The 25 most recently reported publications
Soweit grundsätzlich als gemeinnützig anerkannte Sportvereine neben dem Betrieb einer Abteilung mit ideeller und gemeinnütziger Zwecksetzung (Kinder- und Jugendfußball) auch einen wirtschaftlichen Geschäftsbetrieb (erste Fußballmannschaft in der Regionalliga, Bistro) unterhalten, entfällt die Befreiung von den Umlagen zum Lastenausgleich und zur Lastenverteilung in diesem Umfang.
Assembling robotic multi-agent systems is becoming increasingly attractive due to the emergence of affordable robots. For coordinated missions such fleets usually have to communicate over unreliable channels and still achieve adequate performance. To support system designers in quantifying adequateness, in this paper we present a domain-specific language (DSL) that allows domain-experts to specify (i) quality of service (QoS) requirements of the communication channels; and (ii) QoS capabilities of the involved software components. Such QoS specifications complement the QoS management that has recently been introduced into ROS 2. To fully utilize this approach we have also developed an associated ROS 2 DSL which enables us to verify QoS specifications and provide feedback to the users already at design time. We have evaluated the developed language workbench following the Goal-Question-Metric (GQM) approach which demonstrates that the QoS DSL is complete with respect to ROS 2 and can be easily extended. Additionally, we generate a proof-of-concept implementation for a QoS monitor that can be seamlessly integrated into existing ROS 2 projects.
The article contributes to understanding the political economy of implementation of social protection programmes at local level. Current debates are dominated by technocratic arguments, emphasizing the lack of financial resources, technology or skills as major barriers for effective implementation. Describing how chiefs, assistant-chiefs and community elders are routinely at the centre stage of core implementation processes, including targeting, enrolment, delivery, monitoring, awareness and information, data collection or grievance and redress, this study on Kenya argues for the need to look more closely into the local political economy as an important mediating arena for implementing social policies. Implementation is heavily contingent upon the local social, political and institutional context that influences and shapes its outcomes. These processes are ambivalent involving multiple forms of interactions between ‘formal’ and ‘informal’ institutional structures, which may support initial policy objectives or induce policy outcomes substantially diverging from intended policy objectives.
Atomic oxygen in the mesosphere and lower thermosphere measured by terahertz heterodyne spectroscopy
(2021)
Atomic oxygen is a main component of the mesosphere and lower thermosphere (MLT). The photochemistry and the energy balance of the MLT are governed by atomic oxygen. In addition, it is a tracer for dynamical motions in the MLT. It is difficult to measure with remote sensing techniques. Concentrations can be inferred indirectly from the oxygen air glow or from observations of OH, which is involved in photochemical processes related to atomic oxygen. Such measurements have been performed with several satellite instruments such as SCIAMACHY, SABER, WINDII and OSIRIS. However, the methods are indirect and rely on photochemical models and assumptions such as quenching rates, radiative lifetimes, and reaction coefficients. The results are not always in agreement, particularly when obtained with different instruments.
Photovoltaic (PV) power data are a valuable but as yet under-utilised resource that could be used to characterise global irradiance with unprecedented spatio-temporal resolution. The resulting knowledge of atmospheric conditions can then be fed back into weather models and will ultimately serve to improve forecasts of PV power itself. This provides a data-driven alternative to statistical methods that use post-processing to overcome inconsistencies between ground-based irradiance measurements and the corresponding predictions of regional weather models (see for instance Frank et al., 2018). This work reports first results from an algorithm developed to infer global horizontal irradiance as well as atmospheric optical properties such as aerosol or cloud optical depth from PV power measurements.
The genetic basis of brain tumor development is poorly understood. Here, leukocyte DNA of 21 patients from 15 families with ≥ 2 glioma cases each was analyzed by whole-genome or targeted sequencing. As a result, we identified two families with rare germline variants, p.(A592T) or p.(A817V), in the E-cadherin gene CDH1 that co-segregate with the tumor phenotype, consisting primarily of oligodendrogliomas, WHO grade II/III, IDH-mutant, 1p/19q-codeleted (ODs). Rare CDH1 variants, previously shown to predispose to gastric and breast cancer, were significantly overrepresented in these glioma families (13.3%) versus controls (1.7%). In 68 individuals from 28 gastric cancer families with pathogenic CDH1 germline variants, brain tumors, including a pituitary adenoma, were observed in three cases (4.4%), a significantly higher prevalence than in the general population (0.2%). Furthermore, rare CDH1 variants were identified in tumor DNA of 6/99 (6%) ODs. CDH1 expression was detected in undifferentiated and differentiating oligodendroglial cells isolated from rat brain. Functional studies using CRISPR/Cas9-mediated knock-in or stably transfected cell models demonstrated that the identified CDH1 germline variants affect cell membrane expression, cell migration and aggregation. E-cadherin ectodomain containing variant p.(A592T) had an increased intramolecular flexibility in a molecular dynamics simulation model. E-cadherin harboring intracellular variant p.(A817V) showed reduced β-catenin binding resulting in increased cytosolic and nuclear β-catenin levels reverted by treatment with the MAPK interacting serine/threonine kinase 1 inhibitor CGP 57380. Our data provide evidence for a role of deactivating CDH1 variants in the risk and tumorigenesis of neuroepithelial and epithelial brain tumors, particularly ODs, possibly via WNT/β-catenin signaling.
Die vorliegende Studie untersucht als Erste simultan die Auswirkungen des dreidimensionalen Konstrukts der prozeduralen, distributiven und kommunikativen Lohntransparenz auf Arbeitnehmer, auch unter Berücksichtigung von persönlichen Einstellungen und dem tatsächlichen Gehalt anhand einer deutschen Stichprobe (N = 159). Hierfür wurden Angestellte in einer querschnittlichen Online-Fragebogenstudie zu der wahrgenommenen Lohntransparenz in ihrer Organisation sowie zu weiteren arbeitnehmer- und organisationsrelevanten Variablen befragt. Mittels regressionsanalytischer Untersuchungen konnten hypothesenkonform positive Zusammenhänge der Lohntransparenz mit der Lohnzufriedenheit, der Wahrnehmung prozeduraler und distributiver Gerechtigkeit sowie mit dem Empfinden organisationalen Vertrauens nachgewiesen werden. Von wesentlicher Bedeutung für die Zusammenhänge war allerdings lediglich die prozedurale Lohntransparenz als eine der drei Dimensionen. Weiterhin ergaben Moderatoranalysen, dass ein geringes Bedürfnis nach informationeller Privatheit sowie ein geringes Bruttoentgelt die positiven Zusammenhänge der Lohntransparenz mit den Kriteriumsvariablen partiell verstärken. Abschließend werden Implikationen der Befunde für die Forschung und Praxis vor dem Hintergrund der Einschränkungen, denen diese Studie unterliegt, erläutert.
The solvent exchange as one of the most important steps during the manufacturing process of organic aerogels was investigated. This step is crucial as a preparatory step for the supercritical drying, since the pore solvent must be soluble in supercritical carbon dioxide to enable solvent extraction. The development and subsequent optimization of a suitable system with a peristaltic pump for automatic solvent exchange proved to be a suitable approach. In addition, the influence of zeolites on the acceleration of the process was found to be beneficial. To investigate the process, the water content in acetone was determined at different times using Karl Fischer titration. The shrinkage, densities, as well as the surface areas of the aerogels were analyzed. Based on these, the influence of various process parameters on the final structure of the obtained aerogels was investigated and evaluated. Modeling on diffusion in porous materials completes this study.
Notizzettel
(2021)
Der Kommunikations- und Medienwissenschaftler Hektor Haarkötter hat die erste Kulturgeschichte des Notizzettels geschrieben und gleichzeitig eine Philosophie dieses unscheinbaren Mediums verfasst. Denn Notizzettel – Einkaufszettel, Spickzettel, Schmierzettel, Skizzen, Entwürfe, Karteikarten, Haftnotizen, Wandkritzeleien – sind der erste Haltepunkt vom Gedanken zum Geschriebenen: Ich denke, also notiere ich. Wer den Menschen beim Notieren zusieht, der kann ihnen beim Denken zusehen. (Verlagsangaben)
Die Analytik ist zwar ein grundlegendes Thema innerhalb der Chemie, hat es aber ganz schön in sich. Aber keine Sorge, Ulf Ritgen erklärt Ihnen in diesem Buch was Sie zur Analytischen Chemie Wissen sollten. Wie erhält man eigentlich analytische Infos? Welche Standards gibt es? Und wie sollte man überhaupt mit den Stoffgemischen umgehen? All diese Grundlagen werden ausführlich erläutert. Aber auch die Anwendungsgebiete und Methoden kommen keinesfalls zu kurz. Egal ob Gravimetrie, Titration, Fällung oder Konduktometrie, endlich wird alles verständlich erklärt. Jetzt können Prüfung und Praktikum kommen! (Verlagsangaben)
The identification of energetic materials in containments is an important challenge for analytical methods in the field of safety and security. Opening a package without knowledge of its contents and the resulting hazards is highly involved with risks and should be avoided whenever possible. Therefore, preferable methods work non-destructive with minimal interaction and are capable of identifying target substances in a containment quickly and reliably. Most spectroscopic methods find their limits, if the target substance is shielded by a covering material. To solve this problem, a combined laser drilling method with subsequent identification of the target substance by means of Raman spectroscopic measurements through microscopic bore holes of the covering material is presented. A pulsed laser beam is used for both the drilling process and as an excitation source for Raman measurements in the same optical setup. Results show the ability of this new method to gain high-quality spectra even when performed through microscopic small bore channels. With the laser parameters chosen right, the method can even be performed on highly sensitive explosives like triacetone triperoxide (TATP). Another advantageous effect arises in an observed reduction in unwanted fluorescence signal in the spectral data, resulting from the confocal-like measurement setup with the bore hole acting as aperture.
At the end of 2019, about 4.1 billion people on earth were using the internet. Because people entrust their most intimate and private data to their devices, the European legislation has declared the protection of natural persons in relation to the processing of personal data as a fundamental right. In 2018 23 million people worldwide, having the responsibility of implementing data security and privacy, were developing software. However, the implementation of data and application security is a challenge, as evidenced by over 41 thousand documented security incidents in 2019. Probably the most basic, powerful, and frequently used tools software developers work with are Application Programming Interfaces (APIs). Security APIs are essential tools to bring data and application security into software products. However, research results have revealed that usability problems of security APIs lead to insecure API use during development. Basic security requirements such as securely stored passwords, encrypted files or secure network connections can become an error-prone challenge and in consequence lead to unreliable or missing security and privacy. Because software developers hold a key position in the development processes of software, not properly operating security tools pose a risk to all people using software. However, little is known about the requirements of developers to address the problem and improve the usability of security APIs. This thesis is one of the first to examine the usability of security APIs. To this end, the author examines to what extent information flows can support software developers in using security APIs to implement secure software by conducting empirical studies with software developers. This thesis has contributed fundamental results that can be used in future work to identify and improve important information flows in software development. The studies have clearly shown that developer-tailored information flows with adapted security-relevant content have a positive influence on the correct implementation of security. However, the results have also led to the conclusion that API producers need to pay special attention to the channels through which they direct information flows to API users and how the information is designed to be useful for them. In many cases, it is not enough to provide security-relevant information via the documentation only. Here, proactive methods like the API security advice proposed by this thesis achieve significantly better results in terms of findability and actionable support. To further increase the effectiveness of the API security advice, this thesis developed a cryptographic API warning design for the terminal by adopting a participatory design approach with experienced software developers. However, it also became clear that a single information flow can only support up to a certain extent. As observed from two studies conducted in complex API environments in web development, multiple complementary information flows have to meet the extensive information needs of developers to be able to develop secure software. Some evaluated new approaches provided promising insights towards more API consumer-focused documentation designs as a complement to API warnings.
Despite their age, ray-based rendering methods are still a very active field of research with many challenges when it comes to interactive visualization. In this thesis, we present our work on Guided High-Quality Rendering, Foveated Ray Tracing for Head Mounted Displays and Hash-based Hierarchical Caching and Layered Filtering. Our system for Guided High-Quality Rendering allows for guiding the sampling rate of ray-based rendering methods by a user-specified Region of Interest (RoI). We propose two interaction methods for setting such an RoI when using a large display system and a desktop display, respectively. This makes it possible to compute images with a heterogeneous sample distribution across the image plane. Using such a non-uniform sample distribution, the rendering performance inside the RoI can be significantly improved in order to judge specific image features. However, a modified scheduling method is required to achieve sufficient performance. To solve this issue, we developed a scheduling method based on sparse matrix compression, which has shown significant improvements in our benchmarks. By filtering the sparsely sampled image appropriately, large brightness variations in areas outside the RoI are avoided and the overall image brightness is similar to the ground truth early in the rendering process. When using ray-based methods in a VR environment on head-mounted display de vices, it is crucial to provide sufficient frame rates in order to reduce motion sickness. This is a challenging task when moving through highly complex environments and the full image has to be rendered for each frame. With our foveated rendering sys tem, we provide a perception-based method for adjusting the sample density to the user’s gaze, measured with an eye tracker integrated into the HMD. In order to avoid disturbances through visual artifacts from low sampling rates, we introduce a reprojection-based rendering pipeline that allows for fast rendering and temporal accumulation of the sparsely placed samples. In our user study, we analyse the im pact our system has on visual quality. We then take a closer look at the recorded eye tracking data in order to determine tracking accuracy and connections between different fixation modes and perceived quality, leading to surprising insights. For previewing global illumination of a scene interactively by allowing for free scene exploration, we present a hash-based caching system. Building upon the concept of linkless octrees, which allow for constant-time queries of spatial data, our frame work is suited for rendering such previews of static scenes. Non-diffuse surfaces are supported by our hybrid reconstruction approach that allows for the visualization of view-dependent effects. In addition to our caching and reconstruction technique, we introduce a novel layered filtering framework, acting as a hybrid method between path space and image space filtering, that allows for the high-quality denoising of non-diffuse materials. Also, being designed as a framework instead of a concrete filtering method, it is possible to adapt most available denoising methods to our layered approach instead of relying only on the filtering of primary hitpoints.
The analysis of used engine oils from industrial engines enables the study of engine wear and oil degradation in order to evaluate the necessity of oil changes. As the matrix composition of an engine oil strongly depends on its intended application, meaningful diagnostic oil analyses bear considerable challenges. Owing to the broad spectrum of available oil matrices, we have evaluated the applicability of using an internal standard and/or preceding sample digestion for elemental analysis of used engine oils via inductively coupled plasma optical emission spectroscopy (ICP OES). Elements originating from both wear particles and additives as well as particle size influence could be clearly recognized by their distinct digestion behaviour. While a precise determination of most wear elements can be achieved in oily matrix, the measurement of additives is performed preferably after sample digestion. Considering a dataset of physicochemical parameters and elemental composition for several hundred used engine oils, we have further investigated the feasibility of predicting the identity and overall condition of an unknown combustion engine using the machine learning system XGBoost. A maximum accuracy of 89.6% in predicting the engine type was achieved, a mean error of less than 10% of the observed timeframe in predicting the oil running time and even less than 4% for the total engine running time, based purely on common oil check data. Furthermore, obstacles and possibilities to improve the performance of the machine learning models were analysed and the factors that enabled the prediction were explored with SHapley Additive exPlanation (SHAP). Our results demonstrate that both the identification of an unknown engine as well as a lifetime assessment can be performed for a first estimation of the actual sample without requiring meticulous documentation.
