Browsing by Subject "Sulfides"

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    Combinatorial effect of non-steroidal anti-inflammatory drugs and NF-kappaB inhibitors in ovarian cancer therapy
    (Public Library of Science, 2011) Zerbini, Luiz F; Tamura, Rodrigo E; Correa, Ricardo G; Czibere, Akos; Cordeiro, Jason; Bhasin, Manoj; Simabuco, Fernando M; Wang, Yihong; Gu, Xuesong; Li, Linglin
    Several epidemiological studies have correlated the use of non-steroidal anti-inflammatory drugs (NSAID) with reduced risk of ovarian cancer, the most lethal gynecological cancer, diagnosed usually in late stages of the disease. We have previously established that the pro-apoptotic cytokine melanoma differentiation associated gene-7/Interleukin-24 ( mda -7/IL-24) is a crucial mediator of NSAID-induced apoptosis in prostate, breast, renal and stomach cancer cells. In this report we evaluated various structurally different NSAIDs for their efficacies to induce apoptosis and mda -7/IL-24 expression in ovarian cancer cells. While several NSAIDs induced apoptosis, Sulindac Sulfide and Diclofenac most potently induced apoptosis and reduced tumor growth. A combination of these agents results in a synergistic effect. Furthermore, mda -7/IL-24 induction by NSAIDs is essential for programmed cell death, since inhibition of mda -7/IL-24 by small interfering RNA abrogates apoptosis. mda -7/IL-24 activation leads to upregulation of growth arrest and DNA damage inducible (GADD) 45 α and γ and JNK activation. The NF-κB family of transcription factors has been implicated in ovarian cancer development. We previously established NF-κB/IκB signaling as an essential step for cell survival in cancer cells and hypothesized that targeting NF-κB could potentiate NSAID-mediated apoptosis induction in ovarian cancer cells. Indeed, combining NSAID treatment with NF-κB inhibitors led to enhanced apoptosis induction. Our results indicate that inhibition of NF-κB in combination with activation of mda -7/IL-24 expression may lead to a new combinatorial therapy for ovarian cancer.
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    Open Access
    Fine-grained pyroxenites from the Gansfontein kimberlite, South Africa: Evidence for megacryst magma-mantle interaction
    (Geological Society of South Africa, 2004) Doyle, P M; Bell, D R; Le Roex, A P
    The Gansfontein kimberlite contains a suite of fine-grained xenoliths dominated by orthopyroxene, and containing ilmenite, phlogopite, and occasional garnet, with minor quantities of olivine and sulphide. Lamellar intergrowths of orthopyroxene and ilmenite were observed in one sample. The fine grained orthopyroxenite assemblages were observed as discrete xenoliths as a vein in lherzolite, and as a zone margin surrounding a megacrystic dunite. The minerals are characterized by intra- and inter-grain chemical heterogeneity, but are on the whole compositionally similar to those in the abundant, highly evolved Cr-poor megacryst suite at Gansfontein. However, they differ to varying degrees from megacrysts in the concentration of minor elements such as Cr, Al and Ti. Mineral compositions in a pyroxenite vein in lherzolite are higher Cr and Mg#, and lower in Fe3+ than the discrete fine-grained pyroxenites, indicating chemical interaction with peridotite. A single zircon-bearing mica-clinopyroxenite has mineral compositions similar to MARID xenoliths. Fine-grained orthopyroxenites, recognized previously from the Weltevreden and Mzongwana kimberlites and interpreted as rapidly crystallized magmas, are here suggested to result from a reaction between megacryst magma and solid mantle peridotite. Mica-clinopyroxenite may represent the liquid end-product of this reaction. Chemical and modal differences of orthopyroxenites from megacrysts result from reaction with peridotitic components, lack of buffering by typical megacryst mineral assemblages, and possibly shallower origins. Textures and fine-scale chemical disequilibrium indicate that reaction postdates some episodes of megacryst formation and was probably underway when the xenoliths were sampled by ascending kimberlite. Orthopyroxene-garnet thermobarometry indicates an origin of one Gansfontein pyroxenite at ∼1215°C and ∼3.3 GPA, similar to the locus of megacryst crystallization under East... [ABSTRACT FROM AUTHOR]
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    Interaction of milling media and water chemistry in the flotation of selected base metal sulfides
    (2026) Nyoni, Sancho; Corin, Kirsten; O'connor, Cyril
    As the mineral processing industry advances toward more sustainable operations, many factors must be considered, extending beyond the primary goals of ore beneficiation. Notable chemical and operational considerations include process water recycling and the choice of milling media, which can significantly affect metallurgical performance. A primary consideration of the study was how the pulp phase changes during milling, focusing on the chemical interactions of dissolved species common in recycled water with milling media, minerals, and xanthates, and then using flotation as a diagnostic tool to examine the effects on metallurgical performance. Most studies focus on particle size and liberation, with limited attention to the chemical changes occurring during milling. Therefore, this study specifically investigated the chemical effects of milling, including considerations of pulp and mineral surface chemistry. The research was conducted in three distinct phases, examining changes in the pulp phase without any mineral present (the control phase) and during the processing of single sulfide mineral and mixed sulfide mineral ores. Pyrite (Py) and Galena (Gn) were selected for the study. Py is an iron (Fe)-bearing sulfide mineral, often regarded as problematic in flotation operations, while Gn contains no Fe. Each phase involved testing three milling media options: forged steel (FS), 21% high chrome (HiCr), and ceramic (Cer).In the case of FS, milling media are the main producers of Fe ions, which can form complexes capable of modifying pulp chemistry and mineral surface interactions, in ways that complicate ore metallurgy. Synthetic plant water (SPW) was used in each phase to mimic plant water recycling at four progressively higher ionic strengths, and the effects of pH were compared between natural pH and controlled pHs of 4 and 10. Decoupling the effects of the milling media type, mill shell construction, and water type from that of the ore in Phase 1 provided an understanding of the baseline electrochemical properties of the pulp entering flotation and how the behaviour of xanthate collectors was affected by the water type used and the presence of Fe ions and complexes arising from milling media galvanic contact with the aqueous phase during milling. The oxidation state of the iron species present was found to significantly affect collector availability in free form for attachment to the mineral surface, with the Fe(III) state having a more significant impact on the pH and mixed or redox potential (Eh) of the pulp phase than the Fe(II) state. Furthermore, a more oxidising Eh was found to be important in retaining the xanthate collector in dixanthogen form. The water type was also found to have had significant effects on the galvanic activity of the pulp, despite the absence of minerals, thus influencing the extent of milling media dissolution, particularly in the case of FS media. Analysis of how Py and Gn independently respond to changes in water type, milling media, and pH conditions in Phase 2 revealed different behaviours for each mineral. The extent to which each mineral affected milling media dissolution and the chemical properties of the pulp phase entering flotation was compared with Phase 1 results. Milling media type and pH were found to have a greater impact on metallurgical performance than water type. However, it was noted that water type had a more significant effect on the flotation of Gn compared to Py. Besides insights gained from milling and flotation data, several analytical techniques were employed to examine changes in mineral and water composition across different process streams in milling and flotation. The impact of the investigated conditions on mineral surface chemistry was assessed using X-ray photoelectron spectroscopy. Phase 3 was a mixed ore study focused on identifying suitable milling media, water type, and pH conditions that aid in separating Gn from Py and gangue. The dissolution of Gn and FS milling media was higher in the mixed ore case, while the dissolution of Py, the mineral with the higher rest potential, did not change significantly, as was shown by comparisons between FS and Cer milling results. Compared to the single mineral cases, the residual SIBX concentrations in the mixed ore case were higher than those for Gn, but lower and less influenced by water type than in the Py case. Gn recovery was higher at pH 10 compared to Py recovery across all milling media and water type conditions. On the other hand, Py recoveries were notably lower when FS was employed, regardless of water type. This could be due to the depression of quartz and talc, which comprised the gangue, by dissolved Fe species. Therefore, flotation separation of Gn from Py was most effective using FS milling media at high pH levels, and this outcome could be sustained under high ionic strength water conditions. To optimise milling media costs and efficiently operate in regions with high water demand and limited water catchment areas, it is often preferable to use FS media and recycle process water. This study demonstrates that the concerns about the negative metallurgical impacts of their use can be mitigated by combined pH and water ionic strength control. Overall, the research offers a scientific understanding of the effect of the chemical characteristics of the mill pulp phase on flotation performance. It highlights factors influencing the choice of milling media and addresses issues related to process water recycling in flotation operations.