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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 16 (1990), S. 1731-1738 
    ISSN: 1573-1561
    Keywords: Ilex opaca ; Aquifoliaceae ; Lymantria dispar ; gypsy moth ; Lepidoptera ; Lymantriidae ; saponins ; siaresinolic acid ; qualitative plant defenses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A greater variety of qualitative chemical defenses has been reported in eastern forest trees than might be expected from current interpretation of the plant apparency theory. For the gypsy moth there is an association between the occurrence of alkaloids and unfavorability of certain tree species, as well as the presence of saponins. The latter association, however, is not statistically significant. Species in the genusIlex have been reported to contain both alkaloids and saponins (Barbosa and Krischick, 1987). In this study, determinations were made of the occurrence of alkaloids and saponins inI. opaca and their changes in concentration over time. No alkaloids were detected. Saponins were isolated, and the aglycone siaresinolic acid was identified. Saponin concentration changes seasonally, being highest in early May and lowest in early June leaves.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-1561
    Keywords: Lymantria dispar ; Lepidoptera ; Lymantriidae ; Liriodendron tulipifera ; Acer rubrum ; Cornus florida ; gypsy moth ; alkaloids ; N-methyl-crotsparine ; 1-(3,4,5-trimethoxyphenyl)-2-(4-allyl-2,6-dimethoxy)propane ; bisphenylpropanoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Early theories on plant chemical defense against herbivory emphasized that apparent and unapparent plants were primarily defended by different types of compounds. More and more evidence suggests that both quantitative and qualitative defenses are found in apparent plants and that they can play a defensive role against herbivores. A survey of the literature on the gypsy moth suggests not only that there is a large variety of qualitative compounds, as well as the expected quantitative ones, but that unfavored hosts of the gypsy moth are associated with the presence of alkaloids. Foliage of three tree species,Liriodendron tulipifera L.,Acer rubrum L., andCornus florida L., was examined to confirm the presence of alkaloids and other major secondary metabolites. The known sesquiterpene lactone, lipiferolide, and the sugar derivative, liriodendritol, were components ofL. tulipifera leaves, along with a bisphenylpropanoid previously found only in nutmeg. Alkaloid content [i.e., (−)-N-methylcrotsparine content] was low and leaves tested positive for HCN. Leaves ofA. rubrum L. were examined for the presence of gramme, but none could be detected. No alkaloids were detected inCornus florida.
    Type of Medium: Electronic Resource
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  • 3
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    Unknown
    In:  Other Sources
    Publication Date: 2011-08-18
    Description: This paper examines several mechanisms for generation of field-aligned currents in the magnetospheres of earth and Jupiter. Implications for planetary radio emission in relation to field-aligned current systems are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 4
    Publication Date: 2019-06-28
    Description: The flyby of Voyager 1 at Saturn resulted in the detection of a large variety of plasma waves, e.g., chorus, hiss, and electron cyclotron harmonics. Just before the outbound equator crossing, at about 6.1 R(sub s), the Voyager 1 plasma wave instrument detected a strong, well-defined low-frequency enhancement. Initially it was suggested that plasma waves might be responsible for the spectral feature but more recently dust was suggested as at least a partial contributor to the enhancement. In this report we present evidence which supports the conclusion that dust contributes to the low-frequency enhancement. A new method has been used to derive the dust impact rate. The method relies mainly on the 16-channel spectrum analyzer data. The few wide band waveform observations available (which have been used to study dust impacts during the Voyager 2 ring plane crossing) were useful for calibrating the impact rate from the spectrum analyzer data. The mass and, hence, the size of the dust particles were also obtained by analyzing the response of the plasma wave spectrum analyzer. The results show that the region sampled by Voyager 1 is populated by dust particles that have rms masses of up to few times 10(exp -11) g and sizes of up to a few microns. The dust particle number density is on the order of 10(exp -3) m(exp 3). The optical depth of the region sampled by the spacecraft is 1.04 x 10(exp -6). The particle population is centered about 2500 km south of the equatorial plane and has a north-south thickness of about 4000 km. Possible sources of these particles are the moons Enceladus and Tethys whose orbits lie within the E-ring radial extent. These results are in reasonable agreement with photometric studies and numerical simulations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-194694 , NAS 1.26:194694 , U-OF-IOWA-93-19
    Format: application/pdf
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  • 5
    Publication Date: 2019-06-28
    Description: The effects of a combined convection and corotation electric field across the Io plasma torus are considered. A dawn-to-dusk electric field E sub C will modify the orbits of charged particles shifting them toward dawn. The radial drift imposed by the perturbed orbits implies a local time-dependent modulation of low-energy ion and electron temperatures with particles hotter at dusk than at dawn. With E sub C approximately 4 mV/m, the orbits near 6 Jupiter radii would be shifted by approximately 0.2 Jupiter radius. Then the electron temperature would be 20% higher at dust than at dawn, an effect which could explain the local time asymmetry of EUV intensity found by the Voyager ultraviolet spectrometer. The source of the convection electric field is internal to the magnetosphere, and is attributed to the tailward escape of Iogenic and Jovian plasma beyond the Alfven surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 10; Mar. 198
    Format: text
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  • 6
    Publication Date: 2019-06-28
    Description: The effects of boundary surface fluctuations on a spectrum of electromagnetic radiation trapped in a high Q (quality) cavity are considered. Undulating walls introduce small frequency shifts at reflection to the radiation, and it is argued that the process is entirely analogous to both Fermi (particle) acceleration and inverse Compton scattering. A Fokker-Planck formalism is pursued; it yields a diffusion equation in frequency for which the Green's function and steady-state solutions are found. Applying this analysis to the Jovian continuum radiation discovered by Voyager spacecraft, it is suggested that characteristic diffusion times are greater than 1 year, and that in order to account for the steep frequency spectra observed, an unidentified loss mechanism must operate in the cavity with a decay time constant approximately equal to the characteristic diffusion time divided by 28. A radiator-reactor model of the cavity is investigated to provide an estimate for the intrinsic luminosity of the low frequency (approximately 100 Hz) continuum source whose power is approximately 7 x 10 to the 6th W.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 243
    Format: text
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  • 7
    Publication Date: 2019-06-28
    Description: A theoretical model for generation of banded electrostatic emissions by low density, superthermal electrons is developed for application to Jupiter's magnetosphere. The model employs a power law form for the energy dependence and a loss cone pitch angle distribution of the superthermals to drive convective instability of Bernstein modes. A direct correspondence between spectral features of the 3/2 band and resonant superthermal electrons is found. The concept of a critical flux of resonant electrons able to provide 10 e-foldings of electric field amplification yields an explicit relation in terms of the background thermal electron pressure. This result is used to construct a theoretical/empirical model of thermal electron density and temperature from 6-20 Jupiter radii in the Jovian magnetosphere which suggests that the electron temperature is less than the ion temperature which is approximately equal to 10 times the electron temperature in this region. Finally, wave ray paths are computed for propagation in the magnetic equator and in the magnetic meridional plane of a dipole magnetic field. These ray paths suggest that intense wave activity is tightly confined to a small latitudinal extent, less than + or - approximately 4 deg, about the magnetic equator.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 1
    Format: text
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  • 8
    Publication Date: 2019-06-27
    Description: Observations by the plasma wave receivers on Voyagers 1 and 2 show that a wide variety of electrostatic waves are present within the Jovian magnetosphere and that the Jovian electrostatic waves are for the most part very similar to those observed in the terrestrial magnetosphere. Bands of emission near the upper hybrid resonance frequency in the dayside outer magnetosphere are detected between higher harmonics of the electron gyrofrequency. Inside of about 23 Jupiter radii, electron cyclotron harmonic emissions appear to be durable features of the inner Jovian magnetosphere and are extremely well confined to the Jovian magnetic equator. The cyclotron emissions extend from just above the local electron gyrofrequency to the upper hybrid resonance frequency.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Jan. 198
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  • 9
    Publication Date: 2019-06-28
    Description: Major observational features of magnetospheric VLF-LF radio noise that have been uncovered by the IMP, Hawkeye and ISEE satellites, are examined with emphasis on the capabilities of the noise to diagnose local and remote plasma parameters. The relationship of the radiation to not less than 1-mV/m electrostatic upper hybrid emissions is assessed, and indirect observational evidence suggests that upper noise is associated with the generation of the VLF-LF radiation. Theoretical luminosities of mechanisms including synchrotron radiation, linear mode conversion of upper hybrid waves and nonlinear scattering of upper hybrid waves off plasma density irregularities are estimated, and the wave-wave scattering hypothesis is considered to be a viable mechanism if the presence of low-frequency waves as a scattering agent can be established.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Reviews of Geophysics and Space Physics; 20; May 1982
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  • 10
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    In:  Other Sources
    Publication Date: 2019-06-28
    Description: Dispersion properties of electrostatic waves in a multi-ion plasma are examined, with an analysis that incorporates the effects of finite temperature, finite parallel wavenumber, and wave growth/damping in a systematic development of equations. Numerical solutions and analytic formulas are given for an ion plasma consisting of H(+), O(+), and S(+) for application to Jupiter's magnetosphere. It is demonstrated how observations of plasma resonance lines may be used as a diagnostic of ion composition in magnetospheric plasma. This potential use of high-sensitivity/high-resolution plasma wave instrumentation may provide information necessary to resolve issues concerning the origin of plasmas in the earth's neighborhood.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 254
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