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Abstract Background Increasing evidence shows the pivotal significance of miRNAs in the pathogenesis of osteoporosis. miR-381-3p has been identified as an inhibitor of osteogenesis. This study explored the role and mechanism of miR-381-3p in postmenopausal osteoporosis (PMOP), the most common type of osteoporosis. Methods Bilateral ovariectomy (OVX) rat model was established and miR-381-3p antagomir was administrated through the tail vein in vivo. The pathological changes in rats were assessed through the evaluation of serum bone turnover markers (BALP, PINP, and CTX-1), hematoxylin and eosin (H&E) staining, as well as the expression of osteoblast differentiation biomarkers. Moreover, isolated bone marrow mesenchymal stem cells from OVX-induced rats (OVX-BMMSCs) were utilized to explore the impact of miR-381-3p on osteoblast differentiation. In addition, the target gene and downstream pathway of miR-381-3p were further investigated both in vivo and in vitro. Results miR-381-3p expression was elevated, whereas KLF5 was suppressed in OVX rats. miR-381-3p antagomir decreased serum levels of bone turnover markers, improved trabecular separation, promoted osteoblast differentiation biomarker expression in OVX rats. ALP activity and mineralization were suppressed, and levels of osteoblast differentiation biomarkers were impeded after miR-381-3p overexpression during osteoblast differentiation of OVX-BMMSCs. While contrasting results were found after inhibition of miR-381-3p. miR-381-3p targets KLF5, negatively affecting its expression as well as its downstream Wnt/β-catenin pathway, both in vivo and in vitro. Silencing of KLF5 restored Wnt/β-catenin activation induced by miR-381-3p antagomir. Conclusion miR-381-3p aggravates PMOP by inhibiting osteogenic differentiation through targeting KLF5/Wnt/β-catenin pathway. miR-381-3p appears to be a promising candidate for therapeutic intervention in PMOP.

The “seesaw relationship” between thermal conductivity and thermal expansion coefficient (CTE) in most high temperature ceramics has become an obstacle to the design of long-life multilayer thermal/environmental barrier coatings (T/EBC). Due to low thermal conductivity and CTE, defect fluorite type high-entropy rare earth (RE) hafnates have drawn a lot of interest for potential application in T/EBC systems. This work designs and synthesizes the (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7 with comprehensive thermal performance and investigates the thermophysical mechanism from the phonon scale. In addition to the lattice distortion effect caused by the point defects of multicomponent substitutional atoms in (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7, the oxygen vacancies in the defect fluorite lattice also play a critical role in reducing the thermal conductivity. From microscopic thermal expansion behavior, the low-frequency optic phonons originated from the vibration of RE atoms are the key factors in altering CTE for hafnates. And doping smaller RE ions is beneficial for enhancing the RE–O bond strength and further reducing CTE. The results contribute to the understanding of high-entropy strategic design and suggest that (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7 is a promising top layer material in the implementation of T/EBC.

During the boiling process, the heating surface has a substantial influence on the growth of the bubbles, the wetting of dry spots, and the deposition of the particles. Therefore, improving the surface properties is one of the main ways to enhance heat transfer. In this study the heating coatings were prepared by boiling deposition using GNP nanofluids, GNP/Ag mixed nanofluids, and GNP-Ag hybrid nanofluids with different mass fractions (wt% = 0.001,0.002,0.003) as raw materials. The boiling heat transfer characteristics of DI water on the bare copper surface and heating coatings were studied, and the heat transfer mechanism was analyzed. The results show that GNP-Ag hybrid nanoparticle coating has the most outstanding enhanced heat transfer effect. DI water achieves the highest critical heat flux (CHF) of 163.65 W/cm2 and heat transfer coefficient (HTC) of 9.69 W/cm2K on the coating, which are respectively 45.84% and 82.14% higher than the smooth copper surface. The wettability was analyzed by measuring the contact angle. Scanning electron microscope image was used to analyze the microstructure of the coating. The microstructure of Ag modified functionalized GNP nanoparticle has a great change compared with mixed nanoparticles. It was observed that the hybrid nanoparticle deposit into a large number of bulges and cavies, and the bulges accumulate in clusters and form self-assembled flower-shaped bulges. Combined with the energy spectrum test results of the heating coating, the coverage of the nanoparticles in the coating on the copper substrate and the variation trend of each deposited element with the concentration are analyzed. The novel heating coating enhances heat transfer under the combined action of nanoparticle functional groups, coating microstructure, and wettability. GNP-Ag hybrid nanoparticle coating was applied towards the heat dissipation of electronic devices. When the input power is 300 W, the maximum temperature of electronic devices is 108.52 °C, which is much lower than that of other coatings.

With the increasingly stringent CO2 emission regulations, the degree of strengthening of the engines is increasing. Under high-pressure conditions, the airway throat parts of the intake and exhaust systems have a great influence on the flow loss of the diesel engine. The reasonable distribution of the throat area of the intake and exhaust ports in the limited cylinder headspace is key to improving the performance of supercharged engines. This study took a large-bore, high-pressure ratio diesel engine as the research object. Firstly, the three-dimensional (3D) flow simulation method was used to reveal the influence law of different throat areas on the engine intake and exhaust flow under steady-state conditions, and a steady-flow test bench was built to verify the accuracy of the simulation model and law. Secondly, based on the 3D steady-state calculation and test results, a more accurate one-dimensional simulation model was constructed, and a joint optimization simulation platform was established based on the dynamic data link library. On this basis, the mathematical description of the multi-objective optimization of airway throat size was established using machine learning methods, such as a genetic algorithm, the design domain and boundary conditions of variable parameters were clarified, and the collaborative optimization objective of integrated flow coefficient and flow loss is proposed to achieve the fast and accurate optimization of intake and exhaust throat diameters.

The experimental study on the boiling heat transfer performance and visualization of Al2O3-H2O, SiO2-H2O and Al2O3-SiO2-H2O nanofluids with 0.01% mass concentration were carried out. Alumina and silica nanoparticles with average particle diameters of 30 nm and 50 nm were selected. Al2O3-SiO2-H2O was the mixed aqueous nanofluids with a mass ratio of Al2O3 to SiO2 of 1: 1. The results show that the effect of particle size on the boiling heat transfer performance is small. For nanofluids with a particle size of 30 nm, the boiling heat transfer performance of Al2O3-H2O nanofluids is better than that of Al2O3-SiO2-H2O and SiO2-H2O nanofluids under the working pressure of 101 kPa. The critical heat fluxes increased by 7.9% and 22.1% respectively, and the maximum heat transfer coefficients increased by 18.3% and 32.6% respectively. The critical heat flux and the maximum heat transfer coefficient are 162.1 W/cm2 and 7.01W/(m2·K). The working pressure has an important effect on the boiling heat transfer performance of nanofluids. Compared with the boiling heat transfer performance under high pressure conditions, the boiling heat transfer performance of nanofluids is better under low pressure.

In this paper, a three dimensional mathematical model of zinc-ickel single flow battery with 32-cells was established for flow field analysis. Based on the non-uniformity index, the analyses of the internal flow field and the non-uniformity for the stack structure were carried out. On the basis above, the channel structure at the bottom and the inlet were changed to realise internal flow field optimisation of the battery. Simulation results show that decreasing the distance between the plate and the inlet channel, adding a baffle in front of the inlet channel and adjusting the inclination of the trapezoidal channel can make the flow field distribution inside the battery more uniform. [ABSTRACT FROM AUTHOR]

A three-dimensional steady state model of internal reaction and mass transfer has been established for a better understanding of electrochemical performance of zincnickel single flow battery (ZNB). Combining with a global kinetic, the model is based on a comprehensive description of mass, momentum, charge for reactions considering the flow between anode and cathode, species transport, and electrochemical reaction between electrodes and electrolyte. This paper emphasizes an internal ion concentration and electrode current density distribution of the ZNB. The effect of channel width and electrolyte flow rate on the electrochemical performance is also studied in the simulation. In addition, the verification of the mathematical model is illustrated by the agreement between the numerical and experimental I-V curves. [ABSTRACT FROM AUTHOR]