Rich Chemistry in Inorganic Halide Perovskite Nanostructures.

Halide perovskites have emerged as a class of promising semiconductor materials owing to their remarkable optoelectronic properties exhibiting in solar cells, light-emitting diodes, semiconductor lasers, etc. Inorganic halide perovskites are attracting increasing attention because of the higher stability toward moisture, light, and heat as compared with their organic-inorganic hybrid counterparts. In particular, inorganic halide perovskite nanomaterials provide controllable morphology, tunable optoelectronic properties, and improved quantum efficiency. Here, the development controlled synthesis of desired inorganic halide perovskite nanostructures by various chemical approaches is described. Utilizing these nanostructures as platforms, anion exchange chemistry for wide compositional and optical tunabilities is described, and the rich structural phase transition phenomenon and mechanism investigated systematically. Furthermore, these nanostructures and extracted knowledge are applied to design photonic, photovoltaic, and thermoelectric devices. Finally, future directions and challenges toward improvement of the optical, electrical, and optoelectronic properties, exploration of the anion and cation exchange kinetics, and alleviation of the stability and toxicity issues in inorganic lead based halide perovskites are discussed to provide an outlook on this promising field

Giant Light-Emission Enhancement in Lead Halide Perovskites by Surface Oxygen Passivation.

Surface condition plays an important role in the optical performance of semiconductor materials. As new types of semiconductors, the emerging metal-halide perovskites are promising for next-generation optoelectronic devices. We discover significantly improved light-emission efficiencies in lead halide perovskites due to surface oxygen passivation. The enhancement manifests close to 3 orders of magnitude as the perovskite dimensions decrease to the nanoscale, improving external quantum efficiencies from <0.02% to over 12%. Along with about a 4-fold increase in spontaneous carrier recombination lifetimes, we show that oxygen exposure enhances light emission by reducing the nonradiative recombination channel. Supported by X-ray surface characterization and theoretical modeling, we propose that excess lead atoms on the perovskite surface create deep-level trap states that can be passivated by oxygen adsorption

Evaluation of ultrasonography in fetal intestinal malrotation with midgut volvulus

Objectives: To investigate the clinical significance of prenatal diagnosis and prognostic evaluation of fetal intestinal malrotation with midgut volvulus via ultrasonography. Material and methods: Ultrasonographic findings and clinical outcomes of fetal intestinal malrotation with midgut volvulus prenatally diagnosed via ultrasound at the Zhangzhou Hospital Affiliated of Fujian Medical University from January 2013 to May 2020 were summarised and analyzed. Results: Eleven cases of fetal intestinal malrotation with midgut volvulus were accurately prenatally diagnosed according to the specific ultrasound signs, such as ‘whirlpool sign’ and ‘twining sign’. Indirect and nonspecific ultrasonographic signs included ascites in four cases and echogenic bowel in nine, all of which were accompanied by intestinal dilatation at various degrees. Among all cases, two were complicated with other system abnormalities, and one had a chromosome abnormality. Three pregnant women chose termination of pregnancy, and eight neonates were transferred to the pediatric department for surgery after obtaining written informed consent. An accurate prenatal diagnosis was confirmed postoperatively, and the fetus recovered well postoperatively. Conclusions: Fetal intestinal malrotation with midgut volvulus has typical sonographic features, and ultrasonography is the method of choice for prenatal diagnosis of this disease. Fetal intestinal malrotation with midgut volvulus is a non-fatal congenital malformation that can be treated. Prenatal diagnosis is essential for early postnatal treatment, and early surgery can often obtain good efficacy and prognosis

Minimal Cut Sets-Based Reliability Evaluation of the More Electric Aircraft Power System

The More Electric Aircraft (MEA) stands for the direction of aviation development in the new era, and the reliability of power systems on the MEA has attracted widespread attention. Based on the characteristics of MEA power systems, an equivalent method of electrical topology structure is presented in this article, and evaluation method is proposed which shows the reliability of the overall system with the reliability of specific nodes. Firstly, electrical topology structure of a MEA power system is converted into a network node diagram according to the proposed equivalent method. Then, the minimal path sets of specific nodes are obtained by the adjacent matrix algorithm, and the low-order minimal cut sets of disjointed are obtained. After that, the actual failure rate of components is converted to node failure rate, and the reliability of the overall system is evaluated by operational reliability indexes of specific nodes. Finally, taking the MEA A380 as an example, this paper compares and analyzes the reliability of AC loads, DC loads, and key loads to verify the validity and feasibility of the proposed evaluation method. This evaluation system can predict the weak points existing in the MEA power system, as well as providing theoretical support for maintenance schedule

Study on the quantitative assessment of Staphylococcus aureus in the broiler chicken slaughtering line

Objective To analyze the risk and key prevention and control points of Staphylococcus aureus in a large broiler slaughterhouse and to provide guidance for the scientific prevention and control of Staphylococcus aureus contamination in broiler slaughter. Methods Combining the monitoring data and investigation data of Staphylococcus aureus contamination in a large broiler chicken slaughterhouse, a quantitative assessment model was constructed using @ RISK 7 software, and a quantitative assessment was conducted on the four stages of chicken slaughter (depilation, cleaning chamber, pre-cooling and segmentation). Results Our research determined the predictive growth and decline pattern of Staphylococcus aureus in slaughtering process. It showed that the pre-cooling and segmentation and transmission links were the main risk contributor links of Staphylococcus aureus contamination. The critical risk control points of Staphylococcus aureus in broiler slaughtering were the concentration of Staphylococcus aureus in precooled pool water and hand-borne Staphylococcus aureus in workers with the correlation coefficient of 0.62 and 0.50, respectively. Conclusion The identification of key control points and precise control measures of Staphylococcus aureus in broiler slaughtering can effectively guarantee the health and safety of terminal chicken products

Effects of Al3+ Substitution on Structural and Magnetic Behavior of CoFe2O4 Ferrite Nanomaterials

A sol-gel autocombustion method was used to synthesize Al3+ ion-substituted cobalt ferrite CoAlxFe2−xO4 (x = 0–1.5). According to X-ray diffraction analysis (XRD), cobalt ferrite was in a single cubic phase after being calcined at 1000 °C for 3 h. Moreover, the lattice constant decreased with increase in aluminum substituents. When the sample was analyzed by Scanning Electron Microscopy (SEM), we found that uniformly sized, well-crystallized grains were distributed in the sample. Furthermore, we confirmed that Al3+ ion-substituted cobalt ferrite underwent a transition from ferrimagnetic to superparamagnetic behavior; the superparamagnetic behavior was completely correlated with the increase in Al3+ ion concentration at room temperature. All these findings were observed in Mössbauer spectra. For the cobalt ferrite CoAlxFe2−xO4, the coercivity and saturation magnetization decrease with an increase in aluminum content. When the annealing temperature of CoAl0.1Fe1.9O4 was steadily increased, the coercivity and saturation magnetization initially increased and then decreased

Magnetic and Mössbauer Spectroscopy Studies of Zinc-Substituted Cobalt Ferrites Prepared by the Sol-Gel Method

Zinc ion-substituted cobalt ferrite powders Co1−xZnxFe2O4 (x = 0–0.7) were prepared by the sol-gel auto-combustion process. The structural properties and magnetic of the samples were investigated with X-ray diffraction (XRD), superconducting quantum interference device, and a Mössbauer spectrometer. The results of XRD showed that the powder of a single cubic phase of ferrites calcined when kept at 800 °C for 3 h. The lattice constant increases with increase in Zn concentration, but average crystallite size does not decrease constantly by increasing the zinc content, which is related to pH value. It was confirmed that the transition from ferrimagnetic to superparamagnetic behaviour depends on increasing zinc concentration by Mössbauer spectra at room temperature. Magnetization at room temperature increases for x ≤ 0.3, but decreases for increasing Zn2+ ions. The magnetization of Co0.7Zn0.3Fe2O4 reached maximum value (83.51 emu/g). The coercivity decreased with Zn2+ ions, which were doped on account of the decrease of the anisotropy constant