A facile method for the preparation of monodisperse hollow silica spheres with controlled shell thickness

This article presents a facile, effective, mild synthesis process for well‐defined hollow spheres by using cationic polystyrene (PS) submicro‐particles as templates. In this approach, the cationic PS templates can be first prepared via emulsifier‐free polymerization by using the cationic monomer 2‐(methacryloyloxy) ethyltrimethylammonium chloride as comonomer, then, the silica shells from the sol‐gel process of tetraethoxysilane were coated on the surfaces of template particles via electrostatic interaction, finally the PS was dissolved in situ by modification of the reaction conditions in the same medium to form monodisperse hollow silica spheres with controlled shell thickness. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, Brunauer‐Emmett‐Teller, transmission electron microscopy, and scanning electron microscope measurements were used to characterize these hollow silica spheres. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1332–1338, 2010     

一种基于云计算的关联规则Apriori算法

关联规则是数据挖掘的重要方法之一,它基于支持度和置信度等对规则进行选择,以生成有用的规则。传统的关联规则算法需要读取数据库计算频繁集,开销巨大。随着云计算的发展,MapReduce编程架构已经成为云计算中的重要技术,针对Apriori算法的不足,设计了一种算法将云计算MapReduce框架进行了适当改进,并在此基础上编写了Apriori算法,以解决Apriori算法扩展性差的弱点。实验表明：该算法能有效提高Apriori算法的性能。     

Two New Diterpene Alkaloids from the Roots of Spiraea japonica var. Acuta

Spiraea japonica L. (Rosaceae) is widely distributed in Yunnan Provence, P. R. China. Previous chemical investigations on S. japonica and its varieties have led to the report of 7 new atisane-type diterpenoids and 38 new diterpene alkaloids of atisine- and hetisine-type1-11. This paper describes the isolation and structure elucidation of two new diterpene alkaloids named spiratines A and B (1-2). Their structures were elucidated on the basis of 1D and 2D NMR experiments (HMQC, HMBC, 1…     

Highly Efficient Oxidative Bromination of Alkanes with the HBr-H2O2 System in the Presence of Catalyst

Various cycloalkanes and straight‐chain alkanes were efficiently brominated with an aqueous HBr‐H₂O₂ system. This oxidative brominating process was promoted by catalysis and irradiation with light. The cycloalkanes were converted to the corresponding bromo‐cycloalkanes in moderate yields and the straight‐chain alkanes produced dominantly secondary bromides. This simple but effective bromination method of alkanes is characterized by high atom efficiency, inexpensive reagents and the absence of organic waste, which make it a good alternative to the existing method for C? H activation through bromination.     

Facile,efficient functionalization of polyethylene via regioselective copolymerization of ethylene with cyclic dienes

The copolymerizations of ethylene with cyclic dienes [dicyclopentadiene (DCPD) and 2,5‐norbornadiene (NBD)] using bis(β‐enaminoketonato)titanium complexes [PhN = C(R₂)CHC(R₁)O]₂TiCl₂ ( 1a : R₁ = CF₃, R₂ = CH₃; 1b : R₁ = t‐Bu, R₂ = CF₃; 1c : R₁ = Ph, R₂ = CF₃) have been investigated. In the presence of modified methylaluminoxane, these complexes exhibited high catalytic activities in the copolymerization of ethylene with DCPD or NBD, affording high molecular weight copolymers with unimodal molecular weight distributions. ¹H and ¹³C‐NMR spectra reveal ethylene/DCPD copolymerizations by catalysts 1a – c proceeds through the enchainment of norbornene ring. Catalysts 1a and 1c showed a tendency to afford alternating copolymers. More noticeably, catalysts 1b and 1c bearing bulky substituents on the ligands promote ethylene/NBD copolymerization without crosslinking, affording the copolymer containing intracyclic double bonds. The NBD incorporation as high as 27.2 mol % has been achieved by catalyst 1c . Moreover, the microstructures of the copolymers were further confirmed by the measurement of reactivity ratios and dyad monomer sequences as well as mean sequence lengths. The intracyclic double bonds of ethylene/DCPD or ethylene/NBD copolymers can be fully converted into polar groups such as epoxy, amine, silane, and hydroxyl groups under mild conditions. Convenient synthesis of hydroxylated polyethylene can be provided for the first time through the ring opening reaction of epoxide. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1764–1772, 2010     

Two New Steroidal Saponins from Diuranthera inarticulata

There are only three species in the genus Diuranthera (Liliaceae), which is endemic in the southwest of China1. Four steroidal saponins, diuranthosides A-C and chloromalo-side A were isolated from the fresh roots of D. major. This paper deals with the structure elucidation of two new steroidal saponins, diuranthosides D and E, which were isolated from the methanolic extract of whole plant of D. inarticulata Wang et K. Y. Lang.Diuranthoside D (1), [(]-38 (c 0.08, pyridine), afforded galac…     

Study on the Structure of Supramolecular Inclusion Complex of β-Cyclodextrin with Retinoic Acid

The importance of Vitamin A for human health has been stressed in resent studies1, meanwhile its derivative so-called retinoic acid (RA) has been widely used as pharmaceutical to treat several types of skin disease and cancer2,3. However the application of retinoic acid is restrained for its poor water solubility, unstability and side effect on the human body.Cyclodextrins (CDs) are macrocyclic oligosaccharides built up from 6, 7, or 8 glucopyranose units called (, (, and (-CD, respectively…     

3,6‐Bis(2‐pyridyl)di‐1,2,4‐triazolo­[3,4‐a:4′,3′‐c]­phthalazine

The title compound, C₂₀H₁₂N₈, (I), has been prepared by the reaction of 1,4‐dihydrazinophthalazine and pyridine‐2‐carbox­aldehyde, followed by an oxidative cyclization by treatment with bromine. In the solid state, the mol­ecules of (I) are discrete, comprising a fused and twisted four‐ring system with an overall helical appearance. The distance between the two intramolecular pyridyl N atoms is 3.075 (2) Å, this short contact distance suggesting a π–π interaction.