Although the organo hydride derivatives of boron and aluminum are well characterized, little work has been reported on the corresponding gallium systems. The present study was initiated to determine the relative stabilities and reactivity of organo gallium hydride derivatives as compared with the stabilities and reactions of the corresponding compounds of boron and aluminum. Various preparative routes to this new class of gallium compounds have been investigated. These include the use of organo-mercury, organo-lithium and lithium hydride derivatives in reactions with gallium hydride and gallium alkyl compounds and their halogen substituted derivatives: Me₃NGaH₃ + HgR₂ → Me₃NGaH₂R + 1/2Hg + 1/2H₂ Me₃NGaH₂Cl + LiR → Me₃NGaH₂R + LiCl Me₃NGaR₂Cl + LiH → Me₃NGaHR₂ + LiCl A fourth preparative method involves disproportionation reactions between gallium hydride compounds and organo gallium compounds to yield the mixed organo hydride derivatives. Alkyl-hydride disproportionation reactions were also examined using organo and hydride derivatives of different Group IIIB elements in order to obtain a better understanding of the exchange process. Both infrared and proton NMR spectroscopy have been used extensively in following the progress of these reactions and in the characterization of the products. / Science, Faculty of / Chemistry, Department of / Graduate

Since only one example of an asymmetric synthesis which involved an intermediate containing an optically active ligand has been reported, two questions immediately arise: "Is this type of asymmetric synthesis an isolated example, or is it a stepping stone toward a generalized trend for Co (III) which may be extended to include levo rotatory, as well as dextro rotatory molecules?" In addition, asymmetric synthesis affords a new avenue for synthesizing resolved neutral complexes.

Il existe actuellement aucune étude ayant regardé le patron de coordination de mouvement des rotations du bassin et des épaules lors de la marche sur place et en absence de vision (test de Fukuda). Cette étude descriptive vise à répondre à cette question. Les données analysées proviennent d’une collecte de données antérieure (Grostern et al., 2021) qui incluait 14 jeunes adultes en bonne santé (moyenne = 22 ans). Un système 3D de caméras infrarouges captaient leurs mouvements au niveau des épaules et du bassin pendant qu’ils faisaient leurs 5 essais du test de Fukuda. Les résultats ont démontré que : 1) tous les participants avaient une rotation horizontale des épaules ou du bassin durant le test, 2) les mouvements de rotation au niveau du bassin étaient principalement opposés à la jambe en appui lors de chaque pas, et 3) trois patrons de coordination de mouvement ont été observé : mouvement synchrone épaule-bassin (patron dominant), mouvement asynchrone et absence de mouvement de bassin. Ces nouveaux patrons de coordination serviront de base de données pour les études ultérieures sur ce sujet.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

No description available.

No description available.

Popular theories of motor learning (e.g., Adams, 1971; Schmidt, 1975) rely heavily on formation of new skills through refinements of pre-existing ones. Dynamic Pattern Theory has the advantage of being able to assess initial individual differences on the required task so that the subject becomes the important unit of measure. The general purpose was to identify the reciprocal influence of intrinsic patterns and learning a new pattern. In two experiments subjects were required to practice a rhythmic bimanual coordination task of the forearms using linear sliding devices. In the first experiment, 7 subjects practiced a 90° relative phase pattern for 45, 15 s trials on each of 6 practice days. In-phase and anti-phase trials were performed pre-and post-practice. Subjects were provided terminal feedback with a Lissajou figure after each practice trial and augmented feedback was provided after every 5th practice trial. Mean constant error (CE) for individual subject data and absolute CE (|CE|) for group data were used as measures of accuracy. Standard deviation of relative phase was used as a measure of stability (VE). Subjects were able to learn the 90° pattern and performance plateaued by the fourth practice day. Neither intrinsic pattern showed any destabilization, although a temporary decrease in accuracy (CE) within days was found. The four week retention test revealed no change for any pattern. Experiment 2 compared two groups practicing either 45° or 135° relative phase. It was predicted that the 135° relative phase pattern would be easier to learn because of the reduced competition from the less stable 180° intrinsic pattern. The procedure was similar to Experiment 1 except that subjects practiced for only four days. Performance of the practiced patterns was never as accurate as 0° and 180° but variability of performance was not different for both practiced and intrinsic patterns by Day 4. There was no difference in either accuracy or stability between the two groups on the practiced patterns. As in Experiment 1, there was no change from the last day of practice to the four week retention test. Individual subject data revealed numerous different paths to learning the required pattern. Constant error and VE values for intrinsic patterns were not particularly good predictors of ability to learn the practiced pattern. Additionally, a low VE was not indicative of a low CE or vice-versa when practicing the required pattern. The results from both experiments show that early in learning, competition biases performance away from the intrinsic attractors. Later in practice, subjects stabilize their performance of the new pattern and the intrinsic patterns do not destabilize. Differences in performance of the required pattern may have depended, not only on dynamic principles, but also on motivation, handedness, and conceptualization of the task. / Thesis / Master of Science (MSc)

No description available.

Thesis advisor: Mehmet Ekmekci / This dissertation consists of two independent essays. In the first essay, Coordination in Complex Environments, I introduce a framework to study coordination in highly uncertain environments. Coordination is an important aspect of innovative contexts, where: the more innovative a course of action, the more uncertain its outcome. To explore the interplay of coordination and informational complexity, I embed a beauty-contest game into a complex environment. I uncover a new conformity phenomenon. The new effect may push towards exploration of unknown alternatives, or constitute a status quo bias, depending on the network structure of the connections among players. In the second essay, The Extensive Margin of Bayesian Persuasion, I study the persuasion of a receiver who accesses information only if she exerts attention effort. The sender uses the information to incentivize the receiver to pay attention. I show that persuasion mechanisms are equivalent to signals. In a model of media capture, the sender finds it optimal to censor high states. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

Esse trabalho tem como foco a condição mencionada acima, nomeada como Transtorno do Desenvolvimento da Coordenação (TDC) pela AMERICAN PSYCHIATRIC ASSOCIATION DSM IV (2002) e Transtorno específico do desenvolvimento motor, pela ORGANIZAÇÃO MUNDIAL DA SAÚDE - CID-10 (1993). Foi discutido que a base da classificação usada nas pesquisas acerca desse transtorno tem como finalidade primária o diagnóstico clínico, e também apontado as conseqüências desse tipo de definição para orientação de pesquisas. A heterogeneidade das amostras de TDC utilizadas em pesquisas prévias pode ser vista como um obstáculo à própria investigação do fenômeno. Foi explorada uma possibilidade de superar esse problema através de uma abordagem diferencial, na qual se buscou diferença na capacidade de organização temporal do movimento (timing) dentro da própria população que sofre desse transtorno, na tentativa de caracterizar grupos com maior homogeneidade. Para isso 44 sujeitos, entre 9 e 11 anos, foram selecionados com base no seu desempenho do teste MABC (HENDERSON & SUGDEN, 1992), sendo 20 sujeitos com TDC e 24 normais. Esses sujeitos foram submetidos a uma bateria de tarefas de timing para caracterizá-los. As variáveis foram analisadas conjuntamente através de uma análise de clusters. O exame do coeficiente de fusão e observação do dendograma sugeriu a partição em dois clusters. Os resultados mostraram que os sujeitos uma dos clusters podem ser caracterizados com relação apenas ao timing sincronizório. As demais variáveis de timing não discriminam os dois subgrupos / The focus of this study was the condition above mentioned, named Developmental Coordination Disorder (DCD) by the AMERICAN PSYCHIATRIC ASSOCIANTION DSM IV (2002) and by WORLD HEALTH ORGANIZATION CID - 10 (1993). It was discussed that the purpose of the classification DSM IV and CID 10 is to guide the clinical diagnostic, and pointed out the implications of this criteria to orient how to select subjects in the researches. The heterogeneity of the DCD samples used in previous researches can be seen as a hindrance to investigating the problem itself. To try to overcome that obstacle, a differential approach was used, in which the difference in timing within the population who suffers that disorder was searched for, in order to characterize more homogenous groups. We selected 44 children, ranging from 9 to 11 years old, based on their performance in the MABC test (HENDERSON & SUGDEN, 1992), being 20 children with DCD and 24 without it (normal). The variables are analyzed together through a clusters analyzes. Examination of the fusion coefficients and the cluster dendogram suggested two groups. The results suggested that the DCD subjects who were grouped in each of the clusters can be characterized by their performance in the synchronic timing tasks only. The other timing variables do not discriminate the two subgroups