Hanna Rademaker

• MSc
• PhD Student at Technical University of Denmark

We study the viscous dissipation in pipe flows in long channels with porous or semipermeable walls, taking into account both the dissipation in the bulk of the channel and in the pores. We give simple closed-form expressions for the dissipation in terms of the axially varying flow rate Q(x) and the pressure p(x), generalizing the well-known express...

The export of photosynthetically produced sugars from leaves depends on plasmodesmatal transport of sugar molecules from mesophyll to phloem. Traditionally, the density of plasmodesmata (PD) along this phloem-loading pathway has been used as a defining feature of different phloem-loading types, with species proposed to have either many or few PD be...

We give an overview of the current understanding of the coupled water—and sugar flows in plants with special emphasis on the leaves. We introduce the Münch mechanism and discuss the particularities of osmotically driven flow in the phloem and the consequences for the allometry of the vasculature. This is first done in the context of the entire tree...

Plant leaf size varies by more than three orders of magnitude, from a few millimeters to over one meter. Conifer leaves, however, are relatively short and the majority of needles are no longer than 6 cm. The reason for the strong confinement of the trait-space is unknown. We show that sugars produced near the tip of long needles cannot be exported...

We study the flow of water and solutes in linear cylindrical pipes with semipermeable walls (membranes), driven by concentration differences across the membranes, inspired by the sieve tubes in conifer needles. The aim is to determine the efficiency of such systems. For single pipes, we assume that the velocity at the entrance (the tip of the needl...

Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyse the feasibility of a particular loading mechanism, active symplasmic loading, also ca...

Mimicry of the tough natural composite nacre in future bioengineering requires knowledge of the biomineralisation process. The insoluble organic matrix isolated from the shell of the gastropod Haliotis laevigata was characterised by protein chemistry, topographical and mechanical measurements. Demineralisation of nacre in dilute acetic acid or ethy...

The natural composite nacre is characterised by astonishing mechanical properties, although the main constituent is a brittle mineral shaped as tablets interdispersed by organic layers. To mimic the natural formation process which takes place at ambient conditions an understanding of the mechanism responsible for a defined microstructure of nacre i...