608 research outputs found
Paul Henry Gore-Booth and President F.L. Hovde
No full textPhotograph of President F.L. Hovde; Mr. Paul Henry Gore - Booth (British Diplomat and Author) and President Hovde, Ca. late 1940's
Assessing the risks and benefits of flowering field edges. Strategic use of nectar sources to boost biological control
No full textThe intensification of agricultural production systems during the last decades hadaenormous impact on the landscape structure in agro-ecosystems. Landscape elements like hedges andvegetationalrichfieldmarginsdissapearedand crops are cultivated in large monocultures. To let beneficial insects play a role in these 'ecological deserts' and tofullfilltheir food requirements in form of pollen and nectar the establishment of flowering field edges gets increasingly popular.But not everything that flowers is naturally exclusively positive for beneficial insects.Pestinsects can profit from flowering field edges as well. In my PhD research Ianalyseda number of nectar plants with respect to their potential benefit for cabbage pests and/or their natural enemies. In field studies I observed theattractivityof nectar plants for pest insects and beneficial insects. In the laboratory I studied in how far the plant species differ in their nectar accessibility and their impact on insect longevity. In addition, I examined the impact of different nectar and honeydew sugars on the gustatory response and the longevity of the insects.Based on the results I found, I conducted field experiments with plants that provide food for either the herbivores or for the beneficial insects. I collected individuals of the diamondback mothPlutellaxylostella and its parasitoidDiadegmasemiclausum and tested them for their sugar content. The results indicated food uptake in the field for both species. I also could show in a field experiment, that suitable nectar plants, such as buckwheat, have an enormous positive impact on longevity and fecundity of the parasitoid D.semiclausum . In addition, I could demonstrate that nectar plants that selectively are used by herbivores, such asCentaureajacea by the cabbage whitePierisrapae , can lead to higher pest densities in adjacent cabbage plantings. My most important conclusion is therefore that a selective approach and a careful choice of plant species are necessary to achieve improved biological control by flowering field edges
An empirical relationship between the Deacon profile number and the Richardson number under convective conditions
Get PDFMean low-level temperature and wind profiles were constructed for 44 cases of free convection using the data O'Neill, Nebraska, during July and August 1956. Based upon the expression for the normalized logarithmic wind shear first suggested by Ellison and later refined by Panofsky, a theoretical formula for the Deacon number as a function of the Richardson number was derived, and values of the Deacon profile were computed. One of the parameters entering into this formula is the ration of the eddy diffusitivities for heat and momentum. This parameter was, in turn, computed from Priestley's expression for the dimensionless heat flux for free-convective cases. In using observed wind data from the mean profile in order to verify the theoretical computations of B, some marked discrepancies
occurred above the 100 cm level. These were due to inconsistent wind speed readings, and it was necessary to employ control data, based on neutral profiles to correct the wind speed. When this was done, the theoretical and
observed Deacon profile nurnbers were in very good agreement.
The author is deeply indebted to Dr. F.L. Martin
(Professor of Meteorology) for his suggestions and continued help throughout the investigations and during preparation of this paper. Special credit is due to Professor Martin for his large share in developing the derivations in this study.Approved for public release; distribution is unlimited.Captain, Republic of Indonesian Navyhttp://archive.org/details/anempiricalrelat109451210
De stad van de toekomst wortelt in een gezonde bodem
No full textDe stad van de toekomst is een circulaire stad waar de toestand van de bodem cruciaal is voor de leefbaarheid en voor het succesvol doorvoeren van noodzakelijke transities. Gezien de huidige staat van de Nederlandse bodem is een gestructureerde aanpak nodig om de balans tussen boven- en ondergrond te herstellen.The city of the future is a circular city in which the condition of the soil is crucial to liveability and to the successful achievement of necessary transitions. Given the present condition of the soil in the Netherlands, a structure approach is needed to restore balance between subsurface and surface.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Environmental Technology and Desig
Amfibisch wonen in de delta
No full textAlle signalen wijzen erop: onze manier van bouwen en wonen in de delta is op de lange termijn niet vol te houden. Onderzoeker milieutechnisch ontwerpen en universitair hoofddocent aan de TU Delft Fransje Hooimeijer pleit daarom voor een radicale herijking van het deltabeheer. Een ontwerpende, interdisciplinaire aanpak is de eerste stap om de Nederlandse delta in de toekomst veilig en leefbaar te houden. En ja, dat levert soms provocatieve ontwerpen op.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Environmental Technology and Desig
De boven- en ondergrond van de stad als een samenhangend systeem: The surface and subsurface of the city as a united system
No full textNo healthy city without a healthy surface. And yet the soil and its associated eco- and water system are a final piece in area development practice. What if we were to draw cross-sections through the above- and underground city more often and pay more attention to the 'technical space' of nature and the city below ground level? Can we achieve a more sustainable design of urban space with this?Accepted Author ManuscriptEnvironmental Technology and DesignPractice Chair Urban Area Developmen
Rotterdam: A dynamic polder city in the Randstad
No full textThis chapter examines the case of Rotterdam as one of the most representative cities in the Randstad in dealing with water and adapting to the current challenges. The dynamics of the regional water system, which include groundwater and rainwater in combination with surface water in a lowland delta facing the North Sea, is crucial for the process of development and urbanisation of the Dutch polders. By creating the Waterstad area, Rotterdam took profit from its strategic position in the Randstad Delta. Van der Ham described eighth century period of time until the year 1000 as distinguished by ‘natural water management’, as nature ruled over culture. At the end of the nineteenth century, explosive urbanisation and technological prosperity put pressure on the polder cities. The manipulative era is marked by the introduction of the engine and electricity, which had an immense influence on the city and the water system.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Environmental Technology and Desig
How to be sweet? Extrafloral nectar allocation in Gossypium hirsutum fits optimal defense theory predictions.
No full textPlants employ nectar for two distinct functions. Floral nectar has traditionally been viewed in the context of pollination. Extrafloral nectar on the other hand, can act as an indirect defense, allowing the plant to recruit predators and parasitoids. Whereas this makes for a clear-cut categorization, in reality the functions may not be so discrete. Extrafloral nectar may serve a role in pollination, while floral nectar can be utilized by predators and parasitoids and thus can contribute to plant defense. Here we use the optimal defense theory to generate predictions with respect to allocation patterns of defensive nectar. These predictions are then tested using novel data on the production patterns of bracteal and foliar nectar in cotton, Gossypium hirsutum. Bracteal nectar production shows a distinct peak on the day of anthesis, followed by a prolonged secretion during fruit maturation. This suggests that bracteal nectaries function in pollination as well as defense. Constitutive nectar production at the bracteal nectaries exceeds foliar nectar secretion by a factor of between 80 and 110. Whereas nectar production at foliar nectaries is induced following herbivore damage to leaves, bracteal nectar production is not induced in response to fruit damage and even decreases when the fruiting structure is subjected to herbivory. This shows that both an inducible and a constitutive variant of an indirect defense can occur within one plant species. This pattern of nectar allocation fits the optimal defense theory, which predicts high levels of constitutive defenses in valuable tissues such as fruits and induced defenses in less valuable tissues such as leaves. This result lends support to the interpretation that indirect defense has been a selective force in the evolution of bracteal nectaries. Although optimal defense theory has described direct defense allocation solely in terms of probability of attack and value of the plant structure, we argue that herbivore accessibility is an additional factor shaping the allocation of indirect defenses
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