Paderborn University

While studying biofilm formation in industrial settings with a quartz crystal microbalance with dissipation monitoring (QCM-D), it was found that the shift in half bandwidth, ΔΓ, often was much larger than the shift in frequency, Δ f . Also, ΔΓ was almost independent of overtone order. The microbial biofilms were mostly composed of prokaryotic cells, which contact the resonator surface across soft filament like structures at their cell wall called pili. A simple model is proposed, which explains the peculiar QCM response induced by these biofilms. The key element of the model is a coupled dashpot, representing small, dissipative contacts between the sample and the resonator. The dashpot replaces the coupled mass known from gravimetric sensing. The coupled-dashpot model predicts the shift in frequency to be close to zero (Δ f ≈ 0) and the shift in half bandwidth to be about the same on the different overtones (ΔΓ ≈ const ). The value of ΔΓ is proportional to the product of the number density of the contacts and their stiffness. The model – if found to agree with experiment – yields structural information on the sample and can guide data aggregation. The model was substantiated and illustrated with numerical simulations. A side aspect is a simple and economical instrument design, which brings QCM-based biofilm monitoring closer to routine practice. • New inexpensive setup for QCM measurements. • Biofilm formation mainly affects the bandwidth. • Modeling of behavior with a mechanical dashpot.

One of the major topics in the modern automotive industry is reducing emissions and increasing the mileage range. To tackle this challenge, on the one hand, modifying the powertrain system is a possibility, and on the other hand, lightweight design offers various possibilities. Multi-Material Design (MMD) involves designing car bodies that combine different materials that require joining. Given the variety of materials, mechanical joining processes are preferred. Especially the current development of the Giga/Mega-casting process concerning aluminium casting and the subsequent mechanical joining illustrates the challenges of this material group. In car production, aluminium castings are mainly made from aluminium-silicon (AlSi) alloys. Ultimately, the alloy system's insufficient ductility leads to crack initiation during mechanical joining. Cast parts are therefore often used in areas of the car body that are exposed to high-pressure loads. For example, self-piercing riveting (SPR) is used due to its high load-bearing capacity. In this study, improved joinability is demonstrated by influencing the microstructure through tailored solidification rates and a developed heat-treatment chain strategy adapted for hypoeutectic AlSi systems. Data on microstructure, mechanical, and joining properties are used to develop a solidification-joining correlation for the SPR process across a range of Si contents and solidification rates. The purpose is to develop the ability to produce suitable aluminium castings with sufficient joinability, thereby improving versatility.

The demand for sustainable chemical production methods has led to significant advancements in photocatalysis. This study explores the photocatalytic production of hydrogen peroxide (H2O2) from water using a covalent organic framework (CYANO-COF) synthesized from triformylphloroglucinol (Tp) and 4,4'-diamino-[1,1'-biphenyl]-3,3'-dicarbonitrile (Bp-CN) via Schiff-base condensation. The synthesized COF material exhibited a predominantly AB stacking structure with an optimal band gap (2.22 eV) for visible-light absorption and effective charge separation. Furthermore, the photoelectrochemical characterizations revealed the photoresponsive nature of the material by creating a high charge density under illumination. Under illumination, the photocatalyst demonstrated efficient H2O2 generation with production rates of 550 μmolg-1h-1 using only water and 371 μmolg-1h-1 in the presence of ethanol. The sacrificial-agent-free system aligns with green chemistry principles, simplifying reaction conditions and reducing the environmental impact. Mechanistic studies confirmed the role of photoinduced electron-hole pairs in water oxidation and oxygen reduction. This research underscores the potential of CYANO-COF materials in sustainable H2O2 production using only water and sunlight thus highlighting avenues for optimizing long-term stability and efficiency.

Research on procrastination mostly focuses on person-related antecedents and neglects situational and social factors, such as group work. Prior research indicates that conjunctive and additive group work may increase individual effort and performance as compared to individual work. Based on these findings, we investigate whether conjunctive and additive group work may also help reduce procrastination as compared to individual work. In a registered field experiment, N = 218 students with high levels of trait procrastination worked on an academic task over the course of 10 days in one of three conditions (individual work vs. conjunctive group work vs. additive group work). Dependent variables comprised task procrastination, task performance, and positive and negative task-related affect. Regarding conjunctive group work, results are mixed, with some evidence that conjunctive group work leads to lower procrastination as compared to individual work. Both types of group work resulted in higher negative task-related affect when assessed prospectively. No other effects were found. The findings contribute to the idea that targeted changes in the learning environment, such as the implementation of group work, may help reduce procrastination.

ABSTRACT Creativity and innovation are often understood as the result of a complex interplay of hierarchical factors, such as national, regional and firm characteristics, or between organisational and individual factors. While recent applications of qualitative comparative analysis (QCA) have begun to model such configurational links, their hierarchical nature has received little empirical attention. As this paper demonstrates, theories that posit hierarchical configurations can and should be explored using the two‐step variant of QCA. The paper outlines the potential of the method for the field of creativity and innovation and helps to navigate key modelling decisions. An illustrative study explores the occurrence of informal employee innovation behaviour—workarounds—based on the Ability‐Motivation‐Opportunity (AMO) framework. The results of the two‐step QCA are superior in terms of reduced limited diversity and complexity to those of the conventional one‐step QCA. Overall, the method has considerable potential for empirically capturing the complex, hierarchical interactions inherent in many innovation processes.

Light structured in amplitude, phase, and polarization offers new routes for encoding quantum information and probing matter at the nanoscale. We present two complementary approaches to harnessing structured-light–matter interactions for quantum technologies. First, we introduce an inversely designed vector beam decoder (VBD) that enables on-chip manipulation of non-paraxial modes with complex 3D polarization, expanding the Hilbert space for high-dimensional quantum key distribution (HD QKD) and integrated quantum photonic platforms. Second, we develop a theoretical framework for controlling multipolar excitations of a single nanoparticle using tightly focused Generalized Cylindrical Vector Beams (GCVBs). This approach allows selective excitation and suppression of dipolar and quadrupolar modes as well as their superpositions, offering tunable nanoscale control. Together, these advances establish structured light as a versatile tool for integrated quantum devices and precision sensing.

ABSTRACT This study shows the applicability of ultrasonic sensors for measuring two‐phase layer heights in sieve tray columns under dynamic operating conditions. Although these sensors are known for their precision in stationary systems, their reliability under fluctuating flow conditions has remained unclear. To validate their accuracy, ultrasonic measurements were compared with both automated image analysis via a Python algorithm and manual video evaluation. Results show that ultrasonic sensors maintain high precision at moderate gas loads and with small hole diameters. Increased gas loads and turbulence, however, reduced measurement accuracy due to signal scattering. The findings highlight the potential of ultrasonic sensing for real‐time, noninvasive monitoring in dynamic multiphase systems.

Developing plasmonic nanogaps via simple, lithography-free methods is essential for advancing practical surface-enhanced Raman spectroscopy (SERS) sensors. Here, we present a functionalization-free, lithography-free plasmonic hole-sphere nanogap (HSNG) platform, enabling sensitive differentiation of oxidation states at trace levels. The HSNG structure, fabricated by straightforward thermal annealing and metal deposition, achieves highly uniform nanogaps (signal deviation <15%), resulting in a strong (∼108) and uniform Raman enhancement. The fully metal-coated nanocavity structure eliminates background interference, significantly enhancing the analytical reliability in complex environmental samples. Using this platform, we demonstrated the ability to distinguish trace concentrations of As3+ and As5+, which were difficult to distinguish with conventional gold nanoparticles due to low signal intensity, at the on-site analysis level. Remarkably, reliable oxidation state identification remains possible even under reduced spectral resolution, ensuring compatibility with simplified detection setups such as bandpass filters or smartphone-based spectrometers. This HSNG-based SERS platform provides a scalable, accessible, and field-applicable approach to chemical sensing, readily extendable to the detection of diverse environmental contaminants.