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In the intensive cyanidation of gravity gold concentrates, sodium m-nitrobenzene sulfonate (NBS) is often used to supplement dissolved oxygen as the oxidant in the process. This paper presents the results of a largely electrochemical study of the behaviour of NBS during cyanidation. The results have confirmed that NBS acts as an oxidant in the cyanidation of gold and that the mixed potential model can be applied to describe the mechanism of its action. The mixed potential is a good initial indicator of the rate of gold dissolution and, as expected, the anodic dissolution of pure gold in cyanide solutions is characterized by passivation at potentials above about −0.35 V. The reduction of oxygen under the conditions of the present study occurs in two 2-electron steps with peroxide as an intermediate. Dissolution of gold occurs at potentials in the diffusion-controlled region for the first step. The cathodic reduction of NBS occurs in the same potential region as the reduction of oxygen. The reaction is first order in the concentration of NBS and is largely independent of the pH. The stoichiometry of the reaction involves six moles of gold per mole of NBS confirming that the amine is the final product of reduction of NBS. Rates of gold dissolution in various solutions have been measured using a calibrated linear polarisation method. The rate increases approximately linearly with increasing NBS concentration and is independent of pH. The rate in 0.5 g/L NBS is approximately the same as in oxygenated solutions. A relatively simple titration has been adapted for use in determining NBS concentrations. • The mixed potential is a good initial indicator of the rate of gold dissolution. • Cathodic reduction of sodium m-nitrobenzene sulfonate (NBS) occurs in the same potential region as the reduction of oxygen. • The stoichiometry of the reaction involves six mole gold per mole of NBS. • Rate increases linearly with increasing NBS concentration and is independent of pH. • The rate in 0.5 g/L NBS is approximately the same as in oxygenated solutions. [ABSTRACT FROM AUTHOR]

In the intensive cyanidation of gravity gold concentrates, sodium m-nitrobenzene sulfonate (NBS) is often used to supplement dissolved oxygen as the oxidant in the process. A previous paper presented the results of a largely electrochemical study of the behaviour of NBS during cyanidation of gold. The results confirmed that NBS acts as an oxidant in the cyanidation of gold and that the mixed potential model can be applied to describe the mechanism of its action. This paper explores the corresponding oxidation of sulfide minerals, that inevitably are contained in gold concentrates, by either dissolved oxygen or NBS. Using electrochemical techniques it was found that dissolved oxygen is effective in the oxidation of several sulfide minerals at pH values between 9 and 11. The effect of cyanide on both the anodic and cathodic processes has been studied. NBS has been found to be ineffective as an oxidant for all minerals tested except galena, even in the presence of cyanide. • Effect of oxygen and NBS on mineral mixed potential good indicator of the rate of mineral oxidation. • Cathodic reduction of NBS occurs at potentials too negative to oxidise the sulfide minerals. • Relative rates of oxidation of minerals by dissolved oxygen in absence and presence of cyanide. • The presence of cyanide results in reduced rates of oxidation of most minerals except chalcopyrite and galena. [ABSTRACT FROM AUTHOR]

Background The World Health Organization–approved Xpert MTB/XDR test detects Mycobacterium tuberculosis and resistance to isoniazid, fluoroquinolones, ethionamide, and injectable drugs directly in specimens. This pragmatic, laboratory-based study assessed the diagnostic accuracy and feasibility of a reflex testing approach, where Xpert MTB/XDR was performed on residual specimens previously processed for Xpert MTB/RIF Ultra. Methods Routine respiratory specimens, processed for Xpert MTB/RIF Ultra, were stored in sample reagent buffer at 2°C–8°C. If rifampicin resistant, the residual specimen was assessed for adequate volume (≥2 mL) and tested with Xpert MTB/XDR, with storage time recorded. A second specimen was used for routine and reference standard testing (culture and sequencing). Results Specimens (99% sputum) from 763 participants submitted to 2 large routine laboratories were included. Xpert MTB/XDR yielded valid resistance detection results in 639 (84%), compared with 507 (66%) for routine testing (difference [95% CI], 18% [13%–22%]). The median turnaround time for results was 23 hours for Xpert MTB/XDR and 15 days for routine testing. While 748 specimens (98%) were ≥2 mL, only 102 (13%) were stored for ≤4 hours. By the reference standard, 284 of 394 (72%) were isoniazid resistant, and 57 of 380 (15%) were fluroquinolone resistant. The sensitivities of Xpert MTB/XDR were 94% (95% CI, 91%–97%) for isoniazid and 91% (81%–97%) for fluoroquinolone resistance detection. The specificities were 98% (94%–100%) and 100% (98%–100%), respectively. Conclusions Xpert MTB/XDR performed favorably compared with the reference, and the reflex testing approach increased results availability over routine testing, while dramatically decreasing turnaround time from weeks to hours. Laboratory workflow precluded testing within the manufacturer-recommended 4-hour storage time, but longer storage did not appear detrimental. [ABSTRACT FROM AUTHOR]

The importance of urban tree diversity for improving resilience is increasingly understood by decision makers. Urban foresters want to prevent the overrepresentation of species on their streets and in their city, which could result in a significant loss of canopy cover in the event of a large-scale disturbance such as a drought or an exotic pest or disease. Although numerous software and tools exist to visualize tree inventories and plan tree maintenance work, only a few offer support for increasing tree diversity. After reviewing the existing tools available for urban forest managers, we present SylvCiT, a novel decision-support and open-source software available on a web platform designed to consolidate information related to the urban forest in one place and facilitate decision-making at different scales. While the first interfaces provide the user with a spatially explicit portrait of the urban forest (species richness, functional diversity, structural diversity, i.e., diameter classes) and associated ecosystem benefits (e.g., stored carbon, ornamental value), the software is designed to produce a list of functional groups and appropriate species to plant considering tree species already present. Based on an artificial intelligence algorithm, SylvCiT identifies the types of trees (species and functional groups) that are absent or underrepresented at different scales to make recommendations that increase species and functional diversity to improve resilience to global change. SylvCiT will continue to be developed to evaluate other ecosystem benefits and integrate criteria such as site characteristics into the recommendation algorithm. [ABSTRACT FROM AUTHOR]