A detailed design study of leaching and ancillary processes in the hydrometallurgical extraction of iron from iron bearing feedstocks

A systematic survey of the possible methods of chemical extraction of iron by chloride formation has been presented and supported by a comparable study of :feedstocks, products and markets. The generation and evaluation of alternative processes was carried out by the technique of morphological analysis vihich was exploited by way of a computer program. The final choice was related to technical feasibility and economic viability, particularly capital cost requirements and developments were made in an estimating procedure for hydrometallurgjcal processes which have general applications. The systematic exploration included the compilation of relevant data, and this indicated a need.to investigate precipitative hydrolysis or aqueous ferric chloride. Arising from this study, two novel hydrometallurgical processes for manufacturing iron powder are proposed and experimental work was undertaken in the following .areas to demonstrate feasibility and obtain basic data for design purposes: (1) Precipitative hydrolysis of aqueous ferric chloride. (2) Gaseous chloridation of metallic iron, and oxidation of resultant ferrous chloride. (3) Reduction of gaseous ferric chloride with hydrogen. (4) Aqueous acid leaching of low grade iron ore. (5) Aqueous acid leaching of metallic iron. The experimentation was supported by theoretical analyses dealing with: (1) Thermodynamics of hydrolysis. (2) Kinetics of ore leaching. (3) Kinetics of metallic iron leaching. (4) Crystallisation of ferrous chloride. (5) Oxidation of anhydrous ferrous chloride. (6) Reduction of ferric chloride. Conceptual designs are suggested fbr both the processes mentioned. These draw attention to areas where further work is necessary, which are listed. Economic analyses have been performed which isolate significant cost areas, und indicate total production costs. Comparisons are mode with previous and analogous proposals for the production of iron powder.

Selectivity of response in fluorescent polymers imprinted with N1-benzylidene pyridine-2-carboxamidrazones

Fluorescent polymers imprinted with various N1-benzylidene pyridine-2-carboxamidrazones were evaluated for their recognition of the original template and cross-reactivity to similar molecules. Dramatic quenching of fluorescence approaching background levels was observed for most cases where the "empty" MIP was re-exposed to its template. Molecules too large to enter the imprinted cavities gave no reduction of fluorescence. Other compounds were found to quench the fluorescence and are assumed to have entered the imprinted cavities. There is also evidence for partial responses which may give some measure of partial binding. The fluorescence response profiles of substrates containing polycyclic aromatics were found to be quite different from those containing flexible substituents. In order to make this approach more suitable for high-throughput screening a method has been validated wherein the extent of substrate-induced fluorescence quenching may be obtained without having to know how much polymer is present. © 2001 Elsevier Science B.V. All rights reserved.

Studies on the deactivation and reactivation of spent hydroprocessing catalyst

A study is reported on the deactivation of hydroprocessing catalysts and their reactivation by the removal of coke and metal foulants. The literature on hydrotreating catalyst deactivation by coke and metals deposition, the environmental problems associated with spent catalyst disposal, and its reactivation/rejuvenation process were reviewed. Experimental studies on catalyst deactivation involved problem analysis in industrial hydroprocessing operations, through characterization of the spent catalyst, and laboratory coking studies. A comparison was made between the characteristics of spent catalysts from fixed bed and ebullating bed residue hydroprocessing reactor units and the catalyst deactivation pattern in both types of reactor systems was examined. In the laboratory the nature of initial coke deposited on the catalyst surface and its role on catalyst deactivation were studied. The influence of initial coke on catalyst surface area and porosity was significant. Both catalyst acidity and feedstock quality had a remarkable influence on the amount and the nature of the initial coke. The hydroenitrogenation function (HDN) of the catalyst was found to be deactivated more rapidly by the initial coke than the hydrodesulphurization function (HDS). In decoking experiments, special attention was paid to the initial conditions of coke combustion, since the early stages of contact between the coke on the spent catalyst surface and the oxygen are crucial in the decoking process. An increase in initial combustion temperature above 440oC and the oxygen content of the regeneration gas above 5% vanadium led to considerable sintering of the catalyst. At temperatures above 700oC there was a substantial loss of molybdenum from the catalyst, and phase transformations in the alumina support. The preferred leaching route (coked vs decoked form of spent catalyst) and a comparison of different reagents (i.e., oxalic acid and tartaric acid) and promoters (i.e., Hydrogen Peroxide and Ferric Nitrate) for better selectivity in removing the major foulant (vanadium), characterization and performance evaluation of the treated catalysts and modelling of the leaching process were addressed in spent catalyst rejuvenation studies. The surface area and pore volume increased substantially with increasing vanadium extraction from the spent catalyst; the HDS activity showed a parallel increase. The selectivity for leaching of vanadium deposits was better, and activity recovery was higher, for catalyst rejuvenated by metal leaching prior to decoking.

Synthesis and cytotoxity of oxysterols:studies on the A,B ring polyoxygenated sterols

Oxysterols (OS), the polyoxygenated sterols, represent a class of potent regulatory molecules for important biological actions. Cytotoxicity of OS is one of the most important aspects in studies of OS bioactivities. However, studies, the structure-activity relationship (SAR) study in particular, have been hampered by the limited availability of structurally diverse OS in numbers and amounts. The aim of this project was to develop robust synthetic methods for the preparation of polyhydroxyl sterols, thereof, evaluate their cytotoxicity and establish structure-activity relationship. First, we found hydrophobicity of the side chain is essential for 7-HC's cytotoxicity, and a limited number of hydroxyl groups and a desired configuration on the A, B ring are required for a potent cytotoxicity of an OS, after syntheses and tests of a number of 7-HC's analogues against cancer cell lines. Then polyoxygenation of cholesterol A, B rings was explored. A preparative method for the synthesis of four diastereomerically pure cholest-4-en-3,6-diols was developed. Epoxidation on these cholest-4-en-3,6-diols showed that an allyl group exerts an auxiliary role in producing products with desired configuration in syntheses of the eight diastereomerically pure 45-epoxycholestane-3,6-diols. Reduction of the eight 45-epoxycholestane-3,6-diols produced all eight isomers of the cytotoxic 5α-acholestane 3β,5,6β-triol (CT) for the first time. Epoxide ring opening with protic or Lewis acids on the eight 45-epoxycholestane-3,6-diols are carefully studied. The results demonstrated a combination of an acid and a solvent affected the outcomes of a reaction dramatically. Acyl group participation and migration play an important role with numbers of substrates under certain conditions. All the eight 4,5-trans cholestane- 3,4,5,6-tetrols were synthesised through manipulation of acyl participation. Furthermore these reaction conditions were tested when a number of cholestane-3,4, 5,6,7-pentols and other C3-C7 oxygenated sterols were synthesised for the first time. Introduction of an oxygenated functional group through cholest-2-ene derivatives was studied. The elimination of 3-(4-toluenesulfonate) esters showed the interaction between the existing hydroxyls or acyls with the reaction centre often resulted in different products. The allyl oxidation, epoxidation and Epoxide ring opening reactions are investigated with these cholest-2-enes.

The growth, structure and properties of sputtered barium titanate thin films

The design and construction of a sputtering system for the deposition of barium titanate thin films is described. The growth and structure of barium titanate films deposited on a variety of substrates including amorphous carbon fi1ms, potassium bromide single crystals, and polycrystalline gold films has been studied. Films deposited on all substrates at room temperature were amorphous. Polycrystalline titanate films were formed on polycrystalline and amorphous substrates at temperatures above 450°C while films with a pronounced texture could be expitaxially deposited on single crystal potassium bromide above a temperature of only 200°C. Results of dielectric measurements made on the films are reported. Amorphous films were highly insulating (resistivities ~1014 ohm.cm with dielectric constants of between 10 and 20.

Molecular basis for reduced estrone sulfate transport and altered modulator sensitivity of transmembrane helix (TM) 6 and TM17 mutants of multidrug resistance protein 1 (ABCC1)

Multidrug resistance protein 1 (MRP1) confers drug resistance and also mediates cellular efflux of many organic anions. MRP1 also transports glutathione (GSH); furthermore, this tripeptide stimulates transport of several substrates, including estrone 3-sulfate. We have previously shown that mutations of Lys(332) in transmembrane helix (TM) 6 and Trp(1246) in TM17 cause different substrate-selective losses in MRP1 transport activity. Here we have extended our characterization of mutants K332L and W1246C to further define the different roles these two residues play in determining the substrate and inhibitor specificity of MRP1. Thus, we have shown that TM17-Trp(1246) is crucial for conferring drug resistance and for binding and transport of methotrexate, estradiol glucuronide, and estrone 3-sulfate, as well as for binding of the tricyclic isoxazole inhibitor N-[3-(9-chloro-3-methyl-4-oxo-4H-isoxazolo-[4,3-c]quinolin-5-yl)-cyclohexylmethyl]-benzamide (LY465803). In contrast, TM6-Lys(332) is important for enabling GSH and GSH-containing compounds to serve as substrates (e.g., leukotriene C(4)) or modulators (e.g., S-decyl-GSH, GSH disulfide) of MRP1 and, further, for enabling GSH (or S-methyl-GSH) to enhance the transport of estrone 3-sulfate and increase the inhibitory potency of LY465803. On the other hand, both mutants are as sensitive as wild-type MRP1 to the non-GSH-containing inhibitors (E)-3-[[[3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl][[3-(dimethylamino)-3-oxopropyl]thio]methyl]thio]-propanoic acid (MK571), 1-[2-hydroxy-3-propyl-4-[4-(1H-tetrazol-5-yl)butoxy]phenyl]-ethanone (LY171883), and highly potent 6-[4'-carboxyphenylthio]-5[S]-hydroxy-7[E], 11[Z]14[Z]-eicosatetrenoic acid (BAY u9773). Finally, the differing abilities of the cysteinyl leukotriene derivatives leukotriene C(4), D(4), and F(4) to inhibit estradiol glucuronide transport by wild-type and K332L mutant MRP1 provide further evidence that TM6-Lys(332) is involved in the recognition of the gamma-Glu portion of substrates and modulators containing GSH or GSH-like moieties.

Zirconium phosphate supported tungsten oxide solid acid catalysts for the esterification of palmitic acid

A series of zirconium phosphate supported WOx solid acid catalysts with W loadings from 1–25 wt% have been prepared on high surface area zirconium phosphate by a surface grafting method. Catalysts were characterized by N2 adsorption, FTIR, Raman, UV-Vis, 31P MAS NMR, pyridine TPD and X-ray methods. Spectroscopic measurements suggest a Keggin-type structure forms on the surface of zirconium phosphate as a ([triple bond, length as m-dash]ZrOH2+)(ZrPW11O405−) species. All catalysts show high activity in palmitic acid esterification with methanol. These materials can be readily separated from the reaction system for re-use, and are resistant to leaching of the active heteropolyacid, suggesting potential industrial applications in biodiesel synthesis. © The Royal Society of Chemistry 2006.

The development of functional astrocyte-neuron networks derived from stem cells

There is currently great scientific and medical interest in the potential of tissue grown from stem cells. These cells present opportunities for generating model systems for drug screening and toxicological testing which would be expected to be more relevant to human outcomes than animal based tissue preparations. Newly realised astrocytic roles in the brain have fundamental implications within the context of stem cell derived neuronal networks. If the aim of stem cell neuroscience is to generate functional neuronal networks that behave as networks do in the brain, then it becomes clear that we must include and understand all the cellular components that comprise that network, and which are important to support synaptic integrity and cell to cell signalling. We have shown that stem cell derived neurons exhibit spontaneous and coordinated calcium elevations in clusters and in extended processes, indicating local and long distance signalling (1). Tetrodotoxin sensitive network activity could also be evoked by electrical stimulation. Similarly, astrocytes exhibit morphology and functional properties consistent with this glial cell type. Astrocytes also respond to neuronal activity and to exogenously applied neurotransmitters with calcium elevations, and in contrast to neurons, also exhibited spontaneous rhythmic calcium oscillations. Astroctyes also generate propagating calcium waves that are gap junction and purinergic signalling dependent. Our results show that stem cell derived astrocytes exhibit appropriate functionality and that stem cell neuronal networks interact with astrocytic networks in co-culture. Using mixed cultures of stem cell derived neurons and astrocytes, we have also shown both cell types also modulate their glucose uptake, glycogen turnover and lactate production in response to glutamate as well as increased neuronal activity (2). This finding is consistent with their neuron-astrocyte metabolic coupling thus demonstrating a tractable human model, which will facilitate the study of the metabolic coupling between neurons and astrocytes and its relationship with CNS functional issues ranging from plasticity to neurodegeneration. Indeed, cultures treated with oligomers of amyloid beta 1-42 (Aβ1-42) also display a clear hypometabolism, particularly with regard to utilization of substrates such as glucose (3). Both co-cultures of neurons and astrocytes and purified cultures of astrocytes showed a significant decrease in glucose uptake after treatment with 2 and 0.2 μmol/L Aβ at all time points investigated (p <0.01). In addition, a significant increase in the glycogen content of cells was also measured. Mixed neuron and astrocyte co-cultures as well as pure astrocyte cultures showed an initial decrease in glycogen levels at 6 hours compared with control at 0.2 μmol/L and 2 μmol/L P <0.01. These changes were accompanied by changes in NAD+/NADH (P<0.05), ATP (P<0.05), and glutathione levels (P<0.05), suggesting a disruption in the energy-redox axis within these cultures. The high energy demands associated with neuronal functions such as memory formation and protection from oxidative stress put these cells at particular risk from Aβ-induced hypometabolism. As numerous cell types interact in the brain it is important that any in vitro model developed reflects this arrangement. Our findings indicate that stem cell derived neuron and astrocyte networks can communicate, and so have the potential to interact in a tripartite manner as is seen in vivo. This study therefore lays the foundation for further development of stem cell derived neurons and astrocytes into therapeutic cell replacement and human toxicology/disease models. More recently our data provides evidence for a detrimental effect of Aβ on carbohydrate metabolism in both neurons and astrocytes. As a purely in vitro system, human stem cell models can be readily manipulated and maintained in culture for a period of months without the use of animals. In our laboratory cultures can be maintained in culture for up to 12 months months thus providing the opportunity to study the consequences of these changes over extended periods of time relevant to aspects of the disease progression time frame in vivo. In addition, their human origin provides a more realistic in vitro model as well as informing other human in vitro models such as patient-derived iPSC.

Alternative exon usage in the single CPT1 gene of Drosophila generates functional diversity in the kinetic properties of the enzyme:differential expression of alternatively spliced variants in drosophila tissues

The Drosophila melanogaster genome contains only one CPT1 gene (Jackson, V. N., Cameron, J. M., Zammit, V. A., and Price, N. T. (1999) Biochem. J. 341, 483-489). We have now extended our original observation to all insect genomes that have been sequenced, suggesting that a single CPT1 gene is a universal feature of insect genomes. We hypothesized that insects may be able to generate kinetically distinct variants by alternative splicing of their single CPT1 gene. Analysis of the insect genomes revealed that (a) the single CPT1 gene in each and every insect genome contains two alternative exons and (ii) in all cases, the putative alternative splicing site occurs within a small region corresponding to 21 amino acid residues that are known to be essential for the binding of substrates and of malonyl-CoA in mammalian CPT1A.Weperformed PCR analyses of mRNA from different Drosophila tissues; both of the anticipated splice variants of CPT1mRNAwere found to be expressed in all of the tissues tested (both in larvae and adults), with the expression level for one of the splice variants being significantly different between flight muscle and the fat body of adult Drosophila. Heterologous expression of the full-length cDNAs corresponding to the two putative variants of Drosophila CPT1 in the yeast Pichia pastoris revealed two important differences between the properties of the two variants: (i) their affinity (K 0.5) for one of the substrates, palmitoyl-CoA, differed by 5-fold, and (ii) the sensitivity to inhibition by malonyl-CoA at fixed, higher palmitoyl-CoA concentrations was 2-fold different and associated with different kinetics of inhibition. These data indicate that alternative splicing that specifically affects a structurally crucial region of the protein is an important mechanism through which functional diversity of CPT1 kinetics is generated from the single gene that occurs in insects. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.

Sulphide ore minerals:surface chemical properties

The surfaces of iron-containing sulphide minerals were oxidised by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The characterisation of surface oxidation is relevant to the alteration of ores in nature and their behaviour during flotation and leaching, of importance to the metallurgical industry. The sulphides investigated included pyrite (FeS2), hexagonal pyrrhotine (Fe9S10), monoclinic pyrrhotine (Fe7Se), violarite (FeNi2S4), pentlandite ((FeiNi)9Se), chalcopyrite (CuFeS2) and arsenopyrite (FeAsS). The surfaces were oxidised by various methods including acid (sulphuric), alkali (ammonium hydroxide), hydrogen peroxide, steam, electrochemical and air/oxygen (in a low-temperature (150ºC) furnace), The surfaces were examined using surface sensitive chemical spectroscopic methods including x-ray photoelectron spectroscopy (ms), Auger electron spectroscopy (LES) and conversion electron Mössbauer spectroscopy (CEKS). Physical characterisation of the surfaces was undertaken using scanning electron microscopy (SM), spectral reflectance measurements and optical microscopy. Bulk characterisation of the sulphide minerals was undertaken using x-ray diffraction and electron microprobe techniques. Observed phases suggested to form in most of the sulphide surfaces include Fe204, Fe1-x0, Fe202, Fe00H, Fe(OH)3, with iron II & III oxy-sulphates. The iron sulphides show variable extents of oxidation, indicating pyrite to be the most stable. Violarite shows stability to oxidation, suggested to result from both its stable spinel crystal structure, and from the rapid formation of sulphur at the surface protecting the sub-surface from further oxidation. The phenomenon of sub-surface enrichment (in metals), forming secondary sulphides, is exhibited by pentlandite and chalcopyrite, forming violarite and copper sulphides respectively. The consequences of this enrichment with regard to processing and leaching are discussed. Arsenopyrite, often a hindrance in ore processing, exhibits the formation of arsenic compounds at the surface, the dissolution of which is discussed in view of the possible environmental hazard caused by the local pollution of water systems. The results obtained allow a characterisation of the sulphides in terms of their relative stability to oxidation, and an order of stability of the sulphide surfaces is proposed. Models were constructed to explain the chemical compositions of the surfaces, and the inter-relationships between the phases determined at the surface and in the sub-surface. These were compared to the thermo-chemically predicted phases shown in Eh/pH and partial pressure diagrams! The results are discussed, both in terms of the mineralogy and geochemistry of natural ores, and the implications for extraction and processing of these ore minerals.

Biological interactions with synthetic polymers

Anchorage dependent cell culture is a useful model for investigating the interface that becomes established when a synthetic polymer is placed in contact with a biological system. The primary aim of this interdisciplinary study was to systematically investigate a number of properties that were already considered to have an influence on cell behaviour and thereby establish the extent of their importance. It is envisaged that investigations such as these will not only further the understanding of the mechanisms that affect cell adhesion but may ultimately lead to the development of improved biomaterials. In this study, surface analysis of materials was carried out in parallel with culture studies using fibroblast cells. Polarity, in it's ability to undergo hydrogen bonding (eg with water and proteins), had an important affect on cell behaviour, although structural arrangement and crystallinity were not found to exert any marked influence. In addition, the extent of oxidation that had occurred during the process of manufacture of substrates was also important. The treatment of polystyrene with a selected series of acids and gas plasmas confirmed the importance of polarity, structural groups and surface charge and it was shown that this polymer was not unique among `hydrophobic' materials in it's inability to support cell adhesion. The individual water structuring groups within hydrogel polymers were also observed to have controlling effects on cell behaviour. An overall view of the biological response to both hydrogel and non-hydrogel materials highlighted the importance of surface oxidation, polarity, water structuring groups and surface charge. Initial steps were also taken to analyse foetal calf serum, which is widely used to supplement cell culture media. Using an array of analytical techniques, further experiments were carried out to observe any possible differences in the amounts of lipids and calcium that become deposited to tissue culture and bacteriological grade plastic under cell culture conditions.

Efficient THz radiation from a nanocrystalline silicon-based multi-layer photomixer

In this paper we propose a novel type of multiple-layer photomixer based on amorphous/nano-crystalline-Si. Such a device implies that it could be possible to enhance the conversion efficiency from optical power to THz emission by increasing the absorption length and by reducing the device overheating through the use of substrates with higher thermal conductivity compared to GaAs. Our calculations show that the output power from a two-layer Si-based photomixer is at least ten times higher than that from conventional LT-GaAs photomixers at 1 THz.

Structure-activity relations in Cs-doped heteropolyacid catalysts for biodiesel production

A series of insoluble heteropolytungstate (H3PW12O40 HPW) salts, CsxH3−xPW12O40 (x=0.9–3x=0.9–3), were synthesized and characterized using a range of bulk and surface sensitive probes including N2 porosimetry, powder XRD, FTIR, XPS, 31P MAS NMR, and NH3 calorimetry. Materials with Cs content in the range x=2.0–2.7x=2.0–2.7 were composed of dispersed crystallites with surface areas ∼100 m2 g−1 and high Brönsted acid strengths [ΔH0ads(NH3)=−150 kJmol−1], similar to the parent heteropolyacid. The number of accessible surface acid sites probed by α -pinene isomerization correlated well with those determined by NH3 adsorption calorimetry and surface area measurements. CsxH3−xPW12O40 were active toward the esterification of palmitic acid and transesterification of tributyrin, important steps in fatty acid and ester processing for biodiesel synthesis. Optimum performance occurs for Cs loadings of x=2.0–2.3x=2.0–2.3, correlating with the accessible surface acid site density. These catalysts were recoverable with no leaching of soluble HPW.

Amyloid β 1-42 induces hypometabolism in human stem cell-derived neuron and astrocyte networks

Alzheimer's disease (AD) is the most common form of dementia, affecting more than 35 million people worldwide. Brain hypometabolism is a major feature of AD, appearing decades before cognitive decline and pathologic lesions. To date, the majority of studies on hypometabolism in AD have used transgenic animal models or imaging studies of the human brain. As it is almost impossible to validate these findings using human tissue, alternative models are required. In this study, we show that human stem cell-derived neuron and astrocyte cultures treated with oligomers of amyloid beta 1-42 (Aβ1-42) also display a clear hypometabolism, particularly with regard to utilization of substrates such as glucose, pyruvate, lactate, and glutamate. In addition, a significant increase in the glycogen content of cells was also observed. These changes were accompanied by changes in NAD+ /NADH, ATP, and glutathione levels, suggesting a disruption in the energy-redox axis within these cultures. The high energy demands associated with neuronal functions such as memory formation and protection from oxidative stress put these cells at particular risk from Aβ-induced hypometabolism. Further research using this model may elucidate the mechanisms associated with Aβ-induced hypometabolism.