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A water quality model for shallow river-lake systems and its application in river basin management
(2007)
This work documents the development and application of a new model for simulating mass transport and turnover in rivers and shallow lakes. The simulation tool called 'TRAM' is intended to complement mesoscale eco-hydrological catchment models in studies on river basin management. TRAM aims at describing the water quality of individual water bodies, using problem- and scale-adequate approaches for representing their hydrological and ecological characteristics. The need for such flexible water quality analysis and prediction tools is expected to further increase during the implementation of the European Water Framework Directive (WFD) as well as in the context of climate change research. The developed simulation tool consists of a transport and a reaction module with the latter being highly flexible with respect to the description of turnover processes in the aquatic environment. Therefore, simulation approaches of different complexity can easily be tested and model formulations can be chosen in consideration of the problem at hand, knowledge of process functioning, and data availability. Consequently, TRAM is suitable for both heavily simplified engineering applications as well as scientific ecosystem studies involving a large number of state variables, interactions, and boundary conditions. TRAM can easily be linked to catchment models off-line and it requires the use of external hydrodynamic simulation software. Parametrization of the model and visualization of simulation results are facilitated by the use of geographical information systems as well as specific pre- and post-processors. TRAM has been developed within the research project 'Management Options for the Havel River Basin' funded by the German Ministry of Education and Research. The project focused on the analysis of different options for reducing the nutrient load of surface waters. It was intended to support the implementation of the WFD in the lowland catchment of the Havel River located in North-East Germany. Within the above-mentioned study TRAM was applied with two goals in mind. In a first step, the model was used for identifying the magnitude as well as spatial and temporal patterns of nitrogen retention and sediment phosphorus release in a 100~km stretch of the highly eutrophic Lower Havel River. From the system analysis, strongly simplified conceptual approaches for modeling N-retention and P-remobilization in the studied river-lake system were obtained. In a second step, the impact of reduced external nutrient loading on the nitrogen and phosphorus concentrations of the Havel River was simulated (scenario analysis) taking into account internal retention/release. The boundary conditions for the scenario analysis such as runoff and nutrient emissions from river basins were computed by project partners using the catchment models SWIM and ArcEGMO-Urban. Based on the output of TRAM, the considered options of emission control could finally be evaluated using a site-specific assessment scale which is compatible with the requirements of the WFD. Uncertainties in the model predictions were also examined. According to simulation results, the target of the WFD -- with respect to total phosphorus concentrations in the Lower Havel River -- could be achieved in the medium-term, if the full potential for reducing point and non-point emissions was tapped. Furthermore, model results suggest that internal phosphorus loading will ease off noticeably until 2015 due to a declining pool of sedimentary mobile phosphate. Mass balance calculations revealed that the lakes of the Lower Havel River are an important nitrogen sink. This natural retention effect contributes significantly to the efforts aimed at reducing the river's nitrogen load. If a sustainable improvement of the river system's water quality is to be achieved, enhanced measures to further reduce the immissions of both phosphorus and nitrogen are required.
Das Metabolische Syndrom stellt eine Kombination verschiedener metabolischer Anomalien in einem Individuum dar. Starkes Übergewicht gilt als maßgebende Größe in der Genese des Syndroms, welches mit einem enormen Risiko für kardiovaskuläre Erkrankungen einhergeht. Um die stark steigende Prävalenz des Metabolischen Syndroms einzudämmen, sind dringend Konzepte für die Behandlung, vor allem jedoch für die Prävention von Übergewicht erforderlich. Einen wichtigen Beitrag leisten diesbezüglich Ballaststoffe in der Ernährung. Sie tragen auf unterschiedlichen Wegen zur Gewichtskontrolle bei und beeinflussen zudem verschiedene mit dem Metabolischen Syndrom assoziierte Blutparameter. Ebenso werden protektive Effekte von Polyphenolen, welche zur Gruppe der sekundären Pflanzenstoffe zählen, beschrieben. Diese wirken u. a. auf den Glukose- sowie den Insulinhaushalt und greifen darüber hinaus in die Regulation der Fettverbrennung sowie des Energieverbrauches ein. Die Kombination beider Substanzgruppen verspricht bedeutendes gesundheitsförderndes Potential; dieses wurde gegenwärtig jedoch kaum untersucht. Carobballaststoff ist ein polyphenolreicher und vorwiegend unlöslicher Extrakt der Frucht des Johannisbrotbaumes (Ceratonia siliqua L). Bislang publizierte Studien zur physiologischen Wirksamkeit dieses Ballaststoffpräparates weisen sowohl beim Tier als auch beim Menschen bemerkenswerte hypocholesterinämische Eigenschaften nach. Inwiefern sich der Verzehr des Carobballaststoffes ebenso auf die Entwicklung von Übergewicht sowie anderen Messgrößen des Metabolischen Syndroms auswirkt, ist allerdings nicht bekannt. Die Zielstellung der Promotionsarbeit bestand darin, die postprandialen Wirkungen des Carobballaststoffverzehrs mit Hilfe einer Humanstudie aufzuzeigen. In die randomisierten, einfach verblindeten Untersuchungen im cross-over-Design wurden 20 gesunde Erwachsene im Alter zwischen 22 und 62 Jahren eingeschlossen. Unter Verwendung variierender Begleitmahlzeiten wurden die postprandialen Effekte verschiedener Mengen des Carobballaststoffes untersucht. Hierbei standen die Veränderungen der Plasmakonzentrationen von Glukose, Triglyceriden (TG), totalem und acyliertem Ghrelin sowie der Serumkonzentrationen von Insulin und nicht-veresterten Fettsäuren (NEFA) im Mittelpunkt der Betrachtungen. Der Verzehr des Carobballaststoffes in Kombination mit 200 ml Wasser und 50 g Glukose erhöhte die postprandialen Glukose- und Insulinkonzentrationen gegenüber der Glukoselösung ohne Ballaststoffzusatz. In Kombination mit 400 ml einer Flüssigmahlzeit verzehrt, senkte Carobballaststoff die postprandialen TG-, NEFA- und Ghrelin- (acyliert) Antworten. Die Untersuchung des respiratorischen Quotienten nach Zusatz von Carobballaststoff zur Flüssigmahlzeit mittels indirekter Respirationskalorimetrie bekräftigte die bereits bekannten Effekte auf den Lipidmetabolismus und wies zudem eine Steigerung der Fettverwertung unter Verminderung der Glukoseoxidation nach. Wurde Carobballaststoff schließlich in Lebensmittel eingebracht, sanken nach dem Verzehr dieser Lebensmittel erneut die postprandialen Konzentrationen an TG und NEFA. Gleichzeitig erhöhten sich die Glukose-, Insulin- sowie Ghrelin- (acyliert) Antworten. Carobballaststoff löst in Abhängigkeit von der jeweils verzehrten Begleitmatrix unterschiedliche Effekte aus. Das Präparat weist beachtliche Wirkungen auf die Blutlipide sowie den Energieverbrauch auf, hat indes ungünstige Wirkungen auf die Blutglukose, sofern er in Kombination mit einer veränderten Nährstoffmatrix aufgenommen wird. Carobballaststoff besitzt starkes gesundheitsförderndes Potential; jedoch sind weitere Studien notwendig, um seine Wirkungen sowie deren Voraussetzungen besser zu verstehen. Ferner sollten Untersuchungen über einen längeren Zeitraum vorgenommen werden, um die langfristige Relevanz der gewonnenen Ergebnisse darzulegen. Danach stellt die Anreicherung spezieller Lebensmittel mit Carobballaststoff einen geeigneten Weg dar, um von den viel versprechenden protektiven Wirkungen des Präparates zu profitieren.
The need to develop sustainable resource management strategies for semi-arid and arid rangelands is acute as non-adapted grazing strategies lead to irreversible environmental problems such as desertification and associated loss of economic support to society. In such vulnerable ecosystems, successful implementation of sustainable management strategies depends on well-founded under-standing of processes at different scales that underlay the complex system dynamic. There is ample evidence that, in contrast to traditional sectoral approaches, only interdisciplinary research does work for resolving problems in conservation and natural resource management. In this thesis I combined a range of modeling approaches that integrate different disciplines and spatial scales in order to contribute to basic guidelines for sustainable management of semi-arid and arid range-lands. Since water availability and livestock management are seen as most potent determinants for the dynamics of semi-arid and arid ecosystems I focused on (i) the interaction of ecological and hydro-logical processes and (ii) the effect of farming strategies. First, I developed a grid-based and small-scaled model simulating vegetation dynamics and inter-linked hydrological processes. The simulation results suggest that ecohydrological interactions gain importance in rangelands with ascending slope where vegetation cover serves to obstruct run-off and decreases evaporation from the soil. Disturbances like overgrazing influence these positive feedback mechanisms by affecting vegetation cover and composition. In the second part, I present a modeling approach that has the power to transfer and integrate ecological information from the small scale vegetation model to the landscape scale, most relevant for the conservation of biodiversity and sustainable management of natural resources. I combined techniques of stochastic modeling with remotely sensed data and GIS to investigate to which ex-tent spatial interactions, like the movement of surface water by run-off in water limited environments, affect ecosystem functioning at the landscape scale. My simulation experiments show that overgrazing decreases the number of vegetation patches that act as hydrological sinks and run-off increases. The results of both simulation models implicate that different vegetation types should not only be regarded as provider of forage production but also as regulator of ecosystem functioning. Vegetation patches with good cover of perennial vegetation are capable to catch and conserve surface run-off from degraded surrounding areas. Therefore, downstream out of the simulated system is prevented and efficient use of water resources is guaranteed at all times. This consequence also applies to commercial rotational grazing strategies for semi-arid and arid rangelands with ascending slope where non-degraded paddocks act as hydrological sinks. Finally, by the help of an integrated ecological-economic modeling approach, I analyzed the relevance of farmers’ ecological knowledge for longterm functioning of semi-arid and arid grazing systems under current and future climatic conditions. The modeling approach consists of an ecological and an economic module and combines relevant processes on either level. Again, vegetation dynamics and forage productivity is derived by the small-scaled vegetation model. I showed that sustainable management of semi-arid and arid rangelands relies strongly on the farmers’ knowledge on how the ecosystem works. Furthermore, my simulation results indicate that the projected lower annual rainfall due to climate change in combination with non-adapted grazing strategies adds an additional layer of risk to these ecosystems that are already prone to land degradation. All simulation models focus on the most essential factors and ignore specific details. Therefore, even though all simulation models are parameterized for a specific dwarf shrub savanna in arid southern Namibia, the conclusions drawn are applicable for semi-arid and arid rangelands in general.
Analysis and modelling of nutrient transport and transformation processes on the catchment scale
(2007)
Analysis and modelling of nutrient transport and transformation processes on the catchment scale
(2007)
Sulphur, a macronutrient essential for plant growth, is among the most versatile elements in living organisms. Unfortunately, little is known about regulation of sulphate uptake and assimilation by plants. Identification of sulphate signalling processes will allow to control sulphate acquisition and assimilation and may prove useful in the future to improve sulphur-use efficiency in agriculture. Many of genes involved in sulphate metabolism are regulated on transcriptional level by products of other genes called transcription factors (TF). Several published experiments revealed TF genes that respond to sulphate deprivation, but none of these have been so far been characterized functionally. Thus, we aimed at identifying and characterising transcription factors that control sulphate metabolism in the model plant Arabidopsis thaliana. To achieve that goal we postulated that factors regulating Arabidopsis responses to inorganic sulphate deficiency change their transcriptional levels under sulphur-limited conditions. By comparing TF transcript profiles from plants grown on different sulphate regimes, we identified TF genes that may specifically induce or repress changes in expression of genes that allow plants to adapt to changes in sulphate availability. Candidate genes obtained from this screening were tested by reverse genetics approaches. Transgenic plants constitutively overproducing selected TF genes and mutant plants, lacking functional selected TF genes (knock out), were used. By comparing metabolite and transcript profiles from transgenic and wild type plants we aimed at confirming the role of selected AP2 TF candidate genes in plant adaptation to sulphur unavailability. After preliminary characterisation of WRKY24 and MYB93 TF genes, we postulate that these factors are involved in a complex multifactorial regulatory network, in which WRKY24 and MYB93 would act as superior factors regulating other transcription factors directly involved in the regulation of S-metabolism genes. Results obtained for plants overproducing TOE1 and TOE2 TF genes suggests that these factors may be involved in a mechanism, which is promoting synthesis of an essential amino acid, methionine, over synthesis of another amino acid, cysteine. Thus, TOE1 and TOE2 genes might be a part of transcriptional regulation of methionine synthesis. Approaches creating genetically manipulated plants may produce plant phenotypes of immediate biotechnological interest, such as plants with increased sulphate or sulphate-containing amino acid content, or better adapted to the sulphate unavailability.
The overall program "arborescent numbers" is to similarly perform the constructions from the natural numbers (N) to the positive fractional numbers (Q+) to positive real numbers (R+) beginning with (specific) binary trees instead of natural numbers. N can be regarded as the associative binary trees. The binary trees B and the left-commutative binary trees P allow the hassle-free definition of arbitrary high arithmetic operations (hyper ... hyperpowers). To construct the division trees the algebraic structure "coppice" is introduced which is a group with an addition over which the multiplication is right-distributive. Q+ is the initial associative coppice. The present work accomplishes one step in the program "arborescent numbers". That is the construction of the arborescent equivalent(s) of the positive fractional numbers. These equivalents are the "division binary trees" and the "fractional trees". A representation with decidable word problem for each of them is given. The set of functions f:R1->R1 generated from identity by taking powers is isomorphic to P and can be embedded into a coppice by taking inverses.
Atmospheric circulation and the surface mass balance in a regional climate model of Antarctica
(2007)
Understanding the Earth's climate system and particularly climate variability presents one of the most difficult and urgent challenges in science. The Antarctic plays a crucial role in the global climate system, since it is the principal region of radiative energy deficit and atmospheric cooling. An assessment of regional climate model HIRHAM is presented. The simulations are generated with the HIRHAM model, which is modified for Antarctic applications. With a horizontal resolution of 55km, the model has been run for the period 1958-1998 creating long-term simulations from initial and boundary conditions provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA40 re-analysis. The model output is compared with observations from observation stations, upper air data, global atmospheric analyses and satellite data. In comparison with the observations, the evaluation shows that the simulations with the HIRHAM model capture both the large and regional scale circulation features with generally small bias in the modeled variables. On the annual time scale the largest errors in the model simulations are the overestimation total cloud cover and the colder near-surface temperature over the interior of the Antarctic plateau. The low-level temperature inversion as well as low-level wind jet is well captured by the model. The decadal scale processes were studied based on trend calculations. The long-term run was divided into two 20 years parts. The 2m temperature, 500 hPa temperature, MSLP, precipitation and net mass balance trends were calculated for both periods and over 1958 - 1998. During the last two decades the strong surface cooling was observed over the Eastern Antarctica, this result is in good agreement with the result of Chapman and Walsh (2005) who calculated the temperature trend based on the observational data. The MSLP trend reveals a big disparity between the first and second parts of the 40 year run. The overall trend shows the strengthening of the circumpolar vortex and continental anticyclone. The net mass balance as well as precipitation show a positive trend over the Antarctic Peninsula region, along Wilkes Land and in Dronning Maud Land. The Antarctic ice sheet grows over the Eastern part of Antarctica with small exceptions in Dronning Maud Land and Wilkes Land and sinks in the Antarctic Peninsula; this result is in good agreement with the satellite-measured altitude presented in Davis (2005) . To better understand the horizontal structure of MSLP, temperature and net mass balance trends the influence of the Southern Annual Mode (SAM) on the Antarctic climate was investigated. The main meteorological parameters during the positive and negative Antarctic Oscillation (AAO) phases were compared to each other. A positive/negative AAO index means strengthening/weakening of the circumpolar vortex, poleward/northward storm tracks and prevailing/weakening westerly winds. For detailed investigation of global teleconnection, two positive and one negative periods of AAO phase were chosen. The differences in MSLP and 2m temperature between positive and negative AAO years during the winter months partly explain the surface cooling during the last decades.
Die Untersuchung widmet sich der aktuellen Bedeutung von Ethnizität im ländlichen Raum der rumänischen Dobrudscha unter dem Einfluss der politischen und ökonomischen Dimension von Globalisierung. Im Mittelpunkt der Betrachtung von Ethnizität stehen die Aspekte von Inklusion und Exklusion sowie Selbst- und Fremdbeschreibung, die dem sozialen Wandel unterliegen. Mit einem Überblick über die Geschichte der räumlich, wirtschaftlich und sozial peripheren Untersuchungsregion Dobrudscha und der ausgewählten Minderheitengruppen wird die Entwicklung der ethnischen Zusammensetzung der Bevölkerung in der Region dargestellt. Als Fallbeispiele werden sechs Minderheitengruppen gewählt: Aromunen, Roma, russische Lipowaner, Tataren, Türken und Ukrainer. Zentrales Element der Studie bilden qualitative Interviews mit professionellen Beobachtern und Akteuren einerseits, die selbst Einfluss auf die soziale Bedeutung von Ethnizität nehmen, und andererseits mit Einwohnern in 15 ausgewählten Untersuchungsorten in der Dobrudscha. Die erhobenen Daten werden mit Blick auf die soziale Rolle von Ethnizität anhand von drei Faktorengruppen ausgewertet: Globalisierung der Ökonomie, Minderheiten- und Kulturpolitik sowie internationale Beziehungen. Auf dieser Grundlage wird die regionale und lokale Bedeutung ethnischer Kategorisierungen analysiert, um die Wahrnehmung und Bewertung ethnischer Zuordnungen im örtlichen Lebensumfeld zu erfassen.
Biogene Amine sind eine Substanzklasse, die bei Vertebraten und Invertebraten eine wichtige Komponente des endokrinen Systems darstellen. Sie binden an spezifische Rezeptoren der Gruppe der G-Protein gekoppelten Rezeptoren. In dieser Arbeit wurden zwei neue Rezeptoren aus der Schabe Periplaneta americana kloniert. Durch verschiedene Ansätze konnten zwei vollständige cDNA-Sequenzen isoliert werden. Die Aminosäuresequenzen weisen die größte Ähnlichkeit zu bereits bekannten Tyraminrezeptoren aus Locusta/Bombyx bzw. zu Dopaminrezeptoren aus Apis/Drosophila auf. Entsprechend wurden diese Rezeptoren Pea (P. americana) TYR1 und PeaDOP2 genannt. Deutliche Hinweise auf ihre Funktion lassen sich an den abgeleiteten Aminosäuresequenzen ablesen. Aminosäuren, die wichtig bei der Bildung der Bindungstasche, der Rezeptoraktivierung und der Kopplung eines G-Proteins sind, treten bei beiden Rezeptoren auf. Sequenzalignments stellen die Rezeptoren in die Gruppe anderer Tyraminrezeptoren bzw. der Invertebraten-Typ Dopaminrezeptoren. Das Transkript der beiden Rezeptoren konnte durch RT-PCR in verschiedenen Geweben nachgewiesen werden. Ein Ziel der Arbeit war die Gewinnung eines polyklonalen Antiserums gegen PeaTYR1. Dieses Serum detektiert im Homogenat von Gehirnen mehrere Banden, darunter auch eine mit der kalkulierten Masse von PeaTYR1. Präabsorption des Serums mit dem Peptid, welches zur Reinigung verwendet wurde, zeigt dessen Spezifität. An Gehirnschnitten markiert das Serum große Teile des Protocerebrums aber auch feinere Strukturen der Antennalloben, der optischen Loben und des Zentralkomplexes. Ein weiteres Serum gegen Tyramin führte zu einer Markierung von mehreren Neuronengruppen, welche sich in die optischen Loben und den Zentralkomplex verzweigen. Der αPeaTYR1-CPL3 Antikörper markierte die Plasmamembran von transfizierten HEK293-Zellen. Die Lokalisierung von Rezeptor und Ligand deuten darauf hin, dass Tyramin die optische und olfaktorische Wahrnehmung beeinflussen könnte.
Box-Simulationen von rotierender Magnetokonvektion im flüssigen Erdkern Numerische Simulationen der 3D-MHD Gleichungen sind mit Hilfe des Codes NIRVANA durchgeführt worden. Die Gleichungen für kompressible rotierende Magnetokonvektion wurden für erdähnliche Bedingungen numerisch in einer kartesischen Box gelöst. Charakteristische Eigenschaften mittlerer Größen, wie der Turbulenz-Intensität oder der turbulente Wärmefluss, die durch die kombinierte Wirkung kleinskaliger Fluktuationen entstehen, wurden bestimmt. Die Korrelationslänge der Turbulenz hängt signifikant von der Stärke und der Orientierung des Magnetfeldes ab, und das anisotrope Verhalten der Turbulenz aufgrund von Coriolis- und Lorentzkraft ist für schnellere Rotation wesentlich stärker ausgeprägt. Die Ausbildung eines isotropen Verhaltens auf kleinen Skalen unter dem Einfluss von Rotation alleine wird bereits durch ein schwaches Magnetfeld verhindert. Dies resultiert in einer turbulenten Strömung, die durch die vertikale Komponente dominiert wird. In Gegenwart eines horizontalen Magnetfeldes nimmt der vertikale turbulente Wärmefluss leicht mit zunehmender Feldstärke zu, so dass die Kühlung eines rotierenden Systems verbessert wird. Der horizontale Wärmetransport ist stets westwärts und in Richtung der Pole orientiert. Letzteres kann unter Umständen die Quelle für eine großskalige meridionale Strömung darstellen, während erstes in globalen Simulationen mit nicht axialsymmetrischen Randbedingungen für den Wärmefluss von Bedeutung ist. Die mittlere elektromotorische Kraft, die die Erzeugung von magnetischem Fluss durch die Turbulenz beschreibt, wurde unmittelbar aus den Lösungen für Geschwindigkeit und Magnetfeld berechnet. Hieraus konnten die entsprechenden α-Koeffizienten hergeleitet werden. Aufgrund der sehr schwachen Dichtestratifizierung ändert der α-Effekt sein Vorzeichen nahezu exakt in der Mitte der Box. Der α-Effekt ist positiv in der oberen Hälfte und negativ in der unteren Hälfte einer auf der Nordhalbkugel rotierenden Box. Für ein starkes Magnetfeld ergibt sich zudem eine deutliche abwärts orientierte Advektion von magnetischem Fluss. Ein Mean-Field Modell des Geodynamos wurde konstruiert, das auf dem α-Effekt basiert, wie er aus den Box-Simulationen berechnet wurde. Für eine äußerst beschränkte Klasse von radialen α-Profilen weist das lineare α^2-Modell Oszillationen auf einer Zeitskala auf, die durch die turbulente Diffusionszeit bestimmt wird. Die wesentlichen Eigenschaften der periodischen Lösungen werden präsentiert, und der Einfluss der Größe des inneren Kerns auf die Charakteristiken des kritischen Bereichs, innerhalb dessen oszillierende Lösungen auftreten, wurden untersucht. Reversals werden als eine halbe Oszillation interpretiert. Sie sind ein recht seltenes Ereignis, da sie lediglich dann stattfinden können, wenn das α-Profil ausreichend lange in dem periodische Lösungen erlaubenden Bereich liegt. Aufgrund starker Fluktuationen auf der konvektiven Zeitskala ist die Wahrscheinlichkeit eines solchen Reversals relativ klein. In einem einfachen nicht-linearen Mean-Field Modell mit realistischen Eingabeparametern, die auf den Box-Simulationen beruhen, konnte die Plausibilität des Reversal-Modells anhand von Langzeitsimulationen belegt werden.
Characterisation of silica in Equisetum hyemale and its transformation into biomorphous ceramics
(2007)
Equisetum spp. (horsetail / “Schachtelhalm”) is the only surviving genus of the primitive Sphenopsids vascular plants which reached their zenith during the Carboniferous era. It is an herbaceous plant and is distinguished by jointed stems with fused whorl of nodal leaves. The plant has been used for scouring kitchen utensils and polishing wood during the past time due to its high silica encrustations in the epidermis. Equisetum hyemale (scouring rush) can accumulate silica up to 16% dry weight in its tissue, which makes this plant an interesting candidate as a renewable resource of silica for the synthesis of biomorphous ceramics. The thesis comprises a comprehensive experimental study of silica accumulations in E.hyemale using different characterisation techniques at all hierarchical levels. The obtained results shed light on the local distribution, chemical form, crystallinity, and nanostructure of biogenic silica in E.hyemale which were quite unclear until now. Furthermore, isolation of biogenic silica from E.hyemale to obtain high grade mesoporous silica with high purity is investigated. Finally, syntheses of silicon carbide (b-SiC) by a direct thermoconversion process of E.hyemale is attempted, which is a promising material for high performance ceramics. It is found that silica is deposited continuously on the entire epidermal layer with the highest concentration on the knobs. The highest silicon content is at the knob tips (≈ 33%), followed by epidermal flank (≈ 17%), and inner lower knob (≈ 6%), whereas there is almost no silicon found in the interior parts. Raman spectroscopy reveals the presence of at least two silica modifications in E.hyemale. The first type is pure hydrated amorphous silica restricted to the knob tips. The second type is accumulated on the entire continuous outer layer adjacent to the epidermis cell walls. It is lacking silanol groups and is intimately associated with polysaccharides (cellulose, hemicellulose, pectin) and inorganic compounds. Silica deposited in E.hyemale is found to be mostly amorphous with almost negligible amounts of crystalline silica in the form of a-quartz (< 7%). The silica primary particles have a plate-like shape with a thickness of about 2 nm. Pure mesoporous amorphous silica with an open surface area up to 400 m2/g can be obtained from E.hyemale after leaching the plant with HCl to remove the inorganic impurities followed by a calcination treatment. The optimum calcination temperature appears to be around 500°C. Calcination of untreated E.hyemale causes a collapse of the biogenic silica structure which is mainly attributed to the detrimental action of alkali ions present in the native plant. Finally, pure b-SiC with a surface area of about 12 m2/g is obtained upon direct pyrolysis of HCl-treated E.hyemale samples in argon atmosphere. The original structure of native E.hyemale is substantially retained in the biomorphous b-SiC. The results of this thesis lead to a better understanding of the silicification process and allow to draw conclusions about the role of silica in E.hyemale. In particular, a templating role of the plant biopolymers for the synthesis of the nanostructured silica within the plant body can be deduced. Moreover, the high grade ultrafine amorphous silica isolated from E.hyemale promises applications as adsorbent and catalyst support and as silica source for the fabrication of silica-based composites. The synthesis of biomorphous b-SiC from sustainable and low-cost E.hyemale is still in its initial stage. The present thesis demonstrates the principal possibility of carbothermal synthesis of SiC from E.hyemale with the prospect of potential applications, for instance as refractory materials, catalyst supports, or high performance advanced ceramics.
Our Solar system contains a large amount of dust, containing valuable information about our close cosmic environment. If created in a planet's system, the particles stay predominantly in its vicinity and can form extended dust envelopes, tori or rings around them. A fascinating example of these complexes are Saturnian rings containing a wide range of particles sizes from house-size objects in the main rings up to micron-sized grains constituting the E ring. Other example are ring systems in general, containing a large fraction of dust or also the putative dust-tori surrounding the planet Mars. The dynamical life'' of such circumplanetary dust populations is the main subject of our study. In this thesis a general model of creation, dynamics and death'' of circumplanetary dust is developed. Endogenic and exogenic processes creating dust at atmosphereless bodies are presented. Then, we describe the main forces influencing the particle dynamics and study dynamical responses induced by stochastic fluctuations. In order to estimate the properties of steady-state population of considered dust complex, the grain mean lifetime as a result of a balance of dust creation, life'' and loss mechanisms is determined. The latter strongly depends on the surrounding environment, the particle properties and its dynamical history. The presented model can be readily applied to study any circumplanetary dust complex. As an example we study dynamics of two dust populations in the Solar system. First we explore the dynamics of particles, ejected from Martian moon Deimos by impacts of micrometeoroids, which should form a putative tori along the orbit of the moon. The long-term influence of indirect component of radiation pressure, the Poynting-Robertson drag gives rise in significant change of torus geometry. Furthermore, the action of radiation pressure on rotating non-spherical dust particles results in stochastic dispersion of initially confined ensemble of particles, which causes decrease of particle number densities and corresponding optical depth of the torus. Second, we investigate the dust dynamics in the vicinity of Saturnian moon Enceladus. During three flybys of the Cassini spacecraft with Enceladus, the on-board dust detector registered a micron-sized dust population around the moon. Surprisingly, the peak of the measured impact rate occurred 1 minute before the closest approach of the spacecraft to the moon. This asymmetry of the measured rate can be associated with locally enhanced dust production near Enceladus south pole. Other Cassini instruments also detected evidence of geophysical activity in the south polar region of the moon: high surface temperature and extended plumes of gas and dust leaving the surface. Comparison of our results with this in situ measurements reveals that the south polar ejecta may provide the dominant source of particles sustaining the Saturn's E ring.
There is already strong evidence that temperate lakes have been highly vulnerable to human induced climate warming during the last century. Hitherto climate impact studies have mainly focussed on the impacts of the recent long-term warming in winter and spring and little is known on the influence of climate warming on temperate lakes in summer. In the present thesis, I studied some aspects, which may have been strongly involved in determining the response of a lake to climate warming in summer. Thereby I have focussed on climate induced impacts on the thermal characteristics and the phenology and abundance of summer plankton in a shallow polymictic lake (Müggelsee, Germany). First, the influence of climate warming on the phenology and abundance of the lake plankton was investigated across seasons. Fast-growing spring phytoplankton and zooplankton (Daphnia) advanced largely synchronously, whereas long-term changes in the phenology of slow-growing summer zooplankton were clearly species-specific and not synchronised. The phenology and/or abundance of several summer copepod species changed according to their individual thermal requirements at decisive developmental stages such as emergence from diapause in spring. The study emphasises that not only the degree of warming, but also its timing within the annual cycle is of great ecological importance. To analyse the impact of climate change on the thermal characteristics of the lake, I examined the long-term development of the daily epilimnetic temperature extrema during summer. The study demonstrated for the first time for lakes that the daily epilimnetic minima (during nighttime) have increased more rapidly than the daily epilimnetic maxima (during daytime), resulting in a distinct decrease in the daily epilimnetic temperature range. This day-night asymmetry in epilimnetic temperature was likely caused by an increased nighttime emission of long-wave radiation from the atmosphere. This underlines that not only increases in air temperature, but also changes in other meteorological variables such as wind speed, relative humidity and cloud cover may play an important role in determining the lake temperature with respect to further climate change. Furthermore, a short-term analysis on the mixing regime of the polymictic lake was conducted to examine the frequency and duration of stratification events and their impacts on dissolved oxygen, dissolved nutrients and summer phytoplankton. Even during the longest stratification events (heatwaves in 2003 and 2006) the thermal characteristics of the lake differed from those typically found in shallow dimictic lakes, which exhibit a continuous stratification during summer. Particularly, hypolimnetic temperatures were higher, favouring the depletion of oxygen and the accumulation of dissolved nutrient in the hypolimnion. Thermal stratification will be very likely amplified in the future, thus, I conclude that polymictic lakes will be very vulnerable to alterations in the thermal regime with respect to projections of further climate change during summer. Finally, a long-term case study on the long and short-term changes in the development of the planktonic larvae of the freshwater mussel Dreissena polymorpha was performed to analyse the impacts of simultaneous changes in the thermal and in the trophic regime of the lake. Both the climate warming and the decrease in external nutrient load were important in determining the abundance of the pelagic larvae by affecting different features of the life-history of this species throughout the warm season. The long-term increase in the abundance and length of larvae was related to the decrease in external nutrient loading and the change in phytoplankton composition. However, the recent heatwaves in 2003 and 2006 have offset this positive effect on larval abundance, due to unfavourable low oxygen concentrations that had resulted from extremely long stratification events, mimicking the effects of nutrient enrichment. Climate warming may thus induce counteracting effects in productive shallow lakes that underwent lake restoration through a decrease in external nutrient loading. I conclude that not only the nature of climate change and thus the timing of climate warming throughout the seasons and the occurrence of climatic extremes as heatwaves, but also site-specific lake conditions as the thermal mixing regime and the trophic state are crucial factors governing the impacts of climate warming on internal lake processes during summer. Consequently, further climate impact research on lake functioning should focus on how the different lake types respond to the complex environmental forcing in summer, to allow for a comprehensive understanding of human induced environmental changes in lakes.
Being living systems unable to adjust their location to changing environmental conditions, plants display homeostatic networks that have evolved to maintain transition metal levels in a very narrow concentration range in order to avoid either deficiency or toxicity. Hence, plants possess a broad repertoire of mechanisms for the cellular uptake, compartmentation and efflux, as well as for the chelation of transition metal ions. A small number of plants are hypertolerant to one or a few specific transition metals. Some metal tolerant plants are also able to hyperaccumulate metal ions. The Brassicaceae family member Arabidopis halleri ssp. halleri (L.) O´KANE and AL´SHEHBAZ is a hyperaccumulator of zinc (Zn), and it is closely related to the non-hypertolerant and non-hyperaccumulating model plant Arabidopsis thaliana (L.) HEYNHOLD. The close relationship renders A. halleri a promising emerging model plant for the comparative investigation of the molecular mechanisms behind hypertolerance and hyperaccumulation. Among several potential candidate genes that are probably involved in mediating the zinc-hypertolerant and zinc-hyperaccumulating trait is AhHMA3. The AhHMA3 gene is highly similar to AtHMA3 (AGI number: At4g30120) in A. thaliana, and its encoded protein belongs to the P-type IB ATPase family of integral membrane transporter proteins that transport transition metals. In contrast to the low AtHMA3 transcript levels in A. thaliana, the gene was found to be constitutively highly expressed across different Zn treatments in A. halleri, especially in shoots. In this study, the cloning and characterisation of the HMA3 gene and its promoter from Arabidopsis halleri (L.) O´KANE and AL´SHEHBAZ and Arabidopsis thaliana (L.) HEYNHOLD is described. Heterologously expressed AhHMA3 mediated enhanced tolerance to Zn and to a much lesser degree to cadmium (Cd) but not to cobalt (Co) in metal-sensitive mutant strains of budding yeast. It is demonstrated that the genome of A. halleri contains at least four copies of AhHMA3, AhHMA3-1 to AhHMA3-4. A copy-specific real-time RT-PCR indicated that an AhHMA3-1 related gene copy is the source of the constitutively high transcript level in A. halleri and not a gene copy similar to AhHMA3-2 or AhHMA3-4. In accordance with the enhanced AtHMA3mRNA transcript level in A. thaliana roots, an AtHMA3 promoter-GUS gene construct mediated GUS activity predominantly in the vascular tissues of roots and not in shoots. However, the observed AhHMA3-1 and AhHMA3-2 promoter-mediated GUS activity in A. thaliana or A. halleri plants did not reflect the constitutively high expression of AhHMA3 in shoots of A. halleri. It is suggested that other factors e. g. characteristic sequence inserts within the first intron of AhHMA3-1 might enable a constitutively high expression. Moreover, the unknown promoter of the AhHMA3-3 gene copy could be the source of the constitutively high AhHMA3 transcript levels in A. halleri. In that case, the AhHMA3-3 sequence is predicted to be highly homologous to AhHMA3-1. The lack of solid localisation data for the AhHMA3 protein prevents a clear functional assignment. The provided data suggest several possible functions of the AhHMA3 protein: Like AtHMA2 and AtHMA4 it might be localised to the plasma membrane and could contribute to the efficient translocation of Zn from root to shoot and/or to the cell-to-cell distribution of Zn in the shoot. If localised to the vacuolar membrane, then a role in maintaining a low cytoplasmic zinc concentration by vacuolar zinc sequestration is possible. In addition, AhHMA3 might be involved in the delivery of zinc ions to trichomes and mesophyll leaf cells that are major zinc storage sites in A. halleri.
In the present dissertation paper we study problems related to synchronization phenomena in the presence of noise which unavoidably appears in real systems. One part of the work is aimed at investigation of utilizing delayed feedback to control properties of diverse chaotic dynamic and stochastic systems, with emphasis on the ones determining predisposition to synchronization. Other part deals with a constructive role of noise, i.e. its ability to synchronize identical self-sustained oscillators. First, we demonstrate that the coherence of a noisy or chaotic self-sustained oscillator can be efficiently controlled by the delayed feedback. We develop the analytical theory of this effect, considering noisy systems in the Gaussian approximation. Possible applications of the effect for the synchronization control are also discussed. Second, we consider synchrony of limit cycle systems (in other words, self-sustained oscillators) driven by identical noise. For weak noise and smooth systems we proof the purely synchronizing effect of noise. For slightly different oscillators and/or slightly nonidentical driving, synchrony becomes imperfect, and this subject is also studied. Then, with numerics we show moderate noise to be able to lead to desynchronization of some systems under certain circumstances. For neurons the last effect means “antireliability” (the “reliability” property of neurons is treated to be important from the viewpoint of information transmission functions), and we extend our investigation to neural oscillators which are not always limit cycle ones. Third, we develop a weakly nonlinear theory of the Kuramoto transition (a transition to collective synchrony) in an ensemble of globally coupled oscillators in presence of additional time-delayed coupling terms. We show that a linear delayed feedback not only controls the transition point, but effectively changes the nonlinear terms near the transition. A purely nonlinear delayed coupling does not affect the transition point, but can reduce or enhance the amplitude of collective oscillations.
Die Technologie der Computer Erweiterten Realität (engl.: Computer Augmented Reality, CAR) ermöglicht die Anreicherung der Sinneswahrnehmung des Menschen mit computergenerierten Informationen. Diese situationsangepassten Informationen unterstützen den Benutzer bei der Ausführung seiner Handlungen in der Realität. Durch den Einsatz dieser Technologie im industriellen Bereich wird eine Steigerung der Qualität und Effizienz von Industrieprozessen erwartet. Die vorliegende Arbeit untersucht den CAR-Einsatz zur Unterstützung von Tätigkeiten im Bereich technischer Instandhaltung. Am Institut für Prozess- und Produktionsleittechnik der Technischen Universität Clausthal wurde der Prototyp eines CAR-basierten Informations- und Dokumentationssystems für die Instandhaltung entwickelt. Er stellt eine alternative, praxistaugliche und kostengünstige Systemlösung dar, verglichen mit traditionellen CAR-Systemen, deren industrieller Einsatz durch technische, ergonomische und kostenbedingte Probleme nach wie vor erschwert wird. In einer Reihe von Benutzertests wurde die Gebrauchstauglichkeit dieses Prototyps zur Unterstützung von Instandhaltungstätigkeiten durch die Bereitstellung CAR-basierter Bedienungsanleitungen evaluiert. Des Weiteren wurde der Einfluss der speziellen interaktiven Eigenschaften des virtuell erweiterten Umgebungsbildes dieses Prototyps auf die räumliche Orientierung des Benutzers in einer größeren, unbekannten Umgebung untersucht. Die Ergebnisse sprechen deutlich für eine Eignung des Systems. Neben zeitlichen Einsparungen sind insbesondere reduzierte Fehlerzahlen und eine erleichterte räumliche Orientierung in größeren, komplex aufgebauten sowie in nicht oder wenig bekannten Umgebungen zu nennen. Durch die Möglichkeit, Objekte einer Anlage eindeutig zu identifizieren, wird letztlich die Arbeitssicherheit erhöht.
Conceptual Capacities
(2007)
The biological function and the technological applications of semiflexible polymers, such as DNA, actin filaments and carbon nanotubes, strongly depend on their rigidity. Semiflexible polymers are characterized by their persistence length, the definition of which is the subject of the first part of this thesis. Attractive interactions, that arise e.g.~in the adsorption, the condensation and the bundling of filaments, can change the conformation of a semiflexible polymer. The conformation depends on the relative magnitude of the material parameters and can be influenced by them in a systematic manner. In particular, the morphologies of semiflexible polymer rings, such as circular nanotubes or DNA, which are adsorbed onto substrates with three types of structures, are studied: (i) A topographical channel, (ii) a chemically modified stripe and (iii) a periodic pattern of topographical steps. The results are compared with the condensation of rings by attractive interactions. Furthermore, the bundling of two individual actin filaments, whose ends are anchored, is analyzed. This system geometry is shown to provide a systematic and quantitative method to extract the magnitude of the attraction between the filaments from experimentally observable conformations of the filaments.
The cytoskeletal motor protein kinesin-1 (conventional kinesin) is the fast carrier for intracellular cargo transport along microtubules. So far most studies aimed at investigating the transport properties of individual motor molecules. However, the transport in cells usually involves the collective work of more than one motor. In the present work, we have studied the movement of beads as artificial loads/organelles pulled by several kinesin-1 motors in vitro. For a wide range of motor coverage of the beads and different bead (cargo) sizes the transport parameters walking distance or run length, velocity and force generation are measured. The results indicate that the transport parameters are influenced by the number of motors carrying the bead. While the transport velocity slightly decreases, an increase in the run length was measured and higher forces are determined, when more motors are involved. The effective number of motors pulling a bead is estimated by measuring the change in the hydrodynamic diameter of kinesin-coated beads using dynamic light scattering. The geometrical constraints imposed by the transport system have been taken into account. Thus, results for beads of different size and motor-surface coverage could be compared. In addition, run length-distributions obtained for the smallest bead size were matched to theoretically calculated distributions. The latter yielded an average number of pulling motors, which is in agreement with the effective motor numbers determined experimentally.
This thesis describes two main projects; the first one is the optimization of a hierarchical search strategy to search for unknown pulsars. This project is divided into two parts; the first part (and the main part) is the semi-coherent hierarchical optimization strategy. The second part is a coherent hierarchical optimization strategy which can be used in a project like Einstein@Home. In both strategies we have found that the 3-stages search is the optimum strategy to search for unknown pulsars. For the second project we have developed a computer software for a coherent Multi-IFO (Interferometer Observatory) search. To validate our software, we have worked on simulated data as well as hardware injected signals of pulsars in the fourth LIGO science run (S4). While with the current sensitivity of our detectors we do not expect to detect any true Gravitational Wave signals in our data, we can still set upper limits on the strength of the gravitational waves signals. These upper limits, in fact, tell us how weak a signal strength we would detect. We have also used our software to set upper limits on the signal strength of known isolated pulsars using LIGO fifth science run (S5) data.
Vitamin E ist der Überbegriff für 4 Tocopherole (α, β, γ und δ) sowie 4 Tocotrienole (α, β, γ und δ), die als gemeinsames Merkmal ein Chromanolringsystem sowie eine gesättigte (Tocopherole) bzw. ungesättigte (Tocotrienole) Seitenkette aufweisen. Neben ihrer antioxidativen Wirkung (Schutz von Membranen vor Lipidperoxidaton) konnten für einige Vitamin E - Formen auch eine Reihe von hochspezifischen, nicht-antioxidativen Wirkungen in vitro nachgewiesen werden. Meist bleibt jedoch unklar, ob ein solcher Effekt auch in vivo, also im Tiermodel oder direkt im Menschen, gefunden werden kann. In erster Linie müsste hierbei geklärt werden, ob die jeweilige Vitamin E - Form auch bioverfügbar, also in für eine Wirkung ausreichender Konzentration im Organismus vorhanden ist, oder aber vorher eliminiert und ausgeschieden wird. In dieser Doktorarbeit wurden deshalb wichtige Grundlagen zum Abbau der Tocopherole und Tocotrienole erarbeitet. • In HepG2-Zellen konnte der Abbau der Tocotrienole mit Hilfe flüssig- sowie gaschromatographischer Analysemethoden vollständig aufgeklärt werden. Wie sich hierbei ergab, verläuft der Abbau weitgehend in Analogie zum Abbau der Tocopherole über eine durch Cytochrom P450 katalysierte initiale ω-Hydroxylierung mit 5 nachfolgenden β-Oxidationsschritten. • In vitro konnten in HepG2 – Zellen die Abbauraten der verschiedenen Vitamin E - Formen bestimmt werden. Dies nahmen in folgender Reihenfolge zu: α-Tocopherol < γ-Tocopherol < α-Tocotrienol < γ-Tocotrienol. • Wie sich mit Hilfe eines mit Cytochrom P450 hochangereicherten Homogenats aus Rattenlebern ergab, stellt die initiale ω-Hydroxylierung einen geschwindigkeitsbestimmenden Schritt des Abbaus dar: α-Tocopherol wurde weit langsamer hydroxyliert als alle anderen Vitamin E – Formen. • Der unterschiedliche Abbau von α-Tocopherol und γ-Tocotrienol konnte auch im Mäuseversuch in vivo bestätigt werden. Nach Fütterung von Mäusen mit α-Tocopherol wurden nur geringe Mengen von α-Tocopherolmetaboliten im Urin der Mäuse gefunden, während nach Applikation von γ-Tocotrienol hohe Konzentrationen der γ-Tocotrienolmetabolite nachgewiesen wurden. In Plasma und Leber wiederum wurden (dem Futtergehalt entsprechende) hohe α-Tocopherolkonzentrationen entdeckt, während γ-Tocotrienol selbst nach hoher Gabe nicht oder nur in Spuren nachweisbar war. In HepG2 – Zellen konnte gezeigt werden, dass γ-Tocotrienol eine cytotoxische Wirkung auf die Hepatocarcinoma-Zelllinie HepG2 entfalten kann, indem durch die Aktivierung der proteolytischen Caspase 3 die Induktion des programmierten Zelltodes (Apoptose) ausgelöst wird. Abschliessend lässt sich festhalten, dass der Körper lediglich das natürliche α-Tocopherol vor dem Abbau bewahrt, die anderen Vitamin E – Formen jedoch als Fremdstoffe behandelt und rapide ausscheidet. Als doppelter Schutz vor Verlust des “wertvollen” α-Tocopherol dienen hierbei das α-Tocopherol Transfer Protein sowie die in dieser Arbeit gefundenen Unterschiede im ersten Schritt des Abbaus, der Cytochrom P450 - katalysierten ω-Hydroxylierung. Beides erklärt die bevorzugte Retention von α-Tocopherol im Organsimus und seine hohe Bioaktivität. Will man deshalb in vitro Ergebnisse anderer Vitamin E – Formen auf die in vivo Situation übertragen, muss man die geringe Bioverfügbarkeit dieser Substanzen berücksichtigen.
It is desirable to reduce the potential threats that result from the variability of nature, such as droughts or heat waves that lead to food shortage, or the other extreme, floods that lead to severe damage. To prevent such catastrophic events, it is necessary to understand, and to be capable of characterising, nature's variability. Typically one aims to describe the underlying dynamics of geophysical records with differential equations. There are, however, situations where this does not support the objectives, or is not feasible, e.g., when little is known about the system, or it is too complex for the model parameters to be identified. In such situations it is beneficial to regard certain influences as random, and describe them with stochastic processes. In this thesis I focus on such a description with linear stochastic processes of the FARIMA type and concentrate on the detection of long-range dependence. Long-range dependent processes show an algebraic (i.e. slow) decay of the autocorrelation function. Detection of the latter is important with respect to, e.g. trend tests and uncertainty analysis. Aiming to provide a reliable and powerful strategy for the detection of long-range dependence, I suggest a way of addressing the problem which is somewhat different from standard approaches. Commonly used methods are based either on investigating the asymptotic behaviour (e.g., log-periodogram regression), or on finding a suitable potentially long-range dependent model (e.g., FARIMA[p,d,q]) and test the fractional difference parameter d for compatibility with zero. Here, I suggest to rephrase the problem as a model selection task, i.e.comparing the most suitable long-range dependent and the most suitable short-range dependent model. Approaching the task this way requires a) a suitable class of long-range and short-range dependent models along with suitable means for parameter estimation and b) a reliable model selection strategy, capable of discriminating also non-nested models. With the flexible FARIMA model class together with the Whittle estimator the first requirement is fulfilled. Standard model selection strategies, e.g., the likelihood-ratio test, is for a comparison of non-nested models frequently not powerful enough. Thus, I suggest to extend this strategy with a simulation based model selection approach suitable for such a direct comparison. The approach follows the procedure of a statistical test, with the likelihood-ratio as the test statistic. Its distribution is obtained via simulations using the two models under consideration. For two simple models and different parameter values, I investigate the reliability of p-value and power estimates obtained from the simulated distributions. The result turned out to be dependent on the model parameters. However, in many cases the estimates allow an adequate model selection to be established. An important feature of this approach is that it immediately reveals the ability or inability to discriminate between the two models under consideration. Two applications, a trend detection problem in temperature records and an uncertainty analysis for flood return level estimation, accentuate the importance of having reliable methods at hand for the detection of long-range dependence. In the case of trend detection, falsely concluding long-range dependence implies an underestimation of a trend and possibly leads to a delay of measures needed to take in order to counteract the trend. Ignoring long-range dependence, although present, leads to an underestimation of confidence intervals and thus to an unjustified belief in safety, as it is the case for the return level uncertainty analysis. A reliable detection of long-range dependence is thus highly relevant in practical applications. Examples related to extreme value analysis are not limited to hydrological applications. The increased uncertainty of return level estimates is a potentially problem for all records from autocorrelated processes, an interesting examples in this respect is the assessment of the maximum strength of wind gusts, which is important for designing wind turbines. The detection of long-range dependence is also a relevant problem in the exploration of financial market volatility. With rephrasing the detection problem as a model selection task and suggesting refined methods for model comparison, this thesis contributes to the discussion on and development of methods for the detection of long-range dependence.
Development and application of novel genetic transformation technologies in maize (Zea mays L.)
(2007)
Plant genetic engineering approaches are of pivotal importance to both basic and applied research. However, rapid commercialization of genetically engineered crops, especially maize, raises several ecological and environmental concerns largely related to transgene flow via pollination. In most crops, the plastid genome is inherited uniparentally in a maternal manner. Consequently, a trait introduced into the plastid genome would not be transferred to the sexually compatible relatives of the crops via pollination. Thus, beside its several other advantages, plastid transformation provides transgene containment, and therefore, is an environmentally friendly approach for genetic engineering of crop plants. Reliable in vitro regeneration systems allowing repeated rounds of regeneration are of utmost importance to development of plastid transformation technologies in higher plants. While being the world’s major food crops, cereals are among the most difficult-to-handle plants in tissue culture which severely limits genetic engineering approaches. In maize, immature zygotic embryos provide the predominantly used material for establishing regeneration-competent cell or callus cultures for genetic transformation experiments. The procedures involved are demanding, laborious and time consuming and depend on greenhouse facilities. In one part of this work, a novel tissue culture and plant regeneration system was developed that uses maize leaf tissue and thus is independent of zygotic embryos and greenhouse facilities. Also, protocols were established for (i) the efficient induction of regeneration-competent callus from maize leaves in the dark, (ii) inducing highly regenerable callus in the light, and (iii) the use of leaf-derived callus for the generation of stably transformed maize plants. Furthermore, several selection methods were tested for developing a plastid transformation system in maize. However, stable plastid transformed maize plants could not be yet recovered. Possible explanations as well as suggestions for future attempts towards developing plastid transformation in maize are discussed. Nevertheless, these results represent a first essential step towards developing chloroplast transformation technology for maize, a method that requires multiple rounds of plant regeneration and selection to obtain genetically stable transgenic plants. In order to apply the newly developed transformation system towards metabolic engineering of carotenoid biosynthesis, the daffodil phytoene synthase (PSY) gene was integrated into the maize genome. The results illustrate that expression of a recombinant PSY significantly increases carotenoid levels in leaves. The beta-carotene (pro-vitamin A) amounts in leaves of transgenic plants were increased by ~21% in comparison to the wild-type. These results represent evidence for maize to have significant potential to accumulate higher amounts of carotenoids, especially beta-carotene, through transgenic expression of phytoene synthases. Finally, progresses were made towards developing transformation technologies in Peperomia (Piperaceae) by establishing an efficient leaf-based regeneration system. Also, factors determining plastid size and number in Peperomia, whose species display great interspecific variation in chloroplast size and number per cell, were investigated. The results suggest that organelle size and number are regulated in a tissue-specific manner rather than in dependency on the plastid type. Investigating plastid morphology in Peperomia species with giant chloroplasts, plasmatic connections between chloroplasts (stromules) were observed under the light microscope and in the absence of tissue fixation or GFP overexpression demonstrating the relevance of these structures in vivo. Furthermore, bacteria-like microorganisms were discovered within Peperomia cells, suggesting that this genus provides an interesting model not only for studying plastid biology but also for investigating plant-microbe interactions.
Nature has always served as a model for mimicking and inspiration to humans in their efforts to improve their life. Researchers have been inspired by nature to produce biomimetic materials with molecular recognition properties by design rather than evolution. Molecular imprinting is one way to prepare such materials. Such smart materials with new functionalities are at the forefront of the development of a relevant number of ongoing and perspective applications ranging from consumer to space industry. Molecularly imprinted polymers were developed by mimicking the natural enzymes or antibodies that serve as host for binding target molecules. These imprints were used as a recognition element to substitute natural biomolecules in biosensors. The concept behind molecular imprinting is to mold a material (with the desired chemical properties) around individual molecules. Upon removal of the molecular templates, one is left with regions in the molded material that fit the shape of the template molecules. Thus, molecular imprinting results in materials that can selectively bind to molecules of interest. Imprinted materials resulted in applications ranging from chemical separation to bioanalytics. In this work attempts were made particularly in the development of molecularly imprinted polymer based thermometric sensors. The main effort was focused towards the development of an covalently imprinted polymer that would be able to selectively bind fructosyl valine (Fru-Val), the N-terminal constituent of hemoglobin A1c ß-chains. Taking into account the known advantages of imprinted polymers, e.g. robustness, thermal and chemical stability, imprinted materials were successfully used as a recognition element in the sensor. One of the serious problems associated with the development of MIP sensors and which lies in the absence of a generic procedure for the transformation of the polymer-template binding event into a detectable signal has been addressed by developing the "thermometric" approach. In general the developed approach gives a new insight on MIP/Analyte interactions.