cuvillier dez 2011 (53 risultati)

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Fagus sylvatica is one of the most important tree species in Europe. Due to its extensive distributionand dominance in its range, the performance of European forests in the contexts of perceived climate change will largely depend on the reaction of beech forests. Adequate information about the genetic diversity and structure of the species is indispensable for the conservation and sustainable utilization of the forests. Forest management systems currently in use in Germany are considered sustainable. However, their impact on the genetic diversity and spatial genetic structure of F. sylvatica is largely unknown. In these contexts, the main objectives of this dissertation were a) to assess the genetic diversity and differentiation of F. sylvatica at different spatial scales, b) to determine the level and magnitude of fine-scale genetic structure of the beech stands, c) to investigate the effect of forest management activities on the genetic diversity and fine-scale genetic structure of the beech stands independent of the marker used and d) to compare microsatellite and AFLP markers to estimate genetic diversity and structure of the stands, and their applicability to detect management impacts on genetic structure of the stand. 140 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -The main target of this work is the development of a risk assessment approach of groundwater contaminations in an urban area. A multidisciplinary approach was performed to assess degradation potential of contaminant species in soil and the inherent risk posed by anthropogenic substances. Experimental and theoretical methods range from chemical and biochemical to geoengineering applications. This especially concerns molecular biological, wet-chemistry techniques and Finite Element groundwater transport and reaction modelling. The spatial dimensions considered in the studies range from small laboratory to field scales. With regard to these applied methods the overall goal was a holistic risk approach to intertwine both, reactive transport of contaminants in groundwater and human health risks. An experimental area polluted with chlorinated ethenes and located in Braunschweig was chosen to validate the model. Based on repeated measurement campaigns pollutant concentrations as well as other environmental parameters and chemical data were determined and their quality was valued at assessed literature data. With the obtained experimental data a groundwater reactive transport model was established and validated. Further, to test the influence of the flow, transport and reaction model parameters a sensitivity analysis was performed. Based on this analysis, contaminant specific probabilities of occurrence were calculated with a Monte-Carlo simulation approach. Additionally, model optimisation techniques were applied to improve conformity of simulated and experimental data. It could be shown, that a simplified first-order reaction kinetic is only partially capable of rendering the measured field data. Hence, it was necessary to extend and improve the underlying degradation kinetics by means of modified Monod-equations. Here, the extension mainly comprises the introduction of inorganic electron acceptors as well as inhibiting reactions to refine the reductive dechlorination process of the chlorinated hydrocarbons. The next important step concerns the derivation of a health risk approach from the aforementioned concentration probabilities of occurrence. The combined model approach finally enables to calculate spatial and temporal health risk occurrence. 154 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Despite economic growths observed over the last half-century, global poverty and hunger still remain big challenges to overcome. Most of the poor people live in rural areas and depend on agriculture for livelihood. Advancements and access to agricultural innovations and skills are thus essential components for mass poverty alleviation. Apparently, a wide range of agricultural technologies are readily available for potential uptake; some of these technologies are specifically devised to address productivity improvements in crops that would otherwise be difficult to breed conventionally. However, the rate and scale of adoption of these technologies in developing countries is still less than expected. Technology adoption rates are even much lower in sub-Saharan Africa, a region that is persistently characterized by stagnated economic growth rates and deteriorating welfare conditions for its citizens.Literature on agricultural technology adoption and its actual or potential impacts in developing countries is vast. However, the general understanding of these effects is still hampered by the limited scope of robust economic studies. Particularly, most new technologies require farmers to substantially change traditional production practices in order to make significant gains, which often also requires access to new information and complementary input resources. The failure for existing studies to give considerable empirical detail to information and other related institutional constraints as well as the role of complementary inputs limits avenues for wider policy making. Moreover, it is reasonable that impact studies address broader welfare outcomes such as, the net effects of new technology on household income and food security. Although relatively more empirical evidence is available for income, quite little is known about the effect of new technology on improving household food security. The latter could be partly due to the conceptual complexities and costs involved in estimating household food security. 168 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -A regression analysis describes the dependency of random variables in the form of a functional relationship. One distinguishes between the dependent response variable and one or more independent influence variables. There is a variety of model classes and inference methods available, ranging from the conventional linear regression model up to recent non- and semiparametric regression models. The so-called generalized regression models form amethodically consistent framework incorporating many regression approaches with response variables that are not necessarily normally distributed, including the conventional linear regression model based on the normal distribution assumption as a special case. When repeated measurements are modeled in addition to fixed effects also random effects or coefficients can be included. Such models are known as Random Effects Models or Mixed Models. As a consequence, regression procedures are applicable extremely versatile and consider very different problems. In this dissertation regularization techniques for generalized mixed models are developed that are able to perform variable selection. These techniques are especially appropriate when many potential influence variables are present and existing approaches tend to fail. First of all a componentwise boosting technique for generalized linear mixed models is presented which is based on the likelihood function and works by iteratively fitting the residuals using weak learners. The complexity of the resulting estimator is determined by information criteria. For the estimation of variance components two approaches are considered, an estimator resulting from maximizing the profile likelihood, and an estimator which can be calculated using an approximative EM-algorithm. Then the boosting concept is extended to mixed models with ordinal response variables. Two different types of ordered models are considered, the threshold model, also known as cumulative model, and the sequential model. Both are based on the assumption that the observed response variable results from a categorized version of a latent metric variable. In the further course of the thesis the boosting approach is extended to additive predictors. The unknown functions to be estimated are expanded in B-spline basis functions, whose smoothness is controlled by penalty terms. Finally, a suitable L1-regularization technique for generalized linear models is presented, which is based on a combination of Fisher scoring and gradient optimization. Extensive simulation studies and numerous applications illustrate the competitiveness of the methods constructed in this thesis compared to conventional approaches. For the calculation of standard errors bootstrap methods are used. 176 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -W.B. Yeats: Realms of the Romantic Imagination shows us how Yeats¿s unorthodox approaches to poetic meaning, especially within modernist poetry, are part of the how the poet ¿astonishes¿ his contemporary readers. By astonishment, I refer to the Aesthetics of the Canon in which Frank Kermode explains how each generation of reader must always discover anew the wonder of transcendent meaning in poetry. What John Nkemngong Nkengasong does here is demonstrate how Yeats ultimately adhered to forms of creativity more aligned with Romanticism, undergirded with the sense of transcendence that is part of poetry itself and not necessarily part of the wider forms of belief which modernism engages and perhaps battles. 226 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Thermal diffusion (or the Soret effect) describes the diffusion of matter in the presence of atemperature gradient. Although this process is studied and applied since more than 100 years the underlying molecular mechanism in liquids is still far from being understood. Colloidal dispersions are versatile model systems to study the thermal diffusion behavior of large particles in a solvent. However, the synthesis of colloidal particles with identical morphology is a complex task. On the other hand aqueous surfactant solutions and microemulsions are promising systems to study the Soret effect. Compared to colloidal particles the aggregates form spontaneously and do not require any additional stabilisation. Furthermore the radius and the shape of the diffusing aggregates, as well as their interfacial tension can be systematically adjusted via the variation of the composition and temperature. In order to address some important aspects of the thermal diffusion behavior three different types of self-assembled surfactant systems were formulated and systematically studied: (i) At first the role of the ionic dye Basantol® Yellow 215, which causes an unexpected two-mode signal in the classical Thermal Diffusion Forced Rayleigh Scattering (TDFRS) experiment [Ning et al. Progr Colloid Polym Sci (2006) 133: 111¿115], is examined using the system H2O ¿ C12E6. Systematic phase behavior studies and small angle neutron scattering experiments (SANS) proved that the dye is incorporated into the aggregates like an ionic co-surfactant, influencing not only the thermal diffusion behavior but also the overall properties of the systems. These results strongly suggest that one should refrain from the use of surface-active dyes in TDFRS experiments on self-assembled systems. (ii) To study the dependence of the Soret coefficient ST on the radius of the aggregates and the slope of the interfacial tension, both being controversially discussed in the literature, different microemulsions of the type H2O ¿ C12E5 ¿n-alkane were formulated that allow for an isothermal study of these dependencies. Correlating the results of the systematic SANS and interfacial tension measurements with the Soret coefficient ST it was found that within the measurement range ST depends almost linearly on the droplet radius, the slope of the interfacial tension as well as on the product of both quantities. (iii) In the last part systematic surface tension and TDFRS measurements were performed in binary aqueous n-alkyl glucoside (CiGj) solutions to study the thermal diffusion behavior around the critical micelle concentration (cmc). The obtained results clearly show that the Soret coefficient exhibits an abrupt change at the cmc. To sum up, this work shows that aqueous surfactant systems and microemulsions are eminently suited to elucidate some of the underlying molecular mechanism of the Soret effect. 210 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Ever since the energy crisis in 1970¿s, hydrogen (H) has been regardedas one of the carbon-free secondary energy sources. In this context, hydrogen storage materials have been considered as possible candidates of clean energy storage media (see e.g. website of Department of Energy in US [DOE]). Hydrogen is the smallest and the lightest element and thus can be easily absorbed in interstitial sites of metal lattice. A pioneering work in this field is known by Sieverts [Siev29]. In some of metal alloys with tailored composition, considerable amount of hydrogen (several wt%) can be reversibly stored through metal/metal hydride (MH) phase transition, just by controlling pressure or temperature [Vught70]. Practically, some of them (LaNi5, TiFe) are really easy to handle and have already been utilized for technical applications like in fuel cell system [Iwas03] or in MH refrigerator [Uchi04] after intensive studies and developments in this field. Owing to its extraordinary high volume density and high stability, such metal hydrides still hold advantage to other storage methods like liquid hydrogen or high-pressure H2 gas tanks. Currently, further research and development is on the way focusing on improvement of gravimetric hydrogen density and reaction kinetics [Orimo07, Dornh07]. 194 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Enzymes with multicopper active sites play important roles in many biological processes. Recently a novel multinuclear copper site was discovered in N2O-Reductase and its exact structure and mechanism has been much discussed since then. The so called CuZ center contains a unique tetranuclear Cu4S2-Cluster, which is coordinated by seven histidine residues. Until now no synthetic model complex could be isolated that emulates the Cu4S2 core of the active site.In this thesis a new strategy towards such model systems is introduced. To mimic the nitrogen-rich environment of the copper ions, pyrazolate-based ligand scaffolds with chelating N-donor side arms are employed. The resulting binuclear metal complexes were isolated and fully characterized. Additionally the reactivity of these binuclear building blocks towards various sulfur-containing coligands and sulfur-transfer reagents was investigated. 206 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -The agriculture sector in Ghana is the backbone of the rural economy. Agriculture employs about 60 percent of the population and contributes significantly to the GDP of the country. It is also a major foreign exchange earner. However, low productivity and inefficient resource use have resulted in a substantial threat to the livelihoods of the population that depend on this sector. 282 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Tetragonales Zirconiumdioxid wird aufgrund seiner Biokompatibilität und mechanischen Eigenschaften für Implantate verwendet, die starken Beanspruchungen ausgesetzt sind. Alle konventionellen Bearbeitungsverfahren, auch unter Verwendung von Lasern bis in den Nanosekundenbereich, gehen jedoch mit Qualitätseinbußen am Endprodukt einher. Femtosekundenlaser dagegen ermöglichen einen präzisen schädigungsarmen Materialabtrag. Die Produktivität des Verfahrens wird an drei Anwendungsfeldern untersucht: der Mikrostrukturierung von Oberflächen, dem Ausschneiden von Materialblöcken sowie der Erzeugung von Nanopartikeln in Flüssigkeiten. Für jeden dieser Bereiche werden optimale Prozessbedingungen und Bearbeitungsparameter bestimmt. Erstmals demonstriert und untersucht wird unter anderem die Erzeugung stabiler Zirconiumdioxidnanopartikel durch Femtosekundenlaserabtrag in Flüssigkeiten. Anwendungsschwerpunkt der untersuchten Verfahren ist die Mikrostukturierung der Innenfläche von Zahnkronen: Durch lasererzeugte Gräben wird die Verklebung zwischen Probekörpern und einem Dentalbefestigungszement nachweislich verbessert. 116 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -Fagus sylvatica is one of the most important tree species in Europe. Due to its extensive distributionand dominance in its range, the performance of European forests in the contexts of perceivedclimate change will largely depend on the reaction of beech forests. Adequate informationabout the genetic diversity and structure of the species is indispensable for the conservation andsustainable utilization of the forests. Forest management systems currently in use in Germany areconsidered sustainable. However, their impact on the genetic diversity and spatial genetic structureof F. sylvatica is largely unknown. In these contexts, the main objectives of this dissertationwere a) to assess the genetic diversity and differentiation of F. sylvatica at different spatialscales, b) to determine the level and magnitude of fine-scale genetic structure of the beechstands, c) to investigate the effect of forest management activities on the genetic diversity andfine-scale genetic structure of the beech stands independent of the marker used and d) to comparemicrosatellite and AFLP markers to estimate genetic diversity and structure of the standsand their applicability to detect management impacts on genetic structure of the stand.Cuvillier Verlag, Nonnenstieg 8, 37075 Göttingen 138 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -The main target of this work is the development of a risk assessment approach of groundwater contaminations in an urban area. A multidisciplinary approach was performed to assess degradation potential of contaminant species in soil and the inherent risk posed by anthropogenic substances. Experimental and theoretical methods range from chemical and biochemical to geoengineering applications. This especially concerns molecular biological, wet-chemistry techniques and Finite Element groundwater transport and reaction modelling. The spatial dimensions considered in the studies range from small laboratory to field scales. With regard to these applied methods the overall goal was a holistic risk approach to intertwine both, reactive transport of contaminants in groundwater and human health risks. An experimental area polluted with chlorinated ethenes and located in Braunschweig was chosen to validate the model. Based on repeated measurement campaigns pollutant concentrations as well as other environmental parameters and chemical data were determined and their quality was valued at assessed literature data. With the obtained experimental data a groundwater reactive transport model was established and validated. Further, to test the influence of the flow, transport and reaction model parameters a sensitivity analysis was performed. Based on this analysis, contaminant specific probabilities of occurrence were calculated with a Monte-Carlo simulation approach. Additionally, model optimisation techniques were applied to improve conformity of simulated and experimental data. It could be shown, that a simplified first-order reaction kinetic is only partially capable of rendering the measured field data. Hence, it was necessary to extend and improve the underlying degradation kinetics by means of modified Monod-equations. Here, the extension mainly comprises the introduction of inorganic electron acceptors as well as inhibiting reactions to refine the reductive dechlorination process of the chlorinated hydrocarbons. The next important step concerns the derivation of a health risk approach from the aforementioned concentration probabilities of occurrence. The combined model approach finally enables to calculate spatial and temporal health risk occurrence.Cuvillier Verlag, Nonnenstieg 8, 37075 Göttingen 152 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -Despite economic growths observed over the last half-century, global poverty and hunger still remain big challenges to overcome. Most of the poor people live in rural areas and depend on agriculture for livelihood. Advancements and access to agricultural innovations and skills are thus essential components for mass poverty alleviation. Apparently, a wide range of agricultural technologies are readily available for potential uptake; some of these technologies are specifically devised to address productivity improvements in crops that would otherwise be difficult to breed conventionally. However, the rate and scale of adoption of these technologies in developing countries is still less than expected. Technology adoption rates are even much lower in sub-Saharan Africa, a region that is persistently characterized by stagnated economic growth rates and deteriorating welfare conditions for its citizens.Literature on agricultural technology adoption and its actual or potential impacts in developing countries is vast. However, the general understanding of these effects is still hampered by the limited scope of robust economic studies. Particularly, most new technologies require farmers to substantially change traditional production practices in order to make significant gains, which often also requires access to new information and complementary input resources. The failure for existing studies to give considerable empirical detail to information and other related institutional constraints as well as the role of complementary inputs limits avenues for wider policy making. Moreover, it is reasonable that impact studies address broader welfare outcomes such as, the net effects of new technology on household income and food security. Although relatively more empirical evidence is available for income, quite little is known about the effect of new technology on improving household food security. The latter could be partly due to the conceptual complexities and costs involved in estimating household food security.Cuvillier Verlag, Nonnenstieg 8, 37075 Göttingen 168 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -A regression analysis describes the dependency of random variables in the form of a functional relationship. One distinguishes between the dependent response variable and one or more independent influence variables. There is a variety of model classes and inference methods available, ranging from the conventional linear regression model up to recent non- and semiparametric regression models. The so-called generalized regression models form amethodically consistent framework incorporating many regression approaches with response variables that are not necessarily normally distributed, including the conventional linear regression model based on the normal distribution assumption as a special case. Whenrepeated measurements are modeled in addition to fixed effects also random effects or coefficients can be included. Such models are known as Random Effects Models or Mixed Models. As a consequence, regression procedures are applicable extremely versatile andconsider very different problems.In this dissertation regularization techniques for generalized mixed models are developed that are able to perform variable selection. These techniques are especially appropriate when many potential influence variables are present and existing approaches tend to fail. First of all a componentwise boosting technique for generalized linear mixed models is presented which is based on the likelihood function and works by iteratively fitting the residuals using weak learners. The complexity of the resulting estimator is determined by information criteria. For the estimation of variance components two approaches are considered, an estimator resultingfrom maximizing the profile likelihood, and an estimator which can be calculated using an approximative EM-algorithm. Then the boosting concept is extended to mixed models with ordinal response variables. Two different types of ordered models are considered, the threshold model, also known as cumulative model, and the sequential model. Both are based on the assumption that the observed response variable results from a categorized version of a latent metric variable. In the further course of the thesis the boosting approach is extendedto additive predictors. The unknown functions to be estimated are expanded in B-spline basis functions, whose smoothness is controlled by penalty terms. Finally, a suitable L1-regularization technique for generalized linear models is presented, which is based on acombination of Fisher scoring and gradient optimization. Extensive simulation studies and numerous applications illustrate the competitiveness of the methods constructed in this thesis compared to conventional approaches. For the calculation of standard errors bootstrap methods are used.Cuvillier Verlag, Nonnenstieg 8, 37075 Göttingen 176 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -W.B. Yeats: Realms of the Romantic Imagination shows us how Yeats's unorthodox approaches to poetic meaning, especially within modernist poetry, are part of the how the poet 'astonishes' his contemporary readers. By astonishment, I refer to the Aesthetics of the Canon in which Frank Kermode explains how each generation of reader must always discover anew the wonder of transcendent meaning in poetry. What John Nkemngong Nkengasong does here is demonstrate how Yeats ultimately adhered to forms of creativity more aligned with Romanticism, undergirded with the sense of transcendence that is part of poetry itself and not necessarily part of the wider forms of belief which modernism engages and perhaps battles.Cuvillier Verlag, Nonnenstieg 8, 37075 Göttingen 224 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -The substitution of fossil fuels by renewables is one way to contribute to a sustainable energy supply. Renewables had a share of 6.7 % of the total primary energy consumption in Germany in 2007. Biomass is the most important energy source among the renewables with a share of 5.1 % of the primary energy consumption. Although, the share of renewables is still relatively low, it has grown considerably in the last years from 2.6 % in 2000 to 6.7 % in 2007 due to several aid programmes in Germany. A further growth is expected due to national and European goals to increase the share of renewables in final energy consumption to 20 % in 2020. Longterm, the share of renewables shall be increased even to 50 %. In order to achieve these ambitious goals not only high-quality biomass but also biogenic residues and waste will play an important role in energy production from renewables. Besides already used biomass sources, e.g. firewood, wood residues from wood processing industry, treated wood, and partly straw, other biomass sources and biogenic residues, e.g. timbered wood residues, lop, residues from roadside, biogenic residues from agriculture as well as energy crops, are still unused. In Germany about 550 PJ of biogenic residues and waste are available for energy production each year. This could cover about 4 % of the current primary energy demand. The growing interest in utilization of these low-grade biomass sources is not only because of their availability but also due to their low prices. As a result of the high demand of wood both for material and energetic utilization as well as the limited availability of high-quality biomass, the fuel costs increased rapidly in the last years. However, high fuel costs prevent an economic operation of combustion plants, and thus the utilization of low-cost biomass resources becomes necessary. Reasons for the still limited exploitation of these biomass sources are the high costs of the conversion technologies for heat and power generation. These biomasses cannot be utilized in conventional combustion plants for wood without additional adaptations due to their different physical and chemical properties compared to wood. 158 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -Thermal diffusion (or the Soret effect) describes the diffusion of matter in the presence of atemperature gradient. Although this process is studied and applied since more than 100 years theunderlying molecular mechanism in liquids is still far from being understood. Colloidaldispersions are versatile model systems to study the thermal diffusion behavior of large particlesin a solvent. However, the synthesis of colloidal particles with identical morphology is acomplex task. On the other hand aqueous surfactant solutions and microemulsions are promisingsystems to study the Soret effect. Compared to colloidal particles the aggregates formspontaneously and do not require any additional stabilisation. Furthermore the radius and theshape of the diffusing aggregates, as well as their interfacial tension can be systematicallyadjusted via the variation of the composition and temperature. In order to address someimportant aspects of the thermal diffusion behavior three different types of self-assembledsurfactant systems were formulated and systematically studied: (i) At first the role of the ionicdye Basantol® Yellow 215, which causes an unexpected two-mode signal in the classicalThermal Diffusion Forced Rayleigh Scattering (TDFRS) experiment [Ning et al. Progr ColloidPolym Sci (2006) 133: 111-115], is examined using the system H2O - C12E6. Systematic phasebehavior studies and small angle neutron scattering experiments (SANS) proved that the dye isincorporated into the aggregates like an ionic co-surfactant, influencing not only the thermaldiffusion behavior but also the overall properties of the systems. These results strongly suggestthat one should refrain from the use of surface-active dyes in TDFRS experiments onself-assembled systems. (ii) To study the dependence of the Soret coefficient ST on the radius ofthe aggregates and the slope of the interfacial tension, both being controversially discussed in theliterature, different microemulsions of the type H2O - C12E5 -n-alkane were formulated thatallow for an isothermal study of these dependencies. Correlating the results of the systematicSANS and interfacial tension measurements with the Soret coefficient ST it was found that withinthe measurement range ST depends almost linearly on the droplet radius, the slope of theinterfacial tension as well as on the product of both quantities. (iii) In the last part systematicsurface tension and TDFRS measurements were performed in binary aqueous n-alkyl glucoside(CiGj) solutions to study the thermal diffusion behavior around the critical micelle concentration(cmc). The obtained results clearly show that the Soret coefficient exhibits an abrupt change atthe cmc. To sum up, this work shows that aqueous surfactant systems and microemulsions areeminently suited to elucidate some of the underlying molecular mechanism of the Soret effect.Cuvillier Verlag, Nonnenstieg 8, 37075 Göttingen 210 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -Enzymes with multicopper active sites play important roles in many biological processes. Recently a novel multinuclear copper site was discovered in N2O-Reductase and its exact structure and mechanism has been much discussed since then. The so called CuZ center contains a unique tetranuclear Cu4S2-Cluster, which is coordinated by seven histidine residues. Until now no synthetic model complex could be isolated that emulates the Cu4S2 core of the active site.In this thesis a new strategy towards such model systems is introduced. To mimic the nitrogen-rich environment of the copper ions, pyrazolate-based ligand scaffolds with chelating N-donor side arms are employed. The resulting binuclear metal complexes were isolated and fully characterized. Additionally the reactivity of these binuclear building blocks towards various sulfur-containing coligands and sulfur-transfer reagents was investigated.Cuvillier Verlag, Nonnenstieg 8, 37075 Göttingen 206 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -Ever since the energy crisis in 1970's, hydrogen (H) has been regardedas one of the carbon-free secondary energy sources. In this context, hydrogenstorage materials have been considered as possible candidates ofclean energy storage media (see e.g. website of Department of Energy inUS [DOE]). Hydrogen is the smallest and the lightest element and thuscan be easily absorbed in interstitial sites of metal lattice. A pioneeringwork in this field is known by Sieverts [Siev29]. In some of metal alloyswith tailored composition, considerable amount of hydrogen (several wt%)can be reversibly stored through metal/metal hydride (MH) phase transitionjust by controlling pressure or temperature [Vught70]. Practicallysome of them (LaNi5, TiFe) are really easy to handle and have alreadybeen utilized for technical applications like in fuel cell system [Iwas03] orin MH refrigerator [Uchi04] after intensive studies and developments inthis field. Owing to its extraordinary high volume density and high stabilitysuch metal hydrides still hold advantage to other storage methodslike liquid hydrogen or high-pressure H2 gas tanks. Currently, further researchand development is on the way focusing on improvement of gravimetrichydrogen density and reaction kinetics [Orimo07, Dornh07].Cuvillier Verlag, Nonnenstieg 8, 37075 Göttingen 194 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - Print on Demand Titel. Neuware -The agriculture sector in Ghana is the backbone of the rural economy. Agriculture employs about 60 percent of the population and contributes significantly to the GDP of the country. It is also a major foreign exchange earner. However, low productivity and inefficient resource use have resulted in a substantial threat to the livelihoods of the population that depend on this sector.Cuvillier Verlag, Nonnenstieg 8, 37075 Göttingen 280 pp. Englisch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Durch den Einsatz intelligenter eingebetteter Echtzeitsysteme werden zunehmend sichere und effiziente Automobile entwickelt. Internationale Standards wie die ISO 26262 stellen hierbei neue Anforderungen an die Methoden zur Spezifikation, Verifikation und Validierung. In dieser Arbeit wird eine agile, modellzentrierte Methode zur Spezifikation und zum systematischen Test von eingebetteten Systemen vorgestellt. Eine integrale Eigenschaft ist die Berücksichtigung von Echtzeitanforderungen im gesamten Entwicklungsprozess. Das Zeit-Benutzungsmodell ist das durchgängige Artefakt zur Spezifikation und zu den Aktivitäten der Qualitätssicherung. Die Methode wird an einem automobilen Funktionsbeispiel vorgestellt. Zwei durchgeführte Projekte ¿ ¿Energiemanagement im Hardware-in-the-Loop Test¿ und ¿Testgetriebene Entwicklung von Funktionen der aktiven Sicherheit im Modell-in-the-Loop Test¿ ¿ stellen die erzielten Verbesserungen dar. 178 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Hohe Laserleistungen im Dauerstrichbetrieb bei gleichzeitig guter Strahlqualität, kleinen Linienbreiten und geringem Leistungs- und Frequenzrauschen sind die Anforderungen an Lasersysteme, die in Gravitationswellendetektoren eingesetzt werden sollen, die nach dem Prinzip eines Michelson-Interferometers arbeiten. In der vorliegenden Arbeit werden Untersuchungen vorgestellt, mit denen das Laserkonzept für den Gravitationswellendetektor LIGO (Laser Interferometer Gravitational-Wave Observatory) weiter entwickelt wurde. In seiner aktuellen Ausbaustufe soll das LIGO Lasersystem um einen injektionsgekoppelten Nd:YAG Hochleistungsoszillator ergänzt werden, mit dessen Hilfe die Laserleistung von 35 W auf 165 W skaliert werden soll. Die Komplexität dieses Oszillators erlaubt nur bedingt eine genaue Untersuchung seiner Limitierungen in Ausgangsleistung und Strahlprofil. Daher wurde das System für die in dieser Arbeit vorgestellten Experimente stark vereinfacht, lässt aber trotzdem Rückschlüsse auf das LIGO-Lasersystem zu. Es wird ein asymmetrischer Stehwellenresonator verwendet, der aus zwei sich gegenüber stehenden, longitudinal gepumpten Nd:YAG Kristallen besteht. Zwischen den Kristallen befindet sich eine Doppelbrechungskompensation, die aus einer 4f-Abbildung und ein 90° Quarzrotator besteht. 162 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Die fortschreitende Ausrichtung der tierärztlichen Tätigkeit zu einer Dienstleistungbelegt deutlich einen strukturellen Wandel des Berufsbildes und zeigt diezunehmende Bedeutung betriebswirtschaftlicher Themen innerhalb der Veterinärmedizin. Das Ziel dieses Buches ist es, ein Konzept zu entwerfen, wie und mitwelchen Inhalten eine betriebswirtschaftliche Lehrveranstaltung in das Curriculumdes veterinärmedizinischen Studiums eingebunden werden kann.Für ein einheitliches Verständnis über den aktuellen Stand des tierärztlichenBerufsbildes werden zu Beginn die Entwicklungen der tierärztlichen Tätigkeit imAllgemeinen und der tierärztlichen Fort- und Weiterbildung im Speziellen analysiert(Kapitel 2). Anschließend fokussiert sich die weitere Betrachtung auf die für dieTiermedizin bedeutungsvollsten betriebswirtschaftlichen Themengebiete MarketingPraxismanagement und Finanzwirtschaft. Methodisch werden diese drei übergeordneten Gebiete in inhaltliche Schwerpunkte differenziert und eingehenderläutert. Der Bereich Marketing (Kapitel 3.2) unterteilt sich in die Wettbewerbsanalyse, die Außendarstellung und das Kundenmanagement. Der Abschnitt Praxismanagement (Kapitel 3.3) wird in die strategische und operative Planung, diePraxisorganisation, die Wahl der Praxisform, die Personalwirtschaft und dasQualitätsmanagement gegliedert. Im dritten Themengebiet Finanzwirtschaft (Kapitel3.4) werden die Schwerpunkte Kapitalbedarf, Finanzierung, tierärztlichesAbrechnungsverfahren und Rechnungswesen detailliert vorgestellt.Es werden jedoch keine neuen betriebswirtschaftlichen Theorien für die Erörterungder Thematik entwickelt. Ausgangspunkt ist vielmehr die vorhandene Literatur derallgemeinen Betriebswirtschaftslehre aus der gezielt diejenigen Ansätze herausgearbeitet und vorgestellt werden, die nach Meinung des Verfassers amgeeignetsten für eine Lehre im veterinärmedizinischen Studium sind. Diese Thesenwerden dann modifiziert und den spezifischen tiermedizinischen Anforderungenangepasst. Letztlich bilden die daraus gewonnen Erkenntnisse die inhaltlicheGrundlage für den am Schluss vorgestellten Lehrplan für eine Lehrveranstaltung mitder Bezeichnung ¿Tierärztliche Betriebswirtschaftslehre¿ (Kapitel 4.2). Das Zieldieser Veranstaltung sollte es sein, den Studierenden der Veterinärmedizin diekaufmännisch-wirtschaftlichen Zusammenhänge im Rahmen der tierärztlichenTätigkeit aufzuzeigen und verständlich zu machen. Die dadurch vermittelteGrundlage betriebswirtschaftlichen Wissens ist eine wesentliche Voraussetzung, umals Tierarzt erfolgreich tätig sein zu können. 240 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Schwankende und unsichere Nachfragemengen in der deutschen Automobilindustrie führen auf Seiten der Zulieferunternehmen zu einer ungünstigen Planungsgrundlage. Diese sind daraufhin gezwungen zusätzliche Ressourcen aufrecht zu erhalten, um eine mengen- und termingerechte Versorgung des Herstellers sicher zu stellen. Höhere Gesamtkosten für Lieferanten sowie steigende Beschaffungskosten für Automobilhersteller sind die Folge. In der vorliegenden Arbeit werden vier alternative Abrufkonzepte diskutiert und die hieraus resultierenden Kostensenkungspotentiale für die Lieferkette in mehreren Fallstudien und einer Befragung analysiert. Aufgrund einer ungleichen Verteilung der Effizienzgewinne durch eine effizientere Koordination der Informationsflüsse wird eine Systematik zur Klassifizierung von Zulieferunternehmen vorgestellt. 194 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Die Fortschritte in der Halbleitertechnik führten über die letzten Jahrzehnte zuausgereiften Leistungshalbleiterschaltern auf Basis von Silizium (Si). Um zukünftig die physikalischen Grenzen dieser Bauelemente erweitern zu können, ist der Einsatz eines Halbleitermaterials mit größerem Bandabstand ein Erfolg versprechender Ansatz. Hierzu zählt das Material Siliziumkarbid (SiC), welches robustere und effizientere Leistungshalbleiter und somit kompaktere Systeme in Aussicht stellt. In der Arbeit werden zunächst ausgewählte Anwendungen mit erhöhten Anforderungen (Automobil, Photovoltaik) vorgestellt, bei denen eine Erweiterung des Temperaturbereiches oder eine höhere Effizienz mittels SiC-Halbleiter vorteilig wären. Die aktuellen Si-Leistungshalbleiterbauelemente, deren Aufbau- und Verbindungstechnik, Verlustmechanismen und Kühlung stellen hierfür den Stand der Technik und somit die Vergleichsreferenz neuer Halbleiter dar. Die Unterschiede zwischen der SiC- und der Si-Technologie werden anhand der Materialeigenschaften und der darauf basierenden Halbleiterstrukturen erläutert. Die dynamischen und statischen Eigenschaften wurden experimentell an verfügbaren SiC-Mustern untersucht und unter Berücksichtigung gleicher Betriebsbedingungen und gleicher Chip-Flächen sowie Auslastungen der Si-Referenz gegenübergestellt. Anhand der Variation der Untersuchungsparameter werden weiter die Abhängigkeiten der Verlustanteile aufgezeigt, woraus günstige Anwendungsvoraussetzungen abgeleitet werden können. Die Ergebnisse spiegeln einen Vergleich zwischen den Technologien der untersuchten Si und SiC-Muster wieder, wobei die hierbei verfolgte Vorgehensweise auch auf andere Prototypen übertragbar ist. 214 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Private Militär- und Sicherheitsfirmen (PMSCs) sind spätestens seit dem Beginn des Afghanistan-Krieges 2001 und des einige Jahre später folgenden Krieges im Irak verstärkt in die öffentliche Wahrnehmung gerückt. Neben einer Reihe von ethischen, politischen und rechtlichen Fragen, die der Einsatz solcher Organisationen zweifellos aufwirft, ist die Branche bislang sowohl in medialöffentlicher wie in politischer Hinsicht vor allem durch eines gekennzeichnet: eine ausgesprochen ¿dünne¿ Faktenlage im Hinblick auf ihre Verfasstheit und viel Spekulation und Vermutung. Die vorliegende Arbeit verlässt den bislang vorherrschenden makroskopischen Untersuchungsrahmen und versucht, die Konstitution eines Sicherheitsbegriffs aus der Binnenperspektive einer PMSC und ihrer Mitglieder zu rekonstruieren. Die auf diese Weise in Form einer organisationssoziologischen explorativen Einzelfallstudie unter Rückgriff auf die Methodologie der Grounded Theory gewonnenen Ergebnisse liefern einerseits eine Reihe von Hinweisen und Ansatzpunkten, um den Umgang mit und die Einschätzung von PMSCs auf ein empirisches Fundament zu stellen. Zum anderen rückt der sozialwissenschaftlich amorphe Begriff der ¿Sicherheit¿ und seine konkrete Ausgestaltung und Operationalisierung in Abhängigkeit von organisationalen und Umweltvariablen in den Fokus des Interesses. Zu guter Letzt liefert die Kontextualisierung der gewonnenen Erkenntnisse mit dem in den letzten Jahren zunehmend populärer gewordenen Theorie- und Forschungsprogramm des soziologischen Neoinstitutionalismus konzeptionelle Anregungen und kann so die Weiterentwicklung dieses vielversprechenden Ansatzes unterstützen. 230 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -/ 236 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Seit den 90er Jahren taucht Nachhaltigkeit in der Politik und Wirtschaft immer häufiger als Leitbild, Zieldefinition oder symbolische Begrifflichkeit auf. Auf der Suche nach einem grundlegenden Nachhaltigkeitsverständnis lasst sich die Definition der Brundtland- Kommission von 1987 für eine nachhaltige Entwicklung heranziehen: ¿Entwicklung, die die Bedürfnisse der Gegenwart befriedigt, ohne zu riskieren, dass künftige Generationen ihre eigenen Bedürfnisse nicht befriedigen konnen¿.1 Unbestritten ist dabei das Verständnis von Nachhaltigkeit als ein integratives Mehrsäulenkonzept, welches ökonomische, ökologische und soziale Aspekte vereint.2 Damit repräsentiert Nachhaltigkeit, mit seinem Kerngedanken vom Ertrag und nicht von der Substanz zu leben, ein grundlegendes Konzept für ökonomisches Handeln. Eine dauerhafte und erfolgreiche ökonomische Entwicklung ist folglich ohne Berücksichtigung des Nachhaltigkeitsleitbildes nicht möglich. 240 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -In der vorliegenden Dissertation wird mit Methoden der experimentellen Wirtschaftsforschung überprüft, wie kulturelle Faktoren die Mitarbeitermotivation beeinflussen und ob ein Anreizsystem in China und Deutschland eine unterschiedliche Wirkung zeigt. Die Autorin stellt zunächst die chinesische und die deutsche Kultur gegenüber und arbeitet aus den bekanntesten Kulturstudien die typischen Verhaltensmuster in der Betriebspraxis heraus. Während die Daten kulturvergleichender Studien meistens durch Befragungen und Interviews gesammelt werden, wendet die Autorin zur Überprüfung der Erkenntnisse die quantitative Methode der experimentellen Wirtschaftsforschung an. Die Vorteile liegen darin, dass die Rahmenbedingungen eines Experiments kontrollierbar sind und damit ein bestimmter Faktor auch in mehreren Ländern zielgerichtet untersucht werden kann. Für die vorliegende Forschungsarbeit haben ca. 500 Studierende aus China und Deutschland an den Experimenten teilgenommen. In der ersten Experimentserie wurden materielle und immaterielle Anreize betrachtet. Während sich bei den materiellen Anreizen kaum Unterschiede in China und Deutschland ergaben, sind bei den immateriellen Anreizen signifikante Wirkungsunterschiede nachzuweisen. In der zweiten Experimentserie wurde die Reaktion der Probanden bei einer ungleichen Entlohnungssituation getestet. Entgegen der Erwartung wurden die deutschen Probanden durch die Bekanntmachung einer ungleichen Entlohnung für die gleiche Tätigkeit nicht demotiviert. 252 pp. Deutsch.

Taschenbuch. Condizione: Neu. This item is printed on demand - it takes 3-4 days longer - Neuware -Die Einbeziehung lokaler Gemeinschaften in das Management natürlicher Ressourcen ist in vielen Ländern Afrikas ein Erfolg versprechender Ansatz, um ökologische und sozioökonomische Ziele miteinander zu verbinden. Nach der Unabhängigkeit Namibias im Jahr 1990 haben sich die politischen und rechtlichen Rahmenbedingungen für die Bevölkerung auf kommunalem Land stark verändert. Unter bestimmten Voraussetzungen werden ihr die Verfügungsrechte an nutzbaren Naturressourcen übertragen. Unmittelbar damit verbunden sind staatliche Anforderungen und die Etablierung neuer Institutionen.Die vorliegende Studie untersucht die Stabilität dieser Institutionen und versucht eine Antwort auf die Frage zu finden, ob sie in der Lage sind, die nachhaltige Nutzung von Weide, Wasser und Wild zu gewährleisten und letztendlich der Komplexität eines integrierten Ressourcenmanagements gerecht zu werden. 244 pp. Deutsch.