Carsten Gundlach

This work introduces a methodology for numerical predictions of the compressive strength of unidirectional composites with realistic fiber orientation distributions, which were obtained via structure tensor analysis of 3D X-ray computed tomography scans of specific carbon fiber-reinforced polymer samples. Experimental characterization was performed on the material properties of the constituents, as well as the actual composite. The extracted fiber orientation distribution and the material parameters of the constituents were implemented in a two-dimensional finite element model. The model performs mesh-objective material homogenization for the fibers and matrix constituents, in which the fiber diameter defines the characteristic material length scale. The numerical prediction of the compressive strength was compared with experimental measurements. A kink band-driven failure mechanism was predicted by using the finite element model. The results show that the model can predict the compressive strength potential of the pultruded material, while accounting for the actual distribution of fiber orientation.

A comprehensive experimental dataset for unidirectional carbon fiber pultruded composites is presented, including mechanical testing results, microscopy images, and X-ray computed tomography volumes. In contrast to typical datasets, all measurements consistently describe a single material system, encompassing both the composite and its constituents (carbon fibers and vinyl ester matrix), thereby enabling a comprehensive and coherent multiscale material characterization. X-ray-computed tomography images of samples extracted from three pultruded composite profiles were acquired with a voxel size of 0.55 µm and analyzed to determine the fiber orientation distribution. Scanning electron microscopy with a pixel size of 0.098 µm was used to determine the overall and local fiber volume fractions. Compression testing of 17 composite specimens provided the compressive properties. The tensile and shear properties of the matrix were obtained from tensile and shear tests on seven and four matrix specimens, respectively. The Ramberg-Osgood model was fitted to the matrix’s tensile stress–strain response. Single-fiber tensile testing was conducted on 255 carbon fibers with three gauge lengths to determine fiber properties and Weibull parameters. All mechanical tests were performed up to material failure. The dataset is suitable for semi-analytical predictions and numerical finite-element modeling of composite mechanical behavior.

Aim: To investigate the ecological and evolutionary drivers of morphological variation in grey wolves ( Canis lupus ) across their global range: Location: The entire Holarctic distribution of grey wolves, from Greenland to New Mexico in North America, from Norway to Israel in Eurasia, including several samples from Russia and India. Methods: We analysed 227 wolf skulls using high‐resolution 3D geometric morphometrics (585 cranial and 96 mandibular landmarks) to assess the influence of continental separation, latitude, prey mass and population history on skull (cranium and mandible) size and shape. Results: Skull size was primarily influenced by population identity, increasing with average prey mass and latitude up to roughly 65°, with minimal differences between continents. Skull shape was mainly determined by population identity, with minor contributions from skull size, continent, and latitude; prey mass had no detectable effect. Average crania differed in the length‐to‐width ratio, shape and relative position of the frontal bones and zygomatic arches. Populations with the most distinct skull shapes included Modern Scandinavian wolves, Arctic wolves (East Greenland and Ellesmere Island), Italy and Coastal Alaska. These disparities are consistent with expected changes associated with long‐term isolation, demographic events (e.g., bottlenecks, founder effects), human‐driven fragmentation and extirpation of wolves, shifts in prey availability, and possible hybridization. Main Conclusions: Morphological variation in wolves is shaped by a combination of ecological pressures, geography and human impacts. Past isolation and human‐induced declines have increased divergence, emphasizing the importance of considering ecomorphological patterns when assessing evolutionary resilience and informing conservation planning for large carnivores.

This work introduces a methodology for accurate numerical predictions of the compressive strength of specific uni-directional composites. Fiber orientation distributions were acquired through structure tensor analysis of 3D X-ray computed tomography scanning of specific carbon fiber reinforced polymer samples. Experimental characterization was performed on the material properties of the constituents as well as the actual composite. The extracted fiber orientation distribution and the material parameters of the constituents were implemented in a two-dimensional finite element model. The model performs a mesh independent material homogenization, with regard to the fibers and the matrix, where it accounts for the fiber diameter as the material length scale. The numerical prediction of the compressive strength was compared with experimental measurements. A kink band driven failure mechanism was predicted by the finite element model. The results show that the model can predict the actual compressive strength, considering the real fiber orientation distribution.

Background Natural history museum specimens of historical honey bees have been successfully used to explore the genomic past of the honey bee, indicating fast and rapid changes between historical and modern specimens, possibly as a response to current challenges. In our study we explore a potential untapped archive from natural history collections - specimens relating to historical beeswax. Methods We examine an Apis mellifera mellifera queen cell specimen from the 19th century. The intact and closed cell was analysed by X-ray Computed Tomography (CT) to reveal a perfectly preserved queen bee inside her cell. Subsequently, a micro-destructive approach was used to evaluate the possibility of protein extraction for a palaeoproteomic approach. Results Using proteomics by liquid-chromatography-tandem mass spectrometry, we were able to recover 120 non-contaminant proteins, mostly bee-related, including major royal jelly proteins (MRJPs) crucial for queen nutrition and development, and silk fibroin proteins. Analysis of the protein modifications indicate their endogenous source and show the presence of in vivo glycosylation. This probably helped protein preservation and allows for the study of antimicrobial and metabolic functions of bees in the past. Conclusion Our exploratory results show that studies on specimens such as these can provide biomolecular information. Such specimens can inform future research on queen development, diet, and hive conditions, providing valuable context for understanding how honey bee populations have responded to changing environments and pressures over time. This highlights further the scientific potential of natural history collections in addressing contemporary challenges in honey bee conservation and health.

Humans have directly or indirectly contributed to the genetic and thus often phenotypic changes of many species. Anthropogenic pressures, such as persecution and hunting, have negatively affected wolf populations in northern Europe. In line with the genetic replacement that occurred during the twentieth century following the extirpation of wolves from Scandinavia (Norway and Sweden) and their near-extirpation from Finland, we provide evidence of morphological changes in wolf cranial morphology across these populations. Using three-dimensional landmark-based geometric morphometrics, we show that modern wolves in Scandinavia and Finland have, on average, crania with wider frontal bones, wider and higher positioned zygomatic arches and more ventral flexion of the rostrum compared to the historical wolf populations. Although both populations differ in the magnitude and direction of shape change over time, the centroid size or overall size of the cranium, is significantly larger only in the modern Scandinavian wolves. Different genetic origins of the historical and modern populations have probably played a role in the observed morphological variation; however, it is also likely that morphology has been affected by the availability of different prey, which has changed over time.

Background Natural history museum specimens of historical honeybees have been successfully used to explore the species’ genomic past, indicating fast and rapid changes between historical and modern specimens, possibly as a response to current challenges. In our study we explore a potential new untapped archive from natural history collections - specimens of historical beeswax. We examine an intact and closed Apis mellifera mellifera queen cell specimen from the 19th century. Methods In our study, we examine the queen cell by X-ray Computed Tomography (CT). Subsequently, a micro-destructive approach was used to explore the possibility of protein extraction from the cell for a palaeoproteomic analysis. Results Our results to reveal a perfectly preserved queen bee inside her cell. We were successful in extracting proteins from the residual material inside the queen cell, and were able to identify the material as containing several bee-related proteins, including major royal jelly proteins (MJRPs). Conclusions Our study show that studies on specimens such as the queen cell provide valuable information about the past rearing of queens, their diet, and their development, which is relevant for understanding current honeybees and their challenges.

Speothos pacivorus is an extinct South American canid (Canidae: Cerdocyonina) from the Pleistocene of Lagoa Santa Karst, Central Brazil. This taxon is one of the hypercarnivore canids that vanished from the continent at the end of Pleistocene. Although all remains of Speothos pacivorus were collected in the 19th century by the Danish naturalist Peter W. Lund, few studies have committed to an in-depth analysis of the taxon and the known specimens. Here, we analyzed all biological remains of S. pacivorus hosted in the Peter Lund/Quaternary Collection at the Natural History Museum of Denmark, Copenhagen, by listing and illustrating all its specimens known to date. We also conducted a reconstruction of the holotype, an almost complete cranium, based on a µCT scan, producing an undeformed and crack-free three-dimensional model. With this data available we aim to foster new research on this elusive species.