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Objective: To investigate autonomic modulation of the sinus node, by analyzing heart rate variability (HRV) among young and middle-aged individuals, and to assess the effect of an resistance strength training program on this modulation among middleaged individuals. Method: Thirty-two healthy nonsmoking men with sedentary lifestyles, of whom 10 were young (22.2 ± 1.5 years) and 22 were middle-aged (49.3 ± 5.3 years), underwent electrocardiogram signal acquisition for time-domain HRV analysis. The middle-aged individuals were divided into two groups: experimental (n= 12) and control (n= 10). The individuals in the experimental group were enrolled in a strength training program lasting three months. The data analysis was carried out using the Wilcoxon and Mann-Whitney tests (p< 0.05). Results: The middle-aged group presented significant reductions (in relation to the young group) for all the variables used in investigating HRV (SDNN= 33.4 vs. 49.7 ms; RMSSD= 29.9 vs. 49.5 ms; pNN50= 6.5 vs. 27%). The training caused a significant increase in muscle strength and resistance for all muscular groups and non-significant increases in the variables SDNN (33.4 vs. 37.6 ms), RMSSD (30.2 vs. 31.3 ms) and pNN50 (7.5 vs. 11.4%). Conclusions: The findings from this study confirm that increased age causes alteration to the autonomic modulation of the sinus node, as demonstrated by reduced HRV in middle-aged individuals, which was not significantly modified by the type of physical training studied.

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The structure of stationary adiabatic premixed flames within porous inert media under intense interphase heat transfer is investigated using the asymptotic expansion method. For the pore sizes of interest for combustion in porous inert media, this condition is reached for extremely lean mixtures where lower flame velocities are found. The flame structure is analysed in three distinct regions. In the outer region (the solid-phase diffusion length scale), both phases are in local thermal equilibrium and the problem formulation is reduced to the one-equation model for the energy conservation. In the first inner region (the gas-phase diffusion length scale), there is local thermal non-equilibrium and two equations for the energy conservation are required. In this region, the gas-phase temperature at the flame is limited by the interphase heat transfer. In the second inner region (the reaction length scale), the chemical reaction occurs in a very thin zone where the highest gas-phase temperature is found. The results showed that superadiabatic effects are reduced for leaner mixtures, smaller pore sizes and smaller fuel Lewis numbers. The results also show that there is a minimum superadiabatic temperature for the flame propagation to be possible, which corresponds to the lean flammability limit for the premixed combustion in porous inert media. A parameter that universalizes the leading-order flame properties is identified and discussed.

Soot emission has been the focus of numerous studies due to the numerous applications in industry, as well as the harmful e ects caused to the environment. Thus, the purpose of this work is to analyze the soot formation in a at ame burner using premixed compressed natural gas and air, where these quasi-adiabatic ames have one-dimensional characteristics. The measurements were performed applying the light extinction technique. The air/fuel equivalence ratio was varied to assess the soot volume fractions for di erent ame con gurations. Soot production along the ame was also analyzed by measurements at di erent heights in relation to the burner surface. Results indicate that soot volume fraction increases with the equivalence ratio. The higher regions of the ame were analyzed in order to map the soot distribution on these ames. The results are incorporated into the experimental database for measurement techniques calibration and for computational models validation of soot formation in methane premixed laminar ames, where the equivalence ratio ranging from 1.5 up to 8.