A síndrome fêmoro-patelar (SFP) acomete adultos jovens e caracteriza-se por dor no joelho durante a realização de atividades funcionais. Os fatores etiológicos incluem o aumento do ângulo Q e desequilíbrios musculares e para seu tratamento normalmente são realizados exercícios de fortalecimento do músculo quadríceps femoral, não sendo encontradas referências quanto ao uso de alongamento muscular no reequilíbrio da articulação fêmoro-patelar. Dessa forma, os objetivos deste estudo foram comparar a eficácia de exercícios de fortalecimento do músculo quadríceps femoral e alongamento dos músculos da cadeia posterior na recuperação funcional de pacientes com SFP. Para isso, foram selecionadas 40 mulheres sedentárias com idade entre 18 e 32 anos com SFP. Antes do tratamento foram avaliados: medida da flexibilidade, do encurtamento dos músculos isquiotibiais, do ângulo Q, aplicação de escalas da capacidade funcional (escala de contagem de Lysholm e escala de avaliação para a articulação fêmoro-patelar) e eletromiografia (EMG) dos músculos vasto medial (VM), vasto lateral (VL), bíceps femoral (BF) e gastrocnêmio porção lateral (GT) durante contrações isométricas de flexão e extensão da perna. Posteriormente, os pacientes foram divididos em quatro grupos de tratamento: o Grupo 1 (G1) realizou alongamento dos músculos da cadeia posterior pela técnica de reeducação postural global, o Grupo 2 (G2) realizou alongamento segmentar dos músculos isquiotibiais e gastrocnêmio, o Grupo 3 (G3) fortaleceu o músculo quadríceps femoral em cadeia cinética aberta e o Grupo 4 (G4) fortaleceu o mesmo músculo em cadeia cinética fechada, ambos com aumento progressivo da carga. Antes e após cada sessão de tratamento, as pacientes preenchiam a intensidade da dor no joelho numa escala visual analógica. O tratamento durou oito semanas com freqüência de duas vezes semanais. As variáveis obtidas antes e após o tratamento para cada grupo foram analisadas pelo teste de Wilcoxon e entre os grupos pela Anova e teste de Duncan ou Anova de Friedman ou Manova (&#945; < 0,05). Comparando as variáveis antes e após o tratamento, os resultados mostram que a intensidade da dor apresentou melhora significante no G1 e G3 e o ângulo Q diminuiu no G1 e G2. Para a atividade EMG, o músculo VM não sofreu alteração após o tratamento, o músculo VL aumentou no G2 e G3, o músculo BF aumentou apenas no G3 e o músculo GT aumentou no G3 e G4. Em todos os grupos, as escalas mostram melhora da capacidade funcional, diminuição do encurtamento dos músculos isquiotibiais e aumento da flexibilidade. Entre os grupos, o G1 tendeu a apresentar maior flexibilidade, o G4 maior atividade EMG do músculo BF, enquanto o G1 e G3 mostraram maior ativação do músculo GT. Os dados sugerem que os exercícios de alongamento muscular, em especial o global, também devem ser indicados no tratamento de pacientes com SFP, principalmente nas fases iniciais, onde se objetiva uma redução efetiva da intensidade da dor. Além disso, também possibilitou maior realinhamento do joelho (redução do ângulo Q) e aumento da flexibilidade, o que pode facilitar o fortalecimento muscular. / The patellofemoral syndrome (PFS) affects young adults and is characterized by knee pain during functional activities. PFS etiology includes bigger Q angle and muscular imbalances. For treatment, quadriceps femoris strengthening are normally performed, but we were unable to locate documentation about the application of stretching exercises in the patellofemoral joint rehabilitation. The aim of this study was to compare the efficacy of quadriceps femoris muscle strengthening and posterior chain stretching exercises in the functional recovery of PFS patients. Forty female nonathletes aged between 18 and 32 years old were recruited. Before treatment, it was measured: flexibility, hamstring tightness, Q angle, functional injury level of the knee by the application of questionnaires and electromyography (EMG) of the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and lateral gastrocnemius(LG) muscles during isometric contractions of leg flexion and extension. After this initial evaluation, patients were divided into four treatment groups: Group 1 (G1) performed posterior chain global stretching exercises, Group 2 (G2) segmentary stretching exercises of hamstring and gastrocnemius muscles, Group 3 (G3) quadriceps femoris strengthening exercises in open kinetic chain and Group 4 (G4) quadriceps femoris strengthening exercises in closed kinetic chain, with progressively resistance increases. This treatment lasted eight weeks, twice a week. Before and after each treatment session, the visual analogue scale accessed pain intensity. The data obtained before and after treatment for all groups were analyzed by Wilcoxon test, and the data between groups by Anova and Duncan test or Friedman Anova or Manova (&#945; < 0.05). Comparing the data before and after treatment, the results showed a significant improvement in pain intensity in G1 and G3 and a decreased Q angle in G1 and G2. For the EMG activity, VM muscle activity was not modified after treatment, VL activity increased in G2 and G3, BF activity increased only in G3 and LG activity increased in G3 and G4. Between groups, G1 showed greatest flexibility, G4 greatest EMG activity of BF muscle, while G1 and G3 showed greatest activity of LG muscle. Based on these results, we suggest that stretching exercises, specifically in global modality, can be prescribed in PFS treatment, especially in its initial phases, for an effective reduction of pain intensity. Moreover, this treatment caused a knee alignment (by reducing Q angle)and flexibility improvement, which may facilitate muscular strengthening.

A Distrofia Muscular Congênita (DMC) se caracteriza clinicamente por hipotonia e fraqueza muscular, retardo do desenvolvimento motor e retrações fibrotendíneas. Instrumentos de avaliação clínica, como as escalas funcionais, motoras e de qualidade de vida, têm como objetivo quantificar o impacto da doença sobre as atividades diárias da vida do paciente, além de auxiliarem na caracterização de grupos de estudo heterogêneos. Sendo a DMC altamente heterogênea, traçar o perfil funcional dos pacientes com diferentes subtipos seria útil para caracterizar padrões funcionais e auxiliar no tratamento em equipe multidisciplinar. Objetivos: Caracterizar o perfil de funcionalidade e qualidade de vida de pacientes com DMC de diferentes subtipos e correlacioná-lo com a força muscular e grau de amplitude de movimento. Metodologia: Em uma amostra de 18 pacientes com DMC com idade de 12 + 3,2 anos e 13 pacientes com outras miopatias congênitas com idade de 13 + 2,6 anos foram aplicados em três visitas (V1, V2 e V3) os questionários SF-36 e Índice de Barthel (IB), além de realizada avaliação físico-motora (goniometria, força muscular) seguido de correlação com a escala funcional MFM-32 (Medida de Função Motora). Resultados: Houve significativa queda na qualidade de vida em pacientes Merosina (-) e em outras formas de DMC. O índice de Barthel (IB) apontou \"grave dependência\" final em pacientes merosina (-) e \"moderada dependência\" em outras formas de DMC. A goniometria mostrou diminuição da movimentação global em todos os grupos articulares avaliados em pacientes com merosina (-). Em outras formas de DMC, houve exceção de diminuição apenas em articulação distal de membros superiores. A força de todos os grupos musculares é significativamente afetada em ambos os grupos. Pacientes merosina (-) mostram diminuição significativa de funcionalidade nas três dimensões da escala MFM-32 (D1, D2 e D3), e em outras formas de DMC, apenas diminuição em D2 e D3. Houve moderada correlação positiva entre força muscular e D1 da escala MFM-32, forte correlação positiva entre goniometria e D2 e D3 em pacientes com merosina (-), não havendo correlação entre nenhuma variável e MFM-32 em outras formas de DMC. Conclusão: Pacientes com DMC apresentaram perfil funcional \"gravemente dependente\", com diminuição da qualidade de vida, observada em cinco de oito quesitos do questionário SF-36. A força muscular e a amplitude de movimento articular foram afetadas de forma generalizada em ambos os grupos de pacientes. Pacientes com merosina (-) mostraram-se mais afetados funcionalmente em posturas eretas e transferências, sendo correlacionada positivamente com a força muscular dos grupos dessa tarefa / Congenital Muscular Dystrophy (CMD) is characterized by hypotonia and weakness, motor development delay and muscular contractures. Instruments of clinical assessment, such as functional motor and quality of life scales are essential to quantify the impact of the disease on daily activities of the patient\'s life in addition to helping in the characterization of heterogeneous study groups. As the DMC highly heterogeneous, trace the functional profile of patients with different subtypes would be useful to characterize functional patterns and aid in the treatment by a multidisciplinary team. Objectives: To characterize the functionality and quality of life of children with different subtypes of DMC and to correlate them with the degree of muscle strength and range of motion. Methods: In a sample of 18 patients with CMD (aged 12 + 3.2 years) and 13 patients with other congenital myopathies (aged 13 ± 2.6 years) were applied in three visits (V1, V2 and V3) the SF-36 and Barthel Index (BI), and performed physical-motor assessment (goniometry, muscle strength) followed by correlation with functional scale MFM-32 (motor Function Measure. ). Results: There was a significant decrease in the quality of life in patients Merosin (-) and other forms of CMD. IB indicated \"severe dependence\" final in Merosin patients (-) and \"moderate dependence\" in other forms of CMD. Goniometry showed a decrease of the overall joint movement in all groups evaluated in patients with merosin (-).In other forms of DMC was decreased joint movement in all joint groups, except for the distal joint of the upper limbs. The strength of each muscle group was significantly affected in both groups. Patients merosin (-) show a significant decrease in the functionality on the 3 dimensions of MFM-32 scale (D1, D2, D3) in patients with other forms of DMC only reduction in D2 and D3. There was a moderate positive correlation between muscle strength and D1 of the SF-32 scale, strong positive correlation between goniometry and D2 and D3 in patients with Merosin (-), there was no correlation between this variable and MFM-32 in other forms of CMD. Conclusion: Patients with CMD showed functional profile \"severely dependent\" to low quality of life observed in five of eight areas of the SF-36 questionnaire. Muscle strength and range of motion were affected in a generalized manner in both patient groups. Patients with Merosin (-) are even more affected functionally in standing and transfers being positively correlated with muscle strength of the groups of this task postures

Software Defined Radios (SDRs) and Cognitive Radios (CRs) pave the way for next-generation radio technology. They promise versatility, flexibility and cognition which can revolutionize communications systems. However they present greater challenges to the design of radio frequency (RF) front-ends. RF front-ends for the radios in use today are narrow-band in their frequency response and are optimized and tuned to the carrier frequency of interest. SDRs and CRs demand front-ends which are versatile, configurable, tunable and be capable of transmitting and receiving signals with different bandwidths and modulation schemes. Integrating power amplifiers (PAs) with transmitters in CMOS has many advantages and challenges. This thesis deals with the design of an RF transmitter front-end for SDRs and CRs in CMOS. The thesis begins with an introduction to SDRs and the requirements they place on transmitters and the challenges involved in designing them in CMOS. After a brief overview of the existing techniques, the proposed architecture is presented and explained. A digitally intensive transmitter solution is proposed. The transmitter covers a wide frequency range of 750 MHz to 2.5 GHz. The inputs to the proposed transmitter are in-phase and quadrature (I & Q) data bit streams. Multiple stages of up-sampling and filtering are used to remove all spurs in the spectrum such that only the harmonics of the carrier remain. Differential rail-to-rail quadrature clocks are generated from a continuous wave signal at twice the carrier frequency. The clocks are corrected for their duty cycle and quadrature impairments. The heart of the transmitter is an integrated reconfigurable CMOS power amplifier (PA). A methodology to design reconfigurable Class E PAs with a series fixed inductor has been presented. A CMOS power amplifier that can span a wide frequency range with sufficient output power and efficiency, supporting varying envelope complex modulation signals, with good linearity has been designed. Digital pre-distortion (DPD) is used to linearize the PA. The full transmitter and the clock correction blocks have been designed and fabricated in a commercial 130-nm CMOS process and experimentally characterized. The PA delivers a maximum power of 13 dBm with an efficiency of 27% at 1 GHz. While transmitting a 16-QAM signal at 1 GHz, the measured EVM is 4%. It delivers a maximum power of around 11-13 dBm from 750 MHz to 1.5 GHz and up to 6.5 dBm of power till 2.5 GHz. Comparing the proposed system with recently published literature, it can be seen that the proposed design is one of the very few transmitters which has an integrated matching network, tunable across the frequency range. The proposed PA produces the highest output power and with largest efficiency for systems with on-chip output networks.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Ischemic heart diseases stands out among the diseases that affect the cardiovascular system due to its high prevalence and its impact on mortality in the general population. Ischemic heart disease is the leading worldwide cause of mortality. Fenomenum that also happens in the Americas and Brazil. The term acute coronary syndrome (ACS) is used to describe a heterogeneous spectrum of clinical conditions associated with acute myocardial ischemia, including unstable angina and acute myocardial infarction (AMI). The plurality in its clinical presentation represents a diagnostic challenge for clinicians. Moreover, appropriate risk stratification is mandadatory in all patients with ACS. Some clinical tools such as physical examination, electrocardiographic observations and risk scores are extremely usefull to identify patients at high risk of unfavorable clinical outcomes. Scores of risk stratification, among those the Global Registry of Acute Coronary Events (GRACE), are widely used in the prognostic evaluation of patients with ACS.Some plasma biomarkers have also been used to improove risk stratification. The GRACE score is a fundamental part of the assessment of patients with ACS and may even prevent or minimize adverse consequences in these individuals. Nevertheless, the search for new potential prognostic parameters that could add information to these establised scores has been the subject of intense research. In this context, stands out the use of routine hematological tests , since the complete blood count is readily available for clinical use and has a good cost-benefit relationship. Recent studies have investigated the potential role of some of red cell indices, especially anemia and red cell distribution width (RDW), in the prognostic evaluation of patients with several cardiovascular conditions. The presence of anemia and elevated RDW in patients with ACS have been independently associated with increased risk of adverse events such as heart failure, recurrent ischemic events, and death. We have hipotezazed that the addition of the hemalological indices to the GRACE score would improve its ability to stratify patients.The main objective of this study was to investigate whether inclusion of anemia or RDW, assessed at admission, in the GRACE score model to predic in-hospital mortality, could improve the discrimination and calibration of these model, as well as risk stratification in patients with ACS. For this, a cohort study, including 109 patients with AMI was carried out. Cox regression models including the variables of the GRACE score and RDW or anemia were constructed. Measures of calibration and discrimination, and reclassification of patients were also calculated for the new models. The new models, either with the inclusion of anemia, or the addition of RDW showed adequate calibration and discrimination. Furthermore, the addition of these parameters to the original model allowed adequate reclassification of patients in different categories of risk. The red cell indices, anemia and RDW showed potential prognostic for use in risk assessment of patients with ACS, allowing the improvement of risk stratification performed through the GRACE score. / A cardiopatia isquêmica destaca-se entre as doenças que acometem o sistema cardiovascular, devido à sua alta prevalência e a seu impacto sobre a mortalidade na população em geral. As doenças isquêmicas do coração são a principal causa de mortalidade mundial, nas Américas e no Brasil. O termo SCA é usado para descrever um espectro heterogêneo de condições clínicas associadas com isquemia aguda do miocárdio, incluindo angina instável e infarto agudo do miocárdio (IAM). A diversidade na apresentação clínica de pacientes com esta patologia representa um desafio para os clínicos em termos de diagnóstico e de estratificação de risco apropriada. Algumas ferramentas clínicas como exame físico, observações eletrocardiográficas e escores de risco, são de extrema relevância na identificação de pacientes com alto risco de desfechos clínicos desfavoráveis. Além disso, alguns biomarcadores plasmáticos também vêm sendo utilizados com este propósito e a busca por novos parâmetros com potencial prognóstico tem sido alvo de intensas pesquisas. Neste contexto, destaca-se a utilização dos testes hematológicos de rotina na estratificação de risco, uma vez que o hemograma é um exame amplamente disponível para uso clínico e possui uma boa relação custo benefício. Estudos recentes tem investigado o potencial papel de alguns dos índices hematimétricos, especialmente anemia e amplitude de distribuição dos eritrócitos (RDW), na avaliação prognóstica de pacientes apresentando diversas condições cardiovasculares. A presença de anemia, bem como valores elevados de RDW em pacientes com SCA tem sido independentemente associados com maior risco de eventos adversos como mortalidade, desenvolvimento de insuficiência cardíaca e ocorrência de eventos isquêmicos recorrentes. Os escores de estratificação de risco, principalmente o Global Registry of Acute Coronary Events (GRACE), são amplamente utilizados na avaliação prognóstica de pacientes com SCA. No entanto, os modelos disponíveis atualmente não incluem os índices hematimétricos na determinação do risco do paciente. Considerando que a estratificação de risco é parte fundamental da avaliação de pacientes com SCA, podendo evitar ou mesmo minimizar consequências adversas nestes indivíduos, o principal objetivo deste estudo foi investigar se a inclusão de anemia ou RDW, avaliados na admissão hospitalar, ao escore GRACE para a predição de mortalidade durante o período de internação hospitalar, podem melhorar a calibração e discriminação do modelo, bem como a estratificação de risco em pacientes com SCA. Para isso, um estudo de coorte, incluindo 109 pacientes com IAM, foi realizado. Modelos de regressão de Cox incluindo as variáveis do escore GRACE e o RDW ou a anemia foram construídos. Medidas de calibração e discriminação também foram calculadas, bem como o percentual de reclassificação dos pacientes para os novos modelos propostos. Os novos modelos, tanto com a inclusão de anemia, quanto com a adição de RDW, apresentaram adequada calibração e discriminação. Além disso, a adição destes parâmetros ao modelo original permitiu uma adequada reclassificação dos pacientes em diferentes categorias de risco. Os índices hematimétricos, anemia e RDW, demonstraram potencial prognóstico para utilização na avaliação de risco de pacientes com SCA, permitindo o aprimoramento da estratificação de risco realizada através do escore GRACE.

The submitted thesis is composed of three different articles dealing with issues of financial innovation, credit constraints, and their impact on welfare. The first article treats the contemporary theoretical grasp of the interaction between the financial and real economies, focusing primarily on the role of modern financial innovation in the business cycle. For this purpose, a framework promoted by the Regulation School and Post Keynesians is frequently employed, whilst some other unorthodox streams and mainstream economics are partially discussed as well. All of them aspire -- either per se or under the pressure of the contemporary economic agenda -- to clarify the evolution of financial innovation and credit in the recent era. It is generally found that certain consensus across the schools of economic thought exists, but some of them have done a better job in predicting the consequences of the financial innovation for real economic activity than others. Further, two dynamic macroeconomic models are developed in order to, inter alia, identify the possible effects of extended credit availability presented in the former article on the example of the housing market, and simulate the effects of housing price changes on general welfare. Clearly, this part of the thesis exhibits the indirect consequences of financial innovation as, once again, being rather ambiguous: after having partially unleashed the unprecedented credit granting in the economy, impacting interest rates and loan-to-value ratios, with a subsequent impact on housing prices, it has also influenced credit constrained and unconstrained households in a different manner. Based on an analysis of the situation using partial and general equilibrium analytical frameworks, two somewhat different conclusions are drawn up with respect to the occurrence of various shocks in the models. Under the partial equilibrium framework the effects of relaxation of credit constraints are visible and quite straightforward, indicating relatively simple and intuitive relationship between the price appreciation and general welfare. This is primarily perspicuous for the credit constrained households. In the general equilibrium framework, on the other hand, the transitional dynamics of shock proliferation is more transparent and the impact on credit constrained vs. unconstrained households is more ambiguous and much different from the basic intuition used in the article anchored in the partial equilibrium toolbox.

An algorithm that is capable of estimating the parameters of non-stationary sinusoids in real-time lends application to various branches of engineering. Non-stationary sinusoids are sinusoidal signals with time-varying parameters. In this dissertation, a nonlinear filter is applied to power system applications to test its performance. The filter has a structure which renders it fully adaptive to tracking time variations in the parameters of the targeted sinusoid, including its phase and frequency. Mathematical properties of the differential equations which govern the proposed filter are presented. The performance of the proposed filter in the field of power systems is demonstrated with the aid of computer simulations and practical experimentations. The filter is applied to synchronous generator excitation control, voltage dip mitigation as well as the real-time estimation of symmetrical components. The parameter settings of the filter are tested and optimized for each of the applications. This dissertation demonstrates the simulation and experimental results of the filter when applied to the various power system applications. AFRIKAANS : 'n Filter wat bevoeglik is met die beraming van die parameters van beweeglike sinusoïdale in ware-tyd, kan bruikbaar aangewend word in verskeie takke van ingenieurswese. Beweeglike sinuskrommes is sinusoïdale seine met tyd-wisselende parameters. In hierdie verhandeling word `n nie-liniêre filter aangewend in verskeie kragstelseltoepassings om die werksverrigting van die filter te toets. Die filter het 'n struktuur wat dit toelaat om wisselende tydvariasies in die parameters van die teikensinusoïdaal op te spoor, insluitende die fase en frekwensie. Wiskundige eienskappe van die differensiaalvergelykings wat die voorgestelde filter beheer is ondersoek. Die werksverrigting van die voorgestelde filter in die veld van kragstelsels is gedemonstreer met die hulp van rekenaarsimulasies asook praktiese eksperimente. Die filter is toegepas tot opgewekte, sinkrone eksitasie-beheer, spanningsverlaging versagting, asook die ware tyd estimasie van simmetriese komponente. Die parameter verstellings van die filter is getoets en geoptimeer vir elk van die toepassings. Hierdie verhandeling demonstreer die simulering en eksperimentele resultate van die filter wat aangewend is vir verskeie kragstelseltoepassings. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted

This thesis contributes to a development of a method for rheological characterization of microfibrillated cellulose. The intended use of the method is to be able to distinguish between different grades of microfibrillated cellulose. The method that was developed had preparation procedure of suspensions, pH, dry content and conductivity as well as measuring geometry and measuring sequence in mind. The method resulted in using a propeller mixer for sample preparation and the most suitable properties of the samples for comparison of different qualities of microfibrillated cellulose was evaluated to be pH 8 with a dry content of 2.0 wt% and a conductivity of 110 µS/cm. The rheology of the microfibrillated cellulose suspensions was examined by using a dynamic rotational rheometer and a splined bob and cup (C25G/PC25G). The complex viscosity from amplitude sweeps is used as the parameter to distinguish between different grades of 2 wt% microfibrillated cellulose suspensions. At 1.0 wt% the pH of the suspensions appeared to have a very small impact on the results from rheological measurements while an increased conductivity of the suspensions resulted in an increased complex viscosity. The dry content dependency appeared to be exponential in the range of 0.5 to 3.0 wt% and it was thus easier to distinguish between different grades of microfibrillated cellulose when the dry content is 2.0 wt% compared to 1.0 or 1.5 wt%.

Cette recherche visait à clarifier les mécanismes de bas niveau impliqués dans la détection de la modulation de fréquence (FM). Les sons naturels véhiculent des modulations d’amplitude et de fréquence saillantes essentielles à la communication. L’analyse des réponses de neurones auditifs du noyau cochléaire montre que les propriétés spectro-temporelles des stimuli de FM de basse cadence sont représentées par deux mécanismes distincts basés sur le verrouillage en phase à l’enveloppe temporelle (ENV) et à la structure temporelle fine (TFS). La contribution relative de chaque mécanisme s’avère très dépendante des paramètres de stimulation (fréquence porteuse, cadence de modulation et profondeur de modulation) mais aussi du type de neurones, chacun étant spécialisé pour un type de représentation ou l'autre. L’existence de ces deux mécanismes de codage neuronal a été confirmée chez les auditeurs humains en utilisant deux paradigmes psychophysiques. Les résultats de ces études démontrent également que le mécanisme de codage de TFS est efficace dans des conditions d'écoute défavorables (e.g. en présence de modulations interférentes). Cependant, le mécanisme de codage de TFS est susceptible de se dégrader avec l'âge et plus encore avec la perte auditive, alors que le mécanisme de codage d’ENV semble relativement épargné. Deux modèles computationnels ont été développés afin d’expliquer les contributions des indices d’ENV et de TFS dans le système auditif normal et malentendant. / This research aimed at clarifying the low-level mechanisms involved in frequency-modulation (FM) detection. Natural sounds convey salient amplitude- and frequency-modulation patterns crucial for communication. Results from single auditory neurons in the cochlear nucleus show that the spectro-temporal properties of low-rate FM stimuli are accurately represented by two distinct mechanisms based on neural phase-locking to temporal envelope (ENV) and temporal fine structure (TFS) cues. The relative contribution of each mechanism was found to be highly dependent on stimulus parameters (carrier frequency, modulation rate and modulation depth) and also on the type of neuron, with clear specializations for one type of representation or the other. The validity of those two neural encoding mechanisms was confirmed for human listeners using two psychophysical paradigms. Results from those studies also demonstrate that the TFS coding mechanism is efficient in adverse listening conditions, like in the presence of interfering modulations. However, the TFS coding mechanism is prone to decline with age and even more with hearing loss, while the ENV coding mechanism seems relatively spared. Two computational models were developed to fully explain the contributions of ENV and TFS cues in the normal and impaired auditory system.

Les signaux de communication, dont la parole, contiennent des modulations d'amplitude et de fréquence relativement lentes qui jouent un rôle capital dans l'identification et la discrimination des sons. Le but de ce programme de recherche doctorale est de comprendre plus finement les mécanismes impliqués dans la perception de l'AM et de la FM, et de clarifier les effets du vieillissement et de la perte auditive neurosensorielle sur ceux-ci. Les seuils auditifs de détection d'AM et de FM sont mesurés pour des sujets normo-entendants (NE) jeunes et âgés, ainsi que pour des sujets malentendants (ME) âgés, à basse fréquence porteuse (500 Hz) et à basse cadence de modulation (2 et 20 Hz). Le nombre de cycles de modulation, N, varie entre 2 et 9. Les seuils de détection de FM sont mesurés en présence d'une AM interférente, de façon à contraindre l'utilisation des indices d’enveloppe temporelle. Pour l'ensemble des groupes, les seuils de détection d'AM et de FM sont meilleurs à 2 qu'à 20 Hz. La sensibilité à l'AM et la FM s'améliore lorsque N augmente, démontrant une intégration temporelle des indices d’AM et de FM. Pour l’AM, les effets du vieillissement et de la perte auditive sont antagonistes: aux deux cadences de modulation, la sensibilité à l'AM décline avec l'âge, tandis qu'elle s'améliore en présence d'une perte auditive. L'intégration temporelle est similaire pour les deux groupes de NE, tandis que l'intégration temporelle est améliorée chez les sujets ME. Pour la sensibilité à la FM, l'âge dégrade sélectivement les seuils de détection de FM à basse cadence de modulation, tandis que la perte auditive a un effet délétère global aux deux cadences de modulation. L'intégration temporelle est similaire pour l'ensemble des groupes. Deux modèles computationnels (mono-bande et multi-bandes) utilisant un banc de filtres de modulation et un processus d'appariement de gabarit sont développés pour rendre compte des données. Pris ensemble, les données psychophysiques et de modélisation suggèrent que: 1) pour des cadences de modulation rapides, la détection d'AM et de FM sont encodés par un mécanisme commun, probablement basé sur les indices d’enveloppe temporelle. A l'inverse, à basse cadence de modulation, l'AM et la FM sont encodés par des mécanismes distincts, utilisant probablement et respectivement des indices d’enveloppe temporelle et de structure temporelle fine; 2) le vieillissement dégrade la sensibilité à l'AM et la FM (i.e. les indices d’enveloppe temporelle et de structure temporelle fine), mais affecte plus fortement ces derniers; 3) la perte auditive n'affecte pas la sensibilité à l'AM (indices d’enveloppe temporelle), mais dégrade la sensibilité à la FM aux deux cadences de modulation; 4) Les processus décisionnels et mnésiques impliqués dans l'intégration temporelle d'AM et de FM sont préservés par le vieillissement. En présence d'une perte auditive, l'intégration temporelle d'AM est améliorée, probablement en raison de la perte de compression cochléaire, tandis que l'intégration temporelle en FM reste préservée. Toutefois, certains aspects de l’efficacité de traitement (modélisés par un bruit interne) déclinent avec l’âge et encore plus fortement avec une perte auditive. Les implications de ces résultats pour la définition, le diagnostic et la réhabilitation de la presbyacousie sont discutés. / Communication sounds, including speech, contain relatively slow (<5-10 Hz) patterns of amplitude modulation (AM) and frequency modulation (FM) that play an important role in the discrimination and identification of sounds. The goal of this doctoral research program was to better understand the mechanisms involved in AM and FM perception and to clarify the effects of age and hearing loss on AM and FM perception. AM and FM detection thresholds were measured for young and older normal-hearing (NH) listeners and for older hearing-impaired (HI) listeners, using a low carrier frequency (500 Hz) and low modulation rates (2 and 20 Hz). The number of modulation cycles, N, varied between 2 to 9. FM detection thresholds were measured with and without an interfering AM to disrupt temporal-envelope cues. For all groups of listeners, AM and FM detection thresholds were lower for the 2-Hz than for the 20-Hz rate. AM and FM sensitivity improved with increasing N, demonstrating temporal integration for AM and FM detection. As for AM thresholds, opposite effects of age and hearing loss were observed: AM sensitivity declines with age, but improves with hearing loss at both modulation rates. Temporal integration of AM cues was similar across NH listeners, but better for HI listeners. As for FM sensitivity, ageing degrades FM thresholds at the low modulation rate only, whereas hearing loss has a deleterious effect at both modulation rates. Temporal integration of FM cues was similar across all groups. Two computational models (a single-band and a multi-band version) using the modulation filterbank concept and a template-matching decision strategy were developed in order to account for the data. Overall, the psychophysical and modeling data suggest that: 1) at high modulation rates, AM and FM detection are coded by a common underlying mechanism, possibly based on temporal-envelope cues. In contrast, at low modulation rates, AM and FM are coded by different mechanisms, possibly based on temporal-envelope cues and temporal-fine-structure cues, respectively. 2) Ageing reduces sensitivity to both AM and FM (i.e., both temporal-envelope and temporal-fine-structure cues), but more so for the latter. 3) Hearing loss does not affect sensitivity to AM (temporal-envelope cues) but impairs FM sensitivity at both rates. 4) The memory and decision processes involved in the temporal integration of AM and FM cues are preserved with age. With hearing loss, the temporal integration of AM cues is enhanced, probably due to the loss of amplitude compression, while the temporal integration of FM cues remains unchanged. Still, some aspects of processing efficiency (as modeled by internal noise) decline with age and even more following cochlear damage. The implications for the definition, diagnosis and rehabilitation of presbyacysis are discussed.

Objectives: The inverse relationship between QT interval variability (QTV) and T wave amplitude potentially confounds QT variability assessment. We quantified the influence of the T wave amplitude on QTV in a comprehensive dataset and devised a correction formula. Methods: Three ECG datasets of healthy subjects were analyzed to model the relationship between T wave amplitude and QTV. To derive a generally valid correction formula, linear regression analysis was used. The proposed correction formula was applied to patients enrolled in the Evaluation of Defibrillator in Non-Ischemic Cardiomyopathy Treatment Evaluation trial (DEFINITE) to assess the prognostic significance of QTV for all-cause mortality in patients with non-ischemic dilated cardiomyopathy. Results: A strong inverse relationship between T wave amplitude and QTV was demonstrated, both in healthy subjects (R2 = 0.68, p < 0.001) and DEFINITE patients (R2 = 0.20, p < 0.001). Applying the T wave amplitude correction to QTV achieved 2.5-times better group discrimination between patients enrolled in the DEFINITE study and healthy subjects. Kaplan-Meier estimator analysis showed that T wave amplitude corrected QTVi is inversely related to survival (p < 0.01) and a significant predictor of all-cause mortality. Conclusion: We have proposed a simple correction formula for improved QTV assessment. Using this correction, predictive value of QTV for all-cause mortality in patients with non-ischemic cardiomyopathy has been demonstrated.