Search results for "barium"

A new look atOrthotrichum scanicumGrönvall (Orthotrichaceae, Bryophyta)

2009

Abstract Orthotrichum scanicum Gronvall has been considered a European endemic whose main range corresponded to the central and northern region of the continent, and it is currently included in the 2007 IUCN World Red List as Vulnerable. However, a large number of recent reports and the examination of herbarium specimens have remarkably expanded the limits of its area in the Mediterranean and Caucasian regions. Additionally, the revision of the original collections of Orthotrichum holmenii from Kazakhstan shows that this taxon is conspecific with O. scanicum. An updated description of the species comprising the known range of its morphological variability is provided, and its exclusion from…

Morphological and molecular evidence for interspecific hybridisation in the introduced African genusCrassocephalum(Asteraceae: Senecioneae) in Asia

2009

Abstract The genus Crassocephalum in Asia, introduced there from Africa, was examined by extensive field work, herbarium studies, analyses of pollen and seed fertility, chromosome counts and ITS and trnL‐F sequencing. We found that Crassocephalum in Asia comprises two species and their interspecific hybrid. The two species are C. crepidioides (Benth.) S. Moore and C. rubens (Juss. ex Jacq.) S. Moore, of which the latter is a new record for Asia (north Thailand). The hybrid between these two species in north Thailand originated from a cross between C. crepidioides (2n = 40) as female and C. rubens (2n = 40) as male parent.

Earliest herbarium evidence for the occurrence of Lewinskya acuminata (Orthotrichaceae) in East Africa

2019

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Bryology on 23th September 2019, available online: http://www.tandfonline.com/10.1080/03736687.2019.1655871

Lectotypification of the name Cistus stipulatus, basyonim of Helianthemum stipulatum (Cistaceae)

2015

The typification of the name Cistus stipulatus Forsskål (≡ Helianthemum stipulatum (Forsskål) Christensen) is discussed. The designation of the nomenclatural type is based on an assessment of Forsskål’s original material. The name is lectotypified selecting a specimen from the Herbarium Forsskålii in the National Herbarium Copenhagen at C.

Polar relaxation mode in pure and iron-doped barium titanate

1989

A dielectric relaxation peak is reported in ${\mathrm{BaTiO}}_{3}$ and in ${\mathrm{BaTi}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Fe}}_{\mathrm{x}}$${\mathrm{O}}_{3}$. It is nearly monodispersive, centered in the ${10}^{8}$-Hz range, and slowest at the transition temperature ${T}_{c}$\ensuremath{\simeq}413 K from the cubic to the tetragonal phase. Iron doping lowers ${T}_{c}$ and slows down this relaxation mode.

ChemInform Abstract: Continuous Hydrothermal Synthesis of Nanometric BaZrO3in Supercritical Water.

2008

Abstract Nanocrystalline barium zirconate (BaZrO 3 ) was synthesized using a hydrothermal synthesis process working in supercritical conditions and in a continuous way. By this method, we succeeded in the continuous and rapid production of nanopowders. As a preliminary work three barium precursors have been investigated: barium hydroxide (Ba(OH) 2 ), barium acetate (Ba(CH 3 COO) 2 ) and barium nitrate (Ba(NO 3 ) 2 ). Two of them (Ba(CH 3 COO) 2 and Ba(NO 3 ) 2 ) led to the pure perovskite phase. Then an experimental design has been conducted in order to determine the influence of the experimental parameters on the crystallinity and the grain size of the final product.

Some Aspects of the Influence of Particle Size on Properties and Behaviour of a Dielectric Material : Example of Barium Titanate

1989

Anybody agrees with the idea that particle size plays an important role in the behaviour of a polycrystalline material but very few studies are giving precise information about this role. In this paper some experimental results are presented succintly to illustrate the importance of this physico-chemical factor. They are related to barium titanate, the main component of the dielectric material in the type II ceramic capacitors.

Electronics and Electromagnetism

2007

Theoretical study of Fe doping and oxidation–reduction influence on the photorefractive effect in BaTiO_3

1993

We numerically solve charge-transport and Poisson equations for photorefractive BaTiO3 single crystals with a band model, using four impurity levels, Fe2+–Fe3+, Fe3+–Fe4+, VO••–VO•, and VO•-VOx. Densities and photoinduced spatial distributions of each population are computed as a function of annealing O partial pressure. Space-charge field and beam-coupling gain are also computed as a function of annealing O partial pressure, temperature, Fe concentration, grating wave vector, and light intensity. We discuss the intervening mechanism of impurity centers and the correlations between experimental conditions of crystal growth, oxidation–reduction treatments, and measurement parameters.

Taxonomic clarification in W-Mediterranean Androcymbium (Colchicaceae): A. wyssianum sunk in the synonymy of A.gramineum and A.europaeum restored

2010

Abstract Hoyo A. del & Pedrola-Monfort J.: Taxonomic clarification in W Mediterranean Androcymbium (Colchicaceae): A. wyssianum sunk in the synonymy of A. gramineum and A. europaeum restored. — Willdenowia 40: 47–53. — Online ISSN 1868-6397. — © 2010 BGBM Berlin-Dahlem. doi:10.3372/wi.40.40103 (available via http://dx.doi.org/) Capsule dehiscence has been used as a diagnostic character for W Mediterranean species of Androcymbium. Depending on the state of capsule maturity, the character, however, can be ambiguous in herbarium material. Based on morphological, phenological and cpDNA characters it is shown that misinterpretation of the capsule as indehiscent in the type material of A. gramine…