Novel and Accessible Physical Recycling for Expanded Polystyrene Waste with the Use of Acetone as a Solvent and Additive Manufacturing (Direct Ink-Write 3D Printing).

The current high production of plastics has prompted the exploration of alternative pathways to facilitate recycling, aiming for a progressively sustainable society. This paper presents an alternative and affordable technology for treating waste expanded polystyrene (EPS) mixed with acetone in a 100:1 volume ratio to be used as 3D printing ink for Direct Ink Write technology. In order to optimize the printing parameters, a comprehensive study was conducted, evaluating different needle diameters, printing speeds, and bed temperature values to achieve homogenous pieces and a highly repeatable 3D printing process. Results showed that the main optimum printing parameters were using needles with diameters of 14 to 16 G and printing speeds ranging from 2 to 12 mm/s, which were found to yield the most uniform ribbons. Increasing the bed temperature, despite favoring acetone evaporation, led to the generation of more heterogeneous structures due to void growth inside the printed ribbons. Thus, employing room temperature for the bed proved to be the optimal value. Lastly, a comparative study between the starting material and the EPS after the printing process was conducted using FTIR-ATR and GPC analyses, ensuring the preservation of the original polymer's integrity during physical recycling.

Efectividad de la colecistectomía laparoscópica de puerto único asistida con imanes bajo anestesia espinal

Objetivo: Determinar la efectividad de la colecistectomía laparoscópica de puerto único asistida por imanes bajo anestesia espinal en el tratamiento quirúrgico de la colecistopatía litiásica crónica. Material y Métodos: Estudio prospectivo de cohorte en 51 pacientes entre octubre de 2019 y febrero de 2021. 17 pacientes fueron sometidos a colecistectomía laparoscópica de puerto único asistida por imanes y 34 a colecistectomía laparoscópica convencional por un mismo equipo quirúrgico. Se aplicó la técnica quirúrgica descrita por Dominguez et al y SAGES, bajo anestesia espinal. Se realizó estadística descriptiva e inferencial, analizando el dolor postoperatorio a las 3, 6, 12, 24 y 72 h y la satisfacción de los pacientes. Resultados: Se encontró diferencia significativa en el dolor postoperatorio en el grupo de estudio a las 6 h (p = 0,022), 12 h (p = 0,039), 24 h (p = 0,025) y 72 h (p < 0,001). En la satisfacción se encuentra un RR de 3 (p = 0,001), sin diferencia significativa en el tiempo operatorio y horas de hospitalización postquirúrgicas. Conclusiones: La colecistectomía laparoscópica de puerto único asistida por imanes, bajo anestesia espinal, ha demostrado efectividad en la reducción importante del dolor postoperatorio a partir de las 6 h, y en la superación de las expectativas en los intervenidos, sin aumento significativo de tiempo operatorio ni estancia hospitalaria.

Aim: To determine the effectiveness of magnet-assisted single-port laparoscopic cholecystectomy under spinal anesthesia in surgical treatment of chronic lithiasic cholecystopathy. Materials and Method: Prospective cohort study in 51 patients between October 2019 and February 2021. 17 patients underwent magnet-assisted single-port laparoscopic cholecystectomy and 34 underwent conventional laparoscopic cholecystectomy by the same surgical team. The surgical technique described by Dominguez and SAGES was used, under spinal anesthesia. Descriptive and inferential statistics were performed, analyzing postoperative pain at 3, 6, 12, 24 and 72 hours and patient satisfaction. Results: A significant difference in postoperative pain was found in the study group at 6 h (p = 0.022), 12 h (p = 0.039), 24 h (p = 0.025) and 72 h (p < 0.001). In satisfaction, there is an RR of 3 (p = 0.001), with no significant difference in operative time and postoperative hospitalization hours. Conclusions: Magnet-assisted single-port laparoscopic cholecystectomy under spinal anesthesia has shown effectiveness in significantly reducing postoperative pain after 6h, associated with significantly exceeding expectations in those operated on, without a significant increase in operative time or hospital stay.

Flexural Fatigue in a Polymer Matrix Composite Material Reinforced with Continuous Kevlar Fibers Fabricated by Additive Manufacturing.

Fatigue bending tests, under controlled displacement, were performed on a polymer matrix composite material reinforced with continuous Kevlar fibers. The samples were fabricated using the Fused Filament Fabrication (FFF) technique in a Markforged Two® 3D printer. The static characterization delivered a flexural modulus of elasticity of 4.73 GPa and flexural strength of 110 MPa. The applied loading corresponded to 92.3, 88.5, 86.2, and 84.7% of the static flexural displacement, giving 15, 248, 460, and 711 cycles for failure. Additionally, two numerical models were created: one using orthotropic properties for static loading conditions; and a second one using isotropic in-bulk properties for fatigue modeling. The second model was able to reproduce the experimental fatigue results. Finally, morphological analysis of the fractured surface revealed fiber breakage, fiber tearing, fiber buckling, matrix cracking, and matrix porosity.