Investigation of the electrostatic charging of dust particles in a Paul-trap     

S. Pintér  J. Švestka  E. Grün 《Astrophysics and Space Science》1990,171(1-2):217-218

Dust particles (glass, tungsten, and nickel) with sizes ranging from 0.25 to 3m were levitated in a Paul-trap and charged by ions or electrons. For ions the particle potential is limited at field strength of about 1×10⁹ V m^–1 by a temperature-dependent discharge mechanism. The particles interaction with 2 to 20 keV electrons always leads to positive surface potentials which can be explained in terms of a decreased absorption of electrons by small particles. Micrometer sized agglomerates were used for the investigation of the electrostatic fragmentation. Fragmentation takes place in a twofold manner: small surface flufl can be removed or the parent particle can be disrupted into smaller agglomerates.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

A combined study of macroseismic data and focal mechanisms applied to the West-Bohemian earthquake,Czechoslovakia     

J. Zahradník  M. Antonini  G. Grünthal  J. Janský  D. Procházková  E. Schmedes  A. Špičak  J. Zedník 《Pure and Applied Geophysics》1990,133(1):53-71

The main shock of the West-Bohemian earthquake swarm, Czechoslovakia, (magnitudem=4.5, depthh=10 km) exhibits an irregular areal distribution of macroseismic intensities 6° to 7° MSK-64. Four lobes of the 6° isoseismal are found and the maximum observed intensity is located at a distance of 8 km from the instrumentally determined epicentre. This distribution can be explained by the energy flux of the directS wave generated by a circular source, the hypocentral location and focal mechanism of which are taken from independent instrumental studies. The theoretical intensity, which is assumed to be logarithmically proportional to the integrated squared ground-motion velocity (i.e.,I=const+log v ² (t)dt), fits the observed intensity with an overall root-mean-square error less than 0.5°. It is important that the present intensity data can also be equally well explained by the isotropic source. The fit was attained by means of a horizontally layered model though large fault zones and an extended sedimentary basin suggest a significant lateral heterogeneity of the epicentral region. The results encourage a broader application of the simple modelling technique used.  相似文献   

Solar rotation velocity as determined from sunspot drawings of J. Hevelius in the 17th century     

Claudia Abarbanell  Hubertus Wöhl 《Solar physics》1981,70(1):197-203

Using two original copies of Hevelius' Selenographia and reducing spot positions with two different methods, we found that the solar angular rotation velocity at the beginning of the Maunder minimum was about the same as today. The gradient of the differential rotation was slightly steeper than given in modern reductions, but not significantly different. These findings are in contradiction to those published by Eddy et al. (1976).  相似文献   

The dependence of the frequency spectra of the interplanetary magnetic-field fluctuations on the direction of the mean field     

Jörn E. Kunstmann 《Earth, Moon, and Planets》1978,18(1):91-104

The frequency spectra of the interplanetary magnetic field fluctuations are the projection of their wavenumber spectra onto one dimension. Only the frequency spectra can be measured by spacecrafts. It is studied how their measured size depends on the direction of the mean fieldB ₀, which structures the symmetry of the fluctuations relative to the solar wind system. It is specialized for the slab model, Alfvén waves, magneto-acoustic waves and the isotropic case. For the slab model the frequency spectra are proportional to , whereq is the spectral index and the angle betweenB ₀ and the radial direction. For the diffusion coefficientK _TT the relation holds.  相似文献   

The evolution of massive close binaries     

De Grève  J. P.  De Loore  C.  Van Dessel  E. L. 《Astrophysics and Space Science》1978,53(1):105-130

The results of evolutionary computations for massive binary systems (initial masses of the primary 10M ) with mass ratios between 0.3 and 0.8 are summarized and compared with observations in order to verify how far one can go with the conservative assumption of mass exchange. It is found that conservative mass exchange leads to acceptable first-order models of W-R and massive X-ray binaries. However, the comparison between this theory and observation reveals that for the observed systems (W-R and X-ray binaries) a preference exists for low intial mass ratios; moreover, the X-ray luminosities of the theoretical models are systematically too low, though this may be due to the adopted wind model. In addition, the influences of several parameters (distance between the components, chemical composition, primary mass, mass ratio and atmosphere) are examined. These parameters influence the remnant mass and any further evolution only marginally. Attention is also given to the effect on the system parameters of a supernova explosion of the remnant of the mass-losing component. For a large range of systems a disruption probability smaller than 25% is found.  相似文献   

Differential rotation and giant cell circulation of solar Ca+-network     

E. H. Schröter  H. Wöhl 《Solar physics》1976,49(1):19-32

We report new results obtained from high precision computer controlled tracings of ca. 400 bright Ca⁺-mottles made during summer 1975 in continuation of our 1974 program (Schröter and Wöhl, 1975). In particular, we looked in 1975 for the existence of a giant circulation pattern in the equatorial zone. We find for the differential rotation: = 13.93 – 2.90 sin² B (deg/day, sidereal) when combining the new measurements with those obtained in 1974. Observations from 26th April until June 19th give strong evidence that at that time four giant circulation cells, crossing the solar equator, (i.e. a nonaxisymmetric velocity field pattern with respect to the solar equator) did exist. This yields two more rapid and two slower rotating sectors with v = ±80 m s^–1. These giant cells transport angular momentum towards the equator.  相似文献   

Fraktionierung der spurenelemente bei der kristallisation: Hans-Eberhard Usdowski. Springer-Verlag,Berlin, 1975, 104 S., 42 Abb., DM 29,80     

Heinrich M. Köster 《Chemical Geology》1976,18(4):327

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Shape of the Cassini division in different colors     

Karl Lumme 《Icarus》1975,24(4):483-491

The true shape of the Cassini division of Saturn's rings in red, yellow, green, and blue light has been derived from photographs of high quality, taking into account the correction due to the spreading of light. It is evident that the division is not completely dark. Its minimum brightness is about 20% of that of ring B and the width of the division 0″.44±0″.05.  相似文献   

Transport and emplacement of crater and basin deposits     

Verne R. Oberbeck  Robert H. Morrison  Friedrich Hörz 《Earth, Moon, and Planets》1975,13(1-3):9-26

Material is ejected from impact craters in ballastic trajectories; it impacts first near the crater rim and then at progressively greater ranges. Ejecta from craters smaller than approximately 1 km is laid predominantly on top of the surrounding surface. With increasing crater size, however, more and more surrounding surface will be penetrated by secondary cratering action and these preexisting materials will be mixed with primary crater ejecta. Ejecta from large craters and especially basin forming events not only excavate preexisting, local materials, but also are capable of moving large amounts of material away from the crater. Thus mixing and lateral transport give rise to continuous deposits that contain materials from within and outside the primary crater. As a consequence ejecta of basins and large highland craters have eroded and mixed highland materials throughout geologic time and deposited them in depressions inside and between older crater structures.Because lunar mare surfaces contain few large craters, the mare regolith is built up by successive layers of predominantly primary ejecta. In contrast, the lunar highlands are dominated by the effects of large scale craters formed early in lunar history. These effects lead to thick fragmental deposits which are a mixture of primary crater material and local components. These deposits may also properly be named regolith though the term has been traditionally applied only to the relatively thin fine grained surficial deposit on mare and highland terranes generated during the past few billion year. We believe that the surficial highland regolith - generated over long periods of time - rests on massive fragmental units that have been produced during the early lunar history.  相似文献   

Characterization of a major refractory component of marine dissolved organic matter   总被引：2，自引：0，他引：2  

Norbert Hertkorn  Ronald Benner  Philippe Schmitt-Kopplin  Karl Kaiser  John I. Hedges 《Geochimica et cosmochimica acta》2006,70(12):2990-3010

Refractory carboxyl-rich alicyclic molecules (CRAM) are characterized in marine dissolved organic matter (DOM) using nuclear magnetic resonance spectroscopy and ultrahigh resolution mass spectrometry. CRAM are distributed throughout the water column and are the most abundant components of deep ocean DOM ever characterized. CRAM are comprised of a complex mixture of carboxylated and fused alicyclic structures with a carboxyl-C:aliphatic-C ratio of 1:2 to 1:7. CRAM are expected to constitute a strong ligand for metal binding, and multiple coordination across cations could promote aggregation and marine gel formation thereby affecting CRAM reactivity and the bioavailability of nutrients and trace metals. It appears CRAM are ultimately derived from biomolecules with structural similarities to sterols and hopanoids. The occurrence of CRAM in freshwater and terrestrial environments seems likely, considering the global distribution of biomolecules and the similarities of biogeochemical processes among environments.  相似文献