Intensity of vlf and elf phenomena in the outer ionosphere     

Ya. I. Likhter  V. I. Larkina  František Jiříček  Pavel Tříska  Reviewer S. Fischer 《Studia Geophysica et Geodaetica》1987,31(1):85-91

Summary Spatial and temporal variability of natural ELF-VLF phenomena field intensity has been studied using data from Interkosmos satellites with apogees below 2000 km. The results show a distinct dependence of the diurnal variation and latitudinal intensity distribution on the magnetic activity. The L-value at which the maximum of plasmaspheric noise occurs, e.g., correlates better with the Dst-index than with other indicies.

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Recommendations on the project of monitoring of crustal movements in the western part of the Aswan region in Egypt     

Pavel Vyskocil 《Journal of Geodynamics》1987,7(3-4)

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Overcoring measurements in the příbram mine area and their relation to the regional stress field     

Pavel Peška 《Studia Geophysica et Geodaetica》1993,37(2):141-150

Summary A set of overcoring measurements in deep mines near Píbram is re-interpreted in order to obtain information on the regional component of in situ stress. This is achieved by averaging 17 complete stress tensors measured at the deepest level of the mine, at a depth of 1240 m. The computations indicate that (1) the mean principal stresses act roughly in the horizontal and vertical directions, and (2) the maximum principal stress is horizontal, acting NW - SE, which was also confirmed by the data from all 42 sites of the mine area. The NW - SE orientation of S_H is consistent with the stress pattern in Western Europe and also with borehole breakouts observed within the Bohemian Massif, but the quality of the stress indicator obtained is poor — the standard deviation of the S_H direction is 26°. High variance of the directional data is discussed with respect to stress redistribution due to the mine workings and the contact separating Proterozoic sediments from the Variscan pluton.  相似文献   

哈萨克斯坦北部Kumdy-Kol金刚石矿床地质与变质金刚石成因   总被引：1，自引：0，他引：1  

Pavel NITSENKO 《地学前缘》2004,11(2):333-338

哈萨克斯坦北部Kokchetav地区的Kumdy Kol金刚石矿床是世界上惟一的变质金刚石矿床。对该金刚石矿床成因以及相关岩石的诸多研究成果不仅深化了对超高压变质岩的研究 ,而且推动了大陆动力学研究的进展。在该金刚石矿床中找到的岩相学证据证明 ,该金刚石矿床的主要含矿岩石大理岩曾经在俯冲带中循环到 >2 4 0km的深部。文章在介绍Kokchetav变质金刚石矿床的地质特征和大地构造背景的基础上 ,讨论了该变质金刚石矿床的形成过程以及变质金刚石的成因。Kokchetav变质金刚石主要表现出蜂窝状或草莓状的特征外形。这种蜂窝状或草莓状金刚石是快速生长条件下结晶的结果。结合最近的研究成果 ,笔者认为Kokchetav金刚石矿床中金刚石的形成与深俯冲大理岩中的白云石分解作用密切相关。白云石分解反应形成文石和菱镁矿组合 ,菱镁矿继续分解形成金刚石 (MgCO3 =金刚石 +MgO +O2 )。基于这个认识 ,Kokchetav金刚石矿床中碳 (金刚石和石墨 )的来源应该是碳酸盐岩  相似文献   

Paleolimnology of a freshwater estuary to inform Area of Concern nutrient delisting efforts     

Elizabeth E. Alexson  Euan D. Reavie  Richard P. Axler  Sergiy V. Yemets  Pavel A. Krasutsky  Mark B. Edlund  Robert W. Pillsbury  Diane Desotelle 《Journal of Paleolimnology》2018,59(3):373-395

The St. Louis River Estuary (SLRE), a freshwater estuary bordering Duluth, Minnesota, Superior, Wisconsin, and the most western point of Lake Superior (46.74°, ? 92.13°), has a long history of human development since Euro-American settlement ~ 200 years ago. Due to degradation from logging, hydrologic modification, industrial practices, and untreated sewage, the SLRE was designated an Area of Concern in 1987. Action has been taken to restore water quality including the installation of the Western Lake Superior Sanitary District in 1978 to help remove beneficial use impairments. A better understanding of historical impacts and remediation is necessary to help document progress and knowledge gaps related to water quality, so a paleolimnological study of the SLRE was initiated. Various paleolimnological indicators (pigments, diatom communities, and diatom-inferred phosphorus) were analyzed from six cores taken throughout the SLRE and another from western Lake Superior. Reductions in eutrophic diatom taxa such as Cyclotella meneghiniana and Stephanodiscus after 1970 in certain cores suggest an improvement in water quality over the last 40 years. However, in cores taken from estuarine bay environments, persistence of eutrophic taxa such as Cyclostephanos dubius and Stephanodiscus binderanus indicate ongoing nutrient problems. Sedimentary pigments also indicate cyanobacteria increases in bays over the last two decades. Diatom model-inferred phosphorus and contemporary monitoring data suggest some of the problems associated with excess nutrient loads have been remediated, but modern conditions (internal phosphorus loading, changing climate) may be contributing to ongoing water quality impairments in some locations. The integrated record of biological, chemical, and physical indicators preserved in the sediments will aid state and federal agencies in determining where to target their resources.  相似文献   

On the variation of the initial mass function     

Pavel Kroupa 《Monthly notices of the Royal Astronomical Society》2001,322(2):231-246

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Accumulation peculiarities of artificial radionuclides in the elements of coastal ecosystems on the Kola Peninsula     

D. G. Matishov  I. S. Usyagina  N. E. Kasatkina  E. V. Pavel’skaya 《Doklady Earth Sciences》2007,413(2):448-451

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Long-term variability in the hydrochemical regime of the Manych-Chograi hydrological system     

D. G. Matishov  T. A. Orlova  Yu. M. Gargopa  E. V. Pavel’skaya 《Water Resources》2007,34(5):527-531

Data collected from the scientific literature and field studies carried out by the specialists from the Azov Branch of the Murmansk Institute of Marine Biology and from the Southern Scientific Center in July and August of 2004 are used to confirm the further salinization of the Manych-Gudilo Lake. The aforesaid salinization was accompanied by a change in the water state index, caused by an increase in the salinity of inflowing water, which determines the water-and-salt budget of the lake.  相似文献   

First recorded eruption of Mount Belinda volcano (Montagu Island), South Sandwich Islands     

Matthew R. Patrick  John L. Smellie  Andrew J. L. Harris  Robert Wright  Ken Dean  Pavel Izbekov  Harold Garbeil  Eric Pilger 《Bulletin of Volcanology》2005,67(5):415-422

The MODVOLC satellite monitoring system has revealed the first recorded eruption of Mount Belinda volcano, on Montagu Island in the remote South Sandwich Islands. Here we present some initial qualitative observations gleaned from a collection of satellite imagery covering the eruption, including MODIS, Landsat 7 ETM+, ASTER, and RADARSAT-1 data. MODVOLC thermal alerts indicate that the eruption started sometime between 12 September and 20 October 2001, with low-intensity subaerial explosive activity from the islands summit peak, Mount Belinda. By January 2002 a small lava flow had been emplaced near the summit, and activity subsequently increased to some of the highest observed levels in August 2002. Observations from passing ships in February and March 2003 provided the first visual confirmation of the eruption. ASTER images obtained in August 2003 show that the eruption at Mount Belinda entered a new phase around this time, with fresh lava effusion into the surrounding icefield. MODIS radiance trends also suggest that the overall activity level increased significantly after July 2003. Thermal anomalies continued to be observed in MODIS imagery in early 2004, indicating a prolonged low-intensity eruption and the likely establishment of a persistent summit lava lake, similar to that observed on neighboring Saunders Island in 2001. Our new observations also indicate that lava lake activity continues on Saunders Island.Editorial responsibility: J. Gilbert  相似文献   

Palaeobotanical evidence for warm summers in the East Siberian Arctic during the last cold stage     

Frank Kienast  Lutz Schirrmeister  Christine Siegert  Pavel Tarasov 《Quaternary Research》2005,63(3):175-300

Plant macrofossils from the “Mamontovy Khayata” permafrost sequence (71°60′N, 129°25′E) on the Bykovsky Peninsula reflect climate and plant biodiversity in west Beringia during the last cold stage. 70 AMS and 20 conventional ¹⁴C dates suggest sediment accumulation between about 60,000 and 7500 ¹⁴C yr B.P. The plant remains prove that during the last cold-stage arctic species (Minuartia arctica, Draba spp., Kobresia myosuroides) coexisted with aquatic (Potamogeton vaginatus, Callitriche hermaphroditica), littoral (Ranunculus reptans, Rumex maritimus), meadow (Hordeum brevisubulatum, Puccinellia tenuiflora) and steppe taxa (Alyssum obovatum, Silene repens, Koeleria cristata, Linum perenne). The reconstructed vegetation composition is similar to modern vegetation mosaics in central and northeast Yakutian relict steppe areas. Thus, productive meadow and steppe communities played an important role in the Siberian Arctic vegetation during the late Pleistocene and could have served as food resource for large populations of herbivores. The floristic composition reflects an extremely continental, arid climate with winters colder and summers distinctly warmer than at present. Holocene macrofossil assemblages indicate a successive paludification possibly connected with marine transgression, increased oceanic influence and atmospheric humidity. Although some steppe taxa were still present in the early Holocene, they disappeared completely before 2900 ¹⁴C yr B.P.  相似文献