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Abstract A ridge-loaded staggered double-vane slow-wave structure is proposed for terahertz radiation sources employing a sheet electron beam. This slow-wave structure has the advantages of enhanced electric field and energy density distribution and improved interaction impedance in the beam-wave interaction region. High-frequency characteristics are investigated for the proposed slow wave structure and compared with those of the staggered double-vane slow wave structure. The slow wave structure is fabricated and experimentally tested for transmission and reflection properties, revealing $$S_{21}$$ above -2 dB and $$S_{11}$$ below -17 dB at 0.34 THz for a backward wave oscillator. Steady transmission of the 21.7 kV sheet electron beam is achieved by designing a periodic cusped magnetic system (0.2 T) along with a sheet electron beam gun (50 mA). Beam-wave interaction simulations utilizing 100 periods demonstrate a peak power of 14 W and continuous frequency tuning from 0.295-0.375 THz for the proposed slow wave structure, whereas the staggered double-vane slow wave structure achieves 8.5 W peak power and frequency tuning from 0.308-0.366 THz. The sensitivity of the output power to the added ridge geometry is also analyzed. These findings indicate that the novel ridge-loaded staggered double vane slow-wave structure is promising for developing high-power broad frequency tunable terahertz radiation sources.

Abstract Mammalian voltage‐gated calcium channels (CaV) play critical roles in cardiac excitability, synaptic transmission, and gene transcription. Dysfunctions in CaV are implicated in a variety of cardiac and neurodevelopmental disorders. Current pharmacological approaches to enhance CaV activity are limited by off‐target effects, drug metabolism issues, cytotoxicity, and imprecise modulation. Additionally, genetically‐encoded channel activators and optogenetic tools are restricted by gene delivery challenges and biosafety concerns. Here a novel terahertz (THz) wave‐based method to upregulate CaV1.2, a key subtype of CaV, and boost CaV1‐mediated Ca2+ signaling in neurons without introducing exogenous DNA is presented. Using molecular dynamics simulations, it is shown that 42.5 THz (7.05 µm, 1418 cm−1) waves enhance Ca2+ conductance in CaV1.2 by resonating with the stretching mode of the ‐COO− group in the selectivity filter. Electrophysiological recordings and Ca2+ imaging confirm that these waves rapidly, reversibly, and non‐thermally increase calcium influx of CaV1.2 in HEK293 cells and induce acute Ca2+ signals in neurons. Furthermore, this irradiation upregulates critical CaV1 signals, including CREB phosphorylation and c‐Fos expression, in vitro and in vivo, without raising significant biosafety risks. This DNA‐free, non‐invasive approach offers a promising approach for modulating CaV gating and Ca2+ signaling and treating diseases characterized by deficits in CaV functions.

BackgroundKaposiform hemangioendothelioma (KHE) is a rare vascular tumor with a high risk of mortality. Few studies with large samples of KHE have been reported. KHE may develop into the Kasabach–Merritt phenomenon (KMP), which is characterized by thrombocytopenia and consumptive coagulopathy. The features of severe symptomatic anemia and life-threatening low platelets make the management of KHE associated with KMP challenging.ObjectiveThe aim of this study was to examine the clinical characteristics of patients with KHE and discuss the treatment experience for different risk groups of KHE.MethodsThrough a retrospective review of 70 patients diagnosed with KHE between 2017 and 2022 in our center, we classify lesions into three clinicopathological stages based on the tumor involving depth, and divided the severity of KHE into three levels by estimating clinicopathological stages and severity of thrombocytopenia. Treatments of different severity groups were estimated with sufficient data.ResultsIn our cohort, 27% were neonates, and KHE lesion occurred at birth in 84% of patients. There was a slight male predominance (32 girls and 38 boys). Common clinical characteristics included associated coagulation disorder (100%), locally aggressive cutaneous blue–purple mass (89%), thrombocytopenia (78%), and local pain or joint dysfunction (20%). The lower extremities were the dominant location (35%), followed by the trunk (29%), the maxillofacial region and neck (24%), and the upper extremities (10%). Of the total cohort, 78% developed KMP; the median age at which thrombocytopenia occurred was 27.8 days. The median platelet count of patients who were associated with KMP was 24,000/µL in our cohort. Ninety-two percent of patients were given surgery treatment and 89% of these patients were given high-dose methylprednisolone (5-6 mg/kg daily) before surgery. In 55 patients with KMP, 36% were sensitive to high-dose corticosteroid therapy. Patients from the low-risk group (eight cases) underwent operation, all of whom recovered without recurrence after a maximum follow-up of 5 years. Out of 26 patients from the high-risk group, 25 underwent surgery treatment, with 1 case undergoing secondary surgery after recurrence and 1 case taking sirolimus. Out of 36 cases from the extremely high-risk group, 32 underwent surgery (including 2 cases who underwent external carotid artery ligation and catheterization), 3 of whom underwent secondary operation after recurrence, and the remaining 4 cases took medicine. The mean length of having sirolimus was 21 months; two cases stopped taking sirolimus due to severe pneumonia. Two cases died at 1 and 3 months after discharge.ConclusionsOur study describes the largest assessment of high-risk patients with KHE who have undergone an operation to date, with 5 years of follow-up to track recovery, which provides invaluable knowledge for the future treatment of patients with KHE and KMP from different risk groups: Early surgical intervention may be the most definitive treatment option for most patients with KHE; multimodality treatment is the best choice for the extremely high-risk group.

The computer-assisted inverse design of photonic computing, especially by leveraging artificial intelligence algorithms, offers great convenience to accelerate the speed of development and improve calculation accuracy. However, traditional thickness-based modulation methods are hindered by large volume and difficult fabrication process, making it hard to meet the data-driven requirements of flexible light modulation. Here, we propose a diffractive deep neural network (D2NN) framework based on a three-layer all-dielectric phased transmitarray as hidden layers, which can perform the classification of handwritten digits. By tailoring the radius of a silicon nanodisk of a meta-atom, the metasurface can realize the phase profile calculated by D2NN and maintain a relative high transmittance of 0.9 at a wavelength of 600 nm. The designed image classifier consists of three layers of phase-only metasurfaces, each of which contains 1024 units, mimicking a fully connected neural network through the diffraction of light fields. The classification task of handwriting digits from the ‘0’ to ‘5’ dataset is verified, with an accuracy of over 90% on the blind test dataset, as well as demonstrated by the full-wave simulation. Furthermore, the performance of the more complex animal image classification task is also validated by increasing the number of neurons to enhance the connectivity of the neural network. This study may provide a possible solution for practical applications such as biomedical detection, image processing, and machine vision based on all-optical computing.

Entanglement is one of the most striking features of quantum systems, whereby its non-classical correlation is an essential resource in numerous quantum protocols. Entanglement can be divided into two categories: interparticle and intraparticle entanglement. There are both distinctions and similarities between these two kinds of entangled states. This work delves into these distinctions and similarities from the following aspects: correlation and non-locality, robustness, the mechanisms of generation and separation, and practical applications. Entanglement swapping is a technique based on quantum entanglement. As entanglement has different categories, entanglement swapping also has various types, including interparticle to interparticle and intraparticle to interparticle. Swapping protocols from intraparticle entanglement to interparticle entanglement can be applied to super quantum dense encoding, quantum information transmission, quantum teleportation, etc. Thus, this work proposes three swapping protocols, from spin–orbit intraparticle entanglement to spin–spin interparticle entanglement, based on Bell state joint measurement, the cross-Kerr medium, and linear optical elements. This work can help us better understand entanglement by analyzing the differences and similarities between the two types of entangled states. It can also enhance entanglement swapping protocols, from spin–orbit intraparticle to spin–spin interparticle entanglement, for use in quantum information transfer.

Summary: The biosafety of terahertz (THz) waves has emerged as a new area of concern with the gradual application of terahertz radiation. Even though many studies have been conducted to investigate the influence of THz radiation on living organisms, the biological effects of terahertz waves have not yet been fully revealed. In this study, Caenorhabditis elegans (C. elegans) was used to evaluate the biological consequences of whole-body exposure to 0.263 THz irradiation. The integration of transcriptome sequencing and behavioral tests of C. elegans revealed that high-power THz irradiation damaged the epidermal ultrastructures, inhibited the expression of the cuticle collagen genes, and impaired the movement of C. elegans. Moreover, the genes involved in the immune system and the neural system were dramatically down-regulated by high-power THz irradiation. Our findings offer fresh perspectives on the biological impacts of high-power THz radiation that could cause epidermal damage and provoke a systemic response.

We have simulatively studied the electrical excitation of acoustic and optical plasmons in double-channel AlGaN/GaN high electron mobility transistors (HEMT) under asymmetric boundaries. By solving the self-consistent hydrodynamic model with Maxwell’s equations, it is found that the drift plasmons are excited in the bilayer 2DEGs under asymmetric boundaries. The oscillation intensity in a bilayer system is much stronger than that in a monolayer 2DEG system because of the simultaneous excitation of the fundamental and the second harmonic components. The fundamental component always corresponds to the acoustic plasmon, while the optical plasmon can be excited when it is resonant with the second harmonic of the acoustic plasmon. Because of the out-of-phase properties of the acoustic plasmons, their radiated power is limited by the current cancellation. On the other hand, as the optical plasmons are excited, the radiated powers are much higher than those of the single channel HEMT due to the in-phase currents generated in the double layers. The effects of different parameters such as gate lengths, 2DEG spacings, and electron concentrations on plasmon excitations and THz emissions of double-channel HEMTs are analyzed in detail. The numerical results provide a more powerful terahertz radiation mechanism in double-channel HEMT compared with the Dyakonov–Shur instability in traditional single-channel HEMT.

Comorbid anxiety in chronic pain is clinically common, with a comorbidity rate of over 50%. The main treatments are based on pharmacological, interventional, and implantable approaches, which have limited efficacy and carry a risk of side effects. Here, we report a terahertz (THz, 1012 Hz) wave stimulation (THS) technique, which exerts nonthermal, long-term modulatory effects on neuronal activity by reducing the binding between nano-sized glutamate molecules and GluA2, leading to the relief of pain and comorbid anxiety-like behaviors in mice. In mice with co-occurring anxiety and chronic pain induced by complete Freund’s adjuvant (CFA) injection, hyperactivity was observed in glutamatergic neurons in the anterior cingulate cortex (ACCGlu). Using whole-cell recording in ACC slices, we demonstrated that THS (34 THz) effectively inhibited the excitability of ACCGlu. Moreover, molecular dynamics simulations showed that THS reduced the number of hydrogen bonds bound between glutamate molecules and GluA2. Furthermore, THS target to the ACC in CFA-treatment mice suppressed ACCGlu hyperactivity and, as a result, alleviated pain and anxiety-like behaviors. Consistently, inhibition of ACCGlu hyperactivity by chemogenetics mimics THS-induced antinociceptive and antianxiety behavior. Together, our study provides evidence for THS as an intervention technique for modulating neuronal activity and a viable clinical treatment strategy for pain and comorbid anxiety.

Summary: Terahertz science and technology has recently shown new application prospects in artificial intelligence. It is found that terahertz unipolar stimulation can activate cell membrane hydrophilic pores. However, the behaviors of Na+, K+-ATPase and energy consumption during this period remain unknown. This paper investigates these behaviors by Na+, K+-ATPase and electroporation models, based on the interaction theory between terahertz fields and ions at the cellular level. The effective diameters of life ions are considered in the aqueous solution. From results, Na+, K+-ATPases can be activated and stay for a while before close after the stimulation. Their life ion flows are far lower than the flows via the pores. And their power dissipation is as low as 10−11 W in both rat neostriatal neurons and guinea pig ventricular myocytes. The results keep tenable in 0.1–1.2 THz. These lay the basis for investigations of information communication mechanisms in cells under terahertz stimulation.

Summary: Intermolecular interactions, including hydrogen bonds, dominate the pairing and unpairing of nucleic acid chains in the transfer process of genetic information. The energy of THz waves just matches with the weak interactions, so THz waves may interact with biomolecules. Here, the dynamic effects of THz electromagnetic (EM) waves on the mechanical unfolding process of RNA hairpins (WT-30nt and its mutants, rHP, SARS-CoV-2, and SRV-1 SF206) are investigated using steered molecular dynamics (SMD) simulations. The results show that THz waves can either promote the unfolding of the double helix of the RNA hairpin during the initial unfolding phase (4–21.8 THz) or significantly enhance (23.8 and 25.5 THz) or weaken (37.4 and 41.2 THz) its structural stability during unfolding. Our findings have important implications for applying THz waves to regulate dynamic deconvolution processes, such as gene replication, transcription, and translation.

Surface plasmon polaritons (SPPs) have become a research hotspot due to their high intensity and subwavelength localization. Through free-electron excitation, a portion of the momentum of moving electrons can be converted into SPPs. Converting highly localized SPPs into a radiated field is an approach with the potential to aid in the development of a light radiation source. Reducing losses of SPPs is currently a critical challenge that needs to be addressed. The lifetime of SPPs in metal films is longer than that in metal blocks. Traditional optical gratings can transform SPPs into radiation to avoid the decay of SPPs in metal; however, they are created by etching metal films, so they tend to alter the dispersion characteristics of these films and will emit radiation in the direction perpendicular to the metal surface. This paper proposes an approach to converting the SPPs of a metal film excited by free electrons into a radiation field via lateral grating and obtaining in-plane radiation. We investigate the properties of SPP lateral radiation. The study of lateral radiation from metal films holds significant importance for SPP radiation sources and SPP on-chip circuit development.

A novel approach for flow velocity measurements on a microfluidic chip using near-field scanning microwave microscopy (NSMM) is proposed. It does not require the tested sample to contain visible particles, as the intrinsic electromagnetic properties of the fluid can be detected. Compared with conventional flowmetry, NSMM can measure flow velocity of the tested specimen without any invasive detectors inside or in contact with the specimen, and it can preserve original characteristics of the sample. The flow velocity of different types of solutions is obtained in point scanning, and flow velocity distribution in a microfluidic channel is illustrated in line scanning of NSMM measurement. The flow velocity distribution in microfluidic channel demonstrates distinctive differences between flow velocities of adjacent points, and the microfluidic channel is recognized with a lateral resolution of 10 μm. This approach can help optimize localized flow velocity measurement in drug screening and chemical reaction, and it can be developed for 2D/3D flow velocity imaging in chemical industry and biomedical field.

Highly aligned TiO2 nanoarrays (TNAs) are fabricated on free-standing diamond (FSD) films and Si wafers (for comparison). Different anodizing times (e.g., 5, 15, 25, 45, and 60 min) are used to investigate the morphologies of TNAs and their effect on the electron field emission (EFE) properties. With the increase of the anodizing time, the features of TNAs grown on the FSD film undergo the transition from nanorods to nanopores and then to nanotubes. The XRD, Raman, and TEM results reveal that TNAs synthesized on the FSD film are preferentially oriented rutile phase, while those synthesized on the Si wafers show the anatase structure. Rutile TiO2 has a relatively low work function and is favorable to EFE performance. Importantly, the nanotubes on the FSD substrate with a 45 min anodizing time grow perpendicularly to each crystal face of the diamond grains and exhibit a superior EFE behavior, which can be turned on at a low field of 0.7 V/μm and attain a high current density of 0.6 mA/cm2 at an applied field of 1.6 V/μm. The enhanced EFE performance of TNAs/FSD composite film is ascribed to the synergetic effects among the electron acceleration layer played by the FSD film, more electron emission sites provided by the nanotubes with large aspect ratios, and lower work function of rutile TiO2. Moreover, the heterogeneity of the FSD substrate and TNAs also can decrease the interface barrier to make electrons transmit effectively.

How terahertz signals perform in the neural system has attracted widespread interest in the life sciences community. Relevant experimental reveals that in animal nerve cells, the myelin sheath of the nerve axon has a higher refractive index than the intracellular and extracellular fluids in the Terahertz-far-infrared (THz-FIR) frequency band. This makes THz-FIR wave transmission possible in nerve fibers. Based on this premise, this article carries out the following work from the theoretical level to investigate the electromagnetic (EM) characteristics of in vivo nerve fibers at the THz-FIR band. First, the EM transmission model of the nerve fibers is established and studied theoretically. The dispersion curves of THz-FIR wave modals transmission in nerve fibers are calculated, which predict that nerve fibers can act as dielectric waveguides for transmitting THz-FIR waves and the THz-FIR waves can transmit at speeds up to 108 m/s. Second, a mode matching algorithm is proposed, which is named RNMMA, to calculate the transmission characteristics of THz-FIR waves at the nodes of Ranvier. The scattering matrix obtained from the proposed algorithm is in good agreement with the results from EM simulation software, which reveals how THz-FIR signals are transmitted forward through the nodes of Ranvier with low loss.

Smith–Purcell radiation (SPR) is a phenomenon in that free electrons moving above a periodic structure deliver a part of their kinetic energies to electromagnetic waves. It plays an important role in the development of radiation sources and beam diagnosis. With the development of nanofabrication technology, various complex micro‐nano‐metallic periodic or aperiodic structures have been adopted to improve the efficiency and coherence of SPR. In general, when free electrons move above the metallic periodic structure, the localized surface wave and Smith–Purcell radiation wave are excited simultaneously. As the frequency of the surface wave is always lower than the threshold of Smith–Purcell radiation, the surface wave cannot be radiated. Here, the surface wave is transformed into SPR by using a novel composite subwavelength hole array, thus the SPR is enhanced and it becomes coherent and easy to tune. This work provides a competitive approach to achieve a coherent and high‐efficiency THz radiation source.

Microwave-induced thermoacoustic imaging (MTAI) has emerged as a potential biomedical imaging modality with over 20-year growth. MTAI typically employs pulsed microwave as the pumping source, and detects the microwave-induced ultrasound wave via acoustic transducers. Therefore, it features high acoustic resolution, rich electromagnetic contrast, and large imaging depth. Benefiting from these unique advantages, MTAI has been extensively applied to various fields including pathology, biology, material and medicine. Till now, MTAI has been deployed for a wide range of biomedical applications, including cancer diagnosis, joint evaluation, brain investigation and endoscopy. This paper provides a comprehensive review on (1) essential physics (endogenous/exogenous contrast mechanisms, penetration depth and resolution), (2) hardware configurations and software implementations (excitation source, antenna, ultrasound detector and image recovery algorithm), (3) animal studies and clinical applications, and (4) future directions.

In this paper, a novel staggered double-segmented grating slow-wave structure (SDSG-SWS) is developed for wide-band high-power submillimeter wave traveling-wave tubes (TWTs). The SDSG-SWS can be considered as a combination of the sine waveguide (SW) SWS and the staggered double-grating (SDG) SWS; that is, it is obtained by introducing the rectangular geometric ridges of the SDG-SWS into the SW-SWS. Thus, the SDSG-SWS has the advantages of the wide operating band, high interaction impedance, low ohmic loss, low reflection, and ease of fabrication. The analysis for high-frequency characteristics shows that, compared with the SW-SWS, the SDSG-SWS has higher interaction impedance when their dispersions are at the same level, while the ohmic loss for the two SWSs remains basically unchanged. Furthermore, the calculation results of beam–wave interaction show that the output power is above 16.4 W for the TWT using the SDSG-SWS in the range of 316 GHz–405 GHz with a maximum power of 32.8 W occurring at 340 GHz, whose corresponding maximum electron efficiency is 2.84%, when the operating voltage is 19.2 kV and the current is 60 mA.

In this paper, an angular radial extended interaction amplifier (AREIA) that consists of a pair of angular extended interaction cavities is proposed. Both the convergence angle cavity and the divergence angle cavity, which are designed for the converging beam and diverging beam, respectively, are investigated to present the potential of the proposed AREIA. They are proposed and explored to improve the beam–wave interaction capability of W-band extended interaction klystrons (EIKs). Compared to conventional radial cavities, the angular cavities have greatly decreased the ohmic loss area and increased the characteristic impedance. Compared to the sheet beam (0°) cavity, it has been found that the convergence angle cavity has a higher effective impedance and the diverging beam has a weaker space-charge effect under the same ideal electron beam area; the advantages become more obvious as the propagation distance increases. Particle-in-cell (PIC) results have shown that the diverging beam (8°) EIA performs better at an output power of 94 GHz under the condition of lossless, while the converging beam (−2°) EIA has a higher output power of 6.24 kW under the conditions of ohmic loss, an input power of 0.5 W, and an ideal electron beam of 20.5 kV and 1.5 A. When the loss increases and the beam current decreases, the output power of the −2° EIA can be improved by nearly 30% compared to the 0° EIA, and the −2° EIA has a greatly improved beam–wave interaction capacity than conventional EIAs under those conditions. In addition, an angular radial electron gun is designed.

Summary: The question of whether terahertz (THz) waves can interact with ions in channels of nerve cells and cause a further reaction has attracted much attention. To answer this question, we investigate the spontaneous radiation generated by Ca2+ moving in calcium channels and the effect of THz radiation on the transport of Ca2+ by solving the mathematical physical model through Brownian dynamics (BD) simulations. It is obtained that the moving Ca2+ in a calcium channel can generate electromagnetic radiation, the corresponding spectrum of which is concentrated in the THz range. Meanwhile, both the ion number in the channel and the background temperature are proved to have significant effects on the spontaneous emission spectra. The studies also show that external THz radiation can accelerate Ca2+ transport through the ion channel. These results are expected to provide a theoretical basis for the future treatment of THz waves in the neurological field.

Microwave-induced thermoacoustic imaging (MI-TAI) remains one of the focus of attention among biomedical imaging modalities over the last decade. However, the transmission and distribution of microwave inside bio-tissues are complicated, thus result in severe artifacts. In this study, to reveal the underlying mechanisms of artifacts, we deeply investigate the distribution of specific absorption rate (SAR) inside tissue-mimicking phantoms with varied morphological features using both mathematical simulations and corresponding experiments. Our simulated results, which are confirmed by the associated experimental results, show that the SAR distribution highly depends on the geometries of the imaging targets and the polarizing features of the microwave. In addition, we propose the potential mechanisms including Mie-scattering, Fabry-Perot-feature, small curvature effect to interpret the diffraction effect in different scenarios, which may provide basic guidance to predict and distinguish the artifacts for TAI in both fundamental and clinical studies.

This paper simulates Ca2+ transmembrane transport through voltage-gated Ca2+ channels in response to terahertz electromagnetic irradiation. The active transport of Ca2+ ions is taken into considerations in the Ca2+ transport. Temperature variations due to terahertz electromagnetic loss in physiological medium are simulated. The electromagnetic interaction between terahertz fields and physiological mobile ions at the cellular level is deduced from relativistic electrodynamics. It shows that effects of 0.1 ~ 3 THz electromagnetic fields on cell mobile ions are primarily due to effects of electric fields, and effects of magnetic fields at the cellular level are insignificant. In addition, numerical simulation reveals that terahertz irradiation causes vibration of membrane potential, which is able to activate voltage-gated Ca2+ channels. Besides, bioeffects of terahertz frequency, irradiation duration and electric intensity on the increment of intracellular Ca2+ concentration due to activation of voltage-gated Ca2+ channels are revealed. Meanwhile, numerical results show that temperature rises are inconsequential in the case of different irradiation parameters, indicating the non-thermal bioeffects of voltage-gated Ca2+ transmembrane transport due to terahertz irradiation. Furthermore, the results also reveal that thermal bioeffect can be significant if the irradiation duration is raised long enough for high-dose terahertz irradiation. The numerical simulations lay the basis for understanding the bioeffects of terahertz irradiation on Ca2+ transmembrane transport and pave the way for further exploration in modulation of intracellular Ca2+ concentration with terahertz electromagnetic wave.

In this paper, an eight-arm Archimedean spiral antenna (ASA) is proposed to generate multiple orbital angular momentum (OAM) modes over a respectable frequency band (1.9-3GHz). Firstly, the principle of radiation by eight-arm ASA with right-hand spiral line is analyzed and simulated. It is demonstrated that the OAM modes and polarizations of the generated vortex waves are reconfigurable by changing the fed phases of the eight arms and controlling the radius of the antenna arm. Meanwhile, a prototype is fabricated and measured, in which experimental results agree well with simulation ones. At last, compared with other recently reported OAM-generating antennas, the proposed antenna with the smaller structure (Φ2.45λ0, where λ0 is the wavelength of the center frequency) can produce the higher gain (4.5-11.2dBi) vortex waves carrying multiple OAM modes (five modes) in the broad band of 1.9-3GHz.

The voltage-gated calcium influxes modulated with terahertz Gaussian pulse is presented in this paper, and temperature rise is evaluated to monitor the terahertz thermal effects involved in the modulation. From the numerical results, inhibition effect on voltage-gated calcium influx because of the loss of the influx from electric drift is transparently revealed in the modulation with terahertz Gaussian pulse. And the inhibition effect becomes significant reflected by considerable reduction in voltage-gated calcium influx as the irradiated amplitude is raised intense enough. Compared to the terahertz sinusoidal wave, Gaussian pulse reduces the inhibition effect dramatically. The decrease in the increment of intracellular calcium concentration with the irradiated amplitude due to the inhibition effect is substantially relieved by the modulation of the calcium influx with terahertz Gaussian pulse. The thermal analyses reveal that the modulation is non-thermal effect. Meanwhile, to raise the intracellular calcium concentration to a same amount by means of the voltage-gated calcium influx, application of terahertz Gaussian pulse induces much less concurrent temperature rise than application of terahertz sinusoidal wave of the same amplitude that is intense enough to cause the inhibition effect. Additionally, terahertz Gaussian pulse irradiation remains the dependence of the increment of the calcium concentration on the irradiated time duration and frequency in terahertz sinusoidal wave irradiation. These numerical results lay the theoretical basis for the modulation of voltage-gated calcium fluxes with terahertz Gaussian pulse and for further potential clinical applications of terahertz Gaussian pulse.

In this paper, we focus on the generation of broadband underwater vortex waves carrying multiple OAMs. Based on a wideband underwater antenna, a water-immersed horn antenna array is designed and tested. The experimental results, which are in agreement with the simulation ones, validate that the proposed antenna array can readily generate high-quality vortex waves. To further validate the performance of the proposed underwater antenna array, experimental verifications of 2-D underwater imaging for the targets of two corner reflectors have been carried out, and the result shows that the targets can be distinguished efficiently. Meanwhile, two generation methods and one detection method of the multiplexed OAMs are also presented, from which the multiplexed OAMs can be generated and detected efficiently. And the performances of two generation methods have also been compared and discussed, from which we can know that the first generation method with a smaller structure costs lower and is more efficient.

A novel electron-optical system is proposed for dual azimuthally stacked radial sheet electron beams (ARSEBs). The two sheet beams are emitted from curved surfaces of two cathodes and are focused by a focusing electrode, which is carefully designed to produce a symmetric field distribution for the two beams and to avoid interference between the beams. A common tunable periodic cusped magnetic focusing system is also designed to focus the two ARSEBs. The dual sheet beams are used in a traveling wave tube (TWT) consisting of a cascade of two azimuthally supported angular log-periodic strip-line (ASALS) slow-wave structures (SWSs). The transmission efficiency in the presence of beam–wave interaction is 93%. The particle-in-cell simulation results show that for a beam voltage of 4400 V and a current of 0.39 A, the proposed cascaded TWT has a maximum gain of 32.5 dB at 35 GHz and a maximum output power of 180 W; this is a significant gain improvement over a TWT using a single ASALS SWS.

The limitation of mechanical manufacturing will result in a small tilt angle of the sample stage in the horizontal direction, which decreases the spatial resolution of imaging in near-field scanning microwave microscopy (NSMM). In this paper, we focus on the tilt correction and improve the spatial resolution of the NSMM image. The results of electromagnetic simulation and line scan measurement demonstrate the critical parameters affecting the sensitivity of NSMM, such as the length of the probe extending out of the cavity, the tip–sample distance, and the tip apex size. The tilt images can rotate successfully to the horizontal plane with the tilt correction methods, and the local average and re-interpolation are applied to denoise the images. Experimental NSMM images of copper thin film grid, coin texture, lithography mask, and leaf vein are obtained. The images before and after correction verify the improvement of the spatial resolution with all the above methods.

A terahertz metamaterial sensor for thin film sensing is proposed and investigated by a numerical study. The designed metamaterial sensor consists of an array of back to back c-shaped double-gap resonators, which can be obtained by simple manufacturing processes. By checking the shift of the resonate frequency of the sensor, the thickness of the analytes deposited on the sensor surface can be identified. We analyzed the sensitivities and corresponding quality factors of the sensor excited by two orthogonal polarized terahertz waves individually for both loss-free and lossy coating analyte layers. The electric field distributions of the metamaterial sensor with different analyte thicknesses are analyzed in detail to illustrate the principle of thin film detection and the principle of improving sensitivity. The transmission line model is built to verify the results of the numerical simulation. This study provides a useful reference for the design of biosensors based on metamaterial sensors in the future.

Usually, the fluidity of liquids is considered to make the temperature field uniform, when it is heated, because of the heat convection, but there is something different when microwave heating. The temperature of the top is always the highest in the liquid when heated by microwaves. In this paper, the multiphysics simulation and experimental comparison of the temperature distribution of microwave heated water and alcohol and microwave reheated rice are performed. In order to make the temperature distribution of liquids heated by microwaves uniform, the cut-off waveguide is used to control microwave heating and improve the temperature uniformity. The experimental results show that when the modified glass cup with 7 cm metal coating is used to heat water in a microwave oven, the temperature difference between the upper and lower parts of the water is reduced from 7.8 °C to 0.5 °C. The modified glass cup is placed in the center of the ceramic plate, far away from the cavity wall, and there is no spark ignition.

In this paper, a nested dual-arm spiral antenna (NDASA) is proposed to generate multiple orbital angular momentum (OAM) modes at the same operating frequency. The NDASA consists of the feeding network and three nested dual-arm spiral structures with different sizes. Meanwhile, a metal reflector is located between the spiral structures and the feeding network to enhance the radiation directivity, which can also reduce the impact of the radio frequency (RF) coaxial cables. Both the experimental and simulated results show OAM waves with topological charges of l = 1, l = 3 and l = 5 can be independently generated at f = 3 GHz, and their maximum gains are 6.94dBi, 6.76dBi and 5.49dBi, respectively. In addition, the OAM modes multiplexing and demultiplexing technology are investigated in simulations and experiments. The isolations between the OAM modes of l = 1, l = 3 and l = 5 and the other different OAM modes are greater than 13.8dB, 13.2dB and 25.1dB, respectively, which proves the potential ability of the proposed NDASA for multiplexing and demultiplexing multiple OAM modes.

In this paper, a novel angular log-periodic folded groove waveguide (ALFGW) slow-wave structure (SWS) has been investigated theoretically and experimentally for application in Ka-band traveling-wave tubes (TWTs). The dispersion relation for the ALFGW is derived analytically, and the dispersion characteristics are calculated for a Ka-band design. The designed SWS is fabricated using oxygen-free-copper that is silver electroplated. The measured cold-test parameters show good agreement with the simulation results, with S21 varying from −2.7 dB to −4.8 dB and S11 better than −13.6 dB over the frequency range of 30–38 GHz. Simulations of beam–wave interactions using a 4850 V and 0.4 A sheet beam with a high aspect ratio of 28:1 indicate an output power of 128 W, corresponding to a maximum gain and electronic efficiency of 18.1 dB and 6.6%, respectively. Due to the log-periodic form, a higher output power, higher efficiency, wider bandwidth, and lower operating voltage are achieved as compared to a TWT based on the conventional folded groove waveguide (FGW) SWS. These results show that the proposed ALFGW SWS has good potential for application in relatively high-power wideband TWTs.

Electrical gating has been typically used for Graphene-based devices to deliver high performance with superior electrical controllability. In this study, we utilize direct electron beam irradiation to attain the electrical controllability of graphene. The newly established system combines terahertz time-domain spectroscopy (TDS) with scanning electron microscopy (SEM). We experimentally demonstrate the precise localized tuning of graphene terahertz metamaterials, as the size and position of the electron beam generated by SEM are highly controllable. Furthermore, graphene metamaterials with different chemical potentials are simulated, and the results are highly consistent with the experiments.

The nucleation of graphene at different locations in the quartz boat was studied, and the lowest nucleation density of graphene in the quartz boat was found. The nucleation density of graphene is the lowest at the bottom of the quartz boat near the gas inlet side. Based on the above results, a simple and reproducible way is proposed to significantly suppress the nucleation density of graphene on the copper foil during the chemical vapor deposition process. Placing the copper foil with an area of 1.3 cm × 1 cm in the middle of the bottom of the quartz boat or further back, and placing two copper pockets in front of the copper foil, an ultra-low nucleation density of ~42 nucleus/cm2 was achieved on the back of the copper foil. Single-crystal monolayer graphene with a lateral size of 800 μm can be grown on the back of copper foils after 60 min of growth. Raman spectroscopy revealed the single-crystal graphene to be in uniform monolayers with a low D-band intensity.

Reversed Cherenkov radiation has not been observed due to the absence of suitable all-metal left-handed materials for beam transport and suitable couplers for extracting the signal. Here, Duanet al. develop a metamaterial to observe reversed Cherenkov radiation using real charged particles.

A complex permittivity characterization method for liquid samples has been proposed. The measurement is carried out based on a self-designed microwave sensor with a split ring resonator (SRR), the unload resonant frequency of which is 5.05 GHz. The liquid samples in capillary are placed in the resonant zone of the fabricated senor for high sensitivity measurement. The frequency shift of 58.7 MHz is achieved when the capillary is filled with ethanol, corresponding a sensitivity of 97.46 MHz/μL. The complex permittivity of methanol, ethanol, isopropanol (IPA) and deionized water at the resonant frequency are measured and calibrated by the first order Debye model. Then, the complex permittivity of different concentrations of aqueous solutions of these materials are measured by using the calibrated sensor system. The results show that the proposed sensor has high sensitivity and accuracy in measuring the complex permittivity of liquid samples with volumes as small as 0.13 μL. It provides a useful reference for the complex permittivity characterization of small amount of liquid chemical samples. In addition, the characterization of an important biological sample (inositol) is carried out by using the proposed sensor.

Single-crystal graphene has attracted much attention due to its excellent electrical properties in recent years, and many growth methods have been proposed, including the copper pockets method. In the copper pockets method, a piece of copper foil is folded into a pocket and put into a chemical vapor deposition (CVD) system for the growth of graphene. The dynamic balance of evaporation and deposition of copper on the inner surfaces of the copper pockets avoids high surface roughness caused by the evaporation of copper in open space, such as the outer surfaces of copper pockets. Much lower partial pressure of methane in the copper pockets and lower surface roughness reduce the nucleation density of graphene and increase the size of single-crystal graphene. It is found that the growth pressure is closely related to the size of single-crystal graphene prepared by the copper pockets method; the higher the growth pressure, the larger the size of single-crystal graphene. It is also found that the growth pressure has an effect on the inner surface roughness of the copper pockets, but the effect is not significant. The main factor affecting the size of the single-crystal graphene is the change in the volume of the copper pockets caused by the change in the growth pressure, and the volume of the copper pockets determines the content of methane in the copper pockets. According to the above law, the size of single-crystal graphene prepared by the copper pockets method can be enlarged by increasing the growth pressure. The size of single-crystal graphene can be enlarged in a wide range as the growth pressure can be increased in a wide range. In our experiments, when the growth pressure reached 450 Pa, single-crystal graphene with a diameter of 450 μm was prepared.

Recently, the study of analog optical computing raised renewed interest due to its natural advantages of parallel, high speed and low energy consumption over conventional digital counterpart, particularly in applications of big data and high-throughput image processing. The emergence of metamaterials or metasurfaces in the last decades offered unprecedented opportunities to arbitrarily manipulate the light waves within subwavelength scale. Metamaterials and metasurfaces with freely controlled optical properties have accelerated the progress of wave-based analog computing and are emerging as a practical, easy-integration platform for optical analog computing. In this review, the recent progress of metamaterial-based spatial analog optical computing is briefly reviewed. We first survey the implementation of classical mathematical operations followed by two fundamental approaches (metasurface approach and Green’s function approach). Then, we discuss recent developments based on different physical mechanisms and the classical optical simulating of quantum algorithms are investigated, which may lead to a new way for high-efficiency signal processing by exploiting quantum behaviors. The challenges and future opportunities in the booming research field are discussed.

Since its invention in 2009, Perovskite solar cells (PSCs) has attracted great attention because of its low cost, numerous options of efficiency enhancement, ease of manufacturing and high-performance. Within a short span of time, the PSC has already outperformed thin-film and multicrystalline silicon solar cells. A current certified efficiency of 25.2% demonstrates that it has the potential to replace its forerunner generations. However, to commercialize PSCs, some problems need to be addressed. The toxic nature of lead which is the major component of light absorbing layer, and inherited stability issues of fabricated devices are the major hurdles in the industrialization of this technology. Therefore, new researching areas focus on the lead-free metal halide perovskites with analogous optical and photovoltaic performances. Tin being nontoxic and as one of group IV(A) elements, is considered as the most suitable alternate for lead because of their similarities in chemical properties. Efficiencies exceeding 13% have been recorded using Tin halide perovskite based devices. This review summarizes progress made so far in this field, mainly focusing on the stability and photovoltaic performances. Role of different cations and their composition on device performances and stability have been involved and discussed. With a considerable room for enhancement of both efficiency and device stability, different optimized strategies reported so far have also been presented. Finally, the future developing trends and prospects of the PSCs are analyzed and forecasted.

A millimeter-wave wideband antenna is presented for the 5th generation applications. The operation band ranges from 24 GHz to 39 GHz which covers most of the Ka band. Furthermore, a 9×9 multiple-input-multiple-output (MIMO) antenna is developed. The high isolation is achieved without introducing external decoupling structures. The transmission coefficient is under −20 dB within only 0.4 mm space between antenna elements. The radiation pattern also shows the stability within the wide operation band. Both simulated and measured results show that this proposed MIMO antenna is suitable for the future wireless communications.

In this paper, a mathematical physics model is set up to study dielectric constant profile of aqueous solvent in ionic solution, to revise Brownian dynamics simulation in ionic solution by considering time-variant dielectric constant profile with change in ion positions, and to study the effect of high-intensity electric pulses on the profile. The validation of the model is confirmed with verification calculations. By means of the proposed model, dielectric constant profiles in calcium chloride and sodium chloride solutions and their response to pulses are simulated. Based on numerical results, dielectric constants of aqueous solvent spatially vary instead of being the same value in ionic solutions. And the profiles are variant with time due to ion motion in solutions. From the profiles, overall dielectric constant in calcium chloride solution is lower than that in sodium chloride solution. And overall dielectric constant decreases with increment of solution concentration. In addition, the results show that influence on the profiles depends on solution concentration and field intensity of the pulse. The profile in solutions with low concentration is more vulnerable to the pulse than that with high concentration. And overall dielectric constant decreases dramatically as field intensity increases. Those understandings provide basis for application of pulses in biomedical engineering at the molecular level. Meanwhile, pulse radiation provides a potential way to constrain water molecules at room temperature reflected by significantly reducing dielectric constant, and to lower absorption loss of electromagnetic field in millimeter and far infrared band.

A W-band sheet electron beam (SEB) traveling-wave tube (TWT) based on flat-roofed sine waveguide slow-wave structure (FRSWG-SWS) is proposed. The sine wave of the metal grating is replaced by a flat-roofed sine wave around the electron beam tunnel. The slow-wave characteristics including the dispersion properties and interaction impedance have been investigated by using the eigenmode solver in the 3-D electromagnetic simulation software Ansoft HFSS. Through calculations, the FRSWG SWS possesses the larger average interaction impedance than the conventional sine waveguide (SWG) SWS in the frequency range of 86-110 GHz. The beam-wave interaction was studied and particle-in-cell simulation results show that the SEB TWT can produce output power over 120 W within the bandwidth ranging from 90 to 100 GHz, and the maximum output power is 226 W at typical frequency 94 GHz, corresponding electron efficiency of 5.89%.

Meander lines (MLs) in two configurations are presented to reduce the mutual coupling (MC) between two microstrip patch antenna elements. Inserting a slot in the ground plane between the antenna elements is a simple method to reduce the MC, while adding the MLs in the slot of the ground can further reduce the MC. In the first configuration, one ML is inserted in the slot of the ground and a maximum MC reduction of 39 dB throughout the −10 dB bandwidth is achieved. What’s more, the radiation patterns are not changed compared with the dual-element microstrip antenna array with a slotted ground. For the second configuration, two MLs are added in the slot of the ground. It is found that a maximum isolation of 53 dB can be obtained. However, the radiation patterns are slightly changed compared with the dual-element microstrip antenna array with a slot in the ground. Meanwhile, the measured peak gain and efficiency of the dual-element microstrip antenna array in the two configurations are given. Along with this paper, several prototypes have been fabricated and measured. The simulated results are in good accordance with the measurements, which are presented to verify that MC reduction can be achieved between microstrip antenna elements by adding the MLs in the slotted ground.

The poloidal electric filed, which is the drive field of poloidal rotation, has been observed and increases obviously after the injection of electron cyclotron resonance wave in HL-2A experiment, and the amplitude of the poloidal electric field is in the order of 103 V/m. Through theoretical analysis using Stringer rotation model, the observed poloidal electric field is of the same order as the theoretical calculation value. In addition, the magnetic pump damping which would damp the poloidal rotation is calculated numerically and the calculation results show that the closer to the core plasmas, the stronger the magnetic pump damping will be. Meanwhile, according to the value of the calculated magnetic pump damping, the threshold of the poloidal electric field which could overcome magnetic pump damping and drive poloidal rotation in tokamak plasmas is given out. Finally, the poloidal rotation velocity over time at different minor radius is studied theoretically.

A theoretical model for calculation of the high frequency characteristics of the sine waveguide slow-wave structure (SWS) is proposed. The formulas of dispersion and interaction impedances of the hybrid modes are obtained by combining the Helmholtz equation with the appropriate boundary conditions. Using the full wave analysis method, it is proved that the periodic structures with a half-period shift followed leads to a pairwise closing of passbands characteristic of adjacent mode. The sine waveguide SWS for 0.22THz traveling wave tube (TWT) is chosen as an illustrative example to verify the validity of the theoretical model, and the calculation results of the dispersion curve and interaction impedance curve are consistent with the HFSS simulation results. In addition, the influences of dimensions of sine waveguide on the high frequency characteristics of +1st spatial harmonic wave are investigated by numerical calculation. The study indicates that the appropriate SWS parameters are helpful for improving the bandwidth and increasing output power of TWT.

Kaposiform hemangioendothelioma, a rare vascular pediatric tumor often associated with Kasabach–Merritt phenomenon, is characterized by severe thrombocytopenia and consumptive coagulopathy. Kaposiform hemangioendothelioma is a severe disease and may progress quickly, resulting in a high mortality. However, standard treatment regimens for Kasabach–Merritt phenomenon have not yet been established. We reported here an infant with a large congenital kaposiform hemangioendothelioma in his chest wall who responded extremely well to surgical excision.