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  • 1
    Electronic Resource
    Electronic Resource
    The structure of Venus’ middle atmosphere and ionosphere (2007)
    [s.l.] : Nature Publishing Group
    Nature 450 (2007), S. 657-660 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The atmosphere and ionosphere of Venus have been studied in the past by spacecraft with remote sensing or in situ techniques. These early missions, however, have left us with questions about, for example, the atmospheric structure in the transition region from the upper troposphere to the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06239
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  • 2
    Electronic Resource
    Electronic Resource
    Interleukin-4 in mononuclear cells and histamine release in peripheral blood from an atopic patientin vitro (1992)
    Springer
    Inflammation research 36 (1992), S. C298 
    Details
    ISSN: 1420-908X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In this study, we investigated whether stimulated and unstimulated peripheral blood mononuclear cells (PBMNCs) from atopic and healthy donors produce interleukin-4 (IL-4)in vitro in response to various stimulants. Furthermore we examined if histamine release in leucocyte incubates from the same donors corresponded to the induced IL-4 production. We found a significantly increased IL-4 production in both stimulated and unstimulated PBMNCs during the first 48 h in culture (p〈0.01,n=18 cultures). Comparing atopic to healthy PBMNCs no significant differences in the IL-4 production could be detected (p〉0.1). The kinetics of the induced IL-4 production showed a maximum after 24 h in culture in the stimulated atopic and healthy samples. Both mitogens PHA and PWM induced a similar pattern of IL-4 production. As for histamine liberation, it was significantly increased in the atopic incubates compared with the healthy samples. From these data it can be suggested that PBMNCs from atopic and healthy donors are able to produce small amounts (3–8 pg/ml) of IL-4in vitro, but this IL-4 production does not correspond to elevated histamine release by the atopic patient's leucocytesin vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01997356
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  • 3
    Electronic Resource
    Electronic Resource
    Radio occultation studies with Solar Corona Sounders (1995)
    Springer
    Space science reviews 72 (1995), S. 77-80 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Solar Corona Sounders (SCS), a mission designed to utilize the radio occultation technique for investigations of the inner heliosphere, was submitted to ESA in response to a call for new mission concepts. The SCS platforms are two small multifrequency transmitters placed at the “anti-Earth” position (superior solar conjunction) for continuous radio sounding of the solar corona. Appropriately specifying certain orbital elements for the heliocentric trajectories of the spacecraft, their radially-aligned positions as seen from Earth appear to circle the solar disk over the course of a year. The two radio sources would be most effectively positioned at apparent solar distances inside and outside the nominal solar wind critical point, respectively, e.g., at ∼3 R⊙ and ∼10 R⊙. Radio parameters to be measured using the linearly polarized, coherent dual-frequency links to ground include the group time delay, signal amplitude, the phase (Doppler) shift, linewidth, and Faraday rotation. The link frequencies for coronal sounding observations this close to the Sun could be the interplanetary standards at S-band (2.3 GHz) and X-band (8.4 GHz). These measurements are used to derive both mean values and fluctuation spectra of such coronal parameters as the electron density, the solar wind velocity, and the magnetic field. The geometry afforded by the two radio ray paths from the SCS transmitters would provide unprecedented observations of the radial evolution of dynamic coronal events such as coronal mass ejections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768757
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  • 4
    Electronic Resource
    Electronic Resource
    Galileo radio science investigations (1992)
    Springer
    Space science reviews 60 (1992), S. 565-590 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The radio science investigations planned for Galileo's 6-year flight to and 2-year orbit of Jupiter use as their instrument the dual-frequency radio system on the spacecraft operating in conjunction with various US and German tracking stations on Earth. The planned radio propagation experiments are based on measurements of absolute and differential propagation time delay, differential phase delay, Doppler shift, signal strength, and polarization. These measurements will be used to study: the atmospheric and ionospheric structure, constituents, and dynamics of Jupiter; the magnetic field of Jupiter; the diameter of Io, its ionospheric structure, and the distribution of plasma in the Io torus; the diameters of the other Galilean satellites, certain properties of their surfaces, and possibly their atmospheres and ionospheres; and the plasma dynamics and magnetic field of the solar corona. The spacecraft system used for these investigations is based on Voyager heritage but with several important additions and modifications that provide linear rather than circular polarization on the S-band downlink signal, the capability to receive X-band uplink signals, and a differential downlink ranging mode. Collaboration between the investigators and the space-craft communications engineers has resulted in the first highly-stable, dual-frequency, spacecraft radio system suitable for simultaneous measurements of all the parameters normally attributed to radio waves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216868
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  • 5
    Electronic Resource
    Electronic Resource
    The mean coronal magnetic field determined from HELIOS Faraday rotation measurements (1971)
    Springer
    Solar physics 109 (1971), S. 91-105 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Coronal Faraday rotation of the linearly polarized carrier signals of the HELIOS spacecraft was recorded during the regularly occurring solar occultations over almost a complete solar cycle from 1975 to 1984. These measurements are used to determine the average strength and radial variation of the coronal magnetic field at solar minimum at solar distances from 3–10 solar radii, i.e., the range over which the complex fields at the coronal base are transformed into the interplanetary spiral. The mean coronal magnetic field in 1975–1976 was found to decrease with radial distance according to r −α, where α = 2.7 ± 0.2. The mean field magnitude was 1.0 ± 0.5 × 10 −5 tesla at a nominal solar distance of 5 solar radii. Possibly higher magnetic field strengths were indicated at solar maximum, but a lack of data prevented a statistical determination of the mean coronal field during this epoch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167401
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  • 6
    Electronic Resource
    Electronic Resource
    Coronal velocity measurements with Ulysses: multi-link correlation studies during two superior conjunctions (1999)
    Springer
    Solar physics 184 (1999), S. 157-172 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A well-known method for studying the solar wind very close to the Sun (heliocentric distances: 4 to 40 solar radii) is by radio sounding between a spacecraft at superior conjunction and the Earth. The Ulysses Solar Corona Experiment was performed at the spacecraft's two solar conjunctions in summer 1991 and winter 1995, during which dual-frequency ranging and Doppler observations were conducted globally on a nearly continuous basis at the NASA Deep Space Network and other ground stations. The dual-frequency Doppler measurements were used to determine coronal plasma velocities by a cross-correlation analysis during those occasions when tracking data were recorded simultaneously at two well-separated ground stations. A ‘filtering’ technique was developed to suppress noise and enhance the 2-station correlations, a procedure particularly effective at small solar offsets. From the electron content measurements during the two solar conjunctions it was found that regions of higher electron density tend to occur when the two-station correlations yield slower outward flow velocities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005097028501
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  • 7
    Electronic Resource
    Electronic Resource
    Long-Term Radio Scintillation Variations in the Circumsolar Plasma (1999)
    Springer
    Solar physics 189 (1999), S. 387-398 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Long-term scintillation measurements of the solar wind formation zone at solar elongations ranging from 1°–8° (Sun impact parameters: 4–30 R ⊙) were recorded using the water maser source IRC-20431 at the wavelength λ=1.35 cm during its annual solar occultations in December 1981–1998. Dramatic changes in the spatial dependence of the scintillation index were recorded over the course of the 11-year solar cycle. Markedly diminished scattering, attributed to a pronounced heliolatitude effect, was observed at the closest solar approach distances in the years around solar activity minimum. From parallel investigations of the solar magnetic field structure it was determined that the field strength at the source of the solar wind streamlines is the governing factor for the solar wind acceleration process. Particularly apparent in the scintillation data during solar activity minimum is the increasing role of the polar coronal holes with their associated open magnetic field structure. The dependence of the solar scattering intensity on heliolatitude fades in the years of high solar activity as the level of scintillations increases at polar latitudes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005271415011
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