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  • COMPUTER OPERATIONS AND HARDWARE  (2)
  • AERODYNAMICS
  • Life and Medical Sciences
  • 1985-1989  (3)
  • 1987  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Acute exposure of rats to air ions: Effects on the regional concentration and utilization of serotonin in brain (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 8 (1987), S. 173-181 
    Details
    ISSN: 0197-8462
    Keywords: DC electric fields ; 5-hydroxyindoleacetic acid ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Exposure to electrically charged gas molecules (air ions) has been reported to influence physiological and behavioral functions in animals and humans although there is controversy as to whether these findings are valid. A popular hypothesis concerning the reported effects of air ions is that alterations in serotonin (5HT) metabolism, particularly in the brain, are involved. We measured the concentration and turnover of 5HT in rats exposed to 5.0 × 105 ions/cm3 for up to 66 hours. Contrary to previous reports of other investigators, we were unable to demonstrate any effect of exposure to air ions or associated DC electric fields on the concentration or turnover of 5HT in rats under carefully controlled and characterized exposure conditions.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250080208
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    Paper (German National Licenses)
    Fulltext
  • 2
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    A comparison of the Cray-2 performance before and after the installation of memory pseudo-banking (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A suite of 13 large Fortran benchmark codes were run on a Cray-2 configured with memory pseudo-banking circuits, and floating point operation rates were measured for each under a variety of system load configurations. These were compared with similar flop measurements taken on the same system before installation of the pseudo-banking. A useful memory access efficiency parameter was defined and calculated for both sets of performance rates, allowing a crude quantitative measure of the improvement in efficiency due to pseudo-banking. Programs were categorized as either highly scalar (S) or highly vectorized (V) and either memory-intensive or register-intensive, giving 4 categories: S-memory, S-register, V-memory, and V-register. Using flop rates as a simple quantifier of these 4 categories, a scatter plot of efficiency gain vs Mflops roughly illustrates the improvement in floating point processing speed due to pseudo-banking. On the Cray-2 system tested this improvement ranged from 1 percent for S-memory codes to about 12 percent for V-memory codes. No significant gains were made for V-register codes, which was to be expected.
    Keywords: COMPUTER OPERATIONS AND HARDWARE
    Type: NASA-CR-177462 , NAS 1.26:177462 , TN-86-7104-939-13
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Vector computer memory bank contention (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A number of vector supercomputers feature very large memories. Unfortunately the large capacity memory chips that are used in these computers are much slower than the fast central processing unit (CPU) circuitry. As a result, memory bank reservation times (in CPU ticks) are much longer than on previous generations of computers. A consequence of these long reservation times is that memory bank contention is sharply increased, resulting in significantly lowered performance rates. The phenomenon of memory bank contention in vector computers is analyzed using both a Markov chain model and a Monte Carlo simulation program. The results of this analysis indicate that future generations of supercomputers must either employ much faster memory chips or else feature very large numbers of independent memory banks.
    Keywords: COMPUTER OPERATIONS AND HARDWARE
    Type: IEEE Transactions on Computers (ISSN 0018-9340); C-36; 293-298
    Format: text
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    NASA TECHNICAL REPORTS
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