45 resultados para prey development stage
Resumo:
This research characterizes the weathering of natural building stone using an unsteady-state portable probe permeameter. Variations between the permeability properties of fresh rock and the same rocks after the early stages of a salt weathering simulation are used to examine the effects of salt accumulation on spatial variations in surface rock permeability properties in two limestones from Spain. The Fraga and Tudela limestones are from the Ebro basin and are of Miocene age. Both stone types figure largely in the architectural heritage of Spain and, in common with many other building limestones, they are prone to physical damage from salt crystallization in pore spaces. To examine feedbacks associated with salt accumulation during the early stages of this weathering process, samples of the two stone types were subjected to simulated salt weathering under laboratory conditions using magnesium sulphate and sodium chloride at concentrations of 5% and 15%. Permeability mapping and statistical analysis (aspatial statistics and spatial prediction) before and after salt accumulation are used to assess changes in the spatial variability of permeability and to correlate these changes with salt movement, porosity change, potential rock deterioration and textural characteristics. Statistical analyses of small-scale permeability measurements are used to evaluate the drivers for decay and hence aid the prediction of the weathering behaviour of the two limestones.
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In this paper we provide a detailed profile and analysis of the regional risk capital market in Scotland, using an innovative methodology and specially developed databases which cover risk capital investment in young companies in the periods 2000–04 and 2005–07. This identifies the investment activity of all actors in the market and provides estimates of the total flow of risk capital investment into early-stage Scottish companies over the period. The paper concludes by drawing out the implications for policy makers (providing a more robust evidence base for the development, implementation and monitoring of policy) and for academic researchers (on the methodologies for estimating market scale and efficiency).
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The development of methods providing reliable estimates of demographic parameters (e. g., survival rates, fecundity) for wild populations is essential to better understand the ecology and conservation requirements of individual species. A number of methods exist for estimating the demographics of stage-structured populations, but inherent mathematical complexity often limits their uptake by conservation practitioners. Estimating survival rates for pond-breeding amphibians is further complicated by their complex migratory and reproductive behaviours, often resulting in nonobservable states and successive cohorts of eggs and tadpoles. Here we used comprehensive data on 11 distinct breeding toad populations (Bufo calamita) to clarify and assess the suitability of a relatively simple method [the Kiritani-Nakasuji-Manly (KNM) method] to estimate the survival rates of stage-structured populations with overlapping life stages. The study shows that the KNM method is robust and provides realistic estimates of amphibian egg and larval survival rates for species in which breeding can occur as a single pulse or over a period of several weeks. The study also provides estimates of fecundity for seven distinct toad populations and indicates that it is essential to use reliable estimates of fecundity to limit the risk of under- or overestimating the survival rates when using the KNM method. Survival and fecundity rates for B. calamita populations were then used to define population matrices and make a limited exploration of their growth and viability. The findings of the study recently led to the implementation of practical conservation measures at the sites where populations were most vulnerable to extinction. © 2010 The Society of Population Ecology and Springer.
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The increasing importance placed upon regional development and the knowledge-based economy as economic growth stimuli has led to a changing role for Universities and their interaction with the business community through (though not limited to) the transfer of technology from academia to industry. With the emergence of Local Enterprise Partnerships (LEPs) replacing the Regional Development Agencies (RDAs), there is a need for policy and practice going forward to be clearly informed by a critique of TTO (Technology Transfer Office)–RDA stakeholder relationship in a lessons learned approach so that LEPs can benefit from a faster learning curve. Thus, the aim of this paper is to examine the stakeholder relationship between three regional universities in the context of its TTO and the RDA with a view to determining lessons learned for the emerging LEP approach. Although the issues raised are contextual, the abstracted stakeholder conceptualisation of the TTO–RDA relationship should enable wider generalisation of the issues raised beyond the UK. Stakeholder theory relationship and stage development models are used to guide a repeat interview study of the TTO and RDA stakeholder groupings. The findings, interpreted using combined category and stage based stakeholder models, show how the longitudinal development of the TTO–RDA stakeholder relationship for each case has progressed through different stakeholder pathways, and stages where specific targeting of funding was dependant on the stakeholder stage. Greater targeted policy and funding, based on the stakeholder relationship approach, led to the development of joint mechanisms and a closer alignment of performance measures between the TTO and the RDA. However, over-reliance on the unitary nature of the TTO–RDA relationship may lead to a lack of cultivation and dependency for funding from other stakeholders.
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The aim of this paper is to analyse credit union industries within a development framework. Explicit consideration is given to credit union industries in four countries – Great Britain, Ireland, New Zealand and the United States. It is argued that in terms of a developmental typology the credit union industry in Great Britain is at a nascent stage of development, the industries in Ireland and New Zealand are at a transition stage while the US credit union industry is mature in nature. In progression between stages the analysis considers the influence of factors such as situational leadership, the complexion of trade associations, professionalisation, regulatory and legislative initiatives and technology. The analysis concluded that while there was a substantial commonality of experience, there were also significant differences in the impact of these factors. This consequently encouraged the recognition of the existence of ‘a variety of the species’ in respect of credit union development.
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In the present study of Dugesia tigrina the development of the nervous system is followed and compared during regeneration after fission and after decapitation. Immunocytochemistry was used, with antisera raised against the biogenic amine, 5-hydroxytryptamine (5-HT) and the two neuropeptides, neuropeptide F (NPF), and FMRF amide. The results indicate that two processes are involved in the formation of the new cerebral ganglion. First, new processes sprouting from the original main longitudinal nerve cords bend transversely, indicating the position of the developing horseshoe-shaped anterior cerebral commissure. Then new nerve cells in front of the commissure differentiate from neoblasts and their growth cones fasciculate with the fibres from the old main longitudinal nerve cords. In the cerebral ganglion, 5-HT-IR cells appear before NPF-IR cells, in contrast to the pharynx where NPF-IR cells differentiate before the 5-HT-IR cells. In the peripheral nervous system, NPF-IR fibres and cells appear at a very early stage and dominate the whole regeneration process. A role for the PNS in early pattern formation is suggested.
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This longitudinal study sought to identify developmental changes
in strategy use between 5 and 7 years of age when solving exact
calculation problems. Four mathematics and reading achievement
subtypes were examined at four time points. Five strategies were
considered: finger counting, verbal counting, delayed retrieval,
automatic retrieval, and derived fact retrieval. Results provided
unique insights into children’s strategic development in exact calculation
at this early stage. Group analysis revealed relationships
between mathematical and/or reading difficulties and strategy
choice, shift, and adaptiveness. Use of derived fact retrieval by
7 years of age distinguished children with mathematical difficulties
from other achievement subtypes. Analysis of individual differences
revealed marked heterogeneity within all subtypes,
suggesting (inter alia) no marked qualitative distinction between
our two mathematical difficulty subtypes.
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Purpose: In ischemic retinopathies, the misdirection of reparative angiogenesis away from the hypoxic retina leads to pathologic neovascularization. Thus, therapeutic strategies that reverse this trend would be extremely beneficial. Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) is an important mediator of vascular endothelial growth factor (VEGF) function facilitating vascular growth and maturation. However, in addition to NO, eNOS can also produce superoxide (O), exacerbating pathology. Here, our aim was to investigate the effect of eNOS overexpression on vascular closure and subsequent recovery of the ischemic retina.
Methods: Mice overexpressing eNOS-GFP were subjected to oxygen-induced retinopathy (OIR) and changes in retinal vascularization quantified. Background angiogenic drive was assessed during vascular development and in aortic rings. NOS activity was measured by Griess assay or conversion of radiolabeled arginine to citrulline, nitrotyrosine (NT), and superoxide by immunolabeling and dihydroethidium fluorescence and VEGF by ELISA.
Results: In response to hyperoxia, enhanced eNOS expression led to increased NOS-derived superoxide and dysfunctional NO production, NT accumulation, and exacerbated vessel closure associated with tetrahydrobiopterin (BH) insufficiency. Despite worse vaso-obliteration, eNOS overexpression resulted in elevated hypoxia-induced angiogenic drive, independent of VEGF production. This correlated with increased vascular branching similar to that observed in isolated aortas and during development. Enhanced recovery was also associated with neovascular tuft formation, which showed defective NO production and increased eNOS-derived superoxide and NT levels.
Conclusions: In hyperoxia, reduced BH bioavailability causes overexpressed eNOS to become dysfunctional, exacerbating vaso-obliteration. In the proliferative phase, however, eNOS has important prorepair functions enhancing angiogenic growth potential and recovery in ischemia. © 2012 The Association for Research in Vision and Ophthalmology, Inc.
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Using the foraging movements of an insectivorous bat, Myotis mystacinus, we describe temporal switching of foraging behaviour in response to resource availability. These observations conform to predictions of optimized search under the Lévy flight paradigm. However, we suggest that this occurs as a result of a preference behaviour and knowledge of resource distribution. Preferential behaviour and knowledge of a familiar area generate distinct movement patterns as resource availability changes on short temporal scales. The behavioural response of predators to changes in prey fields can elicit different functional responses, which are considered to be central in the development of stable predator-prey communities. Recognizing how the foraging movements of an animal relate to environmental conditions also elucidates the evolution of optimized search and the prevalence of discrete strategies in natural systems. Applying techniques that use changes in the frequency distribution of movements facilitates exploration of the processes that underpin behavioural changes. © 2012 The Author(s) Published by the Royal Society. All rights reserved.
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This essay investigates an intricate drama of cultural identity in performances of Shakespeare on the nineteenth-century Melbourne stage. It considers the rivalry between Charles and Ellen Kean and their competitor, Barry Sullivan, for the two-month period in 1863 during which their Australian tours overlapped. This Melbourne Shakespeare war was anticipated,augmented, and richly documented in Melbourne’s papers: The Age, The Argus and Melbourne Punch. This essay pursues two seams of inquiry. The first is an investigation of the discourses of cultural and aesthetic value laced through the language of reviews of their Shakespearean roles.The essay identifies how reviewers register affective engagement with the performers in these roles, and suggests how the roles themselves reflected, by accident or design, the terms of the dispute. The second is concerned with the national identity of the actors. Kean, although born in Waterford, Ireland, had held the post of Queen Victoria’s Master of the Revels and identified himself as English. Sullivan, although born in Birmingham, was of Cork parentage and was identified as Irish by both his supporters and his detractors. This essay tracks the development of the actors’ national and artistic identities established prior to Melbourne and ask how they played out on in the context of the particularities of Australian reception. It shows that, in this instance, these actors were implicated in complex debates over national authority and cultural ownership.
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Within the management literature, there is an emergent discourse on horizontal collaboration among small and medium-sized enterprises (SMEs), whereby individual rivalries are overcome by the need for more resources and innovation, leading to increased competitiveness through joint product development. In particular, a number of these horizontal collaborations between SMEs have occurred within the agri-food sector. As a consequence, this article aims to explore the longitudinal development of horizontal innovation networks within an artisan bakers’ network as part of the UK SME agri-food sector. An interpretivist research approach was used, whereby the development and evolution of an artisan bakers’ horizontal network was studied over a 27-month period. The findings, as summarised in conceptual models which draw upon knowledge-based open innovation and social network constructs, illustrate that a complex three-stage life cycle development occurred within the bakers’ horizontal network.
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Objective: Aflatoxin is known to cross the placental barrier and exposures in utero could influence genomic programming, foetal growth and development, resulting in long-term health effects. We aimed to determine aflatoxin exposure in Gambian women at two stages of pregnancy and during the rainy and dry seasons.
Methods: We examined aflatoxin exposure in pregnant Gambian women at early (<16 weeks) and later (16 weeks onward) stages of pregnancy and at different times of the year, during the rainy (June to October 2009) or dry (November to May 2010) season, using aflatoxin–albumin adducts (AF-alb).
Results: Mean AF-alb was higher during the dry season than in the rainy season, in both early and later pregnancy although the difference was strongest in later pregnancy. There was a modest increase in AF-alb in later than early pregnancy (geometric mean 41.8 vs. 34.5 pg/mg, P < 0.05), but this was restricted to the dry season when exposures were generally higher.
Conclusions: The study confirmed that Gambian pregnant women were exposed to aflatoxin throughout the pregnancy, with higher levels in the dry season. There was some evidence in the dry season that women in later pregnancy had higher AF-alb levels than those in earlier pregnancy. Further research on the effects of exposure to this potent mutagen and carcinogen throughout pregnancy, including the epigenetic modification of foetal gene expression and impact on pre- and post-natal growth and development, are merited.
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We explored the development of sensitivity to causal relations in children’s inductive reasoning. Children (5-, 8-, and 12-year-olds) and adults were given trials in which they decided whether a property known to be possessed by members of one category was also possessed by members of (a) a taxonomically related category or (b) a causally related category. The direction of the causal link was either predictive (prey → predator) or diagnostic (predator → prey), and the property that participants reasoned about established either a taxonomic or causal context. There was a causal asymmetry effect across all age groups, with more causal choices when the causal link was predictive than when it was diagnostic. Furthermore, context-sensitive causal reasoning showed a curvilinear development, with causal choices being most frequent for 8-year-olds regardless of context. Causal inductions decreased thereafter because 12-year-olds and adults made more taxonomic choices when reasoning in the taxonomic context. These findings suggest that simple causal relations may often be the default knowledge structure in young children’s inductive reasoning, that sensitivity to causal direction is present early on, and that children over-generalize their causal knowledge when reasoning.
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Semiconductor fabrication involves several sequential processing steps with the result that critical production variables are often affected by a superposition of affects over multiple steps. In this paper a Virtual Metrology (VM) system for early stage measurement of such variables is presented; the VM system seeks to express the contribution to the output variability that is due to a defined observable part of the production line. The outputs of the processed system may be used for process monitoring and control purposes. A second contribution of this work is the introduction of Elastic Nets, a regularization and variable selection technique for the modelling of highly-correlated datasets, as a technique for the development of VM models. Elastic Nets and the proposed VM system are illustrated using real data from a multi-stage etch process used in the fabrication of disk drive read/write heads. © 2013 IEEE.
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Recent literature suggests that the increasingly blurred relationship between paid employment and retirement facilitates a retirement transition period, a life course stage which may involve a change of residence. The role of pre-retirement mobility in the repopulation of rural areas has, however, received relatively little academic scrutiny from UK geographers. This article draws upon findings from a two-year study conducted in three UK case study areas. It examines the extent of pre-retirement age (aged 50-64) migration into rural communities and the impacts this type of movement has upon economic activity, social and community engagement and service provision. It is argued that while this under-researched group offers significant potential to support the social and economic sustainability of rural communities (at least in the short and medium term), there are notable regional variations which are likely to have important long term implications for rural communities as this cohort ages in situ.