Room-temperature ferromagnetism in Sr_(1-x)Y_xCoO_(3-delta) (0.2 < x < 0.25)

We have measured magnetic susceptibility and resistivity of Sr$_{1-x}$Y$_x$CoO$_{3-\delta}$ ($x=$ 0.1, 0.15, 0.2, 0.215, 0.225, 0.25, 0.3, and 0.4), and have found that Sr$_{1-x}$Y$_x$CoO$_{3-\delta}$ is a room temperature ferromagnet with a Curie temperature of 335 K in a narrow compositional range of 0.2 $\leq x\leq$ 0.25. This is the highest transition temperature among perovskite Co oxides. The saturation magnetization for $x=$ 0.225 is 0.25 $\mu_B$/Co at 10 K, which implies that the observed ferromagnetism is a bulk effect. We attribute this ferromagnetism to a peculiar Sr/Y ordering.Comment: 5 pages, 4 figure

Medical Image Retrieval Using Multimodal Semantic Indexing

Large collections of medical images have become a valuable source of knowledge, taking an important role in education, medical research and clinical decision making. An important unsolved issue that is actively investigated is the efficient and effective access to these repositories. This work addresses the problem of information retrieval in large collections of biomedical images, allowing to use sample images as alternative queries to the classic keywords. The proposed approach takes advantage of both modalities: text and visual information. The main drawback of the multimodal strategies is that the associated algorithms are memory and computation intensive. So, an important challenge addressed in this work is the design of scalable strategies, that can be applied efficiently and effectively in large medical image collections. The experimental evaluation shows that the proposed multimodal strategies are useful to improve the image retrieval performance, and are fully applicable to large image repositories.Maestrí

Control of hole distribution through isovalent R-cation substitution in Cu2Ba2RCu2O8 superconductors

Superconductive Cu2Ba2RCu2O8 samples with R ranging from Gd to Tm have been synthesized through a sol-gel route. Both iodometric titration and Cu L-edge x-ray absorption near-edge structure (XANES) spectroscopy data indicate that the average Cu valence remains constant, whereas Tc increases with decreasing size of the R constituent. An explanation for this trend is revealed from O K-edge XANES spectra, which show that the smaller-for-larger R-cation substitution results in a shift of holes from the Cu2O2 charge reservoir to the superconductive CuO2 planes. Since Cu2Ba2RCu2O8 samples are underdoped, such a shift of holes raises the value of Tc.Peer reviewe

Wet Polymeric Precipitation Synthesis for Monophasic Tricalcium Phosphate

Tricalcium phosphate (β-Ca3(PO4)2, β-TCP) powders were synthesized using wet polymeric precipitation method for the first time to our best knowledge. The results of X-ray diffraction analysis showed the formation of almost single a Ca-deficient hydroxyapatite (CDHA) phase of a poor crystallinity already at room temperature. With continuously increasing the calcination temperature up to 800 °C, the crystalline β-TCP was obtained as the main phase. It was demonstrated that infrared spectroscopy is very effective method to characterize the formation of β-TCP. The SEM results showed that β-TCP solids were homogeneous having a small particle size distribution. The β-TCP powders consisted of spherical particles varying in size from 100 to 300 nm. Fabricated β-TCP specimens were placed to the bones of the rats and maintained for 1-2 months

Effect of magnesium ferrite doping with lanthanide ions on dark-, visible- and UV-driven methylene blue degradation on heterogeneous Fenton-like catalysts

Abstract The catalytic behavior of magnesium ferrites doped with lanthanide ions (La³⁺, Ce³⁺, Sm³⁺, Gd³⁺, and Dy³⁺) on Methylene Blue (MB) degradation using Fenton process was studied. A slow increase in cubic Fd3m crystalline structure parameters and increase in crystallite size of doped samples magnesium ferrites were observed. A dramatic decrease in catalytic activity of catalysts obtained at 600 °C as compared to catalysts obtained at 300 °C was explicitly observed and this was grossly attributed to the elimination of surface hydroxyl groups as ascertained by FT-IR analysis. The initial magnesium ferrite demonstrated the highest catalytic activity under dark- (kˈ 0.0555 min⁻¹) and visible-light (kˈ 0.1029 min⁻¹) conditions. Catalytic efficiency of the lanthanides doped catalysts under UV-irradiation in accordance with the maximum appearance rate constant kˈ decreased in the following order Ce³⁺ &gt; Dy³⁺ &gt; La³⁺ ≈ MgFe₂O₄ &gt; Sm³⁺ &gt; Gd³⁺. The most active ferrites provided up to 99% of MB degradation in 60 and 20 min for visible- and UV-driven Fenton processes. Findings obtained from this study were observed to be competitive with other heterogeneous Fenton catalysts