Publication Server of Constructor University Library
Not a member yet
858 research outputs found
Sort by
Contact resistance effects in thin film solar cells and thin film transistors
No full textThin film technology is the keystone in the modern applied science and it has been used for several decades in making electronic devices. Recent researches on various thin film solar cells and organic electronic devices have pioneered improvements in performance and miniaturization. As devices further miniaturize, performance of thin film devices suffers as a result of high electrical Ohmic losses which occur. In thin film devices, such as solar cells, radio frequency identification tags (RFID tags) and thin film transistors (TFTs), the main contributor to high parasitic losses is the contact resistance between metal electrodes and active semiconductor materials. Contact resistance effects in electrical devices are undesirable, but unavoidable. The minimization of these effects on a device's functionality has drawn the attention of many researchers from various fields. This thesis has an aim to examine closer contact resistance effects in chalcopyrite thin film solar cells and organic thin film transistors. As new areas of thin film devices continue to expand, new and different materials have been under investigation for the manufacturing of thin film transistors. On account of miniaturizing devices, contact effects have become a prominent factor on a device's performance. Contact effects may reduce the charge carrier mobility of the devices, as well as the switching frequency in thin film transistors. On the other hand, in thin-film photovoltaic industry the process temperature is one of the limiting parameters for the formation of electrical contacts, especially in the case of devices manufactured on plastic substrates. Due to the high contact resistance, conversion efficiency of the thin film solar cells may be reduced
Enhancing XML Preservation and Workflows
No full textWith the proliferation of computers and networked resources the amount of data available on personal computers and on the Web is growing exponentially. Handling of data becomes more complex as the scale expands. Moreover, data collections change in place over time, so that one of the important challenges consists in supporting a life-cycle of data. In particular, relevant parts of information have to be preserved and made accessible for future retrieval. XML is a wide-spread language for encoding documents that is both machine-readable and human-readable. It plays a unique role on the Web and in other areas of digital life: publishers, libraries, warehouses, technical writers, to name a few, - all make extensive use of XML for encoding books, articles, product information, documentation, interchanging and transformation of data, and the extraction and aggregation of relevant pieces of information. Contemporary web services are stepping away from traditional relational data models and are moving towards semi-structured data representations and utilization of NoSQL, and, in particular, XML databases for persisting data. A considerable technological stack has been built around XML, making it even stronger as a format. The development of XML technologies specifications is a never-ending process and emerging implementations of them push the progress further. However, there are still many open problems and challenges to be addressed in the XML domain. This thesis selects a number of the unsolved ones and suggests solutions; concretely (i) Versioning support for XML, (ii) XML databases views as counterparts of relational database views, (iii) Support for XML document templating. Solving the XML versioning problem for a subset of use cases enables an XML persistence layer that tracks the history of changes and provides XML database functionality like querying or indexing of data. The XML database views concepts allows to abstract away from the notion of XML files and think in terms of customizable and editable abstract XML entities with origins in some XML documents. Finally, support for XML document templating facilitates separation of responsibilities while authoring XML documents. Being able to use diverse expertise of developers in different phases of document creation, in turn, optimizes the whole authoring workflow. Highlighting the practical value of this work, all the concepts described in this thesis are implemented and integrated into the TNTBase system. Over the last 4 years TNTBase has been constantly utilized in a number of mainly research projects maturing by receiving feedback from its users. The main target of the TNTBase project was providing a versioned repository for the Open Mathematical Documents (OMDoc) with a strong focus on XML-related functionality. Since the OMDoc format combines data-like aspects (axioms, theorems, examples, etc.) with document-like aspects (sections, paragraphs, etc.), the number of applications was diverse, and therefore all the approaches have been generalized to make it possible to adapt TNTBase to other domains and XML languages. As a result, TNTBase has been deployed in multiple real-life scenarios where it has been used on a daily basis
Bio-Mimetic Supramolecular Host–Guest Interactions
No full textEnzymes are unique in their ability to shift the pKa values of substrates by up to 5 units and thus catalyze acid–base reactions. Drawing inspiration from nature, chemists have long endeavored to design host molecules capable of modifying the protonation state of encapsulated guest molecules to catalyze their chemical reactions and thereby mimic biological effects in supramolecular assemblies. This doctoral thesis deals with the investigations of bio-mimetic supramolecular pKa shifts in different host–guest complexes, and the translation of this physicochemically interesting supramolecular phenomenon into practically relevant applications.
The first part of this thesis demonstrates the successful employment of cucurbit[n]uril (a synthetic class of macrocycles) -induced pKa shifts to enhance the bioavailability (activity, solubility, ionization degree, and photostability) of drug molecules. Furthermore, a structure–activity relationship, which allows predictions of cucurbit[n]uril-induced absolute pKa shifts of encapsulated guest molecules, is discussed as well.
The second part of this thesis describes a strategic supramolecular approach to modulate the excited state protonation-coupled electron transfer and photo-induced electron transfer properties of ditopic donor–acceptor type molecules. Such host-assisted modulation not only facilitates the electron transfer between two interacting redox partners of a guest molecule in a completely different solution condition, but also allows the development of fluorescence-based host–guest reporter pairs for the detection of optically-inactive, biologically important analytes via an indicator displacement approach.
In the third part of the thesis, employment of size- and shape-selective molecular recognition in the design and development of heterocapsule-type ternary nanostructures is discussed. The obtained nanostructures show markedly different fluorescence and chiro-optical properties with respect to the guest molecules, and therefore, have enormous potential in modulating the circularly polarized luminescence properties of encapsulated guests.
Finally, the effects of supramolecular host molecules on the photophysical properties of aggregation-prone fluorescent dyes and polymers are documented. Isolation, or rather separation, of the dye molecules from each other via a supramolecular approach, and the formation of mechanically interlocked rotaxane architectures immensely improved the photophysical properties of the investigated molecules
Biochemical and biophysical characterization of various cell wall channel-forming proteins
No full textThe mycolic-acid layer of certain gram-positive bacteria, the mycolata, represents an additional permeability barrier for the permeation of small water-soluble solutes. Consequently, it was shown in recent years that the mycolic acid layer of individual bacteria of the group mycolata contains pores, called porins, for the passage of hydrophilic solutes. Corynebacterium amycolatum, a pathogenic Corynebacterium species, belongs to the Corynebacteriaceae family but it lacks corynomycolic acids in its cell wall. Despite the absence of corynomycolic acids the cell wall of C. amycolatum contains a cation-selective cell wall channel, which may be responsible for the limited permeability of the cell wall of C. amycolatum. In the first project of this thesis and based on partial sequencing of the protein responsible for channel formation derived from C. amycolatum ATCC 49368 we were able to identify the corresponding gene coram0001_1986 within the known genome sequence of C. amycolatum SK46 that codes for the cell wall channel. The corresponding gene of C. amycolatum ATCC 49368 was cloned into the plasmid pXHis for its expression in Corynebacterium glutamicum. Biophysical characterization of the purified protein (PorAcoram) suggested that coram0001_1986 is indeed the gene coding for the pore-forming protein PorAcoram in C. amycolatum ATCC 49368. The protein belongs to the DUF3068 superfamily of proteins, mainly found in bacteria from the family Corynebacteriaceae. The nearest relative to PorAcoram within this family is an ORF which codes for PorAcres, which was also recognized in reconstitution experiments as a channel-forming protein in Corynebacterium resistens. More general view of the distribution of this pore-forming proteins within the genus Corynebacterium was performed by extending the search for the homologous proteins to PorAcoram to pathogenic representatives of Corynebacteriales, the C. jeikeium strain K411, the C. urealyticum strain DSM 7109 and C. variabile DSM 44702. A further objective of this thesis was to elucidate the presence of the human VDAC I-like protein in the gram-negative pathogen Legionella pneumophila. Genome sequence screening of different strains such as Paris, Lens and Philadelphia has revealed the arrangement of eukaryotic-like proteins which is unique in Legionella. It is hypothesized that these eukaryotic-like proteins likely contribute in adaptation to the eukaryotic host cells. The existence of protein sequences forming a multi-protein complex comparable to the mammalian mitochondrial permeability transition pore (MPTP) of eukaryotes contributing in the cell apoptosis has been recently described. The most abundant protein in the outer membrane of mitochondria forming the core of (MPTP) is the voltage-dependent anion-selective channel (VDAC) which transports metabolites through the outer membrane as the major conduit. Blast alignment research has shown homologous sequence (Lpg1974) in the genome of L. pneumophila with 22% identity and 35% conservative replacement with the human mitochondrial VDAC 1 protein which has unknown function up to now. To consider the hypothesize whether or not the Lpg1974 is a VDAC-like protein, the Lpg1974 was cloned in pGEX-2T vector and expressed in E. coli KS26 which lacks major porins. Biophysical characterization of this protein after purification exhibited that the Lpg1974 has a channel forming activity with a single-channel conductance around 5.5 nS
Film growth and electrical properties of solution processed zinc oxide in thin film transistors
No full textHigh performance TFTs showing excellent stability even in air were developed based on investigations describing physical and chemical mechanisms related to zinc oxide film growth and its electrical properties. Therefore the growth and nucleation of zinc oxide thin films deposited by pulsed spray pyrolysis utilizing non-toxic materials were correlated to the boiling curve and Leidenfrost effect of water which was employed as solvent. The optimized deposition parameters were utilized to fabricate ZnO-TFTs. Different growth conditions and their impact on trap state formation inside the bulk material were analyzed taking chemical purity and grain boundary models into account. Moreover it was distinguished between the contribution of surface and bulk trap state on the storage and gate bias stress stability in different atmospheres. Mainly surface states which are sensitive to humid atmosphere show significant impact on the electrical stability of TFTs. Hence different fluoro-terminated compounds which bind selective on active surface sites which are either related to Zn2+-ions or hydroxyl-groups were investigated. 4,4,4-Trifluoro-1-phenylbutane-1,3-dione which chalets to Zn2+-ions was found to be a suitable candidate to reduce the number of surface trap states significantly which leads to highly stable TFT performance and a strong increase in mobility. Since this approach has not been reported elsewhere yet a patent application was filed
Capturing biodiversity in Metagenomic data: Design, implementation and evaluation of a bioinformatic method for binning and classification of DNA sequences
No full textThe number of available completely sequenced genomes has grown exponentially in the last two decades. Today, the total number of DNA sequences stored in public databases doubles about every 18 months, a development fuelled by continuous improvements in DNA sequencing technologies. Next-generation sequencing (NGS) has caused a dramatic drop in sequencing costs that not only propelled the growth of available DNA sequences in public databases but also has encouraged the establishment of metagenomic community-sequencing approaches. Full genome sequencing is restricted to cultivable strains, considering that only a minor fraction of the microbial species in a given habitat can be cultivated with current techniques, metagenomics, the sequencing of DNA from an environmental sample, is the method of choice. With the huge amount of data that has to be processed in metagenomic projects, new challenges arise, especially addressing metagenomics classic problem of binning and classification. For example the direct sequencing of microbial communities, using NGS technologies, often yields longer assemblies of the abundant species and a wealth of sequences that have to be taxonomically clustered into bins (taxobins), same applies to standard Sanger sequencing. This approach requires methods that allow to taxonomically classify- ing sequences with reasonable accuracy. Binning names the process of clustering metagenomic sequences according to certain features and parameters, while classification terms the assignment of metagenomic sequences to known organisms and taxonomic groups. The aim of this thesis was to aid in the analysis of metagenomic data concerning the classification and binning task in metagenomic projects. First the technology to perform binning and classification was set up by implementing a software capable of performing taxonomic classification and binning of metagenomic sequence fragments pursuing the aim to make this software ready to deal with the amount of sequence data present in today's public databases. A second aim was to provide easy access to the software by creating an easy to use web- interface, enabling a broader audience to use the software. The result of fulfilling these tasks is the software tool TaxSOM, an implementation of two variants of the Self-Organizing Map algorithm, utilizing the algorithms pattern-recognition abilities to capture intrinsic features of the DNA to provide taxonomic classifi- cation and binning as needed in metagenomic analysis. TaxSOM was applied in a number of studies included in this thesis, offering a wealth of data to measure TaxSOMs accuracy and performance when comparing results of application to ar- tificial and real-world metagenomic datasets. The possibilities offered by TaxSOM were successfully used to aid scientists in real-world projects, regarding taxonomic classification and binning, providing new insights when applied to metagenomic sequence data
Most Watched: Family representations in high-rating programmes on German television
No full textGermany has faced low birth rates since the 1970s. No policies have changed this trend as yet. This study focuses on the role of TV as a socialising agent contributing to viewers' attitudes and beliefs that ultimately result in having no or few children. This study, which is situated within the agenda-setting theory, social cognitive theory as well as cultivation theory is descriptive in kind. The material under analysis consists, first, of 50 highest-rating programmes as watched by 14 to 49 year-olds during an average week, considered to reflect preferences of viewers of potentially child-bearing age, and, second, the ten most watched programmes shown during a week focusing on the representation of families ("Children are the Future"). The results are related to one another with the aim of obtaining a coincidental picture from the first subset, and an intentionally constructed one from the second. The most striking finding is how little family life is shown. Where it is shown, the representations often lack detail preventing an in-depth analysis. Where recognisable, well-off two-parent families with one or two children older than six years predominate. Traditional models for the division of labour and unchanged gender roles feature. Inner-familial discourse about combining work and family issues is scarce and completely absent in the families' surroundings. Financial aids for families or external child care are virtually not shown nor discussed. Results indicate few significant differences between the two programme subsets. The description of family representations in high-rating programmes is considered an important step towards an understanding of the kind of mediated picture television viewers experience. The results of the present study seek to stimulate interest in the field of cultivaton analysis, e.g. to explore effects of televised patterns on viewers' attitudes towards family life in general or, more specifically, on their wish to have children
The Imperative of an Empire : Italian China Policy 1867-1901
No full textThe vying of western powers for privileges and concessions in China at the end of the 19th and the beginning of the 20th century has been the subject of many books and articles in the past decades. While much of this research has concentrated on the interaction between China and major western powers like Britain, France, Germany and the United States, and the humiliation of China at the hands of these powers, it has been almost entirely left out of sight that for one western power,
China was a theatre of repeated humiliations, as well.
This thesis examines Italian imperialistic action in China between 1867 and 1901 and by placing it in the political context of the recently proclaimed Italian state, it seeks to understand its motivation, goals and idiosyncrasies. In order to highlight the uniqueness of Italian China policy and the Italian approach to imperialism in general, Italian imperialistic action in China is compared to that of Germany, another newcomer in the colonial race for territories and privileges, and another newly born nation state. Unlike imperialistic policies of other western powers, which were dictated by long-term political strategy, Italian imperialistic policies were more often than not impromptu actions of a political class that had failed to achieve a real internal unification of the various Italian regions and couple political modernisation with a thorough process of economic modernisation as Germany had done. Furthermore, whereas the imperialism of successful colonial powers rested on solid foundations of economic interest, Italian imperialism was rather a reflection of emotional needs of a political class unwilling to accept Italy’s real position in the European power relations of the late 19th century. These two factors combined, inevitably led Italy from one colonial disaster into another, but due to the emotional rather rational than rational origin of Italian imperialistic policy, these disasters failed to have a sobering effect on the Italian political class. Instead, the desire of an empire grew even more ardent – a circumstance from which only the fascists would know how to draw political profit
Lesion segmentation and tracking for CT-based chemotherapy monitoring
No full textThis PhD thesis makes contributions in the field of medical image analysis for assisting CT-based staging and follow-up examinations of patients under chemotherapy.
First, an algorithm for semi-automatic segmentation of liver metastases in CT images is presented. The runtime was kept within a clinically acceptable limit of less than 1 s on average. The method is able to deal with inhomogeneous density distributions and prevents leakage through the liver boundary. A comprehensive evaluation was performed on 371 lesions with manual segmentations. The method produces results of similar quality as other state-of-the-art methods but is significantly faster.
In order to accelerate follow-up examinations in the clinic, I implemented a framework for automatic lesion tracking. For a segmented baseline lesion, it identifies the corresponding lesion in follow-up, automatically initializes the segmentation, and performs a plausibility check. No other framework automatizes follow-up examinations to this degree. A problem analysis, examining the change of 994 lesions under chemotherapy, and a simulation of similarity measures on a lesion phantom motivate the presentation of a template matching algorithm tailored to this problem. The method is validated from a technical point of view on 207 cases before reporting a user study that evaluated possible benefits for the clinical workflow.
For validating segmentation algorithms, manual delineations are often used, but their high variability makes it difficult to achieve reliable statements. To quantify this problem and to overcome it in practice, I present a generalization of the MICCAI score that takes the variability of multiple reference segmentations into account for each case. An analysis of the variability in manual delineations of ten experts is performed. The thesis is concluded by a concept and a validation study for a tool that allows experts to generate probabilistic reference segmentations
Effects of environmental contamination on the immune system of the blue mussel Mytilus spp. in brackish water systems of the Baltic Sea
No full textThe Baltic Sea is one of the largest brackish water areas in the world. The maintenance of its functioning strongly depends on habitat-forming key species, such as Mytilus spp. The health of these key species is dependent on effective immune responses that provide protection against infectious agents (bacteria, viruses, fungi and parasites) and tumours. Environmental contaminants have been shown to impair immune defences, leading to increased disease susceptibility.
The present study, being part of the BEAST project, aimed to test the suitability of selected immunotoxic effects of contaminants on the bioindicator Mytilus spp., with particular focus on the confounding factor salinity. Even though, organisms have adapted to low ambient salinities in the Baltic Sea, permanent osmoregulation is energetically costly and affects stress susceptibility. Until now, the synergistic effects of salinity and pollution on the immune system of invertebrate species have not yet been explored. Studies conducted addressed the impact of the model contaminant copper on immune responses and disease susceptibility of Mytilus spp from differing ambient salinities, the effect of contaminant mixtures and ambient salinity in the natural environment in individuals indigenous to the region of concern and in transplanted organisms. Salinity slightly affected immune responses, in particular phagocytic activity and bacterial clearance, in Mytilus exposed to copper in the laboratory study. However, results from both field surveys showed contradictory results. In individuals indigenous to the locations of interest it was shown that contaminants had a greater impact on cellular immune responses than salinity.
In conclusion, I recommend the implementation of immunological parameters, accompanied with assessments of higher biological levels, in monitoring surveys of environments with low salinities and brackish water conditions. In particular, the functional endpoint “phagocytic activity” and the morphometric endpoint “cytoplasmic vacuolation” are promising tools for the assessment of immunotoxicity. Nevertheless, further research on the impact of salinity with or without additional anthropogenic stressors are needed to elucidate the underlying mechanisms of the biological effects that are being assessed