This work presents a study of chitosan/carbon nanotube (CS/CNTs) membranes, crosslinked with ethylene glycol diglycidyl ether (EDGE) and doped with polypyrrole (PPy), for use as proton exchange membranes (PEM). The membranes were synthesized by evaporation and treated with glow discharge plasma (GDP). Morphological analysis showed that membranes m2 and m3 had more homogeneous surface roughness compared to membranes m4, m5, and m6, which showed more irregularities. Membrane m1, without CNTs, showed a more homogeneous surface. FT-IR spectroscopy confirmed chemical interactions such as O–H, C–H, C–N, and C–O–C associated with chitosan, along with C = O interactions linked to the EDGE crosslinking. Thermogravimetric analysis showed that membranes m2 and m3 exhibited the best thermal stability. The highest electrical conductivity (2.01 × 10−2 S/cm) was obtained with membrane m3, while membranes m4, m5, and m6 showed lower conductivity. Overall, carbon nanotubes and GDP improved the thermal and electrical stability of PEMs.
BackgroundInflammation-related ocular degenerations include dry eye syndrome, diabetic retinopathy, age-related macular degeneration, and glaucoma. Until now, there are no efficient protocols for treating inflammation-related ocular degenerations. On the other hand, acupuncture therapy modulates the inflammatory and oxidative stress responses in several inflammatory diseases and has been proposed as an emerging therapy for the potential treatment of ocular pathologies.ObjectiveThis work aimed to conduct a comprehensive systematic review to address the efficacy of acupuncture therapy for Inflammation-related ocular degenerations.MethodsThe designs of the included studies were clinical trials and observational studies, whereas case series, in vivo, and in vitro studies were excluded. The search was performed in five databases. Relevant data from all included studies were recorded, the outcomes analyzed were intraocular pressure and visual acuity for glaucoma; score of symptoms, pain, tear-film breakup time, and mm of Schirmer test for dry eye syndrome; visual acuity, retinal structure or disease progression for diabetic retinopathy; and finally visual acuity and scores of symptoms for age-related macular degeneration. Risk of bias (using the RoB 2 tool) and quality (using the Grading of Recommendations Assessment, Development, and Evaluation [GRADE] tool) assessments were conducted.ResultsThe included studies showed heterogeneity, risk of bias, inconsistency, and very low certainty of evidence.ConclusionThere is no conclusive evidence to support that acupuncture is an effective therapy in patients with inflammation-related ocular degeneration disease.Systematic Review Registrationhttps://www.crd.york.ac.uk/PROSPERO/view/CRD42022368882, identifier PROSPERO (CRD42022368882).
Composite membranes based on chitosan (CS), polytetrafluoroethylene (PTFE), and polypyrrole (PPy) were synthesized and characterized for potential use as proton exchange membranes (PEM). Fourier transform infrared spectroscopy (FT-IR) confirmed effective integration of the polymers, while scanning electron microscopy revealed a more homogeneous morphology and improved dispersion of the components in the CS/PTFE/PPy membranes. Incorporation of PTFE and PPy enhanced thermal stability and increased electrical conductivity, reaching 1.37 × 10−5 S cm−1 after polypyrrole incorporation, compared to 7.17 × 10−6 S cm−1 in pure CS. The CS/PTFE/PPy membrane exhibited a water retention capacity (WRC) of 25.6
Microplastics (MP) in landfill leachate represent an analytical challenge due to matrix complexity and the need for methods that remove interferents without degrading polymers. This study evaluated the efficiency of four digestion methods (30% H2O2, Fenton, 10% NaOH, and 20% HCl) and three density separation solutions (CaCl2, NaI, and ZnCl2) for MP quantification in leachate from the Zinacantepec Sanitary Landfill, Mexico. Samples were spiked with seven polymer types (polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), and polyamide (PA)). Results analyzed by ANOVA (p < 0.05) showed that Fenton reagent was the most efficient digestion method, achieving 99% MP recovery, whereas alkaline and acid digestions caused degradation of PET, PS, and PA. Regarding density separation, ZnCl2 (1.7 g/cm3) achieved recovery exceeding 99% for all polymers. The proposed protocol enables effective isolation and identification of degraded microplastics, contributing to advance the understanding of degradation processes and transformation pathways of MP in complex environmental matrices. The combination of Fenton digestion and ZnCl2 separation showed the highest overall performance, with an efficiency greater than 96%, supporting its use as a reliable protocol for MP quantification in leachate and contributing to methodological standardization in this field.
Este libro pone énfasis en la física elemental con la que se construye la ingeniería molecular. En el capítulo 1 se aplican tanto la mecánica cuántica como las fuerzas intermoleculares para explicar la construcción de la estructura molecular de sistemas basados en interacciones núcleo-electrón y electrón-electrón para una energía cinética electrónica. En el capítulo 2 se emplea el cálculo variacional para resolver las ecuaciones de Hartree-Fock a partir tanto del método SCF de Roothaan como de funciones base pertinentes. Esto es lo mínimo necesario para introducir la teoría de funcionales de la densidad (DFT). También se introducen los métodos semiempíricos, con el hamiltoniano π-electrónico efectivo con aplicación en sistemas hasta diez veces mayores que DFT, y mecánica molecular basada en mecánica clásica, con aplicación en sistemas mucho mayores que los métodos semiempíricos y tan grandes como los recursos computacionales lo permitan. En el capítulo 3 se explica cómo la dinámica molecular tiene esencia en las ecuaciones de movimiento de sistemas atómicos, que se resuelven numéricamente utilizando, por ejemplo, el método de Verlet o algún otro análogo. La parte esencial del capítulo 4 destaca el método de Montecarlo como un método alternativo a la dinámica molecular. De manera sencilla se explica cómo es que el método de Montecarlo requiere de bases de datos muy grandes para tener buenas aproximaciones a los resultados. Finalmente, el capítulo 5 es una introducción a la aplicación de ‘software’ de simulación.
