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  • SOCIAL SCIENCES (GENERAL)  (5)
  • Life and Medical Sciences  (3)
  • Domain decomposition  (2)
  • COMPUTER SYSTEMS
  • GROUND SUPPORT SYSTEMS AND FACILITIES (SPACE)
  • 1
    ISSN: 1573-7691
    Keywords: Domain decomposition ; nested dissection ; LU-factorization ; time integration ; Newton's method ; spectral elements ; finite elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Domain decomposition by nested dissection for concurrent factorization and storage (CFS) of asymmetric matrices is coupled with finite element and spectral element discretizations and with Newton's method to yield an algorithm for parallel solution of nonlinear initial-and boundary-value problem. The efficiency of the CFS algorithm implemented on a MIMD computer is demonstrated by analysis of the solution of the two-dimensional, Poisson equation discretized using both finite and spectral elements. Computation rates and speedups for the LU-decomposition algorithm, which is the most time consuming portion of the solution algorithm, scale with the number of processors. The spectral element discretization with high-order interpolating polynomials yields especially high speedups because the ratio of communication to computation is lower than for low-order finite element discretizations. The robustness of the parallel implementation of the finite-element/Newton algorithm is demonstrated by solution of steady and transient natural convection in a two-dimensional cavity, a standard test problem for low Prandtl number convection. Time integration is performed using a fully implicit algorithm with a modified Newton's method for solution of nonlinear equations at each time step. The efficiency of the CFS version of the finite-element/Newton algorithm compares well with a spectral element algorithm implemented on a MIMD computer using iterative matrix methods.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7691
    Keywords: Domain decomposition ; nested dissection ; LU-factorization ; parallel computers ; MIMD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A multilevel algorithm is presented for direct, parallel factorization of the large sparse matrices that arise from finite element and spectral element discretization of elliptic partial differential equations. Incomplete nested dissection and domain decomposition are used to distribute the domain among the processors and to organize the matrix into sections in which pivoting is applied to stabilize the factorization of indefinite equation sets. The algorithm is highly parallel and memory efficient; the efficient use of sparsity in the matrix allows the solution of larger problems as the number of processors is increased, and minimizes computations as well as the number and volume of communications among the processors. The number of messages and the total volume of messages passed during factorization, which are used as measures of algorithm efficiency, are reduced significantly compared to other algorithms. Factorization times are low and speedups high for implementation on an Intel iPSC/860 hypercube computer. Furthermore, the timings for forward and back substitutions are more than an order-of-magnitude smaller than the matrix decomposition times.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to provide evidence as to whether sex chromatin (SC) of interphase cells is equivalent to the late replicating X chromosome in female mammalian cells, time-lapse cinephotometric and autoradiographic methods were used to give precise data for comparison of the DNA replication patterns of SC with that of each of the X chromosomes throughout the S period. Canine kidney epithelial cells were selected because they have distinct large metacentric X chromosomes and typical SC. Time-lapse cinephotometry was used to avoid possible alteration of DNA synthesis by chemical cell synchronization agents. Determination of the incidence of SC during the stages of the cell life cycle of proliferating cells of the same origin was performed in order hopefully to clarify conflicting reports on the subject. Our results clearly show that time and intensity of the SC replication throughout S period is like that of the late replicating X chromosome and unlike that of the early replicating X chromosome. The incidence of SC in proliferating cells in culture was found to vary with the stage of the cell life cycle, increasing with increasing postmitotic interval  -  least in G1, greater in S, and greatest in G2. The SC incidence increased strikingly from G1 to S and a less marked increase was observed between S and G2.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 132 (1987), S. 57-64 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Potassium and sodium fluxes believed to be important in the cellular response to serum and growth factors have not been widely investigated in cells which have undergone terminal differentiation. In this study we have analyzed two main K+ transport systems - the ouabain-sensitive Na+/K+ pump and the bumetanide-sensitive transporter - in human muscle in vitro at two developmental stages: proliferating myoblasts and differentiated myotubes. Myoblast differentiation to myotubes was accompanied by a marked decrease in both the ouabain-sensitive and the bumetanide-sensitive K+ (Rb+) influxes. The addition of serum to the terminally differentiated myotubes had no effect on these K+ transporters. However, serum addition to serum-deprived, undifferentiated myoblasts produced a marked stimulation of these K+ fluxes.The bumetanide-sensitive K+ transporter in human myoblasts and myotubes has the following properties: (1) It carries 30% and 40% of the total K+ influx in myoblasts and myotubes, respectively. (2) It performs net efflux of K+ in the undifferentiated myoblasts and zero net flux (self-exchange) in terminally differentiated myotubes. (3) It is dependent on extracellular Na+ and Cl- in addition to K+. (4) In myoblasts, the Km value for K+ is 1.36 mM, similar to the Km for K+ of the Na+/K+ pump. (5) It is resistant to ouabain (up to 2 mM) and sensitive to furosemide (K0.5 = 5 × 10-6 M) and bumetanide (K0.5 = 10-7 M). These data indicate that following terminal differentiation of proliferating myoblasts to mitotically inactive myotubes there is an irreversible reduction of K+ fluxes with a change in the net flux of K+ carried by the bumetanide-sensitive transporter.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 2 (1933), S. 467-478 
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 2 Ill.
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  • 6
    Publication Date: 2019-06-28
    Description: As part of the Telescience Testbed Pilot Program, the Universities Space Research Association/ Research Institute for Advanced Computer Science (USRA/RIACS) proposed to support remote communication by providing a network of human/machine interfaces, computer resources, and experimental equipment which allows: remote science, collaboration, technical exchange, and multimedia communication. The telescience workstation is intended to provide a local computing environment for telescience. The purpose of the program are as follows: (1) to provide a suitable environment to integrate existing and new software for a telescience workstation; (2) to provide a suitable environment to develop new software in support of telescience activities; (3) to provide an interoperable environment so that a wide variety of workstations may be used in the telescience program; (4) to provide a supportive infrastructure and a common software base; and (5) to advance, apply, and evaluate the telescience technolgy base. A prototype telescience computing environment designed to bring practicing scientists in domains other than their computer science into a modern style of doing their computing was created and deployed. This environment, the Telescience Windowing Environment, Phase 1 (TeleWEn-1), met some, but not all of the goals stated above. The TeleWEn-1 provided a window-based workstation environment and a set of tools for text editing, document preparation, electronic mail, multimedia mail, raster manipulation, and system management.
    Keywords: GROUND SUPPORT SYSTEMS AND FACILITIES (SPACE)
    Type: NASA-CR-188878 , NAS 1.26:188878 , RIACS-TR-89-1
    Format: application/pdf
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  • 7
    Publication Date: 2019-06-28
    Description: A workshop was held in an attempt to program real problems on the MIT Static Data Flow Machine. Most of the architecture of the machine was specified but some parts were incomplete. The main purpose for the workshop was to explore principles for the evaluation of computer systems employing new architectures. Principles explored were: (1) evaluation must be an integral, ongoing part of a project to develop a computer of radically new architecture; (2) the evaluation should seek to measure the usability of the system as well as its performance; (3) users from the application domains must be an integral part of the evaluation process; and (4) evaluation results should be fed back into the design process. It is concluded that the general organizational principles are achievable in practice from this workshop.
    Keywords: COMPUTER SYSTEMS
    Type: NASA-CR-185399 , NAS 1.26:185399 , RIACS-TR-85.3
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  • 8
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    In:  Other Sources
    Publication Date: 2019-08-28
    Description: The role of the International Space Station in future U.S. aerospace education efforts is discussed from a NASA perspective. The overall design concept and scientific and technological goals of the Space Station are reviewed, and particular attention is given to education projects such as the Davis Planetarium Student Space Station, the Starship McCullough, the Space Habitat, the working Space Station model in Austin, TX, the Challenger Center for Space Life Education, Space M+A+X, and the Space Science Student Involvement Program. Also examined are learning-theory aspects of aerospace education: child vs adult learners, educational objectives, teaching methods, and instructional materials.
    Keywords: SOCIAL SCIENCES (GENERAL)
    Type: IAF PAPER 88-467
    Format: text
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  • 9
    Publication Date: 2019-08-27
    Description: The status of a multiagency endeavor to involve U.S. Federal agencies in the attainment of National Education Goals for the 1990's is presented. Emphasis is placed on the educational activities of NASA, which is one of 16 Federal agencies on the Federal Coordinating Council for Science, Engineering and Technology. NASA's is a prototype education program for achieving excellence in mathematics and science in the coming generations of Americans.
    Keywords: SOCIAL SCIENCES (GENERAL)
    Type: IAF PAPER 91-524
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  • 10
    Publication Date: 2019-08-28
    Description: The educational activities of NASA which is one of 16 agencies on the Federal Coordinating Council for Science, Engineering and Technology is discussed. NASA's education mission is to utilize its unique facilities and its specialized workforce to conduct and to leverage externally conducted science, mathematics, and technology education programs and activities. These efforts aimed at meeting the national education goals should help to preserve U.S. leadership in aeronautics, space science, and technology.
    Keywords: SOCIAL SCIENCES (GENERAL)
    Type: AIAA PAPER 92-1687
    Format: text
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