Fruit fly Drosophila melanogaster is one of the most important model organisms used to study embryonic development. In this work we employed precise measurements of displacement and deformation of cells in the embryonic epithelial tissue of the fruit fly to find that its elastic properties are very inhomogeneous. Using high-resolution three-dimensional microscopic technique we studied the deformation of the tissue during the formation of ventral furrow as the first stage of gastrulation. Additional insight into the process was obtained by observing partly cauterized samples, whose preparation was a considerable technical challenge. The measured cell displacement and deformation was compared to the predictions of the mechanical model based on the surface energy of cells. We found that the effective elastic moduli of the lateral and the dorsal tissue are much larger and much smaller than that of the ventral tissue, respectively, and that the orchestrated morphogenesis of the whole epithelium is essential for correct development. These conclusions show that the formation of the ventral furrow is a collective process engaging the whole embryonic tissue.
COBISS.SI-ID: 28987687
We propose a novel approach to chromatin structure, based on symmetry properties of individual nucleosomes that give rise to mesophase order parameters, like in many other soft-matter systems. Basing our approach on the Landau–de Gennes phenomenology, we describe the mesoscale order in chromatin by antipolar and anticlinic correlations of chiral individual nucleosomes. This approach leads to a unifying physical picture of a whole series of soft locally ordered states with different apparent structures, including the recently observed heteromorphic chromatin, stemming from the antipolar arrangement of nucleosomes complemented by their chiral twisting. Properties of these states under an external force field can reconcile apparently contradictory results of single-molecule experiments.
COBISS.SI-ID: 2818660
We have studied the compressibility properties of liquid crystals in the twist-bend (TB) nematic phase formed by chiral dimers. The compressibility modulus of the TB nematic phase was found to be as large as in smectic phases. Because the modulation pitch in the TB nematic is by an order of magnitude larger than the smectic layer thickness, one would expect the compressibility modulus to be by at least two orders of magnitude smaller. Since the existing and widely accepted flexoelectric model cannot explain this finding, the limits of its validity have to be reconsidered.
COBISS.SI-ID: 28844839
Using computer simulations in combination with basic theoretical arguments, we studied hydration-induced interactions between surfaces with different polarities in water environment. Based on surface contact angels and surface--surface binding affinities, we construct a universal interaction diagram featuring three different interaction regimes: hydration repulsion, cavitation-induced attraction, and dry adhesion regime in between. These results not only explain how surfaces interact in water but are also relevant for designing synthetic surfaces that efficiently bind the particles with given surface properties.
COBISS.SI-ID: 28926759
We demonstrate that high-transconductance organic thin film transistors can be achieved by depositing electrochemically exfoliated graphene flakes at the gate-dielectric/organic semiconductor (OS) interface. This effect is applicable to both, solution processed, polymer-based and vacuum-evaporated small-molecule OS-based transistors. Poly(3-hexylthiophene) (P3HT) transistors exhibit a factor of seven higher charge carrier mobility, while pentacene transistors exhibit a fourfold increase in charge carrier mobility, if graphene flakes are present at the dielectric/OS interface.
COBISS.SI-ID: 4056059