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Boreal Forest Cover Delays Thermokarst Onset in Central Siberia's Yedoma Deposits
No full textBoreal forests, covering more than half of the world's permafrost, are essential for maintaining permafrost stability. However, climate change and forest shifts are threatening the delicate balance in the thermal equilibrium between the atmosphere, vegetation, and permafrost. We focus on Central Yakutia's ice‐rich boreal regions, specifically two sites located in Spasskaya‐Pad and Churapcha, to investigate the interplay of hydrothermal and climatic conditions that induce thermokarst. We employ a numerical permafrost model (CryoGrid), with a canopy model, and features for excess ground ice, lateral water flow and lake formation, to simulate the underlying physical processes under two forcing scenarios until 2060. The results reveal that forest delays the onset of thermokarst and ground ice melting by 3–18 years, depending on ice depth, climate forcing, and local conditions. Our simulations additionally reveal that a canopy slows excess ice melt by up to 7 years compared to bare ground simulations. Furthermore, in exceptionally warm and wet years, thermokarst initiation occurred rapidly in the bare ground simulations. In contrast, the canopy buffered against these conditions, suggesting that canopies might mitigate the impacts of small temperature and precipitation anomalies. This research highlights the critical role of forests in shaping the trajectory of thermokarst‐related landscape transformations in ice‐rich boreal permafrost regions. With the study region warming faster than average, forest cover transformations could significantly alter the hydrological balance. By integrating thermodynamics, hydrology, and ecology, our findings underscore the importance of forests in delaying thermokarst initiation and slowing ground ice melt, ultimately stabilizing permafrost ecosystems.Peer Reviewe
Band-Gap Regression with Architecture-Optimized Message-Passing Neural Networks
No full textGraph-based neural networks and, specifically, message-passing neural networks (MPNNs) have shown great potential in predicting physical properties of solids. In this work, we train an MPNN to first classify materials through density functional theory data from the AFLOW database as being metallic or semiconducting/insulating. We then perform a neural-architecture search to explore the model architecture and hyperparameter space of MPNNs to predict the band gaps of the materials identified as nonmetals. The top-performing models from the search are pooled into an ensemble that significantly outperforms the best single model. Uncertainty quantification is evaluated with Monte Carlo dropout and ensembling, with the ensemble method proving superior. The domain of applicability of the ensemble model is analyzed with respect to the crystal systems, the inclusion of a Hubbard parameter in the density-functional-theory calculations, and the atomic species building up the materials.Horizon 2020 Framework Programme 10.13039/100010661Deutsche Forschungsgemeinschaft 10.13039/501100001659Peer Reviewe
The Austrian German discourse particle leicht: a version of the discourse particle denn?
No full textThe Austrian German discourse particle leicht can be used in polar questions and wh-questions. It shares this potential with the better-known and more widely used discourse particle denn. An investigation of the possible contexts of use for leicht and denn, following Theiler (2021), shows that leicht is not merely the Austrian German version of denn. While some of the types of contexts that license the use of denn also license the use of leicht, leicht is more restricted in its use and questions with leicht may differ from questions with denn in their pragmatic effects
Benefits from urban green in Guatemala City
No full textLateinamerika und die Karibik gehören zu den Regionen der Welt, die sich am schnellsten urbanisieren, und ihre Städte stehen vor zahlreichen Herausforderungen im Zusammenhang mit der Umwelt, den negativen Auswirkungen des Klimawandels, dem Erbe der großen sozialen Ungleichheit und den prekären Siedlungen. Das Hauptziel dieser Dissertation war es, die Bedeutung des städtischen Grüns in einer zentralamerikanischen Stadt zu verstehen, indem man Guatemala-Stadt als Fallstudie nutzte. Die Struktur der Dissertation beginnt mit der Einführung, in der die in der Dissertation verwendeten theoretischen Aspekte dargestellt werden, die die gewählten Methoden und Rahmen rechtfertigten. Vom zweiten bis zum vierten Kapitel werden die veröffentlichten und verschickten wissenschaftlichen Artikel vorgestellt, um schließlich die Zusammenfassung der Ergebnisse im letzten Kapitel zu zeigen. Das zweite Kapitel zeigt die historische Entwicklung der Stadt Guatemala aus sozio-ökologischer Sicht. Im dritten Kapitel wird beschrieben, wie die Grünflächen, die das städtische Grüngefüge der Stadt bilden, identifiziert wurden. Das vierte Kapitel zeigt die räumliche Lokalisierung von Angebot und Nachfrage nach sechs Ökosystemdienstleistungen, die von verschiedenen Akteuren in der Stadt priorisiert werden. Das letzte Kapitel schließlich enthält eine Zusammenfassung der wichtigen Funde der städtischen Umwelt in Guatemala-Stadt in historischer Hinsicht, ihrer Merkmale, räumlichen Muster und der Auswirkungen auf die Verwaltung und Planung der Stadt. Abschließend werden neue Fragen gestellt, die im Laufe der Arbeit auftauchten, und es werden weitere Informationslücken diskutiert. Mögliche Forschungen über städtische Ökologie werden vorgeschlagen, um letztlich für städtische Nachhaltigkeit zu argumentieren.Latin America and Caribbean is the one of the fastest urbanizing regions in the world and their cities are facing many challenges related to the environment, the negative effects of climate change, their legacies of high social inequality and their precarious settlements. As climate change enhance the risks of these cities, they also pose challenges for urban planning and for new trajectories towards sustainable futures.
This dissertation aimed to understand the importance of urban green in a Central American city. The study case is Guatemala City. The structure of the dissertation starts with the introduction in which theoretical aspects are reviewed that were the base of the methods and framework chosen. The second chapter through the fourth, are published and submitted papers in peer reviewed journals, and the last one is the synthesis of findings. Second chapter shows the historical development of urban green in the city through socioecological lenses. It is an historical account on how urban green dynamics occurred simultaneously with urbanization processes and the current socio-ecological problems found in the city. Third chapter discusses the identification of the urban green spaces that form part of the urban green fabric in Guatemala City. The fourth chapter is related to where the benefits provided by the urban green fabric are. Spatial models show the location of the supply and demand of six ecosystem services prioritized by different stakeholders. The last chapter discuss the major findings of Guatemala City’s urban green in terms of history, characteristics, spatial pattern, management and planning implications. The chapter finalizes with a discussion of new questions that emerged from this work and future path for research on the urban ecology of the city and finally, arguments towards urban sustainability
First-order phase transition of the Schwinger model with a quantum computer
No full textWe explore the first-order phase transition in the lattice Schwinger model in the presence of a topological θ -term by means of the variational quantum eigensolver (VQE). Using two different fermion discretizations, Wilson and staggered fermions, we develop parametric ansatz circuits suitable for both discretizations, and compare their performance by simulating classically an ideal VQE optimization in the absence of noise. The states obtained by the classical simulation are then prepared on the IBM’s superconducting quantum hardware. Applying state-of-the art error-mitigation methods, we show that the electric field density and particle number, observables which reveal the phase structure of the model, can be reliably obtained from the quantum hardware. To investigate the minimum system sizes required for a continuum extrapolation, we study the continuum limit using matrix product states, and compare our results to continuum mass perturbation theory. We demonstrate that taking the additive mass renormalization into account is vital for enhancing the precision that can be obtained with smaller system sizes. Furthermore, for the observables we investigate we observe excellent agreement in the continuum limit of both fermion discretizations.EC | Horizon 2020 Framework Programme (EU Framework Programme for Research and Innovation H2020)100010661“Future-proofing Scientific Applications for the Super- computers of Tomorrow (FAST)”, contract no. COM- PLEMENTARY/0916/0048 Quantum Computing for Lattice Gauge Theories (QC4LGT)”, contract no. EXCELLENCE/0421/0019“Innopool Project Variational Quantum Computer Simulations (VQCS).”Peer Reviewe
A global threshold model of enabling conditions for social tipping in pro-environmental behaviours – the role of sea level rise anticipation and climate change concern
No full textEffective climate change mitigation necessitates swift societal transformations. Positive social tipping processes, where small triggers initiate qualitative systemic shifts, are potential key mechanisms towards instigating the desired emissions mitigation. A necessary foundation for societal tipping processes is the creation of enabling conditions. Here, we assess future sea level rise estimates and social survey data within the framework of a network-based threshold model to exemplify the enabling conditions for tipping processes. We find that in many countries, the level of climate change concern is already sufficient, suggesting the enabling conditions and opportunities for social activation already exist. Further, drawing upon the interrelation between climate change concern and anticipation of future sea level rise, we report three qualitative classes of tipping potential that are regionally clustered, with the greatest potential for tipping in western Pacific Rim and East Asian countries. These findings propose a transformative pathway where climate change concern increases the social tipping potential, while extended anticipation time horizons can trigger the system towards an alternative trajectory of larger social activation for climate change mitigation.Leibniz-GemeinschaftBundesministerium für Bildung und ForschungEuropean Research CouncilStordalen FoundationEarth LeaguePeer Reviewe
The Urdu/Hindi perfective-based future
No full textWe explore the emergence of the Modern Urdu/Hindi -g- future, which is built historically from a combination of an imperfective-marked main verb and perfective-marked motion verb ‘go’. Given that both verbs are members of the finite tense/aspect subsystem in the linguistic system in which the construction is innovated, we suggest that this construction starts out as a combination of clauses which pragmatically gives rise to a teleological inference. It is this inference that, under certain assumptions, generates future reference
Three-dimensional architecture and linearized mapping of vibrissa follicle afferents
No full textThe article processing charge was funded by the Open Access Publication Fund of Humboldt-Universität zu Berlin.Understanding vibrissal transduction has advanced by serial sectioning and identified afferent recordings, but afferent mapping onto the complex, encapsulated follicle remains unclear. Here, we reveal male rat C2 vibrissa follicle innervation through synchrotron X-ray phase contrast tomograms. Morphological analysis identified 5% superficial, ~32 % unmyelinated and 63% myelinated deep vibrissal nerve axons. Myelinated afferents consist of each one third Merkel and club-like, and one sixth Ruffini-like and lanceolate endings. Unsupervised clustering of afferent properties aligns with classic morphological categories and revealed previously unrecognized club-like afferent subtypes distinct in axon diameter and Ranvier internode distance. Myelination and axon diameters indicate a proximal-to-distal axon-velocity gradient along the follicle. Axons innervate preferentially dorso-caudally to the vibrissa, presumably to sample contacts from vibrissa protraction. Afferents organize in axon-arms innervating discrete angular territories. The radial axon-arm arrangement around the vibrissa maps into a linear representation of axon-arm bands in the nerve. Such follicle linearization presumably instructs downstream linear brainstem barrelettes. Synchrotron imaging provides a synopsis of afferents and mechanotransductory machinery.Deutsche Forschungsgemeinschaft (German Research Foundation)https://doi.org/10.13039/501100001659Deutsches Elektronen-Synchrotron (DESY)https://doi.org/10.13039/501100001647SFB1456/A3 Mathematics of ExperimentPeer Reviewe
Just a peep on a green twig: negation affinity and NPI-hood
No full textThis paper looks at two German expressions that are usually found in negative contexts: einen Mucks machen ‘make a peep’, and auf einen grünen Zweig kommen ‘do fine (in some relevant domain)’ (lit. ‘get on a green twig’). I argue that both differ from jemals ‘ever’, the common textbook example of a Negative Polarity Item (NPI). I propose to capture the distribution of the two expressions in a representational model of the semantics-pragmatics interface: Einen Mucks machen must be in the scope of negation at some level of semantic representation. Auf einen grünen Zweig kommen contributes negative use-conditional content, which needs to be compatible with the asserted content. The paper proposes a definition of NPI-hood that comprises these two expressions as well as standard NPIs such as jemals ‘ever’. Throughout the paper I use Eckardt (2012) as my basis for comparison with other approaches
Measurement of Astrophysical Neutrino flavour composition with Twelve Years of IceCube Data
No full textKosmische Strahlung und hochenergetische Neutrinos stammen aus extremen astrophysikalischen Umgebungen, wo kosmische Strahlen mit Materie oder Photonen interagieren und Neutrinos erzeugen. Die auf der Erde beobachtete Flavour-Zusammensetzung liefert Einblicke in deren Ursprünge. Durch Neutrinooszillationen erscheinen Tau-Neutrinos – an der Quelle nicht vorhanden – beim Eintreffen auf der Erde. Ihre Detektion ist entscheidend für das Verständnis dieser Quellen. Diese Arbeit untersucht die Flavour-Zusammensetzung hochenergetischer astrophysikalischer Neutrinos, mit Fokus auf Tau-Neutrino-Ereignisse aus zwölf Jahren IceCube-Daten. Ein ternärer Klassifikator teilte die Ereignisse in Einzel-Kaskaden, Doppel-Kaskaden und Spuren ein. Es wurden fünf Doppel-Kaskaden (davon vier neu), 64 Einzel-Kaskaden und 28 startende Spuren identifiziert. Diese Ergebnisse stimmen mit einem Power-Law-Spektrum überein. Fortschritte bei Simulationen und Rekonstruktionen umfassten u.,a. verbesserte Wirkungsquerschnitte und Lichtausbreitung im aktuellen Eismodell des Südpols. Die Analyse ergab eine Flavour-Zusammensetzung: mit 68\% Unsicherheiten. Dies favorisiert leicht ein muon-gedämpftes Szenario. Obwohl keine Quelle signifikant ausgeschlossen wurde, zeigen sich Schwächen in der aktuellen Doppel-Kaskaden-Rekonstruktion. Abschließend skizziert die Arbeit zukünftige Möglichkeiten mit IceCube-Gen2 zur Tau-Neutrino-Detektion und präziseren Flavour-Messung mit Potenzial zur Unterscheidung verschiedener Quellenszenarien.Cosmic rays and high-energy neutrinos are linked, originating from extreme astrophysical environments where cosmic rays interact with matter or photons to produce neutrinos. The flavor composition of neutrinos observed on Earth provides insights into their production mechanisms. Due to neutrino oscillations, tau neutrinos—absent at the sources—appear by the time they reach Earth, making their detection crucial for studying astrophysical sources. This thesis measures the flavor composition of high-energy astrophysical neutrinos, focusing on tau neutrino events from a twelve-year sample collected by the IceCube Neutrino Observatory. A ternary classifier categorized events as single cascades, double cascades, and tracks. Five double cascade events were identified, including four previously unobserved, along with 64 single cascades and 28 starting tracks. These findings align with expectations from a single power-law spectrum of neutrinos. Significant advancements in simulations and reconstruction methods included corrections for cross sections and better accounting for light propagation in recent South Pole ice models. The analysis yielded a flavor composition of with 68% uncertainties, slightly favoring a muon-damped flavor production scenario. Although specific source scenarios were not excluded with high significance, the study highlighted limitations in current reconstruction methods, particularly for double-cascade classifications. In conclusion, the thesis projects future work for the IceCube-Gen2 observatory to detect high-energy tau neutrinos and measure the flavor composition of the neutrino spectrum, indicating strong potential to exclude various source scenarios and resolve energy-dependent flavor compositions