Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Dynamical mass-transfer paradox (1990)
    [s.l.] : Nature Publishing Group
    Nature 347 (1990), S. 433-433 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-Although the periodically varying frequency of the emission lines of the star SS433 can be described kinematically1 by two precessing jet sources emanating from one component of a binary system, many of its physical and dynamical properties remain enigmatic. In particular, the jet speed and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/347433a0
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Foreword (1994)
    Springer
    Space science reviews 68 (1994), S. xvii 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749111
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Return current and collisional effects in nonthermal electron beams with pulsed injection (1990)
    Springer
    Solar physics 129 (1990), S. 325-341 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The evolution of a pulse of nonthermal electrons, with a truncated power-law spectrum, injected into a uniformly dense coronal plasma, is studied by the 1-D particle simulation of return current and direct collisional effects. The beam pulse injection profile varies gradually enough for total current neutrality, and a steady-state Ohm's law for the return current, to apply at each point and time. Quasi-linear relaxation of the beam is deliberately ignored in order to isolate the modification of return current effects by pulsed injection. When parameters are such that return current losses dominate, the resulting energetic electron trajectories differ very markedly between the pulsed injection case and the continuous injection case for the same beam current at injection. In general, the energy losses to return current dissipation are lower in the pulsed case. This is due to the rapid fall in the local beam current as the pulse disperses in space. Conditions necessary for the beam to comprise a series of pulses sufficiently separated for dispersion effects to be significant are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159044
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Energy release in solar flares (1994)
    Springer
    Solar physics 153 (1994), S. 19-31 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Team 2 of the Ottawa FLARES 22 Workshop dealt with observational and theoretical aspects of the characteristics and processes of energy release in flares. Main results summarized in this article stress the global character of the flaring phenomenon in active regions, the importance of discontinuities in magnetic connectivity, the role of field-aligned currents in free energy storage, and the fragmentation of energy release in time and space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712490
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Effect of electron beams during solar flares (1990)
    Springer
    Solar physics 130 (1990), S. 243-251 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Electron bombardment of the solar atmosphere has two effects: one is to enhance hydrogen recombination emission, the other is to increase the opacity via an increase of H− population. The first effect is the most important in the upper part of the atmosphere and the second in the lower part. We predict that, when enhanced absorption dominates in the part of the atmosphere where radiation originates, there will be a decrease in the white-light emission, leading to a ‘negative flare’, or what we call a ‘Black-Light Flare’. This phenomenon occurs only for a short duration, not more than ∼ 20 s. ‘Black-Light Flares’ have already been observed in the case of flare stars and we suggest here that they could also be present on the Sun, just prior to a White-Light Flare.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156792
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Asymmetric flux loops in active regions, II (1990)
    Springer
    Solar physics 127 (1990), S. 51-64 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We propose that magnetic flux loops in the subphotospheric layers of the Sun are seriously asymmetrical as a consequence of the drag force exerted on them because of the different rotational rate of the surrounding plasma. In numerical models of stationary slender flux loops in the plane parallel approximation we show that a serious tilt is both possible and probable. Observational facts (see van Driel-Gesztelyi and Petrovay, 1989; Paper I) strongly support the case for high asymmetry. The different stability of p and f spots may also be related to such an asymmetry. The tilts are very sensitive to the rotational profile and to the magnetic field structure. Nevertheless the characteristic maximal tilts can be tentatively estimated to be 20° for thin flux tubes and 5° for thick tubes. For two of the five observational consequences of such a tilt (described in detail in Paper I) order-of-magnitude estimates of the effects are given. The estimates are in reasonable accord with observations. We also explore the possibilities of an inverse treatment of the problem whereby subphotospheric rotation and/or flux tube shapes can be inferred from observations of velocities of photospheric spot motions. In particular we demonstrate how analytic inverse solutions can be obtained in special cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00158513
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The role of active Bradyrhizobium japonicum in iron stress response of soybeans (1991)
    Springer
    Plant and soil 130 (1991), S. 225-230 
    Details
    ISSN: 1573-5036
    Keywords: Bradyrhizobium japonicum ; chlorosis ; Glycine max ; nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this study was to identify the sites of H-ion exudation and Fe(III) reduction along both inoculated and non-inoculated roots of A7 and T203 soybeans. A split-root system was used in which half the roots of each plant were inoculated and actively fixing nitrogen and the other half were not. Expectedly, the Fe-stress response was strong on both sides of the split-root system in the +N-Fe treatment of variety A7 (inactive nodules) but not of variety T203. The Fe-stress response of A7 was enhanced by the presence of active nodules. Variety T203 is Fe inefficient and normally fails to produce any Fe-stress response, but in the absence of nitrogen and iron (−N−Fe), inoculated roots responded to Fe stress with exudation of both H-ions and reductants. Intact split-root systems were embedded in agar to determine the location of H-ion exudation and Fe(III) reduction. On the inoculated side of the −N−Fe and −N+Fe treatments (active nodules) of both soybean varieties, H-ion production was associated mainly with the active nodules. However, quantities of H-ion release were much greater under Fe stress (−N−Fe) than with adequate Fe (−N+Fe). Reduction of Fe(III) to Fe(II) was found only on the nodulated side with T203, but on both sides with A7. In variety T203 the Fe reduction was associated with younger roots located just below the nodule clusters on the inoculated side of the −N treatments. Active nodules appear to play a key role in the Fe-deficiency stress response of T203 soybean.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011877
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Iron-efficient and iron-inefficient oats and corn respond differently to iron-deficiency stress (1991)
    Springer
    Plant and soil 130 (1991), S. 165-172 
    Details
    ISSN: 1573-5036
    Keywords: Avena byzantina C. Koch. ; BPDS ; corn ; EDDHA ; grasses ; iron-efficient ; iron-inefficient ; oats ; reduction ; Zea mays L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Iron-efficient (WF9 corn and Coker 227 oat) and Fe-inefficient (ys1 corn and TAM 0–312 oat) cultivars were comparatively tested for their response to Fe-deficiency stress induced by the use of either ferrous or ferric chelators. Corn and oats were grown in 20 μM Fe with 0, 60, and 120 μM BPDS and 40 μM Fe with 0, 120, and 240 μM BPDS and 20 μM Fe with 0 and 40 μM EDDHA. All four cultivars tested, both Fe-efficient and Fe-inefficient, continuously reduced Fe3+ to Fe2+ at a low level as evidenced by the production of Fe2+ (BPDS)3 in test nutrient solutions over time. Severity of chlorosis increased as more BPDS was added to the nutrient solutions for both WF9 and ys1 corn, but unlike corn, Coker 227 and TAM 0-312 oats were both able to obtain Fe from the Fe2+ (BPDS)3 complex and were less chlorotic as a result. In short-term (4-hour) in vivo measurements, iron-stressed WF9 (Fe-efficient) corn reduced more Fe3+ to Fe2+ than similarly stressed ys1 corn, Coker 227 oat or TAM 0-312 oat. Thus, at the same time that Fe-efficient WF9 corn reduces more Fe than the other cultivars, it is also unable to compete with BPDS for that Fe in the nutrient solution. These differences coupled with the observation that only Coker 227 oat produced measureable iron solubilizing substances (phytosiderophores) suggest that these two species differ in their mechanisms for obtaining Fe during Fe-deficiency stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011871
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    A genetically related response to iron deficiency stress in muskmelon (1991)
    Springer
    Plant and soil 130 (1991), S. 87-92 
    Details
    ISSN: 1573-5036
    Keywords: BPDS ; Cucumis melo L. ; EDDHA ; ferric reduction ; iron efficient ; iron inefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A mutant muskmelon (Cucumis melo L.) with characteristic Fe-deficiency chlorosis symptoms was compared to related cultivars in its ability to obtain Fe via the widely known Fe-stress response mechanisms of dicotyledonous plants. The three cultivars (fefe, the ‘Fe-inefficient’ mutant; Mainstream and Edisto, both ‘Fe efficient’ plants) were grown in nutrient solution in either 0 or 3.5 mg L-1 Fe as FeCl3. None of the three cultivars released ‘reductants’ or ‘phytosiderophores’, but both Edisto and Mainstream produced massive amounts of H+ ions to reduce and maintain the pH of nutrient solutions below pH 4.0. The roots of these two Fe-efficient cultivars were also capable of reducing Fe3+ to Fe2+. These responses maintained green plants, resulted in high leaf Fe in both Edisto and Mainstream, and produced Mn toxicity in Mainstream. The lack of Fe-deficiency stress response in fefe not only affected leaf Fe concentration and chlorosis, but also resulted in reduced uptake of Mn. The importance of reduced Fe (Fe2+) to the Fe-efficient cultivars was confirmed by growing the cultivars with BPDS (4, 7-diphenyl-1, 10-phenanthroline disulfonic acid, a ferrous chelator) and EDDHA [ethylene-diamine di (0-hydroxphenylacetic acid)] (a ferric chelator), and observing increased chlorosis and reduced Fe uptake in BPDS grown plants. The Fe-deficiency response observed in these cultivars points out the diversity of responses to Fe deficiency stress in plants. The fefe mutant has a limited ability to absorb Fe and Mn and perhaps could be used to better understand Mn uptake in plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011860
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Comparative evaluation of iron solubilizing substances (phytosiderophores) released by oats and corn: Iron-efficient and iron-inefficient plants (1991)
    Springer
    Plant and soil 130 (1991), S. 157-163 
    Details
    ISSN: 1573-5036
    Keywords: Avena byzantina C. Koch. ; corn ; grass ; iron efficient ; iron inefficient ; oats ; phytosiderophore ; Zea mays L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Release of phytosiderophores from barley (Hordeum vulgare L.) in response to Fe-deficiency stress prompted further testing of other graminaceous (grass) species for phytosiderophore release and results have prompted characterization of these plants into a Strategy II designation. This classification denotes an enhanced release of phytosiderophore in response to Fe-deficiency stress with a concomitant uptake of Fe by the plant. The objective of this study was to determine if Fe-inefficient and Fe-efficient corn (Zea mays L.) differ in their release of ‘Fe solubilizing substances’ in response to Fe-deficiency stress. We have not identified the specific structure of these substances but refer to them as ‘phytosiderophores’ to further characterize their behavior. By our indirect method, there was no measurable release of Fe solubilizing substances (phytosiderophores) from either the Fe-efficient WF9 or the Fe-inefficient ys1 corn despite WF9 being greener and apparently more Fe efficient than ys1. Fe-efficient Coker 227 oats (Avena byzantina C. Koch.) has been found to release a phytosiderophore whereas the Fe-inefficient TAM 0-312 does not. Iron-stressed Coker 227 oats released Fe solubilizing substances when grown in the same solution with WF9 corn which resulted in greening and Fe uptake by WF9 corn. Iron efficiency in these two graminaceous species appears to be controlled by different mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011870
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...