Error analysis of truncated expansion solutions to high-dimensional parabolic PDEs

We study an expansion method for high-dimensional parabolic PDEs which constructs accurate approximate solutions by decomposition into solutions to lower-dimensional PDEs, and which is particularly effective if there are a low number of dominant principal components. The focus of the present article is the derivation of sharp error bounds for the constant coefficient case and a first and second order approximation. We give a precise characterisation when these bounds hold for (non-smooth) option pricing applications and provide numerical results demonstrating that the practically observed convergence speed is in agreement with the theoretical predictions

Representing chord sequences in OWL

Chord symbols and progressions are a common way to describe musical harmony. In this paper we present SEQ, a pattern representation using the Web Ontology Language OWL DL and its application to modelling chord sequences. SEQ provides a logical representation of order information, which is not available directly in OWL DL, together with an intuitive notation. It therefore allows the use of OWL reasoners for tasks such as classification of sequences by patterns and determining subsumption relationships between the patterns. The SEQ representation is used to express distinctive pattern obtained using data mining of multiple viewpoints of chord sequences

Essays on skills, wages, and inequality in Germany

Income inequality has increase in almost all OECD countries over the last three decades (OECD 2014) and that increase is mostly driven by increasing inequality in labor incomes (Piketty and Saez 2014). In my dissertation “Essays on Skills, Wages, and Inequality in Germany” I study various aspects related to the question of what drives inequality in labor incomes. In my first chapter (“The State of the German Labor Market”), I use some of the best data available to provide an evidence-based, up-to-date description of recent wage structure and employment trends in Germany. In my second chapter (“Skill Premiums and the Supply of Young Workers” joint with Albrecht Glitz) I ask whether changes in the supply of skills, i.e. for instance the number of college graduates or workers with vocational training, can help to explain wage inequality, in particular at the lower end of the distribution. My third chapter (“Compensating Differentials and the Introduction of Smoking Bans”) starts from the idea that up to 15% of wage inequality might be due to compensating differentials (Sorkin 2016), i.e. the extra pay associated with jobs that are more dangerous or unpleasant than others. This argument, however, relies on indirect evidence while direct evidence for such compensating differentials has been largely missing. I fill this gap by exploiting the introduction of smoking bans in Germany looking at wages of waiters in the hospitality industry as a natural experiment to provide quasi-experimental evidence for compensating differentials in the labor market

Chord Sequence patterns in OWL

This thesis addresses the representation of and reasoning on musical knowledge in the Semantic Web. The Semantic Web is an evolving extension of the World Wide Web that aims at describing information that is distributed on the web in a machine-processable form. Existing approaches to modelling musical knowledge in the context of the Semantic Web have focused on metadata. The description of musical content and reasoning as well as integration of content descriptions and metadata are yet open challenges. This thesis discusses the possibilities of representing musical knowledge in the Web Ontology Language (OWL) focusing on chord sequence representation and presents and evaluates a newly developed solution. The solution consists of two main components. Ontological modelling patterns for musical entities such as notes and chords are introduced in the (MEO) ontology. A sequence pattern language and ontology (SEQ) has been developed that can express patterns in a form resembling regular expressions. As MEO and SEQ patterns both rewrite to OWL they can be combined freely. Reasoning tasks such as instance classification, retrieval and pattern subsumption are then executable by standard Semantic Web reasoners. The expressiveness of SEQ has been studied, in particular in relation to grammars. The complexity of reasoning on SEQ patterns has been studied theoretically and empirically, and optimisation methods have been developed. There is still great potential for improvement if specific reasoning algorithms were developed to exploit the sequential structure, but the development of such algorithms is outside the scope of this thesis. MEO and SEQ have also been evaluated in several musicological scenarios. It is shown how patterns that are characteristic of musical styles can be expressed and chord sequence data can be classified, demonstrating the use of the language in web retrieval and as integration layer for different chord patterns and corpora. Furthermore, possibilities of using SEQ patterns for harmonic analysis are explored using grammars for harmony; both a hybrid system and a translation of limited context-free grammars into SEQ patterns have been developed. Finally, a distributed scenario is evaluated where SEQ and MEO are used in connection with DBpedia, following the Linked Data approach. The results show that applications are already possible and will benefit in the future from improved quality and compatibility of data sources as the Semantic Web evolves

Investigating the epidemiology of trypanosomiasis in domestic livestock at the micro-scale in Busia, Kenya

Trypanosomiasis in Kenya is no longer viewed as a public health issue, as only sporadic sleeping sickness cases are reported from historic foci such as Busia. Trypanosomiasis is thus mainly perceived as a constraint on livestock production. The responsibility for tsetse and trypanosomiasis control in Kenya has therefore increasingly shifted from the state to individual livestock owners; this drastically reduced the scale of control approaches. This thesis examines the epidemiology of both animal infective and zoonotic trypanosome species in a range of domestic livestock at the micro-scale, in Busia, Kenya. The work is based on a unique crosssectional census data set of the entire livestock population in two study sites in Busia, employing sensitive molecular tools (PCR) to detect trypanosome infections.Cattle were the largest reservoir of trypanosomes with an infection prevalence of 20.1%, followed by pigs (11.5%). A low prevalence of infection was detected in small ruminants (3.3%). Human infective trypanosomes (71 b. rhodesiense) were detected at a low prevalence in cattle (1.5%) and pigs (2.9%). Key clinical signs for trypanosomiasis infection (anaemia & poor body condition) were only observed in a minority of infected cattle (<20%). Confinement of livestock to the homesteads, instead of grazing in communal grounds and watering at the river did not provide protection from trypanosome infections. An investigation of the micro-geographic variation in the distribution of trypanosome infections over the study population, revealed significant clustering in one of the two study sites. However, there was no significant effect of distance to water features on trypanosomiasis risk at the herd level. A convenience sampling protocol was shown to give a good estimate of overall trypanosomiasis in cattle, but failed to detect the low prevalence of T. b. rhodesiense.The sustainability of small-scale trypanosomiasis control based on trypanocide treatment of visibly diseased cattle is appraised and the feasibility of additional vector control is discussed. Furthermore, the potential human health implications of a livestock reservoir of T. b. rhodesiense to the local population are examined