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1.
Ralf Freund Christos Allagiannis Peter Schnholzer Karl Bernauer 《Helvetica chimica acta》1994,77(3):615-621
A crude hydrate 6 and a crystalline hemiacetal 7 of glyoxylamide 4 were prepared from crotonamide 5 (Scheme 2). Particularly hemiacetal 7 , but also 6 and the ‘dimer’ 8 (obtained from 7 ) may serve as homochiral auxiliaries. The structure of 8 was determined by X-ray analysis. By arenesulfonyl halides, tryptimines 12–14 of 4 were diastereoselectively transformed into spirotricycles 15–17 and 19 . 相似文献
2.
We evaluate the practical relevance of two measures of conic convex problem complexity as applied to second-order cone problems solved using the homogeneous self-dual (HSD) embedding model in the software SeDuMi. The first measure we evaluate is Renegar's data-based condition measure C(d), and the second measure is a combined measure of the optimal solution size and the initial infeasibility/optimality residuals denoted by S (where the solution size is measured in a norm that is naturally associated with the HSD model). We constructed a set of 144 second-order cone test problems with widely distributed values of C(d) and S and solved these problems using SeDuMi. For each problem instance in the test set, we also computed estimates of C(d) (using Peña’s method) and computed S directly. Our computational experience indicates that SeDuMi iteration counts and log (C(d)) are fairly highly correlated (sample correlation R = 0.675), whereas SeDuMi iteration counts are not quite as highly correlated with S (R = 0.600). Furthermore, the experimental evidence indicates that the average rate of convergence of SeDuMi iterations is affected by the condition number C(d) of the problem instance, a phenomenon that makes some intuitive sense yet is not directly implied by existing theory. 相似文献
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Budde F Hamza AV Ferm PM Ertl G Weide D Andresen P Freund H 《Physical review letters》1988,60(15):1518-1521
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Although stable binary Pd carbonyls are unknown in the gas phase, we found strong evidence for a stable carbonyl-like Pd compound on an oxide surface: by in situ vapour deposition of Pd at a rate of 2 × 1013 atoms s−1 cm−2 onto an alumina substrate (90 K) at a pressure of 2 × 10−6 mbar CO, a binary compound of Pd and CO is formed which is stable up to 190 K. As substrate serves a well-ordered aluminium oxide film grown on a NiAl(110) single crystal surface. The system was characterized under UHV (ultrahigh vacuum) conditions by means of TDS, LEED, UPS and XPS in a coverage range between 1.4 × 1014 Pd atoms cm−2 and 1.4 × 1016 Pd atoms cm−2. The decomposition at 190 K results in the formation of metallic Pd particles and is accompanied by a sharp and dominant feature in the thermal desorption spectra. 相似文献
8.
Recksiedler CL Deore BA Freund MS 《Langmuir : the ACS journal of surfaces and colloids》2005,21(8):3670-3674
Poly(anilineboronic acid) thin films are treated under various conditions to achieve substitution or condensation reactions involving the boronic acid moiety. These reactions are studied with polarization modulated infrared reflection absorption spectroscopy, cyclic voltammetry, and UV-vis spectroscopy. The results suggest the single-step formation of substituted polyanilines, such as poly(hydroxyaniline), halogenated polyanilines, and mercury chloride-substituted polyaniline. A condensation reaction of poly(anilineboronic acid) with cis-diol compounds in aqueous solution, as well as with phenylenebisboronic acid and salycilamide in THF, indicates the formation of boronic esters. The latter reactions appear to be a good entry point for the formation of complex or supramolecular polymer structures. 相似文献
9.
Ehret R Baumann W Brischwein M Lehmann M Henning T Freund I Drechsler S Friedrich U Hubert ML Motrescu E Kob A Palzer H Grothe H Wolf B 《Fresenius' Journal of Analytical Chemistry》2001,369(1):30-35
The identification of drug targets for pharmaceutical screening can be greatly accelerated by gene databases and expression studies. The identification of leading compounds from growing libraries is realized by high throughput screening platforms. Subsequently, for optimization and validation of identified leading compounds studies of their functionality have to be carried out, and just these functionality tests are a limiting factor. A rigorous preselection of identified compounds by in vitro cellular screening is necessary prior to using the drug candidates for the further time consuming and expensive stage, e.g. in animal models. Our efforts are focused to the parallel development, adaptation and integration of different microelectronic sensors into miniaturized biochips for a multiparametric, functional on-line analysis of living cells in physiologically environments. Parallel and on-line acquisition of data related to different cellular targets is required for advanced stages of drug screening and for economizing animal tests. 相似文献
10.
Mixtures of BCl3 and H2S are irradiated with 10.55 μm radiation (P(16) line of the 001–100 band of CO2) from a TEA laser. After several hours of irradiation it is found that the maximum 10B to 11B ratio of recovered gaseous boron containing material (primarily unreacted BCl3) is 0.413 ± 0.004. The corresponding ratio of the BCl3 starting material is 0.242 ± 0.002. The 10B concentration has therefore been increased from 19.5% to 29.2%. Further, by irradiating similar mixtures with 10.18 μm radiation (R(30) line of the same CO2 vibrational band) this ratio changes to 0.169 ± 0.002, the 10B concentration being lowered to 14.4%. All experiments are performed in a small static system and chemical procedures for recovering milligram quantities of BCl3 selectively enriched in either isotope are described. 相似文献