Advanced Marginality as a comparative research strategy in praxis: the Danish “Grey Belt” in conversation with the French “Red Belt”     

Troels Schultz Larsen 《Urban geography》2018,39(8):1131-1151

Urban Outcast and advanced marginality belongs to a theory culture rarely engaged in comparative urban studies. Here the potential of advanced marginality as a comparative research strategy is explored paying special attention to the concepts of epistemic reflexivity, analogical reasoning and homology. These concepts are applied as the foundation of a comparative research design comprising three necessary and interconnected analytical moments linking reflexivity, theory and empirical analysis. Empirically this strategy and design is confronted in the case of four Danish “Grey belt” housing estates. The empirical confrontation demonstrates that both strategy and design are relevant and productive. Nevertheless, there is a need to question, adapt and extent the six original properties of advanced marginality. Secondly the empirical confrontation demonstrates that both strategy and design can contribute to the current conversations on the comparative in urban studies empirically and conceptually, underscoring the curiosity of its eclipse in these conversations.  相似文献   

A Textural Record of Solidification and Cooling in the Skaergaard Intrusion, East Greenland   总被引：2，自引：0，他引：2  

Holness  Marian B.; Tegner  Christian; Nielsen  Troels F. D.; Stripp  Gemma; Morse  Stearns A. 《Journal of Petrology》2007,48(12):2359-2377

The clinopyroxene–plagioclase–plagioclase dihedralangle, _cpp, in gabbroic cumulates records the time-integratedthermal history in the sub-solidus and provides a measure oftextural maturity. Variations in _cpp through the Layered Seriesof the Skaergaard intrusion, East Greenland, demonstrate thatthe onset of crystallization of clinopyroxene (within LZa),Fe–Ti oxides (at the base of LZc) and apatite (at thebase of UZb) as liquidus phases in the bulk magma is recordedby a stepwise increase in textural maturity, related to an increasein the contribution of latent heat to the total heat loss tothe surroundings and a reduction in the specific cooling rateat the crystallization front of the intrusion. The onset ofboth liquidus Fe–Ti oxide and apatite crystallizationis marked by a transient increase in textural maturity, probablylinked to overstepping before nucleation. Textural maturationat pyroxene–plagioclase–plagioclase triple junctionseffectively ceases in the uppermost parts of the Layered Seriesas a result of the entire pluton cooling below the closure temperaturefor dihedral angle change, which is 1075°C. Solidificationof the Layered Series of the Skaergaard intrusion occurred viathe upwards propagation of a mush zone only a few metres thick. KEY WORDS: magma; partial melting; asthenosphere; olivine; mantle  相似文献   

Evaluation of MODFLOW-LGR in connection with a synthetic regional-scale model     

Vilhelmsen TN  Christensen S  Mehl SW 《Ground water》2012,50(1):118-132

This work studies costs and benefits of utilizing local-grid refinement (LGR) as implemented in MODFLOW-LGR to simulate groundwater flow in a buried tunnel valley interacting with a regional aquifer. Two alternative LGR methods were used: the shared-node (SN) method and the ghost-node (GN) method. To conserve flows the SN method requires correction of sources and sinks in cells at the refined/coarse-grid interface. We found that the optimal correction method is case dependent and difficult to identify in practice. However, the results showed little difference and suggest that identifying the optimal method was of minor importance in our case. The GN method does not require corrections at the models' interface, and it uses a simpler head interpolation scheme than the SN method. The simpler scheme is faster but less accurate so that more iterations may be necessary. However, the GN method solved our flow problem more efficiently than the SN method. The MODFLOW-LGR results were compared with the results obtained using a globally coarse (GC) grid. The LGR simulations required one to two orders of magnitude longer run times than the GC model. However, the improvements of the numerical resolution around the buried valley substantially increased the accuracy of simulated heads and flows compared with the GC simulation. Accuracy further increased locally around the valley flanks when improving the geological resolution using the refined grid. Finally, comparing MODFLOW-LGR simulation with a globally refined (GR) grid showed that the refinement proportion of the model should not exceed 10% to 15% in order to secure method efficiency.  相似文献   

丹麦北部浅层生物气的渗漏与聚集作用     

Troels Laier  龚建明 《海洋地质前沿》2006,22(5):35-35

在丹麦北部的陆上和海底沉积物中浅层气分布十分普遍。来自海底两个渗漏区的天然气主要由CH4和少量的N2、CO2和O2组成(表1)。样品中未检测出存在有重烃。表1海底渗漏区气体的化学成分和同位素组成Table 1 Chemical and isotopic composition ofgas from submarine seeps地点水深/mCH4/%CO2/%N2/%O2+Ar/%δ13CCH4(‰)δ2HCH4(‰)NordreRonner12 94·8 2·1 3·0 0·1-68·4-191Hirsholmene 10 98·6 0·3 0·8 0·2-65·3-168上述两个渗漏区甲烷的C、H同位素比率(表1)表明,天然气为CO2降解产生的细菌成因气。细菌成因气的另外一…  相似文献   

Caprock interaction with CO₂: A laboratory study of reactivity of shale with supercritical CO₂ and brine     

Binyam L. Alemu  Per Aagaard  Ingrid Anne Munz  Elin Skurtveit 《Applied Geochemistry》2011,26(12):1975-1989

Crushed rock from two caprock samples, a carbonate-rich shale and a clay-rich shale, were reacted with a mixture of brine and supercritical CO₂ (CO₂–brine) in a laboratory batch reactor, at different temperature and pressure conditions. The samples were cored from a proposed underground CO₂ storage site near the town of Longyearbyen in Svalbard. The reacting fluid was a mixture of 1 M NaCl solution and CO₂ (110 bar) and the water/rock ratio was 20:1. Carbon dioxide was injected into the reactors after the solution had been bubbled with N₂, in order to mimic O₂-depleted natural storage conditions. A control reaction was also run on the clay-rich shale sample, where the crushed rock was reacted with brine (CO₂-free brine) at the same experimental conditions. A total of 8 batch reaction experiments were run at temperatures ranging from 80 to 250 °C and total pressures of 110 bar (∼40 bar for the control experiment). The experiments lasted 1–5 weeks.Fluid analysis showed that the aqueous concentration of major elements (i.e. Ca, Mg, Fe, K, Al) and SiO₂ increased in all experiments. Release rates of Fe and SiO₂ were more pronounced in solutions reacted with CO₂–brine as compared to those reacted with CO₂-free brine. For samples reacted with the CO₂–brine, lower temperature reactions (80 °C) released much more Fe and SiO₂ than higher temperature reactions (150–250 °C). Analysis by SEM and XRD of reacted solids also revealed changes in mineralogical compositions. The carbonate-rich shale was more reactive at 250 °C, as revealed by the dissolution of plagioclase and clay minerals (illite and chlorite), dissolution and re-precipitation of carbonates, and the formation of smectite. Carbon dioxide was also permanently sequestered as calcite in the same sample. The clay-rich shale reacted with CO₂–brine did not show major mineralogical alteration. However, a significant amount of analcime was formed in the clay-rich shale reacted with CO₂-free brine; while no trace of analcime was observed in either of the samples reacted with CO₂–brine.  相似文献   

Observations of beach cusps     

Troels Aagaard 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):27-31

Aagaard. Troels: Observations of beach cusps. Geografisk Tidsskrift 85: 27–31 Copenhagen, October 1985.

Observations of beach cusps have been conducted under low-energy conditions on the northern coast of Zealand, Denmark. The distance between cusps showed consistently good correlation with values calculated from a hypothetical occurrence of synchronous or subharmonic edge waves. A relationship is implied between the edge wave frequency and the value of the surf scaling parameter. Supplementary observations from the southern coast of England indicate that the edge wave theory may not be adequate in explaining the distance between cusps on pocket beaches.  相似文献   

Glimpses of Arctic Ocean shelf–basin interaction from submarine-borne radium sampling     

David Kadko  Knut Aagaard 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(1):32-40

Evidence of shelf-water transfer from temperature, salinity, and ²²⁸Ra/²²⁶Ra sampling from the nuclear submarine USS L. Mendel Rivers SCICEX cruise in October, 2000 demonstrates the heterogeneity of the Arctic Ocean with respect to halocline ventilation. This likely reflects both time-dependent events on the shelves and the variety of dispersal mechanisms within the ocean, including boundary currents and eddies, at least one of which was sampled in this work. Halocline waters at the 132 m sampling depth in the interior Eurasian Basin are generally not well connected to the shelves, consonant with their ventilation within the deep basins, rather than on the shelves. In the western Arctic, steep gradients in ²²⁸Ra/²²⁶Ra ratio and age since shelf contact are consistent with very slow exchange between the Chukchi shelf and the interior Beaufort Gyre. These are the first radium measurements from a nuclear submarine.  相似文献   

Sorption and anaerobic biodegradation of soluble aromatic compounds during groundwater transport. 1. Laboratory column experiments     

Zuoping Zheng  Per Aagaard  Gijs D. Breedveld 《Environmental Geology》2002,41(8):922-932

. This paper deals with sorption and anaerobic biodegradation of the soluble aromatic fraction of jet fuel and how it is influenced by pore-water velocity during transport in a groundwater aquifer. The study was carried out as controlled laboratory column experiments. A binary mixture of toluene and 1,2,4-trimethylbenzene with a concentration ratio of 2:1 was used through the entire investigations. The column experiments were conducted with contaminated sediments and groundwater, taken from wells at a field research site. The columns were operated anaerobically under continuous-flow conditions at 10 °C in a temperature-controlled refrigerator. Two percent sodium azide was added to the injection solution of two of the columns to prevent biodegradation of the studied organic mixture. Chloride was used as a conservative tracer to characterize the hydrodynamic parameters such as dispersivity and porosity of the columns. The results showed that both compounds in the mixture were attenuated because of sorption and biodegradation processes in the columns. 1,2,4-trimethylbenzene was attenuated more significantly than toluene. Biodegradation of toluene was coupled mainly with the microbial reduction of ferric iron, whereas 1,2,4-trimethylbenzene, in contrast, was mostly sorbed. Their sorption and biodegradation were studied with different pore-water velocities, and a mass balance approach was applied to calculate biodegradation rates. The biodegradation rates of toluene were –0.16, –0.21, and –0.26 (unit: mM day^–1) for pore-water velocities of 96, 82.4, and 54.9 (unit: cm day^–1), respectively. This indicates that a decrease in the pore-water velocity significantly enhanced the biodegradation of toluene, consistent with other reports in the literature. For 1,2,4-trimethylbenzene the biodegradation rates were –0.05, –0.13 (unit: mM day^–1) for pore-water velocities of 96 and 82.4 (unit: cm day^–1), respectively. The biodegradation rate of 1,2,4-trimethylbenzene did not increase at the lowest pore water velocity as expected. This might be a result of substrate competition.  相似文献   

Fate of Point‐Source Pesticide Spill in Clayey Till after 15 Years          下载免费PDF全文

Peter R. Jørgensen  Niels H. Spliid  Troels Laier  Stefan Outzen 《Ground Water Monitoring & Remediation》2016,36(3):33-42

This study investigated the development of pesticide pollution two, three, and 17 years after spills of the herbicides dichlorprop, mecoprop (MCPP), MCPA, 2,4‐D (phenoxy acids), simazine, and terbutylazine (triazines) in a former orchard machinery service yard. The spills had occurred over several decades on a 23‐m thick, mainly anaerobic fractured clayey till aquitard. Angled monitoring wells were installed in the aquitard 3 years after the spills ceased in 1989. In 1993, monitoring revealed that high groundwater concentrations of dichlorprop (677 µg/L) and MCPP (139 µg/L) were accumulated as a zone of maximum pollution in anaerobic and largely immobile pore water at 5 to 6 m depth in the aquitard profile. In contrast, 2,4‐D was determined in only one water sample, and MCPA and simazine and terbutylazine were determined only in low concentrations (below10 µg/L), although these pesticides had been handled at the site in greater amounts than dichlorprop and MCPP according to detailed historic information obtained for the site. Repeated monitoring in the same wells after a further 14 years in 2007 revealed that no identifiable degradation of MCPP had occurred, while dichlorprop had degraded by 75% to 80% (estimated half‐life of approximately 5 years). Furthermore, degradation products related to the phenoxy acids had accumulated, especially 4‐CPP with a maximum concentration of 218 µg/L. In the same zone, MCPA and simazine had almost disappeared. As the pollution was mainly accumulated in largely immobile pore water of the aquitard clayey matrix, and the groundwater recharge was low (30 to 60 mm/year), only minor vertical displacement of the zone with maximum pollution zone had occurred during the 15 years of monitoring. However, concentrations of dichlorprop (0.01 to 0.02 µg/L), MCPP (0.1 to 0.2 µg/L), and 4‐CPP (0.6 to 0.7 µg/L) had spread along textural heterogeneities in the aquitard into the underlying sandy aquifer at 23‐m depth.  相似文献   

Coastal profile response to sea level rise: a process‐based approach     

Troels Aagaard  Per Sørensen 《地球表面变化过程与地形》2012,37(3):354-362

Prevailing ideas and calculations of coastal response to sea level rise (SLR) are often based on the Bruun model (Bruun P., Sea‐level rise as a cause of shore erosion, Journal Waterways Harbors Division, ASCE 88 : 117–130, 1962) that predicts upward and landward transfer of an equilibrium profile during SLR through offshore sediment transport on the shoreface. The model is based on a number of assumptions of questionable validity as well as outdated concepts on how sediment is transported across the shoreface. This contribution takes a numerical modelling approach that is based on first‐order processes contributing to the movement of sediment across the shoreface. Using a wave transformation model that predicts hydrodynamic processes driving cross‐shore sediment transport and an energetics‐based model for the coupling between hydrodynamics and sediment transport, we show that cross‐shore sediment transport is mainly onshore directed at the boundary between the lower and the upper shoreface, in agreement with the model proposed by Davidson‐Arnott (Conceptual model of the effects of sea level rise on sandy coasts, Journal of Coastal Research 21 : 1166–1172, 2005). The transition from onshore to offshore directed transport is located well within the surf zone and with a rising sea level this transition point becomes displaced landward and upward. Tests also show that substrate slope is of fundamental importance to the manner in which beaches react to rising sea level. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献