•Deep learning based semantic segmentation method with fully convolutional network is proposed.•Defect images are captured via a self-developed image acquisition equipment (MTI-200a).•The proposed ...method can rapidly and accurately recognize defects for metro shield tunnels.
The performance of traditional visual inspection by handcrafted features for crack and leakage defects of metro shield tunnel is hardly satisfactory nowadays because it is low-efficient to distinguish defects from some interference such as segmental joints, bolt holes, cables and manual marks. Based on deep learning (DL), this paper proposes a novel image recognition algorithm for semantic segmentation of crack and leakage defects of metro shield tunnel using hierarchies of features extracted by fully convolutional network (FCN). The defect images in training dataset and testing dataset are captured via a self-developed image acquisition equipment named Moving Tunnel Inspection (MTI-200a). After the establishment of image datasets, FCN models of crack and leakage are separately trained through several iterations of forward inference and backward learning. Semantic segmentation of defect images is implemented via the corresponding FCN models using two-stream algorithm, i.e. one stream is used to recognize the crack by sliding-window-assembling operation and the other is adopted for the leakage by resizing-interpolation operation. Compared with two frequently-used traditional methods, i.e. region growing algorithm (RGA) and adaptive thresholding algorithm (ATA), great superiority of the proposed method in terms of recognition results, inference time and error rates is shown based on four typical types of defect images which are crack-only image, leakage-only image, two-defect-nonoverlapping (TDN) image, two-defect-overlapping (TDO) image. The proposed method using DL can be employed to rapidly and accurately recognize defects for structure health monitoring and maintenance of metro shield tunnels.
Dopamine (DA) is an important neurotransmitter associated with nerve signaling and some diseases. Therefore, it is very significant to detect DA in patients to regulate body function. Compared with ...other traditional methods, these electrochemical sensors have their intrinsic advantages of high sensitivity, celerity, simplicity, and economy. In this article, a graphene quantum dots/multiwalled carbon nanotubes (GQDs-MWCNTs) composite-based ultrasensitive electrochemical sensor for detecting dopamine (DA) was fabricated. As the carbon nanomaterials, GQDs have large surface areas to improve the conductivity of the electrodes, and the MWCNTs are excellent electrode materials. As expected, the sensor has excellent selectivity of dopamine among other interfering bioanalytes. Under optimum conditions, this electrochemical sensor exhibited maximum performance toward DA determination with good linearity in a broad linear range of 0.005 to 100.0 μM with the detection limit of 0.87 nM (3S/N). Furthermore, this electrochemical sensor was successfully applied for detecting DA in human serum, and it was the first example to measure DA secreted from live PC12 cells with excellent performance.
•Recent advances on nanoparticles for NRR are summarized.•Fundamentals of NRR and brief theoretical calculations are discussed.•Strategies for boosting the intrinsic catalytic properties of the NRR ...are outlined.•The challenges, perspectives, and research directions in NRR are highlighted.
Ammonia is an essential raw ingredient for fertilizers, a carbon-free hydrogen carrier, and an alternative fuel. The natural process of producing ammonia cannot meet the rapidly growing global demand. On the other hand, the conventional industrial Haber-Bosch process for ammonia production demands high energy and generates massive greenhouse gases. Recently, the research community has focused on designing environmentally friendly nanocatalysts for the electrocatalytic N2 reduction reaction (NRR) that involves less energy consumption. However, the NRR is still far from industrial implementation because of the low faradic efficiency and ammonia formation rate. In this comprehensive review, we start with a brief overview of the fundamentals of NRR related to thermodynamic perspectives and discuss the reaction mechanisms for ammonia synthesis. We then critically introduce the research methods for electrocatalytic NRR and various nanocatalysts, including transition metals, non-metals, main group elements, and noble-metal-based NRR electrocatalysts. Finally, some outlooks are provided on the research progress of the NRR electrocatalytic nanomaterials, methods and techniques toward ammonia production.
•One-step green synthesis of CDs from 5-sulfosalicylic acid and diethylene glycol.•CDs was used as the surface modifier and reductant to prepare the CDs/α-Fe2O3-Fe3O4 nanocomposite.•Development of a ...novel electrochemical aptasensor for the ultrasensitive determination of AFB1 based on CDs/α-Fe2O3-Fe3O4 nanocomposite.•This aptasensor could act as a good candidate to determine AFB1 in Beer, Rice, and Peanuts with satisfying results.
Developing an effective method for the detection of aflatoxin B1 (AFB1) remains an arduous task due to the high toxicity of AFB1 to a health concern. In this study, a sensitive and reliable electrochemical aptasensor based on carbon dots/α-Fe2O3-Fe3O4 nanocomposite (CDs/α-Fe2O3-Fe3O4) is constructed for the determination of AFB1. The CDs have good electrical conductivity and large specific surface areas to improve the aptasensor’s sensitivity. The α-Fe2O3-Fe3O4 can not only improve the catalytic performance of the aptasensor but also have magnetism, which can realize the recovery of CDs/α-Fe2O3-Fe3O4 to avoid material waste and environmental pollution. This electrochemical aptasensor can achieve a good linear (0.001–100.0 nM) and excellent detection limit (0.5 pM) for the determination of AFB1. In addition, the aptasensor was also applied to determine AFB1 in beer, rice, and peanuts, all results were in good agreement with HPLC, indicating that the electrochemical aptasensor has a broad application prospect.
In this study, a green and fast method was developed to synthesize high-yield carbon dots (CDs) via one-pot microwave treatment of banana peels without using any other surface passivation agents. ...Then the as-prepared CDs was used as the reducing agent and stabilizer to synthesize a Pd-Au@CDs nanocomposite by a simple sequential reduction strategy. Finally, Pd-Au@CDs nanocomposite modified glassy carbon electrode (Pd-Au@CDs/GCE) was obtained as a biosensor for target DNA after being immobilized a single-stranded probe DNA by a carboxyl ammonia condensation reaction. Under the optimal conditions, the sensor could detect target DNA concentrations in the range from 5.0×10–16 to 1.0×10−1°molL−1. The detection limit (LD) was estimated to be 1.82×10–17molL−1, which showed higher sensitivity than other electrochemical biosensors reported. In addition, the DNA sensor was also successfully applied to detect colitoxin DNA in human serum.
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•One-step green synthesis of high-yield carbon dots (CDs) from banana peels.•CDs as reductant and stabilizer for synthesizing Pd-Au@CDs composites.•Development of an ultrasensitive electrochemical DNA biosensor based on Pd-Au@CDs composites with a ultralow detection limit of 1.82×10–17molL−1 for colitoxin DNA.
Visible-light photoredox catalysis has been established as a popular and powerful tool for organic transformations owing to its inherent characterization of environmental friendliness and ...sustainability in the past decades. The thiol-ene/yne reactions, the direct hydrothiolation of alkenes/alkynes with thiols, represents one of the most efficient and atom-economic approaches for the carbon-sulfur bonds construction. In traditional methodologies, harsh conditions such as stoichiometric reagents or a specialized UV photo-apparatus were necessary suffering from various disadvantages. In particular, visible-light photoredox catalysis has also been demonstrated to be a greener and milder protocol for the thiol-ene/yne reactions in recent years. Additionally, unprecedented advancements have been achieved in this area during the past decade. In this review, we will summarize the recent advances in visible-light photoredox catalyzed thiol-ene/yne reactions from 2015 to 2021. Synthetic strategies, substrate scope, and proposed reaction pathways are mainly discussed.
•PRRSV has evolved to arm with various strategies to modify host antiviral response.•Viral modulation of homeostatic cellular processes provides favorable conditions for PRRSV survival during ...infection.•PRRSV modulation of cellular processes includes pathways for interferons, apoptosis, microRNAs, cytokines, autophagy, and viral genome recombination.
Porcine reproductive and respiratory syndrome virus (PRRSV) has caused tremendous amounts of economic losses to the swine industry for more than three decades, but its control is still unsatisfactory. A significant amount of information is available for host cell-virus interactions during infection, and it is evident that PRRSV has evolved to equip various strategies to disrupt the host antiviral system and provide favorable conditions for survival. The current study reviews viral strategies for modulations of cellular processes including innate immunity, apoptosis, microRNAs, inflammatory cytokines, and other cellular pathways.
The widely used pseudorabies virus (PRV) Bartha-K61 vaccine has played a key role in the eradication of PRV. Since late 2011, however, a disease characterized by neurologic symptoms and a high number ...of deaths among newborn piglets has occurred among Bartha-K61-vaccinated pigs on many farms in China. Clinical samples from pigs on 15 farms in 6 provinces were examined. The PRV gE gene was detectable by PCR in all samples, and sequence analysis of the gE gene showed that all isolates belonged to a relatively independent cluster and contained 2 amino acid insertions. A PRV (named HeN1) was isolated and caused transitional fever in pigs. In protection assays, Bartha-K61 vaccine provided 100% protection against lethal challenge with SC (a classical PRV) but only 50% protection against 4 challenges with strain HeN1. The findings suggest that Bartha-K61 vaccine does not provide effective protection against PRV HeN1 infection.
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•The mild-condition synthesized metal-complex nanozymes in the colorimetric and fluorescence analysis are reviewed.•The mild-condition synthesis processes of metal-complex nanozymes ...are discussed.•Strategy in developing colorimetric and fluorescent assays with high performance and specificity are summarized.
The metal complexes, which are prepared through the coordination of metal ions with organic ligands, have various characteristics such as high porosity and specific surface area. In recent years, the metal complexes with enzyme-like activities have been widely used in colorimetric and fluorescence analysis. The synthesis process of metal complexes under mild conditions is particularly significant as it is not only easy to operate but also safe. In this article, the synthesis processes, catalytic mechanisms, activity regulation methods, and recent research progress of metal-complex nanozymes in the past years (2018 to present) have been summarized. Furthermore, the applications of metal-complex nanozymes-based biosensors in colorimetric and fluorescence detection of various analytes, such as antibiotics, metal ions, mycotoxins, pathogens, pesticides, and proteins, have been summarized and discussed. This review is prospective to promote the further applications of metal complexes with enzyme-like activity synthesized under mild conditions.
High‐performance deep‐blue emitters with external quantum efficiencies (EQEs) exceeding 5 % are still scarce in organic light‐emitting diodes (OLEDs). In this work, by introducing a ...1,2,4triazolo1,5‐a pyridine (TP) unit at the N1 position of phenanthroimidazole (PI), two luminescent materials, PTPTPA and PTPTPA, were obtained. Systematic photophysical analysis showed that the TP block is suitable for constructing hybridized local and charge‐transfer (HLCT) emitters. Its moderate electron‐withdrawing ability and rigid planar structure can enhance the CT component while ensuring color purity. In addition, compared with PTPTPA, the additional phenyl ring of PTPBPTA not only increased the oscillator strength, but also decreased the Stokes shift. TDDFT calculations pointed out facile reverse intersystem crossing processes in PTPTPA from high‐lying triplet states to the singlet excited state. A nondoped device based on PTPTPA as emitter showed impressive performance with EQEmax of 7.11 % and CIE coordinates of (0.15, 0.09). At the same time, it was also an efficient host for yellow and red phosphorescent OLEDs. By doping yellow (PPYBA) and red (BTPG) phosphorescent dyes into PTPTPA, a white OLED with a high EQE of 23.85 % was achieved. The successful design of PTPTPA not only provided an optimization choice for OLED emitters, but also demonstrated the empirical rules for the design of multifunctional deep‐blue emitters.
Deeper blue: On the basis of multifunctional phenanthroimidazole‐based material PTPBPTA, which acts both as a deep‐blue fluorescent emitter and as a host material for phosphors, high‐performance deep‐blue fluorescent organic light‐emitting diodes (OLEDs), yellow and red phosphorescent OLEDs, and a white OLED were fabricated.
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