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  • ASTRONOMY  (74)
  • METEOROLOGY AND CLIMATOLOGY  (63)
  • SOLAR PHYSICS  (58)
  • Life and Medical Sciences  (45)
  • 1980-1984  (240)
  • 1975-1979
  • 1970-1974
  • 1980  (240)
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  • 1980-1984  (240)
  • 1975-1979
  • 1970-1974
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  • 11
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of inhibition of the cell membrane Na+-K+ pump on the Balb/c-3T3 cell growth cycle was studied. Inhibition of the Na+-K+ pump resulted in a dose-dependent reduction of intracellular K+ concentration ({K+}i). However, inhibition of protein synthesis in G0/G1 and of subsequent entry into S phase occurred only after {K+}i fell below a critical threshold (50-60 mmoles/liter). Thus, when the {K+}i falls below a critical threshold, protein synthesis is inhibited, preventing cells from entering the S phase.The platelet-derived growth factor (PDGF) induces cells to become “competent” to traverse the cell cycle; the platelet-poor plasma component of serum allows competent cells to progress through G0/G1 and enter S phase. Inhibition of the Na+-K+ pump did not prevent the induction of competence by PDGF, but it did reversibly inhibit plasma-mediated events in early G0/G1. Similarly, cycloheximide inhibited plasma-mediated events but did not prevent PDGF-induced competence. Thus, protein synthesis may not be required for induction of competence; alternatively, the induction of the competent state may occur in these cells after removal of PDGF and protein synthesis inhibitor. Protein synthesis is required for subsequent plasma-mediated events in G0/G1.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 1 (1980), S. 131-147 
    ISSN: 0197-8462
    Keywords: electric fields ; rat ; sciatic nerve ; vagus nerve ; superior cervical sympathetic ganglion ; chronic exposure ; 60 Hz ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Several reports have suggested that the nervous system can be affected by exposure to electric fields and that these effects may have detrimental health consequences for the exposed organism. The purpose of this study was to investigate the effects of chronic (30-day) exposure of rats to a 60-Hz, 100-kV/m electric field on synaptic transmission and peripheral-nerve function. One hundred forty-four rats, housed in individual polycarbonate cages were exposed to uniform, vertical, 60-Hz electric fields in a system free of corona discharge and ozone formation and in which the animals did not receive spark discharges or other shocks during exposure. Following 30 days of exposure to the electric field, superior cervical sympathetic ganglia, vagus and sciatic nerves were removed from rats anesthetized with urethan, placed in a temperature-controlled chamber, and superfused with a modified mammalian Ringer's solution equilibrated with 95% O2 and 5% CO2. Several measures and tests were used to characterize synaptic transmission and peripheral-nerve function. These included amplitude, area, and configuration of the postsynaptic or whole-nerve compound-action potential; conduction velocity; accommodation; refractory period; strength-duration curves; conditioning-test (C-T) response, frequency response; post-tetanic response; and high-frequency-induced fatigue. The results of a series of neurophysiologic tests and measurements indicate that only synaptic transmission is significantly and consistently affected by chronic (30-day) exposure to a 60-Hz, 100-kV/m electric field. Specifically, an increase in synaptic excitability was detected in replicated measurements of the C-T response ratio. In addition, there are trends in other data that can be interpreted to suggest a generalized increase in neuronal excitability in exposed animals.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 1 (1980), S. 55-64 
    ISSN: 0197-8462
    Keywords: 60-Hz electric fields ; electrocardiogram (ECG) ; heart rate ; blood pressure ; vascular reactivity ; cold stress ; rats ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Recently, it has been reported that exposure to high-strength electric fields can influence electrocardiogram (ECG) patterns, heart rates, and blood pressures in various species of animals. Our studies were designed to evaluate these reported effects and to help clarify some of the disagreement present in the literature. Various cardiovascular variables were measured in Sprague-Dawley rats exposed or sham-exposed to 60-Hz electric fields at 80 or 100 kV/m for periods up to four months. No significant differences in heart rates, ECG patterns, blood pressures, or vascular reactivity were observed between exposed and sham-exposed rats after 8 hours, 40 hours, 1 month, or 4 months of exposure. Blood pressure and heart rate measurements, made during exposure to a 100-kV/m electric field for one hour, revealed no significant differences between exposed and sham-exposed groups. In addition, physiologic reserve capacity, measured in rats subjected to low temperature after exposure to 100 kV/m for one month, showed that electric-field exposure had no significant effect on physiological response to cold stress. Our studies cannot be directly compared to the work of other investigators because of differences in animal species and electric-field characteristics. However, our failure to detect any cardiovascular changes may have been the result of 1) eliminating secondary field effects such as shocks, audible noise, corona, and ozone; 2) minimizing steady-state microcurrents between the mouth of the animal and watering devices; and 3) minimizing electric-field-induced vibration of the electrodes and animal cages.
    Additional Material: 2 Ill.
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  • 14
    Publication Date: 2006-01-16
    Description: The adaptation of proven space probe technology is proposed as a means of providing a solar activity monitoring platform which could be injected behind the Earth's orbital position to give 3 to 6 days advanced coverage of the solar phenomenon on the backside hemisphere before it rotates into view and affects terrestrial activities. The probe would provide some three dimensional discrimination within the ecliptic latitude. This relatively simple off-Earth probe could provide very high quality data to support the SCADM program, by transmitting both high resolution video data of the solar surface and such measurements of solar activity as particle, X-ray, ultraviolet, and radio emission fluxes. Topics covered include the orbit; constraints on the spacecraft; subsystems and their embodiments; optical imaging sensors and their operation; and the radiation-pressure attitude control system are described. The platform would be capable of mapping active regions on an hourly basis with one arc-second resolution.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center Study of the Solar Cycle from Space; p 45-54
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  • 15
    Publication Date: 2019-06-28
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 240
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  • 16
    Publication Date: 2019-06-27
    Description: It is noted that although the 11 year solar cycle was first recognized in 1843, it is still only poorly understood. Further, while there are satisfactory models for the magnetic variations, the underlying physics is still obscure. New observations on the changing three-dimensional form of the solar wind are presented which help relate some of the modulations observed in geomagnetic activity, the ionosphere, and the flux of galactic cosmic rays.
    Keywords: SOLAR PHYSICS
    Type: AD-A099231 , AFGL-TR-81-0113 , Nature; 286; July 17
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  • 17
    Publication Date: 2019-06-27
    Description: The mechanical energy flux of observed macroscopic mass plasma motions in the solar flare of Sept. 5, 1973, is estimated. Consideration is given to the cool eruptive material in the eruptive filament and large surge as revealed by H alpha observations, the moving emission front seen in Ca II as well as H alpha, the piston-driven shock and mass ejection coronal transient observed in radio spectra and flare core motions, and mechanical energy estimates of 5.6 x 10 to the 29th to 8.9 x 10 to the 30th, 9.0 x 10 to the 29th, 2 x 10 to the 30th (thermal) and 10 to the 31st (magnetic), and 9 x 10 to the 24th erg are obtained, respectively, in agreement with previous estimates. It is concluded that the mechanical energy of large-scale mass motions dominates the radiative output of the flare by more than two orders of magnitude, and that a significant portion of the mechanical energy is in the form of magnetic flux delivered to interplanetary space.
    Keywords: SOLAR PHYSICS
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  • 18
    Publication Date: 2019-06-27
    Description: Observations and model simulations of solar mass ejection phenomena are examined in an investigation of flare processes. Consideration is given to Skylab and other observations of flare-associated sprays, eruptive prominences, surges and coronal transients, and to MHD, gas dynamic and magnetic loop models developed to account for them. Magnetic forces are found to confine spray material, which originates in preexisting active-region filaments, within steadily expanding loops, while surges follow unmoving, preexisting magnetic field lines. Simulations of effects of a sudden pressure pulse at the bottom of the corona are found to exhibit many characteristics of coronal transients associated with flares, and impulsive heating low in the chromosphere is found to be able to account for surges. The importance of the magnetic field as the ultimate source of energy which drives eruptive phenomena as well as flares is pointed out.
    Keywords: SOLAR PHYSICS
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  • 19
    Publication Date: 2019-06-27
    Description: The accumulation, storage and irreversible release of the free energy necessary for a solar flare are discussed on the basis of data obtained from the Apollo Telescope Mount on Skylab and other pertinent sources. Skylab and OSO 7 observations of possible flare precursors and flare evolution are presented, and the evolution of the flare of Sept. 5, 1973, the most completely observed flare of the Skylab program, is described in detail, with account given to magnetic structures and H alpha radiation. Theories of the preflare state are then reviewed, with attention given to the force-free fields and coronal arcades, thermal and magnetic structures and the MHD stability of coronal loops.
    Keywords: SOLAR PHYSICS
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  • 20
    Publication Date: 2019-06-27
    Description: The paper is an extension of previous papers by Lund and Shanklin (1972, 1973). It presents probabilities of cloud-free fields-of-view (CFFOV) to supplement probabilities of cloud-free lines-of-sight (CFLOS) contained in the earlier papers. A model is developed for estimating the probability of obtaining a CFFOV as a function of ground-observer-reported total sky cover for earth-to-space applications. The development of the model and examples of its application are described. A comparison of CFFOV and CFLOS results is made. In conclusion, climatic probabilities of CFFOV overhead through the entire atmosphere between the surface of the earth and space can be estimated for any desired geographical location through the use of a specified equation and conditional probabilities contained in the paper, if the frequency distribution of total sky cover categories for the desired location is known.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: AD-A086320 , AFGL-TR-80-0183 , Journal of Applied Meteorology; 19; Apr. 198
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