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Retrieval of stratospheric aerosol characteristics from spaceborne limb sounders
Full text linkIn this thesis, the methods to retrieve aerosol extinction coefficient (Ext) and particle size distribution (PSD) parameters from the remote sensing instruments measuring in the limb-viewing geometry are presented. The Ext retrieval algorithm is applied for SCIAMACHY instrument as well as for OMPS measurements. These products compose global stratospheric aerosol databases, which are covering over 16 years. Additionally, the aerosol PSD parameters are retrieved in the tropical region (20AAdegreeN-20AAdegreeS) from SCIAMACHY limb measurements, creating a unique product. Both, Ext and PSD products were validated through comparison with other space-borne and in situ measurements, showing good and consistent results. In the thesis, the case studies analyzing changes in Ext and PSD parameters after volcanic eruptions of Manam and Tavurvur are presented. Additionally, the evolution of Ext after eruptions of Sarychev Peak and Kelut as well as after Canadian Wildfires of 2017 is analyzed
New Approaches to Simultaneous Multislice Magnetic Resonance Imaging : Sequence Optimization and Deep Learning based Image Reconstruction
Full text linkMagnetic resonance imaging (MRI) is a versatile imaging modality in clinical diagnostics. Despite the impressive range of application, a main drawback of MRI is its inherently low acquisition speed. However, scan time is crucial for many applications and also for an efficient utilization of MRI in clinical routine. Two developments have influenced MRI recently: Simultaneous multislice imaging (SMS) and deep learning (DL). Simultaneous multislice imaging is a paradigm shift in MRI which has re-emerged in the early 2010'. It yields improved image quality compared to in-plane parallel imaging, because it benefits from increased signal-to-noise ratio and robustness for higher accelerations. SMS sequences accelerate data acquisition by undersampling along the slice dimension and specific algorithms allow reconstruction of these undersampled data. In the first part, SMS was extended to measure multiple image contrasts in contrast-enhanced dynamic MRI. Therefore, a bespoke MRI sequence was developed to accelerate segmented echo-planar imaging of three echoes. Dynamic in-vivo data with sufficient spatial coverage were acquired in an animal model. Data acquisition were fast enough to sample the arterial input function which is essential for pharmacokinetic modeling. Imperfections in the excitation of multiple slice and their relevance for reconstruction algorithms were closely investigated and evaluated for processing of multi-contrast data. This work connects SMS and deep learning. Today, the application of deep learning in medicine assists decision making in medical diagnosis, analysis of radiologic data or personalized medicine in genomics. In MRI however, deep learning has just entered the stage. With two abstracts matching the search term 'deep learning' at the ISMRM 2016, the number of abstracts rose to 42 in 2017 and to 139 in 2018. Most of the early contributions to DL in MRI concern image processing and data evaluation. Image reconstruction itself is mostly conducted in standard fashioned way. Common algorithmic approaches applying deep neural networks for (some) processing steps have shown impressive results and can often be generalized to similar problems. In the second part, the separation of overlapping slice content after SMS was performed by an artificial neural network. This novel reconstruction technique, termed SMSnet, does not require any reference data for calibration of the MR machine's receiver characteristics. Omitting the need for reference data could extend the use of modern accelerated imaging sequences to a broad spectrum of applications. Potential and limitations of this approach were investigated in various experiments accounting for image quality, robustness, sensitivity and how the network generalizes. The discussion at the end summarizes and relates the results of this work to state-of-the-art techniques and recent developments in MRI and gives an outlook to future work on SMS and DL-based reconstructions
Entwicklungspfade intelligenter Transportsysteme für den Straßengüterverkehr
Full text linkToday's road network has reached its limits in most major cities and at certain times. Similarly, the capacity of the road network is largely exhausted. In addition, the change in delivery cycles in the food industry from a regular delivery structure to just-in-time deliveries leads to an increased delivery volume. But also E-commerce, the share economy and the customer's demand for faster delivery (same-day delivery) are leading to an additional rise in the supply sector. With the road infrastructure remaining the same, it is therefore not surprising that more and more slow-moving traffic and congestion are occurring. Intelligent transport systems (ITS) offer the possibility to improve the road capacity without excessive structural measures. The aim of this dissertation project is to provide insights of research achieved so far in the field of ITS for road freight transport and to estimate further developments by means of scenario generation. In addition to the presentation of ITS for road freight transport and the creation of environmental scenarios, action implications for the individual areas of ITS in road freight transport are presented. If the first scenario occured, this would have many positive effects on the transport process, but it would be of little importance, as the favourable factors are present in this scenario. If the second scenario occured, this would have many effects and a medium significance for ITS. In the case of the third scenario, this would be of medium to high significance, since in this scenario there are few ITS factors favouring road freight transport. The effects on the intelligent transport sector would be correspondingly small because these systems would not exist. This work provides first future oriented analysis in ITS related research
Finite and Infinite Rotation Sequences and Beyond
Full text linkThe encoding of orbits attained from rigid rotations are investigated from different perspectives. In the first part of the thesis regularity conditions for irrational rotations will be studied in terms of their continued fraction expansions and a categorisation is achieved for continued fraction expansions which do not grow too fast. The second part focuses on the spectral properties of beta-transformations for beta sqrt(2). Here an explicit representation for the Bochner transform of autocorrelations stemming from Dirac combs derived from beta-transformations is achieved, which consists of a Lebesgue absolutely continuous part and a discrete part. The last part focuses on vague limits of these autocorrelations where beta tends to 1. Here a link to subshifts derived from rigid rotations will be established. The Bochner transform of these vague limits can be given explicitly in some cases and is shown to be either discrete, non-discrete singular to Lebesgue, or a mixture of both
Logistik, eine technologisch-ökonomische Revolution? - Eine historisch-konzeptionelle Studie aus innovationswissenschaftlicher Perspektive
Full text linkIt s all about the base : Marine biofilms in the plastic age
Full text linkPlastic litter is entering and accumulating in our oceans and can be found in the marine environment all over the globe. When entering marine waters, plastics as any other surface, is rapidly colonized by a plethora of organisms, which form dense biofilms on the plastic surface, the so-called a Plastispherea . Despite growing concerns about the ecological impact of plastics on the marine environment during the last decade, the number of studies addressing Plastisphere-related questions remains limited. This thesis aimed to tackle this knowledge gap by comprehensively describing and analysing specificities of Plastisphere communities attached to chemically distinct plastic types. The specificity of mature Plastisphere communities was investigated on nine chemically different plastic types, and compared to the inert control substrate glass. The Plastisphere communities attached to diverse plastic types were found to be distinct from glass-associated communities. A more general marine biofilm core community serves as shared core among all tested plastic types and glass, rather than specific Plastisphere communities. The general heterogeneity of eukaryotic communities was much higher, indicating that the term Plastisphere is valid for mature prokaryotic biofilm communities, but may not be for eukaryotic ones. This work also showed that the prokaryotic shared core of the various mature Plastisphere communities are rather substrate unspecific, pointing towards the importance of rather rare species in plastic associated marine biofilms. A high-pressure water Jet treatment technique was developed to remove the cohesive layer of mature biofilms, while the adhesive layer remains on the plastics surface . It was shown that tightly attached microorganisms might account rather to the rare biosphere in mature Plastisphere communities, which suggests the presence of plastic a specifica microorganisms/assemblages. Due to their longevity, plastics could be transported over long distances in marine environments, and therefore may function as a vector for the dispersal of pathogenic species. To test this, plastic particles were collected in the North Sea and the Baltic Sea and screened for the presence of pathogens. Potentially pathogenic Vibrio parahaemolyticus were discovered on a number of microplastic particles, e.g. polyethylene, polypropylene and polystyrene. Mostly, this species co-occurred also in surrounding seawater, suggesting that seawater serves as a possible source for Vibrio colonization on microplastics. The confirmed occurrence of potentially pathogenic bacteria on marine microplastics highlights the urgent need for detailed biogeographical analyses of marine microplastics. The results from this thesis substantially increase our understanding of the diversity and specificity of Plastisphere communities. This thesis comprises a detailed and descriptive approach, which provides a fundamental knowledge basis for future research on Plastisphere questions related to e.g. potential biodegradation of marine plastics and the vector function for alien and potentially pathogenic species
The implications of automation for economic growth when investment decisions are irreversible
Full text linkThis paper discusses automation embedded into a standard growth model without exogenous growth when investment decisions for physical and automation capital are irreversible. The imposed nonnegativity constraints on physical and automation capital induces an imbalance effect between the growth rate of output and the fraction between physical and automation capital. The paper shows that this imbalance effect leads (i) to transitional dynamics off the steady state while (ii) retaining perpetual growth of the AK style in the steady state without exogenous technological progress. We also show that the resulting transition path does not have to be on the saddle path of the system without the nonnegativity constraints
Polysaccharide utilization loci and associated genes in marine Bacteroidetes - compositional diversity and ecological relevance
Full text linkThe synthesis of marine organic carbon compounds by photosynthetic macroalgae, microalgae (phytoplankton) and bacteria provide a basis for life in the ocean. In marine surface waters this primary production is largely dominated by microalgae and is especially pronounced during spring phytoplankton blooms. During and after these often diatom-dominated blooms, increased amounts of organic matter are released into the surrounding waters. Here, the organic matter, rich in polysaccharides, can trigger blooms of heterotrophic bacteria. Marine members of the Bacteroidetes are consistently found related to such bloom events. These bacteria are regularly detected as the first responders to thrive after phytoplankton spring blooms in temperate coastal regions and are often equipped with a variety of polysaccharide utilization gene clusters. These gene clusters, termed polysaccharide utilization loci (PULs), encode enzymes for the extracellular hydrolysis of polysaccharides and the subsequent uptake of oligosaccharides into the periplasm, where they are shielded from competing bacteria. This mechanism allows for rapid uptake and substrate hoarding, and thus could be one reason why Bacteroidetes are often seen as the first responders of the bacterioplankton community. The investigation of the so far largely unknown diversity and the ecological relevance of PULs in marine Bacteroidetes was the major goal of the work presented here. We could show that genomes of Bacteroidetes isolates from the North Sea, with free-living to micro- and macro-algae associated lifestyles, harboured a variety of these loci predicted to target in total 18 different substrate classes. Overall PUL repertoires of these isolates showed considerable intra-genus and inter-genus, variations suggesting that Bacteroidetes species harbour distinct glycan niches, independent of their phylogenetic relationships. By investigating the PUL repertoires of uncultured free-living Bacteroidetes during three consecutive years of spring phytoplankton blooms at the North Sea island of Helgoland, I could further reveal that the set of targeted substrates during these bloom events was dominated by only five of the substrate classes targeted by the isolates. These were the diatom storage polysaccharide laminarin, alpha-glucans, alginates, as well as substrates rich in alpha-mannans and sulfated xylans. In addition to this constrained set of substrate classes targeted by the free-living Bacteroidetes community, I could show that the species diversity during these blooms was limited and dominated by only 27 abundant and recurrent species that carried a limited number of abundant PULs. The majority of these PULs were targeting laminarin and alpha-glucan substrates, which were likely targeted during the entire time of the blooms. The less frequent PULs, targeting alpha-mannans and sulfated xylans, were predominantly detected during mid- and late- bloom phases, suggesting a relevance of these two substrate classes in the later phases of phytoplankton blooms. Overall these findings highlight the recurrence of a few specialized Bacteroidetes species and the environmental relevance of specific polysaccharide substrate classes during spring phytoplankton blooms. However, for some of these substrate classes the origin, structural details and their abundance during blooms are as yet largely unknown. To further shed light on the polysaccharide niches of abundant key-players, these findings can serve as a guide for future laboratory studies
Round Table Discussion on Nation(alism), Identity and Video Gaming with Megan Condis, Marijam Didzgalvyt , Georg Hobmeier and Souvik Mukherjee
No full textQuestions of nation and identity not only concern multiple aspects of video games, their production, and their consumption, but also require further and manifold discussion from different perspectives. In an effort to bring together voices from different fields that engage with video games and gaming practices from various perspectives, this virtual round table discussion attempts to open up the conversation beyond the realms of academia. Kathrin Trattner and Lisa Kienzl talked to Megan Condis, Marijam Didzgalvyt , Georg Hobmeier and Souvik Mukherjee about how concepts such as nation(alism) and identity impact video game representations, the gaming industry, and online gaming cultures in numerous ways