Vortex dynamics differences due to twin-boundary pinning anisotropy in YBa2Cu3Ox at low temperatures for H parallel to ab planes

We measured the magnetization M of a twin-aligned single crystal of YBa2Cu3Ox (YBaCuO), with T-c=91 K, as a function of temperature T and magnetic field H, with H applied along the ab planes. Isothermal M-vs-H and M-vs-time curves were obtained with H applied parallel (parallel to) and perpendicular (perpendicular to) to the twin boundary (TB) direction. M-vs-H curves exhibited two minima below 38 K, which resembled similar curves that have been obtained in YBaCuO for Hparallel toc axis. Above 12 K, the field positions of the minima for Hparallel toTB and Hperpendicular toTB were quite similar. Below 12 K, the position of the second minimum H-min occurred at a higher field value with Hparallel toTB. Below 6 K, only one minimum appeared for both field directions. At low temperatures, these minima in the M-vs-H curves produced maxima in the critical current. It was determined that vortex lines were expelled more easily for Hparallel toTB than for Hperpendicular toTB and, therefore, below a certain field value, that J(c)(Hperpendicular toTB) was larger than J(c)(Hparallel toTB). At T<12 K with Hparallel toTB, the relaxation rate for flux lines leaving the crystal was found to be different from that for flux entering the crystal. We also observed flux jumps at low temperatures, with their sizes depending on the orientation of magnetic field with respect to the TB's.71

Processing Considerations for Adding Nanometer-Scale Oxides to Enhance Flux Pinning in High-Temperature Superconductors

Several nanometer-scale oxide inclusions were added to Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} high-temperature superconductors to determine their effectiveness in creating intragranular flux-pinning sites. Powder pellets were fabricated and heat treated by partial-melt processing. Effects of the additives on melting response, superconducting properties, and microstructural development were examined. Al{sub 2}O{sub 3} additions exhibited the most promise for forming stable pinning centers, ZrO{sub 2} and SnO{sub 2} additions were moderately promising, TiO{sub 2}, Fe{sub 2}O{sub 3}, and ZnO additions were less promising, and Y{sub 2}O{sub 3} additions destroyed superconductivity

Masquelier's grape seed extract:from basic flavonoid research to a well-characterized food supplement with health benefits

Careful characterization and standardization of the composition of plant-derived food supplements is essential to establish a cause-effect relationship between the intake of that product and its health effect. In this review we follow a specific grape seed extract containing monomeric and oligomeric flavan-3-ols from its creation by Jack Masquelier in 1947 towards a botanical remedy and nutraceutical with proven health benefits. The preparation’s research history parallels the advancing insights in the fields of molecular biology, medicine, plant and nutritional sciences during the last 70 years. Analysis of the extract’s flavanol composition emerged from unspecific colorimetric assays to precise high performance liquid chromatography - mass spectrometry and proton nuclear magnetic resonance fingerprinting techniques. The early recognition of the preparation’s auspicious effects on the permeability of vascular capillaries directed research to unravel the underlying cellular and molecular mechanisms. Recent clinical data revealed a multitude of favorable alterations in the vasculature upon an 8 weeks supplementation which summed up in a health benefit of the extract in healthy humans. Changes in gene expression of inflammatory pathways in the volunteers’ leukocytes were suggested to be involved in this benefit. The historically grown scientific evidence for the preparation’s health effects paves the way to further elucidate its metabolic fate and molecular action in humans