News – Page 2 – ActiveMatter ITN

Liam Ruske participates in Current and Future Themes in Soft & Biological Active Matter, 01-19 August 2022, Stockholm

Participants at the Nordita workshop in Stockholm. *(Photo by Boyi Wang)*

Between the 1st and the 19th of August 2022 Liam participated in the Nordita workshop Current and Future Themes in Soft & Biological Active Matter. In his talk titled “Modelling the Dynamics of 3D cell aggregates” he motivated how cell divisions and death act as a source of active forces in cellular aggregates and how these processes can be incorporated into continuum models of tissues. Applying this model to 3D living cell aggregates (spheroids) not only allows the inference of dynamic cell parameters from experimentally measured cell alignment profiles, but more generally motivates novel mechanisms for controlling the alignment of cells within aggregates which has been shown to influence the mechanical properties and invasive capabilities of tumors.

David participates in the MoLE conference, 25-29 July, Donostia-San Sebastián

David and Onofrio during the poster session at MoLE conference in Donostia-San Sebastián. *(Photos provided by D. Bronte Ciriza)*

Between the 25th and the 29th of July 2022 David participated in the MoLE conference in Donostia-San Sebastián. The unexpected demise of Professor Juan José Sáenz, on March 22, 2020, has left his beloved family and friends in shock all over the globe. Following his spirit, MoLE conference 2022 was devoted to honouring his memory the way he would have liked: Appreciated colleagues and friends presenting and discussing their most recent advances, in both electronics and photonics. During this conference David presented a poster on “Elongated active particles in speckle fields“, where he had the chance to discuss the topic with a broad community of interested scientists.

Activity gradients in two- and three-dimensional active nematics

Spatial variations of active stress induce active torques, which aligns self-propelled defects along the gradient direction. Additionally there are also passive torques acting on defects induce by the elastic energy associated with deformations of the director field. The magnitude of active and passive torques acting on defects depends on defect type: While +1/2 defects (2D) and +1/2 disclination lines (3D) are dominated by active torque, twist-type disclination are subject to passive torques which aligns them in a way which minimizes the elastic energy of the system. *(Illustration by Liam Ruske)*

Activity gradients in two- and three-dimensional active nematics
Liam Ruske & Julia Yeomans
Soft Matter 18 5654-5661 (2022)
arxiv: 2206.06499
DOI: 10.1039/D2SM00228K

Abstract:

We numerically investigate how spatial variations of extensile or contractile active stress affect bulk active nematic systems in two and three dimensions. In the absence of defects, activity gradients drive flows which re-orient the nematic director field and thus act as an effective anchoring force. At high activity, defects are created and the system transitions into active turbulence, a chaotic flow state characterized by strong vorticity. We find that in two-dimensional (2D) systems active torques robustly align +1/2 defects parallel to activity gradients, with defect heads pointing towards contractile regions. In three-dimensional (3D) active nematics disclination lines preferentially lie in the plane perpendicular to activity gradients due to active torques acting on line segments. The average orientation of the defect structures in the plane perpendicular to the line tangent depends on the defect type, where wedge-like +1/2 defects align parallel to activity gradients, while twist defects are aligned anti-parallel. Understanding the response of active nematic fluids to activity gradients is an important step towards applying physical theories to biology, where spatial variations of active stress impact morphogenetic processes in developing embryos and affect flows and deformations in growing cell aggregates, such as tumours.

Liam Ruske presented a poster at the Active and Intelligent Living Matter conference, 26 June – 1 July 2022, Erice, Italy

The beatiful view from the conference centre on Mount Cofano. *(Photo by L. Ruske)*

Between the 26th of June and the 1st of July 2022 Liam participated in the Active and Intelligent Living Matter conference on Sicily, where he presented a poster summarizing several of his research projects about active continuum theories and their application to biological systems.

Sandrine Heijnen presented a poster at the 5th Meeting of the UCL Cross-Disciplinary Network on Soft Materials, 20th June 2022.

Sandrine Heijnen and her poster. *(Photos provided by S. Hejnen)*

Sandrine Heijnen attended the 5th Meeting of the UCL Cross-Disciplinary Network on Soft Materials on the 20^th of June 2022. She presented a poster titled “Emergent Collective Behaviours for Active Particles in Optical Landscapes” showing the recent development in her project regarding the behaviour of superparamagnetic particles in a light illuminated field. The Meeting presented a lot of interesting ideas by introducing both art and architecture, giving rise to a lot of interesting discussions.

David was awarded the best Poster Prize at NanoPlasm 2022

David during the poster session at Cetraro. *(Photos provided by D. Bronte Ciriza)*

During the conference NanoPlasm 2022, David was awarded the best Poster Prize, sponsored by Nanophotonics Journal – De Gruyter. The poster session was full of interesting discussions and ideas with curious researchers. After the official poster sesion we organized a small presentation taking advantage of the beautiful location. Is the future of poster presentations in locations like this?

Spontaneous, self-organized poster session at the beach. *(Photos provided by D. Bronte Ciriza)*

David participated in NanoPlasm 2022, 13-17 June, Cetraro, Italy

David during his elevator pitch talk at NanoPlasm 2022. *(Photos provided by D. Bronte Ciriza)*

Between the 13th and the 17th of June David participated in NanoPlasm 2022, which took place in Cetraro, Calabria, Italy. The conference was focused on the rapidly growing fields of Plasmonics and Nano-Photonics, which are opening new frontiers in nanoscience and advanced technologies via novel cross-disciplinary research activities. During this conference David presented 2 posters (titles: “Machine learning enhanced calculations of optical forces in the geometrical optics approximation” and “Elongated active particles in speckle fields“) and an elevator pitch talk, introducing his work on machine learning for optical forces calculations and his recent work on elongated active particles in speckle fields.

David participated in the 2022 Young Minds Leadership meeting

David and Fabio with the poster presenting the activities of the Messina chapter. *(Photos provided by D. Bronte Ciriza)*

Between the 2nd and the 4th of June, David was invited to the YM Leadership meeting in Paris to present the outreach activities carried out by the student chapter in Messina. After three years of virtual engagement the meeting brought together almost 50 YM delegates from 20 different countries as well as many interested students and young researchers from outside of the YM network, making it a great success.

Beyond the programme of the LM the co-location with the EPS Forum, allowed the participants to learn about industrial opportunities and to attend lectures from world-class researchers, including 3 Nobel Laureates. Scientific outreach, cultural exchange, and peaceful international collaboration are more important than ever. Bringing young scientists together and equipping them with tools and skills is a great way of fostering these aspects.

Liam Ruske gives a talk at the CECAM Computational methods and tools for complex suspensions workshop, 23-27 May 2022, Bilbao, Spain

Between the 23rd and the 27th of May 2022 Liam participated in the CECAM workshop on Computational methods and tools for complex suspensions to present some of his work. In his talk titled “Modelling biological matter as active nematic fluids” he highlighted how numerical simulations of active fluids can be used to study the self-organization of three-dimensional tissues in a variety of biological systems, where a continuous influx of energy on a single-cell level drives striking collective behaviour at the tissue scale.

Laura Natali and David Bronte Ciriza presented an effective communication activity in Lisbon

Laura Natali and David Bronte Ciriza during the presentation on the fundamentals of effective communication.(Photo by Alireza Khoshzaban.)

During the ActiveMatter meeting in Lisbon, Laura Natali and David Bronte Ciriza proposed a two hours activity on the fundamentals of effective communication. The activity was structured in an interactive way, and it began with a open discussion about the importance of communication, especially in science.

Then, the ESRs briefly described their research in a popular science style, so addressed to a broader public. The first hour concluded with a presentation about rules to keep in mind while communicating both in oral and written form.

Afterwards, a few examples among the written texts were selected and discussed with all the participants. The aim was to exchange feedback and suggestions on how to make the communication more effective. The feedback was the inspiration for everyone to review their communication example, and the final versions are being uploaded on the official twitter account @ActiveMatterITN.