近红外染料Yb(P4)(CoP) 掺杂 PS/SiO2复合纳米荧光标记物的制备及其性能

利用苯乙烯与3-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)化学反应合成共聚前驱物, 再采用凝胶-溶胶法,与四乙氧基硅烷在一定的条件下共同水解与缩合,合成了近红外染料 合镱(Ⅲ)掺杂的聚苯乙烯/二氧化硅复合纳米粒子。这种制备染料掺杂复合纳米粒子的方法既克服了传统物理包埋方法染料容易泄漏的问题,又不受到化学键合方法对近红外染料分子性质的限制。用扫描电子显微镜表征该复合纳米粒子呈球形,大小均匀,直径约100 nm。所制得的纳米粒子荧光性质稳定,受外界环境的影响小,具潜在生物亲和性,是一种新型的近红外荧光标记物。     

Molecular organization and aggregation in Langmuir and Langmuir-Blodgett films of azo dye/liquid crystal mixtures

A study of azo dye/liquid crystal mixtures in monolayers formed at air-water (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces was performed. Three azo dyes with various molecular structure and two liquid crystal materials: 4-octyl-4′-cyanobiphenyl (8CB) and trans-4-octyl(4′-cyanophenyl)-cyclohexane (8PCH) were used. The morphology of Langmuir films was monitored by means of a Brewster angle microscope (BAM). Moreover, a surface pressure and electronic absorption spectra of the monolayer spread on the water surface of dye/liquid crystal mixtures as a function of a mean molecular area were simultaneously recorded. In addition, the absorption for Langmuir-Blodgett films deposited on quartz plates was measured. Information about intermolecular interactions in the mixtures of the nonamphiphilic dye and the liquid crystal with polar terminal group was obtained. Conclusions about the formation of self-aggregates between dye molecules have been drawn. The influence of the dye molecular structure and its concentration on aggregates’ geometry was found.     

Influence of suspension viscosity on Brownian relaxation of filler particles

Brownian relaxation caused by Brownian movement of particles in suspensions can macroscopically be probed by small-amplitude oscillatory shear experiments. Phenomenological considerations suggest a direct proportionality between suspension viscosity and Brownian relaxation times. To verify this relation experimentally, a set of nanocomposite suspensions with viscosities varying over five decades is presented. The suspensions are chosen in a way to ensure that particle-particle interactions and average particle-particle distances are identical so that they can be used as a model system to study the mere influence of suspension viscosity on Brownian relaxation. The suggested linear relationship between suspension viscosity and Brownian relaxation time can be confirmed. Moreover, a verification of a recently introduced characteristic timescale for Brownian relaxation is presented.     

Enriched multi-point flux approximation for general grids

It is well known that the two-point flux approximation, a numerical scheme used in most commercial reservoir simulators, has O(1) error when grids are not K-orthogonal. In the last decade, the multi-point flux approximations have been developed as a remedy. However, non-physical oscillations can appear when the anisotropy is really strong. We found out the oscillations are closely related to the poor approximation of pressure gradient in the flux computation.In this paper, we propose the control volume enriched multi-point flux approximation (EMPFA) for general diffusion problems on polygonal and polyhedral meshes. Non-physical oscillations are not observed for realistic and strongly anisotropic heterogeneous material properties described by a full tensor. Exact linear solutions are recovered for grids with non-planar interfaces, and a first and second order convergence are achieved for the flux and scalar unknowns, respectively.     

Optimum matching forests III: Facets of matching forest polyhedra

In [3] we presented a linear system which definesP(G), the convex hull of incidence vectors of matching forests of a mixed graphG. However, many of the inequalities of this system may be redundant. Here we describe the dimension of the facets ofP(G) obtained by setting one inequality of the defining system forP(G) to an equation. This leads to a presentation of a minimal defining linear system forP(G), i.e., to a presentation of the facets ofP(G). This generalizes earlier characterizations of facets of 1-matching polyhedra and of branching polyhedra.Research partially supported by a N.R.C. Canada Postdoctorate Fellowship.     

Predicting the product specificity and coupling of cytochrome P450cam

Summary We present an analysis of several molecular dynamics trajectories of substrate-bound cytochrome P450cam. Trajectories were calculated for the native substrate, camphor, as well as for the alternative substrates, norcamphor and thiocamphor. The system modeled consisted of the crystallographically resolved amino acids, the heme group with a single oxygen atom as the distal ligand, the bound substrate, and the crystallographic waters. These trajectories of the presumptive ferryl oxygen intermediate were used to predict regiospecificity of hydroxylation and coupling between NADH consumption and product formation. Simple geometric criteria in combination with electronic considerations were used to calculate the probability of hydroxylation at specific sites on the substrate. We found that for all the cases examined, the predicted product ratios were in good agreement with the experimentally observed values. We also determined that these simple geometric criteria can be used to predict the degree of coupling between NADH consumption and product formation for a given substrate, which was in good agreement with the experimental values.     

The vinylketene acetal route to aklavinone and 11-deoxydaunomycinone

11-Deoxyanthracyclinone precursors $\text{6a}$ and $\text{6b}$ have been prepared regiospecifically by the reaction of bromojuglone methyl ethers $\text{4a}$ and $\text{4b}$ with vinylketene acetal $\text{5}$, prepared from the Hagemann's ester ketal $\text{7a}$.     

Optimum matching forests I: Special weights

We introduce the concept of matching forests as a generalization of branchings in a directed graph and matchings in an undirected graph. Given special weights on the edges of a mixed graph, we present an efficient algorithm for finding an optimum weight-sum matching forest. The algorithm is a careful application of known branching and matching algorithms. The maximum cardinality matching forest problem is solved as a special case.Research partially supported by a N.R.C. of Canada Postdoctorate Fellowship.