A Novel Superhard, Wear-Resistant, and Highly Conductive Cu-MoSi2 Coating Fabricated by High-Speed Laser Cladding Technique.

The pursuit of an advanced functional coating that simultaneously combines high hardness, wear resistance, and superior electrical conductivity has remained an elusive goal in the field of copper alloy surface enhancement. Traditional solid solution alloying methods often lead to a significant increase in electron scattering, resulting in a notable reduction in electrical conductivity, making it challenging to achieve a balance between high hardness, wear resistance, and high conductivity. The key lies in identifying a suitable microstructure where dislocation motion is effectively hindered while minimizing the scattering of conductive electrons. In this study, a novel Cu-MoSi2 coating was successfully fabricated on a CuCrZr alloy surface using the coaxial powder feeding high-speed laser cladding technique, with the addition of 10-30% MoSi2 particles. The coating significantly enhances the hardness and wear resistance of the copper substrate while maintaining favorable electrical conductivity. As the quantity of MoSi2 particles increases, the coating's hardness and wear resistance gradually improve, with minimal variance in conductivity. Among the coatings, the Cu-30%MoSi2 coating stands out with the highest hardness (974.5 HV0.5) and the lowest wear amount (0.062 mg/km), approximately 15 times the hardness of the copper base material (65 HV0.5) and only 0.45% of the wear amount (13.71 mg/km). Additionally, the coating exhibits a resistivity of 0.173 × 10-6 Ω·m. The extraordinary hardness and wear resistance of these coatings can be attributed to the dispersion strengthening effect of MoxSiy particles, while the high electrical conductivity is due to the low silicon content dissolved into the copper from the released MoSi2 particles, as well as the rapid cooling rates associated with the high-speed laser cladding process.

Extreme Learning Machine for Heartbeat Classification with Hybrid Time-Domain and Wavelet Time-Frequency Features.

Automatic heartbeat classification via electrocardiogram (ECG) can help diagnose and prevent cardiovascular diseases in time. Many classification approaches have been proposed for heartbeat classification, based on feature extraction. However, the existing approaches face the challenges of high feature dimensions and slow recognition speeds. In this paper, we propose an efficient extreme learning machine (ELM) approach for heartbeat classification with multiple classes, based on the hybrid time-domain and wavelet time-frequency features. The proposed approach contains two sequential modules: (1) feature extraction of heartbeat signals, including RR interval features in the time-domain and wavelet time-frequency features, and (2) heartbeat classification using ELM based on the extracted features. RR interval features are calculated to reflect the dynamic characteristics of heartbeat signals. Discrete wavelet transform (DWT) is used to decompose the heartbeat signals and extract the time-frequency features of the heartbeat signals along the timeline. ELM is a single-hidden layer feedforward neural network with the hidden layer parameters randomly generated in advance and the output layer parameters calculated optimally using the least-square algorithm directly using the training samples. ELM is used as the heartbeat classification algorithm due to its high accuracy training accuracy, fast training speed, and good generalization ability. Experimental testing is carried out using the public MIT-BIH arrhythmia dataset to perform a 16-class classification. Experimental results show that the proposed approach achieves a superior classification accuracy with fast training and recognition speeds, compared with existing classification algorithms.

[Detection of fetal SRY gene in maternal plasma by real-time fluorescence quantitative PCR].

OBJECTIVE: To isolate fetal DNA from maternal plasma and examine its fetal origin. METHODS: Fetal DNA in maternal plasma was isolated from 150 samples in the first trimester and mid-trimester of pregnancy, respectively. Real-time fluorescence quantitative polymerase chain reaction PCR (FQ-PCR) was used to determine sex-determining region Y (SRY) gene on Y chromosome. RESULTS: Eighty-two women in the first trimester and 90 women in the mid-trimester carried male fetuses,70 and 90 samples of them were positive, respectively. The mean concentrations were (58.82+/-20.90) copies/ml and (152.08+/-62.61) copies/ml. The results of FQ-PCR were negative in the women who carried female fetuses. CONCLUSION: The results show that fetal SRY gene can be found at a time as early as 42 days of gestation in maternal plasma by the use of FQ-PCR. The number of fetal DNA increases with gestational age. The real-time FQ-PCR is of great value in the non-invasive prenatal diagnosis.

[Restriction endonucleases fingerprinting-single strand conformation polymorphism: an efficient method to screen mutations in long segments].

OBJECTIVE: To develop a simple, cheap and efficient restriction endonucleases fingerprinting-single strand conformation polymorphism(REF-SSCP) method applied to screen for mutations in long segments. METHODS: The genomic DNA of Cx26 gene segment of the patients with deafness was amplified. The amplification products were screened with SSCP and REF-SSCP technique and DNA sequencing to evaluate and compare the effect on detection of mutations in long segments. RESULTS: No different band was found in 724 bp segment in SSCP examination. Three kinds of different bands were discovered in REF-SSCP examination and the 79 G -->A mutation detected by DNA sequencing were accorded with the REF-SSCP bands entirely. The rate of detection was 100%. CONCLUSION: The present REF-SSCP method is applicable to screen mutations in long segment DNA of mass specimens.

[Mutation analysis of Cx26 gene in Chinese hereditary nonsyndromic deafness sufferers].

OBJECTIVE: To analyze the mutations in the code region of Cx26 gene in Chinese hereditary nonsyndromic hearing impairment (NSHI) sufferers. METHODS: Thirty-three cases (29 cases in the families of 8 students who were picked out from the Deafness and Muteness School of Tianjin, 2 cases as control and 2 normal cases of genetic counseling) were included in this study. The blood samples were obtained to distill the DNA templates. Using polymerase chain reaction (PCR), the code region of Cx26 gene was amplified. The mutations were screened by restriction endonucleases fingerprinting-single strand conformation polymorphism (REF-SSCP). Afterwards we inspected the polymorphous changes or mutations of these segments with DNA sequence. RESULTS: There were 30 cases with the nucleotide changes in the Cx26 code region. The rate was 90.9% (30/33). Eight kinds of mutations were found, 79G-->A, 109G-->A, 161A-->T, 235delC, 240G-->A, 341A-->G, 571T-->C and 608T-->C. 161A-->T, 240G-->A and 571T-->C were detected primarily. There were 3 cases with 235delC in 22 deafness sufferers and the rate was 13.64% (3/22). CONCLUSIONS: The 235delC of Cx26 gene is the main mutation in Chinese NSHI sufferers, and in NSHI cases many polymorphous changes exist.

[Nonsyndromic hereditary deafness genes research progress and related databases].

Deafness is the most prevalent sensory system impairment of human, and 70% of genetic deafness belongs to nonsyndromic hearing impairment. The total number of genes involved in nonsyndromic hereditary deafness has been estimated to above 100. So far, approximate 80 loci have been mapped to human chromosome, and 23 genes have been identified. In this article,these 23 genes were summarized systematically and some databases about hereditary deafness were provided for reference.