Properties of systems with time delayed feedback

Nonlinear dynamics is a vast field complementary to classical mechanics and statistical physics. Inside this field we have chosen to study dynamical systems with time delayed feedback. Such systems appear as models in the sciences like physics, biology, economy and have at the same time interesting theoretical properties being good candidates to present high dimensional attractors. In this work delayed systems are studied mainly in the limit of large delay were the scaling properties of the attractors are observed. In chapter 2 we describe general properties of periodic orbits of dynamical systems with feedback delay. In chapter 3 it is shown that the marginal invariant density of chaotic attractors of scalar systems with time delayed feedback has an asymptotic form in the limit of large delay. We present general considerations, detailed analytical results in low order perturbation theory for a particular model, and numerics for the understanding of the asymptotic behaviour of the projections of the invariant density. Our approach clarifies how the analytical properties of the model determine the behaviour of the marginal invariant densities for large delay times. In chapter 4 properties of the topological and metric entropies are discussed and arguments for the boundedness of both are given on the basis of periodic orbits and of the asymptotic behavior of the invariant density. In chapter 5 we analyse the representation of maps with time delayed feedback as coupled map lattices. We show that when the delayed map has an anomalous exponent, this representation gives rise to infinitely large comoving Lyapunov exponents of the spatially extended system. Additionally, we present a short discussion regarding the anomalous error propagation in the case of continuous time, i.e. delayed differential equations.</P

Effects of the radio electric asymmetric conveyer (REAC) on motor disorders: An integrative review

IntroductionThe radio electric asymmetric conveyer (REAC) is a technology that has the purpose of restoring the cellular polarity triggering the rebalancing of the endogenous bioelectric field, which considering the neurological dysfunctions, affects the neural communication mechanisms. The studies published so far show that the REAC neuromodulation technology has positive effects in treating these dysfunctions, with the principles of endogenous bioelectricity as a basis to achieve these effects.ObjectivesThis study aims to review the literature that explored the effects of REAC protocols on motor control and to identify which mechanisms would be involved.Materials and methodsThis integrative review considered studies that used REAC as a therapeutic intervention directed at human motor control and experimental research with animals that applied REAC to obtain effects related to motor behavior.ResultsTen articles were included, eight clinical and two experimental studies. The clinical studies used the neuro postural optimization (NPO) protocol in 473 patients, of which 53 were healthy subjects, 91 were Alzheimer's disease patients, 128 were patients with atypical swallowing, 12 subjects with neurological diseases, and 189 were without the specification of disease. The experimental studies used the antalgic neuromodulation and neurodegeneration protocols in animal models.ConclusionThe information integrated in this review made it possible to consider REAC technology a promising resource for treating motor control dysfunctions. It is possible to infer that the technology promotes functional optimization of neuronal circuits that may be related to more efficient strategies to perform motor tasks

O desafio da mobilização institucional na formação docente = The challenge of institutional’s mobilisation on teacher’s formation = El desafío de la movilización institucional en la formación docente

A promoção do desenvolvimento profissional de professores é um desafio para as instituições de ensino superior que buscam a excelência na qualidade de ensino. Dentre os entraves está a dificuldade em equilibrar as necessidades individuais e institucionais, assim como envolver não apenas os professores, mas também colaboradores, gestores e estudantes. Este estudo de caso tem por objetivo examinar o desafio da mobilização institucional na formação docente a partir da atuação do setor responsável por essas estratégias no âmbito de uma universidade comunitária confessional, adotando como referencial teórico para análise Zabalza (2004), Saroyan e Amundsen (2004), Cunha (2010) e Veiga et al. (2012). Estuda-se como o processo de criação e consolidação do Centro de Ensino e Aprendizagem (2014-2016) ocorreu, contemplando o contexto de origem, a articulação administrativa e as características do programa de formação instituído. Destacam-se, dentre as medidas tomadas para engajar e legitimar as ações, a adoção de diversas frentes de atuação simultâneas, o reconhecimento às boas práticas docentes e o incentivo ao compartilhamento de experiência

Duración de los efectos de manipulación vertebral sobre la intensidad de dolor y actividad electromiográfica de la columna en sujetos con dolor lumbar crónico mecánico

En este estudio se evalúan los efectos de intervención manipulativa sobre la actividad electromiográfica de los músculos paravertebrales y la intensidad del dolor lumbar inmediatamente y treinta minutos después de realizada la actividad por sujetos con dolor lumbar crónica mecánica. Participaron 38 sujetos, los cuales fueron divididos al azar en dos grupos: el que había recibido la técnica de manejo vertebral global (n=20) y el grupo control (n=18), lo cual había permanecido en posición lateral por diez segundos sobre cada lado del cuerpo. Se recolectó el signo electromiográfico de los paravertebrales al nivel L4-L5 derecho e izquierdo durante tres ciclos de movimiento de flexión-relajamiento-extensión del tronco. Entre los intervalos de los ciclos, los participantes relataron la intensidad de dolor mediante la Escala Visual Analógica (EVA 100 mm). Los resultados mostraron una significativa disminución en la intensidad de dolor en el grupo que había recibido el manejo, mientras que el grupo control aumentó el puntaje de EVA. El efecto de la intensidad de dolor fue de 1,0 y 0,9 tras el manejo y treinta minutos después. La razón flexión/relajamiento (RFR) aumentó en el grupo al que se sometió al manejo, mientras que había permanecido inalterable en el grupo control. Los valores de los efectos de la RFR entre los grupos fueron de 0,6 y 0,5 en las dos evaluaciones. En estas dos variables se constataron efectos de manejo, que había seguido en el intervalo observado, lo que muestra su permanencia por lo menos durante el periodo.O objetivo desta pesquisa foi avaliar os efeitos de uma intervenção manipulativa sobre a atividade eletromiográfica dos músculos paraverterbais e a intensidade da dor na coluna lombar imediatamente e 30 minutos após sua realização em indivíduos com dor lombar crônica mecânica. Foram avaliados 38 indivíduos, distribuídos aleatoriamente em dois grupos: o que recebeu a técnica de manipulação vertebral global (n=20) e o controle (n=18), que permanecia em decúbito lateral por dez segundos sobre cada lado do corpo. O sinal eletromiográfico dos paravertebrais ao nível L4-L5 direito e esquerdo foi coletado durante três ciclos do movimento de flexão-relaxamento-extensão do tronco. Nos intervalos entre os ciclos, os participantes relataram a intensidade de dor através da Escala Visual Analógica (EVA 100 mm). Foi observada redução significativa na intensidade da dor no grupo que recebeu a manipulação, ao contrário do grupo controle, em que a pontuação na EVA aumentou. O tamanho do efeito na intensidade da dor foi de 1,0 e 0,9 logo após a manipulação e 30 minutos depois. A razão de flexão/relaxamento (RFR) aumentou no grupo que foi submetido à manipulação, mas permaneceu inalterada no grupo controle. A RFR exibiu tamanhos de 0,6 e 0,5 entre os grupos nas duas avaliações. Foi possível constatar efeitos da manipulação nessas duas variáveis e sua continuidade no intervalo observado, concluindo-se que eles perduram pelo menos durante esse tempo.The objective of this research was to evaluate the effects of a manipulative intervention on the electromyographic activity of paraverterbral muscles and low back pain intensity, both immediately and 30 minutes after their application in individuals with chronic low back pain. Thirty-eight individuals were evaluated, being randomly divided into two groups: the one who received global vertebral manipulation technique (n=20), and control (n=18), which remained in lateral decubitus for 10 seconds on each side of the body. The electromyographic signal of paravertebral parts at L4-L5 level both right and left was collected during three cycles of flexion-relaxation-extension of the torso. In the intervals between cycles, participants reported the intensity of pain through the Visual Analog Scale (VAS, 100 mm). A significant reduction in pain intensity in the group that received the manipulation was observed, opposed to the control group, in which the score increased in VAS. The dimension of the effect on pain intensity was 1.0 and 0.9 right after the manipulation and 30 minutes later. The flexion/relaxation ratio (FRR) increased in the group that was subjected to manipulation, but remained unchanged in the control group. The FRR displayed effects between the groups that were 0.6 and 0.5 in both assessments. We were able to see effects of the manipulation in these two variables, and its continuation in the range observed, concluding that they linger at least during that time

Immediate effects of a high-velocity spine manipulation in paraspinal muscles activity of nonspecific chronic low-back pain subjects. Man Ther

a b s t r a c t High-velocity spinal manipulation is commonly adopted for treating chronic low-back pain (CLBP) and has been associated with changes in muscle activity, but the evidence is controversial. The aim of this study was to analyse the immediate effects of high-velocity spine manipulation on paraspinal activity during flexioneextension trunk movements. Forty nonspecific CLBP patients were randomised into two groups, manipulation (n ¼ 20) and control (n ¼ 20). While the manipulation group received high-velocity spine manipulation at the L4-L5 level, the control group remained lying in the same position. EMGrelated variables, perceived pain intensity (100 mm VAS) and finger-floor distance were collected before and after spinal manipulation at the L4-L5 level. EMG surface signals from the right and left paraspinal muscles (L5-S1 level) were acquired during trunk flexioneextension cycles. EMG activity during the static relaxation phase was significantly reduced following intervention for the manipulation group but not for the control group. The extension-phase EMG activity was also reduced after manipulation, but the flexion-phase EMG levels remained unchanged. Accordingly, the percent changes in FRR and ERR were significantly larger for the manipulation group compared to the control. The results suggest that a highvelocity spinal manipulation is able to acutely reduce abnormal EMG activity during the full-flexion static phase and activation during the extension phase

Notes on Dynamics of an External Cavity Semiconductor Lasers

Dynamics of external cavity semiconductor lasers is known to be a complex and uncontrollable phenomenon. Due to the lack of experimental studies on the nature of the external cavity semiconductor lasers, there is a need to theoretically clarify laser dynamics. The stability of laser dynamics in the present paper, is analyzed through plotting the Lyapunov exponent spectra, bifurcation diagrams, phase portrait and electric field intensity time series. The analysis is preformed with respect to applied feedback phase $C_p$, feedback strength $\eta$ and the pump current of the laser. The main argument of the paper is to show that the laser dynamics can not be accounted for through simply a bifurcation diagram and single-control parameter. The comparison of the obtained results provides a very detailed picture of the qualitative changes in laser dynamics.Comment: 7 pages, 34 figure

Performance characteristics of positive and negative delayed feedback on chaotic dynamics of directly modulated InGaAsP semiconductor lasers

The chaotic dynamics of directly modulated semiconductor lasers with delayed optoelectronic feedback is studied numerically. The effects of positive and negative delayed optoelectronic feedback in producing chaotic outputs from such lasers with nonlinear gain reduction in its optimum value range is investigated using bifurcation diagrams. The results are confirmed by calculating the Lyapunov exponents. A negative delayed optoelectronic feedback configuration is found to be more effective in inducing chaotic dynamics to such systems with nonlinear gain reduction factor in the practical value range.Comment: 18 pages, 16 figures. To appear In Pramana - journal of physic