15,561 research outputs found
Strong evidences for a nonextensive behavior of the rotation period in Open Clusters
Time-dependent nonextensivity in a stellar astrophysical scenario combines
nonextensive entropic indices derived from the modified Kawaler's
parametrization, and , obtained from rotational velocity distribution. These
's are related through a heuristic single relation given by , where is the cluster age. In a nonextensive
scenario, these indices are quantities that measure the degree of
nonextensivity present in the system. Recent studies reveal that the index
is correlated to the formation rate of high-energy tails present in the
distribution of rotation velocity. On the other hand, the index is
determined by the stellar rotation-age relationship. This depends on the
magnetic field configuration through the expression , where
and denote the saturation level of the star magnetic field and its
topology, respectively. In the present study, we show that the connection
is also consistent with 548 rotation period data for single
main-sequence stars in 11 Open Clusters aged less than 1 Gyr. The value of
2.5 from our unsaturated model shows that the mean magnetic field
topology of these stars is slightly more complex than a purely radial field.
Our results also suggest that stellar rotational braking behavior affects the
degree of anti-correlation between and cluster age . Finally, we suggest
that stellar magnetic braking can be scaled by the entropic index .Comment: 6 pages and 2 figures, accepted to EPL on October 17, 201
Nonclassical correlation in NMR quadrupolar systems
The existence of quantum correlation (as revealed by quantum discord), other
than entanglement and its role in quantum-information processing (QIP), is a
current subject for discussion. In particular, it has been suggested that this
nonclassical correlation may provide computational speedup for some quantum
algorithms. In this regard, bulk nuclear magnetic resonance (NMR) has been
successfully used as a test bench for many QIP implementations, although it has
also been continuously criticized for not presenting entanglement in most of
the systems used so far. In this paper, we report a theoretical and
experimental study on the dynamics of quantum and classical correlations in an
NMR quadrupolar system. We present a method for computing the correlations from
experimental NMR deviation-density matrices and show that, given the action of
the nuclear-spin environment, the relaxation produces a monotonic time decay in
the correlations. Although the experimental realizations were performed in a
specific quadrupolar system, the main results presented here can be applied to
whichever system uses a deviation-density matrix formalism.Comment: Published versio
Mapeamento da variabilidade genética espontânea das cepas vacinais B19 E RB51 contra Brucella abortus, comercializadas no Brasil.
A brucelose é uma zoonose causada por bactérias intracelulares do gênero Brucella, que infectam humanos, animais domésticos e silvestres. Esta doença apresenta grande impacto econômico, devido à ocorrência de distúrbios reprodutivos nos animais. A prevenção contra infecções causadas por Brucella abortus em bovinos é feita por meio da administração das cepas vacinais B19 e RB51 de B. abortus. Existem relatos de que estas vacinas podem causar aborto às fêmeas vacinadas. Devido a isso, a vacinação de fêmeas jovens é preconizada. Entretanto, há diversos relatos na literatura de persistência da B19 no úbere, proporcionando a eliminação da bactéria pelo leite. Portanto, toda a ocorrência de aborto em animais vacinados, seja por B19 ou por RB51, merece um estudo aprofundado sobre a sua causa. Técnicas moleculares capazes de diferenciar cepas vacinais de cepas selvagens têm sido descritas. O gene ery, ligado ao catabolismo do eritritol, foi caracterizado como um importante marcador nessa diferenciação, por apresentar uma deleção espontânea de 702 pares de base na cepa B19. Como esta cepa é comercializada por diferentes empresas, estudos descreveram que algumas destas cepas comercializadas na Índia não apresentam essa deleção. No Brasil, não há registro sobre a origem das amostras B19 e RB51 utilizadas na confecção das vacinas comerciais, logo um estudo no sentido da verificação de possíveis mutações em relação à amostra padrão se faz necessário, devido a estas poderem reverter a sua virulência. Objetiva-se com este estudo caracterizar genotipicamente as cepas vacinais B19 e RB51 comercializadas no Brasil contra a brucelose bovina. A metodologia utilizada será a genotipagem de genes marcadores de virulência destas cepas vacinais, através da amplificação, sequenciamento e análises in silico das sequências obtidas. Os resultados obtidos permitirão a identificação do genótipo de todas as vacinas comerciais B19 e RB51 utilizadas para a imunização de bovinos no Brasil
Conductivity of La0.95Sr0.05Ga0.90 Mg0.10O3-? obtained by mechanical activation
Dense ceramics of La0.95Sr0.05Ga0.90Mg0.10O3?? (LSGM) were obtained from La2O3, SrO, Ga2O3 and MgO precursors activated by dry grinding in a high-energy planetary ball-mill. Samples sintered at 1450 ?C for 4 h have an average grain size of ca. 250 nm. This value increases to 5 ?m when the sample is annealed for 40 h at the same temperature. Samples prepared by a conventional ceramic route were also obtained with a grain size of 13.5 and 20.5 ?m , after sintering at 1550 ?C for 4 and 40 h, respectively. Impedance spectroscopy data revealed similar grain conductivities for both materials. However, a significant degradation was observed on ageing the LSGM prepared by the conventional ceramic route, probably due to compositional alterations at the grain boundaries. This degradation was not present in the material prepared from mechanically activated precursors. Grain size effects on the electrical conductivity were analysed to determine the effective grain boundary conductivity and the brick-layer model is assumed to estimate the grain boundary thickness.371C-9F16-EBDE | Eduarda GomesN/
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