64 search hits
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Die Spur der Glasperlen. Akteure, Strukturen und Wandel im europäisch-ostafrikanischen Handel mit Glasperlen
(2004)
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Ulf Vierke
- In seiner 2004 eingereichten Dissertation folgt Ulf Vierke der Spur der Glasperlen von ihren europäischen Produktionsorten im oberfränkischen Fichtelgebirge und im böhmischen Isergebirge bis hin zu den Maasai in Ostafrika. Eine Route, die die Glasperlen sogar – jetzt zu Souvenirs verarbeitet – wieder nach Europa zurückführt. Es sind aber keineswegs die Glasperlen selbst, die im Zentrum der Untersuchung stehen, sondern vielmehr die Akteure, die mit diesen umgehen: die Perlenmacher in handwerklichen Betrieben etwa im Fichtelgebirge, die Arbeiter in den grossen Perlenindustrien Böhmens, die Händler in Europa, Indien und Afrika, die Frauen, die in Ostafrika Perlen zu Schmuck verarbeiten, und diejenigen, die letztlich diesen Schmuck tragen. Der Focus der Arbeit liegt auf dem Handeln der Menschen und auf der Vitalität gegenwärtiger Prozesse. Aneignung und Übereignung sind zentrale Begriffe, wenn es um die Interaktionen innerhalb der Vernetzung des globalen Warenaustausches geht. In Prozessen Aneignung, denen bisher das Hauptaugenmerk der Ethnologischen Forschung gilt, ist der Konsument Hauptakteur und dem Händler oder anderen Bringern kommt lediglich eine Hilfsrolle zu. Der Autor wendet die Perspektive und betont gerade die Prozesse der Entäusserung, des Vermittelns, des Werbens, die auf Seiten der Händler und Mittler untersucht werden müssen. Analog zur Aneignung führt er das Konzept der Übereignung ein. Sie umfasst den tatsächlichen Austausch, also den Übergang der Ware von einem Besitzer zu einem neuen, ebenso wie die kulturelle Interpretation und Umdeutung, die gerade zu das bestimmende Element der Handlungen eines Händlers ist. Der Händler ist in diesem Sinn mehr noch als ein Übersetzer, er ist cultural broker. Angeregt durch Sidney Mintzs klassische Studie aus dem Jahr 1985 “Sweetness and Power” bezieht der Autor seine Analyse nicht nur auf eine ethnologische Mikroperspektive sondern bezieht sich ebenso auf Prozesse und Strukturen globaler Integration. Indem er dies tut, eröffnet er auch einen facettenreichen Blick auf die historischen Hintergründe der Produktion, Distribution und Konsumption. Der Schwerpunkt liegt hierbei auf dem 16. bis 20. Jahrhundert. Analog zum weit gespannten Gegenstandsbereich kann der Autor auf ein breites methodologisches Instrumentarium rekurrieren, das von Teilneh-mender Beobachtung über Archiv-, Bibliotheks- und Museumsrecherchen bis hin zu Methoden aus der aktuellen Multi-Sited-Ethnography reicht.
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Abschätzung der mikrobiellen Diversität in anoxisch sauren Sedimenten von Braunkohle-Restseen unter Berücksichtigung des Eisenschwefelkreislaufs
(2004)
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Marco Blöthe
- Das Sediment im Restsee 77 wird durch den Verlauf des pH-Wertes dominiert. Dieser liegt im oberen Bereich bei 3 und steigt mit der Tiefe auf Werte von 5,5-6 an. Anhand des pH-Verlaufs wurde das Sediment in die Zonen I bis IV unterteilt. In Zonen I und III konnte eine spontane Fe(II)ges.-Freisetzung beobachtet werden, wobei diese in Zone I abhängig vom pH-Wert war. Diese konnte durch eine Anhebung des pH um den Faktor 2,2 gesteigert werden. Für die Zone III konnte bei Absenkung des pH-Wertes hingegen kein eindeutiger Effekt beobachtet werden. Mit Anstieg des pH im Sediment konnte zwar eine Abnahme der Zellzahl/ml beobachtet werden, die Diversität der Mikrobiota stieg jedoch an. Dies konnte mit unterschiedlichen molekularbiologischen Methoden bestätigt werden. Die allgemeine sowie die DGGE-Klonbibliothek wiesen in Zonen III eine höhere Diversität als in Zone I auf. Dominierend war die ubiquitär vorkommende Gruppe der Acidobacteria. Allerdings ist bis heute mit A. capsulatum nur eine Art kultiviert worden, von der eine dissimilatorische Fe(III) Reduktion nicht bekannt ist. Die allgemeinen Klondatenbank enthielt keinen Hinweis auf eine spezifische Fe(III)-reduzierende Mikrobiota. Von den bis heute bekannten dissimilatorischen Fe(III)-Reduzierern wurden nur Vertreter aus der Gruppe der Geobacteriaceae gefunden. Mit dem Primer-Set GM3/Geo825R für Geobacter konnte ein positives Signal in Zone III bei einer Verdünnugsstufe von 10-1 erhalten werden. In Zone I und Zone II lag die höchste positive Verdünnungsstufe bei 100. Mit dem Primer-Set Gb564/Gb1290 ergab sich ein leicht abgewandeltes Bild. Mit diesen Primern lag die höchste positive Verdünnungsstufe in Zone II und Zone III bei 10-2. Hingegen konnte in Zone I nur mit der unverdünnten DNA ein positives Signal erhalten werden. Mit den für Geothrix spezifischen Primern konnte nur in Zone II bis zu einer Verdünnungsstufe von 10-1 ein positives Signal erhalten werden. Allerdings bestand das erhaltene Produkt aus einer Doppelbande, was auf eine unspezifischen Reaktion während der PCR hindeutet. Kein positives Signal konnte für Shewanella erhalten werden. Für die azidophilen Fe(III)-Reduzierer konnte eine Anpassung beobachtet werden. Für die Acidiphilium-Spezies konnten acht Phylotypen differenziert werden, von denen vier in Zone I und III vorkamen. Die restlichen vier wurden hingegen nur in Zone III nachgewiesen. Ein Sequenzvergleich der Phylotypen aus Zone I und Zone III mit der EMBL-Datenbank ergab ausschließliche Ähnlichkeiten von 99% zu Acidiphilium-Spezies. Die Sequenzen der vier Phylotypen aus Zone III waren zu 95% sequenzähnlich zu kultivierten Acidiphilium oder Acidosphaera Spezies. Die phylogenetische Analyse ergab zwei Gruppen. Gruppe 1 enthält die Phylotypen, die nur in Zone III gefunden wurden. Die Phylotypen von Zone I und Zone III clusterten in Gruppe 2. Für die 'Bioleaching-Assoziierten'-16S rDNA wurden 20 Klone aus Zone I und 28 Klone aus Zone III auf redundante Klone über RFLP gescreent, wobei nur 1 Phylotyp mit 99%ige Sequenzähnlichkeit mit A. ferrooxidans unterschieden werden konnte. A. ferrooxidans reduziert unter sauren pH-Bedingungen (pH 3) mit 20 mM S° als Elektronenquelle alle getesteten Eisenfestphasen, wobei die Fe(II)ges.-Freisetzung mit abnehmender Kristallinität der Fe(III)-Minerale zunimmt. Unter erhöhten pH-Bedingungen (pH 5) erfolgte keine nennenswerte Fe(III)-Reduktion. Die Ergebnisse mit den Reinkulturen deuten darauf hin, dass autotrophe azidophile Fe(III)-Reduzierer unter erhöhten pH-Werten keinen Beitrag zur Fe(III)-Reduktion in Zone III leisten. Eine Fe(III)-Reduktion konnte ebenfalls für den heterotrophen Modellorganismus A. capsulatum gezeigt werden. In Reinkulturexperimenten mit A. capsulatum wurde die Fähigkeit zur Fe(III)-Reduktion getestet. Dabei konnte gezeigt werden, das sowohl Fe(III)-Minerale als auch lösliche Fe(III)-Formen in einem pH-Bereich von 2,2-5 reduziert werden. Hierbei werden zwischen 5 und 40% der aus der Glukoseoxidation gewonnenen Elektronen auf Fe(III) übertragen. Die von PEINE (1998) formulierte Hypothese eins gekoppelten Eisen-Schwefelkreislaufs konnte an zwei Anreicherungskulturen sowie einem Isolat demonstriert werden. Hierbei wurden unterschiedliche Prozesse identifiziert. Anreicherungskulturen MB1 und MB2 oxidierten elementaren Schwefel bzw. Thiosulfat, wobei die Elektronen auf die Fe(III)-Minerale übertragen werden. Isolat MB3 betrieb eine Disproportionierung, bei der das gebildete Sulfid mit den Fe(III)-Mineralen chemisch zu Fe(II) und elementarem Schwefel reagiert. Beide Prozesse gehen vom elementarem Schwefel aus, der im Sediment durch eine Reaktion des Sulfids aus der Sulfatreduktion mit den Fe(III)-Mineralen entsteht. Die Bildung von elementarem Schwefel als Reaktionsprodukt aus der chemischen Reaktion von Na2S mit Fe(III) unter sauren Bedingungen konnte sowohl in Batch-Versuchen als auch in Mikrokosmenexperimenten gezeigt werden.
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MAS NMR of Nuclei with Spin S=1/2 in Polycrystalline Powders: Experiments and Numerical Simulations
(2004)
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Matthias Bechmann
- The objective of this work is the examination of one-dimensional magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra. These spectra serve as a source of spin-system parameters which are related to structural and conformational parameters. It is to show that all spin-system parameters can be derived in a robust and reliable manner. Further on it is investigated how experimental conditions can be optimised in order to determine parameters in a stepwise fashion and get best accuracy for the derived data. This work is dealing with dipolar coupled spin S = 1/2 systems in polycrystalline powdered samples. MAS is used in order to increase spectral resolution and achieve gain in signal-to-noise ratio. However, MAS also causes a substantial down scaling of the information content about the anisotropic interactions of a spin system. A technique to remedy this drawback, while keeping the advantages of MAS, is the use of pulse sequences that reintroduce ("recouple") anisotropic dipolar coupling interactions. To access the spin-system parameters encoded in the lineshapes of MAS NMR spectra an iterative fitting approach is applied. These procedures make numerically exact simulations mandatory and involve accurate calculations of the complete spin-system dynamics. As a consequence all spin-system parameters sensitively encoded in the spectral lineshapes can principally be extracted. Computation of numerically exact simulations can be quite demanding on hardware (CPU speed). The algorithmic implementation of the spin dynamics has significant impact on the time required to simulate a spectrum. Optimisation and clever design of such algorithms is crucial especially when considering the need for repeated simulations in the process of iterative fitting. Usually spin-system size and the complexity of the pulse sequence are the principal factors determining the computation time of a spectrum. The numerical strategy adopted here is applied to one- to four-spin systems where the limiting factor is less the size of the spin system but rather the spin-system characteristics themselves. Spin systems composed of one to four spins have been chosen such that a representative range of spin-system parameters is covered. A combination R² and DQF proved to build robust and reliable experiments making all spin-system parameters accessible to an iterative fitting approach in a usually stepwise manner. The numerical simulations used in this approach additionally can serve for optimising existing pulse sequences. This usually results in better experimental spectra due to a better prediction of optimum experimental setup parameters. Such pre-experiment simulations are especially useful when large CSA interactions are present in dipolar coupled spin systems, a scenario not amenable to a complete theoretical description. Numerically exact simulations can also be regarded as an additional way of designing new pulse sequences. However, there is a certain lack of insight in the physical mechanisms of a pulse sequence when obtained by numerical methods only. For the future it would be useful to improve further the techniques of NMR that give complete and accurate information about local structure. This includes dipolar recoupling experiments of improved selectivity like R²-DQF. But when aiming for the ability to handle larger dipolar coupled spin systems it would also be advantageous to exploit pulse sequences that completely suppress the influence of CSA interactions while maintaining/recoupling the information about dipolar interactions. Further it is important to vary the information content of the spectra, a task for which e.g. OMAS experiments could be used.
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Intact and Damaged DNA and their Interaction with DNA-Binding Proteins: a Single Molecule Approach
(2004)
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Marina Lysetska
- In the present work we study the architecture of intact and damaged DNA and their interaction with DNA-binding proteins using a combination of atomic force microscopy (AFM) and fluorescence correlation spectroscopy (FCS). In the beginning of this scientific work we therefore focus our efforts on the development of a reproducible protocol for the surface-deposition of different biomolecules, such as linear and circular DNA, different types of proteins and DNA-protein complexes. The analysis of the apparent contour length of intact DNA molecules of different lengths and under different preparation routines is found to be consistent with its B-DNA conformation. In this thesis we report about the first structural study of long DNA molecules that carry UV-light photolesions at random sites. An exposure of DNA to UV light introduces different modifications to the DNA structure: regions of unpaired DNA of different lengths, sharp kinks, the presence of knot like structures and single-strand breaks. In addition, the dynamics of damage accumulation can be traced with AFM. UV-exposure influences both the apparent contour length and the persistence length of the molecules. The structure of UV light damaged DNA strongly depends on the exposure time. Longer UV-light exposure time introduces increasing DNA damage. An FCS study on DNA exposed to UV-light shows that the presence of photoadducts influences the hydrodynamic properties of DNA molecules. The results obtained using both AFM and FCS are compared with gel-electrophoretical experiments. Further, we report about a first AFM study of the hRPA binding properties to intact and damaged DNA. The damage types under investigation were a 6 nt bubble modification, a cisplatin modification as well as lesions induced by UV-light. In our AFM experiment we never find RPA to be bound to the intact dsDNA chain. In complexes with intact DNA human RPA is only found to be bound to the termini of the linear DNA molecules. Human RPA binds with a very low affinity to both DNA containing a 6 nt bubble modification and a single cisplatin modification. Moreover, hRPA showed in this case still a preferential binding to the ends of the linear DNA molecules as seen in the complexes with intact DNA. Because of the low binding strength of hRPA to the cisplatin intrastrand adduct it is easily possible to remove the protein from its DNA complexes by scanning movements of the AFM tip. The images of the DNA molecules after removal of the hRPA proteins show significant distortions of the DNA chain, namely: the separation of the double strand into single-strands resulting in a large region of unpaired bases. Such structures are never observed in images of DNA carrying a cisplatin lesion before the addition of hRPA. This fact may explain a possible role of hRPA in damage excision. Our experiments show a rather high affinity of hRPA to UV-light damaged DNA that increases with UV-light exposition time. The formation of complexes of hRPA and UV-light damaged DNA molecules was studied by both EMSA and AFM. When hRPA was added to the damaged DNA, globular objects sitting on the rod shaped DNA strands were regularly observed in the AFM images. A systematic analysis of the apparent contour length of DNA molecules in protein-DNA complexes reveals a reduction of the contour length in comparison to the one of uncomplexed DNA molecules damaged for the same time. Such reduction of 27.7±7.6 nm suggests a wrapping of the DNA molecule around the hRPA protein. Additionally, using the hRPA-DNA system, we show that the application of the phase signal allows to differentiate between components of similar architecture, but different origin within one AFM image. The last chapter of the thesis is dedicated to the analysis of the DNA-binding properties of ORF80, a novel leuzine protein of unknown physiological role. Our AFM measurements demonstrate that under low protein concentration a specific binding of ORF80 dominates. To the best of our knowledge ORF80 is the smallest protein that was resolved in complexes with DNA by AFM. The single molecule approach in the study of the ORF80 binding properties to DNA with AFM shows that one, at most two ORF80 monomers recognize a specific sequence on the dsDNA. Both AFM and FCS clearly show that higher ORF80 concentrations lead to the formation of big protein-DNA agglomerates that contain numerous DNA and protein molecules. The formation of these agglomerates can be explained both by the unspecific ORF80 binding and its high aggregation properties.
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Effects of land-use changes on the properties of a Nitisol and hydrological and biogeochemical processes in different forest ecosystems at Munesa, south-eastern Ethiopia
(2004)
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Yeshanew Ashagrie
- The effects of conversion of natural forest into different exotic tree species plantations and crop cultivation were investigated at Munesa, south-eastern Ethiopia with the objectives of (i) determining changes on soil physical and chemical properties, (ii) quantifying water and nutrient fluxes under the different forest ecosystems, and (iii) assessing nutrient dynamics in water flowing through the soil under the different forest ecosystems. Soil samples were taken from the organic layer and at 0-20, 20-40, 40-70, 70-100 cm depths from the mineral soil. Rainfall and throughfall were collected using plastic funnels mounted 1 m above the ground. Soil solutions were collected with zero-tension (organic layer) and tension (mineral soil at the depth of 20, 50 and 100 cm) lysimeters. After 26 years of cultivation, surface (20 cm depth) soil structure was deteriorated and total soil organic carbon (SOC) and N contents both in bulk soil and water stable aggregates were significantly reduced. Below 21 years old Eucalyptus plantation no significant changes on the above mentioned parameters could be identified, but significant reductions in SOC, N and S concentrations associated with the sand and silt separates were evident. There were also significant reductions both in quality and quantity of particulate organic matter (POM) due to cultivation and only in quality of POM due to 21 years Eucalyptus plantation. The organic layer mass under 21 years old Pinus patula, 21 years old Eucalyptus globulus and third rotation Eucalyptus globulus (established 42 yr ago) decreased by 43%, 57% and 15%, respectively, relative to the natural forest. There were also significant reductions in the organic layer C and N stocks (9 to 60% and 25 to 68%, respectively), being highest under Pinus and lowest under third rotation Eucalyptus. In the mineral soil, to 1 m depth, there was a significant (P<0.05) reduction (16 to 20%) in SOC stock after conversion of natural forest into forest plantations. The N stocks under the 21 years old Pinus and third rotation Eucalyptus plantations were significantly reduced amounting 27 and 20% respectively, whereas 21 years old Eucalyptus had nearly an equivalent amount of N as that of the natural forest, probably due to a dense forest floor vegetation, fixing N. The changes in the organic layer and mineral soil S stocks after plantation establishment were not significant. Of the total annual rainfall (1190 mm) recorded during the monitoring period (October 2001 to September 2002), about 47% and 18% were intercepted by the canopies of Cupressus and the natural forest, and Eucalyptus, respectively. Total annual nutrients (Ca, Cl, K, Mg, Na, NH4–N, NO3–N, PO4–P, SO4–S ) deposition by rainfall was 12 kg ha–1yr–1. Throughfall K, Mg, Ca and Cl fluxes were enriched relative to rainfall, whereas Na, NO3–N, NH4–N, PO4–P and SO4–S were depleted. Total annual throughfall nutrient inputs (Ca, Cl, K, Mg, Na, NH4–N, NO3–N, PO4–P, SO4–S) were 14 kg ha–1yr–1 under Cupressus, 21 kg ha–1yr–1 under the natural forest and 24 kg ha–1yr–1 under Eucalyptus. Water passing through the different forest floors differed only in K, Mg and NO3–N concentrations, the latter two being higher under the natural forest and Eucalyptus plantation than Cupressus. Potassium was greater under Eucalyptus than the natural forest and Cupressus. Except for NH4–N in the natural forest, forest floor leachate nutrient concentrations were enriched in all forest types in relation to throughfall. Most nutrient fluxes to the mineral soil decreased in relation to throughfall fluxes, whereas NO3–N fluxes increased by over 50% in all forest types. At all soil depths, the concentrations of most nutrients in the mineral soil solution decreased relative to the concentrations in the forest floor leachate, but Mg, Na and NO3–N at all depths in Cupressus plantation and SO4–S and Na at some soil depths in the natural forest and Eucalyptus plantation had increased. The vertical trends in soil solution nutrient concentrations showed a decreasing trend with depth increments for most of the nutrients, but the concentrations of Cl and Na in all forest types and Ca, Mg and NO3–N in Cupressus increased with increasing soil depth. At 1 m soil depth, the concentrations of Ca, Mg and NO3–N in Cupressus, respectively, were 8, 7 and 23 times higher than in the natural forest and 3, 4 and 81 times higher than in Eucalyptus indicating losses by leaching. Generally, the results of this study emphasize the importance of forest type, species composition and management in affecting carbon and nutrient storage, water and nutrient fluxes and dynamics.
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In situ studies of sugar metabolism in Ricinus communis L. and Saccharum officinarum L.
(2004)
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Shih-Long Yan
- In order to find the sucrose efflux transporter of the endosperm of Ricinus communis L., the yeast complementation selection method was used, but it was unsuccessful. Mutation was occurred on the nSC4+ plasmid during the selection. Maybe the stress of the yeast cells was too strong and then induced the mutation in the yeast cells. Using a weak promoter and reducing the copy number of the plasmid may avoid the mutation occur during the selection. The endosperm of Ricinus communis L. stores lipid and converts it to sucrose for the growth of seedlings. Sucrose phosphate phosphatase gene, RcSPP1, was cloned from the endosperm of the germinating seedling of Ricinus communis L. The endosperm cells synthesize sucrose by using SPS and SPP rather than sucrose synthase. Northern blot analysis indicated that the RcSPP1 expression level of the germinating endosperm was very similar from day 2 to day 6. The expression of nsLTPc1 is cotyledon-specific. It is also confirmed by in situ hybridization. The results of nsLTPc1 in situ hybridization indicate that the expression of nsLTPc1 was a cell-specific. The expression of nsLTPc1 was found only in the lower side of the cotyledons of Ricinus communis L. The expression of RcSCR1 is found in the endosperm, hypocotyl and cotyledons of the Ricinus communis L. germinating seeds. By northern blot analysis of the RNA from different days old endosperm, it indicates that the RcSCR1 has a highest expression level at day 5. By in situ hybridization and immunolocalization, the results illustrate that the mRNA and protein can be found in the lower epidermis of cotyledons from day 2 to day 5. In the 6-day-old cotyledons, the mRNA and protein of RcSCR1 are predominantly found in palisade parenchyma cells, but they are also found in the lower epidermis of cotyledons. The results of in situ hybridization indicate that the transcript of RcSCR1 can be found in most of the endosperm cells. RcSCR1 can be found in the middle layer of the endosperm from day 2 to day 5, no transcript of RcSCR1 is found in the cell layers near the seed coat. On the day 6, no RcSCR1 transcript can be detected in the endosperm cells. It is suggest that the function of RcSCR1 protein is to retrieve the sucrose from apoplastic space to avoid sucrose escape. Compared to the amino acid sequence of known sucrose transporters, the putative sucrose transporter of Ricinus communis , RcSCR2, belongs to SUT4 subfamily. The transcript of RcSCR2 is found in the endosperm, hypocotyl and cotyledons of the Ricinus communis L. germinating seeds. The expression of RcSCR2 is very weak. The expression level of RcSCR2 cannot be detected by northern analysis. By quantitative real time RTPCR, it indicates that the RcSCR2 has a highest expression level at 3 day. By in situ hybridization, the results illustrate that the mRNA cannot be found in the endosperm, cotyledons and hypocotyl. The results of in situ RTPCR indicate that the transcript of RcSCR2 can be found in most of the endosperm cells. RcSCR2 can be found in the middle layer of the endosperm from day 2 to day 5, no transcript of RcSCR2 is found in the cell layers near the seed coat. On the day 6, no RcSCR2 transcript can be detected in the endosperm cells. Although RcSCR2 in yeast does not function properly, but it shares high homology to other SUT4 type transporters, so they may have the same function to take up sucrose into cells. It is suggest that the function of RcSCR2 protein is to retrieve the sucrose from the apoplastic space to avoid sucrose escape. How the expression of RcSCR1 and RcSCR2 is regulated in the endosperm is still unknown. Sugarcane is a very important food crop. Sugarcane yellow leaf virus leads to sugarcane yellow syndrome and reduces the sugar production. Starch accumulation was found in the virus-infected plants. Within the starch staining, the results indicate that starch is accumulated in bundle sheath cells and mesophyll cells of virus -infected plants, however, starch can be found only in the bundle-sheath cells of virus-free plants. The in situ hybridization study indicates that the expression of ADP-glucose pyrophosphorylase in the mesophyll cells of virus-infected plant is stronger than it in virus-free plants. The results of in situ hybridization of starch branching enzyme indicates that no significant difference between the virus-free-plants and virus-infected. The results are different to it of starch staining. The mechanisms are still unclear, more carbohydrate metabolism related genes must be studied.
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New Methods for the Investigation of Organic Thin-Film Devices
(2004)
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Helmut Hänsel
- We have developed new techniques for the investigation of organic thin-film devices and have focussed on properties on the molecular scale as well as on macroscopic properties of organic devices. Scanning probe techniques were used to obtain spatially resolved information on morphology and electro-optical properties. Structural changes in composite-based devices were found to have an important influence on device performance. Furthermore, two modes of electroluminescence detection have been developed. Local luminescence detection in the optical near-field by a scanning near-field optical microscope allowed us to monitor the light emission around a dark spot with a resolution better than 134 nm and to observe the electrode ablation. Finally, we have established a new scanning probe technique, named SELM, "Scanning Electroluminescence Microscopy". The simultaneous detection of a PtIr-tip-induced electroluminescence and shear force allows us to distinguish between topography and conductivity. This technique has revealed a strong spatial variation in the electro-optical properties of Alq3 films on ITO substrates. The existing combinatorial preparation method has been supplemented by a variable testing setup that permits the simultaneous investigation of 64 devices under nearly identical conditions. Both OLEDs and photovoltaic cells have successfully been tested over more than 300 hours of continuous operation so that it was possible to study the influence of material combinations and layer thicknesses on the performance and on the degradation of the devices. Variable-angle spectroscopic ellipsometry has been used for the optical characterisation of materials and an automation has been provided for the analysis of combinatorially prepared device arrays. Furthermore, a Mathematica program has been developed for the theoretical description of the short-circuit current in photovoltaic cells. By this means it was possible to explain in detail the observed performance enhancement in heterojunction solar cells, induced by an additional TiO2 layer. The optical and electronic contribution could only be identified by the variation of both layer thickness and device type. The strength of the setup presented is its ability to produce and to test devices under nearly identical conditions and to yield reliable data, which in turn can be used to test physical models. Finally, we have addressed the degradation process of OLEDs. The experiments have shown that inert gas plays an essential role in protecting against degradation, not only by the exclusion of reactive species but also by its heat-transport capabilities. These investigations are only just beginning and further combinatorial studies paired with AFM measurements are currently being developed.
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The use of 10Be surface exposure dating of erratic boulders in the reconstruction of the late Pleistocene glaciation history of mountainous regions, with examples from Nepal and Central Asia
(2004)
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Uwe Abramowski
- Be-10 surface exposure dating (SED) of erratic boulders is an innovative approach in Quaternary geochronology. It proves to be an excellent tool for the reconstruction of the glacial history of mountainous regions, which is an important part of climate change research. In the course of this work, I have 1) installed the analytical procedure to extract in-situ produced Be-10 from quartz-bearing rock surface samples in the laboratory of the Institute of Soil Science and Soil Geography at the University of Bayreuth; 2) developed and calibrated the program TEBESEA for quick calculation of Be-10 surface exposure ages with fully propagated errors, thereby evaluating the existing procedures; 3) deduced a new interpretation scheme for exposure age distributions from several stratigraphically related moraines in an area; 4) provided 37 new Be-10 exposure ages for the Nepal Himalaya, complementing earlier soil geographic studies in the Langtang Valley and the Macha Khola Valley; and finally 5) provided 108 new Be-10 exposure ages for the Pamir, and the Alay- and Turkestan Ranges, defining a new glacial chronology for Central Asia. The analytical procedure used to extract Be-10 from quartz-bearing rocks and to prepare it for measurement closely followed the one established at the ETH Zurich, where all Be-10 measurements have been done. The accuracy of the analytical work in Bayreuth was confirmed by preparation of five calibration samples from the Koefels landslide, Oetz Valley, Austria. The traditional scaling system of Lal (1991) as modified by Stone (2000) still proves to be the most suitable one to be used in Be-10 exposure age calculations. For this procedure, I have calibrated a total standard production rate at sea level, high latitude of 5.35 ± 0.15 atoms/(g a), using a contribution of capture of slow negative muons of 1.2%, and including all possible corrections. The altitude dependency of Be-10 production used in the scaling systems of Dunai (2001) and Desilets & Zreda (2003) is as yet not convincing, given the existing calibration data, but suggests that ages calculated for sites above 2000-3000 m a.s.l. in High Asia may be overestimates. Detailed error propagation shows that the uncertainties of Be-10 surface exposure ages at present are dominated by the errors of the scaling factor, the erosion rate, and the tectonic uplift rate. As long as surface erosion and tectonic uplift rates cannot be constrained to within 10%, however, exposure ages older than 30-40 ka have uncertainties of 20% or more and can be no more than rough approximations. For exposure age distributions from a set of stratigraphically related moraines, a new interpretation scheme is presented, which is able to detect ages older than the deposition age of the moraine (Be-10 inheritance), and to interpret age clusters younger than the deposition age, which may be synchronous on several moraines (phases of regionally enhanced surface activity). In the Nepal Himalaya, glacier advances in the Macha Khola Valley have occurred 70-100, 20-23, 11-12 and around 3 cal. ka B.P. Glacier advances in the Langtang Valley are dated to 14-15, 8-9 and ~3.5 cal. ka B.P. Late Pleistocene and Holocene glacial activity in the Nepal Himalaya seems to be controlled by the Indian monsoon rather than the westerly circulation. Only in the MIS 2, the westerly jetstream appears to have shifted as far south as to affect glaciation all over the Himalaya. During the Younger Dryas, the eastern limit of the influence of the westerly circulation on Himalaya glaciation may have been situated between the Manaslu and Langtang Himal. Glacial advances in the Pamir and in the Alay and Turkestan Ranges have occurred >93->136, ~60-80, (40-55), ~27-25, ~22-20, ~18, ~15.5, ~14.3, and 10.5 cal. ka B.P. The most extensive late Pleistocene glaciation occurred during the MIS 5-3, and is characterized by ELA depressions of ~370-380 m in the eastern Pamir, as well as 600 m and >750 m, in the Alay and Turkestan Ranges, respectively. Late Pleistocene glacier advances in northwestern High Asia, were triggered by climatic cold phases rather than by monsoonal maxima. Climate in the region seems to have been mostly under the influence of the westerly circulation and the Siberian anticyclone. Asynchrony of Central Asian and western hemisphere glacier advances is due to increasing aridity in Central Asia in the course of the last glacial cycle. High altitude glaciers seem to have reached their maximum extent earlier (MIS 5-4) than low altitude glaciers (first half of MIS 3). Some indirect monsoonal influence in the eastern Pamir may be responsible for the existence of some of the lateglacial moraine stages in this area.
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Aerob-thermophile Reinigung mineralölkontaminierter Abwässer
(2004)
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Alexandra Oberthür
- Unter aeroben Bedingungen ist der thermophile Mikroorganismus Geobacillus thermoleovorans im Labor- und Pilotmaßstab fähig, verschiedene mit Mineralölen kontaminierte Abwässer als einzige Kohlenstoffquelle zu nutzen. Die Verwertbarkeit eines synthetischen Dieselöls sowie eines Kühlschmierstoffs standardisierter Zusammensetzung durch die Kultur wurde untersucht. Des Weiteren wurden Kühlschmieremulsionen aus Kfz-Produktionsstätten und Spüllösungen zum Reinigen von Lackleitungen auf deren biologische Abbaubarkeit hin geprüft. Der Nachweis von Metaboliten erfolgte an einem GC-FID-System (Gaschromatograph mit Flammenionisationsdetektor). Im Vergleich zum Standardsubstrat Olivenöl wurden ähnliche, in Einzelfällen sogar höhere Wachstumsraten und Zelldichten erzielt. Hierbei wurde nachgewiesen, dass die Initialisierung der Lipaseexpression durch Triglyceride Voraussetzung für den effizienten Abbau von Mineralölkohlenwasserstoffen (MKW) durch Geobacillus thermoleovorans ist. Da MKW in der Praxis nahezu ausschließlich in Verbindung mit einer Vielzahl von Additiven gebraucht werden, wurde der Einfluss verschiedener Zusatzstoffe auf die Mikroorganismen erforscht. Als Kohlenstoffquelle diente das synthetische Dieselöl, als Zusatzstoffe wurden insbesondere Tenside, Flockungsmittel, Komplexbildner und Entschäumer verwendet. Es zeigte sich, dass alle eingesetzten anionischen Tenside (Natrimlaurylsulfat = SDS, Natriumlaurylbenzolsulfonat = SDBS) und nichtionischen Tenside (Tergitol NPX, Triton X 100) in Konzentrationen unterhalb der kritischen Mizellenbildungskonzentration (CMC, engl. Critical Micelle Concentration) nachweislich das Wachstum der Kultur durch die Verbesserung der Substrat-Bioverfügbarkeit stimulieren. Oberhalb der CMC fördern anionische Tenside das Wachstum der Kultur; nichtionische Tenside wirken mit ansteigender Konzentration zunehmend inhibierend. Triton X 100 unterdrückt in Konzentrationen oberhalb der CMC die extrazelluläre Lipaseaktivität vollständig. Positive und negative Effekte auf das Wachstumsverhalten der Kultur sind gleichermaßen das Resultat von Tensid-Membran-Interaktionen. Durch Einlagerung in die Zellmembranen erhöhen die Tenside die Permeabilität der Membranen für Enzyme, was wiederum zu einer Beschleunigung des MKW-Abbaus führt. Der inhibierende Einfluss von Triton X 100 hingegen kann auf die Konformation des Tensids zurückgeführt werden, die entweder die Ausscheidung von Enzymen behindert oder Zellmembran oder Enzyme direkt schädigt. Die experimentell ermittelten CMC im aerob-thermophilen System betrugen 50 mg/L für SDS und SDBS, 90 mg/L für Tergitol NPX® und 108 mg/L für Triton X 100. Darüber hinaus wurde nachgewiesen, dass SDBS in Anwesenheit von MKW metabolisiert wird. In Abwesenheit anderer Kohlenstoffquellen kann auch SDS von Geobacillus thermoleovorans verwertet werden. Ein Abbau nichtionischer Tenside wurde hingegen nicht beobachtet. Die Anwesenheit nichtionischer Tenside ist daher, wie nach der Durchführung einer Diskriminanzanalyse bestätigt wurde, das wichtigste Entscheidungskriterium bzgl. der Anwendbarkeit des Verfahrens zur Reinigung bislang nicht experimentell untersuchter MKW-haltiger Abwässer. Basierend auf den versuchsbegleitend erhobenen Wachstumsparametern wurde ein Vorhersagemodell zur Übertragbarkeit des aerob-thermophilen Verfahrens entwickelt. Geobacillus thermoleovorans weist eine hohe Resistenz gegenüber Bioziden, Schwermetallen und weiteren in Reinigungs- und Schmiermitteln eingesetzten Zusatzstoffen auf. Erst in Konzentrationen ab 1.500 mg/L bewirkt Antimon(III)oxid eine Inhibierung des Wachstums. Eine Anreicherung der genannten Substanzen im Abstrom der Anlage ist daher zu erwarten. Weiterer Forschungsbedarf besteht hinsichtlich der Aufklärung der Metabolisierungspfade von Geobacillus thermoleovorans in Bezug auf (Poly-)Ether und Biozide. Bei der weiteren Verfahrensoptimierung ist insbesondere die Reduktion des Energiebedarfs der Anlage anzustreben. Darüber hinaus empfiehlt sich der Einsatz des Verfahrens in (sub)tropischen Ländern sowie die Ausnutzung von Prozesswärme. Die Entsorgung metallbelasteter Schlämme und anderer nicht abbaubarer Feststoffe ist sicher zu stellen. Bei der Behandlung von Kühlschmierstoffen und ähnlich hoch CSB-belasteten Abwässern (CSB: Chemischer Sauerstoffbedarf) ist die Bereitstellung von Verdünnungswasser notwendig, da eine Raumlast von 13 kg CSB/m -3 d -3 die Belastungsobergrenze für das Verfahren darstellt. Aufgrund der hohen Prozess-Stabilität, der kurzen Anlaufzeiten, der hohen Wachstumsraten und der einfachen Betreuung ist das Verfahren sehr flexibel und vielfältig einsetzbar. Eine weitere Vertiefung dieses innovativen Ansatzes in der Abwasserreinigung ist von daher wünschenswert.
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Adoption of footprint methods for the quality control of eddy-covariance measurements
(2004)
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Mathias Göckede
- Footprint models determine the spatial context of a measurement by defining a transfer function between sources or sinks of the signal and the sensor position. The resulting source area provides an important quality control tool to improve the interpretation of micrometeorological data sets. However, to date no approaches have been presented in the literature that provide a standardised footprint-based methodology that allows observers to include terrain characteristics into quality assessment and quality control strategies. One problem in this context is the small number of studies that concentrate on the validation of footprint models under the non-ideal conditions in which they are frequently being used. Therefore, for many applications, the accuracy of the source areas computed by the footprint models cannot be evaluated. To further increase the acceptance of footprint-based studies, a stronger focus on footprint validation studies for a wide variety of experimental designs is needed. This dissertation focuses on the development of a footprint-based evaluation tool for complex measurement sites that allows the combination of quality assessment results for micrometeorological measurements with characteristics of the surrounding terrain. The standardised method is easy-to-use in order to encourage its application on a large number of sites. To improve the interpretation of the obtained results, a second objective of this thesis was to develop and test approaches to validation experiments for footprint models. Göckede et al. (2004) presented an approach for the evaluation of micrometeorological measurement sites in complex terrain, which combined a method for quality assessment of eddy-covariance measurements with an analytic footprint model. Their software package provided micrometeorologists a practical tool for determining the average flux contributions from the land use type intended to observe at a specific site, or to identify footprint areas for which a high data quality could be assumed. Rebmann et al. (2005) proved the efficiency of this evaluation approach for extensive studies on a large number of sites organised in a network. Their results may serve as a tool for an improved determination of yearly sums of the net ecosystem exchange, because fluxes originating from sectors of minor quality could be excluded from the analysis. Because of these important contributions to quality control, Foken et al. (2004) integrated the site evaluation approach into a comprehensive survey on micrometeorological post-field data quality control techniques. The experiences obtained during the extensive study by Rebmann et al. (2005) allowed us identification of the major weak points of the approach, which we were able to improve in subsequent studies. Using remote sensing methods Reithmaier et al. (2005) studied the influence of the characteristics of the land use maps and different roughness length assignment schemes on the performance of the site evaluation approach. Finally, Göckede et al. (2005a) developed an updated version of the site evaluation approach, which improved the basic method by replacing the analytic footprint model with a Lagrangian stochastic footprint model that is more suitable for studies above high vegetation, and by applying a more sophisticated microscale flux aggregation method for the determination of areally-averaged roughness lengths. Although the implemented models are far more sophisticated than in the original version, the approach by Göckede et al. (2005a) still permits a practical application that allows for comparative studies of a large number of sites. With respect to the development of validation methods for footprint models using natural tracer measurements from field scale experiments, Göckede et al. (2005b) presented two different experimental approaches. Firstly, a comparison of measured flux differences and modelled land use differences for pairs of measurement positions revealed general correlations between measurement data and model results. Secondly, Göckede et al. (2005b) tested a correlation analysis between measured and modelled parameters using reference measurements and footprint results. This approach resulted in an objective quantitative evaluation of the accuracy of the footprint model. The study by Reth et al. (2005) could not be employed for footprint validation purposes because of a large systemic scatter between these measurement systems. Overall, both the paper by Göckede et al. (2005b) and by Reth et al. (2005) provided successful methods to testing the suitability of natural tracer experiments in the validation of footprint models. Although experimental deficits prevented the working out of significant differences between the results of the employed footprint models, their studies developed an improved design for natural tracer experiments that are especially designed for footprint validation purposes.
