In non‐catalytic direct conversion of propylene with oxygen to propylene oxide by using dielectric barrier discharge under conditions of room temperature and atmospheric pressure, the selectivity to propylene oxide from propylene was >30% at propylene conversion ranging from 3.91% to 81.72%. 相似文献
The influence of the effects associated with the inertia of particles and the surrounding fluid on the electrophoresis in an alternating electric field has been theoretically investigated. From solving the hydrodynamic equations the electrophoretic velocity of a spherical particle was found to depend on the frequency of the external electric field and on the particle-to-fluid-density ratio. It is shown that, due to inertial effects, the liquid flow around particles with a thin electrical double layer (EDL) is no longer potential. A mechanism of the formation of steady-state flow in the vicinity of oscillating particles with a thin EDL is proposed. Using numerical methods, a picture of the fluid streamlines in such a flow is obtained. The spatial distribution of the fluid velocity in the vicinity of a particle is also found. It was established that with an increasing frequency of the electric field the steady-state flow velocity passes through a maximum. The flow direction depends on the ratio between the densities of a particle and the surrounding fluid. The reversal of direction takes place when this ratio is about 0.7. The case of a thick EDL has also been considered, and a comparative analysis of the flow distributions around the particles with a thin and those with a thick EDL has been carried out. 相似文献
Abstract Aqueous micellar solutions can be used in reverse phase TLC providing the ionic strength of the solution is sufficiently high to prevent the destruction of the stationary phase. Stability curves have been determined for sodium dodecyl sulfate and cetyltrimethylammonium chloride containing aqueous mobile phases. These “pseudophase” solutions allow the unique separation of hydrophobic from hydrophilic compounds. Indeed one can estimate the relative hydrophobicity of a compound by observing its chromatographic behavior in this system. 相似文献
Herein we evaluate the influence of an electric field on the coupling of two delocalized electrons in the mixed‐valence polyoxometalate (POM) [GeV14O40]8? (in short V14) by using both a t‐J model Hamiltonian and DFT calculations. In absence of an electric field the compound is paramagnetic, because the two electrons are localized on different parts of the POM. When an electric field is applied, an abrupt change of the magnetic coupling between the two delocalized electrons can be induced. Indeed, the field forces the two electrons to localize on nearest‐neighbors metal centers, leading to a very strong antiferromagnetic coupling. Both theoretical approaches have led to similar results, emphasizing that the sharp spin transition induced by the electric field in the V14 system is a robust phenomenon, intramolecular in nature, and barely influenced by small changes on the external structure. 相似文献
Abstract Donnan dialysis of cations into simple receiver electrolytes such as NaNO3 is inhibited by interaction between the fixed sulfonate exchange sites on the cation exchange membrane and the test cations. Application of a 5 V cm?1 (peak-to-peak) sine wave at 1 MHz across the membrane diminishes the retardation and allows the Donnan dialysis rate to approach the diffusion limit with Cd, Cu, and Zn test metals and a 0.1 M NaNO3 receiver. The transport to Pb is still retarded by about 25%. The use of 0.2 M Mg(II), 0.5 mM Al(III) receiver results in diffusion limited transport for all metals. 相似文献
The effect of an external electric field on the magnetic anisotropy of a single‐molecule magnet has been investigated, for the first time, with the help of DFT. The application of an electric field can alter the magnetic anisotropy from “easy‐plane” to “easy‐axis” type. Excitation analysis performed through time‐dependent DFT predicts that the external electric field facilitates metal to π‐acceptor ligand charge transfer, leading to uniaxial magnetic anisotropy and concomitant spin Hall effect in a single molecule. 相似文献
JPC – Journal of Planar Chromatography – Modern TLC - Thin-layer chromatography (TLC) of fifteen amino acids was performed using silica gel and alumina impregnated with micellar... 相似文献
The formation of a 1D chain-like structure of dust particles in a low-temperature argon plasma was studied. A new numerical model for calculation of the self-consistent spatial distribution of plasma parameters around a chain of dust particles was presented. The model described the motion of positively charged ions in the electric potential of several negatively charged dust particles, taking into account the action of an external electric field. The main advantage of the model was that the charges of the dust particles and the interparticle distances were determined self-consistently. As a result of numerical simulations, the dependencies of the spatial distributions of the plasma parameters (the densities of electrons and ions and the self-consistent electric potential) near the dust particles chain on the strength of the external electric field, an external force acted on the last particle, and the mean free path of the ions was determined. The obtained results made it possible to describe the process of the formation of chain-like structures of dust particles in discharge plasma. 相似文献
Molecular dynamics simulations were carried out to investigate the diffusion of polymer chains in solvent under an external electric field. Polyethylene‐like polymer and methyl chloride molecule were chosen as solute and solvent. The external DC electric field strength was varied from 10 to 50 (4.3×108 V/m). Both polar and non‐polar polymer chains in polar and non‐polar solvents were investigated. The simulation shows that the center of mass diffusion coefficient of polymer is sensitive to the polarities of polymer and solvent, field strength, polymer concentration and the density of the system. Various factors that affect the diffusion constant of the polymer are discussed. The present simulation is consistent with the results from light scattering experiments. 相似文献
A positive change Δλ/λ of the decay constant of 99Tcm has been observed on the application of an external electric field in K2TcX6 (X = F, Cl, Br, I). For its investigation the Tc-complexes were embedded as small conglomerates or more or less as isolated single molecules in a powder of high dielectric constant, which was then compressed into a thin layer of about 0.2 mm and inserted between two capacitor plates. The change Δλ/λ depends on the strength of the chemical bond of 99Tcm. As a first approximation Δλ/λ was assumed to be linearly dependent upon the electric field. The experimental results with an external field of 104 V/cm are: A relationship between Δλ/λ and the electro-negativities of the ligand atoms could be established. Difficulties encountered in the theoretical calculation of Δλ/λ are discussed. 相似文献
The starting point is our previous study of influence of the internal molecular mean field of dipole‐dipole interactions on local orientation and phase transitions in polymer liquid crystal (PLC) systems of longitudinal chains.[1, 2] Electric dipoles are created by LC mesogen moieties. The longitudinal PLC is a macromolecule of consecutively copolymerized LC and flexible polymer sequences. We now amplify the model by inclusion of dipole‐external electric field interactions. We find that the external fields can seriously modify the local orientational order of the system and affect phase transition parameters dependent on that order. In particular, the external fields induce the formation of disoriented nematic phases with negative values of the second order orientation parameter 〈P2〉 for LC sequences in the longitudinal PLCs while the first order parameter 〈P1〉 is positive. However, some rapid decreases in 〈P1〉 are observed at points of positive‐to‐negative transitions of 〈P2〉; thus the LC disorientation manifests itself. The limiting case of the monomer liquid crystal (MLC) systems is included also. 相似文献
Voltage/temperature phase diagrams of liquid-crystalline blue phase (BP) systems CB 15/M 18 and CB 15/E 9 have been determined by means of polarizing microscopy. Above a certain threshold voltage a field-induced BP occurs which is stable in a region of the U/T diagram between the BPI and BPII. 相似文献
Abstract An electric field coupled method for separation of polar compounds using normal phase high performance liquid chromatography is described. The method, which is not based on electrophoresis or electrochromatography, selectively changes the column capacity for polar analytes. The use of different columns showed improved column efficiency and up to a 62% increase in the number of theoretical plates. The theory for the improvement is presented. The significance and utility of the method for selective analysis of polar fractions in environmental samples is discussed. 相似文献
Colloid Journal - Molecular dynamics simulation has been employed to study conformational rearrangements induced by an external field in uniformly charged polypeptides adsorbed on the surface of an... 相似文献
JPC – Journal of Planar Chromatography – Modern TLC - Resolution of the enantiomers of racemic atenolol, metoprolol, propranolol, and labetalol, commonly used β-blockers, has been... 相似文献