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Situating Hydrological Modeling: A Proposal for Engaging With the Power of Models
No full textA growing scholarship suggests hydrological models have political power as they embed and reinforce specific understandings of water and society relations which, in turn, shape future visions of how and for whom water is to be managed. In this commentary, we explore how the power of models can be explicitly and constructively engaged with, thereby expanding their potential to support transformations to water justice and sustainability. To achieve this, we suggest understanding, analyzing, and doing hydrological modeling as a situated knowledge practice. We take inspiration from feminist scholarship that emphasizes that all forms of knowledge are inherently partial, situated within specific contexts, experiences, and circumstances, and shaped by power relations. Situating hydrological modeling, we argue, requires opening up modeling processes to ask where, how, for whom, and by whom models are developed and used, and how outcomes influence water distributions and conditions of access for different social groups. Situating also opens opportunities to explore what it would take for hydrological modeling to explicitly pursue justice and sustainability goals in context‐specific and tangible ways. We present initial insights and invite further experimentation towards making models active agents of a more inclusive, transparent, and transformative water management.Volkswagen Foundation 10.13039/501100001663Peer Reviewe
Twist-noncommutative field theories and integrability
No full textIntegrable Deformationen bilden eine perfekte Landschaft, um neue integrable Modelle zu konstruieren. Im Bereich der AdS/CFT-Korrespondenz spielte die Integrabilität eine wichtige Rolle für Präzisionstests der Korrespondenz zwischen der =4 Super-Yang-Mills-Theorie und dem AdS₅ × S⁵ Superstring. In jüngster Zeit haben integrable Deformationen Aufmerksamkeit erregt, insbesondere auf der Stringtheorie-Seite der Korrespondenz, zum Beispiel in Form von homogenen Yang-Baxter-Deformationen. Es wurde vermutet, dass die dualen Feldtheorien letzterer durch Drinfel'd getwistete Versionen von =4 SYM gegeben sind, einschließlich nicht-kommutativer Deformationen mit nicht-kommutativen Raumzeitkoordinaten. In dieser Arbeit werden Eichtheorien auf getwisteten nichtkommutativen Räumen konstruiert. Es wird gezeigt, dass die Eichinvarianz den Twist einschränkt, der aus Poincar\'e Erzeugern aufgebaut werden muss. Weiterhin konstruieren wir die Kopplung der nichtkommutativen Eichtheorie an alle Arten von adjungierter und fundamentaler Materie, was eine Deformation von =4 SYM ermöglicht. Wir beweisen weiter, dass die deformierte Theorie invariant unter getwisteter (2,2|4) Symmetrie ist. Auf Quantenlevel entwickeln wir ein planares Äquivalenztheorem für planare Feynmandiagramme zwischen der undeformierten und der deformierten Theorie und führen eichinvariante Operatoren für bestimmte Deformationen ein, die vor allem aus der Perspektive der Integrabilität interessant sind. Für diese Operatoren bilden wir Ein-Schleifen Quantenkorrekturen der Zweipunktfunktionen auf Reshetikhin-getwistete (2,2|4)-Spinketten ab.Integrable deformations form a perfect landscape to construct new integrable models. In the realm of the AdS/CFT correspondence, integrability has played an important role in precision tests of the correspondence between the =4 super Yang-Mills (SYM) theory and the AdS₅ × S⁵ superstring. Recently, integrable deformations, particularly in the form of homogeneous Yang-Baxter deformations, have received attention on the string theory side of the correspondence. It has been conjectured that the field theory duals of these deformations are given by Drinfel'd twisted versions of =4 SYM, including noncommutative deformations of the spacetime. In this thesis, we construct gauge theories on twist-noncommutative spaces. It will be shown that gauge invariance restricts the twist to the Poincar\'e algebra. Furthermore, we construct the coupling of noncommutative gauge theory to various types of adjoint and fundamental matter, enabling a deformation of =4 SYM. We demonstrate that the deformed theory is invariant under twisted (2,2|4) symmetry. Moreover, we develop an equivalence theorem for planar Feynman diagrams between the undeformed and deformed theories and introduce gauge invariant operators for particular deformations, which are highly relevant to integrability. For these operators, we relate the one-loop two-point functions to the Reshetikhin twist of the (2,2|4) spin chain
Marital Loss and Well-Being in the Second Half of Life: Sociohistorical Context, Individual Differences, and Methodological Advances
No full textDer Verlust einer Ehe durch Tod oder Scheidung ist ein einschneidendes Lebensereignis mit Folgen für das Wohlbefinden. Unklar ist jedoch, wie sich diese Auswirkungen historisch verändert haben und inwiefern sie sich je nach Art des Verlusts von altersbedingten Veränderungen unterscheiden. Diese Dissertation untersucht die Folgen des Eheverlusts im mittleren und höheren Erwachsenenalter sowie moderierende Effekte von soziodemografischen Merkmalen und sozialen Ressourcen über die Zeit hinweg. Studie I analysiert anhand von Daten des Sozio-oekonomischen Panels (1984–2020; N = 2.044; Durchschnittsalter 65,73; 70 % Frauen) historische Veränderungen nach dem Tod des Ehepartners. Mittels AUC-Metriken und Wachstumsmodellen zeigt sich: Die unmittelbare Reaktion blieb stabil, doch in den 2000er und 2010er Jahren waren die Wohlbefindensverluste insgesamt geringer. Ursache waren flachere Verschlechterungen vor dem Ereignis und schnellere Erholung danach. Einflussfaktoren wie Alter, Gesundheit und soziale Merkmale blieben über die Jahrzehnte konstant. Studie II vergleicht Trauer und Scheidung anhand der Health and Retirement Study (1998–2018; N = 7.234; Alter 66). Mithilfe synthetischer Kontrollgruppen wurde gezeigt: Trauer führte zu deutlichen Einbußen im Wohlbefinden, besonders zwei Jahre vor und vier Jahre nach dem Verlust. Für Scheidung zeigten sich keine konsistent negativen Effekte. Größere soziale Netzwerke, höheres Alter und nicht-weiße Herkunft milderten Trauerfolgen ab. Insgesamt zeigen die Ergebnisse, wie historische Kontexte und individuelle Unterschiede Reaktionen auf Eheverlust prägen und verdeutlichen Unterschiede zwischen Tod und Scheidung des Partners.Marital loss through bereavement or divorce is a major life event with lasting effects on well-being. Yet, it remains unclear how these effects have evolved over historical time or differ by type of loss beyond normal aging. This dissertation addresses these gaps by examining the well-being consequences of marital loss in midlife and older adulthood and exploring how sociodemographic and personal resources moderate these effects across time and type of loss.
Study I investigates historical changes in the well-being implications of spousal bereavement using German Socio-Economic Panel data (1984–2020; N = 2,044; Mage = 65.73; 70% women). Using Area Under the Curve metrics and latent growth models, results show that while acute reactions to spousal loss have stayed stable, individuals in the 2000s and 2010s experienced less severe overall declines than those in earlier decades. This improvement was due to milder anticipatory declines and quicker post-loss recovery. Moderating factors (e.g., social or health characteristics) remained largely unchanged over time. Study II compares impacts of bereavement and divorce on well-being using Health and Retirement Study data (1998–2018; N = 7,234; Mage = 66; 56% women). Synthetic control methods matched individuals with similar pre-loss well-being to serve as counterfactuals. Spousal bereavement led to significant declines, especially two years before and four years after the event. Divorce showed no consistent well-being decline. Social network size, older age, and non-White background buffered bereavement effects. Together, findings highlight how sociohistorical context and individual differences shape responses to marital loss, and distinguish between bereavement and divorce in later life
Enhancing Spectral Coverage, Efficiency, and Photometric Accuracy in Ultrafast Fluorescence Upconversion Spectroscopy
No full textTime‐resolved fluorescence techniques are essential for studying the excited‐state dynamics of molecules and materials, as well as their interactions with the surrounding media. Fluorescence upconversion provides femtosecond time resolution, but its limited spectral coverage often restricts its application. Broadband variants of fluorescence upconversion spectroscopy (FLUPS) offer improved spectral coverage but require balancing spectral bandwidth against signal strength. In this paper, we introduce a three‐angle method (3‐AM) for FLUPS designed to overcome these limitations. This method enhances spectral coverage, photometric accuracy, and signal‐to‐noise ratio by recording and averaging spectrally resolved upconversion signals at three distinct crystal angles. Unlike other techniques that rely on spectral reconstruction or continuous crystal rotation during acquisition, the 3‐AM relies on fixed crystal positions, allowing for robust post‐acquisition corrections. We validate the performance and reproducibility of the 3‐AM by comparing it with the conventional fixed‐angle approach, as well as through blind testing in two independent laboratories. Despite variations in experimental configuration, the 3‐AM consistently produces reproducible spectral line shapes across the two setups. The enhanced performance and reliability demonstrate its practicality for laboratories with broadband FLUPS capabilities. Thus, the 3‐AM is a valuable tool for investigating ultrafast radiative processes in previously inaccessible molecular and material systems.Kekulé fellowship (Fonds der Chemischen Industrie)School of Analytical Sciences AdlershofPeer Reviewe
Bacterial motility depends on a critical flagellum length and energy-optimized assembly
No full textThe flagellum is the most complex macromolecular structure known in bacteria and is composed of around two dozen distinct proteins. The main building block of the long, external flagellar filament, flagellin, is secreted through the flagellar type-III secretion system at a remarkable rate of several tens of thousands of amino acids per second, significantly surpassing the rates achieved by other pore-based protein secretion systems. The evolutionary implications and potential benefits of this high secretion rate for flagellum assembly and function, however, have remained elusive. In this study, we provide both experimental and theoretical evidence that the flagellar secretion rate has been evolutionarily optimized to facilitate rapid and efficient construction of a functional flagellum. By synchronizing flagellar assembly, we found that a minimal filament length of 2.5 μm was required for swimming motility. Biophysical modeling revealed that this minimal filament length threshold resulted from an elasto-hydrodynamic instability of the whole swimming cell, dependent on the filament length. Furthermore, we developed a stepwise filament labeling method combined with electron microscopy visualization to validate predicted flagellin secretion rates of up to 10,000 amino acids per second. A biophysical model of flagellum growth demonstrates that the observed high flagellin secretion rate efficiently balances filament elongation and energy consumption, thereby enabling motility in the shortest amount of time. Taken together, these insights underscore the evolutionary pressures that have shaped the development and optimization of the flagellum and type-III secretion system, illuminating the intricate interplay and cost-benefit tradeoff between functionality and efficiency in assembly of large macromolecular structures.Significance: Our study demonstrates how protein secretion of the bacterial flagellum is finely tuned to optimize filament assembly rate and flagellum function while minimizing energy consumption. By measuring flagellar filament lengths and bacterial swimming after initiation of flagellum assembly, we were able to establish the minimal filament length necessary for swimming motility, which we rationalized physically as resulting from an elasto-hydrodynamic instability of the swimming cell. Our biophysical model of flagellum growth further illustrates how the physiological flagellin secretion rate is optimized to maximize filament elongation while conserving energy. These findings illuminate the evolutionary pressures that have shaped the function of the bacterial flagellum and type-III secretion system, driving improvements in bacterial motility and overall fitness.Peer Reviewe
CRAmed: a conditional randomization test for high-dimensional mediation analysis in sparse microbiome data
No full textMotivation: Numerous microbiome studies have revealed significant associations between the microbiome and human health and disease. These findings have motivated researchers to explore the causal role of the microbiome in human complex traits and diseases. However, the complexities of microbiome data pose challenges for statistical analysis and interpretation of causal effects. Results: We introduced a novel statistical framework, CRAmed, for inferring the mediating role of the microbiome between treatment and outcome. CRAmed improved the interpretability of the mediation analysis by decomposing the natural indirect effect into two parts, corresponding to the presence–absence and abundance of a microbe, respectively. Comprehensive simulations demonstrated the superior performance of CRAmed in Recall, precision, and F1 score, with a notable level of robustness, compared to existing mediation analysis methods. Furthermore, two real data applications illustrated the effectiveness and interpretability of CRAmed. Our research revealed that CRAmed holds promise for uncovering the mediating role of the microbiome and understanding of the factors influencing host health. Availability and implementation: The R package CRAmed implementing the proposed methods is available online at https://github.com/liudoubletian/CRAmed.Peer Reviewe
Affect-Enhancing Speech Characteristics for Robotic Communication
No full textThe attribution of mind to others, either humans or artificial agents, can be conceptualized along two dimensions: experience and agency. These dimensions are crucial in interactions with robots, influencing how they are perceived and treated by humans. Specifically, a higher attribution of agency to robots is associated with greater perceived responsibility, while a higher attribution of experience enhances sympathy towards them. One potential strategy to increase the attribution of experience to robots is the application of affective communication induced via prosody and verbal content such as emotional words and speech style. In two online studies (NI = 30, NII = 60), participants listened to audio recordings in which robots introduced themselves. In study II, robot pictures were additionally presented to investigate potential matching effects between appearance and speech. Our results showed that both the use of emotional words and speaking expressively significantly increased the attributed experience of robots, whereas the attribution of agency remained unaffected. Findings further indicate that speaking expressively and using emotional words enhanced the perception of human-like qualities in artificial communication partners, with a more pronounced effect observed for technical robots compared to human-like robots. These insights can be used to improve the affective impact of synthesized robot speech and thus potentially increase the acceptance of robots to ensure long-term use.Open Access funding enabled and organized by Projekt DEAL.Humboldt-Universität zu Berlin (1034)Peer Reviewe
Deep uncertainty in carbon dioxide removal portfolios
No full textDeep uncertainty about the costs and resource limits of carbon dioxide removal (CDR) options challenges the design of robust portfolios. To address this, we here introduce the CDR sustainable portfolios with endogenous cost model, a mixed-integer linear optimization model for cost-optimal and time-dependent CDR portfolios including endogenous treatment of technology cost dynamics. We explore future uncertainty in three key dimensions: realisable mitigation potentials, cost dynamics, and resource constraints. Our results demonstrate that afforestation and reforestation, and soil carbon sequestration appear as robust options, deployed regardless of the removals required. Direct air carbon capture and storage emerges as the most deployed technology in 2100 at median value (6.7 GtCO2 yr−1), but with the widest range of possible outcomes (interquartile range from 4 to 8.7 GtCO2 yr−1) depending largely on future renewable energy capacity and annual geological storage injection rates. Bioenergy with CCS deployment remains severely constrained by available land, as the median falls from 1.8 to 0.3 GtCO2 yr−1 in land-constrained scenarios, but gains portfolio share when future energy availability is bounded. Our simulations also reveal that ocean alkalinisation could become a dominant solution in high removal scenarios. Evaluating the performance of portfolios beyond economic costs, we also provide a framework to explore trade-offs across different aspects relevant to planetary boundaries.Peer Reviewe
European Contract Law and Narratives of National Identity
No full textDie Dissertation untersucht die Rolle nationaler Identität im europäischen Vertragsrecht unter besonderer Berücksichtigung narrativer Strukturen. Ausgangspunkt ist die Annahme, dass Nationen als soziale Konstrukte durch kulturelle Erzählungen entstehen. Diese Narrative erzeugen kollektive Identitäten, die Zugehörigkeit stiften, aber auch Abgrenzung gegenüber dem „Anderen“ fördern können. Die Arbeit zeigt, wie solche Narrative auch in der Gesetzgebung und Rechtswissenschaft auftreten, etwa in der Legitimierung staatlicher Gewalt durch Verfassungen oder in der Gestaltung europäischer Rechtsordnungen. Durch interdisziplinäre Ansätze aus Geschichte, Psychologie und Literaturwissenschaft wird analysiert, wie rechtliche Diskurse Identitätsnarrative nutzen. Am Beispiel des europäischen Vertragsrechts zeigt der Autor, wie nationale und europäische Narrative miteinander konkurrieren und einander ergänzen. Der Versuch, durch Kodifikationen wie den Draft Common Frame of Reference (DCFR) oder das Common European Sales Law eine europäische Identität im Privatrecht zu schaffen, stieß vielfach auf Ablehnung aufgrund eines national geprägten Rechtsverständnisses. Dabei wurde nicht nur fachliche Kritik geäußert, sondern auch teilweise emotional die Rolle von Recht als nationales Kulturgut betont. Die Arbeit kritisiert essentialistische Kulturverständnisse und plädiert für ein dynamisches, fragmentiertes Kulturmodell. Unter anderem anhand der Reform des französischen Zivilrechts zeigt sie, wie nationale Identität bewahrt und gleichzeitig europäische Impulse integriert werden können. Die Dissertation argumentiert, dass Recht nicht nur auf logischer Deduktion basiert, sondern auch kulturell geprägte Narrative enthält. Sie schlägt daher eine narrativ informierte Rechtswissenschaft vor, um die europäische Rechtsintegration besser zu verstehen und konstruktiv zu begleiten.This doctoral thesis explores the role of national identity in European contract law, with a particular focus on narrative structures. It begins from the premise that nations are socially constructed through cultural narratives. Such narratives foster collective identities, creating a sense of belonging, but can also produce divisions by constructing a boundary between the national “Self” and the “Other”. These identity-forming narratives are also present in legal contexts, for instance in legitimising state authority through constitutional texts or shaping legal systems at the European level. Drawing on interdisciplinary approaches from history, psychology, and literary theory, the thesis analyses how legal discourse utilises national identity narratives. The author demonstrates how national and European narratives compete with and compliment each other in the context of contract law harmonisation. Efforts such as the Draft Common Frame of Reference (DCFR) and the Common European Sales Law aimed to establish a shared European legal identity, yet often encountered resistance shaped by national legal traditions and emotionally charged reactions. The thesis critiques static, essentialist understandings of culture and instead advocates a dynamic, fragmented model. As one example, the reform of the French Civil Code is used as a case study to show how national identity can be preserved while simultaneously incorporating European legal developments. The author argues that law is not solely based on abstract norms and logic, but also shaped by culturally embedded narratives. As such, the study calls for a narratively informed legal scholarship to better understand and support the process of European legal integration
Hegel and White Freedom
No full textHegel's Lectures on the Philosophy of History are notorious for their racist portrayal of Africa. Few scholars, however, have considered their racism to be significant for Hegel's practical philosophy. This is largely because colonialism and Black enslavement appear to conflict with the idea of universal freedom at the heart of Hegel's practical philosophy. In my paper, I argue against this view and defend the claim that Hegel's idea of freedom is linked to white identity. It therefore grounds his racist comments in the Philosophy of History rather than opposing them. In order to show that Hegel's idea of freedom is linked to white identity, I trace its connections with the Western idea of property. My suggestion is that Hegel conceptualizes freedom as appropriation, thereby linking freedom to property and white identity. I conclude that Hegel's idea of freedom is an idea of white freedom and thus not an ‘impartial criterion’ for social critique.Peer Reviewe