Morphological modelling of three-phase microstructures of anode layers using SEM images.

A general method is proposed to model 3D microstructures representative of three-phases anode layers used in fuel cells. The models are based on SEM images of cells with varying morphologies. The materials are first characterized using three morphological measurements: (cross-)covariances, granulometry and linear erosion. They are measured on segmented SEM images, for each of the three phases. Second, a generic model for three-phases materials is proposed. The model is based on two independent underlying random sets which are otherwise arbitrary. The validity of this model is verified using the cross-covariance functions of the various phases. In a third step, several types of Boolean random sets and plurigaussian models are considered for the unknown underlying random sets. Overall, good agreement is found between the SEM images and three-phases models based on plurigaussian random sets, for all morphological measurements considered in the present work: covariances, granulometry and linear erosion. The spatial distribution and shapes of the phases produced by the plurigaussian model are visually very close to the real material. Furthermore, the proposed models require no numerical optimization and are straightforward to generate using the covariance functions measured on the SEM images.

Modeling of the Multiscale Dispersion of Nanoparticles in a Hematite Coating.

Images of a hematite-based epoxy coating are obtained by scanning electron microscopy (SEM). At the scale of a few micrometers, they show aggregates of hematite nano-particles organized along thin curved channels. We first segment the images and analyze them using mathematical morphology. The heterogeneous dispersion of particles is quantified using the correlation function and the granulometry of the embedding (epoxy) phase. Second, a two-scales, 3D random microstructure model with exclusion zones is proposed to simulate the spatial distribution of particles. This simple model is parametrized by four geometrical parameters related to the exclusion zones solely. The microstructure is numerically optimized, in the space of morphological parameters, on the granulometry of the embedding epoxy phase and on the microstructure correlation function, by standard gradient-descent methods. Excellent agreement is found between the SEM images and our optimized model. Finally, the size of the representative volume element associated to the optimized microstructure model is compared with that of the SEM images.

Imaging tools for analysis of the ureteric tree in the developing mouse kidney.

The structure of the ureteric tree in developing mouse and rat kidneys has previously been quantified in two dimensions. While this type of analysis may provide evidence of changes in ureteric growth, these measurements are effectively inaccurate, as the ureteric tree is a three-dimensional (3D) object. Here we describe a method for measuring the ureteric tree in three dimensions. This technique involves (1) culture of the metanephric kidney at embryonic day 12 (mouse) or 14 (rat), (2) whole-mount immunofluorescence to selectively stain ureteric tree epithelium, (3) confocal microscopy to obtain a complete Z series through the ureteric tree, and (4) image analysis algorithms to binarize, skeletonize, and measure individual branch lengths in 3D. This method has been extended to analysis of the same ureteric tree over time (4D). The results obtained provide accurate and precise quantitation of ureteric tree growth in the developing mouse or rat kidney.

Random-walk-based stochastic modeling of three-dimensional fiber systems.

For the simulation of fiber systems, there exist several stochastic models: systems of straight nonoverlapping fibers, systems of overlapping bending fibers, or fiber systems created by sedimentation. However, there is a lack of models providing dense, nonoverlapping fiber systems with a given random orientation distribution and a controllable level of bending. We introduce a new stochastic model in this paper that generalizes the force-biased packing approach to fibers represented as chains of balls. The starting configuration is modeled using random walks, where two parameters in the multivariate von Mises-Fisher orientation distribution control the bending. The points of the random walk are associated with a radius and the current orientation. The resulting chains of balls are interpreted as fibers. The final fiber configuration is obtained as an equilibrium between repulsion forces avoiding crossing fibers and recover forces ensuring the fiber structure. This approach provides high volume fractions up to 72.0075%.

Reconstruction of the rose of directions from a digital microhologram of fibres.

Digital holography makes it possible to acquire quickly the interference patterns of objects spread in a volume. The digital processing of the fringes is still too slow to achieve on line analysis of the holograms. We describe a new approach to obtain information on the direction of illuminated objects. The key idea is to avoid reconstruction of the volume followed by classical three-dimensional image processing. The hologram is processed using a global analysis based on autocorrelation. A fundamental property of diffraction patterns leads to an estimate of the mean geometric covariogram of the objects projections. The rose of directions is connected with the mean geometric covariogram through an inverse problem. In the general case, only the two-dimensional rose of the object projections can be reconstructed. The further assumption of unique-size objects gives access with the knowledge of this size to the three-dimensional direction information. An iterative scheme is suggested to reconstruct the three-dimensional rose in this special case. Results are provided on holograms of paper fibres.

Direct extraction of the mean particle size from a digital hologram.

Digital holography, which consists of both acquiring the hologram image in a digital camera and numerically reconstructing the information, offers new and faster ways to make the most of a hologram. We describe a new method to determine the rough size of particles in an in-line hologram. This method relies on a property that is specific to interference patterns in Fresnel holograms: Self-correlation of a hologram provides access to size information. The proposed method is both simple and fast and gives results with acceptable precision. It suppresses all the problems related to the numerical depth of focus when large depth volumes are analyzed.

Computer-based detection of neonatal changes to branching morphogenesis reveals different mechanisms of and predicts prostate enlargement in mice haplo-insufficient for bone morphogenetic protein 4.

Early changes to branching morphogenesis of the prostate are believed to lead to enlargement of the gland in adult life. However, it has not been possible to demonstrate directly that alterations to branching during the developmental period have a permanent effect on adult prostate size. In order to examine branching morphogenesis in a quantitative manner in neonatal mice, a combination of imaging and computational technology was used to detect and quantify branching using bone morphogenetic protein 4 haplo-insufficient mice that develop enlarged prostate glands in adulthood. Accurate estimates were made of six parameters of branching, including prostate ductal length and volume and number of main ducts, branches, branch points, and tips. The results show that the prostate is significantly larger on day 3, well before the emergence of the phenotype in older animals. The ventral prostate is enlarged because the number of main epithelial ducts is increased; enlargement of the anterior prostate in mutant animals occurs because there are more branches. These lobe-specific mechanisms underlying prostate enlargement indicate the complex nature of gland pathology in mice, rather than a simple increase in weight or volume. This method provides a powerful means to investigate the aetiology of prostate disease in animal models prior to emergence of a phenotype in later life.

Exogenous BMP-4 amplifies asymmetric ureteric branching in the developing mouse kidney in vitro.

BACKGROUND: Exogenous bone morphogenetic protein 4 (BMP-4) has been reported to inhibit ureteric branching morphogenesis and regulate the anterior-posterior axis of the developing kidney in vitro. We examined the role of BMP-4 on ureteric branching in vitro using three-dimensional image analysis software and statistical models. Additionally, in vivo ureteric branching was analyzed and the effect of reduced levels of BMP-4 in vivo on nephron number was examined. METHODS: Embryonic day 12.5 (E12.5) Balb/c mouse metanephroi cultured for 48 hours with or without 260 ng/mL recombinant human BMP-4 (rhBMP-4) were immunostained to identify the ureteric epithelium which was quantified in three dimensions. In vivo ureteric branching morphogenesis in Hoxb7/GFP mice was also analyzed. The effect of reduced in vivo levels of BMP-4 on nephron number was examined in BMP-4(+/-) and wild-type mice using an unbiased stereologic method. RESULTS: Qualitative and quantitative studies identified a decrease in total ureteric length and branch number in wild-type mouse metanephroi cultured in the presence of BMP-4. A marked anterior-posterior asymmetry in both ureteric length and branch number was observed in BMP-4-treated metanephroi. A similar asymmetry was revealed in control metanephroi, both in vitro and in vivo. This asymmetry is the result of reduced ureteric branching morphogenesis in the posterior region of the kidney and appears to be due to slower growth rather than the adoption of an alternate branching pattern. Reduction of endogenous BMP-4 in BMP-4(+/-) mice resulted in no change in total nephron number in macroscopically normal kidneys. CONCLUSION: These results suggest that BMP-4 plays an important role in the regulation of ureteric branching morphogenesis, and that excess BMP-4 in vitro can amplify the existing asymmetry of the normal mouse kidney.

Quantitation of 3D ureteric branching morphogenesis in cultured embryonic mouse kidney.

The growth and branching of the epithelial ureteric tree is critical for development of the permanent kidney (metanephros). Current methods of analysis of ureteric branching are mostly qualitative. We have developed a method for measuring the length of individual branches, and thereby the total length of the ureteric tree in 3 dimensions (3D). The method involves confocal microscopy of whole-mount immunostained metanephroi and computer-based image segmentation, skeletonisation and measurement. The algorithm performs semi-automatic segmentation of a set of confocal images and skeletonisation of the resulting binary object. Length measurements and number of branch points are automatically obtained. The final representation can be reconstructed providing a fully rotating 3D perspective of the skeletonised tree. After 36 h culture of E12 mouse metanephroi, the total length of the ureteric tree was 6103 +/- 291 microm (mean +/- SD), a four-fold increase compared with metanephroi cultured for just 6 h (1522 +/- 149 microm). Ureteric duct length increased at a rate of 153 microm/h over the first 30 h period and was maximal between 18 and 24 h at 325 microm/h. The distribution of branch lengths at the six time points studied was similar, suggesting tight control of ureteric lengthening and branching. This method will be of use in analysing ureteric growth in kidneys cultured in the presence of specific molecules suspected of regulating ureteric growth. The method can also be used to analyse in vivo kidneys and to quantify branching morphogenesis in other developing organs.

A double blind randomized placebo controlled study of cholera treatment with highly diluted and succussed solutions

A pilot study of homoeopathic treatment of cholera during an epidemic in Peru appeared to show that it was effective. A subsequent double blind study showed no difference betwen active homoeopathic treatment and placebo treatment. Various technical problems were encountered