Dissertations / Theses on the topic 'Tripletti'

Durante il dottorato ho investigato il processo fotofisico di "upconversion" assistito da annichilazione tripletto-tripletto (TTA-UC) tramite studi di spettroscopia in sistemi profondamente differenti gli uni dagli altri. In TTA-UC radiazione ad alta energia è emessa dalla ricombinazione radiativa dello stato di singoletto eccitato di una molecola emettitore, popolato precedentemente dall'annichilazione dei tripletti di due emettitori. Un sensibilizzatore immagazzina la luce incidente a bassa energia e trasferisce l'eccitazione agli emettitori tramite trasferimento di energia alla Dexter. Poiché il suo funzionamento si basa su tripletti mestastabili, TTA-UC può essere altamente efficiente anche in condizioni di luce non coerente e a bassa energia. Come tale, è particolarmente adatto per dispositivi che sfruttano l'energia solare poiché è in grado di aumentarne l'efficienza di conversione limitando le perdite per trasmissione. Mi sono concentrata su due problemi importanti che tuttora limitano l'impiego di materiali che attuano TTA-UC (upconverters), ossia la limitata capacità di immagazzinare energia dei comuni sensibilizzatori organici e le scarse prestazioni di TTA-UC in upconverters a stato solido, i quali sono più adatti per applicazioni tecnologiche rispetto a sistemi liquidi. Per risolvere il primo problema ho investigato sensibilizzatori ibridi, composti da nanostrutture a semiconduttore decorate con molecole organiche, con ampio assorbimento. Nanocristalli di CdSe drogati con cationi d'oro e decorati con acido antracenico carbossilico si sono dimostrati essere sensibilizzatori ibridi efficienti ed innovativi. Il drogante introduce nel gap energetico dei nanocristalli livelli localizzati su cui le lacune si localizzano sulla scala dei picosecondi, più velocemente dell'estrazione di lacune sul livello HOMO dei leganti. Con tale strategia ho raggiunto l'efficienza di UC del 12%, record per sistemi ibridi. Ho poi mostrato come le proprietà superficiali e fotofisiche di nanoplatelets di CdSe le rendano ottimali candidati in sensibilizzatori ibridi. Ho mostrato che il ricoprimento delle superfici non è omogeneo, ma procede ad isole e l'interazione di "π- π stacking" porta alla formazione di aggregati sulle superfici delle nanoplatelets, con il risultato di ridurre l'energia dei tripletti dei leganti con profonde ripercussioni sulle prestazioni di TTA-UC e sulla scelta della specie emettitrice. Riguardo al secondo problema, ho studiato due upconverters a stato solido, polimeri vetrosi nanostrutturati che mostrano proprietà macroscopiche simili ma realizzati con tecniche differenti. Essi presentano domini liquidi di dimensione inferiore a 50 nm dove le specie che attuano TTA-UC si accumulano, racchiuse in una matrice rigida polimerica che fornisce protezione da ossigeno e qualità ottica eccellenti e stabilità a lungo termine. Il confinamento molecolare permette di aumentare la densità locale di eccitoni aumentando l'efficienza di UC a basse potenze grazie alle ridotte distanze intermolecolari e all'attivazione del regime di TTA-UC confinato.Ho inoltre studiato un nuovo emettitore derivato da perilene, realizzato con lo scopo di aumentarne l'efficienza di fluorescenza. Grazie a questo emettitore ho raggiunto l'efficienza record di UC di 42%, dovuta proprio alla struttura molecolare dell'emettitore che permette di limitare la formazione di aggregati, garantendo un'eccellente efficienza di generazione di singoletti tramite TTA. Infine, ho presentato una prospettiva riguardo alle prestazioni che possono essere raggiunte combinando le due tematiche trattate, ossia inserendo sensibilizzatori ad ampio assorbimento in polimeri nanostrutturati. Trovando il giusto compromesso tra taglia dei domini liquidi e distribuzione dell'energia di eccitazione si raggiungerebbe la massima efficienza di UC a potenze minori dell'irradianza solare, promuovendo lo sviluppo di upconverters a stato solido per tecnologie a energia solare
In my PhD project, I investigated the photophysical process of photon upconversion assisted by triplet-triplet annihilation (sTTA-UC) through spectroscopy studies in a variety of systems, profoundly different on many levels. In sTTA-UC high energy radiation is emitted from the fluorescent recombination of the excited singlet of an emitter molecule, previously populated via annihilation of the metastable triplet states of two emitters. This is a sensitized process since a sensitizer is necessary to harvest the low energy incident light and to transfer the stored energy to the emitters via Dexter energy transfer. Because its functioning relies on long-lived metastable triplets, this process can be highly efficient also under low power, noncoherent light. As such, sTTA-UC is particularly suited for solar applications as it can increase the conversion efficiency by reducing transmission losses. During my studies, I focused on addressing two crucial issues that still limit the application of upconverters in solar technologies, i.e. the limited storage ability of common organic sensitizers and the poor sTTA-UC performance in solid-state upconverters, which are intrinsically better suited than liquid solutions for technological applications. To solve the first problem, I investigated hybrid sensitizers, composed of semiconductor nanostructures decorated with conjugated organic ligands characterized by broadband absorption. CdSe nanocrystals (NCs) doped with gold cations and decorated with 9-anthracene carboxylic acid demonstrated to be efficient innovative broadband hybrid sensitizers. The doping strategy inserts into the NCs energy gap localized hole-accepting states where the holes localize on the picosecond timescale, outpacing hole transfer to the ligand HOMO. With this strategy, I achieved the UC efficiency of 12%, the record performance obtained so far for hybrid upconverters. I then discussed how the CdSe nanoplatelets surface and photophysical properties make them potential optimal light harvesters. My studies on the nanoplatelets-to-ligands energy transfer dependency on the surface ligand density revealed that the surface coverage is not homogeneous but proceeds in an island-like way promoted by π- π stacking and results in the formation of ligands aggregates on the nanoplatelets surfaces, which causes a redshift of the ligand triplet energy with critical repercussions on the sTTA-UC performance and on the emitter selection. To address the second issue, I investigated two solid-state upconverters, i.e. nanostructured glassy polymers that show similar macroscopic properties but fabricated via different approaches. They both feature liquid droplets of mean size less than 50 nm where the upconverting dyes accumulate, embedded in a rigid polymer matrix that grants excellent oxygen protection and optical quality and long-term stability. The dyes confinement allows to increase the effective local excitons density resulting in an enhanced UC efficiency at low excitation intensities, thanks to the reduced intermolecular distances and the activation of the confined sTTA-UC regime. I also introduced a new perylene derivative as emitter, specifically designed to prevent molecular aggregation to maximize its fluorescence efficiency. By employing this emitter, I achieved the record UC efficiency of 42%, which directly stems from the emitter molecular structure, as it limits the formation of aggregates, while guaranteeing excellent singlet generation efficiency upon TTA. I finally presented a perspective of the performances that can be achieved by combining the two topics considered, i.e. loading broadband sensitizers in nanostructured polymers. I highlighted that if the best trade-off between nanostructure size and energy distribution is met the maximum UC efficiency can be achieved at excitation powers orders of magnitude lower that the solar irradiance, therefore promoting the development of real-world solid-state upconverters.

A cinética de fotopolimerização do monômero metacrilato de metila (MMA) foi investigada usando o fotoiniciador tioxantona (TX) e o co-iniciador trietilamina (TEA), a fim de elucidar o mecanismo de fotopolimerização. A dilatometria foi usada como técnica para a determinação das cinéticas de polimerização. Determinaram-se os rendimentos quânticos de polimerização. Os estados excitados foram estudados por fluorescência estática para determinar as constantes de supressão de fluorescência pela amina e pelo monômero. Medidas de fotólise por pulso de laser permitiram obter o espectro de absorção triplete-triplete da tioxantona, bem como a constante de supressão do estado triplete. Os resultados mostraram que a supressão ocorre por um processo colisional no estado singlete e que os radicais eficientes na fotoiniciação são originados da amina TEA. A massa molecular média dos polímeros obtidos foi determinada por medidas de cromatografia de permeação em gel (GPC). Em uma segunda etapa, foi investigada a polimerização fotoiniciada por fotoiniciadores usados em resinas dentárias, canforquinona (CQ), 1,2-fenilpropanodiona (PPD), Lucirin e Irgacure. A velocidade de polimerização foi acompanhada por dilatometria usando excitação acima de 348 nm. Obteve-se os rendimentos quânticos de polimerização e os polímeros foram caracterizados por GPC. A maior constante de velocidade de polimerização obtida foi para o Irgacure e o maior rendimento quântico de polimerização obtido foi para o Lucirin. As diferenças na eficiência da polimerização são atribuídas à formação de radicais e à capacidade de gerar radicais a partir da absorção da luz incidente. Por fim, investigou-se os espectros de absorção triplete-triplete (TTA) da TX em diferentes solventes usando a técnica de fotólise por pulso de laser. Observou-se a formação de três bandas, duas referentes ao triplete da TX (uma em 300 nm e outra em 600 nm) e em 400 nm, observou-se a formação do radical cetila da TX. A abstração de hidrogênio do solvente pela TX pode ocorrer em 340 nm em solventes com constante de abstração de hidrogênio (kabstr) alto. Esse fator pode ser observado nos solventes 2-propanol e etanol. O substituinte na TX mostrou, através do parâmetro de Hammett do substituinte que com o aumento da eletronegatividade há um deslocamento do máximo de absorção do transiente para comprimentos de onda menores.
The photopolymerization of the monomer methyl methacrylate (MMA) using thioxanthone (TX) as photoinitiator and triethylamine (TEA) as co-initiator, was investigated in order to explain the photopolymerization mechanism. Dilatometry was used to determine the kinetics of polymerization. The polymerization quantum yields were determined. The excited states were studied using static fluorescence in order to determine the fluorescence rate quenching by the amine and the monomer. The triplet-triplet absorption (TTA) spectrum of thioxanthone and the rate constant of quenching of the triplet state were obtained using flash photolysis technique. The results showed that the singlet state quenching occurs by a colisional process and the efficient radicals in the photoinitiation process are originated from the amine TEA. The molar mass of the obtained polymers was determined by gel permeation chromatography (GPC). The polymerization photoinitiated by the photoinitiators used in dental resins, Camphorquinone (CQ), 1,2- Phenylpropanodione (PPD), Lucirine and Irgacure was investigated in a second step. The rate of polymerization was studied by dilatometry with excitation above 348 nm. The polymerization quantum yields were obtained and the polymers were characterized by GPC. The larger rate constant of polymerization was found for Irgacure and the larger polymerization quantum yield was obtained for Lucirine. The differences in polymerization efficiencies can be tracked to the formation of radicals and the capability to produce the radicals after incident light absorption. Finally, the TTA of TX was studied in different solvents using the flash photolysis technique. The spectrum presented three bands, two due to the transient of TX (at 300 and 600 nm), and one at 400 nm assigned to the cetyl radical. The abstraction of a solvent hydrogen by TX is observed at 340 nm in solvents with high hydrogen abstraction constant (kabstr). This fact can be observed in 2-propanol and ethanol. An increase in the solvent polarity stabilizes the electronic pp* states and unstabilizes the np* states. The substitution in the TX molecule produced a shift to lower wavelength in the maximum absorption of transient with the increase of the electronegativity, as indicated by the dependence of the Hammett parameter.

This work focusses on the high brightness performance of phosphorescent organic light-emitting diodes (OLEDs). The use of phosphorescent emitter molecules in OLEDs is essential to realize internal electron-photon conversion efficiencies of 100 %. However, due to their molecular nature, the excited triplet states have orders of magnitude longer time constants compared to their fluorescent counterparts which, in turn, strongly increases the probability of bimolecular annihilation. As a consequence, the efficiencies of phosphorescent OLEDs decline at high brightness – an effect known as efficiency roll-off, for which it has been shown to be dominated by triplet-triplet annihilation (TTA). In this work, TTA of the archetype phosphorescent emitter Ir(ppy)3 is investi- gated in time-resolved photoluminescence experiments. For the widely used mixed system CBP:Ir(ppy)3, host-guest TTA – an additional unwanted TTA channel – is experimentally observed at high excitation levels. By using matrix materials with higher triplet energies, this effect is efficiently suppressed, however further studies show that the efficiency roll-off of Ir(ppy)3 is much more pronounced than predicted by a model based on Förster-type energy transfer, which marks the intrinsic limit for TTA. These results suggest that the emitter molecules show a strong tendency to form aggregates in the mixed film as the origin for enhanced TTA. Transmission electron microscopy images of Ir(ppy)3 doped mixed films give direct proof of emitter aggregates. Based on these results, two concepts are developed that improve the high brightness performance of OLEDs. In a first approach, thin intrinsic matrix interlayers are incorporated in the emission layer leading to a one-dimensional exciton confinement that suppresses exciton migration and, consequently, TTA. The second concept reduces the efficiency roll-off by using an emitter molecule with slightly differ- ent chemical structure, i.e. Ir(ppy)2(acac). Compared to Ir(ppy)3, this emitter has a much smaller ground state dipole moment, suggesting that the improved performance is a result of weaker aggregation in the mixed film. The knowledge gained in the investigation of triplet-triplet annihilation is further used to develop a novel emission layer design for white organic LEDs. It comprises three phosphorescent emitters for blue, green, and red emission embedded in a multilayer architecture. The key feature of this concept is the matrix material used for the blue emitter FIrpic: Its triplet energy is in resonance with the FIrpic excited state energy which enables low operating voltages and high power efficiencies by reducing thermal relaxation. In order to further increase the device efficiency, the OLED architecture is optically optimized using high refractive index substrates and thick electron transport layers. These devices reach efficiencies which are on par with fluorescent tubes – the current efficiency benchmark for light sources
Diese Arbeit richtet ihren Fokus auf die Untersuchung der Leistungsfähigkeit von phosphoreszenten, Licht-emittierenden organischen Dioden (OLEDs) im Bereich hoher Betriebshelligkeiten. Phosphoreszente Emittermoleku ̈le werden in OLEDs eingesetzt, um interne Elektron-Photon Konversionseffizienzen von 100% zu erreichen. Begründet in ihrer chemischen Struktur, weisen die angeregten Triplett-Zustände dieser Emitter um Größenordnungen längere Zeitkonstanten als die Emission fluo- reszenter Materialien auf, sodass die Wahrscheinlichkeit bimolekularer Auslöschung stark ansteigt. Dies resultiert in einem deutlichen Effizienzrückgang phosphoreszenter OLEDs bei großen Leuchtdichten. Dieser als Roll-off bekannter Effekt wird bei hohen Anregungsdichten hauptsächlich durch Triplett-Triplett Annihilation (TTA) bestimmt. In der Arbeit wird TTA an einem Modellmolekül, dem phosphoreszenten Emit- ter Ir(ppy)3, in zeitaufgelösten Photolumineszenz Experimenten untersucht. Für das bekannte Emittersystem CBP:Ir(ppy)3 wird bei hohen Anregungsdichten Host-Guest TTA beobachtet, was einen zusätzlichen, ungewünschten TTA Kanal darstellt. Dieser Effekt wird durch das Verwenden von Matrix Materialien mit höherer Triplett Energie vermieden, jedoch zeigt sich in weiteren Untersuchungen, dass der Roll-off deutlich stärker ist als von einem auf Förster Energieübertrag basierendem Modell vorhergesagt, welches selbst ein intrinsisches Limit für TTA in phosphoreszenten Systemen beschreibt. Die Diskrepanz zwischen experimenteller Beobachtung und Modellvorhersage wird durch eine starke Tendenz des Emitters, Aggregate zu bilden, erklärt, was TTA deutlich verstärkt. Diese Aggregate werden mit Hilfe von Transmissionselektronenmikroskopie an Ir(ppy)3-dotierten Mischsystemen direkt nachgewiesen. Basierend auf diesen Resultaten werden zwei Konzepte entwickelt, um die Effizienz phosphoreszenter Systeme bei hohen Helligkeiten zu verbessern. Im ersten Ansatz werden dünne intrinsische Schichten des Matrixmaterials in die Emissionsschicht eingebaut, was die Exzitonenbewegung in einer Raumrichtung und damit auch TTA stark unterdrückt. Das zweite Konzept reduziert den Effizienz Roll-off durch die Verwendung eines phosphoreszenten Emitters Ir(ppy)2(acac) mit einer leicht abgeänderten Molekularstruktur. Im Vergleich mit Ir(ppy)3 weist dieser ein deutlich kleineres Dipolmoment im molekularen Grundzustand auf, wodurch die Aggregation vermindert wird. Aufbauend auf den Ergebnissen der TTA wird ein neuartiges Emissionsschicht-Design für weißes Licht entwickelt. In diesem Konzept werden drei phosphoreszente Materialien für blaue, grüne und rote Farbe in eine Vielschicht-Architektur eingebracht. Das Hauptmerkmal der Emissionsschicht ist die Wahl des Matrix-Materials für dem blauen Emitter FIrpic: Seine Triplett Energie liegt resonant zu dem FIrpic Triplett Zustand, wodurch niedrige Betriebsspannungen und hohe Leistungseffizienzen ermöglicht werden, da die thermische Relaxierung reduziert wird. Um die Ef- fizienz dieser weißen OLEDs weiter zu erhöhen, wird die entwickelte OLED Architektur zusätzlich durch die Verwendung von hochbrechenden Substraten und dicken Elektronen-Transportschichten optisch optimiert. Bei beleuchtungsrelevanten Helligkeiten erreichen diese OLEDs das Effizienzniveau von Leuchtstoffröhren – letztere stellen heute den Effizienz-Maßstab dar

Organic upconversion of photons through triplet energy exchange between two or more molecules (OUC) has been investigated through transient absorption and fluorescence spectroscopy, kinetic rate modelling and morphological analysis of thin films. An OUC system, consisting of one sensitising molecule (PQ4Pd) and an emitting molecule (rubrene), was first studied to explore the possibility of modelling the entire OUC process with a kinetic rate model. Transient absorption spectroscopy allowed for the intermediate steps of OUC to be directly observed and fitted, producing rate constants for each step in the process. This complete model was then optimised against fluorescence measurements from a system containing PtTPBP (sensitiser) and perylene (emitter) to calculate rate constants for that system from a single fluorescence type experiment, as opposed to several orthogonal Stern-Volmer type experiments. The possibility of fabricating a thin film OUC has been investigated through microscopy, fluorescence spectroscopy and a simple Monte-Carlo model. Using a system of PtOEP (sensitiser) and DPA (emitter), it was shown that the maximal efficiency of a thin film containing these molecules suspended in a PMMA matrix is found when the matrix is between 80 and 85 weight% of the total mixture. It was shown that on short timescales (a few seconds to a few minutes), atmospheric oxygen does not adversely affect thin film upconverters of this type as local oxygen is extremely rapidly quenched (less than a ms) and fresh oxygen is not able to diffuse back into the matrix at a rate that is competitive to OUC. It was shown that the degree of intermixing of active materials is of absolute importance in this fabrication, and a novel optical technique for measuring this intermixing in air was developed, some preliminary results are included.

This thesis details the synthesis, characterisation and photophysical properties of various fluorinated emitters for triplet-triplet annhilation up-conversion systems. The theory and mechanism of TTAUC is evaluated and the molecular design of the annihilating emitter molecule reviewed to allow improvement of the external up-conversion quantum yield and overall energy efficiency of the process. Three main series of chromaphores were investigated, based on diphenylanthracenes, bisphenylperylenes, and 3,5,8-triphenylBODIPYs. These were synthesised by metal catalysed aryl-aryl coupling (Suzuki-Miyaura) or nucleophilic substitution reactions and, when paired with appropriate sensitizing molecules, allowed the up-conversion of green to blue; red to green; and near IR/red to orange respectively. The effect of increasing fluorination on the ease of synthesis and photophysical properties of these emitter systems was studied with a view to their application in up-conversion systems. Fluorinated emitter molecules were shown to be highly resistant to degradation by UV light compared to their non-fluorinated analogues. The up-conversion ability of these systems was evaluated and novel fluorinated BODIPY based dyes were produced that have high fluorescence quantum yields of over 90%. Finally the up-conversion of up-converting nanoparticles incorporating fluorinated emitters was evaluated.

Gracias a resultados experimentales pero tambien a argumentos teoricos, sabemos que el Modelo Estandar de la fsica de partculas es solo una descripcion a bajas energas de una estructura mas fundamental. Supersimetra, una simetra del espacio-tiempo que relaciona bosones y fermiones, proporciona algunos de los candidatos para completar el Modelo Estandar mas favorecidos desde un punto de vista teorico. Sin embargo, la busqueda sin resultado de partculas supersimetricas pone a estos modelos bajo cierta tension, sobre todo porque muchas de las propiedades de supersimetr a en su aplicacion a la fsica de partculas estan directamente relacionadas con su presencia a escalas de energa del orden de las que estan siendo exploradas en LHC. Sin evidencias directas de supersimetra, ¿existe alguna medicion indirecta que los fsicos de partculas podran usar para estudiar estos modelos? La partcula de Higgs descubierta en 2012 en LHC no es solo la ultima pieza del Modelo Estandar, tambien es una nueva ventana que podra ser util en el estudio de fsica mas alla del Modelo Estandar. En la primera parte de esta tesis estudiamos las consecuencias del descubrimiento del boson de Higgs para versiones mnimas (construidas con el menor numero posible de elementos) de supersimetra. Encontramos que la masa del Higgs es mas pesada de lo que uno esperara en las extensiones supersimetricas del Modelo Estandar mas mnimas. Por lo tanto concluimos que puede que la busqueda de \minimalidad” a la hora de formular teoras mas alla del Modelo Estandar, no sea el camino mas adecuado en este caso. Por eso construimos una realizacion un poco mas “barroca” de supersimetra con la esperanza de que solucione el problema de la masa del Higgs, la teora se llama “Modelo de Tripletes con Simetra Custodial”. Este modelo presenta un sector de Higgs extendido y usa simetras para resolver algunos de los problemas asociados a la introduccion de nuevos grados de libertad en el potencial escalar de una teora, al mismo tiempo, es capaz de proporcionar una masa para el Higgs en acuerdo con la medicion experimental. Dedicamos la segunda parte de la tesis al estudio pormenorizado del Modelo de Tripletes con Simetra Custodial, de donde derivamos resultados muy interesantes con aplicaciones tanto en fsica de partculas como en cosmologa.
We know from experimental results but also from theoretical arguments that the very successful Standard Model of particle physics is just a low energy description of a more fundamental structure. Supersymmetry, a space-time symmetry that relates bosons and fermions, provides some of the most theoretically favored candidates to complete the Standard Model. However, null results in the searches for supersymmetric particles put these models under stress, specially since many of the nice properties of supersymmetry at the particle physics level are directly tied with its presence at the energy scales that are now being probed at the LHC. With no direct evidence for supersymmetry, is there an indirect measurement that particle physicists could use to test these models? In 2012 the Higgs particle was discovered at LHC. Its discovery gives closure to the Standard Model but also opens up a new window that could be useful in the study of physics beyond the Standard Model. In the first part of this thesis we study the consequences of the Higgs discovery for minimal versions of supersymmetry. We find that the measured mass of the Higgs particle is heavier than what is expected by the minimal realizations of a supersymmetric Standard Model. We thus consider that the search for minimality, i.e. building models with the least number of elements, in the formulation of beyond the Standard Model theories may not be such a good guiding principle in this case and construct a more baroque realization of supersymmetry, the Supersymmetric Custodial Triplet Model. This theory features an extended Higgs sector and uses symmetry as a tool to get rid of some of the problems associated with the introduction of new degrees of freedom to the scalar potential of a theory, at the same time, it is able to provide a Higgs that fits properly the experimental measurement of its mass. We devoted the second part of the thesis to an in depth study of the Supersymmetric Custodial Triplet Model, deriving very interesting results that can be useful both for particle physics, and cosmology.

This work is concerned with the synthesis and property investigation of a relatively new class of cyclometallated Ir(III) and Pt(II) complexes in which two metal centres are coordinated to a common heterocycle resulting in a rigid polymetallic assembly. Highly luminescent materials which can emit and absorb in a red region of the spectrum were targeted. There are three main parts of the thesis. The first part investigates how luminescent properties of the diplatinum systems are affected by the bridging ligand. A series of novel mono- and dinuclear Pt(II) complexes has been prepared and their luminescent and redox properties investigated. The main observation is that the introduction of the second metal centre leads to a substantial red-shift in absorption and emission. In the second part the role of changing the ligand substituents in a cyclometallated complex has been investigated to determine the extent to which luminescence is affected by the nature of the substituents. A series of mono- and dinuclear Pt(II) complexes have been prepared using substituted pyrazine bridging ligands. It was found that electron donating substituents such as –OMe in the benzene cyclometallating ring cause a red-shift, while electron withdrawing substituents such as –F cause a blue-shift in emission. The final part of the work describes the synthesis of cyclometallated homometallic bis Ir(III) complexes. A series of bis- Ir(III) complexes have been prepared using a terdentate cyclometallating N^C^N coordinating 1,3-di(2-pyridyl)benzene derivative as an auxiliary ligand. It was found that the nature of the bridging ligand determines the overall stability of the complex. Pyrimidine-linked systems were found to be the most stable, while pyrazine analogues readily photodecompose/isomerise. Pyridazine-linked systems lead to ionic complexes where one chloride ligand is shared by two Iridium metal centres.

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The historiography of triplets of Hamilton aims to address the mathematical reasoning that preceded the development of quaternions and their contribution to the study of three-dimensional objects. The study of triplets as geometrical representation of square roots and negative quantities prior to the formalization of hypercomplex numbers, in particular the algebra of quaternions. The origin and the quaternion's fundaments based on triplets, applied in the rotational motion of threedimensional objects in space, evokes further study of their complex structures, a priori. The search of Hamilton for a hypercomplex number able to represent rotations in space presented geometrical concerns, as well as, a vector approach of plane, then their applications determine isometries that still underlie the mathematical morphology of the digital dynamic image
A historiografia dos tripletos de Hamilton pretende abordar o raciocínio matemático que antecedeu o desenvolvimento dos quaternions e sua contribuição ao estudo de objetos tridimensionais. O estudo dos tripletos como representação geométrica das raízes quadradas e quantidades negativas antecedeu a formalização dos números hipercomplexos, em específico da álgebra de quaternions. A origem e os fundamentos dos quaternions baseados nos tripletos, aplicados no movimento rotacional de objetos tridimensionais no espaço suscitam um estudo mais aprofundado de suas estruturas complexas, a priori. A busca de Hamilton por um número hipercomplexo capaz de representar rotações do espaço apresentava preocupações geométricas, assim como uma abordagem vetorial do plano, logo suas aplicações determinariam isometrias que ainda fundamentam a morfologia da imagem digital dinâmica

A presente tese descreve o estudo cinético e mecanístico da desativação do estado singlete- e triplete-excitado de flavinas por esteróis (colesterol e ergosterol), vitamina D, coenzima Q10, vitamina K, ácidos graxos e metabólitos da cafeína. Através da análise de Stern-Volmer da supressão de fluorescência da riboflavina pelo colesterol, ergosterol, vitamina D, vitamina K, e pela coenzima Q10 observa-se que o estado singlete excitado da riboflavina é desativado com constante de velocidade superior ao limite da difusão. No entanto, a presença de colesterol, ergosterol, vitamina D, vitamina K e coenzima Q10 não afeta o tempo de vida do estado singlete excitado da riboflavina como demonstrado por experimentos de contagem de fótons resolvido no tempo sugerindo a formação de um complexo precursor [riboflavina...substrato]. O complexo 1:1 formado entre a riboflavina e a vitamina D apresenta Ka = 4 x 104 ± 3 mol⋅L-1 a 25 0C com ΔH0 = -36 ± 7 kJ⋅mol-1 e ΔS0 = -5 ± 3 J⋅mol-1 ⋅K-1. O complexo 1:1 entre a riboflavina e a vitamina K (vit K) e a riboflavina com a coenzima Q10 (CoQ10) apresentam Ka = 1 x 103 ± 1 mol⋅L-1 com ΔH0 = -110 ± 22 kJ⋅mol-1 e ΔS0 = 51 ± 9 J ⋅mol-1⋅K-1 para a vit K e Ka = 4 x 102 ± 1 mol⋅L-1, ΔH0 = -120 ± 27 kJ ⋅mol-1 e ΔS0 = 41 ± 7 J ⋅mol-1⋅K-1 para a CoQ10 a 25 0C. Para a desativação do estado triplete da riboflavina, foram obtidas constantes bimoleculares de velocidade variando de 1,4 x 108 L ⋅mol-1⋅s-1 (vit D) a 1,4 x 109 L ⋅mol-1⋅s-1 (CoQ10). Observa-se supressão da emissão de fluorescência da riboflavina na presença de metabolitos da cafeína, no entanto, sem alterar o tempo de vida do estado singlete excitado da riboflavina sugerindo a formação de um complexo precursor [riboflavina...substrato]. O complexo formado entre a riboflavina e os metabólitos da cafeína apresentam Ka = 295 ± 1 mol⋅L-1 com ΔH0 = -45 ± 8 kJ⋅mol-1 e ΔS0 = 12 ± 1 J⋅mol-1⋅K-1 para o ácido 1,7-dimetil úrico, Ka = 289 ± 1 mol⋅L-1 com ΔH0 = -38 ± 5 kJ ⋅mol-1 e ΔS0 = 9 ± 2 J ⋅mol-1⋅K-1 para o ácido 1-metil úrico e Ka = 275 ± 1 mol⋅L-1 com ΔH0 = 16 ± 3 kJ ⋅mol-1 e ΔS0 = 6 ± 1J ⋅mol-1⋅K-1 para a 1,7-dimetilxantina a 25 0C. Para a desativação do estado triplete da riboflavina, foram obtidas constantes de velocidade de 3kq = 4,2 x 108 L.mol-1.s-1 para a 1,7-dimetilxantina, 3kq = 1,0 x 108 L.mol-1.s-1 para o ácido 1,7-dimetil úrico e 3kq = 1,4 x 108 L.mol-1.s-1 para o ácido 1-metil úrico. Os ésteres metílicos (oleato de metila, ácido linoléico conjugado (CLA), linoleato de metila, linolenato de metila, araquidonato de metila, eicosapentanoato de metila, e docosahexanoato de metila) não desativam o estado singlete-excitado da riboflavina. Entretanto, os ésteres metílicos se mostraram reativos frente ao estado triplete da riboflavina com constantes de velocidades 3kq variando de 8,4 x 105 a 3,3 x 107 L⋅smol-1 ⋅s-1 com uma dependência linear do número de hidrogênios bis-alílicos com excessão do CLA.
The present thesis describes the kinetic and mechanistic studies of flavin singlet- and triplet-excited states deactivation by sterols (ergosterol and cholesterol), vitamin D, coenzyme Q10, vitamin K, fatty acids, and caffeine metabolites. From the Stern-Volmer analysis of the riboflavin fluorescence quenching by cholesterol, ergosterol, vitamin D, vitamin K and coenzyme Q10, it is noted that the singlet-excited state of riboflavin is deactivated with a rate constant exceeding the diffusion limit. However, the presence of cholesterol, ergosterol, vitamin D, vitamin K, coenzyme Q10 did not affect the lifetime of singlet-excited riboflavin as probed by single photon counting experiments suggesting the formation of a ground-state precursor complex [riboflavin ...substrate]. The 1:1 complex formed between riboflavin and vitamin D showed Ka = 4 x 104 ± 3 mol⋅L-1 a 25 0C with ΔH0 = -36 ± 7 kJ⋅mol-1 and ΔS0 = -5 ± 3 J⋅mol-1 ⋅K-1. The 1:1 complex formed between riboflavin and vitamin K (vit K) and riboflavin with coenzyme Q10 (CoQ10) showed Ka = 1 x 103 ± 1 mol⋅L-1 with ΔH0 = -110 ± 22 kJ⋅mol-1 and ΔS0 = 51 ± 9 J ⋅mol-1⋅K-1 for vit K e Ka =4 x 102 ± 1 mol⋅L-1, ΔH0 = -120 ± 27 kJ ⋅mol-1 and ΔS0 = 41 ± 7 J ⋅mol-1⋅K-1 for CoQ10 a 25 0C. For the deactivation of triplet riboflavin, bimolecular rate constants were found to vary from 1,4 x 108 L ⋅mol-1⋅s-1 (vit D) a 1,4 x 109 L ⋅mol-1⋅s-1 (CoQ10). The caffeine metabolites quench fluorescence emission of riboflavin however, without affecting the lifetime of the singlet-excited state, suggesting the formation of a ground state precursor complex [riboflavin ... substrate]. The complex formed between riboflavin and caffeine metabolites showed Ka = 295 ± 1 mol⋅L-1 with ΔH0 = -45 ± 8 kJ⋅mol-1 and ΔS0 = 12 ± 1 J⋅mol-1⋅K-1for 1,7-dimetyl uric acid, Ka = 289 ± 1 mol⋅L-1 with ΔH0 = -38 ± 5 kJ ⋅mol-1 and ΔS0 = 9 ± 2 J ⋅mol-1⋅K-1 for 1-methyl uric acid and Ka = 275 ± 1 mol⋅L-1 with ΔH0 = 16 ± 3 kJ ⋅mol-1 and ΔS0 = 6 ± 1J ⋅mol-1⋅K-1 for 1,7-dimethylxanthine at 25 0C. For the deactivation of triplet riboflavin, rate constant were obtained with 3kq = 4,2 x 108 L.mol-1.s-1 para a 1,7-dimethylxanthine, 3kq = 1,0 x 108 L.mol-1.s-1 for 1,7-dimethyl uric acid, and 3kq = 1,4 x 108 L.mol-1.s-1 for 1-methyl uric acid. The methyl esters (methyl oleate, conjugated linoleic acid (CLA), methyl linoleate, methyl linoleate, methyl arachidonate, methyl eicosapentanoate, and methyl docosahexanoate) did not quench the singlet-excited riboflavin. However, the methyl esters were shown to be reactive towards triplet riboflavin with rate constants ranging from 8,4 x 105 a 3,3 x 107 L⋅mol-1 ⋅s-1and depending linearly with the number of bis-allylic hydrogens with exception to CLA.

This work focuses on a better understanding of the behavior of organic light emitting devices (OLEDs) under intense electrical excitation. Attaining high exciton densities in organic semiconductors by electrical excitation is of special interest for the field of organic semiconductor lasers (OSLs). In these devices, the high singlet exciton density needed in the active layer to obtain population inversion is easily created by pulsed optical pumping, but direct electrical pumping has not been achieved yet. First, the steps necessary to achieve stable high current densities in organic semiconductors are discussed. After determining the optimal excitation scheme using single p-doped transport layers, the device complexity is increased up to full p-i-n OLEDs with their power dependent emission spectra. For this purpose, two exemplary emitter systems are chosen: the fluorescent laser dye 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) doped into Aluminum(III)bis (2-methyl-8-quinolinato)-4-phenylphenolate (Alq3) and the efficient phosphorescent emitter system N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine (alpha-NPD) doped by Iridium(III) bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate) (Ir(MDQ)2(acac)). For pulsed excitation using 50 ns pulses and a repetition rate of 1 kHz, single 100 nm thin p- and n-doped transport layers sustain current densities of over 6 kA/cm2. While the maximum current density decreases with increasing device thickness, the full OLEDs still sustain current densities beyond 800 A/cm2 and exhibit a continuously increasing emission intensity with increasing input power. Next, the time-resolved emission behavior of the singlet and triplet emitter device at high excitation densities is analyzed on the nanosecond scale. Here, the peak emission intensity of the phosphorescent emitter system is found to be more than eight times lower than for the singlet emitter system at comparable current densities. The triplet emitter system exhibits a slow rise of the EL after turn-on which prevents the usage of shorter pulses to enable higher current densities. The singlet emitter system, in contrast, exhibits a fast turn-on and reaches the maximum emission intensity within less than 20 ns. By several additional experiments including streak camera measurements and pump-probe experiments, the strong EL overshoot observed in the first few ns is successfully attributed to a reduced emission intensity in the steady state due to singlet-triplet annihilation. Hence, the separation of singlet emission and singlet-triplet quenching in time domain is demonstrated. At 550 A/cm2 and 10 ns pulse rise time, a peak luminance of 1.5E6 cd/m2 is recorded. Finally, the experimental results are validated by modeling the singlet and triplet population dynamics in the emission layer of the fluorescent system to explain the time-resolved emission characteristics. Using a set of rate equations for the polaron density and the singlet and triplet exciton densities, the overshoot in singlet exciton density at the device turn-on is attributed to the separation of singlet emission and triplet quenching in time domain. Furthermore, by fitting the experimental data, the triplet-triplet annihilation rate in the host guest system is shown to become exciton density dependent at sufficiently high excitation density
Der Schwerpunkt dieser Arbeit liegt auf dem besseren Verständnis des Verhaltens von organischen Leuchtdioden (OLEDs) bei intensiver elektrischer Anregung. Das Erreichen hoher Exzitonendichten in organischen Halbleitern ist insbesondere für organische Halbleiterlaser (organic semiconductor lasers, OSLs) von Interesse. Hierbei werden die für die Inversion benötigten hohen Singulett Exzitonendichten zwar leicht mittels gepulstem optischen Anregen (Pumpen) erreicht, jedoch konnte eine elektrische Anregung bisher noch nicht realisiert werden. Der erste Abschnitt befasst sich mit dem Erreichen von hohen Stromdichten und den dazu nötigen Schritten. Nach dem Ermitteln des optimalen Anregungsschemas an p-dotierten Einzelschichten wird die Komplexität des Systems Schritt für Schritt bis zur kompletten p-i-n OLED erhöht. Hierfür wurden exemplarisch zwei verschiedene Emittersysteme ausgewählt: Aluminum(III)bis (2-methyl-8-quinolinato)-4-phenylphenolate (Alq3) dotiert mit dem fluoreszenten Laserfarbstoff 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) und der effiziente phosphoreszente Emitter Iridium(III)bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate) (Ir(MDQ)2(acac)) in einer N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine (alpha-NPD) Matrix.Bei gepulster Anregung mit einer Pulsweite von 50 ns und einer Wiederholungsrate von 1 kHz sind in 100 nm dünnen p- und n-dotierten Transportschichten Stromdichten von mehr als 6 kA/cm2 möglich. Der Maximalstrom sinkt mit zunehmender Gesamtschichtdicke ab. Die kompletten p-i-n OLEDs ermöglichen eine Stromdichte von über 800 kA/cm2 und weisen eine kontinuierlich mit der Stromdichte steigende Emissionsintensität auf. Anschließend wird die zeitlich aufgelöste Elektrolumineszenz der Singulett- und Triplett-Emitter OLEDs mit Nanosekunden-Auflösung untersucht. Die phosphoreszente OLED weist hierbei, im Vergleich zur fluoreszenten OLED bei vergleichbarer Stromdichte, eine mehr als achtmal geringere Emissionsintensität auf. Des Weiteren steigt die Emissionsintensität nur langsam an, die maximale Intensität wird erst nach 120 ns erreicht. Dies steht im Widerspruch zum Erreichen höherer Stromdichten mittels kürzerer Pulse. Die fluoreszente OLED hingegen zeigt ein schnelles Ansteigen der Emissionsintensität, die maximale Intensität wird nach weniger als 20 ns erreicht. Anhand von zusätzlichen Untersuchungen kann das beobachtete starke Überschießen der Elektrolumineszenz innerhalb der ersten Nanosekunden einer durch Singulett-Triplett Annihilation reduzierten Emission im Gleichgewichtszustand zugeordnet werden. Diese Experimente dokumentieren somit die zeitliche Trennung von Fluoreszenz und Singulett-Triplett Annihilation. Bei einer Stromdichte von 550 A/cm2 und 10 ns Flankenanstiegszeit wird eine maximale Lumineszenz von 1.5E6 cd/m2 gemessen. Der letzte Abschnitt befasst sich mit der Bestätigung der experimentellen Ergebnisse durch die Simulation der Dynamik von Singulett- und Triplett-Exzitonendichte in der Emissionsschicht. Mit Hilfe eines Satzes von gekoppelten Differenzialgleichungen für die Dichte der Polaronen, Singulett Exzitonen und Triplett Exzitonen lässt sich das Überschießen der Elektrolumineszenz der fluoreszenten OLED eindeutig der zeitlichen Trennung von Singulett Emission und Singulett-Triplett Annihilation zuordnen. Außerdem kann durch das Fitten der experimentellen Daten dargestellt werden, dass die Triplett-Triplett Annihilationsrate in dem untersuchten fluoreszenten Emittersystem bei ausreichend hohen Anregungsdichten eine starke Abhängigkeit von der Dichte der Triplett Exzitonen aufweist

Recentemente, os compostos não-centrossimétricos têm sido intensamente estudados devido à grande variedade de comportamentos magnéticos, os quais são induzidos pela ausência de centro de simetria na sua estrutura cristalográfica. Esta assimetria induz uma modificação na estrutura de bandas, causando um acoplamento spin-orbita antissimétrico quem é responsável por mecanismos de interação magnética inusuais. A supercondutividade em este tipo de compostos apresenta propriedades que divergem do comportamento esperado pela teoria BCS. Neste trabalho será apresentado um estudo sobre a investigação de supercondutividade em dois sistemas ternários, Y-Co-C e Lu-Ni-C particularmente nos compostos YCo1-xC2 e Lu1-xThNiC2. Estes compostos cristalizam na estrutura CeNiC2 de simetria ortorrômbica é do grupo espacial 38 Amm2 que não possui centro de inversão. As técnicas de caracterização usadas neste trabalho incluem medidas de magnetização, resistividade e calor especifico como funções da temperatura, assim como magnetização como função do campo magnético aplicado. O composto YCo0.7C2 é supercondutor com Tc = 4 K e exibe um comportamento que diverge da teoria BCS. As medidas realizadas neste trabalho sugerem que este material é um forte candidato como supercondutor não convencional, onde poderia existir uma mistura de contribuições nos canais singleto e tripleto. No caso do sistema Lu1-xThxNiC2 os resultados preliminares indicam claramente supercondutividade nos compostos dopados com Th, onde a composição Lu0.6Th0.4NiC2 apresenta uma Tc= 8 K.
In recent years, non-centrosymmetric compounds have attracted a great interest because of their wealth variety of topical behaviors, induced by the lack of the inversion center on the crystallographic structure. This asymmetry leads to a strong modification in the band structures, causing an antisymmetric spin-orbit coupling which is responsible for unusual magnetic interaction mechanisms. Superconductivity in compounds whose crystal structure lacks inversion symmetry are known to display intriguing properties that deviate from conventional BCS superconducting behavior. Here we report the analysis of the ternary systems Y-Co-C and Lu-Ni-C, We focused our analysis in the intermetallic compounds YCo1-xC2 and Lu1-xThxNiC2. Magnetization, resistivity, and heat capacity measurements on polycrystalline samples of noncentrosymmetric YCo0.7C2, showing clear evidence of bulk superconductivity with a critical temperature of Tc =4 K. Interestingly the specific heat of the superconducting state deviates from conventional exponential temperature dependence, which is suggestive of possible unconventional superconducting behavior in YCo0.7C2, similar to that seen in the isostructural and isoelectronic superconductor LaNiC2. Besides, these results strongly suggest that this material is a strong candidate of multiband superconductivity. In the case of the system Lu1- xThxNiC2 our results showed a clear superconducting signal in the Th doped samples, where the composition Lu0.6Th0.4NiC2 has a Tc= 8 K.

Triplet states in organic semiconducting devices are often associated with loss processes. Radiative decay to the ground state is a spin disallowed process, which results in triplets in normal organic systems decaying primarily though non-radiative pathways. In OLEDs, where 75% of created excitons are triplets, this has a large impact on device efficiency. The work herein focusses on the synthesis of organic polymers that utilise triplet states in some useful fashion. This was first achieved through incorporation of a heavy metal in the polymer chain, which increased spin-orbit coupling and allowed phosphorescence to occur. The heavy metal was incorporated directly into the polymer backbone as part of a porphyrin complex. Focus then moved to organic polymers that have decreased first excited singlet-triplet energy gaps. This allows excitons to move from singlet to triplet state without the use of a heavy metal, a formally spin disallowed process. Thermally activated delayed fluorescence is observed in one polymer. All synthetic work carried out is linked by the aim of using triplet states usefully in a resultant device. While the applications of the devices may differ, all in some way use triplet states in the movement of energy through the electronic system of the polymer. It is hoped that some of this work may form the basis of new types of materials for organic semiconducting systems.

Carotenoids are essential in photosynthesis. These molecules play several roles in the photosynthetic apparatus: they share with chlorophylls the light-harvesting function, stabilize the pigment-protein complexes and are responsible for the protection of the whole apparatus against the hazardous singlet oxygen. The structural function has been investigated in many different organisms by several biochemical methods: the main finding is that carotenoids are essential for the protein stability. Without carotenoids light-harvesting complexes would not fold and their selective removal from intact proteins often causes unfolding. The light-harvesting function of the carotenoids has been object of extensive investigations. The photo-physics of their singlet states is very complex: it is characterized by the presence of forbidden states, fast dynamics of the excited states and low fluorescence yield. The singlet energy transfer pathways between carotenoids and chlorophylls, which are important for the light-harvesting function, have been also well characterized. Less has been done on the study of the photoprotective role that makes carotenoids essential for the photosynthetic organisms. Carotenoids are involved in photoprotection in many ways and at different stages of the photosynthetic process, in relation to the intensity and duration of the stress conditions. When the sunlight intensity suddenly increases the first photoprotection mechanism activated is the photo-physical triplet-triplet energy transfer from chlorophylls molecules to carotenoids molecules. This interaction scavenges the formation of highly oxidant oxygen species which could be produced by the chlorophyll triplet states, whose production increases under light excess. Carotenoid triplet states are thus very important from a physiological point of view. In contrast to photosynthetic reaction centres, which have very similar structural architecture, light-harvesting complexes show more variability due to different habitat adaptation of the photosynthetic organisms. This heterogeneity stimulated a comparative investigation on light harvesting complexes in order to point out the common and the different key features adopted by the different organisms for reaching an efficient triplet-triplet energy transfer. This thesis represents one of the few detailed studies entirely focused on the role of carotenoids molecules in the triplet-triplet energy transfer mechanism in naturally occurring light-harvesting complexes. By means of EPR spectroscopy, the magnetic properties of the carotenoid triplet states have been exploited to characterize the energy transfer pathways in four different light-harvesting complexes: the LHC-II from higher plants, the LHC and the PCPs from dinoflagellates and the chlorosomes from green sulphur bacteria. These antenna proteins have been selected as representative for the light-harvesting strategy variability adopted by different photosynthetic species. The main results obtained, which have a physiological relevance, can be summarized as follows: - Among all the pigments present in each protein considered, only specific carotenoids are devoted to the dissipation of chlorophyll triplet energy. It is worth noting that the examined proteins belong to different organisms which are not close in the evolutionary scale. Thus, the presence of a specific triplet energy sink seems to be an important point in the photoprotection mechanism played by triplet-triplet energy transfer. - EPR spectroscopy does not show any evidence for the existence of triplet excitons involving carotenoids and chlorophylls. Moreover multiple triplet-triplet energy transfers among carotenoids can also be ruled out. Therefore a localized carotenoid triplet state seems to be a common feature for all the pigment-protein complexes. - The triplet electron density distribution over the conjugate chain of the carotenoids is not heavily influenced by the chemical substitution. It has the same pattern and the same extent even though triplet states belonging to carotenoids with very different molecular structure are considered. This characteristic makes the relative geometry of the chlorophyll/carotenoid couples involved in the triplet-triplet energy transfer not very dependent on the center-to-center distance of the two pigments. Instead the minimum distance between the π-conjugated systems results to be most the important structural requirement. - Triplet-triplet energy transfer in antenna complexes seems to be properly described by a superexchange mechanism involving a molecular bridge interposed between the chlorophyll/carotenoid couple. This bridge is represented by the fifth ligand of the Mg atom bound to the chlorophyll. The mechanism is supported by ENDOR measurements and DFT calculations: the highest electron density calculated for the carotenoid triplet state is located on the carbon atom closest to the Mg fifth ligand. Thus the bridge likely increases the triplet-triplet energy transfer rate leading to a very efficient quenching. Together with the ‘functional’ results, this thesis demonstrates also how triplet state EPR techniques, applied to the study of the molecules involved in triplet-triplet energy transfer, can be used to derive structural information if the crystallographic structure of the light-harvesting protein is not known. As a matter of fact, EPR spectra can be conveniently used to extract some experimental constraints useful in the modelling of protein structure, since their shapes strictly depend on the relative geometry of the couples involved in the triplet-triplet energy transfer. In photosynthesis this is particularly relevant since many proteins involved in the process are large, embedded in the membrane and bound many cofactors. All these characteristics are severe limitations in using x-ray diffraction or NMR
I caroteni sono assi portanti del processo fotosintetico. A queste molecole sono affidati molteplici ruoli: condividono con le clorofille la funzione di raccolta dell’energia luminosa, stabilizzano i complessi proteina-pigmento e sono responsabili della protezione dell’intero apparato fotosintetico contro l’azione ossidante dell’ossigeno di singoletto. La funzione strutturale è stata studiata mediante diverse tecniche biochimiche in molteplici organismi: è stato dimostrato che i carotenoidi sono essenziali per la stabilità strutturale dei complessi proteici. Senza carotenoidi i complessi antenna non sono in grado di assemblarsi e la loro rimozione selettiva da proteine intatte ne causa la denaturazione. La funzione di raccolta della luce è stata estensivamente studiata tramite spettroscopie ottiche. La foto-fisica degli stati di singoletto nei caroteni è molto complessa e caratterizzata dalla presenza di transizioni proibite, dalla dinamica veloce tra stati eccitati e dalla bassa resa di fluorescenza. Anche i cammini di trasferimento di energia di singoletto tra caroteni e clorofille, importanti per la funzione di raccolta della luce, sono stati ampiamente caratterizzati. Molto meno è stato fatto riguardo al ruolo fotoprotettivo che rende i carotenoidi essenziali per gli organismi fotosintetici. I carotenoidi sono implicati nella fotoprotezione in moti modi e in diversi gradi in relazione alla durata e all’intensità delle condizioni di stress. Quando l’intensità della luce solare aumenta improvvisamente il primo meccanismo di fotoprotezione attivato è il trasferimento di energia tripletto-tripletto dalle molecole di clorofilla verso le molecole di carotenoide: questo trasferimento di energia previene la formazione di specie all’ossigeno altamente ossidanti che potrebbero essere prodotte dalla clorofilla in stato di tripletto. Lo stato di tripletto di carotenoide è quindi fisiologicamente importante. A differenza dei centri di reazione fotosintetici, che condividono tutti un’architettura strutturale molto simile, i complessi antenna esibiscono una più spiccata variabilità dovuta ai differenti adattamenti ambientali. Questa eterogeneità ha stimolato un’indagine comparativa al fine di evidenziare le caratteristiche fondamentali comuni o particolari adottate dai diversi organismi per rendere il trasferimento di energia di tripletto efficiente. Questa tesi rappresenta uno dei pochi studi dettagliati completamente focalizzati sul ruolo delle molecole carotenoidi nel meccanismo di trasferimento di energia tripletto-ripletto in complessi antenna naturali. Attraverso la spettroscopia EPR, si sono sfruttate le proprietà magnetiche degli stati di tripletto dei caroteni per caratterizzare i cammini di trasferimento di energia in quattro diversi complessi antenna: la proteina LHC-II caratteristica delle piante superiori, le proteine LHC e PCP caratteristiche dei dinoflagellati ed i clorosomi caratteristici dei batteri verdi sulfurei. Queste proteine sono state selezionate come campione rappresentativo della variabilità nelle strategie di fotoprotezione adottate dai diversi organismi fotosintetici. I risultati ottenuti con rilevanza fisiologica possono essere schematizzati come segue: - Tra tutti i pigmenti presenti in ogni proteina considerata, solo specifici carotenoidi sono deputati alla dissipazione dell’energia di tripletto delle clorofille. Vale la pena notare che le proteine considerate appartengono ad organismi distanti nella scala evolutiva. Sembra perciò che la presenza di specifiche ‘trappole di energia’ sia centrale nella fotoprotezione giocata dai trasferimenti di energia tripletto-tripletto - I dati EPR non mostrano alcuna evidenza circa la formazione di eccitoni di tripletto che coinvolgano caroteni e clorofille. Inoltre, permettono di escludere la presenza trasferimenti multipli di energia di tripletto tra carotenoidi. Perciò, la presenza di uno stato di tripletto di carotenoide localizzato sembra essere una caratteristica comune a tutti i complessi antenna considerati. - La distribuzione della densità elettronica dello stato di tripletto lungo la catena coniugata della molecola di carotenoide non risulta essere particolarmente influenzata dalla presenza di sostituenti chimici: presenta la stesso andamento e la stessa estensione anche tra carotenoidi con strutture chimiche molto differenti. Questa evidenza rende la geometria relativa della coppia clorofilla/carotenoide coinvolta nel trasferimento di energia non particolarmente dipendente dalla distanza tra i centri dei sistemi coniugati delle due molecole. Mentre sembra che la minima distanza tra i sistemi coniugati sia il requisito strutturale fondamentale. - Il trasferimento di energia tripletto-tripletto nei complessi antenna sembra essere correttamente descritto dal meccanismo di super-scambio che coinvolge un ponte molecolare intercalato tra la coppia clorofilla/carotenoide. Questo ponte è rappresentato dal quinto legando dell’atomo di Mg legato al centro della molecola di clorofilla. Gli esperimenti ENDOR ed i calcoli DFT condotti supportano questa conclusione: la densità elettronica più alta riscontrata appartiene all’atomo di carbonio più vicino al quinto legando dell’atomo di Mg. Verosimilmente il ponte molecolare aumenta la velocità di trasferimento di energia garantendo un processo molto efficiente. Parallelamente a questi conclusioni ‘funzionali’, questa tesi dimostra anche come le tecniche EPR, applicate allo studio di molecole coinvolte nei trasferimenti di energia tripletto-tripletto, possano essere utilizzate per ricavare informazioni strutturali quando la struttura cristallografica non sia nota. Infatti, poiché la loro forma spettrale dipende direttamente dalla geometria della coppia coinvolta nel trasferimento di energia di tripletto, gli spettri EPR possono essere opportunamente impiegati per estrarre vincoli sperimentali da impiegare nella modellizzazione di strutture proteiche. In ambito fotosintetico questo risultato è particolarmente rilevante dal momento che molte proteine coinvolte nel processo sono grandi, di membrana e legano molti cofattori. Tutte queste caratteristiche costituiscono importanti limitazioni nell’utilizzo della diffrazione ai raggi x o delle tecniche NMR.

In the face of global warming and shrinking resources of fossil fuels the interest in solar energy has increased in recent years. However, the low energy and cost efficiency of current solar cells has up to this date hindered solar energy from playing a major role on the energy market. Photon upconversion is the process in which light of low energy is converted to high energy photons. Lately, this phenomenon has attracted renewed interest and ongoing research in this field mainly focuses on solar energy applications, solar cells in particular. The aim of this study was to investigate and evaluate amyloid fibrils as nanotemplates for an upconversion system based on the dyes platinum octaetylporphyrin (PtOEP) and 9,10- diphenylanthracene (DPA). This well-known pair of organic dyes upconverts light in the visible spectrum through a mechanism known as sensitized triplet-triplet annihilation. Amyloid fibrils are β-sheet rich protein fibril structures, formed by self-assembly of peptides. Amyloid fibrils were prepared from whey protein isolate using heat and acidic solutions. Dyes were incorporated according to a wellestablished technique, in which dyes are grinded together with the protein in solid state prior to fibrillization. Photophysical properties of pure fibrils and dye-incorporated fibrils were studied using UV-VIS spectroscopy and fluorescence spectroscopy. Atomic force microscopy was further employed to confirm the presence of amyloid fibrils as well as to study fibril structure. Results indicate that amyloid fibrils may not be the optimal host material for the upconversion system PtOEP/DPA. It was found that the absorption and emission spectra of this system overlap to a great deal with that of the fibrils. Though no upconverted emission clearly generated by the dye system was recorded, anti-Stokes emission was indeed observed. Interestingly, this emission appears to be strongly enhanced by the presence of dyes. It is suggested that this emission may be attributed to the protein residues rather than the amyloid structure. Future studies are encouraged to further investigate these remarkable findings.
Intresset för solceller har ökat under de senaste åren, till stor del tillföljd av den globala uppvärmningen och de sinande oljeresurserna. Dagens solceller har dock problem med låg energi- och kostnadseffektivitet, vilket gör att solenergin än så länge har svårt att hävda sig på energimarknaden. Photon upconversion är ett fotofysikaliskt fenomen där fotoner med låg energi omvandlas till fotoner med hög energi. Den senaste tiden har denna process fått förnyat intresse och forskningen inom området har ökat, inte minst med sikte på att integrera processen i solceller och därmed öka dess effektivitet. Målet med denna studie var att undersöka huruvida amyloidfibriller kan användas som stomme för ett photon upconversion-system baserat på platinum-oktaetylporfyrin (PtOEP) och 9,10-difenylantracen (DPA). Dessa två organiska färgämnen är ett välkänt par som konverterar synligt ljus med låg frekvens till mer hög frekvent ljus i det synliga spektrumet, via en mekanism som kallas sensitized triplet-triplet annihilation. Amyloidfibriller är proteinbaserade fiberstrukturer med hög andel β-flak, vilka bildas genom självassociation av peptider. I denna studie skapades amyloidfibriller av vassleprotein genom upphettning i sur lösning. Färgämnena inkorporerades enligt en välbeprövad metod där proteinet mortlas tillsammans med färgämnena i fast tillstånd, innan fibrilleringsprocessen påbörjas. De fotofysikaliska egenskaperna hos fibriller med och utan färgämnen analyserade med UV-VIS samt fluorescensspektroskopi. Atomkraftsmikroskopi användes för att bekräfta att fibriller fanns i proven, samt för att studera dess struktur. De erhållna resultaten antyder att amyloidfibriller inte är ett optimalt material för systemet PtOEP/DPA, delvis på grund av att absorptions- och emissionsspektrumet för systemet överlappar med fibrillernas egna spektrum. Anti-Stokes emission detekterades, men denna är med stor sannolikhet inte orsakad av färgämnena. Dock noterades, intressant nog, att denna emission ökar betydligt i närvaro av färgämnena. En möjlighet är att denna emission är kopplad till monomerer i proteinet snarare än till fibrillstrukturen, eftersom emission observerades hos både nativt och fibrillerat protein. Framtida studier uppmuntras att vidare undersöka dessa effekter.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 107-113).
Our main energy source are burning fossil fuels. Solar energy is a clean, sustainable energy source that does not emit greenhouse gas that causes global warming. In this thesis, singlet fission and triplet-triplet annihilation would be discussed and studied to increase solar cell power conversion efficiency. Singlet fission splits a singlet exciton into two lower energy triplet excitons. This energy down conversion is efficient and have shown near 200% triplet exciton yield. With energy down conversion, thermalization loss in solar cell could be reduced. We have shown singlet fission in tetracene, a suitable down conversion fission material to pair with silicon solar cell, up to 127% of internal quantum yield. To integrate tetracene as the energy down converter for silicon, we have demonstrated triplet exciton transfer from tetracene to silicon with WNx passivation. To show triplet exciton transfer, a spectrally resolved magnetic field effect measurement setup was designed and built. We have also demonstrated a metal-free, solid state optical up conversion system. This is in contrast with most optical up conversion system that uses heavy metal for triplet generation and are limited to solution fabrication based on material restrictions. The novel optical up conversion system provided cheaper material choices as well as better fabrication freedom and potentially longer device operation lifetime.
by Tony Chang-Chi Wu.
Ph. D.

Estudamos nesta dissertação o conteúdo de operadores da cadeia quântica do modelo XY anisotrópico com interações de três spins (XY triplete anisotrópico). Verificamos que, como no caso de interações de dois spins, este modelo pode ser visto como uma superposição de duas cadeias quânticas Ising, que neste caso apresentam interações de três spins (Ising triplete). Como conseqüência, todo o conteúdo de operadores do modelo XY triplete é obtido através de um estudo sistemático do conteúdo de operadores do Ising triplete o que é feito numericamente explorando-se as relações entre as lacunas de massa e as dimensões anômalas dos operadores do modelo, previstas pela invariância conforme.
We study in this work the operator content of the staggered XY model quantum chain with three-spin interactions (staggered XY triplet). We verified that, as quantum Ising chains, but in this case with three-spin interactions (Ising triplet). It is possible therefore to obtain all the operator content of the XY triplet model by a systematic numerical analysis of the Ising triplet´s operator content, which follows by exploiting the relations between the mass gap amplitudes and the anomalous dimension of the operators of the model, predicted by conformal invariance.

Nombreuses sont les applications web sémantique qui s’intéressent à la problématique de l’intégration de données issues de sources RDF distribuées. Pour l’exécution de requêtes distribuées, par exemple, plusieurs solutions sont ainsi proposées comme SPARQL 1. 1 Federation qui définit un ensemble d’extensions au langage de requête SPARQL. Si ces extensions permettent de déléguer une partie de requête à un ensemble de services, un problème majeur subsiste encore pour déterminer automatiquement en amont les services disposant de réponses pour une requête donnée. La résolution de ce problème est particulièrement cruciale dans un contexte comme le Linking Open Data où de nombreuses sources RDF hétérogènes sont publiées. Pour pouvoir envoyer une requête uniquement aux sources de données concernées, une description complète et compacte de chaque source est nécessaire. Pour connaître le contenu d’une source RDF nous pouvons nous baser sur les motifs de graphes qui la composent. Dans cette thèse, nous nous intéressons à l’extraction de ces motifs de graphes. Nous proposons pour cela une extension du codage DFS (Depth-First Search) de (Yan et Han, 2002) aux motifs de graphes RDF qui sont orientés et étiquetés et une opération de jointure entre codes DFS pour construire itérativement les différents niveaux d’une structure d’index de sources de données RDF. La structure d’index ainsi générée est constituée d’une hiérarchie de graphes RDF et permet d’identifier les types de données contenus dans la source indexée. Le choix du codage DFS pour représenter les motifs de graphe facilite entre autre les tests isomorphes et les opérations de jointure entre motifs de graphe mais pose un réel problème d’exploitation de la structure d’index. En effet, les hiérarchies de codes DFSR issues de processus de construction de structures d’index sont difficiles à lire (succession d’entiers) et à interroger. Pour palier cela, nous proposons une interface de visualisation des structures d’index générées et un ensemble d’algorithmes de transformation des codes DFSR dans des formats comme RDF plus « lisibles » et plus facilement exploitables. L’ajout ou la suppression d’annotations de la source de données RDF peut entraîner des changements dans la structure d’index. A la place d’une reconstruction totale de la structure d’index nous proposons une procédure qui identifie d’abord les répercussions des mises à jour de la source dans le premier niveau de la structure d’index et ensuite propage ses modifications si nécessaires aux niveaux supérieurs. Pour la manipulation des sources de données RDF, notre algorithme utilise le moteur de recherche sémantique CORESE/KGRAM de (Corby, 2008) par l’intermédiaire de son API. Nous avons testé notre algorithme en générant des structures d’index à partir de plusieurs sources de données RDF choisies pour la diversité des motifs de graphes qu’elles contiennent
Many semantics web applications address the issue of integrating data from distributed RDF triple stores. There are several solutions for distributed query processing such as SPARQL 1. 1 Federation, which defines extensions to the SPARQL Query Language to support distributed query execution. Such extensions make it possible to formulate a query that delegates parts of the query to a series of services, but one issue remains : how to automate the selection of RDF triple stores containing relevant data to answer a query. This is especially true in the context of the Linking Open data project where numerous and very heterogeneous datasets are interlinked, allowing for interesting queries across several sources. To decompose and send queries targeting only relevant stores, we need a means to describe each RDF triple store, i. E. An index structure which provides a complete and compact index items. In this thesis we present an approach to extract these graph patterns from RDF triple store. For this purpose, we extend Depth-First search coding (DFS) by (Yan and Han, 2002) to RDF labeled and oriented multigraphs and we provide a join operator between two DFS codes so as to sequentially build the different levels of the index structure. Insertion or deletion of annotations in the triple store may cause changes to the index structure. To handle update in triple store, we proposed a procedure to identify exactly the changes in the first level of the index structure and propagate them to the following levels. The DFSR coding makes it possible for us to efficiently manipulate graph patterns, but is difficult to read (succession of integer number). To facilitate the reading of our index structure, we propose a visualization user-interface and algorithms to turn a DFS code into a more legible format like RDF. Our algorithm relies on the CORESE/KGRAM by (Corby, 2008). We have tested our algorithm on many datasets. During the building f index structures we keep a set of data in order to help us to better understand the progress of our algorithm and improve it

En chémoinformatique, les molécules peuvent être décrites en retranscrivant de façon chiffrée leurs caractéristiques. Ceci permet de pouvoir comparer in silico deux molécules pour trouver de nouveaux composés potentiellement intéressants ou pour prédire leur activité. Nous avons développé des descripteurs combinant les informations structurales des composés avec leurs propriétés chimiques. Les 2D-FPTs (triplets pharmacophoriques flous bidimensionnels) se basent sur l'énumération en trois points de caractéristiques pharmacophoriques, combinée à la prise en compte des distances topologiques entre chacune de ces caractéristiques. De plus, les 2D-FPTs introduisent 2 améliorations : La projection floue des triplets d'atomes sur les triplets pharmacophoriques de base (pour mimer la tolérance naturelle des récepteurs par rapport à leurs ligands), et le marquage par pharmacophores dépendants du pKa (qui prend en compte l'équilibre protéolytique). Une nouvelle formule de calcul de similarité est introduite, qui prend en compte l'absence simultanée d'un triplet comme moins contraignante et probante qu'une présence simultanée. Le développement des triplets est détaillé, puis plusieurs applications des triplets sont étudiées. L’échantillonneur SQS (Stochastic QSAR Sampler) est utilisé pour comparer la capacité des 2D-FPTs à construire des modèles de relation structure-activité (QSAR) par rapport à d’autres descripteurs. Ensuite, les 2D-FPTs sont comparés en profondeur avec d’autres descripteurs dans des études QSAR. Enfin, ils sont utilisés pour construire des cartes auto-organisatrices afin de les utiliser pour accélérer les recherches par similarité dans une base de données
In chemoinformatics, compounds can be described by encoding their features as numeric data. This allows in silico comparisons of two molecules (ie calculating distance between two vectors) in order to discover new druglike compounds or to predict their activity. We developed our descriptors, combining structural information but also chemical properties and adding chemically-relevant improvements. The 2D-FPTs (bidimensional fuzzy tricentric pharmacophores) are based on the enumeration of 3 pharmacophoric features points, combined with the topological distances between each of these features. Furthermore, the 2D-FPTs introduce two improvements: the fuzzy mapping of molecular triplets on basis pharmacophoric triplets (this mimics the natural tolerance of receptors towards their ligands), and pKa-dependant pharmacophore flagging (which takes into account the proteolytic equilibrium). Moreover, a new similarity calculation formula is introduced, which accounts for the simultaneus absence of a triplet as a less-constraining indicator of similarity than its simultaneous presence. The fuzzy triplets development is detailed, then, several applications are studied. The SQS (Stochastic QSAR Sampler) is used to compare the ability of 2D-FPTs to build QSAR models to other descriptors. Then, the use of FPTs in QSAR studies was deeply examined and compared with existing descriptors. Finally, they are used to build self-organizing maps (SOM), in order to use the maps as an attempt to accelerate similarity searches in a database

Le biradical m-xylydene et ses derives methyles se forment par photolyse uv des derives methyles du benzene en matrice shpolskii a 5-20 k. Ces especes sont detectees par spectroscopie de fluorescence, en utilisant la technique laser de selection de site. L'energie de la premiere transition triplet-triplet ainsi determinee experimentalement est comparee a la valeur theorique deduite d'un calcul semi-empirique scf-mo avec ic. Le declin non-exponentiel de la fluorescence des biradicaux m-xylylenes est attribue a la fluorescence emise a partir de differents sous-niveaux de l'etat triplet. L'emission a partir des sous-niveaux triplets est plus rapide que la relaxation spin-reseau entre les differents sous-niveaux. Le depeuplement de deux des sous-niveaux triplets est accelere par le croisement intersysteme induit par couplage spin-orbite vers les singulets d'energie inferieure. Cette interpretation est confirmee par l'alteration importante du declin des biradicaux en presence d'un champ magnetique. L'etude de la decroissance de la composante longue du declin en fonction d'un champ faible premet de determiner le parametre d en champ nul de separation des sous-niveaux du premier triplet excite

Ginzburg-Landau theory is the phenomenological theory through which phase transitions are understood. It is within this framework that the first insights into superconductivity were obtained. More recently superconductivity in systems with no inversion symmetry has become a topic of interest. In such systems lack of inversion symmetry is believed to allow singlet and triplet order parameters to be admixed although the pairing mechanism in some cases is unclear. This thesis us.es Ginzburg-Landau theory to analyse the materials LaNiC2l LaNiGa2l Li2(PdxPtl -xhB and Mo2AhC. In the case of centrosymmetric LaNiGa2 a term coupling superconductivity to magnetism is introduced and shown to encourage the time-reversal symmetry (TRS) breaking non-unitary triplet state. In the case of Li2(PdxPtl-xhB an investigation of the nodal topologies arising from the Al irrep of the 0 group and corresponding specific heat signatures reveals a number of unique power law dependencies which can be used to detect topological transitions arising from triplet admixture in this system.

Im Niedertemperaturplasma einer Stickstoff-Hochfrequenzgasentladung werden mit Hilfe der plasmadiagnostischen Methoden LIF und OES räumliche Konzentrationsprofile der N2-Triplett-Zustände A, B und C in verschiedenen Schwingungsniveaus studiert. Dabei wird die Druckabhängigkeit im Bereich 30 bis 100 Pa und die Abhängigkeit von der Brennspannung bis 250 V untersucht. Die deutlich unterschiedlichen räumlichen Verteilungen der verschiedenen Spezies werden mit Hilfe einer Modellierung beschrieben, die sowohl Elektronenstoßanregung in der Plasmarandschicht als auch Diffusion, Stoßabregung, Kaskadenprozesse sowie Deaktivierung durch Wandstöße berücksichtigt. Dabei zeigt sich, daß vor allem Wandstöße für die räumliche Verteilung der langlebigen Spezies A(v=0,1) von zentraler Bedeutung sind. Die kurzlebigen C und B finden sich hingegen hauptsächlich in der Plasmarandschicht. Durch die Kombination der LIF mit Rayleighstreulichtexperimenten werden absolute Teilchendichten der drei Triplett-Zustände bestimmt.

Acetoacetato (AA) e 2-metilacetoacetato (MAA) são compostos β-cetoácidos acumulados em diversas desordens metabólicas como no diabetes e na isoleucinemia, respectivamente. Examinamos o mecanismo de oxidação aeróbica de AA e MAA iniciada por intermediários reativos de mioglobina de coração de cavalo (Mb) gerados pela adição de H2O2. Uma rota quimioluminescente que envolve um intermediário dioxetânico cuja termólise gera espécies α-dicarbonílicas (metilglioxal e biacetilo) foi proposta e estudada. Emissão de luz ultra fraca acompanha a reação, e sua intensidade aumenta linearmente pelo aumento da concentração tanto de Mb (10-500 µM) quando AA (10-100 mM). Estudos de consumo de oxigênio mostraram que MAA é, como esperado, quase uma ordem de grandeza mais reativo que AA. Estudos de EPR com captação de spin, utilizando MNP, possibilitaram detectar adutos de MAA atribuíveis a um radical centrado no Cα (aN = 1.55 mT) e ao radical acetila (aN = 0.83 mT). O sinal do radical acetila é totalmente suprimido por sorbato, um conhecido e eficiente supressor de espécies tripletes, o que é consistente com uma rota reacional envolvendo um intermediário dioxetânico. Clivagem-α da ligação carbonila-carbonila do produto biacetilo triplete produziria, de fato, radicais acetila. Além disso, utilizando AA como substrato para Mb/H2O2, um sinal de EPR atribuível ao aduto MNP-AA• (aN = 1.46 mT e aH = 0.34 mT) foi observado e confirmado por efeito isotópico. O consumo de oxigênio e o rendimento de compostos α-dicarbonílicos foram dose-dependentes à concentração de AA ou MAA (1-50 mM) bem como à concentração de H2O2 adicionado às misturas de reação contendo Mb (até 1:10 quando medido o consumo de oxigênio, e até 1:25 quando medido o rendimento de compostos α-dicarbonílicos) e tert-butilhidroperóxido (até 1:200). Os perfis de pH (5,8-7,8) para consumo de oxigênio e rendimento de compostos α-dicarbonílicos mostraram maiores rendimentos para baixos valores de pH, indicativo de ferrilMb formada no ciclo peroxidático da proteína. Avaliando os níveis de lesão de Mb, os β-cetoácidos diminuíram o nível de desorganização protéica na estrutura secundária e terciária elicitada por H2O2. Ainda, houve maior preservação da estrutura primária da proteína, sendo que MAA protegeu mais em comparação a AA, embora quando utilizado este último composto, foi mostrado que há acetilação dose-dependente de Mb. Acetoacetato aumentou a velocidade de descoramento da hemeproteína, provavelmente por ataque de espécies tripletes geradas no sistema. Músculos de rato, plantar e sóleo, expostos ex vivo a concentrações citotóxicas de glicose oxidase (GOX, gera H2O2 em fluxo), foram protegidas pelos ésteres etílicos AAE e MAAE. Foi detectado biacetilo no meio intracelular em músculos expostos a MAAE e GOX. A concentração deste composto α-dicarbonílico é claramente relacionada à abundância de Mb em cada um dos tipos de músculos estudados. Em resumo, Mb tratada com metabólitos β-cetoácidos (AA e MAA) gera radicais centrados em carbono e produtos α-dicarbonílicos altamente reativos no estado triplete. Experimentos realizados com tecido muscular ex vivo sugerem que esta reação possivelmente ocorra in vivo. Levantamos a hipótese de que a geração de espécies carbonílicas reativas e seus adutos em condições de desbalanço metabólico possam contribuir para a compreensão das bases moleculares de desordens cetogênicas.
Acetoacetate (AA) and 2-methylacetoacetate (MAA) are β-ketoacids accumulated in several metabolic disorders such as diabetes and isoleucinemia, respectively. Here we examine the mechanism of AA and MAA aerobic oxidation initiated by the reactive enzyme intermediates formed by the reaction of muscle horse myoglobin (Mb) with H2O2. A chemiluminescent route involving a dioxetane intermediate whose thermolysis yields triplet α-dicarbonyl species (methylglyoxal and diacetyl) is envisaged. Accordingly, the ultraweak light emission that accompanies the reaction increases linearly by raising the concentration of both Mb (10-500 µM) and AA (10- 100 mM). Oxygen uptake studies revealed that MAA is, expectedly, almost one order of magnitude more reactive than AA. EPR spin-trapping studies with MNP detected spin adducts from MAA attributable to an α-carbon-centered radical (aN = 1.55 mT) and to an acetyl radical (aN = 0.83 mT). As the acetyl radical signal is totally suppressed by sorbate, a well-known efficient triplet species quencher, the dioxetane hypothesis seems to be reliable. The α-cleavage of the carbonyl-carbonyl bond of a putative excited triplet diacetyl product would, in fact, leads to an acetyl radical. Furthermore, using AA as substrate for Mb/H2O2, an EPR signal assignable to a MNP-AA• adduct (aN = 1.46 mT and aH = 0.34 mT) was observed and confirmed by isotope effect. Oxygen consumption and α-dicarbonyl yield were also dependent on AA or MAA concentrations (1-50 mM) as well as on the concentration of peroxide added to the Mb-containing reaction mixtures: H2O2 (up to 1:10 when measuring oxygen uptake and up to 1:25 when measuring the α-dicarbonyl yield) and t-butOOH (up to 1:200). The pH profiles (5.8-7.8) of oxygen consumption and α-dicarbonyl yield show higher reaction rates at lower pHs, indicative of a ferrylMb intermediate. Evaluating Mb lesion, both β-ketoacids reduced disorganization of the secondary and tertiary protein structure elicited by H2O2. Therefore, Mb primary structure was more preserved, and MAA was more protective than AA. Moreover using the later compound, it was shown that Mb acetylation is dose-dependent. Acetoacetate increased the rate of the hemeprotein bleaching, probably due to the attack of triplet products generated in the system. Plantaris and soleous rat muscles exposed to damaging concentrations of glucose oxidase (GOX, generates H2O2 in flux), was cytoprotected by AAE and MAAE. Intracellular diacetyl was detected in muscle samples exposed to MAAE and GOX. The α-dicarbonyl concentration is clearly related to the Mb abundance in the muscle types. In summary, Mb treated with peroxides reacts with β-ketoacid metabolites (AA and MAA), yielding carbon-centered radicals and highly reactive α-dicarbonyl products in the triplet state. Experiments carried out ex vivo with muscle tissue showed that this reaction possibly occurs in vivo. A new route for generation and accumulation of carbonyl reactive species and adducts is here proposed to occur in unbalanced metabolic situations, such as is the case of ketogenic disorders.

La restauration statistique non-supervisée de signaux admet d'innombrables applications dans les domaines les plus divers comme économie, santé, traitement du signal, ... Un des problèmes de base, qui est au coeur de cette thèse, est d'estimer une séquence cachée (Xn)1:N à partir d'une séquence observée (Yn)1:N. Ces séquences sont considérées comme réalisations, respectivement, des processus (Xn)1:N et (Yn)1:N. Plusieurs techniques ont été développées pour résoudre ce problème. Le modèle parmi le plus répandu pour le traiter est le modèle dit "modèle de Markov caché" (MMC). Plusieurs extensions de ces modèles ont été proposées depuis 2000. Dans les modèles de Markov couples (MMCouples), le couple (X, Y) est markovien, ce qui implique que p(x|y) est également markovienne (alors que p(x) ne l'est plus nécessairement), ce qui permet les mêmes traitements que dans les MMC. Plus récemment (2002) les MMCouples ont été étendus aux "modèles de Markov triplet" (MMT), dans lesquels on introduit un processus auxiliaire U et suppose que le triplet T = (X, U, Y) est markovien. Là encore il est possible, dans un cadre plus général que celui des MMCouples, d'effectuer des traitements avec une complexité raisonnable. L'objectif de cette thèse est de proposer des nouvelles modélisations faisant partie des MMT et d'étudier leur pertinence et leur intérêt. Nous proposons deux types de nouveautés: (i) Lorsque la chaîne cachée est discrète et lorsque le couple (X, Y) n'est pas stationnaire, avec un nombre fini de "sauts" aléatoires dans les paramètres, l'utilisation récente des MMT dans lesquels les sauts sont modélisés par un processus discret U a donné des résultats très convaincants (Lanchantin, 2006). Notre première idée est d'utiliser cette démarche avec un processus U continu, qui modéliserait des non-stationnarités "continues" de(X, Y). Nous proposons des chaînes et des champs triplets et présentons quelques expériences. Les résultats obtenus dans la modélisation de la non-stationnarité continue semblent moins intéressants que dans le cas discret. Cependant, les nouveaux modèles peuvent présenter d'autres intérêts; en particulier, ils semblent plus efficaces que les modèles "chaînes de Markov cachées" classiques lorsque le bruit est corrélé; (ii) Soit un MMT T = (X, U, Y) tel que X et Y sont continu et U est discret fini. Nous sommes en présence du problème de filtrage, ou du lissage, avec des sauts aléatoires. Dans les modélisations classiques le couple caché (X, U) est markovien mais le couple (U, Y) ne l'est pas, ce qui est à l'origine de l'impossibilité des calculs exacts avec une complexité linéaire en temps. Il est alors nécessaire de faire appel à diverses méthodes approximatives, dont celles utilisant le filtrage particulaire sont parmi les plus utilisées. Dans des modèles MMT récents le couple caché (X, U) n'est pas nécessairement markovien, mais le couple (U, Y) l'est, ce qui permet des traitements exacts avec une complexité raisonnable (Pieczynski 2009). Notre deuxième idée est d'étendre ces derniers modèles aux triplets T = (X, U, Y) dans lesquels les couples (U, Y) sont "partiellement" de Markov. Un tel couple (U, Y) n'est pas de Markov mais U est de Markov conditionnellement àY. Nous obtenons un modèle T = (X, U, Y) plus général, qui n'est plus de Markov, dans lequel le filtrage et le lissage exacts sont possibles avec une complexité linéaire en temps. Quelques premières simulations montrent l'intérêt des nouvelles modélisations en lissage en présence des sauts.

Les systèmes hybrides supraconducteur-ferromagnétique présentent souvent de nouveaux phénomènes physiques, et pourraient également être utiles pour concevoir de nouvelles mémoires non-volatiles et haute densité pour les circuits supraconducteurs. Cette thèse étudie deux types différents d'hybrides SF, chacun suivant une approche possible de dispositif mémoire, en se focalisant sur les aspects fondamentaux. L'un porte sur l'effet de proximité dans des hétérostructures d'oxydes. Dans celles-ci, des corrélations triplet apparaissent, qui sont à la fois supraconductrices et polarisées en spin. Elles permettraient d'utiliser des effets de la spintronique comme la GMR, mais sont également très sensibles aux propriétés d'interface. Nous les avons étudiées dans des tricouches SFS d'oxydes, par des mesures de conductance. Celles-ci montrent des oscillations, en partie liées à ces états triplets. Nous observons également que les effets d'interface affectent les propriétés électroniques du ferromagnetique, en particulier lorsque cette couche est mince. Un autre genre d'interaction se produit par les champs de fuite provenant des structures de domaines. Des propositions théoriques récentes ont suggéré que de petites structures en tourbillon appelées skyrmion peuvent interagir avec la supraconductivité par ce mécanisme. Nous avons étudié ce couplage dans des bicouches, dans lesquelles les propriétés de transport sont dominées par la dynamique des vortex supraconducteurs. Nous avons vu une augmentation du courant critique en présence de skyrmions comme de domaines. Celles-ci créent également un effet Hall inhabituel dans l'état supraconducteur. La plupart de ces propriétés peuvent être expliquées qualitativement par la dynamique et le mouvement guidé des vortex
Superconductor-ferromagnet hybrid systems often bring about new physics and may as well be useful to design new non-volatile, high-density memory devices for superconducting electronics.In this thesis, we study two different types of SF hybrids, each following a possible approach to memory devices, but focusing on fundamental aspects. One is about the proximity effect in oxide heterostructures. In these, triplet correlations appear, that are both superconducting and spin-polarized. These enable using effects from spintronics like GMR, but are also very dependent on interface properties. We investigated these in SFS oxide trilayers by conductance measurements. These showed oscillations which may, in part, be related to these triplet states. We also observed that interface effects affect the electronic properties of the ferromagnet, especially when that layer is thin. Another type of interaction occurs through stray magnetic fields from the domain structures. Recent theoretical proposals suggested that small swirling spin textures called skyrmions could similarly interact with superconductivity through this mechanism. We investigated such coupling in bilayers, in which the superconducting vortex dynamics dominate the transport properties. We found that the presence of skyrmions and domains alike enhances the critical current. It also leads to an unusual Hall effect in the superconducting state. Most of these properties can be explained qualitatively in terms of vortex pinning and guided motion

Entanglement is one of the most technologically important quantum phenomena and its con-trolled creation brings us a step closer to the realisation of a quantum computer. Hybrid electron and nuclear spin systems which combine long nuclear decoherence times with the high polarisation and rapid processing times of electron spins are considered reliable candidates for the representation of the fundamental building block of a quantum computer, the qubit. In the literature electron spins quite often play the role of a mediator which can access, manipulate and couple states with long coherence times, beneficial for storing quantum information. Despite the fact that an electron spin can be a useful resource for nuclear spin systems, its permanent presence can be a source of decoherence. The use of transient photoexcited electron spins provide an additional advantage and once the operations which involve the electron spin are completed, the electron spin can decay and not interfere further with the evolution of the system. In this thesis we report magnetic resonance experiments and density functional theory calculations for the demonstration of nuclear - nuclear entanglement using photoexcited triplet states. We study homonuclear and heteronuclear fullerene derivatives and we identify in each case the relevant parameters that can lead to high fidelity entangling operations. The hyperfine interaction in a homonuclear system is the key parameter which determines the degree of entanglement between the nucelar spins according to a recent theoretical proposal. We measure and calculate the hyperfine interaction in homonuclear systems with ¹³C nuclear spins in order to prove the feasibility of this scheme. Further experiments on a fullerene system with two nuclear spins a ³¹P and a ¹H show that entangling operations of high fidelity which involve the demonstration of CNOT gates, are possible within the lifetime of the triplet state.