346 research outputs found
Comportamento de cultivares chilenas de batata na zona Sul do Rio Grande do Sul.
bitstream/item/30995/1/comunicado-104.pd
AUTOMATIC BLOB FITTING IN COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY IMAGES
Two-dimensional gas chromatography is a recent technology which is particularly efficient for detailed molecular analysis. However, due to the novelty of the method and the lack of automated analysis tools, quantitative data processing is often performed manually. Hence, results are strongly user-dependent, time consuming and, consequently, relatively inaccurate In this paper, we extend conventional techniques for signal analysis by utilizing specific characteristics of chromatographic data and by developing new methods for estimating the quantitative contribution of chemical regions from the produced images. Data-driven information is retrieved from chemical quantitative analysis based on Savitzky-Golay automatic peaks location determination, which increases both the processing speed and the analysis efficiency and improves our confidence in experimental repeatability. 1
First record of Darwin’s Slimehead, Gephyroberyx darwinii (Johnson, 1866) (Beryciformes: Trachichthyidae), in association with Brazilian deep reefs
Copyright © 2004 aqua, International Journal of Ichthyology.Três espécies da família Trachichthyidae ocorrem no sul do Brasil: Paratrachichthys atlanticus, Hoplostethus occidentalis e Gephyroberyx darwinii. Esta última é uma espécie que atinge tamanhos da ordem dos 600 mm (CT), vive na província bentopelágica até profundidades de 1210 metros. É encontrada em águas subtropicais distribuindo-se entre os paralelos 43ºN e 35ºS, sendo utilizada como fonte de alimento no leste do Atlântico central. O presente trabalho reporta a ocorrência de Gephyroberyx darwinii na costa brasileira entre as localidades de Vila Velha (ES) e Rio Grande (RS), em áreas de plataforma externa e talude superior, com profundidades variando de 70 a 520 metros. Suas ocorrências nestas áreas estiveram relacionadas a lances de pesca (onde Lophius gastrophysus é espécie alvo) sobre formações de corais vivos. Dados biométricos e merísticos de três espécimes são apresentados no trabalho.ABSTRACT: Three species of the Trachichthyidae family occur in the south of Brazil: Paratrachichthys atlanticus, Hoplostethus occidentalis and Gephyroberyx darwinii. G. darwinii may attain a length of 600 mm (TL). This benthopelagic species occurs at depths down to 1210 m and is generally found in subtropical waters between 43ºN and 35ºS. It is commercially exploited in the east central Atlantic for food and for oil. In this paper we report the occurrence of G. darwinii off the south and south-east coasts of Brazil between Vila Velha (Espírito Santo State) and Rio Grande (Rio Grande do Sul State), in outer shelf and slope areas, at depths between 70 and 520 m. In Brazil the trachichthyids were usually caught while fishing for Lophius gastrophysus over deep coral bottoms. Meristic and biometric data are presented for the three collected specimens
Truncation method for Green's functions in time-dependent fields
We investigate the influence of a time dependent, homogeneous electric field
on scattering properties of non-interacting electrons in an arbitrary static
potential. We develop a method to calculate the (Keldysh) Green's function in
two complementary approaches. Starting from a plane wave basis, a formally
exact solution is given in terms of the inverse of a matrix containing
infinitely many 'photoblocks' which can be evaluated approximately by
truncation. In the exact eigenstate basis of the scattering potential, we
obtain a version of the Floquet state theory in the Green's functions language.
The formalism is checked for cases such as a simple model of a double barrier
in a strong electric field. Furthermore, an exact relation between the
inelastic scattering rate due to the microwave and the AC conductivity of the
system is derived which in particular holds near or at a metal-insulator
transition in disordered systems.Comment: to appear in Phys. Rev. B., 21 pages, 3 figures (ps-files
Inelastic quantum transport in superlattices: success and failure of the Boltzmann equation
Electrical transport in semiconductor superlattices is studied within a fully
self-consistent quantum transport model based on nonequilibrium Green
functions, including phonon and impurity scattering. We compute both the drift
velocity-field relation and the momentum distribution function covering the
whole field range from linear response to negative differential conductivity.
The quantum results are compared with the respective results obtained from a
Monte Carlo solution of the Boltzmann equation. Our analysis thus sets the
limits of validity for the semiclassical theory in a nonlinear transport
situation in the presence of inelastic scattering.Comment: final version with minor changes, to appear in Physical Review
Letters, sceduled tentatively for July, 26 (1999
Electric field dependence of pairing temperature and tunneling
Using the Bethe-Salpeter equation including high electric fields, the
dependence of the critical temperature of onsetting superconductivity on the
applied field is calculated analytically. The critical temperature of pairing
is shown to increase with the applied field strength. This is a new field
effect and could contribute to the explanation of recent experiments on field
induced superconductivity. From the field dependence of the Bethe-Salpeter
equation, the two--particle bound state solution is obtained as a resonance
with a tunneling probability analogous to the WKB solution of a single particle
confined in a potential and coupled to the electrical field.Comment: 4 pages 1 figure, revised version from 29.10.02, Rev. B in pres
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