785 research outputs found
A general scaling relation for the critical current density in Nb3Sn
We review the scaling relations for the critical current density (Jc) in
Nb3Sn wires and include recent findings on the variation of the upper critical
field (Hc2) with temperature (T) and A15 composition. We highlight deficiencies
in the Summers/Ekin relations, which are not able to account for the correct
Jc(T) dependence. Available Jc(H) results indicate that the magnetic field
dependence for all wires can be described with Kramer's flux shear model, if
non-linearities in Kramer plots are attributed to A15 inhomogeneities. The
strain (eps) dependence is introduced through a temperature and strain
dependent Hc2*(T,eps) and Ginzburg- Landau parameter kappa1(T,eps) and a strain
dependent critical temperature Tc(eps). This is more consistent than the usual
Ekin unification, which uses two separate and different dependencies on Hc2*(T)
and Hc2*(eps). Using a correct temperature dependence and accounting for the
A15 inhomogeneities leads to a remarkable simple relation for Jc(H,T,eps).
Finally, a new relation for s(eps) is proposed, based on the first, second and
third strain invariants.Comment: Accepted Topical Review for Superconductor, Science and Technolog
Challenges to alcohol and other drug discussions in the general practice consultation
Background. There is a widely held expectation that GPs will routinely use opportunities to provide opportunistic screening and brief intervention for alcohol and other drug (AOD) abuse, a major cause of preventable death and morbidity
Core pinning by intragranular nanoprecipitates in polycrystalline MgCNi_3
The nanostructure and magnetic properties of polycrystalline MgCNi_3 were
studied by x-ray diffraction, electron microscopy, and vibrating sample
magnetometry. While the bulk flux-pinning force curve F_p(H) indicates the
expected grain-boundary pinning mechanism just below T_c = 7.2 K, a systematic
change to pinning by a nanometer-scale distribution of core pinning sites is
indicated by a shift of F_p(H) with decreasing temperature. The lack of scaling
of F_p(H) suggests the presence of 10 to 20% of nonsuperconducting regions
inside the grains, which are smaller than the diameter of fluxon cores 2xi at
high temperature and become effective with decreasing temperature when xi(T)
approaches the nanostructural scale. Transmission electron microscopy revealed
cubic and graphite nanoprecipitates with 2 to 5 nm size, consistent with the
above hypothesis since xi(0) = 6 nm. High critical current densities, more than
10^6 A/cm^2 at 1 T and 4.2 K, were obtained for grain colonies separated by
carbon. Dirty-limit behavior seen in previous studies may be tied to electron
scattering by the precipitates, indicating the possibility that strong core
pinning might be combined with a technologically useful upper critical field if
versions of MgCNi_3 with higher T_c can be found.Comment: 5 pages, 6 figures, submitted to PR
Influence of nonlocal electrodynamics on the anisotropic vortex pinning in
We have studied the pinning force density Fp of YNi_2B_2C superconductors for
various field orientations. We observe anisotropies both between the c-axis and
the basal plane and within the plane, that cannot be explained by usual mass
anisotropy. For magnetic field , the reorientation structural
transition in the vortex lattice due to nonlocality, which occurs at a field
, manifests itself as a kink in Fp(H). When , Fp is
much larger and has a quite different H dependence, indicating that other
pinning mechanisms are present. In this case the signature of nonlocal effects
is the presence of a fourfold periodicity of Fp within the basal plane.Comment: 4 pages, 3 figure
Psychological Outcomes of Living Liver Donors From a Multicenter Prospective Study: Results From the Adult‐to‐Adult Living Donor Liver Transplantation Cohort Study2 (A2ALL‐2)
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136736/1/ajt14134_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136736/2/ajt14134.pd
High magnetic field scales and critical currents in SmFeAs(O,F) crystals: promising for applications
Superconducting technology provides most sensitive field detectors, promising
implementations of qubits and high field magnets for medical imaging and for
most powerful particle accelerators. Thus, with the discovery of new
superconducting materials, such as the iron pnictides, exploring their
potential for applications is one of the foremost tasks. Even if the critical
temperature Tc is high, intrinsic electronic properties might render
applications rather difficult, particularly if extreme electronic anisotropy
prevents effective pinning of vortices and thus severely limits the critical
current density, a problem well known for cuprates. While many questions
concerning microscopic electronic properties of the iron pnictides have been
successfully addressed and estimates point to a very high upper critical field,
their application potential is less clarified. Thus we focus here on the
critical currents, their anisotropy and the onset of electrical dissipation in
high magnetic fields up to 65 T. Our detailed study of the transport properties
of optimally doped SmFeAs(O,F) single crystals reveals a promising combination
of high (>2 x 10^6 A/cm^2) and nearly isotropic critical current densities
along all crystal directions. This favorable intragrain current transport in
SmFeAs(O,F), which shows the highest Tc of 54 K at ambient pressure, is a
crucial requirement for possible applications. Essential in these experiments
are 4-probe measurements on Focused Ion Beam (FIB) cut single crystals with
sub-\mu\m^2 cross-section, with current along and perpendicular to the
crystallographic c-axis and very good signal-to-noise ratio (SNR) in pulsed
magnetic fields. The pinning forces have been characterized by scaling the
magnetically measured "peak effect"
Social and Financial Outcomes of Living Liver Donation: A Prospective Investigation Within the Adult‐to‐Adult Living Donor Liver Transplantation Cohort Study 2 (A2ALL‐2)
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136356/1/ajt14055_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136356/2/ajt14055.pd
Pleiotropic functions of the tumor- and metastasis-suppressing Matrix Metalloproteinase-8 in mammary cancer in MMTV-PyMT transgenic mice
Matrix metalloproteinase-8 (MMP-8; neutrophil collagenase) is an important regulator of innate immunity which has onco-suppressive actions in numerous tumor types
Linking larval transport and fisheries demographic models to study the influence of environmental variability and larval behavior on juvenile recruitment to oyster populations
Abstract Annual variations in freshwater flow and wind may influence the dispersal of oyster larvae (by affecting circulation patterns) and the survival of adults (by influencing salinity-dependent disease mortality) in Chesapeake Bay, a region whose oyster fishery has greatly declined. These observations suggest that environmental variability has important implications for rehabilitation efforts that involve enhancing native oyster broodstock. We tested this hypothesis for the eastern oyster Crassostrea virginica by linking larval transport and fisheries demographic models. Physical conditions in both models were based on five years with differing wind and freshwater flow patterns (1995)(1996)(1997)(1998)(1999). The larval transport model predicted spatial settlement patterns by using a particle tracking model parameterized with larval behaviors discerned in preliminary analysis of ongoing laboratory studies. The demographic model incorporated estimates of stockrecruitment relationships, growth, natural mortality, disease mortality, fishing mortality, and the effect of extreme events such as freshets. A validation analysis of the linked models compared predictions of juvenile oyster settlement success with field observations from 1995 to1999. Larval transport model results indicated that settlement success of C. virginica larvae was influenced by freshwater flow conditions, with larval settlement higher in low freshwater flow years. The validation analysis indicated that including spawning stock abundance and mortality estimates in the linked larvaltransport-demographic model may have improved predictions of juvenile recruitment. Our linked model could be used to assess risks associated with introducing a new species and guide oyster management activities such as locating brood stock sanctuaries and managing harvest in response to climate variability
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