Role of CD36 in central nervous system diseases

CD36 is a highly glycosylated integral membrane protein that belongs to the scavenger receptor class B family and regulates the pathological progress of metabolic diseases.CD36 was recently found to be widely expressed in various cell types in the nervous system,including endothelial cells,pericytes,astrocytes,and microglia.CD36 mediates a number of regulatory processes,such as endothelial dysfunction,oxidative stress,mitochondrial dysfunction,and inflammatory responses,which are involved in many central nervous system diseases,such as stroke,Alzheimer’s disease,Parkinson’s disease,and spinal cord injury.CD36 antagonists can suppress CD36 expression or prevent CD36 binding to its ligand,thereby achieving inhibition of CD36-mediated pathways or functions.Here,we reviewed the mechanisms of action of CD36 antagonists,such as Salvianolic acid B,tanshinone IIA,curcumin,sulfosuccinimidyl oleate,antioxidants,and small-molecule compounds.Moreover,we predicted the structures of binding sites between CD36 and antagonists.These sites can provide targets for more efficient and safer CD36 antagonists for the treatment of central nervous system diseases.

RNA sequencing of exosomes secreted by fibroblast and Schwann cells elucidates mechanisms underlying peripheral nerve regeneration

Exosomes exhibit complex biological functions and mediate a variety of biological processes,such as promoting axonal regeneration and functional recove ry after injury.Long non-coding RNAs(IncRNAs)have been reported to play a crucial role in axonal regeneration.Howeve r,the role of the IncRNA-microRNAmessenger RNA(mRNA)-competitive endogenous RNA(ceRNA)network in exosome-mediated axonal regeneration remains unclear.In this study,we performed RNA transcriptome sequencing analysis to assess mRNA expression patterns in exosomes produced by cultured fibroblasts(FC-EXOs)and Schwann cells(SCEXOs).Diffe rential gene expression analysis,Gene Ontology analysis,Kyoto Encyclopedia of Genes and Genomes analysis,and protein-protein intera ction network analysis were used to explo re the functions and related pathways of RNAs isolated from FC-EXOs and SC-EXOs.We found that the ribosome-related central gene Rps5 was enriched in FC-EXOs and SC-EXOs,which suggests that it may promote axonal regeneration.In addition,using the miRWalk and Starbase prediction databases,we constructed a regulatory network of ceRNAs targeting Rps5,including 27 microRNAs and five IncRNAs.The ceRNA regulatory network,which included Ftx and Miat,revealed that exsosome-derived Rps5 inhibits scar formation and promotes axonal regeneration and functional recovery after nerve injury.Our findings suggest that exosomes derived from fibro blast and Schwann cells could be used to treat injuries of peripheral nervous system.

Characterization methods for additive manufacturing

Additive manufacturing(AM),also generally known as 3D print-ing,is one of the most disruptive technologies that has been widely used in automobile,aerospace,biomedical,weapons,and other industrial fields.Compared with traditional manufacturing technologies,AM has many significant advantages,including rapid production,easy operation,less material waste and labor costs,high efficiency,and is easy to realize personalized design and fab-rication especially for complex components.

Characterization for elastic constants of fused deposition modelling-fabricated materials based on the virtual fields method and digital image correlation

Fused deposition modelling(FDM), a widely used rapid prototyping process, is a promising technique in manufacturing engineering. In this work, a method for characterizing elastic constants of FDM-fabricated materials is proposed. First of all, according to the manufacturing process of FDM, orthotropic constitutive model is used to describe the mechanical behavior. Then the virtual fields method(VFM) is applied to characterize all the mechanical parameters(Q, Q, Q, Q) using the full-field strain,which is measured by digital image correlation(DIC). Since the principal axis of the FDM-fabricated structure is sometimes unknown due to the complexity of the manufacturing process, a disk in diametrical compression is used as the load configuration so that the loading angle can be changed conveniently. To verify the feasibility of the proposed method, finite element method(FEM) simulation is conducted to obtain the strain field of the disk. The simulation results show that higher accuracy can be achieved when the loading angle is close to 30?. Finally, a disk fabricated by FDM was used for the experiment. By rotating the disk, several tests with different loading angles were conducted. To determine the position of the principal axis in each test, two groups of parameters(Q, Q, Q, Q) are calculated by two different groups of virtual fields. Then the corresponding loading angle can be determined by minimizing the deviation between two groups of the parameters. After that, the four constants(Q, Q, Q, Q) were determined from the test with an angle of 27?.

Fabrication of high temperature grating on thermal barrier coatings based on solute-solvent separation soft lithography

In this study, an etched-SiO-film grating fabrication technique based on solute-solvent separation soft lithography is developed. By using this new technique, high temperature grating with frequency of 600 lines/mm is successfully fabricated on the surface of thermal barrier coatings(TBCs). During the fabrication process, the microstructure and chemical compositions of ceramic coating before and after polishing is analyzed with a digital microscope and the energy dispersive X-ray spectroscope(EDS) in scanning electron microscope(SEM). And then the grating on TBCs is heated at the temperature ranging from 300℃ to 1000℃ for examining the high temperature resistance. In the practical application, the displacement and strain field around the crack on the ceramic surface are investigated with geometry phase analysis(GPA). The successful results verify that the etched-SiO-film grating has a good oxidation resistance and can be applied to high temperature deformation measurement of TBCs.

Editorial: Special subject on the mechanical behavior of thermal protection materials and structures

The thermal protection materials and structures are widely used in hypersonic vehicles for the purpose of thermal insulation, and their mechanical behavior is one of the key issues in design and manufacture of hypersonic vehicles. It is our great pleasure to present the seven papers in this special subject of Theoretical ＆ Applied Mechanics Letters （TAML） and introduce the recent progresses on the mechanical behavior of thermal protection materials and structures by the authors.

Identification of the elastic stiffness of composites using the virtual fields method and digital image correlation

This paper presents an effective methodology for characterizing the mechanical parameters of composites using digital image correlation combined with the virtual fields method.By using a three-point bending test configuration,this method can identify all mechanical parameters of the material with merely a single test.Successful results verified that this method is especially effective for characterizing composite materials.In this study,the method is applied to measure the orthotropic elastic parameters of fiber-reinforced polymer-matrix composites before and after the hygrothermal aging process.The results indicate that the hygrothermal aging environment significantly influences the mechanical property of a composite.The components of the parameters in the direction of the fiber bundle decreased significantly.From the accuracy analysis,we found that the actual measurement accuracy is sensitive to a shift of the horizontal edges and rotation of the vertical edges.

Research on synchronous measurement technique of temperature and deformation fields using multispectral camera with bilateral telecentric lens

The hot-section parts easily occur the creep-fatigued interaction under the condition of mechanicalthermal coupled load during the period of service, which may lead to the damage of the parts, and therefore, the measurement and characterization of thermal-deformed fields of the parts are important to understand its damage process. Aiming at relevant demand, the bilateral telecentric-multispectral imaging system was established, the research of synchronous measurement technique of the temperature and deformation fields was developed. On the one hand, the measurement technology for surface temperature of the object was developed using the two-color images captured by the multispectral camera with bilateral telecentric lens and combined with colorimetric method. On the other hand, the 2 D-DIC measurement technique of the multispectral camera was developed by conducting digital image correlation analysis using the blue light images before and after deformation, which can measure the high temperature deformation field of the object(the blue light images were filtered by multispectral camera).Results showed that the bilateral telecentric lens is used to replace the ordinary optical lens for imaging,which can effectively eliminate the distortion of the multispectral imaging system. Since the temperature measurement process of this measurement system is little affected by the emissivity of the object, therefore, it has excellent robustness. The thermal expansion coefficients of the nickel alloys are evaluated at the temperature ranges of 700–1000℃, indicating this system can achieve the synchronous and precise measurement of the temperature and deformation fields of the object.

Elastic constants characterization on graphite at 500℃ by the virtual fields method

In this paper the elastic constants of graphite at elevated temperature were experimentally investigated by using the virtual fields method （VFM）. A new method was presented for the characterization of mechanical properties at elevated temperature. The three-point bending tests were performed on graphite materials by an universal testing machine equipped with heating fumace. Based on the heterogeneous deformation fields measured by the digital image correlation （DIC） technique, the elastic constants were then extracted by using VFM. The measurement results of the elastic constants at 500℃ were obtained. The ef- fect on the experimental results was also analyzed. The successful results verify the feasibility of using the proposed method to measure the properties of graphite at high temperature, and the proposed method is believed to have a good potential for further applications.

Constitutive parameters identification of thermal barrier coatings using the virtual fields method

Thermal barrier coatings (TBCs) are widely applied in thermal components to protect metallic components. Owing to the complex layered structure of TBCs and difficult preparation of coating, the mechanical characterization of TBCs should be of primary importance. With regard to TBCs, this study deals with the constitutive parameters identification of bi-material. Considering the complex construction and boundary of bi material, the virtual fields method (VFM) was employed in this study. A methodology based on the optimized virtual fields method combined with moire interferometry was proposed for the constitutive parameters identification of bi-material. The feasibility of this method is verified using simulated deformation fields of a two-layer material subjected to three point ben ding loading. As an application, the deformation fields of the TBC specimens were measured by moire interferometry. Then, lhe mechanical parameters of the coating were identified by the proposed method. The identification results indicate that Young's modulus of the TBC top coating is 89.91 GPa, and its Poisson's ratio is 0.23.

Determination of the full-field stress and displacement using photoelasticity and sampling moirémethod in a 3D-printed model

The quantitative characterization of the full-field stress and displacement is significant for analyzing the failure and instability of engineering materials.Various optical measurement techniques such as photoelasticity,moiréand digital image correlation methods have been developed to achieve this goal.However,these methods are difficult to incorporate to determine the stress and displacement fields simultaneously because the tested models must contain particles and grating for displacement measurement;however,these elements will disturb the light passing through the tested models using photoelasticity.In this study,by combining photoelasticity and the sampling moirémethod,we developed a method to determine the stress and displacement fields simultaneously in a three-dimensional(3D)-printed photoelastic model with orthogonal grating.Then,the full-field stress was determined by analyzing 10 photoelastic patterns,and the displacement fields were calculated using the sampling moirémethod.The results indicate that the developed method can simultaneously determine the stress and displacement fields.

OPTIMUM DESIGN OF PROCESSING CONDITION AND EXPERIMENTAL INVESTIGATION OF GRATING FABRICATION WITH HOT EMBOSSING LITHOGRAPHY

The cross-section profiles of polymer deformation in the hot embossing lithography process were studied by finite element method for various temperature, time and pressure. In order to successfully fabricate high-frequency grating lines, an optimal imprint condition was selected and the related experiments were carried out. The fabricated gratings were illuminated by the SEM image and AFM analysis, which agree well with the simulated results. Therefore, the finite element methods are helpful for a better comprehension of the polymer flow phenomena governing the pattern definition and the design of optimum processing conditions for successful grating fabrication.

Coherent gradient sensing method for measuring thermal stress field of thermal barrier coating structures

Coherent gradient sensing （CGS） method can be used to measure the slope of a reflective surface, and has the merits of full-field, non-contact, and real-time measurement. In this study, the thermal stress field of thermal barrier coating （TBC） structures is measured by CGS method. Two kinds of powders were sprayed onto Ni-based alloy using a plasma spraying method to obtain two groups of film-substrate specimens. The specimens were then heated with an oxy-acetylene flame. The resulting thermal mismatch between the film and substrate led to out-of-plane deformation of the specimen. The deformation was measured by the reflective CGS method and the thermal stress field of the structure was obtained through calibration with the help of finite element analysis. Both the experiment and numerical results showed that the thermal stress field of TBC structures can be successfully measured by CGS method.

Characterization of the arrangement feature of copper interconnects by Moir inversion method

This paper explores the planar arrangement feature of the copper interconnects in a view field of several millimeters by the focused ion-beam （FIB） Moire inversion method quantitatively. The curved FIB Moire patterns indicate that the copper interconnects are a series of curves with continuous variations instead of beelines. The control equation set of the copper interconnects central lines is attained through the Moire inversion method. This work can be extended to inspect the structural defects and provide a reliable support for the interconnects structure fabrication.

Spatial heterogeneity and source apportionment of soil metal(loid)s in an abandoned lead/zinc smelter

Metal smelting have brought severe metal(loid)s contamination to the soil.Spatial distribution and pollution source analysis for soil metal(loid)s in an abandoned lead/zinc smelter were studied.The results showed that soil was contaminated heavily withmetal(loid)s.The mean of lead(Pb),arsenic(As),cadmium(Cd),mercury(Hg)and antimony(Sb)content in topsoil is 9.7,8.2,5.0,2.3,and 1.2 times higher than the risk screening value for soil contamination of development land of China(GB36600-2018),respectively.Cd ismainly enriched in the 0–6mdepth of site soil while As and Pbmainly deposited in the 0–4mlayer.The spatial distribution of soil metal(loid)s is significantly correlated with the pollution source in the different functional areas of smelter.As,Hg,Sb,Pb and copper(Cu)were mainly distributed in pyrometallurgical area,while Cd,thallium(Tl)and zinc(Zn)was mainly existed in both hydrometallurgical area and raw material storage area.Soil metal(loid)s pollution sources in the abandoned smelter are mainly contributed to the anthropogenic sources,accounting for 84.5%.Specifically,Pb,Tl,As,Hg,Sb and Cumainly from atmospheric deposition(55.9%),Cd and Zn mainly from surface runoff(28.6%),While nickel(Ni)mainly comes from parent material(15.5%).The results clarified the spatial distribution and their sources in different functional areas of the smelter,providing a new thought for the risk prevention and control of metal(loid)s in polluted site soil.

A BRIEF REVIEW AND PROSPECT OF EXPERIMENTAL SOLID MECHANICS IN CHINA

In this review, acritical look at the research progress ofexperimentalsolid mechanics in China for the past years is presented. Issues are discussed of the discovery and development of new fundamental methods and techniques versus performance benchmarking for many of their applications. Included herein are photoelasticity and various forms of modern photomechanics, acoustical techniques, image processing and videometrics, radial and spectrum techniques, and experimental mechanics on micro/nano scale. It is also noticed that both the ever developed instrumentation and specialized synthetical techniques have played important roles in advancing experimental mechanics in scientific researches and industrial applications. Finally, an attempt is made to look into the future of experimental solid mechanics with personal opinions offered on what the future trends will be for the researches in the field.

RECENT PROGRESS IN RESIDUAL STRESS MEASUREMENT TECHNIQUES

Residual stress measurement is of critical significance to in-service security and the reliability of engineering components, and has been an active area of scientific interest. This paper offers a review o[ several prominent mechanical release methods for residual stress measurement and recent developments, focusing on the hole-drilling method combined with advanced optical sensing. Some promising trends for mechanical release methods are also analyzed.

Synergistic therapy of magnetism-responsive hydrogel for soft tissue injuries

Soft tissue injury is very common and associated with pain,tissue swelling and even malformation if not treated on time.Treating methods include cryotherapy,electrical therapy,ultrasound therapy and anti-inflammatory drug,but none of them is completely satisfying.In this work,for a better therapeutic effect,drug therapy and pulsed electromagnetic field(PEMF)therapy were combined.We constructed a drug delivery system using the tetra-PEG/agar hydrogel(PA).By incorporating Fe3O4 NPs into the hydrogel network,a magnetism-responsive property was achieved in the system.The cytotoxicity and in vivo study showed a good biocompatibility of the PA/Fe3O4 hydrogel.A magnetism-controlled release was attained by the incorporation of Fe3O4.Finally,in vivo study showed a better performance of the DS-loaded PA/Fe3O4 compared with the commercially available DS ointment regarding the recovery of the injured soft tissue.Therefore,this magnetism-responsive hydrogel may represent a promising alternative to treat soft tissue injury.

A novel random phase-shifting digital holographic microscopy method

This paper proposes a new method that reconstructs the information of specimen by using random phase shift step in digital holographic microscopy (DHM). The principles of the method are described and discussed in detail. In practical experiment, because the phase shifter is neither perfectly linear nor calibrated, digital holograms with inaccurate phase shift step are recorded by the charge-coupled device (CCD). The phase could be accurately reconstructed from the recorded digital holograms by using the random phase-shifting algorithm, which makes up for reconstructed phase error caused by ordinary phase-shifting algorithm. The phase aberration compensation is also discussed. In order to verify the flexibility of the proposed method, numerical simulation of random phase-shifting DHM was carried out. The simulation results illustrated that the presented method is effective when the phase shift step is unknown or random in DHM.

Coupling of NiFe-Based Metal-Organic Framework Nanosheet Arrays with Embedded Fe-Ni_(3)S_(2) Clusters as Efficient Bifunctional Electrocatalysts for Overall Water Splitting

Developing highly efficient,easy-to-make and cost-effective bifunctional electrocatalysts for water splitting with lower cell voltages is crucial to producing massive hydrogen fuel.In response,the coupled hierarchical Ni/Fe-based MOF nanosheet arrays with embedded metal sulfide nanoclusters onto nickel foam skeleton(denoted as Fe-Ni_(3)S_(2)@NiFe-MOF/NF)are fabricated,in which the Fe-Ni_(3)S_(2) clusters could effectively restrain the aggregation of the layer metal-organic frameworks(MOF)nanosheets and adjust the local electronic structures of MOFs nanosheets.Benefiting from the rapid charge transfer and the exposure of abundant active sites,the well-designed Fe-Ni_(3)S_(2)@NiFe-MOF/NF displays excellent oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)performance.More importantly,when equipped in the alkaline water electrolyzer,the Fe-Ni_(3)S_(2)@Ni Fe-MOF/NF enables the system with a mere 1.6 V for achieving the current density of 10 mA cm^(-2).This work offers a paradigm for designing efficient bifunctional HER/OER electrocatalysts based on the hybrid materials of nanostructured metal sulfide and MOF.