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1.
A survey is made of the present constraints on cosmological parameters from Cosmic Microwave Background Anisotropies.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
3.
We have investigated the evolutionary behaviour of intermediate mass (2, 3, 4, 5, and 7M
) Population I stars, assuming two different rates of rotation at the threshold of stability.In the first part of the study, stars are assumed to start with a critical rotation (fast rotation model) and to progress to the point of rotational instability. The stars evolve by losing mass and become rotationally unstable before they reach the zero-age Main Sequence. It is argued that multiple star systems might be formed through the evolution of rapidly rotating stars. An expression for the rotational mass loss rate is derived as a function of the physical parameters of stars.In the second part of the study, stars are assumed to rotate at a rate below the critical value (slow rotation model). The evolution of slowly rotating stars is followed as far as zero-age Main Sequence on the theoretical Hertzsprung-Russell diagram and compared with that of normal stars. The evolutionary paths are found to be more or less similar to those of normal stars; but their positions on the Main Sequence are characterized by effective temperatures and luminosities lower than those of normal stars. The zero-age Main-Sequence times of these stars are longer than those of normal stars. The rotational rates obtained for the zero-age Main Sequence are in good agreement with observed values. 相似文献
4.
Adnan Özdemir 《Environmental Geology》2008,53(8):1695-1710
This study examines the local geological conditions and soil structure as possible causes of the collapse of the Zümrüt Building
2 February 2004. This catastrophe resulted in 92 fatalities and 35 injuries. This study also examines other views which claim
weak soil structure, elastic and consolidation settlement of soil and excessive groundwater extraction as well as subsidence
resulting from the underground silt erosion as possible factors. Zümrüt Building was constructed on normally consolidated,
low plasticity clay. The underground water table was 30 m in depth. The internal friction angle of soil was 8°–30°, its cohesion
was between 34 and 127 kN/m2 and standard penetration test numbers varied between 11 and 50. The underground water level beneath Zümrüt Building had risen
4.5 m since its construction. Therefore the claim that subsidence resulting from the decrease of underground water level contributed
to the collapse is incorrect. Secondly the settlement, resulting from the filling up of the pores created by the silt receding
with the underground water, was 4.4 mm in total, and attributing this as the primary cause of the collapse is also incorrect.
Soil properties, in situ and laboratory test results showed that the existing and/or expected settlement and the differential
ground settlement in the Zümrüt building vicinity had the potential to cause structural damage. The tensile stresses caused
by differential settlements recorded here are thought to be an indicator, but not the main cause contributing to the collapse
of the building. The Zümrüt Building collapse was due to several compounding mistakes during the construction phase. These
were geotechnical and other project faults and the use of low quality construction materials. The resulting catastrophe caused
92 fatalities, 35 injuries and a material loss of approximately US$7 million. 相似文献
5.
Erdal Dolu Erkan Gökaşan Engin Meriç Mustafa Ergin Tolga Görüm Hüseyin Tur Berkan Ecevitoğlu Niyazi Avşar Muhittin Görmüş Fatmagül Batuk Buğser Tok Oktay Çetin 《Geo-Marine Letters》2007,27(6):355-381
The Quaternary evolution of the Gulf of İzmit, situated on the tectonically active North Anatolian Fault Zone (NAFZ), was
investigated using seismic reflection, paleontologic, and sediment textural data. On the basis of seismic stratigraphic and
sedimentologic-paleontologic interpretations, four depositional units were distinguished within the Plio-Quaternary sequence
of the Gulf of İzmit. According to these data, Plio-Quaternary deposits supplied from the northern terrestrial area started
to accumulate during a progradational phase, in a south-facing half-graben. A coarse-grained sedimentary unit prograding into
the gulf from the south since 200 ka b.p. indicates a dramatic variation in the evolution of the gulf, with the initiation of a new strike-slip fault of the NAFZ
and a corresponding uplift of the Armutlu Peninsula in the south of the gulf. During the evolution of this fault from a wide
shear zone consisting of right-stepped strike-slip faults and pull-apart basins to a localized principal fault zone, sediments
were deposited under the influence of northerly prograding terrestrial and shallow-marine conditions due to relative sea-level
fluctuations in the Marmara Sea. During this period, the Gulf of İzmit was invaded mainly by Mediterranean and partly by Black
Sea waters. In the latest glacial period, shallow areas in the gulf became subaerially exposed, whereas the central and western
sub-basins of the gulf turned into lakes. The present evolution of the Gulf of İzmit is controlled by the after effects of
the new rupture of the NAFZ and the estuarine nature of the gulf environment. 相似文献
6.
O. Algan N. Çağatay A. Tchepalyga D. Ongan C. Eastoe E. Gökaşan 《Geo-Marine Letters》2001,20(4):209-218
The sediment infill over the Paleozoic bedrock in the Bosphorus Strait consists of four sedimentary units which were deposited in the last 26,000 14C years B.P. The stratigraphy of these units suggests that this part of the Bosphorus was a freshwater lake between 26,000 and 5,300 14C years B.P., depositing sands with a freshwater mollusc fauna of Black Sea neo-euxinian affinity (Dreissena rostriformis, Dreissena polymorpha, and Monodacna pontica). The first appearance of euryhaline Mediterranean molluscs (e.g., Ostrea edulis, Mytilus edulis) was observed at 5,300 14C years B.P. in this part of the Bosphorus. Deposition of coarse Mytilus-bank and Ostrea-bank units suggests that the establishment of the present dual-flow regime in the Bosphorus took place at about 4,400 14C years B.P. 相似文献
7.
Atίla Özgüç 《Solar physics》1989,123(2):381-383
After re-examination of data presented by Verma (1984), some misuse of solar parameteres published in Solar Geophysical Data is presented. Consequently some conclusions made by Verma (1984, 1986) on about the longitudinal distribution of cool solar surges based on these misuses are discussed. 相似文献
8.
A sulfur isotope study of volcanogenic massive sulfide deposits of the Eastern Black Sea province,Turkey 总被引:1,自引:0,他引:1
Kuroko-type massive sulfide deposits of the Eastern Black Sea province of Turkey are related to the Upper Cretaceous felsic lavas and pyroclastic rocks, and associated with clay and carbonate alteration zones in the footwall and hangingwall lithologies. A complete upward-vertical section of a typical orebody consists of a stringer-disseminated sulfide zone composed mainly of pyrite and chalcopyrite; a massive pyrite zone; a massive yellow ore consisting mainly of chalcopyrite and pyrite; a black ore made up mainly of galena and sphalerite with minor amounts of chalcopyrite, bornite, pyrite and various sulfosalts; and a barite zone. Most of the deposits in the province are associated with gypsum in the footwall or hangingwall. The paragenetic sequence in the massive ore is pyrite, sphalerite, chalcopyrite, bornite, galena and various sulfosalts, with some overlap between the mineral phases. Massive, stringer and disseminated sulfides from eight kuroko-type VMS deposits of the Eastern Black Sea province have a
34S range of 0–7 per mil, consistent with the
34S range of felsic igneous rocks. Sulfides in the massive ore at Madenköy (4.3–6.1 per mil) differ isotopically from sulfides in the stringer zone (6.3–7.2 per mil) suggesting a slightly increased input of H2S derived from marine sulfate with time. Barite and coarse-grained gypsum have a
34S range of 17.7–21.5 per mil, a few per mil higher than the
34S value of contemporaneous seawater sulfate. The deposits may, therefore, have formed in restricted basins in which bacterial reduction of sulfate was taking place. Fine-grained, disseminated gypsum at Kutlular and Tunca has
34S values (2.6–6.1 per mil) overlapping those of ore sulfides, indicating sulfide oxidation during waning stages of hydrothermal activity. 相似文献
9.
New continental crust was formed in the Svecofennian domain of the Baltic Shield c. 1.9 Ga ago. Approximately 0.1–0.15 Ga later, new crust accreted to the SW part of the Shield. In this paper an attempt is made, on the basis of gravity measurements and lithogeochemistry, to describe the tectonic processes responsible for the continental growth c. 1.75–1.8 Ga ago. The Transscandinavian Granite Porphyry Belt (TGPB) separates the Svecofennian domain from the polymetamorphic terrain of the SW Swedish gneiss region. Red orthogneisses occurring immediately west of the TGPB are the deformed equivalents of the TGPB type granitoids, while grey orthogneisses, displaying a tonalitic-granodioritic trend and situated further west, were generated in a »volcanic arc« environment. The TGPB granitoids and the red SW Swedish gneisses represent a transition from this volcanic arc type rock to contemporaneous »within-plate« type granites intruded in the Svecofennian crust. The volcanic arc was forced against the Svecofennian crust in which large tensional fracture zones ensued with strike directions normal to the collision front. In such tensional environments the »withinplate« type granites were generated. In the collision zone the crust was down-warped, and huge amounts of granitic melts were generated at the base of the crust. This TGPB Magma rose upwards utilizing the fracture zone between the arc rocks, generated slightly earlier, and the Svecofennian crust. A relatively thin upper part of the TGPB that spread laterally westwards became strongly deformed during the collision (i.e. the red SW Swedish gneisses), while the major deep-reaching TGPB root zone that was not completely solidified yet, acted as a buffer against the foliation front.
Zusammenfassung Vor 1,9 Milliarden Jahren kam es zur Neubildung von kontinentaler Kruste im svecofennischen Bereich des Baltischen Schildes. Ungefähr 100–150 Millionen Jahre später wurde im Südwesten des Schildes neue Kruste hinzugefügt. In diesem Artikel wird auf der Basis von Gravimetriemessungen und Lithogeochemie der Versuch unternommen die tektomschen Vorgänge, die zu diesem 1,75–1,8 Milliarden Jahre alten Krustenzuwachs führten, zu beschreiben.Der Transskandinavische-Granit-Porphyr-Gürtel (Transscandinavian-Granite-Porphyry-Belt/TGPB) trennt das Svecofennium von der polymetamorphen, im Südwesten Schwedens gelegenen Gneis-Region. Ein direkt westlich des TGPB gelegenes Vorkommen roter Orthogneise entspricht den deformierten TGPB Granitoiden. Graue Orthogneise, die weiter im Westen aufgeschlossen sind, zeigen eine mehr tonalitische bis granodioritische Zusammensetzung und werden auf einen vulkanischen Inselbogen zurückgeführt. Die TGPB Granitoide und die roten südwest-schwedischen Gneise stellen einen Übergang von den Inselbogen-Vulkaniten zu den zeitgleichen »Intra-Platten-Graniten« der svecofennischen Kruste dar. Der Inselbogen kollidierte mit der svecofennischen Kruste, es entstanden großräumige Bruchzonen mit Streichrichtungen senkrecht zur Kollisionsebene. Während des Zustands der hohen Druckspannung des Gebietes intrudierten die »Intra-Platten-Granite«. Innerhalb des Kollisionsbereiches wurde die Kruste nach unten gebogen, und so entstanden an der Basis der Kruste große Mengen granitischen Magmas. Dieses TGPB Magma stieg entlang der Störungszone innerhalb der Inselbogengesteine, die nur wenig älter sind, und der svecofennischen Kruste, auf. Nur ein, von relativ geringer Mächtigkeit, weiter westlich gelegener Teil des TGPB, die roten südwest-schwedischen Gneise, wurde während der Kollision intensiv deformiert. Dagegen war der Hauptanteil der tiefreichenden TGPB Wurzelzone noch nicht vollständig erstarrt und wirkte deshalb wie eine Pufferzone gegen die Schieferungsfront.
Résumé De la croûte continentale nouvelle s'est formée il y a 1,9 Ga dans le domaine des Svecofennides (Bouclier baltique). Environ 100 à 150 Ma plus tard, de la croûte nouvelle s'est accrétionnée à la bordure sud-ouest du bouclier. Cette note basée sur des mesures de gravité et la lithogéochimie, présente un essai d'analyse des processus tectoniques responsables de cette croissance continentale d'âge 1,75 à 1,8 Ga. Le «Transcandinavian Granite Porphygry Belt» (TGPB) sépare le domaine svécofennien des gneiss polymétamorphiques du sud-ouest de la Suède. Immédiatement à l'ouest de TGPB affleurent des orthogneiss rouges qui représentent l'équivalent déformé de granitoïdes du TGPB, tandis que des orthogneiss gris de tendance tonalitique-granodioritique, situés plus à l'ouest, ont été engendrées dans un environnement d'arc volcanique. Les granitoïdes du TGPB et les gneiss rouges du sud-ouest de la Suède représentent une transition entre ces produits d'arc volcanique et les granites intra-plaque de même âge intrudés dans la croûte svécofennienne. L'arc volcanique a été accrétionné à la croûte svécofennienne avec production dans celleci de grandes fractures d'extension perpendiculaires au front de collision. C'est dans ce domaine en extension que les granites intra-plaque se sont mis en place. Dans la zone de collision, la croûte s'est incurvée vers le bas et de grandes quantités de liquides granitiques ont été engendrées à la base de la croûte. Ces magmas TGPB sont montés à la faveur de la zone fracturée entre les roches de l'arc engendrée un peu plus tôt, et la croûte svécofennienne. Seule une fraction supérieure relativement mince du TGPB, développée vers l'ouest, a subi une déformation importante au cours de la collision, pour former les gneiss rouges du sud-ouest de la Suède; par contre, la partie principale de la racine profonde du TGPB, qui n'était pas encore entièrement solidifiée, a joné le role tampon en avant du front de foliation.
, 1,9 100–150 - . - (Transscandinavian Granite-Porphyry-Belt - TGPB) , - . TGPB , , , - , . TGPB - . , , . («within plate» type granites) , . . TGPB , , . TGPB, , - , . TGPB, , .相似文献
10.
Sven O. Franz Lorenz Schwark Cathrin Brüchmann Burkhard Scharf Ralf Klingel Jon D. Van Alstine Namık Çagatay Umut B. Ülgen 《Journal of Paleolimnology》2006,35(4):715-736
A limnogeological reconnaissance study was carried out on Lake Iznik, located in the southeast of the Marmara region of Turkey,
involving a seismic survey and collection of short sediment cores. This lake is located on the middle branch of the North
Anatolian Fault Zone (NAFZ), a transform plate boundary between the Eurasian and Anatolian Plates. It is, therefore, tectonically
active and offers an opportunity to investigate the interplay of sedimentary and seismo-tectonic processes, as well as climate
change and human impact in the region. Short cores of the three sub-basins, maximum length of 35.5 cm, recovered non-laminated,
blackish clays and silts with varying amounts of biogenic and minerogenic (allochthonous, autochthonous) material, which documented
almost the last 80 years of deposition and environmental history. High sedimentation rates in the deeper core sections are
accompanied by changes in land use (conversion of woodland to farmland) in the northern areas of Lake Iznik, which caused
the deposition of more weathered material (high K/Na ratios) and higher contents of Mn in the lake. A tendency towards eutrophic
conditions within the last 20 years is indicated by high nutrient content (N, TOC, P), decreasing C/N-ratios, and characteristic
diatom and cladoceran associations. Also increased pollution is revealed by higher Pb, Cu, and Zn contents and increased supply
of human and animal faeces (high coprostanol content) during the last two decades. But simultaneous lower sedimentation rates
towards the core tops complicate the reconstruction of recent and past eutrophication and pollution states of Lake Iznik.
This requires an extension of the pilot study and deeper sediment cores, to recover non-anthropogenic influenced sediment
levels. 相似文献