Search

Atherosclerotic plaque formation is largely attributed to the impaired efferocytosis, which is known to be associated with the pathologic upregulation of cluster of differentiation 47 (CD47), a key antiphagocytic molecule. By gene expression omnibus (GEO) datasets analysis, we identified that four miRNAs are aberrantly downregulated in atherosclerosis, coronary artery disease, and obesity. Of them, hsa‐miR‐299‐3p (miR‐299‐3p) was predicted to target the 3′UTR of human CD47 mRNA by bioinformatics analysis. Further, we demonstrated that miR‐299‐3p negatively regulates CD47 expression by binding to the target sequence "CCCACAU" in the 3′UTR of CD47 mRNA through luciferase reporter assay and site‐directed mutagenesis. Additionally, we found that miR‐299‐3p was downregulated by ~32% in foam cells in response to oxidized low‐density lipoprotein (ox‐LDL) stimulation, thus upregulating CD47 and contributing to the impaired efferocytosis. Whereas, restoration of miR‐299‐3p reversed the ox‐LDL‐induced upregulation of CD47, thereby facilitating efferocytosis. In high‐fat diet (HFD) fed ApoE−/− mice, we discovered that miR‐299‐3p was downregulated thus leading to upregulation of CD47 in abdominal aorta. Conversely, miR‐299‐3p restoration potently suppressed HFD‐induced upregulation of CD47 and promoted phagocytosis of foam cells by macrophages in atherosclerotic plaques, thereby reducing necrotic core, increasing plaque stability, and mitigating atherosclerosis. Conclusively, we identify miR‐299‐3p as a negative regulator of CD47, and reveal a molecular mechanism whereby the ox‐LDL‐induced downregulation of miR‐299‐3p leads to the upregulation of CD47 in foam cells thus contributing to the impaired efferocytosis in atherosclerosis, and propose miR‐299‐3p can potentially serve as an inhibitor of CD47 to promote efferocytosis and ameliorate atherosclerosis. [ABSTRACT FROM AUTHOR]

SiBCN ceramics have a wide range of applications in the field of high temperature electromagnetic wave (EMW) absorption owing to their excellent EMW attenuation and oxidation resistance. However, excessive SiC and insufficient Si3N4 in the SiBCN ceramics deteriorate the impedance matching characteristics, and weaken the absorption ability for EMW. In this paper, the amount of SiC and Si3N4 is balanced by a competitive reaction strategy, in which HfZr atoms are introduced to modulate the dielectric phases in the SiBCN ceramics. The formation of a HfZrCN compound produces a cage-like structure around Si3N4, inhibiting the reaction of Si3N4 with carbon to form SiC. The appropriate amounts of SiC and Si3N4, and the abundant interfaces and defects jointly enhance the EMW absorption capability by simultaneously improving the impedance matching and attenuation capability. Thus, an effective absorption band of 4.96 GHz (11.20–16.16 GHz) is reached with a thickness of 1.7 mm for the HfZr-SiBCN ceramics. This work provides a new strategy for simultaneously improving the impedance matching and EMW attenuation capability of polymer-derived ceramics by introducing difficult-to-migrate atoms to regulate the content of the dielectric phase. [ABSTRACT FROM AUTHOR]

So far, developed microwave absorbers exhibit significant changes in absorption with temperature, which hinder their operation within a wide temperature range. In this paper, a microwave absorber based on SiBCN ceramics was prepared. Due to the excellent high‐temperature stability of SiBCN ceramics, its permittivity changes less with temperature, avoiding the issue of performance deterioration or even failure that traditional refractory absorbers face at high temperatures. The experiment proves the absorption bandwidth for –15 dB of the SiBCN metamaterials absorber (SMA) is 12 GHz at 800°C, with a maximum absorptivity of 99.99%. According to the computed data, the resonance loss contributes 81.9 to 94.5% of the microwave absorption of SMA. This work demonstrates significant potential for applications in radar stealth under harsh conditions. [ABSTRACT FROM AUTHOR]

Although human pluripotent stem cell (PSC)‐derived brain organoids have enabled researchers to gain insight into human brain development and disease, these organoids contain solely ectodermal cells and are not vascularized as occurs during brain development. Here it is created less complex and more homogenous large neural constructs starting from PSC‐derived neuroprogenitor cells (NPC), by fusing small NPC spheroids into so‐called concentroids. Such concentroids consisted of a pro‐angiogenic core, containing neuronal and outer radial glia cells, surrounded by an astroglia‐dense outer layer. Incorporating PSC‐derived endothelial cells (EC) around and/or in the concentroids promoted vascularization, accompanied by differential outgrowth and differentiation of neuronal and astroglia cells, as well as the development of ectodermal‐derived pericyte‐like mural cells co‐localizing with EC networks. Single nucleus transcriptomic analysis revealed an enhanced neural cell subtype maturation and diversity in EC‐containing concentroids, which better resemble the fetal human brain compared to classical organoids or NPC‐only concentroids. This PSC‐derived "vascularized" concentroid brain model will facilitate the study of neurovascular/blood‐brain barrier development, neural cell migration, and the development of effective in vitro vascularization strategies of brain mimics. [ABSTRACT FROM AUTHOR]

The contributions of local and remote forcings to the interannual sea level anomalies (SLAs) along the U.S. East Coast (USEC) during the satellite altimetry era from 1993 to 2019 are quantified with analytical models assisted by statistical methods. The local forcings from alongshore wind stress, sea level pressure via inverted barometer (IB) effect, and river discharges together explain 47%, 60.4%, and 66.8% of coastal sea level variance in the South Atlantic Bight (SAB), Mid-Atlantic Bight (MAB), and Gulf of Maine (GOM), respectively, with river discharges having the minimum contribution. Over a longer period of 1960–2019, the contribution of local forcings reduces significantly, with the IB effect having the minimum contribution. The remote forcings associated with open-ocean signals from the east and from the northern boundary at the Scotian coast together with the Gulf Stream (GS) variability explain 45.7%, 28.5%, and 37.7% of coastal sea level variance in the SAB, MAB, and GOM, respectively, playing a role comparable to that of local forcings in the SAB. The open-ocean sea level signals from 35° to 38°N strongly influence coastal SLAs in the SAB. The coastal SLAs in the SAB are also affected by the upstream GS strength (28°–36°N) and basin-scale wind stress curl anomaly, which is linked to the meridional shift in the downstream GS (74°–68°W). Remote forcings from the subpolar North Atlantic and wind stress curl from the Grand Banks to the Scotian coast influence coastal SLAs in the GOM and MAB via the northern boundary of the USEC at the Scotian coast. [ABSTRACT FROM AUTHOR]

Boron carbide (B4C) has excellent high-temperature oxidation resistance, high hardness, low relative density, high melting point and excellent abrasive resistance, which is widely used in fields such as refractories, wear-resistant materials and lightweight protective materials. The research progress and application of B4C materials in China and overseas in recent years were summarized. The influences of sintering processes (pressureless sintering, hot-pressing sintering, hot isostatic pressing sintering, spark plasma sintering and microwave sintering) and sintering additives (simple substances, oxides and carbides) on the B4C densification were analyzed. The development of B4C materials was prospected. [ABSTRACT FROM AUTHOR]

The rectangular pipe jacking method is an efficient, green, trenchless technology for constructing urban underground space. However, some problems, including the high jacking resistance, the instability of the tunneling face, and excessive ground settlement during the large-section rectangular pipe jacking for the underpass of national highways, seriously affect construction safety and traffic. Based on the engineering background of the large-section rectangular pipe jacking in constructing the subway entrance tunnel of Guangzhou Metro Line 7, this work adopts the methods of theoretical calculation, numerical simulation, and engineering application. Five kinds of mechanical models for pipe soil slurry interactions in rectangular pipe jacking are analyzed. An evaluation of the applicability of the jacking force prediction of the different models is conducted. Moreover, the ground settlement law for the large-section rectangular pipe jacking for the underpass of national highways under different influencing factors, including slurry sleeve thickness, grouting pressure, and earth chamber pressure, is revealed. The control countermeasures of the ground settlements, such as installing a waterproof rubber curtain for the tunnel portal, pipe jacking machine receiving techniques, thixotropic slurry for reducing friction resistance, and soil stability at the tunneling face, are carried out. The results show that there is no need to install an intermediate jacking station in the large-section rectangular pipe jacking project with a jacking distance of 63 m. The most reasonable thickness of the thixotropic slurry sleeve is about 150 mm. The most reasonable grouting pressure range is 600–700 kPa. An earth chamber pressure of about 153 kPa is more reasonable to control the soil stability of the tunneling face. The engineering practice shows that the maximum ground settlement of the national highway during jacking is 10 mm. The maintenance effect is excellent, and the traffic operates normally. [ABSTRACT FROM AUTHOR]