<p> This study examines dust in the San Francisco Peaks located on the Colorado Plateau of northern Arizona, USA. Sample dusts were collected from potholes on Humphreys Peak (35^o20'22"N, 111^o41'42"W) in order to detect exogenous material and constrain dust sources. Bulk dust and local rock were characterized by Sr and Nd isotope fingerprints as well as elemental composition. Sr and Nd isotope ratios were analyzed by MC-ICP-MS; trace element concentrations were analyzed by Q-ICP-MS. Mineralogical analyses were also performed in an effort to characterize individual particles. Mineral grains were separated from bulk samples by conventional heavy mineral separations. The heavy fraction was imaged and characterized by SEM/EDX. </p><p> Both the isotopic and elemental bulk analyses indicated that the dust composition reflected not only a weathered local rock material but also exogenous material of continental crust origin. The dust was characterized by an average ⁸⁷Sr/⁸⁶Sr ratio of 0.7095 &plusmn; 0.0010 and an average &epsi;_Nd of -7.13 &plusmn; 0.97. These signatures systematically and significantly deviate from the isotope fingerprints of the local rock, which exhibited an average ⁸⁷Sr/⁸⁶Sr ratio of 0.7037 &plusmn; 0.0002 and an average &epsi;_Nd of -2.43 &plusmn; 0.43. The negative correlation between &epsi;_Nd and ⁸⁷Sr/⁸⁶Sr is consistent with two component mixing of rock evolved from a mantle source and continental crust derived material. </p><p> Several geologically relevant trace elements were found to have significantly different average concentrations in the dust than in the local rock samples. Furthermore, the elemental abundances of most elements in the dust samples suggested a mixture of local rock and continental crust end members with the exception of Pb, which indicated an anthropogenic influence exhibiting enrichment factors between 1.65 and 7.44. </p><p> The mineral analysis provided further evidence of exogenous material and offered the opportunity for further constraint of the sources. Zircons were identified only in the dust and will be analyzed for U-Pb signatures in order to characterize the isotopic fingerprint of individual mineral grains, which will better distinguish external sources. Diatom skeletons were also found exclusively in the dust samples and offer a unique opportunity to more specifically implicate sources through a diatom assemblage.</p>

The goal of this study was the exploration of several techniques for the rapid analysis of aluminum pins by ICP-AES (inductively coupled plasma atomic emission spectrometry). / Direct solid sample analysis of the pin by DSI (direct sample insertion) proved to be unfeasible due to incomplete vaporization of the sample from the DSI probe. / A technique called the Real-time Alloy Analysis Technique (RAAT) allowed analyte signals to be monitored during sample digestion (in dilute HCl) and using a ratio method, quantitative results were obtained after a few minutes of initiating sample digestion. This method exhibited fast and simple sample preparation and high precision of <3% relative standard deviation. / An in-solution spark technique (SAD) was used to produce dispersions of the pins in water. The SAD and DSI proved promising as a very rapid sampling technique.

Photothermal deflection or 'mirage effect' spectroscopy was applied to the quantitative profiling of the optical absorbers in thin polymer films with depth dependent absorption coefficients. In addition, the mirage effect system instrumentation was designed and constructed. Improvements to the precision and accuracy of the instrumentation were implemented, which allowed for quantitative measurements of optical depth dependent layers to be profiled in samples consisting of thin polymer multilayered films. A theoretical model based on one-dimensional heat conduction was developed and used to analyze the experimental results. Further improvements were made to the model by applying diffraction theory to recover heat flux profiles. This added precision for the analysis was required for use in the inverse problem theory. The results from using this theoretical model were interpreted. The mirage effect technique was applied to the dynamic diffusion of solutions containing ionic species through a perfluorosulphonated ionomer membrane. The recovery of the heat flux profiles (solved using inverse problem theory) enabled the recovery of optical absorption profiles, and therefore, concentration profiles. A diffusion model (also developed in this work), enabled the diffusion coefficients of these species to be determined from the concentration profiles. By these means, the diffusion processes of species into the membrane were examined.

The goal of this study was to explore the use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for a variety of human hair analyses. / Optimization of the inductively coupled plasma mass spectrometry (ICP-MS) operating parameters, radiofrequency (RF) power and carrier gas flowrate, for solid sample introduction showed more than one operating condition can (1) produce a statistically similar maximum elemental signal and (2) have statistically similar optimum signal-to-noise (S/N) ratios. The use of an internal standard was shown to increase the number of operating conditions with statistically similar optimum S/N ratios, and the value of S/N ratios. The high degree of precision exhibited by 34S along hair strands from the same individual (2 - 3 % hair strand to hair strand RSDs) suggests that sulphur may be a suitable internal standard for elements in hair. / The single and multi ablation detection limits (DLs) obtained for elements in powdered hair certified reference materials (CRMs) were similar to what was expected for biological materials using LA-ICP-MS. / The possibility of using LA-ICP-MS to depth profile elements in a hair strand was explored. With the correct operating conditions, LA-ICP-MS may be an effective analytical tool for depth profiling elements in a hair strand. / LA-ICP-MS was used to construct mercury calibration plots using powdered hair CRMs and calibrated hair strands having R2 values of 0.9775 and 0.9522, respectively. / Exogenous deposits lead to confusion in the interpretation of findings from hair. LA-ICP-MS was used to remove an artificial exogenous deposit from a hair strand.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 0939. Adviser: Ralph G. Nuzzo. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

<p> Metal containing complexes have been used to catalyze various organic transformations for the past few decades. The success of several mononuclear catalysts led to transition metal catalysts used in pharmaceuticals, environmental, and industrial processes. While mononuclear complexes have been used extensively, bimetallic systems have received far less attention. Bimetallic or polynuclear sites are commonly found in metalloenzymes that perform elegant transformation in biological systems, underlying their significance. Inorganic chemists take inspiration from nature and design model bimetallic complexes to further study this cooperativity effect. A bimetallic platform offers many structural and functional differences such as the identity of the metal atoms and the bonding interactions between metals, which have been reflected in their unique catalytic ability and reactivity. </p><p> This dissertation encompasses work related to the computational study of metal-metal interactions of bimetallic systems, the ¹H NMR study of stereochemical and conformational changes in solution of <i> N,N'</i>-diarylformamidines, the synthesis of dizinc formamidinate complexes, and the synthesis and catalytic ability of dicopper formamidinate complexes. </p><p> In the first part, DFT calculations are used to study factors that influence metal-metal bond lengths in various complexes. Several experimentally obtained X-ray crystal structures were used as the basis for the study. Differences in metal-metal separations were investigated through various functionals, indicating the importance of charge, orbital interactions, and formal bond order. BH&amp;HLYP SDD/aug-CC-PVDZ geometry optimizations of octahalodimetalate anions Tc₂X₈^n- (X = Cl, Br; n=2, 3), Re₂X₈^2- (X = Cl, Br), and Mo₂Cl₈^4- reproduced M-M bond distance trends observed experimentally. The study demonstrated that the increase in &sigma; and &pi; bond strength resulted in the shortening in Tc-Tc bond distance from Tc₂X₈^2- to Tc₂X₈^3-, which was further supported by the short Mo-Mo bond in the Mo₂Cl₈^4- ion. This study was expanded further through the inclusion of [M₂Cl₄(PMe₃)₄]ⁿ⁺ (M = Tc, Re, n = 0-2) and [Mo₂E₄]^n- (E = HPO₄ or SO₄, n = 2-4), allowing a systematic study on the role of charge on the metal atoms. PBEO SDD/aug-CC-PVDZ calculations revealed that both formal bond order and formal charge on the metal atoms dictate the trends in M-M bond strength. </p><p> The second half of this dissertation focuses on the synthesis and characterization of bimetallic Zn- and Cu-formamidinate complexes. The stereochemical exchange of substituted <i>N,N'</i>-diarylformamidines were studied through ¹H NMR in various solvents. Alkyl substituents placed on the ortho positions were found to shift the isomeric equilibrium in solution through destabilization of the hydrogen-bond dimer evident in X-ray crystal structures. The Z-isomer of substituted <i>N,N'</i>-diarylformamidines is observed in CDCl₃, C₆D₆, and DMSO-d₆ when the ligands feature significant steric hinderance. Similar ortho substituted <i> N,N'</i>-diarylformamidines were also used to enforce steric interactions to limit the nuclearity of Zn-formamidinate complexes. Various dizinc formamidinate complexes were synthesized through direct and transmetalation routes. NMR and mass spectrometry were used alongside X-ray crystal structures to fully characterize the dizinc complexes. Dicopper formamidinates formed through a transmetallation route were synthesized and feature distinct short Cu^&hellip;Cu separations thought to be brought about by metalophillic interactions. Preliminary results suggest catalytic ability of dicopper formamidinates in cyclopropanation and aziridination of styrene with various diazo compounds. The catalytic activity suggests the formation of dicopper carbene and nitrene intermediates, of which only few published experimentally observed examples exist in the literature.</p><p>

Axial mole-fraction profiles were measured in a low-pressure reactive flow of propylene/chlorine and a low-pressure, fuel-rich ethylene flame doped with allene. The purpose was to generate data and test models for improving allyl chloride production and pollutant-related C3 flame chemistry. Molecular-beam mass spectrometry was the principal analytical technique. The propylene/chlorine system had feed conditions of 71.2% propylene and 28.8% chlorine, 76.00 ± 0.01 Torr, and 17.5 cm/s burner-surface gas velocity (298 K). Because propylene and chlorine could pre-react, a novel multidiffusion burner was developed. Mole fraction profiles were mapped for seven stable species. Temperature measurements were made using a K-type thermocouple, and the constant flow cross-section was determined visually. By modeling as a plug-flow reactor with literature rate constants and data and rate constants determined here, a self-consistent reaction mechanism was constructed and used to predict concentration profiles for unmeasured species. Predicted profiles were consistent with measured data. Thus, by also accounting for pressure effects, the new model provides a sound basis for modeling the industrial process. The allene-doped ethylene flame had a fuel equivalence ratio of 1.9 and feed gas composition of 0.5% allene, 18.9% C2H4, 30.9% O 2, and 49.7% Ar. It was operated at 20.00 ± 0.01 Torr with a burner surface gas velocity at 298 K of 62.5 cm/s. Mole fraction profiles were measured for 41 stable and radical species. Data from this allene-doped ethylene flame were compared to the data of Bhargava's (1997) nearly identical fuel-rich undoped ethylene flame. Addition of allene enhanced the production of phenyl and benzene, supporting the arguments that C3 species play a very important role in the formation of phenyl and benzene. Using the data and reaction path analysis, Bhargava's (1997) reaction set was improved. New rate constants were determined, incorrect reactions were removed, and new chemistry was added, improving many of the model predictions. Modeling suggested that the major reaction responsible for increased production of phenyl and benzene was 2C3H3 = phenyl +H. Identification and analysis of an important error in Bhargava's reaction set suggest that a reactive boundary condition at the burner surface may be necessary for improved modeling of this flame.

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