31,079 research outputs found
Anisotropic superconducting properties of aligned SmLaFeAsOF microcrystalline powder
The SmLaFeAsOF compound is a quasi-2D
layered superconductor with a superconducting transition temperature T = 52
K. Due to the Fe spin-orbital related anisotropic exchange coupling
(antiferromagnetic or ferromagnetic fluctuation), the tetragonal
microcrystalline powder can be aligned at room temperature using the
field-rotation method where the tetragonal -plane is parallel to the
aligned magnetic field B and -axis along the rotation axis.
Anisotropic superconducting properties with anisotropic diamagnetic ratio
2.4 + 0.6 was observed from low field susceptibility
(T) and magnetization M(B). The anisotropic low-field phase diagram
with the variation of lower critical field gives a zero-temperature penetration
depth (0) = 280 nm and (0) = 120 nm. The magnetic
fluctuation used for powder alignment at 300 K may be related with the pairing
mechanism of superconductivity at lower temperature.Comment: 4 pages, 6 figure
Recommended from our members
Rainfall frequency analysis for ungauged regions using remotely sensed precipitation information
Rainfall frequency analysis, which is an important tool in hydrologic engineering, has been traditionally performed using information from gauge observations. This approach has proven to be a useful tool in planning and design for the regions where sufficient observational data are available. However, in many parts of the world where ground-based observations are sparse and limited in length, the effectiveness of statistical methods for such applications is highly limited. The sparse gauge networks over those regions, especially over remote areas and high-elevation regions, cannot represent the spatiotemporal variability of extreme rainfall events and hence preclude developing depth-duration-frequency curves (DDF) for rainfall frequency analysis. In this study, the PERSIANN-CDR dataset is used to propose a mechanism, by which satellite precipitation information could be used for rainfall frequency analysis and development of DDF curves. In the proposed framework, we first adjust the extreme precipitation time series estimated by PERSIANN-CDR using an elevation-based correction function, then use the adjusted dataset to develop DDF curves. As a proof of concept, we have implemented our proposed approach in 20 river basins in the United States with different climatic conditions and elevations. Bias adjustment results indicate that the correction model can significantly reduce the biases in PERSIANN-CDR estimates of annual maximum series, especially for high elevation regions. Comparison of the extracted DDF curves from both the original and adjusted PERSIANN-CDR data with the reported DDF curves from NOAA Atlas 14 shows that the extreme percentiles from the corrected PERSIANN-CDR are consistently closer to the gauge-based estimates at the tested basins. The median relative errors of the frequency estimates at the studied basins were less than 20% in most cases. Our proposed framework has the potential for constructing DDF curves for regions with limited or sparse gauge-based observations using remotely sensed precipitation information, and the spatiotemporal resolution of the adjusted PERSIANN-CDR data provides valuable information for various applications in remote and high elevation areas
Ab initio many-body calculations of nucleon scattering on 4He, 7Li, 7Be, 12C and 16O
We combine a recently developed ab initio many-body approach capable of
describing simultaneously both bound and scattering states, the ab initio
NCSM/RGM, with an importance truncation scheme for the cluster eigenstate basis
and demostrate its applicability to nuclei with mass numbers as high as 17.
Using soft similarity renormalization group evolved chiral nucleon-nucleon
interactions, we first calculate nucleon-4He phase shifts, cross sections and
analyzing power. Next, we investigate nucleon scattering on 7Li, 7Be, 12C and
16O in coupled-channel NCSM/RGM calculations that include low-lying excited
states of these nuclei. We check the convergence of phase shifts with the basis
size and study A=8, 13, and 17 bound and unbound states. Our calculations
predict low-lying resonances in 8Li and 8B that have not been experimentally
clearly identified yet. We are able to reproduce reasonably well the structure
of the A=13 low lying states. However, we find that A=17 states cannot be
described without an improved treatment of 16O one-particle-one-hole
excitations and alpha clustering.Comment: 18 pages, 20 figure
Recrystallization of epitaxial GaN under indentation
We report recrystallization of epitaxial (epi-) GaN(0001) film under
indentation.Hardness value is measured close to 10 GPa, using a Berkovich
indenter. Pop-in burst in the loading line indicates nucleation of dislocations
setting in plastic motion of lattice atoms under stress field for the
recrystallization process. Micro-Raman studies are used to identify the
recrystallization process. Raman area mapping indicates the crystallized
region. Phonon mode corresponding to E2(high) close to 570 cm-1 in the as-grown
epi-GaN is redshifted to stress free value close to 567 cm-1 in the indented
region. Evolution of A1(TO) and E1(TO) phonon modes are also reported to
signify the recrystallization process.Comment: 10 pages, 3 figures
Surface optical Raman modes in InN nanostructures
Raman spectroscopic investigations are carried out on one-dimensional
nanostructures of InN,such as nanowires and nanobelts synthesized by chemical
vapor deposition. In addition to the optical phonons allowed by symmetry; A1,
E1 and E2(high) modes, two additional Raman peaks are observed around 528 cm-1
and 560 cm-1 for these nanostructures. Calculations for the frequencies of
surface optical (SO) phonon modes in InN nanostructures yield values close to
those of the new Raman modes. A possible reason for large intensities for SO
modes in these nanostructures is also discussed.Comment: 13 pages, 4 figures, Submitted in Journa
Violating conformal invariance: Two-dimensional clusters grafted to wedges, cones, and branch points of Riemann surfaces
We present simulations of 2-d site animals on square and triangular lattices
in non-trivial geomeLattice animals are one of the few critical models in
statistical mechanics violating conformal invariance. We present here
simulations of 2-d site animals on square and triangular lattices in
non-trivial geometries. The simulations are done with the newly developed PERM
algorithm which gives very precise estimates of the partition sum, yielding
precise values for the entropic exponent (). In particular, we studied animals grafted to the tips of wedges
with a wide range of angles , to the tips of cones (wedges with the
sides glued together), and to branching points of Riemann surfaces. The latter
can either have sheets and no boundary, generalizing in this way cones to
angles degrees, or can have boundaries, generalizing wedges. We
find conformal invariance behavior, , only for small
angles (), while for
. These scalings hold both for wedges and cones. A heuristic
(non-conformal) argument for the behavior at large is given, and
comparison is made with critical percolation.Comment: 4 pages, includes 3 figure
- …