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Herein, we report the first example of a highly enantioselective alkylative aziridine ring opening. Under the catalysis of a chiral nickel/pyridine-imidazoline complex, asymmetric C(sp3)–C(sp3) cross-electrophile coupling between racemic N-sulfonyl styrenyl aziridines and readily available primary alkyl bromides furnishes a variety of highly enantioenriched phenethylamine derivatives with complete regiocontrol and good functional group tolerance. Preliminary mechanistic studies support a reaction pathway consisting of regioselective iodolysis of aziridines in situand subsequent enantioconvergent coupling of the generated β-amino benzyl iodides with alkyl bromides.

Multi-resonant metasurfaces are of great significance in the applications of multi-band nanophotonics. Here, we propose a novel metasurface design scheme for simultaneously supporting quasi-bound states in continuum (QBIC) and other resonant modes, in which QBIC resonance is generated by mirror or rotational symmetry breaking in oligomers while other resonant modes can be simultaneously excited by rationally designing the shapes of meta-atoms within oligomers. As an example, the simultaneous excitation of QBIC and anapole modes are demonstrated in a dimer metasurface composed of asymmetric dumbbell-shaped apertures. Based on the far-field multipole decomposition and near-field electromagnetic field distributions, the origin mechanisms of QBIC and anapole mode are elucidated. The symmetry breaking of dumbbell-shaped dimer results in QBIC. Within a certain asymmetric variation range, the contributions of toroidal dipole moment and electric dipole moment with approximately equal magnitudes remain dominant, which allows the anapole mode to always present. The effectiveness of the proposed design scheme is further confirmed by the experimental results identical with the evolutions of numerical simulation. In terahertz biosensing experiments, the anapole mode exhibits a higher sensitivity of 271.3 GHz (nmol/μl)−1, whereas the QBIC can achieve a lower detection limit of 0.015 nmol/μl and expands the detection range by almost an order of magnitude. Our findings are beneficial to designing multi-resonant metasurfaces with different resonance modes and promote the corresponding applications in the fields of biosensing, lasers, filtering, and nonlinearity.

Common-mode chokes (CMCs) are essential components of electromagnetic interference (EMI) filters. Obtaining precise common-mode (CM) and differential-mode (DM) impedance information of CMCs facilitates their performance evaluation and behavioral modeling, ultimately contributing to optimal EMI filter design. Among existing impedance extraction approaches, measurement methods are the most straightforward, not requiring CMC's detailed geometry and material properties. These methods typically use an impedance analyzer (IA) or vector network analyzer (VNA) with specific fixture adapters for measurements. However, these adapters introduce parasitics, which can affect measurement accuracy, particularly at high frequencies. Some solutions have been proposed but limited to single-phase CMCs. This article presents two impedance measurement methods for three-phase CMCs: single-port circuit de-embedding (SCD) and three-port network calibration (TNC). Both methods consider the parasitics of fixture adapters and provide unique solutions for accurate broadband measurements for the CM and DM impedances of three-phase CMCs. The SCD method has good versatility as it can be implemented using either an IA or VNA; however, it requires fixture adapter details for the de-embedding process. Conversely, the TNC method does not need these details but can only be implemented using an IA. Both methods are validated experimentally with good accuracy from 150 kHz to 120 MHz.

The Yangtze finless porpoises (Neophocaena asiaeorientalis a.) are an endemic and critically endangered species in China. Intensive captive breeding is essential for understanding the biology of critically endangered species, especially their pregnancy characteristics, knowledge of which is crucial for effective breeding management. Urine metabolomics can reveal metabolic differences, arising from physiological changes across pregnancy stages. Therefore, we used the urinary metabolomic technology, to explore urinary metabolite changes in pregnant Yangtze finless porpoises. A total of 2281 metabolites were identified in all samples, which including organic acids and derivatives (24.45%), organoheterocyclic compounds (20.23%), benzenoids (18.05%), organic oxygen compounds (7.73%), and phenylpropanoids and polyketides (6.48%). There were 164, 387, and 522 metabolites demonstrating differential abundance during early pregnancy, mid pregnancy, and late pregnancy, respectively, from the levels observed in nonpregnancy. The levels of pregnenolone, 17α-hydroxyprogesterone, and tetrahydrocortisone were significantly higher during all pregnancy stages, indicating their important roles in fetal development. The differential metabolites between nonpregnancy and pregnancy were mainly associated with amino acid and carbohydrate metabolism. Moreover, metabolic activity varied across pregnancy stages; steroid hormone biosynthesis was predominant in early pregnancy, and amino acid biosynthesis and carbohydrate metabolism were predominant in mid pregnancy and late pregnancy, respectively. Our results provide new insights into metabolic characteristics in the Yangtze finless porpoises’ urine during pregnancy, and indicate that the differential levels of urine metabolites can determine pregnancy in Yangtze finless porpoises, providing valuable information for the husbandry and management of pregnant Yangtze finless porpoises in captivity.Pregnenolone, 17α-hydroxyprogesterone, and tetrahydrocortisone play a crucial role in the pregnancy of Yangtze finless porpoises and can serve as biomarkers for pregnancy management.Graphical Abstract

Terahertz (THz) communication and sensing technology has recently gained increasing attention. Metallic parallel-plate waveguides (PPWG) have been researched since they were proven to be the carrier of lossless transmission of THz waves. However, previous reports have focused on the transmission and phase properties of single-polarized THz waves in PPWGs and have barely investigated the polarization properties. To reconstruct the polarization of the output THz wave in a PPWG, we study the transmission and phase properties of both TE and TM modes in detail. The phase difference of the TE and TM modes can be continuously adjusted by varying the propagation length and the gap of the two plates in PPWG due to the different dispersion of the two modes. The polarization ellipticity and rotation angle can be modulated in the range of ±45°. When a photonic cavity structure is applied to a PPWG, the output wave will be converted to 90° linear polarization at the frequency located in the cavity mode. All the proposed polarization control can be tuned by changing the structural parameters forming the PPWGs, making this approach attractive for integrating the function of the THz waveguides, which has significance for THz communication and sensing.

To summarize the characteristics and evaluate the quality of the methodology and evidence within systematic reviews (SRs) of Chinese herbal medicine (CHM) for Mycoplasma pneumoniaepneumonia (MPP) in children.

Optical remote-sensing image target detection holds significant research significance in various domains, including disaster relief, ecological environment protection, and military surveillance. However, since remote-sensing images have multiscale targets, complex backgrounds, and many small targets, the performance of the existing network models in remote-sensing image target detection cannot reach what we expect. In addition, we note that current networks use complex computational mechanisms that make the models time-consuming, which hinders their practicability in remote-sensing target detection scenarios. In response to this challenge, we propose an anchor-free and efficient one-stage target detection method for optical remote-sensing images. First, we propose the lightweight context-aware module GSelf-Attention, injected into the feature fusion network from top-to-bottom and bottom-to-top to enhance the feature information interaction. Second, we proposed that ELAN-RSN uses an optimized residual shrinkage network (RSN) to eliminate background noise and conflicting information in the multiscale feature fusion. Finally, we introduce the decoupled head fused with SPDConv to enhance the detection accuracy of small target objects further. The performance of the proposed algorithm is compared with that of other advanced methods on DIOR and RSOD datasets. The experimental results show that the proposed algorithm significantly improves object detection accuracy while ensuring detection efficiency and has high robustness. The code is available at https://github.com/FF-codeHouse/Object-Detection/tree/remote-sensing.

Metasurface (MS)-based terahertz (THz) biosensors have attracted significant attention in the biological field due to their nondestructive and harmless interaction with biochemical samples. However, it is still challenging for specific detection in mixed samples via THz metasensors. In this work, we modified THz MS chips and target biomolecules, respectively, utilized immune binding and gold nanorods (GNRs), and achieved THz high-sensitive specific detection for Alzheimer’s marker $\text{A}\beta _{\text {1-42}}$ protein via a microfluidic platform. A double-ring coupled metallic MS that can provide a strong localized field enhancement was fabricated and then modified with $\text{A}\beta _{\text {1-42}}$ -antibody by covalent binding to capture $\text{A}\beta _{\text {1-42}}$ . Moreover, GNRs were introduced to bind $\text{A}\beta _{\text {1-42}}$ , and the sensor’s response to $\text{A}\beta _{\text {1-42}}$ is greatly enhanced. Through this sensor-analytes modification, the sensitivity of the sensor can reach 240.91 GHz $\cdot $ mL/nmol, and the limit of detection (LoD) is one order of magnitude higher than that without GNRs. In addition, the LoD for $\text{A}\beta _{\text {1-42}}$ reached 0.2 pmol/mL (1 ng/mL), which is 100 times higher than other nonspecific proteins. More importantly, the biosensor can also recognize $\text{A}\beta _{\text {1-42}}$ in a mixed sample with physiological limiting concentration. Our high selectivity and sensitivity nanomaterial-MS hybrid-based THz biosensor would give access to rich applications in label-free biosensing.

Age estimation is a significant and active research field in radiological medicine. Recently, researchers have turned their attention to magnetic resonance imaging (MRI) for age estimation, primarily due to concerns regarding ionizing radiation in traditional imaging techniques. In this article, based on the knee MRI dataset, we present a novel end-to-end network that combines convolutional neural network (CNN) and visual transformer network to extract complementary features. In addition, we introduce a feature aggregation module (FAM) that aggregates features from different local knee MRI slices. Our proposed method integrates the feature maps from CNN with the patch embeddings of visual transformer branches, allowing for the acquisition of both local and global information necessary for extracting age-related features. Moreover, we introduce an FAM utilizing the graph attention network (GAT) to achieve interaction between multiple slice features at the feature level. Through extensive experiments conducted on a dataset of 80 knee MRI samples spanning ages 12.0–25.9 years, our method has demonstrated state-of-the-art performance in knee MRI age estimation. Specifically, in a fivefold cross-validation setup, we achieved a mean absolute error (MAE) of 1.52 ± 1.27 years in age regression.

The current collector is a key component of most light rail transit (LRT) trains. It draws electric power from the catenary or the power rail for each moving train. Due to wear, tear, and harsh operating environments, the current collector will malfunction, which can lead to unexpected power interruptions for the train and directly affect service reliability. This article presents an inductive coupling method for current collector health monitoring of LRT trains powered by the three-phase ac power rail. The monitoring system developed using the proposed method can be easily fitted on a train so that it doubles up as a train-borne health monitoring system (TBHMS) during revenue hours. The TBHMS monitors the electrical contact quality (ECQ) between the current collector shoe (CCS) and the power rail in a noncontact and safe manner. By doing so, it eliminates the need of inspection during engineering hours, which is both labor-intensive and time-consuming. The current collector of such trains comprises a current collector assembly that holds the CCSs. Two performance indexes, the contact quality index and the contact loss index, are defined to quantify the health conditions of CCS and CCA, respectively.

In this work, a novel semisupervised framework is proposed to tackle the small-sample problem of dental-based human identification (DHI), achieving enhanced performance via a “classifying while generating” paradigm. A generative adversarial network (GAN), called the DHI-GAN, is presented to implement this idea, in which an extra classifier is also dedicatedly proposed to achieve an efficient training procedure. Considering the complex specificities of this problem, except for the noise input of the generator, an identity embedding-guided architecture is proposed to retain informative features for each individual. A parallel spatial and channel fusion attention block is innovatively designed to encourage the model to learn discriminative and informative features by focusing on different regional details and abstract concepts. The attention block is also widely applied to the overall classifier to learn identity-dependent information. A loss combination of the ArcFace and focal loss is utilized to address the small-sample problem. Two parameters are proposed to control the generated samples that are fed into the classifier during the optimization procedure. The proposed DHI-GAN framework is finally validated on a real-world dataset, and the experimental results demonstrate that it outperforms other baselines, achieving a 92.5% top-one accuracy rate. Most importantly, the proposed GAN-based semisupervised training strategy is able to reduce the required number of training samples (individuals) and can also be incorporated into other classification models. Our code will be available at https://github.com/sculyi/MedicalImages/.

Ingesting marine plastics is increasingly common in cetaceans, but little is known about their potential effects. Here, by utilizing 16S rRNA gene sequencing, we profiled the intestinal bacterial communities of a stranded Risso’s dolphin (Grampus griseus) which died because of the ingestion of rubber gloves. In this study, we explored the potential relationships between starvation raised by plastic ingestion with the dolphin gut microbiota. Our results showed significant differences in bacterial diversity and composition among the different anatomical areas along the intestinal tract, which may be related to the intestinal emptying process under starvation. In addition, the intestinal bacterial composition of the Risso’s dolphin showed both similarity and divergence to that of other toothed whales, suggesting potential roles of both host phylogeny and habitat shaping of the cetacean intestinal microbiome. Perhaps, the microbiota is reflecting a potentially disordered intestinal microbial profile caused by the ingestion of macro-plastics which led to starvation. Moreover, two operational taxonomic units (0.17% of the total reads) affiliated with Actinobacillusand Acinetobacter lwoffiiwere detected along the intestinal tract. These bacterial species may cause infections in immunocompromised dolphins which are malnourished. This preliminary study profiles the intestinal microbiota of a Risso’s dolphin, and provides an additional understanding of the potential relationships between starvation raised by ingesting macro-plastics with cetacean gut microbiota.

Dynamic manipulation of terahertz (THz) beams plays an important role in THz application systems. The PB metasurface provides an effective scheme for space separation and deflection of the spin beam. However, mirror symmetry locking of the conjugated spin states severely limits the versatility of the device. In this work, we demonstrate a liquid crystal (LC) cascaded bilayer metasurface that includes an LC layer, anisotropic metasurface, and PB metasurface. By controlling anisotropy and polarization conversion effects, dynamic spin asymmetric transmission is realized. Meanwhile, two different dynamic energy distribution processes are realized between the Land Rstate with the corresponding deflection side. The results show that the device achieves a large angular spatial dispersion within the frequency-angle scanning range of ±35° to ±75° corresponding to the broadband range of 0.6–1.1 THz. Moreover, it achieves a spin beam spatial separation with a maximum proportion of energy distribution greater than 26 dB, and the active modulation rate in the energy distribution process reaches 98 %. This work provides a dynamic THz spin conversion and efficient large-angle beam scanning, with important potentials in wavelength/polarization division multiplexing and frequency-scanning antenna for large-capacity THz wireless communication, radar, and imaging systems.

The single-probe setup (SPS) based on the inductive coupling approach is a promising candidate for in-circuit impedance measurement of an energized electrical system due to its noncontact characteristics and simple configuration. However, the conventional SPS performs the measurement with a frequency-domain measuring instrument via stepped swept-sine excitation. It measures in-circuit impedance at only single frequency at a time while sweeping across frequencies of interest, which is not only inefficient but also not fast enough to capture in-circuit impedance with time-variant characteristics. To overcome these limitations, this article proposes a novel SPS with a time-domain measuring instrument via multisine excitation. The proposed SPS can perform multifrequency simultaneous measurement of in-circuit impedance without direct electrical contact. By combining it with a short-time Fourier transform algorithm, in-circuit impedance with time-variant characteristics can be captured. Experimental case studies validate the capability and accuracy of the proposed SPS.

Differential-mode and common-mode chokes (DMC and CMC) are key components of electromagnetic interference filters. Accurate impedance knowledge of these chokes allows optimal EMI filter design to meet the conducted emission requirements. An impedance analyzer or vector network analyzer with a fixture adapter is commonly adopted for impedance measurement of a passive component. Usually, the non-standard terminals of both DMC and CMC make them incompatible for direct mounting on commercially available fixture adapters. Relying on additional interconnects to the fixture adapters introduce inherent parasitic effects that limit measurement accuracy up to several megahertz. This article proposes a design method of customized fixture adapters which are specifically tailored for impedance measurement of single-phase DMC and CMC. Through a systematic parasitic de-embedding process, the choke impedance can be extracted with excellent accuracy up to 120 MHz.

Lymphatic endothelial cells (LECs) play a critical role in the formation and maintenance of the lymphatic vasculature, which is essential for the immune system, fluid balance, and tissue repair. However, LECs are often difficult to study in vivoand in vitromodels that accurately mimic their behaviors and phenotypes are limited. In particular, LECs have been shown to lose their lymphatic markers over time while being cultured in vitro, which reflect their plasticity and heterogeneity in vivo. Since LECs uniquely express lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1), we hypothesized that surface coating with hyaluronic acid (HA) can preserve LEC phenotypes and functionalities. Dopamine conjugated hyaluronic acid (HA–DP) was synthesized with 42% degree of substitution to enable surface modification and conjugation onto standard tissue culture plates. Compared to fibronectin coating and tissue culture plate controls, surface coating with HA–DP was able to preserve lymphatic markers, such as prospero homeobox protein 1 (Prox1), podoplanin (PDPN), and LYVE-1over several passages in vitro. LECs cultured on HA–DP expressed lower levels of focal adhesion kinase (FAK) and YAP/TAZ, which may be responsible for the maintenance of the lymphatic characteristics. Collectively, the HA–DP coating may provide a novel method for culturing human LECs in vitrotoward more representative studies in basic lymphatic biology and lymphatic regeneration.

Knowledge and technology, as representatives of innovation elements' agglomeration, are keys to enhancing regional innovation ability. Based on panel data from 283 Chinese cities spanning 2004-2017, this study determines the regional innovation efficiency and agglomeration of regional innovation elements, and establishes the spatial matrix of innovation element flow. Using spatial econometric and intermediary effect models, the study investigates the spillover effects and transmission mechanism of the agglomeration of innovation elements and their flow on regional innovation efficiency. The regression results demonstrate that the agglomeration of innovation elements, characterised by knowledge and technology, significantly and positively influences innovation efficiency. The agglomeration of regional knowledge has a positive spatial spillover effect on innovation efficiency, while the agglomeration of regional technology has a negative spatial spillover effect. Moreover, the flow of innovative personnel and innovation capital between regions is conducive to the spatial spillover of knowledge, with the positive spillover effect of regional innovation capital being greater than that of innovative personnel. The agglomeration of regional innovation elements can affect regional innovation efficiency through transmission mechanisms such as the opening-up level, ecological environment, and information services.

Currently, FeNi nanoalloys have received considerable attention for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable aqueous zinc (Zn)-air batteries (ZABs) because of their high content and good chemical stability. However, their poor electronic conductivity, small surface area, and sluggish activity seriously hinder their catalytic performance. Herein, S-modulated FeNi nanoalloys supported by hierarchically porous carbon (S-FeNi/PC) are synthesized through the thermal treatment of metal-organic precursors for efficient bifunctional oxygen catalysis. S decoration endows S-FeNi/PC with a superior OER performance while maintaining an ORR performance that is comparable to that of Pt/C. Hence, S-FeNi/PC exhibits excellent bifunctional oxygen catalytic activity, outperforming the noble-metal-based composite catalysts of Pt/C and RuO2. Notably, the ZABs assembled with S-FeNi/PC exhibit high specific capacity (792 mA h g−1), high peak power density (123.5 mW cm−2), and remarkable durability for 700 charge/discharge cycles at 10 mA cm−2, which surpasses the performance of commercially available Pt/C-RuO2and other catalysts in previously reported studies. This study will provide not only new bifunctional oxygen electrodes for efficient ZAB devices but also new insights into the design of FeNi-based materials for a wide range of catalytic applications.

Chemically inert C(aryl)–F bonds have rarely been used to couple with other unactivated bonds, and this remains a challenge because of the difficulty of the successive cleavage of two unactivated bonds by metal catalysis. We report here the chromium-catalyzed cleavage of chemically inert C(aryl)–F bonds for coupling with unactivated C(aryl)–O bonds, allowing cross-electrophile coupling between unreactive aryl fluorides and aryl esters to be achieved in high regio- and chemoselectivity. The reactive Cr, which was formed in situ by reducing CrCl2, enables cleavage of the o-C(aryl)–F bonds to afford monovalent and quartet cyclochromate; subsequent bipyridyl-enabled insertion into the ester C(aryl)–O bond followed by reductive elimination allowed the orthogonal coupling of these two different and unactivated bonds. Mechanistic studies indicate that the bipyridyl ligand greatly enhances the reactivity of Cr in the cleavage of C(aryl)–O bonds, and the second oxidative addition may occur sluggishly compared with the reductive elimination in the catalytic cycle.

Multifunctional, high-efficiency, and active manipulation devices are significant for terahertz (THz) technology and application. In this Letter, a stacked-graphene meta-atom (SGM) structure is investigated, which is composed of periodically patterned graphene in the 2D plane and stacked graphene–dielectric layers perpendicularly to the plane. This structure not only has strong THz artificial anisotropy but also enhances the cyclotron resonance response of graphene to a THz wave under an external magnetic field (EMF). Based on these two characteristics, the SGM can realize dynamic conversion between two functions for the manipulation of THz spin chiral states under different EMFs: from the reciprocal spin-flip without EMF to nonreciprocal spin-selection with EMF. Furthermore, a Pancharatnam–Berry (P-B) metasurface composed of the SGMs with different discrete orientation angles has been designed, which achieves active conversion between THz spin chiral beam deflection and the nonreciprocal one-way transmission for two conjugated spin beams, dynamically manipulated by both the biased voltage and EMF. The spin-select isolation is 42.3 dB with a transmission efficiency of over 70% at 1.38 THz. This manipulation mechanism of the spin beam and related devices has great potential in future THz communication, dynamical imaging, and radar scanning systems.

The importance of structural variants (SVs) for human phenotypes and diseases is now recognized. Although a variety of SV detection platforms and strategies that vary in sensitivity and specificity have been developed, few benchmarking procedures are available to confidently assess their performances in biological and clinical research. To facilitate the validation and application of these SV detection approaches, we established an Asian reference materialby characterizing the genome of an Epstein-Barr virus (EBV)-immortalized B lymphocyte line along with identified benchmark regions and high-confidence SV calls. We established a high-confidence SV callset with 8938 SVs by integrating four alignment-based SV callers, including 109× Pacific Biosciences (PacBio) continuous long reads (CLRs), 22× PacBio circular consensus sequencing (CCS) reads, 104× Oxford Nanopore Technologies (ONT) long reads, and 114× Bionano optical mapping platform, and one de novoassembly-based SV caller using CCS reads. A total of 544 randomly selected SVs were validated by PCR amplification and Sanger sequencing, demonstrating the robustness of our SV calls. Combining trio-binning-based haplotype assemblies, we established an SV benchmark for identifying false negatives and false positives by constructing the continuous high-confidence regions (CHCRs), which covered 1.46 gigabase pairs (Gb) and 6882 SVs supported by at least one diploid haplotype assembly. Establishing high-confidence SV calls for a benchmark sample that has been characterized by multiple technologies provides a valuable resource for investigating SVs in human biology, disease, and clinical research.

The importance of structural variants (SVs) for human phenotypes and diseases is now recognized. Although a variety of SV detection platforms and strategies that vary in sensitivity and specificity have been developed, few benchmarking procedures are available to confidently assess their performances in biological and clinical research. To facilitate the validation and application of these SV detection approaches, we established an Asian reference materialby characterizing the genome of an Epstein-Barr virus (EBV)-immortalized B lymphocyte line along with identified benchmark regions and high-confidence SV calls. We established a high-confidence SV callset with 8938 SVs by integrating four alignment-based SV callers, including 109× Pacific Biosciences (PacBio) continuous long reads (CLRs), 22× PacBio circular consensus sequencing (CCS) reads, 104× Oxford Nanopore Technologies (ONT) long reads, and 114× Bionano optical mapping platform, and one de novoassembly-based SV caller using CCS reads. A total of 544 randomly selected SVs were validated by PCR amplification and Sanger sequencing, demonstrating the robustness of our SV calls. Combining trio-binning-based haplotype assemblies, we established an SV benchmark for identifying false negatives and false positives by constructing the continuous high-confidence regions (CHCRs), which covered 1.46 gigabase pairs (Gb) and 6882 SVs supported by at least one diploid haplotype assembly. Establishing high-confidence SV calls for a benchmark sample that has been characterized by multiple technologies provides a valuable resource for investigating SVs in human biology, disease, and clinical research.

Protein denaturation has very important research value in nutrition, biomedicine, and the food industry, which is caused by the changes in the molecular structure of the protein. Since the collective vibrational and torsional modes of protein molecules are within the terahertz (THz) frequency range, THz spectroscopy can characterize the protein denaturation with several advantages of non-contact, label-free, real-time, and non-destructive. Therefore, we proposed a reflective THz time-domain polarization spectroscopy sensing method, and use a flexible twisted dual-layer metasurface film as a sensor to realize the thermal denaturation sensing, concentration sensing, and types identification of protein aqueous solutions. The experiment tested three proteins (bovine serum albumin, whey protein, and ovalbumin), and the results show that: for the thermal denaturation sensing, its detection sensitivity can reach 6.30 dB/% and the detection accuracy is 0.77%; for the concentration sensing, the detection sensitivity and detection accuracy reach 52.9 dB·mL/g and 3.6·10^−5 g/mL, respectively; in addition, different protein types can be distinguished by the difference of the circular polarization spectra.

Amplification of terahertz radiation is achieved by combining optically pumped graphene with a dielectric resonant cavity through numerical simulation. Graphene is attached to a one-dimensional grating and sandwiched between two distributed Bragg reflectors. The whole cavity enhances the interaction of graphene with the terahertz wave while being transparent to the pump light. When the femtosecond pulse pump light at 1.5 µm with the peak intensity of 8.7W/mm^2 is considered, graphene is driven to a gain medium. Due to the enhancement of the cavity and the proper complex conductivity of graphene, the amplitude of the transmitted beam is amplified 172 times at 3.82 THz at room temperature, showing great potential in the development of terahertz amplifiers and even lasers.

In this paper, we demonstrate an intensity-tunable THz bandpass filter by introducing liquid crystal (LC) integrated with asymmetric frequency selective surface (FSS) and subwavelength metal gratings. Here, the tunable THz filter is derived from the inner polarization state conversion in composited devices, and the incident linear polarization can be converted into 90° orthogonal components. By controlling the LC orientation under the applied electric field with the metamaterial electrodes, the polarization conversion process can be actively modulated; thus, the polarization-dependent and tunable THz bandpass filter is achieved. Based on the multilayer design and the inner Fabry–Perot-like resonance mechanism, the LC-integrated metamaterials filter presents better filtering performance than the single FSS filter, and the Q-value is improved from 7.7 to 13.8 at the working frequency. Our simulated work paves the way for the design of new and efficient THz filters.

To realize nonreciprocal transmission, it is necessary to break the time-reversal symmetry of the transmission system, but it is very challenging to keep the linear polarized (LP) input and output unchanged in the free space transmission system. Magnetized semiconductor InSb can realize terahertz (THz) nonreciprocal transmission for the two conjugated photonic spin states, but it cannot realize efficient one-way transmission of LP state due to gyro-mirror symmetry. In this work, by introducing a pair of orthogonal uniaxial anisotropies from the meta-gratings on both sides of InSb, both the gyro-mirror and time-reversal symmetries are broken for the LP state, thus making this cascaded grating–InSb–grating structure serves as a high-performance isolator for the LP light. The experiment results indicate isolation of 50 dB at 0.4 THz for the same LP input and output under a weak biased magnetic field of 0.17 T. Moreover, we further illustrate the factors affecting the isolation bandwidth of the device, also demonstrated another broadband structure with the 10 dB isolation bandwidth from 0.2–0.7 THz, and the relative bandwidth achieves 110%. The mechanisms of THz nonreciprocal transmission and polarization manipulation proposed in this work will contribute to the development of efficient THz magneto-optical devices.

Electromagnetic wave (EMW)-absorbing materials have a great impact on civil use and national defense. In this paper, a novel composite, RGO@6CoTe2-300 (the mass ratio of reduced graphene oxide to CoTe2is 1:6, annealed at 300 °C), has been obtained through a facile melt-diffusion method and solvothermal method. The as-prepared samples have shown excellent reflection losses (RL) and effective adsorption bandwidth (EAB) by controlling the loading of CoTe2and the annealing temperature. The sample has exhibited a RL of −62.2 dB at 13.04 GHz with the matching thickness of 3.53 mm, and the EAB reaches 8.2 GHz at 2–18 GHz. Moreover, excellent terahertz (THz) absorption property is also obtained at 0.2–2.0 THz. A RL of 54.07 dB is acquired, and the EAB covers 100% of the entire measured bandwidth. Thus, RGO@6CoTe2-300 can be considered as a promising EMW absorption material in both gigahertz and terahertz band ranges.

In this paper, we propose an ultrasensitive microfluidic refractive index sensor for detecting high-absorption analyte. The sensor is based on heterogeneous dual-core photonic crystal fiber structure and operates in the terahertz (THz) regime. ZeonexE48R is chosen as the background material. The dual-core structure is composed of the gradient porous core and the microfluidic channel. Simulation results show that before infiltrating a liquid analyte, a highly stable modal birefringence can be obtained around 2.0×10^−2 from 0.5 to 2 THz, along with the effective material losses of less than 0.182/cm for both the x- and y-polarization modes. After infiltration, this device can be employed for accurate refractive index (RI) sensing owing to the cross point selective coupling effect between the two core modes. This sensor offers RI sensitivities of 78.095 THz/RIU and 110.931 THz/RIU within dynamic measurement ranges from 1.41 to 1.429 for x-polarization mode and from 1.435 to 1.449 for y-polarization mode, respectively, and the measurable refractive index range reaches 0.0327. Our research gives a unique insight into the sensing mechanism for detecting high-absorption analyte in the THz band, which has broad application prospects for high-accuracy dynamic sensing in the fields of chemistry, biomedicine, and real-time environmental monitoring.

Abstract:Containerization and its impact on structural shifts in maritime transport have attracted the attention of maritime researchers. However, few studies address the impact of China’s current economic reforms and industrial structure upgrades on China’s container ports. To fill this gap, this article delivers new insights on the geographical evolution of China’s ports in international container transport during the upgrade of industrial structure. This study finds that path dependence is evident in the container shipping structure, and major regional connections are still present between China and the maritime regions of East-Southeast Asia, Western Europe, and North America. During the study period, the spatial dynamics of the international linkages of China’s container ports exhibited a tendency to develop from an initial monocentric structure to an isolated double-center structure, and then a polycentric clustering structure. Dynamic panel analysis shows there is a long-term significant equilibrium relationship between industrial structure upgrading and port container transport trade. Proxy indices including the industrial structure advanced index, the industrial structure comprehensive index and the essential evolution of industrial structure have positive effects on the improvement of port container transport trade.

Containerization and its impact on structural shifts in maritime transport have attracted the attention of maritime researchers. However, few studies address the impact of China's current economic reforms and industrial structure upgrades on China's container ports. To fill this gap, this article delivers new insights on the geographical evolution of China's ports in international container transport during the upgrade of industrial structure. This study finds that path dependence is evident in the container shipping structure, and major regional connections are still present between China and the maritime regions of East-Southeast Asia, Western Europe, and North America. During the study period, the spatial dynamics of the international linkages of China's container ports exhibited a tendency to develop from an initial monocentric structure to an isolated double-center structure, and then a polycentric clustering structure. Dynamic panel analysis shows there is a long-term significant equilibrium relationship between industrial structure upgrading and port container transport trade. Proxy indices including the industrial structure advanced index, the industrial structure comprehensive index and the essential evolution of industrial structure have positive effects on the improvement of port container transport trade.

Encapsulation of single cells in a thin hydrogel provides a more precise control of stem cell niches and better molecular transport. Despite the recent advances in microfluidic technologies to allow encapsulation of single cells, existing methods rely on special crosslinking agents that are pre-coated on the cell surface and subject to the variation of the cell membrane, which limits their widespread adoption. This work reports a high-throughput single-cell encapsulation method based on the “tip streaming” mode of alternating current (AC) electrospray, with encapsulation efficiencies over 80% after tuned centrifugation. Dripping with multiple cells is curtailed due to gating by the sharp conic meniscus of the tip streaming mode that only allows one cell to be ejected at a time. Moreover, the method can be universally applied to both natural and synthetic hydrogels, as well as various cell types, including human multipotent mesenchymal stromal cells (hMSCs). Encapsulated hMSCs maintain good cell viability over an extended culture period and exhibit robust differentiation potential into osteoblasts and adipocytes. Collectively, electrically induced tip streaming enables high-throughput encapsulation of single cells with high efficiency and universality, which is applicable for various applications in cell therapy, pharmacokinetic studies, and regenerative medicine.

In order to enhance sampling efficiency and security when robot maintains power transmission line (PTL), this article develops a new approach for the rigid-flexible coupling dynamics of robot/PTL system, which decouples the large system into two small systems and solves them separately by estimating the contact force. The robot is modelled as a system of rigid bodies by screw theory, while the PTL system is modelled using absolute node coordinate formulation (ANCF). The integration of screw theory, ANCF and contact estimator trained by artificial neural network has not been accomplished before in the literature. The main contribution of this paper is to achieve this integration with the goal of developing a new and general approach for the nonlinear dynamic analysis of the interaction of the rigid maintenance robot with flexible PTL cable. A simplified two-dimensional example is used to compute the effect of the robot/PTL interaction under different operating conditions to have an understanding of the coupling approach between the two systems. A more detailed three-dimensional model was developed, and the results obtained validate the utility and effectiveness of our approach.

Recently, the terahertz (THz) chiral field control opens a new window to THz devices and their applications. In this Letter, the active manipulation for THz chiral states based on the cholesteric liquid crystal (CLC) has been demonstrated by THz time domain cross-polarization spectroscopy. The results show that the CLC has strong THz optical activity and circular dichroism (CD) effect, and the strongest THz CD of 22 dB and a polarization rotation angle of 88.4° occur around the phase transition temperature T_S−N=250K. Rising to a room temperature of 300 K, the CLC turns from a chiral state to an isotropic state for THz waves with the phase transition processes of CLC molecules. Therefore, this CLC device can be performed as a thermally active THz circular polarizer, which brings potential applications in THz polarization imaging, broadband communication, and spectroscopy.

Electromagnetic interference (EMI) shielding at Terahertz (THz) frequency range attracts increasing attention due to the rapid development of THz science and technologies. EMI shielding materials with small thickness, high shielding effectiveness (SE), good flexibility and stability are highly desirable. Herein, an ultrathin flexible copper/graphene (Cu/Gr) nanolayered composite are prepared, which can reach the average EMI SE of 60.95 dB at 0.1–1.0 THz with a thickness of only 160 nm, indicating that more than 99.9999% of the THz wave power can be shielded. Furthermore, the Cu/Gr nanolayered composite also exhibits excellent oxidation resistance, with a 93.09% maintenance rate for EMI SE value after heating at 120 °C for 3 h in air, far higher than that of the bare Cu film (62.15%). Besides, the Cu/Gr nanolayered composite exhibits good mechanical flexibility and flexural fatigue resistance. The EMI SE value of the Cu/Gr nanolayered composite shows a maintenance rate of 98.87% even after 1500 times bending cycles, obviously higher than that of multilayer Cu film (93.07%). These results demonstrate that the ultrathin flexible Cu/Gr nanolayered composites with excellent shielding performance and good stability have a broad application prospect in THz shielding for wearable devices and next generation mobile communication equipment. [ABSTRACT FROM AUTHOR]

Reductive cross-coupling between two chemically inert bonds remains a great challenge in synthetic chemistry. We report here the reductive cross-coupling between unactivated C(aryl)–N and C(aryl)–O bonds that was achieved by chromium catalysis. The simple and inexpensive CrCl2salt, combined with important bipyridyl ligand and magnesium reductant, shows high reactivity in the successive cleavage of C(aryl)–N bonds of aniline derivatives and C(aryl)–O bonds of aryl esters, allowing the cross-coupling of these two unactivated and different bonds to occur in a reductive fashion to form a C(aryl)–C(aryl) bond. Mechanistic studies by deuterium-labeling experiments indicate that the C(aryl)–N bonds in anilines are preferentially cleaved by reactive Cr species, in which the ligation of bipyridyl with Cr by adopting a coordination model in 1:1 ratio can be considered.

The inhibition effects of aspirin on cell proliferation are investigated by both traditional THz resonance sensing and the improved THz polarization sensing method based on a polarization dependent metasurface microsensor. Compared to resonance sensing, the quality factor of polarization sensing is 4∼5 times higher than that of resonance sensing, and its figure of merit is at least one order of magnitude higher than that of the resonance sensing with the same metasurface microsensor. Our proposed metasurface-based biosensors may supply a novel viewpoint on cell proliferation from a physical perspective and be a valuable complementary reference for biological study.

Chlorsulfuron has been applied in wheat fields as a recognized herbicide worldwide, yet it was officially banned in China since 2014 for its soil persistence problem. On the basis of our previous research that 5-dimethylamino distinctively accelerated degradation rate in soils, a modified amino moiety (Ia-c) and monosubstituted amino group (Id-e) were introduced onto the fifth position of the benzene ring in sulfonylurea structures, as well as heterocyclic amino substituents (If-g) to seek a suitable soil degradation rate during such an in situ crop rotation system. Referring to the biological data and ScAHAS inhibition and ScAHAS docking results, they turned out to be AHAS inhibitors with high potent herbicidal activities. The various influence on soil degradation rate along with crop safety indicated that different substituents on the fifth position have exerted an apparent impact. Their united study of structure–activity–safety–degradation relationship has great potential to provide valuable information for further development of eco-friendly agrochemicals.

The transverse magneto-optical (MO) effect of InSb has been theoretically and experimentally investigated in the terahertz (THz) regime. The calculated photonic band structure and experimental measurements show that a unique circularly polarized magneto plasmon mode, and a linearly polarized transverse magnetic mode can be sensitively manipulated by a weak magnetic field. Moreover, these results indicate that transverse magnetized InSb can be used as a THz tunable high-pass filter and a MO modulator. The cutoff frequency of the filter can be broadly tuned from 0.4 to 0.8 THz when the magnetic field changes from 0 to 0.22 T, and the modulation depth of 20 dB can be obtained. This research has significance for the deep understanding to the THz MO effect of InSb and promotes the development of THz MO devices.

The direct qualitative identification of pure liquids in laboratories and in security checks is generally performed by the detection of the refractive index or the permittivity. However, refractive indices are strongly influenced by temperature, while the permittivities of some organics are difficult to differentiate. On the other hand, the quantitative monitoring of samples with high concentration in plating baths and in chemical production lines are generally performed via a “Sampling–Dilution–Analysis” approach because of significant deviations from the linear range at high concentration, which makes the real-time monitoring of concentrated samples difficult. Here, we propose a self-reference analysis (SRA) method to directly analyze pure liquids and concentrated samples based on temperature difference absorption spectra (TDAS) without the need for dilution. This method was performed by simultaneously scanning the spectra of the reference and the sample, which are both obtained from the same analyte for detection but are at different temperatures. Compared to conventional absorption spectra with a blank reference, the red-shifted peak wavelengths of TDAS enable the detection of many far UV absorptive compounds in the near-ultraviolet region (λ > 190 nm). More importantly, organic compounds with similar structures can be easily distinguished. In addition, TDAS can also be used for the quantitative detection of concentrated analytes. The proposed SRA-TDAS method is a rapid and effective method; this approach does not require dilution and utilizes a self-reference, implying the wide potential applicability in security checks, and the real-time monitoring of concentrated compounds in chemical production lines.

Fucosylated chondroitin sulfate (fCS), a representative marine polysaccharide isolated from sea cucumber, possesses diverse biological functions especially as a promising anticoagulant. However, its supply suffers from the challenges of high-cost materials, different species, and batch-to-batch variability. In the present study, we designed a concise route for the synthesis of functional glycomimetics by natural fCS as a template. 4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride-mediated amidation was applied on chondroitin sulfates for site-selective alkynylation with controllable ratios between 0.15 and 0.78. A small library of 12 fCS glycomimetics with specific sulfation patterns and fucose branches was prepared through copper-catalyzed azide–alkyne cycloaddition, which was fully characterized by nuclear magnetic resonance spectroscopy and size-exclusion chromatography with multiangle light scattering and refractive index. Through screening of their biological activities, CSE-F1and CSE-SF1exhibited anticoagulant activities through intrinsic pathway and inhibition of factor Xa by antithrombin III. The concise approach developed herein supplies novel glycopolymers to mimic the distinct functions of natural polysaccharides and promote the development of marine carbohydrate-based drugs.

In this work, a three-dimensional (3D) porous MXene/GO foam (MGOF) was successfully synthesized and exhibited an excellent terahertz stealth property covering a whole measurement frequency of 0.2–2.0 THz. This is due to the ingenious assembly of two functional two-dimensional materials that have different advantages. The multiscale micro-nanostructure constructed with the 3D porous MGOF can effectively increase the terahertz scattering and refraction. Furthermore, MXene sheets with high conductivity can enhance the responsiveness to the terahertz wave. By adjusting the content of MXene in the MGOF, it exhibits a maximum reflection loss (RL) of 37 dB with a 100% qualified frequency bandwidth (RL > 10 dB), which is the most outstanding result in the available reference. In addition, the optimal average terahertz RL values of MGOF were up to 30.6 dB, which is 100% higher than the best data presented in previous work. Benefitting from an ultralow density, a high RL value, and a wide bandwidth, the maximum specific average terahertz absorption performance can reach 4.6 × 104dB g–1cm3, which is more than 4000 times that of other materials. In addition, the regulation of the terahertz absorption property through microstructure and morphology control is reported for the first time.