Due to the lack of teachers, students’ writing can not get timely feedback, which makes the effectiveness of calligraphy teaching in higher education institutions poor. An interactive teaching system ...for calligraphy in higher education institutions is constructed using computer multimedia technology in this paper. Through the design of teaching links, the system fully reflects the context and interactivity of teaching content, offers a wealth of learning activities and resources and makes the calligraphy learning process more intuitive. At the same time, through the “human-computer interaction” to improve the internal drive of students to participate in the learning process, to enhance the interest of learners in learning. The denoising of the text in the picture involves the use of discrete Fourier transform, while the smoothing of the edges of the calligraphic text is achieved through binarization operation, erosion, and expansion principle. The results show that the shape similarity of the system fluctuates between 0.57922 and 0.83314, and the overall similarity reaches more than 0.85, which indicates that the system can be applied to the undergraduate classroom of Calligraphy in higher education institutions. Under the teaching environment of the system, the teacher students with different attitudes have significant variability, which also indicates that the system is effective in assisting the short-term writing practice of calligraphy teaching in higher education institutions, reflecting that the detailed evaluation provided by the interactive teaching system of calligraphy in higher education institutions has some valuable significance.
Miniaturized electrochemical (MEC) sensors have been broadly applied to point-of-care testing (POCT) in various fields, including health care, food safety, and environmental monitoring, due to their ...easy operation, portability, high sensitivity, as well as their short analysis time. This review summarizes the state-of-the-art advancements on various types of MEC sensors, applications in POCT, and the future perspectives, opportunities, and challenges in this field.
Display omitted
Most of the current analytical methods depend largely on laboratory-based analytical techniques that require expensive and bulky equipment, potentially incur costly testing, and involve lengthy detection processes. With increasing requirements for point-of-care testing (POCT), more attention has been paid to miniaturized analytical devices. Miniaturized electrochemical (MEC) sensors, including different material-based MEC sensors (such as DNA-, paper-, and screen electrode-based), have been in strong demand in analytical science due to their easy operation, portability, high sensitivity, as well as their short analysis time. They have been applied for the detection of trace amounts of target through measuring changes in electrochemical signal, such as current, voltage, potential, or impedance, due to the oxidation/reduction of chemical/biological molecules with the help of electrodes and electrochemical units. MEC sensors present great potential for the detection of targets including small organic molecules, metal ions, and biomolecules. In recent years, MEC sensors have been broadly applied to POCT in various fields, including health care, food safety, and environmental monitoring, owing to the excellent advantages of electrochemical (EC) technologies. This review summarized the state-of-the-art advancements on various types of MEC sensors and their applications in POCT. Furthermore, the future perspectives, opportunities, and challenges in this field are also discussed.
The efficient extraction of targets from complex surfaces is vital for technological applications ranging from environmental pollutant monitoring to analysis of explosive traces and pesticide ...residues. In our present study, we proposed a proof-of-concept surface enhance Raman scattering (SERS) active substrate serving directly to the rapid extraction and detection of target molecules. The novel substrate was constructed by decorating the commercial tape with colloidal gold nanoparticles (Au NPs), which simultaneously provides SERS activity and "sticky" of adhesive. The utility of SERS tape was demonstrated by directly extracting pesticide residues in fruits and vegetables via a simple and viable "paste and peel off" approach. The obtained strong and easily distinguishable SERS signals allow us to detect various pesticide residues such as parathion-methyl, thiram, and chlorpyrifos in the real samples with complex surfaces including green vegetable, cucumber, orange, and apple.
Gold nanoparticles (AuNPs) have been frequently utilized for the construction of diverse colorimetric biosensors. Normally, AuNPs with sharp edges could have better sensitivity. However, the poor ...monodipersity of AuNPs with sharp edges seriously confines their utility for colorimetric biosensing. Herein, we demonstrate the utility of highly uniform gold nanobipyramids (Au NBPs) for ultrasensitive colorimetric detection of H
N
virus. The proposed method is based on the fact that alkaline phosphatase (ALP) could catalyze the decomposition of 4-aminophenyl phosphate (4-APP) to generate 4-aminophenol (4-AP), which would then reduce silver nitrate to metal silver and then deposited on Au NBPs. The metal silver shell coated on the Au NBPs changed the refractive index of gold and thus resulted in a blue shift of longitudinal localized surface plasmon resonance (LSPR) and accompanied a vivid color change. This method exhibited a higher sensitivity than that of other Au NPs such as gold nanorods due to the high-index-faceted on the tips of the Au NBPs. This method was used to detect the activity of ALP. It exhibited a linear range of 0.1-5 mU/mL with a limit of detection (LOD) of 0.086 mU/mL. Finally, the proposed method was used in immunoassay to detect H
N
virus. The results showed that the corresponding linear range for the detection of H
N
virus antigen was 0.001-2.5 ng/mL, and the LOD was determined to be 1 pg/mL, which is more sensitive than those in most of the colorimetric biosensors reported previously.
The metal-organic framework (MOF) was first utilized as the sensing platform for assaying biomolecules. It has also been demonstrated that this novel strategy is effective and reliable for detection ...of HIV DNA and thrombin with high sensitivity and selectivity.
In this paper, a novel and signal-on electrochemical biosensor based on Hg2+- triggered nicking endonuclease-assisted target recycling and hybridization chain reaction (HCR) amplification tactics was ...developed for sensitive and selective detection of Hg2+. The hairpin-shaped capture probe A (PA) contained a specific sequence which was recognized by nicking endonuclease (NEase). In the presence of Hg2+, probe B (PB) hybridized with PA to form stand-up duplex DNA strands via the Hg2+ mediated thymine-Hg2+-thymine (T-Hg2+-T) structure, which automatically triggered NEase to selectively digest duplex region from the recognition sites, spontaneously dissociating PB and Hg2+ and leaving the remnant initiators. The released PB and Hg2+ could be reused to initiate the next cycle and more initiators were generated. The long nicked double helices were formed through HCR event, which was triggered by the initiators and two hairpin-shaped signal probes labeled with methylene blue, resulting in a significant signal increase. Under optimum conditions, the resultant biosensor showed the high sensitivity and selectivity for the detection of Hg2+ in a linear range from 10 pM to 50nM (R2=0.9990), and a detection limit as low as 1.6 pM (S/N=3). Moreover, the proposed biosensor was successfully applied in the detection of Hg2+ in environment water samples with satisfactory results.
•A novel electrochemical biosensor for Hg2+ detection was constructed by utilizing dual signal amplification strategy.•The signal-on mechanism can efficiently avoid false positive results.•The strategy improved the sensitivity for detection of Hg2+ down to 1.6pM.•The biosensor showed high selectivity for Hg2+ detection.
A disposable, equipment-free, versatile point-of-care testing platform, microfluidic distance readout sweet hydrogel integrated paper-based analytical device (μDiSH-PAD), was developed for portable ...quantitative detection of different types of targets. The platform relies on a target-responsive aptamer cross-linked hydrogel for target recognition, cascade enzymatic reactions for signal amplification, and microfluidic paper-based analytic devices (μPADs) for visual distance-based quantitative readout. A "sweet" hydrogel with trapped glucoamylase (GA) was synthesized using an aptamer as a cross-linker. When target is present in the sample, the "sweet" hydrogel collapses and releases enzyme GA into the sample, generating glucose by amylolysis. A hydrophilic channel on the μPADs is modified with glucose oxidase (GOx) and colorless 3,3'-diaminobenzidine (DAB) as the substrate. When glucose travels along the channel by capillary action, it is converted to H2O2 by GOx. In addition, DAB is converted into brown insoluble poly-3,3'-diaminobenzidine poly(DAB) by horseradish peroxidase, producing a visible brown bar, whose length is positively correlated to the concentration of targets. The distance-based visual quantitative platform can detect cocaine in urine with high selectivity, sensitivity, and accuracy. Because the target-induced cascade reaction is triggered by aptamer/target recognition, this method is widely suitable for different kinds of targets. With the advantages of low cost, ease of operation, general applicability, and disposability with quantitative readout, the μDiSH-PAD holds great potential for portable detection of trace targets in environmental monitoring, security inspection, personalized healthcare, and clinical diagnostics.
Display omitted
•For the first time, the combination of BNQDs with in situ grown AuNPs is used for fluorescence biosensing.•The sensing mechanism is based on FRET principle, showing a high ...specificity and good selectivity toward target, and effective anti-interference ability.•This strategy offers a convenient “mix and detect” approach for the simultaneous detection of AChE activity and paraoxon, which is easy-operation, fast and efficient.•The sensing platform is successfully applied for the detection of serum samples.
A rapid, label-free, and highly sensitive fluorescence biosensing platform has been fabricated for effectively detecting acetylcholinesterase (AChE) activity via fluorescence resonance energy transfer (FRET) between boron nitride quantum dots (BNQDs) and gold nanoparticles (AuNPs). In this work, AChE hydrolyzed acetylthiocholine (ATCh) to generate thiocholine (TCh), which can reduce chloroauric acid (HAuCl4) into AuNPs and in situ formation of TCh-BNQDs/AuNPs aggregates, resulting in fluorescence quenching of BNQDs. Moreover, paraoxon, a organophosphorus pesticide, was used to lower the activity of AChE and hinder the enzymatic hydrolysis reaction, hence weakened the fluorescence quenching of BNQDs. Based on these findings, a simple ‘one-pot’ FRET-based biosensor has been constructed to assess AChE activity and its inhibitor by measuring the fluorescence intensity of BNQDs. The linear range toward AChE was from 0.05 to 6.0 mU/mL with the lower detection limit of 0.0212 mU/mL, indicating the biosensor out-performs most of the reported sensors. Since the activity of AChE has been connected to a number of diseases, this convenient ‘mix and detect’ approach has potentially extensive application in clinic diagnosis. On the other hand, the inhibition effect by paraoxon was evaluated, and the corresponding half maximal inhibitory concentration (IC50) toward AChE was estimated to be 2.987 μg/L.As far as we known, the proposed biosensing platform based on TCh-BNQDs/AuNPs nanocomposites is the first time to demonstrate the application of BNQDs for fluormetric assays of enzyme activity and inhibiting effect. It also opens up a novel pathway of using BNQDs to develop optical biosensors for analyzing many other analytes.
High penetration of wind power in the modern power system renders traditional automatic generation control (AGC) methods more challenging, due to the uncertainty of the external environment, less ...reserve power, and small inertia constant of the power system. An improved AGC method named predictive optimal 2-degree-of-freedom proportion integral differential (PO-2-DOF-PID) is proposed in this paper, which wind farm will participate in the load frequency control process. Firstly, the mathematical model of the AGC system of multi-area power grid with penetration of wind power is built. Then, predictive optimal 2-degree-of-freedom PID controller is presented to improve the system robustness considering system uncertainties. The objective function is designed based on the wind speed and whether wind farm takes part in AGC or not. The controller solves the optimization problem through the predictive theory while taking into account given constraints. In order to obtain the predictive sequence of output of the whole system, the characteristic of the 2-DOF-PID controller is integrated in the system model. A three interconnected power system is introduced as an example to test the feasibility and effectiveness of the proposed method. When considering the penetration of wind power, two cases of high wind speed and low wind speed are analyzed. The simulation results indicate that the proposed method can effectively deal with the negative influence caused by wind power when wind power participates in AGC.
Optimising the supported modes of atom or ion dispersal onto substrates, to synchronously integrate high reactivity and robust stability in catalytic conversion, is an important yet challenging area ...of research. Here, theoretical calculations first show that three-coordinated copper (Cu) sites have higher activity than four-, two- and one-coordinated sites. A site-selective etching method is then introduced to prepare a stacked-nanosheet metal-organic framework (MOF, CASFZU-1)-based catalyst with precisely controlled coordination number sites on its surface. The turnover frequency value of CASFZU-1 with three-coordinated Cu sites, for cycloaddition reaction of CO
with epoxides, greatly exceed those of other catalysts reported to date. Five successive catalytic cycles reveal the superior stability of CASFZU-1 in the stacked-nanosheet structure. This study could form a basis for the rational design and construction of highly efficient and robust catalysts in the field of single-atom or ion catalysis.
PDF
