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- Di Baldassarre, Giuliano, et al.
(författare)
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Is the current flood of data enough? : A treatise on research needs for the improvement of flood modelling
- 2012
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087. ; 26:1, s. 153-158
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Tidskriftsartikel (refereegranskat)abstract
- Flood disasters account for more than 40% of all natural hazardsworldwide and about half of all deaths caused by natural catastrophes(Ohl and Tapsell, 2000). For instance, in 2010, according to theEmergency Events Database (EM-DAT, 2011) floods were responsible forthe loss of more than 8000 human lives and affected about 180 millionpeople. The catastrophic floods in Pakistan and Australia are the mostrecent examples of a worldwide increasing human exposure to flood risk.Figure 1 reports the number of fatalities caused by floods in Africa inthe period 1950–2009 (EM-DAT, 2011).The diagram shows that the number of flood fatalities in Africa hasdramatically increased by more than an order of magnitude in the last60 years (Figure 1). These dramatic figures indicate a need for urgentactions to decrease these staggering numbers (Di Baldassarreet al.,2010a).The flood risk is likely to grow further because of many factors,such as changing demographics, land use changes, climate variabilityand change, technological and socio-economic conditions, industrialdevelopment, urban expansion and infrastructure construction in flood-prone areas as well as unplanned human settlement in floodplains(UN-ISDR Scientific and Technical Committee, 2009). To mitigate thecontinuously increasing flood risk the currently proposed approach isintegrated flood management (more towards ‘living with floods’) that hasreplaced the more traditional flood defense approach (‘fighting floods’).This approach aims to minimize the human, economic and ecologicallosses from extreme floods while at the same time maximising the social,economic and ecological benefits of ordinary floods (e.g. UNESCO-IFI:International Flood Initiative).In this context, the aim of this commentary is twofold. First, to criti-cally discuss the current opportunities for improving flood modelling,which are offered by the increased availability of new data sources,such as the utilisation of remote sensing data of higher resolution andthe increasing availability of globally and freely accessible space-bornedata. Second, to discuss knowledge gaps and research needs to fullyand properly exploit this current ‘flood of data’ (Lincoln, 2007) andimprove flood modelling. This leads to the proposed elements of a futureresearch agenda to support the scientific basis of integrated flood management.
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- Evaldsson, Martin, 1977-
(författare)
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Quantum transport and spin effects in lateral semiconductor nanostructures and graphene
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis studies electron spin phenomena in lateral semi-conductor quantum dots/anti-dots and electron conductance in graphene nanoribbons by numerical modelling. In paper I we have investigated spin-dependent transport through open quantum dots, i.e., dots strongly coupled to their leads, within the Hubbard model. Results in this model were found consistent with experimental data and suggest that spin-degeneracy is lifted inside the dot – even at zero magnetic field.Similar systems were also studied with electron-electron effects incorporated via Density Functional Theory (DFT) in the Local Spin Density Approximation (LSDA) in paper II and III. In paper II we found a significant spin-polarisation in the dot at low electron densities. As the electron density increases the spin polarisation in the dot gradually diminishes. These findings are consistent with available experimental observations. Notably, the polarisation is qualitatively different from the one found in the Hubbard model.Paper III investigates spin polarisation in a quantum wire with a realistic external potential due to split gates and a random distribution of charged donors. At low electron densities we recover spin polarisation and a metalinsulator transition when electrons are localised to electron lakes due to ragged potential profile from the donors. In paper IV we propose a spin-filter device based on resonant backscattering of edge states against a quantum anti-dot embedded in a quantum wire. A magnetic field is applied and the spin up/spin down states are separated through Zeeman splitting. Their respective resonant states may be tuned so that the device can be used to filter either spin in a controlled way.Paper V analyses the details of low energy electron transport through a magnetic barrier in a quantum wire. At sufficiently large magnetisation of the barrier the conductance is pinched off completely. Furthermore, if the barrier is sharp we find a resonant reflection close to the pinch off point. This feature is due to interference between a propagating edge state and quasibond state inside the magnetic barrier.Paper VI adapts an efficient numerical method for computing the surface Green’s function in photonic crystals to graphene nanoribbons (GNR). The method is used to investigate magnetic barriers in GNR. In contrast to quantum wires, magnetic barriers in GNRs cannot pinch-off the lowest propagating state. The method is further applied to study edge dislocation defects for realistically sized GNRs in paper VII. In this study we conclude that even modest edge dislocations are sufficient to explain both the energy gap in narrow GNRs, and the lack of dependance on the edge structure for electronic properties in the GNRs.
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- Fernandez, Marilen, et al.
(författare)
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Diatom assemblage changes in lacustrine sediments from Isla de los Estados, southernmost South America, in response to shifts in the southwesterly wind belt during the last deglaciation
- 2013
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Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 50:4, s. 433-446
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Tidskriftsartikel (refereegranskat)abstract
- Isla de los Estados (54A degrees 45'S, 63A degrees 10'aEuro64A degrees 46'W) lies east of the main island of Tierra del Fuego and is the southeastern-most point in Argentina. Because of its geographic position near the latitudes of the Southern Hemisphere Westerlies and the strong influence of the Antarctic Circumpolar Current (ACC), the area is suitable for paleoecological and paleoclimate research. The island is not far north of the Subantarctic Front, which limits the northern boundary of the ACC. Paleoenvironmental study in this geographic location can shed light on past changes in atmospheric and marine circulation patterns. Diatom analysis of the lower part of a sediment sequence from Laguna Cascada (54A degrees 45' 51.3''S, 64A degrees 20' 20.07''W) enabled inference of changing lake conditions between 16 and 11.1 cal ka BP. Between 16 and 14.4 cal ka BP fragilarioid diatom species, often a pioneer group, dominated the record. Their presence shows seasonally open-water conditions from the onset of sedimentation. In zone II (14.4-12.8 cal ka BP), the dominance of planktonic/tychoplanktonic Aulacoseira spp. might represent longer ice-free periods and windier conditions, which would have kept this heavy species suspended in the water column. This period corresponds to the Antarctic Cold Reversal, when the Southern Hemisphere Westerlies were possibly centered on the latitudes of Tierra del Fuego, resulting in windy and wet conditions. Zone III (12.8-11.1 cal ka BP) is dominated by benthic diatom taxa that are mainly associated with peat and wetland vegetation. This suggests that climate conditions had become milder and less windy, favoring aquatic productivity and terrestrial vegetation development. This change in environmental conditions may have been a consequence of the southward movement of the Southern Hemisphere Westerlies at the start of the Antarctic Holocene thermal optimum.
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- Fujii, N., et al.
(författare)
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Exercise induces isoform-specific increase in 5'AMP-activated protein kinase activity in human skeletal muscle
- 2000
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - San Diego, CA, USA : Academic Press. - 0006-291X .- 1090-2104. ; 273:3, s. 1150-1155
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Tidskriftsartikel (refereegranskat)abstract
- The 5'AMP-activated protein kinase (AMPK) is stimulated by contractile activity in rat skeletal muscle. AMPK has emerged as an important signaling intermediary in the regulation of cell metabolism being linked to exercise-induced changes in muscle glucose and fatty acid metabolism. In the present study, we determined the effects of exercise on isoform-specific AMPK activity (alpha1 and alpha2) in human skeletal muscle. Needle biopsies of vastus lateralis muscle were obtained from seven healthy subjects at rest, after 20 and 60 min of cycle ergometer exercise at 70% of VO(2)max, and 30 min following the 60 min exercise bout. In comparison to the resting state, AMPK alpha2 activity significantly increased at 20 and 60 min of exercise, and remained at a higher level with 30 min of recovery. AMPK alpha1 activity tended to slightly decrease with 20 min of exercise at 70%VO(2)max; however, the change was not statistically significant. AMPK alpha1 activities were at basal levels at 60 min of exercise and 30 min of recovery. On a separate day, the same subjects exercised for 20 min at 50% of VO(2)max. Exercise at this intensity did not change alpha2 activity, and similar to exercise at 70% of VO(2)max, there was no significant change in alpha1 activity. In conclusion, exercise at a higher intensity for only 20 min leads to increases in AMPK alpha2 activity but not alpha1 activity. These results suggest that the alpha2-containing AMPK complex, rather than alpha1, may be involved in the metabolic responses to exercise in human skeletal muscle.
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- Fujii, S., et al.
(författare)
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A cross-country study of fairness and infringement on freedom as determinants of car owners´ acceptance of road pricing.
- 2004
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Ingår i: Transportation. ; 31:3
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Tidskriftsartikel (refereegranskat)abstract
- Jakobsson et al. (2000) found that in Sweden public acceptance of road pricing decreases if it is perceived to be unfair and to infringe on freedom. The present study reports a survey investigating whether the same effects are found in the Asian countries of Japan and Taiwan. The results indicate that fairness plays the same role. However, infringement of freedom may be more important in Japan than in Sweden or Taiwan. Income had a direct effect on acceptance in Taiwan but not in Japan or Sweden.
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