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We reveal and justify, both theoretically and experimentally, the existence of a unifying criterion of the boiling crisis. This criterion emerges from an instability in the near-wall interactions of bubbles, which can be described as a percolation process driven by three fundamental boiling parameters: nucleation site density, average bubble footprint radius and product of average bubble growth time and detachment frequency. Our analysis suggests that the boiling crisis occurs on a well-defined critical surface in the multidimensional space of these parameters. Our experiments confirm the existence of this unifying criterion for a wide variety of boiling surface geometries and textures, two boiling regimes (pool and flow boiling) and two fluids (water and liquid nitrogen). This criterion constitutes a simple mechanistic rule to predict the boiling crisis, also providing a guiding principle for designing boiling surfaces that would maximize the nucleate boiling performance. Boiling crisis is a physical phenomenon limiting the operation of many technologies cooled by boiling. Zhang et al. reveal theoretically and experimentally the existence of a unifying criterion to explain and predict the boiling crisis.

We run pool boiling experiments with a dielectric fluid (FC-72) on Earth and on board an ESA parabolic flight aircraft able to cancel the effects of gravity, testing both highly wetting microstructured surfaces and plain surfaces and applying an external electric field that creates gravity-mimicking body forces. Our results reveal that microstructured surfaces, known to enhance the critical heat flux on Earth, are also useful in microgravity. An enhancement of the microgravity critical heat flux on a plain surface can also be obtained using the electric field. However, the best boiling performance is achieved when these techniques are used together. The effects created by microstructured surfaces and electric fields are synergistic. They enhance the critical heat flux in microgravity conditions up to 257 kW/m2, which is even higher than the value measured on Earth on a plain surface (i.e., 168 kW/m2). These results demonstrate the potential of this synergistic approach toward very compact and efficient two-phase heat transfer systems for microgravity applications.

Background/Objectives: Schizophrenia is a severe psychiatric disorder frequently characterised by sleep and circadian disturbances, which are closely linked to cognitive dysfunction, symptom exacerbation, and poor functional outcomes. A growing body of evidence implicates the orexin (hypocretin) system—an essential regulator of arousal, sleep–wake stability, metabolic processes, and motivated behaviour—in the pathophysiology and treatment response of psychotic disorders. We aimed to investigate the relationships between the orexinergic system and psychoses. Methods: On 3 March 2026, we searched the PubMed, Scopus, PsycInfo/Articles and Cinahl databases for studies dealing with the orexin system and psychotic disorders and treatment response. Results: We found 20 eligible studies reporting variable and inconsistent alterations in orexin signalling in patients with schizophrenia. Studies were mostly cross-sectional and heterogeneous in design. Antipsychotic medications interfere with orexin-dependent pathways, potentially contributing to both therapeutic effects and adverse outcomes such as sleep disruption and metabolic dysregulation. Conclusions: While evidence from preclinical studies could point to an influence of dopaminergic activity through orexinergic mechanisms, with possible attenuation of antipsychotic-induced motor side effects and improvement of attentional deficits associated with NMDA receptor hypofunction, the utility of dual orexin receptor antagonists (DORAs) in psychoses is unclear. Despite the high prevalence of insomnia in schizophrenia, its pharmacological management remains suboptimal, with current treatments often limited by reduced efficacy or tolerability concerns. DORAs, which are currently approved medications for the treatment of insomnia, represent a novel and mechanistically distinct therapeutic option that may improve sleep while modulating arousal- and cognition-related circuits relevant to psychosis.

Background Emotional dysregulation (ED) is a transdiagnostic feature of several psychiatric and neurodevelopmental disorders, characterized by heightened emotional reactivity, mood instability, and difficulties regulating emotional responses. Methods In this study, an activation likelihood estimation (ALE) meta‐analysis was conducted to examine the neural underpinnings of ED across different clinical populations. A systematic search based on preferred reporting items for systematic reviews and meta‐analyses (PRISMA) guidelines identified 35 task‐based fMRI studies (n = 1989 subjects), including patients with borderline personality disorder (BPD), attention‐deficit/hyperactivity disorder (ADHD), bipolar disorder (BD), and other conditions. Results Hyper‐activation was observed in emotion‐related regions, particularly bilateral amygdala and left insula, indicating heightened emotional sensitivity and reactivity. Hypo‐activation, detected through Bayesian thresholding, was found in areas such as the anterior cingulate cortex and supplementary motor area, suggesting impairments in cognitive control and emotional regulation. Functional connectivity analysis revealed distinct patterns of coactivation, with the amygdala showing isolated activity and the left insula coactivating with regions related to sensory processing and cognitive control. Conclusions These findings provide new insights into the neural circuitry of transdiagnostic ED and suggest that disorders, such as BPD, ADHD, and BD, share common neural mechanisms, particularly in regions involved in emotional reactivity and cognitive regulation. The results have important clinical implications for developing targeted interventions to address both emotional and cognitive deficits in ED. Future research should explore causal mechanisms and incorporate diverse clinical populations to further understand neurobiological basis of ED.

Bubble growth, departure and sliding in low-pressure flow boiling has received considerable attention in the past. However, most applications of boiling heat transfer rely on high-pressure flow boiling, for which very little is known, as experimental data are scarce and very difficult to obtain. In this work, we conduct an experiment using high-resolution optical techniques. By combining backlit shadowgraphy and phase-detection imaging, we track bubble shape and physical footprint with high spatial ($6\\,\\mathrm {\\mu }{\\rm m}$) and temporal ($33\\,\\mathrm {\\mu }{\\rm s}$) resolutions, as well as bubble size and position as bubbles nucleate and slide on top of the heated surface. We show that at pressures above 1 MPa bubbles retain a spherical shape throughout the growth and sliding process. We analytically derive non-dimensional numbers to correlate bubble velocity and liquid velocity throughout the turbulent boundary layer and predict the sliding of bubbles on the surface, solely from physical properties and the bubble growth rate. We also show that these non-dimensional solutions can be leveraged to formulate elementary criteria that predict the effect of pressure and flow rate on bubble departure diameter and growth time.

We conducted experiments to analyze water boiling under 10 K subcooling and atmospheric conditions in a horizontal pool boiling test setup, focusing on the effect of liquid height above the heating surface. Our main interest was the transition in boiling crisis mechanisms at liquid heights comparable to bubble size. For pool heights above 4.0 mm, we observed a relatively constant critical heat flux (CHF) of approximately 1.21 MW/m^2. Conversely, CHF significantly dropped to around 0.19 MW/m^2 for liquid heights below 2.5 mm. For depths between 2.5 – 4.0 mm the measured CHF values varied within these limits. Our pool boiling facility featured a stainless-steel chamber filled with deionized water heated by external circulating oil. A ceramic cartridge supported a transparent heater at the cell’s center-bottom, which utilized an indium tin oxide layer on a sapphire substrate for heat dissipation. We monitored bubbles’ footprint dynamics during boiling using infrared and high-speed video cameras. Preliminary high-speed data analysis revealed different hydrodynamic mechanisms corresponding to the obtained CHFs. For heights above 4.0 mm, the formation of an irreversible dry patch is triggered by bubble interactions. Conversely, at heights below 2.5 mm, one of the bubbles nucleating shortly after the onset of boiling failed to detach from the surface shortly. Instead, it grew in size and eventually spread over the entire surface, prematurely triggering a boiling crisis. We attributed this behavior to a lack of buoyancy forces to detach the bubble from the surface as it grew above the liquid level. Pool heights between 2.5 – 4.0 mm showed both behaviors. Further investigations will focus on exploring the transition in boiling mechanisms shifting from buoyancy- to surface-tension-dominated processes by varying bubble dimensions through the introduction of surfactants. Ultimately, we aim to analyze fundamental boiling parameters and heat flux to characterize how boiling dynamics, boiling crisis and CHF value vary with the bubble-to-liquid height ratio.

This paper discusses the results of a computational activity devoted to the prediction of two-phase flows in subchannels and in rod bundles. The capabilities of the FLICA-OVAP code have been tested against an extensive experimental database made available by the Japanese Nuclear Power Energy Corporation (NUPEC) in the frame of the PWR subchannel and bundle tests (PSBT) international benchmark promoted by OECD and NRC. The experimental tests herein addressed involve void fraction distributions and boiling crisis phenomena in rod bundles with uniform and nonuniform heat flux conditions. Both steady-state and transient scenarios have been addressed, including power increase, flow reduction, temperature increase, and depressurization, representative of PWR thermal-hydraulics conditions. After a brief description of the main features of FLICA-OVAP, the relevant physical models available within the code are detailed. Results obtained in the different tests included in the PSBT void distribution and DNB benchmarks are therefore reported. The relevant role of selected physical models is discussed.

In this work, we explore the impact of coatings and microstructures on heat transfer during a cryogenic quenching process. An easily reproducible quenching test is presented as a benchmark for testing different solutions. The study involves two different flat polymeric coatings as well as three porous microstructures. The results show that pairing a low-conductive coating with an appropriate porous surface microstructure on top of a stainless-steel plate can reduce the chill down time, accelerating the transition from room temperature to liquid nitrogen temperature, by a factor of five. High speed video recordings have been used to analyse the quenching process with different coatings and microstructures showing how the suppression of the film boiling regime is the key to enhancing the quenching process.

High resolution measurements of key parameters relevant to bubble departure processes in high-pressure water systems has been a major challenge over the past several decades due to the small size and fast motion of vapor bubbles, making conventional optical measurements unreliable. Addressing this difficulty is critical, as accurate bubble departure data and computationally inexpensive models are needed for future two-phase heat transfer models. To close this gap, we use high-speed imaging to track bubble size and velocity in high-pressure flow boiling conditions (10 – 40 bar). It is observed that bubbles are almost always perfectly spherical in shape and slide along the boiling surface immediately after nucleating. To predict sliding, we conduct a force balance on the bubble and derive an equation of motion in the direction of the bulk flow. Interestingly, we find that at high pressure conditions, the equation of motion can be significantly simplified, resulting in an analytical expression for the bubble motion, growth time and departure diameter, allowing us to develop simple and computationally efficient equations. The applicability of the model and departure criterion across a broader range of high-pressure conditions is discussed, and recommendations for further characterization of bubble departure processes are made.

This work features the boiling of FC72 on a transparent sapphire substrate. Tests are performed using a thin ITO film (indium tin oxide) coated on the sapphire substrate as the heat source, a fast speed video camera to capture the boiling process using a technique to track the phase (liquid or vapor) in contact with the heating surface, an InfraRed video camera to capture the average temperature on the surface, and a metallic grid to impose an electric field perpendicular to the boiling surface. The maximum average electric field tested in this work is 3.3 kV / mm , which led to a 18% increase of the critical heat flux. This study analyses in detail the phase distribution data showing that (1) there is no evidence of microlayer formation, and suggesting that (2) the triple contact line evaporation accounts for approximately 20% of the total heat flux, while (3) the quenching stage accounts for approximately 80%. Finally, phase distribution images are processed to characterize the size of vapor patches, showing that a boiling crisis occurs when the distribution of the vapor patches becomes scale-free, and corroborating the hypothesis that the boiling crisis can be modelled as a bubble interaction instability using a percolation model.