A technique has been developed to localise the path of an ultrasound pulse, launched from a transmitting transducer and travelling within a scattering medium, utilising a separate receiving transducer to detect off-ax...
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A technique has been developed to localise the path of an ultrasound pulse, launched from a transmitting transducer and travelling within a scattering medium, utilising a separate receiving transducer to detect off-axis scattered energy. The operation of the two transducers enables a locus of the sites of detected signals, across a range of angles, to be generated. Two different mathematical approaches were investigated for the analysis of these data, and their relative success quantified. It was found that it was possible to determine the parameters defining the orientation of the beam, by fitting the data to an appropriately formed equation. A clinical application of the technique would be the visualisation of a therapeutic beam, operating initially at relatively low intensity, on a B-mode image. This would enable accurate positioning of its focus in the region of interest, prior to the application of therapeutic intensity levels and the formation of lesions. Similarly, a guidance system for the insertion of a biopsy needle into soft tissues could be developed with this technique and a low intensity path-finding beam. (C) 1999 Elsevier Science B.V. All rights reserved.
A new and practical terminal guidance law is presented for impact angle control for two-dimensional active homing engagement scenarios. Impact angle control is required to enhance terminal effectiveness of antitank an...
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A new and practical terminal guidance law is presented for impact angle control for two-dimensional active homing engagement scenarios. Impact angle control is required to enhance terminal effectiveness of antitank and antiship missile systems in particular. The proposed guidance law is developed to cope with missile velocity reduction due to aerodynamic drag and target maneuver. In actual applications, the proposed guidance law is combined in cascade with a target tracking filter under the certainty equivalence principle. The proposed guidance law in conjunction with the target tracking filter is shown to be effective in antiship active homing engagement scenarios by a series of Monte Carlo simulation runs.
The Food and Drug Administration (FDA) has gained significant experience with computer-assisted licensing applications, and has concluded that continued reliance on customized formats is a burden for the FDA and indus...
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The Food and Drug Administration (FDA) has gained significant experience with computer-assisted licensing applications, and has concluded that continued reliance on customized formats is a burden for the FDA and industry. As a result, the FDA is working to standardize the content and format of electronically submitted applications, and to establish procedures for electronic applications that will: create minimal additional work for industry and reviewers, establish consistency across the FDA's centers, and expedite the review process. The FDA is proposing to move to a paperless regulatory process by the year 2002. Toward that goal, the FDA's Center for Biologics Evaluation and Research (CBER) has released new guidance for the electronic submission of biologic and product license applications;case report forms, tabulations, and statistical data;and lot release protocols. A pilot program for Investigational New Drug applications also has been initiated.
Three strategies for visualisation of MR-dedicated guidewires and catheters have been proposed, namely active tracking, the technique of locally induced field inhomogeneity and passive susceptibility-based tracking. I...
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Three strategies for visualisation of MR-dedicated guidewires and catheters have been proposed, namely active tracking, the technique of locally induced field inhomogeneity and passive susceptibility-based tracking. In this article the pros and cons of these techniques are discussed, including the development of MR-dedicated guidewires and catheters, scan techniques. post-processing tools, and display facilities for MR tracking. Finally, some of the results obtained with MR tracking are discussed.
Advancement of radiologic technologies allows the detection of vertebral lesions at an earlier stage, thereby increasing the proportion of vertebral lesions that are surrounded by intact bone when they are detected. W...
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Advancement of radiologic technologies allows the detection of vertebral lesions at an earlier stage, thereby increasing the proportion of vertebral lesions that are surrounded by intact bone when they are detected. While biopsy guns are effective in obtaining good-quality tissue samples of osteolytic bone lesions, lesions that are covered by intact bone are not accessible with a biopsy gun. For percutaneous biopsy of osteolytic vertebral lesions, an intact-bone transgressing technique is described in which a simple, inexpensive and small-calibre (18-gauge) instrument is used to allow multiple passage of 20-gauge biopsy guns for effective tissue sampling. In this series consisting of metastatic and myeloproliferative lesions, the effectiveness and safety of this well-tolerated technique are demonstrated in thoracic and lumbar vertebrae.
The application of quality assurance to routine analytical testing is fairly well established with widespread availability of general and specific guidance, both on general principles and in support of quality standar...
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The application of quality assurance to routine analytical testing is fairly well established with widespread availability of general and specific guidance, both on general principles and in support of quality standards and accreditation/certification schemes. The application to non-routine work is less straightforward and widely available guidance has only recently become available with the development and publication of the EURACHEM/CITAC Guide 'Quality Assurance Good Practice for Research and Development and Non-routine Analysis'. A workshop on the guide, and the issues which it aims to address was held during the EUROANALYSIS 10 Conference, Basel, Switzerland, 6-11 September 1998. This paper presents a summary of the presentations and discussions from that workshop. In addition to introducing the guide the workshop examined the possibilities of formal quality systems for research and development, aspects of quality assurance in the academic world, and various technical elements of quality assurance. The paper concludes with findings from group discussions on these topics. (C) 1999 LGC (Teddington) Ltd. Published by Elsevier Science B.V. All rights reserved.
The mechanisms that generate the immense complexity of synaptic connections within the developing nervous system have fascinated biologists for decades. Analysis of nervous system development in simple systems, such a...
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The mechanisms that generate the immense complexity of synaptic connections within the developing nervous system have fascinated biologists for decades. Analysis of nervous system development in simple systems, such as insects, has made a major contribution to our understanding of the cellular and molecular mechanisms that control the formation of axon pathways and precise connections. This enterprise has a long, interesting, and somewhat controversial history. This collection of reviews on axon guidance in insects provides a brief update to integrate current molecular and developmental insights in a number of areas from initial axon pathfinding to the recognition of synaptic partners.
A color machine vision based automatic guidance system was developed for precision guidance of an agricultural cultivator. The guidance system was designed to operate in weedy row crop fields at the time of first cult...
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A color machine vision based automatic guidance system was developed for precision guidance of an agricultural cultivator. The guidance system was designed to operate in weedy row crop fields at the time of first cultivation. The performance of the system varied from an RMS guidance error of 7 mm under low weed loads to 12 mm under high weed loads and was capable of operating at travel speeds up to 16 km/h.
A Windows/C/C++ personal computer-based program is developed and used to evaluate the performance of missile guidance and control systems. The program simulates a high-performance missile in pursuit of an evading targ...
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A Windows/C/C++ personal computer-based program is developed and used to evaluate the performance of missile guidance and control systems. The program simulates a high-performance missile in pursuit of an evading target. The simulation includes realistic missile and actuator dynamics, an autopilot, several missile guidance laws, a seeker/navigation system model, various target models, and several integration methods. Missile-target intercepts are simulated and graphically displayed using the C/C++, programming language. This represents a considerable improvement over previous research due to the object-oriented structure, speed, maintainability, and ease of debugging that C/C++ offers. For modularity, the program is organized into three blocks: program-user interface, simulation, and graphics. Various simulations are presented to demonstrate the utility of the program in the evaluation of missile guidance and control systems.
Neurons extend their neurites to a target during neural development in the brain. During this process, guiding substrates play an important role in guiding the growth cones, the tip of the axons/neurites, precisely to...
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Neurons extend their neurites to a target during neural development in the brain. During this process, guiding substrates play an important role in guiding the growth cones, the tip of the axons/neurites, precisely to their specific targets. This guidance result in the establishment of a neural circuit in the brain. In this review, I will describe the substrates which may guide the growth cone of the axons/neurites to their targets thus forming synaptic neural connections, and also discuss the mechanisms of this neuronal guidance.
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