Vivek Nagendra Prakash

Efforts to restore coral reefs using sexually derived coral recruits are often hindered by low survivorship and growth, hence scalable interventions to improve these parameters are urgently needed. We developed settlement substrates that modify the chemical and hydrodynamic environment to provide localized alkalinity enhancement (AE) within the laminar boundary layer. Cement tiles with four different chemistries and two different surface topographies were tested in a flume to quantify their ability to change local pH under reef-like conditions, and their resulting effect on larval settlement, survivorship, and growth of the endangered Caribbean coral,
Orbicella faveolata
. Chemistry had minimal effect on initial larval settlement, and textured tiles were preferred over smooth tiles. Substrates that increased pH in the local environment increased post-settlement survivorship, although they did not affect larval growth. Our results indicate that incorporating carbonate additives into cement used for artificial reef structures could effectively enhance the development of coral cover.
Alkalinity enhancement through tile-based local pH modulation can improve early coral recruit survivorship, as shown in laboratory-fabricated artificial reef structures made by mixing sodium bicarbonate or sodium carbonate into cement

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As research becomes more interdisciplinary, researchers develop new methodologies and technologies for novel experiments that bridge fields. FlumeX’s design features a standard experimental chamber that can be expanded into different configurations, allowing for cross-disciplinary experiments between the fields of fluid dynamics, chemical oceanography, and biology. An open-ended, flow-through configuration is ideal for simulating environments where water is constantly flushed, capable of simulating oceanic environments. A fully enclosed, recirculating configuration is ideal for particle image velocimetry experiments, standard for fluid dynamics. FlumeX is designed to allow for husbandry of sessile organisms, including corals, in tandem with chemical and physical measurements. FlumeX allows for flexibility in experimental design and comparable environments between recirculating and flow-through configurations. It is designed with low-cost, readily available materials, making it easy to build and produce en masse for replicate testing.

Per-and polyfluorinated substances (PFAS) are synthetic compounds used in the production of fluoropolymer coatings found in products such as non-stick pans, clothing, cosmetics, and food packaging. These highly persistent molecules are known as “forever chemicals” since they neither degrade environmentally nor break down enzymatically within biological systems. PFAS compounds readily contaminate water sources, and as a result, certain PFAS molecules have bioaccumulated in exposed species including humans. The purpose of this study was to define the effect of two PFAS molecules, the ostensibly more toxic perfluorooctanoic acid (PFOA) and the more recent, reportedly safer chemical hexafluoropropylene oxide dimer acid (Gen X), on the development of Lytechinus variegatus sea urchin embryos. We examined the effects of PFOA and Gen X on development and patterning using morphological analysis, immunostaining, HCR-FISH, and Particle Image Velocimetry (PIV). The results show that both PFAS compounds are teratogenic to sea urchin embryos. PFOA and Gen X each function at different intervals during development and provoke distinct phenotypic and gene expression outcomes. Despite beliefs that Gen X would be a safer alternative, our findings indicate that Gen X has earlier and more severe effects on endomesoderm and dorsal-ventral axis specification, neural development and function, and pattern formation compared to PFOA. These results illustrate the dangerous teratogenic potential of environmentally accumulating PFAS like Gen X, underscoring the negative ecological implications that accompany continuing commercial and industrial use of PFAS in the absence of remediation strategies. [Display omitted] •Gen X is more teratogenic to sea urchins than PFOA.•Gen X acts earlier than PFOA and perturbs axial and germ layer specification.•Both Gen X and PFOA reduce neural numbers and perturb ciliary behavior and swimming.

A bilateral body plan is predominant throughout the animal kingdom. Bilaterality of amniote embryos becomes recognizable as midline morphogenesis begins at gastrulation, bisecting an embryonic field into the left and right sides, and left-right (LR) asymmetry patterning follows. While a series of laterality genes expressed after the LR compartmentalization has been extensively studied, the laterality patterning prior to and at the initiation of midline morphogenesis has remained unclear. Here, through a biophysical quantification in a high spatial and temporal resolution, applied to a chick model system, we show that a large-scale bilateral counterrotating cellular flow, termed "polonaise movements", display LR asymmetries in early gastrulation. This cell movement starts prior to the formation of the primitive streak (PS) (the earliest midline structure) and the subsequent appearance of Hensen's node (the LR organizer). The cellular flow speed and vorticity unravel the location and timing of the LR asymmetries. The bilateral flows displayed a Right dominance after 6 h since the start of cell movements. Mitotic arrest that diminishes PS formation resulted in changes in the bilateral flow pattern, but the Right dominance persisted. Our data indicate that the LR asymmetry in amniote gastrula becomes detectable earlier than suggested by current models, which assume that the asymmetric regulation of the laterality signals at the node leads to the LR patterning. More broadly, our results suggest that physical processes can play an unexpected but significant role in influencing LR laterality during embryonic development.

Innovations in fluid mechanics have been leading to better food since ancient history, while creativity in cooking has inspired fundamental breakthroughs in science. This review addresses how recent advances in hydrodynamics are changing food science and the culinary arts and, reciprocally, how the surprising phenomena that arise in the kitchen are leading to new discoveries across the disciplines, including molecular gastronomy, rheology, soft matter, biophysics, medicine, and nanotechnology. This review is structured like a menu, where each course highlights different aspects of culinary fluid mechanics. Our main themes include multiphase flows, complex fluids, thermal convection, hydrodynamic instabilities, viscous flows, granular matter, porous media, percolation, chaotic advection, interfacial phenomena, and turbulence. For every topic, an introduction and its connections to food are provided, followed by a discussion of how science could be made more accessible and inclusive. The state-of-the-art knowledge is then assessed, the open problems, along with the likely directions for future research and indeed future dishes. New ideas in science and gastronomy are growing rapidly side by side.

Characterizing the epithelial tissue of a shape-shifting marine animal as an integrated composite material reveals a ductile-to-brittle phase transition that captures how the tissue responds to failure. Epithelial tissues provide an important barrier function in animals, but these tissues are subjected to extreme strains during day-to-day activities such as feeding and locomotion. Understanding tissue mechanics and the adaptive response in dynamic force landscapes remains an important area of research. Here we carry out a multi-modal study of a simple yet highly dynamic organism, Trichoplax adhaerens, and report the discovery of abrupt, bulk epithelial tissue fractures induced by the organism's own motility. Coupled with rapid healing, this discovery accounts for dramatic shape change and physiological asexual division in this early-divergent metazoan. We generalize our understanding of this phenomenon by codifying it in a heuristic model focusing on the debonding-bonding criterion in a soft, active living material. Using a suite of quantitative experimental and numerical techniques, we demonstrate a force-driven ductile-to-brittle material transition governing the morphodynamics of tissues pushed to the edge of rupture.

We present a simple, intuitive algorithm for visualizing time-varying flow fields that can reveal complex flow structures with minimal user intervention. We apply this technique to a variety of biological systems, including the swimming currents of invertebrates and the collective motion of swarms of insects. We compare our results with more experimentally difficult and mathematically sophisticated techniques for identifying patterns in fluid flows, and suggest that our tool represents an essential 'middle ground' allowing experimentalists to easily determine whether a system exhibits interesting flow patterns and coherent structures without resorting to more intensive techniques. In addition to being informative, the visualizations generated by our tool are often striking and elegant, illustrating coherent structures directly from videos without the need for computational overlays. Our tool is available as fully documented open-source code for MATLAB, Python or ImageJ at www.flowtrace.org.

Many marine invertebrates have larval stages covered in linear arrays of beating cilia, which propel the animal while simultaneously entraining planktonic prey(1). These bands are strongly conserved across taxa spanning four major superphyla(2,3), and they are responsible for the unusual morphologies of many invertebrate larvae(4,5). However, few studies have investigated their underlying hydrodynamics(6,7). Here, we study the ciliary bands of starfish larvae, and discover a beautiful pattern of slowly evolving vortices that surrounds the swimming animals. Closer inspection of the bands reveals unusual ciliary 'tangles' analogous to topological defects that break up and re-form as the animal adjusts its swimming stroke. Quantitative experiments and modelling demonstrate that these vortices create a physical trade-off between feeding and swimming in heterogeneous environments, which manifests as distinct flow patterns or 'eigenstrokes' representing each behaviour-potentially implicating neuronal control of cilia. This quantitative interplay between larval form and hydrodynamic function may generalize to other invertebrates with ciliary bands, and illustrates the potential effects of active boundary conditions in other biological and synthetic systems.