A rigorous analysis of the phenomenon of field-flow fractionation (FFF) is presented for particles which are both nonspherical in shape and of sufficient size (compared with apparatus dimensions) to be significantly influenced by wall effects. Calculations are presented for axially-symmetric particles in an arbitrary flow field. Orienting torques directed along the symmetry axis of the particle are also considered. The theory is compared with the experimental data of Berg, Purcell, and Stewart. Reasonably satisfactory agreement is observed.
A Hamaker-type integration of the pairwise en vacuo intermolecular forces is performed for a homogeneous triaxial ellipsoidal particle in proximity to a homogeneous semi-infinite slab bounded by a plane wall. The orientation of the ellipsoid relative to the plane is taken to be arbitrary, as too is its distance from the plane. The integrated potential energy function of the ellipsoid with respect to the slab is found to possess nonadditive positional and orientational contributions. This macroscopic potential is employed to compute the force and torque on the ellipsoid as functions of both its position and orientation relative to the plane.The novel integration scheme pertains to centrally-symmetric pairwise intermolecular potentials of arbitrary functional form. Specific results are derived for classical inverse-power intermolecular potentials possessing both attractive (r-") and repulsive (-r-"' ) additive components (with n > m). In stable equilibrium the ellipsoid aligns itself with the shortest of its three principal axes perpendicular to the bounding wall, and at a separation distance comparable to the length scale ofthe intermolecular potential itself.HOWARD BRENNER et LAWRENCE J. GAJDOS. Can. J. Chem. 59,2004Chem. 59, (1981. On a effectuk une integration du type Hamaker des forces intermoleculaires en vacuo prises deux a deux pour une particule Cllipsoidale triaxiale homogene au voisinage d'une plaque homogene semi-infinie reliee a un mur plan. On considere que l'orientation de I'ellipsoide par rapport au plan ainsi que sa distance par rapport ce plan sont arbitraires. On a trouve que la fonction d'energie potentielle integrte de I'ellipsoide par rapport 21 la plaque possede des contributions de position et d'orientation qui ne sont pas additives. On a employe cette propriete macroscopique pour calculer la force et la torsion appliquee i I'ellipsoide en fonction a la fois de sa position et de son orientation par rapport au plan.Le nouveau schema d'integration s'applique a des potentiels intermoleculaires centro-symetriques considerees sous forme de paire dont la forme fonctionnelle est arbitraire. On a dkduit des resultats specifiques pour des potentials intermoleculaires de puissance inverse classique possedant a la fois des composantes additives (r-") et repulsives ( -r m ) (avec n > m). En Cquilibre stable, I'ellipsoide s'aligne lui-mCme avec le plus court de ses trois axes perpendiculaires principaux par rapport au mur plan liant et la distance qui le &pare d'un mur se compare l'echelle de longueur du potentiel intermoleculaire lui-mCme.
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