Thesis (M.S.)--University of Michigan, 1981.

Thesis (M.S.)--University of Michigan, 1981.

Transcutaneous gas monitoring of oxygen and carbon dioxide is animportant method for monitoring the oxygenation and ventilation inprematurely born infants. The amount of gas diffusing through theskin is very small and current technology rely on heating of theskin to increase the gas amount, where transcutaneous oxygenrequires the highest temperature. Heating damages the delicate skinof the infants and is a major concern among the nurses administeringthe treatment. In this thesis we have investigated a prototype and developedcomponents for a novel transcutaneous gas monitor capable ofperforming transcutaneous carbon dioxide measurements on adultswithout any external heating with a fast start-up time compared toconventional monitors. The technology is based on a microplasmasource developed at the Microsystems Technology department atUppsala university. The thesis has focused on producing three key components of theprototype. Firstly the controller board and radio frequency (RF)amplifier, previously two separate circuit boards, have beencombined into one. The design also incorporates improvementsregarding the power supply of the board, where a buck converterinstead of a linear regulator is used to step down most of thevoltage. This eliminates the need to use a heat sink to remove heatgenerated during voltage transformation. Secondly a sensor pad hasbeen developed from a silicone-based material which is soft,flexible and self-adhesive, allowing it to be placed anywhere on thepatient without tape or glue. And lastly techniques have beendeveloped to efficiently turn the raw data collected from the plasmasource into a usable carbon dioxide concentration signal. Though the plasma-based transcutaneous gas monitoring is yet farfrom clinical trials, the technology has shown promising results andit is deemed to be a viable alternative with better performance inpatient comfort, sensitivity and response time.

Emerging health concern for gaseous nitrogen oxides (NOx) emitted during surface mine blasting has prompted mining authorities in the United States to pursue new regulations. NOx is comprised of various binary compounds of nitrogen and oxygen. Nitric oxide (NO) and nitrogen dioxide (NO2) are the most prominent. Modern explosive formulations are not designed to produce NOx during properly-sustained detonations, and researchers have identified several causes through laboratory experiments; however, direct sampling of NOx following full-scale surface mine blasting has not been accomplished. The purpose of this thesis was to demonstrate a safe, innovative method of directly quantifying NOx concentrations in a full-scale surface mining environment. A small unmanned aircraft system was used with a continuous gas monitor to sample concentrated fumes. Three flights were completed – two in the Powder River Basin. Results from a moderate NOx emission showed peak NO and NO2 concentrations of 257 ppm and 67.2 ppm, respectively. The estimated NO2 presence following a severe NOx emission was 137.3 ppm. Dispersion of the gases occurred over short distances, and novel geometric models were developed to describe emission characteristics. Overall, the direct sampling method was successful, and the data collected are new to the body of scientific knowledge.

Transcutaneous oxygen pressure measurement (TCp02) using a miniaturised Clarke electrode and a heating thermistor was developed independently by Huch et al and Eberhardt et al in 1972. After its initial use to non invasively monitor arterial partial pressure (Pa02) in neonates it was proposed as a useful test of skin blood flow and possibly amputation wound healing level selection in patients with peripheral vascular disease. Unfortunately a wide range of predictive values emerged with some authors reporting amputations healing when the TCp02 value was 0 mmHg. The investigation, while still considered useful, has not gained widespread support. This study investigates the use of TCp02, establishes a value for the use of the TCp02 Index to predict amputation wound healing potential and examines the hypothesis that the use of the TcpO Index to select amputation level can reduce patient morbidity and mortality. The literature is reviewed and a series of studies evaluating TCp02 use, undertaken in the Durban Metropolitan Vascular Service Non-Invasive Laboratories, are presented. TCp02 measurements were performed in a standardised manner with the subject supine breathing room air. Measurements were taken at fixed sites, on the mid dorsum of the foot (Foot), 10 cm distal to the tibial tuberosity and 2 cm lateral to the anterior tibial margin (BKA), 10 cm proximal to the patella in the midline (AKA) and on the chest in the mid-clavicular line. A TCp02 Index, the limb to chest ratio was defined. TCp02 data derived from control subjects asymptomatic of peripheral vascular disease were shown to be similar to age matched pooled data derived from the literature. In patients with peripheral vascular disease, absolute TCp02 and the TCp02 Index were shown to fall from proximal to distal sites and again were no different to pooled data derived from the literature. Based on presenting symptoms, the fall in TCp02 and the TCp02 Index was significant from proximal to distal sites. The reduction in absolute TCp02 and the TCp02 was also related to the most distal pulse present. TCp02 values were found to be no different in patients with peripheral vascular disease with or without diabetes. When comparing TCp02 and the TCp02 Index with Doppler pressure measurements at the Popliteal artery and at the foot, and the Doppler ankle brachial index (ABI), Doppler derived data were significantly higher in diabetic patients than in non-diabetic patients. No differences were noted in TCp02 data. TCp02 was compared with the 133Xe radio-isotope skin washout test. The best correlation was (r = 0.46) was obtained with a logarithmic curve y = 10.862Ln(x) + 38.751. TCp02 was compared with antibiotic concentrations (Cefoxitin) in muscle obtained from the site of amputation and the Cefoxitin Index, the ratio of muscle antibiotic concentration to plasma concentration, as an indication of the relationship of skin TCp02 to muscle blood flow. A significant correlation was shown between the Cefoxitin Index and TCp02 (r = 0.67, p = 0.035) and the TCp02 Index (r = 0.64, P = 0.045), suggesting that skin oxygen delivery may reflect muscle antibiotic delivery and hence blood flow. TCp02 and the TCp02 Index were compared with heated and unheated laser Doppler fluxmetry (LDF) in 35 patients undergoing amputation wound healing assessment. Significant correlations were shown between heated LDF, heated LDF Index and the TCp02 Index (r = 0.63 and r = 0.69, P < 0.0001). TCp02 Index values of 0.5 and 0.55 showed an accuracy of 96.2 % in predicting amputation outcome while LDF values of 3, 4 and 5 arbitrary units gave an accuracy of 88.5 %. Using receiver operator curves, a TCp02 Index of 0.55 was shown to be the best test. Over the years 1987 and 1988, TCp02 data were gathered on 193 patients undergoing lower limb amputation for peripheral vascular disease. Information on the outcome of the amputation was available for 152 amputations. Circumstances which might result in a reduced pre-operative TCp02 reading were identified and criteria were set for the use of TCp02 to predict amputation wound healing potential. 122 amputations which met the defined entry criteria were available for evaluation. A TCp02 Index of 0.50 gave a definitive predictive value below which no amputation healed. Similarly no amputation with an absolute TCp02 of less than 27 mmHg healed. Receiver operator characteristic curves showed the TCp02 Index to be a better test than absolute TCp02. A TCp02 Index of 0.55 was shown to have the best sensitivity of96.7 %, with a specificity of79.8 % and an accuracy of 90.2 %. When introduced to clinical practice, correct use of the TCp02 Index of 0.55 resulted in a reduction in amputation revision rate from 40.3 % in 1987, to 8.2 % in 1990. Initially some surgeons felt that the TCp02 Index predicted amputation wound failure at distal sites at which healing could be expected on clinical criteria, and chose amputate at sites with a TCp02 Index value less than 0.55. These amputations failed to heal. As surgeons gained confidence in the test, they chose to follow the TCp02 data more often and the percentage of amputations performed at sites predicted by the TCp02 Index to fail , fell from 35.5 % in 1987 to 6.6 % in 1990. Over a 15 year period at King Edward VIII Hospital, the amputation revision rate has fallen from an average of 32.7 % in the first five years when Tcp02 data were not available to the surgeon, to 21.4 % and 22.9 % in the two subsequent 5 year periods when Tcp02 data were available. The mortality rates were unchanged. The decline in revision rates was less than expected and relates to the fact that approximately only 42 % of patients requiring amputation undergo the test. This is because it is time consuming and available only during weekday office hours. These studies have confirmed the usefulness of Tcp02 measurement in the non-invasive vascular laboratory. The index is shown to be superior to absolute Tcp02 as a predictive test of amputation wound healing. The introduction of several criteria to define when Tcp02 use is appropriate has refined the investigation and made it clinically useful in our setting. A Tcp02 Index of 0.55 in the appropriate patient is a useful test to predict amputation wound healing and its use has resulted in reduced patient morbidity and mortality, confirming the hypothesis tested. / Thesis (M.D.)-University of Natal, 2001.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (p. 436-460).

Internal sensory neurons monitor the chemical and physical state of the body, providing critical information to the nervous system for maintaining homeostasis and survival. Across species, such neurons innervate visceral organs to detect and relay information about their chemical and physical state to the central nervous system (CNS). While electrophysiology experiments over several decades have revealed a wide of range of stimuli that can activate internal sensory neurons, how stimuli are detected at the cellular and molecular level is only beginning to be elucidated. To elucidate the cellular and molecular basis of chemosensation by internal neurons, I used a population of larval Drosophila sensory neurons, tracheal dendrite (td) neurons, as the model system for my thesis work.I first presented a detailed characterization of the morphology of td neurons and their association with the tracheal system. I found that td dendrites extend along tracheal epithelial cells across their whole length. I further described that td dendrites extend to tracheal fusion sites, and can be observed terminating as enlarged bulbs adjacent to the tube enlargements. This specialized structure formed by td dendrites in relation to the nearby tracheal tissues may serve as an end organ for td sensory functions. I then proceeded to test the sensory functions of the td neurons. I found that td neurons respond to respiratory gases, namely decreases in O2 levels and increases in CO2 levels. Furthermore, I assessed the roles of atypical soluble guanylyl cyclases (Gycs) and a gustatory receptor (Gr) in mediating these responses. I found that Gyc88E/Gyc89Db are necessary for td responses to hypoxia, and that Gr28b is necessary for td responses to CO₂. Rescue of Gr28b isoform c rescued the mutant phenotype and also generalized the response to CO₂ in the td network. Additionally, I presented data suggesting carbonic anhydrases from surrounding tissues are required for td responses to CO₂, further elucidating the sensory transduction pathway of internal CO₂ detection. I further showed that gas-sensitive td neurons are activated when larvae burrow for a prolonged duration, demonstrating a natural-like feeding condition in which td neurons are activated. I also found that Drosophila larvae tend to avoid their td neurons being activated, suggesting td activation is aversive to the animals. Together, my work identified two stimuli that are detected by partially overlapping subsets of internal sensory neurons, and established roles for Gyc88E/Gyc89Db in the detection of hypoxia, and Gr28b together with carbonic anhydrases in the detection of CO₂. Combined with our previous understanding, different td neurons express various combinations of chemosensory receptors and have distinct functions, some of which remain to be discovered, indicating that this is a multifunctional internal sensory system. In conclusion, the results I presented in my thesis established new sensory detection pathways of Drosophila larval internal sensory neurons, which may be generalized across species and facilitate understanding of internal sensory systems.

This study aims the real-time monitoring of gases (CO2, N2, O2, H2, H2S, CH4, He, Ar) discharging from natural pools in the Tekke Hamam geothermal field (Denizli) in addition to the geochemical characterization of the field along with the Kizildere geothermal field, both located at the eastern segment of the B&uuml / y&uuml / k Menderes Graben. The continuous gas monitoring experiment (November 2007-October 2008) conducted in the Tekke Hamam geothermal field has revealed temporal variations in the gas compositions, gas flow rate and pool temperature. Different variation components, such as daily variation profiles and peak/Multi-day signals, are detected in the monitored data, which are mainly correlated with shallow and deep processes involving mainly meteorological factors and seismicity induced variations, respectively. Particularly, the coupled variations in the gas compositions and flow rate seem to correlate with seismicity induced permeability modifications within the subsurface during the absence of significant meteorological factors, such as high rainfall and varying atmospheric pressure. The noble gas characterization of the fields have revealed both high 3He/4He and 4He/20Ne isotopic ratios, suggesting a mantle contribution of about 18% for Kizildere and 34% for Tekke Hamam, whereas the other noble gases (Ar, Ne, Kr, Xe) are of atmospheric nature. The different mantle contributions observed in both fields can suggest a different mantle-He flux variably contaminated by crustal helium. The chemical (cation-trace element-anion) and stable isotopic (&amp / #948 / 18O-&amp / #948 / D) contents of the thermal waters reveal high temperature water-rock interaction accompanied by the effects of deep origined gases (mainly CO2 and H2S) discharging from the fields.

This thesis addresses the problem of gas distribution modelling for gas monitoring and gas detection. The presented research is particularly focused on the methods that are suitable for uncontrolled environments. In such environments, gas source locations and the physical properties of the environment, such as humidity and temperature may be unknown or only sparse noisy local measurements are available. Example applications include air pollution monitoring, leakage detection, and search and rescue operations. This thesis addresses how to efficiently obtain and compute predictive models that accurately represent spatio-temporal gas distribution. Most statistical gas distribution modelling methods assume that gas dispersion can be modelled as a time-constant random process. While this assumption may hold in some situations, it is necessary to model variations over time in order to enable applications of gas distribution modelling for a wider range of realistic scenarios. This thesis proposes two time-dependent gas distribution modelling methods. In the first method, a temporal (sub-)sampling strategy is introduced. In the second method, a time-dependent gas distribution modelling approach is presented, which introduces a recency weight that relates measurement to prediction time. These contributions are presented and evaluated as an extension of a previously proposed method called Kernel DM+V using several simulation and real-world experiments. The results of comparing the proposed time-dependent gas distribution modelling approaches to the time-independent version Kernel DM+V indicate a consistent improvement in the prediction of unseen measurements, particularly in dynamic scenarios under the condition that there is a sufficient spatial coverage. Dynamic scenarios are often defined as environments where strong fluctuations and gas plume development are present. For mobile robot olfaction, we are interested in sampling strategies that provide accurate gas distribution models given a small number of samples in a limited time span. Correspondingly, this thesis addresses the problem of selecting the most informative locations to acquire the next samples. As a further contribution, this thesis proposes a novel adaptive sensor planning method. This method is based on a modified artificial potential field, which selects the next sampling location based on the currently predicted gas distribution and the spatial distribution of previously collected samples. In particular, three objectives are used that direct the sensor towards areas of (1) high predictive mean and (2) high predictive variance, while (3) maximising the coverage area. The relative weight of these objectives corresponds to a trade-off between exploration and exploitation in the sampling strategy. This thesis discusses the weights or importance factors and evaluates the performance of the proposed sampling strategy. The results of the simulation experiments indicate an improved quality of the gas distribution models when using the proposed sensor planning method compared to commonly used methods, such as random sampling and sampling along a predefined sweeping trajectory. In this thesis, we show that applying a locality constraint on the proposed sampling method decreases the travelling distance, which makes the proposed sensor planning approach suitable for real-world applications where limited resources and time are available. As a real-world use-case, we applied the proposed sensor planning approach on a micro-drone in outdoor experiments. Finally, this thesis discusses the potential of using gas distribution modelling and sensor planning in large-scale outdoor real-world applications. We integrated the proposed methods in a framework for decision-making in hazardous inncidents where gas leakage is involved and applied the gas distribution modelling in two real-world use-cases. Our investigation indicates that the proposed sensor planning and gas distribution modelling approaches can be used to inform experts both about the gas plume and the distribution of gas in order to improve the assessment of an incident.

Cette thèse touche à la problématique des échanges de gaz aux interfaces entre la géosphère, la biosphère, l'hydrosphère et l'atmosphère par l'intermédiaire du monitoring géochimique des gaz appliqué aux sites de stockage géologiques du CO2. Au niveau de l'axe « Métrologie », nous avons développé une plate-forme de monitoring géochimique continu, in situ et déportée par spectrométrie FTIR/Raman pour la mesure des gaz du sol (CO2, CH4, N2, O2, H2O). Des protocoles de quantification ont été développés pour la mesure par télédétection infrarouge terrestre en mode passif du CO2, CH4, SO2, H2S dans l'atmosphère. Au niveau des axes « Monitoring » et « Modélisation », les mesures de gaz du sol à proximité du puits d'injection de Rousse (Pilote CO2 Total, Lacq/Rousse, France) sur plus de sept cycles saisonniers ont montré une anti-corrélation entre la teneur en CO2 et les variations du niveau piézométrique de la nappe. Cette relation a permis de modéliser l'enveloppe de variabilité « naturelle » de la teneur en CO2 dans le sol, qui constitue un élément clé pour la surveillance des sites de stockage. Les variations majeures de teneur en CO2 sont attribuées à des processus de dissolution/libération de CO2 par la nappe, jouant un rôle de pompe à CO2. La concentration en CO2 en surface (+1m) serait gouvernée par les variations de teneur en CO2 du sol. Les mesures par télédétection FTIR des gaz dans l'atmosphère ont permis d'établir pour la première fois une simulation expérimentale 3D des enveloppes de CO2 à l'aplomb du site d'injection. Ces résultats constituent un premier pas vers la mise en place d'un outil de surveillance des panaches gazeux dans l'atmosphère / This study is based on the problematic of gas exchanges at the interface between the geosphere, biosphere, hydrosphere and atmosphere through the geochemical monitoring of gas applied to CO2 geological storage sites. Concerning the "Metrological" aspect, we developed and implemented an in situ continuous geochemical monitoring station, based on coupling FTIR/ Raman spectrometry for measuring soil gas (O2, N2, CO2, CH4 and H2O) close to the injection wells of Rousse 1 (CCS Total pilot, Lacq-Rousse, France). We also developed protocols to identify and quantify CO2, CH4, SO2, H2S in the atmosphere (plume) by passive remote sensing FTIR. On the "Monitoring" and "Modelling" aspects, the continuous recording of soil CO2 concentration during more than 7 seasonal cycles indicate that CO2 concentration in the soil was anti-correlated with changes in piezometric level of the groundwater. This correlation was used to model the limits of natural variability of CO2 content in the soil, which is a key to CCS sites monitoring. The main fluctuations in soil CO2 content was assigned to a dissolution/release process of CO2 by the perched water table, acting as a CO2 pump. The CO2 concentration at the near surface (+ 1 m) would be governed by changes of the soil CO2 content. FITR remote sensing measurement of atmospheric gases allowed for the first time to perform an experimental 3D simulation of CO2 layers on the injection site. This type of experimental simulation is a first step for the monitoring of gases in the atmosphere