Coexistence of Multilayered Phases of Confined Water: The Importance of Flexible Confining Surfaces

Flexible nanoscale confinement is critical to understanding the role that bending fluctuations play on biological processes where soft interfaces are ubiquitous or to exploit confinement effects in engineered systems where inherently flexible 2D materials are pervasively employed. Here, using molecular dynamics simulations, we compare the phase behavior of water confined between flexible and rigid graphene sheets as a function of the in-plane density, rho(2D). We find that both cases show commensurate mono-, bi-, and trilayered states; however, the water phase in those states and the transitions between them are qualitatively different for the rigid and flexible cases. The rigid systems exhibit discontinuous transitions between an (n)-layer and an (n+1)-layer state at particular values of rho(2D), whereas under flexible confinement, the graphene sheets bend to accommodate an (n)-layer and an (n+1)-layer state coexisting in equilibrium at the same density. We show that the flexible walls introduce a very different sequence of ice phases and their phase coexistence with vapor and liquid phases than that observed with rigid walls. We discuss the applicability of these results to real experimental systems to shed light on the role of flexible confinement and its interplay with commensurability effects

Investigating the relationship between volume transport and sea surface height in a numerical ocean model

The Agulhas Current Time-series Experiment mooring array (ACT) measured transport of the Agulhas Current at 34∘ S for a period of 3 years. Using along-track satellite altimetry data directly above the array, a proxy of Agulhas Current transport was developed based on the relationship between cross-current sea surface height (SSH) gradients and the measured transports. In this study, the robustness of the proxy is tested within a numerical modelling framework using a 34-year-long regional hindcast simulation from the Hybrid Coordinate Ocean Model (HYCOM). The model specifically tested the sensitivity of the transport proxy to (1) changes in the vertical structure of the current and to (2) different sampling periods used to calculate the proxy. Two reference proxies were created using HYCOM data from 2010 to 2013 by extracting model data at the mooring positions and along the satellite altimeter track for the box (net) transport and the jet (southwestward) transport. Sensitivity tests were performed where the proxy was recalculated from HYCOM for (1) a period where the modelled vertical stratification was different compared to the reference proxy and (2) different lengths of time periods: 1, 3, 6, 12, 18, and 34 years. Compared to the simulated (native) transports, it was found that the HYCOM proxy was more capable of estimating the box transport of the Agulhas Current compared to the jet transport. This was because the model is unable to resolve the dynamics associated with meander events, for which the jet transport algorithm was developed. The HYCOM configuration in this study contained exaggerated levels of offshore variability in the form of frequently impinging baroclinic anticyclonic eddies. These eddies consequently broke down the linear relationship between SSH slope and vertically integrated transport. Lastly, results showed that calculating the proxy over shorter or longer time periods in the model did not significantly impact the skill of the Agulhas transport proxy. Modelling studies of this kind provide useful information towards advancing our understanding of the sensitivities and limitations of transport proxies that are needed to improve long-term ocean monitoring approaches

Design and implementation of a user-level Sockets layer over Virtual Interface Architecture

this paper, we design and implement a user-level Sockets layer over VIA, named SOVIA (Sockets Over VIA). Our objective is to use the SOVIA layer to accelerate the existing Sockets-based applications with a reasonable effort and to provide a portable and high-performance communication library based on VIA to application developer