From the Early Paleozoic Platforms of Baltica and Laurentia to the Caledonide Orogen of Scandinavia and Greenland   总被引：1，自引：0，他引：1  

David G. Gee Haakon Fossen Niels Henriksen Anthony K. Higgins 《《幕》》2008,31(1):44-51

The Caledonide Orogen in the Nordic countries is exposed in Norway, western Sweden, westernmost Finland, on Svalbard and in northeast Greenland. In the mountains of western Scandinavia, the structure is dominated by E-vergent thrusts with allochthons derived from the Baltoscandian platform and margin, from outboard oceanic （lapetus） terranes and with the highest thrust sheets having Laurentian affinities. The other side of this bivergent orogen is well exposed in northeastern Greenland, where W-vergent thrust sheets emplace Laurentian continental margin assemblages onto the platform. Svalbard＇s Caledonides are disrupted by late Caledonian faults, but have close affinity with the Laurentian margin in Northeast Greenland. Only Svalbard＇s Southwestern terrane is foreign to this margin, showing affinity, to the Pearya terrane of northern Ellesmere Island in arctic Canada. Between the margins of western Scandinavia and eastern Greenland, the wide continental shelves, now covered by late Paleozoic and younger successions, are inferred to be underlain by the Caledonide hinterland, probably incorporating substantial Grenville-age basement. In northernmost Norway, the NE-trending Caledonian thrust front truncates the NW-trending Neoproterozoic Timanide orogen of northwest Russia. Much of the central and eastern parts of the Barents Shelf are thought to be underlain by Caledonian-deformed Timanide basement.
Caledonian orogeny in Norden resulted from the closure of the Iapetus Ocean and Scandian collision of continent Baltica with Laurentia. Partial subduction of the Baltoscandian margin beneath Laurentia in the midlate Silurian was followed by rapid exhumation of the highly metamorphosed hinterland in the early Devonian, and deposition of Old Red Sandstones in intramontane basins. Late Scandian collapse of the orogen occurred on major extensional detachments, with defor mation persisting into the late Devonian.  相似文献   

Design rainfall in Qatar: sensitivity to climate change scenarios     

Abdullah Al Mamoon  Niels E. Joergensen  Ataur Rahman  Hassan Qasem 《Natural Hazards》2016,81(3):1797-1810

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Using modular 3D digital earth applications based on point clouds for the study of complex sites     

Oscar Martinez-Rubi  Maurice de Kleijn  Stefan Verhoeven  Niels Drost  Jisk Attema  Maarten van Meersbergen 《International Journal of Digital Earth》2016,9(12):1135-1152

This article discusses the use of 3D technologies in digital earth applications (DEAs) to study complex sites. These are large areas containing objects with heterogeneous shapes and semantic information. The study proposes that DEAs should be modular, have multi-tier architectures, and be developed as Free and Open Source Software if possible. In DEAs requiring high reliability in the 3D measurements, point clouds are proposed as basis for the 3D Digital digital earth representation. For the development of DEAs, we propose to follow a workflow with four components: data acquisition and processing, data management, data analysis and data visualization. For every component, technological challenges of using 3D technologies are identified and solutions applied for a case study are presented. The case study is a modular 3D DEA developed for the archaeological project Mapping the Via Appia. The 3D DEA allows archaeologists to virtually analyze a complex study area.  相似文献   

Reactions of Cl Atoms with Selected VOCs: Kinetics, Products and Mechanisms   总被引：1，自引：0，他引：1  

Gaia Fantechi  Niels R. Jensen  Ole Saastad  Jens Hjorth  Jozef Peeters 《Journal of Atmospheric Chemistry》1998,31(3):247-267

The reactions of isoprene, MBO (2-methyl-3-buten-2-ol) and toluene with chlorine atoms have been studied at 298 ± 5 K and 740 ± 5 Torr with the use of FTIR spectroscopy. Major products of the isoprene-Cl reaction and of the MBO-Cl reaction have been identified and quantified, and reaction mechanisms have been tentatively proposed in order to explain the products formed. The reaction between isoprene and Cl atoms yields mainly HCl, formyl chloride, formic acid, methylglyoxal (pyruvic aldehyde), CO and CO2, while the MBO-Cl reaction forms acetone, HCl, formyl chloride, formic acid, CO, CO2. As products from the reaction between toluene and Cl we identified and quantified HCl and benzaldehyde. The rate constants for the reactions of isoprene and toluene with Cl atoms have also been determined using a relative rate method. The measured values are: kisoprene = (5.5 ± 1.0) × 10–10 cm3 molecule–1 s–1 and ktoluene = (5.6 ± 1.3) × 10–11 cm3 molecule–1 s–1. Atmospheric lifetimes have been estimated from these values.  相似文献   

Changes in abundance of demersal fish species in the North Sea between 1906-1909 and 1990-1995   总被引：4，自引：0，他引：4  

Rijnsdorp  Adriaan D.; van Leeuwen  Piet I.; Daan  Niels; Heessen  Henk J. L. 《ICES Journal of Marine Science》1996,53(6):1054-1062

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Diffusive and total oxygen uptake of deep-sea sediments in the eastern South Atlantic Ocean:in situ and laboratory measurements     

Ronnie Nhr Glud  Jens K. Gundersen  Bo Barker Jrgensen  Niels Peter Revsbech  Horst D. Schulz 《Deep Sea Research Part I: Oceanographic Research Papers》1994,41(11-12)

Total O₂ uptake rates were measured by the benthic flux chamber lander ELINOR, and O₂ microprofiles were measured by the profiling lander PROFILUR in the eastern South Atlantic. Diffusive O₂ fluxes through the diffusive boundary layer and the depth distribution of O₂ consumption rates within the sediment were calculated from the obtained microprofiles. The depth integrated O₂ consumption rate agreed closely with the diffusive O₂ uptake at all stations. Total O₂ uptake was 1.2–4.2 times the diffusive O₂ uptake, and the difference correlated with the abundance of macrofauna in the sediment. Diffusive O₂ uptake and O₂-penetration depths correlated with the organic content of the sediments and exhibited an inverse correlation with water depth. Total and diffusive rates of in situ O₂ uptake were higher than previously published data for shelf and abyssal sediments in the Atlantic, but were comparable to rates from upwelling areas in the eastern Pacific. Laboratory measurements on recovered sediment cores showed lower O₂ penetration depths and higher diffusive uptake rates than in situ measurements. The differences increased with increasing water depth. We primarily ascribe this compression of O₂ profiles to a transiently increased temperature during recovery and enhanced microbial activity in decompressed sediment cores. Total O₂ uptake rates measured in the laboratory on macrofauna-rich stations were, in contrast, lower than those measured in situ because of underrepresentation and disturbance of the macrofauna.  相似文献   

An Afterthought: Ecosystem Metrics and Pressure Indicators   总被引：2，自引：2，他引：2  

Daan  Niels 《ICES Journal of Marine Science》2005,62(3):612-613

Editing the symposium contributions has been an interestingand instructive experience, because they provide a broad overviewof the well-nigh unlimited creativity of marine scientists totry and find building blocks for an ecosystem approach to fisherymanagement. A wealth of ideas appears to be emerging on howdifferent aspects of the state of exploited marine ecosystemscan be measured. Although the metrics produced are commonlyreferred to as "ecosystem indicators", however, it is generallyless clear what they actually indicate. The concept that management must take the wider ranging  相似文献   

The Importance of Posidonia oceanica and Cymodocea nodosa as Contributors of Free Amino Acids in Water and Sediment of Seagrass Beds     

Niels O. G.  Jørgensen  T. Henry  Blackburn  Kai  Henriksen Daniel  Bay 《Marine Ecology》1981,2(2):97-112

Abstract. Dissolved free amino acids (DFAA) were measured in sediment porewater and overlying sea water in seagrass beds of Posidonia oceanica and Cymodocea nodosa at a water depth of 8–10 m in Corsica, France. In the sea water, DFAA concentrations from 0.5 to 1.9μM were found. Lowest concentrations occurred in the afternoon in surface water samples, while higher concentrations were measured in morning surface samples and in all bottom samples. The most abundant amino acids were serine, glycine, and alanine. In the sediment, the upper 4cm contained the highest concentrations of DFAA (177nmol cm^-3 or 367 μM), while lower concentrations (<50nmol cm^-3 or 104 μM) prevailed deeper in the sediment. Glycine, glutamic acid, alanine, and β-alanine were the major components of the DFAA. The photosynthetic activity of the seagrasses influenced sediment porewater pools of DFAA. When a Posidonia bed was covered with a black polyethylene shield, the interstitial amino acids were reduced at a rate of 16nmol cm^-2 h^-1 (0-10cm depth). Conversely, extended daylight (floodlight) increased the DFAA pool in sediment depths below 4 cm. Free amino acids were released to the overlying sea water from both seagrass sediment and individual shoots, the rates being highest in the dark. The present investigation indicates that a substantial portion of the N-cycling of the seagrass sediment includes free amino acids.  相似文献   

Status and trends of the major roundfish, flatfish, and pelagic fish stocks in the North Sea: thirty-year overview     

Serchuk  Fredric M.; Kirkegaard  Eskild; Daan  Niels 《ICES Journal of Marine Science》1996,53(6):1130-1145

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Changes to urban form and commuting patterns: trends in two Danish city regions     

Julien Grunfelder  Thomas A.S. Nielsen  Niels B. Groth 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2015,115(2):73-87

This paper compares indicators of polycentricity in a monocentric (MUR) and a polycentric urban region (PUR) in Denmark at two points in time (1982 and 2002). It describes how population, jobs and commuting indicators of polycentricity develop and interact over time. Both the MUR and the PUR tend towards more balanced development. The increasing size of the main node in the PUR is the only deviation from the general trend. The general tendency towards a more polycentric regional structure was most marked in changing interaction and commuting patterns. Inter-urban commuting increased, while intra-urban commuting decreased, leading to dispersion of commuters and a rapid increase in commuting across the region. Commuting distances were shortest in the polycentric region, but it also had the highest growth rates. In both regions, the balancing trend leads to a dispersal of commuting demand over an increasingly complex web of origins and destination nodes. This tendency compels us to question whether people’s choice of residence is becoming increasingly irrelevant to their place of work. In relation to polycentricity and sustainability, this calls into question the degree to which proximity can be a valuable ‘asset’ in terms of planning sustainable transport outcomes connecting residence, jobs and service.  相似文献