Invited talk by L. Pérez at SPIE Photonics West OPTO

Stable, unstable and saddle points in a speckle optical potential.
FORMA: expanding applications of optical tweezers
Laura Pérez García
Invited talk at SPIE Photonics West OPTO
6 March 2021

In this presentation, Laura Pérez will talk about FORMA  (force reconstruction via maximum-likelihood-estimator analysis) which addresses the need of measuring the force fields acting on microscopic particles. Compared to alternative established methods, FORMA is faster, simpler, more accurate, and more precise. Furthermore, FORMA can also measure non-conservative and out-of-equilibrium force fields. Here, after a brief introduction to FORMA, I will present its use, advantages, and limitations. I will conclude with some recent work where we exploit Bayesian inference to expand the scope of application of FORMA.

Laura Pérez García, Jaime Donlucas Pérez, Giorgio Volpe, Alejandro V. Arzola & Giovanni Volpe, High-Performance Reconstruction of Microscopic Force Fields from Brownian Trajectories, Nature Communications 9, 5166 (2018)

Time: 6 March 2021
Place: Online
Link: FORMA: expanding applications of optical tweezers at SPIE Photonics West OPTO

Nils Jacobson defended his Master thesis on 16 February 2021. Congrats!

Nils Jacobson defended his Master thesis in MPCAS at the Chalmers University of Technology on 16 February 2021. Congrats!

Screenshot of Nils Jacobson’s Master Thesis defence.
Title: Vascular Bifurcation Detection in Cerebral CT Angiography Using CNN and Frangi Filters

Segmentation and feature extraction are important tools for analysing and visualizing information in medical image data, particularly in vascular image data which relates to widely spread vascular diseases. Vessel segmentation is extensively featured in research, recently adapting trends in deep learning image processing. This paper aims to develop a vessel bifurcation detection method to support a seed point based segmentation approach. The suggested approach is a combination of classification, with a convolutional neural network (DenseNet), local vessel segmentation, with Frangi filters, and 3D morphological skeletonization. A small data set is produced for network training and evaluation. Results indicate a high classification accuracy which filters problematic samples for the Frangi filter. Thus the combination is able to suggest quality branch seed points under most circumstances. Next step would be to expand the data set to enable further optimization and more rigid evaluation. In any case a combination of a high performance classifier followed by qualitative assessment of local samples show potential.​

​Name of the master programme: MPCAS – Complex Adaptive Systems
Supervisor: Jonna Hellström and Giovanni Volpe
Examiner: Giovanni Volpe, Department of Physics, University of Gothenburg
Opponent: Eva Škvor

Place: Online via Zoom
Time: 16 February, 2021, 16:00

Link: Master thesis presentation Nils Jacobson

Presentation by F. Schmidt on QED Casimir vs Critical Casimir at MPI Stuttgart, 11 February 2021

Schematic of the experiment with a suspended metallic flake-like particle on a gold-coated substrate.
QED Casimir vs Critical Casimir Forces: Trapping and Releasing of metal flake particles

Falko Schmidt, Agnese Callegari, Giovanni Volpe
(online at) MPI Stuttgart, Germany
11 February 2021, 14:30-16.00

We propose a mechanism for restoration of collapsed structures using critical Casimir forces by investigating the diffusion of metal flake-like particles. By tuning temperature near-criticality and employing selective self-assembled monolayers the resulting repulsive critical Casimir force is large enough to lift off particle and enable transitions previously impeded by QED Casimir attraction.

Intercellular Communication Induces Glycolytic Synchronisation Waves published in PNAS

Intercellular communication induces glycolytic synchronization waves between individually oscillating cells

Intercellular communication induces glycolytic synchronization waves between individually oscillating cells
Martin Mojica-Benavides, David D. van Niekerk, Mite Mijalkov, Jacky L. Snoep, Bernhard Mehlig, Giovanni Volpe, Caroline B. Adiels & Mattias Goksör
PNAS 118(6), e2010075118 (2021)
doi: 10.1073/pnas.2010075118
arXiv: 1909.05187

Metabolic oscillations in single cells underlie the mechanisms behind cell synchronization and cell-cell communication. For example, glycolytic oscillations mediated by biochemical communication between cells may synchronize the pulsatile insulin secretion by pancreatic tissue, and a link between glycolytic synchronization anomalies and type-2 diabetes has been hypotesized. Cultures of yeast cells have provided an ideal model system to study synchronization and propagation waves of glycolytic oscillations in large populations. However, the mechanism by which synchronization occurs at individual cell-cell level and overcome local chemical concentrations and heterogenic biological clocks, is still an open question because of experimental limitations in sensitive and specific handling of single cells. Here, we show how the coupling of intercellular diffusion with the phase regulation of individual oscillating cells induce glycolytic synchronization waves. We directly measure the single-cell metabolic responses from yeast cells in a microfluidic environment and characterize a discretized cell-cell communication using graph theory. We corroborate our findings with simulations based on a kinetic detailed model for individual yeast cells. These findings can provide insight into the roles cellular synchronization play in biomedical applications, such as insulin secretion regulation at the cellular level.

Press release on joint research on intercellular communication mechanism by Biological Physics Lab and Soft Matter Lab

The article Intercellular Communication Induces Glycolytic Synchronisation Waves published in PNAS has been featured in the News of the Faculty of Science of Gothenburg University.

Here the links to the press releases:
Swedish: Forskare har knäckt koden för cellkommunikation
English: Researchers have broken the code for cell communication

Giovanni Volpe is committee member at OSA-OMA 2021

Giovanni Volpe is part of the committee of the conference Optical Manipulation and its Applications (OMA), which is part of the OSA Biophotonics Congress: Optics in the Life Sciences.

Optical Manipulation encompasses all areas of manipulation and measurement using light, from optical manipulation of microparticles to photoactivated materials and optogenetics, emphasizing new and developing application areas in biophysics and biomedicine.

The categories of topics in the conference are Optical Manipulation in Biophysics and Biomedicine, Optical Manipulation Fundamentals, Optical Manipulation Applications, and Alternative Manipulation Techniques.

The conference will be held online 12-16 April 2021.