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1.
Continuous size fractionation of magnetic nanoparticles by using simulated moving bed chromatography
Carsten-Rene Arlt Dominik Brekel Stefan Neumann David Rafaja Matthias Franzreb 《Frontiers of Chemical Science and Engineering》2021,15(5):1346
The size fractionation of magnetic nanoparticles is a technical problem, which until today can only be solved with great effort. Nevertheless, there is an important demand for nanoparticles with sharp size distributions, for example for medical technology or sensor technology. Using magnetic chromatography, we show a promising method for fractionation of magnetic nanoparticles with respect to their size and/or magnetic properties. This was achieved by passing magnetic nanoparticles through a packed bed of fine steel spheres with which they interact magnetically because single domain ferro-/ferrimagnetic nanoparticles show a spontaneous magnetization. Since the strength of this interaction is related to particle size, the principle is suitable for size fractionation. This concept was transferred into a continuous process in this work using a so-called simulated moving bed chromatography. Applying a suspension of magnetic nanoparticles within a size range from 20 to 120 nm, the process showed a separation sharpness of up to 0.52 with recovery rates of 100%. The continuous feed stream of magnetic nanoparticles could be fractionated with a space-time-yield of up to 5 mg/(L∙min). Due to the easy scalability of continuous chromatography, the process is a promising approach for the efficient fractionation of industrially relevant amounts of magnetic nanoparticles. 相似文献
2.
L. Paterson M. P. Macdonald J. Arlt W. Dultz H. Schmitzer W. Sibbett 《Journal of Modern Optics》2013,60(10):1591-1599
Abstract We present a method for the controlled alignment or rotation of birefringent particles trapped in multiple optical trap sites of an interference pattern between two Laguerre—Gaussian laser modes. Controlled spin or alignment of the particles within each individual trap site is achieved independently of the lateral or rotational motion of the interference pattern as a whole. This technique may lead to driving arrays of micro-machines and micro-fluidic studies and can be used in combination with dynamically generated trapping arrays for uniformly distributed stirring throughout microscopic volumes of fluid. 相似文献
3.
Jochen Arlt 《Journal of Modern Optics》2013,60(10):1573-1580
Abstract The propagation of optical vortex beams obstructed by a knife edge is investigated. The intensity profile shows a characteristic rotation around the beam axis which can be used to determine the absolute handedness of the vortex. Evolution of the intensity profile directly visualizes the rotation of the beam's local Poynting vector. 相似文献
4.
Abstract The aging of dielectric, elastic and piezoelectric properties is caused by a reduction of the 90° domain wall mobility. Defect dipoles in the domains orient slowly in energetically preferred directions. The oriented defects increase the force constant for the reversible domain wall displacement by electric or elastic fields. Observations of fatigue in bulk materials are briefly discussed. 相似文献
5.
This work is encouraged by the growing interest and recent success of quantum mechanics‐based methods in modeling of thermodynamic properties in the field of chemical engineering and life sciences. Among those, the COSMO‐RS model has become one of the most popular methods to predict phase equilibria in complex bio‐related systems. Recently, we have shown that the quality of predictions of n‐octanol/water and micelle/water partition coefficients is improved when the weighted mixtures of conformers are used to represent molecules, thereby demanding that the conformation analysis is performed for each component of the system. In this paper, different methods for performing the conformational search are evaluated. Micelle/water partition coefficients of solutes from different homologous series in aqueous solutions of Triton X100 as well as the n‐octanol/water partitioning of three common drugs (aminopinicillanic acid, ampicillin, and penicillin G) are calculated and compared with experimental data. Conformational analysis is made by the HyperChem program for the molecules placed in vacuum as well as by using the molecular dynamics simulation in a solvent medium (n‐octanol and water). It is demonstrated that molecular dynamics simulation is a promising tool to conduct conformational analysis. Along with the possibility of providing the conformers for large surfactant and pharmaceutical molecules, the method accounts for the solvent in a realistic manner. The results for micelle/water partition coefficients illustrate that n‐octanol is a reasonable approximation for the “micelle‐like” medium in molecular dynamics (MD) simulations. Predicted n‐octanol/water partition coefficients of three penicillins are in a good agreement with literature data and values calculated by a common quantitative structure‐activity relationship (QSAR). 相似文献
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Polysaccharides are the most important components of herbal biomass with a high application potential. Their thermochemical characteristics, however, have been little studied. In the present paper, an effective thermodynamic analysis was carried out with the aim of setting a method for reasonably estimating the thermochemical properties of polysaccharides such as cellulose. The properties of formation and heat capacities were estimated by general thermodynamic methods like group contribution methods as well as methods followed from synthetic polymer studies. The results were compared with those obtained by empirical correlations derived from the data for short chain carbohydrates, the only literature data available for validation. The properties were determined depending on the degree of polymerization and temperature. 相似文献
8.
Biomass holds great promise as a renewable source of hydrogen and thus as a zero‐emission, carbon‐neutral, and nearly inexhaustible energy resource. Thermodynamic analysis of biomass hydration is carried out to study the reaction properties considering a series of saccharides as a model. Equilibrium constants and composition are estimated in dependence on the saccharide chain length and temperature. The latter is also studied as a function of the reactant ratios and in the presence of nonreacting additives. Being highly endothermic, the reaction is thermodynamically favorable due to a high entropic contribution. Increase in the saccharide chain length affects the conversion only slightly, so the results for low‐molecular‐weight saccharides can be transferred to long‐chain ones. 相似文献
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