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61.
We present results of a magnetic survey of achondritic meteorites, representing the aubrites (A), diogenites (D), Irowardites (H), and eucrites (E) groups and relate their magnetic behavior to respective class characteristics and models of origin.Magnetic susceptibility (x) values cluster well within each group and decrease systematically between groups (from 2 to 0.1×10–3GOe–1 cm–3), with the average metal contents, (from 1 to <0.1 wt%) in the above order. The natural remanent magnetization (NRM) values range broadly within each group, but group averages decrease roughly as above. However, the considerable within-sample and intra-group variability in NRM level and its demagnetization characteristics attest to inhomogeneous and localized brecciation effects. Although petrological-chemical studies resolve a primary component of magmatic differentiation on the planetoid of origin, no clear magnetic record of such event has been preserved. The magnetization of achondrites is mainly the product of their complex, multi-stage impact brecciation and metamorphism history, in accord with other lines of evidence.The magnetic behavior of achondrites is remarkably similar to that characteristic of lunar breccias and impact-melt rocks and reinforces their analogous mode of genesis, as brought out by chemical and petrographic analyses. 相似文献
62.
The 50% and 90% P-wave detection thresholds of 3 Austrian, 2 Czech, 5 German, 1 Hungarian and 3 Slovak seismic stations have been determined for four intervals of epicentral distances by a direct method using the maximum-likelihood technique. The USGS-NEIC Earthquake Data Reports covering the period from January 1990 to November 1994 were used as the reference system. The seismic stations Kaperské Hory (KHC, Czech Republic) and Collmberg (CLL, Germany) are the stations with the best detection capabilities for all investigated intervals of epicentral distances. 相似文献
63.
Miriam Baglioni Emiliano Giovannetti Maria Vittoria Masserotti Chiara Renso Laura Spinsanti 《Transactions in GIS》2008,12(Z1):31-44
Querying geographical information systems has been recognized as a difficult task for non‐expert users. Furthermore, user queries are often characterized by semantic aspects not directly managed by traditional spatial databases or GIS. Examples of such semantic geospatial queries are the use of implicit spatial relations between objects, or the reference of domain concepts not explicitly represented in data. To handle such queries, we envisage a system that translates natural language queries into spatial SQL statements on a database, thus improving standard GIS with new semantic capabilities. Within this general objective, the contribution of this article is to introduce a methodology to handle semantic geospatial queries issued over a spatial database. This approach captures semantics from an ontology built upon the spatial database and enriched by domain concepts and properties specifically defined to represent the localization of objects. Some examples of the use of the methodology in the urban domain are presented. 相似文献
64.
Ana Valdeolmillos‐Rodríguez Miriam Dorado‐Valiño Maria Blanca Ruiz‐Zapata Ana María Alonso‐Zarza 《第四纪科学杂志》2011,26(1):128-140
The Middle Pleistocene palaeoclimate and palaeoenvironment evolution of the Las Tablas de Daimiel wetlands is described using a combination of sedimentology, pollen and δ13C and δ18O isotopic records of Unit B of core LT‐199906. This unit mostly contains fluvial and palustrine sediments. U/Th and amino acid racemization (AAR) dating and a comparison of the δ18O curve of Unit B with oceanic records suggests that Unit B spans the period from the end of Marine Isotope Stage (MIS) 10 (340 ka) to the first stages of MIS 7 (ca. 210 ka). MIS 9 was characterised by a regional vegetation dominated by Cupressaceae, with Pinus as a tree element. The water level was high and temperatures were very probably higher than during the Holocene. MIS 8 and the first substages of MIS 7 (7e, 7d and 7c) were dominated by xerophilous steppe vegetation in lowlands (elevations around 610 m above sea level) near to the wetland. At higher altitudes, far away from the wetland, there were fewer Pinus than in MIS 9, and a greater presence of warm, temperate and cool climate tree elements. The aquatic system in MIS 9 became shallower, with eutrophication and the accumulation of organic matter occurring; temperatures were similar to or lower than those of the Holocene. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
65.
Miriam Colombi Barbara Borzi Helen Crowley Mauro Onida Fabrizio Meroni Rui Pinho 《Bulletin of Earthquake Engineering》2008,6(3):485-504
The concerted effort to collect earthquake damage data in Italy over the past 30 years has led to the development of an extensive
database from which vulnerability predictions for the Italian building stock can be derived. A methodology to derive empirical
vulnerability curves with the aforementioned data is presented herein and the resulting curves have been directly compared
with mechanics-based vulnerability curves. However, it has been found that a valid comparison between the empirical and analytical
vulnerability curves is not possible mainly due to a number of shortcomings in the database of surveyed buildings. A detailed
discussion of the difficulties in deriving vulnerability curves from the current observed damage database is thus also presented. 相似文献
66.
Miriam Garcia 《Astrophysics and Space Science》2011,335(1):131-136
The Local Group galaxies enable us to study the impact of metallicity on the structure and evolution of massive stars through
spectroscopic analyses. However, color-based target selection for spectroscopy (in absence of known spectral types), though
relatively successful, usually produces lists dominated by B-type modest-mass stars. We have developed a friends of friends
code to find OB associations in Local Group galaxies (Garcia et al. in Astron. Astrophys. 502:1015, 2009; Bull. Soc. R. Sci. Liege 80:381, 2011a). The interpretation of the association’s color-magnitude diagrams (CMDs) and the automatic determination of evolutionary
masses for the members, allow a more insightful choice of candidates for spectroscopy and to spot out potential advanced evolutionary
stages (Garcia et al. in Astron. Astrophys. 523:A23, 2010). We show our results on the dwarf irregular IC 1613 as illustration of the potential of the method. 相似文献
67.
Miriam Baumgartner Ronald J. Bakker Gerald Doppler 《Contributions to Mineralogy and Petrology》2014,168(1):1-14
Re-equilibration processes of natural H2O–CO2–NaCl-rich fluid inclusions quartz are experimentally studied by exposing the samples to a pure H2O external fluid at 600 °C. Experimental conditions are selected at nearly constant pressure conditions (309 MPa) between fluid inclusions and pore fluid, with only fugacity gradients in H2O and CO2, and at differential pressure conditions (394–398 MPa, corresponding to an internal under-pressure) in addition to similar CO2 fugacity gradients and larger H2O fugacity gradients. Modifications of fluid inclusion composition and density are monitored with changes in ice dissolution temperature, clathrate dissolution temperature and volume fraction of the vapour phase at room temperature. Specific modification of these parameters can be assigned to specific processes, such as preferential loss/gain of H2O and CO2, or changes in total volume. A combination of these parameters can clearly distinguish between modifications according to bulk diffusion or deformation processes. Bulk diffusion of CO2 according to fugacity gradients is demonstrated at constant pressure conditions. The estimated preferential loss of H2O is not in accordance with those gradients in both constant pressure and differential pressure experiments. The development of deformation halos in quartz around fluid inclusions that are either under-pressurized or over-pressurized promotes absorption of H2O from the inclusions and inhibits bulk diffusion according to the applied fugacity gradients. 相似文献
68.
We present three new benthic foraminiferal δ13C, δ18O, and total organic carbon time series from the eastern Atlantic sector of the Southern Ocean between 41°S and 47°S. The measured glacial δ13C values belong to the lowest hitherto reported. We demonstrate a coincidence between depleted late Holocene (LH) δ13C values and positions of sites relative to ocean surface productivity. A correction of +0.3 to +0.4 [‰ VPDB] for a productivity-induced depletion of Last Glacial Maximum (LGM) benthic δ13C values of these cores is suggested. The new data are compiled with published data from 13 sediment cores from the eastern Atlantic Ocean between 19°S and 47°S, and the regional deep and bottom water circulation is reconstructed for LH (4–0 ka) and LGM (22–16 ka) times. This extends earlier eastern Atlantic-wide synoptic reconstructions which suffered from the lack of data south of 20°S. A conceptual model of LGM deep-water circulation is discussed that, after correction of southernmost cores below the Antarctic Circumpolar Current (ACC) for a productivity-induced artifact, suggests a reduced formation of both North Atlantic Deep Water in the northern Atlantic and bottom water in the southwestern Weddell Sea. This reduction was compensated for by the formation of deep water in the zone of extended winter sea-ice coverage at the northern rim of the Weddell Sea, where air–sea gas exchange was reduced. This shift from LGM deep-water formation in the region south of the ACC to Holocene bottom water formation in the southwestern Weddell Sea, can explain lower preformed δ13CDIC values of glacial circumantarctic deep water of approximately 0.3‰ to 0.4‰. Our reconstruction brings Atlantic and Southern Ocean δ13C and Cd/Ca data into better agreement, but is in conflict, however, with a scenario of an essentially unchanged thermohaline deep circulation on a global scale. Benthic δ18O-derived LGM bottom water temperatures, by 1.9°C and 0.3°C lower than during the LH at deepest southern and shallowest northern sites, respectively, agree with the here proposed reconstruction of deep-water circulation in the eastern South Atlantic Ocean. 相似文献
69.
Patricia Fernndez-Calvo Christian Nke Luis A. Rivas Miriam García-Villadangos Javier Gmez-Elvira Víctor Parro 《Planetary and Space Science》2006,54(15):1612-1621
We have developed antibodies and a multi-array competitive immunoassay (MACIA) for the detection of a wide range of molecular size compounds, from single aromatic ring derivatives or polycyclic aromatic hydrocarbons (PAHs), through small peptides, proteins or whole cells (spores). Multiple microarrays containing target molecules are used simultaneously to run several competitive immunoassays. The sensitivity of the MACIA for small organic compounds like naphthalene, 4-phenilphenol or 4-tertbutilphenol is in the range of 100–500 ppb (ng ml−1), for others like the insecticide terbutryn it is at the ppt (ng l−1) level, while for small peptides, as well as for more complex molecules like the protein thioredoxin, the sensitivity is approximately 1–2 ppb, or 104–105 spores of Bacillus subtilis per milliliter. For organic compounds, a water–methanol solution was used in order to achieve a better dissolution of the organics without compromising the antibody–antigen interaction. The above-mentioned compounds were detected by MACIA in water–(10%) methanol extracts from spiked pyrite and hematite-containing rock powder samples, as well as from a spiked-sand sample subjected to organic extraction with dichloromethane–methanol (1/1). 相似文献