Evaluation of the greenhouse gas balance in the Eucalyptus globulus sector in Portugal

Este estudio evalúa el balance de gas invernadero en el sector del E. globulus en Portugal. Las eliminaciones y las emisiones de dióxido de carbono (CO2) y el metano (CH4) fueron calculadas a lo largo en todo el sector forestal, incluyendo el ecosistema forestal, el tratamiento industrial de madera y las etapas de empleo y la disposición final de productos forestales. El balance de gas invernadero fue calculado restándose la eliminación de carbono neto a las emisiones de carbono fósil y sumándose las emisiones de carbono como el CH4. El balance global de gas invernadero fue una eliminación neta de carbono que varió entre 401 y 1033 Gg Ceq yr-1, respectivamente con el cambio de reservas y los accesos de flujo atmosférico. La diferencia entre las dos estimaciones es equivalente al carbón exportado en productos de madera y forestales. Tanto productos forestales como forestales eran sumideros de carbono, como sus reservas han estado aumentando. Aproximadamente el 94 % del cambio total de reservas de carbono en el sector era debido al bosque, mientras que el papel era el producto forestal con la contribución principal al aumento de reservas de carbono. Emisiones de carbono de fósil consideradas para el 13 % de las emisiones totales de carbono en el sector y disminuido el retiro neto de carbono por 18 y el 34 %, respectivamente con el flujo atmosférico y los cambio de reservas. El carbón emitido como CH4 tuvo la importancia menor y, por consiguiente, era responsable de una disminución en el retiro neto de carbón de sólo 4 y el 8 %, respectivamente con el flujo atmosférico y los accesos de cambio de reservas.____________________________________This study evaluates the greenhouse gas balance in the E. globulus sector in Portugal. Removals and emissions of carbon dioxide (CO2) and methane (CH4) were calculated along the whole forest sector, including the forest ecosystem, the industrial processing of wood and the stages of use and final disposal of forest products. The greenhouse gas balance was calculated by subtracting to the net carbon removal, the fossil carbon emissions and the additional emissions of carbon as CH4. Two different approaches were applied for estimating the net carbon removal in the sector: the stock-change and the atmospheric-flow approach. The global greenhouse gas balance was a net removal of carbon that varied between 401 and 1033 Gg Ceq yr-1, respectively with the stock-change and the atmospheric-flow approaches. The difference between the two estimates is equivalent to the carbon exported in wood and forest products. Both forest and forest products were carbon sinks, as their stocks have been increasing. About 94% of the total change in carbon stocks in the sector was due to forest, whereas paper was the forest product with the major contribution to the increase of carbon stocks. Fossil carbon emissions accounted for 13% of the total carbon emissions in the sector and decreased the net carbon removal by 18 and 34%, respectively with the atmospheric-flow and the stock-change approaches. Carbon emitted as CH4 was of minor importance and, consequently, was responsible for a decrease in the net carbon removal of only 4 and 8%, respectively with the atmospheric-flow and the stock-change approaches

Piezoelectric actuators for bone mechanical stimulation: exploring the concept.

Arthroplasty is liable to cause intense changes on strain levels and distribution in the boné surrounding the implant, namely stress shielding. Several solutions have been proposed for this, namely design variations and development of controlled-stiffness implants. A new approach to this problem, with potential application to other orthopaedic problems and other medical fields, would be the development of smart implants integrating systems for bone mechanical stimulation. Ideally, the implant should presente sensing capability and the ability to maintain physiological levels of strain at the implant interface. Piezoelectric materials’ huge potential as a mean to produce direct mechanical stimulation lies on the possibility of producing stimuli at a high range of frequencies and in multiple combinations. The present in vitro and preliminary in vivo studies were a first step towards the validation of the concept

Bone mechanical stimulation with piezoelectric materials

This chapter summarized explores in vivo use of a piezoelectric polymer for bone mechanical stimulatio

Thermal fatigue assessment of components made with particulate polymer composites

Many appliance materials are made of PMMA/Si acrylic casting dispersion. In these situations, failure can occur by thermal fatigue induced by severe temperature variations such as alternating flows of cold and hot water. This paper is concerned with the numerical analysis of the thermal stresses in three composites with different volume fractions of filler and particle size. Their trade marks are Asterite, Amatis and Ultra-quartz. Cosmos/M finite element method software was used to study the influence of the cold and hot water temperatures as well as the time of interruption of water flow in the transition between hot and cold water on thermal stresses. Residual stresses were measured and superimposed to thermal stress in fatigue analysis. Typical defects in the corner of holes produced by drilling were predicted using experimental fatigue lives and da/dN curves. Based on predicted defects thermal fatigue assessment of commercially available sinks made with the three materials mentioned earlier was done by taking into account the influence of both cyclic thermal and static residual stresses induced by the manufacturing process.http://www.sciencedirect.com/science/article/B6V55-4DF4C7S-2/1/e913309acfd159679eb06b390853e5e

Fatigue life predictions in polymer particle composites

This paper presents a study on fatigue life predictions in three polymer particle composites with different volume fractions of filler and different particle sizes. Central hole notched specimens were analysed using a fracture mechanics approach. A solution for the stress intensity factor of corner cracks at a hole was obtained using the finite element method and considering quarter-circular and quarter-elliptical cracks of different sizes. The solution was compared with a literature solution and significant differences were found. Fatigue crack propagation tests were performed at room temperature and constant loading amplitude, for stress ratios R=0 and R=-0.75. Finally, fatigue lives, crack shape evolution and final crack length were predicted assuming an initial crack size and considering that the crack maintains a quarter-elliptical shape. The comparison with experimental fatigue lives indicated the presence of initial defects larger than the silica particles; however, these large sizes can be explained by the residual stresses measured near the hole.http://www.sciencedirect.com/science/article/B6V35-454FDJ5-7/1/4231c9abb6a4b1b364cde431359b1e1

Polysaccharides As Viscosupplementation Agents: Structural Molecular Characteristics but Not Rheology Appear Crucial to the Therapeutic Response

IntroductionMost clinical studies and basic research document viscosupplementation (VS) in terms of effectiveness and safety, but only a few highlight its molecular mechanisms of action. Besides, there is generally focus on hyaluronic acid (HA) as being the most relevant polysaccharide to reach the clinical endpoints, attributing its effect mainly to its unique viscoelastic properties, related to a high-molecular weight and gel formulation. Usually, studies do not approach the possible biological pathways where HA may interfere, and there is a lack of reports on other biocompatible polysaccharides that could be of use in VS.AimWe briefly review the main proposed mechanisms of action of intra-articular hyaluronic acid (IA-HA) treatment and discuss its effectiveness focusing on the role of rheological and intrinsic structural molecular properties of polysaccharides in providing a therapeutic effect.MethodsWe conducted a literature search using PubMed database to find articles dealing with the mechanisms of action of IA-HA treatment and/or emphasizing how the structural properties of the polysaccharide used influenced the clinical outcomes.Discussion/conclusionHA is involved in numerous biochemical interactions that may explain the clinical benefits of VS, most of them resulting from HA–cluster of differentiation 44 receptor interaction. There are other important aspects apart from the molecular size or the colloidal state of the IA-HA involved in VS efficiency that still need to be consolidated. Indeed, it seems that clinical response may be dependent on the intrinsic properties of the polysaccharide, regardless of being HA, rather than to rheology, posing some controversy to previous beliefs