Co-precipitation of ferrihydrite and silica from acidic hydrometallurgical solutions and its impact on the paragoethite process

Ferrihydrite is a common iron oxyhydroxide, produced both naturally and industrially. It is often found in association with silica; an example of this is its occurrence in the Paragoethite process applied in zinc hydrometallurgy for the removal of iron from acidic sulphate solutions. In this process, ferrihydrite is the primary constituent of the precipitation residue, but silica also features heavily and is believed to influence both dewatering and the adsorption of ions from solution.While some information is known regarding the physical interaction of ferrihydrite and silica when they are present as distinct phases, the process by which they simultaneously precipitate remains poorly understood. This thesis details investigations leading to a clearer understanding of this process and provides valuable insights into the factors influencing precipitate behaviour.Ferrihydrite precipitates containing varying proportions of silica were prepared via continuous crystallisation, with the aim of achieving a simplified laboratory-based simulation of the reactions that occur within plant liquors during the Paragoethite process. Multiple anionic environments including sulphate (predominant anion in the Paragoethite process), nitrate (common in natural systems) and chloride were used to monitor the influence of anions on the co-precipitation reaction. Accurate control of the slurry pH and temperature were critical to this simulation, as was maintaining steady-state solution concentrations for iron and silicate. The latter was achieved by continuous addition of iron and silicate, with the corresponding continuous removal of reaction product slurry. Analysis focused on the removed slurry using advanced structural and morphological characterisation of the solid phases formed and quantification of solution species depletion. Reaction conditions were selected to favour the formation of ferrihydrite ensuring it was the dominant phase produced.It was found that the presence of ferrihydrite increased both the rate and extent of silica removed by precipitation from solution. This phenomenon is based on surface adsorption and is hindered by the presence of ions that bind strongly with ferrihydrite. Ions such as sulphate compete with soluble silicate molecules for binding sites on the surface, whereas more weakly bound ions like nitrate do not hinder the process. The level of interference was found to be dependent on available surface area, the affinity for the ion’s adsorption and the concentration of both silicate and the ion in question.Oligomeric and colloidal silica were shown to have a significantly different influence on ferrihydrite to that of monosilicic acid. While the crystallinity of ferrihydrite was seen to decrease when precipitated in the presence of monosilicic acid, no similar effect was observed in the presence of silica in a polymeric state. Although a greater proportion of silica was removed from solution when polymerisation had already progressed to a degree, it still imposed less influence on the product crystallinity. This observation underlines the importance of the adsorption-based process that combines the materials during co-precipitation.X-ray scattering pair distribution function (PDF) analysis of the residue solids was instrumental in displaying correlations between declining ferrihydrite crystallinity and particle size. The data indicated that silicon atoms were not incorporated into the ferrihydrite crystal structure, but by inhibiting the growth of primary particles through surface adsorption, co-precipitated silica produced an apparent decrease in ferrihydrite crystallinity.The analyses presented in this thesis were combined to derive proposed mechanisms of co-precipitate formation based on both the presence of monomeric silica and colloidal particles. When monomeric silica (silicic acid) is present ferrihydrite particles form initially followed closely by the adsorption of silicic acid monomers which restrict further growth. The adsorbed silicic acid molecules condense across the ferrihydrite surface and polymerise outward. Particles aggregate before much, if any, silica polymerisation has occurred, and the silica continues to polymerise of the surface of the aggregates. Where oligomeric or colloidal silica is present ferrihydrite particles are produced; there is little or no immediate silica adsorption and therefore the particles grow uninhibited. During aggregation the silica particles aggregate with the ferrihydrite, being incorporated both within and on the surface of the clusters. The results of this work provide the most detailed description of the reaction mechanism in ferrihydrite/silica co-precipitation, and the most thorough analysis of the structure of co-precipitates thus far reported

Einstein on the beach: A study in temporality

This is an Author's Accepted Manuscript of an article published in Performance Research, 17(5), 34 - 40, 2012, copyright @ Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/13528165.2012.728438.In this paper I seek to examine and analyse the sense of duration induced by performances of Einstein on the Beach, and the entailed sense of time which its internal structure creates. I initially sketch out the stylistic context and artistic intentions of this work's creators, Glass and Wilson, and I briefly describe the process of its creation. Certain features of this process indicate how the work may be interpreted. Having cited the creators' thoughts on structure and temporality, I address directly aspects of Einstein's temporal effects, comparing it to works of similar lengths. I give the briefest synopsis of its staging and motifs. I then outline three kinds of devices which seem to inform our temporal sense of this work as spectators. In the final section I invoke two ideas which serve as analogies to help characterise this work's overall effect on us: Heidegger's notion of the ‘hermeneutic circle’ and, more speculatively, Nietzsche's ‘theory’ of Eternal Recurrence

Metabolic role of the hepatic valine/3-hydroxyisobutyrate (3-HIB) pathway in fatty liver disease

Background: The valine (branched-chain amino acid) metabolite 3-hydroxyisobutyrate (3-HIB), produced by 3-Hydroxyisobutyryl-CoA Hydrolase (HIBCH), is associated with insulin resistance and type 2 diabetes, but implicated tissues and cellular mechanisms are poorly understood. We hypothesized that HIBCH and 3-HIB regulate hepatic lipid accumulation. Methods: HIBCH mRNA in human liver biopsies (“Liver cohort”) and plasma 3-HIB (“CARBFUNC” cohort) were correlated with fatty liver and metabolic markers. Human Huh7 hepatocytes were supplemented with fatty acids (FAs) to induce lipid accumulation. Following HIBCH overexpression, siRNA knockdown, inhibition of PDK4 (a marker of FA β-oxidation) or 3-HIB supplementation, we performed RNA-seq, Western blotting, targeted metabolite analyses and functional assays. Findings: We identify a regulatory feedback loop between the valine/3-HIB pathway and PDK4 that shapes hepatic FA metabolism and metabolic health and responds to 3-HIB treatment of hepatocytes. HIBCH overexpression increased 3-HIB release and FA uptake, while knockdown increased cellular respiration and decreased reactive oxygen species (ROS) associated with metabolic shifts via PDK4 upregulation. Treatment with PDK4 inhibitor lowered 3-HIB release and increased FA uptake, while increasing HIBCH mRNA. Implicating this regulatory loop in fatty liver, human cohorts show positive correlations of liver fat with hepatic HIBCH and PDK4 expression (Liver cohort) and plasma 3-HIB (CARBFUNC cohort). Hepatocyte 3-HIB supplementation lowered HIBCH expression and FA uptake and increased cellular respiration and ROS. Interpretation: These data implicate the hepatic valine/3-HIB pathway in mechanisms of fatty liver, reflected in increased plasma 3-HIB concentrations, and present possible targets for therapeutic intervention.publishedVersio

Meal patterns associated with energy intake in people with obesity

It is widely assumed that people with obesity have several common eating patterns, including breakfast-skipping (1), eating during the night (2) and high fast-food consumption (3). However, differences in individual meal and dietary patterns may be crucial to optimizing obesity treatment. Therefore, we investigated the inter-individual variation in eating patterns, hypothesizing that individuals with obesity show different dietary and meal patterns, and that these associate with self-reported energy intake (rEI) and/or anthropometric measures. Cross-sectional data from 192 participants (aged 20–55 years) with obesity, including 6 days of weighed food records, were analyzed. Meal patterns and dietary patterns were derived using exploratory hierarchical cluster analysis and k-means cluster analysis, respectively. Five clear meal patterns were found based on the time-of-day with the highest mean rEI. The daily rEI (mean ± SD kcal) was highest among “midnight-eaters” (2550 ± 550), and significantly (p < 0.05) higher than “dinner-eaters” (2060 ± 550), “lunch-eaters” (2080 ± 520), and “supper-eaters” (2100 ± 460), but not “regular-eaters” (2330 ± 650). Despite differences of up to 490 kcal between meal patterns, there were no significant differences in anthropometric measures or physical activity level (PAL). Four dietary patterns were also found with significant differences in intake of specific food groups, but without significant differences in anthropometry, PAL, or rEI. Our data highlight meal timing as a determinant of individual energy intake in people with obesity. The study supports the importance of considering a person’s specific meal pattern, with possible implications for more person-focused guidelines and targeted advice.publishedVersio

Subtype-specific surface proteins on adipose tissue macrophages and their association to obesity-induced insulin resistance

A chronic low-grade inflammation, originating in the adipose tissue, is considered a driver of obesity-associated insulin resistance. Macrophage composition in white adipose tissue is believed to contribute to the pathogenesis of metabolic diseases, but a detailed characterization of pro- and anti-inflammatory adipose tissue macrophages (ATMs) in human obesity and how they are distributed in visceral- and subcutaneous adipose depots is lacking. In this study, we performed a surface proteome screening of pro- and anti-inflammatory ATMs in both subcutaneous- (SAT) and visceral adipose tissue (VAT) and evaluated their relationship with systemic insulin resistance. From the proteomics screen we found novel surface proteins specific to M1-like- and M2-like macrophages, and we identified depot-specific immunophenotypes in SAT and VAT. Furthermore, we found that insulin resistance, assessed by HOMA-IR, was positively associated with a relative increase in pro-inflammatory M1-like macrophages in both SAT and VAT.publishedVersio

Leishmania aethiopica cell‐to‐cell spreading involves caspase‐3, AkT, and NF‐κB but not PKC‐δ activation and involves uptake of LAMP‐1‐positive bodies containing parasites

Development of human leishmaniasis is dependent on the ability of intracellular Leishmania parasites to spread and enter macrophages. The mechanism through which free promastigotes and amastigotes bind and enter host macrophages has been previously investigated; however, little is known about intracellular trafficking and cell-to-cell spreading. In this study, the mechanism involved in the spreading of Leishmania aethiopica and Leishmania mexicana was investigated. A significant increase in phosphatidylserine (PS) exhibition, cytochrome C release, and active caspase-3 expression was detected (P < 0.05) during L. aethiopica, but not L. mexicana spreading. A decrease (P < 0.05) of protein kinase B (Akt) protein and BCL2-associated agonist of cell death (BAD) phosphorylation was also observed. The nuclear factor kappa-light-chain enhancer of activated B cells (NF-kB) signaling pathway and pro-apoptotic protein protein kinase C delta (PKC-δ) were downregulated while inhibition of caspase-3 activation prevented L. aethiopica spreading. Overall suggesting that L. aethiopica induces host cell’s apoptosis during spreading in a caspase-3-dependent manner. The trafficking of amastigotes within macrophages following cell-to-cell spreading differed from that of axenic parasites and involved co-localization with lysosomal-associated membrane protein 1 (LAMP-1) within 10 min postinfection. Interestingly, following infection with axenic amastigotes and promastigotes, co-localization of parasites with LAMP-1-positive structures took place at 1 and 4 h, respectively, suggesting that the membrane coat and LAMP-1 protein were derived from the donor cell. Collectively, these findings indicate that host cell apoptosis, demonstrated by PS exhibition, caspase-3 activation, cytochrome C release, downregulation of Akt, BAD phosphorylation, NF-kB activation, and independent of PKC-δ expression, is involved in L. aethiopica spreading. Moreover, L. aethiopica parasites associate with LAMP-rich structures when taken up by neighboring macrophages

Stabilization of O-O Bonds by d(0) Cations in Li4+xNi1-xWO6 (0 <= x <= 0.25) Rock Salt Oxides as the Origin of Large Voltage Hysteresis

Multinary lithium oxides with the rock salt structure are of technological importance as cathode materials in rechargeable lithium ion batteries. Current state-of-the-art cathodes such as LiNi1/3Mn1/3Co1/3O2 rely on redox cycling of earth-abundant transition-metal cations to provide charge capacity. Recently, the possibility of using the oxide anion as a redox center in Li-rich rock salt oxides has been established as a new paradigm in the design of cathode materials with enhanced capacities (>200 mAh/g). To increase the lithium content and access electrons from oxygen-derived states, these materials typically require transition metals in high oxidation states, which can be easily achieved using d0 cations. However, Li-rich rock salt oxides with high valent d0 cations such as Nb5+ and Mo6+ show strikingly high voltage hysteresis between charge and discharge, the origin of which is uninvestigated. In this work, we study a series of Li-rich compounds, Li4+xNi1–xWO6 (0 ≤ x ≤ 0.25) adopting two new and distinct cation-ordered variants of the rock salt structure. The Li4.15Ni0.85WO6 (x = 0.15) phase has a large reversible capacity of 200 mAh/g, without accessing the Ni3+/Ni4+ redox couple, implying that more than two-thirds of the capacity is due to anionic redox, with good cyclability. The presence of the 5d0 W6+ cation affords extensive (>2 V) voltage hysteresis associated with the anionic redox. We present experimental evidence for the formation of strongly stabilized localized O–O single bonds that explain the energy penalty required to reduce the material upon discharge. The high valent d0 cation associates localized anion–anion bonding with the anion redox capacity

Crucial role of ultraviolet light for desert ants in determining direction from the terrestrial panorama

Ants use the panoramic skyline in part to determine a direction of travel. A theoretically elegant way to define where terrestrial objects meet the sky is to use an opponent-process channel contrasting green wavelengths of light with ultraviolet (UV) wavelengths. Compared with the sky, terrestrial objects reflect relatively more green wavelengths. Using such an opponent-process channel gains constancy in the face of changes in overall illumination level. We tested the use of UV wavelengths in desert ants by using a plastic that filtered out most of the energy below 400 nm. Ants, Melophorus bagoti, were trained to home with an artificial skyline provided by an arena (experiment 1) or with the natural panorama (experiment 2). On a test, a homing ant was captured just before she entered her nest, and then brought back to a replicate arena (experiment 1) or the starting point (the feeder, experiment 2) and released. Blocking UV light led to deteriorations in orientation in both experiments. When the artificial skyline was changed from opaque to transparent UV-blocking plastic (experiment 3) on the other hand, the ants were still oriented. We conclude that UV wavelengths play a crucial role in determining direction based on the terrestrial surround.10 page(s

One class classification as a practical approach for accelerating π–π co-crystal discovery

Machine learning using one class classification on a database of existing co-crystals enables the identification of co-formers which are likely to form stable co-crystals, resulting in the synthesis of two co-crystals of polyaromatic hydrocarbons.</p

Role of the Neutral Amino Acid Transporter SLC7A10 in Adipocyte Lipid Storage, Obesity and Insulin Resistance

Elucidation of mechanisms that govern lipid storage, oxidative stress, and insulin resistance may lead to improved therapeutic options for type 2 diabetes and other obesity-related diseases. Here, we find that adipose expression of the small neutral amino acid transporter SLC7A10, also known as alanine-serine-cysteine transporter-1 (ASC-1), shows strong inverse correlates with visceral adiposity, insulin resistance, and adipocyte hypertrophy across multiple cohorts. Concordantly, loss of Slc7a10 function in zebrafish in vivo accelerates diet-induced body weight gain and adipocyte enlargement. Mechanistically, SLC7A10 inhibition in human and murine adipocytes decreases adipocyte serine uptake and total glutathione levels and promotes reactive oxygen species (ROS) generation. Conversely, SLC7A10 overexpression decreases ROS generation and increases mitochondrial respiratory capacity. RNA sequencing revealed consistent changes in gene expression between human adipocytes and zebrafish visceral adipose tissue following loss of SLC7A10, e.g., upregulation of SCD (lipid storage) and downregulation of CPT1A (lipid oxidation). Interestingly, ROS scavenger reduced lipid accumulation and attenuated the lipid-storing effect of SLC7A10 inhibition. These data uncover adipocyte SLC7A10 as a novel important regulator of adipocyte resilience to nutrient and oxidative stress, in part by enhancing glutathione levels and mitochondrial respiration, conducive to decreased ROS generation, lipid accumulation, adipocyte hypertrophy, insulin resistance, and type 2 diabetes.acceptedVersio