A high level polarizable force field is used to study the temperature dependence of hydrophobic hydration of small-sized molecules from computer simulations. Molecular dynamics (MD) simulations of liquid water at various temperatures form the basis of free energy perturbation calculations that consider the onset and growth of a repulsive sphere. This repulsive sphere acts as a model construct for the hydrophobic species. In the present study, an extension is pursued for seven independent target temperatures, ranging from close to the freezing point almost up to the boiling point of liquid water under standard conditions. Care is taken to maintain proper physico-chemical model descriptions by cross-checking with experimental water densities at the selected target temperatures. The polarizable force field description of molecular water turns out to be suitable throughout the entire temperature domain considered. Derivatives of the computed free energies of hydrophobic hydration with respect to the temperature give access to the changes in entropy. In practice the entropy differential is determined from the negative of the slope of tangential lines formed at a certain target temperature in the free energy profile. The obtained changes in entropy are negative for small-sized cavities, and hence reconfirm the basic ideas of the Lum-Chandler-Weeks theory on hydrophobic hydration of small-sized solutes.

Combining LDA and PIV techniques to investigate unsteady swirling flows permits a more detailed interpretation of velocity fluctuations than that from LDA alone. This can be necessary when comparing measurements with numerical simulations which attempt to capture the unsteadiness. One possible method of combining the measurement data is introduced and discussed with application to swirling flowfields which exhibit a precessing vortex core. The analysis indicates that in such flows the unsteadiness accounts for up to 70% of the total energy in the velocity fluctuations.

No abstract

While frameworks and application programming interfaces for virtual reality are commonplace today, designing scenarios for virtual environments still remains a tedious and time consuming task. We present a new authoring tool which combines scene assembly and visual programming in a desktop application with instant testing, tuning and planning in an immersive virtual environment. Two authors can work together -one with the desktop authoring application, and the other in the immersive VR-simulation -to build a complete scenario. SAVEThe Safety Virtual Environment (SAVE) is a Virtual Reality system for safety training. It has been developed

No abstract