Direct ink writing of vancomycin-loaded polycaprolactone/ polyethylene oxide/ hydroxyapatite 3D scaffolds

Novel inks were formulated by dissolving polycaprolactone (PCL), a hydrophobic polymer, in organic solvent systems; polyethylene oxide (PEO) was incorporated to extend the range of hydrophilicity of the system. Hydroxyapatite (HAp) with a weight ratio of 55–85% was added to the polymer-based solution to mimic the material composition of natural bone tissue. The direct ink writing (DIW) technique was applied to extrude the formulated inks to fabricate the predesigned tissue scaffold structures; the influence of HAp concentration was investigated. The results indicate that in comparison to other inks containing HAp (55%, 75%, and 85%w/w), the ink containing 65% w/w HAp had faster ink recovery behavior; the fabricated scaffold had a rougher surface as well as better mechanical properties and wettability. It is noted that the 65% w/w HAp concentration is similar to the inorganic composition of natural bone tissue. The elastic modulus values of PCL/PEO/HAp scaffolds were in the range of 4–12 MPa; the values were dependent on the HAp concentration. Furthermore, vancomycin as a model drug was successfully encapsulated in the PCL/PEO/HAp composite scaffold for drug release applications. This paper presents novel drug-loaded PCL/PEO/HAp inks for 3D scaffold fabrication using the DIW printing technique for potential bone scaffold applications.     

“数字信号处理”课程的几何视角

“数字信号处理”的经典课程体系以“系统”为中心，以离散时间傅立叶变换、z变换和离散傅立叶变换为分析工具，以滤波器设计为目的，注重定理和公式推导及其性质分析，很难让学生建立一个形象的、完整统一的知识体系框架。本文从几何视角将 “系统”化和“代数”化的经典课程体系重构为面向“信号”的“几何”知识体系，从而提升学生对本质问题的“洞察力”，帮助学生建立系统的知识体系。     

Presentation attack detection based on two-stream vision transformers with self-attention fusion

Aiming at the performance degradation of the existing presentation attack detection methods due to the illumination variation, a two-stream vision transformers framework (TSViT) based on transfer learning in two complementary spaces is proposed in this paper. The face images of RGB color space and multi-scale retinex with color restoration (MSRCR) space are fed to TSViT to learn the distinguishing features of presentation attack detection. To effectively fuse features from two sources (RGB color space images and MSRCR images), a feature fusion method based on self-attention is built, which can effectively capture the complementarity of two features. Experiments and analysis on Oulu-NPU, CASIA-MFSD, and Replay-Attack databases show that it outperforms most existing methods in intra-database testing and achieves good generalization performance in cross-database testing.     

Tribological and mechanical characteristics of AA5083 alloy reinforced by hybridising heavy ceramic particles Ta2C & VC with light GNP and Al2O3 nanoparticles

In this study, AA5083 sheets were reinforced with four different hybrid nanoparticles by friction stir processing (FSP) for the development of surface nanocomposites used in advanced engineering applications. The present research focused on improving the properties and tribological behaviour of AA5083 alloy surfaces, including novel hybrid nanoparticles and the intermetallic phase formed during FSP. A tribometer tester with a constant normal load was used to examine the tribological performance of the hybrid composites. After the wear test, a surface profiler inspector was used to analyse the morphology and surface roughness of the examined materials. The Vickers micro-hardness of the base metal and the manufactured composites were measured. During FSP, a new intermetallic phase of AlV₃ was successfully formed at 300–400 °C in the hybrid nanocomposites containing VC particles. The reinforcements resulted in additional grain refining than FSP. The AA5083/Ta2C–Al₂O₃ exhibited the greatest grain refinement, a sixty-fold reduction in grain size compared to that of the base alloy. The results revealed that the hybrid nanocomposites containing VC particles demonstrated the most significant microhardness values inside the stirred zone as a result of the presence of the AlV₃ phase, which was increased by 25–30%. Moreover, the mechanical properties were significantly improved for all manufactured nanocomposites. The tensile strength was increased by 28% through the hybridisation of AA5083 using a hybrid of VC-GNPs. The dispersion of Ta₂C-GNPs and VC-GNPs in the matrix led to excellent interfacial adhesion, resulting in an enhancement in the mechanical properties. The AA5083/VC-GNPs surface composite outperformed other manufactured composites regarding wear resistance. In addition, due to GNPs soft nature, it reduced the coefficient of friction (COF) of the manufactured composites by 20–25% compared to other reinforcements.     

Establishment of a color tolerance for yarn-dyed fabrics from different color-depth yarns

Yarn-dyed fabric is often woven from warp and weft yarns in the same color depth to ensure a uniform color appearance. The difference in color depth between warp and weft tends to result in the uneven color of the yarn-dyed fabric. This article aims to establish a color tolerance for yarn-dyed fabric that can be woven with a qualified color appearance but from the warp and weft yarns in different color depths. A total of 27 yarn-dyed fabric samples in three color series (red, yellow, and blue) were evaluated by using the yarn-dyed fabric from warp and weft yarns in the same color depth of 2% (on weight of fabric, owf) as the standard. Visual assessment and instrumental measurement of color were carried out to establish the color tolerance ellipse that was defined as CMC (Color Measurement Committee) color differences (2:1) of no more than 1.00. It was found that the color strengths (K/S) and color differences (ΔE_CMC(2:1)) of these fabric samples for each color series had linear relationships with the color depths of warp and weft yarns. The color tolerance ellipses indicated that, even though the warp and weft yarns had an apparent color difference, they could be woven in fabrics with relatively uniform color appearance and meet the requirements for yarn-dyed fabric. This work provided valuable insight into the production of qualified yarn-dyed fabrics from unqualified dyed yarns.     

Site occupation and energy transfer in full color emitting phosphor Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+

White light-emitting diodes (WLEDs) fabricated by single-phase full color emitting phosphor are an emerging solution for health lighting. The crystallographic site occupation of activators in a proper host lattice is crucial for sophisticated design of such phosphor. Here, we report a high quality white light-emitting phosphor Ba₂Ca(BO₃)₂:Ce³⁺(K⁺),Eu²⁺,Mn²⁺ with spectral distribution covering whole visible region. Blue light emission originates from Ce³⁺ ions occupying preferentially Ba²⁺ site by controlling synthesis conditions. Green and red lights are obtained from Eu²⁺ occupying Ba²⁺ (and Ca²⁺) site and Mn²⁺ occupying Ca²⁺ site, respectively. In this triple-doped phosphor, strong red emission with a low concentration of Mn²⁺ is realized by the efficient energy transfer from Ce³⁺ and Eu²⁺ to Mn²⁺. Furthermore, high quality white light is accomplished by properly tuning the relative doping amount of Ce³⁺(K⁺)/Eu²⁺/Mn²⁺ based on efficient simultaneous energy transfer. The results indicate that Ba₂Ca(BO₃)₂:Ce³⁺(K⁺),Eu²⁺,Mn²⁺ is a promising white light-emitting phosphor in WLEDs application.     

Iodine from brown algae in human nutrition,with an emphasis on bioaccessibility,bioavailability, chemistry,and effects of processing: A systematic review

Brown algae are becoming increasingly popular as a food source and dietary supplement in Europe and other Western countries. As they are highly rich in iodine, they represent a potential new dietary iodine source. Iodine deficiency has been re-emerging in Europe, and it is important to ensure adequate intake through one's diet. However, macroalgae, and especially brown algae, may contain very high amounts of iodine, and both iodine deficiency and excessive iodine may increase the risk of negative health effects. The iodine content of algae or foods containing algae is currently not regulated in the European Union. The aim of this paper is to review the literature to determine the chemical species of iodine in brown algae, the loss of iodine during processing, and the bioavailability and bioaccessibility of iodine. A systematic search of the literature was performed in April 2021, via the databases Web of Science and PubMed. The review includes studies of iodine in brown macroalgae in relation to bioavailability, bioaccessibility, processing and speciation. A meta-analysis was conducted in relation to the following topics: (i) the correlation between total iodine and iodide (I^–) content in brown algae; (ii) the correlation between the loss of iodine during processing and the I^– content; and (iii) the correlation between bioavailability and the I^– content. The bioavailability of iodine from brown algae was generally high, with in vivo bioavailability ranging from 31% to 90%. The in vitro bioavailability of iodine (2%–28%) was systematically lower than in vivo bioavailability (31%–90%), indicating an inadequate in vitro methodology. Processing may reduce the iodine content of brown algae, and a higher I^– content was positively correlated with increased iodine loss during processing. Although processing strategies may reduce the iodine content of brown algae significantly, the iodine content may still be high after processing. These findings may be used in food safety evaluations of brown algae as well as in the development of macroalgae-containing foods with iodine contents suitable for human consumption. Further research on processing techniques to reduce the iodine content in brown macroalgae are warranted.     

Synthesis of thermoresponsive copolymer/silica-coated magnetite nanoparticle composite and its application for heavy metal ion recovery

To enhance chemical stability and suppress of aggregation of magnetite nanoparticles (MNPs), which are used as a support for thermoresponsive copolymer immobilization, silica coating of the MNPs is applied via the electrooxidation method. Although the resulting silica coated-MNPs also formed aggregates, the size distribution of the aggregate shifted to smaller size range. Because of that, the surface area available for copolymer immobilization increased approximately 6.7 times at maximum as compared with that of the uncoated MNPs. It contributed to the increase of the amount of the immobilized copolymer on the silica-coated MNPs, which is approximately four times larger than that on the uncoated MNPs. Fe₃O₄ dissolution test confirmed enhancement of chemical stability of MNPs. The thermoresponsive copolymer immobilized on the silica-coated MNPs shows the ability to recycle Cu(II) ion from Cu(II) containing solution by changing temperature with significantly shorter time than those in other thermoresponsive adsorbents in gel form.     

汽车加油口双色注射模设计

分析了汽车加油口塑件结构,确定了注射成型方案、进胶方式,并介绍了通过滑块与开模动作配合实现塑件脱模的过程。     

Mathematical Modeling of Drying Processes of Selected Fruits and Vegetables

This study investigates the behavior of fruit and vegetable samples during drying. The experimental data are fitted to several different thin-layer drying models. Regression analysis is used to determine model parameters, while statistical indicators serve to evaluate the goodness of fit. The power function model gives the best fit for all examined samples. Based on this model, different drying and heat storage technologies can be combined to ensure that the required residual moisture content of an agricultural product is reached. It is demonstrated on the case of a specific Togolese processing plant that under favorable conditions, fossil fuel consumption can be decreased by 33 %.