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111.
Xiaojing Li Wenming Xiong Hua Lin Liyang Zhuo Shuiyuan Lv Xi Tang Minshi Chen Zhexiang Zou Zhenyu Lin Bin Qiu Guonan Chen 《Journal of separation science》2013,36(3):477-484
An RP LC‐ESI‐MS/MS method for the determination of the migration of 16 primary phthalic acid esters from plastic samples has been developed using distilled water, 3% acetic acid, 10% alcohol, and olive oil as food simulants. Detection limits were 1.6–18.5 μg/kg in distilled water, 1.4–17.3 μg/kg in 3% acetic acid, 1.4–19.2 μg/kg in 10% alcohol, and 31.9–390.8 μg/kg in olive oil. The RSDs were in the range of 0.07–11.28%. The real plastic products inspection showed that only few analyzed samples were phthalates contaminated. Bis‐2‐ethylhexyl ester and dibutyl phthalate were the common items migrated from the plastic products into food and feeds, but the migration concentrations were far below the limits set by European Union (1.5 mg/kg for bis‐2‐ethylhexyl ester and 0.3 mg/kg for dibutyl phthalate). 相似文献
112.
We study existence and stability of stationary solutions of a system of semilinear parabolic partial differential equations that occurs in population genetics. It describes the evolution of gamete frequencies in a geographically structured population of migrating individuals in a bounded habitat. Fitness of individuals is determined additively by two recombining, diallelic genetic loci that are subject to spatially varying selection. Migration is modeled by diffusion. Of most interest are spatially non-constant stationary solutions, so-called clines. In a two-locus cline all four gametes are present in the population, i.e., it is an internal stationary solution. We provide conditions for existence and linear stability of a two-locus cline if recombination is either sufficiently weak or sufficiently strong relative to selection and diffusion. For strong recombination, we also prove uniqueness and global asymptotic stability. For arbitrary recombination, we determine the stability properties of the monomorphic equilibria, which represent fixation of a single gamete. 相似文献
113.
Binominal expressions for the reflection high-energy electron diffraction (RHEED) oscillations during the growth of thin films by molecular beam epitaxy (MBE) were investigated. The dependence of the RHEED oscillation shape on the molecular migration time and the oscillation period was analyzed quantitatively. The peaks and valleys in the calculated oscillation intensities as a function of the oscillation period were in qualitatively reasonable agreement with those obtained from the experimental data. These results can help in controlling the epitaxial film thickness in the growth of films by using the MBE technique. 相似文献
114.
115.
Lev A. Borisov Linda Chen Gregory G. Smith 《Journal of the American Mathematical Society》2005,18(1):193-215
Generalizing toric varieties, we introduce toric Deligne-Mumford stacks. The main result in this paper is an explicit calculation of the orbifold Chow ring of a toric Deligne-Mumford stack. As an application, we prove that the orbifold Chow ring of the toric Deligne-Mumford stack associated to a simplicial toric variety is a flat deformation of (but is not necessarily isomorphic to) the Chow ring of a crepant resolution.
116.
117.
Cui-Tian Wang Peng-Yu Liang Ming Li Bin Wang Yu-Zhao Wang Xue-Song Li Wan-Xu Wei Xue-Ya Gou Ya-Nan Ding Zhe Zhang Yu-Ke Li Xue-Yuan Liu Prof. Yong-Min Liang 《Angewandte Chemie (International ed. in English)》2023,62(28):e202304447
The aryl-to-vinyl nickel 1,4-migration (1,4-Ni migration) reaction has been reported for the first time. The generated alkenyl Ni species undergo a reductive coupling reaction with unactivated brominated alkanes affording a series of trisubstituted olefins. This tandem reaction exhibits mild conditions, a broad substrate scope, high regioselectivity, and excellent Z/E stereoselectivity. A series of controlled experiments have shown that the critical 1,4-Ni migration process is reversible. In addition, the alkenyl nickel intermediates obtained after migration are highly Z/E stereoselective and do not undergo Z/E isomerization. The obtained trace isomerization products are caused by the instability of the product. 相似文献
118.
Qian Lai Rongshan Zhuang Kun Zhang Tai Wu Lin Xie Dr. Rongjun Zhao Lei Yang Prof. Yang Wang Prof. Yong Hua 《Angewandte Chemie (International ed. in English)》2023,62(31):e202305670
Lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) has been identified as the most used and effective p-dopant for hole transport layer (HTL) in perovskite solar cells (PSCs). However, the migration and agglomeration of Li-TFSI in HTL negatively impact PSCs performance and stability. Herein, we report an effective strategy for adding a liquid crystal organic small molecule (LQ) into Li-TFSI doped (2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′- spirobifluorene (Spiro-OMeTAD) HTL. It was found that the introduction of LQ into Spiro-OMeTAD HTL can efficiently enhance the charge carrier extraction and transportation in device, which can strongly retard the charge carrier recombination in device. Consequently, the PSCs efficiency is significantly enhanced to 24.42 % (Spiro-OMeTAD+LQ) from 21.03 % (Spiro-OMeTAD). The chemical coordination between LQ and Li-TFSI can strongly confine Li+ ions migration and agglomeration of Li-TFSI, thus, achieving the enhanced device stability. Only a 9 % efficiency degradation is observed for un-encapsulated device prepared with Spiro-OMeTAD and LQ after 1700 h under air environment, while the efficiency drops by 30 % for the reference device. This work provides an effective strategy for improving the efficiency and stability of PSCs, and gives some important insights for understanding intrinsic hot carriers dynamics for perovskite-based optoelectronic devices. 相似文献
119.
Yuntao Tang Yige Zhang Xi Chen Xiaowen Xie Ning Zhou Dr. Zhifeng Dai Prof. Dr. Yubing Xiong 《Angewandte Chemie (International ed. in English)》2023,62(4):e202215722
Thermally induced reversible up/down migration of poly(ionic liquid)s (PILs) in aqueous two-phase systems (ATPSs) was achieved for the first time in this study. Novel ATPSs were fabricated using azobenzene (Azo)- and benzyl (Bn)-modified PILs, and their upper and lower phases could be easily tuned using the grafting degree (GD) of the Azo and Bn groups. Bn-PIL with higher GDBn could go up into the upper phase and Azo-PIL come down to the lower phase when the temperature increased (>65 °C); this behavior was reversed at lower temperatures. Moreover, a reversible two-phase/single-phase transition was realized under UV irradiation. Experimental and simulation results revealed that the difference in the hydration capacity between Bn-PIL and Azo-PIL accounted for their unique phase-separation behavior. A versatile platform for fabricating ATPSs with tunable stimuli-responsive behavior can be realized based on our findings, which can broaden their applications in the fields of smart separation systems and functional material development. 相似文献
120.
为研究食品接触用纸中铅、砷迁移规律,选择4批次食品接触用纸,通过测定其在不同介质(人造自来水、50%乙醇和4%乙酸三种模拟物)、不同加热方式[常温(22℃)、加热(70℃)、模拟微波(98℃)、实际微波加热]等条件下铅、砷迁移量来考察其迁移规律。结果表明,50%乙醇模拟物中,4个样品铅、砷迁移均未检出。4个样品在自来水和4%乙酸模拟物中,模拟微波15min条件下的铅、砷迁移量高于或接近常温10d条件,铅、砷迁移受温度影响较大,2#和4#两个样品实际微波条件下铅迁移量高于模拟微波条件迁移量的2倍,实际微波加热条件比模拟微波加热更严苛。 相似文献