69 search hits
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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.
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Hochtemperatursynthese von Smectiten und deren dreidimensional geordnete Einlagerungsverbindungen
(2004)
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Wolfgang Seidl
- Mit Hilfe einer Hochtemperatursynthese bei 1750 °C im geschlossenen System konnte eine Reihe neuer, einphasiger und ladungshomogener 2:1 Schichtsilicate hergestellt werden. Durch Kombination unterschiedlicher isomorpher Substitutionen in den 2:1 Schichtsilicaten zur Generierung der negativen Schichtladung mit verschiedenen Zwischenschichtkationen der Alkali- und/oder der Erdalkalielemente konnte gezeigt werden, dass bei den phasenreinen 2:1 Schichtsilicaten die durch zweidimensionale, planare Defekte verursachte Fehlordnung von der Größe des Zwischenschichtkations und der Art der isomorphen Substitution abhängt. Trotz häufigem Wechsel der Kationenaustauschlösung konnte aber aus zwei Gründen bei keinem aus der Hochtemperatursynthese erzeugten dreidimensional geordneten Schichtsilicat eine vollständige Einlagerung erzielt werden. Zum einen wirkt sich das Aspektverhältnis bei dünnen (<< 1 µm), in der lateralen Ausdehnung sehr breiten Silicatkristallen (> 1 mm), negativ auf die Geschwindigkeit und die Vollständigkeit einer Einlagerungsreaktion aus. Zum anderen behindern die Verwachsungen in den Produkten aus der Hochtemperatursynthese die Einlagerungsreaktion beträchtlich. Durch thermische Nachbehandlung knapp unterhalb des Schmelzpunktes wurde versucht, diese beiden Probleme zu beseitigen. Während beim Cs-Hectorit ein exakter Schmelzpunkt bestimmt werden konnte und nach dem Tempern kaum verwachsene Kristalle mit deutlich höherem Aspektverhältnis erhalten wurden, mussten beim K-Vermiculit aufgrund eines inkongruenten Schmelzverhaltens mehrere Temperversuche durchgeführt werden, die sowohl ein eher lockeres Gefüge von Kristallen als auch einen kompakten, „glasartigen“ Bulk ergaben. Bei Kationenaustauschversuchen der verschiedenen K-Vermiculit-Temperproben mit Ba2+ bei gleichen Reaktionsparametern zeigte der „glasartige“, kompakte Bulk zwar die höchste intrakristalline Reaktivität, aber selbst in dieser Temperprobe konnten die Zwischenschichtkationen nicht vollständig gegen Ba2+ ausgetauscht werden. Dagegen konnte durch das Tempern beim Cs-Hectorit die intrakristalline Reaktivität so weit gesteigert werden, dass nach Optimierung der Austauschbedingungen mit mehreren organischen Kationen dreidimensional geordnete Einlagerungsverbindungen erhalten wurden. Bei zwei dieser Verbindungen (DDABCO-Hectorit und TMA-Hectorit) konnte durch Einkristallstrukturanalyse und -verfeinerung die Anordnung der organischen Kationen im Zwischenschichtraum relativ zu den Silicatschichten bestimmt werden. Beim DDABCO-Hectorit wurde außerdem eine reversible Umorientierung des Zwischenschichtkations in Abhängigkeit von der relativen Feuchtigkeit der Umgebung beobachtet, mit der auch das Entstehen bzw. Ausheilen von planaren Defekten einhergeht. Weil die organischen Zwischenschichtkationen bei diesen beiden Einlagerungsverbindungen mehrere entartete Orientierungen relativ zueinander annehmen können, wurde trotz homogener Schichtladungsverteilung im Röntgenpulverdiffraktogramm nur im Ansatz eine zweidimensionale Fernordnung beobachtet. Dagegen traten bei dreidimensional geordneten Einlagerungsverbindungen des getemperten Cs-Hectorits mit 2H-DABCO2+ und H-MDABCO2+ in den Pulverdiffraktogrammen nach vollständiger Einlagerung deutlich Überstrukturreflexe in Erscheinung. Mit dem getemperten Cs-Hectorit liegt nun erstmals ein dreidimensional geordneter Smectit mit ausreichender intrakristalliner Reaktivität vor, aus dem sich durch Einlagerung mit geeigneten Zwischenschichtkationen dreidimensional geordnete Einlagerungsverbindungen erzeugen lassen. Durch Einkristallstrukturanalyse kann bei den Einlagerungsverbindungen die Struktur des Zwischenschichtraums routinemäßig aufgeklärt werden, was in Zukunft zu einem deutlich besseren Verständnis der Wirt-Gast-Wechselwirkungen im Zwischenschichtraum eines 2:1 Schichtsilicates führen sollte.
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A macroscopic and microscopic investigation of the magnesite – otavite solid soluition
(2004)
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Fiona Bromiley
- The magnesite (MgCO3) – calcite (CaCO3) system is the most geologically important of the carbonate minerals. At intermediate compositions a distinct ordered phase exists, dolomite [MgCa(CO3)2], which has symmetry. A complete, disordered ( c symmetry) solid solution exists, but at temperatures in excess of 1400°C. Unmixing and ordering processes that occur at high temperatures in the magnesite – calcite system make experimental work difficult. However, the use of an analogue system allows syntheses under more accessible experimental conditions. The effects of cation substitution and ordering in the magnesite (MgCO3) – otavite (CdCO3) solid solution have, therefore, been investigated using X-ray powder diffraction and Hard Mode Infrared Spectroscopy (HMIS). The results from Rietveld refinements of the X-ray powder diffraction data show that the variation of the a-axis is linear as a function of composition and is not affected by different degrees of order at intermediate compositions. However, the c-axis shows a positive deviation from linearity as a function of composition for the 800°C series. The observed deviation decreases with increasing degree of order for samples of composition Mg0.5Cd0.5CO3. Oxygen-carbon-oxygen bond angles for samples with symmetry showed a decrease in bond angle from 120° (constrained by symmetry in samples with the c structure) with increase in degree of order. Site occupancies were used to determine the long-range order parameter, Q, for samples with symmetry. The square of the order parameter varies linearly as a function of temperature, suggesting a second-order phase transition, and a critical transition temperature of Tc = 719°C. Intensity ratios between reflections present only in the low symmetry phase and reflections present in both the low and high symmetry phases can be used to determine a value proportional to the square of the long-range order parameter, Q. Intensity ratios, between the (101) and (202) reflections for samples of composition Mg0.5Cd0.5CO3, were determined from X-ray powder diffraction patterns and show a linear variation as a function of temperature, with a critical transition temperature, Tc = 716°C. The local mixing and ordering behaviour of the magnesite – otavite solid soluition has been characterised using infrared powder absorption spectroscopy. Phonon bands due to cadmium-oxygen translations, and magnesium-oxygen translations were both observed in the IR spectra for samples of intermediate composition. Band positions for cadmium-oxygen translations remained constant as a function of composition, whereas band positions for magnesium-oxygen translations showed a decrease in wavenumber as a function of composition. Vibrational bands in other spectral regions (libration and translation of carbonate groups and doubly degenetrate in-plane bending and out-of-plane bending of carbonate groups) vary linearly as a function of composition and no effect of order on band position is observed. At high frequencies the samples with c symmetry (800°C series) show a linear shift in band position as a function of composition, whereas, samples in the cadmium dolomite stability field, with symmetry, show a marked increase in frequency compared to their c symmetry counterparts. Cation substitution, or disordering causes broadening of IR vibrational bands for a given material. In this study an alternative method was used, which makes use of the autocorrelation function to establish average line widths for six spectral regions. The autocorrelation results, delta corr, can be interpreted in terms of local strain fields present in the structure due to cation substitution and disordering. In the low frequency region, the delta corr values show a positive deviation from linearity as a function of composition. For samples of composition Mg0.5Cd0.5CO3 the delta corr values are virtually all the same, independent of the degree of order. Over all the spectral regions, the addition of 10mol% MgCO3 (1 Mg atom every 2 unit cells) to the otavite results in a large increase in line width. It is, therefore, suggested that the strain fields surrounding the substituting magnesium atoms into the otavite structure are on the order of 30Å. In the low MIR and at a composition of Mg0.5Cd0.5CO3, an effect of order is observed as a reduction in delta corr values with respect to the sample with c symmetry. The difference in delta corr values between the ordered and disordered samples was used to determine the local-order parameter, q, which scales linearly with the long-range order parameter, Q.
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Transfer and Distribution of Cantharidin within Selected Members of Blister Beetles (Coleoptera: Meloidae) and Its Probable Importance in Sexual Behaviour
(2004)
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Mahmood Reza Nikbakhtzadeh
- Cantharidin (C10H12O4) is a repellent against a wide variety of predators and is known to be produced by blister beetles (Coleoptera: Meloidae) and oedemerid beetles (Col: Oedemeridae) where it is found in hemolymph and various tissues. Males of blister beetles transfer large pockets of cantharidin along with sperm to the female during copulation. Cantharidin movement through different parts of male and female genitalia was surveyed to get a better time sequence of the pharmacodynamic of this compound. Since cantharidin titre in meloid beetles highly depends on the age, sex and mating record of the individuals, deuterated cantharidin (D2C) was introduced into meloids’ body by injection, mixed with artificial diet or floating the beetles’ internal organs in Ringer and D2C solution. All samples were analysed by GC-MS, but because of the approximate coelution of cantharidin and D2C, their exact measurement via normal MS seemed to be very difficult. Therefore, MRM (Multiple Reaction Monitoring) method for cantharidin/D2C separation and independent quantitation was developed for the first time. Cantharidin pharmacodynamic in male of studied species could be quite different over a period of time. As the accessory glands absorb high amount of D2C in short term, they will eventually accumulate less amount than the testis. Confirming the previous studies, it has been concluded that post-farnesyl steps in the cantharidin pathway may occur entirely in the male’s body outside the reproductive system but the ultimate product is transported into male internal genitalia via membrane of the accessory glands which should be permeable to the chemical. It transfers afterwards to epididimis and the vas deferens in higher volume comparing to the other organs of the male genitalia and finally absorbed by the testis. In females, cantharidin is first absorbed by spermatophoral receptacle in high volume while at the same time goes through ovary and is distributed upon eggs; by the way the up-taken volume by ovaries remains considerably lower than the receptacle. By time these two organs stopped accumulating of cantharidin, whereas the bursa copulatrix starts incorporating the gift actively. This reserved amount should be mainly supplied by the receptacle and ovaries directly, so that the internal way of the terpene transfer remains as the main transport way. Analysis of the eggs laid by D2C injected females of Hycleus polymorphus demonstrated that the marker has been transferred from female to the eggs. It was found that D2C had been also incorporated into the triungulin larvae; however the titre decreased significantly from egg to larva. There is a good correlation between density of cuticular pores and the cantharidin/D2C level of the scape and pedicel antennomeres of the male specimens of Cyaneolytta sp. Light microscopy of semi thin cross sections of male scape and pedicel indicates that there are plenty of canal shape structures which have been stretched from the antennal hemolymph to the antennomere surface where cuticular pores situated. These structures can be uni- or multicellular tubules which bring the circulating cantharidin of hemolymph into the surface where later on released via the opening of cuticular pores. Tracing the head capsule and antennal segments of those Cyaneolytta females which were injected by D2C shows that the marker is found mostly in the two first antennal segments. Similarly, a higher concentration of the cuticular pores was also observed on the scape and pedicel. Tubular cells or any other carrying structures such as tyloids were found neither in cross sectioning of female antennomeres nor on integument surface. We suppose a natural system has been evolved in females of genus Cyaneolytta which let them select males with abundant reservoir of cantharidin prior to any mating behaviour. Males and females have antennation during which males antennomeres as well as cantharidin containing pores which are located on the 1st and 2nd antennomeres come into direct contact with the female antennae and thus release cantharidin on its surface. So, the porous area of male antennae can be considered as cantharidin release structures (CRS). In contrast, female porous area of antennae is apparently regarded as multiporous gustatory sensillae (MGS) which means a chemoreceptor to recognize the cantharidin titre of male sexual partner. We hereby refer to cantharidin as a precopulatory sex pheromone and support the idea who suggests cantharidin role in close range sexual selection.
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Electrostatic Trapping as a Self-Consistent Phenomenon in Plasmas and other Collective Systems
(2004)
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Alejandro Luque Estepa
- This thesis investigates self-consistent electrostatic structures in plasmas and related collective systems. They are coherent structures in which particles become trapped in the wave potential. These phenomena require a kinetic description i.e. a description in which the velocity distribution of the particles is taken into account. Trapping structures extend the areas in configuration space in which a plasma is unstable. The main argument and result of this work is that there exist certain kinds of perturbations of an equilibrium that can destabilize the plasma, even if linear theory predicts stability. The usual procedure in plasma theory of analyzing the stability of a plasma by means of a linearization of the equations is therefore questioned. Particle trapping is an essentially nonlinear phenomenon, still present for infinitesimally small wave amplitudes. The effect of the particle trapping is therefore not linked only with the treatment of finite amplitudes, as often assumed, but has also to be taken into account from the very beginning if one wants to arrive at generally valid predictions about stability and the associated anomalous transport. Thus it is not surprising that the problem of transport represents a not yet closed chapter in the theory of plasmas, a fact which is shown in many examples from fusion and space research, where almost collisionless plasmas are present. Particle trapping is however not confined to classic plasmas. Another result of this work is to show that the applied formalism can also be extended to other systems that present a collective behavior. Namely, a quantum extension is possible, which allow us to investigate quantum-like systems and also to draw a connection between electrostatic trapping in plasmas and envelope solitons in nonlinear optical media like e.g. optical fibers. The longitudinal dynamics of charged particle beams in accelerators and storage rings provides a further example of a collective system in which the phenomenon of particle trapping plays an essential role of the dynamics.
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Experimental deformation of forsterite, wadsleyite and ringwoodite: Implications for seismic anisotropy of the Earth’s mantle
(2004)
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Hélène Couvy
- The rheological properties of the major minerals of the Earth’s mantle are still not well constrained. However, these properties are crucial for the understanding of a wide range of processes in the Earth’s interior such as mantle convection. The purpose of this work is to address the issue of the rheology of the lowermost upper mantle and of the transition zone through the mechanical properties at high pressure of olivine (with forsterite composition Mg2SiO4) and of its high-pressure polymorphs wadsleyite and ringwoodite. Indeed, the properties of the Earth’s mantle can be inferred as a first approximation from the mechanical properties of those polymorphs which volumetrically dominate the mineralogy of the region of concern. Deformation experiments have been performed on hot-pressed forsterite samples and on pre-synthesized wadsleyite and ringwoodite samples under pressure conditions of the Earth’s mantle and at 1300-1400°C. The possible influence of the phase transformation from forsterite to wadsleyite on rheology has been also investigated. Deformation has been achieved by shear using the Kawai-type multianvil apparatus. Complementary experiments on forsterite have been performed in the newly developed Deformation-DIA. Some of them have been carried out on a synchrotron beam line to perform in-situ stress and strain measurements. In order to gain a maximum of information on the deformation mechanisms and on the Crystallographic Preferred Orientation (CPO), a special attention has been devoted to the microstructural characterisation of the samples. Electron BackScattering Diffraction (ESBD) and Transmission Electron Microscope (TEM) have been mainly used. An important pressure-induced change in deformation mechanism is shown in forsterite. The deformation of forsterite at high pressure and temperature is dominated by the [001]{hk0} slip system rather than the [100](010) glide which is extensively observed at low pressure and high temperature.. Concerning the high-pressure polymorphs, their plastic behaviour has been studied with a strong emphasis on the formation of CPO. ViscoPlastic Self Consistent (VPSC) modelling is used to link the CPO with known elementary deformation mechanisms of these phases. The main features of the CPO of wadsleyite are characterized by the alignment of the [100] axes parallel to the shear direction and the alignment of the [001] axes toward the normal to the shear plane. Too many uncertainties remain on the ringwoodite CPO for them being used to interpret seismic anisotropy. Finally, we suggest that strain-induced CPO might be responsible for the seismic anisotropy observed in the lowermost upper mantle and in the upper part of the transition zone. The low seismic anisotropy of the lowermost upper mantle can be explained from the slip system change in forsterite and the CPO of wadsleyite point toward a dominant tangential flow in the upper part of the transition zone.
