119 research outputs found
Accuracy quantification by the FFT method in Faro L-20 test - pre-test calculations
No full textThe Fast Fourier Transform Based Method (FFTBM) was developed at University of Pisa to achieve a quantitative evaluation of the accuracy of thermal-hydraulic system code calculations. International cooperation was established to transfer the method with various Institutions all over the world. In the case documented in this report one scientists from University of Pisa (Mario Leonardi) has been invited at the European Commission (EC) Joint Research Center (JRC) of Ispra (Varese, Italy) to implement and to apply the method. The present document has been issued by JSI and describes the application of the method to the severe accident (corium interaction with water) FARO L-20 carried out in the framework of EC EURATOM researches
The aortic wall: ultrastructural observations by FEG-SEM and by Tapping-Mode AFM in fluid
No full textThe fibrillar crimps of the sclera
No full textCrimps are a typical feature of tendons and of some ligaments where they are responsible for the non-linear behaviour of the tissue at low strain values. Previous studies (Raspanti et al., 2005) shown that in tendons these visible crimps always correspond to a distinctive buckling and/or left-handed torsion of the collagen fibrils, subsequently named “fibrillar crimp” (Franchi et al, 2007). These planar crimps are exclusive of the collagen fibrils of tendons and ligaments, whose subfibrils run straight and parallel and tend to behave like stiff rods; by contrast, the collagen fibrils of most tissues, which are sometimes defined as “reticular fibrils” of “type III fibrils” and whose subfibrils follow an helical course, are almost infinitely flexible and can withstand even sharp U-turns without buckling. In the present study we investigated the rat sclera, whose ultrastructure is closely related to that of tendons and ligaments (Raspanti et al., 1992). The tissue was observed by light microscopy, high-resolution scanning electron microscopy and atomic force microscopy. The sclera appears made of flattened fascicles of large and heterogeneous collagen fibrils, running in all directions and often following a wavy course. The individual fascicles are identical in structure and appearance to those of tendon, as are the numerous crimps which can be easily observed along their fibrils. The presence of crimps in the sclera cannot be taken for granted because at variance with tendon, which is subject to intermittent load/recoil cycles, this tissue is held under continuous tension by the intraocular pressure (IOP). A typical intra-ocular pressure of 20-30 mmHg would induce in the rat sclera a tension varying from 50 to 80 kN/m2, and the elastic behaviour of the crimps may have a role in maintaining the shape of the eyeball. The crimps may therefore be fully functional, confirming this tissue as a sort of hemispherical tendon
Structural Aspects of the Extracellular Matrix of Tendon: An Atomic Force and Scanning Electron Microscopy Study
No full text
Visualization of hydrated extracellular matrix by tapping-mode atomic force microscopy in fluid
No full textSTRUCTURES RECOGNITION IN ATOMIC FORCE MICROSCOPY: PRE- AND POST-PROCESSING TECHNIQUES.
No full textItalian Journal of Anatomy and Embryology 105 Suppl.1 Fasc.2, 192, 200
Ultrastructural aspects of mineralization-induced modifications in turkey tendon.
No full textIn all tendons the collagen fascicles follow a wavy course (actually a flattened lefthanded helix) forming visible crimps. Each crimp corresponds to a sharp bend and/ or an axial twisting of individual collagen fibrils (Raspanti et al., 2005; Franchi et al., 2010), and even once the fibril are straightened out a permanent local deformation remains visible, still revealing the original crimp location (Raspanti et al., 2005). The tendons of some birds represent a special case as they undergo a physiological process of gradual mineralization involving heavy modifications of the tissue architecture. In the present research, turkey tendons appeared to be more finely subdivided into thinner fascicles than most tendons; they contained a greater amount of cell-rich endotenon tissue as well as occasional nodules of cartilage-like matrix. The most striking finding, however, was the complete disappearance of the crimps in the calcified portions of the tendon, while they were present with the usual morphology in the non-mineralized portion. The mineralized fibrils ran perfectly straight, but the electron microscopy revealed traces of pre-existing crimps locked in the extended position by the mineralization process. The inorganic phase itself appeared composed of two different types of fine particles, respectively growing inside or around the collagen fibrils and looking as tightly packed fine needles or as larger platelets regularly arranged in relation with the D-period. The perifibrillar mineral could play a critical role in the mechanical coupling of adjoining fascicles and in the transmission of tensile loads along the tendon itself
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