Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

A family of regression methods derived from standard PLSR

The standard PLSR is presented from a geometric point of view consisting of two projections. In the first, the scores are obtained after an oblique projection of the spectra onto the loadings. In the second, the vector of response values is projected orthogonally onto the scores. A metric is introduced for the oblique projection and a new algorithm for the calculation of the loadings into the variables space is proposed. This work also develops a new parameter, a vector, whose different values lead to different regression models with their own abilities of prediction; one of them is the exact form of the standard PLSR. Two applications are described to illustrate the performance of the proposed method called VODKA regression, which is also a way to build least square regressions by introducing additional knowledge into the models

EXPERIMENTAL STUDY OF THE LASER INDUCED PLASMA IN WELDING CONDITIONS WITH CONTINUOUS HIGH POWER CO2 LASERS

It is well known that the metallic plasmas observed in laser welding play an important role in energy transfert during laser materials processing. They are critical to understanding energy transport to the workpiece. This paper reports an experimental investigation characterizing the plasma using visible emission -spectroscopy. These experiments provided the electron density and temperature distributions (~1017 cm-3 and 6000-7000 °K). The experimental data are then used to determine laser attenuation and refraction as the beam propagate through the plasma column. These results are compared with direct absorption measurements where an integrating spere has been used, and with a numerical simulation. It was observed that the absorption coefficient is closely correlated to the spatial and temporal behaviour of the plasma and the effect of refraction is of primary importance for laser processing when using other gases than helium at high laser intensity

Solution structure of maurotoxin, a scorpion toxin from Scorpio maurus, with high affinity for voltage-gated potassium channels

We thank Dr. Mirjam Czjzek for careful reading of the manuscript, and Dr. Christian Cambillau for constant interest and support.International audienceMaurotoxin (MTX), purified from the scorpionid Scorpio maurus is a potent ligand for potassium channels. It shows a broad specificity as being active on Kv1.1 (Kd = 37 nM), Kv1.2 (Kd = 0.8 nM), Kv1.3 (Kd = 150 nM) voltage-gated potassium channels, as well as on small-conductance calcium-activated potassium channels. It has a unique disulfide pairing among the scorpion toxins family. The solution structure of MTX has been determined by 2D-NMR techniques, which led to the full description of its 3D conformation: a bended helix from residues 6 to 16 connected by a loop to a two-stranded antiparallel beta sheet (residues 23 to 26 and 28 to 31). The interaction of MTX with the pore region of the Kv1.2 potassium channel has been modeled according to their charge anisotropy. The structure of MTX is similar to other short scorpion toxins despite its peculiar disulfide pairing. Its interaction with the Kv1.2 channel involves a dipole moment, which guides and orients the toxin onto the pore, toward the binding site, and which thus is responsible for the specificity

A fractional order model for lead-acid battery crankability estimation

With EV and HEV developments, battery monitoring systems have to meet the new requirements of car industry. This paper deals with one of them, the battery ability to start a vehicle, also called battery crankability. A fractional order model obtained by system identification is used to estimate the crankability of lead-acid batteries. Fractional order modelling permits an accurate simulation of the battery electrical behaviour with a low number of parameters. It is demonstrated that battery available power is correlated to the battery crankability and its resistance. Moreover, the high-frequency gain of the fractional model can be used to evaluate the battery resistance. Then, a battery crankability estimator using the battery resistance is proposed. Finally, this technique is validated with various battery experimental data measured on test rigs and vehicles. © 2009 Elsevier B.V. All rights reserved

Challenges and constraints in developing and implementing sports policy and provision in Antigua and Barbuda: which way now for a small island state?

This paper examines the challenges and constraints of sport policy agenda setting and policy development in a small nation context of Antigua and Barbuda. It also aims to understand and explore existing limitations, issues and trajectories in sport policy implementation. The project draws upon a mixed-methods approach encompassing documentary analysis, 30 in-depth interviews and visual methodology in the form of photo observations. Through this methodology, the purpose of the paper is to open up sport policy agendas allowing the ‘voices’ of those local populations, policymakers, coaches and volunteers to be heard within the context of this study and wider sport policy research. Initial findings indicate sport and physical activity as a contested policy priority, barriers in cross-departmental collaboration, elite sport and performance agenda dilemmas and considerable limitations in third sector human infrastructure and physical facilities. Implications from this small nation sport policy context highlight the need for improved public policy problem definition and the need for clarity in agenda setting within tiers of the evolving sport policy community. Finally, the tentative potential positive policy spaces for future implementation and lessons in policy design involving national, regional and local actors and agencies are identified