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- Department Psychologie (8)
This thesis discusses challenges in IT security education, points out a gap between e-learning and practical education, and presents a work to fill the gap. E-learning is a flexible and personalized alternative to traditional education. Nonetheless, existing e-learning systems for IT security education have difficulties in delivering hands-on experience because of the lack of proximity. Laboratory environments and practical exercises are indispensable instruction tools to IT security education, but security education in conventional computer laboratories poses particular problems such as immobility as well as high creation and maintenance costs. Hence, there is a need to effectively transform security laboratories and practical exercises into e-learning forms. In this thesis, we introduce the Tele-Lab IT-Security architecture that allows students not only to learn IT security principles, but also to gain hands-on security experience by exercises in an online laboratory environment. In this architecture, virtual machines are used to provide safe user work environments instead of real computers. Thus, traditional laboratory environments can be cloned onto the Internet by software, which increases accessibility to laboratory resources and greatly reduces investment and maintenance costs. Under the Tele-Lab IT-Security framework, a set of technical solutions is also proposed to provide effective functionalities, reliability, security, and performance. The virtual machines with appropriate resource allocation, software installation, and system configurations are used to build lightweight security laboratories on a hosting computer. Reliability and availability of laboratory platforms are covered by a virtual machine management framework. This management framework provides necessary monitoring and administration services to detect and recover critical failures of virtual machines at run time. Considering the risk that virtual machines can be misused for compromising production networks, we present a security management solution to prevent the misuse of laboratory resources by security isolation at the system and network levels. This work is an attempt to bridge the gap between e-learning/tele-teaching and practical IT security education. It is not to substitute conventional teaching in laboratories but to add practical features to e-learning. This thesis demonstrates the possibility to implement hands-on security laboratories on the Internet reliably, securely, and economically.
The ultimate aim of this study is to better understand the relevance of weak electricity in the adaptive radiation of the African mormyrid fish. The chosen model taxon, the genus Campylomormyrus, exhibits a wide diversity of electric organ discharge (EOD) waveform types. Their EOD is age, sex, and species specific and is an important character for discriminating among species that are otherwise cryptic. After having established a complementary set of molecular markers, I examined the radiation of Campylomormyrus by a combined approach of molecular data (sequence data from the mitochondrial cytochrome b and the nuclear S7 ribosomal protein gene, as well as 18 microsatellite loci, especially developed for the genus Campylomormyrus), observation of ontogeny and diversification of EOD waveform, and morphometric analysis of relevant morphological traits. I built up the first convincing phylogenetic hypothesis for the genus Campylomormyrus. Taking advantage of microsatellite data, the identified phylogenetic clades proved to be reproductively isolated biological species. This way I detected at least six species occurring in sympatry near Brazzaville/Kinshasa (Congo Basin). By combining molecular data and EOD analyses, I could show that there are three cryptic species, characterised by their own adult EOD types, hidden under a common juvenile EOD form. In addition, I confirmed that adult male EOD is species-specific and is more different among closely related species than among more distantly related ones. This result and the observation that the EOD changes with maturity suggest its function as a reproductive isolation mechanism. As a result of my morphometric shape analysis, I could assign species types to the identified reproductively isolated groups to produce a sound taxonomy of the group. Besides this, I could also identify morphological traits relevant for the divergences between the identified species. Among them, the variations I found in the shape of the trunk-like snout, suggest the presence of different trophic specializations; therefore, this trait might have been involved in the ecological radiation of the group. In conclusion, I provided a convincing scenario envisioning an adaptive radiation of weakly electric fish triggered by sexual selection via assortative mating due to differences in EOD characteristics, but caused by a divergent selection of morphological traits correlated with the feeding ecology.
The separation of natural and anthropogenically caused climatic changes is an important task of contemporary climate research. For this purpose, a detailed knowledge of the natural variability of the climate during warm stages is a necessary prerequisite. Beside model simulations and historical documents, this knowledge is mostly derived from analyses of so-called climatic proxy data like tree rings or sediment as well as ice cores. In order to be able to appropriately interpret such sources of palaeoclimatic information, suitable approaches of statistical modelling as well as methods of time series analysis are necessary, which are applicable to short, noisy, and non-stationary uni- and multivariate data sets. Correlations between different climatic proxy data within one or more climatological archives contain significant information about the climatic change on longer time scales. Based on an appropriate statistical decomposition of such multivariate time series, one may estimate dimensions in terms of the number of significant, linear independent components of the considered data set. In the presented work, a corresponding approach is introduced, critically discussed, and extended with respect to the analysis of palaeoclimatic time series. Temporal variations of the resulting measures allow to derive information about climatic changes. For an example of trace element abundances and grain-size distributions obtained near the Cape Roberts (Eastern Antarctica), it is shown that the variability of the dimensions of the investigated data sets clearly correlates with the Oligocene/Miocene transition about 24 million years before present as well as regional deglaciation events. Grain-size distributions in sediments give information about the predominance of different transportation as well as deposition mechanisms. Finite mixture models may be used to approximate the corresponding distribution functions appropriately. In order to give a complete description of the statistical uncertainty of the parameter estimates in such models, the concept of asymptotic uncertainty distributions is introduced. The relationship with the mutual component overlap as well as with the information missing due to grouping and truncation of the measured data is discussed for a particular geological example. An analysis of a sequence of grain-size distributions obtained in Lake Baikal reveals that there are certain problems accompanying the application of finite mixture models, which cause an extended climatological interpretation of the results to fail. As an appropriate alternative, a linear principal component analysis is used to decompose the data set into suitable fractions whose temporal variability correlates well with the variations of the average solar insolation on millenial to multi-millenial time scales. The abundance of coarse-grained material is obviously related to the annual snow cover, whereas a significant fraction of fine-grained sediments is likely transported from the Taklamakan desert via dust storms in the spring season.
This Thesis was devoted to the study of the coupled system composed by El Niño/Southern Oscillation and the Annual Cycle. More precisely, the work was focused on two main problems: 1. How to separate both oscillations into an affordable model for understanding the behaviour of the whole system. 2. How to model the system in order to achieve a better understanding of the interaction, as well as to predict future states of the system. We focused our efforts in the Sea Surface Temperature equations, considering that atmospheric effects were secondary to the ocean dynamics. The results found may be summarised as follows: 1. Linear methods are not suitable for characterising the dimensionality of the sea surface temperature in the tropical Pacific Ocean. Therefore they do not help to separate the oscillations by themselves. Instead, nonlinear methods of dimensionality reduction are proven to be better in defining a lower limit for the dimensionality of the system as well as in explaining the statistical results in a more physical way [1]. In particular, Isomap, a nonlinear modification of Multidimensional Scaling methods, provides a physically appealing method of decomposing the data, as it substitutes the euclidean distances in the manifold by an approximation of the geodesic distances. We expect that this method could be successfully applied to other oscillatory extended systems and, in particular, to meteorological systems. 2. A three dimensional dynamical system could be modeled, using a backfitting algorithm, for describing the dynamics of the sea surface temperature in the tropical Pacific Ocean. We observed that, although there were few data points available, we could predict future behaviours of the coupled ENSO-Annual Cycle system with an accuracy of less than six months, although the constructed system presented several drawbacks: few data points to input in the backfitting algorithm, untrained model, lack of forcing with external data and simplification using a close system. Anyway, ensemble prediction techniques showed that the prediction skills of the three dimensional time series were as good as those found in much more complex models. This suggests that the climatological system in the tropics is mainly explained by ocean dynamics, while the atmosphere plays a secondary role in the physics of the process. Relevant predictions for short lead times can be made using a low dimensional system, despite its simplicity. The analysis of the SST data suggests that nonlinear interaction between the oscillations is small, and that noise plays a secondary role in the fundamental dynamics of the oscillations [2]. A global view of the work shows a general procedure to face modeling of climatological systems. First, we should find a suitable method of either linear or nonlinear dimensionality reduction. Then, low dimensional time series could be extracted out of the method applied. Finally, a low dimensional model could be found using a backfitting algorithm in order to predict future states of the system.
Since 1971, the Freudenthal Institute has developed an approach to mathematics education named Realistic Mathematics Education (RME). The philosophy of RME is based on Hans Freudenthal’s concept of ‘mathematics as a human activity’. Prof. Hans Freudenthal (1905-1990), a mathematician and educator, believes that ‘ready-made mathematics’ should not be taught in school. By contrast, he urges that students should be offered ‘realistic situations’ so that they can rediscover from informal to formal mathematics. Although mathematics education in Vietnam has some achievements, it still encounters several challenges. Recently, the reform of teaching methods has become an urgent task in Vietnam. It appears that Vietnamese mathematics education lacks necessary theoretical frameworks. At first sight, the philosophy of RME is suitable for the orientation of the teaching method reform in Vietnam. However, the potential of RME for mathematics education as well as the ability of applying RME to teaching mathematics is still questionable in Vietnam. The primary aim of this dissertation is to research into abilities of applying RME to teaching and learning mathematics in Vietnam and to answer the question “how could RME enrich Vietnamese mathematics education?”. This research will emphasize teaching geometry in Vietnamese middle school. More specifically, the dissertation will implement the following research tasks: • Analyzing the characteristics of Vietnamese mathematics education in the ‘reformed’ period (from the early 1980s to the early 2000s) and at present; • Implementing a survey of 152 middle school teachers’ ideas from several Vietnamese provinces and cities about Vietnamese mathematics education; • Analyzing RME, including Freudenthal’s viewpoints for RME and the characteristics of RME; • Discussing how to design RME-based lessons and how to apply these lessons to teaching and learning in Vietnam; • Experimenting RME-based lessons in a Vietnamese middle school; • Analyzing the feedback from the students’ worksheets and the teachers’ reports, including the potentials of RME-based lessons for Vietnamese middle school and the difficulties the teachers and their students encountered with RME-based lessons; • Discussing proposals for applying RME-based lessons to teaching and learning mathematics in Vietnam, including making suggestions for teachers who will apply these lessons to their teaching and designing courses for in-service teachers and teachers-in training. This research reveals that although teachers and students may encounter some obstacles while teaching and learning with RME-based lesson, RME could become a potential approach for mathematics education and could be effectively applied to teaching and learning mathematics in Vietnamese school.
Advances in biotechnologies rapidly increase the number of molecules of a cell which can be observed simultaneously. This includes expression levels of thousands or ten-thousands of genes as well as concentration levels of metabolites or proteins. Such Profile data, observed at different times or at different experimental conditions (e.g., heat or dry stress), show how the biological experiment is reflected on the molecular level. This information is helpful to understand the molecular behaviour and to identify molecules or combination of molecules that characterise specific biological condition (e.g., disease). This work shows the potentials of component extraction algorithms to identify the major factors which influenced the observed data. This can be the expected experimental factors such as the time or temperature as well as unexpected factors such as technical artefacts or even unknown biological behaviour. Extracting components means to reduce the very high-dimensional data to a small set of new variables termed components. Each component is a combination of all original variables. The classical approach for that purpose is the principal component analysis (PCA). It is shown that, in contrast to PCA which maximises the variance only, modern approaches such as independent component analysis (ICA) are more suitable for analysing molecular data. The condition of independence between components of ICA fits more naturally our assumption of individual (independent) factors which influence the data. This higher potential of ICA is demonstrated by a crossing experiment of the model plant Arabidopsis thaliana (Thale Cress). The experimental factors could be well identified and, in addition, ICA could even detect a technical artefact. However, in continuously observations such as in time experiments, the data show, in general, a nonlinear distribution. To analyse such nonlinear data, a nonlinear extension of PCA is used. This nonlinear PCA (NLPCA) is based on a neural network algorithm. The algorithm is adapted to be applicable to incomplete molecular data sets. Thus, it provides also the ability to estimate the missing data. The potential of nonlinear PCA to identify nonlinear factors is demonstrated by a cold stress experiment of Arabidopsis thaliana. The results of component analysis can be used to build a molecular network model. Since it includes functional dependencies it is termed functional network. Applied to the cold stress data, it is shown that functional networks are appropriate to visualise biological processes and thereby reveals molecular dynamics.
We analyze the asymptotic behavior in the limit epsilon to zero for a wide class of difference operators H_epsilon = T_epsilon + V_epsilon with underlying multi-well potential. They act on the square summable functions on the lattice (epsilon Z)^d. We start showing the validity of an harmonic approximation and construct WKB-solutions at the wells. Then we construct a Finslerian distance d induced by H and show that short integral curves are geodesics and d gives the rate for the exponential decay of Dirichlet eigenfunctions. In terms of this distance, we give sharp estimates for the interaction between the wells and construct the interaction matrix.
Gegenstand der Arbeit ist die Beanspruchungssituation des Pflegepersonals im Krankenhausbereich. Es wird der Frage nachgegangen, mit welchem Verhaltens- und Erlebensmuster Pflegepersonen ihren Anforderungen gegenübertreten und wie sie über die Art und Weise der persönlichen Auseinandersetzung mit den Anforderungen ihre Beanspruchungsverhältnisse mitgestalten.Den theoretischen Ausgangspunkt der Arbeit bilden salutogenetisch orientierte Ressourcenmodelle, insbesondere Beckers Modell der seelischen Gesundheit (Becker, 1982, 1986). Nach ihm hängt der Gesundheitszustand einer Person davon ab, wie gut es ihr gelingt, externe und interne Anforderungen mithilfe externer und interner Ressourcen zu bewältigen. Hier knüpft das in der Arbeit im Mittelpunkt stehende diagnostische Instrument AVEM (Arbeitsbezogenes Verhaltens- und Erlebensmuster; Schaarschmidt & Fischer, 1996, 2001) an, das die Erfassung interner Anforderungen und Ressourcen der Person sowie deren Zuordnung zu 4 Verhaltens- und Erlebensmustern gegenüber der Arbeit unter Gesundheits- und Motivationsbezug ermöglicht.Mit den Hypothesen wird angenommen, dass in Anbetracht der problematischen Arbeitsbedingungen in der Pflege eine Zurücknahme im Engagement bzw. eine Schutzhaltung vor nicht gewollten und als unangemessen empfundenen Anforderungen sowie wenig beeinflussbaren Bedingungen im Vordergrund stehen. Dort, wo zumindest partiell gesundheitsförderliche und als herausfordernd erlebte Arbeitsbedingungen anzutreffen sind, sollten günstigere Musterkonstellationen auftreten. Wir vermuteten, dass sich die ungünstigen Tendenzen bereits in der Berufsausbildung und in frühen Berufsjahren zeigen. Musterveränderungen in gesundheits- und persönlichkeitsförderlicher Hinsicht sollten durch gezielte Intervention herbeigeführt werden können. Schließlich nahmen wir an, dass die Tätigkeit und die mit ihr verbundenen Anforderungen und Ausführungsbedingungen musterspezifisch wahrgenommen werden.Zur Beantwortung der Fragen werden Ergebnisse aus verschiedenen Quer- und Längsschnittuntersuchungen herangezogen, die in Wiener Spitälern und Krankenpflegeschulen, aber auch in deutschen Krankenhäusern durchgeführt wurden. Zu Vergleichszwecken werden Befunde anderer Berufsgruppen dargestellt. Neben dem AVEM wurden weitere Fragebögen zu folgenden Inhalten eingesetzt: Arbeitsbezogene Werte, Erleben von Ressourcen in der Pflegetätigkeit, Belastungserleben und Objektive Merkmale der Arbeitstätigkeit.Die Ergebnisse bestätigen die Hypothesen in allen wesentlichen Punkten. Im Vergleich mit anderen Berufsgruppen fallen für die Pflegekräfte deutliche Einschränkungen im Arbeitsengagement auf. In Bezug auf die gesundheitlichen Risikomuster nimmt das Pflegepersonal eine Mittelstellung ein. Die Musterdifferenzierung in der Pflegepopulation lässt die stärksten Unterschiede in Abhängigkeit von der Position erkennen: Je höher die Position, desto größer ist der Anteil des Gesundheitsmusters und desto geringer ist die Resignationstendenz. Die meisten Risikomuster zeigen sich bei den Pflegekräften mit der niedrigsten Qualifikation. Für Pflegeschüler ist ein zeitweiliges starkes Auftreten von resignativen Verhaltens- und Erlebensweisen sowie eine kontinuierliche Abnahme des Engagements kennzeichnend. Dieser Trend setzt sich nach Aufnahme der Berufstätigkeit fort. Nur gezielte intensive personenorientierte Interventionen erwiesen sich als geeignet, Musterveränderungen in gesundheits- und persönlichkeitsförderlicher Hinsicht zu erreichen. Die Tätigkeit und die mit ihr verbundenen Anforderungen und Ausführungsbedingungen werden musterspezifisch wahrgenommen, wobei Personen mit eingeschränktem Engagement bzw. mit einer Resignationstendenz wesentliche Tätigkeitsmerkmale, denen persönlichkeits- und gesundheitsförderliche Wirkung zugesprochen wird, für sich als wenig wichtig beurteilen und sich mehr Defizite im Verhalten gegenüber Patienten bescheinigen.Die Ergebnisse verweisen darauf, dass im Pflegeberuf vor allem die Zurückhaltung im Engagement Anlass für eine kritische Betrachtung sein muss. Das Problem "Burnout" stellt sich in seiner Bedeutung relativiert dar. Günstigere Voraussetzungen für die Aufrechterhaltung und Förderung der Gesundheit bestehen dort, wo im konkreten Arbeitsfeld ein erweiterter Tätigkeits- und Handlungsspielraum sowie mehr Verantwortung vorliegen. Diese Befunde stehen in Einklang mit arbeitspsychologischen Ressourcenmodellen. Die Befunde zu den Pflegeschülern verweisen auf teilweise ungünstige Eignungsvoraussetzungen der Auszubildenden und legen nahe, die Angemessenheit der Anforderungen in den Krankenpflegeschulen zu hinterfragen. Hinsichtlich der Möglichkeiten der Veränderung der Muster in gesundheits- und motivationsdienlicher Weise brachten die Ergebnisse zum Ausdruck, dass verhaltensbezogenen Maßnahmen ohne gleichzeitige bedingungsbezogene Interventionen wenig Erfolg beschieden ist. Mit Blick auf die musterspezifische Wahrnehmung der Tätigkeit und der mit ihr verbundenen Anforderungen und Ausführungsbedingungen ist schließlich grundsätzlich festzuhalten, dass arbeitspsychologische Konzepte, die hohen bzw. komplexen Anforderungen und umfangreichen Freiheitsgraden in der Arbeit grundsätzlich persönlichkeits- und gesundheitsförderliche Wirkungen zuschreiben, einer Relativierung durch eine differentielle Perspektive bedürfen. Die vorgefundene Interaktion von Persönlichkeit und Arbeitsbedingungen hat zur Konsequenz, dass Verhaltens- und Verhältnisprävention in untrennbarem Zusammenhang gesehen werden sollten.
Biochemical and cellular characterization of filamin binding proteins in cross striated muscle
(2006)
Biochemical and physiological studies of Arabidopsis thaliana Diacylglycerol Kinase 7 (AtDGK7)
(2006)
A family of diacylglycerol kinases (DGK) phosphorylates the substrate diacylglycerol (DAG) to generate phosphatidic acid (PA) . Both molecules, DAG and PA, are involved in signal transduction pathways. In the model plant Arabidopsis thaliana, seven candidate genes (named AtDGK1 to AtDGK7) code for putative DGK isoforms. Here I report the molecular cloning and characterization of AtDGK7. Biochemical, molecular and physiological experiments of AtDGK7 and their corresponding enzyme are analyzed. Information from Genevestigator says that AtDGK7 gene is expressed in seedlings and adult Arabidopsis plants, especially in flowers. The AtDGK7 gene encodes the smallest functional DGK predicted in higher plants; but also, has an alternative coding sequence containing an extended AtDGK7 open reading frame, confirmed by PCR and submitted to the GenBank database (under the accession number DQ350135). The new cDNA has an extension of 439 nucleotides coding for 118 additional amino acids The former AtDGK7 enzyme has a predicted molecular mass of ~41 kDa and its activity is affected by pH and detergents. The DGK inhibitor R59022 also affects AtDGK7 activity, although at higher concentrations (i.e. IC50 ~380 µM). The AtDGK7 enzyme also shows a Michaelis-Menten type saturation curve for 1,2-DOG. Calculated Km and Vmax were 36 µM 1,2-DOG and 0.18 pmol PA min-1 mg of protein-1, respectively, under the assay conditions. Former protein AtDGK7 are able to phosphorylate different DAG analogs that are typically found in plants. The new deduced AtDGK7 protein harbors the catalytic DGKc and accessory domains DGKa, instead the truncated one as the former AtDGK7 protein (Gomez-Merino et al., 2005).
Charakterisierung von Transportmechanismen in der Speicheldrüse der Schabe Periplaneta americana
(2006)
Die Aktivierung der Speichelsekretion erfolgt in der innervierten Speicheldrüse der Schabe Periplaneta americana durch die biogenen Amine Dopamin (DA) und Serotonin (5-HT). Die Acini der Speicheldrüse sezernieren einen Primärspeichel, der in den Ausführgängen modifiziert wird. Die durch DA und 5-HT aktivierten Signalwege sowie die an der Elektrolyt- und Flüssigkeitssekretion bzw. Speichel-modifikation beteiligten Transportmechanismen sind weitgehend unbekannt. Mikrofluorometrische Ca<sup>2+-, Na<sup>+- und pH-Messungen in Kombination mit pharmakologischen Experimenten, biochemische Messungen der Aktivitäten von Ionentransport-ATPasen sowie videomikroskopische Analysen zu transepithelialen Wasserbewegungen wurden in dieser Arbeit durchgeführt. Sie sollten Informationen über die an der Speichelbildung und -modifikation beteiligten Transportmechanismen und die Signalwege liefern, welche durch DA und/oder 5-HT aktiviert werden. Wesentliche Ergebnisse dieser Arbeit waren: <ul> <li>Messungen des intrazellulären pH (pHi) in Gangzellen zeigten, dass isolierte Ausführgänge mit Acini bei Stimulierung mit DA und 5-HT stark ansäuerten. In isolierten Ausführgängen ohne Acini verursachte nur DA eine schwache Ansäuerung. Da nur die Ausführgänge dopaminerg innerviert sind, die Acini jedoch dopaminerg und serotonerg, zeigt dieses Ergebnis, dass die DA- und/oder 5-HT-induzierte Primärspeichelbildung die Ursache für die pHi-Änderungen in den Gangzellen ist. pHi-Messungen in den Gangzellen geben also auch Hinweise auf Transportvorgänge in den Acini.</li> <li> Der Na<sup>+-K<sup>+-2Cl<sup>--Symporter und der Cl<sup>--HCO3<sup>--Antiporter, gekoppelt mit dem Na<sup>+ H<sup>+-Antiporter (NHE) waren an der NaCl-Aufnahme in die peripheren Zellen der Acini zur Bildung des NaCl-reichen Primärspeichels beteiligt. Die Aktivität dieser Transporter hing von der CO2/HCO3<sup>--Verfügbarkeit ab und war Ca<sup>2+-abhängig.</li> <li>Die starke Ansäuerung in den Gangzellen hing nicht von der Aktivität der apikalen vakuolären Protonen-ATPase (V-H<sup>+-ATPase), aber von der Aktivität der basolateralen Na<sup>+-K<sup>+-ATPase ab, die anscheinend in den Ausführgängen die Speichelmodifikation energetisiert.</li> <li>In isolierten Ausführgängen mit Acini waren die V-H<sup>+-ATPase und Na<sup>+-abhängige Transporter (u. a. NHE) an der Erholung von einer DA-induzierten oder einer NH4Cl-Vorpuls-induzierten Ansäuerung in den Gangzellen beteiligt. Bei der Regulation des pHi in unstimulierten Gangzellen spielten diese Transporter keine Rolle.</li> <li>In isolierten Ausführgängen mit Acini induzierte DA in den Gangzellen einen Anstieg der [Na<sup>+]i und, zeitlich verzögert, auch der [Ca<sup>2+]i. Der [Na<sup>+]i-Anstieg war von der Aktivität der Acini abhängig und erfolgte möglicherweise über apikale Na+-Kanäle. Der [Ca<sup>2+]i-Anstieg war graduiert und tonisch. Der DA-induzierte [Na<sup>+]i-Anstieg in den Gangzellen und deren Depolarisation führten dazu, dass der basolaterale Na<sup>+-Ca<sup>2+-Antiporter in den Ca<sup>2+-Influx-Modus umkehrte. Die daraus resultierende tonische [Ca<sup>2+]i-Erhöhung könnte an der Regulation der Na<sup>+-Rückresorption beteiligt sein.</li> <li>Zum Nachweis transepithelialer Flüssigkeitsbewegungen in isolierten Ausführgängen wurde eine videomikroskopische Methode entwickelt. Isolierte Ausführgänge ohne Acini resorbierten im unstimulierten Zustand Flüssigkeit aus dem Ausführganglumen. Möglicherweise sezernieren die Acini auch im unstimulierten Zustand mit geringerer Rate einen Primärspeichel, der in den Ausführgängen resorbiert wird. Die Resorption war ATP-abhängig. Der ATP-verbrauchende Transportmechanismus konnte nicht identifiziert werden. Weder die Na<sup>+-K<sup>+-ATPase noch die V-H<sup>+-ATPase waren an der Resorption beteiligt.</li> </ul> Diese Arbeit trug zur Kenntnis der komplexen Funktionsweise von Speicheldrüsen in Insekten bei und erweiterte das lückenhafte Wissen über die zellulären Wirkungen biogener Amine in Insekten. Zudem wurden in dieser Arbeit viele Parallelen zu Funktionsweisen der Speicheldrüsen in Vertebraten deutlich.
In view of the importance of charge storage in polymer electrets for electromechanical transducer applications, the aim of this work is to contribute to the understanding of the charge-retention mechanisms. Furthermore, we will try to explain how the long-term storage of charge carriers in polymeric electrets works and to identify the probable trap sites. Charge trapping and de-trapping processes were investigated in order to obtain evidence of the trap sites in polymeric electrets. The charge de-trapping behavior of two particular polymer electrets was studied by means of thermal and optical techniques. In order to obtain evidence of trapping or de-trapping, charge and dipole profiles in the thickness direction were also monitored. In this work, the study was performed on polyethylene terephthalate (PETP) and on cyclic-olefin copolymers (COCs). PETP is a photo-electret and contains a net dipole moment that is located in the carbonyl group (C = O). The electret behavior of PETP arises from both the dipole orientation and the charge storage. In contrast to PETP, COCs are not photo-electrets and do not exhibit a net dipole moment. The electret behavior of COCs arises from the storage of charges only. COC samples were doped with dyes in order to probe their internal electric field. COCs show shallow charge traps at 0.6 and 0.11 eV, characteristic for thermally activated processes. In addition, deep charge traps are present at 4 eV, characteristic for optically stimulated processes. PETP films exhibit a photo-current transient with a maximum that depends on the temperature with an activation energy of 0.106 eV. The pair thermalization length (rc) calculated from this activation energy for the photo-carrier generation in PETP was estimated to be approx. 4.5 nm. The generated photo-charge carriers can recombine, interact with the trapped charge, escape through the electrodes or occupy an empty trap. PETP possesses a small quasi-static pyroelectric coefficient (QPC): ~0.6 nC/(m²K) for unpoled samples, ~60 nC/(m²K) for poled samples and ~60 nC/(m²K) for unpoled samples under an electric bias (E ~10 V/µm). When stored charges generate an internal electric field of approx. 10 V/µm, they are able to induce a QPC comparable to that of the oriented dipoles. Moreover, we observe charge-dipole interaction. Since the raw data of the QPC-experiments on PETP samples is noisy, a numerical Fourier-filtering procedure was applied. Simulations show that the data analysis is reliable when the noise level is up to 3 times larger than the calculated pyroelectric current for the QPC. PETP films revealed shallow traps at approx. 0.36 eV during thermally-stimulated current measurements. These energy traps are associated with molecular dipole relaxations (C = O). On the other hand, photo-activated measurements yield deep charge traps at 4.1 and 5.2 eV. The observed wavelengths belong to the transitions in PETP that are analogous to the π - π* benzene transitions. The observed charge de-trapping selectivity in the photocharge decay indicates that the charge detrapping is from a direct photon-charge interaction. Additionally, the charge de-trapping can be facilitated by photo-exciton generation and the interaction of the photo-excitons with trapped charge carriers. These results indicate that the benzene rings (C6H4) and the dipolar groups (C = O) can stabilize and share an extra charge carrier in a chemical resonance. In this way, this charge could be de-trapped in connection with the photo-transitions of the benzene ring and with the dipole relaxations. The thermally-activated charge release shows a difference in the trap depth to its optical counterpart. This difference indicates that the trap levels depend on the de-trapping process and on the chemical nature of the trap site. That is, the processes of charge detrapping from shallow traps are related to secondary forces. The processes of charge de-trapping from deep traps are related to primary forces. Furthermore, the presence of deep trap levels causes the stability of the charge for long periods of time.
When top sports performers fail or “choke” under pressure, everyone asks: why? Research has identified a number of conditions (e.g. an audience) that elicit choking and that moderate (e.g. trait-anxiety) pressure – performance relation. Furthermore, mediating processes have been investigated. For example, explicit monitoring theories link performance failure under psychological stress to an increase in attention paid to a skill and its step-by-step execution (Beilock & Carr, 2001). Many studies have provided support for these ideas. However, so far only overt performance measures have been investigated which do not allow more thorough analyses of processes or performance strategies. But also a theoretical framework has been missing, that could (a) explain the effects of explicit monitoring on skill execution and that (b) makes predictions as to what is being monitored during execution. Consequently in this study, the nodalpoint hypothesis of motor control (Hossner & Ehrlenspiel, 2006) was taken to predict movement changes on three levels of analysis at certain “nodalpoints” within the movement sequence. Performance in two different laboratory tasks was assessed with respect to overt performance (the observable result, for example accuracy in the target), covert performance (description of movement execution, for example the acceleration of body segements) and task exploitation (the utilization of task properties such as covariation). A fake competition (see Beilock & Carr, 2002) was used to invoke pressure. In study 1 a ball bouncing task in a virtual-reality set-up was chosen. Previous studies (de Rugy, Wei, Müller, & Sternad, 2003) have shown that learners are usually able to “passively” exploit the dynamical stability of the system. According to explicit monitoring theories, choking should be expected either if the task itself evokes an “active control” (Experiment 1) or if learners are provided with explicit instructions (Experiment 2). In both experiments, participants first went through a practice phase on day 1. On day 2, following the Baseline Test participants were divided into a High-Stress or No-Stress Group for the final Performance Test. The High-Stress Group entered a fake competition. Overt performance was measured by the Absolute Error (AE) of ball amplitudes from target height; covert performance was measured by Period Modulation between successive hits and task exploitation was measured by Acceleration (AC) at ball-racket impact and Covariation (COV) of impact parameters. To evoke active control in Exp. 1 (N=20), perturbations to the ball flight were introduced. In Exp. 2 (N=39) half of the participants received explicit skill-focused instructions during learning. For overt performance, results generally show an interaction between Stress Group and Test, with better performance (i. e. lower AE) for the High-Stress group in the final Performance Test. This effect is also independent of the Instructions that participants had received during learning (Exp. 2). Similar effects were found for COV but not for AC. In study 2 a visuomotor tracking task in which participants had to pursuit a target cross that was moving on an invisible curve. This curve consisted of 3 segments of 6 turning points sequentially ordered around the x-axis. Participants learned two short movement sequences which were then concatenated to form a single sequence. It was expected that under pressure, this sequence should “fall apart” at the point of concatenation. Overt Performance was assessed by the Root Mean Square Error between target and pursuit cross as well as the Absolute Error at the turning points, covert performance was measured by the Latency from target to pursuit turning and task exploitation was measured by the temporal covariation between successive intervals between turning points. Experiment 3 (intraindividual variation) as well as Experiment 4 (interindividual variation) show performance enhancement in the pressure situation on the overt level with matching results on covert and task exploitation level. Thus, contrary to previous studies, no choking under pressure was found in any of the experiments. This may be interpreted as a failure in the experimental manipulation. But certainly also important characteristics of the task are highlighted. Choking should occur in tasks where performers do not have the time to use action or thought control strategies, that are more relevant to their “self” and that are discrete in nature.
This study introduces a method for multiparallel analysis of small organic compounds in the unicellular green alga Chlamydomonas reinhardtii, one of the premier model organisms in cell biology. The comprehensive study of the changes of metabolite composition, or metabolomics, in response to environmental, genetic or developmental signals is an important complement of other functional genomic techniques in the effort to develop an understanding of how genes, proteins and metabolites are all integrated into a seamless and dynamic network to sustain cellular functions. The sample preparation protocol was optimized to quickly inactivate enzymatic activity, achieve maximum extraction capacity and process large sample quantities. As a result of the rapid sampling, extraction and analysis by gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF) more than 800 analytes from a single sample can be measured, of which over a 100 could be positively identified. As part of the analysis of GC-TOF raw data, aliquot ratio analysis to systematically remove artifact signals and tools for the use of principal component analysis (PCA) on metabolomic datasets are proposed. Cells subjected to nitrogen (N), phosphorus (P), sulfur (S) or iron (Fe) depleted growth conditions develop highly distinctive metabolite profiles with metabolites implicated in many different processes being affected in their concentration during adaptation to nutrient deprivation. Metabolite profiling allowed characterization of both specific and general responses to nutrient deprivation at the metabolite level. Modulation of the substrates for N-assimilation and the oxidative pentose phosphate pathway indicated a priority for maintaining the capability for immediate activation of N assimilation even under conditions of decreased metabolic activity and arrested growth, while the rise in 4-hydroxyproline in S deprived cells could be related to enhanced degradation of proteins of the cell wall. The adaptation to sulfur deficiency was analyzed with greater temporal resolution and responses of wild-type cells were compared with mutant cells deficient in SAC1, an important regulator of the sulfur deficiency response. Whereas concurrent metabolite depletion and accumulation occurs during adaptation to S deprivation in wild-type cells, the sac1 mutant strain is characterized by a massive incapability to sustain many processes that normally lead to transient or permanent accumulation of the levels of certain metabolites or recovery of metabolite levels after initial down-regulation. For most of the steps in arginine biosynthesis in Chlamydomonas mutants have been isolated that are deficient in the respective enzyme activities. Three strains deficient in the activities of N-acetylglutamate-5-phosphate reductase (arg1), N2 acetylornithine-aminotransferase (arg9), and argininosuccinate lyase (arg2), respectively, were analyzed with regard to activation of endogenous arginine biosynthesis after withdrawal of externally supplied arginine. Enzymatic blocks in the arginine biosynthetic pathway could be characterized by precursor accumulation, like the amassment of argininosuccinate in arg2 cells, and depletion of intermediates occurring downstream of the enzymatic block, e.g. N2-acetylornithine, ornithine, and argininosuccinate depletion in arg9 cells. The unexpected finding of substantial levels of the arginine pathway intermediates N-acetylornithine, citrulline, and argininosuccinate downstream the enzymatic block in arg1 cells provided an explanation for the residual growth capacity of these cells in the absence of external arginine sources. The presence of these compounds, together with the unusual accumulation of N-Acetylglutamate, the first intermediate that commits the glutamate backbone to ornithine and arginine biosynthesis, in arg1 cells suggests that alternative pathways, possibly involving the activity of ornithine aminotransferase, may be active when the default reaction sequence to produce ornithine via acetylation of glutamate is disabled.
Uncertainty about the sensitivity of the climate system to changes in the Earth’s radiative balance constitutes a primary source of uncertainty for climate projections. Given the continuous increase in atmospheric greenhouse gas concentrations, constraining the uncertainty range in such type of sensitivity is of vital importance. A common measure for expressing this key characteristic for climate models is the climate sensitivity, defined as the simulated change in global-mean equilibrium temperature resulting from a doubling of atmospheric CO2 concentration. The broad range of climate sensitivity estimates (1.5-4.5°C as given in the last Assessment Report of the Intergovernmental Panel on Climate Change, 2001), inferred from comprehensive climate models, illustrates that the strength of simulated feedback mechanisms varies strongly among different models. The central goal of this thesis is to constrain uncertainty in climate sensitivity. For this objective we first generate a large ensemble of model simulations, covering different feedback strengths, and then request their consistency with present-day observational data and proxy-data from the Last Glacial Maximum (LGM). Our analyses are based on an ensemble of fully-coupled simulations, that were realized with a climate model of intermediate complexity (CLIMBER-2). These model versions cover a broad range of different climate sensitivities, ranging from 1.3 to 5.5°C, and have been generated by simultaneously perturbing a set of 11 model parameters. The analysis of the simulated model feedbacks reveals that the spread in climate sensitivity results from different realizations of the feedback strengths in water vapour, clouds, lapse rate and albedo. The calculated spread in the sum of all feedbacks spans almost the entire plausible range inferred from a sampling of more complex models. We show that the requirement for consistency between simulated pre-industrial climate and a set of seven global-mean data constraints represents a comparatively weak test for model sensitivity (the data constrain climate sensitivity to 1.3-4.9°C). Analyses of the simulated latitudinal profile and of the seasonal cycle suggest that additional present-day data constraints, based on these characteristics, do not further constrain uncertainty in climate sensitivity. The novel approach presented in this thesis consists in systematically combining a large set of LGM simulations with data information from reconstructed regional glacial cooling. Irrespective of uncertainties in model parameters and feedback strengths, the set of our model versions reveals a close link between the simulated warming due to a doubling of CO2, and the cooling obtained for the LGM. Based on this close relationship between past and future temperature evolution, we define a method (based on linear regression) that allows us to estimate robust 5-95% quantiles for climate sensitivity. We thus constrain the range of climate sensitivity to 1.3-3.5°C using proxy-data from the LGM at low and high latitudes. Uncertainties in glacial radiative forcing enlarge this estimate to 1.2-4.3°C, whereas the assumption of large structural uncertainties may increase the upper limit by an additional degree. Using proxy-based data constraints for tropical and Antarctic cooling we show that very different absolute temperature changes in high and low latitudes all yield very similar estimates of climate sensitivity. On the whole, this thesis highlights that LGM proxy-data information can offer an effective means of constraining the uncertainty range in climate sensitivity and thus underlines the potential of paleo-climatic data to reduce uncertainty in future climate projections.
Corporate Governance von Nonprofit-Organisationen : Ausgewählte Aspekte der Organisation und Führung
(2006)
Bei der hier vorzustellenden Arbeit handelt es sich um eine qualitative Langzeitstudie, die sich mit dem politischem Interesse von acht jungen Frauen in Brandenburg im Alter von 16 bis 20/21 Jahren, dem Alter, in dem sich die bisher ausgebildete individuelle politische Identität stabilisiert, beschäftigt. Die politische Identitätsbildung jugendlicher Schüler und Schülerinnen zu unterstützen, sie auf die Übernahme der Rolle eines mündigen Bürgers bzw. einer mündigen Bürgerin vorzubereiten und demokratisches Bewusstsein zu fördern, gilt als wichtiges Ziel politischer Bildung in der Bundesrepublik Deutschland. In diesem Konzept verbinden sich die aus psychologischer Sicht zu bewältigenden Entwicklungsaufgaben, die mit der Suche nach einem Platz in der Gemeinschaft (Erikson 1950, 1959, 1968) verbunden sind, mit einer Sicht des politischen Systems, nach der dessen Stabilität maßgeblich von der Legitimation seiner Mitglieder und deren Bereitschaft zur politischen Beteiligung abhängt (Easton 1965, 1975). Die Herausbildung politischer Identität und die damit verbundenen Einstellungen und Verhaltensweisen Jugendlicher werden durch die Jugendforschung auf vielfältige Art und Weise untersucht. Nach dem politischen Identitätskonzept von Fend (1991) können politische Einstellungen und Verhaltensweisen nach affektiv-motivationalen, kognitiven und Verhaltensaspekten differenziert betrachtet werden. „Politisches Interesse“ kann als ein Konstrukt gesehen werden, welches im Schnittpunkt dieser drei Dimensionen liegt, da es sowohl motivationale, kognitive als auch handlungsbezogene Aspekte beinhaltet. Ihm kommt als motivationale Basis eine wichtige Bedeutung für die politische Exploration und politische Partizipation, und damit für die politische Identitätsentwicklung zu. In empirischen Untersuchungen wird immer wieder festgestellt, dass das für die politische Identitätsentwicklung so bedeutsame politische Interesse bei jungen Frauen im Vergleich zu jungen Männern niedriger ausfällt. Junge Frauen zeigen eine geringere Bereitschaft, sich mit Politik zu beschäftigen, sie fühlen sich politisch inkompetenter und glauben in stärkerem Maße als ihre männlichen Altersgenossen, keinen Einfluss auf die Politik nehmen zu können (vgl. z.B. Fend 1991; Hoffmann-Lange 1995; Verba et al. 1995; Gille et al. 2000; Torney-Purta et al. 2001; Jugendwerk der Deutschen Shell 2000; 2002; Brandenburger Jugendlängsschnitt). Diese vorgefundenen Geschlechtsunterschiede werden auf unterschiedliche Art und Weise erklärt. In der empirischen Jugendforschung wird im Allgemeinen eine Single-Item-Frage zur Erfassung von politischem Interesse genutzt. Diese kann nicht als ausreichend angesehen werden, wenn es darum geht, der These nachzugehen, dass weibliche Jugendliche nicht unbedingt politisch weniger, sondern politisch anders interessiert sind als männliche Jugendliche. Arbeiten, die das politische Interesse differenzierter erfassen, belegen dies bereits (vgl. z.B. Kuhn et al. 1998; Oesterreich 2002; Albert et al. 2003; Kuhn/Schmid 2004) Diese Arbeit soll dazu beitragen, dass politische Interesse von weiblichen Jugendlichen mittels qualitativer Daten weiterführend zu erklären. Anhand verschiedener Fragen wird dem politischen Interesse weiblicher Gymnasiastinnen aus Brandenburg in seinem Zusammenhang mit dem Informationsverhalten und dem Stellenwert, den Vertrauen in Politik und gegenüber Politikern für die Jugendlichen hat, nachgegangen.
Das Unterrichtsfach "Politische Bildung" in Brandenburg : eine qualitative und quantitative Studie
(2006)
The terrestrial biosphere impacts considerably on the global carbon cycle. In particular, ecosystems contribute to set off anthropogenic induced fossil fuel emissions and hence decelerate the rise of the atmospheric CO₂ concentration. However, the future net sink strength of an ecosystem will heavily depend on the response of the individual processes to a changing climate. Understanding the makeup of these processes and their interaction with the environment is, therefore, of major importance to develop long-term climate mitigation strategies. Mathematical models are used to predict the fate of carbon in the soil-plant-atmosphere system under changing environmental conditions. However, the underlying processes giving rise to the net carbon balance of an ecosystem are complex and not entirely understood at the canopy level. Therefore, carbon exchange models are characterised by considerable uncertainty rendering the model-based prediction into the future prone to error. Observations of the carbon exchange at the canopy scale can help learning about the dominant processes and hence contribute to reduce the uncertainty associated with model-based predictions. For this reason, a global network of measurement sites has been established that provides long-term observations of the CO₂ exchange between a canopy and the atmosphere along with micrometeorological conditions. These time series, however, suffer from observation uncertainty that, if not characterised, limits their use in ecosystem studies. The general objective of this work is to develop a modelling methodology that synthesises physical process understanding with the information content in canopy scale data as an attempt to overcome the limitations in both carbon exchange models and observations. Similar hybrid modelling approaches have been successfully applied for signal extraction out of noisy time series in environmental engineering. Here, simple process descriptions are used to identify relationships between the carbon exchange and environmental drivers from noisy data. The functional form of these relationships are not prescribed a priori but rather determined directly from the data, ensuring the model complexity to be commensurate with the observations. Therefore, this data-led analysis results in the identification of the processes dominating carbon exchange at the ecosystem scale as reflected in the data. The description of these processes may then lead to robust carbon exchange models that contribute to a faithful prediction of the ecosystem carbon balance. This work presents a number of studies that make use of the developed data-led modelling approach for the analysis and interpretation of net canopy CO₂ flux observations. Given the limited knowledge about the underlying real system, the evaluation of the derived models with synthetic canopy exchange data is introduced as a standard procedure prior to any real data employment. The derived data-led models prove successful in several different applications. First, the data-based nature of the presented methods makes them particularly useful for replacing missing data in the observed time series. The resulting interpolated CO₂ flux observation series can then be analysed with dynamic modelling techniques, or integrated to coarser temporal resolution series for further use e.g., in model evaluation exercises. However, the noise component in these observations interferes with deterministic flux integration in particular when long time periods are considered. Therefore, a method to characterise the uncertainties in the flux observations that uses a semi-parametric stochastic model is introduced in a second study. As a result, an (uncertain) estimate of the annual net carbon exchange of the observed ecosystem can be inferred directly from a statistically consistent integration of the noisy data. For the forest measurement sites analysed, the relative uncertainty for the annual sum did not exceed 11 percent highlighting the value of the data. Based on the same models, a disaggregation of the net CO₂ flux into carbon assimilation and respiration is presented in a third study that allows for the estimation of annual ecosystem carbon uptake and release. These two components can then be further analysed for their separate response to environmental conditions. Finally, a fourth study demonstrates how the results from data-led analyses can be turned into a simple parametric model that is able to predict the carbon exchange of forest ecosystems. Given the global network of measurements available the derived model can now be tested for generality and transferability to other biomes. In summary, this work particularly highlights the potential of the presented data-led methodologies to identify and describe dominant carbon exchange processes at the canopy level contributing to a better understanding of ecosystem functioning.
Es ist bekannt, dass Änderungen im Kohlenstoff- bzw. Stickstoffstaus der Pflanzen zu einer parallelen statt reziproken Änderung der kohlenstoff- und stickstoffhaltigen Primärmetabolite führen. Unter diesem Gesichtspunkt wurden in der vorliegenden Arbeit der Aminosäurestoffwechsel und der Sekundärstoffwechsel unter reduzierten Stickstoffbedingungen untersucht. Zur Beeinflussung des Stickstoffstoffwechsels wurden nitratmangelernährte Tabakwildtyppflanzen und Genotypen mit unterschiedlich stark reduzierter Nitratreduktase-Aktivität verwendet. Dieses experimentelle System erlaubt zusätzlich durch den Vergleich Nitrat defizienter Wildtyppflanzen mit Nitrat akkumulierenden NIA-Transformanten Prozesse zu identifizieren, die durch Nitrat gesteuert werden. Die Analysen der Primär- und Sekundärmetabolite wurde in allen Genotypen diurnal durchgeführt, um auch tageszeitlich abhängige Prozesse zu identifizieren. Die Analyse der absoluten Gehalte aller individuellen Aminosäuren enthüllte bei den meisten erstaunlich stabile diurnale Muster mit einem Anstieg während des Tages und einem Abfall in der Nacht in Wildtyppflanzen gewachsen mit ausreichend Nitrat. Dieses Ergebnis legt die Schlussfolgerung nahe, dass die Biosynthese der Aminosäuren koordiniert abläuft. In Pflanzen mit reduziertem Stickstoffstatus haben diese diurnalen Muster jedoch keinen Bestand. Die Kombination des erzeugten stickstoffbasierten Aminosäuredatensatz in Kombination mit einem bereits erzeugten Aminosäuredatensatz unter kohlenstofflimitierten Bedingungen von Matt et al. (2002) führte durch Hauptkomponentenanalyse (PCA) und Korrelationsanalyse zu dem Ergebnis, dass die Hypothese nach einer koordinierten Aminosäurebiosynthese nicht allgemeine Gültigkeit hat. Die PCA identifizierte Glutamin, Glutamat, Aspartat, Glycin, Pheny-lalanin und Threonin als Faktoren, die den Datensätzen ihre charakteristische Eigenschaft und deren Varianz verleihen. Die Korrelationsanalyse zeigte, dass die sehr guten Korrelationen der individuellen Aminosäuren untereinander in reduzierten Stickstoff- und Kohlenstoffbedingungen sich verschlechtern. Das Verhältnis einer einzelnen Aminosäure relativ zu den anderen führte zur Identifizierung einiger Aminosäuren, die individuelle Antworten auf Stickstoff- und/oder Kohlenstoffstatus zeigen, und/oder speziell auf Nitrat, Licht und/oder den E-nergiestatus der Thylakoidmembran. Glutamat beispielsweise verhält sich in den meisten Situationen stabil, Phenylalanin dagegen zeigt in jeder physiologischen Situation eine individuelle Antwort. Die Ergebnisse dieser Arbeit führen zu einer Erweiterung der Hypothese einer koordinierten Synthese der Aminosäuren dahingehend, dass diese nicht generell für alle Aminosäuren angenommen werden kann. Es gibt einige Aminosäuren deren, Anteile sich situationsbedingt anpassen. Die Reduktion des Stickstoffstatus in nitratmangelernährten Tabakwildtyppflanzen führte zu der, nach der „Carbon-Nutrient-Balance“ Hypothese erwarteten Verlagerung der kohlenstoffreichen Phenylpropanoide und des stickstoffreichen Nikotins. Die Erhöhung der Phenylpropanoidgehalte war nicht in der Nitrat akkumulierenden NIA-Transformante zu beobachten und somit konnte Nitrat als regulatorisches Element identifiziert werden. Ein Einfluss der Vorläufermetabolite konnte ausgeschlossen werden, da sowohl nitratmangelernährter Wildtyp als auch die Nitrat akkumulierende NIA-Transformante ähnliche Gehalte dieser aufwiesen. Genexpressionsanalysen über Mikroarray-Hybridisierung und quantitative RT-PCR zeigten, dass Nitrat durch noch nicht geklärte Mechanismen Einfluss auf die Expression einiger Gene nimmt, die dem Phenylpropanoidstoffwechsels zugeordnet sind. Aus der Arbeit hervorgegangene Veröffentlichungen: Christina Fritz, Natalia Palacios-Rojas, Regina Feil und Mark Stitt (2006) Regulation of Secondary Metabolism by the Carbon-Nitrogen Status in Tobacco: Nitrate Inhibits Large Sectors of Phenylpropanoid Metabolism. Plant Journal 46, 533 - 548 Christina Fritz, Petra Matt, Cathrin Müller, Regina Feil und Mark Stitt (2006) Impact of the Carbon-Nitrogen Status on the Amino Acid Profile in Tobacco Source Leaves. Plant, Cell and Environment 29 (11), 2009 - 2111
The primary objective of this work was to develop a laser source for fundamental investigations in the field of laser – materials interactions. In particular it is supposed to facilitate the study of the influence of the temporal energy distribution such as the interaction between adjacent pulses on ablation processes. Therefore, the aim was to design a laser with a highly flexible and easily controllable temporal energy distribution. The laser to meet these demands is an SBS-laser with optional active mode-locking. The nonlinear reflectivity of the SBS-mirror leads to a passive Q-switching and issues ns-pulse bursts with µs spacing. The pulse train parameters such as pulse duration, pulse spacing, pulse energy and number of pulses within a burst can be individually adjusted by tuning the pump parameters and the starting conditions for the laser. Another feature of the SBS-reflection is phase conjugation, which leads to an excellent beam quality thanks to the compensation of phase distortions. Transverse fundamental mode operation and a beam quality better than 1.4 times diffraction limited can be maintained for average output powers of up to 10 W. In addition to the dynamics on a ns-timescale described above, a defined splitting up of each ns-pulse into a train of ps-pulses can be achieved by additional active mode-locking. This twofold temporal focussing of the intensity leads to single pulse energies of up to 2 mJ at pulse durations of approximately 400 ps which corresponds to a pulse peak power of 5 MW. While the pulse duration is of the same order of magnitude as those of other passively Q-switched lasers with simultaneous mode-locking, the pulse energy and pulse peak power exceeds the values of these systems found in the literature by an order of magnitude. To the best of my knowledge the laser presented here is the first implementation of a self-starting mode-locked SBS-laser oscillator. In order to gain a better understanding and control of the transient output of the laser two complementary numerical models were developed. The first is based on laser rate equations which are solved for each laser mode individually while the mode-locking dynamics are calculated from the resultant transient spectrum. The rate equations consider the mean photon densities in the resonator, therefore the propagation of the light inside the resonator is not properly displayed. The second model, in contrast, introduces a spatial resolution of the resonator and hence the propagation inside the resonator can more accurately be considered. Consequently, a mismatch between the loss modulation frequency and the resonator round trip time can be conceived. The model calculates all dynamics in the time domain and therefore the spectral influences such as the Stokes-shift have to be neglected. Both models achieve an excellent reproduction of the ns-dynamics that are generated by the SBS-Q-switch. Separately, each model fails to reproduce all aspects of the ps-dynamics of the SBS-laser in detail. This can be attributed to the complexity of the numerous physical processes involved in this system. But thanks to their complementary nature they provide a very useful tool for investigating the various influences on the dynamics of the mode-locked SBS-laser individually. These aspects can eventually be recomposed to give a complete picture of the mechanisms which govern the output dynamics. Among the aspects under scrutiny were in particular the start resonator quality which determines the starting condition for the SBS-Q-switch, the modulation depth of the AOM and the phonon lifetime as well as the Brillouin-frequency of the SBS-medium. The numerical simulations and the experiments have opened several doors inviting further investigations and promising a potential for further improvement of the experimental results: The results of the simulations in combination with the experimental results which determined the starting conditions for the simulations leave no doubt that the bandwidth generation can primarily be attributed to the SBS-Stokes-shift during the buildup of the Q-switch pulse. For each resonator round trip, bandwidth is generated by shifting a part of the revolving light in frequency. The magnitude of the frequency shift corresponds to the Brillouin-frequency which is a constant of the SBS material and amounts in the case of SF6 to 240 MHz. The modulation of the AOM merely provides an exchange of population between spectrally adjacent modes and therefore diminishes a modulation in the spectrum. By use of a material with a Brillouin-frequency in the GHz range the bandwidth generation can be considerably accelerated thereby shortening the pulse duration. Also, it was demonstrated that yet another nonlinear effect of the SBS can be exploited: If the phonon lifetime is short compared to the resonator round trip time we obtain a modulation in the SBS-reflectivity that supports the modulation of the AOM. The application of an external optical feedback by a conventional mirror turns out to be an alternative to the AOM in synchronizing the longitudinal resonator modes. The interesting feature about this system is that it is ― although highly complex in the physical processes and the temporal output dynamics ― very simple and inexpensive from a technical point of view. No expensive modulators and no control electronics are necessary. Finally, the numerical models constitute a powerful tool for the investigation of emission dynamics of complex laser systems on arbitrary timescales and can also display the spectral evolution of the laser output. In particular it could be demonstrated that differences in the results of the complementary models vanish for systems of lesser complexity.
In this work approaches for new detection system development for an Analytical Ultracentrifuge (AUC) were explored. Unlike its counterpart in chromatography fractionation techniques, the use of a Multidetection system for AUC has not yet been implemented to full extent despite its potential benefit. In this study we tried to couple existing fundamental spectroscopic and scattering techniques that are used in day to day science as tool for extracting analyte information. Trials were performed for adapting Raman, Light scattering and UV/Vis (with possibility to work with the whole range of wavelengths) to AUC. Conclusions were drawn for Raman and Light scattering to be a possible detection system for AUC, while the development for a fast fiber optics based multiwavelength detector was completed. The multiwavelength detector demonstrated the capability of data generation matching the literature and reference measurement data and faster data collection than that of the commercial instrument. It became obvious that with the generation of data in 3-D space in the UV/Vis detection system, the user can select the wavelength for the evaluation of experimental results as the data set contains the whole range of information from UV/Vis wavelength. The detector showed the data generation with much faster speed unlike the commercial instruments. The advantage of fast data generation was exemplified with the evaluation of data for a mixture of three colloids. These data were in conformity with measurement results from normal radial experiments and without significant diffusion broadening. Thus conclusions were drawn that with our designed Multiwavelength detector, meaningful data in 3-D space can be collected with much faster speed of data generation.
Die Erfüllung deliktsrechtlichter Pflichten : durch Übertragung der Verkehrssicherung auf Dritte
(2006)
Das proinflammatorische Zytokin Interleukin-1 (IL-1) spielt eine zentrale Rolle bei Entzündungen und Infektionen. Die zellulären Antworten von IL-1 werden über den IL-1-Rezeptor Typ I (IL-1RI) vermittelt. Adapterproteine und die IL-1RI-assoziierte Kinase IRAK werden nach Ligandenbindung an den Rezeptor rekrutiert. Nach ihrer Phosphorylierung dissoziiert die IRAK vom IL-1RI-Komplex und aktiviert weitere Kinasen, was letztendlich zur Aktivierung von NF-κB und zur Induktion der Transkription von Genen führt. Für eine adäquate Immunantwort ist ein intrazellulärer reduzierter Status von Proteinthiolen essentiell. Vorausgegangene Untersuchungen an der murinen Thymomzelllinie EL-4 zeigten, dass die IL-1-Signalkaskade durch thiolmodifizierende Substanzen wie Menadion (MD) oder Phenylarsinoxid (PAO) gehemmt wird. Eine IL-1-abhängige Aktivierung von IL-1RI-assoziierte Kinasen oder NF-κB fand nicht mehr statt. Ziele dieser Arbeit waren: (i) mögliche Proteine, die für den Angriff von thiolmodifizierenden Agenzien ein Ziel sein könnten, zu identifizieren und (ii) den Einfluss nahrungsrelevanter und redoxaktiver Substanzen auf frühe Ereignisse der IL-1-Signaltransduktion wie der Bildung des IL-1RI-Komplexes zu untersuchen. Als Zellmodell wurden EL-4-Zellen mit stabil überexprimierter IRAK (EL-4<sup>IRAK) verwendet. Um die Bildung des IL-1RI-Komplexes, anschließende Phosphorylierungsereignisse und somit Kinase-Aktivitäten nachzuweisen, wurden Co-Präzipitations-Experimente und in vitro Kinase Tests durchgeführt. Die Markierung von Proteinthiolen erfolgte mit dem thiolspezifischen Reagenz Iodoacetyl-[<sup>125I]-Iodotyrosin ([<sup>125I]-IAIT). Die Vorbehandlung von EL-4<sup>IRAK-Zellen mit MD oder PAO führte zu einer Hemmung der Rekrutierung der IRAK an den IL-1RI und der anschließenden Phosphorylierungen. Zur Identifikation weiterer IL-1RI-assoziierter Proteine wurden IL-1RI-Immunpräzipitate zweidimensional aufgetrennt, Colloidal-Coomassie gefärbte Proteinspots ausgeschnitten und anschließend massenspektrometrisch mittels ESI-Q-TOF analysiert. Bei der Analyse wurden Proteine des Cytoskeletts wie z. B. Actin identifiziert. In Analogie zu den synthetischen Substanzen MD und PAO wurden nahrungsrelevante und redoxaktive Substanzen wie Curcumin (Gelbwurz) und Sulforaphan (Broccoli) eingesetzt, um zu untersuchen, ob sie bereits früh die IL-1-Signaltransduktion beeinflussen. Bislang sind antiinflammatorische Effekte dieser beiden Nahrungsinhaltsstoffe nur auf der Ebene der Zytokin-vermittelten Aktivierung von NF-κB beschrieben. Sowohl Curcumin als auch Sulforaphan blockierten konzentrationsabhängig die Assoziation der IRAK an den IL-1RI in EL-4<sup>IRAK-Zellen, wobei beide Substanzen unterschiedlich wirkten. Curcumin beeinflusste die IRAK-Aktivierung durch direkte Modifikation von Thiolen der IRAK ohne die Bindung von IL-1 mit dem IL-1RI zu beeinträchtigen. Sulforaphan hingegen induzierte auf mRNA- und Proteinebene die Expression von Tollip, welches durch PCR bzw. Western Blot nachgewiesen wurde. Tollip, ein negativer Regulator in TLR/IL-1RI-Signalkaskaden, könnte somit nach Induktion die IRAK-Aktivierung unterdrücken. Die Sulforaphan-abhängige Induktion der Tollip-Expression erfolgte jedoch nicht über Nrf2 und "antioxidant response element" (ARE)-regulierte Transkription, obwohl Sulforaphan ein bekannter Nrf2-Aktivator ist. Diese Ergebnisse veranschaulichen, dass die IRAK ein redoxsensitives Protein ist und für die Bildung des IL-1RI-Komplexes reduzierte Proteinthiole eine Voraussetzung sind. Der Angriffspunkt für die antiinflammatorische Wirkung der beiden Nahrungsbestandteile Curcumin und Sulforaphan ist die Bildung des IL-1RI-Komplexes als ein frühes Ereignis in der IL-1-Signalkaskade. Die Hemmung dieses Prozesses würde die in der Literatur beobachteten Inhibitionen der abwärts liegenden Signale wie die Aktivierung von NF-κB und die Induktion proinflammatorischer Proteine erklären.
Seit etwa zwei Jahrzehnten stellt die kognitive und neuronale Verarbeitung von Nomen und Verben einen bedeutsamen Forschungsschwerpunkt im Bereich der Neurolinguistik und Neuropsychologie dar. Intensive Forschungsbemühungen der letzten Jahre erbrachten eine Reihe von Ergebnissen, die jedoch überwiegend inkonsistent und widersprüchlich sind. Eine häufig vertretene Annahme im Bezug auf die neuronale Basis der Nomen und Verb Verarbeitung ist die so genannte anterior-posterior Dissoziation. Demnach werden Nomen in temporalen und Verben in frontalen Regionen der sprachdominanten, linken Hemisphäre verarbeitet. Die vorliegende Dissertation untersucht mit Hilfe der funktionellen Magnetresonanztomographie, welche kortikalen Regionen in den Abruf von Nomen und Verben beim stillen Bildbennen involviert sind. Ferner wird der Einfluss des Faktors age-of-acquisition (Erwerbsalter) auf die Hirnaktivierung beim Bildbenennen überprüft. Die Ergebnisse der Studie zeigen, dass der Abruf von Nomen und Verben ähnliche kortikale Aktivierungen in bilateral okzipitalen sowie links frontalen, temporalen und inferior parietalen Regionen hervorruft, wobei für Verben stärkere Aktivierungen in links frontalen und bilateral temporalen Arealen beobachtet wurden. Dieses Ergebnis widerspricht der Annahme einer anterior-posterior Dissoziation. Die beobachteten Aktivierungsmuster unterstützen dagegen die Auffassung, dass ein gemeinsames Netzwerk bestehend aus anterioren und posterioren Komponenten für die Verarbeitung von Nomen und Verben beim Bildbenennen verantwortlich ist. Die Studie ergab ferner, dass kortikale Aktivierungen beim Bildbenennen durch das Erwerbsalter moduliert werden. Dabei zeigten sich Aktivierungen für später erworbene Wörter im linken inferioren Frontallappen und im basal temporalen Sprachareal. Die Ergebnisse werden diskutiert und interpretiert vor dem Hintergrund aktueller kognitiver und neuroanatomischer Modelle der Sprachverarbeitung.
Die Arbeit beschäftigt sich im weitesten Sinne mit dem Verhältnis zwischen einem Text, seinen Lesern und deren Kritikern. Ihr Gegenstand sind Anspielungen auf zeitgeschichtliche Ereignisse in antiken literarischen Texten und die Vermutungen, die die Verfasser antiker exegetischer Literatur darüber äußern. Ziel ist dabei - anders als in den meisten einschlägigen Untersuchungen - nicht die Präsentation neuer Interpretationen zu den klassischen Texten, sondern die Analyse der aus Antike und Spätantike überlieferten Anspielungsdeutungen. An diese wird die Frage gestellt, welche Absichten, Ziele und Verfahren die Exegeten den von ihnen kommentierten Dichtern unterstellten und auf welchem Wege sie selbst zu ihrer Interpretation gelangten. Der Vergleich der einzelnen Interpretationen läßt typische Denkweisen und Interpretationsmuster hervortreten, ermöglicht einen Einblick in den geistigen Hintergrund der antiken Kommentatoren und schafft damit erst die Basis für die Beurteilung ihrer auch heute immer wieder diskutierten Vorschläge.
Die Anwendung eines Mikrosimulationsmodells als Instrument der wirtschaftswissenschaftlichen Forschung erfreut sich großer Beliebtheit. Die Verwendung dieses Modelltyps hat vor allem zwei Gründe. Zum einen sind die in den letzten Jahren extrem gesunkenen Kosten der Informationsverarbeitung ursächlich für die mittlerweile häufige Verwendung. Zum anderen besitzt diese Analyseform Eigenschaften, die kein anderes Instrument aufweist. Insbesondere für die Abschätzung der Verteilungswirkungen von Steuer- und Transferreformen ist die Mikrosimulation eine nahezu ideale Methode. Durch die Einbindung eines Nachfragesystems kann sowohl das Anwendungsgebiet eines Mikrosimulationsmodells erweitert als auch dessen potentielle Leistungsfähigkeit gesteigert werden. Die Arbeit hat im Wesentlichen die Beantwortung der Fragestellungen aus den folgenden zwei Fragenkomplexen zum Ziel: - Wann ist die Einbindung eines Nachfragesystems in Mikrosimulationsmodelle sinnvoll und wie kann ein solches System in das eigentliche Mikrosimulationsmodell integriert werden? - Welche Nachfragesysteme können aus den in Deutschland in Querschnittsform vorhandenen Mikrodatensätzen geschätzt werden und welche theoretischen Eigenschaften besitzen diese Systeme bzw. deren in einem zweistufigen Budgetierungsprozess einsetzbare Kombinationen?
Experimentelles Software Engineering durch Modellierung wissensintensiver Entwicklungsprozesse
(2006)
Die vorliegende Arbeit setzt sich aus zwei Teilstudien zusammen. In Teilstudie 1 wird die Stabilität eines allgemeinen Modells zu den Zusammenhängen zwischen Über- und Unterforderungsmerkmalen, sozialen Belastungen, Anforderungen und organisationalen Ressourcen einerseits sowie den Fehlbeanspruchungen emotionale Erschöpfung und Klientenaversion bzw. Distanzierungstendenzen andererseits für personenbezogene Dienstleistungstätigkeiten untersucht. Einbezogen wurden Ärztinnen und Ärzte, Pflegende und Mitarbeitende aus dem paramedizinischen Bereich sowie Lehrkräfte. Die deutlichsten positiven Zusammenhänge zeigen sich zwischen den Belastungen und der emotionalen Erschöpfung, wobei für die quantitative Überforderung die stabilsten Ergebnisse resultieren. Die Belastungen weisen über die emotionale Erschöpfung hinaus signifikante Zusammenhänge mit aversiven Gefühlen gegen Klientinnen und Klienten auf. Hinsichtlich der modellimplizierten Annahmen zu den positiven Zusammenhängen zwischen den Belastungen und der Distanzierung können in dieser Untersuchung zwar signifikante Ergebnisse, aber keine über die Stichproben hinweg stabilen Zusammenhänge gefunden werden. Die Annahmen zu einem negativen Zusammenhang zwischen den Anforderungen/Ressourcen und der Distanzierung können nur für die Anforderungsmerkmale bestätigt werden. In Teilstudie 2 erfolgte auf der Basis des in Teilstudie 1 entwickelten Arbeitsmodells eine vertiefte Betrachtung der Lehrkräftetätigkeit. Dabei wurden sowohl verschiedene Schulsystemebenen einbezogen als auch verschiedene Aufgabentypen unterschieden. Die Ergebnisse zeigen, dass auf organisationaler Ebene Gratifikationskrisen und mangelnde kollektive Selbstwirksamkeitserwartungen fehlbeanspruchungsrelevant sein können. Besonders deutliche Zusammenhänge mit den Fehlbeanspruchungen und der Distanzierung zeigen sich für die primäraufgabenbezogenen Belastungen. Auch die Reziprozitätseinschätzungen in Bezug auf Schülerinnen und Eltern zeigen diesbezüglich ähnliche, wenn auch weniger deutliche, Zusammenhänge. Die Ergebnisse zu den Personmerkmalen lassen darauf schliessen, dass die Rolle der Person bei der Burnoutentwicklung nicht unterschätzt werde sollte. Als praktische Implikationen der Untersuchungsergebnisse werden u.a. Vorschläge für eine Stärkung der unterrichtsbezogenen und der klassenübergreifenden Kooperation, für eine Optimierung der Organisationsstruktur und eine „Professionalisierung“ der Organisation sowie für eine weiterführende Erarbeitung schulhausspezifischer Konzepte und Leitlinien gemacht. Es wird die Frage gestellt, ob die Lehrkräftetätigkeit sinnvollerweise als Lebensberuf verstanden werden sollte. Schliesslich wird auf die Bedeutung der Distanzierungsfähigkeit und der Selbstwirksamkeitserwartungen der Lehrkräfte hingewiesen.
Frauenrechte in Friedensabkommen : eine Analyse der Abkommen von Dayton, Arusha und Petersberg
(2006)
Sucrose synthase (Susy) is a key enzyme of sucrose metabolism, catalysing the reversible conversion of sucrose and UDP to UDP-glucose and fructose. Therefore, its activity, localization and function have been studied in various plant species. It has been shown that Susy can play a role in supplying energy in companion cells for phloem loading (Fu and Park, 1995), provides substrates for starch synthesis (Zrenner et al., 1995), and supplies UDP-glucose for cell wall synthesis (Haigler et al., 2001). Analysis of the Arabidopsis genome identifies six Susy isoforms. The expression of these isoforms was investigated using promoter-reporter gene constructs (GUS) and real time RT-PCR. Although these isoforms are closely related at the protein level they have radically different spatial and temporal patterns of expression in the plant with no two isoforms showing the same distribution. More than one isoform is expressed in all organs examined. Some of them have high but specific expression in particular organs or developmental stages whilst others are constantly expressed throughout the whole plant and across various stages of development. The in planta function of the six Susy isoforms were explored through analysis of T-DNA insertion mutants and RNAi lines. Plants without the expression of individual isoforms show no differences in growth and development, and are not significantly different from wild type plants in soluble sugars, starch and cellulose contents under all growth conditions investigated. Analysis of T-DNA insertion mutant lacking Sus3 isoform that was exclusively expressed in stomata cells only had a minor influence on guard cell osmoregulation and/or bioenergetics. Although none of the sucrose synthases appear to be essential for normal growth under our standard growth conditions, they may be necessary for growth under stress conditions. Different isoforms of sucrose synthase respond differently to various abiotic stresses. It has been shown that oxygen deprivation up regulates Sus1 and Sus4 and increases total Susy activity. However, the analysis of the plants with reduced expression of both Sus1 and Sus4 revealed no obvious effects on plant performance under oxygen deprivation. Low temperature up regulates Sus1 expression but the loss of this isoform has no effect on the freezing tolerance of non acclimated and cold acclimated plants. These data provide a comprehensive overview of the expression of this gene family which supports some of the previously reported roles for Susy and indicates the involvement of specific isoforms in metabolism and/or signalling.
Die kumulative Dissertation umfasst dreizehn Beiträge, die zwischen 1994 und 2006 aus je aktuellen Forschungszusammenhängen entstanden sind und in unterschiedlichen Zeitschriften und Sammelwerken publiziert wurden. Sie widmen sich Funktion und Leistung der Bibliothek für Bildungsgeschichtliche Forschung (BBF) als bildungshistorischer Forschungsbibliothek, die in einer Einleitung entlang einer professionstheoretischen Fragestellung systematisch eingeordnet werden. Beiträge und Einleitung gehen zum einen auf die Bestandsgeschichte der Vorgängereinrichtungen der BBF ein, die als Gebrauchsbibliotheken insbesondere eine institutionelle Grundlage zur Verberuflichung und Professionalisierung der Lehrer bildeten. Zum anderen widmen sie sich neueren Angeboten der 1992 in eine Forschungsbibliothek umgewandelten Einrichtung, die sich besonders an dem Bedarf des veränderten Adressatenkreises orientieren. Es handelt sich um Dienstleistungen, die einerseits dem Kontext einer digitalen Bibliothek zuzuordnen sind, andererseits das Konzept einer Forschungsbibliothek zu einer Forschungsstätte erweitern, mit der Aufgabe, zur Unterstützung des interdisziplinären und internationalen Diskurses der an Themen zur historischen Bildungsforschung arbeitenden Science Community beizutragen.
Unter dem Eindruck einer zunehmenden Einengung finanzieller Spielräume entwickelt die öffentliche Hand Strategien zur Haushaltskonsolidierung, die über den Einsatz des Neuen Steuerungsmodells hinausgehen. Eine zentrale Bedeutung im Rahmen der Verwaltungsoptimierung nehmen aufgaben- und organisationskritische Ansätze ein. Letztgenannte umfassen Überlegungen, wie durch eine Ablösung hergebrachter behördlicher Strukturen nachhaltige Entlastungseffekte ausgelöst werden können. Das Organisationsrecht kennt hierfür auf allen Verwaltungsebenen grundsätzlich zahlreiche Ausgestaltungen von der Beleihung Privater Dritter über Beteiligungsgesellschaften, Anstalten oder Stiftungen bis hin zu Regiebetrieben. Die verbleibenden Möglichkeiten einer Einflussnahme durch Politik und Verwaltung gestalten sich. Im Interesse einer hinreichenden Steuerung durch politische und administrative Leitungsinstanzen erfahren Landesbetriebe nach § 26 der Landeshaushaltsordnungen in den letzten Jahren in vielen Landesverwaltungen eine Renaissance. Obgleich die betreffende Ermächtigung seit 1969 im Haushaltsrecht verankert ist und bereits Gegenstand der Reichshaushaltsordnung war, liegen kaum systematisierte Erkenntnisse über den Einsatz dieser Organisationsform vor. In den Rechts-, Wirtschafts- und Verwaltungswissenschaften finden sich praktisch keine über den Wortlaut des Gesetzes und hierzu kaum ergangene Verwaltungsvorschriften hinausgehenden Hilfestellungen. Die Arbeit widmet sich dem Modell „Landesbetrieb nach § 26 LHO“, indem sie damit verbundene Entwicklungspotenziale für ein betriebswirtschaftliches Handeln und Rahmenbedingungen seines Einsatzes beleuchtet. Sie stellt den Landesbetrieb dabei in ein Verhältnis zu Behörden, welche unter Anwendung von Elementen des Neuen Steuerungsmodells geführt werden und privatrechtlich ausgestalteten Unternehmen. Zu diesem Zweck erfolgt eine vertiefte empirische Untersuchung der Landesbetriebe im amtlichen Geoinformationswesen, welche eine breite Aufgabenpalette aufweisen. Die in diesem Rahmen vollzogene Primäranalyse wird im Interesse einer Verbreiterung der Aussagekraft der Ergebnisse ergänzt um ausgewählte Sekundäranalysen zur praktischen Ausgestaltung weiterer Landesbetriebe insbesondere in den Bereichen Bau- und Liegenschaftsmanagement, Mess- und Eichwesen und der Datenverarbeitung. Ergänzend zu den deskriptiven Darstellungen der empirischen Betrachtung werden normative Betrachtungen für die einzelnen betriebswirtschaftlichen Funktionalbereiche vorgenommen soweit hier spezifische Problemstellungen in der Praxis der Landesbetriebe bekannt geworden sind. Im Ergebnis kommt die Arbeit zu der Erkenntnis, dass Landesbetriebe ein Entwicklungspotenzial über das Neue Steuerungsmodell hinaus bergen, dieses aber weniger als erwartet im Bereich der Finanzwirtschaft und damit in der tatsächlichen Haushaltskonsolidierung liegt, als vielmehr in der strukturellen Optimierung der Verhältnisse zwischen, Betriebsleitung, Kunden sowie administrativer und politischer Spitze und der Gestaltungsräume der einzelnen Akteure.
Our work goes in two directions. At first we want to transfer definitions, concepts and results of the theory of hyperidentities and solid varieties from the total to the partial case. (1) We prove that the operators chi^A_RNF and chi^E_RNF are only monotone and additive and we show that the sets of all fixed points of these operators are characterized only by three instead of four equivalent conditions for the case of closure operators. (2) We prove that V is n − SF-solid iff clone^SF V is free with respect to itself, freely generated by the independent set {[fi(x_1, . . . , x_n)]Id^SF_n V | i \in I}. (3) We prove that if V is n-fluid and ~V |P(V ) =~V −iso |P(V ) then V is kunsolid for k >= n (where P(V ) is the set of all V -proper hypersubstitutions of type \tau ). (4) We prove that a strong M-hyperquasi-equational theory is characterized by four equivalent conditions. The second direction of our work is to follow ideas which are typical for the partial case. (1) We characterize all minimal partial clones which are strongly solidifyable. (2)We define the operator Chi^A_Ph where Ph is a monoid of regular partial hypersubstitutions.Using this concept, we define the concept of a Phyp_R(\tau )-solid strong regular variety of partial algebras and we prove that a PHyp_R(\tau )-solid strong regular variety satisfies four equivalent conditions.
The goal of a Brain-Computer Interface (BCI) consists of the development of a unidirectional interface between a human and a computer to allow control of a device only via brain signals. While the BCI systems of almost all other groups require the user to be trained over several weeks or even months, the group of Prof. Dr. Klaus-Robert Müller in Berlin and Potsdam, which I belong to, was one of the first research groups in this field which used machine learning techniques on a large scale. The adaptivity of the processing system to the individual brain patterns of the subject confers huge advantages for the user. Thus BCI research is considered a hot topic in machine learning and computer science. It requires interdisciplinary cooperation between disparate fields such as neuroscience, since only by combining machine learning and signal processing techniques based on neurophysiological knowledge will the largest progress be made. In this work I particularly deal with my part of this project, which lies mainly in the area of computer science. I have considered the following three main points: <b>Establishing a performance measure based on information theory:</b> I have critically illuminated the assumptions of Shannon's information transfer rate for application in a BCI context. By establishing suitable coding strategies I was able to show that this theoretical measure approximates quite well to what is practically achieveable. <b>Transfer and development of suitable signal processing and machine learning techniques:</b> One substantial component of my work was to develop several machine learning and signal processing algorithms to improve the efficiency of a BCI. Based on the neurophysiological knowledge that several independent EEG features can be observed for some mental states, I have developed a method for combining different and maybe independent features which improved performance. In some cases the performance of the combination algorithm outperforms the best single performance by more than 50 %. Furthermore, I have theoretically and practically addressed via the development of suitable algorithms the question of the optimal number of classes which should be used for a BCI. It transpired that with BCI performances reported so far, three or four different mental states are optimal. For another extension I have combined ideas from signal processing with those of machine learning since a high gain can be achieved if the temporal filtering, i.e., the choice of frequency bands, is automatically adapted to each subject individually. <b>Implementation of the Berlin brain computer interface and realization of suitable experiments:</b> Finally a further substantial component of my work was to realize an online BCI system which includes the developed methods, but is also flexible enough to allow the simple realization of new algorithms and ideas. So far, bitrates of up to 40 bits per minute have been achieved with this system by absolutely untrained users which, compared to results of other groups, is highly successful.
The aim of this study was to provide deeper insights in passerine phylogenetic relationships using new molecular markers. The monophyly of the largest avian order Passeriformes (~59% of all living birds) and the division into its suborders suboscines and oscines are well established. Phylogenetic relationships within the group have been extremely puzzling, as most of the evolutionary lineages originated through rapid radiation. Numerous studies have hypothesised conflicting passerine phylogenies and have repeatedly stimulated further research with new markers. In the present study, I used three different approaches to contribute to the ongoing phylogenetic debate in Passeriformes. I investigated the recently introduced gene ZENK for its phylogenetic utility for passerine systematics in combination and comparison to three already established nuclear markers. My phylogenetic analyses of a comprehensive data set yielded highly resolved, consistent and strongly supported trees. I was able to show the high utility of ZENK for elucidating phylogenetic relationships within Passeriformes. For the second and third approach, I used chicken repeat 1 (CR1) retrotransposons as phylogenetic markers. I presented two specific CR1 insertions as apomorphic characters, whose presence/absence pattern significantly contributed to the resolution of a particular phylogenetic uncertainty, namely the position of the rockfowl species Picathartes spp. in the passerine tree. Based on my results, I suggest a closer relationship of these birds to crows, ravens, jays, and allies. For the third approach, I showed that CR1 sequences contain phylogenetic signal and investigated their applicability in more detail. In this context, I screened for CR1 elements in different passerine birds, used sequences of several loci to construct phylogenetic trees, and evaluated their reliability. I was able to corroborate existing hypotheses and provide strong evidence for some new hypotheses, e.g. I suggest a revision of the taxa Corvidae and Corvinae as vireos are closer related to crows, ravens, and allies. The subdivision of the Passerida into three superfamilies, Sylvioidea, Passeroidea, and Muscicapoidea was strongly supported. I found evidence for a split within Sylvioidea into two clades, one consisting of tits and the other comprising warblers, bulbuls, laughingthrushes, whitethroats, and allies. Whereas Passeridae appear to be paraphyletic, monophyly of weavers and estrild finches as a separate clade was strongly supported. The sister taxon relationships of dippers and the thrushes/flycatcher/chat assemblage was corroborated and I suggest a closer relationship of waxwings and kinglets to wrens, tree-creepers, and nuthatches.
The formation of colloids by the controlled reduction, nucleation, and growth of inorganic precursor salts in different media has been investigated for more than a century. Recently, the preparation of ultrafine particles has received much attention since they can offer highly promising and novel options for a wide range of technical applications (nanotechnology, electrooptical devices, pharmaceutics, etc). The interest derives from the well-known fact that properties of advanced materials are critically dependent on the microstructure of the sample. Control of size, size distribution and morphology of the individual grains or crystallites is of the utmost importance in order to obtain the material characteristics desired. Several methods can be employed for the synthesis of nanoparticles. On the one hand, the reduction can occur in diluted aqueous or alcoholic solutions. On the other hand, the reduction process can be realized in a template phase, e.g. in well-defined microemulsion droplets. However, the stability of the nanoparticles formed mainly depends on their surface charge and it can be influenced with some added protective components. Quite different types of polymers, including polyelectrolytes and amphiphilic block copolymers, can for instance be used as protecting agents. The reduction and stabilization of metal colloids in aqueous solution by adding self-synthesized hydrophobically modified polyelectrolytes were studied in much more details. The polymers used are hydrophobically modified derivatives of poly(sodium acrylate) and of maleamic acid copolymers as well as the commercially available branched poly(ethyleneimine). The first notable result is that the polyelectrolytes used can act alone as both reducing and stabilizing agent for the preparation of gold nanoparticles. The investigation was then focused on the influence of the hydrophobic substitution of the polymer backbone on the reduction and stabilization processes. First of all, the polymers were added at room temperature and the reduction process was investigated over a longer time period (up to 8 days). In comparison, the reduction process was realized faster at higher temperature, i.e. 100°C. In both cases metal nanoparticles of colloidal dimensions can be produced. However, the size and shape of the individual nanoparticles mainly depends on the polymer added and the temperature procedure used. In a second part, the influence of the prior mentioned polyelectrolytes was investigated on the phase behaviour as well as on the properties of the inverse micellar region (L2 phase) of quaternary systems consisting of a surfactant, toluene-pentanol (1:1) and water. The majority of the present work has been made with the anionic surfactant sodium dodecylsulfate (SDS) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) since they can interact with the oppositely charged polyelectrolytes and the microemulsions formed using these surfactants present a large water-in-oil region. Subsequently, the polymer-modified microemulsions were used as new templates for the synthesis of inorganic particles, ranging from metals to complex crystallites, of very small size. The water droplets can indeed act as nanoreactors for the nucleation and growth of the particles, and the added polymer can influence the droplet size, the droplet-droplet interactions, as well as the stability of the surfactant film by the formation of polymer-surfactant complexes. One further advantage of the polymer-modified microemulsions is the possibility to stabilize the primary formed nanoparticles via a polymer adsorption (steric and/or electrostatic stabilization). Thus, the polyelectrolyte-modified nanoparticles formed can be redispersed without flocculation after solvent evaporation.
Soils contain a large amount of carbon (C) that is a critical regulator of the global C budget. Already small changes in the processes governing soil C cycling have the potential to release considerable amounts of CO2, a greenhouse gas (GHG), adding additional radiative forcing to the atmosphere and hence to changing climate. Increased temperatures will probably create a feedback, causing soils to release more GHGs. Furthermore changes in soil C balance impact soil fertility and soil quality, potentially degrading soils and reducing soils function as important resource. Consequently the assessment of soil C dynamics under present, recent past and future environmental conditions is not only of scientific interest and requires an integrated consideration of main factors and processes governing soil C dynamics. To perform this assessment an eco-hydrological modelling tool was used and extended by a process-based description of coupled soil carbon and nitrogen turnover. The extended model aims at delivering sound information on soil C storage changes beside changes in water quality, quantity and vegetation growth under global change impacts in meso- to macro-scale river basins, exemplary demonstrated for a Central European river basin (the Elbe). As a result this study: ▪ Provides information on joint effects of land-use (land cover and land management) and climate changes on croplands soil C balance in the Elbe river basin (Central Europe) presently and in the future. ▪ Evaluates which processes, and at what level of process detail, have to be considered to perform an integrated simulation of soil C dynamics at the meso- to macro-scale and demonstrates the model’s capability to simulate these processes compared to observations. ▪ Proposes a process description relating soil C pools and turnover properties to readily measurable quantities. This reduces the number of model parameters, enhances the comparability of model results to observations, and delivers same performance simulating long-term soil C dynamics as other models. ▪ Presents an extensive assessment of the parameter and input data uncertainty and their importance both temporally and spatially on modelling soil C dynamics. For the basin scale assessments it is estimated that croplands in the Elbe basin currently act as a net source of carbon (net annual C flux of 11 g C m-2 yr-1, 1.57 106 tons CO2 yr-1 entire croplands on average). Although this highly depends on the amount of harvest by-products remaining on the field. Future anticipated climate change and observed climate change in the basin already accelerates soil C loss and increases source strengths (additional 3.2 g C m-2 yr-1, 0.48 106 tons CO2 yr-1 entire croplands). But anticipated changes of agro-economic conditions, translating to altered crop share distributions, display stronger effects on soil C storage than climate change. Depending on future use of land expected to fall out of agricultural use in the future (~ 30 % of croplands area as “surplus” land), the basin either considerably looses soil C and the net annual C flux to the atmosphere increases (surplus used as black fallow) or the basin converts to a net sink of C (sequestering 0.44 106 tons CO2 yr-1 under extensified use as ley-arable) or reacts with decrease in source strength when using bioenergy crops. Bioenergy crops additionally offer a considerable potential for fossil fuel substitution (~37 PJ, 1015 J per year), whereas the basin wide use of harvest by-products for energy generation has to be seen critically although offering an annual energy potential of approximately 125 PJ. Harvest by-products play a central role in soil C reproduction and a percentage between 50 and 80 % should remain on the fields in order to maintain soil quality and fertility. The established modelling tool allows quantifying climate, land use and major land management impacts on soil C balance. New is that the SOM turnover description is embedded in an eco-hydrological river basin model, allowing an integrated consideration of water quantity, water quality, vegetation growth, agricultural productivity and soil carbon changes under different environmental conditions. The methodology and assessment presented here demonstrates the potential for integrated assessment of soil C dynamics alongside with other ecosystem services under global change impacts and provides information on the potentials of soils for climate change mitigation (soil C sequestration) and on their soil fertility status.
Ultrathin, semi-permeable membranes are not only essential in natural systems (membranes of cells or organelles) but they are also important for applications (separation, filtering) in miniaturized devices. Membranes, integrated as diffusion barriers or filters in micron scale devices need to fulfill equivalent requirements as the natural systems, in particular mechanical stability and functionality (e.g. permeability), while being only tens of nm in thickness to allow fast diffusion times. Promising candidates for such membranes are polyelectrolyte multilayers, which were found to be mechanically stable, and variable in functionality. In this thesis two concepts to integrate such membranes in larger scale structures were developed. The first is based on the directed adhesion of polyelectrolyte hollow microcapsules. As a result, arrays of capsules were created. These can be useful for combinatorial chemistry or sensing. This concept was expanded to couple encapsulated living cells to the surface. The second concept is the transfer of flat freestanding multilayer membranes to structured surfaces. We have developed a method that allows us to couple mm2 areas of defect free film with thicknesses down to 50 nm to structured surfaces and to avoid crumpling of the membrane. We could again use this technique to produce arrays of micron size. The freestanding membrane is a diffusion barrier for high molecular weight molecules, while small molecules can pass through the membrane and thus allows us to sense solution properties. We have shown also that osmotic pressures lead to membrane deflection. That could be described quantitatively.