Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 166-173).

Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: disinfection by-products; sonication; ultrasound. Includes bibliographical references (leaves 65-70).

The work was carried out with the aim of developing an optical interferometric detection system. This was to be applied to the quantative measurement of low amplitude, high frequency surface displacements (< 1nm at several MHz). Two forms of interferometric detector are investigated. The performance and limitations in particular measurement situations are assessed for both types of interferometer. The first type of detector investigated is a miniature stabilised interferometer. The design of a stabilisation system is given, along with ways in which it can be optimised for a particular environment. The second type of detector studied is a quadrature interferometer. Various methods of processing the two channels of information from this device are discussed. The design of a new method of processing the signals is given, and its performance determined. The interferometric sensor is combined with a waveform digitiser and microcomputer to form an integrated detection system. Analysis of the waveforms obtained is performed by a system of Pascal programs developed for this purpose. The detection system is applied to tasks such as the calibration of other forms of transducer and the characterisation of artificial sources of acoustic emission. The results of experimental studies are given and the applications of such a system discussed.

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In this thesis the use of real-time ultrasound in the assessment and management of preterm labour has been studied, with particular reference to the observation of fetal breathing movements, gross fetal body movements and the state of the uterine cervix. In addition, a longitudinal analysis of the trends in preterm labour in the John Radcliffe Hospital in Oxford between 1973 and 1981 has been performed. Finally, an attempt has been made to clarify the relationship between prostaglandin E2 and fetal breathing movements. The analysis of the trends in preterm labour in Oxford has shown that the incidence of preterm delivery remains unaltered. Of these patients, however, those eligible for tocolytic therapy (unexplained spontaneous preterm labour) form a small proportion. The incidence of extreme prematurity in this group is very low and the neonatal outcome is good. The presence or absence of Fetal Breathing Movements (FBM) by defined criteria is shown to be a highly sensitive index of whether the preterm labour is going to progress to delivery or not in singleton pregnancies with intact membranes. Its significance is lost when the membranes are ruptured and in multiple pregnancies. In pregnancies complicated by antepartum haemorrhage the presence or absence of Fetal Breathing Movements does not predict further haemorrhage leading to delivery. Fetal Breathing Movement status on admission bears no relationship to neonatal outcome and gives no indication of the presence of intrauterine infection. Silent chorioamnionitis has been highlighted as an important cause of "unexplained" preterm labour. Gross Fetal Body Movements (FM) are shown to give no early indication of impending preterm delivery. Evidence is presented to suggest that significant diminution in Fetal Movements is related to poor neonatal outcome. Ultrasonic measurement of the uterine cervix has been found to be technically feasible but of no benefit in the diagnosis of ongoing preterm labour. The relationship between prostaglandin E2 (PGE2) and the cessation of fetal breathing movement has been approached by elucidating the maternal absorption of PGE2 from a vaginal pessary. This then enabled me to sample fetal blood at the time of maximal maternal concentrations (the time we expect the fetal concentration to be greatest). This was performed by fetoscopy and demonstrated that a significant rise in fetal bicycleprostaglandin-E-metabolite (bicyclo-PGEM) occurs following maternal vaginal administration of PGE2. Using this information FBM has been assessed two and a half hours following the vaginal administration of PGE2. Although inconclusive, no reduction in FBM was demonstrated. as the bicyclo-PGE metabolite is used to assess PGE levels, this evidence decreases the probability that PGE mediates the reduction in FBM with the onset of labour.

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This thesis details advances made within the field of electroanalytical chemistry through the use of working electrodes that have been activated through application of ultrasound, heat, geometry, chemical modification or composition. Initially the thesis reports the enhanced analytical utility of chemically and compositionally modified working electrodes when directed towards the detection and determination of NO₃¯ and NO₂¯ anions in environmental samples. This has been achieved through the use of electrodes that have been a) modified with a Cu deposit and b) fashioned from a Cu-Ni alloy. Nitrate and nitrite anions have been successfully determined in a variety of passivating matrices, at analytically relevant detection limits of the order of 10^-6 M with a dynamic linear range extending from 10 to 200 μM. The methods presented have been shown to surpass existing electrochemical techniques in terms of nitrate/nitrite speciation through separation of the voltammetric signals, where existing analyses have reported the intereference of both species when present in the same solution. The use of ultrasound as a further enhancement to the sensitivity and versatility of the electrochemical detection of nitrate at a chemically modified electrode is then presented. The influence of ultrasound is shown to remove a portion of the deposited copper, but a significant catalytic layer remains, resulting in greater sensitivity during insonation. The effect of temperature on electrochemical systems involving one- and two-electron redox reactions of K₄Fe(CN)₆, Ru(NH₃)₆Cl₃, Fe(C₅H₅)₂, N,N,N',N'tetramethylphenylenediamine, N,N'dimethylphenylenediamine and tris(4- bromophenyl)amine have been studied under hydrothermal conditions using a novel hydrodynamic method based on a conventional channel flow cell where the working electrode is heated by radio frequency radiation. The diffusion activation parameters obtained with the radio frequency channel cell and computer simulation were compared with independent data from microelectrode high temperature experiments. The application of the heated flow cell as a tool for mechanistic studies is discussed with the investigation of the well characterised ECE reaction of m-iodo-nitrobenzene in acetonitrile, giving a value of 80 ± 5 kJ mol^-1 for the activation energy of the rate constant for the decomposition of the m-iodo-nitrobenzene radical anion. This represents the first observation of an ECE or mechanistically complex reaction at a locally heated electrode. The work presented in the final two chapters of this thesis examines the enhanced activation achieved from modification of the electrode geometry, and in particular the application of microelectrodes to the development of electroanalytical techniques. The electrochemical reduction of the inhalation anaesthetic agent enflurane (2-chloro-1,1,2- trifluoroethyl difluoromethyl ether) is reported at a variety of microelectrode substrates (Au, Ag, Cu, Pt and glassy carbon) with electrode dimensions varying from 5 to 60 μm. The solvents water, dimethylsulfoxide and acetonitrile were investigated along with the supporting electrolytes potassium chloride, tetrabutylammonium hexafluorophosphate and various tetraalkylammonium perchlorates. The use of a gold microelectrode with dimethyl sulfoxide solvent and tetraethylammonium perchlorate as the supporting electrolyte was found to give well-defined voltammetry. Linear calibration curves were obtained between 0 and 2 % v/v (gaseous additions) or up to 135 mM (gravimetric additions), offering scope for the development of a rapid, inexpensive electrochemical gas sensor. The analytical utility of the system has been investigated in the presence of oxygen and nitrous oxide in DMSO solvent. The superoxide anion radical, formed from the electro-reduction of dissolved oxygen, is shown to react with enflurane complicating their simultaneous detection. The kinetics of the enflurane / superoxide reaction are found to be first order with respect to both superoxide and enflurane with a rate constant of 0.25 M^-1 s^-1 determined by three independent methods: steady-state voltammetry, digital simulation of cyclic voltammetric data and UV/Vis spectroscopic analysis.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: drinking water; disinfectant; ultrasound. Includes bibliographical references (p.91-95).