The purpose of this study was to quantitatively assess the influence of the Fåhraeus-Lindqvist effect on the microcirculation in the arteriovenous network of the human retina. A mathematical model was used to simulate the arteriovenous distributions of hemodynamic parameters within a microvascular network of successive, symmetric bifurcating branches that were constructed based on both flow conservation and a modified Murray's law with a diameter exponent of 2.85. The vessel calibers ranged from a 108-μm arteriole and a 147-μm venule down to the 5-μm capillaries. The distributions of vascular resistance, pressure drop, and wall shear stress as a function of vessel diameter within the retinal microcirculatory network with the Fåhraeus-Lindqvist effect were lower than those without the Fåhraeus-Lindqvist effect. The efficiency of blood transport to tissues in the microvascular bed, which was evaluated in terms of the inverse of the mechanical energy cost of the product of the driving pressure and blood flow, was 44% greater with the Fåhraeus-Lindqvist effect than without the Fåhraeus-Lindqvist effect. These results quantitatively demonstrated that the Fåhraeus-Lindqvist effect plays an important role in reducing the physical energy required to transport blood that flows through the microcirculatory network. The integrated and interactive relationships between shear stress, circumferential wall stress, vessel radius, and wall thickness in response to acute and chronic increases in perfusion pressure are discussed with regard to their coordinating roles in the control of blood flow and pressure in microcirculation.

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Periodic-stress-induced morphological change on the inside and outside surfaces of polyvinyl chloride (PVC) pump tube, which was produced for the cardiac surgery, was observed on the basis of optical microscopy and atomic force microscopy in order to discuss the feature of the structural change in the pump tube during the operation. Different surface morphology was observed on inside and outside surfaces of the pump tube. Grainy ruggedness appeared on the outside surface, while numerous polygonal lamellae several μm in size spread over the inside surfaces of the original pump tube. After the periodic stress application by the roller pump, rugged stripes were observed on the outside surface sloped at the angle of 30∼50° from the stress direction as well as locally distributed grooves 10μm wide on the inside surface, and the number of the polygonal lamellae on the inside surface of the stressed pump tube was drastically decreased. It seems that the polygonal lamellae were peeled off from the inside surface of the pump tube. Such facts suggest that the inside surfaces of roller and wall sides in the pump tube contacted with each other under the stress, and that the peeled lamellae may flow into the interior of the body.

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Eye-blink activities are major artifacts for electroencephalogram (EEG) measurements. Various methods have been reported for removing eye-blink artifacts from EEGs. Almost all previous methods focus on how much eye-blink artifacts are removed. However, they concurrently remove a part of EEGs together with eye-blink artifacts. Instead, we focus on how much true EEGs remains, and proposed a localized removal method for eye-blink artifacts. The proposed method is based on the combinations of independent component analysis (ICA). empirical mode decomposition (EMD) and Kalman filter. In addition, we proposed a novel simulation model to test performances of the proposed and previous methods. This simulation model indicates that the proposed method shows the best performance and reduces information loss of EEGs than previous methods.

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