14,777 research outputs found
Superconducting gap symmetry of Ba0.6K0.4Fe2As2 studied by angle-resolved photoemission spectroscopy
We have performed high-resolution angle-resolved photoemission spectroscopy
on the optimally-doped BaKFeAs compound and determined
the accurate momentum dependence of the superconducting (SC) gap in four
Fermi-surface sheets including a newly discovered outer electron pocket at the
M point. The SC gap on this pocket is nearly isotropic and its magnitude is
comparable ( 11 meV) to that of the inner electron and hole
pockets (12 meV), although it is substantially larger than that of the
outer hole pocket (6 meV). The Fermi-surface dependence of the SC gap
value is basically consistent with () = coscos
formula expected for the extended s-wave symmetry. The observed finite
deviation from the simple formula suggests the importance of multi-orbital
effects.Comment: 4 pages, 3 figures, 1 tabl
Integration of embryo–endosperm interaction into a holistic and dynamic picture of seed development using a rice mutant with notched-belly kernels
Interaction between the embryo and endosperm affects seed development, an essential process in yield formation in crops such as rice. Signals that mediate communication between embryo and endosperm are largely unknown. We used the notched-belly (NB) mutant with impaired communication between embryo and endosperm to investigate the effect of the embryo on developmental staging of the endosperm and signaling pathways in the embryo that regulate endosperm development. Hierachical clustering of mRNA datasets from embryo and endosperm samples collected during development in NB and a wild type showed a delaying effect of the embryo on the developmental transition of the endosperm by extension of the middle stage. K-means clustering further identified coexpression modules of gene sets specific to embryo and endosperm development. Combined gene expression and biochemical analysis showed that T6P–SnRK1, gibberellin and auxin signaling by the embryo regulate endosperm developmental transition. We propose a new seed developmental staging system for rice and identify the most detailed signature of rice grain formation to date. These will direct genetic strategies for rice yield improvement
Symbolic Dynamics Analysis of the Lorenz Equations
Recent progress of symbolic dynamics of one- and especially two-dimensional
maps has enabled us to construct symbolic dynamics for systems of ordinary
differential equations (ODEs). Numerical study under the guidance of symbolic
dynamics is capable to yield global results on chaotic and periodic regimes in
systems of dissipative ODEs which cannot be obtained neither by purely
analytical means nor by numerical work alone. By constructing symbolic dynamics
of 1D and 2D maps from the Poincare sections all unstable periodic orbits up to
a given length at a fixed parameter set may be located and all stable periodic
orbits up to a given length may be found in a wide parameter range. This
knowledge, in turn, tells much about the nature of the chaotic limits. Applied
to the Lorenz equations, this approach has led to a nomenclature, i.e.,
absolute periods and symbolic names, of stable and unstable periodic orbits for
an autonomous system. Symmetry breakings and restorations as well as
coexistence of different regimes are also analyzed by using symbolic dynamics.Comment: 35 pages, LaTeX, 13 Postscript figures, uses psfig.tex. The revision
concerns a bug at the end of hlzfig12.ps which prevented the printing of the
whole .ps file from page 2
Thermodynamic properties of Ba1-xMxFe2As2 (M = La and K)
The specific heat of BaFeAs single crystal, electron-doped
BaLaFeAs and hole-doped BaKFeAs
polycrystals were measured. For undoped BaFeAs single crystal, a very
sharp specific heat peak was observed at 136 K. This is attributed to the
structural and antiferromagnetic transitions occurring at the same temperature.
of the electron-doped non-superconducting
BaLaFeAs also shows a small peak at 120 K, indicating a
similar but weaker structural/antiferromagnetic transition. For the hole-doped
superconducting BaKFeAs, a clear peak of was
observed at = 36 K, which is the highest peak seen at superconducting
transition for iron-based high- superconductors so far. The electronic
specific heat coefficient and Debye temperature of these
compounds were obtained from the low temperature data
Comparison Between Electropositive and Electronegative Cold Atmospheric-Pressure Plasmas: A Modelling Study
Cold atmospheric-pressure He + N2 and He + O2 plasmas are chosen as the representatives for electropositive and electronegative plasmas, of which the discharge characteristics are studied and then compared to each other by fluid models. As the increase of the impurity (N2 or O2) fraction from 0 to 10%, for He + N2 plasmas the electron density and ion density increase, the spatiotemporal distributions of electron density, ion density, electron temperature and electron generation rate change a little. On contrast, for He + O2 plasmas the electron density decreases, the ion density first increases and then decreases, the electron temperature increases in the bulk region, but decreases in the sheath region, and the plasmas transform from ᵞ mode to α mode as the significant change of electron generation rate distributions. Larger electric field is needed in the bulk region to sustain the electronegative plasma, so the electrical characteristics of He + O2 plasmas transform form capacitive to resistive with increasing O2fraction. Meanwhile, the ion-coupling power increases dramatically, which can be estimated by a formula based on the electronegativity. A new criterion for determining the sheath boundary, |ΔE| = 5 kV/cm2, is put forward, which is found suitable for both the electropositive and electronegative plasmas
Bayesian Centroid Estimation for Motif Discovery
Biological sequences may contain patterns that are signal important
biomolecular functions; a classical example is regulation of gene expression by
transcription factors that bind to specific patterns in genomic promoter
regions. In motif discovery we are given a set of sequences that share a common
motif and aim to identify not only the motif composition, but also the binding
sites in each sequence of the set. We present a Bayesian model that is an
extended version of the model adopted by the Gibbs motif sampler, and propose a
new centroid estimator that arises from a refined and meaningful loss function
for binding site inference. We discuss the main advantages of centroid
estimation for motif discovery, including computational convenience, and how
its principled derivation offers further insights about the posterior
distribution of binding site configurations. We also illustrate, using
simulated and real datasets, that the centroid estimator can differ from the
maximum a posteriori estimator.Comment: 24 pages, 9 figure
Electronic excitations in BiSrCaCuO : Fermi surface, dispersion, and absence of bilayer splitting
From a detailed study, including polarization dependence, of the normal state
angle-resolved photoemission spectra for BiSrCaCuO, we find
only one CuO band related feature. All other spectral features can be
ascribed either to umklapps from the superlattice or to ``shadow bands''. Even
though the dispersion of the peaks looks like band theory, the lineshape is
anomalously broad and no evidence is found for bilayer splitting. We argue that
the ``dip feature'' in the spectrum below arises not from bilayer
splitting, but rather from many body effects.Comment: 4 pages, revtex, 3 uuencoded postscript figure
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