The motion of bubbles in an ultrasonic field is a fundamental physical mechanism in most applications of acoustic cavitation. In these applications, surface-active solutes, which could lower the surface tension of the liquid, are always utilized to improve efficiency by reducing the cavitation threshold. This paper examines the influence of liquids’ surface tension on single micro-bubbles motion in an ultrasonic field. A novel experimental system based on high-speed photography has been designed to investigate the temporary evolution of a single bubble in the free-field exposed to a 20.43 kHz ultrasound in liquids with different surface tensions. In addition, the R-P equations in the liquid with different surface tension are solved. It is found that the influences of the surface tension on the bubble dynamics are obvious, which reflect on the changes in the maximum size and speed of the bubble margin during bubble oscillating, as well as the weaker stability of the bubble in the liquid with low surface tension, especially for the oscillating bubble with higher speed. These effects of the surface tension on the bubble dynamics can explain the mechanism of surfactants for promoting acoustic cavitation in numerous application fields.

Xiaogang Pang, Yifan Xu, Shuoxin Xie, Tianshu Zhang, Lin Cong, Yuchen Qi, Lubing Liu, Qingjun Li, Mei Mo, Guimei Wang, Xiuwei Du, Hui Shen and Yuanyuan Li. Exp Neurobiol 2023;32:285-301. https://doi.org/10.5607/en23015

Background and objective: Antidepressants are widely prescribed to treat depression and anxiety disorders that may become chronic conditions among women. Epidemiological studies have yielded inconsistent results on the correlation between antidepressant use and the incidence risk of female breast and gynecological cancer, along with uncertain dose–response relationship. Therefore, we performed a systematic review and dose–response meta-analysis to investigate the association.Methods: Web of Science, Embase, PubMed, The Cochrane Library, and PsycINFO were systematically searched in January 2022, with no language limits. Random-effect models were used to calculate pooled effect sizes and 95% confidence intervals between studies. Linear and non-linear dose–response analyses were performed to evaluate the dose or duration of antidepressant use affecting the incidence risk of female breast and gynecological cancer. Further subgroup analyses were systematically performed by stratifying almost all study characteristics and important potential confounders, in order to further clarify and validate the important potential hypotheses regarding the biological mechanism underlying this association.Results: Based on a systematic literature search, 34 eligible studies (27 case–control studies and 7 cohort studies) involving 160,727 female breast and gynecological cancer patients found that antidepressant use did not increase the incidence risk of female breast and gynecological cancer (pooled OR: 1.01; 95% CI: 0.97, 1.04, I² = 71.5%, p < 0.001), and even decreased the incidence risk of ovarian cancer (pooled OR: 0.91; 95% CI: 0.83, 1, I² = 17.4%, p = 0.293). There were a non-linear dose–response relationship (p non-linearity < 0.05) between the duration of antidepressant use and incidence risk of female breast cancer, and an inverse linear dose–response relationship between antidepressant use and the incidence risk of gynecological cancer, specifically with an increase of cumulative defined daily dose or duration to a high level, like 25,550 doses (OR: 0.91, 95% CI: 0.85–0.98, p linearity < 0.05) or 4,380 days (OR: 0.82; 95% CI: 0.7, 0.96, p linearity < 0.05), compared to never antidepressant users.Conclusion: This systematic review and dose–response meta-analysis found that antidepressant use did not increase the incidence risk of female breast and gynecological cancer and even decreased the incidence risk of ovarian cancer, along with a non-linear or linear dose–response relationship.Systematic Review Registration: PROSPERO https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=313364, identifier CRD42022313364.

Understanding the behavior of single cavitation bubbles under ultrasonic excitation is crucial for biomedical applications, particularly targeted drug delivery. This study experimentally investigates the physics of acoustically driven bubble shape instabilities within confined tubes (inner diameters 600-800 μm) designed to mimic human micro-vessels. Utilizing an ultrafast photomicrographic system, we captured high-resolution recordings of the spatiotemporal evolution and translational trajectories of micrometric air bubbles. The experimental results demonstrate that when a bubble is positioned on the tube's axial line, an increase in acoustic pressure significantly alters bubble morphology and reduces collapse time. Notably, the formation of high-velocity upward microjets was observed during collapse phases, with peak jet velocities scaling positively with ultrasonic intensity. A comparative analysis of varying initial bubble sizes reveals that the tube boundary induces a fourth-harmonic acoustic response, which substantially enhances the intensity of the bubble's horizontal migration, rotational dynamics, and collapse violence. Furthermore, the initial proximity of the bubble to the tube wall was identified as a critical determinant of cavitation dynamics. Detailed analysis shows that a shorter initial distance to the boundary accelerates the rotational path of the bubble towards the wall, leading to an earlier and more intense asymmetric collapse. These findings provide new quantitative insights into the microscopic mechanisms of ultrasound-induced cavitation in confined geometries, offering a framework for optimizing ultrasonic applications in clinical and microfluidic environments.

The dynamic evolution of microbubbles under ultrasonic excitation is fundamental to applications ranging from targeted drug delivery to acoustic cleaning. This study employs a synchronous high-speed microscopic imaging system to systematically investigate the size-dependent stability and fragmentation of air microbubbles (R₀ = 25–82.5 μm) in a free field at a driving frequency of 16.6 kHz. Our results demonstrate a clear mechanistic transition from stable radial oscillations to complex surface instabilities and, eventually, deterministic fragmentation. Smaller bubbles (R₀ < 55 μm) exhibit long-term stability, transitioning through higher-order surface modes (n = 3 to n = 4) as surface energy accumulates. In contrast, larger bubbles (R₀ > 60 μm) undergo violent non-spherical deformations characterized by centripetal necking and high-speed micro-jetting. Notably, we identify an inverse relationship between initial radius and fragmentation onset time, with larger bubbles reaching instability thresholds significantly earlier. Furthermore, a transition from stochastic breakup to bimodal, volume-symmetric splitting was observed as R₀ increased, where daughter bubbles reached comparable volumes. These findings provide a theoretical and empirical basis for the controlled generation of monodisperse microbubble clouds, offering significant potential for enhancing the efficacy of ultrasonic contrast agents and therapeutic cavitation.

Corrigendum: The incidence risk of breast and gynecological cancer by antidepressant use: A systematic review and dose–response meta-analysis of epidemiological studies involving 160,727 patients