A new archival infrastructure for highly-structured astronomical data     

Erik Dovgan  Cristina Knapic  Massimo Sponza  Riccardo Smareglia 《Experimental Astronomy》2018,45(1):41-55

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High‐resolution bathymetric mapping reveals subaqueous glacial landforms in the Arctic alpine lake Tarfala,Sweden     

Nina Kirchner  Riko Noormets  Jakob Kuttenkeuler  Elias Strandell Erstorp  Erik Schytt Holmlund  Gunhild Rosqvist  Per Holmlund  Marika Wennbom  Torbjrn Karlin 《第四纪科学杂志》2019,34(6):452-462

In Arctic alpine regions, glacio‐lacustrine environments respond sensitively to variations in climate conditions, impacting, for example,glacier extent and rendering former ice‐contact lakes into ice distal lakes and vice versa. Lakefloors may hold morphological records of past glacier extent, but remoteness and long periods of ice cover on such lakes make acquisition of high‐resolution bathymetric datasets challenging. Lake Tarfala and Kebnepakte Glacier, located in the Kebnekaise mountains, northern Sweden, comprise a small, dynamic glacio‐lacustrine system holding a climate archive that is not well studied. Using an autonomous surface vessel, a high‐resolution bathymetric dataset for Lake Tarfala was acquired in 2016, from which previously undiscovered end moraines and a potential grounding line feature were identified. For Kebnepakte Glacier, structure‐from‐motion photogrammetry was used to reconstruct its shape from photographs taken in 1910 and 1945. Combining these methods connects the glacial landform record identified at the lakefloor with the centennial‐scale dynamic behaviour of Kebnepakte Glacier. During its maximum 20^th century extent, attained c. 1910, Kebnepakte Glacier reached far into Lake Tarfala, but had retreated onto land by 1945, at an average of 7.9 m year^–1. Copyright © 2019 John Wiley & Sons, Ltd.  相似文献   

The most frequent interfaces in olivine aggregates: the GBCD and its importance for grain boundary related processes     

Katharina?MarquardtEmail author  Gregory?S.?Rohrer  Luiz?Morales  Erik?Rybacki  Hauke?Marquardt  Brian?Lin 《Contributions to Mineralogy and Petrology》2015,170(4):40

Rocks consist of crystal grains separated by grain boundaries that impact the bulk rock properties. Recent studies on metals and ceramics showed that the grain boundary plane orientation is more significant for grain boundary properties than other characteristics such as the sigma value or disorientation (in the Earth’s science community more frequently termed misorientation). We determined the grain boundary character distribution (GBCD) of synthetic and natural polycrystalline olivine, the most abundant mineral of Earth’s upper mantle. We show that grain boundaries of olivine preferentially contain low index planes, in agreement with recent findings on other oxides (e.g. MgO, TiO₂, Al₂O₃ etc.). Furthermore, we find evidence for a preferred orientation relationship of 90° disorientations about the [001] direction forming tilt and twist grain boundaries, as well as a preference for the 60° disorientation about the [100] axis. Our data indicate that the GBCD, which is an intrinsic property of any mineral aggregate, is fundamental for understanding and predicting grain boundary related processes.  相似文献   

Co-management and the co-production of knowledge: Learning to adapt in Canada's Arctic   总被引：3，自引：0，他引：3  

Derek Armitage  Fikret BerkesAaron Dale  Erik Kocho-SchellenbergEva Patton 《Global Environmental Change》2011,21(3):995-1004

Co-management institutional arrangements have an important role in creating conditions for social learning and adaptation in a rapidly changing Arctic environment, although how that works in practice has not been clearly articulated. This paper draws on three co-management cases from the Canadian Arctic to examine the role of knowledge co-production as an institutional trigger or mechanism to enable learning and adapting. Experience with knowledge co-production across the three cases is variable but outcomes illustrate how co-management actors are learning to learn through uncertainty and environmental change, or learning to be adaptive. Policy implications of this analysis are highlighted and include the importance of a long-term commitment to institution building, an enabling policy environment to sustain difficult social processes associated with knowledge co-production, and the value of diverse modes of communication, deliberation and social interaction.  相似文献   

Spalling Experiments on Large Hard Rock Specimens     

Lars?JacobssonEmail author  Karin?Appelquist  Jan?Erik?Lindkvist 《Rock Mechanics and Rock Engineering》2015,48(4):1485-1503

Specimens of coarse-grained Äspö diorite were axially compressed to observe stress-induced spalling. The specimens had a novel design characterized by two manufactured large radius notches on opposite sides. The tangential stress occurring in the notches aimed to represent the tangential loading around a circular opening. Fracture stages were monitored by acoustic emission measurements. Rock chips were formed similar to those found in situ, which indicates a similar fracture process. Slabs were cut out from the specimens and impregnated using a fluorescent material to visualize the cracks. The cracks were subsequently examined by the naked eye and by means of microscopy images, from which fracture paths could be identified and related to different minerals and their crystallographic orientations. The microscopy analyses showed how the stress field and the microstructure interact. Parallel cracks were formed 2–4 mm below the surface, sub-parallel to the direction of the maximum principal stress. The crack initiation, the roles of minerals such as feldspar, biotite and quartz and their grain boundaries and crystallographic directions are thoroughly studied and discussed in this paper. Scale effects, which relate to the stress gradient and microstructure, are discussed.  相似文献   

Inherited basement canyons: Impact on sediment distribution in the North Atlantic     

Gregers Dam  Martin Snderholm  Erik Vest Srensen 《地学学报》2020,32(4):272-280

Studies of basement‐bounded canyons in West Greenland show that these were long‐lasting features that extended inland for several hundreds of kilometres, acting as prominent sediment conduits sourcing the Albian–Palaeocene Nuussuaq Basin during several phases of basin evolution. The Ilulissat Icefjord canyon was the major conduit for sediment into the basin and provenance data indicate that it had a huge catchment area that extended to East Greenland. The Uparuaqqusuitsut canyon was also an important conduit for sediment in the northern part of the basin. It is suggested that the initial canyon formation occurred during uplift events in the Late Triassic and Late Jurassic when the deeply weathered basement surface formed during Early–Middle Triassic time was eroded. The recognition of these canyons as long‐lasting sediment conduits have huge implications for understanding the sediment distribution, source‐to‐sink studies and the palaeogeography of the North Atlantic basins.  相似文献   

High-precision stellar abundances of the elements: methods and applications     

Poul Erik Nissen  Bengt Gustafsson 《Astronomy and Astrophysics Review》2018,26(1):6

Efficient spectrographs at large telescopes have made it possible to obtain high-resolution spectra of stars with high signal-to-noise ratio and advances in model atmosphere analyses have enabled estimates of high-precision differential abundances of the elements from these spectra, i.e. with errors in the range 0.01–0.03 dex for F, G, and K stars. Methods to determine such high-precision abundances together with precise values of effective temperatures and surface gravities from equivalent widths of spectral lines or by spectrum synthesis techniques are outlined, and effects on abundance determinations from using a 3D non-LTE analysis instead of a classical 1D LTE analysis are considered. The determination of high-precision stellar abundances of the elements has led to the discovery of unexpected phenomena and relations with important bearings on the astrophysics of galaxies, stars, and planets, i.e. (i) Existence of discrete stellar populations within each of the main Galactic components (disk, halo, and bulge) providing new constraints on models for the formation of the Milky Way. (ii) Differences in the relation between abundances and elemental condensation temperature for the Sun and solar twins suggesting dust-cleansing effects in proto-planetary disks and/or engulfment of planets by stars; (iii) Differences in chemical composition between binary star components and between members of open or globular clusters showing that star- and cluster-formation processes are more complicated than previously thought; (iv) Tight relations between some abundance ratios and age for solar-like stars providing new constraints on nucleosynthesis and Galactic chemical evolution models as well as the composition of terrestrial exoplanets. We conclude that if stellar abundances with precisions of 0.01–0.03 dex can be achieved in studies of more distant stars and stars on the giant and supergiant branches, many more interesting future applications, of great relevance to stellar and galaxy evolution, are probable. Hence, in planning abundance surveys, it is important to carefully balance the need for large samples of stars against the spectral resolution and signal-to-noise ratio needed to obtain high-precision abundances. Furthermore, it is an advantage to work differentially on stars with similar atmospheric parameters, because then a simple 1D LTE analysis of stellar spectra may be sufficient. However, when determining high-precision absolute abundances or differential abundance between stars having more widely different parameters, e.g. metal-poor stars compared to the Sun or giants to dwarfs, then 3D non-LTE effects must be taken into account.  相似文献   

Linking past flood frequencies in Norway to regional atmospheric circulation anomalies     

Eivind N. Støren  Erik W. Kolstad  Øyvind Paasche 《第四纪科学杂志》2012,27(1):71-80

Analysis of two continuous, high‐resolution palaeo‐flood records from southern Norway reveals that the frequency of extreme flood events has changed significantly during the Holocene. During the early and middle Holocene, flood frequency was low; by contrast, it was high over the last 2300 years when the mean flood frequency was about 2.5–3.0 per century. The present regional discharge regime is dominated by spring/summer snowmelt, and our results indicate that the changing flood frequency cannot be explained by local conditions associated with the respective catchments of the two lakes, but rather long‐term variations of solid winter precipitation and related snowmelt. Applying available instrumental winter precipitation data and associated sea‐level pressure re‐analysis data as a modern analogue, we document that atmospheric circulation anomalies, significantly different from the North Atlantic Oscillation (NAO), have some potential in explaining the variability of the two different palaeo‐flood records. Centennial‐scale patterns in shifting flood frequency might be indicative of shifts in atmospheric circulation and shed light on palaeo‐pressure variations in the North Atlantic region, in areas not influenced by the NAO. Major shifts are found at about 2300, 1200 and 200 years ago (cal. a BP). Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Transpiration and plant water relations of evergreen woody vegetation on a recently constructed artificial ecosystem under seasonally dry conditions in Western Australia     

Willis Gwenzi  Erik J. Veneklaas  Timothy M. Bleby  Isa A.M. Yunusa  Christoph Hinz 《水文研究》2012,26(21):3281-3292

Understanding transpiration and plant physiological responses to environmental conditions is crucial for the design and management of vegetated engineered covers. Engineered covers rely on sustained transpiration to reduce the risk of deep drainage into potentially hazardous wastes, thereby minimizing contamination of water resources. This study quantified temporal trends of plant water potential (ψ_p), stomatal conductance (g_s), and transpiration in a 4‐year‐old evergreen woody vegetation growing on an artificial sandy substrate at a mine waste disposal facility. Transpiration averaged 0.7 mm day^?1 in winter, when rainfall was frequent, but declined to 0.2 mm day^?1 in the dry summer, when the plants were quite stressed. In winter, the mean ψ_p was ?0.6 MPa at predawn and ?1.5 MPa at midday, which were much higher than the corresponding summer values of ?2.0 MPa and ?4.8 MPa, respectively. The g_s was also higher in winter (72.1–95.0 mmol m^?2 s^?1) than in summer (<30 mmol m^?2 s^?1), and negatively correlated with ψ_p (p < 0.05, r² = 0.71–0.75), indicating strong stomatal control of transpiration in response to moisture stress. Total annual transpiration (147.2 mm) accounted for only 22% of the annual rainfall (673 mm), compared with 77% to 99% for woody vegetation in Western Australia. The low annual transpiration was attributed to the collective effects of a sparse and young vegetation, low moisture retention of the sandy substrate, and a superficial root system constrained by high subsoil pH. Amending the substrate with fine‐textured materials should improve water storage of the substrate and enhance canopy growth and deep rooting, while further reducing the risk of deep drainage during the early stages of vegetation establishment and in the long term. Overall, this study highlights the need to understand substrate properties, vegetation characteristics, and rainfall patterns when designing artificial ecosystems to achieve specific hydrological functions. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

The impact of uncertain emission trading markets on interactive resource planning processes and international emission trading experiments   总被引：1，自引：1，他引：0  

Stefan Pickl  Erik Kropat  Heiko Hahn 《Climatic change》2010,103(1-2):327-338

Interactive resource planning is an increasingly important aspect of emission trading markets. The conferences of Rio de Janeiro, 1992, and Kyoto, 1997, originally focusing on environmental protection at both macro- and micro-economic levels, called for new economic instruments of this kind. An important economic tool in this area is Joint Implementation (JI), defined in Article 6 of the Kyoto Protocol. Sustainable development can be guaranteed only if JI is embedded in optimal energy management. In this contribution we describe and evaluate one international procedure within uncertain markets which helps to establish optimal energy management and interactive resource planning processes within uncertain emission trading markets.  相似文献