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Antonio A. R. Neves visits the Soft Matter Lab. Welcome!

Antonio Alvaro Ranha Neves is a Visiting Professor from the Federal University of ABC in Brazil. His visiting position is financed through a FAPESP-ERC grant. He will visit us for 4 months from May 12, 2018, to September 12, 2018.

He works mainly with optical tweezers studying optical forces with both experimental and theoretical tools.

He obtained his Ph.D. in physics in 2006, at the State University of Campinas (Brazil). From 2006 to 2012, he worked as a postdoctoral researcher at the National Nanotechnology Laboratories of the Nanoscience Institute in Lecce (Italy), within the Soft-matter division. Since 2012, he is a professor at the Federal University of ABC (Brazil), accredited in the graduate program of Nanoscience and Advanced Materials.

His main research interest is in the field of light-matter interaction, with a special focus on the applications of optical tweezers as well as linear and multi-photon spectroscopy as well. His current line of research is the study of bull sperm motility with optical tweezers, and starting the characterization of thermal properties of metallic nanoparticles in optical traps.

Seminar by G. Volpe at TU Dresden, 3 May 2018

Emergent Complex Behaviors in Active Matter
Giovanni Volpe
TU Dresden, Dresden, Germany
3 May 2018

After a brief introduction of active particles, I’ll present some recent advances on the study of active particles in complex and crowded environments.
First, I’ll show that active particles can work as microswimmers and microengines powered by critical fluctuations and controlled by light.
Then, I’ll discuss some examples of behavior of active particles in crowded environments: a few active particles alter the overall dynamics of a system; active particles create metastable clusters and channels; active matter leads to non-Boltzmann distributions and alternative non-equilibrium relations; and active colloidal molecules can be created and controlled by light.
Finally, I’ll present some examples of the behavior of active particles in complex environments: active particles often perform 2D active Brownian motion; active particles at liquid-liquid interfaces behave as active interstitials or as active atoms; and the environment alters the optimal search strategy for active particles in complex topologies.

Mite Mijalkov defended his PhD Thesis. Congrats!

Mite Mijalkov defended his PhD Thesis on 24 April 2018 in the Physics Department seminar room (SA240).

Assoc. Prof. Hande Toffoli (Middle-East Technical University), Prof. Tayfun Ozcelik (Bilkent University), Assoc. Prof. Alpan Bek (Middle-East Technical University), Assist. Prof. Seymur Cahangirov (Bilkent Unievrsity) and Assist. Prof. Giovanni Volpe (Bilkent University) will be the thesis committee members.

Thesis title: Graph Theory Study of Complex Networks in the Brain

Thesis abstract: The brain is a large-scale, intricate web of neurons, known as the connectome. By representing the brain as a network i.e. a set of nodes connected by edges, one can study its organization by using concepts from graph theory to evaluate various measures. We have developed BRAPH – BRain Analysis using graPHtheory, a MatLab, object-oriented freeware that facilitates the connectivity analysis of brain networks. BRAPH provides user-friendly interfaces that guide the user through the various steps of the connectivity analysis, such as, calculating adjacency matrices, evaluating global and local measures, performing group comparisons by non-parametric permutations and assessing the communities in a network. Furthermore, using graph theory, we showed that structural MRI undirected networks of stable MCI (sMCI) subjects, late MCI converters (lMCIc), early MCI converters (eMCIc), and AD patients show abnormal organization. This is indicated, at global level, by decreases in clustering and transitivity accompanied by increases in path length and modularity and, at nodal level, by changes in nodal clustering and closeness centrality in patient groups when compared to controls. In samples that do not exhibit differences in the undirected analysis, we propose the usage of directed networks to assess any topological changes due to a neurodegenerative disease. We demonstrate that such changes can be identified in Alzheimer’s and Parkinson’s patients by using directed networks built by delayed correlation coefficients. Finally, we put forward a method that improves the reconstruction of the brain connectome by utilizing the delays in the dynamic behavior of the neurons. We show that this delayed correlationmethod correctly identifies 70% to 80% of the real connections in simulated networks and performs well in the identification of their global and nodal properties.

Name of the PhD programme: Material Science and Nanotechnology Graduate Program
Thesis Advisor Giovanni Volpe, Department of Physics, Bilkent University

Place: Physics Department seminar room (SA240), Bilkent University
Time: 24 April, 2018, 11:00

Invited talk by G. Volpe at the 9th Nordic Workshop on Statistical Physics, Stockholm, 21-23 Mar 2018

Recent Progress on the Experimental Study of Active Matter
Giovanni Volpe
The 9th Nordic Workshop on Statistical Physics: Biological, Complex and Non-equilibrium Systems, NORDITA, Stockholm, Sweden
21-23 March 2018

Seminar on photophoretic forces by Ayan Banerjee from IISER-Kolkata, Nexus, 20 Mar 2018

Photophoretic forces: A new enabler for robust single fiber-based optical traps in air
Seminar by Ayan Banerjee from the Indian Institute of Science Education and Research (IISER), Kolkata, India

Abstract: Photophoretic forces, which are derived from the momentum exchange of absorbing particles with surrounding fluid molecules, are especially useful for trapping particles in air, where their very large magnitude (about five orders more than optically induced dipole forces) successfully balances gravity. Thus, particles levitate in the direction of gravity, while in the transverse direction, they are trapped by a restoring force emanating from the rotation of the particles around the trapping beam axis. Photophoretic forces thus enable the use of single optical fibers for stable three dimensional traps. In this talk, I shall describe our efforts to develop such single fiber based traps, where we find that a single mode fiber is not necessarily the most efficacious in terms of trapping. Robust trapping is achieved when the off-axis intensity of the trapping beam is high, so that rather unexpectedly, we observe that a single multi-mode fiber allows much stronger trapping in general, and especially in the radial direction compared to a single mode finer. We are able to trap particles at extremely low laser powers (around 5 mW) in air, and can manipulate printer toner particles of diameter less than 20 microns at translation velocities of 5 mm/s in our multi-mode fiber trap. Particles can be manipulated by merely changing the power in the trapping beam, which accentuates the power and promise of this technique as a possible candidate for single fiber-based hand held tweezers for confining and even spectroscopically analysing aerosols or pathogens present in the air.

Bio: Ayan Banerjee has been working in the field of optics and spectroscopy for the last 22 years. He obtained his Ph.D in physics from the Indian Institute of Science, Bangalore, following which he was a research scientist at General Electric Global Research, Bangalore, India. Since 2009, he has been an associate professor of physics at the Indian Institute of Science Education and Research (IISER), Kolkata. His research interests span a wide range of subjects in optics and spectroscopy. At IISER, he has set up an optical tweezers lab to study diverse problems in a truly interdisciplinary mode of research.

Place: Nexus, meeting room, Fysik Origo, Fysik
Time: 20 March, 2018, 14:00

Special Issue on Biophotonics published in Biomed. Opt. Express

Biophotonics feature: introduction
Paolo Campagnola, Daniel Cote, Francesco Pavone, Peter Reece, Vivek J. Srinivasan, Tomasz Tkaczyk & Giovanni Volpe
Biomedical Optics Express 9(3), 1229–1231 (2018)
DOI: 10.1364/BOE.9.001229

Rafal Piwowarczyk defended his Master Thesis. Congrats!

Rafal Piwowarczyk defended his Master thesis in Complex Adaptive Systems at Chalmers University of Technology on 19 February 2018

Title: Influence of Delay on the Vicsek Model

The aim of this work is to show that sensorial delay influences the behaviour of self-propelling agents using self-aligning interactions. The model was based on the Vicsek model, which is a two-dimensional system of self-propelling particles that are able to detect and align with each other within a certain radius. We prove that the introduction of short delays favours cluster and swarm formation, while extending the delay to higher values or implementation of negative delays significantly harms this process. We introduce a global clustering parameter, which is based on the use of the Voronoi tessellation, which allows us to measure the emergence of clusters. The sensorial delay might play a crucial role in systems that exhibit swarming behaviours and it’s better understanding can result in the construction of key tools for the realisation and manipulation of complex networks of autonomous robots.

Name of the master programme: MPCAS – Complex Adaptive Systems
Supervisor: Giovanni Volpe, Department of Physics, University of Gothenburg
Examiner: Giovanni Volpe, Department of Physics, University of Gothenburg
Opponent: Freddie Ogemark, MP Complex Adaptive Systems, Department of Physics, Chalmers University of Technology

Place: PJ, lecture hall, Fysik Origo, Fysik
Time: 19 February, 2018, 11:00

Seminar by G. Volpe at Chalmers University, Gothenburg, 15 Feb 2018

Active Matter in Complex and Crowded Environments
Giovanni Volpe
Statistics and Biomathematics Seminar
Chalmers University of Technology, Gothenburg, Sweden
15 February 2018

13:15 seminar room MV:L14, Chalmers tvärgata 3

https://www.chalmers.se/en/departments/math/research/seminar-series/statistics-and-biomathematics-seminar/Pages/default.aspx

Microscopic Critical Engine featured in Phys.Org

Microscopic engine powered by critical demixing

Our recent article Microscopic engine powered by critical remixing
by Falko Schmidt, Alessandro Magazzù, Agnese Callegari, Luca Biancofiore, Frank Cichos & Giovanni Volpe, published in Physical Review Letters 120(6), 068004 (2018) has been featured in “Tiny engine powered by demixing fluid” Phys.Org (February 12, 2018)

Microscopic Critical Engine featured in Optics & Photonics News

Our recent article Microscopic engine powered by critical remixing
by Falko Schmidt, Alessandro Magazzù, Agnese Callegari, Luca Biancofiore, Frank Cichos & Giovanni Volpe, published in Physical Review Letters 120(6), 068004 (2018) has been featured in “Laser + Critical Liquid = Micro-Engine”, Optics & Photonics News (February 12, 2018)

Optics & Photonics News (OPN) is The Optical Society’s monthly news magazine. It provides in-depth coverage of recent developments in the field of optics and offers busy professionals the tools they need to succeed in the optics industry, as well as informative pieces on a variety of topics such as science and society, education, technology and business. OPN strives to make the various facets of this diverse field accessible to researchers, engineers, businesspeople and students. Contributors include scientists and journalists who specialize in the field of optics.