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The dentate gyrus (DG) of the hippocampus is one of the stem cell housing niches in the adult mammalian brain. Canonical Wingless-type (Wnt) signals provided by the microenvironment are one of the major niche factors that regulate the differentiation of adult neural stem cells (aNSCs) towards the neuronal lineage. Wnts are part of a complex and diverse set of signaling pathways with a wide range of possible interactions. It remains unknown whether different canonical and non-canonical Wnt signals act in a stage-specific manner to regulate distinctive steps of adult hippocampal neurogenesis. Using in vitro assays on adult hippocampal NSCs, we identified an attenuation of canonical Wnt/ß-Catenin signaling responsiveness in the course of neuronal differentiation, while non-canonical Wnt/Planar Cell Polarity (PCP) signaling events progressively increased. Single-cell genetic manipulations were performed by using retroviral vectors to target dividing progenitor cells in the murine hippocampus. Retrovirus-mediated knockdown of ATP6AP2, a recently discovered core protein involved in both Wnt signaling pathways, revealed that the dual role of this adaptor protein is dependent on the signaling context that is present. We were able to confirm its dual role in neurogenic Wnt signaling in cultured adult hippocampal progenitors (AHPs) for both canonical Wnt signaling in proliferating AHPs and non-canonical Wnt signaling in differentiating AHPs. Specific knockdown of ATP6AP2 in neural progenitor cells in vivo resulted in a decreased induction of neuronal cell fate and severe morphological defects of newborn neurons, likely via altering both canonical and non-canonical Wnt signaling. Furthermore, in vivo knockdown of PCP core proteins CELSR1-3 and FZD3 mimicked the maturational defects of ATP6AP2-deficient neuroblasts but did not affect granule cell fate. In summary, the data presented here characterize a transition of Wnt signaling responsiveness from Wnt/ß-Catenin signaling to non-canonical Wnt/PCP signaling in the course of granule cell fate that was confirmed in a human pluripotent stem cell (hPSC)-based model of dentate granule neurogenesis. Our findings suggest that these pathways show stage-dependent activities and regulate distinct steps of adult dentate granule cell neurogenesis. Conclusively, we provide evidence for a stage-specific regulation of fate determination through the Wnt/ß-Catenin pathway and granule cell morphogenesis through the Wnt/PCP signaling pathway, including the FZD3-CELSR1-3 system. Additionally, the Wnt adaptor protein ATP6AP2 is involved in earlier and later stages of adult neurogenesis and its knockdown in vivo resembles all phenotypic features of both canonical and Wnt/PCP signaling mutants.
Governance and Management of Tourism in two Biosphere Reserves in Ecuador: Galapagos and Sumaco
(2014)
Tourism is multi-faceted phenomenon and various stakeholders, levels of government, and sectors are closely interlinked. Governmental and non-governmental institutions, local communities, diverse professionals, and different sectors and tourists do show various perspectives about the management of tourism. In this dissertation, a comprehensive analysis on the current situation of tourism in two biosphere reserves (Galapagos and Sumaco) in Ecuador is presented. Tourism is considered as one of the key strategies to promote environmental conservation and socio-economic development of local communities living in these places. UNESCO biosphere reserves are protected areas of extraordinary natural and cultural value, conceived as places for reconciliation between conservation and development. The concept of sustainable tourism can be seen as an umbrella that unites various forms of tourism in these protected areas (e.g. ecotourism, community-based tourism). The primary objective was to evaluate the main factors of success and failure in the management of tourism and its contribution to biodiversity conservation. Thus, a detailed review of the legal, political, and institutional framework of the country and a description of the two biosphere reserves (physical, biogeographic, demographic, socio-economic, institutional and legal elements) was given. Data collection for the case studies (Galapagos and Sumaco) was performed by the combination of qualitative and quantitative methods. As for qualitative tools, in-depth semi-structured interviews with the main stakeholders in both biosphere reserves were applied. Experts and specialists in the management of protected areas, as well as representatives of different sectors directly and indirectly associated with tourism were interviewed. Moreover, surveys were applied to two different target groups. Tourists were surveyed in order to establish their socio-demographic profile, travel preferences, and degree of knowledge about sustainable tourism, as well as their perception of the sustainability of tourism in the destinations visited. Furthermore, residents in both reserves were surveyed in order to find out about their socio-demographic characteristics, their main economic activities for supporting themselves and their attitude towards tourism, their level of knowledge about biosphere reserves, and their perception about advantages or disadvantages of living in a biosphere reserve. In general, although tourism is a concept that could be developed in accordance with the environment in these natural areas, in the case of Galapagos it is one of the main risk factors for the conservation of biodiversity in the archipelago due to the increasing number of tourists. In contrast, in Sumaco tourism could be an important sustainable alternative to mining, oil extraction and hydroelectric projects, which are the current threats to the conservation of the area. From the environmental point of view, there are serious problems in both reserves, mainly linked to the contamination of water resources. Such pollution imposes risks to the health to both, residents and tourists. The lack of freshwater is particularly critical in Galapagos, given its insular habitat. The invasion of exotic species in Galapagos is one of the most serious threats to the conservation, while deforestation in combination with illegal logging and mining activities is the greatest danger in Sumaco. In terms of sociocultural factors, migration processes undoubtedly shape the attitudes and values of the current population in both reserves. In Galapagos most residents are immigrants, whereas in Sumaco a significant portion are Kichwa people who belong to the area’s native population. In general, the inhabitants in both areas have not yet developed a true environmental awareness. The distribution of human population groups is also associated with the different types of tourism. In both reserves, tourist services offered by local communities have low quality standards and are targeted on a market segment consisting of tourists with a low budget. Thus, the community revenues obtained from tourism are generally only a small percentage of the total tourism market. This situation is much more noticeable in Galapagos where large companies that operate luxury cruises and hotels gain most of their revenues from tourism. Many of them have their headquarters in the main cities of Ecuador and abroad, which means that they pay their taxes in those cities and not in the places where they operate. Inequality in the distribution of the economic benefits of tourism leads to a situation of frustration and discontentment among the residents of the regions involved. Despite this situation, tourism is still a profitable business and residents try to make the most of it, no matter the cost impacts. Temporary and illegal tourism activities is often the normal state of the things: unregistered houses that offer rooms for tourists, taxi drivers who offer tours without being in possession of permits, tourist boat owners, tour guides and even large tourist companies that operate without legal licenses. This situation inevitably leads to a decrease of the quality of services, an uncontrolled increase of business, a consequent dumping of prices and the overall decline of the destination. Ultimately, this means fewer tourists, more environmental degradation and less economic benefits for residents. In this context, there is a serious conflict between the local community and large foreign companies. Governance and management of tourism are essential elements to ensure its development in a sustainable way. The country has a large number of laws, rules, regulations, and plans that regulate the development of sustainable tourism legally and institutionally, especially in protected areas. However, monitoring and law enforcement are major constraints for achieving proper management of tourism. This problem is particularly noticeable in small communities such as Galapagos and Sumaco where interpersonal relationships of kinship and friendship are close, which complicates control and regulation. There are some serious limitations regarding the technical and logistical capacity of the institutions responsible for controlling and managing the tourist activity; they consist mainly in the lack of staff and funding. Galapagos, given its special status, has increased the number of funding managers and staff members for controlling and management, but in many cases, these people are not fully qualified for their positions. Sumaco has only few tourism experts who can help to develop the tourism. The coordination and planning among all stakeholders involved in tourism is still a work in progress to ensure proper management of the tourist destinations. In any case, local communities are developing important initiatives in both biosphere reserves. After all, sometimes planning, coordination and local activities do not necessarily coincide with the national agenda. In general, in both biosphere reserves it is necessary to ensure higher standards of education, both formal and informal. Also it is urgent that the government as a regulating entity ensures the equitable participation of local communities in tourism benefits, control, monitoring, and law enforcement. Moreover, there is the need to encourage and ensure integrated planning of tourism in the different levels of government: local, regional, and national. Sustainable tourism means that the protection of cultural heritage and natural resources is granted at least the same level of importance as the involved economic interests. The unique nature that currently attracts tourists to Galapagos and Sumaco should be preserved not only for ensuring the continuity of the tourism activity itself, but also in order to safeguard biodiversity and natural resources for the coming generations. Responsible tourism practices which care about their social and environmental impacts are not necessarily opposed to economic interests. On the contrary, they need each other for a long-term development.
Modern cavity QED and cavity optomechanical systems realize the interaction of light with mesoscopic devices, which exhibit discrete (atom-like) energy spectra or perform micromechanical motion. In this thesis we have studied the crossover from the quantum regime to the classical limit of two prototypical models, the Dicke model and the generic optomechanical model. The physical problems considered in this approach range from a ground state phase transition, its dynamical response to general nonequilibrium dynamics including Hamiltonian and driven dissipative chaotic motion. The classical limit of these models follows from the classical limit of at least one of its subsystems. The classical equations of motion result from the respective quantum equations through the application of the semiclassical approximation, i.e., the neglect of quantum correlations. The approach of the results from quantum mechanics to the prediction of the classical equations can be obtained by subsequently decreasing the respective scaling parameter. In order to obtain exact results we have utilized advanced numerical methods, e.g., the Lanczos diagonalization method for ground state calculations, the Kernel Polynomial Method for dynamical response functions, Chebyshev recursion for time propagation, and quantum state diffusion for open system dynamics. We have studied the quantum phase transition of the Dicke model in the classical oscillator limit. Our work shows that in this limit the transition occurs already for finite spin length but with the same critical behavior as in the classical spin limit. We have derived an effective model for the oscillator degrees of freedom and have discussed the differences of both classical limits with respect to quantum fluctuations around the mean-field ground state and spin-oscillator entanglement. In this thesis we have proposed a variational ansatz for the Dicke model which extends the mean-field description through the inclusion of spin-oscillator correlations. The ansatz becomes correct in the limit of large oscillator frequency and in the limit of a large spin. For the latter it captures the leading quantum corrections to the classical limit exactly including the spin-oscillator entanglement entropy. We have studied the dynamics of spin and oscillator coherent states in the nonresonant Dicke model at weak coupling. In this regime periodic collapses and revivals of Rabi oscillations occur, which are accompanied by the buildup and decay of atom-field entanglement. The spin-oscillator wave function evolves into a superposition of multiple field coherent states that are correlated with the spin configuration. In our work we provide a description of the underlying dynamical mechanism based on perturbation theory. Our analysis shows that collapse and revival at nonresonance is distinguished from the resonant case treated within the rotating wave approximation by the appearance of two time scales instead of one. We have extended our study of the Dicke dynamics to the case of increasing spin length, as the system approaches the classical spin limit. We described the emergence of collective excitations above the ground state that converge to the coupled spin-oscillator oscillations observed in the classical limit. With increased spin length the corresponding Green functions thus reveal quantum dynamical signatures of the quantum phase transition. For the dynamics at larger coupling and energy, classical phase space drift and quantum diffusion hinders the direct comparison of quantum and classical observables. As we show in our work, signatures of classical quasiperiodic orbits can be identified in the Husimi phase-space functions of the propagated wave function and individual eigenstates with energies close to that of the quasiperiodic orbits. The analysis of the generic optomechanical system complements our study of cavity QED systems by a quantum dissipative system. In this thesis we have shown for the first time, how the route to chaos in the classical optomechanical system takes place, given as a sequence of consecutive period doubling bifurcations of self-induced cantilever oscillations. In addition to the semiclassical dynamics we have analyzed the possibility of chaotic motion in the quantum regime. Our results showed that quantum mechanics protects the optomechanical system against irregular dynamics. In sufficient distance to the semiclassical limit simple periodic orbits reappear and replace the classically chaotic motion. In this way direct observation of the dynamical properties of an optomechanical system makes it possible to pin down the crossover from quantum to classical mechanics.
The systemic renin-angiotensin system (RAS) is an endocrine system that is mainly known to regulate blood pressure, fluid and electrolyte balance as well as volume homeostasis in the body through different active metabolites, the angiotensin (Ang) peptides. In addition, local renin-angiotensin systems have been discovered in various tissues, including the islet of Langerhans. Starting with angiotensinogen, the precursor of all angiotensin peptides which is cleaved into the decapeptide Ang I by renin, the RAS is divided into three axes. The main classical RAS axis is composed of angiotensin converting enzyme (ACE), angiotensin (Ang) II, and the Ang II type 1 receptor (AT1R), whereas the two alternative RAS axes comprise either ACE2, Ang-(1-7) and the receptor Mas or the aminopeptidase N (APN), Ang IV and the insulin-regulated aminopeptidase (IRAP). The activation of the main ACE/Ang II/AT1R RAS axis has been associated with metabolic syndrome, type 2 diabetes mellitus, and islet dysfunction. The detrimental effects resulting from the pathological activation of this axis have been shown to be attenuated or even abolished by the pharmacological inhibition of components of the main RAS axis. However, the impact of the two alternative ACE2/Ang-(1-7)/Mas and APN/Ang IV/IRAP RAS axes on islet function is less well understood. Previous studies mainly focused on the possible protective actions of Ang-(1-7) via the receptor Mas in insulin-sensitive tissues and on well known risk factors of metabolic syndrome (insulin resistance, hyperglycemia, obesity, hypertension and dyslipidemia). Thus, the impact of this axis on β-cell function and, in particular, insulin production and release was examined in the present study. Glucose and fatty acids have been subjects of diabetic research because they are established pathophysiologically relevant features of the metabolic syndrome and are known to harm β cells, phenomena which are referred to as gluco- or lipotoxicity, respectively. The pathophysiologically relevant factors glucose, saturated fatty acid (FA) palmitic acid (PA), and the methyl ester of the omega-3 fatty acid docosahexaenoic acid (DHA-ME) were used in the present study to characterize the local β-cell RAS as well as β-cell function under pathophysiological conditions. Results of the present work demonstrate the expression of selected components of the RAS in isolated murine islets of Langerhans and the rat insulinoma cell line BRIN-BD11 under basal conditions. The alternative ACE2/Ang-(1-7)/Mas and APN/Ang IV/IRAP RAS axes were activated by high glucose in BRIN-BD11 cells after 24 h. Coincidently with these findings insulin production was found to be increased. In contrast, the expression of components of the main ACE/Ang II/AT1R RAS axis and the Ang II type 2 receptor (AT2R) were not affected under the same conditions (Härdtner et al., 2013). Both FAs, PA and DHA-ME were shown to alter the expression of components of the renin-angiotensin system in BRIN-BD11 cells. PA increased the expression of AT1R, the receptor of the main RAS axis, and of AT2R, whereas that of the receptor of the alternative ACE2/Ang-(1-7)/Mas RAS axis, Mas, appeared to be down-regulated at basal low glucose concentrations (5.5 mM). These effects were accompanied by a dose-dependent reduction of the insulin production and secretion. In contrast, DHA-ME augmented the expression of components of the ACE2/Ang-(1-7)/Mas axis and IRAP at low glucose concentrations, an effect which could be partially enhanced under high glucose conditions (25 mM). At basal glucose concentrations DHA-ME reduced the insulin secretion, whereas it was increased under high glucose conditions. However, the insulin mRNA amount remained unaffected by DHA-ME. Additionally, in contrast to glucose and palmitic acid, DHA-ME significantly increased the production of reactive oxygen species, at least hydrogen peroxide after 30 min. Expression alterations of components of the alternative ACE2/Ang-(1-7)/Mas RAS axis by glucose and PA correlated strongly with the corresponding insulin secretion and production. Therefore, an involvement of the ACE2/Ang-(1-7)/Mas RAS axis in the regulation of insulin secretion and production was hypothesized and validated in primary islets of Langerhans of both Mas-deficient and wild-type mice. Islets were exposed to the preferred natural ligand for Mas, Ang-(1-7), or to its pharmacological agonists or antagonists, respectively....
Chemistry and biology of Phenolics isolated from Myricaria germanica (L.) Desv. (Tamaricaceae)
(2014)
In accordance with the recent worldwide interest in plant phenolics, which emerges from their broad range of biological activities, particular emphasis has been focused, in the present thesis, on the constitutive phenolics of the extract of Myricaria germanica (L.) Desv. (Tamaricaceae). During the current thesis twenty phenolics (1 – 20) were isolated and identified from the aqueous/ethanol extract of the whole Myricaria germanica plant. The isolates include four hitherto unknown natural phenolics (2, 10, 12 and 20). Also, the cytotoxic activities of M. germanica extract, column fractions, and one new natural isolate against three different solid tumor cell lines, namely, breast cancer (MCF-7), prostate (PC-3), and liver (Huh-7) cancer cell using SRB viability assay have been investigated and first insights into mode of action have been obtained.
In this thesis we have revisited the formation of the excitonic insulator (EI), which realizes an exciton condensate. In contrast to optically created exciton condensates, the EI forms in thermal equilibrium and is solely driven by the Coulomb attraction between electrons and holes. The EI phase is anticipated to occur near the semimetal-semiconductor (SM-SC) transition at low temperatures. Depending from which side the EI is approached, it forms due to a BCS-type condensation of electron-hole pairs or a Bose-Einstein condensation (BEC) of excitons. The extended Falicov-Kimball model (EFKM) is the minimal model the EI can be described with. This model describes spinless fermions in two dispersive bands (f band and c band), that interact via a local Coulomb repulsion. The EFKM is also used to describe electronic ferroelectricity (EFE). Both phases, the EI and EFE-type ordering, are characterized by a spontaneous f-c hybridization in the EFKM. We have presented the EI phase, the EFE phase, and the orderings they compete with. Moreover, we have determined the ground-state phase diagram of the EFKM. We have focused particularly on the anticipated BCS-BEC crossover within the EI and have analyzed the formation scenarios. The exciton spectrum and the exciton density in the normal phase close to the critical temperature give information about relevant particles and therefore the nature of the transition. We have demonstrated that the whole EI is surrounded by a halo", that is, a phase composed of electrons, holes and excitons. However, on the SM side, only excitons with a finite momentum exist. These excitons appear only in a small number and barely influence the SM-EI transition. This phase transition is driven by critical electron-hole fluctuations, generated by electrons and holes at the Fermi surface. On the SC side, excitons with arbitrary momenta exist. Most notably, we have found the number of zero-momentum excitons to diverge at the SC-EI transition, signaling the BEC of these particles. Within the EI phase, there is a smooth crossover from the BCS regime to the BEC regime. One of the promising candidates to observe the EI experimentally, is the transition-metal dichalcogenide 1T-TiSe2. Strong evidences were found favoring an EI scenario of the charge-density-wave (CDW) formation in this material. However, some aspects point to a lattice instability to drive the CDW transition. We have addressed this issue by analyzing the recently discovered chiral property of the CDW in 1T-TiSe2. We have found that the EI scenario is insufficient to explain a stable, long range chiral charge ordering. Lattice degrees of freedom must be taken into account. In particular, nonlinear electron-phonon coupling and phonon-phonon interaction are crucial. By estimating appropriate model parameters for 1T-TiSe2, we have suggested a combination of excitonic and lattice instability to drive the CDW transition in this material. Experiments in 1T-TiSe2 and other materials suggest that the coupling to the lattice is non-negligible. We have extended therefore the model by an explicit exciton-phonon interaction, and have analyzed crucial effects of this interaction. While the single-particle spectrum is not modified qualitatively, the electron-hole pair spectrum changes significantly. The inclusion of the phonons lead to a massive collective mode in the ordered ground state in contrast to the case for vanishing exciton-phonon coupling, where the mode is acoustic. We have suggested that a gapless collective mode leads to off-diagonal long range order. This questions that the ground state for finite exciton-phonon coupling represents a condensate.
Magnetic reconnection is a fundamental plasma process where a change in field line connectivity occurs in a current sheet at the boundary between regions of opposing magnetic fields. In this process, energy stored in the magnetic field is converted into kinetic and thermal energy, which provides a source of plasma heating and energetic particles. Magnetic reconnection plays a key role in many space and laboratory plasma phenomena, e.g. solar flares, Earth’s magnetopause dynamics and instabilities in tokamaks. A new linear device (VINETAII) has been designed for the study of the fundamental physical processes involved in magnetic reconnection. The plasma parameters are such that magnetic reconnection occurs in a collision-dominated regime. A plasma gun creates a localized current sheet, and magnetic reconnection is driven by modulating the plasma current and the magnetic field structure. The plasma current is shown to flow in response to a combination of an externally induced electric field and electrostatic fields in the plasma, and is highly affected by axial sheath boundary conditions. Further, the current is changed by an additional axial magnetic field (guide field), and the current sheet geometry was demonstrated to be set by a combination of magnetic mapping and cross-field plasma diffusion. With increasing distance from the plasma gun, magnetic mapping results in an increase of the current sheet length and a decrease of the width. The control parameter is the ratio of the guide field to the reconnection magnetic field strength. Cross-field plasma diffusion leads to a radial expansion of the current sheet at low guide fields. Plasma currents are also observed in the azimuthal plane and were found to originate from a combination of the field-aligned current component and the diamagnetic current generated by steep in-plane pressure gradients in combination with the guide field. The reconnection rate, defined via the inductive electric field, is shown to be directly linked to the time-derivative of the plasma current. The reconnection rate decreases with increasing ratio of the guide field to the reconnection magnetic field strength, which is attributed to the plasma current dependency on axial boundary conditions and the plasma gun discharge. The above outlined results offer insights into the complex interaction between magnetic fields, electric fields, and the localized current flows during reconnection.
The impact of inbreeding under different environmental conditions and of artificial selection on cold tolerance was investigated in laboratory populations of the tropical butterfly Bicyclus anynana. The investigation focused on (1) the effects of inbreeding on several fitness-related traits and whether inbred individuals are more susceptible to stress, (2) interactions between inbreeding, genetic adaptation to cold stress and environmental conditions, (3) the effects of artificial selection and inbreeding in the adult stage in other developmental stages, and (4) the effect of inbreeding depression on the heat shock response. Environmental conditions are not constant over time; consequently organisms have to deal with environmental changes. Besides naturally fluctuating conditions, human-induced climate change may increase temperature changes as well as the severity of heat or cold waves. Temperature-stress resistance describes an organism’s ability to cope with stressful temperatures. Enhanced resistance to temperature stress can be reached by phenotypic plasticity or genetic adaptation. Plastic organisms are able to react fast to changing environmental conditions, whereas genetic adaptation is more important for long-term adaptation. Natural habitats may also be affected by human impact, causing habitat loss or fragmentation and changes in population structure. A decrease in the population size may result in inbreeding and inbreeding depression (ID). Consequences of inbreeding are well documented, and inbred individuals are predicted to be more sensitive to environmental stress than outbred individuals. The long term persistence of species and populations depends on their ability to adapt to novel conditions which in turn depends on genetic diversity. Therefore, studies of temperature resistance and its evolution in relation to inbreeding are very important. First a higher susceptibility of inbred individuals to environmental stress was determined in different populations of B. anynana. Inbreeding depression was revealed for several fitness-related traits, but not for immunity traits or heat tolerance. Temperature affected most traits, revealing the importance of temperature on ectotherms; just two hours of thermal stress affected important reproductive, life-history and immunity traits already. Importantly though, no evidence were found that inbred individuals are more susceptible to stressful temperatures than outbred individuals. Genetic adaptation and phenotypic plasticity can interact with one another, resulting in genotype-environmental interactions (G x E). The hypotheses tested here were that some genotypes are more plastic than others and that lines with increased cold stress resistance are less plastic with regard to cold resistance than control lines. To induce plastic responses the exposed lines differed in cold tolerance and inbreeding to different temperatures as well as different feeding regimes and measured fitness-related traits. Several interactions were detected in which a selection regime was involved, but these interactions did not show a clear overall pattern. In summary though, findings were that marginal impacts of directional selection and inbreeding on plastic responses and suggest that, at least for my study organism, the genetic architecture of fitness-related traits is not connected with the architecture of plastic responses. The next investigation concerned with the manifestation of genetic adaptation to produce one specific phenotype across development stages and possible trade-offs. The assumption tested was that there is a genetic link between different developmental stages to produce one definite phenotype by imposing selection in the adult stage only. Lines selected for increased cold resistance in the adult stage were used and increased cold resistance throughout all developmental stages was expected. However, higher cold resistance was found only in the adult stage and not in developmental stages. This could be either the result of a resource allocation trade-off between different stages or that there is no cold resistance phenotype. Thus, if selection takes place in the adult stage it does not affect the others. In the last experiment investigation was directed to determine whether there are negative inbreeding effects on the heat shock protein (HSP) response. Under stressful conditions, organisms produce the HSPs and they act as chaperons required for refolding and repairing of stress degraded proteins. Testing was oriented to find if inbreeding as a genetic stressor´ provokes a higher HSP expression and if there is evidence for higher temperature stress susceptibility on inbred individuals. Findings indeed showed a stronger HSP up-regulation in control compared to inbred lines with a negative inbreeding impact occurrence, which may causally underlie inbreeding depression.
The laser-matter interaction is a topic of current research. In this context, the interaction of intensive laser radiation with atomic clusters is of special interest. Du to the small cluster size, the laser field can penetrate the whole cluster volume, which leads to a high absorption of energy in the cluster. As a result, plasmas with high density and high temperature are produced. In the early phase of the laser-cluster interaction, free electrons are initially created in the cluster due to tunnel ionization or photoionization. Via collisions of these electrons with the cluster atoms, the ionization is increased and thus a dense nanoplasma is produced, which is heated by the laser. If free electrons leave the cluster during the laser-cluster interaction (outer ionization), a positive charge buildup is created. The associated charge repulsion finally can lead to the fragmentation of the cluster due to Coulomb explosion. Experimentally, interesting phenomena emerging from laser-excited clusters are observed, e.g., the creation of fast electrons, the production of highly charged ions, and X-ray emission. In this dissertation, the interaction of Gaussian laser pulses in the infrared regime with argon and xenon clusters is simulated by means of a nanoplasma model. Considering laser intensities in the non-relativistic regime, the relevant processes such as ionization, heating and expansion are theoretically described in this model with a set of coupled rate equations and hydrodynamic equations. One focus of the thesis is on the heating of the nanoplasma via inverse bremsstrahlung (IB), which is due to the absorption of laser photons in electron-ion collisions. In particular, the important question is investigated whether the consideration of the ionic structure – that means, the nuclear charge and the bound electrons – modifies the electron-ion collisions and thus the IB heating rate. Starting from a quantum statistical description, effective electron-ion potentials are used which account for both the screening due to the dense plasma and the inner ionic structure. Within the quantum mechanical first Born approximation, the consideration of the ionic structure leads to a drastic increase of the IB heating rate, in particular for high nuclear charges and low ionic charge states. However, for the parameters relevant in experiments, the applicability of the first Born approximation is questionable. Therefore, quantum mechanical calculations going beyond the first-order perturbation theory are performed. In addition, the IB heating rate is investigated with different classical methods. These are based either on transport cross sections for elastic electron-ion scattering or on classical simulations of inelastic scattering processes. Also within the classical approaches, the consideration of the ionic structure leads to an increase of the heating rate. However, this increase is shown to be only moderate. In a further part, the thesis focuses on the question how the dynamics of the laser-cluster interaction is influenced by the consideration of excited states. This is explored exemplarily for argon clusters excited by single or double laser pulses. The consideration of excitation processes in the nanoplasma leads to a decrease of the electron temperature and to an increase of the density of free electrons. Moreover, it is shown that the consideration of excitation processes results in an essential acceleration of the ionization dynamics. As a consequence, the mean ionic charge state in the plasma as well as the number of highly charged ions is significantly increased. For the population of ground states and excited states within an ionic charge state Z, collisional deexcitation processes play an important role. By means of an analytical relation between excitation and deexcitation cross sections, the rates for the respective processes in the presence of the laser field are calculated. The role of deexcitation processes is studied in detail, showing that the inclusion of these processes is essential for the correct theoretical description of the photon emission from laser-excited clusters. Based on these results, the photon yield is calculated for selected radiative transitions resulting from highly charged argon ions in the UV and X-ray regime.