@phdthesis{Hermanns2021, author = {Hermanns, Jolanda}, title = {Development, use and evaluation of concepts and materials for teaching organic chemistry at university}, school = {Universit{\"a}t Potsdam}, year = {2021}, language = {en} } @phdthesis{KabothBahr2021, author = {Kaboth-Bahr, Stefanie}, title = {Deciphering paleoclimate sensitivity across time and space}, school = {Universit{\"a}t Potsdam}, year = {2021}, abstract = {This habilitation thesis includes seven case studies that examine climate variability during the past 3.5 million years from different temporal and spatial perspectives. The main geographical focus is on the climatic events of the of the African and Asian monsoonal system, the North Atlantic as well as the Arctic Ocean. The results of this study are based on marine and terrestrial climate archives obtained by sedimentological and geochemical methods, and subsequently analyzed by various statistical methods. The results herein presented results provide a picture of the climatic background conditions of past cold and warm periods, the sensitivity of past climatic climate phases in relation to changes in the atmospheric carbon dioxide content, and the tight linkage between the low and high latitude climate system. Based on the results, it is concluded that a warm background climate state strongly influenced and/or partially reversed the linear relationships between individual climate processes that are valid today. Also, the driving force of the low latitudes for climate variability of the high latitudes is emphasized in the present work, which is contrary to the conventional view that the global climate change of the past 3.5 million years was predominantly controlled by the high latitude climate variability. Furthermore, it is found that on long geologic time scales (>1000 years to millions of years), solar irradiance variability due to changes in the Earth-Sun-Moon System may have increased the sensitivity of low and high latitudes to Influenced changes in atmospheric carbon dioxide. Taken together, these findings provide new insights into the sensitivity of past climate phases and provide new background conditions for numerical models, that predict future climate change.}, language = {en} } @phdthesis{Laeger2021, author = {Laeger, Thomas}, title = {Protein-dependent regulation of feeding, metabolism, and development of type 2 diabetes}, school = {Universit{\"a}t Potsdam}, pages = {224}, year = {2021}, abstract = {Food intake is driven by the need for energy but also by the demand for essential nutrients such as protein. Whereas it was well known how diets high in protein mediate satiety, it remained unclear how diets low in protein induce appetite. Therefore, this thesis aims to contribute to the research area of the detection of restricted dietary protein and adaptive responses. This thesis provides clear evidence that the liver-derived hormone fibroblast growth factor 21 (FGF21) is an endocrine signal of a dietary protein restriction, with the cellular amino acid sensor general control nonderepressible 2 (GCN2) kinase acting as an upstream regulator of FGF21 during protein restriction. In the brain, FGF21 is mediating the protein-restricted metabolic responses, e.g. increased energy expenditure, food intake, insulin sensitivity, and improved glucose homeostasis. Furthermore, endogenous FGF21 induced by dietary protein or methionine restriction is preventing the onset of type 2 diabetes in the New Zealand Obese mouse. Overall, FGF21 plays an important role in the detection of protein restriction and macronutrient imbalance in rodents and humans, and mediates both the behavioral and metabolic responses to dietary protein restriction. This makes FGF21 a critical physiological signal of dietary protein restriction, highlighting the important but often overlooked impact of dietary protein on metabolism and eating behavior, independent of dietary energy content.}, language = {en} } @phdthesis{Omelchenko2021, author = {Omelchenko, Oleh}, title = {Synchronit{\"a}t-und-Unordnung-Muster in Netzwerken gekoppelter Oszillatoren}, doi = {10.25932/publishup-53596}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-535961}, school = {Universit{\"a}t Potsdam}, pages = {152}, year = {2021}, abstract = {Synchronization of coupled oscillators manifests itself in many natural and man-made systems, including cyrcadian clocks, central pattern generators, laser arrays, power grids, chemical and electrochemical oscillators, only to name a few. The mathematical description of this phenomenon is often based on the paradigmatic Kuramoto model, which represents each oscillator by one scalar variable, its phase. When coupled, phase oscillators constitute a high-dimensional dynamical system, which exhibits complex behaviour, ranging from synchronized uniform oscillation to quasiperiodicity and chaos. The corresponding collective rhythms can be useful or harmful to the normal operation of various systems, therefore they have been the subject of much research. Initially, synchronization phenomena have been studied in systems with all-to-all (global) and nearest-neighbour (local) coupling, or on random networks. However, in recent decades there has been a lot of interest in more complicated coupling structures, which take into account the spatially distributed nature of real-world oscillator systems and the distance-dependent nature of the interaction between their components. Examples of such systems are abound in biology and neuroscience. They include spatially distributed cell populations, cilia carpets and neural networks relevant to working memory. In many cases, these systems support a rich variety of patterns of synchrony and disorder with remarkable properties that have not been observed in other continuous media. Such patterns are usually referred to as the coherence-incoherence patterns, but in symmetrically coupled oscillator systems they are also known by the name chimera states. The main goal of this work is to give an overview of different types of collective behaviour in large networks of spatially distributed phase oscillators and to develop mathematical methods for their analysis. We focus on the Kuramoto models for one-, two- and three-dimensional oscillator arrays with nonlocal coupling, where the coupling extends over a range wider than nearest neighbour coupling and depends on separation. We use the fact that, for a special (but still quite general) phase interaction function, the long-term coarse-grained dynamics of the above systems can be described by a certain integro-differential equation that follows from the mathematical approach called the Ott-Antonsen theory. We show that this equation adequately represents all relevant patterns of synchrony and disorder, including stationary, periodically breathing and moving coherence-incoherence patterns. Moreover, we show that this equation can be used to completely solve the existence and stability problem for each of these patterns and to reliably predict their main properties in many application relevant situations.}, language = {en} } @phdthesis{Samaniego2021, author = {Samaniego, Luis}, title = {Drought modeling and forecasting}, school = {Universit{\"a}t Potsdam}, pages = {xxvii, 273}, year = {2021}, abstract = {Over millennia, droughts could not be understood or defined but rather were associated with mystical connotations. To understand this natural hazards, we first needed to understand the laws of physics and then develop plausible explanations of inner workings of the hydrological cycle. Consequently, modeling and predicting droughts was out of the scope of mankind until the end of the last century. In recent studies, it is estimated that this natural hazard has caused billions of dollars in losses since 1900 and that droughts have affected 2.2 billion people worldwide between 1950 and 2014. For these reasons, droughts have been identified by the IPCC as the trigger of a web of impacts across many sectors leading to land degradation, migration and substantial socio-economic costs. This thesis summarizes a decade of research carried out at the Helmholtz Centre for Environmental Research on the subject of drought monitoring, modeling, and forecasting, from local to continental scales. The overarching objectives of this study, systematically addressed in the twelve previous chapters, are: 1) Create the capability to seamless monitor and predict water fluxes at various spatial resolutions and temporal scales varying from days to centuries; 2) Develop and test a modeling chain for monitoring, forecasting and predicting drought events and related characteristics at national and continental scales; and 3) Develop drought indices and impact indicators that are useful for end-users. Key outputs of this study are: the development of the open source model mHM, the German Drought Monitor System, the proof of concept for an European multi-model for improving water managent from local to continental scales, and the prototype of a crop-yield drought impact model for Germany.}, language = {en} } @phdthesis{BacskaiAtkari2021, author = {Bacskai-Atkari, Julia}, title = {The syntax of functional left peripheries}, school = {Universit{\"a}t Potsdam}, pages = {Vi, 215}, year = {2021}, language = {en} } @phdthesis{Vogel2021, author = {Vogel, Heike}, title = {Genetics of obesity and type 2 diabetes}, address = {Potsdam}, school = {Universit{\"a}t Potsdam}, pages = {183}, year = {2021}, abstract = {By using mouse outcross populations in combination with bioinformatic approaches, it was possible to identify and characterize novel genes regulating body weight, fat mass and β-cell function, which all contribute to the pathogenesis of obesity and T2D. In detail, the presented studies identified 1. Ifi202b/IFI16 as adipogenic gene involved in adipocyte commitment, maintenance of white adipocyte identity, fat cell size and the inflammatory state of adipose tissue. 2. Pla2g4a/PLA2G4A as gene linked to increased body weight and fat mass with a higher expression in adipose tissue of obese mice and pigs as well as in obese human subjects. 3. Ifgga2/IRGM as novel regulator of lipophagy protecting from excess hepatic lipid accumulation. 4. Nidd/DBA as a diabetogenic locus containing Kti12, Osbpl9, Ttc39a and Calr4 with differential expression in pancreatic islets and/or genetic variants. 5. miR-31 to be higher expressed in adipose tissue of obese and diabetic mice and humans targeting PPARy and GLUT4 and thereby involved in adipogenesis and insulin signaling. 6. Gjb4 as novel gene triggering the development of T2D by reducing insulin secretion, inducing apoptosis and inhibiting proliferation. The performed studies confirmed the complexity and strong genetic heritability character of obesity and T2D. A high number of genetic variations, each with a small effect, are collectively influencing the degree and severity of the disease. The use of mouse outcross populations is a valid tool for disease gene identification; however, to facilitate and accelerate the process of gene identification the combination of mouse cross data with advanced sequencing resources and the publicly available data sets are essential. The main goal for future studies should be the translation of these novel molecular discoveries to useful treatment therapies. More recently, several classes of novel unimolecular combination therapeutics have emerged with superior efficacy than currently prescribed options and pose the potential to reverse obesity and T2D (Finan et al., 2015). The glucagon-like peptide-1 (GLP-1)- estrogen conjugate, which targets estrogen into cells expressing GLP-1 receptors, was shown to improve energy, glucose and lipid metabolism as well as to reduce food reward (Finan et al., 2012; Schwenk et al., 2014; Vogel et al., 2016). Another possibility is the development of miRNA-based therapeutics to prevent obesity and T2D, such as miRNA mimetics, anti-miRNA oligonucleotides and exosomes loaded with miRNAs (Ji and Guo, 2019; Gottmann et al., 2020). As already described, genome-wide association studies for polygenic obesity and T2D traits in humans have also led to the identification of numerous gene variants with modest effect, most of them having an unknown function (Yazdi et al., 2015). These discoveries resulted in novel animal models and have illuminated new biologic pathways. Therefore, the integration of mouse-human genetic approaches and the utilization of the synergistic effects have the potential to lead to the identification of more genes responsible for common Mendelian forms of obesity and T2D, as well as gene × gene and gene × environment interactions (Yazdi et al., 2015; Ingelsson and McCarthy, 2018). This combination may help to unravel the missing heritability of obesity and T2D, to identify novel drug targets and to design more efficient and personalized obesity prevention and management programs.}, language = {en} }