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61.
Dwight P. Sipler Barry B. Luokkala Manfred A. Biondi 《Planetary and Space Science》1982,30(10):1025-1032
Fabry-Perot interferometer measurements of the Doppler shifts and widths of the nightglow 630.0 nm line at Laurel Ridge Observatory, Pennsylvania are presented for the period 1975 to 1979, covering both solar minimum and solar maximum conditions. The F-region neutral wind vectors vn and temperatures Tn deduced from these measurements show both day-to-day changes and overall seasonal patterns in the nocturnal variations during geomagnetically quiet conditions. Divergence in both the meridional and zonal horizontal flow is noted on occasion. The vn results are compared with models including only solar EUV heating and those with EUV plus a high latitude heat source. The aggregate vn data for solar cycle minimum conditions agree best with model predictions for winter zonal and equinoctal meridional winds and worst for winter meridional and summer zonal winds. At solar cycle maximum the predicted, rapid transition at equinox from summer to winter wind patterns and vice-versa is observed. The Tn data are in reasonable agreement with the MSIS model predictions. 相似文献
62.
Aromatic ketones were concentrated from filtered Baltic Sea water by liquid—solid adsorption. After wet-chemical separation from acidic and basic components, the neutral fraction was column chromatographed to yield sub-fractions of increasing polarity. A subfraction eluted from silica gel with cyclopentane/diethyl ether contained a number of compounds which were identified by GC and GC—MS techniques as fluorenone, anthraquinone, benzanthrone, and benzene derivatives carrying an oxo group in the α-position relative to the aromatic ring. Formation and abiotic chemical reactions of these compounds in seawater are discussed. 相似文献
63.
The question whether paleoclimatic systems are governed by a small number of significant variables (low-dimensional systems) is of importance for modeling such systems. As indicators for global Plio-/Pleistocene climate variability, four marine, sedimentary oxygen isotope time series are analyzed with regard to their dimensionality using a modified Grassberger-Procaccia algorithm. An artificial, low-dimensional chaotic time series (Hénon map) is included for the validation of the method. In order to extract equidistant data the raw data are interpolated with the Akima-subspline method since this method minimizes the change in variance due to the interpolation. The nonlinear least-squares Gauss-Marquardt regression method is used instead of the linear least-squares fit to the logarithmically transformed points, in order to acquire an unbiased estimate of the correlation dimension. The dependences of the estimated correlation dimension on the embedding dimension do not indicate a small number (i.e., less than 5) of influencing variables on the investigated paleoclimatic system, whereas the low dimension for the Hénon map is verified (dimension 1.22–1.28). Because of the limited amount of data in the oxygen isotope records, dimensions greater than about 5 cannot be examined. 相似文献
64.
Alan B. Binder Manfred A. Lange Heinz-Jürgen Brandt Susanne Kähler 《Earth, Moon, and Planets》1980,23(4):445-481
A synthesis of the majority of the available mare basalt data shows that basalts and glasses came from 28 different volcanic units. The compositions of the magmas of 12 of these units can be calculated with a high degree of confidence. Reasonable estimates can be made for the compositions of nine of the remaining units. In addition, the compositions of three general magma types can be obtained from data derived from the Luna 16, Luna 24, and Apollo 17 fines. The compositional data presented provide a firm basis for the further study of the characteristics of the mare basalt magma source region. 相似文献
65.
Jeffrey A. Macdonald Manfred A. Biondi Rainer Johnsen 《Planetary and Space Science》1984,32(5):651-654
The dissociative recombination coefficients α for capture of electrons by H3+ and H5+ ions have been determined as a function of electron temperature Te using a microwave afterglow-mass spectrometer apparatus. At ion and neutral temperatures Tu+ = Tn = 240 K, the coefficient α (H3+) is found to vary slowly with Te at first, decreasing from 1.6 × 10?7 cm3/s at Te = 240 K to 1.2 × 10?7 cm3/s at Te = 500 K, thereafter falling as Te?1 over the range 500 K ? Te, ? 3000 K. These results, which have a ± 20% uncertainty, agree satisfactorily over the common energy range (0.03–0.36 eV) with the recombination cross sections determined in merged beam measurements by Auerbach et al. At T+ = Tn = 128 K, the coefficient α(H5+) is found to be (1.8 ± 0.3) × 10?6 [Te(K)/300]?0.69 cm3/s over the range 128 K ? Te ? 3000 K, with a more rapid decrease, as Te?1, between 3000 K and 5500 K. The implications of these results for modelling planetary atmospheres and interstellar clouds are briefly touched on. 相似文献
66.
67.
Manfred Domroes Prof. Dr. 《GeoJournal》1985,10(1):119-126
Maldive Islands are characterized by a unique coral nature and thus they posses unique tourism resources though in a one-sided way, namely in the submarine and littoral environment of the islands, lagoons and reefs, associated with the year-round tropical climate. Therefore, not only divers and snorklers enjoy the profuse underwater resources, but also beach tourists are attracted by the nature of the beaches and the climatic conditions as well. This environment really guarantees relaxation and recreation. Tourism in Maldives which was introduced in 1972 only, has successfully developed so far. Proof is given by the rapidly growing number of tourists and tourist resorts (islands) over the past 10 year period. On the European market, Maldives today rank among the most attractive tourist destinations in the tropics. Maldives offer large natural resources for tourism to be further developed in the future. The sensitive environment does however call for most considerate measures. 相似文献
68.
Both hypervelocity impact and dynamic spall experiments were carried out on a series of well-indurated samples of gabbro to examine the relation between spall strength and maximum spall ejecta thickness. The impact experiments carried out with 0.04- to 0.2-g, 5- to 6-km/sec projectiles produced decimeter- to centimeter-sized craters and demonstrated crater efficiencies of 6 × 10?9 g/erg, an order of magnitude greater than in metal and some two to three times that of previous experiments on less strong igneous rocks. Most of the crater volume (some 60 to 80%) is due to spall failure. Distribution of cumulative fragment number, as a function of mass of fragments with masses greater than 0.1 g yield values of b = d(log Nf)/d log(m) ?0.5 ?0.6, where N is the cumulative number of fragments and m is the mass of fragments. These values are in agreement or slightly higher than those obtained for less strong rocks and indicate that a large fraction of the ejecta resides in a few large fragments. The large fragments are plate-like with mean values of B/A and C/A 0.8 0.2, respectively (A = long, B = termediate, and C = short fragment axes). The small equant-dimensioned fragments (with mass < 0.1 g and B ~ 0.1 mm) represent material which has been subjected to shear failure. The dynamic tensile strenght of San Marcos gabbro was determined at strain rates of 104 to 105 sec?1 to be 147 ± 9 MPa. This is 3 to 10 times greater than inferred from quasi-static (strain rate 100 sec?1) loading experiments. Utilizing these parameters in a continuum fracture model predicts a tensile strenght of , where ε is strain rate. It is suggested that the high spall strenght of basic igneous rocks gives rise to enhanced cratering efficiencies due to spall in the <102-m crater diamter strength-dominated regime. Although the impact spall mechanism can enhance cratering efficiencies it is unclear that resulting spall fragments achieve sufficient velocities such that fragments of basic rocks can escape from the surfaces of planets such as the Moon or Mars. 相似文献
69.
Alwin Keil Manfred Zeller Anastasia Wida Bunasor Sanim Regina Birner 《Climatic change》2008,86(3-4):291-307
Crop production in the tropics is subject to considerable climate variability caused by the El Niño-Southern Oscillation (ENSO) phenomenon that is likely to become even more pronounced during the twenty-first century. Little is known about the impact of ENSO-related drought on crop yields and food security, especially at the household level. This paper seeks to contribute to closing this knowledge gap with a case study from Central Sulawesi, Indonesia. Its main objective is to measure household resilience towards drought periods and to identify its influencing factors to deduce policy implications. Using indicators for consumption expenditures, we construct an index measuring household drought resilience; we then apply an asset-based livelihood framework to identify its determinants. Most of the drought-affected farm households are forced to substantially reduce expenditures for food and other basic necessities. Households’ drought resilience is strengthened by the possession of liquid assets, access to credit, and the level of technical efficiency in agricultural production. The results suggest a number of policy recommendations, namely improvement of the farmers’ access to ENSO forecasts, the provision of credit and savings products to facilitate consumption smoothing, and the intensification of agricultural extension in view of low levels of productivity found in agricultural production. 相似文献
70.
Erika?Kaufmann Günter?Kargl Norbert?I.?K?mleEmail author Manfred?Steller Johann?Hasiba Florian?Tatschl Stefan?Ulamec Jens?Biele Marc?Engelhardt Jens?Romstedt 《Earth, Moon, and Planets》2009,105(1):11-29
One possibility to explore the subsurface layers of icy bodies is to use a probe with a “hot tip", which is able to penetrate
ice layers by melting. Such probes have been built and used in the past for the exploration of terrestrial polar ice sheets
and may also become useful tools to explore other icy layers in the Solar System. Examples for such layers are the polar areas
of Mars or the icy crust of Jupiter’s moon Europa. However, while on Earth a heated probe launched into an ice sheet always
causes melting with subsequent refreezing, the behaviour of such a probe in a low pressure environment is quite different.
We report on the results of some experiments with a simple “melting probe" prototype with two different kinds of hot tips
in a vacuum environment. For one of the tips the probe moved into two types of ice samples: (i) compact water ice and (ii)
porous water ice with a snow (firn) like texture. It was also found that the penetration behaviour was basically different
for the two sample types even when the same kind of tip was used. While in the porous sample the ice was only subliming, the
phase changes occurring during the interaction of the tip with the compact ice are much more complex. Here alternating phases
of melting and sublimation occur. The absence of the liquid phase has severe consequences on the performance of a “melting
probe" under vacuum conditions: In this environment we find a high thermal resistance between the probe surface and the underlying
ice. Therefore, only a low percentage of the heat that is generated in the tip is used to melt or sublime the ice, the bulk
of the power is transferred towards the rear end of the probe. This is particularly a problem in the initial phases of an
ice penetration experiment, when the probe has not yet penetrated the ice over its whole length. In the compact ice sample,
phases could be observed, where a high enough gas pressure had built up locally underneath the probe, so that melting becomes
possible. Only during these melting periods the thermal contact between the probe and the ice is good and in consequence the
melting probe works effectively. 相似文献