Leibniz University Hannover

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    Blue LED trap and commercial lure improve western flower thrips (Frankliniella occidentalis) monitoring in cucumber crops

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    Blue sticky traps contribute substantially to monitoring the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), in greenhouses. Although sticky traps can detect the initial presence of thrips reliably, an estimation of the actual thrips density in the crop by counting number of thrips on the traps is often not accurate. To overcome this issue, we compared blue sticky traps and newly developed sticky LED-enlightened traps in combination with the commercial thrips kairomone Lurem-TR under commercial growing conditions. Therefore, an experiment was conducted in cucumber, Cucumis sativus L. (Cucurbitaceae), crop stands in greenhouse cabins investigating the correlation between thrips caught on (LED) traps and the thrips density in the crop for an accurate and reliable thrips monitoring. Additionally, experiments aiming to understand underlying mechanisms of thrips orientation towards traps in different scenarios were conducted under controlled conditions. Results show that thrips catches on sticky LED enlightened coloured traps correlated strongly positive with number of thrips in the crop, especially at low thrips population densities. Adding Lurem to this trap type further improved accuracy of the correlation in the greenhouse cabin experiment. Moreover, LED traps with and without Lurem were more attractive towards thrips in small follow-up experiments compared to standard blue sticky traps. The results are discussed in the context of general orientation of thrips and its behaviour towards visual and olfactory cues when considering different scenarios. Our study shows the successful integration of blue LEDs into an existing trapping system and underlines the advantages compared with standard sticky plates. In conclusion, sticky LED enlightened coloured traps have a potential as an improved thrips monitoring device that might improve pest management decisions

    On the displacement accumulation of monopiles under lateral cyclic loading

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    Up to now, the monopile is the most popular foundation type for supporting offshore wind turbines (OWTs). However, the current design guidance for monopile foundations is largely based on experience from the oil and gas industry, where both the pile dimensions as well as the design load conditions are different from offshore wind. As OWTs are quite sensitive to tilting, a key concern in the monopile foundation design is the accurate prediction of accumulated deformations due to long-term cyclic horizontal loads. Although the offshore guidelines (OGLs) and certification authorities require compliance with certain deformation criteria, no generally accepted method for the calculative verification currently is given by the OGLs. Therefore, in the past decades, several researchers investigated the displacement accumulation of monopiles to develop calculation methods for the estimation of permanent displacements due to lateral cyclic loading. However, a problem is the complexity of the pile-soil interaction and the multitude of influencing factors. This leads to the fact that different proposed methods partly provide very different or even contradictory results. As a consequence, the design of monopile foundations is often very conservative, which prevents the desired cost optimization. This thesis presents experimental and theoretical research, aimed at improving the knowledge concerning the behaviour of large diameter monopiles subjected to long-term lateral cyclic loading in cohesionless soils. Based on a literature review including the topics of current design regulations as well as different empirical and numerical investigations on the prediction of the monopile bearing and deformation behaviour with a special focus on lateral cyclic loading, selected methods for the determination of the displacement accumulation were examined and their results were compared using example calculations. The findings of this review were used to identify relevant parameters affecting the displacement accumulation of monopiles and to develop a comprehensive 1 g small-scale model test campaign for a systematic investigation of the key mechanisms driving the pile response. The parameters that have been assessed include the cyclic load magnitude, cyclic load ratio, load eccentricity, grain size distribution and soil relative density as well as the pile embedment length. In order to get additional insights into the reasons for different accumulation rates due to varying system or load configurations, further experimental tests involving the visualization of soil redistribution or densification effects resulting from lateral cyclic loading using digital image correlation (DIC) were carried out and evaluated. In addition to the experimental tests, the present thesis includes numerical finite element (FE) investigations in which the stiffness degradation method (SDM) was applied to calculate the monopile response to one-way lateral cyclic loading. Within the FE studies, the focus was mainly on scale effects resulting from different stress states in small and large scale as well as the influence of the relative pile-soil stiffness. The physical model tests revealed the cyclic load ratio to be a decisive parameter influencing the pile head displacement accumulation. For nearly rigid piles, it was found that asymmetrical two-way loading results in approximately 40% higher accumulation rates compared to simple one-way loads with complete unloading. The load magnitude influences the absolute value of the pile head displacement, but it changes the accumulation rate only marginally, at least for the load range studied experimentally. For a constant relative load magnitude also load eccentricity, type of sand or soil relative density seem to have a minor influence on the rate of accumulation within the investigated range. From the DIC experiments and the numerical studies, it is concluded that the relative pile-soil stiffness is a significant factor. The numerical parameter study shows the stiffer the pile responds to loading in relation to the soil, the greater the rate of displacement accumulation. Since the stiffness of a non-cohesive soil is stress-dependent, a different relative pile-soil stiffness can result for a defined system when calculated in different scales. Furthermore, also the load magnitude may influence the relative pile-soil stiffness and therefore accumulation rate when being very low and below a certain threshold. In the end, the observations made from the experimental and numerical investigations were used to derive a simple procedure for a first estimation of the global pile head displacement accumulation rate considering load characteristics as well as the relative pile-soil stiffness without large computational effort

    Trauma Unleashed

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    Shirin Shokrollahi’s video essay “Trauma Unleashed” delves into the intricate layers of Everything Everywhere All at Once (2022) to unravel the visceral portrayal of trauma and its aftermath, mapping the journey from fragmentation to wholeness within the film's multiversal chaos

    Contributions to IT project portfolio management and individual digital study assistants in higher education

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    Diese kumulative Dissertation beschreibt und diskutiert 12 wissenschaftliche Artikel, die einen Beitrag zur Forschung in den Themenbereichen Informationstechnik (IT) Projektportfoliomanagement und individuelle, digitale Studienassistenten an Universitäten umfasst. Dafür wurden Modelle und Rahmenwerke entwickelt, die wesentliche IT Projektportfoliomanagement Phasen und Aktivitäten beschreiben, eine objektive IT Projektevaluation ermöglichen und Reifegrade von IT Projektportfoliomanagement Prozessen bestimmen. Außerdem wurde ein Optimierungsmodell zur Auswahl und Planung des IT Projektportfoliomanagement Prozesses aufgestellt und in einem Entscheidungsunterstützungssystem-Prototypen integriert. Bestehende IT Projektportfoliomanagement Tools, sowie Anforderungen und unternehmerische Vorteile für IT Projektmanager wurden jeweils in Taxonomien klassifiziert, Muster erkannt und Gemeinsamkeiten und Unterschiede aufgezeigt. Zusätzlich wurden kritische Erfolgsfaktoren, Herausforderungen und Anforderungen für individuelle, digitale Studienassistenten identifiziert, analysiert und diskutiert. In mehreren Iterationen wurde basierend darauf ein Prototyp entwickelt, evaluiert, modifiziert und allgemeine Leitlinien für das Design, die Entwicklung und den Betrieb eines individuellen, digitalen Studienassistenten abgeleitet. Die Forschungsarbeiten ermöglichen IT Projektportfoliomanagement Prozesse effizienter und werteorientiert zu gestalten und subjektive Einflüsse zu minimieren sowie Hochschulen bei dem Design, der Entwicklung und dem Betrieb von individuellen, digitalen Studienassistenten zu unterstützen. Basierend auf Limitationen wird eine Forschungsagenda aufgestellt, die 13 weitere Forschungsmöglichkeiten im Themenbereich IT Projektportfoliomanagement und individuelle, digitale Studienassistenten aufzeigt und als Grundlage für weitere Forschung in diesen Themenfeldern dient.This cumulative dissertation outlines and discusses 12 scientific publications that contribute to the knowledge of Information Technology (IT) project portfolio management and individual digital study assistants in higher education. The papers developed models and frameworks that describe crucial IT project portfolio management phases and activities, enable an objective IT project evaluation, and define IT project portfolio management maturity levels. In addition, they deduced an optimization model for IT project portfolio management evaluation, selection, and scheduling decisions and implemented it in a decision support system prototype. Developed taxonomies and archetypes classify existing IT project portfolio management tools as well as requirements and corporate benefits of IT project manager positions to identify patterns, similarities, and differences. Further, critical success factors, challenges, and requirements for an individual digital study assistant were identified, analyzed, and discussed. Based on these and during several iterations, an individual digital study assistant prototype was developed, evaluated, adapted, and guidelines derived. The articles contribute knowledge on how to design more efficient and value-driven IT project portfolio management processes to minimize subjective influences. Also, they provide knowledge to support higher education institutions in the design, development, and operation of individual digital study assistants. Based on existing limitations, a further research agenda is deduced, including 13 further research directions for IT project portfolio management and individual digital study assistants in higher education institutions. They serve as a basis for further researchers in these fields of topics

    Convolutional neural network for retrieval of the time-dependent bond length in a molecule from photoelectron momentum distributions

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    We apply deep learning for retrieval of the time-dependent bond length in the dissociating two-dimensional H+2 molecule using photoelectron momentum distributions. We consider a pump-probe scheme and calculate electron momentum distributions from strong-field ionization by treating the motion of the nuclei classically, semiclassically or quantum mechanically. A convolutional neural network trained on momentum distributions obtained at fixed internuclear distances retrieves the time-varying bond length with an absolute error of 0.2–0.3 a.u

    Die „Begeisterung“ der Wälder: die Beziehung zwischen Mensch und Wald im Spiegel der Zeit

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    In der Geschichte der Menschheit kommt dem Kulturraum Wald eine zentrale Rolle als Lebensgrundlage zu. Mit dem Beginn der Sesshaftigkeit änderte sich das Verhältnis von Mensch und Wald radikal, der Mensch begann die Wildnis durch Urbarmachung zu verändern und nahm zum ersten Mal den Unterschied zwischen der Wildnis (dem Außen) und der vom Menschen urbar gemachten Umwelt (dem Innen) als unterschiedliche Räume wahr. Die veränderte Nutzung und Rodung der Wälder führte dazu, dass sich die Umwelt veränderte, und damit zogen neue Glaubensvorstellungen in das Leben der Menschen ein. Die endstanden Räume wurden mit den unterschiedlichsten Geistern besiedelt, in den Bergen, Wäldern, Flüssen und Ozeanen auf der ganzen Welt tummelten sich übernatürliche Gestalten die gefährlich, hilfreich und unberechenbar waren, wie die Natur selbst, was sie gleichzeitig zu einem Spiegel der Menschen werden ließ, die sie erdachten. Erst Jahrhunderte später begannen die Menschen in Europa damit diese Glaubensinhalte schriftlich zu fixieren, die ältesten Überlieferungen vermischten antikes mit christlichem Gedankengut, es endstanden die ersten christlichen Dämonologien. Zusätzlich dazu, kamen weitere einheimische Glaubensvorstellungen der Landbevölkerung deren Wurzeln in der Forschung als pagan und vorchristlich angesehen werden. Zwischen diesen Traditionen gab es im Laufe des Mittelalters Überschneidungen und Beeinflussungen, bis sie schließlich im 19. Jahrhundert kurz vor ihrem Verschwinden durch die Industrialisierung schriftlich in Form von Sagen festgehalten wurden. Diese Dissertation geht Frage nach, wie dieser sich der stehts verändernde Volksglaube in Bezug auf Waldgeister ausgesehen hat und untersucht nicht nur dessen Ausprägungen im „natürlichen Lebensraum“ der Genien, sondern begleitet deren Wanderung vom „Außen“ (Wald und Wildnis), in das „Dazwischen“ (Felder und Hudewälder) und das „Innen“ (Hof und Dorf). Hierbei steht immer das Verhältnis zum Menschen im Vordergrund und welche Auswirkungen diese Glaubensvorstellungen auf deren alltägliches Leben hatten. Zusätzlich, werden auch Vergleiche zu den Geistern vorgenommen, die in den jeweiligen Räumen zuhause sind, wie den Feld- und den Hausgeistern. Schließlich wird einen Versuch unternommen eins der größten Probleme der Forschung auf diesem Gebiet aufzulösen, nämlich die angenommene Unvereinbarkeit zwischen der im Mittelalter und der Frühen Neuzeit immer stärker zunehmenden Nutzung und Zerstörung der Wälder und deren Beseelung in Form von Geistern. In the history of mankind, the forest has played a central role as the basis of life. With the beginning of sedentarisation, the relationship between man and forest changed radically, man began to change the wilderness through reclamation and for the first time perceived the difference between the wilderness (the outside) and the environment reclaimed by man (the inside) as different spaces. The changing utilisation and clearing of the forests led to a change in the environment, and with it new beliefs entered people's lives. The resulting spaces were colonised by a wide variety of spirits; in the mountains, forests, rivers and oceans all over the world, supernatural creatures were to be found that were dangerous, helpful and unpredictable, just like nature itself, which at the same time made them a mirror of the people who created them. It was only centuries later that people in Europe began to put these beliefs into writing, the oldest traditions mixed ancient with Christian ideas and the first Christian demonologies emerged. In addition to this, there were other indigenous beliefs of the rural population whose roots are regarded in research as pagan and pre-Christian. There were overlaps and influences between these traditions in the course of the Middle Ages until they were finally recorded in writing in the form of legends in the 19th century shortly before their disappearance due to industrialisation. This dissertation explores the question of what this constantly changing folk belief in forest spirits looked like and not only examines its manifestations in the "natural habitat" of the genii, but also follows their migration from the "outside" (forest and wilderness) to the "in-between" (fields and woodland) and the "inside" (farmyard and village). The focus here is always on the relationship with people and the impact these beliefs had on their everyday lives. In addition, comparisons are also made with the spirits that are at home in the respective areas, such as the field and house spirits. Finally, an attempt is made to resolve one of the biggest problems of research in this field, namely the assumed incompatibility between the ever-increasing use and destruction of the forests in the Middle Ages and the early modern period and their animation in the form of spirit

    Construction of higher genus CMC surfaces in R3 via the generalized Whitham flow

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    In this thesis, we use the generalized Whitham flow to construct symmetric higher genus g > 1 CMC surfaces in R3. It is well-known that the existence of a conformally immersed CMC surface f : M → R3 is equivalent to the existence of a family of flat connections satisfying the intrinsic (periodicity of the conformal metric) and extrinsic (periodicity of the immersion) closing conditions. The generalized Whitham flow preserves the intrinsic while varies the extrinsic closing conditions. Thereby, the flow parameter, denoted by ρ, determines the genus of the resulting CMC surface. At the initial value ρ = 0 a torus has to be chosen, which in our case is the 3-lobed Wente torus T 2. For tori, the monodromy of the associated family can be parameterized by algebraic data on a hyperelliptic curve, called the spectral curve. The spectral curve of the 3-lobed Wente torus has spectral genus 2 and hyperelliptic reduction allows us to characterize the spectral data in terms of data on elliptic curves. This will help us to derive closing conditions at the initial value ρ = 0. In order to constructed closed symmetric higher genus CMC surfaces in R3, we will study families of flat connections on higher genus Riemann surfaces as the pullback of Fuchsian systems on the 4-punctured sphere, i.e., logarithmic connections on the holomorphically trivial rank two bundle. By that, the underlying Fuchsian system will be parameterized by flat line bundle connections on a torus. This particularly provides useful coordinates to study closing conditions of higher genus CMC surfaces.Investigating the spectral data shows that we have to open two double points outside the unit circle and increase the genus of the spectral curve to 6. By an implicit function theorem argument, we will show that the closing conditions are satisfied for ρ ∈ (−ϵ, ϵ) and prove the existence of compact and branched higher genus CMC surfaces in R3

    Regionsspezifische Immunreaktionen werden maßgeblich durch Stromazellen des Lymphknotens beeinflusst

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    Das Immunsystem ist ein hochkomplexes und sensibles Netzwerk, das den Körper gegen fremde Substanzen und Keime schützt aber auch Toleranz gegenüber harmlosen Stoffen induziert. Lymphknoten (LN) spielen dabei eine wichtige Rolle, da sie als zentrale Kontrollstationen Infektionen erkennen und eindämmen oder Toleranz induzieren. Periphere LN (pLN) drainieren große Gebiete der Haut, wohingegen die Mesenteriallymphknoten (mLN) das Gebiet des Magen-Darm-Traktes drainieren. Das Grundgerüst des LN wird durch Stromazellen gebildet. Zu diesen gehören Blutendothelzellen (BEC) und Lymphendothelzellen (LEC) sowie Retikulumzellen (FRC: Fibroblastische Retikulumzellen, FDC: Follikuläre dendritische Zelle, MRC: marginale Retikulumzellen). Mit Hilfe eines Transplantationsmodells konnten wir zeigen, dass in Tieren mit einem pLN im drainierenden Gebiet des mLN (pLNtx: transplantierter pLN) phänotypische Merkmale des drainierenden Gebietes weiterhin nachweisbar blieben. Mein Ziel war es aufzuklären, inwiefern Stromazellen die Funktionen des LN im Mausmodell beeinflussen, wie sie andere Zellen innerhalb des LN leiten und somit das drainierende Gebiet verändern. Zunächst konnten wir Stromazellen durch Einzelzell-RNA-Sequenzierung genauer identifizieren. Naive Stromazellen des mLN und pLN zeigten Unterschiede in der Zytokinexpression und der Expression von Genen des Lipidmetabolismus. Weiterhin haben wir innerhalb des Transplantationsmodells untersucht, inwiefern Stromazellen an der Regeneration der Lymphknotenfragmente beteiligt sind. Wir konnten zeigen, dass Stromazellen des Cortex und des Paracortex wichtige Zellpopulationen sind, um einen funktionsfähigen LN aufzubauen. Werden alle Stromazellen des LN transplantiert, entwickelt sich ein LN mit ortsspezifischen Expressionsmerkmalen. Die Mikrobiota oder Nahrungsbestandteile wie Fette haben einen Einfluss auf Stromazellen und somit auf die Funktion des LN. Tregs werden zu einem höheren Prozentsatz im mLN im Vergleich zum pLN induziert, und dabei scheint die Mikrobiota eine wichtige Rolle für die Prägung der Stromazellen zu spielen. Weiterhin kommt es aufgrund erhöhter Lipidaufnahme zu Änderungen in der Mikroarchitektur und zur Akkumulation von Lipidtröpfchen in Stromazellen. Diese beeinflussen die immunologische Funktion der mLN. Stromazellen sind somit eine wichtige Komponente sowohl für den Aufbau des LN als auch für die Ausübung regionsspezifischer immunregulatorischer Funktionen

    Qualification of Austenitic Stainless Steels for the Development of Load-Sensitive Material Sensors

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    To detect mechanical overloads on the component directly in operation, a metastable material can be used as a load-sensitive sensor when combined with an eddy current testing system. In order to find a suitable metastable sensor material that exhibits microstructural changes at an early stage before fatigue failure, quasi-static tensile tests and cyclic rotating bending tests were carried out with the austenitic stainless steels 1.4301 (2 batches), 1.4305, 1.4541 and 1.4550. For the detection of microstructural changes, electromagnetic testing was used in-situ in the tensile test and ex-situ between the rotating bending test after a pre-defined number of cycles. The investigated materials 1.4301 batch2 and 1.4550 showed the largest signal changes and the lowest austenite stability both in the tensile test and under cyclic bending load. Due to the better mechanical properties, 1.4301 batch2 should be preferred. The order of the austenitic stainless steels tested was similar in terms of transformation behavior in both tests. Thus, the tensile test combined with in-situ electromagnetic testing appears to have potential as a suitable benchmark test for austenite stability. With regard to the cyclic bending stress, an overload of the specimens could be detected for the materials 1.4301 batch2, 1.4305, 1.4541 and for the 1.4550 on the basis of a significant amplitude change. At low bending stresses, uncritical for structural integrity, no increase in amplitude was measured. The results have shown that an early detection of overloads is possible with several materials, however, the potential for detecting overloads varies between materials and also between individual batches. In addition, it has been observed that as the bending stress increases, the gradient of the change in amplitude over the number of cycles increases as well. Thus, with a known number of cycles, it could be possible to classify the previous load spectrum based on the difference in amplitude between two measurements

    An experimental history of positive psychology

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    The aim of this thesis is twofold: To give a historical account of the experiments and development of instruments needed for positive psychology to flourish, and to find a framework within which the epistemic status of another discipline can be assessed. The narrative follows the operationalizations and measurements of happiness research in psychology. This narrative is then compared with the 'problem of nomic measurement', the feedback loop between theory and measurement, of the historical cases of the theory of temperature and the definition of water as H2O.DFG über den GRK 2073/GRK 2073/13360500/60300585/E

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