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Bendadaite, a new iron arsenate mineral of the arthurite group
- U. Kolitsch, D. Atencio, N. V. Chukanov, N. V. Zubkova, L. A. D. Menezes Filho, J. M. V. Coutinho, W. D. Birch, J. Schlüter, D. Pohl, A. R. Kampf, I. M. Steele, G. Favreau, L. Nasdala, S. Möckel, G. Giester, D. Yu. Pushcharovsky
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- Journal:
- Mineralogical Magazine / Volume 74 / Issue 3 / June 2010
- Published online by Cambridge University Press:
- 05 July 2018, pp. 469-486
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Bendadaite, ideally Fe2+Fe23+ (AsO4)2(OH)2·4H2O, is a new member of the arthurite group. It was found as a weathering product of arsenopyrite on a single hand specimen from the phosphate pegmatite Bendada, central Portugal (type locality). Co-type locality is the granite pegmatite of Lavra do Almerindo (Almerindo mine), Linópolis, Divino das Laranjeiras county, Minas Gerais, Brazil. Further localities are the Veta Negra mine, Copiapó province, Chile; Oumlil-East, Bou Azzer district, Morocco; and Pira Inferida yard, Fenugu Sibiri mine, Gonnosfanadiga, Medio Campidano Province, Sardinia, Italy.
Type bendadaite occurs as blackish green to dark brownish tufts (<0.1 mm long) and flattened radiating aggregates, in intimate association with an intermediate member of the scorodite–mansfieldite series. It is monoclinic, space group P21/c, with a = 10.239(3) Å, b = 9.713(2) Å, c = 5.552(2) Å, β = 94.11(2)°, V = 550.7(2) Å3, Z = 2. Electron-microprobe analysis yielded (wt.%): CaO 0.04, MnO 0.03, CuO 0.06, ZnO 0.04, Fe2O3 (total) 43.92, Al2O3 1.15, SnO2 0.10, As2O5 43.27, P2O5 1.86, SO3 0.03. The empirical formula is (Fe2+0.52Fe3+0.32☐0.16)Σ1.00(Fe3+1.89Al0.11)Σ2.00(As1.87P0.13)Σ2.00O8(OH)2.00·4H2O based on 2(As,P) and assuming ideal 8O, 2(OH), 4H2O and complete occupancy of the ferric iron site by Fe3+ and Al. Optically, bendadaite is biaxial, positive, 2Vest. = 85±4°, 2Vcalc. = 88°, with α 1.734(3), β 1.759(3), γ 1.787(4). Pleochroism is medium strong: X pale reddish brown, Y yellowish brown, Z dark yellowish brown; absorption Z > Y > X, optical dispersion weak, r > v. Optical axis plane is parallel to (010), with X approximately parallel to a and Z nearly parallel to c. Bendadaite has vitreous to sub-adamantine luster, is translucent and non-fluorescent. It is brittle, shows irregular fracture and a good cleavage parallel to {010}. Dmeas. 3.15±0.10 g/cm3, Dcalc. 3.193 g/cm3 (for the empirical formula). The five strongest powder diffraction lines [d in Å (I)(hkl)] are 10.22 (10)(100), 7.036 (8)(110), 4.250 (5)(111), 2.865 (4)(), 4.833 (3)(020,011). The d spacings are very similar to those of its Zn analogue, ojuelaite. The crystal structure of bendadaite was solved and refined using a crystal from the co-type locality with the composition (Fe2+0.95☐0.05)Σ1.00(Fe3+1.80Al0.20)Σ2.00(As1.48P0.52)Σ2.00O8(OH)2·4H2O (R = 1.6%), and confirms an arthurite-type atomic arrangement.
Diversity of neuronal phenotypes expressed in monolayer cultures from immature rabbit retina
- V. Möckel, S. Löhrke, H.-D. Hofmann
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- Journal:
- Visual Neuroscience / Volume 11 / Issue 4 / July 1994
- Published online by Cambridge University Press:
- 02 June 2009, pp. 629-642
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We have used monolayer cultures prepared from early postnatal rabbit retinae (days 2–5) by the sandwich technique to study the capacity of immature neurons to express specific neuronal phenotypes in a homogeneous in vitro environment. Applying morphological, immunocytochemical, and autoradiographic criteria, we demonstrate that a variety of phenotypes could be distinguished after 7–14 days in vitro, and correlated with known retinal cell types. Bipolar cell-like neurons (approximately 4% of total cell number) were identified by cell type-specific monoclonal antibodies (115A10) and their characteristic bipolar morphology. Small subpopulations (about 1%) of GABA-immunoreactive neurons acquired elaborate morphologies strikingly similar to those of A- and B-type horizontal cells. Amongst putative amacrine cells several different subpopulations could be classified. GABA-immunoreactive amacrine-like neurons (6.5%), which also showed high affinity [3H]-GABA uptake, comprised cells of varying size and shape and could be subdivided into subpopulations with respect to their response to different glutamate receptor agonists (NMDA, kainic acid, quisqualic acid). In addition, a small percentage of [3H]-GABA accumulating cells with large dendritic fields showed tyrosine-hydroxylase immunoreactivity. Presumptive glycinergic amacrine cells (18.5%) were rather uniform in shape and had small dendritic fields. Release of [3H]-glycine from these neurons was evoked by kainic and quisqualic acid but not by NMDA. Small [3H]-glutamate accumulating neurons with few short processes were the most frequent cell type (73%). This cell type also exhibited opsin immunoreactivity and probably represented incompletely differentiated photoreceptor cells. Summing the numbers of characterized cells indicated that we were able to attribute a defined retinal phenotype to most, if not all of the cultured neurons. Thus, we have demonstrated that immature neuronal cells growing in monolayer cultures, in the absence of a structured environment, are capable of maintaining or producing specific morphological and functional properties corresponding to those expressed in vivo. These results stress the importance of intrinsic factors for the regulation of neuronal differentiation. On the other hand, morphological differentiation was far from perfect indicating the requirement for regulatory factors.