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Par intuition, j'ai toujours pensé que le cycliste faisait de la philosophie sans forcément le savoir. "A quoi pensez-vous tout ce temps ?" La question m'a souvent été posée à l'occasion de mes Grands Tours de trois semaines à vélo. A chaque fois, la même réponse m'est venue : à tout et à rien ! Ce qui ne serait sans doute pas la plus mauvaise approche de la philosophie". Dans la lignée d'Alfred Jarry, Jules Renard, Cioran ou encore Maurice Leblanc, grands écrivains cyclistes, Bernard Chambaz allie dans cet essai souplesse des mots et ressort de la pédale. Mouvement, espace, durée, effort : tous les amateurs, passionnés, fous de vélo, trouveront au fil des réflexions de l'auteur de quoi réfléchir à leur tour sur des notions pour eux bien concrètes. Car détrompons-nous : le vélo n'est pas détaché des idées ! De concept en concept, convoquant avec espièglerie les plus grands philosophes - Heidegger, Kant, Spinoza ou encore Husserl -, Bernard Chambaz dévoile une autre facette du vélo : celle d'un objet qui prolonge notre être et nous donne à penser.

Cycling

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Le vélo est un moyen de transport rapide, fiable, bon marché, sain, peu consommateur d'espace, économe en énergie et non polluant. Pour les distances comprises entre 500 mètres et 10 kilomètres, il constitue souvent le mode de déplacement le plus efficace, le plus bénéfique pour l'économie locale et aussi le plus agréable. De nombreux usagers, ainsi que certains décideurs, semblent avoir pris conscience de ces atouts innombrables. Mais lorsqu'on présente la bicyclette comme un moyen de transport amené à se développer, on assiste à une levée de boucliers : le vélo devient soudain "véhicule du pauvre", "instrument difficile à manier" ou "talisman écologique pour bourgeois rêveur". Avec cet essai "poil à gratter", Olivier Razemon bat en brèche les idées reçues qui empêchent encore l'essor du vélo et livre un vibrant plaidoyer pour une transition cyclable.

Cycling --- Cycling --- Cycling --- Transportation

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Bacteria can sequester metals and other ions intracellularly in various forms ranging from poorly ordered deposits to well- ordered mineral crystals. Magnetotactic bacteria provide one example of such intracellular deposits. They synthesize intracellular magnetic minerals of magnetite (Fe3O4) and/or greigite (Fe3S4) magnetosomes which are generally less than 150 nm and organized into one or multiple chain structures. The magnetosome chain(s) act like a compass needle to facilitate the navigation of magnetotactic bacteria by using the Earth's magnetic field. Due to their ubiquitous distribution in aquatic and sedimentary environments, magnetotactic bacteria play important roles in global iron cycling. Other intracellular mineral phases have been evidenced in bacteria such as As2S3, CaCO3, CdS, Se(0) or various metal phosphates which may play as well a significant role in the geochemical cycle of these elements. However, in contrast to magnetotactic bacteria, the biological and environmental function of these particles remains a matter of debate. In recent years, such intracellularly biomineralizaing bacteria have become an attractive model system for investigating the molecular mechanisms of organelle-like structure formation in prokaryotic cells. The geological significance of intracellular biomineralization is important; spectacular examples are fossil magnetosomes that may significantly contribute to the bulk magnetization of sediments and act as potential archives of paleoenvironmental changes. In addition, intracellular mineral deposits formed by bacteria have potentially versatile applications in biotechnological and biomedical fields. After more than four decades of research, the knowledge on intracellularly biomineralizing bacteria has greatly improved. The aim of this Research Topic is to highlight recent advances in our understanding of intracellular biomineralization by bacteria. Magnetotactic bacteria are a system of choice for that topic but other intracellularly biomineralizing bacteria may bring a unique perspective on that process. Research papers, reviews, perspectives, and opinion papers on (i) the diversity and ecology of intracellularly biomineralizing bacteria, (ii) the molecular mechanisms of intracellular biomineralization, (iii) the chemo- and magneto-taxis behaviors of magnetotactic bacteria, (iv) the involvement of intracellularly biomineralizing bacteria in local or global biogeochemical cycling, (v) the paleoenvironmental reconstructions and paleomagnetic signals based on fossil magnetosomes, (vi) and the applications of intracellular minerals in biomaterial and biotechnology were welcomed.

Biomineralization. --- Magnetotactic bacteria. --- microbial biomineralization --- biosignature --- iron cycling --- magnetotactic bacteria --- magnetosome --- Magnetotaxis --- ancient environment --- microbial biomineralization --- biosignature --- iron cycling --- magnetotactic bacteria --- magnetosome --- Magnetotaxis --- ancient environment

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Sport --- Sports professions --- Book --- Cycling --- Cooke, Nicole --- anno 1900-1999 --- anno 2000-2099 --- United Kingdom

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Bacteria can sequester metals and other ions intracellularly in various forms ranging from poorly ordered deposits to well- ordered mineral crystals. Magnetotactic bacteria provide one example of such intracellular deposits. They synthesize intracellular magnetic minerals of magnetite (Fe3O4) and/or greigite (Fe3S4) magnetosomes which are generally less than 150 nm and organized into one or multiple chain structures. The magnetosome chain(s) act like a compass needle to facilitate the navigation of magnetotactic bacteria by using the Earth's magnetic field. Due to their ubiquitous distribution in aquatic and sedimentary environments, magnetotactic bacteria play important roles in global iron cycling. Other intracellular mineral phases have been evidenced in bacteria such as As2S3, CaCO3, CdS, Se(0) or various metal phosphates which may play as well a significant role in the geochemical cycle of these elements. However, in contrast to magnetotactic bacteria, the biological and environmental function of these particles remains a matter of debate. In recent years, such intracellularly biomineralizaing bacteria have become an attractive model system for investigating the molecular mechanisms of organelle-like structure formation in prokaryotic cells. The geological significance of intracellular biomineralization is important; spectacular examples are fossil magnetosomes that may significantly contribute to the bulk magnetization of sediments and act as potential archives of paleoenvironmental changes. In addition, intracellular mineral deposits formed by bacteria have potentially versatile applications in biotechnological and biomedical fields. After more than four decades of research, the knowledge on intracellularly biomineralizing bacteria has greatly improved. The aim of this Research Topic is to highlight recent advances in our understanding of intracellular biomineralization by bacteria. Magnetotactic bacteria are a system of choice for that topic but other intracellularly biomineralizing bacteria may bring a unique perspective on that process. Research papers, reviews, perspectives, and opinion papers on (i) the diversity and ecology of intracellularly biomineralizing bacteria, (ii) the molecular mechanisms of intracellular biomineralization, (iii) the chemo- and magneto-taxis behaviors of magnetotactic bacteria, (iv) the involvement of intracellularly biomineralizing bacteria in local or global biogeochemical cycling, (v) the paleoenvironmental reconstructions and paleomagnetic signals based on fossil magnetosomes, (vi) and the applications of intracellular minerals in biomaterial and biotechnology were welcomed.

Biomineralization. --- Magnetotactic bacteria. --- microbial biomineralization --- biosignature --- iron cycling --- magnetotactic bacteria --- magnetosome --- Magnetotaxis --- ancient environment