service-dominant logic.

Scanning electrochemical microscopy (SECM) was used for the study and characterization of catalytic and electrocatalytic processes occurring at electrodes. The Surface Interrogation mode (SI-SECM) was introduced for the detection and quantification of adsorbed intermediates and products of catalyzed chemical and electrochemical reactions at noble metals (Pt, Au). In SI-SECM two micro electrodes (i.e. an SECM tip and a substrate of the desired material) are aligned concentrically at a micrometric distance where SECM feedback effects operate. A contrast mechanism based on feedback effects allows for the detection of reactive adsorbed intermediates at the substrate: the SECM tip generates a reactive homogeneous species that “micro-titrates” the substrate adsorbates to yield an electrochemical signal that contains information about the amount of intermediate and about its kinetics of reaction with the redox mediator. The technique was used for the study of the reactivity of three model small adsorbates: 1) the reactivity of adsorbed oxygen on Au and Pt with a reducing mediator was explored and suggested the detection of “incipient oxides” at these surfaces; kinetic parameters of the reactivity of Pt oxides with mediators were obtained, fit to theory and used to explain observations about the electrocatalytic behavior of Pt under anodizing conditions; 2) the reactivity of oxidizing mediators with adsorbed hydrogen on Pt was studied and showed the cation of N,N,N,N-tetramethyl-p-phenylenediamine (TMPD) to be a successful interrogation agent, the detection of hydrogen generated by the decomposition of formic acid on Pt at open circuit was investigated; 3) electrogenerated bromine was used to catalytically interrogate carbon monoxide at Pt, this reaction was previously unreported. The mentioned applications of SECM were validated through the use of digital simulations of diffusion in the complex SECM geometry through flexible commercial finite element method software. / text

Radicals are interesting to study because of importance in so many processes such as semiconductor growth or stellar evolution. Laser induced fluorescence (LIF) and wavelength resolved emission spectra of jet cooled HPS, HAsO, AsD2, H2PS, and F2BO have been measured using the pulsed discharge jet technique. Several bands in the à 1A′′ − X̃ 1A′ transition of HPS were observed and assigned with the help of ab initio calculations. The ab initio geometries showed that HPS does not follow Walsh’s predictions for the angle change upon electronic excitation; Walsh predicts an increase in HPS upon excitation while a decrease is calculated. Ab initio Walsh-style orbital angular correlation diagrams for both electronic states show a change in correlation for some orbitals upon electronic excitation, an effect that Walsh did not predict. The à 1A′′ − X̃ 1A′ transitions were measured in HAsO and DAsO for the first time. A molecular geometry was derived for each electronic state from experimental rotational constants. The experimental geometries prove that HAsO also violates Walsh’s rules for the same reason shown in HPS. The à 2A1 – X̃ 2B1 electronic transition of AsD2 and AsHD were measured. Vibrational levels observed in emission were fit to a local mode vibrational Hamiltonian. Using the previously reported rotational constants for AsH2 and those determined for AsD2 in this work, an improved estimate of the excited state geometry was obtained. The discovery of the B̃ 2A′ − X̃ 2A′ band system of H2PS is the first report of this molecule. Both D2PS and HDPS were also observed. Ab initio calculations helped assign the transition. H2PS is one of the few tetra-atomic or larger molecules that violates Kasha’s empirical rule due to the large separation between the B̃ and à states. Finally, laser induced fluorescence spectra of the F2BO radical was observed for the first time. Previous work showed two band systems with only a tentative assignment. The measured LIF spectra confirm the identity of the two band systems as the B̃ 2A1 – X̃ 2B2 and the B̃ 2A1 – à 2B1 transitions showing F2BO also violates Kasha’s rule.

The study of catalysis is a fundamental aspect of chemical engineering, as its implications affect all chemical transformations. Traditionally, catalysis has been subdivided into two areas: homogeneous and heterogeneous catalysis. Homogeneous catalysis refers to single-sited catalysts that exist in the same phase as the reaction media. These catalysts tend to be highly active and selective but often difficult to recover and reuse. In contrast, heterogeneous catalysts are typically multi-sited catalysts that exist in a different phase from the reaction media. These catalysts tend to be less active and selective than their homogeneous counterparts. However, the vast majority of industrial scale catalysts are heterogeneous because they can be easily separated, making them easily implemented in continuous processes, allowing for efficient, large scale operations. Due to the limitations of traditional homogeneous and heterogeneous catalysts, researchers have increasingly investigated hybrid catalysts that incorporate aspects of homogeneous and heterogeneous catalysis. This is accomplished via immobilization of homogeneous catalyst analogues onto solid-phase supports, thereby preserving the activity and selectivity of homogeneous catalysts while allowing for facile recovery and reuse from the insoluble, heterogeneous support. A variety of systems is presented here including organic and organometallic catalysts immobilized on organic and inorganic supports. Five cases are included. The first discusses utilization of supported acid and base catalysts for use in one-pot cascade reactions. The second example illustrates use of silica-coated magnetic nanoparticle supported acid catalysts for organic transformations. The third case presents novel polymer brush supported Cobalt-salen catalysts for the enantioselective, hydrolytic kinetic resolution of epoxides. A fourth case presents novel, magnetic polymer brush supported organic and organometallic catalysts for organic transformations. The fifth example illustrates polymer and silica supported ruthenium-salen catalysts for the asymmetric cyclopropanation of olefins. The overall goal of this thesis work is to develop novel supports and immobilization techniques to advance the field of hybrid organic/inorganic catalysts for the production of fine chemical and pharmaceutical intermediates.