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1. Dynamics of inertial particles on the ocean surface with unrestricted reserve buoyancy

   https://doi.org/10.1063/5.0226779  

   Beron-Vera, F J (October 2024, Physics of Fluids)

   The purpose of this note is to present an enhancement to a Maxey–Riley theory proposed in recent years for the dynamics of inertial particles on the ocean surface [Beron-Vera et al., “Building a Maxey–Riley framework for surface ocean inertial particle dynamics,” Phys. Fluids 31, 096602 (2019)]. This updated model removes constraints on the reserve buoyancy, defined as the fraction of the particle volume above the ocean surface. The refinement results in an equation that correctly describes both the neutrally buoyant and fully buoyant particle scenarios. 

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2. Photothermal Mirror Z-Scan

   Marcano, A. (May 2019, Conference on Lasers and Electro-Optics, OSA Technical Digest)

   This work describes a pump-probe photothermal mirror Z-scan experiment aimed at the determination of thermal diffusivity, thermoelastic coefficient, and quantum yield of thermal heating of the surface of transparent and non- transparent solid samples including films. 

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3. Deep Learning Based Prediction of Perovskite Lattice Parameters from Hirshfeld Surface Fingerprints

   https://doi.org/10.1021/acs.jpclett.0c02201  

   Williams, Logan; Mukherjee, Arpan; Rajan, Krishna (August 2020, The Journal of Physical Chemistry Letters)

   This Letter describes the use of deep learning methods on Hirshfeld surface representations of crystal structure, as an automated means of predicting lattice parameters in cubic inorganic perovskites. While Hirshfeld Surface Analysis is a well-established tool in organic crystallography, we also introduce modified computational protocols for Hirshfeld Surface Analysis tailored specifically to account for nuanced but important differences dealing with inorganic crystals. We demonstrate how two-dimensional Hirshfeld surface fingerprints can serve as a rich “database” of information encoding the complexity of relationships between chemical bonding and bond geometry characteristics of perovskites. Our results are compared with other studies on lattice parameter prediction involving both experimental and computationally derived data, and it is shown that our approach is an improvement over other reported methods. The paper concludes by discussing how this work opens new avenues for data-driven high throughput computational predictions of structure–property relationships involving complex crystal chemistries. 

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4. Transit Time Theory for a Droplet Passing through a Slit in Pressure-Driven Low Reynolds Number Flows

   https://doi.org/10.3390/mi14112040  

   Borbas, Spencer W.; Shen, Kevin; Ji, Catherine; Viallat, Annie; Helfer, Emmanuèle; Peng, Zhangli (November 2023, Micromachines)

   Soft objects squeezing through small apertures are crucial for many in vivo and in vitro processes. Red blood cell transit time through splenic inter-endothelial slits (IESs) plays a crucial role in blood filtration and disease progression, while droplet velocity through constrictions in microfluidic devices is important for effective manipulation and separation processes. As these transit phenomena are not well understood, we sought to establish analytical and numerical solutions of viscous droplet transit through a rectangular slit. This study extends from our former theory of a circular pore because a rectangular slit is more realistic in many physiological and engineering applications. Here, we derived the ordinary differential equations (ODEs) of a droplet passing through a slit by combining planar Poiseuille flow, the Young–Laplace equations, and modifying them to consider the lubrication layer between the droplet and the slit wall. Compared to the pore case, we used the Roscoe solution instead of the Sampson one to account for the flow entering and exiting a rectangular slit. When the surface tension and lubrication layer were negligible, we derived the closed-form solutions of transit time. When the surface tension and lubrication layer were finite, the ODEs were solved numerically to study the impact of various parameters on the transit time. With our solutions, we identified the impact of prescribed pressure drop, slit dimensions, and droplet parameters such as surface tension, viscosity, and volume on transit time. In addition, we also considered the effect of pressure drop and surface tension near critical values. For this study, critical surface tension for a given pressure drop describes the threshold droplet surface tension that prevents transit, and critical pressure for a given surface tension describes the threshold pressure drop that prevents transit. Our solutions demonstrate that there is a linear relationship between pressure and the reciprocal of the transit time (referred to as inverse transit time), as well as a linear relationship between viscosity and transit time. Additionally, when the droplet size increases with respect to the slit dimensions, there is a corresponding increase in transit time. Most notably, we emphasize the initial antagonistic effect of surface tension which resists droplet passage but at the same time decreases the lubrication layer, thus facilitating passage. Our results provide quantitative calculations for understanding cells passing through slit-like constrictions and designing droplet microfluidic experiments. 

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5. The role of non-affine deformations in the elastic behavior of the cellular vertex model

   https://doi.org/10.1039/D2SM01580C  

   Staddon, Michael F.; Hernandez, Arthur; Bowick, Mark J.; Moshe, Michael; Marchetti, M. Cristina (May 2023, Soft Matter)

   The vertex model of epithelia describes the apical surface of a tissue as a tiling of elastic polygonal cells. We show how non-affine deformations allow the tissue to have a softer mechanical response under strain, such as a vanishing shear modulus. 

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