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1.
Astrid Baumann 《Mathematische Semesterberichte》1998,45(2):167-188
Zusammenfassung. Mit Hilfe der projektiven Geometrie werden neuartige Summationsformeln hergeleitet, die die Tschebyscheff-Polynome und modifizierte Polynome enthalten; z. B. gilt für alle :
Daraus ergeben sich wiederum interessante Summationsformeln für die Hyperbelfunktionen; es gilt z. B. für positive reelle
Zahlen t:
Eingegangen am 28.02.96, revidierte Fassung am 25.08.97 / Angenommen am 09.10.97 相似文献
2.
Simulation of coupled chemical reactions and fluid flow in porous sedimentary basins over long time periods is a numerical
challenge. Most models representing such a physical problem are solved as PDEs where efficient timestepping with controlled
error is difficult. We use the differential algebraic equation system approach where robust adaptive timestepping algorithms
are available in the solvers, e.g., RADAU5 and DASSL. Mathematical and numerical models for coupled chemical reactions and
fluid flow are derived. The models have several interesting properties, e.g., strong nonlinearities and stiffness, which are
discussed. We test the performance of our code.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
Anette Munch Elmr Patric Jannasch 《Journal of polymer science. Part A, Polymer chemistry》2006,44(7):2195-2205
Methacrylate‐functionalized poly(ethylene oxide‐co‐ethylene carbonate) macromonomers were prepared in two steps by the anionic ring‐opening polymerization of ethylene carbonate at 180 °C, with potassium methoxide as the initiator, followed by the reaction of the terminal hydroxyl groups of the polymers with methacryloyl chloride. The molecular weight of the polymer went through a maximum after approximately 45 min of polymerization, and the content of ethylene carbonate units in the polymer decreased with the reaction time. A polymer having a number‐average molecular weight of 2650 g mol?1 and an ethylene carbonate content of 28 mol % was selected and used to prepare a macromonomer, which was subsequently polymerized by UV irradiation in the presence of different concentrations of lithium bis(trifluoromethanesulfonyl)imide salt. The resulting self‐supportive crosslinked polymer electrolyte membranes reached ionic conductivities of 6.3 × 10?6 S cm?1 at 20 °C. The coordination of the lithium ions by both the ether and carbonate oxygens in the polymer structure was indicated by Fourier transform infrared spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2195–2205, 2006 相似文献
4.
Lukin O Müller WM Müller U Kaufmann A Schmidt C Leszczynski J Vögtle F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(15):3507-3517
The readily available in gram quantities tris(allyloxy)knot of the amide-type 5 (knotane) can be completely and partially deprotected with nBu(3)SnH in the presence of a palladium catalyst resulting in hydroxyknotanes 7-9. These, in turn, react with diethylchlorophosphate giving rise to knotanes equipped with between one and three phosphoryl groups. Sulfonylation of bis(allyloxy)monohydroxyknotane 8 with p-toluenesulfonyl chloride and, following removal of one or two allyl groups from the intermediate monosulfonate 13, give rise to sulfonyloxy-allyloxy-hydroxy- and sulfonyloxy-dihydroxy-knotanes 15 and 14, respectively. This provides a convenient method for the preparation of knotanes with any substitution pattern. All new knotanes have been isolated in preparative amounts and as highly pure substances with an exception of allyloxy-dihydroxyknotane 9. This compound could only be obtained as a mixture with the corresponding monohydroxy-derivative 8. The structures of all synthesized compounds were established by means of FAB and MALDI TOF mass spectrometry, (1)H and (31)P NMR spectroscopy. The triphosphorylated knotane 10 exhibits high solubility in alcohols, allowing its complete enantiomeric resolution with a commercially available chiral HPLC column. (1)H,(1)H DQF-COSY correlation spectroscopy along with H/D exchange experiments and ab initio calculations provided the first detailed (1)H NMR signal assignments of knotanes in [D(6)]DMSO solution. The combination of variable temperature (1)H and (31)P NMR spectroscopy and molecular modeling has been applied to study the conformational behavior of the new knotanes in different solvents. It has been shown that in DMSO solution at room temperature knotanes exist in a relatively rigid nonsymmetrical conformation similar to that found in the solid state while faster conformational exchange leading to the average D(3) symmetrical structure was detected in a number of other solvents. 相似文献
5.
Campa C Oust A Skjåk-Braek G Paulsen BS Paoletti S Christensen BE Ballance S 《Journal of chromatography. A》2004,1026(1-2):271-281
The average degree of polymerisation (DP) and distribution of oligosaccharides in partially acid hydrolysed mannuronans were quantitatively evaluated by 1H NMR, electrospray ionisation mass spectrometry (ESI-MS), micellar electrokinetic capillary chromatography with UV detection (MEKC-UV), and high-pressure anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Our investigation shows that 1H NMR, MEKC-UV and, in particular, HPAEC-PAD can be used as quantitative tools to aid the investigation of polysaccharide structure, function and synthesis. For the latter two techniques, especially, this represents a significant new development as it enables calculation of the quantity of individual oligomers of nominal DP by direct analysis of a defined oligomer mixture. Appropriate statistical averages of number and weight distributions were also calculated and found to fit very well to predicted Kuhn distributions that assume random depolymerisation. 相似文献
6.
Martina Dotzler Astrid Schmidt Jochen Ellermann Falk A. Knoch Matthias Moll Walter Bauer 《Polyhedron》1996,15(24):4425-4433
BiBr3 or SbI3 react at 20°C with LiN(PPh2)2 (1) to give elementary Bi or Sb and the P---P coupled phosphazene ligand Ph2P---N=PPh2---PPh2=N---PPh2 (2). The reaction of AsI3 with 1 at room temperature formed yellow needles of the eight-membered heterocycle
(3), whereas AsI3 interacted at 80°C with 1 in the molar ratio of 1:3 to give elementary arsenic and 2. Treatment of AsI3 and 1 at 20°C in a 1:2 stoichiometry yielded the seven-membered, cyclic arsenium(I) salt I·4THF (5·4THF), which was characterized by elemental analysis, conductivity, mass, IR and NMR spectroscopy and single-crystal X-ray structural analysis. 相似文献
7.
Astrid Döppenschmidt 《Czechoslovak Journal of Physics》1995,45(7-8):657-661
0-production in the system12C+12C was studied with the two-arm photon spectrometer TAPS at projectile energies of 800 and 1000 MeV/u. The experiments focus on the determination of the cross sections and the correspondingp
t
-distributions. The results will extend the existing systematics of
0-production in heavy-ion collisions to a system with small mass.Presented at the International School-Workshop Relativistic Heavy-Ion Physics, Prague (Czech Republic), 19–23 September 1994. 相似文献
8.
9.
Mikkelsen LM Hernáiz MJ Martín-Pastor M Skrydstrup T Jiménez-Barbero J 《Journal of the American Chemical Society》2002,124(50):14940-14951
The conformational properties of the C-glycosyl analogue of the core trisaccharide alpha-D-Man-(1 --> 3)-[alpha-D-Man-(1 --> 6)]-D-Man in solution have been carefully analyzed by a combination of NMR spectroscopy and time-averaged restrained molecular dynamics. It has been found that both the alpha-1,3- and the alpha-1,6-glycosidic linkages show a major conformational averaging. Unusual Phi ca. 60 degrees orientations for both Phi torsion angles are found. Moreover, a major conformational distinction between the natural compound and the glycomimetic affects to the behavior of the omega(16) torsion angle around the alpha-1 --> 6-linkage. Despite this increased flexibility, the C-glycosyl analogue is recognized by three mannose binding lectins, as shown by NMR (line broadening, TR-NOE, and STD) and surface plasmon resonance (SPR) methods. Moreover, a process of conformational selection takes place, so that these lectins probably bind the glycomimetic similarly to the way they recognize the natural analogue. Depending upon the architecture and extension of the binding site of the lectin, loss or gain of binding affinity with respect to the natural analogue is found. 相似文献
10.
Rhodococcus equi A4, Rhodococcus erythropolis NCIMB 11540 and Rhodococcus sp. R312 were investigated towards their ability to produce β-amino amides and acids from β-amino nitriles. The microorganisms show comparable trends: five-membered alicyclic 2-amino nitriles were transformed significantly faster than the six-membered compounds and the products of trans-2-amino nitriles (amides and acids) were formed considerably faster than the cis-counterparts (amides). The trans-five membered nitriles gave the amides (1b, 5b) in excellent enantiomeric excess (94-99%), the biotransformation of trans-six membered substrates resulted in the formation of the acid (3c, 7c) in excellent ee (87-99%). The ee's of the cis-compounds were throughout lower. Fifteen new substances were synthesized and characterized in the course of this work. 相似文献