Origin of Polarization in Bismuth Sodium Titanate-Based Ceramics.

The classical view of the structural changes that occur at the ferroelectric transition in perovskite-structured systems, such as BaTiO3, is that polarization occurs due to the off-center displacement of the B-site cations. Here, we show that in the bismuth sodium titanate (BNT)-based composition 0.2(Ba0.4Sr0.6TiO3)-0.8(Bi0.5Na0.5TiO3), this model does not accurately describe the structural situation. Such BNT-based systems are of interest as lead-free alternatives to currently used materials in a variety of piezo-/ferroelectric applications. A combination of high-resolution powder neutron diffraction, impedance spectroscopy, and ab initio calculations reveals that Ti4+ contributes less than a third in magnitude to the overall polarization and that the displacements of the O2- ions and the A-site cations, particularly Bi3+, are very significant. The detailed examination of the ferroelectric transition in this system offers insights applicable to the understanding of such transitions in other ferroelectric perovskites, particularly those containing lone pair elements.

Antiferroelectric-like Behavior in a Lead-Free Perovskite Layered Structure Ceramic.

Antiferroelectric (AFE) materials have been intensively studied due to their potential uses in energy storage applications and energy conversion. These materials are characterized by double polarization-electric field (P-E) hysteresis loops and nonpolar crystal structures. Unusually, in the present work, Sr1.68La0.32Ta1.68Ti0.32O7 (STLT32), Sr1.64La0.36Ta1.64Ti0.36O7 (STLT36), and Sr1.85Ca0.15Ta2O7 (SCT15), lead-free perovskite layered structure (PLS) materials, are shown to exhibit AFE-like double P-E hysteresis loops despite maintaining a polar crystal structure. The double hysteresis loops are present over wide ranges of electric field and temperature. While neutron diffraction and piezoresponse force microscopy results indicate that the STLT32 system should be ferroelectric at room temperature, the observed AFE-like electrical behavior suggests that the electrical response is dominated by a weakly polar phase with a field-induced transition to a more strongly polar phase. Variable-temperature dielectric measurements suggest the presence of two-phase transitions in STLT32 at ca. 250 and 750 °C. The latter transition is confirmed by thermal analysis and is accompanied by structural changes in the layers, such as in the degree of octahedral tilting and changes in the perovskite block width and interlayer gap, associated with a change from non-centrosymmetric to centrosymmetric structures. The lower-temperature transition is more diffuse in nature but is evidenced by subtle changes in the lattice parameters. The dielectric properties of an STLT32 ceramic at microwave frequencies was measured using a coplanar waveguide transmission line and revealed stable permittivity from 1 kHz up to 20 GHz with low dielectric loss. This work represents the first observation of its kind in a PLS-type material.

[Structure Design of the Supporting Device of Proton Radiotherapy Equipment Based on Workbench].

To reduce contact deformation between the supporting device and the contact area of the rotating gantry rollers, this paper mainly uses the workbench to perform finite element analysis on the contact deformation from two aspects of the layout of the ribs of the rotating gantry roller and the contact width with the supporting roller of the supporting device. The results show that for the proton therapy equipment corresponding to this article, the contact deformation is relatively small and the structure is more reasonable when the ribs are close to the symmetrical position and the contact width between the rotating gantry roller and the supporting roller of the supporting device is 200 mm. This article provides theoretical basis for the design of the proton radiotherapy equipment supporting device.

Terahertz Characterization of Lead-Free Dielectrics for Different Applications.

In this spotlight on applications, we describe our recent progress on the terahertz (THz) characterization of linear and nonlinear dielectrics for broadening their applications in different electrical devices. We begin with a discussion on the behavior of dielectrics over a broadband of frequencies and describe the main characteristics of ferroelectrics, as they are an important category of nonlinear dielectrics. We then move on to look at the influence of point defects, porosities, and interfaces, including grain boundaries and domain walls, on the dielectric properties at THz frequencies. Based on our studies on linear dielectrics, we show that THz characterization is able to probe the effect of porosities, point defects, shear planes, and grain boundaries to improve dielectric properties for telecommunication applications. Further, we demonstrate that THz measurements on relaxor ferroelectrics can be successfully used to study the reversibility of the electric field-induced phase transitions, providing guidance for improving their energy storage efficiency in capacitors. Finally, we show that THz characterization can be used to characterize the effect of domain walls in ferroelectrics. In particular, our studies indicate that the dipoles located within domain walls provide a lower contribution to the permittivity at THz frequencies than the dipoles present in domains. The new findings could help develop a new memory device based on nondestructive reading operations using a THz beam.

Does adenomatous polyposis coli gene promoter 1A methylation increase non-small cell lung cancer risk? A meta-analysis.

BACKGROUND: The promoter region of the adenomatous polyposis coli (APC) gene is hypermethylated in several types of cancers, including non-small cell lung cancer (NSCLC). The prevalence of methylation in the promoter region of this gene in tumor tissues and autologous controls has not been consistent in previous studies. We evaluated the frequency of APC gene promoter 1A methylation between tumor tissues and autologous controls in NSCLC patients by meta-analysis. METHODS: Open published studies of APC gene promoter 1A methylation between tumor tissues and autologous samples in NSCLC patients were identified using a systematic search. Odds ratios (OR) and 95% confidence intervals (CI) of APC gene promoter 1A methylation in lung cancer tissues versus autologous controls were calculated. Fourteen studies, involving a total of 1345 patients and 2182 samples, were finally included. RESULTS: The pooled proportion of APC promoter 1A methylation was 0.62 (95% CI 0.52-072) and 0.34 (95% CI 0.21-0.50) in cancer tissues and autologous controls, respectively. The APC gene promoter 1A methylation rate in cancer tissues was much higher than in autologous controls, with a pooled OR of 3.66 (95% CI 2.12-6.33). A strong and significant correlation of APC gene promoter 1A methylation between tumor tissues and autologous controls was detected (correlation coefficient rpearson = 0.77; P = 0.0013). CONCLUSION: The proportion of APC promoter 1A methylation in lung cancer tissues was higher than in autologous controls, indicating that promoter 1A methylation of the APC gene may play an important role in NSCLC carcinogenesis.

Direct common gram-negative bacterial identification from positive blood culture bottles by SELDI-TOF MS.

A protein database was constructed and validated with identification rate over 90% for the 4 most common Gram-negative bacteria on agar plates. By protein masses comparison, 120 bacteria of the 4 species from blood culture bottles were identified. The concordance was high (Kappa=0.906) between our method and conventional approach.

[Sequential Changes of Serum Tumor Markers Before and After the Radioactive (125)I-seed Implantation in the Treatment of Lung Cancer.].

BACKGROUND: The brachytherapy with iodine seeds is characterized by radioactive (125)I very close to or in contact with the target organ. This study is to evaluate the clinical value of implanted radioactive (125)I-seed in the treatment of lung cancer patients. METHODS: Sixty-three cases of lung cancer were enrolled in this study, and in every case, (125)I-seeds were planted into tumor mass guided by CT. Serum CEA, CA125, NSE and CYFRA21-1 were detected by radioimmunoassay in lung cancer patients before and after planting. The therapeutic effect was evaluated by WHO standards. The relation between the therapeutic effect and the tumor markers levels was observed. RESULTS: Just one month after planting, the levels of serum CEA, CA125, NSE and CYFRA21-1 were induced significantly in all cases. There was no significant difference among 1 month, 3 month and 6 month in the levels of tumor markers after therapy. CONCLUSIONS: (125)I-seed could effectively decrease the level of tumor markers in the treatment of lung cancer patients.