Now showing items 1-20 of 33

    • Asymmetric Mutualism in Two- and Three-Dimensional Range Expansions 

      Lavrentovich, Maxim Olegovich; Nelson, David R. (American Physical Society, 2014)
      Genetic drift at the frontiers of two-dimensional range expansions of microorganisms can frustrate local cooperation between different genetic variants, demixing the population into distinct sectors. In a biological context, ...
    • Bending forces plastically deform growing bacterial cell walls 

      Amir, Ariel; Babaeipour, F.; McIntosh, D. B.; Nelson, David R.; Jun, Suckjoon (Proceedings of the National Academy of Sciences, 2014)
      Cell walls define a cell shape in bacteria. They are rigid to resist large internal pressures, but remarkably plastic to adapt to a wide range of external forces and geometric constraints. Currently, it is unknown how ...
    • Collapse and Folding of Pressurized Rings in Two Dimensions 

      Katifori, Eleni; Alben, Silas; Nelson, David R. (American Physical Society, 2009)
      Hydrostatically pressurized circular rings confined to two dimensions (or cylinders constrained to have only z-independent deformations) undergo Euler-type buckling when the outside pressure exceeds a critical value. We ...
    • Competition and cooperation in one-dimensional stepping-stone models 

      Korolev, K.; Nelson, David R. (American Physical Society, 2011)
      Mutualism is a major force driving evolution and sustaining ecosystems. Although the importance of spatial degrees of freedom and number fluctuations is well known, their effects on mutualism are not fully understood. With ...
    • Cooperativity, Fluctuations and Inhomogeneities in Soft Matter 

      Paulose, Jayson Joseph (2013-09-30)
      This thesis presents four investigations into mechanical aspects of soft thin structures, focusing on the effects of stochastic and thermal fluctuations and of material inhomogeneities. First, we study the self-organization ...
    • Defect-Mediated Emulsification in Two Dimensions 

      Korolev, Kirill Sergeevich; Nelson, David R. (American Physical Society, 2008)
      We consider two-dimensional dispersions of droplets of isotropic phase in a liquid with an XY-like order parameter, tilt, nematic, and hexatic symmetries being included. Strong anchoring boundary conditions are assumed. ...
    • Delayed Buckling and Guided Folding of Inhomogeneous Capsules 

      Datta, Sujit; Kim, Shin-Hyun; Paulose, Jayson; Abbaspourrad, Alireza; Nelson, David R.; Weitz, David A. (American Physical Society, 2012)
      Colloidal capsules can sustain an external osmotic pressure; however, for a sufficiently large pressure, they will ultimately buckle. This process can be strongly influenced by structural inhomogeneities in the capsule ...
    • Diffusion, Absorbing States, and Nonequilibrium Phase Transitions in Range Expansions and Evolution 

      Lavrentovich, Maxim Olegovich (2014-10-21)
      The spatial organization of a population plays a key role in its evolutionary dynamics and growth. In this thesis, we study the dynamics of range expansions, in which populations expand into new territory. Focussing on ...
    • Elastic Instability of a Crystal Growing on a Curved Surface 

      Meng, Guangnan; Paulose, Jayson Joseph; Nelson, David R.; Manoharan, Vinothan N. (American Association for the Advancement of Science, 2014)
      Although the effects of kinetics on crystal growth are well understood, the role of substrate curvature is not yet established. We studied rigid, two-dimensional colloidal crystals growing on spherical droplets to understand ...
    • Elastic Platonic Shells 

      Yong, Ee; Nelson, David R.; Mahadevan, Lakshminarayanan (American Physical Society, 2013)
      On microscopic scales, the crystallinity of flexible tethered or cross-linked membranes determines their mechanical response. We show that by controlling the type, number, and distribution of defects on a spherical elastic ...
    • Evolutionary dynamics with fluctuating population sizes and strong mutualism 

      Chotibut, Thiparat; Nelson, David R. (American Physical Society (APS), 2015)
      Game theory ideas provide a useful framework for studying evolutionary dynamics in a well-mixed environment. This approach, however, typically enforces a strictly fixed overall population size, deemphasizing natural growth ...
    • Fisher Equation with Turbulence in One Dimension 

      Benzi, Roberto; Nelson, David R. (Elsevier, 2009)
      As an example of life at high Reynolds number, we investigate the dynamics of the Fisher equation for the spreading of micro-organisms in one dimension subject to both turbulent convection and diffusion. We show that for ...
    • Foldable structures and the natural design of pollen grains 

      Katifori, Eleni; Alben, Silas; Cerda, Enrique; Nelson, David R.; Dumais, Jacques (Proceedings of the National Academy of Sciences, 2010)
      Upon release from the anther, pollen grains of angiosperm flowers are exposed to a dry environment and dehydrate. To survive this process, pollen grains possess a variety of physiological and structural adaptations. Perhaps ...
    • Gene Surfing in Expanding Populations 

      Hallatschek, Oskar; Nelson, David R. (Elsevier, 2008)
      Spatially resolved genetic data is increasingly used to reconstruct the migrational history of species. To assist such inference, we study, by means of simulations and analytical methods, the dynamics of neutral gene ...
    • Genetic Demixing and Evolution in Linear Stepping Stone Models 

      Korolev, K.; Avlund, Mikkel; Hallatschek, Oskar; Nelson, David R. (American Physical Society, 2010)
      Results for mutation, selection, genetic drift, and migration in a one-dimensional continuous population are reviewed and extended. The population is described by a continuous limit of the stepping stone model, which leads ...
    • Genome Landscapes and Bacteriophage Codon Usage 

      Lucks, Julius B.; Nelson, David R.; Kudla, Grzegorz R.; Plotkin, Joshua B.; Regev, Aviv (Public Library of Science, 2008)
      Across all kingdoms of biological life, protein-coding genes exhibit unequal usage of synonymous codons. Although alternative theories abound, translational selection has been accepted as an important mechanism that shapes ...
    • Growth, Competition and Cooperation in Spatial Population Genetics 

      Pigolotti, S.; Benzi, R.; Perlekar, P; Jensen, M. H.; Toschi, F.; Nelson, David R. (Elsevier, 2013)
      We study an individual based model describing competition in space between two different alleles. Although the model is similar in spirit to classic models of spatial population genetics such as the stepping stone model, ...
    • How Obstacles Perturb Population Fronts and Alter Their Genetic Structure 

      Möbius, Wolfram; Murray, Andrew W.; Nelson, David R. (Public Library of Science, 2015)
      As populations spread into new territory, environmental heterogeneities can shape the population front and genetic composition. We focus here on the effects of an important building block of heterogeneous environments, ...
    • Life at the Front of an Expanding Population 

      Hallatschek, Oskar; Nelson, David R. (Wiley-Blackwell, 2010)
      Environmental changes have caused episodes of habitat expansions in the evolutionary history of many species. These range changes affect the dynamics of biological evolution in multiple ways. Recent microbial experiments ...
    • Localization Behavior of Vibrational Modes in Granular Packings 

      Zeravcic, Zorana; Saarloos, Wim; Nelson, David R. (EDP Sciences, 2008)
      We study the localization of vibrational modes of frictionless granular media. We introduce a new method, motivated by earlier work on non-Hermitian quantum problems, which works well both in the localized regime where the ...