White Rose Research Online

    The formation of broad emission line regions in supernova-QSO wind interactions

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    We show that a cooled region of shocked supernova ejecta forms in a type II supernova-QSO wind interaction, and has a density, an ionization parameter, and a column density compatible with those inferred for the high ionization component of the broad emission line regions in QSOs. The calculations are based on the assumption that the ejecta flow is described initially by a similarity solution investigated by Chevalier (1982) and Nadyozhin (1985) and is spherically symmetric. Heating and cooling appropriate for gas irradiated by a nearby powerful continuum source is included in our model, together with reasonable assumptions for the properties of the QSO wind. The model results are also in agreement with observational correlations and imply reasonable supernova rates

    Notch sensitivity of mammalian mineralized tissues in impact

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    The toughness of bone is an important feature in preventing it from fracturing. We consider the notch sensitivity in impact, and the associations between brittleness, notch sensitivity and post-yield energy absorption of mammalian mineralized tissues. Specimens of bone-like tissues covering a wide range of mineralization were broken, either notched or un-notched, in impact. The greater the mineral content, the greater was the notch sensitivity. Also, the more brittle tissues dissipated the least post-yield energy and were the most notch sensitive. It is suggested that since antler bone, the least mineralized of all known mammalian mineralized tissues, seems to be notch insensitive in impact, no adaptive purpose would be served by having mineralized tissues of a lower mineralization than antler. This may explain the lower cut-off in mineralization seen in mammals

    Deformation in Moffat Shale detachment zones in the western part of the Scottish Southern Uplands

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    A study of the décollement zones in the Moffat Shale Group in the Ordovician Northern Belt of the Southern Uplands of Scotland reveals a progressive sequence of deformation and increased channelization of fluid flow. The study concentrates on exposures of imbricated Moffat Shale on the western coast of the Rhins of Galloway. Initial deformation occurred in partially lithified sediments and involved stratal disruption and shearing of the shales. Deformation then became more localized in narrower fault zones characterized by polyphase hydrothermal fluid flow/veining events. Deformation continued after vein formation, resulting in the development of low-temperature crystal plastic microstructures and further veining. Late-stage deformation is recorded as a pressure solution event possibly reflecting the cessation of slip on these faults as the slice became accreted. Most deformation can be ascribed to SE-directed thrusting and incorporation of the individual sheets into the Southern Uplands thrust stack. Later sinistral shear deformation, not observed in overlying turbidites, is also localized in these fault zones. The study reveals the likely structures formed at levels of an accretionary prism deforming under diagenetic to low-grade metamorphic conditions

    Flow in a double-film-fed fluid bead between contra-rotating rolls, Part 2: bead break and flooding

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    Two-dimensional flow is considered in a fluid bead located in the gap between a pair of contra-rotating cylinders and bounded by two curved menisci. The stability of such bead flows with two inlet films, and hence no contact line, are analysed as the roll speed ratio S is increased. One of the inlet films can be regarded as an ‘input flux’ whilst the other is a ‘returning film’ whose thickness is specified as a fraction [zeta] of the outlet film on that roll. The flow is modelled via lubrication theory and for Ca [double less-than sign] 1, where Ca represents the capillary number, boundary conditions are formally developed that account for S [not equal] 1 and the non-constant gap. It is shown that there is a qualitative difference in the results between the single and double inlet film models unless small correction terms to the pressure drops at the interfaces are taken into account. Futhermore, it is shown that the inclusion of these small terms produces an O(1) effect on the prediction of the critical value of S at which bead break occurs. When the limits of the returning film fraction are examined it is found that as [zeta] [rightward arrow] 0 results are in good agreement with those for the single inlet film. Further it is shown for a fixed input flux that as [zeta] [rightward arrow] 1 a transition from bead break to upstream flooding of the nip can occur and multiple two-dimensionally stable solutions exist. For a varying input flux and fixed and ‘sufficiently large’ values of [zeta] there is a critical input flux &[lambda]macr;([zeta]) such that as S is increased from zero: (i) bead break occurs for [lambda] < &[lambda]macr;; (ii) upstream flooding occurs for [lambda] > &[lambda]macr;; (iii) when [lambda] = &[lambda]macr; the flow becomes neutrally stable at a specific value of S beyond which there exist two steady solutions (two-dimensionally stable) leading to bead break and upstream flooding, respectively

    Patient acceptability of larval therapy for leg ulcer treatment: a randomised survey to inform the sample size calculation of a randomised trial

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    BACKGROUND A trial was commissioned to evaluate the effectiveness of larval therapy to debride and heal sloughy and necrotic venous leg ulcers. Larval therapy in the trial was to be delivered in either loose or bagged form. Researchers were concerned that resistance to larval therapy may threaten the feasibility of the trial. Additionally there was concern that the use of larval therapy may require a larger effect size in time to healing than originally proposed by the investigators. METHODS To formally evaluate patient preferences a survey using two randomly allocated, nurse administered questionnaires was undertaken. Patients were randomised to receive one of the two following questionnaires (i) preferences between loose larvae and standard treatment (hydrogel) or (ii) patient preferences between bagged larvae and standard therapy (hydrogel). The study was undertaken in a Vascular Clinic, in an Outpatients Department of a large teaching hospital in the North of England. The sample consisted of 35 people aged 18 years and above with at least one leg ulcer of venous or mixed (venous and arterial) aetiology. RESULTS Approximately 25% of participants would not consider the use of larval therapy as an acceptable treatment option for leg ulcers, regardless of the method of containment. For the patients that would consider the use of larval therapy, different preferences in healing times required to use the therapy were observed depending upon the method of containment. The median response of those participants questioned about bagged larvae found that they would be willing to use this therapy even if they were equally able to achieve healing with the use of hydrogel by 20 weeks. For those participants questioned about the use of loose larvae complete healing would have to have taken place over 17 weeks for them to choose larvae as their preferred option rather than hydrogel. This difference was not significant (p = 0.075). CONCLUSION We found no evidence of widespread resistance to the utilisation of larval therapy from patients regardless of the method of larval therapy containment. These methods have the potential to inform sample size calculations where there are concerns of patient acceptability

    Development of the orifice plate with a cone swirler flow conditioner

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    Purpose - The sensitivity of orifice plate metering to poorly conditioned and swirling flows are subjects of concerns to flow meter users and manufacturers. The distortions caused by pipe fittings and pipe installations upstream of the orifice plate are major sources of this type of non-standard flows. These distortions will alter the accuracy of metering up to an unacceptable degree. Design/methodology/approach - The design of orifice plate meters that are independent of the initial flow conditions of the upstream is a major object of flow metering. Either using a long straight pipe or a flow conditioner upstream of an orifice plate usually achieves this goal. The effect of cone swirler flow conditioner for both standard and non-standard flow conditions has been carried out in the experimental rig. The measuring of mass flow rate under different conditions and different Reynolds numbers were used to establish a change in discharge coefficient relative to a standard one. Findings - The experimental results using the cone swirler flow conditioner showed that the combination of an orifice plate and cone swirler flow conditioner is broadly insensitive to upstream disturbances. The results clearly show that this flow conditioner can attenuate the effect of both swirling and asymmetric flows on metering to an acceptable level. Originality/value - Previous work on the orifice plate has shown that the concept has promise. The results of using a combination of a cone swirler and orifice plate for non-standard flow conditions including swirling flow and asymmetric flow show this package can preserve the accuracy of metering up to the level required in the standards, providing that a new discharge coefficient is used for the combined swirler and orifice plate

    Explicit equations for leak rates through narrow cracks

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    Explicit equations to describe the leak rate of a single phase fluid through a narrow crack under a low pressure gradient have been developed and are presented. Four distinct flow regimes, which change with crack opening displacement, have been previously identified and are the basis of this model. The fluid flow is governed by the pressure gradient and the tortuosity of the crack, which is particularly important when the opening displacement is small. The equations have been developed by considering the pressure forces created when the fluid flows down an idealized zig-zag channel. The nature of the flow, and hence the governing equations, change as the crack aperture increases. The power of this approach is clearly seen when the flow rates predicted using this model are compared both to the flow rates obtained from computational fluid dynamics analysis and those found by experimentation. The agreement between these sets of data is good, showing that the major effects governing the flow rate have been identified and then accounted for

    Beyond information: factors in participation in networks of practice, a case study of web management in UK Higher Education

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    Purpose To explore the pattern and significance of cross-organizational ties in an emergent professional field, web production in UK Higher Education. Methodology/Approach The research is based on in-depth interviews with 21 practitioners and analysis of activity in cross-organizational spaces, such as an online community and a series of annual practitioner conferences on the web in HE (1997-). Findings The cross organizational spaces have support and symbolic roles as well as informational ones. They have overlapping but different membership and agendas. Key factors that govern individual participation and so the shape of cross-organizational spaces are differential involvement in technical innovation, degree of organizational embedding or marginality, differences in organizational position and role, orientation towards centralisation or decentralisation and orientation towards marketing or IT. There is some sense of occupational community among web managers, but within that also diversity and a significant fracture line between marketing and IT perspectives on the role. This may explain the lack of formal professionalization. As a more natural boundary practice between organizations than marketing, IT has more public visibility, possibly influencing the course jurisdictional struggles over who should control the web. Research limitations/implications As a heavily contextualised study, its detail reflects particular features of HE in the UK at one period as well as specific aspects of the web as a technology. Nevertheless, underlying factors which seem to influence participation and non-participation in cross-organizational networks may be generalisable to many occupations, particularly where knowledge is rapidly changing. Practical implications Some suggestions about how cross-organizational knowledge sharing is most effectively supported can be derived from the analysis. IT is a natural focus for cooperation, but there is a risk of this masking the importance of other professional practices. Efforts at formal professionalization may be devisive because people have different professional ambitions and there are individual and organizational benefits in not professionalizing the role formally. New practitioners may be the most active in using extra-organizational networks to assist them to become more embedded locally. Old hands, though they have high prestige and centrality, may increasingly take their own path away from the community. Aspects of local roles such as involvement in innovation or decentralist strategies favour participation in cross-organizational networks. Originality/value of paper Most studies of knowledge sharing have focussed on the factors which influence it within an organization, yet cross-organizational sharing is also of importance, even for established professions as the boundaries of organizations become more open. For new occupations cross-organizational ties may be a critical resource, and not only for sharing information or support, but for making sense of what the job is about at the deepest level. The research is also original in analysing a relatively little researched occupational group, those producing web sites for a living. It will be relevant to those interested in online and people centred information seeking, in professionalization and occupational identity

    Modelling the impact of alternative fare structures on train overcrowding

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    The Strategic Rail Authority (SRA) provides the backbone to rail regulation in Great Britain. As part of its responsibilities, the SRA monitors overcrowding on trains which it measures in terms of the proportion of passengers on trains in excess of the seat capacity for longer distance services, and with an allowance for standing passengers on shorter journeys of less than 20 minutes. Overcrowding on Britain’s railways fell during the early 1990s but has been on the increase since 1996 with particularly acute problems in the morning peak for services travelling to London. In a study conducted on behalf of the SRA we developed the PRAISE rail operations model to include penalties for overcrowding based upon journey purpose, journey time and degree of overcrowding. Using demand, fares and timetable information for an actual case study route, we examine how fares and ticketing restrictions can be set to manage demand throughout the day without significantly reducing the overall demand for rail travel

    How highly does the freight transport industry value journey time reliability - and for what reasons?

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    Delays to road freight vehicles impose a very high cost on the nation. Delayed arrival time can occur for a variety of reasons. This paper presents the findings of a Highways Agency funded study, which has investigated the user valuations of three different kinds of delay: • A delay resulting from an increased journey time, with fixed departure time • An increase in the spread (or range) of arrival times for a fixed departure time • A schedule delay where the departure time is effectively put back. The paper summarises the findings of the study, which centred on an interview survey of forty shippers, hauliers and third party logistics operators. Respondents were asked to consider one of their freight flows on the trunk road network in detail. Various reasons why respondents value a high degree of predictability of journey times on the trunk road network are identified and discussed. The paper then moves on to present and discuss user valuations of each kind of delay, estimated using the Leeds Adaptive Stated Preference (LASP) methodology
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