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The frequent occurrence of global flood disasters leads to millions of people falling into poverty each year, which poses immense pressure on governments and hinders social development. Therefore, providing more data support for flood disaster detection is of paramount importance. To facilitate the development of water body detection algorithms, we create the DaliWS dataset for water segmentation, which contains abundant pixel-level annotations, and consists of high spatial resolution SAR images collected from the GaoFen-3 (GF-3) satellite. For comprehensive analysis, extensive experiments are conducted on the DaliWS dataset to explore the performance of the state-of-the-art segmentation models, including FCN, SegNeXt, U-Net, and DeeplabV3+, and investigate the impact of different polarization modes on water segmentation. Additionally, to probe the generalization of our dataset, we further evaluate the models trained with the DaliWS dataset, on publicly available water segmentation datasets. Through detailed analysis of the experimental results, we establish a valuable benchmark and provide usage guidelines for future researchers working with the DaliWS dataset. The experimental results demonstrate the F1 scores of FCN, SegNeXt, U-Net, and DeeplabV3+ on the dual-polarization data of DaliWS dataset reach to 90.361%, 90.192%, 92.110%, and 91.199%, respectively, and these four models trained using the DaliWS dataset exhibit excellent generalization performance on the public dataset, which further confirms the research value of our dataset. [ABSTRACT FROM AUTHOR]

Ultrasonic inspection is a widely used nondestructive testing approach in industrial fields for more accurate life prediction and efficient management strategies of critical structural components. However, it is quite challenging to detect a kind of micro-defect, whose size is much smaller than the ultrasonic wavelength but larger than the ultrasonic amplitude (namely, there is no appearance of non-classical acoustic nonlinearity). In this article, identification and imaging of a micro-defect of this size range with an improved resolution is conducted by the combination of the second-harmonic generation (SHG) of ultrasonic Lamb waves and the reconstruction algorithm for the probability inspection of damage. An intuitive model is first developed to explore the physical mechanism of a micro-defect-induced variation of generated second harmonic of a primary Lamb wave in a plate. Variations of amplitudes of second harmonics generated in propagation paths are used to construct the micro-defect image. A phase-reversal technique is employed to enhance the signal-to-noise ratio of the SHG. Comparisons between images constructed by linear and nonlinear acoustic features of Lamb wave propagation are presented. Results show that the image of the micro-defect with an improved resolution is successfully obtained by the proposed approach, while there is no visualized result obtained by the conventional linear ultrasonic one. [ABSTRACT FROM AUTHOR]

A nonlinear acoustic response can be an effective indicator of early-stage damage in a material. However, it is challenging to use this approach to assess thermal damage in highly attenuating materials such as polymethyl methacrylate by measurement of the generated second harmonics, which are present at double the fundamental frequency of the primary waves. Using the quasi-static components (QSCs) generated by ultrasonic-wave propagation in damaged structures—an approach that combines the high sensitivity of acoustic nonlinearities with low attenuation—has great potential for evaluation of early-stage damage in highly attenuating materials. In this paper, an experimental approach for directly detecting the QSC pulses from ultrasonic-wave tone bursts is proposed. In this approach, a high-frequency longitudinal-wave transducer is used for exciting the primary ultrasonic-wave tone burst, and the co-propagating QSC pulse is detected using a low-frequency ultrasonic transducer. The phase-reversal technique is employed to enhance the signal-to-noise ratio of the QSC pulse and to counteract the signals of the primary ultrasonic waves. In the experimental results, variations in the amplitudes of the QSC pulse in response to different degrees of thermal damage are clearly illustrated in a repeatable manner, even though the changes in the linear ultrasonic features in these specimens are negligible. These results indicate that the measurement of QSC pulse generation from ultrasonic-wave propagation is a promising alternative for evaluating thermal degradation in highly attenuating materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Self-assembly of colloidal particles enables the versatile fabrication of highly ordered structures and materials for optical, sensing, and other applications. Nevertheless, many traditional assembly processes are inefficient, because there exists an inevitable contradiction between time efficiency and crystalline quality. In this work, we introduce an ultrafast, robust, and scalable approach of imbibition-induced assembly. We assume that the instantaneous solvent imbibition induced by the nanoporous media could direct ultrafast self-assembly of colloidal particles into ordered structures. Self-assembly of colloidal particles from a droplet on a nanoporous substrate was firstly observed and investigated. A phase diagram of the thickness of the colloidal crystal as a function of the printing speed and the particle volume fraction was presented through systematic experiments. The nanoporous substrate can induce strong capillary flow that will direct the rapid self-assembly of particles into colloidal crystals. The imbibition-induced assembly was spatially and temporally combined with the meniscus-guided printing approach, and the printing speed can be improved by two orders of magnitude than the traditional evaporative assembly methods. We finally demonstrate an effective and ultrafast approach for assembling colloidal particles into photonic crystals with controllable sizes and shapes on the macroscale. [ABSTRACT FROM AUTHOR]

Summary: Increasing seawater exposure is killing coastal trees globally, with expectations of accelerating mortality with rising sea levels. However, the impact of concomitant changes in atmospheric CO2 concentration, temperature, and vapor pressure deficit (VPD) on seawater‐induced tree mortality is uncertain.We examined the mechanisms of seawater‐induced mortality under varying climate scenarios using a photosynthetic gain and hydraulic cost optimization model validated against observations in a mature stand of Sitka spruce (Picea sitchensis) trees in the Pacific Northwest, USA, that were dying from recent seawater exposure.The simulations matched well with observations of photosynthesis, transpiration, nonstructural carbohydrates concentrations, leaf water potential, the percentage loss of xylem conductivity, and stand‐level mortality rates. The simulations suggest that seawater‐induced mortality could decrease by c. 16.7% with increasing atmospheric CO2 levels due to reduced risk of carbon starvation. Conversely, rising VPD could increase mortality by c. 5.6% because of increasing risk of hydraulic failure.Across all scenarios, seawater‐induced mortality was driven by hydraulic failure in the first 2 yr after seawater exposure began, with carbon starvation becoming more important in subsequent years. Changing CO2 and climate appear unlikely to have a significant impact on coastal tree mortality under rising sea levels. [ABSTRACT FROM AUTHOR]

The increasing anthropogenic nitrogen (N) input is expected to affect soil total respiration (Rs), whereas the mechanisms of Rs components (autotrophic respiration, Ra; heterotrophic respiration, Rh) in response to aggravated N input remains controversial, especially in the subalpine ecosystems. A multi-level simulated N deposition experiment was designed at a subalpine grassland to explore the effects of Rs components in response to N deposition and their potential mechanisms. Results showed that both Ra and Rs firstly increased and subsequently decreased at a threshold of ca. 5 g N m−2 yr−1, with the maximum of Ra and Rs increased by 22.98 % and 13.93 %, respectively. By comparison, Rh decreased along with N addition duration (year) at ca. 15 g N m−2 yr−1. Similarly, growing season average cumulative Ra and Rs also showed a bell-shaped mode in response to elevated N inputs, with a peak appearing at ca. 5 g N m−2 yr−1. Increased Ra with N addition rates enhanced the Ra/Rs ratio in the fourth experimental year only. The temperature sensitivity (Q 10) of Ra, Rh and Rs spanned from 1.86 to 2.58, 1.85 to 2.31 and 1.86 to 2.45 respectively. Additionally, N addition reduced the Q 10 of Ra, Rh and Rs at ca. 10 g N m−2 yr−1, ca. 15 g N m−2 yr−1 and ca. 10 g N m−2 yr−1, respectively. The changes in Ra and Rh were largely affected by root TN and soil C/N, respectively. Our results address that Ra exerts a leading role in regulating Rs and Ra/Rs ratio with N enrichment. These findings supply a relatively comprehensive insight of N-induced effects on soil respirations (Ra and Rh) and their potential mechanisms, which have an important implication for evaluating soil C emission in the subalpine ecosystems under aggravating N deposition. [Display omitted] • We find a nonlinear response of Ra along with N gradient. • High-level N addition reduced the temperature sensitivity of soil respiration. • Our results addressed the predominant role of Ra in regulating Rs. • The changes in Ra and Rh were mainly regulated by root TN and soil C/N, respectively. [ABSTRACT FROM AUTHOR]

As an emerging pollutant, microplastics (MPs) cause widespread concern around the world owing to the serious threat they pose to ecosystems. In particular, sediments are thought to be the long-term sink for the continual accumulation of MPs in freshwater ecosystems. Polyethylene (PE) and polyethylene terephthalate (PET) have been frequently detected with large concentration variations in freshwater sediments from the lower reaches of the Yangtze River, one of the most economically developed regions in China, characterized by accelerated urbanization and industrialization, high population density and high plastics consumption. However, the impact of PE and PET on the sedimental bacterial community composition and its function has not been well reported for this specific region. Herein, PE and PET particles were added to freshwater sediments to assess the effects of different MP types on the bacterial community and its function, using three concentrations (500, 1500 and 2500 items/kg) per MP and incubations of 35, 105 and 175 days, respectively. This study identified a total of 68 phyla, 211 classes, 518 orders, 853 families and 1745 genera. Specifically, Proteobacteria, Chloroflexi, Acidobacteriota, Actinobacteriota and Firmicutes were the top five phyla. A higher bacterial diversity was obtained in control sediments than in the MP-treated sediments. The presence of MPs, whether PET or PE, had significant impact on the bacterial diversity, community structure and community composition. PICRUSt2 and FAPOTAX predictions demonstrated that MPs could potentially affect the metabolic pathways and ecologically functional groups of bacteria in the sediment. Besides the MP-related factors, such as the type, concentration and incubation time, the physicochemical parameters had an effect on the structure and function of the bacterial community in the freshwater sediment. Taken together, this study provides useful information for further understanding how MPs affect bacterial communities in the freshwater sediment of the lower reaches of the Yangtze River, China. [Display omitted] • Impact of microplastics in freshwater sediments in the lower reaches of Yangtze River, China was explored. • MP presence reduces the richness and diversity of bacterial communities, alters bacterial community composition. • The type, exposure time and concentration of MP had a significant impact on sedimental bacterial communities. • MP presence shifted a part of the bacterial function in freshwater sediment. [ABSTRACT FROM AUTHOR]

The application of deep learning in the field of power electronics fault diagnosis has garnered considerable attention and research interest. In the coil power supply of the HL-3 tokamak device, there exist practical challenges in dealing with fault data from 12-pulse thyristor power converters, including large data volume, variable frequency operation, and sensor noise, among others. To solve these problems, this paper proposes a method that combines wavelet threshold denoising and Meta Pseudo Labels. Firstly, discrete wavelet transform is used to transform the original voltage signals of the 12-pulse thyristor rectifier operating across a wide frequency range into the wavelet domain. Subsequently, a reasonable threshold is employed to filter out high-frequency noise, resulting in the output of wavelet threshold denoising. Then, Meta Pseudo Labels algorithm, an idiographic semi-supervised learning approach, is applied to learn the features of the denoised data, yielding classification models and experimental results. The model identifies three types of states in single thyristor branches of the rectifier circuit, which are normal, short-circuit fault, and open-circuit fault. The experimental results indicate that the accuracy and robustness of the model trained using the Meta Pseudo Labels algorithm outperform those of a convolutional neural network with the same network architecture. Especially, one of the experiments accomplishes a diagnosis accuracy exceeding 90% while training with the whole unlabeled training dataset and only 10% of stratified subsamples from the labeled training dataset. • Method that combines wavelet threshold denoising and Meta Pseudo Labels is proposed. • Wavelet threshold denoising can filter out high-frequency noise. • Meta Pseudo Labels helps mitigate the labeling challenges related to large dataset. • Accuracy of proposed method surpass those of CNN with the same network architecture. [ABSTRACT FROM AUTHOR]

Bone metastases caused by breast cancer pose a major challenge to the successful treatment of breast cancer patients. Many researchers have suggested that herbal medicines are extremely effective at preventing and treating cancer-associated osteolysis. Previous studies have revealed that Morusin (MOR) is cytotoxic to many cancer cells ex vivo. Nevertheless, how MOR contributes to osteolysis induced by breast cancer is still unknown, and the potential mechanism of action against osteolysis is worthy of further study. The protective effect and molecular mechanism of MOR in inhibiting breast cancer cell-induced osteolysis were verified by experiments and network pharmacology. Cell function was assessed by cell proliferation, osteoclast (OC) formation, bone resorption, and phalloidin staining. Tumour growth was examined by micro-CT scanning in vivo. To identify potential MOR treatments, the active ingredient–target pathway of breast cancer was screened using network pharmacology and molecular docking approaches. This study is the first to report that MOR can prevent osteolysis induced by breast cancer cells. Specifically, our results revealed that MOR inhibits RANKL-induced osteoclastogenesis and restrains the proliferation, invasion and migration of MDA-MB-231 breast cells through restraining the PI3K/AKT/MTOR signalling pathway. Notably, MOR prevented bone loss caused by breast cancer cell-induced osteolysis in vivo , indicating that MOR inhibited the development of OCs and the resorption of bone, which are essential for cancer cell-associated bone distraction. This study showed that MOR treatment inhibited osteolysis induced by breast cancer in vivo. MOR inhibited OC differentiation and bone resorption ex vivo and in vivo and might be a potential drug candidate for treating breast cancer-induced osteolysis. [Display omitted] • MOR can inhibit the differentiation of osteoclasts and the function of tumor cells. • MOR can inhibit bone resorption in the context of breast cancer-induced osteolysis. • MOR inhibited osteolysis through the PI3K/AKT/mTOR pathway. • The network pharmacological analysis enhanced the novelty of MOR on osteolysis. Summary: Morusin, a natural plant compound, effectively suppresses breast cancer-associated osteolysis by preventing both osteoclastogenesis progression and breast cancer cell function. Our study showed that Morusin exhibited therapeutic potential for the successful management of osteolysis induced by breast cancer. [ABSTRACT FROM AUTHOR]

In this work, we analyze theoretically and observe experimentally the frequency mixing response induced by the collinear interaction of two primary Lamb waves with different frequencies in an isotropic and homogenous plate. The internal resonance conditions for generating the combined harmonics are analyzed by using a perturbation approach and a normal-mode-expansion technique for waveguide excitation. The second- and third-order combined harmonics generated by the collinear wave mixing of two primary Lamb waves propagating in a specimen are analyzed, and the existence of the combined harmonics at specific frequencies is predicted. An experimental procedure is proposed to measure the combined harmonics induced by the collinear cross-interaction of the two specific primary Lamb waves at given frequencies. The theoretical prediction of the appearance of the combined harmonics at the specific mixing frequencies is consistent with experiment. The theoretical analysis and experimental observation provide a clear physical insight into the frequency-mixing response induced by the collinear cross-interaction of two primary ultrasonic Lamb waves. [ABSTRACT FROM AUTHOR]

• Imaging of delamination in CFRP laminates based on integration of multiple LDR modes. • LDR frequencies calculated by frequency-domain finite element approach. • Quantitative assesment of delamination with various shapes and sizes. Accurately visualizing the geometry and dimensions of internal delamination in fiber-reinforced polymer (CFRP) composites is a challenging endeavor. In this paper, we develop a method to identify and characterize delamination in composites by the integration of multiple local defect resonance (LDR) modes. The proposed method was validated by using T300/M914 CFRP plates containing three distinct defect geometries, employing both numerical simulations and experimental measurements. The approach commences with the application of a frequency-domain finite element method for LDR frequency determination, emphasizing improved computational efficiency. This technique is further corroborated through the use of the defect-to-background ratio (DBR) method, which identifies LDR frequencies in both numerical simulations and experimental testing. The integration of multiple LDR modes (IMLDR) at various frequencies enables precise imaging of delamination defects of diverse geometries and sizes. Experimental results closely align with the numerical findings, confirming that the integrated imaging results accurately correspond to artificial defects. This method furnishes precise descriptions of damage location, geometry, and dimensions. The obtained results indicate that the proposed IMLDR-based technique significantly enhances the accuracy and reliability of delamination imaging in composites. Consequently, it offers an effective approach for quantitatively assessing delamination damage in composites. [ABSTRACT FROM AUTHOR]

• This paper explores the quasistatic pulse (QSP) generation in composite pipes. • The nonlinear QSP of different guided waves exhibits axial displacement. • Numerical study reveals the waveform and multiple generation effects of QSP. • The experiment verifies the QSP generation in fiber reinforced laminated pipes. The quasistatic pulse (QSP) generation of ultrasonic guided waves in composite pipes can exhibit many features that are useful for early-stage material characterization and structural health monitoring. The intrinsic relationship between the QSP generation and the weak elastic nonlinearity of solids is complex. It has yet promised for developing the nonlinear ultrasonic guided wave technique that combines its advantages of high sensitivity to microdamage and low ultrasonic attenuation in composite materials. This study presents a systematic investigation of the QSP generation in fiber reinforced composite pipes. Using a three-dimensional finite element simulation with a nonlinear material model, the temporal waveform, mode conversion effect, cumulative effect, generation efficiency, and duration effect of QSP generation are revealed. The nonlinear QSP signals in laminated composite pipes are confirmed as the fastest wave mode that only has axial displacement. The shape of QSP depends on the group velocity difference between the QSP and the primary wave. The magnitude of QSP is related to the excitation level, frequency, and tone-burst duration of the primary wave. Experiments are conducted using carbon fiber reinforced composite pipes and the signals are measured using a laser vibrometer scanning system for verifying the QSP generation. The experimental results are consistent with the numerical findings. A relative nonlinear acoustic parameter based on the QSP generation is proposed and used to evaluate the early-stage thermal fatigue damage in the pipes. The measured nonlinear acoustic parameter demonstrates high sensitivity to the damage, indicating considerable potential for industrial applications. [ABSTRACT FROM AUTHOR]

Liver fibrosis remains a great challenge in the world. Spinosin (SPI), a natural flavonoid-C-glycoside, possesses various pharmacological activities including anti-inflammatory and anti-myocardial fibrosis effects. In this study, we investigate whether SPI can be a potential lead for the treatment of liver fibrosis and explore whether the orphan nuclear receptor Nur77, a negative regulator of liver fibrosis development, plays a critical role in SPI's action. A dual luciferase reporter system of α-SMA was established to evaluate the effect of SPI on hepatic stellate cell (HSC) activation in LX2 and HSC-T6 cells. A mouse model of CCl 4 -induced liver fibrosis was used to test the efficacy of SPI against liver fibrosis. The expression levels of Nur77, inflammatory cytokines and collagen were determined by Western blotting and qPCR. Potential kinase pathways involved were also analyzed. The affinity of Nur77 with SPI was documented by fluorescence titration. SPI can strongly suppress TGF-β1-mediated activation of both LX2 and HSC-T6 cells in a dose-dependent manner. SPI increases the expression of Nur77 and reduces TGF-β1-mediated phosphorylation levels of ASK1 and p38 MAPK, which can be reversed by knocking out of Nur77. SPI strongly inhibits collagen deposition (COLA1) and reduces inflammatory cytokines (IL-6 and IL-1β), which is followed by improved liver function in the CCl 4 -induced mouse model. SPI can directly bind to R515 and R563 in the Nur77-LBD pocket with a Kd of 2.14 μM. Spinosin is the major pharmacological active component of Ziziphus jujuba Mill. var. spinosa which has been frequently prescribed in traditional Chinese medicine. We demonstrate here for the first time that spinosin is a new therapeutic lead for treatment of liver fibrosis by targeting Nur77 and blocking the ASK1/p38 MAPK signaling pathway. Mechanisms for the Antifibrotic Effect of SPI in liver Fibrosis. [Display omitted] [ABSTRACT FROM AUTHOR]

• A model was proposed to analyze the feature guided wave (FGW) propagating in a L-shaped bend. • Dispersive characteristics of different families of FGWs modes and the interaction between these FGW modes and defects were obtained. • Feasibility of combining the FGWs and time-reversal (TR) method for defect detection in topographic structure is validated. The utilization of L-shaped bends has become widespread due to their versatility and ease of application in various industrial fields. Nevertheless, the geometric configuration of these bends makes them susceptible to stress concentration in the bending zone, which can lead to wall thinning caused by accelerated corrosion. This poses a profound challenge to the bearing capacity and reliability of L -shaped bends and highlights the urgent necessity for an effective technique to assess corrosion-induced wall thinning in the bending zone. In this study, we propose a nondestructive testing (NDT) method based on ultrasonic feature guided waves (FGWs) for the evaluation of local corrosion-induced wall thinning in L -shaped bends. Propagation characteristics of FGWs in L -shaped bends were analyzed using the semi-analytical finite element (SAFE) method and perfectly matched layer (PML) technique. Time-reversal (TR) method was employed to address the dispersion and multi-modes phenomenon of the selected guided wave modes and improve the signal-to-noise ratio (SNR) of measured FGW signals. Enhanced SNR of two types of FGW modes signals at different frequencies were verified by experimental and numerical results. Obtained results reveal that FGWs can effectively detect corrosion-induced wall thinning inside L -shaped bends, with improving the signal reflection coefficient by TR method. [ABSTRACT FROM AUTHOR]

• Generation of quasistatic component (QSC) in hollow cylindrical structures is studied. • Mode conversion, cumulative effect, and generation efficiency of QSC are investigated. • A microdamage localization method is proposed using QSC generation. • Experiment in aluminum pipes with different early corrosions validates the method. Quasistatic component (QSC) of guided wave (GW) has relatively low attenuation due to low frequency and high sensitivity to microdamage. The group velocity matching between primary GW and its QSC or higher harmonics usually facilitates the measurement of nonlinear signals due to cumulative effect of amplitude, but it restricts the determination of microdamage location. While group velocity mismatch is general for most of the wave mode pairs in nonlinear GW testing, this study presents a novel method for identifying the location of early stage microdamage using QSC generation of ultrasonic GW propagation in tubular structures under group velocity mismatching condition. A three-dimensional finite element (FE) model is developed to provide insights into the generation and propagation characteristics of the QSC induced by both global material weak nonlinearity and simulated local microdamage in metallic pipes. The FE analysis verifies the L(0,1) mode of the QSC generated from propagations of different fundamental wave modes. The generation efficiency and cumulation feature of the QSC pulse are obtained and discussed. By exploiting the group velocity mismatching condition, a microdamage localization method is proposed based on the L(0,1)-QSC mode pair, which requires one-way excitation of only one primary wave. Experiments are conducted using early corrosion aluminum specimens to investigate the QSC pulse signals and verify the proposed method. The FE and experimental results demonstrate the fundamental properties of QSC generation by GWs in isotropic metallic hollow cylindrical structures. The feasibility of the proposed microdamage localization method is validated experimentally for promising industrial applications. [ABSTRACT FROM AUTHOR]

Livestock grazing, a common method of grassland utilization, has profound effects on the plant biomass and biodiversity of grassland ecosystems. However, the overall directions and magnitudes of such effects, especially involving multiple livestock types and grazing seasons, remain poorly understood on a global scale. We conducted a meta-analysis to evaluate the size and direction of the overall effects of grazing on grassland plant biomass and plant diversity; and to estimate the variation of these responses with area types, livestock types, grazing seasons, and grazing intensities. We performed a comprehensive search of the Web of Science® and the China National Knowledge Infrastructure (CNKI) (1950–2019) using certain search terms, and considered the studies cited by several recent related syntheses. We compiled data from 175 field manipulative studies at 200 sites by selecting studies that satisfied five criteria. Grazing significantly decreased aboveground (−38.5%), belowground (−14.7%), and total biomass (−20.6%), but did not significantly change root–shoot ratio, species richness, or evenness. The effects of grazing on plant biomass and diversity depended on climate types and grazing patterns. Specifically, grazing significantly decreased plant total biomass and belowground biomass in dry areas only, but increased rootshoot ratio in wet areas only. Growing season and year-long grazing decreased total biomass, whereas non-growing season grazing had not changed total biomass. Among livestock types (bulk feeder, concentrate selectors, intermediate feeder or mixed), only intermediate feeder grazing significantly decreased belowground biomass (−16.5%) and total biomass (−25.3%). Heavy grazing significantly decreased belowground biomass (−19.2%), total biomass (−24.3%) and plant evenness (−21.2%), but not light and moderate grazing. Aboveground biomass was more sensitive to grazing than belowground biomass, and only over grazing decreased grassland biodiversity. Under the same grazing intensities, mixed livestock or bulk feeder grazing in the non-growing season probably is one of the ways to maintain plant diversity and sustainable development of grassland agriculture. Our results highlight the key role of grazing patterns and climate types in mediating plant biomass and biodiversity in response to grazing disturbance, and should be considered in devising the sustainable grazing management of grasslands. [Display omitted] • Only over grazing decreased grassland biodiversity. • Aboveground biomass is more sensitive to grazing than belowground biomass. • Grazing had a greater negative effect on plant biomass in dry areas than wet areas. • Mixed livestock grazing in non-growing season is benefits to grassland management. [ABSTRACT FROM AUTHOR]

Increasing seawater exposure is causing mortality of coastal forests, yet the physiological response associated with seawater-induced tree mortality, particularly in non-halophytes, is poorly understood. We investigated the shifts in carbon and nitrogen (N) metabolism of mature Sitka-spruce trees that were dying after an ecosystem-scale manipulation of tidal seawater exposure. Soil porewater salinity and foliar ion concentrations increased after seawater exposure and were strongly correlated with the percentage of live foliated crown (PLFC; e.g. crown 'greenness', a measure of progression to death). Co-occurring with decreasing PLFC was decreasing photosynthetic capacity, N-investment into photosynthesis, N-resorption efficiency and non-structural carbohydrate (soluble sugars and starch) concentrations, with the starch reserves depleted to near zero when PLFC dropped below 5%. Combined with declining PLFC, these changes subsequently decreased total carbon gain and thus exacerbated the carbon starvation process. This study suggests that an impairment in carbon and N metabolism during the mortality process after seawater exposure is associated with the process of carbon starvation, and provides critical knowledge necessary to predict sea-level rise impacts on coastal forests. [ABSTRACT FROM AUTHOR]

Reduced web section (RWS) connections and welded flange plate (WFP) connections can both effectively improve the seismic performance of a structure by moving plastic hinges to a predetermined location away from the column face. In this paper, two kinds of steel frames—with RWS connections and WFP connections—as well as different frames with welded unreinforced flange connections were studied through seismic fragility analysis. The numerical simulation was conducted by using multiscale FE modelling. Based on the incremental dynamic analysis and pushover analysis methods, probabilistic seismic demand analysis and seismic capability analysis were carried out, respectively. Finally, combined with the above analysis results, probabilistic seismic fragility analysis was conducted on the frame models. The results showed that the RWS connection and WFP connection (without double plates) have little influence on reducing the maximum inter-storey drift ratio under earthquake action. RWS connections slightly reduce the seismic capability in non-collapse stages and improve the seismic collapse resistance of a structure, which exhibits good structural ductility. WFP connections can comprehensively improve the seismic capability of a structure, but the seismic collapse resistance is worse than that of RWS connections when the structure has a large number of storeys. The frame with WFP connections has a lower failure probability at every seismic limit state, while the frame with RWS connections sacrifices some of its structural safety in non-collapse stages to reduce the collapse probability. [ABSTRACT FROM AUTHOR]

• Theoretical model for SHG of guided waves developed in topographic structure. • Verification of energy trapping effect for guided waves in topographical structure. • Cumulative SHG of feature guided waves observed in a welded joint. Cumulative second harmonic generation (SHG), where the amplitude of the generated second harmonic increases with propagation distance, is commonly utilized to enhance the measurability of nonlinear guided waves by providing a sufficient signal-to-noise ratio. Investigating and confirming the cumulative SHG of feature guided waves (FGWs) in topographical waveguides is crucial for accurately assessing material nonlinearity in such structures. This study examines the cumulative SHG of FGWs propagating in a typical topographic structure of a welded joint through both numerical simulations and experimental investigations. A theoretical model is developed using the semi-analytical finite-element (SAFE) method and perfectly matched layer (PML) to analyze the propagation characteristics of FGWs in a welded joint. The numerical and experimental results provide verification of the "trapping effect" of FGWs within the welded joint. Furthermore, the "cumulative effect" of SHG of FGWs is observed. Remarkably, both the experimental and numerical findings demonstrate that cumulative SHG of FGWs can be achieved by employing suitable mode selection and frequency tuning in the topographic structure, which aligns well with the theoretical predictions. This investigation contributes to advancing our understanding of cumulative SHG in FGWs propagated within topographical structures. These findings have practical implications for accurately characterizing material nonlinearity in topographic waveguides. [ABSTRACT FROM AUTHOR]

A new internal meshing gear transmission with curve element is put forward in this paper. The mathematical principle of tooth profile generation is described based on conjugate curves theory. For a given spatial curve, the meshing equation and its conjugated spatial curve under the motion law were derived. Considering the equidistant kinematic method, general internal tooth profiles models were established by the conjugate-curve pair. Numerical example of the internal gear pair was developed according to gear parameters and gear solid models were established by MATLAB and UG software. Motion simulation result shows that the gear pair satisfies point contact condition and design requirements. Meshing analysis of tooth profiles using FEA method was carried out. Stress analysis results of tooth profiles with single point contact and two points contact were, respectively, obtained. The conclusions lay the foundation for multi-point contact generation and tooth profile design. Also, further studies on transmission characteristics and manufacturing technology of the new gear drive will be carried out. [ABSTRACT FROM AUTHOR]

Aim: Nutrient resorption from senescing tissues is the most critical nutrient source for plants in degradation grasslands, playing critical roles to primary productivity and interspecies competitiveness. Hence within-species and among-species variation of nutrient resorption is one of the mechanisms explaining the increasing productivity and decreasing biodiversity after enclosure. Yet, the response of plant nutrient resorption to enclosure remains poorly documented. Methods: We conducted a 6-year manipulative field study to estimate the effects of enclosure on nutrient resorption efficiency in five dominant species in a degraded subalpine pasture. Results: Both soil, mature and senesced leaves showed significant increases in N, P, and K contents in response to enclosure. Despite some species-specific differences, enclosure generally increased the nutrient resorption in graminoids, but decreased in forbs (with the exception of phosphorus for Potentilla anserine), indicating an important difference in the adaptation of plant functional types to enclosure which may in turn strongly impact the productivity and structure of pasture vegetation under long-term enclosure. Conclusions: This study shows the positive effects of enclosure management on soil and plant nutrients accumulation, and our results highlight the importance of among-species and within-species variations in plant nutrient resorption to explain the effects of enclosure on biodiversity loss and productivity increase in a degraded ecosystem. [ABSTRACT FROM AUTHOR]

Nickel and nickel-based composites are of vital importance in many fields, while temperature loading can greatly influence the strength and performance of the materials. Nondestructive evaluation and characterization of such thermal damage can be used to predict the failure of metallic structures, thermal barrier coatings and so on, especially in a non-contact way under certain strict circumstances, such as testing at high temperature or in radiative environment. Herein, a contactless ultrasonic technique employing electromagnetic acoustic transducers (EMATs) combined with the resonance ultrasound spectroscopy is applied to make up the low energy transition efficiency of EMATs and enhance the signal-to-noise ratio of ultrasonic testing signals. The method is adopted to assess the thermal damages of different levels in artificially heat loaded nickel plates. The damage sensitivity of third order harmonics generated from shear waves is discussed, along with linear ultrasonic features including wave velocity and attenuation. Experimental results show that the proposed nonlinear electromagnetic acoustic resonance (EMAR) technique can be used to evaluate the thermal damage in ferromagnetic material with improved reliability and sensitivity over linear ones. [ABSTRACT FROM AUTHOR]

The generation of second- and third-order combined harmonics induced by the interaction of two primary Lamb waves with different frequencies has been analyzed theoretically and observed experimentally in our previous research [W. Li et al., J. Appl. Phys. 124, 044901 (2018)]. However, only third-order combined harmonics were observed experimentally because in the experimental investigations, the conditions for both synchronism and the symmetric feature were not satisfied simultaneously for the generation of the second-order combined harmonics. In this paper, first, the numerical perspective of the second-order combined harmonic generation by the collinear interaction of two primary Lamb waves with different frequencies in an isotropic and homogeneous plate is investigated. The results indicate that the synchronism and symmetric feature of two primary Lamb waves selected significantly affect the generation of second-order combined harmonics at the mixing frequencies. Next, an experimental scheme is proposed to measure the second-order combined harmonics predicted theoretically and numerically, through which it is found that the experimental results agree well with that of the theoretical and numerical predictions. The numerical and experimental results in this paper provide a clear physical insight, not previously available, into the second-order combined harmonic generation induced by the collinear interaction of two primary ultrasonic Lamb waves. [ABSTRACT FROM AUTHOR]

Aim: Increased atmospheric nitrogen deposition may have profound effects on tree carbon allocation dynamics. However, a comprehensive understanding of how nitrogen (N) enrichment influences carbon (C) allocation across plant functional processes and tree organs in individual trees remains elusive. Location: Global forest ecosystems. Time period: 1990–2018. Major taxa studied: Trees. Methods: We compiled data from 75 N addition experiments and conducted a meta‐analysis to evaluate the responses of C source (photosynthesis), sinks (growth and respiration) and storage (non‐structural carbohydrate concentrations) in different tree organs (foliage, above‐ground wood and roots) to N enrichment. Results: N enrichment significantly enhanced C supply via photosynthesis (+39.6%, n = 128). C allocation to growth (biomass increment/production) significantly increased in foliage (+15.9%, n = 68) and above‐ground wood (+31.8%, n = 64; bole, branch, stem and/or twig) with increasing N availability, but not in roots, whereas allocation increased in roots via increasing fine root turnover rate (+22.6%, n = 11). N fertilization significantly increased C allocation to respiration in above‐ground wood (+46.6%, n = 12) and roots (+5.5%, n = 57), but not in foliage. N addition decreased non‐structural carbohydrate (NSC) concentrations in foliage (−5.4%, n = 16) and roots (−5.0%, n = 21), but increased NSC in above‐ground wood (+6.1%, n = 22). In addition, N enrichment effects were strongly affected by moderator variables. Main conclusions: Our results demonstrate that N addition increased C allocation to growth and respiration more strongly than C allocation to NSC storage, and increased C allocation to above‐ground parts more strongly than to below‐ground parts. Our results are useful for better understanding the response of tree functional processes at organ level to N enrichment. The existing data also reveal that more long‐term experimental studies on mature trees in tropical and boreal forests are urgently needed to provide a basis for forecasting tree responses to N enrichment at the global scale. [ABSTRACT FROM AUTHOR]

In Tokamak device, many larger capacity pulsed power supplies have been installed to provide high-energy magnetic field to control plasma. In this article, a new digital control system for satisfying larger capacity pulse power supply is introduced. This control scheme uses programmable automation controller (PAC) architecture, which consists of software platform and hardware platform to design a new digital control system, and in this system, real-time operation system (OS) and real-time communication network can provide much more precise and predictable timing characteristics to fulfill the requirements of the real-time control for pulse power supply in Tokamak device. Its hardware architecture based on integration and modularization can provide reliability, stability, and flexibility for digital control application; meanwhile, its software platform is used to handle data communication, close-looping control, protection strategy execution, and trigger output. After the digital control system of the large-capacity pulse power supply is built, its performance is verified through the HL-2A experiments. The result shows that the digital control system achieves the design goals and has high reliability and stability. [ABSTRACT FROM AUTHOR]

Structural strength and integrity of composites can be considerably affected by the low-velocity impact damage due to the unique characteristics of composites, such as layering bonded by adhesive and the weakness to impact. For such damage, there is an urgent need to develop advanced nondestructive testing approaches. Despite the fact that the second harmonics could provide information sensitive to the structural health condition, the diminutive amplitude of the measured second-order harmonic guided wave still limits the applications of the second-harmonic generation–based nonlinear guided wave approach. Herein, laminated composites suffered from low-velocity impact are characterized by use of nonlinear guided waves. An enhancement in the signal-to-noise ratio for the measure of second harmonics is achieved by a phase-reversal method. Results obtained indicate a monotonic correlation between the impact-induced damage in composites and the relative acoustic nonlinear indicator of guided waves. The experimental finding in this study shows that the measure of second-order harmonic guided waves with a phase-reversal method can be a promising indicator to impact damage rendering in an improved and reliable manner. [ABSTRACT FROM AUTHOR]

Glucose is one of the major energy sources in organisms, which also is an important biomarker in clinic diabetes diagnosis. Owing to urgent requirements in clinic diabetes diagnosis, developing glucose detection method with accuracy, sensitivity and stability becomes urgently important. A sensitively and stably photoelectrochemical (PEC) non-enzymatic glucose sensor was constructed using the graphitic carbon nitride/α-Fe 2 O 3 (g-CN/α-Fe 2 O 3) heterojunction. The g-CN/α-Fe 2 O 3 heterojunction was synthesized using a facile hydrothermal process in the presence of ionic liquids. The α-Fe 2 O 3 nanoparticles anchored to the surface of g-CN, which contributed to forming formation the heterojunction between α-Fe 2 O 3 and g-CN. The heterojunction can accelerate the migration of photogenerated carriers, resulting in enhanced PEC performance. As a result, the g-CN/α-Fe 2 O 3 heterojunction achieved the enhancing photocurrent density compared to α-Fe 2 O 3 alone. In addition, the introduction of glucose can boost electron-hole separation, resulting in sensitive PEC tracing of glucose level in aqueous solution. The sensor can trace the contents of glucose among 0.1 to 11.5 mg L−1 with an acceptable stability. Furthermore, the detection limit of the PEC non-enzymatic glucose sensor is significantly lowered to 0.03 mg L−1. It means the PEC non-enzymatic glucose sensor constructed by the g-CN/α-Fe 2 O 3 heterojunction can be a promising platform to detect glucose. Unlabelled Image • g-CN/α-Fe 2 O 3 heterojunction was successfully prepared via a facile hydrothermal process in the presence of ionic liquids. • g-CN/α-Fe 2 O 3 heterojunction showed enhanced photoelectrochemical (PEC) performance. • Benefiting from enhanced PEC performance of the heterojunction, a sensitive PEC non-enzymatic glucose sensor was realized. [ABSTRACT FROM AUTHOR]

High-dimensional quantum entanglement characterizes the entanglement of quantum systems within a larger Hilbert space, introducing more intricate and complex correlations among the entangled particles' states. The high-dimensional Greenberger–Horne–Zeilinger (GHZ) state, symbolic of this type of entanglement, is of significant importance in various quantum information processing applications. This study proposes integrating a neutral atom platform with quantum reservoir engineering to generate a high-dimensional GHZ state deterministically. Leveraging the advantages of neutral atoms in a modified unconventional Rydberg pumping mechanism, combined with controlled dissipation, we achieve a three-dimensional GHZ state with a fidelity surpassing 99% through multiple pump and dissipation cycles. This innovative approach paves the way for experimentally feasible, deterministic preparation of high-dimensional GHZ states in Rydberg atom systems, thereby advancing the capabilities of quantum information processing. [ABSTRACT FROM AUTHOR]

Abstract One of the effective ways to quantitatively inspect or monitor an industrial structure is to obtain images via either scanning or tomography. A combination of ultrasonic guided wave approach and tomographic technique by employing a reconstruction algorithm for the probabilistic inspection of damage (RAPID) can be used to inspect effectively the damage area via visual images. In this paper, surface cracks in polymer bonded explosives (PBXs) were quantitatively evaluated by a Rayleigh surface wave tomographic approach. Considering the relative low wave velocity in the material tested, special surface wave transducers with silicone wedge were designed and produced. The measured signals of Rayleigh surface wave propagation in the specimen with and without cracks were used in a tomographic algorithm to reconstruct images of defects. Results indicate that the setup of the array of transducers has significant influence on the appearance of images. Optimal transducer array setups were also proposed to measure the ultrasonic wave signals for irregular shaped defects to quantitatively image irregular surface cracks in PBXs. It was shown that the image generated by the proposed approach with the optimal transducer array and shape factor calculation method has good agreement with the real defect shape. The present approach provides an alternative tool that can be applied to detecting, locating and imaging the surface defects in PBXs. Highlights • Specific transducers for generation and detection of surface waves in PBXs are designed and manufactured. • The effect of transducer setup on reconstructed image is investigated to optimize setup to get the defects images. • The quantifications via imaging of surface crack with irregular shape in PBXs is achieved by specific transducers designed. [ABSTRACT FROM AUTHOR]

This study aimed to screen DNA aptamers against the signal molecule C4-HSL of the rhl system for the inhibition of biofilm formation of Pseudomonas aeruginosa using an improved systematic evolution of ligand by exponential enrichment (SELEX) method based on a structure-switching fluorescent activating bead. The aptamers against the C4-HSL with a high affinity and specifity were successfully obtained and evaluated in real-time by this method. Results of biofilm inhibition experiments in vitro showed that the biofilm formation of P. aeruginosa was efficiently reduced to about 1/3 by the aptamers compared with that of the groups without the aptamers. Independent secondary structure simulation and computer-aided tertiary structure prediction (3dRNA) showed that the aptamers contained a highly conserved Y-shaped structural unit. Therefore, this study benefits the search for new methods for the detection and treatment of P. aeruginosa biofilm formation. [ABSTRACT FROM AUTHOR]

Non-structural carbohydrates (NSC) play a central role in plant functioning as energy carriers and building blocks for primary and secondary metabolism. Many studies have investigated how environmental and anthropogenic changes, like increasingly frequent and severe drought episodes, elevated CO2and atmospheric nitrogen (N) deposition, influence NSC concentrations in individual trees. However, this wealth of data has not been analyzed yet to identify general trends using a common statistical framework. A thorough understanding of tree responses to global change is required for making realistic predictions of vegetation dynamics. Here we compiled data from 57 experimental studies on 71 tree species and conducted a meta-analysis to evaluate general responses of stored soluble sugars, starch and total NSC (soluble sugars + starch) concentrations in different tree organs (foliage, above-ground wood and roots) to drought, elevated CO2and N deposition. We found that drought significantly decreased total NSC in roots (−17.3%), but not in foliage and above-ground woody tissues (bole, branch, stem and/or twig). Elevated CO2significantly increased total NSC in foliage (+26.2%) and roots (+12.8%), but not in above-ground wood. By contrast, total NSC significantly decreased in roots (−17.9%), increased in above-ground wood (+6.1%), but was unaffected in foliage from N fertilization. In addition, the response of NSC to three global change drivers was strongly affected by tree taxonomic type, leaf habit, tree age and treatment intensity. Our results pave the way for a better understanding of general tree function responses to drought, elevated CO2and N fertilization. The existing data also reveal that more long-term studies on mature trees that allow testing interactions between these factors are urgently needed to provide a basis for forecasting tree responses to environmental change at the global scale. [ABSTRACT FROM AUTHOR]

In this paper, BN‐BiOI materials are prepared via an ionic liquid 1‐butyl‐3‐methyl‐imidazolium iodine ([Bmim]I)‐assisted solvothermal method. Through a series of characterizations (XRD, TEM, DRS, PC, and so on), the structures, morphologies, and optical properties of BN‐BiOI samples are investigated. The photocatalytic activity of the graphene‐analogue BN‐BiOI materials is evaluated by the degradation of methyl orange (MO) under visible light irradiation (λ > 400 nm). The results show the 3 wt.% BN‐BiOI composites exhibit the highest performance. The improved photocatalytic activity is attributed to the superior light absorption and higher separation efficiency of the electron–hole pairs by the introduction of graphene‐analogue BN. [ABSTRACT FROM AUTHOR]

• Modeling of zero-group velocity (ZGV) combined harmonic generation by counter-directional guided waves mixing. • Presentation of an insight into the ZGV combined harmonic generation induced by guided waves mixing. • Validation of feasibility of localized degradation assessment by generated ZGV combined harmonic. In this paper, modelling and numerical perspective of zero-group velocity (ZGV) combined harmonic generated by guided waves mixing are investigated. The conditions for the generation of the ZGV combined harmonic are analyzed by S 0 - S 0 and SH 0 - SH 0 guided waves mixing in an isotropic plate, respectively. The generation of ZGV combined harmonics at sum frequency caused by counter-directional guided waves mixing is observed. It is confirmed that the ZGV combined harmonic with a considerable magnitude can be generated by this counter-directional guided waves mixing when both the internal resonant condition and non-zero power flux are satisfied. The application of generated ZGV combined harmonics for localized material degradation assessment is numerically examined in the given plate. The obtained results indicate that the generated ZGV combined harmonic induced by the counter-directional guided waves mixing can be used to assess the localized material degradation with improved signal-to-noise ratio. This study provides an insight into the physical process of the ZGV combined harmonic generation, and meanwhile offer a promising means for localized material degradation assessment by ZGV combined harmonics generated by guided waves mixing. [ABSTRACT FROM AUTHOR]

We show a superplastic diffusion bonding method to join metallic glasses (MGs) via high-speed heating at 2000 K/min taking a timescale of the order of microseconds to milliseconds at ambient pressure because the minimum viscosity of supercooled liquid drastically decreases as the heating rate increases. The results show strong metallic bonds are formed but the amorphous structure is still maintained. Finally, we establish a general equation containing the involved parameters for high-speed heating bonding. This method provides a new path to join MGs rapidly and benefits for improving the critical size of MGs. [ABSTRACT FROM AUTHOR]

In the era of big data, making full use of remote sensing images to automatically extract surface water bodies (WBs) in complex environments is extremely challenging. Due to the weak capability of existing algorithms in extracting small WBs and WB edge information from remote sensing images, we proposed a new method—Multiscale Fusion SegFormer (MF-SegFormer)—for WB extraction in the Weihe River Basin of China using Landsat 8 OLI images. The MF-SegFormer method adopts a cascading approach to fuse features output by the SegFormer encoder at multiple scales. A feature fusion (FF) module is proposed to enhance the extraction of WB edge information, while an Atrous Spatial Pyramid Pooling (ASPP) module is employed to enhance the extraction of small WBs. Furthermore, we analyzed the impact of four kinds of band combinations on WB extraction by the MF-SegFormer model, including true color composite images, false color images, true color images, and false color images enhanced by Gaussian stretch. We also compared our proposed method with several different approaches. The results suggested that false color composite images enhanced by Gaussian stretching are beneficial for extracting WBs, and the MF-SegFormer model achieves the highest accuracy across the study area with a precision of 77.6%, recall of 84.4%, F1-score of 80.9%, and mean intersection over union (mIoU) of 83.9%. In addition, we used the determination coefficient (R2) and root-mean-square error (RMSE) to evaluate the performance of river width extraction. Our extraction results in an overall R2 of 0.946 and an RMSE of 28.21 m for the mainstream width in the "Xi'an-Xianyang" section of the Weihe River. The proposed MF-SegFormer method used in this study outperformed other methods and was found to be more robust for WB extraction. [ABSTRACT FROM AUTHOR]

Soil respiration is the largest terrestrial carbon flux into the atmosphere, and different tree species could directly influence root derived respiration and indirectly regulate soil respiration rates by altering soil chemical and microbial properties. In this study, we assessed the small scale spatial heterogeneity of soil respiration and the microbial community below the canopy of three dominant tree species (Korean pine ( Pinus koraiensis ), Mongolian oak ( Quercus mongolica ), and Manchuria ash ( Fraxinus mandshurica )) in a temperate mixed forest in Northeast China. Soil respiration differed significantly during several months and increased in the order of oak < ash < pine, while soil temperature was greater in the order of pine < oak < ash, suggesting that soil respiration variations among tree species were not mainly regulated by soil temperature. In addition, the lower N and higher C concentrations of pine litter resulted in a higher C/N ratio than ash and oak, which might lead to a higher recalcitrance and slower decomposition rate, and decreased heterotrophic respiration under pine. By contrast, fine root biomass was significantly higher under pine than ash and oak, which induced higher soil autotrophic respiration under pine compared to ash and oak. Tree species sharply regulated the bacterial communities through altering the litter and soil properties, while the fungal communities were relatively consistent among tree species. This study revealed the connection between species specific traits and soil respiration, which is crucial for understanding plant-soil feedbacks and improving forecasts of the global carbon cycle. [ABSTRACT FROM AUTHOR]

Snowpack in winter is very sensitive to climate change, and may in turn induce complex effects on terrestrial biochemistry processes. Here we synthesized the results from 49 papers based on snow depth manipulation experiments and conducted a meta-analysis to evaluate the general response of 9 variables related to terrestrial carbon pools and dynamics to the altered snowpack depth. Our meta-analysis results indicated that increasing snowpack depth significantly increased litter biomass (+18.4%), MBC (+18.2%) and CO 2 emission (+15.5%), and significantly decreased litter C: N ratio (−5.8%) and total soil carbon (−28.5%) under snow addition manipulation, but did not significantly affect fine root biomass, MBC: MBN ratio and soil dissolved organic carbon (DOC). However, increasing snowpack depth only significantly altered litter C: N ratio (+11.2%) under snow removal manipulation. The different responses between snow addition and removal were possibly related to the higher soil temperature and moisture under snow addition than under snow removal manipulation experiments. In addition, the effect of increasing snowpack depth on CH 4 flux was not significant, presumably because all these studies were compiled from snow-removal experiments. These results are useful for a better understanding of the effects of altered snowpack on terrestrial carbon cycling under climate change scenarios. [ABSTRACT FROM AUTHOR]

Second harmonic generation of ultrasonic waves propagating in unbounded media and plate-like structure has been vigorously studied for tracking material nonlinearity, however, second harmonic guided wave propagation in tube-like structures is rarely studied. Considering that second harmonics can provide sensitive information for structural health condition, this paper aims to study the second harmonic generation of guided waves in metallic tube-like structures with weakly nonlinearity. Perturbation method and modal analysis approach are used to analyze the acoustic field of second harmonic solutions. The conditions for generating second harmonics with cumulative effect are provided in present investigation. Flexible polyvinylidene fluoride comb transducers are used to measure fundamental wave modes and second harmonic ones. The work experimentally verifies that the second harmonics of guided waves in pipe have a cumulative effect with propagation distance. The proposed procedure of this work can be applied to detect material nonlinearity due to damage mechanism in tube-like structure. [ABSTRACT FROM AUTHOR]

Snowpack in winter is very sensitive to climate change, and may in turn induce complex effects on nutrient cycling in terrestrial ecosystems. This study synthesized data from 41 publications based on snow depth manipulation experiments and conducted a meta-analysis to assess the general responses of 12 variables related to terrestrial nitrogen (N) pools and dynamics to altered snowpack depth. Our results indicated that increasing snow depth significantly increased foliar N (+4.5%) and microbial N (MBN, +35.9%), but significantly decreased soil N 2 O efflux (−34.1%). However, altered snow depth did not significantly affect soil dissolved organic N (DON), total inorganic N, nitrate and N leaching. The decreased net nitrification (−24.8%) by deeper snowpack suggested that less soil N transformed to nitrate, which might contribute to reduce soil N losses. Since increasing snowpack depth promoted MBN, the unchanged net N mineralization and soil ammonium content were probably due to limitation of the soil N availability and other soil abiotic factors rather than soil microbes. In addition, long-term and snowfence or shelter methods generated the most significant effects on N dynamics for snow addition or removal experiments, respectively. Our results provide a comprehensive understanding of how N cycling responses to altered snow cover under climate change scenarios. [ABSTRACT FROM AUTHOR]

The use of guided wave tomography has become an attractive alternative to convert ultrasonic wave raw data to visualized results for quantitative signal interpretation. For more accurate life prediction and efficient management strategies for critical structural components, there is a demand of imaging micro-damages in early stage. However, there is rarely investigation on guided wave tomographic imaging of micro-defects. One of the reasons for this might be that it becomes challenging to monitor tiny signal difference coefficient in a reliable manner for wave propagation in the specimens with micro-damages. Nonlinear acoustic signal whose frequency differs from that of the input signal can be found in the specimens with micro-damages. Therefore, the combination of guided wave tomography and nonlinear acoustic response induced by micro-damages could be a feasibility study for imaging micro-damages. In this paper, the nonlinear Rayleigh surface wave tomographic method is investigated to locate and size micro-corrosive defect region in an isotropic solid media. The variations of acoustic nonlinear responses of ultrasonic waves in the specimens with and without defects are used in guided wave tomographic algorithm to construct the images. The comparisons between images obtained by experimental signals and real defect region induced by hydrogen corrosion are presented in this paper. Results show that the images of defect regions with different shape, size and location are successfully obtained by this novel technique, while there is no visualized result constructed by conventional linear ultrasonic tomographic one. The present approach shows a potential for inspecting, locating and imaging micro-defects by nonlinear Rayleigh surface wave tomography. [ABSTRACT FROM AUTHOR]

Microporous carbon material with a high surface area of 1562 m 2 /g is prepared via an impregnation method with NaY zeolite as hard template. The results indicate that glucose, an environmental friendly material, could be used as the carbon precursor of zeolite templated carbons, in comparison with the toxicity of furfuryl alcohol and lower surface area of carbons generated from sucrose. Effects of reactant molar ratios and carbonization conditions on the textural properties are addressed. Although higher carbonization temperature favors more complete carbonization reactions, it also causes the collapse of small pores and the formation of large pores at the same time. Further characterizations of the obtained carbon materials with XRD, SEM and N 2 adsorption–desorption measurements are presented. Methane adsorption tests on carbon materials are investigated with the static volumetric method at 300 K. The higher adsorption amount of 9.9 wt.% was achieved at 3.5 MPa on sample with a higher micropore volume, indicating that micropores were playing a crucial role for the methane storage process. [ABSTRACT FROM AUTHOR]

Ultrasonic guided wave tomography provides an imaging potential over a hidden and inaccessible damage zone. The use of shear horizontal guided waves has been proposed as an attractive technique for surface defect characterization. In this study, the quantification and imaging of corrosion wall thinning in a plate are investigated by using shear horizontal guided waves. Simulations of shear horizontal wave propagation in the specimens using hybrid boundary element method are studied in this paper. Magnetostrictive patch transducers are designed to generate and measure the shear horizontal wave mode experimentally. The quantification via imaging of wall thinning is achieved by a modified reconstruction algorithm for the probabilistic inspection of damage tomography algorithm. The comparisons of the imaging obtained by modeling data and experimental ones of defects with different shapes in the specimens are presented in this paper. The results obtained by experimental tests are comparable with that produced by boundary elements method. The present approach provides an alternative tool, that can be applied to detecting, locating and imaging the wall thinning defects in plate-like structures. [ABSTRACT FROM AUTHOR]

Aptamers are single-stranded deoxyribonucleic acid or ribonucleic acid oligonucleotides generated in vitro based on affinity for certain target molecules by a process known as Systematic Evolution of Ligands by Exponential Enrichment. Aptamers can bind their target molecules with high specificity and selectivity by means of structure compatibility, stacking of aromatic rings, electrostatic and van der Waals interactions, and hydrogen bonding. With several advantages over monoclonal antibodies and other conventional small-molecule therapeutics, such as high specificity and affinity, negligible batch to batch variation, flexible modification and stability, lack of toxicity and low immunogenicity, aptamers are becoming promising novel diagnostic and therapeutic agents. This review focuses on the development of aptamers as potential therapeutics for autoimmune diseases, including diabetes mellitus, multiple sclerosis, rheumatoid arthritis, myasthenia gravis, and systemic lupus erythematosus. [ABSTRACT FROM AUTHOR]

Chemically bonded graphene/TiO 2 nanorod hybrid composites with superior dispersity were synthesized by a one-step in situ hydrothermal method using graphene oxide (GO) and TiO 2 (P25) as the starting materials. The as-prepared samples were characterized by XRD, XPS, TEM, FE-SEM, EDX, Raman, N 2 adsorption, and UV–vis DRS techniques. Enhanced light absorption and a red shift of absorption edge were observed for the composites in the ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS). Their effective photocatalytic activity was evaluated by the photodegradation of methylene blue under visible light irradiation. An enhancement of photocatalytic performance was observed over graphene/TiO 2 nanorod hybrid composite photocatalysts, as 3.7 times larger than that of pristine TiO 2 nanorods. This work demonstrated that the synthesis of TiO 2 nanorods and simultaneous conversion of GO to graphene “without using reducing agents” had shown to be a rapid, direct and clean approach to fabricate chemically bonded graphene/TiO 2 nanorod hybrid composites with enhanced photocatalytic performance. [ABSTRACT FROM AUTHOR]

• Numerical perspectives of the generation, propagation, and mode conversion of QSPs of GWs in composites are firstly obtained. • Unique features of QSPs generated by GWs propagation along principle and non-principle material directions in composites are provided. • Both cumulative and divergence effects of generated QSPs are analyzed. • Factors affecting the generation efficiency of QSPs are analyzed and given. In this paper, the generation of quasistatic pulses (QSPs) of guided waves propagation in fiber reinforced plastic (FRP) thin plates is investigated. Numerical perspective of the generation, propagation, and mode conversion of QSPs of GWs in the composites are obtained. It is indicated that the displacement direction and generation efficiency of QSPs depend on the wave propagation direction, the coefficients of the strain energy function, and the primary GW field. Group velocity, wave structure, and wavenumber domain analyses show that the generated QSPs are either S0 mode, or partly coupled S0 and SH0 modes with only in-plane displacements with different direction, regardless of the excitation of primary waves. For GWs propagation in principal material directions, comparative studies show that the generation efficiency of QSPs are depended on both the mode types and primary GW propagation direction. With the considerations of both cumulative effect and the divergence effect, comparative study of generation efficiency of QSP and second harmonics shows that, although the divergence loss is not negligible, appropriate excitation of primary GW can achieve a higher efficiency of cumulative QSP generation than that of the phase matched second harmonics. [ABSTRACT FROM AUTHOR]