Filtern
Erscheinungsjahr
Dokumenttyp
- Wissenschaftlicher Artikel (30174)
- Ausgabe (Heft) zu einer Zeitschrift (11860)
- Buch (Monographie) (8242)
- Dissertation (5653)
- Teil eines Buches (Kapitel) (3662)
- Arbeitspapier (3374)
- Rezension (2872)
- Beitrag zu einer (nichtwissenschaftlichen) Zeitung oder Zeitschrift (2307)
- Preprint (1851)
- Bericht (1544)
Sprache
- Deutsch (42194)
- Englisch (28619)
- Französisch (1067)
- Portugiesisch (723)
- Mehrsprachig (307)
- Kroatisch (302)
- Spanisch (301)
- Italienisch (194)
- mis (174)
- Türkisch (148)
Gehört zur Bibliographie
- nein (74354) (entfernen)
Schlagworte
- Deutsch (1038)
- Literatur (804)
- taxonomy (747)
- Deutschland (542)
- Rezension (491)
- new species (441)
- Frankfurt <Main> / Universität (341)
- Rezeption (322)
- Geschichte (292)
- Linguistik (268)
Institut
- Medizin (7547)
- Präsidium (5123)
- Physik (4173)
- Wirtschaftswissenschaften (2664)
- Extern (2661)
- Gesellschaftswissenschaften (2368)
- Biowissenschaften (2149)
- Biochemie und Chemie (1964)
- Center for Financial Studies (CFS) (1611)
- Informatik (1593)
The elliptic flow (v2) of D0 mesons from beauty-hadron decays (non-prompt D0) was measured in midcentral (30-50%) Pb-Pb collisions at a centre-of-mass energy per nucleon pair sNN−−−√ = 5.02 TeV with the ALICE detector at the LHC. The D0 mesons were reconstructed at midrapidity (|y|<0.8) from their hadronic decay D0→K−π+, in the transverse momentum interval 2<pT<12 GeV/c. The result indicates a positive v2 for non-prompt D0 mesons with a significance of 2.7σ. The non-prompt D0-meson v2 is lower than that of prompt non-strange D mesons with 3.2σ significance in 2<pT<8 GeV/c, and compatible with the v2 of beauty-decay electrons. Theoretical calculations of beauty-quark transport in a hydrodynamically expanding medium describe the measurement within uncertainties.
Controlling and understanding electron correlations in quantum matter is one of the most challenging tasks in materials engineering. In the past years a plethora of new puzzling correlated states have been found by carefully stacking and twisting two-dimensional van der Waals materials of different kind. Unique to these stacked structures is the emergence of correlated phases not foreseeable from the single layers alone. In Ta-dichalcogenide heterostructures made of a good metallic “1H”- and a Mott insulating “1T”-layer, recent reports have evidenced a cross-breed itinerant and localized nature of the electronic excitations, similar to what is typically found in heavy fermion systems. Here, we put forward a new interpretation based on first-principles calculations which indicates a sizeable charge transfer of electrons (0.4-0.6 e) from 1T to 1H layers at an elevated interlayer distance. We accurately quantify the strength of the interlayer hybridization which allows us to unambiguously determine that the system is much closer to a doped Mott insulator than to a heavy fermion scenario. Ta-based heterolayers provide therefore a new ground for quantum-materials engineering in the regime of heavily doped Mott insulators hybridized with metallic states at a van der Waals distance.
Highlights
• Pathways for a circular economy towards the EU goals require policy support that, in turn, requires legitimacy.
• Legitimacy is often contested in the public discourse at all phases in the technological innovation system.
• Legitimacy remains poorly understood for ‘in-between’ technologies that struggle to move from the formative to the growth stage.
• The article explores legitimacy for chemical recycling primarily based on evidence from the UK, Germany, and Italy.
Abstract
The European Commission aims to increase the recycling of plastic packaging to 60% by 2025, requiring fundamental changes towards a more circular economy. Pathways for this transition require policy support that largely depends on their legitimacy in the public discourse. These normative aspects remain poorly understood for ‘in-between’ technologies, i.e., technologies that are no longer novel but struggle to move to the growth phase within the technological innovation system. Therefore, we ask: How do discourses shape technology legitimacy for in-between technologies? Drawing on the empirical example of chemical recycling, the analysis renders two principal findings. First, legitimising and delegitimising storylines present contesting views on in-between technologies regarding their technological aspects, environmental and social impacts, and economic and policy implications. Second, how discourses contribute to technology legitimacy depends on the actors and interests that drive the prevalent storylines in particular contexts.
Trait-dependent effects of biotic and abiotic filters on plant regeneration in Southern Ecuador
(2024)
Tropical forests have always fascinated scientists due to their unique biodiversity. However, our understanding of ecological processes shaping the complexity of tropical rainforests is still relatively poor. Plant regeneration is one of the processes that remain understudied in the tropics although this is a key process defining the structure, diversity and assembly of tropical plant communities. In my dissertation, I combine experimental, observational and trait-based approaches to identify processes shaping the assembly of seedling communities and compare associations between environmental conditions and plant traits across plant life stages. By working along a steep environmental gradient in the tropical mountains of Southern Ecuador, I was able to investigate how processes of plant regeneration vary in response to biotic and abiotic factors in tropical montane forests.
My dissertation comprises three complementary chapters, each addressing an individual research question. First, I studied how trait composition in plant communities varies in relation to the broad- and local-scale environmental conditions and across the plant life cycle. I measured key traits reflecting different ecological strategies of plants that correspond to three stages of the plant life cycle (i.e., adult trees, seed rain and recruiting seedlings). I worked on 81 subplots along an elevational gradient covering a large climatic gradient at three different elevations (1000, 2000 and 3000 m a.s.l.). In addition, I measured soil and light conditions at the local spatial scale within each subplot. My findings show that the trait composition of leaves, seeds and seedlings changed similarly across the elevational gradient, but that the different life stages responded differently to the local gradients in soil nutrients and light availability. Consequently, my findings highlight that trait-environment associations in plant communities differ between large and small spatial scales and across plant life stages.
Second, I investigated how seed size affects seedling recruitment in natural forests and in pastures in relation to abiotic and biotic factors. I set up a seed sowing experiment in both habitat types and sowed over 8,000 seeds belonging to seven tree species differing in seed size. I found that large-seeded species had higher proportions of recruitment in the forests compared to small-seeded species. However, small-seeded species tended to recruit better in pastures compared to large-seeded species. I showed that high surface temperature was the main driver of differences in seedling recruitment between habitats, because it limited seedling recruitment of large-seeded species. The results from this experiment show that pasture restoration requires seed addition of large-seeded species and active protection of recruiting seedlings in order to mitigate harmful conditions associated with high temperatures in deforested areas.
Third, I examined the associations between seedling beta-diversity and different abiotic and biotic factors between and within elevations. I applied beta-diversity partitioning to obtain two components of beta-diversity: species turnover and species richness differences. I associated these components of beta-diversity with biotic pressures by herbivores and fungal pathogens and environmental heterogeneity in light and soil conditions. I found that species turnover in seedling communities was positively associated with the dissimilarity in biotic pressures within elevations and with environmental heterogeneity between elevations. Further, I found that species richness differences increased primarily with increasing environmental heterogeneity within elevations. My findings show that the associations between beta-diversity of seedling communities and abiotic and biotic factors are scale-dependent, most likely due to differences in species sorting in response to biotic pressures and species coexistence in response to environmental heterogeneity.
My dissertation reveals that studying processes of community assembly at different plant life stages and spatial scales can yield new insights into patterns and processes of plant regeneration in tropical forests. I investigated how community assembly processes are governed by abiotic and biotic filtering across and within elevations. I also experimentally explored how the process of seedling recruitment depends on seed size-dependent interactions, and verified how these effects are associated with abiotic and biotic filtering. Identifying such processes is crucial to inform predictive models of environmental change on plant regeneration and successful forest restoration. Further exploration of plant functional traits and their associations with local-scale environmental conditions could effectively support local conservation efforts needed to enhance forest cover in the future and halt the accelerating loss of biodiversity.
Highlights
• Investigates the effect of a nearly fare-free public transport ticket.
• In-depth analysis of the 9-Euro-Ticket using qualitative empirical research.
• Low-income people's mobility and social participation benefits from affordable PT.
• This study reveals six main findings of interest for policy and practice.
From June to August 2022, the financial barrier to public transport use almost completely disappeared in Germany due to the 9-Euro-Ticket. It enabled anyone with access to public transport infrastructure across Germany to use public transport for 9 euros per person per month. As this completely changed the conditions for public transport use, especially for low-income households with children, the following research questions arise: (1) what effect does the 9-Euro-Ticket have on the travel practices and social participation of low-income households with children? (2) how and by what were the travel practices shaped by the 9-Euro-Ticket? and (3) what happened to the interviewees’ travel practices after the measure expired? To answer these questions, twelve qualitative interviews were conducted with low-income households with children in the Hanover region.
This study found that the 9-Euro-Ticket removed the financial constraint of public transport use, changed the travel practices of most interviewees and had a wide range of positive meanings. The respondents associate the 9-Euro-Ticket with freedom, joy at being able to offer their children something, along with financial and psychological relief. Additionally, the 9-Euro-Ticket enabled the interviewees to engage in leisure activities, to visit relatives, contributed to integration, had an empowering effect, especially for women and children, and thus represents a measure to increase social participation. After the three months of the 9-Euro-Ticket, financing public transport use challenges low-income households again and financial constraints prevent them from reaching certain places and engaging in out-of-home activities.
Neanderthal diet has been on the spotlight of paleoanthropological research for many years. The majority of studies that tried to reconstruct the diet of Neanderthals were based on the analysis of zooarchaeological remains, stable isotopes, dental calculus and dental microwear patterns. In the past few years, there have been a few studies that linked dental macrowear patterns of Neanderthals and modern humans to diet and cultural habits. However, they mostly focused on maxillary molars. Although mandibular molars have been widely used in microwear dietary research, little is known about their usage at the macroscopic scale to detect information about human subsistence strategies. In this study, we compare the macrowear patterns of Neanderthal (NEA), fossil Homo sapiens (FHS), modern hunter-gatherers (MHG), pastoralists, early farmers and Australian Aborigines from Yuendumu mandibular molars in order to assess their utility in collecting any possible information about dietary and cultural habits among diverse human groups. We use the occlusal fingerprint analysis method, a quantitative digital approach that has been successfully employed to reconstruct the diet of living non-human primates and past human populations. Our results show macrowear pattern differences between meat-eater MHG and EF groups. Moreover, while we did not find eco-geographical differences in the macrowear patterns of the fossil sample, we found statistically significant differences between NEA and FHS inhabiting steppe/coniferous forest. This latter result could be associated with the use of distinct technological complexes in these two species, which ultimately could have allowed modern humans to exploit natural resources in a different way compared to NEA.
Highlights
• 153 chemicals of emerging concern detected in complex multi-component mixtures.
• 108 possible mixture risk assessment scenarios were investigated.
• Non-detects, QSARs, and experimental ecotoxicological data were integrated for risk assessment.
• 8 chemicals were the main risk drivers in at least one site across the River Aconcagua basin.
Abstract
Environmental risk assessments strategies that account for the complexity of exposures are needed in order to evaluate the toxic pressure of emerging chemicals, which also provide suggestions for risk mitigation and management, if necessary. Currently, most studies on the co-occurrence and environmental impacts of chemicals of emerging concern (CECs) are conducted in countries of the Global North, leaving massive knowledge gaps in countries of the Global South.
In this study, we implement a multi-scenario risk assessment strategy to improve the assessment of both the exposure and hazard components in the chemical risk assessment process. Our strategy incorporates a systematic consideration and weighting of CECs that were not detected, as well as an evaluation of the uncertainties associated with Quantitative Structure-Activity Relationships (QSARs) predictions for chronic ecotoxicity. Furthermore, we present a novel approach to identifying mixture risk drivers. To expand our knowledge beyond well-studied aquatic ecosystems, we applied this multi-scenario strategy to the River Aconcagua basin of Central Chile. The analysis revealed that the concentrations of CECs exceeded acceptable risk thresholds for selected organism groups and the most vulnerable taxonomic groups. Streams flowing through agricultural areas and sites near the river mouth exhibited the highest risks. Notably, the eight risk drivers among the 153 co-occurring chemicals accounted for 66–92 % of the observed risks in the river basin. Six of them are pesticides and pharmaceuticals, chemical classes known for their high biological activity in specific target organisms.
• Zahlen und Maßsysteme sind bereits aus dem antiken Ägypten und aus Mesopotamien belegt. Im 4. Jahrtausend vor unserer Zeitrechnung haben sich mit der hierarchisierten Gesellschaft auch Zahl- und Schriftzeichen entwickelt. Sie dienten vor allem der Zuteilung von Ressourcen.
• Die 13 Bücher der »Elemente« von Euklid (3. Jahrhundert vor unserer Zeit) sind die früheste erhaltene axiomatisch-deduktiv aufgebaute Sammlung mathematischen Wissens. Die Begeisterung für dieses Werk hielt über Jahrhunderte an.
• Die Ordnung von Beobachtungen durch die mathematische Erfassung und Auswertung von Daten ist in Wissenschaft und Alltag selbstverständlich. Mathematische Techniken der Statistik und Kartierung halfen Dr. John Snow im 19. Jahrhundert, die Ausbreitung der Cholera zu erforschen und zu bekämpfen.
• Trotzdem stößt die Mathematik bei der Schaffung von Ordnungen auch an Grenzen: Denn es gibt weder eine Garantie noch eine Anleitung für deren bestmögliche Nutzung. Dies zeigen nicht zuletzt Krisen wie die Coronapandemie oder die Klimakrise.
Der Anblick ist überwältigend. Ein buntes Sammelsurium der unterschiedlichsten Dinge, die sich dicht an dicht in den Fächern des raumhohen Regals drängen, eine Steilwand aus Wimmelbildern im Wunderkammer-Format. Wenn wir die Fächer allerdings genauer betrachten, stellt sich allmählich der Eindruck ein, dass es doch so etwas wie eine Ordnung der Dinge gibt. Nur welche?