Abstract Trichodesmium is an important dinitrogen (N2)-fixing cyanobacterium in marine ecosystems. Recent nucleic acid analyses indicate that colonies with their diverse epibionts support various nitrogen (N) transformations beyond N2 fixation. However, rates of these and concentration gradients N compounds remain largely unresolved. We combined isotope-tracer incubations, micro-profiling numeric modelling to explore carbon fixation, cycling processes as well oxygen, ammonium nitrate...

Abstract. Mesoscale eddies are pervasive in the global ocean and suggested to play a significant role enhancing carbon export from surface deep ocean. However, their dynamic nature associated challenges of in-situ sampling have limited direct measurements flux within these features, leaving contribution uncertain. In-situ optical devices offer promising solution by providing high-resolution data on particle abundance size distribution (PSD) eddies, both vertically horizontally. Yet,...

The effect of a step wise change in the pillar density on dynamics droplets is investigated via three-dimensional lattice Boltzmann simulations. For same gradient but different arrangements, both motion over zone as well complete arrest are observed. In moving case, droplet velocity scales approximately linearly with texture gradient. A simple model provided reproducing observed linear behavior. also predicts dependence surface tension. This prediction clearly confirmed our computer...

The stability and dynamics of droplets on solid substrates are studied both theoretically via experiments. Focusing our recent achievements within the DFG-priority program 1164 (Nano- Microfluidics), we first consider case (large) so-called gradient substrates. Here term refers to a change wettability (chemical gradient) or topography (roughness gradient). While motion droplet perfectly flat substrate upon action chemical appears be natural consequence considered situation, show that...

Via numerical simulations, we investigate the dynamics of cylindrical drops on flat substrates. In agreement with common understanding, in limit Stokes flow and negligible drop deformation, drop's centre-of-mass velocity scales linearly applied force second power radius. this paper, go a step further perform detailed study dissipation loss inside drop. An important result is that dominant part viscous arises from region below centre mass. Based observation, propose simple analytic model...

The viscous stress in nonideal fluid lattice Boltzmann methods is investigated theoretically and by simulations. Three representative liquid-gas models are compared a steady-state situation, where an analytical expression for the available. It shown that, presence of interactions or strong body forces, accuracy computed depends strongly on underlying model.

New mathematical model explains physical-biological coupling of processes occurring within sinking aggregates in the ocean.

We review recent advances on the mesoscopic modeling of water-like fluids,based lattice Boltzmann (LB) methodology.The main idea is to enrich basic LB (hydro)-dynamics with angular degrees freedom responding suitable directional potentials between molecules.The model shown reproduce some microscopic features liquid water, such as an average number hydrogen bonds per molecules (HBs) $3$ and $4$, well a qualitatively correctstatistics bond angle function temperature.Future developments, based...

For situations, in which the size of a droplet is comparable to roughness scale solid substrate, we explore possible wetting morphologies on patterned hydrophobic substrates and investigate their dependence initial position, volume surface geometry. regular array cubical pillars, small perturbations symmetric state are restored by capillary forces. Larger deviations, other hand, may lead completely new morphologies. Our studies also suggest that previously reported 'reentrant transition'...

A hydro-kinetic scheme for water-like fluids, based on a lattice version of the Boltzmann equation, is presented and applied to popular TIP3P model liquid water. By proceeding in much larger steps than molecular dynamics, proves be very effective attaining global minima classical pair potentials with directional radial interactions, as confirmed by further simulations using three-dimensional Ben-Naim water potential. The shown reproduce propensity form nearly four hydrogen bonds per...

We develop a three-dimensional lattice Boltzmann (LB) model accounting for directional interactions between water-like molecules, based on the so-called Ben-Naim (BN) potential [A. Ben-Naim, Molecular Theory of Water and Aqueous Solutions: Part I: Understanding (World Scientific Publishing Company, 2010); A. “Statistical mechanics ‘waterlike’ particles in two dimensions. I. Physical application Percus-Yevick equation,” J. Chem. Phys. 54, 3682 (1971)]10.1063/1.1675414. The molecules are...

Abstract The marine biological carbon pump is mainly driven by the interplay between aggregate sinking velocity and remineralization. Sinking of natural aggregates not routinely measured but often calculated using Stokes’ law, which does consider size-dependent changes in porosity. We analyzed flow fields around 81 situ -formed Particle Image Velocimetry (PIV) to determine factors controlling settling. Using an independently derived scaling porosity with size, we predicted laboratory-formed...

The steady state motion of cylindrical droplets under the action external body force is investigated both theoretically and via lattice Boltzmann simulation. As long as shape-invariance droplet maintained, droplet's center-of-mass velocity linearly scales with density square radius. However, a non-linear behavior appears deformation becomes significant. This associated drop elongation occurring at sufficiently high forcing. Yet, independent either or size, found to be linear in terms inverse...

Abstract. Mesoscale eddies are abundant in the eastern tropical North Atlantic and act as oases for phytoplankton growth due to local enrichment of nutrients otherwise oligotrophic waters. It is not clear whether these can efficiently transfer organic carbon other flux components depth if they important marine budget. Due their transient regionally restricted nature, measurements eddies' contribution bathypelagic particle difficult obtain. Rare observations export associated with low-oxygen...

A kinetic over-relaxation minimizer, based on a lattice version of the Boltzmann equation is presented. The method validated against standard Metropolis Monte Carlo, and proves very effective in attaining (global) minima classical pair potentials, involving solid body rotations. Linear scaling computational time to minimum with system size demonstrated.

Abstract. Mesoscale eddies are abundant in the eastern tropical North Atlantic and can form an oasis for phytoplankton growth due to local enrichment of nutrients otherwise oligotrophic ocean. It is not clear, whether these efficiently transfer organic carbon other flux components depth if they important marine budget. Due their transient regionally restricted nature, measurements eddies’ contribution bathypelagic particle difficult obtain. The rare observations export associated with low...

Our understanding of the small-scale processes that drive global biogeochemical cycles and Earth’s climate is dependent on accurate estimations interfacial diffusive fluxes to from biologically-active substrates in aquatic environments. In this study, we present a novel model approach for calculations dissolved gases, nutrients, solutes concentration profiles measured across substrate-water interfaces using microsensors. The offers robust computational scheme automatized determination...