4 resultados para paleo drought
em Repositório Científico do Instituto Politécnico de Lisboa - Portugal
Resumo:
Quem, como nós, ainda se abisma diante da frontalidade na história do retrato pictural e fotográfico, diante da "facialidade" de certo teatro e da figuralidade não-narrativa de personagens num certo cinema "moderno", cedo ou tarde confrontar-se-á com a "nova" figuração da pessoa humana no vasto período que vai desde o paganismo da antiguidade tardia e da arte paleo-cristã à Bizâncio pós-iconoclasma: é nessa longa duração que tal frontalidade e figurabilidade se enraízam. O fenómeno centra-se no Mediterrâneo oriental e tem como turning points o édito constantiniano sobre a liberdade de culto (Milão, 313), a mudança da capital imperial para Constantinopla e a transformação desta em "nova Roma", a progressiva autarcia dos bispos romanos que passam a ser designados por "papas". Das catacumbas a Bizâncio, nasce a figuração de uma divino-humanidade que habita uma temporalidade e ecceidade novas, as da parousia cristã. É esse fenómeno que aqui nos interessa, por causa da figuralidade retratista de pintores contemporâneos como Francis Bacon, Lucian Freud ou Chuck Close, e da frontalidade em cineastas "modernos" como Bresson, Ozu, Dreyer, Godard — gente de "hoje", que fica momentaneamente fora da presente reflexão. O que a seguir se lerá é uma mera introdução, suscitada por uma urgência pedagógica, a um pequeno núcleo de questões que merecem ser projectadas na figuração moderna e contemporânea.
Resumo:
Catastrophic tsunamis are described in historical sources for all regions around the Gulf of Cadiz, at least since 60 BC. Most of the known events are associated with moderate to large earthquakes and among them the better studied is 1 November 1755. We present here a review of the events which effects, on the coasts of the Portuguese mainland and Madeira Island, are well described in historical documents or have been measured by tide gauges since the installation of these instruments. For a few we include new relevant information for the assessment of the tsunami generation or effects, and we discard events that are included in existing compilations but are not supported by quality historical sources or instrumental records. We quote the most relevant quantitative descriptions of tsunami effects on the Portuguese coast, including in all pertinent cases a critical review of the coeval sources, to establish a homogenous event list. When available, instrumental information is presented. We complement all this information with a summary of the conclusions established by paleo-tsunami research.
Resumo:
High salinity causes remarkable losses in rice productivity worldwide mainly because it inhibits growth and reduces grain yield. To cope with environmental changes, plants evolved several adaptive mechanisms, which involve the regulation of many stress-responsive genes. Among these, we have chosen OsRMC to study its transcriptional regulation in rice seedlings subjected to high salinity. Its transcription was highly induced by salt treatment and showed a stress-dose-dependent pattern. OsRMC encodes a receptor-like kinase described as a negative regulator of salt stress responses in rice. To investigate how OsRMC is regulated in response to high salinity, a salt-induced rice cDNA expression library was constructed and subsequently screened using the yeast one-hybrid system and the OsRMC promoter as bait. Thereby, two transcription factors (TFs), OsEREBP1 and OsEREBP2, belonging to the AP2/ERF family were identified. Both TFs were shown to bind to the same GCC-like DNA motif in OsRMC promoter and to negatively regulate its gene expression. The identified TFs were characterized regarding their gene expression under different abiotic stress conditions. This study revealed that OsEREBP1 transcript level is not significantly affected by salt, ABA or severe cold (5 °C) and is only slightly regulated by drought and moderate cold. On the other hand, the OsEREBP2 transcript level increased after cold, ABA, drought and high salinity treatments, indicating that OsEREBP2 may play a central role mediating the response to different abiotic stresses. Gene expression analysis in rice varieties with contrasting salt tolerance further suggests that OsEREBP2 is involved in salt stress response in rice.
Resumo:
The contribution of the evapotranspiration from a certain region to the precipitation over the same area is referred to as water recycling. In this paper, we explore the spatiotemporal links between the recycling mechanism and the Iberian rainfall regime. We use a 9 km resolution Weather Research and Forecasting simulation of 18 years (1990-2007) to compute local and regional recycling ratios over Iberia, at the monthly scale, through both an analytical and a numerical recycling model. In contrast to coastal areas, the interior of Iberia experiences a relative maximum of precipitation in spring, suggesting a prominent role of land-atmosphere interactions on the inland precipitation regime during this period of the year. Local recycling ratios are the highest in spring and early summer, coinciding with those areas where this spring peak of rainfall represents the absolute maximum in the annual cycle. This confirms that recycling processes are crucial to explain the Iberian spring precipitation, particularly over the eastern and northeastern sectors. Average monthly recycling values range from 0.04 in December to 0.14 in June according to the numerical model and from 0.03 in December to 0.07 in May according to the analytical procedure. Our analysis shows that the highest values of recycling are limited by the coexistence of two necessary mechanisms: (1) the availability of sufficient soil moisture and (2) the occurrence of appropriate synoptic configurations favoring the development of convective regimes. The analyzed surplus of rainfall in spring has a critical impact on agriculture over large semiarid regions of the interior of Iberia.