1,964 research outputs found

    Householder responses to flood risk: the consequences of the search for ontological security

    Get PDF
    As the recent floods in the UK have shown, most householders in at-risk areas are not prepared for floods. In fact, even amongst those who know they are at risk, less than 10% have taken any practical steps to prepare for flooding. This research attempts to explain that phenomenon by examining the effects of the rhetorical strategies that lay-people employ to help them cope with household flood risk. Looking at at-risk householders who have been flooded, as well as at those who have not, it combines close textual analysis of spoken interviews with secondary analysis of survey data to identify the rationalities that structure lay-people's talk and behaviour on the issue of flood risk. The low take-up of mitigation measures, it concludes, can be explained by the fact that householders prioritise the reduction of anxiety over the reduction of the risk of physical harm. Anxiety is familiar, predictable and causes immediate harm; flooding is unfamiliar to most residents, is unpredictable and is represented as difficult to control. As a result, householders eschew mitigation measures if they are uncertain of their efficacy and if they feel they will make them more anxious. Instead, they choose to protect a representation of life that enables them to feel secure. If state agencies are to influence householder responses to flood risk, it is suggested, they need to understand this rationale and to work with it. In order to increase the take-up of mitigation measures they should minimise the anxiety associated with taking mitigation measures - avoiding messages that provoke fear responses, making flood risk mitigation seem a normal part of home security and providing householders with individually tailored advice so that they feel less anxious about making a mistake when they choose which measures to implement

    Line and continuum radiative transfer modelling of AA Tau

    Get PDF
    We present photometric and spectroscopic models of the Classical T Tauri star AA Tau. Photometric and spectroscopic variability present in observations of AA Tau is attributed to a magnetically induced warp in the accretion disc, periodically occulting the photosphere on an 8.2--day timescale. Emission line profiles show signatures of both infall, attributed to magnetospherically accreting material, and outflow. Using the radiative transfer code TORUS, we have investigated the geometry and kinematics of AA Tau's circumstellar disc and outflow, which is modelled here as a disc wind. Photometric models have been used to constrain the aspect ratio of the disc, the offset angle of the magnetosphere dipole with respect to the stellar rotation axis, and the inner radius of the circumstellar disc. Spectroscopic models have been used to constrain the wind and magnetosphere temperatures, wind acceleration parameter, and mass loss rate. We find observations are best fitted by models with a mass accretion rate of 5×1095\times10^{-9} M_\odot yr1^{-1}, a dipole offset of between 1010^\circ and 2020^\circ, a magnetosphere that truncates the disc from 5.2 to 8.8 R_\star, a mass-loss-rate to accretion-rate ratio of ~ 0.1, a magnetosphere temperature of 8500 -- 9000 K, and a disc wind temperature of 8000 K.Comment: 22 pages, 32 figures, 4 tables. Accepted by MNRAS. V3: Corrected typ

    The effect of episodic accretion on the phase transition of CO and CO_2 in low-mass star formation

    Full text link
    We study the evaporation and condensation of CO and CO_2 during the embedded stages of low-mass star formation by using numerical simulations. We focus on the effect of luminosity bursts, similar in magnitude to FUors and EXors, on the gas-phase abundance of CO and CO_2 in the protostellar disk and infalling envelope. The evolution of a young protostar and its environment is followed based on hydrodynamical models using the thin-disk approximation, coupled with a stellar evolution code and phase transformations of CO and CO_2. The accretion and associated luminosity bursts in our model are caused by disk gravitational fragmentation followed by quick migration of the fragments onto the forming protostar. We found that bursts with luminosity on the order of 100-200 L_sun can evaporate CO ices in part of the envelope. The typical freeze-out time of the gas-phase CO onto dust grains in the envelope (a few kyr) is much longer than the burst duration (100-200 yr). This results in an increased abundance of the gas-phase CO in the envelope long after the system has returned into a quiescent stage. In contrast, luminosity bursts can evaporate CO_2 ices only in the disk, where the freeze-out time of the gas-phase CO_2 is comparable to the burst duration. We thus confirm that luminosity bursts can leave long-lasting traces in the abundance of gas-phase CO in the infalling envelope, enabling the detection of recent bursts as suggested by previous semi-analytical studies.Comment: 12 pages, 6 figures, accepted for publication in Astronomy & Astrophysic

    Studies of molecular properties of polymeric materials

    Get PDF
    Aerospace environment effects (high energy electrons, thermal cycling, atomic oxygen, and aircraft fluids) on polymeric and composite materials considered for structural use in spacecraft and advanced aircraft are examined. These materials include Mylar, Ultem, and Kapton. In addition to providing information on the behavior of the materials, attempts are made to relate the measurements to the molecular processes occurring in the material. A summary and overview of the technical aspects are given along with a list of the papers that resulted from the studies. The actual papers are included in the appendices and a glossary of technical terms and definitions is included in the front matter

    Radiation-hydrodynamical simulations of massive star formation using Monte Carlo radiative transfer II. The formation of a 25 solar-mass star

    Get PDF
    This is the author accepted manuscript. The final version is available from OUP via the DOI in this record.We present a numerical simulation of the formation of a massive star using Monte- Carlo-based radiation hydrodynamics (RHD). The star forms via stochastic disc ac- cretion and produces fast, radiation-driven bipolar cavities. We nd that the evolution of the infall rate (considered to be the mass ux across a 1500 au spherical boundary), and the accretion rate onto the protostar, are broadly consistent with observational constraints. After 35 kyr the star has a mass of 25M and is surrounded by a disc of mass 7 M and 1500 au radius, and we nd that the velocity eld of the disc is close to Keplerian. Once again these results are consistent with those from recent high-resolution studies of discs around forming massive stars. Synthetic imaging of the RHD model shows good agreement with observations in the near- and far-IR, but may be in con ict with observations that suggests that MYSOs are typically circularly symmetric on the sky at 24.5 m. Molecular line simulations of a CH3CN transition compare well with observations in terms of surface brightness and line width, and indicate that it should be possible to reliably extract the protostellar mass from such observations.The calculations for this paper were performed on the University of Exeter Supercomputer, a DiRAC Facility jointly funded by STFC, the Large Facilities Capital fund of BIS, and the University of Exeter, and on the Complexity DiRAC Facility jointly funded by STFC and the Large Facilities Capital Fund of BIS. TJH and TAD acknowledge funding from Exeter's STFC Consolidated Grant (ST/M00127X/1). We thank Takashi Hosokawa for kindly providing us with the protostellar evolutionary model. We are grateful to Maite Beltran for providing the data for Figure 4, and we thank Dave Acreman, John Ilee and Tom Haworth for useful discussions. We thank the anonymous referee for a helpful report

    Building leadership capacity and future leaders in operational research in low-income countries: why and how?

    Get PDF
    Very limited operational research (OR) emerges from programme settings in low-income countries where the greatest burden of disease lies. The price paid for this void includes a lack of understanding of how health systems are actually functioning, not knowing what works and what does not, and an inability to propose adapted and innovative solutions to programme problems. We use the National Tuberculosis Control Programme as an example to advocate for strong programme-level leadership to steer OR and build viable relationships between programme managers, researchers and policy makers. We highlight the need to create a stimulating environment for conducting OR and identify some of the main practical challenges and enabling factors at programme level. We focus on the important role of an OR focal point within programmes and practical approaches to training that can deliver timely and quantifiable outputs. Finally, we emphasise the need to measure successful OR leadership development at programme level and we propose parameters by which this can be assessed. This paper 1) provides reasons why programmes should take the lead in coordinating and directing OR, 2) identifies the practical challenges and enabling factors for implementing, managing and sustaining OR and 3) proposes parameters for measuring successful leadership capacity development in OR

    The timing of death in patients with tuberculosis who die during anti-tuberculosis treatment in Andhra Pradesh, South India

    Get PDF
    Background: India has 2.0 million estimated tuberculosis (TB) cases per annum with an estimated 280,000 TBrelated deaths per year. Understanding when in the course of TB treatment patients die is important for determining the type of intervention to be offered and crucially when this intervention should be given. The objectives of the current study were to determine in a large cohort of TB patients in India:- i) treatment outcomes including the number who died while on treatment, ii) the month of death and iii) characteristics associated with “early” death, occurring in the initial 8 weeks of treatment. Methods: This was a retrospective study in 16 selected Designated Microscopy Centres (DMCs) in Hyderabad, Krishna and Adilabad districts of Andhra Pradesh, South India. A review was performed of treatment cards and medical records of all TB patients (adults and children) registered and placed on standardized anti-tuberculosis treatment from January 2005 to September 2009. Results: There were 8,240 TB patients (5183 males) of whom 492 (6%) were known to have died during treatment. Case-fatality was higher in those previously treated (12%) and lower in those with extra-pulmonary TB (2%). There was an even distribution of deaths during anti-tuberculosis treatment, with 28% of all patients dying in the first 8 weeks of treatment. Increasing age and new as compared to recurrent TB disease were significantly associated with “early death”. Conclusion: In this large cohort of TB patients, deaths occurred with an even frequency throughout anti-TB treatment. Reasons may relate to i) the treatment of the disease itself, raising concerns about drug adherence, quality of anti-tuberculosis drugs or the presence of undetected drug resistance and ii) co-morbidities, such as HIV/ AIDS and diabetes mellitus, which are known to influence mortality. More research in this area from prospective and retrospective studies is needed

    A survey of the views of program implementers on success factors of solar PV programs in Asia and the Pacific

    Get PDF
    Much effort has been invested in identifying the important barriers to the widespread take-up of renewable energy systems and in using information to develop best practice guidelines for the implementation of rural renewable energy electrification programs in developing countries. Many renewable electrification programs have been implemented in developing countries of Asia and the Pacific to improve the quality of life of the people living in remote rural areas. Those that have been successful demonstrate that a market for household renewable energy systems can be developed quickly and efficiently given the right combination of institutional, financial and policy instruments. The literature indicates, however, that a number of these programs have met with limited success. Much effort has been invested in attempting to identify the reasons behind this lack of success. Understanding the reasons behind the limited success of some programs, and for the relatively high success of others, is important as this information can inform program implementers and improve the success rates of future programs. Most of the research effort to date has focused on the identification of barriers to the widespread take-up of renewable energy systems and this information has been used in the development of best practice guidelines for the implementation of these programs. This narrow focus on barriers, however, does not consider other important factors behind the success of programs. An email survey of those implementing programs in SE Asian and Pacific countries was therefore undertaken with the aim of obtaining the views of program implementers on not only what barriers they see as hindering the uptake, but also on what essential factors they consider need to be included in designing and implementing programs in order ensure program success and the criteria to measure the program success

    Radiative Transfer in Star Formation: Testing FLD and Hybrid Methods

    Full text link
    We perform a comparison between two radiative transfer algorithms commonly employed in hydrodynamical calculations of star formation: grey flux limited diffusion and the hybrid scheme, in addition we compare these algorithms to results from the Monte-Carlo radiative transfer code MOCASSIN. In disc like density structures the hybrid scheme performs significantly better than the FLD method in the optically thin regions, with comparable results in optically thick regions. In the case of a forming high mass star we find the FLD method significantly underestimates the radiation pressure by a factor of ~100.Comment: 4 Pages; to appear in the proceedings of 'The Labyrinth of Star Formation', Crete, 18-22 June 201
    corecore