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Jessica D. Virdo Alan J. Lough Timothy P. Bender 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(4):297-307
The crystal structure of boron subphthalocyanine chloride [systematic name: chlorido(subphthalocyaninato)boron], C24H12BClN6, a material of widespread interest in organic electronic device applications, has been redetermined with a higher precision using large single crystals obtained via slow train sublimation. Details are given for the construction and operation of the train sublimation system, which has been designed to reproducibly yield single crystals suitable for diffraction experiments in a manner which approximates the vacuum deposition conditions commonly used to fabricate organic electronic devices. Diffraction experiments were conducted using two crystal samples and four temperatures (90, 123, 147 and 295 K), enabling a discussion of changes in the unit cell and intermolecular interactions with respect to temperature and in comparison to two previously published structures of Cl‐BsubPc. The redetermined structure confirms the original structure published 41 years ago [Meller & Ossko (1972). Monatsh. Chem. 103 , 150–155], with significantly improved precision for the geometric parameters. Analysis of the crystal structure revealed three intersecting ribbon motifs formed through a combination of π–π and halogen–π (specifically B—Cl…π) interactions. H atoms were refined independently in order to facilitate a thorough discussion of these intermolecular interactions using Hirshfeld surface analysis. 相似文献
224.
D. S. Cross J. L. Pore C. Andreoiu G. C. Ball P. C. Bender A. S. Chester R. Churchman G. A. Demand A. Diaz Varela R. Dunlop A. B. Garnsworthy P. E. Garrett G. Hackman B. Hadinia B. Jigmeddorj A. T. Laffoley A. Liblong R. Kanungo D. T. Miller B. Noakes C. M. Petrache K. Starosta C. E. Svensson P. Voss Z-M. Wang J. M. Wilson J. L. Wood S. W. Yates 《The European Physical Journal A - Hadrons and Nuclei》2017,53(11):216
225.
Homogeneous reorientation processes of two nematic liquid crystals in electric and magnetic fields have been observed using proton nuclear magnetic resonance spectroscopy (NMR). Using a recently developed experimental set-up, it is possible to study reorientation processes in liquid crystals by means of NMR experiments in a very flexible way. The time constant τ describing these processes has been determined as a function of the applied electric field. It emerges that the electric field cannot only be used to increase the reorientation time but also to slow the director reorientation by approximately one order of magnitude. Experimental data for 5CB and a fluorinated liquid crystal (BCH-5 FFF) are presented. The reorientation time measured as a function of the electric field can be used to calculate the rotational viscosity γ 1. By repeating these experiments at different temperatures it was possible to investigate the temperature behaviour of γ 1. 相似文献
226.
This paper examines numerically the complex classical trajectories of the kicked rotor and the double pendulum. Both of these
systems exhibit a transition to chaos, and this feature is studied in complex phase space. Additionally, it is shown that
the short-time and long-time behaviours of these two PT-symmetric dynamical models in complex phase space exhibit strong qualitative similarities. 相似文献
227.
Chandra Chekuri Michael Bender 《Journal of Algorithms in Cognition, Informatics and Logic》2001,41(2):212
We give a new and efficient approximation algorithm for scheduling precedence-constrained jobs on machines with different speeds. The problem is as follows. We are given n jobs to be scheduled on a set of m machines. Jobs have processing times and machines have speeds. It takes pj/si units of time for machine i with speed si to process job j with processing requirement pj. Precedence constraints between jobs are given in the form of a partial order. If j k, processing of job k cannot start until job j's execution is completed. The objective is to find a non-preemptive schedule to minimize the makespan of the schedule. Chudak and Shmoys (1997, “Proceedings of the Eighth Annual ACM-SIAM Symposium on Discrete Algorithms (SODA),” pp. 581–590) gave an algorithm with an approximation ratio of O(log m), significantly improving the earlier ratio of
due to Jaffe (1980, Theoret. Comput. Sci.26, 1–17). Their algorithm is based on solving a linear programming relaxation. Building on some of their ideas, we present a combinatorial algorithm that achieves a similar approximation ratio but runs in O(n3) time. Our algorithm is based on a new and simple lower bound which we believe is of independent interest. 相似文献
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M. Bender 《The European physical journal. Special topics》2008,156(1):217-228
Starting from successful self-consistent mean-field models,
this paper discusses why and how to go beyond the mean field
approximation. To include long-range correlations
from fluctuations in collective degrees of freedom, one has
to consider symmetry restoration and configuration mixing,
which give access to ground-state correlations and spectroscopy. 相似文献