7,811 research outputs found
Avaliações ecofisiológicas em plantas de pimenta longa (Piper hispidinervium C.DC) em diferentes condições ambientais.
Planck intermediate results. XLVIII. Disentangling Galactic dust emission and cosmic infrared background anisotropies
Using the Planck 2015 data release (PR2) temperature maps, we separate Galactic thermal dust emission from cosmic infrared background (CIB) anisotropies. For this purpose, we implement a specifically tailored component-separation method, the so-called generalized needlet internal linear combination (GNILC) method, which uses spatial information (the angular powerspectra) to disentangle the Galactic dust emission and CIB anisotropies. We produce significantly improved all-sky maps of Planck thermal dust emission, with reduced CIB contamination, at 353, 545, and 857 GHz. By reducing the CIB contamination of the thermal dust maps, we provide more accurate estimates of the local dust temperature and dust spectral index over the sky with reduced dispersion, especially at high Galactic latitudes above b = ±20°. We find that the dust temperature is T = (19.4 ± 1.3) K and the dust spectral index is β = 1.6 ± 0.1 averaged over the whole sky, while T = (19.4 ± 1.5) K and β = 1.6 ± 0.2 on 21% of the sky at high latitudes. Moreover, subtracting the new CIB-removed thermal dust maps from the CMB-removed Planck maps gives access to the CIB anisotropies over 60% of the sky at Galactic latitudes |b| > 20°. Because they are a significant improvement over previous Planck products, the GNILC maps are recommended for thermal dust science. The new CIB maps can be regarded as indirect tracers of the dark matter and they are recommended for exploring cross-correlations with lensing and large-scale structure optical surveys. The reconstructed GNILC thermal dust and CIB maps are delivered as Planck products
Comportamento ecofisiológico sazonal de plantas de pimenta longa (Piper hispidinervium C. DC), nas condições ambientais de Belém-PA.
Planck intermediate results. L. Evidence of spatial variation of the polarized thermal dust spectral energy distribution and implications for CMB B-mode analysis
The characterization of the Galactic foregrounds has been shown to be the main obstacle in thechallenging quest to detect primordial B-modes in the polarized microwave sky. We make use of the Planck-HFI 2015 data release at high frequencies to place new constraints on the properties of the polarized thermal dust emission at high Galactic latitudes. Here, we specifically study the spatial variability of the dust polarized spectral energy distribution (SED), and its potential impact on the determination of the tensor-to-scalar ratio, r. We use the correlation ratio of the C^(BB)_ℓ angular power spectra between the 217 and 353 GHz channels as a tracer of these potential variations, computed on different high Galactic latitude regions, ranging from 80% to 20% of the sky. The new insight from Planck data is a departure of the correlation ratio from unity that cannot be attributed to a spurious decorrelation due to the cosmic microwave background, instrumental noise, or instrumental systematics. The effect is marginally detected on each region, but the statistical combination of all the regions gives more than 99% confidence for this variation in polarized dust properties. In addition, we show that the decorrelation increases when there is a decrease in the mean column density of the region of the sky being considered, and we propose a simple power-law empirical model for this dependence, which matches what is seen in the Planck data. We explore the effect that this measured decorrelation has on simulations of the BICEP2-Keck Array/Planck analysis and show that the 2015 constraints from these data still allow a decorrelation between the dust at 150 and 353 GHz that is compatible with our measured value. Finally, using simplified models, we show that either spatial variation of the dust SED or of the dust polarization angle are able to produce decorrelations between 217 and 353 GHz data similar to the values we observe in the data
Estudos comparativos de plantas de pimenta longa (Piper hispidinervum C. DC.), de aspectos vegetativos extremos, para a extração de óleo essencial e quantificação de safrol.
Asymmetric I-V characteristics and magnetoresistance in magnetic point contacts
We present a theoretical study of the transport properties of magnetic point
contacts under bias. Our calculations are based on the Keldish's
non-equilibrium Green's function formalism combined with a self-consistent
empirical tight-binding Hamiltonian, which describes both strong ferromagnetism
and charging effects. We demonstrate that large magnetoresistance solely due to
electronic effects can be found when a sharp domain wall forms inside a
magnetic atomic-scale point contact. Moreover we show that the symmetry of the
- characteristic depends on the position of the domain wall in the
constriction. In particular diode-like curves can arise when the domain wall is
placed off-center within the point contact, although the whole structure does
not present any structural asymmetry.Comment: 7 figures, submitted to PR
Non-collinear coupling between magnetic adatoms in carbon nanotubes
The long range character of the exchange coupling between localized magnetic
moments indirectly mediated by the conduction electrons of metallic hosts often
plays a significant role in determining the magnetic order of low-dimensional
structures. In addition to this indirect coupling, here we show that the direct
exchange interaction that arises when the moments are not too far apart may
induce a non-collinear magnetic order that cannot be characterized by a
Heisenberg-like interaction between the magnetic moments. We argue that this
effect can be manipulated to control the magnetization alignment of magnetic
dimers adsorbed to the walls of carbon nanotubes.Comment: 13 pages, 5 figures, submitted to PR
Crescimento e produção do cacaueiro em sistemas agroflorestais em função do manejo de plantas daninhas.
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