Molecules and activities which repulse growing neurites or induce growth cone collapse and longlasting growth inhibition have been defined over the last 10 years. Recently, specific guidance roles for developing axons...
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Molecules and activities which repulse growing neurites or induce growth cone collapse and longlasting growth inhibition have been defined over the last 10 years. Recently, specific guidance roles for developing axons and pathways could be associated with such repulsive effects. A high molecular weight membrane protein located in CNS myelin acts as potent neurite growth inhibitor and may play a role as a negative control element for sprouting, neurite growth and regeneration, and for the plasticity of the adult CNS. Interestingly, some guidance molecules can have positive, growth-promoting as well as negative, repulsive effects for specific types of neurons. These results underline the complex mechanisms involved in neurite guidance which depends on the interpretation of combinations of incoming signals by particular growth cones.
The neural cell adhesion molecule N-CAM has been proposed to function in the guidance of outgrowing axons in the peripheral and central nervous system. Light microscopic observations have shown that the embryonic form...
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The neural cell adhesion molecule N-CAM has been proposed to function in the guidance of outgrowing axons in the peripheral and central nervous system. Light microscopic observations have shown that the embryonic form of N-CAM (200-230 kDa) is present in the ventralmost part of the dorsal funiculus during corticospinal tract (CST) ingrowth in the first postnatal week (Joosten, Dev. Brain Res., 78 (1994) 226-236). Here, the subcellular localization of the embryonic form of N-CAM (E-NCAM) is determined by pre-embedding staining on vibratome sections and by postembedding immunogold-labelling on Epon embedded spinal cord sections. The electron microscopical observations indicate that E-NCAM is present on the outer membrane of CST growth cones as well as other unmyelinated axons which are present in the ventralmost part of the dorsal funiculus. Furthermore, E-NCAM is localized in an irregular patchy way on the outer side of the axonal membrane of small unmyelinated, later arriving CST axons. From these results it may be deduced that E-NCAM is involved in CST tract formation through guidance of outgrowing pioneer CST growth cones along other unmyelinated axons and through mediation of axon fasciculation of later arriving CST axons.
Augmented proportional navigation requires the information of a target acceleration, which must be estimated by a filtering logic. The process necessary accompanies a time lag, which degrades the guidance performance....
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ISBN:
(纸本)0780337514
Augmented proportional navigation requires the information of a target acceleration, which must be estimated by a filtering logic. The process necessary accompanies a time lag, which degrades the guidance performance. A trade-off study between augmented and conventional proportional navigation is conducted with the time lag taken into consideration. The result shows that, the augmented proportional navigation has good performance even if a time lag exists in estimating the target acceleration, and is particularly useful against the target out-of-coplane maneuvers.
The modular integrated avionics group (MIAG) is a single unit approach to combining position, inertial and baro-altitude/air data sensors to provide optimized navigation, guidance and control performance. Lear Astroni...
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ISBN:
(纸本)0819421197
The modular integrated avionics group (MIAG) is a single unit approach to combining position, inertial and baro-altitude/air data sensors to provide optimized navigation, guidance and control performance. Lear Astronics Corporation is currently working within the navigation community to upgrade existing MIAG performance with precise GPS positioning mechanization tightly integrated with inertial, baro and other sensors. Among the immediate benefits are the following: (1) accurate target location in dynamic conditions; (2) autonomous launch and recovery using airborne avionics only; (3) precise flight path guidance; and (4) improved aircraft and payload stability information. This paper will focus on the impact of using the MIAG with its multimode navigation accuracies on the UAV targeting mission. Gimbaled electro-optical sensors mounted on a UAV can be used to determine ground coordinates of a target at the center of the field of view by a series of vector rotation and scaling computations. The accuracy of the computed target coordinates is dependent on knowing the UAV position and the UAV-to-target offset computation. Astronics performed a series of simulations to evaluate the effects that the improved angular and position data available from the MIAG have on target coordinate accuracy.
The growing interest in occupational stress is discussed, focusing on a recent successful claim againt an employer. Key legal issues, guidance for employers and the implications for health educators are covered.
The growing interest in occupational stress is discussed, focusing on a recent successful claim againt an employer. Key legal issues, guidance for employers and the implications for health educators are covered.
Studies of the long-term outcome of schizophrenia in Japan are reviewed. In nine studies over a 10 year period, recent reports on three patient cohorts show that the liability to relapse is the major difficulty in the...
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Studies of the long-term outcome of schizophrenia in Japan are reviewed. In nine studies over a 10 year period, recent reports on three patient cohorts show that the liability to relapse is the major difficulty in the treatment and care of schizophrenia. Other research on relapse-related problems in schizophrenia are also reviewed Relapses appear mainly in the first decade after onset of the condition;in stressful situations related to a family or larger social context;and on cessation of psychotropic drugs. Relapse liability develops during the course of schizophrenia, but the characteristics of the relapses vary with both the duration and the episodic nature of the schizophrenic condition. Two types of unique treatments that are specifically aimed at coping with relapses, and which were developed in Japan, are described: 'Seikatsu-Rinsho' (clinical guidance to the way of life) and 'Soegi-Ryoho' (splint therapy).
The hemidecussation of retinal fibers that occurs in mammals offers the opportunity to study several aspects of growth cone guidance in a single model system. Recent studies suggest that growth cones of crossed and un...
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The hemidecussation of retinal fibers that occurs in mammals offers the opportunity to study several aspects of growth cone guidance in a single model system. Recent studies suggest that growth cones of crossed and uncrossed retinal fibers respond in differential manners when they contact cells at the optic chiasm midline, and that such contact interactions are the main event involved in their divergence. Observations of the in situ behaviors of these growth cones disclose that their guidance in this decision region involves two different processes: an orientational response, mediated by the selective guidance of the filopodia of frowth cones away or towards the midline of the optic chiasm, and a dynamic response, in which growth cones go through cycles of advance and pauses while in the optic chiasm. We hypothesize that these two aspects of growth cone motility represent two different aspects of the biology of growth cones in response to extrinsic cues, which are both used in their guidance during development.
A new data extrapolation algorithm is presented for guidance and target recognition application. The algorithm firstly uses DFT or FFT computation of L points data of response over band (f/sub o/,f/sub o/+/spl Delta/F...
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ISBN:
(纸本)0780318935
A new data extrapolation algorithm is presented for guidance and target recognition application. The algorithm firstly uses DFT or FFT computation of L points data of response over band (f/sub o/,f/sub o/+/spl Delta/F) to obtain the rough outline of target range profile. Then a CFAR detector is used to obtain the structure window function X/sub w/(e/sup j/spl omega) and its IFT series X/sub w/(l) and several filtering functions {H/sub j/(z)} are constructed. Finally, the extrapolation process by using the filtered series {y/sub j/(l)} based on X/sub w/(e/sup j/spl omega) restriction is established. The algorithm has the advantage of robustness under clutter background.
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