323 research outputs found
Mixing the Immiscible: Improvisation within Fixed-Media Composition
No full textThis paper will explore ways in which mastered improvisation practice, with the studio as an instrument, is a proposed avenue to bridge the historical dichotomy between what Ted Gioia describe as ‘the aesthetics of perfection’ and ‘the aesthetics of imperfection’. It is proposed as a way to re-embody fixed music, as experimented by the author through the composition of his last fixed-media work. This will be put in the context of a wider trend observed amongst the current emerging generation of composers interested in the aesthesics of the work, by opposition to the previous generations that placed the value of the work in its poietics. The vital and primal importance of practice outcome as practice-based research’s main document will also be advocated for, as these trends are happening in the laboratory of live music
Nature, ecology and chemistry: An unusual combination for a new green catalysis, ecocatalysis
No full textInternational audienceDespite the enforcement of European regulations, the dissemination of metal trace elements in nature is evolving, while the depletion of mineral resources is alarming. The aim of ecocatalysis is the implementation of breakthrough innovation and crossdisciplinary research in ecological restoration, organic chemistry and green catalysis to overcome this paradox. Ecocatalysis focuses on the ecological rehabilitation of mining sites by phytoextraction, treatment of industrial effluents by remedial phytotechnology, named rhizofiltration. Based on the ability of specific plants to concentrate metals, we address the transformation of plant-derived transition metals to green catalysts. The structure, activity, selectivity and recyclability of ecocatalysts are showcased in selected reactions, such as oxidations, reductions and coupling reactions.The concept of ecocatalysis provides catalytic and ecological tools for tomorrow's chemistry, based on the recycling of primary and strategic metals to create scientific and economical values. It offers pioneering solutions to initiate an unprecedented program in green catalysis
Inside Back Cover: A Simple Synthesis of Triangular All-Metal Aromatics Allowing Access to Isolobal All-Metal Heteroaromatics (Chem. Eur. J. 35/2015)
No full textThe famous dream of the ouroboros, the symbol of the circle, which inspired Kekulè’s structure of benzene leading to the concept of aromatic chemistry, can also be applied to metals. Noble metals can be assembled in molecules with an equilateral metal core. This regular geometry remains untouched even if mixing different atoms, as a result of cyclic electron delocalization, leading to all-metal aromatics and all-metal heteroaromatics. More details can be found in the Communication by G. Maestri et al. on page 12271 f
All-Metal Aromatic Cationic Palladium Triangles Can Mimic Aromatic Donor Ligands towards Lewis Acidic Cations
No full textWe present that cationic rings could act as donor ligands thanks to suitably delocalized metal-metal bonds. This could grant to parent complexes the peculiar properties of aromatic rings crafted with main group elements. We assembled Pd nuclei into equilateral mono-cationic triangles with unhindered faces. Like their main-group element counterparts and despite their positive charge, these noble-metal rings form stable bonding interactions with other cations, as positively charged silver atoms, delivering the corresponding tetranuclear dicationic complexes. Through a mix of modeling and experimental techniques we propose that this bonding mode is an original coordination-like one rather than a 4-centres-2-electrons bond, which were already observed in three dimensional aromatics. Present results thus opens the way to the use of suitable metal rings as ligands for coordination chemistry and catalysi
Voie d'accès aux benzophenanthridines naturelles et la chimie des composés métallo-aromatiques stables
No full textRecent developments on dual palladium/norbornene catalytic reactions led to one-pot synthesis of complexes polyheterocyclic molecules. By extension of this reaction, the coupling of aryl triflates and bromobenzylamines permitted us to synthesize natural benzophenanthridine. In parallel, a new family of triangular palladium complexes has been isolated in our research group. These 44 valence electrons complexes possessing a positive charge delocalized on the trimetallic core were the first stable compounds which presented δ-type aromaticity. After optimization of a new synthetic route, we could be able to isolate platinum analogues and also heterometallic clusters which interestingly had the same asymmetric unit than their homonuclear peers. Despite the unavoidable charge repulsion, the Lewis basic character revealed to be strong enough to bind other cationic species. Indeed, we reached to synthesize tetrahedral [M”(M₃)(Ln)]²⁺ complexes. In another side, we wondered if the stability and special properties of [Pd₃]⁺ clusters could confer to it some catalytic activities. Our studies were focused on semi-reduction reactions of alkynes. After optimization process, the catalyst [Pd₃(SMe)₃{P(C₇H)₃)₃}]⁺ showed results beyond our greatest expectations. Indeed, this cluster selectively produced thermodynamically less stable Z-alkene without traces of over-reduced compound. Total chemioselectivity towards alkynes was proved by the reaction on several molecules bearing functional groups which are sensitive to hydrogenation conditions.Depuis plusieurs décennies, la chimie du palladium a connu un véritable essor. Afin de de continuer dans cette optique, plusieurs axes de recherche ont été investigués dans le cadre de cette thèse. Grâce aux récents développements de la catalyse duale palladium/norbornène, la réaction de couplage entre des triflates aryliques et des partenaires bromobenzylamines nous a permis d’accéder à des motifs benzophénanthridines naturels. En parallèle, une nouvelle famille de complexes triangulaires de palladium a été isolée dans notre groupe. Cette espèce arborant 44 électrons de valence et une charge positive délocalisée sur son cœur tri-métallique, est la première molécule stable qui présente un caractère métallo-aromatique de type δ. Après l’optimisation d’une nouvelle voie de synthèse, nous avons pu accéder à des analogues de platine mais aussi à des composés hétéro-métalliques possédant des unités asymétriques similaires. Le caractère base de Lewis de ces complexes ont permis l’isolation de composés tétraédriques de type [M”(M₃)(Ln)]²⁺ malgré la répulsion des charges positives. Ces espèces triangulaires aromatiques ont aussi prouvé leur habileté en tant que catalyseur pour la réaction de semi-hydrogénation d’alcynes. En effet, ce complexe transforme chimiosélectivement les alcynes en alcènes de configuration Z sans présence de produit doublement réduit
Catalytic Semireduction of Internal Alkynes with All-Metal Aromatic Complexes
No full textA simple catalytic method involving all-metal aromatic frameworks as precatalysts ensures an efficient route to (Z)-alkenes. Aromatic triangular palladium clusters were used to reduce internal alkynes without any trace of the formation of alkane side products. These trinuclear complexes provide a catalytic system that parallels the activity and selectivity of their best mononuclear peers, and the catalyst likely operates through complementary mechanism
Boosting catalyst activity in cis-selective semi-reduction of internal alkynes by tailoring the assembly of all-metal aromatic tri-palladium complexes
No full textInternational audienceHighly symmetric [Pd3]+ clusters that present delocalized metal–metal bonds can catalyse the selective semi-reduction of internal alkynes to cis-alkenes. Studies on factors governing the formation of all-metal aromatics enabled the design of an optimised catalytic system that delivers cis-alkenes with almost complete selectivity on a gram scale with very low catalyst loadings (0.03 mol%)
Lagging Behind: Productivity and the Good Fortune of Canadian Provinces
No full textThe good fortune of bountiful natural resources is not enough to ensure rising incomes for Canadians in the long term. Growing labour productivity is the most important determinant of future economic welfare and on that measure, Canada is falling behind its major trading partners. Increasing labour productivity does not mean workers working harder for less money, a common canard. It means more investment in one of three factors: 1) human capital (education or other learning); 2) physical capital (plants or other infrastructure); or 3) technology. Just as an individual’s income is in the long-run dependent on how productive he or she is, so too is that of the nation as a whole. If Canada fails to improve its productivity, the incomes of both individual Canadians and the nation as a whole will fall behind those of other developed countries.Economic Growth and innovation, Canadian provinces, labour productivity
A Simple Synthesis of Triangular All-Metal Aromatics Allowing Access to Isolobal All-Metal Heteroaromatics
No full textInternational audienceA simple synthetic method allows the one-pot assembly of C-3-symmetric, 44-core-valence-electron, triangular Pd or Pt clusters and their heterobimetallic mixed Pd/Pt analogues. These mixed metal complexes are the first examples of stable triangular all-metal heteroaromatics. In contrast to traditional heteroaromatic molecules formed combining main-group elements, they actually retain structural and electronic features of their homonuclear analogues
Histoire d'une marque
No full textGeschichte eines Warenzeichens : der Vogesen-Sirup Cazé.
Der Verfasser schildert zuerst den Ursprung dieses Erzeugnisses, am Anfang des Jahrhunderts, durch Alexandre Cazé (1871-1942), Apotheker in Saint-Quentin, erfunden, welcher es verstand dessen Verkauf durch Zeitungsinseraten schnell zu steigern. Das Unternehmen welches sich 1911 in Paris niederliess, und von 1929 an durch die Mitarbeit von Michel Cazé verstärckt wurde, setzte seine Ausbreitung fort bis es 1977 durch die Beecham Gesellschaft gekauft wurde. Der Verfasser erklärt durch Text und Bild die Ausweitung und Mannigfaltigkeit der Werbung welche den Erfolg unterhielt. Er schildert besonders den Werdegang des berühmten Plakats «Wie das Wasser das Feuer löscht, so löscht der Vogesen-Sirup den Husten».History of a trade-mark : Sirop des Vosges Cazé.
The author first traces the origins of the product, created at the beginning of the century by Alexandre Cazé (1871-1942), a pharmacist from Saint-Quentin, who knew how to rapidly develop sales by means of advertisements in newspapers. Established in Paris in 1911 and strengthened after 1929 by the cooperation of Michel Cazé, the enterprise continued to expand until it was acquired in 1977 by the Beecham company. The author reveals via text and image the extent and the diversity of the advertising which underscored its success. He retraces in particular the genesis of the well-known poster « As water extinguishes fire, Sirop des Vosges extinguishes coughs ».Cazé Pierre. Histoire d'une marque. In: Revue d'histoire de la pharmacie, 80ᵉ année, n°293, 1992. pp. 140-168
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