Superconducting properties of novel BiSe2_{2}-based layered LaO1−x_{1-x}Fx_{x}BiSe2_{2} single crystals

F-doped LaOBiSe$_{2}$ superconducting single crystals with typical size of 2$\times$4$\times$0.2 mm$^{3}$ are successfully grown by flux method and the superconducting properties are studied. Both the superconducting transition temperature and the shielding volume fraction are effectively improved with fluorine doping. The LaO$_{0.48}$F$_{0.52}$BiSe$_{1.93}$ sample exhibits zero-resistivity at 3.7 K, which is higher than that of the LaO$_{0.5}$F$_{0.5}$BiSe$_{2}$ polycrystalline sample (2.4K). Bulk superconductivity is confirmed by a clear specific-heat jump at the associated temperature. The samples exhibit strong anisotropy and the anisotropy parameter is about 30, as estimated by the upper critical field and effective mass modelComment: 5 pages, 5 figures, 2 tables, accepted for publication in Europhysics Lette

Molecular origins of the loss of deformability in Plasmodium -falciparum infected erythrocytes: a coarse-grained modeling

Plasmodium falciparum, the most virulent human malaria parasite, invades human erythrocytes, exports proteins to modify erythrocyte membranes, endows erythrocyte with high stiffness and cytoadherence, and subsequently leading to blockage of blood vessels and dysfunction of organs. Despite continuous progress in experimental studies on erythrocyte remodeling triggered by P. falciparum infection, the underlying molecular mechanisms regarding how the microstructural modifications of erythrocyte membrane lead to the impressive loss of deformability remains elusive. Using a coarse-grained erythrocyte membrane model, capable of incorporating molecular level structural modifications caused by P. falciparum, we systematically investigated shear elasticity of the erythrocyte membranes. Our simulation results show that though the spectrin network accounts for the shear modulus of healthy erythrocyte, pure alteration of the spectrin network could not induce remarkable increase in the shear modulus. Instead, knob formation in the bilayer membrane significantly influences erythrocyte membrane via tightening the associations between spectrin network and lipid bilayer, thereby resulting in increased shear modulus and the loss of deformability. Evolution of knob density and size also plays an important role in enhancing the shear modulus. Shear moduli of P. falciparum-infected erythrocyte at different asexual stages obtained from our model are in good agreement with experimental results. Our findings offer molecular insights into the stiffening mechanism of P. falciparum infected erythrocytes

One-particle-thick, Solvent-free, Course-grained Model for Biological and Biomimetic Fluid Membranes

Biological membranes are involved in numerous intriguing biophysical and biological cellular phenomena of different length scales, ranging from nanoscale raft formation, vesiculation, to microscale shape transformations. With extended length and time scales as compared to atomistic simulations, solvent-free coarse-grained membrane models have been exploited in mesoscopic membrane simulations. In this study, we present a one-particle-thick fluid membrane model, where each particle represents a cluster of lipid molecules. The model features an anisotropic interparticle pair potential with the interaction strength weighed by the relative particle orientations. With the anisotropic pair potential, particles can robustly self-assemble into fluid membranes with experimentally relevant bending rigidity. Despite its simple mathematical form, the model is highly tunable. Three potential parameters separately and effectively control diffusivity, bending rigidity, and spontaneous curvature of the model membrane. As demonstrated by selected examples, our model can naturally simulate dynamics of phase separation in multicomponent membranes and the topological change of fluid vesicles