Jingxian Yu

Evolutionary Modeling of Systems of Ordinary Differential Equations with Genetic Programming

This paper describes an approach to the evolutionary modeling problem of ordinary differential equations including systems of ordinary differential equations and higher-order differential equations. Hybrid evolutionary modeling algorithms are presented to implement the automatic modeling of one- and multi-dimensional dynamic systems respectively. The main idea of the method is to embed a genetic algorithm in genetic programming where the latter is employed to discover and optimize the structure of a model, while the former is employed to optimize its parameters. A number of practical examples are used to demonstrate the effectiveness of the approach. Experimental results show that the algorithm has some advantages over most available modeling methods.

Ruthenium Porphyrin Functionalized Single-Walled Carbon Nanotube Arrays-A Step Toward Light Harvesting Antenna and Multibit Information Storage

Ruthenium porphyrin functionalized single-walled carbon nanotube arrays have been prepared using coordination of the axial position of the metal ion onto 4-aminopyridine preassembled single-walled carbon nanotubes directly anchored to a silicon(100) surface (SWCNTs-Si). The formation of these ruthenium porphyrin functionalized single-walled carbon nanotube array electrodes (RuTPP-SWCNTs-Si) has been monitored using infrared spectroscopy (IR), differential pulse voltammetry (DPV), atomic force microscopy (AFM), laser desorption time-of-flight mass spectroscopy (LDI-TOF-MS), UV-vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. Electrochemical results show two successive one-electron reversible redox waves. The surface concentration of the ruthenium porphyrin molecules is 3.44 x 10 (-8) mol cm (-2). Optical results indicate that the immobilization of ruthenium porphyrin enhances the light absorption of SWCNTs-Si surfaces in the visible light region. Moreover mixed assembly of ferrocene/porphyrin onto carbon nanotube arrays has been achieved by altering the ratio of two redox-active species in the deposition solution. These results suggest the ruthenium porphyrin modified electrodes are excellent candidates for molecular memory devices and light harvesting antennae.

A study of calcium zincate as negative electrode materials for secondary batteries

The properties of calcium zincate as negative electrode materials for secondary batteries were examined by powder microelectrode, cyclic voltammetry, charge–discharge cycle measurements and X-ray diffraction (XRD) analysis. The results show that the cycleability of calcium zincate is obviously superior to that of ZnO and that of the mixture of ZnO and Ca(OH)2 (the molar ratio of Zn:Ca ¼ 2:1). Calcium zincate forms zinc metal during the charging and exhibits an initial discharge capacity 230 mAh g � 1 . With the discharge cut-off voltage of 1.0 V, the discharge capacity of the experimental Zn/NiOOH cell does not decay much during 500 cycles, exhibiting good prospect for practical use. # 2001 Elsevier Science B.V. All rights reserved.

Spectroscopic studies on the interaction of efonidipine with bovine serum albumin

The binding of efonidipine to bovine serum albumin (BSA) was investigated by fluorescence spectroscopy and circular dichroism (CD) technique. The quenching mechanism of fluorescence BSA by efonidipine showed that efonidipine quenched the fluorescence of tryptophan residue mainly through the collision mode. The thermodynamic parameters DeltaH0 and DeltaS0 were calculated to be 75.95 kJldrmo-1 and 342.32 kJldrmol-1, respectively, indicating that the hydrophobic force played a major role. The results of CD spectrum and synchronous fluorescence spectrum showed that the binding of efonidipine to BSA leads to conformational change of BSA. Binding studies in the presence of ANS indicated that efonidipine competed with ANS for hydrophobic sites on BSA. The effects of metal ion on the binding constant of efonidipine-BSA complex were also investigated.

Direct attachment of well-aligned single-walled carbon nanotube architectures to silicon (100) surfaces : a simple approach for device assembly

A new approach for the attachment of vertically-aligned shortened carbon nanotube architectures to a silicon (100) substrate by chemical anchoring directly to the surface has been demonstrated for the first time. The ordered assembly of single-walled carbon nanotubes (SWCNTs) was accomplished by hydroxylating the silicon surface followed by a condensation reaction with carboxylic acid functionalised SWCNTs. This new nanostructure has been characterised by X-ray photoelectron, Raman and Fourier transform infrared (FTIR) spectroscopy as well as scanning electron and atomic force microscopy. The assembly behaviour of SWCNTs onto the silicon surface shows a fast initial step producing isolated functionalised carbon nanotubes or nanotube bundles anchored to the silicon surface followed by a slower step where the adsorbed nanotubes grow into larger aggregates via van der Waals interactions between adsorbed and solvated nanotubes. The electrochemical and optical properties of the SWCNTs directly attached to silicon have also been investigated. These new nanostructures are excellent electrochemical electrodes. They also fluoresce in the wavelength range 650-800 nm. The successful attachment of the SWCNTs directly to silicon provides a simple, new avenue for fabrication and development of silicon-based nanoelectronic, nano-optoelectronic and sensing devices. Compared to existing techniques, this new approach has several advantages including low operating temperature, low cost and the possibility of further modification.

Effect of surface functionality of magnetic silica nanoparticles on the cellular uptake by glioma cells in vitro

The cellular uptake efficiency of nanoparticles depends mainly on the surface characteristics of these materials. In this study, amine- and ester-terminated polyamidoamine (PAMAM) dendrimers were used to functionalize fluorescein-doped magnetic mesoporous silica nanoparticles (FMNPs) to evaluate the effect of surface functionality on cellular uptake by glioma cells. The successful synthesis of these materials was confirmed by transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and zeta potential titration. Neither of these materials showed acute cytotoxicity and it was demonstrated that the different surface functionalities regulated the ability of the nanoparticles to cross cell membranes. In addition to serving as an imaging agent, fluorescein isothiocyanate isomer I (FITC) was used as a model drug to evaluate the drug release rates of these drug delivery systems.

The Influences of Organic Additives on Zinc Electrocrystallization from KCl Solutions

The effects of some conventional additives such as triton X-10 (TX-10), sodium methylene bis(naphthalene sulfonate) (NNO), phenylbenzylketone (PBK), and a CH- 1 brightener on the electrodeposition of zinc onto the glassy carbon electrode were examined using chronoamperometry. The surface morphology, grain size, and texture of the deposits were characterized by scanning electron microscope, transmission electron microscope, and X-ray diffraction. It was found that the electrocrystallization mechanisms of zinc and microstructure of deposits are sensitive to the identity of organic additives. On one hand, in the absence of additive or in the presence of NNO or PBK, zinc deposition proceeds by three-dimensional instantaneous nucleation and growth, while in the presence of TX-10 or a CH- I brightener, zinc deposition follows the three-dimensional progressive nucleation and growth. On the other hand, in the absence of additive, the deposit forms a loose and porous structure with no texture. In the presence of PBK and TX-10, the deposits are (101) and (110) texture, respectively. And in the presence of a CH- brightener, deposit is smooth and bright and forms a (101) and (110) texture, where a homogeneous distribution of small 8 nm grains appears. These facts show that the effects of a CH- brightener on the zinc electrodeposition mainly result from the combinational action of TX-10 and PBK. In addition, we also found that surface morphology of deposits is strongly correlated to deposit texture.

Structural and electrochemical characterization of mechanochemically synthesized calcium zincate as rechargeable anodic materials

Hydrated calcium zincate was synthesized by mechanical ball milling of ZnO and Ca(OH)2 in water at room temperature. The structural and electrochemical properties of this material used as rechargeable anodic material were examined by microelectrode voltammetry, charge–discharge measurements and structural analysis. The results showed that during mechanical milling, ZnO, Ca(OH)2 and H2O reacted rapidly to form Ca[Zn(OH)3]2 · 2H2O which was subsequently transformed to a stable structure CaZn2(OH)6 · 2H2O. Since this composite oxide has lower solubility in KOH solution (<35 wt %) and better electrochemical reversibility than ZnO-based negative materials, the zinc anodes using this material can overcome the problems of shape changes and dendritc formation, and therefore exhibit improved cycling life.

The kinetic evolutionary modeling of complex systems of chemical reactions

Abstract To overcome the drawbacks of most available methods for kinetic analysis, this paper proposes a hybrid evolutionary modeling algorithm called HEMA to build kinetic models of systems of ordinary differential equations (ODEs) automatically for complex systems of chemical reactions. The main idea of the algorithm is to embed a genetic algorithm (GA) into genetic programming (GP) where GP is employed to optimize the structure of a model, while a GA is employed to optimize its parameters. The experimental results of two chemical reaction systems show that by running the HEMA, the computer can discover the kinetic models automatically which are appropriate for describing the kinetic characteristics of the reacting systems. Those models can not only fit the kinetic data very well, but also give good predictions.

Effects of Anions on the Zinc Electrodeposition onto Glassy-Carbon Electrode

The zinc electrodeposition onto glassy-carbon electrode from the sulfate, chloride and acetate solutions is examined using cyclic voltammetry and chronoamperometry. The surface morphology of zinc deposited films is observed by scanning electron microscopy. The results show that all mechanisms of the zinc electrocrystallization on glassy-carbon electrode in the three solutions follow the same three-dimensional instantaneous nucleation and growth. The anions mainly affect the nucleation densities during zinc deposition, which results in different surface morphology. In the presence of acetate and chloride ions, the deposited zinc film tends to grow in a multi-layered pattern, while in sulfate solution the zinc deposition forms irregular grains.