A trait-based trade-off between growth and mortality: Evidence from 15 tropical tree species using size-specific relative growth rates

A life-history trade-offbetween low mortality in the dark and rapid growth in the light is one of the most widely accepted mechanisms underlying plant ecological strategies in tropical forests. Differences in plant functional traits are thought to underlie these distinct ecological strategies; however, very few studies have shown relationships between functional traits and demographic rates within a functional group. We present 8 years of growth and mortality data from saplings of 15 species of Dipterocarpaceae planted into logged-over forest in Malaysian Borneo, and the relationships between these demographic rates and four key functional traits: wood density, specific leaf area (SLA), seed mass, and leaf C:N ratio. Species-specific differences in growth rates were separated from seedling size effects by fitting nonlinear mixed-effects models, to repeated measurements taken on individuals at multiple time points. Mortality data were analyzed using binary logistic regressions in a mixed-effects models framework. Growth increased and mortality decreased with increasing light availability. Species differed in both their growth and mortality rates, yet there was little evidence for a statistical interaction between species and light for either response. There was a positive relationship between growth rate and the predicted probability of mortality regardless of light environment, suggesting that this relationship may be driven by a general trade-offbetween traits that maximize growth and traits that minimize mortality, rather than through differential species responses to light. Our results indicate that wood density is an important trait that indicates both the ability of species to grow and resistance to mortality, but no other trait was correlated with either growth or mortality. Therefore, the growth mortality trade-offamong species of dipterocarp appears to be general in being independent of species crossovers in performance in different light environments. © 2014 The Authors

Forest diversity promotes individual tree growth in central European forest stands

Most experimental evidence on the relationship between biodiversity and ecosystem functioning comes from ecosystems with fast-growing plants, such as grasslands. Although forests provide essential ecological services, they have been less well investigated.  We used dendrochronology to compare the tree radial growth rates of four important timber species in replicated, spatially mapped stands that differed in tree composition and diversity within a central European managed forest.  Growth rates differed among species but were largely unaffected by the density of neighbouring trees.  Increasing stand diversity enhanced individual growth rates, after accounting for the effects of tree density and size. These increases were statistically indistinguishable among the four species. In contrast, the effects of stand and neighbourhood species composition on growth rates were non-significant.  Policy implications. Our study of long-established central European forest stands revealed levels of tree diversity can be increased in managed forests, with the potential for modest increases in tree growth rates. These results suggest that in addition to the biodiversity and risk mitigation benefits associated with shifting practices away from monoculture management, increased carbon sequestration and yields in mature forests are likely to be realized. Our results suggest that it is possible to increase forest diversity with little or no costs to production and even with the potential for modest increases in tree growth rates

Simple scoring system to predict in-hospital mortality after surgery for infective endocarditis

BACKGROUND: Aspecific scoring systems are used to predict the risk of death postsurgery in patients with infective endocarditis (IE). The purpose of the present study was both to analyze the risk factors for in-hospital death, which complicates surgery for IE, and to create a mortality risk score based on the results of this analysis. METHODS AND RESULTS: Outcomes of 361 consecutive patients (mean age, 59.1\ub115.4 years) who had undergone surgery for IE in 8 European centers of cardiac surgery were recorded prospectively, and a risk factor analysis (multivariable logistic regression) for in-hospital death was performed. The discriminatory power of a new predictive scoring system was assessed with the receiver operating characteristic curve analysis. Score validation procedures were carried out. Fifty-six (15.5%) patients died postsurgery. BMI >27 kg/m2 (odds ratio [OR], 1.79; P=0.049), estimated glomerular filtration rate 55 mm Hg (OR, 1.78; P=0.032), and critical state (OR, 2.37; P=0.017) were independent predictors of in-hospital death. A scoring system was devised to predict in-hospital death postsurgery for IE (area under the receiver operating characteristic curve, 0.780; 95% CI, 0.734-0.822). The score performed better than 5 of 6 scoring systems for in-hospital death after cardiac surgery that were considered. CONCLUSIONS: A simple scoring system based on risk factors for in-hospital death was specifically created to predict mortality risk postsurgery in patients with IE

Equivalent Thermal Conductivities for Twisted Flat Windings

The authors of this paper intend to develop a method of determination of equivalent thermal conductivities for twisted flat windings. The conductivities determined are radial and parallel to the principal directions of the windings. A design has been realized thanks to the thermal modulus of the computation software Flux2D using a finite elements method. Following that phase, numerical correlations permitting to express the radial conductivities as a function of temperature, filling rate and insulation conductivities are proposed.Les auteurs de cet article se proposent de développer une étude de détermination de conductivités thermiques équivalentes d'empilements de bobinages plats torsadés. Les conductivités sont déterminées dans le plan radial (perpendiculaire à l'axe des bobinages) et parallèlement aux directions principales de la structure. La méthode utilisée est exclusivement numérique et est réalisée à l'aide du logiciel de calculs bidimensionnels par éléments finis Flux2D. Des corrélations numériques exploitables permettent d'obtenir directement les conductivités radiales en fonction du taux de remplissage, de la température du milieu et des conductivités des isolants électriques

Modelling of the steady state thermal behaviour of a permanent magnet direct current motor with commutator. 3D finite elements study

The aim of this work concerns the development and the validation of a thermal steady state model applied to a permanent magnet direct current motor with commutator. The rated power of the machine is 120 W. Design has been realized thanks to the thermal modulus of the computation software with the finite element method Flux3D. It is shown in this work how it is possible to use only the heat equation to simulate the thermal behaviour of the motor. It implies calculating of new fluid conductivities (considering also all thermal modes) by comparison of calculated and experimental temperatures. To realize these 3D modelizations, it is necessary to know and to locate all the losses of the motor which are considered as thermal sources. The experimental temperatures are given by 40 chromel-alumel thermocouples of 100 μm diameter located in the rotor and the stator of the machine. Numerical computations use Dirichlet boundary layer conditions given by an IR camera

Dimensionnement technico-économique de conduite forcee pour microcentrale hydroelectrique en utilisant les algorithmes genetiques

La conduite forcée est l’un des principaux éléments à considérer dans les projets d’aménagement de microcentrale hydroélectrique. Ainsi, son dimensionnement porte un intérêt scientifique élevé et fait l’objet de diverses méthodes. Ces méthodes sont basées sur des relations empiriques ou analytiques permettant d’optimiser les pertes de charge. Dans cet article, un nouveau concept de dimensionnement est développé en utilisant l’optimisation bi-objective avec les algorithmes génétiques NSGA II. Les deux fonctions objectives considérées sont le coût d’investissement et le rendement de la conduite forcée. Le diamètre et la longueur de la conduite forcée sont considérés comme variables d’optimisation. La méthode de dimensionnement est appliquée à trois sites potentiels en aménagement hydroélectrique du Bénin. Pour chaque site, les résultats de simulation présentent des courbes de front de Pareto qui représentent l’ensemble des solutions non dominées. Nous avons noté que le diamètre est un paramètre déterminant dans l’optimisation bi-objectif du coût d’investissement et du rendement de la conduite forcée. La longueur ne constitue pas un paramètre d’optimisation mais est plutôt est un paramètre spécifique à définir en tenant compte des contraintes environnementales du site. Cette étude présente aussi l’avantage qu’elle peut permettre de dimensionner la conduite forcée pour un site quelconque.Mots clés: Algorithmes génétiques ; Conduite forcée ; Coût ; Dimensionnement ;RendementEnglish Title: Techno-economic sizing of penstock for micro-hydropower using genetic algorithmsEnglish AbstractPenstock is one of the most important components to consider in micro hydropower projects. Thus, Penstock sizing has an interest and is subject of various methods. These methods either based on empirical or analytical relations, allowed to optimize friction Loss. In this paper, a new sizing concept is developed using bi-objective optimization with genetic algorithms NSGA II. Investment cost and efficiency of the penstock constitute the both objective functions of the optimization process. The decision variables considered are the diameter and the length of the penstock. The case study is applied to the three potential hydro sites (Affon, Beterou and Vossa) in Benin. For each potential hydro site, the simulation results give Pareto front curves which show nondominated solutions sets. We noted that diameter is a decisive parameter for optimization of investment cost and efficiency of Penstock, simultaneously. The length  of the penstock is not an optimization parameter but is a specific parameter to define considering the environmental constraints of the site. This study has the advantage to be applied to any site for sizing Penstock.Keywords: Genetic Algorithms; Penstock; Cost; sizing; Efficienc

Reluctance network modeling tubular linear alternator considering iron nonlinearities

International audienc

Design and Performance Prediction for Miniaturized Stirling Power generators

International audienc

Analysis of the thermal variations in a moving pantograph strip using an electro-thermal simulation tool and validating by experimental tests

The performance of the pantograph-catenary system is very significant in supplying reliable electrical power for the operation of trains. Many problems arise due to the increase in temperature inside the pantograph strip. More research works have been done to study the temperature extrema of the system but it is quite difficult to obtain the experimental values during a real-time train operation. Moreover, performing experimental tests needs a representative test bench of the system or a real train. This is challenging owing to the time and availability of materials and taking into account the number of physical phenomena to control and measure. To address this problem, the authors of this study present an electro-thermal modeling tool. The heat sources which characterize the system are analyzed to generate a heat equation formulation. This equation is solved with the finite differences numerical method in order to obtain the temperature distribution in the pantograph strip. In addition, some specifications such as computation time or required memory are taken into account. More precisely, mathematical and numerical optimizations are proposed to improve these specifications. The tool is validated by comparing the simulated results with the experimental tests obtained from a test bench located at POLIMI (Polytechnico Di Milano, Milan). Finally, thermal interpretations as well as relative gap analyses are done in different situations

Forest diversity promotes individual tree growth in central European forest stands

Most experimental evidence on the relationship between biodiversity and ecosystem functioning comes from ecosystems with fast-growing plants, such as grasslands. Although forests provide essential ecological services, they have been less well investigated. We used dendrochronology to compare the tree radial growth rates of four important timber species in replicated, spatially mapped stands that differed in tree composition and diversity within a central European managed forest. Growth rates differed among species but were largely unaffected by the density of neighbouring trees. Increasing stand diversity enhanced individual growth rates, after accounting for the effects of tree density and size. These increases were statistically indistinguishable among the four species. In contrast, the effects of stand and neighbourhood species composition on growth rates were non-significant. Policy implications. Our study of long-established central European forest stands revealed levels of tree diversity can be increased in managed forests, with the potential for modest increases in tree growth rates. These results suggest that in addition to the biodiversity and risk mitigation benefits associated with shifting practices away from monoculture management, increased carbon sequestration and yields in mature forests are likely to be realized. Our results suggest that it is possible to increase forest diversity with little or no costs to production and even with the potential for modest increases in tree growth rates