886 research outputs found

    The relationship between the Aphis gossypii Glover group and cucumber mosaic virus in autumn cucumbers.

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    The results of studies involving aphid trapping and natural virus infection of test plants showed that A. gossypii played an important part in cucumber and gherkin infection by CMV, which occurred most frequently in August. However, only a small percentage of any of the aphids found was responsible for virus transmission. (Abstract retrieved from CAB Abstracts by CABI’s permission

    Ecosystem heating experiment reveals sex-specific growth responses in fish

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    Size-specific body growth responses to warming are common among animal taxa, but sex-specific responses are poorly known. Here we ask if body growth responses to warming are sex-dependent, and if such sex-specific responses vary with size and age. This was tested with sex-specific data of back-calculated individual growth trajectories, in European perch (Perca fluviatilis) from a long-term whole-ecosystem warming experiment (6.3 C above the surrounding sea). Warming led to both size- and sex-specific differences in growth responses. Warming had a consistent positive effect on body growth of females, but negative effects on male growth at size > 10 cm and age > 2 years. These sex-specific growth responses translate to an increased degree of female-biased sexual size dimorphism (in length-at-age) with warming. Although the exact temperature-mediated effects underlying differential growth responses could not be resolved, results imply global warming may have highly different effects during ontogeny of male and female perch. Such effects should be considered in climate warming scenarios concerning fish growth, population size-structure, and dynamics of aquatic food webs that include fish exhibiting sexual size dimorphism

    How deep is deep? A four-layer model of insights into human needs for design innovation

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    It is generally acknowledged that knowledge about the people that are affected by a design proposal, supports successful design and innovation processes. In this paper we explore the question: what needs to be known about involved people to be able to innovate through design? Based on a literature analysis of human-centred design we propose a model with four levels of human insights: 1) the desired solutions; 2) the desired scenarios; 3) which goal drives this need; and 4) which human value or theme underlies these goals. We argue that radical innovation-which involves a reframe of the problem-can be supported by an investigation of the deepest level of this human insights framework: the thematic level. We show how themes are explored through a hermeneutic phenomenological exercise. This approach is illustrated with a design case in the context of social housing

    Recovering Greater Fungal Diversity from Pristine and Diesel Fuel Contaminated Sub-Antarctic Soil Through Cultivation Using Both a High and a Low Nutrient Media Approach

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    Novel cultivation strategies for bacteria are widespread and well described for recovering greater diversity from the “hitherto” unculturable majority. While similar approaches have not yet been demonstrated for fungi it has been suggested that of the 1.5 million estimated species less than 5% have been recovered into pure culture. Fungi are known to be involved in many degradative processes, including the breakdown of petroleum hydrocarbons, and it has been speculated that in Polar Regions they contribute significantly to bioremediation of contaminated soils. Given the biotechnological potential of fungi there is a need to increase efforts for greater species recovery, particularly from extreme environments such as sub-Antarctic Macquarie Island. In this study, like the yet-to-be cultured bacteria, high concentrations of nutrients selected for predominantly different fungal species to that recovered using a low nutrient media. By combining both media approaches to the cultivation of fungi from contaminated and non-contaminated soils, 91 fungal species were recovered, including 63 unidentified species. A preliminary biodegradation activity assay on a selection of isolates found that a high proportion of novel and described fungal species from a range of soil samples were capable of hydrocarbon degradation and should be characterized further

    How do warmer and darker waters influence population dynamics in size-structured fish communities?

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    Changes associated with an increased water temperature due to global climate change have potentially large consequences for aquatic organisms. However, not only temperature but also the amount of precipitation is increasing. This increased precipitation leads to increased runoff from terrestrial ecosystems into lakes and coastal waters, introducing brown coloured humic substances containing dissolved organic carbon, leading to browner waters. This browning leads to a decrease of light in the water, which may reduce both primary production and visibility. The reduced visibility can, in turn, impact organisms dependent on light for e.g. feeding, mating, and predator evasion. Warmer and browner waters can influence aquatic ecosystems on several levels of biological organization: individuals, populations and communities. The impacts on fish populations and communities mostly arise from individual-level impacts and interactions. To understand how this works, knowledge of how food-dependent body growth and size-dependent food intake impact fish population and community dynamics is needed. Some of the separate impacts of warming and browning on fish are well studied on multiple organizational levels. It is known that both warming and browning can have considerable influences on both availability and uptake of resources in aquatic systems. This influence can have immediate impact on fish individuals and populations, but also shift competitive ability among individuals of different sizes. As a consequence, there may be changes in growth rates, mean body size, fish productivity and species composition in response to warming and browning. Climate change often results in both warmer and darker lakes. Still, the combination of warmer and darker water bodies on fish individuals, populations, and communities, have not been studied extensively. In combination, the various effects of warming and browning might even be more pronounced than individually. As fish populations and communities are important for both ecosystem function, and recreational and commercial fisheries, it is important to identify the knowledge gaps concerning the combined impact of an increase in temperature and browning. In this essay I identify big gaps in our current knowledge on the combined effects of temperature and browning on interacting fish individuals and populations. The knowledge arising from future studies on combined climate change effects on interacting fish species can, for example, be used to adapt current fisheries management strategies to a future climate characterized by warmer and darker lakes

    Tobben met de was : een techniekgeschiedenis van het wassen in Nederland 1890-1968

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    Making explicit in design education: generic elements in the design process

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    In general, designing is conceived as a complex, personal, creative and open-ended skill. Performing a well-developed skill is mainly an implicit activity. In teaching, however, it is essential to make explicit. Learning a complex skill like designing is a matter of doing and becoming aware how to do it. For teachers and students therefore, it will be helpful to make the design process explicit. In this paper, a conceptual framework is developed to be more explicit about the design process. Based on research of the design process, on differences between novices and expert designers, and on personal experience in design education practice, five generic elements in the design process are distinguished: (1) experimenting or exploring and deciding, (2) guiding theme or qualities, (3) domains, (4) frame of reference or library, (5) laboratory or (visual) language. These elements are generic in the sense that they are main aspects and always present in the complex, personal, creative and open-ended design process
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