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Machine Learning for 3D Particle Tracking in Granular Gases (2020)

Puzyrev, Dmitry ; Harth, Kirsten ; Trittel, Torsten ; [weitere]

Springer

In: Microgravity Science and Technology. 2020; 32(5): 897-906. Published 2020 Jul 18. doi: 10.1007/s12217-020-09800-4.

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Publikationsdatum: 2020-07-18

Beschreibung: Dilute ensembles of granular matter (so-called granular gases) are nonlinear systems which exhibit fascinating dynamical behavior far from equilibrium, including non-Gaussian distributions of velocities and rotational velocities, clustering, and violation of energy equipartition. In order to understand their dynamic properties, microgravity experiments were performed in suborbital flights and drop tower experiments. Up to now, the experimental images were evaluated mostly manually. Here, we introduce an approach for automatic 3D tracking of positions and orientations of rod-like particles in a dilute ensemble, based on two-view video data analysis. A two-dimensional (2D) localization of particles is performed using a Mask R-CNN neural network trained on a custom data set. The problem of 3D matching of the particles is solved by minimization of the total reprojection error, and finally, particle trajectories are tracked so that ensemble statistics are extracted. Depending on the required accuracy, the software can work fully self-sustainingly or serve as a base for subsequent manual corrections. The approach can be extended to other 3D and 2D particle tracking problems.

Print ISSN: 0938-0108

Digitale ISSN: 1875-0494

Thema: Maschinenbau , Allgemeine Naturwissenschaft , Technik allgemein

Publiziert von Springer

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Microtubules and Vimentin Fiber Stability during Parabolic Flights (2020)

Wuest, Simon L. ; Arnold, Jaro ; Gander, Sarah ; [weitere]

Springer

In: Microgravity Science and Technology. 2020; 32(5): 921-933. Published 2020 Jul 19. doi: 10.1007/s12217-020-09818-8.

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Publikationsdatum: 2020-07-19

Beschreibung: Adequate mechanical stimulation is essential for cellular health and tissue maintenance, including articular cartilage, which lines the articulating bones in joints. Chondrocytes, which are the sole cells found in articular cartilage, are responsible for matrix synthesis, maintenance and degradation. It is generally believed that chondrocytes require mechanical stimuli through daily physical activity for adequate cartilage homeostasis. However, to date, the molecular mechanisms of cellular force sensing (mechanotransduction) are not fully understood. Among other mechanisms, the cytoskeleton is thought to play a key role. Despite that gravity is a very small force at the cellular level, cytoskeletal adaptations have been observed under altered gravity conditions of a parabolic flight in multiple cell types. In this study, we developed a novel hardware which allowed to chemically fix primary bovine chondrocytes at 7 time points over the course of a 31-parabola flight. The samples were subsequently stained for the microtubules and vimentin network and microscopic images were acquired. The images showed a large heterogeneity among the cells in morphology as well as in the structure of both networks. In all, no changes or adaptions in cytoskeleton structure could be detected over the course of the parabolic flight.

Print ISSN: 0938-0108

Digitale ISSN: 1875-0494

Thema: Maschinenbau , Allgemeine Naturwissenschaft , Technik allgemein