Background and Purpose Dyspnea, fatigue, and reduced exercise tolerance are common in post‐COVID‐19 patients. In these patients, rehabilitation can improve functional capacity, reduce deconditioning after a prolonged stay in the intensive care unit, and facilitate the return to work. Thus, the present study verified the effects of cardiopulmonary rehabilitation consisting of continuous aerobic and resistance training of moderate‐intensity on pulmonary function, respiratory muscle strength, maximum and submaximal tolerance to exercise, fatigue, and quality of life in post‐COVID‐19 patients. Methods Quasi‐experimental study with a protocol of 12 sessions of an outpatient intervention. Adults over 18 years of age ( N = 26) with a diagnosis of COVID‐19 and hospital discharge at least 15 days before the first evaluation were included. Participants performed moderate‐intensity continuous aerobic and resistance training twice a week. Maximal and submaximal exercise tolerance, lung function, respiratory muscle strength, fatigue and quality of life were evaluated before and after the intervention protocol. Results Cardiopulmonary rehabilitation improved maximal exercise tolerance, with 18.62% increase in peak oxygen consumption (VO2peak) and 29.05% in time to reach VO 2 peak. VE/VCO 2 slope reduced 5.21% after intervention. We also observed increased submaximal exercise tolerance (increase of 70.57 m in the 6‐min walk test, p = 0.001), improved quality of life, and reduced perceived fatigue after intervention. Discussion Patients recovered from COVID‐19 can develop persistent dysfunctions in almost all organ systems and present different signs and symptoms. The complexity and variability of the damage caused by this disease can make it difficult to target rehabilitation programs, making it necessary to establish specific protocols. In this work, cardiopulmonary rehabilitation improved lung function, respiratory muscle strength, maximal and submaximal exercise tolerance, fatigue and quality of life. Continuous aerobic and resistance training of moderate intensity proved to be effective in the recovery of post‐COVID‐19 patients.
Nanocomposites of PMMA+MMT Brazilian clays were developed by mechanical mixing in co-rotational twinscrew extrusion and injection molding with varying weight fraction of MMT Brazilian clays. The clays were purchased in crude form and then washed and purified to extract the organic materials and contaminants. Dynamic friction and wear rate of these composites were studied as a function of concentration of the Brazilian clay. With an increase in the amount of MMT Brazilian clay, the dynamic friction of the nanocomposites increases, a clear but not large effect. It can be explained by sticky nature of clay; clay in the composite is also on the surface and sticks to the partner surface. The wear rate as a function of the clay concentration passes through a minimum at 1 wt% MMT; at this concentration the clay provides a reinforcement against abrasion. At higher clay concentrations we see a dramatic increase in wear – a consequence of clay agglomeration and increased brittleness. The conclusions are confirmed by microscopy results
Nowadays, is expected that for most materials to be environmentally friendly. Besides, waste from end-of-life products may be considered a secondary source of materials with an energetic advantage due to its high energy content. This paper deals with the study of friction and wear characteristics of Glass fibre-reinforced polymer (GFRP) composites with polyester/glass fiber (P/GF) waste as filler, replacing the widely used calcium carbonate (CaCO 3 ). Polyester composites based on two or three components, using a combination of polyester, CaCO 3 , GF, and GF waste, were produced. Pin-ondisc sliding wear test was performed using a polished stainless steel counterface. Roughness, surface energy, and hardness of the composites were characterized before the tests. The GF content (15, 25, 35, and 50 wt.%), the sliding velocity (0.021 and 0.042 m/s), and the normal load (1, 5, and 10 N) were varied. Based on the experimental results, it was observed that the friction coefficient and wear rate were influenced by material composition, surface roughness and energy, adhesive, and abrasive contact mechanisms. P/GF composites having P/GF waste presented enhanced performance considering friction and wear in relation to those with CaCO 3 in their composition.
In this work, the performance of polyester (P)/glass fiber mats (G) and P/G/calcium carbonate (CaCO 3 ) composites was compared with that of P/G/ fiberglass waste composites. The residues used were conventional P/G postconsumer light resin-transfer-molding parts, obtained via knife or ball milling. Composites with up to 50 wt % reinforcement were prepared by hot compression molding and characterized via physical (density and water sorption), thermal (thermogravimetry and burnout), and mechanical (impact, Barcol hardness, and tensile) testing. The results show that the simple grinding and reincorporation of the composite residues yielded new composites with generally worse characteristics than the ones with calcium carbonate. Then, the waste was sorted by removing most of the pure resin particles from it. This yielded a resin-rich fraction, which could be better used for energy recovery and resin-covered fibers. The use of the latter as a filler yielded composites with better overall properties than those with calcium carbonate for a controlled amount of W; thus showing potential use as a replacement for the commonly used inorganic filler, maintaining the mechanical properties, decreasing the raw material cost, and reducing the amount of composite waste discarded in the environment.
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