VSR-Seminar

Im VSR-Seminar tragen zwei FZJ-Mitarbeitende über die Themen ihrer Rechenzeitprojekte vor.

Conferencing tool Zoom: https://us02web.zoom.us/j/89135335324?pwd=SFRIOUgrS0ZlRkQwZ3pMNWd1OFhtUT09
Meeting ID: 891 3533 5324
Passcode: pRS5B9

Vortrag 1: Relevance of hydrodynamic interactions in the collective properties thermophoretic microswimmers

Referentin: Dr. Marisol Ripoll, Institute of Biological Information Processing, Theoretical Physics of Living Matter (IBI-5/IAS-2), Forschungszentrum Jülich, Germany

Active matter, or systems made of autonomously moving units, are ubiquitous in nature (birds, algae, bacteria) and display a myriad of different collective behaviors. The design of active synthetic materials is a current scientific challenge with a larger number of potential applications in systems such as microfluidic lab-on-a-chip, drug delivery, or even microsurgery. Phoresis is a physical mechanism which has recently arisen as an avenue for the construction of such active materials. Thermophoresis in particular refers to the directed motion of colloidal particles in the presence of a solvent with a temperature gradient, which can occur towards cold (thermophobicity) or to the warm areas (thermophilicity). Self-propelled motion can be induced for particles where an asymmetric heating is possible, such as laser heated particles with partial metal coating (Janus or multimeric colloids). The collective properties of these microswimmers is strongly influenced by their surface properties, size, and shape, which deteremine not only the propulsion speed but also the interswimmer phoretic and hydrodynamic interactions, both fluid mediated. We employ a hydrodynamic fluctuating mesoscale simulation approach to study both single and collective swimming, where both solvent and colloidal particles need to be explicitly considered. Furthermore, we develop an effective Brownian model in which most of these interactions are accounted for, in order to determine in which cases the detailed hydrodynamic interactions are of relevance. Examples of the investigated collective behaviour are clustering, swarming, or rotational motions.

Vortrag 2: Optimizing Current Imaging Pipelines by Whole-Brain Dynamical Models

Referent: Dr. Oleksandr Popovych, Institute of Neuroscience and Medicine, Brain and Behavior (INM-7), Forschungszentrum Jülich, Germany

Investigation of the resting-state brain dynamics involves mathematical modeling of brain activity by whole-brain dynamical models. The structural and functional brain connectomes extracted from the neuroimaging data are essentially employed for the model derivation and validation. At this the brain is represented as a functional network of brain regions defined by a brain atlas (or brain parcellation), while edges represent the structural or functional connectivity among them. There is however no consensus and golden standard for the approaches and parameters of the neuroimaging data processing, which in most cases remain at the level of best practice. In this project we investigate how such parameters of the data processing can influence the modeling results. In particular, we considered several brain parcellations and densities of the whole-brain tractography to evaluate the inter-subject and inter-parcellation variability of the model fitting and its dependence on a few indices calculated from empirical data. Such data indices can be used to accounting for the variation of the modeling results across simulation conditions and individual subjects, which can help to find optimal data processing and mechanisms for improved personalized modeling of the resting-state brain dynamics.