Julen Ibarretxe

The stranding network of the Basque Country (SAREUS) attended a stranded juvenile female Kogia breviceps on Zarautz (Gipuzkoa, Spain) on 2 October 2025. The necropsy revealed severe pathological findings: (1) plastic and plant debris occupying most of the volume of the main stomach, (2) pulmonary congestion, pink froth in respiratory airways and presence of sand in the oesophagus, and (3) haemorrhagic liver and meninges together with serosanguineous liquid in the pericardium. Results indicate that the individual stranded alive and drowned because of a debilitated condition most likely caused by plastic and plant material ingestion. To understand what happened in the last days of the animal, and to identify behaviours that could lead to plastic ingestion, the stomach content was analysed, including the chemical characterization of the plastic debris through ATR-FTIR and the identification of vegetal and prey species. One possible explanation of the stranding event could have been that reduced foraging ability in a juvenile animal contributed to ingestion of foreign material, although this hypothesis cannot be confirmed from the available evidence.

Purpose: This study investigates whether polylactide (PLA)/hydroxyapatite (HA) composites fabricated by industrially scalable melt-processing can achieve a favorable balance between mechanical performance and in vitro bioactivity for bone-graft substitute applications, and identifies the HA concentration thresholds that govern key material transitions. Methods: PLA composites containing 2.5, 5, and 10 wt% HA were produced by twin-screw extrusion and injection molding. Composites were characterized by capillary rheometry, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, tensile testing, and Charpy impact testing. In vitro bioactivity was assessed by immersion in simulated body fluid at 36.5 °C for up to 42days, with surface evolution monitored by optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Results: HA addition progressively reduced melt viscosity (up to about 21-fold at 300 s⁻¹ for 10 wt% HA) and lowered the maximum degradation temperature by about 70 °C, consistent with HA-catalyzed chain scission during melt processing. Young’s modulus increased modestly from 3.6 to 4.3 GPa, but tensile strength, elongation at break, and impact resistance decreased markedly above 2.5 wt% HA, indicating a ductile-to-brittle transition. In vitro SBF immersion confirmed the formation of a bone-like apatite layer on composites containing ≥ 5wt% HA within 21 days, a response absent in neat PLA and minimal at 2.5 wt% HA. Conclusions: A 5 wt% HA loading represents an optimal trade-off, conferring confirmed bioactivity while retaining acceptable mechanical properties for melt-processed PLA-based bone substitutes. The HA content can be adjusted to match the mechanical demands of different anatomical sites, highlighting the versatility of this composite system for bone-regeneration applications.

This study investigates the long-term mechanical performance of highly reinforced long glass fiber thermoplastic polypropylene composites, focusing on the effects of processing parameters, fiber length, and skin–core structures. Dynamic mechanical and creep analyses were conducted to evaluate the impact of injection molding on the final microstructure and long-term mechanical properties. The findings confirm that a significant microstructural change occurs at a fiber length of 1000 µm, which strongly influences the material’s mechanical behavior. Samples with fiber lengths above this threshold reveal greater creep resistance due to the reduced flowability that leads to more entangled, three-dimensional fiber networks in the core. This structure limits chain mobility and consequently improves the resistance to long-term deformation under load. Conversely, fiber lengths below 1000 µm promote a planar arrangement of fibers, which enhances chain relaxation, fiber orientation, and creep strain. Specifically, samples with fiber lengths exceeding 1000 µm exhibited up to a 15% lower creep strain compared to shorter fiber samples. Additionally, a direct relationship is observed between the findings in the viscoelastic response and quasi-static tensile properties from previous studies. Finally, the impact of the microstructure is more pronounced at low temperatures and becomes nearly negligible at high temperatures, indicating that beyond the glass transition temperature, the microstructural effect diminishes gradually until it becomes almost non-existent.

The generation of pyrolysis liquids and gases with poor quality is a limiting factor for the development of the recycling process of fiber-reinforced plastic waste. In this article, the life cycle assessment (LCA) of an advanced two-step pyrolysis process to recycle glass fiber-reinforced polyamide waste is presented. First, the solid waste is pyrolyzed by heating up at 3 °C/min to 500 °C in a tank reactor. The generated volatiles are subsequently thermally cracked at 900 °C in a tubular packed bed reactor. The process is able to reclaim the glass fibers similarly to the conventional one reactor pyrolysis, while producing liquids and gases with better properties. The large quantity of oxygenated pyrolysis oils generated in the conventional pyrolysis are cracked into gaseous hydrocarbons, CO, CO₂ and a minor aqueous liquid. The pyrolysis gases become the main product of the process, presenting an interesting composition of hydrogen (39.9 vol.%), methane (22.5 vol.%), carbon monoxide (19.5 vol.%) and ethylene (10.8 vol.%). The LCA shows that advanced pyrolysis demonstrates better environmental performance than conventional pyrolysis, avoiding fossil resource scarcity and reducing global warming by half and human carcinogenic toxicity by one third.

Although increasing student motivation is widely accepted to enhance learning outcomes, this relationship has scarcely been studied quantitatively. Therefore, this study aimed to address this knowledge gap by exploring the effects of gamification on students’ motivation and consequently their learning performance, regarding the proper application of the scientific method. To motivate students and enhance their acquisition of new skills, we developed a gamification framework for the laboratory sessions of first-year physics in an engineering degree. Data regarding student motivation were collected through a Likert-scale-type satisfaction questionnaire. The inter-item correlations and Cronbach’s alpha confirmed the internal consistency of the questionnaire. In addition, the learning outcome was assessed based on the students’ laboratory reports. Students participating in gamified activities were more motivated than those participating in non-gamified activities and obtained better learning results overall. Our findings suggest that gamified laboratory sessions boost students´ extrinsic motivation, and consequently inspire their intrinsic motivation and increase their learning performance. Finally, we discuss our results, with a focus on specific skills and the short- and long-term effects of gamification.

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) is a bio-based polyester with the potential to replace some common polymers of fossil origin. However, PHBH presents serious limitations, such as low stiffness, tendency to undergo crystallization over long time periods and low resistance to thermal degradation during processing. In this work, we studied the use of alumina nanowires to generate PHBH–alumina nanocomposites, modifying the properties of PHBH to improve its usability. Solvent casting and melt blending were used to produce the nanocomposites. Then, their physicochemical properties and aquatic toxicity were measured. Finally, LCA was used to evaluate and compare the environmental impacts of several scenarios relevant to the processing and end of life (EoL) conditions of PHBHs. It was observed that, at low concentrations (3 wt.%), the alumina nanowires have a small positive impact on the stiffness and thermal degradation for the samples. However, for higher concentrations, the observed effects differed for each of the applied processing techniques (solvent casting or melt blending). The toxicity measurements showed that PHBH alone and in combination with alumina nanowires (10 wt.%) did not produce any impact on the survival of brine shrimp larvae after 24 and 48 h of exposure. The 18 impact categories evaluated by LCA allowed defining the most environmentally friendly conditions for the processing and EoL of PHBHs, and comparing the PHBH-related impacts to those of some of the most common fossil-based plastics. It was concluded that the preferable processing technique for PHBH is melt blending and that PHBH is unquestionably more environmentally friendly than every other analyzed plastic.

Bio-based polymeric nanocomposites (NCs) with enhanced electrical conductivity and rigidity were obtained by adding multi-walled carbon nanotubes (CNTs) to a commercial bio-based polyamide 4,10 (PA410). Two different types of commercial CNTs (Cheap Tubes and Nanocyl NC7000^TM) and two different preparation methods (using CNTs in powder form and a PA6-based masterbatch, respectively) were used to obtain melt-mixed PA410/CNT NCs. The effect of the preparation method as well as the degree of dispersion and aspect ratio of the CNTs on the electrical and mechanical properties of the processed NCs was studied. Superior electrical and mechanical behavior was observed in the Nanocyl CNTs-based NCs due to the enhanced dispersion and higher aspect ratio of the nanotubes. A much more significant reduction in aspect ratio was observed in the Cheap Tubes CNTs than in the Nanocyl CNTs. This was attributed to the fact that the shear stress applied during melt processing reduced the length of the CNTs to similar lengths in all cases, which pointed to the diameter of the CNTs as the key factor determing the properties of the NCs. The PA6 in the ternary PA410/PA6/CNT system led to improved Young’s modulus values because the reinforcing effect of CNTs was greater in PA6 than in PA410.