Structural composite based on 3D printing polylactic acid/carbon fiber laminates (PLA/CFRC) as an alternative material for femoral stem prosthesis.

In recent years, surgical procedures for hip prostheses have increased. These implants are manufactured with materials with high stiffness compared to the bone, causing bone loss or aseptic loosening. This research proposes an alternative structural composite consisting of 3D-printing polylactic acid layers and carbon fiber laminates (PLA/CFRC) with potential application in prosthetic implants. Fourier-transform infrared spectroscopy (FTIR) achieved to characterize starting materials and structural composites revealed secondary chemical interactions between the carbonyl group of PLA with the hydroxyl group of epoxy resin from CFRC. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results show both components (PLA and CFRC) influence the structural composite's thermal behavior, observed in the temperatures of degradation, glass transition, and melting. Furthermore, the composite reached cell viability above 80%, a tensile modulus of 19.29 ± 0.48 GPa and tensile strength of 238.91 ± 25.95 MPa, with mechanical properties very similar to the bone. The results of this study demonstrated that the proposed PLA/CFRC composite can be used as candidate base material for the manufacturing of a hip femoral stem prostheses.

Evaluación del crecimiento radial de Lactarius volemus en medio semisólido / Evaluation of radial growth of Lactarius volemus in semisolid medium

Objetivo: Evaluar el crecimiento radial de Lactarius volemus en cinco medios de cultivo semisólidos in vitro.Materiales y métodos: Cuerpos fructíferos de L. volemus provenientes de la Sierra Norte del estado de Oaxaca, México, se cultivaron en laboratorio en medios Agar Papa Dextrosa, Agar Czapek-Dox, Agar Extracto de Malta, Agar Papa Sacarosa y Agar Dextrosa Saboraud; mediante dos técnicas de sembrado. Se evaluaron las características morfológicas de colonias obtenidas de distintas muestras del cuerpo fructífero, así como el crecimiento radial de cada una.Resultados: El crecimiento colonial evaluado permitió seleccionar un medio que reúne las condiciones óptimas para el cultivo de Lactarius volemus in vitro. No todas las muestras utilizadas desarrollan un crecimiento abundante: la muestra proveniente del látex presenta un crecimiento escaso.Conclusiones: Con la evaluación del crecimiento radial de Lactarius volemus se obtiene una referencia directa del ciclo de crecimiento de esta especie; es posible identificar las fases exponencial y estacionaria pero las condiciones del medio no permiten evaluar la fase de muerte debido a la deshidratación y reducción del agar.(AU)

Objective: To evaluate the radial growth of Lactarius volemus in five semi-solid culture media in vitro.Materials and methods: Fruitful bodies of L. volemus from the Sierra Norte of the state of Oaxaca, Mexico, were cultured in the laboratory in Potato Dextrose Agar Papa, Czapek-Dox Agar, Malt Extract Agar, Potato Sucrose Agar and Dextrose Saboraud Agar; using two seeding techniques. The morphological characteristics of colonies obtained from different samples of the fruiting body were evaluated, as well as the radial growth of each one.Results: The evaluated colonial growth allowed to select a culture medium that meets the optimal conditions for the cultivation of Lactarius volemus in vitro. Not all samples used develop abundant growth: the sample from latex shows little growth.Conclusions: With the evaluation of the radial growth of Lactarius volemus a direct reference to the growth cycle of this species is obtained; it is possible to identify the exponential and stationary phases but the conditions of the medium do not allow evaluating the phase of death due to dehydration and reduction of the agar.(AU)

Tolerant chalcogenide cathodes of membraneless micro fuel cells.

The most critical issues to overcome in micro direct methanol fuel cells (µDMFCs) are the lack of tolerance of the platinum cathode and fuel crossover through the polymer membrane. Thus, two novel tolerant cathodes of a membraneless microlaminar-flow fuel cell (µLFFC), Pt(x)S(y) and CoSe(2), were developed. The multichannel structure of the system was microfabricated in SU-8 polymer. A commercial platinum cathode served for comparison. When using 5 M CH(3)OH as the fuel, maximum power densities of 6.5, 4, and 0.23 mW cm(-2) were achieved for the µLFFC with Pt, Pt(x)S(y), and CoSe(2) cathodes, respectively. The Pt(x)S(y) cathode outperformed Pt in the same fuel cell when using CH(3)OH at concentrations above 10 M. In a situation where fuel crossover is 100 %, that is, mixing the fuel with the reactant, the maximum power density of the micro fuel cell with Pt decreased by 80 %. However, for Pt(x)S(y) this decrease corresponded to 35 % and for CoSe(2) there was no change in performance. This result is the consequence of the high tolerance of the chalcogenide-based cathodes. When using 10 M HCOOH and a palladium-based anode, the µLFFC with a CoSe(2) cathode achieved a maxiumum power density of 1.04 mW cm(-2). This micro fuel cell does not contain either Nafion membrane or platinum. We report, for the first time, the evaluation of Pt(x)S(y)- and CoSe(2)-based cathodes in membraneless micro fuel cells. The results suggest the development of a novel system that is not size restricted and its operation is mainly based on the selectivity of its electrodes.