Data visualization: foundations, techniques, and applications

The idea that there is no precedence for the amount of data that is being generated today, and that the need to explore and analyze this vast volumes of data has become an increasingly difficult task that could benefit from using Data visualization is presented. It is pointed that the goals of data visualization are data-driven and depend largely on the type of application, but the final objective is to convey to people information that is hidden in large volumes of data. Finally, the visualization pipeline is presented to review aspects of visualization methodology and visualization tool design, to conclude that the true potential of visualization emerge from the interaction of the user with the visualization model. The paper concludes establishing that the current processes of digital transformation will increase the need for visual analytics tools

Dust and gas emission from cometary nuclei: the case of comet 67P/Churyumov-Gerasimenko

Comets display with decreasing solar distance an increased emission of gas and dust particles, leading to the formation of the coma and tail. Spacecraft missions provide insight in the temporal and spatial variations of the dust and gas sources located on the cometary nucleus. For the case of comet 67P/Churyumov-Gerasimenko (67P/C-G), the long-term observations from the Rosetta mission point to a homogeneous dust emission across the entire illuminated surface. Despite the homogeneous initial distribution, a collimation in jet-like structures becomes visible. We propose that this observation is linked directly to the complex shape of the nucleus and projects concave topographical features into the dust coma. To test this hypothesis, we put forward a gas-dust description of 67P/C-G, where gravitational and gas forces are accurately determined from the surface mesh and the rotation of the nucleus is fully incorporated. The emerging jet-like structures persist for a wide range of gas-dust interactions and show a dust velocity dependent bending.Comment: 17 pages, with 7 figures. To appear in Advances in Physics X (2018

Bi-invariant Dissimilarity Measures for Sample Distributions in Lie Groups

Data sets sampled in Lie groups are widespread, and as with multivariate data, it is important for many applications to assess the differences between the sets in terms of their distributions. Indices for this task are usually derived by considering the Lie group as a Riemannian manifold. Then, however, compatibility with the group operation is guaranteed only if a bi-invariant metric exists, which is not the case for most non-compact and non-commutative groups. We show here that if one considers an affine connection structure instead, one obtains bi-invariant generalizations of well-known dissimilarity measures: a Hotelling $T^2$ statistic, Bhattacharyya distance and Hellinger distance. Each of the dissimilarity measures matches its multivariate counterpart for Euclidean data and is translation-invariant, so that biases, e.g., through an arbitrary choice of reference, are avoided. We further derive non-parametric two-sample tests that are bi-invariant and consistent. We demonstrate the potential of these dissimilarity measures by performing group tests on data of knee configurations and epidemiological shape data. Significant differences are revealed in both cases.Comment: An incomplete (and thus incorrect) statement in the background section on the connection of the CCS connection to Riemannian metrics was corrected. It was not used anywhere in the pape

Betriebliche Gewerkschaftsvertreter ohne Gewerkschaftsbindung? Das Paradox der zunehmend gewerkschaftlich organisierten Comités d'entreprise in Frankreich

"Der Anteil der gewerkschaftlich organisierten InteressenvertreterInnen innerhalb des Comité d'entreprise nahm in Frankreich zu Beginn der Jahre 2000 zu. Eine Stärkung des gewerkschaftlichen Einflusses in französischen Betrieben kann daraus jedoch nur bedingt abgeleitet werden. Dieser Beitrag stellt die Ergebnisse einer empirischen Untersuchung vor, die vor allem in Klein- und Mittelbetrieben durchgeführt wurde. Vertretungspraxis und Gewerkschaftsbindung neu organisierter Comités d'entreprise werden beschrieben und mit den Praktiken langjährig organisierter bzw. unorganisierter Vertreterkollektive verglichen. Anschließend wird nach den Verschiebungen im Beziehungsgeflecht der Akteure gefragt, die parallel zur Tendenz zur Instrumentalisierung des Gewerkschaftsbezugs und Lokalisierung des Vertretungsanspruchs zu beobachten sind. Es zeigt sich, dass viele neu organisierten Comités d'entreprise äußerst fragile Beziehungen zu ihren Gewerkschaften unterhalten; die Bindung traditionell organisierter Vertreterkollektive zu ihren Dachverbänden nimmt ab. Lokale Identität erweist sich oft als prägnanter als gewerkschaftliche Identität. Vor diesem Hintergrund verwischen sich die Unterschiede zwischen gewerkschaftlich organisierten und gewerkschaftsfreien Gremien." (Autorenreferat)"The share of unionized representatives increased in the workplace elections for the French Comité d'entreprise at the beginning of the new century. A case study research conducted in mostly small and medium enterprises suggests that the increase in votes does not necessarily mean stronger union influence in French workplaces. The paper describes representative practices and union links in newly unionized Comités d'entreprise comparing them with historically organized and unorganized committees. It then discusses changes in the relationships between the actors which appear simultaneously with the tendency to instrumentalize unionization and to localize representative claims. Newly unionized committees often maintain fragile links with their unions, whereas their historically unionized counterparts distance themselves from their confederations. Often, local identities prove to be stronger than union identities. In this context, differences between union and non-union representation become blurred." (author's abstract

Exploring cavity dynamics in biomolecular systems

Background The internal cavities of proteins are dynamic structures and their dynamics may be associated with conformational changes which are required for the functioning of the protein. In order to study the dynamics of these internal protein cavities, appropriate tools are required that allow rapid identification of the cavities as well as assessment of their time-dependent structures. Results In this paper, we present such a tool and give results that illustrate the applicability for the analysis of molecular dynamics trajectories. Our algorithm consists of a pre-processing step where the structure of the cavity is computed from the Voronoi diagram of the van der Waals spheres based on coordinate sets from the molecular dynamics trajectory. The pre-processing step is followed by an interactive stage, where the user can compute, select and visualize the dynamic cavities. Importantly, the tool we discuss here allows the user to analyze the time-dependent changes of the components of the cavity structure. An overview of the cavity dynamics is derived by rendering the dynamic cavities in a single image that gives the cavity surface colored according to its time-dependent dynamics. Conclusion The Voronoi-based approach used here enables the user to perform accurate computations of the geometry of the internal cavities in biomolecules. For the first time, it is possible to compute dynamic molecular paths that have a user-defined minimum constriction size. To illustrate the usefulness of the tool for understanding protein dynamics, we probe the dynamic structure of internal cavities in the bacteriorhodopsin proton pump