arXiv subjects

E. Moses

Publications and source records attributed to E. Moses.

3 recordsLinked to original sources

arXiv2005

A quantitative analysis of concepts and semantic structure in written language: Long range correlations in dynamics of texts

Understanding texts requires memory: the reader has to keep in mind enough words to create meaning. This calls for a relation between the memory of the reader and the structure of the text. To investigate this interaction, we first identify a connectivity matrix defined by co-occurrence of words in the text. A vector space of words characterizing the text is spanned by the principal directions of this matrix. It is useful to think of these weighted combinations of words as representing ``concepts''. As the reader follows the text, the set of words in her window of attention follows a dynamical motion among these concepts. We observe long range power law correlations in this trajectory. By explicitly constructing surrogate hierarchical texts, we demonstrate that the power law originates from structural organization of texts into subunits such as chapters and paragraphs.

physics.soc-ph↗

arXiv2003

Cytokinesis: the initial linear phase crosses over to a multiplicity of non-linear endings

We investigate the final stage of cytokinesis in two types of amoeba, pointing out the existence of biphasic furrow contraction. The first phase is characterized by a constant contraction rate, is better studied, and seems universal to a large extent. The second phase is more diverse. In Dictyostelium discoideum the transition involves a change in the rate of contraction, and occurs when the width of the cleavage furrow is comparable to the height of the cell. In Entamoeba invadens the contractile ring carries the cell through the first phase, but cannot complete the second stage of cytokinesis. As a result, a cooperative mechanism has evolved in that organism, where a neighboring amoeba performs directed motion towards the dividing cell, and physically causes separation by means of extending a pseudopod. We expand here on a previous report of this novel chemotactic signaling mechanism.

q-bio.CB↗

arXiv1997

Fingering Instability in Combustion

A thin solid (e.g., paper), burning against an oxidizing wind, develops a fingering instability with two decoupled length scales. The spacing between fingers is determined by the Péclet number (ratio between advection and diffusion). The finger width is determined by the degree two dimensionality. Dense fingers develop by recurrent tip splitting. The effect is observed when vertical mass transport (due to gravity) is suppressed. The experimental results quantitatively verify a model based on diffusion limited transport.

cond-mat↗