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Sensitive and specific assay of microRNAs (miRNAs) is beneficial to early disease screening. Herein, we for the first time proposed clustered regularly interspaced short palindromic repeats (CRISPR)/Cas13a-mediated photoelectrochemical biosensors for the direct assay of miRNA-21. In this study, compared with traditional nucleic acid-based signal amplification strategies, the CRISPR/Cas13a system can greatly improve the specificity and sensitivity of target determination due to its accurate recognition and high-efficient trans-cleavage capability without complex nucleic acid sequence design. Moreover, compared with the CRISPR/Cas12a-based biosensing platform, the developed CRISPR/Cas13a-mediated biosensor can directly detect RNA targets without signal transduction from RNA to DNA, thereby avoiding signal leakage and distortion. Generally, the proposed biosensor reveals excellent analysis capability with a wider linear range from 1 fM to 5 nM and a lower detection limit of 1 fM. Additionally, it also shows satisfactory stability in the detection of human serum samples and cell lysates, manifesting that it has great application prospects in the areas of early disease diagnosis and biomedical research.

In analyzing the drug resistance phenotype and mechanism of resistance to macrolide antibiotics of clinical Pseudomonas aeruginosaisolates, the agar dilution method was used to determine the minimum inhibitory concentrations (MICs), and PCR (polymerase chain reaction) was applied to screen for macrolide antibiotics resistance genes. The macrolide antibiotics resistance genes were cloned, and their functions were identified. Of the 13 antibiotics tested, P. aeruginosastrains showed high resistance rates (ranging from 69.5–82.1%), and MIC levels (MIC90 > 256 μg/ml) to macrolide antibiotics. Of the 131 known macrolide resistance genes, only two genes, mphEand msrE, were identified in 262 clinical P. aeruginosaisolates. Four strains (1.53%, 4/262) carried both the msrEand mphEgenes, and an additional three strains (1.15%, 3/262) harbored the mphEgene alone. The cloned msrEand mphEgenes conferred higher resistance levels to three second-generation macrolides compared to two first-generation ones. Analysis of MsrE and MphE protein polymorphisms revealed that they are highly conserved, with only 1–3 amino acids differences between the proteins of the same type. It can be concluded that even though the strains showed high resistance levels to macrolides, known macrolide resistance genes are seldom present in clinical P. aeruginosastrains, demonstrating that a mechanism other than this warranted by the mphEand msrEgenes may play a more critical role in the bacteria’s resistance to macrolides.

The existing Bug algorithms, which are the same as wall-following algorithms, offer good performance in solving local minimum problems caused by potential fields. However, because of the odometer drift that occurs in actual environments, the performance of the paths planned by these algorithms is significantly worse in actual environments than in simulated environments. To address this issue, this article proposes a new Bug algorithm. The proposed algorithm contains a potential field function that is based on the relative velocity, which enables the potential field method to be extended to dynamic scenarios. Using the cumulative changes in the internal and external angles and the reset point of the robot during the wall-following process, the condition for state switching has been redesigned. This improvement not only solves the problem of position estimation deviation caused by odometer noise but also enhances the decision-making ability of the robot. The simulation results demonstrate that the proposed algorithm is simpler and more efficient than existing wall-following algorithms and can realise path planning in an unknown dynamic environment. The experimental results for the Kobuki robot further validate the effectiveness of the proposed algorithm.

This study presents the microstructure and properties of vacuum electron beam welded WE43 magnesium alloy joint. The process parameters of acceleration voltage 150 kV, electron beam current 120 mA and welding speed 35 mm/s are used for vacuum electron beam welding of WE43 rare earth magnesium alloy plate. In this study, the main compositions of the weld are α-Mg and a small amount of eutectic rare earth phase β-Mg24Y5. The mass fraction of the rare earth phase β-Mg24Y5in the weld area is more than that of the base metal. Segregation of Zr-rich particles can occur in weld zone. The average hardness of the weld is about 27% higher than that of the base metal, and the hardness near the center line of the weld is the highest. The yield strength, tensile strength and elongation of the joint are higher than that of the base metal by approximately 17%, 14% and 41%. Tensile fracture morphology of the welded joint is characterized by ductile and brittle mixed fracture. So, electron beam welding can achieve the connection of WE43 magnesium alloy plate with excellent microstructure and performance. It may be of great significance for this study to expand the application of rare earth magnesium alloy.

A novel method of object pose estimation based on three dimensional registration for assembly robot is presented. The spatial registration parameters can be computed by finding which projection of the volume is the most similar to the camera image. We compute the Fourier Transform (FT) of the volume projection by using FT projection theorem. A cost function is designed according to the magnitude of projection FT and image FT. Registration parameters is obtained by using Complicated System Genetic Algorithm (CSGA) to minimise the cost function. Assembly experiment made on our robot system shows our method is efficient and practical.

In order to study the micro-table three-dimensional motion measurement errors, this article proposed that realizes the goal of three dimensional position and orientation examination based on the monocular vision. The micro work table abstracts to rectangular platform with a regular shape, the rectangle platform selects vertices and edges as the feature elements. Based on the measurement principle of monocular vision, with the coordinate transformation, it obtains method for solving three-dimensional position and orientation based on the feature element.

In this paper, a feature extraction method has been studied for visual inspection system of micro-platform. In this paper, an improved algorithm for Harris to improve the accuracy and detection speed based on introducing the principle Harris algorithm for the importance of the feature extraction for image matching, camera calibration, three-dimensional reconstruction and so on. Finally, a very good corner has been got by the algorithm research in MATLAB and experimental. And we proved the feasibility of this method.

FeCoCrNiTiX(X = 0.5,0.75,1) series high entropy alloys with different contents were prepared by vacuum arc melting method. The effects of Ti content on the magnetic properties and electrochemical corrosion properties of FeCoCrNi high entropy alloys were studied by SEM, XRD, VSM, hardness tester and other methods. The experimental results show that the face-centered cubic structure composed of many plate-like structures between dendrites and interdendritic is found in the as-cast alloy of CoCrFeNiTix. With the further increase of Ti content, the volume fraction of Laves phase increases, and the morphology of Laves phase changes from granular to reticular structure. The hardness of the alloy increased with Ti content at x = 0.5 to x = 0.75, but decrease when Ti reached x = 1.Compared to FeCoCrNiTi0.5and FeCoCrNiTi0.75alloys, FeCoCrNiTi1alloys has a wider hysteresis area, while FeCoCrNiTi0.75alloys has the smallest hysteresis. When the content of Ti continues to increase to 1 at.%, the paramagnetism of FeCoCrNiTi weakens. The FeCoCrNiTi1alloy presents the largest semicircle radius of the Nyquist curve and the highest diffusion impedance. With the increase of Ti element in the alloy, the diameter of the semicircular arc decreases at first and then increases, and FeCoCrNiTi1has better corrosion resistance.