## Appl Rheol online available publications for selected issue

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Bacchelli F, Pirini MF, Coppola S: The 10th Conference of the Italian Society of Rheology, Appl. Rheol. 18 (2008) 320.

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Schaffler M, Miller R: User Seminar of 2D and 3D Rheology of Fluids and Liquid Interfaces, Appl. Rheol. 18 (2008) 318.

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Mitchell G, Davis F, Vaughan A, Mossman S: 75 Years of Polyethylene: Past Successes and Future Challenges, Appl. Rheol. 18 (2008) 316.

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Fischer P, Nicolai T: Food Colloids 2008 - Creating Structure, Delivering Functionality, Appl. Rheol. 18 (2008) 315.

Investigations of rheological properties of ferrofluids have shown strong changes of the viscosity in magnetic fluids with an applied magnetic field. The change of the viscosity . the magnetoviscous effect . can theoretically be described with chain and structure formation under the influence of a magnetic field. Moreover, the formation of these structures leads to the appearance of viscoelastic effects or other non-Newtonian features like yield stress in ferrofluids with an applied magnetic field. With a shear rate controlled rheometer . as it as been used in former experiments . the yield stress could not be investigated directly. Therefore the results concerning a field dependent yield stress based on an extrapolation of shear controlled measurements. For the direct investigations of the yield stress, a dedicated stress controlled rheometer is required, allowing direct investigations of the magnitude and field dependence of this effect. In this work the design of the stress controlled rheometer with its main parameters has been described in detail. The rheological investigations with differently composed fluids show that the stress controlled rheometer enables direct measurements of even small yield stresses in ferrofluids as well as large effects like they are found in magnetorheological fluids (MRF).► Cite this publication as follows:

Shahnazian H, Odenbach S: New driving unit for the direct measurement of yield stress with a stress controlled rheometer, Appl. Rheol. 18 (2008) 54974.

Rheological properties of elastomeric nanocomposites with organically modified Montmorillonite clays, as possible replacements or supplements to classical active fillers, such as carbon black or silica, have been intensively studied in recent years. Possessing large specific surface areas acquired through the melt-mixing processes of elastomeric intercalation and subsequent filler exfoliation, the clay particles have indeed proved to be highly eligible reinforcing and thermally stabilizing ingredients for application in elastomers. In fact, their performance has shown to be in many respects superior to that of classical fillers, particularly owing to some unusual, though beneficial, exhibited properties. Namely, apart from uncommonly high surface activity, manifested by creation of a host of van der Waals type secondary linkages with elastomer molecules, the main curiosity of clay filler is its dissipative action. Using dynamic mechanical functions under different deformational and temperature conditions, as means for rheological characterization of nanocomposites, the foregoing nano-scale traits are clearly reflected in substantial stiffness at low strains and, unexpectedly, dwindling energy loss with increasig filler content and/or decreasing temperature. Besides, rheological analysis of this kind, together with appropriate theoretical grounds, has enabled elucidation of peculiar conduct, as well as macroscopic insight into the very nature of secondary interactions in elastomers.► Cite this publication as follows:

Susteric Z, Kos T: Rheological Idiosyncrasies of Elastomer/Clay Nanocomposites, Appl. Rheol. 18 (2008) 54894.

Complex fluids exhibit time-dependent changes in viscosity that have been ascribed to both thixotropy and aging. However, there is no consensus for which phenomenon is the origin of which changes. A novel thixotropic model is defined that incorporates aging. Conditions under which viscosity changes are due to thixotropy and aging are unambiguously defined. Viscosity changes in a complex fluid during a period of rest after destructuring exhibit a bifurcation at a critical volume fraction φ_{C2}. For volume fractions less than φ_{C2}the viscosity remains finite in the limittto infnity. For volume fractions above critical the viscosity grows without limit, so aging occurs at rest. At constant shear rate there is no bifurcation, whereas under constant shear stress the model predicts a new bifurcation in the viscosity at a critical stress σ_{B}, identical to the yield stress σ_{y}observed under steady conditions. The divergence of the viscosity for σ ≤ σ_{B}is best defined as aging. However, for σ > σ_{B}, where the viscosity remains finite, it seems preferable to use the concepts of restructuring and destructuring, rather than aging and rejuvenation. Nevertheless, when a stress σ_{A}(≤ σ_{B}) is applied during aging, slower aging is predicted and discussed as true rejuvenation. Plastic behaviour is predicted under steady conditions when σ > σ_{B}. The Herschel-Bulkley model fits the flow curve for stresses close to σ_{B}, whereas the Bingham model gives a better fit for σ >> σ_{B}. Finally, the model's predictions are shown to be consistent with experimental data from the literature for the transient behaviour of laponite gels.► Cite this publication as follows:

Quemada D: Aging, rejuvenation, and thixotropy in complex fluids: Time-dependence of the viscosity at rest and under constant shear rate or shear stress, Appl. Rheol. 18 (2008) 53298.

Investigations on the behaviour of superparamagnetic nanoparticles under the influence of a high gradient magnetic field in the vascular system is required for a better under-standing of magnetic drug targeting. The influence on the particle transport of the non-Newtonian and Newtonian properties of blood as well as the influence of the heart rate was therefore studied. An analytical model was developed and the calculation of particle trajectories is presented and evaluated.The results show that the non-Newtonian properties of the blood have a positive influence on the number of retended nanoparticles. The calculations also showed that the number of retained nanoparticles was lower in oscillatory flow profile than in steady flow. The influence of the heart rate can be neglected for Womersley numbers smaller than 1.5.► Cite this publication as follows:

Gleich B, Weyh T, Wolf B: Magnetic Drug Targeting: an analytical model for the influence of blood properties on particle trajectories, Appl. Rheol. 18 (2008) 52023.

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