From tilapia (Oreochromis niloticus) farming, the by-products have been identified as a source of collagen that could be used for the development of dermocosmetics or pharmaceutical products. However, the characteristics of collagen related to a specific strain or culture must be well defined prior to its application. Collagen was extracted from the skin of three strains of tilapia: red YY males (YY: two Y-type sex chromosomes), XX gray females, and the F1: offspring of crossing red YY males with XX gray females; at different ages in the adult phase, using acetic acid and pepsin enzyme. The characteristics of acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were shown by SDS-PAGE band profiles to be similar to bovine collagen type I (SIGMA), the PSC of gray tilapia being more fragile to temperature changes, consistent with the results of fractional viscosity. The characteristics of the F1 progeny were prioritized for being a commercially productive and sustainable source for the extraction of collagen, and the ASC form, being the one with the greatest stability and advantage over PSC, of importance to our investigations, leads to a controlled digestion as in the case of peptide induction, and also in the development of natural products in the pharmaceutical and/or dermocosmetic industry. Evaluations of the triple helix structure by FT-IR, X-ray diffraction and UV–visible spectroscopy give similar results between the strains: red, gray, and F1, and between ages in the adult form F1 (15, 24, and 36 months of age). Consequently, the skin of tilapia in adult form is recommended sustainably for up to 24 months of age where the collagen is obtained with the use of acetic acid without enzymatic treatment.

Tracker is a piece of freeware software, designed to use video recorded images of the motion of objects as input data, and has been mostly applied in physics education to analyse and simulate physical phenomena in mechanics. In this work we report the application of Tracker to the study of experiments in electricity and magnetism using analog instruments for electrical signal measurements. As we are unable to directly video-track the motion of electrons in electric circuits, the angular deflections of the instruments’ pointers were video captured instead. The kinematic variables (angular position as a function of time) had to be related to the electrical ones (voltages and currents as a function of time). Two well-known experiments in physics teaching, the RC circuit for charging and discharging a capacitor and Faraday electromagnetic induction, were chosen to illustrate the procedures. The third experiment analysed and modeled with Tracker was the rather well-known electromagnetic retardation of disk- or cylinder-shaped magnets falling inside non-magnetic metallic pipes. Instead of metallic pipes we used an aluminum plate with an arrangement of a couple of parallelepiped-shaped magnets falling parallel to the plate. In the three cases studied, the experimental and the Tracker simulation results were in very good agreement. These outcomes show that it is possible to exploit the potential of Tracker software in areas other than mechanics, in areas where electrical signals are involved. The experiments are inexpensive and simple to perform, and are suitable for high school and introductory undergraduate courses in electricity, magnetism and electronics. We propose the use of Tracker combined with analog measuring devices to explore further its applications in electricity, magnetism, electronics and in other experimental sciences where electrical signals are involved.

Mn₃O₄ nanoparticles have been synthesized using alcoholic extracts, at pH = 7 and low temperature (60 °C), from different masses (1.00, 3.00, 5.00, and 7.00 g) of fresh leaves from Nerium oleander and Bixa orellana, without additional heat treatment. Appropriate techniques were used to identify the secondary metabolites of the extracts and evaluate the structural, optical, and chemical properties of the nanoparticles. The XRD results confirmed the formation of Mn₃O₄ nanoparticles with crystallite size in the 5−8 nm range, with more notable effects on the crystallinity of the nanoparticles obtained with B. orellana extracts. The greatest effect on the bandgap was observed in nanoparticles synthesized with N. oleander extracts. Raman spectra confirmed phonon confinement, and in the PL spectra, emission bands associated with structural defects, such as oxygen vacancies, were observed. In FTIR spectra, the main bands of Mn₃O₄ were identified, whose intensity decreased as the concentration of extract and other bands associated with functional groups of the extract increased. TEM images showed nanoparticles were spherical with 7.81 nm (N1) and 7.94 nm (B1) average diameters. The extract from N. oleander leaves was more appropriate than that from B. orellana for the synthesis of Mn₃O₄ nanoparticles under the conditions used.

Permalloy can exhibit magnetic vortex configurations depending on their dimensions and geometry, being of great interest due to potential applications in data storage and for cancer treatment. This work focuses on the effects of perpendicular uniaxial anisotropy, dimensions of permalloy nanodisks, and magnetostatic interactions on the annihilation and nucleation fields of magnetic vortices by means of micromagnetic simulations. Nanodisks with different diameters were evaluated, considering the effect of anisotropy generated by a platinum substrate for isolated nanodisks of 20 nm thickness. The effect of magnetostatic interactions for different arrays of identical nanodisks and a 10 x 10 array with random diameters from a normal distribution was also evaluated. The results show that the annihilation and nucleation fields are influenced by the perpendicular uniaxial anisotropy. The higher the anisotropy, the more the annihilation field decreases, and the nucleation field increases, thus favoring the monodomain magnetic configuration. It was also shown that the magnetic interaction between the nanodisks and the lattice geometry led to a variation of the annihilation and nucleation fields. The magnetostatic interaction in the lattice leads to a collective rotation of the magnetic moments, so that the closing of the magnetic flux occurs randomly in a series of nanodisks minimizing the energy. Permalloy puede exhibir configuraciones de vórtices magnéticos dependiendo de sus dimensiones y geometría, siendo de gran interés debido a sus potenciales aplicaciones en el almacenamiento de datos y para el tratamiento del cáncer. Este trabajo se centra en los efectos de la anisotropía uniaxial perpendicular, las dimensiones de nanodiscos de aleación permalloy y las interacciones magnetostáticas sobre los campos de aniquilación y nucleación de vórtices magnéticos mediante simulaciones micromagnéticas. Se evaluaron nanodiscos con diferentes diámetros, considerando el efecto de la anisotropía generada por un sustrato de platino para nanodiscos aislados de 20 nm de espesor. También, se evaluó el efecto de las interacciones magnetostáticas para diferentes arreglos de nanodiscos idénticos y un arreglo de 10 x 10 con diámetros aleatorios con una distribución normal. Los resultados muestran que los campos de aniquilación y nucleación están influenciados por la anisotropía uniaxial perpendicular. Cuanto mayor es la anisotropía, más disminuye el campo de aniquilación y aumenta el campo de nucleación, favoreciendo así la configuración magnética monodominio. También se demostró que la interacción magnética entre los nanodiscos y la geometría de la red provocaba una variación de los campos de aniquilación y nucleación. La interacción magnetostática en la red conduce a una rotación colectiva de los momentos magnéticos, de modo que el cierre del flujo magnético se produce de forma aleatoria en una serie de nanodiscos, minimizando la energía.