Chemical abundances and ionizing clusters of H ii regions in the LINER galaxy NGC 4258     

Angeles I. Díaz  Marcelo Castellanos  Elena Terlevich †  María Luisa García-Vargas 《Monthly notices of the Royal Astronomical Society》2000,318(2):462-474

We present long-slit observations in the optical and near-infrared of eight H  ii regions in the spiral galaxy NGC 4258. Six of the observed regions are located in the south-east inner spiral arms, and the other two are isolated in the northern outer arms. A detailed analysis of the physical conditions of the gas has been performed. For two of the regions, an electron temperature has been derived from the [S  iii ] λ 6312 line. For the rest, an empirical calibration based on the red and near-infrared sulphur lines has been used. The oxygen abundances derived by both methods are found to be significantly lower (by a factor of 2) than previously derived by using empirical calibrations based on the optical oxygen lines.
In the brightest region, 74C, the observation of a prominent feature caused by Wolf–Rayet (WR) stars provides an excellent constraint over some properties of the ionizing clusters. In the light of the current evolutionary synthesis models, no consistent solution is found to explain at the same time both the WR feature characteristics and the emission-line spectrum of this region. In principle, the presence of WR stars could lead to large temperature fluctuations and also to a hardening of the ionizing radiation. None of these effects is found in region 74C, for which the electron temperatures found from the [S  iii ] λ 6312 line and the Paschen discontinuity at 8200 Å are equal within the errors, and the effective temperature of the ionizing radiation is estimated at around 35 300 K.
Both more observations of confirmed high-metallicity regions and a finer metallicity grid for the evolutionary synthesis models are needed in order to understand the ionizing populations of H  ii regions.  相似文献   

Hybrid derivative-free extended Kalman filter for unknown lever arm estimation in tightly coupled DGPS/INS integration     

Yanrui Geng  Richard Deurloo  Luisa Bastos 《GPS Solutions》2011,15(2):181-191

Differential carrier phase observations from GPS (Global Positioning System) integrated with high-rate sensor measurements, such as those from an inertial navigation system (INS) or an inertial measurement unit (IMU), in a tightly coupled approach can guarantee continuous and precise geo-location information by bridging short outages in GPS and providing a solution even when less than four satellites are visible. However, to be efficient, the integration requires precise knowledge of the lever arm, i.e. the position vector of the GPS antenna relative to the IMU. A previously determined lever arm by direct measurement is not always available in real applications; therefore, an efficient automatic estimation method can be very useful. We propose a new hybrid derivative-free extended Kalman filter for the estimation of the unknown lever arm in tightly coupled GPS/INS integration. The new approach takes advantage of both the linear time propagation of the Kalman filter and the nonlinear measurement propagation of the derivative-free extended Kalman filter. Compared to the unscented Kalman filter, which in recent years is typically used as a superior alternative to the extended Kalman filter for nonlinear estimation, the virtue of the new Kalman filter is equal estimation accuracy at a significantly reduced computational burden. The performance of the new lever arm estimation method is assessed with simulated and real data. Simulations show that the proposed technique can estimate the unknown lever arm correctly provided that maneuvers with attitude changes are performed during initialization. Field test results confirm the effectiveness of the new method.  相似文献   

Overview of the Italian strong motion database ITACA 1.0   总被引：3，自引：2，他引：1  

Francesca Pacor  Roberto Paolucci  Lucia Luzi  Fabio Sabetta  Andrea Spinelli  Antonella Gorini  Mario Nicoletti  Sandro Marcucci  Luisa Filippi  Mauro Dolce 《Bulletin of Earthquake Engineering》2011,9(6):1723-1739

The Italian Strong Motion Database, ITACA, was developed within projects S6 and S4, funded in the framework of the agreements between the Italian Department of Civil Protection (Dipartimento della Protezione Civile, DPC) and the Istituto Nazionale di Geofisica e Vulcanologia (INGV), starting from 2005. The alpha version of the database was released in 2007 and subsequently upgraded to version 1.0 after: (i) including the most recent strong motion data (from 2005 to 2007) recorded in Italy, in addition to the 2008 Parma earthquake, M 5.4, and the M ≥  4.0, 2009 Abruzzo seismic events; (ii) processing the raw strong motion data using an updated procedure; (iii) increasing the number of stations with a measured shear wave velocity profile; (iv) improving the utilities to retrieve time series and ground motion parameters; (v) implementing a tool for selecting time series in agreement with design-response spectra; (vi) compiling detailed station reports containing miscellaneous information such as photo, maps and site parameters; (vii) developing procedures for the automatic generation of station reports and for the updating of the header files. After such improvements, ITACA 1.0 was published at the web site , in 2010. It presently contains 3,955 three-component waveforms, comprising the most complete catalogue of the Italian accelerometric records in the period 1972–2007 (3,562 records) and the strongest events in the period 2008–2009. Records were mainly acquired by DPC through its Accelerometric National Network (RAN) and, in few cases, by local networks and temporary stations or networks. This paper introduces the published version of the Italian Strong Motion database (ITACA version 1.0) together with main improvements and new functionalities.  相似文献   

Magnetic classification of stony meteorites: 1. Ordinary chondrites     

Pierre ROCHETTE  Leonardo SAGNOTTI  Michle BOUROT‐DENISE  Guy CONSOLMAGNO  Luigi FOLCO  Jrme GATTACCECA  Maria Luisa OSETE  Lauri PESONEN 《Meteoritics & planetary science》2003,38(2):251-268

Abstract— We present a database of magnetic susceptibility measurements on 971 ordinary chondrites. It demonstrates that this parameter can be successfully used to characterize and classify ordinary chondrite meteorites. In ordinary chondrites, this rapid and non‐destructive measurement essentially determines the amount of metal in the sample, which occurs in a very narrow range for each chondrite class (though terrestrial weathering can result in a variable decrease in susceptibility, especially in finds). This technique is particularly useful not only for a rapid classification of new meteorites, but also as a check against curation errors in large collections (i.e., unweathered meteorites, the measured susceptibility of which lies outside the expected range, may well be misclassified or misidentified samples). Magnetic remanence, related to magnetic field measurements around asteroids, is also discussed.  相似文献   

Nondestructive spectroscopic and petrochemical investigations of Paleoarchean spherule layers from the ICDP drill core BARB5, Barberton Mountain Land,South Africa          下载免费PDF全文

Jörg Fritz  Roald Tagle  Luisa Ashworth  Ralf Thomas Schmitt  Axel Hofmann  Béatrice Luais  Phillip D. Harris  Desirée Hoehnel  Seda Özdemir  Tanja Mohr‐Westheide  Christian Koeberl 《Meteoritics & planetary science》2016,51(12):2441-2458

A Paleoarchean impact spherule‐bearing interval of the 763 m long International Continental Scientific Drilling Program (ICDP) drill core BARB5 from the lower Mapepe Formation of the Fig Tree Group, Barberton Mountain Land (South Africa) was investigated using nondestructive analytical techniques. The results of visual observation, infrared (IR) spectroscopic imaging, and micro‐X‐ray fluorescence (μXRF) of drill cores are presented. Petrographic and sedimentary features, as well as major and trace element compositions of lithologies from the micrometer to kilometer‐scale, assisted in the localization and characterization of eight spherule‐bearing intervals between 512.6 and 510.5 m depth. The spherule layers occur in a strongly deformed section between 517 and 503 m, and the rocks in the core above and below are clearly less disturbed. The μXRF element maps show that spherule layers have similar petrographic and geochemical characteristics but differences in (1) sorting of two types of spherules and (2) occurrence of primary minerals (Ni‐Cr spinel and zircon). We favor a single impact scenario followed by postimpact reworking, and subsequent alteration. The spherule layers are Al₂O₃‐rich and can be distinguished from the Al₂O₃‐poor marine sediments by distinct Al‐OH absorption features in the short wave infrared (SWIR) region of the electromagnetic spectrum. Infrared images can cover tens to hundreds of square meters of lithologies and, thus, may be used to search for Al‐OH‐rich spherule layers in Al₂O₃‐poor sediments, such as Eoarchean metasediments, where the textural characteristics of the spherule layers are obscured by metamorphism.  相似文献   

Simulated effect of soil depth and bedrock topography on near‐surface hydrologic response and slope stability     

Cristiano Lanni  Jeff McDonnell  Luisa Hopp  Riccardo Rigon 《地球表面变化过程与地形》2013,38(2):146-159

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Depth of faulting and ancient heat flows in the Kuiper region of Mercury from lobate scarp topography     

Isabel Egea-González  Javier Ruiz  Carlos Fernández  Jean-Pierre Williams  Álvaro Márquez  Luisa M. Lara 《Planetary and Space Science》2012,60(1):193-198

Mercurian lobate scarps are interpreted to be the surface expressions of thrust faults formed by planetary cooling and contraction, which deformed the crust down to the brittle–ductile transition (BDT) depth at the time of faulting. In this work we have used a forward modeling procedure in order to analyze the relation between scarp topography and fault geometries and depths associated with a group of prominent lobate scarps (Santa Maria Rupes and two unnamed scarps) located in the Kuiper region of Mercury for which Earth-based radar altimetry is available. Also a backthrust associated with one of the lobate scarps has been included in this study. We have obtained best fits for depths of faulting between 30 and 39 km; the results are consistent with the previous results for other lobate scarps on Mercury.The so-derived fault depths have been used to calculate surface heat flows for the time of faulting, taking into account crustal heat sources and a heterogeneous surface temperature due to the variable insolation pattern. Deduced surface heat flows are between 19 and 39 mW m^?2 for the Kuiper region, and between 22 and 43 mW m^?2 for Discovery Rupes. Both BDT depths and heat flows are consistent with the predictions of thermal history models for the range of time relevant for scarp formation.  相似文献   

Organic matter fractionation in aggregates typical Argiudolls southeastern Buenos Aires and its relation to different soil uses: a preliminary study     

Maria Fernanda Alvarez  Margarita Luisa Osterrieth  Julio Luis del Río 《Environmental Earth Sciences》2012,65(2):505-515

Organic matter is a fundamental factor in the biogeochemical cycle of carbon; it influences the chemical, physical, and biological properties of the soil. The aim of this paper is to determine the organic fractions in the three predominant morphologies of aggregates found in Typical Argiudolls of the Buenos Aires southeastern area and to link them to different soil uses, as possible indicators of soil quality. The study was carried out in the basin de Los Padres Pound (General Pueyrredón, Buenos Aires). We analyzed the first 5 cm of mollic epipedons of plots with different soil uses: (a) cultivated plots, (b) pine and eucalyptus forests, (c) pastures, and (d) a natural plot in the de Los Padres Pound Reserve as a reference. The percentage of soil organic carbon (SOC), light organic carbon (LOC), fulvic acids (FA), humic acids (HA), and humins (H) in elongated, quadrangular and spherical aggregates were determined. The results show slight variations in SOC (7.2–8.6%) in the spherical aggregates of all the plots and a greater variability in elongated and quadrangular aggregates (5.6–10% and 6.9–13.6%, respectively). HA are minimal in the agroecosystems with extreme values of 0.02% in the spherical aggregates of cultivated plots, and maximal in the elongated and quadrangular aggregates of natural plots (0.3–0.5%). Fulvic acids display a similar behavior, while H decrease slightly with the morphologies and the different practices. The substantial decrease of humic substances in cultivated plots translates into a lower biologic activity; this, in turn, influences the aggregation, thus lowering the structural stability of these plots, which have been under agro-horticultural management for more than 50 years.  相似文献   

Reconstruction of hydrocarbons accumulation in sediments affected by the oil refinery industry: the case of Tehuantepec Gulf (Mexico)     

Ana Carolina Ruiz-Fernández  Mario Sprovieri  Mauro Frignani  Joan Albert Sanchez-Cabeza  Maria Luisa Feo  Luca Giorgio Bellucci  Libia Hascibe Pérez-Bernal  Michel Preda  María Luisa Machain-Castillo 《Environmental Earth Sciences》2012,67(3):727-742

The Isthmus of Tehuantepec corresponds to the shortest distance (~200?km) between the Gulf of Mexico and the Pacific Ocean in Southern Mexico, and the main economical activity of this region is oil extraction and refining. Polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) were determined in a ²¹⁰Pb dated sediment core collected from the continental shelf of Tehuantepec Gulf, in the vicinity of the oil refinery of Salina Cruz, Oaxaca, the main oil refining facility of the country. The sediments were mostly of coarse nature and hence PAHs and TPHs concentrations throughout the core (61?C404???g?g^?1 and 29?C154?mg?kg^?1, respectively) were below international quality benchmarks. Depth profiles of both PAHs and TPHs concentrations showed increasing trends since the early 1900s but the higher values were found from the 1950s to present. PAH congener ratios showed that these contaminants had both petrogenic and pyrolitic sources, although the former has been predominant since the 1970s. The Salina Cruz refinery started operations in 1978 but the oil industry activities in the Tehuantepec Isthmus go back to the beginning of the twentieth century with the operation of Minatitlan refinery in the Gulf of Mexico, and the Gulf of Tehuantepec being the main conduit for oil distribution in the Pacific coast. The observed changes in contaminant distributions described well the oil industry development in the area.  相似文献   

The relevance of preferential flow in catchment scale simulations: Calibrating a 3D dual-permeability model using DREAM     

Luisa Hopp  Barbara Glaser  Julian Klaus  Thilo Schramm 《水文研究》2020,34(5):1237-1254

The occurrence of preferential flow in the subsurface has often been shown in field experiments. However, preferential flow is rarely included in models simulating the hydrological response at the catchment scale. If it is considered, preferential flow parameters are typically determined at the plot scale and then transferred to larger-scale simulations. Here, we successfully used the optimization algorithm DiffeRential Evolution Adaptive Metropolis (DREAM) to calibrate a 3D physics-based dual-permeability model directly at the catchment scale. In order to keep computational costs of the optimization routine at a reasonable level, we limited the number of parameters to be calibrated to the ones that had been shown before to be most influential for the simulation of discharge. We also calibrated parameters of the matrix domain and the macropore domain with a fixed parameter ratio between soil layers instead of calibrating every layer separately. These ratios reflected observed depth profiles of soil hydraulic properties at our study site. The dual-permeability parameter sets identified during calibration were able to simulate observed discharge time series satisfactorily but did not outperform a calibrated single-domain reference model scenario. Saturated hydraulic conductivities of the macropore domain were calibrated such that they became very similar to matrix saturated hydraulic conductivities, thereby effectively removing the effect of macropores. This suggests that the incorporation of vertical preferential flow as represented by the dual-permeability approach was not relevant for reproducing the hydrometric response reasonably well in the studied catchment. We also tested the scale-invariance of the calibrated dual-permeability parameter sets by using the parameter sets performing best at catchment scale to simulate plot-scale bromide depth profiles obtained from tracer irrigation experiments. This parameter transfer proved to be not successful, indicating that soil hydraulic parameters are scale-variant, independent of the direction of parameter transfer.  相似文献