Synthesis of TiO2–SiO2/polymer core–shell microspheres with a microphase‐inversion method

A novel microphase‐inversion method was proposed for the preparation of TiO₂–SiO₂/poly(methyl methacrylate) core–shell nanocomposite particles. The inorganic–polymer nanocomposites were first synthesized via a free‐radical copolymerization in a tetrahydrofuran solution, and the poor solvent was added slowly to induce the microphase separation of the nanocomposite and result in the formation of nanoparticles. The average particle sizes of the microspheres ranged from 70 to 1000 nm, depending on the reaction conditions. Transmission electron microscopy and scanning electron microscopy indicated a core–shell morphology for the obtained microspheres. Thermogravimetric analysis and X‐ray photoelectron spectroscopy measurements confirmed that the surface of the nanocomposite microspheres was polymer‐rich, and this was consistent with the core–shell morphology. The influence of the synthetic conditions, such as the inorganic composition and the content of the crosslinking monomer, on the particle properties was studied in detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3911–3920, 2006     

A highly sensitive and rapid assay for protein determination in human urine and penicillin using a Rayleigh light-scattering technique with benzeneazo-8-acetylamino-1-naphthol-3,6-disulfonic acid sodium salt.

A simple and sensitive method was conducted for the determination of trace amounts of proteins with benzeneazo-8-acetylamino-1-naphthol-3,6-disulfonic acid sodium salt (azophloxine, AP) using a Rayleigh light-scattering (RLS) technique. At pH 2.60 and in the presence of an emulsifier OP microemulsion, the RLS of AP can be greatly enhanced by proteins, owing to the interaction between AP and protein. The enhanced intensity is proportional to the concentration of proteins. Four proteins, including bovine serum albumin (BSA), human serum albumin (HSA), lysozyme (Lys) and gamma globulin (gamma-G) have been tested. For example, the linear range of BSA was 0 - 0.06 microg mL(-1) with detection limits of 2.38 ng mL(-1). The method was applied to the analysis of protein in human urine and penicillin samples with satisfactory results. The relative standard deviation was in all instances less than 4.0%, and the recovery was in the range of 97.5 - 104%.     

Learning With Weblogs: Enhancing Cognitive and Social Knowledge Construction

This study investigated the impact of weblog use on individual learning in the context of university senior-level business education. As an emergent form of personal communication, weblogs enable people to publish their thoughts as webpages, and to share information and knowledge. Recognizing the potential impact of weblogs on knowledge expression and sharing, this research sought to empirically examine whether the continuous use of weblogs as online learning logs would affect student learning performance. The assumption was that effective use of weblogs promoted the constructivist models of learning by supporting both cognitive and social knowledge construction, and by reinforcing individual accountability in learning. Results from an Information Systems undergraduate course with 31 participants indicated that the performance of students' weblogs was a significant predictor of the learning outcome (while traditional coursework was not). Moreover, individuals' cognitive construction effort to build their own mental models and social construction effort to further enrich/expand knowledge resources appeared to be two key aspects of the constructivist learning with weblogs. Our results imply the potential benefit of using weblogs as a knowledge construction tool and a social learning medium     

一种新型频域均衡器在水声通信中的应用

在传统频域均衡器的基础上,结合多载波频移键控调制方式的频谱结构,利用接收信号和参考信号的相关性及均衡器的滤波系数,提出了一种兼具均衡与解调功能的新型频域均衡器结构.该均衡器简单、有效地克服了水声信道中多径传播产生的码间干扰和频率选择性衰落等问题,简化了水声通信系统接收机的复杂度. 新型频域均衡器的解调原理以非相关解调算法为基础,但由于利用了均衡器的计算结果,其差错性能优于传统的非相关解调算法,计算机仿真试验表明,改进后的方法使差错性能提高了2 dB;实际水声通信实验表明,该均衡器能够有效地提高水声通信系统的可靠性,具有很好的应用前景.     

折反光学系统最佳红外像面位置的研究

较深入地研究了折反光学系统的红外像面,为确定实际的红外像面提出了一个新方法—计算从可见光边缘无色的弥散圆到红外最佳像面的距离。实践证明,这是确定这类光学系统最佳像面的一个方便、可靠的方法。     

The measurements of correlation times of molecules adsorbed on silica gel,alumina and charcoal using NOESY and MAS NMR

The correlation times (τ_c) and cross relaxation rates of toluene, dimethylformamide, tetrahydrofuran, water-acetone and water-dioxane adsorbed on silica gel, alumina and charcoal were obtained by measurements of the integrated intensities of cross and diagonal peaks in their NOESY spectra. The (τ_c) of the above mentioned systems is in the range of 10^?6?10^?9 s, much longer than that in the liquid (10^?12?10^?14 s). It was found that intramolecular rotation of toluene adsorbed on charcoal is slower than that on SiO₂, Al₂O₃ and the inversion of α and β protons in tetrahydrofuran is very fast (τ_c = 1.76×10^?9 s). The cross relaxation plays an important role in the relaxation of molecules adsorbed on solid surfaces with low electron densities.     

Notes on polynomial levelability

We consider the polynomial levelability with respect to approximation algorithms (PLAA). A setA isPLAA if given any approximation algorithm forA and a polynomialp, there are another approximation algorithm forA and a polynomialq such that for infinitely many inputsx, acceptsx but has running time greater thanp(|x|) and acceptsx within timeq(|x|). In this paper, an algorithm is called an approximation algorithm forA if the symmetric differenceA L() is sparse, whereL() is the set of strings recognized by. We prove that all naturalNP-complete sets arePLAA unlessP=NP and allEXP-complete sets arePLAA.This work was supported in part by the NSF under Grant DCR 83-12472 and was done while the author studied at the Department of Mathematics, University of California at Santa Barbara. The work was also supported by Chinese National Science Foundation     

膨润土对结晶紫的吸附

用分光光度、显微电泳和ｘ－射线衍射等方法研究了膨润土对结晶紫的吸附；实验表明，钙型膨润土在吸收结晶紫溶液时，加入钠盐可明显改善吸附效果。     

统计模拟分光光度法测定复方消咳新片组分含量

用统计模拟分光光度法测定复方消咳新片４个组分含量。按均匀设计表制备合成样品，绘制溶液的ＵＶ－ＶＩＳ吸收曲线，获得有限但足够的实验数据，用逐步回归法构造反映该复方制剂组分在灵敏波长的吸光度－组分含量经验关系的“最优”数学模型，用改进单纯形法寻优，求出未知样品的各组分含量。磺胺甲基异恶唑、甲氧苄胺嘧啶、盐酸溴已新、枸橼酸维静宁的回收率分别为１００３％、１００４％、９９９％、９９０％，标准差分别为０９１％、１４％、１２％、３９％。