21,741 research outputs found
Experience with the Open Source based implementation for ATLAS Conditions Data Management System
Conditions Data in high energy physics experiments is frequently seen as
every data needed for reconstruction besides the event data itself. This
includes all sorts of slowly evolving data like detector alignment, calibration
and robustness, and data from detector control system. Also, every Conditions
Data Object is associated with a time interval of validity and a version.
Besides that, quite often is useful to tag collections of Conditions Data
Objects altogether. These issues have already been investigated and a data
model has been proposed and used for different implementations based in
commercial DBMSs, both at CERN and for the BaBar experiment. The special case
of the ATLAS complex trigger that requires online access to calibration and
alignment data poses new challenges that have to be met using a flexible and
customizable solution more in the line of Open Source components. Motivated by
the ATLAS challenges we have developed an alternative implementation, based in
an Open Source RDBMS. Several issues were investigated land will be described
in this paper:
-The best way to map the conditions data model into the relational database
concept considering what are foreseen as the most frequent queries.
-The clustering model best suited to address the scalability problem.
-Extensive tests were performed and will be described.
The very promising results from these tests are attracting the attention from
the HEP community and driving further developments.Comment: 8 pages, 4 figures, 3 tables, conferenc
Constraints on Cold Dark Matter Accelerating Cosmologies and Cluster Formation
We discuss the properties of homogeneous and isotropic flat cosmologies in
which the present accelerating stage is powered only by the gravitationally
induced creation of cold dark matter (CCDM) particles (). For
some matter creation rates proposed in the literature, we show that the main
cosmological functions such as the scale factor of the universe, the Hubble
expansion rate, the growth factor and the cluster formation rate are
analytically defined. The best CCDM scenario has only one free parameter and
our joint analysis involving BAO + CMB + SNe Ia data yields
() where
is the observed matter density parameter. In particular, this implies that the
model has no dark energy but the part of the matter that is effectively
clustering is in good agreement with the latest determinations from large scale
structure. The growth of perturbation and the formation of galaxy clusters in
such scenarios are also investigated. Despite the fact that both scenarios may
share the same Hubble expansion, we find that matter creation cosmologies
predict stronger small scale dynamics which implies a faster growth rate of
perturbations with respect to the usual CDM cosmology. Such results
point to the possibility of a crucial observational test confronting CCDM with
CDM scenarios trough a more detailed analysis involving CMB, weak
lensing, as well as the large scale structure.Comment: 12 pages, 3 figures, Accepted for publication by Physical Rev.
Counter-rotation in relativistic magnetohydrodynamic jets
Young stellar object observations suggest that some jets rotate in the
opposite direction with respect to their disk. In a recent study, Sauty et al.
(2012) have shown that this does not contradict the magnetocentrifugal
mechanism that is believed to launch such outflows. Signatures of motions
transverse to the jet axis and in opposite directions have recently been
measured in M87 (Meyer et al. 2013). One possible interpretation of this motion
is the one of counter rotating knots. Here, we extend our previous analytical
derivation of counter-rotation to relativistic jets, demonstrating that
counter-rotation can indeed take place under rather general conditions. We show
that both the magnetic field and a non-negligible enthalpy are necessary at the
origin of counter-rotating outflows, and that the effect is associated with a
transfer of energy flux from the matter to the electromagnetic field. This can
be realized in three cases : if a decreasing enthalpy causes an increase of the
Poynting flux, if the flow decelerates, or, if strong gradients of the magnetic
field are present. An illustration of the involved mechanism is given by an
example of relativistic MHD jet simulation.Comment: Accepted for publication in ApJ
New Cosmic Accelerating Scenario without Dark Energy
We propose an alternative, nonsingular, cosmic scenario based on
gravitationally induced particle production. The model is an attempt to evade
the coincidence and cosmological constant problems of the standard model
(CDM) and also to connect the early and late time accelerating stages
of the Universe. Our space-time emerges from a pure initial de Sitter stage
thereby providing a natural solution to the horizon problem. Subsequently, due
to an instability provoked by the production of massless particles, the
Universe evolves smoothly to the standard radiation dominated era thereby
ending the production of radiation as required by the conformal invariance.
Next, the radiation becomes sub-dominant with the Universe entering in the cold
dark matter dominated era. Finally, the negative pressure associated with the
creation of cold dark matter (CCDM model) particles accelerates the expansion
and drives the Universe to a final de Sitter stage. The late time cosmic
expansion history of the CCDM model is exactly like in the standard
CDM model, however, there is no dark energy. This complete scenario is
fully determined by two extreme energy densities, or equivalently, the
associated de Sitter Hubble scales connected by , a result that has no correlation with the cosmological constant
problem. We also study the linear growth of matter perturbations at the final
accelerating stage. It is found that the CCDM growth index can be written as a
function of the growth index, . In this
framework, we also compare the observed growth rate of clustering with that
predicted by the current CCDM model. Performing a statistical test
we show that the CCDM model provides growth rates that match sufficiently well
with the observed growth rate of structure.Comment: 12 pages, 3 figures, accepted for publication by Phys. Rev. D. (final
version, some references have corrected). arXiv admin note: substantial text
overlap with arXiv:1106.193
Effect of particle polydispersity on the irreversible adsorption of fine particles on patterned substrates
We performed extensive Monte Carlo simulations of the irreversible adsorption
of polydispersed disks inside the cells of a patterned substrate. The model
captures relevant features of the irreversible adsorption of spherical
colloidal particles on patterned substrates. The pattern consists of (equal)
square cells, where adsorption can take place, centered at the vertices of a
square lattice. Two independent, dimensionless parameters are required to
control the geometry of the pattern, namely, the cell size and cell-cell
distance, measured in terms of the average particle diameter. However, to
describe the phase diagram, two additional dimensionless parameters, the
minimum and maximum particle radii are also required. We find that the
transition between any two adjacent regions of the phase diagram solely depends
on the largest and smallest particle sizes, but not on the shape of the
distribution function of the radii. We consider size dispersions up-to 20% of
the average radius using a physically motivated truncated Gaussian-size
distribution, and focus on the regime where adsorbing particles do not interact
with those previously adsorbed on neighboring cells to characterize the jammed
state structure. The study generalizes previous exact relations on monodisperse
particles to account for size dispersion. Due to the presence of the pattern,
the coverage shows a non-monotonic dependence on the cell size. The pattern
also affects the radius of adsorbed particles, where one observes preferential
adsorption of smaller radii particularly at high polydispersity.Comment: 9 pages, 5 figure
Optimization conditions of UV-C radiation combined with ultrasound-assisted extraction of cherry tomato (Lycopersicon esculentum) lycopene extract
The aim of this work was to study the effect of UV-C radiation on ultrasound assisted extraction
(UAE) of cherry tomato bioactive compounds. Cherry tomatoes were exposed to two UV-C radiation
doses (0.5 and 1.0 J cm−2
) and stored at 20 ± 0.5 oC for 7 days. Next, they were lyophilized, and
the bioactive compounds were extracted by UAE at 20 KHz. To evaluate the effectiveness of the
extraction process of the bioactive compounds, a CCRD (central composite rotational design) was
used together with RSM (response surface methodology), for extraction times from 4 to 12 minutes
and concentrations (g of lyophilized product / L of ethanol) of 1:10, 1:20 and 1:30. The extracts
obtained from the irradiated tomatoes presented 5.8 times more lycopene content than the controls
and higher antioxidant activity was obtained for 4 and 8 min, in the concentrations 1:10 and 1:20 (m
v−1). Through numerical model optimization, optimal extraction conditions were obtained. The results
demonstrated that by previously irradiating tomatoes with UV-C light, the UAE yielded considerably
higher amounts of lycopene and other bioactives.CNPq (National Council of Technological and Scientific
Development, Brazil), Erasmus Mundus action 2; Fellow
Mundus Project; Department of Chemical Engineering and Food Engineering
(UFSC - Brazil) and the Department of Food Engineering (UAlg - Portugal) .info:eu-repo/semantics/publishedVersio
Majority-Vote Model on a Random Lattice
The stationary critical properties of the isotropic majority vote model on
random lattices with quenched connectivity disorder are calculated by using
Monte Carlo simulations and finite size analysis. The critical exponents
and are found to be different from those of the Ising and
majority vote on the square lattice model and the critical noise parameter is
found to be .Comment: 4 pages, 6 figure
Accelerating Cold Dark Matter Cosmology ()
A new kind of accelerating flat model with no dark energy that is fully
dominated by cold dark matter (CDM) is investigated. The number of CDM
particles is not conserved and the present accelerating stage is a consequence
of the negative pressure describing the irreversible process of gravitational
particle creation. A related work involving accelerating CDM cosmology has been
discussed before the SNe observations [Lima, Abramo & Germano, Phys. Rev. D53,
4287 (1996)]. However, in order to have a transition from a decelerating to an
accelerating regime at low redshifts, the matter creation rate proposed here
includes a constant term of the order of the Hubble parameter. In this case,
does not need to be small in order to solve the age problem and the
transition happens even if the matter creation is negligible during the
radiation and part of the matter dominated phase. Therefore, instead of the
vacuum dominance at redshifts of the order of a few, the present accelerating
stage in this sort of Einstein-de Sitter CDM cosmology is a consequence of the
gravitational particle creation process. As an extra bonus, in the present
scenario does not exist the coincidence problem that plagues models with
dominance of dark energy. The model is able to harmonize a CDM picture with the
present age of the universe, the latest measurements of the Hubble parameter
and the Supernovae observations.Comment: 9 pages, 6 figures, typos corrected, references added, discussion in
Appendix B extende
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