5,062 research outputs found
Multilayer Graphene Synthesized by CVD Using Liquid Hexane as the Carbon Precursor
We produce multilayer graphene by the Chemical Vapor Deposition (CVD) method
at atmospheric pressure and 1000 {\deg}C, using flexible copper substrates as
catalyst and liquid hexane as the source of carbon. We designed an optical
device to measure the transmittance of the carbon films; with this information
we calculate that the approximate number of layers is 11.Comment: 6 pages, 5 figures. Accepted for publication in World Journal of
Condensed Matter Physic
Implementing TOPbase/Iron Project: Continuous Absorption from Fe II
We discuss implementation of TOPbase and Iron Project opacities for stellar
spectral codes. We use a technique employed by Peach, where a
Boltzmann-averaged cross section is calculated for selected temperatures, and
the opacity obtained from double interpolation in temperature and wavelength.
It is straightforward to include {\it all} levels for which cross sections have
been calculated. Boltzmann-averaged cross sections for Fe II show a local
maximum between 1700 and 2000[A]. We suggest this feature arises from 3d^5 4snl
to 3d^5 4pnl transitions within Fe II. IUE spectra of iron-rich CP stars show
local minima in this region. Theoretical calculations of a representative
stellar continuum demonstrate that Fe II photoionization contributes
significantly to the observed minima.Comment: 6 pages, 5 figures. See
http://www.astro.lsa.umich.edu/users/cowley/paper2r for better definition
figure
Graphene coherent states
In this paper, we will construct the coherent states for a Dirac electron in
graphene placed in a constant homogeneous magnetic field which is orthogonal to
the graphene surface. First of all, we will identify the appropriate
annihilation and creation operators. Then, we will derive the coherent states
as eigenstates of the annihilation operator, with complex eigenvalues. Several
physical quantities, as the Heisenberg uncertainty product, probability density
and mean energy value, will be as well explored.Comment: 17 pages, 32 figure
Strong color fields and heavy flavor production
The clustering of color sources provides a natural framework for soft
partonic interactions producing strong color fields. We study the consequences
of these color fields in the production of heavy flavor and the behavior of the
nuclear modification factor.Comment: 11 pages, 7 figures, to appear in Physical Review
Rapidity long range correlations, parton percolation and color glass condensate
The similarities between string percolation and Glasma results are
emphasized, special attention being paid to rapidity long range correlations,
ridge structure and elliptic flow. As the string density of high multiplicity
pp collisions at LHC energies has similar value as the corresponding to Au-Au
semi-central collisions at RHIC we also expect in pp collisions long rapidity
correlations and ridge structure, extended more than 8 units in rapidity.Comment: 3 pages, 3 figures, conference Quark Confinement and the hadron
spectrum I
Elliptic flow at RHIC and LHC in the string percolation approach
The percolation of strings gives a good description of the RHIC experimental
data on the elliptic flow, v2 and predicted a rise on the integrated v2 of the
order of 25% at LHC such as it has been experimentally obtained. We show that
the dependence of v2 on pT for RHIC and LHC energies is approximately the same
as it has been observed, for all the centralities. We show the results for
different particles and the dependence of v2 on the centralities and rapidity.
Our results are compatible with an small value of the ratio eta/s in the whole
energy range such as it was expected in the percolation framework.Comment: 20 pages, 12 figure
NLTE analysis of Sr lines in spectra of late-type stars with new R-matrix atomic data
We investigate statistical equilibrium of neutral and singly-ionized
strontium in late-type stellar atmospheres. Particular attention is given to
the completeness of the model atom, which includes new energy levels,
transition probabilities, photoionization and electron-impact excitation
cross-sections computed with the R-matrix method. The NLTE model is applied to
the analysis of Sr I and Sr II lines in the spectra of the Sun, Procyon,
Arcturus, and HD 122563, showing a significant improvement in the ionization
balance compared to LTE line formation calculations, which predict abundance
discrepancies of up to 0.5 dex. The solar Sr abundance is log A = 2.93 \pm 0.04
dex, in agreement with the meteorites. A grid of NLTE abundance corrections for
Sr I and Sr II lines covering a large range of stellar parameters is presented.Comment: 11 pages, 7 figures, accepted for publication in Astronomy &
Astrophysic
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