Multimodal Resonance Research Articles

CO2 in Ionene–Ionic Liquid Composite Membranes

AbstractIonene – ionic liquid (IL) composites are promising materials for CO2 separation, yet a molecular‐level understanding of their structure and its impact on CO2 speciation, solubility, rotation, and diffusivity remains unclear. Herein, using multimodal nuclear magnetic resonance (NMR), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), atomic force microscopy (AFM), and molecular dynamics (MD) simulations, we reveal that the composites contain IL‐rich domains extending across hundreds of nanometres within the ionene matrix, and these bicontinuous domains span the entire membrane depth. CO2 also absorbs into the ionene matrix, with the distribution between two CO2 species varying with temperature and time. The rotational correlation times of these two species are on the timescale of 0.1 and 1 ns, respectively. As IL content increases, the ionic domains expand, resulting in higher CO2 solubility due to enhanced molecular dynamics and increased free volume in both ionene backbones and IL‐rich regions. Although CO2 diffusion in the membranes is an order of magnitude slower than in bulk IL, the activation energy for CO2 diffusion remains comparable. Ionene‐IL composites represent a promising platform for designing CO2 separation membranes, offering enhanced CO2diffusion and selectivity through IL‐rich domains, and increased CO2 solubility and mechanical integrity from the ionene matrix.

Quantum State Transfer via a Multimode Resonator

Quantum State Transfer via a Multimode Resonator

Symmetric deformable registration of multimodal brain magnetic resonance images via appearance residuals.

Deformable registration of multimodal brain magnetic resonance images presents significant challenges, primarily due to substantial structural variations between subjects and pronounced differences in appearance across imaging modalities. Here, we propose to symmetrically register images from two modalities based on appearance residuals from one modality to another. Computed with simple subtraction between modalities, the appearance residuals enhance structural details and form a common representation for simplifying multimodal deformable registration. The proposed framework consists of three serially connected modules: (i) an appearance residual module, which learns intensity residual maps between modalities with a cycle-consistent loss; (ii) a deformable registration module, which predicts deformations across subjects based on appearance residuals; and (iii) a deblurring module, which enhances the warped images to match the sharpness of the original images. The proposed method, evaluated on two public datasets (HCP and LEMON), achieves the highest registration accuracy with topology preservation when compared with state-of-the-art methods. Our residual space-guided registration framework, combined with GAN-based image enhancement, provides an effective solution to the challenges of multimodal deformable registration. By mitigating intensity distribution discrepancies and improving image quality, this approach improves registration accuracy and strengthens its potential for clinical application.

Multimode resonant microstrip antennas with electrically small patch and frequency scannable circularly polarised angle

AbstractSemi‐analytical design approach to electrically small, dual‐mode resonant, wideband circularly polarised (CP) microstrip annular sector patch antenna (MASPA) with variable polarization is proposed for satellite‐assisted Internet‐of‐vehicle (IoV). At first, the upper bound of electrically small patch is theoretically laid down by advancing an interpolated algorithm to the eigen‐roots of the characteristic equation, so that the radius of patch can be rapidly determined in the initial design step. In this way, MASPA with electrically small patch, multimode resonant, and frequency scannable CP angle can be yielded. Dual‐mode resonant MASPAs with flare angles of 330° on air substrate, and 270° on suspended microstrip air/F4B substrates having a profile less than 0.05‐wavelength are then numerically studied and experimentally validated. In the suspended microstrip case, MASPA with maximum patch radius of 0.159‐wavelength (electrically small), equal impedance and tilted CP bandwidths up to 26.6%, and tilted CP angle of θt = −10°–35°, has been successfully implemented. Therefore, the proposed approach should be highly effective for low‐profile, electrically small, wideband CP antenna designs.

Silicon-Based 3-D Self-Packaged Filtering Power Divider Based on a Multimode Resonator

Silicon-Based 3-D Self-Packaged Filtering Power Divider Based on a Multimode Resonator

An SIW-Based Wideband 5G mmWave Bandpass Filter by Using Multimode Resonator

An SIW-Based Wideband 5G mmWave Bandpass Filter by Using Multimode Resonator

Multi-modal resonance of topological hybrid graphene foam for enhanced acoustic absorption

Multi-modal resonance of topological hybrid graphene foam for enhanced acoustic absorption

Nonlinear coupling of closely spaced modes in atomically thin MoS2 nanoelectromechanical resonators

Nanoelectromechanical systems (NEMS) incorporating atomic or molecular layer van der Waals materials can support multimode resonances and exotic nonlinear dynamics. Here we investigate nonlinear coupling of closely spaced modes in a bilayer (2L) molybdenum disulfide (MoS2) nanoelectromechanical resonator. We model the response from a drumhead resonator using equations of two resonant modes with a dispersive coupling term to describe the vibration induced frequency shifts that result from the induced change in tension. We employ method of averaging to solve the equations of coupled modes and extract an expression for the nonlinear coupling coefficient (λ) in closed form. Undriven thermomechanical noise spectral measurements are used to calibrate the vibration amplitude of mode 2 (a2) in the displacement domain. We drive mode 2 near its natural frequency and measure the shifted resonance frequency of mode 1 (f1s) resulting from the dispersive coupling. Our model yields λ = 0.027 ± 0.005 pm−2 · μs−2 from thermomechanical noise measurement of mode 1. Our model also captures an anomalous frequency shift of the undriven mode 1 due to nonlinear coupling to the driven mode 2 mediated by large dynamic tension. This study provides a direct means to quantifying λ by measuring the thermomechanical noise in NEMS and will be valuable for understanding nonlinear mode coupling in emerging resonant systems.

Deterministic Parity‐Time Symmetry Single‐Mode Oscillation in Filterless Multimode Resonators

AbstractParity‐time symmetry has great potential for mode selection in multimode resonators. However, in a PT‐symmetry system with saturable absorption mechanisms, the random background noise can initiate single‐mode oscillation at any of the maxima within the gain spectrum, that is, potential PT frequencies. Such randomness impedes the acquisition of high‐quality signals at desired frequencies. Here, this work proposes a method to obtain deterministic PT‐symmetry single‐mode oscillation in a filterless multimode resonator through one‐shot injection. With this technique, this work changes the system's gain spectrum and enhances the gain discrepancy. Utilizing the frequency domain saturable absorption of the resonator, oscillation at desired mode can maintain its frequency after the withdrawal of the injection signal. To validate the concept, this work establishes a polarization‐division multiplexed dual‐loop optoelectronic oscillator (OEO) with a 1‐km long cavity operated under PT‐symmetry conditions. By one‐shot injecting the PT‐OEO, this work effectively eliminates the randomness arising from the relatively flat gain spectrum, facilitating oscillation at any desired potential PT frequencies from 1.8 to 9 GHz without requiring elaborate frequency tuning structures. Moreover, the one‐shot injection technique produces ultra‐low phase noise performance, achieving a remarkable −158.6 dBc Hz−1@10 kHz. This performance level stands in close comparison with the best phase noise values recorded for OEOs.

Dual- and triple-band quasi-elliptic bandpass filters based on single-cavity multi-mode hybrid cavities

In this paper, a novel construction method for a single hybrid cavity is proposed for the first time, which integrates a quarter-mode substrate integrated waveguide structure into a patch cavity (QMSIWP), and a novel single-cavity multi-mode resonator is realized through the incorporation of cross-slot lines. A detailed analysis of its characteristics, combined with a specialized feed structure, leads to the design of multiple dual-band quasi-elliptic bandpass filters (BPFs) with varying frequency ratios and a triple-band quasi-elliptic BPF. The finite frequency transmission zeros (FTZs) and bandwidths (BWs) can be controlled by adjusting various parameters. For the demonstration, a triple-band quasi-elliptic BPF is fabricated and measured to validate the performance and design method of the proposed QMSIWP hybrid cavity and feed structure. The measured results agree with the synthesized and simulated results, confirming the proposed method's feasibility and universality. The proposed filter exhibits advantages such as compact size, high selectivity, and excellent group delay, which expands its application prospects and potential value.

Delayed blood arrival partially mediates the association between arterial dilatation and cerebral small vessel disease

AbstractBackgroundCerebral arterial dilatation, signifying outward vascular remodeling, is linked to a higher risk of Alzheimer’s disease and a higher burden of white matter hyperintensities (WMH). Arterial dilatation may disrupt cerebral hemodynamics and lead to delayed blood arrival to the brain, which is itself linked to an increased burden of WMH. We examined if arterial dilatation was associated with blood arrival timing and if blood arrival timing mediated the effect of arterial dilatation on WMH burden.MethodsVanderbilt Memory and Aging Project participants free of clinical dementia or stroke at enrollment (n=249, 73±8 years, 85% cognitively unimpaired, 41% female) underwent multimodal 3T brain magnetic resonance imaging. Internal carotid artery (ICA) and basilar artery (BA) arterial inner diameters were quantified by an expert rater using vessel wall imaging. An established marker of blood arrival timing, the arterial spin labeling spatial coefficient of variation (ASL‐sCoV), was quantified using pseudo‐continuous ASL. Higher ASL‐sCoV indicates slower blood arrival. WMH burden was quantified using semi‐automated methods. Linear regressions related ICA and BA inner diameters to ASL‐sCoV and log‐transformed WMH burden in anterior and posterior arterial territories, individually. Models were adjusted for age, sex, race/ethnicity, cognitive status, Framingham Stroke Risk Profile, intracranial volume, and apolipoprotein E‐ε4 status. We also assessed if ASL‐sCoV mediated associations between arterial diameters and WMH burden.ResultsLarger ICA inner diameter was associated with higher anterior ASL‐sCoV (p=1.7x10‐8) and higher anterior WMH burden (p=9.6x10‐5). Anterior ASL‐sCoV partially mediated the association between ICA inner diameter and anterior WMH burden (proportion mediated=15%, p=0.04). Larger BA inner diameter was associated with higher posterior ASL‐sCoV (p=1.3x10‐8) but not with higher posterior WMH burden (p=0.06).ConclusionsOur study illustrates novel links between cerebral vascular structure, cerebrovascular hemodynamics, and vascular brain pathology. Because most of the effect of arterial dilatation on WMH burden was not mediated through blood arrival timing, future work will consider other potential mediators, such as arterial stiffness.

Challenges in clinical translation of cardiac magnetic resonance imaging radiomics in non-ischemic cardiomyopathy: a narrative review.

Radiomics is an emerging technology that facilitates the quantitative analysis of multi-modal cardiac magnetic resonance imaging (MRI). This study aims to introduce a standardized workflow for applying radiomics to non-ischemic cardiomyopathies, enabling clinicians to comprehensively understand and implement this technology in clinical practice. A computerized literature search (up to August 1, 2024) was conducted using PubMed to identify relevant studies on the roles and workflows of radiomics in non-ischemic cardiomyopathy. Expert discussions were also held to ensure the accuracy and relevance of the findings. Only English-language publications were reviewed. The paper details the essential processes of radiomics, including feature extraction, feature engineering, model construction, and data analysis. It emphasizes the role of MRI in assessing cardiac structure and function and demonstrates how MRI-based radiomics can aid in diagnosing and differentiating non-ischemic cardiomyopathies such as hypertrophic cardiomyopathy, dilated cardiomyopathy, and myocarditis. The study also investigates various cardiac MRI sequences to enhance the clinical application of radiomics. The standardized radiomics workflow presented in this study aims to assist clinicians in effectively utilizing MRI-based radiomics for the diagnosis and management of non-ischemic cardiomyopathies, thereby improving clinical decision-making.

Evaluation of neostriatum changes in Crohn's disease: a multimodal brain magnetic resonance imaging study.

Abnormalities of neostriatum have been reported to be implicated in Crohn's disease (CD). However, there are few systematic explorations. We aim to explore the changes that occur in the structure and function of the neostriatum and whether these changes are related to the clinical characteristics of CD. In this cross-sectional and prospective study, we enrolled 34 CD patients and 31 healthy controls (HCs) for analysis. We performed voxel-based morphometry (VBM) and seed-based functional connectivity (FC) to evaluate the structural and functional changes in the neostriatum. Correlation analysis was used to evaluate the possible relationships between clinical characteristics and neuroimaging findings. CD patients had significantly increased gray matter volume (GMV) in the bilateral putamen compared with HCs. The results showed that CD patients had significantly decreased FC related to the putamen-calcarine cortex, putamen-fusiform gyrus, putamen-inferior temporal cortex (ITC), putamen-parahippocampus, and increased FC associated with the putamen-cuneus/precuneus. Moreover, CD patients showed a positive correlation between the GMV in the left putamen and illness duration (r=0.42, P=0.013). Our study indicated that CD patients had increased GMV and abnormal FC related to the putamen. The structural and functional differences could reflect that neostriatum may be linked with alterations of aberrant patterns of the default mode network (DMN) and visual processing area.

A Planar Single-Layer Differentially-Fed Dual-Band Dual-Polarized Filtenna Based on Multimode Resonant Structure

A Planar Single-Layer Differentially-Fed Dual-Band Dual-Polarized Filtenna Based on Multimode Resonant Structure

Design of a Half-Mode Substrate-Integrated Waveguide (HMSIW) Multimode Resonator Bandpass Filter Using the Minkowski Fractal for C-Band Applications.

A substrate-integrated waveguide (SIW) bandpass filter (BPF) with extraordinary selectivity and an adequate upper stopband for C-band Satellite Communication (SATCOM) applications is proposed in this paper. The design comprises comb-shaped slots engraved on a half-mode SIW (HMSIW) that constitute a multimode resonator (MMR). Its performance is further ameliorated by applying the first and second iterations of the Minkowski fractal curve in the ground plane as a defected ground structure (DGS). The Minkowski fractal has advantages in terms of better bandwidth and miniaturization. The filter is first simulated using the commercial full-wave electromagnetic simulator HFSS v19 and then fabricated on a 0.062'' (1.6 mm) FR4 with dielectric constant εr = 4.4. The measured results are comparable with the simulated ones and demonstrate that the BPF has a resonant frequency (f0) of 4.75 GHz, a 3 dB bandwidth of 770 MHz (fractional bandwidth of 21.4%), an insertion loss of 1.05 dB, and an out-of-band rejection (in the stopband) of more than 28 dB up to 8 GHz, demonstrating a wide and deep stopband. Using the multimode resonator (MMR) technique, a wide bandwidth has been achieved, and by virtue of using half-mode SIW (HMSIW), the proposed BPF is compact in size. Also, the fractal DGS aids in better stopband performance.

Laterally Excited Resonators Based on Single-Crystalline LiTaO3 Thin Film for High-Frequency Applications.

High-performance acoustic resonators based on single-crystalline piezoelectric thin films have great potential in wireless communication applications. This paper presents the modeling, fabrication, and characterization of laterally excited bulk resonators (XBARs) utilizing the suspended ultra-thin (~420 nm) LiTaO3 (LT, with 42° YX-cut) film. The finite element analysis (FEA) was performed to model the LT-based XBARs precisely and to gain further insight into the physical behaviors of the acoustic waves and the loss mechanisms. In addition, the temperature response of the devices was numerically calculated, showing relatively low temperature coefficients of frequency (TCF) of ~-38 ppm/K for the primary resonant mode. The LT-based XBARs were fabricated and characterized, which presents a multi-resonant mode over a wide frequency range (0.1~10 GHz). For the primary resonance around 4.1 GHz, the fabricated devices exhibited a high-quality factor (Bode-Q) ~ 600 and piezoelectric coupling (kt2) ~ 2.84%, while the higher-harmonic showed a greater value of kt2 ~ 3.49%. To lower the resonant frequency of the resonator, the thin SiO2 film (~20 nm) was sputtered on the suspended device, which created a frequency offset between the series and shunt resonators. Finally, a ladder-type narrow band filter employing five XBARs was developed and characterized. This work effectively demonstrates the performance and application potential of micro-acoustic resonators employing high-quality LT films.

Near‐Infrared Dual‐Band Frequency Comb Generation from a Silicon Resonator

AbstractBenefitting from the mature, cost‐effective, and scalable manufacturing capabilities of complementary metal‐oxide‐semiconductor (CMOS) technology, silicon photonics has facilitated the seamless and monolithic integration of diverse functionalities, including optical sources, modulators, and photodetectors. Microresonators can generate multiple coherent optical frequency comb lines and serve as optical sources. However, at the telecom band, silicon suffers from two‐photon absorption and free‐carrier absorption, which severely hampers the realization of microcombs from a single silicon chip at telecom wavelengths until now. In this paper, a novel approach is presented and demonstrated with near‐infrared dual‐band frequency combs from a multimode silicon resonator. With a single pumping configuration, dual‐band combs are generated from the interaction between the pump and Raman Stokes fields by involving two different optical mode families but with similar group velocities. It is observed that the pump power required to generate dual‐band combs is as low as 0.7 mW. The work in bringing telecom microcombs to the silicon platform will advance silicon photonics for the next generation of monolithically integrated technology based on a single silicon chip, enabling new possibilities for further exploring silicon photonics‐based applications in optical telecommunications, sensing, and quantum metrology in the telecom band using a monolithic single silicon chip.

Multiplexing Integration Meta‐Absorber in an Ultrathin Planar Board

A meta‐absorber is a type of metamaterial capable of absorbing incident electromagnetic waves, primarily used for isolating and attenuating these waves. Due to their unique properties, meta‐absorbers are widely used in areas of electronic shielding, radar cross‐section reduction, as well as military camouflage. To enhance the working bandwidth, conventional meta‐absorbers integrate multiresonance modes in different layers, resulting in increased thickness and limiting their applications. Herein, a multiplexing integration meta‐absorber is proposed in a one‐layer planar board, achieving an ultrathin thickness of 0.053 λ and an ultrawide absorption band covering the whole X and Ku bands (8.0–18.0 GHz) by harnessing the coupling of four resonant modes. Moreover, the designed meta‐absorber is insensitive to the polarization of incident waves and exhibits good angle stability within ±45°. The experimental results agree well with the simulations. These findings may inspire the development of ultrathin metadevices with multifunctionalities operating across different frequency domains.

Single- and dual-band high-order polarization rotating frequency selective surface

Abstract This work presents the design and development of dual- and single-band polarization rotating frequency selective surfaces (PR-FSSs) based on aperture-coupled patch multimode resonators. Initially, an open-loop slot is incorporated into the patch of a second-order resonator to design a dual-band second-order PR-FSS (DPR-FSS), which enables effective polarization rotation and frequency selection across two distinct passbands. Then, to develop a single-band fourth-order PR-FSS (SPR-FSS), we introduce a metallic via into the DPR-FSS. This modification results in a single-band fourth-order response. The SPR-FSS offers a bandwidth of 41% with minimal insertion loss and high roll-off characteristics. Finally, experiments are conducted to verify the performance of the proposed structures. Good agreement can be observed between simulation and measurement.

A wideband reconfigurable filtering phase shifter based on Stub-loaded multimode resonators

Abstract In this paper, a type of reconfigurable filtering phase shifters (RFPSs) composed of stepped-impendence stub-loaded multimode resonators (SLMMR) is proposed. High frequency selectivity and wideband characteristics are realized in the presented work. Four transmission poles (TPs) are generated in the passband to exhibit a flat and wide passband. Meanwhile, the proposed SLMMR produces two controllable transmission zeros (TZs), which improves the frequency selectivity effectively. Meanwhile, radiofrequency switches are utilized to facilitate the transition between different phase shifts. Finally, the proposed RFPSs are designed and fabricated to verify the method. The measured results indicate that the designed RFPSs, which can be turned from 45° to 90° and from 135° to 180°, are capable of realizing more than 40 % FBW with a center frequency of 3.5 GHz.