Bavand Keshavarz

Stemflow hydrodynamics offers rich physics that seeks to describe water and matter cycling within the atmosphere-biosphere-geosphere with implications for water resources planning.

Abstract Stemflow hydrodynamics is the study of water movement along the exterior surface area of plants. Its primary goal is to describe water velocity and water depth along the stem surface area. Its significance in enriching the rhizosphere with water and nutrients is not in dispute. Yet, the hydrodynamics of stemflow have been entirely overlooked. This review seeks to fill this knowledge gap by drawing from thin film theories to seek outcomes at the tree scale. The depth‐averaged conservation equations of water and solute mass are derived at a point. These equations are then supplemented with the conservation of momentum that is required to describe water velocities or relations between water velocities and water depth. Relevant forces pertinent to momentum conservation are covered and include body forces (gravitational effects), surface forces (wall friction), line forces (surface tension), and inertial effects. The inclusion of surface tension opens new vistas into the richness and complexity of stemflow hydrodynamics. Flow instabilities such as fingering, pinching of water columns into droplets, accumulation of water within fissures due to surface tension and their sudden release are prime examples that link observed spatial patterns of stemflow fronts and morphological characteristics of the bark. Aggregating these effects at the tree‐ and storm‐ scales are featured using published experiments. The review discusses outstanding challenges pertaining to stemflow hydrodynamics, the use of dynamic similarity and 3D printing to enable the interplay between field studies and controlled laboratory experiments.

Abstract Vertebral body compression fractures are a major cause of chronic back pain, particularly in older adults. Augmentation is currently performed by injecting a poly(methyl methacrylate) (PMMA) slurry of polymer, monomer, and initiator mixed with barium sulfate (BaSO 4 ) into the vertebrae, which then polymerizes in vivo. Herein, a solvent‐free polymer system using poly(allyl glycidyl ether succinate) (PAGES) is developed for vertebral augmentation. PAGES crosslinks in situ through thiol‐ene click chemistry with a cure time at 37 °C ranging from 17 to 53 min based on degree of polymerization and crosslinker concentration. The addition of SrCO 3 increased the ultimate compressive strength (σ max ) of the PAGES composite to 4.4 ± 0.4 MPa. Furthermore, SrCO 3 increases osteoblast proliferation and differentiation of mesenchymal stem cells seeded onto the surface of PAGES composite. Finally, the compressive strength of fractured vertebrae is increased in an ex vivo surrogate rabbit model when filled with injected PAGES composite, demonstrating its potential as a bone augmentation material.

Aluminosilicate hydrogels are often considered to be precursors for the crystallisation of zeolites carried out under hydrothermal conditions. The preparation of mechanically homogeneous aluminosilicate gels enables the study of these materials through bulk rheology and observation of the aging dynamics until the precipitation of crystalline zeolites. The first part of this study deals with the establishment of ternary state diagrams, in order to identify the range of chemical formulations that enable preparation of single-phase homogeneous gels. Then, by studying the viscoelastic moduli during the gelation reaction, and by yielding the gel under large deformation, we propose an empirical law considering the partial order of reaction on each chemical element, to predict the gelation time according to the chemical formulation. The scaling behavior of the elastic properties of this colloidal gel shows a transition from a strong link behavior to a weak link regime. Long term aging results in the shrinkage of the gel, accompanied by syneresis of interstitial liquid at the surface. Zeolites precipitate through crystallisation by a particle attachment mechanism, when thermodynamic equilibrium is reached. The stoichiometry of the precipitated zeolites is not only consistent with the concentration of the remaining species in the supernatant but, surprisingly, it is also very close to the partial order of the reaction of the chemical elements involved in the determination of the critical gel point. This indicates a strong correlation between the morphology of the soft amorphous gel network that is formed at an early age and those of the final solid precipitated crystals.

This paper is associated with a video winner of a 2022 APS/DFD Gallery of Fluid Motion Award for work presented at the DFD Gallery of Fluid Motion. The original video is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2022.GFM.V0115

This dataset contains data for the manuscript "The hidden hierarchical nature of soft particulate gels".

This dataset contains data for the manuscript "The hidden hierarchical nature of soft particulate gels".