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The reaction of the diferrocenylphosphenium ion with four terminal allenes follows two different pathways, via allyl or vinyl carbocations, which proceed with electrophilic substitution reactions at one ferrocenyl moiety to form persistent Wheland intermediates and eventually alkenyldiferrocenylphosphonium salts. The reaction of the diferrocenylphosphenium ion with 2‐(trimethylsilyl)‐2,3‐pentadiene affords a stable Wheland intermediate of ferrocene in high yields, which is isolated and fully characterized. A kinetically stable Wheland intermediate of the electrophilic aromatic substitution at ferrocene is isolated from the reaction of the diferrocenylphosphenium ion with the allene 2‐(trimethylsilyl)‐2,3‐pentadiene and fully characterized.

The Front Cover shows a round‐bottomed flask containing a burgundy solution of diferrocenylphosphenium ion [Fc2P][B(C6F5)4], which was used in this work to activate various allenes. Dropwise addition to 2‐(trimethylsilyl) penta‐2,3‐diene yields a bright red solution of a stable Wheland intermediate of ferrocene, whose solid‐state structure is depicted as a ball‐and‐stick model. In front lies Saint Peter’s Key, a prominent feature of the City of Bremen’s coat of arms, representing the unlocked potential of highly reactive main group species. More information can be found in the Research Article by E. Hupf, J. Beckmann and co‐workers (DOI: 10.1002/ceur.202500031).

Metallic (M) and polymer (P) materials as layered hybrid metal-polymer-metal (MPM) sandwiches offer a wide range of applications by combining the advantages of both material classes. The interfaces between the materials have a considerable impact on the resulting mechanical properties of the composite and its structural performance. Besides the fact that the experimental methods to determine the properties of the single constituents are well established, the characterization of interface failure behavior between dissimilar materials is very challenging. In this study, a mixed numerical–experimental approach for the determination of the mode I energy release rate is investigated. Using the example of an interface between a steel (St) and a thermoplastic polyolefin (PP/PE), the process of specimen development, experimental parameter determination, and numerical calibration is presented. A modified design of the Double Cantilever Beam (DCB) is utilized to characterize the interlaminar properties and a tailored experimental setup is presented. For this, an inverse calibration method is used by employing numerical studies using cohesive elements and the explicit solver of LS-DYNA based on the force-displacement and crack propagation results.

The energy absorption behavior of crashboxes made of steel/polymer/steel (SPS) sandwich sheets can be influenced by numerous parameters, such as the materials used, their thicknesses and stacking, and the adhesion properties between their layers. Therefore, in the present study, the impact of steel/polymer adhesion quality on the occurring failure modes of the crashboxes and the resulting energy absorptions are experimentally analyzed. For this purpose, axial crushing and three-point bending tests on double-hat and top-hat crash boxes were performed, respectively. Three levels of adhesion quality are investigated: none, weak, and strong adhesion strengths. Additionally, the structural crash properties, such as energy absorption and maximal intrusion, are determined and analyzed at both of the quasi-static and highly dynamic loading rates. The results of these investigations show that the adhesion strengths chosen here significantly influence both the failure modes and the energy absorption values. In particular, the structural parameters, in the case of no adhesion, are at most half of those in the case of strong adhesion. However, it is also shown that, in the case of weak adhesion, the structural characteristics are slightly reduced. Based on these results, the possibility to adjust the adhesion strength—globally and/or locally—could be used in future activities to purposefully tailor the failure behavior of hybrid crashboxes.

Carbon fibre-reinforced plastics (CFRP) are predestined for use in high-performance components due to their superior specific mechanical properties. In addition, these materials have the advantage that the material properties and in particular, the failure behaviour can be adjusted. Fibre-dominated failure modes are usually brittle and catastrophic. In contrast, delaminations successively absorb energy and retain in-plane structural integrity. Previous investigations have shown that interface modifications can be used to selectively adjust the interlaminar properties, which decisively influence the delamination behaviour and the associated failure behaviour of structures. However, a systematic analysis of the influences of the positioning and characteristics of the interface modifications on the structural failure behaviour is still missing. Based on existing experimental investigations on the energy dissipation of CFRP impact-loaded beams, the failure behaviour is described here with the help of numerical simulations. The structural failure behaviour and the energy dissipation are represented in a three-dimensional, parameterised finite element analysis (FEA) model. Furthermore, the parameterised models are used to maximise the energy absorption of the three-point bending test through three concepts of interface modification. The large number of model input parameters requires a metamodel-based description of the correlation between the positioning and characteristics of the interface modification and the energy dissipation. Within the scope of the present work, a procedure is therefore developed which enables an efficient design of interface-modified CFRP under impact loads.

Multilayered fibre–metal laminates (FMLs) are composed of metal semifinished products and fibre-reinforced plastics, and benefit from the advantages of both material classes. Light metals in combination with fibre-reinforced thermoplastics are highly suitable for mass production of lightweight structures with good mechanical properties. As the formability of light metal sheets is sometimes limited at room temperature, increasing the process temperature is an appropriate approach to improve formability. However, the melting of thermoplastic materials and resulting loss of stiffness limit the processing temperature. Since single-ply layers have different through-thickness stiffnesses, the forming process changes the ply thickness of the multilayered laminate. In the present study, the deformation behaviour of multilayered FMLs was investigated using a two-dimensional finite-element model assuming plane strain. The thermoelastic-plastic finite-element analysis made investigation of the variation in thickness made possible by incorporating sufficient mesh layers in the thickness direction. The results indicate that a thermoelastic-plastic finite-element model can predict the delamination of plies during deformation, as well as in the final product. Additionally, the predicted changes in thickness of the plies are in good agreement with experimental results when a temperature-dependent friction coefficient is used.

One of the biggest challenges when using anti-vascular endothelial growth factor (VEGF) agents to treat retinopathy of prematurity (ROP) is the need to perform long-term follow-up examinations to identify eyes at risk of ROP reactivation requiring retreatment. To evaluate whether an artificial intelligence (AI)-based vascular severity score (VSS) can be used to analyze ROP regression and reactivation after anti-VEGF treatment and potentially identify eyes at risk of ROP reactivation requiring retreatment. This prognostic study was a secondary analysis of posterior pole fundus images collected during the multicenter, double-blind, investigator-initiated Comparing Alternative Ranibizumab Dosages for Safety and Efficacy in Retinopathy of Prematurity (CARE-ROP) randomized clinical trial, which compared 2 different doses of ranibizumab (0.12 mg vs 0.20 mg) for the treatment of ROP. The CARE-ROP trial screened and enrolled infants between September 5, 2014, and July 14, 2016. A total of 1046 wide-angle fundus images obtained from 19 infants at predefined study time points were analyzed. The analyses of VSS were performed between January 20, 2021, and November 18, 2022. An AI-based algorithm assigned a VSS between 1 (normal) and 9 (most severe) to fundus images. Analysis of VSS in infants with ROP over time and VSS comparisons between the 2 treatment groups (0.12 mg vs 0.20 mg of ranibizumab) and between infants who did and did not receive retreatment for ROP reactivation. Among 19 infants with ROP in the CARE-ROP randomized clinical trial, the median (range) postmenstrual age at first treatment was 36.4 (34.7-39.7) weeks; 10 infants (52.6%) were male, and 18 (94.7%) were White. The mean (SD) VSS was 6.7 (1.9) at baseline and significantly decreased to 2.7 (1.9) at week 1 (P < .001) and 2.9 (1.3) at week 4 (P < .001). The mean (SD) VSS of infants with ROP reactivation requiring retreatment was 6.5 (1.9) at the time of retreatment, which was significantly higher than the VSS at week 4 (P < .001). No significant difference was found in VSS between the 2 treatment groups, but the change in VSS between baseline and week 1 was higher for infants who later required retreatment (mean [SD], 7.8 [1.3] at baseline vs 1.7 [0.7] at week 1) vs infants who did not (mean [SD], 6.4 [1.9] at baseline vs 3.0 [2.0] at week 1). In eyes requiring retreatment, higher baseline VSS was correlated with earlier time of retreatment (Pearson r = -0.9997; P < .001). In this study, VSS decreased after ranibizumab treatment, consistent with clinical disease regression. In cases of ROP reactivation requiring retreatment, VSS increased again to values comparable with baseline values. In addition, a greater change in VSS during the first week after initial treatment was found to be associated with a higher risk of later ROP reactivation, and high baseline VSS was correlated with earlier retreatment. These findings may have implications for monitoring ROP regression and reactivation after anti-VEGF treatment.