Bifurcation of rough heteroclinic loop with orbit and inclination flips

In this paper, we are concerned with the heteroclinic loop bifurcations accompanied by one orbit flip and one inclination flip under some roughness conditions. The existence of one 1-periodic orbit, one 1-homoclinic orbit, two 1-periodic orbits, one double 1-periodic orbit is obtained, respectively, approximate expressions of the corresponding bifurcation curves (or surfaces) and the corresponding bifurcation graphs under nontwisted or twisted conditions are also given.     

拟变分包含系统(英文)

本文提出一些新的拟变分包含系统,利用向量映射的锥连续性与Park不动点定理,得到解的存在定理与解集的闭性.作为应用,得到对称强向量拟均衡问题与理想向量鞍点的存在性,推广与改进了近期的一些相关研究工作.     

Malonate-type bis(oxazoline) ligands with sp hybridized bridge carbon: synthesis and application in Friedel-Crafts alkylation and allylic alkylation

A series of simple and new C₂-symmetric diphenylmethylidene malonate-type bis(oxazoline) ligands were synthesized and applied to the Friedel-Crafts reaction and allylic alkylation. The Cu(II) complex of ligand 4b bearing the benzyl group afforded good to excellent enantioselectivity for the F-C adducts (up to >99% ee) between indole and alkylidene malonate, and the palladium complex of ligand 4c bearing the phenyl group afforded excellent enantioselectivity (up to 94% ee) for the allylic alkylation product.     

离散单因素投资组合模型的对偶算法

本文研究金融优化中的离散单因素投资组合问题,该问题与传统投资组合模型的不同之处是决策变量为整数(交易手数),从而导致要求解一个二次整数规划问题．针对该模型的可分离性结构,我们提出了一种基于拉格朗日对偶和连续松弛的分枝定界算法。我们分别用美国股票市场的交易数据和随机产生的数据对算法进行了测试．数值结果表明该算法是有效的,可以求解多达150个风险证券的离散投资组合问题．     

THE OPTIMAL HARVESTING OF A PREDATOR-PREY SYSTEM WITH STAGE-STRUCTURE

In this paper,we establish the exploitation of continuous harvest of preda- tor and prey with stage-structures.We investigate the properties of harvesting multispecies systems.With some special methods,we obtain boundedness and global attractiveness of all the nonnegative equilibria for proportional harvest. Finally,we solve the problem of optimal harvest policy using Pontragin's ma- ximal principle.     

Grafting modification and structural degradation of multi-walled carbon nanotubes under the effect of ultrasonics sonochemistry

Polyvinyl pyrrolidone (PVP) grafted multi-walled carbon nanotubes (MWCNTs) were prepared by the degradation effect of ultrasonics sonochemistry. PVP macroradicals formed by sonochemical degradation of a PVP solution were trapped by MWCNTs and grafted onto the surface of MWCNTs. It was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis that the PVP was covalently bonded on the MWCNTs. Transmission electron microscopy showed nanotubes in the grafted samples were shorter than the original MWCNTs due to the crushing effect of ultrasonics sonochemistry. Both the decrease in length of the MWCNTs and the PVP grafted onto them are beneficial for their dispersion in solvents.     

Quantification of Effector Binding to the Hemoglobin Central Cavity by Intrinsic and Extrinsic Steady-State Fluorescence

The relative intrinsic and extrinsic fluorescence of hemoglobins are established markers of the R (oxy) T (deoxy) transition and reveal site-specific conformational differences amongst hemoglobin (Hb) mutants. The Hb central cavity has been probed by binding the fluorescent analogue of 2,3-diphosphoglycerate, 8-hydroxy-1,3,6-pyrenetrisulfonate (HPT). An approach to quantify binding of HPT to HbC (6 Lys) and HbA (6 Glu), by steady-state front-face fluorescence spectroscopy using both the intrinsic and extrinsic emissions, is presented. When HPT specifically binds to Hb, efficient fluorescence energy transfer from the intrinsic fluorescence of Hb to HPT occurs, decreasing the intrinsic fluorescence of Hb that plateaus upon stoichiometric binding. HPT fluorescence is significantly but not totally quenched upon binding to HbA and HbC. HPT exhibits a molecular binding ratio of 2:1 to HbC, in contrast to HbA (1:1 binding). The apparent secondary binding site for HbC is weaker (K_D1 = 25 M vs. K_D2 = 0.15 mM). Conformational alterations of HbC at the and clefts of the central cavity are further supported by these data.     

Synthesis,structure and electrochemical behaviour of cobalt(II) complexes with 2,6-bis(benzimidazol-2′-yl) pyridine

Summary The complexes Co(BBP)Cl₂, Co(BBP)₂SO₄·H₂O, Co(BBP)₂(NO₃)₂·H₂O, Co(BBP)₂(ClO₄)₂ and Co(BBP−H)₂· 2H₂O, where BBP is 2,6-bis(benzimidazol-2′-yl) pyridine, were prepared and characterized by elemental analysis, electrical conductance, i.r. and electronic spectra. The electrochemical behaviour of the complexes was recorded and the X-ray crystal structure of Co(BBP)Cl₂(MeOH)₂ was determined. The geometry about cobalt is a distorted octahedron.     

网络时代的高校思想政治工作

知识经济和网络时代的今天，大学生对计算机网络的依赖比过去更加强烈，网络已经成为他们了解世界科技前沿动态，学习现代化知识，获取外部信息的重要手段，但由于网络中各种资讯的良莠不齐，给高校的思想政治工作者提出了新的课题：如何在网络时代加强高校的思想政治工作，本文通过对当前形势的分析，从网络主流教育、网络道德建设、“网上网下”协调发展三个方面对新时期加强网络时代的思想政治教育进行了阐述。