Network Structure and User Roles of a Crowdsourcing Community – The Context of Social Innovations for a Development Project

The principles of crowdsourcing are increasingly applied in social contexts like development projects. In this study we explore a crowdsourcing community, which aims to enhance conditions in low income communities. We investigate the network structures of the community and detect behavioral pattern and user roles based on participation behavior for this specific context. Overall, the observed community shows a high level of collaboration and reciprocal dialogue. On the individual level we located four different user roles distinct in their interaction and contribution behavior. So called “collaborators” are considered as unique user role in an online community within a social context. We contribute to the theory of crowdsourcing by illustrating that context and purpose of crowdsourcing initiatives may influence the behavioral pattern of users. Further we add insights to the junctures between crowdsourcing and social innovation in the context of open development

Learning Heuristic Selection with Dynamic Algorithm Configuration

A key challenge in satisficing planning is to use multiple heuristics within one heuristic search. An aggregation of multiple heuristic estimates, for example by taking the maximum, has the disadvantage that bad estimates of a single heuristic can negatively affect the whole search. Since the performance of a heuristic varies from instance to instance, approaches such as algorithm selection can be successfully applied. In addition, alternating between multiple heuristics during the search makes it possible to use all heuristics equally and improve performance. However, all these approaches ignore the internal search dynamics of a planning system, which can help to select the most useful heuristics for the current expansion step. We show that dynamic algorithm configuration can be used for dynamic heuristic selection which takes into account the internal search dynamics of a planning system. Furthermore, we prove that this approach generalizes over existing approaches and that it can exponentially improve the performance of the heuristic search. To learn dynamic heuristic selection, we propose an approach based on reinforcement learning and show empirically that domain-wise learned policies, which take the internal search dynamics of a planning system into account, can exceed existing approaches.Comment: Long version of the paper at the International Conference on Automated Planning and Scheduling (ICAPS) 202

Interferometry of ϵ\epsilon Aurigae: Characterization of the asymmetric eclipsing disk

We report on a total of 106 nights of optical interferometric observations of the $\epsilon$ Aurigae system taken during the last 14 years by four beam combiners at three different interferometric facilities. This long sequence of data provides an ideal assessment of the system prior to, during, and after the recent 2009-2011 eclipse. We have reconstructed model-independent images from the 10 in-eclipse epochs which show that a disk-like object is indeed responsible for the eclipse. Using new 3D, time-dependent modeling software, we derive the properties of the F-star (diameter, limb darkening), determine previously unknown orbital elements ($\Omega$, $i$), and access the global structures of the optically thick portion of the eclipsing disk using both geometric models and approximations of astrophysically relevant density distributions. These models may be useful in future hydrodynamical modeling of the system. Lastly, we address several outstanding research questions including mid-eclipse brightening, possible shrinking of the F-type primary, and any warps or sub-features within the disk.Comment: 105 pages, 57 figures. This is an author-created, un-copyedited version of an article accepted for publication in Astrophysical Journal Supplement Series. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

Kilometer-scale digital elevation models of the sea ice surface with airborne laser scanning during MOSAiC

An integrated sensor platform including an inertial navigation system (INS) and a commercial airborne laser scanner (ALS) among other sensor was mounted in the cargo compartment in one of the Polarstern helicopters during MOSAiC. ALS data was acquired from more than 60 flights between October 2019 and September 2020 with a range of survey types intended to map changes of the sea ice surface during the full annual cycle at high spatial resolution and coverage. Here, we provide an overview of the collected data, the challenge of achieving centimeter elevation accuracy with a helicopter platform at high polar latitudes as well as the content and specifications of ALS data products. The high spatial resolution and repeated coverage of the larger area around Polarstern allow studying various surface features (e.g. pressure ridges, floes, melt ponds, snow drifts, etc.), their seasonal evolution, and their impact on atmosphere and ocean. Finally, we outline methods for planned applications, such as identifying individual floes and surface types using both measured freeboard and surface reflectance. Collocated helicopter-based optical and infrared imagery allow analyzing sea ice properties in further applications and to upscale comparable in-situ observations

Time course of the interaction between tadalafil and nitrates

AbstractObjectivesThis study was designed to determine the time course of nitrate interaction with tadalafil, a phosphodiesterase 5 (PDE5) inhibitor with a half-life (t1/2) of 17.5 h.BackgroundThe PDE5 inhibitors augment the blood pressure (BP)-lowering effects of nitrates, yet the time course of this interaction is unclear. Recent guidelines from the American College of Cardiology/American Heart Association recommend that nitrates be withheld for 24 h after taking sildenafil (t1/2= 4 h).MethodsMale subjects (n = 150) received seven consecutive daily doses of placebo or tadalafil (20 mg). On day 7 and beyond, subjects received repeated doses of sublingual nitroglycerin (0.4 mg) after the last dose of placebo or tadalafil. After a 10- to 21-day washout period, subjects crossed over to either placebo or tadalafil, and nitrate dosing was repeated.ResultsIn response to nitroglycerin at 4, 8, and 24 h, standing systolic BP fell below 85 mm Hg in more subjects on tadalafil compared with placebo (p < 0.05), with no difference in the response to nitroglycerin at 48, 72, and 96 h (p > 0.2). Similar observations were made for standing diastolic BP <45 mm Hg, decrease in systolic BP >30 mm Hg, and decrease in diastolic BP >20 mm Hg. Nitroglycerin also evoked greater mean maximal decreases in standing systolic BP at 8 and 24 h after taking tadalafil versus placebo (p < 0.02), with no significant difference at 48, 72, or 96 h (p > 0.49).ConclusionsThe hemodynamic interaction between tadalafil and sublingual nitroglycerin lasted 24 h, but was not seen at 48 h and beyond. Similar to other PDE5 inhibitors, tadalafil should not be administered in combination with organic nitrates

Multi-sensor airborne observations of freeboard, snow depth, and sea-ice thickness in the Arctic

Sea-ice thickness is a key factor and indicator in understanding the impact of the global climate change. Deriving basin-wide sea-ice thickness estimates from satellite laser and radar altimetry relies on freeboard measurements. The freeboard-to-thickness conversion in turn requires information of snow mass and the density of the sea-ice layer that have unknown spatio-temporal variabilities and trends directly translating into the uncertainty of decadal sea-ice thickness data records. In addition, inter-mission biases arise from, e.g., different sensor types and frequencies as well as varying footprint sizes affected by surface roughness across regions and seasons. Therefore, carrying out validation and inter-calibration studies is crucial for reliable and continuous observation of the Earth’s cryosphere. To achieve this, it is beneficial to have simultaneous measurements of freeboard, snow depth, and sea-ice thickness, which provide reference data for both direct satellite observations and geophysical target parameters. Here, we present Alfred Wegener Institute’s (AWI) IceBird program, which is a series of fixed-wing aircraft campaigns to measure Arctic sea ice and to monitor its change. During two late-winter campaigns in the western Arctic Ocean in 2017 and 2019, we have carried out surveys with the unique scientific instrument configuration including an airborne laser scanner (ALS) for surface topography and freeboard measurements, a tethered electromagnetic induction sounding instrument (EM-Bird) for total (snow+ice) thickness measurements, and an ultrawideband frequency-modulated continuous-wave microwave radar to measure snow thickness. Therefore, we are able to observe all three bounding interfaces in the sea-ice–snow system in high resolution along survey tracks on regional scales. During the ship-based drift expedition Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) between October 2019 and September 2020, helicopter surveys were carried out in high spatio-temporal resolution throughout the year, including the polar night, to measure freeboard and roughness with the ALS both in local grid pattern and in larger scale. Coincident EM-Bird ice thickness data and information from snow measurements on the ground will help linking these parameters and monitor them and their effect on satellite retrievals for a full seasonal cycle. The individual parameters are important for describing and monitoring the state of the Arctic sea ice and validating retrievals from satellite data, but combined they offer further possibilities to characterise sea ice. By assuming isostatic equilibrium, we are able to estimate up-to-date bulk density values for different sea-ice types from the IceBird data and to derive a parametrisation of sea-ice bulk density based on sea-ice freeboard. These data allow us to explore spatio-temporal variations in sea-ice parameters observable from space and to evaluate the validity of the freeboard-to-thickness conversion in satellite altimetry through comparison against dedicated satellite overpasses and orbit collections

Predictors for New-Onset Complete Heart Block After Transcatheter Aortic Valve Implantation

ObjectivesThe aim of this study was to identify risk factors for new-onset atrioventricular (AV) block requiring pacemaker (PM) implantation after transcatheter aortic valve implantation (TAVI).BackgroundHigh-grade AV block and consecutive PM implantation are frequent complications following TAVI.MethodsFor logistic regression analysis, we included 159 patients (mean age: 81 ± 6 years, EuroSCORE: 22 ± 13%) who underwent TAVI (n = 116 transfemoral, n = 4 via subclavian artery, n = 37 transapical, n = 2 transaortic) between June 2007 and January 2009 and who had no previously implanted PM.ResultsThirty-five patients (22%) developed new-onset post-operative AV block with the need of PM implantation. Logistic regression revealed a 2-fold increased risk for new-onset AV block in patients in whom a large valve is implanted in a small annulus (32% pacemaker implantations, odds ratio [OR]: 2.378, p = NS), a 4-fold increased risk with the implantation of the CoreValve (Medtronic, Minneapolis, Minnesota) versus the Edwards Sapien valve (Edwards Lifesciences, Irvine, California) (27% pacemaker implantations, OR: 3.781, p = NS), and a 5-fold increased risk for patients who exhibit an AV block episode instantly during the implantation procedure (49% pacemaker implantations, OR: 4.819, p = 0.001). Pre-existing ECG alterations were not identified as risk factors for AV block after transcatheter aortic valve implantation.ConclusionsWe assume that conduction tissue impairment is provoked by mechanical compression with large prostheses in smaller annuli or in the larger area of the CoreValve covering the outflow tract and may appear instantly during the implantation procedure. Continuous post-operative electrocardiogram monitoring should be performed for at least 3 days in all patients after TAVI procedures and until discharge in patients with increased risk for this complication