A calcium phosphate coating improving corrosion resistance of the biodegradable magnesium alloy with graphene oxide modifying the deposition

Biodegradable magnesium alloy is an ideal material for medical implant applications, but its application is limited by its rapid degradation. Therefore, it becomes the main goal to improve corrosion resistance. In this study, a calcium phosphate dihydrate/graphene oxide composite coating was designed on the AZ60 alloy for medical applications. A calcium phosphate dihydrate coating was first prepared by biomimetic deposition on the alkali pretreated magnesium alloy, and graphene oxide was dispersed in the solution to modify the deposition. The results showed that graphene oxide could not only alter the loose striped calcium phosphate coating to the compact flaked composite coating, but also enhance the corrosion resistance with a reduced corrosion current density by 2 orders of magnitude, an increased impedance by 3 orders of magnitude and a corrosion rate down to 7/20. The in vitro biocompatibility of the composite coating was also demonstrated by a series cell experiments, with a cell viability of 120%. The composite coating provides a feasible method to enhance the corrosion resistance and biocompatibility of magnesium alloys.     

云南省东南部新寨锡矿床矿化趋势面分析

本文系统收集整理了云南省东南部新寨锡矿资源勘查过程中形成的85个探矿工程编录资料,建立了三维空间数据库,对具有空间属性的锡品位数据进行了基本统计分析和矿化趋势分析,并绘制了矿化等值线图和矿化趋势图,认为新寨矿区矿化富集带走向与矿化趋势等值线走向均与地层走向方向一致,显示出赋矿地层对锡的富集具有明显的控制作用;矿区南东浅部矿化富集带较北西深部矿化富集带锡矿化强度高,总体矿化趋势北西低南东高,结合地质背景推测矿区发育的向斜挠曲构造影响了锡的富集,远离向斜轴部锡品位有增强趋势。     

A biotemplate synthesized hierarchical Sn-doped TiO2 with superior photocatalytic capacity under simulated solar light

Despite a number of studies have been carried out on TiO₂ based materials as photocatalysts for water pollutant treatment, it still needs sustained effort to extend the optical range of the photocatalysts and inhibit the recombination of photo-induced carriers to improve their catalytic activities under solar light. In this work, a series of Sn-doped TiO₂ with different amounts of Sn doping (1, 5, 10 and 20 mol%) were biomimetically synthesized by a facile sol–gel method using cellulosic cotton as biotemplate. The Sn-doped TiO₂ materials possess a typical three-dimensional hierarchical structure of microtubes consisting of interwoven nanofibers. The photocatalytic performance was evaluated via the degradation of methylene blue (MB) (10.0 mg L^?1) under Xenon lamp simulated solar irradiation. The results show that Sn(5)-TiO₂ (5 mol% Sn doping) sample exhibits an outstanding photocatalytic capacity with a superior degradation rate of higher than 98% within 30 min and a good reusability without significant decrease of activity after reused for four cycles. The most significantly improved photocatalytic capacity of TiO₂ is ascribed to more extra surface hydroxyl groups and accessible active sites provided by the relatively high surface area, and a higher light capturing and utilization efficiency with less recombination of the photogenerated electron-hole pairs endowed by the good synergistic effect of the special hierarchically porous microstructure and the appropriate amount of Sn doping. Whereas, the excessive Sn doping reduces the photocatalytic activity obviously, resulting from the phase transformation of TiO₂ generating more rutile phase with less reactivity, the phase separation with clear grain boundary blocking the active sites, and the extra Sn⁴⁺ acting as the recombination center. This research presents a facile biomimetic synthesis strategy combined with the traditional sol–gel method to develop various ion doped metal oxides as photocatalysts with enhanced activity.     

Effect of sodium carbonate addition on the properties of calcium silicate scaffolds fabricated by 3DIP

3D ink printing (3DIP) technology can accurately control the macroscopic size and microstructure of bioceramic scaffolds. However, nonceramic components in the printing ink used in 3DIP severely affect densification, resulting in less desirable mechanical properties of the scaffolds. In this study, a strategy of sintering assisted by a sintering aid (sodium carbonate) was used to prepare calcium silicate (CSi) scaffolds with high strength. The addition of 1% sintering aid to a CSi scaffold sintered at 1100 °C led to an appreciable compressive strength (47.8 MPa) and high elastic modulus (1847 MPa). Moreover, the CSi scaffolds with sintering aids showed better degradation ability and mineralization ability than the CSi scaffolds without sintering aids. It is expected that the method involving strengthening with sintering aids will promote the application of 3DIP bioceramic scaffolds in the repair of bone defects.     

Interactions of Surfactants with Biomimetic Membranes. 1. Ionic Surfactants

When impregnated with esters of fatty acids, nitrocellulose filters can be used as a biomimetic membrane. They are easy to make, cheap, and may be used not only as an imitation of biological membranes but also as a sensor to characterize surfactant interactions with dirty fabric. These impregnated filters when fixed in a thermostatically controlled chamber separated into two compartments that contain stirred aqueous solutions by the filter, may be considered as a simple model of a laundry machine. The results revealed that the addition of ionic surfactants into one of the solutions led to the formation of transmembrane electrical potential that is proportional to the logarithm of surfactant concentration. Thus, our biomimetic membranes can be used as electrochemical sensors to detect and measure surfactant concentration. When concentration is near the critical micelle concentration (CMC), a new phenomenon was observed, i.e., spontaneous oscillations of both transmembrane potential and transmembrane current, which mimics the opening and closing of aqueous channels in biological membranes. A further increase of surfactant concentration les to a sharp 100-fold decrease of transmembrane electrical resistance and the disappearance of any transmembrane voltage. This effect, explained by the washing out of fatty acids from the pores, may be used for screening and development of new detergents.     

Liquid water transport in PEMFC cathode with symmetrical biomimetic flow field design based on Murray's law

Water management in the flow field as well as the flooding process in the gas diffusion and catalyst layers enormously influence proton exchange membrane fuel cells (PEMFCs) performance and reliability. Researchers have developed many different designs for flow channels that can be used to distribute fuel or oxidant in PEMFCs (proton exchange membrane fuel cells). Among these designs, novel biomimetic designs have captured special attentions from researchers due to their capability of distributing fluids effectively. This study presents an investigation of the liquid water transport within a porous layer and a symmetrical biomimetic flow field based on Murray's law. The volume of fluid (VOF) method is employed, and the dynamic contact angle (DCA) effects are also considered for better prediction of water distribution. The water transport process and water distribution inside the porous layer and flow field are obtained from the simulation results. Recommendations are given for this type of flow field design based on the behaviors of liquid water in the porous layer and flow field.     

Advancing biomaterials of human origin for tissue engineering

Biomaterials have played an increasingly prominent role in the success of biomedical devices and in the development of tissue engineering, which seeks to unlock the regenerative potential innate to human tissues/organs in a state of deterioration and to restore or reestablish normal bodily function. Advances in our understanding of regenerative biomaterials and their roles in new tissue formation can potentially open a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multi-component construction of native extracellular matrices (ECMs) for cell accommodation, the synthetic biomaterials produced today routinely incorporate biologically active components to define an artificial in vivo milieu with complex and dynamic interactions that foster and regulate stem cells, similar to the events occurring in a natural cellular microenvironment. The range and degree of biomaterial sophistication have also dramatically increased as more knowledge has accumulated through materials science, matrix biology and tissue engineering. However, achieving clinical translation and commercial success requires regenerative biomaterials to be not only efficacious and safe but also cost-effective and convenient for use and production. Utilizing biomaterials of human origin as building blocks for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural tissue with regard to its physical and chemical properties for the orchestration of wound healing and tissue regeneration. In addition to directly using tissue transfers and transplants for repair, new applications of human-derived biomaterials are now focusing on the use of naturally occurring biomacromolecules, decellularized ECM scaffolds and autologous preparations rich in growth factors/non-expanded stem cells to either target acceleration/magnification of the body's own repair capacity or use nature's paradigms to create new tissues for restoration. In particular, there is increasing interest in separating ECMs into simplified functional domains and/or biopolymeric assemblies so that these components/constituents can be discretely exploited and manipulated for the production of bioscaffolds and new biomimetic biomaterials. Here, following an overview of tissue auto-/allo-transplantation, we discuss the recent trends and advances as well as the challenges and future directions in the evolution and application of human-derived biomaterials for reconstructive surgery and tissue engineering. In particular, we focus on an exploration of the structural, mechanical, biochemical and biological information present in native human tissue for bioengineering applications and to provide inspiration for the design of future biomaterials.     

仿生合成碳酸钙的制备及其在PVC中的应用

以十二烷基苯磺酸钠(SDBS)、乙二醇、聚乙二醇-400(PEG-400)和聚乙烯醇(PVA)为模板,仿生合成了碳酸钙,并将其应用在聚氯乙烯(PVC)中。用FTIR、XRD和SEM对所得碳酸钙进行了表征,并测试了PVC/碳酸钙共混物的拉伸性能。结果表明:有机添加剂对碳酸钙形貌有显著影响;仿生合成碳酸钙极大地提高了PVC的拉伸强度和断裂伸长率其,最佳用量范围为5~10份。     

青海五龙沟地区金多金属矿成矿规律

五龙沟金矿是青海省东昆仑成矿带最具找矿潜力的矿床。在搜集五龙沟地区金多金属矿床成矿大地构造背景、区域地层、岩性、构造、岩浆岩等方面资料的基础上,首先对区内典型金多金属矿床地质特征分别进行了描述,然后从地层、岩浆岩、构造等方面对区内金多金属矿床的控矿因素进行了系统分析,最后从矿床成矿时间、空间分布及成因等方面对成矿规律进行了总结。结果表明：①五龙沟地区金多金属矿床产于构造韧性剪切带中,受构造及其演化控制明显;②金矿床在时间上具有多阶段性和长期性的分布规律,在空间上严格沿3条韧性、脆-韧性剪切带分布,各剪切带内矿床具有等距性和平行性的分布特点;③多金属矿床多分布于剪切带与后期NE-SW向的断裂带交汇部位,往往成群成组分布;④金矿体形成于多金属矿之前,以深部岩浆为主的壳幔混源、壳源是金多金属矿的重要成矿物质来源,伴随构造演化使成矿物质进一步活化并富集形成金多金属矿体。上述研究成果对于区内进一步开展金多金属矿、构造热液蚀变型矿床的找矿工作具有一定的参考价值。