YBa2Cu3O7-δ (YBCO) is a well-known high-temperature superconductor. However, its critical current density and thus maximum trapped magnetic field can be improved significantly by introducing the secondary phases (artificial pinning centers). In this contribution, we successfully prepared YBCO single-grain bulks with Y2Ba4CuWO10.8 phase serving as a source of pinning centers. This phase was prepared by solid-state reaction and further refined by milling. In the next step single-grain YBCO bulks with homogeneously distributed Y2Ba4CuWO10.8 were prepared by top-seeded melt growth. Precursors as well as the final product were characterized by XRD, SEM and EDS. The phase composition of YBCO bulks containing Y2Ba4CuWO10.8 was analyzed using Rietveld analysis. Thermal stability of YBCO bulk was studied by STA. Furthermore, PPMS was used to study electrical resistivity and critical current density. Bulk superconducting properties such as levitation force and trapped field ability were also measured. 相似文献
Gasoline engine emissions have been classified as possibly carcinogenic to humans and represent a significant health risk. In this study, we used MucilAir™, a three-dimensional (3D) model of the human airway, and BEAS-2B, cells originating from the human bronchial epithelium, grown at the air-liquid interface to assess the toxicity of ordinary gasoline exhaust produced by a direct injection spark ignition engine. The transepithelial electrical resistance (TEER), production of mucin, and lactate dehydrogenase (LDH) and adenylate kinase (AK) activities were analyzed after one day and five days of exposure. The induction of double-stranded DNA breaks was measured by the detection of histone H2AX phosphorylation. Next-generation sequencing was used to analyze the modulation of expression of the relevant 370 genes. The exposure to gasoline emissions affected the integrity, as well as LDH and AK leakage in the 3D model, particularly after longer exposure periods. Mucin production was mostly decreased with the exception of longer BEAS-2B treatment, for which a significant increase was detected. DNA damage was detected after five days of exposure in the 3D model, but not in BEAS-2B cells. The expression of CYP1A1 and GSTA3 was modulated in MucilAir™ tissues after 5 days of treatment. In BEAS-2B cells, the expression of 39 mRNAs was affected after short exposure, most of them were upregulated. The five days of exposure modulated the expression of 11 genes in this cell line. In conclusion, the ordinary gasoline emissions induced a toxic response in MucilAir™. In BEAS-2B cells, the biological response was less pronounced, mostly limited to gene expression changes. 相似文献
Potential alternatives for conventional sitting and standing postures are hybrid sit-stand postures (i.e. perching). The purposes of this study were (i) to identify where lumbopelvic and pelvic angles deviate from sitting and standing and (ii) to use these breakpoints to define three distinct postural phases: sitting, perching, and standing, in order to examine differences in muscle activations and ground reaction forces between phases. Twenty-four participants completed 19 1-min static trials, from sitting (90°) to standing (180°), sequentially in 5°trunk–thigh angle increments. The perching phase was determined to be 145–175° for males and 160–175° for females. For both sexes, knee extensor activity was lower in standing compared to perching or sitting (p < .01). Anterior–posterior forces were the highest in perching (p < .001), requiring ~15% of body-weight. Chair designs aimed at reducing the lower limb demands within 115–170° trunk–thigh angle may improve the feasibility of sustaining the perched posture.
Practitioner summary: Individuals who develop low back pain in sitting or standing may benefit from hybrid sit-stand postures (perching), yet kinematic and kinetic changes associated with these postures have not been investigated. Perching can improve lumbar posture at a cost of increased lower limb demands, suggesting potential avenues for chair design improvement.
Abbreviations: A/P: anterior-posterior; M/L: medial-lateral; LBP: low back pain; EMG: electromyography; TES: thoracic erector spinae; LES: lumbar erector spinae; VMO: vastus medialis obliquus; MVC: maximum voluntary contraction; ASIS: anterior superior iliac spine; PSIS: posterior superior iliac spine; BW: body weight; RMSE: root mean square error; SD: standard deviation; ROM: range of motion 相似文献
Mobile Networks and Applications - Solid fuels combustion is rather complicated because there is always environment pollution by emissions, mainly by particulate matter. The efforts of heat sources... 相似文献
Over the last decade, dendritic structures including hyperbranched polymers, dendrigrafts, dendrons, and dendrimers due to their distinct structural design such as highly branched structure and a large number of reactive end groups have received considerable attention. Among various kind of dendrimer, particularly amine-terminated dendritic materials like polyamidoamine (PAMAM), polypropylene imine (PPI), and polyethylene imine (PEI) have been introduced as the potential candidates in a wide range of areas, particularly in the field of textiles engineering. Hence, this review provides an introduction of amine-terminated dendritic polymers and new potential applications of them in textiles engineering such as improvement of dyeability, salt-free dyeability, antimicrobial activity, long-lasting fragrant fabric, anti-ultraviolet property, drug delivery through fabric, flame retardancy, and wastewater treatment. Regarding the complex synthesis of dendrimers which makes them expensive products, application of amine-terminated hyperbranched polymers provides affordable dendritic polymers to create novel features. 相似文献
Investigation of pristine g-C3N4 and copper ions doped g-C3N4 as dispersed phases in silicone-oil based electrorheological (ER) fluids is reported for the first time. Pristine g-C3N4 was prepared via standard thermal polycondensation of urea. Introduction of Cu ions into g-C3N4 polymeric network was performed by treatment of pristine powder by a solution containing tetraammoniumdiaquacopper(II) complex ions followed by annealing. The structure and properties of products were revealed with the aid of XRD, FTIR, UV–Vis and XPS, and complemented by SEM investigation of morphology, pycnometry, BET analysis, and conductivity measurements. The response of prepared ER fluids to an external electric field was examined by rheometry and the effects visualized with optical microscopy. While ER fluids based on g-C3N4 exhibited negative ER effect (decrease in viscosity when the field is switched-on), ER fluids based on a g-C3N4/Cu-doped analogue exhibited positive ER effect. Dielectric spectroscopy using Havriliak-Negami model revealed that introduction of the dopant almost doubled the dielectric relaxation strength while the relaxation time was halved. The ability of g-C3N4/Cu as a candidate for further studies necessary to increase the ER effect was demonstrated. Thereto, described modification of g-C3N4 by copper ions shall be applicable also for other metals forming ammonia complexes. 相似文献
Journal of Materials Science - Powder-based directed energy deposition (DED) technology with separate feeders for different individual materials enables the deposition of functionally graded... 相似文献
Principles and advantages of a new concept based on the ab initio aided strain gradient elasticity theory are shown in comparison with the classical Barenblatt cohesive model. The method is applied to the theoretical prediction of the critical energy release rate and the crack tip opening displacement at the crack instability in nanopanels made of germanium and molybdenum crystals. The necessary length scale parameter l1 is determined for germanium and molybdenum by the best gradient elasticity fits of ab initio computed screw dislocation displacements and phonon dispersions. Values of ab initio computed critical energy release rates and crack opening profiles revealed that the length l1 is related to inflexion points of profiles. A novel ab initio method in combination with continuum mechanics was successfully tested to replace molecular statics dependent of availability of interatomic potentials. The asymptotic strain gradient elasticity solution for displacement components near the crack tip in materials with cubic lattice was also derived. 相似文献