Flanched-Cross: An Efficient Cell Geometry for Beam Steering Metasurfaces with Orthogonal Polarisation Handling Capability

Geometry plays an important part in the characteristics of meta-cells used to design beam steering metasurfaces. One of the most desirable aspects of these cells is a large phase shift range that can be achieved with good transmission amplitude. However, the existing and most commonly used geometries for these cells are not able to produce a complete 360° phase range with an acceptable level of transmission amplitude. In this article, we present a new cell geometry, Flanched-Cross, that has superior transmission properties due to its unique shape and parametric variability than the commonly used geometries. The results are verified in simulation and further confirmed through prototyping and measurement. One- and two-dimensional steering are also performed for a dual-polarised base array to confirm the applicability of Flanched-Cross cell for beam steering purposes.

Flanched-Cross: An Efficient Cell Geometry for Beam Steering Metasurfaces with Orthogonal Polarisation Handling Capability

Geometry plays an important part in the characteristics of meta-cells used to design beam steering metasurfaces. One of the most desirable aspects of these cells is a large phase shift range that can be achieved with good transmission amplitude. However, the existing and most commonly used geometries for these cells are not able to produce a complete 360° phase range with an acceptable level of transmission amplitude. In this article, we present a new cell geometry, Flanched-Cross, that has superior transmission properties due to its unique shape and parametric variability than the commonly used geometries. The results are verified in simulation and further confirmed through prototyping and measurement. One- and two-dimensional steering are also performed for a dual-polarised base array to confirm the applicability of Flanched-Cross cell for beam steering purposes.

Cell geometry distinguishes migration-associated heterogeneity in two-dimensional systems

Background: In vitro migration assays are a cornerstone of cell biology and have found extensive utility in research. Over the past decade, several variations of the two-dimensional (2D) migration assay have improved our understanding of this fundamental process. However, the ability of these approaches to capture the functional heterogeneity during migration and their accessibility to inexperienced users has been limited. Methods: We downloaded published time-lapse 2D cell migration datasets and subjected them to feature extraction with the Fiji software. We used the 'Analyze Particles' tool to extract ten cell geometry features (CGFs), which were grouped into 'shape, 'size and 'position' descriptors. Next, we defined the migratory status of cells using the 'MTrack2' plugin. All data obtained from Fiji were further subjected to rigorous statistical analysis with R version 4.0.2. Results: We observed consistent associative trends between size and shape descriptors and validated the robustness of our observations across four independent datasets. We used these descriptors to resolve the functional heterogeneity during migration by identifying and characterizing 'non-migrators (NM)' and 'migrators (M)'. Statistical analysis allowed us to identify considerable heterogeneity in the NM subset, that has not been previously reported. Interestingly, differences in 2D-packing appeared to affect CGF trends and heterogeneity of the migratory subsets for the datasets under investigation. Conclusion: We developed an analytical pipeline using open source tools, to identify and morphologically characterize functional migratory subsets from label-free, time-lapse migration data. Our quantitative approach identified a previously unappreciated heterogeneity of non-migratory cells and predicted the influence of 2D-packing on migration.

Combined effect of cell geometry and polarity domains determines the orientation of unequal division

Cell division orientation is thought to result from a competition between cell geometry and polarity domains controlling the position of the mitotic spindle during mitosis. Depending on the level of cell shape anisotropy or the strength of the polarity domain, one dominates the other and determines the orientation of the spindle. Whether and how such competition is also at work to determine unequal cell division (UCD), producing daughter cells of different size, remains unclear. Here, we show that cell geometry and polarity domains cooperate, rather than compete, in positioning the cleavage plane during UCDs in early ascidian embryos. We found that the UCDs and their orientation at the ascidian third cleavage rely on the spindle tilting in an anisotropic cell shape, and cortical polarity domains exerting different effects on spindle astral microtubules. By systematically varying mitotic cell shape, we could modulate the effect of attractive and repulsive polarity domains and consequently generate predicted daughter cell size asymmetries and position. We therefore propose that the spindle position during UCD is set by the combined activities of cell geometry and polarity domains, where cell geometry modulates the effect of cortical polarity domain(s).

Derivation of continuum models from discrete models of mechanical forces in cell populations

In certain discrete models of populations of biological cells, the mechanical forces between the cells are center based or vertex based on the microscopic level where each cell is individually represented. The cells are circular or spherical in a center based model and polygonal or polyhedral in a vertex based model. On a higher, macroscopic level, the time evolution of the density of the cells is described by partial differential equations (PDEs). We derive relations between the modelling on the micro and macro levels in one, two, and three dimensions by regarding the micro model as a discretization of a PDE for conservation of mass on the macro level. The forces in the micro model correspond on the macro level to a gradient of the pressure scaled by quantities depending on the cell geometry. The two levels of modelling are compared in numerical experiments in one and two dimensions.

Numerical simulation of the formation of dry spots during film evaporation

This paper presents a developed methodology for calculating heat and mass transfer processes in a cylindrical evaporation cell. The mathematical model reproduces all significant features of the evaporation cell geometry. In this cell, a layer of liquid is formed on a substrate with a diameter of 51 mm, heated below. To simulate heat transfer during film evaporation on a heated substrate, a numerical technique based on the Volume of Fluid method was used. The developed model was used to study the process of dry spot formation during film evaporation. The calculated data are compared with the experiment on the profile of the free surface of the film during evaporation and rupture. In general, results of this testing demonstrated good agreement with experiment. As a result, it was shown that developed numerical method makes it possible to describe process of formation dry spots.

Effective in-plane elastic properties of honeycomb-polymer composites

Honeycomb composites are now common materials in applications where high specific stiffness is required. Previous research has found that honeycombs with polymer infills in their cells, here referred to as honeycomb-polymer composites (HPCs), exhibit effective stiffnesses greater than the honeycomb or polymer alone. Currently, the state of analytic models for predicting the elastic properties of these composites is limited, and further research is needed to better characterize the behavior of these materials. In this research, a nonlinear finite element analysis was employed to perfor2m parametric studies of a filled honeycomb unit cell with isotropic wall and infill materials. A rigid wall model was created as an upper bound on the deformable wall model’s performance, and an empty honeycomb model was employed to better understand the mechanisms of stiffness amplification. Parametric studies were completed for infill material properties and cell geometry, with the effective Young’s modulus studied in two in-plane material directions. The mechanisms by which the stiffness amplification occurs are studied, and comparisons to existing analytic models are made. It has been observed that both the volume change within the honeycomb cell under deformation and the mismatch in Poisson’s ratios between the honeycomb and infill influence the effective properties. Stiffness amplifications of over 4000 have been observed, with auxetic behavior achieved by tailoring of the HPC geometry. Additionally, the effect of large effective strains up to 10% is explored, where the cell geometry changes significantly. This research provides an important step toward understanding the design space and benefits of HPCs.

The root meristem is shaped by brassinosteroid control of cell geometry

Growth extent and direction determine cell and whole-organ architecture. How they are spatio-temporally modulated to control size and shape is not well known. Here we tackled this question by studying the effect of brassinosteroid (BR) signalling on the structure of the root meristem. Quantification of the three-dimensional geometry of thousands of individual meristematic cells across different tissue types showed that the modulation of BR signalling yields distinct changes in growth rate and anisotropy, which affects the time that cells spend in the meristem and has a strong impact on the final root form. By contrast, the hormone effect on cell volume was minor, establishing cell volume as invariant to the effect of BR. Thus, BR has the highest effect on cell shape and growth anisotropy, regulating the overall longitudinal and radial growth of the meristem, while maintaining a coherent distribution of cell sizes. Moving from single-cell quantification to the whole organ, we developed a computational model of radial growth. The simulation demonstrates how differential BR-regulated growth between the inner and outer tissues shapes the meristem and thus explains the non-intuitive outcomes of tissue-specific perturbation of BR signalling. The combined experimental data and simulation suggest that the inner and outer tissues have distinct but coordinated roles in growth regulation.