N170 Asymmetry as an Index of Inferior Occipital Dysfunction in Patients With Symptomatic Occipital Lobe Epilepsy

Objective: Localizing epileptic foci in posterior brain epilepsy remains a difficult exercise in surgery for epilepsy evaluation. Neither clinical manifestations, neurological, EEG nor neuropsychological evaluations provide strong information about the area of onset, and fast spread of paroxysms often produces mixed features of occipital, temporal and parietal symptoms. We investigated the usefulness of the N170 event-related potential to map epileptic activity in these patients. Methods: A group of seven patients with symptomatic posterior cortex epilepsy were submitted to a high-resolution EEG (78 electrodes), with recordings of interictal spikes and face-evoked N170. Generators of spikes and N170 were localized by source analysis. Range of normal N170 asymmetry was determined in 30 healthy volunteers. Results: In 3 out of 7 patients the N170 inter-hemispheric asymmetry was outside control values. Those were the patients whose spike sources were nearest (within 3 cm) to the fusiform gyrus, while foci further away did not affect the N170 ratio. Conclusions: N170 event-related potential provides useful information about focal cortical dysfunction produced by epileptic foci located in the close neighborhood of the fusiform gyrus, but are unaffected by foci further away. Significance: The N170 evoked by faces can improve the epileptic foci localization in posterior brain epilepsy

Padrões espaciais da neve durante o verão nas áreas livres de gelo das Ilhas Shetlands do Sul (Antártida)

Os neveiros são mantos de neve, com área e espessura variáveis, que ocorrem em áreas não glaciadas e que perduram, habitualmente, durante o verão austral. Estas acumulações de neve resultam da conjugação de diversos fatores topoclimáticos e são uma importante fonte para a compreensão e análise das alterações climáticas e da sua influência na dinâmica geomorfológica (Christiansen, 1997). O clima no arquipélago das ilhas Shetland do Sul, onde a temperatura média anual ao nível do mar ronda os -2oC e, no verão as médias mensais são positivas e a precipitação é frequente, favorece a fusão estival da neve nas áreas mais baixas. É nas áreas livres de gelo, que se observam de Dezembro a Abril, numerosos neveiros, sendo que alguns se mantêm durante todo o ano. A investigação efetuada na última década na Antártida Marítima demonstrou que os neveiros são fatores importantes para a dinâmica dos ecossistemas terrestres (Bockheim et al. 2013, Guglielmin et al. 2014, Goyanes et al. 2014, Vieira et al. 2014). O objetivo deste trabalho consiste na identificação, quantificação e análise da influência dos fatores topoclimáticos na ocorrência e distribuição da neve durante o verão. Os procedimentos necessários para a concretização deste objetivo assentaram, numa fase inicial, na análise e classificação de imagens de satélite de alta resolução das penínsulas de Fildes, Barton e Weaver (Ilha King George), Byers e Hurd (ilha Livingston) e da Ilha Deception. A primeira etapa, referente à classificação das imagens de satélite, consistiu na identificação e posterior classificação de neve e na avaliação da precisão dessa mesma classificação, através de testes estatísticos. Numa segunda etapa aplicaram-se técnicas de análise espacial utilizando variáveis modeladas a partir dos modelos digitais de elevação (i.e. altimetria, declive, curvatura, radiação solar e exposição ao vento). A determinação da importância das diferentes variáveis foi assegurada pela aplicação de testes estatísticos. Esta metodologia permitiu construir modelos espaciais, recorrendo à regressão logística e ao valor informativo, com o desiderato de mapear a suscetibilidade à ocorrência de neveiros em cada uma das áreas de pormenor. Os resultados finais consistem nos mapas e modelos de suscetibilidade à de neveiros para cada local que permitem, com a sua elaboração, a identificação dos fatores que condicionam a sua ocorrência. A análise dos dados estatísticos e dos resultados dos modelos de suscetibilidade destacaram a altimetria (altitude elevada), declives (moderados a acentuados) e a exposição das vertentes (sul e sudeste) como as variáveis que, independentemente da área pormenor e do método, demonstraram maior influência na manutenção da neve no solo. O peso das restantes varia consoante o método e, sobretudo, a área pormenor. Os resultados dos métodos estatísticos, obtidos nas taxas de sucesso e predição, revelam-se próximos e bastante satisfatórios para todas as áreas pormenor à exceção da Península Barton, Weaver e ilha Deception.Snowpatches are late lying mantles of snow cover occurring outside glacier areas and that are frequently pervasive during the summer season. They normally occur as a result of various topoclimatic factors (e.g. concavities, lee effects, shadow effects, etc.) and their occurrence provides an important source of information regarding climate change and geomorphological processes induced by snow (Christiansen, 1997). The climate of the South Shetlands archipelago, with mean annual air temperatures of -2oC at sea-level and summers showing mean monthly temperatures above freezing, with frequent rainfalls, favours the development of snow free areas normally at low altitude, where snow patches are frequent from December to April, many of them showing a perennial presence. Research conducted in the previous decade in the Maritime Antarctic has shown that snow patches are very important factors for the natural system dynamics and especially for permafrost (e.g. Bockheim et al. 2013, Guglielmin et al. 2014, Goyanes et al. 2014, Vieira et al. 2014). Given this framework, the objective is identifying, quantifying and analysing the influence of topoclimatic factors on the occurrence and distribution of snow in the summer season. The research is based on the classification and analysis of high resolution multispectral remote sensing imagery from Fildes and Barton Peninsula (King George Island), Hurd and Byers Peninsula (Livingston Island) and Deception Island. The imagery is classified for snow patch detection and different classification algorithms are tested for accuracy. The second step consists on applying spatial analysis techniques using variables derived from digital elevation models (i.e. altimetry, slope, aspect, curvature, hillshade, global radiation). The influence of the different variables is assessed through exploratory statistical analysis and discussed according to local factors of each ice-free area and snow melt conditions preceding image acquisition. This approach allows the development of spatial modelling (e.g. logistical regression and informative value) aiming at mapping the probability of occurrence of snowpatches. The analysis of statistical data and the results of susceptibility models highlighted the altitude (high altitude), slopes (moderate to high) and exposure of the slopes (south and southeast) as the variables that regardless of the study area and method, demonstrated greater influence in maintaining snow on the ground. The weight of the remaining variables varies depending on the method and especially on the study area. The results of statistical methods obtained in the success and prediction rates, are close and satisfactory for all areas, except for Barton Peninsula, Weaver and Deception Island

Metabolic responses to water deficit in two Eucalyptus globulus clones with contrasting drought sensitivity

We compared the metabolic responses of leaves and roots of two Eucalyptus globulus Labill. clones differing in drought sensitivity to a slowly imposed water deficit. Responses measured included changes in concentrations of soluble and insoluble sugars, proline, total protein and several antioxidant enzymes. In addition to the general decrease in growth caused by water deficit, we observed a decrease in osmotic potential when drought stress became severe. In both clones, the decrease was greater in roots than in leaves, consistent with the observed increases in concentrations of soluble sugars and proline in these organs. In roots of both clones, glutathione reductase activity increased significantly in response towater deficit, suggesting that this enzyme plays a protective role in roots during drought stress by catalyzing the catabolism of reactive oxygen species. Clone CN5 has stress avoidance mechanisms that account for its lower sensitivity to drought compared with Clone ST51

Drought stress effects on C metabolism of sun and shade leaves of Vitis vinifera growing under field conditions

info:eu-repo/semantics/publishedVersio

Partial root-drying: Effects on gas exchange, water use efficiency and carbon isotope composition in field-grown grapevines

info:eu-repo/semantics/publishedVersio

Differences in the response of carbon assimilation to summer stress (water deficits, high light and temperature) in four Mediterranean tree species

Daily changes in photoprotective mechanisms were studied in sun leaves of Quercus suber L., Quercus ilex L., Olea europaea L. and Eucalyptus globulus Labill. trees during the summer in Portugal. Even though stomatal closure explained most of the diurnal variation in carbon assimilation along the summer, a decline in the photochemical yield of photosystem II (F(v)/'/F(m)/') also occurred, as a result of an excess of intercepted solar radiation when carbon assimilation is limited by stomatal closure due to high vapour pressure deficits and/or soil water deficits. These changes were accompanied by the conversion of violaxanthin to antheraxanthin and zeaxanthin which were correlated with thermal dissipation of excess photon energy. In spite of a common general response, differences between species were observed - Olea europaea, which is a slow-growing tree, had the lowest net photosynthetic rates, the highest proportion of carotenoids in relation to chlorophyll and the highest rates of de-epoxidation of violaxanthin. This enabled a large thermal dissipation of the excess intercepted radiation but led to rather small values of light utilisation for photochemistry (ca 20%). In contrast, in E. globulus, a fast-growing tree, photosynthetic rates were the highest, thermal dissipation of absorbed radiation the lowest and maximal values of light utilisation for photochemistry reached ca 50%. The two Quercus species exhibited an intermediate response. A high degree of co-ordination is apparent between stomatal behaviour, photosynthetic capacity and photoprotection mechanisms.Peer Reviewe