Made available in DSpace on 2014-07-29T16:02:20Z (GMT). No. of bitstreams: 1 Dissertacao Kamila - A coexistencia de quatro ciclos limite.pdf: 385468 bytes, checksum: 7bfc558e3fb5ab2755c2afa480f819c8 (MD5) Previous issue date: 2012-07-30 / In this work we study continuous, symmetric and piecewise linear vector fields on R3, we investigate the existence of limit cycles using the closing equations method. More specifically, we study a two parameters family of this vector fields and we show the coexistence of four limit cycles and too, its realization on Chua s circuit. / Neste trabalho estudamos campos vetoriais seccionalmente lineares, contínuos e simétricos, com três zonas em R3, investigamos a existência de ciclos limite utilizando o método das closing equations. Mais especificamente, estudamos uma família a dois parâmetros e mostramos a coexistência de quatro ciclos limites para esta família e também sua realização no circuito de Chua.

Kasdienis veiksmo kartojimas formos paieškų sėkmės labui tapo pagrindine darbo tema: ką daryti su vizualių bei rašytinių išraiškų kiekybe? Asmeniniai įrašai, atrinkti ir persipynę su Paul Klee, Eugene Delacroix bei Edvard Munch dienoraščių analize autorei rūpimais aspektais, įgavo „Sąsiuvinio nr. 4“ – rašto darbo formą, bylojančią apie kūrybinių procesų įtakas ir ištakas. Estampai bei savaitiniai piešiniai susivienijo kolekcijoje „Fermo“, Išvertus iš Esperanto kalbos – uždarymas, baigimas. Baigiamasis darbas – tai neišvengiamai pasikartojančių vaizdinių ir verbalių išraiškų, surinktų paskutiniųjų mokslo metų Vilniaus dailės akademijoje metu, sintezė. / The repetition of a daily action for the sake of luck in a form reaserch became the main problem of the work: what to do with the amount of visual and written expressions? Selected personal entries overlapped with Paul Klee, Eugene Delacroix and Edvard Munch diaries analysies gained a form of „Jounal nr. 4“ – a written work, pointing the interests and outflows of the working processes. The prints and weekly drawings united in a collection „Fermo“. The comlplete work is a sythesis of necesarilly repetitive pictorial and verbal expresions, collected during the last years of studies in Vilnius Academy of Arts.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Owing to its unique electronic properties, the CF₂ group has the potential to affect the conformation and polarity of molecules. The Introduction provides an overview of the conformational effects induced by the incorporation of fluorine into hydrocarbons, e.g. gauche effect, 1,3-C,F bond repulsion and angle deviation in organofluorine compounds. A summary of synthetic strategies for the introduction of the gem-difluoride motif into organic molecules is also presented. In order to explore the conformational impact of the CF₂ group in alicyclic hydrocarbon systems, cyclododecane was employed as the molecular framework. In 1,1,4,4- and 1,1,7,7- tetrafluorocyclododecanes, two CF₂ groups replaced CH₂ units within the square [3333] cyclododecane ring where the spacing enables the CF₂ groups to occupy adjacent or opposite corner locations. In the case of 1,1,6,6-tetrafluorocyclododecane, one of the CF₂ groups was forced to the edge position, which changes the ring conformation dramatically. Strategic incorporation of two CF₂ groups is shown to either stabilise or significantly alter the conformation of the cyclododecane framework, a revealing conformational preference of the CF₂ group to locate at the corner rather than the edge position of hydrocarbon rings. The study extends to larger cycloalkanes, rectangular [3434] cyclotetradecanes and square [4444] cyclohexadecanes. The target cycloalkanes bearing two CF₂ units were assembled through a novel synthetic route, employing ring-closing metathesis (RCM) as the key step. X-Ray structure analyses revealed that the CF₂ groups occupy exclusively corner locations of these rings too. The spacing between the CF₂ moieties dictates the overall ring conformations and offers a useful tool for controlling molecular arrangement. An accelerating role of the CF₂ group, relative to the CH₂ group, on the ring-closing metathesis of C5-substituted 1,8-nonadienes has also been studied. Remarkably, the CF₂ group exhibited a similar reaction rate to that observed for nonadienes bearing 1,3-dioxolane or dimethylmalonate groups. This effect was rationalised by the thermodynamic stability of the cycloheptene products, rather than a Thorpe-Ingold effect.

This thesis describes a system which is able to track the pose of a hand-held camera as it moves around a scene. The system builds a 3D map of point landmarks in the world while tracking the pose of the camera relative to this map using a process called simultaneous localisation and mapping (SLAM). To achieve real-time performance, the map must be kept sparse, but rather than observing only the mapped landmarks like previous systems, observations are made of features across the entire image. Their deviation from the predicted epipolar geometry is used to further constrain the estimated inter-frame motion and so improves the overall accuracy. The consistency of the estimation is also improved by performing the estimation in a camera-centred coordinate frame. As with any such system, tracking failure is inevitable due to occlusion or sudden motion of the camera. A relocalisation module is presented which monitors the SLAM system, detects tracking failure, and then resumes tracking as soon as the conditions have improved. This relocalisation process is achieved using a new landmark recognition algorithm which is trained on-line and provides high recall and a fast recognition time. The relocalisation module can also be used to achieve place recognition for a loop closure detection system. By taking into account both the geometry and appearance information when determining a loop closure this module is able to outperform previous loop closure detection techniques used in monocular SLAM. After recognising an overlap, the map is then corrected using a novel trajectory alignment technique that is able to cope with the inherent scale ambiguity in monocular SLAM. By incorporating all of these new techniques, the system presented can perform as a robust augmented reality system, or act as a navigation tool which could be used on a mobile robot in indoor and outdoor environments.

Thesis advisor: Vincent Cho / District leaders are under tremendous pressure to narrow disparities in achievement in an effort to close the achievement gap without tremendous guidance from policy makers, researchers or literature. Rorrer, Skrla, and Scheurich (2008) proposed a theory that district leaders enact four essential roles when engaging in systemic reform that improves achievement and equity: (1) providing instructional leadership which consists of building capacity and generating will, (2) reorienting the organization, (3) establishing policy coherence, and (4) maintaining an equity focus. This research examined the essential role of maintaining a focus on equity as a complex multiple construct. This qualitative case study explored how leaders in a Massachusetts public school district that made gains in improving achievement, attempted to maintain a focus on equity when enacting the role of instructional leadership. Drawing upon semi-structured interviews and a review of documents, this study concluded that leaders enacted the role to varying degrees in some ways that were consistent with Rorrer, et al. (2008). Data revealed that leaders attempted to address inequities through responsive leadership practices that connected with their notion of equity as it related to language, special needs, emotional wellness and poverty. Recommendations include how leaders can enact the role in a more informed, intentional, and deliberate manner through the development of Culturally Responsive Instructional Leadership. / Thesis (EdD) — Boston College, 2016. / Submitted to: Boston College. Lynch School of Education. / Discipline: Educational Leadership and Higher Education.

Student Number : 0002306V - MSc dissertation - School of Chemistry - Faculty of Science / The first part of the dissertation involves the use of ring closing metathesis (RCM) and ruthenium mediated isomerisation-RCM tandem reactions to form a wide range of nitrogencontaining benzo-fused heterocycles. Those synthesized include the 6-membered isoquinolines, the 7-membered benzazepines and the 8-membered benzazocines. In order to put these compounds into perspective, a review of selected naturally occurring nitrogencontaining benzo-fused heterocycles is included along with some of their synthetic approaches. Of major significance is our utilization of the Wits methodology allowing one to access the 6-, 7- and 8-membered ring systems from a common synthetic intermediate. The 1,2,3,6-tetrahydro-2-benzazocines were all obtained after RCM in excellent yields (82-99%). We were also able to show that some ofthe protecting groups used were easily removed and that the ring could be hydrogenated after RCM to yield the 1,2,3,4,5,6-hexahydro-2- benzazocines. The isoquinolines were synthesized in 78% and 27% yield for the Ac- and Tsprotected compounds respectively, with no product isolated for the Boc- or SO2Bn-protected compounds. These poor results, caused a change to our strategy and we then used a “combinatorial-type” approach for the synthesis of the 2,5-dihydro-1H-2-benzazepines and the 2,3-dihydro-1H-2-benzazepines with yield of 9, 47, 58 and 82% and 8, 26, 39 and 82% obtained respectively for the RCM reaction Futhermore, we attempted the synthesis of the substituted 4-phenyl isoquinolines and 5-phenyl benzazepines, but we found that the systems would not undergo RCM even at high temperatures and with large amounts of Grubbs II metathesis catalyst. A short review is given in the second part of the dissertation concerning the naturally occurring and pharmaceutically useful indenols, indenones and indanones. It further highlights how our methodology was extended to include the synthesis of 4-isopropoxy-5- methoxy-1H-inden-1-ol (X), 4-isopropoxy-5-methoxy-1H-inden-1-one (X) and 4-isopropoxy- 5-methoxy-1H-indanone (X) through the use of ruthenium-mediated isomerisation and RCM from a similar common intermediate. We have shown the synthesis of 3-substituted indenols, indenones and indanones using the same synthetic procedure, but by changing the reaction temperature during RCM. This dissertation also answers many of the questions posed during the post-doctoral work of Coyanis. Namely, we were able to support our proposed mechanism that the conversion of the unsubstituted indenol to the indenone was occurring via a dehydrogenative-oxidation, through the use of 1H NMR studies that were coupled with an ICP-MS analysis. To the best of our knowledge, this is the first reported use of the Grubbs II catalyst (or its degradation products) in a tandem RCM-oxidation procedure by our group recently.

Student Number : 0410864E - MSc dissertation - School of Chemistry - Faculty of Science / The aim of the project described in this dissertation is to explore the application of ring closing metathesis (RCM) to the synthesis of 6-, 7-, 8- and 9-membered N,N-, N,O- and O,O-benzo-fused heterocyclic compounds which are interesting structural motifs in medicinal chemistry. In recent times, their structures have been widely used as molecular scaffolds. Some of these heterocycles have been identified as antitumour agents, antibiotics and anti-HIV agents. In our laboratories, a variety of 6-, 7- and 8-membered nitrogen- and oxygen- containing benzo-fused rings have been synthesized through ruthenium-mediated isomerisation and RCM in moderate to good yields. The first step in the present project was N-protection of suitable 2-aminophenols or o-phenylenediamines followed by allylation. Rutheniummediated isomerisation followed by RCM was then used for the synthesis of the 6- membered ring system tert-butyl 4H-1,4-benzoxazine-4-carboxylate 91 and the 7- membered ring system tert-butyl 1,5-benzoxazepine-5(4H)-carboxylate 103 while only RCM was used for the 8-membered ring systems, di(tert-butyl) 2,3,4,5-tetrahydro-1,6- benzodiazocine-1,6-carboxylate 130, di(tert-butyl) 2,5-dihydro-1,6-benzodiazocine-1,6- dicarboxylate 129, 1,6-dibenzoyl-1,2,5,6-tetrahydro-1,6-benzodiazocine 132, 7-methoxy- 2,5-dihydro-1,6-benzodioxocine 137 and the 9-membered ring system 1,6-bis[(4- methylphenyl)sulfonyl]-2,5,6,7-tetrahydro-1H-1,6-benzodiazonine 159. In the synthesis of the 7-membered ring systems, based on established methodology, we encountered problems with the RCM from suitable benzylamine or benzyl alcohol precursors. The reasons for this are not clear but we suspect this could be as a result of electronic and kinetic factors. Nevertheless, we were able to synthesize a 7-membered ring system, tert-butyl 1,5-benzoxazepine-5(4H)-carboxylate 103, from a readily available precursor using a different methodology. Approaches to the synthesis of the 8-membered ring systems, di(tert-butyl) 2,3,4,5- tetrahydro-1,6-benzodiazocine-1,6-carboxylate 130, di(tert-butyl) 2,5-dihydro-1,6- benzodiazocine-1,6-dicarboxylate 129, 1,6-dibenzoyl-1,2,5,6-tetrahydro-1,6- benzodiazocine 132 and 7-methoxy-2,5-dihydro-1,6-benzodioxocine 137, as described in this dissertation, made extensive use of RCM in moderate to good yields, but the deprotection of the Boc group after hydrogenation proved to be a problem. The synthesis of the 9-membered nitrogen containing benzo-fused compounds, 1,6- bis[(4-methylphenyl)sulfonyl]-2,5,6,7-tetrahydro-1H-1,6-benzodiazonine 159 by RCM was successful but in the synthesis of the N,O-benzo-fused compound by RCM, we suspect that polymerization, which is a side reaction in RCM reactions that are slow, occurred. In the synthesis of the 9-membered O,O-benzo-fused compounds, we only isolated the starting material. The final approach in this dissertation involved the use of ruthenium-mediated isomerisation to afford internal isomerisation of the double bond within the heterocyclic rings of the 8-membered and 9-membered benzo-fused compounds previously prepared in our laboratory. This gave a mixture of regioisomers of 10-methoxy-2,3-dihydro-1,6- benzodioxocine 163 and 7-methoxy-2,3-dihydro-1,6-benzodiazocine 164, 1,6-bis[(4- Methylphenyl)sulfonyl]-1,2,3,6-tetrahydro-1,6-benzodiazocine 166, a regioisomeric mixture of 6-[(4-methylphenyl)sulfonyl]-3,6-dihydro-2H-1,6,-benzoxazocine 161 and 6-[(4-methylphenyl)sulfonyl]-5,6-dihydro-4H-1,6,-benzoxazocine 162, and the 9- membered benzo-fused ring system, 1,6-bis[(4-methylphenyl)sulfonyl]-2,3,6,7- tetrahydro-1H-1,6-benzodiazonine 170. The yields were good and the solid state structures of these isomerised compounds were examined by X-ray crystallography. Xray diffraction was also performed on the solid state 8- and 9-membered benzo-fused ring systems. We also compared the crystal structures of the 8- and 9-membered benzo-fused compounds with their isomerised compounds.

Thesis advisor: Amir H. Hoveyda / Chapter 1. The first examples of highly Z- and enantioselective ring-opening/cross-metathesis reactions are disclosed. Transformations involve meso cyclic olefin substrate and styrenes or enol ethers as olefin cross partners. A stereogenic-at-Mo monoaryloxide monopyrrolide (MAP) complex, prepared and used in situ, is discovered for the efficient formation of Z olefins. Such complex, bearing a relatively smaller adamantylimido and a larger chiral aryloxide ligand, leads to kinetic Z-selectivity due to the size differential. In most cases, the resulting disubstituted Z olefins are formed with excellent stereoselectivity (>95% Z). Chapter 2. The protocols for efficient Z-selective formation of macrocyclic disubstituted alkenes through catalytic ring-closing metathesis (RCM) is described. Stereoselective cyclizations are performed with either Mo- or W-based monoaryloxide monopyrrolide (MAP) complex at 22 oC. Synthetic utility of such broadly applicable transformation is demonstrated by synthesis of several macrocyclic natural products: relatively simpler molecules such as epilachnene (91% Z) and ambrettolide (91% Z), as well as advanced precursors to epothilones C and A (97% Z) and nakadomarin A (94% Z). Several principles of catalytic stereoselective olefin metathesis reactions are summarized based on the studies: 1) Mo-based catalysts are capable of delivering high activity but can be more prone to post-RCM isomerization. 2) W-based catalysts, though furnish lower activity, are less likely to cause the loss of kinetic Z selectivity by isomerization. 3) Reaction time is critical for retaining the stereoselectivity gained from kinetic, which not only applicable with MAP complexes but potentially with other complexes as well. 4) By using W-based catalyst, polycyclic alkenes can be accessed with sequential RCM reactions, without significant erosion of the existing Z olefins in the molecule. Chapter 3. An enantioselective total synthesis of anti-proliferative agent (+)-neopeltolide is presented. The total synthesis is accomplished in 11 steps for the longest linear sequence and 28 steps in total, including 8 catalytic reactions. Particularly, several Mo- or Ru-catalyzed stereoselective olefin metathesis reactions as well as N-hetereocyclic carbene (NHC)-catalyzed enantioselective boron conjugate addition to an acyclic enoate have proven to be effective for convergent construction of the molecule. The most important novelty of the study incorporates the explorations of feasibility of Z-selective cross-metathesis reactions to solve the challenge of installing two Z olefins with excellent selectivity. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Marc L. Snapper / Tandem processes can have several advantages over multiple single step processes. Non-metathesis transformations of ruthenium alkylidenes were studied and applied to tandem processes. Ruthenium catalyzed tandem RCM/hydroacylation that allows access to tricyclic ring systems from readily available substrates was developed. Mechanistic investigations indicated that this reaction may proceed through a mechanism involving [Ru]-H species. A Ru-catalyzed tandem RCM/olefin isomerization/C-H activation sequence that provides significant advantages in terms of rapid elaboration of simple reaction partners to more complex entities was developed. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.