Search

This dissertation investigates the wide-ranging implications of a simple fact: language unfolds over time. Whether as cognitive symbols in our minds, or as their physical realization in the world, if linguistic computations are not made over transient and shifting information as it occurs, they cannot be made at all. This dissertation explores the interaction between the computations, mechanisms, and representations of language acquisition and language processing--with a central theme being the unique study of the temporal restrictions inherent to information processing that I term the "immediacy of linguistic computation". This program motivates the study of "intermediate representations" recruited during online processing and acquisition rather than simply an Input/Output mapping. While ultimately extracted from linguistic input, such intermediate representations may differ significantly from the underlying distributional signal. I demonstrate that, due to the immediacy of linguistic computation, such intermediate representations are necessary, discoverable, and offer an explanatory connection between competence (linguistic representation) and performance (psycholinguistic behavior). The dissertation is comprised of four case studies. First, I present experimental evidence from a perceptual learning paradigm that the intermediate representation of speech consists of probabilistic activation over discrete linguistic categories but includes no direct information about the original acoustic-phonetic signal. Second, I present a computational model of word learning grounded in category formation. Instead of retaining experiential statistics over words and all their potential meanings, my model constructs hypotheses for word meanings as they occur. Uses of the same word are evaluated (and revised) with respect to the learner's intermediate representation rather than to their complete distribution of experience. In the third case study, I probe predictions about the time-course, content, and structure of these intermediate representations of meaning via a new eye-tracking paradigm. Finally, the fourth case study uses large-scale corpus data to explore syntactic choices during language production. I demonstrate how a mechanistic account of production can give rise to highly "efficient" outcomes even without explicit optimization. Taken together these case studies represent a rich analysis of the immediacy of linguistic computation and its system-wide impact on the mental representations and cognitive algorithms of language. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]

The hole doped transition metal oxides show remarkable properties that are related to the influence of charge and spin correlations. In this thesis charge correlations in hole doped manganite and nickelate systems are smdied using soft (˂2 keV), normal (10 keV) and high energy x-ray scattering (100 keV).The charge and J aim-Teller (JT) order is studied in the bi-layer manganite La(_2)-(_2r) Sr(_1)+(_2x)Mn(_2)O(_7) for x = 0.5, 0.55 and 0.60 using high energy x-ray scattering. In the x = 0.55 sample the charge ordered state existed in the same checkerboard pattern as observed in the x = 0.5 sample with no change in behaviour. However, in the x = 0.6 doped sample the charge ordered state entered a new regime characterised by incommensurate JT and charge order. The magnitude of the incommensurability was inversely proportional to the intensity of the JT and charge peaks. High resolution x-ray measurements of the charge stripe order in the La(_2-x)Sr(_x)NiO(_4) system in the doping range 0.20 ≤ x ≤ 0.50 are presented. As the doping was moved away in either direction from the commensurate x = 0.33 the charge stripes changed from a highly correlated state to an increasingly disordered charge glass state. At the commensurate 0.5 composition there was no increase in the intensity or correlation of the charge order despite a significantly higher transition temperature than in the lower doped compositions. Finally the first measurements of the orbital order in La(_0.5)Sr(_1.5) MnO(_4) using soft x-ray scattering at the manganese L edges are presented. The measurements directly probe the orbital order unlike the previously reported measurements at the manganese K-edge. Energy scans were carried out on the orbital order and compared with theoretical predictions. From this it was determined that both the Jahn-Teller distortions and direct orbital ordering contribute to the observed scattering.

The anatomical organisation of projections from the ventral midbrain and the distribution of their terminals throughout the hippocampus, were studied using retrograde fluorescent-labelling and degeneration techniques. By taking advantage of the potential fluorescent properties of monoamines, the retrograde-tracing studies were extended to assess the dopamine-content of any filled cells. In vivo electrophysiological studies were also performed to characterise the events which occur in the hippocampus following stimulation of the substantia nigra or the ventral tegmental area. Pharmacological manipulations were then carried out to test for the possible involvement of certain neurotransmitters. The retrograde-tracing studies identified a projection from the ventral tegmental area to both the ventral and dorsal hippocampus. Only 5-10% of the retrogradely-filled cells were also fluorescent for dopamine, indicating the existence of a substantial non-dopaminergic projection. A pathway from the subsantia nigra was detected only by degeneration studies. Terminals, identified using the Fink-Heimer technique, were confined to the ventral hippocampus ipsilateral to the chemical lesion. The projection from the ventral tegmental area could not be detected using similar degeneration techniques. Electrical stimulation of either nucleus resulted in a profound suppression of pyramidal cell activity throughout the CA1 region of the hippocampus, but not the dentate gyrus. This inhibition was expressed bilateral to the site of midbrain stimulation, and was a long-lasting, postsynaptic event. Systemic or iontophoretic application of dopamine antagonists failed to block the inhibition, suggesting that this was mediated by a non-dopaminergic pathway. Iontopheresis of the GABA A receptor antagonist bicuculline did not block the inhibition and furthermore, flurazapam did not potentiate the effects evoked by midbrain stimulation. These observations suggest that GABA A receptors are not involved in mediating the inhibition. However, the inhibitory effects of stimulating the substantia nigra or the ventral tegmental area were abolished seven days following the intracerebroventricular injection of kainic acid. This treatment is known to destroy CA3 pyramidal cells and is believed to interfere with inhibitory interneurone function in CA1, by attenuating both GABA A and GABA B receptor-mediated events. This work substantiates previous anatomical descriptions of projections to the hippocampus from the substantia nigra and the ventral tegmental area. Bilateral, postsynaptic modulation of hippocampal pyramidal cell discharge was found to follow stimulation of either of these midbrain nuclei. The involvement of dopamine in this pathway and its role in mediating the inhibiton described is questioned, and the possible involvement of GABA B receptors is discussed.

Death and dying are emerging as substantial topics for political and social debate in contemporary UK society. The management of end of life, traditionally defined within a medical model of care, is being challenged by a cultural shift that is apparent in the changing trajectory of dying, increasing healthcare consumerism and a rising human rights rhetoric. To a significant extent, liberty to determine one’s own death, and to request assistance to die, has come to be articulated by some as a “right to die”. Human rights discourses grounded in the values of dignity and freedom of choice are important and relevant to dying in the UK. These discourses have the potential to influence law and policy, practices and public opinion on end of life. However, there is no sociological analysis of how or when rights have come to be appropriated in an end of life context and no explanation of in what way, or to what extent, social actors are using rights discourses in relation to death and dying. This research explores the centrality of human rights discourses to end of life policy and debate on assisted death in the UK. A broad social constructionist approach to rights is taken to illuminate the ways in which selected actors understand and articulate rights in an end of life context, and how, as a result of this, a right to die may be conceived. It includes the examination of: current UK law and policy documents; transcripts of the historical and contemporary House of Lords debates; a case study of a highly influential organisation (Dignity in Dying) who campaign to legalise assisted dying, and three focus group discussions with Death Café Hampstead participants. Analysis of the data reveals that rights discourses involving individual liberty, dignity and human vulnerability are central to defining the end of life debate and policy. A notion of rights at the end of life has impacted our perception of dying but in ways that are complex, and arise as a reflection of dying at a specific period in time.

The dissertation seeks to address three sets of questions: Why have the United States and France become involved in the issue of the Armenian genocide several decades after the genocide? How and why do the American and French debates have different outcomes? What conclusions can be drawn from these differences? It examines how the unresolved conflict between the competing Turkish narrative of denial and the Armenian narrative affirming the reality of the genocide has led the Armenian diaspora and the Turkish state to influence political actors in the United States and France to support their arguments for and against the reality of the genocide. This thesis focuses on the debates in the United States in 2007 and 2010 on a Congressional Resolution to recognise the genocide. It also traces the progress of French legislation from French official recognition of the genocide in 2001 to the passage of legislation to criminalise denial of the Armenian genocide in 2012, ultimately ruled unconstitutional by the French Constitutional Council. The contribution to knowledge this thesis makes is to demonstrate that recognition of genocide is a political question that involves more than the perpetrators and victims. Just as genocide does not only involve these two actors, recognition of genocide also involves other states and societies. Just as bystander states have to think about what they do when a genocide is being perpetrated when it comes to recognition they have to evaluate what to do, particularly when they have been involved from the outset.