493 research outputs found
Louise Robert : Histoire d'une singularité
No full textGascon analyses how Robert's work draws from the expressive possibilities of painting; the author links this production's quality of lyricism and formal consistency to the Québécois investigation of identity and, more specifically, to the generation of artists born with the 1970s. Biographical notes. 68 bibl. ref.; 2 videogr. ref
Roland Brener, Michel Goulet : Canada XLIII Biennale di Venezia 1988
No full textGascon discusses the relationship existing between sculpture and its architectural shelter, and more specifically between the works of the exhibition and the Canadian pavilion of the Giardini di Castello in Venice. In their reference to industrial fabrication, Brener and Goulet's sculptures are seen to set a schism between functionality and artistic expression; the author explores this phenomenon, seeing it as a political feature. Biographical notes. Bibl. 4 p
Monique Mongeau : L'herbier
No full textHighlighting the Musée de Joliette's role with regards to Montreal art, Gascon introduces the painted works of one of its representatives through two series produced between 1993 and 1997 which focus on motifs drawn from nature that are related to botany. The author examines Mongeau's paintings from a formal perspective, and according to notions of naturalistic expression, observation, and the "effect of reality". Biographical notes. 32 bibl.ref
DSLA 2023: Facing the dangers of data illiteracy
No full textThe Data Science and Literacy Act (DSLA) of 2023 aims to boost data literacy and data science education across the USA. Gregg M. Gascon, Katherine K. Wallman, Sridhar Ravula, Joseph Cappelleri, Julia Lee, Kristian Lum, Chaitra H. Nagaraja, Sudeshna Paul, Dooti Roy and Edward Wu explain why this opportunity demands our attentio
Voyage aux Enfers ou rêve de jeune-fille ? Les révélations curieuses de la Fille dans Le Gascon extravagant
No full text« A trip into Hell or a teen girl’s dream ? Young woman’s curious revelations in The Gascon extravagant » 1637. The demonic possession of the Ursulines of Loudun enters its sensationalist stage. The Jesuit exorcists put their best efforts into fighting disbelief. Jeanne des Anges, the Mother Superior of the convent, who has been freed from Béhémot, a devil supposed to have engraved names on her hand, becomes a walking “miracle”. During the same year the anonymous author of Gascon extravagant decides to publish his « Histoire comique »: a supposedly possessed « Young woman » and an exorcist-« Hermit » become, for the first time, the main characters in a comic fiction. This romanesque « invention » ought not to be taken lightly: in « borrowing » this couple from the realm of demonic possession, The Gascon extravagant « negotiates » a critical space with possession. The representation denounces the dangerous power of the fable of demonic possession by situating it in a fictional medium. We will see how the so-called « Young woman » and the story of her Voyage into Hell partake of this critical representation by way of creating a narrative of rare ambiguity
Agricultural Policy, Crop Failure and the 'Ruriganiza' Famine (1989) in Southern Rwanda: a Prelude to Genocide ?
No full textThe paper analyses the agricultural policy of the Habyarimana regime, which ruled Rwanda from 1973 to 1994. Econometric analysis of rural household survey data is used to investigate the effects of the 1989 crop failure in southern Rwanda on children’s health status. The paper shows that children in southern Rwanda are chronically malnourished, more then in other prefectures of Rwanda. It is shown that the 1989 crop failure developed into famine and the causes of this development are investigated. It turns out that the Habyarimana regime did not respond to early warnings of famine conditions and pretend it did not know what was going on. The relationship between this non-response to famine, agricultural policy in general and the 1994 genocide is demonstrated.agriculture, famine, survey research, Rwanda
Two mid-17th century villancets in Gascon: Orray cat de bius Arnauton and Bartolatje, Mauvisatje
No full textEl present treball mostra l’estudi i la transcripció de dos villancets de la meitat del segle xvii escrits en un dialecte de l’occità, el gascó, un en un subdialecte de l’àrea oriental i l’altre de l’occidental. Cadascuna d’aquestes composicions és obra d’un autor diferent: fra Josep Reduà i Francesc Fadrés. L’estudi també ens mostra la relació de cada autor amb l’àrea geogràfica concreta del subdialecte en què s’escrigueren ambdues composicions.This paper presents the study and transcription of two villancets from the mid-17th century, written in two subdialects of an Occitan dialect, Gascon: an eastern and a western one. Each of these compositions was by a different author: Friar Josep Reduà and Francesc Fadrés. We also discuss the relation of each author with the specific geographical area of the respective subdialects used in the two compositions. 
Neuroplasticity of spinal cord neurons based on piezoelectric stimulation and electrophysiological analysis after stem cell-derived progenitor transplant
No full textRepair strategies in the context of spinal cord injury cover a broad amount of fields. Different approaches have been considered ranging from the chemical, mechanical, pharmacological, material sciences, electrical and chemical engineering sphere. There is much interest in combinational therapies since many approaches yield promising results yet none is beneficial enough in functional terms. There is also a necessity of properly evaluate the improvement these therapies pose from a functional point of view and do it with sufficient resolution to target and invest in strategies with higher potential. This thesis is born with the interest of contributing to the spinal cord injury field at those two levels. On one side, I have developed an injury model and techniques to test the efficacy of a therapy for spinal cord repair as compared to controls. On the other, I have proposed a combinational therapy in the form of a scaffold that combines biomaterials and electrical fields to stimulate regeneration In the first part of this thesis, I have developed an animal model to test effectiveness of treatment by analyzing the electromyography signal of the intercostal muscles. The respiratory system is a good test bench, usually neglected in regeneration studies. I have used a mix of engineering approaches from signal processing to animal physiology analysis to provide the test with enough resolution to identify improvement. Then, I have proved the efficacy of the model by using a stem cell therapy. In the second part of the thesis, I have tested piezoelectric polymers as a useful platform to deliver electrical fields to neurons. I have shown the resulting increase in neuronal growth upon exposure to alternating electrical fields, in concrete, in neuronal branching. These results encourage the use of biocompatible piezoelectric polymers which are very versatile in nature, as a source for combinational therapies. Future studies will translate this in vitro model into an in vivo treatment which will be assessed with the strategy explained in the first part.Ph. D.Includes bibliographical referencesby Maria Nuria Royo Gasco
Une main pleine de jokers, un gabarit riche en grain fin de primitives opaques: le vocalisme « noir » et « gris » du gascon landais
No full textInternational audienceDas Gascogne Landais ist unter Okzitanisten und Romanisten berühmt für den Vokalismus seines "schwarzen Sprechens". In der maritimen Gascogne bedeutet "schwarz sprechen", den Vokalismus der nicht hohen Palatalvokale zu einem einzigen neutralen Timbre zu nivellieren, wie Theobald Lalanne (1949: 20) anhand dieses lokalen Schibboleths zusammenfasst: lë pëlyë dë lë hëmnë k'ës nëgë oder 'das Kleid der Frau ist schwarz' oder 'das Kleidungsstück der Frau ist schwarz'. Ebenfalls laut diesem Autor, der einer der wichtigsten Ermittler des ALG war, für den westlichen Teil der gaskognischen Domäne: "Die hellen Sprechweisen sagen zwar éstelé, estélë, ëstélë 'Stern', aber nur die schwarze Sprechweise sagt ëstëlë (ebd.). Lalanne argumentiert darüber hinaus, dass nicht weniger als 30% des Vokalismus im schwarzen Gascon auf diese Weise "entfärbt" würden. Die Areologie des Phänomens lässt sich als eine relativ neue Innovation des zentralen Seegaskans beschreiben, die auf eine Intensivierung einer Reduktionsregel für die mittleren vorderen Vokale nach der eben erwähnten Reihe éstelé, estélë, ëstélë zurückzuführen ist: Eine Harmonisierung hätte stattgefunden, vom atonischen (insbesondere posttonischen) Bereich zum tonischen (mittlere Position) und dann zum prätonischen Bereich (bestätigt durch den Vokalismus der proklitischen Pronomen, wie in dem oben genannten Syntagma). Die Peripherien, die "heller" sind und nur atonale Vokale reduzieren, wären demnach retinierend (vgl. die Daten von Viaut & Burov 2011 für das Médoc, s. auch Daten von Lartigue 2004). Es würde sich um eine regressive Harmonie von rechts nach links handeln, entsprechend der allgemeinen Theorie gabarischer Interaktionen in den Sprachen der Welt (vgl. Scheer 2015). Oberflächlich betrachtet - an der Oberfläche - haben wir also CVCV-Schablonen voller "Joker": geladen mit Kernen, die wie Schwas (wie //) aussehen, also unterspezifizierte Vokale, oder wie labiopalatale Vokale (wie //), die mehr oder weniger aus Schwas hervorgegangen sind, aber keine sind. Dieses Phänomen der vokalischen "Verfärbung" des "schwarzen Gascogne" und teilweise auch des "hellen Gascogne", das es geolinguistisch umfasst, wurde meist phonetisch mit Hilfe von Schwas notiert, obwohl diese Vokale keineswegs Schwas sind (abgesehen von pronominalen Items oder internen Prätonika, entsprechend der galloromanischen Tendenz, zugegeben). Die Vielfalt der Notationen ist groß und trübt den Weg zu einer typologischen Charakterisierung dieser Sprache wie auch des westlichen Gascogne auf phonologischer Ebene. Dieses Phänomen der Reduktion chromatischer Merkmale, das einer scheinbar redundanten harmonischen Strategie entspringt, muss auch mit anderen Phänomenen korreliert werden, die in einer dialektischen Beziehung zueinander stehen, da sie der Entlassung oder Anreicherung von Merkmalen oder "zusätzlichen" Silbeneinheiten (vgl. Millardet, 1979) zuzuordnen sind. Millardet 1910a), wie z. B. die Prothese eines vorrhotischen Bassvokals (Nordwestgaskon razimétë, rodë, rat, règë, ribèrë usw. vs. Südwest arazimétë, arodë, arat, arègë, aribèrë usw. 'Stachelbeere, Rad, Ratte, Furche, Fluss' usw.). Es handelt sich hier um ein einziges Phänomen: die Einfügung eines {A}-Elements in das Klang- und Chromatisierungsraster, das die Schablone [CV]CVCV[CV] dominiert, das jeweils entweder eine Pharyngalisierung (für den Vokalismus des "schwarzen Gascogne" und der "parlers clairs" mit Atonreduktion, Umgebung) im Herzen und am dexteren Rand des Bereichs CVCV[CV] in Form eines sekundären {@}-Primitivs oder eine prothetische Silbentrennung an seiner ursprünglichen Peripherie ergeben wird. Dieses Phänomen lässt sich also mithilfe einer lokalen Pharyngalisierungsregel beschreiben, die neben der prothetischen Resyllabation auf einer mittleren Ebene des Zyklus der geordneten Regeln für das westliche Gaskon agiert. Seit über einem Jahrhundert haben die phonetischen Notationen der Deskriptoren, einschließlich der ALG, die Daten getrübt und die Interpretation verhindert, die wir hier vorschlagen werden und die mit der phonologischen Typologie auf einer nicht mehr lokalen, sondern globalen Ebene für Sprachen mit pharyngealen Kontrasten übereinstimmt: Unserer Ansicht nach ist V1 in einer Form wie ëstëlë des schwarzen Gascogne, die die Phantasie von Lalanne und den Sprechern so sehr beeindruckt, ein prothetischer Vokal vom Schwa-Typ und damit /, V2 ist ein halbhoher palataler Vokal +RTR (Retracted Tongue Root), den man als /ɘ/ oder sogar als // (leicht grau unterlegtes Feld) beschreiben kann, während die prothetischen Kerne zu einem Phonotyp wie // gehören. Das schwarze Gascon aktiviert also die drei Vokale der Ordnung [-avant, -labial] in einer kontrastierenden Ateritätsbeziehung. Mit anderen Worten, es ändert alles, dass die "undurchsichtige Monotonie" der "Verfärbung" des schwarzen Gaskognisch nicht auf eine Verallgemeinerung eines Schwa oder eines labiopathischen Vokals vom Typ //, "à la française", reduziert wird.Landes Gascon is famous among Occitanists and Romanists for the vocalism of its 'black speech'. 'Parler noir', in maritime Gascony, means levelling the vocalism of the non-high palatal vowels into a single neutral timbre, as Théobald Lalanne (1949: 20) summarizes with the help of this local shibboleth: lë pëlyë dë lë hëmnë k'ës nëgë or 'the woman's dress is black' or 'the woman's garment is black'. Still according to this author, who was one of the main investigators of the ALG, for the western part of the Gascon domain, "the clear languages say éstelé, estélë, ëstélë 'star', but only the black language says ëstëlë (ibidem). Lalanne also argues that no less than 30% of the vocalism would be "decoloured" in Black Gascon. The areology of the phenomenon can be described as a relatively recent innovation in Central Maritime Gascon, arising from an intensification of a rule of reduction of the middle anterior vowels according to the éstelé, estélë, ëstélë series just mentioned: a harmonization would have operated, from the atonic domain (notably posttonic) towards the tonic domain (median position), then pretonic (reinforced by the vocalism of proclitic pronouns, as in the above-mentioned syntagma). The peripheries, which are "clearer" and reduce only atonic vowels, would therefore be retentative (cf. data from Viaut & Burov 2011 for the Médoc, see also data from Lartigue 2004). This would be a regressive harmony from right to left, in accordance with the general theory of gabaritic interactions in world languages (cf. Scheer 2015). In appearance - on the surface - we thus have CVCV templates full of "wildcards": loaded with nuclei that resemble schwas (such as //), thus underspecified vowels, or labiopalatal vowels (such as ) more or less derived from schwas, but which are not. This phenomenon of the vowel "discolouration" of "black Gascon" and, in part, of the "clear Gascon" which encompasses it geolinguistically, has most often been noted phonetically, using schwas, even though these vowels are not schwas at all (apart from pronominal items or internal pretonics, according to the Galloromanian tendency, certainly). The diversity of notations is great, and obscures the way to a typological characterisation of this language as well as of Western Gascon, on the phonological level. This phenomenon of reduction of chromatic features, which is part of an apparently redundant harmonic strategy, must also be correlated with other dialectically related phenomena, as they are related to the redundancy or enrichment of features or "additional" syllabic units (cf. Millardet 1910a), such as the prosthesis of a pre-rhotic low vowel (north-western Gascon razimétë, rodë, rat, règë, ribèrë, etc. vs. south-western arazimétë, arodë, arat, arègë, aribèrë, etc. 'gooseberry, wheel, rat, furrow, river', etc.) There is a single phenomenon here: the insertion of an {A} element into the sonority and chromaticity framework which dominates the [CV]CVCV[CV] template, which will respectively give either a pharyngealization (for the vocalism of 'black Gascon' and 'clear speakers' with reduction of atones, respectively) in the core and in the dexter margin of the CVCV[CV] domain, in the form of a secondary {@} primitive, or else a prosthetic syllabification in its initial periphery. This phenomenon can thus be described by a local pharyngealization rule, acting at an intermediate level of the ordered rule cycle for Western Gascon, in addition to prosthetic resyllabication. For more than a century, the phonetic notations of the descriptors, including the ALG, have opacified the data and prevented the interpretation we propose here, which is consistent with the phonological typology at a global rather than local level, for languages with pharyngeal contrasts: In our view, in a form like ëstëlë of Black Gascon which so captures the imagination of Lalanne and the speakers, V1 is a schwa-like prosthetic vowel, while V2 is a mid-high palatal vowel +RTR (Retracted Tongue Root) which can be described as /ɘ/, or even as // (lightly shaded box), while the prosthetic nuclei belong to a phonotype such as //. Black Gascon thus activates the three vowels of the order [-avant, -labial] in an atypical contrast relationship. In other words, it changes everything, not to reduce the "opaque monotony" of the "fading" of Black Gascon to a generalization of a schwa or a labiopatalate vowel of the type, "à la française". This the prospect, indeed, since this tripartite hypothesis not only allows us to do what phonology is made for (extracting and reconstructing abstract categories of phonetic form beyond the vagaries of phonetic substance and roof-language-induced biases, both graphemically and sociolinguistically), but also to explore a heuristic dimension in general phonology: the systemic texture of fine-contrast inventories, and the role of the [Pharyngeal] feature as well as syllabic aperture in such systems. Before undertaking empirical field surveys, we will propose in this paper a phonemic conceptualization of these three local phonotypes, based on the work of Allières (1961), Lalanne, Lartigue (op. cit.), Millardet (1010a-b, 1918), without forgetting the ALF. We shall see that these surveys are rich in clues but also in aporias, and we shall see once again that it is wrong to think that phonetic notation in the field can or even must do without theorising upstream [Cf. the article by Ch-Y. Morin's article on the importance of vowel reduction in the phonological system of the Auvergne speech of Vinzelles, once described by Albert Dauzat, and the importance of a theory of vowel reduction in Occitan, including for a better description of morphology. Not having a theory upstream means not having truly readable data downstream. Or else they will always be readable in a trivial way, and will only ever reveal, at best, a routine, at worst, a certain doxa, and a lot of shadow on the empirical level. We will therefore try to shed some light beyond the (apparently and only apparently) opaque surface of this 'black Gascon'.Le gascon landais est célèbre chez les occitanistes et les romanistes pour le vocalisme de son « parler noir ». « Parler noir », en Gascogne maritime, c’est niveler le vocalisme des voyelles palatales non hautes en un timbre neutre unique, comme le résume Théobald Lalanne (1949 : 20) à l’aide de ce schibboleth local : lë pëlyë dë lë hëmnë k’ës nëgë ou ‘la robe de la femme est noire’ ou ‘le vêtement de la femme est noir’. Toujours selon cet auteur, qui fut l’un des principaux enquêteurs de l’ALG, pour l’ouest du domaine gascon, « les parlers clairs disent bien éstelé, estélë, ëstélë ‘étoile’, mais seul le parler noir dit ëstëlë (ibidem). Lalanne argue en outre que pas moins de 30% du vocalisme serait ainsi « décoloré » en gascon noir. L’aréologie du phénomène peut se décrire comme une innovation relativement récente du gascon maritime central, relevant d’une intensification d’une règle de réduction des voyelles antérieures moyennes d’après la série éstelé, estélë, ëstélë que nous venons de mentionner : une harmonisation aurait opéré, du domaine atone (notamment posttonique) vers le domaine tonique (position médiane), puis prétonique (conforté par le vocalisme des pronoms proclitiques, comme dans le syntagme supra). Les périphéries, plus « claires », ne réduisant que les voyelles atones, seraient donc rétentrices (cf. les données de Viaut & Burov 2011 pour le Médoc, v. aussi données de Lartigue 2004). Il s’agirait d’une harmonie régressive de droite à gauche, conformément à la théorie générale d’interactions gabaritiques dans les langues du monde (cf. Scheer 2015). En apparence – en surface – on a donc des gabarits CVCV pleins de « jokers » : chargés en noyaux qui ressemblent à des schwas (comme //), donc des voyelles sous-spécifiées, ou à des voyelles labiopalatales (comme ) plus ou moins issues de schwas, mais qui n’en sont pas. Ce phénomène de la « décoloration » vocalique du « gascon noir » et, en partie, du « gascon clair » qui l’englobe sur le plan géolinguistique, a le plus souvent été noté de manière phonétique, à l’aide de schwas, alors que ces voyelles ne sont aucunement des schwas (hormis les items pronominaux ou les prétoniques internes, selon la tendance galloromane, certes). La diversité des notations est grande, et opacifie la voie vers une caractérisation typologique de ce parler aussi bien que du gascon occidental, sur le plan phonologique. Il faut aussi corréler ce phénomène de réduction de traits chromatiques, qui relève d’une stratégie harmonique en apparence redondante, avec d’autres phénomènes en relation dialectique, car relevant du licenciement ou enrichissement en traits ou en unités syllabiques « additionnelles » (cf. Millardet 1910a), comme par exemple la prothèse d’une voyelle basse pré-rhotique (nord-ouest gascon razimétë, rodë, rat, règë, ribèrë, etc. vs sud-ouest arazimétë, arodë, arat, arègë, aribèrë, etc. ‘groseille, roue, rat, sillon, rivière’, etc.). Il y a là un seul et unique phénomène : l’insertion d’un élément {A} dans la trame de sonorité et de chromatisme qui domine le gabarit [CV]CVCV[CV], qui va donner respectivement soit une pharyngalisation (pour le vocalisme du « gascon noir » et des « parlers clairs » à réduction des atones, alentours) au cœur et en marge dextre du domaine CVCV[CV], sous forme de primitive {@} secondaire, soit une syllabation prothétique à sa périphérie initiale. Ce phénomène peut donc se décrire à l’aide d’une règle locale de pharyngalisation, agissant à un niveau intermédiaire du cycle des règles ordonnées pour le gascon occidental, outre la resyllabation prothétique. Depuis plus d’un siècle, les notations phonétiques des descripteurs, y compris de l’ALG, ont opacifié les données et ont empêché l’interprétation que nous proposerons ici, qui concorde avec la typologie phonologique à un niveau non plus local mais global, pour les langues à contrastes pharyngaux : selon nous, dans une forme comme ëstëlë du gascon noir qui frappe tant l’imagination de Lalanne et des locuteurs, V1 est une voyelle prothétique de type schwa, tandis que V2 est une voyelle palatale mi-haute +RTR (Retracted Tongue Root) qu’on peut décrire comme /ɘ/, voire comme // (case en léger grisé), tandis que les noyaux prothétiques relèvent d’un phonotype tel que //. Le gascon noir active donc les trois voyelles de l’ordre [-avant, -labial] en relation de contraste d’atérité. Autrement dit, cela change tout, que de ne pas réduire la « monotonie opaque » de la « décoloration » du gascon noir à une généralisation d’un schwa ou d’une voyelle labiopatalate de type , « à la française ». Cela change tout, parce que cette hypothèse tripartite permet non seulement de faire ce pour quoi la phonologie est faite (extraire et reconstruire les catégories abstraites de la forme phonémique au-delà des aléas de la substance phonétique et des biais induits par les langues-toit, sur le plan graphémique et sociolinguistique), mais aussi d’explorer une dimension heuristique en phonologie générale : la texture systémique des inventaires à contrastes fins, et le rôle du trait [Pharyngal] ainsi que de l’aperture syllabique dans ce type de systèmes. Avant d’entreprendre des relevés empiriques sur le terrain, nous proposerons dans cette communication une conceptualisation phonémique de ces trois phonotypes locaux, en nous basant sur les travaux d’Allières (1961), Lalanne, Lartigue (op. cit.), Millardet (1010a-b, 1918), sans oublier l’ALF. Nous verrons que ces relevés sont riches en indices mais aussi en apories, et on verra une fois de plus se vérifier qu’il est faux de penser qu’une notation phonétique sur le terrain peut ou même doit se passer d’une théorisation en amont[ Cf. l’article de Ch-Y. Morin sur l’importance de la réduction vocalique dans le système phonologique du parler auvergnat de Vinzelles, jadis décrit par Albert Dauzat, et de l’importance d’une théorie de la réduction vocalique en occitan y compris pour mieux décrire la morphologie. Ne pas avoir de théorie en amont revient à ne pas avoir de données vraiment lisibles en aval. Ou bien elles seront toujours lisibles de manière triviale, et ne feront jamais que révéler, au mieux une routine, au pire, une certaine doxa, et beaucoup d’ombre sur le plan empirique. Nous tenterons donc d’apporter un peu de lumières au-delà de la surface (en apparence et uniquement en apparence) opaque de ce « gascon noir ».Lo gascon landés qu'ei celèbre en çò deus occitanistas e los romanistas entau vocalisme de la soa « parlar negre ». « Parlar negre », en Gasconha maritima, qu'ei nivelar lo vocalisme de las vocalas palataus non hautas en un timbre neutre unic, com ac resumeish Théobald Lalanne (1949 : 20) dab l'ajuda d'aqueth schibboleth locau : lë pëlyë dë lë hëmnë k’ës nëgë o ‘la rauba de la hemna qu'ei negra’ o ‘lo vestit de la hemna que ’ei negre. Tostemps segon aqueth autor, qui estó l'un deus principaus enquestaires de l'ALG, entà l'oèst deu maine gascon, « los parlars clars que disen plan éstelé, estélë, ëstélë ‘estela’, mes sol lo parlar negre que digó ëstëlë (ibidem). Lalanne qu'argüeish en mei que pas mensh de 30% deu vocalisme que seré atau « descolorat » en gascon negre. L'aréologie deu fenomèn que's pòt descríver com ua innovacion relativament recenta deu gascon maritime centrau, relhevant d'ua intensificacion d'ua règla de reduccion de las vocalas anterioras mejanas segon la seria éstelé, estélë, ëstélë que vienem de mencionar : ua armonizacion qu'auré operat, deu maine atòne (sustot posttonique) cap au maine tonic (posicion mediana), puish prétonique (confortat peu vocalisme deus pronoms proclitics, com dens lo sintagma supra). Las periferias, mei « claras », ne redusint pas que las vocalas atònas, que serén donc rétentrices (cf. las dadas de Viaut & Burov 2011 entau Medòc, v. tanben balhadas de L'Artiga 2004). Que s'agiré d'ua armonia regressiva de dreta a esquèrra, confòrmament a la teoria generau d'interaccions gabaritiques dens las lengas deu monde (cf. Scheer 2015). En aparéncia – en susfàcia – que s'a donc gabarits CVCV plens de « joquèrs » : cargats en nuclèus qui semblan a schwas, donc vocalas devath-especificadas, o a vocalas labiopalatales (com ) mei o mensh gessidas de schwas, mes qui'n son pas. Aqueth fenomèn de la « descoloracion » vocalica deu « gascon negre » e, en partida, deu « gascon clar » qui l'englòba suu plan géolinguistique, qu'a lo mei sovent estat notat de faiçon fonetica, dab l'ajuda de schwas, mentre qu'aqueras vocalas son pas briga schwas (lhevat las items pronominaus o las prétoniques intèrnas, segon la tendéncia galloromane, cèrtas). La diversitat de las notacions qu'ei grana, e opacifie la via cap a ua caracterizacion tipologica de çò parlar tanben maugrat que gascon occidentau, suu plan fonologic. Que cau tanben corréler aqueth fenomèn de reduccion de trèits cromatics, qui relhèva d'ua estrategia armonica en aparéncia redondanta, dab autes fenomèns en relacion dialectica, pr'amor que relhevant deu licenciament o enriquiment en trèits o en unitats sillabicas « addicionaus » (cf. Millardet 1910), com per exemple la protèsi d'ua vocala baisha pre-rhotica (nòrd-oèst gascon razimétë, rodë, arrat, règë, ribèrë, etc. vs sud-oèst arazimétë, arodë, arat, arègë, aribèrë, etc. ‘colindron, ròda, arrat, rega, arriu’, etc.). Qu'i a aquí un sol e unic fenomèn : l'insercion d'un element {A} dens la trama de sonoritat e de cromatisme qui domina lo gabarit [CV]CVCV[CV], qui va balhar respectivament sia ua pharyngalisation (entau vocalisme deu « gascon negre » e deus « parlars clars » a reduccion deus atònes, entorns) au còr e en marge dextre deu maine CVCV[CV], devath fòrma de primitiva {@} segondària, sia ua sillabacion protetica a la soa periferia iniciau. Aqueth fenomèn que pòt donc se descríver dab l'ajuda d'ua règla locau de pharyngalisation, agint a un nivèu intermediari deu cicle de las règlas ordenadas entau gascon occidentau, otra la resyllabation protetica. Despuish mei d'un sègle, las notacions foneticas de las descripteurs, dont de l'ALG, qu'an opacifié las dadas e qu'an empachat l'interpretacion qui prepausaram ací, qui concòrda dab la tipologia fonologica a un nivèu tanpòc locau mes globau, entà las lengas a contrastes faringaus : segon nosauts, dens ua fòrma com ëstëlë deu gascon negre qui frapa tant l'imaginacion de Lalanne e deus locutors, V1 qu'ei ua vocala protetica de tipe schwa, V2 qu'ei ua vocala palatau mi-hauta +RTR (Retracted Tongue Root) qui's pòt descríver com /ɘ/. Lo gascon negre qu'activa donc las tres vocalas de l'ordi [-abans, -labiau] en relacion de contraste d'atérité. Autament dit, aquò que càmbia tot, qu
Metal-Organic Frameworks for solar energy utilization
No full textThe research strategy followed in this work was inspired by natural photosynthesis that, for simplicity, can be divided into three principal steps: (i) efficient light absorption at wavelengths abundant in the solar light; (ii) long-lived charge separation achieved by funnelling of the photogenerated electrons away from the light-absorbing antenna; (iii) chemical reaction taking place at the specific catalytic sites. The idea of the present research was to mimic the key-principles of photosynthesis and implement them in Metal-Organic Frameworks. The first principle is covered in Chapter 4 where the light absorption properties of a Ti-based framework were synthetically tuned as to allow for lowering the excitation energy and sensitizing the MOF to a larger fraction of the solar spectrum. Chapters 2 and 3 investigate the photoexcitation processes in MOFs with the aim of prolonging the lifetime of photoexcited states similarly to (ii). Finally, in Chapter 5 additional catalytic sites (iii) were introduced in NH2-MIL-125(Ti) improving the catalytic activity by one order of magnitude. Chapter 1 introduces Metal-Organic Frameworks (MOFs) as potential photocatalysts and their characteristics. At first, general synthetic strategies of improving photocatalytic activity are discussed and a brief historical overview of the TiO2-based catalysts development is given followed by recent advances in the field. Further, the pioneering examples of using MOFs as photocatalysts are reviewed. The development of MOF-based photocatalysts is compared against more common photocatalysts such as TiO2. Some of the strategies such as sensitization towards a desired wavelength and introduction of additional catalytic sites are similar in both cases. At the same time MOFs are characterized by the microporous and well-defined structure, excellent tuneability and the lack of photoconductivity. All these aspects have strong implications for the synthetic strategies of the catalyst development. In this chapter three different roles of MOFs are discussed: a) MOFs as mere containers for photocatalytically active species; b) MOFs as photocatalysts both absorbing light and carrying out catalytic reactions; c) MOF-based composites where the frameworks are multifunctional, they absorb light and carry additional catalytic sites. Chapter 2. Here fundamentals of photoexcitation in NH2-MIL-125(Ti) are investigated with the help of ultrafast spectroscopy. MIL-125(Ti)-type frameworks are known to undergo ligand-to-metal charge transfer (LMCT) yielding Ti3+ and the positively charged organic-defined counterparts. UV-pump Visible-probe spectroscopy has shown that the excited states of NH2-MIL-125(Ti) possess a substantially longer lifetime as compared to the amine-free analogous MOF, MIL-125(Ti). Moreover, the difference in spectral signatures of the excited MIL-125(Ti) and NH2-MIL-125(Ti) was documented and associated to the difference in the organic-defined positively charged holes. The assignment of the transient spectral features of NH2-MIL-125(Ti) was carried out with the help of spectroelectrochemistry. Vis-pump IR-probe spectroscopy demonstrated that the photogenerated holes within NH2-MIL-125(Ti) are likely localized on the NH2-group of aminoterephthalates as the N-H stretch vibrations are heavily involved in the photoexcitation process. Kinetics of the photogenerated charge carriers in different solvents is described: in contrast to what was expected we found that the lifetimes of the excited states do not change depending on the solvent polarity. Chapter 3. In this chapter the role of d0 metal ion constituting frameworks of NH2-MIL-125 and NH2-UiO-66 is unravelled. In their works Walsh et al. have shown for the case of the MIL-125(Ti) series MOFs that the highest occupied crystal orbital (HOCO) is localized at the organic linker whereas the lowest unoccupied crystal orbital (LUCO) localizes at the inorganic secondary building unit (SBU), titanium oxocluster. Thus the HOCO-LUCO optical gap can be tuned by introducing various substituents into the aromatic system of the linker for the cost of modifying the oxidative power of the resulting photocatalyst. In this chapter the target reaction was hydrogen evolution. In this case, the reductive power of a photocatalyst is of crucial importance. The main hypothesis was that by changing the metal in the same group from Ti to Zr or Hf one should be able to tune this reductive power for the frameworks bearing the same organic linker and a similar topology. However, this is only true if LMCT operates in all MOFs considered. With the help of DFT it was found that the LUCO of NH2-MIL-125(Ti) is localized at the titanium oxocluster whereas the ones of NH2-UiO-66(Zr/Hf) are localized at the organic linker. The same conclusion was confirmed by EPR. This LMCT of NH2-MIL-125(Ti) possesses a substantially longer lifetime compared to the purely organic-based transitions found in the UiOs as revealed by transient absorption spectroscopy. This in turn results in a superior performance in photocatalytic H2 evolution in the case of Ti-based MOF. The positive role of structural defects in H2 evolution catalysed by the UiOs, although modest, was also documented. Chapter 4 introduces a framework with an extended conjugated aromatic system of the linker derived from NH2-MIL-125(Ti). The NH2-containing parent MOF was post-functionalized with dye-like molecular fragments resembling a well-known organic dye, methyl red. This was done by following a traditional synthetic pathway of obtaining organic dyes through the diazotization reaction. At the first stage the NH2-groups of NH2-MIL-125(Ti) react with nitrosonium ions, NO+, generated in situ by the HCl/NaNO2 pair while the second step is the reaction of the obtained N?N+-MIL-125(Ti) with diethylaniline. The resulting MOF absorbs a larger fraction of visible light extending to ca. 620 nm and thus has a superior performance in photocatalytic oxidation of benzyl alcohol. Furthermore, the photoconductance of MIL-125(Ti) was assessed by time-resolved microwave conductivity (TRMC). The experiments revealed that the material demonstrates very low levels of photoconductance that are temperature dependent. This type of behaviour is characteristic of the temperature-activated hopping as a type of charge carrier transport and is in contrast to the conductance of semiconductors that hardly changes with temperature. Based on these results it was recovered that MIL-125(Ti) and possibly many other MOFs should not be seen as true semiconductors but rather as arrays of coordination complexes arranged in a crystalline lattice. Chapter 5 illustrates an example of Active Site Engineering in Metal-Organic Frameworks. A well-known electrocatalyst, cobaloxime was encapsulated within the cavities of NH2-MIL-125(Ti). The direct sorption of the molecular complex into the pores of MOF did not proceed likely due to the size-selectivity of the pore windows. Therefore, a two-step synthetic strategy was developed where at the first stage the pores of the MOF were loaded with a flexible organic ligand while at the second CoBr2 was added under oxidative conditions. The organic ligand complexates with cobalt ions in the pores of NH2-MIL-125(Ti) forming a cobaloxime bearing Co(III) encapsulated the pores. The chapter contains an extensive characterization of the obtained composite and a discussion of possible differences between the molecular cobaloxime in solution vs. the one encapsulated in the MOF. The obtained Co@MOF catalyst evolves hydrogen at a rate 20 times greater than the one of the bare MOF. The external quantum efficiency for the composite was found to be 0.5%. This is a rather modest number if compared against the state of the art semiconductor-based systems. However, it should be emphasized that this catalyst outperforms the majority of reported MOF-based photocatalysts as explained in Chapter 5. Moreover, the composite purely consists of abundant elements (Ti, Co, C, O, N, Br, H) and, from that perspective, fulfils the global scale up requirements. Cobaloximes typically act as excellent catalytic sites yet they are not able to undergo charge separation upon illumination and require an external source of electrons. The electrons can be supplied by electrodes as well as by excited organic dye molecules. In this work with the help of EPR it was found that the MOF acts as a photosensitizer absorbing photons and injecting electrons in the cobalt complex. At the same time no Ti3+ was detected in irradiated Co@MOF composite in contrast to what was found in the bare NH2-MIL-125(Ti). Instead, cobalt reduction from Co3+ to Co2+ was detected. This suggests that the electron injection from the photoexcited MOF is fast while the resting state of the Co@MOF composite is Co(II). However, the turn-over frequency of the composite is still rather moderate and a more detailed investigation of the mechanism is needed to rationalize this performance. This is an elegant example of a multifunctional catalytic system for photocatalytic generation of hydrogen by water splitting, based on the abundant element Co.Chemical EngineeringApplied Science
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