Chemobrionics: From Self-Assembled Material Architectures to the Origin of Life.

Self-organizing precipitation processes, such as chemical gardens forming biomimetic micro- and nanotubular forms, have the potential to show us new fundamental science to explore, quantify, and understand nonequilibrium physicochemical systems, and shed light on the conditions for life's emergence. The physics and chemistry of these phenomena, due to the assembly of material architectures under a flux of ions, and their exploitation in applications, have recently been termed chemobrionics. Advances in understanding in this area require a combination of expertise in physics, chemistry, mathematical modeling, biology, and nanoengineering, as well as in complex systems and nonlinear and materials sciences, giving rise to this new synergistic discipline of chemobrionics.

Influence of microscopic precipitate structures on macroscopic pattern formation in reactive flows in a confined geometry.

Thanks to the coupling between chemical precipitation reactions and hydrodynamics, new dynamic phenomena may be obtained and new types of materials can be synthesized. Here we experimentally investigate how the characteristic microscopic crystal properties affect the macroscopic pattern obtained. To shed light on such interactions, different reactant solutions are radially injected into a calcium chloride solution at different volumetric flow rates in a confined geometry. Depending on the reactants used and the flow conditions, deformed precipitate membranes have been observed due to reaction-driven viscous fingering. In such cases we show that upon injection a large number of small particles is produced in situ by the reaction at the miscible interface between the two reactant solutions. Therefore, a colloidal gel composed of those tiny particles is pushed forward by the injected aqueous solution giving rise to a viscosity gradient-driven hydrodynamic instability.

Filament dynamics in confined chemical gardens and in filiform corrosion.

Two reaction systems that are at first sight very different produce similar macroscopic filamentary product trails. The systems are chemical gardens confined to a Hele-Shaw cell and corroding metal plates that undergo filiform corrosion. We show that the two systems are in fact very much alike. Our experiments and analysis show that filament dynamics obey similar scaling laws in both instances: filament motion is nearly ballistic and fully self-avoiding, which creates self-trapping events.

Convective dynamics of traveling autocatalytic fronts in a modulated gravity field.

When traveling in thin solution layers, autocatalytic chemical fronts may be deformed and accelerated by convective currents that develop because of density and surface tension gradients related to concentration and thermal gradients across the front. On earth, both buoyancy and Marangoni related flows can act in solution layers open to the air while only buoyancy effects operate in covered liquid layers. The respective effects of density and surface tension induced convective motions are analysed here by studying experimentally the propagation of autocatalytic fronts in uncovered and covered liquid layers during parabolic flights in which the gravity field is modulated periodically. We find that the velocity and deformation of the front are increased during hyper-gravity phases and reduced in the micro-gravity phase. The experimental results compare well with numerical simulations of the evolution of the concentration of the autocatalytic product coupled to the flow field dynamics described by Navier-Stokes equations.

Unraveling dispersion and buoyancy dynamics around radial A + B → C reaction fronts: microgravity experiments and numerical simulations.

Radial Reaction-Diffusion-Advection (RDA) fronts for A + B → C reactions find wide applications in many natural and technological processes. In liquid solutions, their dynamics can be perturbed by buoyancy-driven convection due to concentration gradients across the front. In this context, we conducted microgravity experiments aboard a sounding rocket, in order to disentangle dispersion and buoyancy effects in such fronts. We studied experimentally the dynamics due to the radial injection of A in B at a constant flow rate, in absence of gravity. We compared the obtained results with numerical simulations using either radial one- (1D) or two-dimensional (2D) models. We showed that gravitational acceleration significantly distorts the RDA dynamics on ground, even if the vertical dimension of the reactor and density gradients are small. We further quantified the importance of such buoyant phenomena. Finally, we showed that 1D numerical models with radial symmetry fail to predict the dynamics of RDA fronts in thicker geometries, while 2D radial models are necessary to accurately describe RDA dynamics where Taylor-Aris dispersion is significant.

Intraoperative conditions of patients undergoing pancreatoduodenectomy.

BACKGROUND: Postoperative pancreatic fistula (POPF) is a severe complication following pancreatoduodenectomy (PD). Previous research in colorectal surgery demonstrated suboptimal intraoperative conditions to be related with an increased risk of anastomotic leakage. Aim of this study was to evaluate the intraoperative condition of patients undergoing PD by both assessing whether these known intraoperative modifiable risk factors in colorectal surgery are also present during PD and by measuring compliance to intraoperative ERAS guidelines. Secondly, to determine the relation of these factors with POPF. MATERIALS AND METHODS: This prospective single center study included patients undergoing PD from 2016 to 2020. Parameters regarding the patient's general condition, local perfusion, oxygenation, surgical factors and ERAS elements were measured with a checklist intraoperatively, before the creation of the pancreatojejunal anastomosis. Uni- and multivariable logistic regression analyses were performed. RESULTS: 83 patients were included. POPF occurred in 27.7% (9.0% grade B, 10.0% grade C). Patients with POPF significantly had more other postoperative complications compared to patients without POPF (100% vs. 76.2%, p = 0.017). A suboptimal intraoperative condition was observed in 89.2%. Overall compliance to the intraoperative ERAS guideline was 0%. In univariable analysis, soft pancreatic tissue, pancreatic duct <3 mm, tumor location and intraoperative vasopressor administration were significantly associated with POPF. In multivariable analysis, only soft pancreatic tissue was independently associated with POPF (OR 13.627; 95% CI 1.656-112.157, p = 0.015). CONCLUSION: Awareness amongst surgeons and anesthesiologists should be created. The influence of these intraoperative factors on POPF should be further evaluated in future, larger studies.

A + B → C reaction fronts in Hele-Shaw cells under modulated gravitational acceleration.

The dynamics of A + B → C reaction fronts is studied under modulated gravitational acceleration by means of a combination of parabolic flight experiments and numerical simulations. During modulated gravity the front position undergoes periodic modulation with an accelerated front propagation under hyper-gravity together with a slowing down under low gravity. The underlying reason for this is an amplification and a decay, respectively, of the buoyancy-driven double vortex associated with the front propagation under standard gravitational acceleration, as explained by reaction-diffusion-convection simulations of convection around an A + B → C front. Deeper insights into the correlation between grey-value changes in the experimental shadowgraph images and characteristic changes in the concentration profiles are obtained by a numerical simulation of the imaging process.