Soft Matter Lab

Seminar on effective drifts in generalized Langevin systems by Soon Hoe Lim from Nordita, Soliden 3rd floor, 12 Dec 2018

Effective Drifts in Generalized Langevin Systems
Seminar by Soon Hoe Lim
from Nordita, Stockholm, Sweden, EU

Generalized Langevin equations (GLEs) are stochastic integro-differential equations commonly used as models in non-equilibrium statistical mechanics to describe the dynamics of a particle coupled to a heat bath. From modeling point of view, it is often desirable to derive effective mathematical models, in the form of stochastic differential equations (SDEs), to capture the essential dynamics of the systems. In this talk, we consider effective SDEs describing the behavior of a large class of generalized Langevin systems in the limits when natural time scales become very small. It turns out that additional drift terms, called noise-induced drifts, appear in the effective SDEs. We discuss recent progress on the phenomena of noise-induced drift in these systems. This is joint work with Jan Wehr and Maciej Lowenstein.

Place: Soliden 3rd floor
Time: 12 December 2018, 13:00

Jalpa Soni is MSCA Fellow of the Week

Our Marie-Curie postdoctoral researcher Jalpa Soni becomes the #MSCA Fellow of the Week, and gets her project highlighted on Tweeter and Facebook pages of the Marie-Skłodowska-Curie Actions

Jalpa is studying the behaviour of micro swimmers like bacteria in 3D complex environments. That will give us the understanding of how they propagate in living systems, which in turn will be used to manipulate them for medicinal advantages.One such example would be to create artificial swimmers (active particles) mimicking natural bacteria for more efficient and targeted drug-delivery applications.To monitor the movement of such micro swimmers in 3D, Jalpa has developed a customised light-sheet microscope that is capable of fast volumetric imaging. The long term goal of the project is to create active particle induced drug-delivery methods for organ-on-chip devices and to monitor the drug efficacy in real time.

This is Jalpa’s insight as a MSCA fellow:

“The unique opportunity to build a new collaborative network has been the most beneficial aspect of my MSCA fellowship. The travels for the project has allowed me to experience different research organisations and to meet experts of various fields which is very important for interdisciplinary research that I love doing.”

Project Name: ActiveMotion3D – Experimental study of three-dimensional dynamics of Active particles

Learn more about Jalpa and her project:
CORDIS: https://bit.ly/2Rz1rVD

Tweeter: https://twitter.com/MSCActions/status/1070985015754919936
FB: https://www.facebook.com/135877696485772/posts/2441038415969677/ …

Giovanni Volpe on the Panel on the 2018 Nobel Prize in Physics, Stockholm, 7 Dec 2018

Panel on the 2018 Nobel Prize in Physics
Friday, December 7, 15:00 – 18:00
Oscar Klein hall, Albanova, Roslagstullsbacken 21, Stockholm

Albanova, Stockholm’s center for Physics, Astronomy and Biotechnology cordially organizes a panel discussion about this year’s Nobel Prize in Physics, followed by a social gathering with drinks and snacks.

Panel Members:
Felix Ritort, University of Barcelona
Cord Arnold, Lunds University
Giovanni Volpe, Göteborg University
Valdas Pasiskevicius, KTH Royal Institute of Technology

Moderator:
Eva Lindroth, Stockholms University

https://www.fysik.su.se/om-oss/evenemang/the-2018-nobel-prize-in-physics-1.415146

Here is the direct videolink:
http://video.albanova.se/ALBANOVA20181207/video.mp4 (817MB)

The event web-page is at:
http://video.albanova.se/arc2018_32.html

FORMA – Enhanced Optical Tweezers Calibration published in Nature Commun.

High-Performance Reconstruction of Microscopic Force Fields from Brownian Trajectories
Laura Pérez García, Jaime Donlucas Pérez, Giorgio Volpe, Alejandro V. Arzola & Giovanni Volpe
Nature Communications 9, 5166 (2018)
doi: 10.1038/s41467-018-07437-x
arXiv: 1808.05468

The accurate measurement of microscopic force fields is crucial in many branches of science and technology, from biophotonics and mechanobiology to microscopy and optomechanics. These forces are often probed by analysing their influence on the motion of Brownian particles. Here we introduce a powerful algorithm for microscopic force reconstruction via maximum-likelihood-estimator analysis (FORMA) to retrieve the force field acting on a Brownian particle from the analysis of its displacements. FORMA estimates accurately the conservative and non-conservative components of the force field with important advantages over established techniques, being parameter-free, requiring ten-fold less data and executing orders-of-magnitude faster. We demonstrate FORMA performance using optical tweezers, showing how, outperforming other available techniques, it can identify and characterise stable and unstable equilibrium points in generic force fields. Thanks to its high performance, FORMA can accelerate the development of microscopic and nanoscopic force transducers for physics, biology and engineering.

See also freeware software at 10.6084/m9.figshare.7181888

Featured in:
Optimerad optisk pincett, Forskning.se

Short course by G. Volpe at Imaging in Neurosciences, Karolinska Institute, Stockholm, 29 Nov 2018

Lectures Graph theory concepts and Hands-on practice (Graph theory) by Giovanni Volpe within the graduate course Imaging in Neuroscience: With a focus on structural MRI methods organised by Karolinska Institute.

Venue: Alfred Nobels allé 23, room 317, campus Huddinge (Flemingsberg), Stockholm

Phototactic Robot Tunable by Sensorial Delays published in Phys. Rev. E

Tuning phototactic robots with sensorial delays (Editors’ suggestion)
Maximilian Leyman, Freddie Ogemark, Jan Wehr & Giovanni Volpe
Physical Review E 98(26), 052606 (2018)
DOI: 10.1103/PhysRevE.98.052606
arXiv: 1807.11765

The presence of a delay between sensing and reacting to a signal can determine the long-term behavior of autonomous agents whose motion is intrinsically noisy.
In a previous work [M. Mijalkov, A. McDaniel, J. Wehr, and G. Volpe, Phys. Rev. X 6, 011008 (2016)], we have shown that sensorial delay can alter the drift and the position probability distribution of an autonomous agent whose speed depends on the illumination intensity it measures. Here, using theory, simulations, and experiments with a phototactic robot, we generalize this effect to an agent for which both speed and rotational diffusion depend on the illumination intensity and are subject to two independent sensorial delays. We show that both the drift and the probability distribution are influenced by the presence of these sensorial delays. In particular, the radial drift may have positive as well as negative sign, and the position probability distribution peaks in different regions depending on the delay.
Furthermore, the presence of multiple sensorial delays permits us to explore the role of the interaction between them.

Laura Pérez-García joins the Soft Matter Lab

Laura Pérez-García starts her PhD at the Physics Department of the University of Gothenburg on 15th November 2018.

Laura has a Master degree in physical sciences from Universidad Nacional Autónoma de México in México City, where she submitted a Master thesis about optical forces in speckle fields.

The aim of her PhD project is to study the behavior of active matter using Light Sheet Microscopy.

Talk by A. Callegari at LAOP, Lima, 14 Nov 2018

Active Matter Alters the Growth Dynamics of Coffee Rings
Agnese Callegari, Tugba Andaç, Pascal Weigmann, Sabareesh K. Velu, Erçag Pince, Giorgio Volpe & Giovanni Volpe
LAOP – Latin America Optics & Photonics Congress, Lima, Peru
12-15 November 2018

Abstract: We show that bacterial mobility starts playing a major role in determining the growth dynamics of the edge of drying droplets, as the droplet evaporation rate slows down.

Talk by G. Volpe at LAOP, Lima, 13 Nov 2018

Microscopic Engine Powered by Critical Demixing
Falko Schmidt, Alessandro Magazzù, Agnese Callegari, Luca Biancofiore, Frank Cichos & Giovanni Volpe
LAOP – Latin America Optics & Photonics Congress, Lima, Peru
12-15 November 2018

Abstract: An optically trapped absorbing microsphere in a sub-critical mixture rotates around the optical trap thanks to diffusiophoretic propulsion, which can be controlled by adjusting the optical power, the temperature, and the criticality of the mixture.

Giovanni Volpe New Docent in Physics

From the article New Docent in Physics (English) and Ny docent i fysik (Swedish)

Three questions for Giovanni Volpe, appointed Docent in Physics at the Faculty of Science, University of Gothenburg.

Interview by: Linnéa Magnusson
Photo by: Malin Arnesson

What is your research about?

“I am conducting research in several different areas. Part of my work concerns artificial micro swimmers. In simple terms, this is about biological and artificial objects of microscopic size that can get around by themselves and counteract microorganisms. Research on micro swimmers involves many possibilities within basic science, nanoscience and nanotechnology.

“I am collaborating with Karolinska Institutet on a project that deals with neurodegenerative diseases such as Alzheimer’s, Parkinson’s and ALS (amyotrophic lateral sclerosis). We have developed software that serves as a toolkit, helping us to detect these diseases at an early stage.

“Another project deals with optical trapping and optical manipulation. Using optical tweezers, I can measure microscopic forces, for example.

“Finally, I am also working on a project that involves managing the challenges of condensed matter physics – in other words, matter and processes at the atomic level. With the help of machine learning, we can handle complex algorithms.”

What can society learn from your research?

“I hope that our work with micro swimmers can become a foundation on which we can build, so that in the future we can use them in real life. For example, this could involve cleaning contaminated soil or developing what are known as chiral drugs – medications that are more selective and more controllable and that have fewer side effects. It is to be hoped that our work in neuroscience will lead us to quickly detect and treat neurodegenerative diseases.”

What do you think is most exciting about the future?

“What is most exciting is the possibility of using artificial intelligence to solve physical and medical problems. In the future we will go from people developing and testing ideas to have data and systems under investigation speak for themselves.

Tre frågor till Giovanni Volpe som antagits som oavlönad docent i fysik vid Naturvetenskapliga fakulteten, Göteborgs universitet.

Vad handlar din forskning om?

– Jag forskar inom flera olika områden. En del i mitt arbete handlar om konstgjorda ”micro swimmers”. Förenklat så handlar det om biologiska och artificiella föremål i mikroskopisk storlek som kan ta sig fram själva och motverka mikroorganismer. Forskning om ”Micro Swimmers” innebär en mängd möjligheter inom grundvetenskap, nanovetenskap och nanoteknik.

– Jag samarbetar med Karolinska Institutet inom ett projekt som handlar om neurodegenerativa sjukdomar, som Alzheimers sjukdom, Parkinsons sjukdom och ALS. Vi har utvecklat en programvara som fungerar som en verktygslåda, som hjälper oss att tidigt upptäckta dessa sjukdomar.

– Ett annat projekt handlar om optisk fångst och optisk manipulation. Med hjälp av optiska pincetten kan jag exempelvis mäta mikroskopiska krafter.

– Till sist arbetar jag även med ett projekt som handlar om att hantera utmaningar med den kondenserade materiens fysik, alltså materia och processer på atomär nivå. Till hjälp har vi inlärningsmaskiner som kan hantera komplexa algoritmer.

Vad kan samhället lära av din forskning?

– Jag hoppas att arbetet med ”Micro swimmers ” kan bli en grund att bygga vidare på. Så att vi i framtiden kan använda ”Micro swimmers ” i verkliga livet. Det kan exempelvis handla om att kunna rengöra förorenad jord eller utveckla så kallade kirala läkemedel, det vill säga mediciner som är både mer selektiva, mer styrbara och har mindre biverkningar. Arbetet inom neurovetenskap kommer förhoppningsvis leda till att vi snabbt kan upptäcka och behandla neurodegenerativa sjukdomar.

Vad tycker du är mest spännande i framtiden?

– Det som är mest spännande är möjligheten att använda artificiell intelligens för att lösa fysiska och medicinska problem. I framtiden kommer vi att gå från att det är människor som utvecklar och testar idéer till att det är datorer och system som kommer att undersöka och analysera varandra.