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In this work, we synthesized and studied the spectroscopic properties of (NH4)2(SO4)2Y(H2O)6 (Y = Ni, Mg) crystals doped with AgNO3 or H3BO3. These crystals constitute a series of hexahydrated salts known as Tutton salts. We investigated the influence of dopants on the vibrational modes of the tetrahedral ligands NH4 and SO4, octahedral complexes Mg(H2O)6 and Ni(H2O)6, and H2O molecules present in these crystals through Raman and infrared spectroscopies. We were able to identify bands that are attributed to the presence of Ag and B dopants, as well as band shifts caused by the presence of these dopants in the crystal lattice. A detailed study of the crystal degradation processes was performed by thermogravimetric measurements, where there was an increase in the initial temperature of crystal degradation due to the presence of dopants in the crystal lattice. Raman spectroscopy of the crystal residues after the thermogravimetric measurements helped us to elucidate the degradation processes occurring after the crystal pyrolysis process.
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The original version of this Article had an incorrect Received date of 21 November 2016; it should have been 21 November 2017. This has been corrected in the PDF and HTML versions of the Article.
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Skyrmions are topologically protected non-collinear magnetic structures. Their stability is ideally suited to carry information in, e.g., racetrack memories. The success of such a memory critically depends on the ability to stabilize and manipulate skyrmions at low magnetic fields. The non-collinear Dzyaloshinskii-Moriya interaction originating from spin-orbit coupling drives skyrmion formation. It competes with Heisenberg exchange and magnetic anisotropy favoring collinear states. Isolated skyrmions in ultra-thin films so far required magnetic fields as high as several Tesla. Here, we show that isolated skyrmions in a monolayer of Co/Ru(0001) can be stabilized down to vanishing fields. Even with the weak spin-orbit coupling of the 4d element Ru, homochiral spin spirals and isolated skyrmions were detected with spin-sensitive scanning tunneling microscopy. Density functional theory calculations explain the stability of the chiral magnetic features by the absence of magnetic anisotropy energy.
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OBJECTIVE: this study investigated the in vitro effects of a chitosan-gelatin scaffold on growth and osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMMSCs) in three-dimensional (3D) cultures and evaluated the biomaterial biocompatibility and degradability after its grafting into tooth sockets of rats. DESIGN: a porous chitosan-gelatin scaffold cross-linked by glutaraldehyde was synthesised and characterised by light (LM), scanning electronic microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). Rat BMMSCs were isolated, expanded and seeded onto scaffold using Dulbecco's Modified Eagle's Medium (DMEM) with or without an osteogenic supplement. Cell viability by MTT assay, alkaline phosphatase (ALP) activity and morphological LM and SEM analysis were performed after 1, 3, 8 and 14 days in culture. Free-cell scaffolds were implanted into tooth sockets of Lewis rats after upper first molars extraction. Fifteen male recipient rats were sacrificed after 5, 21 and 35 days for histological analysis. RESULTS: scaffold characterisation revealed the porous structure, organic and amorphous content. This biomaterial promoted the adhesion, spreading and in vitro viability of the BMMSCs. Osteogenic-supplemented media did not improve the cellular response compared to DMEM. The biomaterial presented high biocompatibility and slow biodegradation in vivo. Remains of biomaterial were still observed at 21 and 35 days after implantation. However, on the 21st day, alveolar bone and epithelial healing were completely established. CONCLUSIONS: these results indicate that chitosan-gelatin support the adhesion and osteogenic differentiation of rat BMMSCs and offer adequate physico-chemical and biological properties for use as scaffolds in bone tissue engineering-related strategies.
