Critical current density: Measurements vs. reality

Different experimental techniques are employed to evaluate the critical current density (Jc), namely transport current measurements and two different magnetisation measurements forming quasi-equilibrium and dynamic critical states. Our technique-dependent results for superconducting YBa 2Cu3O7 (YBCO) film and MgB2 bulk samples show an extremely high sensitivity of Jc and associated interpretations, such as irreversibility fields and Kramer plots, which lose meaning without a universal approach. We propose such approach for YBCO films based on their unique pinning features. This approach allows us to accurately recalculate the magnetic-field-dependent Jc obtained by any technique into the Jc behaviour, which would have been measured by any other method without performing the corresponding experiments. We also discovered low-frequency-dependent phenomena, governing flux dynamics, but contradicting the considered ones in the literature. The understanding of these phenomena, relevant to applications with moving superconductors, can clarify their dramatic impact on the electric-field criterion through flux diffusivity and corresponding measurements. © Copyright EPLA, 2013

A bio-inspired system for simultaneous vibration isolation and energy harvesting in post-capture spacecraft

Vibrations and drifting motions of a post-capture spacecraft may lead to its instability and safety risk, which therefore need to be absorbed or isolated. However, it is expected that the vibrational energy is not wasted but harvested to power the wireless sensors. Motivated by this concept and inspired by the movement of a bird, a quadrilateral shape isolation system with an energy harvester is proposed for the simultaneous broadband vibration isolation and energy harvesting of the post-capture spacecraft. The governing equations of the proposed system are derived based on Hamilton's principle. The corresponding dimensionless approximate analytical model is deduced based on the harmonic balance method and validated through the comparison with the numerical Runge–Kutta method. Simulation results demonstrate that compared with its counterpart without the energy harvester, the proposed system can further improve the broadband vibration isolation performance, and achieve the energy harvesting function simultaneously. The operation principle is the energy localization effect, which is demonstrated through the investigation on system dynamics. The guideline for improving the dual performances is proposed according to the parametric studies on the mass ratios, the equivalent stiffness and damping induced by the quadrilateral shape structures, and the mechanical and electrical parameters of the energy harvester.</p

Sensitive fluorescence ELISA with streptavidin scaffolded DNA tetrads for the detection of Escherichia coli O157:H7

ABSTRACT: Escherichia coli O157:H7 poses a threat to humans. Traditional ELISA is not a sensitive method for the detection of E. coli O157:H7. Here, an efficient method was designed for improving the load capacity of alkaline phosphatase (ALP) with streptavidin scaffolded DNA tetrad (SS-DNAt). With more ALP, more ascorbic acid 2-phosphate was catalyzed to ascorbic acid that was used to synthesize fluorescence poly adenine-thymine–templated copper nanoclusters. Based on SS-DNAt, fluorescence ELISA was successfully proposed for improving the sensitivity for detection of E. coli O157:H7 in milk samples. The method showed a linear range of 104 to 106 cfu/mL. The limit of detection of fluorescence ELISA was 3.75 × 103 cfu/mL and 6.16-fold better than that of traditional ELISA. The recovery of the fluorescence ELISA was 86.7 to 93.6% with the coefficient of variation of 5.6 to 10.5% in milk. This method could be used to detect hazardous material in food

Ultra-sensitive method based on time-resolved fluorescence immunoassay for detection of sulfamethazine in raw milk

A novel lateral flow assay (LFA) was developed by introducing Eu (III)-doped polystyrene nanoparticles (EuNPs) for rapid and ultra-sensitive detection of sulfamethazine (SM2) in raw milk. The limit of detection and linear range of the proposed method were 0.0045 and 0.05–10 ng/mL, respectively. The recovery of LFA for the detection of SM2 in raw milk was 96.1–108.2%. The proposed LFA provides a rapid and convenient strategy for fast and ultra-sensitive screening of SM2 in raw milk. EuNP-LFA may be a remarkable method for the detection of other targets at low concentrations to ensure food safety

miR-194 Inhibits Innate Antiviral Immunity by Targeting FGF2 in Influenza H1N1 Virus Infection

Fibroblast growth factor 2 (FGF2 or basic FGF) regulates a wide range of cell biological functions including proliferation, angiogenesis, migration, differentiation, and injury repair. However, the roles of FGF2 and the underlying mechanisms of action in influenza A virus (IAV)-induced lung injury remain largely unexplored. In this study, we report that microRNA-194-5p (miR-194) expression is significantly decreased in A549 alveolar epithelial cells (AECs) following infection with IAV/Beijing/501/2009 (BJ501). We found that miR-194 can directly target FGF2, a novel antiviral regulator, to suppress FGF2 expression at the mRNA and protein levels. Overexpression of miR-194 facilitated IAV replication by negatively regulating type I interferon (IFN) production, whereas reintroduction of FGF2 abrogated the miR-194-induced effects on IAV replication. Conversely, inhibition of miR-194 alleviated IAV-induced lung injury by promoting type I IFN antiviral activities in vivo. Importantly, FGF2 activated the retinoic acid-inducible gene I signaling pathway, whereas miR-194 suppressed the phosphorylation of tank binding kinase 1 and IFN regulatory factor 3. Our findings suggest that the miR-194-FGF2 axis plays a vital role in IAV-induced lung injury, and miR-194 antagonism might be a potential therapeutic target during IAV infection

Highly ordered iron oxide nanotube arrays as electrodes for electrochemical energy storage

Highly ordered α-Fe2O3 nanotube arrays have been fabricated by a simple and cost-effective anodization method on iron foils. The α-Fe2O3 nanotube arrays exhibit high specific capacitance (138 F·g−1 at 1.3 A·g−1), remarkable rate capability (91 F·g−1 at 12.8 A·g−1) and good cycling stability (the capacitance retention close to 89% after 500 cycles), due to the unique nanostructures of the α-Fe2O3 nanotube arrays, which providing high surface area, fast ion transport pathways and robust structures. These features made the α-Fe2O3 nanotube array electrode very attractive for supercapacitor applications. Keywords: Iron oxide, Anodization, Nanotube array, Supercapacitor

Non-Synergistic Changes in Migration Processes between Soil Salt and Water in the Salt Patch of the Coastal Saline Soil

Salt patches (SPs) with surface salt accumulation pose a serious threat to agriculture in coastal saline lands. However, the migration and distribution of soil water and salt in SPs remain unclear due to complex water–salt transport dynamics. In this study, we focused on typical SPs in the Yellow River Delta region and selected center site (Site 1), transition site (Site 2), edge site (Site 3), and outer site (Site 4) with varying levels of salinization. Field sampling and the HYDRUS-1D model were employed to investigate the migration process and distribution of soil water and salt in SPs, as well as the influencing factors. The results indicated significantly higher salt contents in the central sites (Site 1 and Site 2) compared to the edge sites (Site 3 and Site 4), while no significant differences were observed in soil water content. The bottom soil exhibited greater stability in terms of water and salt content compared to the surface soil. Additionally, soil water content increased with soil depth, whereas salt content decreased from Site 1 to Site 3. Interestingly, Site 4 exhibited the opposite salt distribution pattern in the whole soil depth. We observed that SPs displayed a salt aggregation structure radiating from the center to the periphery, gradually weakening in intensity. Our correlation analysis indicated that the formation of SPs may be influenced by soil particle size distribution, precipitation, and evaporation. Specifically, fine soil structure can impede the upward transport of highly mineralized groundwater, while precipitation and evaporation directly affect the leaching and upward movement of surface soil salt, resulting in uneven salt distribution in the field and the formation of SPs. These findings provide valuable theoretical and technical insights for the prevention and improvement of saline farmlands in the Yellow River Delta

Nanozyme-based lateral flow assay for the sensitive detection of Escherichia coli O157:H7 in milk

Lateral flow assay (LFA) has been applied in many fields due to its relative ease of use and cost-effectiveness. However, it has low sensitivity and its applications are limited. Probe materials play a significant role in improving the detection efficiency and sensitivity of LFA. In this study, by using concave palladium-platinum (Pd-Pt) nanoparticles as a nanozyme probe, we developed a sensitive LFA based on the sandwich format for qualitative and quantitative detection of Escherichia coli O157:H7. The sensitivity of the LFA. was improved by applying the 3,3',5,5'-tetramethylbenzidine (TMB) substrate onto the test line where the nanozyme was accumulated in the presence of analytes. The nanozyme showed high catalytic performance toward TMB and greatly enhanced the signal intensity of the test line. The sensitivity of the nanozyme-based LFA was 9.0 x 10(2) cfu/mL in milk, which was 111-fold higher than that of traditional colloidal gold-based LFA. The proposed method has remarkable potential in the detection of various pathogens in real samples

Nanozyme-based lateral flow assay for the sensitive detection of Escherichia coli O157:H7 in milk

Lateral flow assay (LFA) has been applied in many fields due to its relative ease of use and cost-effectiveness. However, it has low sensitivity and its applications are limited. Probe materials play a significant role in improving the detection efficiency and sensitivity of LFA. In this study, by using concave palladium-platinum (Pd-Pt) nanoparticles as a nanozyme probe, we developed a sensitive LFA based on the sandwich format for qualitative and quantitative detection of Escherichia coli O157:H7. The sensitivity of the LFA. was improved by applying the 3,3',5,5'-tetramethylbenzidine (TMB) substrate onto the test line where the nanozyme was accumulated in the presence of analytes. The nanozyme showed high catalytic performance toward TMB and greatly enhanced the signal intensity of the test line. The sensitivity of the nanozyme-based LFA was 9.0 x 10(2) cfu/mL in milk, which was 111-fold higher than that of traditional colloidal gold-based LFA. The proposed method has remarkable potential in the detection of various pathogens in real samples