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  • 1
    Publication Date: 2016-09-02
    Description: Dusty olivine (olivine containing multiple sub-micrometer inclusions of metallic iron) in chondritic meteorites is considered an ideal carrier of paleomagnetic remanence, capable of maintaining a faithful record of pre-accretionary magnetization acquired during chondrule formation. Here we show how the magnetic architecture of a single dusty olivine grain from the Semarkona LL3.0 ordinary chondrite meteorite can be fully characterized in three dimensions, using a combination of focused ion beam nanotomography (FIB-nT), electron tomography, and finite-element micromagnetic modeling. We present a three-dimensional (3D) volume reconstruction of a dusty olivine grain, obtained by selective milling through a region of interest in a series of sequential 20 nm slices, which are then imaged using scanning electron microscopy. The data provide a quantitative description of the iron particle ensemble, including the distribution of particle sizes, shapes, interparticle spacings and orientations. Iron particles are predominantly oblate ellipsoids with average radii 242 ± 94 x 199 ± 80 x 123 ± 58 nm. Using analytical TEM we observe that the particles nucleate on sub-grain boundaries and are loosely arranged in a series of sheets parallel to (001) of the olivine host. This is in agreement with the orientation data collected using the FIB-nT and highlights how the underlying texture of the dusty olivine is crystallographically constrained by the olivine host. The shortest dimension of the particles is oriented normal to the sheets and their longest dimension is preferentially aligned within the sheets. Individual particle geometries are converted to a finite-element mesh and used to perform micromagnetic simulations. The majority of particles adopt a single vortex state, with "bulk" spins that rotate around a central vortex core. We observed no particles that are in a true single domain state. The results of the micromagnetic simulations challenge some preconceived ideas about the remanence-carrying properties of vortex states. There is often not a simple predictive relationship between the major, intermediate, and minor axes of the particles and the remanence vector imparted in different fields. Although the orientation of the vortex core is determined largely by the ellipsoidal geometry (i.e., parallel to the major axis for prolate ellipsoids and parallel to the minor axis for oblate ellipsoids), the core and remanence vectors can sometimes lie at very large (tens of degrees) angles to the principal axes. The subtle details of the morphology can control the overall remanence state, leading in some cases to a dominant contribution from the bulk spins to the net remanence, with profound implications for predicting the anisotropy of the sample. The particles have very high switching fields (several hundred millitesla), demonstrating their high stability and suitability for paleointensity studies.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 75 (1953), S. 5840-5841 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 75 (1953), S. 5835-5839 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 106 (1920), S. 46-46 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] TOADS are associated with some wonderful myths, and my scepticism was naturally great when my friend Mr. H. Martin Leake assured me, while on a visit to Cawnpore in October of 1915, that toads would eat red-hot charcoal. An after-dinner demonstration, however, soon dispelled my doubts. Small ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 105 (1920), S. 455-455 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] I HAVE on frequent occasions (in the Mediterranean, the Red Sea, and the Indian Ocean) carefully observed with a field-glass (×8) the supposed “flight” of flying-fish, and have always concluded that the “leap and glide” theory is the correct one, with one or two modifications. Dr. J. McNamara, ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 112 (1923), S. 436-436 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] IN the recently issued third volume of “The Practice of Medicine in the Tropics,” edited by Byam and Archibald, Drs. Clayton Lane and Low call in question (on pp. 1821–2) the one-host account of the life-cycle of the well-known tapeworm Hymenolepis fraterna, Stiles. This account is principally ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 113 (1924), S. 891-891 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] PROF. SWALE VINCENT, in his recently issued “Introduction to the Study of Secretion”, refers, in the chapter on kidney secretion, to my proof (Journ. and Proc. Asiatic Soc., Bengal, N.S., vol. xviii. pp. 85–193, 1922) that the network of renal afferent veins in the substance of the frog's ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 113 (1924), S. 675-675 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] JOYEUX, in 1920, after a survey of most of the evidence, arrived at the conclusion that Hymenolepis nana of man, and H. fraterna of rodents, though apparently indistinguishable in all characters, both of the adult worm and of the egg, are yet two distinct physiological species. More recently, ...
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Inst. and Methods in Physics Research, B 42 (1989), S. 523-526 
    ISSN: 0168-583X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 38 (1951), S. 309-327 
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Gleichgewichte elf verschiedener Verbindungen der Elemente Cu, N, C, H und O, die für die Stickstoffbestimmung nachDumas von Belang sind, wurden eingehend erforscht. Die thermodynamischen Beziehungen für Stickstoffdioxyd sind in der Literatur nicht angegeben und wurden aus den neuesten spektrographischen Daten errechnet. Die Gleichgewichtskonstanten von elf Reaktionen für Temperaturintervalle von je 100° innerhalb 300 bis 1500° K wurden graphisch dargestellt und tabellarisch wiedergegeben. Ebenso auch die perzentuellen Abweichungen der verschiedenen Reaktionen hiervon. Daraus ergeben sich folgende Schlußfolgerungen: Alle Abweichungen sind positiv, sie verursachen daher eine Erhöhung der Analysenwerte. Alle Abweichungen werden bei steigender Temperatur größer. Niedere Temperaturen sind daher vorzuziehen. Die Temperatur darf aber nicht zu tief gewählt werden, da sonst die Verbrennung der organischen Substanz nicht mehr vollständig verläuft. Die üblicherweise eingehaltenen Temperaturen von 700 bis 800°C erweisen sich als bester Ausgleich dieser Forderungen. Bei dieser Temperatur bleibt der durch unvollständige Reduktion von Stickoxyd und Stickstoffdioxyd verursachte Fehler vernachlässigbar klein, aber die durch thermische Dissoziation des Kohlendioxyds, des Wassers und des Stickoxyduls verursachten Fehler sind beträchtlich. Dies rechtfertigt Vorkehrungen zur Entfernung von Sauerstoff, Wasserstoff und Kohlenmonoxyd. Der Gesamtfehler beträgt bei 1000° K (827° C) etwa 1 × 10−3%, sofern unsere Annahme über die erreichte Gleichgewichtslage zutrifft. Wir schließen daraus, daß die Ausführung derDumas-Methode nachJ. B. Niederl undV. Niederl durchaus befriedigend ist.
    Abstract: Résumé On a étudié soigneusement les équilibres de 11 composés différents des éléments Cu, N, C, H et O qui sont importants pour le dosage de l'azote par la méthode deDumas. Les relations thermodynamiques pour le bioxyde d'azote ne sont pas données dans la littérature; elles furent calculées d'après les données spectrographiques récentes. Les constantes d'équilibre de 11 réactions pour les intervalles de température de 100° entre 300 et 1500° K sont représentées graphiquement et fournies aussi sous forme de tableau. On y trouve les écarts en pourcent des différentes réactions. On en tire les conclusions suivantes: Tous les écarts sont positifs et causent, par conséquent, une élévation des nombres d'analyse. Tous les écarts augmentent avec la température; il faut donc préférer les basses températures. Cependant la température ne doit pas être choisie trop basse car alors la combustion de la matière organique ne serait plus complète. Les températures qui se tiennent ordinairement entre 700 et 800° C se montrent les meilleures pour concilier ces exigences. A cette température, l'erreur causée par la réduction incomplète de l'oxyde azotique et du peroxyde d'azote reste négligeable, mais les erreurs produites par la dissociation thermique du gaz carbonique, de l'eau et du protoxyde d'azote sont importantes. Il faut donc prendre des précautions pour éliminer l'oxygène, l'hydrogène et l'oxyde de carbone. L'erreur globale atteint à 1000° K (827° C) environ 1 × 10−3% tant que notre hypothèse sur le domaine d'équilibre atteint est vérifiée. Nous concluons que le mode opératoire de la méthode deDumas d'aprèsJ. B. Niederl etV. Niederl est tout à fait satisfaisant.
    Notes: Summary and Conclusions Eleven equilibria involving compounds of Cu, N, C, H and O, important in theDumas method of determination of nitrogen, are fully studied. These equilibria are summarized in the equations of Table I. The data needed are given by equations (12), (17), (21), (23), (26), (27), (34), (40), and (41). The heat capacity equation of NO2 is not available in the literature and has been calculated here from the recent spectroscopic data. The equilibrium constants of reactions (1) to (11) at temperature intervals of 100° in the range 300–1500° K are given in Tables II, IV–XIII. They are also plotted in Figure 1. The % errors due to various reactions are summarized in Tables XIV and XV and plotted in Figs. 2 and 3. The following conclusions may be drawn: 1. All errors are positive (i. e. they make the results high). 2. All errors increase with increasing temperatures so that low temperatures are preferable. But the temperature must not be chosen too low, lest the combustion of the organic substance would become incomplete. As a compromise a working temperature range of 700–800° C, as usually adopted, is satisfactory. 3. In this temperature range the relative errors due to incomplete reduction of NO and NO2 are negligibly small, but those due to the dissociation of CO2, H2O and N2O are considerable (see Table IX). This justifies the use of provisions for the removal of O2, H2 and CO. 4. After these provisions are made, the errorsy 5,y 6 andy 7 are replaced by the much smaller errorsy 8,y 10, andy 11. In Table XV we have groupedy 1,y 2, andy 8 together because the corresponding reactions take place at the combustion temperature (700–800° C), whiley 10 andy 11 correspond to reactions taking place in the last portion of the tube fillings which is outside the combustion zone and has much lower temperatures (about 200–300° C). This is desirable because the errors are thus made much smaller than it would be if the last part of the CuO filling were within the combustion furnace. 5. The overall error is about 3 × 10−5% at 1000° K (727° C) and 1 × 10−3% at 1100° K (827° C) if our assumption regarding the extent to which the equilibrium is reached is correct. Therefore we conclude that theDumas method as adopted byJ. B. andV. Niederl is quite satisfactory.
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