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排序方式: 共有216条查询结果,搜索用时 15 毫秒
101.
Kateřina Plachká Veronika Pilařová Ondřej Horáček Taťána Gazárková Hana Kočová Vlčková Radim Kučera Lucie Nováková 《Journal of separation science》2023,46(18):2300431
Within this review, we thoroughly explored supercritical fluid chromatography (SFC) columns used across > 3000 papers published from the first study carried out under SFC conditions in 1962 to the end of 2022. We focused on the open tubular capillary, packed capillary, and packed columns, their chemistries, dimensions, and trends in used stationary phases with correlation to their specific interactions, advantages, drawbacks, used instrumentation, and application field. Since the 1990s, packed columns with liquid chromatography and SFC-dedicated stationary phases for chiral and achiral separation are predominantly used. These stationary phases are based on silica support modified with a wide range of chemical moieties. Moreover, numerous unconventional stationary phases were evaluated, including porous graphitic carbon, titania, zirconia, alumina, liquid crystals, and ionic liquids. The applications of unconventional stationary phases are described in detail as they bring essential findings required for further development of the supercritical fluid chromatography technique. 相似文献
102.
In order to investigate the effect of presence of well defined nano-sized inorganic particles on the molecular mobility a
conformation statistics of polymer chains, well defined polystyrene (PS) and poly(methyl methacrylate) (PMMA) macromolecules
containing polyhedral oligomeric silsesquioxanes nanoparticles (POSS) were synthesized by copper-mediated atom transfer radical
polymerization (ATRP). Two approaches were used for the synthesis — the first involves POSS as the initiator of ATRP; the
second way considers an addition of POSS to the polymer (prepared by ATRP) with an appropriate functional group. Kinetics
of polymerization was determined using common analytical methods and it was compared to the polymerizations initiated by low-molecular
weight initiators, regarding the polymerization rate, initiation efficiency and polydispersity of the polymer. Efficiency
of the initiation with POSS-containing initiators was low, causing remnants of inseparable free POSS in polymer. The second
approach bypassed these disadvantages —POSS is connected to the polymer through a pending allyl group using the very efficient
hydrosilylation reaction.
Presented at the 1st Bratislava Young Polymer Scientists Workshop, Bratislava, 20–23 August 2007. 相似文献
103.
Stanislav Rádl Josef ?erný Ond?ej Klecán Jan Stach Lukáš Pla?ek Zuzana Mandelová 《Tetrahedron letters》2008,49(36):5316-5318
An efficient synthesis of licofelone, an anti-inflammatory drug currently undergoing phase-III clinical studies, based on Fenton-type radical alkylation of 2,3-dihydro-1H-pyrrolizine 3 with iodoacetonitrile or iodoacetates is reported. The iodoacetates can be replaced by NaI and by the corresponding bromoacetate. 相似文献
104.
Ondřej Došlý 《Applications of Mathematics》1997,42(3):195-212
We study polyconvex envelopes of a class of functions related to the function of Kohn and Strang introduced in [4]. We present an example of a function of this class for which the polyconvex envelope may be computed explicitly and we also point out some general features of the problem. 相似文献
105.
106.
MnO and Mn2O3 nanoparticles were prepared in air and argon atmosphere by thermal decomposition of nanocrystalline manganese carbonate synthesized by reaction of manganese(II) nitrate with glycerol. Samples were characterized using transmission electron microscopy, simultaneous thermal analysis and X-ray diffraction analysis. Average sizes of prepared nanoparticles were calculated from XRD patterns using Scherrer equation. Also, the conditions for decomposition of manganese carbonate were optimized to obtain optimal nanoparticle sizes. Due to suitable sizes of prepared nanoparticles and the initial material, this method can be used in a wide range of industrial applications. 相似文献
107.
We study pure radiation spacetimes of algebraic types O and N with a possible cosmological constant. In particular, we present
explicit transformations which put these metrics, that were recently re-derived by Edgar, Vickers and Machado Ramos, into
a general Ozsváth–Robinson–Rózga form. By putting all such metrics into the unified coordinate system we confirm that their
derivation based on the GIF formalism is correct. We identify only few trivial differences. 相似文献
108.
Petr Jansa Ondřej Hradil Ondřej Baszczyňski Martin Dračínský Blanka Klepetářová Antonín Holý Jan Balzarini Zlatko Janeba 《Tetrahedron》2012,68(3):865-871
Polysubstituted pyrimidinylphosphonic and 1,3,5-triazinylphosphonic acids with potential biological properties were prepared in high yields by the microwave-assisted Michaelis–Arbuzov reaction of trialkyl phosphite with the corresponding halopyrimidines and halo-1,3,5-triazines, respectively, followed by the standard deprotection of the phosphonate group using TMSBr in acetonitrile. 4,6-Diamino-5-chloropyrimidin-2-ylphosphonic acid (7a) was found to exhibit a weak to moderate anti-influenza activity (28–50 μM) and may represent a novel hit for further SAR studies and antiviral improvement. 相似文献
109.
Ond?ej Došlý 《Journal of Mathematical Analysis and Applications》2006,323(1):426-440
We investigate oscillatory properties of the half-linear second order differential equation
110.
The longstanding open problem of approximating all singular vertex couplings in a quantum graph is solved. We present a construction in which the edges are decoupled; an each pair of their endpoints is joined by an edge carrying a δ potential and a vector potential coupled to the “loose” edges by a δ coupling. It is shown that if the lengths of the connecting edges shrink to zero and the potentials are properly scaled, the limit can yield any prescribed singular vertex coupling, and moreover, that such an approximation converges in the norm-resolvent sense. 相似文献