Comparing non-hierarchical models: Application to non-linear mixed effects modeling

1996 ◽  
Vol 26 (6) ◽  
pp. 505-512 ◽  
Author(s):  
Ene I. Ette
2016 ◽  
Vol 12 ◽  
pp. P356-P356
Author(s):  
Akshay Pai ◽  
Stefan Sommer ◽  
Lars Lau Raket ◽  
Lauge Sørensen ◽  
Mads Nielsen

2011 ◽  
Vol 38 (No. 1) ◽  
pp. 43-47 ◽  
Author(s):  
I. Ozturk ◽  
C.O. Ottosen ◽  
C. Ritz ◽  
J.C. Streibig

hotosynthetic response to light was measured on the leaves of two cultivars of Rosa hybrida L. (Escimo and Mercedes) in the greenhouse to obtain light-response curves and their parameters. The aim was to use a model to simulate leaf photosynthetic carbon gain with respect to environmental conditions. Leaf gas exchanges were measured at 11 light intensities from 0 to 1,400 µmol/m2s, at 800 ppm CO2, 25°C, and 65 ± 5% relative humidity. In order to describe the data corresponding to different measurement dates, the non-linear mixed-effects regression analysis was used. The model successfully described the photosynthetic responses. The analysis indicated significant differences in light saturated photosynthetic rates and in light compensation points. The cultivar with the lower light compensation points (Escimo) maintained a higher carbon gain despite its lower (but not-significant) quantum efficiency. The results suggested acclimation response, as carbon assimilation rates and stomatal conductance at each measurement date were higher for Escimo than Mercedes. Differences in photosynthesis rates were attributed to the adaptive capacity of the cultivars to light conditions at a specific day when the experiments were undertaken.


Author(s):  
Michiel J. van Esdonk ◽  
Jasper Stevens

AbstractThe quantitative description of individual observations in non-linear mixed effects models over time is complicated when the studied biomarker has a pulsatile release (e.g. insulin, growth hormone, luteinizing hormone). Unfortunately, standard non-linear mixed effects population pharmacodynamic models such as turnover and precursor response models (with or without a cosinor component) are unable to quantify these complex secretion profiles over time. In this study, the statistical power of standard statistical methodology such as 6 post-dose measurements or the area under the curve from 0 to 12 h post-dose on simulated dense concentration–time profiles of growth hormone was compared to a deconvolution-analysis-informed modelling approach in different simulated scenarios. The statistical power of the deconvolution-analysis-informed approach was determined with a Monte-Carlo Mapped Power analysis. Due to the high level of intra- and inter-individual variability in growth hormone concentrations over time, regardless of the simulated effect size, only the deconvolution-analysis informed approach reached a statistical power of more than 80% with a sample size of less than 200 subjects per cohort. Furthermore, the use of this deconvolution-analysis-informed modelling approach improved the description of the observations on an individual level and enabled the quantification of a drug effect to be used for subsequent clinical trial simulations.


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