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

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

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

Hybrid model for vascular tree structures

This paper proposes a new representation scheme of the cerebral blood vessels. This model provides information on the semantics of the vascular structure: the topological relationships between vessels and the labeling of vascular accidents such as aneurysms and stenoses. In addition, the model keeps information of the inner surface geometry as well as of the vascular map volume properties, i.e. the tissue density, the blood flow velocity and the vessel wall elasticity. The model can be constructed automatically in a pre-process from a set of segmented MRA images. Its memory requirements are optimized on the basis of the sparseness of the vascular structure. It allows fast queries and efficient traversals and navigations. The visualizations of the vessel surface can be performed at different levels of detail. The direct rendering of the volume is fast because the model provides a natural way to skip over empty data. The paper analyzes the memory requirements of the model along with the costs of the most important operations on it.Postprint (published version

Mujeres que estudian informática y matemáticas: quiénes son y por qué son tan pocas

Cuesta encontrar estudiantes de informática que sean mujeres. En la Universidad de Barcelona, apenas son un 15 %. En el Día Internacional de las Niñas en las Tecnologías de la Información y la Comunicación, las autoras les han preguntado las razones de su elección

Testing Universality in Critical Exponents: the Case of Rainfall

One of the key clues to consider rainfall as a self-organized critical phenomenon is the existence of power-law distributions for rain-event sizes. We have studied the problem of universality in the exponents of these distributions by means of a suitable statistic whose distribution is inferred by several variations of a permutational test. In contrast to more common approaches, our procedure does not suffer from the difficulties of multiple testing and does not require the precise knowledge of the uncertainties associated to the power-law exponents. When applied to seven sites monitored by the Atmospheric Radiation Measurement Program the test lead to the rejection of the universality hypothesis, despite the fact that the exponents are rather close to each other

Diferenciació de vins de la varietat trepat : utilització de tècniques moleculars

Determinar la varietat amb la qual ha estat elaborat un vi es presenta com un aspecte interessant des del punt de vista de la traçabilitat del producte i de la detecció de fraus en el sistema de controls reglamentaris de les diferents denominacions d'origen. En el cas de la DO Conca de Barberà, on la varietat autòctona trepat i els vins elaborats a partir d'aquesta representen un símbol de reconeixement de la zona, el fet de poder autentificar l'origen varietal del producte és un dels factors de qualitat més valorats pels consumidors en la decisió d'adquirir-lo. L'obtenció i anàlisi de l'ADN procedent de possibles restes de raïm encara presents en els vins s'utilitza per a identificar la varietat amb què s'han elaborat. Això ha estat possible en el cas de vins negres, en què el contacte amb la pell durant un període més o menys llarg durant la fase de maceració permet obtenir restes d'ADN vegetal. Però en vins rosats, en què la possibilitat d'obtenir- ne és més reduïda pel menor temps de maceració, l'aplicació d'aquesta tècnica ha estat menys estudiada. El treball que es presenta demostra la utilitat d'una tècnica molecular: l'anàlisi de l'ADN mitjançant marcadors microsatèl·lits, per a la caracterització varietal de vins de la varietat trepat. S'han analitzat deu vins en rama monovarietals de trepat, sis d'elaborats a escala industrial i quatre d'elaborats a escala experimental, mitjançant vint marcadors microsatèl·lit. Els resultats obtinguts s'han comparat amb l'anàlisi de la varietat trepat a partir de material vegetal (fulla) i també amb els valors resultants de l'anàlisi de quatre vins elaborats a partir de tempranillo, garnatxa negra, monestrell i pinot negre. La identificació del trepat en vins i la diferenciació d'aquesta varietat respecte a altres varietats negres utilitzades per a elaborar vins monovarietals ha estat possible gràcies a la utilització d'aquesta tècnica molecular.Determinar la variedad con la que se ha elaborado un vino se presenta como un aspecto interesante desde el punto de vista de la trazabilidad del producto y de la detección de fraudes en el sistema de controles reglamentarios de las diferentes denominaciones de origen. En el caso de la DO Conca de Barberà, donde la variedad autóctona trepat y los vinos elaborados a partir de esta representan un símbolo de reconocimiento de la zona, el hecho de poder autentificar el origen varietal del producto es uno de los factores de calidad más valorados por los consumidores en la decisión de su adquisición. La obtención y análisis del ADN procedente de posibles restos de uva aún presentes en los vinos se utiliza para identificar la variedad con la que han sido elaborados. Esto ha sido posible en el caso de vinos tintos, en los que el contacto con el hollejo durante un periodo más o menos largo durante la fase de maceración permite obtener restos de ADN vegetal. Pero en vinos rosados, en los que la posibilidad de obtenerlo es más reducida debido al menor tiempo de maceración, la aplicación de esta técnica ha sido menos estudiada. El trabajo que se presenta demuestra la utilidad de una técnica molecular: el análisis del ADN mediante marcadores microsatélites, para la caracterización varietal de vinos de la variedad trepat. Se han analizado diez vinos en rama monovarietales de trepat, seis elaborados a escala industrial y cuatro elaborados a escala experimental mediante veinte marcadores microsatélite. Los resultados obtenidos se han comparado con el análisis de la variedad trepat a partir de material vegetal (hoja) y también con los valores resultantes del análisis de cuatro vinos elaborados a partir de tempranillo, garnacha tinta, monastrell y pinot noir. La identificación del trepat en vinos y la distinción de esta variedad respecto a otras variedades tintas utilizadas para elaborar vinos monovarietales ha sido posible gracias a la utilización de esta técnica molecular

Chatbot-Based Natural Language Interfaces for Data Visualisation: A Scoping Review

Rapid growth in the generation of data from various sources has made data visualisation a valuable tool for analysing data. However, visual analysis can be a challenging task, not only due to intricate dashboards but also when dealing with complex and multidimensional data. In this context, advances in Natural Language Processing technologies have led to the development of Visualisation-oriented Natural Language Interfaces (V-NLIs). In this paper, we carry out a scoping review that analyses synergies between the fields of Data Visualisation and Natural Language Interaction. Specifically, we focus on chatbot-based V-NLI approaches and explore and discuss three research questions. The first two research questions focus on studying how chatbot-based V-NLIs contribute to interactions with the Data and Visual Spaces of the visualisation pipeline, while the third seeks to know how chatbot-based V-NLIs enhance users' interaction with visualisations. Our findings show that the works in the literature put a strong focus on exploring tabular data with basic visualisations, with visual mapping primarily reliant on fixed layouts. Moreover, V-NLIs provide users with restricted guidance strategies, and few of them support high-level and follow-up queries. We identify challenges and possible research opportunities for the V-NLI community such as supporting high-level queries with complex data, integrating V-NLIs with more advanced systems such as Augmented Reality (AR) or Virtual Reality (VR), particularly for advanced visualisations, expanding guidance strategies beyond current limitations, adopting intelligent visual mapping techniques, and incorporating more sophisticated interaction methods