Recursive Estimation of Orientation Based on the Bingham Distribution

Directional estimation is a common problem in many tracking applications. Traditional filters such as the Kalman filter perform poorly because they fail to take the periodic nature of the problem into account. We present a recursive filter for directional data based on the Bingham distribution in two dimensions. The proposed filter can be applied to circular filtering problems with 180 degree symmetry, i.e., rotations by 180 degrees cannot be distinguished. It is easily implemented using standard numerical techniques and suitable for real-time applications. The presented approach is extensible to quaternions, which allow tracking arbitrary three-dimensional orientations. We evaluate our filter in a challenging scenario and compare it to a traditional Kalman filtering approach

Cell death in allergic diseases

Apoptosis, the most common form of cell death, is a key mechanism in the build up and maintenance of both innate and adaptive immunity. Central to the apoptotic process is a family of intracellular cysteine proteases with aspartate-specificity, called caspases. Caspases are counter-regulated by multiple anti-apoptotic molecules, and the expression of the latter in leukocytes is largely dependent on survival factors. Therefore, the physiologic rates of apoptosis change under pathologic conditions. For instance, in inflammation, the expression of survival factors is usually elevated, resulting in increased cell survival and consequently in the accumulation of the involved immune cells. In many allergic diseases, eosinophil apoptosis is delayed contributing to both blood and tissue eosinophilia. Besides eosinophils, apoptosis of other leukocytes is also frequently prevented or delayed during allergic inflammatory processes. In contrast to inflammatory cells, accelerated cell death is often observed in epithelial cells, a mechanism, which amplifies or at least maintains allergic inflammation. In conclusion, deregulated cell death is a common phenomenon of allergic diseases that likely plays an important role in their pathogenesis. Whether the apoptosis is too little or too much depends on the cell type. In this review, we discuss the regulation of the lifespan of the participating leukocytes in allergic inflammatory response

Ideological and Temporal Components of Network Polarization in Online Political Participatory Media

Political polarization is traditionally analyzed through the ideological stances of groups and parties, but it also has a behavioral component that manifests in the interactions between individuals. We present an empirical analysis of the digital traces of politicians in politnetz.ch, a Swiss online platform focused on political activity, in which politicians interact by creating support links, comments, and likes. We analyze network polarization as the level of intra- party cohesion with respect to inter-party connectivity, finding that supports show a very strongly polarized structure with respect to party alignment. The analysis of this multiplex network shows that each layer of interaction contains relevant information, where comment groups follow topics related to Swiss politics. Our analysis reveals that polarization in the layer of likes evolves in time, increasing close to the federal elections of 2011. Furthermore, we analyze the internal social network of each party through metrics related to hierarchical structures, information efficiency, and social resilience. Our results suggest that the online social structure of a party is related to its ideology, and reveal that the degree of connectivity across two parties increases when they are close in the ideological space of a multi-party system.Comment: 35 pages, 11 figures, Internet, Policy & Politics Conference, University of Oxford, Oxford, UK, 25-26 September 201

Unscented Orientation Estimation Based on the Bingham Distribution

Orientation estimation for 3D objects is a common problem that is usually tackled with traditional nonlinear filtering techniques such as the extended Kalman filter (EKF) or the unscented Kalman filter (UKF). Most of these techniques assume Gaussian distributions to account for system noise and uncertain measurements. This distributional assumption does not consider the periodic nature of pose and orientation uncertainty. We propose a filter that considers the periodicity of the orientation estimation problem in its distributional assumption. This is achieved by making use of the Bingham distribution, which is defined on the hypersphere and thus inherently more suitable to periodic problems. Furthermore, handling of non-trivial system functions is done using deterministic sampling in an efficient way. A deterministic sampling scheme reminiscent of the UKF is proposed for the nonlinear manifold of orientations. It is the first deterministic sampling scheme that truly reflects the nonlinear manifold of the orientation

Gradient dynamics model for drops spreading on polymer brushes

When a liquid drop spreads on an adaptive substrate the latter changes its properties what may result in an intricate coupled dynamics of drop and substrate. Here we present a generic mesoscale hydrodynamic model for such processes that is written as a gradient dynamics on an underlying energy functional. We specify the model details for the example of a drop spreading on a dry polymer brush. There, liquid absorption into the brush results in swelling of the brush causing changes in the brush topography and wettability. The liquid may also advance within the brush via diffusion (or wicking) resulting in coupled drop and brush dynamics. The specific model accounts for coupled spreading, absorption and wicking dynamics when the underlying energy functional incorporates capillarity, wettability and brush energy. After employing a simple version of such a model to numerically simulate a droplet spreading on a swelling brush we conclude with a discussion of possible model extensions

Modelling Immunological Memory

Accurate immunological models offer the possibility of performing highthroughput experiments in silico that can predict, or at least suggest, in vivo phenomena. In this chapter, we compare various models of immunological memory. We first validate an experimental immunological simulator, developed by the authors, by simulating several theories of immunological memory with known results. We then use the same system to evaluate the predicted effects of a theory of immunological memory. The resulting model has not been explored before in artificial immune systems research, and we compare the simulated in silico output with in vivo measurements. Although the theory appears valid, we suggest that there are a common set of reasons why immunological memory models are a useful support tool; not conclusive in themselves

Cell Death Modulation by Intravenous Immunoglobulin

The induction of cell death in immune cells by naturally occurring antibodies specific for death receptors may present an important antiinflammatory mechanism of intravenous immunoglobulin (IVIG). Conversely, the protection of tissue cells from death receptor-mediated apoptosis by blocking antibodies is thought to contribute to the beneficial effects of IVIG in certain inflammatory disorders such as toxic epidermal necrolysis, also known as Lyell's syndrome. In this review, we focus on recent insights into the role of functional antibodies against Fas, sialic acid-binding immunoglobulin-like lectin (Siglec)-8, and Siglec-9 receptors in IVIG-mediated cell survival or death effects. In addition, we examine a variety of factors in inflammatory disease that may interplay with these cellular events and influence the therapeutic efficacy or potency of IVIG. These involve activation status of the target cell, cytokine microenvironment, pathogenesis and stage of disease, individual genetic determinants, species characteristics, and batch-to-batch variations of IVIG preparation