Estudo comparativo do desempenho de três sistemas de colheita mecânica de azeitona

Ao longo de três anos, foi realizado trabalho experimental em olivais com densidades de plantação compreendidas entre 100 e 150 árvores por hectare, utilizando três sistemas de colheita mecânica de azeitona, que permitiram obter resultados de capacidade de trabalho (árvores por hora). Nos três sistemas, para o destaque dos frutos foi usado o mesmo vibrador de troncos. A diferença está na recolha dos frutos derrubados: no sistema (A) foi realizada manualmente; no sistema (B) foi efectuada com um enrolador de panos montado em tractor; no sistema (C) utilizou-se um apara-frutos. Os resultados obtidos nos ensaios de campo, permitem (1) apontar as limitações de cada um dos sistemas e (2) sendo conhecida a capacidade de trabalho do sistema que recolhe manualmente a azeitona, estimar para os mesmos olivais e condições de trabalho, os valores de capacidade de trabalho dos sistemas que recolhem a azeitona mecanicamente

Exomoon habitability constrained by energy flux and orbital stability

Detecting massive satellites of extrasolar planets has now become feasible, which led naturally to questions about their habitability. In a previous study we presented constraints on the habitability of moons from stellar and planetary illumination as well as from tidal heating. Here I refine our model by including the effect of eclipses on the orbit-averaged illumination. Moons in low-mass stellar systems must orbit their planet very closely to remain bound, which puts them at risk of strong tidal heating. I first describe the effect of eclipses on stellar illumination of satellites. Then I calculate the orbit-averaged energy flux including illumination from the planet and tidal heating. Habitability is defined by a scaling relation at which a moon loses its water by the runaway greenhouse process. As a working hypothesis, orbital stability is assumed if the moon's orbital period is less than 1/9 of the planet's orbital period. Due to eclipses, a satellite in a close orbit can experience a reduction in orbit-averaged stellar flux by up to about 6%. The smaller the semi-major axis and the lower the inclination of the moon's orbit, the stronger the reduction. I find a lower mass limit of ~0.2M_sun for exomoon host stars to avoid the runaway greenhouse effect. Precise estimates depend on the satellite's orbital eccentricity. Deleterious effects on exomoon habitability may occur up to ~0.5M_sun. Although the habitable zone lies close to low-mass stars, which allows for many transits of planet-moon binaries within a given observation cycle, resources should not be spent to trace habitable satellites around them. Gravitational perturbations by the star, another planet, or another satellite induce eccentricities that likely make any moon uninhabitable. Estimates for individual systems require dynamical simulations that include perturbations among all bodies and tidal heating in the satellite.Comment: 4 pages, 2 figures, accepted by A&

Influência da vibração ao tronco ou às pernada na capacidade de trabalho e nos custos da colheita mecânica de azeitona

Ensaios de campo realizados em Trás-os-Montes e no Alentejo mostram como a capacidade de trabalho e custos de operação são afectados quando em consequência da geometria e dimensão das oliveiras há necessidade de efectuar a vibração à pernadas, em vez da mais expedita vibração ao tronco. Os resultados obtidos são úteis para uma tomada de decisão, particularmente por parte dos agricultores possuidores de olivais menos adaptados, que tenham como objectivo adoptar a colheita mecânica

Influence of trunk or bough shaking on the performance and costs of mechanical harvesting of olives

Field trials carried out in Portugal showed the penalty to be paid, both in terms of work rate and costs, whenever, due to tree geometry and size, trees had to be bough shaked rather than the normal trunk shaking. If an olive orchard with trees requiring two bough shakings could be adapted to an entirely trunk shaking orchard, simulation shows an increment between 9% and 33% in the work rate at harvesting and a reduction between 4% and 22% in harvesting cost per kilogram of olive, assuming a 4000 trees size orchard. The data collected is regarded to be very useful for decision support, particularly for those farmers owning less adapted olive orchards, aiming to adopt mechanized harvesting

Mechanical harvesting of 400 trees per hectare olive orchards based on a rolling canvas prototype

Towards higher densities of trees per hectare different alternatives are required 10 collect olives harvested by trunk shakers. This paper puts forward a revised concept of the trailed can with a rolling canvas system. The equipment consists of a 6m lung box welded 10 a wheeled chassis with a rolling canvas system placed over its full length

Topographical analysis of the subependymal zone neurogenic niche

The emerging model for the adult subependymal zone (SEZ) cell population indicates that neuronal diversity is not generated from a uniform pool of stem cells but rather from diverse and spatially confined stem cell populations. Hence, when analysing SEZ proliferation, the topography along the anterior-posterior and dorsal-ventral axes must be taken into account. However, to date, no studies have assessed SEZ proliferation according to topographical specificities and, additionally, SEZ studies in animal models of neurological/psychiatric disorders often fail to clearly specify the SEZ coordinates. This may render difficult the comparison between studies and yield contradictory results. More so, by focusing in a single spatial dimension of the SEZ, relevant findings might pass unnoticed. In this study we characterized the neural stem cell/progenitor population and its proliferation rates throughout the rat SEZ anterior-posterior and dorsal-ventral axes. We found that SEZ proliferation decreases along the anterior-posterior axis and that proliferative rates vary considerably according to the position in the dorsal-ventral axis. These were associated with relevant gradients in the neuroblasts and in the neural stem cell populations throughout the dorsal-ventral axis. In addition, we observed spatially dependent differences in BrdU/Ki67 ratios that suggest a high variability in the proliferation rate and cell cycle length throughout the SEZ; in accordance, estimation of the cell cycle length of the neuroblasts revealed shorter cell cycles at the dorsolateral SEZ. These findings highlight the need to establish standardized procedures of SEZ analysis. Herein we propose an anatomical division of the SEZ that should be considered in future studies addressing proliferation in this neural stem cell niche.Fundação para a Ciência e a Tecnologia (FCT

In Vivo Fate Analysis Reveals the Multipotent and Self-Renewal Features of Embryonic AspM Expressing Cells

Radial Glia (RG) cells constitute the major population of neural progenitors of the mouse developing brain. These cells are located in the ventricular zone (VZ) of the cerebral cortex and during neurogenesis they support the generation of cortical neurons. Later on, during brain maturation, RG cells give raise to glial cells and supply the adult mouse brain of Neural Stem Cells (NSC). Here we used a novel transgenic mouse line expressing the CreERT2 under the control of AspM promoter to monitor the progeny of an early cohort of RG cells during neurogenesis and in the post natal brain. Long term fate mapping experiments demonstrated that AspM-expressing RG cells are multi-potent, as they can generate neurons, astrocytes and oligodendrocytes of the adult mouse brain. Furthermore, AspM descendants give also rise to proliferating progenitors in germinal niches of both developing and post natal brains. In the latter –i.e. the Sub Ventricular Zone- AspM descendants acquired several feature of neural stem cells, including the capability to generate neurospheres in vitro. We also performed the selective killing of these early progenitors by using a Nestin-GFPflox-TK allele. The forebrain specific loss of early AspM expressing cells caused the elimination of most of the proliferating cells of brain, a severe derangement of the ventricular zone architecture, and the impairment of the cortical lamination. We further demonstrated that AspM is expressed by proliferating cells of the adult mouse SVZ that can generate neuroblasts fated to become olfactory bulb neurons