Pulse-induced acoustoelectric vibrations in surface-gated GaAs-based quantum devices

We present the results of a numerical investigation which show the excitation of acoustoelectric modes of vibration in GaAs-based heterostructures due to sharp nano-second electric-field pulses applied across surface gates. In particular, we show that the pulses applied in quantum information processing applications are capable of exciting acoustoelectric modes of vibration including surface acoustic modes which propagate for distances greater than conventional device dimensions. We show that the pulse-induced acoustoelectric vibrations are capable of inducing significant undesired perturbations to the evolution of quantum systems.Comment: To be published in Phys. Rev.

A numerical investigation of a piezoelectric surface acoustic wave interaction with a one-dimensional channel

We investigate the propagation of a piezoelectric surface acoustic wave (SAW) across a GaAs/Al$_X$Ga$_{1-X}$As heterostructure surface, on which there is fixed a metallic split-gate. Our method is based on a finite element formulation of the underlying equations of motion, and is performed in three-dimensions fully incorporating the geometry and material composition of the substrate and gates. We demonstrate attenuation of the SAW amplitude as a result of the presence of both mechanical and electrical gates on the surface. We show that the incorporation of a simple model for the screening by the two-dimensional electron gas (2DEG), results in a total electric potential modulation that suggests a mechanism for the capture and release of electrons by the SAW. Our simulations suggest the absence of any significant turbulence in the SAW motion which could hamper the operation of SAW based quantum devices of a more complex geometry.Comment: 8 pages, 8 figure

Modeling the Influence of a Variable Permeability Inclusion on Free-Surface Flow in an Inclined Aquifer

The interaction of sub-surface, gravity-driven flows with inclusions of different permeabilities are investigated theoretically using a model that exploits the relative shallowness of the motion. Numerically computed solutions for steady motion around cylindrical inclusions reveal a range of behaviors dependent on the ratio of the interior to exterior permeability and a dimensionless flow parameter that measures the far-field thickness to the product of the gradient of the slope down which the fluid flows and the width of the inclusion. When the inclusion is relatively narrow, the depth of the flow is little changed from its far-field value and the fluid is focused into inclusions of higher permeability and deflected around those of lower permeability. However, if the inclusion is relatively wide then three qualitatively different regimes emerge, dependent on the ratio of permeabilities. When the interior and exterior permeabilities are similar, then negligible deviation of the flow occurs apart from within thin transition layers at the boundary of the inclusion. When the permeabilities differ significantly, the flow forms deep ponds at either the upstream or downstream boundary of the inclusion for relatively low or high permeability inclusion, respectively, which arise due to deflection or focusing. In each case, asymptotic relationships are derived between the depth of the flow and the parameters. Inclusions of differing cross-section are also analyzed numerically and analytically to draw out the interplay between adjustment, deflection and focusing

Stationary shapes of deformable particles moving at low Reynolds numbers

Lecture Notes of the Summer School ``Microswimmers -- From Single Particle Motion to Collective Behaviour'', organised by the DFG Priority Programme SPP 1726 (Forschungszentrum J{\"{u}}lich, 2015).Comment: Pages C7.1-16 of G. Gompper et al. (ed.), Microswimmers - From Single Particle Motion to Collective Behaviour, Lecture Notes of the DFG SPP 1726 Summer School 2015, Forschungszentrum J\"ulich GmbH, Schriften des Forschungszentrums J\"ulich, Reihe Key Technologies, Vol 110, ISBN 978-3-95806-083-

Prescription for nursing informatics in pre-registration nurse education.

Nurses need to be able to use information and communications technology not only to support their own practice, but also to help their patients make best use of it. This article argues that nurses are not currently adequately prepared to work with information and technology through their pre-registration education. Reflecting the lack of nursing informatics expertise, it is recommended that all pre-registration nursing programmes should have access to a nursing informatics specialist. A prescription to meet the informatics needs of the newly qualified nurse is proposed. This places the areas that need to be included in pre-registration education into broad groups that both articulate the competencies that nurses need to develop, and indicate why they are needed, rather than providing context-free checklists of skills. This is presented as a binary scatter chart with two axes, skill to knowledge and technology to information

A Standard Platform for Testing and Comparison of MDAO Architectures

The Multidisciplinary Design Analysis and Optimization (MDAO) community has developed a multitude of algorithms and techniques, called architectures, for performing optimizations on complex engineering systems which involve coupling between multiple discipline analyses. These architectures seek to efficiently handle optimizations with computationally expensive analyses including multiple disciplines. We propose a new testing procedure that can provide a quantitative and qualitative means of comparison among architectures. The proposed test procedure is implemented within the open source framework, OpenMDAO, and comparative results are presented for five well-known architectures: MDF, IDF, CO, BLISS, and BLISS-2000. We also demonstrate how using open source soft- ware development methods can allow the MDAO community to submit new problems and architectures to keep the test suite relevant