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  • 1
    Schriftenreihen ausleihbar
    Schriftenreihen ausleihbar
    A spectrochemical method for the semiquantitative analysis of rocks minerals, and ores (1961)
    Washington, DC : United States Gov. Print. Off.
    Dazugehörige Bände
    Details Verfügbarkeit
    Signatur: SR 90.0001(1084-I)
    In: U.S. Geological Survey bulletin
    Materialart: Schriftenreihen ausleihbar
    Seiten: III S., S. 207-229
    Serie: U.S. Geological Survey bulletin 1084-I
    Sprache: Englisch
    Standort: Kompaktmagazin unten
    Zweigbibliothek: GFZ Bibliothek
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Magnetic Rotation of Direct Current Arc in Spectographic Analysis (1947)
    s.l. : American Chemical Society
    Analytical chemistry 19 (1947), S. 71-71 
    Details
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac60001a022
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    Preparation of Carbon Electrodes for Spectrographic Analysis: Two Useful Lathe Tools (1939)
    s.l. : American Chemical Society
    Industrial and engineering chemistry 11 (1939), S. 218-219 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac50132a017
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Metal Content of Twenty-Four Petroleums. (1960)
    s.l. : American Chemical Society
    Journal of chemical & engineering data 5 (1960), S. 553-557 
    Details
    ISSN: 1520-5134
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/je60008a038
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Properties of Porphyrins in Petroleum (1954)
    s.l. : American Chemical Society
    Industrial & engineering chemistry 46 (1954), S. 2000-2007 
    Details
    ISSN: 1520-5045
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ie50537a061
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Fertilisation of the Pansy (1873)
    [s.l.] : Nature Publishing Group
    Nature 8 (1873), S. 202-202 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] I AM glad to be able to confirm, to-some extent, from observation, Mr. Bennett's theory of the fertilisation of the Pansy, given in NATURE, vol. viii. p. 49. I watched a considerable number of specimens of Viola tricolor on a grassy hill-top where the smaller insects were very numerous and ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/008202b0
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
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    What physics determines the peak of the IMF? Insights from the structure of cores in radiation-magnetohydrodynamic simulations (2016)
    Oxford University Press
    Details
    Publikationsdatum: 2016-06-19
    Beschreibung: As star-forming clouds collapse, the gas within them fragments to ever-smaller masses. Naively one might expect this process to continue down to the smallest mass that is able to radiate away its binding energy on a dynamical time-scale, the opacity limit for fragmentation, at ~0.01 M . However, the observed peak of the initial mass function (IMF) lies a factor of 20–30 higher in mass, suggesting that some other mechanism halts fragmentation before the opacity limit is reached. In this paper we analyse radiation-magnetohydrodynamic simulations of star cluster formation in typical Milky Way environments in order to determine what physical process limits fragmentation in them. We examine the regions in the vicinity of stars that form in the simulations to determine the amounts of mass that are prevented from fragmenting by thermal and magnetic pressure. We show that, on small scales, thermal pressure enhanced by stellar radiation heating is the dominant mechanism limiting the ability of the gas to further fragment. In the brown dwarf mass regime, ~0.01 M , the typical object that forms in the simulations is surrounded by gas whose mass is several times its own that is unable to escape or fragment, and instead is likely to accrete. This mechanism explains why ~0.01 M objects are rare: unless an outside agent intervenes (e.g. a shock strips away the gas around them), they will grow by accreting the warmed gas around them. In contrast, by the time stars grow to masses of ~0.2 M , the mass of heated gas is only tens of percent of the central star mass, too small to alter its final mass by a large factor. This naturally explains why the IMF peak is at ~0.2 M .
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
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    The CH+ abundance in turbulent, diffuse molecular clouds (2015)
    Oxford University Press
    Details
    Publikationsdatum: 2015-09-27
    Beschreibung: The intermittent dissipation of interstellar turbulence is an important energy source in the diffuse interstellar medium. Though on average smaller than the heating rates due to cosmic rays and the photoelectric effect on dust grains, the turbulent cascade can channel large amounts of energy into a relatively small fraction of the gas that consequently undergoes significant heating and chemical enrichment. In particular, this mechanism has been proposed as a solution to the long-standing problem of the high abundance of CH + along diffuse molecular sight lines, which steady-state, low-temperature models underproduce by over an order of magnitude. While much work has been done on the structure and chemistry of these small-scale dissipation zones, comparatively little attention has been paid to relating these zones to the properties of the large-scale turbulence. In this paper, we attempt to bridge this gap by estimating the temperature and CH + column density along diffuse molecular sight lines by post-processing three-dimensional magnetohydrodynamic(s) turbulence simulations. Assuming reasonable values for the cloud density ( $\bar{n}_{\rm {H}} = 30$ cm –3 ), size ( L  = 20 pc), and velocity dispersion ( v  = 2.3 km s –1 ), we find that our computed abundances compare well with CH + column density observations, as well as with observations of emission lines from rotationally excited H 2 molecules.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
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    Star cluster formation in turbulent, magnetized dense clumps with radiative and outflow feedback (2014)
    Oxford University Press
    Details
    Publikationsdatum: 2014-03-25
    Beschreibung: We present three orion simulations of star cluster formation in a 1000 M , turbulent molecular cloud clump, including the effects of radiative transfer, protostellar outflows, and magnetic fields. Our simulations all use self-consistent turbulent initial conditions and vary the mean mass-to-flux ratio relative to the critical value over μ  = 2, μ  = 10, and μ  =  to gauge the influence of magnetic fields on star cluster formation. We find, in good agreement with previous studies, that magnetic fields corresponding to μ  = 2 lower the star formation rate by a factor of 2.4 and reduce the amount of fragmentation by a factor of 2 relative to the zero-field case. We also find that the field increases the characteristic sink particle mass, again by a factor of 2.4. The magnetic field also increases the degree of clustering in our simulations, such that the maximum stellar densities in the μ  = 2 case are higher than the others by again a factor of 2. This clustering tends to encourage the formation of multiple systems, which are more common in the rad-MHD runs than the rad-hydro run. The companion frequency in our simulations is consistent with observations of multiplicity in Class I sources, particularly for the μ  = 2 case. Finally, we find evidence of primordial mass segregation in our simulations reminiscent of that observed in star clusters like the Orion Nebula Cluster.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    facet.materialart.
    Unbekannt
    The CH+ abundance in turbulent, diffuse molecular clouds (2015)
    Oxford University Press
    Details
    Publikationsdatum: 2015-09-05
    Beschreibung: The intermittent dissipation of interstellar turbulence is an important energy source in the diffuse interstellar medium. Though on average smaller than the heating rates due to cosmic rays and the photoelectric effect on dust grains, the turbulent cascade can channel large amounts of energy into a relatively small fraction of the gas that consequently undergoes significant heating and chemical enrichment. In particular, this mechanism has been proposed as a solution to the long-standing problem of the high abundance of CH + along diffuse molecular sight lines, which steady-state, low-temperature models underproduce by over an order of magnitude. While much work has been done on the structure and chemistry of these small-scale dissipation zones, comparatively little attention has been paid to relating these zones to the properties of the large-scale turbulence. In this paper, we attempt to bridge this gap by estimating the temperature and CH + column density along diffuse molecular sight lines by post-processing three-dimensional magnetohydrodynamic(s) turbulence simulations. Assuming reasonable values for the cloud density ( $\bar{n}_{\rm {H}} = 30$ cm –3 ), size ( L  = 20 pc), and velocity dispersion ( v  = 2.3 km s –1 ), we find that our computed abundances compare well with CH + column density observations, as well as with observations of emission lines from rotationally excited H 2 molecules.
    Print ISSN: 0035-8711
    Digitale ISSN: 1365-2966
    Thema: Physik
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    AKTUELLE ARTIKEL
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