2,695 research outputs found
The self-consistent quantum-electrostatic problem in strongly non-linear regime
The self-consistent quantum-electrostatic (also known as
Poisson-Schr\"odinger) problem is notoriously difficult in situations where the
density of states varies rapidly with energy. At low temperatures, these
fluctuations make the problem highly non-linear which renders iterative schemes
deeply unstable. We present a stable algorithm that provides a solution to this
problem with controlled accuracy. The technique is intrinsically convergent
including in highly non-linear regimes. We illustrate our approach with (i) a
calculation of the compressible and incompressible stripes in the integer
quantum Hall regime and (ii) a calculation of the differential conductance of a
quantum point contact geometry. Our technique provides a viable route for the
predictive modeling of the transport properties of quantum nanoelectronics
devices.Comment: 28 pages. 14 figures. Added solution to a potential failure mode of
the algorith
When native species become invasive: the case of bamboos in fragmented forests of Southern Brazil.
ESA 2013. Abstract. COS 29-2
Forest succession stagnation in southern Brazil forests: the role of bamboos.
Edição dos abstracts do 24º IUFRO World Congress, 2014, Salt Lake City. Sustaining forests, sustaining people: the role of research
Near-infrared spatially resolved spectroscopy of (136108) Haumea's multiple system
The transneptunian region of the solar system is populated by a wide variety
of icy bodies showing great diversity. The dwarf planet (136108) Haumea is
among the largest TNOs and displays a highly elongated shape and hosts two
moons, covered with crystalline water ice like Hamuea. Haumea is also the
largest member of the sole TNO family known to date. A catastrophic collision
is likely responsible for its unique characteristics. We report here on the
analysis of a new set of observations of Haumea obtained with SINFONI at the
ESO VLT. Combined with previous data, and using light-curve measurements in the
optical and far infrared, we carry out a rotationally resolved spectroscopic
study of the surface of Haumea. We describe the physical characteristics of the
crystalline water ice present on the surface of Haumea for both regions, in and
out of the Dark Red Spot (DRS), and analyze the differences obtained for each
individual spectrum. The presence of crystalline water ice is confirmed over
more than half of the surface of Haumea. Our measurements of the average
spectral slope confirm the redder characteristic of the spot region. Detailed
analysis of the crystalline water-ice absorption bands do not show significant
differences between the DRS and the remaining part of the surface. We also
present the results of applying Hapke modeling to our data set. The best
spectral fit is obtained with a mixture of crystalline water ice (grain sizes
smaller than 60 micron) with a few percent of amorphous carbon. Improvements to
the fit are obtained by adding ~10% of amorphous water ice. Additionally, we
used the IFU-reconstructed images to measure the relative astrometric position
of the largest satellite Hi`iaka and determine its orbital elements. An orbital
solution was computed with our genetic-based algorithm GENOID and our results
are in full agreement with recent results.Comment: Accepted for publication in A&
Sistemas agroflorestais: restauração ambiental e produção no âmbito da Floresta Ombrófila Mista.
bitstream/item/121202/1/Doc.-276-Izabel.pd
High magnetic field thermal-expansion and elastic properties of CeRhIn
We report high magnetic field thermal-expansion and magnetostriction results
on CeRhIn single crystals. Several transitions, both first and second
order, are observed when the field is applied perpendicular to the
crystallographic c-axis. The magnetic field dependence of the thermal-expansion
coefficient above 15 K, where the magnetic correlations are negligible, can be
explained supposing an almost pure ground state doublet, in
apparent contradiction with neutron scattering experiments. Although the
spin-lattice interaction is relevant in this compound, the effect of the
magnetic correlations on the elastic properties is relatively weak, as revealed
by resonant ultrasound spectroscopy experiments.Comment: 5 pages, 6 figure
Characterisation of candidate members of (136108) Haumea's family: II. Follow-up observations
From a dynamical analysis of the orbital elements of transneptunian objects
(TNOs), Ragozzine & Brown reported a list of candidate members of the first
collisional family found among this population, associated with (136108) Haumea
(a.k.a. 2003 EL61). We aim to distinguish the true members of the Haumea
collisional family from interlopers. We search for water ice on their surfaces,
which is a common characteristic of the known family members. The properties of
the confirmed family are used to constrain the formation mechanism of Haumea,
its satellites, and its family. Optical and near-infrared photometry is used to
identify water ice. We use in particular the CH4 filter of the Hawk-I
instrument at the European Southern Observatory Very Large Telescope as a short
H-band (Hs), the (J-Hs) colour being a sensitive measure of the water ice
absorption band at 1.6 {\mu}m. Continuing our previous study headed by
Snodgrass, we report colours for 8 candidate family members, including
near-infrared colours for 5. We confirm one object as a genuine member of the
collisional family (2003 UZ117), and reject 5 others. The lack of infrared data
for the two remaining objects prevent any conclusion from being drawn. The
total number of rejected members is therefore 17. The 11 confirmed members
represent only a third of the 36 candidates. The origin of Haumea's family is
likely to be related to an impact event. However, a scenario explaining all the
peculiarities of Haumea itself and its family remains elusive.Comment: 8 pages, 4 figures, accepted for publication in A&
Bamboo influence on natural regeneration - a case study in a Araucaria Forest fragment in Brazil.
IUFROLAT 2013. Disponibilizado online. Resumen
Avaliação do comportamento da regeneração natural em duas subtipologias de Floresta Ombrófila Mista.
Resumo
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