Symmetric Structure Research Articles

Coupling between topological edge state and defect mode-based biosensor using phononic crystal

A wealth of details regarding an individual’s state of health, like a person’s respiratory and metabolic functioning, can be studied by analyzing the volatile molecules and atoms in human exhaled breath. Besides, the salinity of seawater is a crucial factor in understanding its characteristics because any variation in the salinity of seawater represents the variations in the hydrological, biological, and chemical distributions. In this paper, a symmetrical one-dimensional phononic structure is theoretically designed using two symmetrical crystals separated with a defective cavity. This structure has been designed to excite a topological edge state coupled with defect mode. The coupled mode achieves high sensitivity to NaCl concentration in an aqueous solution, seven times higher than the defective one. By ranging the NaCl concentration from 0 to 21%, the average sensitivity is 467 and 3160 Hz/% for defect mode and coupled modes, respectively. The bandwidth of the coupled mode of 170 Hz is much narrower than that of the defect mode of 671 Hz for detecting salinity. For detecting the increase in concentration in dry exhaled breath by ranging the concentration from 0 ppm to 100 ppm, the average sensitivity is Hz/ppm for coupled mode. As a result of these enhancements in the sensitivity and bandwidth of the coupled mode, the coupled mode is recommended to be used in different biosensing applications.

Design and Energy Absorption Study of an Asymmetric Windmill‐Style Negative Poisson's Ratio Honeycomb Structures

The negative Poisson's ratio (NPR) structure, as one of the representatives of advanced lightweight honeycomb materials, has good application prospects in aerospace, vehicles, biomedical, and other fields due to its unique deformation mechanism and huge energy absorption potential. In this article, a 2D asymmetric windmill‐style composite honeycomb (AWH) with NPR effects is presented and its compression properties are systematically assessed using both axial compression experiments and simulations. Through the experimental results, the accuracy and applicability of the finite‐element model are verified, indicating that the shape of the rotating arrangement and the stable internal design of the triangle make it have significantly higher energy absorption capacity than traditional symmetric reentrant honeycomb structures. In addition, the influence of the height, width, and cell spacing of asymmetric unit cell indentation points on the compression characteristics of AWH under axial quasi‐static compression conditions is further analyzed through orthogonal simulation experiments. In this study, a certain theoretical basis for the design and energy absorption application of NPR materials is provided, indicating that AWH has excellent mechanical properties and broad application prospects.

Numerical investigation of an anti-symmetric nanophotonic structure for accelerating sub-relativistic electron beams

This study investigates an anti-symmetrically positioned nanophotonic dual-pillar structure, in which the dielectric and vacuum components are evenly distributed along the direction of electron propagation, with each dielectric pillar facing a vacuum region. Our numerical simulation results show that the previously proposed symmetric dielectric grating structure, where dielectric pillars facing each other are alternated with vacuum gaps, is accompanied by a deceleration region, preventing the achievement of high gradients during the acceleration process. By contrast, the anti-symmetric grating structure eliminates the deceleration field and generates a uniformly distributed acceleration field. This requires that the two oppositely directed laser beams crossing the structure in the transverse region must have a phase shift of π in the anti-symmetric case. This structure has significant potential for accelerating sub-relativistic electron beams. In this numerical simulation, the initial energy of the sub-relativistic electron beams is selected as 79 keV. The acceleration gradient provided by the symmetric design for sub-relativistic electrons is approximately 70 MeV/m; however, the anti-symmetric structure can provide a maximum acceleration gradient of up to ∼430 MeV/m.

A compact microstrip quint-band bandpass filter using shorted stub-loaded SIRs based on the interdigital feedline structure

ABSTRACT A compact microstrip quint-band bandpass filter (BPF) composed of two pairs of shorted stub-loaded step-impedance resonators (SSLSIRs) with interdigital feedline structure is designed in this paper. The two pairs of resonators are bent and placed back-to-back on the upper and lower sides of the feedline in order to miniaturise the filter. Due to the symmetric structure of the resonators, the even-odd mode analysis method can be used to derive the resonant frequency equations. Based on the simulation, the filter is fabricated on the substrate of Rogers 4350 and measured. The measured S-parameter results are in good agreement with the simulation results. The operating frequencies of five passbands are measured at 2.2/2.8/4.3/5.4/6.7 GHz and the 3-dB fractional bandwidth (FBW) is 12.7/3.8/6.6/3.2/6.9%, respectively. The measured in-band minimal return losses and the insert losses within five passbands are 11/12/13/12/13 dB and 1.7/2.5/2.7/1.5/1.6 dB. Furthermore, the proposed BPF has good frequency selectivity with steep skirt property via the interdigital feedline structure, which yields seven transmission zeros (TZs). The four measured band-to-band isolations among the five passbands are higher than 20 dB. The filter’s total dimension occupies only 0.18 λg × 0.15 λg, where λg represents the free space wavelength corresponding to the centre frequency of the lowest passband.

Broadband negative refraction based on a pair of anti-parity-time structures

Abstract An anti-parity-time(A-PT) symmetric system, of which the refractive index satisfies n( - x) = - n*(x), can present intriguing scattering properties like continuous coherent perfect absorption(CPA) spectrum and laser spectrum, which are symmetric to each other in the parameter space. In this work, an acoustic parity-time(PT) symmetric system consisting of two A-PT symmetric structures is introduced to realize a broadband negative refraction. When the two A-PT symmetric structures are at their CPA mode and laser mode respectively, the PT symmetric system can display its unidirectional negative refraction property. As the two A-PT structures we design here have a broadband CPA and laser modes, the PT symmetric negative refraction system would be broadband. Besides, the exceptional point(EP) of the proposed PT-symmetric system corresponds to the CPA point and laser point of its two components, and it's unidirectionally transparent on broadband as well.

Molecular Design and Theoretical Study on Dioxadiazine Energetic Compounds Involving Intramolecular Hydrogen Bonds

ABSTRACTThe high nitrogen and high oxygen content of energetic dioxadiazine compounds makes them exhibit high detonation performance and good stability, showing possible application in both military and civilian fields. Energetic dioxadiazine compounds with intramolecular hydrogen bonds were designed and optimized, while introducing —NH2, —NHNO2, —CH3, —NO2, and —OH as modified groups. The bond order, density, enthalpy of formation, stability, detonation performance and inter/intramolecular interactions were analyzed. Results showed that the skeleton of 1,4,2,6‐dioxadiazine and 1,4,2,5‐dioxadiazine had good stability and symmetrical structure. Analysis of bond length revealed the strong hydrogen bonding between the hydroxyl group and dioxadiazine ring. The introduction of —NH2 and —OH groups proved beneficial in increasing molecular planarity. Bond order analysis, molecular electrostatic potential (ESP) analysis and detonation parameter calculations showed that B5 and C5 have good stability and detonation properties. Crystal structure prediction suggested that B5 would most likely crystallize in monoclinic (P21 space group) while C5 would crystallize in orthorhombic (Pbca space group). Hirshfeld surface analysis indicated strong O···H and N···H interactions for compounds B5 and C5. The above results have a positive promoting effect on obtaining high‐energy dioxadiazine compounds with high stability.

Diversification and recurrent adaptation of the synaptonemal complex in Drosophila.

The synaptonemal complex (SC) is a protein-rich structure essential for meiotic recombination and faithful chromosome segregation. Acting like a zipper to paired homologous chromosomes during early prophase I, the complex is a symmetrical structure where central elements are connected on two sides by the transverse filaments to the chromatin-anchoring lateral elements. Despite being found in most major eukaryotic taxa implying a deeply conserved evolutionary origin, several components of the complex exhibit unusually high rates of sequence turnover. This is puzzlingly exemplified by the SC of Drosophila, where the central elements and transverse filaments display no identifiable homologs outside of the genus. Here, we exhaustively examine the evolutionary history of the SC in Drosophila taking a comparative phylogenomic approach with high species density to circumvent obscured homology due to rapid sequence evolution. Contrasting starkly against other genes involved in meiotic chromosome pairing, SC genes show significantly elevated rates of coding evolution due to a combination of relaxed constraint and recurrent, widespread positive selection. In particular, the central element cona and transverse filament c(3) G have diversified through tandem and retro-duplications, repeatedly generating paralogs with novel germline activity. In a striking case of molecular convergence, c(3) G paralogs that independently arose in distant lineages evolved under positive selection to have convergent truncations to the protein termini and elevated testes expression. Surprisingly, the expression of SC genes in the germline is prone to change suggesting recurrent regulatory evolution which, in many species, resulted in high testes expression even though Drosophila males are achiasmic. Overall, our study recapitulates the poor conservation of SC components, and further uncovers that the lack of conservation extends to other modalities including copy number, genomic locale, and germline regulation. Considering the elevated testes expression in many Drosophila species and the common ancestor, we suggest that the activity of SC genes in the male germline, while still poorly understood, may be a prime target of constant evolutionary pressures driving repeated adaptations and innovations.

Overcoming the Conductance versus Crossover Trade-off in State-of-the-Art Proton Exchange Fuel-Cell Membranes by Incorporating Atomically Thin Chemical Vapor Deposition Graphene.

Permeance-selectivity trade-offs are inherent to polymeric membranes. In fuel cells, thinner proton exchange membranes (PEMs) could enable higher proton conductance and increased power density with lower area-specific resistance (ASR), smaller ohmic losses, and lower ionomer cost. However, reducing thickness is accompanied by an increase in undesired species crossover harming performance and long-term efficiency. Here, we show that incorporating atomically thin monolayer graphene synthesized via scalable chemical vapor deposition (CVD) and tunable defect density into PEMs (Nafion, ∼5-25 μm thick) can allow for reduced H2 crossover (∼34-78% of Nafion of a similar thickness) while maintaining adequate areal proton conductance for applications (>4 S cm-2). In contrast to most prior work using >50 μm symmetric Nafion sandwich structures, we elucidate the interplay of graphene defect density and Nafion proton transport resistance on the performance of Nafion|graphene composite membranes and find high-quality low-defect density CVD graphene (G) supported on Nafion 211 (∼25 μm); i.e., N211|G has a high areal proton conductance (∼6.1 S cm-2) and the lowest H2 crossover (∼0.7 mA cm-2). Fully functional centimeter-scale N211|G fuel-cell membranes demonstrate performance comparable to that of state-of-the-art Nafion N211 at room temperature as well as standard operating conditions (∼80 °C, ∼150-250 kPa-abs) with H2/air (power density ∼0.57-0.63 W cm-2) and H2/O2 feed (power density ∼1.4-1.62 W cm-2) and markedly reduced H2 crossover (∼53-57%).

NHSH: Graph Hybrid Learning with Node Homophily and Spectral Heterophily for Node Classification

Graph Neural Network (GNN) is an effective model for processing graph-structured data. Most GNNs are designed to solve homophilic graphs, where all nodes belong to the same category. However, graph data in real-world applications are mostly heterophilic, and homophilic GNNs cannot handle them well. To address this, we propose a novel hybrid-learning framework based on Node Homophily and Spectral Heterophily (NHSH) for node classification in graph networks. NHSH is designed to achieve state-of-the-art or superior performance on both homophilic and heterophilic graphs. It includes three core modules: homophilic node extraction (HNE), heterophilic spectrum extraction (HSE) and node feature fusion (NFF). More specifically, HNE identifies symmetric neighborhoods of nodes with the same category, extracting local features that reflect these symmetrical structures. Then, HSE uses filters to analyze the high and low-frequency information of nodes in the graph and extract the global features of the nodes. Finally, NFF fuses the above two node features to obtain the final node features in graphs. Moreover, an elaborate loss function drives the network to preserve critical symmetries and structural patterns in the graph. Experiments on eight benchmark datasets validate that NHSH performs comparably or better than existing methods across diverse graph types.

Polarization-Insensitive, High-Efficiency Metasurface with Wide Reception Angle for Energy Harvesting Applications

This research presents an innovative polarization-insensitive metasurface (MS) harvester designed for energy harvesting applications at 5 GHz, capable of operating efficiently over wide reception angles. The proposed MS features a novel wheel-shaped resonator array whose symmetrical structure ensures insensitivity to the polarization of incident electromagnetic (EM) waves, enabling efficient energy absorption and minimizing reflections. Unlike conventional designs, the metasurface achieves near-unity harvesting efficiency, exceeds 94% under normal incidence, and maintains superior performance across various incident angles for TE and TM polarizations. To validate the design, a 5 × 5-unit cell array of the MS structure was fabricated and experimentally tested, demonstrating excellent agreement between simulation and measurement results. This work significantly advances metasurface-based energy harvesting by combining polarization insensitivity, wide-angle efficiency, and high absorption, making it a compelling solution for powering wireless sensor networks in next-generation applications.

Catalytic Hydrolysis of Perfluorinated Compounds in a Yolk-Shell Micro-Reactor.

Perfluorinated compounds (PFCs) are emerging environmental pollutants characterized by their extreme stability and resistance to degradation. Among them, tetrafluoromethane (CF4) is the simplest and most abundant PFC in the atmosphere. However, the highest C─F bond energy and its highly symmetrical structure make it particularly challenging to decompose. In this work, a yolk-shell Al2O3 micro-reactor is developed to enhance the catalytic hydrolysis performance of CF4 by creating a local autothermic environment. Finite element simulations predict that the yolk-shell Al2O3 micro-reactor captures the heat released during the catalytic hydrolysis of CF4, resulting in a local autothermic environment within the yolk-shell structure that is 50 °C higher than the set temperature. The effectiveness of this local autothermic environment is experimentally confirmed by in situ Raman spectroscopy. As a result, the obtained yolk-shell Al2O3 micro-reactor achieves 100% CF4 conversion at a considerably low temperature of 580 °C for over 150h, while hollow and solid Al2O3 structures required higher temperatures of 610 and 630 °C, respectively, to achieve the same conversion rate, demonstrating the potential of yolk-shell Al2O3 micro-reactor to significantly reduce the energy requirements for PFCs degradation and contribute to more sustainable and effective environmental remediation strategies.

Prediction of Thermodynamic Properties of C60-Based Fullerenols Using Machine Learning.

Traditional machine learning methods face significant challenges in predicting the properties of highly symmetric molecules. In this study, we developed a machine learning model based on graph neural networks (GNNs) to accurately and swiftly predict the thermodynamic and photochemical properties of fullerenols, such as C60(OH)n (n = 1 to 30). First, we established a global method for generating fullerenol isomers through isomer fingerprinting, which can generate all possible isomers or produce diverse structural types on demand. Significantly, by incorporating interpretable descriptors such as atomic labels, bond lengths, and bond angles from highly symmetric isomers, our multilayer GNN model achieved over 90% accuracy in predicting the thermodynamic stability of fullerenols. The model also performed excellently in predicting electronic properties, including the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and the energy gap. Overall, this work demonstrates a new strategy using interpretable descriptors for accurately predicting the properties of highly symmetric structures, offering theoretical chemists a valuable tool for studying these materials.

Sym- and Asym-Expanded Heterohelicene Isomers Featuring Extended Multi-Resonance Skeleton for Narrowband Deep-Blue Fluorescence.

Expanded heterohelicenes composed of alternating linearly and angularly fused multi-resonance (MR) skeletons have gained wide interest owing to their promising narrowband emissions. Herein, a pair of sym- and asym-expanded heterohelicene isomers was obtained by merging boron/oxygen (B/O)-embedded MR triangulene and indolo[3,2,1-jk]carbazole units via one-pot synthesis. Owing to their fully resonating extended helical skeleton, the target heterohelicenes exhibit a significantly narrowed spectra bandwidth while emission red-shifting, thus affording deep-blue narrowband emission with a peak at approximately 460 nm, full-width-at-half-maximum (FWHM) of only 18 nm, and near-unity photoluminescence quantum yields. In comparison to the symmetrical structure, the asym-expanded heterohelicene displays suppressed aggregation within doped films, thereby showing superior narrowband electroluminescence in devices with CIE coordinates of (0.12, 0.18) and a high external quantum efficiency of up to 25 %, which retains 18.1 % even at a high luminance of 10,000 cd m-1. Overall, this work provides a novel paradigm for the development of narrowband expanded heterohelicenes.

Symmetry Breaking of FeN4 Moiety via Edge Defects for Acidic Oxygen Reduction Reaction.

Fe-N-C catalysts, with a planar D4h symmetric FeN4 structure, show promising as noble metal-free oxygen reduction reaction catalysts. Nonetheless, the highly symmetric structure restricts the effective manipulation of its geometric and electronic structures, impeding further enhancements in oxygen reduction reaction performance. Here, a high proportion of asymmetric edge-carbon was successfully introduced into Fe-N-C catalysts through morphology engineering, enabling the precise modulation of the FeN4 active site. Electrochemical experimental results demonstrate that FeN4@porous carbon (FeN4@PC), featuring enriched asymmetric edge-FeN4 active sites, exhibits higher acidic oxygen reduction reaction catalytic activity compared to FeN4@flaky carbon (FeN4@FC), where symmetric FeN4 is primarily distributed within the basal-plane. Synchrotron X-ray absorption spectra, X-ray emission spectra, and theoretical calculations indicate that the enhanced oxygen reduction reaction catalytic activity of FeN4@PC is attributed to the higher oxidation state of Fe species in the edge structure of FeN4@PC. This finding paves the way for controlling the local geometric and electronic structures of single-atom active sites, leading to the development of novel and efficient Fe-N-C catalysts.

Optimizing solar performance of CFTSe-based solar cells using MoSe2 as an innovative buffer layers

In this study, we explore the photovoltaic performance of an innovative high efficiency heterostructure utilizing the quaternary semiconductor Cu2FeSnSe4 (CFTSe). This material features a kesterite symmetrical structure and is distinguished by its non-toxic nature and abundant presence in the earth’s crust. Utilizing the SCAPS simulator, we explore various electrical specifications such as short circuit current (Jsc), open circuit voltage (Voc), the fill factor (FF), and power conversion efficiency (PCE) were explored at a large range of thicknesses, and the acceptor carrier concentration doping (NA). Our results demonstrate that optimized parameters yield a remarkable PCE of 26.47%, accompanied by a Voc of 1.194 V, Jsc of 35.37 mA/cm2, and FF of 62.65% at a CFTSe absorber thickness of 0.5 μm. Furthermore, the performance of the photovoltaic cell is assessed for the defect levels in the CFTSe absorber and MoSe2 buffer layers. Results indicate that deep defect levels above 1 × 1017 cm− 3 lead to a decrease in Jsc. The study also investigates the effect of operating temperature on cell performance within the 300–500 K range. A notable decline in Voc is observed, likely due to an increase in saturation current, suggesting an interaction between temperature and cell behavior. In this work, we propose a practical CFTSe-based structure that replaces conventional buffer layers, such as CdS, with MoSe2 TMDC as a promising alternative buffer layer, paving the way for more sustainable solar technology.

Symmetrical and asymmetrical surface structure expansions of silver nanoclusters with atomic precision.

Controlling symmetrical or asymmetrical growth has allowed a series of novel nanomaterials with prominent physicochemical properties to be produced. However, precise and continuous size growth based on a preserved template has long been a challenging pursuit, yet little has been achieved in terms of manipulation at the atomic level. Here, a correlated silver cluster series has been established, enabling atomically precise manipulation of symmetrical and asymmetrical surface structure expansions of metal nanoclusters. Specifically, the C 3-axisymmetric Ag29(BDTA)12(PPh3)4 nanocluster underwent symmetrical and asymmetrical surface structure expansions via an acid-mediated synthetic procedure, giving rise to C 3-axisymmetric Ag32(BDTA)12(PPh3)10 and C 1-axisymmetric Ag33(BDTA)12(PPh3)11, respectively. In addition, structural transformations, including structural degradation from Ag32 to Ag29 and asymmetrical structural expansion from Ag32 to Ag33, were rationalized theoretically. More importantly, the asymmetrically structured Ag33 nanoclusters followed a chiral crystallization mode, and their crystals displayed high optical activity, derived from CD and CPL characterization. This work not only provides an important model for unlocking the symmetrical/asymmetrical size growth mechanism at the atomic level but also pioneers a promising approach to activate the optical activity of cluster-based nanomaterials.

One-step fabrication of high energy storage polymer films with a wide bandgap and high melting temperature induced by the fluorine effect for high temperature capacitor applications with ultra-high efficiency.

The development of polymer dielectrics with both high energy density and low energy loss is a formidable challenge in the area of high-temperature dielectric energy storage. To address this challenge, a class of polymers (Parylene F) are designed by alternating fluorinated aromatic rings and vinyl groups in the polymer chain to confine the conjugating sequence and broaden the bandgap with the fluorine effect. The target films with desired thickness, ultra-high purity, and a wide bandgap are facilely fabricated by a one-step chemical vapor deposition (CVD) technique from monomers. The symmetric and bulky aromatic structures exhibit high crystalline performance and excellent stability at high temperature. The presence of strongly electronegative fluorine atoms effectively enhances bandgap and electron trapping capability, which effectively reduces the conduction loss as well as the possibility of breakdown at high temperatures. CVD technology avoids the post-processing film-forming process, ensuring the fabrication of thin films with high quality. These benefits allow Parylene F films to effectively store electrical energy at temperature up to 150 °C, exhibiting a record discharged energy density of 2.92 J cm-3 at charge-discharge efficiency exceeding 90%. This work provides a new idea for the design and synthesis of all-organic polymer dielectric films for high temperature applications.

An optimization method for terahertz metamaterial absorber based on MOPSO

Metamaterials can freely control terahertz waves to obtain the desired electromagnetic characteristics by designing the geometry and direction of the unit structure, which is widely used in sensing, communication and stealth technology in radar. The traditional design of terahertz metamaterial absorber usually requires continuous structural adjustment and a large number of simulations to meet the expected requirements. The process is heavily dependent on the experience of researchers, and the physical modeling and simulation solution process is time-consuming and inefficient, which has greatly hindered the development of metamaterial absorbers. Therefore, deep learning has been used to predict the structural parameters or spectra of metamaterial absorbers due to its powerful learning ability. However, when designing a new structure, a large number of training samples need to be reprepared, which is time-consuming and not universal. Particle swarm optimization can quickly converge to the optimal solution through the sharing and cooperation of individual information in the group, without prior preparation. Therefore, this paper proposed a fast design method of terahertz metamaterial absorber based on multi-objective particle swarm optimization algorithm. Taking a new center symmetric absorber structure composed of four L as an example, the structure parameters are optimized to achieve fast automatic design of metamaterial absorber. The multi-objective particle swarm optimization takes the absorptivity and quality factor as independent targets to design the structure parameters of the absorber, realizes the dual-objective optimization of the absorber, and overcomes the shortcoming of the multi-objective conflict that PSO cannot solve. The optimally-designed absorber achieves perfect absorption at 1.613THz with a quality factor of up to 319.72 and a sensing sensitivity of 264.5GHz/RIU when used for refractive index sensing. In addition, the causes of absorption peaks are analyzed in detail using impedance matching, surface current, and electric field distribution. By studying the polarization characteristics of the absorber, it is found that it is not sensitive to polarization, which is more stable in practical application. In summary, the multi-objective particle swarm optimization algorithm can realize the design according to the demand, reduce the experience requirement of researchers in the design of metamaterial absorber, improve the design efficiency and performance, and have great application potential in the design of terahertz functional devices.

Deciphering the impacts of symmetric and asymmetric structures in heptazine units over g-C3N4 on piezo-photocatalysis for H2O2 production from pure water

Deciphering the impacts of symmetric and asymmetric structures in heptazine units over g-C3N4 on piezo-photocatalysis for H2O2 production from pure water

Progressive Collapse of Steel Structures Under Blast Loads Considering Soil‐Structure Interaction

This study focuses on the effect of soil‐structure interaction on the occurrence of progressive collapse due to an external blast. Therefore, a 3‐story fixed base steel moment‐resisting frame structure was first modeled and subjected to an external blast load. Then, the same structure was modeled considering soil‐structure interaction. In another stage of this study, the effect of plan irregularity on progressive failure resulting from the explosion was investigated, assuming the presence or absence of soil‐structure interaction. The direct simulation method and alternative load path method are all employed to simulate the progressive collapse process of steel frames using the commercial finite element program LS‐DYNA. The results of the numerical simulations demonstrated that the presence of soil‐structure interaction, significantly influences the response of the structure to the blast and this interaction increases the likelihood of progressive failure occurring even at symmetric and asymmetric structures. It was also shown that silty sand soil yields more critical conditions than other types of soil in the event of failure after the occurrence of an explosion in the structure.