Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2015-11-11T12:04:05Z No. of bitstreams: 1 AdrianeGomesPinheiro_DISSERT.pdf: 10218634 bytes, checksum: 453d06220a02c6da49df0e0d885f5429 (MD5) / Approved for entry into archive by Elisangela Moura (lilaalves@gmail.com) on 2015-11-11T13:59:35Z (GMT) No. of bitstreams: 1 AdrianeGomesPinheiro_DISSERT.pdf: 10218634 bytes, checksum: 453d06220a02c6da49df0e0d885f5429 (MD5) / Approved for entry into archive by Elisangela Moura (lilaalves@gmail.com) on 2015-11-11T14:11:33Z (GMT) No. of bitstreams: 1 AdrianeGomesPinheiro_DISSERT.pdf: 10218634 bytes, checksum: 453d06220a02c6da49df0e0d885f5429 (MD5) / Made available in DSpace on 2015-11-11T14:27:50Z (GMT). No. of bitstreams: 1 AdrianeGomesPinheiro_DISSERT.pdf: 10218634 bytes, checksum: 453d06220a02c6da49df0e0d885f5429 (MD5) Previous issue date: 2014-03-07 / A zona de transi??o do manto est? definida por duas descontinuidades s?smicas, nominalmente a 410 e 660 km de profundidade, que resultam de transforma??es de fase no mineral olivina. A topografia dessas descontinuidades fornece informa??es sobre as varia??es laterais de temperatura da zona de transi??o. Neste trabalho, foram utilizadas convers?es P-para-S teless?smicas registradas em 32 esta??es s?smicas de banda larga na Prov?ncia Borborema para determinar a espessura da zona de transi??o abaixo desta regi?o e para investigar se h? mudan?as laterais da temperatura neste intervalo de profundidade, para isso foi feito o empilhamento e a migra??o de fun??es do receptor. Na Prov?ncia Borborema, estudos geof?sicos revelaram a exist?ncia de uma anomalia de ge?ide que poderia refletir a presen?a de uma anomalia t?rmica, a qual estaria relacionada ? origem do vulcanismo intraplaca e da epirog?nese que atingiram a Prov?ncia no Cenoz?ico. V?rios modelos t?m sido propostos para explicar esses eventos, dentre eles o modelo de pluma do manto e de eventos rasos como c?lulas de convec??o de pequena escala. Os resultados deste trabalho mostram que essa anomalia t?rmica n?o atinge a profundidade da zona de transi??o do manto, visto que n?o foram identificadas varia??es significativas na espessura da zona de transi??o. Contudo foram observadas regi?es de topografia baixa para ambas as descontinuidades (410 e 660 km) que aproximadamente se sobrep?em no espa?o, sugerindo que varia??es laterais negativa nas velocidades acima de 410 km de profundidade podem existir abaixo da Prov?ncia Borborema. O que ? consistente com a estrutura de baixa densidade que seria consequ?ncia de uma altera??o t?rmica. Portanto a fonte magm?tica que teria provocado no Cenoz?ico o vulcanismo intraplaca e estaria relacionada ao soerguimento na Prov?ncia, estaria confinada acima da zona de transi??o. / The mantle transition zone is defined by two seismic discontinuities, nominally at 410 and 660 km depth, which result from transformations in the mineral olivine. The topography of these discontinuities provides information about lateral temperature changes in the transition zone. In this work, P-to-S conversions from teleseismic events recorded at 32 broadband stations in the Borborema Province were used to determine the transition zone thickness beneath this region and to investigate whether there are lateral temperature changes within this depth range. For this analysis, stacking and migration of receiver functions was performed. In the Borborema Province, geophysical studies have revealed a geoid anomaly which could reflect the presence of a thermal anomaly related to the origin of intraplate volcanism and uplift that marked the evolution of the Province in the Cenozoic. Several models have been proposed to explain these phenomena, which include those invoking the presence of a deep-seated mantle plume and those invoking shallower sources, such as small-scale convection cells. The results of this work show that no thermal anomalies are present at transition zone depths, as significant variations in the transition zone thickness were not observed. However, regions of depressed topography for both discontinuities (410 and 660 km) that approximately overlap in space were identified, suggesting that lower-thanaverage, lateral variations in seismic velocity above 410 km depth may exist below the the Borborema Province. This is consistent with the presence of a thermally-induced, low-density body independently inferred from analysis of geoid anomalies. Therefore, the magma source responsible for the Cenozoic intraplate volcanism and related uplift in the Province, is likely to be confined above the upper mantle transition zone.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-07-06T20:38:09Z No. of bitstreams: 1 TiagoSiebertAltavini_TESE.pdf: 2131166 bytes, checksum: e6857312ffe2ac0d8a4cdc18238707e4 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-07-08T17:47:44Z (GMT) No. of bitstreams: 1 TiagoSiebertAltavini_TESE.pdf: 2131166 bytes, checksum: e6857312ffe2ac0d8a4cdc18238707e4 (MD5) / Made available in DSpace on 2016-07-08T17:47:44Z (GMT). No. of bitstreams: 1 TiagoSiebertAltavini_TESE.pdf: 2131166 bytes, checksum: e6857312ffe2ac0d8a4cdc18238707e4 (MD5) Previous issue date: 2016-01-29 / A atividade cerebral espont?nea exibe padr?es que lembram o de coativa??o de conjuntos neuronais em resposta a est?mulos ou tarefas. Estes padr?es tem sido atribu?dos a arquitetura funcional do c?rebro, e.g. conex?es de longo alcance em patches (manchas, fragmentos). N?s investigamos diretamente a contribui??o destas conex?es em patches entre hemisf?rios para mapas espont?neos e evocados na ?rea 18 pr?xima a borda 17/18 de gatos. Registramos mapas com imageamento por votage-sensitive dye (VSD) e atividade despiking enquanto manipulamos o input interhemisf?rico pela desativa??o revers?vel das ?reas correspondentes contralaterais. Durante a desativa??o os mapas espont?neos continuaram sendo gerados com frequ?ncia e qualidade semelhante ao da rede intacta, mas um vi?s de orienta??es cardinais desapareceu. Neur?nios com prefer?ncia por orienta??es horizontais (HN) ou verticais (VN), ao contr?rio dos de prefer?ncia obl?qua, diminuiram sua atividade de repouso, no entanto, HN tiveram a atividade diminu?da mesmo quando estimulados visualmente. Conclu?mos que mapas espont?neos estruturados s?o primariamente gerados por conex?es t?lamo- e/ou intracorticais. Entretanto, conex?es de longo alcance pelo corpo caloso - como um prolongamento da rede de longo alcance intracortical - contribui para um vi?s cardinal, possivelmente porque estas conex?es s?o mais fortes ou mais frequentes entre neur?nios preferindo orienta??es horizontais e/ou cardinais. Estes contornos s?o mais f?ceis de perceber e aparecem com mais frequ?ncia no ambiente natural, cone x?es de longo alcance podem prover o c?rtex visual com um grid de opera??es probabil?sticas de agrupamento em uma cena visual maior. / In the primary visual cortex, neurons with similar physiological features are clustered together in columns extending through all six cortical layers. These columns form modular orientation preference maps. Long-range lateral fibers are associated to the structure of orientation maps since they do not connect columns randomly; they rather cluster in regular intervals and interconnect predominantly columns of neurons responding to similar stimulus features. Single orientation preference maps ? the joint activation of domains preferring the same orientation - were observed to emerge spontaneously and it was speculated whether this structured ongoing activation could be caused by the underlying patchy lateral connectivity. Since long-range lateral connections share many features, i.e. clustering, orientation selectivity, with visual inter-hemispheric connections (VIC) through the corpus callosum we used the latter as a model for long-range lateral connectivity. In order to address the question of how the lateral connectivity contributes to spontaneously generated maps of one hemisphere we investigated how these maps react to the deactivation of VICs originating from the contralateral hemisphere. To this end, we performed experiments in eight adult cats. We recorded voltage-sensitive dye (VSD) imaging and electrophysiological spiking activity in one brain hemisphere while reversible deactivating the other hemisphere with a cooling technique. In order to compare ongoing activity with evoked activity patterns we first presented oriented gratings as visual stimuli. Gratings had 8 different orientations distributed equally between 0? and 180?. VSD imaged frames obtained during ongoing activity conditions were then compared to the averaged evoked single orientation maps in three different states: baseline, cooling and recovery. Kohonen self-organizing maps were also used as a means of analysis without prior assumption (like the averaged single condition maps) on ongoing activity. We also evaluated if cooling had a differential effect on evoked and ongoing spiking activity of single units. We found that deactivating VICs caused no spatial disruption on the structure of either evoked or ongoing activity maps. The frequency with which a cardinally preferring (0? or 90?) map would emerge, however, decreased significantly for ongoing but not for evoked activity. The same result was found by training self-organizing maps with recorded data as input. Spiking activity of cardinally preferring units also decreased significantly for ongoing when compared to evoked activity. Based on our results we came to the following conclusions: 1) VICs are not a determinant factor of ongoing map structure. Maps continued to be spontaneously generated with the same quality, probably by a combination of ongoing activity from local recurrent connections, thalamocortical loop and feedback connections. 2) VICs account for a cardinal bias in the temporal sequence of ongoing activity patterns, i.e. deactivating VIC decreases the probability of cardinal maps to emerge spontaneously. 3) Inter- and intrahemispheric long-range connections might serve as a grid preparing primary visual cortex for likely junctions in a larger visual environment encompassing the two hemifields.