Typescript (photocopy). / Digitized by Kansas Correctional Industries

The objective of this dissertation is to provide insight into the mechanisms that are responsible for the nonlinearities and asymmetries of the voltage current characteristic of the human skin. Furthermore to provide an explanation for the partially reversible breakdown of the electrical resistance of the skin that results in a rapid decrease of the skin resistance and occurs when the skin is stimulated with a dry electrode. The skin resistance and impedance was investigated with low frequency constant voltage pulses and with sinusoidal stimulation over a range of amplitudes (10 - 20 V) and frequencies (3 - 30 Hz), using a dry 79 mm2 Ag/AgCI electrode. Evidence is presented that electroporation of the lipid bilayer membranes occurs in the dry skin over in the voltage range 10-20 V, a wider range than previously thought; it is further shown that experimental results are predicted by electroporation theory, if it is assumed that a small percentage of the total surface area of the dry skin consists of 15 lipid bilayers in series, rather than the generally accepted estimate of 70-100 layers. By modeling the dry skin as 15 lipid bilayers in series undergoing electroporation, the non-linearity of voltage-current characteristic of the skin is accurately predicted. Evidence is presented in support of a new hypothesis that the asymmetry of the skin's voltage-current characteristic can be attributed to electro-osmosis occurring within the lipid bilayers of the stratum corneum. It is further suggested that the existing mathematical description of electro-osmosis would not accurately describe this situation and equations were introduced to model the effect of electro-osmosis on the voltage-current characteristic of the skin. An electrical model of the skin is presented based on the hypothesis that the VOltage-current characteristic of the skin is due to the combined effect of electroporation and electro-osmosis on the lipid bilayers in the stratum corneum. In addition the model accounts for the effect of trans epidermal water loss. / Dissertation (M Eng (Bio-Engineering))--University of Pretoria, 2006. / Civil Engineering / unrestricted

Thesis (MScMedSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Swallowing disorders are prevalent in many elderly individuals and are common amongst individuals suffering from neurological diseases. These individuals are affected from slight swallowing difficulty to total swallowing inability. In severe cases this may cause aspiration pneumonia, dehydration, malnutrition and ultimately death. Swallowing disorders can be diagnosed and treated to increase quality of life. New treatment strategies to understand the pathophysiology and impaired swallowing response are needed. Neuromuscular electrical stimulation is used as rehabilitation method in various disciplines. This method of rehabilitation of physiological dysfunction is used in treating swallowing disorders and has become a focus for current research. To understand the effect of electrical stimulation to the swallowing centre it is proposed to study its mechanism on normal swallowing musculature. The outcome of the effect that electrical stimulation has on healthy individuals may possibly be used to extrapolate to clinical settings and its benefit for modern dysphagia rehabilitation. The purpose of this study was to report on the hyo-laryngeal movement pattern of young healthy, male and female, individuals and to measure the effect of a single neuromuscular electrical stimulation session on the hyo-laryngeal complex of 22 young healthy individuals. Lastly, the aim was to determine the detraining or lasting effect on the hyo-laryngeal swallowing complex of a single neuromuscular electrical stimulation session. The study reported on baseline hyo-laryngeal complex movement patterns by measuring the anterior movement and elevation of the hyo-laryngeal complex through the use of videofluoroscopy swallow study. Analysis of these measurements where done to report on the effect of electrical stimulation on the hyo-laryngeal complex movement pattern pre- and post- electrical stimulation. Significant changes were revealed with elevation of the hyo-laryngeal complex, however no significant effects could be found with anterior movement of the hyo-laryngeal complex pre- and post- electrical stimulation. It was found that elevation of the hyo-laryngeal complex lowered after a single electrical stimulation session. The hyo-laryngeal complex movement pattern remained similar between genders. Lastly it was found that a single electrical stimulation session showed significant reversibility towards baseline levels. This might be related to muscle fatigue and one would need to take into account muscle recovery for future research. / AFRIKAANSE OPSOMMING: Sluk versteurings is algemeen onder bejaardes asook individue wat ly aan neurologiese siektes. Hierdie individue word geaffekteer deur matige sluk probleme tot totale sluk onvermoë. In ernstige gevalle kan dit aanleiding gee tot aspirasie longontsteking, dehidrasie, wanvoeding en selfs dood. Sluk versteurings kan gediagnoseer en behandel word om die kwaliteit van lewe te verbeter. Dit is daarom noodsaaklik om die patofisiologiese en verswakte sluk reaksie te verstaan om sodoende nuwe behandeling strategieë te ontwikkel. Neuromuskulêre elektriese stimulasie word gebruik as rehabilitasie tegniek in verskeie dissiplines. Hierdie metode van behandeling van fisiologiese disfunksie word ook gebruik in die behandeling van sluk afwykings en geniet tans baie navorsings aandag. Om die effek van elektriese stimulasie op die sluk sentrum te verstaan word dit dus voorgestel dat die meganisme op die normale sluk spierstelsel bestudeer word. Hierdie bevindinge kan dus moontlik toegepas word op persone met sluk afwykings en sodoende meer effektiewe rehabilitasie tegnieke bevorder. Die doel van hierdie studie was om die effek op die hyo-laringeale bewegings patroon van jong, gesonde, manlike en vroulike individue te bestudeer, asook om verslag te doen oor die uitwerking van 'n enkele neuromuskulêre elektriese stimulasie sessie op die hyo-laringeale kompleks van 22 jong, gesonde individue. Laastens was die doel van hierdie studie ook om die blywende effek van 'n enkele sessie neuromuskulêre elektriese stimulasie op die sluk sentrum te bepaal. Die studie het basislyn hyo-laringeale kompleks bewegings patrone gerapporteer deur die voorwaartse asook opwaartse beweging van die hyo-laringeale kompleks te meet deur gebruik te maak van videofluoroskopie sluk studies. Ontleding van hierdie metings is gedoen om die uitwerking van elektriese stimulasie op die hyo-laringeale kompleks bewegings patroon voor en na elektriese stimulasie te bepaal. Beduidende veranderinge is in die opwaartse beweging van die hyo-laringeale kompleks gevind, alhoewel geen veranderinge gevind is in die voorwaartse beweging van die hyo-laringeale kompleks voor en na elektriese stimulasie nie. Daar is vasgestel dat die opwaartse beweging van die hyo-laringeale kompleks verlaag het na 'n enkele elektriese stimulasie sessie. Verder het die hyo-laringeale kompleks bewegings patroon geen beduidende verskille tussen geslagte getoon nie. Laastens is bevind dat 'n enkele elektriese stimulasie sessie beduidende omkeerbaarheid terug na basislyn vlakke van beweging toon. Dit kan verband hou met die uitputting van die hyo-laringeale spiere as gevolg van die elektriese stimulasie en toekomstige navorsing sal dus uitputting, asook die tempo van herstel in ag moet neem.

Thesis (M.Eng.(Bio-Engineering))--University of Pretoria, 2003. / Summaries in Afrikaans and English. Includes bibliographical references.