Interpolação projetual : explorando o espaço de possibilidades entre a menor complexidade e o maior desempenho

Tese de doutoramento, Belas-Artes (Design de Equipamento), Universidade de Lisboa, Faculdade de Belas-Artes, 2016

Temporal Control of Leaf Complexity by miRNA-Regulated Licensing of Protein Complexes

The tremendous diversity of leaf shapes has caught the attention of naturalists for centuries. In addition to interspecific and intraspecific differences, leaf morphologies may differ in single plants according to age, a phenomenon known as heteroblasty. In Arabidopsis thaliana, the progression from the juvenile to the adult phase is characterized by increased leaf serration. A similar trend is seen in species with more complex leaves, such as the A. thaliana relative Cardamine hirsuta, in which the number of leaflets per leaf increases with age. Although the genetic changes that led to the overall simpler leaf architecture in A. thaliana are increasingly well understood, less is known about the events underlying age-dependent changes within single plants, in either A. thaliana or C. hirsuta. Here, we describe a conserved miRNA transcription factor regulon responsible for an age-dependent increase in leaf complexity. In early leaves, miR319-targeted TCP transcription factors interfere with the function of miR164-dependent and miR164-independent CUC proteins, preventing the formation of serrations in A. thaliana and of leaflets in C. hirsuta. As plants age, accumulation of miR156-regulated SPLs acts as a timing cue that destabilizes TCP-CUC interactions. The destabilization licenses activation of CUC protein complexes and thereby the gradual increase of leaf complexity in the newly formed organs. These findings point to posttranslational interaction between unrelated miRNA-targeted transcription factors as a core feature of these regulatory circuits.

Tropical climate and vegetation simulations during the Heinrich event 1 using an Earth System Model of Intermediate Complexity (EMIC) - the University of Victoria Earth System-Climate Model (UVic ESCM)

Abrupt climate changes from 18 to 15 thousand years before present (kyr BP) associated with Heinrich Event 1 (HE1) had a strong impact on vegetation patterns not only at high latitudes of the Northern Hemisphere, but also in the tropical regions around the Atlantic Ocean. To gain a better understanding of the linkage between high and low latitudes, we used the University of Victoria (UVic) Earth System-Climate Model (ESCM) with dynamical vegetation and land surface components to simulate four scenarios of climate-vegetation interaction: the pre-industrial era, the Last Glacial Maximum (LGM), and a Heinrich-like event with two different climate backgrounds (interglacial and glacial). We calculated mega-biomes from the plant-functional types (PFTs) generated by the model to allow for a direct comparison between model results and palynological vegetation reconstructions. Our calculated mega-biomes for the pre-industrial period and the LGM corresponded well with biome reconstructions of the modern and LGM time slices, respectively, except that our pre-industrial simulation predicted the dominance of grassland in southern Europe and our LGM simulation resulted in more forest cover in tropical and sub-tropical South America. The HE1-like simulation with a glacial climate background produced sea-surface temperature patterns and enhanced inter-hemispheric thermal gradients in accordance with the "bipolar seesaw" hypothesis. We found that the cooling of the Northern Hemisphere caused a southward shift of those PFTs that are indicative of an increased desertification and a retreat of broadleaf forests in West Africa and northern South America. The mega-biomes from our HE1 simulation agreed well with paleovegetation data from tropical Africa and northern South America. Thus, according to our model-data comparison, the reconstructed vegetation changes for the tropical regions around the Atlantic Ocean were physically consistent with the remote effects of a Heinrich event under a glacial climate background.

(Table 1) Lithium contents and isotopic composition in sediments from DSDP Holes 64-477 and 64-477A

Lithium isotopic compositions of hydrothermally altered sediments of Deep Sea Drilling Project (DSDP) site 477/477A, as well as high temperature vent fluids of the Guaymas Basin, have been determined to gain an understanding of lithium exchange during fluid-sediment interaction at this sediment-covered spreading center. Unaltered turbidite of the basin has a d6Li value of -10%, 5-7% heavier than fresh oceanic basalts. Contact metamorphism induced by a shallow sill intrusion results in a decrease of the lithium content of the adjacent sediments and a lighter isotopic value (-8%). Below the sill, sediments altered by a deep-seated hydrothermal system show strong depletions in lithium, while lithium isotopic compositions vary greatly, ranging from -11 to +1%. The shift to lighter composition is the result of preferential retention of the lighter isotope in recrystallized phases after destruction of the primary minerals. The complexity of the isotope profile is attributed to inhomogeneity in mineral composition, the tortuous pathway of fluids and the temperature effect on isotopic fractionation. The range of lithium concentration and d6Li values for the vent fluids sampled in 1982 and 1985 overlaps with that of the sediment-free mid-ocean ridge systems. The lack of a distinct expression of sediment input is explained in terms of a flow-through system with continuous water recharge. The observations on the natural system agree well with the results of laboratory hydrothermal experiments. The experimental study demonstrates the importance of temperature, pressure, water/rock ratio, substrate composition and reaction time on the lithium isotopic composition of the reacted fluid. High temperature authigenic phases do not seem to constitute an important sink for lithium and sediments of a hydrothermal system such as Guaymas are a source of lithium to the ocean. The ready mobility of lithium in the sediment under elevated temperature and pressure conditions also has important implications for lithium cycling in subduction zones.