Anti-parity-time topologically undefined state

We constructed an anti-parity-time-symmetric photonic lattice by using perturbations. The results show the topological state will appear when the waveguide coupling constants $\kappa_1<\kappa_2$; Interestingly, a state with undefined winding numbers occurs when $\kappa_1=\kappa_2$, in which the light distributes only in the wide waveguides with equal magnitude distribution. Further studies show that the edge state will be strengthened by introducing defect for the topologically non-trivial case, while it will not affect the equal intensity transmission for the topologically undefined state. Our work provides a new way to realize the topological state and equally divided light transmission and might be applicable in optical circuits and optical interconnect

Mechanical Properties and Damage in Lignite under Combined Cyclic Compression and Shear Loading

In this paper, uniaxial cyclic compression and shear test was carried out for lignite samples. The effects of inclination angle (&theta;) and upper limit of cyclic stress (&sigma;max) on mechanical properties of coal samples were analyzed, and the damage variables of coal samples were studied based on energy dissipation theory. The results show that the uniaxial compressive strength (UCS) of coal samples after uniaxial cyclic compression and shear tests decreases with the increase of the upper limit of cyclic stress and inclination angle. The shear stress component generated by the increase of inclination angle can effectively reduce the UCS and increase the damage degree of coal samples. With the increase of inclination angle, the failure mode of coal samples is changed from tensile failure (&theta; = 0&deg;), the combined tensile failure and shear failure (&theta; = 5&deg;) to shear failure (&theta; = 10&deg;). The peak axial and radial strain of coal samples first increases rapidly and then stagnates. The peak volume strain rapid increases and then stagnates (&theta; = 0&deg; and &theta; = 5&deg;). When the inclination angle is 10&deg;, the peak volume strain first decreases rapidly and then stagnates. Even if the upper limit of cyclic stress is lower than its UCS, it will still promote the propagation of micro cracks and the generation of new cracks and increase the internal damage of coal samples. With the increase of the cycle number, damage variables of coal samples after uniaxial cyclic compression and shear tests nonlinearly increase, and the growth rate decreases gradually

Utilization of bio-based glycolaldehyde aqueous solution in organic synthesis: application to the synthesis of 2,3-dihydrofurans

International audienceGlycolaldehyde is a biomass-derived chemical compound available from cellulose or glucose. Until now, little attention has been devoted to its use towards value-added chemicals. To explore novel transformations of glycolaldehyde, in this work, a three-component reaction of glycolaldehyde, indole and a 1,3-dicarbonyl compound was developed to synthesize a class of 3-(indol-3-yl)-2,3-dihydrofurans. Using glycolaldehyde diethyl acetal as a glycolaldehyde source, the reaction can be performed in organic solvents, and two catalytic systems were proved to be effective: (a) Sc(OTf) 3 /nitromethane and (b) Ni(ClO 4) 2 ·6H 2 O/ acetonitrile. However, these conditions applied to the direct use of the bio-based glycolaldehyde aqueous solution did not provide the dihydrofurans efficiently. To enable the use of an aqueous solution of glycolaldehyde, a hitherto unreported deep eutectic solvent (DES) was developed by using FeCl 3 ·6H 2 O and meglumine (N-methylglucamine) as precursors. The FeCl 3 ·6H 2 O/meglumine DES was characterized by FTIR, TGA and DSC, and the obtained results demonstrated unambiguously the formation of a DES. This DES was found to be an efficient and water-compatible promoting medium for the abovementioned three-component reaction. A variety of 3-(indol-3-yl)-2,3-dihydrofurans were synthesized in good yields. The FeCl 3 ·6H 2 O/meglumine DES system can also be recycled without significant loss of activity

Synthesis of two aminosilanes as CVD precursors of SiC_xN_y films: Tuning film composition by Molecular Structures

<p></p> <p>Two aminosilanes derived from hexamethyldisilazane as chemical vapor deposition (CVD) precursors for SiC_xN_y and relevant films have been reported and characterized by ¹H, ¹³C, and ²⁹Si NMR as well as by EI-MS and elemental analysis, where necessary. Thermal stability, transport behavior and vapor pressures were evaluated by simultaneous thermal analyses (STA). Chemical vapor deposition was accomplished in a hot wall CVD reactor system to further demonstrate the ability of these compounds as CVD precursors. Most importantly, characterization (XPS) of the as-grown films proved that the composition of the films can be controlled by the molecular structure of the precursors. The result suggests future strategy for the design of CVD precursors for SiC_xN_y and related films.</p

Application of several novel natural antioxidants to inhibit oxidation of tree peony seed oil

Tree peony seed oil (TPSO) is novel edible oil enriched in omega-3 polyunsaturated fatty acid. To inhibit TPSO oxidation, several individual and combined natural antioxidants were added and evaluated by peroxide value, DPPH and ABTS radical scavenging capacity under accelerated storage condition. The effects were also compared with synthetic antioxidants. We found that all the natural compounds have certain antioxidant effect at different concentrations, especially tea polyphenols (TP) that significantly prevented TPSO from oxidation at the concentration of 0.04%. Additionally, composite antioxidants significantly improved antioxidant effects, especially synergist ascorbyl palmitate (AP) was added. The composite 0.02% TP + 0.01% DMY (dihydromyricetin) + 0.01% AP exhibited the most effective inhibition effect on TPSO oxidation and strongest DPPH and ABTS radical scavenging capacity. These results demonstrated that the candidates individual and combined natural antioxidants are beneficial for lipid stabilization and health promotion, which are desirable substitutes for synthetic antioxidants

Synthesis of 1,3-Butadiene and Its 2-Substituted Monomers for Synthetic Rubbers

Synthetic rubbers fabricated from 1,3-butadiene (BD) and its substituted monomers have been extensively used in tires, toughened plastics, and many other products owing to the easy polymerization/copolymerization of these monomers and the high stability of the resulting material in manufacturing operations and large-scale productions. The need for synthetic rubbers with increased environmental friendliness or endurance in harsh environments has motivated remarkable progress in the synthesis of BD and its substituted monomers in recent years. We review these developments with an emphasis on the reactive routes, the products, and the synthetic strategies with a scaling potential. We present reagents that are primarily from bio-derivatives, including ethanol, C4 alcohols, unsaturated alcohols, and tetrahydrofuran; the major products of BD and isoprene; and the by-products, activities, and selectivity of the reaction. Different catalyst systems are also compared. Further, substituted monomers with rigid, polar, or sterically repulsive groups, the purpose of which is to enhance thermal, mechanical, and interface properties, are also exhaustively reviewed. The synthetic strategies using BD and its substituted monomers have great potential to satisfy the increasing demand for better-performing synthetic rubbers at the laboratory scale; the laboratory-scale results are promising, but a big gap still exists between current progress and large scalability

PrLPAAT4, a Putative Lysophosphatidic Acid Acyltransferase from Paeonia rockii, Plays an Important Role in Seed Fatty Acid Biosynthesis

Lysophosphatidic acid acyltransferases (LPAATs) are essential for the acylation of lysophosphatidic acid (LPA) and the synthesis of phosphatidic acid (PA), a key intermediate in the synthesis of membrane phospholipids and storage lipids. Here, a putative lysophosphatidic acid acyltransferase gene, designated PrLPAAT4, was isolated from seed unsaturated fatty acid (UFA)-rich P. rockii. The complete PrLPAAT4 cDNA contained a 1116-bp open reading frame (ORF), encoding a 42.9 kDa protein with 371 amino acid residues. Bioinformatic analysis indicates that PrLPAAT4 is a plasma membrane protein belonging to acyl-CoA:1-acylglycerol-sn-3-phosphate acyltranferases (AGPAT) family. PrLPAAT4 shared high sequence similarity with its homologs from Citrus clementina, Populus trichocarpa, Manihot esculenta, and Ricinus communis. In Arabidopsis, overexpression of PrLPAAT4 resulted in a significant increase in the content of oleic acid (OA) and total fatty acids (FAs) in seeds. AtDGAT1, AtGPAT9, and AtOleosin, involved in TAG assembly, were upregulated in PrLPAAT4-overexpressing lines. These results indicated that PrLPAAT4 functions may be as a positive regulator in seed FA biosynthesis