Dissertations / Theses on the topic 'Contractional system'

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.
Includes bibliographical references (leaves 87-90).
This thesis derives new results in nonlinear system analysis using methods inspired from fluid mechanics and differential geometry. Based on a differential analysis of convergence, these results may be viewed as generalizing the classical Krasovskii the­orem, as well as linear eigenvalue analysis. A central feature is that convergence and limit behavior are in a sense treated separately, leading to significant conceptual simplifications. We establish new combination properties of nonlinear dynamic systems and use them to derive simple controller and observer designs for mechanical systems such as aircraft, underwater vehicles, and robots. The method is also applied to chemical chain reactions and mixture processes. The relative simplicity of these designs stems from their effective exploitation of the systems' structural specificities. Next, we analyze and quantify the global stability properties of physical partial differential equations such as the heat equation, or the Schroedinger equation. Lyapunov exponents are not coordinate-invariant, and thus their exact physical meaning is somewhat questionable. As an alternative, we suggest an extension of linear eigenvalue analysis to nonlinear dynamic systems. Finally, the thesis derives new controller and observer designs for general nonlinear dynamic systems. In particular, an extension of feedback linearization is proposed when the corresponding integrability conditions are violated.
by Winfried Stefan Lohmiller.
Ph.D.

Deux systèmes biologiques distincts, les muscles squelettiques et les sites d'adhésion de cellules kératocytes en mouvement, sont considérés dans un même cadre en raison de la similitude profonde de leur structure et de leur fonctionnalité. La réponse passive de l'un et de l'autre peut être modélisée à l'aide d'un grand nombre d'unités multi-stables couplées par des interactions à longue portée, et exposées à un désordre spatial fixé et un bruit thermique/mécanique. Les interactions à longue portée dans de tels systèmes conduisent à une synchronisation malgré les fluctuations temporelles et spatiales. Bien que les deux systèmes biologiques considérés présentent des différences structurelles importantes, nous montrons que l'on peut identifier une structure de verre de spin sous-jacente commune. À la lumière de cette analogie, ces systèmes vivants semblent être proches de points critiques et, à cet égard, le désordre gelé, reflétant l’incommensurabilité stérique des unités parallèles, peut être fonctionnel. Un autre paramètre important fixant la réponse est la rigidité interne du système qui couple les unités entre elles
Two biological systems, a half-sarcomere of a skeletal muscle and an adhesive cluster of a crawling keratocyte, are considered in parallel because of the deep similarity in their structure and functionality. Their passive response can be modeled by a large number of multi-stable units coupled through long-range interactions, frustrated by quenched disorder and exposed to thermal noise. In such systems, long-range interactions lead to synchronization, defying temporal and spatial fluctuations. We use a mean-field description to obtain analytic results and elucidate the remarkable ensemble-dependence of the mechanical behavior of such systems in the thermodynamic limit. Despite important structural differences between muscle cross-bridges and adhesive binders, one can identify a common underlying spin glass structure, which we fully exploit in this work. Our study suggests that the muscle machinery is fine-tuned to operate near criticality, and we argue that in this respect the quenched disorder, reflecting here steric incommensuration, may be functional. We use the analogy between cell detachment and thermal fracture of disordered solids to study the statistics of fluctuations during cellular adhesion. We relate the obtained results to recent observations of intermittent behavior involved in cell debonding, also suggesting near-criticality. In addition to the study of the equilibrium properties of adhesive clusters, we also present the first results on their kinetic behavior in the presence of time-dependent loading

The one which is considered the standard model of theory change was presented in [AGM85] and is known as the AGM model. In particular, that paper introduced the class of partial meet contractions. In subsequent works several alternative constructive models for that same class of functions were presented, e.g.: safe/kernel contractions ([AM85, Han94]), system of spheres-based contractions ([Gro88]) and epistemic entrenchment-based contractions ([G ar88, GM88]). Besides, several generalizations of such model were investigated. In that regard we emphasise the presentation of models which accounted for contractions by sets of sentences rather than only by a single sentence, i.e. multiple contractions. However, until now, only two of the above mentioned models have been generalized in the sense of addressing the case of contractions by sets of sentences: The partial meet multiple contractions were presented in [Han89, FH94], while the kernel multiple contractions were introduced in [FSS03]. In this thesis we propose two new constructive models of multiple contraction functions, namely the system of spheres-based and the epistemic entrenchment-based multiple contractions which generalize the models of system of spheres-based and of epistemic entrenchment-based contractions, respectively, to the case of contractions (of theories) by sets of sentences. Furthermore, analogously to what is the case in what concerns the corresponding classes of contraction functions by one single sentence, those two classes are identical and constitute a subclass of the class of partial meet multiple contractions. Additionally, and as the rst step of the procedure that is here followed to obtain an adequate de nition for the system of spheres-based multiple contractions, we present a possible worlds semantics for the partial meet multiple contractions analogous to the one proposed in [Gro88] for the partial meet contractions (by one single sentence). Finally, we present yet an axiomatic characterization for the new class(es) of multiple contraction functions that are here introduced.
Eduardo Fermé

Autogenous shrinkage is of concern in high performance concrete mixtures, when specific properties like strength and durability are enhanced. Factors like low watercement ratio, low porosity and increased hydration kinetics which are associated with high performance concrete mixtures are also responsible for the development of autogenous shrinkage. With about two decades of research into autogenous shrinkage, uncertainties still exist with testing procedure, effect of supplementary cementitious materials, modelling and prediction of autogenous shrinkage. The primary focus of this study is to understand mechanisms which have been postulated to cause autogenous shrinkage like chemical shrinkage and self desiccation. In addition, this study has considered properties like porosity and internal empty voids in the analysis of the causes of bulk volume deformations of the cementitious paste systems with and without mineral admixtures. The study begins with an experimental investigation of chemical shrinkage in hydrating cementitious paste systems with the addition of fly ash, slag and silica fume using the test method recently accepted by the ASTM. This was followed by the experimental investigation of autogenous shrinkage in cementitious paste. The autogenous shrinkage in paste mixtures is studied from an early age (~1.5 hours after addition of water) for cementitious systems at a water-cementitious ratio of 0.32 (w/c 0.25 for limited mixture proportions). A non-contact measurement method using eddy current sensors were adopted. The hydration mechanism of the cementitious paste systems was then modelled using CEMHYD3D, which is a 3 dimensional numerical modelling method successfully used to study, simulate and present the hydration developments in cementitious systems. Properties like chemical shrinkage, degree of hydration, total porosity and free water content; all of which have been obtained from the CEMHYD3D simulation have been cross correlated with the experimental results in order to more comprehensively understand the mechanism contributing to bulk volume change under sealed conditions. The experimental investigations are extended to study the development in concrete with and without mineral admixtures (i.e., silica fume, fly ash and slag). Self desiccation driving the development of autogenous shrinkage has been used extensively across literature but as an alternative the author has proposed using internal drying factor in modelling autogenous shrinkage. The "internal drying factor" is described as the ratio of the empty voids (due to chemical shrinkage) to the total porosity at any point of time of hydration. Independent of the mixture proportions, a linear trend was observed between the autogenous shrinkage strain and increase in internal drying factor. Thus the internal drying factor could be incorporated into semiempirical models while attempting to predict autogenous shrinkage. An increase in the compressive strength of matured concrete at 1 year had a strong correlation to the observed autogenous shrinkage strains irrespective of the cementitious system. It is believed this could be because of the increase in gel-space ratio which is intern linked to the degree of hydration and porosity of the microstructure. The author has obtained strong evidence that the micro-structural changes associated with high strength and durable concrete have a direct impact on the autogenous shrinkage of concrete. Hence, the author suggests that autogenous shrinkage should be investigated and allowable values be stipulated as design criterion in structures that use high strength-high performance concrete.

Currently, the plastics industry has a wide range of applications due to the possibility of a fully automated process or through increased production efficiencies. The reason for this choice of the thesis was to understand the whole issue of plastic injection molding process. The specified component is used to atach the sail, which serves to protect workers in the welding sector. A specified number of the series is 350 000. The work includes a theoretical problem of injection molding process, selection of technology, material selection and design of mold. An integral part of every design mold is a simulation of injection, which is also included. In conclusion of thesis is the calculation of the various stages of production and operation of the injection mold.

A promising approach to treat patients with vocal fold paralysis using electrical stimulation is investigated throughout this research work. Functional Electrical Stimulation works by stimulating the atrophied muscle or group of muscles directly by current when the transmission lines between the central nervous system are disrupted. This technique helps maintain muscle mass and promote blood flow in the absence of a functioning nervous system. The goal of this work is two-fold: develop control techniques for muscle contraction to optimize muscle stimulation and develop a small-scale electromagnetic system to provide stimulation to the laryngeal muscles for patients with vocal fold paralysis. These studies; therefore, focus on assessing a linear Proportional-Integral (PI) controller and two nonlinear controllers: Model Reference Adaptive Controller (MRAC) and an Adaptive Augmented PI (ADP-PI) system to identify the most appropriate controller providing effective stimulation of the muscle. Direct stimulation is applied to mouse skeletal muscle in vitro to test the controllers along with numerical simulations for validation of these experimental tests. The experiments included muscle contractions following four distinct trajectories: a step, sine, ramp, and square wave. Overall, the closed-loop controllers followed the stimulation trajectories set for all the simulated and tested muscles. When comparing the experimental outcomes of each controller, we concluded that the ADP-PI algorithm provided the best closed-loop performance for speed of convergence and disturbance rejection. Next, the focus of the research work was on the implementation of an electromagnetic system to generate appropriate currents of stimulation using the aforementioned controllers. For this study, Nickel-Titanium shape memory alloys were used to assess activation (contraction) through a two-coil system guided by the controllers. The application of the two-coil system demonstrated the effectiveness of the approach and a main effect was observed between the PI, MRAC, and ADP-PI controllers when following the trajectories. Lastly, a small scale two-coil system is developed for animal testing in the muscle-mass-spring setup. Experiments were successful in generating the appropriate stimulation controlled by the output-based algorithms for muscle contraction. Trials conducted for this study were compared to the muscle contractions observed in the first study. The controllers were able to provide appropriate stimulation to the muscle system to follow the set trajectories: a step, ramp, and sinusoidal input. More trials are required to draw statistical conclusions about the performance of each controller. Regardless, the small-scale two-coil system along with the applied controllers can be reconfigured to be an implantable system and tested for appropriate stimulation of the laryngeal muscles.
Ph. D.

Asthma is characterised by airway remodelling and an increase in airway resistance. A greater understanding of the mechanisms involved in airway inflammation and airway hyper-responsiveness (AHR) may highlight therapeutic opportunities for asthma. This study initially aimed to optimise the preparation of precision cut lung slices (PCLS) in mouse and pig to investigate the influence of calcium (Ca2+) homeostasis on airway smooth muscle (ASM) contraction as a prelude to human studies. The PCLS technique was then applied to a murine model of allergic airway disease to explore the inflammatory process and pathogenesis of airway hyper-reactivity in sensitised mice. Initial experiments using murine and porcine airways validated the PCLS model and demonstrated the significance of release and refilling of Ca2+ from internal stores to induce and maintain an airway contraction. Results also highlight interesting species differences in agonist sensitivity, with the porcine system sharing similar pharmacology to human airways. Using a murine model of allergic airway disease, agonist induced contractile responses in peripheral airways were measured in vitro using the PCLS technique. BALB/c mice underwent initial sensitisation by intraperitoneal administration of ovalbumin, receiving a 3 day challenge with aerosolised OVA l% (vlv), for varying periods of up to 3 weeks for acute, mid-chronic and chronic sensitisation protocols. To investigate the influence of the inflammatory environment, naive murine lung slices were incubated with selected inflammatory mediators. OVA sensitisation led to progressive structural remodelling and AHR to methacholine (MCh) challenge. However, this hyperresponsiveness was decreased 48 hours post lung removal. Of the inflammatory mediators selected for lung slice incubation, IL-33 significantly increased AHR to MCh. IL-33 is a proinflammatory cytokine with transcriptional repressor properties, playing a role in initiating the TH2 inflammatory response. In lung slices prepared from IL-33 receptor (ST2) KO mice IL-33 was unable to sensitise the contractile response. These data suggest the inflammatory environment promotes AHR and disassociates this airway sensitivity from structural remodelling. These data suggest a key role for IL-33 in mediating AHR in this murine model. Investigation of the mechanisms involved in airway hyper-reactivity revealed mRNA expression of IL-33 and the IL-33 receptor (ST2) in soluble and membrane bound forms were significantly increased in the mid-chronic and chronic ovalbumin sensitised murine lung tissue. Further quantitative analysis in human lung showed expression of IL-33 in epithelial and ASM cells. The human ST2 receptor (also known as IL-IRL-l) was expressed in mast cells. Together these results suggest IL-33 is a sensor of tissue damage; indirectly inducing AHR through further inflammatory cell activation to target ASM. This study demonstrates IL-33's role as an inflammatory marker of asthma and suggests a novel therapeutic intervention by targeting of the ST2 receptor.

Diagnosing cardiac patient problems contains many uncertainties, and to fully diagnose the patient's condition usually requires a lengthy drug regimen to see what works and what does not. Compounding this problem is that even after the correct drug regimen has been discovered, the underlying cause for the problem may remain a mystery. Thus, the uncertainty and the length of time required to provide an accurate and adequate solution makes it very difficult to provide quality care to the patient. Templeton and others have shown that lumped cardiac muscle parameters can be extracted from an isolated heart by injecting small volumes at high frequencies relative to the heart rate and measuring the pressure response to this volume change. Using the Hill muscle model of two springs and a dash pot to portray the different elements of the cardiac muscle, the pressure and volume relationship makes it possible to calculate these muscle parameters using frequency response analysis techniques. The hypothesis to be tested is "Is it possible to develop a method to test cardiac muscle for stiffness, resistance, and contractile force from measuring ventricular pressure and injected flow?" To test this hypothesis, an isovolumic heart model is developed and allowed to develop pressure, along with a small volume injected to create a pressure response. Analysis of the pressure and flow waveforms produces a measured value of the cardiac model parameter values to compare to the model values. Results from injecting small volume changes into a mathematical heart model show that it is possible to extract the muscle model parameters of non-linear resistance, inertia of the fluid and muscle, and stiffness of the muscle while filling and contracting. The injected frequency and volume were varied to find usable conditions, both with regard to the calculations and the practical limits. Analyzing the error between the measured and model values for a large number of different combinations of model parameters shows an average error of less than 1%.
Iron Range Engineering

The availability of oxygen (O2) is vital for maintaining neurological function during exercise. This is clear when performing exercise in low oxygen environments, such as high altitude, where reductions in O2 availability result in limitations in motor performance. However, the ongoing contribution of central and peripheral mechanisms to hypoxia-related limitations in motor performance is yet to be fully understood. A wide variety of experimental designs have been used to test motor pathways during hypoxic exposure. Indeed, there is little consistency in the literature with regards to 1) the severity of hypoxic exposure, 2) the duration of hypoxic exposure, 3) the fatigue-state of the motor system, and 4) the intensity of exercise. This Thesis presents a series of controlled laboratory experiments which assess the effects of acute hypoxia (2 hr at 80% SpO2) on central and peripheral motor mechanisms. The experiments used high-density electromyography, electrical stimulation of the motor nerve (MNS), and transcranial magnetic stimulation (TMS) of the motor cortex, to clarify how motor activity is affected with hypoxia. The first experiment assessed how the firing characteristics of biceps brachii motor units (MU) were modulated by acute hypoxia when performing sustained isometric elbow flexions. Maximal voluntary contraction (MVC) toque remained unaffected during hypoxia, however, individuals exhibited specific changes in MU firing. Bidirectional changes in MU discharge were strongly correlated to the rate of desaturation and sensitivity to O2 availability during the titration phase. Differences in intrinsic properties of neurons, afferent input to motoneurones, neuromodulation, and sympathetic nerve activity may explain these differences. The second experiment assessed how corticospinal excitability, voluntary activation using motor nerve stimulation (VAMNS) and perception of fatigue (RPF) during brief and sustained MVCs were modulated by acute hypoxia. RPF and corticospinal excitability increased, while VAMNS decreased across the hypoxia protocol. Changes in the motor evoked potential (MEP) area and VAMNS were only seen during the brief MVCs and not the sustained MVCs. This may be due to redirection of blood flow to active areas of the motor system during prolonged contraction. The third experiment assessed how acute hypoxia altered neural mechanisms of muscle activation during, and following recovery from, a sustained submaximal (20% MVC) fatiguing contraction. MVC torque, root mean square EMG (EMGRMS), VAMNS and voluntary activation using TMS (VATMS), RPF, MEP area, and silent period duration (SP) were measured to characterise muscle activation. Hypoxia effects were only seen during the recovery phase, where VAMNS and VATMS, as well as MEP area, was reduced during acute hypoxia. This was likely due to hypoxia-related mechanisms involving supraspinal motor circuits that were impaired during the recovery phase. The fourth experiment assessed how acute hypoxia altered the neural mechanisms of muscle activation across a full range of force output once fatigued. MVC torque, EMGRMS, VAMNS and VATMS, MEP area, and SP were assessed following the sustained MVC. VATMS was reduced during hypoxia, which was not reflected in VAMNS. This indicates that acute hypoxia significantly impaired the ability of the motor cortex to voluntarily activate the fatigued muscle. This was partly due to suboptimal output from the motor cortex. Collectively, the findings of the four experiments in this Thesis provide novel evidence that a moderate acute hypoxic stimulus 1) reduces VA of a muscle during maximal and submaximal contraction due to suboptimal output from the motor cortex, 2) modulates the excitability of the corticospinal pathway, and 3) enhances perceptions of muscle fatigue during maximal, but not submaximal, fatiguing contractions. For these findings to occur, the elbow flexor muscle group needed to be sufficiently fatigued during at least 2 hr of prolonged exposure to a moderate hypoxic stimulus.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Health Sci & Soc Wrk
Griffith Health
Full Text

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 107-110).
A wide variety of stability and performance problems for linear and certain classes of nonlinear dynamical systems can be formulated as convex optimization problems involving linear matrix inequalities (LMIs). These formulations can be solved numerically with computationally-effcient interior-point methods. Many of the first LMI-based stability formulations applied to linear systems and the class of nonlinear systems representable as an interconnection of a linear system with bounded uncertainty blocks. Recently, stability and performance analyses of more general nonlinear deterministic systems, namely those with polynomial or rational dynamics, have been converted into an LMI framework using sum of squares (SOS) programming. SOS programming combines elements of computational algebra and convex optimization to provide e±cient convex relaxations for various computationally-hard problems. In this thesis we extend the class of systems that can be analyzed with LMI-based methods.
(cont.) We show how to analyze the robust stability properties of uncertain non-linear systems with polynomial or rational dynamics, as well as a class of systems with external inputs, via contraction analysis and SOS programming. Specifically, we show how contraction analysis, a stability theory for nonlinear dynamical systems in which stability is designed incrementally between two arbitrary trajectories via a contraction metric, provides a useful framework for analyzing the stability of uncertain systems. Then, using SOS programming we develop an algorithmic method to search for contraction metrics for these systems. The search process is made computationally tractable by relaxing matrix deniteness constraints, the feasibility of which indicates the existence of a contraction metric, to SOS constraints on polynomial matrices. We illustrate our results through examples from the literature and show how our contraction-based approach offers advantages when compared with traditional Lyapunov analysis.
by Erin M. Aylward.
S.M.

In the last ten years the techniques for non invasive investigation of the neuromuscular system made consider¬able progress. Recently they have been associated to multichannel surface electromyography (EMG) detected with linear or two-dimensional elec¬trode arrays. This approach consists in measuring electrical muscle activ¬ity, generated by the most superficial motor units (MUs), with multiple (more than two) closely spaced elec¬trodes overlying either a restricted area of the skin or the entire surface of the muscle. Although the behavior of the MUs is classically studied with intramuscular EMG, these recently developed techniques allow the analy¬sis of EMG recorded in multiple loca¬tions over the skin surface. The analy¬sis of MUs from the surface EMG is useful when the insertion of needles is not desirable or not possi¬ble. Moreover, multichannel surface EMG allows the measure of MU properties which are difficult to assess with inva¬sive technology (e.g., muscle fiber conduction velocity, location of inner¬vation zones, global and single motor unit manifestations of fatigue) and increases the number of detectable motor units with respect to selective intramuscular recordings. The application of surface EMG to the study of electrically elicited con¬tractions allows a study of the com¬pound muscle action potentials (CMAPs) or massed action potentials (M-waves) which represent the syn¬chronous summation of the MUAPs that add asynchronously during a vol¬untary contraction. M-wave analysis represents an important investigative tool in several different areas of neuro¬physiological research. Evoking the maximum M-wave by supramaxi¬mal stimulation of either a peripheral nerve or the muscle motor point is the electrical equivalent of the recruitment of all motor units within the selected motoneuron pool and allows to inves¬tigate the properties of these motor units. Moreover, progressive incre¬ments of stimulation intensity elicit progressively greater M-waves. The difference between M-waves elicited using two different stimulation levels allows the analysis of the MUs whose activation thresholds are in between the two stimulation levels. This proc¬ess allows the characterization of small groups of MUs and therefore the order of recruitment and MU charac¬terization during electrical stimula¬tion. The use of incremental M-wave technique together with bi-dimen-sional detection systems is an inter¬esting application to study the spatial localization of MU territories within pinnate muscles. Electrical stimulation (combined with surface EMG) provides also in¬teresting experimental paradigms to study muscular properties during fa¬tiguing contractions, because it gives to the experimenter the control of MU firing frequency and recruitment and, if selectively applied, eliminates the problem of cross-talk from nearby muscles. In fact, selective electrical stimulation of a nerve branch or of the motor point of a muscle allows, in first approximation, to “disconnect” the investigated muscle from the central nervous system and to activate only one (or a portion of one) muscle at a time at a controlled frequency and with a motor unit pool that is more likely to be stable. During fatiguing muscle contractions, M-waves (de¬tected with linear or two-dimensional electrode arrays) change shape be¬cause of the presence of motor units with different conduction velocities and fatigue profiles. With respect to the analysis of myoelectric fatigue during voluntary contractions, electri¬cally elicited contractions provide es¬timates of the changes in surface EMG signal variables that have lower esti¬mation errors. The issue of fatigue during electrically elicited contrac¬tions is of paramount importance in functional electrical stimulation tech¬niques for external control of para¬lyzed extremities. Furthermore, the application of bursts of electrical pulses to a periph¬eral nerve (or to the muscle motor point) may induce, in certain muscles, involuntary muscle activity that per¬sists for some time after the interrup¬tion of the stimulation. Such activity is referred to as “fascicula¬tion” and “cramp”, which are defined, respectively, as “the random, sponta¬neous twitching of a group of muscle fibers belonging to a single motor unit” and “an involuntary, painful muscle contraction associated with electrical activity”. Even if cramps are a common complaint encountered by both neurologists and primary care physicians, their pathophysiology still remains poorly understood, mainly due to the unpredictable occurrence and the relative inaccessibility to experi¬mental investigation. However, sur¬face EMG signals detected during cramps induced by means of electrical stimulation of the muscle, in con¬trolled conditions of fibre length and orientation, provide interesting infor¬mation about cramp pathophysiology. This PhD thesis contributes to this research field through the analysis and interpretation of multichannel surface EMG signals during electrically elic¬ited contractions and during different types of involuntary muscle contrac¬tions, such as fasciculations and cramps.The main objectives of the thesis were to: (1) establish the influence of selected parameters of the electrical stimu¬lation (current amplitude, pulse shape, injected charge) on the de¬gree of MU activation during transcutaneous stimulation; (2) assess the differences in the myoelectric fatigue profiles during electrical stimulation among differ¬ent muscles and subject popula¬tions; (3) evaluate whether the electrical stimulation of the muscle motor point can trigger a cramp in differ¬ent foot and leg muscles, as it was already observed in foot muscles following the electrical stimulation of the nerve trunk; (4) study surface EMG signals during cramp contractions; (5) examine whether different bursts of electrical stimulation, applied to the muscle motor point, trigger dif¬ferent cramps of the muscle under study; (6) provide novel insights into cramp pathophysiology from detection and analysis of surface and intra¬muscular EMG signals during electrically elicited cramps. Part 1. NMES: Methodological issues This section focuses on methodological aspects concerning neuromuscular electrical stimulation (NMES). Chapters I and II include a brief introduction to the stimulation techniques, to the spinal involvement in electrically elicited muscle contractions, and to the acquisition of EMG signals during electrically elicited contractions (study of M-waves and incremental M-waves). Further, Chapter II reports a study on the incremental M waves detected from the medial gastrocnemius muscle. It has been preliminarly demonstrated that the use of incremental M-waves acquired with high density detection systems allows the spatial localization of MU territories in a pinnate muscle. This could have an important application in the study of the compartmentalization of muscles involved in posture, such as the gastrocnemii. Chapter III describes an experimental study on the effect of the stimulation parameters (stimulation waveform, amplitude, and injected charge) on the degree of MU activation in electrically-elicited contractions of the biceps brachii. The main outcome of this work was that the degree of MU activation was a function of the injected charge and not of the stimulation waveform. Moreover, MUs tended to be recruited in order of increasing conduction velocity with increasing charge of transcutaneous stimulation (regardless of the pulse waveform). This study concerned the biceps brachii, a muscle which is not usually electrically stimulated other than for M-wave studies. Other muscles, particularly the thigh muscles, are either of greater interest in sport sciences and rehabilitation medicine. Whether MUs are recruited in an orderly or random manner during motor point electrical stimulation of these muscles was one of the topics of the study reported in Chapter IV. The objectives of the study described in Chapter IV were to investigate, in three muscles of the thigh, the MU recruitment order in stimulated contractions and the electrically-induced manifestations of muscle fatigue. This study, performed on two groups of healthy subjects, was also aimed to test the possibility of detecting differences among muscles and subject groups in the response to the transcutaneous stimulation. Results of this study confirmed the observations of the previous study (Chapter III) on the recruitment order: MUs tended to be activated from low to high conduction velocities with increasing current of the transcutaneous stimulation. Moreover, EMG variables during electrically-evoked fatigue showed different properties in different muscles and subject groups. Overall, the results of the above-described methodological studies contributed to the design of clinical protocols for neuromuscular function assessment (sarcolemmal excitability and fatigability) in clinical relevant conditions. These studies are described in the second part of this thesis. Part 2. NMES: clinical applications Chapter V describes two experimental protocols aimed to investigate the neuromuscular effects of both glucocorticoid administration in healthy subjects and chronic endogenous hypercortisolism in pathological subjects (affected by Cushing’s disease). Results from the protocol performed on healthy subjects showed that muscle fiber conduction velocity and myoelectric manifestations of fatigue significantly decreased after the short-term administration of a synthetic glucocorticoid (dexamethasone), in doses well within the range used clinically. Results from the protocol conducted on pathological subjects showed that muscle fiber conduction slowing is a sensitive marker of steroid myopathy which is suitable to be used in combination with standard electrodiagnostic tests for identifying early signs of myopathy. Part 3. NMES induced muscle cramps The third section is focused on the study of involuntary muscle contractions. Chapter VI reports the description of a method, developed within this project, for inducing cramps in an intrinsic foot muscle, the abductor hallucis, by means of electrical stimulation of the main muscle motor point. This method was reliable and suitable to be used concomitantly with multichannel surface EMG. The test of this method in different foot and leg muscles is the topic of the second part of Chapter VI. We found that the neurostimulation method was effective in eliciting cramps in four muscles of the lower limb bilaterally, and that differences exist between the cramp elicitability profiles of the different foot and leg muscles. The analysis of surface EMG signals during cramp contractions as well as the study of the effect of different stimulation frequencies on the elicited muscle cramp is reported in Chapter VII. The aim of this study was to provide new insight into cramp pathophysiology (generation and self-sustaining mechanisms) through the analysis of EMG signals. Results showed that the choice of the frequency of the stimulation burst affects the temporal and spectral properties of EMG in electrically-elicited cramps. However, these findings did not provide insight into the exact physiological mechanism(s) underlying cramp generation since they could fit both the hypothesis of peripheral origin and that of spinal origin of cramps. Hence, the differences between cramps elicited with different stimulation frequencies were further investigated by means of a joint analysis of surface and intramuscular EMG signals (Chapter VIII). The analysis of the discharge behaviour of single MUs during cramp (discharge rate and variability, and coherence between discharge rate oscillations of different MUs) indicated that cramp development and self-sustaining mechanisms involve spinal pathways, although the origin may be peripheral. Future studies will be aimed to confirm recent preliminary evidences supporting the hypothesis of cramps being initialized at the peripheral level but subsequently supported by spinal reflex loops. HDsEMG and decomposition of cramp signals into the constituent trains of motor unit action potential represent a promising approach to investigate the behavior of individual MUs during cramp contractions.

Les systèmes neuromusculaire et musculosquelettique sont des systèmes de systèmes complexes qui interagissent parfaitement entre eux afin de produire le mouvement. En y regardant de plus près, ce mouvement est la résultante d'une force musculaire créée à partir d'une activation du muscle par le système nerveux central. En parallèle de cette activité mécanique, le muscle produit aussi une activité électrique elle aussi contrôlée par la même activation. Cette activité électrique peut être mesurée à la surface de la peau à l'aide d'électrode, ce signal enregistré par l'électrode se nomme le signal Électromyogramme de surface (sEMG). Comprendre comment ces résultats de l'activation du muscle sont générés est primordial en biomécanique ou pour des applications cliniques. Évaluer et quantifier ces interactions intervenant durant la contraction musculaire est difficile et complexe à étudier dans des conditions expérimentales. Par conséquent, il est nécessaire de développer un moyen pour pouvoir décrire et estimer ces interactions. Dans la littérature de la bioingénierie, plusieurs modèles de génération de signaux sEMG et de force ont été publiés. Ces modèles sont principalement utilisés pour décrire une partie des résultats de la contraction musculaire. Ces modèles souffrent de plusieurs limites telles que le manque de réalisme physiologique, la personnalisation des paramètres, ou la représentativité lorsqu'un muscle complet est considéré. Dans ce travail de thèse, nous nous proposons de développer un modèle biofidèle, personnalisable et rapide décrivant l'activité électrique et mécanique du muscle en contraction isométrique. Pour se faire, nous proposons d'abord un modèle décrivant l'activité électrique du muscle à la surface de la peau. Cette activité électrique sera commandé par une commande volontaire venant du système nerveux périphérique, qui va activer les fibres musculaires qui vont alors dépolariser leur membrane. Cette dépolarisation sera alors filtrée par le volume conducteur afin d'obtenir l'activité électrique à la surface de la peau. Une fois cette activité obtenue, le système d'enregistrement décrivant une grille d'électrode à haute densité (HD-sEMG) est modélisée à la surface de la peau afin d'obtenir les signaux sEMG à partir d'une intégration surfacique sous le domaine de l'électrode. Dans ce modèle de génération de l'activité électrique, le membre est considéré cylindrique et multi couches avec la considération des tissus musculaire, adipeux et la peau. Par la suite, nous proposons un modèle mécanique du muscle décrit à l'échelle de l'Unité Motrice (UM). L'ensemble des résultats mécaniques de la contraction musculaire (force, raideur et déformation) sont déterminées à partir de la même commande excitatrice du système nerveux périphérique. Ce modèle est basé sur le modèle de coulissement des filaments d'actine-myosine proposé par Huxley que l'on modélise à l'échelle UM en utilisant la théorie des moments utilisée par Zahalak. Ce modèle mécanique est validé avec un profil de force enregistré sur un sujet paraplégique avec un implant de stimulation neurale. Finalement, nous proposons aussi trois applications des modèles proposés afin d'illustrer leurs fiabilités ainsi que leurs utilité. Tout d'abord une analyse de sensibilité globale des paramètres de la grille HDsEMG est présentée. Puis, nous présenterons un travail fait en collaboration avec une autre doctorante une nouvelle étude plus précise sur la modélisation de la relation HDsEMG/force en personnalisant les paramètres afin de mimer au mieux le comportement du Biceps Brachii. Pour conclure, nous proposons un dernier modèle quasi­ dynamique décrivant l'activité électro-mécanique du muscle en contraction isométrique. Ce modèle déformable va actualiser l'anatomie cylindrique du membre sous une hypothèse isovolumique du muscle
The neuromuscular and musculoskeletal systems are complex System of Systems (SoS) that perfectly interact to provide motion. From this interaction, muscular force is generated from the muscle activation commanded by the Central Nervous System (CNS) that pilots joint motion. In parallel an electrical activity of the muscle is generated driven by the same command of the CNS. This electrical activity can be measured at the skin surface using electrodes, namely the surface electromyogram (sEMG). The knowledge of how these muscle out comes are generated is highly important in biomechanical and clinical applications. Evaluating and quantifying the interactions arising during the muscle activation are hard and complex to investigate in experimental conditions. Therefore, it is necessary to develop a way to describe and estimate it. In the bioengineering literature, several models of the sEMG and the force generation are provided. They are principally used to describe subparts of themuscular outcomes. These models suffer from several important limitations such lacks of physiological realism, personalization, and representability when a complete muscle is considered. In this work, we propose to construct bioreliable, personalized and fast models describing electrical and mechanical activities of the muscle during contraction. For this purpose, we first propose a model describing the electrical activity at the skin surface of the muscle where this electrical activity is determined from a voluntary command of the Peripheral Nervous System (PNS), activating the muscle fibers that generate a depolarization of their membrane that is filtered by the limbvolume. Once this electrical activity is computed, the recording system, i.e. the High Density sEMG (HD-sEMG) grid is define over the skin where the sEMG signal is determined as a numerical integration of the electrical activity under the electrode area. In this model, the limb is considered as a multilayered cylinder where muscle, adipose and skin tissues are described. Therefore, we propose a mechanical model described at the Motor Unit (MU) scale. The mechanical outcomes (muscle force, stiffness and deformation) are determined from the same voluntary command of the PNS, and is based on the Huxley sliding filaments model upscale at the MU scale using the distribution-moment theory proposed by Zahalak. This model is validated with force profile recorded from a subject implanted with an electrical stimulation device. Finally, we proposed three applications of the proposed models to illustrate their reliability and usefulness. A global sensitivity analysis of the statistics computed over the sEMG signals according to variation of the HD-sEMG electrode grid is performed. Then, we proposed in collaboration a new HDsEMG/force relationship, using personalized simulated data of the Biceps Brachii from the electrical model and a Twitch based model to estimate a specific force profile corresponding to a specific sEMG sensor network and muscle configuration. To conclude, a deformableelectro-mechanicalmodelcouplingthetwoproposedmodelsisproposed. This deformable model updates the limb cylinder anatomy considering isovolumic assumption and respecting incompressible property of the muscle

Abstract Background – The heart cell is a prime example of a system, in which numerous interconnected regulatory mechanisms affect the dynamic balance of cellular function. The function of the system emerges from the interactions of its components rather than from their individual properties. Thus, it is a challenging task to understand the causal relations within such a system, based on the analysis of experimental results. Facing this complexity, the systems biological approach has gained interest during recent years, since with using it we can make an effort to observe, quantitatively and simultaneously, multiple components and their interdependencies in biological networks. Methods and aims – One of the most important tools in systems biology is mathematical modelling. In this thesis, novel model components have been developed and existing components integrated to describe mathematically the calcium dynamics in cardiac myocytes with improved physiological accuracy. Special attention was paid to both the activity-dependent and automatic regulation of the dynamics. This enabled the quantitative analysis of the regulation’s role in both physiological and pathophysiological conditions. Results – Validation of the novel model components that describe the calcium transport mechanisms indicates that the developed schemes are accurate and applicable also beyond the normal physiological state of the cardiac myocyte. Results also highlight the importance of autoregulation of calcium dynamics in the excitation-contraction coupling. Furthermore, the analysis indicates that the CaMK-dependent regulation of the calcium uptake to and release from the sarcoplasmic reticulum calcium stores could have substantial roles as downstream effectors in beta-adrenergic stimulation. Conclusions – Results emphasize mathematical modelling as a valuable complement to experiments in understanding causal relations within complex biological systems such as the cardiac myocytes. That is, rigorous data integration with mathematical models can provide significant insight to the quantitative role of both the individual model components and the interconnected regulatory loops. This is especially true for the analysis of genetically engineered animal models, in which the intended modification is always accompanied by compensatory changes that can mask to a varying degree the actual phenomenon of interest.

Thermoplastic injection technology is widely used in all sectors of consumer electronics and automotive industry. The biggest advantage of this manufacturing technology is a high degree of automatization and good reproducibility of the manufacturing process. Another advantage is the possibility of recycling of the gating scrap and defective products. The main task of this work is to calculate the necessary parameters for the injection process, which takes place at the designed injection form. Next part is technical design which includes choice of standard parts of injection mold and idividual semi-finished parts for mold. Thesis continues with selecting the type of injection press based on calculated parameters of the injection process. Thesis is finished by technical-economic evaluation.

The electrical activity of skeletal muscle¡ªthe electromyogram (EMG)¡ªis of value to many different application areas, including ergonomics, clinical biomechanics and prosthesis control. For many applications the EMG is related to muscular tension, joint torque and/or applied forces. In these cases, a goal is for an EMG-torque model to emulate the natural relationship between the central nervous system and peripheral joints and muscles. This thesis mainly describes an experimental study which relates the simultaneous biceps/triceps surface EMG of 12 subjects to elbow torque at seven joint angles (ranging from 45¡ÃƒÂ£to 135¡ÃƒÂ£) during constant-posture, quasi-constant-torque contractions. The contractions ranged between 50% maximum voluntary contractions (MVC) extension and 50% MVC flexion. Advanced EMG amplitude (EMG¦Ãƒâ€™) estimation processors were investigated, and three nonlinear EMG¦Ãƒâ€™-torque models were evaluated. Results show that advanced (i.e., whitened, multiple-channel) EMG¦Ãƒâ€™ processors lead to improved joint torque estimation, compared to unwhitened, single-channel EMG¦Ãƒâ€™ processors. Depending on the joint angle, use of the multiple-channel whitened EMG¦Ãƒâ€™ processor with higher polynomial degrees produced a median error that was 50%-66% that found when using the single-channel, unwhitened EMG¦Ãƒâ€™ processor with a polynomial degree of 1. The best angle-specific model achieved a minimum error of 3.39% MVCF90 (i.e., error referenced to MVC at 90¢X flexion), yet it does not allow interpolation across angles. The best model which parameterizes the angle dependence achieved an error of 3.55% MVCF90. This thesis also summarizes other collaborative research contributions performed as part of this thesis. (1) Decomposition of needle EMG data was performed as part of a study to characterize motor unit behavior in patients with amyotrophic lateral sclerosis (ALS) [with Spaulding Rehabilitation Hospital, Boston, MA]. (2) EMG-force modeling of force produced at the finger tips was studied with the purpose of assessing the ability to determine two or more independent, continuous degrees of freedom of control from the muscles of the forearm [with WPI and Sherbrooke University]. (3) Identification of a nonlinear, dynamic EMG-torque relationship about the elbow was studied [WPI]. (4) Signal whitening preprocessing for improved classification accuracies in myoelectric control of a prosthesis was studied [with WPI and the University of New Brunswick].

Thesis (M.S.)--West Virginia University, 2001.
Title from document title page. Document formatted into pages; contains vii, 65 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 59-62).

In cerebral palsied adults, the cardiovascular responses to different types of exercise have not previously been ascertained. Therefore, the purpose of this study was to determine the blood pressure and heart rate responses of adults with cerebral palsy to static muscular contractions and to dynamic muscular contractions. Fifteen adults with cerebral palsy and 15 able-bodied adults (average age for each group = 30 years) performed a static exercise protocol and a dynamic resistance exercise protocol using each limb (or the limbs capable of meeting the requirements of the exercise protocol). Heart rate and blood pressure were assessed before, during, and after each exercise bout with each limb. During the static exercise protocol, each subject performed static contractions at 40% of maximal voluntary contraction to fatigue. The dynamic exercise protocol for each limb consisted of three 20-second bouts of hydraulic resistance exercise each of which was followed by 20 seconds of rest. No differences were found between the two groups of subjects in heart rate and blood pressure during static exercise. In dynamic exercise, however, the trend in heart rate from bout to bout differed between the groups. In addition, the cerebral palsied group's diastolic pressure was higher than that of the able-bodied group at the end of dynamic exercise. The findings of this study indicate that although the heart rate and blood pressure responses to dynamic resistance exercise in the cerebral palsied subjects differed from the responses of the able-bodied subjects, healthy adults with cerebral palsy may safely perform both static and dynamic resistance exercise. More research using this disabled population is needed so that guidelines for prescribing exercise for adults with cerebral palsy may be developed.

The Central Nervous System (CNS) exerts extensive control over muscle activation in order to produce accurate voluntary movement, such as the complex movements of the human shoulder joint. Muscles surrounding multi-planar joints are selectively activated depending upon the movement performed, and within the radiate musculature of the shoulder, individual muscle segments exist that are capable of exhibiting specific myoelectric intensity and temporal activation patterns. The aim of this thesis was to assess the influence of inter-segment variations in contractile properties on the strategies employed by the CNS when producing voluntary movements. Experiments were designed to test the hypothesis that muscle segment neuromotor coordination (as determined by electromyographic analysis) would be sensitive to the contractile properties of individual muscle segments. A key component was the variation in isometric contraction speed ranging from slow to ballistic.Mechanomyography (MMG), which is the measure of a muscle’s physical dimensional change during contraction, is founded on the premise that the temporal aspect of muscle displacement is reflective of motor unit contractile properties and consequently the muscle fibre type composition. A series of studies were completed to establish the validity of the new Laser-MMG technique for quantifying contractile properties. The results confirmed: 1) the sensitivity of the Laser-MMG technique to modulators of physiological performance (thermal state, fatigue state, and fibre type composition variation between segments); and 2) that the contractile properties of muscle fibres varied between the individual segments of the muscles following maximal percutaneous neuromuscular stimulation (PNS). Most notably, ‘slow-twitch’ contractile properties were found in muscle segments that have a greater role in producing movement in the coronal plane, while ‘fast-twitch’ contractile properties were associated with segments having more efficient moment arms to produce movement in the sagittal plane. Furthermore, each of the muscles investigated was associated with a distinctive anatomical distribution of muscle fibre types. Muscle segment contractile properties were heterogeneous and their arrangement appears to reflect the most common or important joint movements. Moreover, the muscle segments located at the periphery of all three shoulder muscles exhibited faster contractile properties than those located in the middle of the muscle. It appears that this internal arrangement may be a consistent organisational characteristic of radiate muscles. Muscle segments within the pectoralis major, deltoid and latissimus dorsi muscles were found to be independently controlled by the CNS through manipulation of the myoelectric activation patterns, in particular: onset time; and discharge rate. The lower segments of the pectoralis major and the latissimus dorsi were identified as prime mover segments, initiating the movement and contributing the greatest myoelectric intensity. The immediately superior segments were classified as assistant movers, activating after the prime movers and contributing less to the overall movement. Furthermore, similarities in neuromotor coordination were identified between adjacent segments of individual muscles. The sequential “wave of segment activation” identified within each whole muscle appeared to ignore the anatomical boundaries between muscles, suggesting that the CNS coordinates individual muscle segments rather than the whole muscle as one unit in order to complete a motor task. This further complicates the process of controlling motor tasks as there appear to be no defined limits of muscles to which discrete functions can be applied.Coordination between prime mover segments of agonist muscles was identified, with the lower segments of pectoralis major and latissimus dorsi showing no significant difference in any of the temporal myoelectric measures. The similarity in neuromotor coordination between these segments may be the result of a common drive, suggesting that the CNS uses a simple strategy of combining the segments into one functional unit. No gross disordering of the muscle segments’ onset was identified within any of the investigated muscles, with regard to movement speed. However, the pectoralis major exhibited altered relative timing between the segments. This was particularly evident during the fast movement. The sequential “wave of activation” present during the slow movements became disordered as muscle contraction speed was increased. During fast contraction, the assistant mover segments within pectoralis major were activated later than the prime mover segments changing the relative timing of their activation. This indicates that the CNS may initially prioritise the activation of only the most essential muscle segments to commence the movement during ballistic movements, perhaps due to the imposed time constraints. This form of change in relative timing can be interpreted as a direct reflection of the differences in muscle segment fibre type composition and hence the neuromotor control of the muscle segments involved in producing the movement. Most notably, variation to the control of muscle segment excitation and contraction onset exist in the more centrally located muscle segments that exhibit slower segment contractile properties. This finding appears logical when coupled with the finding of homogeneous myoelectric peak activity. The CNS must manipulate the onset of these slower contracting segments, especially during fast movements, in order to allow enough time for all segments to achieve a uniform peak of muscle activity that occurs just prior to peak force. The variations and coordination of contractile properties, myoelectric properties and electromyographic burst patterns between adjacent muscle segments within the same skeletal muscle confirms the notion that for CNS control, individual muscle segments are considered as sub-volumes of muscle tissue that require individual neuromotor control – that they are, in effect, muscles within muscles.

Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: system identification; EMG; optimal sampling rate; linear torque model; EMG-torque model; EMG amplitude; torque. Includes bibliographical references (p. 77-86).

Abstract Excitation-contraction coupling (ECC) is a process linking the electrical excitation of the muscle cell (myocyte) membrane to the contraction of the cell. In this study the possibilities of mathematical modeling were studied in current ECC research. Mathematical modeling was employed in two distinct ECC research areas, the enzymatic regulation of ECC and ECC during cardiac myocyte development. Despite the distinction, both of these are extremely complex biological systems characterized by diverse and partly contradictory reported experimental results, with a large part based on genetically engineered animal models. Novel mathematical models were developed for both of these research areas. The model of ventricular myocyte ECC with calmodulin-dependent protein kinase II (CaMKII)-mediated regulation faithfully reproduced the heart-rate dependent regulation of ECC. This regulation is thought to be the major effect of CaMKII-mediated regulation. The model of the embryonic ventricular myocyte provided the first comprehensive system analysis of how the embryonic heartbeat is generated at the cellular level. A similar type of model was also developed to show the notable differences between neonatal and adult ventricular myocyte ECC. The mathematical models of ECC presented in this study were further used to simulate ECC in genetically engineered myocytes. The cellular mechanisms of genetically engineered animal models could be better understood by employing mathematical modeling in parallel to experimental characterization of the animal model. It was found in simulations that the indirect consequences and the compensatory mechanisms induced by genetic modification may have a more significant effect on ECC than the direct consequences of the modification. To understand the overwhelming complexity of biological systems including ECC, competent system analysis tools, such as mathematical modeling, are required. The purpose of mathematical modeling is not to replace the experimental studies, but to provide a more comprehensive system analysis based on the experimental data. This system analysis will help in planning subsequent experiments needed to gain the most relevant information about the studied biological system.

Intermedin (IMD) is a peptide hormone discovered in 2004 belonging to the calcitonin/calcitonin gene-related peptide superfamily. It signals through a Gprotein coupled receptor by the coupling of a calcitonin receptor-like receptor (CRLR) and one of the receptor activity-modifying proteins (RAMPs) 1-3. Due to its similarity to adrenomedullin in structure and functions, IMD is also known as adrenomedullin 2 (ADM2). Among members of the superfamily, IMD shares the highest degree of homology with ADM, which is a multifunctional vasodilator ubiquitously expressed in various tissues and organs and has been studied by our group for its reproductive functions. It is hypothesized that IMD may be present in the reproductive systems of the rat and exert some effects on reproductive functions. The objectives of this study were to investigate the expression of IMD and its receptor components in the male and female reproductive systems of the rat, the changes in expression across the oestrous cycle, and its effect on uterine contraction. The gene expression levels of Imd and its receptor components and peptide levels of IMD were measured by RT-PCR and enzyme immunoassay respectively. The effect of IMD on the uterine contraction was studied by the organ bath technique. Imd mRNA and IMD levels were detected in the testis, epididymis, ventral prostate, coagulating gland, and seminal vesicle of the male rat and the ovary, oviduct, and uterus of the female rat, suggesting possible roles for IMD in both the male and female reproductive systems. In the male, the Imd mRNA levels were the highest in the seminal vesicle but lowest in the testis and the epididymis and IMD peptide levels were the highest in the coagulating gland but lowest in the epididymis. In the female, the Imd mRNA and IMD peptide levels were the highest in the oviduct and the uterus respectively while both the Imd and IMD levels were the lowest in the ovary. Imd mRNA and IMD levels displayed cyclic changes in various female reproductive tissues across the oestrous cycle. In the ovary, positive immunostaining was detected in the follicles and corpora lutea with more staining in the latter. The Imd mRNA level was significantly higher at prooestrus than dioestrus while the IMD peptide level was significantly higher at metoestrus than dioestrus. In the oviduct, the Imd mRNA level was the lowest at dioestrus but the IMD peptide level was the highest at dioestrus. Positive immunostaining was observed in the ciliated epithelial cells. Uterine Imd mRNA level was the highest at prooestrus while the IMD level was the highest at dioestrus. IMD was found in the luminal and glandular epithelia. IMD significantly reduced the uterine contraction amplitude and frequency but not the basal tone. CGRP receptor antagonist hCGRP8-37 and ADM receptor antagonist hADM22-52 partially abolished the inhibitory effect of IMD on uterine contraction while the IMD specific receptor antagonist hIMD17-47 completely blocked the actions. Enzyme inhibitors of NO (L-NAME) and PI3K (Wortmannin) pathways diminished the IMD-mediated effects on uterine contraction while cAMP/PKA blocker KT5720 had no effect.
published_or_final_version
Physiology
Master
Master of Philosophy

Dans un modele d'insuffisance cardiaque chez le chien eveille, les modifications de la fonction ventriculaire globale et regionale ainsi que le role du systeme renine-angiotensine au travers d'inhibiteurs de la renine, de l'enzyme de conversion et d'un antagoniste des recepteurs at1 de l'angiotensine ii ont ete etudies. Dans ce modele, la contraction et la reserve inotrope du ventricule gauche sont alterees de facon globale, mais il existe a l'etat de base des differences regionales importantes. Sous diverses stimulations inotropes, malgre les differences basales, les reserves inotropes regionales apparaissent similaires. Ces donnees soulignent le role potentiel de la perte d'homogeneite de la contraction comme facteur aggravant de l'insuffisance cardiaque, ainsi que l'importance de la recherche de zones hypocontractiles eventuellement recrutables par une stimulation inotrope. Dans ce modele le systeme renine angiotensine est stimule, cependant le blocage specifique du systeme par un inhibiteur de la renine n'entraine pas des effets hemodynamiques equivalents a ceux d'un inhibiteur de l'enzyme de conversion (enalaprilate) malgre un niveau de blocage du systeme similaire. Ces resultats s'expliquent par la participation de la bradykinine dans les effets hemodynamiques aigus de l'enalaprilate. Des resultats similaires ont ete retrouves avec un antagoniste des recepteurs de l'angiotensine ii avec la notion que les effets hemodynamiques de ce dernier sont dependant du degre d'activation du systeme tandis que ceux de l'enalaprilate le sont moins. A cote du role du systeme renine-angiotensine, ces resultats soulignent l'importance du role des systemes vasodilatateurs dans l'insuffisance cardiaque

Assessments of skeletal muscle functional capacity or bilateral muscular asymmetry often necessitate maximal contractile effort, which exacerbates muscle fatigue or injury. Tensiomyography (TMG) has been investigated in laboratory settings, as a means to assess muscle contractile function following fatigue; however observations have not been contextualised by concurrent physiological measures. TMG has more sparingly been applied in the field, with elite athletes. The aim of this thesis was to examine acute alterations and underlying variations in muscle contractile mechanics, through the application of TMG, contextualised with established physiological measures; and to apply TMG within high performance sports programmes. TMG successfully detected fatigue, evident from reduced strength, by displaying impaired muscle displacement, accompanied by elevated resting muscle tension. Greater asymmetry was detected in individuals with asymmetric strength; however, symmetry was masked during more complex tasks. Increased day-to-day variability was detected among highly trained athletes compared to recreationally active individuals. Acute training adaptations were detected, in contractile mechanics, in individual muscles. TMG could be useful in establishing fatigue status of skeletal muscle without exacerbating the functional decrements of the muscle, whilst also providing useful screening information for detecting asymmetry which may not be apparent during functional actions.

Dans cette thèse, nous nous sommes principalement intéressés à l’étude théorique et numérique de quelques équations qui décrivent la dynamique des densités des dislocations. Les dislocations sont des défauts microscopiques qui se déplacent dans les matériaux sous l’effet des contraintes extérieures. Dans un premier travail, nous démontrons un résultat d’existence globale en temps des solutions discontinues pour un système hyperbolique diagonal qui n’est pas nécessairement strictement hyperbolique, dans un espace unidimensionnel. Ainsi dans un deuxième travail, nous élargissons notre portée en démontrant un résultat similaire pour un système d’équations de type eikonal non-linéaire qui est en fait une généralisation du système hyperbolique déjà étudié. En effet, nous prouvons aussi l’existence et l’unicité d’une solution continue pour le système eikonal. Ensuite, nous nous sommes intéressés à l’analyse numérique de ce système en proposant un schéma aux différences finies, par lequel nous montrons la convergence vers le problème continu et nous consolidons nos résultats avec quelques simulations numériques. Dans une autre direction, nous nous sommes intéressés à la théorie de contraction différentielle pour les équations d’évolutions. Après avoir introduit une nouvelle distance, nous construisons une nouvelle famille des solutions contractantes positives pour l’équation d’évolution p-Laplace
In this thesis, we are mainly interested in the theoretical and numerical study of certain equations that describe the dynamics of dislocation densities. Dislocations are microscopic defects in materials, which move under the effect of an external stress. As a first work, we prove a global in time existence result of a discontinuous solution to a diagonal hyperbolic system, which is not necessarily strictly hyperbolic, in one space dimension. Then in another work, we broaden our scope by proving a similar result to a non-linear eikonal system, which is in fact a generalization of the hyperbolic system studied first. We also prove the existence and uniqueness of a continuous solution to the eikonal system. After that, we study this system numerically in a third work through proposing a finite difference scheme approximating it, of which we prove the convergence to the continuous problem, strengthening our outcomes with some numerical simulations. On a different direction, we were enthused by the theory of differential contraction to evolutionary equations. By introducing a new distance, we create a new family of contracting positive solutions to the evolutionary p-Laplacian equation

This study investigated whether acute myocardial ischemia of the anterior left ventricular wall induced an increase in cardiac sympathetic efferent nerve activity and thereby affected regional myocardial blood flow and contractile function.

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A crotamina, um peptídeo catiônico que possui 42 aminoácidos e 4,88 kDa, é proveniente do veneno de Crotalus durissus terrificus. Ela apresenta características que permitem sua forte interação com alvos moleculares e membranas biológicas e assim foi o primeiro peptídeo de veneno a ser classificado como um CPP (cell penetrating peptide), justificando seus importantes efeitos biológicos e suas diversas atividades farmacológicas. A crotamina é descrita por sua atividade miotóxica, tendo como efeito a paralisia e espasmos das patas traseiras de ratos e camundongos. Esse fenômeno é descrito por ações em canais de Na+ e/ou K+ e consequente aumento do influxo intracelular dos níveis do íon Ca2+. Estudos a descrevem como um agente despolarizante utilizando a musculatura esquelética como modelo experimental. Outra atividade descrita da crotamina é um aumento na liberação basal de acetilcolina (ACh) e dopamina no sistema nervoso central de ratos. Até o momento, pouco ou nenhum estudo foi realizado em musculatura lisa. A junção neuromuscular autônoma difere em vários aspectos importantes da já conhecida junção neuromuscular esquelética. O ducto deferente de rato (DDR), um órgão par e tubular pertencente à genitália acessória masculina, foi utilizado como modelo experimental por ser um dos órgãos periféricos mais densamente inervados pelo sistema nervoso autônomo simpático. Esse fato, o torna uma importante ferramenta para estudos que envolvam a neurotransmissão e a ação de drogas adrenérgicas. O objetivo do presente trabalho é investigar o efeito da crotamina na contração da musculatura lisa. A crotamina foi isolada a partir do veneno de C. d. terrificus por cromatografia de exclusão molecular seguida de troca iônica. Os estudos em modelos animais foram realizados utilizando o DD (porção prostática) de ratos Wistar com 5 meses de idade entre 350 g (protocolo CEUA 1261/14). O estudo de neurotransmissão foi feito em sistema de órgão isolado (n=6) por estimulação elétrica transmural com tensão de 70V, 3ms de duração em frequências de 0,05 (30 min) e 1; 5 10 e 20Hz (30 seg). A contração isométrica foi registrada em gramas de tensão. Em todos os experimentos a crotamina (0,1;0,5 e 1g/ml) incubada 30 min antes da estimulação. O efeito máximo de contração (Emax) do componente fásico e tônico foi usado como medida. O componente pós-sináptico foi avaliado por meio de curvas dose-resposta de noradrenalina e dose única de ATP (10-3M) na presença ou ausência da crotamina. A diferença estatística foi avaliada pelo teste-t de student (P0,05). Os ensaios de estimulação elétrica de baixa frequência (0,05Hz) revelaram que a crotamina (0,1 e 0,5g/ml) promoveu uma diminuição da contração do DDR (95,7±4,6% e 85,4±5,9%, respectivamente) enquanto que na dose de 1 g/mL de crotamina este efeito não foi significativo. Na curva de freqüência observamos também com as mesmas concentrações de crotamina uma tendência à diminuição da contração fásica e tônica enquanto que a dose de 1 g/mL promoveu um aumento na contração fásica na freqüência de 20,0Hz ((3,2±0,3) em relação ao controle (2,2±0,2). O componente pós-sináptico não foi alterado pela crotamina conforme evidenciado pela curva concentração-resposta de noradrenalina e concentração única de ATP. Com base nos resultados obtidos, concluímos que a crotamina atua apenas no componente pré-sináptico da contração do DDR, provavelmente interferindo na neuroliberação de ATP e noradrenalina. Ela apresenta um efeito bifásico, dependendo da dose utilizada, inibindo ou potencializando a resposta, efeito semelhante ao da -defensinas, uma proteína cuja estrutura se assemelha bastante com a da crotamina.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

The purpose of the present study was to test the use of visually displayed EMG biofeedback as a means for training hearing impaired adolescents to reduce anterior temporalis or frontalis muscle tension . Five male and four female hearing impaired students between the ages of 13 and 15 were chosen from the California School for the Deaf, Fremont, CA to serve as participants. Each participant was randomly assigned to either an experimental or control condition. Participants in the experimental groups were given five 15 minute EMG biofeedback training sessions. An additional group of 4 adolescents with normal hearing from Marshall Junior High School, Stockton, CA served as a hearing control group. The dependent measure was a 5 minute pretest and post-test measurement of muscle tension (in microvolts). Split-plot analyses were performed to determine if there were significant differences between a ) the .hearing impaired experimental and the hearing impaired control groups, b) the hearing impaired control and the hearing control groups, and c) the hearing impaired experimental group and the hearing control group. Results of the analyses showed that at post-test both the hearing impaired experimental group and the hearing control group showed a significant decrease in muscle tension F(1,7)=5.85 p< .05. The interaction was nonsignificant. Comparison of the two control groups showed that at post-test the two groups were not significantly different in levels of muscle tension. The comparison between the hearing impaired experimental and the hearing control groups resulted in a significant interaction (Group X Time of Testing) F( 1,6)=9.47, p=.02, and the main effect for time of testing approached significance.