A high efficiency and great tunability of bandwidth and absorption‐range electromagnetic wave absorber is proposed without precedent. A series of 2D carbon‐based nanocomposites with the loading of ...cerium oxide (CN‐Ce) and other types of rare earth oxides (CN‐REOs) can be successfully synthesized by a simple solvothermal‐sintering method. As‐synthesized 2D nanocomposites with local graphite‐like C3N4 structure and trace N‐doped are identified by transmission electron microscopy, X‐ray photoelectron spectroscopy, X‐ray powder diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. The CN‐REOs and polyvinylidene fluoride composite absorbers with reflection loss values above −40 dB are obtained in C‐band, X‐band, and Ku‐band, respectively. The empirical rules on effective bandwidth and frequency range are discovered and summarized, which can be successfully realized by simply tuning the doping amount or type of REO. The mechanism is explained by enhanced attenuation and tunable impedance matching. In addition co‐filled samples by two types of CN‐REOs nanocomposites are prepared to support these findings and inspire the preparation of absorber with desirable frequency band in the range of 2–18 GHz.
In the system of composites of PVDF and trace n‐doped carbon nanocomposites loaded with rare earth oxide, a high‐performance electromagnetic wave‐absorbing composite with adjustable electromagnetic wave absorption frequency range and adjustable effective absorption width is obtained. Regular performance is found based on extensive experimental data and analysis of intrinsic performance. In addition, the empirical conclusions are well‐validated by co‐filled (CN‐Ce+CN‐Eu)/PVDF samples.
We report herein a catalyst‐free method to perform decarboxylative conjugated addition and hydrodecarboxylation of aliphatic N‐(acyloxy)phthalimides (redox active esters, RAEs) through ...photoactivation of electron‐donor‐acceptor (EDA) complex with Hantzsch ester (HE) in N,N‐dimethylacetamide (DMA) solution. The reactions present a green method to decarboxylatively construct carbon‐carbon bond and to perform hydrodecarboxylation with broad substrate scope and functional group tolerance under mild blue light irradiation condition without recourse of popularly used photoredox catalysts.
Nanoreactors with hollow structures have attracted great interest in catalysis research due to their void‐confinement effects. However, the challenge in unambiguously unraveling these confinement ...effects is to decouple them from other factors affecting catalysis. Here, we synthesize a pair of hollow carbon sphere (HCS) nanoreactors with presynthesized PdCu nanoparticles encapsulated inside of HCS (PdCu@HCS) and supported outside of HCS (PdCu/HCS), respectively, while keeping other structural features the same. Based on the two comparative nanoreactors, void‐confinement effects in liquid‐phase hydrogenation are investigated in a two‐chamber reactor. It is found that hydrogenations over PdCu@HCS are shape‐selective catalysis, can be accelerated (accumulation of reactants), decelerated (mass transfer limitation), and even inhibited (molecular‐sieving effect); conversion of the intermediate in the void space can be further promoted. Using this principle, a specific imine is selectively produced. This work provides a proof of concept for fundamental catalytic action of the hollow nanoreactors.
A pair of hollow carbon sphere (HCS) nanoreactors with PdCu nanoparticles encapsulated inside the HCS (PdCu@HCS) and supported outside the HCS (PdCu/HCS) have been prepared. Based on the two comparable systems, the void‐confinement effects of hollow nanoreactors in liquid‐phase hydrogenation have been extensively investigated in a two‐chamber reactor.
Absorbers with lightweight, low filler loading and broad absorption band are highly desirable for electromagnetic wave absorption field. Here, hollow Co1–xS microspheres constructed by nanosheets are ...fabricated via a facile synthetic method based on hydrothermal route. As an efficient wave absorber, the Co1–xS hollow spheres demonstrate excellent microwave absorption performance. With a weight content of only 3 wt%, the maximum reflection loss (RL) can reach as strong as −46.1 dB at 13.92 GHz and its qualified frequency bandwidth (with RL value over −10 dB) remarkably achieves 5.6 GHz, covering 35% of the entire measured bandwidth. In addition, compared with other cobalt sulfides (such as CoS2 and Co9S8), the Co1–xS microspheres with hollow structure exhibit more superior absorption intensity and broader qualified bandwidth. Therefore, this work provides a promising approach for the design and synthesis of hollow Co1–xS microspheres with lightweight and high‐performance microwave absorption.
The hollow Co1–xS microspheres with understanding microwave absorption performance are successfully fabricated through a facile hydrothermal route. The RLmax can reach to −46.1 dB at 13.92 GHz with an ultralow filler loading (3 wt%) and the effective frequency bandwidth is up to 5.6 GHz. Moreover, the possible wave absorption mechanism is also depicted comprehensively in this article.
Chiral symmetry and its spontaneous breaking play an important role both in the light hadron and heavy hadron systems. The chiral perturbation theory (χPT) is the low energy effective field theory of ...the Quantum Chromodynamics. In this work, we shall review the investigations on the chiral corrections to the properties of the heavy mesons and baryons within the framework of χPT. We will also review the scatterings of the light pseudoscalar mesons and heavy hadrons, through which many new resonances such as the Ds0∗(2317) could be understood.
Moreover, many new hadron states were observed experimentally in the past decades. A large group of these states is near-threshold resonances, such as the charged charmoniumlike Zc and Zcs states, bottomoniumlike Zb states, hidden-charm pentaquark Pc and Pcs states and the doubly charmed Tcc state, etc. They are very good candidates of the loosely bound molecular states composed of a pair of charmed (bottom) hadrons, which are very similar to the loosely bound deuteron. The modern nuclear force was built upon the chiral effective field theory (χEFT), which is the extension of the χPT to the systems with two matter fields. The long-range and medium-long-range interactions between two nucleons arise from the single- and double-pion exchange respectively, which are well constrained by the chiral symmetry and its spontaneous breaking. The short-distance interactions can be described by the low energy constants. Such a framework works very well for the nucleon–nucleon scattering and nuclei. In this work, we will perform an extensive review of the progress on the heavy hadronic molecular states within the framework of χEFT. We shall emphasize that the same chiral dynamics not only govern the nuclei and forms the deuteron, but also dictates the shallow bound states or resonances composed of two heavy hadrons.
Reduced graphene oxide (rGO)/Ni hybrids with different mass ratio are successful synthesized in order to tune the microwave absorption together with the electromagnetic shielding performance. By ...properly adjusting the permittivity and permeability derived from different contents of the rGO and Ni, an rGO/Ni composite with excellent microwave absorption properties is obtained. An optimal reflection loss value of −39.03 dB at 13 GHz is achieved for the composite with rGO/Ni ratio of 1:1, and the bandwidth less than −10 dB can reach up to 4.3 GHz (from 11 to 15.3 GHz) with a thickness of 2.0 mm. Furthermore, the composite with rGO/Ni ratio of 4:1 shows superior electromagnetic shielding performance as high as 52 dB, which far surpasses the best value for most carbon-based materials. Fundamental mechanisms for absorbing and shielding performance are discussed.
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Abstract
Tuning the magneto optical response and magnetic dynamics are key elements in designing magnetic metamaterials and devices. This theoretical study uncovers a highly effective way of ...controlling the magnetic permeability via shaping the magnonic properties of coupled magnetic waveguides separated by a nonmagnetic spacer with strong spin–orbit interaction (SOI). We demonstrate how a spacer charge current leads to enhancement of magnetic damping in one waveguide and a decrease in the other, constituting a bias-controlled magnetic parity–time (PT) symmetric system at the verge of the exceptional point where magnetic gains/losses are balanced. We find phenomena inherent to PT-symmetric systems and SOI-driven interfacial structures, including field-controlled magnon power oscillations, nonreciprocal propagation, magnon trapping and enhancement as well as an increased sensitivity to perturbations and abrupt spin reversal. The results point to a new route for designing magnonic waveguides and microstructures with enhanced magnetic response.
Tumor cells with stemness (stem‐cell) features contribute to initiation and progression of hepatocellular carcinoma (HCC), but involvement of long noncoding RNAs (lncRNAs) remains largely unclear. ...Genome‐wide analyses were applied to identify tumor‐associated lncRNA‐DANCR. DANCR expression level and prognostic values of DANCR were assayed in two HCC cohorts (China and Korea, n = 135 and 223). Artificial modulation of DANCR (down‐ and overexpression) was done to explore the role of DANCR in tumorigenesis and colonization, and tumor‐bearing mice were used to determine therapeutic effects. We found that lncRNA‐DANCR is overexpressed in stem‐like HCC cells, and this can serve as a prognostic biomarker for HCC patients. Experiments showed that DANCR markedly increased stemness features of HCC cells to promote tumorigenesis and intra‐/extrahepatic tumor colonization. Conversely, DANCR knockdown attenuated the stem‐cell properties and in vivo interference with DANCR action led to decreased tumor cell vitality, tumor shrinkage, and improved mouse survival. Additionally, we found that the role of DANCR relied largely on an association with, and regulation of, CTNNB1. Association of DANCR with CTNNB1 blocked the repressing effect of microRNA (miR)−214, miR‐320a, and miR‐199a on CTNNB1. This observation was confirmed in vivo, suggesting a novel mechanism of tumorigenesis involving lncRNAs, messenger RNAs, and microRNAs. Conclusions: These studies reveal a significance and mechanism of DANCR action in increasing stemness features and offer a potential prognostic marker and a therapeutic target for HCC. (Hepatology 2016;63:499–511)
Thielavin A (1) is a fungal depside composed of one 3‐methylorsellinic acid and two 3,5‐dimethylorsellinic acid units. It displays diverse biological activities. However, the mechanism underlying the ...assembly of the heterotrimeric structure of 1 remains to be clarified. In this study, we identified the polyketide synthase (PKS) involved in the biosynthesis of 1. This PKS, designated as ThiA, possesses an unusual domain organization with the C‐methyltransferase (MT) domain situated at the C‐terminus following the thioesterase (TE) domain. Our findings indicated that the TE domain is solely responsible for two rounds of ester bond formation, along with subsequent chain hydrolysis. We identified a plausible mechanism for TE‐catalyzed reactions and obtained insights into how a single PKS can selectively yield a specific heterotrimeric product. In particular, the tandem acyl carrier protein domains of ThiA are critical for programmed methylation by the MT domain. Overall, this study highlighted the occurrence of highly optimized domain–domain communication within ThiA for the selective synthesis of 1, which can advance our understanding of the programming rules of fungal PKSs.
The polyketide synthase ThiA that forms the heterotrimeric fungal depside thielavin A (1) has been identified and characterized. The thioesterase (TE) domain of ThiA was found to perform two consecutive esterification reactions as well as subsequent hydrolysis, and a plausible reaction mechanism for the TE‐catalyzed reactions has been proposed. Furthermore, this study provides insights into how ThiA selectivity yields the heterotrimeric product.
Partial least squares (PLS) is an efficient tool widely used in multivariate statistical process monitoring. Since standard PLS performs oblique projection to input space X, it has limitations in ...distinguishing quality-related and quality-unrelated faults. Several postprocessing modifications of PLS, such as total projection to latent structures (T-PLS), have been proposed to solve this issue. Further studies have found that these modifications fail to reduce false alarm rates (FARs) of quality-unrelated faults when fault amplitude increases. To cope with this problem, this paper proposes an enhanced quality-related fault detection approach based on orthogonal signal correction (OSC) and modified-PLS (M-PLS). The proposed approach removes variation orthogonal to output space Y from input space X before PLS modeling, and further decomposes X into two orthogonal subspaces in which quality-related and quality-unrelated statistical indicators are designed separately. Compared with T-PLS, the proposed approach has a more robust performance and a lower computational load. Two case studies, including a numerical example and the Tennessee Eastman (TE) process, show the effeteness of the proposed approach.
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