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    Wyświetlanie 1-4 z 4
    Tytuł:
    A review of investigations into the management of gangue in the flotation of platinum group minerals
    Autorzy:
    O’Connor, C.
    Wiese, J.
    Corin, K.
    McFadzean, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/110708.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    Depressants
    chromite
    copper sulphate
    platinum group minerals
    Opis:
    The Bushveld Complex of South Africa contains almost 90% of the world’s reserves of platinum group minerals (PGMs). In the flotation of PGMs, there are significant challenges arising from the need to treat ever-decreasing grades of the relevant ore deposits. The major challenge in the flotation of these ore bodies is the control and management of the gangue minerals, particularly silicates such as orthopyroxene, plagioclase feldspar, and pyroxene which are often rimmed with talc which makes them naturally floatable. It has been shown that various polysaccharide depressants such as CMC and guar have different properties in terms of depressing the gangue minerals. Since the PGMs are often associated with sulphides, copper sulphate is widely used as an activator in PGM flotation but can inadvertently activate the gangue minerals as well as reduce the recovery of PtTe2 which accounts for up to 40% of the Pt in the Platreef ore body. Depressants also reduce the mass of solids reporting to the froth and can thus destabilize the froth. This effect on the froth can be mitigated by using higher frother dosages or water of higher ionic strength. In summary due care needs to be taken to carry out site test work to develop an optimum ratio of collector, frother, activator and depressant to ensure that the highest grades and recoveries of the PGEs are obtained while reducing depressant dosage as much as possible. Chromite recoveries can be reduced through the application of gravity separation or reducing entrainment through reduced water recovery.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2018, 54, 4; 1107-1115
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Anatomy of the Early Cretaceous enantiornithine bird Rapaxavis pani
    Autorzy:
    O'Connor, J.K.
    Chiappe, L.M.
    Gao, C.
    Zhao, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/21083.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    anatomy
    Early Cretaceous
    enantiornithine bird
    bird
    Rapaxavis pani
    Aves
    Enantiornithes
    Longipterygidae
    Rapaxavis
    Jiufotang Formation
    Cretaceous
    China
    paleontology
    Opis:
    The exquisitely preserved longipterygid enantiornithine Rapaxavis pani is redescribed here after more extensive preparation. A complete review of its morphology is presented based on information gathered before and after preparation. Among other features, Rapaxavis pani is characterized by having an elongate rostrum (close to 60% of the skull length), rostrally restricted dentition, and schizorhinal external nares. Yet, the most puzzling feature of this bird is the presence of a pair of pectoral bones (here termed paracoracoidal ossifications) that, with the exception of the enantiornithine Concornis lacustris, are unknown within Aves. Particularly notable is the presence of a distal tarsal cap, formed by the fusion of distal tarsal elements, a feature that is controversial in non−ornithuromorph birds. The holotype and only known specimen of Rapaxavis pani thus reveals important information for better understanding the anatomy and phylogenetic relationships of longipterygids, in particular, as well as basal birds as a whole.
    Źródło:
    Acta Palaeontologica Polonica; 2011, 56, 3
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A second Cretaceous ornithuromorph bird from the Changma Basin, Gansu Province, northwestern China
    Autorzy:
    You, H.-L.
    Atterholt, J.
    O'Connor, J.K.
    Harris, J.D.
    Lamanna, M.C.
    Li, D.-Q.
    Powiązania:
    https://bibliotekanauki.pl/articles/22506.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Cretaceous
    ornithuromorph bird
    bird
    Aves
    Ornithuromorpha
    Aptian
    Early Cretaceous
    paleontology
    Changma basin
    Gansu province
    China
    Opis:
    Finely−bedded lacustrine deposits of the Aptian (Lower Cretaceous) Xiagou Formation exposed in the Changma Basin of Gansu Province, northwestern China, have yielded numerous fossil vertebrate remains, including approximately 100 avian specimens. Though the majority of these birds appear referable to the ornithuromorph Gansus yumenensis, a number of enantiornithine fossils have also been recovered. Here we report on a specimen consisting of a complete, three−dimensionally preserved sternum, furcula, and sternal ribs that represents a second ornithuromorph taxon from the Xiagou Formation at Changma. The fossil exhibits morphologies that distinguish it from all previously−known Xiagou birds and demonstrate that it represents a derived non−ornithurine member of Ornithuromorpha. Though it is morphologically distinct from the equivalent elements of all other described ornithuromorphs, the material is too incomplete to justify the erection of a new taxon. Nonetheless, it increases the taxonomic diversity of the Xiagou avifauna, thereby expanding our knowledge of Early Cretaceous avian diversity and evolution.
    Źródło:
    Acta Palaeontologica Polonica; 2010, 55, 4
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A new mammal from the Turonian–Campanian (Upper Cretaceous) Galula Formation, southwestern Tanzania
    Autorzy:
    O’Connor, P.M.
    Krause, D.W.
    Stevens, N.J.
    Groenke, J.R.
    MacPhee, R.D.E.
    Kalthoff, D.C.
    Roberts, E.M.
    Powiązania:
    https://bibliotekanauki.pl/articles/20223.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Opis:
    We here establish a new mammaliaform genus and species, Galulatherium jenkinsi (Mammalia), from the Upper Cretaceous Galula Formation in the Rukwa Rift Basin of southwestern Tanzania. This represents the first named taxon of a mammaliaform from the entire Late Cretaceous of continental Afro-Arabia, an interval of 34 million years. Preliminary study of the holotypic and only known specimen (a partial dentary) resulted in tentative assignation to the Gondwanatheria, a poorly known, enigmatic clade of Late Cretaceous–Paleogene Gondwanan mammals (Krause et al. 2003). The application of advanced imaging (μCT) and visualization techniques permits a more detailed understanding of key anatomical features of the new taxon. It reveals that the lower dentition consisted of a large, procumbent lower incisor and four cheek teeth, all of which were evergrowing (hypselodont). Importantly, all of the teeth appear devoid of enamel. Comparisons conducted with a range of Mesozoic and selected Cenozoic mammaliaform groups document a number of features (e.g., columnar, enamel-less and evergrowing teeth, with relatively simple occlusal morphology) expressed in Galulatherium that are reminiscent of several distantly related groups, making taxonomic assignment difficult at this time. Herein we retain the provisional referral of Galulatherium (RRBP 02067) to Gondwanatheria; it is most similar to sudamericids such as Lavanify and Bharratherium from the Late Cretaceous of Madagascar and India, respectively, in exhibiting relatively simple, high-crowned, columnar cheek teeth. Other features (e.g., enamel-less dentition) are shared with disparate forms such as the Late Jurassic Fruitafossor and toothed xenarthrans (e.g., sloths), here attributed to convergence. Revised analyses of the depositional context for the holotype place it as having lived sometime between the late Turonian and latest Campanian (roughly 91–72 million years ago). This enhanced geochronological context helps to refine the palaeobiogeographical significance of Galulatherium among Cretaceous mammals in general and those from Gondwanan landmasses specifically.
    Źródło:
    Acta Palaeontologica Polonica; 2019, 64, 1
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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