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  • Articles: DFG German National Licenses  (5)
  • Polymer and Materials Science  (3)
  • Allium  (2)
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  • Articles: DFG German National Licenses  (5)
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Years
  • 1
    ISSN: 1573-6849
    Keywords: Allium ; chiasmata ; crossing over ; genomic in situ hybridization ; recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Genomic in situ hybridization (GISH) successfully differentiated homoeologous genomes in the interspecific hybrid Allium cepa × fistulosum, thus allowing the detection of reciprocal crossover events as label exchanges in separating anaphase I chromosomes. Three of the eight chromosome pairs were positively identified by fluorescence in situ hybridization (FISH) to rDNA sequences. There was a general similarity of the GISH-based label exchange frequencies and metaphase I chiasma frequencies, but with a 20% deficit of chiasmata. Reasons for this apparent deficit are discussed. The locations of chiasmata and label exchanges are in broad agreement.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant systematics and evolution 217 (1999), S. 31-42 
    ISSN: 1615-6110
    Keywords: Alliaceae ; Allium ; Fluorescent in-situ hybridisation ; cytotaxonomy ; telomeric repeat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Information about evolutionary relationships between species of the genusAllium is desirable in order to facilitate breeding programmes. One approach is to study the distribution of repetitive DNA sequences among species thought on taxonomic grounds, to be closely related. We have used fluorescent in-situ hybridisation (FISH) to examine seven species within sect.Cepa of the genus (A. altaicum, A. cepa, A. fistulosum, A. galanthum, A. pskemense, A. oschaninii andA. vavilovii), one species from sect.Rhizirideum (A. roylei), two species from sect.Allium (A. sativum andA. porrum) and one species from sect.Schoenoprasum (A. schoenoprasum). Each species was probed using a 375 bp repeat sequence isolated fromA. cepa (Barnes & al. 1985), which was generated and labelled by polymerase chain reaction (PCR). No signals were detected in anyAllium species not belonging to sect.Cepa with the exception ofA. roylei, whose designation in sect.Rhizirideum is now questioned. Within sect.Cepa the probe was found to hybridize to the ‘terminal’ regions of the chromosome arms of all the species examined. In addition a number of interstitial bands were detected. Use of FISH reveals a more detailed map of the location of the repeat sequences than has previously been obtained by C-banding and other staining procedures. The distribution of the terminal and interstitial sites when compared, allow us to identify three species groups namely,A. altaicum andA. fistulosum; A. cepa, A. roylei, A. oschaninii andA. vavilovii; andA. galanthum andA. pskemense.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 54 (1961), S. 457-470 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A method is demonstrated by which both crystallite orientation and spiral angle can be directly determined from the x-ray tracings of the 002 diffraction arcs of combed bundles of cotton fibers. Sisson has shown, qualitatively, that the 002 arcs displayed by fibers with a spiral structure can be explained by assuming two equal crystallite distributions separated by twice the spiral angle. If this distribution of crystallites is assumed to be Gaussian, the experimental are can be generated theoretically. Such an analysis is applied to several cottons of widely different orientations and the calculated parameters are compared with those of the gross arcs.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 54 (1961), S. 471-489 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A method is demonstrated by which both crystallite orientation and spiral angle can be directly determined from the x-ray tracings of the 002 diffraction are of combed bundles of cotton fibers. Balls has shown that cotton has a spiral structure, and Sisson has shown qualitatively that these 002 arcs can be explained by applying two equal crystallite distributions separated by twice the spiral angle. If this distribution of crystallites is assumed to be a Gaussian distribution, the experimental are can be generated theoretically. This method of analysis is applied to x-ray data for decrystallized and mercerized cottons. X-ray diffraction shows the effects on fine structure of after-treatments, such as tension and boiling in water, applied to samples of slack amine-decrystallized and mercerized cotton yarns. The comparison of the calculated parameters with those of the gross arcs are given, as well as the relationships of these quantities to the tensioning force which produced them.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 1415-1445 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A reaction rate model of fracture in polymer fibers is described. This model assumes that bond rupture is governed by absolute reaction rate theory with a stress-aided activation energy. It is demonstrated that the key in obtaining good agreement between the model and experiment lies in taking proper account of the variation of stress on the tie-chain molecules. The more taut chains rupture first, and the load is redistributed among the remaining unruptured tie chains. The effect of varying the temperature both in the model and in experiments on fracture in fibers is explored. Good agreement between predictions of the model and experiment is possible only with an undeterstanding of the distribution in stress on the tie chains. The distribution in stress on the chains was experimentally determined by monitoring the kinetics of bond rupture with electron paramagnetic resonance (EPR) spectroscopy. Temperature is found to have two effects on macroscopic strength. (1) The thermal energy aids the atomic stress in breaking the atomic bonds; as a consequence the rate of bond rupture of a family of bonds under a given molecular stress is increased. In this respect temperature might be viewed as decreasing the “strength” of a bond. (2) Temperature also serves to “loosen” the molecular structure and in this way modify the distribution in stress on the tie chains. To explain bond rupture and macroscopic fracture behavior quantitatively, account must be taken of both effects.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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