13,316 research outputs found
Sustainable forest management of miombo woodlands in Niassa National Reserve, northern Mozambique: a multidisciplinary approach of fire resistance analysis.
Poster presented at XIII World Forestry Congress. Buenos Aires (Argentina). 18 - 23 Oct 2009
Sustainable management of miombo woodlands in the Northern part of Mozambique (Niassa National Reserve - NNR).
Poster presented at Commiting Science to Global Development. Lisbon (Portugal). 29-30 Sep 2009
INJECTABLE HYBRID SYSTEM FOR STRONTIUM LOCAL DELIVERY TO PROMOTE BONE REGENERATION
In bone tissue regeneration strategies, injectable bone substitutes are very attractive since they can
be applied with minimally invasive surgical procedures and can perfectly fill irregular defects created
in cases of trauma, infection or tumor resection. These materials must combine adequate mechanical
properties with the ability to induce new bone formation. Incorporating strontium (Sr) in bone
substitute biomaterials may be a strategy to achieve high Sr concentrations, not in a systemic but in
a local environment, taking advantage of the osteoanabolic and anti-osteoclastic activity of Sr, for
the enhancement of new bone formation. In this context, the aim of the present work was to
evaluate the response of a Sr-hybrid injectable system for bone regeneration, designed by our
group, consisting of hydroxyapatite microspheres doped with Sr and an alginate vehicle crosslinked in
situ with Sr, in an in vivo scenario. Two different animal models were used, rat (Wistar) and sheep
(Merino Branco) critical sized bone defect. Non Sr-doped similar materials (Ca-hybrid) or empty
defects were used as control. Sr-hybrid system led to an increased bone formation in both center
and periphery of a rat critical sized defect compared to a non Sr–doped similar system, where new
bone formation was restricted to the periphery. Moreover newly formed bone was identified as early
as one week after its implantation in a sheep model. After eight weeks, the bone surrounded the
microspheres, both in the periphery and in the center of the defect. Most importantly, the hybrid
system provided a scaffold for cell migration and tissue ingrowth and offered structural support, as
observed in both models. The effective improvement of local bone formation suggests that this might
be a promising approach for bone regeneration, especially in osteoporotic conditions
Entanglement dynamics via coherent-state propagators
The dynamical generation of entanglement in closed bipartite systems is
investigated in the semiclassical regime. We consider a model of two particles,
initially prepared in a product of coherent states, evolving in time according
to a generic Hamiltonian, and derive a formula for the linear entropy of the
reduced density matrix using the semiclassical propagator in the coherent-state
representation. The formula is explicitly written in terms of quantities that
define the stability of classical trajectories of the underlying classical
system. The formalism is then applied to the problem of two nonlinearly coupled
harmonic oscillators and the result is shown to be in remarkable agreement with
the exact quantum measure of entanglement in the short-time regime. An
important byproduct of our approach is a unified semiclassical formula which
contemplates both the coherent-state propagator and its complex conjugate.Comment: 10 page
The motion of two masses coupled to a massive spring
We discuss the classical motion of a spring of arbitrary mass coupled to two
arbitrary massive blocks attached at its ends. A general approach to the
problem is presented and some general results are obtained. Examples for which
a simple elastic function can be inferred are discussed and the normal modes
and normal frequencies obtained. An approximation procedure to the evaluation
of the normel frequencies in the case of uniform elastic function and mass
density is also discussed.Comment: Standard Latex file plus three eps figure
Avaliação do crescimento foliar de hĂbridos interespecĂficos de dendezeiro (Elais guineensis x Elais oleifera), em MojĂş no Estado do Pará.
Chemical abundances for the transiting planet host stars OGLE-TR-10, 56, 111, 113, 132 and TrES-1. Abundances in different galactic populations
We used the UVES spectrograph (VLT-UT2 telescope) to obtain high-resolution
spectra of 6 stars hosting transiting planets, namely for OGLE-TR-10, 56, 111,
113, 132 and TrES-1. The spectra are now used to derive and discuss the
chemical abundances for C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni,
Cu and Zn. Abundances were derived in LTE, using 1-D plane-parallel Kurucz
model atmospheres. For S, Zn and Cu we used a spectral synthesis procedure,
while for the remaining cases the abundances were derived from measurements of
line-equivalent widths. The resulting abundances are compared with those found
for stars in the solar neighborhood. Distances and galactic coordinates are
estimated for the stars. We conclude that besides being particularly
metal-rich, with small possible exceptions OGLE-TR-10, 56, 111, 113, 132 and
TrES-1 are chemically undistinguishable from the field (thin disk) stars
regarding their [X/Fe] abundances. This is particularly relevant for the most
distant of the targets, located at up to ~2 Kpc from the Sun. We also did not
find any correlation between the abundances and the condensation temperature of
the elements, an evidence that strong accretion of planetary-like material,
tentatively connected to planetary migration, did not occur.Comment: Accepted for publication in Astronomy & Astrophysics (June 2006
Ballistic heat transport of quantum spin excitations as seen in SrCuO2
Fundamental conservation laws predict ballistic, i.e., dissipationless
transport behaviour in one-dimensional quantum magnets. Experimental evidence,
however, for such anomalous transport has been lacking ever since. Here we
provide experimental evidence for ballistic heat transport in a S=1/2
Heisenberg chain. In particular, we investigate high purity samples of the
chain cuprate SrCuO2 and observe a huge magnetic heat conductivity
. An extremely large spinon mean free path of more than a
micrometer demonstrates that is only limited by extrinsic
scattering processes which is a clear signature of ballistic transport in the
underlying spin model
Oligosarcus jacuiensis (Characiformes: Characidae), a new species from the Uruguay and JacuĂ River basins, southern Brazil
Limit theorem for a time-dependent coined quantum walk on the line
We study time-dependent discrete-time quantum walks on the one-dimensional
lattice. We compute the limit distribution of a two-period quantum walk defined
by two orthogonal matrices. For the symmetric case, the distribution is
determined by one of two matrices. Moreover, limit theorems for two special
cases are presented
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