5 resultados para Centre for Theoretical Studies

em Brock University, Canada


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A fluorescence excitation spectrum of formic acid monomer (HCOOH) , has been recorded in the 278-246 nm region and has been attributed to an n >7r* electron promotion in the anti conformer. The S^< S^ electronic origins of the HCOOH/HCOOD/DCOOH/DCOOD isotopomers were assigned to weak bands observed at 37431.5/37461.5/37445.5/37479.3 cm'''. From a band contour analysis of the 0°^ band of HCOOH, the rotational constants for the excited state were estimated: A'=1.8619, B'=0.4073, and C'=0.3730 cm'\ Four vibrational modes, 1/3(0=0), j/^(0-C=0) , J/g(C-H^^^) and i/,(0-H^yJ were observed in the spectrum. The activity of the antisymmetric aldehyde wagging and hydroxyl torsional modes in forming progressions is central to the analysis, leading to the conclusion that the two hydrogens are distorted from the molecular plane, 0-C=0, in the upper S. state. Ab initio calculations were performed at the 6-3 IG* SCF level using the Gaussian 86 system of programs to aid in the vibrational assignments. The computations show that the potential surface which describes the low frequency OH torsion (twisting motion) and the CH wagging (molecular inversion) motions is complex in the S^ excited electronic state. The OH and CH bonds were calculated to be twisted with respect to the 0-C=0 molecular frame by 63.66 and 4 5.76 degrees, respectively. The calculations predicted the existence of the second (syn) rotamer which is 338 cm'^ above the equilibrium configuration with OH and CH angles displaced from the plane by 47.91 and 41.32 degrees.

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The natural abundance of the N-heterocycle containing compounds has pushed the synthetic community toward the invention of new synthetic methods that result in the structural diversity of N-heterocycles. Among this, is the efficient and highly selective diamine mediated asymmetric lithiation process. Amongst the diamine chiral ligands, (-)-sparterine, which is a naturally occurring alkaloid proved to be an efficient one. Many successful, good yielding and highly selective lithiation reactions have been accomplished with the mediation by this chiral diamine base. Although, there are some examples of experimental and theoretical mechanistic studies in the literature, there is a lack of detailed understanding as to how it exactly induces the chirality. In this thesis is described a systematic investigation of how (-)-sparteine influences the stereoselectivity in the course of asymmetric lithiation reaction. This led us to the establishment of the function of A-ring’s β-CH2 effect and D-ring effect. Consequently, the importance of the A-ring and D-ring portions of (-)-sparteine in the stereoselectivity is unraveled. Another part of this thesis deals with the asymmetric lithiation of BF3-activated N,N- dimethylaminoferrocene in the presence of (1R, 2R)-N1,N2-bis(3,3-dimethylbutyl)-N1,N2-dimethylcyclohexane-1,2-diamine ( a (R,R)-TMCDA surrogate) with i-PrLi. Computational findings were in full accord with the experimental observations. Subsequently, the theoretically provided insights into the mechanism of the reaction were exploited in computational design of a new ligand. Unfortunately, the outcome of this design was not experimentally robust and an updated approach towards a successful design was explained.

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There is a body of academic literature addressing two issues of importance for leveling the playing field for all classes of investors: 1) the impact of institutional investors on liquidity; and 2) the impact of Regulation Fair Disclosure on institutional investors and liquidity. Our study addresses both issues with the purpose of attaining a better understanding and explanation of this relationship. We classify institutional ownership according to Bushee's (1998, 2001) methodology; transient institutions, dedicated institutions and quasi-indexers. Our results indicate that while transient institutions and quasi-indexers have a positive impact on liquidity, dedicated institutional ownership is negatively associated with liquidity. This result is consistent with prior theoretical studies. We also find that the effectiveness ofthe Regulation Fair Disclosure in improving liquidity is limited to firms with higher transient institutional ownership, whereas quasi-indexed institutions have not been significantly affected by the regulations. In fact, the liquidity of firms is lower for firms with higher dedicated institutional holdings, which is evidence of the "chilling effect".

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Dr. James A. Gibson was born in Ottawa on January 29, 1912 to John W. and Belle Gibson. At an early age the family moved to Victoria, B.C. where John W. Gibson was a director of the Elementary Agricultural Education Branch, Department of Education. Gibson received his early education in Victoria, receiving a B.A. (honours) at UBC in 1931. In 1931 he was awarded the Rhodes scholarship and received his B.A., M.A., B.Litt and D. Phil at New College, Oxford. This was to be the beginning of a long and dedicated relationship with the Rhodes Scholar Association. Upon his return to Canada, Dr. Gibson lectured in Economics and Government at the University of British Columbia. In 1938 he was married to Caroline Stein in Philadelphia, and the same year joined the staff of the Department of External Affairs as a Foreign Service officer. Within twenty minutes of his arrival he was seconded to the Office of the Prime Minister and Secretary of State for External Affairs, W. L. Mackenzie King in charge of War Records and Liaison Officer. This was a critical time in the history of Canada, and Dr. Gibson experienced firsthand several milestones, including the Royal Visit of King George VI and Queen Elizabeth in 1939. Dr. Gibson was present at the formation of the United Nations in San Francisco in 1945, being part of the Prime Minister’s professional staff as well as attending conferences in Washington, Quebec and London as an advisor to the Canadian delegation. Gibson contributed many articles to the publication bout de papier about his experiences during these years. After his resignation in 1947, Gibson joined the staff of the fledgling Carleton College, as a lecturer. In 1949 he was appointed a professor and in 1951 became Dean of Arts and Sciences. Dr. Gibson acted as President from 1955 to 1956 upon the sudden death of Dr. MacOdrum. In 1963 Dr. Gibson accepted the invitation of the Brock University Founders’ Committee, chaired by Arthur Schmon, to become the founding president. Dr. Gibson guided the new University from a converted refrigeration plant, to an ever expanding University campus on the brow of the Niagara Escarpment. Dr. Gibson remained firmly “attached” to Brock University. Even after official retirement, in 1974, he retained the title President Emeritus. Gibson’s final official contribution was an unpublished ten year history of the University. In retirement Gibson remained active in scholarly pursuits. He was a visiting scholar at the Center of Canadian Studies, University of Edinburgh; continued his ongoing research activities focusing on W. L. Mackenzie King, the Office of the Governor General of Canada, and political prisoners transported to Van Dieman’s Land. He remained active in the Canadian Association of Rhodes Scholars, becoming editor from 1975 to 1994 and was appointed Editor Emeritus and Director for Life in 1995 in honour of his dedicated and outstanding service. In 1993 he was awarded one of Canada’s highest achievements, the Order of Canada. Gibson retained close ties with Brock University and many of its faculty. He maintained an office in the Politics Department where he became a vital part of the department. In 1996 Brock University honoured Gibson by naming the University Library in his honour. James A. Gibson Library staff was instrumental in celebrating the 90th birthday of Gibson in 2002, with a widely attended party in the Pond Inlet where many former students, including Silver Badgers. The attendees also included former and current colleagues from Brock University, Canadian Rhodes Scholars Association, family and friends. Gibson was later to remark that the highlight of this event was the gift of his original academic robe which he had personally designed in 1964. In 2003 Dr. Gibson moved to Ottawa to be near some of his children and the city of his birth and early career. In that year “two visits to Brock ensued: the first, to attend a special celebration of the James A. Gibson Library; his late to attend the 74th Convocation on Saturday, October 18, 2003. A week later, in Ottawa, he went for a long walk, returned to his residence, Rideau Gardens, went into the lounge area, took off his coat and folded it up, put it on the back of his chair, sat down, folded his hands in his lap, closed his eyes, and died”. With sources from: Carleton University The Charlatan, Gibson CV, and Memorial Service Programme

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In Part I, theoretical derivations for Variational Monte Carlo calculations are compared with results from a numerical calculation of He; both indicate that minimization of the ratio estimate of Evar , denoted EMC ' provides different optimal variational parameters than does minimization of the variance of E MC • Similar derivations for Diffusion Monte Carlo calculations provide a theoretical justification for empirical observations made by other workers. In Part II, Importance sampling in prolate spheroidal coordinates allows Monte Carlo calculations to be made of E for the vdW molecule var He2' using a simplifying partitioning of the Hamiltonian and both an HF-SCF and an explicitly correlated wavefunction. Improvements are suggested which would permit the extension of the computational precision to the point where an estimate of the interaction energy could be made~