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Exploring, exploiting and evolving diversity of aquatic ecosystem models: a community perspective
(2015)
Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5-10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary.
Auxology has developed from mere describing child and adolescent growth into a vivid and interdisciplinary research area encompassing human biologists, physicians, social scientists, economists and biostatisticians. The meeting illustrated the diversity in auxology, with the various social, medical, biological and biostatistical aspects in studies on child growth and development.
Objective: We analyse temporal trends and regional variation among the most recent available anthropometric data from German conscription in the years 2008-2010 and their historical contextualization since 1956. Design/setting/subjects: The overall sample included German conscripts (N 13 857 313) from 1956 to 2010. Results: German conscripts changed from growing in height to growing in breadth. Over the analysed 54 years, average height of 19-year-old conscripts increased by 6.5 cm from 173.5 cm in 1956 (birth year 1937) to 180.0 cm in 2010 (birth year 1991). This increase plateaued since the 1990s (1970s birth years). The increase in average weight, however, did not lessen during the last two decades but increased in two steps: at the end of the 1980s and after 1999. The weight and BMI distributions became increasingly right-skewed, the prevalence of overweight and obesity increased from 11.6 % and 2.1 % in 1984 to 19.9 % and 8.5 % in 2010, respectively. The north-south gradient in height (north = taller) persisted during our observations. Height and weight of conscripts from East Germany matched the German average between the early 1990s and 2009. Between the 1980s and the early 1990s, the average chest circumference increased, the average difference between chest circumference when inhaling and exhaling decreased, as did leg length relative to trunk length. Conclusions: Measuring anthropometric data for military conscripts yielded year-by-year monitoring of the health status of young men at a proscribed age. Such findings contribute to a more precise identification of groups at risk and thus help with further studies and to target interventions.
The dual isotopes of deep nitrate as a constraint on the cycle and budget of oceanic fixed nitrogen
(2009)
We compare the output of an 18-box geochemical model of the ocean with measurements to investigate the controls on both the mean values and variation of nitrate delta N-15 and delta O-18 in the ocean interior. The delta O-18 of nitrate is our focus because it has been explored less in previous work. Denitrification raises the delta N-15 and delta O-18 of mean ocean nitrate by equal amounts above their input values for N-2 fixation (for delta N-15) and nitrification (for delta O-18), generating parallel gradients in the delta N-15 and delta O-18 of deep ocean nitrate. Partial nitrate assimilation in the photic zone also causes equivalent increases in the delta N-15 and delta O-18 of the residual nitrate that can be transported into the interior. However, the regeneration and nitrification of sinking N can be said to decouple the N and O isotopes of deep ocean nitrate, especially when the sinking N is produced in a low latitude region, where nitrate consumption is effectively complete. The delta N-15 of the regenerated nitrate is equivalent to that originally consumed, whereas the regeneration replaces nitrate previously elevated in delta O-18 due to denitrification or nitrate assimilation with nitrate having the delta O-18 of nitrification. This lowers the delta O-18 of mean ocean nitrate and weakens nitrate delta O-18 gradients in the interior relative to those in delta N-15. This decoupling is characterized and quantified in the box model, and agreement with data shows its clear importance in the real ocean. At the same time, the model appears to generate overly strong gradients in both delta O-18 and delta N-15 within the ocean interior and a mean ocean nitrate delta O-18 that is higher than measured. This may be due to, in the model, too strong an impact of partial nitrate assimilation in the Southern Ocean on the delta N-15 and delta O-18 of preformed nitrate and/or too little cycling of intermediate-depth nitrate through the low latitude photic zone.