The paper argues that the notion of learning environment is not a theoretical concept that can serve as the centerpiece and unit of analysis in research on computersupported collaborative learning, and that the preoccupation in this research domain with implementation of digital learning environments is a largely misguided consequence of the unquestioned expectation that technology will radical...

Expansive laminoplasty for ossification of the posterior longitudinal ligament (OPLL) has had favorable outcomes. Many modifications of expansive laminoplasty have been developed, including expansive laminoplasty with and without spinous process spacers (SPS). The purpose of this study was to determine whether surgical outcomes were similar between expansive laminoplasty surgeries with and with...

We introduce the property of pre-expansivity for cellular automata (CA): it is the property of being expansive on asymptotic pairs of configurations (i.e. configurations that differ in only finitely many positions). Pre-expansivity therefore lies between expansivity and pre-injectivity, two important notions of CA theory. We show that there exist one-dimensional pre-expansive CAs which are not ...

In this paper theorems are proved which provide for lifting and projecting expansive homeomorphisms through pseudocovering mappings so that the lift or projection is also an expansive homeomorphism. Using these techniques it is shown that the compact orientable surface of genus 2 admits an expansive homeomorphism.

Methods Using herbarium records from the Oklahoma Vascular Plants Database from 1903 to 2004, we reconstructed the spatial and temporal collection history of two alien invasive taxa (Lonicera japonica and Tamarix spp.) and three native expansive species (Ambrosia psilostachya, Amphiachyris dracunculoides and Juniperus virginiana). To compare the overall collecting trend, groups of native non-ex...

We consider the problem of straightening chains in d ≥ 3 dimensions, possibly embedded into higher dimensions, using expansive motions. For any d ≥ 3, we show that there is an open chain in d dimensions that is not straight and not self-touching yet has no expansive motion. Furthermore, for any ∆ > 0 and d ≥ 3, we show that there is an open chain in d dimensions that cannot be straightened usin...

A framework for understanding the geometry of continuous actions of Z was developed by Boyle and Lind using the notion of expansive behavior along lower-dimensional subspaces. For algebraic Z-actions of entropy rank one, the expansive subdynamics is readily described in terms of Lyapunov exponents. Here we show that periodic point counts for elements of an entropy rank one action determine the ...

A framework for understanding the geometry of continuous actions of Z was developed by Boyle and Lind using the notion of expansive behavior along lower-dimensional subspaces. For algebraic Z-actions of entropy rank one, the expansive subdynamics is readily described in terms of Lyapunov exponents. Here we show that periodic point counts for elements of an entropy rank one action determine the ...

BACKGROUND The aim of this project was to explore the process of change in a busy community dental clinic following a team development intervention designed to improve the management of student supervision during clinical placements. METHODS An action research model was used. Seven members of a community dental clinic team (three dentists, two dental therapists, one dental assistant and the c...

We investigate the interrelationships between the dynamical properties of commuting continuous maps of a compact metric space. Let X be a compact metric space. First we show the following. If τ : X → X is an expansive onto continuous map with the pseudo-orbit tracing property (POTP) and if there is a topologically mixing continuous map φ : X → X with τφ = φτ , then τ is topologically mixing. If...