Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Thermodynamic stabilities of eighteen cyclic C5H6 isomers were explored computationally both on singlet and triplet state potential energy surfaces (PES). All isomers have singlet ground states except for bicyclo[2.1.0]pent-5-ylidene (B5) having no stable geometry on the singlet C5H6 PES. Cyclopenta-1,3-diene (M1) is the most stable cyclic C5H6 isomer while cyclopent-1,4-diylidene is the least stable one among all. Cyclopenta-1,2-diene (M2) and cyclopentyne (M3) have biradical characters of 46.9 and 21.5%, respectively. Seven unimolecular isomerization reactions occurring among several of these molecules were investigated by DFT and ab initio methods. The conversion of bicyclo[2.1.0]pent-2-ene (B1) and tricyclo[2.1.0.02,5]-pentane (T1) into 1,3-cyclopentadiene (M1) are shown to be concerted processes whose reaction paths pass through TSs with a high degree of biradical character. The reaction enthalpies (DH0) are predicted to be -47.7 kcal/mol for B1 and -63.8 kcal/mol for T1 at UB3LYP/6-31G(d) level. The activation enthalpy (DH0&sup1 / ) for the ring opening of B1 was calculated by the CR-CCSD(T) method to be 25.2 kcal/mol, in good agreement with experiment. Furthermore, the DH0&sup1 / for the ring opening of T1 was obtained by the CR-CCSD(T) method to be 48.2 kcal/mol. The self-conversion of M1 via 1,5-hydrogen shift is a facile and concerted reaction with aromatic TS. The DH0&sup1 / estimations of B3LYP and CC methods are 25.24 and 28.78 kcal/mol, respectively. For 1,2-hydrogen shift reactions of cyclopent-3-enylidene (M4) and cyclopenten-2-ylidene (M5), the single point CC calculations predicted the DH0&sup1 / values of 3.13 and 10.12 kcal/mol, as well as, the DH0 values of -71.28 and -64.05 kcal/mol, respectively. The reason of M5 being more stable than M4 is due to the conjugation of the carbene carbon and the double bond in M5. The reaction path of cyclobutylidene methylene to cyclopentyne rearrangement is found to be rather shallow. The DH0&sup1 / and DH0 values predicted by the RCCSD(T) method to be 3.65 and -5.72 kcal/mol, respectively. Finally, triplet state isomerization of bicyclo[2.1.0]pent-5-ylidene to cyclopenta-1,2-diene, as well as, its parent reaction, cyclopropylidene to 1,2-propadiene were investigated at several levels of theory including DFT, CASSCF and CC methods. The UCCSD(T) method estimated a moderate barrier whose value is 8.12 kcal/mol for the isomerization of 3B5 with the reaction enthalpy of -44.63 kcal/mol.

URhGe has garnered interest recently as one of the few known ferromagnetic superconductors. The superconductivity in this material appears to arise from magnetic fluctuations rather than phonons, and take a triplet form which is remarkably resistant to field. In this thesis, a number of measurements on the material are presented. Some probe the Fermiology, with strong evidence appearing for a model which as both light open sheets and heavy, small, closed pockets. The open sheets, associated with chains of real-space electron density running along the b axis, dominate the conductivity in most circumstances. Evidence for their existence arises from the general large and non-saturating magnetoresistance, and from the unusual observation of negative temperature coefficient of resistance at high fields. The closed pockets have provided a few Shubnikov-de Haas oscillations, but mostly they remain inferred from the high specific heat γ and their role in the magnetism. In order to better probe the superconductivity, a high precision low noise DC resistance measurement bridge was built using a SQUID. Along with conventional measurements, this provides evidence that the two pockets of superconductivity on the phase diagram are the same phase. The re-entrance an be understood simply as a result of magnetic field being a tuning parameter, but also suppressing bulk superconductivity through orbital limiting. The SQUID bridge allowed the detection of domain wall superconductivity linking up these two pockets. The SQUID bridge was also used to study the highly structured superconducting transition in BiPd. This material lacks inversion symmetry in its crystal structure, so is a good candidate for unusual forms of superconductivity. Here again non-bulk superconductivity is considered the most likely cause for the structure. Unusual and distinctive IV curves have been measured, and a simple model of inhomogeneous conductivity channels with different critical currents is proposed as an explanation.

Huntington's disease (HD) is an autosomal dominant inherited neuro-psychiatric disease with usual onset in the middle age. The mutation, located on the short shoulder of chromosome 4, is an expansion of a nucleotide triplet, containing cytosine, adenine, guanine (CAG), with critical limit of 40+ repetitions. The principal symptoms include motor symptoms (chorea, dystonia, disorders of voluntary movements), progressive cognitive deterioration and neuropsychiatric symptoms (behaviour disorders, affective symptoms and so on). The clinical diagnosis is confirmed by a genetic test, which may also be carried out presymptomatically in offsprings of the diseased person. The objective of the 1st study consisted in the characterization of differences in psychiatric examination and neuropsychological testing among the people at risk (PAR), in whom it was recommended to delay the test, and people at risk, who were recommended to continue in the so-called predictive protocol. The total of 52 people have been examined (32 females, 20 males). In addition to the common psychiatric examination we have also administered the Eysenck Personality Questionnaire (EPQ-A), self-rating scale of general psychopathology (SCL- 90), three short cognitive tests - Trail making test, test of Verbal fluency and...

abstract: Text classification, in the artificial intelligence domain, is an activity in which text documents are automatically classified into predefined categories using machine learning techniques. An example of this is classifying uncategorized news articles into different predefined categories such as "Business", "Politics", "Education", "Technology" , etc. In this thesis, supervised machine learning approach is followed, in which a module is first trained with pre-classified training data and then class of test data is predicted. Good feature extraction is an important step in the machine learning approach and hence the main component of this text classifier is semantic triplet based features in addition to traditional features like standard keyword based features and statistical features based on shallow-parsing (such as density of POS tags and named entities). Triplet {Subject, Verb, Object} in a sentence is defined as a relation between subject and object, the relation being the predicate (verb). Triplet extraction process, is a 5 step process which takes input corpus as a web text document(s), each consisting of one or many paragraphs, from RSS feeds to lists of extremist website. Input corpus feeds into the "Pronoun Resolution" step, which uses an heuristic approach to identify the noun phrases referenced by the pronouns. The next step "SRL Parser" is a shallow semantic parser and converts the incoming pronoun resolved paragraphs into annotated predicate argument format. The output of SRL parser is processed by "Triplet Extractor" algorithm which forms the triplet in the form {Subject, Verb, Object}. Generalization and reduction of triplet features is the next step. Reduced feature representation reduces computing time, yields better discriminatory behavior and handles curse of dimensionality phenomena. For training and testing, a ten- fold cross validation approach is followed. In each round SVM classifier is trained with 90% of labeled (training) data and in the testing phase, classes of remaining 10% unlabeled (testing) data are predicted. Concluding, this paper proposes a model with semantic triplet based features for story classification. The effectiveness of the model is demonstrated against other traditional features used in the literature for text classification tasks. / Dissertation/Thesis / M.S. Computer Science 2013

Cette thèse montre en quoi la quantification de Berezin--Toeplitz peut être incorporée dans le cadre de la géométrie non commutative.Tout d'abord, nous présentons les principales notions abordées : les opérateurs de Toeplitz (classiques et généralisés), les quantifications géométrique et par déformation, ainsi que quelques outils de la géométrie non commutative.La première étape de ces travaux a été de construire des triplets spectraux (A,H,D) utilisant des algèbres d'opérateurs de Toeplitz sur les espaces de Hardy et Bergman pondérés relatifs à des ouverts Omega de Cn à bord régulier et strictement pseudoconvexes, ainsi que sur l'espace de Fock sur Cn. Nous montrons que les espaces non commutatifs induits sont réguliers et possèdent la même dimension que le domaine complexe sous-jacent. Différents opérateurs D sont aussi présentés. Le premier est l'opérateur de Dirac usuel sur L2(Rn) ramené sur le domaine par transport unitaire, d'autres sont formés à partir de l'opérateur d'extension harmonique de Poisson ou de la dérivée normale complexe sur le bord de Omega.Dans un deuxième temps, nous présentons un triplet spectral naturel de dimension n+1 construit à partir du produit star de la quantification de Berezin--Toeplitz. Les éléments de l'algèbre correspondent à des suites d'opérateurs de Toeplitz dont chacun des termes agit sur un espace de Bergman pondéré. Plus généralement, nous posons des conditions pour lesquelles une somme infinie de triplets spectraux forme de nouveau un triplet spectral, et nous en donnons un exemple. / The results of this thesis show links between the Berezin--Toeplitz quantization and noncommutative geometry.We first give an overview of the three different domains we handle: the theory of Toeplitz operators (classical and generalized), the geometric and deformation quantizations and the principal tools we use in noncommutative geometry.The first step of the study consists in giving examples of spectral triples (A,H,D) involving algebras of Toeplitz operators acting on the Hardy and weighted Bergman spaces over a smoothly bounded strictly pseudoconvex domain Omega of Cn, and also on the Fock space over Cn. It is shown that resulting noncommutative spaces are regular and of the same dimension as the complex domain. We also give and compare different classes of operator D, first by transporting the usual Dirac operator on L2(Rn) via unitaries, and then by considering the Poisson extension operator or the complex normal derivative on the boundary.Secondly, we show how the Berezin--Toeplitz star product over Omega naturally induces a spectral triple of dimension n+1 whose construction involves sequences of Toeplitz operators over weighted Bergman spaces. This result led us to study more generally to what extent a family of spectral triples can be integrated to form another spectral triple. We also provide an example of such triple.

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.

Espécies carbonílicas tripletes formadas quimicamente no escuro, por exemplo, durante a peroxidação de lipídios, têm reatividade química análoga à de radicais alcoxilas. Aventou-se que tais espécies possam estar implicadas na fisiopatologia de doenças degenerativas (\"estresse carbonílico\"). A pesquisa dos efeitos de espécies tripletes sobre algumas biomoléculas e consequentes respostas biológicas, propostas e pesquisadas no período 1970 - 1990 (hipótese de \"fotoquímica sem luz\" dos Profs. G. Cilento, IQUSP, e Emil H. White, Johns Hopkins University), encontrou empecilhos instrumentais e relativamente poucas propostas foram confirmadas. Com o uso de técnicas de alta resolução, tais como EPR, HPLC e MS, este trabalho teve como objetivo analisar intermediários e produtos de tais processos e estudar mecanismos de reação de acetona triplete, produzida quimicamente pela decomposição térmica de 3,3,4,4-tetrametildioxetano (TMD) ou, enzimaticamente, pela oxidação aeróbica de isobutanal (IBAL), catalisada por peroxidase de raiz forte (HRP), na presença de aminoácidos e proteínas. Este trabalho demonstra a formação de um radical acetila, presumidamente formado da clivagem α de acetona triplete, e um radical terciário centrado em carbono, formado pela abstração de hidrogênio do IBAL. Resultados de espectrometria de massas demonstraram a formação de três diferentes adutos entre o radical terciário de IBAL, com L-Trp. Aventou-se que um dos produtos era resultante de alteração no nitrogênio e os outros no carbono 3, ambos no anel indólico. Observou-se também a formação de produto correspondente ao radical hidroxipropionil com L-Trp. Também se observaram dois produtos de L-Trp típicos de sua oxidação por oxigênio singlete, a formilquinurenina, e um aduto de função álcool. A formação de base de Schiff entre o L-Trp estudado e o IBAL também é apresentada. A formação de oxigênio singlete foi evidenciada indiretamente via EPR utilizando o spin trap TEMP e através de um captador de adição-9,10 (tipo Diels-Alder) em derivado de antraceno. Foram realizados, também, experimentos com precursores de melanina e demonstrou-se a formação de espécies excitadas do ácido 5,6-dihidroxi-indol-2-carboxílico (DHICA) que poderiam explicar a formação de produtos de DNA tipicamente resultantes de reação fotoquímica, mas na ausência de luz. Tais resultados corroboram a reação de espécies tripletes com biomoléculas, possibilitando a compreensão de número significativo de eventos biológicos conhecidos, mas teoricamente \"proibidos\" de ocorrer no estado fundamental, em tecidos não expostos à luz / Electronically excited triplet carbonyl species formed as products of some biochemical reactions, such as lipid peroxidation, behave similarly as alcoxyl radicals. It has long been hypothesized that such excited species could have a role in some diseases (\"carbonyl stress\"). Research of chemical lesions of triplet carbonyls over biomolecules and their biological response took place principally from 1970 to 1990 (the \"photochemistry without light\" hypothesis proposed by Profs. G. Cilento, IQUSP, and Emil H. White, Johns Hopkins University), but it suffered from the lack of required instrumentation, and just few cases of photo(bio)chemistry without light were confirmed. The aim of this work, using high resolution techniques (EPR, HPLC, and MS), is to analyze the reaction products of excited triplet acetone with aminoacid and protein targets. Triplet acetone was produced from the thermal decomposition of 3,3,4,4-tetramethyldioxetane (TMD) or from the aerobic oxidation of isobutanal (IBAL) catalyzed by horseradish peroxidase (HRP). We revealed the generation of acetyl radical, putatively originated from α-cleavage of triplet acetone, and a carbon-centered tertiary radical, proposed as an IBAL radical formed by hydrogen abstraction from IBAL. Mass spectrometry showed production of three adducts from the reaction of IBAL radical with L-Trp, one of them at the nitrogen 1 and the other two at carbon 3 from the amino acid indole ring. Two adducts with m/z correspondent to the reaction between L-Trp (at carbon 3) and a hydroxypropionyl radical, and two products typically formed from singlet oxygen (formylkynurenine and an alcohol L-Trp adduct) were also observed. A Schiff base between L-Trp and IBAL was also observed. Singlet oxygen production from triplet-triplet energy transfer from excited acetone to ground state molecular oxygen was indirectly showed by EPR spin trapping with TEMP, and by MS using the anthracene derivative EAS to trap (9,10-cycloaddition) of 18O2 (1Δg). Other data reported here include the demonstration of excited species formed when DHICA, a melanin precursor, was oxidized. These results might explain the generation of DNA photochemical products (thymine dimers) in the absence of light. Altogether, we collect strong and significant evidence in this thesis that corroborate the reactivity of triplet excited species with a couple of biomolecules, providing insights over some reportedly known molecular events that are theoretically forbidden to occur in the ground state but happen in tissues non-exposed to light

The GERDA experiment searches for the neutrinoless double beta (0𝜈𝛽𝛽) decay of Ge-76. The observation of this decay would prove the Majorana character of the neutrino, i.e. that it is its own antiparticle. This would clarify the question which neutrino mass ordering is realized in nature and give a hint of the effective Majorana neutrino mass. Furthermore, the existence of the 0𝜈𝛽𝛽 decay would imply the violation of lepton number conservation which is a key feature in some theories explaining the asymmetry of matter and antimatter in the universe. The effective Majorana neutrino mass is connected with the half life of the 0𝜈𝛽𝛽 decay via a nuclear matrix element (NME), which is predicted by various theoretical models that are afflicted by large uncertainties. The accuracy of the different NMEs and their internal model assumptions can be increased by considering experimental investigations. While the NMEs for the 0𝜈𝛽𝛽 decay and the neutrino accompanied double beta (2𝜈𝛽𝛽) decay are numerically different, they rely on similar model assumptions. Thus, experimental constraints can be given by the 2𝜈𝛽𝛽 decay into the ground state, which has been already measured by GERDA with unprecedented precision for Ge-76, but also by the investigation of the 2𝜈𝛽𝛽 decay into excited states, which has not yet been observed for Ge-76. GERDA operates enriched germanium detectors in liquid argon (LAr) which serves as an additional background veto using the scintillation light that is created when energy is deposited in LAr. The signal signature of the decay into excited states can be enhanced with the application of the LAr veto, however, for that the efficiency of the LAr veto needs to be determined. One of the key parameters of the LAr efficiency is the attenuation of the scintillation light in LAr, which is dependent on the impurity composition and concentration in LAr. Therefore, the attenuation length of the scintillation light in LAr has been measured in GERDA with a dedicated setup in the course of this work. The analysis of the acquired data required intense computer simulations in order to describe the background for the measurement sufficiently. This also involved the measurement of the steel reflectivity in the visible and the UV region, where LAr scintillates. Therewith, the search for excited states has been performed in this work for the data accumulated in GERDA Phase I, Phase II and Phase II+ including the LAr veto for the latter two data sets. New limits have been set on the investigated excited states decay modes and some of the corresponding theoretical half life predictions could be disfavored, i.e. the underlying NMEs models can be constrained. The successor experiment LEGEND will continue searching for the 0𝜈𝛽𝛽 decay of Ge-76 using more germanium detectors together with an improved LAr veto. The investigation of the decay of Ge-76 into excited states will also be further pursued in LEGEND.

This thesis focuses on the possibility of using current methods in the field of computer vision to re-identify graffiti tags. The work examines the possibility of using convolutional neural networks to re-identify graffiti tags, which are the most common type of graffiti. The work experimented with various models of convolutional neural networks, the most suitable of which was MobileNet using the triplet loss function, which managed to achieve a mAP of 36.02%.