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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 10 (1959), S. 268-277 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A wide diversity in chromosome complement is found in two species of phasmids of the primitive group Prisopini—Prisopus ariadne Hebard and Prisopus berosus Westwood. P. ariadne has a diploid male complement of 28, comprising 13 pairs of relatively large mediokinetic autosomes and Neo XY sex chromosomes. P. berosus, 2n ♂=49, has relatively small autosomes most of which are mediokinetic, and retains the XO—XX sex mechanism. Chromosomal polymorphism in this species is suggested by the presence of an unequal pair of autosomes and a structural differentiation in the X in one of two males studied. The relative amount of DNA per nucleus in male germ cells (Peulgen cytophotometry) shows a significant difference in total chromosomal content between the complements of the two species. These data are discussed with reference to the cytotaxonomy of phasmids.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Atomic energy 1 (1956), S. 715-725 
    ISSN: 1573-8205
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Notes: Synopsis In the past few years slow neutron spectrometers of greatly improved resolving power have been developed at many laboratories throughout the world. During the same period advances in techniques of data analysis have aided in producing the information now available on hundreds of neutron resonances. The manner in which the parameters of these resonances give valuable information on nuclear structure will be described. The experimental findings will be reviewed and particular emphasis paid to their bearing on current theoretical nuclear models. The following aspects will be emphasized. 1) The radiation widths of nuclear energy levels and their relationship to theoretical transition probabilities. 2) The size distributions of neutron widths of levels and recent theoretical treatments of these distributions. 3) The average spacings of levels for different nuclei as well as the apparent non-random distribution of spacings for individual nuclei. 4) The probability of compound nucleus formation, or strength function, compared to recent calculations based on the cloudy crystal nuclear model. 5) Recent determinations of the nuclear radius at high and low neutron energies.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 14 (1958), S. 301-302 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Ein neuer Apparat wird beschrieben, in welchem die Wirkungen von Chlorpromazin, Reserpin und Natriumglutamat auf Furcht und Lernen in Ratten untersucht wurden.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 14 (1958), S. 178-180 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Es gelang nicht, mit physikalisch-chemischen Methoden einen HT-Komplex in hämolysierten oder homogenisierten Suspensionen von Kaninchen-Thrombozyten nachzuweisen. Versuchsergebnisse über die HT-Aufnahme durch Thrombozyten stimmen mit der Möglichkeit überein, dass das Amin in den Zellen durch einen aktiven Transportmechanismus konzentriert wird. Es wird angenommen, dass die Abgabe von normalem HT aus der Zelle unter Reserpineinwirkung, durch eine Hemmung des Aufnahmemechanismus und langsame, passive Diffusion aus den Zellen erfolgt.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 8 (1957), S. 89-96 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Zusammenfassung Eine Untersuchung wurde durchgeführt über die adiabatische Strömung der Luft zwischen zwei parallelen Platten, bei einem Druckunterschied quer über die sich bewegende Platte. Die Lösung lässt eine thermale Keilwirkung der hydrodynamischen Schmierung erwarten und gibt eine quantitative Analyse des allgemeineren Problems, wo ein Druckunterschied quer über die Gleitplatte vorhanden ist. Die Ergebnisse deuten an, dass der Beitrag des hydrodynamischen Druckes oft äusserst klein sein kann (für mässige Geschwindigkeiten) im Vergleich zum hydrodynamischen Druck in den dem Druck ausgesetzten Lagern. Im Falle von stillstehenden Platten ist die adiabatische Lösung gleich der isothermen Lösung; weswegen keine Temperaturerhöhung stattfindet.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 8 (1956), S. 135-151 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. ThePentatomini, which constitute a single Tribe within one of the Subfamilies of the hemipteran FamilyPentatomidae, include an unusually large number of species. Though these species vary considerably in their size and color, they are very uniform in their essential external and internal morphology. 2. Uniformity also characterizes such features in the Tribe as the chromosome number and meiotic behavior. But in the eleven species here investigated, this uniformity does not extend to the DNA content of the male meiotic cells, as determined by Feulgen cytophotometry. 3. The lowest DNA content is found inThyanta which, in this respect, is well separated from an intermediate group whose DNA values vary around a mean that is roughly double the lowest amount. Some evidence is available that a still higher multiple of DNA may be represented in theAcrosternum-Nezara complex of species. 4. In view of these cytochemical data, the multiplicity of species coupled with a striking uniformity of morphological and cytological features is provisionally explained on the basis of varying polyteny.
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  • 7
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The chromosomes of the African scale, Aspidoproctus maximus Louns., number 5 in the male, 6 in the female; sex chromosomes are of the XO male, XX female type. 2. Male meiosis is similar to that found in the Neotropical Llaveiini, with vesiculation of prophase nuclei, broadly dispersed polar centers, and divergent chromosomal fibers. The usual sequence of co-orientation and auto-orientation in meiosis is inverted; the chromosomes are autooriented at Metaphase I, and co-oriented at Metaphase II. 3. Asynapsis of one pair of autosomes occurs in from 14% to 52% (in different individuals) of the primary spermatocytes. Regular segregation of asynaptic chromosomes is ensured by a secondary pairing during interkinesis. 4. In spermiogenesis the chromosomes, linearly aligned, move out of the nucleus into the tail filament which forms a non-flagellated sperm.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 8 (1956), S. 709-718 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Male germ cells ofPseudaulacaspis pentagona (TARG.), an exceptional species of the coccid subfamilyDiaspinae, contain only approximately half as much DNA (measured by Feulgen cytophotometry) as do those ofChrysomphalus ficus Ash. — a typical representative of the group. 2. Reversing this relationship, the chromosomes ofP. pentagona number 16 in the female, 8 in the male — whileC. ficus has the basic complement of the subfamily, numbering 8 in the female, 4 in the male (Brown andBentsnett 1957). 3. The total mass of the chromosomes in the 2 complements is roughly proportional to the DNA values. It is concluded that 2 downward shifts in the level of chromosomal polyteny have been associated with the doubling of the chromosome number inPseudaulacaspis pentagona. 4. The cytology of the diaspines is discussed in relation to the evolutionary origin of male haploidy in coccids.
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  • 9
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The tropical species of the genus Thyanta conform, in their chromosome formula (2n♂=12+XY, 2n♀=12+2X), to that which is typical for the Family of Pentatomidae (Hemiptera), while the more northern species examined by us have either added a pair of chromosomes (T. custator and T. pallidovirens) or have doubled the basic number (T. calceata). 2. Hybrids between T. custator and T. pallidovirens show only minor disturbances in their meiosis, and the hybrid spermatids carry the same number of chromosomes and amount of DNA as are present in the spermatids of either parent species. 3. The meiosis of the hybrid between T. calceata and T. pallidovirens is quite abnormal and there is no chromosome pairing. Nevertheless, chromosome segregation is not completely at random and some functional sperms are formed. 4. The nuclei of the six species of Thyanta tested show little difference in their DNA contents. On the other hand, the nuclei of another pentatomid, Arvelius, contain at least twice as much DNA. 5. In considering the evolutionary origin of such a high chromosome number as that of T. calceata, the evidence adduced in the present investigation more or less precludes the involvement of polyploidy. Instead, some type of fragmentation was probably responsible for the doubled number. 6. It is difficult to conceive of such fragmentation as occurring transversely through the chromosomes. We propose a consideration of “longitudinal fragmentation” or better, a separation of the chromatids of each chromosome and the establishment of “echromatid autonomy”. 7. Except where polyploidy is involved, great differences in the nuclear contents of DNA, as observed between some Classes and Orders, must in certain cases be due to different degrees of polyteny and not to the addition of new or different genes. Our evidence demonstrates that relatively large differences of DNA may also exist in systematic groups of a lower category, such as the Genera of the same Tribe, or perhaps even the Species of the same Genus. On this basis, the degree of polyteny may differ even in closely related forms.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 45 (1958), S. 366-367 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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