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