Inleiding symposium 'Silent Spring, 50 jaar later'

Een halve eeuw geleden publiceerde Rachel Carson het boek Silent Spring, dat de aandacht vestigde op milieuproblemen en het begin betekende van de milieubeweging. Op zaterdag 17 november 2012 vond in Leiden het symposium ‘Silent Spring, 50 jaar later’ plaats. De Nederlandse Entomologische Vereniging (NEV) organiseerde deze dag met medewerking van de Uyttenboogaart-Eliasen Stichting, De Vlinderstichting, Stichting Natuur en Milieu, Vereniging Natuurmonumenten en de Faunabescherming. Het was een groot succes met tien gezaghebbende sprekers en circa 130 bezoeker

Blood sampling at two slaughterhouses and serological screening of salmonella infections in swine using an indirect ELISA

The Animal Health Service in the Netherlands is currently investigating Salmonella infections in finishing pigs in the Netherlands. The investigations combine 2 projects: the SALINPORK-project, financed by the European Union, and a national project \u27Speerpunt Salmonella\u27, financed by the Dutch Ministry of Agriculture, Nature management and Fisheries and the Dutch Product Board for Livestock and Meat

Pollination ecology of Succisa pratensis: a comparison between populations differing in size and flower diversity

In this study, the effects of population structure on the pollination success of Succisa pratensis Moench (Dipsacaceae) were investigated. Pollination services and their effects on plants' reproductive success are compared for four (natural) populations of S. pratensis that differ in size and flower diversity. Pollination services include quantity (total visitation frequency) as well as quality (per visit efficiency) components of pollination. In all populations, Succisa was visited by a large variety of insect species (22 species in total), belonging to the Syrphidae, other Diptera, Hymenoptera and Lepidoptera. Syrphid flies were the main visitors of Succisa during the whole flowering period, especially members of the Eristalinae (a subfamily of the Syrphidae). Helophilus trivittatus, Eristalis horticola, Helophilus pendulus, Eristalis tenax/pertinax and Eristalis arbustorunilnemorum (all members of the Eristalinae, arranged according to their abundance) showed by far the highest numbers of individuals at the sites. These syrphid fly species are (very) common in The Netherlands. On average, a flower head of Succisa received between 24 and 83 insect visits a day. Such a visitation rate is quite high in comparison with other flowering plant species and this means that Succisa is an attractive plant species for insects. The visitation rates (quantity component of pollination) did not differ between populations varying in size and flower diversity. The most frequent Succisa visitors carried a high proportion of heterospecific pollen on their bodies (ranging from 22 to 80%) due to their generalistic feeding behaviour. Heterospecific pollen consisted mainly of Asteraceae pollen grains. The composition of the pollen loads of the visiting insects is reflected very well in the pollen deposited on Succisa stigmas. A small fraction of conspecific pollen was deposited on the stigmas of Succisa in all populations. In contrast to the quantity component of pollination, this quality component differed between the studied populations. Large populations received a higher proportion of conspecific pollen (45% and 64%) than small ones (17% and 18%). Presumably, this difference is the result of passive flower constancy of the most frequent Succisa visitors. Therefore, in The Netherlands, qualitative aspects of pollination seem to be more important in determining differences between populations of Succisa than quantitative aspects. No difference in the proportion of conspecific pollen deposited was found between populations differing in flower diversity. This is probably caused by large flight distances of the visiting insects. Long foraging distances of the pollinators of Succisa may lead to substantial gene flow by pollen between Succisa populations. This reduces the threat of genetic erosion to Succisa populations. The difference in proportion of conspecific pollen deposited does not lead to differences in seed germination rates between populations. The germination rate was low in all populations (<50%). Probably, this is (partly) caused by the deposition of large amounts of heterospecific pollen, even in large Succisa populations. Thus, Succisa plants suffer from competition through interspecific pollen transfer. Artificial hand pollinations are needed to determine the susceptability of Succisa to the deposition of heterospecific pollen, unambiguously.

Store sales evaluation and prediction using spatial panel data models of sales components

This paper sets out a general framework for store sales evaluation and prediction. The sales of a retail chain with multiple stores are first decomposed into five components, and then each component is explained by store, competitor and consumer characteristics using random effects models for components observable at the store level and spatial error random effects models for components observable at the zip code level. We use spatial panel data over four years for estimation and a subsequent year for evaluating one-year-ahead predictions. Set against a benchmark model that explains total sales directly, the prediction error of our framework is reduced by 34% for existing stores during the sample period, by 5% for existing stores one year ahead and by 26% for new stores.publishedVersio

Indicatieve plantensoorten voor habitattypen : rapport in het kader van het WOT programma Informatievoorziening Natuur i.o. (WOT IN)

In het kader van de Europese Habitatrichtlijn zijn de lidstaten verplicht om periodiek te rapporteren over de Staat van Instandhouding van Habitatgebieden. Een van de aspecten waarover gerapporteerd dient te worden is 'Structuur en Functie'. Dit aspect bestaat uit verschillende onderdelen, waarvan abiotische condities er één is. Abiotische condities kunnen direct gemeten worden, maar in sommige gevallen is het efficiënter die condities te schatten via indicatorsoorten. Dit rapport geeft een overzicht van de soorten die daarvoor gebruikt kunnen worden, en de condities die zij indiceren in relatie tot de per Habitattype gewenste condities. Deze analyse heeft plaatsgevonden voor een selectie van kritische (meest aan grondwater gebonden) Habitattypen, en bouwt voort op eerder door KIWA verrichte analyses op dit gebied

SMALL SIZED HIGH-GAIN PHEMT HIGH-POWER AMPLIFIERS FOR X-BAND APPLICATIONS

ABSTRACT The development of two small sized broadband X-band high-power amplifiers is discussed. The amplifiers are realised with the help of the pseudomorphic HEMT technology of the Fraunhofer Institute for Applied Solid State Physics (FhG-IAF). With the help of this technology the feasibility of integrating a driver and high-power amplifier on a single, small sized, chip is demonstrated. This integration will reduce the number of chips necessary in a Transmit/Receive (T/R) module used in e.g. a phased-array radar antenna. Consequently, the cost of a T/R module is reduced

Long-term effects of drainage on species richness of a fen meadow at different spatial scales

Changes in species richness on a local scale are illustrated with an example of vegetation changes over 26 years in a species-rich fen meadow (Calthion palustris), which had been impacted by a deep drainage channel. The changes were monitored in the meadow as a whole and in 19 permanent plots situated in sites with various intensities of drainage. The similarity with an undisturbed local reference type of the hay meadow community was calculated for all. plots and every year. After 26 years, the overall loss of species in the meadow as a whole (including all ditches) was less than 12%, white the overal loss in species in the permanent plots was 45%. Several species that declined in the permanent plots had survived in the ditches, while others, in particular sedges had migrated to tow-tying areas. This example illustrates the need to survey changes in species richness on multiple scales. (c) 2005 Elsevier GmbH. All. rights reserved