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71.
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73.
Le Fang Wei-Tao Gong Manivannan Kalavathi Dhinakaran Li Shang Gui-Ling Ning 《Chemical Papers》2016,70(5):663-666
A novel Hg2+ ion induced reversible ring contraction was achieved employing the intramolecular reaction of isobutylene with an aromatic hydroxyl group of cyclophane; reversibility of the reaction was facilitated by excess addition of NaBH4 which also resulted in complexation. The ring contraction and expansion was monitored by UV-VIS absorption, and by fluorescence and 1H NMR spectra. Switchable fluorescence behavior (on—off—on) was observed when the ring-size was tuned from a 19-membered ring to an 18-membered and vice versa. This fine tuning has the potential to be applied in the construction of new supramolecular devices. 相似文献
74.
Synthesis and properties of novel soluble poly(amide‐imide)s with different pendant substituents
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Wenze Li Xinyu Qian Haibiao Shi Weiyi Zhou Yuting Cai Yu Liu Kunzhi Shen 《Journal of polymer science. Part A, Polymer chemistry》2017,55(19):3243-3252
Two types of novel fluorinated diimide‐diacid monomers—[2,2′‐(4,4′‐(3′‐methylbiphenyl‐2,5‐diyl)bis(oxy)bis(3‐(trifluoromethyl)‐4,1‐phenylene))bis(1,3‐dioxoisoindoline‐5‐carboxylic acid)] (III) and [2,2′‐(4,4′‐(3′‐(trifluoromethyl)biphenyl‐2,5‐diyl)bis(oxy)bis(3‐(trifluoromethyl)‐4,1‐phenylene))bis(1,3‐dioxoisoindoline‐5‐carboxylic acid)] (IV)—were respectively designed and prepared by the condensation of diamines I and II with two molar equivalents of trimellitic anhydride. From both diimide‐diacids, two series of novel poly(amide‐imide)s (PAIs) (IIIa–IIIe and IVa–IVe) bearing different pendant groups were prepared by direct polymerization with various aromatic diamines (a–e). All the PAIs had a high glass transition temperatures (Tgs, 232–265 °C), excellent thermal stability (exhibiting only 5% weight loss at 493–542 °C under nitrogen) and good solubility in various organic solvents due to the introduction of the bulky pendant groups. The cast films of these PAIs (80–90 μm) had good optical transparency (73–81% at 450 nm, 85–88% at 550 nm and 87–89% at 800 nm) and low dielectric constants (2.65–2.98 at 1 MHz). The spin‐coated films of these PAIs presented a minimum birefringence value as low as 0.0077–0.0143 at 650 nm and low optical absorption at the near‐infrared optical communication wavelengths of 1310 and 1550 nm. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3243–3252 相似文献
75.
Xiao Hu An Zeng Ming-Sheng Shang 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(2):46
Recommender system is an effective tool to find the most relevant information for onlineusers. By analyzing the historical selection records of users, recommender system predictsthe most likely future links in the user-item network and accordingly constructs apersonalized recommendation list for each user. So far, the recommendation process ismostly investigated in static user-item networks. In this paper, we propose a model whichallows us to examine the performance of the state-of-the-art recommendation algorithms inevolving networks. We find that the recommendation accuracy in general decreases with timeif the evolution of the online network fully depends on the recommendation. Interestingly,some randomness in users’ choice can significantly improve the long-term accuracy of therecommendation algorithm. When a hybrid recommendation algorithm is applied, we find thatthe optimal parameter gradually shifts towards the diversity-favoring recommendationalgorithm, indicating that recommendation diversity is essential to keep a high long-termrecommendation accuracy. Finally, we confirm our conclusions by studying therecommendation on networks with the real evolution data. 相似文献
76.
The traditional surfactant sodium dodecyl sulfate (SDS) and ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]) have been combined to create a novel efficient medium for chromogenic catalysis of 3,3',5,5'-tetramethylbenzidine with horseradish peroxidase in presence of H2O2. The results have shown the [Emim][BF4] in the mediums can promote the rate of formation of the blue chromogen, the SDS is responsible for the stabilization of the blue chromogen due to the electrostatic attraction between positively charged blue chromogen and the negatively charged surfactant. The SDS/[Emim][BF4] combination not only enhance catalytic activity of HRP remarkably but also stabilize the blue chromogen formed in the HRP oxidation of the substrate TMB compared to the conventional medium. Based on the superior combination of SDS and [Emim][BF4], the colorimetric assay for detecting HRP activity and H2O2 concentration was established. This work demonstrates a novel efficient medium for chromogenic catalysis with potential applications in biosensors and clinical diagnosis. 相似文献
77.
Based on the independent, continuous and mapping (ICM) method and homogenization method, a research model is constructed to propose and deduce a theorem and corollary from the invariant between the weight filter function and the corresponding stiffness filter function of the form of power function. The efficiency in searching for optimum solution will be raised via the choice of rational filter functions, so the above mentioned results are very important to the further study of structural topology optimization. 相似文献
78.
Dr. Zhijia Wang Mikhail Ivanov Dr. Yuting Gao Laura Bussotti Prof. Paolo Foggi Huimin Zhang Prof. Nino Russo Prof. Bernhard Dick Prof. Jianzhang Zhao Prof. Mariangela Di Donato Dr. Gloria Mazzone Prof. Liang Luo Prof. Matvey Fedin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1091-1102
Spin–orbit charge-transfer intersystem crossing (SOCT-ISC) is useful for the preparation of heavy atom-free triplet photosensitisers (PSs). Herein, a series of perylene-Bodipy compact electron donor/acceptor dyads showing efficient SOCT-ISC is prepared. The photophysical properties of the dyads were studied with steady-state and time-resolved spectroscopies. Efficient triplet state formation (quantum yield ΦT=60 %) was observed, with a triplet state lifetime (τT=436 μs) much longer than that accessed with the conventional heavy atom effect (τT=62 μs). The SOCT-ISC mechanism was unambiguously confirmed by direct excitation of the charge transfer (CT) absorption band by using nanosecond transient absorption spectroscopy and time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The factors affecting the SOCT-ISC efficiency include the geometry, the potential energy surface of the torsion, the spin density for the atoms of the linker, solvent polarity, and the energy matching of the 1CT/3LE states. Remarkably, these heavy atom-free triplet PSs were demonstrated as a new type of efficient photodynamic therapy (PDT) reagents (phototoxicity, EC50=75 nm ), with a negligible dark toxicity (EC50=78.1 μm ) compared with the conventional heavy atom PSs (dark toxicity, EC50=6.0 μm, light toxicity, EC50=4.0 nm ). This study provides in-depth understanding of the SOCT-ISC, unveils the design principles of triplet PSs based on SOCT-ISC, and underlines their application as a new generation of potent PDT reagents. 相似文献
79.
Shang Chen Shuiyin Chen Dengji Han Christopher W. Bielawski Jianxin Geng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(51):e202201580
Lithium (Li) metal has attracted significant attention in areas that range from basic research to various commercial applications due to its high theoretical specific capacity (3860 mA h g−1) and low electrochemical potential (−3.04 vs. standard hydrogen electrode). However, dendrites often form on the surfaces of Li metal anodes during cycling and thus lead to battery failure and, in some cases, raise safety concerns. To overcome this problem, a variety of approaches that vary the electrolyte, membrane, and/or anode have been proposed. Among these efforts, the use of three-dimensional frameworks as Li hosts, which can homogenize and minimize the current density at the anode surface, is an effective approach to suppress the formation of Li dendrites. Herein, we describe the development of using carbon-based materials as Li hosts. While these materials can be fabricated into a variety of porous structures, they have a number of intrinsic advantages including low costs, high specific surface areas, high electrical conductivities, and wide electrochemical stabilities. After briefly summarizing the formation mechanisms of Li dendrites, various methods for controlling structural and surface chemistry will be described for different types of carbon-based materials from the viewpoint of improving their performance as Li hosts. Finally, we provide perspective on the future development of Li host materials needed to meet the requirements for their use in flexible and wearable devices and other contemporary energy storage techniques. 相似文献
80.
Strain bursts are often observed during compression tests of single crystal micropillars. In this work, we formulate a new continuum model that accounts for the strain bursts within the framework of crystal plasticity. The strain bursts are separated from the loading stage (nearly elastic loading) by introducing a dimensionless constant in the continuum model, and are detected by load serrations. The boundary conditions in the context of micropillar compression are studied and they are shown to be changing and unpredictable as plastic deformation proceeds. To evaluate the validity of our model, finite element simulations of the uniaxial compression tests on nickel micropillars are performed. Our simulations produce clearly visible strain bursts during the plastic flow and the produced intermittent flows are comparable with the experimental observations. For the bulk crystal, a series of strain bursts is identified in the course of plastic flow, despite an apparently smooth stress–strain response. We also show that the intermittent flow is intensified in the micrometer-scale due to both increasing numbers of the successive strain bursts and increasing amplitude of the strain burst, when the specimen size decreases. Finally, we show that the occurrences of the strain bursts are always associated with negative values of the second-order work. 相似文献