Experimental Progress on Layered Topological Semimetals

We review recent experimental progresses on layered topological materials, mainly focusing on transitional metal dichalcogenides with various lattice types including 1T, Td and 1T' structural phases. Their electronic quantum states are interestingly rich, and many appear to be topological nontrivial, such as Dirac/Weyl semimetallic phase in multilayers and quantum spin hall insulator phase in monolayers. The content covers recent major advances from material synthesis, basic characterizations, angle-resolved photoemission spectroscopy measurements, transport and optical responses. Following those, we outlook the exciting future possibilities enabled by the marriage of topological physics and two dimensional van der Waals layered heterostructures.Comment: 2D Materials (2019

A comprehensive review on the ferroelectric orthochromates: Synthesis, property, and application

Multiferroics represent a class of advanced materials for promising applications and stand at the forefront of modern science for the special feature possessing both charge polar and magnetic order. Previous studies indicate that the family of RECrO3 (RE = rare earth) compounds is likely another rare candidate system holding both ferroelectricity and magnetism. However, many issues remain unsolved, casting hot disputes about whether RECrO3 is multiferroic or not. For example, an incompatibility exists between reported structural models and observed ferroelectric behaviors, and it is not easy to determine the spin canting degree. To address these questions, one key step is to grow single crystals because they can provide more reliable information than other forms of matter do. In this review, the parent and doped ferroelectric YCrO3 compounds are comprehensively reviewed based on scientific and patent literatures from 1954 to 2022. The materials syntheses with different methods, including poly-, nano-, and single-crystalline samples and thin films, are summarized. The structural, magnetic, ferroelectric and dielectric, optical, and chemical-pressure (on Y and Cr sites by doping) dependent chemical and physical properties and the corresponding phase diagrams, are discussed. Diverse (potential) applications, including anti-corrosion, magnetohydrodynamic electrode, catalyst, negative-temperature-coefficient thermistor, magnetic refrigeration, protective coating, and solid oxide fuel cell, are present. To conclude, we summarize general results, reached consensuses, and existing controversies of the past nearly 69 years of intensive studies and highlight future research opportunities and emerging challenges to address existing issues.Comment: 69 pages, 35 figures, accepted by Coordination Chemistry Review

Design Optimization of a Disc Brake Based on a Multi-Objective Optimization Algorithm and Analytic Hierarchy Process Method

Multiple optimization objectives and the Pareto set often arise from engineering structural optimization. Normalization methods (such as the weighting method) have the disadvantage that the weighted value is not set by the decision maker but the designer and is greatly influenced by the opinion of the designer. On this basis, in this paper a non-dominated sorting genetic algorithm - analytic hierarchy process (NSGA-AHP) method is proposed for decision making and analysis of the Pareto solution set of the multiple-objective optimization in a structural optimal model. In addition, illustrated by the example of a disc brake, a multiple-objective optimization model for a disc brake has been here developed. Besides, the NSGA-AHP method is adopted for the analysis optimization. The research results show that the NSGA-AHP method can be utilized to select the Pareto solution set in an effective way and that this method is effective in solving a multiple-objective problem in the structural optimization design

A study on the nonlinear vibration of the generator rotor based on the unbalanced electromagnetic force and the oil film force coupling model

To account for the phenomenon that the winding inter-turn short circuit fault of the turbine generator rotor leads to intensified vibration, a coupled nonlinear vibration model of the oil film force and electromagnetic force is established, and a dynamic stability analysis method is proposed. An improved shooting method for solving the periodic solutions of the bearing-rotor system with the unbalanced electromagnetic force is developed; and the system damping criterion used in examining the system stability margin is presented. The calculation on the nonlinear vibration for the 300 MW turbine generator is finished, and the vibration response characteristics and instability margin in a typical winding inter-turn short circuit fault are obtained. The results show that the winding inter-turn short circuit fault may result in the synchronized vortex phenomenon, and a comparison between the numerical results and the site test results is completed. The results will provide technical support and theoretical basis for directly predicting the winding inter-turn short-circuit fault via the vibration detection

Silica nanoparticles enhance autophagic activity, disturb endothelial cell homeostasis and impair angiogenesis

BACKGROUND: Given that the effects of ultrafine fractions (<0.1 μm) on ischemic heart diseases (IHD) and other cardiovascular diseases are gaining attention, this study is aimed to explore the influence of silica nanoparticles (SiNPs)-induced autophagy on endothelial cell homeostasis and angiogenesis. METHODS AND RESULTS: Ultrastructural changes of autophagy were observed in both vascular endothelial cells and pericytes in the heart of ICR mice by TEM. Autophagic activity and impaired angiogenesis were further confirmed by the immunohistochemistry staining of LC3 and VEGFR2. In addition, the immunohistochemistry results showed that SiNPs had an inhibitory effect on ICAM-1 and VCAM-1, but no obvious effect on E-selectin in vivo. The disruption of F-actin cytoskeleton occurred as an initial event in SiNPs-treated endothelial cells. The depolarized mitochondria, autophagic vacuole accumulation, LC3-I/LC3-II conversion, and the down-regulation of cellular adhesion molecule expression were all involved in the disruption of endothelial cell homeostasis in vitro. Western blot analysis indicated that the VEGFR2/PI3K/Akt/mTOR and VEGFR2/MAPK/Erk1/2/mTOR signaling pathway was involved in the cardiovascular toxicity triggered by SiNPs. Moreover, there was a crosstalk between the VEGFR2-mediated autophagy signaling and angiogenesis signaling pathways. CONCLUSIONS: In summary, the results demonstrate that SiNPs induce autophagic activity in endothelial cells and pericytes, subsequently disturb the endothelial cell homeostasis and impair angiogenesis. The VEGFR2-mediated autophagy pathway may play a critical role in maintaining endothelium and vascular homeostasis. Our findings may provide experimental evidence and explanation for cardiovascular diseases triggered by nano-sized particles. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12989-014-0050-8) contains supplementary material, which is available to authorized users

Temperature-dependent structure of an intermetallic ErPd2_2Si2_2 single crystal: A combined synchrotron and in-house X-ray diffraction study

We have grown intermetallic ErPd$_2$Si$_2$ single crystals employing laser-diodes with the floating-zone method. The temperature-dependent crystallography was determined using synchrotron and in-house X-ray powder diffraction measurements from 20 to 500 K. The diffraction patterns fit well with the tetragonal $I$4/$mmm$ space group (No. 139) with two chemical formulas within one unit cell. Our synchrotron X-ray powder diffraction study shows that the refined lattice constants are $a$ = 4.10320(2) {\AA}, $c$ = 9.88393(5) {\AA} at 298 K and $a$ = 4.11737(2) {\AA}, $c$ = 9.88143(5) {\AA} at 500 K, resulting in the unit-cell volume $V$ = 166.408(1) {\AA}$^3$ (298 K) and 167.517(2) {\AA}$^3$ (500 K). In the whole studied temperature range, we did not find any structural phase transition. Upon cooling, the lattice constants a and c are shortened and elongated, respectively.Comment: 5 Figures, 4 Table

Toxic Effects of Silica Nanoparticles on Zebrafish Embryos and Larvae

Silica nanoparticles (SiNPs) have been widely used in biomedical and biotechnological applications. Environmental exposure to nanomaterials is inevitable as they become part of our daily life. Therefore, it is necessary to investigate the possible toxic effects of SiNPs exposure. In this study, zebrafish embryos were treated with SiNPs (25, 50, 100, 200 μg/mL) during 4-96 hours post fertilization (hpf). Mortality, hatching rate, malformation and whole-embryo cellular death were detected. We also measured the larval behavior to analyze whether SiNPs had adverse effects on larvae locomotor activity. The results showed that as the exposure dosages increasing, the hatching rate of zebrafish embryos was decreased while the mortality and cell death were increased. Exposure to SiNPs caused embryonic malformations, including pericardial edema, yolk sac edema, tail and head malformation. The larval behavior testing showed that the total swimming distance was decreased in a dose-dependent manner. The lower dose (25 and 50 μg/mL SiNPs) produced substantial hyperactivity while the higher doses (100 and 200 μg/mL SiNPs) elicited remarkably hypoactivity in dark periods. In summary, our data indicated that SiNPs caused embryonic developmental toxicity, resulted in persistent effects on larval behavior. © 2013 Duan et al.published_or_final_versio