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Ultrasonic guided wave non-destructive testing technology, as one of the most widely used techniques in non-destructive testing, has encountered challenges in breaking the diffraction limit to achieve finer super-resolution imaging during its development. As a type of wave accompanying ultrasonic guided wave damage detection, the transient wave has had the potential to achieve super-resolution imaging in recent years due to its high wave number and sub-wavelength characteristics. In order to overcome its spatial attenuation characteristics, this study constructs a periodic plate-column structure metamaterial. By utilizing its resonance with sub-wavelength Bloch modes at specific frequencies and the interaction with transient waves carrying sub-wavelength information, the wave carrying sub-wavelength signals is amplified, transformed, and transmitted to the far field, thereby achieving super-resolution imaging. The dispersion characteristics of the periodic plate-column structure were simulated and experimentally investigated. The super-resolution imaging effect of the periodic plate-column structure metamaterial was simulated using the time-reversal imaging method and experimentally validated, providing a basis for achieving damage super-resolution imaging with periodic plate-column structures. [ABSTRACT FROM AUTHOR]

Apoptosis is a naturally occurring process generating plenty of apoptotic vesicles (apoVs), but the feature, fate and function of apoVs remain largely unknown. Notably, as an appealing source for cell therapy, mesenchymal stem cells (MSCs) undergo necessary apoptosis and release apoVs during therapeutic application. In this study, we characterized and used MSC‐derived apoVs to treat type 2 diabetes (T2D) mice, and we found that apoVs were efferocytosed by macrophages and functionally modulated liver macrophage homeostasis to counteract T2D. We showed that apoVs can induce macrophage reprogramming at the transcription level in an efferocytosis‐dependent manner, leading to inhibition of macrophage accumulation and transformation of macrophages towards an anti‐inflammation phenotype in T2D liver. At the molecular level, we discovered that calreticulin (CRT) was exposed on the surface of apoVs to act as a critical 'eat‐me' signal mediating apoV efferocytosis and macrophage regulatory effects. Importantly, we demonstrated that CRT‐mediated efferocytosis of MSC‐derived apoVs contributes to T2D therapy with alleviation of T2D phenotypes including glucose intolerance and insulin resistance. These findings uncover that functional efferocytosis of apoVs restores liver macrophage homeostasis and ameliorates T2D. [ABSTRACT FROM AUTHOR]

Aims. Recurring jets are observed in the solar atmosphere. They can erupt intermittently over a long period of time. By the observation of intermittent jets, we wish to understand what causes the characteristics of the periodic eruptions. Methods. We report intermittent jets observed by the Goode Solar Telescope (GST) with the TiO Broadband Filter Imager (BFI), the Visible Imaging Spectrometer (VIS) in Hα, and the Near-InfraRed Imaging Spectropolarimeter (NIRIS). The analysis was aided and complemented by 1400 Å and 2796 Å data from the Interface Region Imaging Spectrograph (IRIS). These observational instruments allowed us to analyze the temporal characteristics of the jet events. By constructing the Hα dopplergrams, we found that the plasma first moves upward, but during the second phase of the jet, the plasma flows back. Working with time slice diagrams, we investigated the characteristics of the jet dynamics. Results. The jet continued for up to 4 h. The time-distance diagram shows that the peak of the jet has clear periodic-eruption characteristics (5 min) during 18:00 UT–18:50 UT. We also found a periodic brightening phenomenon (5 min) during the jet bursts in the observed bands in the transition region (1400 Å and 2796 Å), which may be a response to intermittent jets in the upper solar atmosphere. The time lag is 3 min. Evolutionary images in the TiO band revealed a horizontal movement of the granulation at the location of the jet. By comparison to the quiet region of the Sun, we found that the footpoint of the jet is enhanced at the center of the Hα spectral line profile, without significant changes in the line wings. This suggests prolonged heating at the footpoint of the jet. In the mixed-polarity magnetic field region of the jet, we observed the emergence of magnetic flux, its cancellation, and shear, indicating possible intermittent magnetic reconnection. This is confirmed by the nonlinear force-free field model, which was reconstructed using the magneto-friction method. Conclusions. The multiwavelength analysis indicates that the events we studied were triggered by magnetic reconnection that was caused by mixed-polarity magnetic fields. We suggest that the horizontal motion of the granulation in the photosphere drives the magnetic reconnection, which is modulated by p-mode oscillations. [ABSTRACT FROM AUTHOR]

The three-dimensional (3D) morphological structure of wheat directly reflects the interrelationship among genetics, environments, and cropping systems. However, the morphological complexity of wheat limits its rapid and accurate 3D modelling. We have developed a 3D wheat modelling method that is based on the progression from skeletons to mesh models. Firstly, we identified five morphological parameters that describe the 3D leaf features of wheat from amounts of 3D leaf digitizing data at the grain filling stage. The template samples were selected based on the similarity between the input leaf skeleton and leaf templates in the constructed wheat leaf database. The leaf modelling was then performed using the as-rigid-as-possible (ARAP) mesh deformation method. We found that 3D wheat modelling at the individual leaf level, leaf group, and individual plant scales can be achieved. Compared with directly acquiring 3D digitizing data for 3D modelling, it saves 79.9% of the time. The minimum correlation R2 of the extracted morphological leaf parameters between using the measured data and 3D model by this method was 0.91 and the maximum RMSE was 0.03, implying that this method preserves the morphological leaf features. The proposed method provides a strong foundation for further morphological phenotype extraction, functional–structural analysis, and virtual reality applications in wheat plants. Overall, we provide a new 3D modelling method for complex plants. [ABSTRACT FROM AUTHOR]

The surface chemistry of garnet electrolyte is sensitive to air exposure. The poor LLZO/Li interface caused by Li2CO3/LiOH contaminants on garnet electrolyte surface easily induces large interfacial resistance resulting in the growth of Li dendrites. Herein, a versatile modification strategy is designed to convert the contaminants on Li6.4La3Zr1.4Ta0.6O12 (LLZTO) surface into a LiF and Li2PO3F‐rich lithiophilic interface by targeted chemical reactions at the interface between LiPO2F2 and Li2CO3/LiOH. The newly formed LiF‐Li2PO3F interfacial layer not only facilitates the interface wettability between Li and LLZTO, but also helps to resist corrosion of the LLZTO surface by moisture in the air. The Li|LiF&Li2PO3F‐LLZTO|Li symmetric cell exhibits a low interfacial resistance of 5.1 Ω cm2 and ultrastable galvanostatic cycling, over 1500 h at 0.6 mA cm−2 and over 70 h at 1.0 mA cm−2. In addition, LiCoO2|LiF&Li2PO3F‐LLZTO|Li hybrid solid‐state full cells display high initial specific capacity of 192 mAh g−1 at 0.1 C, and excellent cycling stability with a capacity retention over 76% even after 1000 cycles at 0.5 C at a high cut‐off voltage of 4.5 V. This study provides a simple and practical strategy for the feasibility of the application of high‐voltage cathodes in this modified garnet all‐solid‐state batteries. [ABSTRACT FROM AUTHOR]

The surface chemistry of garnet electrolyte is sensitive to air exposure. The poor LLZO/Li interface caused by Li2CO3/LiOH contaminants on garnet electrolyte surface easily induces large interfacial resistance resulting in the growth of Li dendrites. Herein, a versatile modification strategy is designed to convert the contaminants on Li6.4La3Zr1.4Ta0.6O12 (LLZTO) surface into a LiF and Li2PO3F‐rich lithiophilic interface by targeted chemical reactions at the interface between LiPO2F2 and Li2CO3/LiOH. The newly formed LiF‐Li2PO3F interfacial layer not only facilitates the interface wettability between Li and LLZTO, but also helps to resist corrosion of the LLZTO surface by moisture in the air. The Li|LiF&Li2PO3F‐LLZTO|Li symmetric cell exhibits a low interfacial resistance of 5.1 Ω cm2 and ultrastable galvanostatic cycling, over 1500 h at 0.6 mA cm−2 and over 70 h at 1.0 mA cm−2. In addition, LiCoO2|LiF&Li2PO3F‐LLZTO|Li hybrid solid‐state full cells display high initial specific capacity of 192 mAh g−1 at 0.1 C, and excellent cycling stability with a capacity retention over 76% even after 1000 cycles at 0.5 C at a high cut‐off voltage of 4.5 V. This study provides a simple and practical strategy for the feasibility of the application of high‐voltage cathodes in this modified garnet all‐solid‐state batteries. [ABSTRACT FROM AUTHOR]

Aqueous zinc‐ion batteries (AZIBs) are expected to be an attractive alternative in advanced energy storage devices due to large abundance and dependable security. Nevertheless, the undesirable energy density and operating voltage still hinder the development of AZIBs, which is intimately associated with the fundamental properties of the cathode. In this work, polyvinylpyrrolidone (PVP) intercalated Mn0.07VOx (PVP‐MnVO) with a large interlayer spacing of 13.5 Å (against 12.5 Å for MnVO) synthesized by a facile hydrothermal method is adopted for the cathode in AZIBs. The experimental results demonstrate that PVP‐MnVO with expanded interlayer spacing provides beneficial channels for the rapid diffusion of Zn2+, resulting in a high discharge capacity of 402 mAh g−1 at 0.1 A g−1, superior to that of MnVO (275 mAh g−1 at 0.1 A g−1). Meanwhile, the PVP molecule remains in the layer structure as a binder/pillar, which can maintain its structural integrity well during the charging/discharging process. Consequently, PVP‐MnVO cathode exhibits superior rate capability and cycling stability (89% retention after 4300 cycles at 10 A g−1) compared to that of MnVO (≈51% retention over 500 cycles at 2 A g−1). This work proposes a new approach to optimize the performance of vanadium‐based electrode materials in AZIBs. [ABSTRACT FROM AUTHOR]

Objectives: Skin serves as the major interface between the external environment and body which is liable to many kinds of injuries. Mesenchymal stem cell (MSC) therapy has been widely used and became a promising strategy. Pre‐treatment with chemical agents, hypoxia or gene modifications can partially protect MSCs against injury, and the pre‐treated MSCs show the improved differentiation, homing capacity, survival and paracrine effects regard to attenuating injury. The aim of this study was to investigate whether the exosomes from the educated MSCs contribute to accelerate wound healing process. Materials and methods: We extracted the exosomes from the two educated MSCs and utilized them in the cutaneous wound healing model. The pro‐angiogenetic effect of exosomes on endothelial cells was also investigated. Results: We firstly found that MSCs pre‐treated by exosomes from neonatal serum significantly improved their biological functions and the effect of therapy. Moreover, we extracted the exosomes from the educated MSCs and utilized them to treat the cutaneous wound model directly. We found that the released exosomes from MSCs which educated by neonatal serum before had the more outstanding performance in therapeutic effect. Mechanistically, we revealed that the recipient endothelial cells (ECs) were targeted and the exosomes promoted their functions to enhance angiogenesis via regulating AKT/eNOS pathway. Conclusions: Our findings unravelled the positive effect of the upgraded exosomes from the educated MSCs as a promising cell‐free therapeutic strategy for cutaneous wound healing. [ABSTRACT FROM AUTHOR]

Highlights • Identification of hydrogen risk during a refueling outage. • Verification of current configuration of PAR systems. • Optimization of hydrogen mitigation strategies are discussed. • Ignitors are suggested to be added to the refueling pool. Abstract This study deals with the identification of hydrogen risk and optimization of current hydrogen mitigation systems in the CPR1000 nuclear power plant (NPP) during a refueling outage. A detailed MELCOR input is developed, which includes detailed containment nodalization, accurate configuration of the passive autocatalytic recombiner (PAR) systems, and realistic boundary conditions based on design data and technical specifications. Two cases that represent different plant operation states (POS) and specific hydrogen release paths are selected, and the accident progression and hydrogen risk are analyzed subsequently. The analysis indicates that the hydrogen risk is still of great importance during a refueling outage, although the accident progression is relatively slow. PAR systems with the current configuration are added to the plant model to verify the effectiveness of the hydrogen mitigation system in the CPR1000 during a refueling outage. The results indicate that the current configuration of PAR systems is still effective in mitigating the hydrogen risk during an accident in POS E but is insufficient in mitigating the hydrogen risk during an accident in POS H. Therefore, two strategies to improve the hydrogen mitigation systems are proposed, and their effectiveness is compared. It is concluded that mobile ignitors should be employed in the refueling pool region to avoid severe hydrogen risk during a refueling outage. The results of this study can support the development of the low power and shutdown (LPSD) probabilistic safety assessment (PSA) model and improve the capacity of NPPs to reduce the hydrogen risk during a refueling outage. [ABSTRACT FROM AUTHOR]

The manipulation of acoustic waves plays an important role in a wide range of applications. Currently, acoustic wave manipulation typically relies on either acoustic metasurfaces or phased array transducers. The elements of traditional metasurfaces are usually designed with complex artificial structures and limited by the additive manufacturing capability, which are difficult to apply in MHz frequency underwater acoustic wave control. Phased array transducers, suffering from high‐cost and complex control circuits, are usually limited by the array size and the filling ratio of the control units. Coding piezoelectric metasurfaces are reported; three wave functionalities, including beam steering, beam focusing, and vortex beam focusing are demonstrated; and acoustic tweezers and ultrasound imaging are eventually realized. The information coded on the piezoelectric metasurfaces herein is frequency independent and originates from the polarization directions, pointing either up or down, of the piezoelectric materials. Such a piezoelectric metasurface is driven by a single electrode and acts as a controllable active sound source, which combines the advantages of acoustic metasurfaces and phased array transducers while keeping the devices structurally simple and compact. The coding piezoelectric metasurfaces lead to potential technological innovations in underwater acoustic wave modulation, acoustic tweezers, biomedical imaging, industrial nondestructive testing, and neural regulation. [ABSTRACT FROM AUTHOR]

The performance of the piezo-composite transducer is greatly influenced by the matching layers. Based on finite element analysis and artificial intelligence, an optimization design method is proposed to optimize the matching layers of a 2–2 piezo-composite transducer for biomedical imaging. The neural networks are trained by the finite element analysis data to build up the mapping relationship between the thickness of matching layers and the performance. The optimization criteria are established based on the performance (centre frequency, bandwidth, and peak-to-peak voltage) and minimizing the material consumption. The thicknesses of matching layers are optimized by using a particle swarm optimization algorithm. The optimized thicknesses of both matching layers are 49 μm. The optimized centre frequency, bandwidth, and peak-to-peak voltage are 9.1 MHz, 72.5%, and 2.26 V, which can nearly achieve the designed targets (9.5 MHz, 75%, and 2.20 V). According to the optimized thicknesses of matching layers, the fabricated 2–2 piezo-composite transducer exhibits a centre frequency of 9.8 MHz, a bandwidth of 79.6%, and a peak-to-peak voltage of 2.11 V verifies the effectiveness and availability of the proposed method. Then, the piezo-composite transducer is hard-pressed for ultrasonic imaging. The press-focused piezo-composite transducer has an insertion loss of -19.1 dB at 10 MHz, a lateral resolution of 125 μm at 4 mm, and an axial resolution of 132 μm. The good resolution was confirmed by scanning the pig eyeball, which suggests that the 2–2 piezo-composite transducer with optimized matching layers has great potential in biomedical imaging. [ABSTRACT FROM AUTHOR]

The control of acoustic field has great potential in many applications such as medical treatment, neuro-modulation, and bio-imaging. Recently, acoustic lenses and phased arrays have become common ways of controlling acoustic fields. However, the shortcomings of the two ways are obvious. Acoustic lenses lack flexibility after design, and phased arrays have complicated structures and need to adjust the parameters of each array element. In this work, we propose an alternative for sound field control using a flexible and adjustable “acoustic projector,” and two symmetric mirrors are used to change the direction of propagation of an acoustic wave produced by a piezoelectric element and realize acoustic focusing in the target region. The 2-D “acoustic projector” model was built in finite element simulation, and the feasibility was verified with an actual prototype. The sound intensity produced by the piezoelectric element at different horizontal and vertical positions along the target area can be accurately controlled by two adjustable mirrors. When the angle of the mirror ranges from 30° to 40°, the focal depth can change from 39 to 140 mm. Furthermore, the focus can be controlled in a sector with an angle of 60°. The “acoustic projector” demonstrates simple but precise control of acoustic fields and may broaden their applicability. To show its imaging ability, the three groups of target balls at different positions were imaged and their position information by scanning the mirrors in simulation was given. [ABSTRACT FROM AUTHOR]

In order to effectively and flexibly control acoustic pattern, an efficient optimization design method of acoustic liquid lens (ALL) is developed by the frame of particle swarm optimization (PSO) algorithm. The ALL is composed of ethanol and dimethicone, and its parameters include ethanol concentration (EC), volume fraction of dimethicone (VFD), and total volume (TV). Based on the established finite element model and orthogonal design method, the data of acoustic pattern and ALL can be obtained by using COMSOL Multiphysics. Based on the simulation data, the neural network models are constructed to characterize the relationship between the parameters of ALL and the performance of acoustic pattern. The optimization design criteria of ALL are constructed based on the performance parameters of acoustic pattern, including focal distance (FD), transverse resolution (TR), and longitudinal resolution (LR). Based on the optimization criteria, the modified PSO algorithm is utilized to optimize the design parameters of ALL in the developed method. According to the desired FD, TR, and LR of acoustic pattern (20, 1, and 17 mm), the optimized EC, VFD, and TV of ALL are about 0.838, 0.165, and 164.4 μL. The performance parameters of acoustic pattern verified by simulation and experiments agree with the desired ones. In addition, using 6 MHz ultrasonic transducer with the optimized ALL, the ultrasonic imaging of tungsten wires and porcine eyeball further demonstrates the effectiveness and feasibility of the developed method. [ABSTRACT FROM AUTHOR]

An acoustic lens is an attractive device due to its superior ability to image and focus acoustic beams. Nevertheless, the limitation of such a solid-phase device is apparent in that once an acoustic lens is made, its focal length remains fixed. On the contrary, the liquid acoustic lens can not only flexibly tune the position of focus, but also avoid greater acoustic impedance. This paper presented a liquid acoustic convex lens with a tunable focus. The focal distance of the liquid acoustic lens is derived from the focal length formula of the optical lens group. The interface curvature of the lens and the dependent focus as a function of the infused liquid volume in the lens were studied theoretically and experimentally. Furthermore, the refraction index of the liquid can be accurately selected as needed by adjusting the concentrations of liquid. This also results in a modification of the lens focal length. The magnification ability of this acoustic lens in combination with a single element 6.8 MHz transducer was evaluated by imaging steel probes which were embedded at different position without performing mechanical axial scanning. The error caused by the difference of sound speed between the liquid in the lens and the host medium is corrected. [ABSTRACT FROM AUTHOR]

Background: As the major interface between the body and the external environment, the skin is liable to various injuries. Skin injuries often lead to severe disability, and the exploration of promising therapeutic strategies is of great importance. Exogenous mesenchymal stem cell (MSC)-based therapy is a potential strategy due to the apparent therapeutic effects, while the underlying mechanism is still elusive. Interestingly, we observed the extensive apoptosis of exogenous bone marrow mesenchymal stem cells (BMMSCs) in a short time after transplantation in mouse skin wound healing models. Considering the roles of extracellular vesicles (EVs) in intercellular communication, we hypothesized that the numerous apoptotic bodies (ABs) released during apoptosis may partially contribute to the therapeutic effects. Methods: ABs derived from MSCs were extracted, characterized, and applied in mouse skin wound healing models, and the therapeutic effects were evaluated. Then, the target cells of ABs were explored, and the effects of ABs on macrophages were investigated in vitro. Results: We found ABs derived from MSCs promoted cutaneous wound healing via triggering the polarization of macrophages towards M2 phenotype. In addition, the functional converted macrophages further enhanced the migration and proliferation abilities of fibroblasts, which together facilitated the wound healing process. Conclusions: Collectively, our study demonstrated that transplanted MSCs promoted cutaneous wound healing partially through releasing apoptotic bodies which could convert the macrophages towards an anti-inflammatory phenotype that plays a crucial role in the tissue repair process. [ABSTRACT FROM AUTHOR]

Background: Skeletal muscle plays an important role in the body's physiology but there are still no effective treatments for volumetric muscle loss (VML) resulting from severe traumatic injury or tumor excision. Recent studies show that a tissue engineering strategy using a compound containing mesenchymal stem cells (MSCs) and decellularized extracellular matrix (ECM) scaffold generates significant regenerative effects on VML injury, but the underlying mechanisms are not fully understood. Methods: The characteristics of human umbilical cord MSCs, including multiplication capacity and multidifferentiation ability, were determined. We constructed a compound containing MSCs and decellularized ECM scaffold which was used for tissue regeneration in a VML model. Results: We found that MSCs and decellularized ECM scaffold generated synergistic effects on promoting skeletal muscle tissue regeneration. Interestingly, both MSCs and decellularized ECM scaffold could promote macrophage polarization toward the M2 phenotype and suppress macrophage polarization toward the M1 phenotype, which is widely regarded as an important promoting factor in tissue regeneration. More importantly, MSCs and decellularized ECM scaffold generate synergistic promoting effects on macrophage polarization toward the M2 phenotype, not just an additive effect. Conclusions: Our findings uncover a previously unknown mechanism that MSCs and decellularized ECM scaffold promote tissue regeneration via collaboratively regulating macrophage polarization. [ABSTRACT FROM AUTHOR]