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Bifunctional organocatalysts containing primary amines for asymmetric Michael additions
No full textThe asymmetric Michael addition of nucleophilic carbonyls (via enamine) to a diverse number of Michael acceptors produces an important carbon-carbon bond, producing a truly large number of products. Over the past decade an enormous number of organocatalysts have been developed for the asymmetric Michael addition. Challenging nucleophilic carbonyl additions, e.g. a-substituted carbonyls and some cyclic carbonyls, e.g. cyclopentanone, remain and require attention in terms of stereoselectivity, catalyst loading reaction time and yield. Here we have focused on designing new organocatalysts with primary amines to overcome the above outlined challenges. We have developed two types of organocatalysts: 1) primarytertiary diamine organocatalysts and 2) non-covalent bifunctional organocatalysts. Diamines were found to be better organocatalysts for the asymmetric Michael addition of cyclopentanone to various nitroolefins. While the assembled catalysts were found to be superior for the asymmetric Michael addition of a-substituted aldehydes addition to maleimides
Organizational culture, control, and innovation
No full textThis research was conducted in order to attain three main research objectives. First, a theoretical basis for the relationship of organizational culture and innovation as well as a model for culture analysis was to be established. It was shown that the Competing Values Framework and Ouchi’s Control Theory as the underlying concept allow a comprehensive analysis of organizational culture’s relationship with innovation. Second, organizational culture’s influence on the innovation process with regards to the conflicting requirements of innovation was to be uncovered. It was a goal to find out how organizational culture could be used to improve an organization’s ambidexterity in innovation. Data from Chinese and German organizations showed that a developmental culture supports information acquisition and obtaining innovation outcomes. The people oriented group culture fosters efficient innovation project execution. Third, specific differences between organizational culture’s influence on innovation in China and in Germany as an example of a Western cultural setting were to be identified. While structural equation modeling revealed certain similarities in both samples, the differences were not as systematic as predicted by the theory. Based on these results a theoretical model was developed that explains radical innovation on the organizational, group, and the individual level
Beneath the Surface of Intolerance Studies on the acceptance of Muslims in Western Europe
No full textResearch on the accommodation and integration of minorities in their host societies typically pays little attention to the acceptance of minorities by the host society’s population. The studies collected in this dissertation focus on the opinions of the non-Muslim Western majority population and examine (1) if there is public support among the non-Muslim majority population for Muslims to follow their own practices and lifestyle, (2) whether the willingness to restrict Muslims’ civil liberties is limited to those who are prejudiced against Muslims, (3) if individual value orientations and perceptions of threat posed by Muslims and Islam explain variation in support for such restrictions, and (4) how individual value orientations and perceptions of threat interact with having an anti-Muslim attitude in explaining support for restricting Muslims’ liberties.The studies in this dissertation use a quantitative approach and analyse large sets of survey data collected in Germany, the Netherlands, France and the United Kingdom. Results show that the majority population is generally quite supportive of Muslims who want to follow their own lifestyle. The willingness to restrict Muslims’ liberties differs according to the societal context and the specifics of what people were asked to support, and is influenced by major international events such as 9/11. Furthermore, support for restrictions is also found among non-prejudiced respondents, indicating that other factors than a personal dislike are important in explaining support for a minority’s liberties. Individual value orientations and perceptions of threat are two of such factors that contribute to explaining support for Muslims’ liberties and of which the relevance stretches beyond those being prejudiced against Muslims
Wave packet simulations of nonlinear spectroscopy and excitation transfer in molecular systems
No full textThe theoretical framework of wave packet dynamics can be applied to describe many aspects in molecular physics and the interaction of matter and light. In this thesis wave packet dynamics occurring in various molecular systems have been investigated. This includes the simulations of nuclear wave packet dynamics in different electronic states of diatomic molecules initiated by femtosecond laser pulses. With these simulations the theoretical analyses of femtosecond time-resolved four-wave mixing experiments was possible. Furthermore a theoretical description of non-resonant multi-photon excitations has been given, which allows to study the wave packet dynamics initiated by such processes in the time domain. This is essential for the application of non-resonant femtosecond laser pulse excitations to control and investigate molecular dynamics. A further focus of this thesis is the investigation of excitation energy transfer in biological pigment complexes. A hybrid quantum classical approach is applied to describe excitonic wave packet dynamics in such complex molecular aggregates. This approach was verified within an artificial test system an then applied to the light harvesting system II of a purple bacteria. To perform simulations on this system, data from all-atom classical molecular dynamics simulations have been used to construct a model system for this complex. This allowed for the investigation of the excitation energy transfer dynamics which are an important aspect of the light harvesting process in photosynthesis. For these systems it was shown that the wave packet approach in combination with classical molecular dynamics simulations is a powerful tool to describe quantum dynamical processes in large molecular systems
Towards a Specification-based Quality Guarantee for Geo Raster Web Services
No full textGeo raster web services provide access to detailed and rich sets of geospatial information used in multidisciplinary earth system science research, such as solar, atmosphere, ocean, cryosphere, solid earth, and biosphere research. However, the heterogeneity of services deployed in these disciplines tends to weaken the interoperability of todays highly multidisciplinary earth system science research. Several syntactical and semantic approaches have been investigated, such as similarity assessment, inconsistency resolution and standardization, to overcome this heterogeneity obstacle. Among them, standardization is a promising approach, which has the potential to achieve interoperability by combing methods of best practices and making them generally accepted within communities at large. Families of geo service standards have been developed and maintained by international organizations, such as the Open Geospatial Consortium (OGC) and the International Standardization Organization (ISO). To ensure the interoperability of implementations which claim to adhere to those standards, conformance testing programs have been set up by some of the standardizing bodies. For instance, the OGC has set up a conformance testing program with open test for each OGC standard. This constitutes a more comprehensive conformance testing in the field of geo web services than human inspection and closed source approaches. The approach follows a specification-based black box approach. This approach organizes specification requirements as assertions and groups them by functional modules. However, there is no methodology to coherently classify these assertions; neither the maturity of derived tests nor their completeness can be proven based on this approach. The goal of this thesis is to establish a model to evaluate an existing standardization approach and to evaluate the extent to which the specification itself supports the evaluation of confidence in service implementations, tests and test results. We propose a Request Parameter Relationship Analysis approach to master service testing complexity and maturity. Deductive reasoning is used to address reference output adoption according to the corresponding conditional statements and service facts. By addressing the relations among individual conformance statements, we propose the integrated dependency and goal model. We present a sequential evaluation schedule and prove the stable status in an isolated testing environment. These approaches provide a basis for analyzing service compliance, test maturity, and the validity of global statements. As our study example, we use the OGC WCS standard series as it offers a suitably formalized model for conformance testing. These approaches are applied to a real-life application, concretely testing the OGC WCS 2.0 geo service standard. The outcomes of this thesis contribute to the development of specifications, services and test suites for several standards whose normative conformance tests are specified using our approach. As a result, improved interoperation of geo raster web services under evolving implementations is expected in the future
Reservoir Computing and Self-Organized Neural Hierarchies
No full textThere is a growing understanding that machine learning architectures have to be much bigger and more complex to approach any intelligent behavior. There is also a growing understanding that purely supervised learning is inadequate to train such systems. A recent paradigm of artificial recurrent neural network (RNN) training under the umbrella-name Reservoir Computing (RC) demonstrated that training big recurrent networks (the reservoirs) differently than supervised readouts from them is often better. It started with Echo State Networks (ESNs) and Liquid State Machines ten years ago where the reservoir was generated randomly and only linear readouts from it were trained. Rather surprisingly, such simply and fast trained ESNs outperformed classical fully-trained RNNs in many tasks. While full supervised training of RNNs is problematic, intuitively there should also be something better than a random network. In recent years RC became a vivid research field extending the initial paradigm from fixed random reservoir and trained output into using different methods for training the reservoir and the readout. In this thesis we overview existing and investigate new alternatives to the classical supervised training of RNNs and their hierarchies. First we present a taxonomy and a systematic overview of the RNN training approaches under the RC umbrella. Second, we propose and investigate the use of two different neural network models for the reservoirs together with several unsupervised adaptation techniques, as well as unsupervisedly layer-wise trained deep hierarchies of such models. We rigorously empirically test the proposed methods on two temporal pattern recognition datasets, comparing it to the classical reservoir computing state of art
Resource-Aware Decomposition of Geoprocessing Services Based on Declarative Request Languages
No full textDistributed, service-oriented systems are often used today for geospatial data access and processing. However, it is difficult to find methods for easy, flexible, and automatic composition and orchestration of workflow of geo-services. A promising approach at addressing this problem is provided by the Open Geospatial Consortium (OGC) Web Coverage Processing Service (WCPS). This service offers a multidimensional raster processing query language with formal semantics and we believe that this language contains sufficient information for an automatic orchestration. Therefore, this thesis focuses on investigating the means to dynamically and efficiently distribute WCPS-based web service request across several heterogeneous nodes as sub-requests, and managing the execution of, and the aggregation of the results of those sub-requests. Task distribution is based, among others, on the individual node capabilities and availability, network capabilities, and source data locations. A key goal is to dynamically optimize a global service quality function while also considering a global service cost function. This thesis, therefore, involves a highly interdisciplinary approach which combines results from geo-processing, distributed computing, workflow scheduling, service oriented computing, and distributed query optimization and execution. We propose D-WCPS (Distributed WCPS), a framework in which coverage processing query can be dynamically distributed among several WCPS servers . Servers can join the network by registering with any server in the network, and every server publishes its processing capacities and locally available data to the WCPS registry which is mirrored across all servers. Likewise, each of the servers in the framework can decompose a query to a distributed query, and also, coordinate the execution of a distributed query using information from its WCPS registry. Other contributions of this thesis include query optimization and decomposition algorithms; inter-operator, intra-operator, and inter-tuple parallelism methods for coverage processing; cost model and sever calibrations for distributed coverage processing; P2P-based orchestration model; mirrored registry synchronization techniques etc. D-WCPS has been implemented and tested in clusters and clouds. Evaluation of our scheduling and distributed execution model shows remarkable speedups in the execution of different distributed WCPS queries. Several servers can, therefore, efficiently share data and computation with respect to dynamic, resource-aware coverages processing
Complexes of Selected Main Group Element Chlorides and Fluorides with Sterically Non-Demanding Carbenes
No full textSince their first isolation in 1991, N-heterocyclic carbenes (NHC) have become an established class of ligands in organometallic and coordination chemistry. In the beginning, these compounds were considered as a chemical curiosity, synthesized for fundamental studies in the laboratory. Later on, their extraordinary properties as ligands in coordination chemistry were recognized and found to be superior by means of electron donation, thermal stability and chemical inertness compared to the already established class of phosphine-ligands. Although many routes for the synthesis of carbene-coordinated transition metal complexes have become established, almost all carbene complexes of main group elements are synthesized by addition of free uncoordinated carbenes. The aim of this work was to investigate synthetic procedures to obtain main group element complexes coordinated with sterically non-demanding carbenes. As these carbene ligands are not stable in their free form, indirect routes for the synthesis of complexes thereof needed to be developed. The two synthetic methods of oxidative addition and carbene-transfer were successfully adopted for the synthesis of carbene-coordinated main group element complexes. As precursors for the oxidative addition reactions, cyclic and acyclic chloro-amidinium chlorides were chosen, which are already used for the synthesis of transition metal carbene complexes. Furthermore, the symmetric fluorine analogs α,α-difluoro-dialkylamines, as well as asymmetric α,α-difluoro-dialkylamines are introduced as carbene precursors. Neutral, hexacoordinated complexes of phosphorus(V) are presented, prepared by oxidative addition of the aforementioned fluorine-containing precursors to different phosphorus(III) compounds. The complexes are characterized and discussed by means of multinuclear NMR spectroscopy and single crystal XRD. Furthermore, three different applications for these phosphorus(V) carbene complexes are given; as an overcharge additive used in state-of-the-art lithium-ion batteries, as liquid crystal compounds and as ionic liquid precursors for carbene-phosphorus cleavage reactions using anhydrous HF. A comparative study on the carbon homologs silicon, germanium and tin was made by synthesizing chloro- and fluoro- complexes in oxidation state +IV, coordinated by cyclic and acyclic carbene ligands via oxidative addition to the respective precursors. All complexes are characterized and discussed by means of multinuclear NMR spectroscopy and by single crystal XRD. Moreover, computational (DFT) studies were made for the silicon(IV) carbene complex NHC-SiCl4 (NHC = 1,3-dimethylimidazolidin-2-ylidene), which conclude that NHC-transfer reactions are feasible using this compound. The theoretical results were proven by NHC-transfer reactions from NHC-SiCl4 to phosphorus(III) compounds to give the NHC-coordinated complexes NHC-PCl2R (R = Cl, Ph, Me), which were studied and discussed by multinuclear NMR-spectroscopy and by single crystal XRD. The complex NHC-PCl3 was oxidized to give a hexacoordinated complex of phosphorus(V), without loss of the NHC-ligand. Furthermore, NHC-transfer was made towards nickel(II) and palladium(II) chloride, to obtain the respective bis-carbene complexes (NHC)2MCl2 (M = Ni, Pd)
Scalable bioinformatic methods and resources for ribosomal RNA gene based studies
No full textThe identification and classification of microorganisms relies heavily on the interpretation and manipulation of genetic material. In constrast to for example plants or animals, microbes have few easily observed morphological or phenetic traits by which they can be distinguished. Yet, microorganisms are ubiquitous, having adapted to essentially every environment on earth. The extreme diversity that can therefore be expected is observable on a genetic level. In order to structure microbial life into taxonomic hierarchies and assess both diversity and relative abundances, molecular and computational methods make use of marker genes. In microbiology, the most frequently used marker genes are the small and large subunit (SSU and LSU) ribosomal RNA (rRNA) genes (16S/18S and 23S/28S, respectively). Their popularity in combination with technological progress, especially relating to sequencing methods, has created a vast pool of characterized SSU and LSU gene sequences. The breadth of available and described sequences is of great benefit to diversity studies, as it enhances the precision at which organisms can be identified. The wealth of information inherent in this pool of data can also be harnessed in phylogenetic studies. However, the work-flows employed were developed at a time when sequence data was scarce and expensive, thus made no consideration of scalability in their design. Yet today, sequence data has become both cheap and abundant. With the SILVA database project we have created a central resource that provides a comprehensive collection of preprocessed, high quality sequence data. The databases include both the small and the large subunit rRNA genes (SSU and LSU) and cover all three domains. The sequences are quality controlled, enriched with contextual data from diverse sources and mutually aligned. A taxonomically labeled phylogenetical guide tree is included with the databases. Standardized subsets of the databases are offered to address the competing demands for comprehensiveness (Parc dataset), optimal quality (Ref dataset) and manageable database size (RefNR dataset). The alignment tool SINA was developed for use in the SILVA pipeline and made generally available. SINA pursues an add-to-alignment approach using POA techniques and a modified dynamic programming recursion that guarantees fixed alignment width. SINA is sufficiently reliable and robust to allow unsupervised MSA computation. As the sequences are aligned individually, it also scales very well to large sequence numbers. Scalability limitations in the ARB software for sequence analysis were resolved. This included porting ARB to 64 bit architecture, fixing database schema limitations and improving performance and usability. Several tools have been implemented as part of the SILVA web interface. These allow extracting arbitrarily defined subsets through search and filtering mechanisms, aligning user submitted sequence data and evaluating probes using entire respective SILVA database. Three related studies aiming at improving the primary data situation have been completed. A standardization effort was undertaken to increase the availability of complete and consistent contextual data. A comparison between SSU and LSU resolution based on the GOS meta-genomes showed the potential of relying on LSU data instead of or in addition to SSU data. Lastly, the large amount of high quality sequence data in the SILVA database and the mechanisms developed to build these databases were employed in an evaluation of commonly used primers
Influence of Lipopolysaccharides (LPS) on Antibiotic Permeation
No full textThe outer membrane of Gram-negative bacteria and the interaction of different antimicrobial agents were in the focus of this work. It could be shown that classical antibiotics like enrofloxacin as well as different antimicrobial peptides interact with membrane components such as lipopolysaccharides (LPS) as well as with membrane proteins. The outer membrane protein which was investigated in this study was the outer membrane protein F (OmpF). It showed different behaviours if it was reconstituted into membranes depending on the membrane composition and different interactions with various antimicrobial agents. The antimicrobial agents which were used in this work were enrofloxacin, as one example for classical antibiotics (quinolones), and a selection of different antimicrobial peptides including LL20, polymyxin B, hBD-3-l, and poly-Llysine. All of these substances were tested to determine if they showed interactions with LPS and OmpF utilizing several methods. The methods applied were biophysical as well as biological techniques like the Montal-Mueller technique, Foerster resonance energy transfer (FRET) spectroscopy, polarisation measurements, the analysis of the minimal inhibitory concentration, and several others. The results of this study indicate complex interactions of different membrane components of the Gram-negative bacterial outer membrane with different antimicrobial agents. All components and substances influence each other