Nanoindentation of Isometric Viruses on Deterministically Corrugated Substrates.

It has been just over 100 years since inventor Joseph Coyle perfected the egg carton-a package format that has known very little changes since its first appearance ( Dhillon , S. B. C. Inventor Created Better Way to Carry Eggs. In The Globe and Mail Vancouver , 2013 ). In this article, we extend Coyle's old idea to the study of mechanical properties of viruses. Virus stiffness, strength, and breaking force obtained by force spectroscopy atomic force microscopy (AFM) provide the knowledge required for designing nanocontainers for applications in biotechnology and medicine, and for understanding the fundamentals of virus-host interaction such as virus translocation from one cellular compartment to another. In previous studies, virus particles adsorbed on flat surfaces from a physiological buffer were subjected to directional deformation by a known force exerted via a microscopic probe. The affinity between the virus shell and surface is required to be strong enough to anchor particles on the substrate while they are indented or imaged, yet sufficiently weak to preserve the native structure and interactions prior deformation. The specific question addressed here is whether an experimental scheme characterized by increased contact area and stable mechanical equilibrium under directional compression would provide a more reliable characterization than the traditional flat substrate approach.

Resolution of a stochastic weakly damped nonlinear Schrödinger equation by a multilevel numerical method.

We consider a stochastic nonlinear Schrödinger equation related to signal propagation in waveguides and optical fibers. We first describe the modeling of the problem and the desired objectives concerning the transmission. We then present a new multilevel numerical method for its solution, which is based on a separation between low and high frequencies. We show that this method gives results of the same quality with significantly shorter CPU time compared with those of the other numerical methods commonly presented in the literature.