Nanostructure of the fibrin clot.

The nanostructure of the fibrin fibers in fibrin clots is investigated by using spectrometry and small angle x-ray scattering measurements. First, an autocoherent analysis of the visible light spectra transmitted through formed clots is demonstrated to provide robust measurements of both the radius and density of the fibrin fibers. This method is validated via comparison with existing small-angle and dynamic light-scattering data. The complementary use of small angle x-ray scattering spectra and light spectrometry unambiguously shows the disjointed nature of the fibrin fibers. Indeed, under quasiphysiological conditions, the fibers are approximately one-half as dense as their crystalline fiber counterparts. Further, although the fibers are locally crystalline, they appear to possess a lateral fractal structure.

Aging and yielding in a sheared AOT/iso-octane/water lyotropic lamellar phase.

We define a creep-flow-based measurement procedure to allow reliable and reproducible results on aging and yielding materials to be obtained. Investigation of the effects of different parameter such as the pre-shear time, the recovery time and the applied stress magnitude on the viscoelastic properties of a lyotropic liquid crystal phase is reported. Cryo-TEM observations indicate the formation of multiconnected bilayers at rest. Shearing the investigated material shows a propensity to acquire all the macroscopic properties of "soft jammed systems". These properties are then interpreted in terms of shear-induced structural rearrangement on the basis of cryofracture observation obtained at different times after the preshear imposed.

Incoherent light transport in an anisotropic random medium: a probe of human erythrocyte aggregation and deformation.

This paper investigates the flow induced disaggregation, deformation and orientation of several modified human red blood cells suspended in concentrated, physiological like conditions (volume fraction in erythrocytes of 0.4). The aim is to determine simultaneously, and under flow, the aggregate sizes as well as the deformation and orientation of the cells. The measurement method uses steady, incoherent, unpolarized light transport while the sample is sheared in a flow cell controlled by a rheometer. Several blood samples were prepared to alter the erythrocyte's aggregating, deformability and shape properties. The measurements using these samples show a clear relationship between the intrinsic properties of the cells and the evolution of aggregate sizes, average cell orientation and anisotropy as a function of the applied shear, which may lead to clinical applications. In other words, the careful analysis of the incoherent light transport in concentrated media provides quantitative insight into their microscopic details. In particular, the topological properties (average anisotropy and orientation) and size of the suspended objects can be determined.

The influence of the microscopic characteristics of a random medium on incoherent light transport.

In this paper the influence of the microscopic characteristics of a random medium on non polarized, incoherent steady light transport (ISLT) is investigated. After close examination of current diffusion models, the source term in those models is modified, allowing a complete modeling of experimental and simulated radial dependance of backscattered and transmitted intensities for media thicknesses larger than the transport length. The new model only presents an additional source with respect to the elementary point source model. Thanks to more than 200 Monte-Carlo simulations, this parameter is correlated to the backscattering part of the Mie phase function. Incoherent Steady Light Transport measurements on two industrial emulsions at various volume fractions validate experimentally this correlation. This establishes a complete link between the microscopic characteristic of the random medium (size, optical indexes and volume fraction) and its macroscopic description in terms of diffusion and source parameters, opening new potential applications of the ISLT technique to, for example, the evaluation of the particles interaction potential in concentrated suspensions.

Steady light transport under flow: characterization of evolving dense random media.

We describe in this letter a new rheo-optical apparatus able to measure the photon transport length l* in an evolving random medium. First, the appropriate solution of the diffusion equation for oil in water, stable, micron-sized emulsions is compared successfully with the measured spatial distribution of incoherent backscattered light given by the new apparatus. Further validation is provided using stable samples of varying sizes and volume fractions (1% to 64%) and comparing measurements with Mie-Percus-Yevick calculations based on independent small-angle light scattering (SALS) measurements. As a typical example application of the system, the emulsification of a different oil in water system is studied in situ and dynamically. The continuous temporal measurements show the decrease of the average size versus time, in excellent quantitative agreement with independent SALS measurements. This evidences that this system is able to probe continuously and nonintrusively the microscopic and macroscopic flow-induced organization of suspensions.

[Role of renal autotransplantation in the treatment of renal arterial lesions]. / Place de l'autotransplantation rénale dans le traitement des lésions artérielles rénales.

112 patients with hypertensive lesions of the renal artery were studied. 33 patients with stenosis of the trunk of the renal artery were operated with autotransplantation. 10 patients had lesions of the main branches of the renal artery and in these cases autotransplantation with the anastomosis of the two main renal artery branches to the two main branches of the hypogastric artery was performed. 24 patients with complex lesions of renal artery branches were treated with autotransplantation associated with extracorporeal repair of the renal artery. 45 patients, with lesions of the trunk of the renal artery were operated by aortorenal bypass. For lesions of the main renal artery, results were better in the group of patients treated by simple autotransplantation (82% of patients cured versus 46% with bypass operation). For lesions involving multiple branches of the renal artery extracorporeal replacement of the renal artery followed by autotransplantation often represents to the sole technique to prevent nephrectomy. Hypertension was cured or improved in more than 80% of cases. We believe autotransplantation to be the best operation for lesions of the renal artery in most cases.