93 research outputs found
A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State
This article gives an overview of the available literature on simplified,
well defined (quasi-)homogeneous laboratory samples. After more than 50 years
of research on superconductivity in Nb3Sn, a significant amount of results are
available, but these are scattered over a multitude of publications. Two
reviews exist on the basic properties of A15 materials in general, but no
specific review for Nb3Sn is available. This article is intended to provide
such an overview. It starts with a basic description of the Niobium-Tin
intermetallic. After this it maps the influence of Sn content on the the
electron-phonon interaction strength and on the field-temperature phase
boundary. The literature on the influence of Cu, Ti and Ta additions will then
be briefly summarized. This is followed by a review on the effects of grain
size and strain. The article is concluded with a summary of the main results.Comment: Invited Topical Review for Superconductor, Science and Technology.
Provisionally scheduled for July 200
Characterization of 4-HNE Modified L-FABP Reveals Alterations in Structural and Functional Dynamics
4-Hydroxynonenal (4-HNE) is a reactive α,β-unsaturated aldehyde produced during oxidative stress and subsequent lipid peroxidation of polyunsaturated fatty acids. The reactivity of 4-HNE towards DNA and nucleophilic amino acids has been well established. In this report, using proteomic approaches, liver fatty acid-binding protein (L-FABP) is identified as a target for modification by 4-HNE. This lipid binding protein mediates the uptake and trafficking of hydrophobic ligands throughout cellular compartments. Ethanol caused a significant decrease in L-FABP protein (P<0.001) and mRNA (P<0.05), as well as increased poly-ubiquitinated L-FABP (P<0.001). Sites of 4-HNE adduction on mouse recombinant L-FABP were mapped using MALDI-TOF/TOF mass spectrometry on apo (Lys57 and Cys69) and holo (Lys6, Lys31, His43, Lys46, Lys57 and Cys69) L-FABP. The impact of 4-HNE adduction was found to occur in a concentration-dependent manner; affinity for the fluorescent ligand, anilinonaphthalene-8-sulfonic acid, was reduced from 0.347 µM to Kd1 = 0.395 µM and Kd2 = 34.20 µM. Saturation analyses revealed that capacity for ligand is reduced by approximately 50% when adducted by 4-HNE. Thermal stability curves of apo L-FABP was also found to be significantly affected by 4-HNE adduction (ΔTm = 5.44°C, P<0.01). Computational-based molecular modeling simulations of adducted protein revealed minor conformational changes in global protein structure of apo and holo L-FABP while more apparent differences were observed within the internal binding pocket, revealing reduced area and structural integrity. New solvent accessible portals on the periphery of the protein were observed following 4-HNE modification in both the apo and holo state, suggesting an adaptive response to carbonylation. The results from this study detail the dynamic process associated with L-FABP modification by 4-HNE and provide insight as to how alterations in structural integrity and ligand binding may a contributing factor in the pathogenesis of ALD
Thin Film Magnesium Boride Superconductor with Very High Critical Current Density and Enhanced Irreversibility Field
The discovery of superconductivity at 39 K in magnesium diboride offers the
possibility of a new class of low-cost, high-performance superconducting
materials for magnets and electronic applications. With twice the critical
temperature of Nb_3Sn and four times that of Nb-Ti alloy, MgB_2 has the
potential to reach much higher fields and current densities than either of
these technological superconductors. A vital prerequisite, strongly linked
current flow, has already been demonstrated even at this early stage. One
possible drawback is the observation that the field at which superconductivity
is destroyed is modest. Further, the field which limits the range of practical
applications, the irreversibility field H*(T), is ~7 T at liquid helium
temperature (4.2 K), significantly lower than ~10 T for Nb-Ti and ~20 T for
Nb_3Sn. Here we show that MgB_2 thin films can exhibit a much steeper
temperature dependence of H*(T) than is observed in bulk materials, yielding
H*(4.2 K) above 14 T. In addition, very high critical current densities at 4.2
K, 1 MA/cm_2 at 1 T and 10_5 A/cm_2 at 10 T, are possible. These data
demonstrate that MgB_2 has credible potential for high-field superconducting
applications.Comment: 4 pages pdf, submitted to Nature 3/20/0
Electronic anisotropy, magnetic field-temperature phase diagram and their dependence on resistivity in c-axis oriented MgB2 thin films
An important predicted, but so far uncharacterized, property of the new
superconductor MgB2 is electronic anisotropy arising from its layered crystal
structure. Here we report on three c-axis oriented thin films, showing that the
upper critical field anisotropy ratio Hc2par/Hc2perp is 1.8 to 2.0, the ratio
increasing with higher resistivity. Measurements of the magnetic
field-temperature phase diagram show that flux pinning disappears at H* ~
0.8Hc2perp(T) in untextured samples. Hc2par(0) is strongly enhanced by alloying
to 39 T for the highest resistivity film, more than twice that seen in bulk
samples.Comment: 5 pages Acrobat 3.02 pd
X-ray detector based on a bulk micromachined photodiode combined with a scintillating crystal
This paper reports the design, fabrication, assembly and testing of
a x-ray detector based on a bulk micromachined photodiode (BMMPD)
with a cavity filled with a scintillating crystal. The x-ray photons
that reach the detector are first converted to visible light by the
scintillating crystal. The visible light is then detected by the BMMPD,
producing an electric current with value proportional to the
incident x-ray intensity. Tests were performed using two x-ray setups:
an experimental one and a professional one.
The first was powered with a maximum voltage of 35kV, and a
current ranging to 1mA and the second was powered with voltages from
40kV to 60kV and currents ranging from 10mA to 55mA
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