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Ce manuel vise à sensibiliser les acteurs du développement et du monde professionnel aux enjeux de la conversion à l'AB, en articulant les problèmes auxquels se trouvent concrètement confrontés les agriculteurs, et les perspectives beaucoup plus larges qu'ouvre la conversion à l'AB pour le monde agricole et nos systèmes agroalimentaires. Il s'agit, en prenant l'AB comme « prototype », d'appuyer les professionnels en charge du changement et de transitions vers des agricultures alternatives signifiantes (production intégrée, agriculture de conservation, agroécologie.). L'ouvrage propose des arguments qui touchent concrètement les agriculteurs que ces professionnels trouvent en face d'eux (comment se tourner vers le bio ? quelles sont les étapes ? qu'est-ce que cela change aux cultures ? aux conduites ? à la commercialisation ?.), et des arguments plus larges, liés au devenir de l'agriculture et aux exigences de durabilité. L'objectif est aussi de présenter l'AB sous un regard critique, en rendant compte des principaux débats qu'elle suscite, pour contribuer à outiller la réflexion des professionnels sur leurs pratiques (agricoles, de conseil, de formation).
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Organic chemistry --- organic chemistry --- organische chemie --- nomenclatuur
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As more and more people seek locally grown food, independent family owned and operated agriculture has expanded, creating local networks for selling and buying produce, meat, and dairy products and reviving local agricultural economies throughout the United States. Pamela Walker and Linda Walsh portray eleven farming and ranch families who are part of this food revival in Texas..
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Aromaticity is a notion that appeared in the mid-nineteenth century to differentiate between unsaturated hydrocarbons and formally unsaturated benzene [1-3]. At the end of the nineteenth century it seemed that cyclicity was a necessary condition for differentiation between the two, but at the beginning of the twentieth century it turned out that the above assumption was not correct because cyclooctatetraene exhibited typical properties known for polyenes [4]. The essential property of b- zene-like compounds, often identified with aromatic compounds, was low react- ity. Hence thermodynamic stability was defined as resonance energy [5, 6] and was the first quantitative measure of aromaticity. Many theoretical approaches were proposed later to estimate this quantity, and now the criterion is often considered to be the most fundamental [7]. Almost at the same time, magnetic susceptibility was used to describe aromaticity [8, 9]. Consequently, many concepts based on mag- tism were developed, probably the most effective in assessment of aromaticity being nucleus independent chemical shift (NICS) [10] or Fowler's maps of ring currents [11]. The criterion served Schleyer as a basis for a definition of aromat- ity: Compounds which exhibit significantly exalted diamagnetic susceptibility are aromatic. Cyclic delocalisation may also result in bond length equalization, abn- mal chemical shifts and magnetic anisotropies, as well as chemical and physical properties which reflect energetic stabilisation [12].
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