Microstructure and microhardness of aluminium alloy with underwater and in-air wire-feed laser deposition

This study carried out the underwater and in-air wire-feed laser deposition of an aluminium alloy with a thin-walled tubular structure. For both the underwater and in-air deposition layers, both were well-formed and incomplete fusion, cracks, or other defects did not exist.Compared with the single-track deposition layer in air, the oxidation degree of the underwater single-track deposition layer was slightly higher.In both the underwater and in-air deposition layers, columnar dendrites nucleated close to the fusion line and grew along the direction of the maximum cooling rate in the fusion region(FR), while equiaxed grains formed in the deposited region(DR). As the environment changed from air to water, the width of DR and height of FR decreased, but the deposition angle and height of DR increased. The grain size and ratio of the high-angle boundaries also decreased due to the large cooling rate and low peak temperature in the water environment.Besides, the existence of a water environment benefitted the reduction of magnesium element burning loss in the DR. The microhardness values of the underwater deposition layer were much larger than those of the in-air layer, owing to the fine grains and high magnesium content.

Commutative regulation between endothelial NO synthase and insulin receptor substrate 2 by microRNAs

Endothelial NO synthase (eNOS) expression is regulated by a number of transcriptional and post-transcriptional mechanisms, but the effects of competing endogenous RNAs (ceRNAs) on eNOS mRNA and the underlying mechanisms are still unknown. Our bioinformatic analysis revealed three highly expressed eNOS-targeting miRNAs (miR-15b, miR-16, and miR-30b) in human endothelial cells (ECs). Among the 1103 mRNA targets of these three miRNAs, 15 mRNAs share a common disease association with eNOS. Gene expression and correlation analysis in patients with cardiovascular diseases identified insulin receptor substrate 2 (IRS2) as the most correlated eNOS-ceRNA. The expression levels of eNOS and IRS2 were coincidentally increased by application of laminar shear but reduced with eNOS or IRS2 siRNA transfection in human ECs, which was impeded by Dicer siRNA treatment. Moreover, luciferase reporter assay showed that these three miRNAs directly target the 3′UTR of eNOS and IRS2. Overexpression of these three miRNAs decreased, whereas inhibition of them increased, both mRNA and protein levels of eNOS and IRS2. Functionally, silencing eNOS suppressed the Akt signal pathway, while IRS2 knockdown reduced NO production in ECs. Thus, we identified eNOS and IRS2 as ceRNAs and revealed a novel mechanism explaining the coincidence of metabolic and cardiovascular diseases.

The role of caveolae in endothelial dysfunction

Caveolae,the specialized cell-surface plasma membrane invaginations which are abundant in endothelial cells,play critical roles in regulating various cellular processes,including cholesterol homeostasis,nitric oxide production,and signal transduction.Endothelial caveolae serve as a membrane platform for compartmentalization,modulation,and integration of signal events associated with endothelial nitric oxide synthase,ATP synthaseβ,and integrins,which are involved in the regulation of endothelial dysfunction and related cardiovascular diseases,such as atherosclerosis and hypertension.Furthermore,these dynamic microdomains on cell membrane are modulated by various extracellular stimuli,including cholesterol and flow shear stress.In this brief review,we summarize the critical roles of caveolae in the orchestration of endothelial function based on recent findings as well as our work over the past two decades.

Interplay between entanglement and crosslinking in determining mechanical behaviors of polymer networks

In polymer physics,the concept of entanglement refers to the topological constraints between long polymer chains that are closely packed together.Both theory and experimentation suggest that entanglement has a significant influence on the mechanical properties of polymers.This indicates its promise for materials design across various applications.However,understanding the relationship between entanglement and mechanical properties is complex,especially due to challenges related to length scale constraints and the diffculties of direct experimental observation.This research delves into how the polymer network structure changes when deformed.We specifically examine the relationship between entanglement,crosslinked networks,and their roles in stretching both entangled and unentangled polymer systems.For unentangled polymers,our findings underscore the pivotal role of crosslinking bond strength in determining the system's overall strength and resistance to deformation.As for entangled polymers,entanglement plays a pivotal role in load bearing during the initial stretching stage,preserving the integrity of the polymer network.As the stretching continues and entanglement diminishes,the responsibility for bearing the load increasingly shifts to the crosslinking network,signifying a critical change in the system's behavior.We noted a linear correlation between the increase in entanglement and the rise in tensile stress during the initial stretching stage.Conversely,the destruction of the network correlates with a decrease in tensile stress in the later stage.The findings provide vital insights into the complex dynamics between entanglement and crosslinking in the stretching processes of polymer networks,offering valuable guidance for future manipulation and design of polymer materials to achieve desired'mechanical properties.