2,723 research outputs found

    The impact of freight transport capacity limitations on supply chain dynamics

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    We investigate how capacity limitations in the transportation system affect the dynamic behaviour of supply chains. We are interested in the more recently defined, 'backlash' effect. Using a system dynamics simulation approach, we replicate the well-known Beer Game supply chain for different transport capacity management scenarios. The results indicate that transport capacity limitations negatively impact on inventory and backlog costs, although there is a positive impact on the 'backlash' effect. We show that it is possible for both backlog and inventory to simultaneous occur, a situation which does not arise with the uncapacitated scenario. A vertical collaborative approach to transport provision is able to overcome such a trade-off. © 2013 Taylor & Francis

    What is the extent and distribution of evidence on effectiveness of systematic conservation planning around the globe? A systematic map protocol

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    Background: Systematic conservation planning involves the prioritisation of conservation actions to optimise biodiversity conservation outcomes whilst considering implementation challenges such as minimising costs. Thousands of systematic conservation plans have been developed around the globe (a popular software package, 'Marxan', has over 4200 active users from more than 180 countries). However, the effects of systematic approaches on conservation actions and outcomes are not generally known, nor are the factors which distinguish effective from ineffective plans. Previous reviews of conservation planning outcomes have been limited in scope and to narrow time intervals, and have revealed very few formal evaluations of plans. Given systematic approaches are widely perceived to offer the best chance to rapidly and efficiently achieve biodiversity protection targets, a thorough, up-to-date synthesis of the evidence is required. Methods: This protocol outlines the methodology for a systematic mapping exercise to identify retrospective studies measuring the effects of systematic conservation planning on biodiversity conservation at regional, national and subnational scales. Our primary research question is: what is the extent and distribution of evidence on the conservation outcomes of systematic conservation planning? Outcomes will be categorised according to types of capital: natural, financial, social, human and institutional, given the range of potential direct and indirect effects of systematic conservation planning on conservation outcomes. A comprehensive and repeatable search strategy will be undertaken, utilising a wide range of sources including grey literature sources and targeted searches of organisational websites and databases. Sources will be restricted to English language publications between 1983 and 2016. The resultant studies will be screened using standardised inclusion and exclusion criteria and data from included studies will be categorised according to a standardised data extraction form. Information about the study design of relevant articles will be recorded to determine study robustness. A searchable database of studies will be made publicly accessible and available for updating in future. The results will be published in this journal and also presented as an interactive online resource to aid conservation planners in identifying impacts and outcomes of conservation plans

    Interleukin 1-Beta (IL-1) Production by Innate Cells Following TLR Stimulation Correlates With TB Recurrence in ART-Treated HIV-Infected Patients

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    BACKGROUND: Tuberculosis (TB) remains a major cause of global morbidity and mortality, especially in the context of HIV co-infection, since immunity is not completely restored following antiretroviral therapy (ART). The identification of immune correlates of risk for TB disease could help in the design of host-directed therapies and clinical management. This study aimed to identify innate immune correlates of TB recurrence in HIV+ ART-treated individuals with a history of previous successful TB treatment. METHODS: Twelve participants with a recurrent episode of TB (cases) were matched for age, sex, time on ART, pre-ART CD4 count with 12 participants who did not develop recurrent TB in 60 months of follow-up (controls). Cryopreserved peripheral blood mononuclear cells from time points prior to TB recurrence were stimulated with ligands for Toll like receptors (TLR) including TLR-2, TLR-4, and TLR-7/8. Multi-color flow cytometry and intracellular cytokine staining was used to detect IL-1β, TNF-α, IL-12 and IP10 responses from monocytes and myeloid dendritic cells (mDCs). RESULTS: Elevated production of IL-1β from monocytes following TLR-2, TLR-4 and TLR-7/8 stimulation was associated with reduced odds of TB recurrence. In contrast, production of IL-1β from both monocytes and mDCs following Bacillus Calmette-Guérin (BCG) stimulation was associated with increased odds of TB recurrence (risk of recurrence increased by 30% in monocytes and 42% in mDCs respectively). CONCLUSION: Production of IL-1β by innate immune cells following TLR and BCG stimulations correlated with differential TB recurrence outcomes in ART-treated patients and highlights differences in host response to TB

    Self-aligned fabrication process for silicon quantum computer devices

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    We describe a fabrication process for devices with few quantum bits (qubits), which are suitable for proof-of-principle demonstrations of silicon-based quantum computation. The devices follow the Kane proposal to use the nuclear spins of 31P donors in 28Si as qubits, controlled by metal surface gates and measured using single electron transistors (SETs). The accurate registration of 31P donors to control gates and read-out SETs is achieved through the use of a self-aligned process which incorporates electron beam patterning, ion implantation and triple-angle shadow-mask metal evaporation

    The Rising Light Curves of Type Ia Supernovae

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    We present an analysis of the early, rising light curves of 18 Type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory (PTF) and the La Silla-QUEST variability survey (LSQ). We fit these early data flux using a simple power-law (f(t)=α×tn)(f(t) = {\alpha\times t^n}) to determine the time of first light (t0)({t_0}), and hence the rise-time (trise)({t_{rise}}) from first light to peak luminosity, and the exponent of the power-law rise (nn). We find a mean uncorrected rise time of 18.98±0.5418.98 {\pm} 0.54 days, with individual SN rise-times ranging from 15.9815.98 to 24.724.7 days. The exponent n shows significant departures from the simple 'fireball model' of n=2n = 2 (or f(t)t2{f(t) \propto t^2}) usually assumed in the literature. With a mean value of n=2.44±0.13n = 2.44 {\pm} 0.13, our data also show significant diversity from event to event. This deviation has implications for the distribution of 56Ni throughout the SN ejecta, with a higher index suggesting a lesser degree of 56Ni mixing. The range of n found also confirms that the 56Ni distribution is not standard throughout the population of SNe Ia, in agreement with earlier work measuring such abundances through spectral modelling. We also show that the duration of the very early light curve, before the luminosity has reached half of its maximal value, does not correlate with the light curve shape or stretch used to standardise SNe Ia in cosmological applications. This has implications for the cosmological fitting of SN Ia light curves.Comment: 19 pages, 19 figures, accepted for publication in MNRA
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