1,721,002 research outputs found
Dioxirane-Mediated Metal-Free Oxidations of Target Molecules containing unsaturated Carbons
No full textA remarkable example of the progress in metal-free oxidation is the development of oxidation with dioxiranes. The reactivity of these peroxides seems to be due to the tendency for easy electrophilic O-atom transfer to nucleophilic substrates. This has been applied in order to achieve high regio- and stereoselective epoxidation and oxyfunctionalizations of target molecules. This review addresses a new approach consisting of the application of homogeneous and heterogeneous dioxiranes isolated and generate in situ.
This method has shown promise to contribute to resolving a well-recognized general problem in the organic synthesis to achieve efficient synthetic methods that take into account the fundamental principles of green chemistry
Terme e complessi religiosi paleocristiani: il caso di San Giusto,
No full textIl contributo illustra contesto, caratteri planivolumetrici e costruttivi, aspetti funzionali e ruolo insediativo delle piccole terme rinvenute nei pressi del battistero del complesso religioso paleocristiano di San Giusto (Foggia), fatto oggetto di indagini archeologiche alla fine del secolo scorso. In particolare G. Volpe (pp. 217-223) ha riassunto i caratteri dell'insediamento, nel Tardoantico verosimilmente elemento notevole all’interno della proprietà imperiale del saltus Carminianensis e di una diocesi di natura rurale. C. Annese (pp. 223-231) ha passato in rassegna il quadro stratigrafico e i principali tratti costruttivi e architettonici del piccolo balneum, che inducono a una datazione fra fine V e metà VI sec. e una sua identificazione quali terme di uso vescovile. P. Favia (pp. 232-252) interpreta il piccolo bagno del clero come segno della volontà delle diocesi rurale di qualificarsi appieno con attributi propri di una condizione episcopale. L'episodio di S. Giusto si inquadra in una più generale tendenza dell'edilizia religiosa paleocristiana a dotare le basiliche e i palazzi episcopali di terme, pur di ridotta spazialità. Su questa scia vengono esaminate le possibilità di reperire echi e riscontri su ampio spettro dell’impianto daunio, individuando esempi comparabili in Francia meridionale per quanto riguarda soprattutto le dimensioni contenute e l'essenzialità architettonica; per la posizione immediatamente a ridosso della dimora del vescovo l’installazione di San Giusto trova riflesso nuovamente in Francia e nei gruppi architettonici nord africani di V-VI (seppure spesso legati a realtà insediative ben più importanti), ma anche nella Basilica Ursiana di Ravenna e in area ellenico-balcanica (vengono peraltro passati in rassegna anche soluzioni molto diverse nel binomio terme-complessi religiosi). Nell'ultima parte del contributo viene analizzata, in prospettiva le possibilità ma anche le difficoltà archeologica di individuare, nelle aree periferiche e nelle realtà rurali, non urbane, i modi e le figure di fruizione dell’impianti termali ecclesiali, ovvero di individuare o distinguere un uso limitato al vescovo o al clero o immaginare un allargamento a fedeli, pellegrini e bisognosi, in una logica igienico-sanitario oppure purificatoria e devozionale come accade nel peculiare caso di Roma, dove le fonti permettono di supportare un’analisi del genere
Ceramiche della prima e media età imperiale dai riempimenti delle latrine della domus A
No full textReactivity of 1,3-dimethylimidazolium-2-carboxylate with dimethylcarbonate at high temperature: Unexpected 2-ethyl-functionalisation of the imidazolium moiety and employment of the NHC-CO2/dimethylcarbonate system in a base promoted reaction
No full textThe reaction of 1,3-dimethylimidazolium-2-carboxylate and dimethylcarbonate (DMC) at high temperature yielded the new compounds 2-ethyl-1,3-dimethylimidazolium methyl carbonate salt and 2-ethyl-1,3-dimethylimidazolium-4-carboxylate zwitterion which were obtained as a mixture in approximately 4:1 molar ratio. The compounds were also isolated in pure form through alternative synthetic procedures and characterized by ESI-HRMS, 1H, 13C NMR and FTIR spectroscopy. The 1,3-dimethylimidazolium-2-carboxylate/dimethylcarbonate system was employed in the synthesis of 1,7-heptanedioic acid dimethyl ester from cyclohexanone and DMC. The target compound was obtained in 49% yield and 66% selectivity
Stereoselective epoxidation of cyclic dienes and trienes by dioxiranes
No full textEpoxides are essential building blocks in organic chemistry. The epoxidation of unsubstituted cyclic dienes 2, 3, 4 and triene 5 using dimethyldioxirane (1a) and its trifluoro analog 1b methyl(trifluoromethyl)dioxirane has been investigated. The excellent yields obtained (90-98%) are accompanied by outstandingly high diastereoselectivities (90-98%). Interpretation of results based upon the early idea that polar groups can direct the dioxirane attack by dipole-dipole interaction provides a likely rationale, along with a more generalized mechanistic vie
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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