Capillary electrophoresis to mass spectrometry interface using a porous junction

A new capillary electrophoresis interface to electrospray ionization mass spectrometry (CE/ESI-MS) is introduced in which the electrical connection to the CE capillary outlet/ESI electrode is achieved by transfer of small ions related to the background electrolyte (BGE) through a porous section near the CE capillary outlet. In this design, only a small section of the capillary wall is made porous. The porous section is created by first thinning a small section of the capillary wall by drilling a well into it and then etching the remaining thin wall porous. This design has two advantages over previous designs (in which the whole circumference of the capillary was made porous): first, the capillary interface is more robust because only a small section of it is made porous, and therefore, no liquid junction is needed to secure the porous section. The electrical connection is achieved simply by inserting the capillary outlet containing the porous junction into the existing ESI needle and filling the needle with the BGE. Second, the time required to make the fused silica porous is reduced from approximately 1 h to a few minutes. In addition, there is no dead volume associated with the porous design, and because the actual metal/liquid contact occurs outside of the CE capillary, bubble formation due to redox reactions of water at the electrode does not affect CE/ESI-MS performance. The performance of this interface is demonstrated by the analyses of peptide and protein mixtures.     

Structure–properties-performance relationships in complex epoxy nanocomposites: A complete picture applying chemorheological and thermo-mechanical kinetic analyses

Herein the kinetics of network formation (cross-linking) and network degradation (thermal decomposition) in a complex system based on epoxy resin reinforced with hyperbranched amino polymer-functionalized nanoparticles (HAPF) were discussed. Five classes of nanoparticles, that is, nano-SiO₂, halloysite nanotubes (HNTs), HNTs@nano-SiO₂ core/shell, HAPF/nano-SiO₂, HAPF/HNTs@nano-SiO₂ core/shell were loaded at 0.5, 1.0, 2.0 (optimal loading among prepared samples), and 5 wt% were examined. Parameters of the cure kinetics and degradation were correlated, and the mechanical properties were interpreted in terms of microstructure and rheological analyses. The isothermal chemorheological cure kinetics study (60, 70, and 80°C) revealed a low activation energy for epoxy/HAPF/HNTs@nano-SiO₂ core/shell nanocomposite (72.21 kJ/mol), compared with the blank epoxy (79.99 kJ/mol). Correspondingly, gel time of the system decreased from 1040 to 515 to 237 s upon isotherms of 60, 70, and 80°C, respectively. Tensile strength was also increased vividly (ca. 32%), possibly due to the strong interfacial adhesion, which reflected in an induced shear yielding. Nitrogen-mediated thermal decomposition kinetics suggested an average degradation activation energies of ca. 150 and 210 kJ/mol for the assigned nanocomposites and the blank epoxy, respectively. Overall, there was a complete agreement between the kinetics of network formation and network degradation in the studied epoxy nanocomposite. This work enables understanding of structure-properties-performance in complex epoxy nanocomposites.     

Prediction of Minerals Producing Acid Mine Drainage Using a Computer-Assisted Thermodynamic Chemical Equilibrium Model

Methods such as optical microscopy, electron microscopy, and X-ray diffraction are sometimes used to identify minerals involved in the production of acid mine drainage (AMD). A simpler method to identify the minerals without losing accuracy would decrease costs. This paper presents an overview of the important oxidation reactions of sulphide minerals and related chemical components produced by these oxidation reactions. A methodology for predicting the minerals producing AMD using MINTEQ is also discussed. This method can be used in conjunction with analytical techniques to characterize AMD for a specific site. While it does not replace analytical tests, it can decrease the number and frequency of these expensive tests. The model has been validated with data from the Wolverine coal mine in northeastern BC, Canada.     

Direct use of discrete complex image method for evaluating electric field expressions in a lossy half space

A modelling technique is proposed for direct use of the discrete complex image method (DCIM) to derive closed-form expressions for electric field components encountered in the electric field integral equation (EFIE) representing a lossy half space problem. The technique circumvents time consuming numerical computation of Sommerfeld integrals by approximating the kernel of the integrals with appropriate mathematical functions. This is done by appropriate use of either the least-square Prony (LS-Prony) method or the matrix pencil method (MPM) to represent electric field expressions in terms of spherical waves and their derivatives. A comparison is made between the two methods based on the computation time and accuracy and it is shown that the LS-Prony method performs two?three times faster than the MPM in approximating the integral kernels depending on the platform. The main feature of the proposed technique is its ability for direct inclusion in the kernel of computational tools based on the method of moments solution of the EFIE. This can be viewed as an advantage over the conventional DCIM approximation of spatial Green's functions for mixed potential integral equation for cases where the problem in hand can be more efficiently represented by the EFIE (e.g. the thin-wire EFIE). The accuracy of the proposed technique is validated against numerical integration of Sommerfeld integrals for an arbitrary electric dipole inside a lossy half space.     

Making vinyl ester resin greener: Succinic acid–glycerol-derived reactive diluent as an alternative to styrene

A bio-based reactive diluent (BRD) was synthesized from succinic acid and glycerol, and successfully copolymerized with epoxy acrylate (EA). Chemical structure of BRD was studied by nuclear magnetic resonance and Fourier transform infrared. The performance of vinyl ester resin compositions has been examined through differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis, as well as tensile and flexural tests. Results demonstrated good compatibility between EA and the BRD. Compared to styrene, the BRD contribution of 50 wt% enhanced the elastic modulus (~40%). Samples copolymerized with BRD or styrene, have shown a similar thermal stability. Mechanical properties of cured blends, containing up to 25 wt% of BRD, found to be superior than styrene-diluted compartments. Viscosities of EA–BRD blends were in range of 3.25–0.43 Pa/s at 30°C. Inexpensive bio-based source, good thermomechanical and rheological properties, and great compatibility with EA are of advantages of these BRD-containing formulations.     

Hexagonal Boron Nitride and Graphite Oxide Reinforced Multifunctional Porous Cement Composites

The synthesis and characterization of multifunctional cement and concrete composites filled with hexagonal boron nitride (h‐BN) and graphite oxide (GO), is reported and their superior mechanical strength and oil adsorption properties compared to composites devoid of fillers are illustrated. GO is utilized to bridge the cement surfaces while h‐BN is used to mechanically reinforce the composites and adsorb the oil. Introduction of these fillers even at low filler weight fractions increases the compressive strength and toughness properties of pristine cement and of porous concrete significantly, while the porous composite concrete illustrates excellent ability for water separation and crude oil adsorption. Experimental results along with theoretical calculations show that such nanoengineered forms of cement based composites would enable the development of novel forms of multifunctional structural materials with a range of environmental applications.     

Computing electromagnetic field distribution due to an arbitrary shape exciter near multilayer slab conductors

We present a semianalytical method for calculating the electromagnetic field distribution in a multilayer slab conductor. This is a very advanced and comprehensive method because there is no limitation for the shape of the exciter and the number of layers (i.e., an exciter of any arbitrary shape and at any distance near the surface of a multilayer conductor with a large number of layers can be modeled). We solve the Helmholtz equation in three dimensions by separation of variables. We develop a two-dimensional fast Fourier transform (FFT) integral model and use exponential functions in the third dimension. We solve this integral model analytically and numerically by using the custom matrix form AX = B and a system of algebraic equations, respectively. To verify this method, we solve a simple example problem both by the new method and a finite-element method (FEM) program. The results are in good agreement with each other.     

Capillary electrophoresis/electrospray ionization high mass accuracy time-of-flight mass spectrometry for protein identification using peptide mapping

Capillary electrophoresis/electrospray ionization (CE/ESI) high mass accuracy time-of-flight mass spectrometry was used for the first time to characterize small proteins using peptide mapping. To identify small proteins, the intact proteins were first analyzed to obtain their average molecular weights with errors less than 1 Da. On-line capillary electrophoresis mass spectrometry of the tryptic digests of these small proteins was then performed to obtain the accurate molecular weights of the peptides with accuracies of approximately 10 ppm. Next, this information was used for the identification of the proteins using a protein database. It was found that high mass accuracy is an effective tool in reducing the list of most-likely proteins generated by the database. In addition, on-line collision-induced dissociation of the completely or partially resolved capillary electrophoresis peaks of the protein digests was used to unambiguously identify the sequences of these peptides. Each CE/ESI-MS analysis used only 5 nL of sample containing approximately 120 fmol of each peptide in protein digests. The results indicate that the combination of capillary electrophoresis and high resolution, high mass accuracy time-of-flight mass spectrometry is a viable option for the identification of small proteins using peptide mapping.     

Practical Improvement of SAP Hydrogel Properties via Facile Tunable Cross-linking of the Particles Surface

To improve gel toughness, surface cross-linking of partiallyneutralized acrylic acid based superabsorbent polymers (superabsorbent polymers, prepared by solution polymerization) was performed by diethylene glycol diglycidyl ether. Considering effective factors (treatment solution, surface cross-linker content, post-treatment temperature, and duration), a two-step surface modification procedure was performed on dried superabsorbent polymers particles. Attenuated total reflection–Fourier transform infrared spectroscopy has proved chemical cross-linking reaction. Mechanical properties have also been investigated. Besides, the modified rubber elasticity theory and Flory–Rehner equations have been used to investigate how they work in core–shell-like structure. The optimum condition provides at least a 100% raise in gel strength and appropriate absorbency.     

MHD copper-water nanofluid flow and heat transfer through convergent-divergent channel

This work is focused on the analytical solution of a nanofluid consisting of pure water with copper nanoparticle steady flow through convergent-divergent channel. The velocity and temperature distributions are determined by a novel method called Reconstruction of variational iteration method (RVIM). The effects of angle of the channel, Reynolds and Hartmann numbers on the nanofluid flow are then investigated. The influences of solid volume fraction and Eckert number upon the temperature distribution are discussed. Based on the achieved results, Nusselt number enhances with increment of solid volume fraction of nanoparticles, Reynolds and Eckert numbers. Also the fourth order Runge-Kutta method, which is one of the most relevant numerical techniques, is used to investigate the validity and accuracy of RVIM and good agreement is observed between the solutions obtained from RVIM and some known numerical results.