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  • 1960-1964  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 15 (1962), S. 271-281 
    ISSN: 0001-5520
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 193 (1962), S. 941-942 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] CHROMATOGRAPHY on adsorbent-coated glass strips or plates is frequently used as a qualitative analytical method. We have modified the techniques described by Kirchner1 and Stahl2 to make it applicable for preparative purposes. The method compares favourably with column chromatography in many ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 201 (1964), S. 315-315 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1. Psammechinus miliaris, 16 h gastrula, 2 cells of the oral field. n, nucleus; m, mitochondrium; y, yolk sphere. The arrows indicate the elongated tips of the inner surface of the cells, (× c. 11,700) Examining thin sections of 16-h gastrulse of Psammech-inus miliaris in search of specific ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Morphological manifestations of the chromosomal metabolism have been found in the first spermatocyte nucleus of Drosophila melanogaster. These “metabolic structures” include several types of well defined components, among which the „tubuli“ and the „reticular elements“ are most conspicuous. The metabolic nature of these elements follows from their phase specifity and from cytochemical data. 2. Masses of tubuli of 300–400 Å diameter are found all over the meiotic prophase chromosomes in the spermatocyte nucleus, but not in the spermatogonial nucleus. The reticular elements appear somewhat later and usually form a single group. Both types of metabolic structures are decomposed during diakinesis when they separate from the chromosomes. 3. The tubuli are mainly composed of a basic protein. In addition they seem to contain RNA. The presence of DNA in small concentration can not yet be excluded. 4. The chromosomal origin of the tubular as well as the reticular elements follows not only from the observed contact with the chromosomes but also from the fact that spermatocyte nuclei of X/O-males of Drosophila melanogaster do not contain these components. This shows that the Y-chromosome is involved. 5. The role of the Y-chromosome in the formation of the metabolic structures has been further elucidated by studying males with partial Y-chromosomes, such as YS, YL, and Y″. Spermatocytes with the long arm of the Y (X/YLc) as a rule contain tubular and reticular elements in nearly normal quantity. X/YS and X/Y″ testes show a highly variable pattern. Some spermatocyte nuclei resemble the X/O-type while the rest represent all intermediate stages between the X/O- and the X/YL-type. 6. The lack of tubuli in X/O or in X/YS and X/YL spermatocyte nuclei is always correlated with the appearance of crystal needles in the nucleus as well as in the cytoplasm. Only very rarely in X/YS spermatocytes is an intranuclear crystal found together with a small amount of tubuli. The X/O crystal needles persist during spermatogenesis and are still found in sperm bundles. The crystal material seems to be a protein which is different from the tubular protein. 7. The possibilities of the involvement of the Y-chromosome in the formation of the metabolic chromosomal structures are discussed. It seems probable that tubuli represent a highly modified state of the Y-chromosome, or parts of this chromosome. The formation of protein crystals in X/O-spermatocytes indicates the presence of a biochemical block. The relation to fertility i.e. sperm motility is unclear. X/YL males do not produce motile sperms although tubuli are regularly present in spermatocyte nuclei.
    Type of Medium: Electronic Resource
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 159 (1960), S. 563-583 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In a previous paper direct electron-intensity measurements in Debye-Scherrer diagrams of aluminium have been described. A retarding field apparatus was used for investigations into the influence of crystal size and electron energy (15 to 50 keV) on the elastic diffraction intensities. The validity range of the kinematical theory could be determined. By means of a retarding field the inelastically scattered electrons were separated from the elastically scattered electrons (energy loss below 2 eV). In this paper the retarding field apparatus by which scattering intensities can be measured with good accuracy (≈ 2%) is described in detail. It is compared with other arrangements for the measurements of angular and energy distributions of scattered electrons.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 164 (1961), S. 21-39 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Absolute intensity measurements of the electrons scattered by a polycrystalline Aluminium foil were carried out in the energy range between 25 and 50 keV. The electrons scattered elastically were separated from those scattered inelastically by means of a retarding field. The intensities of the electrons having passed the foil unscattered and of those which were scattered elastically into the Debye-Scherrerrings and into the continuous background can be interpreted by the assumption of reasonable thicknesses of the crystalline Aluminium and the amorphous Aluminium-Oxide. These values agree approximately with the thickness measured by light absorption. Additionally the probability of the inelastic scattering process can be deduced from these measurements. Investigations of the angular distribution were carried out in order to study the influence of the inelastic scattering on the shape of the primary beam, the rings and the continuous background. The results are discussed in detail. Some results are given in particular, concerning the increase of the half width of the rings due to inelastic scattering processes.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 1 (1963), S. 208-213 
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Résumé Cette communication décrit l'influence des vibrations thermiques sur les intensités de rayons électroniques diffractés par une feuille polycristalline d'aluminium à différentes températures (150–800°K). Au moyen d'un champ retardateur on a déterminé les intensités d'électrons (50 keV) diffusés élastiquement. Les résultats montrent que les intensités de toutes les réflexions obéissant à la théorie cinématique sont décrites par le facteur de Debye-Waller exp(−2M) dans un grand domaine de variation de la grandeur 2M. A l'aide de cette dernière, on a calculé la température de DebyeΘ M de l'aluminium pour différentes températures. Ces valeurs concordent avec celles qui découlent de la mesure des rayons X.
    Abstract: Abstract The influence of thermal vibrations on the electron diffraction intensities of a polycristalline aluminium-foil has been studied. The intensities of the electrons (50 keV) scattered elastically at various foil temperatures (150–800°K) were measured by means of a retarding field apparatus. The experimental results show, that the temperature dependence of the diffraction intensities of all reflections, for which the kinematical theory holds, can be well described by the Debye-Waller factor exp(−2M) within a large range of 2M. From the value of 2M the Debye-temperatureΘ M for aluminium at different temperatures was determined. The absolute value as well as the temperature dependence ofΘ M are in agreement with the results obtained from X-ray measurements.
    Notes: Zusammenfassung Der Einfluß der thermischen Gitterschwingungen auf die Elektronenbeugungsintensitäten einer polykristallinen Aluminium-Folie wurde untersucht. Die Intensitäten der bei verschiedenen Folientemperaturen (150–800°K) elastisch gestreuten Elektronen (50 keV) wurden mit einer Gegenfeldanordnung gemessen. Die experimentellen Ergebnisse zeigen, daß die Temperaturabhängigkeit der Beugungsintensitäten aller Reflexe, die sich kinematisch verhalten, über einen großen Bereich von 2M sehr gut durch den Debye-Waller Faktor exp(−2M) beschrieben werden kann. Aus den gemessenen Werten 2M wurde die Debye-TemperaturΘ M von Aluminium bei verschiedenen Temperaturen bestimmt. Sowohl der Absolutwert als auch die Temperaturabhängigkeit vonΘ M stimmen mit den Ergebnissen von Röntgenstrahlmessungen überein.
    Type of Medium: Electronic Resource
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