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991.
The reaction of NF4+SbF6− with alkali metal nitrates in either CH3CN or SO2 solution at low temperatures produces FONO2 in quantitative yield. Attempts were unsuccessful to prepare FONO from NF4SbF6 and KNO2 in an analogous manner. 相似文献
992.
Mathematical Programming - It is a challenging task to fairly compare local solvers and heuristics against each other and against global solvers. How does one weigh a faster termination time... 相似文献
993.
Timo Berthold 《Mathematical Programming Computation》2014,6(1):33-54
This article introduces rens, the relaxation enforced neighborhood search, a large neighborhood search algorithm for mixed integer nonlinear programs (MINLPs). It uses a sub-MINLP to explore the set of feasible roundings of an optimal solution $\bar{x}$ of a linear or nonlinear relaxation. The sub-MINLP is constructed by fixing integer variables $x_j$ with $\bar{x} _{j} \in \mathbb {Z}$ and bounding the remaining integer variables to $x_{j} \in \{ \lfloor \bar{x} _{j} \rfloor , \lceil \bar{x} _{j} \rceil \}$ . We describe two different applications of rens: as a standalone algorithm to compute an optimal rounding of the given starting solution and as a primal heuristic inside a complete MINLP solver. We use the former to compare different kinds of relaxations and the impact of cutting planes on the so-called roundability of the corresponding optimal solutions. We further utilize rens to analyze the performance of three rounding heuristics implemented in the branch-cut-and-price framework scip. Finally, we study the impact of rens when it is applied as a primal heuristic inside scip. All experiments were performed on three publicly available test sets of mixed integer linear programs (MIPs), mixed integer quadratically constrained programs (MIQCPs), and MINLP s, using solely software which is available in source code. It turns out that for these problem classes 60 to 70 % of the instances have roundable relaxation optima and that the success rate of rens does not depend on the percentage of fractional variables. Last but not least, rens applied as primal heuristic complements nicely with existing primal heuristics in scip. 相似文献
994.
The category of dendroidal sets is an extension of that of simplicial sets, suitable for defining nerves of operads rather than just of categories. In this paper, we prove some basic properties of inner Kan complexes in the category of dendroidal sets. In particular, we extend fundamental results for simplicial sets of Boardman and Vogt, of Cordier and Porter, and of Joyal to dendroidal sets. 相似文献
995.
Eike Jahnke Dr. Jan Weiss Sonja Neuhaus Tobias N. Hoheisel Holger Frauenrath Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(2):388-404
A series of functional iodoacetylenes was prepared and converted into the corresponding diacetylene‐substituted amino acids and peptides via Pd/Cu‐promoted sp–sp carbon cross‐coupling reactions. The unsymmetrically substituted diacetylenes can be incorporated into oligopeptides without a change in the oligopeptide strand's directionality. Thus, a series of oligopeptide‐based, amphiphilic diacetylene model compounds was synthesized, and their self‐organization as well as their UV‐induced topochemical polymerizability was investigated in comparison to related polymer‐substituted macromonomers. Solution‐phase IR spectroscopy, gelation experiments, and UV spectroscopy helped to confirm that a minimum of five N‐H???O?C hydrogen‐bonding sites was required in order to obtain reliable aggregation into stable β‐sheet‐type secondary structures in organic solvents. Furthermore, the non‐equidistant spacing of these hydrogen‐bonding sites was proven to invariably lead to β‐sheets with a parallel β‐strand orientation, and the characteristic IR‐spectroscopic signatures of the latter in organic solution was identified. Scanning force micrographs of the organogels revealed that compounds with six hydrogen‐bonding sites gave rise to high aspect ratio nanoscopic fibrils with helical superstructures but, in contrast to the related macromonomers, did not lead to uniform supramolecular polymers. The UV‐induced topochemical polymerization within the β‐sheet aggregates was successful, proving parallel β‐strand orientation and highlighting the effect of the number and pattern of N‐H???O?C hydrogen‐bonding sites as well as the hydrophobic residue in the molecular structure on the formation of higher structures and reactivity. 相似文献
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999.
J. C. Hostetter H. S. Roberts R. B. Sosman A. Stähler E. Tiede F. Richter R. Peters H. M. Goodwin L. L. de Koninck J. M. Kolthoff W. D. Treadwell L. Weiss Schindler H. Willard Florence Fenwick J. F. King R. N. Washburne R. G. Gustavson C. W. Knudson Th. F. Buehrer O. E. Schupp B. S. Evans E. Zintl und P. Drossbach 《Fresenius' Journal of Analytical Chemistry》1928,75(1-2):47-63
Ohne Zusammenfassung 相似文献
1000.
Berthold König 《Monatshefte für Chemie / Chemical Monthly》1902,23(5):469-478
Ohne ZusammenfassungEs sei mir gestattet, meinem hochverehrten Lehrer, dem Herrn Hofrath Prof. Ad. Lieben, meinen innigsten Dank für die mir bei der Ausführung dieser Arbeit gütigst ertheilten Rathschläge auszusprechen. Auch Herrn Dr. C. Pomeranz fühle ich mich verpflichtet, für die Förderung meiner Arbeit wärmstens zu danken. 相似文献