Phase-field modelling of the dynamics of Z-ring formation in liposomes: Onset of constriction and coarsening

We propose a model for the dynamics of the formation of rings of FtsZ on tubular liposomes which produce constriction on the corresponding membrane. Our phase-field model is based on a simple bending energy that captures the dynamics of the interplay between the protein and the membrane. The short-time regime is analyzed by a linear dispersion relation, with which we are able to predict the number of rings per unit length on a tubular liposome. We study numerically the long-time dynamics of the system in the non-linear regime where we observe coarsening of Z-rings on tubular liposomes. In particular, our numerical results show that, during the coarsening process, the number of Z-rings decreases as the radius of tubular liposome increases. This is consistent with the experimental observation that the separation between rings is proportional to the radius of the liposome. Our model predicts that the mechanism for the increased rate of coarsening in liposomes of larger radius is a consequence of the increased interface energy

Preventive approach to reduce risk caused by failure of a rainwater drainage system: The case study of Corato (Southern Italy)

The presence of ancient underground urban drainage system in cities entails serious risks to public safety. Often, the presence of these hydraulic structures is forgotten and their projects missing in public offices. In this work the critical issues of the old urban drainage system of Corato, a city in the south of Italy, are described. In particular, through a targeted identification, acquisition and spatialization of key variables, and subsequent processing in a GIS software, a method for risk assessment has been provided. The choice of key variables was carried out through visual inspections and acquisition of “historical criti-calities” of the urban drainage system. Finally, this paper presents a methodology, calibrated on the old city of Corato, to evaluate the risk caused by the presence of this hydraulic infrastructure, in order to help technicians to define the correct order of operations to be carried out.3n

Atomistic description of pressure-driven flow of aqueous salt solutions through charged silica nanopores

Lab-on-a-chip devices and nanoscale porous membranes made from silica substrates are currently of significant interest for application to water desalination, biosensing, and chemical separation technologies. In each of these applications, the interaction between ionic solutions and the silica interface is key to developing design rules. In this paper, we present the results of extensive all-atom molecular dynamics simulations of the streaming current flow of 0.5 M NaCl and 0.5 M CaCl2 ionic solutions through cylindrical charged silica nanopores with diameters of 1.5, 2.0, 2.5, and 3.0 nm. We present the results from these simulations which provide a detailed description of the ion transport through the pores. We investigate the effect of pore size on ion pairing, ion hydration, and the structure of ions within the aqueous solutions. We also present the flux of the various species of the solutions through the various pores and the average current that is carried by the ions through the pores. In the 0.5 M NaCl systems, we observe that as the pore diameters increase the average current becomes increasingly positive, while for the 0.5 M CaCl2 system, the average current becomes increasingly negative as the pore diameter increases. This difference is a result from the fact that charge inversion is present in the CaCl2 systems but not in the NaCl systems