209 research outputs found
Data analysis Pipeline for EChO end-to-end simulations
No full textAtmospheric spectroscopy of extrasolar planets is an intricate business. Atmospheric signatures typically require a photometric precision of in flux over several hours. Such precision demands high instrument stability as well as an understanding of stellar variability and an optimal data reduction and removal of systematic noise. In the context of the EChO mission concept, we here discuss the data reduction and analysis pipeline developed for the EChO end-to-end simulator EChOSim. We present and discuss the step by step procedures required in order to obtain the final exoplanetary spectrum from the EChOSim`raw data' using a simulated observation of the secondary eclipse of the hot-Neptune 55 Cnc e
Enhancing 3D planetary atmosphere simulations with a surrogate radiative transfer model
No full textThis work introduces an approach to enhancing the computational efficiency of 3D atmospheric simulations by integrating a machine-learned surrogate model into the OASIS global circulation model (GCM). Traditional GCMs, which are based on repeatedly numerically integrating physical equations governing atmospheric processes across a series of time-steps, are time-intensive, leading to compromises in spatial and temporal resolution of simulations. This research improves upon this limitation, enabling higher resolution simulations within practical timeframes. Speeding up 3D simulations holds significant implications in multiple domains. Firstly, it facilitates the integration of 3D models into exoplanet inference pipelines, allowing for robust characterisation of exoplanets from a previously unseen wealth of data anticipated from JWST and post-JWST instruments. Secondly, acceleration of 3D models will enable higher resolution atmospheric simulations of Earth and Solar System planets, enabling more detailed insights into their atmospheric physics and chemistry. Our method replaces the radiative transfer module in OASIS with a recurrent neural network-based model trained on simulation inputs and outputs. Radiative transfer is typically one of the slowest components of a GCM, thus providing the largest scope for overall model speed-up. The surrogate model was trained and tested on the specific test case of the Venusian atmosphere, to benchmark the utility of this approach in the case of non-terrestrial atmospheres. This approach yields promising results, with the surrogate-integrated GCM demonstrating above 99.0% accuracy and 147 factor GPU speed-up of the entire simulation compared to using the matched original GCM under Venus-like conditions
Alfnoor: A Retrieval Simulation of the Ariel Target List
No full textIn this work, we present Alfnoor, a dedicated tool optimized for population studies of exoplanet atmospheres. Alfnoor combines the latest version of the retrieval algorithm, TauREx 3, with the instrument noise simulator ArielRad and enables the simultaneous retrieval analysis of a large sample of exo-atmospheres. We applied this tool to the Ariel list of planetary candidates and focus on hydrogen dominated, cloudy atmospheres observed in transit with the Tier-2 mode (medium Ariel resolution). As a first experiment, we randomized the abundances—ranging from 10^−7 to 10^−2—of the trace gases, which include H2O, CH4, CO, CO2, and NH3. This exercise allowed us to estimate the detection limits for Ariel Tier-2 and Tier-3 modes when clouds are present. In a second experiment, we imposed an arbitrary trend between a chemical species and the effective temperature of the planet. A last experiment was run requiring molecular abundances being dictated by equilibrium chemistry at a certain temperature. Our results demonstrate the ability of Ariel Tier-2 and Tier-3 surveys to reveal trends between the chemistry and associated planetary parameters. Future work will focus on eclipse data, on atmospheres heavier than hydrogen, and will be applied also to other observatories
Fast Regression of the Tritium Breeding Ratio in Fusion Reactors
No full textThe tritium breeding ratio (TBR) is an essential quantity for the design of
modern and next-generation D-T fueled nuclear fusion reactors. Representing the
ratio between tritium fuel generated in breeding blankets and fuel consumed
during reactor runtime, the TBR depends on reactor geometry and material
properties in a complex manner. In this work, we explored the training of
surrogate models to produce a cheap but high-quality approximation for a Monte
Carlo TBR model in use at the UK Atomic Energy Authority. We investigated
possibilities for dimensional reduction of its feature space, reviewed 9
families of surrogate models for potential applicability, and performed
hyperparameter optimisation. Here we present the performance and scaling
properties of these models, the fastest of which, an artificial neural network,
demonstrated and a mean prediction time of ,
representing a relative speedup of with respect to the expensive
MC model. We further present a novel adaptive sampling algorithm,
Quality-Adaptive Surrogate Sampling, capable of interfacing with any of the
individually studied surrogates. Our preliminary testing on a toy TBR theory
has demonstrated the efficacy of this algorithm for accelerating the surrogate
modelling process.Comment: 13 pages, 8 figure
Dataset: A scalable method to improve gray matter segmentation at ultra high field MRI.
No full text<p><strong>Dataset description: </strong>Accompanying data for manuscript “<a href="https://www.biorxiv.org/content/early/2018/01/10/245738">A scalable method to improve gray matter segmentation at ultra high field MRI</a>” written by Omer Faruk Gulban, Marian Schneider, Ingo Marquardt, Roy Haast, Federico De Martino, submitted for publication in PLOS One, January 2018.</p>
<p>Folder structure is organized according to Brain Imaging Data Structure (BIDS). Further details can be found the README files.</p>Acknowledgments:
This work was financed by the Netherlands Organisation for Scientific Research (NWO). The authors O.F.G. and F.D.M. as well as data acquisition for the MPRAGE data set were supported by NWO VIDI grant 864-13-012. Author M.S. was supported by NWO research talent grant 406-14-108. Author R.H. and acquisition of the MP2RAGE was funded by Technology Foundation STW (grant 12724)
A Structural Solution to Roaming in Europe
No full textThis paper suggests that international roaming markets suffer from structural flaws in the way that roaming agreements are established in Europe. The initial roaming interventions by the European Commission in 2007 have been very welfare enhancing and the transfer of producer surplus to consumers has brought significant benefits to end users. Nevertheless, there are clear opportunity costs of maintaining and/or extending the current roaming Regulation. The price for wholesale roaming services in a given country is driven principally by the amount of traffic that an operator is willing to send back to the country requesting a price offer and not on the basis of the roaming services requested. The paper suggests that by breaking the link between the prices offered in one country and the volume of returned traffic will enable the wholesale market for international roaming to operate competitively. It is further suggested that retail price regulation is unwarranted when the wholesale market can operate competitively irrespective of the issue of the retail elasticity of demand for these services. Preliminary, suggestions are put forward as to how policy makers could transition from the current regime to a future market based regime by putting a number of required enablers in place.Roaming regulation, mobile telephony, European single market
On the dangers of decentralization
No full textThe author highlights some of the dangers of decentralizations. The benefits of decentralization in allocative efficiency are not as obvious as suggested by the standard theory of fiscal federalism. The assumptions of this theory are fragile. These doubtful benefits might carry a cost in production efficiency, but more empirical research is needed on this point. What is not doubtful is that decentralization runs counter to redistribution and stabilization. Decentralization makes redistributive policies, whether interpersonal or interjurisdictional, more difficult, if not impossible. Decentralization also makes macroeconomic stabilization programs more difficult to implement because subnational government fiscal policies can run counter to national policies. Serious drawbacks or potential drawbacks should be considered in designing any decentralization program. The arguments that the author develops make it easier to understand some of the real choices. These choices are not so much whether to decentralize in general but rather what functions to decentralize - in which sectors, and in which regions. Guidelines can be provided on this. Often, the problem is not so much whether a certain service should be provided by a central, regional, or local government, since the service often has to be provided with the intervention of all three levels of government. The real challenge is how to organize the joint production of the service. Decentralization refers simultaneously to a state and to a process. The virtues and dangers of decentralization are often discussed simultaneously for both concepts. This is a dangerous confusion because decentralization is path-dependent. What is desirable in a given country at a certain point in time depends on the present state of decentralization and the speed at which it has been reached. Much more work, particularly empirical work, is needed -- in review of decentralization (or centralization) experiences in general, as well as those encouraged or supported by the World Bank.National Governance,Banks&Banking Reform,Municipal Financial Management,Economic Theory&Research,Pharmaceuticals&Pharmacoeconomics
Part 1: The Congestion of Humanitarian Space
No full textYes¿Part 1: The congestion of humanitarian space¿, assesses what affect the rapid proliferation
of the international aid community¿s presence in Sri Lanka has had on local level
relationships and emergency response capacities. It contends that the burgeoning presence
of aid agencies resulted in humanitarian assistance becoming a hotly contested and
competitive activity. It goes on to identify the possible factors that have contributed to the
rapid congestion of this space in suggesting an explanation of why the humanitarian
communities¿ normative standards appear to have failed
Werkzeuge zur Messung der datenschutzkonformen Einhaltung des Verarbeitungsstandorts in der Cloud
No full textPIPKs are essential for rhizoid elongation and caulonemal cell development in the moss Physcomitrella patens
No full textPtdIns-4,5-bisphosphate is a lipid messenger of eukaryotic cells playing critical roles in processes such as cytoskeleton organization, intracellular vesicular trafficking, secretion, cell motility, regulation of ion channels and nuclear signalling pathways. The enzymes responsible for the synthesis of PtdIns(4,5)P2 are phosphatidylinositol phosphate kinases (PIPKs). The moss Physcomitrella patens contains two PIPKs, PpPIPK1 and PpPIPK2. To study their physiological role, both genes were disrupted by targeted homologous recombination and as a result mutant plants with lower PtdIns(4,5)P2 levels were obtained. A strong phenotype for pipk1, but not for pipk2 single knockout lines, was obtained. The pipk1 knockout lines were impaired in rhizoid and caulonemal cell elongation, whereas pipk1-2 double knockout lines showed dramatic defects in protonemal and gametophore morphology manifested by the absence of rapidly elongating caulonemal cells in the protonemal tissue, leafy gametophores with very short rhizoids, and loss of sporophyte production. pipk1 complemented by overexpression of PpPIPK1 fully restored the wild type phenotype whereas overexpression of the inactive PpPIPK1E885A did not. Overexpression of PpPIPK2 in the pipk1-2 double knockout did not restore the wild type phenotype demonstrating that PpPIPK1 and PpPIPK2 are not functionally redundant. In vivo imaging of the cytoskeleton network revealed that the shortened caulonemal cells in the pipk1 mutants was the result of the absence of the apicobasal gradient of cortical F-actin cables normally observed in wild type caulonemal cells. Our data indicate that both PpPIPKs play a crucial role in the development of the moss P. patens, and particularly in the regulation of tip growth
- …
