Deformation in volcanic areas: a numerical approach for their prediction in Teide volcano (Tenerife, Canary Islands)

[ES] El estudio de áreas volcánicas activas depende tanto de la disponibilidad de observaciones físicas de los cambios que se producen en el medio natural como de la interpretación de estos cambios. Así, hoy en día, el desarrollo y aplicación de técnicas geodésicas espaciales, como el GPS (Global Positioning System) o el InSAR (Interferometry with Synthetic Aperture Radar), proporciona una visión sin precedentes de las deformaciones en zonas volcánicas. Estas deformaciones son el reflejo de distintos procesos de origen tectónico, magmático e hidrotermal, de difícil observación y registro, que se producen en el interior del medio. En este sentido, el desarrollo de modelos para la predicción de deformaciones permite establecer un enlace directo entre los procesos observados en superficie y los que se producen en profundidad, lo que podría resultar crucial para la evaluación de riesgos volcánicos. En este trabajo, nos planteamos el desarrollo de un modelo físico para estudiar las deformaciones elásticas consecuencia de una variación de presión en el medio. Este modelo lo hemos implementado numéricamente mediante el Método de Elementos Finitos (FEM). La utilización del FEM permite considerar distintas características estructurales y morfológicas del medio así como sus heterogeneidades mecánicas. La simulación de deformaciones en Tenerife (Islas Canarias), considerando diferentes hipótesis sobre el medio, nos permite concluir que las predicciones de un modelo pueden describir de forma muy precisa cualquier conjunto de datos observacionales. Sin embargo, la exactitud de estas predicciones va a depender de las hipótesis realizadas sobre el medio.[EN] Active volcanic areas study comprises both, observation of physical changes in the natural media and the interpretation of such changes. Nowadays, the application of spatial geodetic techniques, such as GPS (Global Positioning System) or InSAR (Interferometry with Synthetic Aperture Radar), for deformation understanding in volcanic areas, revolutionizes our view of this geodetic signals. Deformation of the Earth's surface reflects tectonic, magmatic and hydrothermal processes at depth. In this way, the prediction of volcanic deformation through physical modelling provides a link between the observation and depth interior processes that could be crucial for volcanic hazards assessment. In this work, we develop a numerical model for elastic deformation study. The Finite Element Method (FEM) is used for the implementation of the numerical model. FEM allows to take into account different morphology, structural characteristics and the mechanical heterogeneities of the medium. Numerical simulations of deformation in Tenerife (Canary Islands) taking into account different medium hypothesis allow us to conclude that the accuracy of the predictions depends on how well the natural system is described.Peer reviewe

Kinetic modeling of tumor growth and dissemination in the craniospinal axis: implications for craniospinal irradiation

BACKGROUND: Medulloblastoma and other types of tumors that gain access to the cerebrospinal fluid can spread throughout the craniospinal axis. The purpose of this study was to devise a simple multi-compartment kinetic model using established tumor cell growth and treatment sensitivity parameters to model the complications of this spread as well as the impact of treatment with craniospinal radiotherapy. METHODS: A two-compartment mathematical model was constructed. Rate constants were derived from previously published work and the model used to predict outcomes for various clinical scenarios. RESULTS: The model is simple and with the use of known and estimated clinical parameters is consistent with known clinical outcomes. Treatment outcomes are critically dependent upon the duration of the treatment break and the radiosensitivity of the tumor. Cross-plot analyses serve as an estimate of likelihood of cure as a function of these and other factors. CONCLUSION: The model accurately describes known clinical outcomes for patients with medulloblastoma. It can help guide treatment decisions for radiation oncologists treating patients with this disease. Incorporation of other treatment modalities, such as chemotherapy, that enhance radiation sensitivity and/or reduce tumor burden, are predicted to significantly increase the probability of cure

Хирургическое лечение холециститов и их осложнений

ЖЕЛЧНОКАМЕННАЯ БОЛЕЗНЬЖЕЛЧНЫХ ПУТЕЙ БОЛЕЗНИПЕЧЕНИ БОЛЕЗНИХИРУРГИЯ ЖЕЛЧНЫХ ПУТЕЙХИРУРГИЯ ПЕЧЕНИХОЛЕЦИСТИТКурс лекций включает в себя 8 лекций, посвященных анатомическим сведениям о желчевыводящих путях, этиопатогенезу острого и хронического холецистита. Освещены современные методы диагностики заболевания желчевыводящих путей, приведена клиническая картина различных форм острого холецистита, включая поражения желчевыводящих путей, хирургическая тактика, способы хирургических вмешательств, ошибки в хирургии желчевыводящих путей, постхолецистэктомический синдром

Efficient inversion of three-dimensional finite element models of volcano deformation

Numerical techniques, as such as finite element method, allow for the inclusion of features, such as topography and/or mechanical heterogeneities, for the interpretation of volcanic deformation. However, models based on these numerical techniques usually are not suitable to be included in non-linear estimations of source parameters based on explorative optimization schemes because they require a calculation of the numerical approach for every evaluation of the misfit function.We present a procedure for finite element (FE) models that can be combined with explorative inversion schemes. The methodology is based on including a body force term representing an infinitesimal source in the model formulation that is responsible for pressure (volume) changes in the medium. This provides significant savings in both the time required for mesh generation and actual computational time of the numerical approach. Furthermore, we develop an inversion algorithm to estimate those parameters that characterize the changes in location and pressure (volume) of deformation sources. Both provide FE inversions in a single step, avoiding remeshing and assembly of the linear system of algebraic equations that define the numerical approach and/or the automatic mesh generation. After providing the theoretical basis for the model, the numerical approach and the algorithm for the inversions, we test the methodology using a synthetic example in a stratovolcano. Our results suggest that the FE inversion methodology can be considered suitable for efficiently save time in quantitative interpretations of volcano deformation. © The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society.Peer Reviewe

Near real-time monitoring of volcanic surface deformation from Finite Element models

Trabajo presentado en el XXV CEDYA (Congreso de Ecuaciones Diferenciales y Aplicaciones) + XV CMA (Congreso de Matemática Aplicada), celebrado en Cartagena (España), del 26 al 30 de junio de 2017Volcanic eruptions affect the society and environment around hazardous rural and urban areas. Improvement of the hazard assessment is critical for the development of a resilient and wealthy society. Nowadays, multivariate collected data and robust mathematical models at volcano observatories are becoming crucial for providing effective volcano monitoring, early warnings to civil authorities and eruption forecast. Nevertheless, the forecast of volcanic eruptions is notoriously difficult. One of the most promising methods to evaluate the volcano hazard is the use of surface ground deformation since it is a proxy of magma transport through the crust [1]. Therefore, deformation is informative of where and how much magma could be eruptible. To this end, in the last decades many developments in the field of deformation modelling and their applications have been achieved [2]. A number of mathematical models of volcano deformation can be used to infer source location, depth and volume changes. Analytical deformation models limit the problem to rough approximations of the source and media although they may be useful in applications where priority is given to the fast computation of inverse solutions. In contrast, numerical modelling allows realistic media features such as topography and crustal heterogeneities to be included although it is still very time-consuming to solve the inverse problem for the real-time monitoring purposes. Here, we present a method that can be effiently used to estimate the location and evolution of magmatic sources base on real-time surface deformation data and Finite Element models that consider realistic media features. Generally, the search for the best-fitting magmatic (point) source(s) is conducted for an array of 3-D locations extending below a predefined volume region and the Green functions for all the array components have to be pre-computed. We propose a Finite Element model for the calculation of Green functions in a mechanically heterogeneous domain which eventually will lead to better description of the status of a volcanic area. The pre-computed Green functions are reduced here to the number of observational points by using their reciprocity relationship. We present and test this methodology with an optimization method base on a Genetic Algorithm for modelling data associated with volcanic deformation. Following synthetic and sensitivity tests, we apply the improved tool for tracking magma position during the June 2007 Kilauea Volcano intrusion and eruption. We show how data inversion with numerical models can speed up the source parameters estimation for a given volcano showing signs of unrest.Research supported by CGL2014-58821-C-1-R projectPeer reviewe

Tracking Volume changes through realistic mechanical models

Trabajo presentado en GeoMod 2018, celebrado en Barcelona (España), del 1 al 4 de octubre de 2018Peer reviewe

Father’s Day Intrusion at Kilauea volcano: Tracking volume changes through realistic mechanical models

Trabajo presentado en la European Geosciences Union General Assembly, celebrada en Viena (Austria), del 8 al 13 de abril de 2018Kilauea Volcano (Hawaii, USA) is one of the most active volcanoes in the world, providing an excellent natural laboratory to study processes of basaltic magmatism. Within the last 20 years, the establisment of a dense global positioning system (GPS) network and acquisitions of satellite synthetic aperture radar (SAR) data sets provide a way to measure surface displacement on the volcano. Here, we study the subsidence at the summit caldera occurred during east rift zone dike intrusion and eruption in 2007. We use GPS and InSAR measurements of surface deformation. Understanding the magmatic system is important because measurements of surface ground deformation could be use as a proxy of magma transport through the crust. Therefore, surface deformation is informative of where and how much magma could be eruptible. Moreover, the inference process is not direct and surface deformation observations need to be coupled with mechanical numerical models. Current numerical modelling allows realistic media features such as topography and crustal heterogeneities to be included, although it is still very time-consuming to solve the inverse problem for 1) studying volcano processes or 2) even volcano monitoring purposes. At Kilauea, we apply efficient and realistic mechanical models that show how the mechanical heterogenities and topographic features of the medium could bias the deformation source depth (and therefore volume decrease). Specifically, the effect of rock rigidity around the source is taken into account to revise the depth of the active magma reservoir underneath the Kilauea’s summit caldera in 2007. In addition to show the effects of medium features at Kilauea, this work aims to show how data inversion with numerical models can speed up the source parameters estimation. The tools and methods presented in the study (efficient state-of-the-art numerical solving schemes) will allow us to gain new knowledge that can be applied to any unrest volcano by accounting for a realistic mechanical medium. This will have implications for providing effective volcano monitoring, early warnings to civil authorities and eruption forecast.Peer reviewe