13,313 research outputs found
Ionization states of heavy elements observed in the 1974 May 14-15 anomalous solar particle event
The charge states of heavy ions accelerated in the (3)He-Fe rich solar particle event of 1974 May 14-15 are determined using data from the Interplanetary Monitoring Platform-8. In addition to Fe(+11,12) both 0(+5) and Fe(+16,17,18) are also present suggesting variations in coronal temperatures over a range from approximately 400,000 to 5,000,000 K. The presence of 0(+5) and Fe(+16-18) may be explained by a resonant plasma heating mechanism proposed to account for the enhancements of (3)He and Fe
Robust nodal superconductivity induced by isovalent doping in Ba(FeRu)As and BaFe(AsP)
We present the ultra-low-temperature heat transport study of iron-based
superconductors Ba(FeRu)As and
BaFe(AsP). For optimally doped
Ba(FeRu)As, a large residual linear term
at zero field and a dependence of are observed,
which provide strong evidences for nodes in the superconducting gap. This
result demonstrates that the isovalent Ru doping can also induce nodal
superconductivity, as P does in BaFe(AsP).
Furthermore, in underdoped Ba(FeRu)As and heavily
underdoped BaFe(AsP), manifests similar
nodal behavior, which shows the robustness of nodal superconductivity in the
underdoped regime and puts constraint on theoretical models.Comment: 5 pages, 4 figures - with two underdoped samples added, this paper
supersedes arXiv:1106.541
P1 finite element methods for an elliptic state-constrained distributed optimal control problem with Neumann boundary conditions
We investigate two P finite element methods for an elliptic state-constrained distributed optimal control problem with Neumann boundary conditions on general polygonal domains.
Microstructure and superconducting properties of hot isostatically pressed MgB2
Bulk samples of MgB2 have been formed by hot isostatic pressing (HIPping) of
commercial powder at 100MPa and 950=B0C. The resulting material is 100% dense
with a sharp superconducting transition at 37.5K. Microstructural studies have
indicated the presence of small amounts of second phases within the material,
namely MgO and B rich compositions, probably MgB4. Magnetisation measurements
performed at 20K have revealed values of Jc=1.3 x 106A/cm2 at zero field, and
9.3 x 105A/cm2 at 1T. Magneto optical (MO) studies have shown direct evidence
for the superconducting homogeneity and strong intergranular current flow in
the material.Comment: 3 pages, 6 figures, text updated, new references included and
discussed. Submitted to Superconductor Science and Technolog
20 K superconductivity in heavily electron doped surface layer of FeSe bulk crystal
A superconducting transition temperature Tc as high as 100 K was recently
discovered in 1 monolayer (1ML) FeSe grown on SrTiO3 (STO). The discovery
immediately ignited efforts to identify the mechanism for the dramatically
enhanced Tc from its bulk value of 7 K. Currently, there are two main views on
the origin of the enhanced Tc; in the first view, the enhancement comes from an
interfacial effect while in the other it is from excess electrons with strong
correlation strength. The issue is controversial and there are evidences that
support each view. Finding the origin of the Tc enhancement could be the key to
achieving even higher Tc and to identifying the microscopic mechanism for the
superconductivity in iron-based materials. Here, we report the observation of
20 K superconductivity in the electron doped surface layer of FeSe. The
electronic state of the surface layer possesses all the key spectroscopic
aspects of the 1ML FeSe on STO. Without any interface effect, the surface layer
state is found to have a moderate Tc of 20 K with a smaller gap opening of 4
meV. Our results clearly show that excess electrons with strong correlation
strength alone cannot induce the maximum Tc, which in turn strongly suggests
need for an interfacial effect to reach the enhanced Tc found in 1ML FeSe/STO.Comment: 5 pages, 4 figure
IL-12 priming during initial antigen contact increases generation of effector and memory CD8 T cells by changing properties
open11sciescopu
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