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Skript zur Vorlesung "Character Theory of finite groups".

Mixed-mode chromatography (MMC), which combines features of ion exchange chromatography (IEC) and hydrophobic interaction chromatography (HIC), is an interesting method for protein separation and purification. The design of MMC processes is challenging as adsorption equilibria are influenced by many parameters, including ionic strength and the presence of different salts in solution. Systematic studies on the influence of those parameters in MMC are rare. Therefore, in the present work, the influence of four salts, namely, sodium chloride, sodium sulfate, ammonium chloride, and ammonium sulfate, on the adsorption of lysozyme on the mixed-mode resin Toyopearl MX-Trp-650M at pH 7.0 and 25°C was studied systematically in equilibrium adsorption experiments for ionic strengths between 0 mM and 3000 mM. For all salts, a noticeable adsorption strength was observed over the entire range of studied ionic strengths. An exponential decay of the loading of the resin with increasing ionic strength was found until approx. 1000 mM. For higher ionic strengths, the loading was found to be practically independent of the ionic strength. At constant ionic strength, the highest lysozyme loadings were observed for ammonium sulfate, the lowest for sodium chloride. A mathematical model was developed that correctly describes the influence of the ionic strength as well as the influence of the studied salts. The model is the first that enables the prediction of adsorption isotherms of proteins on mixed-mode resins in a wide range of technically interesting conditions, accounting for the influence of the ionic strength and four salts of practical relevance.

Carbon fibre reinforced epoxies (CFRE) are a class of high performance, light-weight composites
that show outstanding, weight-specific (thermo-)mechanical properties. A glassy and
highly cross-linked epoxy matrix provides the composite with a high thermal resistance, but
makes the CFRE also inherently brittle and susceptible to cracks and impacts. One strategy
to overcome this drawback and to improve fracture toughness of epoxy matrices is to modify
the underlying morphology with additional substructures (domains in the nano and/or micron
size range). This allows increasing the energy that is required to initiate or propagate a crack
within the material. The present work contributes to a better understanding of the effect
of substructure-forming, self-assembling block copolymers (BCP) and pre-formed core-shell
rubber particles (CSR) on the toughness and impact behaviour of thin CFREs and their epoxy
matrices. Using a new thermo-optical measurement technique, it is shown that the phaseseparation
process of BCP-rich domains is solely driven by the degree of cure of the epoxy
matrix. Also, it is found that the process of BCP phase-separation, e.g. the BCP-rich domain
size, changes strongly in the presence of carbon fibres. Low concentrations of BCPs (7wt.-%)
yield a 2.5-fold enhancement of the resistance to interlaminar fracture of the CFRE (Mode),
already. Using CSR particles, on the other hand, the energy required to initiate delamination
(Mode II) within the CFRE increases by 160 %. Subsequently, by a hybridization of BCP
and CSR modifiers, after low energy impacts, when both load cases occur in combination, a
synergistic damage volume reduction by more than 67% is achieved. Hence, the generated
material systems and the acquired understanding allow future CFRE based structures to be
even thinner than current design solutions, without affecting their structural integrity under
impact loads.

The subject of this thesis is the probabilistic reliability assessment of notched metallic components under periodic constant-amplitude loads with respect to the failure mode of high-cycle fatigue. The latter refers to the crack initiation within the considered component caused by a high number, typically millions, of load cycles characterized by their small magnitude in terms of the material's static strength. In order to estimate the probability of failure due to high-cycle fatigue for a specified component under given loads, a new empirical model based on weakest-link theory is developed which describes a probabilistic and component specific constant-life diagram with respect to the anticipated design life. A conventional, non-probabilistic constant-life diagram reflects a discrete design boundary in terms of mean stress and stress amplitude, typically based on test results with respect to unnotched coupons made from the material of interest. Its application to the design of a notched component is established by identifying the stress conditions at the component's hot spot with those acting in the smooth coupons during the tests, and comparing those hot-spot conditions with the design boundary described in the constant-life diagram. Disregarded influences, such as notch and statistical size effect have to be incorporated by respective correction factors. The proposed probabilistic model on the other hand describes a continuous field of failure probabilities in the design stress plane, taking into account not only the hot-spot stresses, but the entire cyclic stress field acting throughout the component. In this way, the methodology directly accounts for notch and statistical size effects. Responsible for providing this greater scope is the weakest-link concept, which represents a non-local stochastic approach for quantifying the failure probability of loaded solids. The four model parameters can be calibrated with fatigue test data sets containing entirely unrelated test results on arbitrary specimen geometries, obliterating the constraining need for test data following staircase or probit schemes. This work contains the formulation, analysis, validation and application of the proposed model. After its introduction and a comparison with existing methods, it is analyzed in terms of its numerical properties when applied to finite element models, its efficient calibration and the corresponding model uncertainty. The validation is split into two parts. In a first analysis, the model is fitted to test data, containing results on several types of notched specimens, reflecting predominantly elastic material behavior. In a second step, this restriction is lifted and the model is used in order to predict the failure behavior of notched test specimens experiencing notch root plasticity due to high mean stresses. In both validation studies, the derived model predictions are, for the most part, well in line with the experimentally observed failure behavior of the test specimens. Finally, the applicability of the proposed probabilistic methodology in a design context is demonstrated on the example of a gas turbine compressor blade and the corresponding compressor stage.

Synaptic transmission is controlled by re-uptake systems that reduce transmitter concentrations in the synaptic cleft and recycle the transmitter into presynaptic terminals. The re-uptake systems are thought to ensure cytosolic concentrations in the terminals that are sufficient for reloading empty synaptic vesicles (SVs). Genetic deletion of glycine transporter 2 (GlyT2) results in severely disrupted inhibitory neurotransmission and ultimately to death. Here we investigated the role of GlyT2 at inhibitory glycinergic synapses in the mammalian auditory brainstem. These synapses are tuned for resilience, reliability, and precision, even during sustained high-frequency stimulation when endocytosis and refilling of SVs probably contribute substantially to efficient replenishment of the readily releasable pool (RRP). Such robust synapses are formed between MNTB and LSO neurons (medial nucleus of the trapezoid body, lateral superior olive). By means of patch-clamp recordings, we assessed the synaptic performance in controls, in GlyT2 knockout mice (KOs), and upon acute pharmacological GlyT2 blockade. Via computational modeling, we calculated the reoccupation rate of empty release sites and RRP replenishment kinetics during 60-s challenge and 60-s recovery periods. Control MNTB-LSO inputs maintained high fidelity neurotransmission at 50 Hz for 60 s and recovered very efficiently from synaptic depression. During 'marathon-experiments' (30,600 stimuli in 20 min), RRP replenishment accumulated to 1,260-fold. In contrast, KO inputs featured severe impairments. For example, the input number was reduced to ~1 (vs. ~4 in controls), implying massive functional degeneration of the MNTB-LSO microcircuit and a role of GlyT2 during synapse maturation. Surprisingly, neurotransmission did not collapse completely in KOs as inputs still replenished their small RRP 80-fold upon 50 Hz | 60 s challenge. However, they totally failed to do so for extended periods. Upon acute pharmacological GlyT2 inactivation, synaptic performance remained robust, in stark contrast to KOs. RRP replenishment was 865-fold in marathon-experiments, only ~1/3 lower than in controls. Collectively, our empirical and modeling results demonstrate that GlyT2 re-uptake activity is not the dominant factor in the SV recycling pathway that imparts indefatigability to MNTB-LSO synapses. We postulate that additional glycine sources, possibly the antiporter Asc-1, contribute to RRP replenishment at these high-fidelity brainstem synapses.

To improve efficiency of memory accesses, modern multiprocessor architectures implement a whole range of different weak memory models. The behavior of performance-critical code depends on the underlying hardware. There is a rising demand for verification tools that take the underlying memory model into account. This work examines a variety of prevalent problems in the field of program verification of increasing complexities: testing, reachability, portability and memory model synthesis.
We give efficient tools to solve these problems. What sets the presented methods apart is that they are not limited to some few given architectures. They are universal: The memory model is given as part of the input. We make use of the CAT language to succinctly describe axiomatic memory models. CAT has been used to define the semantics of assembly for x86/TSO, ARMv7, ARMv8, and POWER but also the semantics of programming languages such as C/C++, including the Linux kernel concurrency primitives.
This work shows that even the simple testing problem is NP-hard for most memory models. It does so using a general reduction technique that applies to a range of models. It examines the more difficult program verification under a memory model and introduces Dartagnan, a bounded model checker (BMC) that encodes the problem as an SMT-query and makes use of advanced encoding techniques. The program portability problem is shown to be even harder. Despite this, it is solved efficiently by the tool Porthos which uses a guided search to produce fast results for most practical instances. A memory model is synthesized by Aramis for a given set of reachability results. Concurrent program verification is generally undecidable even for sequential consistency. As an alternative to BMC, we propose a new CEGAR method for Petri net invariant synthesis. We again use SMT-queries as a back-end.

Reflectance anisotropy spectroscopy (RAS), which was originally invented to monitor
epitaxial growth, can—as we have previously shown—also be used to monitor the reactive ion
etching of III/V semiconductor samples in situ and in real time, as long as the etching rate is not
too high and the abrasion at the etch front is not totally chaotic. Moreover, we have proven that—
using RAS equipment and optical Fabry-Perot oscillations due to the ever-shrinking thickness of the
uppermost etched layer—the in situ etch-depth resolution can be as good as +/-0.8 nm, employing a
Vernier-scale type measurement and evaluation procedure. Nominally, this amounts to +/-1.3 lattice
constants in our exemplary material system, AlGaAsSb, on a GaAs or GaSb substrate. In this
contribution, we show that resolutions of about +/-5.6 nm can be reliably achieved without a Vernier
scale protocol by employing thin doped layers or sharp interfaces between differently doped layers
or quantum-dot (QD) layers as etch-stop indicators. These indicator layers can either be added
to the device layer design on purpose or be part of it incidentally due to the functionality of the
device. For typical etch rates in the range of 0.7 to 1.3 nm/s (that is, about 40 to 80 nm/min), the RAS
spectrum will show a distinct change even for very thin indicator layers, which allows for the precise
termination of the etch run.

Laser-induced interstitial thermotherapy (LITT) is a minimally invasive procedure to destroy liver
tumors through thermal ablation. Mathematical models are the basis for computer simulations
of LITT, which support the practitioner in planning and monitoring the therapy.
In this thesis, we propose three potential extensions of an established mathematical model of
LITT, which is based on two nonlinearly coupled partial differential equations (PDEs) modeling
the distribution of the temperature and the laser radiation in the liver.
First, we introduce the Cattaneo–LITT model for delayed heat transfer in this context, prove its
well-posedness and study the effect of an inherent delay parameter numerically.
Second, we model the influence of large blood vessels in the heat-transfer model by means
of a spatially varying blood-perfusion rate. This parameter is unknown at the beginning of
each therapy because it depends on the individual patient and the placement of the LITT
applicator relative to the liver. We propose a PDE-constrained optimal-control problem for the
identification of the blood-perfusion rate, prove the existence of an optimal control and prove
necessary first-order optimality conditions. Furthermore, we introduce a numerical example
based on which we demonstrate the algorithmic solution of this problem.
Third, we propose a reformulation of the well-known PN model hierarchy with Marshak
boundary conditions as a coupled system of second-order PDEs to approximate the radiative-transfer
equation. The new model hierarchy is derived in a general context and is applicable
to a wide range of applications other than LITT. It can be generated in an automated way by
means of algebraic transformations and allows the solution with standard finite-element tools.
We validate our formulation in a general context by means of various numerical experiments.
Finally, we investigate the coupling of this new model hierarchy with the LITT model numerically.

The present study deals with the cause of head-curve instability and the influence of impeller-outlet and diffuser-inlet width on pump performances. Experiments and Computational Fluid Dynamics (CFD) simulations were carried out on a 4-stage model pump. Three impellers and diffusers with different meridional-widths were designed for a specific speed around 30 [m\(^3\)/s, m, rpm]. Overall-performance curves, stage-head curves, inlet recirculation in the 1\(^{st}\) stage, internal-head curves in the 2\(^{nd}\) stage and pressure profiles in the impeller side room were measured with 29 pressure sensors. Pressure pulsations were recorded at various positions in the multistage pump.
When the pump ran at the onset of the instability, an excessive head-loss was detected in the inlet triangular section of the diffuser. The pressure profiles in the side room and flow patterns in the impeller showed a sudden shift of flow recirculation at the impeller outlet across the span. According to [1, 2], this flow phenomenon is called flow pattern switching. The abrupt movement of outlet recirculation across the span produced a large momentum-exchange between streamlines and a massive mixing-loss in the inlet triangular section. This was considered the main cause of the instability.
As the meridional-width increased, flow recirculation at the impeller outlet was intensified, giving a higher head and power at shut-off. In contrast, the onset of the instability did not vary systematically with the meridional width. Diffuser rotating-stall was detected at \(f/f_n\) = 0.029 when the pump with the largest width ran at the onset of the instability. Even though all three designs generated a head-curve instability, the rotating stall appeared only in the largest meridional-width.
The uncertainty in the CFD prediction of pressure pulsations was evaluated. The discrepancy between measured and calculated values was largely dependent on the sampling location and operating points.

Estimation and Portfolio Optimization with Expert Opinions in Discrete-time Financial Markets
(2021)

In this thesis, we mainly discuss the problem of parameter estimation and
portfolio optimization with partial information in discrete-time. In the portfolio optimization problem, we specifically aim at maximizing the utility of
terminal wealth. We focus on the logarithmic and power utility functions. We consider expert opinions as another observation in addition to stock returns to improve estimation of drift and volatility parameters at different times and for the purpose of asset optimization.
In the first part, we assume that the drift term has a fixed distribution, and
the volatility term is constant. We use the Kalman filter to combine the two
types of observations. Moreover, we discuss how to transform this problem
into a non-linear problem of Gaussian noise when the expert opinion is uniformly distributed. The generalized Kalman filter is used to estimate the parameters in this problem.
In the second part, we assume that drift and volatility of asset returns are both driven by a Markov chain. We mainly use the change-of-measure technique to estimate various values required by the EM algorithm. In addition,
we focus on different ways to combine the two observations, expert opinions and asset returns. First, we use the linear combination method. At the same time, we discuss how to use a logistic regression model to quantify expert
opinions. Second, we consider that expert opinions follow a mixed Dirichlet distribution. Under this assumption, we use another probability measure to
estimate the unnormalized filters, needed for the EM algorithm.
In the third part, we assume that expert opinions follow a mixed Dirichlet distribution and focus on how we can obtain approximate optimal portfolio
strategies in different observation settings. We claim the approximate strategies from the dynamic programming equations in different settings and analyze the dependence on the discretization step. Finally we compute different
observation settings in a simulation study.

We present a study of optoelectronically active Ga(As)As quantum dots (QDs) on Al-rich AlxGa1-xAs layers with Al concentrations
up to x=90%. So far, however, it has not been possible to grow optoelectronically active Ga(As)As QDs epitaxially
directly on and in between Al-rich barrier layers in the AlGaInAsSb material system. A QD morphology might appear on the
growth front, but the QD-like entities will not luminesce. Here, we use photoluminescence (PL) measurements to show that thin
Al-free capsule layers between Al-rich barrier layers and the QD layers can solve this problem; this way, the QDs become
optoelectronically active; that is, the dots become QDs. We consider antimonide QDs, that is, Ga(As)Sb QDs, either on GaAs for
comparison or on AlxGa1-xAs barriers (x >10%) with GaAs capsule layers in between. We also discuss the influence of QD
coupling both due to stress/strain from neighboring QDs and quantum-mechanically on the wavelength of the photoluminescence
peak. Due to their mere existence, the capsule layers alter the barriers by becoming part of them. Quantum dots
applications such as QD semiconductor lasers for spectroscopy or QDs as binary storage cells will profit from this additional
degree of design freedom.

Deligne-Lusztig theory allows the parametrization of generic character tables of finite groups of Lie type in terms of families of conjugacy classes and families of irreducible characters "independently" of \(q\).
Only in small cases the theory also gives all the values of the table.
For most of the groups the completion of the table must be carried out with ad-hoc methods.
The aim of the present work is to describe one possible computation which avoids Lusztig's theory of "character sheaves".
In particular, the theory of Gel'fand-Graev characters and Clifford theory is used to complete the generic character table of \(G={\rm Spin}_8^+(q)\) for \(q\) odd.
As an example of the computations, we also determine the character table of \({\rm SL}_4(q)\), for \(q\) odd.
In the process of finding character values, the following tools are developed.
By explicit use of the Bruhat decomposition of elements, the fusion of the unipotent classes of \(G\) is determined.
Among others, this is used to compute the 2-parameter Green functions of every Levi subgroup with disconnected centre of \(G\).
Furthermore, thanks to a certain action of the centre \(Z(G)\) on the characters of \(G\), it is shown how, in principle, the values of any character depend on its values at the unipotent elements.
It is important to consider \({\rm Spin}_8^+(q)\) as it is one of the "smallest" interesting examples for which Deligne--Lusztig theory is not sufficient to construct the whole character table.
The reasons is related to the structure of \({\mathbf G}={\rm Spin}_8\), from which \(G\) is constructed.
Firstly, \({\mathbf G}\) has disconnected centre.
Secondly, \({\mathbf G}\) is the only simple algebraic group which has an outer group automorphism of order 3.
And finally, \(G\) can be realized as a subgroup of bigger groups, like \(E_6(q)\), \(E_7(q)\) or \(E_8(q)\).
The computation on \({\rm Spin}_8^+(q)\) serves as preparation for those cases.

Code coverage analysis plays an important role in the software testing process. More recently, the remarkable effectiveness of coverage feedback has triggered a broad interest in feedback-guided fuzzing. In this work, we discuss static instrumentation techniques for binary-level coverage analysis without compiler support. We show that the proposed techniques are precise, efficient, and transparent significantly beyond the state of the art.
We implement these techniques into two tools, namely, Spedi and bcov. Both tools are open source and publicly available. Spedi shows that the disassembly and function identification of stripped binaries can be highly accurate without resort to any external information. We build on these important results in bcov where we statically instrument x86-64 ELF binaries to track code coverage. However, improving efficiency and scaling to large real-world software required an orchestrated effort combining several techniques.
First, we bring a well-known probe pruning technique, for the first time, to binary-level instrumentation and effectively leverage its notion of superblocks to reduce overhead. Second, we introduce sliced microexecution, a robust technique for jump table analysis which improves CFG precision and enables us to instrument jump table entries. Additionally, smaller instructions in x86-64 pose a challenge for inserting detours. To address this challenge, we aggressively exploit padding bytes. Also, we introduce a greedy scheme to systematically host detours in neighboring basic blocks.
We evaluate bcov on a corpus of 95 binaries compiled from eight popular and well-tested packages like FFmpeg and LLVM. Two instrumentation policies, with different edge-level precision, are used to patch all functions in this corpus - over 1.6 million functions. Our precise policy has average performance and memory overheads of 14% and 22%, respectively. Instrumented binaries do not introduce any test regressions. The reported coverage is highly accurate with an average F-score of 99.86%. Finally, our jump table analysis is comparable to that of IDA Pro on gcc binaries and outperforms it on clang binaries.
Our work demonstrates that static instrumentation can offer unique advantages in comparison to established methods like compiler instrumentation and dynamic binary instrumentation. It also opens the door for many interesting applications of static instrumentation, which can go well beyond coverage analysis.

The construction of number fields with given Galois group fits into the framework of the inverse Galois problem. This problem remains still unsolved, although many partial results have been obtained over the last century.
Shafarevich proved in 1954 that every solvable group is realizable as the Galois group of a number field. Unfortunately, the proof does not provide a method to explicitly find such a field.
This work aims at producing a constructive version of the theorem by solving the following task: given a solvable group $G$ and a $B\in \mathbf N$, construct all normal number fields with Galois group $G$ and absolute discriminant bounded by $B$.
Since a field with solvable Galois group can be realized as a tower of abelian extensions, the main role in our algorithm is played by class field theory, which is the subject of the first part of this work.
The second half is devoted to the study of the relation between the group structure and the field through Galois correspondence.
In particular, we study the existence of obstructions to embedding problems and some criteria to predict the Galois group of an extension.

Background: The positive effect of carbohydrates from commercial beverages on soccer-specific exercise has been clearly demonstrated. However, no study is available that uses a home-mixed beverage in a test where technical skills were required. Methods: Nine subjects participated vol-untarily in this double-blind, randomized, placebo-controlled crossover study. On three testing days, the subjects performed six Hoff tests with a 3-min active break as a preload and then the Yo-Yo Intermittent Running Test Level 1 (Yo-Yo IR1) until exhaustion. On test days 2 and 3, the subjects received either a 69 g carbohydrate-containing drink (syrup–water mixture) or a carbo-hydrate-free drink (aromatic water). Beverages were given in several doses of 250 mL each: 30 min before and immediately before the exercise and after 18 and 39 min of exercise. The primary target parameters were the running performance in the Hoff test and Yo-Yo IR1, body mass and heart rate. Statistical differences between the variables of both conditions were analyzed using paired samples t-tests. Results: The maximum heart rate in Yo-Yo IR1 showed significant differ-ences (syrup: 191.1 ± 6.2 bpm; placebo: 188.0 ± 6.89 bpm; t(6) = −2.556; p = 0.043; dz = 0.97). The running performance in Yo-Yo IR1 under the condition syrup significantly increased by 93.33 ± 84.85 m (0–240 m) on average (p = 0.011). Conclusions: The intake of a syrup–water mixture with a total of 69 g carbohydrates leads to an increase in high-intensive running performance after soccer specific loads. Therefore, the intake of carbohydrate solutions is recommended for intermit-tent loads and should be increasingly considered by coaches and players.

The present work investigates the role of higher education experience in the process of students’ adult identity formation. In the broadest sense, adult identity is “seeing oneself as an adult” (Macmillan, 2007: 20), and it lays in the core of intensive processes of personal identity formation in the years following adolescence, which are for an increasing number of youth over the past decades spent in higher education. Approaches to adulthood in prior studies reveal ongoing discussions and attempts at re-conceptualisation against changing conditions and regimes of transition to adulthood. Traditionally, the so-called “objective markers” of adulthood have dominated the discourses for a long time, emphasising role transitions and demographic features as criteria for adulthood. The new research venues adding biographical approaches and subjective experiences reveal significance of inner, psychological processes of becoming an adult. However, the problem of the role of higher education in the process of students’ adult identity has not been fully illuminated thus far. The reason for this might be sought within the domain of disciplinary orientation of the field of higher education and Educational Sciences.
Higher education research focuses on the overall, “grand” effects of education, while traditional Educational Sciences have not been showing much interest in higher education topics. Substantial work has been produced from developmental sciences, psychology in particular, which has revealed an intricate forest of today’s adulthood and conditions for its attainment, leaving open a whole set of educational, social, economic, cultural antecedents, correlates and experiences affecting transition to adulthood. Besides, as analyses presented in Chapter 2 show, students’ position in dominant discourses marked by political and economic imperatives is marginal. Their experiences and voices are in a sense excluded, making it almost impossible to infer on actual students’ personal benefits of the higher education process.
The theoretical framework for this research consists of Erikson’s (Erikson, 1959; 1963; 1968) positions on human development in post-adolescent years, and McAdams’s model of narrative identity (1988; 2011; 2018), which also arose from Eriksonian tradition. Psychosocial theory (Erikson, 1959; 1963; 1968) assumes that social institutions provide structure and guidance to personal development, whereby they create a niche for psychosocial moratorium enabling youth a period of “identity work” before taking on long-term adult commitments. Research over recent decades reporting that higher education provides opportunities for students’ self-growth, exploration and resolving key identity questions in a variety of fields (e.g., Adams and Fitch, 1983; Arnett, 2004a; Berman, Kennerley, Kennerley, 2008; Mayhew, Rockenbach, Bowman, Seifert, Wolniak, Pascarella, Terenzin, 2016) supports such theoretical stances. The present research intends to extend existing knowledge raising the central question: What role of higher education experience students perceive in their adult identity formation?
The empirical part reports on biographical research into senior year students’ lived experiences of their developmental path and their meaning to the higher education process. Students’ experiences are approached using the qualitative technique of problem-centred interviewing (PCI), which helps focus participants’ narration on the researcher’s interest and subsequent in-depth analysis of collected experiences. In total, 40 senior year students coming from diverse backgrounds were interviewed. Data were analysed in Atlas.ti software, which enabled the coding system’s better organization and browsing through transcripts. The qualitative analysis process consisted of both inductive and deductive approaches, wherein open and thematic coding techniques were performed interchangeably.
Research findings indicate that in certain groups of students – but not in all – higher education experience facilitates and enriches the process of adult identity formation granting orientation and guidelines. Students identify experiences with the highest adult identity formational potential organised in the four broad categories: relationships with teachers and peers, respectively, teaching approach and study material, and extra-curricular activities. Based on the obtained findings, four patterns of thinking about the role of higher education in students’ adult identity formation have been identified: generator of adult identity formation, a safe-zone for exploration processes, interim phase leading to adulthood, and higher education suspending adult identity formation. This formed the basis for constructing the four student types; proactive, explorer, comfort-zone and atypical student. Research findings give the rationale for rethinking the educative potential of higher education in terms of its relevance for diverse students personally – for their self-growth and forming their personal identities, in addition to the professional ones.

Mussel-inspired catechol-containing polymers provide a promising basis for developing strong biogenic adhesives (see chapter 1). In order to develop a biomimetic adhesive, solvent stable laccases were investigated for their application as biochemical catalyst for the functionalization of natural polymers (see chapter 2), such as chitosan and lignin, with catechols. Investigation of the laccase-catalysed C–N bond formation between primary amines and catechols, such as protocatechuic acid (PCA) and dihydrocaffeic acid (DHC), suggest that the reaction is promoted by a low pKa value of the primary amine used and a neutral or mildly acidic reaction pH. Since the pKa of chitosan’s amine groups is below 7, spontaneous reactions with catechols were possible, resulting in a PCA-functionalized chitosan, which achieved a tensile strength of 4.56 MPa ± 0.54 MPa on aluminum surfaces blasted with corundum (see chapter 3). For the functionalization of lignin, which was extracted with the Organosolv (OS) process, a two-step concept was required, where first L-lysine and subsequently DHC and PCA were grafted onto lignin. For DHC-lignin, a tensile strength of 169.3 kPa ± 130.6 kPa was measured (see chapter 4). Since the functionalization and curing processes use naturally occurring substances exclusively and are free of toxic chemicals, novel and sustainable bioadhesives were developed.
Moreover, differential scanning calorimetry (DSC) analysis was used to characterize the mussel-inspired chitosan adhesive (see chapter 5). Furthermore, DSC measurements were validated for monitoring biodegradation quantitatively using small sample quantities and simple sample preprocessing. Using only DSC measurements, quantifiable detection of degradation progress was possible, while at the same time qualitative assessment of changes in crystallinity (indicating incomplete biodegradation) was obtained. The implemented method is recommended for the quantification of the biodegradability of the PCA-chitosan adhesive.
This work introduces novel bio-based adhesives, as well as a new measuring technique for measuring biodegradability of various material.

Study aim: To find out, without relying on gait-specific assumptions or prior knowledge, which parameters are most important for the description of asymmetrical gait in patients after total hip arthroplasty (THA).
Material and methods: The gait of 22 patients after THA was recorded using an optical motion capture system. The waveform data of the marker positions, velocities, and accelerations, as well as joint and segment angles, were used as initial features. The random forest (RF) and minimum-redundancy maximum-relevance (mRMR) algorithms were chosen for feature selection. The results were compared with those obtained from the use of different dimensionality reduction methods.
Results: Hip movement in the sagittal plane, knee kinematics in the frontal and sagittal planes, marker position data of the anterior and posterior superior iliac spine, and acceleration data for markers placed at the proximal end of the fibula are highly important for classification (accuracy: 91.09%). With feature selection, better results were obtained compared to dimensionality reduction.
Conclusion: The proposed approaches can be used to identify and individually address abnormal gait patterns during the rehabilitation process via waveform data. The results indicate that position and acceleration data also provide significant information for this task.

In cake filtration processes, where particles in a suspension are separated by forming a filter
cake on the filter medium, the resistances of filter cake and filter medium cause a specific pressure
drop which consequently defines the process energy effort. The micromechanics of the filter cake
formation (interactions between particles, fluid, other particles and filter medium) must be considered
to describe pore clogging, filter cake growth and consolidation correctly. A precise 3D modeling
approach to describe these effects is the resolved coupling of the Computational Fluid Dynamics with
the Discrete Element Method (CFD-DEM). This work focuses on the development and validation of a
CFD-DEM model, which is capable to predict the filter cake formation during solid-liquid separation
accurately. The model uses the Lattice-Boltzmann Method (LBM) to directly solve the flow equations
in the CFD part of the coupling and the DEM for the calculation of particle interactions. The developed
model enables the 4-way coupling to consider particle-fluid and particle-particle interactions. The
results of this work are presented in two steps. First, the developed model is validated with an
empirical model of the single particle settling velocity in the transition regime of the fluid-particle
flow. The model is also enhanced with additional particles to determine the particle-particle influence.
Second, the separation of silica glass particles from water in a pressurized housing at constant pressure
is experimentally investigated. The measured filter cake, filter medium and interference resistances
are in a good agreement with the results of the 3D simulations, demonstrating the applicability of the
resolved CFD-DEM coupling for analyzing and optimizing cake filtration processes.

Model-based Systems Engineering (MBSE) has established itself as a successful approach to realize increasingly complex systems within an acceptable timeframe. However, rapidly changing and evolving systems as well as their growing distributed development pose additional challenges, especially with regard to the modifiability, adaptability and reusability of their components. In addition, the demand for highly flexible and customizable systems continues to grow. This results in a significantly greater need for an efficient variant management. Proven approaches and methods already exist in the respective development disciplines to face these challenges. A solid MBSE approach, however, must provide a system-wide solution and answer how concurrent changes in a system model can be handled efficiently, especially if several similar system variants are developed in parallel. Industrial practice still shows a great deal of uncertainty in this respect. There are no conclusive answers to many questions. How can changes in a SysML model best be supported and, in particular, transferred effectively between model variants and versions? Should one model contain all configurations or is a separate variability model more useful? Which strategies are best suited to avoid imminent discrepancies between variant configuration and implementation and how can individual model components be efficiently reused? In order to address these questions and provide practitioners with a helpful guideline, this master’s thesis examines and compares existing approaches for realizing model variants in SysML with regard to their functionality as well as their effects (positive and negative) on the overall system concept. Since the focus lies on the feasibility of the shown approaches, they are applied by means of typical evolution scenarios and subsequently evaluated with regard to relevant performance indicators such as understandability, effort, granularity and independence. It is not expected that one approach is the best choice for every initial situation and under all circumstances. The introduced evaluation system thus aims to serve on the one hand as a situational decision support and on the other hand to offer the opportunity to examine, classify and evaluate own approaches and procedures more thoroughly.