The impulsive phase of a large solar limb flare of June 20, 1989   总被引：1，自引：0，他引：1  

Martin Graeter  Therese A. Kucera 《Solar physics》1992,141(1):91-107

On 1989 June 20, we observed in H the impulsive phase of a 3B/X1.6 limb flare with high temporal resolution. Line profiles have been acquired every 2.3 s with an imaging spectrograph. During the eruption of a filament we observed in H a moving plasma blob from what we believe to be a second loop which correlated spatially and temporally with a microwave source at 1.4 GHz observed by VLA. A magnetodynamic model is used to understand the development of the moving plasma blob.  相似文献   

Composition-Induced Variations in SIMS Instrumental Mass Fractionation during Boron Isotope Ratio Measurements of Silicate Glasses     

Martin Rosner  Michael Wiedenbeck  Thomas Ludwig 《Geostandards and Geoanalytical Research》2008,32(1):27-38

An analytical artefact is reported here related to differences in instrumental mass fractionation between NIST SRM glasses and natural geological glasses during SIMS boron isotope determinations. The data presented demonstrated an average 3.4‰ difference between the NIST glasses and natural basaltic to rhyolitic glasses mainly in terms of their sputtering-induced fractionation of boron isotopes. As no matrix effect was found among basaltic to rhyolitic glasses, instrumental mass fractionation of most natural glass samples can be corrected by using appropriate glass reference materials. In order to confirm the existence of the compositionally induced variations in boron SIMS instrumental mass bias, the observed offset in SIMS instrumental mass bias has been independently reproduced in two laboratories and the phenomenon has been found to be stable over a period of more than one year. This study highlights the need for a close match between the chemical composition of the reference material and the samples being investigated.  相似文献   

Illite crystallinity patterns in the Anti-Atlas of Morocco     

Geoffrey M. H. Ruiz  Urs Helg  François Negro  Thierry Adatte  Martin Burkhard 《Swiss Journal of Geoscience》2008,101(2):387-395

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山东莒南地质公园发现小型兽脚类恐龙 足迹化石Minisauripus   总被引：2，自引：0，他引：2  

李日辉  Lockley Martin G  Matsukawa Masaki  刘明渭 《地质通报》2008,27(1):121-125

在山东省莒南地质公园内发现6个小型恐龙足迹化石,被归入足迹属Minisauripus。化石产于下白垩统大盛群田家楼组．时代为早白垩世巴列姆（Barremian）-阿普特期（Apdan）。5个较大,长约6cm,产于下部“主”层面上,其中4个组成2节行迹：1个较小,长约3cm,位于“主”层面30cm之上的上部层面上。山东Minisauripus的特征是：足迹个体小（长3．1～5．6cm,宽2．0～3．7cm）,三趾型,略不对称;足迹纵长,各趾近平行,趾垫较清晰;趾末端较钝,但爪迹较尖。Ⅲ趾比Ⅳ趾略长,而Ⅳ趾比Ⅱ趾略长且窄。此外,步幅较长,足长与步长之比约为10：1。与四川、韩国Minisau却淞不同之处是：足迹个体较大,长约是它们的2倍。继中国四川和韩国之后,山东是Minisau而淞在全球的第三个发现点。  相似文献   

Environment,society and geographical organization: The problem of integral knowledge     

Martin Hampl 《GeoJournal》1994,32(3):191-198

This contribution emphasizes the limits constraining the synthetical ability of contemporary science, which are a consequence of the imbalance between the search for partial and relatively simple phenomena and the search for comprehensive complexes. The development of our integral knowledge can be supported by geography which is a discipline studying complex systems. However, it is necessary to search for regularities showing the organization of complex systems. This contribution is an attempt to specify such regularities. Emphasis is put on the role of hierarchical principles in the organization of complex systems. The interaction between hierarchical differentiation of the environment and homogeneous sets of kinds of partial phenomena seems to represent the primary conditioning of evolution: the occurrence of similar phenomena in different external conditions. Regularities of complex systems can be specified in connection with the differentiation of these systems according to principles of rank/scale and evolution. The combination of the two principles enables us to understand the nature of development of society in the environment.  相似文献   

Early Cretaceous volcaniclastic and quartzose sandstones from north central Nepal: composition,sedimentology and geotectonic significance     

Sören B. Dürr  Martin R. Gibling 《International Journal of Earth Sciences》1994,83(1):62-75

Early Cretaceous sandstones and shales from the Thakkhola region (Chukh and Tangbe Formations) were deposited on the subsiding northern (Tethyan) margin of Gondwana; current directions indicate a source area to the south. Whereas the Berriasian Chukh Formation is dominated by quartz arenites, volcaniclastic sandstones and minor conglomerates dominate the Tangbe Formation of Valanginian to Aptian age. Upsection, the composition of the volcaniclastic components changes from mainly basaltic to dominantly dacitic/rhyolitic. Magmatism was preceded and accompanied by strong uplift in the source area of the Chukh and Tangbe clastics, resulting in the erosion of probably more than several hundred meters of pre-Cretaceous sedimentary, metamorphic and plutonic rocks. A geochemical whole rock analysis of basaltic pebble fragments shows their alkaline character and suggests a within-plate geotectonic setting for the volcanic source. This volcanotectonic event is probably related to rifting between Australia and Greater India, where seafloor spreading began in late Valanginian/Hauterivian times.  相似文献   

Site occupation and electric field gradient in acentric neptunite-measurements and evaluations concerning powder- and single crystal – Mössbauer spectroscopy and x-ray diffractometry     

Werner Lottermoser  Karl Forcher  Georg Amthauer  Martin Kunz  Thomas Armbruster 《Physics and Chemistry of Minerals》1997,24(1):2-6

Mössbauer measurements on neptunite (KNa₂Li(Fe,Mn,Mg)₂Ti₂Si₈O₂₄) at 400?K reveal the distribution of Fe-ions on the crystallographic sites in agreement with neutron diffraction results published elsewhere. Even the previously postulated small amount of Fe-ions on the Ti(2) site has been detected, combined with a charge transfer which is in agreement with optical absorption investigations by other authors. A qualitative site occupation model is able to explain the different features of our observations. Single crystal Mössbauer measurements with the k-vector of incident γ-rays parallel to the crystallographic b-axis (space group Cc) of neptunite at different temperatures yield the angle β between the main component of the electric field gradient (EFG), V _zz and b. This angle is in close accordance with a calculated value of β for the Fe(1) position from electron density maps. The latter also reveal an absolute value of V _zz which is in satisfactory agreement with V _zz derived from Mössbauer spectroscopy.  相似文献   

The circumstellar shells of carbon miras     

Martin Groenewegen 《Astrophysics and Space Science》1995,224(1-2):321-324

The relation between mass loss rate and pulsation period in carbon Miras is discussed. The dust mass loss rate is very low (about 2 × 10^–10 M/yr) up to aboutP = 380 days, where there is a sudden increase. ForP > 400 days there is a linear relation between logM andP. The change in the mass loss rate near 380 days may be related to radiation pressure on dust becoming effective in driving the outflow.  相似文献   

Study of the post-flare loops on 29 July 1973     

Sara F. Martin 《Solar physics》1979,64(1):165-176

Bright and dark curvilinear structures observed between the two major chromospheric ribbons during the flare of 29 July 1973 on films from the Big Bear Solar Observatory are interpreted as a typical system of coronal loops joining the inner boundaries of the separating flare ribbons. These observations, made through a 0.25 Å H filter, only show small segments of the loops having Doppler shifts within approximately ± 22 km s^–1 relative to the filter passband centered at H, H -0.5 Å or H +0.5 Å. However, from our knowledge of the typical behavior of such loop systems observed at the limb in H and at 5303 Å, it has been possible to reconstruct an appoximate model of the probable development of the loops of the 29 July flare as they would have been viewed at the limb relative to the position of a prominence which began to erupt a few minutes before the start of the flare. It is seen that the loops ascended through the space previously occupied by the filament. On the assumption that H fine structures parallel the magnetic field, we can conclude that a dramatic reorientation of the direction of the magnetic field in the corona occurred early in the flare, subsequent to the start of the eruption of the filament and prior to the time that the H loops ascended through the space previously occupied by the filament.  相似文献   

The study of comets: Parts 1 and 2. Proceedings of a conference held at Goddard Space Flight Center,Greenbelt, Md., October 28–November 1, 1974. Edited by B. Donn,M. Mumma,W. Jackson,M. A'Hearn,and R. Harrington. NASA SP-393, U.S. Government Printing Office,Washington, D.C. 1083 pp. $11.25     

Martin Harwit 《Icarus》1977,30(2):435-436

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