Assessing the perceived environment through crowdsourced spatial photo content for application to the fields of landscape and urban planning

Assessing information on aspects of identification, perception, emotion, and social interaction with respect to the environment is of particular importance to the fields of natural resource management. Our ability to visualize this type of information has rapidly improved with the proliferation of social media sites throughout the Internet in recent years. While many methods to extract information on human behavior from crowdsourced geodata already exist, this work focuses on visualizing landscape perception for application to the fields of landscape and urban planning. Visualization of people’s perceptual responses to landscape is demonstrated with crowdsourced photo geodata from Flickr, a popular photo sharing community. A basic, general method to map, visualize and evaluate perception and perceptual values is proposed. The approach utilizes common tools for spatial knowledge discovery and builds on existing research, but is specifically designed for implementation within the context of landscape perception analysis and particularly suited as a base for further evaluation in multiple scenarios. To demonstrate the process in application, three novel types of visualizations are presented: the mapping of lines of sight in Yosemite Valley, the assessment of landscape change in the area surrounding the High Line in Manhattan, and individual location analysis for Coit Tower in San Francisco. The results suggest that analyzing crowdsourced data may contribute to a more balanced assessment of the perceived landscape, which provides a basis for a better integration of public values into planning processes.:Contents 3 1 Introduction 7 1.1 Motivation 7 1.2 Literature review and conceptual scope 9 1.3 Terminology 11 1.4 Related research 12 1.5 Objectives 14 1.6 Methodology 16 1.7 Formal conventions 21 I. Part I: Conceptual framework 23 1.1 Visual perception 23 1.2 Theory and practice in landscape perception assessment 27 1.2.1 Expert valuation versus participation 27 1.2.2 Photography-based landscape perception assessment 32 1.2.2.1. Photo-based surveys 32 1.2.2.2. Photo-based Internet surveys 35 1.2.2.3. Photo-interviewing and participant photography 37 1.2.3 Conclusions 40 1.3 Conceptual approach 42 1.3.1 A framing theory: Distributed cognition 42 1.3.2 Description of the approach 46 1.3.3 Choosing the right data source 48 1.3.3.1. Availability of crowdsourced and georeferenced photo data 48 1.3.3.2. Suitability for analyzing human behavior and perception 51 1.3.4 Relations between data and the phenomenon under observation 55 1.3.4.1. Photo taking and landscape perception 55 1.3.4.2. User motivation in the context of photo sharing in communities 61 1.3.4.3. Describing and tagging photos: Forms of attributing meaning 66 1.3.5 Considerations for measuring and weighting data 70 1.3.6 Conclusions 77 II. Part II: Application example – Flickr photo analysis and evaluation of results 80 2.1 Software architecture 80 2.2 Materials and methods 86 2.2.1 Data retrieval, initial data structure and overall quantification 86 2.2.2 Global data bias 89 2.2.3 Basic techniques for filtering and classifying data 94 2.2.3.1. Where: photo locations 94 2.2.3.2. Who: user origin 96 2.2.3.3. When: time of photo taking 102 2.2.3.4. What: tag frequency 108   2.2.4 Methods for aggregating data 113 2.2.4.1. Clustering of photo locations 113 2.2.4.2. Clustering of tag locations 115 2.3 Application to planning: techniques for visualizing data 118 2.3.1 Introduction 118 2.3.2 Tag maps 121 2.3.2.1. Description of technique 121 2.3.2.2. Results: San Francisco and Berkeley waterfront 126 2.3.2.3. Results: Berkeley downtown and university campus 129 2.3.2.4. Results: Dresden and the Elbe Valley 132 2.3.2.5. Results: Greater Toronto Area and City of Toronto 136 2.3.2.6. Results: Baden-Württemberg 143 2.3.2.7. Summary 156 2.3.3 Temporal comparison for assessing landscape change 158 2.3.3.1. Description of technique 158 2.3.3.2. Results: The High Line, NY 159 2.3.3.3. Summary 160 2.3.4 Determining lines of sight and important visual connections 161 2.3.4.1. Description of technique 161 2.3.4.2. Results: Yosemite Valley 162 2.3.4.3. Results: Golden Gate and Bay Bridge 167 2.3.4.4. Results: CN Tower, Toronto 168 2.3.4.5. Summary 170 2.3.5 Individual location analysis 171 2.3.5.1. Description of technique 171 2.3.5.2. Results: Coit Tower, San Francisco 171 2.3.5.3. Results: CN Tower, Toronto 172 2.3.5.4. Summary 173 2.4 Quality and accuracy of results 175 2.4.1 Methodology 175 2.4.2 Accuracy of data 175 2.4.3 Validity and reliability of visualizations 178 2.4.3.1. Reliability 178 2.4.3.2. Validity 180 2.5 Implementation example: the London View Framework 181 2.5.1 Description 181 2.5.2 Evaluation methodology 183 2.5.3 Analysis 184 2.5.3.1. Landmarks 184 2.5.3.2. Views 192 2.5.4 Summary 199 III. Discussion 203 3.1 Application of the framework from a wider perspective 203 3.2 Significance of results 204 3.3 Further research 205   3.4 Discussion of workshop results and further feedback 206 3.4.1 Workshops at University of Waterloo and University of Toronto, Canada 206 3.4.2 Workshop at University of Technology Dresden, Germany 209 3.4.3 Feedback from presentations, discussions, exhibitions: second thoughts 210 IV. Conclusions 212 V. References 213 5.1 Literature 213 5.2 List of web references 228 5.3 List of figures 230 5.4 List of tables 234 5.5 List of maps 235 5.6 List of appendices 236 VI. Appendices 237  Als Wahrnehmung wird der Bewusstseinsprozess des subjektiven Verstehens der Umwelt bezeichnet. Grundlage für diesen Prozess ist die Gewinnung von Informationen über die Sinne, also aus visuellen, olfaktorischen, akustischen und anderen Reizen. Die Wahrnehmung ist aber auch wesentlich durch interne Prozesse beeinflusst. Das menschliche Gehirn ist fortlaufend damit beschäftigt, sowohl bewusst als auch unbewusst Sinneswahrnehmungen mit Erinnerungen abzugleichen, zu vereinfachen, zu assoziieren, vorherzusagen oder zu vergleichen. Aus diesem Grund ist es schwierig, die Wahrnehmung von Orten und Landschaften in Planungsprozessen zu berücksichtigen. Jedoch wird genau dies von der Europäischen Landschaftskonvention gefordert, die Landschaft als einen bestimmten Bereich definiert, so wie er von Besuchern und Einwohnern wahrgenommen wird (“as a zone or area as perceived by local people or visitors”, ELC Art. 1, Abs. 38). Während viele Fortschritte und Erkenntnisse, zum Beispiel aus den Kognitionswissenschaften, heute helfen, die Wahrnehmung einzelner Menschen zu verstehen, konnte die Stadt- und Landschaftsplanung kaum profitieren. Es fehlt an Kenntnissen über das Zusammenwirken der Wahrnehmung vieler Menschen. Schon Stadtplaner Kevin Lynch beschäftigte dieses gemeinsame, kollektive ‚Bild‘ der menschlichen Umwelt ("generalized mental picture", Lynch, 1960, p. 4). Seitdem wurden kaum nennenswerte Fortschritte bei der Erfassung der allgemeinen, öffentlichen Wahrnehmung von Stadt- und Landschaft erzielt. Dies war Anlass und Motivation für die vorliegende Arbeit. Eine bisher in der Planung ungenutzte Informationsquelle für die Erfassung der Wahrnehmung vieler Menschen bietet sich in Form von crowdsourced Daten (auch ‚Big Data‘), also großen Mengen an Daten die von vielen Menschen im Internet zusammengetragen werden. Im Vergleich zu konventionellen Daten, zum Beispiel solchen die durch Experten erhoben werden und durch öffentliche Träger zur Verfügung stehen, eröffnet sich durch crowdsourced Daten eine bisher nicht verfügbare Quelle für Informationen, um die komplexen Zusammenhänge zwischen Raum, Identität und subjektiver Wahrnehmung zu verstehen. Dabei enthalten crowdsourced Daten lediglich Spuren menschlicher Entscheidungen. Aufgrund der Menge ist es aber möglich, wesentliche Informationen über die Wahrnehmung derer, die diese Daten zusammengetragen haben, zu gewinnen. Dies ermöglicht es Planern zu verstehen, wie Menschen ihre unmittelbare Umgebung wahrnehmen und mit ihr interagieren. Darüber hinaus wird es immer wichtiger, die Ansichten Vieler in Planungsprozessen zu berücksichtigen (Lynam, De Jong, Sheil, Kusumanto, & Evans, 2007; Brody, 2004). Der Wunsch nach öffentlicher Beteiligung sowie die Anzahl an beteiligten Stakeholdern nehmen dabei konstant zu. Durch das Nutzen dieser neuen Informationsquelle bietet sich eine Alternative zu herkömmlichen Ansätzen wie Umfragen, die genutzt werden um beispielsweise Meinungen, Positionen, Werte, Normen oder Vorlieben von bestimmten sozialen Gruppen zu messen. Indem es crowdsourced Daten erleichtern, solch soziokulturelle Werte zu bestimmen, können die Ergebnisse vor allem bei der schwierigen Gewichtung gegensätzlicher Interessen und Ansichten helfen. Es wird die Ansicht geteilt, dass die Nutzung von crowdsourced Daten, indem Einschätzungen von Experten ergänzt werden, letztendlich zu einer faireren, ausgeglichenen Berücksichtigung der Allgemeinheit in Entscheidungsprozessen führen kann (Erickson, 2011, p.1). Eine große Anzahl an Methoden ist bereits verfügbar, um aus dieser Datenquelle wichtige landschaftsbezogene Informationen auszulesen. Beispiele sind die Bewertung der Attraktivität von Landschaften, die Bestimmung der Bedeutung von Sehenswürdigkeiten oder Wahrzeichen, oder die Einschätzung von Reisevorlieben von Nutzergruppen. Viele der bisherigen Methoden wurden jedoch als ungenügend empfunden, um die speziellen Bedürfnisse und das breite Spektrum an Fragestellungen zur Landschaftswahrnehmung in Stadt- und Landschaftsplanung zu berücksichtigen. Das Ziel der vorliegenden Arbeit ist es, praxisrelevantes Wissen zu vermitteln, welches es Planern erlaubt, selbstständig Daten zu erforschen, zu visualisieren und zu interpretieren. Der Schlüssel für eine erfolgreiche Umsetzung wird dabei in der Synthese von Wissen aus drei Kategorien gesehen, theoretische Grundlagen (1), technisches Wissen zur Datenverarbeitung (2) sowie Kenntnisse zur grafischen Visualisierungen (3). Die theoretischen Grundlagen werden im ersten Teil der Arbeit (Part I) präsentiert. In diesem Teil werden zunächst Schwachpunkte aktueller Verfahren diskutiert, um anschließend einen neuen, konzeptionell-technischen Ansatz vorzuschlagen der gezielt auf die Ergänzung bereits vorhandener Methoden zielt. Im zweiten Teil der Arbeit (Part II) wird anhand eines Datenbeispiels die Anwendung des Ansatzes exemplarisch demonstriert. Fragestellungen die angesprochen werden reichen von der Datenabfrage, Verarbeitung, Analyse, Visualisierung, bis zur Interpretation von Grafiken in Planungsprozessen. Als Basis dient dabei ein Datenset mit 147 Millionen georeferenzierte Foto-Daten und 882 Millionen Tags der Fotoaustauschplatform Flickr, welches in den Jahren 2007 bis 2015 von 1,3 Millionen Nutzern zusammengetragen wurde. Anhand dieser Daten wird die Entwicklung neuer Visualisierungstechniken exemplarisch vorgestellt. Beispiele umfassen Spatio-temporal Tag Clouds, eine experimentelle Technik zur Generierung von wahrnehmungsgewichteten Karten, die Visualisierung von wahrgenommenem Landschaftswandel, das Abbilden von wahrnehmungsgewichteten Sichtlinien, sowie die Auswertung von individueller Wahrnehmung von und an bestimmten Orten. Die Anwendung dieser Techniken wird anhand verschiedener Testregionen in den USA, Kanada und Deutschland für alle Maßstabsebenen geprüft und diskutiert. Dies umfasst beispielsweise die Erfassung und Bewertung von Sichtlinien und visuellen Bezügen in Yosemite Valley, das Monitoring von wahrgenommenen Veränderungen im Bereich der High Line in New York, die Auswertung von individueller Wahrnehmung für Coit Tower in San Francisco, oder die Beurteilung von regional wahrgenommenen identitätsstiftenden Landschaftswerten für Baden-Württemberg und die Greater Toronto Area (GTA). Anschließend werden Ansätze vorgestellt, um die Qualität und Validität von Visualisierungen einzuschätzen. Abschließend wird anhand eines konkreten Planungsbeispiels, des London View Management Frameworks (LVMF), eine spezifische Implementation des Ansatzes und der Visualisierungen kurz aufgezeigt und diskutiert. Mit der Arbeit wird vor allem das breite Potential betont, welches die Nutzung von crowdsourced Daten für die Bewertung von Landschaftswahrnehmung in Stadt- und Landschaftsplanung bereithält. Insbesondere crowdsourced Fotodaten werden als wichtige zusätzliche Informationsquelle gesehen, da sie eine bisher nicht verfügbare Perspektive auf die allgemeine, öffentliche Wahrnehmung der Umwelt ermöglichen. Während der breiteren Anwendung noch einige Grenzen gesetzt sind, können die vorgestellten experimentellen Methoden und Techniken schon wichtige Aufschlüsse über eine ganze Reihe von wahrgenommenen Landschaftswerten geben. Auf konzeptioneller Ebene stellt die Arbeit eine erste Grundlage für weitere Forschung dar. Bevor jedoch eine breite Anwendung in der Praxis möglich ist, müssen entscheidende Fragen gelöst werden, beispielsweise zum Copyright, zur Definition von ethischen Standards innerhalb der Profession, sowie zum Schutz der Privatsphäre Beteiligter. Längerfristig wird nicht nur die Nutzung der Daten als wichtig angesehen, sondern auch die Erschließung der essentiellen Möglichkeiten dieser Entwicklung zur besseren Kommunikation mit Auftraggebern, Beteiligten und der Öffentlichkeit in Planungs- und Entscheidungsprozessen.:Contents 3 1 Introduction 7 1.1 Motivation 7 1.2 Literature review and conceptual scope 9 1.3 Terminology 11 1.4 Related research 12 1.5 Objectives 14 1.6 Methodology 16 1.7 Formal conventions 21 I. Part I: Conceptual framework 23 1.1 Visual perception 23 1.2 Theory and practice in landscape perception assessment 27 1.2.1 Expert valuation versus participation 27 1.2.2 Photography-based landscape perception assessment 32 1.2.2.1. Photo-based surveys 32 1.2.2.2. Photo-based Internet surveys 35 1.2.2.3. Photo-interviewing and participant photography 37 1.2.3 Conclusions 40 1.3 Conceptual approach 42 1.3.1 A framing theory: Distributed cognition 42 1.3.2 Description of the approach 46 1.3.3 Choosing the right data source 48 1.3.3.1. Availability of crowdsourced and georeferenced photo data 48 1.3.3.2. Suitability for analyzing human behavior and perception 51 1.3.4 Relations between data and the phenomenon under observation 55 1.3.4.1. Photo taking and landscape perception 55 1.3.4.2. User motivation in the context of photo sharing in communities 61 1.3.4.3. Describing and tagging photos: Forms of attributing meaning 66 1.3.5 Considerations for measuring and weighting data 70 1.3.6 Conclusions 77 II. Part II: Application example – Flickr photo analysis and evaluation of results 80 2.1 Software architecture 80 2.2 Materials and methods 86 2.2.1 Data retrieval, initial data structure and overall quantification 86 2.2.2 Global data bias 89 2.2.3 Basic techniques for filtering and classifying data 94 2.2.3.1. Where: photo locations 94 2.2.3.2. Who: user origin 96 2.2.3.3. When: time of photo taking 102 2.2.3.4. What: tag frequency 108   2.2.4 Methods for aggregating data 113 2.2.4.1. Clustering of photo locations 113 2.2.4.2. Clustering of tag locations 115 2.3 Application to planning: techniques for visualizing data 118 2.3.1 Introduction 118 2.3.2 Tag maps 121 2.3.2.1. Description of technique 121 2.3.2.2. Results: San Francisco and Berkeley waterfront 126 2.3.2.3. Results: Berkeley downtown and university campus 129 2.3.2.4. Results: Dresden and the Elbe Valley 132 2.3.2.5. Results: Greater Toronto Area and City of Toronto 136 2.3.2.6. Results: Baden-Württemberg 143 2.3.2.7. Summary 156 2.3.3 Temporal comparison for assessing landscape change 158 2.3.3.1. Description of technique 158 2.3.3.2. Results: The High Line, NY 159 2.3.3.3. Summary 160 2.3.4 Determining lines of sight and important visual connections 161 2.3.4.1. Description of technique 161 2.3.4.2. Results: Yosemite Valley 162 2.3.4.3. Results: Golden Gate and Bay Bridge 167 2.3.4.4. Results: CN Tower, Toronto 168 2.3.4.5. Summary 170 2.3.5 Individual location analysis 171 2.3.5.1. Description of technique 171 2.3.5.2. Results: Coit Tower, San Francisco 171 2.3.5.3. Results: CN Tower, Toronto 172 2.3.5.4. Summary 173 2.4 Quality and accuracy of results 175 2.4.1 Methodology 175 2.4.2 Accuracy of data 175 2.4.3 Validity and reliability of visualizations 178 2.4.3.1. Reliability 178 2.4.3.2. Validity 180 2.5 Implementation example: the London View Framework 181 2.5.1 Description 181 2.5.2 Evaluation methodology 183 2.5.3 Analysis 184 2.5.3.1. Landmarks 184 2.5.3.2. Views 192 2.5.4 Summary 199 III. Discussion 203 3.1 Application of the framework from a wider perspective 203 3.2 Significance of results 204 3.3 Further research 205   3.4 Discussion of workshop results and further feedback 206 3.4.1 Workshops at University of Waterloo and University of Toronto, Canada 206 3.4.2 Workshop at University of Technology Dresden, Germany 209 3.4.3 Feedback from presentations, discussions, exhibitions: second thoughts 210 IV. Conclusions 212 V. References 213 5.1 Literature 213 5.2 List of web references 228 5.3 List of figures 230 5.4 List of tables 234 5.5 List of maps 235 5.6 List of appendices 236 VI. Appendices 237

Anyonic Defect Braiding and Spontaneous Chiral Symmetry Breaking in Dihedral Liquid Crystals

Dihedral ('$k$-atic') liquid crystals (DLCs) are assemblies of microscopic constituent particles that exhibit $k$-fold discrete rotational and reflection symmetries. Generalizing the half-integer defects in nematic liquid crystals, two-dimensional $k$-atic DLCs can host point defects of fractional topological charge $\pm m/k$. Starting from a generic microscopic model, we derive a unified hydrodynamic description of DLCs with aligning or anti-aligning short-range interactions in terms of Ginzburg-Landau and Landau-Brazovskii-Swift-Hohenberg theories for a universal complex order-parameter field. Building on this framework, we demonstrate in both particle and continuum simulations how adiabatic braiding protocols, implemented through suitable boundary conditions, can emulate anyonic exchange behavior in a classical system. Analytic solutions and simulations of the mean-field theory further predict a novel spontaneous chiral symmetry breaking transition in anti-aligning DLCs, in quantitative agreement with the patterns observed in particle simulations.Comment: Figs. 3, 6 and S1 added; Analytic solutions added (Sec. V.B.4, Appendix C), Refs. [8], [14], [26], [53]-[60], [80], [81] adde

A Phase-Field Approach to Diffusion-Driven Fracture

In recent years applied mathematicians have used modern analysis to develop variational phase-field models of fracture based on Griffith\u27s theory. These variational phase-field models of fracture have gained popularity due to their ability to predict the crack path and handle crack nucleation and branching. In this work, we are interested in coupled problems where a diffusion process drives the crack propagation. We extend the variational phase-field model of fracture to account for diffusion-driving fracture and study the convergence of minimizers using gamma-convergence. We will introduce Newton\u27s method for the constrained optimization problem and present an algorithm to solve the diffusion-driven fracture problem numerically. For the implementation of this method, we use a finite difference scheme

Swimmer-tracer scattering at low Reynolds number

Understanding the stochastic dynamics of tracer particles in active fluids is important for identifying the physical properties of flow generating objects such as colloids, bacteria or algae. Here, we study both analytically and numerically the scattering of a tracer particle in different types of time-dependent, hydrodynamic flow fields. Specifically, we compare the tracer motion induced by an externally driven colloid with the one generated by various self-motile, multi-sphere swimmers. Our results suggest that force-free swimmers generically induce loop-shaped tracer trajectories. The specific topological structure of these loops is determined by the hydrodynamic properties of the microswimmer. Quantitative estimates for typical experimental conditions imply that the loops survive on average even if Brownian motion effects are taken into account.Comment: 14 pages, to appear in Soft Matte

Learning developmental mode dynamics from single-cell trajectories

Embryogenesis is a multiscale process during which hierarchical symmetry breaking transitions give rise to a fully developed organism. Recent advances in high-resolution live-cell microscopy provide unprecedented insights into the collective cell dynamics at various stages of embryonic development. The rapid experimental progress poses the theoretical challenge of translating high-dimensional imaging data into predictive low-dimensional models that capture the essential ordering principles governing developmental cell migration in complex geometries. Here, we combine mode decomposition ideas that have proved successful in condensed matter physics and turbulence theory with recent advances in sparse dynamical systems inference to realize a computational framework for learning quantitative continuum models from single-cell imaging data. Considering pan-embryo cell migration during early gastrulation in zebrafish as a widely studied example, we show how cell trajectory data on a curved surface can be coarse-grained and compressed with suitable harmonic basis functions. The resulting low-dimensional representation of the early gastrulation process reveals a multilayer interaction network between dominant dynamical modes that enables the symmetry breaking transition from a homogeneous animal pole to an increasingly structured cell assembly. Due to its generic conceptual foundation, we expect this approach to be broadly applicable to obtain a quantitative biophysical understanding of a wide range of developmental structure formation processes.Comment: main text: 11 pages, 3 figures; si text: 14 pages, 7 figure

Active topolectrical circuits

The transfer of topological concepts from the quantum world to classical mechanical and electronic systems has opened fundamentally new approaches to protected information transmission and wave guidance. A particularly promising technology are recently discovered topolectrical circuits that achieve robust electric signal transduction by mimicking edge currents in quantum Hall systems. In parallel, modern active matter research has shown how autonomous units driven by internal energy reservoirs can spontaneously self-organize into collective coherent dynamics. Here, we unify key ideas from these two previously disparate fields to develop design principles for active topolectrical circuits (ATCs) that can self-excite topologically protected global signal patterns. Realizing autonomous active units through nonlinear Chua diode circuits, we theoretically predict and experimentally confirm the emergence of self-organized protected edge oscillations in one- and two-dimensional ATCs. The close agreement between theory, simulations and experiments implies that nonlinear ATCs provide a robust and versatile platform for developing high-dimensional autonomous electrical circuits with topologically protected functionalities.Comment: 10 pages, 4 figures, includes supplementary material. This version adds 2D experiment

Low Reynolds number hydrodynamics of asymmetric, oscillating dumbbell pairs

Active dumbbell suspensions constitute one of the simplest model system for collective swimming at low Reynolds number. Generalizing recent work, we derive and analyze stroke-averaged equations of motion that capture the effective hydrodynamic far-field interaction between two oscillating, asymmetric dumbbells in three space dimensions. Time-averaged equations of motion, as those presented in this paper, not only yield a considerable speed-up in numerical simulations, they may also serve as a starting point when deriving continuum equations for the macroscopic dynamics of multi-swimmer suspensions. The specific model discussed here appears to be particularly useful in this context, since it allows one to investigate how the collective macroscopic behavior is affected by changes in the microscopic symmetry of individual swimmers.Comment: 10 pages, to appear in EPJ Special Topic

Learning hydrodynamic equations for active matter from particle simulations and experiments

Recent advances in high-resolution imaging techniques and particle-based simulation methods have enabled the precise microscopic characterization of collective dynamics in various biological and engineered active matter systems. In parallel, data-driven algorithms for learning interpretable continuum models have shown promising potential for the recovery of underlying partial differential equations (PDEs) from continuum simulation data. By contrast, learning macroscopic hydrodynamic equations for active matter directly from experiments or particle simulations remains a major challenge. Here, we present a framework that leverages spectral basis representations and sparse regression algorithms to discover PDE models from microscopic simulation and experimental data, while incorporating the relevant physical symmetries. We illustrate the practical potential through applications to a chiral active particle model mimicking swimming cells and to recent microroller experiments. In both cases, our scheme learns hydrodynamic equations that reproduce quantitatively the self-organized collective dynamics observed in the simulations and experiments. This inference framework makes it possible to measure a large number of hydrodynamic parameters in parallel and directly from video data.Comment: Added statistical analysis of learned parameters, Added comparison to analytic coarse-graining approaches, Added spectral comparisons, Added framework application on fish dat

A conceptual framework for studying collective reactions to events in location-based social media

Events are a core concept of spatial information, but location-based social media (LBSM) provide information on reactions to events. Individuals have varied degrees of agency in initiating, reacting to or modifying the course of events, and reactions include observations of occurrence, expressions containing sentiment or emotions, or a call to action. Key characteristics of reactions include referent events and information about who reacted, when, where and how. Collective reactions are composed of multiple individual reactions sharing common referents. They can be characterized according to the following dimensions: spatial, temporal, social, thematic and interlinkage. We present a conceptual framework, which allows characterization and comparison of collective reactions. For a thematically well-defined class of event such as storms, we can explore differences and similarities in collective attribution of meaning across space and time. Other events may have very complex spatio-temporal signatures (e.g. political processes such as Brexit or elections), which can be decomposed into series of individual events (e.g. a temporal window around the result of a vote). The purpose of our framework is to explore ways in which collective reactions to events in LBSM can be described and underpin the development of methods for analysing and understanding collective reactions to events

Dynamics, scaling behavior, and control of nuclear wrinkling

The cell nucleus is enveloped by a complex membrane, whose wrinkling has been implicated in disease and cellular aging. The biophysical dynamics and spectral evolution of nuclear wrinkling during multicellular development remain poorly understood due to a lack of direct quantitative measurements. Here, we combine live-imaging experiments, theory, and simulations to characterize the onset and dynamics of nuclear wrinkling during egg development in the fruit fly, Drosophila melanogaster, when nurse cell nuclei increase in size and display stereotypical wrinkling behavior. A spectral analysis of three-dimensional high-resolution data from several hundred nuclei reveals a robust asymptotic power-law scaling of angular fluctuations consistent with renormalization and scaling predictions from a nonlinear elastic shell model. We further demonstrate that nuclear wrinkling can be reversed through osmotic shock and suppressed by microtubule disruption, providing tunable physical and biological control parameters for probing mechanical properties of the nuclear envelope. Our findings advance the biophysical understanding of nuclear membrane fluctuations during early multicellular development.Comment: Main text: 10 pages, 3 figures. SI: 19 pages, 10 figures, 1 tabl