排序方式: 共有22条查询结果,搜索用时 31 毫秒
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Fernanda V. Corrêa Sibele R.R. Comim Aline M. de Cesaro Aline A. Rigo Marcio A. Mazutti Haiko Hense J. Vladimir Oliveira 《The Journal of chemical thermodynamics》2011,43(1):34-38
The compound oryzanol available in the rice bran (oriza sativa) is well known for its antioxidant activity. Phase equilibrium data involving oryzanol in compressed fluids, hardly found in the literature, are important to provide the basis for the extraction and fractionation processes. In this sense, the aim of this work is to report phase equilibrium measurements for the system (γ-oryzanol + chloroform) in compressed propane. Phase equilibrium experiments were performed using the static synthetic method (cloud points transition data) in a high-pressure variable-volume view cell in the temperature range of 303 K to 353 K, pressures up to 17 MPa, for oryzanol overall mass fractions of 2 wt%, 5 wt% and 10 wt% in (propane + chloroform) mixtures. A complex phase behaviour comprising vapour–liquid, liquid–liquid, vapour–liquid–liquid, solid–liquid, solid–liquid–liquid, solid–liquid–liquid–vapour transitions were visually observed for the system studied. 相似文献
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On stable cutsets in claw-free graphs and planar graphs 总被引:4,自引:0,他引:4
A stable cutset in a connected graph is a stable set whose deletion disconnects the graph. Let and (claw) denote the complete (bipartite) graph on 4 and vertices. It is NP-complete to decide whether a line graph (hence a claw-free graph) with maximum degree five or a -free graph admits a stable cutset. Here we describe algorithms deciding in polynomial time whether a claw-free graph with maximum degree at most four or whether a (claw, )-free graph admits a stable cutset. As a by-product we obtain that the stable cutset problem is polynomially solvable for claw-free planar graphs, and also for planar line graphs.Thus, the computational complexity of the stable cutset problem is completely determined for claw-free graphs with respect to degree constraint, and for claw-free planar graphs. Moreover, we prove that the stable cutset problem remains NP-complete for -free planar graphs with maximum degree five. 相似文献
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Besma Mellah Rym Abidi Haiko Herchbach Kwanghyun No Jong Seung Kim Françoise Arnaud Hubscher Veronique 《Journal of inclusion phenomena and macrocyclic chemistry》2010,66(1-2):153-161
The binding properties of four amido derivatives of p-tetraphenyl tetrahomodioxacalix[4]arene towards alkali and alkaline-earth metal cations using UV-absorption spectrophotometry, 1H NMR and ESI-mass spectrometry techniques are reported. 相似文献
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Marquis A Smith V Harrowfield J Lehn JM Herschbach H Sanvito R Leize-Wagner E Van Dorsselaer A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(21):5632-5641
Double helicates are known to exhibit self-recognition characteristics determined by the coordination geometry of the metal involved as well as by the topicity of the ligands. Combining tridentate (terpyridine, T) or bidentate (bipyridine, B) subunits in a tritopic strand affords a set of ligands able to assemble by pairs to form double helicates, homo- or heterostranded, homo- or heterotopic, depending on the coordination properties of the metals involved. The four ligand strands, BBB, TTT, BBT, and TBT form constitutionally dynamic sets of double helicates with the metal ions Cu(I), Cu(II), and Zn(II); these helicates correspond to the correct coding of the BB, BT, and TT pairs for tetra-, penta-, and hexacoordinate Cu(I), Cu(II), and Zn(II) cations, respectively. 相似文献
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Stefan Wild Michael Fickert Aleksandra Mitrovic Vicent Lloret Christian Neiss Jos Alejandro Vidal‐Moya Miguel ngel Rivero‐Crespo Antonio Leyva‐Prez Katharina Werbach Herwig Peterlik Mathias Grabau Haiko Wittkmper Christian Papp Hans‐Peter Steinrück Thomas Pichler Andreas Grling Frank Hauke Gonzalo Abelln Andreas Hirsch 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5820-5826
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Herschbach H Brisach F Haddaoui J Saadioui M Leize E Van Dorsselaer A Arnaud-Neu F Böhmer V 《Talanta》2007,74(1):39-46
The binding of lanthanide(III) cations with organophosphorous ligands like CMPO and related calix[4]arene-based derivatives have been investigated using two experimental methods. The stability constants of the lanthanum, europium and ytterbium complexes were first determined in methanol by UV absorption spectrophotometry in the presence of nitrate or chloride anions. The results showed that the stoichiometry and the stability of the complexes formed depend on the position of the CMPO moieties either on the wide or the narrow rim of the calixarene scaffold, the nature of the medium, the conformational mobility of the ligands. Complexation of lanthanum was also followed by ESI-mass spectrometry in the same solvent. This method confirmed the stoichiometry of the complexes, giving also structural information, like coordination of anion or solvent molecules to the complexes, and allowed the calculation of distribution curves in good agreement with those derived from the spectrophotometric results. This is an important result showing that ESI-MS can be used to provide with quantitative information when absorption spectrophotometry is not applicable, i.e. for systems where complexation leads to weak spectral changes. 相似文献
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Three batches of leather samples were coloured with nine azo dyes that can yield eight proven or suspected carcinogenic aromatic
amines under reduction conditions. The samples were milled to grains and bottled in jars. A group of five laboratories has
established the mass fraction of the amines in a ring test using different analytical methods. The methods included a reduction
step in order to cleave the azo dyes into the aromatic amines. Quantification was by standard addition: sub-samples of the
leathers were spiked with known amounts of azo dyes of known purity. It was possible to establish the mass fractions of six
of the eight aromatic amines in three of the leather samples. 相似文献
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Dr. Mingchao Wang Dr. Gang Wang Dr. Chandrasekhar Naisa Dr. Yubin Fu Dr. Sai Manoj Gali Dr. Silvia Paasch Dr. Mao Wang Haiko Wittkaemper Dr. Christian Papp Prof. Eike Brunner Dr. Shengqiang Zhou Dr. David Beljonne Prof. Hans-Peter Steinrück Prof. Renhao Dong Prof. Xinliang Feng 《Angewandte Chemie (International ed. in English)》2023,62(46):e202310937
Electrochemical proton storage plays an essential role in designing next-generation high-rate energy storage devices, e.g., aqueous batteries. Two-dimensional conjugated covalent organic frameworks (2D c-COFs) are promising electrode materials, but their competitive proton and metal-ion insertion mechanisms remain elusive, and proton storage in COFs is rarely explored. Here, we report a perinone-based poly(benzimidazobenzophenanthroline) (BBL)-ladder-type 2D c-COF for fast proton storage in both a mild aqueous Zn-ion electrolyte and strong acid. We unveil that the discharged C−O− groups exhibit largely reduced basicity due to the considerable π-delocalization in perinone, thus affording the 2D c-COF a unique affinity for protons with fast kinetics. As a consequence, the 2D c-COF electrode presents an outstanding rate capability of up to 200 A g−1 (over 2500 C), surpassing the state-of-the-art conjugated polymers, COFs, and metal–organic frameworks. Our work reports the first example of pure proton storage among COFs and highlights the great potential of BBL-ladder-type 2D conjugated polymers in future energy devices. 相似文献