8,848 research outputs found
Existence of periodic solutions for the Lotka-Volterra type systems
In this paper we prove the existence of non-stationary periodic solutions of
delay Lotka-Volterra equations. In the proofs we use the degree for
-equivariant maps
Potential Profiling of the Nanometer-Scale Charge Depletion Layer in n-ZnO/p-NiO Junction Using Photoemission Spectroscopy
We have performed a depth-profile analysis of an all-oxide p-n junction diode
n-ZnO/p-NiO using photoemission spectroscopy combined with Ar-ion sputtering.
Systematic core-level shifts were observed during the gradual removal of the
ZnO overlayer, and were interpreted using a simple model based on charge
conservation. Spatial profile of the potential around the interface was
deduced, including the charge-depletion width of 2.3 nm extending on the ZnO
side and the built-in potential of 0.54 eV
Onset of Melting in Quark-Gluon Fluid at RHIC
A strong suppression in central Au+Au collisions has been observed
by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). We
develop a hydro+ model in which hot quark-gluon matter is described by
the full (3+1)-dimensional relativistic hydrodynamics and is treated
as an impurity traversing through the matter. The experimental
suppression pattern in mid-rapidity is reproduced well by the sequential
melting of , , and in dynamically expanding
fluid. The melting temperature of directly produced is well
constrained by the participant-number dependence of the suppression
and is found to be about with being the
pseudo-critical temperature.Comment: 5 pages, 5 figures, Submitted to Phys. Rev. C. (Rapid Communication
In vitro reactivation of spindle elongation in fission yeast nuc2 mutant cells.
To investigate the mechanisms of spindle elongation and chromosome separation in the fission yeast Schizosaccharomyces pombe, we have developed an in vitro assay using a temperature-sensitive mutant strain, nuc2. At the restrictive temperature, nuc2 cells are arrested at a metaphase-like stage with short spindles and condensed chromosomes. After permeabilization of spheroplasts of the arrested cells, spindle elongation was reactivated by addition of ATP and neurotubulin both at the restrictive and the permissive temperatures, but chromosome separation was not. This suggests that the nuc2 cells are impaired in function at a stage before sister chromatid disjunction. Spindle elongation required both ATP and exogenous tubulin and was inhibited by adenylyl imidodiphosphate (AMPPNP) or vanadate. The ends of yeast half-spindle microtubules pulse-labeled with biotinylated tubulin moved past each other during spindle elongation and a gap formed between the original half-spindles. These results suggest that the primary mechanochemical event responsible for spindle elongation is the sliding apart of antiparallel microtubules of the two half-spindles
Analysis of one- and two-particle spectra at RHIC based on a hydrodynamical model
We calculate the one-particle hadronic spectra and correlation functions of
pions based on a hydrodynamical model. Parameters in the model are so chosen
that the one-particle spectra reproduce experimental results of
GeV Au+Au collisions at RHIC. Based on the numerical solution,
we discuss the space-time evolution of the fluid. Two-pion correlation
functions are also discussed. Our numerical solution suggests the formation of
the quark-gluon plasma with large volume and low net baryon density.Comment: LaTeX, 4pages, 4 figures. To appear in the proceedings of Fourth
International Conference on Physics and Astrophysics of Quark-Gluon Plasma
(ICPAQGP-2001), Nov 26-30, 2001, Jaipur, Indi
Can transport peak explain the low-mass enhancement of dileptons at RHIC?
We propose a novel relation between the low-mass enhancement of dielectrons
observed at PHENIX and transport coefficients of QGP such as the charge
diffusion constant and the relaxation time . We parameterize
the transport peak in the spectral function using the second-order relativistic
dissipative hydrodynamics by Israel and Stewart. Combining the spectral
function and the full (3+1)-dimensional hydrodynamical evolution with the
lattice EoS, theoretical dielectron spectra and the experimental data are
compared. Detailed analysis suggests that the low-mass dilepton enhancement
originates mainly from the high-temperature QGP phase where there is a large
electric charge fluctuation as obtained from lattice QCD simulations.Comment: To appear in the conference proceedings for Quark Matter 2011, May 23
- May 28, Annecy, Franc
Mechanism of phase transitions and the electronic density of states in (La,Sm)FeAsOF from ab initio calculations
The structure and electronic density of states in layered
LnFeAsOF (Ln=La,Sm; =0.0, 0.125, 0.25) are investigated using
density functional theory. For the =0.0 system we predict a complex
potential energy surface, formed by close-lying single-well and double-well
potentials, which gives rise to the tetragonal-to-orthorhombic structural
transition, appearance of the magnetic order, and an anomaly in the specific
heat capacity observed experimentally at temperatures below 140--160 K.
We propose a mechanism for these transitions and suggest that these phenomena
are generic to all compounds containing FeAs layers. For 0.0 we demonstrate
that transition temperatures to the superconducting state and their dependence
on correlate well with the calculated magnitude of the electronic density
of states at the Fermi energy.Comment: 4 pages, 3 figures, 1 tabl
Electron localization and a confined electron gas in nanoporous inorganic electrides
The nanoporous main group oxide 12CaO.7Al(2)O(3) (C12A7) can be transformed from a wide-gap insulator to an electride where electrons substitute anions in cages constituting a positive frame. Our ab initio calculations of the electronic structure of this novel material give a consistent explanation of its high conductivity and optical properties. They show that the electrons confined in the inert positive frame are localized in cages and undergo hopping between neighboring cages. The results are useful for the understanding of behavior of confined electron gas of different topology and electron-phonon coupling, and for designing new transparent conductors, electron emitters, and electrides
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