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121.
Bert Lutz Jan A. Kanters John van der Maas Jan Kroon Thomas Steiner 《Journal of Molecular Structure》1998,440(1-3)
Structural and IR-spectroscopic evidence is given that directed contacts from terminal alkynes to C=C double bonds possess the essential characteristics of weak hydrogen bonds. The contacts are directed at the center of the π-bond rather than at one of the individual C-atoms. The contact distances from H to the center of the C=C bond are typically 2.8 Å, with the shortest distances being 2.5 Å. The interaction is of pronounced long-range nature and can be detected in the infrared spectrum even with a long H…π distance of almost 3.0 Å. The sample used is mainly composed of ethynyl steroids belonging to the progestine family. 相似文献
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In this paper, we review several important features of the out-of-equilibrium dynamics of spin glasses. Starting with the
simplest experiments, we discuss the scaling laws used to describe the isothermal aging observed in spin glasses after a quench
down to the low-temperature phase. We report in particular new results on the sub-aging behaviour of spin glasses. We then
discuss the rejuvenation and memory effects observed when a spin glass is submitted to temperature variations during aging,
from the point of view of both energy landscape pictures and real-space pictures. We highlight the fact that both approaches
point out the necessity of hierarchical processes involved in aging. Finally, we report an investigation of the effect of
small temperature variations on aging in spin glass samples with various anisotropies which indicates that this hierarchy
depends on the spin anisotropy. 相似文献
124.
This paper presents a large deviation analysis of the steady-state sojourn time distribution in the GI/G/1 PS queue. Logarithmic estimates are obtained under the assumption of the service time distribution having a light tail,
thus supplementing recent results for the heavy-tailed setting. Our proof gives insight into the way a large sojourn time
occurs, enabling the construction of an (asymptotically efficient) importance sampling algorithm. Finally our results for
PS are compared to a number of other service disciplines, such as FCFS, LCFS, and SRPT.
2000 mathematics subject classification: 60K25. 相似文献
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