Structural and dielectrics properties of Pr3+ doped BaTi0.925(Yb0.5Nb0.5)(0.075)O-3 ceramics

International audienceBa1-xPr2x/3Ti0.925(Yb0.5Nb0.5)(0.075)O-3:(xPrBTYN) (0.02 <= x <= 0.08) ceramics were prepared by a high temperature solid-state reaction technique. The effects of the Pr3+ addition to structural and dielectric properties were examined. The X-ray study has evidenced a cubic single phase in the Pm-3m space group. Raman spectra showed that the replacement of the Ba2+ by Pr3+ ions induced a down shift of active modes accompanied with a significant reduction in the intensity. Further, a new mode appeared at 115 cm(-1) with an intensity depended on the composition. Dielectric study as a function of temperature and frequency of ceramic samples has revealed a normal ferroelectric behavior where x <= 0.06, instead to a relaxor character in the case of ceramic with an optimum value of Pr3+ doping (x = 0.08). (C) 2017 Elsevier B.V. All rights reserved

Effect of Pr3+ doping on structural, electrical, and optical properties of BaTi0.925(Yb0.5Nb0.5)0.075O3 ceramics

cited By 5International audienceThe effect of Pr3+ addition on structural, electrical, and optical properties of Ba1-xPr2x/3Ti0.925(Yb0.5Nb0.5)0.075O3 (0.3% ≤ x ≤ 1%) ceramics was investigated. X-ray studies have allowed the identification of a continuous solid solution with P4mm-tetragonal symmetry of all prepared samples. Incorporation of Pr3+ was found to improve ferroelectric and piezoelectric properties with an optimum at the critical concentration of 0.005. Photoluminescence properties revealed that the introduction of Pr3+ ions gives rise to the green and red photoemissions and permitted to shed more light on the created structural disorder and shallow defects. This effect was confirmed by Raman spectroscopy investigation. The presence of Pr element in such materials may have significant technological promise in novel multifunctional devices. © 2016 Elsevier B.V

Effects of lanthanide amphoteric incorporation on structural, electrical, and photoluminescence properties of BaTi0.925(Yb0.5Nb0.5)(0.075)O-3 ceramic

International audienceThe influence of the lanthanide incorporation in lead-free ferroelectric BaTi0.925(Yb0.5Nb0.5)(0.075)O-3 (BTYN) perovskite on its structural, dielectric, ferroelectric behavior, piezoelectric and photoluminescence properties was investigated. X-ray diffraction study permitted the identification of an isostructural phase with P4mm-tetragonal symmetry. Praseodymium was found to occupy only Ba-sites instead of the distribution over both sites as in the case of Nd and Eu elements. The improvement of dielectric and ferroelectric properties obtained from Nd- and Eu-phase is discussed in terms of amphoteric behavior effect of these elements. Incorporation of Ln(3+) was found to improve piezoelectric properties from 3 pC/N for BTYN to 18, 40 and 26 pC/N for BTYN:Eu, BTYN:Nd and BTYN:Pr respectively. The photoluminescence (PL) properties of Pr-phase gives rise to the expected electronic transitions associate to Pr3+ ions. In contrast, PL carried out on Eu- and Nd-phases showed dominate strong red emission centered at 690 nm attributed to defect structure and non-stoichiometry. The simultaneous existence of ferroelectric piezoelectric and luminescence properties in the titled system could be promising for electro-optical applications. (C) 2017 Elsevier B.V. All rights reserved

The Regenerative Effect of Trans-spinal Magnetic Stimulation After Spinal Cord Injury: Mechanisms and Pathways Underlying the Effect

International audienceAbstract Spinal cord injury (SCI) leads to a loss of sensitive and motor functions. Currently, there is no therapeutic intervention offering a complete recovery. Here, we report that repetitive trans-spinal magnetic stimulation (rTSMS) can be a noninvasive SCI treatment that enhances tissue repair and functional recovery. Several techniques including immunohistochemical, behavioral, cells cultures, and proteomics have been performed. Moreover, different lesion paradigms, such as acute and chronic phase following SCI in wild-type and transgenic animals at different ages (juvenile, adult, and aged), have been used. We demonstrate that rTSMS modulates the lesion scar by decreasing fibrosis and inflammation and increases proliferation of spinal cord stem cells. Our results demonstrate also that rTSMS decreases demyelination, which contributes to axonal regrowth, neuronal survival, and locomotor recovery after SCI. This research provides evidence that rTSMS induces therapeutic effects in a preclinical rodent model and suggests possible translation to clinical application in humans

Reaction of ependymal cells to spinal cord injury: a potential role for oncostatin pathway and microglial cells

Abstract Ependymal cells with stem cell properties reside in the adult spinal cord around the central canal. They rapidly activate and proliferate after spinal cord injury, constituting a source of new cells. They produce neurons and glial cells in lower vertebrates but they mainly generate glial cells in mammals. The mechanisms underlying their activation and their glial-biased differentiation in mammals remain ill-defined. This represents an obstacle to control these cells. We addressed this issue using RNA profiling of ependymal cells before and after injury. We found that these cells activate STAT3 and ERK/MAPK signaling during injury and downregulate cilia-associated genes and FOXJ1, a central transcription factor in ciliogenesis. Conversely, they upregulate 510 genes, six of them more than 20 fold, namely Crym, Ecm1, Ifi202b, Nupr1, Rbp1, Thbs2 and Osmr . OSMR is the receptor for the inflammatory cytokine oncostatin (OSM) and we studied its regulation and role using neurospheres derived from ependymal cells. We found that OSM induces strong OSMR and p-STAT3 expression together with proliferation reduction and astrocytic differentiation. Conversely, production of oligodendrocyte-lineage OLIG1 + cells was reduced. OSM is specifically expressed by microglial cells and was strongly upregulated after injury. We observed microglial cells apposed to ependymal cells in vivo and co-cultures experiments showed that these cells upregulate OSMR in neurosphere cells. Collectively, these results support the notion that microglial cells and OSMR/OSM pathway regulate ependymal cells in injury. In addition, the generated high throughput data provides a unique molecular resource to study how ependymal cell react to spinal cord lesion