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111.
Ulrich Herber Birgit Weberndrfer Helmut Werner 《Angewandte Chemie (International ed. in English)》1999,38(11):1609-1613
Significantly different coordination spheres are displayed by the two central atoms of 2 , the first representative of a novel type of mixed-valence dinuclear Rh0–RhII compound, which was synthesized from the stibane-bridged complex 1 . The Rh−Rh distance determined by an X-ray crystal structure analysis of 2 indicates a metal–metal interaction between the two metal centers. 相似文献
112.
Flix Zamora Pilar Amo-Ochoa Birgit Fischer Arnd Schimanski Bernhard Lippert 《Angewandte Chemie (International ed. in English)》1999,38(15):2274-2275
Not only UV radiation can bring about the dimerization of the pyrimidine nucleobase uracil, a metal ion can as well! The reaction proceeds by a reductive elimination process of two cis-oriented uracil entities, each bonded to AuIII through C5 [Eq. (a)]. R/R′=H/CH3, CH3/CH3, H,C5H9O4 相似文献
113.
Matthias Wittemann Steffen Kelch Jürgen Blaul Peter Hickl Birgit Guilleaume Gisela Brodowski Andreas Horvath Matthias Ballauff Matthias Rehahn 《Macromolecular Symposia》1999,142(1):43-59
The synthesis and the solution behavior of rigid, rodlike cationic polyelectrolytes having (i) poly(p-phenylene) backbones and (ii) main chains composed of 4,4“-bis(2,2′:6′,2”-terpyridine)2′,5′-dihexyl-p-terphenyl moieties and ruthenium(II) centers are presented. All these polymers are shown to have a homogeneous constitution and degrees of polymerization of up to Pn ≈ 70. Their solution properties were analyzed using viscosimetry, small-angle X-ray scattering (SAXS) and osmometry. Pronounced polyelectrolyte effects were found in salt-free solutions using viscosimetry. Small-angle X-ray scattering demonstrated directly the strong correlation of the counterions and the macroions. The osmotic coefficients measured in salt-free solution as function of polyelectrolyte concentration were found to be lower than predicted by the cell model. 相似文献
114.
Birgit Reiter Marion Lechner Eberhard Lorbeer Reiner Aichholz 《Journal of separation science》1999,22(9):514-520
A rapid method for the isolation and quantitative determination of wax esters in vegetable oils was developed. For the first time wax esters in oils were separated from the triglyceride matrix by means of solid-phase extraction, which allows rapid sample preparation in parallel and therefore a high sample throughput. The thus obtained wax ester fractions of fennel and caraway seed oils were analyzed by high temperature gas chromatography. GC-MS analyses were carried out using electron impact ionization in order to characterize the wax ester fraction. With respect to the results of the GC-MS analyses different isomers of saturated wax esters with the same carbon number were observed. Additional monounsaturated wax esters with an unsaturated fatty acid moiety were identified. 相似文献
115.
116.
Olga N. Zefirova Evgeniya V. Nurieva Birgit Wobith Vladimir V. Gogol Nikolay A. Zefirov Andrei V. Ogonkov Dmitrii V. Shishov Nikolay S. Zefirov Sergei A. Kuznetsov 《Molecular diversity》2017,21(3):547-564
Tubuloclustin [N-(7-adamant-2-yloxy-7-oxoheptanoyl)-N-deacetylcolchicine], a highly cytotoxic anti-tubulin compound is known for its ability to promote microtubule disassembly followed by the formation of tubulin clusters of unique morphology. Three series of antimitotic agents related to tubuloclustin were designed and synthesized in order to enhance the molecular diversity of “tubuloclustin-like” family of compounds. The series of compounds with modified adamantane moiety was highly potent in cytotoxic effect on human lung carcinoma A549 cells (EC50 = 6–400 nM) and was active in affecting the microtubule arrays and induction of strong tubulin clusterization. In two other sets of compounds, the colchicine moiety of tubuloclustin was replaced by podophyllotoxin or combretastatin A-4. All combretastatin A-4 derivatives displayed noticeable cytotoxic activity (\(\hbox {EC}50=0.8{-}1.6\,\upmu \hbox {M}\)) but their effect on microtubules depended on the position of the linker attachment. Podophyllotoxin derivatives were also toxic to A549 cells (\(\hbox {EC}50=0.38{-}0.50\,\upmu \hbox {M}\)) and caused both microtubule depolymerization and some tubulin clustering. The data obtained gave additional evidence that the whole panel of C7-colchicine, podophyllotoxin and combretastatin derivatives could manifest clustering effect, and the strength of this effect correlated with cytotoxic activity of the compounds. 相似文献
117.
Background
Reward value and uncertainty are represented by dopamine neurons in monkeys by distinct phasic and tonic firing rates. Knowledge about the underlying differential dopaminergic pathways is crucial for a better understanding of dopamine-related processes. Using functional magnetic resonance blood-oxygen level dependent (BOLD) imaging we analyzed brain activation in 15 healthy, male subjects performing a gambling task, upon expectation of potential monetary rewards at different reward values and levels of uncertainty. 相似文献118.
119.
Birgit Perret 《Polymer Degradation and Stability》2009,94(12):2204-2212
In this second of a series of two papers, the fire behaviour of halogen-free flame retarded polycarbonate (PC) blends with different impact modifiers was studied. The impact modifiers were acrylonitrile-butadiene-styrene (ABS), a poly(n-butyl acrylate) rubber (PBA) with a poly(methyl methacrylate) (PMMA) shell and two silicone-acrylate rubbers consisting of PBA with different amounts of polydimethylsiloxane (PDMS) and different shell materials (PMMA and styrene-acrylonitrile, SAN). The flame retardant was bisphenol A bis(diphenyl phosphate) (BDP). Flammability was determined by LOI and UL 94. The burning behaviour under forced flaming conditions was studied by cone calorimeter under different external irradiations and by pyrolysis combustion flow calorimeter measurements. The exchange of ABS with the pure acrylate rubber worsened flammability, while similar results were obtained in cone calorimeter measurements. The exchange of ABS with the silicone-acrylate rubbers is promising, particularly with higher amounts of PDMS. In flammability tests strongly enhanced LOI values were obtained and therefore silicone-acrylate rubbers look like promising alternatives for ABS. 相似文献
120.
Markus Ganzera Ivo Nischang Christian Siegl Birgit Senzenberger Frantisek Svec Hermann Stuppner 《Electrophoresis》2009,30(21):3757-3763
Two microscale separation techniques for the analysis of bioactive naphthoquinones in Eleutherine americana were developed and validated. By MEKC four compounds (eleuthoside B, isoeleutherin, eleutherol and eleutherinoside A) could be determined in plant extracts using an aqueous electrolyte solution composed of 25 mM sodium tetraborate, 50 mM sodium cholate and 20% THF. CEC on a polymeric methacrylate‐based monolith with strong cationic properties showed promising results, as it additionally enabled the separation of two enantiomers, eleutherin and isoeleutherin. The mobile phase for CEC experiments comprised 3 mM ammonium formate in a mixture of ACN and water. At an applied voltage of ?25 kV, all five markers were baseline separated in less than 12 min. Both methods were successfully validated for linearity (MEKC: R2≥0.999; CEC: R2≥0.997), sensitivity (MEKC: LOD=4–5 μg/mL; CEC: LOD=2–8 μg/mL), accuracy (MEKC: 96.5–102.7% recovery; CEC: 97.1–103.5% recovery) and precision (MEKC: σrel≤2.43%; CEC: σrel≤2.21%). The quantitative analysis of naphthoquinone derivatives in several E. americana samples showed that both methods are suitable for practical applications, because the results were well comparable to those obtained by established techniques such as HPLC. 相似文献