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191.
192.
Organic‐rich deposits, uncovered during overburden removal from mantled gypsum karst at Knocknacran opencast gypsum mine, Co. Monaghan, are the best candidate to date for a last interglacial record in Ireland. The two till and organic‐rich deposits (preserved at different quarry elevations) were emplaced on to a Tertiary dolerite surface during high‐energy flood events and subsequently folded and faulted by movement towards sinkholes in underlying gypsum. Uranium–thorium disequilibrium dating suggests that the organic‐rich deposits in the upper section were hydrologically isolated at ca. 41 ka and those in the lower section at ca. 86 ka. Interpretation of the pollen content, although tentative because of the depositional and post‐depositional history of the material, suggests that the organic material originated in a warm stage possibly warmer than the post‐Eemian interstadials. The unusual setting of preservation may indicate that in situ, last interglacial deposits have generally been removed by erosion in Ireland. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
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194.
We examine time variations of the total magnetospheric output UT and the two geomagnetic indices AE and Dst during the magnetospheric storm of 31 December 1967–1 January 1968. A unique feature of this particular storm is that the solar-wind magnetosphere dynamo power ε was nearly constant for about 24 h by maintaining a high value of ~1019 erg s?1. It is found that UT was also nearly constant during that period, indicating that the magnetosphere is primarily a directly driven system. However, during an early epoch of the storm, the electrojet intensity levelled off, while the ring current began to grow during the same epoch. Subsequently, there occurred a sudden surge of the electrojet intensity, while the growth of the ring-current levelled off. Later variations of both the AE and Dst indices were very complex. After the surge, the AE index continued to decline and became as low as ~250 nT during the maximum epoch of this major storm (when the Dst decrease attained the maximum values). This trend can also be seen in many other major storms, but is often masked by changes of ε. One possible cause for such features for ε ? 1019erg/s?1 is that the neutral wind is generated by the (E × B) motion in the lower ionosphere, reducing the electrojet intensity and enhancing the ring-current particle-injection rate.  相似文献   
195.
Measurements of energy dissipation have been made with an oscillating tray apparatus similar to that of Bagnold (1946). Two different bed profiles were examined: one was sinusoidal and the other consisted of fins projecting perpendicularly fromthe plate in a regular two-dimensional pattern. The tests with the sinusoidal profile showed that significant variation in energy dissipation coefficient with Reynolds number occurs near the point at which vortex formation first starts to take place. It is suggested that Bagnold did not observe this effect because of the particular profile used in his tests. The tests with the finned beds showed that even when vortex formation is fully developed there is still some variation in energy dissipation coefficient with Reynolds number, at constant a/ks, at high Reynolds numbers.  相似文献   
196.
Summary. We give a systematic formulation and a rigorous justification of a perturbation technique for the computation of the eigenvalues and eigenfunctions of Love waves (and toroidal oscillations by an appropriate change for variables) in an anelastic medium with a constitutive law modelling geophysical media of current interest such as the Kelvin—Voigt Solid, the Maxwell Solid, the Standard Linear Solid, and the Standard Linear Solid with a continuous spectrum of relaxation times. We develop expressions relating the eigenvalues of eigenfunctions for Love waves in a continuously varying vertically stratified anelastic half-space to the corresponding elastic eigenvalues and eigenfunctions. Analytically, our correspondence principle has the form of a regular perturbation expansion in terms of a parameter for both the eigenvalues and eigenfunctions. The identification of ɛ is motivated by the dissipativity principle of viscoelasticity theory. Moreover, we show that our correspondence principle applies respectively only in the high and low frequency range for the Maxwell and Kelvin—Voigt Solids. Outside of the applicable range of frequencies, our correspondence principle yields no useful information. For the family of Standard Linear Solids it is uniformly applicable for all non-zero frequencies.
We also derive an explicit formula to estimate the radius of convergence of our perturbation expansions. This estimate of the radius of convergence for each eigenvalue and eigenfunction is functionally defined by the constitutive model for the anelastic medium. The estimate is frequency dependent and depends on the separation distance between the eigenvalue and the remainder of the spectrum of the corresponding elastic problem.  相似文献   
197.
The recent twelve-state R-matrix calculations of electron excitation rates in Ciii by Berrington are used to derive level populations applicable to the solar transition region. Line ratios R = I(2p 2 3 P e - 2s2p 3 P °)/I(2s2p 1 P ° - 2s 2 1 S e ) and R 2=I(2p 2 1 S e - 2s2p 1 P °)/I(2p 2 3 P e - 2s2p 3 P °) deduced from these data in conjunction with the relevent transition probabilities are found to be in much better agreement with the observed quiet Sun values than those determined from the level population calculations of Keenan et al.  相似文献   
198.
199.
The effect of a transverse magnetic field and of the viscosity diffusion on the free-convection flow of an electrically-conducting incompressible fluid past a uniformally accelerated vertical plate is discussed. A finite difference method has been used to obtain a numerical solution. The influence of the various parameters on the flow field is discussed.  相似文献   
200.
For several years now, an experimental simulation of Titan's atmosphere has been on going at LISA. A cold plasma is established in a gas mixture representative of the atmosphere of the satellite. In these experiments, more than 70 organic compounds have been identified, including the first identification in this type of experimental simulation of C4N2 already detected in its solid form on Titan, which suggests that the setup correctly mimics the chemistry of Titan's atmosphere.We have carried out the first experimental simulation including O-containing compounds in order to study the influence of the presence of CO on the chemical behavior of Titan's atmosphere. With the help of gas chromatography–mass spectrometry (GC–MS) and infrared spectroscopy (IRS) we can thus determine which minor species still undetected in Titan's atmosphere are likely to be present and understand the complex chemistry of the atmosphere of this satellite. Surprisingly we have identified unpredicted O-containing gaseous compounds, mainly ethylene oxide (also named oxirane, C2H4O). This molecule has been observed in the interstellar medium by observation in the millimeter region (Astrophys. J. 489 (1997) 553; Astron. Astrophys. 337 (1998) 275). On the contrary, the predicted O-compounds (formaldehyde and methanol) have not been identified in this experiment. Furthermore, we have identified NH3 in the gaseous products with an initial mixture of N2 (98%) and CH4 (2%).The paper describes the experimental device used in this work, in particular the IRS and GC–MS techniques. We also comment the results related to the detection of the O-containing compounds and NH3 and their implications on our knowledge of the chemistry of Titan's atmosphere and on the retrieval of the future Titan data expected from Cassini-Huygens.  相似文献   
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