Open Access

We report time-resolved diffuse extreme ultraviolet (EUV) scattering measurements of optically excited acoustic waves in thin Ti/SiN bilayers in transmission geometry. Following femtosecond optical excitation, the EUV diffuse scattering signal yields circular fringe patterns evolving as a function of the time delay between the optical pump and EUV probe pulses. We demonstrate that these patterns originate from multiple guided acoustic modes (Lamb waves) with wavelengths in the range 60–400 nm. By comparing the experimental frequency–wavevector maps with calculated dispersion curves, we show that diffuse scattering signal from Lamb waves is enhanced at discrete frequencies corresponding to longitudinal thickness resonances of the membrane. This observation indicates that Lamb waves with high in-plane wavevectors originate from the scattering of longitudinal thickness resonances by surface roughness. Our findings establish time-resolved diffuse EUV scattering as an efficient tool for probing nanoscale Lamb waves, applicable to the characterization of elastic properties of thin membranes.

Subsociality and wood-eating or xylophagy are understood as key drivers in the evolution of eusociality in Blattodea (cockroaches and termites), two features observed in the cockroach genus Cryptocercus, the sister group of all termites. We analyze two high-quality genomes from this genus, C. punctulatus from North America and C. meridianus from Southeast Asia, to explore the evolutionary transitions to xylophagy and subsociality within Blattodea. Our analyses reveal evidence of relaxed selection in both Cryptocercus and termites, indicating that a reduction in effective population size may have occurred in their subsocial ancestors. These findings challenge the expected positive correlation between dN/dS ratios and social complexity, as Cryptocercus exhibits elevated dN/dS values that may exceed those of eusocial termites. Additionally, we infer a reduction in the number of Ionotropic Receptors and a change from uni- to bimodal methylation signatures in protein coding genes in a common ancestor of Cryptocercus and termites, mechanisms previously thought to have evolved with the emergence of eusociality in termites. Future studies incorporating additional genomic data from diverse blattodean species can further build on these findings and provide deeper insights into the molecular mechanisms driving transitions to xylophagy and eusociality.

Additive manufacturing by DED-Arc enables the production of large and complex high-strength steel components. However, the residual stress state generated during deposition can be significantly altered when the component is separated from the substrate plate as a final manufacturing step. This study investigates the residual stress relaxation and redistribution caused by substrate detachment in DED-Arc manufactured high-strength steel hollow cuboids. The component geometry was varied in terms of height, length, and wall thickness. Longitudinal residual stresses were measured by X-ray diffraction on the side wall surfaces before and after mechanical separation from the substrate plate. In addition, 3D scanning was used to quantify the resulting component distortion. The results show that substrate detachment causes a pronounced redistribution of longitudinal residual stresses, including a reduction of tensile stresses and, in some regions, the formation of compressive residual stresses. The stress differences before and after detachment can be interpreted as a superposition of relaxed longitudinal shrinkage stresses and released bending stresses arising from inhomogeneous restraint over the build height. The sign and magnitude of the bending contribution depend strongly on the component geometry. Low-build and high-build components show opposite bending tendencies after detachment, which is attributed to the interaction between substrate restraint, component stiffness and transformation-affected upper layers. Regression analysis of the geometry variation indicates that height, length, wall thickness, and the height–length interaction significantly affect the released bending stress, while component height is the dominant factor for the normal tensile stress relaxation. The findings demonstrate that substrate detachment is a critical step for residual stress redistribution and distortion in DED-Arc manufactured high-strength steel components and that geometry tailoring is usable to influence the resulting stress state.

Rapid detection and localization of liquid fuel spills is critical for first responders assessing fire and health hazards, yet current methods require ground-based sampling or specialized instrumentation, limiting their practicality for wide-area emergency response. We present a drone-based passive colorimetric sensor system using test strips impregnated with Nile red, similar to colored confetti. Nile red is a solvatochromic dye that undergoes distinct visible color transitions upon exposure to different liquids. The dye is embedded within a polymer matrix that minimizes leaching while providing high optical contrast between dry, water-exposed, and fuel-exposed states. The sensor strips exhibit solvent-specific colorimetric responses within one minute of exposure, readily detectable by standard RGB cameras mounted on unmanned aerial vehicles (UAVs) at altitudes up to 50 m. Automated classification was validated at 20 m altitude, enabling remote surveillance of contaminated surfaces without specialized equipment. Color-corrected image analysis using Calibrite ColorChecker calibration ensures reliable interpretation under variable field illumination (625–77,000 lux). Systematic laboratory evaluation of twelve fossil and bio-derived fuels revealed characteristic hue shifts that clearly discriminate ethanol-containing gasoline blends from diesel-range fuels. Rather than identifying specific molecules, the method functionally categorizes contamination into gasoline/ethanol blends versus diesel-type fuels, reflecting bulk polarity rather than molecular composition. Field validation confirmed localization and classification of fuel-exposed sensors, achieving F1 scores of 0.94 for gasoline and 0.98 for diesel detection with no false positives in the tested scenarios. This cost-effective and scalable approach provides actionable information on both contamination location and fuel type, crucial for rapid hazard assessment in emergency response scenarios.

Intumescent coatings enhance the fire resistance of steel structures by forming a thermal protective char when exposed to fire. Thereby, significantly slowing the rise in steel temperature. However, environmental conditions can cause ageing of the intumescent coating, potentially reducing its thermal protection performance. Therefore, the durability of intumescent coatings is checked as part of the European assessment and the approval procedure. The assessment primarily relies on accelerated artificial ageing tests followed by fire testing. The corresponding test and assessment programme is designed to ensure a working life of at least 10 years. If the working life has expired or there are concerns about the coating's performance, a coated steel member from the existing structure can be extracted and tested in a fire laboratory. However, this approach is rarely used in practice due to its destructive nature and high cost. Since a visual inspection is not sufficient to determine the effectiveness of the intumescent coating in case of fire, there is a practical need for a minimally invasive, in situ test method. The development of a mobile prototype furnace for in situ testing to assess the actual fire protection performance of the intumescent coating has already been described by the authors. The current paper presents the test results obtained from uncoated and coated steel plates, as well as IPE and HEB sections. Particular attention is given to the influence of the specimen geometry, dry film thickness, heating regime, and heat transition within the specimen on the resulting steel temperature and char morphology.