Papers by Keyword: Strontium

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Authors: Gabriel Maia Kammer, Suelen Cristina Sartoretto, Rodrigo Resende, Marcelo Uzeda, Jhonathan Raphael Nascimento, Adriana Terezinha Alves, Jose Calasans-Maia, Alexandre Malta Rossi, J.M. Granjeiro, Mônica Diuana Calasans-Maia
Abstract: Bone tissue is a composite material that has hydroxyapatite (HA) as its main inorganic phase component. The biological apatites have low crystallinity and contain cationic and anionic substitutions in their structure, which differ from the available synthetic ceramics. The purpose of this study is to evaluate the biocompatibility of nanostructured carbonated hydroxyapatite microspheres containing 5 wt% strontium (SrcHA) compared with the biocompatibility of carbonated hydroxyapatite (cHA), both synthesized at 37°C and non-sintered, used to control stoichiometric HA microspheres in subcutaneous tissue of mice. The biomaterials (BM) were characterized using X-ray Diffraction (XRD), Vibrational Spectroscopy in an Infrared Fourier Transform (VSIRFT) and Scanning Electron Microscopy (SEM). Forty five balb-C mice were randomly divided into four groups of 15 animals each: SrcHA, cHA, HA, and without material implantation (Sham group). All samples were histologically processed for descriptive evaluation of the biological effect. At each experimental period (1, 3 and 9 weeks), there was a higher biosorption of the tested biomaterials observed in contrast with the HA. The cHA group was the only group completely phagocytosed by macrophages and giant cells after 9 weeks. All biomaterials proved to be biocompatible, and the cHA and SrcHA 3% groups exhibited a faster bioabsorption in comparison with the control group. The doping of strontium did not cause a greater biological response after the 3 experimental periods.
Authors: Qing Chun Yang
Abstract: Safety assessment of nuclear waste disposal in a deep geological repository requires understanding and quantifying radionuclide transport through the hosting geological formation. Determining diffusion parameters under real conditions is necessary for the performance assessment of a deep geological repository where high level wastes are placed for safety disposal. The in situ diffusion and retention (DR) experiments are designed to study the transport and retention properties of the Opalinus clay formation. In this paper, a scoping numerical simulation is performed in Opalinus Clay, The simulated results for all the traces illustrate that the maximum transport distance perpendicular to the bedding is larger in the isotropic case and those along the bedding is larger in the anisotropic case. Tracer depletion in the isotropic case is a little larger than in the anisotropic case. Deuterium and iodide can be detected in the other interval but strontium can’t. Since the length of injection interval is shorter than the transport distance, the anisotropy effect is clearly measurable. This numerical simulation of diffusion experiment aims at contributing to the optimum design of the experiment. The results of this experiment will provide additional insight into the role of diffusion anisotropy and sorption parameters for radionuclides in clays.
Authors: Lian Xi Chen, Xiao Jian Wang, Wei Li
Abstract: A biodegradable Mg-4Zn-0.6Zr alloy with different content of strontium (Sr) was prepared and studied for orthopedic applications biomaterials. The effects of Sr on the microstructure and corrosion degradation of the as-cast Mg-4Zn-0.6Zr-xSr (ZK40xSr) alloys were investigated. The optical micrograph (OM) observation, energy-dispersive spectrometer (EDS), X-ray diffractometer (XRD) and immersion test were used. The grain size of Mg-4Zn-0.6Zr alloys was reduced obviously with the addition of Sr. The excess of Sr would lead to grain size increasing and grain boundaries widening. The possible presence of the following constituent phases in the grain boundaries: α-Mg, Mg17Sr2, MgZn, ZnxSry binary and MgxZnySrz ternary phase. The formation of ZnxSry and MgxZnySrz phase owed to the larger difference of electronegativity values of Zn and Sr. The immersion tests indicated that the average corrosion rate of the as-cast ZK40xSr alloys increased with the increase of Sr content. It contributed to the micro-galvanic corrosion between the α-Mg with the continuous distribution of grain boundaries precipitates.
Authors: Han Zhou, Xue Gang Luo, Xiao Yan Lin
Abstract: The removal of strontium from aqueous solution with collagen fiber immobilized tannins was studied. The effects of several experimental parameters such as pH, dosage, temperature, contact time and initial concentration of strontium on removal efficiency of strontium were investigated to determine the optimum conditions of strontium sorption process. The adsorbent was characterized by SEM and FTIR analysis. The results of regression analysis indicated that temperature parameters were not individually statistically significant for Sr2+ adsorption. However, the efficiency of strontium adsorption increased with the increase in pH and dosage. The adsorption capacity was increased with increasing initial concentration of Sr2+. The removal efficiency of Sr2+ was 49% at optimum pH of 6 and initial concentration of 20mg/L. Moreover, the absorption data were fitted well to the Langmuir sorption isotherm model.
Authors: Monika Tokár, György Fegyverneki, Valéria Mertinger
Abstract: In this work we show the effect of various concentrations of strontium and antimony on the level of modification in the Al-Si alloy. The scale of the modification rate was determined in two ways: thermal analysis was performed and the images of the samples. The eutectic temperature registered during the analysis were compared to the eutectic temperature of the unmodified alloy and on the basis of them was determined which samples are registered as modified, which are not. On the basis of the results of the cooling curves the partially modified category was introduced, if the ΔT value is less than 9°C and more than 7.5°C. The samples made of the alloys were examined with a computer image analysis and the samples were grouped on the basis of the size of the eutectic silicon phases. The aim of our research work was the examination of cross-effects of strontium and antimony.
Authors: M.A. Platonov, I.S. Sulimova, Irina D. Rozhikhina
Abstract: The paper considers carbon, silicon and aluminum reduction of barium and strontium from natural materials by thermodynamic modeling in conditions of out-of-furnace steel treatment. X-rays phase and differential thermal methods of analysis were applied to investigate the samples of natural barium and strontium containing material. A process flowsheet of steel treatment by barium-strontium modifier in induction furnace was developed on the basis of carried out research.
Authors: A.L. Oliveira, Rui L. Reis, Pan Jian Li
Abstract: In this study we explore the possibility of incorporating Sr into nano-apatite coatings prepared by a solution-derived biomimetic methodology for coating titanium based implants. The way this element is incorporated in the apatite structure and its effects on the stereochemistry and morphology of the resulting apatite layers were investigated, as well as the resulting mineralization kinetics. The presence of Sr in solution induced an inhibitory effect on mineralization, leading to a decrease in the thickness of the mineral layers. This ion was incorporated in the apatite structure through a substitution mechanism by replacing Ca in the crystal lattice. The obtained Sr-substituted biomimetic coatings are expected to enhance bone formation and osteointegration.
Authors: L. Leroux, M. Frèche, J.L. Lacout
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