18,730 research outputs found
Black hole formation in bidimensional dilaton gravity coupled to scalar matter systems
This work deals with the formation of black hole in bidimensional dilaton
gravity coupled to scalar matter fields. We investigate two scalar matter
systems, one described by a sixth power potential and the other defined with
two scalar fields containing up to the fourth power in the fields. The
topological solutions that appear in these cases allow the formation of black
holes in the corresponding dilaton gravity models.Comment: Latex, 9 pages. Published in Mod. Phys. Lett. A14 (1999) 268
An Optical Approach to the Dynamical Casimir Effect
We recently proposed a new approach to analyze the parametric resonance in a
vibrating cavity based on the analysis of classical optical paths. This
approach is used to examine various models of cavities with moving walls. We
prove that our method is useful to extract easily basic physical outcome.Comment: 9 page
Chemical abundances for 11 bulge stars from high-resolution, near-IR spectra
It is debated whether the Milky Way bulge has the characteristics of a
classical bulge sooner than those of a pseudobulge. Detailed abundance studies
of bulge stars is a key to investigate the origin, history, and classification
of the bulge. The aim is to add to the discussion on the origin of the bulge
and to study detailed abundances determined from near-IR spectra for bulge
giants already investigated with optical spectra, the latter also providing the
stellar parameters which are very significant for the results of the present
study. Especially, the important CNO elements are better determined in the
near-IR. High-resolution, near-infrared spectra in the H band are recorded
using the CRIRES spectrometer on the Very Large Telescope. The CNO abundances
can all be determined from the numerous molecular lines in the wavelength range
observed. Abundances of the alpha elements are also determined from the near-IR
spectra. [O/Fe], [Si/Fe] and [S/Fe] are enhanced up to metallicities of at
least [Fe/H]=-0.3, after which they decline. This suggests that the Milky Way
bulge experienced a rapid and early star-formation history like that of a
classical bulge. However, a similarity between the bulge trend and the trend of
the local thick disk seems present. Such a similarity could suggest that the
bulge has a pseudobulge origin. Our [C/Fe] trend does not show any increase
with [Fe/H] which could have been expected if W-R stars have contributed
substantially to the C abundances. No "cosmic scatter" can be traced around our
observed abundance trends; the scatter found is expected, given the
observational uncertainties.Comment: Accepted for publication in A&
Functionalizing self-assembled GaN quantum dot superlattices by Eu-implantation
Self-assembled GaN quantum dots (QDs) stacked in superlattices (SL) with AlN spacer layers were implanted with Europium ions to fluences of 1013, 1014, and 1015 cm−2. The damage level introduced in the QDs by the implantation stays well below that of thick GaN epilayers. For the lowest fluence, the structural properties remain unchanged after implantation and annealing while for higher fluences the implantation damage causes an expansion of the SL in the [0001] direction which increases with implantation fluence and is only partly reversed after thermal annealing at 1000 °C. Nevertheless, in all cases, the SL quality remains very good after implantation and annealing with Eu ions incorporated preferentially into near-substitutional cation sites. Eu3+ optical activation is achieved after annealing in all samples. In the sample implanted with the lowest fluence, the Eu3+ emission arises mainly from Eu incorporated inside the QDs while for the higher fluences only the emission from Eu inside the AlN-buffer, capping, and spacer layers is observed.
© 2010 American Institute of PhysicsFCT-PTDC/CTM/100756/2008program PESSOA EGIDE/GRICESFCT-SFRH/BD/45774/2008FCT-SFRH/BD/44635/200
Aplicabilidade de marcadores SSR em estudos genéticos em Gossypium Mustelinun Miers.
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