Modelling Sulphur Clusters for an Understanding of Ultramarine

Ultramarine pigments are aluminosilicate-based and contain sulphur-based chromophores. Self-consistent-field Hartree-Fock and Møller-Plesset second order perturbation theory were applied to determine the relative stability of S2, S2 –., S2 2–, and S3, S3 –., S3 2–. The singly charged species was found to be the most stable in both sets. The transition from green to blue ultramarine is thought to be the transformation of the doubly charged species to the singly charged species and is known to be exothermic. Modelling studies supported this hypothesis. The open,C2v, isomer was found to be the most stable for the S3 –. molecule, which is the blue chromophore in ultramarine. The closed, D3h, geometry represents a transition state. The S4 molecule is the most likely chromophore in ultramarine red; however the specific isomer is uncertain. Under the assumption that S4 was formed by a concerted reaction between S3 –. and S+., aWoodward-Hoffmann analysis of the molecular orbitals of S3 –. and S+. supported the formation of the puckered square S4, pyramidal S4, double triangle S4, and gauche S4 chain isomers. The gauche S4 chain is the most likely isomer in ultramarine red.Keywords: Ultramarine pigments, Woodward-Hoffmann analysis, modelling

HIV/AIDS, Security and Conflict: New Realities, New Responses

Ten years after the HIV/AIDS epidemic itself was identified as a threat to international peace and security, findings from the three-year AIDS, Security and Conflict Initiative (ASCI)(1) present evidence of the mutually reinforcing dynamics linking HIV/AIDS, conflict and security

Exploration for magmatic Ni-Cu-PGE sulphide deposits : a review of recent advances in the use of geochemical tools, and their application to some South African ores

Most major magmatic Cu-Ni-PGE sulphide deposits are thought to have formed by segregation of an immiscible sulphide melt from a silicate host magma, in response to processes such as magma mixing, rapid cooling, differentiation, and contamination. The metal content of the sulphides is governed by the concentration of the metals in the silicate host magma, the sulphide melt/silicate melt partition coefficients (D values) of the metals, and the R-factor during sulphide segregation. Fractionation between the metals occurs during partial melting of the upper mantle source, crystallization of oxides, platinum-group minerals (PGM), and silicates (mainly olivine and less so orthopyroxene), segregation of sulphide melt, and crystallization of the sulphide melt. The latter process may yield zoned ore bodies consisting of Os, Ir, Ru, Rh, Fe, (Ni)-rich monosulphide solid solution (mss) cumulate ore and fractionated sulphide ore rich in Cu, Pt, and Pd. It is possible to model these processes and thereby to estimate the potential of a magmatic body to host economic Cu-Ni-PGE sulphide deposits. The location of Cu-Ni-PGE sulphide ores may be facilitated by applying a number of geochemical tools. PGE-rich horizons within layered intrusions are particularly difficult to locate because the ore zones are generally thin compared to the thickness of the intrusions. Variation in Cu/Pd ratios of the silicate rocks may delineate the position of some of these horizons, since the strongly chalcophile Pd is preferentially depleted during sulphide segregation, resulting in an increase in Cu/Pd of the subsequently crystallizing overlying cumulates. Cu/Pd ratios may also be applied in sill-like bodies such as the Uitkomst intrusion, Mpumalanga, to estimate the potential for conduit-type deposits, and in lavas where they may help to locate possible Noril'sk-type mineralized feeder zones to basalt flows. Other methods of determining whether igneous bodies have experienced magma mixing and sulphide segregation are based on Ni contents of olivines, Ti contents, and Cr/Fe ratios of spinels, and petrographic features such as the presence of plagioclase inclusions within ferromagnesian phases. Se/S ratios may help to determine whether magmatic sulphide ores underwent post-magmatic (metamorphic or hydrothermal) sulphur loss. They may also discriminate between a magmatic or sedimentary source of the S, and between a magmatic or hydrothermal origin of the metals. Hydrothermal sulphide ores may further be distinguished from magmatic ores by means of significantly higher Cu/Ni and Pd/Ir ratios of the former. Such distinction is important because it would be futile to investigate hydrothermal deposits for magmatic ore zonation

Het cyanophore karakter van witte klaver (Trifolium repens L.)

The positive correlation found in New Zealand between quality of white clover and its hydrocyanic acid content, could not be confirmed for Dutch white clover in the Netherlands. HCN occurred bound to an incompletely identified glucoside. As Weevers and Treub et al. found the glucoside and HCN contents varying in other plants during the day, the author tried to find out whether similar variations occur in the 1ICN content of white clover. The bromometric method of Schulek was modified so that 1ICN was titrable at a definitely alkaline pH (instead of acid or neutral). The experimental plants were grown under close control: constant illumination, and, within limits, usually constant temperature and air humidity.HCN in Dutch and New Zealand white clover increased rather sharply after sunrise, reaching a maximum rather soon (e.g. after 4 h), then decreasing. This variation only occurred if the weather conditions of the successive days were much alike. Otherwise it was disturbed, often with a second maximum after noon. A maximum must be assumed for the night also. At least 50 leaves must be analysed.These and other results seemed sufficient to start breeding research on HCN content in the Netherlands.<p/

High level of treatment failure with commonly used anthelmintics on Irish sheep farms

peer-reviewedBackground: In 2013 a Technology Adoption Program for sheep farmers was established to encourage the implementation of best management practices on sheep farms in Ireland. There were 4,500 participants in this programme in 2013. As part of this programme, farmers had the option to carry out a drench test to establish the efficacy of their anthelmintic treatment. Results: Flock faecal samples were collected before and after treatment administration and gastrointestinal nematode eggs enumerated. In total there were 1,893 participants in the task, however only 1,585 included both a pre- and post-treatment faecal sample. Of those, 1,308 provided information on the anthelmintic product that they used with 46%, 23% and 28% using a benzimidazole (BZ), levamisole (LEV) and macrocyclic lactone (ML) product respectively. The remaining farmers used a product inapplicable for inclusion in the task such as a flukicide or BZ/LEV combination product. Samples were included for analysis of drench efficacy if the pre-treatment flock egg count was ≥200 eggs per gram and the interval post-sampling was 10–14 days for BZ products, 4–7 days for LEV products and 14–18 days for ML products. These criteria reduced the number of valid tests to 369, 19.5% of all tests conducted. If the reduction post-treatment was ≥95% the treatment was considered effective. Only 51% of treatments were considered effective using this criterion. There was a significant difference in efficacy between the anthelmintic drug classes with BZ effective in only 30% of treatments, LEV effective in 52% of cases and ML effective in 76% of cases. Conclusions: Gastrointestinal nematode anthelmintic treatments, as practiced on Irish farms, have a high failure rate. There was a significant difference between the efficacies of the anthelmintic classes with BZ the least effective and ML the most effective

Research Chimpanzees May Get a Break

A recent report by the Institute of Medicine leaves few urgent reasons standing for the continued use of chimpanzees in biomedical research. It is high time to think about their retirement, Frans de Waal argues, without neglecting prospects for non-invasive research on behavior, cognition, and genetics

Van God los: Post-Christelijk cultureel conflict in Nederland.

Internationale waarnemers verbazen zich al tijden over het verhitte integratiedebat dat in Nederland woedt. Ze vragen zich af hoe zoiets mogelijk is in een land dat bekendstaat als baken van seculiere tolerantie. Dit roept de vraag op hoe etnische tolerantie en afwijzing van traditionele christelijke stellingnamen over morele vraagstukken zich tot elkaar verhouden. In dit artikel onderzoeken we daarom of en waarom het aanhangen van een post-Christelijke moraal voor sommigen leidt tot etnische intolerantie, terwijl het voor anderen samengaat met etnische tolerantie