Who makes better use of technology for learning in D&T? Schools or university?

University teacher training departments have many functions in their role as Schools for Initial Teacher Education (ITE), these include accrediting qualified teacher status, teaching subject knowledge and pedagogy, and influencing change in a school subject's content and pedagogy. This paper discusses this latter area. It can be easy for teacher training in universities to become ivory towers, modelling new ideas for curriculum delivery and content in a 'bubble' away from the real world of the school classroom. A centre of design and technology (D&T) education at an English university has undertaken research-led developments in the use of web 2.0 technologies and technology enhanced learning (TEL), modelling how they can be used in the classroom. The research examined in this paper is the next stage of the centre's curriculum development to ensure the relevance of the university curriculum content and practices. Anecdotal evidence suggests that the use of TEL in secondary schools is inconsistent and sporadic with D&T teachers using TEL, with minimal awareness of research available, which could inform their practice. This impacts on the centre's trainee teachers as they begin teaching in schools during their final year of the course, with a possible unrealistic expectation of how TEL is used in schools, based on their university experiences

First Principles Calculations of Ionic Vibrational Frequencies in PbMg1/3Nb2/3O3

Lattice dynamics for several ordered supercells with composition PbMg1/3Nb2/3O (PMN) were calculated with first-principles frozen phonon methods. Nominal symmetries of the supercells studied are reduced by lattice instabilities. Lattice modes corresponding to these instabilities, equilibrium ionic positions, and infrared (IR) reflectivity spectra are reported.Comment: 6 pages; Fundamental physics of Ferroelectrics 200

Control of P2X2 Channel Permeability by the Cytosolic Domain

ATP-gated P2X channels are the simplest of the three families of transmitter-gated ion channels. Some P2X channels display a time- and activation-dependent change in permeability as they undergo the transition from the relatively Na+-selective I1 state to the I2 state, which is also permeable to organic cations. We report that the previously reported permeability change of rat P2X2 (rP2X2) channels does not occur at mouse P2X2 (mP2X2) channels expressed in oocytes. Domain swaps, species chimeras, and point mutations were employed to determine that two specific amino acid residues in the cytosolic tail domain govern this difference in behavior between the two orthologous channels. The change in pore diameter was characterized using reversal potential measurements and excluded field theory for several organic ions; both rP2X2 and mP2X2 channels have a pore diameter of ~11 Å in the I1 state, but the transition to the I2 state increases the rP2X2 diameter by at least 3 Å. The I1 to I2 transition occurs with a rate constant of ~0.5 s^-1. The data focus attention on specific residues of P2X2 channel cytoplasmic domains as determinants of permeation in a state-specific manner

Effects of Vacancies on Properties of Relaxor Ferroelectrics: a First-Principles Study

A first-principles-based model is developed to investigate the influence of lead vacancies on the properties of relaxor ferroelectric Pb(Sc1/2Nb1/2)O3 (PSN). Lead vacancies generate large, inhomogeneous, electric fields that reduce barriers between energy minima for different polarization directions. This naturally explains why relaxors with significant lead vacancy concentrations have broadened dielectric peaks at lower temperatures, and why lead vacancies smear properties in the neighborhood of the ferroelectric transition in PSN. We also reconsider the conventional wisdom that lead vacancies reduce the magnitude of dielectric response.Comment: 11 pages, 1 figur

Building effective models from sparse but precise data

A common approach in computational science is to use a set of of highly precise but expensive calculations to parameterize a model that allows less precise, but more rapid calculations on larger scale systems. Least-squares fitting on a model that underfits the data is generally used for this purpose. For arbitrarily precise data free from statistic noise, e.g. ab initio calculations, we argue that it is more appropriate to begin with a ensemble of models that overfit the data. Within a Bayesian framework, a most likely model can be defined that incorporates physical knowledge, provides error estimates for systems not included in the fit, and reproduces the original data exactly. We apply this approach to obtain a cluster expansion model for the Ca[Zr,Ti]O3 solid solution.Comment: 10 pages, 3 figures, submitted to Physical Review Letter

Grain Boundary Loops in Graphene

Topological defects can affect the physical properties of graphene in unexpected ways. Harnessing their influence may lead to enhanced control of both material strength and electrical properties. Here we present a new class of topological defects in graphene composed of a rotating sequence of dislocations that close on themselves, forming grain boundary loops that either conserve the number of atoms in the hexagonal lattice or accommodate vacancy/interstitial reconstruction, while leaving no unsatisfied bonds. One grain boundary loop is observed as a "flower" pattern in scanning tunneling microscopy (STM) studies of epitaxial graphene grown on SiC(0001). We show that the flower defect has the lowest energy per dislocation core of any known topological defect in graphene, providing a natural explanation for its growth via the coalescence of mobile dislocations.Comment: 23 pages, 7 figures. Revised title; expanded; updated reference

Diffusion of Point Defects in Two-Dimensional Colloidal Crystals

We report the first study of the dynamics of point defects, mono and di-vacancies, in a confined 2-D colloidal crystal in real space and time using digital video microscopy. The defects are introduced by manipulating individual particles with optical tweezers. The diffusion rates are measured to be $D_{mono}/a^{2}\cong3.27\pm0.03$Hz for mono-vacancies and $D_{di}/a^{2}\cong3.71\pm0.03$Hz for di-vacancies. The elementary diffusion processes are identified and it is found that the diffusion of di-vacancies is enhanced by a \textit{dislocation dissociation-recombination} mechanism. Furthermore, the defects do not follow a simple random walk but their hopping exhibits memory effects, due to the reduced symmetry (compared to the triangular lattice) of their stable configurations, and the slow relaxation rates of the lattice modes.Comment: 6 pages (REVTEX), 5 figures (PS