Microstructural characteristic,outward-inward growth behavior and formation mechanism of MAO ceramic coating on the surface of ADC12 Al alloy with micro-groove

The ceramic coatings on the surface of aluminum alloy substrates with micro-grooves have been successfully fabricated in the silicate solution via micro-arc oxidation (MAO) approach. Microstructure characterization showed that the larger main discharge channels were located in the center of micro-groove, the smaller secondary discharge channels were located on both sides of main discharge channel; and a few irregular micro-pores existed in the vicinity of all discharge channels, which were mainly cause by the rapid cooling and solidification of discharge channels hindering the removal of gases produced via reaction. Moreover, the growing direction of coating in the initial stage was mainly outward-growth and resulted in the formation of inverted triangle coating structure, which was due to the sharp-angled effect. But in the final growing stage, the inward-growth behavior played a key role owing to the spark transfer. According to above results and discussion, the formation of smooth, uniform and homogeneous ceramic coating on the surface of whole trapezoidal micro-groove substrate contained four stages: anodic oxidation growth, sharp corner rapid growth, coating homogenization and groove self-filling.     

PCEC hydrogel used on sustained‐release hyaluronic acid delivery with lubrication effect

Injection of bionic synovial fluid (BSF) is a conventional method to improve the lubricity of artificial joints, but BSF cannot maintain long due to the dilution and degradation of BSF in human body. To prolong the effectiveness of hyaluronic acid (HA), which is the major component of BSF, this study applies a temperature‐sensitive poly(?‐caprolactone)–poly(ethylene glycol)–poly(?‐caprolactone) (PCEC) hydrogel loaded with HA to achieve long‐term lubrication. In addition, Fourier transform infrared, nuclear magnetic resonance analysis, X‐ray diffraction, scanning electron microscopy (SEM), and gel permeation chromatography spectra were used to analyze the structure of the synthetic hydrogel. Rheological test and test tube inverting method were used to characterize the thermosensitivity. The lubrication properties of the released solution were characterized by UV–vis, tribological tests, SEM, and 3D laser confocal scanning microscope. The experimental results reveal that the triblock PCEC hydrogel contains both hydrophilic block and hydrophobic block, and both PCEC and PCEC/HA hydrogels have phase‐changed effect when the temperature increases from room temperature to body temperature. Moreover, the friction coefficient of the released solution from PCEC/HA hydrogel is approximatively 38% lower than that of phosphate buffer saline. And the ability of shear resistance and creep recovery of PCEC/HA hydrogel are better than that of PCEC hydrogel. This study provides an effective approach to achieve long‐time lubrication effect for artificial joints. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46228.     

Right Way of Using Graphene Oxide Additives for Water-Lubricated PEEK: Adding in Polymer or Water?

Water-lubricated polymer is attracting more and more interest from the industry. Adding nanoparticles is considered to be an effective way to improve the tribological performance. In this work, water-lubricated Polyetheretherketone (PEEK)-steel contacts were employed as the objects of study. A careful comparative study was made by investigating the effect of adding graphene oxide (GO) into water or into PEEK. Results show that adding GO into water can significantly reduce the wear and friction coefficient of pure PEEK, which is much more effective than adding GO into PEEK. Under the lubrication of GO aqueous dispersion, the wear of PEEK remains very low even under a harsh condition where the pressure reaches 50 MPa and the linear sliding speed is 0.7 m/s. Neat PEEK and GO/PEEK composites in pure water exhibit serious wear under this harsh condition. The excellent lubricating properties of GO aqueous dispersion are attributed to GO nanosheets entering into solid contacts, which can not only form a protective layer on steel counterpart repairing the worn surface, but also strongly adhere to the PEEK matrix resulting in an in situ-formed GO coating and prevent the scratch by steel counterpart.     

Biodegradable Spheres Protect Traumatically Injured Spinal Cord by Alleviating the Glutamate‐Induced Excitotoxicity

New treatment strategies for spinal cord injury with good therapeutic efficacy are actively pursued. Here, acetalated dextran (AcDX), a biodegradable polymer obtained by modifying vicinal diols of dextran, is demonstrated to protect the traumatically injured spinal cord. To facilitate its administration, AcDX is formulated into microspheres (≈7.2 µm in diameter) by the droplet microfluidic technique. Intrathecally injected AcDX microspheres effectively reduce the traumatic lesion volume and inflammatory response in the injured spinal cord, protect the spinal cord neurons from apoptosis, and ultimately, recover the locomotor function of injured rats. The neuroprotective feature of AcDX microspheres is achieved by sequestering glutamate and calcium ions in cerebrospinal fluid. The scavenging of glutamate and calcium ion reduces the influx of calcium ions into neurons and inhibits the formation of reactive oxygen species. Consequently, AcDX microspheres attenuate the expression of proapoptotic proteins, Calpain, and Bax, and enhance the expression of antiapoptotic protein Bcl‐2. Overall, AcDX microspheres protect traumatically injured spinal cord by alleviating the glutamate‐induced excitotoxicity. This study opens an exciting perspective toward the application of neuroprotective AcDX for the treatment of severe neurological diseases.     

基于多尺度结构特征的快速异源图像匹配

针对异源图像提出一种基于多尺度密集结构特征的快速匹配算法。算法首先利用Gabor滤波器逐像素提取图像中的结构响应,再根据主方向响应对多尺度结构特征融合,然后使用快速傅里叶变换在频域计算各特征分量图像之间的卷积,最后将卷积生成的系数矩阵求和计算出图像之间的相似性并选择相似性最大位置作为匹配结果输出。本文算法能有效适应异源图像间的非线性灰度变化和噪声干扰问题。测试使用可见光、红外、雷达图像组成的异源图像数据集对本文算法和现有算法进行测试比较,结果表明:本文算法的平均误匹配率最低,并且计算速度有明显优势。     

基于差动共焦显微技术的微区拉曼光学系统构建与实验研究

研制了一种基于差动共焦显微技术的微区拉曼光学系统装置,对无机样品进行微区拉曼光谱探测。传统显微共焦拉曼光谱技术没有强调系统的定焦能力,而所研制的光学系统装置利用差动共焦曲线过零点与焦点位置精确对应的特性,采用反馈控制技术,具有长时间定焦功能。在微区拉曼散射信号收集时,采用多模光纤空间耦合技术,以光纤代替传统物理探测针孔,提高了环境抗干扰能力,优化了系统结构和装调性能。实验结果表明:该装置具有较高稳定性,可有效探测单壁碳纳米管在1581.510 cm^-1,2708.065 cm^-1特征峰处的拉曼频移及纯物质硫在153.113 cm^-1,219.917 cm^-1,473.322 cm^-1特征峰处的拉曼频移并且实现碳管的单线检测,满足了光谱探测系统装置设计需求。     

ZerNet: Convolutional Neural Networks on Arbitrary Surfaces Via Zernike Local Tangent Space Estimation

In this paper, we propose a novel formulation extending convolutional neural networks (CNN) to arbitrary two-dimensional manifolds using orthogonal basis functions called Zernike polynomials. In many areas, geometric features play a key role in understanding scientific trends and phenomena, where accurate numerical quantification of geometric features is critical. Recently, CNNs have demonstrated a substantial improvement in extracting and codifying geometric features. However, the progress is mostly centred around computer vision and its applications where an inherent grid-like data representation is naturally present. In contrast, many geometry processing problems deal with curved surfaces and the application of CNNs is not trivial due to the lack of canonical grid-like representation, the absence of globally consistent orientation and the incompatible local discretizations. In this paper, we show that the Zernike polynomials allow rigourous yet practical mathematical generalization of CNNs to arbitrary surfaces. We prove that the convolution of two functions can be represented as a simple dot product between Zernike coefficients and the rotation of a convolution kernel is essentially a set of 2 × 2 rotation matrices applied to the coefficients. The key contribution of this work is in such a computationally efficient but rigorous generalization of the major CNN building blocks.