University of Pisa

• PA12 fatigue life characterization with Average Strain Energy Density (ASED) method. • An algorithm is developed for lattice structure fatigue predictions. • Fatigue predictions are conducted on as-designed lattice geometries. • The critical radius for the ASED method is identified for MJF PA12 material. The industrial sector continues to explore innovative strategies to exploit the full potential of Additive Manufacturing (AM). Among its many advantages, AM enables the fabrication of lattice structures; these are lightweight metamaterials with tunable mechanical properties and excellent energy absorption capabilities. Despite their promise, the widespread industrial use of such structures is limited by the difficulty in accurately assessing their fatigue behavior. This study presents a methodology aimed at predicting the fatigue life of polymer-based lattice components, with a specific focus on PA12 manufactured using the Multi Jet Fusion (MJF) process. This is an industrially relevant technology offering large production volumes, high printing quality and low production costs. The approach begins with fatigue testing of bulk PA12 specimens to establish baseline material behavior. Based on these results, a predictive algorithm is developed to estimate the fatigue performance of lattice structures. The model adopts an energy-based framework inspired by the Average Strain Energy Density (ASED) method, previously used for metallic materials, and adapts it to the characteristics of polymer lattices. The proposed methodology contributes to the development of efficient fatigue assessment tools, supporting the broader adoption of lattice structures in cost-sensitive industrial applications where polymer-based materials are effective.

Transthyretin amyloidosis (ATTR) is a systemic disease characterized by the deposition of misfolded transthyretin (TTR) fibrils. It most commonly presents as cardiomyopathy (ATTR-CM), particularly in elderly patients with the wild-type form, whereas hereditary variants may manifest with polyneuropathy (ATTRv-PN) and/or cardiac involvement. The widespread adoption of non-invasive diagnostic pathways has increased disease recognition and facilitated the early initiation of disease-modifying therapies. Stabilizers limit dissociation of the TTR tetramer and the formation of new amyloid fibrils. Tafamidis demonstrated a benefit on mortality and cardiovascular hospitalizations in the ATTR-ACT trial and remains the treatment supported by the most robust evidence, with greater efficacy when initiated at earlier disease stages. Acoramidis, a next-generation stabilizer, improved a hierarchical composite end-point in the ATTRibute-CM trial and has been approved for ATTR-CM treatment, too. Gene-silencing therapies (small interfering RNA and antisense oligonucleotides) reduce hepatic TTR synthesis and circulating protein levels. Patisiran is approved for ATTRv-PN and, in the APOLLO-B trial, showed a functional benefit in ATTR-CM, although it has not been approved for this indication in the United States. Vutrisiran, a subcutaneously administered siRNA given every 12 weeks, reduced mortality and recurrent cardiovascular events in the HELIOS-B trial and has been approved for ATTR-CM treatment. This review summarizes the rationale and principal clinical evidence supporting tetramer stabilizers and gene-silencing therapies, which are now central to the management of ATTR-CM.

Friction plays a crucial role in both natural phenomena, from the flow of blood cells to earthquakes, and technological applications, from car engines to wind turbines. One of the most fundamental aspects of tribology is friction anisotropy, that is, the dependence of the friction force vector on the direction of sliding. Even when two identical surfaces slide against each other, differences in sliding direction can lead to significantly different friction forces. While atomistic and semi-empirical models provide a good understanding of friction and friction anisotropy at the molecular and macroscale levels, a comprehensive understanding at the nano- and microscale remains elusive. Unravelling the mechanisms of friction anisotropy at these intermediate length scales is crucial for bridging the gap between the current atomistic and macroscale models, as well as for advancing technological applications, such as nano-/micro-electromechanical systems (NEMS/MEMS). One experimental technique which has significantly contributed to the study of nano- and micro-scale friction anisotropy is scanning probe microscopy, particularly the form of atomic force microscopy (AFM). AFM enables investigations at the nanometre-scale resolution, providing at equilibrium topographical, physical, and chemical information of interfaces with atomic precision. AFM can also measure friction forces with pN-level sensitivity while operating in vacuum, air or fluid environments. The versatility of AFM and its applicability to both soft and hard materials have made it an indispensable tool for understanding the nano- and microscale mechanisms of friction. In this review, we examine the contributions of AFM-based techniques to the study of friction anisotropy. First, we summarise key AFM findings on friction anisotropy arising from the periodic corrugation of atomically flat crystals, quasicrystals, 2D materials and organic materials. In the second part, we explore friction anisotropy mechanisms influenced by the presence of solid or fluid adsorbates, such as polymers or liquid lubricants. By synthesising insights from the last 30 years of research, our review contributes to a deeper understanding of friction anisotropy, identifying common mechanisms across the diverse systems. This knowledge will not only refine theoretical models but also drive technological advancements, in a wide range of applications from biomedical devices and 3D printing to engines and advanced lubricant formulations.

Fluorescent protein (FP) variants have recently emerged as promising intracellular nitric oxide (NO) sensors based on NO-induced fluorescence loss due to cysteine S-nitrosylation - the covalent addition of a nitroso group to a cysteine thiol within a protein to form an S-nitrosothiol. Here, we investigate the mechanisms underlying this fluorescence loss using a combined experimental and computational approach. We focus on mTagBFP2, a blue fluorescent protein that undergoes a 70% reduction in fluorescence quantum yield and lifetime upon exposure to micromolar NO concentrations. We discriminate, through mutagenesis, the contributions of two key cysteine residues and propose an unprecedented excitation energy transfer (EET) from the mTagBFP2 chromophore to the S-nitroso groups as a potential quenching mechanism. Our EET efficiency calculations incorporate full couplings, the effects of the surrounding protein and solvent, and molecular dynamics-based configurational flexibility. The computed EET efficiencies broadly align with experimental observations, with remaining discrepancies for which we advance potential explanations. Our findings establish a mechanistic basis for NO-induced fluorescence loss in mTagBFP2, providing guidelines for the rational design of next-generation NO-sensitive FPs. Moreover, they suggest that analogous S-nitrosylation-driven quenching mechanisms could be operative in other FPs with exposed cysteine residues, underscoring the risk of artefacts in cellular imaging under physiological NO levels.

This study aimed to assess how food-related behavioral traits, examined with the Three-Factor Eating Questionnaire (TFEQ) and the Perceived Stress Scale (PSS), influence adlibitum intake after fasting and during and after cold exposure compared to thermoneutral conditions, beyond what is explained by energy expenditure alone. Healthy participants (n = 46; 30 males; age 36.9 ± 10.5 years; BMI 32.3 ± 8.7 kg/m2) completed the TFEQ, PSS, and dual-energy x-ray absorptiometry (DXA) scan. The Hunger subscale of the TFEQ was further divided into internal and external hunger based on the methodology of Bond etal. Participants ate adlibitum from a food intake paradigm on five separate occasions, each over 24 h: (1) after a 36-h fast at thermoneutral temperature, (2) during cold exposure (19.0°C) in the chamber, (3) during thermoneutral conditions (23.5°C) in the chamber, (4) after cold exposure, and (5) after thermoneutral exposure. Total hunger score predicted intake across all five conditions (β = 0.58 MJ/day, p = 0.02). Internal and external subscales also predicted intake in separate models (β = 1.04 MJ/day, p = 0.02; β = 1.46 MJ/day, p = 0.01). Participants ate more during the cold condition than during thermoneutrality (mean = 1.69 MJ/day, or 404 kcal/day, p = 0.009). Higher external hunger scores correlated with greater intake (partial r = 0.38; p = 0.01), but internal hunger scores did not (partial r = 0.22, p = 0.16), after accounting for sex, race, fat mass, and fat-free mass. Restraint, disinhibition, and PSS were not associated with intake. Increased susceptibility to hunger cues, particularly external cues, was associated with higher food intake during cold stress. These findings suggest that behavioral approaches, such as reducing responsivity to food cues, are important targets for weight loss interventions. ClinicalTrials.gov: NCT02939404.

Cervical cancer is the first cancer potentially eliminable through widespread HPV vaccination. In Italy, despite free access, vaccine coverage among adolescents remains low. Psychological factors such as information avoidance (IA), the tendency to ignore threatening information, can influence vaccine decisions and contribute to vaccine hesitancy (VH). While social media offers new avenues for health communication, their effectiveness in reducing VH is uncertain. This study investigates the impact of Instagram-based communication strategies on adolescents' HPV knowledge and VH. A three-arm randomized controlled trial was conducted in 22 high school classes in Tuscany, involving 526 students. Classes were randomized to follow one of three Instagram pages for one month: a neutral control, an information-based account, or a bias-aware account designed to address cognitive biases related to vaccination decisions. Data were collected through online surveys at three time points: baseline (T1), after the intervention (T2), followed by in-class lesson, and at three-month follow-up (T3). HPV knowledge and VH were assessed at all time points, whereas cognitive biases, including IA, were measured only at T1. The final analysis included 301 students (mean age 15.2, 74% female). Overall, no significant changes in VH or knowledge were found between T1 and T2 overall. However, in students with low IA the info-based page reduced VH significantly compared to the control (-6.9%, p=.009). In contrast, among high-IA students, the same intervention increased VH (estimated: +8.9%, p=.002). Willingness to seek information increased in the info group among low-IA students (logg odds β=+1.639 vs. control, p=.034). At T3, we measured significant increase in knowledge compared to T1 despite the smaller sample collected. Social media campaigns showed limited effects on VH reduction in adolescents and can even backfire among high-IA individuals. Future strategies should incorporate personalized, bias-aware and interactive tools to address VH and HPV vaccine uptake effectively.