À ce jour, cette thèse n’a pas été déposée auprès de l’université de soutenance. L’Université Clermont Auvergne est donc dans l’impossibilité d’en assurer le traitement, la conservation et la diffusion. / To date, this thesis has not been deposited. The Université Clermont Auvergne is therefore unable to ensure its processing, conservation and dissemination.

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Projections of the World Energy Council indicate a significant increase in global energy consumption in the medium and long term due to a growing world population and rising prosperity whilst global fossil fuel reserves are in decline. Eighty percent of the world’s energy consumption is generated from fossil fuels and this is unlikely to change in the short and medium term inevitably leading to energy shortfalls. The CO2-less energy of nuclear fuel shows strong potential to meet the future energy demands. However economic, politic and environmental requirements mean that the nuclear industry must adapt its current technology and present fuel usage. A pyroelectrochemical reprocessing system utilising liquid cathode technology could provide an efficient and secure reprocessing cycle essential for reduction in volume and toxicity of nuclear waste and extension of natural nuclear resources. The electrochemistry of aqueous copper(II) and zinc(II) chloride was studied upon a liquid mercury cathode using cyclic voltammetry. Bulk deposition of the Cu upon the liquid mercury cathode was studied using both amperometry and Electrochemical Impedance Spectroscopy. The surface deposits formed by copper deposition upon the mercury liquid cathode were analysed using x-ray powder diffraction and determined to be the rare naturally occurring mineral Belendorffite, Cu7Hg6. Electrochemical diagnostics for surface deposition upon the mercury liquid cathode surface were investigated as a potential analogue system for high temperature liquid cathode systems. Bulk deposition investigation of lanthanum upon the high temperature bismuth system demonstrated transfer of EIS diagnostics for surface growth, with the system demonstrating a similarity to the zinc-mercury ambient system. An electrochemical technique for purifying LiCl/KCl molten salt using an electrolysis technique was demonstrated. The electrochemical cleaning method forgoes the standard chemical treatments that can leave contaminants within the treated salt and results in a cleaner less oxidising molten salt eutectic.

Impedance pneumography is a non-invasive and a very convenient technique for monitoring breathing. However, a major drawback of this technique is that it is impossible to monitor breathing due to large artefacts introduced by the body movements. The aim of this project was to develop a technique for reducing these 'movement artefacts'. In the first stage of the project, experimental and theoretical studies were carried out to identify an 'optimum' electrode placement that would maximise the 'sensitivity' of measured thoracic impedance to lung resistivity changes. This maximum sensitivity was obtained when the drive and the receive electrode pairs were placed in two different horizontal planes. This sensitivity was also found to increase with increase in electrode spacing. In the second stage, the optimum electrode placement was used to record thoracic impedance during movements. Movement artefacts occurred only when the electrodes moved from their initial location along with the skin, during movements. Taking into consideration these observations, a strategy was decided for placing 4 electrodes in one plane so that movement artefacts could be reduced by combining the two independent measurements. Further studies showed that movement artefacts could be reduced using a strategic 6- electrode placement in three dimensions. It was also possible to detect obstructive apnoea, as the amplitude of the breathing signal was higher than that due to obstructive apnoea and this difference was statistically significant. In these studies, the main cause of movement artefacts was identified as the movement of electrodes with the skin. A significant reduction in movement artefacts was obtained using the 6-electrode placement. This advantage of the 6-electrode placement proposed in this project, can be of great use in clinical applications such as apnoea monitoring in neonates. Further studies can be carried out to determine an optimum frequency of injected current to achieve reduction in residual movement artefacts.

This paper is an attempt to appraise the usefulness of the dropping gallium electrode (DGE) in fused LiNO3-KNO3, to compare it with the dropping mercury electrode (DME), and to study the DGE in fused LiCl-KCl.

<p>Background and purpose: The relevance of skin preparation</p><p>by abrasion preceded or not by alcohol cleansing for digital</p><p>ECG (dECGs) variables was prospectively evaluated.</p><p>Methods: In 22 healthy male subjects (40.2±9.7 years) dECGs</p><p>were recorded continuously over 5 minute periods at 5 different</p><p>time points at 3 separate 24-hour visits, employing 2 electrode</p><p>types and no skin preparation, abrasion and alcohol cleansing</p><p>before abrasion. Smoothed means dECG data covering 5</p><p>minutes used for statistical analysis on leads V2-3 and V5.</p><p>Results: Significant of skin preparation with reductions for</p><p>skin-impedance and noise (p<0.0001 – p=0.35) for all leads,</p><p>and with no further effect by alcohol cleansing (p>0.46). PRintervals</p><p>were significantly prolonged by skin preparation</p><p>(p=0.0003 – p=0.0165) in leads V2-3 at 120 and 1 440 minutes;</p><p>with additional impact of alcohol at 1 440 minutes (p=0.0005).</p><p>Subject comfort was markedly higher with one of the electrode</p><p>types (p<0.0001).</p><p>Conclusion: Skin preparation by abrasion should be employed</p><p>prior to dECG recordings to improve signal properties.</p><p>Cleansing with alcohol is generally not warranted. Skin</p><p>irritation is dependant on choice of electrode.</p>

Background and purpose: The relevance of skin preparation by abrasion preceded or not by alcohol cleansing for digital ECG (dECGs) variables was prospectively evaluated. Methods: In 22 healthy male subjects (40.2±9.7 years) dECGs were recorded continuously over 5 minute periods at 5 different time points at 3 separate 24-hour visits, employing 2 electrode types and no skin preparation, abrasion and alcohol cleansing before abrasion. Smoothed means dECG data covering 5 minutes used for statistical analysis on leads V2-3 and V5. Results: Significant of skin preparation with reductions for skin-impedance and noise (p<0.0001 – p=0.35) for all leads, and with no further effect by alcohol cleansing (p>0.46). PRintervals were significantly prolonged by skin preparation (p=0.0003 – p=0.0165) in leads V2-3 at 120 and 1 440 minutes; with additional impact of alcohol at 1 440 minutes (p=0.0005). Subject comfort was markedly higher with one of the electrode types (p<0.0001). Conclusion: Skin preparation by abrasion should be employed prior to dECG recordings to improve signal properties. Cleansing with alcohol is generally not warranted. Skin irritation is dependant on choice of electrode.