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The emergence of space-time modulated metasurface (STMM) as a novel platform for signal modulation holds significant promise for wireless secure communication, particularly within modern information technologies such as Internet of things and the 5th generation and beyond. While previous secure communication methods based on STMM have primarily focused on ensuring information security within both the time and frequency domains, in this study, we introduce a novel code domain modulation scheme in STMM to facilitate wireless secure communications, which is difficult to be detected in both time and frequency domains. The core concept involves synthesizing a smart modulation waveform by using a new code domain so that both secure information transmission and mitigation of jamming are realized. To achieve this, we build a Q-dimensional signal space that has a minimum overlap with the jamming signal space and where orthogonal or quasi-orthogonal basis functions are used for information transmission. Furthermore, this methodology can be readily extended to other abstract signal domains. To exemplify this approach, we implement an STMM and utilize it to transmit the logos of our universities accurately, while eavesdroppers are unable to acquire any useful information through direct identification from the constellation diagrams. This showcases the effectiveness of the proposed secure communication system.

Abstract Stretching elastic materials containing nanoparticle lattices is common in research and industrial settings, yet our knowledge of the deformation process remains limited. Understanding how such lattices reconfigure is critically important, as changes in microstructure lead to significant alterations in their performance. This understanding has been extremely difficult to achieve due to a lack of fundamental rules governing the rearrangements. Our study elucidates the physical processes and underlying mechanisms of three-dimensional lattice transformations in a polymeric photonic crystal from 0% to over 200% strain during uniaxial stretching. Corroborated by comprehensive experimental characterizations, we present analytical models that precisely predict both the three-dimensional lattice structures and the macroscale deformations throughout the stretching process. These models reveal how the nanoparticle lattice and matrix polymer jointly determine the resultant structures, which breaks the original structural symmetry and profoundly changes the dispersion of photonic bandgaps. Stretching induces shifting of the main pseudogap structure out from the 1st Brillouin zone and the merging of different symmetry points. Evolutions of multiple photonic bandgaps reveal potential optical singularities shifting with strain. This work sets a new benchmark for the reconfiguration of soft material structures and may lay the groundwork for the study of stretchable three-dimensional topological photonic crystals.

Abstract Objective The aim of the present study was to investigate the therapeutic effect of ammidin on hypoxia/reoxygenation (H/R) injury in primary neonatal rat cardiomyocytes by observing the role of ferroptosis in the process of H/R injury, and to verify its target and regulatory signaling pathways. Methods The network pharmacology analysis was used to predict the biological processes, core targets and related signaling pathways of Angelica dahurica in the treatment of ferroptosis. Cell viability was assessed using live cell imaging and cell counting kit-8. Lactate dehydrogenase (LDH), reactive oxygen species (ROS) production, and malondialdehyde (MDA), superoxide dismutase (SOD) and mitochondrial membrane potential (MMP) content were determined to assess the level of ferroptosis. Western blotting was performed to measure protein expression. Results Network pharmacology predicted that Acyl-CoA synthetase long chain family member 4 (ACSL4) was highly associated with myocardial H/R injury in the intersection of Angelica dahurica and ferroptosis. The top three active components of Angelica dahurica were found to be mandenol, alloisoimperatorin and ammidin, among which ammidin was found to have the strongest binding to the target proteins of the ACSL4/AMPK/mTOR pathway. H/R reduced the viability of cardiomyocytes, while the inhibition of ferroptosis by ferrostatin-1 alleviated the H/R-induced inhibition of cardiomyocyte viability. This was evidenced by the increased cell viability, SOD release, MMP level and glutathione peroxidase 4 (GPX4) protein expression, as well as the decreased LDH and MDA release and ROS production and ACSL4 protein expression (P

A wearable antenna functioning in the 2.4 GHz band for health monitoring and sensing is proposed. It is a circularly polarized (CP) patch antenna made from textiles. Despite its low profile (3.34 mm thickness, 0.027 λ0), an enhanced 3-dB axial ratio (AR) bandwidth is achieved by introducing slit-loaded parasitic elements on top of analysis and observations within the framework of Characteristic Mode Analysis (CMA). In detail, the parasitic elements introduce higher-order modes at high frequencies that may contribute to the 3-dB AR bandwidth enhancement. More importantly, additional slit loading is investigated to preserve the higher-order modes while relaxing strong capacitive coupling invoked by the low-profile structure and the parasitic elements. As a result, unlike conventional multilayer designs, a simple single-substrate, low-profile, and low-cost structure is achieved. While compared to traditional low-profile antennas, a significantly widened CP bandwidth is realized. These merits are important for the future massive application. The realized CP bandwidth is 2.2–2.54 GHz (14.3%), which is 3–5 times that of traditional low-profile designs (thickness < 4 mm, 0.04 λ0). A prototype was fabricated and measured with good results.

Abstract With the development of nanotechnologies, researchers have brought the concept of antenna to the optical regime for manipulation of nano-scaled light matter interactions. Most optical nanoantennas optimize optical function, but are not electrically connected. In order to realize functions that require electrical addressing, optical nanoantennas that are electrically continuous are desirable. In this article, we study the optical response of a type of electrically connected nanoantennas, which we propose to call “dendritic” antennas. While they are connected, they follow similar antenna hybridization trends to unconnected plasmon phased array antennas. The optical resonances supported by this type of nanoantennas are mapped both experimentally and theoretically to unravel their optical response. Photoluminescence measurements indicate a potential Purcell enhancement of more than a factor of 58.

This paper extends current knowledge on electromagnetic wave scattering from bounded moving media in several regards. First, it complements the usual dispersion relation of moving media, ω(θk) (θk: phase velocity direction, associated with the wave vector, k), with the equally important impedance relation, η(θS) (θS: group velocity direction, associated with the Poynting vector, S). Second, it explains the interluminal-regime phenomenon of double-downstream wave transmission across a stationary interface between a regular medium and the moving medium, assuming motion perpendicular to the interface, and shows that the related waves are symmetric in terms of the energy refraction angle, while being asymmetric in terms of the phase refraction angle, with one of the waves subject to negative refraction, and shows that the wave impedances of the two transmitted waves are equal. Third, it generalizes the problem to the case where the medium moves obliquely with respect to the interface. Finally, it highlights the connection between this problem and a spacetime modulated medium.

Within the framework of a method-of-moments algorithm, the natural frequencies and natural modes of a scatterer/antenna can be found by looking for the complex frequencies where the determinant of the impedance matrix becomes zero. However, for nanotopologies, the value of this determinant can easily go beyond the resolution or representation limits available on present-day computers. In this work, we propose a substitute for the matrix determinant that avoids this problem altogether: the characteristic term. A robust numerical procedure for locating natural frequencies using this new target function is outlined. Then, the natural frequencies of three different nanostructures, namely, a gold and nickel nanopatch and a gold nanodimer, are calculated and validated by numerically and experimentally obtained scattering/extinction spectra.

In order to model the interaction between light and plasmonic structures at deep-nanometer scale, which is governed by non-classical effects, a nonlocal hydrodynamic approach has been extensively studied. Several hydrodynamic models have been proposed, solving the coupled equations: the linearized hydrodynamic equation of motion and the electrodynamic Maxwell’s equations, by employing additional boundary conditions. This work compares four hydrodynamic models: the hard wall hydrodynamic model (HW-HDM), the curl-free hydrodynamic model (CF-HDM), the shear forces hydrodynamic model (SF-HDM), and the quantum hydrodynamic model (Q-HDM). The analysis is conducted for a metallic spherical nanoparticle, as an example. The above hydrodynamic models are also compared with experiments available in literature. It is demonstrated that HW-HDM and QHDM outperform the other two hydrodynamic models. [ABSTRACT FROM AUTHOR]