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561.
The observations of intensity reductions or absorption bursts in the solar decametric radio-continuum are reported. The reductions
are interpreted as the absorption of continuum radiation by a shock-generated ion-sound turbulence present in the layer above
the continuum level. The duration of the absorption is attributed to the lifetime of the ion-sound turbulence while the depth
of absorption is determined by the level of Langmuir waves generated as a result of absorption. 相似文献
562.
Methyl esters of saturated and unsaturated fatty acids were isolated as trace components from organic material suspended in seawater. Methyl palmitate and methyl stearate were accumulated from the filtrate by adsorption onto Amberlite XAD-2 resin. Identification of most methyl esters is based on the comparison of gas chromatographic retention indices and mass spectrometric fragmentation with those of authentic standard compounds. In cases where reference substances were not available, identification is based on mass spectrometric and gas chromatographic properties of the unknown compounds. 相似文献
563.
564.
We use three different dynamical models for describing the motion in the meridian plane of an elliptical galaxy. Orbital characteristics of two polynomial models are compared with those given by a logarithmic potential for a fixed axial ratio of the equipotential surfaces, We also study the effects of an asymmetric perturbation caused by a companion galaxy on the orbital behaviour of the above models. Finally we present some theoretical arguments in order to support the numerical results. 相似文献
565.
Ch. Hollenstein A. Geiger H.-G. Kahle G. Veis 《Geophysical Journal International》2006,164(1):182-191
566.
567.
568.
A whitefish population considered to consist of two morphologically similar subpopulations is analyzed. Since a reproductive
barrier existing earlier between the two subpopulations has lost its effectiveness, only one population exists today, having
a very long reproductive period.
相似文献
569.
This paper considers the solution of linear least squares problems arising in space geodesy, with a special application to
multi-station adjustment by a short arc method based on Doppler observations. We recall briefly the widely used second-order
regression algorithm due to Brown for reducing the normal equations system. Then we propose two algorithms which avoid the
use of the normal equations. The first one is a direct method that applies orthogonal transformations to the observation matrix
directly, in order to reduce it to upper triangular form. The solution is then obtained by backsubstitution. The second method
is iterative and uses a preconditioned conjugate gradient technique. A comparison of the three procedures is provided on data
of the second European Doppler Observation Campaign (EDOC-2). 相似文献
570.
Cryoturbated facies are found at the boundary between soil horizons and Cretaceous chalk. Several types of secondary calcite appear in soil horizons: orange coloured and rounded (partially dissolved) nodules, deeply coloured angular aggregates, transparent isolated rhombs and polycrystalline nodules, needles. The carbon and oxygen isotope compositions of these calcites are correlated: δ13C = 4.9δ18OPDB + 15.9End members of this correlation are the orange rounded nodules (δ13C ? + 8%., ) and the transparent angular polycrystalline nodules (δ13C ? ?13; δ18O ? ?6).Partially dissolved nodules have formed under periglacial climatic conditions. Crystallisation would have occurred under the following (equilibrium) environmental conditions: δ18OSMOW (soil solution) ?7, δ13C (gaseousCO2) ? ?5.2, t ? ?2°C. Soil solution was enriched in 18O by evaporation and atmospheric CO2 was enriched in 13C as compared to present day. Transparent polycrystalline nodules are compatible with present day environmental conditions: δ18O (soil solution) ranging from ?9 to ?4 and δ13C (soil CO2) ranging from ?24.5 to ?23. These nodules crystallize between May and October at soil temperatures ranging from 10 to 25°C, from evaporated soil solutions. Angular coloured aggregates may form under present day winter conditions for temperatures between 0 and 10°C. However they may also result from present accretion of fragments of periglacial nodules.All recent secondary calcite results from CO2 degassing and evaporation of soil solutions. Degassing is controlled by the gradient of CO2 partial pressure within the soil profile. During winter this gradient is low and the resulting calcite precipitation is not significant. During summer a large difference in pCO2 appears between the root zone and deep soil horizons. The degassing accounts for an increase of about 2‰ in δ13C of the total dissolved inorganic carbon and of the related solid carbonate. Evaporation is the main driving force for secondary calcite precipitation. 相似文献