Introduction
The structural integrity of platelet receptors is essential for platelets to function normally in hemostasis and thrombosis in response to physiological and pathological stimuli. The aim of this study was to examine the shedding of two key platelet receptors, glycoprotein (GP) Ibα and GPVI, after exposed to the non-physiological high shear stress environment which commonly exists in blood contacting medical devices and stenotic blood vessels.
Materials and Methods
In this in vitro experiment, we exposed healthy donor blood in our specially designed blood shearing device to three high shear stress levels (150, 225, 300Pa) in combination with two short exposure time conditions (0.05 and 0.5 sec.). The expression and shedding of platelet GPIbα and GPVI receptors in the sheared blood samples were characterized using flow cytometry. The ability of platelet aggregation induced by ristocetin and collagen related to GPIbα and GPVI in the sheared blood samples, respectively, was evaluated by aggregometry.
Results and Conclusions
Compared to the normal blood, the surface expression of platelet GPIbα and GPVI in the sheared blood significantly decreased with increasing shear stress and exposure time. Moreover, the platelet aggregation induced by ristocetin and collagen reduced remarkably in a similar fashion. In summary non-physiological high shear stresses with short exposure time can induce shedding of platelet GPIbα and GPVI receptors, which may lead platelet dysfunction and influence the coagulation system. This study may provide a mechanistic insight into the platelet dysfunction and associated bleeding complication in patients supported by certain blood contacting medical devices.
Abstract-Cognitive radio technology is an innovative radio design concept which aims to increase spectrum utilization by exploiting unused spectrum in dynamically changing environments. By extending previous results, we investigate the capacity gains achievable with this dynamic spectrum approach in asymmetric fading channels. More specifically, we allow the secondary-toprimary and secondary-to-secondary user channels to undergo Rayleigh or Rician fading, with arbitrary link power. In order to compute the capacity, we derive the distributions of ratios of Rayleigh and Rician variables. Compared to the symmetric fading scenario, our results indicate several interesting features of the capacity behaviour under both average and peak received power constraints. Finally, the impact of multiple primary users on the capacity under asymmetric fading has also been studied.
Limitations in modern sensing technologies result in large errors in sensed target object geometry and location in unstructured environments. As a result, positioning a robotic end-effector includes inherent error that will often lead to unsuccessful grasps. In previous work, we demonstrated that optimized configuration, compliance, viscosity, and adaptability in the mechanical structure of a robot hand facilitates reliable grasping in unstructured environments, even with purely feedforward control of the hand. In this paper we describe the addition of a simple contact sensor to the fingerpads of the SDM Hand (Shape Deposition Manufactured Hand), which, along with a basic control algorithm, significantly expands the grasp space of the hand and reduces contact forces during the acquisition phase of the grasp. The combination of the passive mechanics of the SDM Hand along with this basic sensor suite enables positioning errors of over 5cm in any direction. In the context of mobile manipulation, the performance demonstrated here may reduce the need for much of the complex array of sensing currently utilized on mobile platforms, greatly increase reliability, and speed task execution, which can often be prohibitively slow.
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