An isobaric flow loop added to the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI) is being investigated as a means of rapidly forming methane hydrate in watersaturated sand from methane dissolved in water. Water circulates through a relatively warm source chamber, dissolving granular methane hydrate that was pre-made from seed ice, then enters a colder hydrate growth chamber where hydrate can precipitate in a water-saturated sand pack. Hydrate dissolution in the source chamber imparts a known methane concentration to the circulating water, and hydrate particles from the source chamber entrained in the circulating water can become nucleation sites to hasten the onset of hydrate formation in the growth chamber. Initial results suggest hydrate grows rapidly near the growth chamber inlet. Techniques for establishing homogeneous hydrate formation throughout the sand pack are being developed.

Water, suspended particle and sediment samples from Gao-ping coastal water column were collected and measured to determine the spatial and temporal distributions of polycyclic aromatic hydrocarbons (PAHs) during August 2010 and June 2011. In addition, principal component analysis (PCA) and hierarchical the cluster analysis (HCA) were performed with chemical fingerprinting to understand the possible sources of PAHs in Gao-ping coast. The correlations between PAHs and several factors such as salinity, temperature and organic carbon were also discussed in the present study. The total PAH concentrations (dissolved and particulate phase) at four sampling campaigns ranged from 2.09 to 45 ng/L. Concentrations of dissolved PAHs ranged from 2.0 to 39 ng/L and the highest average concentrations were found in November 2010 (10.0 ¡Ó 9.90 ng/L). The particulate PAHs ranged from 0.13 to 40 ng/L and the maximum concentration was found in the estuary in August 2010. The total PAH concentrations of sediment ranged from 125-648 ng/g, which were lower than the Effect Range Low (ERL) and Threshold Effect Level (TEL) values, suggesting that few adverse ecological effects would arise from the PAHs in Gao-ping canyon. Results from chemical fingerprinting, PCA and HCA indicate that PAHs in this area were from complex sources such as combustion, petroleum, diagenesis or biogenic sources. Sources of PAHs in dissolved phase were mainly from petrogenic and mixed sources, while particulate PAHs were mainly from a mixed source. However, sources of PAHs in November 2010 and February 2011 were mostly from mixed combustion, suggesting that the PAH concentrations in particulate phase might be affected by atmospheric transport. The results showed that perylene in Gao-ping coast and canyon was mainly from the biogenic source. A significant correlaction was found in PAH fingerprinting between the esturine particles and sediment, indicating that the sediments in Gao-ping canyon might mainly come from Gao-ping River. Correlation analysis showed a significant positive correlation between concentrations of suspended particle and PAHs, while a negative correlation was found between PAH concentrations and temperature. In addition, organic carbon showed a significant correlation with PAHs in sediment samples. The partition coefficients (Koc) values of PAHs were higher than the values from other literatures, suggesting that it might be attributed to soot carbon.

<p>The diagnosis and treatment of pulmonary diseases still rely on pulmonary function tests that offer archaic or insensitive biomarkers of lung structure and function. As a consequence, chronic obstructive pulmonary disease is the third leading cause of death in the US, and the hospitalization costs for asthma are on the order of $29 Billion. Pulmonary diseases have created a large and unsustainable economic burden, and hence there is still a dire need for biomarkers that can predict early changes in lung function. The work presented in this thesis looks to address this very issue, by taking advantage of the unique properties of hyperpolarized (HP) <super>129</super>Xe in conjunction with magnetic resonance imaging (MRI), to probe the fundamental function of the lung - gas-exchange. </p><p>While a bulk of the inhaled HP <super>129</super>Xe stays in the alveolar spaces, its moderate solubility in the pulmonary tissues causes a small fraction of this xenon in the alveolar spaces to diffuse into the pulmonary barrier tissue and plasma, and further into the red blood cells (RBC). Additionally, when in either of these compartments, xenon experiences a unique shift in its resonance frequency from the gas-phase (barrier - 198 ppm, RBC - 217 ppm). These unique resonances are collectively called the dissolved-phase of xenon. As the pathway taken by xenon to reach the RBCs is identical to that of oxygen, this dissolved-phase offers a non-invasive probe to study the oxygen transfer pathway, and imaging its distribution, to first order, would give us an image of gas-exchange in the lung.</p><p>Gas-exchange is controlled by ventilation, perfusion, and lastly diffusion of gases across the capillary membrane. This process of diffusion is dictated by Fick's first law of diffusion, and hence the volume of gas taken up by the capillary blood stream depends on the alveolar surface area, and the interstitial thickness. Interestingly, changes in these factors can be measured using the resonances of xenon. Changes in the alveolar surface area brought on by diseases like emphysema will increase the diffusion of xenon within the alveolus. Thus, by using diffusion-weighted imaging of the gas-phase of <super>129</super>Xe, which is the focus of chapter 3, one can extract the `apparent diffusion coefficient' (ADC) of xenon, that is sensitive to the changes in the alveolar surface area. The dissolved-phase on the other hand, while sensitive to the surface area, is also sensitive to subtle changes in the interstitial thickness. In fact, after the application of an RF pulse on the dissolved-phase, the recovery time for the xenon signal in the RBCs is significantly delayed by micron scale thickening of the interstitium. This delayed signal recovery can be used as a sensitive marker for diffusion impairment in the lung. </p><p>While direct imaging of the dissolved-phase was shown to be feasible, truly quantifying gas-exchange in the lung will require two additional technical advances - 1) As the gas-phase is the source magnetization for the dissolved-phase signal, it is imperative to acquire both the gas and dissolved-phase images in a single breath. The technical details of this achievement are discussed in chapters 4 and 5. 2) As the dissolved-phase consists of both the barrier and the RBC components, obtaining a fundamental image of gas-exchange in the lung will require creating independent images of <super>129</super>Xe in the barrier and <super>129</super>Xe in the RBCs. This goal first required creating a global metric of gas-transfer in the lung (chapter 6), which aided the implementation of the 1-point Dixon acquisition strategy to separate the components of the dissolved-phase. In conjunction with aim 1, it was finally possible to image all three resonances of <super>129</super>Xe in a single breath (chapter 7). These <super>129</super>Xe-RBC images were acquired in healthy volunteers and their efficacy was tested in subjects with idiopathic pulmonary fibrosis (IPF). These IPF subjects are known for their characteristic diffusion limitation, and in regions of fibrosis shown on their CT scans, the <super>129</super>Xe-RBC images showed gas-transfer defects. </p><p>Hyperpolarized <super>129</super>Xe MRI thus provides a non-invasive, ionizing radiation free method to probe ventilation, microstructural changes and most importantly, gas-exchange. These preliminary results indicate that xenon MRI has potential as a sensitive tool in therapeutic clinical trials to evaluate longitudinal changes in lung function.</p> / Dissertation

In this study our purposes were to investigate the spatial distribution and seasonal variation of polycyclic aromatic hydrocarbons (PAHs) in the dissolved and particulate phase of PAHs in Er-Jen River. In addition, the potential sources of PAHs in Er-Jen River were investigated not only by finger printing, but also principal component analysis (PCA) and hierarchical cluster analysis (HCA). ¡@¡@Concentrations of dissolved and particulate PAHs ranged from 13.8 to 516 ng/L and from 4.05 to 55.9 ng/L, respectively. In March (dry season), concentrations of dissolved and particulate PAHs ranged from 38.3 to 186 ng/L and from 4.05 to 25.9 ng/L, respectively. In addition, concentrations of dissolved and particulate PAHs ranged from 32.3 to 82.8 ng/L and from 14.8 to 85.3 ng/L, respectively in September (wet season). The highest total PAH concentration in this area was found in Station Er-3 which is located on a tributary of Er-Jen River. Total PAH concentrations in wet season were higher than those found in dry season for all stations in Er-Jen River, except for station Er-3, which suggesting that different geography might be the reason. ¡@¡@Results from correlation analysis indicated that distributions of PAH concentrations for particulate phase in Er-Jen River correlated well with flow rate, suspended solid concentrations and salinity. Total PAH concentration of station Er-2, which was located at the downstream Er-Jen River, was highly correlated with salinity; while total PAH concentrations in other stations were mainly affected by flow rate, suspended solid concentrations and some potential sources of pollution. Results from PCA, HCA and finger printing all indicated the origins of PAHs were complex sources in the study area, including pyrogenic, petrogenic and diagenetic/biogenic origins. The origins of PAHs in dissolved phase were mainly from both pyrogenic and petrogenic sources; while those in particulate phase were mainly from pyrogenic sources. In addition, the pyrogenic origins in both dissolved and particulate phase were mostly from liquid fuel combustion. In wet season, howerer, diagenetic/biogenic origins were also found in particulate phase at the sampling sites of Er-Jen River. ¡@¡@The annual total PAH fluxes of Er-Jen River were estimated to be 23.1 kg For dissolved phase, the average daily fluxes in dry and wet season were 5.9 g/day and 65.8 g/day, respectively, with an annual mean fluxe of 11.3 kg/year. For particulate phase, the mean daily fluxes in dry and wet season were 0.8 g/day and 76.2 g/day, respectively, with an annual mean flux of 11.8 kg/year. In general, the total PAH fluxes in wet season were higher than dry season. The total annual PAH fluxes in Er-Jen River were generally less than those reported worldwide, and comparable to those in San Francisco River in USA, but higher than those in Le Havre River in France.