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The relative effects were investigated of frother and collector type, feed particle size, solids percent, ore composition and grinding environment in relation to the use of mild steel or stainless steel and high or low pH on the froth stability in the flotation of a typical porphyry Cu ore. Experiments were carried out using a Cu ore containing 1.2 wt% chalcopyrite, 0.9 wt% pyrite and 0.04 wt% molybdenite and the frothers MIBC, PPG425, a propylene glycol, and Cytec Oreprep F593, a blend of glycol ethers. The results showed that the frother type and chemistry was the most important factor, with the glycol-based frothers providing a much higher froth stability, while other relevant factors were, in order, feed solids percent, grind size and pH. The type of xanthate collector employed had little effect on froth stability. Mild steel grinding media generally resulted in higher froth stability. From an operational point of view, controlling factors such as frother type and concentration, solids percent, and grind size can be used to compensate for changes in froth stability due to different grinding media or changes in feed grade and Cu/Fe ratio in the ore, without affecting overall metallurgical performance., The relative effects were investigated of frother and collector type, feed particle size, solids percent, ore composition and grinding environment in relation to the use of mild steel or stainless steel and high or low pH on the froth stability in the flotation of a typical porphyry Cu ore. Experiments were carried out using a Cu ore containing 1.2 wt% chalcopyrite, 0.9 wt% pyrite and 0.04 wt% molybdenite and the frothers MIBC, PPG425, a propylene glycol, and Cytec Oreprep F593, a blend of glycol ethers. The results showed that the frother type and chemistry was the most important factor, with the glycol-based frothers providing a much higher froth stability, while other relevant factors were, in order, feed solids percent, grind size and pH. The type of xanthate collector employed had little effect on froth stability. Mild steel grinding media generally resulted in higher froth stability. From an operational point of view, controlling factors such as frother type and concentration, solids percent, and grind size can be used to compensate for changes in froth stability due to different grinding media or changes in feed grade and Cu/Fe ratio in the ore, without affecting overall metallurgical performance.

We introduce a novel method to represent time independent, scalar data sets as complex networks. We apply our method to investigate gene expression in the response to osmotic stress of Arabidopsis thaliana. In the proposed network representation, the most important genes for the plant response turn out to be the nodes with highest centrality in appropriately reconstructed networks. We also performed a target experiment, in which the predicted genes were artificially induced one by one, and the growth of the corresponding phenotypes compared to that of the wild-type. The joint application of the network reconstruction method and of the in vivo experiments allowed identifying 15 previously unknown key genes, and provided models of their mutual relationships. This novel representation extends the use of graph theory to data sets hitherto considered outside of the realm of its application, vastly simplifying the characterization of their underlying structure.

The effect of stirrer speed, grinding time, pH, solid content, charge volume, water salinity, and optimum rheological conditions were investigated in relation to the selective grinding of siliceous goethitic nickel laterite. The target was to produce a -38 micron fraction. The optimum grinding conditions for selective grinding were found to be 1000 rpm with 50% charge volume and a grinding time for the highest Ni upgrade of 0.25 min. The Ni grade increased from 0.88% to 1.35% with 24% Ni recovery., 18 refs., The effect of stirrer speed, grinding time, pH, solid content, charge volume, water salinity, and optimum rheological conditions were investigated in relation to the selective grinding of siliceous goethitic nickel laterite. The target was to produce a -38 micron fraction. The optimum grinding conditions for selective grinding were found to be 1000 rpm with 50% charge volume and a grinding time for the highest Ni upgrade of 0.25 min. The Ni grade increased from 0.88% to 1.35% with 24% Ni recovery.

Process water used in mineral processing plants is usually a blend of different water supplies, including fresh water, bore and surface waters, waters from treated or untreated sewage plants and industrial effluents, and recycled waters. The quality and more particularly their constituents may impact flotation performance. The objective of this study is to investigate the effect of various natural acidic organic polymers, such as humic and fulvic acids, and tannic acid on the flotation of Cu and Mo sulphides in alkaline conditions (pH 9.3). Adsorption studies of these polymers on chalcopyrite and molybdenite were also conducted to interpret the flotation results. It was shown that Cu and Mo grades decreased with addition of humic, fulvic and tannic acid in that order, and the effect was more pronounced for molybdenite grade and recovery. UV-visible spectroscopy solution analysis also confirmed that these polymers were indeed adsorbed on the surface of molybdenite and chalcopyrite. The detrimental effect of organic materials in flotation is explained in terms of changes in froth characteristics, enhanced entrainment of fine particles, and a decrease in the overall hydrophobicity of the sulphide mineral surfaces, due to the adsorption of hydrophilic groups in these polymers which then prevent bubble-particle adhesion., Process water used in mineral processing plants is usually a blend of different water supplies, including fresh water, bore and surface waters, waters from treated or untreated sewage plants and industrial effluents, and recycled waters. The quality and more particularly their constituents may impact flotation performance. The objective of this study is to investigate the effect of various natural acidic organic polymers, such as humic and fulvic acids, and tannic acid on the flotation of Cu and Mo sulphides in alkaline conditions (pH 9.3). Adsorption studies of these polymers on chalcopyrite and molybdenite were also conducted to interpret the flotation results. It was shown that Cu and Mo grades decreased with addition of humic, fulvic and tannic acid in that order, and the effect was more pronounced for molybdenite grade and recovery. UV-visible spectroscopy solution analysis also confirmed that these polymers were indeed adsorbed on the surface of molybdenite and chalcopyrite. The detrimental effect of organic materials in flotation is explained in terms of changes in froth characteristics, enhanced entrainment of fine particles, and a decrease in the overall hydrophobicity of the sulphide mineral surfaces, due to the adsorption of hydrophilic groups in these polymers which then prevent bubble-particle adhesion.

The deportment of chalcocite (Cu2S) and heazlewoodite (Ni3S2) in Vale's Bessemer matte flotation circuit in Sudbury, Ontario, was investigated both in the plant and in laboratory flotation experiments. Insufficient selectivity was reported due to Cu2S not being entirely recovered in the rougher/scavengers and Ni3S2, depressed in the process, contaminating the flotation concentrate. It was found that Cu2S misreporting to the flotation tailings is mainly ultrafine, smaller than 6 micrometers, suggesting that surface oxidation and the low collision efficiency of fine particles in flotation are the possible causes of Cu2S losses. By contrast, Ni3S2 misreporting to the flotation concentrate is mainly in the intermediate size fractions from 6 to 38 micrometers and less than 40% of the heazlewoodite is in composites with chalcocite, the majority being liberated. Particle surface analysis by means of time-of-flight secondary ion mass spectrometry revealed that Ni3S2 in the concentrate is Cu-activated, and that the diphenyl guanidine collector adsorbs on the exposed Cu on the mineral surface. The role of pulp electrochemistry was also investigated, showing that the pulp potential in primary grinding is critical for selectivity. Strategies to reduce Cu activation of Ni3S2 in the process are suggested, as well as modifications to the current circuit flowsheet for improved plant performance., The deportment of chalcocite (Cu2S) and heazlewoodite (Ni3S2) in Vale's Bessemer matte flotation circuit in Sudbury, Ontario, was investigated both in the plant and in laboratory flotation experiments. Insufficient selectivity was reported due to Cu2S not being entirely recovered in the rougher/scavengers and Ni3S2, depressed in the process, contaminating the flotation concentrate. It was found that Cu2S misreporting to the flotation tailings is mainly ultrafine, smaller than 6 micrometers, suggesting that surface oxidation and the low collision efficiency of fine particles in flotation are the possible causes of Cu2S losses. By contrast, Ni3S2 misreporting to the flotation concentrate is mainly in the intermediate size fractions from 6 to 38 micrometers and less than 40% of the heazlewoodite is in composites with chalcocite, the majority being liberated. Particle surface analysis by means of time-of-flight secondary ion mass spectrometry revealed that Ni3S2 in the concentrate is Cu-activated, and that the diphenyl guanidine collector adsorbs on the exposed Cu on the mineral surface. The role of pulp electrochemistry was also investigated, showing that the pulp potential in primary grinding is critical for selectivity. Strategies to reduce Cu activation of Ni3S2 in the process are suggested, as well as modifications to the current circuit flowsheet for improved plant performance.

Froth stability is known to play a significant role in determining mineral grade and recovery in a flotation operation, but although it is understood that the collection zone and the froth zone are deeply interconnected and that reagents, particularly collectors and frothers, cannot be selected without considering their synergistic effect, this concept is rarely applied in plant practice. Feed mineralogy also has an important role in how particles and reagents interact in flotation, which is sometimes overlooked by operators. A case study is presented of plant trials at the Prominent Hill Cu-Au mine in South Australia combined with batch laboratory flotation tests and froth stability measurements. The methodology was applied to the trial plant, which was experiencing high variability in froth stability in the roughers when the feed ore mineralogy was changing. It was hypothesised that chalcopyrite in the feed in combination with isobutyl-xanthate had a destabilising effect on the froth phase under the reagent scheme used. Froth stability was restored if a shorter-chain, less hydrophobic xanthate was employed. It is apparent that the hydrophobicity of adsorbed films at the solid/liquid/air interfaces has a critical role in enhancing or reducing froth stability. Unstable froth causes a reduction in Cu recovery in spite of a high collection-zone flotation rate. The case study suggests that collection zone and froth zone can rarely be optimised independently of each other. With the laboratory procedure adopted, a more suitable reagent scheme was determined to respond to changes in the feed mineralogy, avoiding fluctuations in plant performance due to unexpected froth instability. The methodology adopted could be applied to any mineral system and operation, assisting operators in determining factors affecting flotation performance and measures to mitigate the effect., Froth stability is known to play a significant role in determining mineral grade and recovery in a flotation operation, but although it is understood that the collection zone and the froth zone are deeply interconnected and that reagents, particularly collectors and frothers, cannot be selected without considering their synergistic effect, this concept is rarely applied in plant practice. Feed mineralogy also has an important role in how particles and reagents interact in flotation, which is sometimes overlooked by operators. A case study is presented of plant trials at the Prominent Hill Cu-Au mine in South Australia combined with batch laboratory flotation tests and froth stability measurements. The methodology was applied to the trial plant, which was experiencing high variability in froth stability in the roughers when the feed ore mineralogy was changing. It was hypothesised that chalcopyrite in the feed in combination with isobutyl-xanthate had a destabilising effect on the froth phase under the reagent scheme used. Froth stability was restored if a shorter-chain, less hydrophobic xanthate was employed. It is apparent that the hydrophobicity of adsorbed films at the solid/liquid/air interfaces has a critical role in enhancing or reducing froth stability. Unstable froth causes a reduction in Cu recovery in spite of a high collection-zone flotation rate. The case study suggests that collection zone and froth zone can rarely be optimised independently of each other. With the laboratory procedure adopted, a more suitable reagent scheme was determined to respond to changes in the feed mineralogy, avoiding fluctuations in plant performance due to unexpected froth instability. The methodology adopted could be applied to any mineral system and operation, assisting operators in determining factors affecting flotation performance and measures to mitigate the effect.

A study on the recovery of molybdenum at three different concentrators treating low grade porphyry copper ores formed part of the AMIRA P260E project. The study revealed common issues relating to molybdenite recovery. As well as an overview of the major findings, there is a discussion of the mechanisms and factors affecting molybdenite flotation, and process improvements., A study on the recovery of molybdenum at three different concentrators treating low grade porphyry copper ores formed part of the AMIRA P260E project. The study revealed common issues relating to molybdenite recovery. As well as an overview of the major findings, there is a discussion of the mechanisms and factors affecting molybdenite flotation, and process improvements.

BACKGROUND: Topical microbicides, used by women to prevent the transmission of HIV and other sexually transmitted infections are urgently required. Dendrimers are highly branched nanoparticles being developed as microbicides. However, the anti-HIV and HSV structure-activity relationship of dendrimers comprising benzyhydryl amide cores and lysine branches, and a comprehensive analysis of their broad-spectrum anti-HIV activity and mechanism of action have not been published. METHODS AND FINDINGS: Dendrimers with optimized activity against HIV-1 and HSV-2 were identified with respect to the number of lysine branches (generations) and surface groups. Antiviral activity was determined in cell culture assays. Time-of-addition assays were performed to determine dendrimer mechanism of action. In vivo toxicity and HSV-2 inhibitory activity were evaluated in the mouse HSV-2 susceptibility model. Surface groups imparting the most potent inhibitory activity against HIV-1 and HSV-2 were naphthalene disulfonic acid (DNAA) and 3,5-disulfobenzoic acid exhibiting the greatest anionic charge and hydrophobicity of the seven surface groups tested. Their anti-HIV-1 activity did not appreciably increase beyond a second-generation dendrimer while dendrimers larger than two generations were required for potent anti-HSV-2 activity. Second (SPL7115) and fourth generation (SPL7013) DNAA dendrimers demonstrated broad-spectrum anti-HIV activity. However, SPL7013 was more active against HSV and blocking HIV-1 envelope mediated cell-to-cell fusion. SPL7013 and SPL7115 inhibited viral entry with similar potency against CXCR4-(X4) and CCR5-using (R5) HIV-1 strains. SPL7013 was not toxic and provided at least 12 h protection against HSV-2 in the mouse vagina. CONCLUSIONS: Dendrimers can be engineered with optimized potency against HIV and HSV representing a unique platform for the controlled synthesis of chemically defined multivalent agents as viral entry inhibitors. SPL7013 is formulated as VivaGe

Background: Topical microbicides, used by women to prevent the transmission of HIV and other sexually transmitted infections are urgently required. Dendrimers are highly branched nanoparticles being developed as microbicides. However, the anti-HIV and HSV structure-activity relationship of dendrimers comprising benzyhydryl amide cores and lysine branches, and a comprehensive analysis of their broad-spectrum anti-HIV activity and mechanism of action have not been published. Methods and Findings: Dendrimers with optimized activity against HIV-1 and HSV-2 were identified with respect to the number of lysine branches (generations) and surface groups. Antiviral activity was determined in cell culture assays. Timeof- addition assays were performed to determine dendrimer mechanism of action. In vivo toxicity and HSV-2 inhibitory activity were evaluated in the mouse HSV-2 susceptibility model. Surface groups imparting the most potent inhibitory activity against HIV-1 and HSV-2 were naphthalene disulfonic acid (DNAA) and 3,5-disulfobenzoic acid exhibiting the greatest anionic charge and hydrophobicity of the seven surface groups tested. Their anti-HIV-1 activity did not appreciably increase beyond a second-generation dendrimer while dendrimers larger than two generations were required for potent anti-HSV-2 activity. Second (SPL7115) and fourth generation (SPL7013) DNAA dendrimers demonstrated broad-spectrum anti-HIV activity. However, SPL7013 was more active against HSV and blocking HIV-1 envelope mediated cell-to-cell fusion. SPL7013 and SPL7115 inhibited viral entry with similar potency against CXCR4-(X4) and CCR5-using (R5) HIV-1 strains. SPL7013 was not toxic and provided at least 12 h protection against HSV-2 in the mouse vagina. Conclusions: Dendrimers can be engineered with optimized potency against HIV and HSV representing a unique platform for the controlled synthesis of chemically defined multivalent agents as viral entry inhibitors. SPL7013 is formulated as VivaGe

A study of the effect of changes in feed solids density on copper and molybdenite flotation recovery was conducted in two mineral processing plants treating copper-molybdenum ores. Plant surveys and laboratory tests were conducted in parallel. The decrease in flotation feed density considerably improved recovery of molybdenite, especially the coarse particles, with Cu recovery unchanged or improved only marginally. In laboratory cells the recovery of molybdenite was 3-13% higher than in plant cells, but for copper minerals recovery was comparable. These findings have been linked to turbulence-related changes in local energy dissipation, the flotation of molybdenite probably being controlled by bubble-particle collision frequency, which is increased by turbulence. For chalcopyrite, the flotation recovery is determined by attachment and stability, which may be adversely affected by local turbulent energy dissipation., A study of the effect of changes in feed solids density on copper and molybdenite flotation recovery was conducted in two mineral processing plants treating copper-molybdenum ores. Plant surveys and laboratory tests were conducted in parallel. The decrease in flotation feed density considerably improved recovery of molybdenite, especially the coarse particles, with Cu recovery unchanged or improved only marginally. In laboratory cells the recovery of molybdenite was 3-13% higher than in plant cells, but for copper minerals recovery was comparable. These findings have been linked to turbulence-related changes in local energy dissipation, the flotation of molybdenite probably being controlled by bubble-particle collision frequency, which is increased by turbulence. For chalcopyrite, the flotation recovery is determined by attachment and stability, which may be adversely affected by local turbulent energy dissipation.

BACKGROUND: The catalytically active 66-kDa subunit of the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) consists of DNA polymerase, connection, and ribonuclease H (RNase H) domains. Almost all known RT inhibitor resistance mutations identified to date map to the polymerase domain of the enzyme. However, the connection and RNase H domains are not routinely analysed in clinical samples and none of the genotyping assays available for patient management sequence the entire RT coding region. The British Columbia Centre for Excellence in HIV/AIDS (the Centre) genotypes clinical isolates up to codon 400 in RT, and our retrospective statistical analyses of the Centre's database have identified an N348I mutation in the RT connection domain in treatment-experienced individuals. The objective of this multidisciplinary study was to establish the in vivo relevance of this mutation and its role in drug resistance. METHODS AND FINDINGS: The prevalence of N348I in clinical isolates, the time taken for it to emerge under selective drug pressure, and its association with changes in viral load, specific drug treatment, and known drug resistance mutations was analysed from genotypes, viral loads, and treatment histories from the Centre's database. N348I increased in prevalence from below 1% in 368 treatment-naïve individuals to 12.1% in 1,009 treatment-experienced patients (p = 7.7 x 10(-12)). N348I appeared early in therapy and was highly associated with thymidine analogue mutations (TAMs) M41L and T215Y/F (p < 0.001), the lamivudine resistance mutations M184V/I (p < 0.001), and non-nucleoside RTI (NNRTI) resistance mutations K103N and Y181C/I (p < 0.001). The association with TAMs and NNRTI resistance mutations was consistent with the selection of N348I in patients treated with regimens that included both zidovudine and nevirapine (odds ratio 2.62, 95% confidence interval 1.43-4.81). The appearance of N348I was associated with a significant increase in viral

A procedure is described for evaluating the froth properties of plant slurries and/or the response to different frothers. A device was developed in which air flow rates, pulp agitation and frother concentration can be varied, and froth formation and decay measured. Parameters describing froth stability such as formation velocity, maximum froth height, froth retention time and froth half-life time can be measured in tests on pulp samples, allowing real time comparison between different plant streams and/or frothing reagents. Expensive and time consuming trials at plant scale can be avoided. The procedure was tested in the optimisation of the flotation of an Australian sulphide ore., A procedure is described for evaluating the froth properties of plant slurries and/or the response to different frothers. A device was developed in which air flow rates, pulp agitation and frother concentration can be varied, and froth formation and decay measured. Parameters describing froth stability such as formation velocity, maximum froth height, froth retention time and froth half-life time can be measured in tests on pulp samples, allowing real time comparison between different plant streams and/or frothing reagents. Expensive and time consuming trials at plant scale can be avoided. The procedure was tested in the optimisation of the flotation of an Australian sulphide ore.