Ultra-Fast Generation of Air Shower Images for Imaging Air Cherenkov Telescopes using Generative Adversarial Networks

For the analysis of data taken by Imaging Air Cherenkov Telescopes (IACTs), a large number of air shower simulations are needed to derive the instrument response. The simulations are very complex, involving computational and memory-intensive calculations, and are usually performed repeatedly for different observation intervals to take into account the varying optical sensitivity of the instrument. The use of generative models based on deep neural networks offers the prospect for memory-efficient storing of huge simulation libraries and cost-effective generation of a large number of simulations in an extremely short time. In this work, we use Wasserstein Generative Adversarial Networks to generate photon showers for an IACT equipped with the FlashCam design, which has more than $1{,}500$ pixels. Using simulations of the H.E.S.S. experiment, we demonstrate the successful generation of high-quality IACT images. The analysis includes a comprehensive study of the generated image quality based on low-level observables and the well-known Hillas parameters that describe the shower shape. We demonstrate for the first time that the generated images have high fidelity with respect to low-level observables, the Hillas parameters, their physical properties, as well as their correlations. The found increase in generation speed in the order of $10^5$ yields promising prospects for fast and memory-efficient simulations of air showers for IACTs.Comment: 27 pages, 12 figure

Osmotic diuresis due to urea as the cause of hypernatraemia in critically ill patients

Background. Hypernatraemia is common in critically ill patients and has been shown to be an independent predictor of mortality. Osmotic urea diuresis can cause hypernatraemia due to significant water losses but is often not diagnosed. Free water clearance (FWC) and electrolyte free water clearance (EFWC) were proposed to quantify renal water handling. We aimed to (i) identify patients with hypernatraemia due to osmotic urea diuresis and (ii) investigate whether FWC and EFWC are helpful in identifying renal loss of free water. Methods. In this retrospective study, we screened a registry for patients, who experienced intensive care unit (ICU)-acquired hypernatraemia. Among them, patients with hypernatraemia due to osmotic urea diuresis were detected by a case-by-case review. Total fluid and electrolyte balances together with FWC and EFWC were calculated for days of rising serum sodium and stable serum sodium. Results. We identified seven patients (10% of patients with ICU-acquired hypernatraemia) with osmotic diuresis due to urea. All patients were intubated during development of hypernatraemia and received enteral nutrition. The median highest serum sodium level of 153 mmol (Q1: 151-Q3: 155 mmol/L) was reached after a 5-day period of rise in serum sodium. During this period, FWC was −904 mL/day (Q1: −1574-Q3: −572), indicating renal water retention, while EFWC was 1419 mL/day (Q1: 1052-Q3: 1923), showing renal water loss. While FWC did not differ between time of stable serum sodium and development of hypernatraemia, EFWC was significantly higher during rise in serum sodium. Conclusion. Osmotic urea diuresis is a common cause of hypernatraemia in the ICU. EFWC was useful in the differential diagnosis of polyuria during rising serum sodium levels, while FWC was misleadin

Algorithm-Agnostic Interpretations for Clustering

A clustering outcome for high-dimensional data is typically interpreted via post-processing, involving dimension reduction and subsequent visualization. This destroys the meaning of the data and obfuscates interpretations. We propose algorithm-agnostic interpretation methods to explain clustering outcomes in reduced dimensions while preserving the integrity of the data. The permutation feature importance for clustering represents a general framework based on shuffling feature values and measuring changes in cluster assignments through custom score functions. The individual conditional expectation for clustering indicates observation-wise changes in the cluster assignment due to changes in the data. The partial dependence for clustering evaluates average changes in cluster assignments for the entire feature space. All methods can be used with any clustering algorithm able to reassign instances through soft or hard labels. In contrast to common post-processing methods such as principal component analysis, the introduced methods maintain the original structure of the features

Allgemeine Geschäftsbedingungen in Peer-to-Peer-Märkten

Die Arbeit behandelt elektronische Marktplätze, die ohne eine zentrale Instanz auskommen und allein durch die Marktteilnehmer entstehen. Sie bietet technische Ansätze und deren rechtliche Beurteilung, um den Zugangsnachweis für Erklärungen führen zu können und behandelt wie Rechner zur Rechtsfolgenermittlung eingesetzt werden können, um den Nutzer für den Vertragsentwurf und -abschluss einzelfallbezogenes rechtliches Expertenwissen zur Verfügung stellen zu können

Topic Embeddings – A New Approach to Classify Very Short Documents Based on Predefined Topics

Traditional unsupervised topic modeling approaches like Latent Dirichlet Allocation (LDA) lack the ability to classify documents into a predefined set of topics. On the other hand, supervised methods require significant amounts of labeled data to perform well on such tasks. We develop a new unsupervised method based on word embeddings to classify documents into predefined topics. We evaluate the predictive performance of this novel approach and compare it to seeded LDA. We use a real-world dataset from online advertising, which is comprised of markedly short documents. Our results indicate the two methods may complement one another well, leading to remarkable sensitivity and precision scores of ensemble learners trained thereupon

Monitoring winter spawning activity of Western Baltic cod (Gadus morhua) (2021-25) Cruise No. AL568b

January 24th – February 1st 2022 Kiel (Germany) – Kiel (Germany) Winter cod 2021-2

Influence of Nutrient Availability, Stand Age, and Canopy Structure on Isoprene Flux in a Eucalyptus saligna Experimental Forest

Eucalyptus plantations occupy approximately 10 million ha of land in the tropics and, increasingly, afforestation and reforestation projects are relying on this genus to provide rapid occupation of degraded sites, large quantities of high-quality wood products, and high rates of carbon sequestration. Members of the genus Eucalyptus are also very high emitters of isoprene, the dominant volatile organic compound emitted by trees in tropical ecosystems, which significantly influences the oxidative capacity of the atmosphere. While fertilization growth response of these trees has been intensively studied, little is known about how fertilization and tree age alter isoprene production from plantations of these trees. Here we examined the effects of fertilization and tree age on leaf-level isoprene flux from 2- and 6-year-old trees in a Eucalyptus saligna experimental forest in Hawaii. Leaf-level emission at a given canopy height did not differ between fertilized and unfertilized 6-year-old trees likely because leaf nitrogen content did not vary with fertilization. Across treatments, however, the standardized emission rate of isoprene (emission at a standard light and temperature) followed patterns of leaf N content and declined with canopy depth. Although leaf nitrogen content was similar between 2-year and 6-year fertilized trees, leaf-level emission rates declined with stand age. Surprisingly, despite differences in stand leaf area and leaf area distribution, modeled canopy-level isoprene flux was similar across stands varying in fertilization and tree age. Model results suggest that leaf area index was high enough in all treatments to absorb most of the light penetrating the canopy, leading to similar canopy flux rates despite the very different sized canopies

DISKNET – A Platform for the Systematic Accumulation of Knowledge in IS Research

The accumulation of knowledge is key for any discipline, IS being no exception. With the number of publications, theoretical constructs, and empirical findings growing, surging demand for structuring and meta-analysis is foreseeable. We introduce DISKNET, an online platform that enables the extraction, exploration, and aggregation of construct’s definitions, semantic relations, and analytical relations. While these aspects exhibit a rather standardized structure in theory, their practical documentation is non-uniform, highly dispersed, and tricky to seize technically. This has impeded the efficiency and effectiveness of review and meta-analytical processes, and resulted in a fragmented theoretical superstructure. We suggest that tool support for systematic knowledge accumulation is a central step to counteract these issues and to build to a consistent body of knowledge within the IS discipline. The current prototype of DISKNET draws on a large sample of SEM-based studies to demonstrate relevant design principles for a platform for systematic accumulation of knowledge

Wo steht die Jugendforschung heute?

Der Text leistet eine Ortsbestimmung der deutschen Jugendforschung, die im Rahmen des 18. DJI-Symposiums 2003 in Berlin mit dem Programmthema 'Jugendforschung zwischen Tradition und Innovation. Bilanz und Ausblick nach vier Jahrzehnten' diskutiert wird. Dazu werden in einem ersten Abschnitt die Grundzüge der Podiumsdiskussion 'Wo steht die Jugendforschung heute' dargelegt. Sie umfassen die folgenden Thesen der Debatte: (1) Gemeinsame inhaltliche Bezugspunkte sind in der Jugendforschung kaum auszumachen, zu breit und heterogen sind die Fragestellungen, methodologischen Zugänge, die Analyseebenen und Datensätze sowie das bunte Spektrum der Ergebnisse. (2) Es ist eine gegenseitige Abschottung von Jugendforschung und Schul- bzw. Schülerinnen- und Schülerforschung zu beobachten, als ob es sich um zwei Welten handeln würde, während doch zugleich immer wieder die Akteursperspektive als zentraler Ausgangspunkt der Forschung postuliert wird. (3) Die Jugendforschung unterliegt einer fortschreitenden Versozialwissenschaftlichung. Daran knüpft im zweiten Teil eine kritische Nachlese der Podiumsdiskussion 'Jugendforschung ohne Biss, oder: die Zukunft ist europäisch (oder gar nicht)'. Beide Abschnitte bringen persönliche Meinungen und Wertungen zum Ausdruck und nicht etwa institutionelle 'Verlautbarungen des DJI'. So spiegeln sie auch den Zustand der deutschen Jugendforschung, die - trotz oder gerade wegen ihrer Medienwirksamkeit und Fülle - keinen klar definierbaren wissenschaftlichen Korpus mehr darstellt und ihren Gegenstand, die Jugend, derzeit nicht mehr eindeutig zu bestimmen vermag. (ICG2