Influence of Sensorial Delay on Clustering and Swarming published in Phys. Rev. E

Influence of Sensorial Delay on Clustering and Swarming

Influence of Sensorial Delay on Clustering and Swarming
Rafal Piwowarczyk, Martin Selin, Thomas Ihle & Giovanni Volpe
Physical Review E 100(1), 012607 (2019)
doi: 10.1103/PhysRevE.100.012607
arXiv:  1803.06026

We show that sensorial delay alters the collective motion of self-propelling agents with aligning interactions: In a two-dimensional Vicsek model, short delays enhance the emergence of clusters and swarms, while long or negative delays prevent their formation. In order to quantify this phenomenon, we introduce a global clustering parameter based on the Voronoi tessellation, which permits us to efficiently measure the formation of clusters. Thanks to its simplicity, sensorial delay might already play a role in the organization of living organisms and can provide a powerful tool to engineer and dynamically tune the behavior of large ensembles of autonomous robots.

Invited talk by G. Volpe at RIAO/Optilas 2019, Cancun, Mexico, 23 Sep 2019

Deep Learning Applications in Digital Video Microscopy and Optical Micromanipulation
Saga Helgadottir, Aykut Argun, Giovanni Volpe
Invited talk at RIAO/Optilas 2019, Cancun, Mexico, 23-27 September 2019

Since its introduction in the mid 90s, digital video microscopy has become a staple for the analysis of data in optical trapping and optical manipulation experiments [1]. Current methods are able to predict the location of the center of a particle in ideal condition with high accuracy. However, these methods fail as the signal-to-noise ratio (SNR) of the images decreases or if there are non-uniform distortions present in the images. Both these conditions are commonly encountered in experiments. In addition, all these methods require considerable user input in terms of analysis parameters, which introduces user bias. In order to automatize the tracking process algorithms using deep learning have been successfully introduced but have not proved to be usable for practical applications.

Here, we provide a fully automated deep learning tracking algorithm with sub-pixel precision in localizing single particle and multiple particles’ positions from image data [2]. We have developed a convolutional neural network that is pre-trained on simulated single particle images in varying conditions of, for example, particle intensity, image contrast and SNR.

We test the pre-trained network on an optically trapped particle both in ideal condition and challenged condition with low SNR and non-uniform distortions [3]. This pre-trained network accurately predicts the location the trapped particle and a comparison of detected trajectories, the distribution of the particle position and the power spectral density of the particle trajectory clearly shows that our algorithm outperforms tracking by radial symmetry [4]. Our algorithm is also able to track non-ideal images with multiple Brownian particles as well as swimming bacteria that are problematic for traditional methods.

In conclusion, our algorithm outperforms current methods in precision and speed of tracking non-ideal images, while eliminating the need for user supervision and therefore the introduction of user biases. 


[1] John C Crocker, David G Grier, Journal of Colloid and Interface Science 179, 298–310 (1996).

[2] Saga Helgadottir, Aykut Argun, Giovanni Volpe,Optica 6, 506–513 (2019).

[3] Philip H Jones, Onofrio M Maragò, Giovanni Volpe, Optical tweezers: Principles and applications. Cambridge University Press, 2015.

[4] Raghuveer Parthasarathy. Nature Methods 9724 (2012).

Falko Schmidt attends the 69th Lindau Nobel laureate meeting

Picture from the open discussion with Steven Chu (Nobel Prize Physics 1997) on the left. 69th Lindau Nobel Laureate Meeting 02.07.2019 Photo/Credit: Patrick Kunkel/ Lindau Nobel Laureate Meetings Open Exhange
Picture of the boat ride to Mainau Island with Donna Strickland (Nobel Prize Physics 2018) on the left. 69th Lindau Nobel Laureate Meeting, 04.07.2019, Lindau, Germany
Picture/Credit: Julia Nimke/Lindau Nobel Laureate Meetings
Picture of the open discussion with David Gross (Nobel Prize Physics 2004) on the left. 69th Lindau Nobel Laureate Meeting 03.07.2019 Photo/Credit: Patrick Kunkel/ Lindau Nobel Laureate Meetings Open Exchange David J. Gross

Falko Schmidt, and Jalpa Soni have been selected to attain the 69th Lindau Nobel Laureate meeting in Lindau, Germany from the 30th June till 5th July 2019.

The Lindau meeting is a platform where 600 young scientists around the world meet former Nobel laureates (as well as Turing-award winners). There they can exchange scientific ideas and experiences, inspire each other and connect for a more interdisciplinary scientific community. These are the three incentives that make this meeting a unique experience.

Falko Schmidt had the privilege to attend it and shares the following insight:

“For me, the Lindau meeting was a unique experience where I was able to meet peers across many disciplines, share ideas and experiences beyond my field of active matter and received much feedback on career choices and daily life as a PhD. Especially fruitful were the many possibilities to engage with senior scientists such as the Nobel laureates which with their humour, insight and advice deepened my passion about science. Personally, I would consider my best encounters with Steven Chu and William Phillips (Nobel Prize in Physics in 1997 on laser cooling),  Donna Strickland (Nobel Prize in Physics in 2018 on ultra-fast lasers), and Stefan Hell (Nobel Prize in Chemistry in 2014 on super-resolution microscopy). I am very grateful for the possibility of attending this meeting and would like to thank the Lindau Nobel committee and Söderbergs Foundation who  were selecting and sponsoring me.
From now on, in times of struggle, I will always look back to this meeting and remember why we all love doing science.”