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  • 1
    Electronic Resource
    Electronic Resource
    Genetic regulation of somatic mutability of two Mu-induced a1 mutants of maize (1992)
    Springer
    Theoretical and applied genetics 84 (1992), S. 225-236 
    Details
    ISSN: 1432-2242
    Keywords: Mutator ; Autonomous elements ; Mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous studies of stocks of two Mutator-induced mutable a1 alleles (a1-Mum2 and al-Mum3) gave results consistent with the presence of one or more autonomous elements regulating the expression of mutability. This article reports on the results of studies designed to map these autonomous elements by using a series of waxy marked translocations. Linkage of waxy with autonomous elements was found for a1-Mum2 by using the translocations wx T2-9d, wx T4-9e and wx T4-9b. Several different linkage values were found in crosses involving wx T2-9d, suggesting that autonomous elements have transposed to different locations on chromosome 2. Linkage of autonomous elements with waxy was found for a1-Mum3 using translocation wx T2-9d. Again, several different linkage values were found. Some of these values were the same as those observed for a1-Mum2, but some were unique. In some crosses, the number of autonomous elements increased by one or two unlinked elements in addition to the linked element in one generation (i. e. the generation of the cross to the translocation series). Such an increase in number is probably the result of transposition of the original autonomous element to an independent locus while retaining the autonomous element at the original locus. Reduction in the number of autonomous elements is probably the result of the independent assortment in crosses of plants with two or more autonomous elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224004
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Concomitant regulation of Mu1 transposition and Mutator activity in maize (1987)
    Springer
    Molecular genetics and genomics 208 (1987), S. 57-62 
    Details
    ISSN: 1617-4623
    Keywords: Transposable elements ; Mutation ; Mutator ; Maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mutagenic activity of the maize transposable element system Mutator can be lost by outcrossing to standard, non-Mutator lines or by repetitive intercrossing of genetically diverse Mutator lines. Lines losing Mutator mutagenic activity in either manner retain high copy numbers (10–15 per diploid genome) of the Mutator-associated Mu transposable elements. Frequent transposition of Mu1-related elements is observed only in active Mutator lines, however. The loss of Mutator activity on intercrossing is correlated with an increase in the copy number of Mu1-like elements to 40–50 per diploid genome, implying a self-encoded or self-activated negative regulator of Mu1 transposition. The outcross loss of Mutator activity is only weakly correlated with a low Mu element copy number and may be due to the loss of a positive regulatory factor encoded by a subset of Mu1-like elements. Transposition of Mu elements in active Mutator lines generates multiple new genomic positions for about half the elements each plant generation. The appearance of Mu1-like elements in these new positions is not accompanied by equally high germinal reversion frequencies, suggesting that Mu1 may commonly transpose via a DNA replicative process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330422
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  • 3
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    Comparison of earth rotation as inferred from radio interferometric, laser ranging and astrometric observations (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results of measurements of the earth's rotation vector for a 400-day period from late September 1980 to December 1981, for which date from VLBI, satellite laser ranging (SLR), and lunar laser ranging (LLR) were available, are compared. The acquisition of the data and their evaluation are described. VLBI, SLR, and classical astrometric determinations of the X-parameter required to describe the location of the rotation pole on the earth's surface are shown, and VLBI, LLR, and classical astrometric determinations of the angle of rotation about this pole (UT1) are presented. The results indicate that VLBI and SLR, at their present stages of development, yield standard errors under 20 cm in the determinations of X, about twofold smaller than obtained from classical measurements, and that VLBI and LLR yield determination of UT1 with standard errors less than 40 cm, somewhat smaller than that of the corresponding determinations from classical observations. Methods for improving these types of intercomparisons are suggested.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 302; April 7
    Format: text
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  • 4
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    Transcontinental baselines and the rotation of the earth measured by radio interferometry (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Nine separate very-long-baseline interferometry experiments, carried out in 1972 and 1973 with radio telescopes 3900 kilometers apart, yielded values for the baseline length with an rms deviation about the mean of less than 20 centimeters. The corresponding fractional spread is about five parts in 100,000,000. Changes in universal time and in polar motion were also determined accurately from these data. The rms scatter of these results with respect to those based on optical methods was 2.9 msec and 1.3 m, respectively. Solid-earth tides were apparently detected, but no useful estimate of their amplitude was extracted.
    Keywords: GEOPHYSICS
    Type: Science; 186; Dec. 6
    Format: text
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  • 5
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    Earth rotation information derived from MERIT and POLARIS VLBI observations (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Advanced methods involving observations of extraterrestrial objects, such as artificial satellites or quasars, may make it possible to monitor geometrical variations in survey networks of regional, continental, and global scale with a spatial resolution of a few centimeters and a temporal resolution of better than one day. However, in connection with a realization of this potential, it is necessary to account for variations in the orientation of the earth in space. The accuracy provided by the conventional approaches for determining the orientation of the earth is not sufficient in this case. However, an appropriate method could be based on the utilization of independent clock radio interferometry (commonly referred to as VLBI) observations of extragalactic radio sources. The project POLARIS (Polar-motion Analysis by Radio Interferometric Sampling) is concerned with an implementation of this method. The MERIT (Monitor Earth Rotation and Intercompare the Techniques of observation and analysis) observations represent an aid to project POLARIS. Attention is given to details regarding these programs and the results obtained thus far.
    Keywords: GEOPHYSICS
    Type: High-precision earth rotation and earth-moon dynamics: Lunar distances and related observations; May 22, 1981 - May 27, 1981; Alpes-Maritimes; France
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  • 6
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    Precision geodesy via radio interferometry. (1972)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Very-long-baseline interferometry experiments, involving observations of extragalactic radio sources, were performed in 1969 to determine the vector separations between antenna sites in Massachusetts and West Virginia. The 845.130-kilometer baseline was estimated from two separate experiments. The results agreed with each other to within 2 meters in all three components and with a special geodetic survey to within 2 meters in length; the differences in baseline direction as determined by the survey and by interferometry corresponded to discrepancies of about 5 meters. The experiments also yielded positions for nine extragalactic radio sources and allowed the hydrogen maser clocks at the two sites to be synchronized.
    Keywords: GEOPHYSICS
    Type: Science; 178; Oct. 27
    Format: text
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  • 7
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    Possible detection of the earth's free-core nutation (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The 5.5 years of VLBI observations primarily collected under project IRIS are used to search for evidence of the free-core nutation (FCN). The observations are consistent with an irregular excitation process, and a model which assumes a step excitation in the FCN amplitude to about 2.0 milliseconds of arc in late 1985 fits the data well. Theoretical analysis appears to rule out the strong Mexican earthquake of September 19, 1985, as a cause of the excitation.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 13; 949-952
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  • 8
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    Recent results of radio interferometric determinations of a transcontinental baseline, polar motion, and earth rotation (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Results are discussed for radio interferometric observations of extragalactic radio sources with antennas at Haystack Observatory in Massachusetts and the Owens Valley Radio Observatory in California (3900-km baseline) during 14 separate experiments distributed between September 1976 and May 1978. Simultaneous analysis of the data from several experiments yields estimates of changes in the x component of pole position and in earth's rotation (UT1). Comparison with the corresponding results obtained by the Bureau International de l'Heure (BIH) reveals systematic differences. In particular, the trends in the radio interferometric determinations of the changes in pole position are found to agree more closely with those from the International Polar Motion Service and from Doppler observations of satellites than with those from the BIH.
    Keywords: GEOPHYSICS
    Type: Time and the earth''s rotation; Eighty-second Symposium; May 08, 1978 - May 12, 1978; San Fernando; Spain
    Format: text
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