University of Konstanz
KOPS - The Institutional Repository of the University of KonstanzNot a member yet
31050 research outputs found
Sort by
The soil microbial community and nitrogen availability affect the growth, biochemistry and potential allelopathic effects of the invasive plant Solidago canadensis
No full textBackground and aims
Plant investment in secondary metabolites can be driven by abiotic factors such as nitrogen (N) availability and variation in biotic factors such as root-associated microbes. However, few studies have tested their combined effect on allelopathy. Here, we test whether and how N addition (i.e. eutrophication) and soil microbes modify allelopathic effects of the invasive plant Solidago canadensis on germination of the native plant Crepidiastrum sonchifolium.
Methods
We first grew Solidago at three N levels with a live or sterilized soil inoculum. Then we exposed seeds of Crepidiastrum to aqueous extracts made of the Solidago plants. We analysed the biomass, soil microbiome (bacteria and fungi), and flavonoid, phenolic and saponin contents of Solidago, and the effects of the aqueous extracts on germination of Crepidiastrum.
Results
We found that Solidago produced 67% more biomass on live soil than on sterilized soil, and that N addition only resulted in more biomass on live soil. Soils that had been sterilized accumulated higher relative abundances of bacteria involved in N transformation, and tended to have higher relative abundances of pathotrophic fungi. When grown in soil that had been sterilized, the total flavonoid content of Solidago was 22% higher, and the aqueous extracts had stronger negative allelopathic effects on germination of Crepidiastrum.
Conclusion
The presence of natural soil microbial communities may enhance invasiveness of Solidago by promoting its growth and thereby competitive ability, but may simultaneously decrease the negative allelopathic impact on native neighbors.publishe
The ping-pong strategy : confronting atrocities from the exile
No full textThis article will focus on the still marginal topic of atrocity crimes, and it will do so by building upon Southern studies, which expose how global power inequalities have helped present knowledge from a small number of Northern societies as universal, timeless and placeless while disregarding valuable knowledges and experiences from the South. Moreover, this article will also dispute the ‘static’ perspective in the literature of atrocities that has largely focused on either domestic or global issues of concern, but without enough attention to the dialogues, connections normative transfers, and even shared practices between the South and the North. Furthermore, it will do so by focusing on a particular unattended actor: those in exile and their role in the confrontation of the atrocities back home. Altogether, this article will go beyond the European-centred and static approaches and instead look at points of dialogue and encounters between Europe and Latin America and the role of the diaspora/exile as a legal and dynamic protagonist in the struggle against atrocities. Particularly, the research will look at the role of Argentinean activists in the European exile and their struggle against the dictatorship that ruled the country between 1976 and 1983, as well as their activism against impunity laws once democracy was re-established.publishe
The TSST triggers self-reported stress and biological stress and frustrates basic psychological needs : general and specific buffering effects of physical activity and social support
No full textSituations characterized by uncontrollability and critical social evaluation frustrate basic psychological needs, as outlined in Self-Determination Theory (SDT). Uncontrollability and social evaluation are central elements of the Trier Social Stress Test (TSST), leading to the hypothesis that the TSST, in addition to increasing self-reported stress and cortisol responses, also frustrates the needs for autonomy, competence, and social relatedness. Participants (N = 195) reported elevated stress and reduced need satisfaction, and increased cortisol responses during the TSST. The roles of assessed physical activity and experimentally-induced social support were also examined. Indeed, in time-sensitive and specific manner, the TSST frustrated basic psychological needs. Social support however mitigated frustration of social relatedness. Physical activity buffered against self-reported stress, the frustration of competence and the cortisol response. Further research is recommended to explore more differentiated interventions that can counteract the negative effects of psychosocial stressors.publishe
A Call to Protect Common Species : Bats as a Case Study
No full textThe ongoing biodiversity crisis highlights the need for targeted conservation efforts, yet the focus often remains on rare and endangered species. This overlooks the vital role of common species, which are the ecological backbone of ecosystems, supporting the stability and functioning of biodiversity. We argue that common species, especially their population dynamics and potential tipping points, are too often neglected and that their conservation is urgent. We illustrate this issue using bats (Chiroptera) as a model. This diverse mammalian order features key ecosystem service providers, including insectivores, pollinators, and seed dispersers. Bats are sensitive to anthropogenic pressures, and many species, including common ones, face population declines and the impact of ecosystem disruption. Research and conservation must urgently be expanded to include common species. Through case studies, we demonstrate how common bat species are indicators of environmental changes and the urgent need to monitor their populations. We provide recommendations for improving research, enhancing conservation policies, and adopting a more inclusive framework acknowledging the indispensable role of common species in ecosystem services and biodiversity.publishe
No Differences in Motor Units Discharge Rate Between Females and Males in Explosive Ankle Dorsiflexions
No full textMales and females exhibit comparable levels of explosive strength if the rate of torque development (RTD) is considered relative to the maximal voluntary isometric torque (MVT). Given the greater proportion of type I to type II fibers area in muscles of females than males (~20% in tibialis anterior muscle), with slower contractile kinetics, the discharge rate of motor units (MUDR) in explosive efforts may be higher to compensate for the slower muscle contractile properties. Yet, it is to date unknown whether sex differences in MUDR in explosive efforts exist. Twenty-two females and 12 males (20–34 years) performed electrically evoked and voluntary rapid isometric ankle dorsiflexions. Electrically evoked contractions consisted of three trains of 50 supramaximal stimuli at the common peroneal nerve at 200 Hz. Ten voluntary explosive contractions were then performed while recording high-density electromyography signals from the tibialis anterior. No significant differences were reported between males and females for both voluntary and electrically evoked relative peak RTD (8.0 ± 2.0 vs. 7.7 ± 0.8 and 6.4 ± 0.7 vs. 6.1 ± 2.1 MVT s−1), and for RTD and muscle activity throughout the first 150 ms (p > 0.07). Despite no significant differences, these metrics were not equivalent between sexes when assessed with equivalence testing. Time to peak RTD was shorter in males than females for both contraction types (voluntary: 61 ± 12 vs. 74 ± 14 ms; electrically evoked: 24 ± 3 vs. 28 ± 7 ms; p < 0.01). MUDR at the beginning of the explosive voluntary efforts was not different between sexes (males: 61 ± 15; females: 67 ± 16 Hz; p < 0.23). Overall, despite known sex-related differences within the skeletal muscle, the control of rapid torque production is not different between sexes.publishe
On the universality of aesthetic preference and inference : a cross-cultural (Chinese–German) study
No full textAesthetic preferences vary widely among individuals and across cultures. These culture-specific aesthetic preferences are reflected in the environment, artistic behaviour, and consumer choices. People have the ability to infer the aesthetic preferences of others within their own culture through their Theory of Aesthetic Preferences, which is a subcategory of the Theory of Mind. An important question is whether people can also infer aesthetic preferences across different cultures. This study aimed to investigate aesthetic preference and aesthetic inference, as well as the underlying mental processes of beauty judgements such as affective and cognitive responses, by comparing ratings on beauty, affective, and cognitive dimensions from participants in China (n = 84) and Germany (n = 82). The results suggest that aesthetic preferences are more dependent on the stimuli than on the culture. Furthermore, the study demonstrates that beauty judgements, as well as intra- and inter-cultural beauty inferences, are generally associated with positive emotions, while the relationship between beauty judgement and cognitive stimulation seems to be culture-specific. Overall, our findings provide evidence for a universal human beauty response mechanism that is linked to positive emotions and support the idea of a universal Theory of Aesthetic Preferences. This theory enables people to infer the aesthetic preferences of others both within and across different cultures.publishe
Using Long‐Term Ecological Datasets to Unravel the Impacts of Short‐Term Meteorological Disturbances on Phytoplankton Communities
No full textExtreme meteorological events such as storms are increasing in frequency and intensity, but our knowledge of their impacts on aquatic ecosystems and emergent system properties is limited. Understanding the ecological impacts of storms on the dynamics of primary producers remains a challenge that needs to be addressed to assess the vulnerability of freshwater ecosystems to extreme weather conditions and climate change.
One promising approach to gain insights into storm impacts on phytoplankton community dynamics is to analyse long-term monitoring datasets. However, such an approach requires disentangling the impacts of short-term meteorological disturbances from the effects of the seasonal trajectories of meteorological conditions. To this end, we applied boosted regression tree models to phytoplankton time series from eight relatively large lakes on four continents, coupled with a procedure adapted to detect and quantify rare events.
Overall, the patterns and potential drivers we identified provide important insights into the responses of lakes to short-term meteorological events and highlight differences in the response of phytoplankton communities according to lake morphological characteristics. Our results indicated that deepened thermoclines and lake-specific combinations of drivers describing altered thermal structures caused deviations from the typical trajectories of seasonal phytoplankton succession. For shallow polymictic lakes, shifts in phytoplankton succession also depended on changes in light availability.
Overall, our study highlights the value of long-term monitoring to improve our understanding of phytoplankton sensitivity to short-term meteorological disturbances.publishe
Simplification of polyline bundles of graphs and trees
No full textPolyline simplification is a well-studied optimization problem, in which a givenpolyline shall be replaced by a polyline with fewer vertices which still represents the shapeof the original polyline faithfully. In this paper, we propose and study a generalization ofthe polyline simplification problem. Instead of a single polyline, we are given a set of ℓ polylines possibly sharing some line segments and vertices. We call such a set apolylinebundle. The task is tosimplifyeach polyline L of a given polyline bundle by keeping a subsetof its vertices such that (i) the Hausdorff or Fréchet distance betweenLand its simplifiedcounterpart does not exceed a given distance threshold δ, (ii) a shared vertex is either kept ordiscarded in all polylines of the polyline bundle (we refer to this requirement asconsistency) and (iii) the number of kept vertices in the polyline bundle is minimized. To justify this definition, we argue that consistency is crucial to get meaningful and aesthetically pleasing outputs.
Regarding the computational complexity of polyline bundle simplification, we prove that this problem is NP-hard to approximate within a factor of n1/3−ε for any ε >0, where n is the number of vertices in the polyline bundle. This inapproximability even applies to planar inputs and also to instances with only ℓ = 2 polylines. However, we identify thesensitivity of the solution to the choice of the distance threshold δ as a reason for this strong inapproximability. In particular, we prove that if we employ the Fréchet distance and allow δ to be exceeded by a factor of 2 in the solution, then we can find a simplified polyline bundlewith no more than O(log(ℓ+n)) · OPT vertices in polytime, providing us with an efficient bi-criteria approximation. In addition, we show that the polyline simplification problem issolvable in polytime in case the polylines form a rooted tree. We further present a greedy heuristic that decomposes general bundles into tree bundles, which then can be simplified individually and optimally. In our experimental study, we compare the performance of the bi-criteria approximation algorithm and the tree bundle decomposition algorithm on public transit networks and movement trajectories. We show that in case the polylines form grid-like structures, the bi-criteria approximation algorithm outputs smaller simplifications, but the tree bundle decomposition algorithm scales better and produces superior results on polyline bundles derived from paths in embedded road networks.publishe
Models for Nucleation and Fluctuations in Structural Phase Transitions
No full textTo simulate a realistic system size that is comparable to experiments, a simplified coarse-grained model is required. For this purpose, several particles are combined into one state. In particular, the large number of degrees of freedom can be reduced by representing the system on a discrete grid. For example, an entire unit cell in the crystal can be represented as a single point on the lattice. In this work, two structural phase transitions are modelled using a novel coarse-grained approach.publishe
Enhancing media literacy : The effectiveness of (Human) annotations and bias visualizations on bias detection
No full textMarking biased texts effectively increases media bias awareness, but its sustainability across new topics and unmarked news remains unclear, and the role of AI-generated bias labels is untested. This study examines how news consumers learn to perceive media bias from human- and AI-generated labels and identify biased language through highlighting, neutral rephrasing, and political orientation cues. We conducted two experiments with a teaching phase exposing them to various bias-labeling conditions and a testing phase evaluating their ability to classify biased sentences and detect biased text in unlabeled news on new topics.
We find that, compared to the control group, both human- and AI-generated sentential bias labels significantly improve bias classification (p < .001), though human labels are more effective (d = 0.42 vs. d = 0.23). Additionally, among all teaching interventions, participants best detect biased sentences when taught with biased sentence or phrase labels (p < .001), while politicized phrase labels reduce accuracy. The effectiveness of different media literacy interventions remains independent of political ideology, but conservative participants are generally less accurate (p = .011), suggesting an interaction between political inclinations and bias detection.
Our research provides a novel experimental framework into assessing the generalizability of media bias awareness and offer practical implications for designing bias indicators in news-reading platforms and media literacy curricula.publishe