Modelling Strategies for Reinforced Concrete Elements under Corrosion Degradation

Aging and corrosion of reinforced concrete structures (RCS) is becoming a global problem, thus proper procedures for simulating the structural performance of corroded RCS should be assessed. Among the main corrosion effects, concrete cover cracking and reinforcement cross-section reduction may influence the materials’ constitutive laws, moreover the confinement contribution and the lateral instability of the longitudinal rebars can be modified. In the present paper, the predictive models available in the scientific literature to assess the materials’ mechanical properties of corroded RCS are recalled and employed into a novel model to derive the theoretical moment–curvature relationships for the cross-section of square and rectangular corroded reinforced concrete elements. The model accounts for cover spalling, buckling of longitudinal reinforcing bars, reduction in confinement pressures, reduction in concrete constitutive law due to the concrete cracking induced by rust formation and decay of mechanical properties for corroded reinforcements. The obtained results are compared with the classical simplified models for corroded RCS, highlighting that buckling and confinement variations cannot be disregarded into a reliable modelling strategy, especially when local ductility plays a key role in the performed investigations.     

Investigation of Potential Use of Soybean Protein Isolate–Chinese Bayberry Tannin Extract Cross-Linked Films in Packaging Applications

The possibility of using commercial bayberry tannin (BT) from a Chinese source as a cross-linker and functional additive to develop soybean protein isolate (SPI)-based films was explored in this study by using the solvent casting method. In particular, the impacts of BT loading on the tensile strength, microstructure, thermal stability, water resistance and antioxidant capacity were fully investigated. The results reveal that SPI incorporated with BT yielded a phenolic–protein hybrid whose relevant films exhibited an improvement in tensile strength of around two times greater compared with native SPI as a result of the formed interactions and covalent cross-links, which could be proven using FTIR spectroscopy. The introduction of BT also led to the compact microstructure of SPI–BT films and enhanced the thermal stability, while the water vapor permeability was reduced compared with the control SPI film, especially at high loading content of tannin. Additionally, the use of BT significantly promoted the antioxidant capacity of the SPI-based films according to DPPH radical scavenging assay results. On this basis, Chinese bayberry tannin is considered a promising natural cross-linker and multifunctional additive that can be dedicated to developing protein-derived films with antioxidant activity for food packaging applications.     

A Three-Dimensional Equivalent Stiffness Model of Composite Laminates with Wrinkle Defects

The stiffness of composite laminates is easily affected by wrinkle defects. In this paper, a new effective analytical model was proposed to predict the three-dimensional equivalent elastic properties of multidirectional composite laminates with wrinkle defects. Firstly, a geometric model was established according to the microscopic characteristics of wrinkle defects. Then, based on the classical laminate theory and homogenization method, the constitutive equation and flexibility matrix of the wrinkle region were established. Finally, the equivalent stiffness parameters of unidirectional and multidirectional laminates were derived, and the effects of different wrinkle parameters and ply-stacking sequences on the stiffness of unidirectional and multidirectional laminates were studied by using the analytical model. The results show that the mechanical properties of the lamina and laminates are affected by the out-of-plane angle and in-plane angle of the wrinkle defects. The accuracy of the analytical model has been verified by the numerical model and other theoretical models, and it has the characteristics of few parameters and a high efficiency. The analytical model can be used to predict the stiffness of composite structures with wrinkle defects simply, effectively, and quantitatively. It can also be used as a tool to provide the mechanical response information of laminates with wrinkle defects.     

虾青素对眼组织保护作用的实验研究及存在的问题

虾青素是一种源于天然生物的类胡萝卜素的含氧衍生物,具有抗氧化、抗炎、抗细胞凋亡,预防心、脑血管疾病及癌症等多种作用,是一类具有一定发展前景的药品和保健食品成份.目前研究表明,虾青素可以透过血-视网膜屏障对眼组织发挥保护作用,已引起研究者的重视.本文针对虾青素在动物实验饲药环节中存在的问题、虾青素的抗氧化作用基础和组织细胞的氧化损伤机制以及在常见眼科疾病中的有关研究现况进行综述.     

Changes in antioxidant,inflammatory and metabolic markers during 1 week cultivation of human skin explants

Human skin explant (HSE) seems to be a useful model for dermatological/cosmetic testing. HSE prepared from donor superfluous skin from plastic surgery operations is cheap and easily obtainable compared to reconstructed models. The HSE use, however, may be limited by the degeneration processes during cultivation. The aim was to monitor changes in metabolic activity and selected apoptotic, inflammatory and antioxidant parameters during 7 day cultivation. The significant changes were found in the superoxide dismutase‐2 level from day 5, glutathione S‐reductase level from day 6, metabolic activity and fibulin‐5 level from day 4, cyclooxygenase‐2, interleukin‐6 and interleukin‐10 from day 1 to 2. Other selected markers (lipid peroxidation products and glutathione level, glutathione S‐transferase, catalase, superoxide dismutase and glutathione S‐reductase activity, glutathione peroxidase and glutathione S‐reductase levels) were not modified significantly due to high inter‐individual variability of skin donors. The HSE microstructure as well as cytokeratin‐10 and proliferation marker Ki67 expression was also only minimally affected during cultivation. Collectively, the results demonstrate that HSE represents a good model for short‐term studies focused on the physical and chemical agent toxicity, protective potential of compounds or metabolic biotransformation. However, reduced metabolic activity, increased inflammation and the high inter‐individual variability and sensitivity of donors have to be taken into consideration.     

Glycation inhibitory activity and the identification of an active compound in Plantago asiatica extract

The glycation reaction involves a series of non-enzymatic reactions between the carbonyl group on reducing sugars and the amino group on proteins leading to the formation of advanced glycation end-products (AGEs), which are acknowledged to be involved in the pathogenesis of diabetic and aging-related complications. Consequently, the development of AGE inhibitors is considered to have therapeutic potential in patients with diabetes or age-related diseases. The preliminary results showed that a methanol extract (PAE) of Plantago asiatica, which is traditionally used as a folk medicine in Asian countries to treat fever, cough, wound etc., had strong glycation inhibitory activity. The effects of the extract on AGE fluorescence were dose-dependent, reaching 41% inhibition at 0.1 microg/mL of extract. The purified principle from PAE was identified as plantamajoside. As well as antioxidant activities, in vitro glycation inhibitory activities with 10 and 25 mm plantamajoside were higher than those with 10 and 25 mm aminoguanidine. The results demonstrate that PAE and plantamajoside had significant effects on in vitro AGE formation, and the glycation inhibitory activity and antioxidant activity of plantamajoside were comparable to those obtained using millimolar concentrations of the standard antiglycation agent aminoguanidine, and the antioxidant ascorbate, respectively.