RESUMEN
Liquid phase exfoliation of graphite is currently one of the most promising graphene production methods at large scale. For this reason, an accurate calculation of the concentration in graphene dispersions is important for standardization and commercialization. Here, graphene dispersions, at high concentrations, were produced by electrochemical exfoliation. Furthermore, a cleaner methodology to obtain graphene oxide by electrochemical exfoliation at high acid concentrations was implemented. The absorption coefficient for graphene and graphene oxide was determined in the optical range (α660 nm= 1414 (±3%) ml mg-1 m-1andα660 nm= 648 (±7%) ml mg-1 m-1, respectively) with an exponential dependence with the wavelength. The difference inαfor both materials is attributed to an increased presence of C=O groups as evidenced by Fourier transform infrared spectroscopy (FTIR), UV-vis and Raman spectroscopy, as well as, in the calculation of the optical extinction coefficient and optical band-gap via Tauc-plots.
RESUMEN
OBJECTIVE: To know better the microscopic arrangement of the bundles of smooth muscle in the human renal parenchyma, their distribution and anatomical relationships, trying to make a reconstruction of this muscular system. METHODS: Five adult human kidneys and one fetal kidney were processed "in toto" with cross sections every 300µm. In the histological sections we identify the smooth muscle fibers trying to determine its insertion, course and anatomical relationship with other structures of the kidney tissue. RESULTS: There are bundles of smooth muscle fibers of variable thickness parallel to the edges of the medullary pyramids, bundles that surrounding the medulla in a spiral course, and bundles that accompany arcuate vessels, the latter being the most abundant and easy to identify. These groups of muscle fibers do not have a precise or constant insertion site, their periodicity is not homogeneous and they are not a direct extension of the muscle of the renal pelvis, although some bundles are in contact with it. There are also unusual and inconstant small muscle fibers no associated to vessels in the interstitium of the cortex and, exceptionally, in the medulla. CONCLUSION: There is a complex microscopic system of smooth muscle fibers that partially surround the renal medulla and are related to renal pelvic muscles without a direct continuity with them. Although this small muscular system is under-recognized, could be very important in urodynamics.