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Aim Myocardial infarction (MI) is a severe disease with increased mortality and disability rates, posing heavy economic burden for society. Exosomes were uncovered to mediate intercellular communication after MI. This study aims to explore the effect and mechanism of lncRNA KLF3-AS1 in exosomes secreted by human mesenchymal stem cells (hMSCs) on pyroptosis of cardiomyocytes and MI. Methods Exosomes from hMSCs were isolated and identified. Exosomes from hMSCs with transfection of KLF3-AS1 for overexpression were injected into MI rat model or incubated with hypoxia cardiomyocytes. Effect of KLF3-AS1 on MI area, cell viability, apoptosis, and pyroptosis was determined. The relationship among miR-138-5p, KLF3-AS1, and Sirt1 was verified by dual-luciferase reporter assay. Normal cardiomyocytes were transfected with miR-138-5p inhibitor or sh-Sirt1 to clarify whether alteration of miR-138-5p or sh-Sirt1 can regulate the effect of KLF3-AS1 on cardiomyocytes. Results Exosomes from hMSCs were successfully extracted. Transfection of KLF3-AS1 exosome in rats and incubation with KLF3-AS1 exosome in hypoxia cardiomyocytes both verified that overexpression of KLF3-AS1 in exosomes leads to reduced MI area, decreased cell apoptosis and pyroptosis, and attenuated MI progression. KLF3-AS1 can sponge miR-138-5p to regulate Sirt1 expression. miR-138-5p inhibitor transfection and KLF3-AS1 exosome incubation contribute to attenuated pyroptosis and MI both in vivo and in vitro, while transfection of sh-Sirt1 could reverse the protective effect of exosomal KLF3-AS1 on hypoxia cardiomyocytes. Conclusion LncRNA KLF3-AS1 in exosomes secreted from hMSCs by acting as a ceRNA to sponge miR-138-5p can regulate Sirt1 so as to inhibit cell pyroptosis and attenuate MI progression.

The aim of this study was to explore the mechanical properties of internally cured concrete with Super Absorbent Polymer (SAP). We studied the composite compression-shear properties of the concrete with varied water-cement ratios under different axial pressures. The compressive, splitting-tensile, and composite compression-shear mechanical properties of concrete examples were characterized by making SAP concrete (SAPC) specimens with different water-cement ratios. The failure modes of the concrete were compared and analyzed, and the load–displacement curves of SAPC under different axial pressures were obtained. The relationship between compression-shear strength, residual strength, and axial pressure was studied by analyzing the characteristic value of load–displacement curves. The results showed that the compression-shear strength and residual strength of SAPC increased linearly with the axial pressure, while the friction coefficient of compression-shear strength and cohesive stresses decreased with the increase of SAP content. By analyzing the compression-shear strength of SAPC, the failure criteria based on the octahedral stress space and twin-shear strength theory were established. The proposed failure criteria were verified by using experimental results of other concretes in literature. The verification results confirmed that the proposed failure criteria were efficient and beneficial for engineering applications of SAPC.

In order to investigate steady, external laminar mixed convection, mainly the correlations about the heat transfer and the critical Reynolds number around a horizontal rotating isothermal cylinder, a particularly manufactured micro-thermocouple is employed to measure the temperature distribution in the thermal boundary layer around the cylinder surface at different rotational speeds, n. The results indicate that there exists a critical Reynolds number Rer,cri as the mean Nusselt number Nu ¯ varies with the rotational Reynolds number Rer. The rotation of the cylinder can lead to a nonuniform distribution of local Nussel number Nuφ, and the phenomenon becomes more obvious as Rer exceeds Rer,cri. Nu ¯ changes according to a certain rule with Rer. As Rer Nu ¯ , and the free convection heat transfer plays a dominant role, but as Rer ≥ Rer,cri, Nu ¯ increases with increasing Rer, and the heat transfer characteristics are influenced by both the natural and the forced rotational convections simultaneously. Based on the experimental data, the correlations about the heat transfer can be expressed as Nu ¯ = 0.53 0.0018 R e r 2.66 + Gr ⋅ Pr 0.25 , and the critical Reynolds number Rer,cri can be determined by Rer,cri = 3.05(Gr ⋅ Pr)0.456.