We studied normal and tumorous three-dimensional (3D) microvascular networks in primate and rat brain. Tissues were prepared following a new preparation technique intended for high-resolution synchrotron tomography of microvascular networks. The resulting 3D images with a spatial resolution of less than the minimum capillary diameter permit a complete description of the entire vascular network for volumes as large as tens of cubic millimeters. The structural properties of the vascular networks were investigated by several multiscale methods such as fractal and powerspectrum analysis. These investigations gave a new coherent picture of normal and pathological complex vascular structures. They showed that normal cortical vascular networks have scaleinvariant fractal properties on a small scale from 1.4 lm up to 40 to 65 lm. Above this threshold, vascular networks can be considered as homogeneous. Tumor vascular networks show similar characteristics, but the validity range of the fractal regime extend to much larger spatial dimensions. These 3D results shed new light on previous two dimensional analyses giving for the first time a direct measurement of vascular modules associated with vessel-tissue surface exchange.

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SummaryThis paper presents the first application of high-resolution X-ray synchrotron tomography to the imaging of large microvascular networks in biological tissue samples. This technique offers the opportunity of analysing the full three-dimensional vascular network from the micrometre to the millimetre scale. This paper presents the specific sample preparation method and the X-ray imaging procedure. Either barium or iron was injected as contrast agent in the vascular network. The impact of the composition and concentration of the injected solution on the X-ray synchrotron tomography images has been studied. Two imaging modes, attenuation and phase contrast, are compared. Synchrotron high-resolution computed tomography offers new prospects in the three-dimensional imaging of in situ biological vascular networks.

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This study revisits Ariely and Levav's previous findings in relation to consumers' need for variety when ordering (food or beverages) in a group setting. We examine how group opinion and unanimity can explain consumers' individual choice in a group setting. We hypothesize that the relationship between individual choice and group opinion is nonmonotonic as it is moderated by the degree of unanimity around an alternative. We demonstrate this effect in two empirical studies. We show that choice patterns are curvilinear, with previous findings accurately reflecting only specific sections of the overall pattern of individual choices in a group setting. (c) 2009 by JOURNAL OF CONSUMER RESEARCH, Inc..