Fractals related to Pascal's triangle

A precise definition of a fractalF _p ^{r 1} derived from Pascal's triangle modulop ^r (p prime) is given. The number of nonzero terms in the firstp ^s lines of Pascal's triangle modulop ^r is computed. From this result the Hausdorff dimension and Hausdorff measure ofF _p ^{r 1} are deduced. The nonself-similarty ofF _p ^{r 1},r2, is also discussed.     

Synthesis of Bi2Se3 thermoelectric nanosheets and nanotubes through hydrothermal co-reduction method

Bi₂Se₃ nanosheets and nanotubes were prepared by a hydrothermal co-reduction method at 150, 180, 200, and 210 °C. Bi₂Se₃ nanosheets, nanobelts and nanotubes were obtained. The Bi₂Se₃ nanoflakes are 50-500 nm in width and 2-5 nm in thickness. The Bi₂Se₃ nanotubes are 5-10 nm in diameter, 80-120 nm in length, and 1.3 nm in wall thickness. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and electron diffraction were employed to characterize the products. Experimental results showed that the nanosheets and the nanotubes are hexagonal in structure with a=4.1354 Å and c=27.4615 Å. A possible formation and crystal growth mechanism of Bi₂Se₃ nanostructures is proposed.     

Influence of the addition of alcohol on the reaction methyl-4-nitrobenzenesulfonate + Br(-) in tetradecyltrimethylammonium bromide aqueous micellar solutions

The reaction methyl-4-nitrobenzenesulfonate + Br(-) was studied in tetradecyltrimethylammonium bromide (TTAB) aqueous micellar solutions in the absence and in the presence of various amounts of n-hexanol, n-pentanol, and n-butanol. Kinetic micellar effects provoked by the addition of the linear alcohols can be rationalized by using simple pseudophase kinetic models. The equilibrium binding constants of the methyl-4-nitrobenzenesulfonate molecules to the cationic micelles decreases when [alcohol] increases. The (k(2)(m)/V(m)) values found are practically the same for the different TTAB-alcohol micellar solutions studied, independent of the nature and concentration of the alcohol present in the reaction medium. This has been explained by considering the balance of two factors operating on reactivity in opposite ways: (1). an increase in the volume of the micellar interfacial region upon increasing alcohol concentration, and (2). a decrease in the polarity of the interfacial region as the amount of alcohol present in the micellar solutions increases.     

邻菲啰啉对固定尿酸酶催化反应动力学的影响

聚苯胺和聚此咯具有很高的稳定性和良好的导电性．用导电高聚物固定酶比用其它材料，如聚丙烯酸胺胶体和导电有机盐（TTF、TCNQ），要方便得入所以导电高聚物是固定酶的一种新型的载体．用聚吡咯和聚苯胺固定的葡萄糖氧化酶形成的电极具有很好的生物电化学响应和很高的稳定性[1-8]．在酶催化反应中，酶的激活和抑制作用，对于医药和生理有重要意义．邻菲少批是尿酸酶的激活剂问，但至今未见有关这方面的动力学报导．由于用酶电极能准确和方便地测定酶催化反应速率，所以本文报名用电化学方法来研究邻菲哮批对失活了的尿酸酶的激活作用及…     

The conformation and dynamics study of amphoteric copolymers,P(sodium 2-methacryloyloxyethanesulfonate-co-2-methacryloyloxyethyltrimethylammonium iodide), using viscometry, 14N-, and 23Na-NMR

Solution conformations and dynamic mobilities of novel amphoteric copolymers were studied for aqueous solutions of p(sodium 2-methacryloxyethanesulfonate-co-2-methacryloy-loxyethyltrimethylammonium iodide) [P(NaMES-co-METMAI)] as a function of com-position, concentration, and addition of HCI or KCI. As HCI or KCI was added successively to 5 w/v% copolymer solutions, the reduced viscosities of the solutions were reduced except the 1:1 copolymer solution. The dynamic mobility of the cationic side chain was estimated with the quadrupolar ¹⁴N-NMR relaxation technique. The motion of the interacting coun-terion, Na⁺, was studied by Poisson-Boltzmann electrostatic theories and the quadrupolar ²³Na-NMR. Since the intramolecular 1:1 ion pair between MES^- and METMA⁺ acts as an effective charge-screening factor, the copolymers P(NaMES-co-METMAI) behave as ordinary polyelectrolytes with the exception of the 1 : 1 copolymer. © 1995 John Wiley & Sons, Inc.     

Solvent effects upon reactions between ions: hexacyanoferrate(II)-peroxodisulphate and sulphite-hexacyanoferate(III)

Summary Different approaches to the interpretation of solvent effects on reactions between ionic reactants are analysed, taking as a basis the kinetic data corresponding to the sulphite-hexacyanoferrate(III) and peroxodisulphate-hexacyanoferrate(III) oxidations. It is concluded that the approach based on the use of solvent parameters is the more promising, although knowledge of the transfer chemical potentials of the reactants may also be useful in the interpretation of kinetic behaviour.     

Partial least squares multicomponent fluorimetric determination of fluoroquinolones in human urine samples

Ternary mixtures of fluoroquinolones, with a 7-piperazinyl substituted group have been simultaneously determined in human urine samples by application of a multivariate calibration partial least squares (PLS) model. The calibration set was designed with 15 urine samples containing different concentrations of the three fluoroquinolones and 16 blank urine samples. The concentration range for the fluoroquinolones were up to 25 ng ml⁻¹ for norfloxacin (NOR), 80 ng ml⁻¹ for ofloxacin (OFLO) and 300 ng ml⁻¹ for enoxacin (ENO). The method is based on the native fluorescence emission of these compounds in sodium dodecyl sulfate (SDS) medium, at pH 4.0, when exciting at 277 nm. A selection of the emission wavelength range used for the analysis was made for each component. Intraday and interday precision values were determined. Figures of merit as selectivity, sensitivity, limit of detection (LOD) and analytical sensitivity were also calculated. Using the standard addition methodology, five urine samples from five different persons, fortified with three concentration levels of the fluoroquinolones, were analyzed. The limits of detection in urine were 10.0, 0.5 and 0.8 ng ml⁻¹ for ENO, NOR and OFLO, respectively.     

Complex surface dynamics during anodic dissolution of Ni

The evolution of the surface roughness during the anodic dissolution of polycrystalline Ni was investigated by means of ex situ AFM in acid phosphate solutions. To characterize the time and spatial scaling behavior of surface roughness, the interface width and the power spectral density of the surface at different dissolution stages were analyzed in terms of dynamic scaling theories. The time dependence of global surface roughness, W(L,t), shows an unstable behavior characterized by a continuous increase without saturation following the relation W approximately t(beta), where beta > 0.5. The unstable behavior results from the development of wide grooves that originates a surface consisting of mounds. Two scaling regimes at scales shorter and larger than the mound dimensions (l(c)) were observed. For l < l(c), we found alpha approximately 1 consistent with mounds exhibiting smooth (faceted) walls, whereas an anomalous scaling behavior with a proper local roughness exponents (alpha(loc) < 1) dominates at l > l(c). The introduction of nitrite in the solution, a common additive used in phosphating baths, leads to some changes in the scaling behavior as a consequence of different generated chemical surface conditions during dissolution. The different dissolution rates of the exposed crystal orientations and surface diffusion of adatoms were identified as the physical processes that govern the interface dynamic for this system.     

Nafion聚离子修饰纳米Pt的合成及其影响因素

采用化学还原的方法成功地合成了Nafion聚离子修饰的纳米Pt颗粒，平均粒径为～4nm；由于表面缺电子的特性，纳米Pt粒子与Nafion高分子长链上的-SO3^-基团有较强的结合，使粒子随-SO3^的存在状态而分散，在水溶液中呈现与离子团簇相似的分散状态。FTIR显示Pt颗粒存在表面原子暴露在修饰离子之外，因此，这种粒子在具有功能结构的催化领域有着很好的应用前景；合成过程中反应速率随Nafion含量的降低、pH的增加而增大。