@article{10860, abstract = {A tight frame is the orthogonal projection of some orthonormal basis of Rn onto Rk. We show that a set of vectors is a tight frame if and only if the set of all cross products of these vectors is a tight frame. We reformulate a range of problems on the volume of projections (or sections) of regular polytopes in terms of tight frames and write a first-order necessary condition for local extrema of these problems. As applications, we prove new results for the problem of maximization of the volume of zonotopes.}, author = {Ivanov, Grigory}, issn = {1496-4287}, journal = {Canadian Mathematical Bulletin}, keywords = {General Mathematics, Tight frame, Grassmannian, zonotope}, number = {4}, pages = {942--963}, publisher = {Canadian Mathematical Society}, title = {{Tight frames and related geometric problems}}, doi = {10.4153/s000843952000096x}, volume = {64}, year = {2021}, } @article{9290, abstract = {Polar subcellular localization of the PIN exporters of the phytohormone auxin is a key determinant of directional, intercellular auxin transport and thus a central topic of both plant cell and developmental biology. Arabidopsis mutants lacking PID, a kinase that phosphorylates PINs, or the MAB4/MEL proteins of unknown molecular function display PIN polarity defects and phenocopy pin mutants, but mechanistic insights into how these factors convey PIN polarity are missing. Here, by combining protein biochemistry with quantitative live-cell imaging, we demonstrate that PINs, MAB4/MELs, and AGC kinases interact in the same complex at the plasma membrane. MAB4/MELs are recruited to the plasma membrane by the PINs and in concert with the AGC kinases maintain PIN polarity through limiting lateral diffusion-based escape of PINs from the polar domain. The PIN-MAB4/MEL-PID protein complex has self-reinforcing properties thanks to positive feedback between AGC kinase-mediated PIN phosphorylation and MAB4/MEL recruitment. We thus uncover the molecular mechanism by which AGC kinases and MAB4/MEL proteins regulate PIN localization and plant development.}, author = {Glanc, Matous and Van Gelderen, K and Hörmayer, Lukas and Tan, Shutang and Naramoto, S and Zhang, Xixi and Domjan, David and Vcelarova, L and Hauschild, Robert and Johnson, Alexander J and de Koning, E and van Dop, M and Rademacher, E and Janson, S and Wei, X and Molnar, Gergely and Fendrych, Matyas and De Rybel, B and Offringa, R and Friml, Jiří}, issn = {1879-0445}, journal = {Current Biology}, number = {9}, pages = {1918--1930}, publisher = {Elsevier}, title = {{AGC kinases and MAB4/MEL proteins maintain PIN polarity by limiting lateral diffusion in plant cells}}, doi = {10.1016/j.cub.2021.02.028}, volume = {31}, year = {2021}, } @article{8824, abstract = {Plants are able to orient their growth according to gravity, which ultimately controls both shoot and root architecture.1 Gravitropism is a dynamic process whereby gravistimulation induces the asymmetric distribution of the plant hormone auxin, leading to asymmetric growth, organ bending, and subsequent reset of auxin distribution back to the original pre-gravistimulation situation.1, 2, 3 Differential auxin accumulation during the gravitropic response depends on the activity of polarly localized PIN-FORMED (PIN) auxin-efflux carriers.1, 2, 3, 4 In particular, the timing of this dynamic response is regulated by PIN2,5,6 but the underlying molecular mechanisms are poorly understood. Here, we show that MEMBRANE ASSOCIATED KINASE REGULATOR2 (MAKR2) controls the pace of the root gravitropic response. We found that MAKR2 is required for the PIN2 asymmetry during gravitropism by acting as a negative regulator of the cell-surface signaling mediated by the receptor-like kinase TRANSMEMBRANE KINASE1 (TMK1).2,7, 8, 9, 10 Furthermore, we show that the MAKR2 inhibitory effect on TMK1 signaling is antagonized by auxin itself, which triggers rapid MAKR2 membrane dissociation in a TMK1-dependent manner. Our findings suggest that the timing of the root gravitropic response is orchestrated by the reversible inhibition of the TMK1 signaling pathway at the cell surface.}, author = {Marquès-Bueno, MM and Armengot, L and Noack, LC and Bareille, J and Rodriguez Solovey, Lesia and Platre, MP and Bayle, V and Liu, M and Opdenacker, D and Vanneste, S and Möller, BK and Nimchuk, ZL and Beeckman, T and Caño-Delgado, AI and Friml, Jiří and Jaillais, Y}, issn = {1879-0445}, journal = {Current Biology}, number = {1}, publisher = {Elsevier}, title = {{Auxin-regulated reversible inhibition of TMK1 signaling by MAKR2 modulates the dynamics of root gravitropism}}, doi = {10.1016/j.cub.2020.10.011}, volume = {31}, year = {2021}, } @article{9301, abstract = {Electrodepositing insulating lithium peroxide (Li2O2) is the key process during discharge of aprotic Li–O2 batteries and determines rate, capacity, and reversibility. Current understanding states that the partition between surface adsorbed and dissolved lithium superoxide governs whether Li2O2 grows as a conformal surface film or larger particles, leading to low or high capacities, respectively. However, better understanding governing factors for Li2O2 packing density and capacity requires structural sensitive in situ metrologies. Here, we establish in situ small- and wide-angle X-ray scattering (SAXS/WAXS) as a suitable method to record the Li2O2 phase evolution with atomic to submicrometer resolution during cycling a custom-built in situ Li–O2 cell. Combined with sophisticated data analysis, SAXS allows retrieving rich quantitative structural information from complex multiphase systems. Surprisingly, we find that features are absent that would point at a Li2O2 surface film formed via two consecutive electron transfers, even in poorly solvating electrolytes thought to be prototypical for surface growth. All scattering data can be modeled by stacks of thin Li2O2 platelets potentially forming large toroidal particles. Li2O2 solution growth is further justified by rotating ring-disk electrode measurements and electron microscopy. Higher discharge overpotentials lead to smaller Li2O2 particles, but there is no transition to an electronically passivating, conformal Li2O2 coating. Hence, mass transport of reactive species rather than electronic transport through a Li2O2 film limits the discharge capacity. Provided that species mobilities and carbon surface areas are high, this allows for high discharge capacities even in weakly solvating electrolytes. The currently accepted Li–O2 reaction mechanism ought to be reconsidered.}, author = {Prehal, Christian and Samojlov, Aleksej and Nachtnebel, Manfred and Lovicar, Ludek and Kriechbaum, Manfred and Amenitsch, Heinz and Freunberger, Stefan Alexander}, issn = {1091-6490}, journal = {Proceedings of the National Academy of Sciences}, keywords = {small-angle X-ray scattering, oxygen reduction, disproportionation, Li-air battery}, number = {14}, publisher = {National Academy of Sciences}, title = {{In situ small-angle X-ray scattering reveals solution phase discharge of Li–O2 batteries with weakly solvating electrolytes}}, doi = {10.1073/pnas.2021893118}, volume = {118}, year = {2021}, } @article{9447, abstract = {Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) based water-in-salt electrolytes (WiSEs) has recently emerged as a new promising class of electrolytes, primarily owing to their wide electrochemical stability windows (~3–4 V), that by far exceed the thermodynamic stability window of water (1.23 V). Upon increasing the salt concentration towards superconcentration the onset of the oxygen evolution reaction (OER) shifts more significantly than the hydrogen evolution reaction (HER) does. The OER shift has been explained by the accumulation of hydrophobic anions blocking water access to the electrode surface, hence by double layer theory. Here we demonstrate that the processes during oxidation are much more complex, involving OER, carbon and salt decomposition by OER intermediates, and salt precipitation upon local oversaturation. The positive shift in the onset potential of oxidation currents was elucidated by combining several advanced analysis techniques: rotating ring-disk electrode voltammetry, online electrochemical mass spectrometry, and X-ray photoelectron spectroscopy, using both dilute and superconcentrated electrolytes. The results demonstrate the importance of reactive OER intermediates and surface films for electrolyte and electrode stability and motivate further studies of the nature of the electrode.}, author = {Maffre, Marion and Bouchal, Roza and Freunberger, Stefan Alexander and Lindahl, Niklas and Johansson, Patrik and Favier, Frédéric and Fontaine, Olivier and Bélanger, Daniel}, issn = {1945-7111}, journal = {Journal of The Electrochemical Society}, keywords = {Renewable Energy, Sustainability and the Environment, Electrochemistry, Materials Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, Condensed Matter Physics}, number = {5}, publisher = {IOP Publishing}, title = {{Investigation of electrochemical and chemical processes occurring at positive potentials in “Water-in-Salt” electrolytes}}, doi = {10.1149/1945-7111/ac0300}, volume = {168}, year = {2021}, }