Adaptivity and a posteriori error control for bifurcation problems II: Incompressible fluid flow in open systems with Z_2 symmetry

In this article we consider the a posteriori error estimation and adaptive mesh refinement of discontinuous Galerkin finite element approximations of the bifurcation problem associated with the steady incompressible Navier-Stokes equations. Particular attention is given to the reliable error estimation of the critical Reynolds number at which a steady pitchfork or Hopf bifurcation occurs when the underlying physical system possesses reflectional or Z_2 symmetry. Here, computable a posteriori error bounds are derived based on employing the generalization of the standard Dual-Weighted-Residual approach, originally developed for the estimation of target functionals of the solution, to bifurcation problems. Numerical experiments highlighting the practical performance of the proposed a posteriori error indicator on adaptively refined computational meshes are presented

Rapid Molecular Detection Methods for Arboviruses of Livestock of Importance to Northern Europe

Arthropod-borne viruses (arboviruses) have been responsible for some of the most explosive epidemics of emerging infectious diseases over the past decade. Their impact on both human and livestock populations has been dramatic. The early detection either through surveillance or diagnosis of virus will be a critical feature in responding and resolving the emergence of such epidemics in the future. Although some of the most important emerging arboviruses are human pathogens, this paper aims to highlight those diseases that primarily affect livestock, although many are zoonotic and some occasionally cause human mortality. This paper also highlights the molecular detection methods specific to each virus and identifies those emerging diseases for which a rapid detection methods are not yet developed

A Lanczos Method for Approximating Composite Functions

We seek to approximate a composite function h(x) = g(f(x)) with a global polynomial. The standard approach chooses points x in the domain of f and computes h(x) at each point, which requires an evaluation of f and an evaluation of g. We present a Lanczos-based procedure that implicitly approximates g with a polynomial of f. By constructing a quadrature rule for the density function of f, we can approximate h(x) using many fewer evaluations of g. The savings is particularly dramatic when g is much more expensive than f or the dimension of x is large. We demonstrate this procedure with two numerical examples: (i) an exponential function composed with a rational function and (ii) a Navier-Stokes model of fluid flow with a scalar input parameter that depends on multiple physical quantities

Energy coupling in short pulse laser solid interactions and its impact for space debris removal

Significant advances have been made over the last decade to improve the performance, efficiency, and contrast of high peak and average power laser systems, driven by their use in a wide variety of fields, from the industrial to the scientific. As the contrast of the lasers has improved, interactions with contrasts of 1012 are now routinely undertaken. At such high contrasts, there is negligible preplasma formation and the ionized surface layer created by subpicosecond-duration pulses typically forms a highly reflective "plasma mirror" capable of reflecting between 70% and 90% of the incident energy. Although such interactions are of significant interest for applications such as harmonic source production and to enable the underlying physics to be studied, their low absorption can limit their usefulness for applications such as space debris removal

Laser ablation loading of a surface-electrode ion trap

We demonstrate loading by laser ablation of $^{88}$Sr$^+$ ions into a mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed, frequency-tripled Nd:YAG with pulse energies of 1-10 mJ and durations of 3-5 ns. An additional laser is not required to photoionize the ablated material. The efficiency and lifetime of several candidate materials for the laser ablation target are characterized by measuring the trapped ion fluorescence signal for a number of consecutive loads. Additionally, laser ablation is used to load traps with a trap depth (40 meV) below where electron impact ionization loading is typically successful ($\gtrsim$ 500 meV).Comment: 4 pages, 4 figure