Lattice-corrected strain-induced vector potentials in graphene

The electronic implications of strain in graphene can be captured at low energies by means of pseudovector potentials which can give rise to pseudomagnetic fields. These strain-induced vector potentials arise from the local perturbation to the electronic hopping amplitudes in a tight-binding framework. Here we complete the standard description of the strain-induced vector potential, which accounts only for the hopping perturbation, with the explicit inclusion of the lattice deformations or, equivalently, the deformation of the Brillouin zone. These corrections are linear in strain and are different at each of the strained, inequivalent Dirac points, and hence are equally necessary to identify the precise magnitude of the vector potential. This effect can be relevant in scenarios of inhomogeneous strain profiles, where electronic motion depends on the amount of overlap among the local Fermi surfaces. In particular, it affects the pseudomagnetic field distribution induced by inhomogeneous strain configurations, and can lead to new opportunities in tailoring the optimal strain fields for certain desired functionalities.Comment: Errata for version

Exciton mediated one phonon resonant Raman scattering from one-dimensional systems

We use the Kramers-Heisenberg approach to derive a general expression for the resonant Raman scattering cross section from a one-dimensional (1D) system explicitly accounting for excitonic effects. The result should prove useful for analyzing the Raman resonance excitation profile lineshapes for a variety of 1D systems including carbon nanotubes and semiconductor quantum wires. We apply this formalism to a simple 1D model system to illustrate the similarities and differences between the free electron and correlated electron-hole theories.Comment: 10 pages, 6 figure

Chirality dependence of the radial breathing phonon mode density in single wall carbon nanotubes

A mass and spring model is used to calculate the phonon mode dispersion for single wall carbon nanotubes (SWNTs) of arbitrary chirality. The calculated dispersions are used to determine the chirality dependence of the radial breathing phonon mode (RBM) density. Van Hove singularities, usually discussed in the context of the single particle electronic excitation spectrum, are found in the RBM density of states with distinct qualitative differences for zig zag, armchair and chiral SWNTs. The influence the phonon mode density has on the two phonon resonant Raman scattering cross-section is discussed.Comment: 6 pages, 2 figures, submitted to Phys. Rev.

Teaching Hidden History: A Case Study of Dialogic Scaffolding in a Hybrid Graduate Course

Using an expanded version of Alexander’s (2008) theory of dialogic teaching developed by Rojas-Drummond, Torreblanca, Pedraza, Vélez, and Guzmán (2013), this case study explored how instructors and students in a hybrid graduate course engaged in the process of dialogic teaching and learning (DTL). In particular, we examined the ways in which scaffolding strategies used in the course supported inquiry-based learning. Our findings suggest that instructors and students engaged in all five dimensions of DTL as defined by Rojas-Drummond et al. (2013), and illuminate the ways in which scaffolding can facilitate inquiry-based learning in interdisciplinary instructional settings

Social presence in the 21st Century: an adjustment to the Community of Inquiry framework

The Community of Inquiry framework, originally proposed by Garrison, Anderson and Archer (2000) identifies teaching, social and cognitive presences as central to a successful online educational experience. This article presents the findings of a study conducted in Uruguay between 2007 and 2010. The research aimed to establish the role of cognitive, social and teaching presences in the professional development of 40 English language teachers on Continuous Professional Development (CPD) programmes delivered in blended learning settings. The findings suggest that teaching presence and cognitive presence have themselves 'become social'. The research points to social presence as a major lever for engagement, sense-making and peer support. Based on the patterns identified in the study, this article puts forward an adjustment to the Community of Inquiry framework, which shows social presence as more prominent within the teaching and cognitive constructs than the original version of the framework suggests

Record of a Sixteen-year-old White-tailed Deer (Odocoileus virginianus) in Carbondale, Illinois: a Brief Note.

In May 2004, a dead white-tailed deer (Odocoileus virginianus) radiocollared in 1991 was found in Carbondale, Illinois, and was aged at 16 years old via cementum annuli analysis. She was a member of an unharvested, free-ranging population and likely died of natural causes. Given the average longevity of deer in unharvested populations at about 8 years of age, our finding is quite rare. Increased longevity of deer can heighten lifetime reproductive output, which may contribute to elevated deer abundance and concentrated herbivory in urban settings