- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Enzyme-free fluorometric assay for chloramphenicol based on double stirring bar-assisted dual signal amplification
摘要： An enzyme-free fluorometric assay is described that accomplishes dual signal amplification by making use of a two stirring bars. Two Y-shaped DNA probes were designed and placed on the bars. When the target (with chloramphenicol as model analyte) is added, it triggers target recycling and simultaneously catalyzes hairpin assembly (CHA). A large fraction of DNA primers is released by the analyte from the bar to the supernatant and open hairpins with G-quadruplex DNA sequence. The G-quadruplex can specifically bind thioflavin T (ThT) to emit fluorescence (with excitation/emission maxima at 445 and 485 nm) for quantification of chloramphenicol. An enzyme is not needed. ThT is added to the system as a fluorescent DNA probe. All this strongly reduces the cost for sensor construction and usage. The dual signal amplification steps occur simultaneously which reduces the detection time. The assay was successfully employed to the determination of CAP in spiked milk and fish samples within 60 min and with a 16 pM limit of detection (at S/N = 3).
关键词： Food safety,Antibiotics detection,Thioflavin T,Catalyzed hairpin assembly,Target recycling
更新于2025-11-19 16:46:39
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Zero background and triple-signal amplified fluorescence aptasensor for antibiotics detection in foods
摘要： It's important to eliminate matrix interference for accurate detecting antibiotic residues in complex food samples. In this study, we designed a zero-backgrounded fluorescence aptasensor to achieve on-site detection of antibiotic residues, with chloramphenicol (CAP) as representative analyte. Moreover, a three stir-bars assisted target recycling system (TSBTR) was designed to achieve triple signal amplification and increase the sensitivity. The bars included one magnetic stir-bar modified with two kinds of long DNA chains, and two gold stir-bars modified with Y shape-duplex DNA probes respectively. In the presence of CAP, the target could recurrently react with the probes on the bars and replace a large amount of long DNA chains into supernatant. After then, the bars were taken out and SYBR green dye was added to the solution. The dye can specifically intercalate into the duplex structures of DNA chains to emit fluorescence while not emitting a signal in its free state. Under the optimized experimental conditions, a wide linear response range of 5 orders of magnitude from 0.001 ng mL?1 to 10 ng mL?1 was achieved with a detection limit of 0.033 pg mL?1 CAP. The assay was successfully employed to detect CAP in food samples (milk & fish) with consistent results with ELISA's. High selectivity and sensitivity were attributed to the zero background signal and triple signal-amplification strategy. Moreover, the detection time can be shortened to 40 min due to that three signal amplified process can occur simultaneously. The fluorescent aptasensor was also label- and enzyme-free. All these ensure the platform to be rapid, cost-effective, easily-used, and is especially appropriate for detection antibiotics in food safety.
关键词： Three stir-bars assisted target recycling,Triple signal amplification,Zero background signal,Fluorescence aptasensor,Antibiotics
更新于2025-11-19 16:46:39
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Controllable preparation of phase-separated Pb/Zn heterogeneous nanoparticles by laser ablation and their application in the growth of PbS tipped ZnS nanorods heterostructures
摘要： Phase-separated Pb/Zn heterogeneous nanoparticles (Pb/Zn HNPs) with a controllable phase ratio were firstly prepared by long-pulse-width millisecond laser ablation of Pb/Zn binary metal target immersed in anhydrous ethanol under room conditions. The phase ratio in the as-ablated Pb/Zn HNPs was mainly determined by the molar ratio of Pb/Zn in the initial binary metal target and the structure of Pb/Zn HNPs was partly influenced by the pulse laser width. Then the PBS tipped ZnS nanorods heterostructures (PbS/ZnS heterostructures) were grown by simply heating the mixture of the as-ablated Pb/Zn HNPs and thioacetamide (TAA) at 450 (cid:1)C in a tube furnace. The size and morphology of Pbs/ZnS heterostructures were decided by the original absolute size and relative size between phase-separated Pb and Zn nanoparticle. The formation of Pbs/ZnS heterostructures was the result of the diffusion-limited of S atoms in the Pb/Zn HNPs. This study not only provides a new strategy for the controllable preparation of phase-separated bimetallic nanoparticles that can be used for the growth of specific heterostructures but a new view on the fundamental physical and chemical aspects of nanocrystal formation after laser ablation of solids in liquids.
关键词： Heterostructure,Phase-separated,Heterogeneous nanoparticles,Laser ablation,Binary metal target,Diffusion-limited
更新于2025-11-14 17:04:02
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Sensitive surface-enhanced Raman scattering detection of atrazine based on aggregation of silver nanoparticles modified carbon dots
摘要： The development of precise detection methods with simply operation for pesticides in various environmental samples is a particular challenge. Here a highly sensitive surface-enhanced Raman scattering (SERS) approach for the selective detection of trace atrazine was proposed with R6G as a Raman reporter, which was adsorbed on silver nanoparticles modified carbon dots. The latter were prepared by the reduction of Ag+ by carbon dots. In the presence of atrazine, the aggregation of the modified carbon dots due to the interaction between silver nanoparticles and atrazine led to great enhancement of the SERS signal of R6G. Under optimal assay conditions, the limit of quantification was estimated to be 10 nM, which matched with the standard for drinking water quality of China and WHO defined limit. A good linear response to atrazine was found in the concentration range of 10-1000 nM with the relative standard deviations between 1.8% and 5.6%. The determination of atrazine in real water samples was also carried out to confirm the practicability of the proposed method, which showed the recoveries from 95% to 117.5%. The target induced aggregation for enhancing the signal offered great potential for sensitive on-site detection of atrazine in environments.
关键词： Silver nanoparticles,Pesticides,SERS detection,Target induced aggregation,Atrazine,Carbon dots
更新于2025-11-14 17:03:37
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Detection probability for moving ground target of normal distribution using infrared satellite
摘要： In this article, we discuss the detection probability for a moving ground target such as vehicles using an infrared imaging satellite. In the ?rst part, we discuss a basic detection model for a regional ground target using a satellite. The probability of detection is calculated. In the second part, a basic model for the recognition of a ground target using an infrared imaging satellite is developed based on the model in the ?rst part. Based above two parts,we discuss a basic model of the detection probability for a moving ground target using an infrared imaging satellite in the third part. As the normal distribution has the maximum entropy, we analyze the normal distribution of a moving ground target such as some vehicles, and based on our conclusions, we develop a basic probability model for the detection of a moving ground target using an infrared imaging satellite. Finally, the simulation was carried on by STK software.
关键词： Moving ground target,Normal distribution,Detection probability,Regional ground target,Infrared light imaging satellite
更新于2025-09-23 15:23:52
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Based on Spectrum Modeling and Optimization
摘要： Bistatic synthetic aperture radar (SAR) is able to break through the limitation of monostatic SAR on forward-looking area imaging with appropriate geometry configurations. Thanks to such an ability, bistatic forward-looking SAR (BFSAR) has extensive potential practical applications. For the focusing problem of conventional side-looking SAR, ω–k algorithm is accepted as the ideal solution. In this paper, the ω–k algorithm will be discussed in BFSAR geometry. As for the bistatic configuration, spatial domain linearization procedure should be carried out to extract a range variable from the point target reference spectrum (PTRS) in the existing ω–k algorithms. With respect to the BFSAR geometry, nevertheless, the linearization procedure reduces the accuracy of PTRS seriously. To cope with such a problem, a novel ω–k algorithm for BFSAR is proposed. In the proposed method, the range variable is modeled as a parameterized polynomial, and the corresponding PTRS with respect to two-dimensional frequencies is established. Then, the parameters are estimated by differential evolution to minimize the PTRS errors for each range coordinate and frequency point. Based on the estimated PTRS, the BFSAR data can be focused well by the proposed ω–k algorithm. Simulation results verify the effectiveness of the proposed method.
关键词： Bistatic forward-looking synthetic aperture radar (BFSAR),differential evolution (DE),ω–k,point target reference spectrum (PTRS)
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - Shenzhen, China (2018.7.13-2018.7.15)] 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - Spacecraft Detection Based on Deep Convolutional Neural Network
摘要： Spacecraft detection is one of essential issues on aerospace information processing and control, and can provide reliable dynamic state of target, so as to support decisions made on target recognition, classification, catalogue, et al. Although numerous spacecraft detection methods exist, most of them cannot achieve real-time detection, and are still lack of better accuracy and fault-tolerance for different scenes. Recently, deep learning algorithms have achieved fantastic detection performance in computer vision community, especially the regression-based convolutional neural network YOLOv2, which has good accuracy and speed, and outperforming other state-of-the-art detection methods. This paper for the first time applies CNN to the detection of spacecraft and sets up a dataset for target detection in space. Our method starts with image annotation and data augmentation, and then uses our improved regression-based convolutional neural network YOLOv2 to detect spacecraft in an image. The experimental results have shown that our algorithm achieves 97.8% detection rate in the test set, and the average detection time of each image is about 0.018s, which has lower time overhead and better robustness to rotation and illumination changes of spacecraft.
关键词： Spacecraft,CNN,Target detection,YOLOv2
更新于2025-09-23 15:23:52
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Building a Fluorescent Aptasensor Based on Exonuclease-Assisted Target Recycling Strategy for One-Step Detection of T-2 Toxin
摘要： In this work, a rapid and accurate assay was successfully developed for T-2 toxin detection based on exonuclease-catalyzed target recycling strategy. Upconversion nanoparticles (UCNPs) were conjugated with T-2 aptamer and used as signal probes, while magnetic nanoparticles (MNPs) were conjugated with the complementary DNA of T-2 aptamer (cDNA) and used as capture probes. The results reveled that good linear correlation (R2 = 0.9988) was achieved for T-2 toxin detection over the concentration range of 0.1–100 ng/mL with a detection limit as low as 0.035 ng/mL (S/N = 3). In addition, the reliability of the proposed method was also applied to the determination of T-2 toxin contents in real food samples and the average recoveries ranged from 95.97 to 104.00%. The sensing platform developed in our study demonstrated great potential for simple and sensitive detection of T-2 toxin contents in food samples.
关键词： T-2 toxin,Food safety,Fluorescence,Aptasensor,Target recycling strategy
更新于2025-09-23 15:23:52
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Co-polarization channel imbalance phase estimation by corner-reflector-like targets
摘要： Polarimetric calibration is a critical step to suppress the potential system distortion before implementing any applications for polarimetric synthetic aperture radar (PolSAR). Among all the distortion elements, the crosstalk and cross-pol channel imbalance are generally estimated by the use of natural media, and the co-pol channel imbalance is traditionally solved by the use of corner reflectors (CRs). However, the deployment of ground CRs is costly and may even be impossible in some areas. Many bright point targets, such as poles, lamps, and corner points of structures, are commonly found in manmade regions. In particular, if the object orientation is parallel or perpendicular to the radar flight direction, some points will present similar polarimetric responses to trihedral or dihedral CRs. These points, which are referred to here as "CR-like targets", can be treated as a supplement to approximately solve the system distortion elements when CRs are unavailable. In this paper, we propose a novel step-by-step algorithm to determine the CR-like targets and estimate the co-pol channel imbalance phase in uncalibrated PolSAR imagery. Chinese X-band airborne and C-band satellite PolSAR data were used to test the proposed method. Compared with the CR-derived co-pol channel imbalance phase, the solution errors of the CR-like targets were 1.305° and 0.03° for the X- and C-band experiments, respectively. The results of the experiments confirm that the solutions of the CR-like targets are very close to those of ground-deployed CRs, and the proposed method can be considered as an effective way to calibrate PolSAR images when sufficient CR-like point targets are detected in manmade regions.
关键词： Corner reflector,Polarimetric synthetic aperture radar,Calibration,Target detection
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Conference on Signal Processing, Communications and Computing (ICSPCC) - Qingdao, China (2018.9.14-2018.9.16)] 2018 IEEE International Conference on Signal Processing, Communications and Computing (ICSPCC) - A Real-time Detection Algorithm for Unmanned Aerial Vehicle Target in Infrared Search System
摘要： Aiming at the difficulty of infrared target detection of 'low and slow small' unmanned aerial vehicles (UAV) in complex low-altitude background, this paper proposes a new target detection algorithm based on multiscale fusion filtering. Combined with spatial multiscale decomposition filtering and temporal multiscale difference processing, the algorithm can effectively overcome many difficulties such as complex low-altitude background interference, unknown target scale, unknown angular velocity and low target signal-to-noise ratio (SNR). The test result shows that the algorithm can effectively detect the UAV targets with different distances in complex low-altitude background, and the false alarm rate is low. The algorithm is realized in TI 6657 DSP and realizes 100Hz real-time processing of mid-wave infrared images with 640*512 resolution, which has been effectively applied to the large-field circumferential scanning infrared search system developed by ATR Lab.
关键词： real-time algorithm,multiscale fusion filtering,UAV target detection,low-altitude background,low and slow small targets
更新于2025-09-23 15:23:52