Search

To investigate the pattern recognition of complex defect types in XLPE (cross-linked polyethylene) cable partial discharges and analyze the effectiveness of identifying partial discharge signal patterns, this study employs the variational mode decomposition (VMD) algorithm alongside entropy theories such as power spectrum entropy, fuzzy entropy, and permutation entropy for feature extraction from partial discharge signals of composite insulation defects. The mean power spectrum entropy (PS), mean fuzzy entropy (FU), mean permutation entropy (PE), as well as the permutation entropy values of IMF2 and IMF13 (Pe) are selected as the characteristic quantities for four categories of partial discharge signals associated with composite defects. Six hundred samples are selected from the partial discharge signals of each type of compound defect, amounting to a total of 2400 samples for the four types of compound defects combined. Each sample comprises five feature values, which are compiled into a dataset. A Snake Optimization Algorithm-optimized Support Vector Machine (SO-SVM) model is designed and trained, using the extracted features from cable partial discharge datasets as case examples for recognizing cable partial discharge signals. The identification outcomes from the SO-SVM model are then compared with those from conventional learning models. The results demonstrate that for partial discharge signals of XLPE cable composite insulation defects, the SO-SVM model yields better identification results than traditional learning models. In terms of recognition accuracy, for scratch and water ingress defects, SO-SVM improves by 14.00% over BP (Back Propagation) neural networks, by 5.66% over GA-BP (Genetic Algorithm–Back Propagation), and by 12.50% over SVM (support vector machine). For defects involving metal impurities and scratches, SO-SVM improves by 13.39% over BP, 9.34% over GA-BP, and 12.56% over SVM. For defects with metal impurities and water ingress, SO-SVM shows enhancements of 13.80% over BP, 9.47% over GA-BP, and 13.97% over SVM. Lastly, for defects combining metal impurities, water ingress, and scratches, SO-SVM registers increases of 11.90% over BP, 9.59% over GA-BP, and 12.05% over SVM. [ABSTRACT FROM AUTHOR]

Dibutyl phthalate (DBP) is widely used as a plasticizer in the production of polymeric materials to give them flexibility, strength and extensibility. However, due to its negative impact on human health, in particular reproductive functions and fetal development, the content of DBP must be controlled in food and the environment. The present study aims to develop a sensitive, fast and simple fluorescence polarization immunoassay (FPIA) using monoclonal antibodies derived against DBP (MAb-DBP) for its detection in open waters. New conjugates of DBP with various fluorescein derivatives were obtained and characterized: 5-aminomethylfluorescein (AMF) and dichlorotriazinylaminofluorescein (DTAF). The advantages of using the DBP-AMF conjugate in the FPIA method are shown, the kinetics of binding of this chemical with antibodies are studied, the analysis is optimized, and the concentration of monoclonal antibodies is selected for sensitivity analysis—16 nM. The calibration dependence of the fluorescence polarization signal for the detection of DBP was obtained. The observed IC50 (DBP concentration at which a 50% decrease in the fluorescence polarization signal occurs, 40 ng/mL) and the limit of detection (LOD, 7.5 ng/mL) values were improved by a factor of 45 over the previously described FPIA using polyclonal antibodies. This technique was tested by the recovery method, and the high percentage of DBP discovery in water ranged from 85 to 110%. Using the developed method, real water samples from Lake Onega were tested, and a good correlation was shown between the results of the determination of DBP by the FPIA method and GC-MS. Thus, the FPIA method developed in this work can be used to determine DBP in open-water reservoirs. [ABSTRACT FROM AUTHOR]

The preparation of glass–ceramics with red mud and steel slag can not only solve the pollution problem caused by industrial waste slag but also produce economic benefits. It is difficult to analyze the high-temperature melt with the existing test methods, so the simulation experiment with molecular dynamics calculation becomes an important research method. The effects of steel slag content on the microstructure of red mud glass–ceramics were studied by molecular dynamics method. The results show that the binding ability of Si-O, Al-O, and Fe-O decreases with the increase in steel slag content. The number of Si-O-Si bridge oxygen increased gradually, while the number of Al-O-Al, Al-O-Fe, and Fe-O-Fe bridge oxygen decreased significantly. The number of tetrahedrons [SiO4] increased, the number of tetrahedrons [FeO4] and [AlO4] decreased, and the total number of three tetrahedrons decreased. The mean square displacement value of Si4+ and O2− increases first and then decreases, resulting in the viscosity of the system decreasing first and then increasing. The molecular dynamics method is used to analyze the structure of red mud–steel slag glass–ceramics on the microscopic scale, which can better understand the role of steel slag and has guiding significance for the experiment of this kind of glass–ceramics. [ABSTRACT FROM AUTHOR]

With 45# transformer oil as the base fluid, different concentrations of TiO2 nanomodified transformer oil were prepared via the thermal oscillation method. Nanomodified transformer oil with a concentration of 0.01 g/L was selected for evaluation via the breakdown test. Then, 0.01 g/L nanomodified transformer oil and ordinary 45# transformer oil were subjected to the variable control of different moisture contents and different temperatures, and breakdown tests under different types of electrodes were performed within the temperature range of −30 °C to 30 °C. The test results showed the following: Under severe cold conditions, the improvement effect of the breakdown voltage in different temperature ranges was different. Within the temperature range of −30 °C to −10 °C, the enhancement effect could reach 13% to 15%. Within the temperature range of −10 °C to 0 °C, the enhancement effect could reach 8% to 9%. Within the temperature range of 0 °C to 30 °C, the enhancement effect could reach 18% to 21%. Compared with the test results at high water contents, the improvement in the breakdown voltage amplitude of transformer oil by nanomaterials was more obvious at low water contents. In addition, nanomaterials could reduce the dispersion of the breakdown voltage to make the breakdown voltage more stable. Lastly, COMSOL was used to simulate the polarization process of nanoparticles under a uniform electric field and the influence of the trajectory of charged particles in the oil to further analyze the mechanism of the influence of nanoparticles in oil on the breakdown voltage of the oil gap. The simulation results showed that, when the particles were accelerated by the electric field, they moved irregularly. After adding nanoparticles, the charged particles were adsorbed by the nanoparticles when passing through the nanoparticles, which reduced the migration rate of charged particles in the oil. The breakdown voltage of the oil gap increased. [ABSTRACT FROM AUTHOR]

Aiming at the problems of the traditional planetary gear fault diagnosis method of wind turbines, such as the poor timeliness of data transmission, weak visualization effect of state monitoring, and untimely feedback of fault information, this paper proposes a planetary gear fault diagnosis method for wind turbines based on a digital twin. The method was used to build the digital twin model of wind turbines and analyze the wind turbines' operating state utilizing virtual and real data. Empirical mode decomposition (EMD) was used, and an atom search optimization–support vector machine (ASO-SVM) model was established for planetary gear fault diagnosis. The digital twin model diagnoses faults and constantly revises the model based on the diagnostic results. The digital twin fault diagnosis system was implemented in the Unity3D platform. The experimental results demonstrate the feasibility of the proposed early-warning system for the real-time diagnosis of planetary gear faults in wind turbines. [ABSTRACT FROM AUTHOR]

Imidacloprid (IMP) is toxic and a potential carcinogen that is most widely used as an insecticide for pest control and seed treatment. It is important to produce a rapid and sensitive assay for on-site monitoring. We have developed a novel lateral flow assay (LFA) using a sensitive monoclonal antibody (mAb) for monitoring IMP residues on fruits and vegetables. The 50% inhibition concentration result that was found when using the ELISA method was 0.247 ng mL−1, with the cut-off limits using the LFA method the result was 10 ng mL−1 (0.01 M PBS), and in the samples it was 20 ng mL−1 (with a recovery rate of 96–104.7% for Chinese cabbage, cowpea, apple, and pear samples, respectively). All of the results can be determined within seven minutes. The proposed LFA method is a valid, quick, and stable assay for the on-site detection of IMP in large numbers of samples. [ABSTRACT FROM AUTHOR]

Position errors of inertial navigation systems (INS) increase over time after long-term voyages of the autonomous underwater vehicle. Terrain-aided navigation (TAN) can effectively reduce the accumulated error of the INS. However, traditional TAN algorithms require a long positioning time and need better positioning accuracy, and nonmatching and mismatching are prone to occur, especially when the initial position error is large. To solve this problem, a new algorithm combining the artificial bee colony (ABC) and particle swarm optimization (PSO) was proposed according to the principle of terrain matching, to improve the matching effect. Considering that PSO easily falls into a local optimum, the acceleration factor and inertia weight of PSO were improved. The improved PSO was called WAPSO. ABC was introduced based on WAPSO and could help WAPSO escape local optimum. The final algorithm was termed ABC search-based WAPSO (F-WAPSO). During the continuous iteration of particles, F-WAPSO seeks the optimal position for the particles. Simulation tests show that F-WAPSO can effectively improve the matching accuracy. When the initial position error is 1000 m, the matching error can be reduced to 93.5 m, with a matching time of only 13.7 s. [ABSTRACT FROM AUTHOR]

Recently, discriminative correlation filters (DCF) based trackers have gained much attention and obtained remarkable achievements for their high efficiency and outstanding performance. However, undesirable boundary effects occur when the DCF-based trackers suffer from challenging situations, such as occlusion, background clutters, fast motion, and so on. To address these problems, this work proposes a novel adaptive spatial regularization and temporal-aware correlation filters (ASTCF) model to deal with the boundary effects which occur in the correlation filters tracking. Firstly, our ASTCF model learns a more robust correlation filter template by introducing spatial regularization and temporal-aware components into the objective function. The adaptive spatial regularization provides a more robust appearance model to handle the large appearance changes at different times; meanwhile, the temporal-aware constraint can enhance the time continuity and consistency of this model. They make correlation filters model more discriminating, and also reduce the influence of the boundary effects during the tracking process. Secondly, the objective function can be transformed into three sub-problems with closed-form solutions and effectively solved via the alternating direction method of multipliers (ADMM). Finally, we compare our tracker with some representative methods and evaluate using three different benchmarks, including OTB2015, VOT2018 and LaSOT datasets, where the experimental results demonstrate the superiority of our tracker on most of the performance criteria compared with the existing trackers. [ABSTRACT FROM AUTHOR]

Simple Summary: Porcine reproductive and respiratory syndrome, caused by the porcine reproductive and respiratory syndrome virus, is considered one of the most devastating swine diseases worldwide. Porcine reproductive and respiratory syndrome virus 1 was first isolated in China in 2006, and there have been few reports concerning its genetic characteristics in China. We hope to find out the regularity of genetic diversity, recombination, and evolution of the virus by analyzing all available genomic sequences during 1991–2018. We found that high-frequency recombination regions were concentrated in non-structural protein 2 and structural proteins 2 to 4 and extensive deletions in non-structural protein 2; phylogenetic analysis revealed four independent introductions in China. Our results suggest that attention should be paid to the prevention and control of porcine reproductive and respiratory syndrome virus 1 and the rational use of vaccine strains. These results will help us to understand the recombination of porcine reproductive and respiratory syndrome virus and strengthen viral inspection before mixing herds of swine to reduce the probability of novel recombinant variants. Moreover, our study might form the basis of monitoring and control measures to prevent the spread of this economically important virus. Porcine reproductive and respiratory syndrome (PRRS), caused by the PRRS virus (PRRSV), is considered one of the most devastating swine diseases worldwide. PRRSV-1 was first isolated in China in 2006. However, there were few reports concerning the genetic characteristics of PRRSV-1 in China. In this study, three PRRSV-1 strains (HL85, HeB3, and HeB47) were detected by a general RT-qPCR method from clinical samples in 2018. HeB47 was identified as a recombinant between the BJEU06-1 and CReSA228-like strains. To further analyze the recombination and deletion features of PRRSV-1, all the available 88 complete genome sequences (isolated in 19 countries) from 1991 to 2018 in GenBank were analyzed. The high-frequency recombination regions were concentrated in NSP2 and GP2 to GP4. More importantly, phylogenetic analysis of PRRSV-1 revealed four independent introductions in China. Therefore, it is necessary to strengthen the important monitoring of breeding pigs and pork products and epidemiological surveys on pig farms to prevent the further spread of PRRSV-1. [ABSTRACT FROM AUTHOR]

Mercury is a major pollutant in food crops. In this study, we synthesized an anti-mercury monoclonal antibody (mAb; IC50 was 0.606 ng mL−1) with high sensitivity and specificity and different immunogens and coating antigens and developed an immuno-chromatographic assay (ICA) for the detection of mercury in rice. The ICA strip had a visible detection limit of 20 ng g−1 and a cut-off value of 500 ng g−1 in rice. The performance of the ICA strip was consistent with that of ICP-MS and ic-ELISA. The recoveries of mercury in rice ranged from 94.5% to 113.7% with ic-ELISA and from 93.6% to 116.45% with ICP-MS. Qualitative analysis by ICA can be obtained with the naked eye. The ICA strip is an effective and practical method for the rapid and high-throughput determination of mercury in rice. [ABSTRACT FROM AUTHOR]

0.9KNbO3-0.1BaTiO3 ceramics, with a bimodal grain size distribution and typical tetragonal perovskite structure at room temperature, were prepared by using an induced abnormal grain growth (IAGG) method at a relatively low sintering temperature. In this bimodal grain size distribution structure, the extra-large grains (~10–50 μm) were evolved from the micron-sized filler powders, and the fine grains (~0.05–0.35 μm) were derived from the sol precursor matrix. The 0.9KNbO3-0.1BaTiO3 ceramics exhibit relaxor-like behavior with a diffused phase transition near room temperature, as confirmed by the presence of the polar nanodomain regions revealed through high resolution transmission electron microscope analyses. A large room-temperature electrocaloric effect (ECE) was observed, with an adiabatic temperature drop (ΔT) of 1.5 K, an isothermal entropy change (ΔS) of 2.48 J·kg−1·K−1, and high ECE strengths of |ΔT/ΔE| = 1.50 × 10−6 K·m·V−1 and ΔS/ΔE = 2.48 × 10−6 J·m·kg−1·K−1·V−1 (directly measured at E = 1.0 MV·m−1). These greatly enhanced ECEs demonstrate that our simple IAGG method is highly appreciated for synthesizing high-performance electrocaloric materials for efficient cooling devices. [ABSTRACT FROM AUTHOR]

Recently due to the good balance between performance and tracking speed, the discriminative correlation filter (DCF) has become a popular and excellent tracking method in short-term tracking. Computing the correlation of a response map can be efficiently performed in the Fourier domain by the discrete Fourier transform (DFT) of the input, where the DFT of an image has symmetry in the Fourier domain. However, most of the correlation filter (CF)-based trackers cannot deal with the tracking results and lack the effective mechanism to adjust the tracked errors during the tracking process, thus usually perform poorly in long-term tracking. In this paper, we propose a long-term tracking framework, which includes a tracking-by-detection part and redetection part. The tracking-by-detection part is built on a DCF framework, by integrating with a multifeature fusion model, which can effectively improve the discriminant ability of the correlation filter for some challenging situations, such as occlusion and color change. The redetection part can search the tracked object in a larger region and refine the tracking results after the tracking has failed. Benefited by the proposed redetection strategy, the tracking results are re-evaluated and refined, if it is necessary, in each frame. Moreover, the reliable estimation module in the redetection part can effectively identify whether the tracking results are correct and determine whether the redetector needs to open. The proposed redetection part utilizes a saliency detection algorithm, which is fast and valid for object detection in a limited region. These two parts can be integrated into DCF-based tracking methods to improve the long-term tracking performance and robustness. Extensive experiments on OTB2015 and VOT2016 benchmarks show that our proposed long-term tracking method has a proven effectiveness and high efficiency compared with various tracking methods. [ABSTRACT FROM AUTHOR]

In this paper, a novel anti-jamming technique based on black box variational inference for INS/GNSS integration with time-varying measurement noise covariance matrices is presented. We proved that the time-varying measurement noise is more similar to the Gaussian distribution with time-varying mean value than to the Inv-Gamma or Inv-Wishart distribution found by Kullback–Leibler divergence. Therefore, we assumed the prior distribution of measurement noise covariance matrices as Gaussian, and calculated the Gaussian parameters by the black box variational inference method. Finally, we obtained the measurement noise covariance matrices by using the Gaussian parameters. The experimental results illustrate that the proposed algorithm performs better in resisting time-varying measurement noise than the existing Variational Bayesian adaptive filter. [ABSTRACT FROM AUTHOR]

In this study, the b-values for acoustic emission (AE) events during stick-slip cycles of pre-cut faults in granite (as an analogue of unfavorably oriented immature faults) under triaxial compression (confining pressure: 40 MPa) are investigated. Using a multi-channel AE waveform recording system and two peak detectors, we recorded AE waveforms at 16 bits and at a sampling rate of 25 MHz, as well as the maximum amplitude of AE events with a dynamic range of 55 dB. For stick-slip events, the b-value decreases from 1.2 to 1.5 to approximately 0.6 as the shear stress increases, and then quickly jumps back to 1.0 to 1.3 immediately prior to the dynamic stress drop. The minimum b-value coincides with the maximum event rate and a stress level of 70 to 95% of the shear strength. It is also observed that the AE activity during each cycle was linked with the pre-failure fault slip, which accounts for 30% of the dynamic slip. Our results on b-value evaluation preceding repeated stick-slips can be used as an indicator of the degree of fault maturity and shear stress acting on the fault, which is important in seismic hazard assessment and earthquake prediction, especially for the injection-induced seismicity for fields in which reactivated shear rupture of unfavorable and immature faults or tensile fractures is important. [ABSTRACT FROM AUTHOR]

Increasing attention is now being directed to the utilization of polymyxin B (PMB) as a last-line treatment for life-threatening infections caused by multidrug resistant Gram-negative bacteria. Unfortunately, polymyxins resistance is also increasingly reported, leaving a serious threat to human health. Therefore, the establishment of rapid detection methods for PMB residues is highly essential to ensure public health. In this study, two monoclonal antibodies (mAb; 2A2 and 3C6) were obtained using PMB-bovine serum albumin as the immunogen and PMB-ovalbumin as the coating antigen, which were prepared with N-(γ-maleimidobutyryloxy) succinimide ester and glutaraldehyde as cross-linking agents, respectively. Through an indirect competitive enzyme-linked immunosorbent assay, resultant two mAbs were compared and the results indicated that 3C6 showed higher sensitivity with a half maximum inhibition concentration of 13.13 ng/mL. Based on 3C6, a gold nanoparticles (AuNPs)-based immunochromatographic test (ICT) strip was then established, the mechanism of which is that free PMB competes with the fixed coating antigen to combine with mAb labeled by AuNPs. Using ICT strip to detect milk and animal feed samples revealed the visible detection limits were 25 ng/mL and 500 μg/kg, respectively and the cutoff limits were 100 ng/mL and 1000 μg/kg, respectively. The ICT strip provides results within 15 min, facilitating rapid and semi-quantitative analysis of PMB residues in milk and animal feed. [ABSTRACT FROM AUTHOR]

In this paper, a high-temperature low-cycle fatigue life prediction model, based on the total strain energy density method, was established. Considering the influence of the Masing and non-Masing behavior of materials on life prediction, a new life prediction model was obtained by modifying the existing prediction model. With an 800H alloy of the heat transfer tube of a steam generator as the research object, the high-temperature and low-cycle fatigue test was carried out at two temperatures. The results show that the predicted and experimental results are in good agreement, proving the validity of the life prediction model. [ABSTRACT FROM AUTHOR]

Spray cooling with liquid nitrogen is increasingly utilized as an efficient approach to achieve cryogenic cooling. Effects of injection mass flow rate fluctuations on the evaporation, temperature distribution, and droplet distribution of a spray field were examined by employing a validated Computational Fluid Dynamics (CFD) numerical model. The numerical results indicated that injection fluctuations enhanced the volume-averaging turbulent kinetic energy and promoted the evaporation of the whole spray field. The strengthened mass and heat transfer between the liquid nitrogen droplets and the surrounding vapor created by the fluctuating injection led to a lower temperature of the whole volume. A relatively smaller droplet size and a more inhomogeneous droplet distribution were obtained under the unsteady inlet. The changes of the frequency and the amplitude of the fluctuations had little effects on the overall spray development. The results could enrich the knowledge of the relation between the inevitable fluctuations and the overall spray development and the cooling performance in a practical spray cooling system with cryogenic fluids. [ABSTRACT FROM AUTHOR]

The effects of laser heat treatment on the microstructure and properties of alloy 800H were investigated. The fracture morphology, elemental changes, and phase composition of the specimens were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffractometry (XRD). The results show that the long-lasting life of the specimen after laser heat treatment increased by 28.6%, and the elongation after fracture increased by 20.7%. The macroscopic morphology of the fracture specimen exhibited obvious ductile fracture morphology, and the changes in the elemental content and grain size significantly affected the ductility and toughness of the alloy. This study has certain guiding significance for the optimization of the heat treatment process of this type of alloy. [ABSTRACT FROM AUTHOR]

In this paper, a high-temperature low-cycle fatigue life prediction model, based on the total strain energy density method, was established. Considering the influence of the Masing and non-Masing behavior of materials on life prediction, a new life prediction model was obtained by modifying the existing prediction model. With an 800H alloy of the heat transfer tube of a steam generator as the research object, the high-temperature and low-cycle fatigue test was carried out at two temperatures. The results show that the predicted and experimental results are in good agreement, proving the validity of the life prediction model.

An indirect competitive enzyme-linked immunosorbent assay (icELISA) and an immunochromatographic strip assay using a highly specific monoclonal antibody, were developed to detect methyltestosterone (MT) residues in animal feed. The optimized icELISA had a half-inhibition concentration value of 0.26 ng/mL and a limit of detection value of 0.045 ng/mL. There was no cross-reactivity with eight analogues, revealing high specificity for MT. Based on icELISA results, the recovery rate of MT in animal feed was 82.4%-100.6%. The results were in accordance with those obtained by gas chromatography-mass spectrometry. The developed immunochromatographic strip assay, as the first report for MT detection, had a visual cut-off value of 1 ng/mL in PBS, 2.5 ng/g in fish feed, and 2.5 ng/g in pig feed. Therefore, these immunoassays are useful and fast tools for MT residue detection in animal feed.

Murine monoclonal antibodies to target Salmonella typhimurium flagellin and lipopolysaccharide (LPS) were prepared and characterized. For the immunological detection of S. typhimurium, different pairs of monoclonal antibodies (MAbs) were tested in a sandwich enzyme linked immunosorbent assay (ELISA) format. After comparison, a sandwich ELISA and immunochromatographic strip based on LPS MAbs was established to detect S. typhimurium. The determination limits of the immunochromatographic strip in phosphate-buffered saline (PBS) containing 0.1% Tween 20 (PBST) and pure milk sample were found to be 1.25 × 10(5) colony-forming units (cfu)/mL and 1.25 × 10(6) cfu/mL S. typhimurium, respectively. Results can be obtained with the naked eye in 10 min. Cross-reactivity was observed with Salmonella paratyphi B, but not S. paratyphi A or Salmonella enteritidis. The LPS MAbs based immunochromatographic strip is rapid and convenient to detect S. typhimurium in milk samples.

A rapid, simple, sensitive, and specific immunochromatographic test strip was developed for the detection of Pantoea stewartii subsp. stewartii (Pss) in corn seed which was soaked overnight and then centrifuged for precipitate re-dissolved as samples. A pair of sensitive monoclonal antibodies for the immunochromatographic test strip was generated by mice immunization and cell fusion. Under optimized conditions, the lower detection limit of the strips for Pss was 1 × 10(5) cfu/mL both in 0.01 M phosphate buffer solution and corn seed samples, with no cross-reactivity with other common plant pathogens. The developed strip is useful and rapid for the detection of Pss in corn seed samples.

A rapid, simple, and sensitive immunochromatographic test strip has been developed for testing residues of ciprofloxacin (CIP). A specific and sensitive monoclonal antibody (mAb) for CIP was generated by immunizing BALB/c mice with well-characterized CIP-Keyhole limpet haemocyanin. Under the optimized conditions, the cut-off limits of test strips for CIP were found to be 5 ng/mL in phosphate-buffered saline and 2.5 ng/mL in milk samples. Each test can be evaluated within 3 min. The cross-reactivities of the CIP test strip to enrofloxacin (ENR), norfloxacin (NOR), nadifloxacin (NDF), danofloxacin (DANO), pefloxacin (PEX), lomefloxacin (LOME), enoxacin (ENO), and sarafloxacin (SAR) were 71.4%, 71.4%, 66%, 50%, 33%, 20%, 12.5%, and 6.25%, respectively. The data indicate that the method is sensitive, specific, and has the advantages of simplicity and speed, therefore, this test strip is a useful screening method for the detection of CIP residues in milk samples.

A monoclonal antibody for microcystin-leucine-arginine (MC-LR) was produced by cell fusion. The immunogen was synthesized in two steps. First, ovalbumin/ bovine serum albumin was conjugated with 6-acetylthiohexanoic acid using a carbodiimide EDC (1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride)/ NHS (N-hydroxysulfosuccinimide) reaction. After dialysis, the protein was reacted with MC-LR based on a free radical reaction under basic solution conditions. The protein conjugate was used for immunization based on low volume. The antibodies were identified by indirect competitive (ic)ELISA and were subjected to tap water and lake water analysis. The concentration causing 50% inhibition of binding of MC-LR (IC50) by the competitive indirect ELISA was 0.27 ng/mL. Cross-reactivity to the MC-RR, MC-YR and MC-WR was good. The tap water and lake water matrices had no effect on the detection limit. The analytical recovery of MC-LR in the water samples in the icELISA was 94%-110%. Based on this antibody, an immunochromatographic biosensor was developed with a cut-off value of 1 ng/mL, which could satisfy the requirement of the World Health Organization for MC-LR detection in drinking water. This biosensor could be therefore be used as a fast screening tool in the field detection of MC-LR.

We have established a highly sensitive sandwich enzyme-linked immunosorbent assay (ELISA) based on two monoclonal antibodies (mAb) to measure the content of the major peanut allergen Ara h 1 in foods. Two mAbs were selected out of 12 murine hybridoma cells secreting Ara h 1-specific antibody. Using mAb 6 as the capture antibody and HRP-labelled mAb 4 as the detection antibody, the limit of detection (LOD) the assay was 0.34 ng/mL. Cross-reaction analysis showed that this method was strongly specific and had no cross-reactions with Ara h 2, pea protein or soy protein. Sample analysis showed that this ELISA was a useful tool to monitor peanut allergens in food products by measuring Ara h 1 content.

β-Lactamase residues in milk represent a public health risk. The cylinder plate detection method, which is based on bacterial growth, is laborious and time consuming. In this study, 15 monoclonal antibodies (mAbs) were selected against Temoneira (TEM) 1 β-lactamase. A sandwich enzyme-linked immunosorbent assay (ELISA) based on an optimum mAb pair was developed and validated for the detection of β-lactamase. The limit of detection and linear dynamic range of the method were 4.17 ng/mL and 5.5-100 ng/mL, respectively. β-Lactamase recovery in pure milk was 96.82-103.13%. The intra- and inter-assay coefficients of variation were 6.21-7.38% and 12.96-13.74%, respectively. Our developed sandwich ELISA can be used as a rapid detection method of β-lactamase in milk.

A monoclonal antibody specifically recognizing dibutyl phthalate (DBP) was prepared based on a hapten (di-n-butyl-4-aminophthalate). After optimizing various parameters such as concentrations of antibody, coating antigen and composition of the assay buffer, an inhibition curve was plotted with the 50% inhibition concentration value (IC50) 33.6 ± 2.5 ng/mL. A low level of cross-reactivity (<5%) was found for other phthalate esters. Recovery tests were conducted using liquor simulant (a mixture of water and ethanol) at two fortification levels (100 ng/mL and 300 ng/mL). The recovery rates ranged from 84.7% to 94.5% with a coefficient of variation between 7.1% and 12.8%. Nine liquor samples of different alcoholic strengths were detected using the proposed measure and confirmatory analysis was performed using liquid chromatography-mass spectroscopy (LC-MS). The detection results showed good consistency between the two measures and all the data above indicated that the proposed ELISA could be applied in DBP screening.

A sensitive and specific monoclonal antibody-based sandwich enzyme-linked immunosorbent assay (ELISA) was established and validated for the detection of staphylococcal enterotoxin A (SEA). After routine fusion and selection, 10 monoclonal antibodies showed high affinity for SEA. An optimal pair for sandwich ELISA was selected by pairwise interaction analysis. After optimization, the limit of detection (LOD) and linear dynamic range of the method were established, and were found to be 0.0282 ng/mL and 0.06-2 ng/mL, respectively. The recovery in pure milk ranged from 82.67% to 111.95% and the intra- and inter-assay coefficients of variation ranged from 3.16% to 6.05% and from 5.16% to 10.79%, respectively. Cross-reactivity with staphylococcal enterotoxin B (SEB), staphylococcal enterotoxin C (SEC), staphylococcal enterotoxin D (SED), and staphylococcal enterotoxin E (SEE) in this method were insignificant. These results indicate that the sandwich ELISA method developed in our study is effective for routine identification of SEA in food samples.

In this study, we have first developed a rapid and sensitive strip immunosensor based on two heterogeneously-sized gold nanoparticles (Au NPs) probes for the detection of trace lead ions in drinking water. The sensitivity was 4-fold higher than that of the conventional LFA under the optimized conditions. The visual limit of detection (LOD) of the amplified method for qualitative detection lead ions was 2 ng/mL and the LOD for semi-quantitative detection could go down to 0.19 ng/mL using a scanning reader. The method suffered from no interference from other metal ions and could be used to detect trace lead ions in drinking water without sample enrichment. The recovery of the test samples ranged from 96% to 103%. As the detection method could be accomplished within 15 min, this method could be used as a potential tool for preliminary monitoring of lead contamination in drinking water.