Deforest D.K.,Windward |
Van Genderen E.J.,ZINC Inc
Environmental Toxicology and Chemistry | Year: 2012
The United States Environmental Protection Agency's (U.S. EPA) current ambient water quality criteria (AWQC) for zinc in freshwater are hardness-based and were last updated in 1995. The acute and chronic freshwater toxicity databases have since expanded substantially and the U.S. EPA's minimum phylogenetic diversity requirements for chronic zinc toxicity are now met (an acute:chronic ratio was previously required). Additionally, several acute and chronic biotic ligand models (BLMs) for zinc have since been developed and validated for freshwater organisms. Using the expanded toxicity database and existing BLMs, we developed a unified zinc BLM that could efficiently predict both acute and chronic toxicity over a wide range of zinc bioavailabilities. The unified BLM, developed by objectively averaging the biotic ligand binding constants for zinc (Zn2+) and competing cations (Ca2+, Mg2+, Na+, H+) from existing BLMs, performed better in predicting toxicity to a diverse set of organisms than any individual existing BLM. Performance of the unified BLM was further improved by optimizing the biotic ligand binding constant for the ZnOH+ species. The updated freshwater zinc toxicity database and unified BLM were then used to estimate the fifth percentiles of the acute and chronic species sensitivity distributions following the U.S. EPA guidelines for AWQC development. © 2012 SETAC.
Barton N.,Nick Barton and Associates |
Pandey S.K.,ZINC Inc
International Journal of Rock Mechanics and Mining Sciences | Year: 2011
Two Indian mines are the subject of a comparative study of a strain-softened Hoek-Brown and FLAC 3D modelling, and a novel '. c then tan.φ' strain-softening-strain-mobilization approach, using Q-system based input data. This approach is also used with FLAC 3D, using identical stope geometries. The parameters CC and FC, denoting the cohesive component and frictional component of shear strength, are extracted directly from the Q-logging and knowledge of UCS, and are the source of the peak values. Measured deformations, or the strains recorded over the total length of pre-mining installed MPBX, are compared and effectively calibrate the models, in view of the very similar deformations obtained from empirical formulations based on Q using the competence factor approach, as in SRF. The '. c then tan.φ' approach appears to give the most realistic match to observations in the mines, including the modelling of a shear band within the back or roof of a stope, rather than at the surface of the stope. The Q-based approach also uses a depth-dependent modulus, and this is perhaps the reason why the strain-softened Hoek-Brown model, without this stiffening with depth, shows 'global failure' in a second mine having a wider range of depths within one model, and many openings, since modulus is not increased in standard-method approaches. © 2011 Elsevier Ltd.
Boreiko C.J.,ZINC Inc
Journal of Toxicology and Environmental Health - Part A: Current Issues | Year: 2010
Zinc is an essential trace mineral nutrient required for growth and reproduction in man and other living organisms. Zinc deficiency has been identified as global public health issue that significantly impacts developing countries; as a result, zinc essentiality and the impacts of deficiency have been extensively studied. Zinc is also widely used in commercial products and is a high-production-volume industrial metal. This has provided opportunities for human exposure and prompted multiple assessments of adverse health impacts that might result from exposure excess. Zinc thus provides an illustrative case study of the methodological contrasts between nutritional and toxicological evaluations and highlights the need for risk assessment guidelines that may be tailored to accommodate the properties of essential trace elements.
ZINC Inc | Date: 2012-08-24
A method of operating a redox flow battery includes a step of observing a difference in relative volume between the anolyte fluid volume and the catholyte fluid volume. The ionic molality of anolyte fluid is increased if the relative volume of the anolyte fluid decreases. A redox flow battery having balanced anolyte and catholyte initial ionic molalities is also provided.
ZINC Inc | Date: 2013-05-10
A membrane electrode assembly includes a gas diffusion layer, a catalytic layer in fluid communication with the gas diffusion layer, an anodic layer and a bipolar solid electrolyte disposed between the catalytic and anodic layers. The bipolar solid electrolyte inhibits carbonate formation in air breathing alkaline cells and inhibits dendritic growth between the anodic and catalytic layers.