University of Bremen

Accurate cloud phase classification in the near-infrared is challenging due to the overlapping radiative properties of water, ice, and mixed-phase clouds. This study presents a new composite Phase Classification Index (PCI NIR,DV ) for near-infrared satellite measurements in a dual-viewing geometry. The index is defined as the product of two physically derived components: (1) a spectral ratio of top-of-atmosphere radiances at 1.61 μ m and 2.25 μ m, which exploits the differences in absorption between water and ice, and (2) a directional ratio of 0.87 μ m radiances from oblique and nadir views, which are influenced by scattering. Theoretical simulations using the SCIATRAN radiative transfer model demonstrate that the PCI NIR,DV effectively distinguishes between pure water and ice clouds, enabling mixed-phase clouds to be identified. Sensitivities are analyzed for ranges of particle sizes, ice fractions, and surface types. Theoretical results show that water clouds, excluding thin clouds over snow surfaces, exhibit high PCI NIR,DV values (above 3.5), ice clouds yield low values (below 2.75), and intermediate values correspond to mixed-phase clouds. Validation of PCI NIR,DV derived from the Sea and Land Surface Temperature Radiometer (SLSTR) dual-view observations (onboard Sentinel-3A) against CloudSat-CALIPSO phase classifications confirms its applicability, yielding 86% classification accuracy, including over 63% for mixed-phase clouds. The results demonstrate that PCI NIR,DV provides a robust physical framework for dual-view satellite missions, which aim to measure the cloud phase. • An index is formulated from spectral absorption and angular scattering properties of clouds, which provides robust separation between water, ice, and mixed-phase clouds for a range of cloud optical and microphysical properties. • As the ice fraction in the mixed-phase clouds exceeds 80%, phase discrimination between mixed-phase and ice clouds in the NIR wavelengths becomes increasingly challenging.

Mass spectrometry imaging (MSI) is widely used in biomedical sciences, as well as in plant sciences or microbiological studies. However, it is much less prominent in the earth sciences, despite holding enormous potential. For example, marine and lake sediments are excellent archives of the past, as they store the remnants of organisms from the water column and from surrounding land. These organisms leave behind fossil molecules that can be employed to reconstruct the environmental conditions during their lifetime, and hence to study the climate evolution of Earth. Focusing on matrix-assisted laser desorption/ionization (MALDI) imaging, we herein show that it is possible to read these molecular signatures in micrometer-sized spots, and thus to characterize climate variability with unprecedented resolution. However, obtaining this information is not trivial, and challenges arise from the nature of geological samples, low analyte concentrations, strong matrix effects, and from the need to reference the micrometer-scale maps to the original, large samples. Here we present a detailed tutorial on (i) how to select and prepare suitable samples, (ii) how to analyze them while avoiding the most common pitfalls and (iii) how to process the resulting large and complex dataset. We hope that this tutorial might contribute to inspire the use of MALDI in paleoenvironmental reconstructions in particular and in the earth sciences in general, and at the same time be useful to imaging applications across research fields.

Schizophrenia encompasses positive, negative, and cognitive symptoms, and accumulating evidence suggests that the orexin system may modulate circuits relevant to these domains. Here, we investigated whether orexin-related interventions influence schizophrenia-like behaviors induced by the NMDA receptor antagonist dizocilpine in female and male mice. Two distinct approaches were used: nasal orexin A administration and chemogenetic activation of orexin neurons via DREADDs. Behavioral assessments included prepulse inhibition (PPI), locomotion and exploratory activity in the open field, social behavior, and working memory in the Y-maze. Overall, dizocilpine robustly induced schizophrenia-like phenotypes across these paradigms. Nasal orexin A exacerbated the dizocilpine-induced PPI deficit but attenuated the associated increase in startle reactivity, did not modify dizocilpine-induced hyperactivity, and partially rescued working memory impairments. Chemogenetic activation reproduced the PPI pattern observed with nasal orexin A, increased locomotion in both control- and dizocilpine-treated mice, induced anxiolytic-like effects in the open field, restored exploratory rearing, facilitated social recognition, and fully rescued working memory deficits. In some cases, the effects of these orexin-related interventions were differently pronounced in the two sexes. These findings indicate that activating the orexin system may worsen behavioral endophenotypes related to positive symptoms while alleviating those associated with negative and cognitive symptoms. However, substantial variability across assays, potentially related to the dosing of dizocilpine, orexin A, and CNO, as well as protocol-dependent constraints in some behavioral paradigms, limits definitive interpretation. Nevertheless, the present data reveal novel and domain-specific effects of orexin signaling in schizophrenia-relevant behavioral circuits and highlight the importance of exploring interventions with intermediate efficacy, including newly emerging orexin receptor agonists, to more precisely delineate orexin-dependent mechanisms and their therapeutic potential for negative and cognitive symptom domains.

Scholarship on power resources theory has often understood ‘institutional resources’ as restricted to labour market institutions, despite the concept of ‘institutions’ extending beyond the regulation of the labour market and into goods and services markets. During the pandemic, trade unions assumed such an important, extended role of co-managing functions beyond the labour market. However, under which conditions can unions effectively assume this extended role? We argue that an important condition is the existence of ‘political power resources’: political characteristics of a given field that empower unions to assume an extended role. We develop this new form of institutional power resource by examining the success of union-led, anti-privatization campaigns in German and English healthcare. In doing so, we explain why campaigns in England succeeded more than in Germany by virtue of the politics of the two countries’ healthcare systems: in England, the system’s high level of politicization prompted policymakers to follow anti-privatization campaigns and halt privatization; by contrast, in Germany, policymakers could legally circumvent anti-privatization campaigns.

Atrial tachycardias (AT) represent an increasingly common cause of morbidity and mortality. Driven by substantial advances in mapping and ablation technologies, the mechanistic understanding and therapeutic strategies for AT management have evolved rapidly in recent years, and catheter ablation is now regarded as the most effective strategy for maintaining sinus rhythm. Against this background, the recently published international clinical consensus statement on the management of patients with AT introduces, for the first time, astructured 10-point plan for "SMART-AT care" as aframework for the diagnosis and treatment of regular AT. This review highlights key developments and clinical implications, taking into account recent changes within the healthcare system.

Objective: This study examines the competitive and collaborative dynamics between entrepreneurship through acquisition (ETA) and small- and micro-cap private equity (PE) in acquiring small and medium-sized enterprises (SMEs). Focusing on the DACH region (Germany, Austria, Switzerland), it explores how both actors overlap in target firm size, compete in deals, and identify opportunities for co-investment – an area that has received limited academic attention. Research Design & Methods: To address this gap, we used an inductive mixed-methods approach rooted in entrepreneurship theory and the resource-based view (RBV). We drew on interviews with twelve PE firms in the DACH region, complemented by eight expert interviews, to develop a theoretical model grounded in both practice and strategic intent. Findings: The study revealed an intensifying level of competition between ETA entrepreneurs and PE firms for smaller businesses, which are frequently central to PE buy-and-build strategies. Despite this competition, there is evidence of collaboration between the two parties. Private equity firms show a willingness to co-invest with ETA entrepreneurs, provided that they retain majority ownership and that the entrepreneurs bring relevant, task-related human capital to the table. Implications & Recommendations: These findings have practical implications for aspiring ETA entrepreneurs, suggesting the importance of strategic career planning and the development of industry-specific expertise to align with PE firms’ partnership expectations. Additionally, the research encourages future studies to explore which types of SMEs are particularly attractive to both ETA entrepreneurs and PE firms. Contribution & Value Added: This study contributes to entrepreneurship theory by offering a nuanced perspective on the relationship between ETA and PE in SME acquisitions. It presents a novel theoretical model capturing both competitive and collaborative dynamics, while also enriching the empirical understanding of the often-overlooked small- and micro-cap PE segment.

Abstract. Predicting the trajectory of aquatic deoxygenation under global warming requires a mechanistic understanding of lacustrine responses to rapid climate shifts. We investigated how climate-driven changes in catchment vegetation and local iron-rich lithology regulated lake stratification and ecosystem resilience in the maar lake Holzmaar (Central Europe). We focused on the Late Glacial, specifically on transitions during Dansgaard-Oeschger Event 1 (DOE-1; ca. 14,690–11,700 cal yr BP), a period of rapid natural warming and cooling that serves as an analogue for future high amplitude climate variation and for modern Arctic lakes undergoing rapid climate-driven transitions. Combining non-destructive hyperspectral imaging (HSI) of sedimentary pigments with high-resolution XRF geochemistry, we resolved parts of the ecosystem trajectory during DOE-1. Ecological succession progress from a pioneer community of cyanobacteria to a stable anoxic late-successional community characterized by planktonic diatom Stephanodiscus minutulus and anoxygenic purple sulphur bacteria (PSB) in the photic zone. While regional warming (mean summer temperature increased ~2.8 °C) provided the physical potential for lake stratification, our data suggest that intense anoxia was primarily triggered by the expansion of Betula in the watershed. This afforestation stabilized the water column through wind shielding. The termination of the anoxic phase coincided with the onset of the Younger Dryas cooling and increased aridity, which effectively destabilized the existing stratification. While the shift from Betula to Pinus forest may have caused a change in the terrestrial-aquatic linkage, the primary driver of the transition was the physical forcing (lake mixing) of the climatic shift (cooling). Geochemically, the lake exhibited remarkable resilience. Unlike carbonate-dominated systems prone to internal phosphorus loading, Holzmaar efficiently sequesters nutrients via a dual mechanism of reactive iron binding (authigenic vivianite) and stable mineral burial. The phosphorous trap prevents nutrient release by permanently sequestering P in the sediment, allowing rapid ecosystem recovery without delay once the specific climate and vegetation drivers shift. Our findings demonstrate that in volcanic maar lakes, catchment vegetation characteristics and local lithology can modulate, and even override, the direct effects of climate warming on aquatic anoxia.

The utilisation of composite materials has the potential to play a vital role in the development of lightweight structures for future generations of aircraft, with the objective to reduce emissions. Ultrasonic welding is a process that has been proven to exhibit advantageous qualities, including the capacity to achieve welds with a comparatively short process time. Furthermore, its capacity to function as both a static and a continuous process makes it a viable candidate for facilitating the realisation of this objective. The present study investigates the potential of a novel explicit modelling approach for the static ultrasonic welding process to more accurately represent the welding process by incorporating a more precise representation of the hammering effect. The hammering effect describes the partial loss of contact between the sonotrode and the upper adherend. The model's validation was achieved through a multifaceted approach that incorporates high-speed camera recording, encompassing digital image correlation, laser displacement sensor measurements, and static ultrasonic welding experiments. These experiments encompassed varying welding times, followed by fracture surface analysis. The findings showed that an explicit time-domain model can effectively represent the static welding process of unidirectional materials utilising a film energy director. The experimental validation demonstrated a high degree of correlation between the thermal behaviour of the welding interface and the simulation results. The study demonstrated that the neutral position of the sonotrode exhibited an increase during the initial phase of the welding process due to dynamic stresses. This phenomenon enables reduced constraint movement of the adherends and the energy director, which results in the disconnection of the sonotrode from both the upper adherend and the energy director, as well as the adherends and the anvil. The higher neutral position of the sonotrode was then implemented in an explicit simulation of the static ultrasonic welding process.