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Leydetite, Fe(UO2)(SO4)2(H2O)11, a new uranyl sulfate mineral from Mas d’Alary, Lodève, France
- J. Plášil, A. V. Kasatkin, R. Škoda, M. Novák, A. Kallistová, M. Dušek, R. Skála, K. Fejfarová, J. Čejka, N. Meisser, H. Goethals, V. Machovič, L. Lapčák
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- Journal:
- Mineralogical Magazine / Volume 77 / Issue 4 / June 2013
- Published online by Cambridge University Press:
- 05 July 2018, pp. 429-441
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Leydetite, monoclinic Fe(UO2)(SO4)2(H2O)11(IMA 2012–065), is a new supergene uranyl sulfate from Mas d'Alary, Lodève, Hérault, France. It forms yellow to greenish, tabular, transparent to translucent crystals up to 2 mm in size. Crystals have a vitreous lustre. Leydetite has a perfect cleavage on (001). The streak is yellowish white. Mohs hardness is ∼2. The mineral does not fluoresce under long- or short-wavelength UV radiation. Leydetite is colourless in transmitted light, non-pleochroic, biaxial, with α = 1.513(2), γ = 1.522(2) (further optical properties could not be measured). The measured chemical composition of leydetite, FeO 9.28, MgO 0.37, Al2O30.26, CuO 0.14, UO340.19, SO321.91, SiO20.18, H2O 27.67, total 100 wt.%, leads to the empirical formula (based on 21 O a.p.f.u.), (Fe0.93Mg0.07Al0.04Cu0.01)Σ1.05(U1.01O2)(S1.96Si0.02)Σ1.98O8(H2O)11. Leydetite is monoclinic, space group C2/c, with a = 11.3203(3), b = 7.7293(2), c = 21.8145(8) Å, β = 102.402(3)°, V = 1864.18(10) Å3, Z = 4, and Dcalc = 2.55 g cm–3. The six strongest reflections in the X-ray powder diffraction pattern are [dobs in Å (I) (hkl)]: 10.625 (100) (002), 6.277 (1) (11), 5.321 (66) (004), 3.549 (5) (006), 2.663 (4) (008), 2.131 (2) (0 0 10). The crystal structure has been refined from single-crystal X-ray diffraction data to R1 = 0.0224 for 5211 observed reflections with [I > 3σ(I)]. Leydetite possesses a sheet structure based upon the protasite anion topology. The sheet consists of UO7 bipyramids, which share four of their equatorial vertices with SO4 tetrahedra. Each SO4 tetrahedron, in turn, shares two of its vertices with UO7 bipyramids. The remaining unshared equatorial vertex of the bipyramid is occupied by H2O, which extends hydrogen bonds within the sheet to one of a free vertex of the SO4 tetrahedron. Sheets are stacked perpendicular to the c direction. In the interlayer, Fe2+ ions and H2O groups link to the sheets on either side via a network of hydrogen bonds. Leydetite is isostructural with the synthetic compound Mg(UO2)(SO4)2(H2O)11. The name of the new mineral honours Jean Claude Leydet (born 1961), an amateur mineralogist from Brest (France), who discovered the new mineral.
Application of Bayesian Belief Networks for the prediction of macroinvertebrate taxa in rivers
- V. Adriaenssens, P. L.M. Goethals, J. Charles, N. De Pauw
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- Journal:
- Annales de Limnologie - International Journal of Limnology / Volume 40 / Issue 3 / September 2004
- Published online by Cambridge University Press:
- 15 February 2009, pp. 181-191
- Print publication:
- September 2004
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Integrated ecological models are of great potential as predictive tools in decision support of river management. Such models need to be transparent and consistent with the existing expert knowledge, and give the river manager adequate information regarding their inherent uncertainty. One way to fulfil these needs is through the use of Bayesian Belief Networks (BBNs). Such networks represent cause-and-effect assumptions between system variables in a graphical structure. To establish the potential of Bayesian Belief Networks in river management, a small-scale study was performed with the aim of assessing the success of prediction of macroinvertebrate taxa in rivers by means of a selected number of environmental variables. Gammaridae and Asellidae were chosen because of their high relative abundances in small and large brooks in contrast to other macroinvertebrate taxa. Based on one-layered BBN networks, the predictive capacity of the models was assessed by means of the number of Correctly Classified Instances (CCI) and Cohen’s Kappa (K). The performance of these models was moderate to good for presence/absence classifications but showed a low to moderate performance when predicting abundance classes. When extending the former BBN network to a two-layered one, enhancing the number of links and variables, no obvious improvement in model performance was detected. The results indicate that thoughtful input variable selection as well as sensitivity analysis will improve the models for practical use in river restoration management.
3 - Cladistics of Gentianaceae: a morphological approach
- Edited by Lena Struwe, New York Botanical Garden, Victor A. Albert, University of Alabama, Tuscaloosa
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- Book:
- Gentianaceae
- Published online:
- 08 August 2009
- Print publication:
- 09 May 2002, pp 310-376
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Summary
ABSTRACT
The infrafamilial relationships of the Gentianaceae are investigated by means of a cladistic analysis of 84 phenotypic characters, based mainly on data from the literature. The 41 genera that were selected for the analysis, including the formerly loganiaceous genera Anthocleista and Fagraea and the monotypic genus Saccifolium, are a fair representation of the character diversity in the family. The diverse genus Gentiana is represented by six of its sections. As outgroups we used Strychnos and Geniostoma (Loganiaceae), Gelsemium (Gelsemiaceae), and two genera each of Apocynaceae and Rubiaceae.
In the strict consensus cladogram of all most-parsimonious trees Gentianaceae has an unresolved basal trichotomy between Saccifolium (of tribe Saccifolieae), Potaliinae, and a major clade including all other genera. In this clade only tribe Gentianeae and subtribe Chironiinae of tribe Chironieae (Ixanthus excepted) are recognized as monophyletic groups. Within tribe Gentianeae, subtribe Gentianinae is nested in a paraphyletic subtribe Swertiinae. The relationships between the representatives of Exaceae, Canscorinae and Coutoubeinae (Chironieae), and Helieae are almost completely unresolved. An interesting exception is the sister-group relationship between Exacum and Cotylanthera.
Two complementary explanations for the lack of resolution in most parts of the cladogram are discussed: (1) the morphological characters of most tropical members of the family are insufficiently known, and (2) morphological characters are not well suited to resolve the more basal relationships in Gentianaceae.
Keywords: Gentianaceae, infrafamilial classification, morphology, phylogeny, phytochemistry.
5 - The seeds of Gentianaceae
- Edited by Lena Struwe, New York Botanical Garden, Victor A. Albert, University of Alabama, Tuscaloosa
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- Book:
- Gentianaceae
- Published online:
- 08 August 2009
- Print publication:
- 09 May 2002, pp 498-572
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Summary
ABSTRACT
Seeds of representatives of 78 genera of the Gentianaceae were studied using scanning electron microscopy. Seeds of most taxa are relatively small, often between 0.3 mm and 0.7 mm in length. They develop from unitegmic, tenuinucellate ovules and are exotestal or sometimes have collapsed or reduced testas. In spite of their small size, the seeds show an extensive diversity in micromorphology.
Seed structure is often characteristic at the tribal, subtribal, or generic level. Testa cells vary in orientation, shape, undulation of the anticlinal walls and pitting of the inner walls. The outer wall is always thin and without a cuticular structure. Except for the inclusion of the Potaliinae, and the delimitation of the Saccifolieae, seed structure sustains the new classification of the Gentianaceae as proposed by Struwe et al. in Chapter 2 of this volume. Crystallized structures were found upon and under the exotestal cuticle of several genera of the Chironieae, Coutoubeinae, and Faroinae.
Seeds of the mycotrophic/saprophytic genera are all small and may be strongly reduced. Owing to adaptations to a saprophytic lifestyle, seed characters of saprophytes are of limited taxonomic use at the subgeneric level.
The seeds of the majority of species are dispersed by the wind. Most species are wind ballists. Endozoochorous dispersal is known in Potaliinae and in one species of Chironia. Seeds may belong to different seed bank types. Seed germination is epigeal. Seedlings are small and phanerocotylar.
Keywords: dispersal, embryology, Gentianaceae, germination, seed morphology, testa.