Proteoglycans influence aging and plasticity in the nervous system. Particularly prominent are the chondroitin sulfate proteoglycans (CSPGs), which are generally inhibitory to neurite outgrowth. During development, CS...
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Proteoglycans influence aging and plasticity in the nervous system. Particularly prominent are the chondroitin sulfate proteoglycans (CSPGs), which are generally inhibitory to neurite outgrowth. During development, CSPGs facilitate normal guidance, but following nervous system injury and in diseases of aging (e.g., Alzheimer's disease), they block successful regeneration, and are associated with axon devoid regions and degenerating nerve cells. Whereas previous studies used non-nervous system sources of CSPGs, this study analyzed the morphology and behavior of sensory (dorsal root ganglia) neurons, and a human nerve cell model (SH-SY5Y neuroblastoma cells) as they contacted nervous system-derived CSPGs, using a variety of microscopy techniques. The results of these qualitative analyses show that growth cones of both nerve cell types contact CSPGs via actin-based filopodia, sample the CSPGs repeatedly without collapse, and alter their trajectory to avoid nervous system-derived CSPGs. Turning and branching are correlated with increased filopodial sampling, and are common to both neurons and Schwann cells. We show that CSPG expression by rat CNS astrocytes in culture is correlated with sensory neuron avoidance. Further, we show for the first time the ultrastructure of sensory growth cones at a CSPG-laminin border and reveal details of growth cone and neurite organization at this choice point. This type of detailed analysis of the response of growth cones to nervous system-derived CSPGs may lead to an understanding of CSPG function following injury and in diseases of aging, where CSPGs are likely to contribute to aberrant neurite outgrowth, failed or reduced synaptic connectivity, and/or ineffective plasticity. Microsc. Res. Tech. 54:273-286, 2001. (C) 2001 Wiley-Liss, Inc.
The main objective of this study was to develop an automated agricultural vehicle guidance system capable of controlling the vehicle during high-speed agricultural field operations. The posture sensor used in the stud...
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The main objective of this study was to develop an automated agricultural vehicle guidance system capable of controlling the vehicle during high-speed agricultural field operations. The posture sensor used in the study was a kinematic differential Global Positioning System (GPS) receiver Experimental frequency response tests were used to develop models of steering equipment and vehicle dynamics. Classical feedback control was developed based on these models. guidance controller effectiveness was evaluated with experimental step response tests. Frequency response tests of vehicle dynamics showed that the transfer function relating vehicle lateral deviation to steering angle was a double integrator The dynamics of the automatic steering were within the same frequency range as desired vehicle dynamics. guidance controller design had to compensate for both vehicle and steering equipment dynamics. When the GPS sensor was mounted above the front axle of the vehicle, guidance control to within 16 cm of the desired path was demonstrated at speeds up to 6.8 m/s. Moving the sensor rearward to a more practical location added phase lag to the system, and guidance control was less effective.
The theory in this paper is motivated by the problem of aircraft guidance in automatic flight control, in which plant models are nonlinear. This leads us to consider the stable inversion problem, which in turn can be ...
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The theory in this paper is motivated by the problem of aircraft guidance in automatic flight control, in which plant models are nonlinear. This leads us to consider the stable inversion problem, which in turn can be cast as the problem of finding a bounded solution of a time-varying nonlinear system subject to a bounded input. Under the appropriate assumptions there is a unique bounded (for all time) continuous solution to this time-varying nonlinear system in response to the bounded (for all time) input. We show that there is a (local) stable manifold containing-all bounded continuous solutions for non-negative time, and that all such solutions converge to the aforementioned unique solution as time: goes to infinity. Likewise there is a (local) unstable manifold containing all bounded solutions for non-positive time and these converge to the unique solution as time goes to minus infinity. In fact, the unique solution (cross the time axis) is the intersection of the stable and unstable manifolds. (C) 1999 John Wiley & Sons, Ltd.
In positioning and localization problems, two or more different sensors are often used to obtain the best estimation data for control system. Extended Kalman Filter (EKF) is widely used to fuse those data to obtain on...
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In positioning and localization problems, two or more different sensors are often used to obtain the best estimation data for control system. Extended Kalman Filter (EKF) is widely used to fuse those data to obtain one optimal result. One consideration when using EKF is the signal used during navigation is a white noise signals. This consideration is hardly found in real application. This paper presents the sensor fusion for dead-reckoning mobile robot navigation. Odometry and sonar signals are fused using Extended Kalman Filter (EKF) and Adaptive Fuzzy Logic System (AFLS). The AFLS was used to adapt the gain and therefore prevent the Kalman filter divergence. The fused signal is more accurate than any of the original signals considered separately. The enhanced, more accurate signal is used to guide and navigate the robot.
The Object Oriented Control Architecture for Autonomy (O 2 CA 2 ) is a control architecture being developed at the University of Girona for the GARBI underwater vehicle. Conceived as a hybrid, it is organised in three...
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The Object Oriented Control Architecture for Autonomy (O 2 CA 2 ) is a control architecture being developed at the University of Girona for the GARBI underwater vehicle. Conceived as a hybrid, it is organised in three layers (Deliberative, Control Execution and Reactive) merging the deliberation mechanisms of planning with reactive behaviours in charge of controlling the robot. The aim of this paper is to provide an overall description of the whole architecture and an in depth description of the Reactive-layer. The concepts of the architecture have been tested with the simulation of a simple mission consisting of navigating through a sequence of way-points while avoiding contact with obstacles.
As the ocean attracts great attention on environmental issues and resources as well as scientific and military tasks, the need for and use of underwater robotic systems has become more apparent. Underwater robotics re...
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As the ocean attracts great attention on environmental issues and resources as well as scientific and military tasks, the need for and use of underwater robotic systems has become more apparent. Underwater robotics represent a fast growing research area and promising industry as advanced technologies in various subsystems develop and potential application areasare explored. Great efforts have been made in developing autonomous underwater robots or vehicles (AUVs) to overcome challenging scientific and engineering problems caused by the unstructured and hazardous ocean environment. With the development of new materials, advanced computing and sensorytechnology, as well as theoretical advancements, R & D activities in the AUV community have increased. This paper describes advanced underwater robot research activities at the Autonomous Systems Laboratory
Objective: The objective was to develop a fixation-based three-dimensional presurgical planner and an intraoperative guidance system for distal radius osteotomy. Fixation-based surgery is a technique premised on using...
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Objective: The objective was to develop a fixation-based three-dimensional presurgical planner and an intraoperative guidance system for distal radius osteotomy. Fixation-based surgery is a technique premised on using a fixation device, such as a fracture-fixation plate, during the alignment and distraction phases of an *** and Methods: The planning system and guidance system were coded using OpenGL on UNIX *** vitrotests were performed to compare the reproducibility of the computer-enhanced technique to that of the traditional technique, and anin vivopilot study was ***:In vitro, the computer-enhanced technique produced a significant reduction by more than one half in both the maximum error of correction and the standard deviation of the correction error. Preliminaryin vivoresults on six patients suggest that similar error diminution will occur during regular clinical application of the ***: Both studies showed that the computer system is simple to use. The planning system allowed the surgeon to perform multiple simulations of the surgical procedure preoperatively, which were used to optimize the plan and identify potential problems during realignment. The use of a fixation-based technique avoided the complexity of attempting to guide the surgeon to realign a bone fragment in six degrees of freedom of correction, and eliminated the use of X-ray fluoroscopy for achieving the alignment.
The most critical form of guidance that a teacher or coach can offer to students or athletes is augmented information feedback. Such feedback comes from a source external to a learner. It includes knowledge of results...
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The most critical form of guidance that a teacher or coach can offer to students or athletes is augmented information feedback. Such feedback comes from a source external to a learner. It includes knowledge of results (KR), which is the extrinsic verbalizable information about the outcome of an action, and knowledge of performance (KP), which is the extrinsic verbalizable information about the action itself. One example of KR is to say "Good job, John" after a player finishes a nice move. A golf coach can provide KP for an athlete in this way: "Mary, your elbows were not straight during the swing." While students have internal sources of feedback, it is usually the external, expert point of view of a teacher or a coach that provides the most potent basis for improvement.
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