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  • 1
    Electronic Resource
    Electronic Resource
    Partitioning of biologically fixed nitrogen in cowpea during pod development (1989)
    Springer
    Plant and soil 116 (1989), S. 129-131 
    Details
    ISSN: 1573-5036
    Keywords: 15N ; nitrogen fixation ; nitrogen partitioning ; translocationVigna unguiculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two days after exposure of roots to15N labeled N2, partitioning of biologically fixed N into leaves, stems, peduncles, pods, roots and nodules was measured in the early pod development stage of cowpea (Vigna unguiculata (L.). The experimental objective was to determine the quantity of biologically fixed N that is incorporated into vegetative tissue before being mobilized to pods. For the three varieties of cowpea included in the experiment a maximum of 50% of the N, biologically fixed two days earlier, was contained in the pods. The remaining N was distributed throughout the vegetative portion of the plant with at least 30% in stems and leaves which indicates that much of the newly fixed N must cycle through a N pool in these tissues before reaching the pods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02327269
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Distribution of 15N from ammonium fertilizer in field grown Acacia (1993)
    Springer
    Plant and soil 151 (1993), S. 147-150 
    Details
    ISSN: 1573-5036
    Keywords: Acacia ; isotope dilution ; nitrogen fixation ; N15 ; nitrogen partitioning ; tree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An experiment was conducted in the field to determine the partitioning of 15N from ammonium sulfate fertilizer in two-year old trees of Acacia mangium and Acacia auriculiformis. For both species, most of the 15N excess was partitioned into woody tissue, green material and root biomass present at the beginning of the experiment. Approximately one third of the 15N excess was contained in leaves that developed during the 60 days of the experiment. The concentration of 15N excess in the newly developed leaves indicated that more than 90% of the N came from a source other than the fertilizer. Based on the large quantity of N applied in the fertilizer and the inherently infertile soil, it appears that much of the N contained in the newly developed leaves came from N remobilized from other tree parts. ei]{gnR O D}{fnDixon}
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010796
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  • 3
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    On the formation and confinement of dense clouds in QSOs and active galactic nuclei (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A model for the formation and confinement of dense (at least about 1 billion per cu cm) clouds in QSOs and active galactic nuclei is presented wherein thermal instabilities behind radiative shocks cause the collapse of regions where the preshock density is enhanced over that of the surrounding medium. Such shocks (of total energy around 10 to the 51st ergs) are likely to occur if the frequent optical outbursts observed in many of these objects are accompanied by mass ejections of comparable energy. It is found that clouds quite similar to those thought to exist in QSOs etc. can be created in this manner at radii of the order of 10 to the 17th cm. The clouds can be subsequently accelerated to observed bulk velocities by either radiation pressure or a collision with a much stronger (total energy around 10 to the 53 ergs) shock. Alternatively, their high observed velocities could be caused by gravitational infall or rotation. The mass production required at inner radii by the outflow models can be supplied through a mechanism previously discussed by Shields (1977).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
    Format: text
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  • 4
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    Consequences of narrow cyclotron emission from Hercules X-1 (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Explanations of the line feature in the hard X-ray (58 keV) spectrum of the compact X-ray source Hercules X-1 are presented. The most important characteristic of the emission (interpreted as a cyclotron emission from a strong magnetic field, i.e., B greater than one trillion Gauss) is that the FWHM is less than 12 keV, with a total observed luminosity in the line of approximately 1% of the total X-ray luminosity. If the source region is only at the magnetic poles of a neutron star, the electrons are confined to a path nearly parallel to the B-field lines, and the angle of emission will be narrow. Photon emission under such circumstances is also discussed; and it is suggested that photons can leave either through holes in the shell formed by the hard X-rays, or can escape through the shell itself. Attention is given to the accretion flow structure near the magnetopause, as a critical parameter of narrow line emission.
    Keywords: ASTROPHYSICS
    Type: Nature; vol2 274
    Format: text
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  • 5
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    Structure of the iron fluorescence line in X-ray binaries (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The paper presents an approximate solution to the iron K alpha line transfer problem in a stellar atmosphere illuminated by an external X-ray source as in a binary X-ray system. The emergent Comptonized line profile can independently yield information on the abundance of heavy elements in the primary atmosphere and on the solid angle subtended by the primary at the X-ray source.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 215
    Format: text
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  • 6
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    A new luminosity limit for spherical accretion onto compact X-ray sources (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Preheating of infalling gas by emergent X-rays can suppress accretion on to a compact X-ray source. For spherically symmetric accretion, the effect results in a new luminosity limit, orders of magnitude less than the Eddington limit, above which steady flow is impossible. The model may apply to the globular-cluster X-ray sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 208; Sept. 1
    Format: text
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  • 7
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    Interstellar bubbles. II - Structure and evolution (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The detailed structure of the interaction of a strong stellar wind with the interstellar medium is presented. First, an adiabatic similarity solution is given which is applicable at early times. Second, a similarity solution is derived which includes the effects of thermal conduction between the hot (about 1 million K) interior and the cold shell of swept-up interstellar matter. This solution is then modified to include the effects of radiative energy losses. The evolution of an interstellar bubble is calculated, including the radiative losses. The quantitative results for the outer-shell radius and velocity and the column density of highly ionized species such as O VI are within a factor 2 of the approximate results of Castor, McCray, and Weaver (1975). The effect of stellar motion on the structure of a bubble, the hydrodynamic stability of the outer shell, and the observable properties of the hot region and the outer shell are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 218
    Format: text
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  • 8
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    The Comptonization of iron X-ray features in compact X-ray sources (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The formation of X-ray spectral features due to iron in a relatively cool cloud of gas with a Thomson depth greater than 1 surrounding a compact source of continuum X-rays is described. Coupled equations are solved for the ionization structure of the cloud and for the radiative transfer of the X-rays. Photoionization suppresses the strength of emission lines and absorption edges. Comptonization of the radiation broadens emission lines, fills in absorption edges, and produces a high-energy cutoff. In order to describe multiple scattering, a Fokker-Planck equation is derived which includes an important modification of the Kompaneets equation. Narrow resonance lines are treated with an escape probability formalism.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 219
    Format: text
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