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In YBCO coils, the increased transport current density and magnetic field will induce larger electromagnetic force, and YBCO coated conductors (CCs) may suffer interlayer delamination by shear forces, which may give rise to performance degradation of the conductor. The delamination characteristics of YBCO CCs under shear stress should be well understood for better application of YBCO tapes to high-temperature superconducting equipment. This paper describes the experimental results for different delamination strength and critical current I c degradation behaviors of the YBCO CCs under shear stress at the unslit edge, center, and slit edge of the conductor. The results show that the average delaminated shear strengths of 4.9, 5.9, and 3.7 MPa are recorded for the unslit edge, center, and slit edge at room temperature, whereas 6.8, 7.2, and 5.1 MPa are recorded for the unslit edge, center, and slit edge at liquid nitrogen. The different degradation behaviors of I c under shear stress are related to the location where delamination occurs in the sample. According to the finite-element method analysis for the stress distribution of the conductor under shear stress, stress concentration leads to initial delamination of the conductor. The decrease of moment arm is suggested to reduce the effect of moment on the delamination test.

Despite some recent developments on the portable on-site sensor of Aflatoxin B1 (AFB1), the complex and expensive preparation of recognition elements have still limited their wide applications. In this paper, using the fast, low-cost, and stable recognition of aptamer DNA-AFB1, a portable aptasensor was constructed for the on-site detection of AFB1 in food matrixes, with the readout of personal glucose meter (PGM) and DNA walking machine for signal probe separation. In such an assay protocol, the target could trigger the DNA walker to autonomously move on the electrode surface, propelled by unidirectional Pb-specific DNAzyme digestion, which could amplify the signal and separate the signal probe as well for further quantification by the PGM. Under optimized conditions, the increase of PGM signal was relative with the concentration of AFB1 ranging from 0.02 to 10 nM and the low limit of detection (LOD) was 10 pM (S/N = 3). With the features of portability, and cheapness, the presented user-friendly method could be extended to various other analytes for wide point-of-care applications.

The electrical properties of Nd‐doped bismuth titanate, Bi4−xNdxTi3O12 (BNT) ceramics prepared by a conventional electroceramic technique have been investigated. XRD analyses revealed Bi‐layered perovskite structure in all samples, and indicated that Bi ions were only substituted near the Ti–O octahedron layers by Nd ions. SEM micrographs show randomly oriented and plate‐like morphology. For the samples with x < 0.5, the current–voltage characteristics exhibit a negative differential resistance behavior, whereas that of the samples with x ≥ 0.5 exhibit a simple ohmic behavior. The conducting filamentary model has been extended and used to explain the negative differential resistance phenomenon in Nd‐doped bismuth titanate ceramics. The P–V hysteresis loop of sample with x = 0.25 were characterized by a large leakage current, and that of samples with x ≥ 0.5 showed the saturated and undistorted hysteresis loops; the remanent polarization (Pr) and coercive field (Ec) of the BNT ceramic with x = 0.5 were above 19 μC/cm2 and 50 KV/cm, respectively. The large value of remanent polarization and low coercive field of Nd‐doped bismuth titanate ceramics promote these materials to potential applications. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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