3,361 research outputs found
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 determines the ground state of
the molecule. Here is the spin, is the moment of inertia, and
is the tunnel splitting. The magnetic moment of the molecule is zero
at . At 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 Symbol with One Small Angular Momentum
We derive an asymptotic formula for the Wigner symbol, in the limit of
one small and 11 large angular momenta. There are two kinds of asymptotic
formulas for the 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 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 symbol with small and large angular momenta. When applying the same
technique to the 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
symbol is expressed in terms of the vector diagram for a symbol. This
illustrates a general geometric connection between asymptotic limits of the
various symbols. This work contributes the first known asymptotic formula
for the symbol to the quantum theory of angular momentum, and serves as a
basis for finding asymptotic formulas for the Wigner 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
- …