Search results for "barium"
showing 10 items of 262 documents
Y:BaZrO3 Perovskite Compounds I: DFT Study on the Unprotonated and Protonated Local Structures
2011
Y-doped BaZrO(3) derivatives were studied by density functional theory (DFT) to investigate the local arrangements of the octahedral sites in Pm3m cubic frameworks. Single- and double substitution of zirconium by yttrium were considered, including in the presence of a nearby oxygen vacancy. Although the structural symmetry of undoped barium zirconate was not modified after yttrium doping, the presence of yttrium induced several differences in the oxygen sites around it, according to the local geometrical arrangement of yttrium in the host matrix. As an example, the differences between such oxygen sites were shown in the presence of a proton. In this case, different stabilization energies ch…
Fabrication and characterization of barium silicate ultrathin films as an alternative gate oxide
2008
Down-scaling of elementary CMOS elements requires the replacement of SiO2 as a gate oxide. By the identification of the formation conditions of barium silicate in direct contact of a silicon substrate, this study revealed a potential candidate. First of all, a reaction between Ba and SiO2 leading to the formation of barium silicate as been evidenced by in-situ XPS and SR-PES analyses. Then, barium silicate films have been elaborated by oxygen and barium co-deposition at 580 °C. Thermal treatments under vacuum showed that barium silicate was thermally stable up to 900 °C. TEM and SIMS ex-situ analyses revealed a sharp interface with the substrate. Finally, an experimental setup dedicated to …
Introduction et dispersion d'une espèce envahissante : le cas de l'ambroisie à feuilles d'armoise (Ambrosia artemisiifolia L.) en France
2011
National audience; Ambrosia artemisiifolia L. (common ragweed) was accidentally introduced into France in the 1860s. Its single vector of introduction in Europe was red clover seeds (Trifolium pratense L.), probably coming from Pennsylvania, United States at the time. A. artemisiifolia was later introduced into France in many places and at different times. This species has no natural or effective seed dispersal mechanisms and the spread of this weed in the territory is ensured by human activities that carry the seeds and create disturbed environments favourable to its development. It is now established in the Rhone Valley and a number of different factors (cropping system evolution, climate…
Variability of pesticide mineralization in individual soil aggregates of millimeter size
2002
The aim of this study was to compare the 2,4-D mineralization in individual aggregates of millimeter size (3 size classes and 96 aggregates per size class). 14 CO 2 coming from the mineralization of 14 C ring-labeled 2,4-D and evolved by each aggregate incubated in microtiter plates was trapped with barium hydroxide on filters and measured using a Phosphorimager. We observed an important variability of mineralization in aggregates of each size class and in the different size classes of aggregates. The main factors responsible for these fluctuations could be a heterogeneous distribution of degrading microorganisms or of available carbon necessary for cometabolism.
Eight microsatellite markers isolated from common ragweed (Ambrosia artemisiifolia L.) and cross-amplification with herbarium specimens
2009
; Eight microsatellite markers were developed for population genetic analyses of the common ragweed, Ambrosia artemisiifolia. Markers were tested for amplification with three populations (two recent populations from France and North America, and one historical population from herbarium specimens). These loci revealed a high level of genetic variability (5-19 alleles per locus; expected heterozygosity, 0.48-0.92). No significant deviation from Hardy-Weinberg equilibrium and no linkage disequilibrium were observed. The data thus demonstrate their utility as efficient genetic markers for determining the genetic diversity, population differentiation, and gene flow among invasive, native, and h…
Céramiques diélectriques commandables pour applications micro-ondes : composites à base de titanate de baryum-strontium et d'un oxyde non ferroélectr…
2001
Since the last decades, dielectric ceramics have been considered as attractive for microwave applications as tunable dielectric resonators or phase shifters. For that, ceramic devices should be tunable – change in dielectric constant with applied voltage- with moderate to low dielectric constant (30 to 1000) and loss tangent as low as possible. To reconcile these properties, composite ceramics based on Ba0.6Sr0.4TiO3 (BSTO) and a non-ferroelectric oxide with a low dielectric constant (MgTiO3 or MgO) were synthesised. The aim of this study was to correlate the microstructure with the dielectric properties, especially the Curie temperature and the dielectric relaxation phenomena.Ceramics with…
Typification of Dioscorea communis and its synonym Tamus communis var. subtriloba (Dioscoreaceae)
2016
The typification of Dioscorea communis (≡ Tamus communis, Dioscoreaceae) is discussed. The designation of the nomenclatural type is based on the consultation of Linnaeus’s original material preserved at LINN, the Clifford Herbarium at BM, the Herbarium Joachim Burser at UPS, and the literature cited in the protologue. The name is lectotypified using a herbarium sheet preserved at LINN. A lectotype is also selected for the name Tamus communis var. subtriloba, from a specimen preserved at the Gussone’s herbarium at NAP.
Typification of two Linnaean names: Centaurea aspera and Centaurea isnardii (Asteraceae)
2014
The typification of the names Centaurea aspera L. and C. isnardii L. (Asteraceae) is discussed. A lectotype for C. aspera is designated from original material conserved in UPS-BURSER (Joachim Burser Herbarium). Centaurea isnardii is typified by an illustration of Isnard (1719) confirming this name as a synonym of C. aspera subsp. aspera.
Tipificación de Inula montana L. (Asteraceae)
2014
Ferrer-Gallego, P., E. Laguna, R. Rosello, J. Gomez & J. B. Peris (2014). Typification of Inula montana L. (Asteraceae). Candollea 69: 5–8. In Spanish, English and French abstracts.The name Inula montana L. (Asteraceae) is lecto- and epitypified. The designated lectotype corresponds to an icon from Robert Morison published in 1699 and the epitype to a plant specimen collected by Morison and conserved at OXF (Morisonian Herbarium).
Typification of the marine siphonous green algae Caulerpa prolifera (Bryopsidales, Chlorophyta)
2015
The typification of the marine siphonous green algae Caulerpa prolifera (Forsskål) J.V. Lamouroux (≡ Fucus prolifer Forsskål) (Caulerpaceae), including f. obovata (J. Agardh) Weber-van Bosse and f. zosterifolia Børgesen, is discussed. Original material conserved in the Natural History Museum of Denmark (Copenhagen) at C (Herbarium Forsskålii) and in the Botanical Museum of Lund University at LD are designated as the corresponding lectotypes.