Tuning of magnetic and electronic states by control of oxygen content in lanthanum strontium cobaltites

We report on the magnetic, resistive, and structural studies of perovskite La$_{1/3}$Sr$_{2/3}$CoO$_{3-\delta}$. By using the relation of synthesis temperature and oxygen partial pressure to oxygen stoichiometry obtained from thermogravimetric analysis, we have synthesized a series of samples with precisely controlled $\delta=0.00-0.49$. These samples show three structural phases at $\delta=0.00-0.15$, $\approx0.25$, $\approx0.5$, and two-phase behavior for other oxygen contents. The stoichiometric material with $\delta=0.00$ is a cubic ferromagnetic metal with the Curie temperature $T_{\rm C}=274$ K. The increase of $\delta$ to 0.15 is followed by a linear decrease of $T_{\rm C}$ to $\approx$ 160 K and a metal-insulator transition near the boundary of the cubic structure range. Further increase of $\delta$ results in formation of a tetragonal $2a_p\times 2a_p \times 4a_p$ phase for $\delta\approx 0.25$ and a brownmillerite phase for $\delta\approx0.5$. At low temperatures, these are weak ferromagnetic insulators (canted antiferromagnets) with magnetic transitions at $T_{\rm m}\approx230$ and 120 K, respectively. At higher temperatures, the $2a_p\times 2a_p \times 4a_p$ phase is $G$-type antiferromagnetic between 230 K and $\approx$360 K. Low temperature magnetic properties of this system for $\delta<1/3$ can be described in terms of a mixture of Co$^{3+}$ ions in the low-spin state and Co$^{4+}$ ions in the intermediate-spin state and a possible spin transition of Co$^{3+}$ to the intermediate-spin state above $T_{\rm C}$. For $\delta>1/3$, there appears to be a combination of Co$^{2+}$ and Co$^{3+}$ ions, both in the high-spin state with dominating antiferromagnetic interactions.Comment: RevTeX, 9 pages, 7 figures, to be published in Physical Review

Evaluation of the Chemical Composition, TG – DTA and Tensile Strength Tests of Commercial Gypsum Kinds for Foundry Sandmixes Application

The paper presents the preliminary results of research on determining the possibilities of using available on the market commercial gypsum kinds as a binder for foundry moulding and core sandmixes. Construction gypsum and plaster gypsum, finishing coat and jewelry casting gypsum were tested. Elemental composition of gypsum kinds were carried out using a scanning electron microscope (SEM) with EDS/EDX probe, their crystal structure and phase composition was determined by analyzing the results of X-ray diffraction measurements (XRD) and thermogravimetric studies (TG-DTA). Evaluation of the mechanical properties of selected materials was carried out at the tensile strength test of the dog-bone samples after initial hardening of gypsum mortar at 25°C for 5 h and drying at 110°C for 24 hours. The impact of the properties of the used commercial gypsum kinds on the possibility of their use as a valuable binders in the manufacture of the foundry sandmixes for moulds and cores was evaluated. Construction gypsum and finishing coat have the highest tensile strength. Plaster gypsum and finishing coat have the longest setting time. In all tested types of gypsum, the initial water loss during heating occurs at a temperature of about 200°C. The lowest valuable properties as a binder for sand moulding mixtures has jewelry casting gypsum mass

Clinical usefulness of assessing VEGF and soluble receptors sVEGFR-1 and sVEGFR-2 in women with breast cancer

Introduction. The biological activity of VEGF depends on the presence of its specific receptors on the endothelial surface: VEGFR-1, VEGFR-2, and on their soluble forms sVEGFR-1 and sVEGFR-2. The binding of the membrane-bound receptors with VEGF affects the permeability, proliferation and migration of vascular endothelial cells. This creates the necessary conditions for the vascularisation of solid tumours and for the spread of remote metastases. The sVEGFR-1 and sVEGFR-2 receptors are believed to be natural inhibitors of VEGF. Objective. To determine the clinical usefulness of VEGF and the sVEGFR-1 and sVEGFR-2 receptors level assay in women with primary breast cancer. The assessment also took into account: patient’s age, stage of the disease, histological grade, status of the axillary lymph nodes and size of the primary tumour. Material and methods. The concentrations of VEGF, sVEGFR-1 and sVEGFR-2 were ascertained in 103 women with primary breast cancer. The concentrations of VEGF in the plasma, and those of the soluble receptors sVEGFR-1 and sVEGFR-2 in the serum, were assessed by ELISA, R&D Systems. Results. The study found significantly raised concentrations of VEGF, sVEGFR-1 and sVEGFR-2 in the serum of women with breast cancer, relative to the values obtained from the control group. It was found that with increasing clinical stages of the disease, the levels of VEGF and concentrations of sVEGFR-1 and sVEGFR-2 also increased. Similar findings were noted when assessing the degree of the histological grade of the tumours. Significantly higher values of VEGF protein and the assessed receptors were obtained from women with metastases to the axillary lymph nodes. A positive relationship, though without statistical significance, was noted between the concentration of sVEGFR-2 and the size of the tumour. Conclusions. The high concentrations of the VEGF cytokine and the sVEGFR-1 and sVEGFR-2 receptors in women with breast cancer are responsible for giving rise to the processes of tumour angiogenesis. The concentrations of the VEGF protein and the soluble forms of the receptors sVEGFR-1 and sVEGFR-2 in the serum of breast cancer patients showed positive correlations with the clinical stage of the disease. These results point to the usefulness of VEGF assessment and its soluble receptors in the clinical evaluation of patients with breast cancer

Corrosion Resistance of Tin Coatings Deposited by Different Methods

This article describes the study of corrosion resistance of tin coatings deposited onto aluminum alloy substrates using the low pressure cold spraying and electroplating methods. The chemical corrosion resistance was examined using the Kesternich and cyclic salt spray tests inside SO₂ and NaCl climate chambers, respectively. The selected tests allowed simulation of the conditions of the coatings during service. The results were satisfactory for low pressure cold spraying coatings. Coatings produced by electroplating exhibit substantial corrosive losses due to their method of application and low thickness. Evaluation of corrosion were carried out by analyzing changes in the microstructure. Additionally, the physicochemical tests were carried out using X-ray diffraction to verify corrosion changes on the coatings surface

Corrosion resistance of tin coatings deposited by different methods

This article describes the study of corrosion resistance of tin coatings deposited onto aluminum alloy substrates using the low pressure cold spraying and electroplating methods. The chemical corrosion resistance was examined using the Kesternich and cyclic salt spray tests inside SO₂ and NaCl climate chambers, respectively. The selected tests allowed simulation of the conditions of the coatings during service. The results were satisfactory for low pressure cold spraying coatings. Coatings produced by electroplating exhibit substantial corrosive losses due to their method of application and low thickness. Evaluation of corrosion were carried out by analyzing changes in the microstructure. Additionally, the physicochemical tests were carried out using X-ray diffraction to verify corrosion changes on the coatings surface

Microscopic Examination of Cold Spray Cermet Sn+In 2

Low-pressure cold spraying is a newly developed technology with high application potential. The aim of this study was to investigate potential application of this technique for producing a new type of transparent conductive oxide films target. Cold spraying technique allows the manufacture of target directly on the backing plate; therefore the proposed sputtering target has a form of Sn+In2O3 coating sprayed onto copper substrate. The microstructure and properties of the feedstock powder prepared using three various methods as well as the deposited ones by low-pressure cold spraying coatings were evaluated, compared, and analysed. Produced cermet Sn+In2O3 targets were employed in first magnetron sputtering process to deposit preliminary, thin, transparent conducting oxide films onto the glass substrates. The resistivity of obtained preliminary films was measured and allows believing that fabrication of TCO (transparent conducting oxide) films using targets produced by cold spraying is possible in the future, after optimization of the deposition conditions