@techreport{BruttelEisenkopfNithammer2024, type = {Working Paper}, author = {Bruttel, Lisa Verena and Eisenkopf, Gerald and Nithammer, Juri}, title = {Pre-election communication in public good games with endogenous leaders}, series = {CEPA Discussion Papers}, journal = {CEPA Discussion Papers}, number = {73}, issn = {2628-653X}, doi = {10.25932/publishup-62395}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-623952}, pages = {28}, year = {2024}, abstract = {Leadership plays an important role for the efficient and fair solution of social dilemmas but the effectiveness of a leader can vary substantially. Two main factors of leadership impact are the ability to induce high contributions by all group members and the (expected) fair use of power. Participants in our experiment decide about contributions to a public good. After all contributions are made, the leader can choose how much of the joint earnings to assign to herself; the remainder is distributed equally among the followers. Using machine learning techniques, we study whether the content of initial open statements by the group members predicts their behavior as a leader and whether groups are able to identify such clues and endogenously appoint a "good" leader to solve the dilemma. We find that leaders who promise fairness are more likely to behave fairly, and that followers appoint as leaders those who write more explicitly about fairness and efficiency. However, in their contribution decision, followers focus on the leader's first-move contribution and place less importance on the content of the leader's statements.}, language = {en} } @techreport{EstrinKhavulKritikosetal.2024, type = {Working Paper}, author = {Estrin, Saul and Khavul, Susanna and Kritikos, Alexander and L{\"o}her, Jonas}, title = {Access to digital finance}, series = {CEPA Discussion Papers}, journal = {CEPA Discussion Papers}, number = {72}, issn = {2628-653X}, doi = {10.25932/publishup-62326}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-623261}, pages = {27}, year = {2024}, abstract = {Financing entrepreneurship spurs innovation and economic growth. Digital financial platforms that crowdfund equity for entrepreneurs have emerged globally, yet they remain poorly understood. We model equity crowdfunding in terms of the relationship between the number of investors and the amount of money raised per pitch. We examine heterogeneity in the average amount raised per pitch that is associated with differences across three countries and seven platforms. Using a novel dataset of successful fundraising on the most prominent platforms in the UK, Germany, and the USA, we find the underlying relationship between the number of investors and the amount of money raised for entrepreneurs is loglinear, with a coefficient less than one and concave to the origin. We identify significant variation in the average amount invested in each pitch across countries and platforms. Our findings have implications for market actors as well as regulators who set competitive frameworks.}, language = {en} } @phdthesis{Baumgart2024, author = {Baumgart, Lene}, title = {Die Ambivalenz der Digitalisierung}, doi = {10.25932/publishup-63040}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-630401}, school = {Universit{\"a}t Potsdam}, pages = {137}, year = {2024}, abstract = {Ausgehend von der Beobachtung, dass die aktuelle Digitalisierungsforschung die Ambivalenz der Digitalisierung zwar erkennt, aber nicht zum Gegenstand ihrer Analysen macht, fokussiert die vorliegende kumulative Dissertation auf die ambivalente Dichotomie aus Potenzialen und Problemen, die mit digitalen Transformationen von Organisationen einhergeht. Entlang von sechs Publikationen wird mit einem systemtheoretischen Blick auf Organisationen die spannungsvolle Dichotomie hinsichtlich dreier ambivalenter Verh{\"a}ltnisse aufgezeigt: Erstens wird in Bezug auf das Verh{\"a}ltnis von Digitalisierung und Postb{\"u}rokratie deutlich, dass digitale Transformationen das Potenzial aufweisen, postb{\"u}rokratische Arbeitsweisen zu erleichtern. Parallel ergibt sich das Problem, dass auf Konsens basierende postb{\"u}rokratische Strukturen Digitalisierungsinitiativen erschweren, da diese auf eine Vielzahl von Entscheidungen angewiesen sind. Zweitens zeigt sich mit Blick auf das ambivalente Verh{\"a}ltnis von Digitalisierung und Vernetzung, dass einerseits organisationsweite Kooperation erm{\"o}glicht wird, w{\"a}hrend sich andererseits die Gefahr digitaler Widerspruchskommunikation auftut. Beim dritten Verh{\"a}ltnis zwischen Digitalisierung und Gender deutet sich das mit neuen digitalen Technologien einhergehende Potenzial f{\"u}r Gender Inklusion an, w{\"a}hrend zugleich das Problem einprogrammierter Gender Biases auftritt, die Diskriminierungen oftmals versch{\"a}rfen. Durch die Gegen{\"u}berstellung der Potenziale und Probleme wird nicht nur die Ambivalenz organisationaler Digitalisierung analysierbar und verst{\"a}ndlich, es stellt sich auch heraus, dass mit digitalen Transformationen einen doppelte Formalisierung einhergeht: Organisationen werden nicht nur mit den f{\"u}r Reformen {\"u}blichen Anpassungen der formalen Strukturen konfrontiert, sondern m{\"u}ssen zus{\"a}tzlich formale Entscheidungen zu Technikeinf{\"u}hrung und -beibehaltung treffen sowie formale L{\"o}sungen etablieren, um auf unvorhergesehene Potenziale und Probleme reagieren. Das Ziel der Dissertation ist es, eine analytisch generalisierte Heuristik an die Hand zu geben, mit deren Hilfe die Errungenschaften und Chancen digitaler Transformationen identifiziert werden k{\"o}nnen, w{\"a}hrend sich parallel ihr Verh{\"a}ltnis zu den gleichzeitig entstehenden Herausforderungen und Folgeproblemen erkl{\"a}ren l{\"a}sst.}, language = {de} } @book{BrosiusGersdorfGersdorf2024, author = {Brosius-Gersdorf, Frauke and Gersdorf, Hubertus}, title = {Das neue System der Beschaffung von Leistungen zur medizinischen Rehabilitation durch die Rentenversicherung}, publisher = {Duncker \& Humblot}, address = {Berlin}, isbn = {978-3-428-19066-9}, doi = {10.3790/978-3-428-59066-7}, pages = {168}, year = {2024}, abstract = {Die Beschaffung von Leistungen zur medizinischen Rehabilitation wurde durch den neuen \S 15 SGB VI zum 1. Juli 2023 grundlegend reformiert. Seither gilt ein mehrstufiges System aus Zulassung der Rehabilitationskliniken, Belegungsvertrag, Belegungsentscheidung und Verg{\"u}tung. S{\"a}mtliche Beschaffungsstufen werden von der DRV Bund durch verbindliche Entscheidungen gesteuert. Dieses neue Beschaffungssystem verst{\"o}ßt gegen das Wettbewerbsrecht der Europ{\"a}ischen Union und ist deshalb unwirksam. Das Unionsrecht (Art. 106 Abs. 1 AEUV), aber auch das nationale Kartellrecht (\S 19 Abs. 2 Nr. 1 GWB) und das Verfassungsrecht (Art. 12 Abs. 1 GG) verlangen eine Trennung von hoheitlichen Befugnissen und unternehmerischen Funktionen der Rentenversicherungstr{\"a}ger. Anderenfalls ist die gebotene Gleichbehandlung (Nichtdiskriminierung) der Rehabilitationskliniken freigemeinn{\"u}tziger und privater Tr{\"a}ger mit den Rehabilitationskliniken der Rentenversicherungstr{\"a}ger bei der Erbringung von Leistungen zur medizinischen Rehabilitation nicht gew{\"a}hrleistet. Dieses Trennungsprinzip ist verletzt. Denn die Rentenversicherungstr{\"a}ger nehmen hoheitliche Zulassungs-, Belegungs- und Verg{\"u}tungsaufgaben wahr und sind gleichzeitig unternehmerisch mit eigenen Rehabilitationseinrichtungen auf dem Markt der Erbringung von Leistungen zur medizinischen Rehabilitation t{\"a}tig. Freigemeinn{\"u}tzige und private Rehabilitationskliniken werden auf allen Stufen der Beschaffung gegen{\"u}ber den Kliniken der Rentenversicherungstr{\"a}ger diskriminiert. Das gilt insbesondere f{\"u}r die Belegungsentscheidungen der Rentenversicherungstr{\"a}ger, weil hierdurch systematisch eigene Kliniken gegen{\"u}ber freigemeinn{\"u}tzigen und privaten Kliniken beg{\"u}nstigt werden.}, language = {de} } @phdthesis{Grohmann2024, author = {Grohmann, Nils-Hendrik}, title = {Strengthening the UN Human Rights Treaty Bodies}, series = {Jus Internationale et Europaeum}, journal = {Jus Internationale et Europaeum}, number = {202}, publisher = {Mohr Siebeck}, address = {T{\"u}bingen}, isbn = {978-3-16-162825-2}, issn = {1861-1893}, doi = {10.1628/978-3-16-162826-9}, pages = {XV, 315}, year = {2024}, abstract = {Nils-Hendrik Grohmann besch{\"a}ftigt sich mit dem noch andauernden St{\"a}rkungsprozess der UN-Menschenrechtsvertragsorgane. Er analysiert, welche rechtlichen Befugnisse die Aussch{\"u}sse haben, ob sie von sich aus Vorschl{\"a}ge einbringen k{\"o}nnen und inwieweit sie ihre Verfahrensweisen bisher aufeinander abgestimmt haben. Ein weiterer Schwerpunkt liegt auf der Zusammenarbeit zwischen den verschiedenen Aussch{\"u}ssen und der Frage, welche Rolle das Treffen der Vorsitzenden bei der St{\"a}rkung spielen kann.}, language = {en} } @phdthesis{AlhosseiniAlmodarresiYasin2024, author = {Alhosseini Almodarresi Yasin, Seyed Ali}, title = {Classification, prediction and evaluation of graph neural networks on online social media platforms}, doi = {10.25932/publishup-62642}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-626421}, school = {Universit{\"a}t Potsdam}, pages = {xviii, 78}, year = {2024}, abstract = {The vast amount of data generated on social media platforms have made them a valuable source of information for businesses, governments and researchers. Social media data can provide insights into user behavior, preferences, and opinions. In this work, we address two important challenges in social media analytics. Predicting user engagement with online content has become a critical task for content creators to increase user engagement and reach larger audiences. Traditional user engagement prediction approaches rely solely on features derived from the user and content. However, a new class of deep learning methods based on graphs captures not only the content features but also the graph structure of social media networks. This thesis proposes a novel Graph Neural Network (GNN) approach to predict user interaction with tweets. The proposed approach combines the features of users, tweets and their engagement graphs. The tweet text features are extracted using pre-trained embeddings from language models, and a GNN layer is used to embed the user in a vector space. The GNN model then combines the features and graph structure to predict user engagement. The proposed approach achieves an accuracy value of 94.22\% in classifying user interactions, including likes, retweets, replies, and quotes. Another major challenge in social media analysis is detecting and classifying social bot accounts. Social bots are automated accounts used to manipulate public opinion by spreading misinformation or generating fake interactions. Detecting social bots is critical to prevent their negative impact on public opinion and trust in social media. In this thesis, we classify social bots on Twitter by applying Graph Neural Networks. The proposed approach uses a combination of both the features of a node and an aggregation of the features of a node's neighborhood to classify social bot accounts. Our final results indicate a 6\% improvement in the area under the curve score in the final predictions through the utilization of GNN. Overall, our work highlights the importance of social media data and the potential of new methods such as GNNs to predict user engagement and detect social bots. These methods have important implications for improving the quality and reliability of information on social media platforms and mitigating the negative impact of social bots on public opinion and discourse.}, language = {en} } @phdthesis{Antonoglou2024, author = {Antonoglou, Nikolaos}, title = {GNSS-based remote sensing: Innovative observation of key hydrological parameters in the Central Andes}, doi = {10.25932/publishup-62825}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-628256}, school = {Universit{\"a}t Potsdam}, pages = {xxii, 116}, year = {2024}, abstract = {The Central Andean region is characterized by diverse climate zones with sharp transitions between them. In this work, the area of interest is the South-Central Andes in northwestern Argentina that borders with Bolivia and Chile. The focus is the observation of soil moisture and water vapour with Global Navigation Satellite System (GNSS) remote-sensing methodologies. Because of the rapid temporal and spatial variations of water vapour and moisture circulations, monitoring this part of the hydrological cycle is crucial for understanding the mechanisms that control the local climate. Moreover, GNSS-based techniques have previously shown high potential and are appropriate for further investigation. This study includes both logistic-organization effort and data analysis. As for the prior, three GNSS ground stations were installed in remote locations in northwestern Argentina to acquire observations, where there was no availability of third-party data. The methodological development for the observation of the climate variables of soil moisture and water vapour is independent and relies on different approaches. The soil-moisture estimation with GNSS reflectometry is an approximation that has demonstrated promising results, but it has yet to be operationally employed. Thus, a more advanced algorithm that exploits more observations from multiple satellite constellations was developed using data from two pilot stations in Germany. Additionally, this algorithm was slightly modified and used in a sea-level measurement campaign. Although the objective of this application is not related to monitoring hydrological parameters, its methodology is based on the same principles and helps to evaluate the core algorithm. On the other hand, water-vapour monitoring with GNSS observations is a well-established technique that is utilized operationally. Hence, the scope of this study is conducting a meteorological analysis by examining the along-the-zenith air-moisture levels and introducing indices related to the azimuthal gradient. The results of the experiments indicate higher-quality soil moisture observations with the new algorithm. Furthermore, the analysis using the stations in northwestern Argentina illustrates the limits of this technology because of varying soil conditions and shows future research directions. The water-vapour analysis points out the strong influence of the topography on atmospheric moisture circulation and rainfall generation. Moreover, the GNSS time series allows for the identification of seasonal signatures, and the azimuthal-gradient indices permit the detection of main circulation pathways.}, language = {en} } @phdthesis{MartinezGuajardo2024, author = {Mart{\´i}nez Guajardo, Alejandro}, title = {New zwitterionic polymers for antifouling applications}, doi = {10.25932/publishup-62682}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-626820}, school = {Universit{\"a}t Potsdam}, pages = {XIX, 145}, year = {2024}, abstract = {The remarkable antifouling properties of zwitterionic polymers in controlled environments are often counteracted by their delicate mechanical stability. In order to improve the mechanical stabilities of zwitterionic hydrogels, the effect of increased crosslinker densities was thus explored. In a first approach, terpolymers of zwitterionic monomer 3-[N -2(methacryloyloxy)ethyl-N,N-dimethyl]ammonio propane-1-sulfonate (SPE), hydrophobic monomer butyl methacrylate (BMA), and photo-crosslinker 2-(4-benzoylphenoxy)ethyl methacrylate (BPEMA) were synthesized. Thin hydrogel coatings of the copolymers were then produced and photo-crosslinked. Studies of the swollen hydrogel films showed that not only the mechanical stability but also, unexpectedly, the antifouling properties were improved by the presence of hydrophobic BMA units in the terpolymers. Based on the positive results shown by the amphiphilic terpolymers and in order to further test the impact that hydrophobicity has on both the antifouling properties of zwitterionic hydrogels and on their mechanical stability, a new amphiphilic zwitterionic methacrylic monomer, 3-((2-(methacryloyloxy)hexyl)dimethylammonio)propane-1-sulfonate (M1), was synthesized in good yields in a multistep synthesis. Homopolymers of M1 were obtained by free-radical polymerization. Similarly, terpolymers of M1, zwitterionic monomer SPE, and photo-crosslinker BPEMA were synthesized by free-radical copolymerization and thoroughly characterized, including its solubilities in selected solvents. Also, a new family of vinyl amide zwitterionic monomomers, namely 3-(dimethyl(2-(N -vinylacetamido)ethyl)ammonio)propane-1-sulfonate (M2), 4-(dimethyl(2-(N-vinylacetamido)ethyl)ammonio)butane-1-sulfonate (M3), and 3-(dimethyl(2-(N-vinylacetamido)ethyl)ammonio)propyl sulfate (M4), together with the new photo-crosslinker 4-benzoyl-N-vinylbenzamide (M5) that is well-suited for copolymerization with vinylamides, are introduced within the scope of the present work. The monomers are synthesized with good yields developing a multistep synthesis. Homopolymers of the new vinyl amide zwitterionic monomers are obtained by free-radical polymerization and thoroughly characterized. From the solubility tests, it is remarkable that the homopolymers produced are fully soluble in water, evidence of their high hydrophilicity. Copolymerization of the vinyl amide zwitterionic monomers, M2, M3, and M4 with the vinyl amide photo-crosslinker M5 proved to require very specific polymerization conditions. Nevertheless, copolymers were successfully obtained by free-radical copolymerization under appropriate conditions. Moreover, in an attempt to mitigate the intrinsic hydrophobicity introduced in the copolymers by the photo-crosslinkers, and based on the proven affinity of quaternized diallylamines to copolymerize with vinyl amides, a new quaternized diallylamine sulfobetaine photo-crosslinker 3-(diallyl(2-(4-benzoylphenoxy)ethyl)ammonio)propane-1-sulfonate (M6) is synthesized. However, despite a priori promising copolymerization suitability, copolymerization with the vinyl amide zwitterionic monomers could not be achieved.}, language = {en} } @phdthesis{Benson2024, author = {Benson, Lawrence}, title = {Efficient state management with persistent memory}, doi = {10.25932/publishup-62563}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-625637}, school = {Universit{\"a}t Potsdam}, pages = {xiii, 124}, year = {2024}, abstract = {Efficiently managing large state is a key challenge for data management systems. Traditionally, state is split into fast but volatile state in memory for processing and persistent but slow state on secondary storage for durability. Persistent memory (PMem), as a new technology in the storage hierarchy, blurs the lines between these states by offering both byte-addressability and low latency like DRAM as well persistence like secondary storage. These characteristics have the potential to cause a major performance shift in database systems. Driven by the potential impact that PMem has on data management systems, in this thesis we explore their use of PMem. We first evaluate the performance of real PMem hardware in the form of Intel Optane in a wide range of setups. To this end, we propose PerMA-Bench, a configurable benchmark framework that allows users to evaluate the performance of customizable database-related PMem access. Based on experimental results obtained with PerMA-Bench, we discuss findings and identify general and implementation-specific aspects that influence PMem performance and should be considered in future work to improve PMem-aware designs. We then propose Viper, a hybrid PMem-DRAM key-value store. Based on PMem-aware access patterns, we show how to leverage PMem and DRAM efficiently to design a key database component. Our evaluation shows that Viper outperforms existing key-value stores by 4-18x for inserts while offering full data persistence and achieving similar or better lookup performance. Next, we show which changes must be made to integrate PMem components into larger systems. By the example of stream processing engines, we highlight limitations of current designs and propose a prototype engine that overcomes these limitations. This allows our prototype to fully leverage PMem's performance for its internal state management. Finally, in light of Optane's discontinuation, we discuss how insights from PMem research can be transferred to future multi-tier memory setups by the example of Compute Express Link (CXL). Overall, we show that PMem offers high performance for state management, bridging the gap between fast but volatile DRAM and persistent but slow secondary storage. Although Optane was discontinued, new memory technologies are continuously emerging in various forms and we outline how novel designs for them can build on insights from existing PMem research.}, language = {en} } @phdthesis{Woebbeking2024, author = {W{\"o}bbeking, Cordula}, title = {K{\"o}rper - Karte - Text}, series = {Sanssouci - Forschungen zur Romanistik}, volume = {22}, journal = {Sanssouci - Forschungen zur Romanistik}, publisher = {Frank \& Timme}, address = {Berlin}, isbn = {978-3-7329-1016-8}, issn = {2193-9985}, school = {Universit{\"a}t Potsdam}, pages = {280}, year = {2024}, abstract = {Rabelais' Pentalogie um die Riesen Gargantua und Pantagruel spiegelt Aspekte des sich ver{\"a}ndernden Weltbildes ihrer Entstehungszeit. Diese Studie untersucht auf der Folie der Theorie des Simulakrum Schrift, wie K{\"o}rpermodellierungen und kartographisches imaginaire durch den Autor als Strategien der Verh{\"u}llung verborgener Botschaften eingesetzt werden. Sie zeigt an ausgew{\"a}hlten Beispielen des Quart Livre die Aufweichung der Grenzen von K{\"o}rper, Karte und Text und deren Durchdringung. Die Metaphorizit{\"a}t des Textes gibt Aufschluss {\"u}ber seine Autoreflexivit{\"a}t und bewirkt eine gleichsam ganzheitliche Lekt{\"u}reerfahrung. Schließlich avanciert die Fiktion in ihrer Trugbildhaftigkeit als grotesk-sinnlicher K{\"o}rper und polysemantische Karte zum Welterkl{\"a}rungsmodell, das jedoch erst dechiffriert werden muss.}, language = {de} }