Search

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]

Electron backscatter diffraction (EBSD) can be employed to determine crystal structures but has not been used alone to identify defects at the atom scale due to the lack of understanding of the EBSD patterns generated by various structure defects. In the present work, the EBSD patterns of FCC‐Fe with 9‐layer, 6‐layer and 3‐layer twin structures are simulated, respectively, using the revised real space (RRS) method and compared with the counterpart of perfect crystals. Our results show that when the electron beam is incident along a direction parallel to the twin plane, the pattern appears symmetrical with respect to the corresponding Kikuchi band of the twin plane, and the diffraction details within the Kikuchi band also exhibit symmetry with respect to the middle line of the Kikuchi band. Moreover, the overall clarity of the patterns decreases, and the pattern becomes more blurred with increasing the distance from the Kikuchi band corresponding to the twin plane. By contrast, the incident electron beam along the direction perpendicular to the twin plane results in diffraction superposition of the matrix region and the shear region, which shows twofold rotational symmetry with respect to the Kikuchi pole corresponding to the normal to the twin plane. In addition, some extra Kikuchi bands appear in the EBSD patterns due to the long‐period structures of the multilayer twins. As the number of multilayer twins decreases, the number of extra Kikuchi bands decreases and the area of the blurring pattern increases. The correlation between twin structures and EBSD patterns provides theoretical insights for identifying twin structures by the EBSD technique. [ABSTRACT FROM AUTHOR]

B4C ceramics have been widely used in armor plate and cutting tools due to their high hardness. However, their poor sintering performance and low fracture toughness have limited their extended applications. In order to solve these problems, B4C@TiB2 composite powders with core–shell structure were prepared by a sol–gel method using B4C and TiCl4 as raw materials and then sintered by spark plasma sintering. The composite powders were characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, and scanning electron microscopy. The mechanical properties of B4C ceramics were tested by indentation and three‐point bending methods. The results showed that the B4C@TiB2 composite powders exhibited a tight core–shell structure, and the chemical bonds on the surface were mainly B–C and B–Ti bonds. When the molar ratio of B4C:TiCl4 was 2:1, the relative density and bulk density of B4C ceramics reached 96.2% and 2.92 g/cm3, respectively. Because of the good sintering performance of the B4C@TiB2 composite powders, the Vickers hardness and fracture toughness reached 26.6 GPa and 5.22 MPa m1/2, respectively. The bending strength reached a maximum of 570 MPa. The excellent fracture toughness can be attributed to crack deflection, crack branching, and the residual thermal stress of the core–shell structure. [ABSTRACT FROM AUTHOR]

Excellent thermostable performance is the basis for the further development of microwave absorbing materials in the field of military stealth. Herein, a high‐temperature metamaterial absorber (HMA) with high impedance patterns (multi‐octagonal‐rings), two quartz (SiO2) layers, and a metallic ground film is designed and simulated. The optimal structural parameters are obtained by optimizing the circuit parameters and the size of HMA. The interaction of electric and magnetic resonance in multioctagonal rings results in a wide absorption bandwidth and excellent absorption performance. The experimental results show that the structure has good impedance matching performance, and the effective absorption bandwidth (−10 dB) (EAB) of the structure can reach 10.6 GHz from room temperature to 700 °C under the combined effect of resonance loss and ohmic loss. [ABSTRACT FROM AUTHOR]

Herein, an ideal metamaterial absorber with broadband, ultrathin, and wide incidence angle is proposed. The absorption unit of the proposed metamaterial absorber consists of two double rings. And, eight chip resistors are loaded between them to increase the absorption bandwidth. It is showed in the simulation results that the structure absorbs more than 90% in the range of 8.6–17.4 GHz at vertical incidence. The total thickness of the absorber is 2.4 mm (0.069 λL), where λL is the lowest‐absorption frequency, smaller than the absorber structure of the same type of bandwidth. To understand the broadband absorption performance of this absorber, the effects of design parameters such as substrate thickness and resistive resistance are investigated. In addition, herein, to investigate the absorption mechanism of this absorber, the normalized impedance, electric field distribution, and surface current density are demonstrated. Finally, the absorber is fabricated and measured at vertical incidence, and the experimental results are in good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

A transmission‐type metasurface (MS) based on the combined geometric and transmission phase is proposed and investigated here numerically, which can achieve independently manipulation of the circular polarization (CP) and linear polarization (LP) wavefront at terahertz (THz) region. The unit‐cell of the proposed MS is composed of the dielectric substrate sandwiched with the bilayered inner centrosymmetric‐notched‐elliptic (CNE), outer C‐shaped, and single‐split‐ring (SSR) structures. The proposed MS can convert the normal incident LP wave to its orthogonal one at the lower frequency (f1 = 0.68 THz) after transmission and left‐handed circular polarization to the transmitted right‐handed circular polarization wave or vice versa at the higher frequency (f2 = 1.34 THz). The full 2π phase shifts of the both transmitted LP and CP waves can be realized independently and simultaneously by varying the opening and orientation angles of the outer SSR structure based on the transmission phase and the orientation angle of the inner CNE structure based on geometric phase, respectively. As proofs of concept, anomalous refraction, planar focusing, and vortex beam generation for both LP and CP waves are demonstrated numerically. These findings show great potential applications in imaging and communication systems, providing new possibilities to develop multifunctional THz device for both LP and CP waves. [ABSTRACT FROM AUTHOR]

A broadband metamaterial absorber (MA) with high‐temperature resistance is designed and fabricated using a regular octagonal ring‐cross structure as a frequency‐selective surface (FSS). A high‐temperature conductive paste and SiO2 are used as the FSS raw materials and middle layer, respectively. Simulation and experimental results show that the absorber reaches a reflection loss below −5 dB at the 5.17–18 GHz range with normal incidence at room temperature. The measured values are in good agreement with the simulation results. At 800 °C, the absorption bandwidth expands to 13.3 GHz (4.72–18 GHz). The equivalent impedance of the absorber is obtained using an inversion method to qualitatively explain its working mechanism. The electric energy density, magnetic energy density, and surface current at the resonance frequency provide an intuitive understanding of the power loss of the structure. Comprehensive analysis illustrates that the main absorption mechanisms of the high‐temperature broadband MA (HBMA) are ohmic and resonance losses. [ABSTRACT FROM AUTHOR]

Liver fibrosis is a progressive disease accompanied by the deposition of extracellular matrix (ECM). Numerous reports have demonstrated that alterations in the expression of microRNAs (miRNAs) are related to liver disease. However, the effect of individual miRNAs on liver fibrosis has not been studied. Hepatic stellate cells (HSCs), being responsible for producing ECM, exert an important influence on liver fibrosis. Then, microarray analysis of non‐activated and activated HSCs induced by transforming growth factor β1 (TGF‐β1) showed that miR‐130b‐5p expression was strongly up‐regulated during HSC activation. Moreover, the progression of liver fibrosis had a close connection with the expression of miR‐130b‐5p in different liver fibrosis mouse models. Then, we identified that there were specific binding sites between miR‐130b‐5p and the 3′ UTR of Sirtuin 4 (SIRT4) via a luciferase reporter assay. Knockdown of miR‐130b‐5p increased SIRT4 expression and ameliorated liver fibrosis in mice transfected with antagomiR‐130b‐5p oligos. In general, our results suggested that miR‐130b‐5p promoted HSC activation by targeting SIRT4, which participates in the AMPK/TGF‐β/Smad2/3 signalling pathway. Hence, regulating miR‐130b‐5p maybe serve as a crucial therapeutic treatment for hepatic fibrosis. [ABSTRACT FROM AUTHOR]

To explore the effects of air‐sea interaction on the eyewall replacement cycle (ERC) of tropical cyclones (TCs), an ERC of Typhoon Sinlaku (2008) was reproduced using the high‐resolution coupled ocean‐atmosphere‐wave‐sediment transport (COAWST) model. The numerical simulations were evaluated with a wide range of observational datasets. Moreover, the importance of the ocean to ERC is discussed by comparing six sensitive experiments, that is, three uncoupled experiments with different time‐invariant sea surface temperatures, an ocean‐atmosphere coupled experiment, an ocean‐wave coupled experiment, and an ocean‐atmosphere‐wave fully coupled experiment. The results show that Sinlaku simulated by the fully coupled experiment was highly consistent with the observations, and the evolution of ERC varies from those only simulated by the atmospheric models in previous studies. When the ocean and waves were both considered, the lifetime of the ERC was significantly prolonged, even though the simulated Sinlaku was weakened by the cooling of the sea; the asymmetric distribution of the concentric eyewalls (CEs) which caused by the non‐uniform energy exchanges was also prominent. By contrast, without ocean coupling, the simulated secondary eyewall, composed of axisymmetric convections, exhibited false enhancement and fake inward contraction, and the duration of the ERC was also shorter than that actually observed. In conclusion, the results highlight the significance of ocean coupling for the numerical simulation of the ERC of a TC, including survival time and asymmetric structure.Plain Language Summary: A tropical cyclone (TC) is a severe weather system that is generated on warm tropical ocean and brings strong wind, heavy rainfall, and drastic storm surge. The eyewall of a TC is the most disaster‐prone area. In an intense TC, there are often two concentric eyewalls (CEs) over a period of time due to an eyewall replacement cycle (ERC), which is an important process that affects TC intensity and rainfall forecast. However, little work has been done to accurately forecast a real case of an ERC under the real atmospheric and ocean conditions. Therefore, our study aims to reproduce an ERC of Typhoon Sinlaku (2008) by the fully coupled ocean‐atmosphere‐wave model and validate the accuracy of simulations against the observations. The results show that the duration of the ERC and CEs structure are very sensitive to the underlying ocean, and air‐sea interaction is requisite for accurate simulation of CEs. On the basis of successful simulation under air‐sea interaction, the subsequent theoretical research for CEs can be more reliable and convincing.Key Points: The eyewall replacement cycle can be successfully simulated by the air‐sea coupled model at a high resolutionThe ocean plays a significant role in the formation and duration of the eyewall replacement cycleA long survival time and asymmetric structure of the secondary eyewall were reproduced when the ocean was considered [ABSTRACT FROM AUTHOR]

The mechanical properties, thermal shock resistance, and microstructure evolution of corundum spinel castables with different nano‐alumina contents were investigated. The results show that the addition of nano‐alumina has advantages on the microstructure evolution and properties of castables. An optimum nano‐alumina amount is 2 wt%. When nano‐alumina addition changes from 0 to 2 wt%, the cold modulus of rupture (CMOR) and cold compressive strength (CCS) improved by 69.7% and 78.1% after firing at 1100°C, respectively. The CMOR and CCS increased by 42.5% and 35.2% after firing at 1500°C, respectively. Meanwhile, the hot modulus of rupture (HMOR) was enhanced by 21.5% to 13.4 MPa. The retained Young's modulus values of castables were improved from 49.6% to 59.6% after eight thermal shock cycles. Furthermore, the HMOR and the retained Young's modulus values of castables slightly reduced when nano‐alumina content up to 3 wt%. XRD, DSC, SEM, and EDS analyses revealed that the addition of nano‐alumina leads to the formation of calcium dialuminate (CaO·2Al2O3) at 1100°C and it is beneficial to the formation of more platelet hibonite (CaO·6Al2O3) at 1500°C. As a result of using nano‐alumina with large surface area, the solid phase sintering of the nanoscale particles can occur at lower temperatures. Moreover, the mechanical properties and thermal shock resistance of the castables were improved remarkably. [ABSTRACT FROM AUTHOR]

Al2O3–SiC–C composites were prepared using tabular corundum, ball pitch and silicon carbide as the main raw materials. The carbon nanotubes (CNTs) and SiC whiskers (SiCw) were in situ synthesized and their effects on the thermo–mechanical properties of Al2O3–SiC–C composites have been studied. The experimental results indicated that the high yield of SiCw and CNTs with large aspect ratio could be obtained due to addition of Ni(NO3)2·6H2O as catalyst in the composites. The cold modulus of rupture values were increased by 24% to 7.2 MPa, and the flexural modulus was increased from 19 GPa to 24 GPa. Additionally, the hot modulus of rupture reached a maximum value of 3.6 MPa, which presented a 71% increase over that of composites without catalyst. After three thermal shock cycles, the residual cold crush strength was improved from 57.1% to 76.9%. It is believed that the enhancement in the thermo‐mechanical properties of Al2O3–SiC–C composites could be attributed to the reinforcement effect of SiCw and CNTs. [ABSTRACT FROM AUTHOR]

Abstract: The complete transformation of lignocellulosic biomass into valuable platform chemicals is of great significance. Herein, a catalytic process for the upgrading of lignocellulose to arenes, 5‐hydroxymethylfurfural (HMF), and furfural is reported. Firstly, the lignin fraction in lignocellulosic biomass is selectively converted into lignin oil (82.9 mol % yield of lignin monomers from birch wood) over a Pd/C catalyst and then further hydrodeoxygenated to arenes in catalytic hydrogen‐transfer reactions over a Ru/Nb2O5 catalyst. High yields of C7–C9 hydrocarbons (95.6 mol %) with 85.6 wt % selectivity to arenes based on lignin oil are achieved owing to the synergistic effect between Ru and Nb2O5, which enables direct hydrogenolysis of the Caromatic−OH bond in phenolics. Secondly, the cellulose and hemicellulose fractions in the Pd/C‐containing solid residue, as well as methylated C5 sugars produced during the stripping of lignin, are converted into HMF and furfural with a total yield of up to 24.5 wt % (based on the amount of birch wood) in a THF/concentrated seawater (ca. 30 wt % salts) biphasic reaction system. Here, seawater played a key role in the conversion of cellulose and hemicellulose into HMF and furfural, respectively; more importantly, it made the separation and reuse of the Pd/C catalyst easier. With this catalytic process, the complete and efficient transformation of lignocellulose into highly value‐added products with recycling of each catalyst and solvent has been realized. [ABSTRACT FROM AUTHOR]

The conversion of glucose and selectivity into 5-hydromethylfurfural (HMF) were investigated over various silica-alumina composite (AlSiO) catalysts. The type, amount, and strength of the acidic sites were characterized by using NH3 temperatureprogrammed desorption and FTIR spectroscopy and then correlated to the catalytic conversion of glucose into HMF to provide a quantitative relationship between the acidity and product selectivity. Lewis acid sites played an important role in glucose conversion, which can enhance the isomerization of glucose to fructose, whereas Brønsted acid sites had a detrimental effect. HMF selectivity had an almost linear relationship with the weak/total Lewis acid ratio (L*/L), indicating that weak Lewis acids could promote formation of HMF. The medium-tostrong Lewis acid sites can enhance the formation of undesired byproducts (levulinic acid, humins). The Brønsted to Lewis acid ratio (B/L) had an influence on the HMF selectivity; at similar L*/L ratios, volcano curves were obtained with the increase of the B/L ratio, but the influence was not as great as that of the L*/L ratio. Nb-doped AlSiO catalysts were prepared and used in the conversion of glucose into HMF, which also confirmed the above findings. Under the optimized conditions, the HMF selectivity can reach 71% at 92.6% conversion of glucose with no clear decline after four catalytic cycles. [ABSTRACT FROM AUTHOR]

The physical properties, including flow value, apparent porosity, and mechanical strength, increased significantly with submicron spinel contents in this study. The excellent physical properties can be attributed to the close-packed microstructure and high bonding strength between spinel and aggregates/matrix. Additionally, the submicron spinel powders promoted the formation of tabular CA6 grains that generated a cross-linked structure and enhanced the mechanical properties. The microstructures of corroded castables suggested that submicron spinel powders contributed to the formation of a continuous and thick spinel layer at the slag-refractory interface and subsequently improved the slag resistance of the castables. [ABSTRACT FROM AUTHOR]

Background and Aim One single-nucleotide polymorphisms ( SNPs) rs738409 in the patatin-like phospholipase domain-containing 3 gene ( PNPLA3) has been implicated in susceptibility to non-alcoholic fatty liver disease ( NAFLD) across different populations. One meta-analysis confirmed this association, but within it, only two Asian studies were included. This meta-analysis aimed to investigate the association in Asian population. Methods All eligible case-control studies were identified by searching through PubMed and Chinese language databases ( CNKI and WanFang) up to July 1, 2014. Pooled estimates (odds ratio [OR] and standardized mean difference) were used to assess the strength of associations in fixed or random-effects models. Results A total of 12 studies with 4495 cases and 7431 controls were included. SNP rs738409 G allele was confirmed as a risk factor for NAFLD ( G allele vs C allele: OR = 1.92, 95% confidence interval [95% CI]: 1.54-2.39). In addition, based on studies with certain clinical measurements data, G allele carriers were more likely to have higher level of serum alanine aminotransferase ( ALT) (standard mean difference [ SMD] = 7.03, 95% CI: 2.47-11.60), and higher fibrosis score ( SMD = 0.39, 95% CI: 0.18-0.60). Conclusion This study provided evidence of SNP rs738409 G allele as a strong risk factor of NAFLD susceptibility and higher level of serum ALT in Asian population. [ABSTRACT FROM AUTHOR]

Background and Aim Downregulation of the WW domain containing oxidoreductase ( WWOX) has been reported to be involved in tumorigenesis in several neoplasms. This study sought to investigate the expression and role of WWOX in intrahepatic cholangiocarcinoma ( ICC). Methods WWOX expression was measured by quantitative real-time polymerase chain reaction ( PCR), immunoblot, immunofluorescence, and immunohistochemistry. The prognostic significance was assessed by Kaplan- Meier and Cox regression analyses. The role of WWOX in proliferation, anchorage-independent growth, gene expression regulation, and tumorigenesis was assessed by WWOX re-expression using lentivirus. Methylation-specific PCR was performed to evaluate the methylation status of the WWOX gene regulatory region. A DNA methyltransferase inhibitor, 5-aza-2′-deoxycytidine ( AZA), was used to activate the endogenous WWOX gene in ICC cells both in vitro and in vivo. Results The expression of WWOX in ICC tissues was much lower than that in nontumorous samples and showed reverse correlation with proliferative status. Restoration of WWOX expression resulted in suppression of the growth of WWOX-deficient ICC cells through activation of the intrinsic apoptotic signaling pathway, but did not affect growth of WWOX-sufficient human intrahepatic biliary epithelial derived non-cancer cells. Multivariate analyses revealed that downregulation of WWOX was an unfavorable predictor for overall survival and cumulative recurrence rates. The WWOX gene regulatory region was frequently methylated in ICC tissues and cell lines, and intratumoral WWOX restoration, through AZA injection, suppressed tumor growth in nude mice. Conclusion Downregulation of WWOX may occur as a result of hypermethylation and implies a poor prognosis in ICC; WWOX re-expression may be a potential molecular therapeutic target for ICC. [ABSTRACT FROM AUTHOR]

Background and Aims Methods Results Conclusions Increasing evidence suggested that miRNAs regulated the expression of pivotal genes involved in oncogenesis and malignant phenotype. In this project, the purpose was to make an inquiry to the effect and mechanism of miR‐182‐5p in the progression of cholangiocarcinoma.By analysing TCGA and GEO databases, combined with tissue expression levels, miR‐182‐5p was identified as one of the most valuable miRNAs for research. The function and relationships between miR‐182‐5p and downstream target genes were both verified by in vitro and in vivo experiments. Methylation‐specific PCR and bisulphite sequencing were used to detect the methylation level changes of downstream gene promoter.We found that miR‐182‐5p could be taken up by exosomes secreted from cholangiocarcinoma. Moreover, exosomal derived miR‐182‐5p promoted vascular endothelial cell proliferation and migration and induced angiogenesis by targeting ADK/SEMA5a. Subsequently, the PI3K/AKT/mTOR signalling pathway was activated and ultimately caused resistance to gemcitabine and cisplatin.Our findings suggested that the miR‐182‐5p/ADK/SEMA5a axis might serve as a potential therapeutic target for cholangiocarcinoma. [ABSTRACT FROM AUTHOR]

Background and Aims: Increasing evidence suggested that miRNAs regulated the expression of pivotal genes involved in oncogenesis and malignant phenotype. In this project, the purpose was to make an inquiry to the effect and mechanism of miR-182-5p in the progression of cholangiocarcinoma., Methods: By analysing TCGA and GEO databases, combined with tissue expression levels, miR-182-5p was identified as one of the most valuable miRNAs for research. The function and relationships between miR-182-5p and downstream target genes were both verified by in vitro and in vivo experiments. Methylation-specific PCR and bisulphite sequencing were used to detect the methylation level changes of downstream gene promoter., Results: We found that miR-182-5p could be taken up by exosomes secreted from cholangiocarcinoma. Moreover, exosomal derived miR-182-5p promoted vascular endothelial cell proliferation and migration and induced angiogenesis by targeting ADK/SEMA5a. Subsequently, the PI3K/AKT/mTOR signalling pathway was activated and ultimately caused resistance to gemcitabine and cisplatin., Conclusions: Our findings suggested that the miR-182-5p/ADK/SEMA5a axis might serve as a potential therapeutic target for cholangiocarcinoma., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)