15,205 research outputs found
Experimental determination of the non-extensive entropic parameter
We show how to extract the parameter from experimental data, considering
an inhomogeneous magnetic system composed by many Maxwell-Boltzmann homogeneous
parts, which after integration over the whole system recover the Tsallis
non-extensivity. Analyzing the cluster distribution of
LaSrMnO manganite, obtained through scanning tunnelling
spectroscopy, we measure the parameter and predict the bulk magnetization
with good accuracy. The connection between the Griffiths phase and
non-extensivity is also considered. We conclude that the entropic parameter
embodies information about the dynamics, the key role to describe complex
systems.Comment: Submitted to Phys. Rev. Let
Use of perfusion bioreactors and large animal models for long bone tissue engineering
Tissue engineering and regenerative medicine (TERM) strategies for generation of new bone tissue includes the
combined use of autologous or heterologous mesenchymal stem cells (MSC) and three-dimensional (3D) scaffold
materials serving as structural support for the cells, that develop into tissue-like substitutes under appropriate
in vitro culture conditions. This approach is very important due to the limitations and risks associated with
autologous, as well as allogenic bone grafiting procedures currently used. However, the cultivation of osteoprogenitor
cells in 3D scaffolds presents several challenges, such as the efficient transport of nutrient and oxygen
and removal of waste products from the cells in the interior of the scaffold. In this context, perfusion bioreactor
systems are key components for bone TERM, as many recent studies have shown that such systems can provide
dynamic environments with enhanced diffusion of nutrients and therefore, perfusion can be used to generate
grafts of clinically relevant sizes and shapes. Nevertheless, to determine whether a developed tissue-like substitute
conforms to the requirements of biocompatibility, mechanical stability and safety, it must undergo
rigorous testing both in vitro and in vivo. Results from in vitro studies can be difficult to extrapolate to the in vivo
situation, and for this reason, the use of animal models is often an essential step in the testing of orthopedic
implants before clinical use in humans. This review provides an overview of the concepts, advantages, and
challenges associated with different types of perfusion bioreactor systems, particularly focusing on systems that
may enable the generation of critical size tissue engineered constructs. Furthermore, this review discusses some
of the most frequently used animal models, such as sheep and goats, to study the in vivo functionality of bone
implant materials, in critical size defects.Leandro Gardel acknowledges the Portuguese Foundation for Science and Technology (FCT) for the PhD scholarship (ref SFRH/BD/66714/2009)
Competição de cultivares de alface crespa.
Avaliar o desempenho produtivo de variedades de alface crespa nos condições do Distrito Federal.RESUMO EXPANDIDO
Dynamic fluctuations of elastic lines in random environments
We study the fluctuations of the two-time dependent global roughness of
finite size elastic lines in a quenched random environment. We propose a
scaling form for the roughness distribution function that accounts for the
two-time, temperature, and size dependence. At high temperature and in the
final stationary regime before saturation the fluctuations are as the ones of
the Edwards-Wilkinson interface evolving from typical initial conditions. We
analyze the variation of the scaling function within the aging regime and with
the distance from saturation. We speculate on the relevance of our results to
describe the fluctuations of other non-equilibrium systems such as models at
criticality.Comment: 7 pages, 3 figure
Morphological and biochemical changes in trisomy 21
Introdução: A Trissomia 21 (T21) é a aneuploidia mais comum, apresentando uma prevalência de 1/670 nascimentos. É a principal causa de défice intelectual moderado a grave, e está associada a diversas anomalias congénitas, sendo as malformações cardiovasculares as mais frequentes. O objetivo deste trabalho é caracterizar as alterações morfológicas e bioquímicas nos casos de T21.
Material e Métodos: Estudo prospetivo, realizado no nosso Hospital entre 1998 e 2008, de avaliação dos casos com rastreio bioquímico considerado positivo para T21. Foram também analisados os resultados dos exames invasivos realizados no mesmo período e revistos os processos com diagnóstico de T21 neste exame, assim como os processos das mães cujos recém-nascidos foram codificados com diagnóstico de T21 na alta. Resultados: Neste período foram efetuados 12163 rastreios. Foram identificados 18 casos de T21. Houve 2 resultados falsos-negativos, representando uma taxa de deteção do rastreio de 88,9%. A mediana das MoM's dos marcadores bioquímicos nas grávidas com fetos afetados foi: 0,735 de AFP, 0,685 de µE3 e 2,54 de βHCG. Quinze dos 18 casais optaram por interromper a gravidez. Nasceram 3 recém-nascidos com T21. As anomalias presentes nos fetos afetados foram essencialmente alterações do hábito externo, nomeadamente a existência de pregas palmares transversais em uma ou ambas as mãos e alterações craniofaciais. Quanto às alterações do hábito interno as mais comuns foram as malformações cardiovasculares, nomeadamente a comunicação interventricular (CIV).
Discussão: Neste estudo a taxa de deteção do rastreio foi elevada. A maioria dos casais optou por interromper a gravidez. A maioria dos fetos e recém-nascidos afetados apresentou alterações morfológicas subtis, difíceis de detetar ecograficamente, salientando a importância do rastreio bioquímico.info:eu-repo/semantics/publishedVersio
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