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Cosmic repulsion represented by a small positive value of the cosmological constant changes significantly properties of central gravitational fields at large distances, leading to existence of a static (or turnaround) radius where gravitational attraction of a center is just balanced by cosmic repulsion. Analyzing behavior of radial timelike geodesics in the Schwarzschild-de Sitter spacetime near its static radius we show that the particles with specific energy close to unity have tendency to slow down and cluster just below the static radius, forming clumps which, subsequently, start to expand uniformly due to cosmic repulsion. For central masses of $(10^6$-$10^{11}){\rm M_{\odot}}$ and current value of the cosmological constant $1.1\times 10^{-52}\,{\rm m^{-2}}$, this phenomenon takes place at distances of tens to hundreds of kiloparsecs from the center, being comparable with distances in which huge radio-lobes from some active galaxies were observed., Comment: 4 pages, 3 figures

Both circular and epicyclic motion of test particles along equatorial circular orbits in the revisited Kerr-de Sitter spacetime is analyzed. We present relations for specific energy, specific angular momentum and Keplerian angular velocity of particles on equatorial circular orbits, and discuss criteria for the existence and stability of such orbits giving limits on spacetime parameters. Finally, we discuss the epicyclic motion along equatorial circular orbits obtaining relations for radial and vertical epicyclic frequencies. The results are compared with those for the standard Kerr-de Sitter geometry., Comment: 9 pages, 5 figures; to be published in Phys. Rev. D

We aim to access entropy sources available within smartphones in order to construct and evaluate a random number generator which is competitive in comparison with existing and proven random number generators. A prototype utilizing the herein proposed algorithm shall generate data that can be tested against the Statistical Test Suit provided by NIST. Although our initial intention of using cosmic radiation failed, we were able to extract randomness from incoming video and audio sources. We found that it is possible to access these sources of entropy utilizing sensors from smartphones resulting in 15 out of 15 successful passed tests within the Statistical Test Suit. We also found that wrong methods of sensor data collection using our prototype eventually generates weak random numbers and fails NIST's Statistical Test Suit. Finally, we suggest that in order to reach the initial goal of providing a smartphone-based true nondeterministic random number generator the detection of muons shall be researched., Comment: Submitted to (IEEE) International Conference on Electrical, Computer, Communications and Mechatronics Engineering - ICECCME'22; 16-18 November 2022, Maldives

Would you trust physicians if they cannot explain their decisions to you? Medical diagnostics using machine learning gained enormously in importance within the last decade. However, without further enhancements many state-of-the-art machine learning methods are not suitable for medical application. The most important reasons are insufficient data set quality and the black-box behavior of machine learning algorithms such as Deep Learning models. Consequently, end-users cannot correct the model's decisions and the corresponding explanations. The latter is crucial for the trustworthiness of machine learning in the medical domain. The research field explainable interactive machine learning searches for methods that address both shortcomings. This paper extends the explainable and interactive CAIPI algorithm and provides an interface to simplify human-in-the-loop approaches for image classification. The interface enables the end-user (1) to investigate and (2) to correct the model's prediction and explanation, and (3) to influence the data set quality. After CAIPI optimization with only a single counterexample per iteration, the model achieves an accuracy of $97.48\%$ on the Medical MNIST and $95.02\%$ on the Fashion MNIST. This accuracy is approximately equal to state-of-the-art Deep Learning optimization procedures. Besides, CAIPI reduces the labeling effort by approximately $80\%$., Comment: Manuscript accepted at IFIP AIAI 2022, correct typo in Discussion

Charged fluids rotating around compact objects can form unique equilibrium structures when ambient large-scale electromagnetic fields combine with strong gravity. Equatorial as well as off-equatorial toroidal structures are among such figures of equilibrium with a direct relevance for astrophysics. To investigate their geometrical shapes and physical properties in the near-horizon regime, where effects of general relativity play a significant role, we commonly employ a scheme based on the energy-momentum conservation written in a standard representation. Here, we develop its interesting alternatives in terms of two covariant force representations, both based on a hypersurface projection of the energy-momentum conservation. In a proper hypersurface, space-like forces can be defined, following from a decomposition of the fluid four-acceleration. Each of the representations provides us with an insight into properties of the fluid flow, being well reflected in related conformal hypersurface geometries; we find behaviour of centrifugal forces directly related to geodesics of these conformal hypersurfaces and their embedding diagrams. We also reveal correspondence between the charged fluid flow world-lines from an ordinary spacetime, and world-lines determined by a charged test particles equation of motion in a conformal spacetime., Comment: 23 pages, 3 figures

Educational games are commonly used to motivate students and provide enhanced learning opportunities. Apps and mobile games play an increasingly important role in education and smartphones are part of the daily lives of most female teenagers: Half of mobile gamers are women and 64% of women prefer smartphones to other platforms. However, gender differences in playing behaviour and preferences raises concerns about potential gender inequalities when games are developed for education. In order to develop a tutorial game that suits the female target group and provides challenging tasks to solve, girls were involved at a very early stage of the development cycle and the idea was developed on the basis of surveys and focus group discussions. A first prototype of the game has been tested in a mixed-gender group to get feedback about the learning content, the worked examples, and the whole structure of the game. Finally, a tutorial game with six worked examples has been released in our Luna&Cat app, a programming tool that has been designed for our female target group in particular., Comment: Constructionism 2020, Dublin/Ireland May, 24-25, 2020, 12 figures, 9 pages

Knowledge in Computer Science (CS) is essential, and companies have increased their demands for CS professionals. Despite this, many jobs remain unfilled. Furthermore, employees with computational thinking (CT) skills are required, even if they are not actual technicians. Moreover, the gender disparity in technology related fields is a serious problem. Even if companies want to hire women in technology, the number of women who enter these fields is remarkably low. In high schools, most teenagers acquire only low-level skills in CS. Thus, they may never understand the fundamental concepts of CS, have unrealistic expectations or preconceptions, and are influenced by stereotype-based expectations. Consequently, many teenagers exclude computing as a career path. In this research study, we present two promising concepts to overcome these challenges. First, we consider alternative paths to enter the field of CS. In 2018, a voluntary lecture "Design your own app" at the University of Graz for students of all degree programs was introduced. In total, 202 students participated. We applied a Game Development-Based Learning (GDBL) approach with the visual coding tool Pocket Code, a mobile app developed at Graz University of Technology. The students were supposed to create simple games directly on smartphones. The course received positive evaluations and led to our second concept; In January 2019, we started to design a MOOC (Massive Open Online Course) with the title "Get FIT in Computer Science". First, this course can be used to encourage young women who have little to no previous knowledge in CS. Second, it should help all teenagers to get a more realistic picture of CS to its basic concepts. Third, teachers can use the course materials to lead high school classes (Open Educational Resources). Finally, the MOOC can be accessed by everyone interested in this topic., Comment: 9 pages, 4 figures, ECGBL 2019, Odense, Denmark

Recent studies from all over the world show that more boys than girls play video games. The numbers are different for mobile gaming apps, where 65% of women are identified as gamers. Adapting game design activities for academic purposes is a widely applied approach at schools or off-school initiatives is seen as a promising opportunity for all teenagers to learn to code in an entertaining way. This raise the questions do special girls' game-design patterns exist, and what can we learn from them? This paper describes a girl-only intervention where girls were asked to create their own games. This "Girls' Coding Week" was designed as an off-school event and took place during summer 2018 with 13 girls between 11 to 14 years old. To explain the basic steps of programming and to create personalized games, the visual coding app Pocket Code, an app developed at Graz University of Technology, was used. The girls created their own games with the help of a storyboard after receiving all important information about coding. Qualitative and quantitative data was collected through open interviews, as well as created artefacts and surveys which refer to motivational aspects. The findings show that gaming elements female teenagers tend to like, create, and play, mostly follow stereotypical expectations. In contrast to our experiences in heterogeneous course settings, this was not seen as something negative by girls. Furthermore, the findings provided evidence for game-making environments for girls. Subsequently, the results contributed to the development of new featured games to be used in our app to inspire female users around the world to code their own games. The authors argue that by understanding these differences in game design, we can support girls so that they become game designers and thereby more interested in coding., Comment: 10 pages, 11 Figures, 13th European Conference on Game Based Learning

The number of women in IT-related disciplines is far below the number of men, especially in developed countries. Middle-school girls appear to be engaged in coding courses, but when they choose academic majors relevant to their future careers, only few pursue computer science as a major. In order to show students a new way of learning and to engage them with coding activities, we used the learning app Pocket Code. In the "No One Left Behind" H2020 European project, the app was evaluated in several school subjects. An evaluation of the attractiveness of the app shows that students were motivated by Pocket Code's ease of use and its appealing design; however, girls rated the app less enthusiastically. To appeal to female teenagers in particular, a tailored version of the app "Luna&Cat" has been developed. This customised version stands in contrast to the "one size fits all" solution Pocket Code, which may discourage certain user groups. For apps to have a higher chance to appeal to a specific target group, it is, among many other points, necessary to optimise their store listing on app stores, especially as we found that app stores are the most effective way to reach teenagers. Thus, this paper covers the following research question. What customizations are necessary in Pocket Code to reinforce female teenagers in their coding activities? To answer this question, a focus group discussion was performed. This discussion first brought insights about our target group and suggested names and designs for the new app; and second, allowed each student to make proposals for their desired games. Later, these game ideas were analysed, graphically designed, and further developed together with university design students. By showing female teenagers games designed by other young women in their age group, we help them to get ideas and inspiration to code their own programs., Comment: 10 pages, 6 figures, Proceedings of the 2nd International Conference on Gender Research ICGR 2019 Rom, Italy, 11-12 April 2019 isbn: 978-1-912764-16-7,issn: 2516-2810, Academic Conferences and Publishing International Limited

Although female students engage in coding courses, only a small percentage of them plan to pursue computer science (CS) as a major when choosing a career path. Gender differences in interests, sense-of belonging, self-efficacy, and engagement in CS are already present at an early age. This article presents an overview of gender stereotypes in CS and summarizes negative impressions female students between 12 and 15 experience during CS classes, as well as influences that may be preventing girls from taking an interest in CS. The study herein draws on a systematic review of 28 peer-reviewed articles published since 2006. The findings of the review point to the existence of the stereotypical image of a helpless, uninterested, and unhappy "Girl in Computer Science". It may be even more troubling a construct than that of the geeky, nerdy male counterpart, as it is rooted in the notion that women are technologically inept and ill-suited for CS careers. Thus, girls think they must be naturally hyper-intelligent in order to pursue studies in CS, as opposed to motivated, interested, and focused to succeed in those fields. Second, based on the review, suggestions for inclusive CS education were summarized. The authors argue that in order to make CS more inclusive for girls, cultural implications, as well as stereotypization in CS classrooms and CS education, need to be recognized as harmful. These stereotypes and cultural ideas should be eliminated by empowering female students through direct encouragement, mentoring programs, or girls-only initiatives., Comment: 22 pages

We discuss the effects of electric charging on the equilibrium configurations of magnetized, rotating fluid tori around black holes of different mass. In the context of gaseous/dusty tori in galactic nuclei, the central black hole dominates the gravitational field and it remains electrically neutral, while the surrounding material acquires some electric charge and exhibits non-negligible self-gravitational effect on the torus structure. The structure of the torus is influenced by the balance between the gravitational and electromagnetic forces. A cusp may develop even in Newtonian tori due to the charge distribution., Comment: 5 pages, 1 figure; to appear in Proceedings of the 15th Marcel Grossman Meeting on General Relativity - the session AC3 on "Accretion Discs and Jets" by Eva Hackmann & Audrey Trova (Rome, 1-7 July 2018), edited by Elia Battistelli, Robert T. Jantzen, and Remo Ruffini, in preparation

Most of the 700 million teenagers everywhere in the world already have their own smartphones, but comparatively few of them have access to PCs, laptops, OLPCs, Chromebooks, or tablets. The free open source non-profit project Catrobat allows users to create and publish their own apps using only their smartphones. Initiated in 2010, with first public versions of our free apps since 2014 and 47 releases of the main coding app as of July 2018, Catrobat currently has more than 700,000 users from 180 countries, is available in 50+ languages, and has been developed so far by almost 1,000 volunteers from around the world ("the world"). Catrobat is strongly inspired by Scratch and indeed allows to import most Scratch projects, thus giving access to more than 30 million projects on our users' phones as of July 2018. Our apps are very intuitive ("rock bottom"), have many accessibility settings, e.g., for kids with visual or cognitive impairments, and there are tons of constructionist tutorials and courses in many languages. We also have created a plethora of extensions, e.g., for various educational robots, including Lego Mindstorms and flying Parrot quadcopters ("the sky"), as well as for controlling arbitrary external devices through Arduino or Raspberry Pi boards, going up to the stratosphere and even beyond to interplanetary space ("the sky"). A TurtleStitch extension allowing to code one's own embroidery patterns for clothes is currently being developed. Catrobat among others intensely focuses on including female teenagers. While a dedicated version for schools is being developed, our apps are meant to be primarily used outside of class rooms, anywhere and in particular outdoors ("rock bottom", "the world"). Catrobat is discovered by our users through various app stores such as Google Play and via social media channels such as YouTube as well as via our presence on Code.org., Comment: Constructionism 2018

Game jams are a way to create games under fast-paced conditions and certain constraints. The increase in game jam events all over the world, their engaging and creative nature, with the aim of sharing results among players can be seen in the high participation rate of such events (2013: 16,705 participants from 319 jam sites in 63 countries produced 3248 games) . This promising concept can be easily transferred to a classroom setting., Comment: 4 pages, 3 figures, ICGBL 2016