Three Reflection Telescopes for Wide Field Space Astronomy. First Results from a 30 cm Prototype and Prospects     

Roberto Viotti  Cesare D. La Padula  Domenico Nanni  Agostino Vignato 《Astrophysics and Space Science》2001,276(1):81-88

We present the basic concepts of the two-mirror, three-reflection optical system (2MTRT), and discuss the important benefits of such a system for space projects: wide ( 2^°) correctedand unvignetted FOV, without the use of refractive optics for thefield correction, planarity of the focal surface for an optimizedinstallation of wide area detectors, easy telescope adjustement, small volume and little mass.We also report the results of optical tests made with a 30 cm prototype,equipped with a 2k × 2k CCD camera, and give examples of scientific programmes which can be performed from space and in hostile terrestrial sites such as the Antarctic Plateau.  相似文献   

Volcanic hazards at Fossa of Vulcano: Data from the last 6,000 years     

G. Frazzetta  P. Y. Gillot  L. La Volpe  M. F. Sheridan 《Bulletin of Volcanology》1984,47(1):105-124

Stratigraphic reconstruction of the complete sequence of deposits that formed the Fossa cone of Vulcano has distinguished four principal eruptive cycles: Punte Nere, Palizzi, Commenda, and Pietre Cotte. At least three additional eruptive cycles, one of which ends with the Campo Sportivo lava, occur between deposits of the Punte Nere and Palizzi cycles. However, exposure is inadequate for their characterization. The assignment of the modern deposits that follow the Pietre Cotte lava is uncertain.Deposits of each cycle follow a similar stochastic pattern that is controlled by a decrease in the effect of water/melt interaction. The normal sequence of pyroclastic products for each cycle starts with wet-surge beds, followed by dry-surge horizons, fall deposits, and finally lava flows. Absolute age determinations have been made on each cycle-ending lava flow.Wet-surge deposits normally occur near the crater rim, whereas dry-surge deposits are more widespread, reaching the surrounding caldera wall in many places. Thick fall deposits are confined to a zone extending about 800 m from the crater rim. Lava flows normally reach the base of the cone. The greatest hazard at Fossa is related to surge eruptions. The thickness of dry-surge deposits on the flanks of the cone increases away from the crater, but they pinch out toward the source near the crater rim. SEM analysis of the surface textures of juvenile glass clasts from dry-surge deposits confirms that the dominant control on the eruptive mechanism is water/melt interaction. Only slight modifications are induced on grain surfaces during transport. Particles from the Palizzi dry-surge beds lack surface textures characteristic of fall pyroclasts which suggests that ballistic fragments were not incorporated into the dense portion of the turbulent surge cloud. A quantitative analysis of the dispersal of products from the Palizzi cycle allowed creation of a computer-generated map for this eruption.Paper presented at the IUGG Inter-disciplinary Symposium on Volcanic Hazard, Hamburg, August 1983.  相似文献   

НЕКОТОРЫЕ СВЯЗЫ ЭЛЕКТРИЧЕСКИХ ПАРАМЕТРоВ ГОРНЫХ ПОРоД И ИХ ХИМИЧЕСКОГО СОСТАВА     

Marcela Laštovičková  Karel Svoboda  Рецензенm A. Janáčková 《Studia Geophysica et Geodaetica》1986,30(2):211-213

au aa ¶rt;a, nuau uuu ma n¶rt; u m muu uu, n¶rt; m¶rt;a nm (). u a m u ¶rt; uuu ma u muuu uuau.

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Summary Analysis of the data set describing the chemical composition of the rocks and their electrical parameters was performed by the principal component method. Some relations between chemical composition and electrical parameters were established.

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The Southern Oscillation,environmental anomalies,and mortality of two Southern African seabirds     

Graeme D. La Cock 《Climatic change》1986,8(2):173-184

Mass mortalities and breeding failures of seabirds in the Pacific Ocean have been directly or indirectly linked to local manifestations of the Southern Oscillation. Similar seabird mortalities have been reported in the Benguela upwelling system along the southern African coast. A Boolean factor analysis of binary data (occurrence vs. non-occurrence) showed that certain worldwide and southern African anomalous climatic events tended to co-occur in the same year, and that seabird mortalities and scarcities of small fish along the southern African coast occurred in either the same year, or the year before, the anomalous climatic events. The environmental conditions leading up to warm-water events in southern Africa appear as detrimental to seabird populations as the warm-water events themselves.  相似文献   

Time patterns of polarization currents generated in measuring the electrical conductivity of rocks     

Josef Bochníček  Marcela Laštovičková  Reviewer A. Janáčková 《Studia Geophysica et Geodaetica》1982,26(4):412-415

amamuu aau m¶rt;a uu mn¶rt;mu n¶rt; nu u mnama, m num , naa, m uau nuau nmu um a mam uu.  相似文献   

Heavy metals in the Tiber river basin     

M. Pettine  T. La Noce  G. Macchi  F.J. Millero 《Marine pollution bulletin》1982,13(9):327-329

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On the disappearance of the imf sector structure effect in the lower atmosphere in 1974–1977     

Jan Laštovička  Reviewer L. Křivský 《Studia Geophysica et Geodaetica》1981,25(2):208-210

1974–1977. aum n mun ma nu mau nam aum n, a¶rt;a anu aum amumu, m, m a¶rt;am u u am, nmu uam. ¶rt;am uuu nuu m uu.  相似文献   

Brazil beyond 2020: from deforestation to the energy challenge     

Emilio Lèbre La Rovere  Carolina Burle Dubeux  Amaro Olimpio Pereira Jr  William Wills 《Climate Policy》2013,13(2):70-86

The main assumptions and findings are presented on a comparative analysis of three GHG long-term emissions scenarios for Brazil. Since 1990, land-use change has been the most important source of GHG emissions in the country. The voluntary goals to limit Brazilian GHG emissions pledged a reduction in between 36.1% and 38.9% of GHG emissions projected to 2020, to be 6–10% lower than in 2005. Brazil is in a good position to meet the voluntary mitigation goals pledged to the United Nations Framework Convention on Climate Change (UNFCCC) up to 2020: recent efforts to reduce deforestation have been successful and avoided deforestation will form the bulk of the emissions reduction commitment. In 2020, if governmental mitigation goals are met, then GHG emissions from the energy system would become the largest in the country. After 2020, if no additional mitigation actions are implemented, GHG emissions will increase again in the period 2020–2030, due to population and economic growth driving energy demand, supply and GHG emissions. However, Brazil is in a strong position to take a lead in low-carbon economic and social development due to its huge endowment of renewable energy resources allowing for additional mitigation actions to be adopted after 2020.

Policy relevance

The period beyond 2020 is now relevant in climate policy due to the Durban Platform agreeing a ‘protocol, legal instrument or agreed outcome with legal force’ that will have effect from 2020. After 2020, Brazil will be in a situation more similar to other industrialized countries, faced with a new challenge of economic development with low GHG energy-related emissions, requiring the adoption of mitigation policies and measures targeted at the energy system. Unlike the mitigation actions in the land-use change sector, where most of the funding will come from the national budgets due to sovereignty concerns, the huge financial resources needed to develop low-carbon transport and energy infrastructure could benefit from soft loans channelled to the country through nationally appropriate mitigation actions (NAMAs).  相似文献   

Aeolian sediment provenance and transport in the upper and middle reaches of the Yarlung Zangbo River,Tibet Plateau     

Zhengcai Zhang  Pengfei Ma  Zhen La  Yan Zhang  Aimin Liang 《Basin Research》2023,35(2):762-783

Frequent and serious aeolian disasters occur in the upper and middle reaches of the Yarlung Zangbo River, which runs through the high-elevation Tibet Plateau. Sediment geochemical characteristics can be used as a proxy to identify the sediment's provenance. To determine the provenance of aeolian sediments in the river's basin, we analysed major and trace element contents from surface samples and local clastic rocks throughout the basin. We found that the major and trace elements differed between the middle reaches, upper reaches and regions south of the river. Major element contents were similar in the upper and middle reaches, but trace elements differed. Al₂O₃, MgO and Na₂O concentrations increased from the upper reaches to the lower reaches, and in the lower reaches, MgO and Na₂O were enriched compared with the crustal average. The similarities between samples in the lower part of the upper reaches and those in the middle reaches indicated that sediment transported by fluvial systems from the upper reaches were first deposited in the wide valleys near Xigaze, where they formed a large area of shifting sand. These deposits were then transported by the wind to the river's middle reaches, where they formed a large area of shifting sand. When we compared aeolian sediment in the middle reaches with the local clastic rocks, they appeared to be unrelated. The difference between sediments south of the river and those in the middle reaches means that the southern sediments were not transported to the middle reaches. Therefore, the aeolian sediment in the middle reaches of the Yarlung Zangbo River mainly came from the lower part of the upper reaches, not from the local clastic rocks.  相似文献