99 research outputs found

    Approximate nonradial solutions for the Lane-Emden problem in the ball

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    In this paper we provide a numerical approximation of bifurcation branches from nodal radial solutions of the Lane Emden Dirichlet problem in the unit ball in ℝ2, as the exponent of the nonlinearity varies. We consider solutions with two or three nodal regions. In the first case our numerical results complement the analytical ones recently obtained in [11]. In the case of solutions with three nodal regions, for which no analytical results are available, our analysis gives numerical evidence of the existence of bifurcation branches. We also compute additional approximations indicating presence of an unexpected branch of solutions with six nodal regions. In all cases the numerical results allow to formulate interesting conjectures

    A light-fuelled nanoratchet shifts a coupled chemical equilibrium

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    Biological molecular machines enable chemical transformations, assembly, replication and motility, but most distinctively drive chemical systems out of-equilibrium to sustain life. In such processes, nanometre-sized machines produce molecular energy carriers by driving endergonic equilibrium reactions. However, transforming the work performed by artificial nanomachines into chemical energy remains highly challenging. Here, we report a light-fuelled small-molecule ratchet capable of driving a coupled chemical equilibrium energetically uphill. By bridging two imine macrocycles with a molecular motor, the machine forms crossings and consequently adopts several distinct topologies by either a thermal (temporary bond-dissociation) or photochemical (unidirectional rotation) pathway. While the former will relax the machine towards the global energetic minimum, the latter increases the number of crossings in the system above the equilibrium value. Our approach provides a blueprint for coupling continuous mechanical motion performed by a molecular machine with a chemical transformation to reach an out-of-equilibrium state

    Nanostructure, osteopontin, and mechanical properties of calcitic avian eggshell

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    Avian (and formerly dinosaur) eggshells form a hard, protective biomineralized chamber for embryonic growth—an evolutionary strategy that has existed for hundreds of millions of years. We show in the calcitic chicken eggshell how the mineral and organic phases organize hierarchically across different length scales and how variation in nanostructure across the shell thicknessmodifies its hardness, elastic modulus, and dissolution properties.We also show that the nanostructure changes during egg incubation, weakening the shell for chick hatching. Nanostructure and increased hardness were reproduced in synthetic calcite crystals grown in the presence of the prominent eggshell protein osteopontin. These results demonstrate the contribution of nanostructure to avian eggshell formation, mechanical properties, and dissolution.This work was supported by a grant from the Canadian Institutes of Health Research (no. MOP-142330) and the Natural Sciences and Engineering Research Council of Canada (NSERC; no. RGPIN-2016-05031) to M.D.M., an NSERC (no. RGPIN-2016-04410) Discovery grant to M.T.H., a Spanish Government grant (CGL2015-64683-P) to A.B.R.-N., an Emmy Noether research grant from the German Research Foundation (no. WO1712/3-1) to S.E.W., and an NSF grant (NSF BMAT; no. 1507736) to J.J.G. M.D.M. is a member of the Fonds de Recherche Quebec–Sante Network for Oral and Bone Health Research and the McGill Centre for Bone and Periodontal Researc
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