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.     

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.     

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.     

Quaternary bioactive glass-derived powders presenting submicrometric particles and antimicrobial activity

The biomedical engineering advances in the last years have been rising demand for multifunctional biomaterials. Bioactive glass (BG) submicron particles are potential candidates for the formulation of composites with improved dispersion and homogeneity between the constituents. This work presents the preparation of SiO₂–Na₂O–CaO–P₂O₅ glass-derived powders composed of particles with homogenous shapes and sizes between 300 and 500 nm. Two types of synthesis were employed for the preparation of the BG powders, the melt-quenching method, and a citric acid-assisted sol-gel route at a low citric acid concentration (0.005 mol L^?1). The morphology of the particles was achieved by a low-energy process using a ball mill. These powders were characterized for their structure and surface area and evaluated for in vitro mineralization and antibacterial behavior. X-ray diffraction (XRD) analysis revealed different crystalline silicate phases in the sol-gel-derived powder and confirmed the amorphous structure of the melt-quenching-derived one. The surface of the particles was covered by hydroxycarbonate-apatite (HCA) after five days in simulated body fluid (SBF). The antibacterial activity against Staphylococcus aureus was higher for the sol-gel-derived powder, showing inhibition >99% of the bacteria growth in 24 h for all concentrations studied. These BG-based powders present a set of characteristics useful for the formulation of multifunctional composites for orthopedic applications.     

Biomimetic approach to tunable adhesion of polyurethane adhesives through Fe3+ crosslinking and hydrophobic tween units with balance of adhesion/cohesion forces

Biocompatible adhesives have some limitations such as weak adhesion and low flexibility. To overcome these limitations, we described multiple strategies to provide strong adhesion and high flexibility through Tweens, chlorogenic acid (CLA) and polyethylene glycol (PEG) by reducing excessive interaction between tissue and the adhesive. We synthesized polyurethane-based adhesives using aliphatic 4,4′-methylenebis(cyclohexyl isocyanate) (HMDI), PEG, CLA and Tween units. Hydrophobic side chains in polymer resulted in lower Tg (−36.95-30.36 °C) which indicated more flexibility. The highest adhesion strengths were found as almost 346 kPa for bare polyurethane and 492 kPa for chelated polymer (PU-T40-CLA-15% (5% Tween 40, 15% chlorogenic acid and 80% PEG 200 containing polymer)) with FeCl₃. The addition of Tween units provided more stable structure to polymers which proved with in vitro erosion studies. Relatively low erosion values were seen as 5.7, 5.6 and 8.2% in PU-T40-CLA-5% (15% Tween 40, 5% chlorogenic acid and 80% PEG 200 containing polymer), PU-T40-CLA-10% (10% Tween 40, 10% chlorogenic acid and 80% PEG 200 containing polymer), and PU-T40-CLA-15% (5% Tween 40, 15% chlorogenic acid and 80% PEG 200 containing polymer), respectively. In vitro biocompatibility results showed high cell viability in PU-T40-15% as more than 100%. Overall, our findings indicated that these material designs (PU-T-CLAs) provided to overcome the significant challenges of tissue adhesives by improving the flexible character and adhesive strength of the adhesives.     

Biomimetic synthesis of cellular SiC based ceramics from plant precursor

A novel biomimetic approach in designing and fabricating engineering ceramic materials has gained much interest in recent times. Following this approach, synthesis has been made of dense Si-SiC duplex ceramic composites and highly porous SiC ceramics in the image of the morphological features inherent in the caudex stem of a local monocotyledonous plant. The process route involves making of a carbonaceous biopreform and its subsequent reaction with an infiltrating silicon melt to yield the biomorphic Si-SiC ceramic composites with flexural strength and Young’s modulus of 264 MPa and 247 Gpa, respectively and loss in weight of only ∼9% during oxidative heating up to 1200°C in flowing air. The Si-SiC composites were transformed into porous (49 vol.%) SiC ceramics with complete preservation of microcellular anatomy of the parent plant, by depleting residual silicon phase in channel pores through reaction with carbon. SiC based materials so derived can be used in structural applications and in designing high temperature filters and catalyst supports.     

高矿化度地层水淹层综合评价方法

科学识别和评价水淹层，准确描油田剩余油分布，提高油注水开发效益。方法：依据取心、岩电实验，试油及测井资料，采用数理统计方法，制定了一套定量划分高矿化度地层水淹层级识别的方法，效果：本方法应用于文东油田文１３块，解释符合率大８５％，产生了较好的经济效益，并对高矿化度地层水淹层谰价和解释具有推广价值。     

Knowledge mining for biomimetic smart antenna shapes

Antennas used on autonomous robots have been optimized very little for the tasks which need to be mastered in order to achieve true autonomy. In contrast to this, natural biosonar systems offer a highly diverse set of optimized antenna solutions. With biosonar as a sufficient far-sense, bats are capable of achieving complete autonomy in unconstrained natural environments. A set of methods is described which can be used to efficiently derive shape information from natural biosonar antennas, to characterize their system properties using numerical methods and visualize the results in a way that gives access to salient features.     

江西省相山铀矿田成矿条件探讨

本文主要阐述了相山铀矿田的成矿条件。相山铀矿田是我国最大的火山岩型铀矿田,研究其成矿条件对今后找矿工作有十分重要的意义。本文主要从构造背景、物质条件、断裂构造和保矿条件这几方面进行探讨。     

Biomimetic in situ nucleation of calcium phosphates by protein immobilization on high strength ceramic materials

Zirconia has been commonly used in the dental industry because of its excellent biological, mechanical and aesthetic properties. This material, however, is classified as nearly inert. To bioactivate the ceramic surface, biomimetic depositions of calcium phosphate coatings have been developed. We demonstrate an accelerated biomimetic coating method on zirconia using a specific pre-treatment with biological agents. We have chosen bovine serum albumin as a standard protein. Through the pre-treatment of the zirconia using a hydroxylation or additionally immobilizing the bovine serum albumin on the surface, we could influence the CaP deposition rate. Immunohistochemical analyses verified the presence of BSA on the zirconia surfaces. After immersion in simulated body fluid at 40 °C, the samples were analyzed by scanning electron microscopy and X-ray diffraction to visualize the CaP formation. Here we could show as proof-of-principle that it is possible to accelerate biomimetic coating processes on zirconia implants containing BSA on their surface.