524 research outputs found

    Environmental constraints influencing survival of an African parasite in a north temperate habitat: effects of temperature on development within the host

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    The monogenean Protopolystoma xenopodis has been established in Wales for >40 years following introduction with Xenopus laevis from South Africa. This provides an experimental system for determining constraints affecting introduced species in novel environments. Parasite development post-infection was followed at 15, 20 and 25 °C for 15 weeks and at 10 °C for51 year and correlated with temperatures recorded inWales. Development was slowed/arrested at410 °C which reflects habitat conditions for >6 months/year. There was wide variation in growth at constant temperature (body size differing by >10 times) potentially attributable in part to genotype-specific host-parasite interactions. Parasite density had no effect on size but host sex did: worms in males were 1·8 times larger than in females. Minimum time to patency was 51 days at 25 °C and 73 days at 20 °C although some infections were still not patent at both temperatures by 105 days p.i. In Wales, fastest developing infections may mature within one summer (about 12 weeks), possibly accelerated by movements of hosts into warmer surface waters. Otherwise, development slows/stops in October–April, delaying patency to about 1 year p.i., while wide variation in developmental rates may impose delays of 2 years in some primary infections and even longer in secondary infections

    Low-loss Materials for high Q-factor Bragg Reflector Resonators

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    A Bragg resonator uses dielectric plates within a metallic cavity to confine the energy within a central free space region. The importance of the permittivity is shown with a better Q-factor possible using higher permittivity materials of larger intrinsic dielectric losses. This is because the electric energy in the reflectors decreases proportionally to the square root of permittivity and the coupling to the metallic losses decrease linearly. In a sapphire resonator with a single reflector pair a Q-factor of 2.34x10^5 is obtained, which may be improved on by up to a factor of 2 using higher permittivity materials

    Environmental constraints influencing survival of an African parasite in a north temperate habitat: effects of temperature on egg development

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    SUMMARYFactors affecting survival of parasites introduced to new geographical regions include changes in environmental temperature. Protopolystoma xenopodis is a monogenean introduced with the amphibian Xenopus laevis from South Africa to Wales (probably in the 1960s) where low water temperatures impose major constraints on life-cycle processes. Effects were quantified by maintenance of eggs from infections in Wales under controlled conditions at 10, 12, 15, 18, 20 and 25°C. The threshold for egg viability/ development was 15°C. Mean times to hatching were 22 days at 25°C, 32 days at 20°C, extending to 66 days at 15°C. Field temperature records provided calibration of transmission schedules. Although egg production continues year-round, all eggs produced during >8 months/ year die without hatching. Output contributing significantly to transmission is restricted to 10 weeks (May-mid-July). Host infection, beginning after a time lag of 8 weeks for egg development, is also restricted to 10 weeks (July-September). Habitat temperatures (mean 15·5°C in summer 2008) allow only a narrow margin for life-cycle progress: even small temperature increases, predicted with 'global warming', enhance infection. This system provides empirical data on the metrics of transmission permitting long-term persistence of isolated parasite populations in limiting environments

    Macrophages Are Required for Dendritic Cell Uptake of Respiratory Syncytial Virus from an Infected Epithelium

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    We have previously shown that the respiratory syncytial virus [RSV] can productively infect monocyte derived dendritic cells [MoDC] and remain dormant within the same cells for prolonged periods. It is therefore possible that infected dendritic cells act as a reservoir within the airways of individuals between annual epidemics. In the present study we explored the possibility that sub-epithelial DCs can be infected with RSV from differentiated bronchial epithelium and that in turn RSV from DCs can infect the epithelium. A dual co-culture model was established in which a differentiated primary airway epithelium on an Air Liquid Interface (ALI) was cultured on a transwell insert and MoDCs were subsequently added to the basolateral membrane of the insert. Further experiments were undertaken using a triple co-culture model in which in which macrophages were added to the apical surface of the differentiated epithelium. A modified RSV [rr-RSV] expressing a red fluorescent protein marker of replication was used to infect either the MoDCs or the differentiated epithelium and infection of the reciprocal cell type was assessed using confocal microscopy. Our data shows that primary epithelium became infected when rr-RSV infected MoDCs were introduced onto the basal surface of the transwell insert. MoDCs located beneath the epithelium did not become infected with virus from infected epithelial cells in the dual co-culture model. However when macrophages were present on the apical surface of the primary epithelium infection of the basal MoDCs occurred. Our data suggests that RSV infected dendritic cells readily transmit infection to epithelial cells even when they are located beneath the basal layer. However macrophages appear to be necessary for the transmission of infection from epithelial cells to basal dendritic cells

    Work Package Report 6: Shared, plural and cultural values of ecosystems – Summary

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    Key findings: Finding 1: Shared values resulting from deliberative, group-based valuation are different from individual values. Case study evidence suggests that they are more informed, considered, confident and reflective of participants’ deeper-held, transcendental values. Deliberated, group-based monetary values may be a better reflection of real welfare impacts than non-deliberated individual values, if derived through a carefully designed and managed process. Although more research is needed to expand the currently small evidence base on deliberative monetary methods, group deliberation has the potential to significantly enhance elicitation of values. Finding 2: The ethical, moral and justice dimensions of many environmental issues necessitate approaches that allow for the elicitation of shared and plural values. Key ethical concerns include: 1) providing a space and opportunity for people to identify values that they may find difficult to articulate (e.g. spiritual, identity); 2) recognising that some values cannot be traded without discussion and negotiation (e.g. the legal or felt rights of local people, intrinsic values of other species); and 3) understanding that it is often difficult to isolate valuation from decision-making processes because people feel there are strong ethical or moral issues at stake that need to be debated (e.g. the justice of the process, fairness in the distribution of benefits or disbenefits, responsibility, and issues of sustainability and future generations). Finding 3: Catalyst and/or conflict points can play a key role in the emergence and articulation of values at a societal or community level that have not previously been outwardly or explicitly articulated. Catalyst and conflict points can be symbolic and are often linked to wider contested issues and meanings about who is involved in decision-making, whose voice counts and who receives the benefits or disbenefits of environmental change. These catalyst points can potentially be connected to feelings of powerlessness that give rise to concern and protest. By recognising transcendental societal and communal values (the deeper-held and overarching values held by society and communities), it becomes possible to make these values explicit and incorporate them in decision-making to better anticipate and manage conflicts. Finding 4: There is a diversity of ways in which shared, plural, cultural and social values are used, but they are rarely conceptualised. The UK NEAFO provides a clear theoretical framework that distinguishes and categorises different dimensions and types of shared values. The proposed range of value types was both identifiable and distinguishable within case study results. This suggests that the framework provides a useful basis for operationalizing shared values for decision-making. Finding 5: Shared and social values in the sense of value to society is conceptualised very differently by conventional economics and other disciplines. Neoclassical economists have generally undertaken valuation by equating social value with the aggregate of individual values. They consider values as fundamentally commensurable. In contrast, literature from other disciplines consistently considers values as plural, not just in the sense that multiple things have value, but also that there are multiple dimensions to value that cannot necessarily be captured in a single metric. Within mainstream economics, the difficulties associated with commensurability and aggregating values have long been recognised, but have also been neglected. An interesting area for future debate between economic and non-economic views on values may be the normative nature of value-aggregation. Finding 6: A mixed method approach is required to elicit the multiple dimensions of shared values and to translate deeper-held, transcendental values into contextual values and preferences. Monetary valuation is limited to quantifying values. Other methods are needed to understand their meaning or content, and the communal, societal and transcendental values that underpin them. Psychometric, non-analytical and interpretive methods (e.g. storytelling) can reveal those shared values. They can be combined with deliberative-analytical methods (e.g. deliberative monetary valuation and multi-criteria analysis) to provide a comprehensive valuation that can quantify values, understand their individual and shared meanings and significance, and better include ethical dimensions. Finding 7: Deliberative and social learning processes help people to understand the values held by others; they can lead to increased sharing of values and/or to greater acceptance of the decisions emerging from such processes. Deliberation clearly affects what values participants express compared to non-deliberated processes. There is also a growing body of theoretical and empirical research suggesting that deliberation has the potential to affect how people understand and shape the values of others. Although rarely considered in the economic literature, the concept of social learning helps to explain some of the processes involved in deliberation. The extent to which deliberation or social learning helps participants express and shape values will depend upon the frequency and depth of interactions and the timescale over which interactions occur. Only a shift in cultural values (e.g. less emphasis on material wealth), reflected in other societal institutions (e.g. changes in the indicators used to measure national progress) is likely to achieve sustainable outcomes in the long-term. Finding 8: Media analysis is a promising avenue for characterising different types of shared values at a large scale, as well as assessing the conflicts between the communal values of different sectors of society. There has been a marked increase in public interest in environmental issues over the last decade, which is reflected in their increased media coverage. Media content and discourse analysis is able to distinguish and characterise the plurality of cultural, societal and transcendental values and their interrelationships, and can offer a picture of the self- and other-regarding values that underpin environmental issues and conflicts. Social media can provide a further forum for understanding societal and communal values surrounding environmental issues. Finding 9: Aesthetic and spiritual values of ecosystems have a strong non-instrumental component. While they benefit human well-being, they should not simply be classified as just ‘services’ or ‘benefits’. Many spiritual discourses about nature resist talk of consequentialist benefits and economic analysis. These discourses counter assertions of the disenchantment of the world, which is associated with an instrumental environmental ethic and the commodification of nature. Allowing the possibility of enchantment can be a richer way of understanding our experience of nature and alerts us to the limitations of using economic models for valuation and informing decisions about these profound cultural ecosystem ‘services’. Faith communities have experience of using these non-utilitarian values in their own decision-making and provide models that could be adapted for use in environmental decision-making. Finding 10: Subjective well-being measures provide a useful means of assessing ‘intangible’ cultural ecosystem services and their benefits. Different user groups associate common elements of subjective well-being with environmental settings, providing opportunities for development of standardised measures. In the UK NEAFO, key facets of well-being associated with places in nature across different user groups included: engagement with nature (incorporating elements of connectedness, getting to know nature and the beauty of nature, and taking care of a place); therapeutic benefits (including physical and mental aspects of health); place identity (including a sense of place and belonging); spiritual value (in the sense of feeling connected or responsible to something larger than oneself); social bonding with others; and transformative and memorable experiences. Further empirical work with different user groups and environmental settings would allow for the continued development of a standardised tool for large-scale non-monetary assessment of cultural ecosystem services
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