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Synthesis, Structure and Properties of Polyoxopalladates
No full textDiphosphonic acids have attracted much interest in the last 50 years due to their potential use in the treatment of degenerative bone-loss disease, cancer, malaria, and other medicinal applications. In a similar sense, some discrete, stable polyxometalates (POMs) have also shown interesting anti-bacterial and anti-viral properties, indicating their potential as biologically active inorganic compounds. Thus, we decided to combine both areas by incorporating fluorinated and non-fluorinated diphosphonates into POMs, possibly leading to synergistic effects and hence enhanced therapeutic properties. This dissertation is subdivided into five chapters. Chapter 1 is an introduction to the research area. In Chapter 2 the non-fluorinated, mixed-valence heteropolymolybdate(V/VI) [(MoVIO3)2(MoV2O4)2{O3P-C(OH)(CH3)-PO3}2{HO3P-C(OH)(CH3)-PO3}2]10- (1) and the fluorinated, mixed-valence heteropolymolybdate(V/VI) [(MoVI2O5)2(MoV2O4)2{O3P-C(O)(CF3)-PO3}4(CH3COO)2]14- (2) as well as the fluorinated heteropolymolybdate(V) [{MoV2O4(H2O)}4{O3P-C(O)(CF3)-PO3}4]12- (3) were prepared. Chapter 3 describes the heteropolymolybdates(V) [(MoV2O4)10{H2C=C(PO3)2}10(CH3COO)8(H2O)4]28- (4) and [(MoV2O4)10{H2C=C(PO3)2}10(HCOO)10]30- (5). Chapter 4 describes reaction of pyridine-based-diphosphonates, resulting in mixed-valence heteropolymolybdate(V/VI) [{MoVIO3}2{MoV2O4}{HO3P-C(O)(CH2-3-C5NH4)-PO3}2]6- (6) and the heteropolymolybdate(V) [{MoV2O4(H2O)}4{O3P-C(O)(CH2-3-C5NH4)-PO3}4]12- (7). The mixed-valence heteropolymolybdates(V/VI) [{MoVI2O6}2{MoV2O4}{O3P-C(O)(CH2-3-C5NH4)-PO3}2]8- (8) and [{MoVI2O6}2{MoV2O4}{O3P-C(O)(CH2-4-C5NH4)-PO3}2]8- (9) demonstrate that the exact position of the nitrogen atom in the pyridine ring influences the orientation of the. In Chapter 5 the non-fluorinated heteropolymolybdate(V) [{MoV2O4}6(OH)6{O3P-CH(CH2NH2-C3H5)-PO3}6]12- (10) and the fluorinated heteropolymolybdate(V) [{MoV2O4}6(OH)6{O3P-CH(CH2NH2CH2CF3)-PO3}6]12- (11) are discussed
Long Short-Term Memory in Echo State Networks: Details of a Simulation Study
No full textEcho State Networks (ESNs) is an approach to design and train recurrent neural networks in supervised learning tasks. An important objective in many such tasks is to learn to exploit long-time dependencies in the processed signals ("long short-term memory" performance). Here we expose ESNs to a series of synthetic benchmark tasks that have been used in the literature to study the learnability of long-range temporal dependencies. This report provides all the detail necessary to replicate these experiments. It is intended to serve as the technical companion to a journal submission paper where the findings are analysed and compared to results obtained elsewhere with other learning paradigms
The Economics of Lifelong Learning and Skill Formation Risk, Return and Individual Choice
No full textWe explore lifelong learning and the job mobility it enables as a means of risk insurance on the labor market. We develop a formal micro-level theoretical model of individual investments in human capital and use option valuation theory to derive a formula for the ex-ante valuation of training benefits on the individual level under conditions of uncertainty. When training is considered as an entitlement to the right to switch job positions, we find that its returns may manifest through its insurance character rather than direct monetary benefits. We next perform one of the first studies on the relationship between spells of general and specific training within individual histories. Using German panel data, we show that in line with our model and unlike the predictions of extant literature, events of different types tend to delay (but not necessarily inhibit) each other, a result we attribute to the interdependence of the payoffs to general and specific training introduced by job mobility considerations. We finally study the characteristics of occupations to delve deeper in the relationship between risk, human capital, and occupational wages. On the basis of US data, we show that occupations characterized by higher levels of wage risk do offer higher remuneration, with our model explaining over 75 percent of occupational wage differentials. We also show that wage risk that cannot be managed by mobility has a much greater impact on wage formation than total wage risk. We demonstrate that the skill requirements and the ease of mobility in and out of the job are crucial to its position within the structure of the market. In conclusion, labor market risk exposure matters for lifelong learning investments, training being one of the key instruments of market-based risk management. The skill allocation across the labor market and individual adaptive action via human capital accumulation over the life course are important aspects of the dynamics of labor market structures
The importance of artificial coastal structures (tetrapods) as refuge and settlement area for fish and crustacea
No full textThis thesis focused on the effects of coastal defence structures on the fish and crustacean community in a subtidal area in the southern North Sea. The findings represent significant effects of natural and artificial substrate characteristics on the species. Through SCUBA, fixed quadrats along line-transects were used to assess firstly the demersal fish and decapod crustacean abundances in relation to natural substratum types (rock, cobbles and large pebbles). The results indicated that significant micro-scale species-habitat associations, especially for native fish, occur. In the same study area experimental fields were established, consisting of four-footed breakwaters (tetrapods) to investigate ecological impacts on the biota. Over a two-year period the fish and decapod community was assessed again, but now in combination with the experimental fields and in distance to the artificial structures. The results demonstrate a significant decrease of fish abundances in the surrounding area caused by migration effects towards the artificial structures. Furthermore, more young-of-the-year fish were observed directly at the structures within the second year after the establishment. I suggest that the availability of adequate refuge in combination with additionally food opportunities were the main factors, which attracted native fish species in greater numbers. Concerning the macro crustaceans it was not possible to give clear statements about the impact on the assemblage in general. The species reacted differently to the alteration of their surrounding. I suggest that for some crustacean species the composition of the tetrapods are attractive as shelter. For smaller species, however, this habitat form may not be optimal because of the lack of microhabitats. I concluded that the preference for a habitat type depends mainly on ecological requirements such as substratum colouration, adequate shelter size and specific species features
Study the Interaction Mechanisms of Block Copolymers with Biological Interfaces
No full textPolyethylene oxide (PEO) and polypropylene oxide (PPO) homopolymers as well as the block copolymers based on them (also called Pluronics) have many applications in biotechnology (e.g. detergent, lubrication, emulsification) and in biomedical sciences (e.g. drug delivery, biocompatible materials). This versatility is a consequence of their peculiar properties in solution and at interfaces. However, despite the large number of the available experimental data, still the molecular mechanism of their interactions with biological systems remains elusive. Fortunately, computational material science is now coming to an age of providing power tools to explore these phenomena with highly realistic accuracy. So far, this is one of the best approaches to study these systems but the application in the direction to explore the interaction of polymers with biological interface is still in its infancy. The research work in this PhD thesis aimed to use the most advanced tool of computational material science to study these polymers in solution and their interactions with biological membranes. The study of these phenomena was conducted using Molecular Dynamics simulations at multiscale level that allowed exploring these systems on scale of different order of magnitude in length and time. For this purpose, atomistic and coarse-grained models of the polymers based on the GROMOS/OPLS and MARTINI force fields respectively have been developed. Using atomistic models, different thermodynamic, dynamic and structural properties of the polymers were studied and compared with the available experimental data. The MARTINI coarse-grained model was then used to study the interaction of the Pluronics F38, P85 an L64 with DMPC lipid bilayer. The results were strongly support the experimental findings. Finally, using a recently proposed and developed Self Consistent density Field (SCF) method, simulation studies of Pluronics micelles formation and their interaction with DPPC lipid bilayers were accomplished. The results of these simulations evidenced a possible scenario of micelle dissolution at the bilayer surface that consists in a progressive diffusion of single Pluronic chains in contact with the interface from the micelle into the bilayer
Cathepsin K functions in the mouse central nervous system
No full textCathepsin K is a cysteine protease well known for its importance in bone remodeling and inhibitors of cathepsin K are currently in clinical trials for osteoporosis treatment. However, severe side effects were induced by cathepsin K inhibitor treatment of rats or mice affecting both, peripheral organs and the central nervous system (CNS). This is due to the fact that cathepsin K has also been detected in brain parenchyma only recently. Lately, we have shown that cathepsin K deficiency in mice induces structural and functional alterations in the CNS which are associated with learning and memory deficits. Furthermore, the proteolytic network was deregulated in the brain of cathepsin K-deficient (Ctsk-/-) animals. Moreover, astroglia-rich primary cell cultures from Ctsk-/- mice revealed an increase in enzymes of the glutathione metabolism, as well as elevated numbers of oligodendrocytes compared to wild type controls. Thus, we propose that cathepsin K contributes significantly to cellular and molecular homeostasis of the CNS. Cathepsin K was also demonstrated to bear a vital function in the thyroid gland, because it contributes to thyroid hormone (TH) liberation. THs are well known to be crucial for proper CNS development and its maintenance during adulthood. Therefore, we hypothesized that brain and thyroid functions of cathepsin K might be linked. However, our results suggest that Ctsk-/- mice do not suffer from classical hypothyroidism. Interestingly, trace amine-associated receptor 1 as well as TH transporters were found to be deregulated in the CNS of Ctsk-/- mice. Since all markers of classical thyroid regulation were comparable in wild type and Ctsk-/- mice, but markers of non-classical thyroid regulation differed significantly, we believe to have identified an animal model suited to study non-classical TH actions on the CNS in addition to serving as a mouse model for studying the general functions of cathepsin K in the CNS
Monitoring the anaerobic digestion process
No full textIn the anaerobic digestion process, microorganisms produce methane and carbon dioxide from organic substrates, either organic waste or renewable primary products. Being a versatile biofuel, biogas can be combusted in a combined heat and power plant to produce electricity and heat or, after purification, fed directly into the natural gas grid as biomethane. Due to the Renewable Energy Sources Act introduced in 1991 in Germany, this process became economically advantageous and led to a boom of biogas plants being built in Germany. A major problem of operating a biogas plant is to monitor an unstable process over time. Parameters like pH or redox potential do not necessarily suffice to estimate the degree of fermentation. At present, the preferred indication parameter are the concentrations of process intermediates, particularly short chain volatile fatty acids. They can be quantified with different gas or liquid chromatographic methods, which requires in-depth knowledge and expensive hardware and is usually carried out by specialized laboratories. Periodically, the digestate is sampled and sent in for analysis. Knowing the absolute concentrations of the different volatile fatty acids can only give a hint about the current fermentation status, though what would be more meaningful would be elucidating the dynamics of generation and degradation of the respective short chain volatile fatty acids. A new online technique using attenuated total-reflectance Fourier-transformed infrared spectroscopy (ATR-MIR-FTIR) was developed, which allows an online monitoring of the concentrations of the different volatile fatty acids in situ. This can give an insight into the dynamics of the anaerobic digestion process. It was adapted to a laboratory scale one-stage biogas plant fed with typically renewable primary products to simulate an agricultural biogas plant. Chemometric models were developed using spiked samples and samples from a real fermentation for acetic, propionic, iso-butyric, butyric, iso-valeric and valeric acid. The methods were evaluated by monitoring the startup phase of the anaerobic digestion of ground wheat in a 10 l continuous-stirred tank reactor. Sample preparation, recording and analysis of IR-spectra of digestate were fully automated. Predictions of the absolute concentration for acetic and propionic acid were reasonable, the existence of other volatile fatty acids could be detected. The developed anaerobic sensor system is able to determine their concentration dynamics and can thereby help to utilize unused potential in biogas plants. Another ascending problem are the substrates being used for the production of biogas. Renewable primary products are in direct rivalry with the agricultural and food industry. For a sustainable future, other biomass sources have to be made accessible for energy production. In contrast to energy crops, especially waste products can be used for energy generation without any concerns. The biogas potential of potential substrates is estimated with parallel running batch experiments. In the process, the minor gas flow rate of these lab-scale fermentations has to be monitored closely and accurately. Especially for this purpose, an easy to build and maintain automated biogas meter was developed to measure the biogas flow in anaerobic digestion experiments. The flow meter is built upon the open-source Arduino platform, and can therefore be easily enhanced or adapted to other environments. Recordings are sent via ethernet to a MySQL database, making the data widely accessible. By combining nine fermenters into an array, triplicate batch experiments according to VDI 4630 with negative control, positive control and the test substrate are monitored effortlessly. Concluding, this thesis focuses on optimizing the biogas production with the development of novel measurement instrumentation. The already well-established process of industrial digestion of energy crops is made transparent with an advanced onli
Synthesis, Structure and Properties of Polyoxopalladates
No full textThis doctoral thesis describes the development of supramolecular sensing ensembles, based on host-dye reporter pairs, for the sensing of biological analytes and monitoring enzymatic transformations. The rational design and selection of host-dye pairs are governed by the size-fit relationship and the favourable photophysical changes, exhibited by the dye upon complexation. The binding constants of the reporter pairs are examined by isothermal titration calorimetry (ITC), which reveals the thermodynamic forces of binding (Ka, delta H, and T delta S). Fluorescence-based techniques are used to study the photophysical characteristics of the dyes upon host complexation. The reporter pairs with pronounced fluorescence differentiation upon binding are selected for further sensing applications of biological analytes. The reporter pairs are used for the sensing of different types of analytes such as various amino acids, including lysine and its methylated derivatives, as well as choline-type of neurotransmitters. The analytes are further implemented in the development of supramolecular tandem assays for monitoring enzymatic activity. The design of tandem assays employs the differential binding affinity of the analysed substrates and products to the selected macrocyclic host. On the basis of the choline studies, a novel type of tandem assay for acetylcholinesterase has been developed. Due to the similar binding of the substrate (acetylcholine) and the product (choline) to the macrocycle of choice, the enzyme is coupled together with choline oxidase, which further converts choline to betaine (a weaker competitor). This constitutes a new tandem assay type, which works in an "enzyme-coupled-substrate-selective" mode. The determination of enzyme-kinetic parameters, the quantification of absolute choline and acetylcholine concentrations, and the screening for inhibitors for Alzheimer's disease is easily achieved with the novel assay
Solutions to the Geodesic Equation in Cosmic String Spacetimes
No full textCosmic strings have become interesting over the past years due to the possible connection to the observ- able part of String theory. Solutions to the geodesic equation in cosmic string spacetimes can be used to predict possibilities of the detection of cosmic strings, in particular the gravitational lensing. Therefore, the objectives of this PhD thesis are to find solutions of the geodesic equation in different spacetimes con- taining cosmic strings and make predictions about observables, e.g., light deflection and perihelion shift of planets. In addition, the energy per unit length of the cosmic string can be estimated. In spacetimes containing Schwarzschild and Kerr black holes pierced by an infinitely thin cosmic string, the components of the geodesic equation have been solved numerically and written as a form of the Weierstrass } function. In spacetimes with Abelian-Higgs strings and (p, q) strings with finite width, the metric functions and solu- tions to the geodesic equation have been determined numerically. We find that cosmic strings and cosmic superstrings can be distinguished from the motion of test particles. In addition, the detection of a negative value of the perihelion shift could be a sign of the detection of cosmic strings
Improving the Usage of ribosomal RNA Gene in Microbiology and Microbial Ecology Importance of Standardization and Biocuration
No full textEnvironmental surveys of ribosomal RNA genes have become the standard approach to microbial ecology in the last twenty-five years. Although the ribosomal RNA approach has been competing with metagenomics during the past years, with high-throughput sequencing technologies presenting the ability to document the diversity and richness of the microbial biome at an astonishing rate, it is once again under spotlight. High-throughput sequencing technologies bring with them a sequence data deluge, and present challenges to the traditional data management, analysis and retrieval practices. Biocuration, which leads to specialized ribosomal RNA datasets, has become an important part of microbial ecology. More recently, the development and use of metadata standards has emerged as an important aid for biocuration in microbiology. With the help of such standards, it will be possible to curate specialized datasets, which integrate data from even more diverse resources, and bring the organisms, its functions, and the environment together. The work accomplished during this Ph.D. thesis aimed in improving the usage of ribosomal RNA gene in microbiology and microbial ecology by means of curating highquality specialized datasets for ribosomal RNA gene sequences, and performing research that demonstrates the value of such datasets. More importantly, a metadata standard for marker genes sequences, such as ribosomal RNA, was developed and disseminated to a variety of bioinformatics service providers for implementation. This standard will greatly aid biocuration work in microbiology, and will improve the quantity and quality of integrative resources for microbiology, ultimately providing researchers the ability to understand the diversity and functioning of the microbial biosphere