Social Integration in a Diverse Society:Social Complexity Models of the Link Between Segregation and Opinion Polarization

There is increasing societal and scholarly interest in understanding how social integration can be maintained in a diverse society. This paper takes a model of the relation between opinion polarization and ethnic segregation as an example for social complexity. Many argue that segregation between different groups in society fosters opinion polarization. Earlier modeling work has supported this theoretically. Here, a simple model is presented that generates the opposite prediction based on the assumption that influence can be assimilative or repulsive, depending on the discrepancy between interacting individuals. It is discussed that these opposite results from similar models point to the need for more empirical research into micro-level assumptions and the micro-to-macro transformation in models of opinion dynamics in a diverse society

The Role of Intracellular Interactions in the Collective Polarization of Tissues and its Interplay with Cellular Geometry

Planar cell polarity (PCP), the coherent in-plane polarization of a tissue on multicellular length scales, provides directional information that guides a multitude of developmental processes at cellular and tissue levels. While it is manifest that cells utilize both intracellular and intercellular mechanisms, how the two produce the collective polarization remains an active area of investigation. We study the role of intracellular interactions in the large-scale spatial coherence of cell polarities, and scrutinize the role of intracellular interactions in the emergence of tissue-wide polarization. We demonstrate that nonlocal cytoplasmic interactions are necessary and sufficient for the robust long-range polarization, and are essential to the faithful detection of weak directional signals. In the presence of nonlocal interactions, signatures of geometrical information in tissue polarity become manifest. We investigate the deleterious effects of geometric disorder, and determine conditions on the cytoplasmic interactions that guarantee the stability of polarization. These conditions get progressively more stringent upon increasing the geometric disorder. Another situation where the role of geometrical information might be evident is elongated tissues. Strikingly, our model recapitulates an observed influence of tissue elongation on the orientation of polarity. Eventually, we introduce three classes of mutants: lack of membrane proteins, cytoplasmic proteins, and local geometrical irregularities. We adopt core-PCP as a model pathway, and interpret the model parameters accordingly, through comparing the in silico and in vivo phenotypes. This comparison helps us shed light on the roles of the cytoplasmic proteins in cell-cell communication, and make predictions regarding the cooperation of cytoplasmic and membrane proteins in long-range polarization.Comment: 15 pages Main Text + 8 page Appendi

Persuasion without polarization? Modelling persuasive argument communication in teams with strong faultlines

Strong demographic faultlines are a potential source of conflict in teams. To study conditions under which faultlines can result in between-group bi-polarization of opinions, a computational model of persuasive argument communication has been proposed. We identify two hitherto overlooked degrees of freedom in how researchers formalized the theory. First, are arguments agents communicate influencing each other's opinions explicitly or implicitly represented in the model? Second, does similarity between agents increase chances of interaction or the persuasiveness of others' arguments? Here we examine these degrees of freedom in order to assess their effect on the model's predictions. We find that both degrees of freedom matter: in a team with strong demographic faultline, the model predicts more between-group bi-polarization when (1) arguments are represented explicitly, and (2) when homophily is modelled such that the interaction between similar agents are more likely (instead of more persuasive)

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

Understanding the Structure-Function Relationship in Peptide-Enabled High Entropy Alloy Nanocatalysts

The structural complexity in high entropy alloy nanocatalysts (HEAs), afforded by the homogeneous mixing of five or more elements, has resulted in a limited understanding about the origin of their promising electrocatalytic properties. This thesis investigates the structure-function relationship in HEAs using advanced material characterization techniques. At first, a methodology for resolving the atomic-scale structure of peptide-enabled HEAs was developed using high-energy X-ray diffraction (HE-XRD) coupled with atomic pair distribution function (PDF) and reverse Monte Carlo (RMC) simulations, yielding structure models over the length scale of HEAs. Coordination analysis of the structure models revealed a multifunctional interplay of geometric and electronic attributes of surface atoms in HEAs that was responsible for the catalytic activity enhancement during the methanol electrooxidation reaction. Using the methodology for resolving the atomic scale structure of HEAs and peptide sequence engineering, the structure-function relationship of model PtPdAuCoSn HEAs during ethanol electrooxidation reaction (EOR) was studied. Compositional analysis of the PtPdAuCoSn HEA structure models revealed distinct miscibility characteristics that were attributed to the unique biotic-abiotic interactions. Analysis of the structure models identified the rapid dehydrogenation of CH3CHO intermediate into CH3COads in an optimized adsorption configuration as the contributing factor for the high selectivity towards CH3COO- in PtPdAuCoSn HEAs. Armed with these insights, a study was designed for understanding the effect of changing the concentration of Pt in the structure-function relationship of PtPdAuCoSn HEAs using spatiotemporal structural insights from in-situ PDF. The structure models demonstrated a degree of metastability as a function of their corresponding configurational entropy. Analysis of the structure models revealed that high selectivity towards CH3COO- in PtPdAuCoSn HEAs during EOR originates from the enhanced distribution of Pd and Co surface atoms. In summary, this thesis uses atomic PDF and RMC simulations to draw structure-function correlations in HEAs, presenting a path forward for developing strategies for the rational design of HEAs. Through collaborative efforts from theoreticians and experimentalists, the methodology presented here can form the basis for accelerating the discovery of promising HEA configurations for emerging electrocatalytic applications

Self-organization in heterogeneous biological systems

Self-organization is an ubiquitous and fundamental process that underlies all living systems. In cellular organisms, many vital processes, such as cell division and growth, are spatially and temporally regulated by proteins -- the building blocks of life. To achieve this, proteins self-organize and form spatiotemporal patterns. In general, protein patterns respond to a variety of internal and external stimuli, such as cell shape or inhomogeneities in protein activity. As a result, the dynamics of intracellular pattern formation generally span multiple spatial and temporal scales. This thesis addresses the underlying mechanisms that lead to the formation of heterogeneous patterns. The main themes of this work are organized into three parts, which are summarized below. The first part deals with the general problem of mass-conserving reaction-diffusion dynamics in spatially non-uniform systems. In section 1 of chapter II, we study the dynamics of the E. coli Min protein system -- a paradigmatic model for pattern formation. More specifically, we consider a setup with a fixed spatial heterogeneity in a control parameter, and show that this leads to complex multiscale pattern formation. We develop a coarse-graining approach that enables us to explain and reduce the dynamics to the "hydrodynamic variables'' at large length and time scales. In another project, we consider a system where spatial heterogeneities are not imposed externally, but self-generated by the dynamics via a mechanochemical feedback loop between geometry and reaction-diffusion system (section 2 of chapter II). We show that the resulting dynamics can be explained from the phase-space geometry of the reaction-diffusion system. The second part focuses on how patterns in realistic cell geometries are controlled by shape and biochemical cues. We examine axis selection of PAR polarity patterns in C. elegans, where we show that spatial variations in the bulk-surface ratio and a tendency of the system to minimize the pattern interface yield robust long-axis polarization of PAR protein patterns (section 1 of chapter III). In a second project, we develop a theoretical model that explains the localization of the B. subtilis Min protein system (section 2 of chapter 3). We show that a biochemical cue -- which acts as a template for pattern formation -- guides and stabilizes Min patterns. In the third part, we study the coupling between lipid membranes and curvature-generating proteins. We demonstrate that myosin-VI motor proteins cooperatively bind to saddle-shaped regions of lipid membranes, and thereby induce large-scale membrane remodeling (section 1 of chapter IV). To understand the dynamics, we develop a coarse-grained geometric model and show that the emergence of regular spatial structures can be explained by a "push-pull'' mechanism: protein binding destabilizes the membrane shape at all length scales, and this is counteracted by line tension. Inspired by this system, we then investigate a general model for the dynamics of growing protein-lipid interfaces (section 2 of chapter IV). A key feature of the model is that the protein binding kinetics is explicitly coupled to the morphology of the interface. We show that such a coupling leads to turbulent dynamics and a roughening transition of the interface that is characterized by universal scaling behaviour

Investigating the implications of edge-city development on integrated spatial planning: case study of Umhlanga, (Prestondale) eThekwini Municipality.

Masters Degree. University of KwaZulu-Natal, Durban.In the global South, the desire for cities to increase their participation in the global economy by cultivating world cities has led to a heightened presence of high-end privatized urban enclaves that have seemingly become key drivers of city development. Conceptualised as edge cities under the Postmodern Urbanisation framework in the Los Angeles school of thought, these urban enclaves showcase how the decentralization of cities and the demand for affluent lifestyle living has dominated city development trajectories in both developed and developing countries. In response to this trend, more cities are embracing urban policy discourses and spatial plans that are orientated around achieving spatial integration with the interest of ensuring equitable access to city resources for all. The planning discourse in South Africa remains committed to transforming the urban morphology of South African cities from one that is plagued with spatial segregation and fragmentation to one that practises urban compaction and integrated urban development. With this background, the main objective of the study was to find out the impact that edge city development has on the transformation agenda that advocates for integrated spatial planning within the South African urban landscape. A qualitative research approach was used to obtain findings using structured key-informant interviews as a primary data collection source, where purposive sampling was used to purposefully select the sample population. The study found that the development of edge cities perpetuates spatial segregation patterns that exist within the South African urban from. Despite legislature and policy commitment to spatial transformation and integrated development processes, edge city development continues to develop along economic and class divisions that are a legacy of apartheid planning. Furthermore, the study found that the implications that edge city development has towards achieving integrated spatial planning includes increased urban sprawl, deepening socio-economic divisions, spatial exclusivity as well as a lack of public facilities that are not privatized

Poverty and Inequality in Middle Income Countries: Policy Achievements, Political Obstacles

This collection offers a timely reassessment of viable ways of addressing poverty across the globe today. The profile of global poverty has changed dramatically over the past decade, and around three-quarters of the poor now live in middle income countries, making inequality a major issue. This requires us to fundamentally rethink anti-poverty strategies and policies, as many aspects of the established framework for poverty reduction are no longer effective. Featuring contributions from Latin America, Africa and Asia, this much-needed collection answers some of the key questions arising as development policy confronts the challenges of poverty and inequality on the global, national and local scale in both urban and rural contexts. Providing poverty researchers and practitioners with valuable new tools to address new forms of poverty in the right way, Poverty and Inequality in Middle Income Countries shows how a radical switch from aid to redistribution-based social policies is needed to combat new forms of global poverty.Comparative Research Programme on Poverty (CROP) at the University of BergenpublishedVersio

Bogoliubov's Vision: Quasiaverages and Broken Symmetry to Quantum Protectorate and Emergence

In the present interdisciplinary review we focus on the applications of the symmetry principles to quantum and statistical physics in connection with some other branches of science. The profound and innovative idea of quasiaverages formulated by N.N. Bogoliubov, gives the so-called macro-objectivation of the degeneracy in domain of quantum statistical mechanics, quantum field theory and in the quantum physics in general. We discuss the complementary unifying ideas of modern physics, namely: spontaneous symmetry breaking, quantum protectorate and emergence. The interrelation of the concepts of symmetry breaking, quasiaverages and quantum protectorate was analyzed in the context of quantum theory and statistical physics. The chief purposes of this paper were to demonstrate the connection and interrelation of these conceptual advances of the many-body physics and to try to show explicitly that those concepts, though different in details, have a certain common features. Several problems in the field of statistical physics of complex materials and systems (e.g. the chirality of molecules) and the foundations of the microscopic theory of magnetism and superconductivity were discussed in relation to these ideas.Comment: 88 pages, 1 figure, Refs.42