The ideal model to describe the nonlinear behavior of viscoelastic materials needs to be low-dimensional, provide ease of use and a straightforward physical interpretation. This is important to create a full picture of the material response in both the linear and nonlinear regime. In this work, we present a simple analysis of the nonlinear regime of oscillatory shear by using a modified Maxwell model. The model can describe a range of nonlinear behaviors by representing the general response of the spring and dashpot as an odd-power series expansion. Elastic and viscous Lissajous curves were calculated using four parameters to represent linear and nonlinear elasticity and viscosity. The model dependence on the strain amplitude, frequency and the nonlinear parameters was studied. Varying the thickening and thinning nature of the dashpot allowed the model to reproduce the Bird-Carreau equation when a sufficient number of terms was employed in the power series expansion. The model is also shown to describe the nonlinear data for a system of mixed carrageenan hydrogels well.

Objective: The objective of this study is to test the hypothesis that hemodynamic stress causes displacement or deformation of coils, resulting in cerebral aneurysm recanalization after treatment. Methods: Twenty-two patients with internal carotid artery cerebral aneurysms treated with coil embolization were included in this study. All patients were imaged with three-dimensional (3D) rotational angiography before and after treatment. The displacement and deformation of the coils were evaluated using a 3D workstation. Hemodynamic parameters were calculated using aneurysm images before treatment. Results: Four aneurysms (18%) showed recanalization one year after treatment. These four recurrence aneurysms had larger displacement after treatment (P = 0.049). Furthermore, they tended to have greater coil deformation. Among several hemodynamic parameters, inflow velocity at the aneurysmal neck before treatment was related to coil displacement (P = 0.0008), which resulted in the recurrence of the aneurysm after treatment (P = 0.049). The inflow velocity was linked to aneurysm recurrence after treatment (P = 0.0002). Furthermore, aneurysm recurrence with a slightly elevated pressure loss coefficient was associated with a greater volume ratio (P = 0.03). Conclusions: High flow velocity at the aneurysmal neck might cause displacement and/or deformation of the coils, resulting in aneurysm recanalization after treatment.

The laser heating in 3D food printings can give a formativeness to food inks by the laser-controlled gelatinization of the paste which improves the handling of the food ink materials. We have elucidated the gelatinization behavior of wheat starch paste by a laser heating. The localized heating by laser irradiation caused the gelatinization of the paste in a millimeter order width which caused a subsequent water migration from the ungelatinized region by the water demand associated with the gelatinization. Polarized microscopy, scanning electron microscope (SEM) observation and magnetic resonance imaging (MRI) have been carried out for the elucidation. The cross-section observation by a polarized microscope showed the melting of starch granule crystals in the laser heated region, and SEM observation indicated the collapse of starch granules to give the gelatinized lumps engulfing the water. MRI measurements gave the distribution of water content in the laser heated paste suggesting the water migration from the ungelatinized region where the gelatinization by the following laser heating was restrained because of the low water content. The water migration was reproduced in a model paste sheet with one side heating where the side was gelatinized with the increase of water content and another side decreased in the water content. The results of this study provide useful information on developing laser cooking techniques, allowing laser heating to find potential applications in the food processing industry including 3D food printing.

The milk-clotting activity of kiwifruit juice, which contains high levels of actinidin, a cysteine protease, was evaluated using rheological methods. Kiwifruit juice and rennet (The concentration added for both is 0.02 mg/ml as protein concentration.) were added to raw milk, and the time development of the dynamic modulus was observed. Both samples with the two coagulants formed milk gels and showed elastic moduli of the same order of magnitude. However, the milk clotting speed induced by kiwifruit juice was about five times faster than that induced by rennet.