76 research outputs found

    Structural Properties of the Caenorhabditis elegans Neuronal Network

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    Despite recent interest in reconstructing neuronal networks, complete wiring diagrams on the level of individual synapses remain scarce and the insights into function they can provide remain unclear. Even for Caenorhabditis elegans, whose neuronal network is relatively small and stereotypical from animal to animal, published wiring diagrams are neither accurate nor complete and self-consistent. Using materials from White et al. and new electron micrographs we assemble whole, self-consistent gap junction and chemical synapse networks of hermaphrodite C. elegans. We propose a method to visualize the wiring diagram, which reflects network signal flow. We calculate statistical and topological properties of the network, such as degree distributions, synaptic multiplicities, and small-world properties, that help in understanding network signal propagation. We identify neurons that may play central roles in information processing and network motifs that could serve as functional modules of the network. We explore propagation of neuronal activity in response to sensory or artificial stimulation using linear systems theory and find several activity patterns that could serve as substrates of previously described behaviors. Finally, we analyze the interaction between the gap junction and the chemical synapse networks. Since several statistical properties of the C. elegans network, such as multiplicity and motif distributions are similar to those found in mammalian neocortex, they likely point to general principles of neuronal networks. The wiring diagram reported here can help in understanding the mechanistic basis of behavior by generating predictions about future experiments involving genetic perturbations, laser ablations, or monitoring propagation of neuronal activity in response to stimulation

    Um sistema conversacional de consulta para artigos de periódicos

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    SCAB (Periodical Article on-line Retrieval System) is a system designed for retrieval via remote terminal of bibliographical references to articles in periodicals. On-line operation is handled' by TSO (Time Sharing Option), which performs the interface with the Operating System. The retrievals of information is controlled through on-line dialogue between the user and the system using a SCAP conversational language which is easy to learn without prior knowledge of computational techniques. The creation and. maintenance of the Data Base is carried out in batch mode, independent of the on-line retrieval operation; the system is designed to maintain large collections of periodicals.O SCAP (Sistema Conversacional de Consulta para Artigos de Periódicos) é um sistema orientado para recuperação, via terminal, de referências bibliográficas de artigos de periódicos. A operação “on-line” é feita através do TSO (Time Sharing Option) que perfaz a interface com o Sistema Operacional. A recuperação da informação é feita através do diálogo “on-line” SCAP - USUÁRIO, por intermédio de uma linguagem conversational própria, de fácil aprendizado, mesmo para pessoas sem qualquer conhecimento na área de computação. A criação e atualização do banco de dados é feita em ‘‘batch”, independentemente do funcionamento “on-line”, tendo sido o sistema projetado para armazenar grandes coleções de artigos

    Cadabra: reference guide and tutorial

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    Cadabra is a computer algebra system for the manipulation of tensorial mathematical expressions such as they occur in “field theory problems”. It is aimed at, but not necessarily restricted to, high-energy physicists. It is constructed as a simple tree-manipulating core, a large collection of standalone algorithmic modules which act on the expression tree, and a set of modules responsible for output of nodes in the tree. All of these parts are written in C++. The input and output formats closely follow TEX, which in many cases means that cadabra is much simpler to use than other similar programs. It intentionally does not contain its own programming language; instead, new functionality is added by writing new modules in C++

    National Aeronautics and Space Administration (NASA)/American Society for Engineering Education (ASEE) summer faculty fellowship program, 1986, volume 2

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    The Johnson Space Center (JSC) NASA/ASEE Summer Faculty Fellowship Program was conducted by the University of Houston and JSC. The ten week program was operated under the auspices of the American Society for Engineering Education (ASEE). The basic objectives of the program are (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of participants' institutions; and (4) to contribute to the research objectives of the NASA Centers. Each faculty fellow spent ten weeks at JSC engaged in a research project commensurate with his interests and background and worked in collaboration with a NASA/JSC colleague. The final reports on the research projects are presented. This volume, 2, contains sections 15 through 30

    Architecture and performance of Devito, a system for automated stencil computation

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    Stencil computations are a key part of many high-performance computing applications, such as image processing, convolutional neural networks, and finite-difference solvers for partial differential equations. Devito is a framework capable of generating highly-optimized code given symbolic equations expressed in Python, specialized in, but not limited to, affine (stencil) codes. The lowering process -- from mathematical equations down to C++ code -- is performed by the Devito compiler through a series of intermediate representations. Several performance optimizations are introduced, including advanced common sub-expressions elimination, tiling and parallelization. Some of these are obtained through well-established stencil optimizers, integrated in the back-end of the Devito compiler. The architecture of the Devito compiler, as well as the performance optimizations that are applied when generating code, are presented. The effectiveness of such performance optimizations is demonstrated using operators drawn from seismic imaging applications

    Flight test trajectory control analysis

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    Recent extensions to optimal control theory applied to meaningful linear models with sufficiently flexible software tools provide powerful techniques for designing flight test trajectory controllers (FTTCs). This report describes the principal steps for systematic development of flight trajectory controllers, which can be summarized as planning, modeling, designing, and validating a trajectory controller. The techniques have been kept as general as possible and should apply to a wide range of problems where quantities must be computed and displayed to a pilot to improve pilot effectiveness and to reduce workload and fatigue. To illustrate the approach, a detailed trajectory guidance law is developed and demonstrated for the F-15 aircraft flying the zoom-and-pushover maneuver

    Aerodynamic preliminary analysis system 2. Part 2: User's manual

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    An aerodynamic analysis system based on potential theory at subsonic and/or supersonic speeds and impact type finite element solutions at hypersonic conditions is described. Three dimensional configurations have multiple nonplanar surfaces of arbitrary planforms and bodies of noncircular contour may be analyzed. Static, rotary, and control longitudinal and lateral-directional characteristics may be generated. The analysis was implemented on a time sharing system in conjunction with an input tablet digitizer and an interactive graphics input/output display and editing terminal to maximize its responsiveness to the preliminary analysis. Computation times on an IBM 3081 are typically less than one minute of CPU/Mach number at subsonic, supersonic, or hypersonic speeds. This is a user manual for the computer programming
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