Résumé: In recent years, the segmentation of short molecular trajectories with varying diffusive properties has drawn particular attention of researchers, since it allows studying the dynamics of a particle. In the past decade, machine learning methods have shown highly promising results, also in changepoint detection and segmentation tasks. Here, we introduce a novel iterative method to identify the changepoints in a molecular trajectory, i.e. frames, where the diffusive behavior of a particle changes. A trajectory in our case follows a fractional Brownian motion and we estimate the diffusive properties of the trajectories. The proposed Bottom-up iterative anomalous diffusion detector (BI-ADD) combines unsupervised and supervised learning methods to detect the changepoints. Our approach can be used for the analysis of molecular trajectories at the individual level and also be extended to multiple particle tracking, which is an important challenge in fundamental biology. We validated BI-ADD in various scenarios within the framework of the 2nd anomalous diffusion challenge 2024 dedicated to single particle tracking. Our method is implemented in Python and is publicly available for research purposes.

Résumé: Cellular imaging of the human anterior eye is critical for understanding complex ophthalmic diseases, yet current techniques are constrained by a limited field of view or insufficient contrast. Here, we demonstrate that Ernst Abbe’s foundational principles on the interference nature of transmission microscopy can be applied in vivo to the human eye to overcome these limitations. The transmission geometry in the eye is achieved by projecting illumination onto the posterior eye (sclera) and using the back-reflected light as a secondary illumination source for anterior eye structures. Specifically, we show that the tightly localized illumination spot at the sclera functions analogously to a closed condenser aperture in conventional microscopy, significantly enhancing interference contrast. This enables clear visualization of cells and nerves across all corneal layers within an extended 2 mm field of view. Notably, the crystalline lens epithelial cells, fibers, and sutures are also distinctly resolved. In patients, Fuch’s endothelial dystrophy - a major ophthalmic disease affecting 300 million people - is highlighted under a transmission contrast, providing complementary information to traditional reflection contrast. Constructed using consumer-grade cameras, the instrument offers a path toward broad adoption for pre-screening and surgical follow-up, as well as for diagnosing corneal infections in low-resource settings, where anterior eye diseases are most prevalent.

Résumé: Achieving low-latency time-reversal of broadband radiofrequency signals is crucial for reliable communications in dynamic, uncontrolled environments. However, existing approaches are either digitally assisted—making broadband extension challenging—or limited to amplitude modulation. In this work, we report the very first, to our knowledge, experimental realization of a fully analog, phase-preserving time-reversal architecture for optically carried radiofrequency signals. The method exploits the exceptional coherence properties of rare-earth ion-doped materials and leverages the well-established photon echo mechanism, widely used in quantum technologies. While our demonstration is conducted with a modest bandwidth, we identify the fundamental cause of this limitation and propose solutions for future scalability.