Ribbon Hopf Superalgebras and Drinfel''d Double

Finite dimensional ribbon Hopf(super) algebras play an important role in constructing invariants of 3-manifolds. In the present paper, the authors give a necessary and sufficient condition for the Drinfeld double of a finite dimensional Hopf superalgebra to have a ribbon element. The criterion can be seen as a generalization of Kauffman and Radford's result in the non-super situation to the ■_2-graded situation, however, the derivation of the result in the ■_2-graded case will be much more complicated.     

浙江省旅游用海质量时空变化特征分析

考虑海洋旅游发展程度、区域经济社会发展水平以及海域环境条件等因素，构建旅游用海质量评价指标体系，依据官方渠道采集的统计数据，采用信息熵模型量化指标权重，根据TOPSIS法原理对沿海县（市、区）旅游海域质量进行排序并应用系统聚类法划分海域等级。结果表明：（1）人均海洋旅游总产值、海洋生物多样性指数以及海水质量指数3个评价因子对旅游用海质量影响显著，海水质量指数有反向影响。（2）2007―2016年，浙江省沿海18个县（市、区）旅游用海等级变动较大，“北强南弱”特征明显。（3）比较2007年标准，第二、三、四等级县（市、区）数量有较大幅度增加，五、六等级县（市、区）数量明显减少，旅游海域质量等级整体提高，等级数量变化与沿海县（市、区）海洋旅游发展态势和海洋生态环境变动相吻合。     

Size and Shape Effect of Gold Nanoparticles in “Far‐Field” Surface Plasmon Resonance

The “far‐field” surface plasmon resonance (FSPR) of metal nanoparticles, which have built a facile way to emission enhancement of red, green, blue, and white with nice reproducibility, has big potential application in solution‐processed organic light‐emitting diodes (OLEDs). According to the theory of the “far‐field” effect, the reflectivity of the metal surface and the phase shift at the reflection play an important role in enhancing ratio, which strongly relate to the size and shape of nanoparticles. In this work, gold nanospheres with different sizes and nanorods are synthesized in order to determine the size and shape effect of FSPR. The results demonstrate that the one with higher reflectivity in a certain range induces a better emission enhancement in the luminous efficiency and the maximum brightness. The nanoparticles with bigger sizes and shape of rods have higher reflectivity, which is consistent with the simulation based on FSPR effect. The phase shifts of different nanoparticles are optimized by the distance between gold nanoparticles and emitters. The metal NPs with a high reflectivity and the applicable phase shift will have big potential for the emission enhancement in OLEDs.     

Enantioselective C−H Activation with Earth‐Abundant 3d Transition Metals

Molecular syntheses largely rely on time‐ and labour‐intensive prefunctionalization strategies. In contrast, C?H activation represents an increasingly powerful approach that avoids lengthy syntheses of prefunctionalized substrates, with great potential for drug discovery, the pharmaceutical industry, material sciences, and crop protection, among others. The enantioselective functionalization of omnipresent C?H bonds has emerged as a transformative tool for the step‐ and atom‐economical generation of chiral molecular complexity. However, this rapidly growing research area remains dominated by noble transition metals, prominently featuring toxic palladium, iridium and rhodium catalysts. Indeed, despite significant achievements, the use of inexpensive and sustainable 3d metals in asymmetric C?H activations is still clearly in its infancy. Herein, we discuss the remarkable recent progress in enantioselective transformations via organometallic C?H activation by 3d base metals up to April 2019.     

Experimental and theoretical electronic absorption spectra of 2,4‐diphenyl‐1,5‐benzothiazepine and its derivatives: Solvatochromic effect and time dependent density functional theory approach

Electronic spectra of 2,4‐diphenyl‐1,5‐benzothiazepine and some of its derivatives in 1,2‐dichloromethane and ethanol are investigated experimentally and theoretically using the time dependent density functional theory (TD‐DFT) method at the B3LYP/6‐311G** level of the theory. The origin of the spectrum of the parent compound is found to be an additive one. The observed ultra violet (UV) spectra in both solvents show two bands S1 in the range between 312–334 nm and S2 in the range between 248–272 nm. The solvent effect is investigated experimentally and theoretically and a blue shift is observed, which is explained in terms of a hydrogen bond model between the solvent and the most negative site of the solute (N atom). This theoretical model is robust in reproducing the experimental blue shift and calculating the hydrogen bond energy and hydrogen bond length. The extent of delocalization and charge transfer processes of the studied compounds is estimated and discussed in terms of natural bond orbital (NBO) analysis and second order perturbation interactions (E²) between donors and acceptors. The effect of substituents of the studied compounds in both solvents shows a noticeable red shift attributed to hyperconjugation effects of the π electron systems of the different moieties.     

Conformational analysis of the disaccharide methyl α‐d‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d‐mannopyranoside monohydrate

The crystal structure of methyl α‐d ‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d ‐mannopyranoside monohydrate, C₁₅H₂₆O₁₂·H₂O, ( II ), has been determined and the structural parameters for its constituent α‐d ‐mannopyranosyl residue compared with those for methyl α‐d ‐mannopyranoside. Mono‐O‐acetylation appears to promote the crystallization of ( II ), inferred from the difficulty in crystallizing methyl α‐d ‐mannopyranosyl‐(1→3)‐β‐d ‐mannopyranoside despite repeated attempts. The conformational properties of the O‐acetyl side chain in ( II ) are similar to those observed in recent studies of peracetylated mannose‐containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C=O bond of the acetyl group. The C2—O2 bond in ( II ) elongates by ～0.02 Å upon O‐acetylation. The phi (?) and psi (ψ) torsion angles that dictate the conformation of the internal O‐glycosidic linkage in ( II ) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated ( II ) using the statistical program MA′AT, with a greater disparity found for ψ (Δ = ～16°) than for ? (Δ = ～6°).     

In situ fabrication of paclitaxel‐loaded core‐crosslinked micelles via thiol‐ene “click” chemistry for reduction‐responsive drug release

In this study, a facile method to fabricate reduction‐responsive core‐crosslinked micelles via in situ thiol‐ene “click” reaction was reported. A series of biodegradable poly(ether‐ester)s with multiple pendent mercapto groups were first synthesized by melt polycondensation of diol poly(ethylene glycol), 1,4‐butanediol, and mercaptosuccinic acid using scandium trifluoromethanesulfonate [Sc(OTf)₃] as the catalyst. Then paclitaxel (PTX)‐loaded core‐crosslinked (CCL) micelles were successfully prepared by in situ crosslinking hydrophobic polyester blocks in aqueous media via thiol‐ene “click” chemistry using 2,2′‐dithiodiethanol diacrylate as the crosslinker. These PTX‐loaded CCL micelles with disulfide bonds exhibited reduction‐responsive behaviors in the presence of dithiothreitol (DTT). The drug release profile of the PTX‐loaded CCL micelles revealed that only a small amount of loaded PTX was released slowly in phosphate buffer solution (PBS) without DTT, while quick release was observed in the presence of 10.0 mM DTT. Cell count kit (CCK‐8) assays revealed that the reduction‐sensitive PTX‐loaded CCL micelles showed high antitumor activity toward HeLa cells, which was significantly higher than that of reduction‐insensitive counterparts and free PTX. This kind of biodegradable and biocompatible CCL micelles could serve as a bioreducible nanocarrier for the controlled antitumor drug release. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 99–107     

Pd based on 2-Aminopyrimidine and 1H-benzo[d]imidazol-2-amine functionalizedFe3O4 nanoparticles as novel recyclable magnetic nanocatalysts for Ullmann coupling reaction

In this study, Pd based on 2-Aminopyrimidine and 1H-benzo[d]imidazol-2-amine functionalized Fe₃O₄ magnetic nanoparticles [(Pd-APM-PSi-Fe₃O₄) and (Pd-BIA-PSi-Fe₃O₄)] was designed and used for the synthesis of di aryl ether by Ulmann cross-coupling reactions. Ulmann reaction performed with mixing of the arylhalides and phenol derivatives in DMF solvent. The prepared catalysts were characterized with various analytical techniques such as FT-IR, XRD, TGA, SEM, TEM, EDX, ICP and VSM. Pd-APM-PSi-Fe₃O₄ and Pd-BIA-PSi-Fe₃O₄ catalysts demonstrated good to excellent yields catalytic efficiency for Ulmann reactions in comparison with to commercial palladium catalysts. The catalyst is easily recycled and reused without loss of the catalytic activity. The combined merits of reusable catalyst conditions make the condensation with safe operation, no leaching of pd into environment, low pollution, rapid access to products and simple workup. Also, these novel magnetic nanocatalysts are superior to the industry standard Pd in every relevant aspect. They feature a way higher initial activity, a much more convenient separation, better recycling, and less contamination of the products. Last but not least, they can be very easily prepared from commercially available Fe₃O₄ nanoparticles using standard laboratory equipment.