Integration of multimodal data based on surface registration

The paper proposes and evaluates a strategy for the alignment of anatomical and functional data of the brain. The method takes as an input two different sets of images of a same patient: MR data and SPECT. It proceeds in four steps: first, it constructs two voxel models from the two image sets; next, it extracts from the two voxel models the surfaces of regions of interest; in the third step, the surfaces are interactively aligned by corresponding pairs; finally a unique volume model is constructed by selectively applying the geometrical transformations associated to the regions and weighting their contributions. The main advantages of this strategy are (i) that it can be applied retrospectively, (ii) that it is tri-dimensional, and (iii) that it is local. Its main disadvantage with regard to previously published methods it that it requires the extraction of surfaces. However, this step is often required for other stages of the multimodal analysis such as the visualization and therefore its cost can be accounted in the global cost of the process.Postprint (published version

Rendering techniques for multimodal data

Many different direct volume rendering methods have been developed to visualize 3D scalar fields on uniform rectilinear grids. However, little work has been done on rendering simultaneously various properties of the same 3D region measured with different registration devices or at different instants of time. The demand for this type of visualization is rapidly increasing in scientific applications such as medicine in which the visual integration of multiple modalities allows a better comprehension of the anatomy and a perception of its relationships with activity. This paper presents different strategies of Direct Multimodal Volume Rendering (DMVR). It is restricted to voxel models with a known 3D rigid alignment transformation. The paper evaluates at which steps of the render-ing pipeline must the data fusion be realized in order to accomplish the desired visual integration and to provide fast re-renders when some fusion parameters are modified. In addition, it analyzes how existing monomodal visualization al-gorithms can be extended to multiple datasets and it compares their efficiency and their computational cost.Postprint (published version

Design of a multimodal rendering system

This paper addresses the rendering of aligned regular multimodal datasets. It presents a general framework of multimodal data fusion that includes several data merging methods. We also analyze the requirements of a rendering system able to provide these different fusion methods. On the basis of these requirements, we propose a novel design for a multimodal rendering system. The design has been implemented and proved showing to be efficient and flexible.Postprint (published version

A Fast hierarchical traversal strategy for multimodal visualization

In the last years there is a growing demand of multimodal medical rendering systems able to visualize simultaneously data coming from different sources. This paper addresses the Direct Volume Rendering (DVR) of aligned multimodal data in medical applications. Specifically, it proposes a hierarchical representation of the multimodal data set based on the construction of a Fusion Decision Tree (FDT) that, together with a run-length encoding of the non-empty data, provides means of efficiently accessing to the data. Three different implementations of these structures are proposed. The simulations results show that the traversal of the data is fast and that the method is suitable when interactive modifications of the fusion parameters are required.Postprint (published version

Speeding up rendering of hybrid surface and volume models

Hybrid rendering of volume and polygonal model is an interesting feature of visualization systems, since it helps users to better understand the relationships between internal structures of the volume and fitted surfaces as well as external surfaces. Most of the existing bibliography focuses at the problem of correctly integrating in depth both types of information. The rendering method proposed in this paper is built on these previous results. It is aimed at solving a different problem: how to efficiently access to selected information of a hybrid model. We propose to construct a decision tree (the Rendering Decision Tree), which together with an auxiliary run-length representation of the model avoids visiting unselected surfaces and internal regions during a traversal of the model.Postprint (published version

Luttinger parameter of quasi-one-dimensional para- H2

We have studied the ground-state properties of para-hydrogen in one dimension and in quasi-one-dimensional configurations using the path-integral ground-state Monte Carlo method. This method produces zero-temperature exact results for a given interaction and geometry. The quasi-one-dimensional setup has been implemented in two forms: the inner channel inside a carbon nanotube coated with H2 and a harmonic confinement of variable strength. Our main result is the dependence of the Luttinger parameter on the density within the stable regime. Going from one dimension to quasi-one dimension, keeping the linear density constant, produces a systematic increase of the Luttinger parameter. This increase is, however, not enough to reach the superfluid regime and the system always remain in the quasicrystal regime, according to Luttinger liquid theory.Postprint (author's final draft

NASE astronomy courses in South America

Postprint (published version

Enseñar Europa : un estímulo para la renovación de la geografía regional

El objetivo de este artículo es analizar la enseñanza de la Geografía de Europa en las universidades españolas. El trabajo pretende detectar la relación entre la práctica docente y las recientes transformaciones geopolíticas en Europa, así como la evolución de los estudios regionales en geografía. Se estudian la organización de la asignatura, el ámbito de estudio y el enfoque adoptado, así como cuáles son los temas recurrentes, ausentes y la presencia de nuevos temas. También se presta atención a los recursos bibliográficos utilizados en el proceso docente y a la opinión de los estudiantes.The aim of this article is to analyse the teaching of the Geography of Europe at Spanish universities. The study aims to detect the relationship between the practice of teaching and recent geopolitical changes in Europe, along with the evolution of regional geography studies. The organisation of the subject, the study environment and the focus adopted are all researched, along with any issues that are recurrent, absent or new. Attention is also given to the bibliographic resources used in the teaching process, as well as to students' opinion

El rol del asociacionismo de inmigrantes africanos en la construcción de cohesión social y la convivencia en Cataluña, Navarra y la Comunidad Valenciana

El objetivo de este artículo es analizar algunas posibles contribuciones de las organizaciones fundadas por personas emigradas desde el continente africano a la integración sociocultural en tres Comunidades Autó- nomas españolas. Para ello, se empieza definiendo la integración como proceso, con particular atención al papel que la literatura nacional e internacional ha otorgado al asociacionismo de inmigrantes en él. Posteriormente, se enfoca el caso particular del asociacionismo de las personas de origen africano y su incidencia en la integración en todo lo referido a la interadaptación social y cultural, según la doble mirada que encontramos en las entrevistas realizadas tanto a representantes de asociaciones de africanos como a técnicos de la Administración y representantes de entidades sociales que colaboran con aquellas asociaciones. Se trata de analizar los discursos de aquellos actores, sobre las razones de la existencia, los objetivos y las actividades de las asociaciones de africanos tanto para los propios asociados como para sus inmigrantes connacionales y para la sociedad de acogida. Los elementos de sintonía y discrepancia en las perspectivas exploradas configuran un campo de acción compartido por ambos actores, en el proceso de construcción de cohesión social y convivencia, pero al mismo tiempo sugieren la existencia de algunas limitaciones en el mismo. This article aims to analyse some possible contributions from organisations funded by immigrants from the African continent to the socio-cultural integration in three Regions in Spain. In order to do so, first there is a definition of integrations as a process, paying special attention to the role that national and international literature have given to the associations of immigrants. Afterwards, there is a focus on associations from people with an African origin, paying attention to the double view point, from one side the one from representatives from African associations and on the other, from administration technicians and representatives of social entities that collaborate with them. The point is to analyse the speech of those actors, about the reasons of its existence, the objectives and activities of the associations of Africans, for the associates themselves as well as for those immigrants from their countries and for the society that welcomes them. The elements in favour and against in the studied perspectives build an action field shared by both actors, in the process of construction of social cohesion and living partnership, but, at the same time, they suggest the existence of some limitations in itself