Independent resolutions for totally disconnected dynamical systems I: Algebraic case

This is the first out of two papers on independent resolutions for totally disconnected dynamical systems. In the present paper, we discuss independent resolutions from an algebraic point of view. We also present applications to group homology and cohomology. This first paper sets the stage for our second paper, where we explain how to use independent resolutions in K-theory computations for crossed products attached to totally disconnected dynamical systems.Comment: 26 pages; minor changes improving the expositio

Modelled Nitrosamine and Nitramine concentrations in Lake Elvåga following amine-based CO2 Capture at FOV Waste Incineration Plant at Klemetsrud

Project Manager Cathrine Brecke GundersenFuture levels of the carcinogenic- and potentially carcinogenic nitrosamines (NSAs) and nitramines (NAs), respectively, were modelled in the drinking water source, Lake Elvåga following the planned full-scale amine-based CO2 capture at the Oslo waste incineration plant. A high-resolution and dynamic catchment model (INCA-Contaminants) was combined with a lake model add-on. NSA and NA deposition rates (provided from COWI/Norsk Energi/CERC) were combined with site specific information (hydrology and climate), and literature values of NSA and NA bio- and photodegradation rates and physiochemical parameters. The three scenarios, “best”, “likely”, and “worst” cases were created to capture the uncertainty of key parameters. Three years of full-scale CO2 capture resulted in maximum annual average sums of NSAs and NAs in the lake water at 0.24, 3.3, and 4.4 ng L-1, for the three scenarios, respectively. For the NSAs, photodegradation was an efficient depletion pathway, nearly balancing out the input rates. Lake water levels of NAs increased with time due to the lack of an efficient depletion pathway. Seasonal variation was evident in both the NSA and NA concentrations and this should be considered for potential future monitoring programs.COWIpublishedVersio

Retention efficiency for microplastic in a landscape estimated from empirically validated dynamic model predictions

Soils are recipients of microplastic that can be subsequently transferred to the sea. Land sources dominate inputs to the ocean, but knowledge gaps about microplastic retention by land hinder assessments of input rates. Here we present the first empirical evaluation of a dynamic microplastic fate model operating at landscape level. This mechanistic model accounts for hydrology, soil and sediment erosion, particle characteristics and behavior. We predict microplastic concentrations in water and sediments of the Henares river (Spain) within the measurement uncertainty boundaries (error factors below 2 and 10, respectively). Microplastic export from land and discharge by river fluctuates in a non-linear manner with precipitation and runoff variability. This indicates the need of accurate dynamic descriptions of soil and stream hydrology even when modeling microplastic fate and transport in generic scenarios and at low spatio-temporal resolution. A time-averaged landscape retention efficiency was calculated showing 20–50% of the microplastics added to the catchment over a multiannual period were retained. While the analysis reveals persistent uncertainties and knowledge gaps on microplastic sources to the catchment, these results contribute to the quantitative understanding of the role of terrestrial environments in accumulating microplastics, delaying their transport to the sea

Sources of skill in lake temperature, discharge and ice-off seasonal forecasting tools

Despite high potential benefits, the development of seasonal forecasting tools in the water sector has been slower than in other sectors. Here we assess the skill of seasonal forecasting tools for lakes and reservoirs set up at four sites in Australia and Europe. These tools consist of coupled hydrological catchment and lake models forced with seasonal meteorological forecast ensembles to provide probabilistic predictions of seasonal anomalies in water discharge, temperature and ice-off. Successful implementation requires a rigorous assessment of the tools' predictive skill and an apportionment of the predictability between legacy effects and input forcing data. To this end, models were forced with two meteorological datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF), the seasonal forecasting system, SEAS5, with 3-month lead times and the ERA5 reanalysis. Historical skill was assessed by comparing both model outputs, i.e. seasonal lake hindcasts (forced with SEAS5), and pseudo-observations (forced with ERA5). The skill of the seasonal lake hindcasts was generally low although higher than the reference hindcasts, i.e. pseudo-observations, at some sites for certain combinations of season and variable. The SEAS5 meteorological predictions showed less skill than the lake hindcasts. In fact, skilful lake hindcasts identified for selected seasons and variables were not always synchronous with skilful SEAS5 meteorological hindcasts, raising questions on the source of the predictability. A set of sensitivity analyses showed that most of the forecasting skill originates from legacy effects, although during winter and spring in Norway some skill was coming from SEAS5 over the 3-month target season. When SEAS5 hindcasts were skilful, additional predictive skill originates from the interaction between legacy and SEAS5 skill. We conclude that lake forecasts forced with an ensemble of boundary conditions resampled from historical meteorology are currently likely to yield higher-quality forecasts in most cases.publishedVersio

Forecasting water temperature in lakes and reservoirs using seasonal climate prediction

ABSTRACT: Seasonal climate forecasts produce probabilistic predictions of meteorological variables for subsequent months. This provides a potential resource to predict the influence of seasonal climate anomalies on surface water balance in catchments and hydro-thermodynamics in related water bodies (e.g., lakes or reservoirs). Obtaining seasonal forecasts for impact variables (e.g., discharge and water temperature) requires a link between seasonal climate forecasts and impact models simulating hydrology and lake hydrodynamics and thermal regimes. However, this link remains challenging for stakeholders and the water scientific community, mainly due to the probabilistic nature of these predictions. In this paper, we introduce a feasible, robust, and open-source workflow integrating seasonal climate forecasts with hydrologic and lake models to generate seasonal forecasts of discharge and water temperature profiles. The workflow has been designed to be applicable to any catchment and associated lake or reservoir, and is optimized in this study for four catchment-lake systems to help in their proactive management. We assessed the performance of the resulting seasonal forecasts of discharge and water temperature by comparing them with hydrologic and lake (pseudo)observations (reanalysis). Precisely, we analysed the historical performance using a data sample of past forecasts and reanalysis to obtain information about the skill (performance or quality) of the seasonal forecast system to predict particular events. We used the current seasonal climate forecast system (SEAS5) and reanalysis (ERA5) of the European Centre for Medium Range Weather Forecasts (ECMWF). We found that due to the limited predictability at seasonal time-scales over the locations of the four case studies (Europe and South of Australia), seasonal forecasts exhibited none to low performance (skill) for the atmospheric variables considered. Nevertheless, seasonal forecasts for discharge present some skill in all but one case study. Moreover, seasonal forecasts for water temperature had higher performance in natural lakes than in reservoirs, which means human water control is a relevant factor affecting predictability, and the performance increases with water depth in all four case studies. Further investigation into the skillful water temperature predictions should aim to identify the extent to which performance is a consequence of thermal inertia (i.e., lead-in conditions).This is a contribution of the WATExR project (watexr.eu/), which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by MINECO-AEI (ES), FORMAS (SE), BMBF (DE), EPA (IE), RCN (NO), and IFD (DK), with co-funding by the European Union (Grant 690462 ). MINECO-AEI funded this research through projects PCIN- 2017-062 and PCIN-2017-092. We thank all water quality and quantity data providers: Ens d’Abastament d’Aigua Ter-Llobregat (ATL, https://www.atl.cat/es ), SA Water ( https://www.sawater.com. au/ ), Ruhrverband ( www.ruhrverband.de ), NIVA ( www.niva.no ) and NVE ( https://www.nve.no/english/ ). We acknowledge the contribution of the Copernicus Climate Change Service (C3S) in the production of SEAS5. C3S provided the computer time for the generation of the re-forecasts for SEAS5 and for the production of the ocean reanalysis (ORAS5), used as initial conditions for the SEAS5 re-forecasts

The KK-Theory of Some Reduced Inverse Semigroup C∗C^*-Algebras

We use a recent result by Cuntz, Echterhoff and Li about the $K$-theory of certain reduced $C^*$-crossed products to describe the $K$-theory of $C^*_r(S)$ when $S$ is an inverse semigroup satisfying certain requirements. A result of Milan and Steinberg allows us to show that $C^*_r(S)$ is Morita equivalent to a crossed product of the type handled by Cuntz, Echterhoff and Li. We apply our result to graph inverse semigroups and the inverse semigroups of one-dimensional tilings

Topological Dynamics and Algebra in the Spectrum of L infinity of a locally compact Group : With Application to Crossed Products

In this text, I will look at some new approaches that may shed some light on the Kadison Singer problem, mainly one instigated by Vern Paulsen using dynamical systems in the Stone-Cech compactification of a discrete group. In order to do this, I will try to develop the theory in a crossed product setting, and look at some aspects of it that may hold interest of their own

Användbarhet hos digitala skolplattformar : En studie om Schoolsofts utvecklingspotential

Skolväsendet är en grundläggande instans i samhällsstrukturen, som i hög grad har påverkats av digitaliseringen. Efterfrågan av väl fungerande skolplattformar, digitala verktyg för administration och kommunikation mellan lärare, elever och föräldrar har ökat därefter. Den svenska staten och dess myndigheter har gjort omfattande investeringar i digitaliseringen av skolan men komplexiteten hos befintliga skolplattformar orsakar i nuläget problem för användarna. Anledningen uppges vara brister i säkerheten och användarvänligheten. Lärarnas Riksförbunds krav på ett enhetligt digitalt skolsystem för hela landet är ett konkret exempel på att digitaliseringen av skolan inte har nått fram till en önskvärd nivå. Projektet har sin utgångspunkt i Design Science och ett teoretiskt ramverk baserat på begreppet användbarhet som det definieras av Jenny Preece m.fl. (2015). samt Jakob Nielsen (1993). Den väletablerade skolplattformen Schoolsoft undersöks för att synliggöra områden som kan vidareutvecklas och som kan vara vägledande för framtida utveckling av digitala plattformar. Undersökningen av den digitala skolplattformen antog ett heuristiskt förhållningssätt och kombinerades med en enkätundersökning som skickades ut till lärare, föräldrar och elever på gymnasienivå. Enkätundersökningen involverar totalt 100 respondenter. Studien indikerar att Schoolsoft har utrymme för vidareutveckling som kan stärka användbarheten. Vidare resulterar studien i en kravspecifikation och en high-fidelity-prototyp av ett delsystem hos Schoolsoft. Kravspecifikationen utgörs av totalt 30 krav och är tänkt att vara vägledande i den fortsatta utvecklingen av befintliga skolplattformar, för att bland annat bidra till en positivare användarupplevelse. Prototypen implementerar 15 av kraven med fokus på Schoolsofts användargränssnitt, medan resterande krav blir ämnen för framtida forskning