Publication Server of Constructor University Library
Not a member yet
858 research outputs found
Sort by
Polyelectrolyte Microcapsules: A versatile and sensitive tool for the detection of protein and nucleic-acid analytes
No full textDevelopment of novel detection systems for the detection of biological intermediates and markers is a challenging and fascinating task in modern diagnostics. Detection of such analytes, particularly at low concentrations, is of prime importance, as it may lead to early detection of disease and eventually better treatment.
In my PhD work described in the thesis, I have developed a simple, sensitive, and selective sandwich assay using microcapsules produced by layer-by-layer assembly, capable of detecting proteins and nucleic acids, using flow cytometry as an optical readout. The microcapsule-based assay described here is a novel single-bead assay, and it can serve as a universal platform for detecting diverse biomarkers, as the surface chemistry of the microcapsules can be adjusted. This makes them suitable for a great variety of applications in biochemistry and cell biology. The microcapsules described here have carboxylate groups at their surface, are chemically crosslinked, and are further surface-functionalized with adaptor proteins such as protein A and streptavidin. Adaptor proteins ensure an optimized orientation of antibodies or biotinylated oligos, which is useful for the detection of analytes and in the development of a sensor.
First, the capability of the protein A-coated microcapsules for detecting the disease biomarker human beta-2 microglobulin (hβ2m) in the femtomolar concentration range in is demonstrated both in buffer and in serum. Second, the streptavidin-coated microcapsules are used to detect nucleic acids in nanomolar concentration range.
The microcapsule based assay showed a 450-fold higher sensitivity than commercially available polystyrene beads for the detection of hβ2m, while both the microcapsules and the PS beads exhibited similar efficiency for the detection of nucleic acids. The developed assay allows rapid quantitative analyte measurement while providing high sensitivity and selectivity at very small sample quantities. The detection of analytes through protein A- and streptavidinmodified microcapsules as a platform for a single bead assay is shown in this study
Social Representations of Intergroup Differences: The Case of Turkish Nationhood
No full textThis thesis is concerned with intergroup difference in the context of nationhood. One of the main aims of this thesis is to problematize certain taken-for-granted assumptions of intergroup relations research in social psychology. The research area of intergroup relations departs from a tacit acceptance of difference as a natural given. Differences between individuals and groups lie at the heart of fundamental concepts like prejudice, conflict or tolerance, and processes like identification or categorisation. In this thesis, I have attempted to develop an approach that incorporates both the consequences of differentiation and the contents of difference. In doing this, I have drawn upon a theoretical approach, social representations theory (Jovchelovitch, 2007; Marková, 2003; Moscovici, 1961/2008), which offers the resources to make sense of the consensual realities and the communication processes through which social knowledge is constructed, maintained and challenged.
I have investigated representations of intergroup differences in the context of Turkish nationhood. This allowed me to explore the fluid nature of nationhood as a social category. Empirical studies and a conceptual study allowed me to show how different manifestations of the Turkish nationhood have been reproduced and contested. As such, this thesis has contributed to intergroup relations research through its emphasis on problematizing, contextualising and distinguishing contents of categories in relation to the fluid nature of boundary-making and differentiation. Such a focus might contribute towards a better conceptualisation of inclusivity, as clarification of taken-for-granted contents of categories are advocated. I hope to have emphasised the importance of deconstructing mechanistic understandings of intergroup relations and the need to construct a more organic conception of superordinate (inclusive) categories.
Analysis of Graphic Narratives: War in Lebanese Comics
No full textIn a country of ongoing conflict like Lebanon, war comics constitute about half of the national comics production, representing an emerging market share of the publishing sector in the country. It is said that Lebanon suffered a 'state of amnesia' after the 1975-1990 Civil War; something which has turned into a 'state-sponsored amnesia'. However, civic movements have been initiating debates around the war, its consequences, and its results as it monopolizes a large part of the cultural production in the country. Indeed, a big portion of recent Lebanese comics contributes that debate. This study examines the large narrative corpus of these particular comics with the interest on the narrative strategies used to tell the violence of war. The system of comics and its narrativity were visualized to facilitates the application of its analysis. The visualization is an analytical interface that enables the annotation and the mapping of comics using the visual, the linguistic and the spatial modes of comics. The interface, called Amphibian, enables the analysis of narratological elements such as events and characters – the focus of the thesis focuses. A survey of thematic reoccurrences was conducted on all the pages of the corpus revealing significant violent events and armed men. Both multimodal and narrative analysis were used to extract the narratives of war from the comics material. Visualization was also used to dissect and map the icono-textual constituents and accommodate the linear and tabular deployment of the comics. A mapping of 'men/guns' was applied, and narratives of war were extracted and analyzed. A chronology of the warfare events and their focalization, and the character's identity and agency, determined the nature of the graphic narratives and their contribution to the war debate
Us vs. Them: Effects of individual acculturation orientation and host culture acculturation orientation on immigrant health behaviours and quality of life
No full textCurrent societal shifts are moving us into an increasingly globalized world. For such
changes to be successful, a deeper understanding of individuals and their behaviours is required. A key area where such an understanding is lacking is in the relationship and communication between doctors and immigrant patients, which is often challenging and can negatively influence the patients (Ng, 2011).
This thesis explores attitudes of immigrant patients and host culture doctors towards immigrants, and how these attitudes interrelate with immigrants’ health behaviours and quality of life. Main theoretical assumptions include the notion that attitudes toward and from members of a host culture can influence a migrant's behaviours, as proposed by Berry's acculturation orientations (Berry, 1998, 2001), and that behaviour change depends on environment, people and behaviour (Bandura, 1986; Ward & Geeraert, 2016).
Acculturation orientations of immigrant patients and their host culture doctors towards immigrant patients are examined for effects on (1) perceived quality of care, (2) immigrants’ health behaviours, and (3) immigrants’ quality of life. Measures were collected via interviews, medical visit video recordings, and questionnaires; health behaviours included nutrition, physical activity, and medical advice adherence, while quality of life was measured via the World Health Organization Quality of Life Instrument (WHOQOL) (WHO, 1991). Semi-structured qualitative interviews were conducted to assess similar topics in greater depth. Qualitative (Thematic Analysis and the Verona Coding System) and quantitative (ANOVA, regression and structural equation modelling) analyses were used.
These investigations provide insights into how increased contact between cultures may impact health on an individual level, and how misunderstandings can be acknowledged and potentially intervened upon, to minimize detrimental effects and foster improved functioning for diverse members of society
Uncertainty in Medical Visualization
No full textThe many steps in the medical visualization pipeline introduce some amount of uncertainty based on errors or assumptions. The rendered images presented to the user, typically a medical expert, most often omit this information. Since medical experts rely on these visualizations to bring conclusions about the existence and severity of a potential disease or to come up with a treatment plan, conveying the uncertainty that is inherent to the displayed information becomes a crucial part towards a better, more informed decision making.
To do so, we describe different types of uncertainties mathematically, which allows us to abstract them from the underlying source and application. We then develop a taxonomy for uncertainty types and identify the biggest challenges when conveying uncertainty through the visualization methods.
We convey the uncertainty information in one of the uncertainty types by rendering a single, non-obstructive, most likely surface and encode the variability around it by using color or textures. We then couple this with interactive investigation methods, which allow for a detailed analysis of the uncertainties. Our visualization methods are applied to a concrete medical application - stenoses assessment in vascular structures and are evaluated with medical experts, who showed a clear preference for our solution. We also investigated using probabilistic ensembles of different segmentation outputs to reduce the final uncertainty.
We then looked into the uncertainty coming in from the simulation parameters in radiofrequency ablation. We developed methods to address the uncertainty in the simulation output to two different target groups - medical experts and simulation experts. To the former, we show the uncertainty using perceptually uniform, intuitive uncertainty glyphs. For the latter, we integrated tools in our system that allow for an interactive analysis of the impact of different parameters and different parameter ranges on the simulation result
Globalizing "Sacred Knowledge": South Asians and the Theosophical Society, 1879-1930
No full textThe dissertation deals with the South Asian members of the Theosophical Society between the landing of the founders Helena Blavatsky and Henry Steel Olcott in India and Jiddu Krishnamurti`s declaration of independence from the Theosophical Society in California. This is also the trajectory of the work - from colonial South Asia to the new world. It follows its South Asian heroes in their global biographies on the paths of the Theosophical Society and far beyond. Though this is not an institutional history one can learn that the Theosophical Society was part of most progressive movements around the turn of the century - be it women`s emancipation, vegetarianism or new education - and fostered the relationship between the "East" and the "West". The non-Eurocentric perspective throws light on the influential but underrepresented South Asian personnel.
The study can be an enriching read for scholars of Global History, South Asian History, Religious Studies or Esoteric History
Facilitation of informal learning at work: Antecedents and tailored intervention designs for the steel industry and beyond
No full textInformal learning is a main form of learning in the workplace today, and is expected to increase in importance. Blue-collar workers profit from informal learning situations, because they generate action-oriented knowledge ad hoc, which makes it easy to apply in a new situation.
Study I performs a meta-analytic summary on the current state of the research on informal workplace learning. After developing and applying a taxonomy for important antecedents, it compares several classes of learning factors and context factors in their relation to informal learning. Important findings are that peer support correlates higher with informal learning than supervisor support, Asian samples make more use of informal learning than Western samples, and blue-collar workers profit more from contextual factors than white-collar workers.
Study II examines the context in depth, using age climate as an important antecedent of learning and productive working in demographic change. As in study I, study II also identifies a difference between blue-collar and white-collar workers in that younger blue-collar workers perceive the age climate in their team much better than their older coworkers.
In the informal learning sector in particular, motivation to learn is a crucial antecedent. Therefore, study III examines correlates of motivation to learn in a blue-collar sample. While in a cross-sectional general analysis, person-related factors seemed to have more weight than supervisor support and job demands, an intervention study suggested that shift leader training is more effective in raising employees’ motivation to learn than individual training of the workers themselves.
The thesis has a strong emphasis on the practical applicability of its findings. All studies focus on factors that can be addressed in interventions, and reflect on the practical implications of all findings for managers who aim to enhance informal learning and learning culture in their organization
Matrix-free techniques for efficient image registration and their application to pulmonary image analysis
No full textThis PhD thesis presents a generic approach to more efficient image registration in a classical optimization-based framework. The calculation of the objective function derivatives is targeted as a whole, thereby fusing the computations for image transformation, interpolation and image similarity to one explicit, matrix-free expression. The employed concept reduces the auxiliary space requirements for derivative computation from linear to constant and greatly facilitates parallel execution. We study its usage both for affine-linear and deformable image registration algorithms designed for monomodal and multimodal problems. Additionally, implementations on alternative platforms such as graphics processing units or embedded digital signal processors are discussed.
The practical value of the considered approach is illustrated on real-world applications from various areas of medical image computing. In particular, pulmonary image registration algorithms are studied for two use cases: computer assistance for lung cancer screening and oncological follow-up assessment, and quantitative analysis for chronic obstructive pulmonary disease. For both applications, efficient solutions are presented that combine state-of-the-art accuracy with clinically acceptable runtime and memory footprint. Our algorithms are extensively evaluated on three publicly available, expert-annotated data collections.
The thesis is completed by a study of three further medical applications of image registration: alignment of positron emission tomography (PET) with computed tomography (CT) scans for joint radiological reading, registration of magnetic resonance and CT images in the context of deep brain stimulation, and real-time tracking of liver vessels in long ultrasound sequences for motion compensation. In all three applications, the proposed matrix-free calculation schemes contribute to moderate resource demands, which allow for unproblematic execution in a clinical environment
Structure-function relation and transport across Gram-negative outer membrane channels investigated by Electrophysiology
No full textThe outer membrane (OM) of Gram-negative bacteria contains channels involved in small molecule uptake. Based on the energy used for the molecular transport, these channels are classified as passive diffusion channels and active transporters. For selective molecular uptake, channels display various structural features such as long extracellular loops, residue constellations near constriction region and various N-terminus extensions.This thesis focuses on two main concepts: the structure-function relation of OM channels and the associated transport. For the investigated passive diffusion channels and active transporters, the role of N-termini in their structure-function relation was studied using electrophysiology. Furthermore, translocation was probed for both charged and uncharged molecules.
The existence and role of electro-osmosis in substrate translocation is the most exciting result, along with the gating behaviour of the N-terminus of the uncharged cyclodextrin specific channel CymA from Klebsiella oxytoca. Moreover, the electro-osmosis phenomenon is not bound to this specific channel.
For the putative channel DcaP from Acinetobacter baumannii, its existence as a trimeric channel and exclusive anion selectivity was revealed. It possesses a long N-terminus, the role of which in the uptake of charged dicarboxylic acids was established.
For the SusCD protein complex involved in the glycan metabolism of human gut bacteria, the role of N-terminus as a plug in SusC transporter was established. Pedal- bin mechanism of the two interacting proteins was also elucidated.
For the efflux protein OM component TolC, its channel opening was explained at extreme applied voltages.
Overall, the results of my doctoral study encompass conclusions on the role of N-termini, the presence and role of electro-osmosis, the uptake of charged dicarboxylic acids, a novel mechanism for inter-protein interactions and even on channel opening mechanisms
Physically accurate chewing simulation for analyzing dental restorations
No full textCAD/CAM software is the state of the art option for replacing a missing or damaged tooth, by virtually designing the replacement, without the need of taking physical imprints of the teeth. When the restoration’s shape is not optimal it can cause discomfort, requiring further adjustments. In order to prevent this event, several algorithms are used to optimize the restoration shape based on a number of parameters. In addition, a virtual articulator can be used to simulate a chewing motion and identify contact points between the proposed restoration and the teeth it comes in contact with. In an effort to take this idea one step further, we have developed an application which can simulate the chewing process together with a deformable substrate, an element missing until now. By enhacing the application with this additional feature, we are able to observe not only the interaction between the teeth but also the manner in which they interract with the food, therefore identifying a larger range of possible problem areas. Based on the results of the simulation, the optimal restoration can be chosen, therefore further minimizing the necessity of further adjustments.
The movements of the lower jaw are based on data acquired from real life subjects chewing a gummy bear. The deformable substrate is based on a Finite Element method which ensures the realism of the deformations. A collision detection mechanism based on shooting rays through the scene is used to detect active areas and compute the resulting chewing forces. When the stress in the substrate exceeds a certain threshold, the object fractures into multiple deformable pieces which continue to interact with each other until the simulation reaches its end. Throughout the simulation, the collision areas on the teeth as well as the stress areas on the substrate are emphasized with a color map