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Characterization of terrestrial organic carbon in the Amazon System : insights from biomarkers and their isotopic composition (Delta-C-13 and Delta 14C)
No full textCharacterizing the origins and compositions of the terrestrial OC is critical for understanding the fate of terrestrial OC in marine sediments and constraining the terrestrial OC cycling. In this study, lignin and its isotope compositions (13C and 14C) are used as the major tools to provide a better understanding of the origins, pattern of distribution, processing, composition and fate of terrestrial OC in the Amazon system. In the Amazon system, Total organic carbon (TOC) and lignin content exhibit positive correlations with aluminium to silicon ratios (Al/Si, indicative of the sediment grain size) implying that the grain size of sediment discharged by the Amazon River plays an important role in the preservation of TOC and leads to preferential preservation of lignin phenols in fine particles. Low I 13C values of bulk OC in the main tributaries consistently correspond with the dominance of C3 vegetation. Compositions of lignin, syringyl to vanillyl (S/V) and cinnamyl to vanillyl (C/V), suggest that non-woody angiosperm tissues are the dominant source of lignin in the Amazon basin. Based on the absolute content of bulk terrestrial OC, lignin, and long-chain n-alkanoic acids and their 14C ages, half-lives of bulk terrestrial OC, lignin and long-chain n-alkanoic acids during transport are estimated to be about 2310 years, 13860 and 470 years, respectively. This suggests that the preservation of terrestrial OC in the mud belt on the Amazon shelf is more efficient than previously assumed
Plankton in an acidifying ocean : from individual responses to community changes and the potential of adaptation
Get PDFOcean acidification has strong direct (decreased seawater pH) and indirect (altered food regimes) effects on the performance of marine organisms, their trophic interactions and, consequently, whole ecosystems. Therefore, the aim of this thesis was to investigate potential direct and indirect effects of elevated pCO2 on marine planktonic organisms and their community composition, with a main emphasise on copepods and their adaptational potential. The development of high throughput sequencing technologies has provided scientists with an efficient tool to assess the biodiversity of marine communities, particularly with the recent advances in community barcoding technologies using universal primers. Another aim of this thesis was therefore, to test whether community barcoding is suitable for the assessment of marine planktonic communities, and allows the detection of compositional changes, which would probably remain unnoticed using classical morphological approaches
Entwicklung von in vivo NMR-Techniken zur Untersuchung der Auswirkung von Ozeanversauerung und -erwärmung auf die Neurophysiologie Antarktischer Fische
Get PDFOcean acidification and warming as a consequence of climate change affect marine organisms. Thus, for example, neurological changes could be observed in polar cod, which were induced by ocean acidification and warming. As a potential cause, a connection between the neurological impairments and changes in intracellular pH (pHi) has been postulated as it was described for animal models in preclinical research. Therefore, the non-invasive determination of pHi with high spatial and temporal resolution is of great interest. A promising tool for non-invasive pH measurements is the CEST contrast (Chemical Exchange Saturation Transfer), which enables the indirect detection of endogenous or exogenous molecules with exchangeable protons using changes in the NMR signal of the water pool. The CEST effect mainly depends on the concentration of a metabolite and the exchange rate between this metabolite and water, which in turn is influenced by physical and physiological parameters. These properties allow for CEST to be used for in vivo determination of changes in metabolite concentration and pH. The present thesis describes the development and adaption of the measurement method CEST MRI (Magnetic Resonance Imaging) and its application for determining changes in pHi with a high temporal and spatial resolution in the brain of marine fish. CEST from glutamate to water (GluCEST) was experimentally investigated in a broad temperature and pH range. The applicability of GluCEST to determine relative changes in pH even at low temperatures depends on glutamate concentration and on the parameters used in the experiments. Localized 1H NMR spectroscopy in combination with the application of quantification algorithms is an established method for the quantification of metabolite concentrations. In most cases, these algorithms use model functions based on chemical shifts at 37AdegreeC. Therefore, the temperature dependency of the chemical shifts for important metabolites has been examined in order to avoid systematic quantification errors caused by the use of incorrect prior knowledge for spectra recorded at temperatures different from 37AdegreeC. The exchange rates show an exponential behaviour as a function of temperature, thus offering a completely new picture of metabolites whose exchange regime offers the possibility to determine a CEST effect at temperatures near the freezing point. In this context, the taurine based TauCEST effect was investigated in a broad pH and temperature range. Investigations showed that the specificity of TauCEST offers the possibility to use this method as a suitable tool to detect pHi changes in the brain of polar cod. The first in vivo application of the TauCEST effect in the brain of polar cod showed an increase of about 1.5-3% under different CO2 concentrations. Localized 1H NMR spectroscopy, which was successfully adapted for the in vivo application in the brain of marine fish at 9.4 T, indicated no significant changes in concentration for those metabolites that mainly determine the CEST effect. Thus, the in vivo application of TauCEST proves to be an adequate method for determining non-invasively relative changes in pHi with high spatial and temporal resolution in the brain of polar cod during exposure to elevated CO2 concentrations
Factors Influencing the Value of CPD Activities Among VET Teachers
Get PDFContext: Teachers in vocational education and training (VET teachers) have specific conditions for their continuing professional development (CPD). They have a background in an initial occupation, in which they now teach and train the next generation. Thus, as VET teachers, they are expected to master the knowledge and skills of that occupation, even if they have now crossed the boundary from the community of their initial occupation to the community of the school. This study explores the perceived values among VET teachers of different activities that may contribute to their CPD in teaching subjects/initial occupations. The study examines VET at the upper secondary level in Sweden. Here, the VET teachers have the main responsibility for students' vocational learning in the vocational subjects, including the work-based parts. In the latter parts, the teachers are supplemented by supervisors at the workplace. Approach: We argue for the duality of a VET teacher identity with a professional competence that comprises two intertwined parts -- teaching skills, and knowledge of the teaching subjects based in the teachers' initial occupations. Our study is based on a situated learning perspective, and the empirical findings particularly concern values created from learning through participation and boundary crossing. CPD activities typically include some form of participation in and/or boundary crossing between school and work-life practices. In the analysis we also include the possible influence of institutional, situational, and dispositional drivers and barriers for participation in different activities. The research question was: what factors can explain the variation in perceived values created by participation in different CPD activities among VET teachers? The study was conducted as a survey of 886 Swedish VET teachers. Focus was put on the values created through different types of activity, values for the teachers' vocational knowledge, for networks in working life, and for teaching. The data were primarily analysed using logistic regression modelling. Findings: Dispositional drivers, the teacher's sex, and regular performance of the activity are important for the perceived value. The dispositional factor is the one most commonly retained, and it has a consistently positive effect. Factors such as educational background and vocational training have weaker influence, which suggests that individual driving factors are important when VET teachers assess the value of CPD activities. Conclusions: The study covers a general challenge for VET teachers, but is of particular relevance in systems with a high degree of school-based VET, full-time employed VET teachers, and VET teachers who are responsible for students' vocational learning. Here, the values for vocational knowledge, for networks, and for teaching that are created through different activities are important for the VET teacher identity. They are also interrelated, and together they provide professional development in relation to the initial occupation, and for the occupation as a vocational teacher
The Affine Uncertainty Principle, Associated Frames and Applications in Signal Processing
Get PDFUncertainty relations play a prominent role in signal processing, stating that a signal can not be simultaneously concentrated in the two related domains of the corresponding phase space. In particular, a new uncertainty principle for the affine group, which is directly related to the wavelet transform has lead to a new minimizing waveform. In this thesis, a frame construction is proposed which leads to approximately tight frames based on this minimizing waveform. Frame properties such as the diagonality of the frame operator as well as lower and upper frame bounds are analyzed. Additionally, three applications of such frame constructions are introduced: inpainting of missing audio data, detection of neuronal spikes in extracellular recorded data and peak detection in MALDI imaging data
Exploring the lipidomes of shallow-water and deep-sea hydrothermal systems
Get PDFThis dissertation focuses on the microbial ecology in hydrothermal systems, more specifically on the lipidome and encoded lipid structure-functions of microbial membranes. Shallow-water hydrothermal sediments off the coast of Milos and Dominica were investigated and analyzed for microbial membrane adaptations to different geochemical parameters. Information encoded in the assemblages of polar lipids revealed an increase in cell membrane fluidity in concert with reduced permeability as an adaptive response of both archaea and bacteria to e.g. elevated sediment temperatures. The final chapter of this thesis shows the carbon transfer from chemosynthetic bacteria to higher trophic levels in the fluids from diffuse-flow vents of the East Pacific Rise. Furthermore, the combined lipidomic approach with stable carbon isotopic analysis of lipids allowed the prediction that eukaryotes rather than bacteria are the dominant source of lipids in the investigated samples
Praxisberichte aus dem Projekt WELLDONE : Weiterentwicklung von Lehr-LernSzenarien an der Hochschule Bremen unter digitalisierten Rahmenbedingungen und in Online-Environments
No full textIm Projekt WELLDONE (Weiterentwicklung von Lehr-Lern-Szenarien an der Hochschule Bremen unter digitalisierten Rahmenbedingungen und in Online-Environments) wurden digitalisierte Methodenbausteine für die Studieneingangsphase entwickelt und in die alltägliche Unterrichtspraxis integriert. 11 Vorhaben zeigen an Praxisbeispielen, was unter Integration digitaler Medien in die Lehre verstanden werden kann und konkretisieren exemplarisch, was mit dem Begriff Online-Environments gemeint ist und wie insbesondere in der Studieneingangsphase die Balance zwischen Förderung der Selbstorganisationskompetenz und strukturierender, angeleiteter Lernbegleitung gelingen kann. Der Bericht schließt mit einem Ausblick auf einen interaktiven Methodenbaukasten als Sammlung von Lehr-Lernszenarien und Handlungsmustern für die Hochschullehre, in den erprobte und reflektierte Vorschläge für digitalisierte Varianten aus der Lehrpraxis an der Hochschule Bremen integriert werden
Macroporous Polymer-Derived Ceramic Monoliths for Cryogenic Applications Manufactured by Water-Based Freeze Casting
Get PDFMacroporous SiOC ceramics were prepared by a water-based freeze casting process, using polysiloxanes as precursors and silica sol as water phase and binder. The obtained porous monoliths have anisotropic porous structure and thermal and mechanical properties. The macroporous SiOC aimed at cryogenic applications which involve mass transport and thermal transport processes. The first part of the thesis focuses on manufacturing macroporous monoliths, in which process the surface characteristics of preceramic polymers in terms of hydrophobicity/hydrophilicity were modified to be used in the water-based freeze casting process. Two approaches were chosen for the surface modification. The first approach to modify the wettability of the precursor was pyrolysis of hydrophobic methyl phenyl polysiloxanes (H44) in inert gas at low temperature, by which hybrid ceramic materials (H44-derived filler) were generated. Depending on the pyrolysis temperatures, the surface characteristics can be varied from hydrophobic to hydrophilic. H44-derived fillers obtained by pyrolyzing methyl phenyl polysiloxane at 600 degree Celsius were hydrophilic enough to be used as solid phase in water-based process. The influence of solid loading, freeze temperatures and pyrolysis temperatures on porosity and specific surface areas were investigated. The combination of polymer derived filler materials with freezing casting method resulted in the trimodal pore structure (micro/meso/macropore) at pyrolysis temperature of 600 to 700 degree Celsius. Even at pyrolysis temperature of 1000 degree Celsius, the specific surface area was be as high as 74 square meter per gram. The pore shape can be tailored from lamellar to tubular depending on freezing temperatures. The second approach to modify the wettability was to introduce more hydrophilic groups to the hydrophobic methyl polysiloxane (MK) by cross-linking with (3-Aminopropyl)triethoxysilane (APTES). The molar ratios between MK and APTES and pyrolysis temperature led to different amounts of aminopropyl groups in the cross-linked products, which altered the basicity and hydrophilicity. For both approaches, besides the surface characteristics, surface charges also account for stable suspension to prepare final homogenous monoliths. Filler material prepared with MK: APTES molar ratio of 1:1, pyrolyzed at 600 degree Celsius was applicable for freeze casting considering the wettability and suspension stability. The monolith prepared with MK-APTES derived filler had also a hierarchical micro/meso/macroporous structure. The vapor adsorption indicated that the high content of silica sol improved the hydrophilicity greatly, and pyrolysis temperature also influenced the hydrophilicity to a minor degree. Notably, the silica sol is responsible for the formation of mesopores. The second part of the thesis was to investigate the mechanical and thermal properties of the obtained unidirectional porous SiOC ceramics prepared with MK and H44 at cryogenic and room temperatures. The compressive strength of monoliths was investigated both in air (293 Kelvin) and in liquid nitrogen (77 Kelvin). The influence of both liquid and cryogenic temperature on compressive strength was investigated. The compressive strength of monoliths showed not only anisotropy, but also a significant increase in liquid nitrogen. This increase may be due to the liquid nitrogen trapped inside the porous structures and cryogenic temperature. The linear thermal expansion coefficients (CTE), thermal conductivity and specific heat capacity of porous SiOC, were studied from cryogenic to room temperature. Both monoliths show anisotropic linear expansion coefficients, with the parallel direction having almost twice the shrinkage of the perpendicular direction. The monolith prepared with H44 showed thermal shrinkage twice as much as that prepared with MK and APTES, which might be due to the composition differences and measurement condition. The thermal conductivities of both monoliths made from two precursors showed anisotropic features and similar values. The minimum and maximum values for thermal conductivity are 0.2 and 0.9 Watts per meter per Kelvin. Thermal conductivities and specific heat capacities displayed an upward trend from low temperature to room temperature. It was assumed that the maximum heat conductivities of these materials were determined mainly by the macroporosity and the thermal conductivity of the hybrid material
Zwischen Druck und Angemessenheit : Deutungsprozesse in der Auseinandersetzung sozialpolitischer Akteure über Reformen der Alterssicherung in Deutschland und Großbritannien
No full textReforms of old age security systems place high demands on policy makers, mainly because these are generally unpopular in society and affect many (political) interests. This dissertation explores how pension reforms that were implemented since the year 2000 are contested within the pension policy community in Germany and the United Kingdom. For this purpose, a concept of 'practise of reasoning' is developed and applied to the data (expert interviews with representatives of socio-political actors and policy documents). In terms of analysis, a reconstruction of 'interpretative frames' which the actors try to maintain throughout the reform debate is accomplished. On the whole, the empirical results reveal the high degree of conflict among two opposing groups of actors in the German discourse, whereas the discourse in UK is grounded on more consensus. The analysis also shows how the institutional and, with that, cultural differences between Germany and the UK give shape to certain arguments used in the discourse
Internationalization of small and medium-sized enterprises related to their dynamic suppy chain flexibilities
Get PDFDuring the last two decades, the internationalization of small and medium-sized enterprises (SMEs) has called the attention of policymakers, practitioners, and scholars due to their role in the economic growth and job creation in their nations. However, due to the complexity and uncertainty of international environments, internationalization has become a high-risk strategy to be embraced. In contrast, flexibility is one of the largest recognized capabilities of SMEs which has been used by these firms to overcome their lack of resources and poor capabilities. This capability leads to a closer link to customers and suppliers allowing at the same time a faster response to both sides. In addition, SMEs need to adopt a network orientation to cope with the nowadays supply-chain competitive scenario. Hence, manufacturing SMEs require a sustainable competitive advantage to enhance their internationalization considering an integrative perspective. This paper addresses this gap by providing an integrative model to investigate the implementation of supply chain flexibility (SCF) to sustain SMEs internationalization by adopting a multi-disciplinary perspective. Three areas of study are included in this paper, i.e. SMEs internationalization, SCF, and logistics capabilities. The paper is among the first on providing an understanding of the relationships between these areas and their impact on manufacturing SMEs internationalization process. It also provides critical elements to support manufacturing SMEs internationalization in their decision-making process with respect to SCF as a source of sustainable competitive advantage