Zinc limitation

Germanium tetrachloride refined for use in making optical fibers is usually specified to contain less than 0.5 to 5 ppb of each of eight impurities vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc. Limits are sometimes specified for a few other elements. Also of concern are hydrogen-bearing impurities therefore, maximum limits of 5 to 10 ppm are usually placed on HCl, OH, CH2, and CH contents. 

The design of a AA-size alkaline manganese dioxide cell is shown in Fig. 1 (Sec. 3.1). Primary and secondary alkaline batteries are constructed in the same way and can be manufactured on essentially the same machinery. The separator material, electrode formulation, and the Mn02 Zn balance are different. Rechargeable cells are zinc-limited to prevent a discharge beyond the first electron-equivalent of the MnOz reduction. The electrolyte is 7-9 mol L KOH. The electrode reactions are ... 

Zhao, H. and Eide, D. (1996). The yeast ZRT1 gene encodes the zinc transporter protein of a high-affinity uptake system induced by zinc limitation, Proc. Natl Acad. Sci., 93, 2454-2458. 

Because zinc is required for the growth of phytoplankton, its availability affects the biological pump. Although zinc limitation of an entire phytoplankton community has never been demonstrated, levels of dissolved zinc are often low enough to limit many taxa (Morel et al, 1994 Sunda and Huntsman, 1995b Timmermans et al, 2001). Zinc is an integral part of the enzyme, carbonic anhydrase (Morel et al, 1994), which helps maintain an efficient supply of CO2 to Rubisco. 

If you combine 0.23 mol Zn and 0.60 mol HCl, would they react completely Using the coefficients from the balanced equation, you can predict that 0.23 mol Zn can form 0.23 mol H2, and 0.60 mol HCl can form 0.30 mol H2. Zinc is called the limiting reactant because the zinc limits the amount of product that can form. The zinc is used up first by the reaction. The HCl is the excess reactant because there is more than enough HCl present to react with all of the Zn. There will be some HCl left over after the reaction stops. 

In the yeast S. cerevisiae, at least four different transporters are involved in zinc uptake. The most important of these is the ZIP family member ZRTl, which is required for growth under low zinc concentrations. ZRTl has a high affinity for zinc with an apparent for free Zn of 10 nM. A second ZIP protein, ZRT2, with a lower affinity for zinc (apparent -100 nM) probably plays a role under less severe zinc limitation. In addition to the two ZIP proteins, two other lower affinity systems also operate. One is the FET4 protein, which we saw earlier is also involved in the low affinity uptake of iron and copper. 

High levels of administered zinc limits copper uptake in humans and certain animals, and provides protection against toxicosis produced by copper in pigs and sheep. Excessive zinc in humans interferes with copper absorption from the intestine, resulting in copper deficiency, and eventually to cardiovascular diseases hi zinc intakes also decrease iron bioavailability, leading to a reduction of erythrocyte life span by 67%. Copper deficiency induced by excess dietary zinc is associated with lameness in horses, donkeys, and mules. 

The direct reductive acid leaching process was developed by Hindustan Zinc Limited, Udaipur. Starch was used in the process as reductant during leaching. The separation process is based on selective sulphide precipitation followed by solvent extraction and electrolysis. The other two processes are based on ammonia leaching, developed at the Institute of Materials and Minerals Technology, Bhubaneshawar (IMMT-B) and National Metallurgical Laboratory,... 

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