Testing End-To-End Chains using Domain Specific Languages

Testing systems is a time consuming (and hence expensive) activity. Nevertheless, it is a very important and necessary step before using systems, especially safety critical systems. Therefore, many different test procedures are used: Unit Tests, Black-Box Tests, Software Integration Tests (SWI), Hardware-Software Integration Tests (HSI), Hardware-In-The-Loop Tests, just to name a few. Especially in the avionics domain, a variety of systems and applications communicate which each other. Furthermore, they depend and rely on the received information. However, some faults are only detected when all systems are connected and in operational mode. A new testing approach is to create model based End-To-End Chain scenarios with original and simulated equipment in any combination. The first aim is to automatically derive test data and test cases from the model, which is defined by a Domain Specific Language (DSL). Test data generators can be attached to quickly create a variety of stimuli for the systems under test. Furthermore, the system under test can be stimulated by either original equipment â which is connected to the test bench â or the test bench can simulate equipment and create inputs for the tested systems. Any mixture of simulated and original equipment is possible and can be changed on the fly. In the end, the results from the system under test are collected. These results can then be displayed back in the model. This method was used and improved in the project â E-Enabled Cabin (E-Cab)â in which the author was involved. Passengers traveling by plane are in the focus of this project. Complete services and service chains â ranging from booking at home with a computer, being en route using mobile devices to leaving the destination airport â are created and used by many systems communicating with each other. A special focus is set on a guidance scenario at an airport. The user of the system signs in to a guidance and notification system which will inform him via his own digital equipment (mobile device/smart phone). The system notifies the user about his in-time status. Either he is in-time for his flight, or he needs to hurry up and proceed to the next area or he will be too late and cannot catch his flight. The DSL itself is designed according to the comprehension of information processes. The ability of the human brain to process visual information in parallel â in contrast to sequential processing of textual information â is described and applied in the design of the DSL and the concepts of the project. The development of the DSL and the workflow is developed with the â real worldâ in mind. This means that the work fits in established workflows and enhances the current situation. As this project took place in the aircraft industry, the appropriate development standards, like DO178B and ABD100/200 (Airbus Directives ABD100/ABD200), build the foundation. The generation of clean code is established by applying generator guidelines (through coding standards) in order to create maintainable tests and test data

Model reduction of controlled Fokker--Planck and Liouville-von Neumann equations

Model reduction methods for bilinear control systems are compared by means of practical examples of Liouville-von Neumann and Fokker--Planck type. Methods based on balancing generalized system Gramians and on minimizing an H2-type cost functional are considered. The focus is on the numerical implementation and a thorough comparison of the methods. Structure and stability preservation are investigated, and the competitiveness of the approaches is shown for practically relevant, large-scale examples

Novel developments in SBGN-ED and applications

Systems Biology Graphical Notation (SBGN, http://sbgn.org) [1] is an emerging standard for graphical representations of biochemical and cellular processes studied in systems biology. Three different views (Process Description, Entity Relationship, and Activity Flow) cover several aspects of the represented processes in different levels of detail. SBGN helps to communicate biological knowledge more efficient and accurate between different research communities in the life sciences. However, to support SBGN, methods and tools for editing, validating, and translating of SBGN maps are necessary.
We present methods for these tasks and novel developments in SBGN-ED (www.sbgn-ed.org) [2], a tool which allows to create all three types of SBGN maps from scratch, to validate these maps for syntactical and semantical correctness, to translate maps from the KEGG database into SBGN, and to export SBGN maps into several file and image formats. SBGN-ED is based on VANTED (Visualization and Analysis of NeTworks containing Experimental Data, http://www.vanted.org) [3].
As applications of SBGN and SBGN-ED we present furthermore MetaCrop (http://metacrop.ipk-gatersleben.de) [4], a database that summarizes diverse information about metabolic pathways in crop plants, and RIMAS (Regulatory Interaction Maps of Arabidopsis Seed Development, http://rimas.ipk-gatersleben.de) [5], an information portal that provides a comprehensive overview of regulatory pathways and genetic interactions during Arabidopsis embryo and seed development. 

[1] Le Novère, N. et al. (2009) The Systems Biology Graphical Notation. Nature Biotechnology, 27, 735-741.
[2] Czauderna, T., Klukas, C., Schreiber, F. (2010) Editing, validating, and translating of SBGN maps. Bioinformatics, 26 (18), 2340-2341.
[3] Junker, B.H., Klukas, C., Schreiber, F. (2006) VANTED: A system for advanced data analysis and visualization in the context of biological networks. BMC Bioinformatics, 7, 109+.
[4] Grafahrend-Belau, E., Weise, S., Koschützki, D., Scholz, U., Junker, B.H., Schreiber, F. (2008) MetaCrop - A detailed database of crop plant metabolism. Nucleic Acids Research, 36, D954-D958.
[5] Junker, A., Hartmann, A., Schreiber, F., Bäumlein, H. (2010) An engineer's view on regulation of seed development. Trends in Plant Science, 15(6), 303-307.
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Essays on Macroeconomics and Labor Markets

Over the last decades, the U.S. labor market has changed significantly. These developments can not only be attributed to cyclical components influencing labor market conditions during economic downturns but also partly to important and slow moving structural factors. How do changing labor markets affect workers? Discussing and answering this question is an important task for researchers, not only because labor earnings are a major source of income, making up around 60 percent of household income, but also because workers spent a large part of their lifetime at work, on average 34 hours a week for 38 years of their lives. I contribute to the understanding of changing labor markets by focusing on three specific aspects: technical change, selective hiring, and judicial ideology. While this thesis consists of three independent research papers, they are connected by an overarching focus on firms’ hiring behavior and associated consequences for workers’ employment conditions and opportunities. Chapter 2, which is joint work with Tobias Föll, explores the effect of routine-biased technical change on both the occupational and the union-membership choice of workers and thus analyses the connection between polarization and deunionization. In Chapter 3, I study the connection between involuntary part-time employment, workers’ job mobility, and the role of firms’ hiring behaviour. In Chapter 4, which is joint work with Christian Bredemeier and Tobias Föll, we examine how the ideological composition of the Supreme Court affects labor market conditions for workers in the U.S

Essays in Labor Economics and Labor Market Policy

The thesis 'Essays in Labor Economics and Labor Market Policy' contributes to the existing literature by advancing our understanding of the forces that have shaped labor market outcomes in recent decades. It consists of three independent research papers, which zoom in on the effects of financial frictions, routine-biased technical change, and judge ideology, respectively. My coauthors and I employ both empirical and analytical methods to analyze the underlying mechanisms and discuss appropriate policy implications. Chapter 2 of this thesis explores the joint role of imperfections in labor and financial markets for the cyclical adjustment of the labor market. I show that jobless recoveries emerge when, upon exiting a recession, firms are faced with deteriorating credit conditions. On the financial side, collateral requirements affect the cost of borrowing for firms. On the employment side, hiring frictions and wage rigidity increase the need for credit, making the binding collateral constraint more relevant. In a general equilibrium business cycle model with search and matching frictions, I illustrate that tightening credit conditions calibrated from data negatively affect employment adjustments during recovery periods. Wage rigidity substantially amplifies this mechanism, generating empirically plausible fluctuations in employment and output. In Chapter 3 of this thesis, using state-level labor market data, Anna Hartmann and I document a positive relationship between the two phenomena in the U.S.: the decrease in unionization rates has been significantly more pronounced in states with a higher employment share in routine-intensive occupations. Contrary to conventional wisdom, deunionization is mainly driven by large within-industry and within-occupation changes in union membership rates and not only by compositional effects. Building on this observation, we argue that the commonly assumed driver of polarization, routine-biased technical change, is also the main driving force behind the decline in union membership rates. In a model with search and matching frictions where workers choose occupations and endogenously form unions, we illustrate that shifts in the structure of labor demand in favor of low- and high-skill occupations worsen the bargaining position of unions and make participation in collective bargaining less attractive for workers. The ensuing within-industry and within-occupation decline in unionization rates in turn provides incentives for middle-wage workers to switch to low-wage occupations, which further amplifies job market polarization. In Chapter 4 of this thesis, Christian Bredemeier, Anna Hartmann, and I provide evidence on the systematic labor market effects of ideological tendencies of the judiciary, employing broad data on court rulings and labor market outcomes. Our identification strategy uses heterogenous effects of ideological shifts of the U.S. Supreme Court on U.S. district court rulings, which we derive from a theoretical model of judge decision making and document empirically. Exploiting this heterogeneity, we find that an increase in the share of conservative rulings substantially increases the employment rate and promotes labor market fluidity but also contributes to wage stagnation, job market polarization, deunionization, and rising income inequality. Our main empirical results can be rationalized in a search and matching model with wrongful-termination lawsuits

Meta-analysis of nutrient budgets in organic farms across Europe

Nutrient supply to organic farms is a highly discussed topic in Europe, due to the restricted availability of external fertilizer resources and the use of contentious inputs. To optimize the flow of nutrients throughout the organic farming system, it is firstly necessary to obtain valid data on the nutrient status of organic farms. Nutrient budgets are a valid tool to investigate the nutrient demand or surplus of a system. However, there is currently no comprehensive overview of nutrient budgets of European organic farms. We therefore carried out a meta-analysis on 56 individual studies that reported either farm-gate or soil-surface budgets. The analysis showed an imbalance between nutrients, a general surplus of nitrogen (45 kg N ha-1 year-1 [95%-confidence interval (CI): 30, 61]), magnesium (16 kg Mg ha-1 year-1 [-9, 40]) and sulphur (45 kg S ha-1 year-1 [-29, 118]), a balanced phosphorus budget (0 kg P ha-1 year-1 [-2,2]), and a deficit for potassium (-12 kg K ha-1 year-1 [-21, -3]). We observed large differences between farms that could be partly explained by farm type and budgeting method. Arable and mixed farms showed lower nitrogen, phosphor, magnesium and sulphur budgets than dairy/beef farms or even vegetable farms, while all farm types besides dairy/ beef farms showed deficits for K budgets. Further, farm-gate budget studies yielded higher budgets than soil surface budgets. Variations between studied countries could also be detected, but the coverage and comparability is low due to differences in studied farm types and budgeting method

The Impact of Vitamin E and Other Fat-Soluble Vitamins on Alzheimer´s Disease

Alzheimer’s disease (AD) is the most common cause of dementia in the elderly population, currently affecting 46 million people worldwide. Histopathologically, the disease is characterized by the occurrence of extracellular amyloid plaques composed of aggregated amyloid-β (Aβ) peptides and intracellular neurofibrillary tangles containing the microtubule-associated protein tau. Aβ peptides are derived from the sequential processing of the amyloid precursor protein (APP) by enzymes called secretases, which are strongly influenced by the lipid environment. Several vitamins have been reported to be reduced in the plasma/serum of AD-affected individuals indicating they have an impact on AD pathogenesis. In this review we focus on vitamin E and the other lipophilic vitamins A, D, and K, and summarize the current knowledge about their status in AD patients, their impact on cognitive functions and AD risk, as well as their influence on the molecular mechanisms of AD. The vitamins might affect the generation and clearance of Aβ both by direct effects and indirectly by altering the cellular lipid homeostasis. Additionally, vitamins A, D, E, and K are reported to influence further mechanisms discussed to be involved in AD pathogenesis, e.g., Aβ-aggregation, Aβ-induced neurotoxicity, oxidative stress, and inflammatory processes, as summarized in this article