Aktuelle Publikationen

Heterogeneous nucleation processes are involved in many important phenomena in nature, including devastating human diseases caused by amyloid structures or the harmful frost formed on fruits. However, understanding them is challenging due to the difficulties of characterizing the initial stages of the process occurring at the interface between the nucleation medium and the substrate surfaces. This work implements a model system based on gold nanoparticles to investigate the effect of particle surface chemistry and substrate properties on heterogeneous nucleation processes. Using widely available techniques such as UV–vis–NIR spectroscopy and light microscopy, gold nanoparticle-based superstructure formation was studied in the presence of substrates with different hydrophilicity and electrostatic charges. The results were evaluated on grounds of classical nucleation theory (CNT) to reveal kinetic and thermodynamic contributions of the heterogeneous nucleation process. In contrast to nucleation from ions, the kinetic contributions toward nucleation turned out to be larger than the thermodynamic contributions for the nanoparticle building blocks. Electrostatic interactions between substrates and nanoparticles with opposite charges were crucial to enhancing the nucleation rates and decreasing the nucleation barrier of superstructure formation. Thereby, the described strategy is demonstrated advantageous for characterizing physicochemical aspects of heterogeneous nucleation processes in a simple and accessible manner, which could be potentially explored to study more complex nucleation phenomena.

The alarm calls of nonhuman primates are occasionally cited as functionally equivalent to lexical word meaning in human language. Recently, however, it has become increasingly unlikely that one-to-one relations between alarm call structures and predator categories are the default, mainly because many call types are produced in multiple contexts, requiring more complex notions of meaning. For example, male vervet monkeys produce the same alarm calls during encounters with terrestrial predators and neighbouring groups, suggesting that recipients require additional information to attribute meaning to the calls. We empirically tested the hypothesis that vervet monkeys take contextual information into account when responding to each other's alarm calls. In playback experiments, we exposed subjects to recordings of male alarm barks during actual intergroup encounters (predator unlikely) or when there was no intergroup encounter (predator likely). Subjects responded more strongly in the no intergroup encounter situations, typically associated with discovering a hiding predator, measured in terms of startle responses, vigilance behaviour and gazing towards the presumed caller. We discuss the significance of using contextual information for meaning attribution in nonhuman primate communication.

In this paper, we propose the t-FDP model, a force-directed placement method based on a novel bounded short-range force (t-force) defined by Student’s t-distribution. Our formulation is flexible, exerts limited repulsive forces for nearby nodes and can be adapted separately in its short- and long-range effects. Using such forces in force-directed graph layouts yields better neighborhood preservation than current methods, while maintaining low stress errors. Our efficient implementation using a Fast Fourier Transform is one order of magnitude faster than state-of-the-art methods and two orders faster on the GPU, enabling us to perform parameter tuning by globally and locally adjusting the t-force in real-time for complex graphs. We demonstrate the quality of our approach by numerical evaluation against state-of-the-art approaches and extensions for interactive exploration.

We study the effect of particle mobility on phase transitions in a spin fluid in two dimensions. The presence of a phase transition of the BKT universality class is shown in an off-lattice model of particles with purely repulsive interaction employing computer simulations. A critical spin wave region 0 < T < T_BKT is found with a nonuniversal exponent η(T) that follows the shape suggested by BKT theory, including a critical value consistent with η_BKT = 1/4. One can observe a transition from power-law decay to exponential decay in the static correlation functions at the transition temperature T_BKT, which is supported by finite-size scaling analysis. A critical temperature T_BKT = 0.17(1) is suggested. Investigations into the dynamic aspects of the phase transition are carried out. The short-time behavior of the incoherent spin autocorrelation function agrees with the Nelson–Fisher prediction, whereas the long-time behavior differs from the finite-size scaling known for the static XY model. Analysis of coherent spin wave dynamics shows that the spin wave peak is a propagating mode that can be reasonably well fitted by hydrodynamic theory. The mobility of the particles strongly enhances damping of the spin waves, but the model still lies within the dynamic universality class of the standard XY model.

The 1958 Delaney amendment to the Federal Food Drug and Cosmetics Act prohibited food additives causing cancer in animals by appropriate tests. Regulators responded by adopting chronic lifetime cancer tests in rodents, soon challenged as inappropriate, for they led to very inconsistent results depending on the subjective choice of animals, test design and conduct, and interpretive assumptions. Presently, decades of discussions and trials have come to conclude it is impossible to translate chronic animal data into verifiable prospects of cancer hazards and risks in humans. Such conclusion poses an existential crisis for official agencies in the US and abroad, which for some 65 years have used animal tests to justify massive regulations of alleged human cancer hazards, with aggregated costs of $trillions and without provable evidence of public health advantages. This article addresses suitable remedies for the US and potentially worldwide, by critically exploring the practices of regulatory agencies vis-á-vis essential criteria for validating scientific evidence. According to this analysis, regulations of alleged cancer hazards and risks have been and continue to be structured around arbitrary default assumptions at odds with basic scientific and legal tests of reliable evidence. Such practices raise a manifold ethical predicament for being incompatible with basic premises of the US Constitution, and with the ensuing public expectations of testable truth and transparency from government agencies. Potential remedies in the US include amendments to the US Administrative Procedures Act, preferably requiring agencies to justify regulations compliant with the Daubert opinion of the Daubert ruling of the US Supreme Court, which codifies the criteria defining reliable scientific evidence. International reverberations are bound to follow what remedial actions may be taken in the US, the origin of current world regulatory procedures to control alleged cancer causing agents.

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dc.contributor.author: Kumaraswamy, Ajayrama; Raiser, Georg; Galizia, C. Giovanni

There is a constant reciprocal flow of information between the malleable sensorimotor states of the body and cognitive functions, and some embodied cognition approaches argue that many cognitive-affective mechanisms depend on the physical characteristics of the body. To examine such influences of bodily state, the current study compared patients with body integrity dysphoria (BID) with an amputation desire of the lower limb to a healthy control group on an Implicit Association Test for self-identity and self-esteem, and a pain evaluation task. Patients with BID completed the tasks once while emulating their desired bodily state and once while simulating their undesired bodily state, while healthy controls were split into two groups: one control group completed the experiment once while either sitting on one leg and once while sitting in a normal position, whereas the other control group completed both experiments while sitting in a normal position. Results demonstrate that patients with BID implicitly identify more strongly with an amputated body, whereas healthy controls demonstrate stronger identification with a complete body, independent of bodily state. Furthermore, implicit self-esteem did not differ between the groups and was also not modulated by bodily state manipulation in any of the groups. Pain evaluation ratings were not influenced by bodily state manipulation, perspective, or consistency. Pain forced choice response times, however, revealed that individuals with BID were faster to judge whether the stimulus depicted was painful when simulating their desired bodily state. These results provide insightful information to how both the subjective sense of body, as well as more transient alterations of objective sensorimotor states of the physical body may exert selective pressure on certain cognitive tasks.

1. Colourful patterns on flowers are thought to benefit both pollinators and the plants they visit, by increasing the plants' pollination success via an increased foraging efficiency of the pollinators. This increased efficiency is assumed to result from a guidance effect of the flower patterns, correspondingly termed ‘nectar guides’, which indicate the position of the nectary to visiting pollinators, thus reducing their flower handling time.
2. Although it is well established that flower patterns play an important role in flower choice, the mechanisms by which they improve the foraging efficiency of flower-visiting insects remain poorly understood.
3. In this study, we quantified the contributions of patterns to all phases of flower interaction in the buff-tailed bumblebee Bombus terrestris. We analysed the bees' flight paths, as well as landing positions and walking tracks on artificial flowers with different pattern types.
4. We reveal that flower patterns reduced the overall flower handling time of the bees by up to 30%, by guiding their approach flight, landing positions and departure decisions. Surprisingly, we observed no improvement in nectary discovery time after the bees landed on the flower.
5. Since we tested experienced foragers, which represent the majority of insect pollinators active in nature, the newly described nectary-independent guidance effects of flower patterns are of high ecological relevance.

This study investigates for the first time the comprehension of rhetorical questions (RhQs) in bilingual children. RhQs are non-canonical questions, as they are not used to request information, but to express the speaker’s belief that the answer is already obvious. This special pragmatic meaning often arises by means of specific prosodic and lexical-syntactic cues. Being childhood learners, children have to acquire the concept of rhetoricity, but being bilinguals, they further need to acquire the different cues marking RhQs in their two languages. We tested 85 bilingual children (aged 6–9 years) with Italian as heritage language (HL) and German as majority language (ML) in both of their languages, using a forced-choice comprehension task. Our results show that RhQ comprehension improves with age in both languages. Bilingual children are able to exploit prosodic and syntactic cues to comprehend RhQs in their ML and HL with a slight advantage in the ML. This advantage could be either an effect of the cues used in the experiments in the two languages or of a higher proficiency in the ML. In addition, our results point to a later acquisition of prosodic rhetorical cues, which has implications for bilingual acquisition of non-canonicity in general.

Multilevel societies are formed when stable groups of individuals spatially overlap and associate preferentially with other groups, producing a hierarchical social structure. Once thought to be exclusive to humans and large mammals, these complex societies have recently been described in birds. However, it remains largely unclear what benefits individuals gain by forming multilevel societies. One hypothesis—based on food sharing in hunter-gatherers—is that multilevel societies facilitate access to a range of cooperative relationships, with individual investment varying across the hierarchical levels of the society. We tested experimentally whether such graded cooperation occurs in the multilevel society of a songbird, the superb fairy-wren (Malurus cyaneus). Specifically, we measured whether responses to playbacks of distress calls—used to recruit help when in extreme danger—varied according to the social level at which the focal individual is connected with the caller. We predicted that anti-predator responses should be highest within breeding groups (the core social unit), intermediate between groups from the same community, and lowest across groups from different communities. Our results confirm that birds exhibit the predicted hierarchical pattern of helping and that, within breeding groups, this pattern is independent of kinship. This pattern of graded helping responses supports the hypothesis that multilevel social structures can sustain stratified cooperative relationships and reveals similarity in cooperation in qualitatively different behaviors—anti-predator behavior and food sharing—in the multilevel societies of songbirds and humans.

1. Intense efforts have focused on ecosystem conservation and restoration (ECR) over the past decades, promoting considerable advances in science and practice in this field. However, the applications of the ecosystem services (ESs) concept are rarely considered in the literature when assessing the success and targets of ECR.

2. The ECR literature was systematically reviewed to analyse the relevance of the ES concept in ECR research published from 2007 to 2019 and to assess how the ES concept is integrated into freshwater ECR.

3. In general, the number of publications focusing on ECR and ESs shows a temporal increase (from 12 to 101 publications, 685 in total). The proportion of publications considering ESs as freshwater ECR targets increased from 33 to 70% until 2019, while the proportion of publications that prioritized ecosystem processes and functions as the target declined from 33 to 16%. Despite the clear upward trend, most studies have focused only on the conceptual framework. In addition, the idea of using market-based approaches for ESs has spread quickly, but it has still not been broadly accepted.

4. The number of academic researchers who have contributed to this research field varies substantially across different countries. A country's economic conditions and the extent of freshwater withdrawal can affect efforts devoted to studies on freshwater ECR and ESs. Some ecosystems, such as rivers and wetlands, have attracted much more attention than others. Although most studies have discussed ESs in general, the provisioning and regulation of ESs are mainly considered in studies that differentiate specific ES categories.

5. Current limitations in applying the ES concept in ECR across different studies suggest that further collaboration is needed among ecologists, practitioners, stakeholders and policy-makers to develop a broad mix of approaches for the best and widest use of the ES concept in protecting and enhancing freshwater ecosystems.

In 1753, artist William Hogarth declared a specific S-shaped line to be the ‘Line of Beauty’ (LoB). Hogarth’s assertion has had a profound impact on diverse fields over the past two and a half centuries. However, only one recent (2022) study has investigated whether Hogarth’s assertion accurately captures humans’ actual aesthetic preferences, and no research has explored why people find the LoB beautiful. We conducted two studies testing the hypothesis that the LoB’s perceived beauty is an incidental by-product of cognitive systems that evolved to attend to fitness-relevant morphological features in people. In Study 1, we replicated the finding that female bodies whose lumbar curvature approximates the biomechanical optimum for dealing with the exigencies of pregnancy are rated as more attractive. In Study 2, we found that abstract lines extracted from these bodies were perceived as more beautiful than other lines. These results suggest that the preference for Hogarth’s LoB is an incidental by-product of psychological mechanisms that evolved for other purposes. More broadly, these findings suggest that an evolutionary psychological approach – in particular the concept of evolutionary by-product – may be useful for understanding, explaining, and predicting people’s aesthetic preferences for certain abstract symbols, which otherwise might seem arbitrary and inexplicable.