Effects of cargo reservation: A review of UNCTAD's code of conduct for liner conferences     

Per Magnus Wijkman 《Marine Policy》1980,4(4):271-289

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Efficiency of mixing by a turbulent jet in a stably stratified fluid     

Magnus Larson  Lennart Jnsson 《Dynamics of Atmospheres and Oceans》1996,24(1-4)

Mixing in a two-layer stably stratified fluid by a turbulent jet was studied by a laboratory experiment. A non-swirling jet was discharged vertically downwards in a confined fluid system consisting initially of a top layer of fresh water and a bottom layer of salt water. In total, 16 experimental cases were considered, where the diameter and exit velocity of the jet were varied together with the density difference between the top and bottom layer. Vertical density profiles were determined from conductivity measurements. A three-layer density structure developed in all cases with an intermediate layer that grew in size with time elapsed as fresh and salt water were mixed. The mixing efficiency, defined as the percentage of the supplied kinetic jet energy that is used for increasing the potential energy of the fluid system, was related to a densimetric Froude number based on the intermediate layer depth. Overall, the calculated jet mixing efficiency displayed higher values than comparable efficiencies for destratification with air-bubble plumes.  相似文献   

Dioxin-like compounds in HPLC-fractionated extracts of marine samples from the east and west coast of Sweden: Bioassay- and instrumentally-derived TCDD equivalents     

Magnus Engwall  Dag Broman  Carina Näf  Yngve Zebühr  Björn Brunström 《Marine pollution bulletin》1997,34(12):1032-1040

Lipophilic extracts of sediment, settling particulate matter (SPM) and blue mussel (Mytilus edulis) samples, collected at coastal locations on the east and west coast of Sweden, were HPLC-separated into three fractions containing 1. monoaromatic/aliphatic, 2. diaromatic (e.g. polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs/Fs)), and 3. polyaromatic compounds (e.g. polycyclic aromatic hydrocarbons (PAHs)). The fractions were tested for dioxin-like effects using a sensitive bioassay, based on EROD-induction in cultured chicken embryo livers. The concentrations of PCDDs/Fs, PCBs and 15 PAHs in the samples were also determined. The polyaromatic fractions of the sediment samples were more potent as EROD-inducers than the diaromatic fractions. Only a small part of the EROD-induction caused by the polyaromatic fractions could be explained by the analysed PAHs in the samples, indicating presence of non-quantified polyaromatic EROD-inducing compounds in the samples. A greater pollution by EROD-inducing diaromatic and polyaromatic compounds on the east coast site than on the west coast site was seen. The filtration activities and faeces production of the mussels on the east coast experimental site increased the sedimentation of PCDDs/Fs, PCBs and PAHs. The described bioassay proved very useful in the assessment of dioxin-like compounds in both abiotic and biotic samples from the marine environment.  相似文献   

Vertical migration of hydrocarbons modelled with fractional flow theory     

Magnus Wangen 《Geophysical Journal International》1993,115(1):109-131

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Structural analysis of a transform fault-rift zone junction in North Iceland   总被引：1，自引：0，他引：1  

Agust Gudmundsson  Sigurdur Brynjolfsson  Magnus Thor Jonsson 《Tectonophysics》1993,220(1-4):205-221

On the north coast of Iceland, the rift zone in North Iceland is shifted about 120 km to the west where it meets with, and joins, the mid-ocean Kolbeinsey ridge. This shift occurs along the Tjörnes fracture zone, an 80-km-wide zone of high seismicity, which is an oblique (non-perpendicular) transform fault. There are two main seismic lineaments within the Tjörnes fracture zone, one of which continues on land as a 25-km-long WNW-trending strike-slip fault. This fault, referred to as the Husavik fault, meets with, and joins, north-trending normal faults of the Theistareykir fissure swarm in the axial rift zone. The most clear-cut of these junctions occurs in a basaltic pahoehoe lava flow, of Holocene age, where the Husavik fault joins a large normal fault called Gudfinnugja. At this junction, the Husavik fault strikes N55°W, whereas Gudfinnugja strikes N5°E, so that they meet at an angle of 60°. The direction of the spreading vector in North Iceland is about N73°W, which is neither parallel with the strike of the Husavik fault nor perpendicular to the strike of the Gudfinnugja fault. During rifting episodes there is thus a slight opening on the Husavik fault as well as a considerable dextral strike-slip movement along the Gudfinnugja fault. Consequently, in the Holocene lava flow, there are tension fractures, collapse structures and pressure ridges along the Husavik fault, and pressure ridges and dextral pull-apart structures subparallel with the Gudfinnugja fault. The 60° angle between the Husavik strike-slip fault and the Gudfinnugja normal fault is the same as the angle between the Tjörnes fracture zone transform fault and the adjacent axial rift zones of North Iceland and the Kolbeinsey ridge. The junction between the faults of Husavik and Gudfinnugja may thus be viewed as a smaller-scale analogy to the junction between this transform fault and the nearby ridge segments. Using the results of photoelastic and finite-element studies, a model is provided for the tectonic development of these junctions. The model is based on an analogy between two offset cuts (mode I fractures) loaded in tension and segments of the axial rift zones (or parts thereof in the case of the Husavik fault). The results indicate that the Tjörnes fracture zone in general and the Husavik fault in particular, developed along zones of maximum shear stress. Furthermore, the model suggests that, as the ridge-segments propagate towards a zero-underlapping configuration, the angle between them and the associated major strike-slip faults gradually increases. This conclusion is supported by the trends of the main seismic lineaments of the Tjörnes fracture zone.  相似文献   

All about water and land? Resource-related conflicts in East and West Africa revisited     

Hanne Seter  Ole Magnus Theisen  Janpeter Schilling 《GeoJournal》2018,83(1):169-187

Recent years have seen an upsurge in the numbers of studies investigating the potential link between climate variability and conflict—and particularly so quantitative studies of this relationship—without reaching any consensus on causal pathways or main findings. This study sets out to explore what the main causes of conflict between resource-user groups in arid and semi-arid areas in Sub-Saharan Africa are, with a particular focus on renewable-resource scarcity. We conduct a comparative analysis of eleven high-quality case studies of the escalation into violence of disputes between pastoralists and farmers or pastoralists in the Western Sahel and East Africa. This enables us to identify the mechanisms underpinning the actors’ motivations. Our analysis shows that the nature of these conflicts is complex. They cannot be reduced to a stimulus (resource scarcity)–response (violence) relationship. We find that drought is a contributing factor in four of the conflicts, and that a poor rainy season plays a role in a fifth one. However, resource scarcity is never the most important cause and it does not explain well the differences in conflict intensity. The most important contributor to explaining different levels of intensity is when local autochthonous and exclusionary claims are coupled with national-level political processes.  相似文献   

Acoustic harassment devices reduce seal interaction in the Baltic salmon-trap, net fishery   总被引：1，自引：0，他引：1  

Fjalling  Arne; Wahlberg  Magnus; Westerberg  Hakan 《ICES Journal of Marine Science》2006,63(9):1751-1758

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Contaminant exposure and effects in Baltic ringed and grey seals as assessed by biomarkers   总被引：3，自引：0，他引：3  

Nyman M  Bergknut M  Fant ML  Raunio H  Jestoi M  Bengs C  Murk A  Koistinen J  Bäckman C  Pelkonen O  Tysklind M  Hirvi T  Helle E 《Marine environmental research》2003,55(1):73-99

The Baltic Sea ecosystem has suffered from a heavy pollutant load for more than three decades. Persistent organic pollutants (POPs) and heavy metals have been of most concern due to their persistence and toxic properties. Ringed seals (Phoca hispida baltica) and grey seals (Halichoerus grypus) living in the Baltic Sea have been suffering from pathological impairments, including reproductive disturbances, which have resulted in a depressed reproductive capacity. We investigated several biochemical parameters as potential biomarkers for exposure to and effects of the contaminant load in the Baltic seals. Seals from less polluted areas were used as reference material in terms of the pollution load. In both Baltic seal populations, the levels of some biochemical parameters diverged from those in the reference seals, and some of these showed a clear correlation with the individual contaminant load. Of the potential bioindicators, we propose cytochrome P4501A activity and vitamin E levels, in blubber or plasma, as exposure biomarkers for polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in both species. The arylhydrocarbon receptor-mediated chemical-activated luciferase gene expression (CALUX) response reflects the whole PCB and DDT burden in ringed seals. Retinyl palmitate (vitamin A) levels showed a negative correlation with the individual POP load, and is proposed as potential effect biomarkers for the depletion of the vitamin A stores. As the nutritional levels of both vitamin A and E have an impact on the vitamin levels in the seals, more information on the dietary vitamin levels is needed before any conclusions can be drawn. As the relationship between biochemical parameters and contaminants varied between the two species, species-specific characteristics has to be considered when monitoring the health status and possible toxic effects of the contaminant load in ringed and grey seals.  相似文献   

The first use of Fulton's K for assessing and comparing the conditions of inter‐tidal fish populations          下载免费PDF全文

Chris J. Barrett  Magnus L. Johnson  Nicola J. Hall  Sue L. Hull 《Marine Ecology》2016,37(1):42-45

Fulton's K condition factor was applied, for the first time, to inter‐tidal specimens of the shanny (Lipophrys pholis) and long‐spined scorpion fish (Taurulus bubalis) from two English rocky shore and two Welsh rocky shore sites during summer 2010 and winter 2011. As both species contribute to the diet of commercial species such as cod (Gadus morhua) and near‐threatened species such as the European otter (Lutra lutra), their condition may affect that of these predators. Fulton's K found that inter‐tidal Welsh fish maintained a ‘good’ condition between seasons, whereas the inter‐tidal English fish were in a poorer condition during winter. Although condition also changed amongst the sites on each coast, further studies are needed into fish morphologies, environmental parameters, prey availabilities and abundances, and fish specimen sex and maturities.  相似文献   

Identifying landslide preconditions in Swedish quick clays—insights from integration of surface geophysical,core sample- and downhole property measurements     

Silvia?Salas-RomeroEmail author  Alireza?Malehmir  Ian?Snowball  Bryan?C.?Lougheed  Magnus?Hellqvist 《Landslides》2016,13(5):905-923

Quick-clay landslides are a serious geohazard in Canada, Norway and Sweden. Identification and mapping of quick clays are essential endeavours because the damage caused by an individual landslide can be large and costly, with potentially fatal consequences. We collected geophysical borehole and soil core data from an area prone to quick-clay landslides in southwestern Sweden. Methodologies included in situ and laboratory measurements, providing information about natural gamma radiation, sonic velocities, electrical conductivity, pH, physical grain size, elemental and mineral composition, magnetic properties, cation exchange capacity and fossil content. A stratigraphic thickness of almost 60 m enables us to study quick clays and their host environment in Sweden at unusually high resolution. Results identify the origin and location of reflections in nearby seismic lines and assign physico-chemical properties to the geological units present in the area. We show that coarse-grained layers are sandwiched between marine clays (some of which are quick clays). These layers function as a conduit for relatively fresh water that infiltrates the marine clays and chemically destabilizes them by leaching out their salts. The salinity distribution in the boreholes indicate that the groundwater movement is downwards, through the coarse-grained layer and towards the Göta river. The presence of these materials is important for the development of quick clays, although not a prerequisite. With the help of surface geophysical methods, the location of the coarse-grained layers can be known faster and more economically, which could be relevant for studying the potential for quick-clay landslide occurrence over large areas.  相似文献