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Surmont R Verniest G De Schrijver M Thuring JW ten Holte P Deroose F De Kimpe N 《The Journal of organic chemistry》2011,76(10):4105-4111
Fluorinated pyrazoles bearing additional functional groups that allow further functionalization are of considerable interest as building blocks in medicinal chemistry. The developed synthetic strategy for new 3-amino-4-fluoropyrazoles consists of a monofluorination of β-methylthio-β-enaminoketones using 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) toward the corresponding monofluorinated enaminoketones, followed by condensation with different hydrazines. 相似文献
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The Ramanujan Journal - We obtain a condition describing when the quasimodular forms given by the Bloch–Okounkov theorem as q-brackets of certain functions on partitions are actually modular.... 相似文献
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High pressure synthesis of late rare earth RFeAs(O,F) superconductors; R = Tb and Dy 总被引:1,自引:0,他引:1
Bos JW Penny GB Rodgers JA Sokolov DA Huxley AD Attfield JP 《Chemical communications (Cambridge, England)》2008,(31):3634-3635
New TbFeAs(O,F) and DyFeAs(O,F) superconductors with critical temperatures T(c) = 46 and 45 K and very high critical fields, >/=100 T, have been prepared at 1100-1150 degrees C and 10-12 GPa, demonstrating that high pressure may be used to synthesise late rare earth derivatives of the recently reported RFeAs(O,F) (R = La-Nd, Sm, Gd) high temperature superconductors. 相似文献
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Jan-Willem Lamberink Dr. Paul D. Boyle Dr. Joe B. Gilroy Dr. James J. Noël Dr. Johanna M. Blacquiere Dr. Paul J. Ragogna 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(52):e202201565
Reactivity of primary phosphines with two stoichiometric equivalents of imine results in the formation of bis-α-aminophosphines ( 2 a – e ), which can be subsequently oxidized in the presence of S8 or H2O2 to generate air stable bis-α-aminophosphine sulfides ( 2 b – m(S/O) ). To elucidate the mechanism of this three-component reaction, Hammett analysis, kinetic isotope effect (KIE), and trapping experiments were performed. Ultimately a P(V)–P(III) tautomerization is invoked, followed by nucleophilic attack by the P(III) species to generate the desired products. 相似文献
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Cytoplasmic streaming circulates the contents of large eukaryotic cells, often with complex flow geometries. A largely unanswered question is the significance of these flows for molecular transport and mixing. Motivated by "rotational streaming" in Characean algae, we solve the advection-diffusion dynamics of flow in a cylinder with bidirectional helical forcing at the wall. A circulatory flow transverse to the cylinder's long axis, akin to Dean vortices at finite Reynolds numbers, arises from the chiral geometry. Strongly enhanced lateral transport and longitudinal homogenization occur if the transverse Péclet number is sufficiently large, with scaling laws arising from boundary layers. 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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Benjamins JW Thuresson K Nylander T 《Langmuir : the ACS journal of surfaces and colloids》2005,21(1):149-159
In the presented study we have developed and implemented a methodology for ellipsometry measurements at liquid interfaces that makes it possible to determine the amount adsorbed without assumptions of refractive index or thickness of the adsorbed layer. It was demonstrated that this is possible by combined measurements from different aqueous phases, H(2)O and D(2)O, which were shown to have sufficiently different refractive indices. The methodology was tested by studying adsorption of two types of nonionic poly(ethylene glycol) alkyl ether surfactants, C(n)H(2)(n)(+1)(OC(2)H(4))(m)OH or C(n)E(m) at the decane--aqueous interface, where C(12)E(5) was adsorbed from the oil phase and C(18)E(50) from the aqueous phase. The observed plateau values of the adsorbed amounts were 1.38 and 0.93 mg/m(2) for C(12)E(5) and C(18)E(50), respectively, which is in agreement with the corresponding values of 1.49 and 1.15 mg/m(2) obtained from applying the Gibbs equation to interfacial tension data for the same systems. We will briefly discuss the adsorption behavior in relation to the molecular structure of the surfactant and the phase behavior of the oil--surfactant--aqueous systems in relation to our experimental results. 相似文献
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Chitneni SK Serdons K Evens N Fonge H Celen S Deroose CM Debyser Z Mortelmans L Verbruggen AM Bormans GM 《Journal of chromatography. A》2008,1189(1-2):323-331
This study describes an efficient method using on-line solid-phase extraction (SPE) (Oasis HLB) for preparative HPLC purification of short-lived radiotracers for positron emission tomography (PET) and for HPLC analysis of radiotracers and their metabolites in cell homogenates, plasma and urine samples. The radiochemical purity of tracers (fluorine-18 labeled) purified using this method (Oasis column) was >99% compared to 90% when no Oasis column was used. Radiometabolites of several fluorine-18 and carbon-11-labeled tracers and one technetium-99m tracer were quantified in cell homogenates, plasma and urine samples. Samples were analyzed using Oasis column and analytical HPLC system without prior precipitation of proteins or removal of other biological matrices. The metabolites observed for the evaluated tracers were all polar relative to the unchanged tracer. The extraction repeatability was found to be good (RSD 2.2%) and recoveries of Oasis column/HPLC-injected radioactivity (plasma) were found to be high (mean recovery >91%). The same Oasis column was used for several times without back pressure build-up or decrease of the HPLC separation characteristics. 相似文献