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Polarization conversion dichroism is of particular interest in manipulating the polarization state of light, whereas high-performance asymmetric transmission (AT) of linearly polarized waves is still inaccessible in the terahertz range. Here, a bilayer chiral metamaterial consisting of orthogonally chained S-shaped patterns with broken symmetry along the light propagation direction is proposed and demonstrated experimentally to realize a dual-band dichroic AT effect for linearly polarized terahertz waves. The AT effects are robust across a wide range of incident angles. The observed strong AT can be theoretically explained by a multiple reflection and transmission interference model and the transfer matrix method. The proposed bilayer chiral metamaterial may have broad applications in polarization manipulation, chiral biosensing and direction-dependent information processing.

In the field of hyperspectral target detection, algorithms based on collaborative representation have shown excellent performance. However, the pollution of background dictionaries by anomaly has always been a problem, which affects the detection performance of this algorithm partly. This paper proposes an improved collaborative representation algorithm for hyperspectral anomaly detection, and designs a double-layer collaborative representation structure. Firstly, the first layer collaborative representation algorithm is used to detect most of the anomaly. Its neighborhood pixels are used for background purification to eliminate the pollution of the detected anomaly on the background dictionary. Then, the purified background dictionary is used to predict the background, and in the second layer, the collaborative representation is used for anomaly detection. Simulation experiments show that a simple double layer collaborative representation structure can effectively alleviate the background pollution caused by anomaly. The detection performance of this algorithm is significantly improved compared to the basic collaborative representation algorithm, and it also has relatively good detection performance.

We numerically and experimentally investigate collective resonant responses of coherent metasurfaces consisting of planar random-flip asymmetrically split rings. The collective narrow band response becomes broader and eventually disappears with increasing the percentage of flipped split rings. The exploited physical mechanism is the degraded collective response due to random microscopic multipole excitation. Our study provides a method to construct random metasurfaces and is helpful to have an insight into their underlying physics. [ABSTRACT FROM AUTHOR]

Optical chiral metasurfaces with high quality factors enhance light–matter interactions. However, intrinsic chirality based on breaking the symmetry-protected BIC hardly reveals strong circular dichroism (CD) against structural perturbations. Here, we propose a design of the intrinsic chirality empowered by a pair of off-Γ accidental BICs and demonstrate a robust intrinsic chiroptical response continuously exhibiting strong and sign-controllable transmitted CD up to 0.98 and stable high-quality factors under a wide range of perturbations of geometrical parameters. A triangular lattice with slant T-shaped meta-atoms is employed to break all mirror symmetries. The at-Γ quality factor of the chiral resonance is enhanced by four C points and maintains the range of 105–106. Our work is beneficial for designing chiral metasurfaces with a strong intrinsic chirality. [ABSTRACT FROM AUTHOR]

To mitigate the challenges posed by transient oscillations and steady-state deviations in the traditional virtual synchronous generator (TVSG) that is subjected to active power and grid frequency disturbances, a VSG control strategy based on Transient Damping Compensation and Virtual Inertia Adaptation is presented. Initially, a closed-loop small-signal model for the grid-connected active power loop (APL) of the TVSG is constructed, which highlights the contradiction between the dynamic and static characteristics of TVSG output power through the analysis of root locus distribution trends. Secondly, a VSG control strategy based on Transient Damping Compensation (TDC) is proposed. The influence of APL system parameters introduced by TDC on system stability is qualitatively analyzed based on pole distribution trends and frequency response, and a comprehensive parameter design scheme is presented. In addition, based on the TDC algorithm, an improved virtual inertia adaptive strategy utilizing the Inverse Square Root Unit (ISRU) approach is designed, and the tuning range of parameters is provided. Finally, simulations and experiments verify that the proposed strategy exhibits superior active response performance and transient oscillation suppression capabilities, effectively eliminating active steady-state deviations caused by frequency disturbances in the power grid. [ABSTRACT FROM AUTHOR]

The aryl hydrocarbon receptor (AhR) plays a crucial role in regulating many physiological processes. Activating the AhR–CYP1A1 axis has emerged as a novel therapeutic strategy against various inflammatory diseases. Here, a practical in situ cell-based fluorometric assay was constructed to screen AhR-CYP1A1 axis modulators, via functional sensing of CYP1A1 activities in live cells. Firstly, a cell-permeable, isoform-specific enzyme-activable fluorogenic substrate for CYP1A1 was rationally constructed for in-situ visualizing the dynamic changes of CYP1A1 function in living systems, which was subsequently used for discovering the efficacious modulators of the AhR–CYP1A1 axis. Following screening of a compound library, LAC-7 was identified as an efficacious activator of the AhR–CYP1A1 axis, which dose-dependently up-regulated the expression levels of both CYP1A1 and AhR in multiple cell lines. LAC-7 also suppressed macrophage M1 polarization and reduced the levels of inflammatory factors in LPS-induced bone marrow-derived macrophages. Animal tests showed that LAC-7 could significantly mitigate DSS-induced ulcerative colitis and LPS-induced acute lung injury in mice, and markedly reduced the levels of multiple inflammatory factors. Collectively, an optimized fluorometric cell-based assay was devised for in situ functional imaging of CYP1A1 activities in living systems, which strongly facilitated the discovery of efficacious modulators of the AhR–CYP1A1 axis as novel anti-inflammatory agents. An optimized fluorometric cell-based assay was devised for in situ functional imaging of CYP1A1 activities in living systems, which was used for discovering efficacious AhR–CYP1A1 axis activators as novel anti-inflammatory agents. [Display omitted] [ABSTRACT FROM AUTHOR]