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, isolated obstacles. With a combination of experiments, theory, and simulation, we show how isolated obstacles both create long-lived distortions of the front shape and amplify th...

Let G be a finite, undirected, d-regular graph and A(G) its normalized adjacency matrix, with eigenvalues 1=?1(A)????n??1. It is classical fact that ?n=?1 if only bipartite. Our main result provides quantitative separation of ?n from ?1 in the case Cayley graphs, terms their expansion. Denoting hout by (outer boundary) vertex expansion G, we show non-bipartite (constructed using group symmetric...

In this paper, we propose a class of linear codes and obtain their weight distribution. Some of these codes are almost optimal. Moreover, several classes of constant composition codes(CCCs) are constructed as subcodes of linear codes.

The uniqueness of some ternary constant-composition codes is proved by combinato-rial methods. 1. Introduction. For all basic notions and facts about coding theory which are not introduced here we refer to [3]. All codes to be considered are ternary constant-composition codes. Ternary constant-composition (TCC) codes of length n are codes with constant composition of " zeros " , " ones " and " ...

Range expansion of spreading organisms has been found to follow three types: (i) linear expansion with a constant rate of spread; (ii) bi-phase expansion with a faster linear expansion following a slower linear expansion; and (iii) accelerating expansion with a continuously increasing rate of spread. To date, no overarching formula exists that can be applied to all three types of range expansio...