Organic expander action at lead electrodes

The instrumentation for digitally driven electrochemical experiments has been developed. Software has been written for experimental control and high speed data aquisition. The digital control methods were successfully used in the study of the electrochemistry of the porous lead electrode (the lead-acid battery negative plate), over an extended temperature range. The effects of a number of commercially pertenent additives have been studied at reduced temperatures. These reaction enhancing materials (expanders) have been studied in detail on both planar and porous lead electrode in sulphuric acid in the range 1M to 5M. Deductions concerning the energetics of the reactions have been made from experimental results. The modes of action of certain expanders are discussed. It was concluded that on the plane lead surface solution phase expander materials modify the mechanism of the lead sulphate electrocrystallisation - the current limiting reaction. This was an effect on the solid state process although a solution Pb2+ process was identified (for the first time) in battery strength acid. Electrode incorporated organic expander materials act by modifying pore geometies and reaction penetration depths. The current transients due to electrocrystallization in porous lead are very complex and require very sophisticated modelling techniques to provide a useful fit

The application of neural networks to anodic stripping voltammetry to improve trace metal analysis

This thesis describes a novel application of an artificial neural network and links together the two diverse disciplines of electroanalytical chemistry and information sciences. The artificial neural network is used to process data obtained from a Differential Pulse Anodic Stripping (DPAS) electroanalytical scan and produces as an output, predictions of lead concentration in samples where the concentration is less than 100 parts per billion. A comparative study of several post analysis processing techniques is presented, both traditional and neural. Through this it is demonstrated that by using a neural network, both the accuracy and the precision of the concentration predictions are increased by a factor of approximately two, over those obtained using a traditional, peak height calibration curve method. Statistical justification for these findings is provided Furthermore it is shown that, by post processing with a neural network, good quantitative predictions of heavy metal concentration may be made from instrument responses so poor that, if using tradition methods of calibration, the analytical scan would have had to be repeated. As part of the research the author has designed and built a complete computer controlled analytical instrument which provides output both to a graphical display and to the neural network. This instrument, which is fully described in the text, is operated via a mouse driven user interface written by the author

Vestibular Function Research (VFR) experiment. Phase B: Design definition study

The Vestibular Functions Research (VFR) Experiment was established to investigate the neurosensory and related physiological processes believed to be associated with the space flight nausea syndrome and to develop logical means for its prediction, prevention and treatment. The VFR Project consists of ground and spaceflight experimentation using frogs as specimens. The phase B Preliminary Design Study provided for the preliminary design of the experiment hardware, preparation of performance and hardware specification and a Phase C/D development plan, establishment of STS (Space Transportation System) interfaces and mission operations, and the study of a variety of hardware, experiment and mission options. The study consist of three major tasks: (1) mission mode trade-off; (2) conceptual design; and (3) preliminary design

Electronics for Sensors

The aim of this Special Issue is to explore new advanced solutions in electronic systems and interfaces to be employed in sensors, describing best practices, implementations, and applications. The selected papers in particular concern photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs) interfaces and applications, techniques for monitoring radiation levels, electronics for biomedical applications, design and applications of time-to-digital converters, interfaces for image sensors, and general-purpose theory and topologies for electronic interfaces

Design and development of a very flexible and completely programmable pain control stimulator

L'utilisation des stimulations nerveuses s'est vue accorder une attention sans cesse croissante, durant les dernières années, comme une méthode de traitement sécuritaire, efficace et facile a utiliser pour contrôler la douleur. La publication par Melzack et Wall de la théorie du mécanisme de contrôle de la douleur (Gate Control Theory of pain) et son application par Shealy pour trailer la douleur chronique en utilisant les stimulations électriques, ont été Ie point de départ de plusieurs travaux de recherche visant à déterminer la meilleure fa9on d'utiliser cette technique de traitement et a concevoir Ie système approprie pour 1'appliquer. Cette théorie stipule que Ie mécanisme qui gère les sensations de la douleur, peut être contrôlé a 1'aide de stimulations artificielles du système périphérique. En effet, des stimulis électriques appliques convenablement peuvent interférer avec les messages des sensations de la douleur transmise vers Ie centre nerveux principal et ainsi réduire la perception de la douleur. L'objectif de ce travail de recherche est de concevoir et implémenter un système de stimulations de la colonne vertébrale, très avancé et complètement programmable, base sur la théorie du mécanisme de contrôle de la douleur énoncée par Melzack et Wall. Le système peut être utilisé comme un traitement de choix pour certaines douleurs chroniques rebelles qui ne peuvent être soignées par un traitement conventionnel. Ce système délivre des stimuli électriques contrôlés a un ensemble de fibres nerveuses de la colonne vertébrale sélectionnées convenablement. La stimulation de ces fibres module les messages de la douleur diriges vers Ie cerveau.Abstract: The objective of this research project is to design and to implement an advanced full programmable spinal cord stimulation (SCS) system, based on Melzack and Wall gate control theory of pain. The system can be used as a treatment of choice for certain intractable chronic pain not responding to conventional treatment. The system delivers controlled electrical stimuli to some properly selected nerve fibers along the spinal cord. The stimulation of these nerve fibers modulates pain messages being transmitted to the brain. This thesis presents the design and implementation of the basic component of the system, which is the dedicated microprocessor, as well as the other functional parts that have been integrated together to get a miniaturized implantable device provided with appropriate programming and operating tools. The spinal cord stimulation system described here is mainly composed of three parts: two external units and a surgically implanted module. The first external part consists of a computer-based system with completely graphical software and appropriate hardware interface, intended for the physician to program and to adjust the internal part. The patient, in order to control stimulation at his convenience, will use the second external unit. As for the implanted part, this one is built around a powerful mixed-signal ASIC, which is mounted together with appropriate demodulation and power recovery circuits, a memory (EEPROM), and a few peripheral discrete components. Communication of power and data between external and internal parts is achieved through a transdermal inductive link. The system proposed is very user-friendly and unique in its way of operation, providing an unlimited flexibility and complete external programmability. In fact, it is the only miniaturized system providing the user with the possibility to get different stimulation algorithms simultaneously making it more adaptable to the conditions and the state of the patient. It also provides several original features that make it possible to perform a wide range of stimulation algorithms and to generate an unlimited number of stimulus waveforms. As examples, we can mention the possibility of using combined stimuli through simultaneous stimulation over two channels, the possibility of generating complex current pulse shapes, and the access to a greater number of stimulation parameters."--Résumé abrégé par UMI

NASA Tech Briefs, December 1988

This month's technical section includes forecasts for 1989 and beyond by NASA experts in the following fields: Integrated Circuits; Communications; Computational Fluid Dynamics; Ceramics; Image Processing; Sensors; Dynamic Power; Superconductivity; Artificial Intelligence; and Flow Cytometry. The quotes provide a brief overview of emerging trends, and describe inventions and innovations being developed by NASA, other government agencies, and private industry that could make a significant impact in coming years. A second bonus feature in this month's issue is the expanded subject index that begins on page 98. The index contains cross-referenced listings for all technical briefs appearing in NASA Tech Briefs during 1988

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences