Conformal frequency selective rasorber in S, C, X-band with low backward-scattering.

In this paper, a polarization-insensitive high transmittance bandpass filter with low radar cross section (RCS) in both S- and X-band is proposed. This is the first study to use the partition layout loading approach for conformal structures with transmissive windows, reducing the operating band RCS. Curved structures have stronger radiation at a smaller angle to the incident wave, and that is how their scattering differs from uniform scattering from flat structures. The structure is divided by analyzing the radiative contribution of different regions. The surface was discussed in regions according to surface angles, and a new partition layout loading method was used to suppress the side currents and decreased backward scattering, achieving a backward RCS reduction of more than 10 dB at 4-8 GHz (66.7%). The bandpass layer operating at 6.9 GHz is designed through equivalent circuit theory. In combination with the lossy layer, absorption above 0.8 at 3.7-5.6 GHz and 9.1-12.5 GHz was achieved. Further, the structure was fashioned into a curved surface with varying curvature, demonstrating its effective absorption and transmission properties across different curvatures. A 15 × 15 cell structure was designed and fabricated, and there was good agreement between the test results and simulation results. The proposed structure has important applications in radomes, conformal structures, and electromagnetic shielding.

Low-RCS low-profile MIMO antenna and array antenna using a polarization conversion metasurface.

A specially designed dumbbell type polarization conversion metasurface (PCM) is proposed. The designed PCM achieves line-to-line polarization conversion in ultra-wideband (UWB) from 7.63 GHz to 18.80 GHz. A low-profile metasurface antenna composed of PCM and slot feed is proposed based on characteristic mode analysis (CMA), which realizes the integrated design of radiation and scattering. Because of the checkerboard scattering properties, low-radar cross section (RCS) low-profile multiple-input-multiple-output (MIMO) antenna and array antenna are designed with PCM. The low-RCS high-isolation low-profile MIMO antenna with size of 1.27×1.27×0.07λ 0 3 (λ0: the free-space wavelength corresponding to the center frequency point) operating at 5.8 GHz consists of four orthogonal arranged metasurface antennas. The isolation is greater than 26 dB with impedance bandwidth from 5.51 GHz to 6.06 GHz. In addition, the low-RCS high-gain low-profile array antenna with size of 2.55×2.55×0.07λ 0 3 is also designed. The operating band covers from 5.63 GHz to 6.12 GHz with the gain of 12-15.6 dBi. The RCS reduction of the two antennas for normal incidence is between 6 dB and 23 dB in both X- and Ku-bands. The measured results of the antennas agree with the simulated results, which shows that they have potential application value in 5.8 GHz WLAN wireless communication.

A reconfigurable ultra-broadband transparent absorber combined with ITO and structural water.

In this paper, a reconfigurable transparent metamaterial absorber consisting of a double-layer indium tin oxide (ITO) complementary resonant structure with a structural water-based substrate is proposed. The double-layer resonant pattern gives rise to two stable resonant peaks, and the loading of the water-based substrate can enhance the microwave absorption of the overall structure. By adjusting the thickness of the water layer in the substrate, the microwave absorption performance of the structure can be switched between dual-band and ultra-broadband, with more than 90% efficient microwave absorption covering the frequency range of 6.1 GHz-35.2 GHz. The absorption mechanism is revealed by analyzing the structure surface current as well as the equivalent dielectric constant. We also experimentally verified its microwave absorption and optical transparency properties. Due to its excellent tunable microwave absorption performance and high optical transparency, the proposed absorber has a large application value in stealth devices and optical windows.

Leaky-Vivaldi antenna covered with metasurface with leaky wave radiation and aperture radiation.

A leaky-Vivaldi antenna covered with metasurface (LVAM) is proposed in this paper. The traditional Vivaldi antenna covered with metasurface realizes backward frequency beam-scanning from -41∘ to 0∘ in the high-frequency operating band (HFOB) and retains aperture radiation in the low-frequency operating band (LFOB). In the LFOB, the metasurface can be regarded as a transmission line to realize a slow-wave transmission. In the HFOB, the metasurface can be considered a 2D periodic leaky-wave structure to realize a fast-wave transmission. The simulated results show that LVAM has the -10 dB return loss bandwidths of 46.5% and 40.0%, and the realized gain of 8.8-9.6 dBi and 11.8-15.2 dBi cover the 5 G Sub-6 GHz band (3.3-5.3 GHz) and the X band (8.0-12.0 GHz), respectively. The test results are in good agreement with the simulated results. As a dual-band antenna covering the 5 G Sub-6 GHz communication band and military radar band, the proposed antenna can guide the future integrated design of communication and radar antenna systems.

Design of a Frequency Selective Rasorber Based on a Band-Patterned Octagonal Ring.

In this study, a dual-polarization and low-profile frequency-selective rasorber (FSR) constructed from a novel band-patterned octagonal ring and dipole slot-type elements is investigated. We show the process of designing from a full octagonal ring to realize a lossy frequency selective surface of our proposed FSR, and it has a passband with low insertion loss between the two absorptive bands. An equivalent circuit for our designed FSR is modeled to explain the introduction of the parallel resonance. Surface current, electric energy, and magnetic energy of the FSR are further investigated to illustrate the working mechanism. Simulated results indicate that S11 < -10 dB bandwidth within 5.2-14.8 GHz, S21 > -3 dB passband within 9.62-11.72 GHz, lower absorptive bandwidth within 5.02-8.80 GHz, and upper absorptive bandwidth within 12.94-14.89 GHz are obtained under normal incidence. Meanwhile, our proposed FSR possesses the properties of dual-polarization and angular stability. To verify the simulated results, a sample with thickness of 0.097 λL is manufactured, and the results are experimentally verified.

Multifunctional water-based metamaterial with polarization conversion and absorption.

A multifunctional metamaterial to realize broadband x-to-y cross-polarization conversion (CPC) and the absorption of electromagnetic waves is proposed in this paper. The presented multifunctional water-based metamaterial (MWM) consists of the top metallic dielectric substrate, the middle 3D printed container, and the bottom metal backplane. When the container is filled with water, the polarization conversion ratio (PCR) reaches more than 90% at 5.8-9.4 GHz, and the excellent absorption performance is achieved in the frequency band of 16.1-16.9 GHz. In addition, the CPC is achieved in two frequency bands (5.9-10.0 GHz and 14.3-16.4 GHz) without water injection. The unique properties of the proposed design are validated by experiments. As expected, the MWM simultaneously achieves polarization conversion and absorption functions, which is meaningful and consequential for multifunction and conformal stealth applications.

Broadband Bi-Directional All-Dielectric Transparent Metamaterial Absorber.

Water-based absorbers have shown great development potential in the past few years. In this paper, an all-dielectric transparent bi-directional water-based broadband metamaterial absorber is designed. The simulation results indicate that absorptance of the absorber is over 90% in 5.7-41.6 GHz, and its fraction bandwidth is 151.8%. The experimental results are greatly consistent with the simulations. The designed absorber has excellent performances of polarization insensitivity, oblique incidence stability and thermal stability. When the absorptance is more than 0.8, the maximum incident angle reaches 40° in TE mode and is over 60° in TM mode. In 0-80 °C, absorptance of the absorber is hardly changed. Because of the optical transparency of the designed absorber, it can be extensively used in stealth window weapons and electromagnetic compatibility equipment.

Ultra-broadband and high-efficiency polarization conversion metamaterial based on a metal combination water structure.

A linear-to-linear polarization conversion metamaterial is proposed with a water-metal structure. The simulation results show that the proposed metamaterial design can achieve ultra-broadband and high-efficiency polarization conversion within the frequency range from 7.46 GHz to 14.84 GHz with a polarization conversion ratio over 90%. This metamaterial exhibits sensitivity to the incidence angle but not to and temperature. The physical mechanism of polarization conversion is analyzed based on the distributions of the surface current and the magnetic field. An experimental sample of the designed metamaterial is fabricated, assembled, and measured in such a way as to realize reflective polarization conversion. This work provides a significant stepping stone for water-based metamaterial design and polarization control.

Lead federated neuromorphic learning for wireless edge artificial intelligence.

In order to realize the full potential of wireless edge artificial intelligence (AI), very large and diverse datasets will often be required for energy-demanding model training on resource-constrained edge devices. This paper proposes a lead federated neuromorphic learning (LFNL) technique, which is a decentralized energy-efficient brain-inspired computing method based on spiking neural networks. The proposed technique will enable edge devices to exploit brain-like biophysiological structure to collaboratively train a global model while helping preserve privacy. Experimental results show that, under the situation of uneven dataset distribution among edge devices, LFNL achieves a comparable recognition accuracy to existing edge AI techniques, while substantially reducing data traffic by >3.5× and computational latency by >2.0×. Furthermore, LFNL significantly reduces energy consumption by >4.5× compared to standard federated learning with a slight accuracy loss up to 1.5%. Therefore, the proposed LFNL can facilitate the development of brain-inspired computing and edge AI.

Flexible and transparent broadband microwave metasurface absorber based on multipolar interference engineering.

Electromagnetic multipoles enable rich electromagnetic interactions in a metasurface and offer another degree of freedom to control electromagnetic responses. In this work, we design and experimentally demonstrate an optically transparent, flexible and broadband microwave metasurface absorber based on multipolar interference engineering. Different from previous works, the designed metasurface simultaneously supports fundamental electric dipole and high-order electric quadrupole mode, whose interference satisfies the back-scattering suppression condition based on the generalized Kerker effect and thus high absorption. The measurement results indicate that the fabricated metasurface exhibits a high average absorption of 89% in the microwave band from 4 GHz to 18 GHz, together with a good optical transparency. Our study offers an alternative approach for designing broadband microwave metasurface absorber, which is potentially applicable in electromagnetic shielding, radar stealth and energy harvesting.

Simultaneous realization of polarization conversion for reflected and transmitted waves with bi-functional metasurface.

Manipulating the polarizations of electroagnetic waves by flexible and diverse means is desirable for myriad microwave systems. More recently, metasurfaces have emerged as promising alternatives to conventional polarization manipulation components because the flexibility of their geometry means that they can be arbitrarily customized. In this context, a bilayered metasurface is presented to simultaneously manipulate the polarized states of reflected and transmitted microwaves. Regardless of whether an incident electromagnetic wave is x-polarized or y-polarized, the reflected and transmitted waves are converted into their orthogonal waves at the operating frequency. The designed metasurface has a high polarization conversion rate, above 90%, for both normal and oblique incidences. Experimental results verify the correctness of the simulated results. Finally, the axial ratio and surface current distributions are employed to reveal the physics of the polarization manipulation. The proposed metasurface will be beneficial in the design of flexible and versatile polarization converters, has great potential for applications in polarization-controlled devices and is believed to be extendable to higher frequency regimes.

Clinical application of mesenchymal stem cells in rheumatic diseases.

Mesenchymal stem cells (MSCs) are pluripotent stem cells derived from mesoderm during early development that are characterized by high self-renewal ability and multidirectional differentiation potential. These cells are present various tissues in the human body and can be cultured in vitro. Under specific conditions, MSCs can differentiate into osteoblasts, neuron-like cells, adipocytes and muscle cells and so on, therefore, have a great application value in cell replacement therapy and tissue repair. In recent years, the application of MSCs in rheumatic diseases has received increasing attention. On the one hand, MSCs have the ability to differentiate into bone and cartilage cells; on the other hand, these stem cells are also involved in immune regulation, resulting in the alleviation of inflammation and anti-fibrotic properties and the promotion of vascular repair, thus bringing new hope for the treatment of rheumatic diseases. This article reviews the clinical progress in MSC application for the treatment of rheumatic diseases.

LncRNA JPX regulates proliferation and apoptosis of nucleus pulposus cells by targeting the miR-18a-5p/HIF-1α/Hippo-YAP pathway.

With the aggravation of global aging, the rapid rise in the obesity rate, and the increasing number of patients with intervertebral disc degeneration (IDD), the principles and mechanism of this disease remain unclear. This study explored the molecular mechanism of IDD treatment through interactions of the lncRNA-miRNA-mRNA-signaling pathways and the effects on the proliferation and apoptosis of human nucleus pulposus cells (HNPCs) cultured in vitro. Our study revealed that lncRNA JPX is expressed at low levels in HNPCs under normoxic conditions. Luciferase and RNA pull-down assays were used to verify that lncRNA JPX directly bound to miR-18a-5p and influenced HNPC proliferation and apoptosis. Subsequently, a luciferase assay confirmed the direct binding of miR-18a-5p to HIF-1α and demonstrated a negative correlation between miR-18a-5p and HIF-1α. In addition, the HIF-1α antagonist reversed the inhibition of the Hippo-YAP pathway by the miR-18a-5p inhibitor. In conclusion, overexpression of lncRNA JPX upregulated HIF-1α by inhibiting the expression of miR-18a-5p, thereby inhibiting the Hippo-YAP pathway. By inhibiting this pathway, JPX overexpression promoted the proliferation of HNPCs and decreased their apoptosis. Therefore, the lncRNA JPX is a potential new target.

Experimental study on preparation and anti-tumor efficiency of nanoparticles targeting M2 macrophages.

This study aimed to develop an effective therapy against M2 macrophages and to investigate the effects of imidazole and mannose modified carboxymethyl chitosan-nanoparticles (MIC-NPs) on tumor growth and antitumor immune responses. MIC-NPs were constructed and analyzed through 1H NMR, nano-laser particle size analyzer, and transmission electron microscopy. The nanoparticles were mainly distributed in 75-85 nm, and zeta potential was 1.5 mV. Cytotoxicity studies in vitro and in vivo indicated that MIC-NPs were safe. The targeting effect of MIC-NPs on M2 macrophages was observed through fluorescence microscope and microplate system. The results demonstrated the uptake of a large amount of FITC-loaded MIC-NPs by M2. Cell growth inhibition experiments showed that MIC-NPs significantly inhibited M2 through cell apoptosis. The evaluation of anti-tumor activity in vivo showed that MIC-NPs could accumulate in the tumor site to exert an anti-tumor effect. Flow cytometry showed that the proportion of M2 macrophages at the tumor site in the experimental group was significantly lower than that in the control group, while the Treg cells and cytotoxic T cells (CTL) were found to be increased. PCR detection showed that the cDNA of FIZZ, MR, TGF-ß, and arginase, closely related to M2 macrophages, in the experimental group, was significantly lower than that in the control group, but there was no significant difference in the cDNA of Treg cell characteristic Foxp3 between the two groups. These results suggest that MIC-NPs are expected to provide a new and effective treatment for tumor.

A simple new method for aged seed utilization based on melatonin-mediated germination and antioxidant nutrient production.

Seed deterioration, coupled with a decrease in nutrients, is unavoidable following long-term storage, and these seeds are therefore used as livestock fodder. Here, we developed a simple, rapid and efficient method of producing high amounts of antioxidants from deteriorated seeds via melatonin-induced germination. Legume seeds were subjected to high humidity at 55 °C for 12-36 h to obtain aged seeds with a 40% germination rate and severely reduced antioxidant nutrition (total phenolics content, ferric reducing power and 1,1-diphenyl-2-picryhydrazyl (DPPH) radical scavenging capacity). Aged seeds were then treated with 0.1 mM melatonin, resulting in the production of sprouts with a higher total phenolics content (fivefold), greater ferric reducing power (sevenfold) and greater DPPH radical scavenging capacity (twofold) compared to the aged seeds. These findings suggest that melatonin treatment efficiently converted aged seed reserve residues into antioxidant nutrients, providing an alternative use for deteriorated seeds in food production.

Fibroblast-like synoviocytes in rheumatoid arthritis: Surface markers and phenotypes.

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease that mainly affects synovial joints. During the course of RA, the synovium transforms into hyperplastic invasive tissue, leading to cartilage and bone destruction. Fibroblast-like synoviocytes (FLS) in the synovial lining develop aggressive phenotypes and produce pathogenic mediators that lead to the occurrence and progression of disease, playing a major role in RA pathophysiology. Therefore, research on FLS has become the main focus within the RA field. With technical advances and the development of multi-omics comprehensive analysis approaches, it has become possible to identify different FLS subsets via high-throughput sequencing and investigate differences between FLS phenotypes, allowing for the detailed study of RA pathogenesis. This review summarizes recent works on FLS subtypes and the surface marker proteins identified for different subtypes, providing a theoretical basis and reference for future studies on FLS in RA. The current work also addresses the clinical potential of FLS surface markers in RA based on related research from other fields.

Secure and private NOMA VLC using OFDM with two-level chaotic encryption.

In this paper, we propose and demonstrate a secure and private non-orthogonal multiple access (NOMA) based visible light communication (VLC) system. Orthogonal frequency division multiplexing (OFDM) modulation is applied in the system and a two-level chaotic encryption scheme is further implemented, which can guarantee both the security of legitimate users against eavesdroppers and the privacy among all the legitimate users. An experimental demonstration with two legitimate users and one eavesdropper successfully verifies the feasibility of the proposed secure and private NOMA VLC system. To the best of our knowledge, it is the first time that simultaneous security and privacy improvement is considered for NOMA VLC systems.

Tunable electromagnetically induced transparency in coupled three-dimensional split-ring-resonator metamaterials.

Metamaterials have recently enabled coupling induced transparency due to interference effects in coupled subwavelength resonators. In this work, we present a three dimensional (3-D) metamaterial design with six-fold rotational symmetry that shows electromagnetically induced transparency with a strong polarization dependence to the incident electromagnetic wave due to the ultra-sharp resonance line width as a result of interaction between the constituent meta-atoms. However, when the six-fold rotationally symmetric unit cell design was re-arranged into a fourfold rotational symmetry, we observed the excitation of a polarization insensitive dual-band transparency. Thus, the 3-D split-ring resonators allow new schemes to observe single and multi-band classical analogues of electromagnetically induced transparencies that has huge potential applications in slowing down light, sensing modalities, and filtering functionalities either in the passive mode or the active mode where such effects could be tuned by integrating materials with dynamic properties.