Refine
Year of publication
- 2017 (52) (remove)
Document Type
- Doctoral Thesis (42)
- Preprint (3)
- Periodical Part (2)
- Article (1)
- Diploma Thesis (1)
- Lecture (1)
- Other (1)
- Working Paper (1)
Language
- English (52) (remove)
Has Fulltext
- yes (52)
Keywords
- sensor fusion (2)
- A/D conversion (1)
- ADAS (1)
- AFDX (1)
- Ableitungsfreie Optimierung (1)
- Accountability (1)
- Achslage (1)
- Anion recognition (1)
- Automation (1)
- Backlog (1)
Faculty / Organisational entity
- Kaiserslautern - Fachbereich Mathematik (17)
- Kaiserslautern - Fachbereich Chemie (11)
- Kaiserslautern - Fachbereich Informatik (7)
- Kaiserslautern - Fachbereich Maschinenbau und Verfahrenstechnik (6)
- Kaiserslautern - Fachbereich Elektrotechnik und Informationstechnik (5)
- Kaiserslautern - Fachbereich Physik (3)
- Kaiserslautern - Fachbereich Wirtschaftswissenschaften (2)
- Kaiserslautern - Fachbereich Biologie (1)
This paper presents a method for simultaneous classification and robust tracking of traffic participants based on the labeled random finite set (RFS) tracking framework. Specifically, a method to integrate the object class information into the tracking loop of the multiple model labeled multi-Bernoulli (MMLMB) filter, using Dempster-Shafer evidence theory is presented. The multi-object state is estimated using the detections from the sensors and by propagation of multi-object density in a Bayesian fashion. Parallelly, the object class information is also predicted and updated recursively. The underlying object class information required for this could typically be obtained from different types of sensor such as radar, lidar and camera, using classical perception or more recent deep learning methods. On one hand, this enables an unified classification and tracking of traffic participants. On the other hand, it also increases the robustness of multi-object tracking, as the parameters of the tracking algorithm could be adapted using the class information. Moreover, using the Dempster-Shafer method for fusing class information from different sensor sources improves the overall performance, especially when the sensors have contradicting classification.
Due to their superior weight-specific mechanical properties, carbon fibre epoxy composites (CFRP) are commonly used in aviation industry. However, their brittle failure behaviour limits the structural integrity and damage tolerance in case of impact (e.g. tool drop, bird strike, hail strike, ramp collision) or crash events. To ensure sufficient robustness, a minimum skin thickness is therefore prescribed for the fuselage, partially exceeding typical service load requirements from ground or flight manoeuvre load cases. A minimum skin thickness is also required for lightning strike protection purposes and to enable state-of-the-art bolted repair technology. Furthermore, the electrical conductivity of CFRP aircraft structures is insufficient for certain applications; additional metal components are necessary to provide electrical functionality (e.g. metal meshes on the outer skin for lightning strike protection, wires for electrical bonding and grounding, overbraiding of cables to provide electromagnetic shielding). The corresponding penalty weights compromise the lightweight potential that is actually given by the structural performance of CFRP over aluminium alloys.
Former research attempts tried to overcome these deficits by modifying the resin system (e.g. by addition of conductive particles or toughening agents) but could not prove sufficient enhancements. A novel holistic approach is the incorporation of highly conductive and ductile continuous metal fibres into CFRP. The basic idea of this hybrid material concept is to take advantage of both the electrical and mechanical capabilities of the integrated metal fibres in order to simultaneously improve the electrical conductivity and the damage tolerance of the composite. The increased density of the hybrid material is over-compensated by omitting the need for additional electrical system installation items and by the enhanced structural performance, enabling a reduction of the prescribed minimum skin thickness. Advantages over state-of-the-art fibre metal laminates mainly arise from design and processing technology aspects.
In this context, the present work focuses on analysing and optimising the structural and electrical performance of such hybrid composites with shares of metal fibres up to 20 vol.%. Bundles of soft-annealed austenitic steel or copper cladded low carbon steel fibres with filament diameters of 60 or 63 µm are considered. The fibre bundles are distinguished by high elongation at break (32 %) and ultimate tensile strength (900 MPa) or high electrical conductivity (2.4 × 10^7 S/m). Comprehensive researches are carried out on the fibre bundles as well as on unidirectional and multiaxial laminates. Both hybrid composites with homogeneous and accumulated steel fibre arrangement are taken into account. Electrical in-plane conductivity, plain tensile behaviour, suitability for bolted joints as well as impact and perforation performance of the composite are analysed. Additionally, a novel non-destructive testing method based on measurement of deformation-induced phase transformation of the metastable austenitic steel fibres is discussed.
The outcome of the conductivity measurements verifies a correlation of the volume conductivity of the composite with the volume share and the specific electrical resistance of the incorporated metal fibres. Compared to conventional CFRP, the electrical conductivity in parallel to the fibre orientation can be increased by one to two orders of magnitude even for minor percentages of steel fibres. The analysis, however, also discloses the challenge of establishing a sufficient connection to the hybrid composite in order to entirely exploit its electrical conductivity.
In case of plain tensile load, the performance of the hybrid composite is essentially affected by the steel fibre-resin-adhesion as well as the laminate structure. Uniaxial hybrid laminates show brittle, singular failure behaviour. Exhaustive yielding of the embedded steel fibres is confined to the arising fracture gap. The high transverse stiffness of the isotropic metal fibres additionally intensifies strain magnification within the resin under transverse tensile load. This promotes (intralaminar) inter-fibre-failure at minor composite deformation. By contrast, multiaxial hybrid laminates exhibit distinctive damage evolution. After failure initiation, the steel fibres extensively yield and sustain the load-carrying capacity of angularly (e.g. ±45°) aligned CFRP plies. The overall material response is thus not only a simple superimposition but a complex interaction of the mechanical behaviour of the composite’s constituents. As a result of this post-damage performance, an ultimate elongation of over 11 % can be proven for the hybrid laminates analysed in this work. In this context, the influence of the steel fibre-resin adhesion on the failure behaviour of the hybrid composite is explicated by means of an analytical model. Long term exposure to corrosive media has no detrimental effect on the mechanical performance of stainless steel fibre reinforced composites. By trend, water uptake increases the maximum elongation at break of the hybrid laminate.
Moreover, the suitability of CFRP for bolted joints can partially be improved by the integration of steel fibres. While the bearing strength basically remains nearly unaffected, the bypass failure behaviour (ε_{max}: +363 %) as well as the head pull-through resistance (E_{a,BPT}: +81 %) can be enhanced. The improvements primarily concern the load-carrying capacity after failure initiation. Additionally, the integrated ductile steel fibres significantly increase the energy absorption capacity of the laminate in case of progressive bearing failure by up to 63 %.
However, the hybrid composite exhibits a sensitive low velocity/low mass impact behaviour. Compared to conventional CFRP, the damage threshold load of very thin hybrid laminates is lower, making them prone for delamination at minor, non-critical impact energies. At higher energy levels, however, the impact-induced delamination spreads less since most of the impact energy is absorbed by yielding of the ductile metal fibres instead of crack propagation. This structural advantage compared to CFRP gains in importance with increasing impact energy. The plastic deformation of the metastable austenitic steel fibres is accompanied by a phase transformation from paramagnetic γ-austenite to ferromagnetic α’-martensite. This change of the magnetic behaviour can be used to detect and evaluate impacts on the surface of the hybrid composite, which provides a simple non-destructive testing method. In case of low velocity/high mass impact, integration of ductile metal fibres into CFRP enables to address spacious areas of the laminate for energy absorption purposes. As a consequence, the perforation resistance of the hybrid composite is significantly enhanced; by addition of approximately 20 vol.% of stainless steel fibres, the perforation strength can be increased by 61 %, while the maximum energy absorption capacity rises by 194 %.
Following the ideas presented in Dahlhaus (2000) and Dahlhaus and Sahm (2000) for time series, we build a Whittle-type approximation of the Gaussian likelihood for locally stationary random fields. To achieve this goal, we extend a Szegö-type formula, for the multidimensional and local stationary case and secondly we derived a set of matrix approximations using elements of the spectral theory of stochastic processes. The minimization of the Whittle likelihood leads to the so-called Whittle estimator \(\widehat{\theta}_{T}\). For the sake of simplicity we assume known mean (without loss of generality zero mean), and hence \(\widehat{\theta}_{T}\) estimates the parameter vector of the covariance matrix \(\Sigma_{\theta}\).
We investigate the asymptotic properties of the Whittle estimate, in particular uniform convergence of the likelihoods, and consistency and Gaussianity of the estimator. A main point is a detailed analysis of the asymptotic bias which is considerably more difficult for random fields than for time series. Furthemore, we prove in case of model misspecification that the minimum of our Whittle likelihood still converges, where the limit is the minimum of the Kullback-Leibler information divergence.
Finally, we evaluate the performance of the Whittle estimator through computational simulations and estimation of conditional autoregressive models, and a real data application.
Computational simulations run on large supercomputers balance their outputs with the need of the scientist and the capability of the machine. Persistent storage is typically expensive and slow, its peformance grows at a slower rate than the processing power of the machine. This forces scientists to be practical about the size and frequency of the simulation outputs that can be later analyzed to understand the simulation states. Flexibility in the trade-offs of flexibilty and accessibility of the outputs of the simulations are critical the success of scientists using the supercomputers to understand their science. In situ transformations of the simulation state to be persistently stored is the focus of this dissertation.
The extreme size and parallelism of simulations can cause challenges for visualization and data analysis. This is coupled with the need to accept pre partitioned data into the analysis algorithms, which is not always well oriented toward existing software infrastructures. The work in this dissertation is focused on improving current work flows and software to accept data as it is, and efficiently produce smaller, more information rich data, for persistent storage that is easily consumed by end-user scientists. I attack this problem from both a theoretical and practical basis, by managing completely raw data to quantities of information dense visualizations and study methods for managing both the creation and persistence of data products from large scale simulations.
In this thesis we address two instances of duality in commutative algebra.
In the first part, we consider value semigroups of non irreducible singular algebraic curves
and their fractional ideals. These are submonoids of Z^n closed under minima, with a conductor and which fulfill special compatibility properties on their elements. Subsets of Z^n
fulfilling these three conditions are known in the literature as good semigroups and their ideals, and their class strictly contains the class of value semigroup ideals. We examine
good semigroups both independently and in relation with their algebraic counterpart. In the combinatoric setting, we define the concept of good system of generators, and we
show that minimal good systems of generators are unique. In relation with the algebra side, we give an intrinsic definition of canonical semigroup ideals, which yields a duality
on good semigroup ideals. We prove that this semigroup duality is compatible with the Cohen-Macaulay duality under taking values. Finally, using the duality on good semigroup ideals, we show a symmetry of the Poincaré series of good semigroups with special properties.
In the second part, we treat Macaulay’s inverse system, a one-to-one correspondence
which is a particular case of Matlis duality and an effective method to construct Artinian k-algebras with chosen socle type. Recently, Elias and Rossi gave the structure of the inverse system of positive dimensional Gorenstein k-algebras. We extend their result by establishing a one-to-one correspondence between positive dimensional level k-algebras and certain submodules of the divided power ring. We give several examples to illustrate
our result.
Annual Report 2017
(2017)
The present situation of control engineering in the context of automated production can be described as a tension field between its desired outcome and its actual consideration. On the one hand, the share of control engineering compared to the other engineering domains has significantly increased within the last decades due to rising automation degrees of production processes and equipment. On the other hand, the control engineering domain is still underrepresented within the production engineering process. Another limiting factor constitutes a lack of methods and tools to decrease the amount of software engineering efforts and to permit the development of innovative automation applications that ideally support the business requirements.
This thesis addresses this challenging situation by means of the development of a new control engineering methodology. The foundation is built by concepts from computer science to promote structuring and abstraction mechanisms for the software development. In this context, the key sources for this thesis are the paradigm of Service-oriented Architecture and concepts from Model-driven Engineering. To mold these concepts into an integrated engineering procedure, ideas from Systems Engineering are applied. The overall objective is to develop an engineering methodology to improve the efficiency of control engineering by a higher adaptability of control software and decreased programming efforts by reuse.
The proliferation of sensors in everyday devices – especially in smartphones – has led to crowd sensing becoming an important technique in many urban applications ranging from noise pollution mapping or road condition monitoring to tracking the spreading of diseases. However, in order to establish integrated crowd sensing environments on a large scale, some open issues need to be tackled first. On a high level, this thesis concentrates on dealing with two of those key issues: (1) efficiently collecting and processing large amounts of sensor data from smartphones in a scalable manner and (2) extracting abstract data models from those collected data sets thereby enabling the development of complex smart city services based on the extracted knowledge.
Going more into detail, the first main contribution of this thesis is the development of methods and architectures to facilitate simple and efficient deployments, scalability and adaptability of crowd sensing applications in a broad range of scenarios while at the same time enabling the integration of incentivation mechanisms for the participating general public. During an evaluation within a complex, large-scale environment it is shown that real-world deployments of the proposed data recording architecture are in fact feasible. The second major contribution of this thesis is the development of a novel methodology for using the recorded data to extract abstract data models which are representing the inherent core characteristics of the source data correctly. Finally – and in order to bring together the results of the thesis – it is demonstrated how the proposed architecture and the modeling method can be used to implement a complex smart city service by employing a data driven development approach.
We continue in this paper the study of k-adaptable robust solutions for combinatorial optimization problems with bounded uncertainty sets. In this concept not a single solution needs to be chosen to hedge against the uncertainty. Instead one is allowed to choose a set of k different solutions from which one can be chosen after the uncertain scenario has been revealed. We first show how the problem can be decomposed into polynomially many subproblems if k is fixed. In the remaining part of the paper we consider the special case where k=2, i.e., one is allowed to choose two different solutions to hedge against the uncertainty. We decompose this problem into so called coordination problems. The study of these coordination problems turns out to be interesting on its own. We prove positive results for the unconstrained combinatorial optimization problem, the matroid maximization problem, the selection problem, and the shortest path problem on series parallel graphs. The shortest path problem on general graphs turns out to be NP-complete. Further, we present for minimization problems how to transform approximation algorithms for the coordination problem to approximation algorithms for the original problem. We study the knapsack problem to show that this relation does not hold for maximization problems in general. We present a PTAS for the corresponding coordination problem and prove that the 2-adaptable knapsack problem is not at all approximable.
The cytosolic Fe65 adaptor protein family, consisting of Fe65, Fe65L1 and Fe65L2 is involved in many intracellular signaling pathways linking via its three interaction domains a continuously growing list of proteins by facilitating functional interactions. One of the most important binding partners of Fe65 family proteins is the amyloid precursor protein (APP), which plays an important role in Alzheimer Disease.
To gain deeper insights in the function of the ubiquitously expressed Fe65 and the brain enriched Fe65L1, the goal of my study was I) to analyze their putative synaptic function in vivo, II) to examine structural analysis focusing on a putative dimeric complex of Fe65, III) to consider the involvement of Fe65 in mediating LRP1 and APP intracellular trafficking in murine hippocampal neurons. By utilizing several behavioral analyses of Fe65 KO, Fe65L1 KO and Fe65/Fe65L1 DKO mice I could demonstrate that the Fe65 protein family is essential for learning and memory as well as grip strength and locomotor activity. Furthermore, immunohistological as well as protein biochemical analysis revealed that the Fe65 protein family is important for neuromuscular junction formation in the peripheral nervous system, which involves binding of APP and acting downstream of the APP signaling pathway. Via Co-immunoprecipitation analysis I could verify that Fe65 is capable to form dimers ex vivo, which exclusively occur in the cytosol and upon APP expression are shifted to membrane compartments forming trimeric complexes. The influence of the loss of Fe65 and/or Fe65L1 on APP and/or LRP1 transport characteristics in axons could not be verified, possibly conditioned by the compensatory effect of Fe65L2. However, I could demonstrate that LRP1 affects the APP transport independently of Fe65 by shifting APP into slower types of vesicles leading to changed processing and endocytosis of APP.
The outcome of my thesis advanced our understanding of the Fe65 protein family, especially its interplay with APP physiological function in synapse formation and synaptic plasticity.
This paper presents a case study of duty rostering for physicians at a department of orthopedics and trauma surgery. We provide a detailed description of the rostering problem faced and present an integer programming model that has been used in practice for creating duty rosters at the department for more than a year. Using real world data, we compare the model output to a manually generated roster as used previously by the department and analyze the quality of the rosters generated by the model over a longer time span. Moreover, we demonstrate how unforeseen events such as absences of scheduled physicians are handled.
For many years, most distributed real-time systems employed data communication systems specially tailored to address the specific requirements of individual domains: for instance, Controlled Area Network (CAN) and Flexray in the automotive domain, ARINC 429 [FW10] and TTP [Kop95] in the aerospace domain. Some of these solutions were expensive, and eventually not well understood.
Mostly driven by the ever decreasing costs, the application of such distributed real-time system have drastically increased in the last years in different domains. Consequently, cross-domain communication systems are advantageous. Not only the number of distributed real-time systems have been increasing but also the number of nodes per system, have drastically increased, which in turn increases their network bandwidth requirements. Further, the system architectures have been changing, allowing for applications to spread computations among different computer nodes. For example, modern avionics systems moved from federated to integrated modular architecture, also increasing the network bandwidth requirements.
Ethernet (IEEE 802.3) [iee12] is a well established network standard. Further, it is fast, easy to install, and the interface ICs are cheap [Dec05]. However, Ethernet does not offer any temporal guarantee. Research groups from academia and industry have presented a number of protocols merging the benefits of Ethernet and the temporal guarantees required by distributed real-time systems. Two of these protocols are: Avionics Full-Duplex Switched Ethernet (AFDX) [AFD09] and Time-Triggered Ethernet (TTEthernet) [tim16]. In this dissertation, we propose solutions for two problems faced during the design of AFDX and TTEthernet networks: avoiding data loss due to buffer overflow in AFDX networks with multiple priority traffic, and scheduling of TTEthernet networks.
AFDX guarantees bandwidth separation and bounded transmission latency for each communication channel. Communication channels in AFDX networks are not synchronized, and therefore frames might compete for the same output port, requiring buffering to avoid data loss. To avoid buffer overflow and the resulting data loss, the network designer must reserve a safe, but not too pessimistic amount of memory of each buffer. The current AFDX standard allows for the classification of the network traffic with two priorities. Nevertheless, some commercial solutions provide multiple priorities, increasing the complexity of the buffer backlog analysis. The state-of-the-art AFDX buffer backlog analysis does not provide a method to compute deterministic upper bounds
iiifor buffer backlog of AFDX networks with multiple priority traffic. Therefore, in this dissertation we propose a method to address this open problem. Our method is based on the analysis of the largest busy period encountered by frames stored in a buffer. We identify the ingress (and respective egress) order of frames in the largest busy period that leads to the largest buffer backlog, and then compute the respective buffer backlog upper bound. We present experiments to measure the computational costs of our method.
In TTEthernet, nodes are synchronized, allowing for message transmission at well defined points in time, computed off-line and stored in a conflict-free scheduling table. The computation of such scheduling tables is a NP-complete problem [Kor92], which should be solved in reasonable time for industrial size networks. We propose an approach to efficiently compute a schedule for the TT communication channels in TTEthernet networks, in which we model the scheduling problem as a search tree. As the scheduler traverses the search tree, it schedules the communication channels on a physical link. We presented two approaches to traverse the search tree while progressively creating the vertices of the search tree. A valid schedule is found once the scheduler reaches a valid leaf. If on the contrary, it reaches an invalid leaf, the scheduler backtracks searching for a path to a valid leaf. We present a set of experiments to demonstrate the impact of the input parameters on the time taken to compute a feasible schedule or to deem the set of virtual links infeasible.
This thesis presents research studies on the fundamental interplay of diatomic molecules with transition metal compounds under cryogenic conditions. The utilized setup offers a multitude of opportunities to study isolated ions: The ions can either be generated by an ElectroSpray Ionization (ESI) source or a Laser VAPorization (LVAP) cluster ion source. The setup facilitates kinetic investigations of the ions with different reaction gases under well-defined isothermal conditions. Moreover it enables cryo InfraRed (Multiple) Photon Dissociation (IR-(M)PD) spectroscopy in combination with tunable OPO/OPA laser systems. In conjunction with density functional theory (DFT) modelling, the IR(M)-PD spectra allow for an assignment of geometric minimum structures. Furthermore DFT modelling helps to identify possible reaction pathways. Altogether the presented methods allow to gain fundamental insights into molecular structures and reactivity of the investigated systems.
The first part of this thesis focuses on the interplay of N2 with different transition metal clusters (Con+, Nin+, and Fen+) by cryo IR spectroscopy and cryo kinetics. In conjunction with DFT modelling the N2 coordination was elucidated (Con+), structures were assigned (Nin+), the concept of structure related surface adsorption behavior was introduced (Nin+), and the a first explanation for the inertness if Fe17+ was given (Fen+). Furthermore this thesis provides for a case study on the coadsorption of H2 and N2 on Ru8+ that elucidates the H migration on the Ru cluster. The last part of the thesis addresses the IR spectra of in vacuo generated [Hemin]+ complexes with N2, O2, and CO. Structures and spin states were assigned with the help of DFT modelling.
Chlorogenic acids (CGA) are phenolic compounds that form during the esterification of certain trans-cinnamic acids with (-)-quinic acid. According to several human intervention studies, they may have potential health benefits. Coffee is the main source of CGA in human nutrition, and is consumed either alone or in combination with a variety of foods. For this reason, the presented study aimed to clarify whether the simultaneous consumption of food, for example, a breakfast rich in carbohydrates, with instant coffee affects the absorption and bioavailability of CGA. The research specifically focused on how various food matrices, which are consumed at the same time as a coffee beverage, will influence kinetic parameters such as area under the curve (AUC), maximum plasma concentration (cmax), and time needed to reach maximum plasma concentration (tmax).
In a randomized crossover study, fourteen healthy participants consumed either pure instant coffee or coffee with a carbohydrate- or fat-rich meal. All of the subjects consumed the same quantity of CGA (3.1 mg CGA/kg body weight). Blood samples, collected at various time points up to 15 h after instant coffee consumption, were quantitatively analysed. Additionally, three urine collection intervals were chosen over a time period of 24h. High performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) was used to determine the CGA present, along with the concentrations of respective metabolites.
During a blind data review meeting, 20 of the 56 analysed plasma metabolites were chosen for further statistical analysis. A total of 36 metabolites were monitored in the urine samples. Similar as in the plasma samples, between-treatment differences, measured through AUC, Cmax, and tmax, of various CGA derived metabolites were to estimate. Each treatment was also analysed in terms of the correlation between the plasma AUC and urinary excretion of seven metabolites.
It is already known that inter-individual variations in CGA absorption depends on gut microbial degradation and affects the efficacy of these compounds. Microorganisms present in the gastrointestinal tract metabolise CGA to form dihydroferulic acid (DHFA) and dihydrocaffeic acid (DHCA) derivatives, which precede the subsequent formation of a wide range of metabolites. Therefore stool samples were collected from the participants within 12 h before the second study day. Subsequent an ex-vivo incubation of faecal samples with 5-O-caffeoylquinic acid (5-CQA), the main chlorogenic acid found in coffee was performed. An HPLC system connected to a CoulArray® detector was used to measure the concentrations of 5-CQA and its metabolites. Reduced concentrations of 5-CQA as well as the appearance of DHCA and caffeic acid (CA) in the gut microbiota medium, were monitored to calculate the inter-individual kinetics for each compound. In addition, these samples were analysed for microbiota content by an external laboratory (L&S, Bad Bocklet, Germany). These results were used to distinguish whether the decreased or increased content of a specific microorganism was related to an individual’s decreased or increased metabolic efficiency. Finally, we used to aforementioned results to evaluate if any correlation could be drawn between the plasma appearance, urinary excretion and ability of microorganisms to degrade 5-CQA.
Strong inter-individual variation was observed for AUC, Cmax and tmax. The AUC measured the quantity of CGA in plasma samples. We noted that pure instant coffee consumption resulted in slightly higher CGA bioavailability than instant coffee with the additional consumption of a meal. However, these differences were not statistically significant. Additionally, the metabolites were divided into groups, according to similarity and chemical properties. They were further classified into three groups according to their physical structure and predicated from the area of appearance: directly from coffee (quinics), after first degradation and metabolism (phenolics, all trans-cinammic acids and their sulfates and glucuronides) as well as colonic degradation and metabolism (colonics, all dihydro compounds). These respective metabolic classes showed significant differences in the AUC values of certain classes yet no significant between-treatment differences. Our results corroborated earlier studies in that the three caffeoylquinic acid (CQA) isomers were absorbed to a lower extent whereas all feruloylquinic acids (FQA) were detected in comparably high amounts in the plasma samples of the volunteers. However, the amount of these quinic acid conjugates in the plasma samples accounted for only 0,5% of the total amount of identified. In contrast, at least 8.7% of the investigated compounds were identified to be phenolics. Dihydro compounds, the so known colonics, were identified as the most common metabolites (90.8%). Additionally, dihydroferulic acid (DHFA), meta-dihydrocoumaric acid (mDHCoA), dihydrocaffeic acid-3-sulfate (DHCA3S) and dihydroisoferulic acid (DHiFA) were identified to account for 78% of the studied metabolites, and thus represent the most abundant compounds circulating in the plasma after coffee consumption.
Irrespective of treatment, the tmax value for early metabolites (quinic and phenolic compounds) was observed between 0 and 2 h after the ingestion of coffee and tmax value for late metabolites (colonic metabolites) was observed between 7 and 10 h. The amount of colonic metabolites had not returned to the baseline level 15 h after the ingestion of coffee. The co-ingestion of breakfast and coffee, when compared to the ingestion of coffee alone, significantly increased the Cmax values for all quinic and phenolic compounds, as well as two colonic metabolites (DHCA and DHiFA). These differences also revealed that the three treatments differed in terms of the kinetics of release. Thus, future studies should use an extended plasma collection time with shorter intervals (e.g. 2 h) to provide a full pharmacokinetic profile.
There were no statistically significant between-treatment differences in the urine samples collected 24 h after coffee ingestion. However, urine samples collected within six hours of the consumption of coffee alone or in combination with a fat-rich meal showed significantly higher CGA quantities than samples collected at the same time point for coffee ingested with a carbohydrate-rich. Strong inter-individual variability and the fact that only 14 healthy subjects participated in the study hindered the identification of any clear trend between the plasma concentrations of metabolites and their excretion in urine.
Four hours after the ex vivo incubation of 5-CQA with individual faecal samples the sum of 5-CQA, CA, and DHCA varied strongly between participants. These findings could result from binding effects of the phenolic compounds with faecal constituents, further degradation or metabolism, and/or the release of bound phenolic substances before the experiment started. We hypothesized that for participants with high plasma AUCs of dihydro compounds, their incubation samples show also high concentrations of CA and DHCA in the incubation medium after four hours. No significant correlation could be found.
This study and all of the outcomes were exploratory. Due to the limited number of participants, we could only investigate tendencies for how the co-ingestion of food affects the bioavailability of CGAs and their respective metabolites following coffee consumption. Therefore, the achieved results are only indicative. Despite this limitation, the data highlight that even though all three treatments had strong similarities in the total bioavailability of CGAs and metabolites from instant coffee, there were between-treatment differences in the kinetics of release. The co-ingestion of breakfast and coffee favoured a slow and continuous release of colonic metabolites while non-metabolized coffee components were observed in plasma within the first hour when coffee was ingested alone.
In conclusion, both a shift in gastrointestinal transit time and the plasma metabolite composition were observed when the ingestion of coffee alone or in combination with breakfast were compared. These results showed that breakfast consumption induces the retarded release of chlorogenic acid metabolites in humans. The data from our human intervention study suggest that the bioavailability of chlorogenic acids from coffee and their derivatives does not only depend on chemical structure, molecular size and active or passive transport ability, but is also influenced by inter-individual differences. Therefore, we strongly recommend that future studies include metabolism experiments that focus on microbiota genotypes and/or the genotyping of individual subjects. This type of research could be pivotal to elucidating whether, and how, genotype affects the metabolic profile after chlorogenic acid intake.
Temporal Data Management and Incremental Data Recomputation with Wide-column Stores and MapReduce
(2017)
In recent years, ”Big Data” has become an important topic in academia
and industry. To handle the challenges and problems caused by Big Data,
new types of data storage systems called ”NoSQL stores” (means ”Not-only-
SQL”) have emerged.
”Wide-column stores” are one kind of NoSQL stores. Compared to relational database systems, wide-column stores introduce a new data model,
new IRUD (Insert, Retrieve, Update and Delete) semantics with support for
schema-flexibility, single-row transactions and data expiration constraints.
Moreover, each column stores multiple data versions with associated time-
stamps. Well-known examples are Google’s ”Big-table” and its open sourced
counterpart ”HBase”. Recently, such systems are increasingly used in business intelligence and data warehouse environments to provide decision support, controlling and revision capabilities.
Besides managing the current values, data warehouses also require management and processing of historical, time-related data. Data warehouses
frequently employ techniques for processing changes in various data sources
and incrementally applying such changes to the warehouse to keep it up-to-
date. Although both incremental data warehousing maintenance and temporal data management have been the subject of intensive research in the
relational database and finally commercial database products have picked up
the ability for temporal data processing and management, such capabilities
have not been explored systematically for today’s wide-column stores.
This thesis helps to address the shortcomings mentioned above. It care-
fully analyzes the properties of wide-column stores and the applicability
of mechanisms for temporal data management and incremental data ware-
house maintenance known from relational databases, extends well-known approaches and develops new capabilities for providing equivalent support in
wide-column stores.
Nonwoven materials are used as filter media which are the key component of automotive filters such as air filters, oil filters, and fuel filters. Today, the advanced engine technologies require innovative filter media with higher performances. A virtual microstructure of the nonwoven filter medium, which has similar filter properties as the existing material, can be used to design new filter media from existing media. Nonwoven materials considered in this thesis prominently feature non-overlapping fibers, curved fibers, fibers with circular cross section, fibers of apparently infinite length, and fiber bundles. To this end, as part of this thesis, we extend the Altendorf-Jeulin individual fiber model to incorporate all the above mentioned features. The resulting novel stochastic 3D fiber model can generate geometries with good visual resemblance of real filter media. Furthermore, pressure drop, which is one of the important physical properties of the filter, simulated numerically on the computed tomography (CT) data of the real nonwoven material agrees well (with a relative error of 8%) with the pressure drop simulated in the generated microstructure realizations from our model.
Generally, filter properties for the CT data and generated microstructure realizations are computed using numerical simulations. Since numerical simulations require extensive system memory and computation time, it is important to find the representative domain size of the generated microstructure for a required filter property. As part of this thesis, simulation and a statistical approach are used to estimate the representative domain size of our microstructure model. Precisely, the representative domain size with respect to the packing density, the pore size distribution, and the pressure drop are considered. It turns out that the statistical approach can be used to estimate the representative domain size for the given property more precisely and using less generated microstructures than the purely simulation based approach.
Among the various properties of fibrous filter media, fiber thickness and orientation are important characteristics which should be considered in design and quality assurance of filter media. Automatic analysis of images from scanning electron microscopy (SEM) is a suitable tool in that context. Yet, the accuracy of such image analysis tools cannot be judged based on images of real filter media since their true fiber thickness and orientation can never be known accurately. A solution is to employ synthetically generated models for evaluation. By combining our 3D fiber system model with simulation of the SEM imaging process, quantitative evaluation of the fiber thickness and orientation measurements becomes feasible. We evaluate the state-of-the-art automatic thickness and orientation estimation method that way.
In the present work the concept of decarboxylative couplings and the strategy to use carboxylates as directing groups for C-H functionalizations have been decisively improved in three ways. These concepts emphasize the multifaceted nature of aromatic carboxylic acids as expedient starting materials in homogeneous catalysis to construct highly desirable molecular scaffolds in a straightforward fashion.
In the first project, the restriction of decarboxylative biaryl synthesis to exclusively couple aryl halides with ortho-substituted benzoic acids has been overcome by a holistic optimization of a Cu/Pd bimetallic catalyst system. Long ago postulated, this is now the proof that decarboxylative cross-couplings are not intrinsically limited to different decarboxylation propensities of benzoic acids or hampered by excess halides, accessing for the first time the entire spectrum of aromatic carboxylic acids as starting materials for the decarboxylative biaryl synthesis. The second project uses the carboxyl moiety as directing group for the ortho-arylation with aryl bromides and -chlorides catalyzed by comparatively inexpensive ruthenium. The carboxylic acid group remains untouched after the ortho-functionalization giving the possibility to a wealth of further diversifications via decarboxylative ipso-substitutions. Within the same project, a Cu/Ru bimetallic catalyst system was found to be able to switch the decarboxylative biaryl coupling from the ipso- to the ortho-position, complementing the Cu/Pd system developed in the first project. In a third project, a redox neutral C-C bond formation revealed the full synthetic potential of the carboxyl group. The COOH moiety acts as a classical directing group for the C-H hydroarylation of internal alkynes to form highly desirable 2-vinyl benzoic acids. With propargylic alcohols the hydroarylation is followed by an in situ esterification, showing that after easing the C-H cleavage, the directing group can be transformed into another functional group, thus, acting as a transformable directing group. Most importantly, a new fascinating reaction mode is activated by embedding the decarboxylation within the C-H functionalization event. This mode of action is capable to solve regioselectivity issues that inherently occur when dealing with carboxylates as directing groups. A so-called deciduous directing group is cast off simultaneously within the C-H functionalization event, resulting in an inherently monoselective pathway.
These methods were developed with the permanent goal of ensuring high sustainability. They do require neither pre-functionalized starting materials nor additional oxidants and provide access to a number of chemically relevant molecules from abundant, inexpensive and toxicologically innocuous educts.
The thesis studies change points in absolute time for censored survival data with some contributions to the more common analysis of change points with respect to survival time. We first introduce the notions and estimates of survival analysis, in particular the hazard function and censoring mechanisms. Then, we discuss change point models for survival data. In the literature, usually change points with respect to survival time are studied. Typical examples are piecewise constant and piecewise linear hazard functions. For that kind of models, we propose a new algorithm for numerical calculation of maximum likelihood estimates based on a cross entropy approach which in our simulations outperforms the common Nelder-Mead algorithm.
Our original motivation was the study of censored survival data (e.g., after diagnosis of breast cancer) over several decades. We wanted to investigate if the hazard functions differ between various time periods due, e.g., to progress in cancer treatment. This is a change point problem in the spirit of classical change point analysis. Horváth (1998) proposed a suitable change point test based on estimates of the cumulative hazard function. As an alternative, we propose similar tests based on nonparametric estimates of the hazard function. For one class of tests related to kernel probability density estimates, we develop fully the asymptotic theory for the change point tests. For the other class of estimates, which are versions of the Watson-Leadbetter estimate with censoring taken into account and which are related to the Nelson-Aalen estimate, we discuss some steps towards developing the full asymptotic theory. We close by applying the change point tests to simulated and real data, in particular to the breast cancer survival data from the SEER study.
Novel Pseudocyclopeptides Containing 1,4-Disubstituted 1,2,3-Triazole Subunits for Anion Recognition
(2017)
Anion recognition is one of the most rapidly growing areas in the field of Supramolecular Chemistry due to the vital role of anions in the environment, in biology and in industry. The development of new anion binding motifs that can also be combined with known ones in a novel receptor is a timely topic. In this context, we have synthesized three cyclic pseudopeptides 16, 17 and 18, containing conventional H-bond donors (amide) in combination with, respectively, triazole C–H or triazole C–I functions.
All three receptors were synthesized by using a combination of peptide and click chemistry. Structural studies show that all three pseudopeptides adopt conformations with the triazole C-H or C-I groups pointing into the cavity center to allow them to contribute to binding. Quantitative binding studies showed that the cyclic pseudohexapeptide 1 coordinates to oxoanions (sulfate, dihydrogenphosphate, and hydrogenpyrophosphate) with different binding strengths and complex stoichiometries in 2.5 vol% water/DMSO.
Anion selectivity of 16 significantly changes when the cavity size of this pseudopeptide is increased to obtain the larger analog 17. This pseudooctapeptide forms well defined complexes with protonated phosphate anions. The complexation involves sandwiching of a cyclic tetramer of dihydrogenphosphate or a dimer of dihydrogenpyrophosphate anions by two pseudopeptide rings. Both complexes were characterized structurally in the solid state. They are stable in solution (2.5 vol% water/DMSO) as result of the interaction between hydrogen bond donors of 17 and the oxygen atoms of the anionic aggregates. The complexes can also be transferred to the gas phase without decomposition.
Anion selectivity of 16 was further altered by introducing iodine atom in the C5 position of the 1,4-disubstituted 1,2,3-triazole units. The corresponding cyclic pseudohexapeptide 18 features a smaller cavity diameter than 17 as a result of the iodide atoms and was therefore found to only coordinate to smaller spherical anions such as chloride. It forms 1:1 complexes with chloride, bromide and iodide in 2.5 vol% water/DMSO. Among the halides, 18 has highest affinity for chloride followed by bromide and iodide. The same stability trend was also observed in the gas phase by ESI/MS.
Concluding, I prepared three new macrocyclic pseudopeptides during my PhD and characterized their complexes with anions in terms of structure and affinity. All of these pseudopeptides were shown to interact with phosphate-derived anions, which renders them unique among the anion receptors developed in the Kubik group before.