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  • Articles: DFG German National Licenses  (6)
  • Electronic Resource  (6)
  • 1995-1999  (2)
  • 1980-1984  (4)
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  • Articles: DFG German National Licenses  (6)
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  • Electronic Resource  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Evolution of the genome size inAkodon (Rodentia, Cricetidae) (1983)
    Springer
    Journal of molecular evolution 19 (1983), S. 362-370 
    Details
    ISSN: 1432-1432
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nuclear DNA contents were estimated by microdensitometry in five species ofAkodon rodents:Adodon molinae, A. dolores, A. mollis, A. azarae, Bolomys obscurus) and in three chromosomal varieties ofA. molinae (2n=42; 2n=43, 2n=22). The data obtained showed that the species with the highest DNA content wasB. obscurus, followed in order of decreasing genome size byA. molinae, A. mollis, A. dolores andA. azarae. InA. molinae the forms with 2n=42 chromosomes had the lowest and the forms with 2n=44 the highest amount of DNA, while the forms with 2n=43 had intermediate DNA contents. The variation in DNA amount detected inA. molinae was interpreted as a phenomenon of amplification occurring in the chromosomal areas involved in the chromosomal rearrangement giving rise to the polymorphism exhibited by this species. The DNA contents of shared chromosomes (chromosomes with similar size, morphology and G banding pattern, which are found in two or more phylogenetically related species), were compared and correlated with values of total nuclear DNA. The information obtained indicates that: (a) shared chromosomes have variable amounts of DNA: (b) in a given species there is a correlation between the amount of nuclear and chromosomal DNA in most shared chromosomes (and perhaps in most of the chromosmal complement), e.g., the higher the amount of nuclear DNA, the higher the content of DNA in shared chromosomes; (c) some chromosomes may undergo processes of amplification or deletion restricted to certain regions and usually related with mechanisms of chromosomal rearrangements. The data obtained seem to indicate that the genome size of a species depends on the interaction of two independent mechanisms: (1) a general process of DNA variation which acts coincidentally in the same direction (gain or loss) in the whole chromosome complement without disturbing the mechanism of chromosome condensation producing G bands and (2) restricted processes of DNA variations (amplifications or deletions) which act on single chromosomes and which are in most cases related with chromosmal rearrangements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02101640
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On Bayes Methods for On-Line Boolean Prediction (1998)
    Springer
    Algorithmica 22 (1998), S. 112-137 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Boolean prediction, On-line algorithms, Bayes theory.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. We examine a general Bayesian framework for constructing on-line prediction algorithms in the experts setting. These algorithms predict the bits of an unknown Boolean sequence using the advice of a finite set of experts. In this framework we use probabilistic assumptions on the unknown sequence to motivate prediction strategies. However, the relative bounds that we prove on the number of prediction mistakes made by these strategies hold for any sequence. The Bayesian framework provides a unified derivation and analysis of previously known prediction strategies, such as the Weighted Majority and Binomial Weighting algorithms. Furthermore, it provides a principled way of automatically adapting the parameters of Weighted Majority to the sequence, in contrast to previous ad hoc doubling techniques. Finally, we discuss the generalization of our methods to algorithms making randomized predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00013825
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Gene controlled condensation in individual chromosomes (1982)
    Springer
    Cellular and molecular life sciences 38 (1982), S. 792-794 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary When cells were irradiated with variable doses of gamma rays, 0.33% showed the appearance of single decondensed chromosomes (SDC) at the moment at which all the other chromosomes of the complement exhibited the normal condensed state corresponding to metaphase stages. Several hypotheses are discussed to explain the origin of SDC. It appears that the most reasonable mechanism to explain our observations is to assume that the process of chromosome condensation is independently controlled in each individual chromosome by a gene/s located in each one of the chromosomes of the complement. A radiation-induced deficiency in one of these genes may produce an impairement in the normal process of condensation of the carrier chromosome which would give rise to SDC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01972274
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Investigations of azimuthal asymmetry in semi-inclusive leptoproduction (1998)
    Springer
    The European physical journal 5 (1998), S. 681-685 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We consider the azimuthal asymmetries in semi-inclusive deep inelastic leptoproduction arising due to both perturbative and nonperturbative effects at HERMES energies and show that the $k_T^2/Q^2$ order corrections to $\langle \cos\phi \rangle$ and $\langle \cos2\phi \rangle$ are significant. We also reconsider the results of perturbative effects for $\langle \cos\phi \rangle$ at large momentum transfers [1] using the more recent sets of scale-dependent distribution and fragmentation functions, which bring up to 18% difference in $\langle \cos\phi \rangle$ . In the same approach we calculate the $\langle \cos2\phi \rangle$ as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100529800873
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Cytogenetics of the South American Akodont rodents (Cricetidae) X. Akodon mollis: a species with XY females and B chromosomes (1982)
    Springer
    Genetica 57 (1982), S. 199-205 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The morphology, G- and C-banding pattern of the Akodon mollis chromosome complement is analysed. Over a total of 14 males and 10 females studied, 8 males and 7 females had a modal chromosome number of 22, while 6 males and 3 females showed a modal number of 23 chromosomes. In the animals with 23 chromosomes the odd element was considered a B chromosome on the basis of: (a) its small size, (b) the lack of an homologous chromosome and the subsequent formation of univalents at diakinesis and metaphase I from testes, (c) the weak or null genetic action as evidenced by the lack of any obvious variation in the phenotype of carriers. Four females exhibited a sex-pair dimorphism indistinguishable from that observed in males. The G-banding analysis showed homology between the pattern found in the Y chromosome and that detected in the short arm of the X. The study of C-band distribution showed that several autosome pairs and the X chromosomes had small masses of centromeric heterochromatin. On the other hand, the Y and B chromosomes were C-band negative. The Y-like chromosome in females with dimorphism of the sex pair was also C-band negative. Accordingly these females were considered to be XY and not Xx (the x being an extensively deleted X chromosome).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00056483
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Microdensitometric evaluation of the DNA content, as ploidy parameter, of spermatozoa in the polymorphic chromosomal system of Akodon molinae cabrera (rodentia, cricetidae) (1982)
    New York, NY : Wiley-Blackwell
    Gamete Research 5 (1982), S. 345-354 
    Details
    ISSN: 0148-7280
    Keywords: chromosome variability ; DNA content ; gametic aneuploidy ; prezygotic selection ; epididymis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The influence of chromosome variability on the production of euploid spermatozoa was investigated in a suitable biological model, the Akodon molinae system. This consists of individuals whose chromosome constitution is 2n = 42, 2n = 43, or 2n = 44. The only difference between these three karyotypes occurs through a Robertsonian rearrangement combined with two pericentric inversions. Thus, the animals with 2n = 42 (simple homozygotes or SH) have two large metacentric chromosomes number 1; animals with 2n = 43 (heterozygotes or Ht) have a chromosome 1 and two subterminal chromosomes la and lb homologues of the long and short arms of the chromosome 1, respectively; animals with 2n = 44 (double homozygotes or DH) have a pair of la and a pair of lb chromosomes. The gametic euploidy frequency correlated with each chromosome constitution was evaluated on the basis of the DNA content of spermatozoa, which was determined microdensitometrically after the Feulgen reaction, taking into account the site of the spermatozoa along the male genital tract. A comparative assessment of gametic aneuploidy frequency in caput epididymis versus vas deferens demonstrated (1) a falloff in euploid production in passing from the 2n = 42 to the 2n = 44 chromosome forms, alongside a high degree of intragroup variability, and (2) a lower aneuploidy frequency in the vas deferens than in caput epididymis in all the forms considered. These two features, taken together with similar results in the mouse chromosome variability system, suggest that a selection mechanism is operative against aneuploid spermatozoa in the epididymis. This finding is of interest in a wider perspective, since it might turn out to be valid for many mammals.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120050405
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    Paper (German National Licenses)
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