Positions of extragalactic objects in the vicinity of M3 and M31 (5C3 radio field) and in the 5C1 radio field     

W. R. Dick  H. Lorenz  P. Notni  E. Schilbach  R.-D. Scholz  G. A. Richter 《Astronomische Nachrichten》1986,307(2):85-88

We have determined the positions of 65 compact extragalactic objects with magnitudes between 16^m and 21^m.7. The mean error of one position is about 0″.3 in α cos δ and in δ. Some hitherto unpublished redshifts are also listed.  相似文献   

The Physical Nature of the Blue Objects in the Field of BD + 15° 2469 (Virgo Cluster)     

L. E. Abati  H. Lorenz 《Astronomische Nachrichten》1984,305(3):105-109

The physical nature of 277 ultraviolet excess objects of the third Asiago field (22 square degrees, 15 ≦ m_pg ≦ 18, U–B ≦≦ -0.2) is investigated on the basis of objective prism plates. Most of them are stars, 8% are quasar candidates and 7% compact galaxies. The proportions of different kinds of objects changes with the magnitude and U–B colour index. The surface density of quasars is estimated to be between 0.5 Q/sq. deg. and 1.0 Q/sq. deg. for the UVX A₃ objects. The results of the A₃ field (located in the Virgo cluster of galaxies) statistically agree with the ones of the A₁ field, outside clusters of galaxies.  相似文献   

Detrital zircon geochronology of Palaeozoic Novaya Zemlya – a key to understanding the basement of the Barents Shelf     

Henning Lorenz  David G. Gee  Evgeny Korago  Galina Kovaleva  William C. McClelland  Jane A. Gilotti  Dirk Frei 《地学学报》2013,25(6):496-503

The Novaya Zemlya fold‐and‐thrust‐belt is the northern continuation of the late Palaeozoic Uralide Orogen. Little is known about its deeper structure and the basement history of the adjacent Barents and Kara shelves. Based on geological evidence and detrital zircon analysis of 28 samples from the northeastern and stratigraphically deepest part of the archipelago, we demonstrate that Cambro‐Ordovician turbidite‐dominated deposition was almost exclusively sourced from rocks consolidated during the Timanian orogeny (Timanian basement). A profound change in provenance occurred near the end of the Ordovician. Over 90% of the zircons from Silurian and about 80% from Devonian strata have ages characteristic of the Sveconorwegian Orogen, implying uplift of these rocks in the vicinity of Novaya Zemlya. The presence of Sveconorwegian and Grenvillian rocks in the high Arctic suggests revision of recent reconstructions of the Rodinia supercontinent, its break‐up and subsequent Caledonian orogeny.  相似文献   

Plate and intraplate processes of Hercynian Europe during the late paleozoic     

Volker Lorenz  Ian A. Nicholls 《Tectonophysics》1984,107(1-2)

It is speculated that until Late Carboniferous time the region of Hercynian Europe was occupied by an elongated island arc system underlain by a segment of continental crust. In the Upper Carboniferous, two subduction zones are assumed to have extended from the north and south beneath Hercynian Europe. An extensive zone of hot, partially molten upper mantle lay above and between these, and diapiric uprise of portions of this material led to separation of mafic magmas, widespread partial melting in the lower and middle crust, high temperature-low pressure metamorphism in crustal rocks, and regional uplift and extension of the crust, as indicated by intermontane troughs and their associated volcanic rocks.In Visean to Westphalian time Hercynian Europe collided with both the large neighbouring plates North America-Europe and Africa. During these diachronous collisions and owing to reduced rigidity of the relatively hot island arc crust, the irregular continental margins of the larger and thicker continental plates induced oroclinal bending of Hercynian Europe. After the collision processes had been terminated, processes of upper mantle activity continued, causing further crustal uplift and even, enhanced crustal extension for several tens of million years into the Lower Permian. Decline of the upper mantle activity beneath Hercynian Europe is indicated by crustal subsidence and formation of a peneplain in Permian time followed by the Upper Permian transgression of both the Zechstein sea and the Tethys sea which mark the end of the Hercynian geodynamic cycle.  相似文献   

Methoxy formation in the reaction of CH3O2 radicals with NO     

R. Zellner  B. Fritz  K. Lorenz 《Journal of Atmospheric Chemistry》1986,4(2):241-251

Formation of methoxy (CH₃O) radicals in the reaction (1) CH₃O₂+NOCH₃O+NO₂ at 298 K has been observed directly using time resolved LIF. The branching ratio % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqOXdyMaae% 4qaiaabIeadaWgaaWcbaGaae4maaqabaGccaqGpbGaaeiiaiaabIca% ieqacaWF9aGaa8hiaiaa-nbicaWFGaGaeuiLdqKaai4waiaaboeaca% qGibWaaSbaaSqaaiaabodaaeqaaOGaae4taiaac2facaWFVaGaeuiL% dqKaai4waiaaboeacaqGibWaaSbaaSqaaiaabodaaeqaaOGaae4tam% aaBaaaleaacaqGYaaabeaakiaac2facaqGPaaaaa!4E31!\[\phi {\rm{CH}}_{\rm{3}} {\rm{O (}} = -- \Delta [{\rm{CH}}_{\rm{3}} {\rm{O}}]/\Delta [{\rm{CH}}_{\rm{3}} {\rm{O}}_{\rm{2}} ]{\rm{)}}\] has been determined by quantitative cw-UV-laser absorption at 257 nm of CH₃O₂ and CH₃ONO, the product of the consecutive methoxy trapping reaction (2) % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaae4qaiaabI% eadaWgaaWcbaGaae4maaqabaGccaqGpbacbeGaa83kaiaa-bcaieaa% caGFobGaa43taiaa+bcacaGFOaGaa83kaiaa+1eacaGFPaGaa4hiai% abgkziUkaabccacaqGdbGaaeisamaaBaaaleaacaqGZaaabeaakiaa% b+eacaqGGaGaaeOtaiaab+eacaqGGaGaa4hkaiaa-TcacaGFnbGaa4% xkaiaa+5cacaGFGaGaa4hiaiabeA8aMnaaBaaajqwaacqaaiaaboea% caqGibWaaSbaaKazcaiabaGaae4maaqabaqcKfaGaiaab+eaaSqaba% aaaa!55AC!\[{\rm{CH}}_{\rm{3}} {\rm{O}} + NO ( + M) \to {\rm{ CH}}_{\rm{3}} {\rm{O NO }}( + M). \phi _{{\rm{CH}}_{\rm{3}} {\rm{O}}} \] is found to be (1.0±0.2). The rate constant k ₁ is (7±2) 10^-12 cm³/molecule · s in good agreement with previous results.  相似文献   

On the growth of maars and diatremes and its relevance to the formation of tuff rings   总被引：8，自引：2，他引：8  

V. Lorenz 《Bulletin of Volcanology》1986,48(5):265-274

Small and large maars exist associated with small and large diatremes, respectively, their subsurface feeder structures. The problem of size and growth of maar-diatreme volcanoes is discussed from a phreatomagmatic point of view from field data, some geophysical data, and short-lived historic maar eruptions. A hydrostatic pressure barrier of usually about 20–30 bars is assumed to control the maximum depth level of explosive magma/groundwater interactions. Similar to the situation in submarine and subglacial volcanism, initial maar-forming water vapour explosions are therefore assumed to occur at shallow depth and to produce a small maar with a shallow diatreme. Because of limited availability of groundwater and ejection of groundwater in the form of steam, the confining pressure barrier is displaced downward. Consequently, water vapour explosions can take place at consecutively deeper levels with the result that the diatreme penetrates downward and grows in size. Since maars are collapse craters resulting from ejection of wallrocks fragmented by water vapour explosions at the level of the diatreme root zone, downward penetration of a diatreme not only results in increase in size of a diatreme but also in increase in size of the overlying maar. As availability of groundwater in limited amounts controls formation of diatremes and their downward penetration, lack of groundwater enables magma to rise within a diatreme and to form a scoria cone or lava lake within the maar, as is frequently found in volcanic fields such as the Eifel area in Germany. In contrast, availability of large amounts of water in near surface environments such as shallow marine, lake, water-rich coastal plains, or water-rich fluviatile gravel beds prevents formation of maars and deep diatremes but causes formation of tuff rings.  相似文献   

External ballistic of volcanic explosions     

G. S. Steinberg  V. Lorenz 《Bulletin of Volcanology》1983,46(4):333-348

In order to determine the kinetic energy of an explosion it is necessary to know the initial velocities of ejected fragments. Calculations of initial velocities made earlier with few exceptions did not take into account the resistance of the air and therefore, greatly underestimated the initial velocities, and consequently the energy of the explosions. A solution of the inverse problem of ballistics which takes into account air resistance makes it possible to find precise values of initial velocities of ejection, determined from the distance of ejected fragments and their ballistic coefficients. The method makes it possible to determine the kinetic energy of explosions for eruptions which were not directly observed. It is shown that the velocity field in volcanic explosions is not spherical,i.e. the velocities of ejection of fragments differ markedly in different directions. Accordingly, the maximum distance of ejection of fragments depends not only on the initial angle of ejection, but also on the character of distribution of initial velocities and the ballistic coefficients of the fragments. For fragments with diameters of 40 cm to 2 m the maximum distance of ejection is realized in the case of angles of ejection of 30–36°. For smaller fragments the optimal angles of ejection are still smaller. The ballistics of explosive eruptions of the volcanoes Asama, Arenal, and Shiveluch are considered.  相似文献   

Chemical composition of lunar meteorites and the lunar crust     

S. I. Demidova  M. A. Nazarov  C. A. Lorenz  G. Kurat  F. Brandstätter  Th. Ntaflos 《Petrology》2007,15(4):386-407

The paper presents the first analyses of major and trace elements in 19 lunar meteorites newly found in Oman. These and literature data were used to assay the composition of highland, mare, and transitional (highland-mare interface) regions of the lunar surface. The databank used in the research comprises data on 44 meteorites weighing 11 kg in total, which likely represent 26 individual falls. Our data demonstrate that the lunar highland crust should be richer in Ca and Al but poorer in mafic and incompatible elements than it was thought based on studying lunar samples and the first orbital data. The Ir concentration in the highland crust and the analysis of lunar crater population suggest that most lunar impactites were formed by a single major impact event, which predetermined the geochemical characteristics of these rocks. Lunar mare regions should be dominated by low-Ti basalts, which are, however, enriched in LREEs compared to those sampled by lunar missions. The typical material of mare-highland interface zones can contain KREEP and magnesian VLT basalts. The composition of the lunar highland crust deduced from the chemistry of lunar meteorites does not contradict the model of the lunar magma ocean, but the average composition of lunar mare meteorites is inconsistent with this concept and suggests assimilation of KREEP material by basaltic magmas. The newly obtained evaluations of the composition of the highland crust confirm that the Moon can be enriched in refractory elements and depleted in volatile and siderophile elements.  相似文献   

Foreign meteoritic material of howardites and polymict eucrites     

K. A. Lorenz  M. A. Nazarov  G. Kurat  F. Brandstaetter  Th. Ntaflos 《Petrology》2007,15(2):109-125

Howardites and polymict eucrites are fragments of regolith breccias ejected from the surface of a differentiated (eucritic) parent body, perhaps, of the asteroid Vesta. The first data are presented demonstrating that howardites contain, along with foreign fragments of carbonaceous chondrites, also fragments of ordinary chondrites, enstatite meteorites, ureilites, and mesosiderites. The proportions of these types of foreign meteoritic fragments in howardites and polymict eucrites are the same as in the population of cosmic dust particles obtained from Antarctic and Greenland ice. The concentrations of siderophile elements in howardites and polymict eucrites are not correlated with the contents of foreign meteoritic particles. It is reasonable to believe that cosmogenic siderophile elements are concentrated in howardites and polymict eucrites mostly in submicrometer-sized particles that cannot be examined mineralogically. The analysis of the crater population of the asteroid Vesta indicates that the flux of chondritic material to the surface of this asteroid should have been three orders of magnitude higher than the modern meteoritic flux and have been comparable with the flux to the moon’s surface during its intense meteoritic bombardment. This provides support for the earlier idea about a higher meteoritic activity in the solar system as a whole at approximately 4 Ga. The lithification of the regolith (into regolith breccia) of the asteroid Vesta occurred then under the effect of thermal metamorphism in the blanket of crater ejecta. Thus, meteorite fragments included in howardites provide record of the qualitative composition of the ancient meteorite flux, which was analogous to that of the modern flux at the Earth surface.  相似文献   

The Spatial Characteristics of a Line and Their Application to Line Simplification     

GUOQingsheng  ChristophBrandenberger 《地球空间信息科学学报》2002,5(1):62-67

This paper discusses the spatial knowledge related to a line,and the characteristic points of lines is detected.According to the requirements of line generalization,new algorithms for identifying characteristic line points are presented.These characteristic points are used to improve the algorithms of line generalization.An algorithm for identifying bends is shown.In this paper,improved algorithms based on those by Douglas-Peucker,Visvalingam and Whyatt are shown.In this test,the progressive process of line generalization is emphasized.  相似文献