Au cours du développement des végétaux, de l’établissement de l’identité cellulaire des premiers organes au guidage du tube pollinique, la communication cellule à cellule est d’une importance capitale. En réponse, les voies de signalisation moléculaires sont élaborées pour la perception d’un signal extérieur et la transduction en une réponse génique via une cascade intracellulaire. Les récepteurs kinases font partie des protéines perceptrices des stimuli et constituent chez les plantes une catégorie de protéines avec une occurrence considérable, mais dont très peu d’informations détaillées sont disponibles à ce jour. Une famille de récepteurs kinases chez Arabidopsis thaliana, AtORK11 (Arabidopsis thaliana Ovule Receptor Kinase 11), a été identifiée par orthologie à un récepteur spécifique aux ovaires chez une solanacéee sauvage, Solanum chacoense. La fonction présumée de cette famille de récepteurs kinases de type leucine-rich repeat, suggérée par son patron d’expression, implique les événements relatifs au développement des gamétophytes et à la reproduction. Afin de caractériser la fonction des quatre gènes de la famille (AtORK11a, AtORK11b, AtORK11c et AtORK11d) une stratégie d’analyse de mutants d’insertion de l’ADN-T et d’évaluation du mode d’action par complémentation bimoléculaire par fluorescence (BiFC) a été entreprise. Aucune fonction précise n’a pu être attribuée aux doubles mutants d’insertion, par contre la surexpression d’une construction dominante négative indique un rôle dans le développement gamétophytique. Il a aussi été démontré que les quatre récepteurs peuvent interagir par homodimérisation aussi bien que par hétérodimérisation. Une hypothèse de redondance fonctionnelle est ainsi mise à jour parmi la famille des gènes AtORK11. / Cell to cell communication is paramount during plant developmental processes, from cellular identity in early organogenesis to pollen tube guidance. In response to this requirement, molecular cell signalling is used to perceive an external signal and transduce the response by an intracellular signalling cascade leading to specific gene activation. The sensing protein is typically a receptor kinase, which will transduce the stimulus by phosphorylation of a cytoplasmic interaction partner. Although plant receptor kinases represent the largest protein kinase family, only handfuls are well characterized. By sequence identity (orthology), a family of leucine-rich repeat receptor kinases from Arabidopsis thaliana was identified as AtORK11 (Arabidopsis thaliana Ovule Receptor Kinase 11). Based upon previous results from its ortholog in Solanum chacoense, the ovary- specific ScORK11 receptor kinase, we hypothesized that members of the AtORK11 receptors would be involved in gametophyte development and reproduction. In order to characterize the role of the four family members (AtORK11a, AtORK11b, AtORK11c and AtORK11d), a T-DNA insertional mutant strategy was undertaken, as well as bimolecular fluorescence complementation assays (BiFC). No precise function could be assigned to the double mutants although a dominant negative strategy revealed an involvement in gametophytic development. It was also shown that all of the receptors could form homodimers as well as heterodimers in a heterologous system, suggesting high functional redundancy for the AtORK11 family.

No description available.

The nuclear design of fusion devices such as ITER (International Thermonuclear Experimental Reactor), which is an experimental fusion reactor based on the "tokamak" concept, rely on the results of neutron physical calculations. These depend on the knowledge of the neutron and photon flux spectra which is particularly important because it permits to anticipate the possible answers of the whole structure to phenomena such as nuclear heating, tritium breeding, atomic displacements, radiation shielding, power generation and material activation. The flux spectra can be calculated with transport codes, but validating measurements are also required. An important constituent of structural materials and divertor areas of fusion reactors is tungsten. This thesis deals with the measurement of the neutron fluence and neutron energy spectrum in a tungsten assembly by means of multiple foil neutron activation technique. In order to check and qualify the experimental tools and the codes to be used in the tungsten benchmark experiment, test measurements in the D-T and D-D neutron fields of the neutron generator at Technische Universität Dresden were performed. The characteristics of the D-D and D-T reactions, used to produce monoenergetic neutrons, together with the selection of activation reactions suitable for fusion applications and details of the activation measurements are presented. Corrections related to the neutron irradiation process and those to the sample counting process are discussed, too. The neutron fluence and its energy distribution in a tungsten benchmark, irradiated at the Frascati Neutron Generator with 14 MeV neutrons produced by the T(d, n)4He reaction, are then derived from the measurements of the neutron induced γ-ray activity in the foils using the STAYNL unfolding code, based on the linear least-square-errors method, together with the IRDF-90.2 (International Reactor Dosimetry File) cross section library. The differences between the neutron flux spectra measured by means of neutron foil activation and the neutron flux spectra obtained in the same assembly, making use of an NE213 liquid-scintillation spectrometer were studied. The comparison of measured neutron spectra with the spectra calculated with the MCNP-4B (Monte Carlo neutron and photon transport) code, which allows a crucial test of the evaluated nuclear data used in fusion reactor design, is discussed, too. In conclusion, this thesis shows the applicability of the neutron foil activation technique for the measurement of neutron flux spectra inside a thick tungsten assembly irradiated with 14 MeV from a D-T generator. / Die Konstruktion von Fusionsreaktoren wie ITER (International Thermonuclear Experimental Reactor), der ein experimenteller Fusionsreaktor ist und auf dem "Tokamak"-Konzept beruht, basiert unter neutronenphysikalischen Gesichtspunkten auf den Ergebnissen von umfangreichen Simulationsrechnungen. Diese setzen die Kenntnis der Spektren des Neutronen- und Photonenflusses voraus die besonders wichtig ist, weil sie, die möglichen Antworten der ganzen Struktur auf physikalische Prozesse vorauszuberechnen erlaubt wie z.B.: Heizen durch nukleare Prozesse, Tritium-Brüten, Atomverschiebung, Abschirmung von Strahlung, Leistungserzeugung und Materialaktivierung. Die Flußspektren können mittels Transportcodes berechnet werden, aber es werden auch Messungen zu ihrer Bestätigung benötigt. Ein wichtiger Bestandteil des Strukturmaterials und der Divertor-Flächen der Fusionsreaktoren ist Wolfram. Diese Dissertation behandelt die Messungen der Neutronspektren und ?fluenz in einer Wolfram-Anordnung mittels der Multifolien-Neutronenaktivierungstechnik. Um die anzuwendenden experimentellen Geräte und die Codes, die im Wolfram-Benchmark-Experiment eingesetzt werden, zu überprüfen und zu bestimmen, wurden Testmessungen in den D-T und D-D Neutronenfeldern des Neutronengenerator der Technischen Universität Dresden durchgeführt. Die Eigenschaften der D-T und D-D Reaktionen, die für die Erzeugung von monoenergetischen Neutronen verwendet werden, sowie die Auswahl der Aktivierungsreaktionen, die für Fusionsanwendungen geeignet sind und die Aktivierungsmessung werden detailliert vorgestellt. Korrekturen, die sich auf den Neutronen-Bestrahlungsprozess und auf den Probenzählungsprozess beziehen, werden ebenfalls besprochen. Die Neutronenfluenz und ihre Energieverteilung in einem Wolfram-Benchmark, bestrahlt am Frascati Neutronen Generator mit 14 MeV-Neutronen aus der T(d, n)4He Reaktion, werden aus den Messungen der γ-Strahlenaktivität, die von Neutronen in den Folien induziert ist, durch den STAYNL Entfaltungscode, der auf der Methode der kleinsten Fehlerquadrate basiert, zusammen mit der IRDF-90.2 Wirkungsquerschnitt-Bibliothek abgeleitet. Die Unterschiede zwischen den Neutronenflußspektren, die mit Hilfe der Multifolien-Neutronenaktivierung ermittelt wurden, und den Neutronenflußspektren, gemessen im selben Aufbau mit einem NE-213 Flüssigszintillator, wurden untersucht. Die gemessenen Neutronenspektren werden den aus MCNP-4B Rechnungen (Monte Carlo neutron and photon transport) ermittelten Spektren gegenüber gestellt. Der Vergleich stellt einen wichtigen Test der evaluierten Kerndaten für Fusionsreaktorkonzepte dar. Zusammenfassend zeigt diese Arbeit die Anwendbarkeit der Multifolien-Neutronenaktivierungstechnik bei Messungen der Neutronenflussspektren innerhalb eines massiven Wolframblocks bei Bestrahlung mit schnellen Neutronen aus D-T Generatoren.

Das Institut für Kern- und Teilchenphysik (IKTP) der Technischen Universität Dresden (TUD) hat im Forschungszentrum Dresden-Rossendorf (FZD) ein Labor zur Untersuchung von neutroneninduzierten kernphysikalischen Prozessen in Materialien, die für die Fusionsforschung relevant sind, aufgebaut. Das Labor ist ausgestattet mit drei intensiven Neutronenquellen: einer 14 MeV-Neutronenquelle, einer weißen kontinuierlichen Photoneutronen-Quelle, die näher in dieser Arbeit beschrieben wird, und einer gepulsten Photoneutronen-Quelle, die vom FZD inKooperation mit der TUD aufgebaut wurde. Die kontinuierliche Photoneutronen-Quelle basiert auf einem Radiator aus Wolfram (engl. Tungsten Photoneutron Source (TPNS)). TPNS nutzt die im ELBE-Beschleuniger (Elektronen Linearbeschleuniger für Strahlen hoher Brillianz und niedriger Emittanz (ELBE)) beschleunigten Elektronen zur Neutronenerzeugung. Der Prozess läuft über Zwischenschritte ab, indem bei der Abbremsung der Elektronen im Radiator Bremsstrahlungsphotonen entstehen, die anschließend Neutronen durch (γ,xn)-Reaktionen erzeugen. Das Neutronenspektrum der TPNS kann mittels Moderatoren so modifiziert werden, dass es dem in der ersten Wand im Fusionsreaktor entspricht. Dies ermöglicht Untersuchungen mit einem für einen Fusionsreaktor typischen Neutronenspektrum. Die technische Verwirklichung des Projektes, die Inbetriebnahme der Anlage sowie die Durchführung der ersten Experimente zur Neutronenerzeugung ist Inhalt dieser Arbeit. Die Neutronenquelle ist insbesondere für qualitative Untersuchungen in der Fusionsneutronik bestimmt. Der Fusionsreaktor produziert, im Vergleich zu einem Spaltungsreaktor, keine langlebigen Isotope als Abfall. Die wesentliche Aktivität des Reaktors ist in Konstruktionsmaterialien akkumuliert. Durch sorgfältige Auswahl der Materialien kann man die Aktivierung minimieren und damit künftig wesentlich weniger radioaktives Inventar produzieren als in Spaltreaktoren. Ziel der kernphysikalischen Untersuchungen ist, solche Materialien für den Aufbau eines Fusionsreaktors zu erforschen, die niedrigaktivierbar sind, das heißt wenig Aktivität akkumulieren können, und eine Halbwertzeit von einigen Jahren haben. Es ist das Ziel, alle Konstruktionsmaterialien nach 100 Jahren wiederverwenden zu können. Die Neutronenflussdichte einer Photoneutronenquelle ist einige Größenordnungen höher als die, die mittels eines DT-Neutronengenerators mit anschließender Moderation erreicht werden kann. Die gesamte Arbeit ist in drei Teile geteilt. Der erste Teil leitet in die Problematik der Energieversorgung ein und zeigt die Kernfusion als eine vielversprechende Energiequelle der naher Zukunft auf. Das Neutronenlabor der TUD, in dem die TPNS aufgebaut ist, wird ebenfalls kurz vorgestellt. Der zweite Teil befasst sich mit der TPNS selbst, mit ihrem physikalischen Entwurf, der Konstruktion und dem Aufbau bis zu der Inbetriebnahme sowie dem ersten Experiment an der TPNS. Der letzte, dritte Teil ist die Zusammenfassung der vorhandenen Ergebnisse und gibt einen Ausblick auf die zukünftige Vorhaben. / The Institute for Nuclear and Particle Physics at the Technische Universität Dresden (TUD) has build a neutron physics laboratory at Forschungszentrum Dresden-Rossendorf (FZD) to investigate nuclear processes in materials. The experiments are focused on materials relevant to nuclear fusion. The laboratory is equipped with three intensive neutron sources. The first is a 14 MeV monochromatic neutron source based on the DT reaction (owned by TUD); the other two are continuous and pulsed white photoneutron sources based on (γ,xn) reactions. One pulsed photoneutron source is realized by FZD in cooperation with the TUD. The continuous photoneutron source utilises a tungsten radiator (Tungsten Photoneutron Source) to produce neutrons with a wide energy spectra. The TPNS uses the ELBE-accelerator as a source of electrons for neutron production. This process involves an intermediate step, where slowed down electrons produce bremsstrahlung (γ -rays) absorbed by tungsten nuclei. Consecutively, the excited nuclei emit neutrons. The neutron flux of the photoneutron source is five orders of magnitude higher than the flux of the DT neutron sources with appropriate moderation. The neutron spectrum of TPNS can be modified by moderators, in such a way that the spectrum is comparable to that in the first wall of a Tokamak-Reactor. That allows investigations with the typical neutron spectrum of the fusion reactor. The technical solution, initial operation and the first experiment are described in this work. The neutron source is, in particular, dedicated to quantitative investigations in fusion neutronics. A fusion reactor produces radioactive isotopes as a nuclear waste. The main activity is accumulated in the structural materials. Carefully selected structural materials can significantly minimize the activity and thereby the amount of nuclear waste. The purpose of this project is to find constructional materials with half-lives shorter than several years, which can be recycled after about 100 years. The work is divided into three parts. The first part is dedicated to the energy supply problem and nuclear fusion is addressed as a promising solution of the near future. The neutron laboratory housing the TPNS is also briefly described. The second part deals with the tungsten photoneutron source, the design, construction, operation and the first experiments for neutron production. The third part summarises results and presents an outlook for future experiments with the TPNS.

Friction stir welding (FSW) of steel is often performed with an insert made of polycrystalline cubic boron nitride (PCBN). Specifically, MS80 is a grade of PCBN made by Smith MegaDiamond that has been optimized for the FSW process. The PCBN insert is attached to a tungsten carbide (WC) shank by a compression fitting. However, FSW tools manufactured by this method inevitably fail by fracture in the PCBN. Permanently bonding PCBN to WC would likely solve the fracturing problem and increase the life of PCBN FSW tools to be economically viable. Partial transient liquid phase (PTLP) bonding, a process used to join ceramics with thin metallic interlayers, was proposed as a method to permanently bond PCBN to WC. PTLP bonding is often performed using three layers of pure elements. On heating, the two thin outer interlayers melt and bond to the ceramics. Concurrently, these liquid layers diffuse into the thicker refractory core until solidification has occurred isothermally. A procedure was developed to reduce the number of possible three-layer PTLP bonding setups to a small set of ideal setups using logical filters. Steps in this filtering method include a database of all existing binary systems, sessile drop testing of 20 elements, and a routine that calculates maximum interlayer thicknesses. Results of sessile drop testing showed that the PCBN grade required for this research could only be bonded with an alloy of Ti, Cu, Mg, and Sb. Two PTLP bond setups were tested using this special coating on the PCBN, but a successful bond could not be achieved. However, a PTLP bond of WC to WC was successful and proved the usefulness of the filtering procedure for determining PTLP bond setups. This filtering procedure is then set forth in generalized terms that can be used to PTLP bond any material. Also, recommendations for future research to bond this grade of PCBN, or some other grade, to WC are presented.

High-performance materials such as stainless steels and nickel based super alloys are widely used in demanding applications where high mechanical and thermal properties are required. The applications of super alloys are mainly found in jet engines, power plants and gas turbines demanding high fatigue strength, corrosion and oxidation resistance as well as wear resistant properties. In order to use them, they go through various machining processes such as milling, turning, cutting, polishing etc. until the final product is achieved. Modern manufacturing industries employs various machining tools and technologies to improve the machining process of heat resistant super alloys. However, there are still challenges which needs to be addressed. Among them, adhesive wear of the machining tools is one of the main wear mechanism during the tribological interaction of tool and workpiece, preventing them to achieve the desired quality and surface finish of the end product. Moreover, it damages the tool reducing its lifecycle and in return, increasing the production cost. Among the cutting tools tungsten carbide (WC/Co) tools coated with TiAlN coating due to their good high temperature performance are extensively used. Nonetheless, these coatings still face issue like adhesive wear, abrasion, oxidation at higher temperature damaging the tools and subsequent machining. Therefore, it is imperative to understand the initiation mechanism of adhesive wear during the tribological interaction of super alloys and coated cutting tool material. In this research work, the tribological response of two coatings deposited by physical vapour deposition (PVD), having the composition Ti60Al40N and Ti40Al60N have been studied against two super alloys material, i.e. Inconel 718 and stainless steel 316L. A high temperature SRV (Schwingung (Oscillating), Reibung (Friction), Verschleiß (Wear)) reciprocation friction and wear test set up was employed to investigate the friction behaviour, wear rate and dominant wear mechanisms.  For Ti60Al40N coating, the experimental results revealed that generally, friction increases in case of sliding against Inconel 718 up to 400 °C and drops at 760 °C. A high wear volume at room temperature and a decrease to a minimum at 760 °C has been observed for Inconel 718. On the other side, Stainless steel 316L (SS 316L) faces a continuous rise in friction coefficient with highest value at 760 °C during sliding against Ti60Al40N coating. Wear is highest at 400 °C for SS 316L pin. The worn surfaces shows that both workpiece materials experience increase in material transfer due to adhesive wear with rise in temperature. At 400 °C, adhesion is the primary wear mechanism for both workpiece materials. A further rise in temperature to 760 °C promotes the adhesive wear through oxides formation on both material surfaces.  Similarly, Ti40Al60N coating shows the same friction behaviour with change in average steady state friction values for both material of Inconel 718 and SS 316L. Both workpiece materials responds in a similar way to wear volume loss, i.e. lowest at room temperature and highest at 760 °C. For Inconel 718, transfer of coating constituents on to the Inconel 718 pin surface was detected and associated with coating rupture and peeling, exacerbating with rise in temperature. Adhesion, abrasion, and oxidation are primary wear mechanisms at 400 °C and 760 °C. For SS 316L, coating transfer only happen at 400 °C. No damage of coating at 40 °C, a complete damage at 400 °C, and formation of dense porous oxides layers at 760 °C have been noticed. At 400 °C, adhesion, abrasion, and chipping while at 760 °C, adhesion, three body abrasion, ploughing and oxidation are the main wear mechanisms.

This thesis aims to investigate the coefficient of friction between steel on steel contacts with the addition of solid lubricants such as h-BN, WS2, MoS2 in powder form, in dry conditions and wet conditions. More specifically, the purpose is to enhance the sliding between the piston rings and cylinder block in a modern high temperature steam engine developed by RANOTOR. The friction test was carried out as a linear sliding test with determined loads and sliding speed. Hertzian contact theory was deployed to calculate contact pressure and shear stresses to make sure the contact was elastic, alternatively plastic. It was found that WS2 and  MoS2 lowered the coefficient of friction quite heavily in dry conditions, acting as a thin protective-lubricating film. h-BN performed rather poorly, increasing the coefficient of friction. In a water slurry, none of the powders managed to decrease the COF due to the particles not interacting with the surfaces.The solid lubricants tested should be further tested as coatings since they acted like it in dry conditions. / Denna rapport syftar till att undersöka friktionskoefficienten i stålkontakter med tillsats av fasta smörjmedel som  h-BN, WS2, MoS2 i pulverform, under torra och våta förhållanden. Mer specifikt är syftet att förbättra glidningen mellan kolvringarna och insidan av cylindern i en modern högtemperatur-ångmotor utvecklad av RANOTOR. Friktionstestet genomfördes som ett linjärt glidtest med bestämda belastningar och glidhastighet. Hertzian-kontaktteorin användes för att beräkna kontakttryck och skjuvspänningar för att säkerställa att kontakten var elastisk alternativt plastisk. Det visade sig att WS2och MoS2 kraftigt sänkte friktionskoefficienten under torra förhållanden genom att agera som en tunn skyddande-smörjfilm. h-BN presterade dåligt och ökade friktionskoefficienten. I vattenblandning lyckades inget av pulverna minska friktionskoefficienten eftersom partiklarna inte interagerade med ytorna. De testade fasta smörjmedlen bör vidare testas som beläggningar eftersom de fungerade som dessa under torra förhållanden.

This thesis describes the design, manufacture and characterisation of thick vacuum plasma sprayed tungsten (W) coatings on steel substrates. Fusion is a potentially clean, sustainable, energy source in which nuclear energy is generated via the release of internal energy from nuclei. In order to fuse nuclei the Coulomb barrier must be breached - requiring extreme temperatures or pressures – akin to creating a ‘star in a box’. Tungsten is a promising candidate material for future fusion reactors due to a high sputtering threshold and melting temperature. However, the large coefficient of thermal expansion mismatch with reactor structural steels such as the low activation steel Eurofer’97 is a major manufacturing and in-service problem. A vacuum plasma spraying approach for the manufacture of tungsten and tungsten/steel graded coatings has been developed successfully. The use of graded coatings and highly textured 3D interface surfi-sculpt substrates has been investigated to allow the deposition of thick plasma sprayed tungsten coatings on steel substrates. Finite element models have been developed to understand the residual stresses that develop in W/steel systems and made use of experimental measurements of coating thermal history during manufacture and elastic moduli measured by nano-indentation. For both the graded and surfi-sculpt coating, the models have been used to understand the mechanism of residual stress redistribution and relief in comparison with simple W on steel coatings, particularly by consideration of stored strain energy. In the case of surfi-sculpt W coatings, the patterned substrate gave rise to regular stress concentrating features, and allowed 2mm thick W coatings to be produced reproducibly without delamination. Preliminary through thickness residual stress measurements were compared to model predictions and provided tentative evidence of significant W coating stress relief by regulated coating segmentation.

Additive Manufacturing (AM) is an innovative manufacturing process which offers near-net shape fabrication of complex components, directly from CAD models, without dies or substantial machining, resulting in a reduction in lead-time, waste, and cost. For example, the buy-to-fly ratio for a titanium component machined from forged billet is typically 10-20:1 compared to 5-7:1 when manufactured by AM. However, the production rates for most AM processes are relatively slow and AM is consequently largely of interest to the aerospace, automotive and biomedical industries. In addition, the solidification conditions in AM with the Ti alloy commonly lead to undesirable coarse columnar primary β grain structures in components. The present research is focused on developing a fundamental understanding of the influence of the processing conditions on microstructure and texture evolution and their resulting effect on the mechanical properties during additive manufacturing with a Ti6Al4V alloy, using three different techniques, namely; 1) Selective laser melting (SLM) process, 2) Electron beam selective melting (EBSM) process and, 3) Wire arc additive manufacturing (WAAM) process. The most important finding in this work was that all the AM processes produced columnar β-grain structures which grow by epitaxial re-growth up through each melted layer. By thermal modelling using TS4D (Thermal Simulation in 4 Dimensions), it has been shown that the melt pool size increased and the cooling rate decreased from SLM to EBSM and to the WAAM process. The prior β grain size also increased with melt pool size from a finer size in the SLM to a moderate size in EBSM and to huge grains in WAAM that can be seen by eye. However, despite the large difference in power density between the processes, they all had similar G/R (thermal gradient/growth rate) ratios, which were predicted to lie in the columnar growth region in the solidification diagram. The EBSM process showed a pronounced local heterogeneity in the microstructure in local transition areas, when there was a change in geometry; for e.g. change in wall thickness, thin to thick capping section, cross-over’s, V-transitions, etc. By reconstruction of the high temperature β microstructure, it has been shown that all the AM platforms showed primary columnar β grains with a <001>β.

The goal of this diploma’s thesis is to inform about present development of light sources, new technologies and about achieved parameters of these light sources. The thesis is mainly directed to describe efficiency of transformation electric energy to light at single types of light sources. There are described the concrete technical parameters of sources quoted by manufacturers and the contructional solution of single types of light sources. There is created a graphic comparation of electrotechnical and light parameters of the light sources.