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  • 11
    Electronic Resource
    Electronic Resource
    Nitrogen nutrition of seedling grain legumes: some taxonomic, morphological and physiological constraints (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 7 (1984), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The growth of young plants of the epigeal species Phaseolus vulgaris and Glycine max is compared with that of the hypogeal species Pisum sativum and Vicia faba, with particular reference to synchronization between the exhuastion of seed reserves of N and the availability of fixed N. It is argued that the N stress symptoms which occur when these two processes are not synchronized are more common and obvious in Phaseolus or Glycine than in Pisum or Vicia. This is primarily because in these species (a) the first fixed N is used for nodule growth rather than being exported to the shoot system and (b) the first foliage leaves have a much greater area and contain a larger proportion of N reserves from the seed.It is further suggested that Phaseolus and Glycine may show the greater response to nitrogen fertilizer applied at sowing since (a) most of the applied nitrate is passed directly to the shoots (rather than being reduced in the roots as in Pisum or Vicia) and (b) in addition to being used for growth (following reduction), it may also be used prior to reduction as part of the osmotic force driving cell expansion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11571523
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  • 12
    Electronic Resource
    Electronic Resource
    Spatial distribution of soft X-ray and EUV emission associated with a chromospheric flare of importance 1B on August 2, 1972 (1974)
    Springer
    Solar physics 34 (1974), S. 349-375 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Soft-X-ray and extreme ultraviolet spectroheliographs carried by the OSO-7 (Orbiting Solar Observatory) have been used to record the development of XUV emission associated with a flare of importance 1b on August 2, 1972. Spatial resolution was 20″ and spectral resolution was adequate to select emission lines originating within well-defined ranges of electron temperature between 5 × 104 and 30 × 106K. The data show that heating only the pre-existing coronal material adjacent to the flare site cannot account for the soft X-ray emission measure observed during the event. The flare emission originating at T e ⩽ 2.3 × 106K exhibits an impulsive component coincident with an impulsive microwave event. This radiation appears to coincide spatially with Hα radiation emitted at that time and is centered on the neutral line separating magnetic fields of opposite polarity. One soft X-ray-emitting feature, estimated to have an initial electron temperature of 2–10 × 106K, forms during the impulsive phase immediately over the Hα flare. A second, arch-like feature observed at wavelengths near 1.9 Å and estimated to have T e≅30 × 106K is located approximately 35000 km above the Hα event. Both regions have lengths of about 27000 km but transverse dimensions small compared to the spatial resolution of the spectroheliograph, i.e., less than 14000 km. The region with highest electron temperature exhibits the greatest stability in position. This region cools to approximately 10 × 106K in 6 to 12 min which is compatible with cooling by conduction to the chromosphere. The best association with a dark surge is found in an emission line of Fe xiv.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00153673
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  • 13
    Electronic Resource
    Electronic Resource
    Ionization equilibrium in soft X-ray-emitting solar flares (1974)
    Springer
    Solar physics 36 (1974), S. 383-401 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Studies of the flare-produced line feature at 1.9 Å due to highly ionized iron show that it is emitted in conditions closely approximating steady-state ionization equilibrium. Calculations of the line flux per unit emission measure from time-dependent and steady-state ionization equilibria are compared with observed values during four flares in particular. Only for electron densities N e ⪞ 1010 cm-3 do the time-dependent equilibrium values give as good an approximation to the observed values as the steady-state equilibrium. This lower limit is compared with values of N e derived from analyses of the temperature decline in each of these events, and with estimates of N e given by other workers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151209
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  • 14
    Electronic Resource
    Electronic Resource
    Polarization results of solar X-rays from OSO-7 (1974)
    Springer
    Solar physics 37 (1974), S. 429-435 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Polarization measurements of solar X-ray events that were obtained with an instrument on OSO-7 are presented. The results appear to be consistent with the results of Tindo et al. on the existence and magnitudes of polarization. A comparison with polarization predictions when X-rays are produced by radial beams of electrons gives two examples of deviations from such a model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152500
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  • 15
    Electronic Resource
    Electronic Resource
    Coronal temperatures and temperature gradients from OSO-7 spectroheliograms (1976)
    Springer
    Solar physics 47 (1976), S. 611-626 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Temperatures and temperature gradients for the outer corona are obtained from brightness gradients of EUV lines that were measured with the spectroheliograph on OSO-7. Brightness gradients show considerable deviations from isothermal model calculations that include collisional excitation and photoexcitation. A negative temperature gradient that gives both positive and negative ion abundance gradients appears to be able to account for the discrepancy. For λ284 of Fe xv, perhaps the strongest line from the outer corona, measurements during 1972 appear to be consistent with (i) a temperature near 2.3×106K near the equator at ϱ = 1.3±0.1 solar radii from the solar center; (ii) (ϱ/T) dT/dϱ values near -0.7 that extend from as low as ϱ = 1.2 to about ϱ = 1.8. Temperatures from strong lines of Fe xiv and Fe xvi indicate that variations of about ±0.2×106K exist along lines of sight where emission is appreciable. There appears to be some agreement between these results and temperature measurements from ion abundances in the solar wind and Doppler width of λ5303.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154770
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  • 16
    Electronic Resource
    Electronic Resource
    Methods for the study of nitrogen assimilation and transport in grain legumes (1987)
    Springer
    World journal of microbiology and biotechnology 3 (1987), S. 3-22 
    Details
    ISSN: 1573-0972
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Résumé L'étude de l'assimilation et du transport de l'azote dans les légumineuses à graines est une nécessité préliminaire pour la sélection des cultivars destinés aux croisements visant à accroître la fixation de l'azote pour la croissance des plantes et le rendement en graines. Les méthodes employées pour ces études sont éparpillées dans la littérature et n'ont pas été suffisamment testées. Dans cet article, il est présenté une étude d'ensemble de méthodes fiables, particulièrement adaptées aux laboratoires des pays en voie de développement qui ne di sposent pas d'instrumentation sophistiquée et coûteuse. Il est notamment décrit un système simple et peu onéreux de flux continu pour mesurer la fixation de l'azote par réduction de l'acétylène, ainsi que des techniques pour déterminer la respiration des nodules, le dégagement d'hydrogéne et l'activité nitrate-réductase des plantes. Plusieurs techniques colorimétriques ont été adaptées à l'analyse de l'azote nitrique, aminé, uréidique et total, dans de faibles volumes de suc de xylème prélevé par saignée.
    Abstract: Resumen El estudio de la asimilación y del transporte de nitrógeno en leguminosas de grano es un preámbulo necesario para la selección de cultivares obtenidos en programas de mejora que tengan como objetivo el incremento de la contribución de la fijación de nitrógeno a la producción de plantas y de semillas. Los métodos utilizados en dichos estudios estan dispersos en la literatura y no siempre se han comprobado lo suficiente. Este trabajo presenta un amplio conjunto de técnicas seguras, que se adaptan particularmente bien para su uso en laboratorios de países en desarrollo que carecen de instrumental caro y sofisticado. Se describe un sistema de flujo continuo para la medida de la fijación de N2 (reducción de acetileno) que utiliza componentes sencillos y baratos, tembién se describen técnicas para estimar la respiración de los nódulos, la evolución del hidrógeno y la actividad nitratò-reductasa de la planta. Se han adaptado varios métodos colorimétricos para el análisis del Nitrógeno total y del Nitrógeno combinado (en forma de aminas, amidas y derivados de la urea) contenidos en pequeños volumenes de savia bruta (xilema).
    Notes: Summary The study of nitrogen assimilation and transport in grain legumes is a necessary preliminary to selecting plant cultivars for breeding programs aimed at increasing the contribution of nitrogen fixation to plant production and seed yield. Methods used in such studies are spread widely throughout the literature and have not always been sufficiently tested. This paper presents a comprehensive set of reliable techniques particularly adapted for use in laboratories in developing countries which lack sophisticated and expensive instruments. A continuous flow system for the measurement of N2 fixation (acetylene reduction) using simple and inexpensive components is described, as are techniques for the estimation of nodule respiration, hydrogen evolution and plant nitrate reductase activity. A number of colorimetric techniques have been adapted for the analysis of nitrate-, amino-, amide-, ureide- and total-N in small volumes of xylem (bleeding) sap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01090491
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  • 17
    Electronic Resource
    Electronic Resource
    OSO-7 results on coronal emission near 304 Å (1975)
    Springer
    Solar physics 43 (1975), S. 337-350 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spectral composition and spatial distribution of equatorial coronal emission near 304 Å is examined. Spectral scans indicate that the predominant line is from Si xi. Comparisons of observations with calculations of intensity changes with altitude indicate that collisional excitation is important near the Sun but that photoexcitation becomes dominant beyond about 1.3 R ⊙ from the solar center. Observed and calculated intensities are in approximate agreement for abundances and electron densities that are within the range of observed values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152358
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  • 18
    Electronic Resource
    Electronic Resource
    On coronal Fe abundances and temperatures from XUV emission lines (1977)
    Springer
    Solar physics 53 (1977), S. 435-444 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Data obtained by the OSO-7 spectroheliograph on strong XUV lines of five, different Fe ions from the outer equatorial corona are presented. Interpretation of the data with a spherically symmetric model atmosphere gives average ion abundances for lines of sight at 0.3R ⊙ from the limb. Fe xvi is usually more abundant than Fe xv, xiv, xii and ix, but there are times when Fe xii is more abundant than the other ions. The deviation of measured relative abundances of Fe xii, xiv, and xvi from predictions of ionization equilibrium at one temperature seems to indicate that there are appreciable temperature variations along lines of sight. Element abundances are very uncertain since they appear to depend so heavily on likely but unknown density irregularities along lines of sight.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160286
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  • 19
    Electronic Resource
    Electronic Resource
    Corona textures in Proterozoic olivine melanorites of the Equeefa Suite, Natal Metamorphic Province, South Africa (1993)
    Springer
    Mineralogy and petrology 49 (1993), S. 91-102 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Aus Olivin-Melanoriten der mittel- bis spätproterozoischen Equeefa Suite im südlichen Natal, Südafrika, wurden Olivin-Plagioklas und Phlogopit-Plagioklas-Koronartexturen beobachtet. Olivin, der mit Plagioklas im Kontakt steht, wird von einem klaren Saum vom Orthopyroxen ummantelt, der seinerseits von blaßgrünem (pargasitischem) Klinoamphibol umsäumt wird. Stellenweise ist ein dritter Saum, bestehend aus feinkörnigem symplektitischem Pargasit-Spinell im Kontakt mit Plagioklas ausgebildet. Die zweite koronabildende Reaktion resultiert in Bildung eines grünbraunen Pargasites an Phlogopit-Plagioklas Kornkontakten. Eine dritte, weniger auffällige Reaktion zwischen Olivin und Phlogopit wurde ebenfalls beobachtet. Zwei-Pyroxen-Thermometrie ergab magmatische Temperaturen der Kernbereiche (∼ 1120°C) und belegt eine Gleichgewichtseinstellung in den Randzonen bei ca. 850°C. Olivin-Plagioklas-Modellreaktionen liegen ebenfalls in einem Temperaturbereich von 830–1050°C bei Wasseraktivitäten von 0.1 bis 1.0 und einem Druck von 7 kbar. Die drei Reaktionen liefen im Zuge einer länger andauernden Abkühlung unter teilweiser Hydratisierung der magmatischen Melanorite in einem Temperaturbereich von 1000°C bis ca. 600°C ab. Die aus den Reaktionen ableitbaren P-T-Bedingungen sprechen für eine im wesentlichen isobare Abkūhlungsgeschichte und zeigen, daß dieses Gebiet wáhrend dieser gesamten Periode keiner raschen Hebung bzw. keiner Versenkung unterworfen worden ist.
    Notes: Summary Olivine-plagioclase and phlogopite-plagioclase coronas have been identified from olivine melanorites of the Mid- to Late Proterozoic Equeefa Suite in southern Natal, South Africa. Olivine, in contact with plagioclase, is mantled by a shell of clear orthopyroxene, in turn rimmed by pale green (pargasitic) clinoamphibole. Locally a third rim, composed of a fine pargasite-spinel symplectite is developed adjacent to the plagioclase. The second corona reaction has produced greenish-brown pargasite at phlogopite-plagioclase interfaces. A third, less obvious reaction, between olivine and phlogopite is also noted. Analytical data of all the mineral phases present, along with the coronas, are given. Two-pyroxene thermometry yields magmatic core temperatures (∼ 1120°C), with rim compositions indicating equilibration at ∼ 850°C. Consistent with this, the modelled olivine-plagioclase reaction occurs between 830–1050°C with awaterbetween 0.1 and 1.0 at 7 kbar. The three reactions took place during a prolonged history of cooling and partial hydration of the magmatic olivine melanorites from over 1000°C down to ∼ 600°C. The P-T conditions indicated by the reactions suggest this cooling process was essentially isobaric, indicating that the area was not subjected to rapid uplift or burial throughout this entire period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01162928
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  • 20
    Electronic Resource
    Electronic Resource
    Oblique collision at about 1.1 Ga along the southern margin of the Kaapvaal continent, south-east Africa (1994)
    Springer
    International journal of earth sciences 83 (1994), S. 322-333 
    Details
    ISSN: 1437-3262
    Keywords: Oblique collision ; Transpression ; Transtensional granitoids ; Grenvillian-Natalian orogeny ; Rodinia super continent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The ≈ 1.1 Ga Natal Metamorphic Province (NMP) lies at the heart of a world-wide system of Grenville age mobile belts which welded early continental fragments into the Mesoproterozoic supercontinent of Rodinia. Structural analysis of the three tectonostratigraphic terranes in Natal reveals a kinematic history characterized by prolonged NE-SW plate convergence, manifested as early thrust tectonics and later pervasive sinistral transcurrent shearing. Consequently, superimposed on the Natal tectonostratigraphic terranes is a kinematic subdivision into tectonic domains which are characterized by shallow, south-west dipping foliations, south-west plunging stretching lineations and north-east verging recumbent folds, and by younger domains with subvertical shear fabrics, subhorizontal to oblique lineations and folding about near-vertical axes. Microtextural and petrographic analyses suggest that the later shearing took place under high temperature conditions of at least 500°C. The recorded kinematic indicators suggest that early subhorizontal compressional tectonics gave rise to tectonic thickening of the crust, progressively followed by oblique transcurrent shearing within a transpressional regime. The shearing event in the southern arc-related terranes was associated with the widespread emplacement of late kinematic rapakivi granite -charnockite plutons, with A-type granite geochemical characteristics. This orogenic event took place around 1100 Ma during prolonged NE-SW collisional convergence along the southern margin of the stable Archean foreland, which lay to the north.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210548
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