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- ItemA sustainable approach to malnutrition eradication: nutrition-sensitive aquaculture, consumption pattern and household dynamics in Bangladesh(Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2025) Hossain, Nusrat ZaitunMalnutrition continues to be a pressing concern in many low- and middle-income countries across Asia and Africa, with Bangladesh serving as a prominent example. Fish is a primary source of protein and micronutrients in the diet of people. Research shows that small indigenous species (SIS) are nutritionally superior to conventionally farmed fish, containing higher levels of vitamin A, calcium, iron, and zinc. However, their availability is declining due to habitat loss, overfishing, and rising demand, making them less accessible and increasingly unaffordable for poor households. In response, nutrition-sensitive aquaculture which integrates nutrient-rich SIS into traditional carp systems has emerged as a promising solution, particularly as aquaculture now contributes the largest share to the overall fish supply. Despite its potential, several barriers continue to limit the expansion of carp-SIS systems. Chief among them is the lack of a commercial framework for producing and distributing SIS seed, a stark contrast to the well-established systems for species such as tilapia and carp. Improving the productivity of carp-SIS polyculture systems, particularly in homestead ponds, requires the adoption of enhanced pond management practices. However, historically, the commercial aquaculture sector has prioritized growth and volume over nutritional value, thereby side-lining SIS in both research and production. A deeper understanding of the factors that drive both the adoption and disadoption of improved pond management techniques (IPMTs) is therefore essential for designing more effective and sustainable interventions. Additionally, the long-term benefits of IPMT adoption, particularly within carp-SIS polyculture systems in homestead ponds, remain underexplored, underscoring the need for focused analysis to unlock their full potential in enhancing productivity and nutritional outcomes. A clear understanding of the determinants and nutritional impacts of SIS consumption is crucial to ensuring the long-term sustainability of carp-SIS polyculture. Research on the drivers and health impacts of SIS consumption remains limited, despite well-established evidence of their nutrient-rich content. Understanding the role of women’s empowerment within aquaculture households is equally important. While women often participate in household decision-making, significant lacking persist in access to financial services, control over productive assets and exposure to social groups or extension services. These raise important questions about the extent to which women’s empowerment influences fish production and nutritional outcomes, questions that remain largely unanswered due to a lack of quantifiable evidence in the context of aquaculture. Consequently, this dissertation intends to examine the interplay between nutrition-sensitive homestead aquaculture, improved pond management techniques in carp-SIS polyculture, patterns of fish production and consumption, the role of SIS and non-SIS fish consumption in household health and finally the association of women’s empowerment with overall fish production, household diet and health indicators. The specific objectives of this dissertation can be summed up as: (a) Examine the adoption and sustainability of improved pond management techniques in nutrition-sensitive carp–SIS polyculture systems within homestead aquaculture, (b) Assess the economic and wellbeing impacts of these techniques on rural households, (c) Explore the determinants and nutritional effects of small indigenous species (SIS) consumption, and (d) Investigate how women’s empowerment in aquaculture households influences aquaculture production, dietary and health indicators. Each of these four objectives corresponds to a distinct article comprising this dissertation. This dissertation draws on multiple datasets, with the first and second articles using two-wave panel data from 234 households in Barishal district (2014 and 2022), collected under the EU-funded Agriculture and Nutrition Extension Project (ANEP) and then by the German Federal Ministry for Economic Cooperation and Development (BMZ) funded project promoting carp–SIS polyculture and improved pond management. The third article employs panel data from the Bangladesh Integrated Household Survey (BIHS), conducted by the International Food Policy Research Institute (IFPRI), covering 5503 rural households surveyed in 2011-12 and 2018-19. The fourth article relies on cross-sectional data from the 2018-19 BIHS, using a subsample of 874 aquaculture households with complete Women’s Empowerment in Agriculture Index (WEAI) data. The four articles employ context-specific data analysis methods. The first article applies descriptive and econometric analyses including fixed effects Poisson and negative binomial models to examine the adoption of IPMTs. The second article uses a two-stage least squares instrumental variable (2SLS IV) model to estimate the wellbeing impacts of IPMT adoption, addressing endogeneity with theory-driven instruments. The third article draws on panel data to analyze trends and determinants of small indigenous species (SIS) consumption, using probit, fractional logit, and instrumental variable (IV) probit regressions. The fourth article explores associations of women’s empowerment with aquaculture, nutrition and health indicators using OLS and probit models, with multiple empowerment specifications and robustness checks. The results of the four articles reveal a complex but promising picture: nutrition-sensitive aquaculture can transform rural livelihoods, but its success depends on affordability, inclusivity, and systems that support resilience from the pond to the plate. To begin with, improved pond management techniques in homestead aquaculture helped rural households with homestead ponds triple their harvests of SIS, boosting both fish consumption and sales. Yet, while households initially adopted these techniques, many later abandoned them due to rising costs and climate challenges such as excessive rainfall. The promised higher yields were offset by economic burdens, particularly due to costly inputs such as commercial feed. Despite these hurdles, the benefits are clear: adopting these methods improves nutrition and reduces poverty. While improved pond management techniques lead to higher fish yields, their financial benefits are limited by high input costs. This suggests use of alternative and organic low-cost substitutes. Meanwhile, SIS remain a vital source of micronutrients, particularly for rural and less affluent households. Although consumption declines over time, its health benefits are evident, with higher intake linked to reduced incidence of household illness. Empowered women play a key role in aquaculture productivity. However, deep-rooted structural inequalities - economic vulnerability, geographic isolation, and household power imbalances - have more influence over dietary and health indicators than empowerment alone. Collectively, these findings offer critical insights into how nutrition-sensitive aquaculture can be optimized through sustainable technologies, inclusive practices, and context-specific policies. By highlighting the interplay of ecological, economic, and social dimensions, particularly the roles of small indigenous species and women’s empowerment, this dissertation contributes to a deeper understanding of the pathways linking aquaculture to nutrition and rural development. The evidence lays a foundation for integrated, scalable interventions that are resilient, equitable, and sustainable in confronting the challenges of food systems in Bangladesh and beyond.
- ItemNaturally and anthropogenically forced sediment dynamics in navigational waters of the Jade-Weser-Estuary(Institutionelles Repositorium der Leibniz Universität Hannover, 2025) Gundlach, JannekSediment management in intensively used estuaries, is currently one of the greatest challenges for coastal engineers. In recent decades, both the volumes and the costs per cubic meter re- located have increased as a result of maintenance dredging. Considering the socio-economic developments of recent decades and the predicted effects of climate change, the need for sus- tainable and innovative sediment management strategies is increasing. As part of the coastal zone, estuaries are semi-enclosed, tidally influenced river mouths. They exhibit extremely complex sediment dynamics, as the sediments can be of marine and fluvial origin and are transported variably over time and space by tides, waves and river discharge. In most estuaries, a net upstream transport of sediments is observed, caused by barotropic, tide- averaged and baroclinic effects. Depending on the geometry of an estuary, its hydrodynamic condidtions and the impact of technical measures, such as channel deepening or hydraulic struc- tures varies, potentially causing undesirable effects, such as hyper-turbidity or loss of intertidal area. Therefore, numerical models are used to simulate the hydro-morphodynamic response of an estuary to technical measures. For an dedicated assessment, it is important to simulate both the natural response of an estuary as well as the anthropogenically influenced response. For the long-term prediction of the estuarine morphodynamic development, assumptions and simplifications are necessary (e.g. morphological scaling factor, model schematization or input reduction). A consideration of purely natural morphodynamics, requires a model-based gen- esis the estuary morphology, as pre-anthropogenic conditions and measurements are hardly available or not detailed enough, when being geologically derived. Simulations of the present estuarine morphodynamic activity, on the other hand, are limited by the ability of a large-scale model to include small-scale structure-induced effects (e.g. individual groynes) or processes (e.g. local sediment disposals). A model-based assessment of sediment management activities requires coupling with specialized models developed for simulating the disposal process which enables more precise predictions of large-scale effects. However, the number and scope of models available in this field is limited. This thesis, addresses these limits by three research objectives. The first research objective focuses on the driving processes of the long-term natural tidal channel evolution of the Jade- Weser Estuary. The second research objective is the mathematical description and development of a specialized near-field model for the dedicated simulation of sediment disposals. The third research objective is the validation and application of the developed model to evaluate the large- scale impact of sediment disposals. For the natural development of the Jade-Weser Estuary a process-based morphodynamic model was built based on a flat-bed approach using simplified boundary conditions and accelerated morphological development. The results were analyzed by checking for morphodynamic equi- librium and by applying a newly developed Correlation analysis of (cross-sectional) evolution (CASE) method. All simulations reached a morphodynamic equilibrium and developed two channels that vary considerably in the location and depth over time and between the simu- lations. Concluding, the development of the two-channel system was mainly caused by the interaction of the tides with the basin geometry, while the alternation pattern and alternation period depended on the relation between tides and river discharge. For the second research objective, to improve model-based representation of sediment dispos- als, the near-field model PROVER-M is presented that projects the active distribution of fine sediments after a disposal of dredged material. PROVER-M provides valuable input for far- field models, enabling a more accurate consideration of fine sediment disposals in larger scale models. Based on the input, PROVER-M calculates the dynamic plume behavior, including the convective descent of sediments and their dynamic collapse on the bottom. The result is a spa- tial distribution of disposed sediments through the water column and on the ground. The model is developed open source and comes with a self-installing executable graphical user interface. To address the third research objective, this model was tested and validated for three sets of disposal simulations. First, new small scale laboratory experiments of instantaneous disposals are presented, documenting the dynamic behavior of fine material disposed in shallow waters. Second, results of the PROVER-M model are shown for: (1) a field-scaled study complemen- tary to the laboratory set-up, (2) a parametric study of sequentially varied model input and (3) a far-field model coupling for estimation of the PROVER-M impact. By comparing results of the laboratory experiments to the PROVER-M model, the physical behavior of PROVER-M is successfully validated. The impact of the ambient setting and dredged material parameters show non-linear, complex interdependencies of these input parameters on disposal properties. Finally, a real set of disposals in the tidally influenced Weser estuary is simulated by coupling PROVER-M to a far-field model, illustrating the potential impact of PROVER-M including an increased maximum suspended sediment concentration (SSC) of up to 10%. By 1) realizing the natural development of an estuary through engineering modeling approaches and idealizations, 2) developing a new near-field model and 3) successfully demonstrating its validity and added value in three different applications the defined research objectives are met and a reconsideration of sediment management in its current form is enabled. The utilization of estuaries in conjunction with climate change-induced transformations of its morphology make sediment a valuable resource and its redistribution an opportunity for synergistic effects. For example, disposed sediments at the right place during the right time in tidal motion could potentially allow the intertidal area to remain intact although exposed to sea-level rises. Such a sediment management concept must aim for a the long-term ecological net added value as its primary maxim. However, this requires dedicated, interdisciplinary studies involving all stakeholders. From an engineering perspective, both the methodology (in terms of modeling and monitoring) and the conceptualization of this collaborative sediment management design is a challenge, neglecting legal or administrative obstacles. Since holistic sediment management is needed on our coasts, this thesis can be one step towards a feasibility study of such a concept.
- ItemGenetic engineering in the oilseed crop camelina: establishment and application(Institutionelles Repositorium der Leibniz Universität Hannover, 2025) Rezayeva, Barno Ruzimurodovna; Leibniz Universität Hannover; Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), GaterslebenAbstract Die in vitro-Regeneration und Agrobakterien-vermittelte genetische Transformation sind essentielle Methoden der Pflanzen- und Züchtungsforschung. Die Anwendungsmöglichkeiten moderner biotechnologischer Methoden sind jedoch bei einigen Nutzpflanzen durch noch zu ineffiziente Protokolle limitiert. Davon betroffen ist insbesondere die Nutzung des erheblichen Potenzials der Genom-Editierung. Um diese Einschränkungen bei der zunehmende Bedeutung gewinnenden Ölsaat Leindotter (Camelina, Camelina sativa) zu überwinden, wurden unreife zygotische Embryonen für die in vitro-Regeneration verwendet, da davon auszugehen war, dass Gewebe dieser Ausgangsexplantate im Verlgeich zu herkömmlichen, ausdifferenzierten Pflanzenteilen eine höhere Totipotenz aufweisen. Nachdem die Bildung von Adventivsprossen und deren Weiterentwicklung zu Pflanzen unter Verwendung der experimentellen Akzession Cam139 tatsächlich mit hoher Effizienz erreicht worden war, wurden die dem zugrunde liegenden initialen Entwicklungsprozesse auf zellulärer Ebene anhand von mikroskopischen Präparaten untersucht und dabei ermittelt, dass die regenerativen Strukturen ihren Ursprung in den äußersten Schichten des Hypokotyls haben. Zudem ist es gelungen dieses für dikotyledone Pflanzen weitgehend neuartige Regenerationsprinzip auch für die aktuelle Camelina-Sorte Ligena anzuwenden. Das neu entwickelte Regenerationsprinzip wurde dazu genutzt, eine Methode der Agrobakterien-vermittelten Transformation für Camelina zu etablieren. Bei diesen experimentellen Arbeiten wurden mehrere Einflussfaktoren variiert, darunter die gezielte mechanische Verwundung, die Dauer der Vor- und Co-Kultur sowie die Konzentration des Selektionsagens Hygromycin. Auch diese Methode erwies sich für aktuelle Sorten anwendbar, wobei Transformationsraten von bis zu 17 % (bezogen auf die Anzahl kultivierter Explantate) erreicht wurden. Schließlich wurde die neu etablierte Transformationsmethode verwendet, um das Gen des Fettsäure-modifizierenden Enzyms FATTY ACID ELONGASE 1 (FAE1) durch genspezifische Mutagenese mittels CRISPR-assoziierter (Cas)9-Endonuklease auszuschalten. Dazu wurde eine protoplastenbasierte Methode der funktionellen Validierung von in silico vorselektierten Cas9-Zielmotiven und den entsprechenden guide (g)RNAs entwickelt. Anhand dieses Tests wurden Mutationen in allen drei vorläufig ausgewählten, FAE1-spezifischen Zielmotiven aller drei homöologen Camelina-Subgenome nachgewiesen. Bei der Tiefensequenzierung Zielregion-spezifischer PCR-Amplicons von genomischer Protoplasten-DNA waren dabei bis zu 15 % der Sequenzier-Reads mutiert. Nach Verwendung des gleichen Konstrukts für die Herstellung stabil transgener Pflanzen wurden Mutationsereignisse ebenfalls in allen drei FAE1-spezifischen Zielmotiven aller drei Homöoallele nachgewiesen. Aufgrund dieser hohen Effizienz wiesen 8 von 9 primär-transgenen Pflanzen Mutationen in allen drei FAE1-Homöoallelen auf. Folglich konnten dreifach-homozygote fae1-Knockout-Mutanten bereits in der ersten Selbstungsgeneration identifiziert werden. Fettsäure-Profilanalysen dieser Knockout-Linien ergaben, dass die ernährungsphysiologisch besonders wertvollen Anteile von Linolsäure (C18:1) und -Linolensäure (C18:2) signifikant erhöht und die zu beeinträchtigter Ölqualität führende Erucasäure (C22:1) auf kaum detektierbare Spuren reduziert war. Insgesamt gesehen umfasst die vorliegende Arbeit bedeutende Fortschritte von der biotechnologischen Erschließung der Ölsaat Camelina bis hin zum erfolgreichen Einsatz der Genom-Editierung mit dem Ergebnis der Entwicklung von Elite-Linien mit bislang unerreicht hoher Ölqualität als wichtige Grundlage einer gesunden Ernährung.
- ItemStudies towards the total syntheses of Antroalbocin A, Berkeleyone A, Pentacaronic Acid, and Penisarin B(Institutionelles Repositorium der Leibniz Universität Hannover, 2025) Siekmeyer, BjörnNatural products are produced as secondary metabolites. These substances often possess complex chemical structures and show broad biological activities making them an important source of lead structures in drug development. The chemical synthesis of natural products enables further investigation of their biological activities, since they are often isolated in insufficient quantities. Additionally, total synthesis represents the ultimate testing ground for newly designed chemical reactions and synthetic strategies. The mutual objective in the studies towards the total syntheses of antroalbocin A, berkeleyone A, pentacaronic acid, and penisarin B was to explore chemical reactivities of advanced intermediates during natural product synthesis. The first bioinspired total synthesis of antroalbocin A was achieved with organocatalytic desymmetrisation and a photochemical domino reaction comprising deconjugation and sigmatropic 1,3-acyl shift. Computational data of this process indicated that the exergonic 1,3-acyl shift benefited from an intermediary highly strained 1,3-enone, which resulted in increased conversion compared to unstrained substrates. Attempts to transfer the photochemical domino reaction to the construction of the bicyclo[3.3.1]nonane motif in berkeleyone A were impeded. The tetracylic precursor for the key step could not be derived from a literature-known tricyclic intermediate. The objective of the total synthesis of pentacaronic acid was the structure elucidation of the C4 stereocentre. A late-stage Heck reaction and a Nozaki–Hiyama–Takai–Kishi (NHTK) scission were chosen as retrosynthetic disconnections to simplify the natural product’s complex structure into three fragments. With the partial synthesis of the western and the synthesis of the middle fragment reported in the literature, the synthesis commenced with work on the eastern fragment’s substituted cyclopentane core. In the first approach (i) based on prior work by K. Bajerke, an allene precursor was synthesised and submitted to MacMillan’s synergistic reaction platform, which did not lead to the eastern fragment. The eastern fragment was accessed with L. Millbrodt’s earlier approach (ii) featuring a Favorskii ring contraction. An increased selectivity (dr > 19 : 1) for the coupling of middle and eastern fragments was achieved with lithiation–borylation chemistry compared to the NHTK scission with tBuLi (dr = 1 : 1.1). An intermolecular Heck reaction in the last fragment coupling did not succeed. Instead, a Suzuki cross-coupling was proposed. Therefore, Grubbs cross metathesis (CM) was investigated to introduce the required handle to the terminal olefin. Insufficient regioselectivity with the 1,2-disubstituted olefin in the side-chain led to approach (iii). Kwon’s dealkenylative alkenylation protocol was proposed to allow coupling of the known middle and a new eastern fragment followed by Grubbs CM prior to installation of the diene side-chain, thereby circumventing the issue of insufficient regioselectivity. Efforts on this approach were ceased due to severe separation problems of both diastereomers obtained from the NHTK reaction and the employed aldehyde. Studies towards the total synthesis of penisarin B were designed to examine a putative dyotropic rearrangement in the proposed biosynthesis. Access to the envisioned triene intermediate, the precursor for the key sequence of epoxypolyene cyclisation and dyotropic rearrangement, was not achieved. Three different retrosynthetic disconnections for pyrone formation after introduction of the farnesyl side-chain were unsuccessful.
- ItemStudien zur Totalsynthese von Illisimonin A(Institutionelles Repositorium der Leibniz Universität Hannover, 2025) Schönwald, AxelDer 2017 von Ma et al. aus den Früchten der immergrünen Pflanze Illicium simonsii Maxim isolierte Naturstoff Illisimonin A, zeichnet sich durch eine ungewöhnliche, käfigartige Struktur aus. Sie bildet ein trans-Tricyclo[5.2.1.0]decan-System und beinhaltet sieben stereogenene Kohlenstoffzentren, wodurch sich dieser Naturstoff als ein interessantes Syntheseziel erweist. Diese Arbeit befasst sich mit der Entwicklung einer Totalsynthese des Naturstoffs Illisimonin A. Dabei wird ein besonderer Fokus auf den schnellen Aufbau des trans-Tricyclo[5.2.1.0]decan-Systems gelegt. Die Gestaltung der Syntheseroute erfolgte sich über mehrere Entwicklungszyklen. In der schließlich etablierten Hauptroute wird durch eine kurze Synthesesequenz, welche Pauson‒Khand-Reaktion, [2+2]-Cycloaddition und SmI₂-induzierte Umlagerung beinhaltet, der schnelle Aufbau eines cis-Tricyclo[5.2.1.0]decan-Systems bewerkstelligt. Das trans-Tricyclo[5.2.1.0]decan-System wird über eine Semipinakol-Umlagerung ohne die Funktionalisierung an C10 aufgebaut. Diese erfolgt erst im Anschluss mittels Suarez-Fragmentierung, allylischer Oxidation und abschließenden SmI₂-induzierten Ringschluss. In anfänglichen Strategien war eine Funktionalisierung von C10 vor der Semipinakol-Umlagerung angedacht. Diese scheiterten jedoch an einer unerwarteten Inversion des Stereozentrums an C5, die sowohl unter ionischen als auch unter radikalischen Bedingungen auftrat. Auch eine geänderte Reihenfolge der anfänglichen Alkylierungsschritte konnte das Problem nicht lösen. Mechanistische Untersuchungen, inklusive Röntgenstrukturanalysen, legen nahe, dass die C5-Inversion während der Semipinakol-Umlagerung über einen schrittweisen Prozess stattfindet. Insgesamt wurde eine 15-stufige Synthese eines fortgeschrittenen Intermediats mit dem trans Tricyclo[5.2.1.0]decan-System in 0.4% Gesamtausbeute entwickelt.