Fruits of Morus alba have been described as source of phytochemicals with antioxidant activity, which is of interest for human consume, and food industry. However, differences in antioxidant capacity among varieties of this species, as well as the potential of other parts of this plant has been little explored. In this work, extracts of roots from twelve (natural or hybrid) varieties of M. alba were evaluated. There were observed differences between varieties, as the range of total phenol content among hexane, ethanol and aqueous extracts (0.55 -1.59; 2.72 -6.61; 5.09 -9.85 gallic acid /100 g of extract, respectively). Antioxidant action of M. alba roots extracts was proved in different assays as radical scavenger and iron reduction capacity. Ethanol was found to be the best solvent to extract antioxidant compounds. Among all extracts assayed, the best association between high phenol and flavonoid content associated to free radicals scavenger and iron reducing power activities were shown by ethanol root extract from hybrid variety IZ 64. This work demonstrated that M. alba roots possess great potential as source of phytochemicals with antioxidant activity and pointed variety IZ 64 as the best cultivar to be used due to its functional properties or as source of natural antioxidants.
Nanofluids can be employed as one of the two fluids needed to improve heat exchanger performance due to their improved thermal and rheological properties. In this review, the impact of nanoparticles on nanofluid properties is discussed by analyzing factors such as the concentration, size, and shape of nanoparticles. Nanofluid thermophysical properties and flow rate directly influence the heat transfer coefficient and pressure drop. High thermal conductivity nanoparticles improve the heat transfer coefficient; in particular, metallic oxide (such as MgO, TiO2, and ZnO) nanoparticles show greater enhancement of this property by up to 30% compared to the base fluid. Nanoparticle size and shape are other factors to consider as well, e.g., a significant difference in thermal conductivity enhancement from 6.41% to 9.73% could be achieved by decreasing the Al2O3 nanoparticle size from 90 to 10 nm, affecting nanofluid viscosity and density. In addition, equations to determine the heat transfer rate and the pressure drop in a double-pipe heat exchanger are presented. It was established that the main factor that directly influences the heat transfer coefficient is the nanofluid thermal conductivity, and nanofluid viscosity affects the pressure drop.
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