Books published by Cuvillier

Tropentag is the largest interdisciplinary conference in Europe on research in sub-/tropical agriculture, food security, natural resource management and rural development. Taking place annually, Tropentag 2019 is jointly organised by the Centre for International Rural Development at the University of Kassel and the Centre of Biodiversity and Sustainable Land Use at the University of Göttingen, and takes place at the University of Kassel's main campus from 18 to 20 September 2019.

The objective of this PhD thesis is the enhancement of understanding and prediction of capillary wetting of heterogeneous, soluble food powders. Therefore, the capillary penetration is studied experimentally by increasing stepwise the complexity. Firstly, the heterogeneity in terms of contact angle and the effect of solubility during capillary wetting as the two main influencing factors are investigated separately and in a second step both factors are combined. Furthermore, a new model based on the coupling of the Washburn and the mass transfer equation is presented dealing simultaneously with capillary penetration and dissolution. It is observed that the viscosity increase is dominant during liquid penetration for the powder systems containing the most soluble component (sucrose) at a high concentration. For powder mixtures containing a less soluble component with less viscosity development (sodium chloride), the hydrophobic contact angle drives the liquid penetration.

History of Horizons. December 4th, 2003. The seminar room in the Gottingen Center for Molecular Biosciences was bustling with activity. Organizers darted in and out of the room, making sure everything was in order and as it should be. Speakers attempted to look through their talking points, whilst entertaining the many curiosities of the next generation gathered around them. The graduate students themselves, whispered to each other and waited apprehensively, with thinly veiled excitement, for the program to begin. There were just under a hundred eager minds crowded into that one room. Students and researchers; all brought together by a shared passion: a passion for science. This was the inaugural Horizons in Molecular Biology Conference: An International PhD Student Symposium! The conference has come a long way since then. Over the years, the number of participants grew steadily and increased in variety. Horizons now regularly attracts around three hundred participants from over thirty countries. The symposium has featured numerous renowned researchers, representing a wide range of fields in the life sciences. This exhaustive list also included several Nobel Laureates, namely: Professors Martin Chalfie, Sir John Walker, Ada Yonath, Thomas Südhof, Kurt Wüthrich, Carol Greider, Venki Ramakrishnan, Sir John Gurdon, Tim Hunt, and this year Michael Rosbash.

Turbulent Taylor-Couette flow, where the fluid is confined by two coaxial and independently rotating cylinders, is experimentally investigated within this thesis for medium and wide gaps. To reveal the influence of flow patterns on the angular momentum transport, direct torque measurements, flow visualizations and particle image velocimetry are performed in two different facilities. For the largely unexplored radius ratio regime of ¿ = 0.357, the directly measured torque features a transition as a function of shear, which is connected to the capacity of the outer cylinder to emit small-scale plumes. When the cylinders rotate slightly in counter-direction, a maximum in torque occurs at ¿max = -0.123, which is induced by the formation of large-scale Taylor vortices. The contribution of these vortices to the overall momentum transport clearly exceeds the contribution of the turbulent fluctuations for ¿ = 0.5. Furthermore, the large-scale Taylor rolls are driven by small-scale plumes and feature azimuthally traveling waves for ¿ = 0.714. Accordingly, the angular momentum transport in medium and wide-gap turbulent Taylor-Couette flow is determined by the interaction of turbulence and flow patterns of different scales.

¿Experimentelle Untersuchung des turbulenten Transports in der Taylor-Couette Strömung¿ Ein berühmtes Beispiel für Stromungsinstabilitaten kommt zwischen zwei konzentrischen, unabhängig rotierenden Zylindern vor. Drehimpuls wird im Falle einer differentiellen Rotation zwischen den Zylindern transportiert. Die so genannte Taylor-Couette (TC) Strömung ist von grundlegender Bedeutung für Transportprozesse in rotierenden Systemen, wie der Erdatmosphäre und Akkretionsscheiben oder industriellen Anwendungen, wie Gleitlagerung, Seperation oder Mischungen. Ein besseres Verständnis der Transportprozesse und turbulenten Strukturen sowie eine einheitliche Beschreibung der komplexen Aspekte sind Aufgaben groser Tragweite vieler Forschungsgebiete. Die Absicht dieser Arbeit ist die experimentelle Untersuchung der turbulenten Taylor-Couette Strömung des Radienverhältnissees ¿ = 0.5 bei hohen Scher-Reynoldszahlen und der Rotation des Innen- sowie Ausenzylinders.

E-government and its connection with administrative reforms are commonly regarded as important milestones for e-democracy and e-participation - although they have been poorly investigated so far. The book attempts to tap the potential of e-government in a pilot study for Germany and Vietnam. At first glance, such an approach seems daring, as the two countries differ considerably in their political systems. All the more surprising are the results reached by the German-Vietnamese working group. The findings on e-government and its service quality are disappointing for both countries. Even the question has arisen as to what advantages citizens can have through it. From the German perspective, critical voices on the potential of e-government for political participation and deliberation predominate. The Vietnamese side considers the possibilities for e-democracy, e-participation and in the fight against environmental pollution and corruption to be much more positive. It can be assumed that this is related to the greater leap in development made by countries such as Vietnam compared with Germany through information and communications technology.E-Government und sein Zusammenhang mit Verwaltungsreformen werden allgemein als wichtige Meilensteine für E-Demokratie und E-Partizipation angesehen - obwohl sie bisher nur unzureichend untersucht wurden. In einer Pilotstudie für Deutschland und Vietnam versucht das Buch, das Potenzial von E-Government zu erschließen. Auf den ersten Blick erscheint ein solcher Ansatz gewagt, da sich die beiden Länder in ihren politischen Systemen stark unterscheiden. Umso überraschender sind die Resultate der deutsch-vietnamesischen Arbeitsgruppe. Die Ergebnisse zum Thema E-Government und dessen Servicequalität sind für beide Länder enttäuschend. Es stellt sich sogar die Frage, welche Vorteile die Bürger durch es haben können. Aus deutscher Sicht dominieren kritische Stimmen über das Potenzial von E-Government für politische Partizipation und Deliberation. Die vietnamesische Seite schätzt die Möglichkeiten für E-Demokratie, E-Beteiligung und im Kampf gegen Umweltverschmutzung und Korruption für wesentlich positiver ein. Es ist davon auszugehen, dass dies mit dem größeren Entwicklungssprung von Ländern wie Vietnam im Vergleich zu Deutschland durch Informations- und Kommunikationstechnologien zusammenhängt.

An efficient post-combustion capture technology is the carbonate looping (CaL) process reducing the amount of CO2 released by fossil fuelled power and industrial plants (CCS/U). Limestone based sorbents are circulated between two interconnected circulating fluidized bed (CFB) reactors. In a first reactor, the carbonator, the main part of CO2 contained in the flue gas of an upstream emission source is absorbed by CaO. The CO2 is released and the sorbent regenerated under oxy-firing conditions in a second reactor, the calciner. The present work discusses the results obtained from experimental investigation of the Carbonate Looping process in semi-industrial 1 MWth scale. Long-term pilot tests were conducted to improve the process and gain reliable experimental data to scale up the CaL process to industrial size. The type of fuel, sorbent, flue gas composition, reactor design, and operating conditions were varied to assess the operability and the long-term effects on the process performance. During periods of up to 60 h, parameters were not changed to achieve steady-state conditions. The stability of the CaL process in semi-industrial size was proven by steady-state CO2 absorption for more than 1,500 h with interconnected circulating fluidized bed reactors with absorption rates in the carbonator higher than 90% and overall capture rates higher than 95 %. The experimental data obtained in this work provide the basis to take the CaL process to the next stage of development, a demonstration pilot with a thermal size of 20 MWth. A conceptual plant setup for this demonstration unit was derived from the operational experience in the 1 MWth pilot plant. Based on evaluation of pilot testing and with the help of a validated process model, the design parameters were defined and verified. The heat and mass balancing for various operating cases was carried out to define the boundary conditions for the engineering of the demonstration pilot. Furthermore, the assessment of the demonstration pilot showed the expected performance.

Im Rahmen der Dissertation wurde eine Methode zur Quantifizierung der Metabolite des zentralen Kohlenstoffwechsels von Mikroorganismen entwickelt. Die Methode wurde genutzt, um das Metabolom verschiedenster Produktionsstämme im nanomolaren Bereich zu analysieren. Bei der Analyse der Daten wurden Ergebnisse aus Metabolom- und Fluxomforschung kombiniert, um einen ganzheitlichen Ansatz zu schaffen. Auf diese Weise konnte unter anderem der Einfluss verschiedener Kultivierungsverfahren auf das Energielevel von E. coli untersucht werden. Weitere Messungen untersuchten den Einfluss von genetischen Veränderungen, Stress und unterschiedlichen C-Quellen auf den zentralen Kohlenstoffwechsel von weiteren Mikroorganismen.

Systemin is a small peptide with important functions in plant wound response signaling. To elucidate systemin perception and signal transduction mechanisms, a phosphoproteomic profiling study was performed to reconstruct a systemin-specific kinase/phosphatase signaling network. Time course analyses revealed early events at the plasma membrane, such as dephosphorylation of H+-ATPase, and the phosphorylation of NADPH-oxidase and Ca2+-ATPase in response to systemin. Later responses included transient phosphorylation of small GTPases and vesicle trafficking proteins, as well as transcription factors. Based on a correlation analysis of systemin-induced phosphorylation profiles, substrate candidates for 44 systemin-responsive kinases and 9 phosphatases were predicted, some of which are involved in a regulatory circuit for the regulation of the plasma membrane H+-ATPase. In this regulatory model, H+-ATPase LHA1 is rapidly de-phosphorylated at its C-terminal regulatory residue T955 by phosphatase PLL5, resulting in the alkalization of the growth medium within two minutes of systemin treatment. LHA1 is re-activated by MAP-Kinase MPK2 later in the systemin response. A valuable resource of proteomic events involved in the systemin signaling cascade is provided with a focus on the prediction of substrates to early systemin-responsive kinases and phosphatases.

The phosphinoamide chemistry has attracted a considerable attention owing to the structural diversity of the associated complexes. To further understand the properties of the P-N bond, Ashby synthesized the compound [(Ph2P-NPh)Li(Et2O)] through the deprotonation reaction of the corresponding aminophosphine with nBuLi. X-ray diffraction analyses indicated the presence of Li-P bonds (2.684 and 3.004 Å). In addition, the P-N bond length (1.672(2) Å) was relatively smaller than that of a single bond (mean value of 1.70).

Today there is an increased focus on a considerable reduction of the total energy consumption in the world. As the heating of buildings constitutes a large part of this consumption, the development of highly efficient thermal insulation materials is highly demanded. The most promising class are polymeric nanofoams, which might be producible by using the "Principle Of Supercritical Microemulsion Expansion" (POSME). Within this approach, microemulsions with a high number density of CO2 nano-pools in a polymerizable material (e.g. polyol) are used as templates. Adjusting supercritical conditions, the nucleation of gaseous CO2 during the expansion is avoided, so that each CO2-swollen micelle should ideally grow to a nanopore. However, due to aging phenomena, so far only polyurethane (PU) foams with microcellular pores could be produced applying this approach. In order to improve the properties of the foamable microemulsion template, microemulsions of the type water - CO2 - non-ionic fluorinated surfactant (Capstone® FS-3100) were studied in the first part of this thesis as a model system. Small angle neutron scattering (SANS) measurements for the first time revealed the phase inversion from CO2-swollen micelles in water via bicontinuous structures to water-swollen micelles in CO2. Using a scaling description developed for microemulsions of the type water -alkane - CiEj, the temperature dependence of the length scales found in classical and CO2-microemulsions fall on top of each other. Moreover, the partial replacement of CO2 by cyclohexane was found to increase the efficiency of the fluorinated surfactant to form a bicontinuous microemulsion. This efficiency boosting could be correlated with the increase of the bending rigidities ¿0,SANS and ¿NSE determined by SANS and neutron spin echo (NSE). In the second part of this thesis the gained knowledge was successfully used to formulate CO2-in-polyol microemulsions appropriate for the production of nanocellular PU foams. Using SANS and partly deuterated polyol, not only the formation of micelles in the binary mixture of polyol and non-ionic siloxane surfactant, but also their swelling with CO2 could be proven. The change of the microstructure upon fast expansion and compression was studied combining time-resolved SANS-measurements and periodic pressure jumps. Interestingly, the pressure induced structural changes follow the pressure profile instantaneously, i.e. faster than the time resolution of 50 ms

The continuous and rapidly growing demand for mobile communication access led to a major increase in the number of base stations worldwide to provide sufficient coverage and quality of service. As a consequence, mobile communication networks have become a significant contributor to global energy consumption. Several advanced topologies for efficiency improvement of RF power amplifiers have been developed. Modulating the amplifier's supply voltage according to the variation of the envelope signal is one of the most promising concepts. This topology is investigated here, with an architecture that switches the supply voltage of the power amplifier in discrete levels with a class-G supply modulator.The thesis addresses comprehensively all aspects of class-G supply modulation. Several prototype designs were realized to validate the theory and to gain experience on the influence of the corresponding parameters. These include the discrete supply voltage levels, the switching thresholds, and the interface between the RF PA and the class-G supply modulator. Efforts both on improving the RF power amplifiers and developing several class-G supply modulators were also involved. This work covers the progress up to a PA module that provides an instantaneous modulation bandwidth of 120 MHz and achieves better performance than state-of-the art continuous supply modulation systems.Class-G supply modulated RF power amplifiers based on gallium nitride technology exhibit a strong nonlinear behavior, therefore linearization is required. For this purpose, the linearization with digital predistortion based on behavioral models is optimized for the class-G topology and a novel predistorter model is developed and analyzed.

BeschreibungWater Security is emerging as a primary sustainability challenge across the globe in the 21st century. It is a determinant for security in various societal and environ-mental aspects including food, energy, economy, environment and public health, and thus has a complex political momentum that goes far beyond the traditional water sector. In order to understand, to project, to address and to plan for water security challenges, one must collectively understand exposure to climate and environment driven hazards, as well as socio-economic determinants, and the cultural and political context, within which mankind live, work and play. Technologies (ranging from model-based scenarios and predictions to green and grey infrastructure and treatment systems, and from remote sensing to social media) and innovative financing and governance systems are proposed to address water security. This proceedings book of an International Workshop in São Paulo, Brazil will provide the reader the opportunity to acquire knowledge on Water Security considering water governance and management, technological innovation and emerging solutions for water conservation, reuse and recycle in order to achieve the Sustainable Development Goals proposed by the United Nations. More specifically, it intends to deliver essential state-of-the-art knowledge concerning- Water Security and its role in addressing the Sustainable Development Goals,- Challenges and opportunities to reach Water Security considering quality and availability, and- Water Security lessons learned and long term implications in developing countries

BeschreibungThe work at hand participates with the energy transition toward decarbonized electricity production by providing a method to analyze the incentives for the dispatchable fleet to provide flexibility. It analyzes the signals set by the energy markets to investors and power plant operators regarding flexible power plant operation and the future requirement of thermal plant flexibilisation, with improvement suggestions. A method for the quantitative, long-term, high-resolution techno-economic assessment of an individual power plant's operational flexibility is proposed. It includes the single unit self-scheduling problem of a merchant power plant solved from a price-taker perspective in the day-ahead, intraday and frequency control markets, as well as a parametric power plant model suited for operational flexibility assessments. The retroactive observation of the merchant power plants' operation strategies in these markets is used to identify best practices in terms of market design for flexibility incentives. The value of operational flexibility improvements is quantified using various metrics, for different technologies and market environments. Despite their sensitivity to market design, technologies and cost structures, these results indicate that if investors further expect a three to five-year return on investment, the existing European conventional fleet is unlikely to experience a significant flexibilization.

Soziale Medien wie Facebook eröffneten neue Kommunkationsmöglichkeiten für das Militär um sich im Arbeitsmarkt als attraktiver Arbeitgeber zu positionieren. Nach der Abschaffung der Wehrpflicht musste sich das Militär neu und attraktiv definieren, um Rekruten im Konkurrenzmarkt gegen den privaten Sektor anzuziehen. Diese Arbeit geht der Frage nach, wie das Militär in Deutschland, USA und Frankreich Attraktivität produziert, mit dem Ziel, die Personalgewinnung digital zu stärken. Dabei geht es um einen cyberanthropologischen Ansatz, der mit verschiedenen quantitativen und qualitativen Methoden die Perspektive von Rekruten und der Institution erfasst. Diese interdisziplinäre Annäherung auf die digitale Ebene der Kommunikation des Militärs versucht das Spektrum der Militäranthropologie und -soziologie auszuweiten, in dem Ansätze des Marketings und des Personalmanagements auch aufgefasst werden.So werden Employer-Branding Perspektiven des Militärs in einem internationalen Vergleich im jeweiligen politischen Kontext und unter mehrdisziplinären theoretischen Betrachtungen vorgestellt und analysiert. Die empirischen Ergebnisse weisen darauf hin, dass jedes Militär heterogen bleibt und jedoch kulturell und historisch geprägt wird, während es eine Attraktivitätspolitik schafft. Während die deutsche Bundeswehr sich eher mit Technik und kaum mit Geschichte befasst, setzt das französische Militär auf das zeremonielle, das design-intensive und das amerikanische Militär eher auf Werte, Patriotismus und nationalen Ikonen, die eine Identität dynamisch mitaufbauen.

Water is a key driver of economic and social development, while it also has a basic function in maintaining the integrity of the natural environment. The traditional fragmented approach of dealing with water issues is no longer viable and a hybrid system, which incorporates modern methods, is essential. This is a rational approach that has now been accepted internationally as the way forward for efficient, equitable and sustainable development of the world's limited but most precious resources.Finding solutions to these challenging hydric problems requires close collaboration between traditional knowledge and current science practices, expert practitioners, and stakeholders from private and public organizations. Therefore, this book encourages to contribute and to be part of the search for efficient solutions to water crisis in Sub Saharan Africa by widening scientific and technological know-how - and more importantly - engaging in knowledge brokerage. This book focuses on a multi-disciplinary diagnosis of water challenges in developing countries in general but specifically in Sub Saharan Africa, and proposes viable solutions with respect to modern and the traditional methods of water resource management. Specific areas of interest include water quality and quantity parameters, water supply in urban and rural areas, wastewater treatment and recycling.

The main topic of this thesis is the influence of the dielectrophoretic (DEP) force on a thermal convection in a cylindrical annulus under microgravity conditions of parabolic flights. To perform these experiments a specialized experimental setup was designed. The annulus is differentially heated to create a temperature gradient and an ac voltage of up to 10kV is applied. Two different experiment setups were build for different measurement methods. One for Shadowgraph and Synthetic Schlieren methods and the other for PIV measurements. Several complex flow patterns can be identified by combining the resulting images from both visualization mthods. The heat transfer is determined under different experimental conditions. Under the given conditions it is possible to make a correlation between the flow patterns and the level of the convective heat transfer. The experimental data is compared to theoretical data from a linear stability analysis. The patterns predicted by the can also found in the experiments.

Increasing vehicle performance requirements and virtualization of its development process require more understanding of physical background of tire behavior, especially in transient rolling conditions with combined slip. The focus of this research is physical description of transient generation of tire lateral force and aligning torque. Using acceleration measurement on the tire inner liner it was observed that the contact patch shape of the rolling tire changes nonlinearly with slip angle and becomes asymmetric. Optical measurement outside and inside the tire has clarified that carcass lateral bending features both shear and rotation angle of its cross-sections. A physical simulation model was developed, which considers the observed effects. A special iterative computing algorithm was proposed. The model was qualitatively validated using not only tire force and torque responses, but also deformation of the tire carcass. The model-based analysis explained which tire structural parameters are responsible for which criteria of tire performance. Contact patch shape change had a low impact on lateral force and aligning torque. Variation of carcass bending behavior perceptibly influenced aligning torque generation. As an example, the gained understanding was applied for feasibility analysis of a novel method to estimate the utilized friction potential rate of a rolling tire.

Scope of the work is the kinetic investigation of two fourth generation Ziegler-Natta catalysts as well as a supported metallocene catalyst for the polymerization of propylene under industrially relevant conditions and the development of simplified phenomenological kinetic models describing the polymerizations. Therein, the influence of different reaction conditions (temperature, pressure, hydrogen concentration) and, in particular, the effect of prepolymerization on catalyst kinetics as well as on polymer characteristics are studied. The Ziegler-Natta catalysts were investigated under gas-phase conditions in a 5 l horizontal stirred tank reactor operating in semi-batch mode. Both catalysts showed a similar kinetic behavior as well as hydrogen response at the different reaction conditions. Applying a prepolymerization led to an increase in activity at higher reaction temperatures as well as an improved polymer morphology. The impact of prepolymerization is catalyst specific and depends on the catalyst activity reached at main polymerization temperature. The supported metallocene catalyst was studied under bulk conditions in liquid propylene using a special 250 ml reaction calorimeter. A focus was set on procedure development (in-situ and external prepolymerization) with the target of defined prepolymerization conditions and early access to the kinetic profile. Final kinetic measurements were carried out using the developed external prepolymerization procedure. Based on the experimental studies, simplified phenomenological kinetic models are developed for each catalyst type enabling the quantitative description of the polymerization reactions at the different reaction conditions including the effect of prepolymerization. Main hypothesis for the mathematical description of the prepolymerization effect is that particle overheating at the beginning of the polymerization is the major reason for lower activities obtained when no prepolymerization is applied. For particle modeling, a quasi-homogeneous particle model is assumed considering particle growth and particle heat-transfer. As similar kinetic behaviors were observed for both Ziegler-Natta catalysts, the same kinetic model can be used; differences can only be described by the catalyst specific amount of polymerization active component. A similar kinetic model approach is used to describe the bulk polymerization with metallocene catalyst. Differences regarding the different polymerization regime, in particular monomer concentration in the polymer particle, hydrogen concentration in liquid phase, are considered. With the estimated sets of kinetic parameters, average activities and average molecular weights can be calculated as well as activity profiles of the catalysts can be quantitatively described at the different reaction conditions.

Consider manufactured parts, such as screws, car doors, lenses, or mirrors for lasers, for example. All these manufactured parts have to go through quality inspections checking if there are unwanted bumps or scratches that should not be there. There are different methods to measure the manufactured parts. The goal is to describe the measured object exactly by the data. This is one example for a so-called inverse problem.The application that we consider in the first part of this thesis is a data fusion process. The given dataset is a result of a deflectometric measurement process. These processes deal with object measurements of specular objects, such as lenses or mirrors. The aim is to calculate a dataset that describes the measured object exactly. The output data consists of two sets of separately measured types of data which suffer from different accuracy due to different sensitivity to noise. We resolve this issue with a data fusion process by solving a minimization problem which uses the more accurat data as a reference value and by duing so increases the other.Taking the gained insights we are able to develop new theories for image denoising. We formulate certain minimization problems in which use suitable reference values. In image denoising the reference value we want to use is an approximation of the image gradient vectors. Consequently, our approaches calculate such an approximation and use it as a reference value. Hence, our approaches are two-stage methods. Another approach to prevent the staircasing effect is to go to higher orders of differentiation within the regularization term. One approach was proposed in 2010 namely the total generalized variation (TGV) functional. We propose different kinds of combinations of these functionals. In this way we are able to formulate different minimization problems that are in some sense equivalent to the TGV problem. One advantage of some of these problems lies in the easy parameter choice rules that perform equally well as the TGV problem. Additionally, the duality gaps of these new problems are finite instead of infinite as it is usually the case in the primal-dual gap for the TGV problem. Hence, these can be used to create a reasonable stopping criterion for the optimization process. An additional advantage is the decreased runtime of the two-stage methods, since the problem is divided into two smaller problems.

Drug delivery systems can increase the pharmacokinetic and pharmacodynamic properties of various therapeutic agents. These systems can ensure a controlled release, improve the specificity of drugs to the target tissue, and therefore decrease side effects to the healthy surrounding tissue. In this work cell penetrating peptoids, which mimic the structure of peptides but exhibit increased stability, were investigated as organelle- and organ-specific carrier molecules. Several fluorescently labelled peptoid libraries, differing for example in length and side-chain composition, were synthesized and investigated with high-throughput screenings in different cell lines. The focus was on the elucidation of structure-function relationships for cellular uptake, intracellular localization and cytotoxicity. Furthermore, the organ targeting of the peptoids was analysed in in vivo studies by using zebrafish as model organism. In addition, the influence of the fluorescent dye on the localization and uptake of the peptoids was investigated.

This book contains a model-based analysis and optimisation of the Haber-Bosch designs for power-to-ammonia. The work presented helps to answer which Haber-Bosch design is suitable for the flexible operation and production by varying process variables: operational pressure, process feed temperature, process feed composition and feed flow rate. Among several Haber-Bosch design possibilities, two synthesis loops and five three-bed autothermal synthesis reactor systems are considered. The synthesis loops vary in terms of ammonia separation unit allocation, i.e. after and before a synthesis reactor system, and the reactor system configurations differ in inter-stage cooling methods. Besides, the operation and production flexibilities, design variants are also compared in terms of yield. All the Haber-Bosch designs allow operation for a large load range span via multi-variable optimisation and therefore are in principle suitable for power-to-ammonia.

The German Alumni Summer School 2018 on 'Education, science and cooperation between German Alumni for sustainable development and biodiversity conservation in Sub-Saharan Africa' was jointly organized by the Faculty of Geography-Department of Cartography, GIS and Remote Sensing, the Faculty of Biology and Psychology-Department of Conservation Biology, and the Karatina University, Kenya - School of Natural Resources and Environmental Studies. This summer school was funded by the German Academic Exchange Service (DAAD) and targeted to the German Alumni from Sub-Saharan Africa as well as scientist and experts from various discipline.The European Union being confronted with mass migration from Sub-Saharan Africa is currently working on a new political and economic strategy for Africa. Moreover German Government initiated and proposed a new level of equal cooperation between Africa and western countries in areas such as education, trade, business development and energy. The main idea is to limit the effects of climate change and avoid climate refugees, to prevent mass migration and to help create a future for Africa's youth', and underscores the current status and efforts of German development policy towards African countries.Sub-Saharan Africa comprises of 49 states with the highest population growth, and by the end of the 21st century the population is likely to triple. The average economic growth rate for Sub-Saharan Africa countries slowed down from 5.1% in 2010 to 1.4 % in 2016. Africa is still the world's poorest continent and widespread poverty is the primary cause of malnutrition and health problems. Catastrophes like famines and the recent hunger in Horn of Africa are additionally induced through climate change and land grabbing. Corruption, armed conflict, political and ethnic tension, terrorist activities, unstable state structures, national debt, dependence on global commodities markets, and inequitable world trade mechanisms are mainly responsible for this unstable and threatening situation. Biodiversity loss and diminishing of African wildlife due to habitat loss and poaching are as well the serious concern and calls for action.

The aim of this work is to develop and characterize widely tunable high-power diode lasers emitting at 976 nm, targeting non-linear frequency conversion applications. This was realized by a master oscillator power amplifier (MOPA) configuration, where the MO provides wavelength stabilization and tuning, while the PA ensures power amplification to the watt level. Two approaches of developing tunable laser sources were investigated.In the first approach, three types of monolithic multi-arm lasers were developed and characterized: two-arm (Y-branch), four- and six-arm distributed-Bragg reflector ridge waveguide (DBR-RW) lasers. Among the main findings of this work is that the performance of these lasers is strongly influenced by the intersection point between the individual arms and less affected by the bend structure. Thermal wavelength tuning of the developed laser sources is obtained by resistor-based micro-heaters embedded on top of the grating sections, where tuning of up to 7.5 nm can be achieved from each arm.The second approach uses sampled-grating (SG) structures to obtain wide wavelength tuning from a single laser cavity. While InP based SG lasers are well established, a milestone of this work is the first-time demonstration of fully functional GaAs-based SG lasers. Up to 21 nm of discrete wavelength tuning is achieved when operating a single SG heater with a SG mode spacing of about 2.3 nm. By operating both heaters, 23.5 nm of quasi-continuous tuning is obtained with a mode spacing of about 115 pm.Among the constructed MOPA systems is a Y-branch based MOPA system with 9.7 nm wavelength tuning and 5.5 W output power. Another system utilizes an SG laser, providing 23 nm of quasi-continuous wavelength tuning with an output power in the watt range.

Contrary to what we might expect, China has a higher proportion of women in senior executive roles than almost any other country in the world, far outstripping Western countries such as the USA, France or Germany ¿ even though there¿s not a gender quota in sight. What makes these female Chinese top managers different? To find out, BettinaAl-Sadik-Lowinski interviewed 35 Chinese women who she came into contact with through her work as an executive coach in China. The result is a unique research project, the ¿Shanghai Women¿s Career Lab¿, which analyses the mechanisms, attitudes and carefully planned career paths that allowed these women to rise to senior positions at multinational corporations in China. The analysis concludes that successful Chinese women and their careers can serve as role models for women around the world. Women can use the results of the research to make their own career planning more successful. By following these examples, they can build on their own strengths and rise to top management. The Shanghai Women¿s Career Lab also offers strategies for company leaders who want to promote talented women to top management positions.

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Unsere Erkenntnisse von der Evolution der frühen, terrestrisch angepassten Reptilien und Amphibien während einer Zeitspanne von vor 320 bis 270 Millionen Jahren auf dem Superkontinent Pangäa sind nur von einer sehr begrenzten Anzahl von Fossilfundstellen bekannt. Die meisten davon liegen in Nordamerika. Die Fossilfundstätte Bromacker in der unterpermischen Tambach-Formation bei Tambach-Dietharz (Deutschland) hat sich während der letzten 25 Jahre mit 11 neuen Arten zur bedeutendsten und produktivsten Fossillagerstätte für unterpermische, terrestrisch angepasste Wirbeltiere außerhalb der USA entwickelt. Der Bromacker enthält die besterhaltenen, terrestrischen Wirbeltierfossilien aus dem Unteren Perm (etwa vor 290 Millionen Jahren). Die Diversität der Fossilien bedeutet, dass der Bromacker das einzige gut dokumentierte Beispiel eines frühen terrestrischen Ökosystems repräsentiert. Das Buch enthält erstmals einen Überblick der Bedeutung des Bromackers mit zahlreichen Fossilabbildungen.Our understanding of the evolution of the earliest terrestrially adapted reptiles and amphibians during the time span 320 to 270 million years ago on the Pangaea supercontinent is known from only very restricted types of fossil localities, most of which are in North America. The fossil locality Bromacker in the Lower Permian Tambach Formation near Tambach-Dietharz (Germany) has developed during the last 25 years with 11 new species to be the most important and productive fossil locality for Lower Permian, terrestrially adapted vertebrates outside USA. The Bromacker locality produces the best preserved terrestrial vertebrate fossils from the Lower Permian time period (about 290 million years ago). The diversity of the fossils indicates that it represents the only fully documented example of an initial stage in the evolution of the modern terrestrial vertebrate ecosystem. The book contains first overview about the importance of the Bromacker with lot of fossil illustrations.

In dieser Arbeit wird eine schiffsbasierte CO2-Transportkette entwickelt und in Hinblick auf einen möglichst geringen Energiebedarf optimiert. Die einzelnen Komponenten der schiffsbasierten CO2-Transportkette werden in Aspen Plus V8.6 modelliert. Für die Verflüssigung von reinem CO2 werden Werte zwischen 7,3 kWh/t CO2 und 14,6 kWh/t CO2 ermittelt. Bei Anwesenheit von typischen CO2-Begleitstoffen aus Post-Combustion- und Oxyfuel-Abscheideprozessen ist der Energiebedarf höher. Für die Injektion von reinem CO2 wird ein Wert von 3,8 kWh/t CO2 für den elektrischen Energiebedarf und ein Wert von 26,5 kWh/t CO2 für den thermischen Energiebedarf ermittelt (Bohrkopfdruck 120 bar). Anschließend wird die entwickelte Transportkette für drei Beispielszenarien mit verschiedenen Transportkapazitäten, Einspeisecharakteristiken und Begleitstoff-Konzentrationen dimensioniert. Für die betrachteten Transportkapazitäten (1 Mt/a bis 20 Mt/a) erscheint der Einsatz von zwei Schiffen bei einer Transportstrecke von 100 km am sinnvollsten. Bei einer Transportstrecke von 1000 km wird für eine Transportkapazität von 20 Mt/a eine größere Anzahl an Schiffen benötigt.

Die Einschlussqualität von Plasmen in toroidalen Magnetfeldern wird maßgeblich durch den turbulenten Transport senkrecht zum Magnetfeld limitiert. Zonalströmungen sind dabei für die Fusionsforschung von großer Bedeutung, da vermutet wird, dass sie mit der Bildung von Transportbarrieren in Zusammenhang stehen. Diese mesoskopischen Scherströmungen tragen auf Grund ihrer Symmetrie nicht zum turbulenten Transport bei und können durch Verscherung von Wirbeln den radialen Transport unterdrücken. Dabei werden Zonalströmungen in einem Selbstorganisationsprozess von der umgebenden Plasmaturbulenz generiert indem Wirbel durch die Zonalströmung verkippt werden, was die Scherströmung weiter antreibt. Ein Maß für die Verkippung ist der sogenannte Reynolds-Stress, wobei der radiale Gradient des Flussflächenmittels die Antriebskraft der Zonalströmung darstellt. Die Dynamik gleicht dabei einer Räuber-Beute-Beziehung, bei der die Driftwellen die Beute für die Zonalströmungen sind. In Fusionsexperimenten konnte beim spontanen Übergang in ein verbessertes Einschlussregime (H-Mode) ein verstärktes Auftreten von Zonalströmungen mit den charakteristischen Räuber-Beute-Oszillationen nachgewiesen werden. Die Rolle und die genaue Wirkungsweise der Zonalströmungen bei dieser Bifurkation des Plasmaeinschlusses sind jedoch ungeklärt. Ein tieferes Verständnis der Physik der Zonalströmungen, speziell in komplexen Magnetfeldgeometrien, ist daher wünschenswert.Diese Arbeit beschäftigt sich vorwiegend mit der Untersuchung des Antriebsmechanismus von Zonalströmungen, im Speziellen mit der Abhängigkeit von der Magnetfeldgeometrie und dem Einfluss der Kollisionalität. Dazu wurden Messungen am Stellarator-Experiment TJ-K durchgeführt, in Plasmen, die dimensional ähnlich zu Randplasmen von Fusionsexperimenten sind. Die relativ geringen Plasmatemperaturen erlauben den Einsatz von Langmuir-Sonden im gesamten Einschlussgebiet. Mit einem poloidalen Sonden Array, bestehend aus 128 Sonden mit je 32 Sonden auf vier benachbarten Flussflächen, können Dichte- und Potentialfluktuationen mit hoher räumlicher und zeitlicher Auflösung gleichzeitig über den gesamten poloidalen Umfang aufgenommen werden.