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The behavior of Ba1-xSrxTiO3 ceramics (x = 0, 0.3, 0.4 and 0.45) in both unpoled and poled states was studied using XRD, SEM, DSC and dielectric methods. The ceramics exhibit pure perovskite structure with tetragonal symmetry for x = 0, 0.3 and 0.4 and pseudocubic for x = 0.45. It was found that the substitution of SrTiO3 to BaTiO3 significantly influences the properties under investigation, leading to a shift of phase transitions and weakness of the dielectric and ferroelectric properties. This suggests that the effects are mainly due to the differences in ionic size between dopant and host ions and to the more covalent nature of the A–O bond following Sr2+ addition and that the former effect is predominant. It was shown that prior electric field poling decreases the disorder introduced by Sr modification through reinforced domains/polar regions ordering. [ABSTRACT FROM AUTHOR]

Ba1-xSrxTiO3 (BST) (x = 0, 0.1 and 0.2) ceramics were prepared by the solid-state reaction method and their structural, thermal and dielectric behavior was studied. The increasing concentration of Sr2+ ions leads to shift of Tc toward lower temperature. The results obtained are discussed in terms of microstructural/structural effects of Sr2+ incorporation into BaTiO3. It is shown that E-poling influences the properties under investigation. This includes modification of local structure, dielectric response and temperature of phase transformations. This could be the result of improvement by the electric field of the polarization ordering, previously disordered by the introduction of Sr2+ to BaTiO3. [ABSTRACT FROM AUTHOR]

The Mn-substituted NBT ceramics were prepared by the conventional ceramic fabrication technique. X-ray diffraction (XRD) studies indicated the formation of perovskite phase with rhombohedral symmetry and with small amount of second phase. It was found that 0.5mol% and 0.1mol% dopant concentration enhances piezoelectric coefficients of d33 and k33, increases the depolarization temperature Td and decreases the dielectric loss. Dielectric study showed the existence of a diffuse phase transition at Tm ≈ 320°C. It was shown that a prior electric field poling process changes the character of ϵ(T) and tanδ(T) functions, as well as shifts of Td and Tm to higher temperature. The effects are mainly caused by the reinforcement of polarization/domain ordering and by the change of content rhombohedral/tetragonal phases by electric field action. The results were discussed in terms of lattice distortion and change of defect concentration. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of (Ba1-xSrx)(Ti1-xZrx)O3(x = 0, 0.05, 0.10) were obtained by means of a conventional high temperature technology. SEM measurements show a well-formed structure with visible layers. The increase in Sr+2and Zr+4ions concentration reduces the temperature of paraelectric - ferrolectric phase transition and its diffusion increases. In the paraelectric state (for all samples) the Curie-Weiss law is fulfilled. From electric modulus measurements the relaxation times and the activation energy were determined. The investigation confirmed the improvement of the electrical properties compared with polycrystalline barium titanate. [ABSTRACT FROM PUBLISHER]

Polycrystalline samples (Ba1-xSrx)(Ti1-xZrx)O3forx= 0.01, 0.05 and 0.10 (abbreviated to BSTZ1, BSTZ5 and BSTZ10) were obtained by means of a conventional ceramic technology. The EDS and EPMA measurements revealed that the samples were perfectly sintered, chemically homogeneous and confirmed their high quality. The DSC and dielectric measurements showed that the addition of strontium and zirconium to BaTiO3(BT) changed the nature of phase transitions. For BT and BSTZ5 three sharp phase transitions were observed, whereas for BSTZ10 sample a diffuse phase transition occurred. [ABSTRACT FROM PUBLISHER]

The X-ray, microstructural and dielectric investigations of the (Ba0.90Sr0.10)(Ti1-ySny)O3(0 ≤y≤ 0.25) polycrystalline solid solutions were performed. The dielectric measurements showed changes of physical properties and the character of the paraelectric - ferroelectric (PE-FE) phase transition with the increase of a tin concentration. The obtained results suggest the occurrence of polar regions in a wide temperature range. The increase of the tin concentration toy= 0.25 leads to the freezing of a cubic phase, which is typical for relaxor ferroelectrics. [ABSTRACT FROM AUTHOR]

Lead-free Ba 1-x Sr x TiO 3 (BST) (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.45) ceramics were successfully prepared via the solid-state reaction route. A pure perovskite crystalline structure was identified for all compositions by X-ray diffraction analysis. The basic phase transition temperatures in these ceramics were studied over a wide temperature range. A change in symmetry from a tetragonal to cubic phase was detected, which was further proven by phonon anomalies in composition/temperature-dependent Raman spectra. The incorporation of Sr 2+ into BaTiO 3 (BT) lead to a shift in the phase transitions to lower temperatures, suppressing the ferroelectric properties and inducing relaxor-like behavior. Therefore, it was reasonable to suppose that the materials progressively lack long-range ordering. The initial second-harmonic generation (SHG) measurements demonstrated that the cubic phase of BST ceramics is not purely centrosymmetric over a wide temperature interval. We discussed the possible origin of the observed effects, and showed that electric field poling seems to reconstruct the structural ordering destroyed by the introduction of Sr 2+ to BT. In the first approximation, substitution of Sr for larger Ba simply reduced the space for the off-central shift in Ti in the lattice and hence the domain polarization. A-site cation ordering in BST and its influence on the density of electronic states were also explored. The effect of doping with strontium ions in the BST compound on the density of electronic states was investigated using ab initio methods. As the calculations showed, doping BT with Sr 2+ atoms led to an increase in the bandgap. The proposed calculations will also be used in the subsequent search for materials optimal for applications in photovoltaics., Competing Interests: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

A library of 27 novel amide derivatives of annelated xanthines was designed and synthesized. The new compounds represent 1,3-dipropyl- and 1,3-dibutyl-pyrimido[2,1- f ]purinedione-9-ethylphenoxy derivatives including a CH 2 CONH linker between the (CH 2 ) 2 -amino group and the phenoxy moiety. A synthetic strategy to obtain the final products was developed involving solvent-free microwave irradiation. The new compounds were evaluated for their adenosine receptor (AR) affinities. The most potent derivatives contained a terminal tertiary amino function. Compounds with nanomolar AR affinities and at the same time high water-solubility were obtained (A 1 ( K i = 24-605 nM), A 2A ( K i = 242-1250 nM), A 2B ( K i = 66-911 nM) and A 3 ( K i = 155-1000 nM)). 2-(4-(2-(1,3-Dibutyl-2,4-dioxo-1,2,3,4,7,8-hexahydropyrimido[2,1- f ]purin-9(6 H )-yl)ethyl)phenoxy)- N -(3-(diethylamino)propyl)acetamide ( 27 ) and the corresponding N -(2-(pyrrolidin-1-yl)ethyl)acetamide ( 36 ) were found to be the most potent antagonists of the present series. While 27 showed CYP inhibition and moderate metabolic stability, 36 was found to possess suitable properties for in vivo applications. In an attempt to explain the affinity data for the synthesized compounds, molecular modeling and docking studies were performed using homology models of A 1 and A 2A adenosine receptors. The potent compound 36 was used as an example for discussion of the possible ligand-protein interactions. Moreover, the compounds showed high water-solubility indicating that the approach of introducing a basic side chain was successful for the class of generally poorly soluble AR antagonists.

Purpose: Patients with Cowden syndrome (CS) with underlying germline PTEN mutations are at increased risk of breast, thyroid, endometrial, and renal cancers. To our knowledge, risk of subsequent cancers in these patients has not been previously explored or quantified., Patients and Methods: We conducted a 7-year multicenter prospective study (2005 to 2012) of patients with CS or CS-like disease, all of whom underwent comprehensive PTEN mutational analysis. Second malignant neoplasms (SMNs) were ascertained by medical records and confirmed by pathology reports. Standardized incidence ratios (SIRs) for all SMNs combined and for breast, thyroid, endometrial, and renal cancers were calculated., Results: Of the 2,912 adult patients included in our analysis, 2,024 had an invasive cancer history. Germline pathogenic PTEN mutations (PTEN mutation positive) were identified in 114 patients (5.6%). Of these 114 patients, 46 (40%) had an SMN. Median age of SMN diagnosis was 50 years (range, 21 to 71 years). Median interval between primary cancer and SMN was 5 years (range, <1 to 35 years). Of the 51 PTEN mutation-positive patients who presented with primary breast cancer, 11 (22%) had a subsequent new primary breast cancer and 10-year second breast cancer cumulative risk of 29% (95% CI, 15.3 to 43.7). Risk of SMNs compared with that of the general population was significantly elevated for all cancers (SIR, 7.74; 95% CI, 5.84 to 10.07), specifically for breast (SIR, 8.92; 95% CI, 5.85 to 13.07), thyroid (SIR, 5.83; 95% CI, 3.01 to 10.18), and endometrial SMNs (SIR, 14.08.07; 95% CI, 7.10 to 27.21)., Conclusion: Patients with CS with germline PTEN mutations are at higher risk for SMNs compared with the general population. Prophylactic mastectomy should be considered on an individual basis given the significant risk of subsequent breast cancer., (© 2014 by American Society of Clinical Oncology.)