Globally ubiquitous negative effects of nitrogen dioxide on crop growth.

Nitrogen oxides (NO) are among the most widely emitted pollutants in the world, yet their impacts on agriculture remain poorly known. NO can directly damage crop cells and indirectly affect growth by promoting ozone (O) and aerosol formation. We use satellite measures of both crop greenness and NO during 2018-2020 to evaluate crop impacts for five major agricultural regions.

Changes in the drought sensitivity of US maize yields.

As climate change leads to increased frequency and severity of drought in many agricultural regions, a prominent adaptation goal is to reduce the drought sensitivity of crop yields. Yet many of the sources of average yield gains are more effective in good weather, leading to heightened drought sensitivity. Here we consider two empirical strategies for detecting changes in drought sensitivity and apply them to maize in the United States, a crop that has experienced myriad management changes including recent adoption of drought-tolerant varieties.

Mapping twenty years of corn and soybean across the US Midwest using the Landsat archive.

Field-level monitoring of crop types in the United States via the Cropland Data Layer (CDL) has played an important role in improving production forecasts and enabling large-scale study of agricultural inputs and outcomes. Although CDL offers crop type maps across the conterminous US from 2008 onward, such maps are missing in many Midwestern states or are uneven in quality before 2008. To fill these data gaps, we used the now-public Landsat archive and cloud computing services to map corn and soybean at 30 m resolution across the US Midwest from 1999-2018.

Theoretical insights into inorganic-organic intercalation products of the layered perovskite HLaNbO: perspectives for hybrid proton conductors.

The modification of metal oxide surfaces with organic moieties has been widely studied as a method of preparing organic-inorganic hybrid materials for various applications. Among the inorganic oxides, ion-exchangeable layered perovskites are particularly interesting, because of their appealing electronic and reactive properties. In particular, their protonated interlayer surface can be easily functionalized with organic groups allowing the production of stable hybrid materials.

Defect interaction and local structural distortions in Mg-doped LaGaO: A combined experimental and theoretical study.

A combined experimental and theoretical study of Mg-doped LaGaO electrolyte was carried out, with the aim to unveil the interaction between oxygen vacancy (Vo) and perovskite B site cations. LaGaO (LG) and LaGaMgO (LGM0125) samples were comprehensively characterized by X-ray absorption spectroscopy (XAS) and X-ray diffraction, in order to investigate short- and long-range structures of both undoped and Mg-doped materials. XAS analysis evidenced a preferential Ga-Vo interaction in LGM0125, confirmed by periodic hybrid density functional theory calculations, which were combined with a symmetry-independent classes (SICs) approach in order to (a) obtain a detailed picture of the different Mg and Vo configurations in the doped material and (b) characterize the structural features of the conducting sites.

Theoretical approaches for predicting the color of rigid dyes in solution.

Aiming at developing an affordable and easily implementable computational protocol for routine prediction of spectral properties of rigid molecular dyes, density functional theory, and time-dependent density functional theory were used in conjunction with a vibronic coupling scheme for band shape estimate. To predict the perceived color of molecules in solution, a model has been setup linking the UV-vis spectra predicted at ab initio level to the L*a*b* colorimetric parameters. The results show that a mixed protocol, implying the use of a global hybrid functional for the prediction of adiabatic energy differences and a range separated hybrid for the prediction of potential energy curvature, allows perceived colors to be quantitatively predicted, as demonstrated by the comparison of L*a*b* colorimetric parameters obtained from computed and experimental spectra.

Toward tailorable surfaces: a combined theoretical and experimental study of lanthanum niobate layered perovskites.

A comprehensive theoretical investigation of the MLaNb2O7 (M = H, Li, Na, K, Rb, and Cs) series of ion-exchangeable layered perovskite is presented. These perovskites are in particular interesting in view of their potential applications as inorganic supports for the design of new hybrid inorganic-organic proton conductors. In particular, their structural and electronic properties have been investigated by periodic calculations in the framework of Density Functional Theory, using different exchange-correlation functionals.

Oxidation mechanism of aliphatic ethers: theoretical insights on the main reaction channels.

This paper presents a quantum chemical study on oxidation process of a series of aliphatic ethers. On the basis of a detailed theoretical work on diethyl ether oxidation, the mechanism has been reduced at three competing reactions: the β-scission of the alkyl radical (R(I)OR(II)(•)) issued from the initiation step, the isomerization of the peroxy radical (R(I)OR(II)OO(•)) produced by reaction of the alkyl radical with molecular oxygen, and the hydroperoxide production, a bimolecular reaction between the peroxy radical and an ether molecule that also regenerates a R(I)OR(II)(•) radical. Results obtained from DFT calculations, including thermochemistry and rate constant evaluations, have been reported and discussed.

Oxidation mechanism of diethyl ether: a complex process for a simple molecule.

A large number of organic compounds, such as ethers, spontaneously form unstable peroxides through a self-propagating process of autoxidation (peroxidation). Although the hazards of organic peroxides are well known, the oxidation mechanisms of peroxidizable compounds like ethers reported in the literature are vague and often based on old experiments, carried out in very different conditions (e.g.

Computational study of alkynes insertion into metal-hydride bonds catalyzed by bimetallic complexes.

Density Functional Theory investigations on the insertion mechanism of phenylacetylene into metal-hydride bonds in bimetallic (Pt,Os) catalysts have been carried out. The results obtained have been also compared with the non-reactive monometallic (Os-based) system, to elucidate the cooperative effects and to explain the observed absence of reactivity. The identified reaction path involves phenylacetylene coordination followed by the insertion into the metal-hydride bond, leading to the formation of the experimentally observed products.