Julkaisuarkisto

Cracking presents a major hurdle for processing non-weldable Ni-base superalloys, such as CM247LC, by powder bed fusion–laser beam (PBF–LB). This study directly observes cracking behavior in standard CM247LC and two admixed alloys (CM247LC + 1 wt.% Hf and CM247LC + 1 wt.% nano-Y₂O₃) using operando synchrotron X-ray radiography synchronized with acoustic emission (AE). Our real-time data confirm extensive cracking in the standard alloy is identified to be primarily solidification cracking. Both Y₂O₃ and Hf additions mitigate solidification cracking, though through distinct mechanisms. Nano-Y₂O₃ addition alters the processing regime from keyhole to conduction mode. Scheil solidification simulations predict a narrower solidification range and lower solidification cracking index (SCI). This indicates that a combination of processing regime shift along with modification in solidification as the primary drivers for crack suppression upon addition of nano-Y₂O₃, despite increased lack of fusion and complex oxide formation. Hf-addition mitigated cracking via enhanced segregation at interdendritic regions, promoting beneficial carbides and improved liquid backfilling. Scheil simulations for alloy with Hf-addition predicted low SCI compared to standard CM247LC due to increased liquid availability in final solidification stages. These insights highlight that nearly crack-free PBF–LB of non-weldable superalloys can be achieved through both the powder modifications.

Decoding composition-sensitive process signatures in Laser Powder Bed Fusion (PBF-LB) of multi-material structures remains challenging due to the complex and transient nature of melt-pool emissions across spatially varying material gradients. In this study, we propose a modality-aware learning framework that fuses acoustic emission (AE) and back-reflected optical emission (OE) at the laser wavelength for spatiotemporally resolved classification of local composition in graded 316L–CuCrZr alloys. The framework integrates learnable shapelet extraction with graph-based attention, where shapelets act as interpretable descriptors of modality-specific temporal behavior and enable compact, discriminative representation learning. The resulting dual-modality representations are organized as a temporal graph of signal segments, and a Graph Attention Network (GAT) with modality-specific attention heads adaptively prioritizes sensor streams based on their relevance to compositional variation. Across five Cu-containing concentrations (20%–100 wt.%), the model achieved up to 92% accuracy with only ~ 4,000 trainable parameters. Beyond accuracy, the results show that sensor fusion is imperative for multi-material PBF-LB, as no single modality consistently captures composition-dependent phenomena across the CuCrZr gradient. The learned attention and saliency trends further reveal that OE becomes increasingly influential at higher CuCrZr fractions, consistent with increased reflectivity at the laser wavelength. Overall, the proposed framework establishes a compact and interpretable approach for decoding composition-dependent multimodal process signatures in multi-material PBF-LB.

Cancers are complex cellular communities comprising tumor cells and their microenvironment. Recent advances in cancer biology have emerged from efforts to analyze tumors as tissues, in which emergent properties arise as tumor cells interact with one another, their microenvironment, and the host tissue. In this review, we consider interactions involving mechanical forces and mechanosignaling pathways that detect changes in physical inputs to regulate cellular behavior. This rapidly developing field provides perspectives for understanding cancer biology and tumor interactions with the host ecosystem.

Cyanobacteria generate electrical current through exoelectrogenesis (extracellular electron transfer) downstream of photosynthesis, yet the identity of the endogenous redox mediator(s) responsible remains unresolved. Here, we apply differential pulse voltammetry (DPV) to detect and characterise redox-active species released by Synechocystis sp. PCC 6803 under illumination. To enable sensitive detection, we developed an electrolyte intermediate between BG11 (Blue-Green-11) growth medium and MOPS (3-(N-morpholino)propanesulfonic acid) buffer that minimises background electrochemical interference while maintaining short-term cellular functionality. DPV revealed multiple light-enhanced oxidation peaks (0.1–0.65 V vs. saturated calomel electrode (SCE)) that were not resolvable using cyclic voltammetry, providing evidence that cyanobacteria release reduced compounds during exoelectrogenesis. These signals were partially reproduced in cell exudates and absent in controls, confirming their biological origin. The lack of corresponding reduction peaks suggests irreversible redox processes. Comparison with candidate mediators showed that NADPH and 4-hydroxybenzoate, an intermediate in plastoquinone biosynthesis, exhibit only partially similar electrochemical behaviour compared to cells and do not fully account for the measured responses. Collectively, our results indicate that exoelectrogenesis in Synechocystis sp. PCC 6803 involves a mixture of redox-active species rather than a single mediator. This study establishes DPV as a powerful tool for in situ detection of cyanobacterial mediators and provides new insights into the mechanisms of photosynthetic extracellular electron transfer.

Tree cavities and nestboxes are crucial resources for cavity-nesting birds. While cavities are essential for reproduction, their importance outside the breeding season remains poorly understood, with most existing evidence focusing on nestbox use by small birds to reduce heat loss during winter. Whether non-breeding cavity use varies geographically along latitudinal gradients is also largely unknown. Here, we conducted a three-year study on tawny owl Strix aluco to investigate nestbox use during autumn and winter using trail cameras in four populations located at different latitudes (Finland, Sweden, Slovenia, Italy). We predicted non-breeding nestbox use to be a daytime behaviour, and to be more common under colder climatic conditions, in more deciduous habitats and in areas with higher predator (both avian and mammalian) and mobber abundance. We indeed find that tawny owls primarily use nestboxes during the day and in winter, but use nestboxes rarely outside the breeding season, except in Italy. PCA-based analyses of population differences in climate, forest habitat and bird community provides some support for the notion that tawny owl nestbox use outside the breeding season is mainly associated with deciduous forest, possibly because these provide less cover in winter. In addition, tawny owl nestbox use is mainly observed in active territories and winter nestbox use is associated with the probability of starting to breed in the subsequent breeding season. Our findings imply nestboxes, and presumably also natural cavities, have multiple ecological functions for tawny owls outside their breeding season. A better understanding of year-round nestbox use is important for developing effective wildlife conservation strategies in forest ecosystems.