Crafting a critical technical practice

In recent years, the category of practice-based research has become an essential component of discourse around public funding and evaluation of the arts in British higher education. When included under the umbrella of public policy concerned with the creative industries", technology researchers often find themselves collaborating with artists who consider their own participation to be a form of practice-based research. We are conducting a study under the Creator Digital Economies project asking whether technologists, themselves, should be considered as engaging in practice-based research, whether this occurs in collaborative situations, or even as a component of their own personal research [1]

Designing and evaluating virtual musical instruments: facilitating conversational user interaction

This paper is concerned with the design of interactive virtual musical instruments. An interaction design strategy which uses on-screen objects that respond to user actions in physically realistic ways is described. This approach allows musicians to 'play' the virtual instruments using the sound of their familiar acoustic instruments. An investigation of user experience identified three modes of interaction that characterise the musicians' approach to the virtual instruments: instrumental, ornamental and conversational. When using the virtual instruments in instrumental mode, musicians prioritise detailed control; in ornamental mode, they surrender detailed control to the software and allow it to transform their sound; in conversational mode, the musicians allow the virtual instrument to 'talk back', helping to shape the musical direction of performance much as a human playing partner might. Finding a balance between controllability and complexity emerged as a key issue in facilitating 'conversational' interaction. © 2008 Elsevier Ltd. All rights reserved

Charcot osteoarthropathy: one disease, two presentations

Charcot osteoarthropathy or Charcot foot is a disabling complication of diabetes and is associated with poor prognosis and high mortality. Its pathogenesis is not fully understood and its treatment is at best symptomatic. Furthermore, it is not known whether there is a specific type of neuropathy which affects osteoclastic activity, and thereby leads to reduction of bone mineral density and the development of Charcot osteoarthropathy. Recently it has been proposed that there is a difference in the presentation of Charcot osteoarthropathy between type 1 and type 2 diabetes. This article reviews the link between underlying osteopenia, abnormal biomechanical forces and type of neuropathy, and their varying interaction in the pathogenesis of Charcot osteoarthropathy in type 1 and type 2 diabetes. Further attention is drawn to the newly discovered osteoprotegerin/receptor activator of nuclear factor kappaB ligand (OPG/RANKL) cytokine system, which controls bone resorption. Increased osteoclastic activity in the acute Charcot foot may be associated with altered expression of OPG/RANKL signaling pathway and modulation of the OPG/RANKL equilibrium in Charcot osteoarthropathy may provide additional therapeutical option to manage this difficult condition.Biomedical Reviews 2005; 16: 43-48

Rotational States of Magnetic Molecules

We study a magnetic molecule that exhibits spin tunneling and is free to rotate about its anisotropy axis. Exact low-energy eigenstates of the molecule that are superpositions of spin and rotational states are obtained. We show that parameter $\alpha = 2(\hbar S)^2/(I\Delta)$ determines the ground state of the molecule. Here $\hbar S$ is the spin, $I$ is the moment of inertia, and $\Delta$ is the tunnel splitting. The magnetic moment of the molecule is zero at $\alpha \alpha_c$. At $\alpha \to \infty$ the spin of the molecule localizes in one of the directions along the anisotropy axis.Comment: 4 pages, 3 figure

Renormalization of the tunnel splitting in a rotating nanomagnet

We study spin tunneling in a magnetic nanoparticle with biaxial anisotropy that is free to rotate about its anisotropy axis. Exact instanton of the coupled equations of motion is found that connects degenerate classical energy minima. We show that mechanical freedom of the particle renormalizes magnetic anisotropy and increases the tunnel splitting.Comment: 4 pages, 3 figure

Reconstructing a Simple Polytope from its Graph

Blind and Mani (1987) proved that the entire combinatorial structure (the vertex-facet incidences) of a simple convex polytope is determined by its abstract graph. Their proof is not constructive. Kalai (1988) found a short, elegant, and algorithmic proof of that result. However, his algorithm has always exponential running time. We show that the problem to reconstruct the vertex-facet incidences of a simple polytope P from its graph can be formulated as a combinatorial optimization problem that is strongly dual to the problem of finding an abstract objective function on P (i.e., a shelling order of the facets of the dual polytope of P). Thereby, we derive polynomial certificates for both the vertex-facet incidences as well as for the abstract objective functions in terms of the graph of P. The paper is a variation on joint work with Michael Joswig and Friederike Koerner (2001).Comment: 14 page

Semiclassical Analysis of the Wigner 12j12j Symbol with One Small Angular Momentum

We derive an asymptotic formula for the Wigner $12j$ symbol, in the limit of one small and 11 large angular momenta. There are two kinds of asymptotic formulas for the $12j$ symbol with one small angular momentum. We present the first kind of formula in this paper. Our derivation relies on the techniques developed in the semiclassical analysis of the Wigner $9j$ symbol [L. Yu and R. G. Littlejohn, Phys. Rev. A 83, 052114 (2011)], where we used a gauge-invariant form of the multicomponent WKB wave-functions to derive asymptotic formulas for the $9j$ symbol with small and large angular momenta. When applying the same technique to the $12j$ symbol in this paper, we find that the spinor is diagonalized in the direction of an intermediate angular momentum. In addition, we find that the geometry of the derived asymptotic formula for the $12j$ symbol is expressed in terms of the vector diagram for a $9j$ symbol. This illustrates a general geometric connection between asymptotic limits of the various $3nj$ symbols. This work contributes the first known asymptotic formula for the $12j$ symbol to the quantum theory of angular momentum, and serves as a basis for finding asymptotic formulas for the Wigner $15j$ symbol with two small angular momenta.Comment: 15 pages, 14 figure

Spin precession and alternating spin polarization in spin-3/2 hole systems

The spin density matrix for spin-3/2 hole systems can be decomposed into a sequence of multipoles which has important higher-order contributions beyond the ones known for electron systems [R. Winkler, Phys. Rev. B \textbf{70}, 125301 (2004)]. We show here that the hole spin polarization and the higher-order multipoles can precess due to the spin-orbit coupling in the valence band, yet in the absence of external or effective magnetic fields. Hole spin precession is important in the context of spin relaxation and offers the possibility of new device applications. We discuss this precession in the context of recent experiments and suggest a related experimental setup in which hole spin precession gives rise to an alternating spin polarization.Comment: 4 pages, 2 figures, to appear in Physical Review Letter