No description available.

No description available.

No description available.

The concentrations of heavy metals (Cd, Cu, Fe, Ni, Pb, Zn) were measured in water, and fish samples caught from the pond at Fishery Park in Unicoi County, TN. The water samples were collected once a week for 8 weeks. The amounts of metals in the muscle tissues, gill, and liver of the two fish species were measured. This was to determine if any correlation exists between the metal contents in water and those in the fish samples. The concentration ranges for the heavy metals found in the water samples are as follows: Zn 0.04-0.13; Cu, 0.00-0.00; Pb, 0.00-0.59; Cd, 0.0067-0.0071; Fe, 0.208-0.512; and Ni, 0.044-0.270 ppm. The concentration range for the heavy metals found in the fish tissues are as follows: Zn 0.0-0.48; Cu, 0.00-0.00; Pb, 0.00-0.43; Cd, 0.00-99.7; Fe, 25.7-1245.5; and Ni, 0.00-268.5 ppm. There was a strong correlation found between the water and fish tissue samples.

This study aims to determine the distribution of particulates carrying heavy metals at selected sites on a college campus using dandelion leaves as collectors. As a comparison, sites far away from the campus surrounding Bristol Motor Speedway Car Racing Stadium were also monitored. To reduce the probability of memory effects from the long-term atmospheric deposition or absorption of metals from soil a seasonal plant, dandelion, was used to monitor the metal contents. The metals monitored are cadmium, calcium, copper, chromium, iron, lead, and zinc. Fourteen sites were monitored and samples were collected once a week initially (growing time of the plant), and later at 4-week interval from 28th March to 31st August of 2007. The metal contents of the nitric acid digested and appropriately diluted samples were determined by flame atomic absorption spectrometry using the regular standard calibration curve and also the standard addition method. From the results obtained, and the careful log of the weather and human activities at the different sites, it is concluded that human activities played a major role in the distribution of metal-laden particulates. Also dandelion leaves were proven to be viable collectors of these particulates without memory effects and as indicators of current particulates generated rather than a long-term cumulative one.

This thesis presents the integration of atomic vapor cells with anti-resonant reflecting optical waveguides (ARROWs) fabricated on silicon chips. These potentially provide a compact platform for a number of optical applications, including the study of quantum coherence effects such as electromagnetically induced transparency and single-photon nonlinearities, as well as frequency stabilization standards. The use of hollow waveguides allows for light propagation in low index (vapor) media with compact mode areas. ARROWs make particularly attractive waveguides for this purpose because they can be interfaced with solid core waveguides, microfabricated on a planar substrate, and are effectively single mode. ARROW fabrication utilizes an acid-removed sacrificial core surrounded by alternating plasma deposited dielectric layers, which act as Fabry-Perot reflectors. To demonstrate the effectiveness of the ARROW as a vapor cell, a platform consisting of solid and hollow core waveguides integrated with rubidium vapor cells was developed. A variety of sealing techniques were tested for vapor cell integration with the ARROW chip and for compatibility with rubidium. Rubidium was used because it is of particular interest for studying quantum coherence effects. Liquefied rubidium was transferred from a bulk supply into an on-chip vapor cell in an anaerobic atmosphere glovebox. Optical absorption measurements confirmed the presence of rubidium vapor within the hollow waveguide platform. Further analysis of the measurements revealed high optical density of rubidium atoms in the hollow core. Saturated absorption spectroscopy measurements verified that the on-chip integrated vapor cell was suitable for common precision spectroscopy applications.

Part 1 The coupled shock-tube/mass spectrometer apparatus is characterized in terms of its capabilities for chemical kinetic studies. Criteria for doing kinetic measurements by this experimental technique are discussed. The characterization experiments showed that our apparatus was capable of giving plausible signal shapes for non-reactive dynamic shots at P₁ = 5 torr. Measurements of ion current under static conditions showed that response of the quadrupole mass spectrometer was linear over a range of P₁ = 0-5 torr. Schlieren measurements indicated that the shock wave velocity was erratic and non-reproducible over the last 5 feet of the test section and that the velocity at the endwall could not be predicted from the schlieren data. The electron beam width was found to be ~.1" and the implications of this measurement for further studies on the free jet are outlined. The present beam width is suitable for jet studies in which bulk ionization of gas from a cross-section of the jet is performed. Design improvements needed for future reactive studies on our system are reviewed. In addition, experimental studies of jet risetime with a pulsed molecular beam apparatus showed poor agreement between the experimental and theoretical jet risetimes. The apparent discrepancy is discussed and possible explanations for it are given. Part 2 The rate constant k₁ for the reaction C₅H₁₂ → C₄H₉ + CH₃ was determined from reflected shock experiments (1100-1300°K) in which the progress of reaction was monitored by the appearance of H atoms. Atomic resonance absorption spectrophotometry at the Lyman-α line was performed on three mixtures (20 ppm, 10 ppm, 5 ppm) of neopentane in argon to give k₁ = .17 x 10¹⁸ exp (-84800±6200/RT) sec⁻¹. This result is in very good agreement with earlier single pulse shock tube experiments. In addition, calibration experiments for H atom were performed by shock-heating two mixtures (10 ppm and 5 ppm) of neopentane in argon. The results obtained were in good agreement with previous calibration data. / Doctor of Philosophy

Charge transfer at the organic/inorganic semiconductor interfaces lies at the heart of interfacial photochemistry. While decades of research have shaped the current understanding that interfacial charge transfer depends crucially on energetic driving force and electronic coupling, much less is known about the role played by the spin degree of freedom. In particular, it is not clear how spin states evolve during the charge transfer process. With the advent of group 6 transition metal dichalcogenides (TMDC), a class of two-dimensional layered materials which permits the optical generation of spin-polarized electron-hole pairs in the monolayer limit, we now have the opportunity to investigate if charge transfer at an organic/inorganic interface could enable the transfer of spin polarization. Using time-resolved Faraday rotation and transient absorption spectroscopy, it is found in the MoSe₂/H₂Pc and C60/WS₂ heterostructures that the photoinduced hole transfer from MoSe₂ to H₂Pc and electron transfer from WS₂ to C60 results in spin polarization lifetimes one order of magnitude longer than that of a monolayer. In the WS₂/MoSe₂/H₂Pc heterostructure, the addition of a WS₂ monolayer drives the dissociation of electron-hole pairs bound at the MoSe₂/H₂Pc interface and leads to the observation of nanosecond-long spin polarization at room temperature. These findings evidence the photoinduced transfer of spin polarization, a mechanism which could potentially be exploited to enhance the efficiency and selectivity of photochemical reactions involving angular momentum change, and may be generalized to other organic/inorganic interfaces composed of crystalline semiconductors with spin-momentum locking.

The main goal of the work presented in this thesis is to improve the reliability of existing methods for speciation analysis of organotin compounds Species-specific isotope dilution (SSID) calibration in combination with gas chromatography – inductively coupled plasma mass spectrometry was used to investigate the transformation of phenyltin species during sample preparation. Isotope-enriched phenyltin species were synthesized from corresponding isotope-enriched tin metals. SSID with a mixture of phenyltin species (PhTs) from one isotope was used to evaluate different extraction procedures for the determination of PhTs in fresh water sediment. Preparative liquid chromatography was used to produce single isotope-enriched phenyltin species making a multi-isotope spike (MI) SSID calibration possible. Different extraction procedures for the analysis of phenyltin species in biological samples were evaluated by applying MI-SSID. Degradation of TPhT and DPhT during sample extraction was observed and quantified. Accurate results were therefore obtained. A sample preparation procedure using mild extraction conditions with reasonable recoveries is described. The stability of organotin standards was investigated under different storage conditions. Mono- and diphenyltin were found to be redistributed and degraded during storage in methanol but were stabilized in sodium acetate/ acetic acid. A fast redistribution between monobutyl- and diphenyl tin has been observed and therefore it is therefore recommended that standards be derivatized as soon as possible after butyl- and phenyltin standards are mixed. Included in the thesis is also an investigation of the analytical potential of using instrumentation based on atomic absorption spectrometry (AAS) for speciation analysis of organotin compounds. The method was based on gas chromatographic separation, atomization in a quartz tube and detection by line source (LS) AAS and for comparison, by state of the art continuum source (CS) AAS. Analytical performances of CSAAS system were found to be better compared to LSAAS.

In this diploma thesis, rubidium in plant material samples was determined by atomic absoption spectrometry. Determination of plant material rubidium was performed on two different atomic absorption spectrometers (GBC 933 AA and ContrAA 700) for comparison. The selection of a proper method of atomization was essential, therefore optimizations for the flame atomizer and electrothermal atomizer were performed. On the GBC 933 AA, flame atomization was tested. The flow rate of the acetylene-air, vertical and horizontal flame profile, spectral interval width was optimized for the instrument. On the ContrAA 700, the conditions for flame atomization were optimized as well as for electrothermal atomization. The optimized parameters included the acetylene-air flow rate and the vertical flame profile again. For the electrothermal atomization, the temperature dependence of pyrolysis and the temperature dependence of atomization were optimized. Under experimentally determined optimal conditions, the determination of rubidium in fruit and vegetable juice samples was performed by the method of calibration curve. Rubidium usually accompanies toher alkali metals. In the absence of essential biogenic elements iportant for plant growth, rubidium is able to help out and take on the role of potassium.