Bøger udgivet af Cuvillier

This dissertation examines concepts for wireless communication in large-scale, dense mesh networks, which can be used in future for plant control or building automation. It is shown that recent communication approaches for resource-constrained, IEEE 802.15.4 hardware do not scale well. This motivates the development of methodologies and protocols for reliable wireless communication in large-scale networks. This work covers the following topics: a ¿toolbox¿ for the development, programming, testing, and simulation of communication protocols for embedded systems; the decomposition of large networks into smaller subnets; concepts for scalable broadcasting and routing; the realization of selected network services such as emergency shutdowns and software updates.

In Brazil, a total of 807,587 farms are considered small-scale (family farm) establishments, where land property is less than 100 ha, work is supervised by the producer and family labor prevails over hired labor. Milk production is a socioeconomically relevant activity for many family farms and plays an important role for the regional development.The performance of small-scale dairy farms differing in cattle management and milk marketing strategies was studied in Rio Grande do Sul state. A baseline questionnaire was administered to 200 farm households to collect information on farm assets and activities. Using categorical principal component and two-step cluster analyses, farmers were classified into three groups: milk producers (M); cash crop and milk producers (CM); cash crop producers with surplus milk marketing (Cm).Cattle herd (heads) and pasture land were larger on M farms (114 ?71.9; 51 ha ?49.4) than on CM (31 ?13.4; 9 ha ?8.9) and Cm (12 ?7.5; 5 ha ?8.1) farms. Milk production (l/day) averaged 11.4 ?10.30 for M, 7.3 ?4.11 for CM and 5.0 ?4.30 for Cm farms. Livestock husbandry contributed 71%, 59% and 16% to family income on M, CM and Cm groups, respectively. Overall, marked differences existed for the various variables between groups M and Cm. Farmers in group M showed a more professional attitude when compared to farmers in groups CM and Cm. Considering that farmers in groups CM and Cm are the majority of farmers at study region, they play an important rule on milk production, results show that they must be supported in feed strategies and herd management in order to improve their milk production systems.Market liberalization and fierce competition within the dairy sector provoked a continued decline of small-scale dairy farms in Brazil since the 1990s. However, small-scale family enterprises still prevail in southern Brazil. Therefore we studied factors influencing choice of milk marketing channel, milk production, and contribution of milk production to farm income in 200 small-scale dairy farms in the south of Rio Grande do Sul state. A structured questionnaire was administered to the randomly selected farms in summer 2010.

Inspired by the possibility to boost the performance of future transistors and optoelectronic devices, we have explored the effect of strain in III-V nanowires. GaAs nanowires are characterized by a large yield strength and exceptional mechanical properties, making them an attractive system to study the enhancement of strain effects. At nanoscale dimensions, it is possible to achieve controllable growth of different crystal structures like zincblende or wurtzite, enabling new degrees of freedom to tailor electronic and optoelectonic properties.We show that the photoluminescence (PL) of zincblende GaAs nanowires can be red-shifted by 290 meV by axially elongating zincblende GaAs nanowires by up to 3.5%, from tension to compression. Fingerprints of symmetry breaking due to the anisotropic nature of the nanowire deformation are found in the Raman spectra, where the lifted degeneracy of the phonons is resolved, and in the PL, which undergoes a more pronounced shift in tension than in compression because of the different symmetry character (heavy or light hole) of the top valence band. In wurtzite GaAs nanowires, we demonstrate a remarkable energy shift of the PL up to 345 meV by varying the axial strain over a range of 2% in tension and compression. For the first time, we show spectroscopic evidence of a direct-to-pseudodirect bandgap transition and demonstrate that light emission can be suppressed by more than three orders of magnitude. Using the Raman scattering spectra as relative strain gauge and fitting the optical transition energies to a k¿p model, we determine all band-structure parameters of wurtzite GaAs in unstrained conditions, clarifying once and for all its band structure. Quantities like the Poisson ratio along the c-axis and the phonon deformation potentials of the GaAs and AlGaAs optical phonons have also been determined. This body of results constitutes a solid foundation for understanding strain effects on the optical and electronic properties of III-V nanowires.

Accurate and easy to handle simulation tools are needed for the design and development of future space transportation systems. The simulation of hypersonic flow fields in thermochemical nonequilibrium is a challenging task, as a variety of flow features on various time and length scales needs to be properly resolved.With this purpose in mind, a general CFD solver framework is developed in this doctoral thesis. It combines the multiscale-based grid adaptation with the necessary physical models and numerical methods for the simulation of arbitrary reaction models in thermochemical nonequilibrium. The developed tools and methods are incorporated into the QUADFLOW solver, an integrated concept of grid generation, grid adaptation and finite-volume flow solver.The modified QUADFLOW solver is then applied to pertinent applications. The injection of various cooling gases into a supersonic boundary layer demonstrates the versatility of the QUADFLOW solver at the example of a low enthalpy configuration. The simulated high-enthalpy Edney type IV and type VII shock-shock interactions represent a complex and challenging flow configuration. A high resolution of the vortex structures in the inner flow field and of the boundary layer is achieved at the same time.Für die Auslegung und Entwicklung zukünftiger Raumtransportsysteme werden Simulationslösungen benötigt, die präzise und einfach in der Handhabung sind. Die Simulation hypersonischer Strömungen im chemischen und thermischen Nichtgleichgewicht ist eine anspruchsvolle Aufgabe, da eine Vielzahl von Strömungseffekten auf verschiedenen Zeit- und Längenskalen aufgelöst werden muss.In der vorliegenden Dissertation wird eine speziell für diese Aufgabe optimierte CFD Simulationslösung entwickelt. Hierzu wird eine multiskalen-basierte Gitteradaption mit den notwendigen physikalischen Modellen und numerischen Methoden kombiniert dieerforderlich sind, um beliebige Reaktionsmodelle im chemischen und thermischen Nichtgleichgewicht zu simulieren. Die entwickelten Modelle und Methoden werden in QUADFLOW implementiert, einer integrierten Simulationslösung bestehend aus Gittergenerierung, Gitteradaption und Finite-Volumen Strömungslöser.Die modifizierte QUADFLOW Simulationslösung wird im Anschluss zur Simulation einschlägiger Anwendungsbeispiele eingesetzt. Die Kühlgaseinspritzung verschiedener Gase in eine Überschallgrenzschicht demonstriert eindrucksvoll die Vielseitigkeit von QUADFLOW am Beispiel einer Konfiguration mit geringer Enthalpie. Die simulierten Edney Typ IV und Typ VIIStoß-Stoß Interaktionen stellen komplexe und anspruchsvolle Konfigurationen mit hoher Enthalpie dar. In diesem Fall konnte eine hohe Auflösung sowohl der Wirbelstrukturen im inneren Strömungsfeld als auch der Grenzschicht erzielt werden.

The demand for functional biosubstrates increased substantially in the last decades through the advances in biomedicine and biosensor development. In the current thesis the modification of biosurfaces, such as cellulose and hyaluronan, via several thermally and photochemically induced ligation techniques is pioneered. The thesis is methodologically driven and aims at establishing toolbox technologies for biosurface modification. Highly efficient and mild conjugation methodologies are employed such as (hetero) Diels-Alder protocols, photoenol and phenacyl sulfide chemistry as well as the nitrile imine mediated tetrazole-ene cycloaddition (NITEC) approach to ligate polymers, peptide strands and proteins. The demonstrated arsenal of ligation protocols features mild and catalyst-free conditions, which is a vital point when handling sensitive biomolecules. Cellulose ¿ as the most abundant and most prominent biopolymer ¿ was placed into the focus of the current work as a platform for the establishment of a new set of ligation techniques applicable for a wide range of biosubstrates.

Inertial waves exist in rotating flows and are an ubiquitous phenomena in geophysical and astrophysical flows. The present work studies inertial waves in a homogeneous weakly viscous liquid confined between two coaxial co-rotating cylinders. In a laboratory experiment waves are continuously excited and they propagate due to radial ¿stratification¿ of angular momentum. Inviscid theory describes the formation of wave attractors. Wave energy is reflected several times at the boundaries of the cavity and focused towards geometry dependent attractor paths. Inviscid analytical results will be confirmed by experimental visualisations. Particle image velocimetry measurements will be presented showing particular properties of inertial waves and the existence of zonal/azimuthal mean flows with different origins. Additionally, a simple theoretical model has been developed for a rotating, homogeneous, viscous fluid. The generation of a ¿mean zonal motion¿ due to momentum transport of vertically propagating gravity waves is well known (Plumb and McEwan, J. Atmos. Sci. 35, (1978)). Based on the mathematical analogy it will be shown that in the meridional plane propagating inertial waves can transfer their momentum in the same manner to a sheared mean flow. Even an oscillating mean flow can be driven by inertial waves. The comparison of numerical results originating from numerical computations of two simple analytical model equations and long-time measurements of velocity fields concludes the study.

The design of safety-critical systems is governed by safety standards, which impose requirements on the design, test, and verification processes, as well as the architecture of an embedded system. Particularly, for the safety evaluation applicable standards demand to regard a system as a whole, rather than its individual components. To offer a way to reduce certification effort, the safety evaluation may be carried out individually whenever the considered components are sufficiently independent of each other. In this context, sufficient independence mandates that failures may not cascade from one component to another.This thesis presents an approach to prevent such cascading failures with respect to real-time properties, i.e. to establish sufficient temporal independence. Particularly, the focus is on methods that avoid static allocation of resources according to the worst-case but permit any application behavior that does not threaten real-time constraints.The approach taken in this thesis is by means of runtime monitoring of real-time properties. In this context several lightweight mechanisms for enforcement of state-of-the-art timing models are presented, and analyses are provided to determine configurations for such monitors that allow a maximum degree of runtime flexibility without voiding the independence requirements.

As enzymatic transformations become more and more recognized as practical alternative for synthetic applications, one objective of this thesis was to contribute to the industrial synthetic portfolio with newly designed tailor-made catalysts.The main objective however was to perform a comprehensive study on the prototypical ThDP-dependent enzyme pyruvate decarboxylase to deduce mechanistic principles by which the fate of reaction intermediates are conferred. Within this thesis, mechanistic studies on pyruvate decarboxylase from Z. mobilis have been performed with relevance for asymmetric carboligation applications. A successful approach has been made to generate tailor-made catalysts through distinct reaction-design, based on mechanistic understanding and genetic engineering rather than on random mutagenesis. With this chemical rational, it was possible to reprogram a carboligase to an efficient and uniquely effective carboligase. Detailed analysis of the catalytic mechanism of Z. mobilis PDC with highly sophisticated kinetic and thermodynamic methods together with structural analysis, could delineate the stereochemical course of the reaction.

About this book¿The disappearance of forests and the continued proliferation of degraded areas requiring rehabilitation are serious problems. Many tree species are becoming rare and endangered due to the vanishing of these forests. Rare tree species contributes largely to biodiversity in natural forests and they are believed to perform important ecosystem functions. Thus it is imperative to identify which tree species are rare, their locations and which requires priority for conservation. Such information together with knowledge on species associations and with sites is useful for land management schemes such as reforestation that aims at restoring and/or conserving biodiversity. Knowledge on species in nurseries and constraints on seedling production are also crucial for a successful reforestation effort that uses a mixed of native tree species.

Devices based on organic semiconductors, like organic light emitting diodes (OLEDs) or organic solar cells, often comprise electrochemically doped charge transport layers, which improve the performance of these devices. Although very efficient devices can be realized nowadays, a comprehensive description of the physical processes taking place in electrochemically doped thin films is still missing. For instance, it was shown for a variety of different material systems that the doping efficiency, defined as the number of free charge carriers compared to the number of incorporated dopants, often amounts to only a few per cent. The organic semiconductor CBP (4,4¿-Bis(N-carbazolyl)-1,1¿-biphenyl), doped with the transition metal oxide molybdenum oxide (MoO3), is used here as a model system to investigate the origin for this low doping efficiency. Results from different measurement techniques, like electron tomography, EF-TEM, PES, FTIR-spectroscopy and (temperature- dependent) electrical measurements were correlated to get insight into the origin of the low doping effiencies and to obtain a model to describe charge transport in MoO3-doped CBP films as a function of the doping concentration.

While multiple qubits in a quantum register should behave independently, their connection to a common environment may spoil that independence, as they start to influence each other via the environment. In this work two qubits, modelled by magnetic spin-1/2 impurities, are investigated which are coupled at a finite distance to the same dissipative environment. From the spin-boson model it is known that there exists a phase for weak coupling where the spin is not localised in any state and may thus explore the whole SU Bloch sphere, while for strong coupling it is localised in one of two configurations, completely destroying its quantum mechanical nature.As a second spin is coupled in direct vicinity of the first, the environment mediates an effective ferromagnetic interaction between the spins, rendering them no longer independent.Within the Numerical Renormalization Group (NRG) it is investigated at which point the two spins can be treated independently as the distance between them is increased. To this end a two-channel bosonic NRG is developed that can deal with the model and its limit of two independent spin-boson models. The two-channel NRG is first tested on a model incorporating a single oscillator as an impurity. While the latter model only involves a single channel, a self-interaction of the impurity oscillator provides accessible limits, where the numerical implementation of the two-channel NRG can be tested. Furthermore signals of the different impurities are traced in the environment by means of thermal averages and their changes due to the presence of the impurities.Das Werk behandelt den Einfluss von Quantenstörstellen innerhalb einer dissipativen Umgebung sowohl aufeinander als auch auf ihre Umgebung. Die Störstellen werden hierbei entweder durch einen Oszillator oder durch zwei Qubits realisiert. Da die betrachteten Systeme für eine Vielzahl von Parametern nicht analytisch lösbar sind, wird eine Zwei-Kanal-NRG (Numerische Renormierungsgruppe) für bosonische Modelle entwickelt. Details dieser NRG und ihrer Implementierung werden in der Arbeit vorgestellt.Eine Untersuchung der Flussdiagramme der Zwei-Qubit-Systeme deutet auf einen Grundzustand hin, in dem die Quantenstörstellen effektiv ferromagnetisch gekoppelt sind.In diesem Zustand zeigen sowohl die mittlere Besetzung als auch die mittlere Auslenkung der Umgebungsorbitale eine deutliche Erhöhung direkt an den Störstellen.Die eindeutige Zuordnung einer Längenskala, auf der die betrachteten Signale abnehmen, ist derzeit nicht möglich.

The project ¿EWATEC-COAST¿ (Technologies for environmental and water protection of coastal zones in Vietnam under climate change conditions) started in autumn, 2012. The project is funded by the German Federal Ministry of Education and Research (BMBF) as a part of the funding programme "CLIENT¿ and by the Vietnam National University of Ho-Chi-Minh City (VNU-HCMC). Study areas are the highly polluted inland water and estuary system of the Thi Vai river and the adjacent Can Gio mangrove forest. Both areas are located south-east of Ho-Chi-Minh City. In the past, various companies, which are mostly situated in industrial zones along the river, discharged wastewater without treatment into the river system. The Thi Vai river was therefore considered as ecologically dead. Most recently, the water quality of the river has been slightly improved because first control initiatives have been realized. A comprehensive strategy for the sustainable rehabilitation is still missing. EWATEC-COAST will significantly contribute to find ecologically and economically sound solutions for the rehabilitation of the affected water bodies, the fauna and the flora with focus on mangroves. Furthermore climate change impacts will be considered. Main task is the development and application of a model-based "management system" for sustainable water and environmental protection of the affected coastal zone. The system will serve for decision making. Components of the integrative system are meteorological data series for the past, present and future including climate change, and data on the quantity and quality of surface water and ground water systems, the mangrove ecosystem, aquatic organisms and coastal protection.

The main focus of the research presented in this dissertation was to broaden the substrate scope of the iridium-catalyzed asymmetric hydrogenation of heterocyclic compounds. In view of the fact that a widely applicable hydrogenation system for the reduction of structurally diverse furans and benzofurans is to date not available, a thorough investigation of furan, benzofuran and thiophene 1,1-dioxide derivatives was carried out. Mono- and disubstituted furan derivatives were synthesized and submitted to iridium-catalyzed hydrogenation reactions. While 3-substituted furans were reduced using a catalyst based on a cyclopentane-annulated bicyclic pyridine-phosphine ligand with high enantiomeric excess (95¿99% ee) and conversion (83¿99%), 2-substituted counterparts proved to be less reactive (80¿97% conv., 65¿82% ee) with the same catalyst. Asymmetric hydrogenation of 2,4-disubstituted furans proved to be challenging for several reasons, not least because of the problem of controlling the cis/trans selectivity. Surprisingly, in the iridium-catalyzed hydrogenation of 3-substituted benzofurans only one catalyst, based on the cyclohexane-annulated pyridine-phosphinite ligand, showed high activity and enantioselectivity (75¿89% conv., 91¿92% ee), whereas the five-membered ring analog suffered from moderate activity and enantioselectivity. In contrast, the 2-alkyl substituted benzofurans gave superior results (99% conv., 97¿99% ee). Disubstituted thiophene 1,1-dioxides were also investigated in the iridium-catalyzed asymmetric hydrogenation. The hydrogenation of 3,4 disubstituted thiophene 1,1 dioxides using a catalyst based on a cyclopentane-annulated bicyclic pyridine-phosphine ligand gave inferior results to those obtained with their 2,5 disubstituted counterparts.

Guaranteeing food security is of critical importance for Central Asia region due to its landlocked nature, big numbers and low incomes of rural population, and transition from planned centralized economy to the market economy.During the transition from planned to market economies, the Central Asian Republics (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan) experienced rising poverty, food insecurity and malnutrition as well as serious degradation of natural resources, in particular of water and land. The transition to a market oriented economy has not been adequately supported by institutional development which resulted in a decline in the living standards of the population and which has further caused in high levels of food insecurity and malnutrition.This contribution provides an empirical examination of the current state and prospects of food and nutrition security in rural area of Uzbekistan. The goal of the present study was to determine the main factors influencing food and nutrition status of farm households such as the level of education and income, kind and number of crops produced on homestead plot and on farm land, profitability of these crops, etc. The main methodological instrument for analysis was the logistic regression modeling. The contribution is finalized by author¿s recommendations for further improvement of food and nutrition security in Uzbekistan.

The world¿s continuously increasing demand for energy, as well as the need to find an environmentally benign alternative to fossil fuels, have motivated the search for a sustainable energy supply. In this respect, dihydrogen is seen among the most promising energy carriers of the future. First steps towards implementing a so-called ¿hydrogen economy¿ have already been made, but problems associated with the efficient production, storage and activation of dihydrogen still persist. Fortunately, nature provides valuable inspiration for the development of novel catalysts which could tackle the existing scientific and technical challenges.This work draws on parallels between a class of naturally occurring dihydrogen activating and producing enzymes called hydrogenases, and the relatively new concept of chemical bond activation by so-called frustrated Lewis pairs. Using this bioinspired approach, a simplified model system capable of heterolytic H2 splitting akin to the H2 splitting occurring in the [Fe] hydrogenase enzyme could be synthesized and analyzed in detail. The results described in this work therefore contribute to a better understanding of the natural enzymes and provide future directions for the development of novel dihydrogen activation and production catalysts.

Surfactants were and still are our inconspicuous companions at macroscopic but more often at microscopic scale. Many technologies are only possible due to surfactant applications, which are of constantly growing scientific and industrial interest for approximately 100 years [1]. Hence, since its definition ¿micro emulsion¿ by Schulman [2] optically isotropic surfactant formulations and their variations have become a significant part in today¿s society. In nowadays¿ most popular sector of nanomaterials surfactants are utilised for productions of such via template strategies [3¿10]. Organic synthesis benefits from the immensely huge interfacial area of microemulsions resulting in bigger yields which were not possible before [11¿21]. Closely related to organic synthesis, pharmaceutical industries enjoy the benefits of drug delivery via e.g. vesicels which play a major role during drug transport into the blood stream [22¿27]. Simpler application of surfactants were reported 1984 where cationic surfactants were utilised as stabiliser for antibiotics [28]. Concerning healthier and conscious nutrition microemulsions are applied for reduction of the caloric value of food [29¿39]. Also, to contribute to environmental protection exhaust emissions can be reduced by introducing water and surfactants into fuels [40¿42]. Surfactant systems or in most cases microemulsions are very adaptable and can therefore be utilised in their most different states. This chapter gives an insightful introduction into the world of microemulsions.

Combustion of water-containing diesel fuels results in a simultaneous reduction of soot and NOx-emissions, i.e. they partially avoid the so-called soot-NOx trade-off. In the frame of the present work new temperature invariant, highly efficient fuel microemulsions of the type water/antifreeze ¿ diesel fuel ¿ oleic acid/monoethanolamine/oleic acid diethanolamide containing up to 24 wt.% water with appropriate physical characteristics for commercial applications were formulated. As unexpected reward of the investigations on formulation of microemulsion fuels, novel water-in-fuel nanoemulsions (

Metalloproteins with iron-sites are essential for almost all living organisms and responsible for a large number of biological redox reactions. To uncover the mechanisms of enzymes and cofactors, bioinorganic chemistry aims to provide low-molecular weight analogues. In this dissertation, the iron-sites of [2Fe¿2S] proteins, [NiFe] hydrogenases and mononuclear oxygenases served as models for bioinspired analogues coordinated by N-heterocyclic carbene (NHC) ligands. Although abiological, NHC ligands have been shown to be capable of stabilizing otherwise labile inorganic intermediates which are crucial for mechanistic understanding. Using this approach, the isolation of the first organometallic oxoiron(IV) complex, mimicking the oxygenase motif, was achieved. Studies on the structural and magnetic characteristics, substrate reactivity, and the decomposition pathway are provided.

This thesis shows that silicon resonators that are infiltrated with nonlinear polymer fulfil the requirements of modern electro-optic modulators such as a small footprint and a large modulation bandwidth. The three major challenges of this hybrid approach are addressed. The first part of this thesis shows that bleaching of a chromophore doped polymer cladding can be used as trimming mechanism in order to compensate random shifts of the resonance frequency during fabrication. In the second part it is described how electro-optically tunable photonic crystal resonantors with high quality factors can be realized. Finally the problem of low electro-optic coefficients inside the polymer for integrated silicon structures is addressed.Diese Arbeit zeigt, dass Siliziumresonatoren, die mit nichtlinearem Polymer infiltriert sind, die Anforderungen an moderne elektro-optische Modulatoren, wie eine geringe Grundfläche und hohe Modulationsbandbreiten, erfüllen. Der erste Teil dieser Dissertation zeigt, dass das Bleichen einer Chromophor dotierten Polymerdeckschicht als Trimmmechanismus genutzt werden kann, um herstellungsbedingte Schwankungen der Resonanzfrequenz auszugleichen. Der zweite Teil beschreibt, wie elektro-optisch verstimmbare photonische Kristallresonatoren hoher Güte realisiert werden können. Im letzten Teil dieser Arbeit wird das Problem niedriger elektro-optischer Koeffizienten des Polymers in Siliziumstrukturen behandelt.

Optical technologies constitute the core of long-haul communication. The large bandwidth and low propagation losses provided by fiber based optical communication systems make it possible to transport large amounts of information over long distances, for instance, between continents [1¿3]. Beyond that, their superior performance is increasingly pushing the introduction of optical interconnects for communication over shorter ranges. In enterprise networks, for example, comprising distances up to a few kilometers, optical interconnects are deployed for applications requiring large bandwidth and propagation lenghts 3. Furthermore, as bandwidth requirements increase and the miniaturization of integrated electronics advances, the performance of electrical interconnects decreases even at the very short ranges (10 m) of board-to-board, chip-to-chip and on-chip communication [3¿11]. At these integration levels, too, optical interconnects have been proposed to overcome the expected limitations [3¿11].

This work focuses on the development, the manufacturing, and the characterisation of melt-extruded rods for the application by the Solid Dosage Pen ¿ a device which permits individual dosing by cutting slices of pre-defined heights from these rods.Tailored dissolution kinetics of the model drug carbamazepine were achieved with immediate, biphasic, and sustained release characteristics. Dose-dependent dissolution behaviour of sustained release formulations was minimised by applying a wax-coating via co-extrusion technologies and completely overcome by the embedding of coated micropellets into rods. The mechanical properties of the rods were systematically investigated by the evaluation of the maximum cutting force, the tensile strength, and the E-modulus.To conclude, innovative production processes, new analytic methods and novel formulations were established for peroral solid dosage forms for the SDP. The melt-extruded formulations allowed for individual dosing by the SDP and could therefore provide a new platform in personalised medicine as well as in paediatrics and geriatrics.

The term ¿lanthanide¿ was introduced by Victor Goldschmidt with the name of its first element ¿lanthanum¿.1It has the outer electronic configuration 6s25d14f0, so it can either be considered as a d-block elements or an f-block element. The relative energy of the 5d and 4f orbitals are very similar and sensitive to occupancy of orbitals but on the basis of stability of 4f shell which is slightly more compare to 5d shell, it was considered as f-block element. This criterion was followed by next 14 elements and electrons enter in the 4f shell until at lutetium.2The lanthanides are 15 elements in the periodic table considered as the first f-block elements, starting from lanthanum (59La) to lutetium (71Lu), which are commonly referred as ¿rare earth metals¿ along with scandium and yttrium. They are chemically represented by the symbol ¿Ln¿.

N-heterocyclic carbenes (NHCs) have found robust development and were widely used as ubiquitous ligands for organometallic complexes in the past two decades. Besides the most popular Arduengo carbenes, i.e. imidazol-2-ylidene and its analogues, novel carbenes derived from N-heterocycles other than imidazole have lately attracted increasing attention. In this work, metal complexes with novel N-heterocyclic carbene ligands, such as imidazol-4/5-ylidene, pyridazin-4-ylidene, and N-metallated N-heterocyclic carbene have been synthesized and characterized. In addition, inspired by a recent discovery that a carbon atom was chelated by NHC ligands to form carbodicarbene, efforts to synthesize a novel indene-derived carbene, in which NHC ligands coordinate to carbon atoms adjacent to the carbenic carbon atom, have been carried out.

The knowledge of behavior of liquids with free surfaces to their surrounding gaseous phase in compensated gravity is essential to the development of tank systems for spacecrafts. In microgravity, the liquid behavior is dominated by capillary forces, which are used to position and redistribute liquid propellant in a desired way for the mission. The body forces occurring due to residual accelerations, which can be caused by spin during the ballistic flight phases, force the liquid to reorient towards a new equilibrium state of the free surface. Due to spin the liquid is driven away from the tank outlet and located along tank walls in partially filled tanks. To assure enough liquid fuel over the tank outlet, so-called Propellant Management Devices (PMD¿s), are employed. A PMD is a static, usually metal structure, which either provides a passage way for a liquid in microgravity or stores a certain amount of liquid at a desired location. Some PMD¿s are designed to be refillable in periods of microgravity due to openings in the outer housing or by a housing composed of perforated metallic sheets. These reservoirs are refilled in periods of compensated gravity in order to provide the required amount of liquid fuel for attitude control or other maneuverings. Relatively large disturbances, such as lateral accelerations and spin, can drive the liquid fuel out of the reservoir, resulting in malfunction of the device. During spilling, gas enters the device such that only a residual amount of liquid propellant can be kept in the reservoir. Moreover, the connection to the bulk liquid in the tank may be interrupted such that refilling of the reservoir is disrupted. Hence, a PMD with two parallel disks forming the inlet and a venting tube at the topmost point of the outer housing shall be designed such that its refillable structure is only filled with liquid without any gas or vapor being easily trapped during operations.