Vacancy capillary zone electrophoresis and differential capillary zone electrophoresis: variations on a well-known theme

Two new variants on capillary zone electrophoresis (CZE) are described and experimentally investigated. In vacancy CZE the sample, diluted with a background electrolyte, fills the electrode vessels and the separation capillary. When pure background electrolyte is injected, the resulting electropherogram represents the composition of the sample. The electropherogram is almost identical with the result of a conventional CZE experiment. In differential CZE the sample again fills the electrode vessels and the separation compartment. After injection of a slightly different sample, a differential electropherogram is obtained that represents the differences between the two samples. The retention times of both new variants are comparable with conventional CZE, the separation efficiency, in terms of theoretical plates, is marginally lower, and both show good quantitative characteristics. The concept of vacancy electrophoresis explains the origin of unexpected system peaks in conventional CZE when multiple co-ions in the background electrolyte are used.     

New method based on capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) to monitor interaction between nanoparticles and the amyloid-β peptide

A novel application of capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was proposed to efficiently detect and monitor the interaction between polymeric nanoparticles and the β-Amyloid peptide (Aβ(1-42)), a biomarker for Alzheimer's Disease (AD), at concentrations close to physiological conditions. The CE-LIF method allowed the interaction between PEGylated poly(alkyl cyanoacrylate) nanoparticles (NPs) and the soluble Aβ(1-42) peptide monomers to be highlighted. These results were confirmed by surface plasmon resonance (SPR) and confocal laser scanning microscopy (CLSM). Whereas SPR showed an interaction between the NPs and the Aβ(1-42) peptide, CLSM allowed the formation of large aggregates/assemblies at high NP and peptide concentrations to be visualized. All these results suggested that these nanoparticles could bind the Aβ(1-42) peptide and influence its aggregation kinetics. Interestingly, the non-PEGylated poly(alkyl cyanoacrylate) NPs did not alter the aggregation kinetics of the Aβ(1-42) peptide, thus emphasizing the high level of discrimination of the CE-LIF method with respect to NPs.     

Formation of molecular doping patterns in organic–inorganic hybrid films by a capillary electrophoresis doping technique

A new technique is proposed for the fabrication of fine patterns of molecular doping in organic–inorganic hybrid materials by the combination of capillary electrophoresis doping (CED) and photolithography. The UV-induced polymerization of bonds in organic groups yields a fine contrast of structures with the desired pattern in organic–inorganic hybrid films, and CED treatment introduces functional molecules only into unirradiated regions to form the doping patterns of molecules inside the films. The fine patterning of rhodamine-6G doping with from 2 to 4 μm resolution is demonstrated in hybrid films of 10 μm thickness.     

A (-)-menthyl bonded silica phase for chiral separations: synthesis and solid state NMR characterization

A new (-)-menthyl bonded silica phase has been prepared by hydrosilation of a hydride silica intermediate. The hydride silica intermediate was synthesized by the reaction of a monoalkoxysilane (CH(3))(2)SiH(OEt) with silica gel, yielding a relatively high surface coverage (4.4 μmol/m(2)) of SiH groups. This intermediate was then used successfully in the preparation of a monomeric (-)-menthyl bonded silica phase. The bonded phase produced has been used for the chromatographic separation of enantiomers in a reversed phase mode (chiral separations). Solid state (13)C and (29)Si CP-MAS NMR spectroscopy and DRIFT spectroscopy provides valuable information on the structure of the different surface species formed on silica after modification. The surface coverage of the hydride silica intermediate and of the final bonded silica phase produced are also determined. It is found that this modification procedure can exclusively produce a monomeric coverage of SiH groups on the silica surface and can further produce a final monomeric bonded organic silica phase for the separation of enantiomers.     

XPS and NEXAFS studies of VUV/O₃-treated aromatic polyurea and its application to microchip electrophoresis

In this study, the authors performed X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) studies of vacuum ultraviolet (VUV)/O?-treated aromatic polyurea films to investigate their treatment effects. XPS and NEXAFS spectra indicate that the benzene ring was cleaved after treatment and that carboxyl, hydroxyl, ketone and aldehyde groups were formed at the cleaved sites. The VUV/O?-treated polyurea film was applied to a polymethylmethacrylate (PMMA) microchip for microchip electrophoresis (MCE) of bovine serum albumin (BSA). Fast electro-osmotic mobility of 4.6×10(-4)?cm2/V/s as well as reduction of the BSA adhesion was achieved. This functional surface is useful for high-speed MCE analysis.     

Immune algorithm with dynamic environments and its application to greenhouse control

A novel immune algorithm with dynamic environments (IADE), suitable for time-varying single-objective optimization problems with the static or variable dimension of design space, is proposed based on the immune response principle. Several immune operators, relying upon the functions or metaphors of somatic maturation, immune memory and immune cells, are designed to adapt the changing environment and track the location of the optimum. Especially, the environmental recognition rule and memory pool are established to speed up to search the optimum of the environment. Several algorithms reported are participated in comparison against IADE through using theoretical test problems and a practical greenhouse control problem. Preliminary experiments show that IADE can not only obtain great superiority, but also track rapidly time-varying environments. Comparative analysis illustrates IADE’s potential value.     

Electron–photon equation of motion with application to the Lamb shift

An equation of motion (EOM) is proposed for the electron which includes the effect of the radiation field on the electron's motion. The new EOM – the electron–photon EOM (EPEOM) – is the same as Dirac's equation with the ‘bare’ or mechanical mass replaced by a complex electromagnetic mass whose real part is interpreted as the observed mass of the electron. The Lamb shift is calculated from the difference of the EPEOM energy and the Dirac-equation energy.     

Spatial–temporal enhancements of material flux analysis methods, with application to cadmium management in an agricultural region in Australia

The accumulation of cadmium (Cd) on agricultural lands and the resultant contamination of the food chain are challenging problems for the agricultural sector in Australia. This paper describes a method to estimate spatial accumulation of Cd on agricultural land, to support policy developments that ensure acceptable limits are not exceeded. This method integrates material flux analysis and geographic information system models. It is demonstrated through application to Cd management within the Murrumbidgee Irrigation Area (MIA). The results of this study include spatially estimated net Cd balance in MIA soils over the 10 years 1992–2000. Combined with initial estimates of spatial Cd contamination in 1992, this permits estimation of soil Cd concentration in the MIA in 2002. The areas that have high soil Cd concentration have seen increases in Cd levels of 1.5–1.6 times of Cd concentration in 1992. The results are used to evaluate the trend of Cd exceeding an acceptable limit on a spatial basis, and development of an effective policy and limit to control Cd input to soil.     

Arbitrary Lagrangian–Eulerian method in plasticity of pressure-sensitive material: application to powder forming processes

In this paper, an application of Arbitrary Lagrangian–Eulerian (ALE) method is presented in plasticity behavior of pressure-sensitive material, with special reference to large deformation analysis of powder compaction process. In ALE technique, the reference configuration is used for describing the motion, instead of material configuration in Lagrangian, and spatial configuration in Eulerian formulation. The convective term is used to reflect the relative motion between the mesh and the material. Each time-step is divided into the Lagrangian phase and Eulerian phase. The convection term is neglected in the material phase, which is identical to a time-step in a standard Lagrangian analysis. The stresses and plastic internal variables are converted to account the relative mesh-material motion in the convection phase. The ALE formulation is then performed within the framework of a three-invariant cap plasticity model in order to predict the non-uniform density distribution during the large deformation of powder die pressing. The plasticity model is based on a hardening rule with the isotropic and kinematic material functions. The constitutive elasto-plastic matrix and its components are derived by using the definition of yield surface, material functions and non-linear elastic behavior, as function of hardening parameters. Finally, the numerical examples are performed to illustrate the applicability of the computational algorithm in modeling of powder forming process and the results are compared with those obtained from Lagrangian simulation in order to demonstrate the accuracy of proposed model.     

Integrated capillary electrophoresis on flexible silicone microdevices: analysis of DNA restriction fragments and detection of single DNA molecules on microchips

Microchips for integrated capillary electrophoresis systems were produced by molding a poly(dimethylsiloxane) (PDMS) silicone elastomer against a microfabricated master. The good adhesion of the PDMS devices on clean planar surfaces allows for a simple and inexpensive generation of networks of sealed microchannels, thus removing the constraints of elaborate bonding procedures. The performance of the devices is demonstrated with both fast separations of φX-174/HaeIII DNA restriction fragments labeled with the intercalating dye YOYO-1 and fluorescently labeled peptides. Detection limits in the order of a few zeptomoles (10(-)(21) mol) have been achieved for each injected DNA fragment, corresponding to a mass detection limit of ～2 fg for the 603 base pair fragment. Single λ-DNA molecules intercalated with YOYO-1 at a base pair-to-dye ratio of 10:1 could be detected with an uncomplicated laser-induced fluorescence detection setup. High single-molecule detection efficiency (>50%) was achieved under electrophoretically controlled mass transport conditions in PDMS microchannels.     

Solutions of solid‐fluid conjugated problems with applications in the capillary die heat transfer

Abstract

Analytical solutions of solid‐liquid conjugated Graetz problems with applications in the analysis of heat transfer in the capillary die are presented. In these problems, temperatures in adjacent phases are coupled through the conjugated conditions, which require that the flux and the rate of transfer are continuous. An analytical solution is obtained by using the direct eigenfunction expansion technique. The resulting generalized Sturm‐Liouville problem is not of the conventional type due to the discontinuity of the coefficient which arises from the conjugated conditions at the phase interface. An efficient numerical algorithm is developed to find the eigenvalues, eigenfunctions and the related coefficients. Sturm's equi‐oscillation theorem is applied to overcome the difficulty due to the discontinuity of the coefficients. The problem of heat removal from a heated solid cylinder by a surrounding annular flow fluid is solved. Results are in good agreement with existing solutions. The same technique is used to analyze the heat transfer in a capillary die. Results obtained show that wall resistance does have a significant effect on the temperature profile of the fluid.     

GGA+U method from first principles: application to reduction–oxidation properties in ceria-based oxides

We implement DFT calculations by a Hubbard-like correction for localized strongly correlated electrons, coupled with a generalized gradient approximation to the exchange-correlation functional to elucidate the role of the ceria based catalytically active supports for the chemical reactions involving reduction–oxidation processes. These catalytic processes are relevant for many industrial applications, such as catalytic converters in automotive applications, solid oxide fuel cells, and hydrogen production from biomass. The Hubbard-like correction U is computed from first principles as physical property of the system. We find that the high performance of ceria-based oxides as an active support for noble metals in catalysis relies on an efficient supply of lattice oxygen at reaction sites governed by oxygen vacancy formation.     

Ultra-stable silica-coated chiral Au-nanorod assemblies: Core–shell nanostructures with enhanced chiroptical properties

Chiral nano-assemblies with amplified optical activity have attracted particular interest for their potential application in photonics, sensing and catalysis. Yet it still remains a great challenge to realize their real applications because of the instability of these assembled nanostructures. Herein, we demonstrate a facile and efficient method to fabricate ultra-stable chiral nanostructures with strong chiroptical properties. In these novel chiral nanostructures, side-by-side assembly of chiral cysteine-modified gold nanorods serves as the core while mesoporous silica acts as the shell. The chiral core–shell nanostructures exhibit an evident plasmonic circular dichroism (CD) response originating from the chiral core. Impressively, such plasmonic CD signals can be easily manipulated by changing the number as well as the aspect ratio of Au nanorods in the assemblies located at the core. In addition, because of the stabilization effect of silica shells, the chiroptical performance of these core–shell nanostructures is significantly improved in different chemical environments.

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Open-ended photoacoustic cells: application to two-layer samples using pulse laser-induced photoacoustics

To measure the difference between samples in situ, two types of open-ended photoacoustic cells were constructed. One type was a differential open-ended photoacoustic cell with a differential microphone, which connected two equivalent open-ended cell chambers through two waveguides. The other design used single open-ended photoacoustic cell chambers, each with an electric condenser microphone. A pair of these was used to suppress background signal by subtraction of the signals. The performance of these cells was compared to that of a conventional photoacoustic apparatus with a chopper. Detection limits of Sudan red for those cells were about 1.29 and 2.35 ng for a differential open-ended cell and a single open-ended cell, respectively. The photoacoustic cells were then applied to the pulse mode operation, using a nitrogen laser as a pulse light source. The laser beams were led to the photoacoustic cells through quartz optical fibers. Using this instrument setup, depth profiling analysis was carried out for two-layer samples made of poly(methyl methacrylate) (PMMA) or polystyrene (PS) films. A linear relationship was obtained between the signal delay time and the film thickness. The delay time of the signal (τ) was expressed in terms of the thermal diffusivity (κ/cm(2) s(-)(1)) of the film as τ (ms) ? (2.25 × 10(-3)) x (μm) κ(-1/2). The method was successful in measuring the thickness of transparent surface layers. We applied this technique to observe the generation of a certain chromophore, thought to be melanin, under the surface of human skin tanned by exposure to long-wavelength UV light.     

Saturation of capillary pores in silicon carbide briqettes with liquid–phase carbon-containing solutions before the reaction-sintering

It has been studied the increasing of the carbon saturation of a porous silicon–carbide briquette by a multiple impregnation of oil coke solutions instead of a traditionally used lamp black hardphase powder or fine-dispersed graphite powder intended for a reaction sintering of silicon carbide aimed to decrease the free silicon part, which remains in the structure after sintering.     

Improved sensitivity of tunable far-infrared spectroscopy: application to the detection of HBr in the ? = 1 state

We report the first detection of the pure rotational spectra of H79 Br and H81 Br in the first excited vibrational state at room temperature. We recorded the spectra with a tunable far-infrared spectrometer equipped with an optimized Ge:Ga photodetector and an improved multiple-pass gas cell to enhance the overall sensitivity. In particular, a minimum detectable absorption of better than 10-7 cm-1 was achieved. We measured a total of 60 frequencies for the two isotopomers with an accuracy of a few parts in 108 . The hyperfine structure was observed at the lower J values. The derived spectroscopic parameters, which include nuclear and quadrupole hyperfine constants, reproduce the assigned transitions within their experimental errors.     

Interfacial capillary–gravity waves due to a fundamental singularity in a system of two semi-infinite fluids

The interfacial capillary–gravity waves due to a transient fundamental singularity immersed in a system of two semi-infinite immiscible fluids of different densities are investigated analytically for two- and three- dimensional cases. The two-fluid system, which consists of an inviscid fluid overlying a viscous fluid, is assumed to be incompressible and initially quiescent. The two fluids are each homogeneous, and separated by a sharp and stable interface. The Laplace equation is taken as the governing equation for the inviscid flow, while the linearized unsteady Navier–Stokes equations are used for the viscous flow. With surface tension taken into consideration, the kinematic and dynamic conditions on the interface are linearized for small-amplitude waves. The singularity is modeled as a simple mass source when immersed in the inviscid fluid above the interface, or as a vertical point force when immersed in the viscous fluid beneath the interface. Based on the integral solutions for the interfacial waves, the asymptotic wave profiles are derived for large times with a fixed distance-to-time ratio by means of the generalized method of stationary phase. It is found that there exists a minimum group velocity, and the wave system observed will depend on the moving speed of the observer. Two schemes of expansion of the phase function are proposed for the two cases when the moving speed of an observer is larger than, or close to the minimum group velocity. Explicit analytical solutions are presented for the long gravity-dominant and the short capillary-dominant wave systems, incorporating the effects of density ratio, surface tension, viscosity and immersion depth of the singularity.