Exceptional electrostatic phenomenon in ultrathin nanorods: the terminal σ‑hole

An in-depth understanding of the physicochemical properties of nanorods during the initial growth process has a profound impact on the rational design of high-performance nanorods catalysts. Herein, we conducted a systematic DFT study on the transition metal Co, Ni and alloyed nanoclusters/rods systems to simulate an atomic process from the initial nanoclusters growth to nanorods/wires. We found that the highly active sites of nanorods depend on an interesting electrostatic phenomenon. The surface electrostatic potential analysis shows that all nanoclusters and nanorods structures have formed σ-hole. Unlike nanoclusters, the σ-hole only appears at terminal sites in nanorods, called terminal σ-hole. The elemental composition in nanorods has a certain influence on the maximal surface electrostatic potential (VS,max) i.e., terminal σ-hole. Interestingly, we found that the terminal σ-hole formed in nanorods is generally higher in magnitude than smaller nanoclusters. First-principle calculations show that terminal σ-hole is closely related to the physicochemical activities of nanorods. For example, the work function of the directions forming terminal σ-hole is smaller than other directions. More interestingly, we found that in almost all nanorods, compared with other atoms, the d-orbital of the atoms forming terminal σ‑hole shifts close to the Fermi level and exhibits a shallower d-band center, showing higher chemical activity. In short, it is the first time that we discovered terminal σ-hole in nanorods, explained the theoretical basis of terminal σ-hole in nanorod systems, and provided theoretical guidance for the rational design of high-performance nanorods catalysts

A Mechanism for Recognizing and Suppressing the Emergent Behavior of UAV Swarm

Similar to social animals in nature, UAV swarm is also a complex system that can produce emergent behavior. The emergent behavior of UAV swarm in specific airspace is undoubtedly the act that the defense side does not expect to see; therefore, recognition and suppression of the emergent behavior of UAVs swarm are needed. Based on the analysis of the UAV swarm emergent behavior mechanism, by adopting f-divergence method, UAV swarm emergent behavior was quantified, and a rapid recognition mechanism of emergent behavior has been established, thus, making preparation for the suppression of the emergent behavior. In the academic circle, for the first time, in accordance with heuristic rules governing the algorithms of UAV swarm suppression, principle of emergent behavior suppression has been proposed, failure judgment model of UAV swarm control under interference conditions has been constructed, the stability of UAV swarm has been analyzed, and the combat command process of UAV swarm based on OODA loop has been put forward. Through the simulation, the comparison of information entropy and f-divergence based emergence measurement method has been made, and f-divergence based method has some advantages for measuring the emergence of UAV swarm. From the analysis and discussion of the inhibitory effect on swarm flocking behavior under different interference intensity and timing, conclusion has been drawn that comprehensive suppression on the premise of correct recognition of flocking behavior is the best strategy fighting against UAV swarm emergent behavior

Red-emitting CaLa4(SiO4)(3)O:Eu3+ phosphor with superior thermal stability and high quantum efficiency for warm w-LEDs

To accelerate the next generation of high power white light-emitting diodes, the development of efficient and stable red-emitting phosphors is urgent. In this regard, a series of CaLa4(SiO4)(3)O: Eu3+ phosphors with red-emitting band centered at 612 nm are prepared by a high temperature solid state reaction. Xray diffraction patterns and Rietveld refinement confirm that all the samples are oxyapatite structure with space group of P63/m. Impressively, the quantum efficiency of the prepared red phosphor reaches as high as 97.5% under blue light excitation, and its emission intensity at 423 K remains 82.4% of that at room temperature, which are comparable to those of the commercial Y2O3: Eu3+ red phosphor. As a consequence, a warm white light-emitting diode with a luminous efficiency of 84.9 lm/W, a correlated color temperature of 4012 K and a color rendering index of 84.4 is realized by blending red-emitting CaLa4(SiO4)(3)O: Eu3+ phosphors and yellow-emitting Y3Al5O12: Ce3+ ones with a blue LED chip. It is expected that the explored CaLa4(SiO4)3O: Eu3+ red phosphor can be a good candidate for application in solid-state lighting. (C) 2016 Elsevier B.V. All rights reserved

Disruption of Abcc6 Transporter in Zebrafish Causes Ocular Calcification and Cardiac Fibrosis

Pseudoxanthoma elasticum (PXE), caused by ABCC6/MRP6 mutation, is a heritable multisystem disorder in humans. The progressive clinical manifestations of PXE are accompanied by ectopic mineralization in various connective tissues. However, the pathomechanisms underlying the PXE multisystem disorder remains obscure, and effective treatment is currently available. In this study, we generated zebrafish abcc6a mutants using the transcription activator-like effector nuclease (TALEN) technique. In young adult zebrafish, abcc6a is expressed in the eyes, heart, intestine, and other tissues. abcc6a mutants exhibit extensive calcification in the ocular sclera and Bruch’s membrane, recapitulating part of the PXE manifestations. Mutations in abcc6a upregulate extracellular matrix (ECM) genes, leading to fibrotic heart with reduced cardiomyocyte number. We found that abcc6a mutation reduced levels of both vitamin K and pyrophosphate (PPi) in the serum and diverse tissues. Vitamin K administration increased the gamma-glutamyl carboxylated form of matrix gla protein (cMGP), alleviating ectopic calcification and fibrosis in vertebrae, eyes, and hearts. Our findings contribute to a comprehensive understanding of PXE pathophysiology from zebrafish models

Enhancement of photoluminescence properties and modification of crystal structures of Si3N4 doping Li2Sr0.995SiO4:0.005Eu(2+) phosphors

Si3N4 modified Li2Sr0.995SiO4:0.005Eu(2+) (Li2Sr0.995SiO4-3x/2Nx:0.005Eu(2+)) phosphors were synthesized with the conventional solid-state reaction in the reduced atmosphere. The crystal structure and vibrational modes were analyzed by X-ray diffraction, Raman scattering spectroscopy and Rietveld crystal structure refinement. Photoluminescence (PL) and photoluminescence excitation (PLE) spectra showed that Li2Sr0.995SiO4-3x/2Nx:0.005Eu(2+) powder exhibited a broad yellow emission band centered at 560 nm under the excitation of 460 nm visible light, due to the 4f(6)5d(1) -> 4f(7) transition of Eu2+. The partial nitridation of Li2Sr0.995SiO4-3x/2Nx:0.005Eu(2+) (x=0.01) phosphors led to a large enhancement in the luminescence intensity, as much as 190%. At the same time, the fluorescence decay behavior curves further showed that the photoluminescence efficiencies of Li2Sr0.995SiO4-3x/2Nx:0.005Eu(2+) phosphors were enhanced by addition of Si3N4. The temperature quenching characteristics confirmed that the oxynitride based Li2Sr0.995SiO4-3x/2Nx:0.005Eu(2+) showed slightly higher stability. It is implied that Li2Sr0.995SiO4-3x/2Nx:0.005Eu(2+) phosphors had a possible potential application on white LEDs to match blue light chips. (C) 2015 Elsevier Ltd. All rights reserved

In Situ Crystallization Synthesis of CsPbBr₃ Perovskite Quantum Dot-Embedded Glasses with Improved Stability for Solid-State Lighting and Random Upconverted Lasing

All-inorganic cesium lead bromide CsPbBr₃ perovskite quantum dots (QDs) are emerging as potential candidates for their applications in optoelectronic devices but they suffer from poor long-term stability due to their high sensitivity to UV irradiation, heat, and especially to moisture. Although great advances in improving stability of perovskite QDs have been achieved by surface modification or encapsulation in polymer and silica, they are not sufficiently refrained from external environment due to nondense structures of these protective layers. In this work, in situ nanocrystallization strategy is developed to directly grow CsPbBr₃ QDs among a specially designed TeO₂-based glass matrix. As a result, QD-embedded glass shows typical bright green emission assigned to exciton recombination radiation and significant improvement of photon/thermal stability and water resistance due to the effective protecting role of dense structural glass. Particularly, ∼90% of emission intensity is even remained after immersing QD-embedded glass in water up to 120 h, enabling them to find promising applications in white-light-emitting device with superior color stability and low-threshold random upconverted laser under ambient air condition

Effect of Centella asiatica

Hyperlipidemia and many other metabolic diseases are related to oxidative stress. Centella asiatica is a traditional Chinese medicine whose antioxidant effect in vitro has been reported. We are interested in whether it possesses this effect in vivo and hence modulates lipid metabolism. Therefore, experiments were carried out on mice and golden hamsters regarding its antioxidant and hypolipidemic effect. We observed that a fraction (CAF3) of the ethanol extract (CAE) of Centella asiatica had a cholesterol decrease of 79% and a triglyceride decrease of 95% in acute mice model, so CAF3 was further investigated in high-fat-fed hamster model. It was shown that CAF3 increased SOD and GSH-Px activities and decreased MDA level, and it also improved TC, TG, LDL-C, HDL-C, AST, and ALT levels. L-CAT and SR-BI gene expression in hamsters were increased. Taken together, our data suggest that the CAF3 fraction of Centella asiatica has antioxidant and hypolipidemic properties

Fibroblasts in metastatic lymph nodes confer cisplatin resistance to ESCC tumor cells via PI16

Abstract Although many studies have compared tumor fibroblasts (T-Fbs) and nontumor fibroblasts (N-Fbs), less is understood about the stromal contribution of metastatic lymph node fibroblasts (LN-Fbs) to the evolving microenvironment. Here, we explored the characteristics of LN-Fbs in esophageal squamous cell carcinoma (ESCC) and the interactions between fibroblasts and ESCC tumor cells in metastatic lymph nodes. Fibroblasts were isolated from tumor, nontumor and metastatic lymph node tissues from different patients with ESCC. Transcriptome sequencing was performed on the fibroblasts. Tumor growth and drug-resistance assays were carried out, and characteristics of T-Fbs, N-Fbs and LN-Fbs were determined. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to assay the culture medium of fibroblasts. The results demonstrated that fibroblasts derived from different tissues had different characteristics. Coculture with LN-Fbs conditioned medium inhibited ESCC tumor cell growth and induced chemoresistance in ESCC cells. LN-Fbs induced chemoresistance to cisplatin in ESCC cells by secreting PI16. Coculture with LN-Fbs conditioned medium decreased cisplatin-induced apoptosis in ESCC cells by regulating the p38 and JNK cell signaling pathways. Survival analyses showed that patients with high PI16 expression in Fbs of lymph nodes exhibited worse overall survival. We also examined PI16 expression in interstitial tissues in ESCC tumor samples of patients receiving platinum-based therapy postsurgery and found that high PI16 expression in tumor interstitial tissues was an independent prognostic factor for ESCC patients. In addition, an in vivo assay demonstrated that PI16 knockdown increased the sensitivity of ESCC cells to cisplatin. Our results suggest that fibroblasts in metastatic lymph nodes decrease apoptosis of ESCC cells via PI16, thereby providing a cisplatin-resistance niche and supporting ESCC tumor cells to survive in metastatic lymph nodes. PI16 is also a potential target for effectively blocking the chemoresistance niche signaling circuit in response to cisplatin

Theoretical Design of Core–Shell 3d-Metal Nanoclusters for Efficient Hydrogen-Evolving Reaction

Co- and Ni-based materials are promising catalysts for the hydrogen evolution reaction (HER) but usually transform into active Co/Ni metal nanoclusters during reductive HER processes, making the rational design of initial states for Co/Ni metal nanoclusters critical. However, the optimal states of Co/Ni metal nanoclusters for the HER are still unclear. Herein, we design 16 pure/alloyed core–shell Co/Ni-metal nanoclusters and give systematic insights into their HER performance and catalysis mechanism, from thermodynamics to kinetics. We find that the HER performance significantly depends on the geometric structures of the Co–Ni metal nanoclusters. Compared to other sized nanoclusters, Co13@Ni20 and Ni@Co12@Ni20 exhibit the optimum HER performance with proton adsorption free energies close to zero, which could be attributed to their special and favorable negative surface electronic structures to adsorb the key protons. Further investigations show that they also exhibit good stability in both thermodynamics and kinetics. Furthermore, we apply metadynamics to directly map the 2D free energy reaction surface and HER pathways, ultimately uncovering the detailed HER mechanism of the best-performing Co13@Ni20 catalyst. Our work helps us understand the optimal states and the catalytic mechanism of active Co/Ni metal nanoclusters for HER