High-sensitivity Detection Methods Research Articles

High-sensitivity determination of ethanol concentration based on weak measurement system with Faraday effect

A high-sensitivity detection method is proposed for ethanol concentration based on weak measurement system with Faraday effect, and the improvement law of the sensitivity is studied. Different from chiral solution determination, the post-selection angle of the system is modified by the Faraday rotation angle of ethanol solution. The amplified photonic spin Hall effect acts as a probe for detecting the ethanol concentration in the system, and the sensitivity of ethanol concentration increases linearly with the increasing magnetic field intensity. Then we use the method to determine the ethanol concentration of commercial liquor, whose determination values are consistent with the label values and Raman spectroscopy results. Compared to other methods such as Raman spectrometry, the method has the advantages of real time, non-invasiveness, low cost and high sensitivity. Finally, the sensitivity of ethanol concentration can be further improved by designing of a suitable BK7-medium structure, and the sensitivity of 9.72 /vol% is achievable for the range 0 vol% ∼100 vol% of ethanol solutions.

Development of a highly sensitive TaqMan method based on multi-probe strategy: its application in ASFV detection.

The establishment of high sensitive detection method for various pathogenic microorganisms remains constantly concerned. In the present study, multi-probe strategy was first systematically investigated followed by establishing a highly sensitive TaqMan real-time fluorescent quantitative PCR (qPCR) method for detecting African swine fever virus (ASFV). Briefly, four probes based on the B646L gene of ASFV were designed and the effects of different combinations of the probes in a single TaqMan qPCR assay on the detection sensitivity were investigated. As less as 0.5-5 copies/μl of the ASFV gene was detected by the established TaqMan qPCR assay. Furthermore, plasmid harboring the B646L in water samples could be concentrated 1000 times by ultrafiltration to enable a highly sensitive detection of trace viral nucleic acids. Moreover, no cross-reactivity was observed with other common clinical swine viruses such as PCV2, PCV3, PCV4, PEDV, PDCoV, CSFV, PRRSV, and PRV. When detecting 173 clinical porcine serum samples, the coincidence rate between the developed method and WOAH (World Organization of Animal Health) recommended method was 100%. This study might provide an integrated strategy to achieve higher detection sensitivity of trace pathogenic microorganisms and applicably sensitive TaqMan-based qPCR assays.

Novel portable photoelectrochemical sensor based on CdS/Au/TiO2 nanotube arrays for sensitive, non-invasive, and instantaneous uric acid detection in saliva

Uric acid (UA) monitoring is the most effective method for diagnosis and treatment of gout, hyperuricemia, hypertension, and other diseases. However, challenges remain regarding detection efficiency and rapid on-site detection. Here, we first synthesized a CdS/Au/TiO2-NTAs Z-scheme heterojunction material using a titanium dioxide nanotube array (TiO2-NTAs) as the substrate and modified with gold nanoparticles (Au) and cadmium sulfide particles (CdS). This material achieves bandgap alignment to generate a large number of electron-hole pairs under illumination. Then, using CdS/Au/TiO2-NTAs as the working electrode and molecularly imprinted polymers (MIP) as the recognition unit, we constructed a portable photoelectrochemical (PEC) sensor for non-invasive instant detection of UA concentration in human saliva, which has unique advantages in the field of high-sensitivity PEC instant detection. The portable MIP-PEC sensor achieves a linear range of 0.01–50 μM and a detection limit as low as 5.07 nM (S/N = 3). At the same time, the portable MIP-PEC sensor exhibits excellent sensitivity, specificity as well as stability, and shows no statistically significant difference compared to traditional high-performance liquid chromatography (HPLC) in practical sample detection. Compared to traditional PEC modes, this work demonstrates a novel and universal method for high-sensitivity instant detection in the field of PEC.

Hydrangea-like AuPtRu/ZnO-rGO Nanocomposites with Enhanced Peroxidase Mimiking Activity for Senitive Colorimetric Determination of H2O2.

In this study, a facile and cost-effective hydrothermal synthesis method was used to synthesize zinc oxide nanoflowers modified by reduced graphene oxide, and subsequently, trimetallic AuPtRu nanoparticles(AuPtRuNPs) were supported via the reduction method for high-sensitivity colorimetric detection of H2O2 in weakly acidic solutions. Compared to monometallic and bimetallic nanoparticles, trimetallic nanoparticles exhibit significant synergistic effects and enhanced catalytic activity. After providing a three-dimensional structure with multiple pores by zinc oxide and enhancing electron transfer ability by reduced graphene, the trimetallic nanocomposites (AuPtRu/ZnO-rGO) exhibited excellent peroxidase-mimicking activity, which can effectively catalyze 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue oxidation product (oxTMB) in the presence of H2O2. Compared to horseradish peroxidase (HRP), AuPtRu/ZnO-rGO demonstrated significantly enhanced catalytic velocity (Vmax = 6.16 × 10-8 M/s) and affinity (Km = 0.02) for H2O2. The study of the catalytic mechanism showed that trimetallic Au, Pt, and Ru could effectively catalyze H2O2 to produce hydroxyl radicals (•OH) to accelerate the oxidation of TMB and enhance the peroxidase-mimicking activity of the AuPtRu/ZnO-rGO nanocomposites. The results showed that the as-synthesized hydrangea-like AuPtRu/ZnO-rGO nanocomposites showed enhanced peroxidase-mimicking activity. It could be used for the colorimetric detection of H2O2 in the range 5-1000 μM with a LOD of 3.0 μM (S/N = 3), and the recoveries are 93.0-101.7%. In addition, the AuPtRu/ZnO-rGO nanocomposites have good applicability for sensitive colorimetric determination of H2O2 in milk, and it has broad application prospects as a multifunctional sensing platform in the food processing industry.

Femtosecond-resolution optical pulse interleaving time error detector

Pulse repetition rate multiplier (PRRM) is an essential component of microwave photonics systems, designed not only to alleviate photodiode saturation but also to provide more frequent pulses. However, the presence of interleaving time errors is known to compromise the advantages of PRRM. In this study, we present a high-sensitivity detection method for identifying these time errors using an electro-optic sampling-based timing detector (EOS-TD). We utilize two EOS-TDs: one for generating precise timing ruler signals and the other as a high-precision timing detector. In comparison to the conventional power ratio comparison method, our approach demonstrates sensitivity improvement by two orders of magnitude. This enhancement facilitates the measurement of femtosecond-level time errors. By enabling higher pulse rates while maintaining the ultralow jitter, this method can be useful for building higher-speed photonic systems.

The Method and Study of Detecting Phenanthrene in Seawater Based on a Carbon Nanotube-Chitosan Oligosaccharide Modified Electrode Immunosensor.

Phenanthrene (PHE), as a structurally simple, tricyclic, polycyclic aromatic hydrocarbon (PAHs), is widely present in marine environments and organisms, with serious ecological and health impacts. It is crucial to study fast and simple high-sensitivity detection methods for phenanthrene in seawater for the environment and the human body. In this paper, a immunosensor was prepared by using a multi-wall carbon nanotube (MWCNTs)-chitosan oligosaccharide (COS) nanocomposite membrane loaded with phenanthrene antibody. The principle was based on the antibody-antigen reaction in the immune reaction, using the strong electron transfer ability of multi-walled carbon nanotubes, coupled with chitosan oligosaccharides with an excellent film formation and biocompatibility, to amplify the detection signal. The content of the phenanthrene in seawater was studied via differential pulse voltammetry (DPV) using a potassium ferricyanide system as a redox probe. The antibody concentration, pH value, and probe concentration were optimized. Under the optimal experimental conditions, the response peak current of the phenanthrene was inversely proportional to the concentration of phenanthrene, in the range from 0.5 ng·mL-1 to 80 ng·mL-1, and the detection limit was 0.30 ng·mL-1. The immune sensor was successfully applied to the detection of phenanthrene in marine water, with a recovery rate of 96.1~101.5%, and provided a stable, sensitive, and accurate method for the real-time monitoring of marine environments.

MoS2 nanosheets based label-free colorimetric aptasensor for Escherichia coli O157: H7 detection

The aggregation behavior of large-scale two-dimensional molybdenum disulfide (MoS2) nanosheets prepared by sonication-assisted exfoliation in environmental friendly 45% ethanol/water mixture under different conditions (e.g., salt concentration, cation valence and nanosheets size) had been examined to make them more appropriate for biological sensing application. Adjustment of sonication time and centrifuging speed could be utilized to select MoS2 nanosheets with various concentrations and sizes. Higher concentrations of salt and cations with higher valence were more effective to aggregate MoS2 nanosheets and settle them than their counterparts, which could be attributed to the perturbation of attractive van der Waals forces and repulsive Coulombic interactions. Moreover, the ethanol in mixture was capable of assisting MoS2 nanosheets to resist this aggregation initiated by salt but it would disturb the stability of aptamer functionalized MoS2 nanosheets in salt solution. The interplay of Escherichia coli O157: H7 (E. coli O157:H7) aptamer functionalized MoS2 nanosheets and salt was then inspired to develop a high sensitive detection method of E. coli O157:H7. The introduction of target bacteria induced MoS2 nanosheets to be exposed to cations, and promoted the aggregation and sedimentation behavior of MoS2 nanosheets. The change in extinction of MoS2 nanosheets had a linear relationship with E. coli O157:H7 concentration in a range of 500–5000 CFU/mL with a detection limit of 116 CFU/mL. This proposed colorimetric sensor expands the application scope of MoS2 nanosheets and shows its promising potential as an alternative tool for bacteria detection in food and water quality monitoring.

Development of specific and rapid detection of human DNA by recombinase polymerase amplification assay for forensic analysis

The determination of human-derived samples is very important in forensic investigations and case investigation in order to determine vital information on the suspect and the case. In this study, we established a recombinase polymerase amplification (RPA) assay for rapid identification of human-derived components. The sensitivity of the assay was 0.003125 ng, with excellent species specificity, and human-derived DNA could be detected in the presence of non-human-derived components at a ratio of 1:1000. Moreover, the RPA assay had a strong tolerance to inhibitors, in the presence of 800 ng/μL humic acid, 400 ng/μL tannic acid, and 8000 ng/μL collagen. In forensic investigation, common body fluids (blood, saliva, semen, vaginal secretions) are all applicable, and the presence of DNA can be detected from samples after simple alkaline lysis, which greatly shortens the detection time. Four simulation and case samples (aged bones, aged bloodstains, hair, touch DNA) were also successfully applied. The above research results show that the RPA assay constructed in this study can be fully applied to forensic medicine to provide high sensitivity and applicability detection methods.

Carbon Nanotube Field-Effect Transistor Biosensor with an Enlarged Gate Area for Ultra-Sensitive Detection of a Lung Cancer Biomarker.

Carcinoembryonic antigen (CEA) is a recognized biomarker for lung cancer and can be used for early detection. However, the clinical value of CEA is not fully realized due to the rigorous requirement for high-sensitivity and wide-range detection methods. Field-effect transistor (FET) biosensors, as one of the potentially powerful platforms, may detect CEA with a significantly higher sensitivity than conventional clinical testing equipment, while their sensitivity and detection range for CEA are far below the requirement for early detection. Here, we construct a floating gate FET biosensor to detect CEA based on a semiconducting carbon nanotube (CNT) film combined with an undulating yttrium oxide (Y2O3) dielectric layer as the biosensing interface. Utilizing an undulating biosensing interface, the proposed device showed a wider detection range and optimized sensitivity and detection limit, which benefited from an increase of probe-binding sites on the sensing interface and an increase of electric double-layer capacitance, respectively. The outcomes of analytical studies confirm that the undulating Y2O3 provided the desired biosensing surface for probe immobilization and performance optimization of a CNT-FET biosensor toward CEA including a wide detection range from 1 fg/mL to 1 ng/mL, good linearity, and high sensitivity of 72 ag/mL. More crucially, the sensing platform can function normally in the complicated environment of fetal bovine serum, indicating its great promise for early lung cancer screening.

Ultrasensitive monoclonal antibodies specific to thermal stable-soluble proteins of buckwheat

Buckwheat is considered a severe food allergen, and its adulteration and mislabeling cause serious health risks. For protecting consumers suffering from buckwheat allergy, a high-sensitivity detection method is necessary to accurately identify intentional or unintentional adulteration of buckwheat in processed foods. The study revealed that buckwheat contains a significant amount of thermally stable-soluble proteins (TSSPs), which keep antigenicity even after heat treatment. Therefore, we used TSSPs to produce three monoclonal antibodies (MAbs) specific to buckwheat. A MAbs cocktail solution was subjected to enhance the sensitivity of an indirect enzyme-linked immunosorbent assay (iELISA), and the LOD was 1 ng/mL. The MAbs cocktail solution based-iELISA can successfully detect buckwheat adulterated in processed foods. The results suggested that the TSSPs in buckwheat can be used as suitable immunogens, and MAbs produced can be used as bioreceptor to develop immunoassays and biosensors for detecting buckwheat in food facilities and processed foods.

High-Sensitivity Detection Method for Metal Foreign Objects Based on Frequency Optimization in Wireless Electric Vehicles Charging

Metal foreign objects will not only reduce the output power and efficiency of the wireless power transfer (WPT) system, but also will be heated under the eddy current effect. The method based on the detection coil array has been wildly adopted for foreign object detection (FOD), especially in high-power level WPT applications. However, the problems of low sensitivity or misjudgment still exist which leads to a safety hazard. Therefore, high sensitivity of the foreign object-detection method based on the excitation frequency optimization has been proposed in this paper. Based on the impedance change of the detection coil caused by the foreign object coupling, the frequency characteristics of detection sensitivity were analyzed under the conditions of different self-inductance detection coils. Then, the detection coil was designed and its corresponding optimal excitation frequency was selected to achieve the optimal detection effect to eliminate the area of low detection sensitivity. Finally, an FOD experimental prototype was established to verify the proposed frequency optimization strategy. The results show that the sensitivity of the FOD system is up to 97.56%. With the optimal excitation frequency of 6.22 MHz, as for 1-yuan coin in the center position and corner position of the detection coil, the detection sensitivity is 92.89% and 40.16%, respectively, which is 22.13% and 23.89% higher than that of the excitation frequency is 1 MHz. The improvement of detection sensitivity is helpful to detect accurately and eliminate the detection blind area.

Dual Imaging Single Vesicle Surface Protein Profiling and Early Cancer Detection.

Single vesicle molecular profiling has the potential to transform cancer detection and monitoring by precisely probing cancer-associated extracellular vesicles (EVs) in the presence of normal EVs in body fluids, but it is challenging due to the small EV size, low abundance of antigens on individual vesicles, and a complex biological matrix. Here, we report a facile dual imaging single vesicle technology (DISVT) for surface protein profiling of individual EVs and quantification of target-specific EV subtypes based on direct molecular capture of EVs from diluted biofluids, dual EV-protein fluorescence-light scattering imaging, and fast image analysis using Bash scripts, Python, and ImageJ. Plasmonic gold nanoparticles (AuNPs) were used to label and detect targeted surface protein markers on individual EVs with dark-field light scattering imaging at the single particle level. Monte Carlo calculations estimated that the AuNPs could detect EVs down to 40 nm in diameter. Using the DISVT, we profiled surface protein markers of interest across individual EVs derived from several breast cancer cell lines, which reflected the parental cells. Studies with plasma EVs from healthy donors and breast cancer patients revealed that the DISVT, but not the traditional bulk enzyme-linked immunosorbent assay, detected human epidermal growth factor receptor 2 (HER2)-positive breast cancer at an early stage. The DISVT also precisely differentiated HER2-positive breast cancer from HER2-negative breast cancer. We additionally showed that the amount of tumor-associated EVs was tripled in locally advanced patients compared to that in early-stage patients. These studies suggest that single EV surface protein profiling with DISVT can provide a facile and high-sensitivity method for early cancer detection and quantitative monitoring.

A Single-Phase-to-Ground Fault Detection Method Based on the Ratio Fluctuation Coefficient of the Zero-Sequence Current and Voltage Differential in a Distribution Network

Because the traditional zero-sequence overcurrent protection method is not effective in detecting single-phase-to-ground faults (SPGF) in a low-resistance grounded system (LRGS), this paper analyzes the fault characteristics of a 10-kV LRGS in detail. From the perspective of the time domain, the relationship between zero-sequence current and zero-sequence voltage is deduced, and the characteristics corresponding to faulty lines and nonfaulty lines are analyzed. The analysis reveals that the ratio fluctuation coefficients of the zero-sequence current to the differential zero-sequence voltage corresponding to faulty lines and nonfaulty lines have notably different characteristics; consequently, a high-sensitivity SPGF detection method is proposed. This method considers the existence of unbalanced loads and asymmetric parameters in the distribution network, can effectively identify high-impedance faults as high as 5000 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> and nonlinear arc grounding faults, and can resist noise interference with a signal-to-noise ratio of 20 dB. Finally, many simulations and comparisons based on PSCAD/EMTDC verify that the proposed detection method has better applicability than the existing methods in detecting high-impedance SPGFs.

High Sensitivity Detection Method for Liquid Concentrations Based on Coupled Microwave Resonators

This paper presents a new measurement method for liquid concentrations based on two inductively coupled resonators with enhanced sensitivity compared with traditional methods in microwave frequency ranges. The equivalent circuit of the coupled resonators is proposed with its eigenequation having three eigenfrequencies derived. We demonstrate that, compared to a single resonator, the sensitivity of the center eigenfrequency shift to the changed capacitance increases by an order of magnitude if the product of the coupling coefficient and Q-factor of the second resonator is close to unity. In addition, that the reflection magnitude changes with the varied capacitance is also giant under impedance matching condition at the down and up eigenfrequencies. Based on the proposed method, a sensor composed of an open quarter-wavelength microstrip-line resonator (OQMR) and a split ring resonator (SRR) for detecting concentrations of water-glucose solutions is designed. By adjusting the sample volume and the distance between two resonators, different coupling coefficients and Q-factors can be attained, enabling marked increases in the sensitivity. Experimental and simulated results show that the sensitivity of the center eigenfrequency shift and of the reflection magnitude change to the concentration are as high as 9.4 MHz/(mg/mL) and 5.41 dB/(mg/mL), respectively, both of which are excellent compared to other sensors.

Development of a reverse-transcription droplet digital PCR method for quantitative detection of Cucumber green mottle mosaic virus

Cucumber green mottle mosaic virus (CGMMV) is a re-emerging threat to the production of greenhouse cucumber and other Cucurbitaceae crops worldwide. This seed-borne virus can easily spread from a contaminated seed to seedlings and adjacent plants by mechanical contact between the foliage of diseased and healthy plants, causing extensive yield losses. An accurate method for detecting and quantifying this virus is urgently needed to ensure the safety of the global seed trade. Here, we report the development of a reverse-transcription droplet digital polymerase chain reaction (RT-ddPCR)-based method for specific and high-sensitive detection of CGMMV. By testing three primer–probe sets and optimizing reaction conditions, we showed that the newly developed RT-ddPCR method is highly specific and sensitive, with a detection limit of 1 fg/μL (0.39 copy/μL). The sensitivity of the RT-ddPCR method was compared with that of real-time fluorescence quantitative RT-PCR (RT-qPCR) using a series of plasmid dilutions and total RNAs extracted from infected cucumber seeds, and the detection limit of RT-ddPCR was 10 times higher than RT-qPCR with plasmid dilutions and 100 times higher than RT-qPCR for detecting CGMMV from infected cucumber seeds. The RT-ddPCR method was further assessed for detecting CGMMV from a total of 323 samples of Cucurbitaceae seeds, seedlings, and fruits as compared with the RT-qPCR method. We found that the infection rate of CGMMV on symptomatic fruits was as high as 100%, whereas infection rates were lower for seeds and lowest for seedlings. Notably, the results of two methods in detecting CGMMV from different cucurbit tissues showed the high consistency with Kappa value from 0.84 to 1.0, demonstrating that the newly developed RT-ddPCR method is highly reliable and practically useful for large-scale CGMMV detection and quantification.

A lanthanide-based high-sensitivity fluorescence method for the on-site rapid detection of thermostable direct hemolysin of Vibrio parahaemolyticus

Vibrio parahaemolyticus is a common foodborne pathogen in seafood, which often causes seafood borne bacterial gastroenteritis or food poisoning. Thermostable direct hemolysin (TDH) is considered to be one of the main virulence factors involved in this pathogen. The most clinical V. parahaemolyticus isolates produce TDH. Therefore, high sensitivity and specificity detection of TDH are of great significance for food safety and early diagnosis of diseases caused by V. parahaemolyticus. In this study, we developed a rapid, sensitive immunochromatographic test paper assay for the quantitative detection of TDH in seafood samples using time-resolved fluorescence techniques. First, we completed the preparation of fluorescent detection antibodies by coupling lanthanide fluorescent nanospheres with homemade high-affinity polyclonal antibodies based on the principle of the double-antibody sandwich. The lanthanide fluorescent nanospheres used in this study are characterized by a large stokes shift and a long fluorescence lifetime, which effectively reduces background noise and improves detection sensitivity. In addition, the method can be completed within 15 min for the detection of TDH, has a detection limit below 50 ng/mL and good linearity in the range of 50–5000 ng/mL. Moreover, it has good specificity and no cross-reactivity with Vibrio vulnificus hemolysin (VVH), Clostridium perfringens α toxin (CPA) or C. perfringens ε toxin (ETX). Finally, the sensitivity of this method was unchanged when the three simulated samples of Patinopecten yessoensis, Ruditapes philippinarum, and Scapharca broughtonii tested, indicating that the method is not affected by samples in a complex matrix. In conclusion, this study establishes a practical new method for on-site rapid detection of TDH, which is easy to operate, fast response, easy to carry and can be implemented under the field conditions without expensive equipment and professional person.

Ozone-3,6-dihydroxynaphtha-2,7-disulphonate chemiluminescence system is used for online ozone detection.

The chemiluminescence (CL) reaction between ozone and 3,6-dihydroxynaphtha-2,7-disulphonate (DNDS) was found under alkaline conditions. Therefore, a novel CL system for ozone detection was established. The CL signal of the CL system is weak, and the CL signal is enhanced by adding nonionic surfactants. It was found that adding 16.4g/l Triton X-100 can enhance the CL signal. The CL reagent activated by ultraviolet (UV) light produced a CL signal was nearly 10 times stronger than the CL reagent not activated by UV light; the CL signal was enhanced by adding 8g/l NaHCO3 to the CL reagent irradiated by UV light. Through the optimization of these test conditions, a high-selectivity, high-sensitivity online detection method for ozone CL was established. The linear range was 0.5-150 ppbv, and the limit of detection (LOD) was 0.092 ppbv (S/N = 3).

Analysis of Off-target Effects and Risk Assessment Leading from Preclinical to Clinical Trials of Gene-edited Therapeutic Products.

Concerns about off-target effects (OTEs) of genomic DNA cleavages by gene-editing enzymes have been raised, especially for OTEs that go undetected due to technical limitations. Since no explicit guidelines have been in place for risk assessment of OTEs, the regulatory authorities' concept of an acceptable evaluation scheme for OTEs in the investigational drug application (IND) has not been clear. Here, we clarify the regulatory expectations by examining reports on OTE evaluations of leading gene-editing products that have achieved IND clearance. We collected and analyzed the gene-editing products that have entered clinical trials by searching on ClinicalTrials.gov and EU-Clinical-Trial-Registries, and related reports for OTE evaluations from Google Scholar, PubMed, and the developers' websites. We found a common two-step verification method used for different products at the preclinical stage. First, numerous potential off-target loci (POLs) are listed with state-of-the-art high-sensitivity detection methods and theoretical screens; Second, these OTEs are checked by amplicon sequencing of the POLs after treatment by enzymes in in vitro models close to clinical use conditions. Only the OTEs that can be detected and verified are addressed in the risk assessment in the translational phase from preclinical to clinical study. Here, we describe a clear scheme for risk assessment of OTEs at the key translational phase, based on the common features in protocols for gene-editing products that were cleared for use in clinical trials. This report will provide a guide for those newly attempting to conduct clinical development in this field.

Single phase line‐broken fault detection and location based on differential voltage in radial distribution network

Single phase line-broken (SPLB) fault is one kind of high impedance fault (HIF). When a SPLB fault occurs, there are four scenarios: SPLB fault with neither side conductors grounded (SPLB-NSCG), with source side conductor grounded only (SPLB-SSCG), with load side conductor grounded only (SPLB-LSCG), with both side conductors grounded (SPLB-BSCG). Traditional HIF detection methods using current or voltage characteristics have low sensitivity to SPLB fault. In this paper, voltage characteristics are analysed firstly in the cases of the first three scenarios of SPLB fault, respectively. Theoretical analysis finds that the voltage at both the sides of the disconnection point is significantly different. A high sensitive SPLB fault detection method based on differential voltage is proposed for radial distribution network with different data synchronization ability. Finally, SPLB fault location methods based on centralized intelligent mode feeder automation (FA) and intelligent distributed mode FA are proposed. Simulations based on PSCAD verify that the proposed SPLB fault detection method is feasible, highly sensitive and immune to the neutral grounded mode, fault scenarios and fault resistance.

Development of a high-sensitivity and short-duration fluorescence in situ hybridization method for viral mRNA detection in HEK 293T cells.

Coronavirus disease 2019 (COVID-19) is an extremely contagious illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Early disease recognition of COVID-19 is crucial not only for prompt diagnosis and treatment of the patients, but also for effective public health surveillance and response. The reverse transcription-polymerase chain reaction (RT-PCR) is the most common method for the detection of SARS-CoV-2 viral mRNA and is regarded as the gold standard test for COVID-19. However, this test and those for antibodies (IgM and IgG) and antigens have certain limitations (e.g., by yielding false-negative and false-positive results). We have developed an RNA fluorescence in situ hybridization (FISH) method for high-sensitivity detection of SARS-CoV-2 mRNAs in HEK 293T cell cultures as a model. After transfection of HEK 293T cells with plasmids, Spike (S)/envelope (E) proteins and their mRNAs were clearly detected inside the cells. In addition, hybridization time could be reduced to 2 hours for faster detection when probe concentration was increased. Our approach might thus significantly improve the sensitivity and specificity of SARS-CoV-2 detection and be widely applied for the high-sensitivity single-molecular detection of other RNA viruses (e.g., Middle East respiratory syndrome coronavirus (MERS-CoV), Hepatitis A virus, all influenza viruses, and human immunodeficiency virus (HIV)) in various types of samples including tissue, body fluid, blood, and water. RNA FISH can also be utilized for the detection of DNA viruses (e.g., Monkeypox virus, human papillomavirus (HPV), and cytomegalovirus (CMV)) by detection of their mRNAs inside cells or body fluid.