Research
Peer-reviewed Papers (Journals & Conferences)
rNCA: Self-Repairing Segmentation Masks
Malte Silbernagel*, Albert Alonso*, Jens Petersen, Bulat Ibragimov, Marleen de Bruijne, Madeleine K. Wyburd
Submitted - December 2025 - MIDL 2026

Biological organisms have developed extraordinary capabilities to fix broken structures. We exploit that and construct a cellular-automata network to fix common issues on pixel-wise segmentation masks, resulting in a surprisingly effective method that efficiently repairs topological artifacts in medical segmentation models.
Extremal Contours: Gradient-driven contours for compact visual attribution
Reza Karimzadeh*, Albert Alonso*, Frans Zdyb, Julius B. Kirkegaard, and Bulat Ibragimov
Accepted (Oral) - September 2025 - NLDL 2026

We introduce a new explainability mask where a closed contour 'relaxes' on top of the object that the Neural Network is basing its decision on. The cool part is that we move the contour by propagating the gradients through the network and the masking process. Very simple and elegant.
Spline refinement with differentiable rendering
Frans Zdyb, Albert Alonso, J. B. Kirkegaard
Accepted (Poster) - March 2025 - MICCAI 2025
Sometimes predicted centerlines look slightly off. We introduce a training-free differentiable rendering approach to spline refinement, achieving both high reliability and sub-pixel accuracy. It serves as a drop-in replacement for the popular active contour model.
Adaptive Node Positioning in Biological Transport Networks
Albert Alonso*, Lars Erik J. Skjegstad*, J. B. Kirkegaard
Published - August 2025 - Physical Review Letters (PRL)

When the hydrodynamic graph model accounts for the energy cost of delivery from node to area, we can apply automatic differentiation to study optimal node positions. Curiously, when the domain is irregular (as in leaves), nodes distribute themselves to maximize efficiency.
Local Clustering and Global Spreading of Receptors for Optimal Spatial Gradient Sensing
Albert Alonso, Robert G. Endres, J. B. Kirkegaard
Published - April 2025 - Physical Review Letters (PRL)

Tiny cells have a hard time sensing their environment due to physical limits. We present a theoretical model exploring how receptors should be placed for optimal information processing. Results show clustering in high-curvature membrane regions, aligning with real-cell observations.
Persistent pseudopod splitting is an effective chemotaxis strategy in shallow gradients
Albert Alonso, J. B. Kirkegaard, Robert G. Endres
Published - May 2025 - Proceedings of the National Academy of Sciences (PNAS)

Decision making is hard for microscopic cells, yet essential for survival. We present a minimal model providing quantitative understanding of how cells use pseudopod splitting to achieve high-performance chemotaxis with minimal regulation—mechanical intelligence.
Irreversibility in Non-reciprocal Chaotic Systems
Tuan Pham, Albert Alonso, Karel Proesmans
Published - February 2025 - New Journal of Physics
A stochastic-thermodynamic framework analyzing the relationship between irreversibility and dynamical behavior in high-dimensional chaotic systems.
Learning optimal integration of spatial and temporal information in noisy chemotaxis
Albert Alonso, J. B. Kirkegaard
Published - July 2024 - PNAS Nexus

Two main chemotaxis strategies exist in nature: temporal (for small cells) and spatial (for larger cells). We show the transition is continuous and a combined strategy outperforms constrained variants.
Fast detection of slender bodies in high-density microscopy data
Albert Alonso, J. B. Kirkegaard
Published - July 2023 - Nature Communications Biology

An end-to-end deep learning approach for extracting precise shape trajectories of motile, overlapping slender bodies in high-density microscopy, applied to swimming nematodes.
PhD Thesis
Mind The Gradient: Differentiable Computational Methods in Microorganism Behaviour Studies
Albert Alonso
Ph.D. Thesis · 2024 · University of Copenhagen - Faculty of Science
Uses differentiable programming techniques to develop computational methods and mathematical models exploring navigation, sensory integration, and behavioral adaptations under physical constraints of the microscopic scale.