769 research outputs found
A Participação Social e as Restrições Orçamentárias no Contexto Brasileiro: os municípios nordestinos e os seus desafios institucionais
A pesquisa aborda os mecanismos de participação popular utilizados pelas gestões municipais brasileiras nos processos de elaboração do Orçamento Público. O texto discute o chamado Orçamento Participativo (OP) e seus respectivos instrumentos institucionais de implementação, questionando como se desdobram as etapas do ciclo de OP nos municípios nordestinos integrantes da Rede Brasileira de Orçamento Participativo (RBOP). Objetiva, portanto, analisar as fases componentes do ciclo do OP nos ditos municípios, identificando as razões limitadoras de um maior engajamento da população no processo participativo. Trata-se de uma pesquisa exploratória, realizada mediante entrevistas semiestruturadas com os coordenadores de OP em cada um dos municípios analisados.---------------------------------------------------------------------------The research approaches the mechanisms of popular participation used by the Brazilian municipal administrations in the processes of elaboration of the Public Budget. The text discusses the so-called Participative Budget (PB) and its institutional implementation instruments, questioning how to unfold the stages of the PB cycle in the Northeastern municipalities that are part of the Brazilian Participatory Budgeting Network (RBOP). It aims, therefore, to analyze the component phases of the PB cycle in these municipalities, identifying the reasons limiting of the greater involvement of the population in the participatory process. This is an exploratory research, carried out through semi-structured interviews with the PO coordinators in each of the municipalities analyzed.Artículo revisado por pare
Zeta function method and repulsive Casimir forces for an unusual pair of plates at finite temperature
We apply the generalized zeta function method to compute the Casimir energy
and pressure between an unusual pair of parallel plates at finite temperature,
namely: a perfectly conducting plate and an infinitely permeable one. The high
and low temperature limits of these quantities are discussed; relationships
between high and low temperature limits are estabkished by means of a modified
version of the temperature inversion symmetry.Comment: latex file 9 pages, 3 figure
Higher Order Evaluation of the Critical Temperature for Interacting Homogeneous Dilute Bose Gases
We use the nonperturbative linear \delta expansion method to evaluate
analytically the coefficients c_1 and c_2^{\prime \prime} which appear in the
expansion for the transition temperature for a dilute, homogeneous, three
dimensional Bose gas given by T_c= T_0 \{1 + c_1 a n^{1/3} + [ c_2^{\prime}
\ln(a n^{1/3}) +c_2^{\prime \prime} ] a^2 n^{2/3} + {\cal O} (a^3 n)\}, where
T_0 is the result for an ideal gas, a is the s-wave scattering length and n is
the number density. In a previous work the same method has been used to
evaluate c_1 to order-\delta^2 with the result c_1= 3.06. Here, we push the
calculation to the next two orders obtaining c_1=2.45 at order-\delta^3 and
c_1=1.48 at order-\delta^4. Analysing the topology of the graphs involved we
discuss how our results relate to other nonperturbative analytical methods such
as the self-consistent resummation and the 1/N approximations. At the same
orders we obtain c_2^{\prime\prime}=101.4, c_2^{\prime \prime}=98.2 and
c_2^{\prime \prime}=82.9. Our analytical results seem to support the recent
Monte Carlo estimates c_1=1.32 \pm 0.02 and c_2^{\prime \prime}= 75.7 \pm 0.4.Comment: 29 pages, 3 eps figures. Minor changes, one reference added. Version
in press Physical Review A (2002
BiLaWO6: Er3+/Tm3+/Yb3+ phosphor: study of multiple fluorescence intensity ratiometric thermometry at cryogenic temperatures
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Asymptotically Improved Convergence of Optimized Perturbation Theory in the Bose-Einstein Condensation Problem
We investigate the convergence properties of optimized perturbation theory,
or linear expansion (LDE), within the context of finite temperature
phase transitions. Our results prove the reliability of these methods, recently
employed in the determination of the critical temperature T_c for a system of
weakly interacting homogeneous dilute Bose gas. We carry out the explicit LDE
optimized calculations and also the infrared analysis of the relevant
quantities involved in the determination of in the large-N limit, when
the relevant effective static action describing the system is extended to O(N)
symmetry. Then, using an efficient resummation method, we show how the LDE can
exactly reproduce the known large-N result for already at the first
non-trivial order. Next, we consider the finite N=2 case where, using similar
resummation techniques, we improve the analytical results for the
nonperturbative terms involved in the expression for the critical temperature
allowing comparison with recent Monte Carlo estimates of them. To illustrate
the method we have considered a simple geometric series showing how the
procedure as a whole works consistently in a general case.Comment: 38 pages, 3 eps figures, Revtex4. Final version in press Phys. Rev.
Interacting Kasner-type cosmologies
It is well known that Kasner-type cosmologies provide a useful framework for
analyzing the three-dimensional anisotropic expansion because of the
simplification of the anisotropic dynamics. In this paper relativistic
multi-fluid Kasner-type scenarios are studied. We first consider the general
case of a superposition of two ideal cosmic fluids, as well as the particular
cases of non-interacting and interacting ones, by introducing a
phenomenological coupling function . For two-fluid cosmological scenarios
there exist only cosmological scaling solutions, while for three-fluid
configurations there exist not only cosmological scaling ones, but also more
general solutions. In the case of triply interacting cosmic fluids we can have
energy transfer from two fluids to a third one, or energy transfer from one
cosmic fluid to the other two. It is shown that by requiring the positivity of
energy densities there always is a matter component which violates the dominant
energy condition in this kind of anisotropic cosmological scenarios.Comment: Accepted for publication in Astrophysics &Space Science, 8 page
Economic outcomes of percutaneous coronary intervention with drug-eluting stents versus bypass surgery for patients with left main or three-vessel coronary artery disease: One-year results from the SYNTAX trial
Objectives: To evaluate the cost-effectiveness of alternative approaches to revascularization for patients with three-vessel or left main coronary artery disease (CAD). Background: Previous studies have demonstrated that, despite higher initial costs, long-term costs with bypass surgery (CABG) in multivessel CAD are similar to those for percutaneous coronary intervention (PCI). The impact of drug-eluting stents (DES) on these results is unknown. Methods: The SYNTAX trial randomized 1,800 patients with left main or three-vessel CAD to either CABG (n = 897) or PCI using paclitaxel-eluting stents (n = 903). Resource utilization data were collected prospectively for all patients, and cumulative 1-year costs were assessed from the perspective of the U.S. healthcare system. Results: Total costs for the initial hospitalization were 2,282/patient higher with PCI due mainly to more frequent revascularization procedures and higher outpatient medication costs. Total 1-year costs were thus 43,486 per quality-adjusted life-year gained. Conclusions: Among patients with three-vessel or left main CAD, PCI is an economically attractive strategy over the first year for patients with low and moderate angiographic complexity, while CABG is favored among patients with high angiographic complexity
The First Magnetic Fields
We review current ideas on the origin of galactic and extragalactic magnetic
fields. We begin by summarizing observations of magnetic fields at cosmological
redshifts and on cosmological scales. These observations translate into
constraints on the strength and scale magnetic fields must have during the
early stages of galaxy formation in order to seed the galactic dynamo. We
examine mechanisms for the generation of magnetic fields that operate prior
during inflation and during subsequent phase transitions such as electroweak
symmetry breaking and the quark-hadron phase transition. The implications of
strong primordial magnetic fields for the reionization epoch as well as the
first generation of stars is discussed in detail. The exotic, early-Universe
mechanisms are contrasted with astrophysical processes that generate fields
after recombination. For example, a Biermann-type battery can operate in a
proto-galaxy during the early stages of structure formation. Moreover, magnetic
fields in either an early generation of stars or active galactic nuclei can be
dispersed into the intergalactic medium.Comment: Accepted for publication in Space Science Reviews. Pdf can be also
downloaded from http://canopus.cnu.ac.kr/ryu/cosmic-mag1.pd
Oxygen abundance in local disk and bulge: chemical evolution with a strictly universal IMF
The empirical differential oxygen abundance distribution (EDOD) is deduced
from subsamples related to two different samples involving solar neighbourhood
(SN) thick disk, thin disk, halo, and bulge stars. The EDOD of the SN thick +
thin disk is determined by weighting the mass, for assumed SN thick to thin
disk mass ratio within the range, 0.1-0.9. Inhomogeneous models of chemical
evolution for the SN thick disk, the SN thin disk, the SN thick + thin disk,
the SN halo, and the bulge, are computed assuming the instantaneous recycling
approximation. The EDOD data are fitted, to an acceptable extent, by their TDOD
counterparts provided (i) still undetected, low-oxygen abundance thin disk
stars exist, and (ii) a single oxygen overabundant star is removed from a thin
disk subsample. In any case, the (assumed power-law) stellar initial mass
function (IMF) is universal but gas can be inhibited from, or enhanced in,
forming stars at different rates with respect to a selected reference case.
Models involving a strictly universal IMF (i.e. gas neither inhibited from, nor
enhanced in, forming stars with respect to a selected reference case) can also
reproduce the data. The existence of a strictly universal IMF makes similar
chemical enrichment within active (i.e. undergoing star formation) regions
placed in different environments, but increasing probability of a region being
active passing from SN halo to SN thick + thin disk, SN thin disk, SN thick
disk, and bulge. On the basis of the results, it is realized that the chemical
evolution of the SN thick + thin disk as a whole cannot be excluded.Comment: 26 pages, 10 tables, and 5 figures; tables out of page are splitted
in two parts in Appendix B; sects.4 and 5 rewritten for better understanding
of the results; further references added. Accepted for publication in
Astrophysics & Space Scienc
Origins of the Ambient Solar Wind: Implications for Space Weather
The Sun's outer atmosphere is heated to temperatures of millions of degrees,
and solar plasma flows out into interplanetary space at supersonic speeds. This
paper reviews our current understanding of these interrelated problems: coronal
heating and the acceleration of the ambient solar wind. We also discuss where
the community stands in its ability to forecast how variations in the solar
wind (i.e., fast and slow wind streams) impact the Earth. Although the last few
decades have seen significant progress in observations and modeling, we still
do not have a complete understanding of the relevant physical processes, nor do
we have a quantitatively precise census of which coronal structures contribute
to specific types of solar wind. Fast streams are known to be connected to the
central regions of large coronal holes. Slow streams, however, appear to come
from a wide range of sources, including streamers, pseudostreamers, coronal
loops, active regions, and coronal hole boundaries. Complicating our
understanding even more is the fact that processes such as turbulence,
stream-stream interactions, and Coulomb collisions can make it difficult to
unambiguously map a parcel measured at 1 AU back down to its coronal source. We
also review recent progress -- in theoretical modeling, observational data
analysis, and forecasting techniques that sit at the interface between data and
theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue
connected with a 2016 ISSI workshop on "The Scientific Foundations of Space
Weather." 44 pages, 9 figure
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