Biomedical subjects

DJ Klingenberg

Publications and source records attributed to DJ Klingenberg.

3 recordsLinked to original sources

PubMed2000

Normal Forces between Cellulose Surfaces Measured with Colloidal Probe Microscopy.

Colloidal probe microscopy was employed to study interactions between cellulose surfaces in aqueous solutions. Hydrodynamic forces must be accounted for in data analysis. Long-range interactions betweeen cellulose surfaces are governed by double-layer forces and, once surfaces contact, by osmotic repulsive forces and viscoelasticity. Increasing the ionic strength decreases surface potentials and increases adhesive forces. Polyelectrolytes cause strong steric repulsion at high surface coverage, where interactions are sensitive to probe velocity. Polymer bridging occurs at low coverage. The conformation of adsorbed polyelectrolytes depends on the polymer concentration. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Mechanical flocculation in flowing fiber suspensions

Non-Brownian fibers commonly flocculate in flowing suspensions. A particle level simulation technique modeling fibers as chains of rods connected by hinges is developed to probe flocculation. Simulations show that flocculation can be induced solely by interfiber friction-attractive forces between fibers are not necessary. Simulated mechanical floc characteristics are consistent with experimental observations. In contrast, simulations of flocs formed by attractive forces behave qualitatively differently.

Journal Article↗

PubMed1996

Two Roles of Nonionic Surfactants on the Electrorheological Response

The influence of three nonionic surfactants (Brij 30, GMO, and GTO) on the electrorheological response of various alumina/silicone oil suspensions is investigated. The dependence of the dynamic yield stress on such variables as surfactant type and concentration, water and ion content, and electric field strength and frequency is reported. The prevalent feature common to all formulations is that the yield stress, tau0, initially increases with surfactant concentration, passes through a maximum, and then decreases with surfactant concentration. Below the maximum, the yield stress increases quadratically with the field strength, E, while above the maximum, yield stress increases slower than E2. The increase in the yield stress with surfactant concentration is due to surfactant-enhanced interfacial polarization, which may arise from increased proton transport via neighboring hydrogen bonds. The nonlinear behavior observed at large surfactant concentrations (i.e., tau0 $\not\propto$ E2) arises from field-induced phase separation of a surfactant-rich phase as opposed to field-dependent conductivity of a homogeneous continuous phase.

Journal Article↗