Understanding the chemical complexity in Circumstellar Envelopes of C-Rich AGB stars: the case of IRC +10216     

M. Agúndez  J. Cernicharo  J. R. Pardo  J. P. Fonfría Expósito  M. Guélin  E. D. Tenenbaum  L. M. Ziurys  A. J. Apponi 《Astrophysics and Space Science》2008,313(1-3):229-233

The circumstellar envelopes of carbon-rich AGB stars show a chemical complexity that is exemplified by the prototypical object IRC +10216, in which about 60 different molecules have been detected to date. Most of these species are carbon chains of the type C _n H, C _n H₂, C _n N, HC _n N. We present the detection of new species (CH₂CHCN, CH₂CN, H₂CS, CH₃CCH and C₃O) achieved thanks to the systematic observation of the full 3 mm window with the IRAM 30m telescope plus some ARO 12m observations. All these species, known to exist in the interstellar medium, are detected for the first time in a circumstellar envelope around an AGB star. These five molecules are most likely formed in the outer expanding envelope rather than in the stellar photosphere. A pure gas phase chemical model of the circumstellar envelope is reasonably successful in explaining the derived abundances, and additionally allows to elucidate the chemical formation routes and to predict the spatial distribution of the detected species.  相似文献   

New spatial dimensions of global cityscapes: From reviewing existing concepts to a conceptual spatial approach     

Isabel Georg  Thomas Blaschke  Hannes Taubenböck 《地理学报(英文版)》2016,26(3):355-380

Current global urbanisation processes are leading to new forms of massive urban constellations. The conceptualisations and classifications of these, however, are often ambiguous, overlap or lag behind in scientific literature. This article examines whether there is a common denominator to define and delimitate–and ultimately map–these new dimensions of cityscapes. In an extensive literature review we analysed and juxtaposed some of the most common concepts such as megacity, megaregion or megalopolis. We observed that many concepts are abstract or unspecific, and for those concepts for which physical parameters exist, the parameters are neither properly defined nor used in standardised ways. While understandably concepts originate from various disciplines, the authors identify a need for more precise definition and use of parameters. We conclude that often, spatial patterns of large urban areas resemble each other considerably but the definitions vary so widely that these differences may surpass any inconsistencies in the spatial delimitation process. In other words, today we have tools such as earth observation data and Geographic Information Systems to parameterise if clear definitions are provided. This appears not to be the case. The limiting factor when delineating large urban areas seems to be a commonly agreed ontology.  相似文献   

Reconstructing the largest explosive eruptions of Mt. Ruapehu,New Zealand: lithostratigraphic tools to understand subplinian–plinian eruptions at andesitic volcanoes     

Natalia Pardo  Shane J. Cronin  Alan S. Palmer  Karoly Németh 《Bulletin of Volcanology》2012,74(3):617-640

We analysed the tephra record of Mt. Ruapehu for the period 27,097 ± 957 to ~10,000 cal. years BP to determine the largest-scale explosive eruptions expected from the most active New Zealand andesitic volcano. From the lithostratigraphic analysis, a systematic change in the explosive behaviour is identified from older deposits suggesting dry magmatic eruptions and steady eruptive columns, characterised by frothy to expanded pumice fabrics, to younger deposits that are products of unsteady conditions and collapsing columns, characterised by microvesicular, fibrous, and colour-banded pumice fabrics. The end-members were separated by eruptions with steady columns linked to water–magma interaction and highly unstable conduit walls. Dry magmatic eruptions producing steady plinian columns were most common between 27,097 ± 957 and shortly after 13,635 + 165 cal. years BP. Following this time, activity continued with eruptions that produced dominantly oscillating unsteady columns, which engendered pyroclastic density currents, until ~10 ka when there was an abrupt transition at Mt. Ruapehu since which eruptions have been an order of magnitude lower in intensity and volume. These data demonstrate long-period transitions in eruption behaviour at an andesitic stratovolcano, which is critical to understand if realistic time-variable hazard forecasts are to be developed.  相似文献   

Dynamics in the trophic structure of the macroinvertebrate community in a Mediterranean, temporary stream     

Maruxa Álvarez  Isabel Pardo 《Aquatic Sciences - Research Across Boundaries》2009,71(2):202-213

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Crustacean assemblages in a polluted estuary from South-Western Spain     

J. Emilio Sánchez-Moyano  Isabel García-Asencio 《Marine pollution bulletin》2010,60(10):1890-1897

The spatial-temporal variation in crustacean assemblages of the Odiel-Tinto estuary, one of the most polluted areas in the world, was studied in 2000, 2002 and 2004. The crustacean assemblages were mainly established according to the natural gradient from estuarine to marine environment (based on water and sediment characteristics such as dissolved oxygen, salinity, granulometry or organic content). Pollutants such as copper, zinc or phosphates could also explain partially this pattern based on BIOENV and canonical correspondence analyses. However, there were clear symptoms of perturbation, mainly in the inner areas, such as a low number of species and a low abundance, especially in relation to the typical estuarine species (e.g. Cyathura carinata, Corophium spp.). This study provides baseline information which can be used as a reference point in a long-term perspective.  相似文献   

Boundaries of air mass trajectory clustering: key points and applications     

I. A. Pérez  M. L. Sánchez  M. A. García  N. Pardo 《International Journal of Environmental Science and Technology》2017,14(3):653-662

Calculating air mass trajectories is common in atmospheric analyses. However, if explainable results are to be achieved, several procedures are needed to process the vast amount of information handled. Clustering methods are statistical tools usually considered for such a purpose. Although they are based on rigorous algorithms, certain questions still remain when these methods are applied. The current review is organised in sections according to the sequence followed by such procedures. First, the types of clustering methods are described, with their core being the distance used. One key point is the stopping rule, which determines the final number of clusters. A simple classification based on this number is then suggested. Finally, the graphical presentation of the results is examined and the main drawbacks are commented on. A range of applications and results are considered to illustrate each section, and certain caveats and recommendations are also presented.  相似文献   

Magnetic imaging of the feeding system of oceanic volcanic islands: El Hierro (Canary Islands)     

Isabel Blanco-Montenegro  Iacopo Nicolosi  Alessandro Pignatelli  Massimo Chiappini 《Geophysical Journal International》2008,173(1):339-350

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Selected contributions from the 6th Spanish Conference on Coastal Geomorphology, 7–9 September 2011, Tarragona, Spain: an introduction     

Isabel Montoya Montes  Maria J. Sánchez García  Inmaculada Rodríguez Santalla 《Geo-Marine Letters》2013,33(2-3):95-99

This special issue of Geo-Marine Letters presents selected contributions from the 6th Spanish Conference on Coastal Geomorphology held from 7–9 September 2011 in Tarragona, Spain. The guest editors are Isabel Montoya Montes, Maria J. Sánchez García and Inmaculada Rodríguez Santalla. These conferences on coastal geomorphology are held biannually and serve as a discussion forum focusing mainly on advances in knowledge about the dynamics of the Spanish littoral environment, although contributions from other coastal regions are encouraged. The papers presented in this Special Issue provide a selective view of the latest research results, the main topics dealing with recent coastal morphodynamics and longer-scale coastal evolution. The 7th Conference will be held in July 2013 in Oviedo, Spain, organized by the Department of Geology at the University of Oviedo.  相似文献   

The Paleocene–Eocene transition in the marginal northeastern Tethys (Kazakhstan and Uzbekistan)     

M.-P. Bolle  A. Pardo  K.-U. Hinrichs  T. Adatte  K. Von Salis  S. Burns  G. Keller  N. Muzylev 《International Journal of Earth Sciences》2000,89(2):390-414

We studied two sections that accumulated during the Paleocene–Eocene transition in shelf waters in the northeastern Tethys. Stable carbon isotopic compositions of marine and terrestrial biomarkers are consistent with a ¹³C depletion in the oceanic and atmospheric carbon dioxide pools during the Late Paleocene Thermal Maximum (LPTM; Subzone P5b). The 2–3‰ negative δ ¹³C excursion in planktic foraminifera coincides with minimum δ ¹⁸O values, an incursion of transient subtropical planktic foraminiferal fauna, and the occurrence of an organic-rich sapropelite unit in Uzbekistan, which accumulated at the onset of a transgressive event. Biomarker distributions and hydrogen indices indicate that marine algae and bacteria were the major organic matter sources. During the Late Paleocene (Subzones P4 and P5a), the marginal northeastern Tethys experienced a temperate to warm climate with wet and arid seasons. Most likely, warm and humid climate initiated during the LPTM (Subzone P5b) and subsequently extended during the Eocene (Zone P6) onto adjacent land areas of the marginal northeastern Tethys. Received: 18 May 1999 / Accepted: 2 February 2000  相似文献   

Understanding acquisition and processing error in microseismic data: An example from Pouce Coupe Field,Canada     

Matthew Bray  Isabel White 《Geophysical Prospecting》2020,68(3):815-829

A challenge in microseismic monitoring is quantification of survey acquisition and processing errors, and how these errors jointly affect estimated locations. Quantifying acquisition and processing errors and uncertainty has multiple benefits, such as more accurate and precise estimation of locations, anisotropy, moment tensor inversion and, potentially, allowing for detection of 4D reservoir changes. Here, we quantify uncertainty due to acquisition, receiver orientation error, and hodogram analysis. Additionally, we illustrate the effects of signal to noise ratio variances upon event detection. We apply processing steps to a downhole microseismic dataset from Pouce Coupe, Alberta, Canada. We use a probabilistic location approach to identify the optimal bottom well location based upon known source locations. Probability density functions are utilized to quantify uncertainty and propagate it through processing, including in source location inversion to describe the three-dimensional event location likelihood. Event locations are calculated and an amplitude stacking approach is used to reduce the error associated with first break picking and the minimization with modelled travel times. Changes in the early processing steps have allowed for understanding of location uncertainty of the mapped microseismic events.  相似文献