Multifluid, Magnetohydrodynamic Shock Waves with Grain Dynamics II. Dust and the Critical Speed for C Shocks

This is the second in a series of papers on the effects of dust on multifluid, MHD shock waves in weakly ionized molecular gas. We investigate the influence of dust on the critical shock speed, v_crit, above which C shocks cease to exist. Chernoff showed that v_crit cannot exceed the grain magnetosound speed, v_gms, if dust grains are dynamically well coupled to the magnetic field. We present numerical simulations of steady shocks where the grains may be well- or poorly coupled to the field. We use a time-dependent, multifluid MHD code that models the plasma as a system of interacting fluids: neutral particles, ions, electrons, and various ``dust fluids'' comprised of grains with different sizes and charges. Our simulations include grain inertia and grain charge fluctuations but to highlight the essential physics we assume adiabatic flow, single-size grains, and neglect the effects of chemistry. We show that the existence of a phase speed v_phi does not necessarily mean that C shocks will form for all shock speeds v_s less than v_phi. When the grains are weakly coupled to the field, steady, adiabatic shocks resemble shocks with no dust: the transition to J type flow occurs at v_crit = 2.76 v_nA, where v_nA is the neutral Alfven speed, and steady shocks with v_s > 2.76 v_nA are J shocks with magnetic precursors in the ion-electron fluid. When the grains are strongly coupled to the field, v_crit = min(2.76 v_nA, v_gms). Shocks with v_crit < v_s < v_gms have magnetic precursors in the ion-electron-dust fluid. Shocks with v_s > v_gms have no magnetic precursor in any fluid. We present time-dependent calculations to study the formation of steady multifluid shocks. The dynamics differ qualitatively depending on whether or not the grains and field are well coupled.Comment: 43 pages with 17 figures, aastex, accepted by The Astrophysical Journa

Strategic alliances and competitive strategies in the European aerospace industry: the case of BMW Rolls-Royce GmbH

Strategic alliances are an important feature of the aerospace industry and there have been many studies that have sought to evaluate their performance. Most have taken a policy perspective exploring the economic and political benefits claimed for collaboration of this type. The perspective is a reflection of the political origins of many aerospace alliances. This study seeks to evaluate, from a managerial perspective, one of the newer alliances established on a strictly commercial basis,. It focuses on BMW Rolls-Royce GmbH, one of a small number of truly European alliances. The study concludes that although Rolls-Royce bought out its German partner after a decade of operation, the alliance was a success. The two engines developed by the alliance over this period were a technical success, overall sales were well on target and the alliance was about to break even. In addition, the study concludes that the alliance formed a key element in Rolls-Royce‟s successful strategy to extend its product portfolio, a strategy that elevated the company to second place in the global aero engine market

European retrospective: the European aerospace industry 1970-2000

The success of Airbus Industrie in challenging Boeing’s dominant position in the highly competitive civil airliner market has been widely reported. In the light of this success this paper reviews the progress made by the European aerospace industry in the last three decades of the twentieth century. In particular the position of Europe in relation to the US aerospace industry is analysed. As well as covering civil airliner production the study also considers the space and aero engine sectors. In order to explore the factors that have led to a European challenge, three organisations, each from different sectors of the industry, are analysed. The paper concludes that there has been a revival in the fortunes of the industry and its position within the world aerospace industry

Benefits to be derived from meteorological satellite technology

The benefits derived from satellite technology in educational communication and meteorology are cited

Optical observation of "band‐to‐band" scattering by time‐resolved phosphorescence line narrowing: Exciton dephasing in a quasi‐one‐dimensional solid

Abstract Unavailable

Protein Import Into Chloroplasts: An Ever-Evolving Story

Chloroplasts are but one type of a diverse group of essential organelles that distinguish plant cells and house many critical biochemical pathways, including photosynthesis. The biogenesis of plastids is essential to plant growth and development and relies on the targeting and import of thousands of nuclear-encoded proteins from the cytoplasm. The import of the vast majority of these proteins is dependent on translocons located in the outer and inner envelope membranes of the chloroplast, termed the Toc and Tic complexes, respectively. The core components of the Toc and Tic complexes have been identified within the last 12 years; however, the precise functions of many components are still being elucidated, and new components are still being identified. In Arabidopsis thaliana (and other species), many of the components are encoded by more than one gene, and it apperas that the isoforms differentially associate with structurally distinct import complexes. Furthermore, it appears that these complexes represent functionally distinct targeting pathways, and the regulation of import by these separate pathways may play a role in the differentiation and specific functions of distinct plastid types during plant growth and development. This review summarizes these recent discoveries and emphasizes the mechanisms of differential Toc complex assembly and substrate recognition

‘Voyager’: An educational card game

‘Voyager’ is an educational card game involving scientific satellites, developed for use in schools with children aged 9 to 13 years. The idea of the game is to improve pupils’ knowledge about the large number of scientific satellites there are in space in a fun way, while also practising numeracy skills. Several copies of the game were produced using funding obtained from the Particle Physics and Astronomy Research Council (PPARC) as a Public Understanding of Science (PUS) award. These initial ‘trial’ versions of the game were taken to three different schools where feedback obtained from both pupils and staff was used to produce a final copy of the game that can be distributed to other schools along with a set of companion notes to form the basis of a science lesson. This article reports the findings of the school trials and indicates possible future developments of other scientific card games that could be beneficial to the classroom.http://www.iop.org/EJ/abstract/0031-9120/38/1/30