11,929 research outputs found
Validação da espectroscopia de ressonância magnética nuclear (RMN) na determinação do teor de óleo em sementes de mamona.
bitstream/item/31248/1/comunicado-153.pd
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
An Integrative Analysis Uncovers a New, Pseudo-Cryptic Species of Amazonian Marmoset (Primates: Callitrichidae: \u3cem\u3eMico\u3c/em\u3e) from the Arc of Deforestation
Amazonia has the richest primate fauna in the world. Nonetheless, the diversity and distribution of Amazonian primates remain little known and the scarcity of baseline data challenges their conservation. These challenges are especially acute in the Amazonian arc of deforestation, the 2500 km long southern edge of the Amazonian biome that is rapidly being deforested and converted to agricultural and pastoral landscapes. Amazonian marmosets of the genus Mico are little known endemics of this region and therefore a priority for research and conservation efforts. However, even nascent conservation efforts are hampered by taxonomic uncertainties in this group, such as the existence of a potentially new species from the Juruena–Teles Pires interfluve hidden within the M. emiliae epithet. Here we test if these marmosets belong to a distinct species using new morphological, phylogenomic, and geographic distribution data analysed within an integrative taxonomic framework. We discovered a new, pseudo-cryptic Mico species hidden within the epithet M. emiliae, here described and named after Horacio Schneider, the pioneer of molecular phylogenetics of Neotropical primates. We also clarify the distribution, evolutionary and morphological relationships of four other Mico species, bridging Linnean, Wallacean, and Darwinian shortfalls in the conservation of primates in the Amazonian arc of deforestation
Nonextensive Thermostatistics and the H-Theorem
The kinetic foundations of Tsallis' nonextensive thermostatistics are
investigated through Boltzmann's transport equation approach. Our analysis
follows from a nonextensive generalization of the ``molecular chaos
hypothesis". For , the -transport equation satisfies an -theorem
based on Tsallis entropy. It is also proved that the collisional equilibrium is
given by Tsallis' -nonextensive velocity distribution.Comment: 4 pages, no figures, corrected some typo
Constant Curvature Coefficients and Exact Solutions in Fractional Gravity and Geometric Mechanics
We study fractional configurations in gravity theories and Lagrange
mechanics. The approach is based on Caputo fractional derivative which gives
zero for actions on constants. We elaborate fractional geometric models of
physical interactions and we formulate a method of nonholonomic deformations to
other types of fractional derivatives. The main result of this paper consists
in a proof that for corresponding classes of nonholonomic distributions a large
class of physical theories are modelled as nonholonomic manifolds with constant
matrix curvature. This allows us to encode the fractional dynamics of
interactions and constraints into the geometry of curve flows and solitonic
hierarchies.Comment: latex2e, 11pt, 27 pages, the variant accepted to CEJP; added and
up-dated reference
Laser-Plasma Interactions Enabled by Emerging Technologies
An overview from the past and an outlook for the future of fundamental
laser-plasma interactions research enabled by emerging laser systems
Optimally combining dynamical decoupling and quantum error correction
We show how dynamical decoupling (DD) and quantum error correction (QEC) can
be optimally combined in the setting of fault tolerant quantum computing. To
this end we identify the optimal generator set of DD sequences designed to
protect quantum information encoded into stabilizer subspace or subsystem
codes. This generator set, comprising the stabilizers and logical operators of
the code, minimizes a natural cost function associated with the length of DD
sequences. We prove that with the optimal generator set the restrictive
local-bath assumption used in earlier work on hybrid DD-QEC schemes, can be
significantly relaxed, thus bringing hybrid DD-QEC schemes, and their
potentially considerable advantages, closer to realization.Comment: 6 pages, 1 figur
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