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201.
Irene Antonenko James W. Head John F. Mustard B. Ray Hawke 《Earth, Moon, and Planets》1995,69(2):141-172
Cryptomaria are mare basalt deposits hidden or obscured by superposed higher albedo material or variations in albedo. They represent a record of the earliest mare volcanism, and may be a significant volumetric contribution to the volcanic and magmatic history of the Moon. In order to assess their global distribution and significance, criteria for the identification of cryptomaria are developed and techniques for locating them are described. These criteria and techniques include the presence of dark halo craters, identification by spectral mixing analysis, identification by geochemical evidence, association with light plains units, location within basin topography, proximity to known mare, relation to mascons indicated by gravity anomalies, and identification of the source of an obscuring agent, such as crater ejecta. On the basis of these criteria and techniques, several types of cryptomare are recognized, depending on the nature of ejecta and mare materials. Cryptomaria may be formed when maria are obscured by coverings of proximal or distal basin ejecta, or by crater ejecta dusting, or when ejecta covers over basalts which lack a distinctive 1µm absorption band. Using these concepts we outline three case studies: 1) the Schiller-Schickard region adjacent to the Orientale basin, classified as a basin-ejecta cryptomare and grading from distal to proximal, with possible crater-ejecta covering occurring in the southwestern portion of the region, 2) the Balmer basin, classified as a crater-ejecta-dusting cryptomare, and 3) the Australe basin, in which two types of cryptomare were identified: a) crater-ejecta-dusting on old mare patches and b) possible distal-basin-ejecta covering even older mare material. These case studies provide criteria for the further global identification and classification of cryptomaria and stress the need for utilization of multiple criteria and data sets. 相似文献
202.
203.
The main purpose of this study is to explore the relationship between three field-based fire severity indices (Composite Burn Index-CBI, Geometrically structure CBI, weighted CBI) and spectral indices derived from Sentinel 2A and Landsat-8 OLI imagery on a recent large fire in Thasos, Greece. We employed remotely sensed indices previously used from the remote sensing fire community (Normalized Difference Vegetation Index (NDVI), Normalized Burn Ratio (NBR), differenced NDVI, differenced NBR, relative differenced NBR, Relativized Burn Ratio) and seven Sentinel 2A-specific indices considering the availability of spectral information recorded in the red-edge spectral region. The statistical correlation indicated a slightly stronger relationship between the differenced NBR and the GeoCBI for both Sentinel 2A (r = 0.872) and Landsat-8 OLI (r = 0.845) imagery. Predictive local thresholds of dNBR values showed slightly higher classification accuracy for Sentinel 2A (73.33%) than Landsat-8 OLI (71.11%), suggesting the adequacy of Sentinel 2A for forest fire severity assessment and mapping in Mediterranean pine ecosystems. The evaluation of the classification thresholds calculated in this study over other fires with similar pre-fire conditions could contribute in the operational mapping and reconstruction of the historical patterns of fire severity over the Eastern Mediterranean region. 相似文献
204.
Cecilia Irene Villaseñor-Reyes Pablo Dávila-Harris Víctor Manuel Hernández-Madrigal Sócrates Figueroa-Miranda 《Landslides》2018,15(9):1867-1879
The study of deep-seated gravitational slope deformations (DSGSD) in Mexico is scarce; therefore, their localization and causes are highly overlooked. The present paper examines the characterization of the DSGSD of Jungapeo and Las Pilas in eastern Michoacan state, currently active and endangering their inhabitants. An integrated study, including detailed lithology, morpho-structural inventories, analysis of land use, and pluviometric regime, was performed and complemented with differential global positioning system monitoring networks. Both landslides developed over highly weathered volcano-sedimentary rocks. On the one hand, the Jungapeo landslide has an estimated volume of 990,455 m3 with steady decreasing velocity rates from 41 to 15 cm/month in the first monitoring period to 13–3 cm/month in the last one. On the other hand, the Las Pilas landslide estimated volume is about 1,082,467 m3 with a stable velocity rate of 1.3 to 0.1 cm/month. Despite the multi-storeyed style of activity, two behaviors of instability were distinguished: slow deformation and secondary landslide stages. The conditioning factors for slow deformation in both DSGSD are the combination of weathered lithology with clay- and sand-rich content, and the shift toward intensive monoculture. The triggering factor is related to excess water produced by an inefficient flood-irrigation system that also generates an atypical acceleration behavior in both landslides during the dry season. The DSGSD activity thus predisposes the generation of tension cracks and secondary scarps from which the collateral landslides are triggered by atypical rainfall, such as that of 2010. 相似文献
205.
In this paper we examine the ways in which mobile phones are becoming integrated into the everyday life of older adults in the UK by drawing on research funded as part of the British New Dynamics of Ageing programme. Specifically we draw on a digital engagement survey and the life history narratives of older men and women resident in the East Midlands of England to illuminate the challenges of remaining digitally engaged in old age focusing specifically on mobile phone use, with particular reference to maintaining social connections with spatially dispersed family and friends. Growing numbers of older adults possess a mobile phone, but the degree to which mobile phone use has been integrated into everyday practices is variable. For episodic users a mobile phone is used to complement a landline, to keep in touch with family and friends when out of the house. For confident users the mobile phone is used in multiple ways, via a range of applications, it is an integral part of numerous aspects of everyday life. 相似文献
206.
Sedimentary evolution and environmental history of Lake Van (Turkey) over the past 600 000 years 总被引:1,自引:0,他引:1
Mona Stockhecke Michael Sturm Irene Brunner Hans‐Ulrich Schmincke Mari Sumita Rolf Kipfer Deniz Cukur Ola Kwiecien Flavio S. Anselmetti 《Sedimentology》2014,61(6):1830-1861
The lithostratigraphic framework of Lake Van, eastern Turkey, has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years. The lithostratigraphy and chemostratigraphy of a 219 m long drill core from Lake Van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity. An age model was established based on the climatostratigraphic alignment of chemical and lithological signatures, validated by 40Ar/39Ar ages. The drilled sequence consists of ca 76% lacustrine carbonaceous clayey silt, ca 2% fluvial deposits, ca 17% volcaniclastic deposits and 5% gaps. Six lacustrine lithotypes were separated from the fluvial and event deposits, such as volcaniclastics (ca 300 layers) and graded beds (ca 375 layers), and their depositional environments are documented. These lithotypes are: (i) graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations; (ii) varved clayey silts reflecting strong seasonality and an intralake oxic–anoxic boundary, for example, lake‐level highstands during interglacials/interstadials; (iii) CaCO3‐rich banded sediments which are representative of a lowering of the oxic–anoxic boundary, for example, lake level decreases during glacial inceptions; (iv) CaCO3‐poor banded and mottled clayey silts reflecting an oxic–anoxic boundary close to the sediment–water interface, for example, lake‐level lowstands during glacials/stadials; (v) diatomaceous muds were deposited during the early beginning of the lake as a fresh water system; and (vi) fluvial sands and gravels indicating the initial flooding of the lake basin. The recurrence of lithologies (i) to (iv) follows the past five glacial/interglacial cycles. A 20 m thick disturbed unit reflects an interval of major tectonic activity in Lake Van at ca 414 ka bp . Although local environmental processes such as tectonic and volcanic activity influenced sedimentation, the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes, making Lake Van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years. 相似文献
207.
Martins I Lopes RJ Lillebø AI Neto JM Pardal MA Ferreira JG Marques JC 《Marine pollution bulletin》2007,54(6):678-690
A spatially dynamic model for the productivity of spores and adults of green macroalgae (Enteromorpha sp.) was developed for a mesotidal estuary (Mondego estuary, Portugal). Many of the algal processes and parameters included in the model were experimentally obtained. Model predictions were compared to a real time series (1993-1997) of macroalgal biomass variation and the two sets show a good agreement (ANOVA, P<0.001). Results suggest that algal growth is highly sensitive to small changes in depth and exhibits different patterns of variation in different seasons. On a yearly basis, global calculations for the south channel of the estuary (137 ha) suggest that during bloom years, macroalgal biomass may reach about 21,205 ton DW compared to 240 ton DW in regular years. On a seasonal basis, the difference may be even more significant. The consequences of such variations on the nitrogen and phosphorus loading of the system and the adjacent coastal area are discussed. 相似文献
208.
Bruny Baret Imre Bartos Boutayeb Bouhou Alessandra Corsi Irene Di Palma Corinne Donzaud Vronique Van Elewyck Chad Finley Gareth Jones Antoine Kouchner Szabolcs Mrka Zsuzsa Mrka Luciano Moscoso Eric Chassande-Mottin Maria Alessandra Papa Thierry Pradier Peter Raffai Jameson Rollins Patrick Sutton 《Astroparticle Physics》2011,35(1):1-7
We derive a conservative coincidence time window for joint searches of gravitational-wave (GW) transients and high-energy neutrinos (HENs, with energies ?100 GeV), emitted by gamma-ray bursts (GRBs). The last are among the most interesting astrophysical sources for coincident detections with current and near-future detectors. We take into account a broad range of emission mechanisms. We take the upper limit of GRB durations as the 95% quantile of the T90’s of GRBs observed by BATSE, obtaining a GRB duration upper limit of ∼150 s. Using published results on high-energy (>100 MeV) photon light curves for 8 GRBs detected by Fermi LAT, we verify that most high-energy photons are expected to be observed within the first ∼150 s of the GRB. Taking into account the breakout-time of the relativistic jet produced by the central engine, we allow GW and HEN emission to begin up to 100 s before the onset of observable gamma photon production. Using published precursor time differences, we calculate a time upper bound for precursor activity, obtaining that 95% of precursors occur within ∼250 s prior to the onset of the GRB. Taking the above different processes into account, we arrive at a time window of tHEN − tGW ∈ [−500 s, +500 s]. Considering the above processes, an upper bound can also be determined for the expected time window of GW and/or HEN signals coincident with a detected GRB, tGW − tGRB ≈ tHEN − tGRB ∈ [−350 s, +150 s]. These upper bounds can be used to limit the coincidence time window in multimessenger searches, as well as aiding the interpretation of the times of arrival of measured signals. 相似文献
209.
Andrey Linhares Bezerra de Oliveira Júlio Carlos Afonso Lilian da Silva Arnaldo Alcover Neto Manuel Castro Carneiro Lílian Irene Dias da Silva Maria Inês Couto Monteiro 《Geostandards and Geoanalytical Research》2019,43(4):689-699
Rare earth elements (REEs) are very important to technological development as well as to geochemical and environmental studies. In this work, hydrofluoric acid (HF) was replaced by condensed phosphoric acid (CPA) in the digestion of geological samples, and the quantification of REEs was performed by inductively coupled plasma‐optical emission spectrometry (ICP‐OES). Six international reference materials (RMs), named DC86318, CGL 111, CGL 124, CGL 126, OKA‐2 and COQ‐1 and three Brazilian ore samples, named Araxá, Catalão and Pitinga were analysed. Only zircon and xenotime, which are potential REE‐bearing minerals, were not completely dissolved. Nevertheless, no REE associated with zircon was detected. The investigated digestion method presented many advantages: It was relatively fast (3 h), avoided fluoride precipitation, it was less hazardous because handling diluted H3PO4 is safer than HF, NH4F or NH4HF2 aqueous solutions, it preserved the quartz fittings of the measurement equipment and the final solution contained lower levels of total dissolved solids than those produced by the fusion method. 相似文献