Search results for "suspensio"
showing 10 items of 266 documents
Design of enzyme-mediated controlled release systems based on silica mesoporous supports capped with ester-glycol groups
2012
[EN] An ethylene glycol-capped hybrid material for the controlled release of molecules in the presence of esterase enzyme has been prepared. The final organic-inorganic hybrid solid S1 was synthesized by a two-step procedure. In the first step, the pores of an inorganic MCM-41 support (in the form of nanoparticles) were loaded with [Ru(bipy) 3]Cl 2 complex, and then, in the second step, the pore outlets were functionalized with ester glycol moieties that acted as molecular caps. In the absence of an enzyme, release of the complex from aqueous suspensions of S1 at pH 8.0 is inhibited due to the steric hindrance imposed by the bulky ester glycol moieties. Upon addition of esterase enzyme, del…
Importance of the liquid to solid weight ratio in the powdered solid-liquid reactions Example drawn from cement constituent hydration
1997
Abstract It seems justified to wonder if the chemical processes which have been evidenced from diluted stirred suspensions are or are not in accordance with those involved in a stagnant paste. The present paper is aimed at clarifying this question which is in connection with the problem of the so called ‘dormant period’ or ‘induction period’ at the beginning of the hydration of Portland cement.
In vitro prediction of in vivo absorption of ibuprofen from suspensions through rational choice of dissolution conditions
2020
Two ibuprofen suspension formulations were investigated for their dissolution in various bicarbonate, phosphate and acetate buffers. Phosphate and acetate gave faster release than bicarbonate at comparable molarities. Nevertheless, mass transport modelling using the reversible non-equilibrium (RNE) approach enabled the calculation of phosphate molarities that gave good matches to physiological bicarbonate in terms of ibuprofen dissolution. This shows that developing surrogate buffers for bicarbonate that are devoid of the technical difficulties associated with the bicarbonate-CO2 systems is possible. In addition, the intestinal dissolution kinetics of the tested suspensions were determined …
Simultaneous measurement of rotational and translational diffusion by forced Rayleigh scattering. Colloid spheres in suspension
1996
Abstract It is shown that the technique of forced Rayleigh scattering, traditionallyemployed to probe translational diffusion, can be employed to probe rotational diffusion as well. Thus with a single experiment both quantities are measured. The system under investigation is colloid spheres suspended in a glass-forming liquid. Furthermore, it is shown that the Stokes-Einstein and Debye-Stokes-Einstein relations for translational and rotational diffusion, respectively, are valid for spherical colloid particles in a supercooled liquid matrix in the vicinity of the glassy state.
Determination of association constants towards carbon nanotubes
2015
Single-walled carbon nanotubes (SWNTs) are one of the most promising nanomaterials and their supramolecular chemistry has attracted a lot of attention. However, despite well over a decade of research, there is no standard method for the quantification of their noncovalent chemistry in solution/suspension. Here, we describe a simple procedure for the determination of association constants (Ka) between soluble molecules and insoluble and heterogeneous carbon nanotube samples. To test the scope of the method, we report binding constants between five different hosts and two types of SWNTs in four solvents. We have determined numeric values of Ka in the range of 1–104 M−1. Solvent effects as wel…
A dihydrogen arsenate-mediated supramolecular network: crystal structure and magnetic properties of {[(bipy)Cu(μ-H2AsO4)(H2AsO4)]2}n
2002
Treatment of an aqueous suspension of Cu(OH)2 and 2,2′-bipyridine (bipy) with either Na2HAsO4·7H2O (1∶1∶2) or As2O5 (1∶1∶1) yields single crystals of {[(bipy)Cu(μ-H2AsO4)(H2AsO4)]2}n, 1, on standing. The solid-state structure of 1 consists of a three dimensional supramolecular network, supported by a combination of coordination covalent, hydrogen bonding and face-to-face π–π interactions. Variable temperature magnetic susceptibility measurements reveal very weak antiferromagnetic coupling between Cu(II) centres across the dihydrogen arsenate bridges (J = −0.58 cm−1).
Interactions between chemical evolution (hydration) and physical evolution (setting) in the case of tricalcium silicate
1994
This paper describes recent experimental results concerning investigation of the parameters which determine, on the one hand, the kinetics of hydration of tricalcium silicate and the thermodynamic, morphological and structural characteristics of C-S-H and, on the other hand, the evolution of the particle interactions at the origin of setting. It is shown that, in both cases, lime concentration in solution is the most important parameter. As a consequence, the chemical evolution of the system, which controls the lime concentration in solution, determines the nature of particle interactions and the physical evolution of the suspension or paste. In return, the contacts, between particles, resu…
Flow properties and hydrodynamic interactions of rigid spherical microswimmers.
2017
We analyze a minimal model for a rigid spherical microswimmer and explore the consequences of its extended surface on the interplay between its self-propulsion and flow properties. The model is the first order representation of microswimmers, such as bacteria and algae, with rigid bodies and flexible propelling appendages. The flow field of such a microswimmer at finite distances significantly differs from that of a point-force (Stokeslet) dipole. For a suspension of microswimmers, we derive the grand mobility matrix that connects the motion of an individual swimmer to the active and passive forces and torques acting on all the swimmers. Our investigation of the mobility tensors reveals tha…
Light scattering - diagnostic methods for colloidal dispersions
1993
Abstract The increasing demand from the colloid research community for quick and noninvasive experimental techniques as well as the rapid progress of modern optics and electronics have led to a considerable expansion in the field of light scattering. This review introduces the basic concepts with some emphasis on novel approaches like the study of interacting particle systems, multiple scattering techniques, and non ergodic samples. Particular attention is then devoted to recent experimental progress towards more compact and rugged instruments.
Influence of drag and turbulence modelling on CFD predictions of solid liquid suspensions in stirred vessels
2014
Abstract Suspensions of solid particles into liquids within industrial stirred tanks are frequently carried out at an impeller speed lower than the minimum required for complete suspension conditions. This choice allows power savings which usually overcome the drawback of a smaller particle-liquid interfacial area. Despite this attractive economical perspective, only limited attention has been paid so far to the modelling of the partial suspension regime. In the present work two different baffled tanks stirred by Rushton turbines were simulated by employing the Eulerian-Eulerian Multi Fluid Model (MFM) along with either the Sliding Grid algorithm (transient simulations) or the Multiple Refe…