Exsertion, flowering and shedding in Panicum maximum (Poaceae)

La floraison, l'exsertion et la maturation des graines ont été observées sur les panicules de quatre clones de #P. maximum$. Les relations à l'intérieur du clone et les différences entre clones ont été étudiées. Floraison, exsertion et maturation des graines sont des processus rapides (< 10 j). Les dates et les durées sont stables à l'intérieur du clone, et les conséquences sur la récolte semencière ont été soulignées. Deux types de comportement floral et leur interaction avec le "seed-set" ont été décrits. La présence de ce polymorphisme montre que ces deux comportements ont soit une "fitness" similaire, soit une fitness dépendante de l'environnement. L'agencement dans le temps de la floraison, de la maturation des graines et de l'apparition successive de plusieurs panicules sur une même talle semble être contrôlé pour minimiser la compétition. Plusieurs points corroborent cette hypothèse : l'arrêt de cette ramification sur la talle lié à un retard de plus de 10 jours entre 2 panicules évite le recouvrement dans le temps des trois processus ; à l'intérieur d'un plant, les talles les plus vigoureuses ont le plus de panicules ; plus le nombre de panicules par talle d'un clone est petit, plus sa panicule est grande. (Résumé d'auteur

Staggering of heading in Panicum maximum Jacq. : origin and regulation

Chez #Panicum maximum$, l'étalement de l'épiaison sur 2 mois, voire plus est un comportement fréquent. L'initiation des talles sur 1 mois est à l'origine de la première vague d'épiaison. Les vagues suivantes sont le résultat d'un processus de ramification paniculaire. Deux principaux systèmes de régulation interviennent durant l'épiaison : 1. une régulation rapide qui alterne les jours de sous-épiaison et de sur-épiaison; 2. une régulation mensuelle qui diminue ou augmente l'intensité de la troisième vague en fonction de l'intensité de la première vague. Ces régulations dans l'étalement des investissements reproductifs peuvent constituer une adaptation aux variations de pluviométrie en milieu tropical. (Résumé d'auteur

Correlation between structural and optical properties of WO3 thin films sputter deposited by glancing angle deposition

International audienceTungsten oxide WO3 thin films are prepared by DC reactive sputtering. The GLancing Angle Deposition method (GLAD) is implemented to produce inclined columnar structures. The incident angle α between the particle flux and the normal to the substrate is systematically changed from 0 to 80°. For incident angles higher than 50°, a typical inclined columnar architecture is clearly produced with column angles β well correlated with the incident angle α according to conventional relationships determined from geometrical models. For each film, the refractive index and extinction coefficient are calculated from optical transmittance spectra of the films measured in the visible region. The refractive index at 589 nm drops from n589 = 2.18 down to 1.90 as α rises from 0 to 80°, whereas the extinction coefficient reaches k589 = 4.27 × 10−3 for an incident angle α = 80°, which indicates that the films produced at a grazing incident angle become more absorbent. Such changes of the optical behaviors are correlated with changes of the microstructure, especially a porous architecture, which is favored for incident angles higher than 50°. Optical band gap Eg, Urbach energy Eu and birefringence Δn617, determined from optical transmittance measurements, are also influenced by the orientation of the columns and their trend is discussed taking into account the disorder produced by the inclined particle flux

South Atlantic mass transports obtained from subsurface float and hydrographic data

Mean total (barotropic + baroclinic) mass transports of the oceanic top 1000 dbar are estimated for two regions of the South Atlantic between 18°S and 47°S. These transports are obtained by using Gravest Empirical Mode (GEM) fields calculated from historical hydrography with temperature and position data from quasi-isobaric subsurface floats deployed from 1992 through 2001. The float-GEM-estimated total mass transports reveal a Brazil Current with a southward flow of 20.9 Sv at 30°S and 46 Sv at 35°S (1 Sverdrup, Sv = 106 m3 s–1). Two recirculation cells are identified in the southwest corner of the subtropical gyre north of 40°S, one centered at 48°W, 37°S recirculating 28.5 Sv and another centered at 40°W, 38°S recirculating 13.9 Sv. The South Atlantic Current (SAC) flows eastward with 50 Sv at 30°W and splits into two branches in the east, one north of 38°S transporting 19 Sv and one south of 41°S transporting 31 Sv. Of the 39.7 Sv of SAC transport that comes from the Malvinas Current/Antarctic Circumpolar Current (ACC) system in the western basin, only 8.7 Sv flow with the northern branch and the remaining 31 Sv flow as the southern branch out of the South Atlantic rejoining the ACC directly (20.6 Sv) or interacting with the Agulhas Current Retroflection (10.4 Sv). From the northern branch, only 4.7 Sv of Malvinas Current/ACC origin and 10.3 Sv of Brazil Current origin (a total of 15 Sv) stays in the South Atlantic forming the Benguela Current, recirculating within the subtropical gyre. The Agulhas Current Retroflection reaches westward as far as 10°E with a transport of 48 Sv. In terms of mean total transport, the cold-water route carries 4.7 Sv in the upper 1000 dbar whereas the warm-water route carries 8.5 Sv. However, considering the interaction between waters from both origins, there is a total of 19.1 Sv of waters entering the Cape Basin from the Pacific Ocean and 18.5 Sv from the Indian Ocean

The mid-depth circulation of the northwestern tropical Atlantic observed by floats

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 56 (2009): 1615-1632, doi:10.1016/j.dsr.2009.06.002.A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e. g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16° N between the Antilles islands and the Mid- Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADWeast of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.MOVE was funded by the Bundesministerium fu¨r Bildung und Forschung (grants 03F0246A and 03F0377B) as well as by the Deutsche Forschungsgemeinschaft (grant SE815/21), NBC by the National Science Foundation through grants OCE 97-29765 and OCE 01-36477, and SAMBA was fully supported by Ifremer

Zonal intermediate currents in the equatorial Atlantic Ocean

Acoustic float data collected near 800 m depth, are used to map zonal mean currents within the Antarctic Intermediate Water (AAIW) tongue in the equatorial Atlantic. Alternating zonal jets of 2° latitudinal width are revealed between 6°S and 6°N. Displacements from profiling floats drifting near 1000 m depth, also reveal similar zonal jets at the base of the AAIW layer. The strongest jets (15 cm s−1 peak) are found at 4°S, 2°S, 0°, 2°N and 4°N. They are coherent longitudinally over order of 3000 km and, poleward of 1°S and 1°N, generally coherent vertically between 800 m and 1000 m. Large seasonal fluctuations exist at both levels: within 1° of equator, AAIW at 800 m flows westward (8 cm s−1 mean) in boreal summer and fall but eastward (3 cm s−1 mean) in winter, whereas the flow at 1000 m is eastward in late fall and winter

Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic

Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 52 (2005): 545-564, doi:10.1016/j.dsr2.2004.12.006.This study combines float data from different projects collected between 1991 and 2003 in the South Atlantic to describe the flow of Antarctic Intermediate Water (AAIW). Velocity spacetime averages are calculated for various grid resolutions and with cells deformed to match the bathymetry, f/H or f/h (with H being the water depth and h being the thickness of the AAIW layer). When judged by the degree of alignment between respective isolines and the resulting average velocity fields, the best grid is based on a nominal cell size of 3º (latitude) by 4º (longitude) with cell shapes deformed according to f/h. Using this grid, objectively estimated mean currents (and their associated errors), as well as meridional and zonal volume transports are estimated. Results show an anticyclonic Subtropical Gyre centred near 36ºS and spanning from 23º±1°S to 46° ± 1ºS. The South Atlantic Current meanders from 33ºS to 46ºS and shows a mean speed of 9.6 ± 7.8 cm s-1 (8.5 Sv ± 3.5 Sv; 1 Sv = 1×106 m3 s-1). The northern branch of the Subtropical Gyre is located between 22ºS and 32ºS and flows westward with a mean speed of 4.7 ± 3.3 cm s-1 (9.3 Sv ± 3.4 Sv). Evidence of a cyclonic Tropical Gyre divided in two sub-cells is visible on the stream function.This work is supported through NSF-Grant no. OCE-0095647 and through the Alfred Wegener Institute for Polar and Marine Research