A second wave of topological phenomena in photonics and acoustics.

Light and sound are the most ubiquitous forms of waves, associated with a variety of phenomena and physical effects such as rainbows and echoes. Light and sound, both categorized as classical waves, have lately been brought into unexpected connections with exotic topological phases of matter. We are currently witnessing the onset of a second wave of active research into this topic. The past decade has been marked by fundamental advances comprising two-dimensional quantum Hall insulators and quantum spin and valley Hall insulators, whose topological properties are characterized using linear band topology. Here, going beyond these conventional topological systems, we focus on the latest frontiers, including non-Hermitian, nonlinear and non-Abelian topology as well as topological defects, for which the characterization of the topological features goes beyond the standard band-topology language. In addition to an overview of the current state of the art, we also survey future research directions for valuable applications.

A universal and scalable transformation of bulk metals into single-atom catalysts in ionic liquids.

Single-atom catalysts (SACs) with maximized metal atom utilization and intriguing properties are of utmost importance for energy conversion and catalysis science. However, the lack of a straightforward and scalable synthesis strategy of SACs on diverse support materials remains the bottleneck for their large-scale industrial applications. Herein, we report a general approach to directly transform bulk metals into single atoms through the precise control of the electrodissolution-electrodeposition kinetics in ionic liquids and demonstrate the successful applicability of up to twenty different monometallic SACs and one multimetallic SAC with five distinct elements. As a case study, the atomically dispersed Pt was electrodeposited onto Ni3N/Ni-Co-graphene oxide heterostructures in varied scales (up to 5 cm × 5 cm) as bifunctional catalysts with the electronic metal-support interaction, which exhibits low overpotentials at 10 mA cm-2 for hydrogen evolution reaction (HER, 30 mV) and oxygen evolution reaction (OER, 263 mV) with a relatively low Pt loading (0.98 wt%). This work provides a simple and practical route for large-scale synthesis of various SACs with favorable catalytic properties on diversified supports using alternative ionic liquids and inspires the methodology on precise synthesis of multimetallic single-atom materials with tunable compositions.

Characterizing Local Electronic States of Twin Boundaries in Copper.

Grain boundaries (GBs) and twin boundaries (TBs) in copper (Cu) are two major planar defects that influence electrical conductivity due to their complex electron transport characteristics, involving electron scattering and electron concentration. Understanding their local electronic states is crucial for the design of future conductor materials. In this study, we characterized electron behaviors at TBs and GBs within one Cu grain using atomic force microscopy. Our findings revealed that, compared with GBs, TBs exhibit better current transport capability (direct-current mode) and larger electromagnetic loss (high-frequency microwave mode). Both kelvin probe force microscopy and theoretical analysis suggested that TBs with smaller lattice disorder possess lower density of states at the Fermi level. The reduced density of states may result in decreased electron scattering and a lower electron concentration at TBs. The latter can be highlighted by the high-frequency skinning effect, manifested as larger electromagnetic loss and weaker high-frequency conductivity.

Mapping of Long-Wavelength Phonon Contribution in the Thermal Transport of Alloyed Semiconductor Superlattices.

The mapping of long-wavelength phonons is important to understand and manipulate the thermal transport in multilayered structures, but it remains a long-standing challenge due to the collective behaviors of phonons. In this study, an experimental demonstration of mapping the long-wavelength phonons in an alloyed Al0.1Ga0.9As/Al0.9Ga0.1As superlattice system is reported. Multiple strategies to filter out the short- to mid-wavelength phonons are used. The phonon mean-free-path-dependent thermal transport properties directly demonstrate both the suppression effect of the ErAs nanoislands and the contribution of long-wavelength phonons. The contribution from phonons with mean free path longer than 1 µm is clearly demonstrated. A model based on the Boltzmann transport equation is proposed to calculate and describe the thermal transport properties, which depicts a clear physical picture of the transport mechanisms. This method can be extended to map different wavelength phonons and become a universal strategy to explore their thermal transport in various application scenarios.

Observation of Free-Boundary-Induced Chiral Anomaly Bulk States in Elastic Twisted Kagome Metamaterials.

Chiral anomaly bulk states (CABSs) can be realized by choosing appropriate boundary conditions in a finite-size waveguide composed of two-dimensional Dirac semimetals, which have unidirectional and robust transport similar to that of valley edge states. CABSs use almost all available guiding space, which greatly improves the utilization of metamaterials. Here, free-boundary-induced CABSs in elastic twisted kagome metamaterials with C_{3v} symmetry are experimentally confirmed. The robust valley-locked transport and complete valley state conversion are experimentally observed. Importantly, the sign of the group velocity near the K and K^{'} points can be reversed by suspending masses at the boundary to manipulate the onsite potential. Moreover, CABSs are demonstrated in nanoelectromechanical phononic crystals by constructing an impedance-mismatched hard boundary. These results open new possibilities for designing more compact, space-efficient, and robust elastic wave macro- and microfunctional devices.

First Report of Rust Disease on Alcea rosea caused by Puccinia modiolae in China.

Alcea rosea, belonging to the Alcea genus in the Malvaceae family, originated from China, but it is now grown worldwide. A. rosea has been widely used in traditional Chinese medicine to alleviate constipation, pain, swelling, and sores. In February 2023, typical symptoms of fungal infection were observed on A. rosea at Guizhou Normal University in Guiyang, Guizhou Province, China. The disease incidence was over 90% (n = 100) for the surveyed A. rosea plants, and the disease severity range from 30% to 90%. The initial symptoms of A. rosea rust were the appearance of chlorotic spots on the leaves. Subsequently, numerous reddish to dark-brown erumpent pustules (telia) were observed. Gradually, the entire plant was covered by rust and the center of each lesion turned brown, necrotic, and ruptured over times, eventually causing defoliation. Voucher specimens of infected A. rosea leaves as representative samples have been deposited at Guizhou Normal University (GNU2023LS008). Telia are round in shape, mostly aggregated in mass, with a diameter of 0.28-0.78 mm (0.46 mm, n = 20). They range in color from reddish-brown to dark brown, and are mainly hypophyllous but occasionally formed on the adaxial leaf surface. The teliospores are fusoid with dimensions of 31.3-93.8 × 10.9-21.3 µm (57.5 × 15.1 µm average, n = 50), hyaline or yellowish to light-brown in color, mostly two-celled, with a smooth wall (1.5-3.0 µm) and a thickened apex (3.0-9.0 µm). However, teliospores which are one-, three-, or four-celled with a notch at the apex, are rarely observed. The morphological characteristics of host symptoms and teliospores were similar to those of Puccinia modiolae (Aime and Abbasi 2018; Albu et al. 2019). For phylogenetic analysis, genomic DNA was extracted from the teliospores of infected leaves. To confirm the species-level identification, PCR was performed on the extracted DNA to amplify the ribosomal DNA internal transcribed spacer (ITS) and large subunit (LSU) regions using primer pairs ITS1/ITS4 (Schoch et al. 2012) and NL1/NL4 (Ziemiecki et al. 1990), respectively. The resulting ITS DNA sequence (GenBank accession no. OR607960) showed 100% identity with P. modiolae sequences (OP369291.1), when the query coverage was 100%. The LSU DNA sequence obtained (OR607961.2) shared 99.85% similarity with P. modiolae (MK458702.1). A phylogenetic tree was constructed using MEGA7.0 and the maximum likelihood method based on the ITS and LSU sequences. The fungal isolates collected in this study and several reference sequences of P. modiolae were grouped within a clade that included the isolates reported on A. rosea in Korea (Ryu et al. 2023), with 100% bootstrap support. Pathogenicity testing was conducted by gently pressing spore powder of naturally diseased leaves onto young leaves of three healthy A. rosea plants, with three noninoculated healthy plants serving as controls. The inoculated and noninoculated plants were kept in a growth chamber at the 26°C with a 12 hour light/dark cycle and 80% humidity. After 2 weeks, all inoculated A. rosea plants showed characteristic disease symptoms of rust infection and telia of P. modiolae, while control plants remained symptomless. The pathogen was identical to that observed on the original diseased leaves. The study results indicate that the causal fungus responsible for the disease is P. modiolae, which has been previously reported on Malvaceae plants (Farr and Rossman 2022). To the best of our knowledge, this is the first report of P. modiolae on A. rosea in China. This study will contribute to an increased understanding of the host range of Puccinia modiolae.

SlMDH3 Interacts with Autophagy Receptor Protein SlATI1 and Positively Regulates Tomato Heat Tolerance.

Autophagy, a highly conserved protein degradation system, plays an important role in protecting cells from adverse environmental conditions. ATG8-INTERACTING PROTEIN1 (ATI1) acts as an autophagy receptor, but its functional mechanisms in plants' heat stress tolerance remain unclear. In this study, using LC-MS/MS, we identified malate dehydrogenase (SlMDH3) as a SlATI1-interacting protein. Further studies showed that heat stress induced the expression of SlMDH3 and SlMDH3 co-localized with SlATI1 under both 22 °C and 42 °C heat treatment conditions. Moreover, silencing of SlMDH3 increased the sensitivity of tomato to heat stress, as evidenced by exacerbated degradation of chlorophyll; accumulation of MDA, H2O2, and dead cells; increased relative conductivity; and inhibition of stress-related gene expression. Conversely, overexpression of SlMDH3 improved tomato's heat tolerance, leading to opposite effects on physiological indicators and gene expression compared to SlMDH3 silencing. Taken together, our study suggests that SlMDH3 interacts with SlATI1 and positively regulates tomato heat tolerance.

Spatiotemporal Acoustic Vortex Beams with Transverse Orbital Angular Momentum.

Recently, the discovery of optical spatiotemporal (ST) vortex beams with transverse orbital angular momentum (OAM) has attracted increasing attention and is expected to extend the research scope and open new opportunities for practical applications of OAM states. The ST vortex beams are also applicable to other physical fields that involve wave phenomena, and here we develop the ST vortex concept in the field of acoustics and report the generation of Bessel-type ST acoustic vortex beams. The ST vortex beams are fully characterized using the scalar approach for the pressure field and the vector approach for the velocity field. We further investigate the transverse spreading effect and construct ST vortex beams with an ellipse-shaped spectrum to reduce the spreading effect. We also experimentally demonstrated the orthogonality relations between ST vortex beams with different charges. Our study successfully demonstrates the versatility of the acoustic system for exploring and discovering spatiotemporally structured waves, inspiring further investigation of exotic wave physics.

Recent advances of food safety detection by nucleic acid isothermal amplification integrated with CRISPR/Cas.

Food safety problems have become one of the most important public health issues worldwide. Therefore, the development of rapid, effective and robust detection is of great importance. Amongst a range of methods, nucleic acid isothermal amplification (NAIA) plays a great role in food safety detection. However, the widespread application remains limited due to a few shortcomings. CRISPR/Cas system has emerged as a powerful tool in nucleic acid detection, which could be readily integrated with NAIA to improve the detection sensitivity, specificity, adaptability versatility and dependability. However, currently there was a lack of a comprehensive summary regarding the integration of NAIA and CRISPR/Cas in the field of food safety detection. In this review, the recent advances in food safety detection based on CRISPR/Cas-integrated NAIA were comprehensively reviewed. To begin with, the development of NAIA was summarized. Then, the types and working principles of CRISPR/Cas were introduced. The applications of the integration of NAIA and CRISPR/Cas for food safety were mainly introduced and objectively discussed. Lastly, current challenges and future opportunities were proposed. In summary, this technology is expected to become an important approach for food safety detection, leading to a safer and more reliable food industry.

The protective role of vitamin C on intestinal damage induced by high-dose glycinin in juvenile Rhynchocypris lagowskii Dybowski.

This study was to evaluate the mitigative effects of vitamin C (VC) on growth inhibition and intestinal damage induced by glycinin in juvenile Rhynchocypris lagowskii Dybowski. 270 healthy juvenile Rhynchocypris lagowskii Dybowski (4.65 ± 0.04 g) were randomly divided into 3 treatments, and fed with control diet, 80 g/kg glycinin diet and 80 g/kg glycinin+200 mg/kg VC diet respectively for 8 weeks. The results showed that glycinin significantly decreased the weight gain rate, specific growth rate, protein efficiency rate, feed efficiency rate and feeding rate of fish compared with the control group (P < 0.05), while VC supplementation improved the growth performance and feed utilization efficiency, and reached a level similar to the control group. Similarly, VC significantly increased the crude protein content of muscle and whole-body, and hepatopancreas and intestinal protease activities of fish fed with glycinin diet (P < 0.05). The distal intestine of fish in glycinin group showed typical damage characteristics, including breakage and atrophy of intestinal mucosal fold, and increased intestinal mucosal permeability. However, fish fed the glycinin + VC diet showed an unimpaired normal intestinal morphology. Usefully, VC supplementation could also restore impaired immune function and antioxidant capacity. VC down-regulated the mRNA levels of pro-inflammatory cytokines TNF-α and IL-1ß, and up-regulated the mRNA levels of anti-inflammatory cytokines IL-10 and TGF-ß in the distal intestine of fish fed with glycinin. Furthermore, glycinin exposure could reduce the mRNA levels of HO-1, CAT and GPx by inhibiting the activation of Nrf2-Keap1 signaling pathway, while VC supplementation reversed this phenomenon and maintained the homeostasis of antioxidant defense system. Concluded, glycinin causes growth inhibition, digestive dysfunction and intestinal damage of Rhynchocypris lagowskii Dybowski, while sufficient VC intake is beneficial for fish to resist the adverse effects of glycinin.

Adaptive Ultrasonic Full Matrix Capture Process for the Global Imaging of Complex Components with Curved Surfaces.

This work proposes a new global FD-RTM method to solve the problem of ultrasonic inspection of parts with complex geometric shapes. With this method, the frequency domain reverse time migration (FD-RTM) algorithm is used to adapt to the complex refraction of ultrasonic waves by the surface, while an interface solution algorithm based on tangent fitting is used to solve the interface position with high precision through the full matrix reception data. Based on high-precision interface information, a hybrid extrapolation algorithm and a situation-specific probe movement strategy are used to enable the probe to find the next sampling point according to the direction of the workpiece surface, allowing complex surface topography features to be identified without relying on the workpiece CAD drawing. This makes it possible to achieve the automated inspection of workpieces. To verify the proposed method's effectiveness, an aluminum alloy model with side-drilled holes (SDH) is used. The geometry of the model consists of multiple convex and concave surfaces. By comparing the local FD-RTM imaging with images synthesized using the entire scan path, it is shown that gFD-RTM improved the imaging performance. Compared with FD-RTM, the average signal-to-noise ratio of gFD-RTM was increased by 20%, and the array performance index (API) was reduced by 70%, indicating effective detection coverage.

Asymmetric Generation of Acoustic Vortex Using Dual-Layer Metasurfaces.

In this Letter, we introduce a new paradigm for achieving robust asymmetric generation of acoustic vortex field through dual-layer metasurfaces by controlling their intrinsic topologic charges and the parity of geometry design. The underlying physics is contributed to the one-way process of orbital angular momentum (OAM) transition ensured by the broken spatial symmetry and the external topologic charge from the vortex diffraction. We further experimentally demonstrate this novel phenomenon. Our findings could provide new routes to manipulate the asymmetric response of vortex fields, including one-way excitation and propagation, and promise potential applications in passive OAM-based diodes.

Taurine can improve intestinal function and integrity in juvenile Rhynchocypris lagowskii Dybowski fed high-dose glycinin.

The present study evaluated the protective effect and the regulatory mechanism of taurine on growth inhibition and intestinal damage induced by glycinin in juvenile Rhynchocypris lagowskii Dybowski. The control diets had no glycinin and taurine, the glycinin diets contained only 80 g/kg glycinin, and the glycinin + taurine diets contained 80 g/kg glycinin+10 g/kg taurine. Juvenile Rhynchocypris lagowskii Dybowski (4.65 ± 0.03 g/tail) were respectively fed with these 3 diets for 8 weeks. The results showed that glycinin significantly decreased the final body weight, weight gain rate, specific growth rate, protein efficiency rate, feed efficiency rate and feeding rate of fish compared with the control group (P < 0.05). While taurine supplementation improved the growth performance and feed efficiency, but final body weight, weight gain rate, specific growth rate of the glycinin + taurine group were still significantly lower than the control group (P < 0.05). Compared with the glycinin group, taurine supplementation significantly increased whole-body and muscle crude protein content, and hepatopancreas and intestinal protease activities (P < 0.05). Distal intestinal villous dysplasia and mucosal damage, and increased intestinal mucosal permeability were observed in the glycinin group, while taurine supplementation alleviated these adverse effects. Usefully, taurine supplementation could also partially restore the impaired immune function and antioxidant capacity of fish fed glycinin diets. Compared with the glycinin group, taurine supplementation down-regulated pro-inflammatory cytokines TNF-α and IL-1ß mRNA levels, and up-regulated anti-inflammatory cytokines IL-10 and TGF-ß mRNA levels. Furthermore, taurine partially reversed the reduction of antioxidant genes Nrf2、HO-1, CAT and GPx mRNA levels in distal intestine induced by glycinin. Concluded, 80 g/kg glycinin led to intestinal damage, digestive dysfunction and increased intestinal mucosal permeability in juvenile Rhynchocypris lagowskii Dybowski, and these adverse effects were ultimately manifested in growth inhibition. But taurine supplementation could partially mitigate the negative effects induced by glycinin.

Valley-Selective Topological Corner States in Sonic Crystals.

Higher-order topological insulators (HOTIs), a new horizon of topological phases of matter, host lower-dimensional corner or hinge states, providing important stepping stones to the realization of robust topological waveguides in higher dimensions. The nontrivial band topology that gives rise to the corner or hinge states is usually enabled by certain crystalline symmetries. As a result, higher-order topological boundary states are tied to specific corners or hinges, lacking the flexibility of switching and selecting. Here, we report the experimental realization of topologically switchable and valley-selective corner states in a two-dimensional sonic crystal. Such intriguing properties are enabled by exploiting the higher-order topology assisted with the valley degree of freedom. For this purpose, we realize a valley HOTI of second-order topology characterized by the nontrivial bulk polarization. Interestingly, the hosted corner states are found to be valley dependent and therefore enable flexible control and manipulation on the wave localization. Topological switch on or off and valley selection of the corner states are directly observed through spatial scanning of the sound field. We further design an arbitrary structure of complex patterns containing corners with various intersection angles, among which selected corners can be illuminated or darkened upon valley selection. The reported valley HOTI and the valley-selective corner states provide fundamental understanding on the interplay between higher-order topology and valley degree of freedom and pave the way for lower-dimensional valleytronics, which may find potential applications in integrated acoustics and photonics.

Observation of Acoustic Skyrmions.

Despite a long history of studies, acoustic waves are generally regarded as spinless scalar waves, until recent research revealed their rich structures. Here, we report the experimental observation of skyrmion configurations in acoustic waves. We find that surface acoustic waves trapped by a designed hexagonal acoustic metasurface give rise to skyrmion lattice patterns in the dynamic acoustic velocity fields (i.e., the oscillating acoustic air flows). Using an acoustic velocity sensing technique, we directly visualize a Néel-type skyrmion configuration of the acoustic velocity fields. We further demonstrate, respectively, the controllability and robustness of the acoustic skyrmion lattices by tuning the phase differences between the acoustic sources and by introducing local perturbations in our setup. Our study unveils a fundamental acoustic phenomenon that may enable unprecedented manipulation of acoustic waves and may inspire future technologies including advanced acoustic tweezers for the control of small particles.

Nanosized Phase-Changeable "Sonocyte" for Promoting Ultrasound Assessment.

Despite the ability of microbubble contrast agents to improve ultrasound diagnostic performance, their application potential is limited due to low stability, fast clearance, and poor tissue permeation. This study presents a promising nanosized phase-changeable erythrocyte (Sonocyte), composed of liposomal dodecafluoropentane coated with multilayered red blood cell membranes (RBCm), for improving ultrasound assessments. Sonocyte is the first RBCm-functionalized ultrasound contrast agent with uniform nanosized morphology, and exhibits good stability, systemic circulation, target-tissue accumulation, and even ultrasound-responsive phase transition, thereby satisfying the inherent requirement of ultrasound imaging. It is identified that Sonocyte displays similar sensitivity as microbubble SonoVue, a clinical ultrasound contrast agent, for effectively detecting normal parenchyma and hepatic necrosis. Importantly, compared with SonoVue lacking of ability to detect tumors, Sonocyte can identify tumors with high sensitivity and specificity due to superior tumor accumulation and penetration. Therefore, Sonocyte exhibits superior capabilities over SonoVue, endowing with a great clinical application potential.

Glutathione Induced Transformation of Partially Hollow Gold-Silver Nanocages for Cancer Diagnosis and Photothermal Therapy.

Gold-silver nanocages (GSNCs) are widely used in cancer imaging and therapy due to excellent biocompatibility, internal hollow structures, and tunable optical properties. However, their possible responses toward the tumor microenvironment are still not well understood. In this study, it is demonstrated that a kind of relatively small sized (35 nm) and partially hollow GSNCs (absorbance centered at 532 nm) can enhance the intrinsic photoacoustic imaging performances for blood vessels around tumor sites. More importantly, the high concentration of glutathione around the tumor cells' microenvironment may induce the aggregation, disintegration, and agglomeration of these GSNCs sequentially, allowing significant shifts in the absorbance spectrum of GSNCs to the near-infrared (NIR) region. This enhanced absorbance in the NIR region entails the significant photothermal therapy (PTT) effect. In vivo experiments, including photoacoustic microscopy (PAM) for cancer diagnosis and PTT in tumor model mice, also show coincident consequences. Taken together, the slightly hollow GSNCs may assist PAM-based tumor diagnosis and induce a tumor targeted PTT effect. This work paves a new avenue for the development of an alternative tumor diagnostic and therapeutic strategy.

Natural variations of growth thermo-responsiveness determined by SAUR26/27/28 proteins in Arabidopsis thaliana.

How diversity in growth thermo-responsiveness is generated for local adaptation is a long-standing biological question. We investigated molecular genetic basis of natural variations in thermo-responsiveness of plant architecture in Arabidopsis thaliana. We measured the extent of rosette architecture at 22°C and 28°C in a set of 69 natural accessions and determined their thermo-responsiveness of plant architecture. A genome-wide association study was performed to identify major loci for variations in thermo-responsiveness. The SAUR26 subfamily, a new subfamily of SAUR genes, was identified as a major locus for the thermo-responsive architecture variations. The expression of SAUR26/27/28 is modulated by temperature and PIF4. Extensive natural polymorphisms in these genes affect their RNA expression levels and protein activities and influence the thermo-responsiveness of plant architecture. In addition, the SAUR26 subfamily genes exhibit a high variation frequency and their variations are associated with the local temperature climate. This study reveals that the SAUR26 subfamily is a key variation for thermo-responsive architecture and suggests a preference for generating diversity for local adaptation through signaling connectors.

Hybrid Acoustic Topological Insulator in Three Dimensions.

Topological insulators (TIs), featured by a symmetry-protected gapless surface Dirac cone(s) in their complete energy band gaps, have been extended from condensed-matter physics to classical bosonic systems in the last decade. However, acoustic TIs in three dimensions remain elusive because of a lack of a spin or polarization degree of freedom for longitudinal airborne sound. Here, we experimentally demonstrate a feasible way to hybridize an acoustic TI in three dimensions based on band inversion through a three-dimensional (3D) hybrid Dirac point (HDP). Such a 3D HDP, with linear dispersion in the layer plane while quadratic out of the layer, is distinct from a general point with linear dispersion in all directions. Interestingly, a single nearly gapless conical-like dispersion for acoustic surface states can be achieved at both zigzag and armchair interfaces, supporting robust sound transport. Our findings can serve as a tabletop platform for exploring unique acoustic applications based on the two-dimensional topological interfaces.

Visualization of Higher-Order Topological Insulating Phases in Two-Dimensional Dielectric Photonic Crystals.

The studies of topological phases of matter have been developed from condensed matter physics to photonic systems, resulting in fascinating designs of robust photonic devices. Recently, higher-order topological insulators have been investigated as a novel topological phase of matter beyond the conventional bulk-boundary correspondence. Previous studies of higher-order topological insulators have been mainly focused on the topological multipole systems with negative coupling between lattice sites. Here we experimentally demonstrate that second-order topological insulating phases without negative coupling can be realized in two-dimensional dielectric photonic crystals. We visualize both one-dimensional topological edge states and zero-dimensional topological corner states by using the near-field scanning technique. Our findings open new research frontiers for photonic topological phases and provide a new mechanism for light manipulating in a hierarchical way.