Multi-Level Modeling of Quotation Families Morphogenesis

This paper investigates cultural dynamics in social media by examining the proliferation and diversification of clearly-cut pieces of content: quoted texts. In line with the pioneering work of Leskovec et al. and Simmons et al. on memes dynamics we investigate in deep the transformations that quotations published online undergo during their diffusion. We deliberately put aside the structure of the social network as well as the dynamical patterns pertaining to the diffusion process to focus on the way quotations are changed, how often they are modified and how these changes shape more or less diverse families and sub-families of quotations. Following a biological metaphor, we try to understand in which way mutations can transform quotations at different scales and how mutation rates depend on various properties of the quotations.Comment: Published in the Proceedings of the ASE/IEEE 4th Intl. Conf. on Social Computing "SocialCom 2012", Sep. 3-5, 2012, Amsterdam, N

Competition and Selection Among Conventions

In many domains, a latent competition among different conventions determines which one will come to dominate. One sees such effects in the success of community jargon, of competing frames in political rhetoric, or of terminology in technical contexts. These effects have become widespread in the online domain, where the data offers the potential to study competition among conventions at a fine-grained level. In analyzing the dynamics of conventions over time, however, even with detailed on-line data, one encounters two significant challenges. First, as conventions evolve, the underlying substance of their meaning tends to change as well; and such substantive changes confound investigations of social effects. Second, the selection of a convention takes place through the complex interactions of individuals within a community, and contention between the users of competing conventions plays a key role in the convention's evolution. Any analysis must take place in the presence of these two issues. In this work we study a setting in which we can cleanly track the competition among conventions. Our analysis is based on the spread of low-level authoring conventions in the eprint arXiv over 24 years: by tracking the spread of macros and other author-defined conventions, we are able to study conventions that vary even as the underlying meaning remains constant. We find that the interaction among co-authors over time plays a crucial role in the selection of them; the distinction between more and less experienced members of the community, and the distinction between conventions with visible versus invisible effects, are both central to the underlying processes. Through our analysis we make predictions at the population level about the ultimate success of different synonymous conventions over time--and at the individual level about the outcome of "fights" between people over convention choices.Comment: To appear in Proceedings of WWW 2017, data at https://github.com/CornellNLP/Macro

Toward major evolutionary transitions theory 2.0

The impressive body of work on the major evolutionary transitions in the last 20 y calls for a reconstruction of the theory although a 2D account (evolution of informational systems and transitions in individuality) remains. Significant advances include the concept of fraternal and egalitarian transitions (lower-level units like and unlike, respectively). Multilevel selection, first without, then with, the collectives in focus is an important explanatory mechanism. Transitions are decomposed into phases of origin, maintenance, and transformation (i.e., further evolution) of the higher level units, which helps reduce the number of transitions in the revised list by two so that it is less top-heavy. After the transition, units show strong cooperation and very limited realized conflict. The origins of cells, the emergence of the genetic code and translation, the evolution of the eukaryotic cell, multicellularity, and the origin of human groups with language are reconsidered in some detail in the light of new data and considerations. Arguments are given why sex is not in the revised list as a separate transition. Some of the transitions can be recursive (e.g., plastids, multicellularity) or limited (transitions that share the usual features of major transitions without a massive phylogenetic impact, such as the micro- and macronuclei in ciliates). During transitions, new units of reproduction emerge, and establishment of such units requires high fidelity of reproduction (as opposed to mere replication)

Construction of artificial skin tissue with placode-like structures in well-defined patterns using dielectrophoresis

During embryonic development of animal skin tissue, the skin cells form regular patterns of high cell density (placodes) where hair or feathers will be formed. These placodes are thought to be formed by the aggregation of dermal cells into condensates. The aggregation process is thought to be controlled by a reaction-diffusion mechanism of activator and inhibitor molecules, and involve mechanical forces between cells and cells with the matrix. In this project, placode formation in chicken embryonic skin cells was used as a model system for the study of the mechanism by which the placodes are formed. Artificial aggregates of chicken embryonic skin cells were created by suspending them in a 300 mM low conductivity sorbitol solution and attracting them by positive dielectrophoresis to high field regions within microelectrode arrays by applying a 10 - 20 Vpk-pk 1 MHz signal across the microelectrodes. It was demonstrated that using this method aggregates can be produced in a large variety of patterns and that the distance between the aggregates and aggregate size and shape within the pattern can be controlled effectively. Custom-built image analysis tools were developed in LabVIEW to analyze the patterns formed. The formation of aggregates by dielectrophoresis was followed by an immobilization phase of the resulting patterns inside a gel matrix, forming an artificial skin. Nutrients and oxygen were supplied externally. Long-term incubation of the artificial skin shows that embryonic skin cells in the aggregates were viable and showed behavior similar to that of developing embryonic skin, including further aggregation of the cells and the formation of cell condensates. The domain size was shown to have an influence on the condensation process, with cells in small aggregates forming only one condensate near the centre of the aggregate, and several condensates in larger aggregates. Whilst the distribution of cell condensates within the aggregates in round large aggregates is predominantly random, some line formation could be observed in linear aggregations, indicating some self-organization may be occurring

Resolving the Anti-Antievolutionism Dilemma: A Brief for Relational Evolutionary Thinking in Anthropology

Anthropologists often disagree about whether, or in what ways, anthropology is “evolutionary.” Anthropologists defending accounts of primate or human biological development and evolution that conflict with mainstream “neo-Darwinian” thinking have sometimes been called “creationists” or have been accused of being “antiscience.” As a result, many cultural anthropologists struggle with an “anti-antievolutionism” dilemma: they are more comfortable opposing the critics of evolutionary biology, broadly conceived, than they are defending mainstream evolutionary views with which they disagree. Evolutionary theory, however, comes in many forms. Relational evolutionary approaches such as Developmental Systems Theory, niche construction, and autopoiesis–natural drift augment mainstream evolutionary thinking in ways that should prove attractive to many anthropologists who wish to affirm evolution but are dissatisfied with current “neo-Darwinian” hegemony. Relational evolutionary thinking moves evolutionary discussion away from reductionism and sterile nature–nurture debates and promises to enable fresh approaches to a range of problems across the subfields of anthropology

The nature of growth in the biofuel feedstock and bloom-forming green macroalga Ulva

Ulva is a genus of multicellular green algae that is phylogenetically similar to uni- cellular green algae such as Chlamydomonas and Ostreococcus. Ulva is present in much of the coastal benthic zones worldwide, and is of great interest for three main reasons. Firstly, Ulva is an important feedstock for biofuels. Secondly, many Ulva species are massively proliferating organisms that cause Harmful Algal Blooms, which are ecologically devastating. Finally, Ulva is an important model organism that could elucidate the evolution of multicellularity. This thesis investigates the physiology of growth in Ulva in four sequential results chapters. The first establishes a statistical proof for the goodness of fit of gene family occupancy data to a discrete power law model. This was an assumption used in the only Ulva genome study, which found no genomic signature for multicellularity. This establishes the baseline for the in- vestigation of bottom-up morphogenesis in Ulva. The second is the investigation of differential growth, by identifying cell tessellation patterns in different morphologies of Ulva thalli, namely the “ribbon” and “leaf” morphotypes, with mathematical mod- els using Voronoi tessellations. The third expands investigates differential growth in the ribbon and leaf morphotypes with a focus on identifying potential mechanisms with further mathematical models using Centroidal Voronoi Tessellations. The fourth aims to develop experimental techniques to confirm the hypotheses arising from the mathematical modelling in the second and third chapters. The first part involves the use of EdU cellular proliferation assays. The remainder of the chapter will investigate the development of a live-imaging biomass monitoring system that aims to improve the accuracy, reliability and temporal resolution of aquatic biomass measurements. It can be concluded that Ulva does not show a genomic signature for multicellularity, and bottom-up mechanisms likely explain its morphogenesis and morphologies

Branching Boogaloo: Botanical Adventures in Multi-Mediated Morphologies

FormaLeaf is a software interface for exploring leaf morphology using parallel string rewriting grammars called L-systems. Scanned images of dicotyledonous angiosperm leaves removed from plants around Bard’s campus are displayed on the left and analyzed using the computer vision library OpenCV. Morphometrical information and terminological labels are reported in a side-panel. “Slider mode” allows the user to control the structural template and growth parameters of the generated L-system leaf displayed on the right. “Vision mode” shows the input and generated leaves as the computer ‘sees’ them. “Search mode” attempts to automatically produce a formally defined graphical representation of the input by evaluating the visual similarity of a generated pool of candidate leaves. The system seeks to derive a possible internal structural configuration for venation based purely off a visual analysis of external shape. The iterations of the generated L-system leaves when viewed in succession appear as a hypothetical development sequence. FormaLeaf was written in Processing