31,023 research outputs found
Uniform semiclassical approximation in quantum statistical mechanics
We present a simple method to deal with caustics in the semiclassical
approximation to the partition function of a one-dimensional quantum system.
The procedure, which makes use of complex trajectories, is applied to the
quartic double-well potential.Comment: 5 pages, 1 figure, Latex. Contribution to the Proceedings of the XXI
Brazilian National Meeting on Particles and Fields (Sao Lourenco, October
23-27, 2000
The Role of Fermions in Bubble Nucleation
We present a study of the role of fermions in the decay of metastable states
of a scalar field via bubble nucleation. We analyze both one and
three-dimensional systems by using a gradient expansion for the calculation of
the fermionic determinant. The results of the one-dimensional case are compared
to the exact results of previous work.Comment: 15 pages, revtex, 9 figure
Improved semiclassical density matrix: taming caustics
We present a simple method to deal with caustics in the semiclassical
approximation to the thermal density matrix of a particle moving on the line.
For simplicity, only its diagonal elements are considered. The only ingredient
we require is the knowledge of the extrema of the Euclidean action. The
procedure makes use of complex trajectories, and is applied to the quartic
double-well potential.Comment: 20 pages, 7 figures. Revised version, accepted for publication in
Phys. Rev.
Sobrevivência e crescimento de doze espécies de eucalipto em Dois Vizinhos, Paraná.
Edição dos Anais do Congresso Florestal Brasileiro, 6., 1990, Campos do Jordão
Probing the Circumnuclear Stellar Populations of Starburst Galaxies in the Near-infrared
We employ the NASA Infrared Telescope Facility's near-infrared spectrograph
SpeX at 0.8-2.4m to investigate the spatial distribution of the stellar
populations (SPs) in four well known Starburst galaxies: NGC34, NGC1614,
NGC3310 and NGC7714. We use the STARLIGHT code updated with the synthetic
simple stellar populations models computed by Maraston (2005, M05). Our main
results are that the NIR light in the nuclear surroundings of the galaxies is
dominated by young/intermediate age SPs (yr), summing from
40\% up to 100\% of the light contribution. In the nuclear aperture of
two sources (NGC1614 and NGC3310) we detected a predominant old SP component
(yr), while for NGC34 and NGC7714 the younger component
prevails. Furthermore, we found evidence of a circumnuclear star formation
ring-like structure and a secondary nucleus in NGC1614, in agreement with
previous studies. We also suggest that the merger/interaction experienced by
three of the galaxies studied, NGC1614, NGC3310 and NGC7714 can explain the
lower metallicity values derived for the young SP component of these sources.
In this scenario the fresh unprocessed metal poorer gas from the
destroyed/interacting companion galaxy is driven to the centre of the galaxies
and mixed with the central region gas, before star formation takes place. In
order to deepen our analysis, we performed the same procedure of SP synthesis
using Maraston (2011, M11) EPS models. Our results show that the newer and
higher resolution M11 models tend to enhance the old/intermediate age SP
contribution over the younger ages
Sustainability index for agribusiness products considering territorial bases and life cycle thinking.
The sustainability index (SI) development for agricultural products was a Brazilian Agricultural, Livestock and Provisioning Ministry, (MAPA) demand. This work seeks by participative process, to define sustainability principles, criteria and agricultural products patterns. Theses principles have universal characters liable to expand its application to several agribusiness links by future criteria in the several territorial contexts through out the patterns to be defined to each biome monitored by satellites. The SI must have credibility and international recognition. Among their principles are: Conformity with the agreement, treaties and international conventions; Conformity with the national legislation; Localization; Integration; Monitoring and continuous improvement. The participative elaboration of the sustainability principles with the more representative agribusiness sectors, science and technology areas and the public and private institutions is allowing delineating the environment conduct, innovation and business for a future guiding to criteria formatting of the and SI patterns
Tuberculosis in a child - search for the infected adult nearby; case report, Portugal, 2007
Case ReportsTuberculosis (TB) transmission in a non-household setting is difficult to detect, because contact with the source case is often not obvious. Here, we report on a case of a four-year-old child who got infected through sporadic non-household exposure at a coffee shop. The source case was a woman who had suffered from weight loss, productive cough and fatigue for two months before being diagnosed with TB. Screening the child s contacts revealed two active TB cases within its family. Overall 148 contacts were screened for both cases and 18 cases of latent TB infection detected. The connection between the child and the source case, who were not aware of their contact, was confirmed by molecular fingerprinting. Our case report illustrates the difficulty in detecting non-household transmission between individuals that do not have significant contact, and draws attention to the need to look for the infected adult whenever a child falls ill with TB. This report is a reminder of the importance to consider possibly neglected ways of TB transmission and highlights once again the need of early diagnosis of TB.N/
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