Understanding cyclic seismicity and ground deformation patterns at volcanoes: intriguing lessons from Tungurahua volcano, Ecuador

Cyclic seismicity and ground deformation patterns are observed on many volcanoes worldwide where seismic swarms and the tilt of the volcanic flanks provide sensitive tools to assess the state of volcanic activity. Ground deformation at active volcanoes is often interpreted as pressure changes in a magmatic reservoir, and tilt is simply translated accordingly into inflation and deflation of such a reservoir. Tilt data recorded by an instrument in the summit area of Tungurahua volcano in Ecuador, however, show an intriguing and unexpected behaviour on several occasions: prior to a Vulcanian explosion when a pressurisation of the system would be expected, the tilt signal declines significantly, hence indicating depressurisation. At the same time, seismicity increases drastically. Envisaging that such a pattern could carry the potential to forecast Vulcanian explosions on Tungurahua, we use numerical modelling and reproduce the observed tilt patterns in both space and time. We demonstrate that the tilt signal can be more easily explained as caused by shear stress due to viscous flow resistance, rather than by pressurization of the magmatic plumbing system. In general, our numerical models prove that if magma shear viscosity and ascent rate are high enough, the resulting shear stress is sufficient to generate a tilt signal as observed on Tungurahua. Furthermore, we address the interdependence of tilt and seismicity through shear stress partitioning and suggest that a joint interpretation of tilt and seismicity can shed new light on the eruption potential of silicic volcanoes

Multidimensional Adaptive Testing with Optimal Design Criteria for Item Selection

adaptive testing, Fisher information matrix, multidimensional IRT, optimal design,

O enfoque qualitativo na avaliação do consumo alimentar: fundamentos, aplicações e considerações operacionais The qualitative approach in the evaluation of food consumption: fundamentals, applications and operational considerations

Disputas grosso modo infundadas entre defensores dos enfoques qualitativo e quantitativo têm impedido o reconhecimento dos benefícios das aplicações combinadas de ambos os métodos em um mesmo estudo, ou seja, de uma abordagem multidimensional e integrada. Não obstante, em anos recentes, o campo da Nutrição em Saúde Coletiva vem vivenciando um aumento na condução de estudos orientados não apenas pela mensuração, mas pela combinação de métodos qualitativos e quantitativos. Com efeito, o enfoque qualitativo tem muito a contribuir para a investigação do consumo alimentar, dentre vários outros objetos e temáticas, nas quais sobressai a importância do aprofundamento da compreensão da produção subjetiva, expressa em crenças, atitudes e comportamentos. Este artigo resume a natureza, os fundamentos e a utilidade do enfoque qualitativo em pesquisas no âmbito da alimentação e nutrição, esclarecendo como esses métodos têm sido ou podem ser usados para estudar os complexos problemas que se apresentam nesse campo, circunscrevendo a discussão ao âmbito dos estudos sobre consumo alimentar. A integração de ambos os métodos, qualitativo e quantitativo, mediante a complementaridade metodológica, pode minimizar os limites do emprego de cada enfoque de forma isolada.<br>Unfounded disputes between advocates of qualitative and quantitative approaches have hindered the recognition of the benefits of combined application of both methods in the same study, ie, a multidimensional and integrated approach. Nevertheless, in recent years, the field of Nutrition in Public Health has experienced an increase in conducting studies guided not only by measurement, but by the combination of qualitative and quantitative methods. Indeed, the qualitative approach has much to contribute to research in food consumption, among many other objects and themes, in which stands the importance of deepening the understanding of subjective production, expressed in beliefs, attitudes and behaviors. This paper summarizes the nature, rationale and usefulness of the qualitative research approach in Food and Nutrition, explaining how these methods have been or may be used to study the complex problems that arise in this field, limiting the discussion to the scope of the studies on food consumption. The integration of both methods, qualitative and quantitative, by the methodological complementarity, can minimize the limits of use of each approach in isolation