Using resistivity measurements for dam safety evaluation at Enemossen tailings dam in southern Sweden

Internal erosion is a major reason for embankment dam failures. Resistivity measurements is an essentially non-destructive technique, which may have the possibility of detecting internal erosion processes and anomalous seepage at an early stage before the safety of the dam is at stake. This paper presents results from part of a dam safety investigation conducted at the Enemossen tailings dam in southern Sweden. Longitudinal resistivity sections, 2D measurements along the dam crest, provided an overview of the whole dam and served to detect anomalous zones. In selected areas, additional cross-sectional 2D surveys gave detailed information about the geo-electrical situations in the embankments. This information is valuable for similar investigations as information about resistivity in embankment construction material is scarce. Known problem areas were associated with low resistivities, even though the resistivity measurements alone did not provide enough information to confidently come to a decision about the status of the dams

Freezing in random graph ferromagnets

Using T=0 Monte Carlo and simulated annealing simulation, we study the energy relaxation of ferromagnetic Ising and Potts models on random graphs. In addition to the expected exponential decay to a zero energy ground state, a range of connectivities for which there is power law relaxation and freezing to a metastable state is found. For some connectivities this freezing persists even using simulated annealing to find the ground state. The freezing is caused by dynamic frustration in the graphs, and is a feature of the local search-nature of the Monte Carlo dynamics used. The implications of the freezing on agent-based complex systems models are briefly considered.Comment: Published version: 1 reference deleted, 1 word added. 4 pages, 5 figure

Warped Vacuum Statistics

We consider the effect of warping on the distribution of type IIB flux vacua constructed with Calabi-Yau orientifolds. We derive an analytical form of the distribution that incorporates warping and find close agreement with the results of a Monte Carlo enumeration of vacua. Compared with calculations that neglect warping, we find that for any finite volume compactification, the density of vacua is highly diluted in close proximity to the conifold point, with a steep drop-off within a critical distance.Comment: 30 pages, 2 figure

Fast and robust chromatic dispersion estimation based on temporal auto-correlation after digital spectrum superposition

We investigate and experimentally demonstrate a fast and robust chromatic dispersion (CD) estimation method based on temporal auto-correlation after digital spectrum superposition. The estimation process is fast, because neither tentative CD scanning based on CD compensation nor specific cost function calculations are used. Meanwhile, the proposed CD estimation method is robust against polarization mode dispersion (PMD), amplified spontaneous emission (ASE) noise and fiber nonlinearity. Furthermore, the proposed CD estimation method can be used for various modulation formats and digital pulse shaping technique. Only 4096 samples are necessary for CD estimation of single carrier either 112 Gbps DP-QPSK or 224 Gbps DP-16QAM signal with various pulse shapes. 8192 samples are sufficient for the root-raised-cosine pulse with roll-off factor of 0.1. As low as 50 ps/nm standard deviation together with a worst estimation error of about 160 ps/nm is experimentally obtained for 7 x 112 Gbps DP-QPSK WDM signal after the transmission through 480 km to 9120 km single mode fiber (SMF) loop using different launch powers

Aerosol ageing in an urban plume - implication for climate

The climate effects downwind of an urban area resulting from gaseous and particulate emissions within the city are as yet inadequately quantified. The aim of this work was to estimate these effects for Malmo city in southern Sweden (population 280 000). The chemical and physical particle properties were simulated with a model for Aerosol Dynamics, gas phase CHEMistry and radiative transfer calculations (ADCHEM) following the trajectory movement from upwind of Malmo, through the urban background environment and finally tens and hundreds of kilometers downwind of Malmo. The model results were evaluated using measurements of the particle number size distribution and chemical composition. The total particle number concentration 50 km (similar to 3 h) downwind, in the center of the Malmo plume, is about 3700 cm(-3) of which the Malmo contribution is roughly 30%. Condensation of nitric acid, ammonium and to a smaller extent oxidized organic compounds formed from the emissions in Malmo increases the secondary aerosol formation with a maximum of 0.7-0.8 mu gm(-3) 6 to 18 h downwind of Malmo. The secondary mass contribution dominates over the primary soot contribution from Malmo already 3 to 4 h downwind of the emission sources and contributes to an enhanced total surface direct or indirect aerosol shortwave radiative forcing in the center of the urban plume ranging from -0.3 to -3.3 Wm(-2) depending on the distance from Malmo, and the specific cloud properties

Effects of magnetic perturbations and radiation on the runaway avalanche

The electron runaway phenomenon in plasmas depends sensitively on the momentum- space dynamics. However, efficient simulation of the global evolution of systems involving runaway electrons typically requires a reduced fluid description. This is needed, for example, in the design of essential runaway mitigation methods for tokamaks. In this paper, we present a method to include the effect of momentum-dependent spatial transport in the runaway avalanche growth rate. We quantify the reduction of the growth rate in the presence of electron diffusion in stochastic magnetic fields and show that the spatial transport can raise the effective critical electric field. Using a perturbative approach, we derive a set of equations that allows treatment of the effect of spatial transport on runaway dynamics in the presence of radial variation in plasma parameters. This is then used to demonstrate the effect of spatial transport in current quench simulations for ITER-like plasmas with massive material injection. We find that in scenarios with sufficiently slow current quench, owing to moderate impurity and deuterium injection, the presence of magnetic perturbations reduces the final runaway current considerably. Perturbations localised at the edge are not effective in suppressing the runaways, unless the runaway generation is off-axis, in which case they may lead to formation of strong current sheets at the interface of the confined and perturbed regions

The paradox of public acceptance of bike sharing in Gothenburg

Bike sharing is one of the most promising urban planning interventions to facilitate an all-necessary transition towards a more sustainable transport paradigm. Regardless of the fact that hundreds of schemes run in more than 50 countries worldwide, bike sharing is still moderately investigated by research. This paper reports on a primarily quantitative study of 558 responses that was set to frame attitudes reflecting public acceptance towards the rapidly expanding bike-sharing scheme in Gothenburg (Styr & Ställ), in an attempt to identify the ‘formula for success’. The respondents generally believed that Styr & Ställ is a pro-environmental, inexpensive and healthy transport mode, which complements the city’s public transport services and promotes a more human-friendly identity for Gothenburg. Even the respondents that self-reported a small (or no) likelihood to use bike sharing were positive towards the scheme. This means that they recognise that bike sharing has a significant pro-social potential and is not a system favouring a particular road-user segment over others that might not be interested or able to use it. The fact that the majority of the respondents do not Bike sharing is one of the most promising urban planning interventions to facilitate an all-necessary transition towards a more sustainable transport paradigm. Regardless of the fact that hundreds of schemes run in more than 50 countries worldwide, bike sharing is still moderately investigated by research. This paper reports on a primarily quantitative study of 558 responses that was set to frame attitudes reflecting public acceptance towards the rapidly expanding bike-sharing scheme in Gothenburg (Styr & Ställ), in an attempt to identify the ‘formula for success’. The respondents generally believed that Styr & Ställ is a pro-environmental, inexpensive and healthy transport mode, which complements the city’s public transport services and promotes a more human-friendly identity for Gothenburg. Even the respondents that self-reported a small (or no) likelihood to use bike sharing were positive towards the scheme. This means that they recognise that bike sharing has a significant pro-social potential and is not a system favouring a particular road-user segment over others that might not be interested or able to use it. The fact that the majority of the respondents do not use the scheme and yet its popularity is still vast indicates that there is much potential for more use in real terms

Autofluorescence insensitive imaging using upconverting nanocrystals in scattering media

Autofluorescence is a nuisance in the field of fluorescence imaging and tomography of exogenous molecular markers in tissue, degrading the quality of the collected data. In this letter, we report autofluorescence insensitive imaging using highly efficient upconverting nanocrystals (NaYF4: Yb3+ /Tm3+) in a tissue phantom illuminated with near- infrared radiation of 85 mW/cm(2). It was found that imaging with such nanocrystals leads to an exceptionally high contrast compared to traditional downconverting fluorophores due to the absence of autofluorescence. Upconverting nanocrystals may be envisaged as important biological markers for tissue imaging purposes. c 2008 American Institute of Physics. [DOI: 10.1063/1.3005588

Long term measurements of aerosol optical properties at a primary forest site in Amazonia

A long term experiment was conducted in a primary forest area in Amazonia, with continuous in-situ measurements of aerosol optical properties between February 2008 and April 2011, comprising, to our knowledge, the longest database ever in the Amazon Basin. Two major classes of aerosol particles, with significantly different optical properties were identified: coarse mode predominant biogenic aerosols in the wet season (January-June), naturally released by the forest metabolism, and fine mode dominated biomass burning aerosols in the dry season (July-December), transported from regional fires. Dry particle median scattering coefficients at the wavelength of 550 nm increased from 6.3 Mm(-1) to 22 Mm(-1), whereas absorption at 637 nm increased from 0.5 Mm(-1) to 2.8 Mm(-1) from wet to dry season. Most of the scattering in the dry season was attributed to the predominance of fine mode (PM2) particles (40-80% of PM10 mass), while the enhanced absorption coefficients are attributed to the presence of light absorbing aerosols from biomass burning. As both scattering and absorption increased in the dry season, the single scattering albedo (SSA) did not show a significant seasonal variability, in average 0.86 +/- 0.08 at 637 nm for dry aerosols. Measured particle optical properties were used to estimate the aerosol forcing efficiency at the top of the atmosphere. Results indicate that in this primary forest site the radiative balance was dominated by the cloud cover, particularly in the wet season. Due to the high cloud fractions, the aerosol forcing efficiency absolute values were below -3.5 Wm(-2) in 70% of the wet season days and in 46% of the dry season days. Besides the seasonal variation, the influence of out-of-Basin aerosol sources was observed occasionally. Periods of influence of the Manaus urban plume were detected, characterized by a consistent increase on particle scattering (factor 2.5) and absorption coefficients (factor 5). Episodes of biomass burning and mineral dust particles advected from Africa were observed between January and April, characterized by enhanced concentrations of crustal elements (Al, Si, Ti, Fe) and potassium in the fine mode. During these episodes, median particle absorption coefficients increased by a factor of 2, whereas median SSA values decreased by 7 %, in comparison to wet season conditions.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)European Integrated FP6 project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) under the scope of LBA experimentUniversidade Federal de São Paulo, Inst Environm Chem & Pharmaceut Sci, Dept Earth & Exact Sci, São Paulo, BrazilUniv São Paulo, Inst Phys, Dept Appl Phys, São Paulo, BrazilLeibniz Inst Tropospher Res, Leipzig, GermanyNatl Inst Amazonian Res INPA, Manaus, Amazonas, BrazilLund Univ, Inst Phys, Div Nucl Phys, Lund, SwedenHarvard Univ, Dept Earth & Planetary Sci, Div Engn & Appl Sci, Cambridge, MA 02138 USAUniv Helsinki, Div Atmospher Sci, Dept Phys Sci, Helsinki, FinlandUniversidade Federal de São Paulo, Inst Environm Chem & Pharmaceut Sci, Dept Earth & Exact Sci, São Paulo, BrazilFAPESP: AEROCLIMA 08/58100-2European Integrated FP6 project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) under the scope of LBA experiment: 34684Web of Scienc