Flowsheet Options for Cobalt Recovery in African Copper–cobalt Hydrometallurgy Circuits

The price of cobalt has increased by some 450% in the past two years, mainly due to increasing demand for lithium–ion batteries. With an official 2017 production of 64 kt, the Democratic Republic of Congo produces more than half of the world’s cobalt. African Copperbelt operations have traditionally focused on copper production; however, it has now become imperative to also consider cobalt recovery from these ores. A plethora of processing routes is possible. Most hydrometallurgical flowsheets recover cobalt from the raffinate of the low-grade copper solvent-extraction circuit. Downstream purification processes include sequential precipitation with a variety of reagents, solvent extraction, and ion exchange. Product choices include hydroxide, carbonate, sulfate, and metal cathode. This study assesses technical and economic advantages and limitations of various approaches to the hydrometallurgical processing of cobalt in an African context.     

Methyltransferase Contingencies in the Pathway of Everninomicin D Antibiotics and Analogues

Everninomicins are orthoester oligosaccharide antibiotics with potent activity against multidrug-resistant bacterial pathogens. Everninomicins act by disrupting ribosomal assembly in a distinct region in comparison to clinically prescribed drugs. We employed microporous intergeneric conjugation with Escherichia coli to manipulate Micromonospora for targeted gene-replacement studies of multiple putative methyltransferases across the octasaccharide scaffold of everninomicin effecting the A₁, C, F, and H rings. Analyses of gene-replacement and genetic complementation mutants established the mutability of the everninomicin scaffold through the generation of 12 previously unreported analogues and, together with previous results, permitted assignment of the ten methyltransferases required for everninomicin biosynthesis. The in vitro activity of A₁- and H-ring-modifying methyltransferases demonstrated the ability to catalyze late-stage modification of the scaffold on an A₁-ring phenol and H-ring C-4’ hydroxy moiety. Together these results establish the potential of the everninomicin scaffold for modification through mutagenesis and in vitro modification of advanced biosynthetic intermediates.     

Relationships between urbanization and the oak resource of the Minneapolis/St. Paul Metropolitan area from 1991 to 1998

Urbanization was associated with loss and transformation of the oak forest in the Twin Cities (Minneapolis and St. Paul) metropolitan area (TCMA) over a recent 7-year interval. Between 1991 and 1998, urbanization increased based on several indicators: population density, area of developed land, and area of impervious surface—total impervious area and area within three classes of increasing degree of imperviousness (protected, affected, and degraded). We quantified relationships between changes in urbanization and changes in several parameters describing the oak forest at the scale of ecological subsection. Increased total and affected impervious area were strongly correlated with decreased area of oak forest when changes of the urbanization indicators and oak were expressed as percentages of the subsection area. Relationships were reversed when changes were expressed as percentages of the 1991 values. Increased population density was strongly correlated with increased loss in numbers and increased isolation of oak patches, but weakly correlated with loss of oak forest area. This is the first study to quantify relationships between changes in urbanization and changes in a specific forest cover type. Our results demonstrate complexities of urbanization impacts on a metropolitan forest resource, and highlight the importance of selected variables, spatial and temporal scales, and expressions of change when quantifying these relationships.     

The ethics of asking about abuse and the harm of "don't ask, don't tell."

Replies to comments by J. Read (see record 2007-07130-012), D. Gleaves et al (see record 2007-07130-013), V. Edwards et al (see record 2007-07130-014), M. Black and R. Black (see record 2007-07130-015), and S. Ullman (see record 2007-07130-016), which raised important points about the authors' original article (see record 2006-03947-003). Those comments extend our thinking about how to ask participants about abuse in an ethical way. Together, the comments point to the importance of researchers examining our own reasons for asking--or not asking--about abuse and of paying attention to how we respond when we ask. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Surfactant behavior and its influence on the viscosity of associative thickeners solutions, thickened latex dispersions, and waterborne latex coatings

Surfactants, varying in their chemical composition and hydrophobic behavior, are used in the formulation of a waterborne coating. These differences influence their aggregation in micellar structures, their interaction with associative thickeners, and in particular, the synergies present in their competitive adsorptions on the disperse phases in a waterborne coating. Adsorption of HEUR thickeners on latexes and the ability of surfactants to displace them from those surfaces is an important variable in the dispersion’s viscosity. With large particle latexes, viscosity increases arise primarily from the network built through the interaction of HEURs with surfactants in the aqueous phase. Fluorescence is used to verify the mechanism by which surfactants enhance associative thickener viscosities. That is best achieved with nonionic surfactants, because of their synergies with large hydrophobe HEURs at low concentration. With decreasing latex particle size the adsorbed species is an important contributor to the dispersion’s viscosity through its contribution to the latex’s effective volume fraction increase and when the size of the adsorbed HEUR is matched to the separation distances of the latex at 0.25 volume fraction. Achieving controlled shear-thinning behavior in small particle size latex paints with the economic constraints on the amount of HEUR required to obtain 90 KU viscosities are discussed. Presented at the 80th Annual Meeting of the Federation of Societies for Coatings Technology, October 30–November 1, 2002, in New Orleans, LA. Polymer and Coatings Dept., Fargo, ND 58103.     

Chlorisondamine inhibits the nicotine-induced stimulation of c-fos in the pigeon brain for up to 2 weeks.

Chlorisondamine is a charged molecule that acts as long-acting nicotinic antagonist in many species, including pigeon. Evidence indicates that, despite the charged nature of chlorisondamine, it blocks some central effects of nicotine. The present study examined the time course of chlorisondamine's blockade of nicotine-induced c-fos expression in the pigeon brain. Chlorisondamine's central blockade was examined from 1 hr to 28 days prior to nicotine administration. Nicotine stimulated increases in c-fos mRNA in the hippocampus, hyperstriatum accessorium, hyperstriatum ventrale, nucleus accumbens, bulbus olfactorius, paleostriatum augmentatum, and stratum griseum et fibrosum superficiale. Nicotinic receptors labeled by [(125)I]-epibatidine were not always found in the same regions as nicotine-induced increases in c-fos expression. Acute chlorisondamine increased the level of c-fos mRNA in the cerebellum, hippocampus, hyperstriatum accessorium, locus parolfactorius, nucleus accumbens, tectum opticum, paleostriatum augmentatum, and stratum griseum et fibrosum superficiale but had no effect on its own 24 hr after administration. Chlorisondamine blocked nicotine-induced increases in c-fos RNA for 4 days in the nucleus accumbens, a week in the bulbus olfactorius, and 2 weeks in the stratum griseum et fibrosum superficiale. The time course of chlorisondamine's blockade of nicotine-induced c-fos expression is consistent with the time course of the ability of chlorisondamine to block behavioral and physiological responses to nicotine.     

Psychological adjustment of children with sickle cell disease: Stability and change over a 10-month period.

Rates of poor psychological adjustment of children with sickle cell disease remained relatively constant over initial and follow-up assessment points. 50 children (aged 7–12 yrs) and their mothers completed the initial protocol. 30 children completed the follow-up plus 5 additional children and their mothers. These Ss were aged 7–24 yrs at follow-up. With initial levels of adjustment controlled, children's strategies for coping with pain accounted for a significant increment in child-reported symptoms and mother-reported internalizing behavior problems at follow-up beyond the contribution of illness and demographic parameters and follow-up interval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)