2,129 research outputs found
Anisotropic properties of MgB2 by torque magnetometry
Anisotropic properties of superconducting MgB2 obtained by torque
magnetometry are compared to theoretical predictions, concentrating on two
issues. Firstly, the angular dependence of Hc2 is shown to deviate close to Tc
from the dependence assumed by anisotropic Ginzburg-Landau theory. Secondly,
from the evaluation of torque vs angle curves it is concluded that the
anisotropy of the penetration depth gamma_lambda has to be substantially higher
at low temperature than theoretical estimates, at least in fields higher than
0.2 T.Comment: 2 p.,2 Fig., submitted to Physica C (M2S-Rio proceedings); v2: 1 ref
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Differential thermal analysis and solution growth of intermetallic compounds
To obtain single crystals by solution growth, an exposed primary
solidification surface in the appropriate, but often unknown, equilibrium alloy
phase diagram is required. Furthermore, an appropriate crucible material is
needed, necessary to hold the molten alloy during growth, without being
attacked by it. Recently, we have used the comparison of realistic simulations
with experimental differential thermal analysis (DTA) curves to address both
these problems. We have found: 1) complex DTA curves can be interpreted to
determine an appropriate heat treatment and starting composition for solution
growth, without having to determine the underlying phase diagrams in detail. 2)
DTA can facilitate identification of appropriate crucible materials. DTA can
thus be used to make the procedure to obtain single crystals of a desired phase
by solution growth more efficient. We will use some of the systems for which we
have recently obtained single-crystalline samples using the combination of DTA
and solution growth as examples. These systems are TbAl, PrNiSi,
and YMnAl.Comment: 17 pages, 8 figure
Ichthyofaunal Utilization of a Man-Made Salt Marsh Creek in Mission Bay, California, 25 Years After Creation
Abstract: Southern California\u27s wetlands are drastically declining due to human activities. Increasingly, marsh restoration and creation are being used to mitigate such losses. This study used minnow traps to resample the ichthyofauna of a created marsh (Crown Point Mitigation Site; CPMS) and an adjacent natural marsh (Kendall Frost) in Mission Bay, California, 26 years following the marsh creation. These data were compared to data collected from 1995-1998, immediately after marsh creation. Fishes trapped included Fundulus parvipinnis, Gillichthys mirabilis, Ctenogobius sagittula, Atherinops affinis, and Mugil cephalus. Species richness and dominance measures were higher in the natural relative to the created marsh. The size-structure of F. parvipinnis in the natural marsh was skewed towards larger sizes relative to those in the created marsh. These size differences are the opposite of those noted in the years immediately following marsh creation and appear to arise from differences in creek morphology between the created and natural systems, with the created marsh having become shallower through time. The differences in size-structure and species richness between the created and natural systems suggest that marsh and creek geomorphology may affect the suitability of habitat for resident fishes, and so should be considered when designing marsh restoration projects
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