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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Dynamic Thermal Imaging for Intraoperative Monitoring of Neuronal Activity and Cortical Perfusion

Hoffmann, Nico 23 November 2017 (has links) (PDF)
Neurosurgery is a demanding medical discipline that requires a complex interplay of several neuroimaging techniques. This allows structural as well as functional information to be recovered and then visualized to the surgeon. In the case of tumor resections this approach allows more fine-grained differentiation of healthy and pathological tissue which positively influences the postoperative outcome as well as the patient's quality of life. In this work, we will discuss several approaches to establish thermal imaging as a novel neuroimaging technique to primarily visualize neural activity and perfusion state in case of ischaemic stroke. Both applications require novel methods for data-preprocessing, visualization, pattern recognition as well as regression analysis of intraoperative thermal imaging. Online multimodal integration of preoperative and intraoperative data is accomplished by a 2D-3D image registration and image fusion framework with an average accuracy of 2.46 mm. In navigated surgeries, the proposed framework generally provides all necessary tools to project intraoperative 2D imaging data onto preoperative 3D volumetric datasets like 3D MR or CT imaging. Additionally, a fast machine learning framework for the recognition of cortical NaCl rinsings will be discussed throughout this thesis. Hereby, the standardized quantification of tissue perfusion by means of an approximated heating model can be achieved. Classifying the parameters of these models yields a map of connected areas, for which we have shown that these areas correlate with the demarcation caused by an ischaemic stroke segmented in postoperative CT datasets. Finally, a semiparametric regression model has been developed for intraoperative neural activity monitoring of the somatosensory cortex by somatosensory evoked potentials. These results were correlated with neural activity of optical imaging. We found that thermal imaging yields comparable results, yet doesn't share the limitations of optical imaging. In this thesis we would like to emphasize that thermal imaging depicts a novel and valid tool for both intraoperative functional and structural neuroimaging.
102

Segmentation and Tracking of Cells and Nuclei Using Deep Learning

Hirsch, Peter Johannes 27 September 2023 (has links)
Die Analyse von großen Datensätzen von Mikroskopiebilddaten, insbesondere Segmentierung und Tracking, ist ein sehr wichtiger Aspekt vieler biologischer Studien. Für die leistungsfähige und verlässliche Nutzung ist der derzeitige Stand der Wissenschaft dennoch noch nicht ausreichend. Die vorhandenen Methoden sind oft schwer zu benutzen für ungeübte Nutzer, die Leistung auf anderen Datensätzen ist häufig verbesserungswürdig und sehr große Mengen an Trainingsdaten werden benötigt. Ich ging dieses Problem aus verschiedenen Richtungen an: (i) Ich präsentiere klare Richtlinien wie Artefakte beim Arbeiten mit sehr großen Bilddaten verhindert werden können. (ii) Ich präsentiere eine Erweiterung für eine Reihe von grundlegenden Methoden zur Instanzsegmentierung von Zellkernen. Durch Verwendung einer unterstützenden Hilfsaufgabe ermöglicht die Erweiterung auf einfache und unkomplizierte Art und Weise Leistung auf dem aktuellen Stand der Wissenschaft. Dabei zeige ich zudem, dass schwache Label ausreichend sind, um eine effiziente Objekterkennung auf 3d Zellkerndaten zu ermöglichen. (iii) Ich stelle eine neue Methode zur Instanzsegmentierung vor, die auf eine große Auswahl von Objekten anwendbar ist, von einfachen Formen bis hin zu Überlagerungen und komplexen Baumstrukturen, die das gesamte Bild umfassen. (iv) Auf den vorherigen Arbeiten aufbauend präsentiere ich eine neue Trackingmethode, die auch mit sehr großen Bilddaten zurecht kommt, aber nur schwache und dünnbesetzte Labels benötigt und trotzdem besser als die bisherigen besten Methoden funktioniert. Die Anpassungsfähigkeit an neue Datensätze wird durch eine automatisierte Parametersuche gewährleistet. (v) Für Nutzer, die das Tracking von Objekten in ihrer Arbeit verwenden möchten, präsentiere ich zusätzlich einen detaillierten Leitfaden, der es ihnen ermöglicht fundierte Entscheidungen zu treffen, welche Methode am besten zu ihrem Projekt passt. / Image analysis of large datasets of microscopy data, in particular segmentation and tracking, is an important aspect of many biological studies. Yet, the current state of research is still not adequate enough for copious and reliable everyday use. Existing methods are often hard to use, perform subpar on new datasets and require vast amounts of training data. I approached this problem from multiple angles: (i) I present clear guidelines on how to operate artifact-free on huge images. (ii) I present an extension for existing methods for instance segmentation of nuclei. By using an auxiliary task, it enables state-of-the-art performance in a simple and straightforward way. In the process I show that weak labels are sufficient for efficient object detection for 3d nuclei data. (iii) I present an innovative method for instance segmentation that performs extremely well on a wide range of objects, from simple shapes to complex image-spanning tree structures and objects with overlaps. (iv) Building upon the above, I present a novel tracking method that operates on huge images but only requires weak and sparse labels. Yet, it outperforms previous state-of-the-art methods. An automated weight search method enables adaptability to new datasets. (v) For practitioners seeking to employ cell tracking, I provide a comprehensive guideline on how to make an informed decision about what methods to use for their project.
103

Enforcement in sovereign debt markets

Schumacher, Julian 08 December 2015 (has links)
Die Arbeit befasst sich mit ökonomischen Effekten der rechtlichen Durchsetzung von Staatsschulden. Die Literatur nimmt weitgehend an, dass diese größtenteils irrelevant sind. Die Dissertation präsentiert neu erstellte Datensätze über Anlegerklagen in den USA und UK, und verbindet diese mit Finanzmarktdaten. Die zentralen Ergebnisse sind: (1) Staatsschuldenkrisen sind zunehmend begleitet von Anlegerklagen, wenn auch die Zahl gering ist. Klagen sind wahrscheinlicher wenn Regierungen hohe Verluste auf ihre Gläubiger abwälzen. Sie können zudem signifikante Kosten durch die Versperrung des Finanzmarktzugangs mit sich bringen. Insbesondere spezialisierte Investoren führen Klagen, und die vertragliche Gestaltung der Anleihen bedingt Teilnahme- und Klageraten. (2) Marktpreise spiegeln diese Entwicklungen wider. Die Marktliquidität nimmt während Schuldenkrisen signifikant ab und Staatsanleihen, die bessere rechtliche Durchsetzungsmöglichkeiten versprechen, werden zu höheren Preisen gehandelt. / This thesis studies the economic impact of legal enforcement of sovereign debt. The literature assumes that legal enforcement mechanisms are largely irrelevant. The thesis presents newly assembled datasets on lawsuits filed by private investors against governments in the US and the UK, and connects them with financial market data. The main findings are: (1) Sovereign defaults are increasingly subject to investor lawsuits, although the numbers are still small. Lawsuits are more likely if governments impose large losses on their creditors. Litigation can create significant costs by affecting governments'' financial market access. Distressed investors are especially likely to file suit, and contract design is a significant predictor of participation and litigation. (2) Sovereign bond pricing reflects these developments. Market liquidity decreases significantly during debt crises. Furthermore, sovereign bonds with stronger legal protection trade at higher prices during financial crises.
104

Leaf Anatomy Of Five Species Of Limonium Mill. (plumbaginaceae)

Bal, Zeynep 01 May 2011 (has links) (PDF)
In this study, leaf anatomies of five species of Limonium Mill. (L. echioides, L. globuliferum, L. tamaricoides, L. anatolicum and L. Sinuatum) are studied. Taca belonging to five different sections of the genus Limonium as / L. echioides of the section Schizyhymenium, L. globuliferum of the section Sphaerostachys, L. tamaricoides of the section Limonium, L. anatolicum of the section Sarcophyllum and L. sinuatum of the section Pteroclados are used in this study. Throughout the species studied, L. tamaricoides and L. anatolicum are endemic to Turkey. In order to examine anatomy of leaves, the paraffin sectioning and hand cross sectioning methods are used. Avarage stomata length, width and number per 210.68&micro / m x 263.27&micro / m area of the leaves are examined and the stomata types due to epidermal cells are defined. Additionally, the vascular bundles, upper and lower epiderms of leaves of each species are defined. It is determined that except the species L. globuliferum and L. tamaricoides, the stomata density per 210.68&micro / m x 263.27&micro / m area of the leaves are approximately same for upper and lower epidermis, but in these species, the stomata numbers at upper epidermis is higher than the stomata numbers in lower epidermis, which might be related with the altitude, microclimate and habitat of these two species. It is also found that except the shoot leaf of L. sinuatum, the phloem is closer to lower epiderm than xylem in vascular bundles. But in shoot leaf of L. sinuatum, the phloem circularly covers the xylem and makes a closed circle around.
105

CASSANDRA: drug gene association prediction via text mining and ontologies

Kissa, Maria 28 January 2015 (has links) (PDF)
The amount of biomedical literature has been increasing rapidly during the last decade. Text mining techniques can harness this large-scale data, shed light onto complex drug mechanisms, and extract relation information that can support computational polypharmacology. In this work, we introduce CASSANDRA, a fully corpus-based and unsupervised algorithm which uses the MEDLINE indexed titles and abstracts to infer drug gene associations and assist drug repositioning. CASSANDRA measures the Pointwise Mutual Information (PMI) between biomedical terms derived from Gene Ontology (GO) and Medical Subject Headings (MeSH). Based on the PMI scores, drug and gene profiles are generated and candidate drug gene associations are inferred when computing the relatedness of their profiles. Results show that an Area Under the Curve (AUC) of up to 0.88 can be achieved. The algorithm can successfully identify direct drug gene associations with high precision and prioritize them over indirect drug gene associations. Validation shows that the statistically derived profiles from literature perform as good as (and at times better than) the manually curated profiles. In addition, we examine CASSANDRA’s potential towards drug repositioning. For all FDA-approved drugs repositioned over the last 5 years, we generate profiles from publications before 2009 and show that the new indications rank high in these profiles. In summary, co-occurrence based profiles derived from the biomedical literature can accurately predict drug gene associations and provide insights onto potential repositioning cases.
106

Local Equilibrium States in Quantum Field Theory in Curved Spacetime / Lokale Gleichgewichtszustände in der Quantenfeldtheorie auf gekrümmter Raumzeit

Solveen, Christoph 11 April 2012 (has links)
No description available.
107

Detection of KRAS Synthetic Lethal Partners through Integration of Existing RNAi Screens

Christodoulou, Eleni 18 December 2014 (has links) (PDF)
KRAS is a gene that plays a very important role in the initiation and development of several types of cancer. In particular, 90% of human pancreatic cancers are due to KRAS mutations. KRAS is difficult to target directly and a promising therapeutic path is its indirect inactivation by targeting one of its Synthetic Lethal Partners (SLPs). A gene G is a Synthetic Lethal Partner of KRAS if the simultaneous perturbation of KRAS and G leads to cell death. In the past, efforts to identify KRAS SLPs with high-throughput RNAi screens have been performed. These studies have reported only few top-ranked SLPs. To our knowledge, these screens have never been considered in combination for further examination. This thesis employs integrative analysis of the published screens, utilizing additional, independent data aiming at the detection of more robust therapeutic targets. To this aim, RankSLP, a novel statistical analysis approach was implemented, which for the first time i) consistently integrates existing KRAS-specific RNAi screens, ii) consistently integrates and normalizes the results of various ranking methods, iii) evaluates its findings with the use of external data and iv) explores the effects of random data inclusion. This analysis was able to predict novel SLPs of KRAS and confirm some of the existing ones.
108

Das Altenheim - immer noch eine "Totale Institution" ? / Eine Untersuchung des Binnenlebens zweier Altenheime / A research of life in two old people´s homes / The old people´s home - still a "total institution"?

Heinzelmann, Martin 16 July 2004 (has links)
No description available.
109

Recently Discovered 18th Dynasty Tombs at Central Dra’ Abu el-Naga

Aglan, Hassan 16 March 2020 (has links)
Gegenstand dieser Studie ist eine Gruppe von acht Felsgräbern und zwei Schaftgräbern im Zentralbereich von Dra’ Abu el-Naga (Central Dra’ Abu el-Naga, CDAN) auf der thebaischen Westseite. Die Errichtung dieser Anlagen geht auf die Zeit des ägyptischen Neuen Reichs zurück, doch wurden sie über viele Generationen nach der Bestattung der ursprünglichen Grabinhaber weiter benutzt. Die Einleitung (Chapter 1) skizziert den Rahmen der Untersuchung und umfasst drei Teile: Zunächst werden Hintergrundinformationen zur geographischen Lage und physischen Gestalt des Fundareals geliefert. Schließlich werden Verlauf und aktueller Stand der Forschungen in CDAN skizziert. In folgenden Hauptkapitel (Chapter 2) werden die vom ägyptische Ministry of State of Antiquities (MSA) in dem Areal durchgeführten Ausgrabungen behandelt. Durch die Konzentration auf die Analyse der vorkommenden Architekturelemente und deren Einordnung in die in CDAN vorkommenden Stiltypen konnten unserem Wissen. Im dritten Hauptteil (Chapter 3) setze ich mich mit den Überbleibseln und Spuren der antiken Bestattungsgebräuche auseinander, also in erster Linie mit Objektgruppen auseinander. Im Letztem Hauptteil (Chapter 4) Wiederbenutzung der Grabanlagen in späteren Perioden. Abschließen wird die Bedeutung der neu entdeckten Grabanlagen für den Gesamtkontext der Archäologie von CDAN beleuchtet. Dabei haben sich neue Erkenntnisse zu den spezifischen Verwendungen und Funktionen sowie Nachverwendungen monumentaler Bestattungen in CDAN ergeben – gerade auch dadurch, dass sich der Betrachtungszeitraum vom Neuen Reich bis zur Moderne erstreckte und so unser Blick für die vielfältigen Bezugnahmen und Entwicklungen geschärft wurde. Die vier Hauptkapitel werden durch einen Katalog der behandelten Objekte ergänzt. / In this thesis, a group of eight rock cut tombs and two shaft-tombs located in Central Dra’ Abu el-Naga (CDAN) at the West Bank of Luxor were studied. The construction of these tombs dates mainly to the period of the New Kingdom (NK, c. 1550-1070 BCE), but they continued to be in use for many generations after the death of the original tomb owners. The framework of this study, as sketched in Chapter 1, is characterized by three approaches: the first section is titled The geographical and geological nature of DAN. The overview of The history of excavation at CDAN Finally, the focus is on the history of research on the necropolis of CDAN. In Chapter 2, the excavations conducted in the area by the Egyptian Ministry of State of Antiquities (MSA) are described. I described and discussed the architectural elements of the newly excavated tombs. At the end, the architectural styles that prevailed in the CDAN were described, as a step in clarifying the development of the history of the area. In Chapter 3, deals with the relics and traces of ancient burial customs, especially with the objects like statues, pottery, coffins, shanties, funerary cones, and other funerary equipment, which came to light during the excavations in the area. Particular attention was given to their dating. The last section, Chapter 4, the frequent re-use of the tombs in later periods, as illustrated, e.g., by ceramics and other small finds. At the end, the significance of the newly discovered tombs is highlighted. Further insights into the specific usages and functions of monumental tombs in CDAN in general were gained, and to increase the understanding of the connections, interrelationships and developments, this started from NK and ended to very modern time. The four main chapters are followed by a catalogue of objects.
110

Distance-based methods for the analysis of Next-Generation sequencing data

Otto, Raik 14 September 2021 (has links)
Die Analyse von NGS Daten ist ein zentraler Aspekt der modernen genomischen Forschung. Bei der Extraktion von Daten aus den beiden am häufigsten verwendeten Quellorganismen bestehen jedoch vielfältige Problemstellungen. Im ersten Kapitel wird ein neuartiger Ansatz vorgestellt welcher einen Abstand zwischen Krebszellinienkulturen auf Grundlage ihrer kleinen genomischen Varianten bestimmt um die Kulturen zu identifizieren. Eine Voll-Exom sequenzierte Kultur wird durch paarweise Vergleiche zu Referenzdatensätzen identifiziert so ein gemessener Abstand geringer ist als dies bei nicht verwandten Kulturen zu erwarten wäre. Die Wirksamkeit der Methode wurde verifiziert, jedoch verbleiben Einschränkung da nur das Sequenzierformat des Voll-Exoms unterstützt wird. Daher wird im zweiten Kapitel eine publizierte Modifikation des Ansatzes vorgestellt welcher die Unterstützung der weitläufig genutzten Bulk RNA sowie der Panel-Sequenzierung ermöglicht. Die Ausweitung der Technologiebasis führt jedoch zu einer Verstärkung von Störeffekten welche zu Verletzungen der mathematischen Konditionen einer Abstandsmetrik führen. Daher werden die entstandenen Verletzungen durch statistische Verfahren zuerst quantifiziert und danach durch dynamische Schwellwertanpassungen erfolgreich kompensiert. Das dritte Kapitel stellt eine neuartige Daten-Aufwertungsmethode (Data-Augmentation) vor welche das Trainieren von maschinellen Lernmodellen in Abwesenheit von neoplastischen Trainingsdaten ermöglicht. Ein abstraktes Abstandsmaß wird zwischen neoplastischen Entitäten sowie Entitäten gesundem Ursprungs mittels einer transkriptomischen Dekonvolution hergestellt. Die Ausgabe der Dekonvolution erlaubt dann das effektive Vorhersagen von klinischen Eigenschaften von seltenen jedoch biologisch vielfältigen Krebsarten wobei die prädiktive Kraft des Verfahrens der des etablierten Goldstandard ebenbürtig ist. / The analysis of NGS data is a central aspect of modern Molecular Genetics and Oncology. The first scientific contribution is the development of a method which identifies Whole-exome-sequenced CCL via the quantification of a distance between their sets of small genomic variants. A distinguishing aspect of the method is that it was designed for the computer-based identification of NGS-sequenced CCL. An identification of an unknown CCL occurs when its abstract distance to a known CCL is smaller than is expected due to chance. The method performed favorably during benchmarks but only supported the Whole-exome-sequencing technology. The second contribution therefore extended the identification method by additionally supporting the Bulk mRNA-sequencing technology and Panel-sequencing format. However, the technological extension incurred predictive biases which detrimentally affected the quantification of abstract distances. Hence, statistical methods were introduced to quantify and compensate for confounding factors. The method revealed a heterogeneity-robust benchmark performance at the trade-off of a slightly reduced sensitivity compared to the Whole-exome-sequencing method. The third contribution is a method which trains Machine-Learning models for rare and diverse cancer types. Machine-Learning models are subsequently trained on these distances to predict clinically relevant characteristics. The performance of such-trained models was comparable to that of models trained on both the substituted neoplastic data and the gold-standard biomarker Ki-67. No proliferation rate-indicative features were utilized to predict clinical characteristics which is why the method can complement the proliferation rate-oriented pathological assessment of biopsies. The thesis revealed that the quantification of an abstract distance can address sources of erroneous NGS data analysis.

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