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Abstract: X-ray imaging of wet foam dynamics with a high temporal resolution (e.g., 3D videos with a 10 Hz frame rate) requires fast rotation of either the foam sample or the X-ray gantry. This, however, strongly limits the number of X-ray projections per rotation that can be acquired. As a result, conventional computed tomography reconstruction methods generate 3D images with severe undersampling artefacts, complicating subsequent foam analysis. Herein, BubSub, a novel tomographic reconstruction approach that reconstructs a 4D (3D plus time) dynamic image of wet foam bubbles from sparse-view X-ray projections by leveraging prior knowledge about the evolving foam structure, is introduced. BubSub adapts a collection of subdivision surfaces with spherical topology to represent liquid–gas interfaces of foam bubbles. Estimation of bubble positions and shapes at each time point is achieved by minimizing the projection distance in relation to the measured projections. BubSub operates efficiently with minimal memory usage, exhibits robustness against noise, and provides accurate reconstructions, even when the available projections are limited, as evidenced by various experiments using both simulated and real wet foam X-ray data.
Keywords: redki pogledi, dinamika pene, rentgenska mikrotomografija, tomografska rekonstrukcija, sparse views, foam dynamics, X-ray microtomography, tomographic reconstruction
Published in DiRROS: 16.12.2024; Views: 73; Downloads: 39
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Abstract: To develop new criteria to distinguish different crystal nucleation mechanisms in silicate melts, we performed crystallization experiments using a synthetic hydrous (2 wt% H2O) trachybasalt and combined three-dimensional information from synchrotron X-ray computed microtomography with two-dimensional mapping of crystallographic orientation relationships (CORs) using electron backscatter diffraction. Crystallization experiments were performed at 400 MPa by cooling the melt from 1300 °C to resting temperatures of 1150 and 1100 °C and maintaining isothermal conditions for 30 min and 8 h. Three distinct titanomagnetite (Tmt) populations formed: (1) skeletal crystals, isolated or partially embedded in clinopyroxene (Cpx); (2) anhedral crystals, always attached to Cpx; (3) flattened needle-shaped crystals, embedded in Cpx. These morphologically different Tmt populations formed in response to one cooling event, with varying nucleation mechanisms and at different undercooling conditions. The clustered three-dimensional distribution of population 2 and 3 Tmt grains and the high proportion of Tmt-Cpx interfaces sharing CORs indicate that these Tmt grains heterogeneously nucleated on Cpx. The near-random three-dimensional distribution of (often isolated) population 1 Tmt grains, together with the low proportion of Tmt-Cpx interfaces sharing CORs, imply their isolated, possibly homogeneous nucleation, potentially followed by heterogeneous nucleation of Cpx on population 1 Tmt. Heterogeneous nucleation in slightly to moderately undercooled magmas should affect the sequence of crystallization as well as morphology and clustering of crystals, which may actively contribute to the variation of rheological parameters like viscosity. Finally, observed intra- and inter-sample variations in Tmt-Cpx COR frequencies indicate the potential for this parameter to record further petrological information.
Keywords: experimental petrology, nucleation mechanisms, X-ray microtomography, crystal clustering, heterogeneous nucleation
Published in DiRROS: 16.12.2024; Views: 74; Downloads: 60
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Published in DiRROS: 16.12.2024; Views: 78; Downloads: 37
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Abstract: This work extends our research on the strong-form meshless Radial Basis Function - Finite Difference (RBF-FD) method for solving non-linear visco-plastic mechanical problems. The polyharmonic splines with second-order polynomial augmentation are used for the shape functions. Their coefficients are determined by collocation. Three different approaches (direct, composed, and hybrid) are used for the numerical evaluation of the divergence operator in the equilibrium equation. They are presented and assessed for a visco-plastic material model with continuously differentiable material properties. It is shown that the direct approach is not suitable in this respect. In comparison to the previously investigated elasto-plasticity, it is shown that the composed approach can successfully cope with visco-plastic problems and is found to be even more accurate than the hybrid approach, which has previously proven to be most stable and effective in solving elasto-plasticity. This work extends the applicability of strong-form RBF-FD methods and opens up new areas of modelling non-linear solid mechanics.
Keywords: visco-plastic material responses, hybrid radial basis, generated finite differences, polyharmonic splines
Published in DiRROS: 16.12.2024; Views: 68; Downloads: 38
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Abstract: Cell-free DNA (cfDNA) has recently emerged as a promising minimally invasive diagnostic biomarker for various cancers. In this study, our aim was to identify cfDNA biomarkers by investigating genes that displayed significant differences between glioma patients and their corresponding controls. To accomplish this, we utilized publicly available data from the Gene Expression Omnibus, focusing on 5-hydroxymethylcytosine (5hmC) profiles in both cfDNA and genomic DNA (gDNA) from glioma patients and healthy individuals. The intersection of gene lists derived from these comparative analyses unveiled LRIG1 and ZNF703 as the two genes with elevated 5hmC levels in both the cfDNA of glioma patients and gDNA of glioma tissue compared to their respective controls. The gene expression data revealed both genes were upregulated in glioma tissue compared to normal brain tissue. Integration of 5hmC data revealed a strong positive correlation in the glioma tissue group between 5hmC and the gene expression of the LRIG1 gene. Furthermore, exploration using the AmiCa web tool indicated that LRIG1 gene expression was elevated compared to 17 other cancers included in the database, emphasizing its potential as a distinctive biomarker across multiple cancer types.
Keywords: cell-free DNA, glioma, 5-hydroxymethylcytosine, biomarkers
Published in DiRROS: 13.12.2024; Views: 98; Downloads: 39
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