Optical, Structural, and Dielectric Properties of Composites Based on Thermoplastic Polymers of the Polyolefin and Polyurethane Type and BaTiO3 Nanoparticles.

In this work, new films containing composite materials based on blends of thermoplastic polymers of the polyurethane (TPU) and polyolefin (TPO) type, in the absence and presence of BaTiO3 nanoparticles (NPs) with the size smaller 100 nm, were prepared. The vibrational properties of the free films depending on the weight ratio of the two thermoplastic polymers were studied. Our results demonstrate that these films are optically active, with strong, broad, and adjustable photoluminescence by varying the amount of TPU. The crystalline structure of BaTiO3 and the influence of thermoplastic polymers on the crystallization process of these inorganic NPs were determined by X-ray diffraction (XRD) studies. The vibrational changes induced in the thermoplastic polymer's matrix of the BaTiO3 NPs were showcased by Raman scattering and FTIR spectroscopy. The incorporation of BaTiO3 NPs in the matrix of thermoplastic elastomers revealed the shift dependence of the photoluminescence (PL) band depending on the BaTiO3 NP concentration, which was capable of covering a wide visible spectral range. The dependencies of the dielectric relaxation phenomena with the weight of BaTiO3 NPs in thermoplastic polymers blends were also demonstrated.

Mechanotransduction in cortical bone and the role of piezoelectricity: a numerical approach.

This paper is a contribution to a plausible explanation of the mechanotransduction phenomenon in cortical bone during its remodelling. Our contribution deals only with the mechanical processes and the biological aspects have not been taken into account. It is well known that osteoblasts are able to generate bone in a suitable bony substitute only under fluid action. But the bone created in this manner is not organised to resist specific mechanical stress. Our aim was to suggest the nature of the physical information that can be transmitted - directly or via a biological or biochemical process - to the cell to initiate a cellular activity inducing the reconstruction of the osteon that is best adapted to local mechanical stresses. For this, the cell must have, from our point of view, a good knowledge of its structural environment. But this knowledge exists at the cellular scale while the bone is loaded at the macroscopic scale. This study is based on the SiNuPrOs model that allows exchange of information between the different structural scales of cortical bone. It shows that more than the fluid, the collagen - via its piezoelectric properties - plays an essential role in the transmission of information between the macroscopic and nanoscopic scales. Moreover, this process allows us to explain various dysfunctions and even some diseases.

Human cortical bone: the SiNuPrOs model. Part II--a multi-scale study of permeability.

Cortical bone is more and more considered as a porous medium and this induces the necessity of the determination of the physical properties associated with such a concept: the porosity and the permeability. If porosity does not present a major problem, at least for the order of magnitude, there is a difficulty for the permeability. According to experimental sources, values vary between 10(- 13) and 10(- 23) m(2): it seems obvious that the same entities have not been measured. This article proposes a new vision of the permeability based on a concept of multi-scale medium corresponding to the scales already introduced in the SiNuPrOs model which has been developed for cortical bone. According to this model, several architectural levels are proposed and a mathematical development based on the homogenisation theory, which can be applied to each of these levels, allows a numerical computation of the permeability tensor coefficients. A comparative analysis of our simulations and some experimental results (already published) shows a good accordance with the literature.

Late hypothyroidism following subacute thyroiditis.

The authors followed up the incidence of permanent hypothyroidism in 35 patients with subacute thyroiditis (SAT) in their past history. The investigations were made one to four years after the acute episode. Ten of these presented repeated recurrences despite the therapy with glucocorticoids. The investigations included serum determination by RIA of T4, T3, TSH and thyroglobulin as well as of circulating thyroid antibodies. Permanent hypothyroidism subsequent to SAT occurred in two patients. In one of them it occurred following thyroid surgery performed for repeated recurrences. Both patients presented high levels of circulating thyroglobulin antibodies suggesting a possible transition to autoimmune thyroiditis. In the authors' opinion permanent hypothyroidism is likely to develop after SAT only in association with an autoimmune process or after thyroid surgery.