Lothar David Jan Kuijper

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Simple stoichiometric models based on the principle that limiting elements are used with high efficiency have been unable to capture the apparently constant and low nitrogen gross growth efficiency that characterizes egg production in marine copepods. A new model of egg production is presented based on Dynamic Energy Budget theory. The model splits(More)
Basic Lotka-Volterra type models in which mutualism (a type of symbiosis where the two populations benefit both) is taken into account, may give unbounded solutions. We exclude such behaviour using explicit mass balances and study the consequences of symbiosis for the long-term dynamic behaviour of a three species system, two prey and one predator species(More)
Traditional models of chemostat systems looking at interactions between predator, prey and nutrients have used only a single currency, such as energy or nitrogen. In reality, growth of autotrophs and heterotrophs may be limited by various elements, e.g. carbon, nitrogen, phosphorous or iron. In this study we develop a dynamic energy budget model chemostat(More)
We study the consequences of omnivory on the dynamic behaviour of a three species food web under chemostat conditions. The food web consists of a prey consuming a nutrient, a predator consuming a prey and an omnivore which preys on the predator and the prey. For each trophic level an ordinary differential equation describes the biomass density in the(More)
BACKGROUND Intake of sugar-sweetened beverages is associated with overweight in observational studies. A possible explanation is that liquid sugars do not satiate and that their intake is not compensated by reduced caloric intake from other foods. However, evidence from intervention studies for this hypothesis is inconclusive because previous studies were(More)
This cross-sectional dietary survey aimed to assess the consumption and relative nutrient contribution of ready-to-eat cereals (RTEC) among schoolchildren from 2 social classes in an urban center in the Guatemalan province of Quetzaltenango. A total of 449 24-hour dietary records were collected using a pictorial workbook registry method among third- and(More)
Normative data are needed to create a reference that indicates optimal development of weight in relation to height and age, particularly in the face of the unfolding obesity epidemic. The body-mass index (BMI) has some serious limitations: it is a relatively poor predictor of current and future fatness. Currently, however, there are few available(More)
OBJECTIVE Our objective was to assess the distribution of energy, macro- and micronutrient intakes by meal (breakfast, lunch, dinner and combined snacks) in a cross-sectional sample of schoolchildren. DESIGN Cross-sectional dietary survey in schoolchildren. SETTING Twelve private and public schools in the urban setting of Quetzaltenango, Guatemala. (More)
BACKGROUND Substituting sugar-free for sugar-sweetened beverages reduces weight gain. This effect may be more pronounced in children with a high body mass index (BMI) because their sensing of kilocalories might be compromised. We investigated the impact of sugar-free versus sugary drinks separately in children with a higher and a lower initial BMI z score,(More)
Basic Lotka-Volterra type models in which mutualism (a type of symbiosis where the two populations benefit both) is taken into account, may give unbounded solutions. We exclude such behaviour using explicit mass balances and study the consequences of symbiosis for the long-term dynamic behaviour of a three species system, two prey and one predator species(More)