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  • LUNAR AND PLANETARY EXPLORATION  (8)
  • Life and Medical Sciences  (2)
  • 1985-1989  (1)
  • 1980-1984  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Cumulative population doublings as the determinant of chick cell lifespan in vitro (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 107 (1981), S. 371-378 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Chick embryo fibroblasts were maintained at confluency for up to 35 days in medium containing 0.5% or 0.75% fetal bovine serum or 2.5% or 5.0% horse serum. At weekly intervals cells were subcultured and serially propagated in medium containing 10% FBS until their replicative lifespans were completed. The results showed that the replicative lifespan of embryonic chick fibroblasts was dependent on the cumulative number of population doublings undergone by the culture and was not related to the calendar time cells were in culture. Further characterization of 0.75% FBS maintained chick cells returned to 10% FBS medium showed that cells had protein contents and incorporated 3H-thymidine into DNA at a rate that resembled that of young cells, despite an advanced chronological age.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041070308
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of division rate-limiting amounts of fetal bovine serum on the proliferation and aging of cultured chick cells (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 110 (1982), S. 175-182 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Chick embryo fibroblasts serially propagated in media containing division ratelimiting amounts of fetal bovine serum underwent premature culture senescence as illustrated by accelerated declines in the number of cells incorporating 3H-thymidine, increased population doubling times, reduced cell densities at subcultivation, and reduced replicative life-spans compared to cells grown in medium containing non-rate-limiting amounts of serum. Low serum serially propagated “senescent” cultures returned to 10% serum containing medium had proliferative rates, incorporated 3H-thymidine, and attained saturation densities at confluency similar to younger cells. “Senescent” cells serially propagated in low serum and returned to 10% serum achieved life-spans similar to cells continuously grown in the presence of 10% serum. The results of these and other studies show that cells serially propagated in the presence of division rate-limiting amounts of fetal bovine serum, or at high inoculation densities, accumulate a substantial number of cells in the population during exponential growth conditions that are not senescent but are prevented from entering DNA synthesis becuase of mitogen limitations. Our results indicate that the amount of serum mitogen in the growth medium affects only the rate at which cells express their genetically predetermined replicative potential and not the replicative lifespan per se. These results are discussed in relation to the techniques that should be employed for studying cellular aging and the mechanism of senescent cell formation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041100211
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    Paper (German National Licenses)
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  • 3
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    Possible dust devils - Vortices on Mars (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper presents the results of a study of local vortices, and dust devils, on Mars as observed by Viking Landers 1 and 2. It is found that these vortices are most common during Martian spring and summer, as occurs on earth. Seven of the vortices involve wind speeds that may raise dust from the Martian surface. There is no indication that these possible dust devils contribute to the planet-wide spread of major dust storms. However, it appears that they may help in maintaining the atmospheric dust content. The data indicate that there is no preference in rotation direction, at least to core diameters of 300 m (corresponding to a region of influence of about 3 km diameter).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 11005-11
    Format: text
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  • 4
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    Two major dust storms, one Mars year apart - Comparison from Viking data (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The Viking Mars Landers have been on the Mars surface for over two Mars years. During the first year two major, probably global, dust storms occurred. The first was unusually early compared to most previous earth-based observations. A major storm occurred during the second year, almost precisely one year after the first storm of the first year. Meteorological data show roughly similar atmospheric behavior for the two early storms. Of particular note is the increase in amplitude of pressure oscillations (probably of baroclinic origin) and concurrent increases in wind speed during the build-up phase of all three storms. The generation of these waves appears to be a natural consequence of seasonal effects not associated with the dust storms. It is suggested that baroclinic waves, should they exist in the Southern Hemisphere during the time of dust storm generation, could be an important factor in the growth and development of the dust storms.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Apr. 20
    Format: text
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  • 5
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    H2O frost point detection on Mars (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The Viking Mars landers contain meteorological instrumentation to measure wind, temperature, and pressure but not atmospheric water content. The landings occurred during local summer, and it was observed that the nocturnal temperature decrease at sensor height (1.6 m) did not exhibit a uniform behavior at either site. It was expected that the rate of decrease would gradually slow, leveling off near sunrise. Instead, a leveling occurred several hours earlier. Temperature subsequently began a more rapid decrease which slowed by sunrise. This suggested that the temperature sensors may be detecting the frost point of water vapor. Analysis of alternative hypotheses demonstrates that none of these are viable candidates. The frost point interpretation is consistent with other lander and orbiter observations, with terrestrial experience, and with modeling of Mars' atmospheric behavior. It thus appears that the meteorology experiment can help provide a basis toward understanding the distribution and dynamics of Martian water vapor.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Jan. 20
    Format: text
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  • 6
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    Local Mars dust storm generation mechanism (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: On an areocentric solar longitude of 340 deg, first Mars year of Viking on the surface, a local dust storm was observed at the Viking Lander No. 1 site by Viking Orbiter A. The storm lasted less than one Martian day (sol) with the dust raised affecting the site for about three sols. It is concluded that this storm was caused by baroclinic waves and that the threshold wind speed for saltation was 25-30 m/sec.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 8; Aug. 198
    Format: text
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  • 7
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    Mars atmosphere pressure periodicities from Viking observations (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The first Martian year of pressure data taken by the Viking landers on Mars is subjected to power spectrum analysis. The analysis suggests that strong periodicities are present in the Martian atmosphere, especially at the high-latitude (48 deg N) site of the second lander. Most of these periodicities are probably due to the passage of baroclinic waves. Inspection of individual segments of data shows that the periodicities of the dominant waves vary significantly with time of year. This may be related to the amount of dust in the atmosphere since the dominant frequencies of the waves during times of major dust storms are quite different than at other times.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of the Atmospheric Sciences; 37; Sept
    Format: text
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  • 8
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    Mars atmospheric circulation - Aspects from Viking Landers (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Winds measured by the two Viking Landers have been filtered and then compared with predictions from the general circulation model and to Orbiter observations of clouds and surface phenomena that indicate wind direction. This was done to determine the degree to which filtered winds may represent aspects of the general circulation. Excellent agreement was found between wind direction data from Lander 1 and the model predictions and Orbiter observations. For Lander 2, agreement was generally good, but there were periods of disagreement which indicate that the filtering did not remove other extraneous effects. It is concluded that Lander 1 gives a good representation of the general circulation at 22.5 deg N latitude but that Lander 2 is suspect. Most wind data from Lander 1 have yet to be analyzed. It appears that when analyzed these Lander 1 data (covering 3.5 Mars years) can provide information about interannual variations in the general circulation at the Lander latitude.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 6319-632
    Format: text
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  • 9
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    The annual cycle of pressure on Mars measured by Viking landers 1 and 2 (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Daily mean atmospheric pressures at the two Viking landers are presented for slightly more than a Martian year. The seasonal variation of pressure owing to exchange of CO2 with the polar caps is quite evident and contradicts, in part, earlier theoretical results. Day-to-day variations are the result of passage of synoptic-scale high and low pressure systems and are an important clue to the general circulation of the atmosphere. The effects of global dust storms on the general circulation and on the diurnal variation of pressure are detected and interpreted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Mar. 198
    Format: text
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  • 10
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    Mars water vapor, near-surface (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: In a previous paper we concluded that the temperature sensors aboard the Viking landers (VL-1 and VL-2) were detecting the water vapor frost point. Analysis of one Mars year of data at both lander sites substantiates this conclusion. At VL-1 it is found that the water vapor mixing ratio is constant with height through the bulk of the atmosphere, most of the time. Exceptions are during the onset phases of the two major dust storms when temporary enhancement of near-surface vapor occurs (the same phenomenon is observed at VL-2), and some depletion of near-surface vapor during the decay phase of the first storm, possibly the second storm as well. The former suggests near-surface, northward transport of water vapor with the storms. The latter suggests adsorption of vapor on dust particles followed by surface deposition. At VL-2, severe near-surface depletion of water vapor occurs during northern autumn and winter. The residual vapor is in equilibrium with the surface condensate observed at the site during this period, indicating that the source region for the condensate must be aloft with downward transport by dust fall-out. Since the near-surface water vapor mixing ratio and concentration at VL-1 generally parallels the column abundance over VL-1 obtained by the orbiters, this suggests that VL-1 can be used to give a measure of column abundance for as long as the temperature sensors remain operational.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 87; Aug. 20
    Format: text
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