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Pavel Vladimirovich Pokrovskiy was a prominent scientist in the field of mineralogy, geochemistry and ore geology, as well as a specialist in tungsten and gold deposits. He was a talented organizer science and educated 17 candidates of geological and mineralogical sciences.

Pavel Vladimirovich Pokrovskiy was a prominent scientist in the field of mineralogy, geochemistry and ore geology, as well as a specialist in tungsten and gold deposits. He was a talented organizer science and educated 17 candidates of geological and mineralogical sciences

Es konnte in dieser Arbeit gezeigt werden, dass die Wahl der Kationen durchaus Einfluss auf die photophysikalischen Eigenschaften von [W6I14]2--Clustern hat. So lassen sich nicht nur die Lage der maximalen Emission (Kation = Li–Cs), sondern auch die Quantenausbeute (Kation = PPN) und Löslichkeit der Verbindungen beeinflussen (Kation = Li, wasserlöslich). Kationen können, sollten sie geeignete Energieniveaus besitzen, eine bedeutende Rolle für die photophyikalischen Eigenschaften in Bezug auf Energie- oder Elektronentransfer von angeregten Clusterzuständen auf Kationenzustände spielen. Neben diesem Übertrag auf z. B. lumineszente Ionen (Yb3+, Nd3+) könnte unter diesen Gesichtspunkt auch ein Energie- oder Elektronentransfer vom Cluster auf redoxaktive Metalle wie Fe, Mn, etc. möglich sein, um hiermit molekulare Solarzellen zu synthetisieren (z. B. Fe3+ ↔ Fe2+). Die Metallionen könnten hierbei mit Kryptaten, DOTA-Komplexen oder Porphyrinderivaten (Häme) stabilisiert werden. Für einen effektiveren Energie- oder Elektronentransfer gäbe es die Möglichkeit nicht nur salzartige Verbindungen in Betracht zu ziehen, sondern kovalente Bindungen zwischen dem anionischen Cluster und einem stabilisierten Kation. Bei Verbindungen mit geeigneten Energieniveaus ist auch ein Energietransfer von (komplexen) Kation auf Cluster möglich, um die photophysikalischen Eigenschaften zu steuern.

The relevance of the work is conditioned by the need for a more complete study of the mineralogy of rare-metal granite pegmatites of the Lipovskoye vein field. The purpose of the study is to describe the findings of native metals (gold, silver, copper, lead, bismuth and tungsten) in granite pegmatites of the Lipovskoye vein field. Research methodology. Detailed study of chemical composition, morphology and relationships of native metals with associated minerals. For this study we have chosen samples from the three types of granitic pegmatites – classical quartz-feldspar (mostly intragranitic), desilicated (apogranite plagioclasite) and contaminated lithium-bearing. Results. The paper describes native metals (gold, silver, copper, lead, bismuth and tungsten), which we have found in rare-metal pegmatites of the Lipovskoye vein field. The discovery of the native metals is the first on this facility. The microprobe analysis of such native metals as gold and silver showed the variability of their chemical composition from the type of pegmatite in which they are present. The formation of native lead should be logically linked to the destruction and recrystallization of high uranium thin rims of zircons. The formation of bismuth and tungsten may have occurred during recrystallization of accessory tantalumniobates. Summary. The finding of the native metals in granitic pegmatites is quite explainable. This is because these core rocks are formed in the post-magmatic stage of the silicate crystallization intrusions and they can contain typomorphic rocks for these metals. The absence of mineral concentrators (sulfides) in pegmatites clearly explains the small size and high dispersion of metals.

Damage-tolerant ceramic matrix composites (CMC) are prone to high temperature applications under severe environmental conditions and usually utilize carbon or ceramic fibres (e.g. SiC) as reinforcements of ceramic matrices with inherent low elongation to break compared to common metals. However, CMC reveal an elongation to break and stiffness similar to the ceramic matrices, and thus need a fibre coating in order to improve the elongation to break length and thus to achieve damage tolerance of the composite. In addition, such fibers often expose a low ductility during failure. As a consequence, design criteria for components of such CMC materials are limited by the low strain of failure. In order to overcome this problem, we follow the idea of a reinforcement concept of a ceramic matrix reinforced by refractory metal fibres to reach pseudo ductile behaviour during failure. Tungsten (W) and molybdenum (Mo) fibers were chosen as reinforcement in SiCN CMC manufactured by polymer infiltration and pyrolysis process. These fibres are commercially available since they are widespread used in light bulbs, etc. , and possess an intrinsic higher elongation to break, compared to ceramic fibres, as well as high stiffness even at high temperatures. W/SiCN and Mo/SiCN composites were manufactured via filament winding and resin transfer moulding of commercially available polysilazanes, pyrolysed and re-densified by multiple reinfiltration and pyrolysis steps. These composites were investigated with respect to microstructure, flexural and tensile strength. Single fibre strengths for W and Mo were investigated and compared to the strength of the composites. Tensile strengths of 206 and 156 MPa as well as bending strengths of 427 and 312 MPa were achieved for W/SiCN and Mo/SiCN composites, respectively. W fibre became brittle across the entire cross section, while the Mo fibre showed a superficial, brittle reaction zone but kept ductile on the inside.

Die Herstellung zunehmend feinerer WC-Pulver als Ausgangsprodukt f��r leistungsf��higere Hartmetalle ist von gro��em technischem Interesse. Da die erzielbare Feinheit der WC-Pulver bei herk��mmlichen industriellen Prozessen limitiert ist, wird versucht mit alternativen Prozessen WC-Pulver mit Korngr����en im nm-Bereich zu produzieren. Zuerst wurde die Herstellung durch einen Gasphasenprozess untersucht. Dabei wurde durch ��berleiten von feuchtem Ar ��ber WO3 bei Temperaturen um 1100 C gasf��rmiges WO2(OH)2 erzeugt und dieses danach mit einer CH4/H2-Mischung carburiert. Die Auswirkung der Temperatur, Feuchte, Dauer, sowie verschiedener Gasfl��sse auf die Pulverzusammensetzung und die Ausbeute wurden untersucht. Durch den Prozess konnte ein WC-Pulver mit Kristallitgr����en von 3 - 10 nm produziert werden. Den Gro��teil des Pulvers bildete kubisches WC1-x, welches durch die kleinen Kristallitgr����en stabilisiert wurde. Anhand der TEM- und RAMAN-Messungen konnte eine d��nne C-Schicht an der Oberfl��che der Pulver nachgewiesen werden. H��here Temperaturen und ein ausgeglichenes Verh��ltnis zwischen den Transportparametern (Ar und Feuchte) gegen��ber den Carburierungs-parametern (H2 und CH4) f��hrten zu einer Verbesserung der Ausbeute auf bis zu 50 % und einem Carbidanteil bis zu 95 %. Der Prozess bietet die M��glichkeit WC-Pulver mit Kristallitgr����en im einstelligen nm-Bereich herzustellen. Aufgrund des geringen Durchsatzes erscheint ein Einsatz im Hartmetallbereich aber unrealistisch. Anwendungen in der Katalyse sollen, aufgrund der geringen Korngr����en, gepr��ft werden. Alternativ wurden verschieden konzentrierte Ammoniummetawolframat (AMT)-L��sungen in fl��ssigen Stickstoff eingespr��ht und gefriergetrocknet. Die erhaltenen AMT-Pulver wurden kalziniert und mittels CH4/H2-Mischungen zu WC umgesetzt. Die durch diesen Prozess produzierten Pulver wiesen je nach Herstellungsart WC-Korngr����en von 50 100 nm auf. Zus��tzlich konnten durch den Zusatz von Cobaltacetat in der AMT-L��sung -Carbide, welche als Ausgangsstoff f��r plattenf��rmiges WC-Co-Hartmetall dienen, hergestellt werden, wobei Korngr����en von 70 400 nm erreicht wurden. Die problematische Abscheidung von freiem Kohlenstoff durch Methanzersetzung, welche vor allem bei den Pulvern mit Cobalt-Zusatz auftrat, konnte durch Temperaturbehandlung bei 1000 C in einer H2-Atmosph��re unter Inkaufnahme von Kornvergr��berungen und Abnahme des -Carbidanteils korrigiert werden. Die hergestellten Pulver k��nnten f��r Hartmetallanwendungen genutzt werden. Der Prozess bietet zus��tzlich die M��glichkeit der Beimischung von Cobalt zu den Ausgangsl��sungen zur Herstellung von -Carbiden., The production of nano-sized WC powders is of high technical interest to increase the properties, such as hardness, of high performance hardmetals, by using smaller grain sizes. Due to the limitation of established industrial processes to achieve grain sizes in the nanometer range, alternative processes for the production of nano-sized WC powders have to be developed. At first, the production of nano-sized WC powders via the chemical vapour transportation (CVT) reaction of WO3 with H2O, generating gaseous WO2(OH)2 at elevated temperatures with a subsequent carburation using CH4/H2-gas mixtures was studied. Therefore, humid Ar-gas was passed over WO3 powder to generate WO2(OH)2 at about 1100 C. The generated hydroxide was brought into contact with a mixture of CH4 and H2 and reacted, forming nano-sized WC powder. The influence of the process parameters such as furnace temperature, humidity and gas flow variations on the product was studied. Using this process, WC powders with grain sizes of 3 10 nm were obtained. The main phase was a cubic WC1-x phase, a high temperature modification of WC, which was stabilized by the low grain sizes. Additionally, thin amorphous carbon layers were observed, covering the carbide, which was verified by TEM and RAMAN spectroscopy. Higher temperatures and balancing the transport parameters (humidity and Ar-gas flow) with the parameters inducing the carburation (H2- and CH4-gas flow) results in an improvement of the process yield up to 50 % and an increase of carbide phases up to 95 %. The process provides a new approach to produce WC powders with grain sizes in the single-digit nanometer range. Due to the low conversion rate applications in hardmetal tools are unrealistic. However, an application in catalysis could be considered, owing to the small grain sizes. Alternatively, ammonium metatungstate (AMT)-solutions with various concentrations were sprayed into liquid nitrogen and subsequently freeze-dried. The obtained AMT powders were calcined and carburized using a CH4/H2-gas mixture. The crystallite sizes of the produced WC powders were in the range of 50 100 nm depending on the manufacturing method. The addition of cobalt acetate to the AMT solution resulted in the formation of -carbides, which are used to produce WC platelets in hardmetals. However, the addition of cobalt led to an increase of the grain size up to 70 400 nm. The deposition of free carbon due to the dissociation of methane, which was especially occurring during the carburation of the powders with addition of cobalt, could be corrected with a heat treatment at 1000 C in a hydrogen atmosphere under the acceptance of the reduction of the -carbide amount and further grain growth. The produced WC powders could be used for hardmetal applications. Due to the addition of cobalt and the ensuing formation of -carbides, the production of WC-platelet-enhanced hardmetal is possible.

In dieser Arbeit wurde die Herstellung von Wolfram- und Molybd��nmetallpulvern untersucht. Die Wolframherstellung hatte als Ziel zum einen sehr grobes und zum anderen sehr feines Wolframpulver zu produzieren. Industriell wird ohne Zugabe von Dotiersubstanzen eine Korngr����enbreite von rund 0,1 bis 10 ��m abgedeckt. Im Falle des groben Wolframpulvers wurde das Edukt Gelboxid (WO3) in einem Rohrofen bei unterschiedlichen Ofentemperaturen und Sch��tth��hen mit Wasserstoff bei hohen Feuchtegraden reduziert. Die Produkte wurden im REM analyisert und die Korngr����enverteilung durch eine Partikelgr����enmessung bestimmt. Es wurden Korngr����en bis zu 30 ��m erreicht. Im Falle des feinen Wolframpulvers wurde ein Ofen gebaut, der aus einem Quarzrohr gr����eren Durchmessers und einem sich darin befindenden k��rzeren Quarzrohr kleineren Durchmessers bestand, wobei Gelboxid in zwei kleinen Quarzschiffchen im inneren Quarzrohr vorgelegt wurde. Durch unabh��ngige Gaszuleitungen wurde feuchtes Argon bei Temperaturen ab 1000��C ��ber das WO3 geleitet, welches in Form des gasf��rmigen WO2(OH)2 durch eine D��se am Ende des kleinen Rohrs in das gr����ere Rohr str��mte, welches wiederum mit Wasserstoff gesp��lt wurde, wodurch das WO2(OH)2 schlie��lich zu Wolfram reduziert werden sollte. Es wurden die Auswirkungen der Variation verschiedener Parameter wie Ofentemperatur, Gasdurchflussraten u.a. untersucht. Das Produkt schied sich an der Quarzrohrwand ab und wurde anschlie��end mittels XRD und Feldemissions-Rasterelektronenmikroskopie analysiert. Es wurden K��rner unter 100 nm erhalten und eine Kristallitgr����e von rund 50 nm bestimmt. Im Rahmen der Herstellung des Molybd��npulvers wurde MoO3 in zwei Schritten mit Wasserstoff zu metallischem Molybd��n reduziert. Dabei wurde der Einfluss der Ofentemperatur auf die Reduktion untersucht. Die Produkte wurden im REM analyisert. Das Ergebnis waren K��rner zwischen ca. 1 und 2 ��m.

Der anaerobe Abbau von Phenylalanin führt über das Zwischenprodukt Phenylacetat zu Benzoyl-CoA, dem häufigsten Intermediat im anaeroben Abbau von aromatischen Verbindungen. Das Zwischenprodukt Phenylacetat entsteht durch die Oxidation von Phenylacetaldehyd. Vor Beginn dieser Arbeit war bekannt, dass Aromatoleum aromaticum sowohl eine Aldehyd:Ferredoxin-Oxidoreduktase (AOR) besitzt, die den Schritt katalysieren könnte, als auch ein oder mehrere Enzyme, die diese Oxidation mit NAD und NADP als Elektronenakzeptoren durchführen könnten. Folglich stellte sich die Frage, welches dieser Enzyme das Schlüsselenzym für den anaeroben Phenylalanin-Stoffwechsel darstellt. Außerdem ist die Entdeckung einer AOR in einem fakultativ anaeroben Bakterium ungewöhnlich, da AORs bisher ausschließlich aus obligat anaeroben, häufig hyperthermophilen Prokaryonten bekannt sind. A. aromaticum braucht ein Molybdän-Enzym zum denitrifizierenden Wachstum, nämlich die Nitrat-Reduktase. Alle bisher beschriebenen AORs enthalten das dem Molybdän sehr ähnliche Metall Wolfram. Vor diesem Hintergrund sollte untersucht werden, welches Metall die AOR aus A. aromaticum enthält. Für beide Fragestellungen war es wichtig, die Phenylacetaldehyd-oxidierenden Enzyme aus A. aromaticum-Zellen anzureichern und im Idealfall aufzureinigen. Durch vielfältige chromatographische Verfahren gelang es, alle Enzymaktivitäten in einem für die Bearbeitung der Fragestellungen ausreichenden Maße anzureichern. Metallanalysen der angereicherten AOR-Fraktionen und begleitende Wachstumsversuche mit verschiedenen Molybdat- und Wolframat-Konzentrationen zeigten, dass die AOR tatsächlich einen Wolfram-Cofaktor enthält und dieser nicht wirksam durch einen Molybdän-Cofaktor ersetzt werden kann. Folglich muss A. aromaticum zur selben Zeit spezifisch mindestens ein Mo- (Nitrat-Reduktase) und ein W-Enzym (AOR) herstellen können. Während die meisten Enzyme aus dem Molybdän-Cofaktor-Biosyntheseweg auch zur Biosynthese des Wolfram-Cofaktors dienen können, wurden in dieser Arbeit durch bioinformatische Analysen mehrere Enzyme gefunden, die eine Metall-Spezifität unterstützen könnten. Dazu gehören Molybdat- und Wolframat-spezifische Transporter und Enzyme, die das Metall auf den Cofaktor übertragen. Außerdem wurden Proteine aus dem Cofaktor-Biosyntheseweg gefunden, die in enger Assoziation mit AORs codiert werden und möglicherweise auch bei der Bereitstellung des richtigen Cofaktors eine Rolle spielen. Durch Anreicherung der NAD(P)-abhängigen Phenylacetaldehyd-oxidierenden Aktivitäten konnte das zugehörige Enzym, eine Aldehyd-Dehydrogenase, die durch das Gen ebA4954 codiert wird, identifiziert werden. Die Phenylacetaldehyd-Dehydrogenase (PDH) wurde heterolog produziert, mithilfe eines C-terminalen Strep-Tags aufgereinigt und biochemisch charakterisiert. Es handelt sich um ein Homotetramer, das sehr spezifisch für Phenylacetaldehyd ist, eine kooperative Kinetik zu diesem Substrat zeigt, stark durch steigende Phenylacetaldehyd-Konzentrationen inhibiert wird und sowohl NAD als auch NADP reduzieren kann. Die Ergebnisse dieser Arbeit führen zu der neuen Hypothese, dass die PDH das Schlüsselenzym für den Phenylalanin-Stoffwechsel ist. Es wurde gezeigt, dass die AOR nicht essentiell für das denitrifizierende Wachstum auf Phenylalanin ist, aber verschiedenste Aldehyde mit ähnlichen Reaktionsgeschwindigkeiten oxidieren kann. Deshalb ist es vorstellbar, dass der AOR eine Funktion zur Detoxifizierung reaktiver Aldehyde zukommt, wenn der Stoffwechsel aus dem Gleichgewicht gerät. Die Erkenntnis, dass A. aromaticum gleichzeitig Molybdän- und Wolfram-Enzyme produzieren kann, eröffnet viele neue Fragestellungen und Forschungsansätze.

Tungsten and tungsten-alloys are presently considered to be the most promising materials for plasma facing components for future fusion power plants. The Karlsruhe Institute of Technology (KIT) divertor design concept for the future DEMO power plant is based on modular He-cooled finger units and the development of suitable mass production methods for such parts was needed. A time and cost effective near-net-shape forming process with the advantage of shape complexity, material utilization and high final density is Powder Injection Molding (PIM). This process allows also the joining of two different materials e.g. tungsten with a doped tungsten alloy, without brazing. The complete technological process of 2-Component powder injection molding for tungsten materials and its application on producing real DEMO divertor parts, characterization results of the finished parts e.g. microstructure, hardness, density and joining zone quality are discussed in this contribution.

Im ersten Teil der Arbeit wurden die Komplexe [FeCp(CO)(K2(C,P)-(C=O)-NiPr-PPh2)], [FeCp(CO)(K2(C,P)-(C=O)-NtBu-PPh2)] und [FeCp(CO)(K2(C,P)-(C=O)-NCy-PiPr2)] mit den Amidophosphin Liganden Li[R2PNR'] (R = Ph, iPr, R' = iPr, tBu, Cy) hergestellt. Diese Komplexe besitzten einen viergliedrigen Carboxyamido-phosphazyklus, welche durch einen nucleophilen Angriff von Stickstoff auf den Kohlenstoff der Carbonylgruppe entsteht. Wenn diese Komplexe mit dem Elektrophil [Me3O]BF4 umgesetzt werden, entsteht ein Aza-phospha-carbenkomplex vom Typ [FeCp(CO)(K2(C,P)=C(OMe)-NiPr-PPh2)]+. Durch Umsetzung der Komplexe cis,trans,cis-[Fe(CO)2(Ph2PNHiPr)2(Br)2] und cis,trans,cis-[Fe(CO)2(Ph2PNHtBu)2 (Br)2] mit KOtBu entstehen ebenfalls Verbindungen mit einem viergliedrigen Carboxyamido-phosphazyklus, wie zum Beispiel trans-[Fe(CO)2(K2(C,P)-(C=O)-NiPr-PPh2)(Ph2PNHiPr)Br] und trans-[Fe(CO)2(K2(C,P)-(C=O)-NtBu-PPh2) (Ph2PNHtBu)Br]. Im zweiten Teil der Arbeit wurden die oktaedrischen Mo(0) und W(0) Komplexe [M(PNP)(CO)3], sowie die oktaedrischen neutralen und siebenfach-koordinierten kationischen Mo(II) und W(II) Komplexe [M(PNP)(CO)X2], [M(PNP)(CO)3Br]+, [M(PNP)(CO)3H]+ mit dreiz��hnigen PNP Pincer Liganden hergestellt (X = Br, I und Cl). Die Synthese von Mo(0) Komplexen erfolgte durch Umsetzung von [Mo(CO)3(CH3CN)3] mit PNP Liganden. Die W(0) Komplexe wurden durch die Reduktion von den Komplexen [W(PNP)(CO)3Br]+ mit NaHg hergestellt, welche durch Umsetzung vom zweikernigen Komplex [W(CO)4(��Br)Br]2 mit den PNP Liganden hergestellt wurden. Die Synthese von den Hydridocarbonylkomplexen erfolgte durch Umsetzung von den Mo(0) und W(0) Komplexen mit HBF4. Diese Komplexe sind in der L��sung dynamisch und k��nnen mit Basen, z.B. NEt3, vollst��ndig zu [M(PNP)(CO)3] deprotoniert werden. Wenn die Mo(0) Komplexe mit Halogenen in Anwesenheit des Sauerstoffs umgesetzt werden, entstehen kationische Monooxo-Molybd��nkomplexe vom Typ [Mo(PNP)(O)X]+. Diese Reaktion verl��uft ��ber mono CO Komplexe [M(PNP)(CO)X2]., In first part of this study the complexes [FeCp(CO)(K2(C,P)-(C=O)-NiPr-PPh2)], [FeCp(CO)(K2(C,P)-(C=O)-NtBu-PPh2)] and [FeCp(CO)(K2(C,P)-(C=O)-NCy-PiPr2)] were produced with adding 1 equiv of the amidophosphine ligands Li[R2PNR'] (R = Ph, iPr, R' = iPr, tBu, Cy) to [FeCp(CO)2Cl]. Complex [FeCp(CO)(K2(C,P)-(C=O)-NiPr-PPh2)] was also formed when [FeCp(PPh2NHiPr)(CO)2]+ was reacted with 1 equiv of KOtBu. These complexes feature an unusual four-membered carboxamido-phospha-ferracycle as a result of an intramolecular nucleophilic attack of the amidophosphine ligand on coordinated CO. Upon treatment of [FeCp(CO)(K2(C,P)-(C=O)-NiPr-PPh2)] with the electrophile [Me3O]BF4 the aminocarbene complex [FeCp(CO)(K2(C,P)=C(OMe)-NiPr-PPh2)]+ was obtained bearing an aza-phospha-carbene moiety. Upon treatment of cis,trans,cis-[Fe(Ph2PNHiPr)2(CO)2(Br)2] and cis,trans,cis-[Fe(Ph2PNHtBu)2(CO)2(Br)2] with KOtBu the carboxamido-phospha-ferracycles trans-[Fe(Ph2PNHiPr)(CO)2(K2(C,P)-(C=O)-NiPr-PPh2)Br] and trans-[Fe(Ph2PNHtBu)(CO)2(K2(C,P)-(C=O)-NtBu-PPh2)Br] were formed. In the second part a series of Mo(0) and W(0) complexes [M(PNP)(CO)3] as well as seven coordinate cationic hydridocarbonyl and halocarbonyl Mo(II) and W(II) complexes of the type [M(PNP)(CO)3H]+ and [M(PNP)(CO)3X]+ and octahedral neutral [Mo(PNP)(CO)X2] featuring PNP pincer ligands were prepared. The synthesis of Mo(0) complexes [Mo(PNP)(CO)3] was accomplished by treatment of [Mo(CO)3(CH3CN)3] with the respective PNP ligands. The analogous W(0) complexes were prepared by reduction of the bromocarbonyl complexes [W(PNP)(CO)3Br]+ with NaHg. These intermediates were obtained from the known dinuclear complex [W(CO)4(��Br)Br]2, prepared in situ from W(CO)6 and stoichiometric amounts of Br2. Addition of HBF4 to [M(PNP)(CO)3] resulted in clean protonation at the molybdenum and tungsten centers to generate cationic Mo(II) and W(II) hydride complexes [M(PNP)(CO)3H]+. The protonation is fully reversible and upon addition of NEt3 as base the Mo(0) and W(0) complexes [M(PNP)(CO)3] are regenerated quantitatively. All heptacoordinate complexes exhibit fluxional behavior in solution. Treatment of Mo(0) complexes with halogens in the presence of oxygen afforded cationic monooxo complexes of the type [Mo(PNP)(O)X]+. This reaction proceeds via the Mo(II) intermediates [Mo(PNP)(CO)X2].

In this work, three current topics were handled in the areas of metalorganic chemistry of the elements bismuth and antimony.The first area involves the synthesis and complete characterization of triorganostibines, -bismuthines and organoantimonyhalogenides and the reactivity studies of these compounds with a view to their behaviour as ligands in carbonylcomplexes of transition metalls.The second topic, the Antimonychalcogenides, is about the synthesis and characterization of Bis(diorganoantimony)chalcogenides with tungsten- and chromiumcarbonylcomplexes, on the other hand was to examine whether these compounds act as one arm or two arm ligands.The third area includes the study of the synthesis and structure characteristics of some hypervalent organobismuthalogenides and their derivatives. As organic substituent was 2-(Dimethylaminomethyl)phenyl used , which is capable of intramolecular coordination via the nitrogen atom.

Primary and secondary hypervascularized liver tumors may be treated with transarterial chemoembolization (TACE). The purpose of this study was to experimentally quantify the effect of different chemoembolization materials on the PET activity concentration in PET/CT.Different concentrations of lipiodol, tungsten, tantalum, and a different number of platinum coils embedded in a carrier substance were placed in a liver phantom. An insert filled with only the carrier substance served as the negative control. The liver phantom was placed in a body phantom. The liver phantom was filled with 63.3 KBq [18-F]-Fluor-2-deoxy-D-glucose (FDG)/ml water, the body phantom was filled with 19.7 KBq FDG/ml water. PET/CT was performed and PET attenuation correction was performed based on the CT data. We defined: Activity concentration over embolization material (kBq/ml) approximately measured activity concentration; activity concentration over negative control (kBq/ml) approximately real activity concentration. An overestimation of the activity concentration was quantified by the following ratio: Activity concentration overestimation = activity concentration over embolization material (kBq/ml)/activity concentration over negative control (kBq/ml).All chemoembolization materials led to an overestimation of the PET activity concentration when using CT information for PET attenuation correction. The extent of overestimation is dependent on the concentration and the density of the chemoembolizing agent. PET activity overestimation was 11-151% with lipiodol, 34-1827% with tungsten, 16-1205% with tantalum, and 4-29% with platinum coils.Conventional chemoembolization materials cause an overestimation of the PET activity concentration in CT-based attenuation-corrected PET/CT images. This is of importance for the clinical routine since activity concentration quantification may not be used in the presence of chemoembolizing agents for imaging follow-up. If an increased FDG uptake is detected after transarterial chemoembolization, non-attenuation-corrected PET images must be assessed in addition to the attenuation-corrected images in order to differentiate artificially increased tracer uptake from a true increase in activity concentration of the tracer. The use of non-attenuating chemoembolizing materials (e.g. drug-eluting beads) for TACE may serve as an alternative to avoid embolization-associated PET artifacts.

Reduction of radiation exposure at an adequate image quality by optimizing the radiation quality for a new system of full-field digital mammography using a digital detector (a-Se).The investigations were performed using a digital mammography system Novation (Siemens, Erlangen). The system was constructed with a bimetal anode (molybdenum and tungsten) and the possibility of changing the filter (molybdenum/rhodium). The test object was the Wisconsin Mammography Random Phantom Model 152 A (Radiation Measurements Inc.) of which images were acquired using the digital technique with the tungsten anode and rhodium filter at different tube voltages (26-35 kV) and tube loads (40-100 mAs) and compared to images in the molybdan/molybdan molybdenum/molybdenum technique. To quantify the image quality, we used the detection rate of the simulated lesions in the phantom.Increasing the tube voltage significantly decreases the average glandular dose when using AEC (Automatic Exposure Control), i. e., constant detector dose. At the same time, the image quality decreases significantly with respect to the detection rate (26 kV, 1 mGy, 95.1 %; 35 kV, 0.7 mGy, 82.7 %). As a good compromise between the necessary diagnostic image quality and the lowest dose exposition, 28 kV and 60 mAs were selected for imaging with the tungsten/rhodium anode/filter combination. A further change to the tube load did not make sense because a decrease of 10 % resulted in a significant decrease in the detection rate while only a 2 % increase in detection rate was achieved for a 65 % increase in radiation exposure.The results of this phantom study demonstrate that the routine use of the tungsten anode in combination with a rhodium filter for full-field digital mammography with an a-Se detector in contrast to a molybdan/molybdan molybdenum/molybdenum anode/filter combination results in a reduction of the average glandular dose of up to 30 % without loss of diagnostic image quality.

Reaction of the freshly prepared phosphenium tungsten complex [(eta(5)-C5H5)(Co)(2)W=PPh2] (3) with the inversely polarized phosphaalkenes RP=C(NMe2)(2) (1) (a: R = tBu; b: Cy; c: Ph) led to the eta(2)-diphosphanyl complexes [(eta(5)-C5H5)(CO)(2)W-P(R)-PPh2] (9a-c) which were isolated by column chromatography as yellow crystals in 24-30 % yield. Similarly, phosphenium complexes [(eta(5)-C5H5)(Co)(2)M=P(H)tBu] (M = W (6); Mo (8)) were converted into [(eta(5)-C5H5)(CO)(2)MP(t-B-u)P(H)tBu] (M = W (11); Mo (12)) by the formal abstraction of the phosphanediyl [PtBu] from 1a. Treatment of [(eta(5)-C5H5)(CO)(2)W=P(Ph)N(SiMe3)(2)] (4) with HP= C(NMe2)(2) (1d) gave rise to the formation of yellow crystalline [eta(5)'-C5H5)(CO)(2)W-P(H)-(Ph)N(SiMe3)(2)] (10). The products were characterized by elemental analyses and spectra (IR, H-1, C-13-, P-31-NMR, MS). The molecular structure of compound 10 was elucidated by an X-ray diffraction analysis.

A systematic solvothermal access towards nanoscale molybdenum and tungsten oxides has been established. Firstly, a versatile precursor material is selected that offers an interesting spectrum of reaction products. In the next step, a wide variety of straightforward ionic additives are screened to reveal and optimise all solvothermal pathways emerging from the precursor material. Finally, the appropriate precursor-additive combinations can be selected for further studies, such as nanorod design or the fabrication of novel materials.

P. acetylenicus is a strictly anaerobic and mesophilic bacterium that is able to grow on acetylene as single energy and carbon source. The first step in the metabolization of acetylene is the transformation of acetylene to acetaldehyde. This addition of water is catalyzed by the W/Fe-S dependent enzyme acetylene hydratase.Acetylene hydratase from P. acetylenicus was purified to homogeneity. It is a monomer with a molecular mass of the amino acid chain of 81.9 kDa. BLASTP searches revealed that the enzyme is highly similar to enzymes of the DMSO-reductase family. Acetylene hydratase is a thermostable enzyme with a temperature optimum between 50 and 55°C. It is a very stable enzyme when stored under exclusion of dioxygen in a nitrogen/hydrogen atmosphere at 6°C (Abt, 2001). Within three months, there was no detectable loss of acetylene hydratase activity from tungstate-grown P. acetylenicus. Although acetylene hydratase catalyzes no redox reaction, it contains one [4Fe-4S] center and one W-bisMGD as redox-cofactors.Crystals of the w-acetylene hydratase were obtained both in presence and in absence (N2: H2 = 94: 6 v/v) of dioxygen. Only the crystals grown in absence of dioxygen were able to diffract X-ray-radiation. Dithionite-reduced enzyme crystals obtained under exclusion of dioxygen, could be measured at the Deutsches Elektronensynchrotron (DESY) in Hamburg up to resolution better then 2,5Å. Also crystals were measured at the ESRF in Grenoble at the tungsten L-edge, however, this dataset could not be used to solve the three dimensional structure because of high mosaicity and decreasing of resolution. This crystal was not stably enough to stand the measurement in the synchrotron radiation.P. acidigallici is a strictly anaerobic bacterium that is able to live on gallic acid (3,4,5-trihydroxybenzoic acid), pyrogallol (1,2,3-trihydroxybenzene), phloroglucinol (1,3,5-trihydroxy-benzene), or 2,4,6-trihydroxybenzoic acid. A crucial step in the fermentation of decarboxylated gallic acid (pyrogallol) is the transhydroxylation of pyrogallol to phloroglucinol. This reaction is catalyzed by the Mo/Fe-S dependent enzyme transhydroxylase (pyrogallol:phloroglucinol hydroxyltransferase E.C. 1.97.1.2).Transhydroxylase from P. acidigallici is a heterodimer consisting of a large subunit (100.4 kDa) and a small subunit (31.3 kDa). This enzyme is closely related to enzymes of the DMSO-reductase family. Although the overall reaction of transhydroxylase is no redox reaction it contains different iron-sulfur centers and one Mo-bisMGD as redox-cofactors.12 of the 13 cysteines in the small β-subunit are highly conserved. Some of them are referred to the [4Fe-4S] ferredoxins. The 15 cysteines of the big subunit do not align with the cysteines of related iron-sulfur proteins. Therefore, it is unlikely that an iron-sulfur center is located in the large subunit. It is more likely that there are three [4Fe-4S] clusters located in the small subunit.Crystals of as isolated transhydroxylase were not able to diffract X-ray radiation. Crystallization of dithionite reduced transhydroxylase under exclusion of dioxygen led to crystals which diffracted to resolution limits higher than 2.5 Å with synchrotron radiation.These crystals were measured with synchrotron radiation and the three-dimensional structure of transhydroxylase was solved. Even structures of transhydroxylase in complex with pyrogallol and inhibitor (1,2,4-trihydroxybenzene) were solved at high resolutions up to 2.0 Å.These result led to a new possible reaction mechanism. Hereby the function of the molybdenum ion is to coordinate the pyrogallol at its C1 position. The amino acids Asp A174, His A144 and Tyr A404 near the active site seem to have catalytic function.

Anion Photoelectron Spectroscopy is a powerful tool for the investigation of the electronic structure of clusters. In this work three investigations are carried out with this method: Using photoelectron spectroscopy and first principle molecular orbital calculations the first observation of a metal-semiconductor transition with increasing number of Oxygen atoms in Tungsten oxide is observed. Tungsten oxide clusters with up to six Tungsten atoms and up to twelve Oxygen atoms were investigated. The transition is caused by the cleavage of the metal-metal bonds. The W4O12 cluster is shown to be a so called baby crystal. This cluster bears all the hallmarks of bulk tungsten oxide, WO3. Contrary to the conventional understanding that atomic clusters usually differ in properties and structure from the bulk constituents of which they are comprised. The second part of this work is about the Nitrogen chemisorption on Tungsten clusters up to four Tungsten atoms. On the Tungsten atom the Nitrogen chemisorbs molecularly, whereas on the Tungsten tetramer dissociative chemisorption is observed. This chemisorption state is metastable. The chemisorption state of the Nitrogen molecule on the Tungsten dimer and trimer could not be determined clearly. In the third part of this dissertation the chemisorption of Oxygen on Gold clusters is investigated. The Oxygen chemisorbs molecularly on the Gold dimer and tetramer, whereas on the Gold atom the chemisorption is dissociative. Altogether the results show, that experiments using free gas-phase clusters in combination with related calculations provide crucial information about their geometrical and electronical properties. For example, thus one may obtain molecular-level understanding of catalysts consisting of nanomaterials.

Analysis of gasochromic switching tungsten oxide layers This thesis describes the properties of reactively dc-magnetron sputtered tungsten oxide (WOx) films. The films are gasochromically switched with diluted hydrogen (H2) in argon or nitrogen, with a very thin surface film of palladium (Pd) as catalyst. The bleaching process happens in oxygen containing atmosphere similar to the reduction and oxidation process known from electrochromic switching. By switching the WOx films, its optical properties change from a transparent state, between the infrared (IR) and ultraviolett (UV), to an absorbing state, in the near infrared. The results portend a big application potential, for a few hundreds nanometer thin functional layer, for energy regulation purposes in 'smart windows' or 'adaptive glazings”. The observed absorption state is ascribed to the creation of small polarons. The main goal of the thesis was to gain a better understanding for the correlations between sputter-deposition parameters and the resulting layer- and switching properties. A new model succeeded in describing the lateral, inhomogeneous switching of the samples. The dependence of the switching behaviour from system parameters like thicknesses of the WOx- or Pd-layers or the hydrogen partial pressure was analyzed in more detail and compared with models from literature dealing with kinetics and thermodynamics. To characterize the coatings, X-ray reflectometry (XRR), optical spectroscopy and in-situ time resolved spectroscopy were mainly used. The determination of relevant physical properties like density, thickness and roughness or the dielectric function (DF) ( index of refraction and absorption index), was achieved by analysis of the measurements with suitable simulation programs. Refinement of existing algorithms was necessary to reveal some minute but significant details. By increase of deposition pressure there was thermalization of high energy incident particles on the growing film. This resulted in more porous and less dense films, which showed a faster switching behaviour. Moreover, the laterally inhomogeneous switching behaviour of the samples could be correlated with the target erosion profile. Its shape determined where fast or thermalized particles impinged on the substrate, causing a more or less dense film growth. The link between density and index of refraction was done via the Lorentz-Lorenz-relation. The application of prevailing models of kinetics in literature enabled time dependent simulation of the measured coloration centers concentration. Identification of the matching simulation led to a classification of the layers into those of fast or slow diffusion according to models from the literature.