In Vitro Macrophage Immunomodulation by Poly(ε-caprolactone) Based-Coated AZ31 Mg Alloy

Due to its excellent bone-like mechanical properties and non-toxicity, magnesium (Mg) and its alloys have attracted great interest as biomaterials for orthopaedic applications. However, their fast degradation rate in physiological environments leads to an acute inflammatory response, restricting their use as biodegradable metallic implants. Endowing Mg-based biomaterials with immunomodulatory properties can help trigger a desired immune response capable of supporting a favorable healing process. In this study, electrospun poly(ε-caprolactone) (PCL) fibers loaded with coumarin (CM) and/or zinc oxide nanoparticles (ZnO) were used to coat the commercial AZ31 Mg alloy as single and combined formulas, and their effects on the macrophage inflammatory response and osteoclastogenic process were investigated by indirect contact studies. Likewise, the capacity of the analyzed samples to generate reactive oxygen species (ROS) has been investigated. The data obtained by attenuated total reflection Fourier-transform infrared (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) analyses indicate that AZ31 alloy was perfectly coated with the PCL fibers loaded with CM and ZnO, which had an important influence on tuning the release of the active ingredient. Furthermore, in terms of degradation in phosphate-buffered saline (PBS) solution, the PCL-ZnO- and secondary PCL-CM-ZnO-coated samples exhibited the best corrosion behaviour. The in vitro results showed the PCL-CM-ZnO and, to a lower extent, PCL-ZnO coated sample exhibited the best behaviour in terms of inflammatory response and receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated differentiation of RAW 264.7 macrophages into osteoclasts. Altogether, the results obtained suggest that the coating of Mg alloys with fibrous PCL containing CM and/or ZnO can constitute a feasible strategy for biomedical applications.     

Three-dimensional visualization and quantification of microporosity in aluminum castings by X-ray micro-computed tomography

Porosity is a major issue in solidification processing of metallic materials.In this work,wedge die casting experiments were designed to investigate the effect of cooling rate on microporosity in an aluminum alloy A356.Microstructure information including dendrites and porosity were measured and observed by optical microscopy and X-ray micro-computed tomography(XMCT).The effects of cooling rate on secondary dendrite arm spacing(SDAS)and porosity were discussed.The relationship between SDAS and cooling rate was established and validated using a mathematical model.Three-dimensional(3-D)porosity information,including porosity percentage,pore volume,and pore number,was determined by XMCT.With the cooling rate decreasing from a lower to a higher position of the wedge die,the observed pore number decreases,the porosity percentage increases,and the equivalent pore radius increases.Sphericity of the pores was discussed as an empirical criterion to distinguish the types of porosity.For different cooling rates,the larger the equivalent pore radius is,the lower the sphericity of the pores.This research suggests that XMCT is a useful tool to provide critical 3-D porosity information for integrated computational materials engineering(ICME)design and process optimization of solidification products.     

Enhanced electrode kinetics and electrochemical properties of low-cost NaFe2PO4(SO4)2 via Ca2+doping as cathode material for sodium-ion batteries

In recent years,sodium-ion batteries(SIBs)have been considered as one of the most promising alterna-tives to lithium-ion batteries(LIBs).Here,a new Na-super-ionic conductor(NASICON)cathode material NaFe2PO4(SO4)2 is successfully prepared through solid state method for SIBs.While the poor electronic conductivity of iron-based materials results in its poor rate and cycle performance.Then the electro-chemical is effectively promoting via Ca2+doping.Na0.84Ca0.08Fe2PO4(SO4)2 have achieved considerable electrochemical properties.The first discharge specific capacity is 121.6mAhg-1 at 25mAg-1 with the voltage platform(～3.1 V)corresponding to Fe2+/3+.After 100 cycles,the capacity retention is 55.1％.The excellent electrochemical performance is caused by some Na+is substituted by Ca2+and leading to the fast sodium kinetics,which is well proved by the powder X-ray diffraction pattern and well corresponding to the galvanostatic intermittent titration technique and cyclic voltammetry testing result(the diffusivity values are around at 10-12 cm2 s-1).     

An antimonene modified hole extraction layer for high efficiency PEDOT:PSS-free nonfullerene organic solar cells

In this paper, a bilayer hole extraction layer (HEL) with solution-processed molybdenum trioxide (MoO₃) and two-dimensional (2D) material of antimonene was developed to achieve high performance nonfullerene organic solar cells (NF–OSCs). The application of antimonene facilitates effective charge extraction and lowered recombination loss, achieving improved photovoltaic performance. By inserting the antimonene layer, power conversion efficiency (PCE) of devices with MoO₃ HEL was increased from 8.92% to 11.30% in OSCs with non-fullerene systems of PBDB-T-2F:IT-4F, which was even much higher than that of the devices with PEDOT:PSS HEL (10.59%). Results make it clear that the solution-processed bilayer MoO₃/antimonene HEL shows great potential for application in high performance PEDOT:PSS-free NF–OSCs.     

Effects of community of inquiry,learning presence and mentor presence on K-12 online learning outcomes

This study extends the community of inquiry (CoI) framework and self-regulated learning (SRL) theory through an exploration of the structural relationships among existing CoI variables, learning presence (i.e., self-efficacy and online SRL strategy) and learning outcomes in the context of K-12 online learning. To help understand the influence of K-12 mentoring – which is unique to online learning in the U.S. – mentor presence is also included. Structural equation modelling of 696 online 8th through 12th graders' survey responses and final grades showed that adding learning presence to the CoI framework helped to explain how these learners translated their online-learning perceptions into cognitive and affective learning outcomes. We also found that mentor presence significantly and positively predicted online SRL strategy, one of the two components of learning presence. Lastly, we established a connection between the CoI model and various types of learning outcomes that are indicators of K-12 online learning success – though it should be noted that important differences existed between a model based on final grades and two other outcome models. It is hoped that the processes identified in this study will be useful and relevant to K-12 online-learning institutions and educators seeking to improve their offering via a wide range of approaches.     

Finite element analysis on shape deformation of the macro-structure region during hot-rolling process for gear steel FAS3420H and its modification

The rectangular macro-segregation region in the core of hot-rolled steel bar has a great influence on the heat treatment distortion of an automotive gear steel FAS3420H. In order to understand the distortion process of the segregation region during hot-rolling process, a finite element (FE) analysis of the whole hot-rolling process was carried out by software DEFORM-3D, and a constructed constitutive model was embedded into DEFORM-3D to describe the deformation process. The results show there is an inhomogeneous strain distribution at the cross-section of hot-rolled round bar, which results in uneven distortion of the segregation region in different directions. A square segregation region, which can reduce inhomogeneous distortion of gear in the subsequent heat treatment, is obtained after being rolled by simulation calculation verified through experiment.