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  1. Over the course of more than three decades, Li-ion batteries have come to revolutionize the way we store and transport energy. These incredibly compact electrochemical devices rely fundamentally on the ability to reversibly insert lithium ions into densely packed arrangements of atoms. Of the tens of thousands of materials reported in the structural databases, only a very small number have been shown to be capable of accommodating the kind of fast ionic diffusion necessary to operate in practical devices. In honor of John B. Goodenough’s 100th birthday, this perspective will overview the current understanding of the kinds of structural features that help and/or hurt fast lithium ion transport through insertion hosts, with a particular focus on the role that the rotation of rigid subunits plays in the movement of lithium through the solid state. 
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  2. Abstract

    Irrigated agriculture in snow-dependent regions contributes significantly to global food production. This study quantifies the impacts of climate change on irrigated agriculture in the snow-dependent Yakima River Basin (YRB) in the Pacific Northwest United States. Here we show that increasingly severe droughts and temperature driven reductions in growing season significantly reduces expected annual agricultural productivity. The overall reduction in mean annual productivity also dampens interannual yield variability, limiting yield-driven revenue fluctuations. Our findings show that farmers who adapt to climate change by planting improved crop varieties may potentially increase their expected mean annaul productivity in an altered climate, but remain strongly vulnerable to irrigation water shortages that substantially increase interannual yield variability (i.e., increasing revenue volatility). Our results underscore the importance for crop adaptation strategies to simultaneously capture the biophysical effects of warming as well as the institutional controls on water availability.

     
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  3. There is an increasing appreciation that food–energy–water (FEW) nexus problems are approaching criticality in both the developing and developed world. As researchers and managers attempt to address these complex resource management issues, the concept of the FEW nexus has generated a rapidly growing footprint in global sustainability discourse. However, this momentum in the FEW nexus space could be better guided if researchers could more clearly identify what is and is not a FEW problem. Without this conceptual clarity, it can be difficult to defend the position that FEW innovations will produce desired outcomes and avoid unintended consequences. Here we examine the growing FEW nexus scholarship to critically evaluate what features are necessary to define a FEW nexus. This analysis suggests that the FEW nexus differs from sector-focused natural resource or sustainability problems in both complexity and stakes. It also motivates two new foci for research: the identification of low-dimension indexes of FEW system status and approaches for identifying boundaries of specific FEW nexuses. 
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  4. Abstract

    The heterogeneous microstructure of semicrystalline polymers complicates the relationship between their electrical conductivity and carrier concentration. Charge transport models typically describe conductivity with an assumption of uniform doping throughout the material. Here, the evolution in morphology and optoelectronic properties of poly(3‐hexylthiophene) (P3HT) is reported as a function of carrier concentration in an organic electrochemical transistor using a polymeric ionic liquid (PIL) as the gate insulator.Operandograzing incidence X‐ray scattering reveals that negatively charged ions from the dielectric first infiltrate the amorphous regions of the semiconductor, and then penetrate the crystalline regions at a critical carrier density of 4 × 1020cm−3. Upon infiltration, the crystallites expand by 12% in the alkyl stacking direction and compress by 4% in the π–π stacking direction. The change in crystal structure of P3HT correlates with a sharply increasing effective carrier mobility. UV–visible spectroscopy reveals that holes induced in P3HT first reside in the crystalline regions of the polymer, which verifies that a charge carrier need not be in the same physical domain as its associated counterion. The dopant‐induced morphological changes of P3HT rationalize the dependence of mobility on carrier concentration, suggesting a phase transition of crystalline regions at high carrier concentration.

     
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