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991.
Gian Piero Spada Giovanni Lesa Giovanni Gottarelli Paolo De Maria Paolo Mariani 《Liquid crystals》1988,3(8):1031-1037
The kinetics of enolization of acetone, 3-pentanone, and 6-undecanone have been studied in lyotropic systems in the isotropic, nematic, and lamellar phases. The data, analysed in terms of spontaneous and acid-catalyzed rate constants, do not show any relevant influence of the physical nature of the phase. Effects are instead observed in relation to the length of the alkyl chains of the ketones and the type of the amphiphilic molecule. 6-undecanone has a surprising effect in stabilizing ordered mesophases. 相似文献
992.
993.
Paolo Buttà 《Letters in Mathematical Physics》1994,31(1):41-55
The convergence to a motion by mean curvature by diffusively scaling a nonlocal evolution equation, describing the macroscopic behavior of a ferromagnetic spin system with Kac interaction and Glauber dynamics has recently been proved. The convergence is proven up to the times when the motion by curvature is regular. Here we show the convergence at all times in the two-dimensional case. Since, in this case, the only singularity is the shrinking to a point of a closed curve, we verify that the curve actually disappears past the singularity. 相似文献
994.
Reduction of α-Fe2O3 with Al, B, Cr and Si by room temperature ball milling is presented. Complete reduction is achieved with the formation of
α-Fe and frequently an iron-reducer agent alloy. The method is suitable for the synthesis of nanometer-sized oxide-metal composites. 相似文献
995.
Paolo Bruni Carla Conti Elisabetta Giorgini Giorgio Tosi Henning Hopf Jorg Hillmer 《Monatshefte für Chemie / Chemical Monthly》1992,123(1-2):73-80
Summary Molecular complexes of mono and disubstituted [2.2]paracyclophanehydrazones with organic acceptors have been studied by means of thermodynamic and spectroscopic properties. Furthermore, the enhancement of the donor strength, induced by the hydrazono group, is viewed in the light of substituent as well as transannular effects.
Molekulare Assoziation von [2.2]Paracyclophanarylhydrazonen mit organischen Akzeptoren, 8. Mitt.
Zusammenfassung Es wurden Molekülkomplexe von mono- und disubstituierten [2.2]Paracyclophanarylhydrazonen mit organischen Akzeptoren mittels thermodynamischer und spektroskopischer Methoden untersucht. Zusätzlich wird der Anstieg in der Donorstärke, der von der Hydrazonogruppe induziert wird, im Hinblick auf Substituenten- und auch transannulare Effekte diskutiert.相似文献
996.
Aldo Andreani Lucedio Greci Giorgio Tosi Paolo Sgarabotto Franco Ugozzoli 《Journal of heterocyclic chemistry》1988,25(1):29-32
The study of the molecular geometry of 1-methyl-1,2,3,4-tetrahydropyrimido[1,2-a]indole-10-carboxaldehyde as determined by X-ray analysis and the electrochemical properties of that compound are reported. These are compared with those of a number of indole-3-carboxaldehyde, differently substituted at 1 and 2 position. This was done in order to understand the unsuccessful attempts to convert the title compound into the corresponding acid. The result indicate that this anomalous behaviour may be attributed to easy oxidizability of the pyrimido ring nitrogen. 相似文献
997.
Maria Antonia Iat Rosalba Saija Arianna Giusto Paolo Denti Ferdinando Borghese Cesare Cecchi-Pestellini 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,100(1-3):157-164
We calculate the energy density distribution in the ultraviolet within small spheres containing concentric cavities, aimed at simulating interstellar dust grains. We explore the dependence on chemical composition by progressively changing, in an arbitrary way, the refractive index of the sphere material. We conclude that a significant fraction of the energy of the impinging radiation is trapped throughout the particle interior. 相似文献
998.
999.
Carmine Di Fiore Stefano Fanelli Filomena Lepore Paolo Zellini 《Numerische Mathematik》2003,94(3):479-500
Summary. In this paper a new class of quasi-Newton methods, named ℒQN, is introduced in order to solve unconstrained minimization problems. The novel approach, which generalizes classical BFGS methods, is based on a Hessian updating formula involving an algebra ℒ of matrices simultaneously diagonalized by a fast
unitary transform. The complexity per step of ℒQN methods is O(n log n), thereby improving considerably BFGS computational efficiency. Moreover, since ℒQN's iterative scheme utilizes single-indexed arrays, only O(n) memory allocations are required. Global convergence properties are investigated. In particular a global convergence result
is obtained under suitable assumptions on f. Numerical experiences [7] confirm that ℒQN methods are particularly recommended for large scale problems.
Received December 30, 2001 / Revised version received December 20, 2001 /
Published online November 27, 2002
Mathematics Subject Classification (1991): 65K10
Correspondence to: P. Zellini 相似文献
1000.
Halide ions increase the rate of decarbalkoxylation of arylmethylene-propanedioic acids dimethyl esters. 相似文献