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31.
Momchilova S Tsuji K Itabashi Y Nikolova-Damyanova B Kuksis A 《Journal of separation science》2004,27(12):1033-1036
The ability of reversed-phase high-performance liquid chromatography (RP-HPLC) to separate some positionally isomeric disaturated and monounsaturated triacylglycerols (TAGs) as intact species is demonstrated for the first time. Mobile phases of acetonitrile modified with methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, acetone, or dichloromethane were tested for the separation of POP-PPO, PLP-PPL, PEP-PPE, and PDP-PPD (P-palmitic, O-oleic, L-linoleic, E-eicosapentaenoic, D-docosahexaenoic acid residue) on a single RP-HPLC column. The resolution improved with increasing number of double bonds in the acyl residues. While POP and PPO were only partially resolved, PDP and PPD were fully separated with all tested mobile phases, except those containing methanol. Also separated were the four TAGs having the same equivalent carbon number (ECN = 42), PEP, PPE, PDP, and PPD, on a single RP-HPLC column with mobile phase acetonitrile-2-propanol (70:30, v/v) at 0.8 mL/min. In all cases the isomer with the unsaturated acyl residue in either 1- or 3-position was retained more strongly than the respective 2-isomer. 相似文献
32.
The chiral separation of halogenated amino acids by ligand-exchange CE is described. Halogenated amino acids attracted increasing interest in recent years because of their physiological activities. Different chiral selectors, as there are L-4-hydroxyproline, L-histidine, and N-alkyl derivatives of L-4-hydroxyproline in form of their copper(II) complexes, are compared for their chiral recognition ability for halogenated amino acids. The influence of various parameters, such as selector concentration, pH, organic modifier, and field strength, on the resolution was investigated. All halogenated amino acids investigated were baseline-separated under optimized conditions. 相似文献
33.
Vyacheslav Z. Grines Dmitry S. Malyshev Olga V. Pochinka Svetlana Kh. Zinina 《Regular and Chaotic Dynamics》2016,21(2):189-203
It is well known that the topological classification of structurally stable flows on surfaces as well as the topological classification of some multidimensional gradient-like systems can be reduced to a combinatorial problem of distinguishing graphs up to isomorphism. The isomorphism problem of general graphs obviously can be solved by a standard enumeration algorithm. However, an efficient algorithm (i. e., polynomial in the number of vertices) has not yet been developed for it, and the problem has not been proved to be intractable (i. e., NPcomplete). We give polynomial-time algorithms for recognition of the corresponding graphs for two gradient-like systems. Moreover, we present efficient algorithms for determining the orientability and the genus of the ambient surface. This result, in particular, sheds light on the classification of configurations that arise from simple, point-source potential-field models in efforts to determine the nature of the quiet-Sun magnetic field. 相似文献
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V. A. Drebushchak Yu V. Seryotkin Svetlana N. Kokh Ella V. Sokol 《Journal of Thermal Analysis and Calorimetry》2013,114(2):777-783
Three natural minerals of ettringite group were investigated by TG to refine their chemical composition. Two samples are ettringite Ca5.97Mg0.01Sr0.02Al1.99Cr0.01(SO4)3(OH)12·23.7H2O and bentorite Ca5.99Mg0.01Cr1.95Al0.01Si0.03(SO4)2.82·(CO3)0.20(OH)12·19.4H2O, but the third one Ca5.99Na0.01Al1.38Si0.62(SO4)2.49·(CrO4)0.36·(CO3)0.46(OH)12·15.8H2O has found to be a solid solution among ettringite, thaumasite, and chromate-ettringite, not registered yet as a new mineral species. Similar phase is well known in concrete formed with Cr6+ admixture, but is found for the first time as a natural compound. X-ray single-crystal investigation allowed us to refine the structure and support substitution (SO4)2? ? (CrO4)2? in natural minerals of ettringite group. 相似文献
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Galina V. Pazynina Svetlana V. Tsygankova Ivan M. Ryzhov Alexander S. Paramonov V. Bovin 《Mendeleev Communications》2018,28(4):421-422
A convenient synthesis of Fucα1-2Galβ1-3GalNAcβ-OCH2CH2CH2NH2 (trisaccharide H type 4) is described. This glycan is the terminal part of glycosphingolipids globo-H and fucosyl-GM1 known as cancer-associated carbohydrate antigens. 相似文献