2,520 research outputs found
A supercritical series analysis for the generalized contact process with diffusion
We study a model that generalizes the CP with diffusion. An additional
transition is included in the model so that at a particular point of its phase
diagram a crossover from the directed percolation to the compact directed
percolation class will happen. We are particularly interested in the effect of
diffusion on the properties of the crossover between the universality classes.
To address this point, we develop a supercritical series expansion for the
ultimate survival probability and analyse this series using d-log Pad\'e and
partial differential approximants. We also obtain approximate solutions in the
one- and two-site dynamical mean-field approximations. We find evidences that,
at variance to what happens in mean-field approximations, the crossover
exponent remains close to even for quite high diffusion rates, and
therefore the critical line in the neighborhood of the multicritical point
apparently does not reproduce the mean-field result (which leads to )
as the diffusion rate grows without bound
The nature of dark matter and the density profile and central behavior of relaxed halos
We show that the two basic assumptions of the model recently proposed by
Manrique and coworkers for the universal density profile of cold dark matter
(CDM) halos, namely that these objects grow inside out in periods of smooth
accretion and that their mass profile and its radial derivatives are all
continuous functions, are both well understood in terms of the very nature of
CDM. Those two assumptions allow one to derive the typical density profile of
halos of a given mass from the accretion rate characteristic of the particular
cosmology. This profile was shown by Manrique and coworkers to recover the
results of numerical simulations. In the present paper, we investigate its
behavior beyond the ranges covered by present-day N-body simulations. We find
that the central asymptotic logarithmic slope depends crucially on the shape of
the power spectrum of density perturbations: it is equal to a constant negative
value for power-law spectra and has central cores for the standard CDM power
spectrum. The predicted density profile in the CDM case is well fitted by the
3D S\'ersic profile over at least 10 decades in halo mass. The values of the
S\'ersic parameters depend on the mass of the structure considered. A practical
procedure is provided that allows one to infer the typical values of the best
NFW or S\'ersic fitting law parameters for halos of any mass and redshift in
any given standard CDM cosmology.Comment: 9 pages, 6 figures, to appear in the ApJ vol. 647, september 20,
2007. Minor changes to match the published versio
Determinação de cromo em própolis de Apis melifera, Scaptotrigona sp e Friseomelitta varia.
A framework for certification of large-scale component-based parallel computing systems in a cloud computing platform for HPC services
This paper addresses the verification of software components in the context of their orchestration to build
cloud-based scientific applications with high performance computing requirements. In such a scenario, components
are often supplied by different sources and their cooperation rely on assumptions of conformity with
their published behavioral interfaces. Therefore, a faulty or ill-designed component, failing to obey to the
envisaged behavioral requirements, may have dramatic consequences in practice. Certifier components, introduced
in this paper, implement a verification as a service framework and are able to access the implementation
of other components and verify their consistency with respect to a number of functional, safety and liveness
requirements relevant to a specific application or a class of them. It is shown how certifier components can be
smoothly integrated in HPC Shelf, a cloud-based platform for high performance computing in which different
sorts of users can design, deploy and execute scientific applications.SmartEGOV:
Harnessing EGOV for Smart Governance (Foundations, methods, Tools) / NORTE-01-0145-FEDER000037, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the
European Regional Development Fund (EFD
On the Formation of Copper Linear Atomic Suspended Chains
We report high resolution transmission electron microscopy and classical
molecular dynamics simulation results of mechanically stretching copper
nanowires conducting to linear atomic suspended chains (LACs) formation. In
contrast with some previous experimental and theoretical work in literature
that stated that the formation of LACs for copper should not exist our results
showed the existence of LAC for the [111], [110], and [100] crystallographic
directions, being thus the sequence of most probable occurence.Comment: 4 pages, 3 figure
Dissipationless Collapse of Spherical Protogalaxies and the Fundamental Plane
Following on from the numerical work of Capelato, de Carvalho & Carlberg
(1995, 1997), where dissipationless merger simulations were shown to reproduce
the "Fundamental Plane" (FP) of elliptical galaxies, we investigate whether the
end products of pure, spherically symmetric, one-component dissipationless {\it
collapses} could also reproduce the FP. Past numerical work on collisionless
collapses have addressed important issues on the dynamical/structural
characteristics of collapsed equilibrium systems. However, the study of
collisionless collapse in the context of the nature of the FP has not been
satisfactorily addressed yet. Our aim in this paper is to focus our attention
on the resulting collapse of simple one-component spherical models with a range
of different initial virial coefficients. We find that the characteristic
correlations of the models are compatible with virialized, centrally homologous
systems. Our results strengthen the idea that merging may be a fundamental
ingredient in forming non-homologous objects.Comment: 9 pages, 4 Postscript figures, Astronomy & Astrophysics in press
(2002). Abstract placement correcte
Draft genome sequence of the blaOXA-436- and blaNDM-1-harboring Shewanella putrefaciens SA70 isolate
ABSTRACT
We sequenced a carbapenem-resistant
Shewanella putrefaciens
isolate cultured from the sink handle of a Pakistan hospital room. Assembly annotation indicates that the isolate has a chromosomal
bla
OXA-436
carbapenemase and a plasmid-borne
bla
NDM-1
gene. To our knowledge, this is the first report of a
Shewanella
species harboring
bla
NDM
.
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DCJ-indel and DCJ-substitution distances with distinct operation costs
BACKGROUND: Classical approaches to compute the genomic distance are usually limited to genomes with the same content and take into consideration only rearrangements that change the organization of the genome (i.e. positions and orientation of pieces of DNA, number and type of chromosomes, etc.), such as inversions, translocations, fusions and fissions. These operations are generically represented by the double-cut and join (DCJ) operation. The distance between two genomes, in terms of number of DCJ operations, can be computed in linear time. In order to handle genomes with distinct contents, also insertions and deletions of fragments of DNA â named indels â must be allowed. More powerful than an indel is a substitution of a fragment of DNA by another fragment of DNA. Indels and substitutions are called content-modifying operations. It has been shown that both the DCJ-indel and the DCJ-substitution distances can also be computed in linear time, assuming that the same cost is assigned to any DCJ or content-modifying operation. RESULTS: In the present study we extend the DCJ-indel and the DCJ-substitution models, considering that the content-modifying cost is distinct from and upper bounded by the DCJ cost, and show that the distance in both models can still be computed in linear time. Although the triangular inequality can be disrupted in both models, we also show how to efficiently fix this problem a posteriori
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