Organic Passivation-Enhanced Ferroelectricity in Perovskite Oxide Films.

Perovskite oxides and organic-inorganic halide perovskite materials, with numerous fascinating features, have been subjected to extensive studies. Most of the properties of perovskite materials are dependence on their ferroelectricity that denoted by remanent polarization (Pr). Thus, the increase of Pr in perovskite films is mainly an effort in material physics. At present, commonplace improvement schemes, i.e., controlling material crystallinity, and post-annealing by using a high-temperature process, are normally used. However, a simpler and temporal strategy for Pr improvement is always unavailable to perovskite material researchers. In this study, an organic coating layer, low-temperature, and vacuum-free strategy is proposed to improve the Pr, directly increasing the Pr from 36 to 56 µC cm-2. Further study finds that the increased Pr originates from the suppression of the oxygen defects and Ti defects. This organic coating layer strategy for passivating the defects may open a new way for the preparation of higher-performance and cost-effective perovskite products, further improving its prospective for application in the electron devices field.

Does pre-scanning training improve the image quality of children receiving magnetic resonance imaging?: A meta-analysis of current studies.

BACKGROUND: Magnetic resonance imaging (MRI) is often used in children for its clear display of body parts. But it is usually hard to acquire high-quality images, for the uncooperative ability of children. It is believed that pre-MRI training could ensure the high quality of images. The current meta-analysis was done to analyze the current evidences in this field. METHODS: PubMed, Cochrane Library, and Web of Science were systematically searched up to July 2018, for studies assessing the effects of training on pediatric MRI. Data, including image quality, failed scanning rate, and sedation use, were extracted and analyzed using Revman 5.2 software. RESULTS: There were 5 studies with 379 subjects in the meta-analysis. Training and control groups were quite comparable when accepted image quality was reviewed (P = .30), but a lower rate of excellent image quality was found in subjects with training (P = .02). The pooling results found no significance between training and control group in sedation use (P = .09) and successful MRI scanning (P = .63). CONCLUSIONS: It is cautious to conclude that pre-MRI training does not improve the image quality and reduce sedation use among children, for the limited number of studies and sample size. More trials should be encouraged to demonstrate this issue.

[Photoelectron decay properties of doped AgCl microcrystals under chemical sensitization].

The photoelectron decay characteristic directly reflects the photographic efficiency of silver halide crystals. Measurement of the electronic decay time-resolved spectrum of silver halide microcrystals can provide important information about the photoelectron decay action in latent image formation process. In order to know the influence of shallow electron trap dopant K4 Fe (CN)6 and S+Au on photoelectron decay, the photoelectron decay time-resolved spectra of AgCl emulsion doped by K4 Fe(CN) and that doped by K4 Fe(CN) firstly and then sensitized by S+Au were detected by microwave absorption dielectric technique, which can be used to study the decay process of free photoelectrons and shallow-trapped electrons in semiconductor crystals. The experimental results show that when the doping content is 10(-8)-10(-7) mol x mol(-1) Ag, the photoelectron decay process becomes slower, namely, the photoelectron decay time is longer, as the doping is near the grain surface before sensitization. After S+Au sensitization, the photoelectron decay becomes faster, showing that the sensitization centre acts as a deep electron trap. And when the doping is near the grain surface with 90% Ag, the photoelectron decay time becomes shorter, showing that the doping centre and the sensitization centre may interact.

[Photoelectron decay time-resolved spectrum of AgCl crystals doped with K4Ru(CN)6 complex].

Microwave absorption and film dielectric spectrum detection technology was used to study the influence of complex K4Ru (CN)6 on the photoelectron decay time-resolved spectrum of cubic AgCl crystals illuminated in this paper. The results indicate that the influence of the doping content and doping position of the complex K4Ru(CN)6 on the photoelectron decay time-resolved spectrum is evident. The photoelectron decay process of this emulsion is slowest, and the photoelectron lifetime is longest when doped with K4Ru (CN)6 of 2.45 x 10(-5) mol x (mol Ag)(-1) at doping positions of 75% Ag.