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Real-time operating systems for mixed-criticality systems
must support different types of software, such as
real-time applications and general purpose applications,
and, at the same time, must provide strong spatial and
temporal isolation between independent software components.
Therefore, state-of-the-art real-time operating systems
focus mainly on predictability and bounded worst-case behavior.
However, general purpose operating systems such as Linux
often feature more efficient---but less deterministic---mechanisms
that significantly improve the average execution time.
This thesis addresses the combination of the two contradicting
requirements and shows thread synchronization mechanisms
with efficient average-case behavior, but without sacrificing
predictability and worst-case behavior.
This thesis explores and evaluates the design space of fast paths
in the implementation of typical blocking synchronization
mechanisms, such as mutexes, condition variables, counting
semaphores, barriers, or message queues. The key technique here
is to avoid unnecessary system calls, as system calls have high
costs compared to other processor operations available in user
space, such as low-level atomic synchronization primitives.
In particular, the thesis explores futexes, the state-of-the-art
design for blocking synchronization mechanisms in Linux
that handles the uncontended case of thread synchronization
by using atomic operations in user space and calls into the
kernel only to suspend and wake up threads. The thesis also
proposes non-preemptive busy-waiting monitors that use an
efficient priority ceiling mechanism to prevent the lock holder
preemption problem without using system calls, and according
low-level kernel primitives to construct efficient wait and
notify operations.
The evaluation shows that the presented approaches
improve the average performance comparable
to state-of-the-art approaches in Linux.
At the same time, a worst-case timing analysis shows
that the approaches only need constant or bounded temporal
overheads at the operating system kernel level.
Exploiting these fast paths is a worthwhile approach
when designing systems that not only have to fulfill
real-time requirements, but also best-effort workloads.
Climate change is an existential threat to human survival, the social organization of society, and the stability of ecosystems. It is thereby profoundly frightening. In the face of threat, people often want to protect themselves instead of engaging in mitigating behaviors. When psychological resources are insufficient to cope, people often respond with different forms of denial. In this dissertation, I contribute original knowledge to the understanding of the multifaceted phenomenon of climate denial from a psychological perspective.
There are four major gaps in the literature on climate denial: First, the spectrum of climate denial as a self-protective response to the climate crisis has not received attention within psychology. Second, basic psychological need satisfaction, a fundamental indicator of human functioning and the ability to cope with threat, has not been investigated as a predictor of climate denial. Third, relations of the spectrum of climate denial to climate-relevant emotions, specifically climate anxiety, have not been examined empirically. Forth, it has not been investigated how the spectrum of climate denial relates to established predictors of climate denial, namely right-wing ideological convictions and male gender. To address those gaps, I investigate what the spectrum of climate denial looks like in the German context and how it relates to basic psychological need satisfaction and frustration, pro-environmental behavior, climate anxiety, ideological conviction, and gender.
Five manuscripts reveal that climate denial exists on a spectrum in the German context, ranging from the distortion of facts (interpretive climate denial, specifically denial of personal and global outcome severity) to the denial of the implications of climate change (implicatory climate denial, specifically avoidance, denial of guilt, and rationalization of one's own involvement). Across analyses, low basic psychological need satisfaction predicted the spectrum of climate denial, which was negatively related to pro-environmental behavior. Climate denial was generally negatively related to climate anxiety, except for a positive association of avoidance and climate anxiety. Right-wing ideological conviction was the strongest predictor of climate denial across the spectrum. However, low need satisfaction and male gender were additional weaker predictors of implicatory climate denial.
These findings suggest that the spectrum of climate denial serves many psychological functions. Climate denial is possibly both a self-protective strategy to downregulate emotions and to protect oneself from loss of privilege. In short, it represents a barrier to climate action that may only be resolved once people have sufficient psychological resources to face the threat of climate change and cope with their underlying self-protective, emotional responses.
There has been little research on out-of-school places of learning and their effec-tiveness in the context of ESD education measures. With the help of a multi-stage analysis, this study identifies out-of-school places of learning with reference to the ESD education concept in the Rhineland-Palatinate study area. To this end, qualita-tive literature analyses were first used to generate ESD criteria, which were opera-tionalised as a methodological instrument in the form of an ESD checklist for out-of-school places of learning. The data obtained in this way provide the basis for the creation of a geographically oriented learning location database with ESD refer-ence. A cartographic visualisation of the data results in a spatial distribution pattern: Thus, there are districts and cities that are well supplied with ESD learning loca-tions, but also real ESD learning location deserts where there is a need to catch up. Furthermore, there is an accumulation of ESD learning sites in areas close to for-ests.
A guideline-based explorative interview with two ESD experts provides additional insights into the question of how ESD has been implemented in the federal state of Rhineland-Palatinate, the extent to which there is a need for optimisation, and which continuing measures are being taken for ESD outside schools within the framework of Agenda 2030.
In addition, a quantitative questionnaire study was carried out with 1358 pupils at 30 out-of-school places of learning after participation in an educational measure, in which environmental awareness, attitudes towards environmental behaviour and local learning were also considered. By including non-ESD learning locations, a comparative study on the effectiveness of ESD learning locations became possible. The statistical data evaluation leads to a variety of interesting results. Contra-intuitively, for instance, the type of learning location (ESD or non-ESD learning lo-cation) is not a significant predictor for the environmental awareness and environ-mental behaviour of the surveyed students, whereas communication structures within educational measures at extracurricular learning locations, the multimediality and action orientation and the duration of educational measures have a significant influence.
Keywords: extracurricular learning locations, education for sustainable develop-ment (ESD), ESD criteria, learning location landscape Rhineland-Palatinate, ESD learning locations, environmental awareness, environmental behaviour.
Der Wettbewerb um die besten Technologien zur Realisierung des autonomen Fahrens ist weltweit in vollem Gange.
Trotz großer Anstrengungen ist jedoch die autonome Navigation in strukturierter und vor allem unstrukturierter Umgebung bisher nicht gelöst.
Ein entscheidender Baustein in diesem Themenkomplex ist die Umgebungswahrnehmung und Analyse durch passende Sensorik und entsprechende Sensordatenauswertung.
Insbesondere bildgebende Verfahren im Bereich des für den Menschen sichtbaren Spektrums finden sowohl in der Praxis als auch in der Forschung breite Anwendung.
Dadurch wird jedoch nur ein Bruchteil des elektromagnetischen Spektrums genutzt und folglich ein großer Teil der verfügbaren Informationen zur Umgebungswahrnehmung ignoriert.
Um das vorhandene Spektrum besser zu nutzen, werden in anderen Forschungsbereichen schon seit Jahrzehnten \sog spektrale Sensoren eingesetzt, welche das elektromagnetische Spektrum wesentlich feiner und in einem größeren Bereich im Vergleich zu klassischen Farbkameras analysieren. Jedoch können diese Systeme aufgrund technischer Limitationen nur statische Szenen aufnehmen. Neueste Entwicklungen der Sensortechnik ermöglichen nun dank der \sog Snapshot-Mosaik-Filter-Technik die spektrale Abtastung dynamischer Szenen.
In dieser Dissertation wird der Einsatz und die Eignung der Snapshot-Mosaik-Technik zur Umgebungswahrnehmung und Szenenanalyse im Bereich der autonomen Navigation in strukturierten und unstrukturierten Umgebungen untersucht. Dazu wird erforscht, ob die aufgenommen spektralen Daten einen Vorteil gegenüber klassischen RGB- \bzw Grauwertdaten hinsichtlich der semantischen Szenenanalyse und Klassifikation bieten.
Zunächst wird eine geeignete Vorverarbeitung entwickelt, welche aus den Rohdaten der Sensorik spektrale Werte berechnet. Anschließend wird der Aufbau von neuartigen Datensätzen mit spektralen Daten erläutert. Diese Datensätze dienen als Basis zur Evaluation von verschiedenen Klassifikatoren aus dem Bereich des klassischen maschinellen Lernens.
Darauf aufbauend werden Methoden und Architekturen aus dem Bereich des Deep-Learnings vorgestellt. Anhand ausgewählter Architekturen wird untersucht, ob diese auch mit spektralen Daten trainiert werden können. Weiterhin wird die Verwendung von Deep-Learning-Methoden zur Datenkompression thematisiert. In einem nächsten Schritt werden die komprimierten Daten genutzt, um damit Netzarchitekturen zu trainieren, welche bisher nur mit RGB-Daten kompatibel sind. Abschließend wird analysiert, ob die hochdimensionalen spektralen Daten bei der Szenenanalyse Vorteile gegenüber RGB-Daten bieten
Thousands of chemicals from daily use are being discharged from civilization into the water cycle via different pathways. Ingredients of personal care products, detergents, pharmaceuticals, pesticides, and industrial chemicals thus find their way into the aquatic ecosystems and may cause adverse impacts on the ecology. Pharmaceuticals for instance, represent a central group of anthropogenic chemicals, because of their designed potency to interfere with physiological functions in organisms. Ecotoxicological effects from pharmaceutical burden have been verified in the past. Therapeutic groups with pronounced endocrine disrupting potentials such as steroid hormones gain increasing focus in environmental research as it was reported that they cause endocrine disruption in aquatic organisms even when exposed to environmentally relevant concentrations. This thesis considers the comprehensive investigation of the occurrence of corticosteroids and progestogens in wastewater treatment plant (WWTP) effluents and surface waters as well as the elucidation of the fate and biodegradability of these steroid families during activated sludge treatment. For the first goal of the thesis, a robust and highly sensitive analytical method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed in order to simultaneously determine the occurrence of around 60 mineralocorticoids, glucocorticoids and progestogens in the aquatic environment. A special focus was set to the compound selection due to the diversity of marketed synthetic steroids. Some analytical challenges have been approved by individual approaches regarding sensitivity enhancement and compound stabilities. These results may be important for further research in environmental analysis of steroid hormones. Reliable and low quantification limits are the perquisite for the determination of corticosteroids and progestogens at relevant concentrations due to low consumption volumes and simultaneously low effect-based trigger values. Achieved quantification limits for all target analytes ranged between 0.02 ng/L and 0.5 ng/L in surface water and 0.05 ng/L to 5 ng/L in WWTP effluents. This sensitivity enabled the detection of three mineralocorticoids, 23 glucocorticoids and 10 progestogens within the sampling campaign around Germany. Many of them were detected for the first time in the environment, particularly in Germany and the EU. To the best of our knowledge, this in-depth steroid screening provided a good overview of single steroid burden and allowed for the identification of predominantly steroids of each steroid
type analyzed for the first time. The frequent detection of highly potent synthetic steroids (e.g. triamcinolone acetonide, clobetasol propionate, betamethasone valerate, dienogest, cyproterone acetate) highlighted insufficient removal during conventional Summary wastewater treatment and indicated the need for regulation to control their emission since the steroid concentrations were found to be above the reported effect-based trigger values for biota. Overall, the study revealed reliable environmental data of poorly or even not analyzed steroids. The results complement the existing knowledge in this field but also providednew information which can beused particularly for compound prioritization in ecotoxicological research and environmental analysis. Based on the data obtained from the monitoring campaign, incubation experiments were conducted to enable the comparison of the biodegradability and transformation processes in activated sludge treatment for structure-related steroids under aerobic and standardized experimental conditions. The compounds were accurately selected to cover manifold structural moieties of commonly used glucocorticoids, including non-halogenated and halogenated steroids, their mono- and diesters, and several acetonide-type steroids. This approach allowed for a structure-based interpretation of the results. The obtained biodegradation rate constants suggested large variations in the biodegradability (half-lifes ranged from < 0.5 h to > 14 d). An increasing stability was identified in the order from non-halogenated steroids (e.g. hydrocortisone), over 9α-halogenated steroids (e.g. betamethasone), to C17-monoesters (e.g. betamethasone 17-valerate, clobetasol propionate), and finally to acetonides (e.g. triamcinolone acetonide), thus suggesting a strong relationship of the biodegradability with the glucocorticoid structure. Some explanations for this behavior have been received by identifying the transformation products (TPs) and elucidating individual transformation pathways. The results revealed the identification of the likelihood of transformation reactions depending on the chemical steroid structure for the first time. Among the identified TPs, the carboxylates (e.g. TPs of fluticasone propionate, triamcinolone acetonide) have been shown persistency in the subsequent incubation experiments. The newly identified TPs furthermore were frequently detected in the effluents of full-scale wastewater treatment plants. These findings emphasized i) the transferability of the lab-scale degradation experiments to real world and that ii) insufficient removals may cause adverse effects in the aquatic environment due to the ability of the precursor steroids and TPs to interact with the endocrine system in biota. For the last goal, the conceptual study for glucocorticoids was applied to progestogens.
Here, two sub-types of the steroid family frequently used for hormonal contraception were selected (17α-hydroxyprogesterone and 19-norstestosterone type). The progestogens showed a fast and complete degradation within six hours, and thus empathizes pronounced biodegradability. However, cyproterone acetate and dienogest Summary have been found to be more recalcitrant in activated sludge treatment. This was consistent with their ubiquitously occurrence during the previous monitoring campaign. The elucidation of TPs again revealed some crucial information regarding the observed behavior and highlighted furthermore the formation of hazardous TPs. It was shown that 19-nortestosterone type steroids are able to undergo aromatization at ring A in contact with activated sludge, leading to the formation of estrogen-like TPs with a phenolic moiety at ring A. In the case of norethisterone the formation of 17α-ethinylestradiol was confirmed, which is a well-known potent synthetic estrogen with elevated ecotoxicological potency. Thus, the results indicated for the very first time an unknown source of estrogenic compounds, particularly for 17α-ethinylestradiol. In conclusion, some steroids were found to be very stable in activated sludge treatment, others degrade well, and others which do degrade but predominantly to active TPs depending on their chemical structure. Fluorinated acetal steroids such as triamcinolone acetonide and fluocinolone acetonide are poorly biodegradable, which is reflected in high concentrations detected ubiquitously in WWTP effluents. Endogenous steroids and their most related synthetic once such as hydrocortisone, prednisolone or 17α-hydroxyprogesterone are readily biodegradable. Regardless their high influent concentrations, they are almost completely removed in conventional WWTPs. Steroids between this range have been found to form elevated quantities of TPs which are partially still active, which particularly the case for betamethasone, fluticasone propionate, cyproterone acetate or dienogest. The thesis illustrates the need for an extensive evaluation of the environmental risks and carried out that corticosteroids and progestogens merit more attention in environmental regulatory and research than it is currently the case
Previous research concerned with early science education revealed that guided play can support young children’s knowledge acquisition. However, the questions whether guided play maintains other important prerequisites such as children’s science self-concept and how guided play should be implemented remain unanswered. The present dissertation encompasses three research articles that investigated 5- to 6-year-old children’s science knowledge, science theories, and science self-concept in the stability domain and their relation to interindividual prerequisites. Moreover, the articles examined whether children’s science knowledge, science theories, and science self-concept can be supported by different play forms, i.e., guided play with material and verbal scaffolds, guided play with material scaffolds, and free play. The general introduction of the present dissertation first highlights children’s cognitive development, their science self-concept, and interindividual prerequisites, i.e., fluid and crystallised intelligence, mental rotation ability, and interest in block play. These prerequisites are applied to possible ways of supporting children during play. The first article focused on the measurement of 5-to-6-year-old children’s stability knowledge and its relation to interindividual prerequisites. Results suggested that children’s stability knowledge could be measured reliably and validly, and was related to their fluid and crystallised intelligence. The second article was concerned with the development of children’s intuitive stability theories over three points of measurement and the effects of guided and free play, children’s prior theories as well as their intelligence on these intuitive theories. Results implied that guided play with material and verbal scaffolds supported children’s stability theories more than the other two play forms, i.e., guided play with material scaffolds and free play. Moreover, consistency of children’s prior theories, their fluid and crystallised intelligence were related to children’s theory adaptation after the intervention. The third article focused on the effect of the playful interventions on children’s stability knowledge and science self-concept over three points of measurement. Furthermore, the reciprocal effects between knowledge acquisition and science self-concept were investigated. Results implied that guided play supported knowledge acquisition and maintained children’s science self-concept. Free play did not support children’s stability knowledge and decreased children’s science self-concept. No evidence for reciprocal effects between children’s stability knowledge and their science self-concept was found. Last, in a general discussion, the findings of the three articles are combined and reflected amidst children’s cognitive development. Summarising, the present dissertation shows that children’s science knowledge, science theories, and science self-concept can be supported through guided play that considers children’s cognitive development.
In der Masterthesis von Benjamin Waldmann mit dem Titel „Flusskrebse in Deutschland – Aktueller Stand der Verbreitung heimischer und invasiver gebietsfremder Flusskrebse in Deutschland; Überblick über die erfolgten Schutzmaßnahmen und den damit verbundenen Erfahrungen; Vernetzung der Akteure im Flusskrebsschutz“ wurden erstmals für alle heimischen wie gebietsfremden Flusskrebsarten (Zehnfußkrebse) Verbreitungskarten für Deutschland vorgelegt. Grundlage der Arbeit waren umfangreiche Recherchen und Abfragen zur Verbreitung der Arten in den Bundesländern bei den zuständigen Behörden, Institutionen, Artexperten und Privatpersonen. Die Rohdaten wurden qualitätsgesichert und in einem Geoinformationssystem aufbereitet und dargestellt, so dass daraus bundesweite Verbreitungskarten für jede Art in einem zehn Kilometerraster (UTM-Gitter im Bezugssystem ETRS89) erstellt werden konnten. Darüber hinaus wurden, ebenfalls auf Basis umfangreicher Recherchen und Abfragen, die unterschiedlichen Möglichkeiten für Schutzmaßnahmen für heimische Flusskrebspopulationen aufgezeigt, bewertet und daraus Empfehlungen abgeleitet. Besonderes Augenmerk wurde dabei auf das Management invasiver gebietsfremder Flusskrebsarten sowie der Umgang mit der Tierseuche Krebspest (Aphanomyces astaci) gelegt. Abschließend wurden Empfehlungen zur Vernetzung der Akteure im Flusskrebsschutz gegeben sowie die Ansprechpartner:innen in den einzelnen Bundesländern aufgeführt.
This thesis focuses on approximate inference in assumption-based argumentation frameworks. Argumentation provides a significant idea in the computerization of theoretical and practical reasoning in AI. And it has a close connection with AI, engaging in arguments to perform scientific reasoning. The fundamental approach in this field is abstract argumentation frameworks developed by Dung. Assumption-based argumentation can be regarded as an instance of abstract argumentation with structured arguments. When facing a large scale of data, a challenge of reasoning in assumption-based argumentation is how to construct arguments and resolve attacks over a given claim with minimal cost of computation and acceptable accuracy at the same time. This thesis proposes and investigates approximate methods that randomly select and construct samples of frameworks based on graphical dispute derivations to solve this problem. The presented approach aims to improve reasoning performance and get an acceptable trade-off between computational time and accuracy. The evaluation shows that for reasoning in assumption-based argumentation, in general, the running time is reduced with the cost of slightly low accuracy by randomly sampling and constructing inference rules for potential arguments over a query.
The belief in a just world in face of injustice: victim, observer, and perpetrator perspectives
(2021)
Injustice happens every day either to us, to our neighbors, or people across the world. Yet, believing that the world is a fair place helps us to cope with this injustice and motivates us to behave fairly. Scholars have found that these functions that the belief in a just world (BJW) serves are crucial for maintaining mental health. However, the conditions under which BJW is functional and when people give up this belief are not well studied. The current dissertation aims to examine: when the BJW can be shattered, the role of the external world and other internal resources in face of injustice, and the role of BJW in predicting corrupt behavior. Three studies were conducted corresponding to each party of injustice: a victim, an observer, and a perpetrator.
Study 1 examined the effects of criminal victimization on BJW and buffering role of perceptions of justice in the criminal justice process. A cross-sectional study showed that victims of very severe crimes such as domestic violence and human trafficking had lower personal BJW than non-victims and victims of less severe crimes, and higher informational justice perceptions reduced the effect of victimization on the personal BJW. Study 2 aimed to test the changes in BJW after observing severe injustice. A longitudinal study showed that after observing school rampage attacks that happened at other schools, BJW of adolescent participants increased. Moreover, life satisfaction and perceived social support moderated the change of BJW. Study 3 examined relationships between BJW and corrupt behavior. A cross-sectional study showed that personal BJW can predict bribery behavior.
The findings of three studies provided evidence that BJW does not function in isolation. An external world and internal resources can reduce the threat of injustice on BJW. BJW plays an important role in predicting unfair behavior therefore authorities should aim to maintain the BJW of their citizens.
Point Rendering
(2021)
In this thesis different methods for rendering point data are shown and compared with each other. The methods can be divided into two categories. For one visual methods are introduced that strictly deal with the displaying of point primitves. The main problem here lies in the depiction of surfaces since point data, unlike traditional triangle meshes, doesn't contain any connectivity information. On the other hand data strucutres are shown that enable real-time rendering of large point clouds. Point clouds often contain large amounts of data since they are mostly generated through 3D scanning processes such as laser scanning and photogrammetry.
In this thesis, the performance of the IceCube projects photon propagation
code (clsim) is optimized. The process of GPU code analysis and perfor-
mance optimization is described in detail. When run on the same hard-
ware, the new version achieves a speedup of about 3x over the original
implementation. Comparing the unmodified code on hardware currently
used by IceCube (NVIDIA GTX 1080) against the optimized version run on
a recent GPU (NVIDIA A100) a speedup of about 9.23x is observed. All
changes made to the code are shown and their performance impact as well
as the implications for simulation accuracy are discussed individually.
The approach taken for optimization is then generalized into a recipe.
Programmers can use it as a guide, when approaching large and complex
GPU programs. In addition, the per warp job-queue, a design pattern used
for load balancing among threads in a CUDA thread block, is discussed in
detail.
Enterprise Collaboration Systems (ECS) have become substantial for computer-mediated communication and collaboration among employees in organisations. As ECS combine features from social media and traditional groupware, a growing number of organisations implement ECS to facilitate collaboration among employees. Consequently, ECS form the core of the digital workplace. Thus, the activity logs of ECS are particularly valuable since they provide a unique opportunity for observing and analysing collaboration in the digital workplace.
Evidence from academia and practice demonstrates that there is no standardised approach for the analysis of ECS logs and that practitioners struggle with various barriers. Because current ECS analytics tools only provide basic features, academics and practitioners cannot leverage the full potential of the activity logs. As ECS activity logs are a valuable source for understanding collaboration in the digital workplace, new methods and metrics for their analysis are required. This dissertation develops Social Collaboration Analytics (SCA) as a method for measuring and analysing collaboration activities in ECS. To address the existing limitations in academia and practice and to contribute a method and structures for applying SCA in practice, this dissertation aims to answer two main research questions:
1. What are the current practices for measuring collaboration activities in Enterprise Collaboration Systems?
2. How can Social Collaboration Analytics be implemented in practice?
By answering the research questions, this dissertation seeks to (1) establish a broad thematic understanding of the research field of SCA and (2) to develop SCA as a structured method for analysing ac-tivity logs of ECS. As part of the first research question, this dissertation documents the status quo of SCA in the academic literature and practice. By answering the second research question, this dissertation contributes the SCA framework (SCAF), which guides the practical application of SCA. SCAF is the main contribution of this dissertation. The framework was developed based on findings from an analysis of 86 SCA studies, results from 6 focus groups and results from a survey among 27 ECS user companies. The phases of SCAF were derived from a comparison of established process models for data mining and business intelligence. The eight phases of the framework contain detailed descriptions, working steps, and guiding questions, which provide a step by step guide for the application of SCA in practice. Thus, academics and practitioners can benefit from using the framework.
The constant evaluation of the research outcomes in focus groups ensures both rigour and relevance. This dissertation employs a qualitative-dominant mixed-methods approach. As part of the university-industry collaboration initiative IndustryConnect, this research has access to more than 30 leading ECS user companies. Being built on a key case study and a series of advanced focus groups with representatives of user companies, this dissertation can draw from unique insights from practice as well as rich data with a longitudinal perspective.
The sediments of surface waters are temporary or final depository of many chemical compounds, including trace metals and metalloids (metal(loid)s) from natural and anthropogenic sources. Whether they act as a source or sink of metal(loid)s depends strongly on the dynamics of the biogeochemical processes that take place at the sediment-water interface (SWI). Important information on biogeochemical processes as well as on the exposure, the fate and the transport of pollutants at the SWI can be obtained by determining chemical concentration profiles in the sediment pore water. A major challenge is to conduct experiments with a spatial resolution, which allows to adequately record existing gradients and to log all the parameters needed, to describe and better understand the complex processes at the SWIs. At the same time, it is from major importance to prevent the formation of any artifacts during sampling, which may occur due to the labile nature of the SWIs and the very steep biogeochemical gradients.
In this context, in the first part of this work, a system was developed and tested that enables the automated, minimal invasive sampling of sediment pore water of undisturbed or manipulated sediments while simultaneously recording parameters such as redox potential, oxygen content and pH value. In an incubation experiment the impact of acidification and mechanical disturbance (re-suspension) on the mobility of 13 metal(loid)s was investigated using a triple quadrupole inductively coupled plasma-mass spectrometry (ICP-QQQ-MS) multi-element approach. Most metals were released as consequence of sulfide weathering whereas mechanical disturbance had a major impact on the mobility of the oxide forming elements As, Mo, Sb, U and V. Additionally, options were demonstrated to address with the system the size fractionation of metal(loid)s in pore water samples and the speciation of As(III/V) and Sb(III/V).
In the second part, the focus, with a similar experimental design, was placed on the processes leading to the release of metal(loid)s. For this purpose, two incubation experiments with different oxygen supply were conducted in parallel. For the first time the nonmetals carbon, phosphorus and sulfur were analyzed simultaneous to 13 metal(loid)s in sediment pore water by ICP-QQQ-MS. Throughout the experiment metal(loid) size fractionation was monitored. It was confirmed that resuspension promotes the mobility of metalloids such as As, Sb and V, while the release of most metals was largely attributed to pyrite weathering. The colloidal (0.45-16 μm) contribution in terms of mobilization was only relevant for a few elements.
Finally, the sampling system was used as part of a new approach to sediment risk assessment. Undisturbed sediment cores from differently contaminated positions in the Trave estuary were examined, considering 16 metal(loid)s, the non-metals C, P and S and the ions NH4+, PO43- and SO42-. By the first in-depth comparison with in-situ dialysis-based pore water sampling the ability of the suction-based approach to represent field conditions was proven. The pore water studies together with supplementing resuspension experiments in bio-geochemical microcosms and sequential extraction identified the most “pristine” sediment of the study area as posing the greatest risk of metal(loid) release. However, the potentially released amounts per kg of sediment are only a few parts per thousand of the average daily loads of the Trave river.
Social media has changed how customers, businesses, employees, and job seekers form their reputation perceptions of a company, that is, how they form their evaluative judgements about a company’s products, services and behaviors towards constituencies. In pre-social media times, companies had control over what they communicated to their stakeholders, for example, by using corporate websites to convey a predefined image. With social media, multiple opinions, experiences, and company perceptions reach the wider public via multiple channels such as Twitter, Facebook, and other social networking sites that enable user-generated content. Although companies usually try to nurture an online reputation by running their own Facebook and Twitter profiles, a large amount of online content related to a company is produced by social media users and thus is beyond companies’ control. This habilitation thesis is devoted to studying consumer and employee responses to employee behavior in social media. Across eight different articles, with multiple studies each, this thesis aims to draw a full picture of how employee behavior in social media affects customers, other employees, job seekers, and the employing company as a whole.
Successful export sectors in manufacturing and agribusiness are important drivers of structural transformation in Sub-Sahara African countries. Backed by industrial policies and active state involvement, a small number of successful productive export sectors has emerged in Sub-Saharan Africa. This thesis asks the question: How do politics shape the promotion of export-driven industrialisation and firm-level upgrading in Sub-Saharan Africa? It exemplifies this question with an in-depth, qualitative study of the cashew processing industry in Mozambique in the period from 1991 until 2019. Mozambique used to be one of the world’s largest producers and processors of cashew nuts in the 1960s and 1970s. At the end of the 20th century, the cashew processing industry broke down completely but has re-emerged as one of the country’s few successful agro-processing exports.
The thesis draws on theoretical approaches from the fields of political science, notably the political settlements framework, global value chain analysis and the research on technological capabilities to explore why the Mozambican Government supported the cashew processing industry and how Mozambican cashew processors acquired the technological capabilities needed to access the global cashew value chain and to upgrade. It makes an important theoretical contribution by linking the political settlements framework and the literature on upgrading in global value chains to study how politics shaped productive sector promotion and upgrading in the Mozambican cashew processing industry. The findings of the thesis are based on extensive primary data, including 58 expert interviews and 10 firm surveys, that was collected in Mozambique in 2018 as well as a broad base of secondary literature.
The thesis argues that the Mozambican Government supported the cashew processing industry because it became important for the Government’s political survival. Promoting the cashew sector formed part of an electoral strategy for the ruling FRELIMO coalition and a means to keep FRELIMO factions united by offering economic opportunities to key constituencies. In 1999, it adopted a protectionist cashew law that created strong incentives for cashew processing in Mozambique. This not only facilitated the re-emergence of the cashew processing industry after its breakdown. The law and the active involvement of the National Cashew Institute (INCAJU) also affected the governance of the local cashew value chain, the creation of backward linkages, and the upgrading paths of cashew processors. The findings of the thesis suggest that the cashew law reduced the pressure on the cashew processing industry to upgrade. The law further created opportunities for formal and informal rent creation for members of the political elite and lower level FRELIMO officials that prevented a far-reaching reform of the law. The thesis shows that international buyers do not promote upgrading among Sub-Sahara African firms in global value chains with market-based or modular governance. Moreover, firms that operate in countries where industrial policies are not enforced effectively cannot draw on the support of government institutions to enhance their capabilities and to upgrade. Firms therefore mainly depended on costly learning channels at firm level, e.g. learning by doing or hiring skilled labour, and/or on technical assistance from donors to build the technological capabilities needed to access global value chains and to remain competitive.
The findings of the thesis suggest that researchers, governments, development practitioners and consultants need to rethink their understanding of upgrading in GVCs in four ways. First, they need to move away from understanding upgrading in terms of moving towards more complex, higher value-added activities in GVCs (functional upgrading). Instead, it is important to consider the potential of other, more realistic types of upgrading for firms in low-income countries, such reducing risks by diversifying suppliers and buyers or increasing rewards by making production processes more efficient. Second, they need to replace an overly positive view on upgrading that neglects possible side-effects at sector and/or country level. Third, GVC participation on its own does not promote upgrading among local supplier firms in Sub-Saharan Africa. The interests of lead firms and Sub-Sahara African supplier firms may not be aligned or even conflicting. Targeted industrial policies and the creation of institutions that effectively promote capability building among firms therefore become even more important. Finally, upgrading needs to be understood as a process that is not only shaped by interactions between firms, but also by local domestic politics.
The findings of the thesis are highly relevant for scholars from the fields of political science, development studies, and economics. Its practical implications and tools, e.g. a technological capabilities matrix for the cashew industry, are of interest for development practitioners, members of public institutions in Sub-Sahara African countries, local entrepreneurs, and representatives of local business associations that are involved in promoting export sectors and upgrading among local firms.
As a multilingual system,Wikipedia provides many challenges for academics and engineers alike. One such challenge is cultural contextualisation of Wikipedia content, and the lack of approaches to effectively quantify it. Additionally, what seems to lack is the intent of establishing sound computational practices and frameworks for measuring cultural variations in the data. Current approaches seem to mostly be dictated by the data availability, which makes it difficult to apply them in other contexts. Another common drawback is that they rarely scale due to a significant qualitative or translation effort. To address these limitations, this thesis develops and tests two modular quantitative approaches. They are aimed at quantifying culture-related phenomena in systems which rely on multilingual user-generated content. In particular, they allow to: (1) operationalise a custom concept of culture in a system; (2) quantify and compare culture-specific content- or coverage biases in such a system; and (3) map a large scale landscape of shared cultural interests and focal points. Empirical validation of these approaches is split into two parts. First, an approach to mapping Wikipedia communities of shared co-editing interests is validated on two large Wikipedia datasets comprising multilateral geopolitical and linguistic editor communities. Both datasets reveal measurable clusters of consistent co-editing interest, and computationally confirm that these clusters correspond to existing colonial, religious, socio economic, and geographical ties. Second, an approach to quantifying content differences is validated on a multilingual Wikipedia dataset, and a multi-platform (Wikipedia and Encyclopedia Britannica) dataset. Both are limited to a selected knowledge domain of national history. This analysis allows, for the first time on the large scale, to quantify and visualise the distribution of historical focal points in the articles on national histories. All results are cross-validated either by domain experts, or external datasets.
Main thesis contributions. This thesis: (1) presents an effort to formalise the process of measuring cultural variations in user-generated data; (2) introduces and tests two novel approaches to quantifying cultural contextualisation in multilingual data; (3) synthesises a valuable overview of literature on defining and quantifying culture; (4) provides important empirical insights on the effect of culture on Wikipedia content and coverage; demonstrates that Wikipedia is not contextfree, and these differences should not be treated as noise, but rather, as an important feature of the data. (5) makes practical service contributions through sharing data and visualisations.
The stands surveyed are among the last closed canopy forests in Rwanda. Their exploration began in the early twentieth century and is still ongoing. Previous studies were mainly concerned with plant sociological issues and presented references to environmental factors in anecdotal form, at best using indirect ordination methods. The present study undertakes a classification of the vegetation with numerical methods and establishes quantitative relationships of the species’ distributional structure to environmental parameters using spatially explicit procedures. For this purpose, 94 samples were taken in 100 m² hexagonal plots. Of these, 70 samples are from Nyungwe, 14 are from Gishwati, and 10 are from Cyamudongo. Given the homogeneity of the terrain and vegetation, all vegetation types encountered, all types of stands, and all vegetation strata were included. The beta diversity is expressed by an average Bray-Curtis dissimilarity of 0.92, and in JOST’S (2007) numbers equivalents, 37.90 equally likely samples would be needed to represent the diversity encountered. Within the survey, 1198 species in 127 families were collected. Among the specimens are 6 local endemics and 40 Albertine Rift endemics. Resulting from UPGMA and FCM-NC, 20 to 40 plant communities were established depending on the level of resolution. It can be inferred by means of a Mantel correlogram that the mean zone of influence of a single vegetation stand, as sampled by a 100 m² plot in Nyungwe Forest, ranges between 0.016 and 3.42 km. Of the communities compiled using FCM-NC and UPGMA, 50% consist of individual samples. Beyond undersampling, natural small-scale discontinuities are reflected by this result. Partial db-RDA resulted in an explained variation of 9.60% and 14.41% for environmental and soil factors, respectively. Utilising variation partitioning analyses based on CCA and tb-RDA, between 21.70% and 37.80% of the variation in vegetation data could be explained. The spatially structured fraction of these parameters accounts for between 30.50% and 49.80% of the explained variation (100%). The purely environmental parameters account for a share of 10.30% to 16.30%, whereby the lower limit originates from the unimodal approach and has lost its statistical significance. The soil variables, also after partial analysis, account for a share of 19.00% to 35.70%. While the residual impact of the climatic parameters is hardly significant, the effect of the soil properties is prevalent. In general, the spatially structured fraction of the parameters is predominant here. While on the broad-scale climatic factors, the altitude a.s.l. and the geology are determining factors, some soil parameters and matrix components also show their impacts here. In the mid-range of the scale, it is the forest matrix, the soil types, and the geology that determine species distribution. While in the fine range of the scale, some unrecorded parameters seem to have an effect, there are also neutral processes that determine species composition.
Water is used in a way as if it were available infinitely. Droughts, increased rainfall or flooding already lead to water shortages and, thus, deprive entire population groups of the basis of their livelihoods. There is a growing fear that conflicts over water will increase, especially in arid climate zones, because life without water - whether for humans, animals or plants - is not possible.
More than 60 % of the African population depend on land and water resources for their livelihoods through pastoralism, fishing and farming. The water levels of rivers and lakes are decreasing. Hence, the rural population which is dependent on land and water move towards water-rich and humid areas. This internal migration increases the pressure on available water resources. Driven by the desire to strengthen the economic development, African governments align their political agendas with the promotion of macro international and national economic projects.
This doctoral thesis examines the complex interrelationships between water shortages, governance, vulnerability, adaptive capacity and violent and non-violent conflicts at Lake Naivasha in Kenya and Lake Wamala in Uganda. In order to satisfy the overall complexity, this doctoral thesis combines various theoretical and empirical aspects in which a variety of methods are applied to different geographical regions, across disciplines, and cultural and political boundaries.
The investigation reveals that Lake Naivasha is more affected by violent conflicts than Lake Wamala. Reasons for this include population growth, historically grown ethnic conflicts, corruption and the preferential treatment of national and international economic actors. The most common conflict response tools are raiding and the blockage of water access. However, deathly encounters, destruction of property and cattle slaughtering are increasingly used to gain access to water and land.
The insufficient implementation of the political system and the governments’ prioritization to foster economic development results, on the one hand, in the commercialization of water resources and increases, on the other hand, non-violent conflict between national and sub-national political actors. While corruption, economic favours and patronage defuse this conflict, resource access becomes more difficult for the local population. Resulting thereof, a final hypothesis is developed which states that the localization of the political conflict aggravates the water situation for the local population and, thereby, favours violent conflicts over water access and water use in water-rich areas.
In Kooperation mit dem TÜV SÜD und 985 Führungskräften aus deutschen Unternehmen wurde erprobt, wie Service-Qualität im Rahmen einer Onlinebefragung gemessen werden kann. Es wurde untersucht, welche Komponenten Service-Qualität umfasst, und ein Rahmenmodell entwickelt, das die Zusammenhänge zwischen Service-Qualität, Kundenzufriedenheit und dem Erfolg von Organisationen beschreibt. Die theoretische Konzeption und Operationalisierung des Konstrukts wurde mittels konfirmatorischer Faktorenanalysen überprüft und bestätigt. Das Rahmenmodell der Studie wurde als Strukturgleichungsmodell formuliert und konnte ebenfalls empirisch bestätigt werden. Die Ergebnisse und deren Auswirkung auf die Weiterentwicklung der bestehenden wissenschaftlichen Theorien zu den Konstrukten Service-Qualität, Kundenzufriedenheit und Erfolg von Organisationen wurden kritisch diskutiert.
Zur Steigerung der Ökonomie des Verfahrens wurde ein adaptiver Test zur Erfassung von Service-Qualität entwickelt. Im Rahmen der probabilistischen Testtheorie wurde geprüft, welches Item Response-Modell die empirischen Daten gut beschreiben kann. Als Grundlage für den adaptiven Test wurden die Item-Parameter modellkonform bestimmt. In einer Simulationsstudie wurde untersucht, ob die Ergebnisse der Onlinebefragung sich bedeutsam von den Ergebnissen adaptiver Tests mit unterschiedlichen Konfigurationen unterscheiden. Der Vergleich der Konfigurationen, die sich darin unterschieden, wie der Personenparameter geschätzt wurde und nach welchem Algorithmus das nächste Test-Item gewählt wurde, zeigte, welche Konfigurationen eingesetzt werden können, um eine möglichst geringe Testlänge zu erzielen, ohne dabei bedeutsame Einbußen bei der Reliabilität und Validität der Messung in Kauf zu nehmen. Unter Berücksichtigung dieser Erkenntnisse wurde der Fragebogen zur Erfassung von Service-Qualität als computerbasierter adaptiver Test umgesetzt. Diese neue Erfassungsmethode wurde in der Praxis erprobt, und abschließend wurden Nützlichkeit, Ökonomie und mögliche Nachteile, die mit dieser Art des Testens verknüpft sind, diskutiert.
Dieses Dokument, detailierte Analyseergebnisse, den adaptiven Test zur Erfassung von Service-Qualität und weitere Begleitmaterialien finden Sie unter: https://promotion.creaval.de
Identifizierung und Quantifizierung von Mikroplastik mittels quantitativer ¹H-NMR Spektroskopie
(2021)
Plastic, and so microplastics (MP), are globally present and represent an increasingly significant problem for the environment. In order to understand the distribution and impact of MP it is important to identify and quantify MP over a wide range of sizes and to ensure comparability of studies. However, comparability of studies is made difficult or even impossible by different MP concentration data. There still is a great need for research in the field of size-independent, quantitative analysis of MP in environmental samples, especially with regard to mass-based MP concentration information. Therefore, this thesis aims to utilize quantitative ¹H-NMR spectroscopy (qNMR) as an alternative method in MP analysis. The qNMR method is a size-independent, mass-based method which can be used as an alternative for MP analysis and has potential for routine analysis. The proof-of-concept was demonstrated for LDPE, PET and PS particles (Chapter 2). Additionally, PVC, PA, and ABS particles were tested to cover the most important polymer types for MP-analysis (Chapter 3). Moreover, using PET, PVC and PS as examples it was examined whether the qNMR method can also be transferred to the more cost-effective NoD method (Chapter 4). Results of method validation of both methods (1D and NoD) show that quantification using the qNMR method is not only possible in principle, but also shows high accuracy (88.0-110 %) and detection limits (1 – 84 µg) that lie within the environmentally relevant range. Furthermore, it was examined whether not only high-field instruments are suitable for MP analysis, but also benchtop devices (low-field instruments), which are much more cost-effective in purchase and maintenance. Increasing measurement times for PET and PS to 30 min and for PVC to 140 min, the lower measuring frequency especially concerning resolving capacity could be compensated (Chapter 4). To address the question of potential matrix effects of environmental samples, matrix effects and recovery rates of sample preparation procedures, which have been developed specifically for the application of the qNMR method were investigated using PET fibers as an example (Chapter 5). It could be shown that environmental matrices do not interfere with the quantitative analysis of MP using qNMR methods. Specific sample preparation methods developed for qNMR analysis can be used with recovery rates > 80 % for different environmental matrices (Chapter 5). Finally, first orienting investigations for the simultaneous determination of several polymer types in one sample are reported (Chapter 6).