Effect of GO content on microstructure and mechanical properties of Ti6Al4V coating reinforced artificial joint.

In this study, we have innovatively proposed a method of in-situ synthesized TiC hard phase to improve the surface mechanical properties of artificial joint materials (Ti6Al4V). In order to explore the optimum graphene oxide (GO) addition, GO/Ti6Al4V composite powders with different proportions (0, 0.5, 1.0, and 1.5 wt.%) were prepared. The homogeneously dispersed GO/Ti6Al4V composite powder was prepared on Ti6Al4V substrate by laser cladding technology. The microstructure, phase composition, and mechanical behavior of GO/Ti6Al4V composite coatings were studied by scanning electron microscope (SEM), optical microscope (OM), energy dispersive spectrometer (EDS), tribometer, hardness tester, and surface profiler. The results showed that the addition of GO could significantly improve the mechanical properties of TC4 substrate. During the preparation of the coating, the grain size of in-situ TiC phase was nanoscale and was distributed between acicular martensite, which played a critical role in enhancing the mechanical properties of the coating. The TiC phase distributed between acicular martensite refine the grain size of α' phase and improve the cutting resistance of the coating. Nevertheless, excessive GO decreased the fluidity of the molten pool, and micro holes tended to generate in the coating, which had a negative impact on the mechanical properties of the coating. At the GO content of 0.5 wt.%, the microhardness of the GO/Ti6Al4V coating was 1.325 times that of pure Ti6Al4V. Under the friction environment of simulated body fluid solution, the average friction coefficient was approximately 0.307 and the wear rate decreased to 3.5 × 10-7 mm3/N · m.

Modified mRNA as a Treatment for Myocardial Infarction.

Myocardial infarction (MI) is a severe disease with high mortality worldwide. However, regenerative approaches remain limited and with poor efficacy. The major difficulty during MI is the substantial loss of cardiomyocytes (CMs) with limited capacity to regenerate. As a result, for decades, researchers have been engaged in developing useful therapies for myocardial regeneration. Gene therapy is an emerging approach for promoting myocardial regeneration. Modified mRNA (modRNA) is a highly potential delivery vector for gene transfer with its properties of efficiency, non-immunogenicity, transiency, and relative safety. Here, we discuss the optimization of modRNA-based therapy, including gene modification and delivery vectors of modRNA. Moreover, the effective of modRNA in animal MI treatment is also discussed. We conclude that modRNA-based therapy with appropriate therapeutical genes can potentially treat MI by directly promoting proliferation and differentiation, inhibiting apoptosis of CMs, as well as enhancing paracrine effects in terms of promoting angiogenesis and inhibiting fibrosis in heart milieu. Finally, we summarize the current challenges of modRNA-based cardiac treatment and look forward to the future direction of such treatment for MI. Further advanced clinical trials incorporating more MI patients should be conducted in order for modRNA therapy to become practical and feasible in real-world treatment.

Application of a water jet for cleaning grease and improving the surface adhesion properties of galvanized steel wire ropes.

Traditional cleaning processes may be banned in the near future because of the hazards they pose to the environment. In this study, a water jet was used to clean grease residues from steel wires for the first time. The EDS and SEM results of the steel wire rope surfaces and supplementary water jet impact experiments on galvanized steel plates revealed that when the pressure was lower than 50 MPa and the traverse speed was higher than 600 mm/min, the water jet caused minimal damage to the coating. When the pressure was 5 MPa, the cleaning ratio was between 45 and 60%, and the level of cleaning increased with increasing pressure. Two proposed concepts of exposure ratio and nonexposed area were applied to quantitatively analyze the theoretical upper and lower limits for grease that could be cleaned from two typical structures. The results showed that the lower and upper cleaning limits for structure 7 × 3 were 38.1% and 83.3%, while the lower and upper limits for structure 1 × 3 + 5 × 7 were 35.5% and 59.2%, respectively. This result explains why the grease content of structure 7 × 3 was lower than that of structure 1 × 3 + 5 × 7 after cleaning. In addition, the adhesion test results showed that adhesion to the two kinds of steel wire ropes after cleaning was increased by 126% and 145.71%, respectively, which means that additional processes for improving adhesion could be omitted after using a water jet for cleaning. This is an advantage that traditional cleaning processes do not offer.

Higenamine Attenuates Doxorubicin-Induced Cardiac Remodeling and Myocyte Apoptosis by Suppressing AMPK Activation.

Background: As an effective antitumor drug, doxorubicin (DOX) is primarily used to treat solid tumors and hematologic malignancies. However, increasing evidence has emerged indicating its cardiotoxicity, and few solutions have been proposed to counter this side effect. Higenamine (HG) is a natural compound widely found in many Chinese herbs and also serves as a component in many healthcare products. Several studies have demonstrated its cardioprotective effect in different models, but little is known about the underlying influences of HG against myocardial damage from DOX-induced chronic cardiotoxicity. Methods and Results: C57BL/6 mice and neonatal rat ventricular cardiomyocytes (NRVMs) were used to evaluate the cardioprotective effect of HG against DOX-induced myocardial damage. In mice, DOX (intraperitoneally injected 5 mg/kg every 3 days for 4 weeks) significantly increased cardiomyocyte apoptosis, cardiac atrophy, and cardiac dysfunction, which were significantly attenuated by HG (intragastrically administered with 10 mg/kg every day for 4 weeks). In NRVMs, DOX (3 µM for 24 h) significantly increased cell apoptosis and the level of reactive oxygen species while reducing the level of superoxide dismutase and mitochondrial membrane potential. Remarkably, HG can reverse these pathological changes caused by DOX. Interestingly, the protective effect of HG on DOX-induced cardiotoxicity was independent of the activation of the beta-2 adrenergic receptor (ß2-AR), known for mediating the effect of HG on antagonizing ischemia/reperfusion-induced cardiac apoptosis. Furthermore, HG attenuated the abnormal activation of phosphorylated adenosine-activated protein kinase (AMPK). Consistently, AMPK agonists (AICAR) can eliminate these pharmacological actions of HG. Conclusion: Collectively, our results suggested that HG alleviated DOX-induced chronic myocardial injury by suppressing AMPK activation and ROS production.

Higenamine attenuates cardiac fibroblast abstract and fibrosis via inhibition of TGF-ß1/Smad signaling.

RATIONALE: Higenamine (HG), is one of the main active components in many widely used Chinese herbs, and a common ingredient of health products in Europe and North America. Several groups, including our own, have previously shown the beneficial effects of HG against cardiomyocyte death during acute ischemic damage. However, the effect of HG on chronic cardiac remodeling, such as cardiac fibrosis, remains unknown. OBJECTIVE: Herein, we aim to investigate the role of HG in cardiac fibrosis in vivo as well as its cellular and molecular mechanisms. METHODS AND RESULTS: Chronic pressure overload with transverse aortic constriction (TAC) significantly increased cardiac hypertrophy, fibrosis, and cardiac dysfunction in mice, which were significantly attenuated by HG. Consistently, cardiac fibrosis induced by the chronic infusion of isoproterenol (ISO), was also significantly reduced by HG. Interestingly, our results showed that HG had no effect on adult mouse CM hypertrophy in vitro. However, HG suppressed the activation of cardiac fibroblasts (CFs) in vitro. Furthermore, TGF-ß1-induced expression of ACTA2, a marker of fibroblast activation, was significantly suppressed by HG. Concomitantly, HG inhibited TGF-ß1-induced phosphorylation of Smad2/3 in CFs. HG also reduced the expression of extracellular matrix molecules such as collagen I and collagen III. To our surprise, the inhibitory effect of HG on CFs activation was independent of the activation of the beta2 adrenergic receptor (ß2-AR) that is known to mediate the effect of HG on antagonizing CMs apoptosis. CONCLUSION: Our findings suggest that HG ameliorates pathological cardiac fibrosis and dysfunction at least partially by suppressing TGF-ß1/Smad signaling and CFs activation.

Surface modification and biotribological behavior of UHMWPE nanocomposites with GO infiltrated by ultrasonic induction.

In this study, we have innovatively proposed a method for surface modification of ultra-high molecular weight polyethylene (UHMWPE) artificial joint materials with graphene oxide (GO) infiltrated into UHMWPE substrate by ultrasonic induction. The mechanical properties of UHMWPE nanocomposites with GO infiltrated by ultrasonic induction were compared with that of GO mixed. The molecular structure, wettability, peak load, and bio-tribological behavior of GO/UHMWPE nanocomposites were studied using fourier transform infrared spectroscopy, contact angle measuring instrument, electronic universal material testing machine, tribometer, and profilometer, respectively. The results show that the ultrasonic-induction method can make GO adhere to UHMWPE surface well, and GO can significantly improve the wettability of UHMWPE substrate. When the ultrasound-inducted time is up to 12 hr, the wetting angle of the nanocomposites (12 h-GO/UHMWPE) is reduced to 65.24°, which is 20.51% lower than that of the pure UHMWPE. The peak load is 183 N, which is 20.22% higher than that of GO/UHMWPE prepared by the mixing method. The bio-tribological property of UHMWPE nanocomposites with GO infiltrated by ultrasonic induction for 12 hr (12 h-GO/UHMWPE) is the best, and its friction coefficient keeps more stable at a value of 0.0605 under the lubrication of calf serum, which is 11.81% lower than that of UHMWPE mixed with GO by a traditional method, and the wear rate is decreased to 3.25 × 10-5 mm3 N-1 m-1 .

Effect of Laser Rescanning on the Characteristics and Residual Stress of Selective Laser Melted Titanium Ti6Al4V Alloy.

The titanium Ti6Al4V alloy has excellent properties, and is one of the most important and widely used metal materials in the field of modern high-tech. Selective laser melting (SLM) is an ideal process for the rapid prototyping of Ti6Al4V alloy components with complex structures, but the performances need to be further improved. In this paper, the relative density, hardness, and microstructure under different scanning conditions were first analyzed in order to clarify the role of rescanning process in improving the performances. Then, the effects of different scanning strategies on the residual stress were analyzed. The results show that the strategy of partition rescanning has the most significant effect on residual stress. Finally, the SLM experiments of aviation nozzle rings were carried out. The results show that the average residual stress of the Re-SLMed sample was reduced from 322 MPa to 254 MPa.

The Release of Cyclophilin A from Rapamycin-Stimulated Vascular Smooth Muscle Cells Mediated by Myosin II Activation: Involvement of Apoptosis but Not Autophagy.

INTRODUCTION: The exocytosis of cyclophilin A (CyPA) by a vesicular pathway in response to reactive oxygen species has been determined. However, other sources of extracellular CyPA remain obscure. OBJECTIVE: The aim of this study was to determine the role of autophagy in the secretion of CyPA. METHODS AND RESULTS: Rapamycin induced the activation of autophagy and release of CyPA from primary cultured rat aortic smooth muscle cells (RASMCs). However, inhibition of autophagy by knockdown of Atg7 or chloroquine did not affect the rapamycin-induced release of CyPA. With the exception of myosin II activity, rho-associated coiled-coil kinase (ROCK), actin remodelling, and synaptic vesicles were not implicated in the release of rapamycin-induced CyPA. Finally, we confirmed that rapamycin-induced extracellular CyPA originated from apoptotic RASMCs. Furthermore, the decreased activation of myosin II by blebbistatin blocked the release of CyPA from apoptotic RASMCs induced by rapamycin. CONCLUSIONS: Rapamycin induced the release of CyPA from apoptotic RASMCs but did not affect exocytosis through autophagosomes. ROCK, actin remodelling, and synaptic vesicles were not involved in the apoptosis-related release of CyPA. Myosin II activation modulated the apoptosis of vascular smooth muscle cells and the release of CyPA from rapamycin-induced apoptotic cell death.

A Proposed Scan Strategy Used on SLM Inner Structure Part.

A model with an inner structure was designed to study the relationship between the surface quality of the inner structure and the scan strategy in this study. The test results showed that the precision of the inner structure was highly affected by the scan strategy, and the specimens printed using different strategies showed different performances on the surface quality of the inner structure. The specimen printed using the square-framed scan strategy had a lower flatness value on the positive face of the inner structure compared to that of the other two specimens printed using Z-shape scan strategies, while the specimen printed using the Z-shape scan strategy (along the inner structure) had a relative optimal surface roughness on the side surface of the inner structure in all three specimens. The bending deformation caused by the scan strategies was considered to be the main factor affecting the flatness on the positive surface, while laser energy fluctuation showed a significant impact on side surface roughness. Combined with the experimental data, a new scan strategy was proposed; we found that the specimen printed using this new strategy improved positive surface flatness and side surface roughness.

Research into the thermal stability and mechanical properties of vitamin E diffusion modified irradiation cross-linked graphene oxide/ultra-high molecular weight polyethylene composites.

Recently, there has been increasing interest in modifying ultra-high molecular weight polyethylene (UHMWPE) due to glaring needs in the artificial joint replacement field. It is generally reported in the literature that irradiation cross-linking and adding graphene oxide (GO)/vitamin E (VE) can enhance the mechanical properties of UHMWPE, but this can sacrifice the oxidation stability and gel content. This paper examines how VE diffusion can influence irradiation cross-linked GO/UHMWPE composites and whether mechanical performance and oxidation resistance can be maintained simultaneously, which will provide new guidance for prolonging the longevity of UHMWPE implants. The GO/UHMWPE composites were fabricated by means of liquid ultrasonic dispersion, hot pressing and irradiation cross-linking, followed by VE diffusion and homogenization treatment. The results indicated that limited VE diffusion decreased the water absorption and wettability. The crystallinity, melting temperature, thermal stability, hardness and scratch resistance of the composites basically remain essentially the same, except in the case of pure UHMWPE. In addition, the oxidation resistance was improved significantly after incorporating VE. Furthermore, the diffusion and enhancement mechanisms were also demonstrated, respectively.

Correction: Research into the thermal stability and mechanical properties of vitamin E diffusion modified irradiation cross-linked graphene oxide/ultra-high molecular weight polyethylene composites.

[This corrects the article DOI: 10.1039/C9RA09893C.].

Effect of Machining-Induced Subsurface Defects on Dislocation Evolution and Mechanical Properties of Materials via Nano-indentation.

Subsurface defects have a significant impact on the precision and performance of nano-structures. In this paper, molecular dynamics simulation of nano-indentation is performed to investigate the effect of machining-induced subsurface defects on dislocation evolution and mechanical properties of materials, in which the specimen model with subsurface defects is constructed by nano-cutting conforming to reality. The formation mechanism of subsurface defects and the interaction mechanism between machine-induced defects and dislocation evolution are discussed. The hardness and Young's elastic modulus of single crystal copper specimens are calculated. The simulation results indicate that there exist stable defect structure residues in the subsurface of workpiece, such as atomic clusters, stacking fault tetrahedral, and stair-rod dislocations. Secondary processing of nano-indentation can restore internal defects of the workpiece, but the subsurface damage in the secondary processing area is aggravated. The nano-indentation hardness of specimens increases with the introduction of subsurface defects, which results in the formation of work-hardening effect. The existence of subsurface defects can weaken the ability of material to resist elastic deformation, in which the mutual evolution between dislocations and subsurface defects plays an important role.

Effect of Fluid Media on Material Removal and Subsurface Defects Evolution of Monocrystal Copper in Nano-Cutting Process.

The effect of fluid media on material removal and subsurface defects evolution in nano-cutting process of single-crystal copper is investigated by means of molecular dynamics simulation. In this paper, the removal mechanism of the chip and formation mechanism of machined surface are investigated by analyzing the atomic migration and dislocation evolution of workpiece during nano-cutting process with the use of aqueous media. The distribution of temperature and subsurface defect crystal structural transformation are investigated, which are analyzed by centro-symmetry parameter and common neighbor analysis methods. The results show that the workpiece material is removed by the extrusion shearing action of the cutting tool. The lubrication of the aqueous media can reduce the cutting force and lower the height of cutting chip. Particularly, the cooling action of the fluid media results in the formation of a typical defect "similar-to-grain boundary" in subsurface of the workpiece. And the temperature of workpiece has a distinct decrease during nano-cutting process with the use of fluid media.

A Study on the Dimension Accuracy on the Inner Structure of the 3D Printed Parts Caused by the Scanning Strategy.

Selective laser melting (SLM) has been used in many fields recently, especially in the aerospace field. Many studies have been done on mechanical properties of the printed parts, but the dimension accuracy of the inner structure received little attention during these years. In this work, the dimension accuracy of the inner structure was measured and compared using different scanning strategies. Compared with the measured data, a new scanning strategy was used and finds that the dimension accuracy was better than the previous one that used a two-scanning strategy. To explain this phenomenon, finite element analysis (FEA) was used to show the temperature distribution after a 0.1 s cooling using two different scanning strategies, which caused the dimensional deviation in printing.

Improving the Strapdown Airborne Vector Gravimetry by a Backward Inertial Navigation Algorithm.

Strapdown airborne gravimetry is an efficient way to obtain gravity field data. A new method has been developed to improve the accuracy of airborne vector gravimetry. The method introduces a backward strapdown navigation algorithm into the strapdown gravimetry, which is the reverse process of forward algorithm. Compared with the forward algorithm, the backward algorithm has the same performance in the condition of no sensor error, but has different error characteristics in actual conditions. The differences of the two algorithms in the strapdown gravimetry data processing are presented by simulations, which show that the two algorithms have different performance in the horizontal attitude measurement and convergence of integrated navigation filter. On the basis of detailed analysis, the procedures of accuracy improvement method are presented. The result of this method is very promising when applying to an actual flight test carried out by a SGA-WZ02 strapdown gravimeter. After applying the proposed method, the repeatability of two gravity disturbance horizontal components were 1.83 mGal and 1.80 mGal under the resolution of 6 km, which validate the effectiveness of the method. Furthermore, the wavenumber correlation filter is also discussed as an alternative data fusion method.

Square-Root Unscented Information Filter and Its Application in SINS/DVL Integrated Navigation.

To address the problem of low accuracy for the regular filter algorithm in SINS/DVL integrated navigation, a square-root unscented information filter (SR-UIF) is presented in this paper. The proposed method: (1) adopts the state probability approximation instead of the Taylor model linearization in EKF algorithm to improve the accuracy of filtering estimation; (2) selects the most suitable parameter form at each filtering stage to simply the calculation complexity; (3) transforms the square root to ensure the symmetry and positive definiteness of the covariance matrix or information matrix, and then to enhance the stability of the filter. The simulation results indicate that the estimation accuracy of SR-UIF is higher than that of EKF, and similar to UKF; meanwhile the computational complexity of SR-UIF is lower than that of UKF.

A Model of Gravity Vector Measurement Noise for Estimating Accelerometer Bias in Gravity Disturbance Compensation.

Compensation of gravity disturbance can improve the precision of inertial navigation, but the effect of compensation will decrease due to the accelerometer bias, and estimation of the accelerometer bias is a crucial issue in gravity disturbance compensation. This paper first investigates the effect of accelerometer bias on gravity disturbance compensation, and the situation in which the accelerometer bias should be estimated is established. The accelerometer bias is estimated from the gravity vector measurement, and a model of measurement noise in gravity vector measurement is built. Based on this model, accelerometer bias is separated from the gravity vector measurement error by the method of least squares. Horizontal gravity disturbances are calculated through EGM2008 spherical harmonic model to build the simulation scene, and the simulation results indicate that precise estimations of the accelerometer bias can be obtained with the proposed method.

TRPC1 Deficiency Impairs the Endothelial Progenitor Cell Function via Inhibition of Calmodulin/eNOS Pathway.

Endothelial progenitor cells (EPCs) promote angiogenesis and play a pivotal role in endothelial repair and re-endothelialization after vascular injury. Transient receptor potential-canonical1 (TRPC1) has been recently implied to play important roles on EPC function. Here, we studied the role of TRPC1 in regulating EPC function in vivo and in vitro. EPCs were cultured from TRPC1-knockout mice and their controls. In vitro, TRPC1 knockout reduced EPC functional activities, including migration and tube formation. Additionally, calmodulin (CaM)/endothelial nitric oxide synthase (eNOS) signaling activity were downregulated after TRPC1 knockout. Administration of CaM or eNOS inhibitor ameliorated TRPC1 knockout-reduced EPC migration and tube formation. In vivo Matrigel plug assay confirmed that TRPC1 knockout decreased formation of functional blood vessels of EPCs compared with wild-type EPCs. Taken together, these data suggest that TRPC1 is a critical regulator of angiogenesis.

Compensation of Horizontal Gravity Disturbances for High Precision Inertial Navigation.

Horizontal gravity disturbances are an important factor that affects the accuracy of inertial navigation systems in long-duration ship navigation. In this paper, from the perspective of the coordinate system and vector calculation, the effects of horizontal gravity disturbance on the initial alignment and navigation calculation are simultaneously analyzed. Horizontal gravity disturbances cause the navigation coordinate frame built in initial alignment to not be consistent with the navigation coordinate frame in which the navigation calculation is implemented. The mismatching of coordinate frame violates the vector calculation law, which will have an adverse effect on the precision of the inertial navigation system. To address this issue, two compensation methods suitable for two different navigation coordinate frames are proposed, one of the methods implements the compensation in velocity calculation, and the other does the compensation in attitude calculation. Finally, simulations and ship navigation experiments confirm the effectiveness of the proposed methods.