Search results for "Suspensions"
showing 10 items of 34 documents
Colloidal layers in magnetic fields and under shear flow
2005
The behaviour of colloidal mono- and bilayers in external magnetic fields and under shear is discussed and recent progress is summarized. Superparamagnetic colloidal particles form monolayers when they are confined to a air–water interface in a hanging water droplet. An external magnetic field allows us to tune the strength of the mutual dipole–dipole interaction between the colloids and the anisotropy of the interaction can be controlled by the tilt angle of the magnetic field relative to the surface normal of the air–water interface. For sufficiently large magnetic field strength crystalline monolayers are found. The role of fluctuations in these two-dimensional crystals is discussed. Fur…
Pharmacokinetic evaluation of oral fenofibrate nanosuspensions and SLN in comparison to conventional suspensions of micronized drug.
2007
An increasing number of newly developed drugs show bioavailability problems due to poor water solubility. Formulating the drugs as nanosuspensions may help to overcome these problems by increasing saturation solubility and dissolution velocity. In the present study the bioavailability of the poorly soluble fenofibrate following oral administration was investigated in rats. Four formulations were tested: a nanosuspension type DissoCube(R), one solid lipid nanoparticle (SLN) preparation and two suspensions of micronized fenofibrate as reference formulations, one suspension in sirupus simplex and a second in a solution of hydroxyethy-cellulose in physiological saline. Both colloidal drug deliv…
Electrophoretic flow behaviour and mobility of colloidal fluids and crystals.
2007
We report on measurements of the electrophoretic mobility mu of charged colloidal spheres in the deionized state, where the suspensions show fluid or crystalline order. In the fluid state, parabolic flow profiles are observed due to electro-osmotic solvent flow. In the crystalline state, complex flow profiles occur due to additional crystal cohesion. The mobility mu then may inferred from the flow velocity averaged over the complete cell cross section as performed in our home built super-heterodyne Doppler velocimeter. For two particle species of 68 and 122 nm diameter we measured mu as a function of particle concentration. Starting from a plateau value at low concentration, mu decreases ap…
Computer active control of damping fluid of a racing superbike suspension scheme for road safety improvement spin-off
2008
This paper describes in detail a computational investigation of a newly-conceived scheme of hydraulic active racing motorcycle suspension and its design application based on a computer-aided control of damping fluid. Through ad hoc tests on a full-scale model setup and the theoretical approach of a non linear 8th-order suspension scheme, this study gives enhancement of the damping fluid active control on the feedback branch of the entire control system for significant improvement of the suspension response to typical road inputs. Briefly, the fluid flow in suspension dampers - generated through well-suited high-pressure hydraulic circuit - shall be conveniently controlled in direction and m…
Kinetics of the lipoperoxyl radical-scavenging activity of indicaxanthin in solution and unilamellar liposomes
2007
Abstract The reaction of the phytochemical indicaxanthin with lipoperoxyl radicals generated in methyl linoleate methanol solution by 2,20-azobis(2,4-dimethylvaleronitrile), and in aqueous soybean phosphatidylcholine unilamellar liposomes by 2,20-azobis(2- amidinopropane)hydrochloride, was studied. The molecule acts as a chain-terminating lipoperoxyl radical scavenger in solution, with a calculated inhibition constant of 3.63 £ 105M21 s21, and a stoichiometric factor approaching 2. Indicaxanthin incorporated in liposomes prevented lipid oxidation, inducing clear-cut lag periods and decrease of the propagation rate. Both effects were concentration-dependent, but not linearly related to the p…
An Artificial Neural Network Assisted Dynamic Light Scattering Procedure for Assessing Living Cells Size in Suspension
2020
Dynamic light scattering (DLS) is an essential technique used for assessing the size of the particles in suspension, covering the range from nanometers to microns. Although it has been very well established for quite some time, improvement can still be brought in simplifying the experimental setup and in employing an easier to use data processing procedure for the acquired time-series. A DLS time series processing procedure based on an artificial neural network is presented with details regarding the design, training procedure and error analysis, working over an extended particle size range. The procedure proved to be much faster regarding time-series processing and easier to use than fitti…
Kinetics of doublet formation in bicomponent magnetic suspensions: The role of the magnetic permeability anisotropy
2017
Micron-sized particles (microbeads) dispersed in a suspension of magnetic nanoparticles, i.e., ferrofluids, can be assembled into different types of structures upon application of an externalmagnetic field. This paper is devoted to theoretical modeling of a relative motion of a pair of microbeads (either soft ferromagnetic or diamagnetic) in the ferrofluid under the action of applied uniform magnetic field which induces magnetic moments in the microbeads making them attracting to each other. The model is based on a point-dipole approximation for the magnetic interactions between microbeads mediated by the ferrofluid; however, the ferrofluid is considered to possess an anisotropic magnetic p…
Crystallization in suspensions of hard spheres: a Monte Carlo and molecular dynamics simulation study
2011
The crystallization of a metastable melt is one of the most important non-equilibrium phenomena in condensed matter physics, and hard sphere colloidal model systems have been used for several decades to investigate this process by experimental observation and computer simulation. Nevertheless, there is still an unexplained discrepancy between the simulation data and experimental nucleation rate densities. In this paper we examine the nucleation process in hard spheres using molecular dynamics and Monte Carlo simulation. We show that the crystallization process is mediated by precursors of low orientational bond-order and that our simulation data fairly match the experimental data sets.
Hiding in plain view: Colloidal self-assembly from polydisperse populations.
2016
We report small-angle x-ray scattering (SAXS) experiments on aqueous dispersions of colloidal silica with a broad monomodal size distribution (polydispersity 18%, size 8 nm). Over a range of volume fractions the silica particles segregate to build first one, then two distinct sets of colloidal crystals. These dispersions thus demonstrate fractional crystallization and multiple-phase (bcc, Laves AB$_2$, liquid) coexistence. Their remarkable ability to build complex crystal structures from a polydisperse population originates from the intermediate-range nature of interparticle forces, and suggests routes for designing self-assembling colloidal crystals from the bottom-up.
Depletion-induced percolation in networks of nanorods.
2006
Above a certain density threshold, suspensions of rod-like colloidal particles form system-spanning networks. Using Monte Carlo simulations, we investigate how the depletion forces caused by spherical particles affect these networks in isotropic suspensions of rods. Although the depletion forces are strongly anisotropic and favor alignment of the rods, the percolation threshold of the rods decreases significantly. The relative size of the effect increases with the aspect ratio of the rods. The structural changes induced in the suspension by the depletant are characterized in detail and the system is compared to an ideal fluid of freely interpenetrable rods.