Abstract
Chemistry Widespread use of functional electrocatalytic water-splitting systems in conjunction with solar power infrastructure will probably require a composition of Earth-abundant materials that remain stable under the reaction conditions and operate efficiently at minimal overpotential (a measure of how much of the input energy gets stored in the products' chemical bonds for later use when the Sun has set, rather than lost as heat). Numerous reports highlight favorable features of particular experimental catalysts in this context, but cross-comparisons have proven challenging in the absence of established standards for the testing conditions. McCrory et al. offer a preliminary framework for making apples-to-apples comparisons of catalysts for the oxygen-evolving half of the couple. They report benchmark tests of nine representative non–precious metal catalysts deposited on glassy carbon electrodes, under standardized acidic (1 M sulfuric acid) and basic (1 M sodium hydroxide) conditions. After first assessing the active surface area for normalization, the authors measured the overpotential necessary to attain a current density of 10 mA/cm2 and then tracked performance over 2 hours. None of the tested non–precious metal catalysts were stable in acid, highlighting a priority for further research. In base, the overpotentials across the test set varied relatively little, spanning a range between 350 and 430 mV. J. Am. Chem. Soc. 135 , 16977 (2013).
Highlights
Models of the uptake of Ca and other trace elements do not entirely explain the concentration and ratio of ions preserved in carbonate shells
Using a combination of isotopic and fluorescent imaging of incubated cultures, Nehrke et al show that passive ion transport is important for trace elements such as Mg and Sr in an extant foraminifera species, but not Ca
The latent reservoir has been measured in the past by one of two methods: forcing all T cells to become active and measuring viruses that have been induced to replicate or identifying all integrated proviral DNA
Summary
Nitrogen-containing compounds have been used to treat heart failure for well over 1000 years, in many cases their mechanisms of action are unclear. Huang et al show that agents that increase the production of nitric oxide (NO) can influence heart function through S-nitrosylation of the enzyme GRK2; this protein kinase phosphorylates G protein—coupled receptors, most notably the β-adrenergic receptor, that have critical roles in regulating heart function. They found that GRK2 associates with endothelial NO synthase, the enzyme that produces NO, and nitrosylation of GRK2 inhibits its activity. HUANG ET AL., SCIENCE SIGNALING 6, 299 (29 OCTOBER 2013); G. NEHRKE ET AL., BIOGEOSCIENCES 10 (29 OCTOBER 2013) © COPERNICUS PUBLICATIONS ON BEHALF OF THE EUROPEAN GEOSCIENCES UNION
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