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Molten salt electrolysis was applied for the boronizing of nickel with Na2B4O7·10H2O-Na2CO3 as the electrolyte and characterizations and the growth kinetics of borided layer is reported. The experiment was carried out in silicon carbide crucible at 1193 K, 1223 K, and 1243 K for 1 h, 2 h, 3 h, and 4 h. The morphology and phases formed on the surface of pure nickel were analyzed by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction analysis (XRD). The surface hardness and corrosion resistance of the boronized sample were tested by micro hardness tester and electrochemical workstation, respectively. The borided layer was composed of nickel borides and its thickness ranged from 71 to 184 μm. After 1 h of boronizing, the hardness of the silicon rich borides is 966 HK, which is a little lower than that of the nickel borides (992-1008 HK); the surface hardness reached 1755 HK after 4 h electrolysis. Electrochemical impedance spectroscopy analysis showed that the corrosion resistance of boronized sample is better than that of pure nickel. Borided layer growth kinetics was studied by analyzing the relationship between thickness of the borided layer and time by mathematical method. Then the diffusion coefficient constant of boron atom in nickel at 1193 K, 1223 K and 1243 K was calculated accordingly and an equation was obtained to estimate the thickness of the borided layer.

Anisotropic photonic structures play a vital role in tailoring micro- and nanoscale light-matter interactions. In this work, we investigate the interference and localization effects in two-dimensional disordered media containing dipolar scatterers with anisotropic positional correlations. We study the anisotropy-induced frequency shifts in the transmission spectra, which cannot be accounted for by the independent scattering approximation or effective medium theory. We reveal that the distribution of eigenmodes strongly depends on the anisotropic structural correlations, and in all cases, Anderson localized modes are observed although their spatial extent exhibits different degrees of anisotropy. By calculating the level statistics, we demonstrate that the introduction of anisotropy to structural correlations has nontrivial effects on the level spacing statistics, which can be somewhat captured by a critical distribution function that works in the metal–insulator transition regime. This work can provide physical insights into the wave aspects of light transport in disordered media due to anisotropic structural correlations and guide the design of novel nanophotonic devices based on resonant scatterers. [ABSTRACT FROM AUTHOR]

Topological photonic crystals inherit the unique properties of topological insulators, including topologically protected energy transfer and unidirectional propagation, which offer an excellent platform for exploring exotic physics and developing photonic devices. However, topological photonic crystals possessing mid-infrared edge modes that have potential applications in infrared imaging, biosensing, thermal radiation energy transfer, etc., are seldom brought into focus. In this work, we study the topological properties of a photonic crystal slab (PCS) consisting of silicon square veins in the mid-infrared, which is intended to mimic the two-dimensional Su–Schrieffer–Heeger model. By interfacing topologically trivial and nontrivial PCSs, mid-infrared edge modes can appear at domain wall, according to the principle of bulk-edge correspondence. It is also demonstrated high-efficiency mid-infrared light transport can be achieved by these edge modes. In addition, adjusting the vertical offset near the interface can manipulate the bandwidth for various applications and turns the connected PCS structure to a photonic realization of Rice–Mele model. We further fabricate the PCS and provide an experimental observation of transverse-electric-like edge modes in mid-infrared by using the scattering-type scanning near-field optical microscope. Additionally, we integrate it with phase change material of nanoscale thickness, Ge2Sb2Te5, to realize an ultrafast and switchable topological waveguide with zero static power. This work not only enriches the fundamental understanding of topological physics in mid-infrared optical settings, but also shows promising prospects in compact devices for energy transfer and information processing for light sources in these wavelengths, for instance, thermal radiation. [ABSTRACT FROM AUTHOR]

We investigate the topological plasmon polaritons (TPPs) in one-dimensional dimerized doped silicon nanoparticle chains, as an analogy of the topological edge states in the Su–Schrieffer–Heeger model. The photonic band structures are analytically calculated by taking all near-field and far-field dipole–dipole interactions into account. For longitudinal modes, it is demonstrated that the band topology can be well characterized by the complex Zak phase irrespective of the lattice constant and doping concentration. By numerically solving the eigenmodes of a finite system, it is found that a dimerized chain with a nonzero complex Zak phase supports nontrivial topological eigenmodes localized over both edges. By changing the doping concentration of Si, it is possible to tune the resonance frequency of the TPPs from far-infrared to near-infrared, and the localization lengths of the edge modes are also modulated accordingly. In addition, it is shown that a higher working temperature can lead to significantly smaller decay rates. Since these TPPs are highly protected modes that can achieve a strong confinement of electromagnetic waves and are also immune to impurities and disorder, they can provide a potentially tunable tool for robust and enhanced light–matter interactions in the infrared spectrum. [ABSTRACT FROM AUTHOR]

With the rise of artificial magnetism and metamaterials, the toroidal family recently attracted more attention for its unique properties. Here, we propose an all-dielectric pentamer metamolecule consisting of nano-cylinders with two toroidal dipolar resonances, whose frequencies, EM distributions, and Q factor can be efficiently tuned due to the additional electric dipole mode offered by a central cylinder. To further reveal the underlying coupling effects and the formation mechanism of toroidal responses, the multiple scattering theory is adopted. It is found that the first toroidal dipole mode, which can be tuned from 2.21 to 3.55 μ m , is mainly induced by a collective electric dipolar resonance, while the second one, which can be tuned from 1.53 to 1.84 μ m , relies on the cross coupling of both electric and magnetic dipolar responses. The proposed low-loss metamolecule and mode coupling analyses may pave the way for the efficient design of toroidal responses in advanced optical devices. [ABSTRACT FROM AUTHOR]

The structural correlations in the microscopic structures of random media can induce the dependent scattering mechanism and thus influence the optical scattering properties. Based on our recent theory on the dependent scattering mechanism in random media composed of discrete dipolar scatterers [B. X. Wang and C. Y. Zhao, Phys. Rev. A 97, 023836 (2018)], in this paper, we study the hard-sphere Yukawa random media, in order to further elucidate the role of structural correlations in the dependent scattering mechanism and hence optical scattering properties. Here, we consider charged colloidal suspensions, whose effective pair interaction between colloids is described by a screened Coulomb (Yukawa) potential. By means of adding salt ions, the pair interaction between the charged particles can be flexibly tailored and therefore the structural correlations are modified. It is shown that this strategy can affect the optical properties significantly. For colloidal TiO2 suspensions, the modification of electric and magnetic dipole excitations induced by the structural correlations can substantially influence the optical scattering properties, in addition to the far-field interference effect described by the structure factor. However, this modification is only slightly altered by different salt concentrations and is mainly because of the packing-density-dependent screening effect. On the other hand, for low refractive index colloidal polystyrene suspensions, the dependent scattering mechanism mainly involves the far-field interference effect, and the effective exciting field amplitude for the electric dipole almost remains unchanged under different structural correlations. The present study has profound implications for understanding the role of structural correlations in the dependent scattering mechanism. [ABSTRACT FROM AUTHOR]

Most cermet-based coatings achieve their solar selectivities by the tandem interference effect, which has been widely studied. This study focused on the spectral selectivity achieved by the scattering effect of metal particles in cermet-based coatings. Previous research proved that reasonable solar selectivities can be obtained for cermets in the regime of particles with a radius of the order of 100 nm, but their solar absorptance is low (<90%). In our research, the effect of metal particles on the spectral selectivity of cermets was studied by the Mie theory and Monte Carlo simulation for Cr, Ni, and W particles with radii of 10 nm, 50 nm, 100 nm, and 200 nm, which were embedded in Al2O3 and occupied 5% of the volume fraction. It was found that by arranging different particles in different layers, a very high solar absorptance (95.6%) could be achieved. Since their thermal emittance (~25% at 600 °) was higher than that of normal coatings, these coatings are recommended to be used in solar absorbers that have a high concentration factor. Finally, the dependent scattering effect was qualitatively considered by the coupled-dipole approach. With a metal volume fraction of 5%, it was found that the effect of dependent scattering was small and should not change the conclusions made based on independent scattering. [ABSTRACT FROM AUTHOR]

The typical yttria-stabilized zirconia material for making the thermal barrier coatings (TBCs) is intrinsically semitransparent to thermal radiation, and the unique disordered microstructures in TBCs make them surprisingly highly scattering. To quantitatively understand the influence of disordered microstructures, this paper presents a quantitative prediction on the radiative properties, especially the transport scattering coefficient of plasma sprayed TBC based on microstructure analysis and rigorous electromagnetic theory. The impact of the porosity, shape, size, and orientation of different types of voids on transport scattering coefficient is comprehensively investigated under the discrete dipole approximation. An inverse model integrating these factors together is then proposed to quantitatively connect transport scattering coefficient with microstructural information, which is also validated by available experimental data. Afterwards, an optimization procedure is carried out based on this model to obtain the optimal size and orientation distribution of the microscale voids to achieve the maximal radiation insulation performance at different operating temperatures, providing guidelines for practical coating design and fabrication. This work suggests that the current model is effective and also efficient for connecting scattering properties to microstructures and can be implemented as a quantitative tool for further studies like non-destructive infrared imaging as well as micro/nanoscale thermal design of TBCs. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The aim of this study was to explore the promoting effect of rosuvastatin on the osteogenic differentiation of mesenchymal stem cells in the rat model of osteoporosis through the Wnt/β-catenin signal. MATERIALS AND METHODS: A total of 30 rats were purchased from the Animal Research Center of Shanxi Medical University. All rats were randomly allocated into three groups, including: group A (control group, n=10), group B (ovariectomized group, n=10), and group C (rosuvastatin gavage group, n=10). The bone metabolism indexes, bone mineral density (BMD) and the Wnt/β-catenin signaling pathway-related proteins in blood samples of rats in each group were measured, respectively. Furthermore, the bone marrow mesenchymal stem cells of rats were used for alkaline phosphatase (ALP) staining. All data were analyzed using the Statistical Product and Service Solutions (SPSS) 22.0 software (IBM Corp., Armonk, NY, USA). RESULTS: T he r ats fi rstly r eceived 9 c onsecutive weeks of feeding with drug intervention. The imaging results revealed that trabecular thickness in group A was significantly higher than that of group B and group C, showing statistically significant differences (p<0.05). After 9 consecutive weeks of feeding with drug intervention, BMD of the femurs of rats in group A and group C was significantly higher than that of group B, showing statistically significant differences (p<0.05). However, there was no significant difference in BMD between group A and group C (p>0.05). The level of calcium representing bone absorption level in serum of rats in group B was remarkably higher than that of group A, and the difference was statistically significant (p<0.05). However, the level of ALP representing bone absorption level in the serum of rats in group B was significantly lower than that of group A (p<0.05). No significant differences were found in the levels of calcium and ALP that represented bone absorption level between group C and group A (p>0.05). Meanwhile. the levels of phosphorus in the three groups were similar, showing no statistically significant difference (p>0.05). Moreover, the expression of ALP-positive cells in the rats of group A and group C was markedly higher than that of group B (p<0.05). After drug intervention through feeding for 9 consecutive weeks, no evident difference was found in the relative expression of Wnt/β-catenin signaling pathway-related protein glycogen synthase kinase-3β (GSK-3β) among the three groups. The relative expression of the protein phosphorylated GSK-3β (p-GSK-3β) in group C was significantly lower than that of group B (p<0.05). Furthermore, the relative protein expressions of β-catenin and cyclin D1 in group C were significantly higher than those in group B (p<0.05). CONCLUSIONS: Rosuvastatin can improve bone metabolism in osteoporosis rats and increasing BMD of bone tissues in rats with osteoporosis. Besides, the Wnt/β-catenin signaling pathway plays a crucial role in the regulation of the stem cell self-renewal and bone genesis. [ABSTRACT FROM AUTHOR]

At present, the air environment in China is characterized by complex pollution. In this paper, the pollutant sources, transport paths and aerosol optical properties during the dust pollution was conducted to analyse based on ground-based lidar, space-borne sensor and atmospheric transmission model. Firstly, the NMMB/BSC-Dust model, the VIIRS-Suomi NPP date and HYSPLIT were carried out to analyse the dust transport paths and the dust particle size, and then the concentration of particles was analysed. Finally, the optical properties of aerosol particles in the dust weather were studied. During the formation of this weather, there is high dust in the Gobi and Taklamakan deserts. With the influence of wind direction, the dust moves from north to south, and the dust load significantly increased in southern China. Dust at the low altitude is generally transported from the Taklamakan Desert, while dust at the high altitude is generally transported from the Gobi Desert. The hourly average change of PM10 is from 36 μg/m3 to 818 μg/m3, while the hourly average change of PM2.5 is from 15 μg/m3 to 197 μg/m3. The dust was the main cause of the pollution weather. In this study, the formation process of the dust pollution revealed which can be used to provide guidance for government for the prevention work of dust pollution. [ABSTRACT FROM AUTHOR]

As the capital of China, the Beijing area needs to be paid special attention to its air quality. We used active remote sensing instrument (ground-based lidar), combined with passive remote sensing instrument (VIIRS onboard the NPP spacecraft), to study the serious pollution event over Beijing in spring of 2019. At the same time, the ground-based particulate matter (PM) data and the meteorological element data were analyzed. It is found that the ratio of concentrations of PM2.5 to PM10 is very large during the pollution period. The mean value of ratio is 0.75464, indicated it is fine particulate matter pollution. The Range correction signal (RCS) of lidar is very large in the layer below 0.5 km. But the volume depolarization ratio (VDR) is much less than 0.05. It indicated it is anthropogenic urban aerosols. The change in the aerosol optical depth (AOD) of VIIRS during pollution is consistent with the change in optical properties observed by lidar. The backward trajectory model of HYSPLIT shows that the pollutant came from the Hebei area where industrial pollution is serious, and the local meteorological conditions in Beijing are conducive to the continuous accumulation of pollutants. This work can deepen the understanding of the mechanism of haze formation and can help and support pollution prevention work. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Cerebrovascular disease is a disease which has the highest mortality in China. Angiogenesis in the ischemic region after cerebral infarction is closely related to its prognosis. Recent studies found that microRNAs (miRNAs) are involved in the regulation of neovascularization. MicroRNA- 153 (MiR-153) has protective effects on the ischemic injury, but its relationship with the Sonic Hedgehog (Shh) signaling pathway is still unclear. This work aimed to investigate the role of miR-153 in angiogenesis of middle cerebral artery occlusion (MCAO) rats through the Shh signaling pathway. MATERIALS AND METHODS: The rat cerebral ischemic injury (MCAO) model was established by thread embolism and treated by Agomir-153 and 5-EI. MiR-153 expression was detected using Real Time-Polymerase Chain Reaction (RTPCR). The neurological function was assessed. The infarct area of the brain and the capillary density were determined using 2,3,5-triphenyl tetrazolium chloride (TTC) method. The Shh signaling pathway and angiogenesis-related factors were tested by Western blot assay. RESULTS: Agomir-153 or Agomir-153 combined with 5-EI significantly increased miR-153 expression, reduced the infarct area, and promoted the generation of cerebral capillaries in the MCAO model. 5-EI partially blocked the protective effects of Agomir-153 and angiogenesis. The up-regulation of miR-153 markedly inhibited patched (PTC) expression and activated the Shh signaling pathway. CONCLUSIONS: The up-regulation of miR- 153 rats activated the Shh signaling pathway to promote angiogenesis and improve prognosis through lipid-coated Patch (PTC) in MCAO. MiR- 153 was considered to be a new therapeutic target for promoting angiogenesis after MCAO. [ABSTRACT FROM AUTHOR]

A one dimensional nanostructure array has been considered as a successful charge transport material for perovskite solar cells (PSCs), because of its large internal surface area, superior charge collection efficiency and fast charge transport. Herein we demonstrate a ZnO nanorod (NR) array as the electron collector in a hole-conductor-free PSC with a carbon counter electrode (CE). A relatively low initial power conversion efficiency (PCE) of 5.6% was achieved using a 1 μm long ZnO NR array as an electron collector. However, by introduction of a thin TiO2 coating layer on the surface of ZnO via TiCl4 treatment, the PCE of the cell has been improved to the highest value of 8.24%. It is revealed that the performance enhancement of the ZnO/TiO2 NR based PSCs is largely attributed to the larger surface area, reduced electron combination, and superior electron transport properties. [ABSTRACT FROM AUTHOR]