Influence of laser power on the orientation and microstructure of CeO2 films deposited on Hastelloy C276 tapes by laser chemical vapor deposition

CeO₂ films were prepared on LaMnO₃/MgO/Gd₂Zr₂O₇ multi-coated Hastelloy C276 tapes by laser chemical vapor deposition at different laser power (P_L) from 46 to 101 W. Epitaxial (1 0 0) CeO₂ films were prepared at P_L = 46-93 W (deposition temperature, T_dep = 705-792 K). Epitaxial CeO₂ films had rectangular-shaped grains at P_L = 46-77 W (T_dep = 705-754 K), while square-shaped grains were obtained at P_L = 85-93 W (T_dep = 769-792 K). CeO₂ films showed a columnar microstructure. Epitaxial (1 0 0) CeO₂ films with rectangular grains exhibited full width at half maximum of ω-scan on (2 0 0) reflection and ?-scan on (2 2 0) reflection of 3.4-3.2° and 6.0-7.2°, respectively. The deposition rate of the epitaxial (1 0 0) CeO₂ films had a maximum of 4.6 μm h⁻¹ at P_L = 77 W (T_dep = 754 K).     

A novel bacterial cellulose-based carbon paste electrode and its polyoxometalate-modified properties

A novel bacterial cellulose nanofiber-based carbon paste electrode (BCPE) was fabricated. It was characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Compared with traditional carbon paste electrode, BCPE exhibited better electrochemical reversibility with the enhancement of the redox currents and decrease of peak potential separation as well as lower charge transfer resistance in Fe(CN)₆^3?/4? redox system. Keggin-type sodium phosphopolyoxomolybdate, PMo₁₂, was successfully assembled on BCPE via cyclic voltametric scan, and the obtained PMo₁₂/BCPE possessed not only a good electrochemical behavior but also an excellent electrocatalytic activity toward the reduction of nitrite. Because of its nano-dimension, lower cost and prominent electrochemical properties, bacterial cellulose-based carbonaceous materials would be a candidate of graphite for the preparation of novel carbon paste electrode.     

Ionic Association of the Ionic Liquids [C4mim][BF4], [C4mim][PF6], and [Cnmim]Br in Molecular Solvents

Considering the ionic nature of ionic liquids (ILs), ionic association is expected to be essential in solutions of ILs and to have an important influence on their applications. Although numerous studies have been reported for the ionic association behavior of ILs in solution, quantitative results are quite scarce. Herein, the conductivities of the ILs [C_nmim]Br (n=4, 6, 8, 10, 12), [C₄mim][BF₄], and [C₄mim][PF₆] in various molecular solvents (water, methanol, 1‐propanol, 1‐pentanol, acetonitrile, and acetone) are determined at 298.15 K as a function of IL concentration. The conductance data are analyzed by the Lee–Wheaton conductivity equation in terms of the ionic association constant (K_A) and the limiting molar conductance (Λ_m⁰). Combined with the values for the Br^? anion reported in the literature, the limiting molar conductivities and the transference numbers of the cations and [BF₄]^? and [PF₆]^? anions are calculated in the molecular solvents. It is shown that the alkyl chain length of the cations and type of anion affect the ionic association constants and limiting molar conductivities of the ILs. For a given anion (Br^?), the Λ_m⁰ values decrease with increasing alkyl chain length of the cations in all the molecular solvents, whereas the K_A values of the ILs decrease in organic solvents but increase in water as the alkyl chain length of the cations increases. For the [C₄mim]⁺ cation, the limiting molar conductivities of the ILs decrease in the order Br^?>[BF₄]^?>[PF₆]^?, and their ionic association constants follow the order [BF₄]^?>[PF₆]^?>Br^? in water, acetone, and acetonitrile. Furthermore, and similar to the classical electrolytes, a linear relationship is observed between ln K_A of the ILs and the reciprocal of the dielectric constants of the molecular solvents. The ILs are solvated to a different extent by the molecular solvents, and ionic association is affected significantly by ionic solvation. This information is expected to be useful for the modulation of the IL conductance by the alkyl chain length of the cations, type of anion, and physical properties of the molecular solvents.     

A hybrid genetic algorithm with dominance properties for single machine scheduling with dependent penalties

In this paper, a hybrid genetic algorithm is developed to solve the single machine scheduling problem with the objective to minimize the weighted sum of earliness and tardiness costs. First, dominance properties of (the conditions on) the optimal schedule are developed based on the switching of two adjacent jobs i and j. These dominance properties are only necessary conditions and not sufficient conditions for any given schedule to be optimal. Therefore, these dominance properties are further embedded in the genetic algorithm and we call it genetic algorithm with dominance properties (GADP). This GADP is a hybrid genetic algorithm. The initial populations of schedules in the genetic algorithm are generated using these dominance properties. GA can further improve the performance of these initial solutions after the evolving procedures. The performances of hybrid genetic algorithm (GADP) have been compared with simple genetic algorithm (SGA) using benchmark instances. It is shown that this hybrid genetic algorithm (GADP) performs very well when compared with DP or SGA alone.     

Efficient experimental design tools for exploring large simulation models

Simulation experiments are typically faster, cheaper and more flexible than physical experiments. They are especially useful for pilot studies of complicated systems where little prior knowledge of the system behavior exists. One key characteristic of simulation experiments is the large number of factors and interactions between factors that impact decision makers. Traditional simulation approaches offer little help in analyzing large numbers of factors and interactions, which makes interpretation and application of results very difficult and often incorrect. In this paper we implement and demonstrate efficient design of experiments techniques to analyze large, complex simulation models. Looking specifically within the domain of organizational performance, we illustrate how our approach can be used to analyze even immense results spaces, driven by myriad factors with sometimes unknown interactions, and pursue optimal settings for different performance measures. This allows analysts to rapidly identify the most important, results-influencing factors within simulation models, employ an experimental design to fully explore the simulation space efficiently, and enhance system design through simulation. This dramatically increases the breadth and depth of insights available through analysis of simulation data, reduces the time required to analyze simulation-driven studies, and extends the state of the art in computational and mathematical organization theory.     

Fragmentation study of protonated chalcones by atmospheric pressure chemical ionization and tandem mass spectrometry

Fragmentation mechanisms of protonated chalcone and its derivatives with different functional groups were investigated by atmospheric pressure chemical ionization with tandem mass spectrometry (MS/MS). The major fragmentation pathways were loss of the phenyl group from the A or B ring, combined with loss of CO. Losses of H(2)O and CO from the precursor ions of [M+H](+) are proposed to occur via rearrangements. Elimination of water from protonated chalcones was observed in all the title compounds to yield a stable ion but it was difficult to obtain skeletal fragmentation of a precursor ion. Loss of CO was found in the MS/MS spectra of all the compounds except the nitro-substituted chalcones. When the [M+H--CO](+) ion was fragmented in the MS/MS experiments, there were distinctive losses of 15 and 28 Da, as the methyl radical and ethylene, respectively. The ion at m/z 130, found only in the nitro-substituted chalcones, was assigned as C(9)H(6)O by Fourier transform ion cyclotron resonance (FTICR)-MS/MS; m/z 130 is a common fragment ion in the electron ionization (EI) spectra of chalcones. In order to more easily distinguish the constitutional isomers of these chalcones, breakdown curves were produced and these provided strong support in this study.     

Formation of nanostructured materials via coalescence of amphiphilic hollow particles

A new, simplified route to amphiphilic core-shell nanotubes, microfibers, and microrods has been developed that does not involve the traditional utilization of well-defined block copolymers. Thus, amphiphilic graft copolymers (PEI-g-PMMA) are prepared by an aqueous free radical polymerization that self-assemble in situ to form uniform core-shell nanoparticles. The hydrophobic homopolymer (PMMA) that is also formed is incorporated in the cores. Slight cross-linking of the shells followed by extraction of the homopolymer results in hollow nanoparticles that coalesce to form nanotubes. When the shells are not cross-linked, the hollow particles coalesce to form microrods and microfibers. The sizes and shapes of the micromaterials can be controlled by varying the experimental conditions.     

Polymer-coated ferromagnetic colloids from well-defined macromolecular surfactants and assembly into nanoparticle chains

A novel synthetic route to polymer-coated ferromagnetic colloids of metallic cobalt has been developed. Well-defined end-functional polystyrenes were synthesized using controlled radical polymerization and used as surfactants in the thermolysis of dicobaltoctacarbonyl to afford uniform ferromagnetic nanoparticles. The presence of the polymer shell enabled prolonged colloidal stability of dispersions in a wide range of organic solvents and formed glassy encapsulating coatings around ferromagnetic cores in the solid state. These polymer-coated colloids assembled into robust, micron-sized nanoparticle chains when cast onto supporting surfaces due to dipolar associations of magnetic cores. Hierarchical assemblies were also prepared by blending polystyrene-coated cobalt colloids with larger silica beads.     

Large rigid blue-emitting pi-conjugated stilbenoid-based dendrimers: Synthesis and properties

Two large pi-conjugated dendrimers (G0 and G1) employing the stilbenoid moiety as the bridge unit have been developed through the Suzuki and the Horner-Wadsworth-Emmons reactions. The molecular weight of G1 is 10 973 Da. Both G0 and G1 have good fluorescence quantum yields and exhibit similar absorption and emission behaviors in solutions and in thin films. They emit strong blue fluorescence in films under the irradiation of UV light.     

The effect of reflector geometry on the acoustic field and bubble dynamics produced by an electrohydraulic shock wave lithotripter

A theoretical model for the propagation of shock wave from an axisymmetric reflector was developed by modifying the initial conditions for the conventional solution of a nonlinear parabolic wave equation (i.e., the Khokhlov-Zabolotskaya-Kuznestsov equation). The ellipsoidal reflector of an HM-3 lithotripter is modeled equivalently as a self-focusing spherically distributed pressure source. The pressure wave form generated by the spark discharge of the HM-3 electrode was measured by a fiber optic probe hydrophone and used as source conditions in the numerical calculation. The simulated pressure wave forms, accounting for the effects of diffraction, nonlinearity, and thermoviscous absorption in wave propagation and focusing, were compared with the measured results and a reasonably good agreement was found. Furthermore, the primary characteristics in the pressure wave forms produced by different reflector geometries, such as that produced by a reflector insert, can also be predicted by this model. It is interesting to note that when the interpulse delay time calculated by linear geometric model is less than about 1.5 micros, two pulses from the reflector insert and the uncovered bottom of the original HM-3 reflector will merge together. Coupling the simulated pressure wave form with the Gilmore model was carried out to evaluate the effect of reflector geometry on resultant bubble dynamics in a lithotripter field. Altogether, the equivalent reflector model was found to provide a useful tool for the prediction of pressure wave form generated in a lithotripter field. This model may be used to guide the design optimization of reflector geometries for improving the performance and safety of clinical lithotripters.