Mare basalt units and the compositions of their magmas     

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   

Search for optical counterparts of gamma-ray burst sources     

J. Greiner  J. Flohrer  W. Wenzel  T. Lehmann 《Astrophysics and Space Science》1987,138(1):155-171

The examination of nearly 9600 archival photographic plates covering six gamma-ray burst error boxes has unveiled several star-like images. Unfortunately, the reality of none of these images can be proved by duplicate plates.A laboratory test was performed to get a more detailed estimation of the number of plate faults. The result emphasizes the necessity of duplicate synchronous plates to exclude plate defects.  相似文献   

Recombination of electrons with H₃⁺ and H₅⁺ ions     

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 T_e using a microwave afterglow-mass spectrometer apparatus. At ion and neutral temperatures T_u+ = T_n = 240 K, the coefficient α (H₃⁺) is found to vary slowly with T_e at first, decreasing from 1.6 × 10^?7 cm³/s at T_e = 240 K to 1.2 × 10^?7 cm³/s at T_e = 500 K, thereafter falling as T_e^?1 over the range 500 K ? T_e, ? 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₊ = T_n = 128 K, the coefficient α(H₅⁺) is found to be (1.8 ± 0.3) × 10^?6 [T_e(K)/300]^?0.69 cm³/s over the range 128 K ? T_e ? 3000 K, with a more rapid decrease, as T_e^?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   

Die Schwermetallgehalte der Sedimente im Klärschlamm—Verklappungsgebiet vor der Elbmündung     

Dr. Manfred Nauke 《Ocean Dynamics》1974,27(5-6):203-213

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Tourism resources and their development in Maldive Islands     

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   

Impact cratering and spall failure of gabbro     

Manfred A. Lange  Thomas J. Ahrens  Mark B. Boslough 《Icarus》1984,58(3):383-395

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 N_f)/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 $\text{σ}{}_{\mathrm{<mtext>m</mtext>}}\text{∝}\text{ε}\text{?}{}^{\mathrm{[0.25–0.3]}}$, 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   

What determines farmers’ resilience towards ENSO-related drought? An empirical assessment in Central Sulawesi, Indonesia     

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   

Melting and Sublimation of Planetary Ices Under Low Pressure Conditions: Laboratory Experiments with a Melting Probe Prototype     

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   

The dependence of galaxy formation on cosmological parameters: can we distinguish between the WMAP1 and WMAP3 parameter sets?     

Jie Wang  Gabriella De Lucia  Manfred G. Kitzbichler  Simon D. M. White 《Monthly notices of the Royal Astronomical Society》2008,384(4):1301-1315

We combine N -body simulations of structure growth with physical modelling of galaxy evolution to investigate whether the shift in cosmological parameters between the first- and third-year results from the Wilkinson Microwave Anisotropy Probe ( WMAP ) affects predictions for the galaxy population. Structure formation is significantly delayed in the WMAP3 cosmology, because the initial matter fluctuation amplitude is lower on the relevant scales. The decrease in dark matter clustering strength is, however, almost entirely offset by an increase in halo bias, so predictions for galaxy clustering are barely altered. In both cosmologies, several combinations of physical parameters can reproduce observed, low-redshift galaxy properties; the star formation, supernova feedback and active galactic nucleus feedback efficiencies can be played off against each other to give similar results. Models which fit observed luminosity functions predict projected two-point correlation functions which scatter by about 10–20 per cent on large scale and by larger factors on small scale, depending both on cosmology and on details of galaxy formation. Measurements of the pairwise velocity distribution prefer the WMAP1 cosmology, but careful treatment of the systematics is needed. Given present modelling uncertainties, it is not easy to distinguish between the WMAP1 and WMAP3 cosmologies on the basis of low-redshift galaxy properties. Model predictions diverge more dramatically at high redshift. Better observational data at   z > 2  will better constrain galaxy formation and perhaps also cosmological parameters.  相似文献   

Geochemical evidence of aeolian deposits in European soils     

Andreas J. Scheib  Manfred Birke  Enrico Dinelli  GEMAS Project Team 《Boreas: An International Journal of Quaternary Research》2014,43(1):175-192

Hafnium (Hf) and zirconium (Zr) concentrations measured in over 4100 agricultural soil samples from Europe were assessed with the focus on their relationship to the distribution of aeolian deposits, such as loess and coversands. Comparison of extractable (aqua regia; ICP‐MS) and total (XRFS) concentrations shows that only 1.0 to 1.7% of the total Hf and Zr is chemically extractable because of the resistant nature of their host minerals. Resistate minerals, such as zircon, are commonly found in the predominantly silty fraction of loess deposits. In this study a statistical analysis of total Hf and Zr soil data from areas with and without loess was carried out to derive threshold values of 10 mg kg^?1 (Hf) and 318 mg kg^?1 (Zr). These values were subsequently applied across the project area in an attempt to indicate the presence of aeolian deposits. The spatial distribution of above‐threshold concentrations suggests a more extensive and coherent loess belt across central and eastern Europe, providing additional evidence of loess across Brittany, Aquitaine and near the Vosges mountains in France as well as in the basins of central and northern Spain. Above‐threshold concentrations were also detected in loess regardless of its thickness, emphasising the importance of the abundance of zircon in the upper part of the soil profile rather than the actual thickness of the deposit. Soil data however, failed to indicate various loess facies within most of the Pannonian Basin, suggesting that this approach only works where deposits contain a sufficient amount of zircon. This may also explain why the extensive coversands across northern Germany and Poland were largely undetected. This study demonstrates that continental‐scale soil geochemical data can help identify and map the distribution of zircon‐rich loess and coversand, and subsequently enhance and improve current knowledge of the extent of these deposits.  相似文献