Abstract: We investigate the coupling factor phi( mu) that quantifies the magnetic flux phi per magnetic moment mu of a point-like magnetic dipole that couples to a superconducting quantum interference device (SQUID). Representing the dipole by a tiny current-carrying (Amperian) loop, the reciprocity of mutual inductances of SQUID and Amperian loop provides an elegant way of calculating phi(mu)(r,e(mu)) vs. position r and orientation e(mu) of the dipole anywhere in space from the magnetic field B-J(r) produced by a supercurrent circulating in the SQUID loop. We use numerical simulations based on London and Ginzburg-Landau theory to calculate phi (mu) from the supercurrent density distributions in various superconducting loop geometries. We treat the far-field regime ( r greater than or similar to a= inner size of the SQUID loop) with the dipole placed on (oriented along) the symmetry axis of circular or square shaped loops. We compare expressions for phi (mu) from simple filamentary loop models with simulation results for loops with finite width w (outer size A > alpha), thickness d and London penetration depth lambda(L )and show that for thin ( d << alpha ) and narrow (w < alpha) loops the introduction of an effective loop size a(eff) in the filamentary loop-model expressions results in good agreement with simulations. For a dipole placed right in the center of the loop, simulations provide an expression phi(mu)(a,A,d,lambda(L)) that covers a wide parameter range. In the near-field regime (dipole centered at small distance z above one SQUID arm) only coupling to a single strip representing the SQUID arm has to be considered. For this case, we compare simulations with an analytical expression derived for a homogeneous current density distribution, which yields excellent agreement for lambda(L)>w,d . Moreover, we analyze the improvement of phi(mu) provided by the introduction of a narrow constriction in the SQUID arm below the magnetic dipole.

Abstract: We have studied tunnelling through Si donors incorporated in the quantum well of double barrier resonant tunnelling devices. In addition to a resonance associated with the ground state of a single donor (1s level), a novel donor-related resonance at a smaller binding energy is observed in high magnetic fields where it becomes dominant over the Is resonance. We attribute this novel feature to a D-minus state of a shallow donor.

Abstract: The mechanism allowing the transition from a two-dimensional strained layer of CdSe on ZnSe to self-assembled islands induced by the use of amorphous selenium is still not fully understood. For a better understanding, atomic force microscopy and transmission electron microscopy studies were performed on CdSe films with a thickness close to that for quantum dot formation. Below this thickness, the sample surface results in undulations along the [110] crystal direction, while few quantum dots are situated in the wave valleys. Plan view transmission electron microscopy studies reveal a strong anisotropy of the islands and show that the Se desorption conditions are crucial. (C) 2006 Elsevier B.V. All rights reserved.

Abstract: This publication introduces the audiovisual geometry database with Gielis transformations as initial records for a prototype of the database. A concise overview is given of the rationale behind the database and studying wave phenomena with Gielis transformations. First results on a form of timbral polyphony observed in Gielis curves and future work are briefly discussed.

Abstract: The richness, diversity, connection, depth and pleasure of studying symmetry continue to open doors. Here we report a connection between Coxeter's Apeirogon and the geometry associated with pictorial space, parabolic rotation and dual numbers.