16,444 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
Optical Properties of Strained Graphene
The optical conductivity of graphene strained uniaxially is studied within
the Kubo-Greenwood formalism. Focusing on inter-band absorption, we analyze and
quantify the breakdown of universal transparency in the visible region of the
spectrum, and analytically characterize the transparency as a function of
strain and polarization. Measuring transmittance as a function of incident
polarization directly reflects the magnitude and direction of strain. Moreover,
direction-dependent selection rules permit identification of the lattice
orientation by monitoring the van-Hove transitions. These photoelastic effects
in graphene can be explored towards atomically thin, broadband optical
elements
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Ionising radiation exposure from medical imaging – A review of Patient's (un) awareness
Introduction: Medical imaging is the main source of artificial radiation exposure. Evidence, however, suggests that patients are poorly informed about radiation exposure when attending diagnostic scans. This review provides an overview of published literature with a focus on nuclear medicine patients on the level of awareness of radiation exposure from diagnostic imaging. Methods: A review of available literature on awareness, knowledge and perception of ionising radiation in medical imaging was conducted. Articles that met the inclusion criteria were subjected to critical appraisal using the Mixed Methods Appraisal Tool. Results: 140 articles identified and screened for eligibility, 24 critically assessed and 4 studies included in synthesis. All studies demonstrated that patients were generally lacking awareness about radiation exposure and highlighted a lack of communication between healthcare professionals and patients with respect to radiation exposure. Conclusion: Studies demonstrate a need to better inform patients about their radiation exposure, and further studies focusing on nuclear medicine patients are particularly warranted. Implications for practice: Adequate and accurate information is crucial to ensure the principle of informed consent is present
Complexity-Entropy Causality Plane as a Complexity Measure for Two-dimensional Patterns
Complexity measures are essential to understand complex systems and there are
numerous definitions to analyze one-dimensional data. However, extensions of
these approaches to two or higher-dimensional data, such as images, are much
less common. Here, we reduce this gap by applying the ideas of the permutation
entropy combined with a relative entropic index. We build up a numerical
procedure that can be easily implemented to evaluate the complexity of two or
higher-dimensional patterns. We work out this method in different scenarios
where numerical experiments and empirical data were taken into account.
Specifically, we have applied the method to i) fractal landscapes generated
numerically where we compare our measures with the Hurst exponent; ii) liquid
crystal textures where nematic-isotropic-nematic phase transitions were
properly identified; iii) 12 characteristic textures of liquid crystals where
the different values show that the method can distinguish different phases; iv)
and Ising surfaces where our method identified the critical temperature and
also proved to be stable.Comment: Accepted for publication in PLoS On
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
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