32 research outputs found
In situ TEM study of twin boundary migration in sub-micron Be fibers
Deformation twinning in hexagonal crystals is often considered as a way to
palliate the lack of independent slip systems. This mechanism might be either
exacerbated or shut down in small-scale crystals whose mechanical behavior can
significantly deviate from bulk materials. Here, we show that sub-micron
beryllium fibers initially free of dislocation and tensile tested in-situ in a
transmission electron microscope (TEM) deform by a twin thickening. The propagation speed of the twin boundary
seems to be entirely controlled by the nucleation of twinning dislocations
directly from the surface. The shear produced is in agreement with the repeated
lateral motion of twinning dislocations. We demonstrate that the activation
volume () associated with the twin boundary propagation can be retrieved
from the measure of the twin boundary speed as the stress decreases as in a
classical relaxation mechanical test. The value of is comparable to the value expected from surface
nucleation.Comment: 13 pages, 9 figure
Chondroitin sulfates and their binding molecules in the central nervous system
Chondroitin sulfate (CS) is the most abundant glycosaminoglycan (GAG) in the central nervous system (CNS) matrix. Its sulfation and epimerization patterns give rise to different forms of CS, which enables it to interact specifically and with a significant affinity with various signalling molecules in the matrix including growth factors, receptors and guidance molecules. These interactions control numerous biological and pathological processes, during development and in adulthood. In this review, we describe the specific interactions of different families of proteins involved in various physiological and cognitive mechanisms with CSs in CNS matrix. A better understanding of these interactions could promote a development of inhibitors to treat neurodegenerative diseases
Die Prognose der fruehen chronischen Polyarthritis und der undifferenzierten Arthritis mit besonderer Beruecksichtigung beruflicher Veraenderungen
Available from TIB Hannover: F94B964+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman