University of Konstanz
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Uncovering Cultural Influences on Perceptual Image and Video Quality Assessment through Adaptive Quantized Metric Models
No full textEvaluating perceptual image and video quality is crucial for multimedia technology development. This study investigated nation-based differences in quality assessment using three large-scale crowdsourced datasets (KonIQ-10k, KADID-10k, NIVD), analyzing responses from diverse countries including the US, Japan, India, Brazil, Venezuela, Russia, and Serbia. We hypothesized that cultural factors influence how observers interpret and apply rating scales like the Absolute Category Rating (ACR) and Degradation Category Rating (DCR). Our advanced statistical models, employing both frequentist and Bayesian approaches, incorporated country-specific components such as variable thresholds for rating categories and lapse rates to account for unintended errors. Our analysis revealed significant cross-cultural variations in rating behavior, particularly regarding extreme response styles. Notably, US observers showed a 35–39% higher propensity for extreme ratings compared to Japanese observers when evaluating the same video stimuli, aligning with established research on cultural differences in response styles. Furthermore, we identified distinct patterns in threshold placement for rating categories across nationalities, indicating culturally influenced variations in scale interpretation. These findings contribute to a more comprehensive understanding of image quality in a global context and have important implications for quality assessment dataset design, offering new opportunities to investigate cultural differences difficult to capture in laboratory environments.publishe
Optimization of District Heating Networks : Differential Algebraic Equations, Hyperbolic Systems and Receding Horizon Control
No full textMany optimization problems arising in applications are constrained by ordinary differential equations (ODEs), partial differential equations (PDEs) or differential algebraic equations (DAEs). Among these, DAEs present a distinctive challenge because they combine both differential and algebraic constraints in an implicit manner. Optimal control problems involving DAEs aim to find the control inputs that optimize a specific objective function while satisfying these complex constraints. This thesis examines the challenging analysis of an optimal control problem for a system of DAEs inspired by the dynamics of district heating networks.
DAEs appear in many application areas such as multibody dynamics, electrical circuits, and district heating networks. The underlying concept is to model systems combining both differential and algebraic equations, addressing complex dynamics and constraints. To classify DAEs several index concepts are used. A well-known concept is the differentiation index. Utilizing Caratheodory's theory, we establish the existence and uniqueness of a solution for the DAE system in the cases of index-1 and index-2 by using the properties inherent in the district heating network model.
Modeling district heating networks involves capturing the dynamics of heat transfer and distribution within networks. These models include various elements such as pipes, consumers, and power plants. The heat distribution is determined by the temperature, velocity and pressure. After semi-discretization of the convective heat equation and implementing coupling conditions at the network nodes, a system of DAEs emerges. In this setting graph theory is used to reproduce the network structure. By neglecting the velocity derivative in the pipe equations, numerical solutions remain largely unchanged, resulting in DAEs with index-1.
Based on this, we consider optimal control problems for a system of DAEs with index-1 and index-2. We show that the optimal control problem possesses optimal solutions by leveraging specific properties of the district heating network model.
Dispensing with the semi-discretization of the convective heat equation and decoupling the system results in a hydrodynamic and a temperature part. The hydrodynamic part is described by a DAE system, while the temperature part is modeled by linear hyperbolic equations with non-homogeneous boundary conditions. In this context, we are concerned with boundary control systems. Solvability results for a specific structure of linear hyperbolic equations with non-homogeneous boundary conditions motivated by district heating networks are presented based on the theory of semigroups of bounded linear operators.
Considering an optimal control problem with linear hyperbolic equations over an infinite time horizon, one method to solve this is the Receding Horizon Framework, also known as Model Predictive Control (MPC). In this approach, the optimal control problem with an infinite time horizon is approximated by a sequence of optimal control problems with a finite time horizon. However, stability is not guaranteed in this method. Therefore, in the final part of this thesis, we deal with the stabilizability of boundary control systems by Receding Horizon Control (RHC).publishe
Alterung der Bevölkerung und Nachfrage Hochbetagter nach Krankenhausbehandlung
No full textDie Bevölkerung Deutschlands altert zusehends. Nicht nur sind die Jahrgänge, die demnächst ins Rentenalter übertreten, deutlich stärker besetzt als die der nachwachsenden Generationen, sondern es steigt auch die ferne Lebenserwartung der bereits Älteren: Konnte eine 65-jährige Frau zur Jahrtausendwende mit 19,4 weiteren Lebensjahren rechnen, so waren es 20 Jahre später schon 21,1 Jahre, also 1,7 Jahre mehr. Bei 65-jährigen Männern waren es sogar volle zwei zusätzliche Jahre (17,8 gegenüber 15,8). Definiert man „Hochbetagte“ als Personen im Alter von über 80 Jahren, so wird der Anteil dieser Gruppe an der Gesamtbevölkerung von derzeit (31.12.2024) 7,3 % auf 8,7 % im Jahr 2040 und sogar 10,9 % im Jahr 2050 zunehmen, also um etwa die Hälfte des Ausgangswerts.publishe
Antisemitism and Pro-Palestine Protests at German Universities : Survey Results Among Students and University Rectorates
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Global well-posedness of 2D Navier–Stokes with Dirichlet boundary fractional noise
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Endosymbiont escape as a mechanism to increase the rate of endosymbiosis formation
No full textEndosymbiosis plays a key role in shaping biodiversity, but its origin and maintenance remain difficult to explain. Vertical transmission of endosymbionts is an important mechanism that can stabilize endosymbiotic interactions, but it also restricts the rate at which new endosymbiotic units can be formed. To explain the prevalence of endosymbiotic interactions, additional mechanisms that could increase the rate at which novel endosymbiotic units are formed should be considered. Horizontal transfer of endosymbionts may increase the rate of endosymbiosis formation. The underlying assumption of this mechanism, that endosymbionts have evolved to escape their host actively, has not been tested experimentally. We tested this mechanism in ciliate and algal species that differ in their ability to form endosymbiosis. We found that algal cells escaped from the ciliate hosts, with endosymbiotic algal species escaping more frequently than those that are intracellular only as prey. We tested the advantage of this mechanism and found that the rate at which new endosymbiotic units are formed was three times higher when both vertical and horizontal transmission by escaped cells was possible, compared to vertical transmission alone. This, together with the finding that the escape of endosymbiotic algae was higher in endosymbiotic than in predatory ciliate species and higher in environments where endosymbiotic units grow slowly, suggests that the escape has evolved as a mechanism. This finding has important implications for the conditions favoring the evolution of endosymbiosis as this mechanism can increase the rate of novel endosymbiotic unit formation and promote more advantageous endosymbiotic partner pairings.publishe
Effects of a general practitioner-led brief narrative exposure intervention on symptoms of post-traumatic stress disorder after intensive care (PICTURE) : multicentre, observer blind, randomised controlled trial
No full textObjective
To determine the effect of a novel brief general practitioner (GP)-led narrative exposure intervention on post-traumatic stress disorder (PTSD) symptoms after intensive care.
Design
Multicentre, observer blind, randomised controlled trial (PICTURE).
Setting
Primary care in 319 general practices across Germany.
Participants
319 adults (18-85 years) who have survived critical illness with symptoms of PTSD, discharged from intensive care and randomised to receive the intervention (n=160) or improved usual care (n=159) from a general practitioner.
Interventions
Intervention group participants had three narrative exposure consultations with a general practitioner and eight scheduled contacts with a nurse. Control group participants received improved treatment as usual based on the German PTSD guideline.
Main outcome measures
The primary clinical outcome was self-reported PTSD symptoms using the Post-Traumatic Diagnostic Scale for DSM-5 (PDS-5, range 0-80, higher scores indicating more severe symptoms) at six months. The minimal clinically important difference was six points. Secondary outcomes included changes in depression, anxiety, patient activation, health related quality of life and disability at six and 12 months.
Results
Between 21 October 2018 and 18 January 2023, 1283 patients discharged from an intensive care unit were screened for PTSD symptoms. 319 study participants were randomly assigned either to the control group (n=159) or the intervention group (n=160). The mean patient age was 57.7 years (standard deviation (SD) 12.7), and 61% of participants were male. The mean baseline PDS-5 score was 30.6 (SD 13.3) in both groups. 271 (85%) study participants completed follow-up assessment after six months and 247 (77%) after 12 months. The intervention effect showed a mean between-group difference in the PDS-5 score of 4.7 points ((95% confidence interval 1.6 to 7.8); P=0.003, Cohen’s d=0.37)) at six months and 5.4 points ((1.8 to 9.0); P=0.003, Cohen’s d=0.41)) at 12 months. Among secondary outcomes, patients in the intervention group had greater improvements in depression, health related quality of life, and disability.
Conclusions
In adults with symptoms of PTSD after critical illness, a brief narrative exposure intervention was feasible and showed a reduction of symptoms, which was less than the predefined minimal clinically important difference. The effect was found to be sustained at 12 months’ follow-up. These findings support the further evaluation of this intervention in primary care.
Trial registration
ClinicalTrials.gov, NCT03315390; DRKS-ID DRKS00012589publishe
Nucleation and Supercooling Mitigation in Fatty Alcohol Phase Change Material Emulsions for Heat Transport and Storage
No full textOrganic phase change slurries (PCS) exhibit significant supercooling in small particles, which diminishes their advantages over sensible heat storage systems by reducing energy efficiency and reliability. While the mechanisms of supercooling in alkanes have been extensively studied, investigations of emulsions containing fatty alcohols are limited. This study examines the impact of nucleating agents on reducing supercooling in oil-in-water (O/W) emulsions of 1-docosanol, a fatty alcohol used as a phase change material (PCM). Emulsions with platykurtic particle size distributions were produced using rotor-stator emulsification. Various material combinations were explored to identify nucleation promoters compatible with 1-docosanol. Thermal analysis revealed that long-chain polymers effectively mitigate supercooling, particularly during rotator phase transitions, as confirmed by crystal structure analysis. On average, supercooling was reduced by 9 K; however, seed deactivation observed over multiple thermal cycles led to a gradual return of supercooling. Similar to alkanes, particle size influences the nucleation rate, surfactants affect the availability of heterogeneous nucleation sites, and nucleating agents can decrease the nucleation barrier. The findings indicate that high structural similarity between emulsion components is beneficial for minimizing supercooling in PCS, enhancing their potential for thermal energy storage applications.publishe
Processing at-issue and non-at-issue content : Evoked and induced brain activities reveal early and long-lasting differences
No full textThe processing of context-dependent expressions has mostly been studied using metaphors, irony or indirect requests. We add to the literature by monitoring the processing of modal particles (MPs) like German ruhig . These lexemes are ambiguous between a modal particle reading and a counterpart reading. While the counterpart contributes at-issue or propositional meaning to the sentence and affects truth conditions, the modal particle contributes non-at-issue meaning, expressing speaker attitudes or linking the sentence to the discourse. In the present study we disambiguated the readings via a preceding context and analysed event-related potentials and the oscillatory brain responses to critical sentences with identical surface forms. Our results show that in comparison to their counterparts, modal particles are associated with enhanced P600 amplitudes on the target lexemes and in the spillover region, and with enhanced P200 amplitudes on target lexemes. In addition, modal particles do not show the gamma power enhancement visible for counterparts. We interpret our findings as showing increased processing cost for modal particles due to them contributing to a higher dimension of meaning. The differences in oscillatory brain activity between both readings may reflect the lack of at-issue meaning contribution for modal particles. Our findings are in line with reports of enhanced P600 amplitudes for semantically and pragmatically complex readings in the literature on context-dependent expressions, and open various future ways of research to check the claims of different models on the processing of complex semantic and pragmatic information.publishe
Is regulatory science ready for artificial intelligence?
No full textTrust is key in AI for regulatory science, but its definition is debated. If AI models use different features yet perform similarly, which should be trusted? If scientific theories must be testable, how critical is explainability? At the Global Summit on Regulatory Science (GSRS24), regulators agreed that successful AI adoption requires ongoing dialogue, adaptability, and AI-trained personnel to harness its potential for regulatory responsibilities in the evolving 21st-century landscape.publishe