Electromyostimulation is a nonpharmacological prevention method for osteoporosis that is safe and feasible for the elderly and people with physical disabilities. Our previous study demonstrated that random pulse train (RdPT) electromyostimulation of rat quadriceps induces an increase in the mechanical properties of the contralateral unstimulated femoral neck. However, the efficacy of this stimulation on other untested bones is still unclear. The objective of this research is to investigate the response of previously unstimulated bones to single-site electromyostimulation. The left quadriceps of rats were stimulated electrically by periodic pulse train (PrPT) or RdPT with 2 mA-magnitude pulses at 552 μs and a 50% duty ratio. The stimulation effect was examined on the diaphysis of long bones and lumbar vertebrae (L2-L5) by quasi-static mechanical tests and microcomputed tomography analysis. RdPT increased the strain energy at the stimulated left femur but did not change the properties of the other long bones. For the lumber vertebrae, on the other hand, both stimulations showed similar results. The stiffness of lumbar vertebra increased in L2, and the stiffness and the maximum load decreased in L4. Additionally, the BMC (bone mineral content), BV (bone volume), and TV (tissue volume) were reduced in L2, but not changed in L4. The other vertebrae were not affected by the stimulations. In conclusion, RdPT influences not only the stimulated femur, but also the lumbar vertebrae site-dependently as well as PrPT. These findings suggest the whole-body scale effect of electromyostimulation, however, which is not positive in all the bones, requiring further investigations for its clinical applications.
The air blast freezer has been used as a freezing method in the fish processing units before being frozen for a long time in cold storage. For this reason, the use of hydrocarbon refrigerants that are more environmental friendly has become a demand and a central issue in the future. This paper presents a performance analysis of using R290 and R600a as a drop-in replacement to R404A and R507A. The system performance analysis is based on the evaporation temperature variation using CYCLE_D-HX software with the condensation temperature maintained constant. The important quantities analyzed are mass flow rate, pressure ratio, temperature discharge, heat released, power consumption, coefficient of performance and refrigeration efficiency. The results show that at minimum evaporation temperature, system performance using R290 and R600a is on average ±14% higher compared to R404A and R507A. R290 has characteristics that are closer to R404A and R507A so it is more suitable to replace the two refrigerants compared to R600a. However, this is a performance analysis that can lead to higher performance than normal conditions.
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