The aortic valve functions in a complex mechanical environment which leads to force dependent cellular and tissue responses. Characterization of these responses provides a fundamental understanding of valve pathogenesis. The aim of this work was to develop an ex vivo organ culture system capable of simulating physiological aortic pressures and flow rates, and study the biological characteristics of native porcine aortic valves cultured in the system. Collagen, sGAG and elastin content of the valve leaflets were measured and cusp morphology, cell phenotype, cell proliferation and apoptosis were examined. Presence of endothelial cells (ECs) on the leaflet surface was also evaluated. The differences in collagen, sGAG and elastin contents were not significant (p greater than0.05) between the cultured and fresh valve leaflets. The cultured valves maintained the structural integrity of the leaflets while preserving the native morphology and cell phenotype. Cell phenotype in leaflets incubated statically under atmospheric conditions decreased compared to fresh and cultured valve leaflets, indicating the importance of mechanical forces in maintaining the natural biology of the valve leaflets. ECs were retained on the surfaces of cultured leaflets with no remodeling of the leaflets. The number of apoptotic cells in the cultured leaflets was significantly (p less than 0.05) less than in the statically incubated leaflets and comparable to fresh leaflets. The sterile ex vivo organ culture system thus maintained the viability and native biological characteristics of the aortic valves that were cultured under dynamic conditions for a period of 48 hours.

The study of wave production and propagation is a common phenomenon seen within a variety of math and physics problems. This thesis in particular will investigate the production and propagation of sound waves through musical instruments. Although this field of work has been examined since the late 1800s, approaching these types of problems can be very difficult. With the exception of the last fifty years, we have only been able to approach such problems by linearizing the necessary equations of gas dynamics. Without the use of a computer, one can only get so far in studying nonlinear acoustic problems. In addition, the numerical theory for nonlinear problems is incomplete. Proving stability is challenging and there are a variety of open problems within this field. This thesis will be examining the propagation of sound waves specifically through brass instruments. However, we will not be able to fully examine this problem in a master’s thesis because of the complexity. Instead, the objective is to provide a foundation and global picture of this problem by merge the fields of nonlinear acoustics as well as computational and analytical gas dynamics. To study the general behaviour of nonlinear wave propagation (and to verify previous findings), experiments have been carried on a trumpet. The purpose of these experiments is take measurements of the sound pressure waves at various locations along the instrument in order to understand the evolution of the wave propagation. In particular, we want to establish if the nonlinear distortion is strong enough to have musical consequences; and if there are such outcomes, what prerequisites are required for the observable behaviour. Additionally, by using the discontinuous Galerkin numerical method, a model of the system will be presented in this thesis. It will then be compared with the experimental data to verify how well we were able to describe the nonlinear wave motion within a trumpet.

abstract: Aortic pathologies such as coarctation, dissection, and aneurysm represent a particularly emergent class of cardiovascular diseases and account for significant cardiovascular morbidity and mortality worldwide. Computational simulations of aortic flows are growing increasingly important as tools for gaining understanding of these pathologies and for planning their surgical repair. In vitro experiments are required to validate these simulations against real world data, and a pulsatile flow pump system can provide physiologic flow conditions characteristic of the aorta. This dissertation presents improved experimental techniques for in vitro aortic blood flow and the increasingly larger parts of the human cardiovascular system. Specifically, this work develops new flow management and measurement techniques for cardiovascular flow experiments with the aim to improve clinical evaluation and treatment planning of aortic diseases. The hypothesis of this research is that transient flow driven by a step change in volume flux in a piston-based pulsatile flow pump system behaves differently from transient flow driven by a step change in pressure gradient, the development time being substantially reduced in the former. Due to this difference in behavior, the response to a piston-driven pump can be predicted in order to establish inlet velocity and flow waveforms at a downstream phantom model. The main objectives of this dissertation were: 1) to design, construct, and validate a piston-based flow pump system for aortic flow experiments, 2) to characterize temporal and spatial development of start-up flows driven by a piston pump that produces a step change from zero flow to a constant volume flux in realistic (finite) tube geometries for physiologic Reynolds numbers, and 3) to develop a method to predict downstream velocity and flow waveforms at the inlet of an aortic phantom model and determine the input waveform needed to achieve the intended waveform at the test section. Application of these newly improved flow management tools and measurement techniques were then demonstrated through in vitro experiments in patient-specific coarctation of aorta flow phantom models manufactured in-house and compared to computational simulations to inform and execute future experiments and simulations. / Dissertation/Thesis / Doctoral Dissertation Bioengineering 2015

Les futurs réseaux sans fil devront être conçus pour répondre aux besoins hétérogènes de systèmes entièrement différents. De nouveaux services soumis à des contraintes variées coexisteront avec les utilisateurs actuels sur la même bande de fréquences. L'OFDM, la couche physique utilisée par les systèmes actuels, souffre d’un mauvais confinement spectral et ne permet pas cette coexistence. De nombreuses nouvelles formes d'onde avec une localisation spectrale améliorée ont donc été proposées. Nous étudions la coexistence de nouveaux systèmes basés sur ces formes d'onde avec des utilisateurs OFDM préexistant. Nous fournissons la première analyse théorique et expérimentale de l'interférence inter-système qui se produit dans ces scenarios. Nous appliquons ensuite cette analyse pour évaluer les performances de différentes formes d'ondes avancées et nous étudions finalement les performances d'un réseau où des utilisateurs cellulaires OFDM coexistent avec des paires D2D utilisant l'une des formes d'ondes améliorées étudiées. / Future wireless networks are envisioned to accommodate the heterogeneous needs of entirely different systems. New services obeying various constraints will coexist with legacy cellular users in the same frequency band. This coexistence is hardly achievable with OFDM, the physical layer used by current systems, because of its poor spectral containment. Thus, a myriad of multi-carrier waveforms with enhanced spectral localization have been proposed for future wireless devices. In this thesis, we investigate the coexistence of new systems based on these waveforms with legacy OFDM users. We provide the first theoretical and experimental analysis of the inter-system interference that arises in those scenarii. Then, we apply this analysis to evaluate the merits of different enhanced waveforms and we finally investigate the performance achievable by a network composed of legacy OFDM cellular users and D2D pairs using one of the studied enhanced waveforms.

The aim of this study was to determine the knowledge of critical care nurses regarding ventilator waveforms in order to develop an educational programme on this topic. A quantitative, descriptive, contextual research design was used, and convenience sampling implemented. A survey, using a questionnaire as measuring instrument, was conducted among critical care nurses in selected private hospitals in Gauteng. The response rate was 69%. Cronbach’s alpha indicated that the questionnaire was fairly reliable. The total average percentage achieved by the group of 111 respondents was 40,28%, which is 19.72% below the set competency indicator of 60%. Only 15 respondents achieved a percentage of or above the competency indicator. Results proved that the respondents required intensive training on the topic. A user-friendly education programme in the format of a PowerPoint presentation was developed to address knowledge deficiencies in critical care nurses’ interpretation of ventilator graphics. / Dissertation (MCur (Clinical))--University of Pretoria, 2007. / Nursing Science / MCur / unrestricted

Estudos utilizando imagens laríngeas de sujeitos normais captadas por videolaringoscopia de alta velocidade revelam o uso de diversas ferramentas e métricas em diferentes populações. No entanto, é evidente a escassez de normatizações operacionais e de parâmetros vocais de referência. Os objetivos desse estudo foram obter parâmetros da dinâmica vocal utilizando ferramentas computacionais de uso corrente pelo Grupo de Pesquisa em Engenharia Médica (GPEM - CNPq) e caracterizar o padrão vibratório das pregas vocais de sujeitos normais por meio das ondas da área glótica e quimografia de alta velocidade do utilizando Videolaringoscopia de alta velocidade. Metodologia: A partir de imagens laríngeas captadas pela videolaringoscopia de alta velocidade foram extraídos os parâmetros quantitativos: i) tempos de fases e período total do ciclo vibratório das pregas vocais das ondas da área glótica, ii) tempos de fases e período total do ciclo vibratório das pregas vocais da quimografia de alta velocidade, iii) coeficientes (de abertura, de fechamento e de velocidade). Além disso, foram analisados os parâmetros qualitativos das ondas da área glótica e da quimografia de alta velocidade de acordo com a aplicação de protocolos elaborados para classificação de padrões visuais. Resultados: Das ondas da área glótica foram obtidos os valores médios, em milissegundos, de fase fechada: feminino=0.83 e masculino= 2.47; de abertura: feminino= 2.43 e masculino= 2.95; de fechamento: feminino=2.08 e masculino= 2.53; aberta: feminino= 6.15 e masculino= 6.18, período total do ciclo vibratório: feminino=6.98 e masculino= 8.65; coeficientes: de fechamento: feminino=0.14 e masculino=0.29, de abertura: feminino=0.85 e masculino=0.70, de velocidade: feminino=1.16 e masculino=1.19, além de 73% dos traçados apresentarem sinal periódico. Quanto à quimografia de alta velocidade os parâmetros quantitativos obtidos foram: fase fechada: feminino=1.75 e masculino=3.32, de abertura: feminino= 1.47 e masculino= 2.32; de fechamento: feminino= 1.51 e masculino= 2.22; aberta: feminino= 2.91 e masculino= 4.56, e período total do ciclo vibratório: feminino= 4.67 e masculino= 7.89. Os coeficientes obtidos foram: de fechamento: feminino= 0.37 e masculino= 0.42.; de abertura: feminino= 0.62 e masculino= 0.57; e de velocidade: feminino= 1.02 e masculino= 1.12. 59% de simetria em amplitude e 54% de assimetria de fase foram encontrados no traçado da quimografia de ata velocidade de sujeitos normais. Conclusão: A partir do uso de ferramentas computacionais específicas para analisar imagens laríngeas da videolaringoscopia de alta velocidade foi possível obter parâmetros quantitativos e qualitativos das ondas da área glótica e quimografia de alta velocidade de sujeitos normais e obter dados de referência quanto à normalidade para futuros estudos. / Several studies using laryngeal images from high-speed videolaryngoscopy of normal subjects reveals the diversity of tools and metrics used for different population. However, shortage of operational standardization and references of vocal fold parameters are evident. The main objectives of this study were to obtain parameters of vocal dynamics using computational tools of Medical Engineering Research Group (GPEM - CNPq) and to characterize the vocal fold\'s vibration pattern of normal subjects using glottal area waveforms and high-speed kymography. Methods: From laryngeal images of high-speed videolaryngoscopy we extracted the following quantitative parameters: i) phase time of glottal area waveforms, ii) phase time of vibratory cicle\'s total period, iii) quocients of high-speed kymography. Furthermore, qualitative parameters of glottal area waveform were analyzed according to visual pattern protocol. Results: Media values of glottal area waveforms, in milliseconds, of closed phase: female=0.83 and male= 2.47; opening phase: female= 2.43 and male= 2.95; closing phase: female= 2.08 and male= 2.53; opened phase: female=6.15 and male= 6.18, vibratory cicle of total period: female= 6.98 and male= 8.65, closing quotient: female= 0.14 and male= 0.29; opening quotient: female= 0.85 and male= 0.70; speed quotient: female= 1.16 and male= 1.19, besides 73% showed periodic signal. As the high- speed kymography the quantitative parameters obtained were: closed phase: female= 1.75 and male= 3.32; opening phase: female= 1.47 and male= 2.32; closing phase: female= 1.51 and male= 2.22; opened phase: female= 2.91 and male= 4.56, and vibratory cicie of total period: female= 4.67 and male= 7.89. The quotients obtained were: closing quotient: female= 0.37and male= 0.42; opening quotient: female= 0.62 and male= 0.57; speed quotient: female= 1.02 and male= 1.12. 59% amplitude symmetry and 54% phase asymmetry were obtained in the high- speed kymography of normal subjects. Conclusion: using specific computational tools to analyse high-speed laryngeal images we obtained quantitative and qualitative parameters of glottal area waveforms and high-speed kymography that can be used as a standard reference data for normal subjects.

In this report metrics for jamming resistance and radar performance of waveform sets are described and developed, and different sets of waveforms are optimized, evaluated and compared. It is shown that without additional processing or PRI jitter, waveform sets can reach jamming resistance a few dB worse than what is provided by PRI jitter alone, and together with PRI jitter a few dB better. Waveforms with better jamming resistance tend to have worse range sidelobes and Doppler tolerance, but show less structure in their spectrograms, suggesting better LPI properties. The Doppler tolerance metric is new, as well as the comparative analysis of waveform sets on multiple metrics including jamming resistance. / Radar är fundamentalt i modern krigsföring. Med en radar kan man avfyra vapen från säkra avstånd och med precision mäta in mål. En radarstörare har som mål att förhindra en radar från att mäta in sitt mål. Då radarn fungerar genom att sända ut specifikt modulerade radiovågspulser och lyssna efter ekot från omgivningen kan störaren förhindra detta genom att antingen sända mycket starkt brus, eller genom att sända radiovågspulser med samma specifika modulation. Den senare metoden kallas för DRFM-störning, där förkortningen står för Digitalt RadioFrekvens-Minne, vilket antyder att störaren kan minnas radarns modulation och själv använda den. Om radarn använder en ny modulation (eng: waveform) för varje puls kan störaren inte använda modulationen den minns från förra pulsen utan måste vänta på att nästa puls träffar den innan den kan repetera pulsen, vilket begränsar dess störförmåga. Denna rapport tänker sig att radarn har en begränsad uppsättning av modulationer att byta mellan, och undersöker olika sådana uppsättningar och bedömer och jämför dem på olika mått av radarprestanda och störtålighet. Radioprestandamåtten inkluderar hur mycket förstärkning och hur fin upplösning man får av modulationen, hur väl modulationen kan hantera mycket snabba mål, och hur stora "sidolober" som uppstår runt starka mål. Sidolobsfenomenet är jämförbart med det optiska fenomenet där små men ljusstarka saker på natten kan se ut att ha en ljus halo eller ljusa utstrålningar runt sig. Störtålighetsmåtten kvantifierar hur distinkta de olika modulationerna i radarns uppsättning är, och på så vis hur väl radarn kan urskilja en modulation från de andra, tillsammans med hur liten sannolikheten är att störaren lyckas välja just den modulation vi kommer använda till nästa puls. Resultaten visar att metoden av modulationsbyten kan ge nästan lika stor störtålighet som en välkänd metod, PRI-jitter, ger själv och något högre i kombination med den metoden. Bättre störtålighet visas gå hand i hand med sämre mått på radarprestanda, men mindre strukturerade spektrogram vilket antyder att de kan vara svårare att upptäckas av radarspanare. Försämringen i måtten på radarprestanda innebär inte nödvändigtvis en lika stor försämring i faktisk radarprestanda, då sidoloberna tar an en brusartad karaktär vilket leder till praktiska fördelar gentemot de vanliga fixa sidoloberna.

Cette thèse est dédiée à l’étude de la texturation de surface du silicium cristallin (c-Si) à l’échelle nanométrique (nanotexturation) par un procédé de gravure ionique réactive en chimie SF6/O2 et en réacteur plasma à couplage capacitif à excitation radiofréquence. Ce travail a pour objectif générique l’optimisation du procédé de nanotexturation de surface en vue d’une intégration pour le traitement de la face avant de l’absorbeur de cellules photovoltaïques c-Si. A cette fin, une étude des interactions plasma-surface est menée dans le cas d’une excitation plasma par tension simple fréquence, ou par tension multifréquence générant des asymétries électriques dans le plasma (méthode des « forme d’ondes sur mesure », abrégé TVW, de l’anglais "Tailored Voltage Waveforms").L’étude se porte premièrement sur les différents mécanismes de chauffage électronique dans le plasma. Les modes de chauffage électronique dominants sont déterminés pour un plasma SF6/O2 à faible pression grâce à l’utilisation de l’excitation TVW. En contrepartie, ce mode d’excitation permet de générer des asymétries électriques variables dans le plasma, affectant ainsi le flux et l’énergie de bombardement ioniques sur l’électrode porte-substrats. Dans les conditions étudiées, l’excitation TVW permet d’élargir la gamme de conditions disponible pour la gravure (en termes de flux et d’énergie de bombardement ioniques) par rapport à une excitation simple fréquence.Deuxièmement, les interactions plasma-surface lors de la gravure du c-Si en chimie SF6/O2 sont étudiées. Une fenêtre process permettant d’obtenir une nanotexturation efficace de la surface de c-Si – à température ambiante – est identifiée. Il est ainsi possible de diminuer drastiquement la réflexion de la lumière en surface du c-Si (dans la gamme de longueurs d’ondes [250,1000nm]) : du « silicium noir » est obtenu. Les conditions de nanotexturation (flux et énergie des d’ions) sont variées expérimentalement grâce à l’excitation TVW. Un modèle phénoménologique de gravure est proposé : le rendement de gravure augmente en fonction avec l’énergie des ions, au-dessus d’un seuil de gravure d’environ 13eV. Grâce à ce modèle, il est démontré que la hauteur moyenne des nanostructures formées est directement (positivement) liée à la fluence ionique, pondérée par l’énergie de bombardement.Les propriétés optiques des surfaces nanotexturées sont ensuite étudiées. Lorsque la largeur des nanostructures est petite devant la longueur d’onde de la lumière (dans le c-Si), la surface nanotexturée agit comme une couche antireflet à gradient d’indice de réfraction : un lien direct entre la hauteur des nanostructures et la réflectance totale de la surface est déterminé. Une très faible réflectance (de l’ordre de 2% en incidence normale) dans une large gamme spectrale (approximativement [250,1000nm]) est atteinte. De plus, une forte diffusion de la lumière est engendrée lorsque la largeur des nanostructures dépasse un seuil déterminé expérimentalement. En conséquence, la lumière est plus efficacement piégée dans le c-Si, améliorant l’absorption dans la gamme [1000,1200nm].Les propriétés optiques des surfaces nanotexturées sont intéressantes pour améliorer la photogénération de charges électriques dans les cellules photovoltaïques c-Si. Cependant, les dommages induits en surface du c-Si par bombardement ionique (lors de la nanotexturation plasma) sont responsables d’une augmentation de la recombinaison des charges électriques en surface. Cet effet est atténué par l’application d’une faible énergie de bombardement ionique. Des conditions optimales de nanotexturation du c-Si par plasma SF6/O2 peuvent être obtenues par la maximisation du flux d’ions, en maintenant l’énergie de bombardement faible. Ces spécifications se révèlent antagonistes dans le cas d’une décharge plasma à couplage capacitif à excitation simple fréquence, mais le conflit peut être (en partie) levé par l’utilisation de l'excitation TVW. / This thesis is dedicated to the study of crystalline silicon (c-Si) surface texturing at the nanoscale (nanotexturing) using capacitively coupled plasma reactive ion etching (CCP-RIE). The general objective consists in tuning the nanotextured surface properties to improve light-management in c-Si solar cells through front surface texturing. To this aim, plasma-surface interactions during etching in a SF6/O2 discharge are investigated using both single-frequency excitation and Tailored Voltage Waveforms (TVWs), i.e. a multifrequency approach triggering electrical asymmetries in the plasma.To gain a full picture of the achievable processing range, the electron heating mechanisms and ion bombardment energy on the surface are first studied. An identification of the dominant electron heating mechanisms in low pressure SF6/O2 plasma is demonstrated using TVWs as an innovative probing tool. Different electrical asymmetry effects are shown to arise depending on the dominant heating mode, which therefore affects both the ion flux and bombardment energy on the etched surface. Although a complete decoupling between ion energy and flux cannot be achieved in the investigated discharge conditions, TVWs do lead to an extended playground for SF6/O2 plasma etching of c-Si surfaces in CCP-RIE.The plasma-surface interaction mechanisms during SF6/O2 plasma etching and texturing of c-Si surfaces are then investigated. A processing window to achieve nanotextured anti-reflective c-Si surfaces (“black silicon”) at room temperature is delimited. Building on the work from the first section, the ion flux and bombardment energy on the c-Si surface are varied independently in this process window. A phenomenological model (etching yield varying with the square root of the ion energy above a threshold around 13 eV) is proposed. From this model, a direct (positive) link between the energy weighted ion fluence and the nanostructure height is identified. Importantly, the final nanostructure average width is shown to also weakly depend on the instantaneous ion flux during the process.Subsequently, anti-reflection and light scattering properties of plasma nanotextured c-Si surfaces are studied. Regarding anti-reflection, when the nanostructure average width is small compared to the wavelength (in c-Si), the nanotextured surface acts as an anti-reflective graded refractive index layer and a direct link between the nanostructure average height and the reflectance can be derived. Very low reflectance (in the order of 2% at normal incidence) on a broad wavelength range (approximately [250, 1000nm]) can be achieved, and the improved anti-reflective properties extend to high angles of incidence. Additionally, strong light scattering is shown to arise when the nanostructure average width overcomes a given threshold determined experimentally. Consequently, light is more efficiently trapped in the c-Si substrate, leading to superior absorption in the range [1000, 1200nm].The aforementioned optical properties of nanotextured c-Si surfaces are of practical interest for improved light management in c-Si photovoltaic devices. However, plasma induced damages (during plasma nanotexturing), as well as enlarged surface area, are responsible for increased carrier recombination. The contribution to recombination from plasma induced defects is shown to be mitigated when ion bombardment energy is kept low. Design rules are consequently proposed: optimized conditions for c-Si nanotexturing in SF6/O2 plasma can be achieved by maximizing the ion flux while keeping ion energy low (but above the etching threshold). These requirements are conflicting in the case of a single frequency CCP discharge, but the trade-off may be (at least partly) resolved using TVWs.

No description available.

<p>Interval timing, defined as timing and time perception in the seconds-to-minutes range, is a higher-order cognitive function that has been shown to be critically dependent upon cortico-striatal circuits in the brain. However, our understanding of how different neuronal subtypes within these circuits cooperate to subserve interval timing remains elusive. The present study was designed to investigate this issue by focusing on the spike waveforms of neurons and their synchronous firing patterns with local field potentials (LFPs) recorded from cortico-striatal circuits while rats were performing two standard interval-timing tasks. Experiment 1 demonstrated that neurons in cortico-striatal circuits can be classified into 4 different clusters based on their distinct spike waveforms and behavioral correlates. These distinct neuronal populations were shown to be differentially involved in timing and reward processing. More importantly, the LFP-spike synchrony data suggested that neurons in 1 particular cluster were putative fast-spiking interneurons (FSIs) in the striatum and these neurons responded to both timing and reward processing. Experiment 2 reported electrophysiological data that were similar with previous findings, but identified a different cluster of striatal neurons - putative tonically-active neurons (TANs), revealed by their distinct spike waveforms and special firing patterns during the acquisition of the task. These firing patterns of FSIs and TANs were in contrast with potential striatal medium-spiny neurons (MSNs) that preferentially responded to temporal processing in the current study. Experiment 3 further investigated the proposal that interval timing is subserved by cortico-striatal circuits by using microstimulation. The findings revealed a stimulation frequency-dependent "stop" or "reset" response pattern in rats receiving microstimulation in either the cortex or the striatum during the performance of the timing task. Taken together, the current findings further support that interval timing is represented in cortico-striatal networks that involve multiple types of interneurons (e.g., FSIs and TANs) functionally connected with the principal projection neurons (i.e., MSNs) in the dorsal striatum. When specific components of these complex networks are electrically stimulated, the ongoing timing processes are temporarily "stopped" or "reset" depending on the properties of the stimulation.</p> / Dissertation