970 resultados para Primary failure of tooth eruption


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The theory of founder-effect speciation proposes that colonization by very few individuals of an empty habitat favors rapid genetic changes and the evolution of a new species. We report here the results obtained in a 10-year-long and large-scale experiment with Drosophila pseudoobscura designed to test the theory. In our experimental protocol, populations are established with variable numbers of very few individuals and allowed to expand greatly for several generations until conditions of severe competition for resources are reached and the population crashes. A few random survivors are then taken to start a new population expansion and thus initiate a new cycle of founding events, population flushes, and crashes. Our results provide no support for the theories proposing that new species are very likely to appear as by-products of founder events.

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Steam technology revolutionised maritime transport during the nineteenth century. Together with the establishment of the first regular lines, steamers soon led to the commencement of pleasure navigation. The aim of this article is to analyse the impact and scope of this process in Spain, by means of a study of the first experiences in the mid-nineteenth century. In addition to a brief introduction and final conclusions, the paper is structured around four sections. The first contains an appraisal of the situation of passenger transport. Some information is then provided regarding the first cruise in 1854. Next, the essay highlights some of the features of short excursions that were very well received by the public, especially in the island of Majorca. Finally, attention is given to a very special type of travel, the main attraction of which lay in the opportunity to witness an event of a military nature.

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Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2014

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In his reflections on the intervening century since the start of the First World War, Erwan Fouéré acknowledges that the EU has brought enormous benefits to its citizens by extending the frontiers of peace and security to include 28 member countries. At the same time, however, he warns that the voices of populism are trying to destroy its very foundations and calls upon the European Union to work much harder at showing that the integration project is both vital and necessary for continued peace and prosperity in Europe.

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Institutional integration processes in the post-Soviet area have ended in failure. It proved impossible to transform the Commonwealth of Independent States into an instrument of real co-operation, even though Russia, which was the most interested in integrating the post-Soviet space, made repeated efforts to this end. The CIS never managed to accomplish its declared objectives and, from this point of view, it does not exist as an integration organisation and de facto never did.

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Summary: Overall the monetary pillar of the EMU project has worked well so that it is incorrect to speak of a 'euro' crisis though it is at the epicentre of the present crisis. The origins of the problems it is facing have more to do with the economic component, particularly because of the breach of budgetary rules which points to a failure of politics. Hence the solution must be political, namely a strong commitment by governments to achieve balanced budgets and implement structural reforms so as to lay the basis for improved competitiveness, job creation and sustainable growth.

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If introduced successfully, national Golden Rules will completely overturn fiscal governance in the eurozone. Golden Rules would almost always be more stringent than EU-level fiscal norms. EU fiscal norms will hence evolve into a safety net in case a Golden Rule fails. The possibility of such a failure is, indeed, not to be dismissed. Because of the severity of the Golden Rules, eurozone leaders should reflect on their design. There is a real risk that they will undercut public investment, which would be at the cost of the EU’s other long-term challenges.

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Primary treatment of rectal cancer was the focus of the second St. Gallen European Organisation for Research and Treatment of Cancer (EORTC) Gastrointestinal Cancer Conference. In the context of the conference, a multidisciplinary international expert panel discussed and voted on controversial issues which could not be easily answered using published evidence. Main topics included optimal pretherapeutic imaging, indication and type of neoadjuvant treatment, and the treatment strategies in advanced tumours. Here we report the key recommendations and summarise the related evidence. The treatment strategy for localised rectal cancer varies from local excision in early tumours to neoadjuvant radiochemotherapy (RCT) in combination with extended surgery in locally advanced disease. Optimal pretherapeutic staging is a key to any treatment decision. The panel recommended magnetic resonance imaging (MRI) or MRI + endoscopic ultrasonography (EUS) as mandatory staging modalities, except for early T1 cancers with an option for local excision, where EUS in addition to MRI was considered to be most important because of its superior near-field resolution. Primary surgery with total mesorectal excision was recommended by most panellists for some early tumours with limited risk of recurrence (i.e. cT1-2 or cT3a N0 with clear mesorectal fascia on MRI and clearly above the levator muscles), whereas all other stages were considered for multimodal treatment. The consensus panel recommended long-course RCT over short-course radiotherapy for most clinical situations where neoadjuvant treatment is indicated, with the exception of T3a/b N0 tumours where short-course radiotherapy or even no neoadjuvant therapy were regarded to be an option. In patients with potentially resectable tumours and synchronous liver metastases, most panel members did not see an indication to start with classical fluoropyrimidine-based RCT but rather favoured preoperative short-course radiotherapy with systemic combination chemotherapy or alternatively a liver-first resection approach in resectable metastases, which both allow optimal systemic therapy for the metastatic disease. In general, proper patient selection and discussion in an experienced multidisciplinary team was considered as crucial component of care.

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We present three new benthic foraminiferal delta13C, delta18O, and total organic carbon time series from the eastern Atlantic sector of the Southern Ocean between 41°S and 47°S. The measured glacial delta13C values belong to the lowest hitherto reported. We demonstrate a coincidence between depleted late Holocene (LH) delta13C values and positions of sites relative to ocean surface productivity. A correction of +0.3 to +0.4 [per mil VPDB] for a productivity-induced depletion of Last Glacial Maximum (LGM) benthic delta13C values of these cores is suggested. The new data are compiled with published data from 13 sediment cores from the eastern Atlantic Ocean between 19°S and 47°S, and the regional deep and bottom water circulation is reconstructed for LH (4-0 ka) and LGM (22-16 ka) times. This extends earlier eastern Atlantic-wide synoptic reconstructions which suffered from the lack of data south of 20°S. A conceptual model of LGM deep-water circulation is discussed that, after correction of southernmost cores below the Antarctic Circumpolar Current (ACC) for a productivity-induced artifact, suggests a reduced formation of both North Atlantic Deep Water in the northern Atlantic and bottom water in the southwestern Weddell Sea. This reduction was compensated for by the formation of deep water in the zone of extended winter sea-ice coverage at the northern rim of the Weddell Sea, where air-sea gas exchange was reduced. This shift from LGM deep-water formation in the region south of the ACC to Holocene bottom water formation in the southwestern Weddell Sea, can explain lower preformed d13CDIC values of glacial circumantarctic deep water of approximately 0.3 per mil to 0.4 per mil. Our reconstruction brings Atlantic and Southern Ocean d13C and Cd/Ca data into better agreement, but is in conflict, however, with a scenario of an essentially unchanged thermohaline deep circulation on a global scale. Benthic delta18O-derived LGM bottom water temperatures, by 1.9°C and 0.3°C lower than during the LH at deepest southern and shallowest northern sites, respectively, agree with the here proposed reconstruction of deep-water circulation in the eastern South Atlantic Ocean.