Void-and-Cluster Sampling of Large Scattered Data and Trajectories

We propose a data reduction technique for scattered data based on statistical sampling. Our void-and-cluster sampling technique finds a representative subset that is optimally distributed in the spatial domain with respect to the blue noise property. In addition, it can adapt to a given density function, which we use to sample regions of high complexity in the multivariate value domain more densely. Moreover, our sampling technique implicitly defines an ordering on the samples that enables progressive data loading and a continuous level-of-detail representation. We extend our technique to sample time-dependent trajectories, for example pathlines in a time interval, using an efficient and iterative approach. Furthermore, we introduce a local and continuous error measure to quantify how well a set of samples represents the original dataset. We apply this error measure during sampling to guide the number of samples that are taken. Finally, we use this error measure and other quantities to evaluate the quality, performance, and scalability of our algorithm.Comment: To appear in IEEE Transactions on Visualization and Computer Graphics as a special issue from the proceedings of VIS 201

Intracellular transport driven by cytoskeletal motors: General mechanisms and defects

Cells are strongly out-of-equilibrium systems driven by continuous energy supply. They carry out many vital functions requiring active transport of various ingredients and organelles, some being small, others being large. The cytoskeleton, composed of three types of filaments, determines the shape of the cell and plays a role in cell motion. It also serves as a road network for the so-called cytoskeletal motors. These molecules can attach to a cytoskeletal filament, perform directed motion, possibly carrying along some cargo, and then detach. It is a central issue to understand how intracellular transport driven by molecular motors is regulated, in particular because its breakdown is one of the signatures of some neuronal diseases like the Alzheimer. We give a survey of the current knowledge on microtubule based intracellular transport. We first review some biological facts obtained from experiments, and present some modeling attempts based on cellular automata. We start with background knowledge on the original and variants of the TASEP (Totally Asymmetric Simple Exclusion Process), before turning to more application oriented models. After addressing microtubule based transport in general, with a focus on in vitro experiments, and on cooperative effects in the transportation of large cargos by multiple motors, we concentrate on axonal transport, because of its relevance for neuronal diseases. It is a challenge to understand how this transport is organized, given that it takes place in a confined environment and that several types of motors moving in opposite directions are involved. We review several features that could contribute to the efficiency of this transport, including the role of motor-motor interactions and of the dynamics of the underlying microtubule network. Finally, we discuss some still open questions.Comment: 74 pages, 43 figure

Unmet goals of tracking: within-track heterogeneity of students' expectations for

Educational systems are often characterized by some form(s) of ability grouping, like tracking. Although substantial variation in the implementation of these practices exists, it is always the aim to improve teaching efficiency by creating homogeneous groups of students in terms of capabilities and performances as well as expected pathways. If students’ expected pathways (university, graduate school, or working) are in line with the goals of tracking, one might presume that these expectations are rather homogeneous within tracks and heterogeneous between tracks. In Flanders (the northern region of Belgium), the educational system consists of four tracks. Many students start out in the most prestigious, academic track. If they fail to gain the necessary credentials, they move to the less esteemed technical and vocational tracks. Therefore, the educational system has been called a 'cascade system'. We presume that this cascade system creates homogeneous expectations in the academic track, though heterogeneous expectations in the technical and vocational tracks. We use data from the International Study of City Youth (ISCY), gathered during the 2013-2014 school year from 2354 pupils of the tenth grade across 30 secondary schools in the city of Ghent, Flanders. Preliminary results suggest that the technical and vocational tracks show more heterogeneity in student’s expectations than the academic track. If tracking does not fulfill the desired goals in some tracks, tracking practices should be questioned as tracking occurs along social and ethnic lines, causing social inequality

ReseArch with Patient and Public invOlvement: a RealisT evaluation - the RAPPORT study

Background Patient and public involvement (PPI) is a prerequisite for many funding bodies and NHS research ethics approval. PPI in research is defined as research carried out with or by the public rather than to, about or for them. While the benefits of PPI have been widely discussed, there is a lack of evidence on the impact and outcomes of PPI in research. Objectives To determine the types of PPI in funded research, describe key processes, analyse the contextual and temporal dynamics of PPI and explore the experience of PPI in research for all those involved. Mechanisms contributing to the routine incorporation of PPI in the research process were assessed, the impact of PPI on research processes and outcomes evaluated, and barriers and enablers to effective PPI identified. Design A three-staged realist evaluation drawing on Normalisation Process Theory to understand how far PPI was embedded within health-care research in six areas: diabetes mellitus, arthritis, cystic fibrosis, dementia, public health and learning disabilities. The first two stages comprised a scoping exercise and online survey to chief investigators to assess current PPI activity. The third stage consisted of case studies tracked over 18 months through interviews and document analysis. The research was conducted in four regions of England. Participants Non-commercial studies currently running or completed within the previous 2 years eligible for adoption on the UK Clinical Research Network portfolio. A total of 129 case study participants included researchers and PPI representatives from 22 research studies, and representatives from funding bodies and PPI networks

2018 FSDG Combined Abstracts

https://scholarworks.gvsu.edu/fsdg_abstracts/1000/thumbnail.jp

Ways of seeing: Conflicting rationalities in contested urban space - the N2 Gateway in the context of Langa

Includes bibliographic references.In 2005 the South African Department of Housing announced the launch of the N2 Gateway – a housing ‘megaproject’ to pilot the Breaking New Ground (BNG) housing plan in Joe Slovo informal settlement in Langa, the oldest African township in Cape Town. This historically contextualised retroductive case study asks what can be learnt from the paradigmatic N2 Gateway to propose to planning theory why such projects, planned with the aim of improving the quality of life of poor and marginal urban residents of the post-apartheid city, so often fail to realise their planned improvements and result in conflict and unintended consequences. A conceptual framework provides the theoretical basis for examining how planning and implementation of the N2 Gateway exposes the underlying rationalities shaping relations amongst and between organs of state and key non-state development actors. Although the BNG policy made provision for in situ upgrading of informal settlements, in practice the state declared war on shacks and through the N2 Gateway set out to eradicate Joe Slovo and replace it with a mix of social and subsidy housing. The case provides the basis for analysis of the clash of rationalities amongst state actors who, together with their intermediaries, sought to exercise their ‘wills to govern and improve’ on the basis of simplifications of perceived problems and their solutions. These were countered by competing ‘wills to survive and thrive’ amongst groupings of Langa residents, which in Joe Slovo were closely bound to the logics of informality. Methodologically the study draws on research methods which embrace the ‘visual turn’, utilising satellite images and photographic compilations as narrative triggers for storytelling by residents, officials and civil society actors. The study draws on more than sixty image-led interview narratives which surface the multiple iv dimensions of the case, including complex interconnections between rural and urban spaces which shape social and spatial geographies of life in Langa. These expose multifaceted struggles within and between ‘molar structures’ of the state in the implementation of the megaproject, highlighting the switch points and reversals of power in state encounters with the micropolitics of local claims on space, place and belonging. The narratives reveal how diverse and concurrent resistance pathways including ‘quiet encroachment’, street protests, ‘elite capture’ and legal proceedings which went to the Constitutional Court disrupted, diverted and redirected the state’s schemes of improvement. The findings examine how the discourses and practices of the aspirant South African ‘developmental state’ show little understanding of or regard for the deep-rooted contestations and social differentiation within Langa between ‘Cape borners’ and generations of rural migrants known as amagoduka or ‘those who return home’. The conflicting rationalities and deep differences amongst and between state agents and within the broad cast of social actors in Langa extend far beyond the simple binary of state and ‘community’. The narratives highlight the fragmented and opaque nature of the state and the bifurcated Langa socialities stratified by the micropolitics of territory, differentiation and belonging. The case study speaks back to planning theory in order to provide important cautions against homogenisation and simplification at the intersection between the apparatus of biopolitics and governmentality and the strategies of struggle of groupings of the poor and not so poor to survive and thrive. It foregrounds a contingent yet historically embedded politics of encounter which eschews homogenising notions of community and a rules-governed communicative rationality in favour of more situated sense-making through agonistic conceptions of planning and development rooted in ‘the geography of what happens’