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Synthesis and Catalytic Studies on Rh- and Ir-Containing Polyoxometalates And Synthesis and Characterization of d- and f-Metal-Containing Tungsto-Germanates(IV) and -Arsenates(V)
No full textPolyoxometalates (POMs) are discrete metal-oxo clusters of early transition metals in high oxidation states. The compositional and structural diversity of POMs combined with their stability and redox activity render them attractive for applications in various fields such as material sciences, medicine, magnetism and especially catalysis.
Chapter 1 consists of an introduction to the field of POMs and its most important aspects, as well as a bibliographic background for the various projects in this thesis. In Chapter 2 all experimental details are presented, such as the synthetic procedures of the starting materials (lacunary POMs, noble metal precursors, catalysts, supports, etc.) as well as the instrumentation used for materials characterization and applications. Chapter 3 introduces the background, motivation and objectives of the work conducted. Chapter 4 presents a new concept for the design and preparation of some sinter-resistant catalysts by grafting organo-rhodium and -iridium species in the cavity of the cyclic P8W48 POM host. These compounds were characterized in the solid state by single-crystal X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis (TGA) and in solution by 31P and 13C NMR spectroscopy. The actual catalysts prepared by supporting the novel POMs on the SBA15 support and these materials were then used for the hydrogenation of aromatics. In Chapter 5, the synthesis of the first examples of fully-inorganic Rh-, Ir-, Pd- and Pt derivatives of P8W48 is reported and these compounds were structurally characterized in the solid state and in solution. Chapter 6 describes the synthesis and characterization of novel RhCp*- and IrCp*-containing heteropolytungstates, which were characterized in the solid state and in solution. One highlight is the observation of W-Rh coupling in the 183W NMR spectra. Chapter 7 deals with the use of polyoxopalladates (POPs) as molecular precursors for catalysts used for the selective hydrogenation of alkynes
Graded and Generalized Geometry Methods for Gravity
No full textWe explore a framework for gauge and gravity theories, based on a combination of methods from graded symplectic and generalized geometry. We reformulate some gravitational theories in this language and establish a relation to gauge theories. The models of gravity we consider range from the type II effective string action for the NS-NS bosonic fields and other actions with T-dual fluxes, to General Relativity in the Palatini formulation with frame fields. A sketch of the technique for reconstructing non-abelian gauge theories is also given. The idea is the following: On the symplectic geometry side, we implement a grading up to degree 2 that enlarges the set of coordinates, so as to naturally support the geometric data of a metric tensor. This is essential since the metric is the fundamental field for a gravity theory. Then we implement interactions with gauge and other fields by deforming the Poisson brackets of the graded phase space coordinates. We do not deform the Hamiltonian but rather retain the free one. The relation to gauge theory is obtained via a graded version of Moser lemma: The deformation can be undone by a change of local phase space coordinates. It is carried by graded diffeomorphisms parametrized by a non-unique gauge field. The freedom is a gauge symmetry. Differential graded manifolds are classified by higher algebraic structures, Lie and Courant algebroids, that encode the symmetries of the bundle of generalized geometry. The correspondence stems from derived brackets with the Hamiltonian vector field. Here the latter is left unchanged by the deformation and all the novelty in the algebroid can be tracked back to the deformed Poisson brackets. Furthermore, we present a new formulation of generalized differential geometry that together with the algebroid brackets, enable us to characterize an affine connection, and torsion and curvature tensors on the generalized bundle. The gravity actions are obtained almost as Hilbert-Einstein actions
Rational and Evolutive Reengineering of Phosphatase: from Method Development to Understanding of Properties
No full textThe thesis focuses on directed evolution and structure function relationship of phytase from Yersinia mollaretii (Ymphytase). The “key beneficial” mutations identified in the directed evolution have been iteratively combined. Ymphytase variant with 54% improvement in thermostability (58°C for 20 min) and 200 U/mg improved activity was achieved. MD simulations results showed decreased overall Ymphytase flexibility in thermostable variant with slight increase in active site loop flexibility. The decreased flexibility might be due to improved intra-protein interactions like hydrogen bonds (G187S, K289E) and salt-bridge interaction (T77K).
Three conceptually novel methods for protein engineering have been developed in part-III (Chapter 6 – 8). Combinatorial assembly of site saturation test in protein segment (ProCASTing), a sequence independent method was developed for parallel site saturation of more than one consecutive site (4 to 8) in any part of the protein. Multisite combinatorial assembly of site saturation test (OmniCASTing), practically simple method was developed for parallel site saturation of more than one site (five) regardless of positions in the gene. Using OmniCASTing, a variant with improved thermostability, pH stability and activity was obtained. Three properties improvement might be due to cooperative effects between the new combinations of mutations compare to parent combination. Protein consensus based surface engineering (ProCoS) method combining computational analysis and molecular biology tools was developed. The utility of ProCoS method has been demonstrated by surface engineering of Ymphytase that yielded a variant with 34 amino acid substitution (20% negative polar amino acids) and 3.8 fold improvement in pH stability (pH 2.8). Two hypotheses have been proposed in part-IV (chapter 8 – 9) and validated by experimental evidences
Der Einfluss von Framing, Medienpriming, Vorurteilen und Debiasing auf die Bewertung eines Betrugs an der Solidargemeinschaft
No full textThe present study investigated to what extent attitudes toward tax evasion and social benefit fraud are influenced by framing, media priming, and the individual tendency to prejudices. It was further examined whether debiasing interventions could reduce or eliminate possible effects of framing and media priming. Tax evasion and social benefit fraud are interpreted here as a fraud on the community of solidarity.
Two experiments were conducted. First, the effect of framing of the mode of accomplishing the fraud (withhold vs withdraw resources) was investigated. Participants evaluated the behavior of individuals that withheld or withdrew resources from a community. In an additional condition, individuals who withheld resources were labeled as “wealthy” and those who withdrew resources as “unemployed” persons (priming condition). Neither framing- nor priming-effects were found. Second, the effects of framing in a more loose sense, media priming, prejudice, and debiasing were investigated. Participants were asked to dis-/agree with 11 statements about either wealthy people in context with tax evasion or unemployed people in context with social benefit fraud. Media priming was considered as a further condition: Before their judgment, participants read a newspaper article about an individual case of tax evasion or social benefit fraud. The tendency to prejudices was measured with the Social-Dominance-Orientation scale. Half of the sample received a debiasing-intervention.
The results suggest that individuals have more negative attitudes toward tax evader than toward people who committed social benefit fraud. Since no framing effects were found in the first experiment, the different attitudes cannot be attributed to the framing of the mode of accomplishing the fraud. Furthermore, media priming, prejudice, and debiasing seem to further influence attitudes towards people who have committed fraud on a community of solidarity
Performing Design Thinking Virtually – A Socio-Cognitive View on Virtual Design Thinking
No full textIn today’s world, corporate teamwork is increasingly characterized by co-creation and dispersed stakeholders that need to collaborate for specific purposes, such as innovation development (Frow et al., 2015; Yoo, 2013). The dispersed setting of team members motivates a virtual instead of an on-site performance of teamwork to increase the possibility of uniting multiple and suitable stakeholders for specific tasks, while reducing the efforts to commonly be in the same place at the same time (Lipnack & Stamps, 1999). To meet the needs of a contemporary, systematic procedure for Innovation Management in a globalized world, the collaborative and co-creative innovation development approach Design Thinking (DT) needs to be facilitated toward a virtual performance (Furmanek & Daurer, 2019; Gräßler et al., 2017; Gumienny et al., 2011).
In order to prepare the foundation for a Virtual Design Thinking (VDT) approach, an in-depth examination of commonly analog-performed DT was conducted, and its underlying principles identified. The examinations on DT enabled to further investigate how the innovation development approach can be applied virtually. This undertaking was accompanied by measurements that indicate the success of the VDT performance in adhering to a socio-cognitive view on effectiveness (Gilson et al., 2015; Hjørland, 2002).
With the aim to enable VDT, the research methodology Action Design Research was applied, which deploys practical, recurring, and meaningful interventions to gain insights regarding the collaboration of team members in a process of improving Information Systems in corporate problem contexts from a user-centered perspective (Sein et al., 2011; Veling et al., 2016). The emerging ensemble artifact, the VDT approach, mirrors an improved setting of given, real-life corporate problems (Purao et al., 2013). As a result, this dissertation presents an applicable VDT approach for companies that is perceived as satisfying and effective by the team members
Computer Simulations of Lipid Interactions and Structural Features of Bacterial Outer Membrane Channels
No full textThe outer membrane (OM) of Gram-negative bacteria contains various channels which are involved in the uptake of nutrients and antibiotics. However, the structures and functions of many OM channels are yet unknown. The research work reported in this thesis is aimed to understand the structural and functional features of three OM channels using molecular dynamics (MD) simulations in collaboration with single-molecule experiments. In the first part of the thesis, we have proposed a new protocol to study the interactions of lipopolysaccharide (LPS) with OM channels. The current state-of-the-art in the field of membrane simulations is to model the membrane channels in realistic membrane models as lipids influence the functional properties of membrane channels. However, due to the high viscosity of LPS, the interactions of OM channel with LPS and their dynamics is highly biased by the system preparation and placement of LPS molecules around the OM channels in the starting structure. Our protocol provides an improved alternative to reduce this bias and study the lipid interactions and dynamics of OM channels. A further focus of the thesis is on studying the structural and transport features of the VhChiP and OprO channels. Our collaborators have determined the crystal structures of the VhChiP channel in the open as well as in the closed state, however, the molecular details of gating are missing. To this end, we have employed MD simulations to estimate the respective free energy barrier and to predict the key residues involved in the gating of VhChiP channel. Overall, the findings presented in this thesis will improve the functional understanding of the N-terminus gating and the specificity of OM channels as well as the role of lipids in fine-tuning the dynamics of OM channels. Moreover, the protocol presented in this thesis will be helpful in studying the LPS in realistic membrane models
On Monitoring, Evaluating and Managing Benthic Ecosystems with Internet Operated Deep-sea Crawlers; The Case of Barkley Canyon Hydrates
No full textThe expansion of the effects of anthropogenic activities towards depths below the shallow continental shelf is constantly increasing, raising questions in relation to the absence of a nationally and globally coordinated monitoring and management plan, partly due to the extreme nature of deep-sea ecosystems. Internet Operated Deep-sea Crawlers operating within a network of seafloor cabled observatories can be the answer to technical and logistical issues that rise from the nature of the previously existing fixed and mobile monitoring platforms, providing long-term, high-frequency, multiparametric environmental and biological data with a broader spatial coverage, and the opportunity for 24/7 remote communication with researchers. In this Thesis I show the use of the crawler “Wally” as a monitoring tool attached to the NEPTUNE Canada cabled observatory, at the methane hydrates site of Barkley Canyon (BC, Canada).
In Chapter 2, I assessed the diel behavioral patterns of three benthic megafaunal species (i.e. sablefish Anoplopoma fimbria; pacific hagfish Eptatretus stoutii and a group of juvenile crabs) in relation to fluctuations of oceanographic parameters at the same frequency and the life habits of each particular species (i.e. movement type and trophic level), using linear video-transects conducted with the crawler in June, July and December of 2013.
In Chapter 3, I used 18 linear imaging transects (each transect ~ 30 m long), conducted with the crawler in November 2016 to detect changes in the biodiversity of the hydrates community and the spatio-temporal distribution of 7 abundant megafaunal morphospecies (i.e. taxa identified based on morphological traits), with an approach based on the Poisson probabilities of animal encounters.
Finally, in Chapter 4 I present the environmental cleaned, re-scaled and calibrated datasets generated by the instrumentation (i.e. ADCP, CTD and current meter) deployed with the crawler during September 2010 to January 2015
Generation and crystallization of empty disulfide-stabilized MHC class I proteins
No full textMHC (Major Histocompatibility complex) class I molecules are membrane proteins that bind intracellular peptides of eight to ten amino acids, bring them to the surface, and present them to cytotoxic T cells of the immune system. MHC class I antigen presentation is critical to protect vertebrates against pathogens. In vitro folding of MHC class I molecules, which is performed with the purpose of studying MHC class I structure and peptide binding as well as for the preparation of recombinant proteins for the detection of T cells, is assisted by adding a specific peptide to occupy the binding groove and form a stable peptide-MHC (pMHC) complex. This process is slow and must be started anew for a different peptide of interest. However, in vitro folding of class I molecules without peptide is difficult to impossible to achieve because empty class I molecules are conformationally unstable and prone to denaturation. This delays the parallel production of multiple recombinant pMHC class I molecules. Therefore, we have developed a novel method to produced empty MHC class I molecules that are stable for subsequent therapeutic applications.
Previously, our group has shown that small molecules, such as the dipeptide GM, can be used to fold class I molecules into a peptide-receptive conformation. We use these dipeptides in conjunction with a stabilized HLA-A*02:01. The additional Y84C/A139C disulfide bond links the α1/α2 helices in the F pocket region of the binding groove. In silico, molecular dynamics simulations show that this new disulfide bond, once formed, stabilizes the peptide-binding groove just like a full-length peptide. Disulfide stabilized HLA-A*02:01 can be folded with dipeptides that are subsequently removed during the purification steps. This results in empty MHC class I molecules that are stable in solution, are freeze-thaw compatible, and bind full-length peptides with rapid kinetics. Thus, the disulfide-stabilized empty class I molecules can be loaded directl
Variation of polyphenols and carbohydrates content in Camellia sinensis tea products
No full textTea is one of the most important horticultural crops which has been used as a medicinal and refreshing drink for many centuries.
Different types of commercial tea are produced from the leaves of the tea plant Camellia sinensis, such as black tea, green, oolong, white, yellow, and Pu-erh. Two varieties are most commonly used, Camellia sinensis var. assamica and Camellia sinensis var. sinensis.
In this work, different aspects of tea chemistry have been addressed, such as the influence of processing, origin or plant variety on the polyphenol and low molecular weight carbohydrates (LMWC) profile. Samples representing all six types of tea, have been analyzed using chromatography coupled to mass spectrometry. Application of a high-resolution and tandem mass spectrometry to the tea extracts allowed identification of a large number of analytes.
Black tea samples from different origins produced from two varieties of Camellia sinensis using two different methods (CTC and orthodox) have been analyzed by HPLC-ESI-MS to evaluate the effect of processing on black tea composition.
Green tea processing was addressed concerning the low molecular weight carbohydrates content. HILIC-ESI-MS was used to access differences in green tea produced in different countries, and using two fixing methods, pan-firing and steaming. Additionally, variation in LMWC in black tea samples of diverse origins was analyzed.
Thearubigins (the most abundant black tea polyphenols) were extracted from the CTC produced black tea and subjected to the model degradation under controlled conditions. Theaflavins, theacitrins, and theasinensins were found to degrade at the elevated temperature.
Last, tea leaves of the Camellia sinensis plants infected with Xyleborus fornicates were analyzed using HPLC-ESI-MS. Leaves of infected plants were found to contain less amount of catechins compared to the non-infected plants
Digital Mediation of Art and Culture. A Database Approach.
No full textThis PhD thesis analyzes digital and data-based practices of mediation of art and culture, focusing on digital cultural repositories and databases as central mediation tools. It embeds the digital mediation practices discussed in this thesis in the media-theoretical and media-historic context of the transformation processes that have taken place in the digital media ecology, which have resulted in challenges for cultural institutions and museums, both in their role as institutions as well as in their daily mediation work. The thesis also situates digital mediation practices in the context of contemporary, analog practices of cultural learning, since the analog and digital realms can no longer be separated in the contemporary media ecology.
One central topic of the analysis is mapping and understanding practices of mediation of art and culture and cultural learning in the digital realm. This is based on the database as a cultural form and repository that defines what can be said and known about a culture or society. The analysis introduces digital and data-based meaning-making processes within databases and database-interfaces themselves as well as cultural learning processes that reuse and contextualize the data in learning resources or by forming new experiences with them. The analysis concentrates mainly on web-based approaches and treats the process of co-creative knowledge generation as a central mode of the mediation of art and culture, using the paradigm of Software Studies developed by Lev Manovich as a lens for analysis.
Moreover, the thesis examines what characteristics of contemporary digital media and the digital media ecology are reflected or play an important role in digital, data-based mediation practices. It raises the question as to whether the employment of digital data leads to a changed notion of what mediation of art and culture can accomplish and highlights central directions for museums to react to and take advantage of ongoing digitization