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81.
Synthesis of a tetrakis(1-pyrenylethynyl)-substituted rigid hinge-like molecule (1) is described. The intramolecular pi-stacking interaction of the pyrene units is studied by 1H NMR and fluorescence spectroscopy. Due to intramolecular pi-stacking interactions, chemical shifts of the pyrene protons in 1 are highly shielded in the NMR spectrum. Fluorescence from the static excimer state is observed due to pi-stacking interactions among the pyrene units in the ground state of 1. Based on the spectroscopic evidence, conformations and dynamics of 1, arising from the hindered rotation of the major axis, are proposed.  相似文献   
82.
[reaction: see text] Synthesis of a pyrene octaaldehyde derivative and its aggregation through pi-pi and C-H...O interactions in solution and in the solid state probed by fluorescence emission and other spectroscopic methods are reported. The effect of solvent, concentration, and temperature on the aggregation is investigated.  相似文献   
83.
Computational Management Science - This paper introduces a fractional version of the classical maximum weight clique problem, the maximum ratio clique problem, which is to find a maximal clique...  相似文献   
84.
Matrices A and B in Mn(C) are said to be mutually orthogonal if AB?+BA?=0, where ? denotes the conjugate transpose. We study cardinalities of certain R-linearly independent families of matrices arising from matrix embeddings of a division algebra of index m with center a number field Z, satisfying the property that matrices from different families are mutually orthogonal. The question is of importance in the context of coding for certain wireless channels, where the cardinalities of such sets is connected to the maximum code rate consistent with low decoding complexity. It follows from our results that the maximum code rate for the codes we consider is severely limited.  相似文献   
85.
We report a method for the fabrication of glassy carbon electrode modified porous graphene-polypyrrole-polyphenol oxidase (GCE−PG−PPy−PPO) modified electrode for the determination dopamine. The optimization of pH, concentration and detection limit of dopamine was employed by amperomatric technique. The detection limit of dopamine was found to be in a linear range of 2×10−8 to 4.6×10−5 M and lower limit detection is 4×10−9 M. Michealis – Menten constant (Km) and the activation energy were calculated as 31.32 μM and 37.4−Kj mol−1, respectively. The developed biosensor was used to quantify the dopamine in human urine sample.  相似文献   
86.
Consider a distinguished, or tagged particle in zero-range dynamics on Zd with rate g whose finite-range jump probabilities p possess a drift ∑jp(j)≠0. We show, in equilibrium, that the variance of the tagged particle position at time t is at least order t in all d?1, and at most order t in d=1 and d?3 for a wide class of rates g. Also, in d=1, when the jump distribution p is totally asymmetric and nearest-neighbor, and the rate g(k) increases, and g(k)/k either decreases or increases with k, we show the diffusively scaled centered tagged particle position converges to a Brownian motion with a homogenized diffusion coefficient in the sense of finite-dimensional distributions. Some characterizations of the tagged particle variance are also given.  相似文献   
87.
In this paper, we develop a family of data clustering algorithms that combine the strengths of existing spectral approaches to clustering with various desirable properties of fuzzy methods. In particular, we show that the developed method “Fuzzy-RW,” outperforms other frequently used algorithms in data sets with different geometries. As applications, we discuss data clustering of biological and face recognition benchmarks such as the IRIS and YALE face data sets.  相似文献   
88.
Consider a problem of scheduling activities of a research and development project, where precedence relations of the activities constituting the project are represented by edges of an in-forest. Each activity is characterized by two parameters: a cost for attempting that activity and a probability that attempting the activity will lead to successful completion. The problem is to find a policy for attempting activities that minimizes the expected cost incurred until termination (successful completion of the project or the first activity failure). The main result of the paper is the design of an efficient algorithm to determine an optimal sequence in which to attempt the activities; a result which is established for linear and exponential utility functions. It is also shown that, unlike the related problem with out-forest precedence relations, there need not exist an optimal policy that is based on an index-rule for determining priority of edges by evaluating their successors.  相似文献   
89.
Proceedings - Mathematical Sciences - It is shown that the interaction between two charged particles reduces to that of a potential with one particle when the mass of the other tends to infinity....  相似文献   
90.
Sequential addition of two different lithium acetylides to p-benzoquinone yielded diastereomeric mixtures of 1,4-diethynylcyclohexa-2,5-diene-1,4-diols wherein the two ethynyl groups bear different protective/functional groups. Selective deprotection to the terminal acetylene followed by Pd(0) mediated coupling with Z-1,2-dichloroethene yielded new enediynes bearing cyclohexa-2,5-diene units.  相似文献   
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