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1.
Nowadays, blue fluorescent organic light-emitting diodes (FOLEDs) have attracted considerable attention from both academia and industry. According to spin statistics, electrical excitation results in the formation of ∼25% singlet excitons and ∼75% triplet excitons (signifying ~75% energy loss), which triggered wide-ranging efforts to harvest as many triplet excitons as possible. The materials that can convert triplet excitons into singlet excitons from the high-lying excited triplet states (referred as “hot exciton” channel) to realize high efficiency were reported, which can also efficaciously avoid the accumulation of triplet excitons in T1 state. In this study, by means of density functional theory (DFT) and time-dependent DFT, we have theoretically investigated the electronic and photophysical properties of 16 newly designed molecules with donor-bridge-acceptor framework to search for the blue FOLED materials exploiting the “hot exciton” path. Important properties, such as singlet-triplet energy gaps, absorption and emission parameters, and reverse intersystem crossing rates (kRISC), of five target molecules were studied. The calculated results demonstrate that thiophene-diphenylamine (kRISC up to 1.03 × 108 seconds−1) may have promising potential as blue FOLED materials by virtue of the “hot exciton” effect.  相似文献   
2.
In this work we are interested in the existence and uniqueness of solutions for the Navier problem associated to the degenerate nonlinear elliptic equations■,in the setting of the weighted Sobolev spaces.  相似文献   
3.
可控/“活性”自由基聚合(CLRP)可以用于制备分子量分布窄、分子链缺陷少的聚合物,如聚乙烯(PE)、聚氯乙烯(PVC)、聚偏氯乙烯(PVDC)和聚偏氟乙烯(PVDF),且易控制上述单体与其他单体共聚得到嵌段聚合物。本文调研了近年来可控/“活性”自由基聚合(如碘转移聚合(ITP)、氮氧稳定自由基聚合(NMP)、可逆加成断裂链转移(RAFT)聚合和金属催化的活性自由基聚合(OMRP)等)制备聚乙烯和聚卤代烯烃等方面的工作,并指出了未来的发展方向。  相似文献   
4.
We prove a Harnack inequality for nonnegative strong solutions to degenerate and singular elliptic PDEs modeled after certain convex functions and in the presence of unbounded drifts. Our main theorem extends the Harnack inequality for the linearized Monge–Ampère equation due to Caffarelli and Gutiérrez and it is related, although under different hypotheses, to a recent work by N.Q. Le.Since our results are shown to apply to the convex functions |x|p with p2 and their tensor sums, the degenerate elliptic operators that we can consider include subelliptic Grushin and Grushin-like operators as well as a recent example by A. Montanari of a nondivergence-form subelliptic operator arising from the geometric theory of several complex variables. In the light of these applications, it follows that the Monge–Ampère quasi-metric structure can be regarded as an alternative to the usual Carnot–Carathéodory metric in the study of certain subelliptic PDEs.  相似文献   
5.
In this note we consider the Schrödinger equation on compact manifolds equipped with possibly degenerate metrics. We prove Strichartz estimates with a loss of derivatives. The rate of loss of derivatives depends on the degeneracy of metrics. For the non-degenerate case we obtain, as an application of the main result, the same Strichartz estimates as that in the elliptic case. This extends Strichartz estimates for Riemannian metrics proved by Burq-Gérard-Tzvetkov to the non-elliptic case and improves the result by Salort for the degenerate case. We also investigate the optimality of the result for the case on 𝕊3 × 𝕊3.  相似文献   
6.
This work reveals ambident nucleophilic reactivity of imidazolium cations towards carbonyl compounds at the C2 or C4 carbene centers depending on the steric properties of the substrates and reaction conditions. Such an adaptive behavior indicates the dynamic nature of organocatalysis proceeding via a covalent interaction of imidazolium carbenes with carbonyl substrates and can be explained by generation of the H-bonded ditopic carbanionic carbenes.  相似文献   
7.
Alkanes composed of C−C and C−H show a low electric polarization, and therefore, there is only very weak interaction between alkanes and adsorbents. Thus, it is difficult to separate a specific alkane from a mixture of alkanes by adsorption. Here, two activated “channel-like” crystals generated from brominated thiacalix[4]arene propyl ethers, which adopt 1,3-alternate and partial cone conformations, recognize specific alkane vapors depending on alkane-shape and -size, sorting in three-type alkane guests such as linear, branched, and cyclic alkanes. Two activated crystals, which are prepared by removal of solvent upon heating under reduced pressure, incorporate branched and/or cyclic alkane vapors by a unique “gate-opening” mechanism via a crystal transformation in the process. Linear alkane vapors do not trigger gate opening and are not taken up by the activated crystals. The shape and size molecular-recognition properties of the activated crystals promises considerable usefulness for the separation of linear, branched, and cyclic alkanes.  相似文献   
8.
Haouamines A, B, and their derivatives were synthesized via Suzuki–Miyaura coupling and three key cyclization reactions as follows: the newly developed palladium(0)-catalyzed arylative cyclization of phenylalanine-derived alkyne–aldehydes with 2-bromoarylboronic acid (an “anti-Wacker”-type cyclization); BF3 ⋅ OEt2-promoted Friedel–Crafts-type cyclization of symmetrical electron-rich aromatic rings adjacent to a tertiary allylic alcohol leading to the indeno-tetrahydropyridine skeleton; and (cyanomethyl)trimethylphosphonium iodide-mediated macrocyclization of amino alcohols to afford aza-paracyclophane precursors. The palladium-catalyzed reduction of mono- and di-triflate intermediates in the later stages enabled the alteration of both the position and number of hydroxyl groups on the C-ring. The instability of haouamine B was dramatically improved by salt formation with formic acid. An unambiguous evaluation of the cytotoxicity of the prepared haouamine derivative formates with and without hydroxyl groups at different positions on the C-ring indicated that the catechol structure in haouamine B produced weak cytotoxicity.  相似文献   
9.
针对两阶段闭环供应链系统,研究了古诺竞争型闭环供应链中的“以旧换再”策略选择问题。研究发现:(1)企业如何及何时实施“以旧换再”策略取决于自身及竞争企业的再制造水平。再制造水平不仅影响了企业的“以旧换再”数量,同时还会影响产品市场份额及利润。(2)“以旧换再”策略可以提高企业竞争力,增加企业产品市场份额和提高收益;(3)提高 “以旧换再”补贴及再制造产品接受度, 降低“二手市场”价格,均可以降低企业实施“以旧换再”策略和提高企业的“以旧换再”数量。  相似文献   
10.
In this article, we study the second-order optimality conditions for a class of circular conic optimization problem. First, the explicit expressions of the tangent cone and the second-order tangent set for a given circular cone are derived. Then, we establish the closed-form formulation of critical cone and calculate the “sigma” term of the aforementioned optimization problem. At last, in light of tools of variational analysis, we present the associated no gap second-order optimality conditions. Compared to analogous results in the literature, our approach is intuitive and straightforward, which can be manipulated and verified. An example is illustrated to this end.  相似文献   
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