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Introduction: This study aimed to evaluate the simultaneous and maximum activities of the sternocleidomastoid (SCM) and pectoralis major (PM) muscles, to determine how the two types of breathing patterns (normal and forced) can affect these activities , and to verify which of these muscles could be used to establish an evaluation protocol for patients undergoing mechanical ventilation. Methods: Eleven healthy men, aged 18 to 25 years, participated in this study. The individuals remained in supine position using a respiratory belt to monitor both inspiratory and expiratory phase during shifts in the rib cage, performing three repetitions for the normal and forced respiratory movements, while keeping the breathing rhythm with a standard metronome. Electromyographic signals were captured using bipolar surface electrodes placed on the lower third of the SCM muscle and on the lower PM muscle fibers. Electromyographic signals were analyzed and the root mean square (RMS) values were calculated for a complete respiratory cycle. The EMG values were analyzed using the Bonferroni test for multiple comparisons. The homogeneity of variances was verified using the logarithmic transformation (LOG). The level of statistical significance was set at 5% (SPSS 19.0). Results: The values showed that there are significant differences between the EMG values of the SCM muscle during normal and forced respiration and the EMG values of the ECM and PM muscles during forced respiration. Conclusion: These results showed that the SCM muscle can be an indicator for the development of parameters to be used in the analysis of patients with respiratory failure.

Refrigeration systems applications are broadly used in food and drug conservation and in air conditioning systems. Commercial buildings may demand as much as 80% of total electrical power just for powering the air-conditioning system based on conventional vapor compression refrigeration systems (VCRS), which contributes to reach peak demands on the electrical distribution network that could cause an unstable condition. Implementing absorption refrigeration systems (ARS) to produce cooling effects driven by thermal energy could decrease that power demand. Thermodynamic models of these systems can be found in the literature with a variety of working fluids and also integrated with other cycles such as power generation plants. However, a few previous analyses have a direct comparison between ARS and VCRS at the same operational conditions. Thus, the current study aims to simulate and compare two different refrigeration technologies: single stage ammonia-water absorption refrigeration system and vapor compression refrigeration system working with refrigerants R-134a and R-717. Thermodynamic simulation was carried out by evaluating heat transfer rates in the main devices, coefficients of performance, and specific areas of evaporator and condenser. As evaporator temperature decreases from 10°C to -20°C, ARS requires 16.9 kW or 67.5% more heat in generator and COP decreased from 0.601 to 0.359. Utilizing the same comparison parameter, VCRS needed 3.26-3.54 kW or 154-160% more compressor power, depending on refrigerant used, and COP decreased from 6.77 to 2.60 with R-134a and 7.07 to 2.79 using R-717 at the same condensation temperature (40°C). Compared to ARS, condenser specific area required for VCRS is smaller, evaporator is twofold smaller when using R-134a, and is equal when using R-717. Those results can justify the usage of ARS in facilities with high amount of waste heat, mainly on applications working with lower evaporator temperatures.

Resumo: Estabeleceu-se a comparação de um programa de ensino no qual se realizaram várias avaliações do rendimento escolar com outro em que se aplicou apenas prova final. Os dados estatísticos obtidos mostraram diferença significativa em favor do primeiro. Discutem-se os possíveis fatores responsáveis pelo bom êxito desse programa e a reação dos alunos à sua execução.