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  • 1
    Electronic Resource
    Electronic Resource
    Observation of stratospheric ozone depletion in rocket exhaust plumes (1997)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 390 (1997), S. 62-64 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Although modelling studies have predicted that particulate and reactive gas-phase species in the exhaust plume of large rockets might cause significant local ozone depletion, the actual response of the stratosphere after rocket launches has never been directly determined. Here we report ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/36318
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  • 2
    Electronic Resource
    Electronic Resource
    STORAGE OF ‘SWEETHEART’ CHERRIES IN SEALED PLASTIC FILM (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food quality 20 (1997), S. 0 
    Details
    ISSN: 1745-4557
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: ‘Sweetheart’ cherries were sealed in perforated or nonperforated polyethylene bags and stored for 6 weeks in air at 0C. Samples were removed after 1, 2, 4 and 6 weeks of storage and evaluated for fruit and sensory quality. Volatile analyses were done on samples kept in storage for 2, 4, 6, 8 and 9 weeks. Atmospheres after 6 weeks of storage were approximately 4.6% O2 and 10% CO2 for the perforated bags (1993) and 6.6% O2 and 3.5% CO2 for the non-perforated bags (1994). Fruit brightness (L* value), firmness and titratable acidity declined during storage. Skin color (hue angle) decreased slightly in redness over the 6-week storage period. Sensory evaluation in 1993 showed a decline in fruit appearance and flavor with storage duration. Texture and juiciness did not change. Acceptability remained high for the first 4 weeks of storage. Twenty-seven volatiles were identified by head-space analysis (1993). Little change occurred in volatile production except for acetaldehyde which increased sharply from week 2 to 4 and ethanol which increased sharply between week 8 and week 9. Butyl acetate behaved much like acetaldehyde. Modified atmosphere packaging maintained high fruit luster and green stems. No differences in fruit quality were observed with bag type, but storage appears to be limited to 4 weeks for ‘Sweetheart’ cherries because of flavor loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4557.1997.tb00463.x
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  • 3
    Electronic Resource
    Electronic Resource
    The analysis and interpretation of solar X-ray photographs (1977)
    Springer
    Solar physics 53 (1977), S. 417-433 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper discusses the methods used to analyse and interpret X-ray filtergrams obtained by solar soft X-ray telescopes such as the S-056 Skylab instrument. First, an appropriate definition of the line-of-sight emission measure ξ L(T) is developed, and it is shown how the X-ray data may be analysed to obtain an approximation to ξ L(T). The accuracy of this approximation is severely limited by the mathematical ill-conditioning of the problem, and additional constraints on the solutions must be imposed through the use of a specific model of the coronal region under study. Such a model is also required for the proper interpretation of the results in terms of coronal plasma processes. Examples of such models are provided and the forms of ξ L(T) derived from them compared with other, semi-empirical forms. The ‘filter ratio method’ (a simplified form of analysis in which the region under study is assumed isothermal) is discussed. It is shown that in the presence of line-of-sight temperature gradients, the values of ‘effective temperature’ and ‘emission measure’ yielded by this method cannot be directly related to the physical state of the plasma and so are of little utility in the study of coronal processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160285
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  • 4
    Electronic Resource
    Electronic Resource
    The Polar Ionospheric X-ray Imaging Experiment (PIXIE) (1995)
    Springer
    Space science reviews 71 (1995), S. 385-408 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Polar Ionospheric X-ray Imaging Experiment (PIXIE) is an X-ray multiple-pinhole camera designed to image simultaneously an entire auroral region from high altitudes. It will be mounted on the despun platform of the POLAR spacecraft and will measure the spatial distribution and temporal variation of auroral X-ray emissions in the 2 to 60 keV energy range on the day side of the Earth as well as the night. PIXIE consists of two pinhole cameras integrated into one assembly, each equipped with an adjustable aperture plate that allows an optimum number of nonoverlapping images to be formed in the detector plane at each phase of the satellite's eccentric orbit. The aperture plates also allow the pinhole size to be adjusted so that the experimenter can trade off spatial resolution against instrument sensitivity. In the principal mode of operation, one aperture plate will be positioned for high spatial resolution and the other for high sensitivity. The detectors consist of four stacked multiwire position-sensitive proportional counters, two in each of two separate gas chambers. The front chamber operates in the 2–12 keV energy range and the rear chamber in the 10–60 keV range. All of the energy and position information for each telemetered X-ray event is available on the ground. This enables the experimenter to adjust the exposure timepostfacto so that energy spectra of each X-ray emitting region can be independently accumulated. From these data PIXIE will provide, for the first time, global images of precipitated energetic electron spectra, energy inputs, ionospheric electron densities, and upper atmospheric conductivities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00751336
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  • 5
    Electronic Resource
    Electronic Resource
    Spectral development of a solar X-ray burst observed on OSO-7 (1973)
    Springer
    Solar physics 28 (1973), S. 175-185 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The UCSD solar X-ray instrument on the OSO-7 satellite observes X-ray bursts in the 2–300 keV range with 10.24 s time resolution. Spectra obtained from the proportional counter and scintillation counter are analyzed for the event of November 16, 1971, at 0519 UT in terms of thermal (exponential spectrum) and non-thermal (power law) components. The energy content of the approximately 20 × 106K thermal plasma increased with the 60 s duration hard X-ray burst which entirely preceded the 5 keV soft X-ray maximum. If the hard X-rays arise by thick target bremsstrahlung, the nonthermal electrons above 10 keV have sufficient energy to heat the thermally emitting plasma. In the thin target case the collisional energy transfer from non-thermal electrons suffices if the power law electron spectrum is extrapolated below 10 keV, or if the ambient plasma density exceeds 4 × 1010 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152922
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  • 6
    Electronic Resource
    Electronic Resource
    Observations of the structure and evolution of solar flares with a soft X-ray telescope (1975)
    Springer
    Solar physics 45 (1975), S. 199-216 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 132 soft X-ray flare events have been observed with The Aerospace Corporation/Marshall Space Flight Center S-056 X-ray telescope that was part of the ATM complement of instruments aboard Skylab. Analyses of these data are reported in this paper. The observations are summarized and a detailed discussion of the X-ray flare structures is presented. The data indicated that soft X-rays emitted by a flare come primarily from an intense well-defined core surrounded by a region of fainter, more diffuse emission. Loop structures are found to constitute a fundamental characteristic of flare cores and arcades of loops are found to play a more important role in the flare phenomena than previously thought. Size distributions of these core features are presented and a classification scheme describing the brightest flare X-ray features is proposed. The data show no correlations between the size of core features and: (1) the peak X-ray intensity, as indicated by detectors on the SOLRAD satellite; (2) the rise time of the X-ray flare event, or (3) the presence of a nonthermal X-ray component. An analysis of flare evolution indicates evidence for preliminary heating and energy release prior to the main phase of the flare. Core features are found to be remarkably stable and retain their shape throughout a flare. Most changes in the overall configuration seem to be the result of the appearance, disappearance or change in brightness of individual features, rather than the restructuring or re-orientation of these features. Brief comparisons with several theories are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152232
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Further remarks on the analysis and interpretation of solar X-ray photographs (1978)
    Springer
    Solar physics 60 (1978), S. 311-314 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the light of a recent discussion by Gerassimenko and Nolte (1978) we re-examine the use of the ‘filter ratio method’ for determining the thermodynamic parameters of coronal plasmas. We conclude that the method gives reliable results only when the observed plasma is nearly isothermal and that presently available data do not demonstrate that active region plasmas generally meet this condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156531
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal and nonthermal phenomena in solar flare loops at 20 cm wavelength and in X-rays (1983)
    Springer
    Solar physics 83 (1983), S. 3-14 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present X-ray images from the P78-1 satellite for a long-lasting burst at 20 cm wavelength mapped with the Very Large Array on 19 May, 1979 by Velusamy and Kundu (1981). The decimeter wave observations were originally interpreted in terms of two models, one invoking thermal electrons radiating at low harmonics of the gyrofrequency, and the other invoking mildly relativistic electrons emitting gyrosynchrotron radiation. If indeed the 20 cm source is thermal, it should also be visible in soft X-rays, while if it is nonthermal, the soft X-ray emission should be weak or spatially or temporally distinct from the 20 cm burst. We find that only one of the three 20 cm sources was approximately co-spatial with the soft X-ray source, and that it was only partially thermal. The 20 cm burst is therefore primarily decimeter type IV emission from mildly relativistic electrons of the post-flare phase. The long lifetime (≳ 2h) and smooth temporal variation of the burst belie its nonthermal nature and suggest continuous acceleration as well as long term storage of energetic electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148239
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  • 9
    Electronic Resource
    Electronic Resource
    Fe XVIII EMISSION LINES IN SOLAR X-RAY SPECTRA (1997)
    Springer
    Solar physics 171 (1997), S. 93-102 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have calculated intensity ratios for emission lines of Fexviii in the 13–94 Å wavelength range at electron temperatures characteristic of the solar corona, T e = 2–10 x 106 K. Our model ion includes data for transitions among the 2s 22p 5 , 2s2p 6, 2s 22p 43l, and 2s2p 53l (l = s, p, and d) states. Test calculations which omit the 2s2p 53l levels show that cascades from these are important. We compare our results with observed ratios determined from four solar X-ray instruments, a rocket-borne spectrograph, and spectrometers on the P78–1, OV1–17 and Solar Maximum Mission (SMM) satellites. In addition, we have generated synthetic spectra which we compare directly with flare observations from SMM. Agreement between theory and observation is generally quite good, with differences that are mostly less than 30%, providing limited support for the accuracy of the atomic physics data used in our calculations. However, large discrepancies are found for ratios involving the 2s 22p 5 2P3/2- 2s2p 6 2S line at 93.84 Å, which currently remain unexplained. Our analysis indicates that the FeXVIII feature at 15.83 Å is the 2s 22p 5 2P3/2 - 2s 22p 4(3P)3s 4P3/2 transition, rather than 2s 22p 5 2P3/2 - 2s 22p 4(3P)3s 2P3/2, as suggested by some authors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004934523755
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