1,721,058 research outputs found
Domain formation on curved membranes: phase separation or Turing patterns?
No full textWe study by computer simulations the physics of domain formation on surfaces, as a model for pattern formation on biological membranes. We compare the dynamics predicted by a simple phase separation model for a binary mixture, with that obtained through a conserved Turing-like reaction-diffusion model. Both types of models have been proposed as frameworks for understanding the formation of domains in biological systems. Our main result is that the models can be qualitatively distinguished by analysing the competition dynamics which is set when initialising the system with a number of potential pattern-forming nuclei. Our simulations also suggest that the location of the steady state domains is not uniquely determined by the curvature. This lack of curvature dependence might be advantageous biologically, as it disentangles pattern formation from the mechanics and morphology of the cell membranes. We hope our study will stimulate further experimental work on pattern formation in cells, especially in relation to the cell polarisation problem
Phase diagram of force-induced DNA unzipping in exactly solvable models
No full textThe mechanical separation of a double helical DNA structure induced by forces pulling apart the two DNA strands ("unzipping") has been the subject of recent experiments. Analytical results are obtained within various models of interacting pairs of directed walks in the (1,1.....1) direction on the hypercubic lattice, and the phase diagram in the force-temperature plane is studied for a variety of cases. The scaling behavior is determined at both the unzipping and melting transitions. We confirm the existence of a cold denaturation transition recently observed in numerical simulations: for a finite range of forces. the system is unzipped by decreasing the temperature. The existence of this transition is rigorously established for generic lattice and continuum space models
Motility-induced phase separation in an active dumbbell fluid
No full textWe study a suspension of active dumbbells of variable density, as a minimal example of an active polar fluid. As in a fluid of spherical swimmers, we find that motility triggers a nonequilibrium phase separation if the density exceeds a critical threshold. We also show that the phase separation is lost when the active force becomes too large, ultimately due to inertial effects. Remarkably, the aggregates which assemble spontaneously break chiral symmetry and rotate; they also display a nematic ordering with spiral patterns
Shearing self-propelled suspensions: Arrest of coarsening and suppression of giant density fluctuations
No full textWe study the effect of a linear shear flow on a collection of interacting active, self-propelled particles modeled via the Vicsek model. The imposed flow has a dramatic effect on the behavior of the model. We find that in the presence of shear there is no order-disorder transition, and that coarsening of the domains is arrested. Shear also suppresses the so-called giant density fluctuations that are observed in the quiescent limit
Bistable Defect Structures In Blue Phase Devices
No full textBlue phases are liquid crystals made up by networks of defects, or
disclination lines. While existing phase diagrams show a striking
variety of competing metastable topologies for these networks, very
little is known as to how to kinetically reach a target structure, or
how to switch from one to the other, which is of paramount importance
for devices. We theoretically identify two confined blue phase I systems
in which by applying an appropriate series of electric field it is
possible to select one of two bistable defect patterns. Our results may
be used to realize new generation and fast switching energy-saving
bistable devices in ultrathin surface treated blue phase I wafers
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
