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21.
Daniel Ozdín Jozef Plavčan Michaela Horňáčková Pavel Uher Vladimír Porubčan Pavel Veis Jozef Rakovský Juraj Tóth Patrik Konečný Ján Svoreň 《Meteoritics & planetary science》2015,50(5):864-879
The Ko?ice meteorite was observed to fall on 28 February 2010 at 23:25 UT near the city of Ko?ice in eastern Slovakia and its mineralogy, petrology, and geochemistry are described. The characteristic features of the meteorite fragments are fan‐like, mosaic, lamellar, and granular chondrules, which were up to 1.2 mm in diameter. The fusion crust has a black‐gray color with a thickness up to 0.6 mm. The matrix of the meteorite is formed mainly by forsterite (Fo80.6); diopside; enstatite (Fs16.7); albite; troilite; Fe‐Ni metals such as iron and taenite; and some augite, chlorapatite, merrillite, chromite, and tetrataenite. Plagioclase‐like glass was also identified. Relative uniform chemical composition of basic silicates, partially brecciated textures, as well as skeletal taenite crystals into troilite veinlets suggest monomict breccia formed at conditions of rapid cooling. The Ko?ice meteorite is classified as ordinary chondrite of the H5 type which has been slightly weathered, and only short veinlets of Fe hydroxides are present. The textural relationships indicate an S3 degree of shock metamorphism and W0 weathering grade. Some fragments of the meteorite Ko?ice are formed by monomict breccia of the petrological type H5. On the basis of REE content, we suggest the Ko?ice chondrite is probably from the same parent body as H5 chondrite Morávka from Czech Republic. Electron‐microprobe analysis (EMPA) with focused and defocused electron beam, whole‐rock analysis (WRA), inductively coupled plasma mass and optical emission spectroscopy (ICP MS, ICP OES), and calibration‐free laser induced breakdown spectroscopy (CF‐LIBS) were used to characterize the Ko?ice fragments. The results provide further evidence that whole‐rock analysis gives the most accurate analyses, but this method is completely destructive. Two other proposed methods are partially destructive (EMPA) or nondestructive (CF‐LIBS), but only major and minor elements can be evaluated due to the significantly lower sample consumption. 相似文献
22.
T. J. Cox Patrik Jonsson Rachel S. Somerville Joel R. Primack Avishai Dekel 《Monthly notices of the Royal Astronomical Society》2008,384(1):386-409
We employ numerical simulations of galaxy mergers to explore the effect of galaxy mass ratio on merger-driven starbursts. Our numerical simulations include radiative cooling of gas, star formation, and stellar feedback to follow the interaction and merger of four disc galaxies. The galaxy models span a factor of 23 in total mass and are designed to be representative of typical galaxies in the local universe. We find that the merger-driven star formation is a strong function of merger mass ratio, with very little, if any, induced star formation for large mass ratio mergers. We define a burst efficiency that is useful to characterize the merger-driven star formation and test that it is insensitive to uncertainties in the feedback parametrization. In accord with previous work we find that the burst efficiency depends on the structure of the primary galaxy. In particular, the presence of a massive stellar bulge stabilizes the disc and suppresses merger-driven star formation for large mass ratio mergers. Direct, coplanar merging orbits produce the largest tidal disturbance and yield the most intense burst of star formation. Contrary to naive expectations, a more compact distribution of gas or an increased gas fraction both decrease the burst efficiency. Owing to the efficient feedback model and the newer version of smoothed particle hydrodynamics employed here, the burst efficiencies of the mergers presented here are smaller than in previous studies. 相似文献
23.
Herslund Lise Byskov Jalayer Fatemeh Jean-Baptiste Nathalie J&#;rgensen Gertrud Kabisch Sigrun Kombe Wilbard Lindley Sarah Nyed Patrik Karlsson Pauleit Stephan Printz Andreas Vedeld Trond 《Natural Hazards》2015,82(2):149-172
In this paper, we develop and apply a multi-dimensional vulnerability assessment framework for understanding the impacts of climate change-induced hazards in Sub-Saharan African cities. The research was carried out within the European/African FP7 project CLimate change and Urban Vulnerability in Africa, which investigated climate change-induced risks, assessed vulnerability and proposed policy initiatives in five African cities. Dar es Salaam (Tanzania) was used as a main case with a particular focus on urban flooding. The multi-dimensional assessment covered the physical, institutional, attitudinal and asset factors influencing urban vulnerability. Multiple methods were applied to cover the full range of vulnerabilities and to identify potential response strategies, including: model-based forecasts, spatial analyses, document studies, interviews and stakeholder workshops. We demonstrate the potential of the approach to assessing several dimensions of vulnerability and illustrate the complexity of urban vulnerability at different scales: households (e.g., lacking assets); communities (e.g., situated in low-lying areas, lacking urban services and green areas); and entire cities (e.g., facing encroachment on green and flood-prone land). Scenario modeling suggests that vulnerability will continue to increase strongly due to the expected loss of agricultural land at the urban fringes and loss of green space within the city. However, weak institutional commitment and capacity limit the potential for strategic coordination and action. To better adapt to urban flooding and thereby reduce vulnerability and build resilience, we suggest working across dimensions and scales, integrating climate change issues in city-level plans and strategies and enabling local actions to initiate a ‘learning-by-doing’ process of adaptation.
相似文献24.
Patrik Kraufvelin Ari T. Ruuskanen Niko Nappu Mikko Kiirikki 《Estuarine, Coastal and Shelf Science》2007,72(4):665-674
During the reproduction period of Fucus vesiculosus, which occurs only once a year (in May–June) along the Finnish coast of the northern Baltic Sea, a thick carpet of filamentous algae often covers hard substrates suitable for zygote settlement. By placing out artificial substrates into the field, monthly over a period of eight months prior to F. vesiculosus settlement (October 2001–June 2002), we investigated the autumn/winter/spring colonisation and succession of filamentous algae and their possible relationships with the settlement success of F. vesiculosus under naturally variable field conditions. The substrates exposed in October 2001 became covered by filamentous brown algal Pilayella littoralis mats, which persisted over the settlement period of F. vesiculosus, but now also were accompanied by large amounts of the filamentous green alga Cladophora glomerata. The substrates exposed from November 2001 onwards hosted smaller amounts of P. littoralis during the winter and different filamentous algal communities at the time of F. vesiculosus settlement, i.e. less P. littoralis and C. glomerata, but Dictyosiphon foeniculaceus, Ceramium tenuicorne and Ulva intestinalis instead. We observed recruits of F. vesiculosus on all substrates, except on the ones placed out in October 2001. Significantly more P. littoralis and C. glomerata on the October substrates may explain the failed F. vesiculosus recruitment, although we could not establish direct causal or correlational relationships between filamentous algae and F. vesiculosus settlement. We compared the results with a previous un-replicated pilot study in the same area demonstrating similar response patterns. 相似文献
25.
We propose a new approach for calculating the dynamic range of an accelerometer based on an Allan deviation analysis of production seismic data. This test is intended as a field audit technique and does not require an unconditioned dataset from a low‐noise environment. We first show that Allan deviation can measure white noise levels using two commercial accelerometers. The analysis accurately captures the manufacturing noise density specifications and known relationships between white noise, preamplifier gain, and group forming. We then show that a production seismic dataset is suitable for an Allan deviation analysis because the results are not critically affected by a recording filter. Finally, we illustrate the proposed technique by calculating the dynamic range of an accelerometer channel in a seismic streamer using a production dataset. 相似文献
26.
The 2003 Marine Parks Congress recommended networks of marine reserves to be established covering 20–30% of habitats by 2012. Most marine reserves are, however, failing to meet their objectives, the main reason being attributed to lack of funding. In light of the growing need for effectively managed marine reserves, a survey ascertaining tourists' support and willingness to pay extra to stay at reserves managed by the private sector – Hotel Managed Marine Reserves (HMMRs) was conducted at Whale Island Resort, Vietnam. A total of 97.5% support HMMR, 86.3% were willing to pay, the median amounting to US$9.6/room/night, or 10% of the average room rate, equaling US$67,277 at 60% occupancy. 相似文献
27.
Karin Högdahl Jaroslaw Majka Håkan Sjöström Katarina Persson Nilsson Stefan Claesson Patrik Konečný 《Contributions to Mineralogy and Petrology》2012,163(1):167-188
Monazite in melt-producing, poly-metamorphic terranes can grow, dissolve or reprecipitate at different stages during orogenic
evolution particularly in hot, slowly cooling orogens such as the Svecofennian. Owing to the high heat flow in such orogens,
small variations in pressure, temperature or deformation intensity may promote a mineral reaction. Monazite in diatexites
and leucogranites from two Svecofennian domains yields older, coeval and younger U–Pb SIMS and EMP ages than zircon from the
same rock. As zircon precipitated during the melt-bearing stage, its U–Pb ages reflect the timing of peak metamorphism, which
is associated with partial melting and leucogranite formation. In one of the domains, the Granite and Diatexite Belt, zircon
ages range between 1.87 and 1.86 Ga, whereas monazite yields two distinct double peaks at 1.87–1.86 and 1.82–1.80 Ga. The
younger double peak is related to monazite growth or reprecipitation during subsolidus conditions associated with deformation
along late-orogenic shear zones. Magmatic monazite in leucogranite records systematic variations in composition and age during
growth that can be directly linked to Th/U ratios and preferential growth sites of zircon, reflecting the transition from
melt to melt crystallisation of the magma. In the adjacent Ljusdal Domain, peak metamorphism in amphibolite facies occurred
at 1.83–1.82 Ga as given by both zircon and monazite chronology. Pre-partial melting, 1.85 Ga contact metamorphic monazite
is preserved, in spite of the high-grade overprint. By combining structural analysis, petrography and monazite and zircon
geochronology, a metamorphic terrane boundary has been identified. It is concluded that the boundary formed by crustal shortening
accommodated by major thrusting. 相似文献
28.
Patrik Ottoson Hans Hauska 《International journal of geographical information science》2013,27(3):213-226
Systems for landscape visualization and geographical data handling require methods for efficient data access. Retrieval of data from large geographical databases, ten to thousands of Gbytes, is usually optimized with spatial indexing mechanisms. The simplest form of spatial indexing is achieved by dividing the database into congruent grid cells. The subsequent subdivision of the grid cells can be based on so-called quadtrees. Quadtrees for two-dimensional division and subdivision are appropriate for cartographical data. A geographical database, with objects stored in geocentric or geodetic (geographical) co-ordinates, requires indexing mechanisms that take into account the shape of the Earth. In this paper, we present a method for indexing of geographical data, named Ellipsoidal Quadtrees (EQT). In contrast to other global indexing methods, EQT is based on the Earth ellipsoid and not a spherical approximation. EQT division and subdivision make it possible to divide the Earth surface into a mesh of quadrangles with equal areas. We will demonstrate that EQT is flexible. It can be used for indexing databases of various sizes, including national and global databases. Tests on real data show that the performance of EQT is good. 相似文献
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30.
Release of long-lived radionuclides such as plutonium and caesium from spent nuclear fuel in deep geological repositories will depend mainly on the dissolution rate of the UO2 fuel matrix. This dissolution rate will, in turn, depend on the redox conditions at the fuel surface. Under oxidative conditions UO2 will be oxidised to the 1000 times more soluble UO2.67. This may occur in a repository as the reducing deep groundwater becomes locally oxidative at the fuel surface under the effect of α-radiolysis, the process by which α-particles emitted from the fuel split water molecules. On the other hand, the groundwater corrodes canister iron generating large amounts of hydrogen. The role of molecular hydrogen as reductant in a deep bedrock repository is questioned. Here we show evidence of a surface-catalysed reaction, taking place in the H2-UO2-H2O system where molecular hydrogen is able to reduce oxidants originating from α-radiolysis. In our experiment the UO2 surface remained stoichiometric proving that the expected oxidation of UO2.00 to UO2.67 due to radiolytic oxidants was absent. As a consequence, the dissolution of UO2 stopped when equilibrium was reached between the solid phase and U4+ species in the aqueous phase. The steady-state concentration of uranium in solution was determined to be 9 × 10−12 M, about 30 times lower than previously reported for reducing conditions. Our findings show that fuel dissolution is suppressed by H2. Consequently, radiotoxic nuclides in spent nuclear fuel will remain immobilised in the UO2 matrix. A mechanism for the surface-catalysed reaction between molecular hydrogen and radiolytic oxidants is proposed. 相似文献