Extraction of three-dimensional soil pore space from microtomography images using a geometrical approach

This paper presents a geometrical model of soil pore space based on the quantitative analysis of synchrotron X-ray microtomography data. Our model calculated the minimal set of balls that recovered the skeleton of the pore space using Delaunay tessellation, and the simply connected sets of balls that could be considered as potential pore channels. This model (DTM software) was then applied to three-dimensional tomography reconstructions of soil aggregates (similar to 5 mm diameter) from two management systems (conventionally tilled soil, namely M and grassland soil, namely GL) with a voxel edge length of 3.2 mu m and 5.4 mu m, respectively. Geometric characteristics such as the frequency distribution of pore radius, length, and tortuosity as well as the retention curve were calculated using our model. The organic matter decomposition was also simulated using DTM approach. The results were compared with pore space statistics obtained during a previously published study on the same data using algorithms based on the medial axis and throat computation (3dma software). The same tendency on the geometrical statistic was obtained using both methods, with more pores of smaller length and diameter calculated for the aggregate from the conventionally tilled site compared to the grassland aggregate. However, the 3dma method generated a larger quantity of voxels (385,673 and 189,250 for CTT and GL, respectively) compared to the amount of balls in DTM (170,250 and 64,273 for M and GL, respectively) and shorter channels because of the presence of throats

Experimental approaches to study mammalian cells glucose metabolism. 47th Canadian Chemical Engineering Conference, Westin Hotel, Edmonton, October 58, 1997.

NRC publication: Ye

Glucose metabolism of 293 S cells

NRC publication: Ye

Ecological interactions in a shallow sand-pit lake (Lake Créteil, Parisian Basin, France): a modelling approach

A large data set (n = 154) of phytoplankton production and biomass in relation to physico-chemical environmental factors was collected from 1979 to 1986 in a recently created sand-pit lake (Paris suburbs). These data are well suited to interpret the oligotrophication observed along the 8 years period, characterized by a regular decrease in chlorophyll (from 16 to 4 μg l-1 as annual averages). A model describing the ecological functioning of the lake has been established. Biological processes related to phyto-, bacterio- and zooplankton as well as sediment-water interactions, are described within several submodels. Most of the parameters involved were determined by in situ measurements in this or similar environments The model provides a good simulation of observed data and confirms that the reduction of nutrient loading, resulting from the diversion - in 1981 - of a sewer previously discharging into the lake, was responsible for the oligotrophication of the system. The model allows to explore the response of planktonic compartments accross a gradient of nutrient loading. The role of hydrology is also tested. The systematic run of the model with and without zooplankton leads to a better understanding of top-down control. © 1994 Kluwer Academic Publishers.SCOPUS: ar.jinfo:eu-repo/semantics/publishe