Isoprene (2-methyl-1,3-butadiene) is the most abundant non-methane hydrocarbon mostly emitted from the trees and its oxidation by hydroxyl radical contributes significantly to the tropospheric ozone production. We investigate the development of a detailed predictive mechanism for isoprene oxidation using both theory and experiment. We have identified a novel cyclization pathway for the radicals formed by hydroxy radical (OH) addition to the inner carbons of isoprene. The pathway predicted that C5 carbonyl compounds are produced, and it may also provide information on the preference of sites for OH addition. The nitrite/nitrate isomerization is directly related to the competition between ozone production and radical termination and was investigated using variational RRKM theory coupled with the master equation. We find that the dominant fate of the β-hydroxy alkoxy radicals produced from the dissociation reaction of nitrite is a prompt dissociation, whereas δ-hydroxy radicals isomerize to form dihydroxy radicals. We have performed experiments using laser photolysis (LP)/ laserinduced fluorescence (LIF) spectroscopy to study the initial addition reaction of the hydroxyl radical to isoprene. The overall reaction rates were estimated from experiments conducted at various pressures and temperatures. The determined Arrhenius rates are k∞(T) = (3.49±0.46)x10-11exp(366±40)/T molecule-1 cm3 s-1 and k∞(T) = (3.58±0.18)x10- 11exp(356±18)/T molecule-1 cm3 s-1, for the OH and OD addition reactions, respectively. Isoprene oxidation in the presence of O2 and NO was studied and, based on simulations to OH cycling curves, we determined a value of (9.0±3.0)x10-12 molecule-1 cm3 s-1 for the overall reaction rate constant of hydroxy peroxy radical with NO at 298 K. We report a rate constant for O2 addition to the hydroxy alkyl radical of (2.3±2.0)x10-12 molecule-1 cm3 s-1 at 298 K. We find little generation of OH from the OD initiated oxidation of isoprene, and no significant differences in OH and OD cycling, which suggests that the H-shift isomerization is the major pathway for δ-hydroxy alkoxy radicals in agreement with theoretical predictions.

Diplomová práce se zabývá připraveností Prahy na možné pořádání olympijských her v roce 2016 nebo 2020. Námět práce vychází z uvažované kandidatury Prahy a probíhajících diskuzí na toto téma. V první části práce je popisována příprava, organizace a finanční výsledky olympijských her v Aténách v roce 2004. Z aténských her jsou vyvozeny závěry pro pražskou kandidaturu. Druhá část práce analyzuje připravenost Prahy a ČR na možné pořádání olympijských her. Jsou zde uváděny hlavní problémy Prahy a ČR, které výrazně ohrožují možné pořádání her v plánovaných termínech.

EFFECTS OF 24R,25(OH)2D3 IN THE TERATMENT OF KNEE OSTEOARTHRITIS Qingfen Pan 117 Pages Directed by Dr. Barbara Boyan Osteoarthritis (OA) is a degenerative disease characterized by joint inflammation and cartilage degeneration due to matrix degradation and chondrocyte apoptosis. Previously, drug therapies have been developed that aim to ease pain and reduce local inflammation. Currently, no effective drug exists that has no significant side effects. Therefore, an unmet medical demand exists for development of tissue-engineering strategies to promote articular cartilage repair and regeneration to treat OA. 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3] is an attractive option for articular cartilage repair because of its anti-inflammatory and anti-apoptotic properties. 24R,25(OH)2D3, which is a naturally occurring metabolite of vitamin D3, also has not been shown to cause toxic side effects. Results from the study demonstrate that 24R,25(OH)2D3 can inhibit chondrocyte apoptosis and suppress the production of catabolic factors that result in cartilage degeneration in the in vitro model. Furthermore, although 24R,25(OH)2D3 regulates components of TGF-β1 pathway, the effect of 24R,25(OH)2D3 is not mediated through TGF-β1 signaling. In vivo delivery of 24R,25(OH)2D3 prevented cartilage degeneration and disease progression. In addition, intraarticular injection of 24R,25(OH)2D3 had an effect on cytokines and growth factors production both locally and systemically. Human articular chondrocytes responded to 24R,25(OH)2D3 treatment in both sex and maturation dependent manner. Collectively, results from this study suggest that 24R,25(OH)2D3 ccould be used as a clinical therapy for knee OA.

Cinematographic stereoscopic PIV, combined with Taylor's frozen flow hypothesis, is used to generate three-dimensional (3D) quasi-instantaneous pseudo volumes of the three-component (3C) velocity field in the far field of turbulent nonpremixed jet flames at jet exit Reynolds number Reδ in the range 8,000-15,300. The effect of heat release, however, lowers the local (i.e., based on local properties) Reynolds number to the range 1,500-2,500. The 3D data enable computation of all nine components of the velocity gradient tensor ∇u from which the major 3D kinematic quantities, such as strain rate, vorticity, dissipation and dilatation, are computed. The volumetric PIV is combined with simultaneously acquired 10 Hz OH planar laser-induced fluorescence (PLIF). A single plane of the OH distribution is imaged on the center-plane of the volume and provides an approximate planar representation of the instantaneous reaction zone. The pseudo-volumes are reconstructed from temporally and spatially resolved kilohertz-rate 3C velocity field measurements on an end-view plane (perpendicular to the jet flame axis) invoking Taylor's hypothesis. The interpretation of the measurements is therefore twofold: the measurements provide a time-series representation of all nine velocity gradients on a single end-view plane or, after volumetric reconstruction, they offer a volumetric representation, albeit approximate, of the spatial structure of the flow. The combined datasets enable investigation of the fine-scale spatial structure of turbulence, the effect of the reaction zone on these structures and the relationship between the jet kinematics and the reaction zone. Emphasis is placed on the energy dissipation field and on the presence and role of dilatation. Statistics of the components of the velocity gradient tensor and its derived quantities show that these jet flames exhibit strong similarities to incompressible turbulent flows, such as in the distribution of the principal strain rates and strain-vorticity alignment. However, the velocity-gradient statistics show that these jet flames do not exhibit small-scale isotropy but exhibit a strong preference for high-magnitude radial gradients, which are attributed to regions of strong shear induced by the reaction zone. The pseudo volumes reveal that the intense-vorticity field is organized in two major classes of structures: tube-like away from the reaction zone (the classical worms observed in incompressible turbulence) and sheet-like in the vicinity of the local reaction zone. Sheet-like structures are, however, the dominant ones. Moreover, unlike incompressible turbulence where sheet-like dissipative structures enfold, but don't coincide with, clusters of tube-like vortical structures, it is observed that the sheet-like intense-vorticity structures tend to closely correspond to sheet-like structures of high dissipation. The primary reason for these features is believed to be due to the stabilizing effect of heat release on these relatively low local Reynolds number jet flames. It is further observed that regions of both positive and negative dilatation are present and tend to be associated with the oxidizer and fuel sides of the OH zones, respectively. These dilatation features are mostly organized in small-scale, short-lived blobby structures that are believed to be mainly due to convection of regions of varying density rather than to instantaneous heat release rate. A model of the dilatation field developed by previous researchers using a flamelet approximation of the reaction zone was used to provide insights into the observed features of the dilatation field. Measurements in an unsteady laminar nonpremixed jet flame where dilatation is expected to be absent support the simplified model and indicate that the observed structure of dilatation is not just a result of residual noise in the measurements, although resolution effects might mask some of the features of the dilatation field. The field of kinetic energy dissipation is further investigated by decomposing the instantaneous dissipation field into the solenoidal, dilatational and inhomogeneous components. Analysis of the current measurements reveals that the effect of dilatation on dissipation is minimal at all times (it contributes to the mean kinetic energy dissipation only by about 5-10%). Most of the mean dissipation arises from the solenoidal component. On average, the inhomogeneous component is nearly zero, although instantaneously it can be the dominant component. Two mechanisms are believed to be important for energy dissipation. Near the reaction zone, where the stabilizing effect of heat release generates layers of laminar-like shear and hence high vorticity, solenoidal dissipation (which is proportional to the enstrophy) dominates. In the rest of the ow the inhomogeneous component dominates in regions subjected to complex systems of nested vortical structures where the mutual interaction of interwoven vortical structures in intervening regions generates intense dissipation. / text

A wide range of surface sensitive techniques (AES, LEED, A^, XPS, UPS and TDS) have been employed to study ultralhin films of copper with neodymium and the intimate interaction of neodymium oxide with a copper surface. This has involved the evaporation of the rare earth onto well defined surfaces of single crystal copper - Cu(100) and Cu(lll) -under ultrahigh vacuum conditions. Such systems may serve as a model for the fundamental processes occurring at the surface of methanol synthesis catalysts derived from intermetallic compounds of copper and rare earth metals. The work aims to characterise the films with regard to structure, electronic interactions, chemisorption properties and reactivity. It is shown that the deposition conditions determine the morphology and properties of the thin films produced; more specifically, at 300 K the systems initially evolved by Frank-van de Merwe (layer-by-layer) growth whereas at elevated temperatures, a stable surface alloy is formed. The effect of exposure to various gases related to the catalytic chemistry of the bulk alloys (H2, CO, O2, CO2, H2O) is discussed and the properties of the oxidized and unoxidized systems compared. The activation of bulk Ce-Cu and Nd-Cu precursors for methanol synthesis catalysts has been investigated by in situ XRD observations, with concurrent measurements of methanol activity, and using a new high pressure microreactor system. The formation of certain intermediate hydride phases is crucial to the eventual production of highly active catalysts and the methanol activity does not correlate with Cu surface area. The role of CO2 as a catalyst poison and the implications of the experimental observations with respect to the reaction mechanism of these novel catalysts are discussed and compared with the properties of conventional Cu/ZnO/Al2/O3 catalysts.

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Combustion instability is a process which involves unsteady chemical kinetic, fluid mechanic, and acoustic processes. It can lead to unstable behavior and be detrimental in ways ranging from faster part fatigue to catastrophic system failure. In terms of combustion methodology, combustion instability has been a key issue for lean premixed combustion. The primary objective of this work is to improve understanding of combustion dynamics through an experimental study of lean premixed combustion using a low swirl combustor. This special burner was developed at the Lawrence Berkeley National Laboratory and has recently received significant interest from the gas turbine industry. In these experiments, acoustic perturbations (chamber modes) are imposed on a low swirl stabilized methane-air flame using loudspeakers. The flame response is examined and quantified with OH planar laser induced fluorescence. Rayleigh index maps of the flame are computed for each frequency and operating condition. Examining the structures in the Rayleigh maps, it is evident that, while the flame shows no significant response in some cases, acoustic forcing in the 70-150 Hz frequency range induces vortex shedding in the flame shear layer. These vortices distort the flame front and generate locally compact and sparse flame areas. This information about the flow field shows that, besides illuminating the combustion dynamics, the Rayleigh index is a useful way to reveal interesting aspects of the underlying flow. The experiments also revealed other interesting aspects of this flame system. It was found that the flame becomes unstable when the perturbation amplitude reaches 0.7% of the mean pressure. Decreasing the swirl number makes the flame shape more jet-like, but does little to alter the shear-layer coupling. In a similar fashion, increasing the pressure was found to alter the flame shape and flame extent, but the thermo-acoustic coupling and induced large scale structure persisted to 0.34MPa, the highest pressure tested.

The measure of chemiluminescence from the transition of the hydroxyl radical from its electronically excited state (A^2 Sigma^positive) to its ground state (X^2 Pi) is used in many combustion applications for diagnostic purposes due to the non-intrusive nature of the chemiluminescence measurement. The presence of the ultraviolet emission at 307nm is often used as an indicator of the flame zone in practical combustion systems, and its intensity may be correlated to the temperature distribution or other parameters of interest. To date, the measurement of the excited state OH, OH*, is mostly qualitative. With the use of an accurate chemical kinetics model, however, it is possible to obtain quantitative measurements. Shock-tube experiments have been performed in highly diluted mixtures of H2/O2/Ar at a wide range of pressures to evaluate the pressure-dependent rate coefficient of the title reaction. In such mixtures the main contributing reaction to the formation of OH* is, O H M = OH* M. R1 Previous work has determined the reaction rate of R1 at atmospheric conditions and accurately predicts the amount of OH* experimentally produced. At elevated pressures up to 15 atm, which are of interest to the gas turbine community, the currently used reaction rate of R1 (i.e., without any pressure dependence) significantly over predicts the amount of OH* formed. This work provides the pressure dependence of R1. The new reaction rate is able to reproduce the experimental data over the range of conditions studied and enables quantitative measurements applicable to practical combustion environments.

The tropospheric oxidation of unsaturated hydrocarbons is a central issue in atmospheric chemistry. These hydrocarbons are emitted into the atmosphere from both natural and anthropogenic sources, and their atmospheric oxidation leads to different atmospheric pollutants, including ground level ozone, photochemical smog and secondary organic aerosols. Isoprene and 1,3-butadiene represent a biogenic and an anthropogenic hydrocarbon, respectively, which primarily undergo electrophilic addition of OH radical, followed by chain propagating radical reactions. Their oxidation is the major source for ground level ozone formation in both rural and urban area and understanding their chemistry is essential for regional air quality modeling. Until recently, most of the studies of isoprene chemistry have been non-isomer specific, reflecting the reactivity of combined pathways and therefore were insensitive to specific details of the isomeric pathways. An isomeric selective approach to studying unsaturated hydrocarbon oxidation is described in this dissertation. A synthesized precursor, whose photolysis can provide a route to the formation of energy selected single isomer in the isoprene oxidation pathway, enables the study of important channels that are difficult to unravel in non isomer specific experiments. The major addition channel in OH isoprene oxidation has been studied following the isomeric selective approach and using Laser Photolysis-Laser Induced Fluorescence (LP-LIF) as the primary experimental technique. The study reveals important information about the oxidative chemistry of the δ-peroxy radicals, accounting for about 20 percent of missing carbon balance in isoprene oxidation, and isomeric specific rate constants. A similar approach was applied to study the oxidation of 1,3-butadiene, and the photolytic precursor for the dominant hydroxy alkyl isomer in the OH initiated oxidation of 1,3-butadiene was synthesized. The subsequent experiments and analysis revealed detailed information about the oxidative chemistry accounting for approximately 26 percent of the missing chemistry. Finally, non isomeric selective OH cycling experiments were carried out on the1,3-butadiene system. By analyzing the OH cycling data with the combined information obtained from the isomeric specific studies of the two isomeric channels of 1,3-butadiene oxidation, the relative branching between the two isomeric channels of OH-1,3-butadiene oxidation was determined.

Increasingly stringent legislations call for more efficient and cleaner combustion technology as well as sustainable fuels. Chemical kinetic models are required in designing and optimizing novel engine concepts as well as selecting appropriate renewable fuels. Among the many reactions controlling fuel reactivity, OH + Fuel elementary reaction is one of the most important reactions that plays a critical role from low to high temperatures. In this thesis, OH + Fuel elementary reactions are studied for a wide spectrum of conventional and renewable fuels. The overall rate coefficients are measured in a shock tube using OH time-history profiles recorded with a UV laser diagnostic. Alkanes constitute important components of gasoline and diesel. Overall rate coefficients are measured for a series of large branched alkanes and the rate rules are derived based on the next-nearest-neighbor classification method. The strength of this method lies in the ability to predict the rate coefficients for large and/or highly-branched alkanes, where both experiments and theoretical calculations are hard to reach. Next, OH reactions with bio-derived fuels, methanol and cyclic-ketones, are studied. For OH + methanol reaction, site-specific contributions from different C-H bonds are quantified using deuterium kinetic isotopic effect, and the measured rate coefficients are found to improve the general behavior of a detailed methanol kinetic model. Reactions of cyclic ketones with OH radicals are found to exhibit similar reactivity as those of similar carbon length acyclic ketones + OH reactions. Acetaldehyde is one of the most abundant hazardous byproducts in the combustion of various fuels. Similar to methanol, OH + acetaldehyde reaction is 4 studied at the site-specific level and the importance of competing reaction channels are quantified at high temperatures. Finally, reactions of OH + cyclohexadienes and OH + trimethylbenzenes, relevant for the fate of polycyclic aromatics hydrocarbons, are investigated. A highly complex temperature dependence is observed for these molecules, a six-parameter Arrhenius expression is needed to describe the overall reactivity. The work reported in this thesis provides elementary reaction data that are highly valuable for increasing the fidelity and accuracy of predictive chemical kinetic models.