Scale and intensity of intertidal habitat use by knots Calidris canutus in the Western Wadden Sea in relation to food, friends and foes

In August-October 1988-1992 we studied the distribution and abundance of knots Calidris canutus around Griend in the western Wadden Sea, and the extent to which these can be explained by benthic prey availability and presence of avian predators. Numbers in the nonbreeding season showed monthly averages of 10000 to 25000 birds. Over 100000 knots were recorded on three occasions. Knots feed in large flocks, individual birds usually experiencing 4000 to 15000 flock-mates. The Siberian-breeding/west-African wintering canutus subspecies passed through in late July and early August. Otherwise the Greenlandic/Canadian breeding islandica subspecies was present. Over the period 1964-1992 there were no clear trends in the number of knots, but canutus-knots were particularly abundant in July-August 1991, whereas in 1992 both subspecies were absent. Macoma balthica was the preferred prey of both subspecies. Hydrobia ulvae, Mytilus edulis and Cerastoderma edule were eaten when Macoma was absent close to the surface of the sediment. As Macoma buried deeper from July onwards, canutus faced better average feeding conditions than islandica later in the year. The spatial distribution of knots feeding on the intertidal flats around Griend was best explained by the harvestable biomass of the prevalent prey species in a particular year and season, i.e. Macoma (main prey when their harvestable biomass densities were greater than ca 0.8 g AFDM per m2) and Cerastoderma, and by the avoidance of situations where they run the risk of attack by bird-eating birds. Flocks of knots covered most of the intertidal flats in the western Dutch Wadden Sea in a couple of tidal cycles. This is about 800 km2, much larger than the equivalent area used by knots on their wintering grounds in Mauritania (10-15 km2), a difference that is correlated with prey spectrum, prey availability and predictability.

Some procedures for computerized ability testing

For computerized test systems to be operational, the use of item response theory is a prerequisite. As opposed to classical test theory, in item response models the abilities of the examinees and the properties of the items are parameterized separately. Hence, when measuring the abilities of examinees, the model implicitly corrects for the item properties, and measurement on an item-independent scale is possible. In addition, item response theory offers the use of test and item information as local reliability indices defined on the ability scale. In this chapter, it is shown how the main features of item response theory have given rise to the development of promising procedures for computerized testing. Among the topics discussed are procedures for item bank calibration, automated test construction, adaptive test administration, generating norm distributions, and diagnosing test scores

Intestinal nuclear receptors in control of energy metabolism

Changes in our lifestyle have resulted in a worldwide increased prevalence of obesity-related metabolic diseases such as type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). Besides excessive caloric intake, a high-fructose consumption has been implicated in the accelerated development of metabolic diseases. The small intestine is the major site for fructose uptake and metabolism, while excessive fructose intake is known to cause metabolic adverse effects in the liver. In the first part of the thesis we studied the transcriptional effects of a fructose diet in the small intestine (duodenum) and liver. Fructose as compared to glucose intake has distinct effects on the small intestinal and liver transcriptomes in mice, and these effects were more profound in the small intestine. Systemic activation of nuclear receptors (NRs) has been successfully applied in the pharmaceutical industry to treat various diseases. This strategy, however, often causes major adverse effects due to the pleiotropic target genes of NRs. Intestinal nutrient uptake and metabolism are important for whole-body energy homeostasis; therefore, we explored the potential of intestinal NR activation in the regulation of whole-body energy homeostasis. We identified several facilitative glucose transporters (GLUT-members) as novel NR target genes. In addition, we identified the NR PPARdelta as an intestinal regulator of whole-body metabolism by protecting against diet-induced obesity and increasing high-density lipoprotein (HDL) HDL-cholesterol levels. Taken together, selective pharmacologic modulators of NRs that act solely in the gastrointestinal tract are an effective way of inducing beneficial effects on whole-body metabolism while minimising systemic adverse effects