Extension of the CVBEM to higher-order trial functions

The higher-order trial functions, such as the parabolic, cubic, and Hermite cubic polynomial functions, for the complex boundary element method are derived and their computer programs are developed. Using the considered higher-order trial function, models obtained compatible results to the linear trial function model.     

Hole structures of polymers and zeolites probed by two-dimensional angular correlation of annihilation radiation

The two-dimensional angular correlation of annihilation radiation (2D-ACAR) technique has been developed to measure the hole structure of stretched and oriented polymers. The determination of polymer hole structure is demonstrated in a stretched semi-crystalline polyaryl-ether-ether-ketone (PEEK) sample. The atomic scale anisotropy is found to be consistent with the macroscopic scale stretch ratio. Applications of the 2D-ACAR method to image the three-dimensional hole, free-volume, and cavity structures of molecular systems are discussed.     

Fungal biomass with grafted poly(acrylic acid) for enhancement of Cu(II) and Cd(II) biosorption

The biomass of Penicillium chrysogenum was modified by graft polymerization of acrylic acid (AAc) on the surface of ozone-pretreated biomass. The sorption capacity for copper and cadmium increased significantly as a large number of carboxyl groups were present on the biomass surface, especially when the carboxylic acid group was converted to carboxylate ions using NaOH. When modeled using the Langmuir isotherm, the sorption capacities were 1.70 and 1.87 mmol g(-1) for copper and cadmium, respectively. The loaded biosorbent was regenerated using HCl solution and used repeatedly over five cycles with little loss of uptake capacity beyond the second cycle. The sorption of the two metals was time-dependent, and the kinetics fitted the pseudo-second-order equation well. The Freundlich, Langmuir, Temkin, and Dubinin-Redushkevich isotherms were used to model the metal sorption isotherms, and the thermodynamic parameters calculated show that the sorption was spontaneous and endothermic under the condition applied and that the biomass has similar sorption affinities for the two metals. Fourier transform infrared and X-ray photoelectron spectroscopy reveal that carboxyl, amide, and hydroxyl groups on the biomass surface were involved in the sorption of copper and cadmium and ion exchange and complexation dominated the sorption process.     

Flow Injection Analysis of Chloramphenicol by Using a Disposable Wall‐Jet Ring Disk Carbon Electrode

A preanodized screen‐printed ring disk carbon electrode was applied to the determination of chloramphenicol (Ph? NO₂, CAP) by flow injection analysis (FIA). By setting up the first irreversible reduction reaction of Ph? NO₂ to Ph? NHOH at the disk electrode, the following reversible oxidation of hydroxylamine (Ph? NHOH) to the nitroso (Ph? NO) derivative can be monitored/collected at the ring electrode for CAP analysis. The interference from dissolved oxygen and others can thus be avoided by using this approach and precise CAP determination can be easily performed by FIA under aerobic conditions. Preanodization treatment helps to lower the overpotential of the electrochemical reaction of CAP and favors the selective detection in aqueous medium. Under the optimum conditions, ten repetitive determinations at 1 μM and 10 μM CAP resulted in relative standard deviations of less than 4%, indicating good reproducibility of the system. A linear calibration range of 0.1–20 μM with a detection limit of 0.074 μM (S/N=3) was obtained. Veterinary pharmaceutics were finally analyzed by this sensor to validate its practical applicability.     

The effects of preparation method on the characteristics of alumina-zirconia powders

Two series of Al₂O₃-ZrO₂ powders with various contents of ZrO₂ were synthesized by sol-gel (chemical polymerization) and coprecipitation methods. The effect of ZrO₂ content and preparation method on the structure and texture of the resultant powders were determined. The samples were characterized by nitrogen sorption, thermal gravimetric analysis, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The sol-gel method yields more homogeneous powder and retards the aggregation of particles. It produces powders with a larger surface area, a smaller pore size, and a narrower pore size distribution than the coprecipitated one. The X-ray diffraction results show that the powders are amorphous at the calcination temperature below 700°C for both methods. Incorporation of zirconia into alumina greatly affects the surface properties of the powders upon heating, exerting a protective effect against sintering, and inhibiting both the crystallization of the -Al₂O₃ phase and the - to -phase transformation. Zirconia is dispersed in alumina matrix and does not form a new structure.     

Photoinduced Electron Transfer Reactions of 3,3‐Dialkylated 4,5‐Diphenyl‐3H‐Pyrazoles: A New Route to the Formation of the Solvent Adducts

3,3‐Dialkyl‐4,5‐diphenyl‐3H‐pyrazoles undergo readily photoinduced electron transfer (PET) reaction with 2,4,6‐triphenylpyrylium tetrafluoroborate (TPP⁺) in acetonitrile to produce cyclopropenes and 2H‐pyrroles. During prolonged irradiation, the new ring‐closure products derived from 2H‐pyrroles as the secondary photoproducts are also produced. However, the corresponding ester analog exhibits different behavior to obtain the cyclopropene as the primary photoproduct and a [2+2] dimer of the cyclopropene as the secondary photoproduct. A rationale for the different behavior is offered.     

Highly effective sulfated zirconia nanocatalysts grown out of colloidal silica at high temperature

A large surface-to-volume ratio is a prerequisite for highly effective catalysts. Making catalysts in the form of nanoparticles provides a good way to achieve the aim. However, agglomeration of nanoparticles during the preparation and utilization of nanocatalysts remains a formidable problem. Here, we present a novel approach in which nano units of catalysts are formed in the matrix of a colloidal carrier, with assistance of a cross-linking agent, and then grow out of the carrier upon calcination at high temperature. This ensures that the catalysts not only do not agglomerate, but also have a low cost and high catalytic efficiency due to the large surface-to-volume ratio and the absence of carbon deposition. The technique is demonstrated by the successful preparation of a binary nanocatalyst that consists of a silica nanoparticle core and a sulfated zirconia (SZ) nanocrystal shell (JML-1). The synthesis was achieved by converting sulfated zirconia (SZ) and silica solutions into a composite gel by means of sol-gel processing in the presence of triethoxysilane as the cross-linking agent, followed by heating at 50 degrees C and calcining at 550 degrees C. Relative to other catalysts, such as pure SZ, non-nanodispersed SZ over silica (SZ/SiO2), and zeolites Y, Beta, and ZSM-5, JML-1 exhibits superior catalytic activity in many reactions. For example, the activity of JML-1 in the production of gasoline by alkylation of 1-butene with isobutene remained at 95% or higher after 20 h of reaction and was over 90% after being regenerated five times. In sharp contrast, SZ and SZ/SiO2 give a high activity only for 2 h and the initial activity of zeolites Beta and ZSM-5 are about 88 and 60%, respectively. These findings demonstrate that non-agglomerated nanoparticles anchored onto a carrier surface can be prepared and the technique provides a versatile route to new highly effective nanocatalyst systems.     

Efficient green coumarin dopants for organic light-emitting devices

We have synthesized a new green fluorescent dopant C-545P having incorporated five strategically placed "methyl" steric spacers on the julolidyl ring system. C-545P has good thermal properties and photostability, and when fabricated as a dopant in an Alq(3)-hosted OLED device, it shows notable improvement in luminance efficiency and is more resistant to concentration quenching than C-545T, particularly in the doping concentration range between 1 and 2% v/v, while achieving comparable device stability. [structure: see text]     

扇形PAMAM树枝状高分子的合成与表征

树枝状化合物是聚合物合成科学上第一次不采用生物技术合成的结构精确的大分子。它被称为是继线形、交联形、支链形聚合物后的第4种结构类型的高分子。树枝状高分子的合成是通过多官能团基元进行逐步的有机反应而非传统的聚合方法。近年来，除了发散法、收敛法合成以外，