Publication Server of Constructor University Library
Not a member yet
858 research outputs found
Sort by
Hot Start Reverse Transcriptase for Molecular Diagnostics
No full textReverse transcriptase (RT) is an indispensable enzyme for real-time reverse transcriptase polymerase chain reaction (real-time RT-PCR), a standard method in molecular diagnostics for detection and quantification of defined RNA molecules. The prevention of non-specific products due to elongation of misprimed oligonucleotides by the enzyme at temperatures beneath the specific annealing temperature is one of the biggest challenges in real-time RT-PCR. A reduction of non-specific products could be achieved by the optimization of the reaction conditions and/or by the use of so called hot start enzymes. Hot start enzymes are inactive at lower temperatures, when mispriming occurs and activated at higher temperatures, appropriate for specific annealing of the primers (short oligonucleotides) and their extension.
Different hot start mechanisms are described for the thermostable DNA-dependent DNA polymerase (the key enzyme in PCR), but for the RT is still missing. The aim of this PhD study is to investigate the potential for a hot start moloney murine leukemia virus (MMLV) RT variant with increased thermostability in real-time RT-PCR, leading to an improved performance of this technique. Therefore, different strategies are followed: temperature-dependent inactivation of RT in real-time RT-PCR by (1) aptamers or antibodies and (2) temperature sensitive encapsulation. Furthermore, the improvement of the thermostability of the enzyme due to mutations, reaction buffer optimization or both, to gain a higher flexibility for the hot start approaches.
In the study a hot start RT for real-time RT-PCR by temperature-dependent inactivation with aptamers was realised, which led to an increase in analytical sensitivity of a real-time RT-PCR assay. Enhanced thermostability of a MMLV RT variant and improved real-time RT-PCR performance, compared to a wild-type MMLV RT was realized
Upper Airway Segmentation and Interactive Visual Analysis to Investigate Obstructive Sleep Apnea in a Cohort Study
No full textObstructive sleep apnea (OSA) is a public health problems affecting at least 2-4% of the middle-aged population and characterized by repeated collapsing of the soft tissue structures of the throat. However, the pathogenesis of this problem is poorly understood. Volumetric analysis of the upper airway and para-pharyngeal fat pads can help us to study the OSA syndrome. A reliable automatic segmentation technique plays a vital role in investigating the OSA.
The proposed context-based automatic algorithm uses prior knowledge about the topology and geometry of the pharynx. The comprehensive segmentation pipeline consists of three major stages for the delineation of pharyngeal structures from the rest of the soft tissues of the head MRI. The first stage consists of a coarse segmentation of soft tissues of the head MRI using intensity clustering. The second stage involves the feature extraction of the coarse objects and designs a supervised classifier using the interactive visual analysis of the multidimensional feature space. The third stage comprises of the refinement on the local region using multiOtsu thresholding and watershed transform. The approach is quantitatively evaluated against the ground truths of ten datasets resulting in an average of approximately 90% Dice coefficient.
An interactive multidimensional visual analytics tool is proposed and implemented to visualize and analyze quantitative and categorical data simultaneously. Visual analysis of quantitative and categorical variables shows that the age variable carries the highest weight in separating healthy subjects group from apneic patients in 2D projection space. Other worth mentioning variables are BMI, gender, blood pressure, minimum pharyngeal laterolateral axial length and parapharyngeal fat pads volume etc. This multidimensional visual analytics tool helps us to study the impact of numerous features and variables to investigate the OSA syndrome
The role of thyroid hormone transporters and thyroglobulin processing enzymes in auto-regulation of the mouse thyroid gland
No full textIntroduction: Thyroid hormones (TH) are important for almost all organs in the body. TH transport into target cells is crucial for their biological action. The thyroid gland, as the TH producing organ, is also a target of its hormones. Therefore regulation of the processing of the TH precursor molecule thyroglobulin and transport of TH across the plasma membrane of thyroid epithelial cells is vital for thyroid development and function.
Objectives and Methods: We hypothesized that the thyroid gland must exhibit TH sensing mechanisms to ensure extra- and intra-thyroidal TH homeostasis and therefore investigated the relationship between thyroglobulin processing enzymes and TH transporters. Thereby, the auto-regulation of the mouse thyroid gland in general and in a TSH-independent manner was addressed. Hence, mouse models were bred combining both, TH transporter- and cysteine cathepsin-deficiency, and a computer-based thyroid phenotyping tool was developed to quantitatively analyse thyroid morphology and functional states. TH transporter expression and localization patterns were analysed in cysteine cathepsin-deficient animals as models of impaired thyroglobulin processing, and in reverse, the protein levels of cathepsins in TH transporter-deficient mice with altered serum TH levels were addressed.
Results: The established diagnostic tool offers a non-biased and reproducible thyroid phenotyping system to basic thyroid research. The functional assessment of the angio-follicular unit by our phenotyping tool reveals how the structure-function-relationship contributes to the compensation of functional losses in the mouse thyroid gland. Additionally, thyroid gland tissue of Mct8- and Mct10- double-deficient mice revealed both, increased cathepsin L expression levels and increased thyroglobulin solubilisation and degradation. Interestingly, animals deficient in both, cathepsin K and Mct8, exhibited apical Lat2 signal, whereas the knock-out of Mct10 led to decreased Lat2 levels in thyrocytes.
Conclusion: These results indicate that a possible sensing mechanism might involve TH transporter Lat2 as `transceptor´ in a localisation-dependent signalling pathway linking sensing capabilities and lysosomal function in thyrocytes, the latter being disrupted in Mct8- and Mct10- double-deficient mice leading to increased TH liberation potential despite the already toxic intra-thyroidal TH levels. In summary, TSH-independent regulative measures of the thyroid gland were described and point towards a more complex thyroid regulation than described before.
Supported by the Deutsche Forschungsgemeinschaft, in the framework of the SPP 1629 “Thyroid Trans Act” project, BR 1308/11-1
The evolution of Precambrian environments and their impact on the trace element and Hf-Nd isotopic compositions of ancient seawater
No full textSeawater archives such as (Banded) Iron Formations (BIFs) may serve as excellent archives of geochemical proxies for the composition of Precambrian seawater to evaluate physico-chemico environmental conditions of the ancient hydrosphere-atmosphere systems. This thesis presents major and trace element analyses by ICP-OES and ICP-MS measurements and high-precision Nd (and Hf)isotope data obtained by isotope dilution technique and MC-ICPMS and TIMS analyses of chemical and clastic sediments of the Mesoarchean Witwatersrand IF, the Late Archean - Early Proterozoic Krivoy Rog IF and the Neoproterozoic Urucum IF to highlight the evolution of ancient oceans and the environmental impacts on ancient seawater chemistry during the Precambrian.
The rare earths and yttrium (REY) coupled with high field strength element (HFSE) systematics are used to (I) identify the purity of each individual chemical sediment sample, but also to investigate (II) the composition of Precambrian seawater, (III) the redox conditions of ancient environments and (IV) the impact of black smoker-style, high-temperature, hydrothermal fluids on local and global Precambrian seawater chemistry. Furthermore Nd and Hf isotopic compositions of representative clastic and chemical sediments were applied as geochronological tools and were used to unravel the sources of elements in dissolved and suspended fractions of ancient seawater and to gain further insights into weathering and erosion processes on Early Earth
Influence of sea ice on protist community structure in the Central Arctic Ocean
No full textProtists form a major part of the Arctic ecosystem and are of great importance for biodiversity and productivity of the Central Arctic Ocean (CAO). The sea ice is considered as one of the main factors that influence protist communities. Current changes in sea ice conditions are assumed to alter protist community biodiversity and composition in ice-influenced habitats with further implications for the overall productivity of the CAO and carbon sequestration to the deep sea. Protist taxa that are adapted to habitat-specific environmental conditions or available food sources might be affected most by the recent sea ice retreat. However, little is known about how drastic sea ice loss might affect biodiversity and composition of sea ice biota and phytoplankton. So far, in-depth knowledge about protist community structure and protist ecology in variable habitats of the CAO is still scarce and mainly based on the analysis of conventional approaches (e.g. light microscopy). Therefore, this thesis analyzed 18S amplicon sequence data in a total of 97 samples collected from the deep-chlorophyll maximum water depth, under-ice water, sea ice and melt pond water. Samples were collected in the CAO during August and September in 2011 and 2012 to investigate the environmental factors driving protist community structure and the potential consequences of sea ice retreat on protists in the CAO.
The following questions will be addressed:
1. What are the influences of different sequence processing procedures on the resulting diversity and composition of protists obtained from environmental samples?
2. How does sea ice retreat and sea ice origin impact protist communities in the sea ice and water column of the CAO?
3. How habitat-specific are Arctic protist communities and is there any protist exchange between sea ice-influenced habitats in the CAO
Redundancy Investments in Manufacturing Systems - The role of redundancies for manufacturing system robustness
No full textToday's manufacturing companies are faced with a large number of fluctuating influence factors, as supply chains in the production environment grow larger with more suppliers and highly sophisticated products. At the same time, throughput times and due date reliability need to stay on a stable level, to fulfill the expectations of short delivery times and high service-levels of increasingly demanding customers. This ability to maintain specific features or a certain performance when subject to fluctuations and disturbances is generally referred to as robustness. As explained above, robustness of performance indicators, such as due date reliability, is a desirable characteristic for producing companies, hence the question arises how it can be achieved or incorporated in a companies manufacturing system. Looking at other scientific disciplines, such as biology or complex network science, robustness of the respective systems is often caused by redundancy, a situation where identical or similar components can replace each other when a component fails. In manufacturing research, redundancy has often been considered as an aspect to be avoided, as it stands in a potential trade-off with cost-efficiency, for example in lean manufacturing where excess inventory is considered as waste. However, as redundancy has been shown to have a strong relation to robustness in other disciplines, the aim of this thesis is to investigate the role that redundancy plays for achieving robustness of manufacturing system performance
Towards sustained employability and quality of life: Findings on single and multiple health behaviour change from four studies in lifestyle-related disease prevention and rehabilitation
No full textLifestyle-related diseases such as cardiovascular diseases and musculoskeletal diseases are the leading cause of work disability and death worldwide. As regular physical activity and sufficient intake of fruit and vegetables play a key role in the prevention and treatment of such diseases, the promotion of these behaviours constitutes a major topic in health psychology. Yet approaches for multiple health behaviour change, as well as the incorporation of work-related outcomes, and quality of life warrant further research.
The research questions were examined in one observational and three experimental studies in various settings (medical rehabilitation; primary prevention) and across different health behaviours (physical activity; fruit and vegetable consumption). The results of this thesis highlight the importance of incorporating quality of life and vocational outcomes in activity-based treatment programmes. The findings of this thesis further suggest that improving a person’s confidence in their abilities may not only set the stage for successful behaviour change by strengthening intentions, but may also diminish the negative effects of compensatory health beliefs. Finally, especially if accompanied by self-regulatory strategies such as self-efficacy and planning, increases in desired behaviour for even more than one behaviour may be reached. The findings show that web-based computer-tailored interventions for multiple health behaviours can be an effective means to improve habit strength for physical activity and fruit and vegetable consumption if they make use of such self-regulatory strategies.
The practical implications for public health, medical rehabilitation, and workplace health promotion on changing employee’s health behaviours given may provide a promising basis for disease prevention, sustaining quality of life and employability, and reintegration of already sick-listed employees
A Q Methodological Investigation of the Kurdish Conflict Frames among Parliamentarians, Experts and Lay People in Turkey
No full textMany societies in different parts of the world have witnessed intractable conflicts. People living in these societies construct conflict frames to understand the ongoing conflicts. Based on Lederach’s (1999) pyramid approach to peace building, the current study investigates how people understand the Kurdish conflict in Turkey in three segments of society: a) politicians, b) scholars and journalists and c) lay people. The Kurdish conflict was approached based on the frame analysis of Entman (1993), which includes four domains: a) problem definition, b) causal interpretation, c) moral evaluation, and d) treatment recommendation. In a first phase, focus group discussions and open-ended questionnaires were used to explore alternative conflict understandings among lay people. In a second phase, Q methodology, a method suitable to uncover socially shared viewpoints, was used to understand the conflict frames of parliamentarians, experts and lay people. In a third phase, after analyzing each participant group’s frames separately, a second-order analysis was performed to see the similarities and differences between the different segments. Five different frames of the Kurdish conflict could be distinguished. In general, the meaning of the different frames, differences and commonalities within and between the segments, the usefulness of Q methodology to explore representations of conflict, and implications for conflict resolution will be discussed
Titanium(IV)- and Lanthanide(III)-Containing Heteropolytungstates
No full textExtensive studies on polyoxometalates (POMs), from synthesis to structural examination, have revealed a versatile structural evolution and its relevance to technological applications of these materials in green catalysis, medicine, magnetism, materials science, and molecular recognition, and so on. Lacunary (vacant) POMs can incorporate additional electrophiles from the p-, d-, and f-blocks by virtue of their exposed, reactive oxo ligands, resulting in products with enhanced structural and compositional diversity.
Titanium(IV)-containing heteropolytungstates are highly interesting for their diverse structural chemistry as well as their catalytic properties. The Ti4+ ion fits well into the vacant addenda sites of various types of Keggin or Wells-Dawson heteropolytungstate precursors. The first part of this thesis is dedicated to the reaction of the [TiO]2+ cation and lone-pair containing, lacunary POM precursors of the type [α-XIIIW9O33]9- (X = As, Sb). This work has resulted in seven novel TiIV-containing heteropolytungstates.
Lanthanide-containing heteropolyanions are of interest due to their highly diverse structural and chemical nature. Due to the large size of the lanthanide(Ln) ions they cannot be fully incorporated into lacunary heteropolyanions, and hence coordinate to several terminal water ligands, resulting in large coordination numbers and compounds with Lewis acidic properties. In the second part of this thesis the reactivity of lanthanide ions with trilacunary Keggin-type polyanions such as [a-XW9O34]10- (X = Si, Ge) has been investigated. This work has resulted in three novel LnIII-containing heteropolytungstates
Art Museums online - New visual challenges of Modern and Contemporary Art Collections
No full textSince the internet developed into a medium used for a worldwide retrieval of information and communication, it also became an important platform for the promotion and self-presentation of cultural institutions. The web presence of cultural institutions like museums means an additional visual experience for the customers. This additional visual experience differs profoundly from its on-site counterpart, as it is determined by the structure of hypermedia, which is multilayered and based on multimedia. Closely intertwined with new visual experiences online are new visual challenges for the institutions as the providers of the said experiences.
This thesis’ purpose has been to assemble new visual challenges for the online provision of collections of modern and contemporary art museums, specifically of the Museum of Modern Art (New York), the San Francisco Museum of Modern Art, the Tate (UK), and the Museum für Moderne Kunst (Frankfurt a.M.). To gain insight about these new challenges, interviews have been conducted with persons in charge of the museums’ online collections. Furthermore, selected webpages of the online collections have been examined closely.
The results of the interview and webpage analysis are used to draw conclusions regarding the primary new visual challenges in this specific field of art presentation