Piezoelectricity of the Transmembrane Protein ba3 Cytochrome c Oxidase

Controlling the electromechanical response of piezoelectric biological structures including tissues, peptides, and amino acids provides new applications for biocompatible, sustainable materials in electronics and medicine. Here, the piezoelectric effect is revealed in another class of biological materials, with robust longitudinal and shear piezoelectricity measured in single crystals of the transmembrane protein ba₃ cytochrome c oxidase from Thermus thermophilus. The experimental findings from piezoresponse force microscopy are substantiated using a range of control measurements and molecular models. The observed longitudinal and shear piezoelectric responses of ≈ 2 and 8 pm V⁻¹, respectively, are comparable to or exceed the performance of commonly used inorganic piezoelectric materials including quartz, aluminum nitride, and zinc oxide. This suggests that transmembrane proteins may provide, in addition to physiological energy transduction, technologically useful piezoelectric material derived entirely from nature. Membrane proteins could extend the range of rationally designed biopiezoelectric materials far beyond the minimalistic peptide motifs currently used in miniaturized energy harvesters, and the finding of robust piezoelectric response in a transmembrane protein also raises fundamental questions regarding the molecular evolution, activation, and role of regulatory proteins in the cellular nanomachinery, indicating that piezoelectricity might be important for fundamental physiological processes.     

新型限力输出保护功能柔性夹钳的设计与参数评估

柔性夹钳因具有微/纳精密操作能力, 常应用于微操作系统中, 但因抓爪无法提供恒定输出力或恒力范围小, 容易造成操作对象的损伤或脱落。根据放大模块与常力模块串联的结构形式, 设计了一种具有常力特性的柔性夹钳。基于伪刚体法, 建立放大模块中桥式机构与杠杆机构的刚度和放大率数学模型, 通过对倾斜导向梁进行分析, 得到常力模块的力-位移关系式, 计算出恒定输出力为42.5 N, 输出范围为370 μm。最后, 结合不同柔顺梁的结构参数, 运用MATLAB仿真探究了各关键参数对常力特性的影响。研究结果可为常力柔性夹钳的构型设计和分析提供一定的理论支撑。     

Understanding stickiness in sugar-rich food systems: A review of mechanisms,analyses, and solutions of adhesion

Stickinessis an inherent textural property in many sugar-rich foods, which can be problematic to the processing of confectionery products. The adhesion between foods and contact surfaces during processing and consumption has not been well understood in academia or industry. The theories of adhesion were discovered by scientists in the adhesive field of study, some of which can explain the stickiness phenomenon of confections. This work reviewed these theories in the context of sugar-rich foods, followed by a survey on the sensory and instrumental analyses of stickiness. Furthermore, the contributions of ingredients, temperature, compression, and contact surfaces to sugar-rich food adhesion are highlighted.     

新型地锚张弦梁式泥石流格栅坝构件受力的简化计算方法

针对常见泥石流防治结构被冲击破坏的问题，基于“柔性消能”理念，结合张弦梁结构和竖向预应力锚杆技术，提出一种既能改善结构受力性能、增加结构整体抗冲击能力、保证结构安全可靠，又能减小结构构件截面尺寸、节约成本、便于现场施工组装和后期运营维护的新型地锚张弦梁式泥石流格栅坝，并阐述其技术原理。根据泥石流荷载分布和新型地锚张弦梁式泥石流格栅坝的受力特征，给出其简化的内力计算方法；并利用SAP2000建立新结构有限元模型，分析了结构的整体受力，验证了构件简化计算方法的合理性；结合Python语言和Qt De? signer软件开发了相应的设计计算软件，对新型地锚张弦梁式泥石流格栅坝的内力进行求解。结果表明：提出的新结构抗冲击性能好，构件受力均匀；以后设计中应关注竖杆的剪切脆性破坏和立柱偏心受力情况，保证结构安全；变形协调仅使底层张弦梁与竖杆内力偏大，实际工程应用时，应着重验算底层构件，防止其破坏；文中提出的简化计算方法能较准确的反映结构的受力特性，具有一定的合理性，研究可为新型地锚张弦梁式泥石流格栅坝的设计计算和推广应用提供理论依据和技术支持。     

Evaluating the profile of myofibrillar proteins and its relationship with tenderness among five styles of dry-cured hams

In order to investigate the relationship between profile of myofibrillar proteins and tenderness among 2 kinds of Chinese hams (Jinhua and Xuanwei) and 3 kinds of European hams (Iberian, Serrano and Parma), shear force, myofibril fragmentation index (MFI), SDS-PAGE, carbonyls content and Raman spectroscopy were investigated. The shear force and salt content of Chinese hams were significantly higher than that of European hams, while moisture content was lower than that of European hams (p < 0.05). MFI values and SDS-PAGE profile revealed that the degradation of myofibrillar proteins in Chinese hams was lower than in European hams. In addition, Chinese hams showed significantly higher carbonyls content and β-sheet content compared with European hams, indicated that proteins aggregation intensively inhibited the degradation of myofibrillar proteins in Chinese hams. These results indicated that the higher shear force in Chinese style hams could be attributed to the lower moisture content and limited proteolysis.     

Theoretical analysis and test verification of pull-out forces in shear connectors of composite beam under negative bending moment

Abstract

A mechanical model of steel-concrete composite beams considering horizontal slip and vertical pull-out effects under negative bending moment was established based on the theory of elastic deformation. By using the principle of force equilibrium and deformation compatibility condition, the differential equation was derived and deduced using computational calculation program, in which the formula of the pull-out force in shear connectors under negative bending moment was obtained. The experiment was conducted in order to verify the reliability of theoretical results. The results show: under the same load condition, the pull-out force of a single stud increases with the increase of the stud spacing. All the theoretical results were verified by comparing with experiment results to illustrate the accuracy and reliability of the calculation method. It provides a theoretical reference for the study of the interface interaction considering horizontal slip and vertical pull-out effect in the negative bending moment region of continuous composite beams.     

退火炉内罩中气体流动及钢卷传热的数值模拟

摘要：轧制力预报一直是热连轧过程控制模型的核心，浅层神经网络对复杂函数的表示能力有限，而深度学习模型通过学习一种深层非线性网络结构，实现复杂函数逼近。利用深度学习框架TensorFlow，构建了一种深度前馈神经网络轧制力模型，采用BP算法计算网络损失函数的梯度，运用融入Mini batch策略的Adam优化算法进行参数寻优，采用Early stopping、参数惩罚和Dropout正则化策略提高模型的泛化能力。基于上述建模策略，针对宝钢1880热连轧精轧机组的大量轧制历史数据进行了建模实验，对比分析了4种不同结构的前馈网络预测精度。结果表明，相比于传统SIMS轧制力模型，深度神经网络可实现轧制力的高精度预测，针对所有机架的预测精度平均提升21.11%。     

Use of cryogenic machining to improve the adhesion of sphene bioceramic coatings on titanium substrates for dental and orthopaedic applications

Rods of commercially pure titanium were machined using standard oil-based emulsion and cryogenic cooling, and were then coated with sphene (CaTiSiO₅) bioceramic by spray coating using an automatic airbrush. The sphene bioceramic was synthesized in-situ starting from a suspension of polysiloxane that used as SiO₂ precursor, CaCO₃ and TiO₂ nanoparticles. The suspension was deposited on the machined substrates, which were heat treated up to 950?°C in order to promote the formation of sphene ceramic. The produced coated prototypes were characterized to evaluate the effect of the machining conditions on surface roughness and microstructure of the substrate, and thereby their effect on coating adhesion. Nanoindentation tests were employed to determine the hardness and elastic modulus of the coating through its thickness. Results showed that the reduced amount of defects on the surface of the cryo-machined substrates, contributed to increase the hardness, elastic modulus and adhesion strength of the coating-substrate interfaces compared to standard machined samples, therefore improving adhesion of the coating to the underlying substrate.