A concise strategy for polymer‐supported regio‐oriented introduction of various building blocks onto glucopyranoside scaffold

A new strategy was devised to stereo‐specifically introduce various building blocks, mainly heterocycles such as pyrimidines and triazines onto a multi‐hydroxy molecule. A glucopyranoside was chosen as a target scaffold. Two polymer‐based protective reagents were jointly integrated in the implementation of the strategy. It was found that in the α‐D‐glucopyranoside, which has four free hydroxyl groups within the same molecule, its 4, 6‐di‐OH could be simultaneously protected by polystyryl boronic acid, which left the 2, 3‐di‐OH free for substitution. Due to the steric effects within the molecule, the 2‐OH is much more liabile to electrophilic substitution. Thus the first and the second building blocks could be introduced regioselectively onto the 2‐OH and the 3‐OH positions. After a facile deprotection, the 4, 6‐di‐OH were left free and by application of a second protecting reagent–‐polystyryltritylchloride onto 6‐OH, a third building block was introduced onto the 4‐OH position. After further deprotection, the fourth building block was later introduced onto the 6‐OH position. The new strategy was successfully applied in the combinatorial synthesis by application of the split‐mix technique. The respective eleven small libraries were obtained and confirmed by HPLC‐MS and NMR. Some preliminary results on chemical structure/herbicidal activity relationship were discussed.     

Target-Searching on Percolation

We study target-searching processes on a percolation, on which a hunter tracks a target by smelling odors it emits. The odor intensity is supposed to be inversely proportional to the distance it propagates. The Monte Carlo simulation is performed on a 2-dimensional bond-percolation above the threshold. Having no idea of the location of the target, the hunter determines its moves only by random attempts in each direction. For lager percolation connectivity p 〉 0.90, it reveals a scaling law for the searching time versus the distance to the position of the target. The scaling exponent is dependent on the sensitivity of the hunter. For smaller p, the scaling law is broken and the probability of finding out the target significantly reduces. The hunter seems trapped in the cluster of the percolation and can hardly reach the goal.     

Longitudinal sound velocity in uniaxially stretched rubberlike polymers

We present a new method to interpret data obtained by Brillouin-scattering from oriented networks. Because in rubberlike samples the transverse sound waves are normally not observable, it is not possible to extract the complete set of elastic constants. We will show that by combining a model of the orientation process with the lattice-model from Kondo and Igarashi, force constants can be determined from the sound velocities. These force constants can be discussed in terms of molecular conformations and interactions. The anisotropic hypersound velocity was measured in polyurethane- and polysiloxane networks. With the help of the combined orientation-lattice-model evaluation, different kinds of forces can be distinguished. By comparing the force constants with Raman- or infrared spectroscopic data, information about the conformation of the polymer chains can be determined. The effective force constants of the segments are an order of magnitude lower than that of the polymer main chains and the ratio of force constants along and between the segments lies between 1 : 1 to 5 : 1. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1661–1676, 1997     

The Feature Description of Formal Context Based on the Relationships among Concept Lattices

Three-way concept analysis (3WCA) is extended research of formal concept analysis (FCA) by combining three-way decision. The three-way object oriented concept lattice (OEOL) is one of the important data structures which integrates rough set, concept lattice and three-way decision in 3WCA. In the paper, we investigate the characteristics of formal context based on the isomorphic relationship among the kinds of concept lattices with OEOL. Firstly, II-dual intersectable attributes and II-dual intersectable context are proposed and the relationship between the type I-dual intersectable context(dual intersectable context) and the type II-dual intersectable context are studied. In addition, the relationship among the kinds of concept lattices with OEOL are studied when the formal context is both I-dual intersectable context and II-dual intersectable context. Finally, the inverse problems of the above conclusions are discussed and the following two conclusions are obtained: (1) the formal context is the type II-dual intersectable context, when the object oriented concept lattice and OEOL are isomorphic. (2) In addition, the formal context is the type I-dual intersectable context, when the concept lattice and OEOL are anti-isomorphic.     

成型压力对PMNT多晶体取向生长的影响

采用添加PbO的TGG方法定向生长PMNT多晶体,研究了素坯成型压力对PMNT多晶体取向生长的影响规律.结果表明,成型压力直接影响PMNT多晶体的取向生长速度和取向程度.随着成型压力逐渐增大,PMNT多晶体的取向生长速度呈先增加后减小的趋势.低于临界成型压力(在本文实验条件下,临界成型压力为600MPa)时,随成型压力增大,PMNT多晶体的取向生长速度越来越快;高于临界成型压力时,随成型压力增大,PMNT多晶体的取向生长速度越来越慢,但是多晶体的取向程度却越来越好.     

Universal crossing probabilities and incipient spanning clusters in directed percolation

Shape-dependent universal crossing probabilities are studied, via Monte Carlo simulations, for bond and site directed percolation on the square lattice in the diagonal direction, at the percolation threshold. In a dynamical interpretation, the crossing probability is the probability that, on a system with size L, an epidemic spreading without immunization remains active at time t. Since the system is strongly anisotropic, the shape dependence in space-time enters through the effective aspect ratio r _eff = ct/L ^z, where c is a non-universal constant and z the anisotropy exponent. A particular attention is paid to the influence of the initial state on the universal behaviour of the crossing probability. Using anisotropic finite-size scaling and generalizing a simple argument given by Aizenman for isotropic percolation, we also obtain the behaviour of the probability to find n incipient spanning clusters on a finite system at time t. The numerical results are in good agreement with the conjecture. Received 10 February 2003 Published online 20 June 2003 RID="a" ID="a"e-mail: turban@lpm.u-nancy.fr RID="b" ID="b"UMR CNRS 7556     

N-cluster correlations in four- and five-dimensional percolation

We study N-cluster correlation functions in four- and five-dimensional (4D and 5D) bond percolation by extensive Monte Carlo simulation. We reformulate the transfer Monte Carlo algorithm for percolation [Phys. Rev. E72, 016126 (2005)] using the disjoint-set data structure, and simulate a cylindrical geometry L^d−1 × ∞, with the linear size up to L = 512 for 4D and 128 for 5D. We determine with a high precision all possible N-cluster exponents, for N =2 and 3, and the universal amplitude for a logarithmic correlation function. From the symmetric correlator with N=2, we obtain the correlationlength critical exponent as 1/ν=1.4610(12) for 4D and 1/ν=1.737(2) for 5D, significantly improving over the existing results. Estimates for the other exponents and the universal logarithmic amplitude have not been reported before to our knowledge. Our work demonstrates the validity of logarithmic conformal field theory and adds to the growing knowledge for high-dimensional percolation.     

Diversity Oriented Clicking (DOC): Divergent Synthesis of SuFExable Pharmacophores from 2-Substituted-Alkynyl-1-Sulfonyl Fluoride (SASF) Hubs

Diversity Oriented Clicking (DOC) is a unified click-approach for the modular synthesis of lead-like structures through application of the wide family of click transformations. DOC evolved from the concept of achieving “diversity with ease”, by combining classic C−C π-bond click chemistry with recent developments in connective SuFEx-technologies. We showcase 2-S ubstituted-A lkynyl-1-S ulfonyl F luorides (SASFs) as a new class of connective hub in concert with a diverse selection of click-cycloaddition processes. Through the selective DOC of SASFs with a range of dipoles and cyclic dienes, we report a diverse click-library of 173 unique functional molecules in minimal synthetic steps. The SuFExable library comprises 10 discrete heterocyclic core structures derived from 1,3- and 1,5-dipoles; while reaction with cyclic dienes yields several three-dimensional bicyclic Diels–Alder adducts. Growing the library to 278 discrete compounds through late-stage modification was made possible through SuFEx click derivatization of the pendant sulfonyl fluoride group in 96 well-plates—demonstrating the versatility of the DOC approach for the rapid synthesis of diverse functional structures. Screening for function against MRSA (USA300) revealed several lead hits with improved activity over methicillin.