MEMS-Based Atomic Force Microscope: Nonlinear Dynamics Analysis and Its Control

In this chapter, we explore a mathematical modelling that describes the nonlinear dynamic behavior of atomic force microscopy (AFM). We propose two control techniques for suppressing the chaotic motion of the system. The proposed model considers the interatomic interactions between the analyzed sample and the cantilever. These acting forces are van der Waals type, and we add a mathematical term that is a simple approximation to the viscoelasticity that possibly occurs in biological samples. We analyzed the behavior of the initial conditions of the proposed mathematical model, which showed a degree of complexity of the basins of attraction that were detected by entropy and uncertainty parameter, both detect if the basins have a fractal behavior. Numerical results showed that the nonlinear dynamic behavior has chaotic regions with the Lyapunov exponent, bifurcation diagram, and the Poincaré map. And, we propose two control techniques to suppress the chaotic movement of the AFM cantilever. First technique is the optimal linear feedback control (OLFC), which does not consider the nonlinearities of mathematical model. On the other hand, the control state dependent Riccati equation (SDRE) considers the nonlinearities of mathematical model. Both control techniques for a desired periodic orbit proved to be efficient

Physical fitness and habitual level of physical activity associated with cardiovascular health in adults and elderly

Modelo do Estudo: Transversal Fundamento: O nível habitual de atividade física (NHAF) vem sendo utilizado para estabelecer uma relação entre estilo de vida ativo e saúde cardiovascular. No entanto, a avaliação da aptidão física permitiria a avaliação real das condições físicas do indivíduo, podendo assim apresentar melhores relações com a saúde cardiovascular. Objetivos: Relacionar o NHAF e aptidão física com a saúde cardiovascular de adultos e idosos e verificar a associação da prática regular de exercícios físicos supervisionada com os diferentes níveis de aptidão física. Método: Foram avaliados 213 adultos e idosos (> 50 anos) participantes de projetos comunitários. Os participantes realizaram as seguintes avaliações: NHAF por meio do questionário IPAQ, aptidão física por meio de uma bateria de testes motores que permitiu o cálculo do Índice de Aptidão Funcional Geral (IAFG), pressão arterial, perfil lipídico e índice de massa corporal. Resultados: O modelo linear generalizado evidenciou um maior número de diferenças com relação às variáveis relacionadas à saúde cardiovascular quando os participantes foram subdivididos em grupos tendo o IAFG como variável independente, comparado ao NHAF. O teste exato de Fisher evidenciou que os grupos de IAFG classificados como “bom” e “muito bom” apresentaram maior proporção de indivíduos com prática regular de exercícios físicos superior a 6 meses, com destaque para um maior número realizando a prática com supervisão (p < 0,0001). Conclusão: O IAFG apresenta melhor associação com a saúde cardiovascular do que o NHAF e o tempo de prática e a supervisão estão associados ao nível de aptidão físicaStudy design: cross-sectional Background: The habitual level of physical activity (HLPA) has been used to establish the relation between active lifestyle and cardiovascular health. However, the assessment of physical fitness would review the actual physical condition of the individual, and thus can have better relations with cardiovascular health. Objectives: Relate HLPA and physical fitness with cardiovascular health of adults and elderly and to verify the association of supervised regular physical exercise with different levels of fitness. Method: 213 adults and elderly (> 50 years) participating in community projects were evaluated. The HLPA were assessed by the IPAQ and physical fitness through a battery of motor tests that allowed the calculation of the General Functional Fitness Index (GFFI). Blood pressure, lipid profile and body mass index were considered as indicators of cardiovascular health. Results: The generalized linear model showed a greater number of differences with respect to variables related to cardiovascular health when participants were subdivided having GFFI as an independent variable, compared to HLPA. The Fisher exact test showed that the groups GFFI classified as “good” and “very good” showed a higher proportion of individuals with regular practice for more than 6 months exercise, especially for a larger number performing the practice under supervision (p < 0,0001). Conclusion: The GFFI has better association with cardiovascular health than HLPA and time of practice and supervision are associated with the level of physical fitnes