A National Adverse Drug Reaction Reporting System for Malta

The mission of the Medicines Authority (MA) in Malta is to contribute to protection of public health through regulation of the safety, quality and efficacy of medicines for human use on the local market and to ensure that healthcare professionals and patients have access to accurate and up to date information about medicines. In order to disseminate information regarding safety of medicines, the MA publishes guidance notes for healthcare professionals and the pharmaceutical industry. The MA also publishes information on its website: http://www.health.gov.mt/mru/ On the 4th of May, 2004 the MA held a seminar to launch a national adverse drug reaction (ADR) reporting system involving the co-operation of doctors, dentists and pharmacists, as well as the pharmaceutical industry. The ADR reporting system will form part of an overall pharmacovigilance system within the Authority and this will be the primary means of collecting information useful in the surveillance of medicinal products.peer-reviewe

Dynamics of viscoelastic snap-through

We study the dynamics of snap-through when viscoelastic effects are present. To gain analytical insight we analyse a modified form of the Mises truss, a single-degree-of-freedom structure, which features an `inverted' shape that snaps to a `natural' shape. Motivated by the anomalously slow snap-through shown by spherical elastic caps, we consider a thought experiment in which the truss is first indented to an inverted state and allowed to relax while a specified displacement is maintained; the constraint of an imposed displacement is then removed. Focussing on the dynamics for the limit in which the timescale of viscous relaxation is much larger than the characteristic elastic timescale, we show that two types of snap-through are possible: the truss either immediately snaps back over the elastic timescale or it displays `pseudo-bistability', in which it undergoes a slow creeping motion before rapidly accelerating. In particular, we demonstrate that accurately determining when pseudo-bistability occurs requires the consideration of inertial effects immediately after the indentation force is removed. Our analysis also explains many basic features of pseudo-bistability that have been observed previously in experiments and numerical simulations; for example, we show that pseudo-bistability occurs in a narrow parameter range at the bifurcation between bistability and monostability, so that the dynamics is naturally susceptible to critical slowing down. We then study an analogous thought experiment performed on a continuous arch, showing that the qualitative features of the snap-through dynamics are well captured by the truss model. In addition, we analyse experimental and numerical data of viscoelastic snap-through times reported in the literature. Combining these approaches suggests that our conclusions may also extend to more complex viscoelastic structures used in morphing applications.Comment: Main text 37 pages, Appendices 13 page

Pull-in dynamics of overdamped microbeams

We study the dynamics of MEMS microbeams undergoing electrostatic pull-in. At DC voltages close to the pull-in voltage, experiments and numerical simulations have reported `bottleneck' behaviour in which the transient dynamics slow down considerably. This slowing down is highly sensitive to external forces, and so has widespread potential for applications that use pull-in time as a sensing mechanism, including high-resolution accelerometers and pressure sensors. Previously, the bottleneck phenomenon has only been understood using lumped mass-spring models that do not account for effects such as variable residual stress and different boundary conditions. We extend these studies to incorporate the beam geometry, developing an asymptotic method to analyse the pull-in dynamics. We attribute bottleneck behaviour to critical slowing down near the pull-in transition, and we obtain a simple expression for the pull-in time in terms of the beam parameters and external damping coefficient. This expression is found to agree well with previous experiments and numerical simulations that incorporate more realistic models of squeeze film damping, and so provides a useful design rule for sensing applications. We also consider the accuracy of a single-mode approximation of the microbeam equations --- an approach that is commonly used to make analytical progress, without systematic investigation of its accuracy. By comparing to our bottleneck analysis, we identify the factors that control the error of this approach, and we demonstrate that this error can indeed be very small.Comment: 18 page

Delayed pull-in transitions in overdamped MEMS devices

We consider the dynamics of overdamped MEMS devices undergoing the pull-in instability. Numerous previous experiments and numerical simulations have shown a significant increase in the pull-in time under DC voltages close to the pull-in voltage. Here the transient dynamics slow down as the device passes through a meta-stable or bottleneck phase, but this slowing down is not well understood quantitatively. Using a lumped parallel-plate model, we perform a detailed analysis of the pull-in dynamics in this regime. We show that the bottleneck phenomenon is a type of critical slowing down arising from the pull-in transition. This allows us to show that the pull-in time obeys an inverse square-root scaling law as the transition is approached; moreover we determine an analytical expression for this pull-in time. We then compare our prediction to a wide range of pull-in time data reported in the literature, showing that the observed slowing down is well captured by our scaling law, which appears to be generic for overdamped pull-in under DC loads. This realization provides a useful design rule with which to tune dynamic response in applications, including state-of-the-art accelerometers and pressure sensors that use pull-in time as a sensing mechanism. We also propose a method to estimate the pull-in voltage based only on data of the pull-in times.Comment: 17 page

Passive control of viscous flow via elastic snap-through

We demonstrate the passive control of viscous flow in a channel by using an elastic arch embedded in the flow. Depending on the fluid flux, the arch may `snap' between two states --- constricting and unconstricting --- that differ in hydraulic conductivity by up to an order of magnitude. We use a combination of experiments at a macroscopic scale and theory to study the constricting and unconstricting states, and determine the critical flux required to transition between them. We show that such a device may be precisely tuned for use in a range of applications, and in particular has potential as a passive microfluidic fuse to prevent excessive fluxes in rigid-walled channels.Comment: Main text 5 pages, Supplementary Information 14 page

Tinea capitis due to Trichophyton tonsurans in a Maltese patient

We report a case of tinea capitis caused by Trichophyton tonsurans in a 16-year-old male. This appears to be the first documented case of tinea capitis caused by this dermatophyte in a native Maltese patient.peer-reviewe

Destination-Based Cash Flow Taxation

This paper presents, analyses, and further develops the idea of a destination-based cash-flow tax (DBCFT). Its purpose is expositional: to describe the DBCFT, how it might work, what its effects would be and some of the challenges that its implementation would face. The paper starts by introducing the basic mechanics of the DBCFT before evaluating it against five criteria: economic efficiency, robustness to avoidance and evasion, ease of administration, fairness and stability. It does so both for the case of universal adoption by all countries and the more plausible case of unilateral adoption. The paper then looks closely at the application of DBCFT treatment to the financial sector, which is a familiar problem under the VAT but has been little considered under the DBCFT. Finally, the paper sets out some core implementation issues, and how they might be addressed. It also compares the implementation of a DBCFT with the economically equivalent reform option that introduces a broad-based, uniform rate VAT (or achieves the same effect through an existing VAT), and reduces taxes on payroll by the same proportion