Experimental realization of chiral Landau levels in two-dimensional Dirac cone systems with inhomogeneous effective mass

Chiral zeroth Landau levels are topologically protected bulk states that give rise to chiral anomaly. Previous discussions on such chiral Landau levels are based on three-dimensional Weyl degeneracies. Their realizations using two-dimensional Dirac point systems, being more promising for future applications, were never reported before. Here we propose a theoretical and experimental scheme for realizing chiral Landau levels in a photonic system. By introducing an inhomogeneous effective mass through breaking local parity inversion symmetries, the zeroth-order chiral Landau levels with one-way propagation characteristics are experimentally observed. In addition, the robust transport of the chiral zeroth mode against defects in the system is experimentally tested. Our system provides a new pathway for the realization of chiral Landau levels in two-dimensional Dirac systems, and may potentially be applied in device designs utilizing the transport robustness

Experimental observation of non-Abelian earring nodal links in phononic crystals

Nodal lines are symmetry-protected one-dimensional band degeneracies in momentum space, which can appear in numerous topological configurations such as nodal rings, chains, links, and knots. Very recently, non-Abelian topological physics has been proposed in space-time inversion (PT) symmetric systems, and attract widespread attention. One of the most special configurations in non-Abelian system is the earring nodal link, composing of a nodal chain linking with an isolated nodal line, is signature of non-Abelian topology and cannot be elucidated using Abelian topological classifications. However, the earring nodal links have not been yet observed in real system. Here we design the phononic crystals with earring nodal links, and verify its non-Abelian topologicial charge in full-wave simulations. Moreover, we experimentally observed two different kinds of earring nodal links by measuring the band structures for two phononic crystals. Specifically, we found that the order of the nodal chain and line can switch after band inversion but their link cannot be severed. Our work provides experimental evidence for phenomena unique to non-Abelian band topology and our simple acoustic system provides a convenient platform for studying non-Abelian charges.Comment: 14 pages, 3 figure

Catalytic removal of 1,2-dichloroethane over LaSrMnCoO6/H-ZSM-5 composite: insights into synergistic effect and pollutant-destruction mechanism

LaxSr2−xMnCoO6 materials with different Sr contents were prepared by a coprecipitation method, with LaSrMnCoO6 found to be the best catalyst for 1,2-dichloroethane (DCE) destruction (T90 = 509 °C). As such, a series of LaSrMnCoO6/H-ZSM-5 composite materials were rationally synthesized to further improve the catalytic activity of LaSrMnCoO6. As expected, the introduction of H-ZSM-5 could remarkably enlarge the surface area, increase the number of Lewis acid sites, and enhance the mobility of the surface adsorbed oxygen species, which consequently improved the catalytic activity of LaSrMnCoO6. Among all the composite materials, 10 wt% LaSrMnCoO6/H-ZSM-5 possessed the highest catalytic activity, with 90% of 1,2-DCE destructed at 337 °C, which is a temperature reduction of more than 70 °C and 170 °C compared with that of H-ZSM-5 (T90 = 411 °C) and LaSrMnCoO6 (T90 = 509 °C), respectively. Online product analysis revealed that CO2, CO, HCl, and Cl2 were the primary products in the oxidation of 1,2-DCE, while several unfavorable reaction by-products, such as vinyl chloride, 1,1,2-trichloroethane, trichloroethylene, perchloroethylene, and acetaldehyde, were also formed via dechlorination and dehydrochlorination processes. Based on the above results, the reaction path and mechanism of 1,2-DCE decomposition are proposed

SO2 promoted in situ recovery of thermally deactivated Fe2(SO4)3/TiO2 NH3-SCR catalysts: from experimental work to theoretical study

Due to high catalytic activity and excellent resistance to SO2 and H2O, sulfate materials are considered to be promising vanadium-free catalysts for selective catalytic reduction of NOx with NH3 (NH3-SCR). Despite this, investigations about thermal stability of sulfate SCR catalysts are limited, which is surprising given that sulfates are typically susceptible to thermal decomposition. In this work, the thermal stability of Fe2(SO4)3/TiO2 catalysts was investigated. It was determined that the thermal decomposition of Fe2(SO4)3 resulted in NOx conversion decreased from 90% to 60% at 350 °C. Interestingly however, the introduction of SO2 into the gas stream was found to reverse the effects of the thermal deactivation and the NOx conversion of 90% (350 °C) was once again observed. Extensive characterization of each catalyst sample and density functional theory (DFT) calculations were subsequently conducted. The reduction in catalytic activity after the thermal treatment was attributed to the transformation of Fe2(SO4)3 to α-Fe2O3, which reduced the quantity of Brønsted acid sites on the catalyst. The presence of SO2 in the gas stream was found to reverse this phase transformation which ultimately led to the recovery of Brønsted acid sites. DFT calculations indicated that SO2 adsorbed selectively on Fe atoms of the thermal deactivated catalysts and S-Fe bond should mainly be formed by electrons from p orbitals of S and Fe atoms. Then NH3 could be adsorbed on the surface by N-S bond with SO2. The recoverable property of this catalyst provides a promising outlook for the commercial application, especially given that industrial flue gas streams regularly contain SO2

Understanding the promotional effect of Mn2O3 on micro-/mesoporous hybrid silica nanocubic-supported Pt catalysts for the low-temperature destruction of methyl ethyl ketone: An experimental and theoretical study

Pt0.3Mnx/SiO2 nanocubic (nc) micro-/mesoporous composite catalysts with varied Mn contents were synthesized and tested for the oxidation of methyl ethyl ketone (MEK). Results show that MEK can be efficiently decomposed over synthesized Pt0.3Mnx/SiO2-nc materials with a reaction rate and turnover frequency respectively higher than 12.7 mmol gPt–1 s–1 and 4.7 s–1 at 100 °C. Among these materials, the Pt0.3Mn5/SiO2-nc catalyst can completely oxidize MEK at just 163 °C under a high space velocity of 42600 mL g–1 h–1. The remarkable performance of these catalysts is attributed to a synergistic effect between the Pt nanoparticles and Mn2O3. NH3-TPD and NH3-FT-IR experiments revealed that exposed Mn2O3 (222) facets enhance the quantity of Brønsted acid sites in the catalyst, which are considered to be responsible for promoting the desorption of surface-adsorbed O2 and CO2. It is suggested that the desorption of these species liberates active sites for MEK molecules to adsorb and react. 18O2 isotopic labeling experiments revealed that the presence of a Pt–O–Mn moiety weakens the Mn–O bonding interactions, which ultimately promotes the mobility of lattice oxygen in the Mn2O3 system. It was determined that the Mn4+/Mn3+ redox cycle in Mn2O3 allows for the donation of electrons to the Pt nanoparticles, enhancing the proportion of Pt0/Pt2+ and in turn increasing the activity and stability of catalyst. In situ DRIFTS, online FT-IR, and DFT studies revealed that acetone and acetaldehyde are the main intermediate species formed during the activation of MEK over the Pt0.3Mn5/SiO2-nc catalyst. Both intermediates were found to partake in sequential reactions resulting in the formation of H2O and CO2 via formaldehyde

Insight into the efficient oxidation of methyl-ethyl-ketone over hierarchically micro-mesostructured Pt/K-(Al)SiO 2 nanorod catalysts: Structure-activity relationships and mechanism

Hierarchically micro-mesostructured Pt/K-Al-SiO2 catalysts with regular nanorod (Pt/KA-NRS) and spherical nanoflower-like (Pt/KA-SNFS) morphologies were prepared. The existence of Al atoms generates Brønsted acid sites and reduces silanol groups over the supports, promoting the dispersion of Pt nanoparticles and stability of catalysts. Potassium atoms balance the negative charge of supports and enhance O2 mobility. The Pt/KA-NRS catalysts exhibit unexceptionable low temperature activity, CO2 selectivity, and stability for MEK oxidation. Amongst, 0.27 wt.% Pt/KA-NRS completely converts MEK at just 170 °C (activation energy as low as 37.22 kJ·mol−1), more than 100 °C lower than other typical Pt/Pd supported catalysts reported in the literature. Diacetyl and 2,3-butandiol are the main intermediates during MEK activation, which convert into H2O and CO2 through aldehydes and acids. The excellent catalytic activity of Pt/KA-NRS is ascribed to their regular morphology, high Pt0 content and dispersion, excellent MEK adsorption capacity and superior O2/CO2 desorption capability under low temperature

In vitro Anticancer Screening of 24 Locally Used Nigerian Medicinal Plants

Background: Plants that are used as traditional medicine represent a relevant pool for selecting plant candidates that may have anticancer properties. In this study, the ethnomedicinal approach was used to select several medicinal plants native to Nigeria, on the basis of their local or traditional uses. The collected plants were then evaluated for cytoxicity. Methods: The antitumor activity of methanolic extracts obtained from 24 of the selected plants, were evaluated in vitro on five human cancer cell lines. Results: Results obtained from the plants screened indicate that 18 plant extracts of folk medicine exhibited promising cytotoxic activity against human carcinoma cell lines. Erythrophleum suaveolens (Guill. & Perr.) Brenan was found to demonstrate potent anti-cancer activity in this study exhibiting IC50 = 0.2-1.3 $\mu$g/ml. Conclusions: Based on the significantly potent activity of some plants extracts reported here, further studies aimed at mechanism elucidation and bio-guided isolation of active anticancer compounds is currently underway.Chemistry and Chemical Biolog

Microglia-endothelial cross-talk regulates diabetes-induced retinal vascular dysfunction through remodeling inflammatory microenvironment

Summary: Inflammation-mediated crosstalk between neuroglial cells and endothelial cells (ECs) is a fundamental feature of many vascular diseases. Nevertheless, the landscape of inflammatory processes during diabetes-induced microvascular dysfunction remains elusive. Here, we applied single-cell RNA sequencing to elucidate the transcriptional landscape of diabetic retinopathy (DR). The transcriptome characteristics of microglia and ECs revealed two microglial subpopulations and three EC populations. Exploration of intercellular crosstalk between microglia and ECs showed that diabetes-induced interactions mainly participated in the inflammatory response and vessel development, with colony-stimulating factor 1 (CSF1) and CSF1 receptor (CSF1R) playing important roles in early cell differentiation. Clinically, we found that CSF1/CSF1R crosstalk dysregulation was associated with proliferative DR. Mechanistically, ECs secrete CSF1 and activate CSF1R endocytosis and the CSF1R phosphorylation-mediated MAPK signaling pathway, which elicits the differentiation of microglia and triggers the secretion of inflammatory factors, and subsequently foster angiogenesis by remodeling the inflammatory microenvironment through a positive feedback mechanism

MicroRNA-1 Regulates the Differentiation of Adipose-Derived Stem Cells into Cardiomyocyte-Like Cells

Stem cell transplantation is one of most valuable methods in the treatment of myocardial infarction, and adipose-derived stem cells (ASCs) are becoming a hot topic in medical research. Previous studies have shown that ASCs can be differentiated into cardiomyocyte-like cells, but the efficiency and survival rates are low. We investigated the role and mechanism of microRNA-1 (miR-1) in the differentiation of ASCs into cardiomyocyte-like cells. ASCs and cardiomyocytes were isolated from neonatal rats. We constructed lentivirus for overexpressing miR-1 and used DAPT, an antagonist of the Notch1 pathway, for in vitro analyses. We performed cocultures with ASCs and cardiomyocytes. The differentiation efficiency of ASCs was detected by cell-specific surface antigens. Our results showed that miR-1 can promote the expression of Notch1 and reduce the expression of Hes1, a Notch pathway factor, and overexpression of miR-1 can promote the differentiation of ASCs into cardiomyocyte-like cells, which may occur by regulating Notch1 and Hes1