67 research outputs found
Fermions in a warped resolved conifold
AbstractWe investigated the localization of the spinorial field in a braneworld built as a warped product between a 3-brane and a 2-cycle of the resolved conifold. This scenario provides a geometric flow that controls the singularity at the origin and changes the properties of the fermion in this background. Furthermore, due the cylindrical symmetry according to the 3-brane and a smoothed warp factor, this geometry can be regarded as a near brane correction of the string-like branes. This geometry allows a normalizable and well-defined massless mode whose decay and value on the brane depend on the resolution parameter. For the Kaluza–Klein modes, resolution parameter also controls the height of the barrier of the volcano potential
Electrochemical behavior of Ti/Al2O3 interfaces produced by diffusion bonding
In the field of biomedical applications a special interest exists regarding the study of the physicochemical and mechanical behaviour of materials, with special focus on the electrochemical degradation of metal/ceramic interfaces. In fact, etal/ceramic interfaces may be present in several
biomedical devices, ranging from external or implantable sensors, to dental implants. Diffusion
bonding represents an important technique since, in opposition to other production technologies,
such as active metal brazing, avoid the possible liberation of certain chemical components
harmful to health. The aim of this work is to study the electrochemical degradation of the interface
formed between commercially pure Ti and Al2O3 produced by diffusion bonding, in contact with
a physiological solution. The present approach included the evaluation of the contribution of individual
and pairs of interfacial layers on the global degradation processes. For this propose d.c.
electrochemical techniques were used to monitor the open-circuit potential, and to perform
potentiodynamic polarization and galvanic corrosion evaluation. Also, electrochemical impedance
spectroscopy was used as a complementary technique of the corrosion behaviour of the
interface. Chemical composition and morphology of samples and corrosion products were evaluated
by SEM and EDS analysis. According to experimental results, two principal reaction layers
were formed in the interface: TiAl and Ti3Al. The TiAl layer appears to be the responsible for the
strong increase in corrosion rate of the interface.Fundação para a Ciência e Tecnologia -POCTI/CTM/33384/2000; SFRH/BPD/
5518/2001
Observational tests of the galaxy formation process
The mutual feedback between star formation and nuclear activity in large
spheroidal galaxies may be a key ingredient to overcome several difficulties
plaguing current semi-analytic models for galaxy formation. We discuss some
observational implications of the model by Granato et al. (2003) for the
co-evolution of galaxies and active nuclei at their centers and stress the
potential of the forthcoming surveys of the Sunyaev-Zeldovich effect on
arcminute scales, down to K levels, to investigate the early galaxy
formation phases, difficult to access by other means.Comment: 6, pages, 1 figure, to appear in proc. of the meeting "Baryons on
Cosmic Structures", Roma, October 20-21, 200
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
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