Search results for "Capillary Action"
showing 10 items of 179 documents
Selectivity tuning in pressurized-flow electrochromatography
1996
Abstract Pressurized-flow electrochromatography (PEC) is a developing separation technique in which both a pressure gradient and an electric field are applied across a packed capillary. In this work we present new results illustrating the principles and the potential of PEC. Home-made capillary columns with silica-based reversed phase packings were operated under PEC conditions separating low molecular weight analytes. Compared to the purely pressure-driven system enhanced selectivity for the charged analytes was observed. It is shown that the retention time of a retained cationic analyte in PEC can be calculated using the chromatographic capacity factor and the electrophoretic mobility of …
Analysis of Rauwolfia Alkaloids Employing Capillary Electrophoresis-Mass Spectrometry
1997
Abstract Capillary electrophoresis-mass spectrometry (CE-MS) was applied to analyse extracts of roots and cell suspension cultures from Rauwolfia serpentina. Most of the alkaloids known to be present in the respective plant material have been resolved via CE and assigned according to their electrospray mass spectra.
Connected pathway relative permeability from pore-scale imaging of imbibition
2016
Abstract Pore-scale images obtained from a synchrotron-based X-ray computed micro-tomography (µCT) imbibition experiment in sandstone rock were used to conduct Navier–Stokes flow simulations on the connected pathways of water and oil phases. The resulting relative permeability was compared with steady-state Darcy-scale imbibition experiments on 5 cm large twin samples from the same outcrop sandstone material. While the relative permeability curves display a large degree of similarity, the endpoint saturations for the µCT data are 10% in saturation units higher than the experimental data. However, the two datasets match well when normalizing to the mobile saturation range. The agreement is p…
An easy-to-use model for O2 supply to red muscle. Validity of assumptions, sensitivity to errors in data
1995
An easy-to-use capillary cylinder model of O2 supply to muscle is presented that considers all those factors that are known to be most important for realistic results: (1) red blood cell (RBC) O2 unloading along the capillary, (2) effects of the particulate nature of blood, (3) free and hemoglobin-facilitated O2 diffusion and reaction kinetics inside RBCs, (4) free and myoglobin-facilitated O2 diffusion inside the muscle cell, and (5) carrier-free region separating RBC and tissue. In a first approach, a highly simplified yet reasonably accurate treatment of the complex three-dimensional oxygen diffusion field in and next to capillaries is employed. As an alternative, a more realistic descri…
Evanescent wave-initiated photopolymerisation as a new way to create monolithic open-tubular capillary columns: use as enzymatic microreactor for on-…
2010
Evanescent wave-initiated photopolymerisation in an optically wave guiding PTFE-coated fused silica capillary using light-emitting diode as a light source, is established here as a way to fabricate monolithic porous layer open-tubular capillary columns with a potential in capillary separation methods; application of the obtained open-tubular columns as enzymatic microreactors for on-line protein digestion is demonstrated.
Thermoosmotic transfer of sterically stabilized ferrofluid particles in non-isothermal capillary porous layer
2005
Experiments on thermodiffusive transfer of ferrofluid nanoparticles in capillary porous layer are presented. The layer consists of a number of capillary filter sheets pressed between two plates of different temperatures. Steady profiles of particle concentration are detected after the experiment from magnetization of each filter sheet. It is shown that particle separation in porous layer is remarkably influenced by thermoosmotic forces. The observed effect is different for colloids of various surfactants and of various carrier liquids.
Velocity of the fourth sound in liquid helium II via extended thermodynamics
2003
This work continues a study begun in previous works, where, using Extended Thermodynamics, a monofluid model of liquid helium II is formulated. The wave propagation in bulk liquid helium II is studied in the hypothesis that the thermal dilatation is not zero. The propagation of fourth sound, studied previously neglecting both the thermal dilatation and finite volume of the powder, is studied without these simplified hypotheses: a scattering correction n is introduced to take into account the porosity. The model is more general than the standard two-fluid model because it allows that a small amount of entropy is associated with helium when it flows through a very thin capillary or a porous m…
Active mixing inside double emulsion segments in continuous flow
2015
Fast mixing is essential for many microfluidic applications, especially for flow at low Reynolds numbers. A capillary tube-in-tube coaxial flow setup in combination with a glass microreactor was used to produce immiscible multiphase segments. These double emulsion segments are composed of an organic solvent as the shell (outer) phase and a completely fluorinated liquid (Fluorinert® FC-40) as the core (inner) phase. Due to the higher density of the core droplets, they are responsive to changing their position to the force of gravity (g-force). By gently shaking or jiggling the reactor, the core drop flows very fast in the direction of the g-field without leaving the shell organic phase segme…
Engineering Polymer Microparticles by Droplet Microfluidics
2013
Capillary-based flow-focusing and co-flow microsystems were developed to produce sphere-like polymer microparticles of adjustable sizes in the range of 50 to 600 μm with a narrow size distribution (CV < 5%) and different morphologies (core-shell, janus, and capsules). Rod-like particles whose length was conveniently adjusted between 400 μm and few millimeters were also produced using the same microsystems. Influence of operating conditions (flow rate of the different fluid, microsystem characteristic dimensions, and design) as well as material parameters (viscosity of the different fluids and surface tension) was investigated. Empirical relationships were thus derived from experimental data…
Experimental studies on the detachment of multi-walled carbon nanotubes by a mobile liquid interface
2017
International audience; Retention and detachment of colloidal particles from surfaces is often considered only in terms of spontaneous chemical dispersion when the surface is already fully submerged. Nevertheless, interfacial processes, where the particles are caught on a mobile liquid contact line by capillary effects are ubiquitous. Theoretical description of such interfacial processes exist for spherical microcolloids, while for anisotropic shapes the literature is limited. Arc-discharge synthesized multiwalled carbon nanotube (MWNT) material contains besides the very anisotropic tubes also irregular amorphous carbon particles (ACP) that both are strongly hydrophobic. As a water–air–soli…