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

Mathematical and computer modeling of electro-optic systems using a generic modeling approach

The conventional approach to modelling electro-optic sensor systems is to develop separate models for individual systems or classes of system, depending on the detector technology employed in the sensor and the application. However, this ignores commonality in design and in components of these systems. A generic approach is presented for modelling a variety of sensor systems operating in the infrared waveband that also allows systems to be modelled with different levels of detail and at different stages of the product lifecycle. The provision of different model types (parametric and image-flow descriptions) within the generic framework can allow valuable insights to be gained

Condensation Risk – Impact of Improvements to Part L and Robust Details on Part C -Interim report number 7: Final report on project fieldwork

This report sets out, in draft1, the results of the fieldwork phase of research into the impacts of the 2002 revisions to Part L of the building regulations (Approved Document L1 - DTLR, 2001), and the adoption of Robust Details (RDs - DEFRA 2001) on the extent of condensation risk in the construction of dwellings (Oreszczyn and Bell, 2003). The objective of the fieldwork was to explore the practical application of the revised Part L and its associated robust details by housing developers. This was done through a qualitative evaluation of the design and construction of 16 housing schemes designed in accordance with the revised part L and making use of robust details2. The results of the analysis are to be used to enable condensation modelling that takes into account not only the guidance of robust details but also the way in which construction details were actually designed and, perhaps more importantly, constructed. To this end the report identifies 7 areas of construction detailing (yielding some 15 separate detail models) that are to be included in the condensation modelling phase of the project

Preliminary estimates of operating costs for lighter than air transports

A preliminary set of operating cost relationships are presented for airship transports. The starting point for the development of the relationships is the direct operating cost formulae and the indirect operating cost categories commonly used for estimating costs of heavier than air commercial transports. Modifications are made to the relationships to account for the unique features of airships. To illustrate the cost estimating method, the operating costs of selected airship cargo transports are computed. Conventional fully buoyant and hybrid semi-buoyant systems are investigated for a variety of speeds, payloads, ranges, and altitudes. Comparisons are made with aircraft transports for a range of cargo densities

Mapping warm molecular hydrogen with Spitzer's Infrared Array Camera (IRAC)

Photometric maps, obtained with Spitzer's Infrared Array Camera (IRAC), can provide a valuable probe of warm molecular hydrogen within the interstellar medium. IRAC maps of the supernova remnant IC443, extracted from the Spitzer archive, are strikingly similar to spectral line maps of the H2 pure rotational transitions that we obtained with the Infrared Spectrograph (IRS) instrument on Spitzer. IRS spectroscopy indicates that IRAC Bands 3 and 4 are indeed dominated by the H2 v=0-0 S(5) and S(7) transitions, respectively. Modeling of the H2 excitation suggests that Bands 1 and 2 are dominated by H2 v=1-0 O(5) and v=0-0 S(9). Large maps of the H2 emission in IC433, obtained with IRAC, show band ratios that are inconsistent with the presence of gas at a single temperature. The relative strengths of IRAC Bands 2, 3, and 4 are consistent with pure H2 emission from shocked material with a power-law distribution of gas temperatures. CO vibrational emissions do not contribute significantly to the observed Band 2 intensity. Assuming that the column density of H2 at temperatures T to T+dT is proportional to T raised to the power -b for temperatures up to 4000 K, we obtained a typical estimate of 4.5 for b. The power-law index, b, shows variations over the range 3 to 6 within the set of different sight-lines probed by the maps, with the majority of sight-lines showing b in the range 4 to 5. The observed power-law index is consistent with the predictions of simple models for paraboloidal bow shocks.Comment: 27 pages, including 11 figures. Accepted for publication in Ap

Analysis of trends in premature mortality by Labour voting in the 1997 general election

Mortality relates to voting patterns within areas: mortality is higher the greater the proportion of the electorate who vote Labour or abstain and the converse is the case with regard to the percentage of the electorate who vote Conservative. This reflects the socioeconomic characteristics of individuals who vote for these parties, with Labour being identified with the working class and the Conservatives with the middle class. In the 1997 election, Labour was returned to office after 18 years in opposition. The government has released targets for reducing health inequalities and made it clear that such a reduction is a principal policy aim. These targets may be difficult to meet for two reasons. Firstly, factors influencing inequalities in adult health act from an early age onwards and may not respond rapidly to social change3; secondly, there has as yet been no reduction in social inequality (as indexed by income inequality) under the Labour government.4 Here we use premature mortality as an indicator of which population groups have fared best under the present government

The Herschel Virgo Cluster Survey. IV. Resolved dust analysis of spiral galaxies

We present a resolved dust analysis of three of the largest angular size spiral galaxies, NGC 4501 and NGC 4567/8, in the Herschel Virgo Cluster Survey (HeViCS) science demonstration field. Herschel has unprecedented spatial resolution at far-infrared wavelengths and with the PACS and SPIRE instruments samples both sides of the peak in the far infrared spectral energy distribution (SED).We present maps of dust temperature, dust mass, and gas-to-dust ratio, produced by fitting modified black bodies to the SED for each pixel. We find that the distribution of dust temperature in both systems is in the range ~19–22 K and peaks away from the centres of the galaxies. The distribution of dust mass in both systems is symmetrical and exhibits a single peak coincident with the galaxy centres. This Letter provides a first insight into the future analysis possible with a large sample of resolved galaxies to be observed by Herschel

Using Evidence in the development of local health policies : Some Evidence from the United Kingdom

Objectives: This paper explores the use of evidence, focusing on economic evidence in particular, in the development of local health policies through an in-depth study of Health Improvement Programmes (HImPs) in England. Methods: A questionnaire was sent to the person responsible for coordinating the development of the HImP in each of the 102 English health authorities. In addition, semi-structured interviews were conducted with 10 HImP leaders, and a random sample of 26 HImP documents was reviewed using a standard pro forma. Results: Of the 102 mail questionnaires sent out, 68 (67%) were returned. It was found that those developing HImPs had multiple objectives, only some of which (e.g., efficiency in healthcare provision) would necessarily require evidence.Where evidence was used, this was a mixture of internal (experiential) and external (empirical) evidence, with the balance (66%) being in favor of the latter. Government reports and guidance from the National Institute for Clinical Excellence (NICE), were the main sources of external evidence, rather than published papers. Key barriers to the use of economic evidence were lack of time and availability and the difficulties in synthesizing information at the local level. Conclusions: Based on responses to our survey, the main ways of increasing the use of evidence in the development of local health policies in England are to produce more evidence-based national guidance and to produce accessible summaries of the available literature for local decision makers

Adiabat_1ph: A new public front-end to the MELTS, pMELTS, and pHMELTS models

The program adiabat_1ph is a simple text-menu driver for subroutine versions of the algorithms MELTS, pMELTS, and pHMELTS [Asimow et al., 2004; Ghiorso et al., 2002; Ghiorso and Sack, 1995]. It may be used to calculate equilibrium assemblages along a thermodynamic path set by the user and can simultaneously calculate trace element distributions. The MELTS family of algorithms is suitable for multicomponent systems, which may be anhydrous, water-undersaturated, or water-saturated, with the options of buffering oxygen fugacity and/or water activity. A wide variety of calculations can be performed either subsolidus or with liquid(s) present; melting and crystallization may be batch, fractional, or continuous. The software is suitable for Linux, MacOS X, and Windows, and many aspects of program execution are controlled by environment variables. Perl scripts are also provided that may be used to invoke adiabat_1ph with some command line options and to produce output that may be easily imported into spreadsheet programs, such as Microsoft Excel. Benefits include a batch mode, which allows almost complete automation of the calculation process when suitable input files are written. This technical brief describes version 1.04, which is provided as ancillary material. Binaries, scripts, documentation, and example files for this and future releases may be downloaded at http://www.gps.caltech.edu/~asimow/adiabat. On a networked computer, adiabat_1ph automatically checks whether a newer version is available