University of Bayreuth
  • Bayreuth, Germany
Recent publications
As one of the most strategically relevant and financially promising developing industries, the requirements for autonomous driving (AD) systems´ reliability are dramatically higher than in the driver-based car industry. Using the analytic hierarchy process method, this study conducts a quantitative empirical study to prioritise the 15 critical success factors (CSFs) of total quality management (TQM) in the AD-ecosystem. The CSFs are derived from VDA and IATF 16949, two widely accepted TQM-frameworks in the car industry. Comparisons are made between Germany and China as two of the most important places in the world for strategic marketing for autonomous driving.
Microscopic electric fields govern the majority of elementary excitations in condensed matter and drive electronics at frequencies approaching the Terahertz (THz) regime. However, only few imaging schemes are able to resolve sub-wavelength fields in the THz range, such as scanning-probe techniques, electro-optic sampling, and ultrafast electron microscopy. Still, intrinsic constraints on sample geometry, acquisition speed and field strength limit their applicability. Here, we harness the quantum-confined Stark-effect to encode ultrafast electric near-fields into colloidal quantum dot luminescence. Our approach, termed Quantum-probe Field Microscopy (QFIM), combines far-field imaging of visible photons with phase-resolved sampling of electric waveforms. By capturing ultrafast movies, we spatio-temporally resolve a Terahertz resonance inside a bowtie antenna and unveil the propagation of a Terahertz waveguide excitation deeply in the sub-wavelength regime. The demonstrated QFIM approach is compatible with strong-field excitation and sub-micrometer resolution—introducing a direct route towards ultrafast field imaging of complex nanodevices in-operando.
Background The recent rise in temperature and shifting precipitation regimes threaten ecosystems around the globe to different degrees. Treelines are expected to respond to climate warming by shifting to higher elevations, but it is unclear whether they can track temperature changes. Here, we integrated high-resolution aerial imagery with local climatic and topographic characteristics to study the treeline dynamic from 1945 to 2015 on the semi-arid Mediterranean island of Crete, Greece. Results During the study period, the mean annual temperature at the treeline increased by 0.81 °C, while the average precipitation decreased by 170 mm. The treeline is characterized by a diffuse form, with trees growing on steep limestone slopes (>50°) and shallow soils. Moreover, the treeline elevation decreases with increasing distance from the coast and with aspect (south > north). Yet, we found no shift in the treeline over the past 70 years, despite an increase in temperature in all four study sites. However, the treeline elevation correlated strongly with topographic exposure to wind (R² = 0.74, p < 0.001). Therefore, the temporal lag in treeline response to warming could be explained by a combination of topographic and microclimatic factors, such as the absence of a shelter effect and a decrease in moisture. Conclusion Although there was no treeline shift over the last 70 years, climate change has already started shifting the treeline altitudinal optimum. Consequently, the lack of climate-mediated migration at the treeline should raise concerns about the threats posed by warming, such as drought damages, and wildfire, especially in the Mediterranean region. Therefore, conservation management should discuss options and needs to support adaptive management.
Negative word-of-mouth is a strong consumer and user response to dissatisfaction. Moral outrages can create an excessive collective aggressiveness against one single argument, one single word, or one action of a person resulting in hateful speech. In this work, we examine the change of vocabulary to explore the outbreak of online firestorms on Twitter. The sudden change of an emotional state can be captured in language. It reveals how people connect with each other to form outrage. We find that when users turn their outrage against somebody, the occurrence of self-referencing pronouns like ‘I’ and ‘me’ reduces significantly. Using data from Twitter, we derive such linguistic features together with features based on retweets and mention networks to use them as indicators for negative word-of-mouth dynamics in social media networks. Based on these features, we build three classification models that can predict the outbreak of a firestorm with high accuracy.
This study examines the factors influencing blockchain’s adoption intention as a whole, relying on an organisational perspective and the Technology-Organisation-Environment Framework (TOE). To organise and investigate the factors and to study blockchain technology adoption intention, this research employs a mixed-methodology. After an extended literature review, first, a qualitative approach is used to discover the factors from primary data collected from 25 interviews. Second, a quantitative survey is employed directly relating the factors to blockchain adoption intention and empirically testing them with 146 employees from 71 North American organisations. A total of 15 factors are discovered, seven are tested, and six are significant. In particular, the technology factors perceived interoperability and perceived data quality have a positive impact upon blockchain adoption intention, while the effect is negative for perceived technological volatility, regulatory uncertainty, standardisation uncertainty and the perceived lack of technological knowledge.
Biogeochemical processes catalyzed by soil microorganisms depend on the soil water content (SWC). Yet, little is known about the sensitivity of non-symbiotic N2 fixation to changes in SWC in comparison to carbon (C) and net nitrogen (N) mineralization. Therefore, we determined the rates of N2 fixation, C mineralization, and net N mineralization in soils at five SWCs that were created by water addition to the field-moist soil (rewetting), resulting in SWCs of 20, 40, 60 and 80% of the soil water holding capacity (WHC) which correspond to 14, 28, 42, and 57% water-filled pore space (WFPS). The soils originated from an arid, semiarid, Mediterranean, and humid site located in the Coastal Cordillera of Chile. The N2 fixation rate was measured immediately after the adjustment of the SWC and additionally after a five-day pre-incubation period. We found that the rates of all three processes where higher in the rewetted soils compared to the field-moist soils, but the sensitivity to changes in SWC differed between the processes. N2 fixation tended not to increase with increasing SWC beyond 20% WHC. Furthermore, the N2 fixation rate increased faster after rewetting in the soils of the semiarid and Mediterranean zone than in the soil of the humid zone. In contrast, C mineralization reached the highest rate at 80% WHC in the soil of the humid zone and at 60% and 80% WHC in the soils of the other three climate zones. The net N mineralization rate was highest at 40% and 60% WHC in the soils of the semiarid and Mediterranean zone, and was significantly decreased at 80% WHC compared to 60% WHC. Our study shows, first, that N2 fixation is less sensitive to changes in SWC than C and net N mineralization and tends to be already at its maximum in a given soil at low SWC, i.e., 20% WHC. This is likely because the diffusion of N2 in soil does not increase with the SWC, in contrast to the diffusion of organic solutes which are the substrate of C and N mineralization. Second, our results indicate that the N2 fixation rate increases more quickly in response to rewetting of soils of the more arid climate zones than of the humid zone, which might indicate a microbial adaptation to the climate conditions. The results have important implications since they suggest that the N2 fixation rate is likely less affected than the C and net N mineralization rates by decreases in the SWC that might occur more frequently in the future due to climate change.
With the increasing demand for customized systems and rapidly evolving technology, software engineering faces many challenges. A particular challenge is the development and maintenance of systems that are highly variable both in space (concurrent variations of the system at one point in time) and time (sequential variations of the system, due to its evolution). Recent research aims to address this challenge by managing variability in space and time simultaneously. However, this research originates from two different areas, software product line engineering and software configuration management, resulting in non-uniform terminologies and a varying understanding of concepts. These problems hamper the communication and understanding of involved concepts, as well as the development of techniques that unify variability in space and time. To tackle these problems, we performed an iterative, expert-driven analysis of existing tools from both research areas to derive a conceptual model that integrates and unifies concepts of both dimensions of variability. In this article, we first explain the construction process and present the resulting conceptual model. We validate the model and discuss its coverage and granularity with respect to established concepts of variability in space and time. Furthermore, we perform a formal concept analysis to discuss the commonalities and differences among the tools we considered. Finally, we show illustrative applications to explain how the conceptual model can be used in practice to derive conforming tools. The conceptual model unifies concepts and relations used in software product line engineering and software configuration management, provides a unified terminology and common ground for researchers and developers for comparing their works, clarifies communication, and prevents redundant developments.
Epoxy (EP) resins exhibit desirable mechanical and thermal properties, low shrinkage during cuing, and high chemical resistance. Therefore, they are useful for various applications, such as coatings, adhesives, paints, etc. On the other hand, carbon nanotubes (CNT), graphene (Gr), and their derivatives have become reinforcements of choice for EP-based nanocomposites because of their extraordinary mechanical, thermal, and electrical properties. Herein, we provide an overview of the last decade's advances in research on improving the thermal and electrical conductivities of EP resin systems modified with CNT, Gr, their derivatives, and hybrids. We further report on the surface modification of these reinforcements as a means to improve the nanofiller dispersion in the EP resins, thereby enhancing the thermal and electrical conductivities of the resulting nanocomposites.
Human land use is of growing concern for island ecosystems. Besides direct impacts on biodiversity, land uses can alter the functioning and structure of ecosystems. Central to this are impacts on food webs. The release of additional nutrients from human origin, habitat homogenization, or environmental filtering due to human land use can change the diet of individual consumer species (i.e., their trophic niches) and the distribution and overlap of trophic niches within a food web. However, it remains largely unclear whether the effects on food web properties vary between the different and predominant human land uses present on islands. Here, we investigated the impact of two dominant human land uses on small oceanic islands (i.e., urban and tourism development) and tested if and how different land uses on islands affect food web structure. To disentangle human land uses, we investigated islands, which were either privately owned by a tourist facility (i.e., exclusively tourism land use) or experienced urban development from the local population (i.e., urban land use), or remained uninhabited, serving as reference sites free of direct land use. Using stable isotope analysis, we show that isotope signature, trophic (isotopic) niches, and overall food web properties of the investigated island invertebrate communities were significantly changed under both land use regimes. While trophic diversity was reduced and trophic niche widths increased under tourism land use, the investigated food webs showed reduced trophic diversity at the food web base and a more uneven trophic niche distribution under urban land use. In summary, these findings show that different human land uses can have contrasting impacts on oceanic island food webs. As oceanic islands experience rapidly growing human land conversion, our results indicate that they may also face increasing yet unpredictable long-term changes in food web dynamics.
Key message An organomercurial phenylmercury activates AtPCS1, an enzyme known for detoxification of inorganic metal(loid) ions in Arabidopsis and the induced metal-chelating peptides phytochelatins are essential for detoxification of phenylmercury. Abstract Small thiol-rich peptides phytochelatins (PCs) and their synthases (PCSs) are crucial for plants to mitigate the stress derived from various metal(loid) ions in their inorganic form including inorganic mercury [Hg(II)]. However, the possible roles of the PC/PCS system in organic mercury detoxification in plants remain elusive. We found that an organomercury phenylmercury (PheHg) induced PC synthesis in Arabidopsis thaliana plants as Hg(II), whereas methylmercury did not. The analyses of AtPCS1 mutant plants and in vitro assays using the AtPCS1-recombinant protein demonstrated that AtPCS1, the major PCS in A. thaliana, was responsible for the PheHg-responsive PC synthesis. AtPCS1 mutants cad1-3 and cad1-6, and the double mutant of PC-metal(loid) complex transporters AtABCC1 and AtABCC2 showed enhanced sensitivity to PheHg as well as to Hg(II). The hypersensitivity of cad1-3 to PheHg stress was complemented by the own-promoter-driven expression of AtPCS1-GFP. The confocal microscopy of the complementation lines showed that the AtPCS1-GFP was preferentially expressed in epidermal cells of the mature and elongation zones, and the outer-most layer of the lateral root cap cells in the meristematic zone. Moreover, in vitro PC-metal binding assay demonstrated that binding affinity between PC and PheHg was comparable to Hg(II). However, plant ionomic profiles, as well as root morphology under PheHg and Hg(II) stress, were divergent. These results suggest that PheHg phytotoxicity is different from Hg(II), but AtPCS1-mediated PC synthesis, complex formation, and vacuolar sequestration by AtABCC1 and AtABCC2 are similarly functional for both PheHg and Hg(II) detoxification in root surficial cell types.
We present a model for the lattice vibrational density of states of MgTiO3 (geikielite) and FeTiO3 (ilmenite) that predicts thermodynamic properties, in agreement with observational data. The model is based on Kieffer’s method combined with spectroscopic data. For both substances experimental data sets are influenced by non-stoichiometry. For geikielite that affects the volume, whereas for ilmenite volume and bulk modulus are affected. We show that Kieffer’s method enables predicting bulk moduli in pressure–temperature space. We demonstrate that intrinsic anharmonicity or electronic effects significantly affect the heat capacity of ilmenite, whereas that is not the case for geikielite. We use Kieffer’s method to derive multiple-Einstein models, from which we demonstrate that thermodynamic properties are insignificantly influenced by dispersion in Grüneisen, mode-q and anharmonicity parameters for both substances. We show that our results enable predicting thermodynamic properties and shear modulus of the solid solution formed from geikielite and ilmenite. Geikielite and ilmenite are added to our thermodynamic database for the system MgO–SiO2–FeO, to enable modeling phase stability and physical properties of titanium-rich reservoirs in the Earth’s Moon.
The environmental fate and toxicity of microplastic particles are dominated by their surface properties. In the environment, an adsorbed layer of biomolecules and natural organic matter forms the so-called eco-corona. A quantitative description of how this eco-corona changes the particles' colloidal interactions is still missing. Here, we demonstrate with colloidal probe-atomic force microscopy that eco-corona formation on microplastic particles introduces a compressible film on the surface, which changes the mechanical behavior. We measure single particle-particle interactions and find a pronounced increase of long-range repulsive interactions upon eco-corona formation. These force-separation characteristics follow the Alexander-de Gennes (AdG) polymer brush model under certain conditions. We further compare the obtained fitting parameters to known systems like polyelectrolyte multilayers and propose these as model systems for the eco-corona. Our results show that concepts of fundamental polymer physics, like the AdG model, also help in understanding more complex systems like biomolecules adsorbed to surfaces, i.e., the eco-corona.
The inneralpine dry valleys of the Swiss Alps are characterized by subcontinental climate, leading to many peculiarities in dry grassland species composition. Despite their well-known uniqueness, comprehensive studies on biodiversity patterns of the dry grasslands in these valleys were still missing. To close this gap, we sampled 161 10-m² vegetation plots in the Rhône, Rhine and Inn valleys, recording vascular plants, terricolous bryophyte and lichen species, as well as environmental data. Additionally, we tested the scale-dependence of environmental drivers using 34 nested-plot series with seven grain sizes (0.0001–100 m2). We analysed the effects of environmental drivers related to productivity/stress, disturbance and within-plot heterogeneity on species richness. Mean species richness ranged from 2.3 species in 0.0001 m2 to 58.8 species in 100 m2. For all taxa combined, the most relevant drivers at the grain size of 10 m2 were southing (negative), litter (negative), mean annual precipitation (unimodal), gravel cover (negative), inclination (unimodal) and mean annual precipitation (unimodal). For vascular plants the pattern was similar, while bryophyte and lichen richness differed by the opposite relationship to mean annual precipitation as well as negative influences of mean herb layer height, grazing and mowing. The explained variance of the multiple regression model increased with grain size, with very low values for the smallest two grain sizes. While southing and litter had high importance for the fiver larger grain sizes, pH and gravel cover were particularly important at the intermediate grain sizes, and inclination and mean annual precipitation for the two largest grain sizes. The findings emphasize the importance of taxonomic group and grain size for patterns and drivers of species richness in vegetation, consistent with ecological theory. Differences in the diversity-environment relationships among the three taxonomic groups can partly be explained by asymmetric competition that leads to low bryophyte and lichen diversity where vascular plants do well and vice versa. The relatively low alpha diversity of vascular plants in dry grasslands in Swiss inneralpine valleys compared to similar communities in other parts of the Palaearctic remains puzzling, especially because Swiss stands are often large and well-preserved.
Comparison and quantification of multiple pre-and post-pollination barriers to interspecific hybridization are important to understand the factors promoting reproductive isolation. Such isolating factors have been studied recently in many flowering plant species which seek after the general roles and relative strengths of different pre-and post-pollination barriers. In this study, we quantified six isolating factors (ecogeographic isolation, phenological isolation, pollinator isolation, pollinia-pistil interactions, fruit production, and seed development) that could possibly be acting as reproductive barriers at different stages among three sympatric Habenaria species (H. limprichtii, H. davidii, and H. delavayi). These three species overlap geographically but occupy different microhabitats varying in soil water content. They were isolated through pollinator interactions both ethologically (pollinator preference) and mechanically (pollinia attachment site), but to a variable degree for different species pairs. Interspecific crosses between H. limprichtii and H. davidii result in high fruit set, and embryo development suggested weak post-pollination barriers, whereas bidirectional crosses of H. delavayi with either of the other two species fail to produce fruits. Our results revealed that pollinators were the most important isolating barrier including both ethological and mechanical mechanisms, to maintain the boundaries among these three sympatric Habenaria species. Our study also highlights the importance of a combination of pre-and post-pollination barriers for species coexistence in Orchidaceae.
Full-text access to our paper in this link:
Mistletoes, as perennial hemiparasitic angiosperms that parasitize woody plants, are an important component of the highly diverse, endemically rich and mosaic African flora, which is attributed to the Holarctic, Paleotropical, and Cape Floristic kingdoms. The richness of African mistletoes from the Loranthaceae and Viscaceae, along with many aspects of their biology and ecology, was covered in the comprehensive monograph of Polhill and Wiens (1998, Mistletoes of Africa, Royal Botanic Gardens). The present review is devoted to the taxonomic and functional diversity of symbionts associated with mistletoes in Africa and adjacent islands that contribute to the major biological functions of mistletoes, such as establishment and growth, nutrition and fitness , resistance to external stresses, as well as pollination and dispersal. These functions are favored by more or less distinct sets of associated bionts, including host plants, animal herbivores, frugivorous birds, nectar-and pollen-feeding insects, and endophytic microorganisms. A separate section is devoted to mistletoe epiparasitism as a special case of host selection. All these organisms, which are components of the mistletoe-associated community and multitrophic network, define the role of mistle-toes as keystone species. Some aspects of the symbiont communities are compared here with patterns reported for mistletoes from other continents, particularly to identify potential relationships that remain to be explored for the African species. In addition , properties of endophytic mistletoe associates that contribute to the plant's communication with coexisting organisms are considered. We also highlight the important gaps of knowledge of the functioning of mistletoe-associated communities in Africa and indicate some applied issues that need future attention. Abstract in French is available with online material.
The trace elements in the public drinking water have a duality: on the one hand, trace elements play an important role in maintaining human metabolism; on the other hand, high trace elements levels lead to significant health risks. To determine the impacts of trace elements in the public drinking water on physical health in China, water samples were collected from 314 Chinese cities to analyze the concentrations and spatial distributions of trace elements on a national scale. On this basis, the non-carcinogenic health risk assessments and the nutrient-based scores of trace elements (NSTEs) were applied to evaluate the public drinking water quality in terms of safety and nutrition. Most of the water samples were weakly alkaline: pH values fell in the range of 6.62-8.54, with a mean of 7.80. The results indicated that Sr and F- had the highest concentrations in public drinking water, with averages of 0.3604 mg/L and 0.2351 mg/L, respectively. Moreover, hazard index (HI) values in different regions followed the order: northwest China (NWC) > northern China (NC) > Qinghai-Tibetan Plateau (QT) > southern China (SC). The percentages of water samples with HI > 1 in SC, NC, NWC, and QT were 5.49%, 16.82%, 25.81%, and 16.67%, respectively, indicating that the public drinking water in some cities had significant non-carcinogenic health risks. In addition, the intakes of Mn, Fe, Cu, and Rb through public drinking water made negligible contributions to their recommended nutrient intakes. In contrast, trace elements like Sr, F, B, Li, Mo, etc., contributed a lot. The NSTEs in NWC and most parts of NC were relatively high with averages of 8.0300 and 11.2082, respectively; however, the NSTEs in SC and the northeast part of NC were low with averages of 3.3284 and 5.2106, respectively. The results from this study provide a reference for establishing the public drinking water standards and improving drinking water quality.
Dissolved oxygen (DO) is crucial for aerobic life in streams and rivers and mostly depends on photosynthesis (P), ecosystem respiration (R) and atmospheric gas exchange (G). However, climate and land use changes progressively disrupt metabolic balances in natural streams as sensitive reflectors of their catchments. Comprehensive methods for mapping fundamental ecosystem services become increasingly important in a rapidly changing environment. In this work we tested DO and its stable isotope (18O/16O) ratios as novel tools for the status of stream ecosystems. For this purpose, six diel sampling campaigns were performed at three low-order and mid-latitude European streams with different land use patterns. Modelling of diel DO and its stable isotopes combined with land use analyses showed lowest P rates at forested sites, with a minimum of 17.9 mg m−2 h−1. Due to high R rates between 230 and 341 mg m−2 h−1 five out of six study sites showed a general heterotrophic state with P:R:G ratios between 0.1:1.1:1 and 1:1.9:1. Only one site with agricultural and urban influences showed a high P rate of 417 mg m−2 h−1 with a P:R:G ratio of 1.9:1.5:1. Between all sites gross G rates varied between 148 and 298 mg m−2 h−1. In general, metabolic rates depend on the distance of sampling locations to river sources, light availability, nutrient concentrations and possible exchanges with groundwater. The presented modelling approach introduces a new and powerful tool to study effects of land use on stream health. Such approaches should be integrated into future ecological monitoring.
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
6,037 members
Andreas Schönleber
  • Chair of Crystallography
Sigrid Liede-Schumann
  • Bayreuth Center of Ecology and Environmental Research (BayCEER)
Florian Rehfeldt
  • Chair of Experimental Physics I
Universitätsstr. 30, 95447, Bayreuth, Germany
Head of institution
Prof. Dr. Stefan Leible