On the air permeability of Populus pit

Sap hydrodynamics in vascular cells of trees seems to be controlled by small membranes called pits. Understanding how the pit junctions regulate the sap flow and stop embolism by cavitation is today a challenging issue. The hypothesis that the pit porosity adjusts the flow under negative pressure and stops the air bubble diffusion need to be validated. In this talk, we will present the experimental results on Populus trees that support the idea that pits operate "passively" in a biological point of view. This work is based on atomic force microscope (AFM) experiments, which have been realised to measure quantitatively the mechanical properties of pits at the nanoscale

On the air permability of Populus pit

Sap hydrodynamics in vascular cells of trees seems to be controlled by small membranes called pits. Understanding how the pit junctions regulate the sap flow and stop embolism by cavitation is today a challenging issue. The hypothesis that the pit porosity adjusts the flow under negative pressure and stops the air bubble diffusion need to be validated. In this talk, we will present the experimental results on Populus trees that support the idea that pits operate ‘passively’ in a biological point of view. This work is based on atomic force microscope (AFM) experiments, which have been realised to measure quantitatively the mechanical properties of pits at the nanoscale

Modelling the mechanical behaviour of pit membranes in bordered pits with respect to cavitation resistance in angiosperms

Background and Aims Various correlations have been identified between anatomical features of bordered pits in angiosperm xylem and vulnerability to cavitation, suggesting that the mechanical behaviour of the pits may play a role. Theoretical modelling of the membrane behaviour has been undertaken, but it requires input of parameters at the nanoscale level. However, to date, no experimental data have indicated clearly that pit membranes experience strain at high levels during cavitation events. Methods Transmission electron microscopy (TEM) was used in order to quantify the pit micromorphology of four tree species that show contrasting differences in vulnerability to cavitation, namely Sorbus aria, Carpinus betulus, Fagus sylvatica and Populus tremula. This allowed anatomical characters to be included in a mechanical model that was based on the Kirchhoff–Love thin plate theory. A mechanistic model was developed that included the geometric features of the pits that could be measured, with the purpose of evaluating the pit membrane strain that results from a pressure difference being applied across the membrane. This approach allowed an assessment to be made of the impact of the geometry of a pit on its mechanical behaviour, and provided an estimate of the impact on air-seeding resistance. Key Results The TEM observations showed evidence of residual strains on the pit membranes, thus demonstrating that this membrane may experience a large degree of strain during cavitation. The mechanical modelling revealed the interspecific variability of the strains experienced by the pit membrane, which varied according to the pit geometry and the pressure experienced. The modelling output combined with the TEM observations suggests that cavitation occurs after the pit membrane has been deflected against the pit border. Interspecific variability of the strains experienced was correlated with vulnerability to cavitation. Assuming that air-seeding occurs at a given pit membrane strain, the pressure predicted by the model to achieve this mechanical state corresponds to experimental values of cavitation sensitivity (P50). Conclusions The results provide a functional understanding of the importance of pit geometry and pit membrane structure in air-seeding, and thus in vulnerability to cavitation

Organización e instrumentación de la gestión a la hora de los cambios socio-productivos

Con este artículo se pretende ilustrar al lector, sobre la forma en que los cambios sociales y/o productivos afectan la gestión, y a la vez, como ésta puede actuar para minimizar los impactos negativos sobre la organización. Por ello, la primera parte es una contextualización de los principales factores que han afectado notoriamente la vida empresarial durante las últimas dos décadas, en una segunda sección se analiza la forma de evaluar y de medir tanto las acciones como los resultados en el nuevo contexto organizacional; por último, se Invita a la reflexión sobre los nuevos criterios y los nuevos dispositivos de evaluación

DMTs and Covid-19 severity in MS: a pooled analysis from Italy and France

We evaluated the effect of DMTs on Covid-19 severity in patients with MS, with a pooled-analysis of two large cohorts from Italy and France. The association of baseline characteristics and DMTs with Covid-19 severity was assessed by multivariate ordinal-logistic models and pooled by a fixed-effect meta-analysis. 1066 patients with MS from Italy and 721 from France were included. In the multivariate model, anti-CD20 therapies were significantly associated (OR = 2.05, 95%CI = 1.39–3.02, p < 0.001) with Covid-19 severity, whereas interferon indicated a decreased risk (OR = 0.42, 95%CI = 0.18–0.99, p = 0.047). This pooled-analysis confirms an increased risk of severe Covid-19 in patients on anti-CD20 therapies and supports the protective role of interferon

Electronic structure of Ni and Mo silicides investigated by x-ray emission spectroscopy and density functional theory

6 pages. can also be found at: http://prb.aps.org/abstract/PRB/v79/i3/e035117International audienceWe report a combined study of the electronic structure of NiSi2, Ni2Si, MoSi2, and Mo5Si3 using x-ray emission spectroscopy and density functional theory. The local and partial metal d and Si p and sd densities of states (DOSs) are obtained for the four compounds both experimentally and theoretically. This allows refined insight into the Si-metal bonding interaction, shown to be determined by a competition between the effects of the lattice structure and of the spatial extent of the metal d wave function. The latter effect is found to prevail for all four compounds, based on the prominent Si-Mo pd hybridization found in the DOS of MoSi2 and Mo5Si3 and the dominant Ni-Ni dd interaction observed in the electronic structure of NiSi2 and Ni2Si

L'espace Wallonie-Bruxelles, Voyage au bout de la Belgique

info:eu-repo/semantics/publishe

Voyage au coeur de la Belgique fédérale

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Toxicokinetics of cocaine and metabolites in a body-packer becoming symptomatic.

Life-threatening complications may occur in body-packers and the rupture of a single packet containing cocaine may lead to fatality. We report the case of a 35-year-old body-packer who developed at the airport clinical signs of cocaine toxicity. There was evidence of bowel obstruction. The plasma concentration of cocaine, benzoylecgonine (BZE) and ecgonine methyl ester (EME) was determined 1 h after symptoms onset, during surgery and postoperative period. The measured peak value at 1 h was 594 ng/ml for cocaine, 9423 ng/ml for BZE and 3261 ng/ml for EME. We confirm the following order BZE > EME > cocaine for peak plasma concentrations. A rebound in plasma levels was found during surgery, together with electrocardiographic changes. A total of 107 packets were eliminated, and the patient survived